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| Illustration 1 | g01392805 |
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Left Propulsion Hydraulic System (Neutral) (1) Forward EDC (2) Reverse EDC (3) To right feeder pump (port "E" (4) Right track tension manifold (5) Relief valve (6) Backflow check valve (7) Needle valve (8) Right track tension cylinder (9) From auxiliary hydraulic system (10) Parking brake cylinder (11) EDC metering spool (12) Forward multifunction valve (13) Pressure limiter (14) Main relief valve (15) Makeup valve (16) Flushing relief valve (17) Flushing spool (18) Motor output shaft (19) Right propulsion pump (20) To left feeder pump case (port "L1") (21) From hydraulic tank suction return filter (22) Charge pump (23) Charge relief valve (24) Reverse multifunction valve (25) From auxiliary valve (port "FDS") (26) To port "B" (cooler bypass manifold) (27) Servo piston (28) Left propulsion motor | |
When the engine is running, the left propulsion pump and the charge pump rotate. The charge pump draws oil from the tank through the suction and return filter. Internal passages distribute output oil from the charge pump to the following components: the charge relief valves, the EDCs, the EDC metering spools, and the multifunction control valves. External lines distribute charge oil to port "E" of the right material feed pump and to port "P" of the right track tension manifold.
When the propulsion lever is in the NEUTRAL position (or the machine ECM has disabled the propulsion system), the EDCs are not energized. Under these conditions, both ends of the EDC metering spool are open to the case drain, and the center envelope of the metering spool is active. The EDC metering spool blocks charge oil. The spool also open a passage between the propulsion pump's servo piston and the pump case drain. The pump swashplate then moves to a minimum angle.
Charge oil that enters the multifunction valves seats the check valves and the charge oil acts against the makeup valves. Since the left propulsion pump is rotating while the engine is running, normal leakage will occur in the left propulsion circuit. When pressure in the left propulsion circuit falls below charge pressure, the makeup valves open and the left propulsion circuit fills with charge oil.
When charge pressure increases to the relief setting, the charge relief valves open. This action directs charge oil into the case drain of the left propulsion pump.
The auxiliary hydraulic system controls the oil flow to and from the parking brakes and the servo piston chamber that is in the left propulsion motor. When the parking brake switch is in the ON position, the parking brake solenoid on the auxiliary manifold is not energized. Therefore, supply oil cannot flow to the parking brake cylinders, and the parking brakes are engaged. When the propulsion mode switch is in the PAVE position or in the MANEUVER position, the shift solenoid on the auxiliary manifold is not energized. Therefore, supply oil cannot flow to the servo piston chamber in the left propulsion motor.
Note: For additional information about hydraulic control of the parking brake and shift solenoids, refer to Specifications, Systems Operation/Testing and Adjusting, KENR5729.
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| Illustration 2 | g01392816 |
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Right Propulsion Hydraulic System (Neutral) (1) Forward EDC (2) Reverse EDC (3) To right feeder pump (port "E" (4) Right track tension manifold (5) Relief valve (6) Backflow check valve (7) Needle valve (8) Right track tension cylinder (9) From auxiliary hydraulic system (10) Parking brake cylinder (11) EDC metering spool (12) Forward multifunction valve (13) Pressure limiter (14) Main relief valve (15) Makeup valve (16) Flushing relief valve (17) Flushing spool (18) Motor output shaft (19) Right propulsion pump (20) To right feeder pump case (port "L1") (21) From hydraulic tank suction return filter (22) Charge pump (23) Charge relief valve (24) Reverse multifunction valve (25) From auxiliary valve (port "FDS") (26) To port "D" (cooler bypass manifold) (27) Servo piston (28) Right propulsion motor | |
With the exception of plumbing differences, the right propulsion hydraulic system is identical to the left propulsion hydraulic system. The plumbing differences include the following:
- The charge pump in the right propulsion pump supplies oil to the left track tension manifold.
- The charge pump in the right propulsion pump supplies charge oil to the left feeder pump.
- The case drain line on the right propulsion pump is connected to port "L2". Case drain oil from the right propulsion pump is sent to port "L1" of the left feeder pump.
- Case drain oil from the right propulsion motor is sent to port "D" of the cooler bypass manifold.
- Port "A" of the right propulsion pump is connected to port "A" of the right propulsion motor. Port "B" of the right propulsion pump is connected to port "B" of the right propulsion motor.
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| Illustration 3 | g01393000 |
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Propulsion Hydraulic System (Forward) (1) Forward EDC (2) Reverse EDC (3) To right feeder pump (port "E" (4) Right track tension manifold (5) Relief valve (6) Backflow check valve (7) Needle valve (8) Right track tension cylinder (9) From auxiliary hydraulic system (10) Parking brake cylinder (11) EDC metering spool (12) Forward multifunction valve (13) Pressure limiter (14) Main relief valve (15) Makeup valve (16) Flushing relief valve (17) Flushing spool (18) Motor output shaft (19) Left propulsion pump (20) To right feeder pump case (port "L1") (21) From hydraulic tank suction return filter (22) Charge pump (23) Charge relief valve (24) Reverse multifunction valve (25) From auxiliary valve (port "FDS") (26) To port "B" (cooler bypass manifold) (27) Servo piston (28) Left propulsion motor | |
Note: Since the right and left propulsion circuits operate in the same manner, the following circuit description can be used to discuss either circuit. The left circuit is shown in the above illustration.
