Air conditioner

Abstract

To provide an air conditioner capable of preventing an outdoor heat exchanger from being frosted.SOLUTION: An air conditioner includes a first outdoor heat exchanger, an indoor heat exchanger, a first pipe, a second pipe, a compressor, a four-way valve, a gas-liquid separator, a first expansion valve, a second expansion valve, a third pipe, a second outdoor heat exchanger, and a fan. The first pipe and the second pipe connect the first outdoor heat exchanger and the indoor heat exchanger. The compressor and the four-way valve are provided in the first pipe. The gas-liquid separator, the first expansion valve, and the second expansion valve are provided in the second pipe. The third pipe is connected to the first pipe between the four-way valve and the indoor heat exchanger, and is connected to the second pipe. The second outdoor heat exchanger is provided in the third pipe. The fan generates an airflow flowing from the second outdoor heat exchanger toward the first outdoor heat exchanger.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to an air conditioning apparatus. [Background technology]

[0002] Air conditioners regulate the indoor temperature by condensing and evaporating the refrigerant in the refrigeration cycle. During heating operation, the refrigerant evaporates in the outdoor heat exchanger (evaporator) and condenses in the indoor heat exchanger (condenser). Conversely, during cooling operation, the refrigerant condenses in the outdoor heat exchanger (condenser) and evaporates in the indoor heat exchanger (evaporator). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-081765 A Summary of the Invention [Problem to be solved by the invention]

[0004] In heating operation, a liquid-phase or two-phase gas-liquid refrigerant is supplied to the outdoor heat exchanger. If the refrigerant does not evaporate properly in the outdoor heat exchanger, the liquid-phase refrigerant may accumulate in the outdoor heat exchanger, causing frost to form on the surface of the outdoor heat exchanger.

[0005] One example of a problem to be solved by the present invention is to provide an air conditioner that can suppress frost formation on an outdoor heat exchanger. [Means for solving the problem]

[0006] An air conditioner according to one embodiment of the present invention includes a first outdoor heat exchanger, an indoor heat exchanger, a first pipe, a second pipe, a compressor, a four-way valve, a gas-liquid separator, a first expansion valve, a second expansion valve, a third pipe, a second outdoor heat exchanger, a first solenoid valve, and a fan. The first pipe connects the first outdoor heat exchanger and the indoor heat exchanger. The second pipe connects the indoor heat exchanger and the first outdoor heat exchanger. The compressor is provided in the first pipe and has an intake port for sucking in a refrigerant and an outlet port for discharging the refrigerant. The four-way valve is provided in the first pipe and is capable of changing the direction in which the refrigerant flows. The gas-liquid separator is provided in the second pipe. The first expansion valve is provided in the second pipe between the indoor heat exchanger and the gas-liquid separator. The second expansion valve is provided in the second piping between the first outdoor heat exchanger and the gas-liquid separator. The third piping is connected to the first piping between the four-way valve and the indoor heat exchanger, and is connected to the second piping between the gas-liquid separator and the first expansion valve. The second outdoor heat exchanger is provided in the third piping. The first solenoid valve is provided in the third piping between the second piping and the second outdoor heat exchanger. The fan generates an airflow that flows from the second outdoor heat exchanger toward the first outdoor heat exchanger.

[0007] The air conditioner further includes a fourth pipe connected to the gas-liquid separator and connected to the first pipe between the suction port and the four-way valve.

[0008] In the above air conditioner, the first outdoor heat exchanger is a microchannel heat exchanger.

[0009] In the above air conditioner, the second outdoor heat exchanger is a microchannel heat exchanger.

[0010] The air conditioner further includes a second solenoid valve provided in the fourth piping.

[0011] The air conditioner further includes a plurality of first branch pipes interposed between the first pipe and the first outdoor heat exchanger, and a plurality of second branch pipes interposed between the second pipe and the first outdoor heat exchanger. The first outdoor heat exchanger has a plurality of flattened tubes. Each of the plurality of first branch pipes connects one or two of the plurality of flattened tubes to the first pipe. Each of the plurality of second branch pipes connects one or two of the plurality of flattened tubes to the second pipe.

[0012] According to the above air conditioner, for example, during heating operation, part of the high-temperature, high-pressure refrigerant discharged from the compressor flows to the second outdoor heat exchanger in the third pipe. Therefore, the second outdoor heat exchanger functions as a condenser. The airflow generated by the fan becomes relatively hot due to the heat released by the second outdoor heat exchanger, and supplies heat to the first outdoor heat exchanger. This allows the air conditioner to improve the efficiency of heat exchange in the first outdoor heat exchanger, which is an evaporator, and to prevent liquid-phase refrigerant from accumulating in the first outdoor heat exchanger. Therefore, the air conditioner can prevent frost from forming on the first outdoor heat exchanger. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a refrigerant system diagram that shows roughly an air conditioner during heating operation according to one embodiment. [Diagram 2] FIG. 2 is a refrigerant system diagram that illustrates the air conditioner of the above embodiment during cooling operation. [Diagram 3] FIG. 3 is a cross-sectional view that typically shows the first outdoor heat exchanger of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment will be described below with reference to Figs. 1 to 3. In this specification, the vertically upward direction is basically defined as the upward direction, and the vertically downward direction is basically defined as the downward direction. In addition, in this specification, components according to the embodiment and their explanations may be described in a plurality of ways. The components and their explanations are merely examples, and are not limited by the expressions in this specification. The components may be specified by names different from those in this specification. The components may be described by expressions different from those in this specification.

