Refrigerant amount estimation device and air conditioner

Abstract

This refrigerant amount estimation device estimates a remaining refrigerant amount in an air conditioner that has an outdoor unit having a compressor, an outdoor heat exchanger, and an expansion valve, and an indoor unit having an indoor heat exchanger, and that is provided with a refrigerant circuit formed by connecting the outdoor unit and the indoor unit with refrigerant piping, wherein a refrigerant circulates in the refrigerant circuit. The refrigerant amount estimation device has a control unit that estimates the remaining refrigerant amount using a learning model in which at least a degree of supercooling, a state quantity correlated with a pipe length of the refrigerant piping, and the remaining refrigerant amount are learned in association with one another. As a result, the present invention provides a refrigerant amount estimation device or the like that aims to improve the estimation accuracy of the remaining refrigerant amount regardless of the pipe length.

Description

Refrigerant amount estimation device and air conditioner

[0001] The present invention relates to a refrigerant amount estimation device and an air conditioner.

[0002] For example, a refrigerant amount estimation device has been proposed that estimates the amount of refrigerant circulating in a refrigerant circuit using operational state quantities detectable in the refrigerant circuit. The refrigerant amount estimation device in Patent Document 1 includes a learning unit that learns the SC expansion valve opening and SC heat exchanger outlet temperature, among multiple operational state quantities detectable in the refrigerant circuit of an air conditioner equipped with a subcooling heat exchanger, in association with the refrigerant amount. The air conditioner then uses the refrigerant amount estimation device with the learning unit to estimate the amount of refrigerant circulating in the refrigerant circuit during operation using the SC expansion valve opening and SC heat exchanger outlet temperature during operation.

[0003] Japanese Patent Application Laid-Open No. 2020-153575

[0004] However, because the distance between the indoor unit and the outdoor unit of an air conditioner varies depending on the installation conditions, the length of the refrigerant piping connecting the indoor unit and the outdoor unit may also vary depending on the installation conditions of the air conditioner. In the refrigerant amount estimation device of Patent Document 1, the relationship between the opening of the SC expansion valve and the SC heat exchanger outlet temperature and the refrigerant amount may change due to the piping length changing depending on the installation conditions of the indoor unit and the outdoor unit, which may result in a deterioration in the accuracy of estimating the refrigerant amount.

[0005] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a refrigerant amount estimation device etc. that can improve the accuracy of estimating the remaining refrigerant amount regardless of the piping length.

[0006] A refrigerant amount estimation device according to one aspect estimates a remaining refrigerant amount in an air conditioner having an outdoor unit having a compressor, an outdoor heat exchanger, and an expansion valve, and an indoor unit having an indoor heat exchanger, the outdoor unit and the indoor unit being connected by refrigerant piping to form a refrigerant circuit through which refrigerant circulates. The refrigerant amount estimation device includes a control unit that estimates the remaining refrigerant amount using a learning model in which a state quantity correlated with at least the degree of subcooling and the piping length of the refrigerant piping is learned in association with the remaining refrigerant amount.

[0007] As one aspect, the accuracy of estimating the amount of refrigerant can be improved regardless of the length of the pipe.

[0008] FIG. 1 is an explanatory diagram showing an example of an air conditioner according to the present embodiment. FIG. 2 is an explanatory diagram showing an example of an outdoor unit and an indoor unit according to the first embodiment. FIG. 3A is a block diagram showing an example of a first control unit. FIG. 3B is a functional block diagram showing an example of a first control unit in a learning phase in which an estimation model is created. FIG. 3C is a functional block diagram showing an example of a first control unit in an inference phase in which a remaining refrigerant amount is estimated. FIG. 4 is a block diagram showing an example of a second control unit. FIG. 5 is an explanatory diagram showing an example of explanatory variables used in the estimation model. FIG. 6 is an explanatory diagram showing an estimable range in which the remaining refrigerant amount can be estimated in terms of the relationship between the degree of subcooling and the degree of superheat. FIG. 7 is a flowchart showing an example of processing operations of the first control unit related to estimation processing. FIG. 8 is a flowchart showing an example of processing operations of the first control unit related to determination processing. FIG. 9 is an explanatory diagram showing an example of the relationship between the pressure difference and the inlet refrigerant circulation amount for the maximum pipe length and the standard pipe length. FIG. 10 is an explanatory diagram showing an example of an air conditioning system according to the second embodiment. FIG. 11 is a block diagram showing an example of a third control unit. FIG. 12 is an explanatory diagram showing an example of an outdoor unit and an indoor unit according to the third embodiment.

[0009] Hereinafter, embodiments of the refrigerant amount estimation device and the like disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to these embodiments. Furthermore, each of the embodiments described below may be modified as appropriate within a range that does not cause inconsistencies.

[0010] <Configuration of Air Conditioner> Fig. 1 is an explanatory diagram showing an example of an air conditioner 1 of this embodiment. The air conditioner 1 shown in Fig. 1 has one outdoor unit 2 and N indoor units 3 (N is a natural number equal to or greater than 2). The outdoor unit 2 is connected in parallel to each of the indoor units 3 by liquid pipes 4 and gas pipes 5. The outdoor unit 2 and the indoor units 3 are connected by refrigerant piping such as the liquid pipes 4 and gas pipes 5, thereby forming a refrigerant circuit 6 of the air conditioner 1.

[0011] 2 is an explanatory diagram showing an example of the outdoor unit 2 and indoor unit 3 of Example 1. The outdoor unit 2 has a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor unit expansion valve 14, a first shut-off valve 15, a second shut-off valve 16, an accumulator 17, an outdoor unit fan 18, an injection circuit 19, and a first control unit 20. The compressor 11, the four-way valve 12, the outdoor heat exchanger 13, the outdoor unit expansion valve 14, the first shut-off valve 15, the second shut-off valve 16, the accumulator 17, and the injection circuit 19 are connected to each other by refrigerant piping to form an outdoor-side refrigerant circuit that forms part of the refrigerant circuit 6.

[0012] The compressor 11 is a high-pressure vessel type variable capacity compressor whose operating capacity can be varied in response to the drive of a motor (not shown) whose rotation speed is controlled by an inverter, for example. The refrigerant discharge side of the compressor 11 is connected to the first port 12A of the four-way valve 12 by a discharge pipe 21. The refrigerant suction side of the compressor 11 is connected to the refrigerant outlet side of the accumulator 17 by a suction pipe 22.

[0013] The four-way valve 12 is a valve for switching the flow direction of refrigerant in the refrigerant circuit 6, and includes a first port 12A to a fourth port 12D. The first port 12A is connected to the refrigerant discharge side of the compressor 11 by a discharge pipe 21. The second port 12B is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 13 by an outdoor refrigerant pipe 23. The third port 12C is connected to the refrigerant inlet side of the accumulator 17 by an outdoor refrigerant pipe 26. The fourth port 12D is connected to the second stop valve 16 by an outdoor gas pipe 24.

[0014] The outdoor heat exchanger 13 exchanges heat between the refrigerant and outside air taken into the outdoor unit 2 by the rotation of the outdoor unit fan 18. One refrigerant inlet / outlet of the outdoor heat exchanger 13 is connected to the second port 12B of the four-way valve 12 by an outdoor refrigerant pipe 23. The other refrigerant inlet / outlet of the outdoor heat exchanger 13 is connected to the first stop valve 15 by an outdoor liquid pipe 25. The outdoor heat exchanger 13 functions as a condenser when the air conditioner 1 is performing cooling operation, and functions as an evaporator when the air conditioner 1 is performing heating operation.

[0015] The outdoor unit expansion valve 14 is provided in the outdoor liquid pipe 25 and is an electronic expansion valve driven by a pulse motor (not shown). The outdoor unit expansion valve 14 adjusts the amount of refrigerant flowing into or out of the outdoor heat exchanger 13 by adjusting its opening depending on the number of pulses applied to the pulse motor. When the air conditioner 1 is performing heating operation, the opening of the outdoor unit expansion valve 14 is adjusted so that the superheat degree on the refrigerant suction side of the compressor 11 becomes the target suction superheat degree. When the air conditioner 1 is performing cooling operation, the opening of the outdoor unit expansion valve 14 is fully open.

[0016] The refrigerant inlet side of the accumulator 17 and the third port 12C of the four-way valve 12 are connected by an outdoor refrigerant pipe 26. Furthermore, the refrigerant outlet side of the accumulator 17 and the refrigerant inlet side of the compressor 11 are connected by a suction pipe 22. The accumulator 17 separates the refrigerant that has flowed into the accumulator 17 from the outdoor refrigerant pipe 26 into gas refrigerant and liquid refrigerant, and allows only the gas refrigerant to be sucked into the compressor 11.

[0017] The outdoor unit fan 18 is made of a resin material and is disposed near the outdoor heat exchanger 13. In response to the rotation of a fan motor (not shown), the outdoor unit fan 18 takes in outside air from an air inlet (not shown) into the outdoor unit 2, and discharges the outside air that has exchanged heat with the refrigerant in the outdoor heat exchanger 13 to the outside of the outdoor unit 2 from an air outlet (not shown).

