Patent ID: 7993228
Filing Date: 2011-08-09
Classification: F16D,F16H

Abstract:
1. A power transmission device comprising: a pulley rotatably fitted to a housing; and a hub adapted to a fit a distal end portion of a rotary shaft protruding outside from said housing, wherein the hub rotates integrally with said rotary shaft, and said hub includes an inner hub fixed to said rotary shaft and arranged inside a torque transmitting elastic member, an outer hub, which is arranged outside said torque transmitting elastic member and is interconnected to a front end face of said pulley, wherein: said torque transmitting elastic member is interposed between said inner hub and said outer hub and held by said inner and outer hubs, the hub includes a hub side engagement portion formed of an elastic material such as rubber or a resin and disposed on either one, or both, of an inner peripheral surface side and an outer peripheral surface side of said outer hub, the pulley includes a pulley side engagement portion disposed at a position corresponding to said outer hub on the front end face of said pulley, the hub side engagement portion and the pulley side engagement portion engage with each other to thereby form a torque transmission structure between said hub and said pulley, the pulley is made of a resin material, an annular concavity is formed in a front surface of the pulley, the annular concavity receives the hub-side engagement portion, the annular concavity has an annular inner surface, an annular outer surface, which is radially outward of the inner surface, and a bottom surface, which extends between a rear end of the inner surface and a rear end of the outer surface, a pulley side engagement portion is provided on at least one of the surfaces of the annular concavity, strength reinforcing ribs are located on the bottom of the annular concavity and extend continuously from the inner surface to the outer surface of the annular concavity, a plurality of slits are located on the hub side engagement portion and are spaced apart from one another in a circumferential direction of the hub side engagement portion, each of the slits extends in an axial direction of the power transmission device from a rear end to a front end of the annular concavity, each of the strength reinforcing ribs extends in an axial direction and is located on the bottom surface of the annular concavity in a fashion to correspond with the slits, the pulley side engagement portion and the hub side engagement portion are assembled such that the strength reinforcing ribs are engaged with the slits in the axial direction, and each of the strength reinforcing ribs includes first and second peripheral side faces that respectively contact the hub side engagement portion in the axial direction.