Patent ID: 6427799
Filing Date: 2002-08-06
Classification: B62D

Abstract:
An electric power steering unit for use with a vehicle having guiding wheels, a steering handle, a steering column linked to the steering handle, and a toothed pinion arranged on the steering column, said steering unit comprising:a toothed rack-shaft to be coupled to the guiding wheels of the vehicle, a first housing for movably containing the rack-shaft and holding therein a coupling section for causing teeth of the rack-shaft to engage those of the pinion arranged on the steering column, an electric motor equipped with a yoke integrally formed with the first housing and coaxially arranged around the rack-shaft to supply assisting power to the rack-shaft, a ball screw mechanism connecting a nut section linked to an armature shaft of the electric motor with a screw section formed on the rack-shaft by disposing ball members therebetween and for transmitting the rotary power of the electric motor to the rack-shaft as assisting power for steering, and a second housing containing the ball screw mechanism, said armature shaft carrying an armature core having first and second ends with the first end being closer to the coupling section than the second end, the first housing and the yoke both extending fully along the armature core between the first and second ends of the armature core, a first threaded portion being formed on an end portion of the yoke defining the farthest extent of the yoke away from the coupling section, a second threaded portion being formed to fit to the first threaded portion on an end portion of the second housing defining the closest approach of the second housing toward the coupling section, and the first housing and the second housing being coupled together by fitting the first threaded portion to the second threaded portion.