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| Illustration 1 | g03716299 |
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(1) Ripper control valve
(1A) Ripper raise solenoid (1B) Ripper lower solenoid (2) Lockout solenoid (3) Lift control valve (3A) Blade raise solenoid (3B) Blade lower solenoid (4) Angle control valve (4A) Right angle solenoid (4B) Left angle solenoid (5) Tilt control valve (5A) Right tilt solenoid (5B) Left tilt solenoid (6) Backup relief valve (7) Makeup valve (8) Line relief valve (9) Dead engine lower (Blade) (10) Dead engine lower (Ripper) | |
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| Illustration 2 | g03716317 |
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Bank Valve Configuration: (Tilt, Angle, Lift, Ripper) (1) Ripper control valve (1A) Ripper raise solenoid (1B) Ripper lower solenoid (2) Lockout solenoid (3) Lift control valve (3A) Blade raise solenoid (3B) Blade lower solenoid (4) Angle control valve (4A) Right angle solenoid (4B) Left angle solenoid (5) Tilt control valve (5A) Right tilt solenoid (5B) Left tilt solenoid (6) Backup relief valve (7) Makeup valve (8) Line relief valve (9) Dead engine lower (Blade) (10) Dead engine lower (Ripper) (12) Implement pump supply (13) Signal line (14) Return oil to hydraulic tank (22) Port "A" (23) Port "B" | |
The work tool system is a closed centered system with an unloading valve. The system is electronically controlled with the assistance of pilot oil. There are separate systems for each group of cylinders on the machine.
If the machine is equipped with an optional ripper, line relief valve (9) for the head end circuit will be part of ripper control valve (2). Backup relief valve (6) is mounted on inlet manifold (1) to maintain hydraulic pressure for the work tool system. All circuits use the backup relief valve for circuit protection.
All the control valves contain load compensator valves. The ripper circuit has a single-line relief valve (9) has the capability of a makeup valve on the rod end circuit. The lift valve section has a makeup valve in the head end circuit.
When the controls are placed in the HOLD position, the control spools in the valves block the flow of oil to the cylinders and from the cylinders. Centering springs in the control valves keep the spools in the HOLD position.
The spools of the implement control valves are shifted by pilot oil. The flow of pilot oil to the end of the control valve spools is controlled by a proportional solenoid. Every control valve has two solenoids.
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| Illustration 3 | g03691540 |
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Solenoid valve (de-energized solenoid) (A) Spring (B) Valve spool (C) Passage to hydraulic oil tank (D) Passage from pilot supply oil (E) Passage from pilot chamber (BB) Cutaway section (CC) Component surface (FF) Activated component (GG) Tank pressure (SS) First pilot pressure reduction | |
When an implement is in the HOLD position, both solenoids on the implement control valve are de-energized. When the solenoid is de-energized, spring (A) forces valve spool (B) upward. In this position, pilot supply oil in passage (D) is blocked. The oil that is from the end of the control valve spool drains through passage (E). The oil flows around valve spool (B) and the oil returns to the hydraulic tank through passage (C).
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| Illustration 4 | g03476289 |
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Solenoid valve (energized solenoid) (A) Spring (B) Valve spool (C) Passage to hydraulic oil tank (D) Passage from pilot supply oil (E) Passage to pilot chamber (BB) Cutaway section (CC) Component surface (FF) Activated component (GG) Tank pressure (SS) First pilot pressure reduction | |
When an implement is activated, the solenoid on one end of the implement control valve is energized. The solenoid forces valve spool (B) downward. In this position, passage (C) to passage (E) is blocked.
Passage (D) is open and pilot supply oil flows around valve spool (B) to passage (E). Pilot oil from passage (E) exerts pressure on the end of the control valve spool and the spool shifts.
The solenoid is a proportional solenoid. The solenoid moves valve spool (B) downward by an amount that is proportional to the amount of movement of the implement control lever. When valve spool (B) is pushed down further, passage (C) is opened more. More pilot oil is allowed into passage (E). The implement control spool shifts proportionally to the pilot oil pressure.
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| Illustration 5 | g01401083 |
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Line relief valve in the CLOSED position (1) Adjustment screw (2) Locknut (3) Chamber (4) Spring (5) Port (6) Seat (7) Passage (8) Poppet (9) Spring chamber (10) Orifice (11) Spring (12) Spring (13) Passage (14) Port (15) Passage (16) Valve (17) Port to the head end of the ripper cylinders (18) Passage | |
Poppet (8) is forced downward against seat (6) by the force of spring (4). Valve (16) is forced downward by the force of spring (11) and by the force of spring (12).