[0018] The injection circuit 19 has a branching section 19A, a subcooling (hereinafter simply referred to as SC) expansion valve 19B, an SC heat exchanger 19C, a mixing section 19D, and a bypass piping 19E. The branching section 19A is provided in the outdoor liquid pipe 25 between the outdoor unit expansion valve 14 and the SC heat exchanger 19C, and branches and outputs the refrigerant from the outdoor unit expansion valve 14 to the SC heat exchanger 19C and the SC expansion valve 19B. The SC expansion valve 19B is provided in the refrigerant pipe between the branching section 19A and the SC heat exchanger 19C, and is a subcooling expansion valve that adjusts the amount of refrigerant injected into the compressor 11. The opening degree of the SC expansion valve 19B is adjusted in accordance with the control of the first control unit 20.

[0019] The SC heat exchanger 19C is provided in the outdoor liquid pipe 25 between the outdoor unit expansion valve 14 and the first shut-off valve 15, and is a subcooling heat exchanger that changes the state of two-phase gas-liquid refrigerant to single-phase liquid subcooled refrigerant.

[0020] The bypass piping 19E is a piping that allows a portion of the refrigerant flowing between the SC heat exchanger 19C and the first stop valve 15 to flow via the SC expansion valve 19B into the outdoor refrigerant pipe 26 that extends from the third port 12C of the four-way valve 12 to the accumulator 17. The mixing unit 19D is provided between the outdoor refrigerant pipe 26 and the bypass piping 19E. The mixing unit 19D mixes the refrigerant from the bypass piping 19E connected to the SC heat exchanger 19C with the refrigerant from the outdoor refrigerant pipe 26 via the third port 12C of the four-way valve 12, and inputs the mixed refrigerant to the refrigerant inlet side of the accumulator 17.

[0021] The SC heat exchanger 19C has a high-pressure side flow path and a low-pressure side flow path (not shown). Refrigerant flowing out from the outdoor unit expansion valve 14 when the indoor unit 3 is in cooling operation flows into the high-pressure side flow path. The refrigerant flowing into the high-pressure side flow path exchanges heat with refrigerant in the low-pressure side flow path and then flows out to the first stop valve 15. Refrigerant flowing out from the SC expansion valve 19B flows into the low-pressure side flow path. The refrigerant flowing into the low-pressure side flow path exchanges heat with refrigerant in the high-pressure side flow path and then flows out to the bypass piping 19E.

[0022] Furthermore, the outdoor liquid pipe 25 is provided with an SC expansion valve 19B upstream of the SC heat exchanger 19C in the refrigerant flow direction when the indoor unit 3 is in heating operation. With these configurations, the section of the outdoor liquid pipe 25 downstream of the SC heat exchanger 19C becomes a flow path through which single-liquid-phase refrigerant flows. The flow path through which single-liquid-phase refrigerant flows corresponds to one section of the outdoor liquid pipe 25. When the indoor unit 3 is in cooling operation, the section of the outdoor liquid pipe 25 between the SC heat exchanger 19C and the first stop valve 15 is the flow path through which single-liquid-phase refrigerant flows. When the indoor unit 3 is in heating operation, the section of the outdoor liquid pipe 25 between the SC heat exchanger 19C and the outdoor unit expansion valve 14 is the flow path through which single-liquid-phase refrigerant flows.

[0023] In addition, a plurality of sensors are arranged in the outdoor unit 2. A discharge pressure sensor 31 that detects the pressure of the refrigerant discharged from the compressor 11, i.e., the discharge pressure, and a discharge temperature sensor 32 that detects the temperature of the refrigerant discharged from the compressor 11, i.e., the discharge temperature, are arranged in the discharge pipe 21. A suction pressure sensor 33 that detects the suction pressure, which is the pressure of the refrigerant sucked into the compressor 11, and a suction temperature sensor 34 that detects the temperature of the refrigerant sucked into the compressor 11 are arranged near the refrigerant inlet of the accumulator 17 in the outdoor refrigerant pipe 26.

[0024] A refrigerant temperature sensor 35 is disposed in the outdoor liquid pipe 25 connecting the outdoor heat exchanger 13 and the outdoor unit expansion valve 14 to detect the temperature of the refrigerant flowing into the outdoor heat exchanger 13 or the temperature of the refrigerant flowing out of the outdoor heat exchanger 13. An outdoor air temperature sensor 36 is disposed near an air inlet (not shown) of the outdoor unit 2 to detect the temperature of the outdoor air flowing into the outdoor unit 2, i.e., the outdoor air temperature.

[0025] The first control unit 20 controls the entire air conditioner 1. FIG. 3A is a block diagram showing an example of the first control unit 20. The first control unit 20 has a first communication unit 41, a first acquisition unit 42, a first storage unit 43, and a first control unit 44. The first acquisition unit 42 acquires sensor values ​​from the various sensors described above. The first communication unit 41 is a communication interface that communicates with the second communication unit 71 of each indoor unit 3. The first storage unit 43 is, for example, a flash memory. The first storage unit 43 stores the control program for the outdoor unit 2, operational state quantities such as sensor values ​​acquired by the first acquisition unit 42, the drive status of the compressor 11 and the outdoor unit fan 18, operational information transmitted from each indoor unit 3 (including, for example, operation / stop information, operating mode such as cooling / heating, etc.), the rated capacity of the outdoor unit 2, and the required capacity of each indoor unit 3.

[0026] The first storage unit 43 also stores an estimation model 431 used to estimate the amount of refrigerant remaining in the refrigerant circuit 6, and a determination program 432 that determines whether or not there is a refrigerant leak in the refrigerant circuit 6, based on the remaining refrigerant amount that is an estimation result using the estimation model 431. In this embodiment, for example, the remaining refrigerant amount is expressed as a relative remaining refrigerant amount (full filling is defined as 100%).

[0027] The first control unit 44 periodically (e.g., every 30 seconds) acquires detection values ​​from various sensors via the first communication unit 41, and receives signals containing operation information transmitted from each indoor unit 3 via the first communication unit 41. Based on this input information, the first control unit 44 adjusts the opening of the outdoor unit expansion valve 14 and controls the drive of the compressor 11. Furthermore, the first control unit 44 is a refrigerant amount estimation device that estimates the amount of refrigerant remaining in the refrigerant circuit 6 using an estimation model 431. In other words, the first control unit 44 can estimate the amount of refrigerant remaining in the refrigerant circuit 6. Furthermore, the first control unit 44 uses a determination program 432 to determine whether or not a refrigerant leak exists in the refrigerant circuit 6 based on the determination result of whether or not the amount of refrigerant estimated by the estimation model 431 is less than a threshold value. In other words, the first control unit 44 can determine whether or not a refrigerant leak exists in the air conditioner 1.

[0028] 2 , the indoor unit 3 has an indoor heat exchanger 51, an indoor unit expansion valve 52, a liquid pipe connection 53, a gas pipe connection 54, an indoor unit fan 55, and a second control unit 50. The indoor heat exchanger 51, the indoor unit expansion valve 52, the liquid pipe connection 53, and the gas pipe connection 54 are connected to each other by refrigerant pipes described later, and constitute an indoor unit refrigerant circuit that forms part of the refrigerant circuit 6.

[0029] The indoor heat exchanger 51 exchanges heat between the refrigerant and indoor air taken into the indoor unit 3 through an air inlet (not shown) by the rotation of the indoor unit fan 55. One refrigerant inlet / outlet of the indoor heat exchanger 51 is connected to a liquid pipe connection part 53 by an indoor liquid pipe 56. The other refrigerant inlet / outlet of the indoor heat exchanger 51 is connected to a gas pipe connection part 54 by an indoor gas pipe 57. The indoor heat exchanger 51 functions as a condenser when the air conditioner 1 is performing heating operation, and functions as an evaporator when the air conditioner 1 is performing cooling operation.

[0030] The indoor unit expansion valve 52 is an electronic expansion valve provided in the indoor liquid pipe 56. When the indoor heat exchanger 51 functions as an evaporator, i.e., when the indoor unit 3 is performing cooling operation, the opening degree of the indoor unit expansion valve 52 is adjusted so that the refrigerant superheat degree at the refrigerant outlet (gas pipe connection 54 side) of the indoor heat exchanger 51 becomes a target superheat degree. When the indoor heat exchanger 51 functions as a condenser, i.e., when the indoor unit 3 is performing heating operation, the opening degree of the indoor unit expansion valve 52 is adjusted so that the refrigerant supercooling degree at the refrigerant outlet (liquid pipe connection 53 side) of the indoor heat exchanger 51 becomes a target supercooling degree. Here, the target superheat degree is the superheat degree required for the indoor unit 3 to provide sufficient cooling capacity. The target subcooling degree is the subcooling degree required for the indoor unit 3 to provide sufficient heating capacity.

[0031] The indoor unit fan 55 is made of a resin material and is disposed near the indoor heat exchanger 51. The indoor unit fan 55 is rotated by a fan motor (not shown) to take in indoor air into the indoor unit 3 through an intake port (not shown), and releases the indoor air that has exchanged heat with the refrigerant in the indoor heat exchanger 51 into the room through an outlet port (not shown).

[0032] Various sensors are provided in the indoor unit 3. A liquid-side refrigerant temperature sensor 61 is disposed in the indoor liquid pipe 56, between the indoor heat exchanger 51 and the indoor unit expansion valve 52, to detect the temperature of the refrigerant flowing into the indoor heat exchanger 51 or the indoor heat exchanger outlet temperature, which is the temperature of the refrigerant flowing out from the indoor heat exchanger 51. A gas-side temperature sensor 62 is disposed in the indoor gas pipe 57 to detect the temperature of the refrigerant flowing out from or into the indoor heat exchanger 51. A suction temperature sensor 63 is disposed near an air inlet (not shown) of the indoor unit 3 to detect the temperature of the indoor air flowing into the indoor unit 3, i.e., the suction temperature.