[0015] In the following description, "inhibit" is defined as, for example, preventing the occurrence of an event, action, or effect, or reducing the magnitude of an event, action, or effect.

[0016] 1 is a refrigerant system diagram that shows an air conditioner 10 during heating operation according to one embodiment. The air conditioner 10 is, for example, a home air conditioner. Note that the air conditioner 10 is not limited to this example and may be another air conditioner such as a commercial air conditioner.

[0017] 1, an air conditioner 10 has an outdoor unit 11, an indoor unit 12, refrigerant piping 13, and a control device 14. The outdoor unit 11 is disposed, for example, outdoors. The indoor unit 12 is disposed, for example, indoors.

[0018] The air conditioner 10 includes a refrigeration cycle in which an outdoor unit 11 and an indoor unit 12 are connected by refrigerant piping 13. A refrigerant flows between the outdoor unit 11 and the indoor unit 12 through the refrigerant piping 13. In addition, the outdoor unit 11 and the indoor unit 12 are electrically connected to each other by, for example, electrical wiring.

[0019] The outdoor unit 11 has a first outdoor heat exchanger 21, a second outdoor heat exchanger 22, an outdoor blower fan 23, a compressor 24, an accumulator 25, a four-way valve 26, a gas-liquid separator 27, a first expansion valve 31, a second expansion valve 32, a first solenoid valve 33, a second solenoid valve 34, a first flow divider 35, a second flow divider 36, a third flow divider 37, and a heat storage material 38. The heat storage material 38 may be omitted. The outdoor blower fan 23 is an example of a fan. The indoor unit 12 has an indoor heat exchanger 41 and an indoor blower fan 42.

[0020] The refrigerant pipe 13 is, for example, a pipe made of metal. The refrigerant pipe 13 has a first pipe 51, a second pipe 52, a third pipe 53, a fourth pipe 54, a plurality of first branch pipes 55, a plurality of second branch pipes 56, and a plurality of third branch pipes 57.

[0021] The first piping 51 connects the indoor heat exchanger 41 and the first outdoor heat exchanger 21. The compressor 24, the accumulator 25, and the four-way valve 26 are provided in the first piping 51. The second piping 52 connects the first outdoor heat exchanger 21 and the indoor heat exchanger 41. The gas-liquid separator 27, the first expansion valve 31, and the second expansion valve 32 are provided in the second piping 52.

[0022] In heating operation, the refrigerant flows from the first outdoor heat exchanger 21 to the indoor heat exchanger 41 through the first piping 51, and flows from the indoor heat exchanger 41 to the first outdoor heat exchanger 21 through the second piping 52. The arrows in Fig. 1 indicate the flow of the refrigerant during heating operation.

[0023] Fig. 2 is a refrigerant system diagram that shows a schematic of the air conditioner 10 during cooling operation of this embodiment. During cooling operation, the refrigerant flows from the indoor heat exchanger 41 to the first outdoor heat exchanger 21 through the first piping 51, and flows from the first outdoor heat exchanger 21 to the indoor heat exchanger 41 through the second piping 52. The arrows in Fig. 2 show the flow of the refrigerant during cooling operation.

[0024] The first outdoor heat exchanger 21 of the outdoor unit 11 absorbs heat from the refrigerant as an evaporator during heating operation, and releases heat from the refrigerant as a condenser during cooling operation. The outdoor blower fan 23 generates an airflow FA passing through the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22, and promotes heat exchange between the refrigerant and air in the first outdoor heat exchanger 21.

[0025] The compressor 24 has a suction port 24a and a discharge port 24b. The compressor 24 draws in a refrigerant from the suction port 24a and discharges the compressed refrigerant from the discharge port 24b. In this way, the compressor 24 compresses the refrigerant in a refrigeration cycle and causes the refrigerant to circulate.

[0026] The accumulator 25 is connected to the suction port 24a of the compressor 24. The accumulator 25 separates the liquid refrigerant from the gaseous refrigerant. This allows the compressor 24 to suck the gaseous refrigerant that has passed through the accumulator 25 from the suction port 24a. The accumulator 25 is configured integrally with the compressor 24, and can serve as the suction port of the compressor 24.

[0027] The four-way valve 26 is connected to the first outdoor heat exchanger 21, the indoor heat exchanger 41, the discharge port 24b of the compressor 24, and the accumulator 25 (the suction port 24a of the compressor 24). The four-way valve 26 switches the flow paths connected to the first outdoor heat exchanger 21, the indoor heat exchanger 41, the discharge port 24b of the compressor 24, and the accumulator 25, respectively, during heating operation and cooling operation, to change the direction in which the refrigerant flows.

