A compressor mounted on a vehicle is disclosed. The compressor includes an apparatus for transmitting rotational power from an engine to drive shaft of the compressor via a pulley. The apparatus has a spring coupled to one of the pulley and the drive shaft. A deformable ring is coupled to the other one of the pulley and the drive shaft. The deformable ring is deformed by heat. The spring and the deformable ring are being held in abutment against each other by the force of the spring so as to transmit the rotational power to each other. A contact ring is interposed between the spring and the deformable ring. The contact ring has a rigidity larger than that of the deformable ring. The spring and the contact ring frictionally contact one another to generate the heat that deform the deformable ring when load generated in the drive shaft is in excess of a predetermined value.
