Patent ID: 8121759
Filing Date: 2012-02-21
Classification: B62D

Abstract:
1. A motor-driven power steering apparatus provided with a steering assist control means calculating an assist base current value on the basis of a steering torque and a vehicle speed, and a damper current computing means computing a damper current on the basis of at least a change amount of the steering torque, and constructing a main control system assisting a human power by controlling so as to drive a motor in accordance with an assist target current determined on the basis of a current obtained by adding the damper current to the assist base current, wherein the motor-driven power steering apparatus is provided with a sub control system, comprising: a map memory means storing a first window time setting map with a first window time and a second window time setting map with a second window time in which the second window time is set shorter than the first window time, as a widow time setting map corresponding to a coordinate map having two variables including a steering torque and a motor current and in which a window time for stopping the motor drive is set within a predetermined motor drive stop region; a torque change amount computing means calculating a torque change amount by differentiating the steering torque; a current change amount computing means calculating a current change amount by differentiating the motor current; a window time setting map selecting means selecting the first window time setting map at a time when the torque change amount and the current change amount are both smaller than respective predetermined change amounts, and selecting the second window time setting map in the other cases; a window time deciding means collating a point coordinate of a combination of the steering torque and the motor current with the window time setting map selected by the window time setting map selecting means so as to extract and decide the corresponding window time in the case that the point coordinate exists in the motor drive stop region; and a motor drive stop determining means determining the motor drive stop in the case that the point coordinate of the combination of the steering torque and the motor current continuously exists in the region corresponding to the decided window time for the window time, and wherein when the motor drive stop determining means of the sub control system determines the motor drive stop, the drive of the motor controlled so as to be driven by the main control system is stopped.