Air conditioner, method for controlling opening of expansion valve, and computer-readable recording medium with expansion valve opening control program recorded thereon

Abstract

An air conditioner includes: a compressor for compressing a refrigerant; an expansion valve for adjusting the flow of the refrigerant; a first temperature sensor for detecting a discharge temperature of the compressor; and a second temperature sensor for detecting a temperature of a condenser. A discharge temperature difference is calculated that is a difference between the discharge temperature detected by the first temperature sensor and the temperature of an outdoor heat exchanger or an indoor heat exchanger functioning as the condenser that is detected by the second temperature sensor. The opening of the expansion valve is set based on the calculated discharge temperature difference and a target discharge temperature difference that is set so that a target degree of superheat is obtained.

1 . An air conditioner comprising:
 a compressor for compressing a refrigerant;   an expansion valve for adjusting a flow of said refrigerant;   a first temperature sensor for detecting a discharge temperature of said compressor;   a second temperature sensor for detecting a temperature of a condenser;and   control means for controlling an opening of said expansion valve,   said control means calculating a discharge temperature difference which is a difference between said discharge temperature detected by said first temperature sensor and the temperature of said condenser detected by said second temperature sensor, and   said control means setting a basic opening which is an opening of said expansion valve under normal control, based on said calculated discharge temperature difference and a target discharge temperature difference (TMP_aim) that is set so that a target degree of superheat is obtained.   
     
     
         2 . The air conditioner according to  claim 1 , wherein when said calculated discharge temperature difference is not less than a predetermined first threshold value (Hth), said control means controls the opening of said expansion valve so that the opening is larger than said basic opening under said normal control. 
     
     
         3 . The air conditioner according to  claim 2 , wherein
 when said calculated discharge temperature difference is not more than a predetermined second threshold value (Lth), said control means controls the opening of said expansion valve so that the opening is smaller than said basic opening under said normal control, and   said second threshold value is smaller than said first threshold value.   
     
     
         4 . The air conditioner according to  claim 1 , wherein when said calculated discharge temperature difference is not more than a predetermined second threshold value (Lth), said control means controls the opening of said expansion valve so that the opening is smaller than said basic opening under said normal control. 
     
     
         5 . The air conditioner according to  claim 1 , wherein said control means calculates said target discharge temperature difference (TMP_aim) from the number of revolutions of said compressor. 
     
     
         6 . The air conditioner according to  claim 1 , further comprising:
 a switch valve for switching direction of circulation of said refrigerant between a cooling cycle operation and a heating cycle operation;   an outdoor heat exchanger for heat exchange between outdoor air and said refrigerant; and   an indoor heat exchanger for heat exchange between indoor air and said refrigerant, wherein   in the cooling cycle operation, said condenser corresponds to said outdoor heat exchanger and, in the heating cycle operation, said condenser corresponds to said indoor heat exchanger.   
     
     
         7 . A method for controlling an opening of an expansion valve of an air conditioner, said air conditioner including: said expansion valve for adjusting a flow of a refrigerant; a first temperature sensor for detecting a discharge temperature of a compressor; and a second temperature sensor for detecting a temperature of a condenser, said method comprising the steps of:
 calculating a discharge temperature difference which is a difference between said discharge temperature detected by said first temperature sensor and the temperature of said condenser detected by said second temperature sensor; and   setting a basic opening which is an opening of said expansion valve under normal control, based on said calculated discharge temperature difference and a target discharge temperature difference (TMP_aim) that is set so that a target degree of superheat is obtained.   
     
     
         8 . A computer-readable recording medium with an expansion valve opening control program recorded thereon for causing
 a computer provided to an air conditioner including: an expansion valve for adjusting a flow of a refrigerant; a first temperature sensor for detecting a discharge temperature of a compressor; and a second temperature sensor for detecting a temperature of a condenser,   to perform the steps of:   calculating a discharge temperature difference which is a difference between said discharge temperature detected by said first temperature sensor and the temperature of said condenser detected by said second temperature sensor; and   setting a basic opening which is an opening of said expansion valve under normal control, based on said calculated discharge temperature difference and a target discharge temperature difference that is set so that a target degree of superheat is obtained.   
     
     
         9 . The air conditioner according to  claim 2 , wherein said control means calculates said target discharge temperature difference (TMP_aim) from the number of revolutions of said compressor. 
     
     
         10 . The air conditioner according to  claim 3 , wherein said control means calculates said target discharge temperature difference (TMP_aim) from the number of revolutions of said compressor. 
     
     
         11 . The air conditioner according to  claim 4 , wherein said control means calculates said target discharge temperature difference (TMP_aim) from the number of revolutions of said compressor. 
     
     
         12 . The air conditioner according to  claim 2 , further comprising:
 a switch valve for switching direction of circulation of said refrigerant between a cooling cycle operation and a heating cycle operation;   an outdoor heat exchanger for heat exchange between outdoor air and said refrigerant; and   an indoor heat exchanger for heat exchange between indoor air and said refrigerant, wherein   in the cooling cycle operation, said condenser corresponds to said outdoor heat exchanger and, in the heating cycle operation, said condenser corresponds to said indoor heat exchanger.   
     
     
         13 . The air conditioner according to  claim 3 , further comprising:
 a switch valve for switching direction of circulation of said refrigerant between a cooling cycle operation and a heating cycle operation;   an outdoor heat exchanger for heat exchange between outdoor air and said refrigerant; and   an indoor heat exchanger for heat exchange between indoor air and said refrigerant, wherein   in the cooling cycle operation, said condenser corresponds to said outdoor heat exchanger and, in the heating cycle operation, said condenser corresponds to said indoor heat exchanger.   
     
     
         14 . The air conditioner according to  claim 4 , further comprising:
 a switch valve for switching direction of circulation of said refrigerant between a cooling cycle operation and a heating cycle operation;   an outdoor heat exchanger for heat exchange between outdoor air and said refrigerant; and   an indoor heat exchanger for heat exchange between indoor air and said refrigerant, wherein   in the cooling cycle operation, said condenser corresponds to said outdoor heat exchanger and, in the heating cycle operation, said condenser corresponds to said indoor heat exchanger.