[0033] The second control unit 50 controls the entire indoor unit 3. FIG. 4 is a block diagram showing an example of the second control unit 50. The second control unit 50 has a second communication unit 71, a second acquisition unit 72, a second storage unit 73, and a second control unit 74. The second acquisition unit 72 acquires sensor values ​​from various sensors in the indoor unit 3. The second communication unit 71 is a communication interface that communicates with the first communication unit 41 of the outdoor unit 2. The second storage unit 73 is, for example, a flash memory. The second storage unit 73 stores the control program for the indoor unit 3, operation state quantities such as detected values ​​corresponding to detection signals from the various sensors, the drive state of the indoor unit fan 55, operation information of the indoor unit 3 (including, for example, operation / stop information, operation mode such as cooling / heating, etc.), and the required capacity of each indoor unit 3.

[0034] The second control unit 74 periodically (for example, every 30 seconds) transmits detected values ​​of various sensors in the indoor unit 3 to the first control unit 20 of the outdoor unit 2 via the second communication unit 71. The second control unit 74 adjusts the opening degree of the indoor unit expansion valve 52 based on the various types of input information.

[0035] <Operation of Refrigerant Circuit> Next, a description will be given of the flow of refrigerant in the refrigerant circuit 6 and the operation of each part during air conditioning operation of the air conditioner 1 in this embodiment. Note that the arrows in Fig. 2 indicate the flow of refrigerant during heating operation.

[0036] When the air conditioner 1 performs heating operation, the four-way valve 12 is switched so that the first port 12A and the fourth port 12D are connected and the second port 12B and the third port 12C are connected. As a result, the refrigerant circuit 6 becomes a heating cycle in which each indoor heat exchanger 51 functions as a condenser and the outdoor heat exchanger 13 functions as an evaporator. For ease of explanation, the flow of refrigerant during heating operation is indicated by solid arrows in Figure 2.

[0037] When the compressor 11 is driven with the refrigerant circuit 6 in the above state, the refrigerant discharged from the compressor 11 flows through the discharge pipe 21 and into the four-way valve 12, then flows from the four-way valve 12 through the outdoor gas pipe 24 and into the gas pipe 5 via the second shut-off valve 16. The refrigerant flowing through the gas pipe 5 is diverted to each indoor unit 3 via each gas pipe connection 54. The refrigerant that flows into each indoor unit 3 flows through each indoor gas pipe 57 and into each indoor heat exchanger 51. The refrigerant that flows into each indoor heat exchanger 51 condenses by exchanging heat with indoor air drawn into each indoor unit 3 by the rotation of each indoor unit fan 55. In other words, each indoor heat exchanger 51 functions as a condenser, and the indoor air heated by the refrigerant in each indoor heat exchanger 51 is blown into the room through an air outlet (not shown), thereby heating the room in which each indoor unit 3 is installed.

[0038] The refrigerant that flows from each indoor heat exchanger 51 into each indoor liquid pipe 56 is decompressed by passing through each indoor unit expansion valve 52, the opening of which is adjusted so that the degree of subcooling at the refrigerant outlet side of each indoor heat exchanger 51 becomes the target degree of subcooling. Here, the target degree of subcooling is determined based on the heating capacity required by each indoor unit 3.

[0039] The refrigerant decompressed by each indoor unit expansion valve 52 flows from each indoor liquid pipe 56 through each liquid pipe connection 53 into the liquid pipe 4. The refrigerant joined in the liquid pipe 4 flows into the outdoor unit 2 through the first shut-off valve 15. The refrigerant that flows into the first shut-off valve 15 of the outdoor unit 2 flows through the outdoor liquid pipe 25 and into the SC heat exchanger 19C. The refrigerant that flows into the SC heat exchanger 19C flows into the outdoor unit expansion valve 14 through the SC heat exchanger 19C. The refrigerant that flows into the outdoor unit expansion valve 14 then passes through the outdoor unit expansion valve 14 and is decompressed. The refrigerant that has been decompressed by the outdoor unit expansion valve 14 flows through the outdoor liquid pipe 25 and into the outdoor heat exchanger 13, where it exchanges heat with outside air that flows in from an air inlet (not shown) of the outdoor unit 2 due to the rotation of the outdoor unit fan 18, and evaporates. The refrigerant that flows out from the outdoor heat exchanger 13 to the outdoor refrigerant pipe 23 flows sequentially through the four-way valve 12, the outdoor refrigerant pipe 26, the accumulator 17, and the suction pipe 22. The refrigerant is then drawn into the compressor 11 and compressed again, and flows out into the outdoor gas pipe 24 via the first port 12A and the fourth port 12D of the four-way valve 12.

[0040] When the air conditioner 1 performs cooling operation, the four-way valve 12 is switched so that the first port 12A and the second port 12B are connected and the third port 12C and the fourth port 12D are connected. As a result, the refrigerant circuit 6 becomes a cooling cycle in which each indoor heat exchanger 51 functions as an evaporator and the outdoor heat exchanger 13 functions as a condenser. For ease of explanation, the flow of refrigerant during cooling operation is indicated by dashed arrows in Figure 2.

[0041] When the compressor 11 is driven in the refrigerant circuit 6, the refrigerant discharged from the compressor 11 flows through the discharge pipe 21 and into the four-way valve 12, and then flows from the four-way valve 12 through the outdoor refrigerant pipe 23 and into the outdoor heat exchanger 13. The refrigerant that has flowed into the outdoor heat exchanger 13 condenses by exchanging heat with outdoor air that has been drawn into the outdoor unit 2 by the rotation of the outdoor unit fan 18. In other words, the outdoor heat exchanger 13 functions as a condenser, and the indoor air heated by the refrigerant in the outdoor heat exchanger 13 is blown outside through an air outlet (not shown).

[0042] The refrigerant that flows from the outdoor heat exchanger 13 into the outdoor liquid pipe 25 passes through the outdoor unit expansion valve 14, which is fully open, and is reduced in pressure. The refrigerant reduced in pressure by the outdoor unit expansion valve 14 flows into the SC heat exchanger 19C via the branching portion 19A. The SC heat exchanger 19C exchanges heat between the refrigerant that passed through the SC expansion valve 19B and the refrigerant flowing through the outdoor liquid pipe 25. The refrigerant that has exchanged heat in the SC heat exchanger 19C flows through the liquid pipe 4 via the first stop valve 15 and is diverted to each indoor unit 3. The refrigerant that flows into each indoor unit 3 flows through the indoor liquid pipe 56 via each liquid pipe connection portion 53, and is reduced in pressure by passing through the indoor unit expansion valve 52, which has an opening adjusted to achieve a target degree of subcooling at the refrigerant outlet of the indoor heat exchanger 51. The refrigerant decompressed by the indoor unit expansion valve 52 flows through the indoor liquid pipe 56 and into the indoor heat exchanger 51, where it evaporates by exchanging heat with indoor air that has flowed in from an intake port (not shown) of the indoor unit 3 due to the rotation of the indoor unit fan 55. In other words, each indoor heat exchanger 51 functions as an evaporator, and the indoor air cooled by the refrigerant in each indoor heat exchanger 51 is blown out into the room from an outlet (not shown), thereby cooling the room in which each indoor unit 3 is installed.

[0043] The refrigerant flowing from the indoor heat exchanger 51 to the gas pipe 5 via the gas pipe connection part 54 flows into the outdoor gas pipe 24 via the second stop valve 16 of the outdoor unit 2 and flows into the fourth port 12D of the four-way valve 12. The refrigerant that has flowed into the fourth port 12D of the four-way valve 12 flows from the third port 12C into the refrigerant inlet side of the accumulator 17. The refrigerant that has flowed into the refrigerant inlet side of the accumulator 17 is sucked into the compressor 11 via the suction pipe 22 and is compressed again.

[0044] The first acquisition unit 42 in the first control unit 20 acquires the sensor values ​​of the discharge pressure sensor 31, discharge temperature sensor 32, suction pressure sensor 33, suction temperature sensor 63, refrigerant temperature sensor 35, and outside air temperature sensor 36 in the outdoor unit 2. Furthermore, the first acquisition unit 42 acquires the sensor values ​​of the liquid side refrigerant temperature sensor 61, gas side temperature sensor 62, and suction temperature sensor 63 of each indoor unit 3.

[0045] During cooling operation of the air conditioner 1, the outdoor heat exchanger 13 functions as a condenser, and the indoor heat exchanger 51 functions as an evaporator. During heating operation of the air conditioner 1, the outdoor heat exchanger 13 functions as an evaporator, and the indoor heat exchanger 51 functions as a condenser.

[0046] The compressor 11 compresses the low-temperature, low-pressure gas refrigerant flowing in from the evaporator and discharges the high-temperature, high-pressure gas refrigerant. The temperature of the gas refrigerant discharged from the compressor 11 is the discharge temperature, which is detected by a discharge temperature sensor 32.

