Air conditioner

Abstract

To provide an air conditioner improved in a refrigeration cycle performance in both of a cooling operation and a heating operation.SOLUTION: An air conditioner includes; a compressor; a four-way valve for switching cooling and heating; an outdoor heat exchanger; an expansion valve; a first check valve connected between the outdoor heat exchanger and the expansion valve and permitting flow to the outdoor heat exchanger from the expansion valve; a first refrigerant passage branched from between the first check valve and the outdoor heat exchanger and joined between the first check valve and the expansion valve; a second check valve connected between the expansion valve and the indoor heat exchanger and permitting flow to the indoor heat exchanger from the expansion valve; a second refrigerant passage branched from between the second check valve and the indoor heat exchanger and joined between the second check valve and the expansion valve; and an internal heat exchanger exchanging heat between the refrigerants flowing through the first refrigerant passage and a suction pipe of the compressor at the time of a cooling operation and exchanging heat between the refrigerants flowing through the second refrigerant passage and the suction pipe at the time of a heating operation.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an air conditioner that can perform both cooling operation and heating operation and can increase the degree of subcooling of the refrigerant flowing out of the condenser. This air conditioner includes an internal heat exchanger that exchanges heat between the liquid refrigerant flowing out of the condenser and the gas refrigerant on the suction side of the compressor during both cooling operation and heating operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides an air conditioner that can improve the performance of the refrigeration cycle during both cooling operation and heating operation.

Means for Solving the Problems

[0005] The air conditioner in the present disclosure is an air conditioner including a compressor, a four-way valve for cooling and heating switching, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger. Between the outdoor heat exchanger and the expansion valve, there is a first check valve connected to allow the flow from the expansion valve to the outdoor heat exchanger, a first refrigerant path branching from between the first check valve and the outdoor heat exchanger and merging between the first check valve and the expansion valve, a second check valve connected between the expansion valve and the indoor heat exchanger to allow the flow from the expansion valve to the indoor heat exchanger, a second refrigerant path branching from between the second check valve and the indoor heat exchanger and merging between the second check valve and the expansion valve, and an internal heat exchanger that exchanges heat between the first refrigerant path and the refrigerant flowing through the suction pipe of the compressor during cooling operation and exchanges heat between the second refrigerant path and the refrigerant flowing through the suction pipe during heating operation.

Effect of the Invention

[0006] The air conditioner in the present disclosure can cool the refrigerant before passing through the expansion valve by the internal heat exchanger and suppress the inflow of the refrigerant after passing through the expansion valve into the internal heat exchanger during both cooling operation and heating operation, so that the evaporation capacity can be improved. Therefore, the performance of the refrigeration cycle can be improved during both cooling operation and heating operation.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0008] (Knowledge, etc. on which the present disclosure is based) When the inventors arrived at the idea of the present disclosure, in the technical field of air conditioners, there was a technique for increasing the subcooling degree of the liquid refrigerant flowing out from the condenser by an internal heat exchanger in order to improve the capacity of the refrigeration cycle. For example, the air conditioner described in Patent Document 1 has an internal heat exchanger into which the refrigerant between the expansion device and the indoor heat exchanger, the refrigerant between the expansion device and the outdoor heat exchanger, and the gas refrigerant on the suction side of the compressor flow respectively. This air conditioner cools the liquid refrigerant flowing out from the condenser with the gas refrigerant on the suction side of the compressor by means of the internal heat exchanger both during the cooling operation and the heating operation. However, in the case of a configuration such as the air conditioner described in Patent Document 1, the refrigerant exchanges heat with the gas refrigerant on the suction side of the compressor not only before passing through the expansion device but also after passing through the expansion device and becoming a low-temperature gas-liquid mixed refrigerant. Therefore, in the air conditioner such as that in Patent Document 1, the gas-liquid mixed refrigerant after passing through the expansion device has an increase in specific enthalpy due to heat absorption from the superheated gas refrigerant on the suction side of the compressor, resulting in a decrease in evaporation capacity, and it is difficult to obtain a sufficient performance improvement effect. The inventors discovered such a problem. And the inventors arrived at the constitution of the subject matter of the present disclosure in order to solve such a problem. Therefore, the present disclosure provides an air conditioner capable of improving the performance of the refrigeration cycle both during the cooling operation and the heating operation.

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings. However, a more detailed description than necessary may be omitted. For example, a detailed description of well-known matters or a redundant description of substantially the same configuration may be omitted. This is to avoid making the following description overly redundant and to facilitate the understanding of those skilled in the art. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0010] (Embodiment 1) Hereinafter, Embodiment 1 will be described with reference to the drawings. [1-1. Configuration] FIG. 1 is a diagram showing the refrigeration circuit of the air conditioner 1 according to Embodiment 1. In FIG. 1, the black arrow indicates the flow of the refrigerant during the cooling operation, and the white arrow indicates the flow of the refrigerant during the heating operation. In this embodiment, R290 refrigerant (propane) is used as the refrigerant.

[0011] The air conditioner 1 includes a compressor 11, a four-way valve 13, an outdoor heat exchanger 15, an expansion valve 17, and an indoor heat exchanger 31. The compressor 11, the four-way valve 13, the outdoor heat exchanger 15, and the expansion valve 17 are provided in the outdoor unit 10, and the indoor heat exchanger 31 is provided in the indoor unit 30. The air conditioner 1 in Embodiment 1 is a household single air conditioner and has one outdoor unit 10 and one indoor unit 30.

[0012] The compressor 11 is a device that sucks and compresses the gaseous refrigerant in the suction pipe 26 and discharges it as a high-temperature and high-pressure gaseous refrigerant. The suction port of the compressor 11 is connected to the four-way valve 13 via the suction pipe 26. The discharge port of the compressor 11 is connected to the four-way valve 13 via the discharge pipe 21. The four-way valve 13 is a device that connects the discharge pipe 21 to one of the heat exchangers 15 and 31 and connects the suction pipe 26 to the other. The four-way valve 13 can switch the connection destinations of the discharge pipe 21 and the suction pipe 26, and switches between the cooling operation and the heating operation of the air conditioner 1 by switching the connection destinations.

