| 摘要 |
PROBLEM TO BE SOLVED: To provide an electric power steering device having a structure capable of preventing occurrence of any permanent set in fatigue or considerable wear in a fitting part between a bush 15a and a part close to a fore end of a worm shaft 7 built in a mechanism for suppressing backlash between a worm tooth and a worm wheel. SOLUTION: A space 18 in which the radial dimension becomes larger toward a fore end face of a worm shaft 7 in a neutral state is provided between an inner circumferential surface 17a of a bush 15a and an outer circumferential surface 16a of a fore end of the worm shaft 7. Thus, the outer circumferential surface 16a forms a cylindrical projecting surface with its outside diameter being not changed in the axial direction. The inner circumferential surface 17a of the bush 15a forms a partially conical recessed surface inclined in the direction in which the inside diameter is increased toward the fore end face of the worm shaft 7. To eliminate the backlash, the contact area of both circumferential surfaces 16a, 17a is ensured while the worm shaft 7 is inclined. COPYRIGHT: (C)2009,JPO&INPIT
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