[0047] The condenser condenses the high-temperature, high-pressure gas refrigerant from the compressor 11 by exchanging heat with air. During this process, after the gas refrigerant has completely turned into liquid refrigerant due to latent heat change in the condenser, the temperature of the liquid refrigerant drops due to sensible heat change, resulting in a supercooled state. The temperature at which the gas refrigerant is changing into liquid refrigerant due to latent heat change is the high-pressure saturation temperature, and the temperature of the refrigerant in the supercooled state at the outlet of the condenser is the heat exchanger outlet temperature. The high-pressure saturation temperature is a temperature equivalent to the pressure value (HPS) detected by the discharge pressure sensor 31. The heat exchanger outlet temperature is detected by the refrigerant temperature sensor 35.

[0048] The expansion valve reduces the pressure of the high-pressure refrigerant that has flowed out of the condenser, and the reduced-pressure refrigerant becomes a gas-liquid two-phase refrigerant in which gas and liquid are mixed.

[0049] The evaporator evaporates the two-phase gas-liquid refrigerant that has flowed in through heat exchange with air. During this process, after the two-phase gas-liquid refrigerant in the evaporator has completely changed to gas refrigerant due to latent heat change, the temperature of the gas refrigerant rises due to sensible heat change, becoming superheated, and is then drawn into the compressor 11. The temperature at which the liquid refrigerant is changing to gas refrigerant due to latent heat change is the low-pressure saturation temperature. The low-pressure saturation temperature is a temperature corresponding to the pressure value (LPS) detected by the suction pressure sensor 33. The temperature of the refrigerant that has been superheated in the evaporator and is drawn into the compressor 11 is the suction temperature. The suction temperature is detected by the suction temperature sensor 34.

[0050] The degree of subcooling of the refrigerant that is in a subcooled state when it flows out of the condenser is the heat exchange subcool, which can be calculated by subtracting the refrigerant temperature at the refrigerant outlet of the heat exchanger functioning as a condenser (the heat exchange outlet temperature) from the high-pressure saturation temperature. The degree of superheat of the refrigerant that is in a superheated state when it flows out of the evaporator is the suction superheat, which can be calculated by subtracting the low-pressure saturation temperature from the suction temperature.

[0051] <Configuration of Estimation Model> The estimation model 431 is generated by a learning algorithm using machine learning, using training data of multiple operating state quantities. The operating state quantities include feature quantities such as state quantities correlated with the outside air temperature, the degree of subcooling, the degree of superheating, and the length of the refrigerant piping. The state quantities correlated with the piping length include, for example, the pressure difference and the inlet refrigerant circulation amount. The estimation model 431 is a learning model in which the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference, and the inlet circulating refrigerant amount are learned in association with the remaining refrigerant amount.

[0052] Nonlinear algorithms such as random forests and neural networks are used for learning algorithms. Using nonlinear algorithms, the remaining refrigerant volume can be estimated by combining the remaining refrigerant volume with values ​​that are not linearly proportional to the remaining refrigerant volume. For example, random forests are an ensemble learning method that combines multiple decision trees. Each tree learns independently, and classification is ultimately performed by majority vote or average. This prevents overfitting and improves the estimation accuracy of the model. On the other hand, neural networks are deep learning models consisting of multiple layers: an input layer, one or more hidden layers, and an output layer. Each layer consists of multiple nodes (neurons), and information is transmitted between nodes in adjacent layers via weighted connections. Neural networks are well-suited to advanced classification problems due to their ability to capture nonlinear relationships and complex patterns.

[0053] <Learning Phase> Fig. 3B is a functional block diagram showing an example of the first control unit 44 in the learning phase for creating an estimation model. The first control unit 44 shown in Fig. 3B includes an outside air temperature acquisition unit 441, a degree of subcooling acquisition unit 442, a degree of superheat acquisition unit 443, a pressure difference acquisition unit 444, an inlet refrigerant circulation amount acquisition unit 445, a remaining refrigerant amount acquisition unit 446, and a learning unit 447. The remaining refrigerant amount acquisition unit 446 receives the remaining refrigerant amount set when acquiring data for learning, and outputs the remaining refrigerant amount to the learning unit 447 as training data.

[0054] The outside air temperature acquisition unit 441 acquires the outside air temperature through the first acquisition unit 42 and outputs the acquired outside air temperature as training data to the learning unit 447. During cooling operation, the degree of subcooling tends to decrease as the outside air temperature increases. Therefore, the outside air temperature is useful as training data for identifying the factors behind fluctuations in the value of the subcooling degree.

[0055] The subcooling degree acquisition unit 442 calculates the subcooling degree based on the heat exchanger outlet temperature of the condenser and the high-pressure saturation temperature of the condenser when the outdoor heat exchanger 13 functions as a condenser. That is, the subcooling degree can be calculated, for example, as (high-pressure saturation temperature - heat exchanger outlet temperature). The high-pressure saturation temperature is a temperature equivalent to the pressure value detected by the discharge pressure sensor 31. The heat exchanger outlet temperature during cooling operation is the outdoor heat exchanger outlet temperature detected by the refrigerant temperature sensor 35. The heat exchanger outlet temperature during heating operation is the indoor heat exchanger outlet temperature detected by the liquid-side refrigerant temperature sensor 61. There are two subcooling degrees: one used during cooling operation and one used during heating operation. The subcooling degree during cooling operation can be calculated as (high-pressure saturation temperature - outdoor heat exchanger outlet temperature). In this embodiment, one outdoor unit 2 is used; however, if multiple outdoor units 2 are connected, a representative outdoor unit 2 can be selected and its operating state quantities can be used. The degree of subcooling during heating operation can be calculated as (high-pressure saturation temperature - indoor heat exchanger outlet temperature). In this embodiment, multiple indoor units 3 are connected to one outdoor unit 2. In this case, the degree of subcooling is calculated using the operating state quantities of the indoor units 3 that are operating. Note that the heat load (cooling capacity) that can be processed by each operating indoor unit 3 may differ. In this case, it is advisable to use a weighted average value in which the operating state quantities of the operating indoor units 3 are weighted by their cooling capacity. The subcooling degree acquisition unit 442 outputs the calculated degree of subcooling to the learning unit 447 as training data.

[0056] The superheat degree acquisition unit 443 calculates the degree of superheat based on the suction temperature of the compressor 11 and the low-pressure saturation temperature of the compressor 11 when the outdoor heat exchanger 13 functions as an evaporator. Specifically, the superheat degree can be calculated by (suction temperature - low-pressure saturation temperature), where the suction temperature is detected by the suction temperature sensor 34 and the low-pressure saturation temperature is a temperature corresponding to the pressure value detected by the suction pressure sensor 33. The outside air temperature is detected by the outside air temperature sensor 36. The superheat degree acquisition unit 443 outputs the calculated degree of superheat to the learning unit 447 as training data.

[0057] The pressure difference acquisition unit 444 calculates a pressure difference, which is a first state quantity, based on the difference between a discharge pressure (HPS), which is the pressure of the refrigerant discharged from the compressor 11, and a suction pressure (LPS), which is the pressure of the refrigerant drawn into the compressor 11. The discharge pressure is a pressure value detected by the discharge pressure sensor 31. The suction pressure is a pressure value detected by the suction pressure sensor 33. The pressure difference acquisition unit 444 outputs the calculated pressure difference to the learning unit 447 as training data.

[0058] The inlet refrigerant circulation amount acquisition unit 445 uses the suction refrigerant density of the compressor 11, the compressor displacement volume of the compressor 11, and the compressor rotation speed of the compressor 11 to calculate the inlet refrigerant circulation amount, which is a second state quantity, based on the suction refrigerant density × compressor displacement volume × compressor rotation speed. The suction refrigerant density varies depending on the operating conditions of the compressor 11 and is calculated using the suction temperature and the suction pressure (LPS). The suction temperature is a temperature detected by the suction temperature sensor 34. The suction pressure is a pressure value detected by the suction pressure sensor 33. The compressor displacement volume is a displacement volume specified by the compressor 11. The compressor rotation speed is the rotation speed of the compressor 11, which varies depending on the operating conditions of the compressor 11 and can be calculated based on the drive frequency of the inverter that drives the compressor 11. The inlet refrigerant circulation amount acquisition unit 445 outputs the calculated inlet refrigerant circulation amount to the learning unit 447 as training data.

[0059] The pressure difference and the inlet refrigerant circulation volume are correlated with the piping length of the refrigerant piping connecting the outdoor unit 2 and the indoor unit 3. The pressure difference at the same inlet refrigerant circulation volume increases as the piping length increases. Specifically, the pressure loss is proportional to the square of the flow velocity and proportional to the piping length. The piping length can be taken into account by using the inlet refrigerant circulation volume and the pressure loss value. Therefore, the pressure difference and the inlet refrigerant circulation volume, which are correlated with the piping length, are useful as training data when estimating the remaining refrigerant volume.

[0060] In generating the estimation model 431, the relationship between each operational state quantity and the remaining refrigerant amount is first reproduced by the learning unit 447, and numerical calculations (hereinafter also referred to as simulations) are performed under predetermined execution conditions. The predetermined execution conditions are, for example, set conditions such as the remaining refrigerant amount, outdoor unit capacity, indoor unit capacity, number of connected indoor units, piping length, number of operating indoor units, and temperature. The remaining refrigerant amount is the amount of refrigerant remaining in the refrigerant piping of the refrigerant circuit 6 (this may include refrigerant remaining in the compressor 11 and the outdoor heat exchanger 13). The outdoor unit capacity is a value based on the capacity of the outdoor unit 2. The indoor unit capacity is a value based on the capacity of the indoor unit 3. The number of connected indoor units is the number of indoor units 3 connected to the outdoor unit 2. The piping length is the length of the refrigerant piping. The number of operating indoor units is the number of indoor units 3 that are operating among the multiple indoor units 3 connected to the outdoor unit 2. The temperature is the outdoor air temperature or indoor temperature in the installation environment of the air conditioner 1.

