| 摘要 |
<p>A vehicle power steering system comprising a power unit (14), a valve unit (16), and a centering unit (18). A piston (24) of the power unit (14) reciprocates in a cylinder (26) to provide power assisted steering and is engaged by a worm (36) connected to the steering shaft (22) for rotation in response to either the centering unit or the vehicle steering member. The valve unit (16) is connected between the worm (36) of the power unit (14) and a steering shaft (22) segment from the centering unit (18), and includes a rotary valve member (42) rigidly fixed to the steering shaft segment (22) and rotatably received in the bore of a sleeve member (38) fixed to the worm (36). The sleeve member (38) is connected to the pair of spool valves (60, 70) formed by valving elements on the rotary valve member (42) and the sleeve member (38). The spool valves are arranged to provide fluid flow to and from the power unit (14) only while the steering shaft (22) is being turned by either the steering member or the centering unit (18), so as to prevent uncontrolled return of the steering system toward its center position in response to road forces acting on the steerable wheels.</p> |