[0013] The indoor heat exchanger 31 is a heat exchanger that exchanges heat between the refrigerant flowing inside and the air in the indoor space. The indoor unit 30 has a blowing device such as a cross-flow fan. The indoor unit 30 promotes the heat exchange between the air in the indoor space and the refrigerant inside the indoor heat exchanger 31 by the blowing device, and blows out the air after the heat exchange into the indoor space to perform air conditioning in the indoor space.

[0014] Connected to the indoor heat exchanger 31 are an indoor-side gas path 22 which is a pipe connected to the four-way valve 13, and an indoor-side liquid path 23 which is a pipe connected to the expansion valve 17. The expansion valve 17 is a valve that reduces the pressure of the flowing liquid refrigerant to a low-temperature gas-liquid mixed refrigerant. Also, the expansion valve 17 can adjust the opening degree by electronic control to adjust the flow rate of the refrigerant.

[0015] The expansion valve 17 is connected to an outdoor liquid path 24 which is a pipe connected to the outdoor heat exchanger 15. The outdoor heat exchanger 15 is a heat exchanger that exchanges heat between the refrigerant flowing inside and the outside air. The outdoor heat exchanger 15 is connected to the four-way valve 13 via an outdoor gas path 25. The outdoor unit 10 has a blower such as an axial flow fan. The outdoor unit 10 promotes the heat exchange between the outside air and the refrigerant inside the outdoor heat exchanger 15 by means of the blower.

[0016] Here, a first check valve 12 is provided in the middle of the outdoor liquid path 24 connecting the outdoor heat exchanger 15 and the expansion valve 17. The first check valve 12 allows the flow of the refrigerant from the expansion valve 17 towards the outdoor heat exchanger 15 and blocks the flow of the refrigerant from the outdoor heat exchanger 15 towards the expansion valve 17.

[0017] Furthermore, a branched first heat exchange side branch portion 24c is formed in a first heat exchange side path 24a which is a portion between the first check valve 12 and the outdoor heat exchanger 15 in the outdoor liquid path 24. A branched first expansion valve side branch portion 24d is formed in a first expansion valve side path 24b which is a portion between the first check valve 12 and the expansion valve 17 in the outdoor liquid path 24. The first expansion valve side path 24b is formed linearly. A first refrigerant path 41 is connected to the first heat exchange side branch portion 24c and the first expansion valve side branch portion 24d. That is, the first refrigerant path 41 bypasses the first check valve 12. For this reason, the refrigerant in the first heat exchange side path 24a flowing from the outdoor heat exchanger 15 towards the expansion valve 17 flows into the first expansion valve side path 24b via the first refrigerant path 41 and reaches the expansion valve 17. At the first expansion valve side branch portion 24d, the first refrigerant path 41 branches off substantially perpendicularly from the first expansion valve side path 24b.

[0018] The flow path cross-sectional area of the first refrigerant path 41 is smaller than that of the outdoor-side liquid path 24. Therefore, the piping resistance per unit length of the first refrigerant path 41 is larger than that of the outdoor-side liquid path 24 per unit length. Also, the flow path cross-sectional area of the first refrigerant path 41 is smaller than that of the first check valve 12. Therefore, the piping resistance per unit length of the first refrigerant path 41 is larger than the piping resistance per unit length of the flow path in the first check valve 12. Further, the length of the first refrigerant path 41 is longer than the length of the outdoor-side liquid path 24 from the first heat exchanger-side branch portion 24c to the first expansion valve-side branch portion 24d. Therefore, the piping resistance of the first refrigerant path 41 is larger than the piping resistance of the outdoor-side liquid path 24 from the first heat exchanger-side branch portion 24c to the first expansion valve-side branch portion 24d.

[0019] A second check valve 14 is provided in the middle of the indoor-side liquid path 23 that connects the indoor heat exchanger 31 and the expansion valve 17. The second check valve 14 allows the flow of refrigerant from the expansion valve 17 toward the indoor heat exchanger 31 and blocks the flow of refrigerant from the indoor heat exchanger 31 toward the expansion valve 17.

[0020] Furthermore, a branched second heat exchanger-side branch portion 23c is formed in a second heat exchanger-side path 23a, which is a portion of the indoor-side liquid path 23 between the second check valve 14 and the indoor heat exchanger 31. A branched second expansion valve-side branch portion 23d is formed in a second expansion valve-side path 23b, which is a portion of the indoor-side liquid path 23 between the second check valve 14 and the expansion valve 17. The second expansion valve-side path 23b is formed linearly. A second refrigerant path 42 is connected to the second heat exchanger-side branch portion 23c and the second expansion valve-side branch portion 23d. That is, the second refrigerant path 42 bypasses the second check valve 14. Therefore, the refrigerant in the second heat exchanger-side path 23a flowing from the outdoor heat exchanger 15 toward the expansion valve 17 flows into the second expansion valve-side path 23b via the second refrigerant path 42 and reaches the expansion valve 17. At the second expansion valve-side branch portion 23d, the second refrigerant path 42 branches off substantially perpendicularly from the second expansion valve-side path 23b.

