PURPOSE: To make it reach the objective value of the discharge temperature in a short time, by changing the opening of an expansion valve from the initial valve aperture to a valve aperture large in refrigerant circulation resistance, when the temperature of an evaporator tops the set temperature for defrosting.
CONSTITUTION: A controller 11b consists of controllers 9a and 10b, and the controller 9a receives the input of the discharge temperature of a compressor detected with a discharge temperature sensor 7, and computes the valve aperture of an electronic expansion valve 3, according to the difference from the objective temperature, and controls it. On the other hand, the controller 10b opens a solenoid valve 6 fully to perform defrosting operation when the temperature of the evaporator 4 detected by a defrosting temperature sensor 8 reaches the defrosting temperature. Then, in case that the defrosting operation terminates, and that the temperature of the evaporator 4 is higher than the defrosting set temperature, it changes the aperture of the expansion valve 3 to the optimum aperture, that is, to the valve opening larger in refrigerant circulation resistance than the initial valve aperture at the time of having turned on power source to the controller, and closes the solenoid valve 6, and then, the controller 9a performs usual discharge temperature control. In this way, the objective discharge temperature can be reached in a short time.
Fujiwara, Katsuhiko
Fukui, Seiji
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