Variable capacity vane compressor

Abstract

A variable capacity vane compressor has a cylinder including a cam ring having an inner peripheral surface with an oblong cross section and within which a rotor is rotatably received, a plurality of vanes carried by the rotor, and a control plate disposed in the cylinder for rotation in opposite circumferential directions and having a peripheral edge formed with at least one cut-out portion. The control plate is disposed to rotate in response to a difference between pressure from a lower pressure zone and pressure from a higher pressure zone to cause a change in the circumferential position of the cut-out portion, thereby varying the compression commencing timing of the compressor and hence the capacity of same. The cut-out portion of the control plate comprises a first portion circumferentially extending from a downstream end of the cut-out portion with respect to the direction of rotation of the rotor to an intermediate portion of the same, and a second portion circumferentially extending from the intermediate portion to an upstream end of the cut-out portion, and being shallower than the first portion. The cut-out portion has such a circumferential position and length that the second portion is positioned radially inwardly of the inner peripheral surface of the cam ring and has an upstream end and a downstream end thereof positioned, respectively, upstream of a downstream end of an inlet port formed in the cylinder and downstream of same, when the control plate member is circumferentially displaced to an extreme circumferential position in which the minimum capacity of the compressor is obtained, whereby unnecessary compression is prevented.