Patent ID: 7143683
Filing Date: 2006-12-05
Classification: B62D

Abstract:
1. A hydraulic power steering apparatus, comprising: an input shaft; an output shaft connected to said input shaft so as to be capable of elastic relative rotation in accordance with steering torque; a hydraulic actuator for generating steering assist power; a control valve for controlling hydraulic pressure of oil supplied to said hydraulic actuator in accordance with the amount of relative rotation between said input shaft and said output shaft; a restricting device for restricting the relative rotation between said input shaft and said output shaft in accordance with a driving condition of a vehicle; said restricting device having a guide bore formed in one of said input shaft and said output shaft, a plunger inserted into said guide bore so as to be capable of reciprocal movement toward the direction in which the plunger approaches to and goes away from the other of said input shaft and said output shaft, and a hydraulic pressure adjustment mechanism for adjusting hydraulic pressure for pressing the other of said input shaft and said output shaft via said plunger in accordance with said driving condition of the vehicle; and said plunger being guided by the inner circumference of said guide bore to the reciprocal movement direction when said input shaft and said output shaft rotate relatively; wherein a friction reducing element is interposed between the inner circumference of said guide bore and the outer circumference of said plunger; wherein said friction reducing element is spheres rolling between the inner circumference of said guide bore and the outer circumference of said plunger; and wherein, in at least one of the inner circumference of said guide bore and the outer circumference of said plunger, three or more rows of raceway grooves are formed along the reciprocal movement direction of said plunger, with spacing in the circumferential direction of said guide bore, and said spheres are disposed in each of said raceway grooves.