Neutral, Parking Brake Engaged
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| Illustration 1 | g06585760 |
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Hydraulic Schematic in Neutral, Parking Brake Engaged (1) Right front motor (2) Shift servo (3) Speed valve (4) Shuttle valve (5) Flushing spool (6) Flushing relief valve (7) Front rotating group (8) Right propel pump (9) Reverse EDC (10) Forward EDC (11) Servo piston (12) Forward crossover relief valve (13) Front pressure sensors (14) Reverse crossover relief valve (15) Sequence valve (parking brake solenoid) (16) Charge relief valve (17) Rear pressure sensors (18) Reverse crossover relief valve (19) Forward crossover relief valve (20) Reverse EDC (21) Servo piston (22) Forward EDC (23) Rear rotating group (24) Brake actuator (25) Speed sensor (26) Right rear motor (27) To cooler bypass valve (28) Left rear motor (29) Left front motor (30) Brake release manifold (31) Shift valve (32) Reverse EDC (33) Front rotating group (34) Left propel pump (35) To hydraulic tank (36) Servo piston (37) Forward EDC (38) Forward crossover relief valve (39) Reverse crossover relief valve (40) Sequence valve (propel-enable solenoid) (41) Front pressure sensors (42) Charge relief valve (43) Rear pressure sensors (44) Reverse crossover relief valve (45) Forward crossover relief valve (46) Reverse EDC (47) Servo piston (48) Rear rotating group (49) To cooler bypass valve (50) Forward EDC (51) Hydraulic tank (52) Charge pump (53) Charge filter (54) To cooler bypass valve | |
When the engine is running, propel pumps (8) and (34) and charge pump (52) rotate. The charge pump draws oil from hydraulic tank (51) through a strainer.
Output oil from the charge pump flows through charge filter (53) to port "E" of each propel pump. Inside the pumps, charge oil flows to the following:
- Charge relief valves (16) and (42)
- Forward crossover relief valves (12), (19), (38) and (45)
- Reverse crossover relief valves (14), (18), (39) and (44)
- Sequence valves (15) and (40)
Charge oil also flows from port"M3" of left propel pump (34) to port"P" shift valve (31).
When charge pressure increases to the relief setting, charge relief valves (16) and (42) open. This action directs charge oil into the case drain of each pump. The charge relief valves are set to open at
The crossover relief valves within each propel pump consist of a makeup check valve and a main relief valve. The makeup valve allows charge oil to fill the low-pressure circuit when pressure in the propel circuit falls below charge pressure. The makeup valve also replenishes the system for normal leakage that occurs in the propel circuit.
The main relief valve protects the high-pressure circuit from pressure spikes during operation of the propel system. If the relief valve opens, high-pressure oil is purged into the charge circuit.
Sequence valve (15) and (40) on each propel pump is controlled by the respective pump interlock solenoid. Sequence valve (15) is controlled by the parking brake solenoid. Sequence valve (40) is controlled by the propel-enable solenoid. The sequence valves control charge oil flow to the propel EDCs. On right propel pump (8), the sequence valve also controls charge oil flow to brake release manifold (30). The brake release manifold controls the flow of charge oil to brake actuators (24), located on each front propel motor.
When the propel system is in neutral (or the transmission ECM has disabled the propel system), sequence valves (15) and (40) block charge oil. In this state, the pump EDC and parking brake circuits are open to case drain. Under these conditions, the swashplate of the rotating group in each pump is at zero angle, and springs in each motor engage the parking brakes.
Shift valve (31) controls charge oil flow to speed valves (3) of the front propel motors and the shift spools in the rear motors. When the propel mode is set to WORK, the shift valve blocks oil flow to the speed valves in the front propel motors. In WORK mode, the shift spools do not limit oil flow to the rear motors. In this case, the machine operates in low speed.
