Variable pump control for hydraulic fan drive has solenoid valve unit with spring that biases three way proportional valve to position to pass fluid from variable displacement pump

摘要

The solenoid valve unit (36) has a spring (86) that biases a three way proportional valve (90) to a position to pass fluid from a variable displacement pump (12). A proportional solenoid (88) at one end of the three way valve generates a variable force which resists force of spring from another end. The proportion valve has three ports leading to reservoir (14), pump outlet port (20), and pressure chamber (42). A captured spring (122) is disposed at a proportional valve end (94) between the proportional solenoid and the housing of the proportional valve. The proportional solenoid valve arrangement controls the flow of pressurized fluid to or from the displacement changing actuator (22) that controls the displacement of the pump.