Demand responsive hydraulic pump

摘要

A hydraulic power steering system has a vane type pump which is operable to supply fluid to a power steering gear at a volumetric rate determined in part by the system pressure requirement or system demand. The pump flow is partially bypassed through an aperture in the cam ring at low system pressures. The bypass flow is controlled by a sleeve valve surrounding the cam ring and being subjected to system pressure to incrementally close the aperture and reduce bypass flow and simultaneously increase the output flow. At a predetermined system pressure, the valve is moved sufficiently to control reopening of the aperture for controlled bypass flow to limit the maximum system pressure.