| 摘要 |
PURPOSE:To effectively prevent a stepping motor from being stepped out due to the increment of a load, by increasing driving torque when the stepping motor is about to be stepped out. CONSTITUTION:According to the detection signal of a steering ratio detecting means 5 for detecting the steering state of a steering ratio changing mechanism 1, the working state of a stepping motor 2 is detected. By a discriminating means 6, it is discriminated whether the stepping motor 2 is about to be stepped out or not, and when it is discriminated that the motor 2 is about to be stepped out, then the pulse rate of the stepping motor 2 is lowered by a torque controlling means 7. Accordingly, according to the increment or the like of the viscosity of the lubricant of the steering ratio changing mechanism 1, the load of the stepping motor 2 is increased, and when the step-out inclination of the stepping motor 2 is generated, then the driving torque of the stepping motor 2 is increased according to the inclination, and the step-out inclination is automatically corrected. |
