Patent ID: 9018876
Filing Date: 2015-04-28
Classification: B62D,Y10T

Abstract:
1. An electric power steering apparatus comprising: steering torque detection means for detecting steering torque input from a steering wheel to a steering shaft; a motor provided in a steering mechanism and generating steering assist torque; a motor drive circuit composed of an H bridge circuit including switching devices for normal rotation which are turned on so as to drive the motor in a normal rotation direction and switching devices for reverse rotation which are turned on so as to drive the motor in a reverse rotation direction; motor current detection means for detecting motor current flowing through the motor; anomaly detection means for detecting an anomaly of the motor current detection means; normal-time motor control means, operable when the anomaly of the motor current detection means is not detected, for controlling the motor drive circuit by current feedback control based on a target current set in accordance with the steering torque detected by the steering torque detection means and the motor current detected by the motor current detection means; and abnormal-time motor control means, operable when the anomaly of the motor current detection means is detected, for controlling the motor drive circuit on the basis of the steering torque, detected by the steering torque detection means, without use of the current feedback control, the electric power steering apparatus being characterized in that the abnormal-time motor control means includes: an off-state-voltage detection section which detects voltage between terminals of the motor in a state in which the motor drive circuit is controlled so as not to apply a power supply voltage between the terminals of the motor; a current-zero timing detection section which detects a timing at which the current flowing through the motor becomes zero on the basis of the voltage between the terminals of the motor detected by the off-state-voltage detection section; an energization time setting section which sets an energization time corresponding to the steering torque detected by the steering torque detection means; and a switching control section which turns on the switching devices for normal rotation or the switching devices for reverse rotation for the energization time, set by the energization time setting section, every time the current-zero timing detection section detects the timing at which the current flowing through the motor becomes zero.