Air conditioner

Abstract

To provide an air conditioner which is further improved in operation efficiency.SOLUTION: An air conditioner comprises: a refrigeration cycle having an outdoor heat exchanger in which refrigerants sequentially circulate, an indoor heat exchanger, a compressor and an expansion valve; a first four-way valve which can perform a heating operation and a cooling operation by switching circulation directions of the refrigerants; a liquid-gas heat exchanger for exchanging heat between a gasified refrigerant at a low-pressure side of the refrigeration cycle and a liquefied refrigerant at a high-pressure side of the refrigeration cycle; and a second four-way valve for switching flows of the refrigerants so that the gasified refrigerant and the liquefied refrigerant form convection flows by the liquefied gas heat exchanger at both the heating operation and the cooling operation. The second four-way valve is arranged in a region in which the gasified refrigerant at the low-pressure side of the refrigeration cycle circulates.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an air conditioner. [Background technology]

[0002] The refrigeration cycle includes an evaporator, a condenser, a compressor, and an expansion valve. For example, during cooling operation, the refrigerant flows through the compressor, the condenser, the expansion valve, and the evaporator in this order. Here, it is desirable that the refrigerant returning from the evaporator to the compressor is in a gas phase with as low a temperature as possible in order to prevent liquid compression in the compressor. In addition, there is a demand to suppress the generation of flash gas in the refrigerant piping by supercooling the refrigerant.

[0003] Therefore, air conditioners equipped with liquid-gas heat exchangers have been put to practical use. A specific example of an air conditioner equipped with a liquid-gas heat exchanger is described in the following Patent Document 1. In the air conditioner according to the following Patent Document 1, for example, during cooling operation, the low-temperature gas-phase refrigerant that has passed through the evaporator and the high-temperature liquid-phase refrigerant that has passed through the condenser are heat-exchanged by the liquid-gas heat exchanger. This is said to be able to meet the above two requirements.

[0004] In order to ensure thermal efficiency, it is desirable for the liquid-phase refrigerant and the gas-phase refrigerant to flow in opposite directions in a liquid-gas heat exchanger. Therefore, in the device disclosed in the following Patent Document 1, the direction of the refrigerant flowing into the liquid-gas heat exchanger can be appropriately changed by a four-way valve between cooling operation and heating operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2003-194432 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the air conditioner according to Patent Document 1, both low-temperature refrigerant and high-temperature refrigerant flow inside the four-way valve, which may cause inadvertent heat exchange between the refrigerants inside the four-way valve, resulting in reduced operating efficiency.

[0007] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide an air conditioner with further improved operating efficiency. [Means for solving the problem]

[0008] In order to solve the above problems, the air conditioner of the present disclosure comprises a refrigeration cycle having an outdoor heat exchanger, an indoor heat exchanger, a compressor, and an expansion valve, each of which allows a refrigerant to flow sequentially, a first four-way valve that enables heating operation and cooling operation by switching the flow direction of the refrigerant, a liquid-gas heat exchanger that exchanges heat between a gas refrigerant on a low pressure side of the refrigeration cycle and a liquid refrigerant on a high pressure side, and a second four-way valve that switches the flow of the refrigerant so that the gas refrigerant and the liquid refrigerant flow in counter directions in the liquid-gas heat exchanger in both the heating operation and the cooling operation, and the second four-way valve is positioned in an area where the gaseous refrigerant on the low pressure side of the refrigeration cycle flows.

