FOUR-WHEEL STEERING SYSTEM FOR VEHICLE

摘要

A four-wheel steering system for a vehicle comprises a steering wheel, a front wheel turning mechanism for turning the front wheels in response to operation of the steering wheel, a rear wheel turning mechanism including a rear wheel steering ratio determining circuit for determining the rear wheel steering ratio and an actuator for turning the rear wheels according to the rear wheel steering ratio determined by the rear wheel steering ratio determining circuit. The four-wheel steering system is provided with a road condition sensor for detecting road surface conditions which can weaken the road gripping force of the wheels and a rear wheel steering ratio controller for changing the rear wheel steering ratio determined by the rear wheel steering ratio determining circuit so that the rear wheel steering ratio is increased when the road condition is such that the road gripping force of the wheels can be weakened.