Electric power steering device

An electric power steering device for giving an assisting steering force to a steering mechanism of a vehicle by driving an electric motor according to a steering torque given to a steering means for steering the vehicle, said device comprising:

• a torque sensor for outputting a voltage corresponding to the steering torque as a torque detection signal;
• middle point voltage storage means for storing a value corresponding to a middle point voltage which is a voltage outputted from the torque sensor when the steering torque is 0;
• steering torque calculation means for calculating the steering torque according to a torque detection signal, which is outputted from the torque sensor, and a value stored by the middle point voltage storage means;
• electric current detection means for detecting an electric current flowing in the electric motor and outputting a detection value of the electric current;
• motor control means for generating a command value used for feedback control conducted for driving the electric motor according to deviation of the electric current detection value from an electric current target value, which is set as a target value of an electric current to be supplied to the electric motor, according to the steering torque calculated by the steering torque calculation means;
• drive means for driving the electric motor according to the command value;
• and
• suppressing means for suppressing the assisting steering force in the case where the value stored in the middle point voltage storage means is out of a predetermined allowable range.