Air conditioner

Abstract

To suppress lowering of comfort when an air conditioning load is low.SOLUTION: An air conditioner includes: a flow passage switching part 31 for switching a flow passage in such a manner that a refrigerant discharged from a compressor 2 flows in one or two out of an outdoor heat exchanger 3, a heat storage heat exchanger 18 and an indoor heat exchanger 6; a first refrigerant pipeline 11 for connecting the flow passage switching part 31 and the outdoor heat exchanger 3; a second refrigerant pipeline 12 for connecting the outdoor heat exchanger 3 and a main expansion valve 5; the heat storage heat exchanger 18 for exchanging heat between the refrigerant flowing in a heat storage flow passage 17 for connecting the second refrigerant pipeline 12 and the flow passage switching part 31 with a heat storage material 64; a bypass flow passage 51 whose both ends are connected to the first refrigerant pipeline 11 and the second refrigerant pipeline 12; a bypass heat exchanger 52 for exchanging heat between the refrigerant flowing in the bypass flow passage 51 and the heat storage material 64; a bypass expansion valve 53 for adjusting the amount of the refrigerant flowing in the bypass flow passage 51; and a control part for controlling the bypass expansion valve 53 based on the heat storage amount which is the absolute value of the heat amount stored in the heat storage material 64.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] When an air conditioner is operating with a low air conditioning load, the actual air conditioning capacity may not match the air conditioning load, causing the room temperature to deviate significantly from the set temperature. To prevent this, an air conditioner is known that maintains the room temperature within a predetermined range by performing intermittent operation, stopping and starting the compressor (Patent Document 1). Another air conditioner is known that can reduce maximum power consumption by performing a heat storage operation in which, while heating the room, a portion of the refrigerant flowing through the indoor heat exchanger is bypassed and stored in a heat storage material, and then performing a heat storage utilization operation in which the heat stored in the heat storage material is used for heating (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-254586 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-337657 Summary of the Invention [Problem to be solved by the invention]

[0004] In air conditioners such as those described in Patent Document 1, even when the compressor is stopped during intermittent operation, the indoor unit fan may be operated to properly detect the indoor temperature. As a result, when the compressor is stopped during heating, cool air is blown out, and when the compressor is stopped during cooling, condensation on the indoor heat exchanger evaporates, causing moisture return, which reduces comfort.

[0005] The air conditioner described in Patent Document 2 further performs heat storage operation when the air conditioning load is low, thereby reducing heating capacity and preventing a decrease in comfort due to intermittent operation. However, once heat storage is complete, it is necessary to switch from heat storage operation to heat storage utilization operation in order to utilize the stored heat. Immediately after switching operation, the evaporation temperature rises rapidly due to the large temperature difference between the heat storage material (heat source) and the outside air, and this in turn makes it easy for the condensation temperature to rise. In other words, because the heating capacity tends to rise rapidly immediately after switching operation, intermittent operation may be performed, which can reduce comfort. Furthermore, repeating heat storage operation and heat storage utilization operation may result in an insufficient amount of stored heat when using the stored heat for other functions such as defrosting.

[0006] The disclosed technology has been made in consideration of the above points, and aims to provide an air conditioner that suppresses a decrease in comfort. [Means for solving the problem]

[0007] An air conditioner according to one aspect of the present disclosure includes a compressor, an outdoor heat exchanger, a main expansion valve, an indoor heat exchanger, a heat storage heat exchanger, a flow path switching unit provided on the discharge side of the compressor and switching a flow path so that refrigerant discharged from the compressor flows to one or two of the outdoor heat exchanger, the heat storage heat exchanger, and the indoor heat exchanger, a first refrigerant pipe connecting the flow path switching unit and the outdoor heat exchanger, a second refrigerant pipe connecting the outdoor heat exchanger and the main expansion valve, a third refrigerant pipe connecting the main expansion valve and the indoor heat exchanger, a heat storage flow path connecting the flow path switching unit and the second refrigerant pipe, through which refrigerant that is heat exchanged with a heat storage material by the heat storage heat exchanger flows, and one end of the first refrigerant pipe and the second refrigerant pipe are connected to the first refrigerant pipe. a bypass flow path the other end of which is connected to either the piping and the second refrigerant piping or the third refrigerant piping; a bypass heat exchanger which exchanges heat between the refrigerant flowing through the bypass flow path and the heat storage material; a bypass expansion valve which adjusts the amount of refrigerant flowing through the bypass flow path; and a control unit which controls the bypass expansion valve so that the refrigerant does not flow into the bypass flow path when a heat storage amount, which is an absolute value of the amount of heat stored in the heat storage material, is smaller than a first heat storage threshold value during a first heat storage heating operation in which the indoor heat exchanger and the heat storage heat exchanger function as condensers or a first cold storage cooling operation in which the indoor heat exchanger and the heat storage heat exchanger function as evaporators, and so that the refrigerant flows into the bypass flow path when the heat storage amount is equal to or greater than the first heat storage threshold value. [Effects of the Invention]

[0008] The disclosed air conditioner can suppress a decrease in comfort. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a refrigerant circuit diagram showing an air conditioner according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing the outdoor unit and the heat storage core. [Figure 3] FIG. 3 is a perspective view showing the heat storage core. [Figure 4]FIG. 4 is a cross-sectional view showing the heat storage core. [Figure 5] FIG. 5 is a block diagram showing the control device. [Figure 6] FIG. 6 is a flowchart showing the first heat-storage heating operation, the second heat-storage heating operation, and the heat-storage-utilization heating operation. [Figure 7] FIG. 7 is a flowchart showing the second heat-storage heating operation. [Figure 8] FIG. 8 is a graph showing changes in the amount of stored heat when the first heat-storage heating operation, the second heat-storage heating operation, and the heat-storage-utilization heating operation are being performed. DETAILED DESCRIPTION OF THE INVENTION

[0010] An air conditioner according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. Note that the following description does not limit the technology of the present disclosure. In addition, in the following description, the same components are given the same reference numerals, and duplicated descriptions will be omitted. [Example]

[0011] As shown in FIG. 1, the air conditioner of the embodiment includes a refrigerant circuit 1. FIG. 1 is a refrigerant circuit diagram showing the air conditioner of the embodiment. The refrigerant circuit 1 includes a compressor 2, an outdoor heat exchanger 3, a main expansion valve 5, an indoor heat exchanger 6, and a flow switching unit 31. The compressor 2, the outdoor heat exchanger 3, and the main expansion valve 5 are arranged inside an outdoor unit 61, which will be described later. The indoor heat exchanger 6 is arranged inside an indoor unit installed in a room (room) to be cooled or heated by the air conditioner. The compressor 2 includes a suction pipe 7 and a discharge pipe 8. The compressor 2 compresses refrigerant supplied to the suction pipe 7 and discharges the refrigerant to the discharge pipe 8 at a flow rate corresponding to the compressor rotation speed. The flow rate of refrigerant discharged from the compressor 2 to the discharge pipe 8 per unit time increases as the compressor rotation speed increases. The compressor 2 and the flow switching unit 31 are connected via the discharge pipe 8 of the compressor 2. A first branch 15 is provided in the discharge pipe 8.

[0012] The refrigerant circuit 1 further includes a first refrigerant pipe 11, a second refrigerant pipe 12, and a third refrigerant pipe 14. The flow path switching unit 31 and the outdoor heat exchanger 3 are connected via the first refrigerant pipe 11. The outdoor heat exchanger 3 and the main expansion valve 5 are connected via the second refrigerant pipe 12. The main expansion valve 5 and the indoor heat exchanger 6 are connected via the third refrigerant pipe 14. A second branch section 16 is provided in the middle of the second refrigerant pipe 12.

[0013] The refrigerant circuit 1 further includes a heat storage flow path 17 and a heat storage heat exchanger 18. The flow path switching unit 31 and the second branching unit 16 are connected via the heat storage flow path 17. The heat storage heat exchanger 18 is provided midway along the heat storage flow path 17.

[0014] The flow path switching unit 31 includes a first four-way valve 32, a fourth refrigerant pipe 33, a fifth refrigerant pipe 34, a sixth refrigerant pipe 35, a second four-way valve 36, a seventh refrigerant pipe 37, and a check valve 38. The first four-way valve 32 and the compressor 2 are connected via a discharge pipe 8 of the compressor 2. The first four-way valve 32 and the indoor heat exchanger 6 are connected via a fourth refrigerant pipe 33. The first four-way valve 32 and the suction pipe 7 of the compressor 2 are connected via a fifth refrigerant pipe 34. A third branch section 41 is provided midway along the fifth refrigerant pipe 34.

[0015] The second four-way valve 36 and the first branch 15 are connected via an eighth refrigerant pipe 39. A sixth branch 42 is provided midway along the eighth refrigerant pipe 39. The sixth branch 42 and the first four-way valve 32 are connected via the sixth refrigerant pipe 35. That is, the first four-way valve 32 and the second four-way valve 36 are connected via the sixth refrigerant pipe 35 and a part of the eighth refrigerant pipe 39. The second four-way valve 36 and the third branch 41 are connected via the seventh refrigerant pipe 37.

[0016] The check valve 38 is provided midway along the sixth refrigerant pipe 35. The check valve 38 is closed to prevent refrigerant from flowing from the flow path 46 to the flow path 45 when the pressure of the refrigerant in the sixth refrigerant pipe 35 between the first four-way valve 32 and the check valve 38 is lower than the pressure of the refrigerant in the flow path 46 between the check valve 38 and the sixth branch portion 42 in the sixth refrigerant pipe 35. The check valve 38 is opened to allow refrigerant to flow from the flow path 45 to the flow path 46 when the pressure of the refrigerant in the flow path 45 is higher than the pressure of the refrigerant in the flow path 46.

[0017] The flow path switching unit 31 switches the refrigerant circuit 1 to one of the normal heating cycle, the first heat-storage heating cycle, the second heat-storage heating cycle, the heat-storage heating cycle, the normal cooling cycle, the first cold-storage cooling cycle, the second cold-storage cooling cycle, and the cold-storage cooling cycle. When the refrigerant circuit 1 is switched to one of the normal heating cycle, the first heat-storage heating cycle, the second heat-storage heating cycle, and the heat-storage heating cycle, the discharge pipe 8 of the compressor 2 is connected to the indoor heat exchanger 6 via the first four-way valve 32. When the refrigerant circuit 1 is switched to one of the normal cooling cycle, the first cold-storage cooling cycle, the second cold-storage cooling cycle, and the cold-storage cooling cycle, the discharge pipe 8 of the compressor 2 is connected to the check valve 38 via the first four-way valve 32, and the indoor heat exchanger 6 is connected to the suction pipe 7 of the compressor 2 via the first four-way valve 32.

[0018] When the refrigerant circuit 1 is switched to one of the normal heating cycle, the first heat-storage heating cycle, and the second heat-storage heating cycle, the eighth refrigerant pipe 39 is connected to the heat-storage heat exchanger 18 via the second four-way valve 36, and the outdoor heat exchanger 3 is connected to the third branch part 41 via the second four-way valve 36. When the refrigerant circuit 1 is switched to one of the heat-storage heating cycle, the normal cooling cycle, the first cold-storage cooling cycle, the second cold-storage cooling cycle, and the cold-storage cooling cycle, the eighth refrigerant pipe 39 is connected to the outdoor heat exchanger 3 via the second four-way valve 36, and the heat-storage heat exchanger 18 is connected to the third branch part 41 via the second four-way valve 36.

