Power transmission device for four wheel drive vehicles

摘要

A differential motion limiting device, for a power transmission device for four wheel drive vehicle, to regulate differential motion of a center differential device includes a wet-type multi plate clutch and an hydraulic actuator. And a switching valve is attached to an oil passage to the hydraulic actuator. In normal running condition, a switching valve is in connecting condition, and a hydraulic pressure being varied by driving conditions is applied to a hydraulic actuator. Under this condition, the clutch is slippingly engaged by certain engaging force so that torque, per certain ratio, is transmitted to the front and the rear wheels. In high speed condition, such as the maximum speed state like an overdrive, or a vehicle speed more than 100 km/h, sensors detect such state, then the switching valve is switched, and the clutch is released. As a result, lubrication oil is flowed between friction plates and separators of the clutch to release heat therefrom.