Multistage compressor

摘要

To provide a multistage compressor including an injection circuit, which can continue high-efficiency and high-capacity operations even if the injection circuit is turned on/off in accordance with operating conditions. A multistage compressor (2) includes a high stage side compressing mechanism (5) suctioning the intermediate pressure refrigerant gas compressed with a low stage side compressing mechanism (4) to perform two-stage compression, and an injection circuit (15) for injecting an intermediate pressure refrigerant into the intermediate pressure refrigerant gas suctioned to the high stage side compressing mechanism (5), the high stage side compressing mechanism (5) including a capacity control mechanism (61) for bypassing a refrigerant gas that is being compressed to a suction side, the injection circuit (15) including an on/off mechanism (75) for performing on/off control of refrigerant injection, and the capacity control mechanism (61) and the on/off mechanism (75) being operated in conjunction with each other.