[0021] The flow path cross-sectional area of the second refrigerant path 42 is smaller than that of the indoor-side liquid path 23. For this reason, the piping resistance per unit length of the second refrigerant path 42 is larger than the piping resistance per unit length of the indoor-side liquid path 23. Also, the flow path cross-sectional area of the second refrigerant path 42 is smaller than the flow path cross-sectional area of the second check valve 14. For this reason, the piping resistance per unit length in the second refrigerant path 42 is larger than the piping resistance per unit length of the flow path in the second check valve 14. Also, the length of the second refrigerant path 42 is longer than the length of the indoor-side liquid path 23 from the second heat exchanger-side branch portion 23c to the second expansion valve-side branch portion 23d. For this reason, the piping resistance of the second refrigerant path 42 is larger than the piping resistance of the indoor-side liquid path 23 from the second heat exchanger-side branch portion 23c to the second expansion valve-side branch portion 23d.

[0022] The first refrigerant path 41 and the second refrigerant path 42 are connected to the internal heat exchanger 16. In the present embodiment, the internal heat exchanger 16 includes a first heat transfer tube 16a, a second heat transfer tube 16b, and a third heat transfer tube 16c. Both ends of the first heat transfer tube 16a are connected to an intermediate portion of the first refrigerant path 41. Both ends of the second heat transfer tube 16b are connected to an intermediate portion of the second refrigerant path 42. Both ends of the third heat transfer tube 16c are connected to an intermediate portion of the suction pipe 26. The internal heat exchanger 16 exchanges heat between the refrigerant flowing in the first heat transfer tube 16a and the refrigerant flowing in the third heat transfer tube 16c. Also, the internal heat exchanger 16 exchanges heat between the refrigerant flowing in the second heat transfer tube 16b and the refrigerant flowing in the third heat transfer tube 16c. However, in the internal heat exchanger 16, the refrigerant flowing in the first heat transfer tube 16a and the refrigerant flowing in the second heat transfer tube 16b are configured to hardly exchange heat with each other.

[0023] Further, the internal heat exchanger 16 is connected to each refrigerant path 41, 42, and the suction pipe 26 such that one of the refrigerants flowing through the first heat transfer pipe 16a or the refrigerant flowing through the second heat transfer pipe 16b is in a counterflow with the refrigerant flowing through the third heat transfer pipe 16c. Specifically, when the refrigerant in the outdoor liquid path 24 flows from the outdoor heat exchanger 15 toward the expansion valve 17, that is, during the cooling operation, the refrigerant in the first heat transfer pipe 16a is in a counterflow with the refrigerant in the third heat transfer pipe 16c. Conversely, during the heating operation, the refrigerant in the first heat transfer pipe 16a is in a parallel flow with the refrigerant in the third heat transfer pipe 16c. Also, when the refrigerant in the indoor liquid path 23 flows from the indoor heat exchanger 31 to the expansion valve 17, that is, during the heating operation, the refrigerant in the second heat transfer pipe 16b is in a counterflow with the refrigerant in the third heat transfer pipe 16c. Conversely, during the cooling operation, the refrigerant in the second heat transfer pipe 16b is in a parallel flow with the refrigerant in the third heat transfer pipe 16c.

[0024] [1-2. Operation] The operation of the air conditioner 1 configured as described above will be described below. [1-2-1. Operation during cooling operation] During the cooling operation, the four-way valve 13 is switched to a mode in which the discharge pipe 21 and the outdoor gas path 25 are communicated. For this reason, the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the outdoor heat exchanger 15. The high-temperature and high-pressure gas refrigerant is cooled in the outdoor heat exchanger 15 and becomes a liquid refrigerant and flows through the outdoor liquid path 24.

[0025] As described above, the first check valve 12 shuts off the flow of the refrigerant from the outdoor heat exchanger 15 toward the expansion valve 17 in the outdoor liquid path 24. Therefore, all of the liquid refrigerant in the outdoor liquid path 24 that has reached the first heat exchange side branch portion 24c flows into the first refrigerant path 41. The liquid refrigerant that has flowed into the first refrigerant path 41 flows into the first heat transfer tube 16a of the internal heat exchanger 16 and exchanges heat with the refrigerant in the suction pipe 26 that has flowed into the third heat transfer tube 16c. The liquid refrigerant flowing through the first heat transfer tube 16a is at a higher temperature than the refrigerant flowing through the third heat transfer tube 16c. Therefore, the liquid refrigerant flowing through the first heat transfer tube 16a is subcooled in the internal heat exchanger 16. Further, during the cooling operation, the refrigerant flowing through the first heat transfer tube 16a is in counterflow with the refrigerant flowing through the third heat transfer tube 16c. Therefore, subcooling of the refrigerant flowing through the first heat transfer tube 16a and heating of the refrigerant flowing through the third heat transfer tube 16c are facilitated.

[0026] Thereafter, the subcooled liquid refrigerant flows from the first refrigerant path 41 through the first expansion valve side branch portion 24d into the first expansion valve side path 24b, and is depressurized by the expansion valve 17 to become a low-temperature gas-liquid mixed refrigerant.

[0027] The gas-liquid mixed refrigerant that has passed through the expansion valve 17 flows through the second expansion valve side path 23b and reaches the second expansion valve side branch portion 23d. As described above, the second check valve 14 allows the flow of the refrigerant from the expansion valve 17 toward the indoor heat exchanger 31 in the indoor liquid path 23. Therefore, the gas-liquid mixed refrigerant branches at the second expansion valve side branch portion 23d and flows into both the second check valve 14 and the second refrigerant path 42. Since the refrigerant branches at the second expansion valve side branch portion 23d in this way, during the cooling operation, the flow rate of the refrigerant in the second refrigerant path 42 is smaller than the flow rate of the refrigerant in the first refrigerant path 41.

[0028] As described above, the piping resistance of the second refrigerant path 42 is greater than the piping resistance of the indoor liquid path 23 between the second expansion valve side branch portion 23d and the second heat exchange side branch portion 23c. Further, the second refrigerant path 42 branches substantially perpendicularly from the linear second expansion valve side path 23b. Therefore, most of the gas-liquid mixed refrigerant that has reached the second expansion valve side branch portion 23d flows straight through the second expansion valve side path 23b, passes through the second check valve 14, and flows into the second heat exchange side path 23a.

