Patent ID: 6148947
Filing Date: 2000-11-21
Classification: B62D

Abstract:
An assisted-power steering unit for a motor vehicle wherein power assistance is dependent upon the vehicle's speed and rate of steering, the unit comprising:a servo-cylinder (3) having two chambers (16, 17);a steering valve (1) for directing pressurized hydraulic fluid from a pump (2) to the respective chambers (16, 17) of the servo-cylinder (3) when there is steering movement;a bypass valve (10) being connected in parallel with the servo-cylinder (3), the bypass valve (10) providing means for controlling a portion of the hydraulic fluid that bypasses the servo-cylinder (3); anda throttle unit (26) being connected in series with the bypass valve (10), the throttle unit (26) automatically throttling hydraulic fluid flow directed through the bypass valve (10) after a predetermined hydraulic fluid flow through the bypass valve (10) is reached, the throttle unit (26) having a cylinder tube (27) that is closed by cylinder heads (28, 29) to form a working chamber, the working chamber being divided into two parts by an axially displaceable piston (30) whereby a first part (31) is hydraulically connected with the servo-cylinder (3) by openings (33) arranged in a corresponding cylinder head (28) and a second part (32) is connected with the steering valve (1) by openings (34) in the wall of the cylinder tube (27), and whereby the piston (30) is provided with at least one orifice type opening (35) in an axial direction.