Main Hydraulic Schematic
 | |
| Illustration 1 | g01142861 |
(1) Right travel motor (2) Left travel motor (3) Right swing motor (4) Solenoid valve (swing parking brake) (5) Left swing motor (6) Stick cylinder (7) Boom cylinders (8) Master cylinder (9) Bucket cylinders (10) Bottom dump cylinders (11) Counterbalance valve (right) (12) Swivel (13) Counterbalance valve (left) (14) Swing control valve (15) Proportional reducing valve (16) Pilot relief valve (17) Valve (hydraulic activation) (18) Solenoid valve (hydraulic activation) (19) Accumulator (20) Main control valve (21) Travel speed solenoid valve (22) Pilot oil manifold (23) Bypass check valve (24) Boom drift reduction valve (25) True load signal port (26) Stick drift reduction valve (27) Back pressure valve (28) Duplicate load signal port (29) Pilot filter (30) Return filter (31) Pressure sensor for the front pump (32) Swing pump pressure sensor (33) Return filter (34) Case drain filter (35) Case drain filter (36) Fan motor (37) Hydraulic tank (38) Front pump (39) Rear pump (40) Pilot pump (41) Fan pump (42) Swing pump | |
Hydraulic Pump Flow and Pressure Control System
 | |
| Illustration 2 | g01143170 |
Pump compartment (38) Front pump (39) Rear pump (40) Pilot pump (41) Fan pump (42) Swing pump | |
 | |
| Illustration 3 | g01143171 |
Main control valve (43) Main control valve (boom side) (44) Main control valve (stick side) | |
This machine is driven and controlled by the following five systems:
- The main hydraulic system controls the cylinders and the travel motors.
- The swing hydraulic system controls the swing motors.
- The pilot hydraulic system supplies oil to the main pump and the control circuits.
- The electronic control system controls the outputs of the engine and pump.
- The separate cooling system supplies oil to the fan motor in order to cool the hydraulic oil.
The main hydraulic system delivers oil flow from front pump (38) and rear pump (39) in order to control the following components: right travel motor (1), left travel motor (2), stick cylinder (6), boom cylinders (7), master cylinder (8), bucket cylinders (9) and bottom dump cylinders (10) .
Front pump (38) and rear pump (39) are variable displacement piston pumps. The performance of the pumps is equal, and the pumps are arranged in series.
Front pump (38) is directly connected to the engine by a coupling. The front pump delivers oil to the center manifold of the main control valve.
Rear pump (39) is connected to the front pump. The rear pump delivers oil to the center manifold of the main control valve.
The oil delivery from both pumps is combined at main control valve (20) .
The pilot hydraulic system controls the output flow of the front pump and the rear pump.
 | |
| Illustration 4 | g01143172 |
Swing (3) Right swing motor (5) Left swing motor (14) Swing control valve | |
The swing hydraulic system delivers oil from the swing pump to right swing motor (3) and left swing motor (5) through swing control valve (14). The swing hydraulic system drives both motors. Swing pump (42) is mechanically connected to the reduction unit of the engine.
For more information concerning the operation of the swing hydraulic system, refer to Systems Operation, "Swing Hydraulic System".
 | |
| Illustration 5 | g01129884 |
Cab (45) Joystick (46) Joystick (47) Left travel pedal (48) Right travel pedal (49) Monitor | |
The pilot hydraulic system receives oil flow from pilot pump (40). The pilot hydraulic system controls the following functions:
- The pilot hydraulic system controls the operation of the implement control valves and the swing control valve.
Pilot oil flows from pilot pump (40) to main control valve (20) through pilot oil manifold (22). When the joysticks or pedals are operated, electrical signals activate the proportional valves at both ends of each implement valve spool in main control valve (20). Electrical signals also activate the proportional valves at each end of the valve spool in swing control valve (14) .
The pilot oil exerts pressure against the end of each spool. When joystick (45), joystick (46), travel pedal (47), and/or travel pedal (48) are operated, the electrical signals from the joysticks and/or travel pedals are sent to the machine electronic control module. The machine electronic control module sends an electrical signal to the proportional valves in the main control valve. An electrical signal is also sent to the proportional valves of the swing control valve.
When a proportional valve at one end of the valve spool is energized, the pilot pressure oil at that end of the valve spool drains to the hydraulic tank. The pilot pressure oil on the other end of the valve spool forces the valve spool toward the energized proportional valve. When the valve spool shifts, oil is delivered from front pump (38), rear pump (39), and/or swing pump (42) to the cylinders and motors.
In this way, pilot oil drives each circuit of the main control valve and the swing control valve.
- The pilot hydraulic system also controls the output flow of the main pumps.
Oil from the pilot pump changes to a signal pressure. This signal pressure is called power shift pressure. The power shift pressure controls the output flow of front pump (38) and rear pump (39) via proportional reducing valve (15). The power shift pressure is sent to the main pump regulators. Power shift pressure adjusts the output flow of the main pumps according to the load on the system.
- The signal pressure from the pilot hydraulic system is also used to perform the following operations:
- Pilot signal pressure releases the swing parking brake.
- Pilot signal pressure automatically changes the travel speed to either HIGH or LOW according to the system load.
- Pilot signal pressure changes the delivery pressure of the main pump according to the usage of the machine (travel mode or work mode).
For more information concerning the pilot hydraulic system, refer to Systems Operation, "Pilot Hydraulic System".
 | |
| Illustration 6 | g01143173 |
Pump compartment (41) Fan pump (50) Proportional reducing valve | |
Fan pump (41) drives the separate hydraulic cooling fan and motor. The fan pump is a variable displacement piston pump. When the oil temperature changes, an electrical signal is sent from the machine electronic control module to proportional reducing valve (50) for the fan pump. The operation of the proportional reducing valve causes the delivery of oil from the fan pump to vary. The rotational speed of the fan motor varies accordingly.