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| Illustration 1 | g06010562 |
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(1) Left travel motor
(2) Right travel motor (3) Swing motor (4) Stick cylinder (5) Boom cylinders (6) Pressure sensor (boom head end) (7) Bucket cylinder (8) Pilot control valve (travel) (9) Swivel (10) High-pressure solenoid (11) Main control valve (12) Pilot control valve (swing and stick) (13) Pilot control valve (boom and bucket) (14) Main relief valve (15) Pressure sensor (idler pump) (16) Pressure sensor (drive pump) (17) Pressure reducing valve for boom priority (18) Bypass check valve (19) Oil cooler (20) Slow return check valve (21) Pressure sensor (boom down control) (22) Implement pressure switch (23) Pressure sensor (swing control) (24) PRV for boom regeneration (25) Travel speed solenoid valve (26) Swing brake solenoid valve (27) Valve (28) Hydraulic activation solenoid valve (29) Accumulator (30) Drain filter (31) Pilot manifold (32) Pilot filter (33) Pilot relief valve (34) Hydraulic tank (35) Drive pump (36) Pilot pump (37) Idler pump (38) Proportional reducing valve (power shift pressure) (39) Negative Flow Control Valve | |
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| Illustration 2 | g06010166 |
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Pump compartment (35) Drive pump (36) Pilot pump (37) Idler pump (40) Outlet line (idler pump) (41) Outlet line (drive pump) | |
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| Illustration 3 | g06008286 |
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Control valve (14) Main relief valve (42) Left side of the control valve body (43) 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 Machine ECM controls the outputs of the engine and pump.
The main hydraulic system delivers oil flow from idler pump (37) and drive pump (35) in order to control the following components: bucket cylinder (7), stick cylinder (4), boom cylinders (5), right travel motor (2), left travel motor (1) and swing motor (3).
Idler pump (37) and drive pump (35) are variable displacement piston pumps. The performance of both pumps is equal.
Drive pump (35) is directly connected to the engine by a flexible coupling. The drive pump delivers oil to the right side (43) of the control valve body of the main control valve. Idler pump (37) is mechanically connected to the drive pump through gears. The idler pump delivers oil to the left side (42) of the control valve body of the main control valve. Pilot pump (36) supplies oil to the pilot hydraulic system. Pilot pump (36) is directly connected to drive pump (35) 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 (11) back to hydraulic tank (34). 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 (11) directs pump oil to the respective cylinders (boom, bucket, and stick) and/or motors (swing and travel). Main control valve (11) 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 (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 (33).
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| Illustration 4 | g06008268 |
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Cab (44) Monitor panel (45) Joystick (stick and swing) (46) Joystick (bucket and boom) (47) Left travel lever/pedal (48) Right travel lever/pedal (49) Engine speed dial | |
The pilot hydraulic system receives oil flow from pilot pump (36). The pilot hydraulic system controls the following functions.
- The pilot hydraulic system controls the operation of the implement control valves.
Pilot oil flows from pilot pump (36) through pilot manifold (31). The pilot oil then flows to the pilot control valves for machine operation (implement operations, swing operations, and travel operation). These pilot control valves are activated by the joysticks and the travel levers/pedals.
When joystick (45), joystick (46), left travel lever/pedal (47), and/or right travel lever/pedal (48) are moved from the NEUTRAL position, the pilot oil flows through the pilot control valves to the corresponding spools at the main control valve (11).
The pilot pressure oil at that end of the valve spool forces the valve spool to shift. The pilot oil on the other end of the valve spool drains to the hydraulic tank. When the valve spool shifts, oil is then delivered from idler pump (37) or drive pump (35) to the cylinders and motors.
Thus, pilot oil drives each system of the main control valve.
- The pilot hydraulic system controls the output flow of the main pumps.
During machine operation, pilot pressure is sent to the main pump regulators as a signal pressure. This signal pressure is called power shift pressure. The machine ECM receives input signals from various components on the machine. The machine ECM processes the input signals. The machine ECM then sends an electrical signal to proportional reducing valve (38) in order to regulate the power shift pressure. The power shift pressure controls the output flow of idler pump (37) and drive pump (35). Power shift pressure adjusts the output flow of the main pumps in accordance with the engine speed. For more information concerning power shift pressure, refer to Systems Operation, "Pilot Hydraulic System".
- The pilot hydraulic system generates signal pressure in order to perform the following operations.
- Pilot signal pressure activates the Automatic Engine Speed Control (AEC) system. This action causes functions to automatically reduce the engine speed when no hydraulic operation is called for.
- Pilot signal pressure releases the swing parking brake.
- Pilot signal pressure will automatically change the travel speed to either HIGH or LOW in accordance with the hydraulic system load.
- Pilot signal pressure operates the straight travel control valve. This action maintains straight travel during the operation of an implement.
- Pilot signal pressure controls the operation of the valves that can be used during a loading operation or a trenching operation.
For more information concerning the pilot hydraulic system, refer to Systems Operation, "Pilot Hydraulic System".