CYLINDER HEAD GP 4155586 - Caterpillar

Illustration 1 g02495642
(1) Hydraulic oil cooler (2) Hydraulic oil cooler bypass valve (3) Steering charge circuit filter (4) Cold start valve (5) Pump control valve (6) Steering motor (7) Flushing valve (8) Charge pump (9) Pressure over-ride valve (10) Charge pressure relief valve (11) Crossover relief and makeup valves (12) Pump control piston (13) Steering pumpWhile both the steering and implement hydraulic systems are separate systems, the two systems share a common hydraulic tank. The steering system and the implement system are fed from the same suction line. The case drain lines from the steering system and the case drain line from the implement pump are connected. These lines share a common filter and a common inlet port to the tank.The steering hydraulic circuit is made up of the following separate hydraulic circuits:
Charge Circuit
Steering Closed LoopIn the charge circuit, steering charge pump (8) produces charge oil that is used by steering pump (13). Steering charge pump (8) also produces pilot oil for the implement control valve. This charge pressure oil is also used by steering pump control valve (5) to direct oil to the actuator piston for the pump. This piston controls the angle of the pump swashplate.The steering closed loop is made up of steering pump (13) and steering motor (6). Steering pump (13) creates flow in the high side of the steering loop. The flow causes steering motor (6) to turn. Oil then flows out of steering motor (6) to the low-pressure side and to the input side of the steering pump. As a result, this oil remains trapped in the closed loop circuit.Some of the oil is lost in the steering closed loop through leakage and through the flushing valve on steering motor (6). The flushing valve diverts oil for lubrication and cooling of the internal components of the steering motor. The lost oil is replaced by the charge circuit through makeup valves.Steering motor (6) converts the oil flow from the steering pump into rotary motion that turns the steering differential. The speed and direction of the motor controls the rate of the turn and the direction of the turn by the machine.Steering pump (13) can produce flow in either direction. The amount of flow and the direction of flow determine the rotation of steering motor (6) .The steering control lever sends an electrical signal to the power train Electronic Control Module (ECM). The power train ECM sends an electrical signal to the appropriate solenoid on steering pump control valve (5). The steering pump control valve directs reduced charge oil pressure in order to move the actuator piston. The actuator piston moves the swashplate to an amount that is directly proportional to the original input signal from the steering control lever. Also, the actuator piston moves the swashplate in the direction that is controlled by the steering control lever.