• Author / Uploaded
• Francisco Alvarado Huenquiao

Citation preview

Service Training Meeting Guide 687

SESV1687 March 1998

TECHNICAL PRESENTATION

D6R/D7R TRACK-TYPE TRACTORS

D6R/D7R TRACK-TYPE TRACTORS MEETING GUIDE 687

SLIDES AND SCRIPT AUDIENCE

Level II--Service personnel who understand the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting.

CONTENT This presentation provides an orientation and describes the operation of the power train and hydraulic systems on the D6R and D7R Track-type Tractors equipped with the Power Train Electronic Control System. These machines may be equipped with differential steering or steering clutches and brakes.

OBJECTIVES After learning the information in this presentation, the serviceman will be able to: 1. locate and identify the major components in the operator's station, power train, and implement hydraulic systems; 2. check fluid levels in the engine, power train, and implement hydraulic systems; 3. trace oil flow through the power train and implement hydraulic systems; and 4. explain the operation of the components in the power train and implement hydraulic systems.

REFERENCES D6R Service Manual (Power Train Electronic Control System) D6R Service Manual (Differential Steering) D7R Service Manual (Power Train Electronic Control System) D7R Service Manual (Differential Steering) STMG 508 "D7H Track-type Tractor" STMG 547 "D8N Track-type Tractor--Power Train and Implements" STMG 641 "D6H/D7H Series II Track-type Tractors"

SENR8350 SENR9490 SENR8335 SENR1700 SESV1508 SESV1547 SESV1641

PREREQUISITES Interactive Video Course "Fundamentals of Mobile Hydraulics" (CD ROM) STMG 546 "Graphic Fluid Power Symbols"

TECD9001 SESV1546

Estimated Time: 4 Hours Visuals: 117 (2 X 2) Slides Serviceman Handouts: 11 Line Drawings Form: SESV1687 Date: 3/98 © 1998 Caterpillar Inc.

STMG 687 3/98

-3-

TABLE OF CONTENTS INTRODUCTION ..................................................................................................................5 OPERATOR'S STATION........................................................................................................8 ENGINE................................................................................................................................16 POWER TRAIN ...................................................................................................................23 Torque Divider ................................................................................................................23 Power Shift Transmission ...............................................................................................26 Steering and Brakes ........................................................................................................36 Standard Power Train Hydraulic System Operation.......................................................40 Differential Steer Power Train Hydraulic System Operation .........................................45 Differential Steer Mechanical Operation ........................................................................46 UNDERCARRIAGE ............................................................................................................52 IMPLEMENT HYDRAULIC SYSTEMS............................................................................54 STANDARD D6R IMPLEMENT HYDRAULIC SYSTEM...............................................57 Pump Operation ..............................................................................................................64 Inlet Manifold Operation ................................................................................................75 Implement Control Valve Operation...............................................................................78 Quick-Drop Valve Operation ..........................................................................................87 STANDARD D7R IMPLEMENT HYDRAULIC SYSTEM...............................................95 Inlet Manifold Operation ................................................................................................99 Implement Control Valve Operation.............................................................................107 DIFFERENTIAL STEER HYDRAULIC SYSTEM..........................................................113 Pump Operation ............................................................................................................126 Steering Circuit Operaion .............................................................................................134 Implement Control Valve Operation.............................................................................143 AUTOSHIFT AND AUTO KICKDOWN OPERATION ..................................................148 CATERPILLAR MONITORING SYSTEM ......................................................................149 CONCLUSION...................................................................................................................160 SLIDE LIST........................................................................................................................161 SERVICEMAN'S HANDOUTS.........................................................................................164

STMG 687 3/98

-4-

INSTRUCTOR NOTES

STMG 687 3/98

-5-

D6R/D7R TRACK-TYPE TRACTORS

© 1998 Caterpillar Inc.

1

INTRODUCTION • Elevated sprocket design • Optional differential steering • 3306 DIT engine in D6R • 3306 DITA engine in D7R

The D6R and D7R Track-type Tractors are part of the Caterpillar line of medium size track-type tractors. Both machines have the elevated sprocket design drive system and can be equipped with optional differential steering. The D6R is powered by a Caterpillar 3306 turbocharged engine and the D7R is powered by a turbocharged and aftercooled 3306 engine. The 3306 DIT in the D6R provides 123 kW (165 hp) in machines with the standard track arrangement, 130 kW (175 hp) in machines with the XL and XR track arrangements, and 138 kW (185 hp) in machines with the Low Ground Pressure (LGP) track arrangement. All the power specifications are given at 1900 rpm for steering clutch and brake machines and for differential steer machines. The 3306 DITA engine in the D7R provides 172 kW (230 hp) at 2100 rpm in machines with the standard and XR track arrangements. Machines with the LGP track arrangement have a 3306 DITA engine that provides 179 kW (240 hp) at 2100 rpm. The D6R and the D7R are both equipped with Advanced Modular Cooling System (AMOCS) radiators.

➥

STMG 687 3/98

-6-

• Standard 3F/3R planetary transmission

Both machines are equipped with a three speed FORWARD, three speed REVERSE (3F/3R) planetary power shift transmission. A torque divider transfers engine power to the planetary transmission.

• LS/PC implement hydraulic system

All D6R machines and the D7R machines with differential steering are equipped with a load sensing, pressure compensating (LS/PC) hydraulic system with variable displacement pumps. The D7R machines with steering clutches and brakes are equipped with a load sensing, pressure compensating implement hydraulic system with a fixed displacement pump and an unloading valve. A margin spool and signal network provide the load sensing feature for the fixed displacement pump on the D7R steering clutch and brake machines.

• "S," "SU," "U" and "A" blades are available

Customers can order the D6R with an "S," "SU" or an "A" blade and the D7R machines with an "S," "SU," "U" or an "A" blade. The "S," "SU" and "U" blades mount to push arms and contain a tag link stabilizer to provide higher penetration forces, better balance, excellent attachment control, and maximum machine maneuverability. The "A" blade mounts to a C-frame through a pinned connection. The "A" blade allows blade angling or tilting, left or right.

• "A" blade mounts to Cframe

• Optional enclosed cab • Cab meets ISO and SAE standards for ROPS and FOPS

Both the optional enclosed cab and open canopy provide the operator with rollover protection (ROPS) and falling object protection (FOPS). The cab meets the standards for ROPS and FOPS structures provided by the Society of Automotive Engineers (SAE) and the International Standards Organization (ISO). Carrier rollers are standard on Low Ground Pressure (LGP) models of the D6R and D7R and are also standard equipment on the D6R XL. This presentation covers the operation of the power train, steering clutches and brakes, differential steering, and implement hydraulic system for the D6R and D7R Track-type Tractors. A basic machine and operator's station orientation are also included.

STMG 687 3/98

-7-

STANDARD TRACK ARRANGEMENT

XR TRACK ARRANGEMENT

TRACK ARRANGEMENTS

XL TRACK ARRANGEMENT

LGP TRACK ARRANGEMENT

2 • XR track extends toward the rear • XL track extends toward the front • LGP has wider track, wider gauge and extends front and rear • XL for aggressive dozing • XR for drawbar application • LGP for increased stability and low ground pressure

The elevated sprocket design provides maximum flexibility in mounting the track roller frames. The D6R and the D7R machines have a standard track configuration or an optional XR track configuration. The XR track configuration has a longer track roller frame (seven rollers on the D6R and eight rollers on the D7R) than the standard track configuration (six rollers on the D6R and seven rollers on the D7R) with more track toward the rear of the machine. The D6R also has an optional XL track configuration. The XL track configuration contains a longer track roller frame (seven rollers) with more track toward the front of the machine. A low ground pressure (LGP) track is also optional on the D6R and D7R. The LGP arrangement has wider track, a wider track gauge, and a longer track roller frame (eight rollers on the D6R and seven rollers on the D7R) than the standard track configuration with the rollers extended forward and to the rear. The XL track configuration provides a more aggressive dozing machine while the XR track arrangement is primarily for drawbar applications. The LGP track configuration provides the machine with a more neutral center of gravity for increased stability and lower ground pressure for operating in soft underfoot conditions.

STMG 687 3/98

-8-

3

OPERATOR'S STATION • Fully adjustable seat

The fully adjustable suspension seat provides comfort and reduces operator fatigue. The operator can adjust the seat height, front to rear position, tilt, and seat back angle. The seat is angled 15° to the right to provide maximum visibility to the rear of the machine.

STMG 687 3/98

-9-

1

2

3

4

5

4

• Lever identification and function: 1. Left steering and brake lever 2. Right steering and brake lever 3. Forward/reverse direction paddle 4. Transmission upshift button 5. Transmission downshift button

Tractors that are not equipped with differential steering are equipped with Finger Tip Control (FTC) steering. The two small levers replace the traditional steering clutch and brake levers and allow the operator to control left and right turns. These levers, when pulled, send an electrical signal from the FTC to the Electronic Control Module (ECM). The ECM then sends a signal to the steering clutch and brake control valve. The proportional solenoids on this valve control the hydraulic circuits for the clutch and brake spools. Pulling the left lever (1) toward the rear of the tractor (approximately one-half the full travel distance) releases the left steering clutch, which disengages the track from the power train. Pulling the left steering lever (1) the full travel distance engages the left brake. The right steering lever (2) operates the same as the left steering lever (1). To make a gradual turn, pull the steering lever approximately one-half the travel distance to the rear of the tractor and to make a sharp turn, pull the steering lever the full travel distance to the rear of the tractor. The tractor direction is controlled by a rotating paddle (3) located on the console. Pushing on the top of the paddle (3) selects the FORWARD direction. Pushing on the bottom of the paddle (3) selects the REVERSE direction. The center position of the paddle (3) is the NEUTRAL position.

• Upshift and downshift buttons

Pushing the top button (4) upshifts the transmission to the next higher gear. Pushing the bottom button (5) downshifts the transmission to the next lower gear.

STMG 687 3/98

- 10 -

1

2

3 4 5

5

• Tiller control lever components: 1. Parking brake switch 2. Key lockout 3. Twist tiller 4. Upshift button 5. Downshift button • Steering • Parking brake switch

The tiller control lever on the differential steer machines combines machine steering, directional changes, and gear selection into a single control. Pressing the top button (4) upshifts the transmission one gear range higher and pressing the bottom button (5) selects a speed one gear range lower. Rotating the tiller lever (3) toward the front selects the FORWARD direction, and rotating the lever toward the rear selects the REVERSE direction. The center position is NEUTRAL. With the machine in FORWARD, moving the tiller lever toward the front causes the machine to turn left, while moving the tiller lever to the rear causes the machine to turn right. When the operator releases the tiller lever, a centering spring returns the lever to the center NO STEER position. The parking brake switch (1) with a key lockout (2) de-energizes the brake solenoids which engages the brakes and shifts the transmission to NEUTRAL.

➥

STMG 687 3/98

- 11 -

WARNING With the engine running and the machine stationary, moving the tiller control lever toward the front or the rear of the machine can cause the machine to steer. To avoid potential personal injury and/or property damage, always ENGAGE the parking brake, which neutralizes the transmission and engages the brakes. The differential steering machines operate with "S-turn logic," not "C-turn logic." With the machine moving FORWARD, moving the tiller lever toward the front of the machine causes the machine to turn to the LEFT. With the machine moving in REVERSE, moving the electronic tiller lever toward the front of the machine causes the machine to turn to the RIGHT.

STMG 687 3/98

- 12 -

1

2

6

• Component locations: 1. Brake pedal 2. Decelerator pedal

Both the FTC and the differential steer models are equipped with two pedals. The large pedal is the service brake pedal (1). Depressing the service brake pedal de-energizes the solenoids on the steering clutch and brake control valve and ENGAGES both brakes. The smaller pedal is the decelerator pedal (2). During normal operation, the operator moves the governor control lever into the HIGH IDLE position and slows the engine using the decelerator pedal.

STMG 687 3/98

- 13 -

7

• Dash components

The instrument panel includes the Caterpillar Monitoring System display which monitors various tractor systems, an action light, a key start switch, and an action alarm (not visible). Also included on the dash are the various light switches, optional air conditioning controls, Autoshift and Auto Kickdown selector buttons, and an operator switch for scrolling different modes. INSTRUCTOR NOTE: The Caterpillar Monitoring System, Autoshift, and Auto Kickdown will be discussed in more detail later in this presentation.

STMG 687 3/98

- 14 -

2

1

8

• Lever functions: 1. Dozer control lever • Dozer lever controls six functions

2. Ripper control lever

• Horn button

The implement controls are at the right of the operator's seat. The standard dozer control lever (1) allows the operator to control all the blade functions with one lever. Pushing the lever to the forward detent position permits the blade to FLOAT. When the lever is in the forward position just to the rear of FLOAT, the blade will LOWER. Pulling the lever to the rear of the center (HOLD) position causes the blade to RAISE. Pushing the lever to the right tilts the right side of the blade down, and pushing the lever to the left tilts the left side of the blade down. Machines equipped with an optional ripper have a ripper control lever (2) behind the implement control lever. To RAISE the ripper, move the control lever from the center (HOLD) position toward the operator's seat, and to LOWER the ripper, move the control lever from the center (HOLD) position away from the operator's seat. The horn button is located between the implement control lever and the ripper control lever.

➥

STMG 687 3/98

• Winch is optional • Winch control lever (if equipped) is behind dozer lever

- 15 -

On machines equipped with winches, the winch control lever (not shown) is to the right of the operator's seat, behind the dozer control lever. The winch control lever has six positions. The first position controls the FREESPOOL function. The FREESPOOL function allows the winch drum to spin freely. A detent mechanism holds the winch lever in the FREESPOOL position. The second position is the BRAKE OFF detent position. When the lever is pushed forward fully to the detent position, the brake is fully released. The third position is the BRAKE OFF position. The BRAKE OFF function provides enough resistance on the winch drum to prevent unreeling the cable by hand, but not so much resistance to prevent the load weight or machine movement from unreeling the cable. When the operator releases the winch lever from the BRAKE OFF position, the lever moves into the BRAKE ON (fourth) position. When the winch is in the BRAKE ON position, the winch brake prevents the winch drum from rotating. The fifth position is the REEL IN position. The final position (if equipped) is for the REEL OUT function. Releasing the lever from either the REEL IN or REEL OUT position returns the winch lever to the BRAKE ON position.

STMG 687 3/98

- 16 -

9

ENGINE • Vented fuel cap (arrow)

The D6R has a 383 Liter (101 gal.) fuel tank and the D7R has a 479 Liter (127 gal.) fuel tank. A strainer in the fuel fill tube keeps debris out of the fuel tank during refueling. The vented cap (arrow) prevents pressure build-up in the fuel tank and also prevents cooling fuel from creating a vacuum.

STMG 687 3/98

- 17 -

10

• Fuel drain valve (arrow)

Opening the fuel tank drain valve (arrow) allows water and sediment to drain from the fuel tank. The fuel drain plug is below the fuel tank on the left side of the machine.

STMG 687 3/98

- 18 -

2

1

11

• 24-Volt electrical system

The battery compartment is located inside a hinged compartment on the left side of the machine just below the fender.

1. Starting and charging analyzer receptacle

Two 12-Volt batteries connected in series provide 24 Volts to start the engine. To access the batteries, loosen the fasteners on the battery compartment and lift the cover.

2. Optional radio connector

Also located in the battery compartment is the starting and charging analyzer receptacle (1) and a connector for an optional radio (2).

STMG 687 3/98

- 19 -

12

• Fuse box location

Opening the battery compartment also provides access to the fuse box. The fuse box contains the electrical system fuses and circuit breakers.

STMG 687 3/98

- 20 -

13

• Air precleaner (arrow)

The precleaner (arrow) removes large debris from the intake air before the air enters the air filters.

STMG 687 3/98

- 21 -

1 2

3

6

8 7 4 5

14

• Component locations: 1. Air filters 2. Engine oil fill tube 3. Engine oil level dipstick 4. Engine oil filter 5. Power train oil cooler 6. Engine oil cooler 7. Scheduled Oil Sampling tap 8. Engine oil pressure tap

Various components visible are on the left side of the engine. Also accessible on the left side of the engine are the Scheduled Oil Sampling (S•O•S) tap (7) which permits live oil sampling, and the engine oil pressure tap (8) which is used when testing the lubrication system pressure NOTE: The engine shown in this view is installed in a D6R.

STMG 687 3/98

- 22 -

4 3 2

1

15

• Component locations: 1. Primary fuel filter 2. Secondary fuel filter 3. Fuel pump and governor 4. Alternator

On the right side of the engine are additional components.

STMG 687 3/98

- 23 -

1

2

16

POWER TRAIN • Torque divider:

Torque Divider

- Transfers power to transmission

The D6R and D7R Track-type Tractors are equipped with a power shift transmission and use a torque divider to transfer engine power to the transmission. The torque dividers on these machines are similar to the torque dividers on other Caterpillar Track-type Tractors.

- Provides a hydraulic and mechanical connection

The torque divider provides both a hydraulic and a mechanical connection from the engine to the transmission. The torque converter provides the hydraulic connection while the planetary gear set provides the mechanical connection. During operation, the planetary gear set and the torque converter work together to provide an increase in torque as the load on the machine increases.

• Component locations: 1. Torque converter outlet relief valve 2. Pressure tap

The torque converter outlet relief valve (1) is mounted on the torque converter case. The torque converter outlet pressure can be checked at the pressure tap (2).

STMG 687 3/98

- 24 -

TORQUE DIVIDER ENGINE FLYWHEEL

HOUSING OUTLET PASSAGE

PLANET GEARS

SUN GEAR

OUTPUT SHAFT STATOR

PLANET CARRIER RING GEAR

INLET PASSAGE

TURBINE IMPELLER

17 • Torque divider operation

• During NO LOAD components rotate as unit

• Under load, relative motion slows turbine rotation

This illustration shows a typical torque divider. The impeller, rotating housing, and sun gear are mechanically connected to the engine flywheel. The turbine and ring gear are connected and the planetary carrier and output shaft are connected. The sun gear and the impeller always rotate at engine speed. As the impeller rotates, it directs oil against the turbine blades, causing the turbine to rotate. Turbine rotation causes the ring gear to rotate. During NO LOAD conditions, the planetary gear set components rotate as a unit with the planet gears stationary on their shafts. As the operator loads the machine, the output shaft slows down. A decrease in output shaft speed causes the rpm of the planetary carrier to decrease. Decreasing the planetary carrier rotation causes the relative motion between the sun gear and the planet carrier to cause the planet gears to rotate. Rotating the planet gears decreases the rpm of the ring gear and the turbine. At this point, the torque splits with the torque converter multiplying the torque hydraulically, and the plantetary gear set multiplying the torque mechanically.

