Torque transmission device for a four-wheel drive vehicle

Abstract

A torque transmission device is provided wherein a rotary housing is connected to one of front and rear drive shafts which respectively drive front and rear axles of a four-wheel drive vehicle, while a rotary shaft coaxially carried by the rotary housing is connected to the other of the front and rear drive shafts. The housing receives therein a multiple disc clutch device for transmitting rotational power between the housing and the shaft through friction engagement between alternately arranged outer and inner clutch discs which are respectively rotatable bodily with the housing and the shaft. The housing also receives an axially movable piston to press the clutch discs for friction engagement. An end wall of the housing or an end cap secured thereto and a facing end surface of the piston define an axially narrow circular chamber, within which a rotor with a plurality of radially extending blade portions provided with a pair of slanted surfaces is received to be rotated by the shaft. A several space sections into which the chamber is divided by the rotor blade portions are filled with silicon oil of a high viscosity. When the rotational speed difference occurs between the rotor and the housing, a pressure is generated within each of the space sections thanks to the high viscosity of the silicon oil and is directly applied to the piston, whereby rotational power is transmitted from the housing to the rotary shaft and vice versa.