Power transmitting system of four-wheel drive vehicle

Abstract

A power transmitting system of a four-wheel drive vehicle having primary driven wheels driven directly by a prime mover, and subsidiary driven wheels driven through a hydraulic clutch. The power transmitting system comprises a first hydraulic pump driven in operative association with the primary driven wheels and a second hydraulic pump driven in operative association with the subsidiary driven wheels. Each hydraulic pump has a pair of ports which serve as an intake and a discharge with the functions of such ports being reversed between forward and backward movement of the vehicle. A first oil passage connects the intake port of one pump with the discharge of the other pump and a second oil passage connects the discharge of the one pump with the intake of the other pump. Third and fourth oil passages connect the first and second oil passages, respectively, with a working hydraulic pressure chamber in the hydraulic clutch. A one-way valve is provided in each of the third and fourth oil passages for permitting only a flow of oil toward the working hydraulic pressure chamber. The reversal of vehicle movement and direction of oil discharged from each of the hydraulic pumps provided in the power transmitting system of the four-wheel drive vehicle is compensated for by a simple structure of oil passages and one-way valves.