air conditioner

Abstract

To obtain an air conditioner which can inhibit deterioration of a compressor in heating during which a temperature of outside air is relatively low.SOLUTION: An air conditioner according to an embodiment includes: a first compressor provided at a first pipe; a second compressor provided at the first pipe; a first expansion valve provided at a second pipe; a gas-liquid separator provided at the second pipe; a first heat exchanger; and a third pipe. The first pipe has: a first portion which connects the first compressor with the second compressor; and a second portion which connects the first compressor with an outdoor heat exchanger. The first heat exchanger enables heat exchange between the first portion and the second portion. The third pipe connects the gas-liquid separator with the first portion and may introduce a refrigerant from the gas-liquid separator into the first portion.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] 2. Description of the Related Art An air conditioner adjusts the temperature inside a room by condensing and evaporating a refrigerant in a refrigeration cycle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-121801 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of air conditioner, it would be beneficial if deterioration of the compressor could be suppressed even during heating when the outside air temperature is relatively low.

[0005] One example of a problem to be solved by the present invention is to provide an air conditioner that can suppress deterioration of the compressor even when heating is performed when the outside air temperature is relatively low. [Means for solving the problem]

[0006] An air conditioner according to an embodiment of the present invention includes an indoor heat exchanger, an outdoor heat exchanger, a first pipe connecting the indoor heat exchanger and the outdoor heat exchanger and through which a refrigerant flows, a second pipe connecting the outdoor heat exchanger and the indoor heat exchanger and through which the refrigerant flows, a first compressor provided in the first pipe, a second compressor provided in the first pipe, a four-way valve provided in the first pipe and capable of changing the direction in which the refrigerant flows, a first expansion valve provided in the second pipe, and a gas-liquid separator provided in a second pipe, a first heat exchanger, and a third pipe, the first pipe including a first portion connecting the first compressor and the second compressor and a second portion connecting the first compressor and the outdoor heat exchanger, the first heat exchanger being capable of heat exchange between the first portion and the second portion, the third pipe connecting the gas-liquid separator and the first portion and capable of introducing the refrigerant from the gas-liquid separator into the first portion, In cooling operation, The first compressor and the second compressor are connected in parallel.

[0007] The air conditioner, for example, is provided with a second heat exchanger, the first piping includes a third portion connecting the first compressor and the indoor heat exchanger, and the second heat exchanger is capable of exchanging heat between the second portion and the third portion.

[0008] The air conditioner may further include a second expansion valve provided in the second piping between the indoor heat exchanger and the gas-liquid separator. The first expansion valve is provided in the second pipe between the outdoor heat exchanger and the gas-liquid separator.

[0009] The air conditioner includes a heat storage material provided in the third section. In the air conditioner, for example, In a heating operation, the first compressor and the second compressor are connected in series, The connection between the first compressor and the second compressor is In the cooling operation The parallel In the heating operation In the series connection of the first compressor and the second compressor, the second compressor is upstream of the first compressor.

[0010] According to the air conditioner described above, for example, deterioration of the compressor can be suppressed even during heating when the outside air temperature is relatively low. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a refrigerant system diagram that schematically shows an air conditioner during cooling operation according to an embodiment. [Figure 2] FIG. 2 is a refrigerant system diagram that schematically shows the air conditioner during heating operation according to the embodiment. [Figure 3] FIG. 3 is a block diagram showing the functional configuration of the air conditioner of the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of cooling operation control of the air conditioner according to the embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of cold storage operation control of the air conditioner according to the embodiment. [Figure 6] FIG. 6 is a flowchart showing an example of heating operation control of the air conditioner according to the embodiment. [Figure 7] FIG. 7 is a Mollier diagram of the air conditioner according to the embodiment. [Figure 8] FIG. 8 is a flowchart showing an example of heat storage operation control of the air conditioner according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of defrosting operation control of the air conditioner according to the embodiment. [Figure 10] FIG. 10 is a block diagram illustrating an example of a hardware configuration of the control device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

[0013] The drawings are schematic, and the dimensional relationships and ratios of elements may differ from reality. Furthermore, the drawings may contain parts with different dimensional relationships and ratios. Furthermore, ordinal numbers in this specification are used only to distinguish between parts, members, locations, positions, directions, etc., and do not indicate order or priority.

[0014] 1 is a refrigerant system diagram that schematically shows an air conditioner 10 according to this embodiment during cooling operation. The air conditioner 10 is, for example, a home air conditioner. However, the air conditioner 10 is not limited to this example and may be another type of air conditioner, such as a commercial air conditioner.

[0015] 1, an air conditioner 10 includes an outdoor unit 11, an indoor unit 12, refrigerant piping 13, and a control device 14. The outdoor unit 11 is disposed outdoors, for example. The indoor unit 12 is disposed indoors, for example.

[0016] 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. The outdoor unit 11 and the indoor unit 12 are also electrically connected to each other by, for example, electrical wiring.

[0017] The outdoor unit 11 has an outdoor heat exchanger 21, an outdoor blower fan 22, a first compressor 23A, a second compressor 23B, accumulators 24A and 24B, a four-way valve 25, a first expansion valve 31A, a second expansion valve 31B, and a third expansion valve 31C, switching valves 33A to 33C, on-off valves 34A and 34B, a check valve 35, and a gas-liquid separator 36. The indoor unit 12 has an indoor heat exchanger 41 and an indoor blower fan 42. The first compressor 23A and the second compressor 23B are collectively referred to as compressor 23, and the first expansion valve 31A, the second expansion valve 31B, and the third expansion valve 31C are collectively referred to as expansion valve 31.

[0018] The refrigerant pipe 13 is a pipe made of a metal such as copper or aluminum, and includes a first pipe 51, a second pipe 52, a third pipe 53, and a fourth pipe 54.

[0019] The first piping 51 connects the indoor heat exchanger 41 and the outdoor heat exchanger 21. The first compressor 23A, the second compressor 23B, the third expansion valve 31C, the accumulators 24A and 24B, the four-way valve 25, the switching valves 33A to 33C, the on-off valve 34A, and the check valve 44 are provided in the first piping 51.

[0020] The second pipe 52 connects the outdoor heat exchanger 21 and the indoor heat exchanger 41. The first expansion valve 31A, the second expansion valve 31B, and the gas-liquid separator 36 are provided on the second pipe 52.

[0021] The third pipe 53 connects the first pipe 51 and the gas-liquid separator 36 in the second pipe 52. The third pipe 53 is provided with a third expansion valve 31C and a switching valve 33C.

[0022] The fourth pipe 54 connects the first pipe 51 and the second pipe 52. The on-off valve 34B is provided on the fourth pipe 54.

[0023] In cooling operation, the refrigerant flows from the indoor heat exchanger 41 to the outdoor heat exchanger 21 through the first pipe 51, and flows from the outdoor heat exchanger 21 to the indoor heat exchanger 41 through the second pipe 52. At this time, the gaseous refrigerant in the second pipe 52 flows from the second pipe 52 through the gas-liquid separator 36 to the third pipe 53 and returns to the first pipe 51 without passing through the indoor heat exchanger 41. The arrows in Fig. 1 indicate the flow of the refrigerant during cooling operation.

[0024] Fig. 2 is a refrigerant system diagram that schematically shows the air conditioner 10 of this embodiment during heating operation. As shown in Fig. 2, during heating operation, the refrigerant flows from the outdoor heat exchanger 21 to the indoor heat exchanger 41 through the first pipe 51, and then flows from the indoor heat exchanger 41 to the outdoor heat exchanger 21 through the second pipe 52. At this time, the gaseous refrigerant in the second pipe 52 flows from the second pipe 52 through the gas-liquid separator 36 to the third pipe 53 and returns to the first pipe 51 without passing through the outdoor heat exchanger 21. The solid arrows in Fig. 2 indicate the refrigerant flow during heating operation.

[0025] The outdoor heat exchanger 21 of the outdoor unit 11 acts as an evaporator to absorb heat from the refrigerant or as a condenser to release heat from the refrigerant depending on the direction of refrigerant flow. The outdoor blower fan 22 blows air toward the outdoor heat exchanger 21 to promote heat exchange between the refrigerant and air in the outdoor heat exchanger 21. In other words, the outdoor blower fan 22 generates an airflow that exchanges heat with the outdoor heat exchanger 21.

