Abstract: A compressor includes: a shell forming an outer portion thereof and having lower part in which an oil pan is formed to store oil; a motor provided in the shell; a compression unit provided in the shell to compress a working gas when being driven by the motor; a frame fixed to the shell and supporting the compression unit; a shaft supported by the frame, connecting the motor and the compression unit, provided to transmit a turning force of the motor to the compression unit, and including an oil passage; and an oil pump provided at lower part of the shaft to draw oil from the pan and supply the oil into the oil passage. The pump includes a bypass valve that is opened, when a pressure of oil flowing in the oil passage is higher than a threshold pressure, to return part of the oil to the pan.

Abstract: Cracking of a ceramic bearing fitted over a metal shaft is prevented by grooves on an inner periphery of a ceramic inner race and/or on an outer periphery of the metal shaft.

Abstract: A pin which acts as a spring directly extends through an outer race without use of an outer-race casing and a pin holder and the central portion of the pin supports the outer race. Axial movement of the pin beyond a predetermined range is restricted by snap rings fitted on the both ends of the pin. An oil film is formed between the outer peripheral surface of the outer race and the inner peripheral surface of casings and oil reservoirs are also defined to damp axial movement of the outer race. That is, the pin which acts as a spring directly extends through the outer race of the bearing in parallel with a rotating shaft and the central portion of the pin elastically supports the outer race. The ends of the pin are supported by the casings through the snap rings. A space in which an oil film functioning as an oil film damper is formed is defined by the outer peripheral surface of the outer race and the inner peripheral surface of the casings.