System pressure oil in passage (18) flows through passage (13) into spring chamber (9). The force of the system pressure oil acts on poppet (8). When the force of system pressure oil in passage (18) is less than the force of spring (4), poppet (8) remains against seat (6). The pressure in passage (18) and the pressure in spring chamber (9) are now equal. System pressure oil in spring chamber (9) and the combined force of spring (11) and of spring (12) maintain the position of valve (16). There is no oil flow from passage (18) to passage (15) through port (14). When system oil pressure in passage (18) is less than the line relief pressure setting, the line relief valve remains in the CLOSED position.
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| Illustration 6 | g01401255 |
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Line relief valve in the OPEN position (1) Adjustment screw (2) Locknut (3) Chamber (4) Spring (5) Port (6) Seat (7) Passage (8) Poppet (9) Spring chamber (10) Orifice (11) Spring (12) Spring (13) Passage (14) Port (15) Passage (16) Valve (17) Port to the head end of the ripper cylinders (18) Passage | |
System oil pressure in passage (18) and spring chamber (9) nears the line relief valve pressure setting. The force of the system oil pressure in spring chamber (9) becomes greater than the force of spring (4). The system oil pressure in spring chamber (9) forces poppet (8) away from seat (6). System oil pressure now flows through orifice (10) of seat (6) into chamber (3). The oil in chamber (3) now flows through port (5) and through passage (7) into passage (15). This low-pressure oil now returns to the hydraulic tank.
At the same time as the oil in spring chamber (9) flows through seat (6), the system pressure oil in passage (18) flows through passage (13). As the system oil pressure flows through orifice (13) into spring chamber (9), the pressure of the oil in spring chamber (9) decreases. The reduced pressure oil in spring chamber (9) allows the high-pressure oil in passage (18) to force valve (16) upward . The high-pressure oil in passage (18) now flows through port (14) into passage (15). The oil flows from passage (15) through the return oil passage back to the hydraulic tank.
The amount of spring force of spring (4) that acts on poppet (8) determines the main relief valve pressure setting. Adjustments to the main relief valve pressure setting are made by changing the spring force of spring (4). The position of adjustment screw (1) determines the spring force of spring (4).
Reference: Refer to Specifications, Systems Operation, Testing and Adjusting, "Relief Valve (Line) - Test and Adjust" for adjustment procedures.
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| Illustration 7 | g01393773 |
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Makeup check valve in the CLOSED position (1) Spring (2) Spring chamber (3) Valve (4) Return oil passage (5) Port passage to cylinder | |
The makeup check valves are mounted in the ports of each circuit for the blade and in the rod end of the ripper circuit. The makeup check valve provides makeup oil to prevent cavitation when the blade is moved or when the ripper is lowered to the ground.
During normal operation, the force of spring (1) and the oil pressure in spring chamber (2) is greater than the pressure in return oil passage (4). As a result, valve (3) is forced downward in the CLOSED position.
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| Illustration 8 | g01393789 |
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Makeup check valve in the OPEN position (1) Spring (2) Spring chamber (3) Valve (4) Return oil passage (5) Port passage to cylinder | |
When the pressure of the oil in passage (5) and the pressure of the oil in spring chamber (2) are less than the pressure of the return oil passage (4), the higher oil pressure in return oil passage (4) overcomes the force of spring (1) and the oil pressure in spring chamber (2). The pressure of the oil in return oil passage (4) moves valve (3) upward.
When valve (3) moves upward, the valve opens a path for the oil in return oil passage (4) to flow into passage (5).
The backup relief valve is located on the inlet side of the bank valve. The backup protects the implement system from any pressure spikes from the implement pump.
Bulldozer Lift Hydraulic System
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| Illustration 9 | g03724686 |
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(3) Lift control valve
(3A) Raise solenoid valve (3B) Lower solenoid valve (7) Makeup valve (8) Line relief valve (9) Dead engine lower blade (12) Implement pump supply (13) Signal line (14) Return oil (16) Valve spool (17) Lift cylinders (18) Machine electronic control module (ECM) (19) Implement control handle | |
When the implement control handle (19) is in the HOLD position, implement control handle (19) sends a pulse width modulated signal to ECM (18).
The ECM (18) interprets the signal as an operator request to hold the blade position. ECM (18) sends a signal to raise solenoid valve (3A). Since the signal is 0 amps, raise solenoid valve (3A) does not energize and raise solenoid valve (3A) blocks the pilot oil from signal line (13) to valve spool (16). While pilot oil supply to valve spool (16) is blocked, return oil from valve spool (16) is open through raise solenoid valve (3A) to return oil (14). Then, the oil flows from return oil (14) passage back to the hydraulic tank.
