PURPOSE: To improve the sealing property of a crank chamber by disposing a condenser, an expansion valve, an evaporator and an evaporation pressure regulating valve in a circulation pipe path from a discharge chamber to a suction chamber of a compressor and affording always communication between the crank chamber and a suction path before the regulating valve from the evaporator to the evaporation pressure regulating valve.
CONSTITUTION: While an evaporation pressure regulating valve 27 is opened and total capacity running is carried out, cooling load is reduced and pressure in a suction path 36 before the regulating valve, i.e., evaporation pressure Pe is reduced so that the opening of said valve 27 is reduced to restrain the reduction of the evaporation pressure. Also, pressure Pc in a crank chamber 7 follows up said pressure Pe to be equalized thereto and restrained with respect to the reduction of crank chamber pressure Pc. Further, when the opening of said valve 27 is reduced, suction pressure Ps is reduced and the difference between pressures Pc and Ps is increased to that the piston stroke is reduced to provide small capacity running. Thus, the pressure in the crank chamber is maintained at the set pressure so that the surface pressure on a shaft seal is constant to improve the sealing property.
DEGUCHI HIROYUKI
KOBAYASHI HISAO
SUGISONO SHUICHI
