Device for controlling vehicle four wheel drive front/rear coupling

Abstract

In a four wheel drive vehicle, a four wheel drive device receives rotational power from an engine and provides it to the combination of the front wheels of the vehicle and also to the combination of the rear wheels of the vehicle. A device is provided for selectively coupling the rotation of the combination of the front vehicle wheels and the rotation of the combination of the rear vehicle wheels. A control device is provided for this front/rear coupling device, and includes: (a) a means for detecting the rotational speed of the combination of the front wheels of the vehicle; (b) a means for detecting the rotational speed of the combination of the rear wheels of the vehicle; and: (c) a means for controlling the front/rear coupling device, so that its operation is substantially not restricted when the discrepancy between the rotational speed of the combination of the front wheels of the vehicle and the rotational speed of the combination of the rear wheels of the vehicle is not greater than a certain threshold value; while, when the discrepancy between the rotational speed of the combination of the front wheels of the vehicle and the rotational speed of the combination of the rear wheels of the vehicle is greater than the certain threshold value, coupling between the rotation of the combination of the front vehicle wheels and the rotation of the combination of the rear vehicle wheels is substantially prohibited. The method of operation of this device is also disclosed.