Air conditioner

Abstract

This air conditioner comprises: an outdoor unit having a compressor and an outdoor heat exchanger; a plurality of indoor units each having an indoor heat exchanger, an indoor expansion valve, and an indoor fan for blowing air to the indoor heat exchanger; and a control device. When the control device activates a cooling operation with at least one of the plurality of indoor units and the at least one of the plurality of indoor units is stopped, the control device determines whether or not refrigerant leakage is occurring at the indoor expansion valve of the stopped indoor unit. When it is determined that refrigerant leakage is occurring, the control device performs a cancellation operation for driving the indoor fan of the indoor unit in which it was determined that the refrigerant leakage is occurring.

Description

air conditioning equipment

[0001] The present disclosure relates to an air conditioner equipped with multiple indoor units.

[0002] Conventionally, air conditioners equipped with one outdoor unit and multiple indoor units are known. Each of the multiple indoor units is connected to the outdoor unit via an expansion valve. When operation is stopped, the expansion valve is controlled to fully close, thereby blocking the flow of refrigerant into the indoor units. However, if the expansion valve does not operate properly, the expansion valve that was controlled to be fully closed may not actually be fully closed, resulting in refrigerant leaking into the stopped indoor unit.

[0003] To solve the above problem, Patent Document 1 proposes an air conditioning system that is configured to determine that refrigerant is leaking from the expansion valve of an indoor unit that is not operating if the difference between the intermediate temperature and the inlet temperature of the indoor heat exchanger of an indoor unit that is operating in cooling mode is higher than a predetermined temperature, and to operate the expansion valve of the indoor unit that is not operating in the closing direction.

[0004] Patent No. 4408825

[0005] However, if a foreign object gets into the expansion valve of the indoor unit or if the expansion valve malfunctions, the expansion valve will not fully close even when operated in the closing direction, resulting in refrigerant leakage into the stopped indoor unit, as described in Patent Document 1. If refrigerant leaks into the stopped indoor unit, there is a risk of malfunction, such as liquid backflow into the compressor due to the leaked refrigerant.

[0006] The present disclosure is intended to solve the above-mentioned problems, and to provide an air conditioner that can suppress the occurrence of malfunctions due to refrigerant leakage from an expansion valve in an indoor unit that is not operating.

[0007] The air conditioning apparatus according to the present disclosure comprises an outdoor unit having a compressor and an outdoor heat exchanger, a plurality of indoor units each having an indoor heat exchanger, an indoor expansion valve, and an indoor fan that blows air to the indoor heat exchanger, and a control device, and when at least one of the plurality of indoor units is performing cooling operation and at least one of the plurality of indoor units is stopped, the control device determines whether or not a refrigerant leak has occurred in the indoor expansion valve of the stopped indoor unit, and if it is determined that a refrigerant leak has occurred, performs a elimination operation to drive the indoor fan of the indoor unit determined to be leaking refrigerant.

[0008] According to the air conditioning device of the present disclosure, by driving the indoor fan of the indoor unit that has been determined to have a refrigerant leak, the evaporation of the leaked refrigerant can be promoted, and even if the indoor expansion valve does not fully close due to a malfunction or the like, problems caused by refrigerant leaks can be suppressed.

[0009] It is a refrigerant circuit diagram showing the configuration of an air conditioning apparatus according to embodiment 1. It is a control block diagram of the air conditioning apparatus according to embodiment 1. It is a flowchart showing the flow of refrigerant leakage determination processing in embodiment 1. It is a flowchart showing the flow of elimination operation in embodiment 1. It is a flowchart showing the flow of elimination operation in embodiment 2.

[0010] Hereinafter, embodiments will be described with reference to the drawings. In each drawing, the same reference numerals are used to denote the same or equivalent parts, and this applies throughout the entire specification. The shapes of the components shown in the entire specification are merely examples and are not intended to be limiting. Furthermore, the size relationships between the components in the drawings may differ from those in reality.