[0028] 1, during heating operation, the four-way valve 26 connects the first outdoor heat exchanger 21 and the accumulator 25. Furthermore, during heating operation, the four-way valve 26 connects the indoor heat exchanger 41 and the discharge port 24b of the compressor 24. As a result, the refrigerant compressed by the compressor 24 flows to the indoor heat exchanger 41, and the refrigerant evaporated in the first outdoor heat exchanger 21 flows to the accumulator 25.

[0029] 2, during cooling operation, the four-way valve 26 connects the first outdoor heat exchanger 21 and the discharge port 24b of the compressor 24. Furthermore, during cooling operation, the four-way valve 26 connects the indoor heat exchanger 41 and the accumulator 25. As a result, the refrigerant compressed by the compressor 24 flows to the first outdoor heat exchanger 21, and the refrigerant evaporated in the indoor heat exchanger 41 flows to the accumulator 25.

[0030] The gas-liquid separator 27 is a container capable of storing a liquid-phase refrigerant. The gas-liquid separator 27 is provided with a first connection port 27a, a second connection port 27b, and a third connection port 27c. The first connection port 27a is connected to the indoor heat exchanger 41 through the second piping 52. The second connection port 27b is connected to the first outdoor heat exchanger 21 through the second piping 52.

[0031] The first connection port 27a and the second connection port 27b are provided, for example, at the bottom of the gas-liquid separator 27. Therefore, the liquid-phase refrigerant stored in the gas-liquid separator 27 can flow out from the first connection port 27a or the second connection port 27b.

[0032] The third connection port 27c is located above the first connection port 27a and the second connection port 27b. For example, the third connection port 27c is located above the liquid level of the liquid-phase refrigerant stored in the gas-liquid separator 27. Therefore, the gas-phase refrigerant stored in the gas-liquid separator 27 can flow out from the third connection port 27c.

[0033] The first expansion valve 31 and the second expansion valve 32 are, for example, electromagnetic expansion valves. The first expansion valve 31 and the second expansion valve 32 may be other expansion valves. The first expansion valve 31 and the second expansion valve 32 have their openings controlled by the control device 14, thereby adjusting the amount of refrigerant passing through the first expansion valve 31 and the second expansion valve 32.

[0034] The first expansion valve 31 is provided in the second piping 52 between the indoor heat exchanger 41 and the gas-liquid separator 27. The second expansion valve 32 is provided in the second piping 52 between the first outdoor heat exchanger 21 and the gas-liquid separator 27.

[0035] The indoor heat exchanger 41 of the indoor unit 12 radiates heat as a condenser during heating operation and absorbs heat as an evaporator during cooling operation. The indoor blower fan 42 blows air toward the indoor heat exchanger 41, promoting heat exchange between the indoor heat exchanger 41 and the air.

[0036] One end of the third pipe 53 is connected to the first pipe 51 between the four-way valve 26 and the indoor heat exchanger 41. Furthermore, the other end of the third pipe 53 is connected to the second pipe 52 between the gas-liquid separator 27 and the first expansion valve 31.

[0037] The second outdoor heat exchanger 22, the first solenoid valve 33, and the heat storage material 38 are provided in the third piping 53. The first solenoid valve 33 is provided in the third piping 53 between the second piping 52 and the second outdoor heat exchanger 22. The heat storage material 38 is provided in the third piping 53 between the first piping 51 and the second outdoor heat exchanger 22.

[0038] One end of the fourth pipe 54 is connected to the third connection port 27c of the gas-liquid separator 27. The other end of the fourth pipe 54 is connected to the first pipe 51 between the accumulator 25 and the four-way valve 26. In other words, the other end of the fourth pipe 54 is connected to the first pipe 51 between the suction port 24a of the compressor 24 and the four-way valve 26. The second solenoid valve 34 is provided in the fourth pipe 54.

[0039] The first solenoid valve 33 and the second solenoid valve 34 have their openings controlled by the control device 14 to adjust the amount of refrigerant passing through the first solenoid valve 33 and the second solenoid valve 34. The heat storage material 38 exchanges heat with the refrigerant flowing through the third pipe 53.

[0040] Each of the multiple first branch pipes 55 is interposed between the first piping 51 and the first outdoor heat exchanger 21. The first flow divider 35 connects the first piping 51 and the multiple first branch pipes 55.

[0041] Each of the multiple second branch pipes 56 is interposed between the second piping 52 and the first outdoor heat exchanger 21. The second flow divider 36 connects the second piping 52 and the multiple second branch pipes 56 to each other.

[0042] The multiple third branch pipes 57 are located between the second outdoor heat exchanger 22 and the first solenoid valve 33. Each of the multiple third branch pipes 57 is interposed between the third piping 53 and the second outdoor heat exchanger 22. The third flow divider 37 connects the third piping 53 and the multiple third branch pipes 57.

[0043] The control device 14 includes, for example, an outdoor control device 14a and an indoor control device 14b. The outdoor control device 14a and the indoor control device 14b are electrically connected to each other by electrical wiring. Note that the control device 14 is not limited to this example. For example, the control device 14 may include only one of the outdoor control device 14a and the indoor control device 14b.

[0044] The outdoor control device 14a controls the outdoor blower fan 23, the compressor 24, the four-way valve 26, the first expansion valve 31, the second expansion valve 32, the first solenoid valve 33, and the second solenoid valve 34 of the outdoor unit 11. The indoor control device 14b controls the indoor blower fan 42 of the indoor unit 12.

