Patent ID: 7080711

Claim:
A rack and pinion type motor-driven power steering apparatus for assisting a steering operation by transmitting a drive force of a motor to a steered wheel from a pinion shaft via a laterally moving rack, comprising: a rack position detecting means for detecting a position of the rack; a rack speed arithmetically operating means for calculating a rack speed corresponding to a moving speed of the rack; a memory means for storing a relation between a predetermined rack speed near a stroke end of the rack and a motor damping control start rack position in which a distance from the stroke end is farther in accordance with the rack speed with respect to a relation curve of a coordinate; a collating means for collating with the relation curve between the rack speed stored in the memory means and the motor damping control start rack position so as to discriminate whether or not a combination position coordinate between the rack speed calculated by the rack speed arithmetically operating means and the rack position detected by the rack position detecting means gets over the relation curve; and a motor drive control means for controlling the motor in a damping state on the basis of a predetermined motor assist decreasing rate where the collating means determines that the combination position coordinate gets over the relation curve.