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| Illustration 1 | g06613804 |
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Main hydraulic system (1) Main control valve (23) Pilot and drain manifold (31) Pilot accumulator (40) Return port (47) Boom cylinders (48) Swing motor (right) (49) Swing motor (left) (50) Left travel motor (51) Right travel motor (52) Swivel (53) Bucket cylinder (54) Stick cylinder (55) Hydraulic tank (56) Pump 2 (57) Pump 1 (58) Pump 2 pressure sensor (59) Pump 1 pressure sensor (60) Fan pump 1 (61) Fan motor 1 (62) Fan pump 2 (63) Fan motor 2 (64) Charge pump (65) Swing pump | |
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| Illustration 2 | g06481104 |
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Main hydraulic system - Main control valve (1) Main control valve (2) Bypass cut solenoid 1 (3) Bypass cut solenoid 2 (4) Stick 2 extend solenoid (5) Stick 2 retract solenoid (6) Bucket 1 retract solenoid (7) Bucket 1 extend solenoid (8) Boom retract solenoid (9) Boom extend solenoid (10) Right travel reverse solenoid (11) Right travel forward solenoid (12) Straight travel solenoid (13) Left travel forward solenoid (14) Left travel reverse solenoid (15) Bucket 2 retract solenoid (16) Bucket 2 extend solenoid (17) Boom 2 extend solenoid (18) Boom 2 retract solenoid (19) Auxiliary retract solenoid (20) Auxiliary extend solenoid (21) Stick 1 retract solenoid (22) Stick 1 extend solenoid (23) Pilot and drain manifold (24) Spool (25) Swing brake solenoid (26) Stick 2 cut solenoid (27) Swing brake pilot line (28) Stick 2 cut pilot line (29) Hydraulic lock solenoid (30) Pump pilot line (31) Pilot accumulator (32) Heavy lift solenoid (33) Travel speed solenoid (34) Main relief valve (35) Pilot manifold (36) Main control valve pilot line (37) Passage (38) Passage (39) Pilot pressure reducing valve (40) Return port (41) Bucket cylinder head end pressure sensor (42) Bucket cylinder rod end pressure sensor (43) Boom cylinder head end pressure sensor (44) Boom cylinder rod end pressure sensor (45) Stick cylinder head end pressure sensor (46) Stick cylinder rod end pressure sensor | |
Assist provides several functions to the operator for ease of use and protection against damage to surrounding assets. These features include:
- Boom Assist - Raises the boom automatically during stick operation when boom head pressure is low or stick rod/head pressure is high. Limits boom down operation when boom head pressure is low.
- Bucket Assist - The system automatically maintains bucket angle relative to the machine. This feature helps reduce operator fatigue and improves productivity.
- Grade Assist - Automatically raises the boom to adjust the bucket height to the target line to prevent over-cutting of the target line.
- 2D E- fence Ceiling - Prevents the implement from raising past a predefined height as entered by the operator. This feature is useful when operating around overhead structures, power lines, and bridges.
- 2D E- fence Floor - Prevents the implement from lowering past a predefined depth as entered by the operator. This feature is useful when operating around underground utilities.
- 2D E- fence Wall - Prevents the implement from reaching past a predefined distance as entered by the operator. This feature is useful when operating around structures in the front of the machine.
- CAB Avoidance - Prevents the implement from coming within a certain area of the cab as entered by the operator.
- 2D E- fence Swing Left/Right - Prevents the machine from swinging to the left/right past a certain angle as entered by the operator. This feature helps the operator from swinging into nearby structures or vehicles like a loading truck.
- Swing Assist Left - The machine will swing to the left and automatically stop at a certain angle as entered by the operator.
- Swing Assist Right - The machine will swing to the right and automatically stop at a certain angle as entered by the operator.
Hydraulic Pump Flow and Pressure Control System
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| Illustration 3 | g06616672 |
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(56) Pump 2
(57) Pump 1 (58) Pump 2 pressure sensor (59) Pump 1 pressure sensor (B) Suction port (Dr1) Case drain port (Dr3) Case drain port (P1) Pump 1 outlet (P2) Pump 2 outlet (Psv) Pilot oil inlet (PH1) Pump 2 pressure tap (PH2) Pump 1 pressure tap | |
This machine is driven and controlled by the following systems:
- The main hydraulic system controls the cylinders and the travel motors.
- The pilot hydraulic system supplies oil to the main control valve, the swing brake, and the travel motors.
- The swing hydraulic system controls the swing motor.
- The electronic control system controls the outputs of the engine, pumps, and main control valve.
- The separate cooling system supplies oil to the fan motors in order to cool the hydraulic oil temperature.
The main hydraulic system delivers oil flow from pump 1 (57) and pump 2 (56) to control the following components: bucket cylinder, stick cylinder, boom cylinders, right travel motor, and left travel motor.
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| Illustration 4 | g06613807 |
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Main control valve (1) Main control valve body (34) Main relief valve | |
Pump 1 and pump 2 are variable displacement piston pumps. The performance of both pumps is equal.
Pump 2 is directly connected to the engine by a flexible coupling. Pump 1 is mechanically connected to pump 2. The pumps deliver oil to main control valve body (1). Pump 1 delivers oil to the right travel control valve, the boom 1 control valve, the bucket 1 control valve, and the stick 2 control valve. Pump 2 delivers oil to the left travel control valve, the boom 2 control valve, the bucket 2 control valve, and the stick 1 control valve. All engine output is used to drive these two pumps.
As the load pressure increases during working conditions, the pumps increase the delivery pressure and the pumps decrease the flow rate. The hydraulic horsepower remains constant even though the delivery pressure and the flow rates change. The hydraulic horsepower is identical to the engine horsepower.
When no work is being performed, pump oil flows through main control valve (1) and into hydraulic tank (55).
If work is being performed, main control valve directs pump oil to the respective cylinders (boom, bucket, and stick) and/or motors (travel). Main control valve contains numerous valve stems, passages, check valves, orifices, and electronic solenoids to perform a single operation or a combined operation. The working pressure of the main hydraulic system is regulated by main relief valve (34).
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| Illustration 5 | g06358398 |
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Cab (74) Cat Grade Control monitor (if equipped) (75) Monitor (76) Engine speed dial (77) Joystick (bucket and boom) (78) Joystick (stick and swing) (79) Left travel lever/pedal (80) Right travel lever/pedal | |
The pilot hydraulic system receives oil flow from pilot pump (64). The pilot hydraulic system controls the following functions.
- The pilot hydraulic system controls the operation of the implement control valves.
Pilot oil flows from pumps through the hydraulic lock solenoid. The pilot oil then flows to the control valves for machine operation (implement operation, swing operation, and travel). These pilot control valves are controlled by the ECM.
When left joystick (77), right joystick (78), left travel lever/pedal (79) and/or right travel lever/pedal (80) are moved from the NEUTRAL position, the pilot oil flows through the control valves to the corresponding spools at the main control valve.
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 pump 1 or pump 2 to the cylinder or motor that is controlled by the shifted spool.
Thus, pilot oil drives each system of the main control valve.
- The pilot hydraulic system generates signal pressure to perform the following operations.
- 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 pressure is used by the pump actuators to stroke the pump.
- 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".