[0019] The refrigerant circuit 1 further includes a first heat storage expansion valve 21 and a second heat storage expansion valve 22. The first heat storage expansion valve 21 is provided between the first branch portion 15 and the second four-way valve 36. The first heat storage expansion valve 21 adjusts the flow rate of refrigerant flowing into the second four-way valve 36 depending on its opening degree. The second heat storage expansion valve 22 is provided in the heat storage flow path 17 between the second branch portion 16 and the heat storage heat exchanger 18. The second heat storage expansion valve 22 adjusts the flow rate of refrigerant flowing through the heat storage flow path 17 depending on its opening degree.

[0020] The refrigerant circuit 1 further includes a bypass flow path 51, a bypass heat exchanger 52, and a bypass expansion valve 53. A fourth branch portion 54 is provided in the first refrigerant pipe 11. A fifth branch portion 55 is provided in the second refrigerant pipe 12 between the outdoor heat exchanger 3 and the second branch portion 16. The fourth branch portion 54 and the fifth branch portion 55 are connected via the bypass flow path 51. The bypass heat exchanger 52 is provided midway along the bypass flow path 51. The bypass expansion valve 53 is provided in the bypass flow path 51 between the bypass heat exchanger 52 and the fifth branch portion 55.

[0021] As shown in Fig. 2, the air conditioner further includes an outdoor unit 61 and a heat storage core unit 62. Fig. 2 is a perspective view showing the outdoor unit 61 and the heat storage core unit 62. The outdoor unit 61 is installed outside (outdoors) of a room to be cooled or heated by the air conditioner. The heat storage core unit 62 is provided on top of the outdoor unit 61. Fig. 3 is a perspective view showing the heat storage core unit 62. The heat storage core unit 62 includes a heat storage container 63, a heat storage material 64, a plurality of fins 65, and a plurality of heat transfer tubes 66. The heat storage material 64 is formed from a liquid that is a sensible heat storage material, and is stored inside the heat storage container 63.

[0022] The multiple fins 65 and the multiple heat transfer tubes 66 form a fin-tube heat exchanger. That is, each of the multiple fins 65 is formed in a flat plate shape. The multiple fins 65 are stacked at intervals from one another, and are disposed inside the heat storage container 63 together with the heat storage material 64, and are in contact with the heat storage material 64. The multiple heat transfer tubes 66 are disposed inside the heat storage container 63 together with the heat storage material 64, and are in contact with the heat storage material 64. The multiple heat transfer tubes 66 are joined to the multiple fins 65 so as to penetrate the multiple fins 65 in the stacking direction, and are in contact with the multiple fins 65, and are in thermal contact with the heat storage material 64 via the multiple fins 65.

[0023] 4 is a cross-sectional view showing the heat storage core 62. The plurality of heat transfer tubes 66 includes a plurality of bypass heat exchange heat transfer tubes 67 and a plurality of heat storage heat exchange heat transfer tubes 68. The plurality of bypass heat exchange heat transfer tubes 67 are arranged above a horizontal plane 69 that divides the plurality of heat transfer tubes 66 into two when the outdoor unit 61 and the heat storage core 62 are installed. The plurality of heat storage heat exchange heat transfer tubes 68 are formed from heat transfer tubes that are different from the plurality of bypass heat exchange heat transfer tubes 67 of the plurality of heat transfer tubes 66. Some of the plurality of heat storage heat exchange heat transfer tubes 68 are arranged below the horizontal plane 69, and some of the remaining plurality of heat storage heat exchange heat transfer tubes 68 are arranged above the horizontal plane 69. In other words, the plurality of heat transfer tubes 66 are arranged such that at least one heat storage heat exchange heat transfer tube of the plurality of heat storage heat exchange heat transfer tubes 68 is arranged below the plurality of bypass heat exchange heat transfer tubes 67.

[0024] The plurality of heat storage heat exchange heat transfer tubes 68 form a part of the heat storage flow path 17, and form the heat storage heat exchanger 18. In other words, the heat storage heat exchanger 18 includes a plurality of heat storage heat exchange heat transfer tubes 68. The heat storage heat exchanger 18 exchanges heat between the refrigerant flowing through the plurality of heat storage heat exchange heat transfer tubes 68 and the heat storage material 64. The plurality of bypass heat exchange heat transfer tubes 67 form a part of the bypass flow path 51, and form the bypass heat exchanger 52. In other words, the bypass heat exchanger 52 includes a plurality of bypass heat exchange heat transfer tubes 67. The bypass heat exchanger 52 exchanges heat between the refrigerant flowing through the plurality of bypass heat exchange heat transfer tubes 67 and the heat storage material 64.

[0025] The heat storage core 62 is further formed so that the heat exchange capacity of the heat storage heat exchanger 18 is greater than the heat exchange capacity of the bypass heat exchanger 52. For example, the number of the bypass heat exchange heat transfer tubes 67 is less than the number of the heat storage heat exchange heat transfer tubes 68. The heat transfer area of ​​the bypass heat exchange heat transfer tubes 67 is smaller than the heat transfer area of ​​the heat storage heat exchange heat transfer tubes 68. The thermal conductivity of the material forming the bypass heat exchange heat transfer tubes 67 is lower than the thermal conductivity of the material forming the heat storage heat exchange heat transfer tubes 68.

[0026] The heat storage material 64 includes a bypass heat exchange portion 71, a heat storage heat exchange portion 72, and a temperature measurement portion 73. The bypass heat exchange portion 71 is a portion of the heat storage material 64 that is arranged near the multiple bypass heat exchange heat transfer tubes 67, and is a portion of the heat storage material 64 that undergoes heat exchange by the bypass heat exchanger 52. The heat storage heat exchange portion 72 is a portion of the heat storage material 64 that is arranged near the multiple heat storage heat exchange heat transfer tubes 68, and is a portion of the heat storage material 64 that undergoes heat exchange by the heat storage heat exchanger 18. The temperature measurement portion 73 is a portion that is arranged between the heat storage heat exchange portion 72 and the bypass heat exchange portion 71. The heat storage material 64 stores heat or cold by exchanging heat with the refrigerant in the heat storage heat exchanger 18 or the bypass heat exchanger 52. For example, the heat storage material 64 stores heat when the heat storage heat exchanger 18 or the bypass heat exchanger 52 functions as a condenser, and stores cold when the heat storage heat exchanger 18 or the bypass heat exchanger 52 functions as an evaporator. In this embodiment, the case where the heat storage heat exchanger 18 functions as a condenser is referred to as heat storage operation, and the case where the heat storage heat exchanger 18 functions as an evaporator is referred to as cold storage operation.

[0027] The air conditioner further includes a heat storage material temperature sensor 74. The heat storage material temperature sensor 74 is arranged in an area inside the heat storage container 63 where the temperature measurement portion 73 is arranged, and is in contact with the temperature measurement portion 73. The heat storage material temperature sensor 74 measures the temperature of the temperature measurement portion 73.

[0028] As shown in Fig. 5, the air conditioner further includes a control device 81. Fig. 5 is a block diagram showing the control device 81. The control device 81 is a computer, and includes a storage device 82 and a CPU (Central Processing Unit) 83. The storage device 82 stores computer programs installed in the control device 81, and stores information used by the CPU 83. The CPU 83 executes the computer programs installed in the control device 81. The control device 81 executes multiple functions in accordance with the computer programs. The control device 81 includes, as its multiple functions, a switching control unit 84, a rotation speed control unit 85, a heat storage amount calculation unit 86, and a control unit 87.

[0029] The switching control unit 84 controls the flow path switching unit 31 so that the refrigerant circuit 1 switches between the normal heating cycle, the first heat storage heating cycle, the second heat storage heating cycle, the heat storage heating cycle, the normal cooling cycle, the first cold storage cooling cycle, the second cold storage cooling cycle, and the cold storage cooling cycle in response to operation of the air conditioner by the user. The rotation speed control unit 85 controls the compressor 2 so that the compressor rotation speed changes based on the temperature difference, which is the absolute value of the difference between the set temperature set in the air conditioner by operation of the user and the room temperature of the room in which the indoor unit is installed.

[0030] The heat storage amount calculation unit 86 acquires the temperature of the temperature measurement portion 73 measured by the heat storage material temperature sensor 74 as the heat storage material temperature from the heat storage material temperature sensor 74 and calculates the heat storage amount based on the heat storage material temperature. The heat storage amount indicates the absolute value of the amount of heat stored in the heat storage material 64. The control unit 87 controls the first heat storage expansion valve 21, the second heat storage expansion valve 22, and the bypass expansion valve 53 based on predetermined first heating mode heat storage threshold, second heating mode heat storage threshold, first cooling mode cold storage threshold, and second cooling mode cold storage threshold, and the heat storage amount calculated by the heat storage amount calculation unit 86. The first heating mode heat storage threshold, second heating mode heat storage threshold, first cooling mode cold storage threshold, and second cooling mode cold storage threshold are stored in the storage device 82. The second heating mode heat storage threshold is greater than the first heating mode heat storage threshold and indicates the upper limit of the amount of heat stored in the heat storage material 64 during heating operation. The second cooling cold storage threshold is greater than the first cooling cold storage threshold, and indicates the upper limit of the amount of cold stored in the heat storage material 64 during cooling operation.

[0031] [Air conditioner operation] When heating is selected by a user operation, the air conditioner starts normal heating operation. When normal heating operation starts, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the normal heating cycle. When normal heating operation starts, the control device 81 further fully closes the first heat storage expansion valve 21 to prevent refrigerant from flowing to the heat storage heat exchanger 18, and slightly opens the second heat storage expansion valve 22 to prevent refrigerant from accumulating in the heat storage heat exchanger 18. When normal heating operation starts, the control device 81 further fully closes the bypass expansion valve 53 to prevent refrigerant from flowing to the bypass heat exchanger 52.

[0032] When the normal heating operation is started, the control device 81 also starts the compressor 2. The compressor 2 compresses the low-pressure gas-phase refrigerant supplied to the compressor 2 from the suction pipe 7. The low-pressure gas-phase refrigerant is compressed by the compressor 2 to become high-pressure gas-phase refrigerant, which is discharged from the compressor 2 to the discharge pipe 8. The high-pressure gas-phase refrigerant discharged from the compressor 2 to the discharge pipe 8 flows into the first branch part 15 and into the first four-way valve 32 via the first branch part 15. The high-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the indoor heat exchanger 6 via the first four-way valve 32 because the refrigerant circuit 1 has switched to the normal heating cycle.

