| 摘要 |
A gearing radius (R) of a worm wheel (12) is set corresponding to a neighborhood region of a steering neutral position, in such a way as to be relatively large. Thus, backlash is made to be relatively small. This prevents noises from being produced when an automobile travels straight on a bad road. Conversely, the backlash is set corresponding to most of regions of steering angles, which are within the remaining region thereof, in such amanner as to be relatively large. Thus, increase in resistance torque is suppressed. This is realized by a simple configuration in which a bias portion (61) is provided in a part of the profile of teeth. In a case where power is transmitted from an electric motor (M) by a worm shaft (11) and a worm wheel (12) during a steering operation, noises are hard to be produced even when the automobile travels on a bad road. <IMAGE> |