[0011] Embodiment 1. Fig. 1 is a refrigerant circuit diagram showing the configuration of an air conditioning apparatus 100 pertaining to Embodiment 1. As shown in Fig. 1, the air conditioning apparatus 100 comprises an outdoor unit 1 installed outdoors, multiple indoor units 2 installed indoors, and a control device 5 that controls the outdoor unit 1 and the indoor units 2. The outdoor unit 1 and the multiple indoor units 2 are connected by piping and wiring such as power lines or signal lines. The multiple indoor units 2 are connected in parallel to the outdoor unit 1. The control device 5 is connected to the outdoor unit 1 and the multiple indoor units 2 via wired or wireless communication. Note that, although two indoor units 2 are connected to the outdoor unit 1 in Fig. 1, the number of indoor units 2 may be three or more.

[0012] As shown in Fig. 1, the outdoor unit 1 includes a compressor 11, a flow path switching valve 12, an outdoor heat exchanger 13, an outdoor expansion valve 14, an accumulator 15, and an outdoor fan 16. Each indoor unit 2 includes an indoor heat exchanger 21, an indoor expansion valve 22, and an indoor fan 23. The compressor 11, the flow path switching valve 12, the outdoor heat exchanger 13, the outdoor expansion valve 14, the indoor expansion valve 22, the indoor heat exchanger 21, and the accumulator 15 are connected by piping to form a refrigerant circuit. The refrigerant circulating in the refrigerant circuit of the air conditioning apparatus 100 is, for example, a natural refrigerant such as carbon dioxide, hydrocarbon, or helium; a chlorine-free refrigerant such as HFC410A or HFC407C; or a fluorocarbon refrigerant such as R22 or R134a.

[0013] The compressor 11 draws in and compresses low-pressure gas refrigerant, and discharges it as high-pressure gas refrigerant. A reciprocating, rotary, scroll, or screw compressor, for example, is used as the compressor 11. The operating frequency of the compressor 11 is controlled by the control device 5.

[0014] The flow path switching valve 12 switches between a cooling operation in which the outdoor heat exchanger 13 functions as a condenser and a heating operation in which the outdoor heat exchanger 13 functions as an evaporator. The flow path switching valve 12 is, for example, a four-way valve, and its switching is controlled by the control device 5. During the cooling operation, the flow path switching valve 12 switches so that the refrigerant discharged from the compressor 11 flows into the outdoor heat exchanger 13, as shown by the solid line in Fig. 1. During the heating operation, the flow path switching valve 12 switches so that the refrigerant discharged from the compressor 11 flows into the indoor heat exchanger 21, as shown by the dashed line in Fig. 1.

[0015] The outdoor heat exchanger 13 is, for example, a fin-tube heat exchanger, and exchanges heat between the refrigerant flowing inside the circular or flat tubes and the air supplied by the outdoor fan 16. The outdoor heat exchanger 13 is disposed between the flow path switching valve 12 and the outdoor expansion valve 14. The outdoor heat exchanger 13 functions as an evaporator during heating operation and as a condenser during cooling operation.

[0016] The outdoor expansion valve 14 is disposed between the outdoor heat exchanger 13 and the indoor expansion valve 22, and reduces the pressure of the refrigerant to cause it to expand. The outdoor expansion valve 14 is, for example, an electronic expansion valve with a variable opening. The opening of the outdoor expansion valve 14 is controlled by the control device 5. Note that in this embodiment, the outdoor expansion valve 14 is not essential and may be omitted.

[0017] The accumulator 15 stores excess refrigerant. The accumulator 15 is connected to the suction port of the compressor 11, separates the refrigerant that flows in from the outdoor heat exchanger 13 or the indoor heat exchanger 21 into gas refrigerant and liquid refrigerant, stores the liquid refrigerant, and causes the gas refrigerant to flow to the compressor 11. The accumulator 15 is not an essential component and may be omitted.

[0018] The outdoor fan 16 draws in outdoor air, passes it through the outdoor heat exchanger 13, and blows it out to the outside. The outdoor fan 16 is, for example, a propeller fan, turbo fan, sirocco fan, or crossflow fan driven by a motor. The rotation speed of the outdoor fan 16 is controlled by the control device 5.

[0019] The indoor heat exchanger 21 is, for example, a fin-tube type heat exchanger, and exchanges heat between the refrigerant flowing inside the circular or flat tubes and the air blown by the indoor fan 23. The indoor heat exchanger 21 is disposed between the indoor expansion valve 22 and the flow path switching valve 12. The indoor heat exchanger 21 functions as a condenser during heating operation and as an evaporator during cooling operation.

