| 摘要 |
<p>PURPOSE:To secure a safety, accurate steering function, by varying a trouble judging level according to a variation in an element being varied in response to a car speed, while selecting a device from a power assist steering to a manual steering at a time when a trouble detecting signal exceeds the said level. CONSTITUTION:An electrically-driven type power steering device detects torque to be added to a steering wheel shaft with a torque sensor 28 and assists steering force by means of driving force of a motor 36 whose output current is controlled according to a control characteristic proportional to the torque. In this case, a current flowing in a motor drive circuit 64 is detected by a detection resistor 82, and a trouble detecting signal is inputted into a trouble judging circuit 56 which is provided with a trouble level detector being set so as to vary a signal level setting value by degrees according to a car speed by a car speed sensor 32, while it turns off a power switch 52 at a time when the trouble detecting signal exceeds the setting level, and constituted to make the motor 36 and a clutch 38 come into a nonoperational state.</p> |