➥

STMG 687 3/98

• During stall, turbine and ring gear rotate in opposite directions • Torque converter provides 70% of output • Planetary gear set provides 30% of output

- 25 -

An extremely heavy load can stall the machine. If the machine stalls, the output shaft and the planetary carrier will not rotate. This condition causes the ring gear and turbine to slowly rotate in the opposite direction of engine rotation. Rotating the ring gear and turbine in the opposite direction provides maximum torque multiplication. During all load conditions, the torque converter provides 70% of the output and the planetary gear set provides the remaining 30% of the output. The size of the planetary gears establishes the torque split between the hydraulic torque and mechanical torque.

STMG 687 3/98

- 26 -

1

2

18

Power Shift Transmission • Component locations: 1.Oil fill tube 2.Dipstick

The D6R power train oil fill tube (1) and dipstick (2) are located in the left side engine compartment.

STMG 687 3/98

- 27 -

2

3 1

19

• Component locations: 1. Transmission pump pressure tap 2. S•O•S tap 3. Filter bypass pressure switch

The power train oil filter is located in the compartment on the right side of the D6R. The power train filter housing contains the power train pump pressure tap (1) and an S•O•S tap (2). The power train filter drain plug is below the filter housing. The filter bypass pressure switch (3) opens during cold start-ups and when the filter is plugged. The bypass valve spool and spring close the switch. The filter bypass pressure switch is connected to the Caterpillar Monitoring System and works with the power train oil temperature sensor.

STMG 687 3/98

- 28 -

2

3 4 5

1

20

• Component locations (D7R differential steer): 1. Power train oil fill tube 2. Power train oil level dipstick 3. Pump pressure tap 4. S•O•S tap 5. Filter bypass pressure switch

The power train oil fill tube (1), dipstick (2), and filter are located in the compartment on the right side of the D7R. On top of the power train filter housing are the power train pump pressure tap (3) and an S•O•S tap (4). The power train filter drain plug is below the filter housing. The filter bypass pressure switch (5) opens during cold start-ups and when the filter is plugged.

STMG 687 3/98

- 29 -

21

• Power train oil pump suction line (arrow)

A magnetic screen is located in the suction line (arrow) to the power train oil pump. Additional power train suction screens are found at the lower rear of the transmission case and at the bottom of the torque divider case. Remove and clean the screens during power train oil changes or if the pump fails.

STMG 687 3/98

- 30 -

3 2

1

22

• Power train oil pump 1. Torque converter and lube section 2. Transmission and controls section 3. Transmission and torque converter scavenge section

A gear on the torque converter impeller drives the gear-type power train oil pump. The power train oil pump supplies flow to the transmission hydraulic controls, the brakes, the steering clutches (non-differential steering machines), and the torque converter.

STMG 687 3/98

- 31 -

1

2

3

23

• 3F/3R planetary power shift transmission 1. Speed sensors 2. Planetary group 3. Transmission control group

The three speed FORWARD, three speed REVERSE planetary power shift transmission transfers power from the engine to the final drives. The transmission contains three hydraulically controlled speed clutches and two hydraulically controlled directional clutches. The transmission shifting function is controlled by the Power Train Electronic Control System. The Electronic Control Module (ECM ) responds to operator shifting requests by controlling the electrical current to the transmission clutch solenoids. The solenoid current controls the hydraulic circuits that engage the transmission clutches. The ECM selects the transmission clutches to be engaged and the clutch pressure is modulated electronically. Solenoid valves control the modulation of the clutch pressure. The ECM uses the transmission speed, engine speed, and the power train oil temperature signals to control smooth engagement of the clutches. Each transmission clutch in the planetary group (2) has a corresponding solenoid valve on the transmission hydraulic control group.(3). The ECM uses the transmission solenoid valves to directly modulate the oil pressure to each transmission clutch. The solenoid valves operate proportionally. The ECM modulates the electrical current to the solenoid valves. Modulating the solenoid valves controls the power train oil flow to the transmission clutches. Electronic clutch modulation allows the ECM to control the time required to fill a clutch with oil and the rate of the clutch pressure modulation.

STMG 687 3/98

- 32 -

TRANSMISSION MODULATING VALVE

TO DRAIN

TO CLUTCH

SUPPLY OIL

24 • Transmission modulating valve

The transmission clutches are hydraulically engaged and spring released. The transmission modulating valve solenoid is energized to send supply oil to the clutch. As current is applied to the solenoid, the rod extends to the right and moves the ball closer to the orifice. The ball begins to restrict the amount of oil to drain. As the pressure at the left end of the spool increases, the spool shifts to the right and the clutch pressure increases. De-energizing the solenoid allows the spool to shift to the left due to the spring force plus the supply oil pressure. This condition reduces the pressure supplied to the clutch below the clutch engagement pressure.

• NEUTRAL

When the transmission is in NEUTRAL, the modulating valve which controls engagement of the No. 3 clutch allows flow to the clutch. The other modulating valves stop flow to the clutches, thereby allowing the clutches to be released by spring force. Since the No. 1 or 2 directional clutch is not engaged, no power is transmitted to the output shaft of the transmission.

➥

STMG 687 3/98

- 33 -

• FIRST FORWARD

When the transmission is in FIRST SPEED FORWARD, the modulating valves which control flow to the No. 2 and 5 clutches receive a signal from the ECM to allow flow to the clutches and, therefore, allow the clutches to engage.

• Transmission main relief valve

The main relief valve is located in the manifold on top of the transmission planetary group. The relief valve limits the system pressure from the control section of the power train oil pump. This oil is used to control the steering clutches, brakes and transmission clutches. Oil to the main relief valve flows from the power train oil filter to supply the steering and brake control valve and transmission modulating valves. The excess oil that flows over the relief valve is used to lubricate the transmission planetary group. The relief valve has a slug chamber connected to pump outlet flow by an orifice contained in the spool. The slug provides a reaction area that balances against a spring force to limit the pressure. The spring has an external adjustment nut located on the side of the manifold. INSTRUCTOR NOTE: The transmission modulating valves must be recalibrated when any of the following procedures are performed: - Transmission modulating valve and/or solenoid is replaced. - Transmission is serviced or replaced. - ECM is replaced. For the calibration procedure, refer to the Power Train Electronic Control System Service Manual (Form SENR8367).

STMG 687 3/98

- 34 -

2

1

25

• Identify components: 1. Power train oil drain plug 2. Transmission scavenge screen

The bevel gear case serves as the oil reservoir for the power train oil system. The power train oil drain plug (1) is in the bottom of the transmission case at the rear of the machine. The transmission case scavenge screen is located behind the cover (2).

STMG 687 3/98

- 35 -

26

• Pump drive lubrication pressure tap (arrow)

The pressure tap (arrow) on the front left of the flywheel housing is used to test the engine rear gear train and pump drive lubrication pressure which is supplied by the power train pump. NOTE: Pump drive lubrication pressure is not adjustable.

STMG 687 3/98

- 36 -

3

4

1

2

27

Steering and Brakes • Pressure tap locations: 1. Right clutch 2. Left clutch 3. Right brake 4. Left brake

The steering clutch and brake control valve (if equipped) is located below the platform, on top of the bevel gear case. The steering clutch pressures (1, right clutch; 2, left clutch) can be tested at the two outer pressure taps and the brake pressures (3, right brake; 4, left brake) can be tested at the two inner pressure taps.

STMG 687 3/98

- 37 -

1 2

28

• Pressure test locations: 1. Right brake lubrication pressure 2. Right brake pressure

The right brake lubrication pressure (1) and right brake pressure (2) can be checked by installing pressure test fittings at these locations on top of the final drive group on the right side of the tractor. This slide shows a differential steer machine. A tractor equipped with steering clutches and brakes will have another tap in the same general location to test the right steering clutch pressure.

STMG 687 3/98

- 38 -

3

2

1

29

• Component locations: 1. Brake control valve 2. Left brake pressure tap 3. Right brake pressure tap

The differential steer machines are not equipped with steering clutches. The differential steer machines are equipped with a brake control valve (1) which applies both brakes simultaneously. The ECM receives an input signal for braking and sends an output signal to the solenoids on the brake control valve. Both brake solenoids are de-energized and the brakes are ENGAGED. Brake pressures can be tested at the pressure taps (2 and 3).

STMG 687 3/98

- 39 -

30

• Parking brake switch (arrow)

The parking brake switch is a four pole, double throw rocker switch. One of the poles of the switch is not used. The function of the three poles are: 1. On/off: Signals the ECM the status of the parking brake switch. When the switch is ON, the ECM shifts the transmission to NEUTRAL and ENGAGES the left and right brakes. 2. Brake back-up: Performs as a back-up for engaging the brakes. When the switch is ON, the brake back-up pole energizes the parking brake solenoid which ENGAGES the brakes. 3. Neutral-start: Performs the neutral-start function. When the switch is OFF, the starter motor cannot be activated. NOTE: The parking brake switch is located on the right front side of the Finger Tip Control console (shown). The parking brake switch on differential steer machines is located on the left side of the tiller lever (see Slide No. 5).

STMG 687 3/98

- 40 -

POWER TRAIN HYDRAULIC SYSTEM D6R WITH FINGER TIP CONTROL

FROM OIL COOLER STEERING AND BRAKE VALVE

4

TO TORQUE CONVERTER

3 5

PRIORITY VALVE 2

1 TRANSMISSION CONTROL GROUP

1

2

3

FROM CONVERTER SCAVENGE

31 Standard Power Train Hydraulic System Operation This diagram shows the power train oil system components on the D6R and D7R machines equipped with steering clutches and brakes. • Three section pump: 1. Scavenge section 2. Clutch and brake lube section 3. Charging section

The power train oil system uses a three section gear pump. The scavenge section (1) returns oil from the torque converter and transmission sumps to the bevel gear case. The center section (2) sends oil at the same time to the steering and brake control valve and the transmission control group. The transmission charging section (3) directs oil from the case to the priority valve, the torque converter and, during certain conditions, sends oil to the steering and brake control valve and the transmission control group. INSTRUCTOR NOTE: For more information on the steering and brake controls, refer to the Technical Instruction Module "Electronically Controlled Steering and Brake System-D5M/D6M/D6R/D7R Track-type Tractors" (Form SEGV2628).

STMG 687 3/98

- 41 -

1

3 2

32

• Priority valve group: 1. Priority valve 2. Torque converter inlet relief valve 3. Solenoid valve • Sends oil to steering and brake valve and transmission control before converter • Operates at high pressure when solenoid is deenergized • Operates at low pressure when solenoid is energized

The priority valve group on the D6R and D7R contains the priority valve (1) and the torque converter inlet relief valve (2). A solenoid valve (3) receives an output signal from the ECM to operate the priority valve at either high or low pressure. The priority valve ensures that the steering clutch and brake control valve receives supply oil along with the transmission control group before supplying oil to the torque converter circuit. The priority valve only operates at high pressure during certain conditions to improve efficiency. The solenoid valve, when DE-ENERGIZED, allows the priority valve to operate at high pressure or 2925 kPa (425 psi). The solenoid is deenergized for the following conditions: When the oil temperature is less than 40°C (104°F), during a speed or directional change, and when the engine speed is below 1300 rpm. The solenoid valve, when ENERGIZED, allows the priority valve to operate at low pressure or 1000 kPa (145 psi) maximum. The solenoid valve is energized for the following conditions: When the above conditions are not fulfilled and when the parking brake is ENGAGED, regardless of oil temperature or engine speed.

➥

STMG 687 3/98

- 42 -

Oil from the torque converter flows through the torque converter outlet relief valve to the oil cooler. By maintaining oil pressure in the torque converter, the outlet relief valve ensures efficient power transfer between the engine and transmission, and also prevents cavitation in the torque converter. Oil from the oil cooler lubricates the steering clutches and brakes and the transmission planetaries before returning to the power train sump. The implement and winch pump drive gears and bearings receive lubrication oil from the inlet side of the torque converter. NOTE: The colors in the valve sections and hydraulic schematics throughout the power train hydraulic system presentation denote various pressures within the system. The legend of color codes is as follows: Red

- Pump supply and P1 pressure

Red and White Stripes

- Reduced and P2 pressure

Orange

- Torque converter pressure

Brown

- Lube oil pressure

Green

- Open to tank

Blue

- Blocked oil

Yellow

- Activated valve envelopes or moving parts

STMG 687 3/98

- 43 -

5 1 4 2

3

33

• Identify components and their functions: 1. No. 1 clutch modulating solenoid valve 2. No. 2 clutch modulating solenoid valve 3. No. 3 clutch modulating solenoid valve 4. No. 4 clutch modulating solenoid valve 5. No. 5 clutch modulating solenoid valve

The transmission control valve groups for the D6R and D7R machines equipped with either differential steering or steering clutches and brakes are the same. The transmission control valve regulates oil pressure to the clutch proportionally to the supplied output current from the ECM. One valve is provided for each clutch. The shift modulation and sequencing are controlled by software--not by springs, orifices, and/or shims.

STMG 687 3/98

- 44 -

PARKING AND SECONDARY BRAKE SOLENOIDS

STEERING AND BRAKE CONTROL VALVE SERVICE BRAKES ENGAGED

TO RIGHT CLUTCH TO RIGHT BRAKE

SUPPLY OIL

TO LEFT BRAKE TO LEFT CLUTCH

34 • Braking controlled electronically

Braking is a function of the Power Train Electronic Control System. This slide shows the steering and brake control valve with the brakes ENGAGED. The brakes are spring engaged and hydraulically released. The service brake pedal sensor signals the ECM the braking requests of the operator. The ECM acts upon the request by de-energizing both the right and left brake solenoid valves on the steering and brake control valve. This condition sends oil to drain and the springs engage the brakes.

STMG 687 3/98

- 45 -

POWER TRAIN HYDRAULIC SYSTEM D6R WITH DIFFERENTIAL STEERING

FROM OIL COOLER BRAKE VALVE 4

TO TORQUE CONVERTER

3 5

PRIORITY VALVE

2

1

TRANSMISSION CONTROL GROUP TO TRANSMISSION CASE 1

2

3

FROM CONVERTER SCAVENGE

35 Differential Steer Power Train Hydraulic System Operation • Differential steer differences

The power train oil system on the differential steer machines is similar to the system on the steering clutch and brake machines. The main difference is the brake control valve. Since the differential steer machines are not equipped with steering clutches, the valve does not include left and right steering clutch solenoid valves. The valve contains left and right brake solenoid valves, a secondary brake solenoid valve, and a parking brake solenoid valve. INSTRUCTOR NOTE: For more information on the brake system, refer to the Technical Instruction Module "Electronically Controlled Brake System--D6R/D7R Track-type Tractors with Differential Steering" (Form SEGV2629).

STMG 687 3/98

- 46 -

DIFFERENTIAL STEER COMPONENTS HYDRAULIC MOTOR INPUT

TRANSMISSION INPUT

TO LEFT FINAL DRIVE

TO RIGHT FINAL DRIVE

STEER DRIVE PLANETARY PLANETARY

EQUALIZING PLANETARY

36 Differential Steer Mechanical Operation Differential steer tractors are not equipped with steering clutches but have a steering differential, a hydraulic pump, a hydraulic steering motor, and steering controls. (The hydraulic components are discussed later.) • Steering differential has two power inputs: - Transmission - Hydraulic motor

The steering differential has two power inputs: a speed and direction (FORWARD and REVERSE) input from the transmission and a steering input (LEFT and RIGHT) from the hydraulic motor. The steering differential uses the hydraulic motor power input to increase the speed of one track and equally decrease the speed of the other track. The resulting track speed difference turns the tractor.

➥

STMG 687 3/98

• Steering differential: - Steer planetary - Drive planetary - Equalizing planetary • Schematic color codes

- 47 -

The steering differential consists of the steer planetary, the drive planetary, and the equalizing planetary. Color codes in this illustration designate the various components. The drive pinion, bevel gear shaft, and the drive planetary carrier are red. The bevel gear shaft is splined to the drive planetary carrier. During turns, the pinion for the hydraulic motor drives the steer planetary ring gear. The hydraulic motor pinion and steer planetary ring gear are orange. The center shaft connects the sun gears for all three planetaries. The sun gears and center shaft are blue. The planet gears for all three planetaries are yellow. The left and right outer axle shafts are splined to the steer planetary and equalizing planetary respectively. Also, the steer planetary carrier is directly connected to the drive planetary ring gear. These components are green. The equalizing planetary ring gear is bolted to the right brake housing and is always stationary. The equalizing planetary is gray.

STMG 687 3/98

- 48 -

DIFFERENTIAL STEER COMPONENTS STRAIGHT LINE OPERATION HYDRAULIC MOTOR INPUT

TRANSMISSION INPUT

TO LEFT FINAL DRIVE

TO RIGHT FINAL DRIVE

STEER PLANETARY

DRIVE PLANETARY

EQUALIZING PLANETARY

37 • Straight line operation - Steering motor does not turn - Transmission provides all power - Arrows show power flow - Outer axles rotate in same direction

This illustration shows the power flow through the differential steer system during straight line operation (FORWARD or REVERSE). In this condition, the hydraulic steering motor does not turn. Since the hydraulic steering motor does not turn, the steering pinion and steer planetary ring gear are stationary (gray) and the transmission provides all power flow through the system. The transmission sends power through the transfer gears, pinion, bevel gear, and bevel gear shaft to the drive planetary carrier. At this point, the power divides causing a torque split. Most of the torque goes through the drive planetary ring gear to the steer planetary carrier. From the steer planetary carrier, the resulting power reaches the left final drive through the left outer axle. The remaining torque from the drive planetary carrier is transmitted to the equalizing planetary sun gear through the drive planetary sun gear and the center axle.

➥

STMG 687 3/98

- 49 -

The equalizing planetary planet gears multiply the torque in the sun gear and send the resulting power through the right outer axle to the right final drive. The effect of this operation is that the left and right outer axles rotate in the same direction with the same power magnitude and the machine, therefore, tracks in a straight line.

