Patent ID: 7231940

Claim:
A method of operating a control valve in a power steering system of a motor vehicle, the method comprising the steps of: (A) supplying working fluid to an inlet passage of the control valve and between inner and outer valve members; (B) moving the inner valve member relative to the outer valve member, the movement representing movement of the control valve from a neutral condition of the control valve towards a closed condition of the control valve; (C) flowing the fluid through first and second flow passages formed between the valve members, the first and second flow passages arranged in parallel and fluidly connecting the inlet passage with an exhaust passage that exhausts fluid from the control valve; (D) forming a pressure orifice in the first flow passage in response to relative movement of the inner valve member; (E) forming a first exhaust orifice and a second exhaust orifice in the second flow passage in response to the relative movement of the inner valve member, the second exhaust orifice downstream from the first exhaust orifice; (F) flowing fluid in the first flow passage through a first motor passage fluidly connecting the first flow passage to a hydraulic motor, the first motor passage downstream from the pressure orifice; (G) flowing fluid in the second flow passage through a second motor passage fluidly connecting the second flow passage to the hydraulic motor, the second flow passage upstream from the first exhaust orifice; (H) closing the first and second exhaust orifices as the control valve moves from the neutral condition towards the closed condition; and (I) flowing fluid through a flow restriction located in the second flow passage between the first and second exhaust orifices whereby the pressure of fluid discharged from the first exhaust orifice is further reduced before reaching the second exhaust orifice.