[0029] Note that part of the refrigerant that reaches the second expansion valve side branch portion 23d flows into the second heat transfer tube 16b of the internal heat exchanger 16 via the second refrigerant path 42. Further, the refrigerant in the second heat transfer tube 16b returns to the second heat exchange side path 23a via the second heat exchange side branch portion 23c after heat exchange with the refrigerant in the suction pipe 26 flowing through the third heat transfer tube 16c. At this time, the refrigerant flowing through the second heat transfer tube 16b is at a lower temperature than the refrigerant flowing through the third heat transfer tube 16c. Therefore, the refrigerant flowing through the second heat transfer tube 16b absorbs heat by heat exchange, and the refrigerant flowing through the third heat transfer tube 16c dissipates heat by heat exchange. However, the refrigerant flowing through the second refrigerant path 42 has a small flow rate and is gas-rich as described above, and is in a parallel flow with respect to the refrigerant flowing through the third heat transfer tube 16c. For this reason, the heat exchanged between the second heat transfer tube 16b and the third heat transfer tube 16c is sufficiently smaller than the heat exchanged between the first heat transfer tube 16a and the third heat transfer tube 16c. Therefore, even if the refrigerant flowing through the second refrigerant path 42 merges with the refrigerant that has passed through the second check valve 14, the specific enthalpy of the refrigerant after merging is unlikely to increase.

[0030] The merged gas-liquid mixed refrigerant flows through the indoor side liquid path 23 and flows into the indoor heat exchanger 31. The refrigerant flowing into the indoor heat exchanger 31, as described above, is not significantly increased in specific enthalpy after being subcooled in the first heat transfer tube 16a until it flows into the indoor heat exchanger 31. For this reason, a high evaporation capacity can be obtained in the indoor heat exchanger 31. As the refrigerant in the indoor heat exchanger 31 absorbs heat from the surrounding air, the space where the indoor unit 30 is provided is cooled.

[0031] Almost all of the refrigerant that has passed through the indoor heat exchanger 31 becomes gas refrigerant and flows into the indoor side gas path 22, and then flows into the third heat transfer tube 16c of the internal heat exchanger 16 via the four-way valve 13 and the suction pipe 26. As described above, during the cooling operation, the refrigerant flowing through the third heat transfer tube 16c easily exchanges heat with the high-temperature refrigerant flowing through the first heat transfer tube 16a, and hardly exchanges heat with the low-temperature refrigerant flowing through the second heat transfer tube 16b. Therefore, the refrigerant in the suction pipe 26 is heated in the internal heat exchanger 16 and flows into the compressor 11 again as gas refrigerant.

[0032] [1-2-2. Operation during heating operation] During the heating operation, the four-way valve 13 is switched to a form that connects the discharge pipe 21 and the indoor-side gas path 22. Therefore, the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the indoor heat exchanger 31. The high-temperature and high-pressure gas refrigerant dissipates heat to the surrounding air in the indoor heat exchanger 31 and becomes a liquid refrigerant, flowing into the indoor-side liquid path 23. As the refrigerant in the indoor heat exchanger 31 dissipates heat to the surrounding air, the space where the indoor unit 30 is installed is heated.

[0033] As described above, the second check valve 14 blocks the flow of the refrigerant from the indoor heat exchanger 31 in the indoor-side liquid path 23 toward the expansion valve 17. Therefore, all of the liquid refrigerant in the indoor-side liquid path 23 that reaches the second heat exchange side branch portion 23c flows into the second refrigerant path 42. The liquid refrigerant that has flowed into the second refrigerant path 42 flows into the second heat transfer pipe 16b of the internal heat exchanger 16 and exchanges heat with the refrigerant in the suction pipe 26 that has flowed into the third heat transfer pipe 16c. The liquid refrigerant flowing through the second heat transfer pipe 16b is at a higher temperature than the refrigerant flowing through the third heat transfer pipe 16c. Therefore, the liquid refrigerant flowing through the second heat transfer pipe 16b is subcooled. During the heating operation, since the refrigerant flowing through the second heat transfer pipe 16b is in a countercurrent flow with the refrigerant flowing through the third heat transfer pipe 16c, subcooling of the refrigerant flowing through the second heat transfer pipe 16b and heating of the refrigerant flowing through the third heat transfer pipe 16c are easily promoted.

[0034] Thereafter, the subcooled liquid refrigerant flows from the second refrigerant path 42 into the second expansion valve side path 23b via the second expansion valve side branch portion 23d and is depressurized at the expansion valve 17 to become a low-temperature gas-liquid mixed refrigerant.

[0035] The gas-liquid mixed refrigerant that has passed through the expansion valve 17 flows through the second expansion valve side path 23b and reaches the first expansion valve side branch portion 24d. As described above, the first check valve 12 allows the flow of the refrigerant from the expansion valve 17 toward the outdoor heat exchanger 15 in the outdoor side liquid path 24. For this reason, the gas-liquid mixed refrigerant branches at the first expansion valve side branch portion 24d and flows into both the first check valve 12 and the first refrigerant path 41. Since the refrigerant branches at the first expansion valve side branch portion 24d in this way, during the heating operation, the flow rate of the refrigerant in the first refrigerant path 41 is smaller than the flow rate of the refrigerant in the second refrigerant path 42.

[0036] As described above, the piping resistance of the first refrigerant path 41 is larger than the piping resistance of the outdoor side liquid path 24 between the first expansion valve side branch portion 24d and the first heat exchange side branch portion 24c. Also, the first refrigerant path 41 branches substantially perpendicularly from the linear first expansion valve side path 24b. For this reason, most of the gas-liquid mixed refrigerant that has reached the first expansion valve side branch portion 24d flows straight through the first expansion valve side path 24b, passes through the first check valve 12, and flows into the first heat exchange side path 24a.

