Refrigeration cycle device

A refrigeration cycle device comprising:

• a main refrigerant circuit having
• a main compressor that compresses a main refrigerant,
• a main heat-source-side heat exchanger that functions as a radiator of the main refrigerant,
• a main use-side heat exchanger that functions as an evaporator of the main refrigerant,
• a main expansion valve that decompresses the main refrigerant that flows between the main heat-source-side heat exchanger and the main use-side heat exchanger,
• a suction injection pipe that causes the main refrigerant that flows between the main heat-source-side heat exchanger and the main use-side heat exchanger to branch off and to be sent to a suction side of the main compressor, and
• a subcooling heat exchanger that cools the main refrigerant that flows between the main expansion valve and the main use-side heat exchanger by heat exchange with the main refrigerant that flows in the suction injection pipe,
• wherein the main refrigerant circuit has a sub-use-side heat exchanger that functions as a cooler of the main refrigerant that flows between the main expansion valve and the main use-side heat exchanger;
• the refrigeration cycle device further comprising:
• a sub-refrigerant circuit having
• a sub-compressor that compresses a sub-refrigerant,
• a sub-heat-source-side heat exchanger that functions as a radiator of the sub-refrigerant, and
• the sub-use-side heat exchanger that functions as an evaporator of the sub-refrigerant and that cools the main refrigerant that flows between the main expansion valve and the main use-side heat exchanger;
• and
• the refrigeration cycle device further comprising:
• a controller that controls constituent devices of the main refrigerant circuit and the sub-refrigerant circuit,
• wherein the controller determines, based on a detection signal from a sensor for outside air temperature, a detection signal from a sensor for temperature of the main refrigerant at the main heat-source-side heat exchanger, a detection signal from a sensor for subcooling degree of the main refrigerant at an outlet of the subcooling heat exchanger, or a detection signal from a sensor for subcooling degree of the main refrigerant at an outlet of the sub-use-side heat exchanger, whether a first switching condition or a second switching condition is satisfied,
• wherein, the controller is configured to switch between a cooling action of the subcooling heat-exchanger, which cools the main refrigerant by using the suction injection pipe and the subcooling heat exchanger and a cooling action of the sub-refrigerant-circuit, which cools the main refrigerant by using the sub-refrigerant circuit, based on whether the first switching condition or the second switching condition is satisfied.