Abstract: A drive train of a steering apparatus for rear wheels of a vehicle transmits a driving force of a rotary motor to a steering shaft of rear wheels that is shiftable in the axial direction. The drive train comprises a reduction mechanism driven by the motor and a converting mechanism driven by the reduction mechanism for converting rotational motion of the motor to a linear motion for steering the rear wheels. The reduction mechanism includes a worm driven by the motor and a worm wheel driven by the worm. The converting mechanism comprises a trapezoidally-threaded screw mechanism including a trapezoidally-threaded female screw member and trapezoidally-threaded male screw member. One of the trapezoidally-threaded male and female screw members is driven by the worm wheel, and the other fixed to the steering shaft of rear wheels. A transmission efficiency of an input from the steering shaft of rear wheels to the trapezoidally-threaded screw mechanism is set to be zero.

Abstract: A rear wheel steering device comprising an input shaft which rotates about an axis oriented from front to rear in response to a steering angle of front wheels, a screw shaft which is united with the input shaft and has an axis eccentrically arranged with the axis of the input shaft, a nut which is meshed with the screw shaft, a rack formed on the nut, and a pinion meshed with the rack and connected to the nut. The pinion is supported in a manner that it is rotatable about a substantially vertical axis and movable in the rightward and leftward transverse direction. The pinion is meshed with a rear wheel steering rack. The rotation of the input shaft causes the screw shaft to rotate and whirl. In response to the rotation and the whirling motion of the screw shaft, the rear wheel steering rack moves in the rightward and leftward transverse direction. The rear wheels are steered by the transverse movement of the rear wheel steering rack.