Patent ID: 6568499
Filing Date: 2003-05-27
Classification: B62D,F15B

Abstract:
A power steering system for a vehicle comprising:a hydraulic pressure source; a hydraulic cylinder having first and second chambers and driven in accordance with a pressure differential between a pressure fluid supplied to the first chamber and that to the second chamber; first and second communication conduits connecting the first and second chambers of the hydraulic cylinder to the hydraulic pressure source, respectively; a controller for selectively switching a supply direction of the pressure fluid from the hydraulic pressure source to the first and second chambers of the hydraulic cylinder in response to a steering operation of a steering wheel; a bypass conduit connecting between the first and second communication conduits and having first and second bypass conduit ports; and first and second valves disposed in the bypass conduit for selectively opening and closing, in response to the pressure fluid from the hydraulic pressure source, the first and second bypass conduit ports in such a manner that the pressure fluid from the hydraulic pressure source is supplied to the first chamber of the hydraulic cylinder while the pressure fluid in the second chamber of the hydraulic cylinder is discharged therefrom when the first valve is in a position of closing the first bypass conduit port and the second valve is in a position of opening the second bypass conduit port and the pressure fluid from the hydraulic pressure source is supplied to the second chamber of the hydraulic cylinder while the pressure fluid in the first chamber of the hydraulic cylinder is discharged therefrom when the first valve is in a position of opening the first bypass conduit port and the second valve is in a position of closing the second bypass conduit port; the first and second valves being placed in the positions of opening the first and second bypass conduit ports and thereby providing communication between the first and second communication conduits when the hydraulic pressure source is inoperative.