Patent ID: 7803056

Claim:
A power transmission device comprising: a pulley rotationally attached to a casing of a compressor; a hub connected to the pulley by an engagement of protrusions with recesses; and a power shutoff member, which is interposed between the hub and a rotary shaft of the compressor, to shut off a transmission of an excessively high torque between the rotary shaft and the pulley, wherein an inner circumferential face of the power shutoff member and an outer circumferential face of the rotary shaft are joined to each other by a screw engagement, and a water intrusion path, which is formed between a hub side seating face of the hub and a shaft side seating face of the rotary shaft, is formed into a labyrinth structure, to suppress intrusion of water into the seating face, and the labyrinth structure is formed when an annular flange portion, which protrudes an axial direction toward the casing of the compressor, is provided in a washer, which is arranged between the hub side seating face of the hub and the shaft side seating face of the rotary shaft.