[0033] The indoor heat exchanger 6 exchanges heat between the high-pressure gas phase refrigerant and the air in the room where the indoor unit is installed, heating the indoor air and cooling the high-pressure gas phase refrigerant. The indoor unit blows the air heated by the indoor heat exchanger 6 into the room to heat the room. The high-pressure gas phase refrigerant is cooled and condensed in the indoor heat exchanger 6, becoming a supercooled high-pressure liquid phase refrigerant which flows out of the indoor heat exchanger 6. In other words, the indoor heat exchanger 6 functions as a condenser when normal heating operation is performed.

[0034] The high-pressure liquid-phase refrigerant flowing out from the indoor heat exchanger 6 flows into the main expansion valve 5. The main expansion valve 5 reduces the pressure of the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is reduced in pressure by the main expansion valve 5 to become a low-pressure gas-liquid two-phase refrigerant, which flows out from the main expansion valve 5. The low-pressure gas-liquid two-phase refrigerant flowing out from the main expansion valve 5 flows into the outdoor heat exchanger 3. The outdoor heat exchanger 3 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and outdoor air, absorbing heat from the outdoor air to heat the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the outdoor heat exchanger 3, becoming a low-pressure gas-phase refrigerant, which flows out from the outdoor heat exchanger 3. In other words, the outdoor heat exchanger 3 functions as an evaporator when normal heating operation is performed.

[0035] The low-pressure gas-phase refrigerant flowing out from the outdoor heat exchanger 3 flows into the second four-way valve 36, and because the refrigerant circuit 1 is switched to the normal heating cycle, it flows into the third branch section 41 via the second four-way valve 36 and into the suction pipe 7 of the compressor 2 via the third branch section 41.

[0036] The control device 81 controls the rotation speed of the compressor 2 while normal heating operation is being performed. In controlling the rotation speed of the compressor 2, the control device 81 obtains the temperature difference between the set temperature set in the air conditioner by user operation and the room temperature of the room in which the indoor unit is installed. The temperature difference indicates the absolute value of the value calculated by subtracting the room temperature from the set temperature. The control device 81 controls the compressor 2 so that the compressor rotation speed increases as the temperature difference increases.

[0037] While the normal heating operation is being performed, the control device 81 further determines whether the air conditioning load is low. For example, the control device 81 determines that the air conditioning load is not low when the compressor rotation speed is greater than the lower limit rotation speed, and determines that the air conditioning load is low when the compressor rotation speed is equal to or less than the lower limit rotation speed. When it is determined that the air conditioning load is not low, the control device 81 continues to perform the normal heating operation. When it is determined that the air conditioning load is low, the control device 81 starts the first heat storage heating operation.

[0038] FIG. 6 is a flowchart showing the first heat-storage heating operation, the second heat-storage heating operation, and the heat-storage-utilization heating operation. When the air conditioner determines that the air conditioning load is low, it starts the first heat-storage heating operation (step S1). When the first heat-storage heating operation starts, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the first heat-storage heating cycle. When the first heat-storage heating operation starts, the control device 81 further controls the aperture of the first heat-storage expansion valve 21 so that the heat storage rate at which heat is stored in the heat storage material 64 is constant, and sets the aperture of the second heat-storage expansion valve 22 to a predetermined aperture so that the refrigerant flows through the heat-storage heat exchanger 18. Here, the predetermined aperture is a fixed value that is predetermined so that the refrigerant dryness at the outlet of the heat-storage heat exchanger becomes an appropriate value (for example, the degree of subcooling = 0 and the refrigerant dryness is 0 to 0.1). When the first heat-storage heating operation is started, the control device 81 further fully closes the bypass expansion valve 53 so that the refrigerant does not flow into the bypass heat exchanger 52.

[0039] The high-pressure gas-phase refrigerant discharged from the compressor 2 flows into the first branch section 15 and is split into two at the first branch section 15. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first four-way valve 32, and because the refrigerant circuit 1 has switched to the first heat-storage heating cycle, it flows into the indoor heat exchanger 6 via the first four-way valve 32.

[0040] The indoor heat exchanger 6 exchanges heat between the high-pressure gas-phase refrigerant and the air in the room where the indoor unit is installed, heating the indoor air and cooling the high-pressure gas-phase refrigerant. The indoor unit blows the air heated by the indoor heat exchanger 6 into the room, heating the room. The high-pressure gas-phase refrigerant is cooled and condensed in the indoor heat exchanger 6, becoming a supercooled high-pressure liquid-phase refrigerant, which flows out of the indoor heat exchanger 6. The high-pressure liquid-phase refrigerant that flows out of the indoor heat exchanger 6 flows into the main expansion valve 5. The main expansion valve 5 decompresses the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is decompressed by the main expansion valve 5, becoming a low-pressure gas-liquid two-phase refrigerant, which flows out of the main expansion valve 5. In other words, the indoor heat exchanger 6 functions as a condenser when the first heat storage heating operation is performed.

[0041] The other high-pressure gas-phase refrigerant of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first heat-storage expansion valve 21 and then flows into the second four-way valve 36 via the first heat-storage expansion valve 21. Because the refrigerant circuit 1 is switched to the first heat-storage heating cycle, the high-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the heat-storage heat exchanger 18 via the second four-way valve 36. The heat-storage heat exchanger 18 exchanges heat between the high-pressure gas-phase refrigerant and the heat storage material 64, heating the heat storage material 64 and cooling the high-pressure gas-phase refrigerant. The amount of heat stored in the heat storage material 64 increases as the heat storage material 64 is heated. The high-pressure gas-phase refrigerant is cooled and condensed in the heat-storage heat exchanger 18, becoming a supercooled high-pressure liquid-phase refrigerant, which then flows out of the heat-storage heat exchanger 18. That is, the heat-storage heat exchanger 18 functions as a condenser when the first heat-storage heating operation is performed. The high-pressure liquid-phase refrigerant flowing out of the heat storage heat exchanger 18 flows into the second heat storage expansion valve 22. The second heat storage expansion valve 22 reduces the pressure of the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is reduced in pressure by the second heat storage expansion valve 22 and becomes a low-pressure gas-liquid two-phase refrigerant, which flows out of the second heat storage expansion valve 22.

[0042] The low-pressure gas-liquid two-phase refrigerant flowing out from the main expansion valve 5 and the low-pressure gas-liquid two-phase refrigerant flowing out from the second heat storage expansion valve 22 flow into the second branch section 16 and merge there. The low-pressure gas-liquid two-phase refrigerant merged at the second branch section 16 flows into the outdoor heat exchanger 3. The outdoor heat exchanger 3 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the outdoor air, absorbing heat from the outdoor air to heat the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the outdoor heat exchanger 3, becoming low-pressure gas-phase refrigerant, which flows out of the outdoor heat exchanger 3. That is, the outdoor heat exchanger 3 functions as an evaporator when the first heat storage heating operation is performed.

[0043] The low-pressure gas-phase refrigerant flowing out from the outdoor heat exchanger 3 flows into the second four-way valve 36. Because the refrigerant circuit 1 is switched to the first heat-storage heating cycle, the low-pressure gas-liquid two-phase refrigerant that has flowed into the second four-way valve 36 flows into the third branch portion 41 via the second four-way valve 36, and then flows into the suction pipe 7 of the compressor 2 via the third branch portion 41.

[0044] While the first heat-storage heating operation is being performed, the control device 81 periodically acquires the heat storage material temperature measured by the heat storage material temperature sensor 74 from the heat storage material temperature sensor 74 and calculates the amount of heat storage based on the heat storage material temperature (step S2). When the amount of heat storage is smaller than the first heating-time heat storage threshold value (step S2, No), the control device 81 continues to perform the first heat-storage heating operation.

[0045] When the amount of stored heat is equal to or greater than the first heating-time heat storage threshold (step S2, Yes), the air conditioner starts the second heat storage heating operation (step S3). The control device 81 determines whether the heat storage utilization condition is met while the second heat storage heating operation is being performed (step S4). For example, the control device 81 determines that the heat storage utilization condition is met when frost forms on the outdoor heat exchanger 3. When it is determined that the heat storage utilization condition is met (step S4, Yes), the air conditioner starts the heat storage utilization heating operation (step S5).

[0046] When the thermal storage heating operation is started, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the thermal storage heating cycle. When the thermal storage heating operation is started, the control device 81 also sets the aperture of the first thermal storage expansion valve 21 to a predetermined aperture and fully opens the second thermal storage expansion valve 22 so that refrigerant flows to the thermal storage heat exchanger 18. Here, the predetermined aperture is a fixed value that is set in advance so that frost formed on the outdoor heat exchanger 3 can be defrosted, for example. When the thermal storage heating operation is started, the control device 81 also fully closes the bypass expansion valve 53 so that refrigerant does not flow to the bypass heat exchanger 52.

[0047] The high-pressure gas refrigerant discharged from the compressor 2 flows into the first branch 15 and is split into two at the first branch 15. One of the high-pressure gas refrigerant flows into the first four-way valve 32. Because the refrigerant circuit 1 is switched to the thermal storage heating cycle, the high-pressure gas refrigerant that flows into the first four-way valve 32 flows into the indoor heat exchanger 6 via the first four-way valve 32. The indoor heat exchanger 6 exchanges heat between the high-pressure gas refrigerant and the air in the room where the indoor unit is installed, heating the indoor air and cooling the high-pressure gas refrigerant. The indoor unit blows the air heated by the indoor heat exchanger 6 into the room to heat the room. The high-pressure gas refrigerant is cooled and condensed in the indoor heat exchanger 6, becoming a supercooled high-pressure liquid refrigerant, which then flows out of the indoor heat exchanger 6. In other words, the indoor heat exchanger 6 functions as a condenser when the thermal storage heating operation is performed. The high-pressure liquid-phase refrigerant flowing out of the indoor heat exchanger 6 flows into the main expansion valve 5 , where it is decompressed to become a low-pressure gas-liquid two-phase refrigerant, which then flows out of the main expansion valve 5 .

[0048] The other of the high-pressure gas-phase refrigerant branched at the first branch section 15 flows into the first heat-storage expansion valve 21 and then into the second four-way valve 36 via the first heat-storage expansion valve 21. Because the refrigerant circuit 1 is switched to the thermal storage heating cycle, the high-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the outdoor heat exchanger 3 via the second four-way valve 36. The outdoor heat exchanger 3 exchanges heat between the high-pressure gas-phase refrigerant and outdoor air, cooling the high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is cooled and condensed in the outdoor heat exchanger 3, becoming a supercooled high-pressure liquid-phase refrigerant, which then flows out of the outdoor heat exchanger 3. In other words, the outdoor heat exchanger 3 functions as a condenser when the thermal storage heating operation is performed.

[0049] The low-pressure gas-liquid two-phase refrigerant flowing out from the main expansion valve 5 and the high-pressure liquid-phase refrigerant flowing out from the outdoor heat exchanger 3 flow into the second branch section 16, where they merge to become a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant flowing out from the second branch section 16 flows into the second heat storage expansion valve 22. The low-pressure gas-liquid two-phase refrigerant flowing out from the second heat storage expansion valve 22 flows into the heat storage heat exchanger 18. The heat storage heat exchanger 18 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the heat storage material 64, heating the low-pressure gas-liquid two-phase refrigerant and cooling the heat storage material 64. The amount of heat stored in the heat storage material 64 decreases as it is cooled. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the heat storage heat exchanger 18, becoming a low-pressure gas-phase refrigerant and flowing out of the heat storage heat exchanger 18. That is, the thermal storage heat exchanger 18 functions as an evaporator when the thermal storage utilization heating operation is performed.