The ECM (18) interprets the signal as an operator request to hold the blade position. ECM (18) sends a signal to lower solenoid valve (3B). Since the signal is 0 amps, lower solenoid valve (3B) does not energize and lower solenoid valve (3B) blocks the pilot oil from signal line (13) to valve spool (16). While pilot oil supply to valve spool (16) is blocked, return oil from valve spool (16) is open through lower solenoid valve (16) to return oil (14). Then, the oil flows from return oil (14) passage back to the hydraulic tank.
Since the oil pressure in valve spool (16) is equal from both solenoid valves. Valve spool (16) remains centered. In this position, oil is blocked by valve spool (16) and the blade maintains the desired position.
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| Illustration 10 | g03724687 |
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(3) Lift control valve
(3A) Raise solenoid valve (3B) Lower solenoid valve (8) Line relief valve (9) Dead engine lower blade (12) Implement pump supply (13) Signal line (14) Return oil (16) Valve spool (17) Lift cylinders (18) Machine electronic control module (ECM) (19) Implement control handle | |
When the implement control handle (19) is in the RAISE position, implement control handle (19) sends a pulse width modulated signal to ECM (18).
ECM (18) sends a signal with a current between initiation current and saturation current to raise solenoid valve (3A). The amount of current is proportional to the duty cycle received from implement control handle (19). As a result, raise solenoid valve (3A) becomes energized and raise solenoid valve (3A) shifts. Raise solenoid valve (3A) is open from signal line (13) to valve spool (16). The amount of oil flowing from signal line (13) to valve spool (16) is proportional to the amount of current energizing raise solenoid valve (3A).
Since the oil pressure is greater on one side of valve spool (16), the pressure overcomes the combined force of the spring on valve spool (16) and valve spool (16) shifts.
Initially, as valve spool (16) shifts, a path opens from implement pump supply (12) to rod end of lift cylinders (17). The cylinder rods retract.
As the cylinder rods retract, oil from the head end of lift cylinders (17) flows through return oil (14). Then, the oil flows from return oil (14) passage back to the hydraulic tank.
The operation of the blade lift control valve in the LOWER position is similar to the operation of the blade lift control valve in the RAISE position.
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| Illustration 11 | g03724688 |
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(3) Lift control valve
(3A) Raise solenoid valve (3B) Lower solenoid valve (8) Line relief valve (9) Dead engine lower blade (12) Implement pump supply (13) Signal line (14) Return oil (15) Passage (16) Valve spool (17) Lift cylinders (18) Machine electronic control module (ECM) (19) Implement control handle | |
When implement control handle (19) is in the FLOAT position, implement control handle (19) sends a pulse width modulated signal to ECM (18).
ECM (18) sends a signal at float setpoint current, which is greater than saturation current, to lower solenoid valve (3B). As a result, lower solenoid valve (3B) becomes energized and lower solenoid valve (3B) shifts. Lower solenoid valve (3B) is open from signal line (13) to valve spool (16).
Since the oil pressure is greater on one side of valve spool (16), the pressure overcomes the combined force of the spring on valve spool (16) and valve spool (16) shifts. As a result, both ends of lift cylinders (17) are open to the hydraulic tank and the blade moves with the contour of the ground. Return oil from return oil (14) replenishes any lost oil in the lines to prevent any cavitation within lift cylinders (17).
Bulldozer Tilt Hydraulic System
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| Illustration 12 | g03724689 |
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(5) Tilt control valve
(5A) Tilt right solenoid valve (5B) Tilt left solenoid valve (12) Implement pump supply (13) Signal line (14) Return oil (16) Valve spool (18) Machine electronic control module (ECM) (19) Implement control handle (21) Tilt cylinder | |
When implement control handle (19) is in the TILT LEFT position, implement control handle (19) sends a pulse width modulated signal to ECM (18).
Since ECM (18) interprets the signal that the implement control handle (19) is in the TITL LEFT position, ECM (18) sends a signal to tilt left solenoid valve (5B). As a result, tilt left solenoid valve (5B) is energized and tilt left solenoid valve (5B) shifts. The pilot oil from signal line (13) passes through tilt left solenoid valve (5B) to valve spool (16).
Since the oil pressure is greater on one side of valve spool (16), the pressure overcomes the combined force of the spring on valve spool (16) and valve spool (16) shifts. As a result, oil flows from implement pump supply (12) through valve spool (16) to the rod end of the tilt cylinder (21).
The operation of TILT RIGHT is similar to TILT LEFT. The oil follows the opposite path as TILT LEFT.
