Demand responsive hydraulic pump

摘要

A hydraulic power steering system has a vane type pump which is operable to supply fluid to a steering gear at a volumetric rate determined in part by the system pressure or system demand. The pump flow is partially bypassed through a valve member disposed in the cam ring at a position adjacent the pumping chambers. The valve is spring loaded radially inward to permit the bypass flow at low system pressure levels. Increasing system pressure levels bias the valve member radially outward thereby reducing bypass flow while simultaneously increasing pump discharge flow. At a predetermined pressure level, the valve member will reach a secondary opening position to bypass fluid flow and thereby limit the maximum system pressure.