[0050] The low-pressure gas-phase refrigerant that flows out of the thermal storage heat exchanger 18 flows into the second four-way valve 36. Because the refrigerant circuit 1 has switched to the thermal storage heating cycle, the low-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the third branch portion 41 via the second four-way valve 36, and then flows into the suction pipe 7 of the compressor 2 via the third branch portion 41. By performing this type of thermal storage heating operation, the air conditioner can, for example, heat the room while defrosting frost that has formed on the outdoor heat exchanger 3.

[0051] The control device 81 determines whether the thermal storage utilization conditions are no longer met while the thermal storage utilization heating operation is being performed. For example, the control device 81 determines that the thermal storage utilization conditions are no longer met when the time during which the thermal storage utilization heating operation is performed exceeds a predetermined time, or after the outdoor heat exchanger 3 is defrosted. When it is determined that the thermal storage utilization conditions are no longer met, the air conditioner ends the thermal storage utilization heating operation and starts normal heating operation.

[0052] FIG. 7 is a flowchart showing the second heat-storage heating operation. When the second heat-storage heating operation is started, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the second heat-storage heating cycle. When the second heat-storage heating operation is started, the control device 81 further controls the opening degree of the first heat-storage expansion valve 21 to a predetermined opening degree so that the refrigerant flows through the heat-storage heat exchanger 18, and controls the opening degree of the second heat-storage expansion valve 22 so that the heat storage rate at which heat is stored in the heat storage material 64 is constant. Here, the predetermined opening degree is, for example, a fixed value that is determined in advance so that the refrigerant dryness at the heat-storage heat exchanger outlet becomes an appropriate value (for example, the degree of subcooling = 0 and the refrigerant dryness is 0 to 0.1). When the second heat-storage heating operation is started, the control device 81 further opens the bypass expansion valve 53 so that the refrigerant flows through the bypass heat exchanger 52 (step S6).

[0053] The high-pressure gas-phase refrigerant discharged from the compressor 2 flows into the first branch section 15 and is split into two at the first branch section 15. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first four-way valve 32. The high-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the indoor heat exchanger 6 via the first four-way valve 32 because the refrigerant circuit 1 has switched to the second heat-storage heating cycle.

[0054] The indoor heat exchanger 6 exchanges heat between the high-pressure gas-phase refrigerant and the air in the room where the indoor unit is installed, heating the indoor air and cooling the high-pressure gas-phase refrigerant. The indoor unit blows the air heated by the indoor heat exchanger 6 into the room to heat the room. The high-pressure gas-phase refrigerant is cooled and condensed in the indoor heat exchanger 6, becoming a supercooled high-pressure liquid-phase refrigerant, which flows out of the indoor heat exchanger 6. In other words, the indoor heat exchanger 6 functions as a condenser when the second heat-storage heating operation is performed. The high-pressure liquid-phase refrigerant that flows out of the indoor heat exchanger 6 flows into the main expansion valve 5. The main expansion valve 5 decompresses the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is decompressed by the main expansion valve 5, becoming a low-pressure gas-liquid two-phase refrigerant, which flows out of the main expansion valve 5.

[0055] The other high-pressure gas-phase refrigerant of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first heat-storage expansion valve 21 and then flows into the second four-way valve 36 via the first heat-storage expansion valve 21. Because the refrigerant circuit 1 is switched to the second heat-storage heating cycle, the high-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the heat-storage heat exchanger 18 via the second four-way valve 36. The heat-storage heat exchanger 18 exchanges heat between the high-pressure gas-phase refrigerant and the heat storage material 64, heating the heat storage material 64 and cooling the high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is cooled and condensed in the heat-storage heat exchanger 18, becoming a supercooled high-pressure liquid-phase refrigerant that flows out of the heat-storage heat exchanger 18. That is, the heat-storage heat exchanger 18 functions as a condenser when the second heat-storage heating operation is performed. The high-pressure liquid-phase refrigerant that has flowed out of the heat-storage heat exchanger 18 flows into the second heat-storage expansion valve 22. The second heat-storage expansion valve 22 depressurizes the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is depressurized by the second heat-storage expansion valve 22 and becomes a low-pressure gas-liquid two-phase refrigerant, which then flows out of the second heat-storage expansion valve 22.

[0056] The low-pressure gas-liquid two-phase refrigerant flowing out of the main expansion valve 5 and the low-pressure gas-liquid two-phase refrigerant flowing out of the second heat-storage expansion valve 22 flow into the second branch section 16 and merge there. The low-pressure gas-liquid two-phase refrigerant merged at the second branch section 16 flows into the fifth branch section 55 and splits into two at the fifth branch section 55. One of the low-pressure gas-liquid two-phase refrigerant split at the fifth branch section 55 flows into the outdoor heat exchanger 3. The outdoor heat exchanger 3 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the outdoor air, absorbing heat from the outdoor air to heat the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the outdoor heat exchanger 3, becoming low-pressure gas-phase refrigerant, which flows out of the outdoor heat exchanger 3. That is, the outdoor heat exchanger 3 functions as an evaporator when the second heat-storage heating operation is performed.

[0057] The other of the low-pressure gas-liquid two-phase refrigerant split at the fifth branch portion 55 flows into the bypass expansion valve 53 and then flows into the bypass heat exchanger 52 via the bypass expansion valve 53. The bypass heat exchanger 52 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the heat storage material 64, cooling the heat storage material 64 and heating the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the bypass heat exchanger 52, becoming low-pressure gas-phase refrigerant and flowing out of the bypass heat exchanger 52. That is, the bypass heat exchanger 52 functions as an evaporator when the second heat-storage heating operation is performed.

[0058] The low-pressure gas-phase refrigerant flowing out from the outdoor heat exchanger 3 and the low-pressure gas-phase refrigerant flowing out from the bypass expansion valve 53 flow into the fourth branch portion 54 and are joined at the fourth branch portion 54. The low-pressure gas-phase refrigerant joined at the fourth branch portion 54 flows into the second four-way valve 36. Because the refrigerant circuit 1 is switched to the second heat-storage heating cycle, the low-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the third branch portion 41 via the second four-way valve 36, and then flows into the suction pipe 7 of the compressor 2 via the third branch portion 41.

[0059] Because the heat storage heat exchanger 18 functions as a condenser, the heat storage heat exchange portion 72 of the heat storage material 64 is heated by the heat storage heat exchanger 18, and the temperature increases. Because the bypass heat exchanger 52 functions as an evaporator, the bypass heat exchange portion 71 of the heat storage material 64 is cooled by the bypass heat exchanger 52, and the temperature decreases. When the second heat storage heating operation is being performed, the heat storage heat exchange portion 72 of the heat storage material 64 is heated by the heat storage heat exchanger 18, and the heat storage material 64 convects inside the heat storage container 63. The temperature of the bypass heat exchange portion 71 of the heat storage material 64 increases due to the convection of the heat storage material 64. Because the temperature of the bypass heat exchange portion 71 increases, the air conditioner can ensure a temperature difference between the low-pressure gas-liquid two-phase refrigerant and the bypass heat exchange portion 71 of the heat storage material 64, and can increase the amount of heat exchange between the low-pressure gas-liquid two-phase refrigerant of the bypass heat exchanger 52 and the heat storage material 64.

[0060] After the bypass expansion valve 53 is opened in step S6, or when it is determined that the thermal storage utilization condition is not satisfied (No in step S4 in FIG. 6 ), the control device 81 acquires the thermal storage material temperature measured by the thermal storage material temperature sensor 74 from the thermal storage material temperature sensor 74. The control device 81 adjusts the aperture of the first thermal storage expansion valve 21, the aperture of the second thermal storage expansion valve 22, and the aperture of the bypass expansion valve 53 so that the amount of thermal storage stored in the thermal storage material 64 by the thermal storage heat exchanger 18 is approximately equal to the amount of thermal release from the thermal storage material 64 by the bypass heat exchanger 52, that is, so that the thermal storage material temperature measured by the thermal storage material temperature sensor 74 becomes constant (step S7). While the second thermal storage heating operation is being performed, the control device 81 calculates the amount of thermal storage based on the thermal storage material temperature measured by the thermal storage material temperature sensor 74, and determines whether the amount of thermal storage is equal to or greater than the first heating thermal storage threshold value plus a predetermined value α (step S8). Here, the predetermined value α is a heat storage amount that, for example, when the change in the heat storage amount over time is decreasing, adjusts the opening degrees of the first heat storage expansion valve 21, the second heat storage expansion valve 22, and the bypass expansion valve 53, and switches the change in the heat storage amount over time to an increase without falling below the first heating-mode heat storage threshold. Because the temperature measurement portion 73 is disposed between the bypass heat exchange portion 71 and the heat-storage heat exchange portion 72, the temperature of the temperature measurement portion 73 is closer to the average temperature of the entire heat storage material 64 than the temperatures of the bypass heat exchange portion 71 and the heat-storage heat exchange portion 72, even when the bypass heat exchange portion 71 is cooled and the heat-storage heat exchange portion 72 is heated. The control device 81 can appropriately calculate the heat storage amount of the heat storage material 64 because the heat storage material temperature sensor 74 measures the temperature of the temperature measurement portion 73. When it is determined that the amount of stored heat is equal to or greater than the first heating-mode heat storage threshold plus the predetermined value α (step S8, Yes), the control device 81 determines whether the amount of stored heat is equal to or greater than the second heating-mode heat storage threshold (step S9).When it is determined that the amount of stored heat is smaller than the second heating-mode heat storage threshold (step S9, No), the control device 81 determines whether the heat storage utilization condition is met (step S4 in FIG. 6).

[0061] When it is determined that the amount of stored heat is smaller than the first heating-mode heat storage threshold plus the predetermined value α (step S8, No), or when it is determined that the amount of stored heat is equal to or larger than the second heating-mode heat storage threshold (step S9, Yes), the control device 81 adjusts the aperture of the first heat-storage expansion valve 21, the aperture of the second heat-storage expansion valve 22, and the aperture of the bypass expansion valve 53 (step S10). That is, when it is determined that the amount of stored heat is smaller than the first heating-mode heat storage threshold plus the predetermined value α, the control device 81 increases the aperture of the first heat-storage expansion valve 21 and the second heat-storage expansion valve 22 and decreases the aperture of the bypass expansion valve 53. At this time, the amount of heat heated by the heat storage heat exchanger 18 to the heat storage material 64 becomes larger than the amount of heat cooled by the bypass heat exchanger 52 to the heat storage material 64, and the amount of stored heat in the heat storage material 64 increases. When it is determined that the amount of stored heat is greater than the second heating-time heat storage threshold, the control device 81 decreases the opening of the first heat storage expansion valve 21 and the second heat storage expansion valve 22, and increases the opening of the bypass expansion valve 53. At this time, the amount of heat heated in the heat storage material 64 by the heat storage heat exchanger 18 becomes smaller than the amount of heat cooled in the heat storage material 64 by the bypass heat exchanger 52, and the amount of heat stored in the heat storage material 64 decreases.