[0045] The control device 14 controls the outdoor unit 11 and the indoor unit 12, causing the air conditioning device 10 to perform cooling operation, heating operation, dehumidification operation, and other operations. The indoor control device 14b may receive signals, for example, from a remote controller, or may receive signals from an information terminal such as a smartphone via a communication device.

[0046] The first outdoor heat exchanger 21, the second outdoor heat exchanger 22, and the indoor heat exchanger 41 are microchannel heat exchangers. At least one of the first outdoor heat exchanger 21, the second outdoor heat exchanger 22, and the indoor heat exchanger 41 may be another type of heat exchanger.

[0047] 3 is a cross-sectional view illustrating a first outdoor heat exchanger 21 of the present embodiment. The first outdoor heat exchanger 21 has a first header 61, a second header 62, a plurality of flat tubes 63, a first relay header 64, a second relay header 65, a plurality of relay tubes 66, and a plurality of fins 67.

[0048] Each of the first header 61, the second header 62, the first relay header 64, and the second relay header 65 is formed in a hollow columnar shape extending in a substantially vertical direction. The first header 61 and the second header 62 are spaced apart from each other. In FIG. 3, the first header 61 and the second header 62 are typically arranged in a substantially vertical direction (the vertical direction in FIG. 3), but may be arranged in a substantially horizontal direction (the direction perpendicular to the paper surface of FIG. 3), for example. The first header 61 and the second header 62 are spaced apart from the first relay header 64 and the second relay header 65 in a substantially horizontal direction (the horizontal direction in FIG. 3).

[0049] A plurality of first chambers 61a are provided inside the first header 61. The plurality of first chambers 61a are arranged in a substantially vertical direction and are separated from one another. A plurality of second chambers 62a are provided inside the second header 62. The plurality of second chambers 62a are arranged in a substantially vertical direction and are separated from one another.

[0050] A plurality of first relay chambers 64a are provided inside the first relay header 64. The plurality of first relay chambers 64a are arranged in a substantially vertical direction and are separated from one another. A plurality of second relay chambers 65a are provided inside the second relay header 65. The plurality of second relay chambers 65a are arranged in a substantially vertical direction and are separated from one another.

[0051] The flat tubes 63 are made of, for example, an aluminum alloy. The material of the flat tubes 63 is not limited to this example. In the example of FIG. 3, each of the flat tubes 63 has a first flat tube 68 and a second flat tube 69. In other words, in the example of FIG. 3, each of the flat tubes 63 is divided into the first flat tube 68 and the second flat tube 69.

[0052] The first flat tubes 68 are arranged at intervals in a substantially vertical direction and extend substantially parallel to each other. The second flat tubes 69 are also arranged at intervals in a substantially vertical direction and extend substantially parallel to each other. The first flat tubes 68 and the second flat tubes 69 are each provided with a plurality of flow paths 68a, 69a extending in parallel to each other. For this reason, the flat tube 63 is also referred to as a flat porous tube. The flow paths 68a, 69a are arranged in a substantially horizontal direction (a direction perpendicular to the paper surface of FIG. 3) and are separated from each other.

[0053] The multiple first flat tubes 68 are connected to the first header 61 and the first relay header 64. One or two first flat tubes 68 are connected to each of the multiple first chambers 61a. Furthermore, one or two first flat tubes 68 are connected to each of the multiple first relay chambers 64a.

[0054] Each of the first flat tubes 68 extends in parallel between the first chamber 61a and the first relay chamber 64a. The first chamber 61a and the first relay chamber 64a communicate with each other via the multiple flow paths 68a of each of the first flat tubes 68.

[0055] The plurality of second flat tubes 69 are connected to the second header 62 and the second relay header 65. One or two second flat tubes 69 are connected to each of the plurality of second chambers 62a. Furthermore, one or two second flat tubes 69 are connected to each of the plurality of second relay chambers 65a.

[0056] Each of the second flat tubes 69 extends in parallel between the second chamber 62a and the second relay chamber 65a. The second chamber 62a and the second relay chamber 65a communicate with each other via the multiple flow paths 69a of each of the second flat tubes 69.

[0057] Each of the relay pipes 66 connects one of the first relay chambers 64a to one of the second relay chambers 65a. Therefore, the first flat tube 68 and the second flat tube 69 are connected to each other via the first relay header 64, the second relay header 65, and the relay pipe 66.

[0058] The fins 67 are, for example, corrugated fins. The fins 67 may be other heat dissipation fins such as straight fins. Each of the multiple fins 67 is thermally connected to the flat tubes 63. At least one of the multiple fins 67 is located between two adjacent ones of the multiple flat tubes 63.

[0059] Each of the first branch pipes 55 is connected to a corresponding one of the first chambers 61a. Therefore, each of the first branch pipes 55 connects one or two of the flat tubes 63 to the first piping 51.

[0060] Each of the second branch pipes 56 is connected to a corresponding one of the second chambers 62a. Therefore, each of the second branch pipes 56 connects one or two of the flat tubes 63 to the second piping 52.