[0061] The simulation generates numerical data (also referred to as data points) that summarize the relationship between each operating state quantity and the remaining refrigerant amount at predetermined time intervals. Each operating state quantity is changed under conditions where the remaining refrigerant amount is relatively different (for example, 40%, 70%, 80%, 100%, 120%, etc.), and multiple data points are generated by simulating the relationship between each operating state quantity and the remaining refrigerant amount when the air conditioner 1 is in a refrigerant leak or refrigerant overfill state. The entire data consisting of these data points is stored as a data set in the first storage unit 43.

[0062] The learning unit 447 generates the estimation model 431 through machine learning using a data set of the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference and inlet refrigerant circulation amount at a specific pipe length, and the remaining refrigerant amount as training data. For example, the maximum pipe length determined for each model of the air conditioner 1 is used as the specific pipe length. This is because the longer the pipe length, the more likely it is that the accuracy of estimating the remaining refrigerant amount will deteriorate. The learning unit 447 then stores the generated estimation model 431 in the first storage unit 43. The estimation model 431 is evaluated using indices such as accuracy, recall, and F1 score. Ultimately, the optimal model is selected as the estimation model 431 based on these indices.

[0063] The estimation model 431 can be generated using not only simulation results but also actual operating data to learn the relationship between each state quantity (subcooling degree, superheat degree, outside air temperature, pressure difference, and inlet refrigerant circulation amount) and the remaining refrigerant amount during cooling operation and heating operation. During this process, parameters are adjusted to optimize the performance of the learning model.

[0064] Fig. 5 is an explanatory diagram showing an example of explanatory variables used in the estimation model 431. As shown in Fig. 5, the explanatory variables used in the estimation model 431 are the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference, and the amount of inlet circulating refrigerant.

[0065] <Inference Phase> Figure 3C is a functional block diagram showing an example of the first control unit 44 in the inference phase for estimating the remaining refrigerant amount. The first control unit 44 shown in Figure 3C includes an outside air temperature acquisition unit 441, a subcooling degree acquisition unit 442, a superheat degree acquisition unit 443, a pressure difference acquisition unit 444, an inlet refrigerant circulation amount acquisition unit 445, an estimation unit 448, and a remaining refrigerant amount output unit 449. The outside air temperature acquisition unit 441 acquires the actual measured value of the outside air temperature through the first acquisition unit 42 and outputs the acquired current outside air temperature as an explanatory variable to the estimation unit 448. The subcooling degree acquisition unit 442 calculates the current measured value of the subcooling degree and outputs the calculated subcooling degree as an explanatory variable to the estimation unit 448.

[0066] The superheat degree acquisition unit 443 calculates the degree of superheat based on the current actual measurement value and outputs the calculated degree of superheat as an explanatory variable to the estimation unit 448. The pressure difference acquisition unit 444 calculates the pressure difference based on the current actual measurement value and outputs the calculated pressure difference as an explanatory variable to the estimation unit 448. The inlet refrigerant circulation amount acquisition unit 445 calculates the inlet refrigerant circulation amount based on the current actual measurement value and outputs the calculated inlet refrigerant circulation amount to the estimation unit 448 as an explanatory variable.

[0067] When the estimation unit 448 receives the actual measured values ​​of the outside air temperature, degree of subcooling, degree of superheat, pressure difference, and inlet refrigerant circulation volume as explanatory variables, it uses the estimation model 431 to relatively estimate the remaining refrigerant volume as the objective variable, and outputs the estimated remaining refrigerant volume to the remaining refrigerant volume output unit 449.

[0068] Next, the accuracy of estimating the remaining refrigerant amount using the estimation model 431 of the first embodiment and the estimation model of the comparative example will be described. The estimation model of the comparative example is a learning model that learns by associating the remaining refrigerant amount with teacher data such as the degree of subcooling, the degree of superheat, and the outside air temperature. In contrast, the estimation model 431 of the first embodiment is a learning model that learns by associating the remaining refrigerant amount with teacher data such as the degree of subcooling, the degree of superheat, the outside air temperature, the pressure difference at the maximum pipe length, and the inlet refrigerant circulation amount.

[0069] 6 is an explanatory diagram showing the estimable range of remaining refrigerant amount as a function of the degree of subcooling and the degree of superheat. The comparative example estimation model can estimate the remaining refrigerant amount with high accuracy within the first estimation range M1. However, as the refrigerant piping length increases, the degree of subcooling tends to decrease and the degree of superheat tends to increase (second estimation range M2). Therefore, because the comparative example estimation model does not take the refrigerant piping length into account, the accuracy of estimating the remaining refrigerant amount significantly decreases outside the first estimation range M1.

[0070] In contrast, the estimation model 431 of this embodiment uses, for example, the pressure difference and the inlet refrigerant circulation volume, which are correlated with the pipe length, in addition to the degree of subcooling, the degree of superheat, and the outside air temperature. That is, the estimation model 431 takes into account the pressure difference and the inlet refrigerant circulation volume, which are correlated with the pipe length, and therefore can estimate the remaining refrigerant volume in the second estimation range M2 with high accuracy in addition to the first estimation range M1.

[0071] <Configuration of Determination Program> The determination program 432 is a program that determines whether the remaining refrigerant amount estimated by the estimation model 431 is less than a threshold value, and determines whether there is a refrigerant leak in the refrigerant circuit 6 based on the determination result. The first control unit 44 in the first control unit 20 executes the determination program 432 and determines whether the remaining refrigerant amount estimated by the estimation model 431 is less than the threshold value. If the remaining refrigerant amount is less than the threshold value, the first control unit 44 determines that there is a refrigerant leak in the refrigerant circuit 6. Furthermore, if the remaining refrigerant amount is not less than the threshold value, the first control unit 44 determines that there is no refrigerant leak in the refrigerant circuit 6.

[0072] <Operation of Estimation Processing> Figure 7 is a flowchart showing an example of the processing operation of the first control unit 20 related to the estimation processing. It is assumed that the first control unit 20 stores a pre-generated estimation model 431 in the first storage unit 43. In Figure 7, the first control unit 44 in the first control unit 20 collects driving state quantities as driving data via the first acquisition unit 42 (step S11). The first control unit 44 executes a data filtering process to extract any driving state quantity from the collected driving data (step S12). Furthermore, the first control unit 44 executes a data cleansing process (step S13).

[0073] The data filtering process does not use all of the multiple operation state quantities, but extracts only a portion of the multiple operation state quantities necessary for estimating the remaining refrigerant amount based on predetermined filter conditions. The remaining refrigerant amount can be more accurately estimated by substituting the operation state quantities that have been subjected to the data filtering process (with abnormal values ​​and outliers removed) as explanatory variables into the generated estimation model 431.

[0074] The predetermined filter condition is, for example, a filter condition for data extracted in common for all operation modes of the air conditioner 1. The predetermined filter condition is, for example, the drive state of the compressor 11, identification of the operation mode, elimination of special operations, elimination of missing values ​​in the acquired values, selection of values ​​with small amounts of change for operation state quantities that have a large impact on the generation of the estimation model 431, etc. The drive state of the compressor 11 is a condition that must be determined because the remaining refrigerant amount cannot be estimated unless the compressor 11 is operating stably and refrigerant is circulating in the refrigerant circuit 6, and is a filter condition set to exclude operation state quantities detected during a transition period, such as when the compressor 11 is starting up.

[0075] The operation mode identification is a filter condition for extracting only the operation state quantities acquired during cooling operation and heating operation. Therefore, the operation state quantities acquired during dehumidification operation and ventilation operation are excluded. The special operation exclusion is a filter condition for excluding the operation state quantities acquired during special operation, such as oil recovery operation and defrosting operation, in which the state of the refrigerant circuit 6 is significantly different from that during cooling operation and heating operation. The missing value exclusion is a filter condition for excluding the operation state quantities containing missing values, because if the operation state quantities used to estimate the remaining refrigerant amount contain missing values, generating an estimation model using those operation state quantities may result in a decrease in accuracy.

[0076] Selecting values ​​with small changes in the operating state quantities to be substituted into the estimation model 431 is a filter condition that extracts only the operating state quantities when the operating state of the air conditioner 1 is stable, and is a necessary condition for improving the estimation accuracy using the estimation model.

[0077] The data cleansing process is a process for excluding operating state variables that may lead to an erroneous determination, rather than using all acquired operating state variables to estimate the remaining refrigerant amount. Specifically, the acquired operating state variables are smoothed to suppress noise and limit the number of data items. Noise suppression by data smoothing is a process for suppressing noise by calculating average values ​​for a corresponding section and then taking moving averages of, for example, the degree of subcooling, suction temperature, and degree of superheat in the estimation model 431. Limiting the number of data items is a process for excluding data items with a small number of items because they are unreliable. For example, if the number of remaining data items after filtering one day's worth of input data is X or more, they are used to estimate the remaining refrigerant amount; if there are fewer, none of the data for that day is used. In other words, the data cleansing process allows for a more accurate determination of the presence or absence of a refrigerant leak by substituting operating state variables, from which abnormal values ​​and outliers have been removed, into the estimation model 431.