[0020] The indoor expansion valve 22 is disposed between the outdoor expansion valve 14 and the indoor heat exchanger 21, and reduces the pressure of the refrigerant to expand it. The indoor expansion valve 22 is, for example, an electronic expansion valve whose opening degree is variable. The opening degree of the indoor expansion valve 22 is controlled by the control device 5.

[0021] The indoor fan 23 draws in indoor air, passes it through the indoor heat exchanger 21, and blows it out into the room. The indoor fan 23 is, for example, a propeller fan, turbo fan, sirocco fan, or crossflow fan driven by a motor. The rotation speed of the indoor fan 23 is controlled by the control device 5.

[0022] The air conditioning apparatus 100 also includes a plurality of sensors. Specifically, the outdoor unit 1 includes an outdoor air temperature sensor 31 that measures the outdoor air temperature Ta, which is the temperature of the outdoor space in which the outdoor unit 1 is installed. Each indoor unit 2 also includes a refrigerant temperature sensor 32 that measures the refrigerant temperature Tr, which is the temperature of the refrigerant flowing into the indoor heat exchanger 21 during cooling operation. The outdoor air temperature sensor 31 and the refrigerant temperature sensor 32 are configured, for example, by a thermistor. The outdoor air temperature Ta measured by the outdoor air temperature sensor 31 and the refrigerant temperature Tr measured by the refrigerant temperature sensor 32 are transmitted to the control device 5.

[0023] The air conditioning apparatus 100 may be equipped with a temperature sensor or pressure sensor other than the above-mentioned temperature sensors. For example, each indoor unit 2 may be equipped with an indoor temperature sensor that measures the indoor temperature, which is the temperature of the indoor space in which the indoor unit 2 is installed, or a sensor that measures the temperature of the refrigerant flowing out of the indoor heat exchanger 21 during cooling operation. The outdoor unit 1 may also be equipped with a sensor that measures the temperature or pressure of the refrigerant discharged from the compressor 11, a sensor that measures the temperature or pressure of the refrigerant sucked into the compressor 11, or a temperature sensor that measures the temperature of the refrigerant flowing through the outdoor heat exchanger 13.

[0024] The control device 5 controls the operation of the outdoor unit 1 and the multiple indoor units 2. The control device 5 is composed of a computer equipped with a memory for storing data and programs required for control and a processor such as a CPU for executing the programs, a dedicated processing circuit such as an ASIC or FPGA, or both. Note that in FIG. 1 , the control device 5 is provided separately from the outdoor unit 1 and the indoor units 2, but the control device 5 may be provided in either the outdoor unit 1 or the multiple indoor units 2, or the outdoor unit 1 and the multiple indoor units 2 may each be equipped with a control device 5.

[0025] (Cooling Operation) The operation of the air conditioner 100 during cooling operation will be described. During cooling operation, first, the refrigerant is compressed by the compressor 11 and becomes a high-temperature, high-pressure gas. It flows into the outdoor heat exchanger 13. The refrigerant releases heat in the outdoor heat exchanger 13, which functions as a condenser, and changes phase from a high-temperature, high-pressure gas to a liquid, heating the air passing through the outdoor heat exchanger 13. The refrigerant is then decompressed by the outdoor expansion valve 14 and the indoor expansion valve 22, becoming a two-phase mixture of low-temperature, low-pressure liquid and gas, and then flows into the indoor heat exchanger 21. The refrigerant absorbs heat in the indoor heat exchanger 21, which functions as an evaporator, and changes phase from liquid to gas, cooling the air passing through the indoor heat exchanger 21. This cools the room. The refrigerant then flows into the compressor 11 via the accumulator 15, where it again becomes a high-temperature, high-pressure gas.

[0026] (Heating Operation) The operation of the air conditioner 100 during heating operation will be described. During heating operation, the refrigerant is compressed by the compressor 11 and becomes a high-temperature, high-pressure gas. It flows into the indoor heat exchanger 21. The refrigerant releases heat in the indoor heat exchanger 21, which functions as a condenser, changing phase from a high-temperature, high-pressure gas to a liquid, and heats the air passing through the indoor heat exchanger 21. This heats the room. The refrigerant is then decompressed by the indoor expansion valve 22 and the outdoor expansion valve 14, becoming a two-phase mixture of low-temperature, low-pressure liquid and gas, and then flows into the outdoor heat exchanger 13. In the outdoor heat exchanger 13, which functions as an evaporator, the refrigerant absorbs heat and changes phase from liquid to gas, cooling the air passing through the outdoor heat exchanger 13. The refrigerant then flows into the compressor 11 via the accumulator 15, where it becomes a high-temperature, high-pressure gas again.