[0061] As described above, the first flow distributor 35 and the multiple first branch pipes 55 connect the first pipe 51 and the multiple flat pipes 63. The second flow distributor 36 and the multiple second branch pipes 56 connect the second pipe 52 and the multiple flat pipes 63. The portion of the first pipe 51 connected to the first flow distributor 35 and the portion of the second pipe 52 connected to the second flow distributor 36 extend in a substantially vertical direction.

[0062] The second outdoor heat exchanger 22 has a similar configuration to the first outdoor heat exchanger 21. That is, as shown in FIG. 1, the second outdoor heat exchanger 22 has a first header 71, a second header 72, and a plurality of flat tubes 73. Furthermore, the second outdoor heat exchanger 22 has a first relay header, a second relay header, a plurality of relay tubes, and a plurality of fins. The first header 71, the second header 72, and the flat tubes 73 are substantially equal to the first header 61, the second header 62, and the flat tubes 63 of the first outdoor heat exchanger 21, except for the points described below.

[0063] The third branch pipes 57 are connected to the first chambers 71a of the first header. Each of the third branch pipes 57 connects one or two of the flat tubes 73 to the third piping 53.

[0064] The second header 72 is provided with one second chamber 72a. The one second chamber 72a is connected to all of the flat tubes 73 and is also connected to the third piping 53. That is, the second header 72 connects the third piping 53 to all of the flat tubes 63. Note that, like the first header 71, the second header 72 may be connected to the third piping 53 via a plurality of branch pipes and a flow divider.

[0065] The second outdoor heat exchanger 22 is smaller than the first outdoor heat exchanger 21. Therefore, the volume of refrigerant that the second outdoor heat exchanger 22 can accommodate is smaller than the volume of refrigerant that the first outdoor heat exchanger 21 can accommodate. Since the second outdoor heat exchanger 22 is small, the outdoor unit 11 can be made compact. Note that the sizes of the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 are not limited to this example.

[0066] The first outdoor heat exchanger 21, the second outdoor heat exchanger 22, and the outdoor blower fan 23 are arranged in a substantially horizontal direction. The first outdoor heat exchanger 21 is located between the second outdoor heat exchanger 22 and the outdoor blower fan 23. Note that the second outdoor heat exchanger 22 may be located between the first outdoor heat exchanger 21 and the outdoor blower fan 23.

[0067] In the direction of the airflow FA generated by the outdoor blower fan 23, the first outdoor heat exchanger 21 is located downstream of the second outdoor heat exchanger 22. For this reason, the outdoor blower fan 23 generates an airflow FA that flows from the second outdoor heat exchanger 22 toward the first outdoor heat exchanger 21.

[0068] The airflow FA generated by the outdoor blower fan 23 passes through the fins of the second outdoor heat exchanger 22, and exchanges heat with the refrigerant flowing through the flat tubes 73 of the second outdoor heat exchanger 22. The airflow FA that has passed through the second outdoor heat exchanger 22 passes through the fins 67 of the first outdoor heat exchanger 21, and exchanges heat with the refrigerant flowing through the flat tubes 63 of the first outdoor heat exchanger 21.

[0069] The air conditioner 10 further has a plurality of temperature sensors 81, 82, 83, 84, 85, 86, and 87. For example, the outdoor control device 14a obtains the temperature of the refrigerant from the temperature sensors 81 to 86. The indoor control device 14b obtains the temperature of the refrigerant from the temperature sensor 87.

[0070] The temperature sensor 81 detects the temperature of the refrigerant in the first outdoor heat exchanger 21. The temperature sensor 82 is located between the first expansion valve 31 and the indoor heat exchanger 41 and detects the temperature of the refrigerant in the second pipe 52.

[0071] The temperature sensor 83 detects the temperature of the refrigerant in the second pipe 52 between the gas-liquid separator 27 and the second expansion valve 32. The temperature sensor 84 detects the temperature of the refrigerant in the second pipe 52 between the first outdoor heat exchanger 21 and the second expansion valve 32.

[0072] The temperature sensor 85 detects the temperature of the refrigerant in the first pipe 51 between the accumulator 25 and the four-way valve 26. The temperature sensor 86 detects the temperature of the refrigerant in the second outdoor heat exchanger 22. The temperature sensor 87 detects the temperature of the refrigerant in the indoor heat exchanger 41.

[0073] 1, in heating operation, the gas-phase refrigerant discharged from the discharge port 24b of the compressor 24 is supplied to the indoor heat exchanger 41 (condenser) through the first pipe 51. The refrigerant condensed in the indoor heat exchanger 41 is decompressed by the first expansion valve 31 and flows into the first connection port 27a of the gas-liquid separator 27.

[0074] The liquid phase refrigerant stored in the gas-liquid separator 27 flows out from the second connection port 27b and is depressurized by the second expansion valve 32. In this embodiment, the refrigerant depressurized by the second expansion valve 32 is mostly liquid phase refrigerant even if the refrigerant is a mixture of gas phase and liquid phase refrigerant. The refrigerant depressurized by the second expansion valve 32 does not need to be at a low temperature. For example, the temperature of the refrigerant depressurized by the second expansion valve 32 is about 18°C.

