Patent ID: 8776942

Claim:
An electric power steering device adapted to apply a steering force to a steerable road-wheel, the electric power steering device comprising: a rack bar configured to transmit a steering manipulation of a steering wheel to the steerable road-wheel; a pinion shaft meshing with the rack bar; a worm wheel provided on the pinion shaft; a worm shaft meshing with the worm wheel; an electric motor provided on the worm shaft and configured to generate the steering force to be applied to the steerable road-wheel; a first housing accommodating at least a part of the rack bar and at least a part of the pinion shaft, wherein the first housing includes a first bolt boss formed with a though-hole; a second housing including a worm-wheel accommodating potion accommodating the worm wheel, and a second bolt boss provided to have a shorter distance to the first housing than that of the worm-wheel accommodating portion, and formed with a female-threaded portion opened toward the first housing, wherein the second bolt boss is opposed to the first bolt boss to cause the female-threaded portion to be continuous with the through-hole of the first bolt boss; and a bolt inserted from the first bolt boss toward the second bolt boss and fastening the first housing to the second housing, wherein the female-threaded portion is formed such that a radially-innermost portion of an inner circumferential surface of the female-threaded portion with respect to a radial direction of the pinion shaft is located more inwardly with respect to the radial direction of the pinion shaft than an outer circumferential surface of the worm-wheel accommodating portion of the second housing.