| 摘要 |
A closed center power steering gear having a spool shaft connected to a steering wheel of the motor vehicle, a pinion head connected to steered wheels of the motor vehicle, and a control valve between a fluid accumulator and a working chamber of a steering assist fluid motor. The control valve includes a poppet on the spool shaft having closed and open positions blocking and permitting, respectively, flow from the accumulator to the fluid motor working chamber, a cam on the pinion head, a cam follower on the spool shaft, and a pressure control spring between the cam follower and the poppet. The cam, the cam follower, and the pressure control spring cooperate during relative rotation between the spool shaft and the pinion head to shift the poppet to its open position. Boost pressure in the fluid motor working chamber increases and reacts against the poppet to compress the pressure control spring and shift the poppet to its closed position. The contour of the cam is calculated to cause steering assist boost pressure in the working chamber to increase at a rate faster than applied torque increases thereby to achieve a nonlinear relationship between boost pressure and applied torque.
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