Rotary compressor

A rotary compressor comprising:

• a rotation mechanism including a cylinder having an annular cylinder chamber;
• a driving mechanism arranged to drive the rotation mechanism;
• a casing containing the rotation mechanism and the driving mechanism;
• an annular piston disposed in the cylinder chamber to be eccentric to the cylinder, the annular piston dividing the cylinder chamber into an outer compression chamber and an inner compression chamber;
• and
• a blade disposed in the cylinder chamber to divide each of the inner and outer compression chambers into a high-pressure side and a low-pressure side, the rotation mechanism compressing a fluid by relatively rotating the cylinder and the piston,
• one of the inner and outer compression chambers being a low-stage side compression chamber arranged to compress a low-pressure fluid into an intermediate-pressure fluid, and the other of the inner and outer compression chambers being a high-stage side compression chamber arranged to compress the intermediate-pressure fluid compressed in the low-stage side compression chamber into a high-pressure fluid,
• the casing having an intermediate-pressure space into which the intermediate-pressure fluid compressed in the low-stage side compression chamber is introduced, with the driving mechanism being disposed in the intermediate-pressure space, and
• the casing having a gas injection pipe connected to the casing that is configured to accommodate gas that is injected into the intermediate pressure space.