[0075] The refrigerant decompressed by the second expansion valve 32 is supplied to the first outdoor heat exchanger 21 (evaporator). Specifically, the refrigerant is distributed from the second flow divider 36 in Fig. 3 to the multiple second chambers 62a via the multiple second branch pipes 56. The refrigerant is distributed from each of the multiple second chambers 62a to the multiple flow paths 68a, 69a of one or two flat tubes 63.

[0076] In general, liquid-phase refrigerant is more susceptible to the effects of gravity and inertia, for example, than gas-phase refrigerant. Therefore, liquid-phase refrigerant is more likely to be biased in the header. However, the diverter (second diverter 36) and the multiple diverter pipes (second branch pipes 56) can distribute the liquid-phase refrigerant with less bias than the header. In addition, the number of flat tubes 63 connected to the multiple second chambers 62a is one or two. Therefore, the refrigerant in the second chamber 62a flows relatively evenly into the multiple flow paths 68a, 69a of the one or two flat tubes 63.

[0077] 1, a portion of the refrigerant discharged from the discharge port 24b of the compressor 24 is supplied to the second outdoor heat exchanger 22 (condenser) through the third pipe 53. The refrigerant is distributed from one second chamber 72a of the second header 72 to the multiple flat tubes 73. Since the refrigerant discharged from the compressor 24 is in a gas phase, it is unlikely to be biased in one second chamber 72a of the second header 72.

[0078] In the second outdoor heat exchanger 22, the high-temperature, high-pressure refrigerant exchanges heat with the airflow FA generated by the outdoor blower fan 23 and condenses. Therefore, the airflow FA that has passed through the second outdoor heat exchanger 22 is warmed by heat exchange with the high-temperature, high-pressure refrigerant. For example, when the outdoor air temperature is about 2°C, the temperature of the airflow FA that has passed through the second outdoor heat exchanger 22 is warmed to about 24°C.

[0079] The airflow FA that has passed through the second outdoor heat exchanger 22 passes through the first outdoor heat exchanger 21 and exchanges heat with the refrigerant in the first outdoor heat exchanger 21. The refrigerant in the first outdoor heat exchanger 21 exchanges heat with the heated airflow FA, and therefore can evaporate efficiently.

[0080] Generally, in a microchannel heat exchanger, a large pressure loss occurs in the liquid phase refrigerant. Therefore, if the evaporation of the refrigerant is insufficient, the liquid phase refrigerant accumulates in the microchannel heat exchanger. However, the refrigerant in the first outdoor heat exchanger 21 can efficiently exchange heat with the heated airflow FA, and therefore can evaporate without accumulating in the first outdoor heat exchanger 21.

[0081] As described above, low-temperature liquid-phase refrigerant is less likely to accumulate in the first outdoor heat exchanger 21, so frost is less likely to form on the surface of the first outdoor heat exchanger 21. Furthermore, even if the outdoor air temperature is below freezing, the first outdoor heat exchanger 21 exchanges heat with the warm airflow FA that has passed through the second outdoor heat exchanger 22, so that the temperature of the refrigerant flowing through the first outdoor heat exchanger 21 can be increased. For this reason, the first outdoor heat exchanger 21 is less likely to frost.

[0082] The refrigerant in the first outdoor heat exchanger 21 passes through a plurality of first branch pipes 55 and merges in the first flow divider 35. The merged refrigerant passes through the first piping 51 and the accumulator 25, and is sucked into the suction port 24a of the compressor 24.

[0083] On the other hand, the refrigerant in the second outdoor heat exchanger 22 passes through a plurality of third branch pipes 57 and merges in the third flow divider 37. The merged refrigerant passes through the first solenoid valve 33 and the second pipe 52, and flows into the first connection port 27a of the gas-liquid separator 27 together with the refrigerant decompressed by the first expansion valve 31.

[0084] In the above heating operation, the control device 14 controls the first expansion valve 31 so as to satisfy, for example, the following formula (1). Tc2 is the refrigerant temperature detected by the temperature sensor 82. Tc3 is the refrigerant temperature detected by the temperature sensor 83. Tc2-Tc3≒15℃ …(Number 1)

[0085] Furthermore, the control device 14 controls the second expansion valve 32 so as to satisfy, for example, the following formula (2): Tc4 is the temperature of the refrigerant detected by the temperature sensor 84. Tc3-Tc4≒4.5℃ …(Number 2) The above temperatures, formula (1), and formula (2) are all just examples.

[0086] The control device 14 also controls the flow rate of the refrigerant supplied to the second outdoor heat exchanger 22 by the first solenoid valve 33. Furthermore, the control device 14 basically closes the second solenoid valve 34 to prevent the liquid-phase refrigerant in the gas-liquid separator 27 from flowing into the suction port 24a of the compressor 24 (liquid backflow). The control device 14 opens the second solenoid valve 34, for example, when the temperature of the refrigerant flowing into the suction port 24a is lower than a predetermined temperature or when the flow rate of the refrigerant flowing into the suction port 24a is lower than a predetermined flow rate.