[0026] The first compressor 23A and the second compressor 23B have suction ports 23Aa and 23Ba and discharge ports 23Ab and 23Bb, respectively. The first compressor 23A and the second compressor 23B draw in refrigerant through the suction ports 23Aa and 23Ba and discharge the compressed refrigerant from the discharge ports 23Ab and 23Bb. In this way, the first compressor 23A and the second compressor 23B compress the refrigerant in the refrigeration cycle and cause the refrigerant to circulate.

[0027] The accumulators 24A and 24B are connected to the suction ports 23Aa and 23Ba of the first compressor 23A and the second compressor 23B, respectively. The accumulators 24A and 24B separate the gaseous refrigerant from the liquid refrigerant. This allows the first compressor 23A and the second compressor 23B to draw the gaseous refrigerant that has passed through the accumulators 24A and 24B from the suction ports 23Aa and 23Ba. The accumulators 24A and 24B are integrally configured with the first compressor 23A and the second compressor 23B, and can serve as the suction ports of the first compressor 23A and the second compressor 23B.

[0028] The four-way valve 25 is connected to the outdoor heat exchanger 21, the indoor heat exchanger 41, the discharge ports 23Ab and 23Bb of the first compressor 23A and the second compressor 23B, and the accumulators 24A and 24B (the suction ports 23Aa and 23Ba of the first compressor 23A and the second compressor 23B). The four-way valve 25 switches the flow paths connected to the outdoor heat exchanger 21, the indoor heat exchanger 41, the discharge ports 23Ab and 23Bb of the first compressor 23A and the second compressor 23B, and the accumulators 24A and 24B between heating operation and cooling operation, thereby changing the direction in which the refrigerant flows.

[0029] 1, during cooling operation, the four-way valve 25 connects the outdoor heat exchanger 21 to the discharge ports 23Ab and 23Bb of the first compressor 23A and the second compressor 23B. Furthermore, during cooling operation, the four-way valve 25 connects the indoor heat exchanger 41 to the accumulators 24A and 24B. As a result, the refrigerant compressed by the first compressor 23A and the second compressor 23B flows to the outdoor heat exchanger 21, and the refrigerant evaporated in the indoor heat exchanger 41 flows to the accumulators 24A and 24B.

[0030] 2, during heating operation, the four-way valve 25 connects the outdoor heat exchanger 21 to the accumulators 24A and 24B. Furthermore, during heating operation, the four-way valve 25 connects the indoor heat exchanger 41 to the discharge ports 23Ab and 23Bb of the first compressor 23A and the second compressor 23B. As a result, the refrigerant compressed by the first compressor 23A and the second compressor 23B flows to the indoor heat exchanger 41, and the refrigerant evaporated in the outdoor heat exchanger 21 flows to the accumulators 24A and 24B.

[0031] The first expansion valve 31A, the second expansion valve 31B, and the third expansion valve 31C are, for example, electromagnetic expansion valves. However, the first expansion valve 31A, the second expansion valve 31B, and the third expansion valve 31C may be other expansion valves. The opening degrees of the first expansion valve 31A, the second expansion valve 31B, and the third expansion valve 31C are controlled to adjust the amount of refrigerant passing through.

[0032] The indoor heat exchanger 41 of the indoor unit 12 absorbs heat as an evaporator or releases heat as a condenser depending on the direction of refrigerant flow. The indoor blower fan 42 blows air toward the indoor heat exchanger 41 to promote heat exchange between the indoor heat exchanger 41 and the air. In other words, the indoor blower fan 42 generates an airflow that exchanges heat with the indoor heat exchanger 41.

[0033] In the air conditioner 10 in which the elements are arranged as described above, the first pipe 51 has a region 51a, a region 51b, a region 51c, a region 51d, a region 51e, a region 51f, and a region 51g.

[0034] The region 51 a is a part of the first pipe 51 between the indoor heat exchanger 41 and the four-way valve 25 .

[0035] Region 51b is a portion of first pipe 51 between four-way valve 25 and accumulators 24A, 24B. Region 51b includes regions 51ba-51bd, branch point 51be, and connection point 51bf. Region 51ba is a portion of region 51b between four-way valve 25 and branch point 51be. Region 51bb is a portion of region 51b between branch point 51be and accumulator 24B. Region 51bc is a portion of region 51b between branch point 51be and connection point 51bf. An on-off valve 34A is provided in region 51bc. The on-off valve 34A opens and closes (opens and closes) region 51bc. Region 51bd is a portion of region 51b between connection point 51bf and accumulator 24B.

[0036] The region 51c is a part of the first pipe 51 between the discharge port 23Ab of the first compressor 23A and the four-way valve 25.

[0037] The region 51d is a part of the first pipe 51 between the four-way valve 25 and the outdoor heat exchanger 21.

[0038] The region 51e is a portion of the first piping between the discharge port 23Bb of the second compressor 23B and the connection point 51bf. The region 51e is provided with the switching valve 33A, the check valve 35, and the switching valve 33B. The check valve 35 is provided downstream of the switching valve 33A, and the switching valve 33B is provided downstream of the check valve 35. The region 51e includes a region 51ea, a region 51eb, and a region 51ec. The region 51ea is a portion of the region 51e between the discharge port 23Bb of the second compressor 23B and the switching valve 33A. The region 51eb is a portion of the region 51e between the switching valve 33A and the switching valve 33B. The check valve 35 is provided in the region 51eb. The region 51eb is also provided with the connection point 51ed. The connection point 51ed is provided between the check valve 35 and the switching valve 33B. The region 51ec is a part of the region 51e between the switching valve 33B and the connection point 51bf.

[0039] The region 51f connects the switching valve 33A and the connection point 51ed.

[0040] The region 51g connects the switching valve 33B and the region 51c without passing through the first compressor 23A.

[0041] Region 51eb and region 51bd constitute region 51h connecting first compressor 23A and second compressor 23B. Region 51h is an example of a first portion. Region 51c and region 51d constitute region 51i connecting first compressor 23A and outdoor heat exchanger 21. Region 51i is an example of a second portion. Region 51a and region 51c constitute region 51j connecting first compressor 23A and indoor heat exchanger 41. Region 51j is an example of a third portion.

[0042] The second piping 52 has regions 52a, 52b, 52c, and 52d. The region 52a is a portion of the second piping 52 between the outdoor heat exchanger 21 and the first expansion valve 31A. The region 52b is a portion of the second piping 52 between the first expansion valve 31A and the gas-liquid separator 36. The region 52c is a portion of the second piping 52 between the gas-liquid separator 36 and the second expansion valve 31B. The region 52d is a portion of the second piping 52 between the second expansion valve 31B and the indoor heat exchanger 41.

[0043] The third piping 53 has regions 53a, 53b, and 53c. Region 53a is a portion of the third piping 53 between the gas-liquid separator 36 and the switching valve 33C. The third expansion valve 31C is provided in region 53a. Region 53b is a portion of the third piping 53 between the switching valve 33C and region 51e of the first piping 51. Region 53c is a portion of the third piping 53 between the switching valve 33C and region 51bc of the first piping 51.

[0044] The fourth pipe 54 connects the region 51a of the first pipe 51 and the region 52a of the second pipe 54. An on-off valve 34B is provided in the fourth pipe 54. The on-off valve 34B opens and closes (opens and closes) the fourth pipe 54.

[0045] The switching valves 33A to 33C are, for example, three-way valves. The switching valve 33A switches the flow paths connected to the regions 51ea, 51eb, and 51f of the first pipe 51, thereby changing the direction of refrigerant flow. That is, the switching valve 33A can selectively connect the region 51ea to the region 51eb and the region 51ea to the region 51f. The switching valve 33B switches the flow paths connected to the regions 51eb, 51ec, and 51g of the first pipe 51, thereby changing the direction of refrigerant flow. That is, the switching valve 33B can selectively connect the region 51eb to the region 51ec and the region 51eb to the region 51g. The switching valve 33C switches the flow paths connected to the regions 53a, 53b, and 53c of the third pipe 53, thereby changing the direction of refrigerant flow. That is, the switching valve 33C can selectively connect the region 53a to the region 53b and the region 53a to the region 53c.

[0046] The gas-liquid separator 36 separates the refrigerant into gaseous and liquid states. The refrigerant flowing into the gas-liquid separator 36 from the region 52b of the second pipe 52 is separated into the gaseous and liquid states by the gas-liquid separator 36, and the gaseous refrigerant flows into the third pipe 53, and the liquid refrigerant flows into the region 52c of the second pipe 52. The refrigerant flowing into the gas-liquid separator 36 from the region 52c of the second pipe 52 is separated into the gaseous and liquid states by the gas-liquid separator 36, and the gaseous refrigerant flows into the third pipe 53, and the liquid refrigerant flows into the region 52b of the second pipe 52.