[0037] Note that a part of the refrigerant that has reached the first expansion valve side branch portion 24d flows into the first heat transfer tube 16a of the internal heat exchanger 16 via the first refrigerant path 41. The refrigerant flowing through the first heat transfer tube 16a exchanges heat with the refrigerant in the suction pipe 26 flowing through the third heat transfer tube 16c, and then returns to the first heat exchange side path 24a via the first heat exchange side branch portion 24c. At this time, the refrigerant flowing through the first heat transfer tube 16a is at a lower temperature than the refrigerant flowing through the third heat transfer tube 16c. For this reason, the refrigerant flowing through the first heat transfer tube 16a absorbs heat by heat exchange, and the refrigerant flowing through the third heat transfer tube 16c dissipates heat by heat exchange. However, the refrigerant flowing through the first refrigerant path 41 has a small flow rate and is gas-rich as described above, and is in a parallel flow with respect to the refrigerant flowing through the third heat transfer tube 16c. For this reason, the heat exchanged between the refrigerant in the first heat transfer tube 16a and the refrigerant in the third heat transfer tube 16c is sufficiently smaller than the heat exchanged between the refrigerant in the second heat transfer tube 16b and the refrigerant in the third heat transfer tube 16c. Therefore, even if the refrigerant that has flowed through the first refrigerant path 41 merges with the refrigerant that has passed through the first check valve 12, the specific enthalpy of the merged refrigerant is unlikely to increase.

[0038] The combined gas-liquid mixed refrigerant flows through the outdoor liquid path 24 and enters the outdoor heat exchanger 15. As described above, the refrigerant flowing into the outdoor heat exchanger 15 is not greatly increased in specific enthalpy before flowing into the outdoor heat exchanger 15 after being subcooled by the second heat transfer tube 16b. Therefore, a high evaporation capacity can be obtained in the outdoor heat exchanger 15.

[0039] Almost all of the refrigerant that has passed through the outdoor heat exchanger 15 becomes gas refrigerant and flows into the outdoor gas path 25, and then flows into the third heat transfer tube 16c of the internal heat exchanger 16 through the four-way valve 13 and the suction pipe 26. As described above, during the heating operation, the refrigerant flowing through the third heat transfer tube 16c is likely to exchange heat with the high-temperature refrigerant flowing through the second heat transfer tube 16b, and is less likely to exchange heat with the low-temperature refrigerant flowing through the first heat transfer tube 16a. Therefore, the refrigerant in the suction pipe 26 is heated in the internal heat exchanger 16 and flows back into the compressor 11 as gas refrigerant.

[0040] In this way, in this embodiment, the evaporation capacity in the evaporator can be improved both during the cooling operation and the heating operation. Further, in this embodiment, compared with the case of using a check valve bridge that requires three or more check valves, the number and space of the check valves can be reduced. Therefore, with a simple configuration, the evaporation capacity in the evaporator can be improved both during the cooling operation and the heating operation.

[0041] [1-3. Effects, etc.] As described above, in this embodiment, the air conditioner 1 includes a compressor 11, a four-way valve 13 for switching between cooling and heating, an outdoor heat exchanger 15, an expansion valve 17, and an indoor heat exchanger 31. In the air conditioner 1, a first check valve 12 is connected between the outdoor heat exchanger 15 and the expansion valve 17 and allows the flow from the expansion valve 17 to the outdoor heat exchanger 15. A first refrigerant path 41 branches from between the first check valve 12 and the outdoor heat exchanger 15 and merges between the first check valve 12 and the expansion valve 17. A second check valve 14 is connected between the expansion valve 17 and the indoor heat exchanger 31 and allows the flow from the expansion valve 17 to the indoor heat exchanger 31. A second refrigerant path 42 branches from between the second check valve 14 and the indoor heat exchanger 31 and merges between the second check valve 14 and the expansion valve 17. During cooling operation, an internal heat exchanger 16 exchanges heat between the first refrigerant path 41 and the refrigerant flowing through the suction pipe 26 of the compressor 11. During heating operation, the internal heat exchanger 16 exchanges heat between the second refrigerant path 42 and the refrigerant flowing through the suction pipe 26. Thereby, in both cooling operation and heating operation, the refrigerant before passing through the expansion valve 17 can be cooled by the internal heat exchanger 16, and the inflow of the refrigerant after passing through the expansion valve 17 into the internal heat exchanger 16 can be suppressed. Therefore, the evaporation capacity can be improved. For this reason, in both cooling operation and heating operation, the performance of the refrigeration cycle can be improved.

[0042] Also, as in this embodiment, in the air conditioner 1, the internal heat exchanger 16 may be configured to include a first heat transfer pipe 16a, a second heat transfer pipe 16b, and a third heat transfer pipe 16c. The first heat transfer pipe 16a is connected to the first refrigerant path 41, the second heat transfer pipe 16b is connected to the second refrigerant path 42, and the third heat transfer pipe 16c is connected to the suction pipe 26. Thereby, in both cooling operation and heating operation, the performance of the refrigeration cycle can be improved by one internal heat exchanger 16. For this reason, the configuration of the air conditioner 1 can be simplified.

[0043] Also, in the air conditioner 1 as in the present embodiment, the internal heat exchanger 16 may be configured such that the first heat transfer pipe 16a and the third heat transfer pipe 16c are in a countercurrent flow during the cooling operation, and the second heat transfer pipe 16b and the third heat transfer pipe 16c are in a countercurrent flow during the heating operation. Thereby, the efficiency of heat exchange between the refrigerant before passing through the expansion valve 17 and the refrigerant in the suction pipe 26 can be improved both during the cooling operation and the heating operation, and the evaporation capacity in the refrigeration cycle of the air conditioner 1 can be improved. For this reason, the performance of the refrigeration cycle can be improved both during the cooling operation and the heating operation.