[0087] 2, in cooling operation, the gas-phase refrigerant discharged from the discharge port 24b of the compressor 24 is supplied to the first outdoor heat exchanger 21 (condenser). The refrigerant condensed in the first outdoor heat exchanger 21 is decompressed by the second expansion valve 32 and flows into the second connection port 27b of the gas-liquid separator 27.

[0088] The liquid phase refrigerant stored in the gas-liquid separator 27 flows out from the first connection port 27a and is depressurized by the first expansion valve 31. The refrigerant depressurized by the first expansion valve 31 is supplied to the indoor heat exchanger 41 (evaporator). The refrigerant evaporated in the indoor heat exchanger 41 passes through the first pipe 51 and the accumulator 25, and is sucked into the suction port 24a of the compressor 24.

[0089] On the other hand, a portion of the liquid-phase refrigerant flowing out from the first connection port 27a is supplied to the second outdoor heat exchanger 22 (evaporator) through the third pipe 53. The liquid-phase refrigerant is distributed stepwise to the multiple third branch pipes 57, the multiple first chambers 71a, and the multiple flat tubes 73. For this reason, the liquid-phase refrigerant flows relatively evenly into one or two flat tubes 73.

[0090] In the second outdoor heat exchanger 22, the refrigerant exchanges heat with the airflow FA generated by the outdoor blower fan 23 and evaporates. Therefore, the airflow FA that has passed through the second outdoor heat exchanger 22 is cooled by heat exchange with the refrigerant. For example, when the outdoor air temperature is about 35°C, the temperature of the airflow FA that has passed through the second outdoor heat exchanger 22 is cooled to about 12°C. Note that this temperature is one example.

[0091] The airflow FA that has passed through the second outdoor heat exchanger 22 passes through the first outdoor heat exchanger 21 and exchanges heat with the refrigerant in the first outdoor heat exchanger 21. The refrigerant in the first outdoor heat exchanger 21 can be efficiently condensed by exchanging heat with the cooled airflow FA. Therefore, the compressor 24 does not need to highly pressurize the refrigerant discharged from the discharge port 24b. The refrigerant in the second outdoor heat exchanger 22 passes through the first pipe 51 and the accumulator 25, and is sucked into the suction port 24a of the compressor 24.

[0092] In the above cooling operation, the controller 14 controls the flow rate of the refrigerant supplied to the second outdoor heat exchanger 22 by the first solenoid valve 33 to suppress liquid backflow. Furthermore, the controller 14 basically closes the second solenoid valve 34 to suppress liquid backflow. For example, when the temperature of the refrigerant discharged from the discharge port 24b is higher than a desired temperature, the controller 14 opens the second solenoid valve 34 to lower the temperature of the refrigerant discharged from the discharge port 24b.

[0093] In the air-conditioning apparatus according to the embodiment described above, the second pipe 52 connects the indoor heat exchanger 41 and the first outdoor heat exchanger 21. The gas-liquid separator 27 is provided in the second pipe 52. The first expansion valve 31 is provided in the second pipe 52 between the indoor heat exchanger 41 and the gas-liquid separator 27. The second expansion valve 32 is provided in the second pipe 52 between the first outdoor heat exchanger 21 and the gas-liquid separator 27. The third pipe 53 is connected to the first pipe 51 between the four-way valve 26 and the indoor heat exchanger, and is connected to the second pipe 52 between the gas-liquid separator 27 and the first expansion valve 31. The second outdoor heat exchanger 22 is provided in the third pipe 53. The outdoor blower fan 23 generates an airflow FA that flows from the second outdoor heat exchanger 22 toward the first outdoor heat exchanger 21.

[0094] In the heating operation, a part of the high-temperature, high-pressure refrigerant discharged from the compressor 24 flows to the second outdoor heat exchanger 22 in the third pipe 53. Therefore, the second outdoor heat exchanger 22 functions as a condenser. The airflow FA generated by the outdoor blower fan 23 becomes relatively hot due to the heat released by the second outdoor heat exchanger 22, and supplies heat to the first outdoor heat exchanger 21. This allows the air conditioning apparatus 10 to improve the efficiency of heat exchange in the first outdoor heat exchanger 21, which is an evaporator, and to suppress accumulation of liquid-phase refrigerant in the first outdoor heat exchanger 21. Therefore, the air conditioning apparatus 10 can suppress frost formation on the first outdoor heat exchanger 21. By suppressing frost formation, the air conditioning apparatus 10 does not need to repeat defrosting operations.

[0095] In cooling operation, a portion of the refrigerant that has passed through the first outdoor heat exchanger 21 and the gas-liquid separator 27 flows to the second outdoor heat exchanger 22 in the third pipe 53. For this reason, the second outdoor heat exchanger 22 functions as an evaporator. The airflow FA generated by the outdoor blower fan 23 absorbs heat in the second outdoor heat exchanger 22, becomes relatively low in temperature, and absorbs heat from the first outdoor heat exchanger 21. As a result, the air conditioner 10 can improve the efficiency of heat exchange in the first outdoor heat exchanger 21, which is a condenser, and can improve the refrigeration capacity.