Reverse, WORK Mode, Parking Brake Released
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| Illustration 2 | g06585761 |
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Hydraulic Schematic in Reverse and WORK Mode, Refer to First Schematic in Section for Component List (1) Right front motor (2) Shift servo (3) Speed valve (4) Shuttle valve (5) Flushing spool (6) Flushing relief valve (7) Front rotating group (8) Right propel pump (9) Reverse EDC (10) Forward EDC (11) Servo piston (12) Forward crossover relief valve (13) Front pressure sensors (14) Reverse crossover relief valve (15) Sequence valve (parking brake solenoid) (16) Charge relief valve (17) Rear pressure sensors (18) Reverse crossover relief valve (19) Forward crossover relief valve (20) Reverse EDC (21) Servo piston (22) Forward EDC (23) Rear rotating group (24) Brake actuator (25) Speed sensor (26) Right rear motor (27) To cooler bypass valve (28) Left rear motor (29) Left front motor (30) Brake release manifold (31) Shift valve (32) Reverse EDC (33) Front rotating group (34) Left propel pump (35) To hydraulic tank (36) Servo piston (37) Forward EDC (38) Forward crossover relief valve (39) Reverse crossover relief valve (40) Sequence valve (propel-enable solenoid) (41) Front pressure sensors (42) Charge relief valve (43) Rear pressure sensors (44) Reverse crossover relief valve (45) Forward crossover relief valve (46) Reverse EDC (47) Servo piston (48) Rear rotating group (49) To cooler bypass valve (50) Forward EDC (51) Hydraulic tank (52) Charge pump (53) Charge filter (54) To cooler bypass valve | |
When the transmission ECM generates a reverse propel signal, sequence valves (15) and (40) open, and reverse EDCs (9), (20), (32) and (46) are energized. The condition of the reverse EDCs is determined by the signal that is sent from the transmission ECM. The transmission ECM analyzes input signals to determine the magnitude of the output signal sent to the reverse EDC solenoids.
When sequence valve (15) in right propel pump (8) opens, charge oil flows to brake release manifold (30). From this manifold, charge pressure is directed to brake actuator (24) of front propel motors (1) and (29). This action releases the parking brakes.
Also, when sequence valves (15) and (40) open, charge pressure flows across the reverse EDC metering spools. The charge oil is metered across the spool to the reverse chamber of servo piston (11), (21), (36) and (47) in each pump. The charge oil causes the servo piston to shift, changing the angle of the swashplate in the propel pump. This action causes the pumps to generate flow, and pressure in the reverse circuit increases.
High-pressure oil in the reverse circuit flows to reverse crossover relief valves (14), (18), (39) and (44). High-pressure oil also flows to the reverse side of propel motors (1), (26), (28) and (29). Low-pressure oil returns to the respective propel pump. Both low-pressure and high-pressure sides of each circuit are monitored by dedicated pressure sensors (13), (17), (41) and (43).
Reverse circuit oil in reverse crossover relief valves (14), (18), (39) and (44) closes the makeup valve, and acts against the relief valve. Spring pressure and charge oil pressure close the relief valve. If the pressure in the reverse high-pressure circuit reaches approximately
The main relief valves are fast acting valves, and each relief pressure setting is higher than the respective ePOR value. With this combination, the main relief valves relieve pressure surges and allow time for the transmission ECM to destroke the respective propel pump. Using the ePOR for sustained relief in this manner generates less heat in the pumps.
Within propel motors (1), (26), (28) and (29), high-pressure oil in the reverse circuit rotates the motors. This oil also acts on flushing spools (5) and shift servos (2) in the front motors. After turning the motors, the pressure of the circuit oil is reduced. Oil at a reduced pressure then flows to the flushing spool before returning to the respective propel pump. The drive circuit is then complete.
The high-pressure reverse circuit oil acting on flushing spool (5) causes the spool to shift. This shift allows return oil from the circuit to act on the flushing relief valve (6). When the return pressure is greater than the setting of the flushing relief valve, the flushing relief valve opens. When the flushing relief valve opens, a portion of oil flows from the return circuit into the motor case drain for lubrication and cooling purposes. Flushing oil from each motor case drain flows to the cooler bypass valve.
When the propel mode is set to WORK, the solenoid of shift valve (31) is not energized, and charge oil is blocked. In this case, the pilot circuit of speed valves (3) in front motors (1) and (29) is open to tank return pressure. Under this condition, shift servos (2) in the front motors are open to case drain through the speed valves. In this mode, high-pressure circuit oil retracts the shift servos within the propel motors. Also, the shift spools in rear motors (26) and (28) provide paths for pump supply oil to feed all pistons in the motors. These conditions operate all four motors in low speed with a high-torque output.