[0009] The air conditioner of the present disclosure comprises a refrigeration cycle having an outdoor heat exchanger, an indoor heat exchanger, a compressor, and an expansion valve, through which a refrigerant flows sequentially, a first four-way valve that enables heating operation and cooling operation by switching the flow direction of the refrigerant, a liquid-gas heat exchanger that exchanges heat between a gas refrigerant on a low pressure side of the refrigeration cycle and a liquid refrigerant on a high pressure side, a second four-way valve that switches the flow of the refrigerant so that the gas refrigerant and the liquid refrigerant flow in counter directions in the liquid-gas heat exchanger in both the heating operation and the cooling operation, and an accumulator that is provided upstream of the compressor and separates the refrigerant into gas and liquid, and the liquid-gas heat exchanger is disposed between the accumulator and the compressor. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide an air conditioner with further improved operating efficiency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a circuit diagram of the air conditioner according to the first embodiment of the present disclosure, illustrating the flow of refrigerant during cooling operation. [Diagram 2] FIG. 2 is a circuit diagram of the air conditioner according to the first embodiment of the present disclosure, showing the flow of refrigerant during heating operation. [Diagram 3] FIG. 11 is a circuit diagram of an air conditioner according to a second embodiment of the present disclosure, illustrating the flow of refrigerant during cooling operation. [Figure 4] FIG. 11 is a circuit diagram of an air conditioner according to a second embodiment of the present disclosure, illustrating the flow of refrigerant during heating operation. [Diagram 5] FIG. 11 is a circuit diagram showing a modified example of the air conditioner according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First Embodiment (Air conditioner configuration) An air conditioner 1 according to a first embodiment of the present disclosure will be described below with reference to Figures 1 and 2. The air conditioner 1 according to this embodiment is a device that is installed in a building such as a house or in transportation machinery such as an automobile, for adjusting the indoor temperature to a specified value.

[0013] 1, the air conditioner 1 includes a refrigeration cycle 10, a first four-way valve 20, a liquid-gas heat exchanger 30, and a second four-way valve 40. The refrigeration cycle 10 is a circuit for performing heat exchange between indoor air and the refrigerant, and between outdoor air and the refrigerant, by compressing and expanding the refrigerant that flows through each device of the refrigeration cycle 10 in sequence.

[0014] (Refrigeration cycle configuration) The refrigeration cycle 10 has an indoor heat exchanger 11, an indoor fan 12, an outdoor heat exchanger 13, an outdoor fan 14, a compressor 15, an accumulator 16, a first expansion valve 17 (expansion valve), a second expansion valve 18 (expansion valve), a first flow path 51, a second flow path 52, a compressor flow path 53, and a low-pressure gas flow path 54.

[0015] The indoor heat exchanger 11 is disposed on a first flow path 51. The first flow path 51 is a flow path that connects a first four-way valve 20 and a liquid-gas heat exchanger 30, which will be described later. The inside of the first flow path 51 is filled with a refrigerant. The indoor heat exchanger 11 exchanges heat between the refrigerant flowing through the first flow path 51 and the indoor air. The indoor heat exchanger 11 is, for example, a fin-and-tube type heat exchanger. An indoor fan 12 is provided near the indoor heat exchanger 11. By operating the indoor fan 12, the indoor air is forcibly supplied to the indoor heat exchanger 11.

[0016] A first expansion valve 17 is disposed on the first flow path 51 at a position on the liquid-gas heat exchanger 30 side of the indoor heat exchanger 11. The first expansion valve 17 is, for example, an electromagnetic expansion valve, and the opening degree is adjusted by an electric signal transmitted from the outside. The first expansion valve 17 is used to expand the refrigerant flowing in the first flow path 51 to reduce its pressure during cooling operation.

[0017] The outdoor heat exchanger 13 is disposed on the second flow path 52. The second flow path 52 is a flow path that connects the first four-way valve 20 and the liquid-gas heat exchanger 30, and is a flow path that is provided separately from the above-mentioned first flow path 51. The inside of the second flow path 52 is filled with a refrigerant. The outdoor heat exchanger 13 exchanges heat between the refrigerant flowing through the second flow path 52 and the outdoor air. The outdoor heat exchanger 13 is, for example, a fin-and-tube type heat exchanger. An outdoor fan 14 is provided near the outdoor heat exchanger 13. By operating the outdoor fan 14, the outdoor air is forcibly supplied to the outdoor heat exchanger 13.

[0018] A second expansion valve 18 is disposed on the second flow path 52 at a position on the liquid-gas heat exchanger 30 side of the outdoor heat exchanger 13. The second expansion valve 18 is, for example, an electromagnetic expansion valve, and the opening degree is adjusted by an electric signal transmitted from the outside. The second expansion valve 18 is used to expand the refrigerant flowing through the second flow path 52 to reduce its pressure during heating operation.

