Steering system for motor vehicle has valve sub-assembly with two separate valves, the first of which establishes acting direction of working cylinder, and second controls working pressure for hydraulic working cylinder

摘要

The steering system for motor vehicle includes a hydraulic working cylinder (19) which has two acting directions, and a hydraulic pressure source (12) which supplies pressure to a valve sub-assembly (30) which has two separate valves (15), the first of which establishes the acting direction of the working cylinder, and the second controlling the working pressure for the hydraulic working cylinder. The first valve may be a digitally controllable or analogue controllable solenoid operated spool valve, and the second valve is an analogue controllable spool valve. An independent claim is included for a method for the operating of a hydraulic steering system in which a relief valve (33) is kept closed against the force of a mechanical spring if a steering force is delivered from the working cylinder, and opens if there is no steering force delivered from the working cylinder or if a malfunction is established.