[0047] The outdoor unit 11 of this embodiment further includes a first heat exchanger 38A, a second heat exchanger 38B, a heat storage material 61, temperature sensors 71A to 71O, pressure sensors 72A and 72B, and a human presence sensor 73.

[0048] The first heat exchanger 38A and the second heat exchanger 38B are, for example, heat storage materials. The heat storage material has a latent heat storage material filled in a block-shaped container. The latent heat storage material is, for example, calcium chloride. The first heat exchanger 38A and the second heat exchanger 38B may have other latent heat storage materials. The first heat exchanger 38A and the second heat exchanger 38B in this embodiment are, for example, heat storage materials that can be used in a temperature range of approximately 10°C to approximately 100°C.

[0049] The first heat exchanger 38A and the second heat exchanger 38B are not limited to the above examples, and may be, for example, other heat storage materials such as sensible heat storage materials, or heat storage materials usable in other temperature ranges. Furthermore, the first heat exchanger 38A and the second heat exchanger 38B may be different heat storage materials.

[0050] The first heat exchanger 38A is thermally connected to each of the region 51eb and the region 51d of the first pipe 51. For example, the region 51eb and the region 51d of the first pipe 51 are spaced apart from each other and pass through the first heat exchanger 38A.

[0051] The first heat exchanger 38A having this configuration exchanges heat between the region 51eb of the first pipe 51 and the region 51d of the first pipe 51. That is, in the first heat exchanger 38A, heat exchange occurs between the refrigerant in the region 51eb of the first pipe 51 and the refrigerant in the region 51d of the first pipe 51.

[0052] The first heat exchanger 38A has a larger amount of heat that can be stored (heat storage capacity) than the region 51eb of the first pipe 51 and the region 51d of the first pipe 51. Furthermore, the region 51eb and the region 51d are made of metal and are in close contact with the latent heat storage material of the first heat exchanger 38A. Therefore, heat conduction is likely to occur between the region 51eb and the region 51d and the latent heat storage material of the first heat exchanger 38A.

[0053] The second heat exchanger 38B is thermally connected to the region 51a and the region 51d of the first pipe 51. For example, the region 51a and the region 51d of the first pipe 51 are spaced apart from each other and pass through the second heat exchanger 38B.

[0054] The second heat exchanger 38B configured as described above exchanges heat between the region 51a of the first pipe 51 and the region 51d of the first pipe 51. That is, in the second heat exchanger 38B, heat is exchanged between the refrigerant in the region 51a of the first pipe 51 and the refrigerant in the region 51d of the first pipe 51.

[0055] The second heat exchanger 38B has a larger amount of heat that can be stored (heat storage capacity) than the region 51a of the first pipe 51 and the region 51d of the first pipe 51. Furthermore, the region 51a and the region 51d are made of metal and are in close contact with the latent heat storage material of the second heat exchanger 38B. For this reason, heat conduction is likely to occur between the region 51a and the region 51d and the latent heat storage material of the second heat exchanger 38B.

[0056] The heat storage material 61 includes, for example, a latent heat storage material filled in a block-shaped container. The latent heat storage material is, for example, calcium chloride. The heat storage material 61 may include other latent heat storage materials. The heat storage material 61 in this embodiment is, for example, a heat storage material that can be used in a temperature range of approximately 10°C to approximately 100°C.

[0057] The heat storage material 61 is not limited to the above example, and may be, for example, another heat storage material such as a sensible heat storage material, or a heat storage material that can be used in other temperature ranges.

[0058] The heat storage material 61 is thermally connected to the region 51 a of the first pipe 51 between the indoor heat exchanger 41 and the four-way valve 25 .

[0059] The heat storage material 61 has a larger amount of heat that can be stored (heat storage capacity) than the region 51a. Furthermore, the region 51a is made of metal and is in close contact with the latent heat storage material of the heat storage material 61. Therefore, heat conduction is likely to occur between the region 51a and the latent heat storage material of the heat storage material 61.

[0060] The temperature sensor 71A is disposed, for example, in the housing of the outdoor unit 11. Specifically, the temperature sensor 71A can be disposed in the central portion of the outdoor heat exchanger 21. For convenience, the temperature sensor 71A is shown in FIG. 1 and other figures as being located at a position separated from the outdoor heat exchanger 21. The temperature sensor 71A detects the outside air temperature of the outdoor environment in which the outdoor unit 11 is disposed.

[0061] The temperature sensor 71B is provided in the outdoor heat exchanger 21. The temperature sensor 71B detects the temperature of the refrigerant flowing through the outdoor heat exchanger 21. For example, the temperature sensor 71B is disposed at a position where the saturation temperature of the refrigerant flowing through the outdoor heat exchanger 21 can be obtained.

[0062] The temperature sensor 71C is provided on the second pipe 52 side of the outdoor heat exchanger 21. The temperature sensor 71C detects the temperature of the refrigerant flowing through the second pipe 52 in the vicinity of the outdoor heat exchanger 21.

[0063] The temperature sensor 71D is provided in the indoor heat exchanger 41. The temperature sensor 71D detects the temperature of the refrigerant flowing through the indoor heat exchanger 41. For example, the temperature sensor 71D is disposed at a position where the saturation temperature of the refrigerant flowing through the indoor heat exchanger 41 can be obtained.

[0064] The temperature sensor 71E is provided on the first pipe 51 side of the indoor heat exchanger 41. The temperature sensor 71D detects the temperature of the refrigerant flowing through the first pipe 51 in the vicinity of the indoor heat exchanger 41.

[0065] The temperature sensor 71O detects the temperature of the indoor air drawn into the indoor unit 12.

[0066] The temperature sensor 71F is provided in the region 51bd of the first pipe 51, near the suction port 23Aa of the first compressor 23A. The temperature sensor 71F detects the temperature of the refrigerant flowing through the region 51bd, near the suction port 23Aa of the first compressor 23A.

[0067] The temperature sensor 71G is provided in the region 51bb of the first pipe 51, near the suction port 23Ba of the second compressor 23B. The temperature sensor 71G detects the temperature of the refrigerant flowing through the region 51bb, near the suction port 23Ba of the second compressor 23B.

[0068] The temperature sensor 71H is provided in the region 51ea of ​​the first pipe 51, near the discharge port 23Bb of the second compressor 23B. The temperature sensor 71H detects the temperature of the refrigerant flowing in the region 51ea, near the discharge port 23Bb of the second compressor 23B.

[0069] The temperature sensor 71I is provided in the region 52a of the second pipe 52 near the first expansion valve 31A. The temperature sensor 71I detects the temperature of the refrigerant flowing through the region 52a of the second pipe 52 near the first expansion valve 31A.

[0070] The temperature sensor 71J is provided in the region 52d of the second pipe 52 near the second expansion valve 31B. The temperature sensor 71J detects the temperature of the refrigerant flowing through the region 52d of the second pipe 52 near the second expansion valve 31B.

[0071] The temperature sensor 71K is provided in the first heat exchanger 38A and detects the temperature of the first heat exchanger 38A.

[0072] The temperature sensor 71L is provided in the second heat exchanger 38B and detects the temperature of the second heat exchanger 38B.

[0073] The temperature sensor 71M is provided in the heat storage material 61. The temperature sensor 71M detects the temperature of the heat storage material 61.

[0074] The temperature sensor 71N is provided near the first heat exchanger 38A in a region 51eb of the first pipe 51 downstream of the first heat exchanger 38A. The temperature sensor 71N detects the temperature of the refrigerant flowing through the region 51eb downstream of the first heat exchanger 38A and near the first heat exchanger 38A.

[0075] The pressure sensor 72A is provided in the region 51bb of the first pipe 51. The pressure sensor 72A detects the pressure of the refrigerant flowing through the region 51bb. The pressure sensor 72B is provided in the region 51c of the first pipe 51. The pressure sensor 72B detects the pressure of the refrigerant flowing through the region 51c. The pressure sensors 72A and 72B can be used, for example, to control the degree of superheat of the second compressor 23B. The control of the degree of superheat of the second compressor 23B can be performed, for example, by controlling the expansion valve 31.

[0076] The human presence sensor 73 is provided in the indoor unit 12. The human presence sensor 73 detects a human (animal) in the room where the indoor unit 12 is installed.

[0077] As shown in FIG. 1, 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 via electrical wiring. At least one of the outdoor control device 14a and the indoor control device 14b is a computer including, for example, a control device such as a CPU (Central Processing Unit) or a microcontroller, and a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory. 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.