[0044] Also, in the air conditioner 1 as in the present embodiment, the flow passage cross-sectional area of the first heat transfer pipe 16a may be smaller than the flow passage cross-sectional area of the first check valve 12, and the flow passage cross-sectional area of the second heat transfer pipe 16b may be smaller than the flow passage cross-sectional area of the second check valve 14. Thereby, the inflow of the refrigerant to the internal heat exchanger 16 after passing through the expansion valve 17 can be suppressed both during the cooling operation and the heating operation, and the evaporation capacity can be improved. For this reason, the performance of the refrigeration cycle can be improved both during the cooling operation and the heating operation.

[0045] Also, in the air conditioner 1 as in the present embodiment, the flow passage cross-sectional area of the first refrigerant path 41 may be smaller than the flow passage cross-sectional area of the first check valve 12, and the flow passage cross-sectional area of the second refrigerant path 42 may be smaller than the flow passage cross-sectional area of the second check valve 14. Thereby, the inflow of the refrigerant to the internal heat exchanger 16 after passing through the expansion valve 17 can be suppressed both during the cooling operation and the heating operation, and the evaporation capacity can be improved. For this reason, the performance of the refrigeration cycle can be improved both during the cooling operation and the heating operation.

[0046] Further, in the air conditioner 1 as in this embodiment, the first refrigerant path 41 may be configured to be connected in a direction orthogonal to the linear first expansion valve side path 24b connecting the expansion valve 17 and the first check valve 12, and the second refrigerant path 42 may be configured to be connected in a direction orthogonal to the linear second expansion valve side path 23b connecting the expansion valve 17 and the second check valve 14. Thereby, in both the cooling operation and the heating operation, the inflow of the refrigerant after passing through the expansion valve 17 into the internal heat exchanger 16 can be suppressed, and the evaporation capacity can be improved. Therefore, in both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0047] (Embodiment 2) Hereinafter, Embodiment 2 will be described with reference to FIG. 2.

[0048] [2-1. Configuration] FIG. 2 is a diagram showing the refrigeration circuit of the air conditioner 101 according to Embodiment 2. As shown in FIG. 2, in Embodiment 2, unlike Embodiment 1, the first refrigerant path 41 and the second refrigerant path 42 are each connected to different internal heat exchangers 116 and 117.

[0049] The first internal heat exchanger 116 has a first liquid heat transfer tube 116a and a first gas heat transfer tube 116b. The first liquid heat transfer tube 116a is connected to the first refrigerant path 41. The first gas heat transfer tube 116b is connected to the suction pipe 26. The first internal heat exchanger 116 is connected such that the refrigerant flowing through the first liquid heat transfer tube 116a and the refrigerant flowing through the first gas heat transfer tube 116b are in counterflow during the cooling operation. The flow path cross-sectional area on the liquid side in the first internal heat exchanger 116, that is, the flow path cross-sectional area of the first liquid heat transfer tube 116a, is configured to be smaller than the flow path cross-sectional area of the first check valve 12 and the flow path cross-sectional area of the outdoor side liquid path 24.

[0050] The second internal heat exchanger 117 has a second liquid heat transfer pipe 117a and a second gas heat transfer pipe 117b. The second liquid heat transfer pipe 117a is connected to the second refrigerant path 42. The second gas heat transfer pipe 117b is connected to the suction pipe 26. The second internal heat exchanger 117 is connected such that the refrigerant flowing through the second liquid heat transfer pipe 117a and the refrigerant flowing through the second gas heat transfer pipe 117b are in counterflow during the heating operation. The flow path cross-sectional area on the liquid side in the second internal heat exchanger 117, that is, the flow path cross-sectional area of the second liquid heat transfer pipe 117a, is configured to be smaller than the flow path cross-sectional area of the second check valve 14 and the flow path cross-sectional area of the indoor-side liquid path 23.

[0051] [2-2. Operation] The operation of the air conditioner 101 configured as described above will be described below.

[0052] In the second embodiment, unlike the first embodiment, the first internal heat exchanger 116 to which the first refrigerant path 41 is connected and the second internal heat exchanger 117 to which the second refrigerant path 42 is connected are not integrated but are provided separately. For this reason, during the cooling operation and the heating operation of the air conditioner 101, it becomes difficult for the refrigerants flowing through the respective liquid heat transfer pipes 116a and 117a to exchange heat with each other. That is, in each of the refrigerant paths 41 and 42, the low-temperature refrigerant after passing through the expansion valve 17 is less likely to be heated by the refrigerant before passing through the expansion valve. For this reason, it becomes easier to obtain a high evaporation capacity in the outdoor heat exchanger 15 or the indoor heat exchanger 31.

[0053] Also, the flow path cross-sectional area of the first liquid heat transfer pipe 116a is smaller than the flow path cross-sectional area of the first check valve 12, and the flow path cross-sectional area of the second liquid heat transfer pipe 117a is smaller than the flow path cross-sectional area of the second check valve 14. Therefore, due to the difference in piping resistance, during the cooling operation, it becomes difficult for the refrigerant to flow through the second refrigerant path 42 and the second liquid heat transfer pipe 117a. Also, due to the difference in piping resistance, during the heating operation, it becomes difficult for the refrigerant to flow through the first refrigerant path 41 and the first liquid heat transfer pipe 116a. That is, the refrigerant after passing through the expansion valve 17 becomes difficult to flow into each refrigerant path 41, 42 and each internal heat exchanger 116, 117. Therefore, it is possible to strongly cool the refrigerant before passing through the expansion valve 17 and weakly heat the refrigerant after passing through the expansion valve 17, and it becomes easier to obtain a high evaporation capacity in the outdoor heat exchanger 15 or the indoor heat exchanger 31.

