Variable capacity vane compressor

Abstract

A variable capacity vane compressor has an annular control element angularly displaceably received within an annular recess formed in one of side blocks defining a cylinder. The control element is angularly displaced in response to a difference in pressure between first and second pressure chambers formed in the one side block and communicating with a zone under lower pressure and a zone under higher pressure, respectively, and to the biasing force of a biasing member, thereby varying the opening angle of at least one second inlet port formed in the one side block and hence controlling the capacity of the compressor. A positioning device is provided at a radially inner portion of the control element to radially position the control element in place within the annular recess of the one side block with reference to the radially inner portion of the control element, thus relieving the hysteresis between angular displacement of the control element in one circumferential directions and that in the opposite direction. At least one oil groove is formed in the inner peripheral surface of the control element to guide lubricating oil for lubricating the same element and its associated sliding parts to a sufficient degree to further reduce the hysteresis.