[0019] The compressor 15 and the accumulator 16 are provided on the compressor flow path 53. The compressor flow path 53 is a flow path that connects the liquid-gas heat exchanger 30 and the first four-way valve 20, and is a flow path different from the first flow path 51 and the second flow path 52 described above. The compressor 15 compresses the gas refrigerant in the compressor flow path 53 to generate a high-temperature and high-pressure gas refrigerant. Specifically, a scroll compressor or a rotary compressor is preferably used as the compressor 15. The accumulator 16 is disposed adjacent to the upstream side of the compressor 15 on the compressor flow path 53. The accumulator 16 separates the refrigerant into gas and liquid, sends only the gas phase component to the compressor 15, and stores the liquid phase component. The liquid phase component stored in the accumulator 16 also contains lubricating oil mixed with the refrigerant.

[0020] The low-pressure gas flow path 54 connects between the first four-way valve 20 and the liquid-gas heat exchanger 30 in parallel with the compressor flow path 53. A second four-way valve 40, which will be described later, is disposed on the low-pressure gas flow path 54.

[0021] (Configuration of the first four-way valve) The first four-way valve 20 switches the flow direction of the refrigerant by switching the connection state of the first flow path 51, the second flow path 52, the compressor flow path 53, and the low-pressure gas flow path 54. By switching the open state of the first four-way valve 20, it is possible to switch between heating operation and cooling operation. Fig. 1 shows the open state of the first four-way valve 20 during cooling operation. Specifically, the compressor flow path 53 and the second flow path 52 are connected, and the first flow path 51 and the low-pressure gas flow path 54 are connected. The state during heating operation will be described later with reference to Fig. 2.

[0022] (Configuration of liquid-gas heat exchanger) The liquid-gas heat exchanger 30 is provided at a position connecting an end of the first flow path 51 on the first expansion valve 17 side and an end of the second flow path 52 on the second expansion valve 18 side. The liquid-gas heat exchanger 30 also connects the low-pressure gas flow path 54 and the compressor flow path 53. As a result, during the cooling operation shown in Fig. 1, heat is exchanged between a high-temperature, high-pressure liquid refrigerant flowing from the second flow path 52 to the first flow path 51 and a low-temperature, low-pressure gas refrigerant flowing from the low-pressure gas flow path 54 to the compressor flow path 53. In the liquid-gas heat exchanger 30, the flow directions of these two refrigerants are determined so that they flow in opposite directions to each other, that is, so that they flow in counterflow.

[0023] (Configuration of the second four-way valve) The second four-way valve 40 switches the flow of the refrigerant so that the two refrigerant flows in the liquid-gas heat exchanger 30 are counter-flowing both during heating operation and cooling operation. Specifically, the second four-way valve 40 switches the opening states of the low-pressure gas flow path 54 and the compressor flow path 53, and the liquid-gas heat exchanger 30. During the cooling operation shown in Fig. 1, the refrigerant that has passed through the low-pressure gas flow path 54 passes through the liquid-gas heat exchanger 30 and heads toward the compressor flow path 53. At this time, the opening state of the second four-way valve 40 is switched so that the flow direction of the refrigerant is opposite to the flow direction of the refrigerant from the second flow path 52 toward the first flow path 51.

[0024] The second four-way valve 40 is provided in a region where the low-pressure gas refrigerant normally flows (i.e., on the low-pressure gas flow path 54). In other words, the second four-way valve 40 is desirably provided between the indoor heat exchanger 11 and the compressor 15. More desirably, the second four-way valve 40 is provided between the first four-way valve 20 and the liquid-gas heat exchanger 30.

[0025] (Action and effect) Next, an example of the operation of the air conditioner 1 will be described with reference to Fig. 1 and Fig. 2. Fig. 1 shows the circuit state of the air conditioner 1 during cooling operation. As shown in the figure, first, the gas refrigerant compressed by the compressor 15 to a high temperature and high pressure passes through the first four-way valve 20 and flows to the outdoor heat exchanger 13 on the second flow path 52. The gas refrigerant that has exchanged heat with the outdoor air in the outdoor heat exchanger 13 becomes a high-pressure liquid refrigerant. This refrigerant then passes through the second expansion valve 18 on the second flow path 52. Note that the second expansion valve 18 is fully open during cooling operation, and the pressure of the refrigerant does not change even when it passes through the second expansion valve 18.