[0054] [2-3. Effects, etc.] As in this embodiment, the air conditioner 101 may be configured to include a first internal heat exchanger 116 and a second internal heat exchanger 117, the first internal heat exchanger 116 being connected to the first refrigerant path 41 and the suction pipe 26, and the second internal heat exchanger 117 being connected to the second refrigerant path 42 and the suction pipe 26. Thereby, during both the cooling operation and the heating operation, while suppressing heat exchange between the refrigerant in the first refrigerant path 41 and the refrigerant in the second refrigerant path 42, the refrigerant before passing through the expansion valve 17 can be cooled. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0055] Also, as in this embodiment, the flow path cross-sectional area of the first liquid heat transfer pipe 116a on the liquid side of the first internal heat exchanger 116 may be configured to be smaller than the flow path cross-sectional area of the first check valve 12, and the flow path cross-sectional area of the second liquid heat transfer pipe 117a on the liquid side of the second internal heat exchanger 117 may be configured to be smaller than the flow path cross-sectional area of the second check valve 14. Thereby, during both the cooling operation and the heating operation, it is possible to suppress the refrigerant after passing through the expansion valve from flowing into the internal heat exchanger and being heated, and the evaporation capacity can be improved. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0056] (Other embodiments) As described above, as examples of the technologies disclosed in the present application, Embodiments 1 and 2 have been described. However, the technologies in the present disclosure are not limited thereto, and can also be applied to embodiments with changes, replacements, additions, omissions, etc. In addition, it is also possible to combine the respective components described in Embodiments 1 and 2 above to form a new embodiment. Therefore, other embodiments will be exemplified below.

[0057] In Embodiments 1 and 2, as an example of an air conditioner, the air conditioners 1 and 101, which are household single air conditioners having only one indoor unit 30, have been described. However, the air conditioner only needs to be capable of switching between heating operation and cooling operation. Therefore, the air conditioner is not limited to a household single air conditioner, and may be for business use or may be a multi-air conditioner including a plurality of indoor units 30.

[0058] In Embodiments 1 and 2, it has been described that R290 refrigerant is used in the refrigeration circuit, but the refrigerant is not limited thereto. For example, as the refrigerant, R32 refrigerant (difluoromethane) or the like may be used. However, since it is known that the coefficient of performance is improved by taking the superheat degree on the suction side of the compressor without taking the superheat degree at the outlet of the evaporator for the R290 refrigerant, it is easy to improve the performance of the refrigeration circuit by using the R290 refrigerant.

[0059] Note that the above-described embodiments are for exemplifying the technologies in the present disclosure, and various changes, replacements, additions, omissions, etc. can be made within the scope of the claims or the equivalent scope thereof.

[0060] [Configuration supported by the above embodiment] The above embodiment supports the following configuration.

[0061] (Supplementary Note) In an air conditioner comprising a compressor, a four-way valve for switching between cooling and heating, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, a first check valve connected between the outdoor heat exchanger and the expansion valve and allowing the flow from the expansion valve to the outdoor heat exchanger, a first refrigerant path branching from between the first check valve and the outdoor heat exchanger and merging between the first check valve and the expansion valve, a second check valve connected between the expansion valve and the indoor heat exchanger and allowing the flow from the expansion valve to the indoor heat exchanger, a second refrigerant path branching from between the second check valve and the indoor heat exchanger and merging between the second check valve and the expansion valve, and an internal heat exchanger that exchanges heat between the first refrigerant path and the refrigerant flowing through the suction pipe of the compressor during cooling operation and exchanges heat between the second refrigerant path and the refrigerant flowing through the suction pipe during heating operation.

[0062] Thereby, during both cooling operation and heating operation, the refrigerant before passing through the expansion valve can be cooled by the internal heat exchanger, and the inflow of the refrigerant after passing through the expansion valve into the internal heat exchanger can be suppressed, so that the evaporation capacity can be improved. Therefore, during both cooling operation and heating operation, the performance of the refrigeration cycle can be improved.

[0063] The internal heat exchanger according to Technology 1, comprising a first heat transfer tube, a second heat transfer tube, and a third heat transfer tube, wherein the first heat transfer tube is connected to the first refrigerant path, the second heat transfer tube is connected to the second refrigerant path, and the third heat transfer tube is connected to the suction pipe.

[0064] Thereby, during both cooling operation and heating operation, the performance of the refrigeration cycle can be improved by one internal heat exchanger. Therefore, the configuration of the air conditioner can be simplified.

[0065] The air conditioner according to Technology 2, wherein the internal heat exchanger is connected such that the first heat transfer tube and the third heat transfer tube are in counterflow during cooling operation and the second heat transfer tube and the third heat transfer tube are in counterflow during heating operation.

[0066] As a result, during both the cooling operation and the heating operation, the efficiency of heat exchange between the refrigerant before passing through the expansion valve and the refrigerant in the suction pipe can be improved, and the evaporation capacity in the refrigeration cycle of the air conditioner can be enhanced. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0067] (Technical 4) The flow passage cross-sectional area of the first heat transfer pipe is smaller than the flow passage cross-sectional area of the first check valve, and the flow passage cross-sectional area of the second heat transfer pipe is smaller than the flow passage cross-sectional area of the second check valve. The air conditioner according to Technical 2 or 3.

[0068] As a result, during both the cooling operation and the heating operation, the inflow of the refrigerant after passing through the expansion valve into the internal heat exchanger can be suppressed, and the evaporation capacity can be improved. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0069] (Technical 5) The internal heat exchanger includes a first internal heat exchanger and a second internal heat exchanger. The first internal heat exchanger is connected to the first refrigerant path and the suction pipe, and the second internal heat exchanger is connected to the second refrigerant path and the suction pipe. The air conditioner according to Technical 1.

