| 摘要 |
The present invention relates to a power transmission device having two or more pistons. The power transmission device comprises: a housing in which a clutch housing, a clutch connection part, a clutch hub, and a disc housing are connected so as to form a mounting space; a power transmission hub selectively and operatively connected to the housing; a plurality of first friction discs spline-coupled to the inner peripheral surface of the disc housing; a plurality of second friction discs spline-coupled to the outer peripheral surface of the power transmission hub and alternatingly arranged with the first friction discs; a piston module having two or more pistons each having a piston chamber, and selectively friction-coupling the first friction discs and the second friction discs by using operation pressure supplied to the piston chambers; and at least one return spring or separating spring providing a spring load, which resists an axial force occurring because of the operation pressure, and being present inside or outside the piston module, wherein friction materials are attached on one surface or both surfaces of each of the first friction discs or the second friction discs. |