[0078] The outdoor control device 14a controls the outdoor blower fan 22, compressor 23, four-way valve 25, expansion valve 31, switching valves 33A to 33C, and on-off valves 34A, 34B of the outdoor unit 11. The indoor control device 14b controls the indoor blower fan 42 of the indoor unit 12, etc.

[0079] The control device 14 controls the outdoor unit 11 and the indoor unit 12, causing the air conditioner 10 to perform cooling operation, heating operation, defrosting operation, cold storage operation, heat storage operation, and other operations. The indoor control device 14b may receive signals from, for example, a remote controller, or may receive signals from an information terminal such as a smartphone via a communication device.

[0080] Fig. 3 is a block diagram functionally illustrating the configuration of the air conditioner 10 of this embodiment. As shown in Fig. 3, the air conditioner 10 of this embodiment further includes an outdoor fan drive circuit 81, an indoor fan drive circuit 82, an inverter circuit 83, a four-way valve drive circuit 84, an expansion valve drive circuit 85, a switching valve drive circuit 87, and an on-off valve drive circuit 88.

[0081] The outdoor fan drive circuit 81 is a drive circuit for the outdoor blower fan 22. The indoor fan drive circuit 82 is a drive circuit for the indoor blower fan 42. The inverter circuit 83 inverter-controls each compressor 23 to change the operating frequency of each compressor 23. The inverter circuit 83 is, for example, a PAM (Pulse Amplitude Modulation) type inverter circuit. However, the inverter circuit 83 is not limited to this example.

[0082] The four-way valve drive circuit 84 is a drive circuit for the four-way valve 25. The expansion valve drive circuit 85 is a drive circuit for the expansion valve 31. The switching valve drive circuit 87 is a drive circuit for the switching valves 33A to 33C. The on-off valve drive circuit 88 is a drive circuit for the on-off valves 34A and 34B.

[0083] The control device 14 is connected to the temperature sensors 71A to 71O, the pressure sensors 72A and 72B, the human presence sensor 73, the outdoor fan drive circuit 81, the indoor fan drive circuit 82, the inverter circuit 83, the four-way valve drive circuit 84, the expansion valve drive circuit 85, the switching valve drive circuit 87, and the on-off valve drive circuit 88. The control device 14 includes a temperature acquisition unit 91, an operation switching unit 92, an outdoor fan control unit 93, an indoor fan control unit 94, a compressor control unit 95, and a valve control unit 96.

[0084] The temperature acquisition unit 91 uses the temperature sensors 71A to 71O to acquire the outside air temperature, the temperature of the refrigerant, the temperature of the first heat exchanger 38A, the temperature of the second heat exchanger 38B, and the temperature of the heat storage material 61. For example, the temperature acquisition unit 91 calculates the outside air temperature, the temperature of the refrigerant, the temperature of the first heat exchanger 38A, the temperature of the second heat exchanger 38B, and the temperature of the heat storage material 61 from the output signals of the temperature sensors 71A to 71O.

[0085] The operation switching unit 92 switches between cooling operation, heating operation, defrosting operation, cold storage operation, and heat storage operation in the air conditioner 10. Note that the operation switching unit 92 may also switch the operation of the air conditioner 10 to another operation mode.

[0086] The outdoor fan control unit 93 controls the outdoor blower fan 22. For example, the outdoor fan control unit 93 controls the outdoor fan drive circuit 81 to control the rotation speed of the motor of the outdoor blower fan 22.

[0087] The indoor fan control unit 94 controls the indoor blower fan 42. For example, the indoor fan control unit 94 controls the indoor fan drive circuit 82 to control the rotation speed of the motor of the indoor blower fan 42.

[0088] The compressor control unit 95 controls the compressor 23. For example, the compressor control unit 95 controls the inverter circuit 83 to control the operating frequency of the compressor 23 through inverter control.

[0089] The valve control unit 96 controls the four-way valve 25, the expansion valve 31, the switching valves 33A to 33C, and the on-off valves 34A and 34B. The valve control unit 96 controls the four-way valve drive circuit 84 to drive the actuator of the four-way valve 25 and cause the four-way valve 25 to change the direction of refrigerant flow. The valve control unit 96 controls the expansion valve drive circuit 85 to change the opening degree of the expansion valve 31. The valve control unit 96 controls the switching valve drive circuit 87 to cause the switching valves 33A to 33C to change the direction of refrigerant flow. The valve control unit 96 controls the on-off valve drive circuit 88 to control the opening and closing (open valve state, closed valve state) of the on-off valves 34A and 34B.

[0090] The cooling operation, cold storage operation, heating operation, heat storage operation, and defrosting operation of the air conditioner 10 of this embodiment will be described below. As described above, the air conditioner 10 is not limited to the cooling operation, cold storage operation, heating operation, heat storage operation, and defrosting operation, and can perform other operations. Furthermore, the cooling operation, cold storage operation, heating operation, heat storage operation, and defrosting operation of the air conditioner 10 are not limited to the examples described below.

[0091] 4 is a flowchart showing an example of cooling operation control of the air conditioner 10 of this embodiment. Note that, for example, when the air conditioner 10 starts up and the cooling operation begins simultaneously, the outdoor blower fan 22, the first compressor 23A, the second compressor 23B, and the indoor blower fan 42 are stopped. In this case, the outdoor fan control unit 93, the indoor fan control unit 94, and the compressor control unit 95 start the outdoor blower fan 22, the first compressor 23A, the second compressor 23B, and the indoor blower fan 42 at the start of the cooling operation.

[0092] During cooling operation, the outdoor fan control unit 93 adjusts the rotation speed of the outdoor blower fan 22. The indoor fan control unit 94 adjusts the rotation speed of the indoor blower fan 42. The compressor control unit 95 adjusts the operating frequencies of the first compressor 23A and the second compressor 23B. For example, the indoor fan control unit 94 controls the indoor blower fan 42 between weak wind (low speed) operation and strong wind (high speed) operation in accordance with the air temperature in the room where the indoor unit 12 is installed or a signal input from a remote controller.

[0093] 4, when the cooling operation is started, the valve control unit 96 controls the four-way valve drive circuit 84 and the switching valve drive circuit 87 to change the direction of refrigerant flow through the four-way valve 25 and the switching valves 33A to 33C (S101). At this time, the valve control unit 96 also opens the on-off valve 34A and closes the on-off valve 34B. This connects the outdoor heat exchanger 21 to the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B, and also connects the indoor heat exchanger 41 to the accumulators 24A, 24B (the suction ports 23Aa, 23Ba of the first compressor 23A and the second compressor 23B). That is, the control device 14 performs a cooling operation by controlling the four-way valve 25 so that the refrigerant flows from the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B to the outdoor heat exchanger 21. Furthermore, the four-way valve 25 is connected to the suction ports 23Aa, 23Ba of the first compressor 23A and the second compressor 23B. The discharge port 23Bb of the second compressor 23B is connected to the four-way valve 25 via the switching valves 33A, 33B, not via the first heat exchanger 38A. Furthermore, the gas-liquid separator 36 is connected to the suction port 23Aa of the first compressor 23A via the regions 53a, 53b of the third pipe 53 and the regions 51bc, 51bd of the first pipe 51.

[0094] Next, the operation switching unit 92 determines whether or not to end the cooling operation (S102). For example, if the air conditioner 10 receives a stop signal or a switch signal to another operation from the remote controller, the operation switching unit 92 determines that the cooling operation should be ended (S102: Yes), and ends the cooling operation.

[0095] If the cooling operation does not end (S102: No), the valve control unit 96 determines whether the difference (degree of superheat) between the temperature C3 and the temperature C1 is 5°C (S103). For example, the temperature acquisition unit 91 acquires the temperature of the refrigerant in the region 52d of the second pipe 52 near the second expansion valve 31B from the temperature sensor 71J. In other words, the temperature acquisition unit 91 acquires the temperature C1 of the refrigerant exiting the second expansion valve 31B from the temperature sensor 71J. Furthermore, the temperature acquisition unit 91 acquires the temperature C1 of the refrigerant in the indoor heat exchanger 41 from the temperature sensor 71D.

[0096] The valve control unit 96 determines whether the degree of subcooling (C3-C1) is 5° C. For example, the valve control unit 96 determines whether the degree of subcooling (C3-C1) is 5° C. over a predetermined time period. Note that the determination in S103 is not limited to this example.

