Hydraulic Schematic for Pilot Oil
(1) Solenoid valve (swing parking brake)
(2) Swing parking brake
(3) Swing parking brake
(4) Left travel motor
(5) Right travel motor
(6) Boom lowering control valves
(7) SmartBoom valve
(8) Boom drift reduction valve
(9) Pressure switch (boom raise operation)
(10) Stick drift reduction valve
(11) Pressure switch (implement and swing)
(12) Pressure switch (travel)
(13) Logic valve
(14) Left travel control valve
(15) Straight travel control valve
(16) Right travel control valve
(17) Boom control valve
(18) Main control valve
(19) Pilot control valve (left and right travel)
(20) Pressure control valve
(21) Main relief valve
(22) Pilot control valve (stick and swing)
(23) Pilot filter
(24) Hydraulic activation control valve
(25) Upper pump
(26) Pilot manifold
(27) Pilot control valve (boom)
(28) Lower pump
(29) Solenoid valve (levelling)
(30) Travel speed solenoid valve
(31) Solenoid valve (trenching)
(32) Proportional reducing valve
(33) Pilot relief valve
(34) Pilot pump
Pilot pump (34) supplies a constant flow of oil to the pilot circuit. The pilot relief valve is set for a maximum oil pressure of 4410 to 4900 kPa (640 to 710 psi).
Pilot Oil Circuits
Pilot system oil from pilot pump (34) has the following three main functions:
- Control main pump output.
- Operate the main control valves.
- Create pilot signal pressure in order to achieve various operations.
The pilot oil from pilot pump (34) passes through pilot filter (23). The oil then enters pilot oil manifold (26). The manifold directs the oil into the following circuits:
- Proportional reducing valve circuit (power shift system)
- Pilot control valve circuits
- Main control valve circuit
- Swing parking brake release circuit
- Logic valve circuit
- Travel speed solenoid valve circuit
Proportional Reducing Valve Circuit (Power Shift System)
Pilot oil flows to proportional reducing valve (32). The proportional reducing valve changes the pilot oil into a hydraulic signal. This signal is called power shift pressure. The hydraulic signal pressure goes to the regulators of the main pumps. The regulators control the pump output flow.
Pilot Control Valve Circuits
The pilot control valve circuits direct pilot pump oil to hydraulic activation control valve (24). Pilot oil goes to the following pilot control valves: left and right travel (19), stick and swing (22) and boom (27) .
When a pilot control valve is operated, pilot oil goes to the main control valve that is selected. The pilot oil shifts the stem of the selected main control valve in order to operate a cylinder and/or a motor.
Circuit for Main Control Valve
Pilot oil to the main control valve flows to pressure switches (11) and (12) .
Travel pressure switch (12) is installed on main control valve (18). An increase in pilot oil pressure causes pressure switch (12) to change to the ON position. When the machine does not travel, the pilot oil pressure is low and switch (12) is OFF. The signal from switch (12) is sent to the electronic controller. The electronic controller processes the signal from pressure switch (12) and the signal from switch (11) so that the automatic engine speed control (AEC) will function.
The pilot oil pressure increases when the right and left control valves are operated at the same time. The pressure increase also activates straight travel control valve (15) so the machine can travel during a combined operation.
Note: For more information, refer to Systems Operation/Testing and Adjusting, "Travel Hydraulic System".
When a swing motor and/or implement control is operated, the pilot oil pressure increases. The increased oil pressure changes pressure switch (11) to "ON". When no implement and swing controls are operated, the pilot oil pressure remains low, and the pilot oil pressure does not activate pressure switch (11) .
Note: For more information on pressure switch (11) and pressure switch (12), refer to Systems Operation, "Engine and Pump Electronic Control System".
Swing Parking Brake Release Circuit
The circuit for the swing parking brake release releases the brake during implement operation and/or swing operation. Solenoid valve (1) is normally in the CLOSED position. Pilot oil from pilot manifold (26) flows through hydraulic activation control valve (24) to solenoid valve (1). When the implement controls and/or swing controls are operated, the increase in pilot oil pressures causes solenoid valve (1) to change to the OPEN position. Pilot oil then flows through solenoid valve (1) to swing parking brake (2). This releases the swing parking brake.
Note: For more information, refer to Systems Operation, "Pilot Valve (Swing Parking Brake)".
Logic Valve Circuit
Pilot oil passes through solenoid valve (13) to pressure control valve (20). Pressure control valve (20) activates to open logic valve (13). Upper pump oil then flows to the swing circuit and the stick circuit.
Note: For more information on the logic valve, refer to Systems Operation, "Combined Function Hydraulic Operation".
Travel Speed Solenoid Valve Circuit
Pilot oil flows to travel speed solenoid valve (30). When the switch for travel is placed in the HIGH SPEED (RABBIT) position, travel speed solenoid valve (30) opens. The pilot oil flows through travel speed solenoid valve (30) to the travel brake valves.
Note: For more information, refer to Systems Operation, "Travel Hydraulic System".