Patent ID: 7195098
Filing Date: 2007-03-27
Classification: B62D

Abstract:
1. A variable transmission ratio steering apparatus for a vehicle having a steering wheel and steerable road wheels, said apparatus comprising: an input shaft coupled to the steering wheel; a steering angle sensor for sensing a rotation angle of said input shaft and generating a signal indicative of the sensed rotation angle; an output shaft operatively linked to the steerable road wheels; an actuator having an electric motor with a rotor, the electric motor being operatively connected between said input shaft and said output shaft and configured to vary a transmission ratio between a rotation angle of said output shaft and the rotation angle of said input shaft; and a controller; wherein said controller comprises: a desired rotation angle calculation unit calculating, at intervals of a predetermined time, a desired rotation angle of the rotor of the electric motor depending on the signal indicative of the rotation angle of said input shaft from the steering angle sensor; a difference calculation unit calculating, at intervals of the predetermined time, a difference between a first value and a second value selected from values of the desired rotation angle of the rotor calculated by said desired rotation angle calculation unit, the first value being calculated earlier than the second value by the predetermined time; and a difference limitation unit limiting, when the difference calculated by said difference calculation unit exceeds a predetermined reference value, the difference to an upper limit thereof.