[0097] If the degree of subcooling (C3-C1) is not 5°C (S103: No), the valve control unit 96 controls the expansion valve drive circuit 85 to adjust the opening of the first expansion valve 31A (S104). The valve control unit 96 adjusts the opening of the first expansion valve 31A so that the degree of subcooling (C3-C1) is 5°C. As a result, the refrigerant is brought to a medium pressure by the first expansion valve 31A, and the quality fraction is, for example, 20%. The quality fraction is the proportion of gas in the refrigerant. If the degree of subcooling (C3-C1) is 5°C in S103 (S103: Yes), S104 is omitted.

[0098] Next, the valve control unit 96 determines whether the superheat degree SH is approximately 2°C (S105). The superheat degree SH is either superheat degree SH1 or superheat degree SH2. The valve control unit 96 adopts the lower of superheat degree SH1 and superheat degree SH2 as the superheat degree SH. The superheat degree SH1 is the difference between temperature Su1 and temperature Th5. Temperature Su1 is the temperature detected by temperature sensor 71F. That is, temperature Su1 is the temperature of the refrigerant flowing through region 51bd near suction port 23Aa of first compressor 23A. Temperature Th5 is the temperature detected by temperature sensor 71H. That is, temperature Th5 is the temperature of the refrigerant flowing through region 51ea near discharge port 23Bb of second compressor 23B. Superheat degree SH2 is the difference between temperature Su2 and saturation temperature LP1. Temperature Su2 is the temperature detected by temperature sensor 71G. That is, the temperature Su2 is the temperature of the refrigerant flowing through the region 51bd in the vicinity of the suction port 23Ba of the second compressor 23B. The saturation temperature LP1 is the temperature of the refrigerant converted from the pressure detected by the pressure sensor 72A.

[0099] The valve control unit 96 determines whether the degree of superheat SH is approximately 2° C. For example, the valve control unit 96 determines whether the degree of superheat SH remains approximately 2° C. for a predetermined period of time. Note that the determination in S105 is not limited to this example.

[0100] If the degree of superheat SH is not approximately 2°C (S105: No), the valve control unit 96 controls the expansion valve drive circuit 85 to adjust the opening of the second expansion valve 31B (S106). The valve control unit 96 adjusts the opening of the second expansion valve 31B so that the degree of superheat SH is approximately 2°C. If the degree of superheat SH is approximately 2°C in S105 (S105: Yes), S106 is omitted.

[0101] If the valve control unit 96 adjusts the second expansion valve 31B or the degree of superheat SH is approximately 2°C, the process returns to S102, and the operation switching unit 92 determines again whether or not to end the cooling operation. S102 to S106 are repeated until the cooling operation ends. The above process prevents liquid from flowing back into the first compressor 23A and the second compressor 23B.

[0102] In the above process, for example, the control device 14 operates the first compressor 23A and the second compressor 23B as follows: When the difference between the temperature of the intake air of the indoor unit 12 and the set temperature is 3°C or more, the first compressor 23A becomes the master unit, and the control device 14 operates the first compressor 23A at the maximum frequency. If the set temperature is not reached even after this operation, the control device 14 increases the frequency of the second compressor 23B. When the difference between the temperature of the intake air of the indoor unit 12 and the set temperature is 1°C or more, the control device 14 operates the first compressor 23A at half the maximum frequency. If the set temperature is not reached even after this operation, the control device 14 increases the frequency of the second compressor 23B. When the difference between the temperature of the intake air of the indoor unit 12 and the set temperature is less than 1°C, the control device 14 operates only one of the first compressor 23A and the second compressor 23B. In this case, the control device 14 switches between the operation of the first compressor 23A and the operation of the second compressor 23B at predetermined time intervals, thereby leveling out the operation time of the first compressor 23A and the operation time of the second compressor 23B.

[0103] 1, in cooling operation, high-temperature, high-pressure gaseous refrigerant discharged from discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B passes through the four-way valve 25 and dissipates heat in the outdoor heat exchanger 21. The medium-temperature, medium-pressure refrigerant condensed in the outdoor heat exchanger 21 is decompressed by the first expansion valve 31A.

[0104] The low-temperature, low-pressure refrigerant decompressed by the first expansion valve 31A is separated into gas and liquid by the gas-liquid separator 36. The liquid refrigerant flows to the indoor heat exchanger 41 and absorbs heat there. The gaseous refrigerant evaporated in the indoor heat exchanger 41 passes through the second heat exchanger 38B, the heat storage material 61, and the accumulators 24A and 24B, and returns to the suction ports 23Aa and 23Ba of the first compressor 23A and the second compressor 23B. At this time, the heat storage material 61 has been cooled by the cold storage operation described below. Therefore, since the refrigerant is cooled by the heat storage material 61, the enthalpy of the refrigerant is reduced, and the cooling capacity is improved.

[0105] 5 is a flowchart showing an example of cold storage operation control of the air conditioner 10 of this embodiment. The control device 14 of this embodiment performs cold storage operation, for example, at night when the air conditioner 10 is stopped. In other words, the control device 14 performs cold storage operation when the load on the air conditioner 10 is low. Note that the time when the cold storage operation is performed is not limited to this example.

[0106] First, the operation switching unit 92 determines whether the start condition for the cold-storage operation is met (S201). For example, if the operation switching unit 92 determines that the air conditioner 10 is stopped and the time is between 1:00 AM and 3:00 AM (nighttime), it determines that the start condition for the cold-storage operation is met.

[0107] The start condition for the cold-storage operation is not limited to the above example. For example, the operation switching unit 92 may determine the start condition for the cold-storage operation based on the outside air temperature. In this case, the temperature acquisition unit 91 acquires the outside air temperature from the temperature sensor 71A. The operation switching unit 92 determines that the start condition for the cold-storage operation is met when the air conditioner 10 is stopped and the outside air temperature is below the threshold for a predetermined time.

[0108] The operation switching unit 92 may also determine the start condition based on the presence of a person in the room. In this case, the operation switching unit 92 determines whether or not the room is unoccupied based on the output signal of the human presence sensor 73 provided in the indoor unit 12. If the operation switching unit 92 determines that the room has been unoccupied for a predetermined period of time, it determines that the start condition for the cool storage operation has been met.

[0109] Furthermore, the operation switching unit 92 may determine the start conditions for the cold storage operation based on the required capacity of the air conditioner 10. In this case, the operation switching unit 92 calculates the required capacity of the air conditioner 10 (the cooling capacity required of the air conditioner 10 to bring the room temperature to the target temperature) based on factors such as the difference between the room temperature and the target temperature set by the user. The operation switching unit 92 determines that the start conditions for the cold storage operation have been met when the required capacity of the air conditioner 10 is equal to or less than a predetermined threshold.

[0110] If the start condition for the cold-storage operation is not met (S201: No), the operation switching unit 92 waits without starting the cold-storage operation. If the start condition for the cold-storage operation is met (S201: Yes), the operation switching unit 92 starts the cold-storage operation (S202). Specifically, the outdoor fan control unit 93, the indoor fan control unit 94, and the compressor control unit 95 start and adjust the outdoor blower fan 22, the first compressor 23A, the second compressor 23B, and the indoor blower fan 42.

[0111] The valve control unit 96 controls the four-way valve 25 and the switching valves 33A-33C to change the direction of refrigerant flow, as in the cooling operation. This connects the outdoor heat exchanger 21 to the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B, and also connects the indoor heat exchanger 41 to the accumulators 24A, 24B (the suction ports 23Aa, 23Ba of the first compressor 23A and the second compressor 23B). That is, the control device 14 performs cold-storage operation by controlling the four-way valve 25 so that the refrigerant flows from the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B to the outdoor heat exchanger 21. Furthermore, the refrigerant passes through the heat storage material 61 and the accumulators 24A, 24B, and returns to the suction ports 23Aa, 23Ba of the first compressor 23A and the second compressor 23B.

[0112] The outdoor fan control unit 93 and the compressor control unit 95 control the outdoor blower fan 22, the first compressor 23A, and the second compressor 23B in the same manner as in the cooling operation. Note that the control of the outdoor fan control unit 93 and the compressor control unit 95 in the cold-storage operation may be different from the control in the cooling operation.

[0113] Meanwhile, the indoor fan control unit 94 controls the indoor blower fan 42 to operate at a gentle breeze (low speed). That is, the indoor fan control unit 94 rotates the indoor blower fan 42 at the minimum speed during cooling operation. Note that the control by the indoor fan control unit 94 is not limited to this example. For example, the indoor fan control unit 94 may stop the indoor blower fan 42.

