Driving force transmitting device for four-wheel drive vehicle

A driving force transmission device for four-wheel-drive vehicle, comprising:

• a switch mechanism for switching between a four-wheel-drive mode in which the fastening power of a multi-disc clutch mechanism is changed continually and the driving force distribution to front and rear wheels is automatically controlled depending on running conditions, and a two-wheel-drive mode in which the multi-disc clutch mechanism is released and the driving force is transmitted only to the rear wheels;
• and
• a disconnection/connection mechanism for disconnecting and connecting a front wheel differential to which the driving force distributed by the multi-disc clutch mechanism is input and one or both of left and right front wheel drive shafts, wherein
• the dragging torque of the multi-disc clutch mechanism is made smaller than the rotation resistance of a front wheel driving force transmission section from the multi-disc clutch mechanism to the disconnection/connection mechanism in the two-wheel-drive mode, and the front wheel differential and one or both of the left and right front wheel drive shafts are disconnected by the disconnection/connection mechanism and thereby the rotation of the front wheel driving force transmission section is stopped.