[0027] During cooling operation and heating operation, the indoor expansion valve 22 of the indoor unit 2 that is not operating is controlled to be fully closed, thereby blocking the flow of refrigerant into the indoor heat exchanger 21.

[0028] FIG. 2 is a control block diagram of the air conditioning apparatus 100 according to Embodiment 1. For simplicity of explanation, FIG. 2 shows one outdoor air temperature sensor 31 and one refrigerant temperature sensor 32 connected to the control device 5. However, in reality, the same number of outdoor air temperature sensors 31 and refrigerant temperature sensors 32 as the number of indoor units 2 are connected to the control device 5. As shown in FIG. 2 , the control device 5 of the air conditioning apparatus 100 includes an operation control unit 51, a determination unit 52, a resolution unit 53, and a storage unit 54. The operation control unit 51, the determination unit 52, and the resolution unit 53 are functional units realized by a processor, such as a CPU, constituting the control device 5 executing a program. Alternatively, at least one of the operation control unit 51, the determination unit 52, and the resolution unit 53 may be realized by a processing circuit, such as an ASIC or FPGA.

[0029] The operation control unit 51 controls the outdoor unit 1 and the multiple indoor units 2 to perform cooling operation and heating operation. Specifically, the operation control unit 51 controls the operating frequency of the compressor 11, the switching of the flow path switching valve 12, the opening degrees of the outdoor expansion valve 14 and the indoor expansion valve 22, and the rotation speeds of the outdoor fan 16 and the indoor fan 23, based on the setting of the operation mode and the set temperature input by the user and the measurement results of each temperature sensor.

[0030] When the air conditioning apparatus 100 is performing cooling operation, the determination unit 52 determines whether or not there is a refrigerant leak in the indoor expansion valve 22 of an indoor unit 2 that is stopped from operating among the multiple indoor units 2. Note that "refrigerant leakage" in the present disclosure refers to liquid refrigerant flowing from the indoor expansion valve 22, which is controlled to be fully closed, to the indoor heat exchanger 21. When the absolute value (|Ta - Tr|) of the difference between the outdoor air temperature Ta measured by the outdoor air temperature sensor 31 and the refrigerant temperature Tr measured by the refrigerant temperature sensor 32 of the stopped indoor unit 2 is equal to or greater than a preset threshold value Tth, the determination unit 52 determines that a refrigerant leak has occurred in the indoor expansion valve 22 of the stopped indoor unit 2.

[0031] During cooling operation, the indoor expansion valve 22 of the stopped indoor unit 2 is controlled to be fully closed. When the indoor expansion valve 22 is normally fully closed, refrigerant does not flow from the indoor expansion valve 22 to the indoor heat exchanger 21, and the refrigerant temperature Tr measured by the refrigerant temperature sensor 32 approaches the outdoor air temperature Ta. On the other hand, if foreign matter is present in the indoor expansion valve 22, even when it is controlled to be fully closed, it is not actually fully closed due to the foreign matter or other reasons, and high-temperature refrigerant flowing in from the outdoor unit 1 leaks from the indoor expansion valve 22 and flows into the indoor heat exchanger 21. Therefore, the refrigerant temperature Tr measured by the refrigerant temperature sensor 32 will be higher or lower than the outdoor air temperature Ta. Therefore, the presence or absence of refrigerant leakage from the indoor expansion valve 22 can be determined based on the difference between the refrigerant temperature Tr of the stopped indoor unit 2 and the outdoor air temperature Ta.

