Method for improving the efficiency of a variable displacement pump

摘要

An auxiliary solenoid controlled variable displacement power steering pump, hydraulic systems incorporating same, and method for improving the efficiency of variable displacement power steering pumps. In one embodiment, a rotor is arranged within a pump body, and a cam fitted on an outer periphery of the rotor and movably arranged within the pump body to form a variable volume pump chamber. The cam is biased towards a position within the pump body to create maximum displacement. A mechanism is provided for forcing the cam into a position of fixed minimum or reduced displacement under certain conditions, such as low engine speed and power steering demand. In a preferred embodiment, the mechanism comprises a solenoid driven connecting rod that is operatively connected to the cam. Activation of the solenoid forces the cam to a position of fixed minimum or reduced displacement.