STMG 687 3/98

- 50 -

DIFFERENTIAL STEER COMPONENTS LEFT TURN - FORWARD HYDRAULIC MOTOR INPUT

TRANSMISSION INPUT

TO RIGHT FINAL DRIVE

TO LEFT FINAL DRIVE

STEER PLANETARY

DRIVE PLANETARY

EQUALIZING PLANETARY

38 • LEFT TURN FORWARD • Transmission input shown with black arrows • Steering motor input shown with white arrows

During a turn, both the transmission and the hydraulic motor provide inputs to the differential steer system with the transmission supplying most of the power to the system. The transmission input power is transmitted to the outer axles in the same manner as during straight line operation. The hydraulic motor input determines the turn direction and turn radius. The rpm of the hydraulic motor controls the turn radius (the higher the rpm, the smaller the turn radius) and the direction of rotation establishes the turn direction.

➥

STMG 687 3/98

- 51 -

During a LEFT TURN in the FORWARD direction, the hydraulic motor sends power through the steering planetary ring gear and planet gears to the sun gear. • Steering motor input causes: - Right outer axle speed to increase - Left outer axle speed to decrease

• Reversing steering motor causes opposite turn

The input from the hydraulic motor has two effects on the system: 1. The first effect is that the speed of all three sun gears and the speed of the center axle increases, causing the speed of the right outer axle to increase. 2. The second effect is that the relative motion of the sun gear and planet gears in the steer and the drive planetaries cause the drive planetary ring gear, the steer planetary carrier, and the left outer axle to slow down. (This relative motion is due to the fact that the drive planetary carrier is turning at a constant rpm.) The speed decrease of the left outer axle is equal to the speed increase of the right outer axle. To make a RIGHT TURN, the direction of the hydraulic motor is opposite of the direction for a LEFT TURN. The motor now applies power to the steering planetary carrier causing an increase in the speed of the steering planetary carrier, the drive planetary ring gear, and the left outer axle. Simultaneously, all three sun gears, the center axle, and the right outer axle slow down. The speed decrease of the right outer axle is equal to the speed increase of the left outer axle. NOTE: During normal operation, this system does not provide a "pivot turn" capability. INSTRUCTOR NOTE: For more information about differential steering operation, see STMG 547 "D8N Track-type Tractor--Power Train and Implements" (Form SESV1547).

STMG 687 3/98

- 52 -

8 1

6 5

7

4

3

2

39

• Component locations: 1. Front idler 2. Front roller frame 3. Rear roller frame 4. Pivot shaft 5. Rear idler 6. Track 7. Track rollers 8. Carrier roller • Sealed and lubricated track • Balanced design

UNDERCARRIAGE The D6R and D7R machines are equipped with sealed and lubricated track and have a balanced undercarriage design. With sealed and lubricated track, oil surrounds the track pin to virtually eliminate internal pin and bushing wear. A rigid shear seal, a rubber load ring, and a thrust ring seals the lubricant inside the track. In a balanced undercarriage design system, all undercarriage components wear at the same rate. The main components of the undercarriage are: the front idler (1), front roller frame (2), rear roller frame (3), pivot shaft (4), rear idler (5), track (6), and track rollers (7). The carrier roller (8) is standard on LGP machines. The pivot shaft (accessed by removing the dozer trunnion) connects the right and left rear roller frames and transmits the ground shocks directly to the main frame rather than through the power train components. The roller frames can oscillate around the pivot shaft. The equalizer bar (not visible) is an additional component of the undercarriage. The equalizer bar is pinned in the center of the tractor and can rotate around the center pin joint. The equalizer bar connects the two front track roller frames and controls the degree that the roller frames can oscillate around the pivot shaft.

➥

STMG 687 3/98

• Track tension is adjustable

- 53 -

The front roller frame slides inside the rear roller frame. A recoil spring maintains the track tension. Pumping grease into a cylinder inside the rear roller frame increases the recoil spring tension. A key and slot mechanism in the front and rear track roller frames allows the front roller frame to slide in and out of the rear roller frame, but prevents the front roller frame from rotating inside the rear. To increase track tension, remove the adjusting valve cover plate and add grease through the adjusting valve. To decrease track tension, loosen the relief valve and allow grease to escape. Then, close the relief valve and add additional grease through the adjusting valve. The Operation and Maintenance Manual (Form SENR8350 for the D6R with Steering Clutches and Brakes, Form SENR9490 for the D6R with Differential Steering, Form SENR8335 for the D7R with Steering Clutches and Brakes, and Form SENR1700 for the D7R with Differential Steering) shows the correct track adjustment procedure. NOTE: The carrier roller can be added to machines with standard gauge track. The carrier roller provides improved fine dozing capabilities and can improve bushing and sprocket wear life in highly abrasive underfoot conditions.

STMG 687 3/98

- 54 -

HYDRAULIC PUMP TYPE PISTON PUMP

MACHINE D6R D6R D7R D7R

GEAR PUMP

X

STANDARD DIFFERENTIAL STEERING

X X

STANDARD DIFFERENTIAL STEERING

X

40 IMPLEMENT HYDRAULIC SYSTEMS • Load sensing/pressure compensated hydraulics

The D6R and D7R machines have load sensing, pressure compensated (LS/PC) hydraulic systems. The D6R equipped with steering clutches and brakes, the D6R differential steer machines, and the D7R differential steer machines use piston-type, variable displacement hydraulic pumps with closed-center valves. The D7R equipped with steering clutches and brakes uses a gear-type, fixed displacement pump with an unloading valve.

STMG 687 3/98

- 55 -

2 1

3

41

• Component locations: 1. Oil fill tube 2. Hydraulic oil filter 3. Sight gauge

The hydraulic tank is located on the right rear of all the machines. This slide shows the oil fill tube (1) and the hydraulic oil filter (2). The main system oil filter is a cartridge-type filter. The sight gauge (3) indicates if the hydraulic system contains the correct amount of oil. NOTE: The hydraulic tank shown in this view is installed on a D6R.

STMG 687 3/98

- 56 -

42

• Drain valve (arrow)

The hydraulic tank drain valve is located below the right fender. The drain on the D7R is located in the same general area, but a cover must be removed to access the drain valve.

STMG 687 3/98

- 57 -

D6R IMPLEMENT HYDRAULIC SYSTEM STANDARD CHARGING RELIEF VALVE VALVE

QUICKDROP VALVE

INLET MANIFOLD DOZER LIFT

PUMP

DOZER TILT RIPPER END COVER

43 STANDARD D6R IMPLEMENT HYDRAULIC SYSTEM • Variable displacement pump • Signal line originates in control valve • Signal network sends highest work port pressure to pump

This diagram shows the implement hydraulic system on the D6R machines equipped with steering clutches and brakes. A variable displacement piston pump draws oil from the tank. Supply oil from the pump flows into the control valves. When the implement control valves direct the pump supply oil to the implement cylinders, the return oil from the control valves flows through a filter before entering the tank. The pump case drain oil flows through the case drain filter as it returns to the tank. A signal line originates in the control valves. The signal line passes through each valve body before reaching the pump control valve. When the operator activates one or more implements, the resulting loads generate work port pressure signals. A signal network (a series of double check valves) inside the control valves compares the work port pressures and sends the highest pressure to the pump control valve.

➥

STMG 687 3/98

- 58 -

NOTE: The colors in the valve sections and hydraulic schematics throughout the implement hydraulic system presentation denote various pressures within the system. The legend of color codes is as follows: Red

- Pump supply

Red and White Stripes

- First reduction of supply pressure

Red Dots

- Second reduction of supply pressure

Orange

- Signal pressure

Orange and White Stripes

- Reduced signal pressure

Green

- Open to tank

Blue

- Blocked oil

Yellow

- Activated valve envelopes or moving parts

STMG 687 3/98

- 59 -

SIGNAL NETWORK TO PUMP CONTROL VALVE INLET MANIFOLD RESOLVERS TO ROD END TO HEAD END TO ROD END TO HEAD END TO ROD END TO HEAD END

DOZER LIFT DOZER TILT RIPPER

44 • Lift and tilt operating

• Tilt pressure is higher than ripper • Lift pressure is lower than tilt

• Signal network sends tilt pressure to pump

This slide illustrates the signal network operation when the operator manipulates the tilt and lift circuits simultaneously. The resolvers are sometimes called "double check valves." In this example, the work port pressure in the lift circuit is 8280 kPa (1200 psi), while the work port pressure in the tilt circuit is 10350 kPa (1500 psi). The resolver in the tilt valve compares the work port pressure from the ripper valve to the work port pressure from the tilt valve. Since the ripper valve is not active, the pressure from the tilt valve seats the ball to the right allowing the 10350 kPa (1500 psi) tilt pressure to reach the resolver in the lift control valve. The resolver in the lift control valve compares pressures from the tilt and lift circuits. Since the pressure from the tilt valve is higher than the pressure from the lift valve, the ball seats to the left and the signal pressure from the tilt valve is sent to the pump control valve.

STMG 687 3/98

- 60 -

2

1

3

45

• Identify components: 1. Pump 2. Compensator valve

A variable displacement, piston-type hydraulic pump (1) provides oil flow to the tilt, lift, and ripper valves. The engine flywheel drives the pump. The compensator valve (2) controls the swashplate angle in the pump. Signal pressure can be checked at the pressure tap (3) on the compensator valve.

3. Pressure tap

A second pressure tap (not shown) near the pump outlet port is used to check pump supply pressure.

STMG 687 3/98

- 61 -

46

• Case drain filter (arrow)

The case drain filter (arrow) is located in front of the transmission filter in the compartment to the right of the operator.

STMG 687 3/98

- 62 -

1 8 2 3 4 5 6 7 47

• Identify components: 1. End cover 2. Ripper control valve 3. Tilt control valve 4. LIft control valve 5. Inlet manifold 6. Check valve 7. Charging valve 8. Main relief valve

The implement control valve group is mounted below the implement control lever near the right fender. The machine configuration determines the valve group configuration. The implement control valve group consists of the end cover (1), ripper control valve (2), tilt control valve (3), lift control valve (4), and the inlet manifold (5). The inlet manifold contains the main relief valve (8), the charging valve (7), and a check valve (6). The main relief valve is set higher than the pressure compensator setting. The main relief valve is used only to limit any sudden pressure increases (spikes). The charging valve prevents cylinder cavitation by restricting the return oil flow from the cylinders. The restriction creates pressure in the cylinder return oil passage which opens the makeup valve. The charging valve also sends some of the return oil to the pump to upstroke the pump when the cylinders begin to void.

STMG 687 3/98

- 63 -

48

• Quick-drop valve (arrow)

The D6R and D7R tractors are equipped with a single quick-drop valve (arrow) for both lift cylinders. The quick-drop valve provides makeup oil to the head end of the lift cylinders to help limit voiding of the cylinders during the quick drop function of the dozer. NOTE: The single quick-drop valves on all of the machines in this presentation are mounted on the hood above the radiator.

STMG 687 3/98

- 64 -

PRESSURE AND FLOW COMPENSATOR VALVE ADJUSTMENT SCREWS

PRESSURE COMPENSATOR (CUTOFF) SPRING

FLOW COMPENSATOR (MARGIN) SPRING

TO TANK

TO ACTUATOR PISTON FLOW COMPENSATOR (MARGIN) SPOOL

FROM OUTPUT PORT PRESSURE COMPENSATOR (CUTOFF) SPOOL

49 Pump Operation • Signal pressure controls pump output • Two spools: - Flow compensator - Pressure compensator

This slide shows the pump control valve on the standard D6R tractors. The pump control valve uses signal pressure to control pump output. The pump control valve contains two spools. The first spool is the flow compensator (or margin) spool. The flow compensator and its control spring maintain a supply pressure of 2100 kPa (305 psi) above the signal pressure. The pressure difference between pump supply pressure and signal pressure is called "margin pressure." The second spool in the control valve is the pressure compensator (or cutoff) spool. The pressure compensator and its control spring serve as the relief valve for the system. NOTE: The pressure settings of both spools can be adjusted.

STMG 687 3/98

- 65 -

PUMP AND COMPENSATOR OPERATION ENGINE OFF NO SIGNAL

PUMP OUTPUT LARGE ACTUATOR

YOKE PAD SWASHPLATE

FLOW COMPENSATOR (MARGIN) SPOOL

DRIVE SHAFT

PRESSURE COMPENSATOR (CUTOFF) SPOOL

SMALL ACTUATOR AND BIAS SPRING PISTON AND BARREL ASSEMBLY

50 • Identify components

When the engine is OFF, the bias spring holds the swashplate at maximum angle. When the operator starts the engine, the drive shaft starts to rotate causing the pump to draw oil into the suction side and force oil out of the discharge side.

STMG 687 3/98

- 66 -

PUMP AND COMPENSATOR OPERATION LOW PRESSURE STANDBY NO SIGNAL

PUMP OUTPUT

51 • LOW PRESSURE STANDBY - As pump produces flow, system pressure increases - Margin spool moves up - Oil fills large actuator - Swashplate moves to reduced angle - At minimum angle, passage in large actuator stem is open to tank

When the implements do not demand flow, the pump is at LOW PRESSURE STANDBY. At LOW PRESSURE STANDBY, the pump produces enough flow to compensate for system leakage at a pressure to ensure instantaneous response when an implement is actuated. At machine start-up, the bias spring holds the swashplate at maximum angle. As the pump produces flow, system pressure begins to increase and work against the margin spool spring force and the pressure compensator spool spring force. When the system pressure increases to the margin spool spring force, the margin spool moves up and permits system oil to flow to the large actuator piston in the pump. As pressure in the large actuator piston increases to overcome the combined force of the bias spring and the pressure in the small actuator piston, the large actuator piston moves the swashplate to a reduced angle. The large actuator piston can move to the right until the piston uncovers the cross-drilled passage in the stem (swashplate is at minimum angle). The cross-drilled passage allows oil to return to the pump case.

➥

STMG 687 3/98

- 67 -

NOTE: LOW PRESSURE STANDBY is higher than margin pressure because of the higher back pressure the blocked oil at the closed-center valves creates when all the valves are in HOLD. During LOW PRESSURE STANDBY, the pump supply oil pushes the margin spool up and further compresses the margin spring. More supply oil now goes to the large actuator piston and flows through the cross-drilled hole in the stem to the pump case. Depending on adjustments made to the margin spool and the amount of pump leakage, LOW PRESSURE STANDBY and margin pressure can be equal. However, margin pressure can never be higher than LOW PRESSURE STANDBY.

STMG 687 3/98

- 68 -

PUMP AND COMPENSATOR OPERATION SIGNAL

PUMP OUTPUT

UPSTROKING REDUCED PRESSURE

52 • UPSTROKE pump - Signal oil moves margin spool down - Large actuator pressure is reduced - Swashplate moves to increased angle

When an implement requires flow, the resolver network signals the pump control valve. This signal causes the force (margin spring plus signal pressure) at the top of the margin spool to become greater than the pump supply pressure at the bottom of the spool. The increased pressure on top of the margin spool causes the spool to move down. The spool reduces or blocks oil flow to the large actuator and opens a passage to drain. Reducing or blocking oil flow to the large actuator reduces or eliminates the pressure acting against the large actuator piston. When the pressure in the large actuator piston decreases, the bias spring and small piston move the swashplate to an increased angle causing the pump to UPSTROKE (produce more flow).

➥

STMG 687 3/98

• Conditions required to upstroke pump

- 69 -

The following conditions can result in UPSTROKING the pump: 1. Operating an implement control when the system is at LOW PRESSURE STANDBY. 2. Moving a control valve spool for additional flow. 3. Activating an additional circuit. 4. Decreasing engine rpm. (In this case, pump speed decreases causing the flow and pump supply pressure to decrease. The pump must UPSTROKE to maintain the system flow requirements.)

STMG 687 3/98

- 70 -

PUMP AND COMPENSATOR OPERATION CONSTANT FLOW SIGNAL

PUMP OUTPUT REDUCED PRESSURE

53 • CONSTANT FLOW - Margin spool moves to metering position

As pump flow increases, pump supply pressure also increases. When the pump supply pressure increases to equal the sum of the signal pressure plus the pressure from the margin spring force, the margin spool moves to a metering position and the system becomes stabilized. The margin spring force determines the difference between the signal pressure and the pump supply pressure. The margin spring force is approximately 2100 kPa (305 psi).

STMG 687 3/98

- 71 -

PUMP AND COMPENSATOR OPERATION DESTROKING SIGNAL

PUMP OUTPUT INCREASED PRESSURE

54 • DESTROKE pump - Margin spool moves up - Pressure in large actuator increases - Swashplate moves to reduced angle

The pump DESTROKES when the system requires less flow. As the force at the bottom of the margin spool becomes greater than the force at the top, the margin spool moves up and allows more flow to the actuator piston causing the pressure in the large actuator piston to increase. The increased pressure in the large actuator piston overcomes the combined force of the small actuator and bias spring and moves the swashplate to a reduced angle.

➥

STMG 687 3/98

• Conditions to destroke the pump

- 72 -

The following conditions can cause the pump to DESTROKE: 1. Moving all valves to the HOLD position. (The pump returns to LOW PRESSURE STANDBY.) 2. Moving the control valve to reduce the flow to the implement. 3. Deactivating a circuit. 4. Increasing engine rpm. (In this case, the pump speed increases causing the flow to increase. The pump destrokes to maintain system flow requirements.)

• Margin spool moves to stabilize system

As pump flow decreases, supply pressure also decreases. When the supply pressure decreases and becomes the sum of signal pressure plus margin pressure, the margin spool moves to a metering position and the system stabilizes.

STMG 687 3/98

- 73 -

PUMP AND COMPENSATOR OPERATION HIGH PRESSURE STALL SIGNAL AT MAX. PRESSURE

PUMP OUTPUT AT MAX. PRESSURE

55 • HIGH PRESSURE STALL - Cutoff and margin spools are in parallel - Signal pressure equals supply pressure - Margin spool moves down - Cutoff spool moves up - Swashplate moves to reduced angle • Pump supplies minimum flow at maximum pressure

The pressure compensator (or cutoff) spool is in parallel with the margin spool. The pressure compensator limits the maximum system pressure for any given pump displacement. During normal operation, the pressure compensator spring forces the compensator spool closed. During a HIGH PRESSURE STALL, signal pressure equals supply pressure. Combining the signal pressure with the margin spring forces the margin spool to move down. Moving the margin spool down normally drains the oil out of the large actuator piston and causes the pump to upstroke. However, during HIGH PRESSURE STALL, the pressure below the cutoff spool overcomes the pressure compensator spring force and moves the cutoff spool up. Moving the cutoff spool up blocks the oil in the large actuator piston from going into the drain passage and allows supply oil to flow to the large actuator. The increased pressure in the large actuator allows the large actuator to overcome the combined force of the small actuator and bias spring and DESTROKE the pump. The pump is now at minimum flow and supply pressure is at maximum. This condition is maintained for a single implement in a stall condition.