[0078] Furthermore, as part of the data cleansing process, the first control unit 44 extracts the current outdoor air temperature, the current degree of subcooling, the current degree of superheating, the current pressure difference, and the current inlet refrigerant circulation volume, and then calculates the theoretical discharge temperature of the compressor 11 based on the high-pressure saturation temperature of the outdoor heat exchanger 13, the low-pressure saturation temperature of the outdoor heat exchanger 13, and the suction temperature of the compressor 11. The first control unit 44 then compares the calculated theoretical discharge temperature with the actual discharge temperature. The first control unit 44 then deletes from the extracted data the current rotation speed of the compressor 11, the current outdoor air temperature, the current degree of subcooling, and the current degree of superheating extracted when the theoretical discharge temperature exceeds the actual discharge temperature. The first control unit 44 also substitutes the current outdoor air temperature, the current degree of subcooling, the current degree of superheating, the current pressure difference, and the current inlet refrigerant circulation volume extracted when the theoretical discharge temperature is equal to or lower than the actual discharge temperature into the estimation model 431 as explanatory variables.

[0079] 7, the first control unit 44 extracts the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference, and the inlet refrigerant circulation volume as explanatory variables from the operating data after the cleansing process (step S14). Specifically, the outside air temperature acquisition unit 441 in the first control unit 44 extracts the outside air temperature as an explanatory variable. The subcooling degree acquisition unit 442 in the first control unit 44 extracts the degree of subcooling as an explanatory variable. The superheat degree acquisition unit 443 in the first control unit 44 extracts the degree of superheating as an explanatory variable. The pressure difference acquisition unit 444 in the first control unit 44 extracts the pressure difference as an explanatory variable. The inlet refrigerant circulation volume acquisition unit 445 in the first control unit 44 extracts the inlet refrigerant circulation volume as an explanatory variable.

[0080] The estimation unit 448 in the first control unit 44 substitutes the extracted actual measured values ​​of the outside air temperature, degree of subcooling, degree of superheating, pressure difference, and inlet refrigerant circulation amount into the estimation model 431 as explanatory variables (step S15).

[0081] The estimation unit 448 in the first control unit 44 estimates and outputs the amount of refrigerant remaining in the refrigerant circuit 6 using the estimation model 431 after substitution of the explanatory variables (step S16), and the processing operation shown in FIG. 7 ends.

[0082] Fig. 8 is a flowchart showing an example of a processing operation of the first control unit 20 related to the determination process. The determination process is a process in which the first control unit 20 executes the determination program 432. In Fig. 8, the first control unit 44 of the first control unit 20 determines whether or not an estimation result of the remaining refrigerant amount has been acquired (step S21).

[0083] When the first control unit 44 obtains the estimated remaining refrigerant amount (step S21: Yes), it determines whether the remaining refrigerant amount is less than a threshold value (step S22). If the remaining refrigerant amount is less than the threshold value (step S22: Yes), the first control unit 44 determines that a refrigerant leak has occurred, outputs a notification indicating that a refrigerant leak has occurred (step S23), and ends the processing operation shown in Fig. 8. As a result, the user of the air conditioner 1 can recognize that a refrigerant leak has occurred based on the notification output indicating that a refrigerant leak has occurred.

[0084] If the remaining refrigerant amount is not less than the threshold value (step S22: No), the first control unit 44 determines that there is no refrigerant leak, outputs a notification that there is no refrigerant leak (step S24), and ends the processing operation shown in Fig. 8. As a result, the user of the air conditioner 1 can recognize that there is no refrigerant leak based on the output notification that there is no refrigerant leak. If the first control unit 44 has not obtained an estimation result of the remaining refrigerant amount (step S21: No), it ends the processing operation shown in Fig. 8.

[0085] Effects of First Embodiment The first control unit 20 of the first embodiment generates an estimation model 431 using a nonlinear algorithm and operating state quantities related to estimation of the remaining refrigerant amount in the refrigerant circuit 6, such as the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference at the maximum pipe length, and the inlet refrigerant circulation amount. As a result, it is possible to generate the estimation model 431 that can accurately estimate the remaining refrigerant amount circulating in the refrigerant circuit 6.

[0086] The first control unit 20 estimates the remaining refrigerant amount using the estimation model 431, the outside air temperature, the degree of subcooling, the degree of superheat, the pressure difference, and the inlet refrigerant circulation amount. As a result, the remaining refrigerant amount in the refrigerant circuit 6 can be estimated with high accuracy without using the opening degree of the SC expansion valve and the SC heat exchanger outlet temperature, and regardless of the piping length.

[0087] In the regression calculation process (or estimation model application process) when estimating the remaining refrigerant amount, the current operating state quantities after the data filtering process and the data cleansing process are substituted into the estimation model 431. In this embodiment, the estimation model 431 is generated using feature quantities obtained by simulation, and the feature quantities obtained by simulation do not include any abnormal values ​​or values ​​that are significantly larger or smaller than others. By performing the data filtering process and the data cleansing process to substitute the operating state quantities from which the abnormal values ​​and the abnormal values ​​have been removed into the estimation model 431 generated using such feature quantities that do not include any abnormal values ​​or abnormal values, the remaining refrigerant amount can be estimated more accurately.

[0088] In the estimation model 431 of Example 1, the training data for the pressure difference and inlet refrigerant circulation rate at the maximum pipe length are used as state quantities correlated with the pipe length. However, the estimation model 431 can further improve estimation accuracy by using training data for the pressure difference and inlet refrigerant circulation rate at the standard pipe length in addition to the training data for the pressure difference and inlet refrigerant circulation rate at the maximum pipe length. The standard pipe length is a pipe length set taking into account normal installation conditions. Specifically, in this example, the training data is set to 400 m as the maximum pipe length and 35 m as the standard pipe length. These are set appropriately depending on the model of the air conditioner 1.

[0089] 9 is an explanatory diagram showing an example of the relationship between the pressure difference and the inlet refrigerant circulation amount when the piping length is the maximum and when the piping length is the standard. In FIG. 9, the first feature quantity is a feature quantity that shows the relationship between the pressure difference and the inlet refrigerant circulation amount when the piping length is the maximum. The first feature quantity is a feature quantity when the piping length is the maximum, at which the influence of the piping length on the refrigerant amount estimation becomes significant.

[0090] The second feature quantity is a feature quantity that indicates the relationship between the pressure difference and the inlet refrigerant circulation volume when the piping length is standard. The second feature quantity is a feature quantity when the piping length is standard. The pressure difference for a given refrigerant flow rate increases as the piping length increases. Therefore, the slope of the second feature quantity is gentler than the slope of the first feature quantity.

[0091] The estimation model 431 includes an estimation model that learns the outside air temperature, the degree of subcooling, the degree of superheat, the pressure difference and the inlet refrigerant circulation volume at the maximum piping length, the pressure difference and the inlet refrigerant circulation volume at the standard piping length, and the remaining refrigerant volume in association with each other. The estimation unit 448 estimates the remaining refrigerant volume by substituting the outside air temperature, the degree of subcooling, the degree of superheat, the pressure difference, and the inlet refrigerant circulation volume as explanatory variables into the estimation model. This allows the remaining refrigerant volume to be estimated with high accuracy regardless of the piping length.

[0092] In the first embodiment, the estimation model 431 used in the first control unit 20 is generated by learning the relationship between the outdoor air temperature, the degree of subcooling, the degree of superheat, the pressure difference, and the inlet refrigerant circulation volume and the remaining refrigerant volume. However, the estimation model 431 may be generated by learning the relationship between at least the degree of subcooling, the pressure difference, and the inlet refrigerant circulation volume and the remaining refrigerant volume, and this can be modified as appropriate. For example, the estimation model 431 may be generated by learning the relationship between the degree of subcooling, the outdoor air temperature, the pressure difference, and the inlet refrigerant circulation volume and the remaining refrigerant volume. Furthermore, the estimation model 431 may be generated by learning the relationship between the degree of subcooling, the degree of superheat, the pressure difference, and the inlet refrigerant circulation volume and the remaining refrigerant volume. Furthermore, the estimation model 431 may be generated by learning the relationship between the number of connected indoor units, the degree of subcooling, the pressure difference, and the inlet refrigerant circulation volume and the remaining refrigerant volume, and this can be modified as appropriate.

[0093] The initial refrigerant charge amount of an air conditioner 1 with multiple indoor units 3 is determined by the "precharged refrigerant amount" and the "refrigerant amount based on piping length," without taking into account the total capacity of the indoor units 3. Because the air conditioner 1 cannot be transported fully charged with refrigerant, additional refrigeration is required at the installation site based on the piping length. Therefore, a configuration with a large total capacity of indoor units 3 results in a smaller refrigerant amount relative to the total volume of the refrigerant circuit 6 than a configuration with a small total capacity. Furthermore, even if the number of indoor units 3 is different, the refrigerant charge amount remains the same if the piping length is the same. In other words, even if the total piping length (total piping volume) is the same, for example, a larger number of indoor units 3 tends to reduce the degree of subcooling. Therefore, the estimation model 431 may use a learning model trained in association with the number of indoor units 3 and the remaining refrigerant amount, in addition to the outdoor air temperature, degree of subcooling, degree of superheat, pressure difference at maximum piping length, and inlet refrigerant circulation volume. In this case, the first control unit 44 must learn under conditions where the total capacity of the indoor units 3 is different.

