Patent ID: 7188700

Claim:
An electric power steering apparatus comprising: a housing; a motor attached to said housing and transmitting an auxiliary steering force to a rotary shaft through a motor shaft; a worm formed on or fitted on said rotary shaft and having a gear portion formed of a metal or a resin; bearings provided in said housing, disposed respectively in positions on both sides of said worm and rotatably supporting said rotary shaft, said bearings including a motor-side bearing and a second bearing which is positioned away from said motor; an output shaft transmitting a steering force for steering an axle and rotatably supported in a predetermined position of said housing; and a worm wheel formed on or fitted on said output shaft in a way that meshes with said worm and having a gear portion formed of a resin, said motor including a worm gear mechanism installed in such a position that a length which is the sum of a working radius of said worm and a working radius of said worm wheel becomes an axis-to-axis distance between said output shaft and said motor shaft, wherein elastic members are disposed on both sides, axially, of said motor-side bearing and adjacent to said motor-side bearing, said rotary shaft being set slightly axially movable, said second bearing is a rolling bearing, an elastic portion being provided on said rotary shaft and biasing said worm in a meshing direction in parallel with said rolling bearing, an outer ring of said rolling bearing is fixedly fitted in a cylindrical bearing holding member fixedly fitted in said housing, an inner ring of said rolling bearing loosely receiving therein a cylindrical buffer member fixedly fitted on said rotary shaft, said elastic portion includes a biasing member rotatably supporting said rotary shaft and an elastic body receiving therein said biasing member in a position eccentric in the meshing direction of said worm with respect to an axis of said rolling bearing, and fixed in a vicinity of said bearing holding member, wherein at least a half, in an axial direction, of a spline connecting portion between said rotary shaft and said motor shaft is so set as to be positioned within a shaft support hole of said motor-side bearing.