[0032] For example, when the outdoor air temperature Ta is 35°C, the refrigerant temperature Tr measured by the refrigerant temperature sensor 32 during normal cooling operation will be approximately 15°C to 25°C, depending on the operating conditions. Therefore, if the difference between the refrigerant temperature Tr of the stopped indoor unit 2 and the outdoor air temperature Ta is 10°C to 20°C or more, it can be determined that a refrigerant leak has occurred in the indoor expansion valve 22. Therefore, the threshold value Tth used by the determination unit 52 is set to, for example, 10°C to 20°C or less. Note that the difference between the refrigerant temperature Tr and the outdoor air temperature Ta at which it is determined that a refrigerant leak has occurred in the indoor expansion valve 22 varies greatly depending on the outdoor air temperature Ta, and the threshold value Tth is not limited to the above temperature. Alternatively, multiple threshold values ​​Tth that differ depending on the outdoor air temperature Ta or the operating state of the air conditioning device 100 may be set in advance, and one of the threshold values ​​Tth may be selected depending on the outdoor air temperature Ta or the operating state of the air conditioning device 100.

[0033] When the determination unit 52 determines that a refrigerant leak has occurred in the indoor expansion valve 22 of a stopped indoor unit 2, the elimination unit 53 performs elimination operation in that indoor unit 2 to eliminate the refrigerant leak. In elimination operation, the elimination unit 53 drives the indoor fan 23 of the stopped indoor unit 2 to evaporate the leaked refrigerant. During elimination operation, the air direction plate (not shown) of the indoor unit 2 remains closed to prevent air from being blown out of the indoor unit 2. This makes it possible to prevent the user from noticing that elimination operation is being performed. The fact that elimination operation is in progress may be notified to the user by displaying a message on the remote controller of the indoor unit 2, etc.

[0034] The storage unit 54 is, for example, a non-volatile semiconductor memory such as a ROM or a flash memory, a volatile semiconductor memory such as a RAM, an HDD, an SSD, etc. The storage unit 54 stores programs executed by the control device 5 and various data such as thresholds used in executing the programs.

[0035] 3 is a flowchart showing the flow of the refrigerant leak determination process in Embodiment 1. This process is performed by the control device 5 while the air conditioning apparatus 100 is in operation. First, the determination unit 52 of the control device 5 determines whether at least one of the multiple indoor units 2 is currently in cooling operation (S1). If no indoor unit 2 is currently in cooling operation (S1: NO), the current operation continues. On the other hand, if at least one indoor unit 2 is currently in cooling operation (S1: YES), the determination unit 52 determines whether at least one indoor unit 2 is stopped (S2). If no indoor unit 2 is stopped (S2: NO), the current operation continues.

[0036] On the other hand, if at least one indoor unit 2 is stopped (S2: YES), the determination unit 52 determines whether a preset standby time has elapsed since the indoor unit 2 was stopped (S3). The standby time is, for example, 30 minutes to 1 hour. If the standby time has not elapsed since the indoor unit 2 was stopped (S3: NO), the determination unit 52 waits until the standby time has elapsed. On the other hand, if the standby time has elapsed since the indoor unit 2 was stopped (S3: YES), the determination unit 52 determines whether the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than the threshold value Tth (S4). For a while after the indoor unit 2 is stopped, the refrigerant temperature Tr measured by the refrigerant temperature sensor 32 is high due to the influence of cooling operation. Therefore, measuring the refrigerant temperature Tr after the preset standby time has elapsed and determining whether there is a refrigerant leak can improve the accuracy of the refrigerant leak determination.

[0037] If the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than the threshold value Tth (S4: YES), the determination unit 52 determines that a refrigerant leak has occurred in the indoor expansion valve 22 of the stopped indoor unit 2, and the elimination unit 53 performs elimination operation (S5). On the other hand, if the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is less than the threshold value Tth (S4: NO), the elimination operation is not performed and the process returns to step S1, and the current operation continues until the condition is satisfied. Note that if multiple indoor units 2 are stopped, the processes of steps S3 to S5 are performed for each indoor unit 2.

[0038] 4 is a flowchart showing the flow of the resolution operation in the first embodiment. The resolution unit 53 first sets the number of times N has been driven to 0 (S51). The number of times N is the number of times the indoor fan 23 has been driven during the resolution operation. The resolution unit 53 then drives the indoor fan 23 of the indoor unit 2 that has been determined to have a refrigerant leak (S52). At this time, the rotation speed of the indoor fan 23 is set to its maximum rotation speed. The resolution unit 53 then determines whether a preset drive time has elapsed since the indoor fan 23 was driven (S53). The drive time is, for example, 3 to 5 minutes.

