An electrically assisted power steering system for a motor vehicle includes a housing, a shaft slidably supported in the housing, a ball-and- nut mechanism operatively mounted on the shaft, and an electric motor mounted in the housing for transmitting rotary force from the electric motor through the ball-and-nut mechanism to the shaft. The ball- and-nut mechanism including a nut assembly disposed around the shaft and having one end rockably and rotatably supported in the housing by a four- point contact bearing or an automatic aligning bearing, and a plurality of balls movably held between an opposite end of the nut assembly and a screw groove defined in the shaft.
展开▼
