Patent ID: 8981690
Filing Date: 2015-03-17
Classification: B62D

Abstract:
1. An electric power steering system, comprising: a steering force assist device that applies assist force to the steering system using a three-phase brushless motor as a drive source, a current detecting device configured to detect an actual current that flows through the three-phase brushless motor, a vehicle speed detecting device configured to detect a speed of a vehicle, a torque detecting device configured to detect a steering torque, a control device configured to control an operation of the steering force assist device such that the assist force that corresponds to the steering torque is generated, and a malfunction determination device configured to determine occurrence of an energization failure phase when an energization failure has occurred in one of phases of the three-phase brushless motor, wherein when the energization failure phase is detected by the malfunction determination device, the control device executes control such that the assist force is generated using the two phases other than the energization failure phase as energization phases, wherein the malfunction determination device includes a short-circuit determination device configured to determine whether a short-circuit between the energization failure phase and one of the two phases other than the energization failure phase has occurred while the assist force is being generated using the two phases other than the energization failure phase as the energization phases; and the control device stops generation of the assist force every time the short-circuit determination device determines that the short-circuit between the energization failure phase and one of the other two phases has occurred.