Main Hydraulic Schematic
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| Illustration 1 | g00786713 |
(1) Swing motor (2) Left travel motor (3) Right travel motor (4) Stick cylinder (5) Boom cylinders (6) Bucket cylinder (7) Swivel (8) Main control valve (9) Implement pressure switch (10) Pilot control valve (travel) (11) Main relief valve (12) Pilot control valve (swing and stick) (13) Pilot control valve (boom and bucket) (14) Shuttle valve (15) Travel pressure switch (16) Boom priority pressure reducing valve (17) Bypass check valve (18) Slow return check valve (19) Swing brake solenoid valve (20) Valve (21) Hydraulic activation solenoid valve (22) Pressure sensor (23) Oil cooler (24) Accumulator (25) Left pump (26) Pilot pump (27) Right pump (28) Travel speed solenoid valve (29) Pilot relief valve (30) Pilot manifold (31) Hydraulic tank (32) Drain filter (33) Pilot filter (34) Pressure sensor | |
Hydraulic Pump Flow
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| Illustration 2 | g00786714 |
Pump compartment (25) Left pump (26) Pilot pump (27) Right pump (35) Outlet line (left pump) (36) Outlet line (right pump) | |
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| Illustration 3 | g00802786 |
Control valve (11) Main relief valve (37) Left side of the control valve body (38) Right side of the control valve body | |
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 pump.
The main hydraulic system delivers oil flow from left pump (25) and right pump (27) in order to control the following components: bucket cylinder (6), stick cylinder (4), boom cylinders (5), right travel motor (3), left travel motor (2) and swing motor (1) .
Left pump (25) and right pump (27) are variable displacement piston pumps. The performance of both pumps is equal.
Right pump (27) is directly connected to the engine by a flexible coupling. The right pump delivers oil to the right side (38) of the control valve body of the main control valve. Left pump (25) is mechanically connected to the right pump through gears. The left pump delivers oil to the left side (37) of the control valve body of the main control valve. Gear type pilot pump (26) supplies oil to the pilot hydraulic system. Gear type pilot pump (26) is directly connected to left pump (25) by a coupling. All engine output is used to drive these three pumps.
As the load pressure increases during working conditions, the 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.
When no work is being performed, pump oil flows through main control valve (8) back to hydraulic tank (31). 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 (8) directs pump oil to the respective cylinders (boom, bucket, and stick) and/or motors (swing and travel). Main control valve (8) contains numerous valve stems, passages, check 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 (11) .
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 (29) .
For more information concerning the pilot hydraulic system, refer to Systems Operation, "Pilot Hydraulic System".