[0094] When the estimation unit 448 employs an estimation model including teacher data on the number of indoor units 3, it can estimate the remaining refrigerant amount with high accuracy according to fluctuations in the number of indoor units 3 by substituting the number of indoor units 3 in addition to the outdoor air temperature, degree of subcooling, degree of superheating, pressure difference, and inlet refrigerant circulation amount.

[0095] In the air conditioner 1 of Example 1, an example is given in which the first control unit 44 in the first control unit 20 generates an estimation model 431 and stores the generated estimation model 431 in the first memory unit 43, but this is not limited to this.

[0096] FIG. 10 is an explanatory diagram showing an example of an air conditioning system 100 of Example 2. Note that the same components as those in the air conditioner 1 of Example 1 are assigned the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The air conditioner 1 of Example 1 differs from the air conditioning system 100 of Example 2 in that an estimation model 431 is generated in a server device 110, and the generated estimation model 431 is stored in a centralized controller 7. The air conditioning system 100 shown in FIG. 10 includes an air conditioner 1, a centralized controller 7, a server device 110, and a communication network 120. The server device 110 generates an estimation model 431 of the air conditioner 1 included in the air conditioning system 100, and includes a fourth control unit 90 that stores the generated estimation model 431. The communication network 120 is, for example, a communication network such as the Internet.

[0097] The fourth control unit 90 in the server device 110 uses data sets of the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference and inlet refrigerant circulation amount at the maximum pipe length, and the remaining refrigerant amount as training data to learn and generate an estimation model 431 through machine learning. The server device 110 transmits the generated estimation model 431 to the centralized controller 7 via the communication network 120.

[0098] The centralized controller 7 has a third control unit 80. FIG. 11 is a block diagram showing an example of the third control unit 80. The third control unit 80 has a third communication unit 81, a third acquisition unit 82, a third storage unit 83, and a third control unit 84. The third acquisition unit 82 acquires sensor values ​​from the various sensors described above. The third communication unit 81 is a communication interface that communicates with the first communication unit 41 of the outdoor unit 2 and with the communication network 120. The third storage unit 83 is, for example, a flash memory. The third control unit 84 stores the estimation model 431 received from the server device 110 via the communication network 120 through the third communication unit 81 in the third storage unit 83.

[0099] The third control unit 84 periodically (for example, every 30 seconds) acquires detected values ​​from various sensors via the third communication unit 81, and receives signals including operation information transmitted from the outdoor unit 2 and each indoor unit 3 via the third communication unit 81. In the case of the air conditioning system 100 shown in FIG. 10 , the third control unit 84 is a refrigerant amount estimation device that estimates the remaining refrigerant amount circulating in the refrigerant circuit 6 using an estimation model 431 stored in the third memory unit 83.

[0100] When the actual measured values ​​of the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference, and the inlet refrigerant circulation volume are input as explanatory variables, the third control unit 84 uses the estimation model 431 to highly accurately estimate the remaining refrigerant volume in the refrigerant circuit 6. Then, the third control unit 84 transmits the remaining refrigerant volume, which is the estimation result of the estimation model 431, to the first control unit 20 of the outdoor unit 2 via the third communication unit 81.

[0101] Then, the first control unit 44 in the first control unit 20 of the outdoor unit 2 executes the determination program 432 and determines whether the remaining refrigerant amount received from the centralized controller 7 is less than the threshold value. If the remaining refrigerant amount is less than the threshold value, the first control unit 44 determines that there is a refrigerant leak in the refrigerant circuit 6. If the remaining refrigerant amount is not less than the threshold value, the first control unit 44 determines that there is no refrigerant leak in the refrigerant circuit 6.

[0102] 10 illustrates an example in which the estimation model 431 generated by the server device 110 is stored in the third storage unit 83 in the centralized controller 7, and the centralized controller 7 estimates the remaining refrigerant amount using the estimation model 431. However, the present invention is not limited to this. The estimation model 431 stored in the centralized controller 7 may be transmitted to the first control unit 20 of the outdoor unit 2, and the estimation model 431 may be stored in the first storage unit 43 of the first control unit 20. The first control unit 44 in the first control unit 20 may estimate the remaining refrigerant amount using the estimation model 431 stored in the first storage unit 43 by inputting actual measured values ​​of the outside air temperature, the degree of subcooling, the degree of superheat, the pressure difference, and the inlet refrigerant circulation rate as explanatory variables, and this can be modified as appropriate.

[0103] In the air conditioner 1 of Example 1, a refrigerant circuit 6 employing an SC heat exchanger 19C is illustrated, but the present invention is also applicable to a refrigerant circuit 6A that does not employ an SC heat exchanger, and therefore this embodiment will be described as Example 3. Note that the same components as those in the air conditioner 1 of Example 1 are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted.

[0104] 12 is an explanatory diagram showing an example of an outdoor unit 2 and an indoor unit 3 of Example 3. The air conditioner 1A of Example 3 differs from the air conditioner 1 of Example 1 in that it has a refrigerant circuit 6A that does not include an injection circuit 19 including an SC heat exchanger 19C and the like.

[0105] The outdoor unit 2 has a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor unit expansion valve 14, a first shut-off valve 15, a second shut-off valve 16, an accumulator 17, an outdoor unit fan 18, and a first control unit 20. The compressor 11, the four-way valve 12, the outdoor heat exchanger 13, the outdoor unit expansion valve 14, the first shut-off valve 15, the second shut-off valve 16, and the accumulator 17 are connected to each other by refrigerant pipes described in detail below to form an outdoor-side refrigerant circuit that forms part of the refrigerant circuit 6A.

[0106] <Operation of Refrigerant Circuit> Next, a description will be given of the flow of refrigerant and the operation of each part in the refrigerant circuit 6A during air conditioning operation of the air conditioner 1A of embodiment 3. Note that the arrows in Fig. 12 indicate the flow of refrigerant during heating operation.

[0107] When the air conditioner 1A performs heating operation, the four-way valve 12 is switched so that the first port 12A and the fourth port 12D are connected and the second port 12B and the third port 12C are connected. As a result, the refrigerant circuit 6A becomes a heating cycle in which each indoor heat exchanger 51 functions as a condenser and the outdoor heat exchanger 13 functions as an evaporator. For ease of explanation, the flow of refrigerant during heating operation is indicated by solid arrows in Figure 12.

[0108] When the compressor 11 is driven with the refrigerant circuit 6A in the above state, the refrigerant discharged from the compressor 11 flows through the discharge pipe 21 and into the four-way valve 12, then flows from the four-way valve 12 through the outdoor gas pipe 24 and into the gas pipe 5 via the second shut-off valve 16. The refrigerant flowing through the gas pipe 5 is diverted to each indoor unit 3 via each gas pipe connection 54. The refrigerant that flows into each indoor unit 3 flows through each indoor gas pipe 57 and into each indoor heat exchanger 51. The refrigerant that flows into each indoor heat exchanger 51 condenses by exchanging heat with indoor air drawn into each indoor unit 3 by the rotation of each indoor unit fan 55. In other words, each indoor heat exchanger 51 functions as a condenser, and the indoor air heated by the refrigerant in each indoor heat exchanger 51 is blown into the room through an air outlet (not shown), thereby heating the room in which each indoor unit 3 is installed.

[0109] The refrigerant that flows from each indoor heat exchanger 51 into each indoor liquid pipe 56 is decompressed by passing through each indoor unit expansion valve 52, the opening of which is adjusted so that the degree of subcooling at the refrigerant outlet side of each indoor heat exchanger 51 becomes the target degree of subcooling. Here, the target degree of subcooling is determined based on the heating capacity required by each indoor unit 3.

[0110] The refrigerant decompressed by each indoor unit expansion valve 52 flows from each indoor liquid pipe 56 through each liquid pipe connection 53 into the liquid pipe 4. The refrigerant that joins in the liquid pipe 4 flows into the outdoor unit 2 through the first shut-off valve 15. The refrigerant that flows into the first shut-off valve 15 of the outdoor unit 2 flows through the outdoor liquid pipe 25 and is decompressed while passing through the outdoor unit expansion valve 14. The refrigerant that is decompressed by the outdoor unit expansion valve 14 flows through the outdoor liquid pipe 25 into the outdoor heat exchanger 13, and evaporates through heat exchange with outside air that flows in from an intake port (not shown) of the outdoor unit 2 due to the rotation of the outdoor unit fan 18. The refrigerant that flows out from the outdoor heat exchanger 13 to the outdoor refrigerant pipe 23 flows in this order: the four-way valve 12, the outdoor refrigerant pipe 26, the accumulator 17, and the suction pipe 22. The refrigerant is then drawn into the compressor 11 and compressed again, and flows out into the outdoor gas pipe 24 via the first port 12A and the fourth port 12D of the four-way valve 12.

[0111] Furthermore, when the air conditioner 1A performs cooling operation, the four-way valve 12 is switched so that the first port 12A and the second port 12B are connected and the third port 12C and the fourth port 12D are connected. As a result, the refrigerant circuit 6A becomes a cooling cycle in which each indoor heat exchanger 51 functions as an evaporator and the outdoor heat exchanger 13 functions as a condenser. For ease of explanation, the flow of refrigerant during cooling operation is indicated by dashed arrows in Figure 12.

