ELECTRIC POWER STEERING DEVICE

PROBLEM TO BE SOLVED: To provide an electric power steering device which hardly loses steering feeling by rapidly increasing steering force even when overloaded steering has continued for a long period of time. SOLUTION: In the electric power steering device, a temperature of a steering assistant motor or its drive control circuit is detected or presumed, a current based on steering torque detected by a torque sensor flows to the motor to perform steering assistance, and when the detected or presumed temperature exceeds a threshold value, the maximum value of the current flowing in the motor is restricted. The device is provided with a temperature determination means (S4, 8) for determining whether the temperature exceeds a first temperature lower than the threshold value; a means (S14) for operating a raising ratio of the temperature; and a raising ratio determination means (S16) for determining whether the operated raising ratio exceeds a predetermined value. When the temperature determination means (S4, 8) determines that it exceeds the first temperature and the rising ratio determination means (S16) determines that it exceeds the predetermined value, the threshold value is reduced (S24). COPYRIGHT: (C)2008,JPO&INPIT