Claims
- 1. A four-wheel steering system for steering front wheels and rear wheels of a vehicle, the rear wheels steered according to vehicle speed, the system comprising:
- a fluid powered front wheels actuator having a left port and a right port for steering the front wheels;
- a front wheels direction control valve for controlling the front wheels actuator in response to a steering wheel having a left, right and neutral position;
- a main pump for providing pressurized fluid to the front wheels direction control valve;
- a fluid powdered rear wheels actuator for steering the rear wheels;
- a rear wheels direction control valve having a left port and a right port for controlling the rear wheels actuator;
- a subpump for providing pressurized fluid through a fluid pressure line;
- a solenoid controlled valve for directing the pressurized fluid from the subpump to a fluid reserve tank when the steering wheel is in a neutral position and the solenoid controlled valve directing the pressurized fluid from the subpump to the rear wheels actuator when the steering wheel is in the left or right positions;
- a first pilot line connecting pressurized fluid from the left port of the front wheels actuator to the left port of the rear wheels direction control valve; and
- a second pilot line connecting pressurized fluid from the right port of the front wheels actuator to the right port of the rear wheels direction control valve wherein the front wheels actuator controls the rear wheels direction control valve.
- 2. The four-wheel steering system of claim 1 wherein the rear wheel direction control valve comprises a three way-four port valve.
- 3. The four-wheel steering system of claims 1 or 2 wherein the pressurized fluid from the first and second pilot lines and the pressurized fluid from the subpump to the rear wheels actuator increase mutually in proportion until reaching a threshold valve.
- 4. The four-wheel steering system of claim 1 wherein the rear wheels actuator has a piston which strokes to increase in proportion to the pressurized fluid supplied from the subpump.
- 5. The four-wheel steering system of claim 1 wherein the rear wheels actuator has a piston biased in a neutral position by a coil spring.
- 6. The four-wheel steering system of claim 1 wherein the front wheels direction control valve has a left port and a right port respectively connected to the left port and right port of the front wheels actuator.
- 7. The four-wheel steering system of claim 1 wherein the rear wheels actuator has a left port and a right port respectively connected to the left port and right port of the rear wheels direction control valve.
- 8. Four-wheel steering system according to claim 1 wherein, with respect to a front and rear wheels steering angle ratio to the speed of a vehicle, rear wheel steering for front wheels is started at an increasing speed step and increases in proportion to the speed to a high speed step, and keeps a constant level after the high speed step.
Priority Claims (1)
Number |
Date |
Country |
Kind |
89-3601 |
Mar 1989 |
KRX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/374,268, filed Jun. 29, 1989, now abandoned.
US Referenced Citations (7)
Continuations (1)
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Number |
Date |
Country |
Parent |
374268 |
Jun 1989 |
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