Abstract: An electric power steering apparatus for applying an auxiliary torque generated in proportion to a steering torque, to a rack shaft to thereby reduce the steering torque. The rack shaft has at one end thereof rack teeth for meshing with a pinion. A rack guide mechanism is provided at the rack shaft one end oppositely from the rack teeth, for urging the rack shaft to the pinion. At the other end of the rack shaft, a screw portion and a ball screw mechanism are provided. A bush is provided for supporting an intermediate portion of the rack shaft to thereby restrict the bending of the intermediate portion beyond a predetermined value when an external force is applied to the rack shaft ends thereby bending the rack shaft intermediate portion. As a result, the vibration of the rack shaft and hence a steering wheel can be minimized.

Abstract: A hydraulic pressure control valve includes a valve body having a slide bore with a circular cross-section, an inlet port opened in an inner surface of the slide bore, a control pressure port and an outlet port at axially spaced-apart distances in this sequence; a valve spool axially slidably fitted in the valve body; and a first variable orifice and a second variable orifice both formed between the valve body and the valve spool. The first variable orifice controls the degree of communication between the inlet port and the control pressure port, and the second variable orifice controls the degree of communication between the control pressure port and the outlet port. In this hydraulic pressure control valve, the valve spool has smaller diameter portions coaxially formed therein to define annular oil passages between the inner surface of the slide bore and the valve spool and each smaller diameter portion has an outer diameter set uniformly over the axially entire length thereof.

Abstract: A hydraulic pressure control valve comprises a valve body having a slide bore of a circular cross-section and an inlet port and an outlet port opened into an inner surface of the slide bore at axially spaced apart points, and a valve spool slidably received in the valve body for axially sliding movement and defining, by cooperation with the valve body, a variable orifice for controlling the degree of communication between the inlet and outlet ports. In the hydraulic pressure control valve, a smaller diameter portion defining an annular oil passage between an inner surface of the slide bore is provided on the valve spool coaxially with the slide bore to define the variable orifice, and has an outside diameter set constant over axially entire length. This facilitates the dimensional control of the variable orifice, so that the variation in property of the variable orifice for every hydraulic pressure control valve may be easily suppressed.