Bulldozer Pitch Hydraulic System
Note: To relieve the pressure in the pitch system refer to the Disassembly and Assembly for your machine.
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| Illustration 13 | g03724692 |
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(5) Tilt control valve
(5A) Tilt right solenoid valve (5B) Tilt left solenoid valve (12) Implement pump supply (13) Signal line (14) Return oil (16) Valve spool (18) Machine electronic control module (ECM) (27) Pitch control (29) Pitch cylinder | |
When pitch forward control (27) button is pushed, pitch forward control (27) sends a pulse width modulated signal to ECM (18).
Since ECM (18) interprets the signal that the pitch forward control (27) is in the PITCH FORWARD position, ECM (18) sends a signal to tilt left solenoid valve (5B). As a result, tilt left solenoid valve (5B) is energized and tilt left solenoid valve (5B) shifts. The pilot oil from signal line (13) passes through tilt left solenoid valve (5B) to valve spool (16).
Since the oil pressure is greater on one side of valve spool (16), the pressure overcomes the combined force of the spring on valve spool (16) and valve spool (16) shifts. As a result, oil flows from implement pump supply (12) through valve spool (16) to diverter valve (20). Oil flows through diverter valve (20) to the rod end of the pitch cylinder (29).
The operation of PITCH BACK is similar to PITCH FORWARD. The oil follows the opposite path as PITCH BACK.
Bulldozer Angle Hydraulic System
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| Illustration 14 | g03724693 |
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(4) Angle control valve
(4A) Angle left solenoid valve (4B) Angle right solenoid valve (12) Implement pump supply (13) Signal line (14) Return oil (16) Valve spool (18) Machine electronic control module (ECM) (22) Angle cylinders (23) Thumb roller angle controls | |
When the thumb roller angle controls (23) is in the ANGLE LEFT position, thumb roller angle controls (23) sends a pulse width modulated signal to ECM (18).
ECM (18) sends a signal with a current between initiation current and saturation current to angle left solenoid valve (4A). The amount of current is proportional to the duty cycle received from thumb roller angle controls (23). As a result, angle left solenoid valve (4A) becomes energized and angle left solenoid valve (4A) shifts. Angle left solenoid valve (4A) is open from signal line (13) to valve spool (16). The amount of oil flowing from signal line (13) to valve spool (16) is proportional to the amount of current energizing angle left solenoid valve (4A).
Since the oil pressure is greater on one side of valve spool (16), the pressure overcomes the combined force of the spring on valve spool (16) and valve spool (16) shifts.
Initially, as valve spool (16) shifts, a path opens from implement pump supply (12) to rod end of right angle cylinder (22) and the head end of the left angle cylinder (22).
As the angle cylinders (22) retract and extend, oil from the opposite end of angle cylinders (22) flows through return oil (14).
The operation of ANGLE RIGHT is similar to ANGLE LEFT. The oil follows the opposite path as ANGLE RIGHT.
Ripper/Fourth Function Hydraulic System
Ripper RAISE Position/Fourth Function Cylinder EXTEND Position
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| Illustration 15 | g03724696 |
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(1) Ripper control valve
(1A) Ripper raise solenoid valve (1B) Ripper lower solenoid valve (8) Line relief valve (10) Dead engine lower ripper (12) Implement pump supply (13) Signal line (14) Return oil (16) Valve spool (18) Machine electronic control module (ECM) (24) Ripper control handle (25) Ripper cylinders | |
When the ripper control handle (24) is in the RAISE/EXTEND position, ripper control handle (24) sends a pulse width modulated signal to ECM (18).
ECM (18) sends a signal with a current between initiation current and saturation current to ripper raise solenoid valve (1A). The amount of current is proportional to the duty cycle received from ripper raise solenoid valve (1A). As a result, ripper raise solenoid valve (1A) becomes energized and ripper raise solenoid valve (1A) shifts. Ripper raise solenoid valve (1A) is open from signal line (13) to valve spool (16). The amount of oil flowing from signal line (13) to valve spool (16) is proportional to the amount of current energizing ripper raise solenoid valve (1A).
Since the oil pressure is greater on one side of valve spool (16), the pressure overcomes the combined force of the spring on valve spool (16) and valve spool (16) shifts.
Initially, as valve spool (16) shifts, a path opens from implement pump supply (12) to rod end of ripper cylinders (25).
As the ripper cylinders (25) extend, oil from the head end of ripper cylinders (25) flows through return oil (14).
Ripper LOWER Position/Fourth Function Cylinder RETRACT Condition
The operation of LOWER/RETRACT is similar to RAISE/EXTEND. The oil follows the opposite path as RAISE/EXTEND.