[0039] If a preset drive time has not elapsed since the indoor fan 23 was driven (S53: NO), the indoor fan 23 continues to be driven until the drive time has elapsed. Here, the indoor fan 23 is driven at the maximum rotation speed for a short period of time to quickly evaporate the refrigerant that has leaked from the indoor expansion valve 22. If a preset drive time has elapsed since the indoor fan 23 was driven (S53: YES), the indoor fan 23 is stopped (S54). Then, 1 is added to the drive count N (S55), and it is determined whether the absolute value of the difference between the outside air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than a threshold value Tth (S56).

[0040] If the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is less than the threshold value Tth (S56: NO), the cancellation unit 53 ends the cancellation operation. On the other hand, if the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than the threshold value Tth (S56: YES), the cancellation unit 53 determines whether the number of times N of driving is equal to or less than the threshold value Nth (S57). The threshold value Nth of the number of times N of driving is, for example, 3.

[0041] If the number of times N is driven is equal to or less than the threshold value Nth (S57: YES), the process returns to step S52, the indoor fan 23 is driven again, and the processes of steps S52 to S57 are repeated. If the number of times N is driven is greater than the threshold value Nth (S57: NO), the resolution unit 53 determines that there is an abnormality in the indoor expansion valve 22 (S58). In this case, the control device 5 notifies the user that there is an abnormality in the indoor expansion valve 22 by using an error code or the like.

[0042] As described above, during the elimination operation, the indoor fan 23 is driven to evaporate the refrigerant leaked from the indoor expansion valve 22, thereby preventing the leaked refrigerant from flowing into the accumulator 15 in a liquid state. This raises the liquid level in the accumulator 15, preventing the liquid refrigerant from being drawn into the compressor 11 (liquid backflow). Furthermore, by evaporating the refrigerant leaked from the indoor expansion valve 22 and circulating it through the indoor expansion valve 22, it is possible to attempt to remove any foreign matter that may have entered the indoor expansion valve 22. If the refrigerant leakage is not resolved even after repeatedly starting and stopping the indoor fan 23 a predetermined number of times (e.g., three times), the elimination unit 53 determines that an abnormality has occurred, such as the foreign matter being unable to be removed or the indoor expansion valve 22 being broken, and notifies the user. This prompts the user to replace the indoor expansion valve 22 or other measures, thereby preventing future refrigerant leaks. During the elimination operation, the elimination unit 53 may drive the indoor fan 23 of the stopped indoor unit 2 and open the indoor expansion valve 22 of the stopped indoor unit 2. In this case, the indoor expansion valve 22 of the stopped indoor unit 2 is opened while the indoor fan 23 is running, and is then fully closed. This allows the refrigerant to flow through the indoor expansion valve 22, and if any foreign matter has entered the indoor expansion valve 22, it is possible to facilitate the removal of the foreign matter.

[0043] As described above, the air conditioning apparatus 100 of this embodiment determines whether a refrigerant leak has occurred in the indoor expansion valve 22 of the stopped indoor unit 2, and if a refrigerant leak has occurred, operates to eliminate the refrigerant leak by driving the indoor fan 23. This makes it possible to prevent problems such as insufficient cooling caused by liquid backflow in the compressor 11, even if the indoor expansion valve 22 does not fully close due to the inclusion of foreign matter or a malfunction.

[0044] Furthermore, in the air conditioning apparatus 100 of this embodiment, the presence or absence of a refrigerant leak is determined for each stopped indoor unit 2 based on the outdoor air temperature Ta and the refrigerant temperature Tr of each indoor unit 2. This makes it possible to identify the indoor unit 2 in which a refrigerant leak has occurred, even when there are multiple stopped indoor units 2. Then, by performing a refrigerant leak elimination operation only for the indoor unit 2 that has been identified as having a refrigerant leak, it is possible to suppress the impact on the entire air conditioning apparatus 100.

[0045] Embodiment 2. Embodiment 2 will be described. The air conditioning apparatus 100 of embodiment 2 differs from embodiment 1 in the cancellation operation. The configuration of the air conditioning apparatus 100 is the same as embodiment 1.

