Patent ID: 6065561
Filing Date: 2000-05-23
Classification: B62D

Abstract:
A power steering system for use on a vehicle having at least one steerable wheel movable to either side of a center position in response to a steering force transmitted through a steering shaft connected to a steering member operable by a driver of the vehicle, said system comprising:a power unit having a power piston confined in a power cylinder having respective left and right end walls defining a left turn chamber and a right turn chamber each pressurizable by a fluid, said power piston being arranged for reciprocal movement in said cylinder to drive a linkage for moving said steerable wheel to either side of said selected position;a sleeve member having an axial bore and arranged for rotation around an axis of said bore, said sleeve member being connected to said piston such that rotation of said sleeve member in one rotary direction causes linear movement of said piston in one linear direction, and rotation of said sleeve member in another rotary direction causes linear movement of said piston in another linear direction; anda rotary valve member received in said axial bore for rotary movement relative to said sleeve member and having a plurality of grooves and lands cooperating with a plurality of ports in said sleeve member to define a first spool valve and a second spool valve, one portion of said rotary valve member being connected to said sleeve member through a torsion rod and another portion of said rotary valve member being connected to said steering shaft such that said torsion rod tends to maintain said rotary valve member in a neutral position relative to said sleeve member when twisting of said torsion rod is caused by rotation of said rotary valve member relative to said sleeve member to either side of said neutral position;wherein said first spool valve includes an inlet port for receiving said fluid from a fluid source, a recycle port for recycling said fluid to said fluid source, and an outlet port for supplying said fluid to a supply conduit;wherein the grooves and lands of said first spool valve are arranged to by-pass said fluid to said recycle port when said rotary valve member is in its neutral position, and to close said recycle port and discharge said fluid to said supply conduit through said outlet port when said rotary valve member rotates relative to said sleeve member to either side of said neutral position;wherein said second spool valve includes a supply port for receiving said fluid from said supply conduit, a left port in fluid communication with said left turn chamber, and a right port in fluid communication with said right turn chamber; andwherein the grooves and lands of said second spool valve are arranged to close said left and right ports when said rotary valve member is in its neutral position, to supply said fluid from said left port to said left turn chamber when said rotary valve member rotates relative to said sleeve member to one side of said neutral position, and to supply said fluid from said right port to said right turn chamber when said rotary valve member rotates relative to said sleeve member to the other side of said neutral position.