Refrigeration cycle device

Abstract

A refrigeration cycle device includes a compressor, a radiator, an expansion valve, an evaporator and a controller controlling an opening degree of the expansion valve. The controller determines an increase/decrease amount of the opening degree of the expansion valve, to a first amount, when a superheat degree of the refrigerant flowing out from the evaporator is equal to or lower than a predetermined superheat degree. In addition, the controller determines the increase/decrease amount of the opening degree of the expansion valve, to a second amount that is set to more suppress an increase of the superheat degree of the refrigerant flowing out from the evaporator, than that of the first amount, when the superheat degree of the refrigerant flowing out from the evaporator is higher than the predetermined superheat degree.

What is claimed is: 
     
         1 . A refrigeration cycle device comprising:
 a compressor configured to suck, compress and discharge a refrigerant;   a radiator configured to dissipate heat from the refrigerant that is discharged from the compressor;   an expansion valve configured to decompress and expand the refrigerant flowing from the radiator;   an evaporator configured to evaporate the refrigerant which has been decompressed and expanded by the expansion valve;   an accumulator configured to separate the refrigerant evaporated in the evaporator into gas and liquid; and   a controller configured to control an opening degree of the expansion valve, wherein   the controller includes at least one of a circuit and a processor having a memory, and is configured to:   determine an increase/decrease amount of the opening degree of the expansion valve, to a first amount, when a superheat degree of the refrigerant flowing out from the evaporator is equal to or lower than a predetermined superheat degree,   determine the increase/decrease amount of the opening degree of the expansion valve, to a second amount that is set to more suppress an increase of the superheat degree of the refrigerant flowing out from the evaporator, than that of the first amount, when the superheat degree of the refrigerant flowing out from the evaporator is higher than the predetermined superheat degree,   determine the first amount to cause a subcooling degree of the refrigerant flowing out from the radiator closer to a target subcooling degree, and   determine the second amount to cause the superheat degree of the refrigerant flowing out from the evaporator closer to a target superheat degree.   
     
     
         2 . The refrigeration cycle device according to  claim 1 , wherein
 the second amount is a value greater than that of the first amount.   
     
     
         3 . The refrigeration cycle device according to  claim 1 , wherein
 the controller determines a shortage of the refrigerant when the opening degree of the expansion valve reaches an upper limit opening degree.   
     
     
         4 . The refrigeration cycle device according to  claim 1 , wherein
 the controller determines a shortage of the refrigerant, when the opening degree of the expansion valve reaches an upper limit opening degree and when an elapsed time since the opening degree of the expansion valve has reached the upper limit opening degree exceeds a predetermined time.   
     
     
         5 . The refrigeration cycle device according to  claim 3 , wherein
 the controller stops the compressor when the controller determines that a shortage of the refrigerant is caused.   
     
     
         6 . The refrigeration cycle device according to  claim 1 , further comprising
 a refrigerant state detector configured to detect a temperature and a pressure of the refrigerant at a position downstream of the accumulator and on a suction side of the compressor, wherein   the controller calculates the superheat degree of the refrigerant flowing out from the evaporator, by using the temperature and the pressure of the refrigerant detected by the refrigerant state detector.   
     
     
         7 . A refrigeration cycle device comprising:
 a compressor configured to suck, compress and discharge a refrigerant;   a radiator configured to dissipate heat from the refrigerant that is discharged from the compressor;   an expansion valve configured to decompress and expand the refrigerant flowing from the radiator;   an evaporator configured to evaporate the refrigerant which has been decompressed and expanded by the expansion valve; and   a controller configured to control an opening degree of the expansion valve, wherein   the controller includes at least one of a circuit and a processor having a memory, and is configured to:   determine an increase/decrease amount of the opening degree of the expansion valve, to a first amount, when a superheat degree of the refrigerant flowing out from the evaporator is equal to or lower than a predetermined superheat degree,   determine the increase/decrease amount of the opening degree of the expansion valve, to a second amount that is set to more suppress an increase of the superheat degree of the refrigerant flowing out from the evaporator, than that of the first amount, when the superheat degree of the refrigerant flowing out from the evaporator is higher than the predetermined superheat degree,   control a subcooling degree of the refrigerant flowing out from the radiator to be closer to a target subcooling degree in accordance with the first amount, and   control the superheat degree of the refrigerant flowing out from the evaporator to be closer to a target superheat degree in accordance with the second amount.