CONTROLLER OF QUANTITY OF REFRIGERANT CIRCULATING IN OPEN SHOW CASE

PROBLEM TO BE SOLVED: To reduce the number of times of start and stoppage of a compressor, by controlling the aperture of an electric expansion valve and controlling the quantity of a refrigerant circulating in a refrigerant circuit, and keeping the quantity of a refrigerant constant at a set temperature within a refrigerator, and adjusting the temperature of the refrigerant at the outlet of an evaporator at a proper temperature. SOLUTION: A refrigerant pressurized and liquefied with a compressor 1 and a condenser 3 is depressurized with an electric control valve whose aperture is controllable with a pulse motor, and is evaporated and gasified with an evaporator 4, and again it is sucked with a compressor 1. The control of the aperture of this expansion valve 5 is performed by relating the two factors of the in-refrigerator temperature of an open case arid the overheat degree of the refrigerant at the outlet of the evaporator to each other. The 0 origin production of the pulse motor, that is, the origin production where the valve part comes to full close position is made at the time of turning on the power of the refrigerant circuit and the time of reopening of the cooling after finish of defrost. A controller outputs the planned number of pulses as initial aperture to the expansion valve 5, and operates and stores the differences between the set in-refrigerator temperature and the degree-of-overheat lower limit value and the actual in-refrigerator temperature and the temperatures detected by the evaporator inlet and outlet refrigerant detection means 6 and 7.