[0046] 5 is a flowchart showing the flow of the cancellation operation in the second embodiment. In this embodiment, as in the first embodiment, the cancellation unit 53 first sets the number of times N is driven to 0 (S501). The number of times N is the number of times the indoor fan 23 is driven during the cancellation operation. Then, the cancellation unit 53 drives the indoor fan 23 of the indoor unit 2 that has been determined to have a refrigerant leak (S502). At this time, the rotation speed of the indoor fan 23 is set to the maximum rotation speed. Then, the cancellation unit 53 controls the outdoor expansion valve 14 in the closing direction (S503).

[0047] When any of the multiple indoor units 2 is performing cooling operation, the operation control unit 51 controls the opening degree of the outdoor expansion valve 14 based on the degree of superheat of the refrigerant flowing out from the indoor heat exchanger 21 of the indoor unit 2 performing cooling operation. In this embodiment, when it is determined that a refrigerant leak has occurred in the indoor expansion valve 22 of a stopped indoor unit 2, the elimination unit 53 controls the outdoor expansion valve 14 in the closing direction. This adjusts the amount of refrigerant in the refrigerant circuit and suppresses the return of liquid refrigerant to the accumulator 15.

[0048] Next, the resolution unit 53 determines whether a preset drive time has elapsed since the indoor fan 23 was driven (S504). The drive time is, for example, 3 to 5 minutes. If the preset drive time has not elapsed since the indoor fan 23 was driven (S504: NO), the indoor fan 23 continues to be driven until the drive time has elapsed. Here, the indoor fan 23 is driven at the maximum rotation speed for a short period of time to quickly evaporate the leaked refrigerant. If the preset drive time has elapsed since the indoor fan 23 was driven (S504: YES), the indoor fan 23 is stopped (S505). Then, 1 is added to the drive count N (S506), and it is determined whether the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than a threshold value Tth (S507).

[0049] If the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is less than the threshold value Tth (S507: NO), the resolution unit 53 returns the outdoor expansion valve 14 to normal control (S508) and terminates the resolution operation. On the other hand, if the absolute value of the difference between the outdoor air temperature Ta and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than the threshold value Tth (S507: YES), the resolution unit 53 determines whether the number of times N of driving is equal to or less than the threshold value Nth (S509). The threshold value Nth of the number of times N of driving is, for example, 3.

[0050] If the number of times N is driven is equal to or less than the threshold value Nth (S509: YES), the process returns to step S502, the indoor fan 23 is driven again, and the processes of steps S502 to S509 are repeated. If the number of times N is driven is greater than the threshold value Nth (S509: NO), the resolution unit 53 determines that there is an abnormality in the indoor expansion valve 22 (S510). In this case, the control device 5 notifies the user that there is an abnormality in the indoor expansion valve 22 by using an error code or the like.

[0051] As described above, in the air conditioning apparatus 100 of this embodiment, if a refrigerant leak occurs in the indoor expansion valve 22 of a stopped indoor unit 2, the indoor fan 23 is driven to evaporate the leaked refrigerant, and the outdoor expansion valve 14 is controlled in the closing direction to adjust the amount of refrigerant. This makes it possible to further suppress the occurrence of problems such as insufficient cooling due to liquid backflow in the compressor 11, even if the indoor expansion valve 22 does not fully close due to the inclusion of foreign matter or a malfunction.

[0052] In the second embodiment, the indoor fan 23 is driven and the outdoor expansion valve 14 is controlled in parallel during the elimination operation, but if the refrigerant leakage is not eliminated by driving the indoor fan 23 (S509: NO), the outdoor expansion valve 14 may be controlled in the closing direction. This makes it possible to prevent malfunctions such as liquid backflow in the compressor 11 due to refrigerant leakage, even if there is an abnormality in the indoor expansion valve 22.

[0053] Although the above is a description of the embodiment, the present disclosure is not limited to the above embodiment and various modifications or combinations are possible within the scope of the gist of the present disclosure. For example, the air conditioning device 100 in the above embodiment is configured to be able to switch between cooling and heating, but the air conditioning device 100 may also be a dedicated cooling device or a freezer. If the air conditioning device 100 is a dedicated cooling device, the flow path switching valve 12 is omitted.

