Importance

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Abstract

There is disclosed a hydraulically operated power steering system which comprises a reciprocating-type hydraulically operated cylinder unit for moving a steering link mechanism and having first and second chambers, a reservoir containing hydraulic fluid therein, a hydraulic pump feeding the hydraulic fluid in the reservoir to the cylinder unit, a control valve unit including a line coupled to communicate the hydraulic pump, a line coupled to communicate the reservoir, a valve cylinder having passages coupled between the first and second chambers to provide fluid communication therebetween, and a valve spool slidably arranged in the valve cylinder and reciprocatingly movable in response to rotation of an input shaft, the cylinder unit including therein right and left reaction chambers to which opposite ends of the valve spool are exposed, the reaction chambers being communicated with the respective first and second hydraulic chambers through orifices, and a valve for dividing the left reaction chamber into a reaction chamber portion and a small chamber portion communicable with the second hydraulic chamber through an orifice, the valve being operable to direct hydraulic pressure to the line coupled to the reservoir when the hydraulic pressure exceeds a predetermined point.

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First Claim