[0114] Next, the operation switching unit 92 determines whether or not to terminate the cold-storage operation (S203). For example, if the air conditioner 10 receives a stop signal or a signal to switch to another operation from the remote controller, the operation switching unit 92 determines that the cold-storage operation should be terminated (S203: Yes) and terminates the cold-storage operation. The operation switching unit 92 also determines that the cold-storage operation should be terminated when a predetermined time has elapsed since the start of the cold-storage operation (S203: Yes) and terminates the cold-storage operation. If the above signal has not been input or the predetermined time has not elapsed, the operation switching unit 92 determines that the cold-storage operation should not be terminated (S203: No) and continues the cold-storage operation.

[0115] In the cold storage operation, the high-temperature, high-pressure gaseous refrigerant discharged from the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B passes through the four-way valve 25 and dissipates heat in the outdoor heat exchanger 21. The medium-temperature, medium-pressure liquid refrigerant condensed in the outdoor heat exchanger 21 is decompressed by the first expansion valve 31A. The low-temperature, low-pressure liquid refrigerant decompressed by the first expansion valve 31A flows from the first expansion valve 31A to the indoor heat exchanger 41 via the second expansion valve 31B.

[0116] In the cold-storage operation, the valve control unit 96 controls the first expansion valve 31A so that the refrigerant discharged from the indoor heat exchanger 41 contains more liquid than gas. Furthermore, in the cold-storage operation, the indoor fan control unit 94 controls the indoor blower fan 42 so that the refrigerant discharged from the indoor heat exchanger 41 contains more liquid than gas.

[0117] The low-temperature, low-pressure liquid refrigerant coming out of the indoor heat exchanger 41 exchanges heat with the heat storage material 61, cooling the heat storage material 61.

[0118] As described above, the cold storage operation is performed for one hour. For example, even in summer, the outside temperature at night is lower than the outside temperature during the day. Therefore, the heat storage material 61 is sufficiently cooled during the night when the cold storage operation is performed.

[0119] 6 is a flowchart showing an example of heating operation control of the air conditioner 10 of this embodiment. Note that, for example, when the air conditioner 10 starts up and the heating operation begins simultaneously, the outdoor blower fan 22, the first compressor 23A, the second compressor 23B, and the indoor blower fan 42 are stopped. In this case, the outdoor fan control unit 93, the indoor fan control unit 94, and the compressor control unit 95 start the outdoor blower fan 22, the first compressor 23A, the second compressor 23B, and the indoor blower fan 42 when the heating operation begins.

[0120] As shown in FIG. 6, when the heating operation is started, the valve control unit 96 controls the four-way valve drive circuit 84 and the switching valve drive circuit 87 to change the refrigerant flow direction through the four-way valve 25 and the switching valves 33A to 33C (S301). At this time, the valve control unit 96 closes the on-off valves 34A and 34B. This connects the indoor heat exchanger 41 to the discharge ports 23Ab and 23Bb of the first compressor 23A and the second compressor 23B, and also connects the outdoor heat exchanger 21 to the accumulators 24A and 24B (the suction ports 23Aa and 23Ba of the first compressor 23A and the second compressor 23B). That is, the control device 14 performs the heating operation by controlling the four-way valve 25 so that the refrigerant flows from the discharge ports 23Ab and 23Bb of the first compressor 23A and the second compressor 23B to the indoor heat exchanger 41 through the heat storage material 61. Furthermore, the switching valves 33A and 33B are controlled so that the refrigerant discharged from the discharge port 23Bb of the second compressor 23B flows through the first heat exchanger 38A to the suction port 23Aa of the first compressor 23A. Also, the switching valve 33C is controlled so that the refrigerant passing through the third pipe 53 flows to the first heat exchanger 38A via the region 51ea of ​​the first pipe 51. Also, the four-way valve 25 is connected to the suction ports 23Aa and 23Ba of the first compressor 23A and the second compressor 23B via the region 51b of the first pipe 51.

[0121] Next, the operation switching unit 92 determines whether or not to end the heating operation (S302). For example, if the air conditioner 10 receives a stop signal or a switch signal to another operation from the remote controller, the operation switching unit 92 determines that the heating operation should be ended (S302: Yes), and ends the heating operation.

[0122] If the heating operation does not end (S302: No), the valve control unit 96 determines whether the difference (degree of superheat) between the temperature C3 and the temperature C1 is 5°C (S303). For example, the temperature acquisition unit 91 acquires the temperature of the refrigerant in the region 52d of the second pipe 52 near the second expansion valve 31B from the temperature sensor 71J. In other words, the temperature acquisition unit 91 acquires the temperature C1 of the refrigerant exiting the second expansion valve 31B from the temperature sensor 71J. Furthermore, the temperature acquisition unit 91 acquires the temperature C1 of the refrigerant in the indoor heat exchanger 41 from the temperature sensor 71D.

[0123] The valve control unit 96 determines whether the degree of supercooling (C3-C1) is 5° C. For example, the valve control unit 96 determines whether the degree of supercooling (C3-C1) is 5° C. over a predetermined time period. Note that the determination in S303 is not limited to this example.

[0124] If the degree of subcooling (C3-C1) is not 5°C (S303: No), the valve control unit 96 controls the expansion valve drive circuit 85 to adjust the opening of the second expansion valve 31B (S304). The valve control unit 96 adjusts the opening of the second expansion valve 31B so that the degree of subcooling (C3-C1) is 5°C. As a result, the refrigerant is brought to a medium pressure by the second expansion valve 31B, and the quality fraction becomes, for example, 20%. If the degree of subcooling (C3-C1) is 5°C in S303 (S303: Yes), S304 is omitted.

[0125] If the valve control unit 96 adjusts the second expansion valve 31B or the degree of subcooling (C3-C1) is 5°C, the process returns to S302, and the operation switching unit 92 determines again whether or not to end the heating operation. S302 to S304 are repeated until the heating operation ends.

[0126] In the above process, for example, the control device 14 operates the first compressor 23A and the second compressor 23B as follows: When the outside air temperature falls to 0°C or below, the control device 14 increases the pressure of the refrigerant from low pressure to medium pressure using the second compressor 23B, and increases the pressure of the refrigerant from medium pressure to high pressure using the first compressor 23A.

[0127] As shown in FIG. 2, during heating operation, the gaseous refrigerant evaporated in the outdoor heat exchanger 21 absorbs heat in the first heat exchanger 38A and the second heat exchanger 38B. The refrigerant discharged from the discharge port 23Bb of the second compressor 23B releases heat in the first heat exchanger 38A and enters the first compressor 23A. That is, the refrigerant discharged from the discharge port 23Bb of the second compressor 23B is cooled in the first heat exchanger 38A and enters the first compressor 23A. The refrigerant discharged from the discharge port 23Ab of the first compressor 23A passes through the four-way valve 25 and exchanges heat with the heat storage material 61. In other words, the high-temperature, high-pressure refrigerant in the region 51a of the first pipe 51 discharged from the discharge port 23Ab of the first compressor 23A exchanges heat with the heat storage material 61. As a result, the refrigerant flowing through region 51b is heated by the heat storage material 61. At this time, the heat storage material 61 stores heat through a heat storage operation, which will be described later. The refrigerant that has passed through the heat storage material 61 releases heat in the second heat exchanger 38B and enters the indoor heat exchanger 41. That is, the refrigerant that has come out from the discharge port 23Ab of the first compressor 23A is cooled in the second heat exchanger 38B and enters the indoor heat exchanger 41.

[0128] The refrigerant discharged from the indoor heat exchanger 41 is decompressed by the second expansion valve 31B. The refrigerant decompressed by the second expansion valve 31B is separated into gas and liquid by the gas-liquid separator 36. The liquid refrigerant is decompressed by the first expansion valve 31A and enters the outdoor heat exchanger 21. The refrigerant absorbs heat in the outdoor heat exchanger 21. The gaseous refrigerant separated by the gas-liquid separator 36 passes through the third pipe 53 and enters the region 51e of the first pipe 51, where it merges with the refrigerant discharged from the second compressor 23B and enters the first heat exchanger 38A.

