Patent ID: 6179570
Filing Date: 2001-01-30
Classification: F04B

Abstract:
A pump control arrangement for controlling the displacement of a variable displacement pump that receives fluid from a reservoir, the variable displacement pump having a pressure outlet port and a displacement changing actuator operative to change the displacement of the variable displacement pump between a minimum and a maximum position, the pump control arrangement being adapted for use in a fan drive system having a fluid motor fluidity connected to the variable displacement pump, the pump control arrangement comprising:a proportional solenoid valve arrangement connected to the pressure outlet port of the variable displacement pump and operative to control the flow of pressurized fluid to and from the displacement changing actuator, the proportional solenoid valve arrangement includes a spring biasing mechanism, a proportional valve, a captured spring having a predetermined pre-load and a proportional solenoid, the proportional valve being a three-way valve having first and second ends with the spring biasing mechanism disposed at the first end and a pressure chamber defined at the second end with the pressure chamber being connected downstream of the proportional valve, the three-way valve having a first port connected to the reservoir, a second port connected to the pressure outlet port of the variable displacement pump, and a third port connected to one of a load margin valve and the displacement changing actuator, the proportional valve being movable between first and second positions and at the first position thereof the one of the load margin valve arrangement and the displacement changing actuator is in communication with the pressure outlet port of the variable displacement pump and blocked from the reservoir and at the second position thereof the one of the load margin valve and the displacement changing actuator is in communication with the reservoir and blocked from the pressure outlet port of the variable displacement pump, the captured spring being disposed between the proportional solenoid and the proportional valve, the spring biasing mechanism being operative to bias the three-way proportional valve to a position to pass fluid from the variable displacement pump therethrough, and the proportional solenoid is disposed at the second end of the three-way proportional valve and operative to provide a variable force in opposition to the spring bias acting at the first end.