Abstract: A screw compressor has a screw rotor and a cylinder having an economizer port. The economizer port communicates with a compression chamber formed between the screw rotor and the cylinder. The economizer port is configured and arranged to jet a refrigerant into the compression chamber before closing the compression chamber. Accordingly, the economizer is in communication with the compression chamber while the inner pressure of the compression chamber is low.

Abstract: A screw compressor has a screw rotor (10) and a cylinder (11) having an economizer port (12). The economizer (12) communicates with a compression chamber (13) before closing the compression chamber (13) between the screw rotor (10) and the cylinder (11). Accordingly, the economizer port (12) can be communicated with the compression chamber (13) while the inner pressure of the compression chamber (13) is low. Thereby, the amount of a refrigerant jetted form the economizer can be increased. Cooling effect by a refrigerant is enhanced by increasing the amount of the refrigerant jetted from the economizer port.