➥

STMG 687 3/98

• Pump will produce flow to meet needs of other implements

• Main relief valve limits pressure spikes

- 74 -

When operating two or more implements with one in stall, the pump will UPSTROKE to produce flow to meet the needs of the other implements operating at the lower work port pressure. In this case, the pump could be producing up to maximum flow while the supply pressure is at the maximum of 39600 kPa (2900 psi). The main relief valve is in the inlet manifold of the implement control valve group. It is a simple relief valve with a pressure setting of 22000 kPa (3200 psi). The relief valve is set above the pressure compensator setting. The main relief valve is used only to limit any sudden pressure increases (spikes).

STMG 687 3/98

- 75 -

D6R INLET MANIFOLD HOLD CHARGING VALVE TO PUMP RELIEF VALVE

RETURN FROM IMPLEMENTS CHECK VALVE

TO TANK SIGNAL FROM VALVES

56 Inlet Manifold Operation • Inlet manifold during LOW PRESSURE STANDBY • Charging valve - Back pressure forces return oil through makeup valves - Can send return oil to pump

The inlet manifold contains the charging valve and the main relief valve. This slide shows the charging valve and the main relief valve with no valves operating and the pump at LOW PRESSURE STANDBY. The charging valve spring keeps the charging valve closed. The charging valve is used to help prevent cylinder voiding. A 1050 kPa (150 psi) back pressure caused by the charging valve spring forces return oil through the makeup valves in the implement control valves and also sends a signal to the pump control valve to UPSTROKE the pump when the work port does not generate a signal.

STMG 687 3/98

- 76 -

D6R INLET MANIFOLD IMPLEMENT VALVE OPERATING CHARGING VALVE

SIGNAL TO PUMP

RELIEF VALVE

RETURN FROM IMPLEMENTS CHECK VALVE

TO TANK SIGNAL FROM VALVES

57 • Operating an implement - Check valve seats - Charging valve opens - Return oil flows to tank

When the operator moves an implement, the implement work port signal oil flows through the orifice, seats the check valve (provided that the signal pressure is higher than return cylinder pressure), and acts on the charging valve. When the pressure in the signal line reaches 1050 kPa (150 psi), the charging valve opens and the return oil from the cylinders has unrestricted flow to the tank.

STMG 687 3/98

- 77 -

D6R INLET MANIFOLD CYLINDER VOIDING CHARGING VALVE

SIGNAL TO PUMP

RELIEF VALVE

RETURN FROM IMPLEMENTS CHECK VALVE

TO TANK SIGNAL FROM VALVES

58 • Implement is lowered - No signal pressure - Check valve opens and sends signal to pump - Charging valve opens • Relief valve limits pressure spikes

When an implement is lowered, signal pressure can be lost due to the cylinder voiding. When the signal pressure is lost, the charging valve closes to restrict the return oil and create a back pressure. When the pressure in the return line is higher than the pressure in the signal line, pressure in the return line opens the check valve and sends a signal to the pump control valve to UPSTROKE the pump. The return oil is also forced through the makeup valves in the implement control valves. The charging valve will open when pressure in the signal network reaches 1050 kPa (150 psi) and allow oil to return to the tank. The relief valve limits pressure spikes in the system.

STMG 687 3/98

- 78 -

D6R TILT CONTROL VALVE HOLD FROM LIFT CONTROL VALVE

TO RIPPER CONTROL VALVE PRIORITY FLOW CONTROL VALVE

LOAD CHECK VALVE

ORIFICE

MAIN CONTROL SPOOL

TO LIFT CONTROL VALVE

RESOLVER

HEAD END

ROD END

PLUG

FROM RIPPER VALVE

59 Implement Control Valve Operation • Control valve operation

- Priority flow control valve

The tilt control valve is a closed-center, manually operated valve with three positions: TILT LEFT, HOLD, and TILT RIGHT. The centering spring returns the spool to the HOLD position when the operator releases the tilt lever and keeps the spool in HOLD when the tilt circuit is not in operation. The operator manually controls spool movement through a mechanical linkage that connects to the control spool. The components of the dozer tilt valve are: Priority flow control valve: Receives oil flow from the lift valve group. The priority flow control valve provides the "pressure compensating" feature of the tilt circuit by controlling the maximum pressure drop across the tilt control spool. This operation results in constant implement speed for a given lever displacement. The flow control valve limits the maximum oil flow allowed to the tilt cylinder to control the tilt speed of the blade.

➥

STMG 687 3/98

- 79 -

- Load check valve

Load check valve: Prevents reverse implement flow when the operator moves a valve from HOLD, but the system pressure is lower than cylinder or work port pressure. Without the load check valve, the implement would drift down. The load check valve will open to allow supply oil to flow to the tilt cylinder when the system pressure is higher than the work port pressure.

- Resolver

Resolver: Also called a "shuttle valve" or "double check valve." Compares the signal between the valve sections in the stack. Although this slide shows the shuttle valve and signal lines as external components, the shuttle valve is actually inside the control valve, and the signal lines are internally drilled passages.

- Main control spool

Main control spool: Controls oil flow to the implements and contains three cross-drilled holes that connect to an axial drilled passage in the center of the control spool. The cross-drilled holes sense work port pressure in the head and rod ends of the cylinders depending on the direction the spool shifts and communicates work port pressure into the signal system.

-`Orifice

Orifice: Provides smoother implement operation by delaying the rate that the signal pressure in the flow control spring cavity decreases when the operator changes implement direction.

• Valve in HOLD - Axial passage open to tank - Priority flow control valve is initially to the left - Priority flow control valve moves to the right - Throttling slot on left closes - Throttling slot on right opens - Priority flow control valve maintains maximum pressure differential

This slide shows the valve in HOLD. In HOLD, the center axial passage is open to the tank through a machined land on the spool to the drain passage in the valve body. With the engine not running, the spring behind the priority flow control valve holds the flow control valve to the left. When the operator starts the machine, the pump sends oil through the inlet manifold and down through the valve stack to the flow control valve. Oil flows to the center of the priority flow control valve and out the throttling slot on the left side of the valve to the load check valve. The increasing pressure in the chamber at the left of the load check valve pushes the priority flow control valve to the right against the force of the flow control valve spring. Moving the priority flow control valve to the right closes the throttling slot on the left side of the valve spool and allows oil to flow to the remaining components in the system through the throttling slots on the right side of the valve spool. In HOLD, pressure at the main control spool is equal to the priority flow control valve spring.

➥

STMG 687 3/98

- 80 -

NOTE: The throttling slot on the left end of the flow control valve spool is never completely closed, and the check valve does not completely block oil from reaching the control spool. A small amount of oil meters through the flow control valve and past the load check valve to maintain a pressure at the main control spool that is equal to the priority flow control valve spring force. Maintaining the pressure at the main control spool improves implement response. If the priority flow control spool is explained as a pressure reducing valve with a variable spring rate due to changes in signal pressure, the operation of the spool is easier to understand. The spool will limit the maximum pressure difference across the control spool to the value of the priority valve spring and cylinder pressure to provide constant flow for a given lever displacement.

STMG 687 3/98

- 81 -

D6R TILT CONTROL VALVE TILT LEFT FROM LIFT CONTROL VALVE

TO RIPPER CONTROL VALVE PRIORITY FLOW CONTROL VALVE

LOAD CHECK VALVE

ORIFICE MAIN CONTROL SPOOL TO LIFT CONTROL VALVE

RESOLVER

ROD END

HEAD END

PLUG

FROM RIPPER VALVE

60 • TILT LEFT condition - Signal oil fills priority flow control valve spring chamber - Work port oil becomes signal oil through center axial passage

As the operator moves the tilt control lever to the TILT LEFT position, the supply passage is connected to the head end of the cylinder. Either oil at the work port pressure or oil at 345 kPa (50 psi) in the supply passage enters the cross-drilled hole to the center axial passage and becomes signal oil. The signal is then sent through the resolver network to the pump. The pump increases flow to meet the flow needs of the tilt circuit. The check valve remains seated until supply pressure exceeds the work port pressure.

➥

STMG 687 3/98

- Priority control valve spool moves left - Flow rate maintained to tilt circuit - Excess flow available to other valves

- 82 -

The signal is sent simultaneously to the pump and the priority flow control valve spring chamber. The oil in the center passage in the main control spool flows through an orifice before reaching the spring chamber. The signal pressure in the priority control valve spring chamber works with the spring force to move the priority control valve spool to the left, allowing the required flow to reach the tilt cylinder while limiting the amount of flow to the downstream control valve functions. When the signal pressure plus the spring force moves the priority flow control valve to the left, the opening at the throttling slot on the left land of the spool increases so more oil can flow to the work port while the throttling slot on the right land of the priority flow control spool closes more. The amount of flow from the pump combined with the amount of flow the tilt work port needs determine the distance that the priority flow control valve shifts. As the tilt circuit flow requirements are met, pressure increases on the left end of the priority valve spool and the valve moves back to the right. The priority valve maintains a maximum pressure differential across the tilt control spool equal to the priority valve spring. Excess flow from the pump is now available for the ripper valve. When the tilt control spool is fully shifted, step diameters on the spool maintain a constant area, and the priority flow control valve limits the maximum flow to the tilt cylinder to 80 Lpm (21 gpm). NOTE: If the implement is resting on the ground, the work port does not generate a cylinder pressure when the operator shifts the main control spool. Instead, the pump standby pressure felt at the main control spool generates the signal pressure when the operator shifts a valve. After the implement is off the ground, cylinder pressure creates a work port signal and the system will respond to the cylinder or the load requirements.

STMG 687 3/98

- 83 -

D6R DOZER CONTROL VALVE HOLD FROM INLET MANIFOLD

TO TILT VALVE

LOAD CHECK VALVE

MAIN CONTROL SPOOL TO INLET MANIFOLD

RESOLVER

ROD END

HEAD END

MAKEUP VALVE

FROM TILT VALVE

61 • Lift valve in HOLD • Lift valve has FLOAT position • Load check and shuttle valves operate same as tilt valve • Not pressure compensated

The components of the lift control valve are similar to those of the tilt valve. The lift control valve is a closed-center, manually operated valve controlled through a mechanical linkage. The centering spring returns the spool to the HOLD position when the operator releases the lift lever and keeps the spool in HOLD when the lift circuit is not in operation. The lift spool has four positions: RAISE, HOLD, LOWER and FLOAT. To operate in the FLOAT condition, the operator must move the control lever forward until the detent balls hold the valve spool. The operator must manually release the lift control lever from the FLOAT position. The load check valve and the shuttle valve operate the same as in the tilt valve. The load check valve prevents excessive blade drift when the operator shifts the lift control spool (until system pressure exceeds work port pressure). The lift control valve does not contain a flow control spool, so the valve is not pressure compensated.

➥

STMG 687 3/98

- 84 -

• Resolver compares ripper and lift pressures

When the lift control valve is shifted, the resolver compares the tilt circuit signal pressure to the lift circuit signal pressure and directs the higher pressure through the inlet valve to the pump control valve.

• Head end passage contains makeup valve

The passage to the head end of the lift cylinder contains a makeup valve for the lift circuit. When the pressure in the cylinder supply passage decreases below the pressure in the tank, the makeup valve opens and allows return oil from the tank to fill voids in the head end of the cylinders.

STMG 687 3/98

- 85 -

D6R DOZER CONTROL VALVE FLOAT TO TILT VALVE

FROM INLET MANIFOLD LOAD CHECK VALVE

MAIN CONTROL SPOOL TO INLET MANIFOLD

RESOLVER

ROD END

HEAD END

MAKEUP VALVE

FROM TILT VALVE

62 • FLOAT condition - No signal from lift - Head and rod end work ports open to tank

This slide shows the positions of the lift control valve components during operation in FLOAT. When the lift circuit is in FLOAT, the lift signal passages and work ports are open to the tank and no signal pressure is generated. The lift control spool is completely to the right, and the balls and detent assembly in the valve body hold the control lever in the FLOAT position. In FLOAT, with the head and the rod ends of the lift cylinders open directly to the tank, the blade and lift arms are free to move up and down with the contour of the ground. The FLOAT position is normally used for back filling material. The system will remain in the FLOAT condition until the operator manually moves the control lever from the detent position.

STMG 687 3/98

- 86 -

D6R RIPPER LIFT CONTROL VALVE HOLD FROM TILT CONTROL VALVE LOAD CHECK VALVE

MAIN CONTROL SPOOL TO TILT VALVE

RESOLVER MAKEUP VALVE

HEAD END

ROD END

63 • Ripper control is last valve in group • Ripper valve same as lift valve except for FLOAT

• Not pressure compensated

The ripper control valve is the last control valve in the implement hydraulic system. The ripper control valve is similar to the lift control valve except the ripper valve does not have a FLOAT position. Since the ripper valve does not have a FLOAT position, the control spool does not have a detent mechanism, and the lands on the spool are different from the lift valve. All other components in the ripper valve and oil flow through the valve are the same as the lift control valve. The ripper control valve does not contain a flow control spool, so the valve is not pressure compensated.

STMG 687 3/98

- 87 -

QUICK-DROP VALVE

QUICK-DROP VALVE TO IMPLEMENT VALVE

TO ROD END

DOZER LIFT TO IMPLEMENT VALVE

TO HEAD END

64 Quick-Drop Valve Operation • Single quick-drop valve • HOLD condition

The D6R steering clutch and brake machines are equipped with a single quick-drop valve for both lift cylinders. This slide shows a schematic of the quick-drop valve with the lift control valve in HOLD. When in HOLD, the lift control valve spool prevents oil from flowing from the pump, through the quick-drop valve, and to the lift cylinders. The lift control valve spool also prevents oil from the cylinders from returning to the tank.

STMG 687 3/98

- 88 -

FROM CYLINDERS (HEAD END)

TO CYLINDERS (ROD END)

QUICK-DROP VALVE RAISE

65 • In HOLD, spool blocks work ports

This slide shows an example of a quick-drop valve with the lift control valve in HOLD. When in HOLD, the lift control valve spool blocks all oil from entering or leaving the lift circuit.

STMG 687 3/98

- 89 -

FROM CYLINDERS (HEAD END)

TO CYLINDERS (ROD END)

QUICK-DROP VALVE RAISE

66 • RAISE condition - Orifice sleeve shifts right - Oil flows to rod end of cylinders - Return oil acts on right end of plunger - Blade RAISE pressure acts on right end of spool - Spool remains shifted to right

When the operator moves the dozer control valve to the RAISE position, pump oil entering the quick-drop valve at the passage on the left moves the orifice sleeve to the right and then flows to the rod end of the cylinders. Return oil from the head end of the cylinders enters the quickdrop valve and flows past the valve spool before flowing to the lift control valve. Return oil also fills the chamber at the right end of the plunger. However, since the blade RAISE pressure on the left end of the plunger is higher than the return oil pressure, the plunger remains shifted to the right. Blade RAISE pressure also enters the passage to the right end of the spool, but since the pressure on the right end of the spool equals the pressure on the left end, the spring keeps the spool shifted to the right. NOTE: The arrows show the direction of oil flow through the quickdrop valve in Slides No. 67 through 70. The orifice sleeve slides on the valve spool. A retaining ring keeps the orifice sleeve on the valve spool.

STMG 687 3/98

- 90 -

TO CYLINDERS (HEAD END)

FROM CYLINDERS (ROD END)

QUICK-DROP VALVE LOWER

67 • LOWER condition - Orifice sleeve moves left - Supply oil acts on right end of plunger

- Return oil acts on left end of plunger

As the operator moves the lever to lower the blade (less than 75 percent of maximum travel), return oil from the rod end of the cylinders enters the quick-drop valve. The return oil flows past the orifice sleeve, out to the control valve, and moves the orifice sleeve to the left against the retaining ring. This oil flow creates a pressure differential across the orifice sleeve. Supply oil entering the quick-drop valve flows past the valve spool before flowing out to the head end of the cylinders. Supply oil enters the passage to the plunger end and acts on the right end of the plunger. However, the return oil pressure on the left end of the plunger is higher than the supply pressure on the right end, and the plunger remains shifted to the right. Rod end return oil pressure enters the passage to the spool end and acts on the right end of the spool. This pressure also acts on the major diameter (the effective area on the left end of the spool, just to the right of the orifice sleeve) of the left end of the spool.

➥

STMG 687 3/98

- Plunger remains shifted to the right

- 91 -

In addition, return oil pressure after the pressure drop across the orifice sleeve acts on the minor diameter of the left end of the spool. The net result is that the spool and plunger are kept to the right because of the spring and the return pressure (red dots). The major diameters of the spool cancel each other. The minor diameter of the right end of the spool does not have enough force to overcome the spring and the return oil pressure on the minor diameter on the left end on the spool.

STMG 687 3/98

- 92 -

TO CYLINDERS (HEAD END)

FROM CYLINDERS (ROD END)

QUICK-DROP VALVE LOWER - QUICK-DROP

68 • LOWER in QUICKDROP mode - Pressure drop across orifice sleeve increases - Spool moves left

When the operator moves the dozer control valve lever more than 75 percent of the maximum travel, the quick-drop valve operates in the quick-drop mode. The increased lever travel results in higher cylinder rod end flow and a higher pressure drop across the orifice sleeve. The only difference from the dozer LOWER position is that the spool starts to move because the pressure drop across the orifice sleeve that acts on the minor diameter at the right end of the spool overcomes the resistance of the spring. The minimum flow required to cause the pressure drop across the orifice sleeve that begins spool movement is called the "trigger point."

➥

STMG 687 3/98

- Trigger point occurs at 75% of maximum lever movement - Spool shifts left to connect rod and head end of cylinders

- 93 -

The trigger point occurs at 75 percent of maximum lever travel. As the spool starts to move, the area of the orifice sleeve decreases and the pressure drop increases, thereby shifting the spool farther. The net result is that after the spool starts to move, it shifts completely to the left and connects the rod end of the cylinders to the head end of the cylinders across the slots in the spool. Downward blade velocity increases due to the rod end oil flowing freely to the head end of each cylinder. The valve also provides a makeup function that minimizes the pause time when the blade contacts the ground before powering down. Some of the rod end oil still flows across the orifice sleeve causing a pressure drop to keep the spool shifted.

