| 摘要 |
PURPOSE:To suppress an increase of an understeering tendency by correcting the steering ratio controlled by a steering ratio control means so that the steering state of front wheels and the steering state of rear wheels are in the opposite phase relationship when a lateral force applied to a vehicle is a predetermined value or more. CONSTITUTION:A rear wheel steering mechanism which steers rear wheels in response to the steering of front wheels has a pulse motor 30 moving a rear wheel steering rod and a pump drive motor 44 for applying a hydraulic assist force to this rod, and they are controlled by a control unit 50 respectively. In this case, the control unit 50 is constituted of a steering ratio characteristic selecting unit 59 selecting one of multiple steering ratio characteristics stored in a memory unit 58 based on the detected value of a lateral force and a rear wheel steering angle arithmetic unit 60 calculating the rear wheel steering angle based on the steering ratio characteristic and the detected values of the steering angle and vehicle speed. This steering ratio is selected so that the steering state of front wheels and the steering state of rear wheels are in the opposite phase relationship when the lateral force is a predetermined value or more. |
