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| Illustration 1 | g00685732 |
Main Hydraulic System (1) Diverter valve (2) Quick coupler cylinder (4) Signal relief valve (5) Bank valve (7) Work tool cylinder (8) Implement section of bank valve (right side stabilizer cylinder) (9) Implement section of bank valve (left side stabilizer cylinder) (11) Stabilizer cylinder (right side) (12) Stabilizer cylinder (left side) (13) Load control valve (left side stabilizer cylinder) (14) Load control valve (right side stabilizer cylinder) (15) End section of bank valve (17) Joystick (20) Inlet section of bank valve (21) Implement section of bank valve (boom extend/retract) (22) Pilot control valve (23) Solenoid valve (24) Solenoid valve (25) Solenoid valve (26) Solenoid valve (differential lock valve) (30) Hydraulic tank (31) Piston pump (32) Filter (33) Outlet section of bank valve (34) Metering pump (35) Load sensing line (36) Compensating cylinders (37) Implement section of bank valve (boom raise/lower) (38) Load control valve for boom cylinder (extend /retract) (39) Boom cylinder (boom raise/ lower) (40) Implement section of the bank valve (coupler tilt) (41) Load control valve (boom raise/lower) (44) Telescoping cylinder (boom extend/retract) (45) Implement section of bank valve (auxiliary section) (46) Control valve for frame level (47) Control valve (compensating cylinders) (48) Load control valve for frame leveling cylinder (49) Frame leveling cylinder (50) Load control valve (coupler tilt) (51) Tilt cylinder (coupler tilt) | |
The piston pump (31) is mounted onto the transmission case. The pump has permanent drive. The pump output is controlled by maximum implement pressure, or by maximum steering pressure.
Bank valve (5) is a directional control valve that consists of the following sections:
- Inlet section (20)
- Implement sections (8), (9), (21), (37), (40), and (45)
- End section (15)
- Outlet section (33)
A flow control valve is installed in inlet section (20). This ensures that the steering system has oil flow priority.
Load signal system resolver valves are connected to the pressure and flow compensator valve on the pump through load sensing line (35). The highest system pressure controls the pump output. All implement sections are operated by joystick (17) except for the following sections: implement section (8) and implement section (9) for the stabilizer cylinders.
Implement section (37) is pilot operated and controls oil flow to boom cylinder (39). Load control valve (41) locks oil into the piston side of the cylinder when the boom cylinder is stationary. The load control valve also regulates the cylinder speed when the boom is being lowered.
Implement section (21) is pilot operated and controls oil flow to telescoping cylinder (44). When the telescoping cylinder is stationary, oil is locked into the piston and rod sides by load control valve (38). The load control valve also regulates the speed of the telescoping cylinder when the boom is being retracted.
Implement section (40) is pilot operated. The implement section controls oil flow to tilt cylinder (51) in order to tilt the quick coupler. Load control valve (50) locks oil into the piston side of the cylinder when the tilt cylinder is stationary. The load control valve also regulates the cylinder speed when the quick coupler is being tilted forward.
The compensating cylinders (36) extend when the boom is being raised. When the boom is being lowered the compensating cylinders retract. The flow of oil between the compensating cylinders and tilt cylinder (51) maintains the selected angle of the quick coupler. Control valve (47) regulates the pressure that acts on the piston sides of the compensating cylinders when the quick coupler is being tilted back.
Implement section (45) is operated by solenoids and controls oil flow to diverter valve (1) on the boom head. The diverter valve can supply the quick coupler cylinder (2) or a work tool cylinder (7).
A pressure reducing valve which supplies oil flow to the joystick and to pilot control valve (22) is installed in end section (15). Signal relief valve (4) that controls maximum pressure in the load signal system is also installed in the end section.
Oil returns to hydraulic tank (30) from outlet section (33).
Note: The steering system and the piston pump (implement and steering) are described in System Operation, Testing and Adjusting, SENR1237, "Steering System".
Pilot control valve (22) consists of solenoid valve (26) for control of the differential lock and solenoid valves (23), (24), and (25) for control of pilot oil.
Note: The brake system is described in System Operation, Testing and Adjusting, SENR1238, "Brake System".
Solenoid valve (26) for control of the differential lock is controlled by a switch that is mounted in the cab. When the solenoid valve is energized, pilot pressure is transmitted to differential lock cylinder in the front axle in order to engage the differential lock. The differential lock is disengaged by spring force when the solenoid valve is de-energized.
Solenoid valves (23), (24) and (25) are controlled by switches in joystick (17). When the switches are released the solenoid valves de-energize.
In order to level the machine frame on uneven ground, the machine frame can be angled to the left or to the right by the frame leveling cylinders. The angle of the machine is in relation to the axles of the machine. The frame leveling cylinder is equipped with a double acting lock valve (48). The frame leveling control valve (46) is directly operated by solenoids. The solenoids are controlled by a three-position switch that is located on the right hand instrument panel.
Implement section (8) and implement section (9) operate stabilizer cylinder (11) and stabilizer cylinder (12). When the stabilizer cylinders are stationary, load control valve (13) and load control valve (14) hold the oil in both sides of the stabilizer cylinder.
Note: Refer to Operation and Maintenance Manual, SEBU7017, "Operation Section" and Operation and Maintenance Manual, SEBU7111, "Operation Section" for information regarding control arrangements.