STMG 687 3/98

- 94 -

TO CYLINDERS (HEAD END)

QUICK-DROP VALVE

FROM CYLINDERS (ROD END)

LOWER - DOWN PRESSURE

69 • Blade contacts ground - Rod end flow stops - Spring shifts spool right - Head end pressure increases - Pump oil acts on right end of plunger - Reduced rod end pressure acts on left end of plunger - Plunger moves left - Spool remains to right

When the blade contacts the ground and stops, flow from the rod end of the cylinders stops. With no pressure drop across the orifice, the spring shifts the spool to the right. After the pump fills the head end of the cylinders (pause time) and the head end cylinder pressure starts to increase, the blade begins to move down. Supply oil pressure enters the passage to the end of the plunger and is felt on the right end of the plunger. Return oil pressure from the rod end of the cylinders is felt on the left end of the plunger. Since this pressure is lower than the pressure on the right end of the plunger, the plunger moves to the left. The pressure drop across the orifice sleeve that is felt on the minor diameter at the right end of the spool works to move the spool to the left. However, this movement is resisted by the spring and the supply oil pressure acting on the plunger, so the spool stays shifted to the right.

STMG 687 3/98

- 95 -

D7R IMPLEMENT HYDRAULIC SYSTEM CHARGING VALVE

RELIEF VALVE PUMP

INLET VALVE QUICKDROP VALVE

DOZER LIFT DOZER TILT RIPPER END COVER

RESOLVERS

70 • D7R hydraulic system - Fixed displacement pump - Unloading valve - Charging valve - Main relief valve - Closed-center valves - Single quick-drop valve

STANDARD D7R IMPLEMENT HYDRAULIC SYSTEM This diagram shows the hydraulic system on the standard D7R tractors. A fixed displacement pump draws oil from the tank. The inlet manifold contains an unloading valve, a charging valve, and the main relief valve. The unloading valve directs the pump supply oil to the tank when the implements do not require flow. The implement control valves are all closed-center. The tilt control valve has a priority flow control valve which acts as a pressure reducing valve to control the maximum pressure drop across the tilt control spool. The D7R tractors contain a single quick-drop valve for both lift cylinders. The quick-drop valve provides makeup oil to the head end of the lift cylinders. The quick-drop valve helps to control the raise, lower at slow speeds, quick-drop, and lower with down pressure functions of the dozer. This quick-drop valve operates identically to the valve on the D6R tractors.

➥

STMG 687 3/98

• Signal network controls pump output

- 96 -

The signal network sends the highest resolved signal from the implements back to the unloading valve in the inlet manifold. When a work port signal reaches the inlet manifold, the unloading valve directs the required flow to the implements and returns the excess flow to the tank. When the system does not need full pump flow, the system pressure will be approximately 1310 kPa (190 psi) above the resolved signal. NOTE: Previous publications identified the hydraulic system as "pressure compensated" only; however, the system should be considered a "load sensing" hydraulic system. The tilt control valve in this system is "pressure compensated."

STMG 687 3/98

- 97 -

71

• Fixed displacement pump (arrow)

A fixed displacement, gear-type hydraulic pump (arrow) provides oil flow to the lift, tilt, and ripper valves. The engine flywheel drives the pump.

STMG 687 3/98

- 98 -

6 5 4 3 2

1

72

• Identify components: 1. Charging valve 2. Inlet manifold 3. Lift control valve 4. Tilt control valve 5. Ripper control valve 6. End cover

The implement control valve group is mounted below the implement control lever above the right fender in the same general location as the D6R valve group. The machine configuration determines the valve group configuration. The implement control valve group consists of the inlet manifold (2), the lift control valve (3), the tilt control valve (4), the ripper control valve (5, if equipped), and the end cover (6). The inlet manifold (2) contains the main relief valve (not visible), the charging valve (1), and the unloading valve (not visible). The main relief valve limits pressure spikes. The charging valve prevents cylinder cavitation during overrunning load conditions by restricting the return oil flow from the cylinders, thereby creating oil pressure in the cylinder return oil passage that opens the makeup valve. The unloading valve directs pump flow back to the tank when all controls are in HOLD.

STMG 687 3/98

- 99 -

D7R INLET MANIFOLD IMPLEMENTS IN HOLD SIGNAL OIL TO TANK

TO CONTROL VALVES

SLUG UNLOADING VALVE CHECK VALVE

MARGIN STEM

ORIFICE

PUMP SUPPLY

MAIN RELIEF VALVE

CHARGING VALVE

73 • Inlet valve components: - Main relief valve - Unloading valve - Margin stem - Charging valve - Slug - Ball check valve

Inlet Manifold Operation This sectional view of the inlet manifold shows all the internal components and identifies the passages with all implements in HOLD. The inlet valve houses the pilot operated main relief valve, the unloading valve, the margin stem, the charging valve, a slug, and a ball check valve. The adjustable pilot operated main relief valve limits the maximum pressure in the system to approximately 22800 kPa (3306 psi). The orifice serves two main functions: First, it isolates the unloading valve and margin stem from pressure spikes which can occur in the return oil passages; and second, it controls the rate that the charging valve opens fully.

• Orifice functions: - Isolates pressure spikes - Controls charging valve

➥

STMG 687 3/98

• Charging valve functions: - Provides better operator control - Blocks return oil to charge signal network

• Unloading valve: - Spring keeps unloading valve to right with engine off - Oil is blocked by implement valves - System pressure builds and unloading valve moves left

• Margin stem does not shift because system pressure is low

- 100 -

The charging valve provides better operator control when lowering the implements. The charging valve provides a restriction between the implement return oil passage and the outlet passage to the tank when the signal pressure is low. The restriction created by the charging valve forces the return oil back through the makeup valves to limit cylinder voiding. The return oil also enters the signal network to move the unloading valve in the inlet manifold to the right. Restricting the return oil lowers the implements under power rather than by the force of gravity. When the oil pressure reaches approximately 1060 kPa (154 psi), the charging valve opens, eliminating the restriction in return oil flow. The spring at the left end of the unloading valve keeps the valve spool to the right (slug end) when the engine is OFF. When the operator starts the engine, supply oil flows around the unloading valve, to the implement valves, and through an internal passage to the chamber at the right end of the slug. With all the control valves in HOLD, the implement valve spools block flow to the cylinders. With a fixed displacement hydraulic pump, blocking the flow to the cylinders causes the load on the pump to increase and system pressure increases. The system pressure on the right end of the slug moves the slug and the unloading valve to the left, compressing the spring. The unloading valve shifts to the left to reduce the load on the pump and directs the pump flow to the tank. The pressure in the system with the control valves in HOLD is approximately 360 kPa (52 psi). The unloading valve has several holes around the outside diameter that connect with the supply passage. These holes also connect with a passage in the center of the margin stem. Supply oil flows through the passage in the center of the margin stem and fills a chamber at the right end. Even though the margin stem feels the pressure at the right end, the resulting force is not high enough to cause the stem to move to the left against the force of the margin spring. With the system in HOLD, the margin stem spring chamber and the unloading valve spring chamber are open to the tank. NOTE: When the implement system is in HOLD, the unloading valve directs most of the supply oil back to the tank. This condition results in a standby pressure of approximately 360 kPa (52 psi) in the system. However, when the operator activates a control lever, the spring chambers for both the margin stem and the unloading valve fill with the highest resolved signal pressure. During system operation, the margin stem provides a difference or "margin" between the supply pressure and the highest signal pressure. The margin spring determines the pressure difference. The combined effect of the margin stem and the signal network provides the implement system with the "load sensing" feature.

STMG 687 3/98

- 101 -

D7R INLET MANIFOLD FULL FLOW REQUIRED SIGNAL OIL TO TANK

TO CONTROL VALVES

SLUG

UNLOADING VALVE MARGIN STEM PUMP SUPPLY

MAIN RELIEF VALVE CHARGING VALVE

74 • Full flow required: - Unloading valve moves to the right - Full pump flow to implements

This illustration shows the position of the inlet valve components when full pump flow is required. During this condition, the control spool(s) direct full pump flow to the cylinder(s). When full flow is required, the highest resolved signal oil from the implements enters the supply chamber around the outside of the unloading valve. The signal oil fills the margin stem spring chamber through the holes around the outside of the unloading valve. At the same time, signal oil flows along the outside diameter of the unloading valve and fills the spring chamber at the left end of the unloading valve spool. The signal oil pressure works in conjunction with the force of the springs to move the unloading valve completely to the right and keep the margin stem against the plug at the right end of the unloading valve. The position of the unloading valve and the margin stem prevents the supply oil from returning to the tank and directs full pump flow to the implements.

➥

STMG 687 3/98

- Margin stem does not shift

- 102 -

At this point, the pressure of the oil supplying the cylinders is slightly higher than the signal oil pressure, but not high enough to overcome the margin spring. The spring force keeps the margin stem moved completely to the right. The margin stem will be in this position any time that the implements require full pump flow. NOTE: A minimum signal pressure of approximately 240 kPa (35 psi) is required to move the unloading valve to the right. During normal system operation, the signal pressure will be higher than the required 240 kPa (35 psi) needed to keep the unloading valve shifted to the right. If the pressure of the signal oil at the left end of the unloading valve does not exceed 240 kPa (35 psi), the unloading valve will not move to the right and, therefore, will not block the flow of pump oil to the tank. This condition can occur when externally applied loads create voids in the cylinders or during rapid lowering of the blade. At this time, the charging valve blocks the return oil and provides the necessary pressure to move the unloading valve. During a HOLD condition, the work port does not send a signal to the spring chamber and the pressure at the right end of the slug moves the unloading valve to the left, allowing the pump oil to "unload" back to the tank.

STMG 687 3/98

- 103 -

D7R INLET MANIFOLD FULL FLOW NOT REQUIRED SIGNAL OIL TO TANK

TO CONTROL VALVES

UNLOADING VALVE MARGIN STEM

PUMP SUPPLY

MAIN RELIEF VALVE CHARGING VALVE

75 • Load sensing position • Full flow not required - Unloading valve moves to the right - Partial pump flow required by implements - Pressure builds on right end of margin stem

This illustration shows both the margin stem and the unloading valve in the "load sensing" position. The margin stem has moved a small distance to the left against the spring force and the signal oil pressure. This movement allows part of the oil in the supply passage to return to the tank through the small holes around the outside of the unloading valve. With a load sensing system, the load on the cylinders determines the amount of pressure the system requires to operate. An increase in the load will require an increase in system pressure. When the implements do not require full pump flow, the signal network sends the highest resolved signal from the cylinders to the inlet manifold and the unloading valve moves to the right, blocking supply oil from returning to the tank. Since the system does not require the full pump output, system pressure increases. The chambers at the right end of the slug and at the right end of the margin stem feel the increased pressure.

➥

STMG 687 3/98

- 104 -

The effective area of the left end of the unloading valve is approximately three times larger than the right end of the slug. During normal implement operation, the pressure in the slug chamber will not cause the slug to move the unloading valve to the left against the combined spring force and signal pressure in the spring chamber. - Margin stem moves to the left

The margin stem, however, reacts to the increased system pressure by moving to the left against the force of the spring and the pressure of the signal oil. The increase in system pressure is a direct result of the restriction at the implement control valve spool. When the operator moves a control valve spool a small distance, the size of the passage provided to fill the cylinders restricts the flow from the pump and causes the pressure at the inlet valve to increase.

- Margin stem moves to metering position

The supply oil pressure at the right end of the margin spool working against the pressure of the signal oil added to the force of the margin spring at the left end controls the movement of the margin stem inside the unloading valve. When the combined signal pressure and spring force equal the pressure of the supply oil, the margin stem will be in the metering position. In the metering position, the supply pressure is approximately 1310 kPa (190 psi) higher than the signal pressure. Any flow not needed by the implements returns to the tank through the inside of the unloading spool.

- Some supply oil sent to tank - Supply oil at fixed value above signal pressure • Margin spool reacts to changes in flow and pressure demands

In summary, if the system does not require full pump flow, the unloading valve moves to the right blocking pump flow to the tank. The margin stem moves to the left inside the unloading valve and meters some pump flow to the tank to maintain the system pressure at a fixed value above the cylinder or work port requirement. This value is equal to the margin spring. The margin spring force determines the pressure differential between the supply oil and signal oil. The margin stem will move or "modulate" inside the unloading valve to maintain the 1310 kPa (190 psi) pressure differential. If the flow requirements change, the margin spool will shift to match the new flow requirements. When the new flow requirements are met, the supply pressure will be 1310 kPa (190 psi) higher than the highest cylinder load. Changes in engine rpm will also cause the margin stem to move to maintain the desired flow rate. NOTE: The operation of the margin stem and the unloading valve provide "pressure compensation" for the operation of a single implement that does not require full flow. However, when multiple implements are operated simultaneously, the margin stem and the unloading valve will provide a supply pressure to the implements at a fixed value above the highest cylinder requirement, providing the "load sensing" feature.

STMG 687 3/98

- 105 -

D7R INLET MANIFOLD CHARGING VALVE OPERATION SIGNAL OIL TO TANK

TO CONTROL VALVES

UNLOADING VALVE MARGIN STEM PUMP SUPPLY

MAIN RELIEF VALVE CHARGING VALVE

76 • Charging valve is normally closed - Opens by signal pressure

A condition can occur when the cylinder pressure (signal pressure) is too low to move the unloading valve to the right to block the pump oil from going to the tank. This condition happens when externally applied loads create voids in the cylinders or when the blade is lowered rapidly. The charging valve helps to eliminate cylinder voiding by creating back pressure which acts as temporary signal pressure to keep the unloading valve shifted, and thus keeps pump flow directed to fill cylinder voids instead of returning to the tank. With the control valves in HOLD, the hydraulic system does not create a signal pressure. The charging valve is a "normally closed" valve. When closed, the charging valve blocks the implement return passage from the tank outlet.

➥

STMG 687 3/98

• Cylinder voids cause loss of signal pressure - Charging valve closes - Restricts return oil • Blocked return oil used to: - Charge signal network to move unloading valve - Open makeup valves

- 106 -

When the operator activates an implement control valve, signal pressure from the implement cylinder flows to the passage at the left end of the unloading valve, to the margin stem, and to the differential area of the charging valve. When the pressure at the differential area increases to approximately 1060 kPa (154 psi), the charging valve compresses the charging valve spring and opens the implement return passage to the tank outlet passage. The ball check valve prevents the signal oil from draining into the return passage. Lowering an implement may create a void in the cylinder. Creating a void in the cylinder causes a loss in signal pressure. Since the system is a load sensing system which reacts to signal pressure, the system will not have good response to the change in flow requirements. The low signal oil pressure from the cavitated cylinder will not move the unloading valve to the right to block the supply passage from draining. Therefore, pump flow cannot reach the control valve and cylinder. The implement will free fall due to the force of gravity. Implement hesitation will occur when the implement contacts the ground. The charging valve minimizes the implement hesitation by blocking the implement return oil from reaching the tank. The blocked implement return oil unseats the ball check valve and flows into the signal pressure circuit. When the pressure in the signal circuit reaches 240 kPa (35 psi), the unloading valve moves to the right and closes the passage between supply and drain. Supply oil is now directed to the implement control valve and cylinder rather than to the tank. By blocking the return oil, the charging valve also forces the makeup valves open to limit cylinder voiding. When the return oil and signal pressure increase to 1060 kPa (154 psi), the charging valve opens. The signal oil created by the return oil keeps the unloading valve to the right, directing all pump flow to the cylinders so the voided cylinder fills rapidly. After the void is filled, the load signal pressure increases. This higher signal pressure then goes through the orifice, closes the check valve, and fully opens the charging valve. NOTE: The charging valve is called a "return restrictor" in some systems. The function of the valve remains the same.

STMG 687 3/98

- 107 -

D7R DOZER LIFT VALVE HOLD TO TILT VALVE

FROM INLET MANIFOLD LOAD CHECK VALVE

MAIN CONTROL SPOOL TO INLET MANIFOLD

RESOLVER

ROD END

HEAD END

MAKEUP VALVE

FROM TILT VALVE

77 Implement Control Valve Operation • Lift valve in HOLD • Lift valve has FLOAT position • Not pressure compensated

The lift control spool is a closed-center, manually operated spool controlled through a mechanical linkage. The centering spring returns the spool to the HOLD position when the operator releases the lift lever and keeps the spool in HOLD when the lift circuit is not in operation. The lift spool has four positions: RAISE, HOLD, LOWER and FLOAT. To initiate the FLOAT condition, the operator must move the hand control lever forward until the spool is held by the detent and balls at the right. The operator must manually release the lift control lever from the FLOAT position. The lift control valve does not contain a flow control spool, so the valve is not pressure compensated. NOTE: This valve operates the same as the lift control valve on the standard D6R.

STMG 687 1/93

- 108 -

D7R TILT CONTROL VALVE HOLD TO RIPPER CONTROL VALVE

PRIORITY FLOW CONTROL VALVE

SIGNAL PRESSURE LIMITER

FROM LIFT CONTROL VALVE LOAD CHECK VALVE

MAIN CONTROL SPOOL

TO LIFT CONTROL VALVE

RESOLVER

ROD END

HEAD END

PLUG

FROM RIPPER VALVE

78 • Same as D6R except for signal pressure limiter

This sectional view shows the tilt control valve in HOLD. The tilt control valve consists of the tilt control spool, load check valve, priority flow control valve, resolver, and a signal pressure limiter. The tilt control spool is a closed-center, manually operated spool with three positions: TILT LEFT, HOLD, and TILT RIGHT. The centering spring on the left returns the spool to the HOLD position when the operator releases the tilt lever and keeps the spool in HOLD when the tilt circuit is not in operation. The operator manually controls spool movement through a mechanical linkage that connects to the left end of the spool. The control spool has three cross-drilled holes that connect with an axial drilled passage in the center of the spool. The purpose of the cross-drilled holes and the axial passage is to sense either the rod end or the head end cylinder pressure, depending on the direction of the spool shift, and to transmit work port pressure through the spool to the signal cavity.

