Air conditioner

Abstract

In an air conditioner having a double-pipe heat exchanger in a refrigerating cycle, the degree of opening of a bypass expansion valve is controlled easily without liquid return to a compressor and without considering the state of a low-pressure two-phase refrigerant in the double-pipe heat exchanger. In the air conditioner including a refrigerating cycle 1 A in which a heating expansion valve 51 is provided between the outdoor heat exchanger 30 and the double-pipe heat exchanger 60 ; a cooling expansion valve 52 is provided between the indoor heat exchanger 40 and the double-pipe heat exchanger 60 ; and in the double-pipe heat exchanger 60 , a high-pressure liquid refrigerant flowing in a liquid-side refrigerant pipe 50 is heat-exchanged with a low-pressure two-phase refrigerant that is formed by decompressing some of the high-pressure liquid refrigerant by a bypass expansion valve 62 , a low-pressure refrigerant outflow portion 60 a of the double-pipe heat exchanger 60 is connected to a refrigerant pipe portion 50 a between the outdoor heat exchanger 30 and the heating expansion valve 51 via a first check valve 71 , and is connected to a refrigerant pipe portion 50 b between the indoor heat exchanger 40 and the cooling expansion valve 52 via a second check valve 72.

1 . An air conditioner including a refrigerating cycle in which a double-pipe heat exchanger is provided in a liquid-side refrigerant pipe between an outdoor heat exchanger and an indoor heat exchanger which are selectively connected to the discharge side of a compressor via a four-way valve; a heating expansion valve is provided between the outdoor heat exchanger and the double-pipe heat exchanger; a cooling expansion valve is provided between the indoor heat exchanger and the double-pipe heat exchanger; and in the double-pipe heat exchanger, a high-pressure liquid refrigerant flowing in the liquid-side refrigerant pipe is heat-exchanged with a gas-liquid low-pressure two-phase refrigerant which is formed by decompressing some of the high-pressure liquid refrigerant by a bypass expansion valve, wherein
 a low-pressure refrigerant outflow portion of the double-pipe heat exchanger is branched in a fork form; one branch is connected to the refrigerant pipe between the outdoor heat exchanger and the heating expansion valve via first valve means; and the other branch is connected to the refrigerant pipe between the indoor heat exchanger and the cooling expansion valve via second valve means.   
     
     
         2 . The air conditioner according to  claim 1 , wherein at the time of cooling operation of the refrigerating cycle, the heating expansion valve is fully opened and the cooling expansion valve is throttled to a predetermined degree of opening; and the low-pressure refrigerant heat-exchanged by the double-pipe heat exchanger is supplied to the indoor heat exchanger on the evaporator side via the second valve means together with the refrigerant decompressed by the cooling expansion valve. 
     
     
         3 . The air conditioner according to  claim 1 , wherein at the time of heating operation of the refrigerating cycle, the cooling expansion valve is fully opened and the heating expansion valve is throttled to a predetermined degree of opening; and the low-pressure refrigerant heat-exchanged by the double-pipe heat exchanger is supplied to the outdoor heat exchanger on the evaporator side via the first valve means together with the refrigerant decompressed by the heating expansion valve. 
     
     
         4 . The air conditioner according to  claim 1 , wherein the first and second valve means consist of check valves which are opened with the low-pressure refrigerant outflow portion being on the high pressure side. 
     
     
         5 . The air conditioner according to  claim 1 , wherein the first and second valve means consist of solenoid valves which are opened and closed by an external signal.