Electric power steering unit

摘要

An electric power steering unit has an armature shaft that is free from axial forces and hence may have less rigorous requirements for its strength so that it may be manufactured more efficiently at reduced cost. It comprises a rack-shaft 2 to be coupled to the guiding wheels of a vehicle, a housing A for slidably containing the rack-shaft 2 and holding therein a coupling section 6 for causing the teeth of the rack-shaft 2 to engage those of a pinion arranged on the steering column 5 linked to the steering handle of the vehicle and an electric motor 1 coaxially arranged around the rack-shaft 2, which the rotary force is transmitted to the rack-shaft 2 by way of a ball screw mechanism 3 as the steering assisting power. A nut section 19 is linked to the armature shaft 11 of the electric motor 1 and rotatably supported by the housing B. The reaction force from the rack-shaft 2 generated by the inertia of the armature shaft 11 is transmitted to the housing B by way of the nut section 19 so that the armature shaft 11 is free from any axial force.