➥

STMG 687 3/98

• Priority flow control valve: - Satisfies flow and pressure needs of tilt circuit first - Additional flow may be available to other valves

- 109 -

During a HOLD condition, the signal cavity is open to the tank across a flat machined on the spool. This illustration shows the resolver directing signal oil from the ripper circuit to the lift control valve while, at the same time, preventing signal oil from entering the tilt control valve. If the ripper valve was not operating or the ripper cylinder pressure was lower than the pressure in the tilt cylinders, the ball in the resolver would move to the right, directing tilt signal oil to the lift valve and blocking the ripper signal oil from flowing into the lift control valve. The priority flow control valve is in the tilt supply passage and receives oil flow from the inlet manifold group. The priority flow control spool ensures that the flow and pressure needs of the tilt circuit are met. For example, if the operator moves the lift control valve first and then without releasing the lift control valve operates the tilt control valve, the lift control valve will slow down even if the tilt circuit has a higher load pressure. With regard to pump flow, the tilt control valve is in parallel with the other implement control valves. The priority flow control valve provides the "pressure compensating" feature of the tilt circuit by controlling the maximum pressure drop across the tilt control spool. This feature results in constant implement speed for a given distance of lever displacement.

• Valve in HOLD - Center axial passage open to tank - Priority flow control valve is initially to the left - Priority flow control valve moves to the right - Throttling slot on left closes - Throttling slot on right opens - Priority flow control valve maintains maximum pressure differential

With a dead engine, the spring at the right holds the priority flow control spool to the left. When the operator starts the machine, the pump sends oil through the inlet manifold to the priority flow control spool. Oil flows to the center of the priority flow control spool and out of the throttling slot on the left end of the spool to the load check valve. The load check valve blocks the oil. As pressure increases at the load check valve, the increased pressure pushes the priority flow control spool to the right against its spring and partially closes the throttling slot on the left end of the spool. The throttling slot on the left end of the spool never completely closes. Also, the load check valve never completely blocks the oil. The priority flow control spool meters a small amount of oil past the load check valve to maintain a pressure equal to the priority flow control valve spring [(345 kPa (50 psi)] at the main control spool. Maintaining pressure at the main control spool improves the tilt response. The priority flow control valve maintains a maximum pressure differential across the tilt main control spool equal to the priority flow control valve spring force. NOTE: The signal pressure limiter may not be present in all tilt control valves. The valve may also be called a "pressure limiter." To avoid confusion with the pressure limiter (pressure cutoff) used in the pump control valve in variable displacement pumps, the preferred term is "signal pressure limiter."

STMG 687 3/98

- 110 -

D7R TILT CONTROL VALVE TILT LEFT TO RIPPER CONTROL VALVE

PRIORITY FLOW CONTROL VALVE

FROM LIFT CONTROL VALVE

SIGNAL PRESSURE LIMITER

LOAD CHECK VALVE

MAIN CONTROL SPOOL TO LIFT CONTROL VALVE

RESOLVER

ROD END

HEAD END

PLUG

FROM RIPPER VALVE

79 • TILT LEFT condition: - Signal fills priority flow control valve spring chamber - Priority flow control valve moves to left

When the operator moves the tilt control lever to the TILT LEFT position, the control spool opens a passage for supply oil to flow to the head end of the tilt cylinder and a passage for oil from the rod end of the cylinder to return to the tank. The control spool movement allows the cylinder pressure to become signal pressure. The signal oil flows to the resolver, through the signal network, and to the inlet manifold. At the inlet valve, the signal oil keeps the unloading valve and the margin stem positioned to provide the correct tilt flow to the tilt circuit. At the same time that the signal oil flows to the inlet manifold, the signal oil also flows through an internal passage, through an orifice, and fills the priority flow control valve spring chamber. The pressure in the chamber increases, causing the valve to move to the left. As supply pressure increases, the supply oil opens the load check valve and sends flow through the cylinder supply passage.

➥

STMG 687 3/98

- Flow rate maintained to tilt circuit

- Excess flow available to other valves

- 111 -

When the signal pressure plus the spring force moves the priority flow control valve to the left, the opening at the throttling slot on the left end of the spool increases so more oil can flow to the work port. The amount of flow from the pump combined with the amount of flow the tilt work port needs determines the distance that the priority flow control valve shifts. As the tilt circuit flow requirements are met, pressure increases on the left end of the priority valve spool and the valve moves back to the right. The priority valve maintains a pressure differential across the tilt control spool equal to the priority spool spring. Excess flow from the pump is now available for lift or for the ripper valve. If the system does not need the oil, the margin stem will return the excess pump flow to the tank. When the tilt control spool is fully shifted, the priority flow control valve limits the maximum flow to the tilt cylinder to 80 Lpm (21 gpm). Since the pump produces more flow than the tilt circuit requires, the margin stem meters excess pump flow back to the tank while maintaining the system pressure at 1310 kPa (190 psi) above the cylinder pressure.

• Signal pressure limiter used to protect circuit - Opens when signal pressure gets too high - Causes priority flow control spool to reduce flow and pressure

To protect the lines and components, the signal pressure limiter valve limits the maximum pressure of the tilt circuit. The tilt section is the only valve section with a pressure limiter. When oil flow fills the priority valve spring chamber, the signal pressure limiter feels the increasing oil pressure. When the pressure reaches the signal pressure limiter setting, the signal pressure limiter opens, draining oil from the priority valve spring chamber. Since the orifice restricts the oil flow into the priority valve spring chamber, the pressure at the left end of the priority valve is higher than the pressure in the spring chamber plus the spring force. The force on the left end of the priority valve causes the valve to move to the right, reducing the supply flow and pressure to the tilt circuit. NOTE: None of the other sections (lift or ripper) have a priority flow control valve. Since all the circuits are in parallel, any remaining oil flows to the implement with the lowest cylinder load.

STMG 687 3/98

- 112 -

D7R RIPPER CONTROL VALVE HOLD FROM TILT CONTROL VALVE

LOAD CHECK VALVE

MAIN CONTROL SPOOL TO TILT VALVE

RESOLVER ROD END

HEAD END

MAKEUP VALVE

80 • Ripper valve is last control valve in group • Ripper valve is same as lift valve except for FLOAT • Not pressure compensated

The ripper control valve (if equipped) is the last control valve in the implement hydraulic system. The ripper control valve is similar to the lift control valve except the ripper valve does not have a FLOAT position. Since the ripper valve does not have a FLOAT position, the control spool is different than the lift valve control spool. The ripper control valve spool does not have a detent mechanism, and the lands on the spool are different from the lift valve. All other components of the ripper valve operate identically to those in the lift control valve. The ripper control valve does not contain a flow control spool, so the valve is not pressure compensated.

STMG 687 3/98

- 113 -

D6R STEERING AND IMPLEMENT HYDRAULIC SYSTEM DIFFERENTIAL STEER MACHINES

END COVER

RESOLVERS

RIPPER LIFT DOZER TILT DOZER LIFT QUICK-DROP VALVE

STEER

INLET MANIFOLD

CHARGING VALVE

MAIN RELIEF VALVE

PUMP CONTROL VALVE

FLOW COMPENSATOR PRESSURE COMPENSATOR COUNTERBALANCE VALVE

OIL COOLING PUMP

COOLER THERMAL BYPASS

STEER MOTOR

CASE DRAIN FILTER

81 DIFFERENTIAL STEER HYDRAULIC SYSTEM • D6R system - Variable displacement pump - Steering has priority over other valves - Steering motor and counterbalance valve

- Thermal bypass valve

This diagram shows the hydraulic system on the D6R differential steer machines. A variable displacement piston pump draws oil from the tank. Supply oil from the pump flows into the control valves. Steering has priority over the other implement valves. During a turn, the steering control valve directs flow to the counterbalance valve and steering motor. The cooling pump directs oil through the hydraulic oil cooler before sending oil flow to the steering motor case. Main system return oil flows through a filter before entering the tank. The pump and motor case drain oil also returns through a filter before entering the tank. A thermal bypass valve for the oil cooler opens and directs oil flow to the tank if the oil is below a specific temperature.

➥

STMG 687 3/98

- Signal network

- Single quick-drop valve

- Relief valve in inlet manifold - Charging valve in inlet manifold

- 114 -

A signal line originates in the control valves. The signal line passes through each valve body before reaching the pump control valve. When the operator activates one or more implements, the resulting loads generate work port pressure signals. A resolver network sends the highest work port pressure to the pump control valve. The differential steer machines are equipped with a single quick-drop valve for both lift cylinders. The quick-drop valve provides makeup oil to the head end of the lift cylinders. The quick-drop valve helps to control the raise, lower at slow speeds, quick-drop, and lower with down pressure functions of the dozer. This quick-drop valve operates the same as the quick-drop valve previously discussed. The inlet manifold contains the main relief valve and the charging valve. The operation of the main relief valve and charging valve is the same as for the standard D6R.

STMG 687 3/98

- 115 -

D7R STEERING AND IMPLEMENT HYDRAULIC SYSTEM DIFFERENTIAL STEER MACHINES RESOLVERS

QUICK-DROP VALVE

END COVER RIPPER LIFT DOZER TILT DOZER LIFT STEER

INLET MANIFOLD

PUMP CONTROL VALVE

MAIN RELIEF VALVE

COOLER BYPASS

FLOW COMPENSATOR PRESSURE COMPENSATOR

COUNTERBALANCE VALVE

COOLER

STEER MOTOR CASE DRAIN FILTER

82 • D7R system: - Variable displacement pump - Steering has priority over other valves - Steering motor and counterbalance valve - Cooler bypass valve - Signal network - Single quick-drop valve - Relief valve in inlet manifold

The D7R differential steer machine hydraulic system is similar to the D6R except the D7R does not have an oil cooler pump. Instead of a thermal bypass valve, the D7R uses a pressure sensing cooler bypass valve which is mounted to the inlet manifold.

STMG 687 3/98

- 116 -

1 3

4 5 2

83

• D6R pump • Identify components: 1. Piston-type pump 2. Compensator valve 3. Pump supply pressure tap 4. Signal pressure tap 5. Oil cooler pump

A variable displacement, piston-type hydraulic pump (1) on the D6R provides oil flow to the steering, lift, tilt, and ripper valves. The engine flywheel drives the pump. The compensator valve (2) controls the swashplate angle in the pump. Use the upper pressure tap (3) to check low pressure standby and maximum system pressure. Use the lower pressure tap (4) to check signal pressure. The oil cooler pump (5) directs oil through the hydraulic oil cooler to provide oil flow to the pump and steering motor case drain circuit for lubrication and cooling.

STMG 687 3/98

- 117 -

1

3

4

2

84

• D7R pump • Identify components: 1. Piston-type pump 2. Compensator valve 3. Pump supply pressure tap 4. Signal pressure tap

A variable displacement, piston-type hydraulic pump (1) on the D7R provides oil flow to the steering, lift, tilt, and ripper valves. The engine flywheel drives the pump. The compensator valve (2) controls the swashplate angle in the pump. Use the upper pressure tap (3) to check low pressure standby and maximum system pressure. Use the lower pressure tap (4) to check signal pressure. The D7R does not have an oil cooler pump.

STMG 687 3/98

- 118 -

2

1

85

• Identify components: 1. Case drain filter 2. S•O•S tap

The case drain filter (1) is in the same compartment as the transmission filter. The tap (2) in the case drain filter housing allows live oil sampling. NOTE: The case drain filter shown in this slide is installed on the D6R.

STMG 687 3/98

- 119 -

86

• D6R hydraulic oil cooler (arrow)

The hydraulic oil cooler (arrow) on the D6R differential steer machines is one of the modules in the radiator group. NOTE: The slide also shows the AMOCS (Advanced Modular Cooling System) radiator. This radiator is used on both the D6R and D7R. The AMOCS radiator provides two-pass cooling and is easier to service since each module can be removed individually without removing the complete radiator. At the top of the radiator is an expansion tank with a sight glass at the left side to check the coolant level. The coolant passes up one side of the module and returns down the other side through a two compartment bottom tank.

STMG 687 3/98

- 120 -

87

• D7R hydraulic oil cooler (arrow)

The hydraulic oil cooler (arrow) on the D7R differential steer machines is at the rear of the fan shield.

STMG 687 3/98

- 121 -

1

2

88

• D6R component locations: 1. Thermal bypass valve 2. Oil cooler pressure tap

The D6R thermal bypass valve (1) for the oil cooler directs the oil from the oil cooler pump to the tank when oil will not flow through the cooler. The oil cooler circuit pressure can be checked at the pressure tap (2).

STMG 687 3/98

- 122 -

89

• D7R oil cooler pressure tap (arrow)

Pressure in the D7R oil cooler circuit can be checked at the oil cooler pressure tap (arrow). The oil cooler bypass valve is located below the floor plate to the left of and just below the implement control valve inlet manifold.

STMG 687 3/98

- 123 -

6 5 4 3 2

1

90

• D6R component locations: 1. Charging valve 2. Inlet manifold 3. Steering control valve 4. Lift control valve

The D6R steering and implement control valve group is behind the case drain filter and above the right fender. The machine configuration determines the valve group configuration. The control valve group consists of the inlet manifold (2), the steering control valve (3), the lift control valve (4), the tilt control valve (5), the ripper control valve (if equipped), and the end cover (6). The inlet manifold contains the main relief valve (not visible), and the charging valve (1). The relief valve is set above the pressure compensator setting. The main relief valve is only used to limit any sudden pressure increases (spikes).

5. Tilt control valve 6. End cover

The charging valve prevents cylinder cavitation by restricting the return oil flow from the cylinders. The oil pressure in the cylinder return oil passage opens the makeup valve and functions as charge oil for the signal network when the signal pressure is lost due to overrunning load conditions.

STMG 687 3/98

- 124 -

5 4 3 2 1

91

• D7R component locations: 1. Inlet manifold 2. Steering control valve 3. Lift control valve 4. Tilt control valve 5. End cover

The D7R implement control valve group is located to the left of the transmission filter above the right fender. The machine configuration determines the valve group configuration. The implement control valve group consists of the inlet manifold (1), the steering control valve (2), the lift control valve (3), the tilt control valve (4), the ripper control valve (if equipped), and the end cover (6). The inlet manifold contains the main relief valve (not visible). The relief valve is set above the pressure compensator setting. The main relief valve is only used to limit any sudden pressure increases (spikes).

STMG 687 3/98

- 125 -

1

2

92

• Component locations: 1. Counterbalance valve 2. Steering motor

When the operator moves the steering lever, the steering control valve directs supply oil to the counterbalance valve (1). The counterbalance valve prevents the fixed displacement steering motor (2) from "overspeeding." The steering motor drives the steering input gears (discussed previously).

STMG 687 3/98

- 126 -

FROM IMPLEMENT CONTROL VALVE

D6R/D7R STEERING AND IMPLEMENT PUMP

TO INLET MANIFOLD

ENGINE OFF SMALL ACTUATOR

DRIVE SHAFT

MARGIN SPOOL

SWASHPLATE CUTOFF SPOOL

LARGE ACTUATOR

PISTON AND BARREL ASSEMBLY

93 Pump Operation • Identify internal pump components

The pump on the differential steer machines is similar in operation to the pump on the standard D6R.

• At start-up swashplate at maximum angle

Before starting the engine, the actuator rod and spring hold the pump swashplate at maximum angle. (The actuator rod and spring are behind the small actuator piston and are not shown.) As the pump starts to rotate, oil flows to the inlet manifold in the valve stack, the left end of the small actuator piston, the left end of the margin spool, and the piston chamber in the right end of the cutoff spool. With all the control valve spools in HOLD, pump flow to the inlet manifold goes through the inlet passages in the control valves to the end cover. The end cover blocks the oil. NOTE: The pump shown in this view is for the differential steer D7R. The D6R pump is different in appearance, but the operation is the same.

STMG 687 3/98

- 127 -

FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP LOW PRESSURE STANDBY

MARGIN SPOOL

CUTOFF SPOOL

94 • LOW PRESSURE STANDBY - As pump produces flow, system pressure increases - Margin spool moves right - Oil fills large actuator chamber - Swashplate moves to reduced angle

As the supply pressure increases to approximately 2100 kPa (305 psi), the pressure at the left end of the margin spool (in the compensator valve) moves the spool a small distance to the right against the spring force. Moving the margin spool permits supply oil to flow around the spool, past the cutoff spool, and into the left end of the large actuator piston chamber. As pressure on the large actuator piston increases to overcome the combined force of the bias spring and the pressure in the small actuator piston chamber, the large actuator piston moves the swashplate to a reduced angle. At the minimum angle, the pump will produce just enough flow to make up for system leakage at a pressure to ensure instantaneous response when an implement is actuated. In LOW PRESSURE STANDBY, all the implement control valves are in HOLD and the signal network allows the signal oil to drain.

➥

STMG 687 3/98

- 128 -

The LOW PRESSURE STANDBY condition ensures that pressure oil is always available at the control spools. This feature provides quick response of the steer motor or implements when the operator moves a control valve out of HOLD. NOTE: LOW PRESSURE STANDBY is higher than margin pressure because of the higher back pressure the blocked oil at the closed center valves creates when all the valves are in HOLD. During LOW PRESSURE STANDBY, the supply oil pushes the margin spool farther to the right to compress the margin spring.

STMG 687 3/98

- 129 -

FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP UPSTROKE

MARGIN SPOOL

CUTOFF SPOOL

95 • UPSTROKE pump - Signal oil moves margin spool down - Large actuator pressure is reduced - Swashplate moves to increased angle

During operation, the pump will maintain the supply pressure at 2100 kPa (305 psi) higher than the signal pressure. The difference between supply pressure and signal pressure is referred to as "margin pressure." As the system requirements increase (due to increased flow demand), the pump will UPSTROKE to maintain the margin pressure. When an implement requires flow, the resolver network signals the pump control valve. This signal causes the force (margin spring plus signal pressure) on the right end of the margin spool to become greater than the supply pressure at the left end of the spool. The higher pressure causes the margin spool to move to the left to reduce or block oil flow to the large actuator. At the same time, the spool drains the large actuator oil to the tank. Reducing or blocking oil flow to the large actuator reduces or eliminates the pressure acting against the large actuator piston. When the pressure in the large actuator piston decreases, the bias spring and small piston move the swashplate to an increased angle causing the pump to UPSTROKE (produce more flow).

STMG 687 3/98

- 130 -

FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP CONSTANT FLOW

MARGIN SPOOL

CUTOFF SPOOL

96 • CONSTANT FLOW - Margin spool moves to metering position

As the supply pressure increases, the pressure at the left end of the margin spool increases. When the supply pressure is approximately 2100 kPa (305 psi) higher than the signal pressure, the margin spool will move a small distance to the right and permit oil to again flow to the large actuator piston. This condition limits additional swashplate movement. As long as the flow requirements remain constant, the margin spool will remain in this metering position and maintain a constant flow to the steer motor or implement.

