Refrigerant flow control system for use with refrigerator

Claim 1

A refrigerant flow control system for a heat pump type air conditioner incorporating a refrigerant circulating circuit having a compressor, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger and a four-way valve, said system comprising: a branch pipe extending from an intermediate portion of a refrigerant pipe connecting a discharge port of said compressor to said four-way valve, and having one sealed free end; a first temperature sensor disposed on said branch pipe in the vicinity of said sealed free end thereof for detecting a saturated condensation temperature of said refrigerant which is condensed in said branch pipe; a second temperature sensor disposed on a discharge pipe of said compressor for detecting a discharge temperature of the gaseous refrigerant discharged from said compressor; and a control device for receiving signals from said first and second temperature sensors, which are representative of the temperatures detected by said sensors, said control device calculating a difference between said saturated condensation temperature and said discharge temperature of said gaseous refrigerant, and a degree of superheat of said gaseous refrigerant discharged, comparing a predetermined degree of superheat with said calculated degree of superheat, delivering to said expansion valve a command signal corresponding to the difference therebetween, and controlling an opening degree of said expansion valve, whereby, if said calculated degree of superheat is higher than said predetermined degree of superheat, said opening degree of said expansion valve is controlled to be increased, while if said calculated degree of superheat is lower than said predetermined degree of superheat, said opening degree of said expansion valve is controlled to be decreased, so that a predetermined degree of superheat is consistently maintained.