| 摘要 |
<p>PURPOSE: To improve reliability on failure by a large margin by providing a sub-motor separately from a main motor, and driving the sub-motor to steer rear wheels in case of the failure of the main motor. CONSTITUTION: At the time of a small steering angle at high speed, a solenoid 63 is excited to fit a stopper pin 65 into a recessed part 67 of a ball nut 57 so as to regulate rotation of the ball nut 57 and also to regulate movement of a shaft 53, thus preventing rear wheels from being steered large at the malfunctioning time of a main motor 69. Driving of this main motor 69 is controlled by an ECU 25, and the ball nut 57 is rotated by the main motor 69 to move the shaft and thereby to steer the rear wheels 7, 9. At the failure time of the main motor 69, an electromagnetic clutch 81 on the main motor 69 side is turned off, and then power supply of a sub-motor 85 is turned on, and an electromagnetic clutch 97 on the sub-motor 85 side is turned on to rotate the ball nut 57 by the sub-motor 85.</p> |
