Hydrostatic load sensitive regenerative steering system

Claim 1

A regenerative hydraulic steering system for a motor vehicle comprising, a variable displacement pump having a pressure compensator for controlling the displacement of the pump responsive to a sensed load pressure, a control valve including a housing defining inlet passage for connection to the pump, a return passage for connection to a reservoir, and actuator passages, a hydraulic actuator for connection to a steering linkage to steer a motor vehicle, said hydraulic actuator including a piston with a rod connected to said piston extending from said hydraulic actuator defining a rod end hydraulic chamber and a base end hydraulic chamber, an actuator conduit connecting the rod end chamber to an actuator passage in said control valve and an actuator passage connecting the base end chamber of said hydraulic actuator to a second actuator passage in the control valve, said control valve including an input shaft adapted for operation by a steering wheel, a commutator sleeve connected to said input shaft adapted for movement in a first direction when said steering wheel is rotated in one direction and for movement in a second direction when said steering wheel is rotated in the other direction, a valve sleeve received in said housing and receiving said commutator sleeve, a metering unit positioned in said valve housing for metering fluid flowing through said control valve, passage means connecting said control valve to and from said metering unit, said commutator sleeve and said valve sleeve defining a plurality of passageways selectively connecting said inlet passage through said metering unit to said actuator passages for regenerative operation and connecting said inlet passage to one of said actuator passages through the metering unit and connecting the other actuating passage to the return passage for non-regenerative operation, said input shaft causing displacement of said commutator sleeve relative to said valve sleeve when said input shaft is rotated in either of said two directions, said displacement between said sleeves selectively connecting said passageways in said commutator sleeve and valve sleeve in said control valve for selective connection of said valve through said metering unit to said hydraulic actuator to selectively extend and contract said hydraulic actuator for steering of the motor vehicle, said commutator sleeve and valve sleeve defining a sensing passage in communication with said passageways for sensing a pressure signal when said variable displacement pump is connected to said hydraulic actuator through said control valve, a pilot line connecting said sensing passage in said control valve to said compensator for selectively sensing load pressures in said control valve to vary the displacement of the pump in response to the sensed pressure.