[0026] Next, the refrigerant that has passed through the second flow path 52 flows into the liquid-gas heat exchanger 30. In the liquid-gas heat exchanger 30, the high-temperature, high-pressure liquid refrigerant that has passed through the second flow path 52 exchanges heat with a low-temperature, low-pressure gas refrigerant, which will be described later. As a result, the refrigerant that passes through the liquid-gas heat exchanger 30 and flows into the first flow path 51 has a lower temperature and a higher degree of subcooling. The subcooled refrigerant then passes through the first expansion valve 17. As a result, the refrigerant expands and becomes a low-temperature, low-pressure liquid refrigerant. Thereafter, the refrigerant that has flowed into the indoor heat exchanger 11 exchanges heat with the indoor air, causing its temperature to rise and it to evaporate, becoming a low-pressure gas refrigerant.

[0027] The low-pressure gas refrigerant passes through the first four-way valve 20 and flows into the low-pressure gas flow path 54. Thereafter, this low-pressure gas refrigerant passes through the second four-way valve 40 and exchanges heat with the high-temperature, high-pressure liquid refrigerant in the liquid-gas heat exchanger 30. This causes the low-pressure gas refrigerant to become superheated. The superheated low-pressure gas refrigerant passes through the second four-way valve 40 again, and then flows into the accumulator 16 and the compressor 15. The above cycle occurs continuously, causing the air conditioner 1 to operate in cooling mode.

[0028] Next, the operation of the air conditioner 1 during heating operation will be described with reference to Fig. 2. As shown in the figure, first, the gas refrigerant compressed by the compressor 15 to a high temperature and high pressure passes through the first four-way valve 20 and flows to the indoor heat exchanger 11 on the first flow path 51. After exchanging heat with the indoor air in the indoor heat exchanger 11, the gas refrigerant becomes a high-pressure liquid refrigerant. After that, this refrigerant passes through the first expansion valve 17 on the first flow path 51. Note that the first expansion valve 17 is fully open during heating operation, and therefore no change occurs in the pressure of the refrigerant even when it passes through the first expansion valve 17.

[0029] Next, the refrigerant that has passed through the first flow path 51 flows into the liquid-gas heat exchanger 30. In the liquid-gas heat exchanger 30, the high-temperature, high-pressure liquid refrigerant that has passed through the first flow path 51 exchanges heat with a low-temperature, low-pressure gas refrigerant, which will be described later. As a result, the refrigerant that passes through the liquid-gas heat exchanger 30 and flows into the second flow path 52 has a lower temperature and a higher degree of subcooling. The refrigerant in the subcooled state then passes through the second expansion valve 18. As a result, the refrigerant expands and becomes a low-temperature, low-pressure liquid refrigerant. Thereafter, the refrigerant that has flowed into the outdoor heat exchanger 13 exchanges heat with the outdoor air, causing its temperature to rise and it to evaporate, becoming a low-pressure gas refrigerant.

[0030] The low-pressure gas refrigerant passes through the first four-way valve 20 and flows into the low-pressure gas flow path 54. Thereafter, this low-pressure gas refrigerant passes through the second four-way valve 40 and exchanges heat with the high-temperature, high-pressure liquid refrigerant in the liquid-gas heat exchanger 30. This causes the low-pressure gas refrigerant to become superheated. The superheated low-pressure gas refrigerant passes through the second four-way valve 40 again, and then flows into the accumulator 16 and the compressor 15. The above cycle occurs continuously, causing the air conditioner 1 to perform heating operation.

[0031] Here, the refrigerant returning to the compressor 15 from the indoor heat exchanger 11 or the outdoor heat exchanger 13 as an evaporator is desirably a gas refrigerant with the lowest possible temperature in order to prevent liquid compression in the compressor 15. In addition, there is also a demand to suppress the generation of flash gas by supercooling the refrigerant in the refrigerant piping. In the air conditioner 1 according to this embodiment, these two demands are met by the liquid-gas heat exchanger 30. Specifically, by using the liquid-gas heat exchanger 30, heat exchange can be performed between a high-temperature, high-pressure liquid refrigerant and a low-temperature, low-pressure gas refrigerant. As a result, the refrigerant returning from the evaporator to the compressor 15 is further vaporized and becomes a gas refrigerant that does not contain liquid phase components. Therefore, the possibility of liquid compression occurring in the compressor 15 is reduced, and the compressor 15 can be operated more stably. On the other hand, the refrigerant flowing through the first flow path 51 or the second flow path 52 is supercooled and becomes in a lower temperature state. This makes it possible to suppress the generation of flash gas.

