Patent ID: 8794027

Claim:
A compressor comprising: a casing; a screw rotor fitted in the casing; compression chambers formed between the screw rotor and the casing; a slide member placed between the casing and the screw rotor, the slide member having at least one economizer port arranged to discharge refrigerant into the compression chambers, the slide member being movable along an axis of the screw rotor so that a position of the at least one economizer port is movable along the axis of the screw rotor; and a control unit controlling a position of the slide member along the axis of the screw rotor to control the position of the at least one economizer port along the axis of the screw rotor in accordance with rotating speed of the screw rotor in order to advance the timing of opening of the at least one economizer port to the compression chambers in accordance with the increase in the rotating speed of the screw rotor, the controller controlling the position of the slide member along the axis of the screw rotor such that the slide member moves upstream toward a suction side of the compressor when the rotating speed of the screw rotor increases, and the slide member moves downstream toward a discharge side of the compressor when the rotating speed of the screw rotor decreases.