Electronic power steering apparatus

An electronic power steering apparatus that is applied to a vehicle having a steering mechanism, causes a motor to generate a steering assisting force with a motor control unit, and transmits the steering assisting force to a steering system to cause a reduction in a steering force, comprising:

• a steering angle sensor for detecting a steering angle of a steering wheel;
• a steering torque sensor for detecting a steering torque of the steering wheel;
• and
• a control device including a CPU configured to provide:
• a target steering torque setting unit configured to set a target steering torque on the basis of the steering angle detected by the steering angle sensor;
• a torque deviation computing unit configured to compute a torque deviation between the target steering torque set by the target steering torque setting unit and the steering torque detected by the steering torque sensor;
• a first target current value computing unit configured to compute a first target current value for generating a steering assisting force by the motor on the basis of the torque deviation computed by the torque deviation computing unit;
• and
• a vehicle speed sensitivity adjusting unit that outputs the adjusted first current value as a second target current value,
• wherein the motor control unit controls the motor to generate the steering assisting force on the basis of the second target current value;
• wherein the steering mechanism has a low ackermann ratio, which is in a range of 0 to 50%,
• wherein in a state that the steering assisting force is not applied to the steering system, the steering reaction force from the steering mechanism decreases as the steering angle increases while the vehicle speed is not greater than 30 km/h, and
• wherein the vehicle speed sensitivity adjusting unit adjusts the first target current value, at least corresponding to a vehicle speed detected by a vehicle speed detecting unit such that a steering reaction force on the steering wheel of the vehicle normally increases as the steering angle increases while the vehicle speed is not greater than 30 km/h.