| 摘要 |
A worm gear and an irreversible clutch mechanism adapted to permit the transmission of a driving force from an actuator toward rear wheels and to inhibit the transmission of the driving force in a reverse direction, are disposed at upstream and downstream locations in a power-transmitting path for transmitting the driving force from the actuator to the rear wheels, respectively. The driving force transmitted in the reverse direction from the rear wheels toward the actuator is blocked by both the irreversible clutch mechanism and the worm gear. Therefore, the steering angle of the rear wheels can be reliably prevented from changing from a desired angle. Further, even when one of the irreversible clutch mechanism and the worm gear is broken, the function of inhibiting the reverse transmission of the driving force can be maintained. Especially, because the irreversible clutch mechanism having a chattering smaller as compared with the worm gear is disposed in the downstream location, the rigidity of the rear wheels against a load from a road surface can be effectively enhanced.
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