Patent ID: 7357216

Claim:
An electric power steering apparatus comprising: a gear box; an input shaft inserted through the gear box; a pinion shaft, an upper end of which is connected to a lower end of the input shaft via a torsion bar spring, and which is accommodated in the gear box; a rack that engages with a pinion formed in a lower portion of the pinion shaft to transmit a steering force to a wheel side; a torque sensor that detects a torque acting on the torsion bar spring; an electric motor that outputs a predetermined steering assist force depending on a detected value in the torque sensor; a worm that is connected to an output shaft of the electric motor, and that engages with a worm wheel connected to an upper portion of the pinion shaft; and a first bearing that supports, directly under the worm wheel, the pinion shaft pivotally in a radial direction and a thrust direction relative to the gear box wherein the first bearing is a ball bearing, and an inner race of the ball bearing is clamped between a step formed in an outer periphery of the pinion shaft or a boss portion of the worm wheel and any one of a caulking ring, a retainer ring, and a nut attached to the pinion shaft.