| 摘要 |
<p>An hydraulic system: a power assisted vehicle steering system which includes such an hydraulic system and a method of alleviating noise in an hydraulic system. The hydraulic system as applied to a vehicle steering gear (1) has an open centre valve (3) which directs hydraulic fluid under pressure derived from a pump (12) and in response to a steering manoeuvre through a shaft(4) to a servo motor of the gear (1). Downstream of the open centre valve (3) is a restrictor (8) through which hydraulic fluid from the valve (3) passes to a reservoir (11). The restriction effected by the restrictor (8) to fluid flow from the valve (3) to the reservoir is variable to provide a throttling action and a back pressure in the line (6) to alleviate noise in the valve (3). The restrictor (8) is preferably in the form of a spool which is subjected to a pressure.</p> |