[0062] When heating a room, the air conditioner performs first and second heat storage heating operations, thereby reducing the heating capacity. This allows the air conditioner to reduce the heating capacity even when the heating load is low, without performing intermittent operation, which stops and starts the compressor 2. A typical air conditioner may operate the indoor unit fan even when the compressor is stopped due to intermittent operation, in order to properly detect the room temperature. For this reason, when the compressor stops during heating, a typical air conditioner blows out cold air. When the compressor stops during cooling, condensation on the indoor heat exchanger evaporates, causing moisture return, reducing comfort. The air conditioner of this embodiment does not perform intermittent operation when the heating load is low, thereby preventing a decrease in comfort when the heating load is low.

[0063] FIG. 8 is a graph showing changes in the amount of heat storage when the first heat storage heating operation, the second heat storage heating operation, and the heat storage utilization heating operation are being performed. When the first heat storage heating operation is being performed, the heat storage material 64 is heated by the heat storage heat exchanger 18, and the amount of heat storage increases over time until the heat storage material 64 becomes equal to the first heat storage threshold. When the second heat storage heating operation is being performed, the heat storage material 64 is heated by the heat storage heat exchanger 18 and cooled by the bypass heat exchanger 52, and the amount of heat storage is maintained in a range greater than the first heat storage threshold and less than the second heat storage threshold. When the heat storage utilization heating operation is being performed, the heat storage material 64 is cooled by the heat storage heat exchanger 18, and the amount of heat storage decreases over time. When the second heat storage heating operation is performed, the air conditioner can increase the amount of heat stored in the heat storage material 64 to or above the first heat storage threshold, and can properly perform the heat storage utilization heating operation. For example, when the first heating-time heat storage threshold is calculated based on the amount of heat required to defrost the frost formed on the outdoor heat exchanger 3, the air conditioner performs the second heat storage heating operation, thereby being able to sufficiently defrost the outdoor heat exchanger 3. In other words, the first heating-time heat storage threshold is determined in advance so that the heat storage heating operation is performed appropriately.

[0064] An air conditioner operates in the same way when cooling a room as when heating a room. That is, when cooling is selected by a user operation, the air conditioner starts normal cooling operation. When normal cooling operation starts, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the normal cooling cycle. When normal cooling operation starts, the control device 81 also fully opens the first heat storage expansion valve 21 to allow refrigerant to flow to the outdoor heat exchanger 3, and fully closes the second heat storage expansion valve 22 to prevent refrigerant from flowing to the heat storage heat exchanger 18. When normal cooling operation starts, the control device 81 also fully closes the bypass expansion valve 53 to prevent refrigerant from flowing to the bypass heat exchanger 52.

[0065] The high-pressure gas-phase refrigerant discharged from the compressor 2 to the discharge pipe 8 flows into the first branch section 15 and is split into two at the first branch section 15. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first heat storage expansion valve 21 and flows into the second four-way valve 36 via the first heat storage expansion valve 21. The other of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first four-way valve 32. Because the refrigerant circuit 1 is switched to the normal cooling cycle, the high-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into flow path 45 via the first four-way valve 32 and into the check valve 38 via flow path 45. The pressure of the refrigerant in flow path 45 becomes higher than the pressure of the refrigerant in flow path 46 due to the high-pressure gas-phase refrigerant flowing into flow path 45. The high-pressure gas-phase refrigerant that has flowed into the check valve 38 flows into the sixth branch portion 42 via the check valve 38 because the pressure of the refrigerant in the flow path 45 is higher than the pressure of the refrigerant in the flow path 46, and then flows into the second four-way valve 36 via the sixth branch portion 42. The high-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the outdoor heat exchanger 3 via the second four-way valve 36 because the refrigerant circuit 1 has switched to the normal cooling cycle.

[0066] The outdoor heat exchanger 3 exchanges heat between the high-pressure gas-phase refrigerant and outdoor air, cooling the high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is cooled and condensed in the outdoor heat exchanger 3 to become a high-pressure liquid-phase refrigerant, which then flows out of the outdoor heat exchanger 3. That is, the outdoor heat exchanger 3 functions as a condenser when normal cooling operation is performed.

[0067] The high-pressure liquid-phase refrigerant flowing out from the outdoor heat exchanger 3 flows into the main expansion valve 5. The main expansion valve 5 reduces the pressure of the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is reduced in pressure by the main expansion valve 5 to become a low-pressure two-phase gas-liquid refrigerant, which flows out from the main expansion valve 5. The low-pressure two-phase gas-liquid refrigerant flowing out from the main expansion valve 5 flows into the indoor heat exchanger 6. The indoor heat exchanger 6 exchanges heat between the low-pressure two-phase gas-liquid refrigerant and the indoor air, heating the low-pressure two-phase gas-liquid refrigerant and cooling the indoor air. The indoor unit blows the air cooled by the indoor heat exchanger 6 into the room to cool the room. The low-pressure two-phase gas-liquid refrigerant is heated and evaporated in the indoor heat exchanger 6, becoming a low-pressure gas-phase refrigerant, which flows out from the indoor heat exchanger 6. In other words, the indoor heat exchanger 6 functions as an evaporator during normal cooling operation.

[0068] The low-pressure gas-phase refrigerant flowing out from the indoor heat exchanger 6 flows into the first four-way valve 32. The low-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the suction pipe 7 of the compressor 2 via the first four-way valve 32 because the refrigerant circuit 1 has switched to the normal cooling cycle.

[0069] While normal cooling operation is being performed, the control device 81 controls the rotation speed of the compressor 2 in the same way as when normal heating operation is being performed. While normal cooling operation is being performed, the control device 81 further determines whether the air conditioning load is low. For example, when the compressor rotation speed is greater than the lower limit rotation speed, the control device 81 determines that the air conditioning load is not low, and when the compressor rotation speed is equal to or less than the lower limit rotation speed, the control device 81 determines that the air conditioning load is low. When it is determined that the air conditioning load is not low, the control device 81 continues to perform normal cooling operation. When it is determined that the air conditioning load is low, the control device 81 starts the first cold storage cooling operation.

[0070] When the first cold-storage cooling operation is started, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the first cold-storage cooling cycle. When the first cold-storage cooling operation is started, the control device 81 also sets the aperture of the second heat-storage expansion valve 22 to a predetermined aperture so that the refrigerant flows to the heat-storage heat exchanger 18. Here, the predetermined aperture is, for example, an aperture that ensures an appropriate degree of superheat in the heat-storage heat exchanger 18, an aperture that ensures a constant cold-storage speed, or a fixed value. When the first cold-storage cooling operation is started, the control device 81 also fully closes the bypass expansion valve 53 so that the refrigerant does not flow to the bypass heat exchanger 52.

[0071] The high-pressure gas-phase refrigerant discharged from the compressor 2 flows into the first branch section 15 and is split into two at the first branch section 15. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first heat-storage expansion valve 21 and flows into the second four-way valve 36 via the first heat-storage expansion valve 21. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first four-way valve 32. Because the refrigerant circuit 1 is switched to the first cold-storage cooling cycle, the high-pressure gas-phase refrigerant that flows into the first four-way valve 32 flows into the check valve 38 via the first four-way valve 32 and then flows into the second four-way valve 36 via the check valve 38. Because the refrigerant circuit 1 is switched to the first cold-storage cooling cycle, the high-pressure gas-phase refrigerant that flows into the second four-way valve 36 flows into the outdoor heat exchanger 3 via the second four-way valve 36.

[0072] The outdoor heat exchanger 3 exchanges heat between the high-pressure gas phase refrigerant and outdoor air, cooling the high-pressure gas phase refrigerant. The high-pressure gas phase refrigerant is cooled and condensed in the outdoor heat exchanger 3 to become a high-pressure liquid phase refrigerant, which then flows out of the outdoor heat exchanger 3. That is, the outdoor heat exchanger 3 functions as a condenser when the first cold-storage cooling operation is performed. The high-pressure liquid phase refrigerant that has flowed out of the outdoor heat exchanger 3 flows into the second branch section 16, where it is split into two.

[0073] One of the high-pressure liquid-phase refrigerants split at the second branch 16, a high-pressure gas-phase refrigerant, flows into the main expansion valve 5. The main expansion valve 5 decompresses the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is decompressed by the main expansion valve 5 to become a low-pressure gas-liquid two-phase refrigerant, which flows out of the main expansion valve 5. The low-pressure gas-liquid two-phase refrigerant flowing out of the main expansion valve 5 flows into the indoor heat exchanger 6. The indoor heat exchanger 6 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the indoor air, heating the low-pressure gas-liquid two-phase refrigerant and cooling the indoor air. The indoor unit blows the air cooled by the indoor heat exchanger 6 into the room to cool the room. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the indoor heat exchanger 6, becoming a low-pressure gas-phase refrigerant, which flows out of the indoor heat exchanger 6. In other words, the indoor heat exchanger 6 functions as an evaporator when the first cold-storage cooling operation is performed. The low-pressure gas-phase refrigerant flowing out from the indoor heat exchanger 6 flows into the first four-way valve 32. The low-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the third branch portion 41 via the first four-way valve 32 because the refrigerant circuit 1 has switched to the first cold-storage cooling cycle.

[0074] The other high-pressure gas-phase refrigerant of the high-pressure liquid-phase refrigerant split at the second branch section 16 flows into the second heat storage expansion valve 22. The second heat storage expansion valve 22 depressurizes the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is depressurized by the second heat storage expansion valve 22 to become a low-pressure gas-liquid two-phase refrigerant, which flows out of the second heat storage expansion valve 22. The low-pressure gas-liquid two-phase refrigerant flowing out of the second heat storage expansion valve 22 flows into the heat storage heat exchanger 18. The heat storage heat exchanger 18 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the heat storage material 64, heating the low-pressure gas-liquid two-phase refrigerant and cooling the heat storage material 64. The amount of heat stored in the heat storage material 64 increases as the heat storage material 64 is cooled. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the heat storage heat exchanger 18, becoming a low-pressure gas-liquid refrigerant, which flows out of the heat storage heat exchanger 18. That is, when the first cold-storage cooling operation is performed, the heat storage heat exchanger 18 functions as an evaporator. The low-pressure gas-phase refrigerant flowing out of the heat storage heat exchanger 18 flows into the second four-way valve 36. The low-pressure gas-phase refrigerant flowing into the second four-way valve 36 flows into the third branch portion 41 via the second four-way valve 36 because the refrigerant circuit 1 is switched to the first cold-storage cooling cycle.

[0075] The low-pressure gas-phase refrigerant that flows from the first four-way valve 32 to the third branch portion 41 and the low-pressure gas-phase refrigerant that flows from the second four-way valve 36 to the third branch portion 41 join together at the third branch portion 41. The low-pressure gas-phase refrigerant that joins together at the third branch portion 41 flows into the suction pipe 7 of the compressor 2.