STMG 687 3/98

- 131 -

FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP DESTROKE

MARGIN SPOOL

CUTOFF SPOOL

97 • DESTROKE pump - Margin spool moves right - Pressure in large actuator increases - Swashplate moves to reduced angle

• Margin spool moves to stabilize system

The conditions required to DESTROKE the pump are basically the opposite of those required for UPSTROKING. The pump DESTROKES when the system requires less flow. As the force at the left end of the margin spool becomes greater than the force at the right end, the margin spool moves to the right and allows more flow to the actuator piston causing the pressure in the large actuator piston to increase. The increased pressure in the large actuator piston overcomes the combined force of the small actuator and bias spring and moves the swashplate to a reduced angle. As the pump flow decreases, the supply pressure also decreases. When the supply pressure decreases and becomes the sum of the signal pressure plus margin pressure, the margin spool moves to a metering position and the system stabilizes. When the operator returns the control lever to HOLD, the signal pressure drops to zero. The pump then DESTROKES to the LOW PRESSURE STANDBY condition.

STMG 687 3/98

- 132 -

FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP HIGH PRESSURE STALL

MARGIN SPOOL

CUTOFF SPOOL

98 • HIGH PRESSURE STALL - Cutoff and margin spools are in parallel - Signal equals supply pressure - Margin spool moves down - Cutoff spool moves up - Swashplate moves to reduced angle

During a HIGH PRESSURE STALL, the signal pressure equals the supply pressure. Combining the signal pressure with the margin spring forces the margin spool to the left. Moving the margin spool to the left normally drains the oil out of the large actuator piston and causes the pump to upstroke. However, during HIGH PRESSURE STALL, the pressure below the cutoff spool overcomes the pressure compensator spring force and moves the cutoff spool to the left. Moving the cutoff spool to the left blocks the oil in the large actuator piston from going into the drain passage and still allows supply oil to flow to the large actuator. The increased pressure in the large actuator allows the large actuator to overcome the combined force of the small actuator and bias spring to DESTROKE the pump. The pump is now at minimum flow and supply pressure is at maximum.

• Pump supplies minimum flow at maximum pressure

➥

STMG 687 3/98

- 133 -

HIGH PRESSURE STALL occurs when the steering circuit is put under an extreme load. One example of this condition occurs when the operator engages the service brakes while making a turn. When operating another implement with steering in stall, the pump will UPSTROKE to produce flow to meet the needs of the other implement operating at the lower work port pressure. All the implement valves used in differential steering systems have signal limiting valves to prevent high steering pressures from getting into the implement circuits.

STMG 687 3/98

- 134 -

FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP HIGH PRESSURE STALL

MARGIN SPOOL

CUTOFF SPOOL

99 • Identify valve components • Valve in HOLD - Shifting spool blocks center axial passage - Priority flow control valve is initially to the left - Priority flow control valve moves to the right

Steering Circuit Operation The directional control spool in the steer section has three positions: LEFT TURN, HOLD, and RIGHT TURN. In this view, the directional control spool is in the HOLD position. With the engine not running, the spring behind the priority flow control valve holds the flow control valve to the left. When the operator starts the machine, the pump sends oil through the inlet manifold to the priority flow control valve. Oil flows out the holes at the left end of the priority flow control valve, opens the load check valve, and fills the chamber around the center of the directional control spool.

➥

STMG 687 3/98

- Holes on left close - Holes on right open - Priority flow control valve maintains maximum pressure differential

- 135 -

The increasing pressure in the chamber at the right of the load check valve pushes the priority flow control valve to the right against the force of the spring. Moving the flow control valve to the right closes the throttling holes on the left end of the valve spool and allows oil to flow to the remaining components in the system through the holes near the right end of the valve spool. In HOLD, pressure at the main control spool is equal to the priority flow control valve spring. The priority control valve ensures that the flow and pressure needs of the steering circuit are met before flow is available to the other valves. The priority valve is designed to permit some flow to always be available to the other circuits. This design permits the operator to steer and operate the blade at the same time. During all steering conditions, the priority flow control valve ensures that a specified minimum pump flow is always available for operation of the steer motor.

STMG 687 3/98

- 136 -

D6R/D7R STEERING CONTROL VALVE LEFT TURN TO NEXT CONTROL VALVE

PRIORITY FLOW CONTROL VALVE

PUMP SUPPLY LOAD CHECK VALVE

MAIN CONTROL SPOOL TO INLET MANIFOLD

RESOLVER

MAKEUP VALVE

STEER LEFT

STEER RIGHT

MAKEUP VALVE

FROM PREVIOUS VALVE

100 • LEFT TURN - Signal oil fills priority flow control valve spring chamber - Signal oil fills center axial passage

This illustration shows the steering control valve in the LEFT TURN position. Movement of the directional control spool permits oil to flow from the work port to the steer circuit. Either oil at the work port pressure or oil at 345 kPa (50 psi) in the supply passage enters the cross-drilled hole to the center axial passage and becomes signal oil. The signal is then sent through the resolver network to the pump. The pump increases flow to meet the flow needs of the steering circuit. The check valve remains seated until supply pressure exceeds the work port pressure.

➥

STMG 687 3/98

- Priority control valve spool moves to left - Flow rate maintained to steering circuit - Excess flow available to other valves

- 137 -

The signal reaches the pump and the priority flow control valve spring chamber simultaneously. The oil in the center passage in the main control spool flows through an orifice before filling the spring chamber. The signal pressure in the priority control valve spring chamber works in conjunction with the spring force to move the priority control valve spool to the left. This movement allows the required flow to reach the steering circuit while limiting the amount of flow to the other control valves. When the signal pressure plus the spring force moves the priority flow control valve to the left, the hole openings near the left end of the spool increase so more oil can flow to the work port, while the holes near the right end of the priority flow control spool close. As the steering circuit flow requirements are met, pressure increases on the left end of the priority valve spool and the valve moves back to the right. The priority valve maintains a maximum pressure differential across the steering control spool equal to the priority spool spring. Excess flow from the pump is now available for the other valves. During the steer conditions shown, a fixed relationship exists between the various pressures in the circuit for a given distance of steering tiller and directional control spool movement. These relationships maintain a constant rpm of the steer motor for all load conditions as long as the distance of steering tiller movement remains fixed. Supply pressure is always maintained at a fixed value (margin) above the signal pressure. The priority flow control valve maintains a fixed pressure differential across the directional control spool which is equal to the value of the priority flow control spring.

STMG 687 3/98

- 138 -

LEFT TURN PASSAGE CHECK VALVE

STEM

RIGHT TURN PASSAGE CHECK VALVE

COUNTERBALANCE VALVE

CROSSOVER RELIEF

CROSSOVER RELIEF

D6R/D7R COUNTERBALANCE VALVE AND STEER MOTOR STEERING MOTOR

STRAIGHT LINE OPERATION

101 • Identify components • STRAIGHT LINE OPERATION - Counterbalance valve centered - Supply oil to motor blocked

This slide shows the counterbalance valve and steer motor during STRAIGHT LINE OPERATION. During STRAIGHT LINE OPERATION, the control spool in the steering control valve blocks the oil in the steering circuit. The counterbalance spool remains centered and the steering motor is hydraulically locked. During STRAIGHT LINE OPERATION, the drive line transmits external forces to the differential steer planetaries and the forces attempt to drive the steering motor. While attempting to drive the steering motor, the external forces create pressure spikes in one side of the loop between the motor and the counterbalance valve.

➥

STMG 687 3/98

• Crossover relief valves dampen pressure spikes

- 139 -

The side of the loop feeling the pressure spike depends on the direction that the forces are attempting to drive the motor. If the pressure spike is significantly high, the crossover relief valve in the affected side of the loop will open. The dump portion of the valve (large area) will then permit some of the high pressure oil to open the poppet (small area) in the opposite relief valve. The crossover relief valve transmits some of the high pressure oil into the low pressure side of the loop thereby dampening the pressure spike. The crossover relief valves open at approximately 41500 kPa (6000 psi).

STMG 687 3/98

- 140 -

CHECK VALVE

STEM

LEFT TURN PASSAGE RIGHT TURN PASSAGE CHECK VALVE

COUNTERBALANCE VALVE

CROSSOVER RELIEF

CROSSOVER RELIEF

D6R/D7R COUNTERBALANCE VALVE AND STEER MOTOR

STEERING MOTOR

RIGHT TURN

102 • RIGHT TURN - Oil enters counterbalance valve - Oil fills right spring chamber - Check valve opens - Oil enters motor - Motor rotates

This slide shows the counterbalance valve and the steering motor during a RIGHT TURN. When the operator moves the steering lever to the RIGHT TURN position, the steering control valve directs oil to the counterbalance valve. Oil flow enters the counterbalance valve and fills the right center chamber in the stem. At the same time, oil also enters the small passage at the right of the inlet, flows through an orifice, and fills the spring chamber at the right end of the stem. Oil in the right center chamber in the stem opens the check valve, flows around the right crossover relief valve, and enters the motor inlet port. As the motor starts to rotate, return oil from the motor outlet port flows around the left crossover relief valve to the stem where the oil is temporarily blocked. The blocked oil causes a rapid increase in the supply pressure.

- Return oil blocked until threshold pressure reached

➥

STMG 687 3/98

- 141 -

When the supply oil reaches approximately 7000 kPa (1015 psi), the stem shifts to the left and uncovers the small cross-drilled holes at the right of the left check valve allowing return flow from the motor to flow to the return port in the steering control valve. • Crossover relief valves

The crossover relief valves operate when the dump section of the valve senses high pressure. The dump valve opens and permits supply pressure oil to reach the poppet in the return side crossover relief valve. If a pressure spike exceeding 41500 kPa (6000 psi) occurs, the left crossover relief valve opens and permits supply pressure oil to flow directly to the return side of the loop.

STMG 687 3/98

- 142 -

LEFT TURN PASSAGE CHECK VALVE

STEM

RIGHT TURN PASSAGE CHECK VALVE

COUNTERBALANCE VALVE

CROSSOVER RELIEF

CROSSOVER RELIEF

D6R/D7R COUNTERBALANCE VALVE AND STEER MOTOR OVERSPEED

STEERING MOTOR

103 • Counterbalance valve prevents overspeed - Threshold pressure lost - Counterbalance valve moves right - Return oil directed to supply side to prevent cavitation

Occasionally, a condition such as making a turn while operating on a downhill slope will attempt to overspeed the steering motor. Overspeeding the motor could cavitate the motor and cause the operator to loose steering control. The counterbalance valve prevents this condition. As the drive line attempts to overspeed the motor, the supply pressure rapidly decreases. Pressure in the spring chamber at the right end of the stem also drops. When the pressure in the supply side of the loop decreases below 7000 kPa (1015 psi), the stem shifts to the right and blocks the flow of return oil. Blocking the return oil creates a high back pressure at the motor which tends to limit the speed of the motor. When the back pressure exceeds 41500 kPa (6000 psi), the left crossover relief valve opens and sends return oil directly to the supply side to prevent motor cavitation. For severe overspeed conditions, the makeup valve in the steering control valve also opens and provides additional oil to the supply side of the loop.

STMG 687 3/98

- 143 -

D6R/D7R RIPPER CONTROL VALVE DIFFERENTIAL STEER MACHINES HOLD FLOW CONTROL VALVE

FROM TILT CONTROL VALVE

SIGNAL LIMITING VALVE

LOAD CHECK VALVE

MAIN CONTROL SPOOL

TO TILT VALVE

RESOLVER

ROD END

HEAD END

MAKEUP VALVE

104 • Identify components

Implement Control Valve Operation The ripper control valve is the last valve in the implement control valve stack on the D7R and the D6R. This slide shows the ripper control valve in HOLD. The ripper control valve is in parallel to the remaining valves in regard to pump flow. The ripper control valve contains one makeup valve in the head end of ripper lift cylinders and also contains a signal limiting valve to prevent steering pressures from entering the ripper circuit. With a dead engine, the spring at the right end of the flow control valve holds the flow control spool to the left. When the machine is started, the pump sends oil through the inlet manifold to the steering priority flow control spool. Flow not needed by steering is available to the remaining valves in the valve stack.

➥

STMG 687 3/98

• Valve in HOLD - Axial passage open to tank - Flow control valve is initially to the left - Flow control valve moves to the right - Throttling slot on left closes - Flow control valve maintains maximum pressure differential

• Signal pressure limiter protects circuit - Opens when signal pressure gets too high - Causes flow control spool to reduce flow and pressure

- 144 -

Oil flows into the flow control spool and out of the throttling slots on the left end of the spool to the load check valve and the main control spool where the oil is blocked. Pressure increases on the left end of the flow control spool and moves the spool to the right against its spring, closing the throttling slots. The throttling slots are never completely closed, and oil is not completely blocked at the load check valve. A small amount of oil is metered through the priority flow control spool and past the load check valve to maintain a pressure equal to the flow control valve spring [345 kPa (50 psi)] at the main control spool. Maintaining this pressure at the main control spool provides quick implement response. The signal pressure limiter valve limits the pressure in the ripper circuit to protect the lines and components. When the operator moves the ripper control valve, signal oil flow fills the flow control valve spring chamber, and the signal pressure limiter feels the increasing oil pressure. When the pressure in the spring chamber reaches the signal pressure limiter setting, the valve opens and drains oil from the spring chamber of the flow control valve. Since the orifice restricts the oil flow into the spring chamber, the pressure at the left end of the flow control valve will increase above the pressure in the spring chamber plus the spring force. The force on the left end of the flow control valve causes the valve to move to the right, reducing the supply flow and pressure to the ripper circuit. NOTE: The slides shown for the control valves used on differential steer machines in this presentation are for the D6R. The valve operation is the same on both tractors.

STMG 687 3/98

- 145 -

D6R/D7R RIPPER CONTROL VALVE DIFFERENTIAL STEER MACHINES LOWER FLOW CONTROL VALVE FROM TILT CONTROL VALVE

SIGNAL LIMITING VALVE

LOAD CHECK VALVE

MAIN CONTROL SPOOL TO TILT CONTROL VALVE

RESOLVER

ROD END

HEAD END

MAKEUP VALVE

105 • Ripper LOWER - Signal oil fills flow control valve spring chamber - Flow control spool moves to left - Flow rate maintained to tilt circuit

Moving the control lever opens a passage from the pump to the head end work port and opens a passage from the rod end work port to the tank. The signal network senses work port pressure through the center passage in the control spool. The pump then senses the change in signal pressure and starts to provide flow. The signal is also felt in the flow control spool spring cavity. This pressure plus the spring will push the flow control spool to the left. As this movement occurs, the throttling slot opens more so more oil can be directed to the work port. The distance that the flow control spool shifts is determined by the amount of flow being sent by the pump and the amount of flow needed at the work port. The flow control spool will maintain a pressure differential across the main control spool equal to the flow control valve spring resulting in constant implement flow to the cylinders. This description assumes the ripper to be powered down with no overrunning load condition.

STMG 687 3/98

- 146 -

D6R/D7R DOZER LIFT CONTROL VALVE DIFFERENTIAL STEER MACHINES HOLD TO TILT VALVE

FLOW CONTROL VALVE

FROM STEERING VALVE

SIGNAL PRESSURE LIMITER

LOAD CHECK VALVE

MAIN CONTROL SPOOL TO STEERING VALVE

RESOLVER

ROD END

HEAD END

MAKEUP VALVE

FROM TILT VALVE

106 • Identify components - Same as ripper except for signal pressure limiter settings

The lift control valve is the second valve in the implement control valve stack on the D7R and the D6R. The lift control valves on the D6R and D7R machines are identical except for different signal pressure limiter settings and different lift spools. The lift control valve contains a makeup valve for the head end of the lift cylinders and a detent mechanism for FLOAT. To protect the lines and components, the signal pressure limiter valve limits the maximum pressure of the lift circuit. The lift control valve operates the same as the ripper control valve.

STMG 687 3/98

- 147 -

D6R/D7R DOZER TILT CONTROL VALVE DIFFERENTIAL STEER MACHINES HOLD TO RIPPER CONTROL VALVE

FLOW CONTROL VALVE

FROM LIFT CONTROL VALVE

SIGNAL LIMITING VALVE

LOAD CHECK VALVE

MAIN CONTROL SPOOL TO LIFT CONTROL VALVE

RESOLVER

ROD END

HEAD END

PLUG

FROM RIPPER VALVE

107 • Identify components - Same as ripper and lift except no makeup valve

The tilt control valve is between the lift and ripper valve in the implement control valve stack on both the D7R and the D6R machines. The tilt control valve operates the same as the ripper and lift control valves except the tilt valve does not contain a makeup valve.

STMG 687 3/98

- 148 -

2

4

5 3

1

108

AUTOSHIFT AND AUTO KICKDOWN OPERATION 1. Autoshift selector button 2. 1F/2R LED indicator 3. 2F/2R LED indicator

The autoshift operation on the D6R and D7R tractors is a function of the Power Train Electronic Control System. The autoshift function allows the operator to preset the different gear speeds for directional shifting. This function allows a directional shift other than FIRST SPEED FORWARD to FIRST SPEED REVERSE. With the autoshift feature, the operator can select either FIRST SPEED FORWARD to SECOND SPEED REVERSE or SECOND SPEED FORWARD to SECOND SPEED REVERSE. The autoshift indicators on the left side of the dash show the operator the status of the autoshift function. The operator selects the Autoshift Mode with the selector button (1). An LED indicator informs the operator which mode is selected, either FIRST SPEED FORWARD to SECOND SPEED REVERSE (2) or SECOND SPEED FORWARD to SECOND SPEED REVERSE (3). If both indicators are OFF, the transmission operates in the Manual Mode.

4. LED indicator 5. Auto kickdown selector button

The tractors equipped with the Power Train Electronic Control System also have an auto kickdown function. When the auto kickdown function is selected by the selector button (5) on the right side of the dash, an LED indicator (4) is illuminated. This function allows the tractor to automatically downshift when a pre-programmed speed is no longer maintained due to an increased work load. When the indicator is OFF, the auto kickdown function is not selected.

