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| Illustration 1 | g06585720 |
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Pilot hydraulic schematic (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 retract solenoid (7) Bucket 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) Swing right solenoid (16) Swing left 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) Travel speed pilot line (35) Pilot manifold (36) Main control valve pilot line (37) Pilot line (38) Check valve (39) Pilot pump | |
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| Illustration 2 | g06611449 |
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Pilot manifold (25) Swing brake solenoid (26) Stick 2 cut solenoid (29) Hydraulic lock solenoid (32) Heavy lift solenoid (33) Travel speed solenoid (35) Pilot manifold | |
Oil from pilot pump (39) supplies pilot manifold (35) with pilot oil. The pilot oil flows directly to travel speed solenoid (33), stick 2 cut solenoid (26), and hydraulic lock solenoid (29) in the pilot manifold. Pilot oil simultaneously flows out of the pilot manifold to bypass cut solenoid 1 (2) and bypass cut solenoid 2 (3) in the main control valve, pilot accumulator (31), and pump pilot line (30). The pump pilot line provides pilot oil for the pump actuator solenoids.
No other path for pilot oil exists when the hydraulic lock solenoid is not energized. When the hydraulic control lever in the cab is shifted to the UNLOCKED position, the machine ECM energizes the hydraulic lock solenoid. Pilot oil now flows through the solenoid valve and shifts spool (24). With the spool shifted, a path now exists for pilot oil to flow to swing brake solenoid (25) and heavy lift solenoid (32). Oil also flows out to passage (36) and into the main control valve for the remaining travel and implement solenoids to use. Oil also flows out of the pilot manifold to pilot and drain manifold (23).
External Pilot Control Valve Circuits
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| Illustration 3 | g06613873 |
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External pilot circuits (1) Main control valve (23) Pilot and drain manifold (27) Swing brake pilot line (30) Pump pilot line (31) Pilot accumulator (34) Travel speed pilot line (36) Main control valve pilot line (37) Pilot line (39) Pilot pump (40) Pump assembly (41) Swivel (42) Swing motors (43) Heavy lift pilot line | |
When the hydraulic control lever is placed in the UNLOCKED position, pilot oil in flows through hydraulic lock solenoid (29) to provide oil to swing brake solenoid valve (25). When any of the joysticks are moved from the NEUTRAL position, the joystick sends an electrical signal to machine ECM. An electrical signal from the machine ECM energizes the swing brake solenoid valve. Pilot oil flows to the swing brakes inside swing motors (42). This oil releases the swing brakes.
For more information concerning the operation of the swing brakes, refer to Systems Operation, "Pilot Valve (Swing Parking Brake)".
Automatic Travel Speed Change Valve
When the travel speed switch on the right console is set to the HIGH SPEED position, travel speed solenoid valve (33) is energized by the ECM. This action allows pilot oil to flow through the travel speed solenoid valve and through swivel (41) to the displacement change valves in the travel motors.
With the displacement change valves activated, the swashplates in the motors move to the minimum angle. This action causes the travel motors to operate at high speed.
For more information concerning the operation of the displacement change valves, refer to Systems Operation, "Displacement Change Valve".
Machines that are equipped with heavy lift have a high-pressure setting and a low-pressure setting for the main relief valve. When heavy lift is active the ECM activates a solenoid valve. The solenoid valve directs pilot oil pressure through pilot line (43) to the pilot oil port on the main relief valve. The pilot oil pressure is ported through the valve to move a piston that creates a higher spring force on the main relief valve. The increase of spring force on the main relief valve causes the relief pressure in the main hydraulic system to rise.
For more information concerning the operation of the heavy lift system, refer to Systems Operation, "Relief Valve (Main) (Heavy Lift)".
Pump Displacement Actuation Circuit
The pilot system provides oil to the pump actuators. When the ECM activates the pump solenoids, the solenoids provide a path for pilot oil to flow to the displacement actuators to upstroke the pump and create more flow.
An accumulator in the pilot circuit helps maintain constant flow to the pump. The accumulator ensures that the pumps have sufficient pilot oil to stroke the pump during all conditions.
For more information concerning the operation of the pump actuators, refer to Systems Operation, "Pump Control (Main Hydraulic)".