[0032] From the viewpoint of ensuring thermal efficiency, it is desirable for the liquid refrigerant and the gas refrigerant to flow in opposite directions in the liquid-gas heat exchanger 30. In order to realize such a state during both cooling and heating operations, the above-mentioned configurations are adopted.

[0033] According to the above configuration, the second four-way valve 40 is disposed in an area (on the low-pressure gas flow path 54) where only the low-pressure side gaseous refrigerant flows. In other words, the high-pressure side refrigerant with a different temperature does not flow into the second four-way valve 40. This reduces the possibility of inadvertent heat exchange between the low-temperature refrigerant and the high-temperature refrigerant inside the second four-way valve 40. This allows the heat quantity of the refrigerant to be stably maintained before and after the second four-way valve 40, thereby further improving the operating efficiency of the air conditioner 1.

[0034] Furthermore, according to the above configuration, the second four-way valve 40 is disposed between the indoor heat exchanger 11 and the compressor 15. Therefore, for example, during cooling operation, only low-pressure refrigerant that has passed through the indoor heat exchanger 11 flows into the second four-way valve 40. This reduces the possibility of inadvertent heat exchange between a low-temperature refrigerant and a high-temperature refrigerant inside the second four-way valve 40. Therefore, the heat quantity of the refrigerant is stably maintained before and after the second four-way valve 40, and the operating efficiency of the air conditioner 1 can be further improved.

[0035] In addition, according to the above configuration, the second four-way valve 40 is disposed between the first four-way valve 20 and the liquid-gas heat exchanger 30. Therefore, regardless of whether cooling operation or heating operation is being performed, only low-pressure refrigerant that has passed through the first four-way valve 20 flows into the second four-way valve 40. This reduces the possibility of inadvertent heat exchange between a low-temperature refrigerant and a high-temperature refrigerant inside the second four-way valve 40. As a result, the operating efficiency of the air conditioner 1 can be further improved.

[0036] The first embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure.

[0037] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Figs. 3 and 4. The same reference numerals are used for the same configurations as those in the first embodiment, and detailed description thereof will be omitted. As shown in Fig. 3, in this embodiment, the position at which the accumulator 16 is provided is different from that in the first embodiment. Specifically, the accumulator 16 is provided between the first four-way valve 20 and the liquid-gas heat exchanger 30 on the low-pressure gas flow path 54. In other words, the second four-way valve 40 and the liquid-gas heat exchanger 30 are disposed between the accumulator 16 and the compressor 15. In other words, the liquid-gas heat exchanger 30 is provided downstream of the accumulator 16. In addition, the compressor 15 is provided downstream of the liquid-gas heat exchanger 30.

[0038] (Action and effect) According to the above configuration, since the liquid-gas heat exchanger 30 is disposed downstream of the accumulator 16, the refrigerant flowing into the accumulator 16 does not undergo heat exchange in the liquid-gas heat exchanger 30 and is not superheated. This makes it possible to keep the fluidity of the lubricating oil that is mixed with the refrigerant in the accumulator 16 low. This makes it possible to smoothly introduce the lubricating oil to each part of the compressor 15.

[0039] In particular, it is known that the fluidity of the lubricant tends to decrease as the temperature increases in refrigerants such as R290, which is mainly composed of propane and has been introduced in recent years. Therefore, if the refrigerant is overheated, the lubricant with reduced fluidity may accumulate in the accumulator 16. However, according to the above configuration, the refrigerant flowing into the accumulator 16 is not superheated, so this possibility can be significantly reduced. As a result, the air conditioner 1 can be operated more stably.

[0040] In addition, according to the above configuration, since the compressor 15 is disposed downstream of the liquid-gas heat exchanger 30, a superheated refrigerant flows into the compressor 15. This causes the liquid phase component of the refrigerant to further vaporize, further reducing the possibility of liquid compression occurring in the compressor 15.

[0041] Furthermore, according to the above configuration, the second four-way valve 40 is provided between the accumulator 16 and the liquid-gas compressor 15. As a result, as described in the first embodiment, the low-pressure side refrigerant and the high-pressure side refrigerant can flow in countercurrent directions in the liquid-gas heat exchanger 30. This can further improve the heat exchange efficiency in the liquid-gas heat exchanger 30.

