| 摘要 |
Meshing conditions between worm teeth (6a) and a worm wheel (4) is made constant regardless of the direction of transmission of power. By doing so, a structure is realized in which a steering force that a driver must apply to a steering wheel does not vary depending on the rotational direction of a steering wheel. A rolling bearing (8a) for rotatably supporting the forward end of a worm shaft (7a) in a housing (3a) is adapted to be displaceable only on a virtual plane perpendicularly intersecting the center axis of the worm wheel (4). To achieve this, an outer ring (16a) forming the rolling bearing (8a) is held between a pair of parallel guide planes formed on the inner peripheral surface of a guide sleeve (19), which is held in the housing (3a), and located on the virtual plane perpendicularly intersecting the central axis of the worm wheel (4). With such an arrangement, the above structure is achived. |
