Electric power steering apparatus

An electric power steering apparatus for performing steering assist by transmitting a driving force produced by an electric motor to a steering mechanism, comprising:

• an operation amount sensor for sensing an operation amount of an operation member for steering a motor vehicle;
• and
• a reference assist characteristics setting section for setting reference assist characteristics which are reference characteristics of a motor driving target value corresponding to the operation amount sensed by the operation amount sensor;
• a motor driving target value setting section for setting a motor driving target value corresponding to the operation amount sensed by the operation amount sensor in accordance with corrected assist characteristics obtained by shifting the reference assist characteristics set by the reference assist characteristics setting section along an axis of coordinates of the operation amount;
• a shifting amount setting section for setting, when forward stroke steering for operating the operation member in a direction away from a steering angle midpoint is done, a shifting amount of the corrected assist characteristics with respect to the reference assist characteristics to zero, while setting, when return stroke steering for operating the operation member toward the steering angle midpoint is done, the shifting amount of the corrected assist characteristics with respect to the reference assist characteristics to a value at which corrected assist characteristics is obtained in which an absolute value of the motor driving target value corresponding to the operation amount sensed by the operation amount sensor is increased;
• and
• a motor driving section for driving the electric motor on the basis of the motor driving target value set by the motor driving target value setting section.