Electric power-assist steering system

摘要

The present invention provides an electric power-assist steering system 1 that can provide a steering assist control in accordance with the steering angle right after the idle stop, thereby to reduce an unpleasant steering feeling for a driver. The electric power-assist steering system 1 is installed in a vehicle 21 having an idle stop mechanism (engine controller) 22 that automatically performs an idle stop operation in a predetermined condition, and the electric power-assist steering system 1 includes a torque sensor 3 for detecting a steering torque, a steering angle sensor 11 for detecting a steering angle relative to a midpoint of a steering angle that is learned, an electric motor 8 whose assist force is controlled based on the steering torque and the steering angle, and a resolver 8a for detecting a rotational angle of the electric motor 8, wherein a steering angle right after the idle stop is determined based on the steering angle detected by the steering angle sensor 11 right before the idle stop and variation in the rotational angle detected by the resolver 8a during the idle stop.