Forward, TRAVEL Mode, Parking Brake Released
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| Illustration 3 | g06585769 |
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Hydraulic Schematic in Forward and TRAVEL Mode (1) Right front motor (2) Shift servo (3) Speed valve (4) Shuttle valve (5) Flushing spool (6) Flushing relief valve (7) Front rotating group (8) Right propel pump (9) Reverse EDC (10) Forward EDC (11) Servo piston (12) Forward crossover relief valve (13) Front pressure sensors (14) Reverse crossover relief valve (15) Sequence valve (parking brake solenoid) (16) Charge relief valve (17) Rear pressure sensors (18) Reverse crossover relief valve (19) Forward crossover relief valve (20) Reverse EDC (21) Servo piston (22) Forward EDC (23) Rear rotating group (24) Brake actuator (25) Speed sensor (26) Right rear motor (27) To cooler bypass valve (28) Left rear motor (29) Left front motor (30) Brake release manifold (31) Shift valve (32) Reverse EDC (33) Front rotating group (34) Left propel pump (35) To hydraulic tank (36) Servo piston (37) Forward EDC (38) Forward crossover relief valve (39) Reverse crossover relief valve (40) Sequence valve (propel-enable solenoid) (41) Front pressure sensors (42) Charge relief valve (43) Rear pressure sensors (44) Reverse crossover relief valve (45) Forward crossover relief valve (46) Reverse EDC (47) Servo piston (48) Rear rotating group (49) To cooler bypass valve (50) Forward EDC (51) Hydraulic tank (52) Charge pump (53) Charge filter (54) To cooler bypass valve | |
When the transmission ECM generates a forward propel signal, sequence valves (15) and (40) open, and forward EDCs (10), (22), (37) and (50) are energized. The condition of the forward EDCs is determined by the signal that is sent from the transmission ECM. The transmission ECM analyzes input signals to determine the magnitude of the output signal sent to the forward EDC solenoids.
When sequence valve (15) in right propel pump (8) opens, charge oil flows to brake release manifold (30). From this manifold, charge pressure is directed to brake actuator (24) of each front propel motor (1) and (29). This action releases the parking brakes.
Also, when sequence valves (15) and (40) open, charge pressure flows across the forward EDC metering spools. The charge oil is metered across the spool to the forward chamber of servo piston (11), (21), (36) and (47) in each pump. The charge oil causes the servo piston to shift, changing the angle of the swashplate in the propel pump. This action causes the pumps to generate flow, and pressure in the forward circuit increases.
High-pressure oil in the forward circuit flows to forward crossover relief valves (12), (19), (37) and (45). High-pressure oil also flows to the forward side of propel motors (1), (26), (28) and (29). Low-pressure oil returns to the respective propel pump. Both low-pressure and high-pressure sides of each circuit are monitored by dedicated pressure sensors (13), (17), (40) and (43).
Forward circuit oil in forward crossover relief valves (12), (19), (38) and (45) closes the makeup valve, and acts against the relief valve. Spring pressure and charge oil pressure close the relief valve. If the pressure in the forward high-pressure circuit reaches approximately
The main relief valves are fast acting valves, and each relief pressure setting is higher than the respective ePOR value. With this combination, the main relief valves relieve pressure surges and allow time for the transmission ECM to destroke the respective propel pump. Using the ePOR for sustained relief in this manner generates less heat in the pumps.
Within propel motors (1), (26), (28) and (29), high-pressure oil in the forward circuit rotates the motors. This oil also acts on flushing spools (5) and shift servos (2) in the front motors. After turning the motors, the pressure of the circuit oil is reduced. Oil at a reduced pressure then flows to the flushing spool before returning to the respective propel pump. The drive circuit is then complete.
The high-pressure forward circuit oil acting on flushing spool (5) causes the spool to shift. This shift allows return oil from the circuit to act on the flushing relief valve (6). When the return pressure is greater than the setting of the flushing relief valve, the flushing relief valve opens. When the flushing relief valve opens, a portion of oil flows from the return circuit into the motor case drain for lubrication and cooling purposes. Flushing oil from each motor case drain flows to the cooler bypass valve.
When the propel mode is set to TRAVEL, the solenoid of shift valve (31) is energized. In this case, charge oil flows into the pilot circuit of speed valves (3) in front propel motors (1) and (29). Under this condition, shift servos (2) are open to high-pressure circuit oil through the speed valves. In this mode, the high-pressure circuit oil extends the shift servos within the front propel motors. This action shifts the propel motors into high speed.
Also, when the propel mode is set to TRAVEL, the shift valve allows oil flow to the speed valves in the front motors. The shift spools limit oil flow to half of the pistons in the rear motors. In this case, the motors operate in high speed.