[0076] While the first cold-storage cooling operation is being performed, the control device 81 periodically acquires the heat storage material temperature measured by the heat storage material temperature sensor 74 from the heat storage material temperature sensor 74 and calculates the amount of heat storage based on the heat storage material temperature. When the amount of heat storage is smaller than the first cold-storage threshold during cooling, the control device 81 continues to perform the first cold-storage cooling operation. When the amount of heat storage is equal to or greater than the first cold-storage threshold during cooling, the air conditioner starts the second cold-storage cooling operation.

[0077] When the second cold-storage cooling operation is started, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the second cold-storage cooling cycle. When the second cold-storage cooling operation is started, the control device 81 also sets the opening degree of the second heat-storage expansion valve 22 to a predetermined opening degree so that the refrigerant flows to the heat-storage heat exchanger 18. Here, the predetermined opening degree is, for example, an opening degree that ensures an appropriate degree of superheat in the heat-storage heat exchanger 18, an opening degree that ensures a constant cold-storage speed, or a fixed value. When the second cold-storage cooling operation is started, the control device 81 also opens the bypass expansion valve 53 so that the refrigerant flows to the bypass heat exchanger 52.

[0078] The high-pressure gas-phase refrigerant discharged from the compressor 2 flows into the first branch section 15 and is split into two at the first branch section 15. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first heat-storage expansion valve 21 and flows into the second four-way valve 36 via the first heat-storage expansion valve 21. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first four-way valve 32. Because the refrigerant circuit 1 is switched to the second cold-storage cooling cycle, the high-pressure gas-phase refrigerant that flows into the first four-way valve 32 flows into the check valve 38 via the first four-way valve 32 and into the second four-way valve 36 via the check valve 38. Because the refrigerant circuit 1 is switched to the second cold-storage cooling cycle, the high-pressure gas-phase refrigerant that flows into the second four-way valve 36 flows into the fourth branch section 54 via the second four-way valve 36. The high-pressure gas-phase refrigerant that has flowed into the fourth branch portion is divided into two at the fourth branch portion .

[0079] One of the high-pressure gas-phase refrigerants split at the fourth branch section 54 flows into the outdoor heat exchanger 3. The outdoor heat exchanger 3 exchanges heat between the high-pressure gas-phase refrigerant and outdoor air, cooling the high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is cooled and condensed in the outdoor heat exchanger 3, becoming a high-pressure liquid-phase refrigerant, which flows out of the outdoor heat exchanger 3. In other words, the outdoor heat exchanger 3 functions as a condenser when the second cold-storage cooling operation is performed. The high-pressure liquid-phase refrigerant that flows out of the outdoor heat exchanger 3 flows into the fifth branch section 55.

[0080] The other high-pressure gas phase refrigerant of the high-pressure gas phase refrigerant split at the fourth branch section 54 flows into the bypass heat exchanger 52. The bypass heat exchanger 52 exchanges heat between the high-pressure gas phase refrigerant and the heat storage material 64, cooling the high-pressure gas phase refrigerant and heating the heat storage material 64. The high-pressure gas phase refrigerant is cooled and condensed in the bypass heat exchanger 52 to become a high-pressure liquid phase refrigerant, which flows out of the bypass heat exchanger 52. In other words, the bypass heat exchanger 52 functions as a condenser when the second cold-storage cooling operation is performed. The high-pressure liquid phase refrigerant that flows out of the bypass heat exchanger 52 flows into the bypass expansion valve 53 and flows into the fifth branch section 55 via the bypass expansion valve 53.

[0081] The high-pressure liquid-phase refrigerant that has flowed into the fifth branch portion 55 from the outdoor heat exchanger 3 and the high-pressure liquid-phase refrigerant that has flowed into the fifth branch portion 55 from the bypass expansion valve 53 are joined at the fifth branch portion 55. The high-pressure liquid-phase refrigerant that has flowed into the fifth branch portion 55 flows into the second branch portion 16. The high-pressure liquid-phase refrigerant that has flowed into the second branch portion 16 is split into two at the second branch portion 16.

[0082] One of the high-pressure liquid-phase refrigerants split into two at the second branch section 16 flows into the main expansion valve 5. The main expansion valve 5 decompresses the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is decompressed by the main expansion valve 5 to become a low-pressure two-phase gas-liquid refrigerant, which flows out of the main expansion valve 5. The low-pressure two-phase gas-liquid refrigerant flowing out of the main expansion valve 5 flows into the indoor heat exchanger 6. The indoor heat exchanger 6 exchanges heat between the low-pressure two-phase gas-liquid refrigerant and the indoor air, heating the low-pressure two-phase gas-liquid refrigerant and cooling the indoor air. The indoor unit blows the air cooled by the indoor heat exchanger 6 into the room to cool the room. The low-pressure two-phase gas-liquid refrigerant is heated and evaporated in the indoor heat exchanger 6, becoming a low-pressure gas-phase refrigerant, which flows out of the indoor heat exchanger 6. In other words, the indoor heat exchanger 6 functions as an evaporator when the second cold-storage cooling operation is performed. The low-pressure gas-phase refrigerant flowing out from the indoor heat exchanger 6 flows into the first four-way valve 32. The low-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the third branch portion 41 via the first four-way valve 32 because the refrigerant circuit 1 has switched to the second cold-storage cooling cycle.

[0083] The other of the two high-pressure liquid-phase refrigerants split by the second branch section 16 flows into the second heat storage expansion valve 22. The second heat storage expansion valve 22 depressurizes the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is depressurized by the second heat storage expansion valve 22 to become a low-pressure gas-liquid two-phase refrigerant, which flows out of the second heat storage expansion valve 22. The low-pressure gas-liquid two-phase refrigerant flowing out of the second heat storage expansion valve 22 flows into the heat storage heat exchanger 18. The heat storage heat exchanger 18 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the heat storage material 64, heating the low-pressure gas-liquid two-phase refrigerant and cooling the heat storage material 64. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the heat storage heat exchanger 18, becoming a low-pressure gas-phase refrigerant, which flows out of the heat storage heat exchanger 18. That is, the heat storage heat exchanger 18 functions as an evaporator when the second cold-storage cooling operation is performed. The low-pressure gas-phase refrigerant flowing out of the heat-storage heat exchanger 18 flows into the second four-way valve 36. The low-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the third branch portion 41 via the second four-way valve 36 because the refrigerant circuit 1 has switched to the second cold-storage cooling cycle.

[0084] The low-pressure gas-phase refrigerant that flows from the first four-way valve 32 to the third branch portion 41 and the low-pressure gas-phase refrigerant that flows from the second four-way valve 36 to the third branch portion 41 join together at the third branch portion 41. The low-pressure gas-phase refrigerant that joins together at the third branch portion 41 flows into the suction pipe 7 of the compressor 2.

[0085] While the second cold-storage cooling operation is being performed, the control device 81 acquires the heat storage material temperature measured by the heat storage material temperature sensor 74 from the heat storage material temperature sensor 74, and adjusts the aperture of the first heat storage expansion valve 21, the aperture of the second heat storage expansion valve 22, and the aperture of the bypass expansion valve 53 so that the heat storage material temperature is constant. While the second cold-storage cooling operation is being performed, the control device 81 further calculates the amount of heat storage based on the heat storage material temperature measured by the heat storage material temperature sensor 74. When the control device 81 determines that the amount of heat storage is smaller than the value obtained by adding a predetermined value β to the first cooling-mode cold storage threshold value, the control device 81 increases the aperture of the second heat storage expansion valve 22 and decreases the aperture of the bypass expansion valve 53. Here, the predetermined value β is a heat storage amount that, for example, when the change in the heat storage amount over time is decreasing, adjusts the apertures of the first heat storage expansion valve 21, the second heat storage expansion valve 22, and the bypass expansion valve 53 to switch the change in the heat storage amount over time to an increase without falling below the first cooling-mode cold-storage threshold. At this time, the amount of heat cooled in the heat storage material 64 by the heat-storage heat exchanger 18 becomes greater than the amount of heat heated in the heat storage material 64 by the bypass heat exchanger 52, and the amount of heat stored in the heat storage material 64 increases. When the control device 81 determines that the heat storage amount is greater than the second cooling-mode cold-storage threshold, it decreases the aperture of the second heat-storage expansion valve 22 and increases the aperture of the bypass expansion valve 53. At this time, the amount of heat cooled in the heat storage material 64 by the heat-storage heat exchanger 18 becomes smaller than the amount of heat heated in the heat storage material 64 by the bypass heat exchanger 52, and the amount of heat stored in the heat storage material 64 decreases. For this reason, when the air conditioner is performing the second cold-storage cooling operation, the cold-storage threshold value is maintained in a range greater than the first cold-storage threshold value during cooling and less than the second cold-storage threshold value during cooling.

[0086] When cooling a room, the air conditioner performs the first cold storage cooling operation and the second cold storage cooling operation, thereby reducing the cooling capacity, and can reduce the cooling capacity without performing intermittent operation even when the cooling load is low.By not performing intermittent operation when the cooling load is low, the air conditioner can prevent a decrease in comfort when the cooling load is low.

[0087] While the second cold storage cooling operation is being performed, the control device 81 further determines whether the cold storage utilization condition is met. For example, the control device 81 determines that the cold storage utilization condition is met during extreme summer heat. When it is determined that the cold storage utilization condition is not met, the air conditioner continues to perform the second cold storage cooling operation. When it is determined that the cold storage utilization condition is met, the air conditioner starts the cold storage utilization heating operation.

[0088] When the cold storage cooling operation is started, the control device 81 controls the flow path switching unit 31 to switch the refrigerant circuit 1 to the cold storage cooling cycle. When the cold storage cooling operation is started, the control device 81 also fully closes the second heat storage expansion valve 22 so that the refrigerant does not flow to the heat storage heat exchanger 18. When the cold storage cooling operation is started, the control device 81 also fully opens the bypass expansion valve 53 so that the refrigerant flows to the bypass heat exchanger 52.

[0089] The high-pressure gas-phase refrigerant discharged from the compressor 2 flows into the first branch section 15 and is split into two at the first branch section 15. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first heat storage expansion valve 21 and flows into the second four-way valve 36 via the first heat storage expansion valve 21. One of the high-pressure gas-phase refrigerant split at the first branch section 15 flows into the first four-way valve 32. Because the refrigerant circuit 1 has switched to the cold storage cooling cycle, the high-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the check valve 38 via the first four-way valve 32 and into the second four-way valve 36 via the check valve 38. Because the refrigerant circuit 1 has switched to the cold storage cooling cycle, the high-pressure gas-phase refrigerant that has flowed into the second four-way valve 36 flows into the fourth branch section 54 via the second four-way valve 36. The high-pressure gas-phase refrigerant that has flowed into the fourth branch portion is divided into two at the fourth branch portion .

[0090] One of the high-pressure gas-phase refrigerants split at the fourth branch section 54 flows into the outdoor heat exchanger 3. The outdoor heat exchanger 3 exchanges heat between the high-pressure gas-phase refrigerant and outdoor air, cooling the high-pressure gas-phase refrigerant. The high-pressure gas-phase refrigerant is cooled and condensed in the outdoor heat exchanger 3, becoming a high-pressure liquid-phase refrigerant, which flows out of the outdoor heat exchanger 3. In other words, the outdoor heat exchanger 3 functions as a condenser when the cold storage cooling operation is performed. The high-pressure liquid-phase refrigerant that flows out of the outdoor heat exchanger 3 flows into the fifth branch section 55.

