| 摘要 |
An electric power steering apparatus capable of outputting an auxiliary steering force by an electric motor, includes a support device (20) supporting a rack shaft (10). The rack shaft (10) has support device guide surfaces, i.e., rolling surfaces (10b, 10b) extending in a longitudinal direction in at least two portions on an outer peripheral surface. The support device (20) has cylindrical rollers (23) rolling on the rolling surfaces (10b, 10b) in directions intersecting each other while pressing the rolling surfaces in a case where the rack shaft (10) is viewed in the longitudinal direction. Therefore, the rack shaft (10) can be supported by the cylindrical rollers (23) with a low friction, and the rolling surfaces (10b, 10b) provided on the outer peripheral surface of the rack shaft (10) are pressed by the cylindrical rollers (23), whereby the rack shaft (10) can be supported from two different directions. Hence, an axis of the rack shaft (10) and an axis of a pinion (3) intersect each other at an angle other than 90 degrees, thereby providing a configuration suitable for supporting the rack shaft (10) where a rotational torque occurs when in operation. When depicting directions of pressing forces applied on the rolling surfaces (10b) from the cylindrical rollers (23) respectively with lines, an intersection (K) of these lines is shifted from a center O of the rack shaft (10). It is therefore possible to prevent the rack shaft (10) from rotating and to press rack teeth (10a) against pinion teeth (3a) in a stable state by a resultant force of the pressing forces. <IMAGE>
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