| 摘要 |
PURPOSE:To enhance the running performance of a vehicle, by changing the drive mode of the vehicle into its four wheel drive mode by means of a 2/4 wheel drive change-over means associated with alternations between the same and reverse phases of the steering ratio in a range in which rear wheels are steered in a phase reverse to that of front wheels within a range of steering angle ratio of the front and rear wheels which are variably con trolled. CONSTITUTION:There are provided, for controlling the feed and discharge of hydraulic oil to and from a power cylinder in a rear wheel steering unit which is controlled in accordance with the steering operation of front wheels, a pulse motor 14, a hydraulic pump drive motor 24 and a 2/4 wheel drive change-over means, and for controlling an actuator 46, a controller 25. There is provided a steering ratio changing means 44 for controlling the motors 14, 24 so that the steering ratio of front and rear wheels is made variable in accordance with a predetermined steering ratio characteristic to set the steering angle of the rear wheels to a desired steering angle. further, there is provided a phase discriminating section 45 for determine the shift of the steering ratio between the same phase and the reverse phase to control the actuator 46 such that the drive mode of the vehicle is turned into the two wheel drive mode when the steering ratio shifts into the same phase range while it is turned into the four wheel drive mode when the steering ratio shifts into the reverse phase range. |