[0096] The fourth pipe 54 is connected to the gas-liquid separator 27, and is connected to the first pipe 51 between the suction port 24a and the four-way valve 26. Therefore, the compressor 24 can be supplied with refrigerant from the gas-liquid separator 27 via the fourth pipe 54. Therefore, the air conditioning device 10 can prevent the refrigerant drawn by the compressor 24 from the suction port 24a from becoming insufficient and from becoming too low in temperature.

[0097] The first outdoor heat exchanger 21 is a microchannel heat exchanger. This allows the air conditioner 10 to reduce the total amount of refrigerant and improve indexes such as the coefficient of degradation (Cd) value. On the other hand, a relatively large pressure loss occurs in the liquid phase refrigerant in the first outdoor heat exchanger 21. However, in the heating operation in which the liquid phase refrigerant is supplied to the first outdoor heat exchanger 21, the outdoor blower fan 23 supplies a high-temperature airflow FA to the first outdoor heat exchanger 21. This allows the air conditioner 10 to suppress accumulation of the liquid phase refrigerant in the first outdoor heat exchanger 21 due to pressure loss.

[0098] The second outdoor heat exchanger 22 is a microchannel heat exchanger. This allows the air conditioning device 10 to reduce the total amount of refrigerant and improve indicators such as the Cd value. Furthermore, since each of the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 has a microchannel heat exchanger, the outdoor unit 11 can be made smaller.

[0099] The second solenoid valve 34 is provided in the fourth pipe 54. That is, the second solenoid valve 34 can close the fourth pipe 54. This enables the air conditioning device 10 to suppress the supply of liquid phase refrigerant from the gas-liquid separator 27 to the suction port 24a of the compressor 24 (liquid backflow).

[0100] The first branch pipes 55 are interposed between the first pipe 51 and the first outdoor heat exchanger 21. The second branch pipes 56 are interposed between the second pipe 52 and the first outdoor heat exchanger 21. The first outdoor heat exchanger 21 has a plurality of flat tubes 63. Each of the first branch pipes 55 connects one or two of the flat tubes 63 to the first pipe 51. Each of the second branch pipes 56 connects one or two of the flat tubes 63 to the second pipe 52. In general, a pipe and a plurality of flat tubes are connected by a header. However, in a header that distributes a refrigerant to a plurality of flat tubes without using a plurality of pipes (branch pipes), a bias of the refrigerant (poor flow division) may generally occur. However, the air conditioning device 10 primarily distributes the refrigerant by the multiple first branch pipes 55 or the multiple second branch pipes 56, and secondarily distributes the refrigerant to the flow paths 68a, 69a of one or two flat tubes 63. This makes it possible for the air conditioning device 10 to suppress uneven distribution of the refrigerant in the multiple flat tubes 63.

[0101] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0102] Reference Signs List 10...air conditioning device, 21...first outdoor heat exchanger, 22...second outdoor heat exchanger, 23...outdoor blower fan, 24...compressor, 24a...suction port, 24b...discharge port, 26...four-way valve, 27...gas-liquid separator, 31...first expansion valve, 32...second expansion valve, 33...first solenoid valve, 34...second solenoid valve, 41...indoor heat exchanger, 51...first piping, 52...second piping, 53...third piping, 54...fourth piping, 55...first branch pipe, 56...second branch pipe, 63...flat pipe, FA...air flow.

Claims

1. A first outdoor heat exchanger; An indoor heat exchanger; a first pipe connecting the first outdoor heat exchanger and the indoor heat exchanger; a second pipe connecting the indoor heat exchanger and the first outdoor heat exchanger; a compressor provided in the first pipe and having a suction port for sucking in a refrigerant and a discharge port for discharging the refrigerant; a four-way valve provided in the first pipe and capable of changing a flow direction of the refrigerant; A gas-liquid separator provided in the second pipe; a first expansion valve provided in the second piping between the indoor heat exchanger and the gas-liquid separator; a second expansion valve provided in the second piping between the first outdoor heat exchanger and the gas-liquid separator; a third pipe connected to the first pipe between the four-way valve and the indoor heat exchanger, and connected to the second pipe between the gas-liquid separator and the first expansion valve; a second outdoor heat exchanger provided in the third pipe; a first solenoid valve provided on the third pipe between the second pipe and the second outdoor heat exchanger; a fan that generates an airflow that flows from the second outdoor heat exchanger toward the first outdoor heat exchanger; An air conditioning device comprising:

2. a fourth pipe connected to the gas-liquid separator and to the first pipe between the suction port and the four-way valve; The air conditioner of claim 1 further comprising:

3. The first outdoor heat exchanger is a microchannel heat exchanger. The air conditioning apparatus of claim 2.

4. The second outdoor heat exchanger is a microchannel heat exchanger. The air conditioning system of claim 3.

5. a second solenoid valve provided in the fourth pipe; The air conditioner of claim 2 further comprising:

6. a plurality of first branch pipes interposed between the first pipe and the first outdoor heat exchanger; a plurality of second branch pipes interposed between the second pipe and the first outdoor heat exchanger; Further comprising: The first outdoor heat exchanger has a plurality of flat tubes, Each of the plurality of first branch pipes connects one or two of the plurality of flat tubes to the first piping, Each of the plurality of second branch pipes connects one or two of the plurality of flat tubes to the second piping. The air conditioning system of claim 3.

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