STMG 687 3/98

- 149 -

THREE LEVELS OF WARNING • CATEGORY 1 • CATEGORY 2 • CATEGORY 3

109 CATERPILLAR MONITORING SYSTEM • Three levels of warning

The Caterpillar Monitoring System notifies the operator of an immediate or impending problem with a machine system. Three levels of warning are provided to the operator.

- Category I requires operator attention

Category I: For the first level of warning, only an alert indicator will flash. No immediate action is required. This category alerts the operator that the machine system needs attention soon.

- Category II requires operator to change method of operation

Category II: For the second level of warning, the alert indicator and the action light flashes. This warning category requires the operator to change the machine operation or perform maintenance to the system. Changing the machine operation will reduce the excessive temperatures or engine overspeeds. Failure to change machine operation will result in severe damage to components.

➥

STMG 687 3/98

- Category III requires immediate machine shutdown

• Cat Monitoring System cycles through self test

- 150 -

Category III: For the third level of warning, the alert indicator flashes, the action lamp flashes, and the action alarm sounds. This category requires the operator to perform an immediate safe engine shutdown. This category could result in possible operator injury or severe damage to machine components. The self test verifies that the main display module and the gauge module are operating properly. The main display module performs an automatic self test each time the key start switch is turned from the OFF to the ON position. The operator must observe the modules to determine if the Caterpillar Monitoring System is operating properly. The alert indicators and display area are tested for approximately one second: all alert indicators FLASH and the display area shows all unit indicators (°Celsius, kPa, MILES, KILOMETERS, RPM, LITERS), a X10 indicator, the service meter symbol, and 888.8.8.8 on the six-digit readout. The gauge modules are tested for approximately three seconds. The four analog gauges in the left module ramp up to half scale, return to zero, then sweep to full scale. After reaching full scale, the tachometer and gauges return to showing current machine values. The action lamp turns ON. The action alarm SOUNDS once. The main display module then goes into the Normal Mode of operation. INSTRUCTOR NOTE: If the control fails to self test, additional investigation will be needed to determine if the control is defective or if a harness code problem exists. Always consult the appropriate service manual before proceeding. For more complete information on the Caterpillar Monitoring System, refer to the Service Manual "Caterpillar Monitoring System" (Form SENR6717-02).

STMG 687 3/98

- 151 -

ENGINE OIL PRESSURE • Category III Warning • Alert indicator flashes • Action lamp flashes • Action alarm sounds

110

• Engine oil pressure

The top left alert indicator of the main module is engine oil pressure.

• Category III Warning

During normal operation, the engine oil pressure switch is closed to ground. The switch opens when engine oil pressure is less than the specified value of the switch. The open switch signals the main display module to notify the operator of low engine oil pressure. Low engine oil pressure is a Category III Warning. The alert indicator will flash, the action lamp will flash, and the action alarm will sound. The operator should perform an immediate and safe shutdown.

STMG 687 3/98

- 152 -

SYSTEM VOLTAGE • Category I Warning • Sensed at "R" terminal • Alert indicator flashes

111

• System voltage sensed directly from "R" terminal

The system voltage is sensed directly from the "R" terminal at the alternator. The alternator does not use a switch; instead, the Caterpillar Monitoring System senses the frequency of the alternator directly from the "R" terminal. The Caterpillar Monitoring System measures and determines if the system voltage is within specified limits. In the event that the voltage drops below a certain level, the alert indicator will flash, alerting that a problem exists with the alternator. Since this alert is a Category I Warning, the operator can continue to operate the machine, but should investigate the cause of the problem when convenient.

STMG 687 3/98

- 153 -

FUEL LEVEL INDICATOR • Category I Warning • Flashes when 10% fuel remains

112

• Fuel level alert indicator

The fuel level alert indicator will flash a Category I Warning when the fuel level reaches 10% of capacity or approximately 38 L (10 gal.) on the D6R and approximately 50 L (13 gal.) on the D7R. The gauge cluster module also contains an analog gauge which measures fuel level. When the needle reaches the red warning area of the gauge, the alert indicator will flash.

STMG 687 3/98

- 154 -

ELECTRONIC BRAKE SYSTEM • Category I Warning if brakes need calibrated • Category III Warning if ECM detects a fault in brake electronic system input or output

113

• Brake system alert indicator

The lower four alert indicators located in the main display module receive information from the power train electronic control system ECM through the CAT Data Link.

• Category I Warning

The power train ECM activates a warning for the brake system. The warning categories are: A Category I Warning is activated when the ECM detects that the brakes are not calibrated. This condition will occur anytime new software has been flash programmed or the ECM has been replaced. Scrolling through the Brake Mode will clear the fault code. The steering clutches and brakes should be calibrated when performance is not satisfactory. The brake system alert indicator will FLASH. This alert tells the operator to check or repair the problem component at the earliest opportunity. The electrical circuits that can cause this warning are: Parking brake switch--ON/OFF pole (CID 070) Parking brake switch--Brake back-up pole (CID 618) Steering system oil temperature sensor (CID 075) Brake pedal position sensor (CID 468) Secondary brake valve solenoid (CID 722) Parking brake solenoid (CID 681) Service brake switch (CID 298) ECM failure (CID 254)

➥

STMG 687 3/98

• Category III Warning

- 155 -

A Category III Warning is activated when the ECM detects that a fault is present in a brake electronic system input or output component or circuit. The brake electronic system alert indicator will FLASH, the action lamp will FLASH, and the action alarm will SOUND. The operator should safely stop the machine and shut the engine off. A service code will be logged for the fault that is present. The fault must be corrected before machine operation is resumed. The electrical circuits that can cause this warning are: Left brake solenoid valve (CID 689) Right brake solenoid valve (CID 690) Harness code (CID 650) ECM failure (CID 254) Service brake switch (CID 298)

STMG 687 3/98

- 156 -

TRANSMISSION ELECTRONIC SYSTEM • Category I or Category III Warning when selected faults in the Transmission Electronic System are detected by the ECM • The Warning Category depends on the specific fault

114

• Transmission system alert indicator

• Category I Warning

The power train electronic control system activates a warning for the transmission electronic system. The warning categories are: A Category I Warning is activated when the ECM detects that a fault is present in a transmission electronic system input or output component or circuit. The transmission electronic system alert indicator will FLASH. This alert tells the operator to check the transmission system at the earliest opportunity. A service code will be logged for the fault that is present. The electrical circuits that can cause this warning are: Downshift switch (CID 621) Upshift switch (CID 622) Direction switch (CID 623) Transmission oil temperature sensor (CID 177) First gear solenoid valve (CID 695) Second gear solenoid valve (CID 694) Third gear solenoid valve (CID 693) Priority valve solenoid (CID 697)

➥

STMG 687 3/98

• Category III Warning

- 157 -

A Category III Warning is activated when the ECM detects that a fault is present in a transmission electronic system input or output component circuit. The transmission alert indicator will FLASH, the action lamp will FLASH, and the action alarm will SOUND. The operator should stop the tractor safely and shut the engine off. A service code will be logged for the fault that is present. The electrical circuits that could cause this warning are: Directional selector position sensor (CID 299) Harness code (CID 650) ECM failure (CID 254) Forward gear solenoid (CID 692) Reverse gear solenoid (CID 691)

STMG 687 3/98

- 158 -

POWER TRAIN FILTER BYPASS • Category II Warning when transmission oil filter becomes restricted and the oil is at normal operating temperature

115

• Power train filter bypass indicator

The power train filter bypass switch is located in the housing of the power train hydraulic filter in the compartment to the right of the operator. If the power train filter becomes restricted, the filter bypass valve will open, permitting oil to flow past the filter. This condition causes the switch to open. If the bypass condition occurs at normal machine operating temperature, the power train oil filter alert indicator, and the master fault light will activate notifying the operator of a Category II Warning. A temperature switch prevents the signal from the bypass switch from alerting the operator when the oil is cold at start-up.

STMG 687 3/98

- 159 -

PARKING BRAKE INDICATOR • Category I Warning when parking brake is engaged • Must be released to place transmission in gear

116

• Parking brake system alert indicator

• Category I Warning

The power train ECM activates a warning for the parking brake. The warning category is: A Category I Warning is activated whenever the parking brake is ENGAGED. The parking brake alert indicator will FLASH. This alert tells the operator to RELEASE the parking brake before placing the transmission in gear.

STMG 687 3/98

- 160 -

117

CONCLUSION This presentation has discussed the component locations and systems operation of the power train and implement hydraulics for the D6R and the D7R Track-type Tractors. When used in conjunction with the service manual, the information in this package should permit the serviceman to do a thorough job of analyzing a problem in these systems.

STMG 687 3/98

- 161 -

SLIDE LIST 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45.

D6R model view Track arrangements graphic Operator's seat FTC steering and transmission control Electronic tiller bar for differential steer Brake and decelerator pedals Dash Implement control levers Fuel tank and fill cap Fuel drain valve Battery compartment Fuse panel Precleaner Left side engine components Right side engine components Torque divider Torque divider graphic D6R power train fill tube D6R D/S transmission filter D7R D/S transmission fill tube and dipstick Power train pump suction screen Power train pump Transmission planetary group and control Transmission modulating valve Power train drain plug and sump screen Pump drive test location Steering clutch and brake valve Steering clutch and brake lubrication plugs Differential steer brake valve Parking brake switch Standard power train hydraulic system Priority valve Transmission modulating solenoid valves Steering and brake valve graphic D/S power train hydraulic schematic D/S component schematic D/S components STRAIGHT LINE schematic D/S--LEFT TURN FORWARD operation Undercarriage Implement hydraulic system chart D6R hydraulic tank D6R hydraulic tank drain Standard D6R implement hydraulic system Standard D6R signal network Standard D6R variable displacement pump

46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89.

D6R case drain filter Control valve group Quick-drop valve Pressure and flow compensator valve Pump schematic--ENGINE OFF Pump schematic--LOW PRESSURE STANDBY Pump schematic--UPSTROKE Pump schematic--CONSTANT FLOW Pump schematic--DESTROKE Pump schematic--STALL Inlet manifold--HOLD Inlet manifold--valve operating Inlet manifold--cylinder voiding Standard D6R tilt valve--HOLD Standard D6R tilt valve--LEFT Standard D6R lift valve--HOLD Standard D6R lift valve--FLOAT Standard D6R ripper valve--HOLD Quick-drop valve schematic Quick-drop valve--HOLD Quick-drop valve--RAISE Quick-drop valve--LOWER Quick-drop valve--LOWER/QUICK DROP Quick-drop valve--DOWN PRESSURE Standard D7R implement hydraulic system Standard D7R fixed displacement pump Control valve group Inlet manifold--HOLD Inlet manifold--FULL FLOW Inlet manifold--PARTIAL FLOW Inlet manifold--CHARGING VALVE Standard D7R lift valve--HOLD Standard D7R tilt valve--HOLD Standard D7R tilt valve--TILT LEFT Standard D7R ripper valve--HOLD D/S D6R hydraulic system D/S D7R hydraulic system D/S D6R variable displacement pump D/S D7R variable displacement pump Case drain filter D/S D6R hydraulic oil cooler D/S D7R hydraulic oil cooler D/S D6R thermal cooler bypass valve D/S D7R cooler pressure test location

STMG 687 3/98

- 162 -

SLIDE LIST 90. D/S D6R valve group 91. D/S D7R valve group 92. D/S steering motor and counterbalance valve 93. Pump schematic--ENGINE OFF 94. Pump schematic--LOW PRESSURE STANDBY 95. Pump schematic--UPSTROKE 96. Pump schematic--CONSTANT FLOW 97. Pump schematic--DESTROKE 98. Pump schematic--STALL 99. Steering control valve--HOLD 100. Steering control valve--LEFT TURN 101. Steering motor--STRAIGHT LINE 102. Steering motor--RIGHT TURN 103. Steering motor--OVERSPEED 104. D/S ripper lift valve--HOLD 105. D/S ripper lift valve--LOWER 106. D/S dozer lift valve--HOLD 107. D/S tilt valve--HOLD 108. Autoshift and Auto Kickdown selector buttons 109. Three levels of warning 110. Cat Monitoring--Engine oil pressure 111. Cat Monitoring--"R" terminal 112. Cat Monitoring--Fuel level 113. Cat Monitoring--Electronic Brake System 114. Cat Monitoring--Transmission Electronic System 115. Cat Monitoring--Power Train filter bypass 116. Cat Monitoring--Parking Brake Indicator 117. D6R Tractor--model view

STMG 687 3/98

- 163 -

INSTRUCTOR NOTES

STMG 687 3/98

- 164 -

Serviceman's Handout No. 1

Engine and Electrical System Checklist Directions: Use this sheet to take notes during the presentation. During a lab exercise, use this sheet as a checklist when identifying components. Engine Components

Electrical Components

Primary fuel filter

Starter

Secondary fuel filter

Alternator

Governor and fuel injection pump

Batteries

Priming pump

Fuse panel

Oil filter

Fuel pressure switch

Engine oil dipstick

Engine oil pressure switch

Live oil sampling test port

Coolant temperature switch and sender

Engine oil pressure test ports

Disconnect switch

Engine oil cooler

Key start switch

Primary and secondary air filters

Power train oil temperature sensor (converter)

Turbocharger Air filter indicator

Power train hydraulic oil temperature switch (filter)

Ether start aid (mounting location)

Hydraulic oil temperature sender

Radiator

Master fault lamp

Water pump

Caterpillar Monitoring System Panel

Temperature regulator housing (thermostat)

STMG 687 3/98

- 165 -

Serviceman's Handout No. 2

Standard Power Train Components Checklist Directions: Use this sheet to take notes during the presentation (i.e. location, functions). During a lab exercise, use this as a checklist when identifying components. Fill tube Filter(s) Suction screen Power train pump Torque converter housing (divider) Torque converter outlet relief valve Transmission range selector Transmission control valve Power train oil cooler Steering and brake control valve Steering and brake controls Pressure test locations: Pump supply Torque converter outlet Transmission clutch lube Pump drive lube Steering clutch pressure Brake clutch pressure Steering and brake clutch lube ____ Transmission clutch pressure

2

4 3

1

5

TRANSMISSION CONTROL GROUP

STEERING AND BRAKE VALVE

D6R WITH FINGER TIP CONTROL

POWER TRAIN HYDRAULIC SYSTEM

1

2

- 166 -

FROM CONVERTER SCAVENGE

3

PRIORITY VALVE

TO TORQUE CONVERTER

FROM OIL COOLER

STMG 687 3/98 Serviceman's Handout No. 3

- 167 -

STMG 687 3/98

Serviceman's Handout No. 4

Differential Steer Power Train System Component Checklist Directions: Use this sheet to take notes during the presentation (i.e. location, functions). During a lab exercise use this as a checklist when identifying components. Fill tube Filter Suction screen Power train pump Torque converter housing (divider) Torque converter outlet relief valve Transmission range selector Transmission control valve Power train oil cooler Brake control valve Steering tiller Pressure test locations: Pump supply Torque converter outlet Brake clutch pressure Transmission clutch lube Brake clutch lube Pump drive lube

2

4 3

1

5

TRANSMISSION CONTROL GROUP TO TRANSMISSION CASE

BRAKE VALVE

D6R WITH DIFFERENTIAL STEERING

POWER TRAIN HYDRAULIC SYSTEM

1

2

- 168 -

FROM CONVERTER SCAVENGE

3

PRIORITY VALVE

TO TORQUE CONVERTER

FROM OIL COOLER

STMG 687 3/98 Serviceman's Handout No. 5

STMG 687 3/98

- 169 -

Serviceman's Handout No. 6

Standard D6R/D7R Hydraulic System Component Checklist Directions: Use this sheet to take notes during the presentation (i.e. location, functions). During a lab exercise, use this as a checklist when identifying components. Hydraulic tank

Hydraulic oil filter(s)

Pump

Pump control valve (D6R)

Inlet manifold

Implement valve group

Tilt control valve

Lift control valve

Implement controls

Pump supply pressure test port

Margin pressure test port (D6R)

Quick-drop valve

Hydraulic oil cooler

STMG 687 3/98

- 170 -

Serviceman's Handout No. 7

D6R Hydraulic Pump Component Checklist Directions: Fill in the blanks with the correct response. Use this sheet to take notes during the presentation.

PUMP AND COMPENSATOR OPERATION ENGINE OFF NO SIGNAL

PUMP OUTPUT

C

D

E

F A

B H

A B C D E F G H

G

STMG 687 3/98

- 171 -

Serviceman's Handout No. 8

D7R Inlet Manifold Component Checklist Directions: Fill in the blanks with the correct response. Use this sheet to take notes during the presentation.

D7R INLET MANIFOLD IMPLEMENTS IN HOLD SIGNAL OIL TO TANK

TO CONTROL VALVES

C A D

B

ORIFICE

PUMP SUPPLY

F E A B C D E F

STMG 687 3/98

- 172 -

Serviceman's Handout No. 9

Implement Control Valve Component Checklist Directions: Fill in the blanks with the correct response. Use this sheet to take notes during the presentation. D6R/D7R DOZER TILT CONTROL VALVE DIFFERENTIAL STEER MACHINES HOLD TO RIPPER CONTROL VALVE

B

FROM LIFT CONTROL VALVE

C

A

D TO LIFT CONTROL VALVE

E ROD END

A B C D E F

HEAD END

F

FROM RIPPER VALVE

STMG 687 3/98

- 173 -

Serviceman's Handout No. 10

Differential Steer Hydraulic System Component Checklist Directions: Use this sheet to take notes during the presentation (i.e. location, functions). During a lab exercise, use this as a checklist when identifying components. ____ Hydraulic tank ____ Hydraulic oil filters ____ Pump ____ Pump control valve ____ Inlet manifold ____ Main relief valve ____ Charging valve ____ Implement valve group ____ Tilt control valve ____ Steer control valve ____ Steering motor ____ Counterbalance valve ____ Lift control valve ____ Implement controls ____ Pump supply pressure test port ____ Margin pressure test port ____ Quick-drop valve ____ Hydraulic oil cooler

STMG 687 3/98

- 174 -

Serviceman's Handout No. 11

Differential Steer Pump Component Checklist Directions: Fill in the blanks with the correct response. Use this sheet to take notes during the presentation. FROM IMPLEMENT CONTROL VALVE

TO INLET MANIFOLD

D6R/D7R STEERING AND IMPLEMENT PUMP ENGINE OFF

D

C

A

B

A B C D E F G

G

F

E

STMG 687 3/98

- 175 -

INSTRUCTOR NOTES

SESV1687 3/98

Printed in U.S.A.