Importance

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Abstract

A steering force control apparatus for a power steering apparatus of a vehicle of the type having a reaction chamber responsive to fluid pressure applied thereto for producing a reaction force to counteract the steering force produced by a power cylinder. A main tubular spool is disposed in a valve case movably relative to the valve case and has an inner valve surface. A sub-spool is disposed in the main spool movably relative to the main spool and has an outer valve surface cooperative with the inner valve surface to define a variable throttle for selectively connecting a fluid pump to the reaction chamber and to the power cylinder according to the movement of the sub-spool relative to the main spool in response to the vehicle speed. The main spool is moved relative to the valve case and the sub-spool in response to the fluid pressure applied to the reaction chamber when the fluid pressure is above a certain value to enable the variable throttle to disconnect the fluid pump from the reaction chamber. A fixed throttle is formed in the sub-spool for connecting the reaction chamber to a fluid tank to release the fluid pressure in the reaction chamber.

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First Claim