| 摘要 |
PURPOSE:To permit the 4-wheel drive always in the proper state by permitting the automatic switching to the 4-wheel drive when the frequency in which the vertical acceleration speed signal becomes over a set value in the set time which gradually becomes smaller as the car speed becomes larger. CONSTITUTION:A vertical acceleration speed sensor 1 for detecting the vertical acceleration speed of a chassis, etc. and a car speed sensor 2 are provided, and the set time signal which gradually reduces as the car speed signal of the car speed sensor 2 increases is generated from a timer circuit 3. The voltage signal of the sensor 1 and the set time signal of the timer circuit 3 are input into a road-state discriminating circuit 6, and a chassis vibration frequency counter 4 counts the number of times of the voltage signals in the set time, and said counted value is compared with a standard value in a comparison circuit 5, and an output is generated when the counted value exceeds a standard value. A solenoid valve 11 is operated by the above-described output through an electromagnetic relay 8, 4-wheel drive selecting switch 9 and an electromagnetic relay 10, and the automatic switching to 4-wheel drive is carried-out by a negative-pressure actuator 12.
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