[0129] The pressure of the refrigerant is reduced from high pressure to medium pressure by the first expansion valve 31A, and the quality fraction becomes 20%. The refrigerant is then separated into gas and liquid by the gas-liquid separator 36, and the gaseous refrigerant is merged with the refrigerant discharged from the second compressor 23B. This lowers the temperature of the refrigerant discharged from the second compressor 23B. Next, the refrigerant is cooled by the first heat exchanger 38A and enters the first compressor 23A with its enthalpy lowered so that the degree of superheat becomes 0.5°C. In addition, in this embodiment, the first heat exchanger 38A gasifies the refrigerant flowing to the second compressor 23B. As a result, while the temperature of the refrigerant flowing to the outdoor heat exchanger 21 generally needs to be about 6°C lower than the outdoor air temperature (for example, when the outdoor air temperature is -15°C, the refrigerant temperature is -21°C), in this embodiment, the temperature of the refrigerant flowing to the outdoor heat exchanger 21 can be only 2°C lower than the outdoor air temperature. Furthermore, as a result, for example, when the outdoor air temperature is -15°C, the temperature of the refrigerant flowing through the outdoor heat exchanger 21 is -17°C, which is a temperature close to the dew point, and therefore frost is less likely to form on the outdoor heat exchanger 21. Furthermore, even if frost forms on the outdoor heat exchanger 21, the time before defrosting operation can be extended.

[0130] Fig. 7 is a Mollier diagram of the air conditioner 1 of the embodiment. The Mollier diagram during the heating operation is as shown in Fig. 7. Points P1 to P7 in Fig. 7 correspond to points P1 to P7 in Fig. 2. As shown in Fig. 7, in this embodiment, the enthalpy decreases between points P7 and P8 as the refrigerant discharged from the second compressor 23B is combined with the gaseous refrigerant discharged from the gas-liquid separator 36.

[0131] 8 is a flowchart showing an example of heat storage operation control of the air conditioner 10 of this embodiment. The control device 14 of this embodiment performs heat storage operation, for example, at night when the air conditioner 10 is stopped. Note that the time when the heat storage operation is performed is not limited to this example.

[0132] First, the operation switching unit 92 determines whether or not the start condition for the heat storage operation is met (S401). For example, if the operation switching unit 92 determines that the air conditioner 10 is stopped and the time is between 1:00 AM and 3:00 AM (nighttime), it determines that the start condition for the heat storage operation is met.

[0133] The start conditions for the heat storage operation are not limited to the above examples. For example, the operation switching unit 92 may determine the start conditions for the heat storage operation based on the outside air temperature. In this case, the temperature acquisition unit 91 acquires the outside air temperature from the temperature sensor 71. The operation switching unit 92 determines that the start conditions for the heat storage operation are met when the air conditioner 10 is stopped and the outside air temperature is below a threshold value for a predetermined period of time. Furthermore, the operation switching unit 92 may use, for example, artificial intelligence to learn the tendency of the time when the user starts the heating operation, and start the heat storage operation one hour before the start of the learned heating operation.

[0134] The operation switching unit 92 may also determine the start condition based on the presence of a person in the room. In this case, the operation switching unit 92 determines whether or not the room is unoccupied based on the output signal of the human presence sensor 73 provided in the indoor unit 12. If the operation switching unit 92 determines that the room has been unoccupied for a predetermined period of time, it determines that the start condition for the heat storage operation has been met.

[0135] Furthermore, the operation switching unit 92 may determine the conditions for starting the heat storage operation based on the required capacity of the air conditioner 10. In this case, the operation switching unit 92 calculates the required capacity of the air conditioner 10 (the cooling capacity required of the air conditioner 10 to bring the room temperature to the target temperature) based on factors such as the difference between the room temperature and the target temperature set by the user. The operation switching unit 92 determines that the conditions for starting the heat storage operation have been met when the required capacity of the air conditioner 10 is equal to or less than a predetermined threshold value.

[0136] If the start condition for the heat storage operation is not met (S401: No), the operation switching unit 92 waits without starting the heat storage operation. If the start condition for the heat storage operation is met (S401: Yes), the operation switching unit 92 starts the heat storage operation. Specifically, the outdoor fan control unit 93, the indoor fan control unit 94, and the compressor control unit 95 start and adjust the outdoor blower fan 22, the first compressor 23A, the second compressor 23B, and the indoor blower fan 42.

[0137] As in the heating operation, the valve control unit 96 controls the four-way valve 25 and the switching valves 33A to 33C to change the direction of refrigerant flow. At this time, the valve control unit 96 closes the on-off valves 34A and 34B. At this time, the compressor control unit 95 does not increase the frequencies of the first compressor 23A and the second compressor 23B above a specified frequency.

[0138] Next, the operation switching unit 92 determines whether or not to terminate the heat storage operation (S403). For example, if a stop signal or a signal to switch to another operation is input from the remote controller to the air conditioner 10, or if a predetermined time has elapsed, the operation switching unit 92 determines that the heat storage operation will end (S403: Yes) and terminates the heat storage operation. The operation switching unit 92 also determines that the heat storage operation will end when a predetermined time has elapsed since the start of the heat storage operation (S403: Yes) and terminates the heat storage operation. If the above signal has not been input or the predetermined time has not elapsed, the operation switching unit 92 determines that the heat storage operation will not end (S403: No) and continues the cold storage operation. Note that the heat storage operation is not limited to the above. For example, the heat storage operation may be a form in which the frequencies of the first compressor 23A and the second compressor 23B are increased until the temperature of the refrigerant in the indoor heat exchanger 41 detected by the temperature sensor 71D remains at 43°C for 10 minutes and the temperature of the heat storage material 61 detected by the temperature sensor 71M reaches 80°C.

[0139] 2, in the heat storage operation, the gaseous refrigerant evaporated in the outdoor heat exchanger 21 passes through the four-way valve 25 and exchanges heat with the heat storage material 61. In other words, the high-temperature, high-pressure refrigerant that exits from the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B and flows through the region 51a of the first pipe 51 exchanges heat with the heat storage material 61. As a result, the refrigerant flowing through the region 51b heats the heat storage material 61. That is, enthalpy (energy) is stored in the heat storage material 61.

[0140] In the air conditioner 10 described above, when heating operation is performed, the outdoor heat exchanger 21 acts as an evaporator, absorbing heat from the refrigerant and becoming cold. This can cause moisture in the air to condense on the outer surface of the outdoor heat exchanger 21 and adhere to the outdoor heat exchanger 21 as frost. For this reason, the air conditioner 10 performs a defrosting operation during heating operation to remove frost that has adhered to the outdoor heat exchanger 21.

[0141] FIG. 9 is a flowchart showing an example of defrosting operation control of the air conditioner 10 of the embodiment.

[0142] First, the operation switching unit 92 determines whether or not the start condition for the defrosting operation is met during the heating operation (S501). For example, the start condition for the defrosting operation is that the temperature of the refrigerant in the outdoor heat exchanger 21 detected by the temperature sensor 71B remains at or below 2°C for five minutes. If the temperature of the refrigerant in the outdoor heat exchanger 21 detected by the temperature sensor 71B remains at or below 2°C for five minutes, the operation switching unit 92 determines that the start condition for the defrosting operation is met (S501: Yes). If the temperature of the refrigerant in the outdoor heat exchanger 21 detected by the temperature sensor 71B does not remain at or below 2°C for five minutes, the operation switching unit 92 determines that the start condition for the defrosting operation is not met (S501: No).

[0143] When the operation switching unit 92 determines that the defrosting operation start condition is met (S501: Yes), it starts the defrosting operation (S502). Specifically, the operation switching unit 92 opens the on-off valve 34B. As a result, high-temperature, high-pressure gaseous refrigerant (hot gas) discharged from the discharge ports 23Ab, 23Bb of the first compressor 23A and the second compressor 23B flows into the outdoor heat exchanger 21 through the fourth pipe 54. The flow of the refrigerant through the fourth pipe 54 at this time is indicated by dashed arrows in FIG. 2. As the hot gas passes through the outdoor heat exchanger 21, the temperature of the outdoor heat exchanger 21 increases. As a result, frost adhering to the outdoor heat exchanger 21 melts and is removed.

[0144] Next, the operation switching unit 92 determines whether or not to terminate the defrosting operation (S503). For example, the operation switching unit 92 determines to terminate the defrosting operation when the defrosting operation has been performed for a predetermined time (S503: Yes). On the other hand, the operation switching unit 92 determines not to terminate the defrosting operation when the defrosting operation has not been performed for a predetermined time (S503: No). When the operation switching unit 92 determines to terminate the defrosting operation (S503: Yes), the operation switching unit 92 terminates the defrosting operation.

