Variable capacity compressor

Claim 1

A variable capacity compressor comprising: an enclosure having cylindrical internal space, a cylindrical-shaped rotor which is rotatably held in said enclosure and driven by an external force and has vanes, plural return ports formed on a wall of volume-decrease-step space in said internal space wherein volume of sectioned space by movements of said rotor and said vanes is changed cyclically, an exit formed on said wall of volume-increase-step space in said internal space wherein volume of sectioned space by movements of said rotor and said vanes is changed cyclically, and a C-shaped guide passage formed in said wall for connecting said plural return ports and said exit; an arc-shaped slider which is provided slidably in said guide passage for opening and closing said plural return ports with a pressure control compartment remained in said guide passage; a bias spring for urging said slider in a direction to close said return ports; and control pressure supply means which supplies control pressure to said pressure control compartment and comprises a pressure detecting part which compares suction pressure with atmospheric pressure, thereby to generate a displacement thereof, a valve urged to close by a spring, a rod driven by said pressure detecting part for opening said valve, and an electromagnetic coil for applying electromagnetic force to said valve, thereby to urge said valve in a direction to open.