Steering system for vehicles

A steering system (1) for vehicles including a front wheel steering mechanism (1a) for steering front wheels (5) at an angle in accordance with a steering operation of a driver, and a rear wheel steering mechanism (1b) for steering rear wheels (11) at an angle (Sr) in accordance with a travelling state of the vehicle. For the steering of the rear wheel, a reference steering angle (Ar) according to a turning state of the vehicle and a corrective steering angle (Ac) according to a velocity derivative thereof are computed, and the steering angle (Sr) of the rear wheel is obtained by making either an addition or a subtraction of the reference and corrective steering angles at least in accordance with the velocity derivative.

We claim:

1. A steering system for a vehicle having front and rear steered wheels, comprising:

means for detecting a turning state of the vehicle;

means for detecting a velocity derivative of the vehicle;

means for determining a steering angle for the vehicle's rear wheels dependent on output signals of said turning state detecting means and said velocity derivative detecting means; and

means for driving the rear wheels to said steering angle as determined by said determining means;

said determining means including means for providing a reference steering angle for the rear wheels dependent on the output signal from said turning state detecting means, and means for correcting said reference steering angle dependent on at least the output signal of said velocity derivative detecting means to establish said steering angle for the rear wheels; and

said correcting means correcting said reference steering angle by way of a correction amount and a correction direction both corresponding to said velocity derivative.

2. A steering system according to claim 1, wherein:

said correcting means corrects said reference steering angle in a correction direction which promotes turning of the vehicle when the detected velocity derivative is indicative of a vehicle accelerating state.

3. A steering system according to claim 1, wherein:

said correcting means corrects said reference steering angle in a correction direction which opposes the turning of said vehicle when the detected velocity derivative is indicative of a vehicle decelerating state.

4. A steering system according to claim 1, wherein:

said correction direction of said correction data is the same as the direction in which the front wheels are steered when the detected velocity derivative is indicative of a vehicle accelerating state and is opposite to the direction in which the front wheels are steered when the detected velocity derivative is indicative of a vehicle decelerating state.

5. A steering system according to claim 1, wherein:

said reference steering angle pertains to a steering direction which is either the same or opposite to a steered direction of the vehicle's front wheels; and

said correcting means does not correct said reference steering angle when the steering direction of said reference steering angle is opposite to the steered direction of the vehicle's front wheels.