When the machine is traveling in the forward direction, the forward EDC is energized. The condition of the forward EDC is determined by the duty cycle of the signal that is sent from the machine ECM. The machine ECM analyzes the input signals in order to determine the magnitude of the output signal which is sent to the forward EDC.
Charge pressure flows across the forward EDC. This pressure acts against the EDC metering spool. The EDC metering spool moves, and charge oil is metered across the spool to the forward chamber of the servo piston. The charge oil causes the servo piston to shift. This shift changes the angle of the swashplate in the pump. Then, the pump generates flow in the forward circuit.
Forward circuit oil flows to the forward multifunction valve and flows to the forward side of the propulsion motor. Forward circuit oil in the forward multifunction valve closes the makeup valve, and then forward oil acts against the pressure limiter and the main relief valves. If the pressure differential between the forward circuit and charge circuit reaches
Oil in the forward circuit causes the motor to turn. After turning the motor, the pressure of the forward circuit oil is reduced. Oil at a reduced pressure then enters the reverse circuit. Reverse circuit oil flows to the following locations: the flushing valves, the reverse multifunction valve and the reverse side of the propulsion pump. The drive circuit is then complete.
Since reverse circuit oil is at a lower pressure than forward circuit oil, forward circuit oil causes the flushing valve to shift. This shift allows oil from the reverse circuit to act on the flushing relief valve. When the pressure that acts against the flushing valve is greater than the setting of the flushing relief valve, the flushing relief valve opens. When the flushing relief valve is open, a maximum of
Reverse circuit oil acts against the following: the makeup valve, the relief valve and the pressure limiter valve in the reverse multifunction valve. As the flushing valve removes oil from the reverse circuit, the pressure in the reverse circuit decreases. When the pressure in the reverse circuit is less than the pressure in the charge circuit, charge pressure unseats the makeup valve. Then, flow from the charge pump enters the reverse circuit. This action allows cool, filtered oil from the charge circuit to flush the propulsion circuit.
When the propulsion mode switch is in the PAVE position and the parking brake switch is in the OFF position, the machine ECM energizes the parking brake solenoid. Oil from the auxiliary pump is allowed to flow into the parking brake cylinder, and the servo piston chamber in each propulsion motor is open to the hydraulic tank. The pressure in the parking brake cylinder overcomes the spring forces, and the parking brake releases. Since the servo piston chamber is open to the hydraulic tank, the propulsion motor remains against the maximum displacement limiter. As a result, the machine operates in the pave speed range.
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| Illustration 4 | g01393012 |
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Propulsion Hydraulic System (Reverse) (1) Forward EDC (2) Reverse EDC (3) To right feeder pump (port "E" (4) Right track tension manifold (5) Relief valve (6) Backflow check valve (7) Needle valve (8) Right track tension cylinder (9) From auxiliary hydraulic system (10) Parking brake cylinder (11) EDC metering spool (12) Forward multifunction valve (13) Pressure limiter (14) Main relief valve (15) Makeup valve (16) Flushing relief valve (17) Flushing spool (18) Motor output shaft (19) Left propulsion pump (20) To right feeder pump case (port "L1") (21) From hydraulic tank suction return filter (22) Charge pump (23) Charge relief valve (24) Reverse multifunction valve (25) From auxiliary valve (port "FDS") (26) To port "B" (cooler bypass manifold) (27) Servo piston (28) Left propulsion motor | |
Note: The following circuit description can be used to discuss either the right or the left circuit.
When the machine is traveling in reverse, the reverse EDC is energized. The condition of the reverse EDC is determined by the duty cycle of the signal that is sent from the machine ECM. The machine ECM analyzes the input signals in order to determine the magnitude of the output signal. The machine ECM then sends this output signal to the reverse EDC.
Charge pressure flows across the reverse EDC and the charge pressure acts against the EDC metering spool. The EDC metering spool moves, and charge oil is metered across the spool to the reverse servo piston. The charge oil causes the reverse servo piston to shift. This shift changes the angle of the swashplate in the pump, and the pump generates flow in the reverse circuit.
While the machine is traveling in reverse, the following occurs: the reverse multifunction valve limits system pressure, oil from the forward circuit flows through the flushing relief valve and the makeup valve in the forward multifunction valve allows charge oil to flow into the forward circuit.
When the propulsion mode switch is in the TRAVEL position and the parking brake switch is in the OFF position, the machine ECM energizes the shift solenoid, and the machine ECM also energizes the parking brake solenoid. Oil from the auxiliary pump is directed into the parking brake cylinder and into the servo piston chamber in the propulsion motor. The pressure in brake cylinders overcomes the spring forces. This causes the parking brakes to release. The pressure in the servo piston chamber in each propulsion motor causes the rotating group in each motor to move against the minimum displacement limiter. Under these conditions, the machine operates in the travel speed range.