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.
