Variable displacement compressor having a spool with a coating layer

Abstract

A compressor has a housing body, a drive shaft, a swash plate, and a piston. The swash plate converts rotation of the drive shaft to reciprocating movement of the piston in a cylinder bore. The piston compresses gas supplied to the cylinder bore from an external circuit via a suction chamber and discharges the compressed gas to a discharge chamber. The swash plate is tiltable with respect to a plane perpendicular to the longitudinal axis of the drive shaft according to differential pressure between the crank chamber and the suction chamber. The swash plate controls the displacement of the compressor based on the inclination thereof. A spool is movable longitudinally between a first position and a second position in response to the inclination of the swash plate. The spool connects the external circuit with the suction chamber in the first position and disconnects the external circuit from the suction chamber in the second position. The housing body has a surface slidably engaged by the spool. A coating layer is provided on at least one of the spool and the slide surface to reduce frictional resistance occurring due to the sliding movement of the spool on the slide surface. A second coating layer is provided on an end surface of the spool to lubricate and thereby reduce frictional resistance with the housing surface along the periphery of the suction passage leading into the shutter chamber occurring due to rotation of the spool, and also to improve the seal between the end surface of the spool and the housing when in the second position closing off the suction passage.