[0054] Furthermore, the method of determining a refrigerant leak by the determination unit 52 is not limited to the example of the above embodiment. For example, an inlet temperature sensor that measures the temperature of the refrigerant flowing into the accumulator 15 may be provided at the inlet of the accumulator 15, and the determination unit 52 may determine whether or not a refrigerant leak has occurred based on the temperature measured by the inlet temperature sensor. In this case, if the temperature measured by the inlet temperature sensor is equal to or greater than a threshold temperature, it is determined that a refrigerant leak has occurred in one of the stopped indoor units 2. Alternatively, a liquid level detection sensor that detects the liquid level may be provided in the accumulator 15, and the determination unit 52 may determine that a refrigerant leak has occurred in one of the stopped indoor units 2 if the measured liquid level is equal to or greater than a threshold. In these cases, the elimination operation described in embodiment 1 or 2 is performed in all stopped indoor units 2.

[0055] Furthermore, in the above embodiment, the outdoor unit 1 is configured to include an outdoor air temperature sensor 31 that measures the outdoor air temperature Ta, but the control device 5 may also obtain the outdoor air temperature Ta from an external device. For example, the control device 5 may obtain the outdoor air temperature Ta from an outdoor air temperature sensor provided separately from the air conditioning device 100, or from an external server that manages weather information. In this case, the outdoor air temperature sensor 31 can be omitted from the air conditioning device 100.

[0056] Furthermore, when the indoor unit 2 is stopped, the indoor temperature Ti, which is the temperature of the indoor space in which the indoor unit 2 is installed, will be close to the outdoor air temperature Ta, and therefore the determination unit 52 may use the indoor temperature Ti instead of the outdoor air temperature Ta. Specifically, the determination unit 52 may determine that a refrigerant leak has occurred in the indoor expansion valve 22 of the stopped indoor unit 2 when the absolute value of the difference (|Ti - Tr|) between the indoor temperature Ti and the refrigerant temperature Tr of the stopped indoor unit 2 is equal to or greater than a preset threshold value Tth. The indoor temperature Ti may be measured by an indoor temperature sensor provided in the indoor unit 2, or may be obtained from an indoor temperature sensor provided separately from the air conditioning apparatus 100.

[0057] REFERENCE SIGNS LIST 1 outdoor unit, 2 indoor unit, 5 control device, 11 compressor, 12 flow path switching valve, 13 outdoor heat exchanger, 14 outdoor expansion valve, 15 accumulator, 16 outdoor fan, 21 indoor heat exchanger, 22 indoor expansion valve, 23 indoor fan, 31 outdoor air temperature sensor, 32 refrigerant temperature sensor, 51 operation control unit, 52 determination unit, 53 resolution unit, 54 memory unit, 100 air conditioning apparatus.

Claims

1. An air conditioning system comprising: an outdoor unit having a compressor and an outdoor heat exchanger; multiple indoor units each having an indoor heat exchanger, an indoor expansion valve, and an indoor fan that blows air to the indoor heat exchanger; and a control device, wherein when at least one of the multiple indoor units is performing cooling operation and at least one of the multiple indoor units is stopped, the control device determines whether or not a refrigerant leak has occurred in the indoor expansion valve of the stopped indoor unit, and if it is determined that a refrigerant leak has occurred, performs a rectification operation to drive the indoor fan of the indoor unit determined to be leaking.

2. The air conditioning apparatus of claim 1, wherein the control device determines that a refrigerant leak is occurring in the indoor expansion valve of the indoor unit that is stopped when the difference between the refrigerant temperature, which is the temperature of the refrigerant flowing between the indoor expansion valve and the indoor heat exchanger, and the outdoor air temperature or the indoor temperature is equal to or greater than a threshold value.

3. An air conditioning apparatus as described in claim 1 or 2, wherein, during the elimination operation, the control device drives the indoor fan of the indoor unit that is determined to have a refrigerant leak for a preset driving time and then stops it, and repeats driving and stopping the indoor fan a preset number of times.

4. An air conditioning apparatus as described in claim 3, wherein the control device determines that there is an abnormality in the indoor expansion valve if the refrigerant leakage is not resolved even after the indoor fan has been started and stopped repeatedly the preset number of times during the resolution operation.

5. An air-conditioning apparatus according to any one of claims 1 to 4, wherein the outdoor unit further comprises an outdoor expansion valve, and the control device controls the outdoor expansion valve in a closing direction during the cancellation operation.

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