CAP 8D4283 - Caterpillar

Hydraulic Pump Flow and Pressure Control System
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Pump compartment (36) Front pump (37) Rear pump (38) Pilot pump (39) Fan pump (40) Swing pump
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Main control valve (41) Main control valve (boom side) (42) Main control valve (stick side)This machine is driven and controlled by the following five systems:
The main hydraulic system controls the cylinders and the travel motors.
The swing hydraulic system controls the swing motors.
The pilot hydraulic system supplies oil to the main pump and the control circuits.
The electronic control system controls the outputs of the engine and pump.
The separate cooling system supplies oil to the fan motors in order to cool the engine coolant and hydraulic oil.The main hydraulic system delivers oil flow from front pump (36) and rear pump (37) in order to control the following components: bucket cylinder (6), stick cylinder (7), boom cylinder (8), right travel motor (1) and left travel motor (2) .Front pump (36) and rear pump (37) are variable displacement piston pumps. The performance of the pumps is equal, and the pumps are arranged in series.Front pump (36) is directly connected to the engine by a coupling. The front pump delivers oil to the center manifold of the main control valve.Rear pump (37) is connected to the front pump. The rear pump delivers oil to the center manifold of the main control valve.The oil delivery from both pumps is combined at main control valve (18) .The pilot hydraulic system controls the output flow of the front pump and the rear pump.
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(5) Front swing motor
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(3) Rear swing motor (12) Swing control valveThe swing hydraulic system delivers oil from the swing pump to rear swing motor (3) and front swing motor (5) through swing control valve (12). The swing hydraulic system drives both motors. Swing pump (40) is mechanically connected to the reduction unit of the engine.For more information concerning the operation of the swing hydraulic system, refer to Systems Operation, "Swing Hydraulic System".
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Cab (43) Joystick (44) Joystick (45) Left travel pedal (46) Right travel pedal (47) MonitorThe pilot hydraulic system receives oil flow from pilot pump (38). The pilot hydraulic system controls the following functions:
The pilot hydraulic system controls the operation of the implement control valves and the swing control valve.Pilot oil flows from pilot pump (38) to main control valve (18) through pilot oil manifold (20). When the joysticks or pedals are operated, electrical signals activate the proportional valves at both ends of each implement valve spool in main control valve (18). Electrical signals also activate the proportional valves at each end of the valve spool in swing control valve (12) .The pilot oil exerts pressure against the end of each spool. When joystick (43), joystick (44), travel pedal (45), and/or travel pedal (46) are operated, the electrical signals from the joysticks and/or travel pedals are