[0070] As a result, during both the cooling operation and the heating operation, while suppressing heat exchange between the refrigerant in the first refrigerant path and the refrigerant in the second refrigerant path, the refrigerant before passing through the expansion valve can be cooled. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0071] (Technical 6) The flow passage cross-sectional area of the first refrigerant path is smaller than the flow passage cross-sectional area of the first check valve, and the flow passage cross-sectional area of the second refrigerant path is smaller than the flow passage cross-sectional area of the second check valve. The air conditioner according to any one of Technical 1 to 5.

[0072] As a result, during both the cooling operation and the heating operation, the inflow of the refrigerant after passing through the expansion valve into the internal heat exchanger can be suppressed, and the evaporation capacity can be improved. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0073] (Technical 7) The flow passage cross-sectional area on the liquid side of the first internal heat exchanger is smaller than the flow passage cross-sectional area of the first check valve, and the flow passage cross-sectional area on the liquid side of the second internal heat exchanger is smaller than the flow passage cross-sectional area of the second check valve. The air conditioner according to Technology 5 or 6.

[0074] As a result, during both the cooling operation and the heating operation, it is possible to suppress the refrigerant after passing through the expansion valve from flowing into the internal heat exchanger and being heated, and the evaporation capacity can be improved. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

[0075] (Technical 8) The first refrigerant path is connected in a direction orthogonal to a linear first expansion valve side path connecting the expansion valve and the first check valve, and the second refrigerant path is connected in a direction orthogonal to a linear second expansion valve side path connecting the expansion valve and the second check valve. The air conditioner according to any one of Technologies 1 to 7.

[0076] As a result, during both the cooling operation and the heating operation, the inflow of the refrigerant after passing through the expansion valve into the internal heat exchanger can be suppressed, and the evaporation capacity can be improved. Therefore, during both the cooling operation and the heating operation, the performance of the refrigeration cycle can be improved.

Industrial Applicability

[0077] The present disclosure is applicable to an air conditioner capable of switching between a cooling operation and a heating operation. Specifically, the present disclosure is applicable to single air conditioners or multi-air conditioners for household or business use.

Explanation of Signs

[0078] 1 Air conditioner 10 Outdoor unit 11 Compressor 12 First check valve 13 Four-way valve 14 Second check valve 15 Outdoor heat exchanger 16 Indoor heat exchanger 16a First heat transfer tube 16b Second heat transfer tube 16c Third heat transfer tube 17 Expansion valve 21 Discharge pipe 22 Indoor gas path 23 Indoor liquid path 23a Second heat exchange side path 23b Second expansion valve side path 23c Second heat exchange side branch 23d Second expansion valve side branch 24 Outdoor liquid path 24a First heat exchange side path 24b First expansion valve side path 24c First heat exchange side branch 24d First expansion valve side branch 25 Outdoor gas path 26 Suction pipe 30 Indoor unit 31 Indoor heat exchanger 41 First refrigerant path 42 Second refrigerant path 101 Air conditioner 116 First internal heat exchanger 116a First liquid heat transfer tube 116b First gas heat transfer tube 117 Second internal heat exchanger 117a Second liquid heat transfer tube 117b Second gas heat transfer tube

Claims

1. In an air conditioner comprising a compressor, a four-way valve for switching between heating and cooling, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, a first check valve connected between the outdoor heat exchanger and the expansion valve and allowing the flow from the expansion valve to the outdoor heat exchanger; a first refrigerant path branching from between the first check valve and the outdoor heat exchanger and merging between the first check valve and the expansion valve; a second check valve connected between the expansion valve and the indoor heat exchanger and allowing the flow from the expansion valve to the indoor heat exchanger; a second refrigerant path branching from between the second check valve and the indoor heat exchanger and merging between the second check valve and the expansion valve; an internal heat exchanger that exchanges heat between the first refrigerant path and the refrigerant flowing through the suction pipe of the compressor during cooling operation, and exchanges heat between the second refrigerant path and the refrigerant flowing through the suction pipe during heating operation; an air conditioner.

2. The internal heat exchanger includes a first heat transfer pipe, a second heat transfer pipe, and a third heat transfer pipe, the first heat transfer pipe is connected to the first refrigerant path, the second heat transfer pipe is connected to the second refrigerant path, and the third heat transfer pipe is connected to the suction pipe, The air conditioner according to claim 1.

3. The internal heat exchanger is connected such that the first heat transfer pipe and the third heat transfer pipe are in countercurrent flow during cooling operation, and the second heat transfer pipe and the third heat transfer pipe are in countercurrent flow during heating operation, The air conditioner according to claim 2.

4. The flow passage cross-sectional area of the first heat transfer pipe is smaller than the flow passage cross-sectional area of the first check valve, and the flow passage cross-sectional area of the second heat transfer pipe is smaller than the flow passage cross-sectional area of the second check valve, The air conditioner according to claim 2.

5. The internal heat exchanger includes a first internal heat exchanger and a second internal heat exchanger, the first internal heat exchanger is connected to the first refrigerant path and the suction pipe, and the second internal heat exchanger is connected to the second refrigerant path and the suction pipe, The air conditioner according to claim 1.

6. The flow passage cross-sectional area of the first refrigerant path is smaller than the flow passage cross-sectional area of the first check valve, and the flow passage cross-sectional area of the second refrigerant path is smaller than the flow passage cross-sectional area of the second check valve, The air conditioner according to any one of claims 1 to 5.

7. The flow passage cross-sectional area of the liquid side of the first internal heat exchanger is smaller than the flow passage cross-sectional area of the first check valve, and the flow passage cross-sectional area of the liquid side of the second internal heat exchanger is smaller than the flow passage cross-sectional area of the second check valve, The air conditioner according to claim 5.

8. The first refrigerant path is connected in a direction orthogonal to a linear first expansion valve side path connecting the expansion valve and the first check valve. The second refrigerant path is connected in a direction orthogonal to a linear second expansion valve side path connecting the expansion valve and the second check valve. The air conditioner according to any one of claims 1 to 5.

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