[0145] As described above, the air conditioner 10 of this embodiment includes the indoor heat exchanger 41, the outdoor heat exchanger 21, the first pipe 51, the second pipe 52, the first compressor 23A, the second compressor 23B, the four-way valve 25, the first expansion valve 31A, the gas-liquid separator 36, the first heat exchanger 38A, and the third pipe. The first pipe 51 connects the indoor heat exchanger 41 and the outdoor heat exchanger 21, and a refrigerant flows through it. The second pipe 52 connects the outdoor heat exchanger 21 and the indoor heat exchanger 41, and a refrigerant flows through it. The first compressor 23A is provided in the first pipe 51. The second compressor 23B is provided in the first pipe 51. The four-way valve 25 is provided in the first pipe 51 and is capable of changing the direction in which the refrigerant flows. The first expansion valve 31A is provided in the second pipe 52. The gas-liquid separator 36 is provided in the second pipe 52. The first pipe 51 includes a region 51h (first portion) connecting the first compressor 23A and the second compressor 23B, and a region 51i (second portion) connecting the first compressor 23A and the outdoor heat exchanger 21. The first heat exchanger 38A is capable of heat exchange between the region 51h and the region 51i. The third pipe 53 connects the gas-liquid separator 36 and the region 51h, and is capable of introducing the refrigerant from the gas-liquid separator 36 into the region 51h.

[0146] With this configuration, since there are two compressors 23, the temperature of the refrigerant discharged from each compressor 23 can be lowered compared to when there is only one compressor 23, thereby reducing the total compression work of the compressors 23. This prevents the compressors 23 from deteriorating even during heating when the outside air temperature is relatively low. Furthermore, since gaseous refrigerant from the gas-liquid separator 36 can be introduced into the region 51h, the dryness of the refrigerant flowing into either the indoor heat exchanger 41 or the outdoor heat exchanger 21, whichever functions as an evaporator, can be reduced. This reduces the expansion loss that occurs in conventional refrigeration cycles.

[0147] The air conditioner also includes a second heat exchanger 38B. The first piping 51 includes a region 51j (third portion) that connects the first compressor 23A and the indoor heat exchanger 41. The second heat exchanger 38B is capable of exchanging heat between the region 51i and the region 51j.

[0148] According to this configuration, the temperature of the refrigerant entering the first compressor 23A can be lowered, and therefore the temperature of the refrigerant discharged from the first compressor 23A can be suppressed.

[0149] The air conditioner also includes a second expansion valve 31B provided in the second pipe 52 between the indoor heat exchanger 41 and the gas-liquid separator .

[0150] With this configuration, the amount of refrigerant entering the gas-liquid separator 36 can be controlled, and therefore the amount of gaseous refrigerant exiting the gas-liquid separator 36 can be adjusted.

[0151] The air conditioner also includes a heat storage material 61 provided in the region 51j.

[0152] According to this configuration, a cold storage operation in which cold is stored in the heat storage material 61 and a heat storage operation in which heat is stored in the heat storage material 61 can be performed.

[0153] According to the air conditioner 10 described above, for example, deterioration of the compressor can be suppressed even during heating when the outside air temperature is relatively low.

[0154] 10 is a block diagram showing an example of the hardware configuration of the control device 14 according to the embodiment. The control device 14 is realized by, for example, a computer 100 having the hardware configuration shown in FIG.

[0155] The computer 100 includes, for example, a CPU 101, a ROM 102, a RAM 103, a storage device 104, and an interface (I / F) 106. The CPU 101, the ROM 102, the RAM 103, the storage device 104, and the I / F 106 are connected via a bus.

[0156] The CPU 101 loads a program stored in the storage device 104 into the RAM 103 and executes it, controls each unit to perform input / output, and processes data. The ROM 102 stores a start program that reads a startup program for the operating system from the storage device 104 to the RAM 103.

[0157] The storage device 104 is, for example, a flash memory. The storage device 104 stores an operating system, application programs, and data. These programs are distributed as installable or executable files recorded on computer-readable storage media. The programs may also be distributed by downloading them from a server.

[0158] I / F106 is an interface device for connecting to, for example, temperature sensors 71A to 71O, outdoor fan drive circuit 81, indoor fan drive circuit 82, inverter circuit 83, four-way valve drive circuit 84, expansion valve drive circuit 85, and switching valve drive circuit 87.

[0159] The program executed by the computer 100 of this embodiment can be provided as a file in an installable or executable format recorded on a computer-readable recording medium such as a CD-ROM, flexible disk (FD), CD-R, or DVD.

[0160] The program executed by the computer 100 of this embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. The program executed by the computer 100 of this embodiment may be provided or distributed via a network such as the Internet. The program of this embodiment may be provided by being pre-installed in the ROM 102 or the like.

[0161] The program for causing the computer 100 to function as the control device 14 has a modular configuration including a temperature acquisition module, an operation switching module, an outdoor fan control module, an indoor fan control module, a compressor control module, and a valve control module. In the actual hardware configuration of the computer 100, a processor (CPU 101) reads and executes the program from a storage medium (such as the storage device 104), thereby loading each module into the main storage device (RAM 103). As a result, the processor (CPU 101) functions as the temperature acquisition unit 91, operation switching unit 92, outdoor fan control unit 93, indoor fan control unit 94, compressor control unit 95, and valve control unit 96 shown in FIG. 3 . Note that the computer 100 may be configured such that some or all of the components of the temperature acquisition unit 91, operation switching unit 92, outdoor fan control unit 93, indoor fan control unit 94, compressor control unit 95, and valve control unit 96 are implemented by hardware.

[0162] In the above embodiment, an example in which the heat storage material 61 is provided is shown, but the present invention is not limited to this. For example, the heat storage material 61 does not have to be provided.

[0163] In the above embodiment, the first heat exchanger 38A and the second heat exchanger 38B are made of a heat storage material, but the present invention is not limited to this. For example, the first heat exchanger 38A and the second heat exchanger 38B may each be a double pipe.

[0164] In the above embodiment, the first heat exchanger 38A and the second heat exchanger 38B are provided separately, but this is not limiting. For example, the first heat exchanger 38A and the second heat exchanger 38B may be integrated to form a triple heat exchanger.

[0165] In addition, in the above embodiment, an example in which the fourth pipe 54 is provided and the defrosting operation is performed has been described, but this is not limiting. For example, the fourth pipe 54 may not be provided and the defrosting operation may not be performed.

[0166] In the above embodiment, an example in which the heat storage operation and the cold storage operation are performed is shown, but the present invention is not limited to this. For example, the heat storage operation and the cold storage operation may not be performed.

[0167] Although several 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 embodied 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 within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0168] 10...air conditioner, 21...outdoor heat exchanger, 23A...first compressor, 23B...second compressor, 25...four-way valve, 31A...first expansion valve, 31B...second expansion valve, 36...gas-liquid separator, 38A...first heat exchanger, 41...indoor heat exchanger, 51...first piping, 51h...area (first part), 51i...area (second part), 51j...area (third part), 52...second piping, 53...third piping, 61...heat storage material.

Claims

1. An indoor heat exchanger; An outdoor heat exchanger; a first pipe connecting the indoor heat exchanger and the outdoor heat exchanger and through which a refrigerant flows; a second pipe connecting the outdoor heat exchanger and the indoor heat exchanger and through which the refrigerant flows; a first compressor provided in the first pipe; a second compressor provided in the first pipe; a four-way valve provided in the first pipe and capable of changing the direction in which the refrigerant flows; a first expansion valve provided in the second pipe; a gas-liquid separator provided in the second pipe; a first heat exchanger; A third pipe; and Equipped with The first pipe includes: a first portion connecting the first compressor and the second compressor; a second portion connecting the first compressor and the outdoor heat exchanger; Including, the first heat exchanger is capable of exchanging heat between the first portion and the second portion; the third pipe connects the gas-liquid separator and the first part and is capable of introducing the refrigerant from the gas-liquid separator into the first part; In the cooling operation, the first compressor and the second compressor are connected in parallel. Air conditioner.

2. a second heat exchanger; the first piping includes a third portion connecting the first compressor and the indoor heat exchanger, the second heat exchanger is capable of exchanging heat between the second portion and the third portion; The air conditioner according to claim 1.

3. a second expansion valve provided in the second piping between the indoor heat exchanger and the gas-liquid separator; The first expansion valve is provided in the second piping between the outdoor heat exchanger and the gas-liquid separator.

3. The air conditioner according to claim 1 or 2.

4. a heat storage material provided in the third portion; The air conditioner according to claim 2.

5. In heating operation, the first compressor and the second compressor are connected in series, a connection between the first compressor and the second compressor is switchable between the parallel connection in the cooling operation and the series connection in the heating operation; In the series connection, the second compressor is upstream of the first compressor. The air conditioner according to claim 1.

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