[0042] Fig. 3 shows the refrigerant flow and the opening state of each valve during cooling operation, and Fig. 4 shows the refrigerant flow and the opening state of each valve during heating operation. As shown in these figures, the refrigerant flow and the opening state of each valve during either operation are the same as in the first embodiment. Furthermore, the above-mentioned effects can be obtained in the same way during either operation.

[0043] The second embodiment of the present disclosure has been described above. Various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure. For example, in the second embodiment, an example in which the second four-way valve 40 and the liquid-gas heat exchanger 30 are disposed between the accumulator 16 and the compressor 15 has been described. However, as a modified example, as shown in FIG. 5, only the liquid-gas heat exchanger 30 may be disposed between the accumulator 16 and the compressor 15, and the second four-way valve 40 may be disposed upstream of the accumulator 16.

[0044] <Additional Notes> The air conditioner 1 described in each embodiment can be understood, for example, as follows.

[0045] (1) An air conditioner 1 according to a first aspect comprises a refrigeration cycle 10 having an outdoor heat exchanger 13, an indoor heat exchanger 11, a compressor 15, and an expansion valve, through which a refrigerant flows in sequence, a first four-way valve 20 that enables heating operation and cooling operation by switching the flow direction of the refrigerant, a liquid-gas heat exchanger 30 that exchanges heat between a gas refrigerant on the low-pressure side of the refrigeration cycle 10 and a liquid refrigerant on the high-pressure side, and a second four-way valve 40 that switches the flow of the refrigerant so that the gas refrigerant and the liquid refrigerant flow in counter directions in the liquid-gas heat exchanger 30 in both the heating operation and the cooling operation, and the second four-way valve 40 is arranged in an area through which the gaseous refrigerant on the low-pressure side of the refrigeration cycle 10 flows.

[0046] According to the above configuration, the second four-way valve 40 is disposed in an area where the low-pressure gaseous refrigerant flows. In other words, the high-pressure refrigerant does not flow into the second four-way valve 40. This reduces the possibility of inadvertent heat exchange between the low-temperature refrigerant and the high-temperature refrigerant inside the second four-way valve 40. This further improves the operating efficiency of the air conditioner 1.

[0047] (2) The air conditioner 1 according to the second aspect is the air conditioner 1 of (1), wherein the second four-way valve 40 is disposed between the indoor heat exchanger 11, which functions as an evaporator during the cooling operation, and the compressor 15.

[0048] According to the above configuration, the second four-way valve 40 is disposed between the indoor heat exchanger 11 and the compressor 15. Therefore, for example, during cooling operation, only low-pressure refrigerant that has passed through the indoor heat exchanger 11 flows into the second four-way valve 40. This reduces the possibility of inadvertent heat exchange between a low-temperature refrigerant and a high-temperature refrigerant inside the second four-way valve 40. This further improves the operating efficiency of the air conditioner 1.

[0049] (3) The air conditioner 1 according to a third aspect is the air conditioner 1 of (1) or (2), wherein the second four-way valve 40 is arranged between the first four-way valve 20 and the liquid-gas heat exchanger 30.

[0050] According to the above configuration, the second four-way valve 40 is disposed between the first four-way valve 20 and the liquid-gas heat exchanger 30. Therefore, regardless of whether cooling operation or heating operation is being performed, only low-pressure refrigerant that has passed through the first four-way valve 20 flows into the second four-way valve 40. This reduces the possibility of inadvertent heat exchange between a low-temperature refrigerant and a high-temperature refrigerant inside the second four-way valve 40. This further improves the operating efficiency of the air conditioner 1.

[0051] (4) An air conditioner 1 according to a fourth aspect is an air conditioner 1 according to any one of the aspects (1) to (3), wherein the refrigeration cycle 10 is provided upstream of the compressor 15 and further has an accumulator 16 which separates the refrigerant into gas and liquid, and the liquid-gas heat exchanger 30 and the second four-way valve 40 are disposed between the accumulator 16 and the compressor 15.

