| 摘要 |
A vehicle steering system (10, 190, 290) includes inner and outer coaxial valve members (40, 42) which are rotatable relative to each other to port fluid to a vehicle power steering motor (30). A plurality of rocker arms (122, 302) are pivotally connected to the inner valve member (40). Each rocker arm (122, 302) is pivotal relative to the inner valve member (40). Each rocker arm (122, 302) engages a recess (132) in the outer valve member (42). Upon relative rotation between the inner and outer valve members (40, 42), the rocker arms (122, 302) pivot relative to the inner valve member (40). Force is applied to each of the rocker arms (122, 302) to resist pivoting of the rocker arms (122, 302) and relative rotation between the inner and outer valve members (40, 42). In one embodiment, a plurality of pistons (222) are disposed in chambers (220) formed in the outer valve member (42). The pistons (222) are exposed to a fluid pressure which varies as a function of vehicle speed. The pistons (222) are effective to vary the force applied against the rocker arms (122) and the resistance to relative rotation between the valve members (40, 42) as a function of vehicle speed.
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