| 摘要 |
The present invention relates to a four-wheel steering system comprising a speed sensor yielding the sped of a vehicle by calculating the pulse in proportion to the number of revolutions of a driving shaft. A frequency oscillating conversion circuit converting and counting detection signal is delivered from the speed sensor. An error amplification circuit amplifying only the error over the pre-designated pulse number from the signal delivered from the frequency oscillating conversion circuit. A solenoid driving circuit drives a solenoid value that opens and shuts the oil pressure passage of the direction control value at the rear wheels according to the signal of the error amplification circuit, and being constituted to the effect that the direction control value of the rear wheels side is set between the oil pressure source and the rear wheels actuator is opened. The fluid pressure direction is controlled at the rear wheels actuator based upon the pressure difference of the left and right side ports of the normal front wheels steering part when the speed of a vehicle is above a standard value, by the control unit which comprises the current detection circuit that feeds back to the error amplification circuit by detecting the current flowing to the solenoid.
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