Patent ID: 8027766

Claim:
An electric power steering device, comprising: a steering force assisting device having a motor that functions as a drive source and providing a steering system with an assist power for assisting a steering operation; and a control device that controls an operation of the steering force assisting device through a supply of a drive power to the motor, the control device including: a motor control signal output part that outputs a motor control signal; a drive circuit that supplies the drive power of three phases to the motor on the basis of the motor control signal; and an abnormality-detecting part that detects an occurrence of a failure caused in the phases of the motor, wherein: the motor control signal output part generates the motor control signal by executing current control on the basis of a rotational angle of the motor and, when the occurrence of the failure is detected, executes output of the motor control signal by means of two electrification phases other than a phase with the failure; and, when the occurrence of the failure is detected, the motor control signal output part performs a correction of the rotational angle so that an angular phase is shifted in a direction of the steering operation, and the motor control signal output part increases an amount of the correction of the rotational angle as rotational angular velocity of the motor is increased.