Power steering apparatus and backlash adjustment mechanism therefor

A power steering apparatus includes a worm gear that transmits a rotational force of an electric motor to a steering mechanism through engagement of a worm shaft and a worm wheel and a backlash adjustment mechanism that reduces backlash between the worm shaft and the worm wheel. The backlash adjustment mechanism has a ball bearing mounted to the worm shaft, a slider movable in a movement direction substantially perpendicular to a rotation axis of the worm shaft, a first sliding surface provided on an outer circumferential side of an outer race of the ball bearing, and a second sliding surface provided on the slider and brought in sliding contact with the first sliding surface such that forward movement of the slider in the movement direction causes relative sliding of the first and second sliding surfaces to bring the worm shaft closer to the worm wheel.