Compressor

A compressor comprising:

• a low-stage side compression mechanism configured to compress refrigerant sucked from outside;
• a high-stage side compression mechanism configured to suck refrigerant discharged from the low-stage side compression mechanism and to compress the sucked refrigerant;
• an injection pipe configured to lead intermediate pressure gas refrigerant in a refrigeration cycle into the high-stage side compression mechanism;
• two end plates with each end plate having a flat surface, the two end plates being disposed with the flat surfaces opposed to each other;
• a fixed member disposed between the two end plates;
• a movable member disposed between the two end plates and arranged to eccentrically move about a predetermined rotational axis to form a compression chamber of one of the low-stage side compression mechanism and the high-stage side compression mechanism between the fixed member and the movable member;
• a bypass passage having an upstream end opened to the compression chamber through which refrigerant is partially ejected from the compression chamber so as to be returned to a suction side of the one of the low-stage side compression mechanism and the high-stage side compression mechanism having the compression chamber;
• and
• an opener/closer arranged to open/close the bypass passage, the opener/closer being arranged to open the bypass passage when a pressure difference between the refrigerant sucked into the low-stage side compression mechanism and the refrigerant discharged from the high-stage side compression mechanism is below a predetermined value, and to close the bypass passage when the pressure difference between the refrigerant sucked into the low-stage side compression mechanism and the refrigerant discharged from the high-stage side compression mechanism is above the predetermined value,
• the upstream end of the bypass passage having a cross section that is elongated circumferentially about the rotational axis.