PURPOSE: To prevent the temperature rise of a refrigerant gas, and to improve the cooling efficiency of a compressor by injecting a refrigerant liquid to a compressor heat section and mixing the refrigerant liquid with a suction gas when a part of the refrigerant liquid delivered from a condenser to the compressor, the suction gas is cooled and the temperature of a discharged gas is controlled.

CONSTITUTION: When the temperature of a discharged gas from a compressor 1 reaches a fixed temperature (such as 120°C) and a thermostat 22 is turned ON when a cooling device such as a refrigerated case is operated, the solenoid valve 19 of a branch pipe 16 is opened, thus passing a refrigerant liquid in quantity proportioned to the temperature of the discharged gas detected by a temperature-sensing cylinder 21 through a temperature expansion valve 20 and forwarding the refrigerant liquid to the compressor 1. A suction gas taken into a suction port 13 from the suction pipe 12 of a compression equipment 3 is passed through a motor 2 in the compression equipment 3 to cool the motor 2, and mixed with the refrigerant liquid from the branch pipe 16 flowing in from the intake port of a head 17 on the suction side. The refrigerant liquid brought into contact with the suction gas is gasified and the temperature of the suction gas is lowered, thus preventing the overheat of the compressor 1.