Main Hydraulic Schematic
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| Illustration 1 | g01205453 |
(1) Swing motor (2) Left travel motor (3) Right travel motor (4) Blade cylinders (5) Stick cylinder (6) Boom cylinders (7) Bucket cylinder (8) Blade control valve (9) Swivel (10) Main control valve (11) Implement pressure switch (12) Pilot control valve (travel) (13) Pilot control valve (blade) (14) Main relief valve (15) Pressure switch (16) Shuttle valve (17) Travel pressure switch (18) Pressure reducing valve (boom priority) (19) Accumulator (20) Valve (21) Hydraulic activation solenoid valve (22) Pilot manifold (23) Pilot control valve (swing and stick) (24) Travel speed solenoid valve (25) Left pump (26) Right pump (27) Pilot pump (28) Blade pump (29) Pilot control valve (boom and bucket) (30) Oil cooler (31) Slow return check valve (32) Bypass check valve (33) Hydraulic tank (34) Drain filter (35) Pilot relief valve (36) Pilot filter (37) Pressure sensor | |
Hydraulic Pump Flow
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| Illustration 2 | g00788857 |
Pump compartment (25) Left pump (26) Right pump (27) Pilot pump (28) Blade pump | |
This machine is driven and controlled by the following systems:
- The main hydraulic system controls the cylinders, the travel motors, and the swing motor.
- The pilot hydraulic system supplies oil to the main pumps, the main control valve, the swing brake, and the travel motors.
- The electronic control system controls the outputs of the engine and the pump.
The left pump (25) and right pump (26) send hydraulic fluid to the main hydraulic system. The left pump and the right pump are variable displacement pumps that have equal performance.
The right pump is directly connected to the engine by a flexible coupling. The pumps are arranged parallel to each other. The gear type pilot pump (27) supplies oil to the pilot hydraulic system. All engine output is used to drive these three pumps.
As the load pressure increases during working conditions, the pump delivery pressure increases and the oil flow rate decreases. The hydraulic horsepower remains constant even though the delivery pressure and the flow rates change. The hydraulic horsepower is approximately identical to the engine horsepower.
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| Illustration 3 | g00802086 |
Main control valve (14) Main relief valve (43) Front body (44) Rear body | |
Hydraulic oil flows from the main pumps to front body (43) and rear body (44) of the main control valve. When no work is being performed, pump oil flows through the main control valve back to hydraulic tank (33). The main control valve sends a negative flow control signal to each main pump regulator in order to destroke the pump to the minimum output flow.
If an operation is being performed, main control valve (10) directs pump oil to the respective cylinders (boom, bucket, and stick) and/or motors (swing and travel). Main control valve (10) contains numerous valve stems, passages, relief valves, and orifices in order to carry out a single operation or a combined operation. The working pressure of the main hydraulic system is regulated by main relief valve (14) .
The oil flow from the pilot pump is constant as the oil enters the pilot system. The maximum pressure of the pilot system is regulated by the pressure setting of pilot relief valve (35). The pressure in the pilot system is limited to 4100 kPa (595 psi).
For more information concerning the pilot hydraulic system, refer to Systems Operation, "Pilot Hydraulic System".