[0091] The other high-pressure gas phase refrigerant of the high-pressure gas phase refrigerant split at the fourth branch section 54 flows into the bypass heat exchanger 52. The bypass heat exchanger 52 exchanges heat between the high-pressure gas phase refrigerant and the heat storage material 64, cooling the high-pressure gas phase refrigerant and heating the heat storage material 64. The high-pressure gas phase refrigerant is cooled and condensed in the bypass heat exchanger 52 to become a high-pressure liquid phase refrigerant, which flows out of the bypass heat exchanger 52. In other words, the bypass heat exchanger 52 functions as a condenser when the cold-storage-utilizing cooling operation is performed. The high-pressure liquid phase refrigerant that flows out of the bypass heat exchanger 52 flows into the bypass expansion valve 53 and flows into the fifth branch section 55 via the bypass expansion valve 53.

[0092] The high-pressure gas-phase refrigerant that flows from the outdoor heat exchanger 3 into the fifth branch section 55 and the high-pressure gas-phase refrigerant that flows from the bypass expansion valve 53 into the fifth branch section 55 join at the fifth branch section 55. The high-pressure gas-phase refrigerant that joins at the fifth branch section 55 flows into the main expansion valve 5. The main expansion valve 5 depressurizes the high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is depressurized by the main expansion valve 5 to become a low-pressure gas-liquid two-phase refrigerant, which flows out of the main expansion valve 5. The low-pressure gas-liquid two-phase refrigerant that flows out of the main expansion valve 5 flows into the indoor heat exchanger 6. The indoor heat exchanger 6 exchanges heat between the low-pressure gas-liquid two-phase refrigerant and the indoor air, heating the low-pressure gas-liquid two-phase refrigerant and cooling the indoor air. The indoor unit blows the air cooled by the indoor heat exchanger 6 into the room to cool the room. The low-pressure gas-liquid two-phase refrigerant is heated and evaporated in the indoor heat exchanger 6, becoming a low-pressure gas-phase refrigerant, which then flows out of the indoor heat exchanger 6. That is, the indoor heat exchanger 6 functions as an evaporator when the cold storage cooling operation is performed.

[0093] The low-pressure gas-phase refrigerant that flows out of the indoor heat exchanger 6 flows into the first four-way valve 32. Because the refrigerant circuit 1 has switched to the cold storage cooling cycle, the low-pressure gas-phase refrigerant that has flowed into the first four-way valve 32 flows into the suction pipe 7 of the compressor 2. By performing this cold storage cooling operation, the air conditioner can, for example, cool the room while reducing power consumption.

[0094] The control device 81 determines whether the cold storage utilization conditions are no longer met while the cold storage utilization cooling operation is being performed. For example, the control device 81 determines that the cold storage utilization conditions are no longer met after the end of a hot summer. When it is determined that the cold storage utilization conditions are no longer met, the air conditioner ends the cold storage utilization cooling operation and starts normal cooling operation.

[0095] By performing the first cold storage cooling operation and the second cold storage cooling operation, the air conditioner can reduce its cooling capacity, and can reduce its cooling capacity without performing intermittent operation even when the cooling load is low. By not performing intermittent operation when the cooling load is low, the air conditioner can prevent a decrease in comfort when the cooling load is low. Furthermore, by performing the second cold storage cooling operation, the air conditioner can increase the amount of heat stored in the heat storage material 64 to equal or exceed the first cooling cold storage threshold, allowing the air conditioner to appropriately perform the cold storage cooling operation at a predetermined time. For example, when the first cooling cold storage threshold is calculated based on the duration of a particularly hot summer period, the air conditioner can appropriately perform peak-cut cooling operation to reduce power consumption during the particularly hot summer period by performing the cold storage cooling operation during the particularly hot summer period. In other words, the first heating cold storage threshold is predetermined so that the cold storage cooling operation is appropriately performed.

[0096] [Effects of the air conditioner of the embodiment] The air conditioner of the embodiment includes a compressor 2, an outdoor heat exchanger 3, a main expansion valve 5, an indoor heat exchanger 6, a heat storage flow path 17, a heat storage heat exchanger 18, a flow path switching unit 31, a first refrigerant pipe 11, a second refrigerant pipe 12, a third refrigerant pipe 14, a bypass flow path 51, a bypass heat exchanger 52, a bypass expansion valve 53, and a control unit 87. The heat storage flow path 17 is connected to the first refrigerant pipe 11 and the second refrigerant pipe 12. The heat storage heat exchanger 18 exchanges heat between the refrigerant flowing through the heat storage flow path 17 and a heat storage material 64. The flow path switching unit 31 is provided on the discharge side of the compressor 2 and switches the flow path so that the refrigerant discharged from the compressor 2 flows to one or two of the outdoor heat exchanger 3, the indoor heat exchanger 6, and the heat storage heat exchanger 18. The first refrigerant pipe 11 connects the flow path switching unit 31 and the outdoor heat exchanger 3. The second refrigerant pipe 12 connects the outdoor heat exchanger 3 and the main expansion valve 5. The third refrigerant pipe 14 connects the main expansion valve 5 and the indoor heat exchanger 6. The bypass flow path 51 has one end connected to the first refrigerant pipe 11 and the other end connected to the second refrigerant pipe 12. The bypass heat exchanger 52 exchanges heat between the refrigerant flowing through the bypass flow path 51 and the heat storage material 64. The bypass expansion valve 53 adjusts the amount of refrigerant flowing through the bypass flow path 51. During the first heat-storage heating operation or the first cold-storage cooling operation, when the heat storage amount, which is the absolute value of the amount of heat stored in the heat storage material 64, is smaller than the first heating heat storage threshold or the first cooling cold storage threshold, the control unit 87 controls the bypass expansion valve 53 so that the refrigerant does not flow into the bypass flow path 51. During the first heat-storage heating operation, the indoor heat exchanger 6 and the heat storage heat exchanger 18 function as condensers. In the first cold-storage cooling operation, the indoor heat exchanger 6 and the heat-storage heat exchanger 18 function as evaporators. The control unit 87 controls the bypass expansion valve 53 so that the refrigerant flows into the bypass flow path 51 when the amount of stored heat is equal to or greater than the first heating-mode heat storage threshold or the first cooling-mode cold-storage threshold.

[0097] This type of air conditioner can reduce the air conditioning capacity by storing heat in the heat storage material 64 using the heat storage heat exchanger 18 so that the amount of heat stored in the heat storage material 64 increases, and can reduce the air conditioning capacity without performing intermittent operation even when the air conditioning load is low. By not performing intermittent operation when the air conditioning load is low, this type of air conditioner can prevent a decrease in comfort when the air conditioning load is low. Furthermore, when storing heat in the heat storage material 64 using the heat storage heat exchanger 18 so that the amount of heat stored increases, this air conditioner can exchange heat between the heat storage material 64 and the refrigerant using the bypass heat exchanger 52 so that the amount of heat stored decreases, and can maintain the amount of heat stored within a predetermined range.

[0098] Furthermore, the bypass expansion valve 53 of the air conditioner of the embodiment is provided in the bypass flow path 51 between the bypass heat exchanger 52 and the second refrigerant pipe 12. In such an air conditioner, when refrigerant flows into the bypass heat exchanger 52, a liquid-phase refrigerant or a two-phase gas-liquid refrigerant can be made to flow through the bypass expansion valve 53, reducing pressure loss and effectively adjusting the flow rate of refrigerant flowing into the bypass heat exchanger 52 even when the diameter of the bypass expansion valve 53 is small.

[0099] The air conditioner of the embodiment further includes a first heat storage expansion valve 21 provided between the compressor 2 and the flow path switching unit 31, and a second heat storage expansion valve 22 provided in the heat storage flow path 17 between the second refrigerant pipe 12 and the heat storage heat exchanger 18. In this case, the first heat storage expansion valve 21 adjusts the amount of refrigerant discharged from the compressor 2 and flowing through the heat storage heat exchanger 18 or the outdoor heat exchanger 3. The control unit 87 further controls the first heat storage expansion valve 21, the second heat storage expansion valve 22, and the bypass expansion valve 53 so that the amount of stored heat does not fall below the first heating-mode heat storage threshold. This air conditioner can appropriately adjust the flow rate of refrigerant flowing through the heat storage heat exchanger 18, appropriately adjust the amount of heat stored in the heat storage material 64, and maintain an appropriate amount of stored heat.

[0100] Furthermore, the control unit 87 of the air conditioner of the embodiment further controls the first heat storage expansion valve 21, the second heat storage expansion valve 22, and the bypass expansion valve 53 to reduce the amount of heat storage when the amount of stored heat is equal to or greater than the second heating heat storage threshold, which is greater than the first heating heat storage threshold. Because the amount of stored heat does not exceed the second heating heat storage threshold, such an air conditioner can continue operation without wasting the heat of the refrigerant flowing into the heat storage heat exchanger 18, and can suppress a decrease in energy efficiency.

[0101] Furthermore, the heat exchange capacity of the heat storage heat exchanger 18 of the air conditioner of the embodiment is greater than the heat exchange capacity of the bypass heat exchanger 52. Such an air conditioner can easily adjust the amount of heat stored in the heat storage material 64 using the heat storage heat exchanger 18, and can easily maintain the amount of heat stored in the heat storage material 64. Furthermore, such an air conditioner can ensure the heat exchange capacity of the heat storage heat exchanger 18, and can efficiently use the heat stored in the heat storage material 64 for other functions.

[0102] Furthermore, the heat storage heat exchanger 18 and the bypass heat exchanger 52 of the air conditioner of the embodiment are provided together with the heat storage material 64 inside a heat storage container 63 in which the heat storage material 64 is stored. The heat storage heat exchanger 18 and the bypass heat exchanger 52 include a plurality of fins 65 in thermal contact with the heat storage material 64 and a plurality of heat transfer tubes 66 in thermal contact with the fins 65. The heat storage heat exchanger 18 is formed by forming heat storage flow paths 17 in a plurality of heat storage heat exchange heat transfer tubes 68 among the plurality of heat transfer tubes 66. The bypass heat exchanger 52 is formed by forming bypass flow paths 51 in a plurality of bypass heat exchange heat transfer tubes 67 that are different from the plurality of heat storage heat exchange heat transfer tubes 68 among the plurality of heat transfer tubes 66. This air conditioner does not need to provide the bypass heat exchanger 52 separately from the heat storage heat exchanger 18 inside the heat storage container 63, thereby enabling space savings.

[0103] Furthermore, the heat storage material 64 of the air conditioner of the embodiment is a sensible heat storage material. In this case, at least one of the plurality of heat storage heat exchange heat transfer pipes 68 is arranged below the plurality of bypass heat exchange heat transfer pipes 67. When a heat storage operation is performed in which a heat storage heat exchange portion 72 of the heat storage material 64 is heated, this air conditioner can generate convection in the heat storage material 64 so that the temperature of the bypass heat exchange portion 71 increases. When a heat storage operation is performed in this air conditioner, the temperature of the bypass heat exchange portion 71 increases, thereby ensuring a temperature difference between the refrigerant flowing through the bypass heat exchange portion 71 and the bypass heat exchange portion 71 of the heat storage material 64, and improving the heat exchange efficiency of the bypass heat exchanger 52.

