Patent ID: 8821136

Claim:
A supercharger comprising: a centrifugal compressor for compressing air with an impeller upon rotation thereof; a rotational shaft coupled to the impeller; a motor comprising a stator mounted in a casing which houses the rotational shaft therein and a rotor mounted on the rotational shaft; and a journal bearing holding the rotational shaft radially in position; wherein the impeller, the journal bearing, and the motor are disposed on the rotational shaft successively in the order named from an end of the rotational shaft; the journal bearing comprises a hollow cylindrical member having an inner space therein and a heat transfer member fitted in the inner space, wherein the journal bearing has a closed end face that at least in part defines the inner space, the closed end face being located at a position nearer to the rotor than the impeller in an axial direction, and wherein the heat transfer member is disposed in contact with the closed end face and fitted in the inner space; the heat transfer member is made of a material which is less rigid and has a greater coefficient of thermal conductivity than the hollow cylindrical member; and the impeller radiates heat transferred through the heat transfer member into ambient air.