[0052] According to the above configuration, since the liquid-gas heat exchanger 30 is disposed downstream of the accumulator 16, the refrigerant flowing into the accumulator 16 is not superheated. This makes it possible to maintain low fluidity of the lubricating oil mixed with the refrigerant in the accumulator 16. This makes it possible to smoothly guide the lubricating oil to each part of the compressor 15. In addition, since the compressor 15 is disposed downstream of the liquid-gas heat exchanger 30, the superheated refrigerant flows into the compressor 15. This causes the liquid phase component of the refrigerant to vaporize, thereby reducing the possibility of liquid compression occurring in the compressor 15.

[0053] (5) The air conditioner 1 of the fifth aspect comprises a refrigeration cycle 10 having an outdoor heat exchanger 13, an indoor heat exchanger 11, a compressor 15, and an expansion valve, through which a refrigerant flows in sequence, a first four-way valve 20 that enables heating operation and cooling operation by switching the flow direction of the refrigerant, a liquid-gas heat exchanger 30 that exchanges heat between a gas refrigerant on the low pressure side of the refrigeration cycle 10 and a liquid refrigerant on the high pressure side, a second four-way valve 40 that switches the flow of the refrigerant so that the gas refrigerant and the liquid refrigerant flow in counter directions in the liquid-gas heat exchanger 30 in both the heating operation and the cooling operation, and an accumulator 16 that is provided upstream of the compressor 15 and separates the refrigerant into gas and liquid, and the liquid-gas heat exchanger 30 is disposed between the accumulator 16 and the compressor 15.

[0054] According to the above configuration, since the liquid-gas heat exchanger 30 is disposed downstream of the accumulator 16, the refrigerant flowing into the accumulator 16 is not superheated. This makes it possible to maintain low fluidity of the lubricating oil mixed with the refrigerant in the accumulator 16. This makes it possible to smoothly guide the lubricating oil to each part of the compressor 15. In addition, since the compressor 15 is disposed downstream of the liquid-gas heat exchanger 30, the superheated refrigerant flows into the compressor 15. This causes the liquid phase component of the refrigerant to vaporize, thereby reducing the possibility of liquid compression occurring in the compressor 15.

[0055] (6) The air conditioner 1 according to a sixth aspect is the air conditioner 1 of (5), wherein the second four-way valve 40 is provided between the accumulator 16 and the liquid-gas heat exchanger 30.

[0056] According to the above configuration, since the second four-way valve 40 is provided between the accumulator 16 and the liquid-gas compressor 15, the low-pressure side refrigerant and the high-pressure side refrigerant can flow in counterflow directions in the liquid-gas heat exchanger 30. This can further improve the heat exchange efficiency in the liquid-gas heat exchanger 30. [Explanation of symbols]

[0057] 1. Air conditioner 10...Refrigeration cycle 11...Indoor heat exchanger 12…Indoor fan 13...Outdoor heat exchanger 14…Outdoor fan 15…Compressor 16…Accumulator 17...First expansion valve 18...Second expansion valve 20...First four-way valve 30...Liquid-gas heat exchanger 40...Second four-way valve 51...First flow path 52...Second flow path 53...Compressor flow path 54...Low pressure gas flow path

Claims

1. a refrigeration cycle including an outdoor heat exchanger, an indoor heat exchanger, a compressor, and an expansion valve through which a refrigerant flows in sequence; a first four-way valve that switches the flow direction of the refrigerant to enable heating operation and cooling operation; a liquid-gas heat exchanger that exchanges heat between a gas refrigerant on a low pressure side and a liquid refrigerant on a high pressure side of the refrigeration cycle; a second four-way valve that switches the flow of the refrigerant so that the gas refrigerant and the liquid refrigerant flow in counter directions in the liquid-gas heat exchanger in both the heating operation and the cooling operation; Equipped with The second four-way valve is disposed in a region of the refrigeration cycle through which the low-pressure side gaseous refrigerant flows.

2. The air conditioner according to claim 1, wherein the second four-way valve is disposed between the indoor heat exchanger, which functions as an evaporator during the cooling operation, and the compressor.

3. The air conditioner according to claim 1 or 2, wherein the second four-way valve is disposed between the first four-way valve and the liquid-gas heat exchanger.

4. The refrigeration cycle includes: The compressor further includes an accumulator that separates the refrigerant into gas and liquid. The air conditioner according to claim 1, wherein the liquid-gas heat exchanger and the second four-way valve are disposed between the accumulator and the compressor.

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