[0104] Furthermore, the heat storage material 64 of the air conditioner of the embodiment includes a heat storage heat exchange portion 72 that undergoes heat exchange by the heat storage heat exchanger 18, and a bypass heat exchange portion 71 that undergoes heat exchange by the bypass heat exchanger 52. The air conditioner of the embodiment further includes a heat storage material temperature sensor 74 that detects the temperature of a temperature measurement portion 73 intermediate between the bypass heat exchange portion 71 and the heat storage heat exchange portion 72, and a heat storage amount calculation unit 86 that calculates the amount of stored heat based on the temperature detected by the heat storage material temperature sensor 74. Such an air conditioner can accurately calculate the amount of stored heat, and can perform the adjustment of the aperture of the first heat storage expansion valve 21, the aperture of the second heat storage expansion valve 22, and the aperture of the bypass expansion valve 53 in the processing of step S9 at an appropriate timing.

[0105] Incidentally, at least one of the plurality of heat storage heat exchange heat transfer pipes 68 in the air conditioner of the previously described embodiment is disposed below the plurality of bypass heat exchange heat transfer pipes 67, but it may also be disposed above the plurality of bypass heat exchange heat transfer pipes 67. In this air conditioner, as in the air conditioner of the previously described embodiment, when heat is stored in the heat storage material 64 by the heat storage heat exchanger 18 so as to increase the heat storage amount, the heat storage material 64 can be heat exchanged with the refrigerant by the bypass heat exchanger 52 so as to decrease the heat storage amount, and the heat storage amount can be maintained within a predetermined range. In this air conditioner, when a cold storage operation is performed in which the heat storage heat exchange portion 72 of the heat storage material 64 is cooled, convection can be generated in the heat storage material 64 so as to decrease the temperature of the bypass heat exchange portion 71. In such an air conditioner, the temperature of the bypass heat exchange section 71 drops when cold storage operation is being performed, so that, compared to the air conditioners of the previously described embodiments, a temperature difference can be maintained between the refrigerant flowing through the bypass heat exchange section 71 and the bypass heat exchange section 71 of the heat storage material 64, thereby improving the heat exchange efficiency of the bypass heat exchanger 52.

[0106] In the air conditioner of the embodiment described above, one end of the bypass flow path 51 is connected to the first refrigerant pipe 11, but the one end of the bypass flow path 51 may be connected to the second refrigerant pipe 12 or the third refrigerant pipe 14. In the air conditioner of the embodiment described above, the other end of the bypass flow path 51 is connected to the second refrigerant pipe 12, but the other end of the bypass flow path 51 may be connected to the first refrigerant pipe 11 or the third refrigerant pipe 14. Even in such an air conditioner, when the heat storage heat exchanger 18 stores heat in the heat storage material 64 so as to increase the heat storage amount, the bypass heat exchanger 52 can exchange heat between the heat storage material 64 and the refrigerant so as to decrease the heat storage amount, and the heat storage amount can be maintained within a predetermined range.

[0107] The bypass expansion valve 53 is provided in the first refrigerant pipe 11 between two branch points to which both ends of the bypass passage 51 are connected when both ends of the bypass passage 51 are connected to the first refrigerant pipe 11. The bypass expansion valve 53 is provided in the second refrigerant pipe 12 between two branch points to which both ends of the bypass passage 51 are connected when both ends of the bypass passage 51 are connected to the second refrigerant pipe 12. An air conditioner provided with the bypass expansion valve 53 in this manner can appropriately flow refrigerant through the bypass passage 51 even when the pressure loss in the bypass passage 51 is large, and can maintain the heat storage amount within a predetermined range, similar to the air conditioners of the previously described embodiments.

[0108] In the air conditioner of the previously described embodiment, the first heating-mode heat storage threshold and the first cooling-mode cold storage threshold are separate, but the first heating-mode heat storage threshold and the first cooling-mode cold storage threshold may be equal to the first heat storage threshold. In the air conditioner of the previously described embodiment, the second heating-mode heat storage threshold and the second cooling-mode cold storage threshold are separate, but the second heating-mode heat storage threshold and the second cooling-mode cold storage threshold may be equal to the second heat storage threshold. Even in such a case, the air conditioner can maintain the amount of heat storage within a predetermined range, similar to the air conditioner of the previously described embodiment.

[0109] Incidentally, the heat storage heat exchanger 18 and the bypass heat exchanger 52 of the air conditioner in the previously described embodiment are formed of fin-tube type heat exchangers in the heat storage core 62, but they may be formed of other types of heat exchangers. Examples of such heat exchangers include tube-type heat exchangers, microchannel heat exchangers, and fin & microchannel heat exchangers. Even in such cases, the air conditioner can maintain the amount of heat storage within a predetermined range, just like the air conditioners in the previously described embodiments.

[0110] Although a sensible heat storage material is used as the heat storage material 64 in the air conditioner of the previously described embodiment, a latent heat storage material may also be used. Even in such a case, by calculating the amount of heat stored in the heat storage material 64 based on the inlet and outlet temperatures of the refrigerant flowing through the heat storage heat exchanger 18 and the bypass heat exchanger 52, the air conditioner can maintain the amount of heat stored within a predetermined range, just like the air conditioner of the previously described embodiment.

[0111] Although the embodiments have been described above, the embodiments are not limited to the above content. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of so-called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, at least one of various omissions, substitutions, and modifications of the components can be made without departing from the spirit of the embodiments. [Explanation of symbols]

[0112] 1: Refrigerant circuit 2: Compressor 3:Outdoor heat exchanger 5: Main expansion valve 6: Indoor heat exchanger 11: First refrigerant piping 12: Second refrigerant piping 14: Third refrigerant piping 17: Heat storage channel 18:Regenerative heat exchanger 21: First heat storage expansion valve 22: Second heat storage expansion valve 31: Flow path switching section 51: Bypass flow path 52: Bypass heat exchanger 53: Bypass expansion valve 63: Heat storage container 64: Heat storage material 65: Multiple Fins 66: Multiple heat transfer tubes 67: Multiple bypass heat exchanger tubes 68: Multiple heat storage heat exchanger tubes 71: Bypass heat exchange section 72: Heat storage heat exchange part 73:Temperature measurement part 74: Heat storage material temperature sensor 86: Heat storage calculation unit 87: Control unit

Claims

1. A compressor; An outdoor heat exchanger; A main expansion valve; An indoor heat exchanger; a thermal storage heat exchanger; a flow path switching unit that is provided on a discharge side of the compressor and switches a flow path so that the refrigerant discharged from the compressor flows to one or two of the outdoor heat exchanger, the heat storage heat exchanger, and the indoor heat exchanger; a first refrigerant pipe connecting the flow path switching unit and the outdoor heat exchanger; a second refrigerant pipe connecting the outdoor heat exchanger and the main expansion valve; a third refrigerant pipe connecting the main expansion valve and the indoor heat exchanger; a heat storage flow path connecting the flow path switching unit and the second refrigerant pipe, through which a refrigerant that is heat exchanged with a heat storage material by the heat storage heat exchanger flows; a bypass flow path having one end connected to one of the first refrigerant pipe and the second refrigerant pipe and the other end connected to one of the first refrigerant pipe, the second refrigerant pipe, and the third refrigerant pipe; a bypass heat exchanger that exchanges heat between the refrigerant flowing through the bypass flow path and the heat storage material; a bypass expansion valve for adjusting the amount of refrigerant flowing through the bypass flow path; a control unit that controls the bypass expansion valve so that refrigerant does not flow into the bypass flow path when a heat storage amount, which is an absolute value of the amount of heat stored in the heat storage material, is smaller than a first heat storage threshold value during a first heat storage heating operation in which the indoor heat exchanger and the heat storage heat exchanger function as condensers or during a first cold storage cooling operation in which the indoor heat exchanger and the heat storage heat exchanger function as evaporators, and so that refrigerant flows into the bypass flow path when the heat storage amount is equal to or larger than the first heat storage threshold value. An air conditioner equipped with the above.

2. the one end is connected to the first refrigerant pipe, The other end is connected to the second refrigerant pipe or the third refrigerant pipe. The air conditioner according to claim 1.

3. The bypass expansion valve is provided in the bypass flow path between the bypass heat exchanger and the other end. The air conditioner according to claim 2.

4. a first heat storage expansion valve provided between the compressor and the flow path switching unit, for adjusting the amount of refrigerant discharged from the compressor and flowing through the heat storage heat exchanger or the outdoor heat exchanger; a second heat storage expansion valve provided in the heat storage flow path between the second refrigerant pipe and the heat storage heat exchanger, The control unit further controls the first heat storage expansion valve, the second heat storage expansion valve, and the bypass expansion valve so that the amount of stored heat does not become smaller than the first heat storage threshold value. The air conditioner according to claim 1.

5. When the amount of stored heat is equal to or greater than a second heat storage threshold value that is greater than the first heat storage threshold value, the control unit further controls the first heat storage expansion valve, the second heat storage expansion valve, and the bypass expansion valve so as to reduce the amount of stored heat. The air conditioner according to claim 4.

6. The heat exchange capacity of the heat storage heat exchanger is greater than the heat exchange capacity of the bypass heat exchanger. The air conditioner according to claim 1.

7. the heat storage heat exchanger and the bypass heat exchanger are provided together with the heat storage material inside a heat storage container in which the heat storage material is stored, The heat storage heat exchanger and the bypass heat exchanger are a plurality of fins in thermal contact with the heat storage material; a plurality of heat transfer tubes in thermal contact with the plurality of fins; the heat storage heat exchanger is formed by forming the heat storage flow paths in a plurality of heat storage heat exchange heat transfer tubes among the plurality of heat transfer tubes, The bypass heat exchanger is formed by forming the bypass flow path in a plurality of bypass heat exchange heat transfer tubes that are different from the plurality of heat storage heat exchange heat transfer tubes among the plurality of heat transfer tubes. The air conditioner according to claim 6.

8. The heat storage material is a sensible heat storage material, At least one of the plurality of heat storage heat exchange heat transfer tubes is disposed below the plurality of bypass heat exchange heat transfer tubes. The air conditioner according to claim 7.

9. The heat storage material is a sensible heat storage material, At least one of the plurality of heat storage heat exchange heat transfer tubes is disposed above the plurality of bypass heat exchange heat transfer tubes. The air conditioner according to claim 7.

10. The heat storage material is a portion where heat is exchanged by the heat storage heat exchanger; a portion where heat is exchanged by the bypass heat exchanger, a heat storage material temperature sensor for detecting the temperature of an intermediate portion between a portion where heat is exchanged by the bypass heat exchanger and a portion where heat is exchanged by the bypass heat exchanger; a heat storage amount calculation unit that calculates the heat storage amount based on the temperature The air conditioner according to claim 1 , further comprising:

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