ELECTRIC POWER STEERING DEVICE

摘要

PROBLEM TO BE SOLVED: To drive a motor based on an estimated torque signal by providing a steering angle sensor for detecting a steering angle of a steering system and by having the steering torque sensor estimate a steering torque based on a steering angle signal and a car-speed signal at the time of failure. SOLUTION: A steering torque sensor 12 for detecting a manual torque and a steering angle sensor 18 for detecting a rotation angle of a steering shaft 3 are provided in a steering gear box. A controlling means 15 converts a steering torque signal T to a corresponding target current signal and issues a motor control signal V0 so as to drive a motor 10 through a motor driving means 16. The controlling means 15 determines that the steering torque sensor 12 fails when the steering torque signal T (T=0) is not put out regardless of output of a steering angle signal D, calculates an estimated torque amount corresponding to a car-speed signal V and the steering angle signal D, and controls the motor 10 based on this new steering torque signal T and the car-speed signal V.