To avoid a sense of incongruity of a driver during changing a lane by carefully controlling a steering ratio to be changed corresponding a speed using an add-subtract type VGR device when a steering wheel is at a small steering angle, in particular.
A transmission ratio varying mechanism 10 having a planetary gear mechanism 16 is provided in a steering force transmission passage for an automobile, so that steering rotation is input into a sun gear 17 of the planetary gear mechanism 16 and output from a ring gear 18 and it is added or subtracted with the rotation of a planetary carrier 20 using a VGR motor 22. The mechanism also basically controls the transmission ratio r corresponding to the speed V (Step S2→S3→S6) and corrects the transmission ratio r to be changed smaller with the change of the speed V (Step S3→S4→S5→S6).
TANAKA KEN
Hiroshi Koyama
Hiroshi Takeuchi
Takahisa Shimada
Yuji Takeuchi
Katsumi Imae
Teshima Masaru
Atsushi Fujita