Multi-plate frictional clutch structure

Abstract

A multi-plate type frictional clutch for a four-wheel drive vehicle is provided in a transfer unit for effecting variable driving force distribution in a 4WD vehicle. An inner wall of a transfer casing includes rotation restriction members so as to restrict rotational movement according to axial movement of a clutch piston disposed within the transfer casing. A cylinder chamber is defined between the rotation restriction members and the clutch piston. Also, the clutch piston is engageable with a rotational portion of a multi-plate type friction clutch via a thrust shaft receiving member disposed between the piston and the rotational portion of the multi-plate clutch. Further, the rotation restriction arrangement includes a casing boss and a piston boss engageable with an input shaft of the transfer unit according to rotational movement thereof. The engagement strength of the casing boss and the piston boss are set to be substantially low. Accordingly, highly accurate control of distribution of driving force variation in a 4WD vehicle may be assured.

Dependencies are inferred from the claim text.