[0112] When the compressor 11 is driven in the refrigerant circuit 6A state, the refrigerant discharged from the compressor 11 flows through the discharge pipe 21 and into the four-way valve 12, and then flows from the four-way valve 12 through the outdoor refrigerant pipe 23 and into the outdoor heat exchanger 13. The refrigerant that has flowed into the outdoor heat exchanger 13 condenses by exchanging heat with outdoor air that has been drawn into the outdoor unit 2 by the rotation of the outdoor unit fan 18. In other words, the outdoor heat exchanger 13 functions as a condenser, and the indoor air heated by the refrigerant in the outdoor heat exchanger 13 is blown outside through an air outlet (not shown).

[0113] The refrigerant that flows from the outdoor heat exchanger 13 into the outdoor liquid pipe 25 is decompressed by passing through the outdoor unit expansion valve 14, which is fully open. The refrigerant decompressed by the outdoor unit expansion valve 14 flows through the liquid pipe 4 via the first stop valve 15 and is diverted to each indoor unit 3. The refrigerant that flows into each indoor unit 3 flows through the indoor liquid pipe 56 via each liquid pipe connection 53 and passes through the indoor unit expansion valve 52, which is adjusted to an opening such that the degree of subcooling at the refrigerant outlet of the indoor heat exchanger 51 becomes the target degree of subcooling, where it is decompressed. The refrigerant decompressed by the indoor unit expansion valve 52 flows through the indoor liquid pipe 56 and flows into the indoor heat exchanger 51, where it exchanges heat with indoor air that flows in from an intake port (not shown) of the indoor unit 3 due to the rotation of the indoor unit fan 55, and evaporates. In other words, each indoor heat exchanger 51 functions as an evaporator, and the indoor air cooled by the refrigerant in each indoor heat exchanger 51 is blown into the room from an air outlet (not shown), thereby cooling the room in which each indoor unit 3 is installed.

[0114] The refrigerant flowing from the indoor heat exchanger 51 to the gas pipe 5 via the gas pipe connection part 54 flows into the outdoor gas pipe 24 via the second stop valve 16 of the outdoor unit 2 and flows into the fourth port 12D of the four-way valve 12. The refrigerant that has flowed into the fourth port 12D of the four-way valve 12 flows from the third port 12C into the refrigerant inlet side of the accumulator 17. The refrigerant that has flowed into the refrigerant inlet side of the accumulator 17 is sucked into the compressor 11 via the suction pipe 22 and is compressed again.

[0115] During cooling operation of the air conditioner 1A, the outdoor heat exchanger 13 functions as a condenser, and the indoor heat exchanger 51 functions as an evaporator. During heating operation of the air conditioner 1A, the outdoor heat exchanger 13 functions as an evaporator, and the indoor heat exchanger 51 functions as a condenser.

[0116] The estimation model 431 is generated using, for example, the outside air temperature, the degree of subcooling, the degree of superheating, the pressure difference at the maximum pipe length, the inlet refrigerant circulation amount, and the remaining refrigerant amount. The estimation model 431 estimates the remaining refrigerant amount in the refrigerant circuit 6A.

[0117] The estimation unit 448 in the first control unit 44 then extracts the outside air temperature, degree of subcooling, degree of superheat, pressure difference, and inlet refrigerant circulation volume from the operating data after the cleansing process. The estimation unit 448 estimates the remaining refrigerant volume in the refrigerant circuit 6A by substituting the extracted actual measured values ​​of the outside air temperature, degree of subcooling, degree of superheat, pressure difference, and inlet refrigerant circulation volume as explanatory variables into the estimation model 431. The first control unit 44 executes the determination program 432 to determine whether the remaining refrigerant volume is less than a threshold. If the remaining refrigerant volume is less than the threshold, the first control unit 44 outputs a notification indicating that a refrigerant leak exists. If the remaining refrigerant volume is not less than the threshold, the first control unit 44 outputs a notification indicating that no refrigerant leak exists.

[0118] Effect of Third Embodiment In the air conditioner 1A of the third embodiment, an estimation model 431 is generated by a nonlinear algorithm using operating state quantities related to estimation of the remaining refrigerant amount in the refrigerant circuit 6A, i.e., the outside air temperature, the degree of subcooling, the degree of superheat, the pressure difference at the maximum piping length, and the inlet refrigerant circulation amount. As a result, it is possible to generate an estimation model 431 that can estimate the remaining refrigerant amount in the refrigerant circuit 6A that does not include the injection circuit 19 including the SC heat exchanger 19C, etc., without using the aperture of the SC expansion valve or the SC heat exchanger outlet temperature.

[0119] In the air conditioner 1A, the amount of refrigerant remaining in the refrigerant circuit 6A is estimated using the estimation model 431, the outside air temperature, the degree of subcooling, the degree of superheat, the pressure difference, and the inlet refrigerant circulation amount. As a result, the amount of refrigerant remaining in the refrigerant circuit 6A can be estimated with high accuracy without using the opening degree of the SC expansion valve and the SC heat exchanger outlet temperature, and regardless of the piping length.

[0120] The air conditioners 1 (1A) of Examples 1 to 3 illustrate an estimation model 431 that estimates the remaining refrigerant amount when N indoor units 3 are connected to one outdoor unit 2. On the other hand, the remaining refrigerant amount can also be estimated in an air conditioner 1 in which one outdoor unit 2 and one indoor unit 3 are connected using a method similar to that of Examples 1 to 3.

[0121] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0122] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or an MCU (Micro Controller Unit)). Needless to say, the various processing functions may be executed in whole or in part on a program analyzed and executed by the CPU (or a microcomputer such as an MPU or MCU), or on hardware using wired logic.

[0123] The various processes described in this embodiment can be realized by executing a prepared estimation program, for example, in the first control unit 20 in the outdoor unit 2 or the fourth control unit 90 in the server device 110. By executing the estimation program, the first control unit 20 or the fourth control unit 90 executes a process of learning an estimation model 431 by correlating at least the degree of subcooling, the outside air temperature, the degree of superheat, the pressure difference at the maximum pipe length, and the inlet refrigerant circulation amount with the remaining refrigerant amount. As a result, it is possible to generate an estimation model 431 that can estimate the remaining refrigerant amount circulating in the refrigerant circuit 6 without using the aperture of the SC expansion valve or the SC heat exchanger outlet temperature.

[0124] REFERENCE SIGNS LIST 1 Air conditioner 2 Outdoor unit 3 Indoor unit 11 Compressor 13 Outdoor heat exchanger 14 Outdoor unit expansion valve 20 First control unit 44 First control unit 51 Indoor heat exchanger 431 Estimation model 447 Learning unit 448 Estimation unit

Claims

1. A refrigerant amount estimation device for estimating the amount of remaining refrigerant in an air conditioner having an outdoor unit with a compressor, an outdoor heat exchanger, and an expansion valve, and an indoor unit with an indoor heat exchanger, with the outdoor unit and the indoor unit connected by refrigerant piping to form a refrigerant circuit through which refrigerant circulates, the refrigerant amount estimation device comprising a control unit that estimates the amount of remaining refrigerant using a learning model in which at least the degree of subcooling and a state quantity that is correlated with the piping length of the refrigerant piping are learned in association with the amount of remaining refrigerant.

2. The refrigerant amount estimation device according to claim 1, characterized in that the state quantities used are a first state quantity indicating a pressure difference, which is the difference between the discharge pressure of the compressor and the suction pressure of the compressor, and a second state quantity indicating the amount of refrigerant circulating at the inlet of the compressor.

3. The refrigerant quantity estimation device described in claim 2, characterized in that the learning model is a learning model that is learned by associating the first state quantity and the second state quantity when the piping length of the refrigerant piping is at least the maximum length, and the degree of subcooling with the remaining refrigerant quantity.

4. The refrigerant amount estimation device described in claim 2, characterized in that the learning model includes: the first state quantity and the second state quantity when the refrigerant piping length is at its maximum length; and the first state quantity and the second state quantity when the refrigerant piping length is at its standard length, and a learning model learned by associating the degree of subcooling with the remaining refrigerant amount.

5. The refrigerant quantity estimation device of claim 1, characterized in that the air conditioner is an air conditioner having a plurality of indoor units, and the learning model is a learning model that is learned in association with the number of indoor units in addition to the degree of subcooling, the state quantity, and the remaining refrigerant quantity.

6. The refrigerant amount estimation device according to claim 2, characterized in that the second state quantity is calculated using the suction refrigerant density of the compressor, the compressor displacement volume of the compressor, and the compressor rotation speed of the compressor.

7. The refrigerant quantity estimation device described in claim 1, characterized in that the learning model is a learning model that is learned by associating at least one of the degree of superheat or the outside air temperature in addition to the degree of subcooling, the state quantity, and the remaining refrigerant quantity.

8. An air conditioner having an outdoor unit having a compressor, an outdoor heat exchanger, and an expansion valve, and an indoor unit having an indoor heat exchanger, and a refrigerant circuit formed by connecting the outdoor unit and the indoor unit with refrigerant piping, and equipped with a refrigerant amount estimation device that estimates the amount of remaining refrigerant in the air conditioner in which refrigerant circulates within the refrigerant circuit, wherein the refrigerant amount estimation device has a control unit that estimates the remaining refrigerant amount using a learning model in which at least the degree of subcooling and a state quantity that is correlated with the piping length of the refrigerant piping are learned in association with the remaining refrigerant amount.

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