To provide an electric power steering device can surely prevent, in an extremely short time, such an event that a closed circuit is formed when an inverter fails and assisting is stopped and a steering assist force and electromagnetic braking which are not expected by a driver occur by a device which is miniaturized, inexpensive, generates no noise, and consumes small power, and imparting a steering assist force can provide better steering feeling during normal steering.
This electric power steering device includes the inverter which calculates a current command value according to at least steering torque and a vehicle speed and supplies a motor phase current to each phase of a motor which provides a steering assist force to a steering mechanism according to the current command value. The electric power steering device includes a first FET group is installed in each phase supply path for supplying the motor phase current to the motor. The electric power steering device has a function of turning off the second FET group and the first FET group of the inverter when the defect of the inverter is detected.
KOBAYASHI NOBUYUKI
Sadayoshi Igarashi
Susumu Kitano