GB2577445A

GB2577445A - Air conditioning device

Info

Publication number: GB2577445A
Application number: GB1918686.5A
Authority: GB
Inventors: Kikuchi Shunichi; Nakagawa Masahiko
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-08-18
Filing date: 2017-08-18
Publication date: 2020-03-25
Anticipated expiration: 2037-08-18
Also published as: GB201918686D0; WO2019035205A1; CN111033154A; CN111033154B; GB2577445B; JPWO2019035205A1; JP6785974B2; GB2577445A8

Abstract

This air conditioning device, in which an outdoor unit provided with a compressor and an indoor unit provided with an expansion valve are connected through a refrigerant pipe, is provided with: a first opening/closing valve provided on a refrigerant inlet side of the indoor unit; a second opening/closing unit provided on a refrigerant outlet side of the indoor unit; a state detection means which detects the state, inside the refrigerant pipe, between the first opening/closing valve and the second opening/closing valve; and a control device which controls the first opening/closing valve and the second opening/closing valve. The control device detects a leak of the refrigerant between the first opening/closing valve and the second opening/closing valve on the basis of the state detected by the state detection means when the first opening/closing valve and the second opening/closing valve are closed.

Description

DESCRIPTION Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field

[0001] The present invention relates to an air-conditioning apparatus that air-conditions an indoor space.

Background Art

[0002] In an existing air-conditioning apparatus, refrigerant is circulated in a refrigerant circuit, and exchanges heat with air, whereby a cooling operation and a heating operation can be performed. In the air-conditioning apparatus, if the refrigerant in the refrigerant circuit leaks therefrom, the amount of refrigerant in the refrigerant circuit decreases to be insufficient. Consequently, heat exchange is not sufficiently performed between the refrigerant and air, and the operation efficiency of the air-conditioning apparatus is thus reduced.

[0003] In recent years, it has been more strictly required to reduce the global warming potential (GWP) according to the Act on Rational Use and Proper Management of Fluorocarbons in Japan and the Montreal Protocol. Therefore, it is conceivable that in the future, it will be necessary to use flammable refrigerants in addition to inflammable refrigerants.

[0004] In the case of using flammable refrigerant, it is necessary to promptly detect a refrigerant leak if it occurs, in order to secure safety. In view of this point, in addition to an air-conditioning apparatus incorporating a refrigerant detection device that detects refrigerant gas, the following two types of air-conditioning apparatuses have been proposed: one is an air-conditioning apparatus that detects insufficiency of refrigerant on the basis of various parameters regarding an operation state, and makes a notification indicating a refrigerant leak; and the other is an air-conditioning apparatus that compares pump-down time at the time of performing a pump-down operation with a set value regarding pump-down time that is stored in advance, to thereby detect whether a refrigerant leak occurs (see, for example, Patent Literature 1).

Citation List Patent Literature [0005] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2012-184889

Summary of Invention

Technical Problem [0006] However, in the existing refrigerant leak detection methods, it is not possible to specify part of the air-conditioning apparatus where refrigerant leaks, and it takes long time to find a leakage point where refrigerant leaks. Particularly, if refrigerant leaks in an indoor unit, and will become possibly dangerous in the indoor unit, it is necessary to promptly detect the refrigerant leak.

[0007] The present invention has been made in view of the problems of the above existing techniques, and an object of the invention is to provide an air-conditioning apparatus capable of promptly detecting whether a refrigerant leak occurs in an indoor unit or not.

Solution to Problem [0008] An air-conditioning apparatus according to an embodiment of the present invention is an air-conditioning apparatus in which an outdoor unit and an indoor unit are connected to each other by a refrigerant pipe, the outdoor unit including a compressor, the indoor unit including an expansion valve. The air-conditioning apparatus includes: a first open/close valve provided on a refrigerant inlet side of the indoor unit; a second open/close valve provided on a refrigerant outlet side of the indoor unit; a state detection unit that detects a state of the inside of a refrigerant pipe between the first open/close valve and the second open/close valve; and a controller that controls the first open/close valve and the second open/close valve. The controller detects whether a refrigerant leak occurs between the first open/close valve and the second open/close valve or not based on the state detected by the state detection unit when the first open/close valve and the second open/close valve are closed.

Advantageous Effects of Invention [0009] As described above, according to the embodiment of the present invention, it is detected whether a refrigerant leak occurs or not on the basis of the pressure in the refrigerant pipe between the first open/close valve and the second open/close valve that are in the closed state. Thereby, it is possible to promptly detect whether a refrigerant leak occurs in the indoor unit or not

Brief Description of Drawings

[0010] [Fig. 1] Fig. 1 is a schematic diagram illustrating an example of the configuration of an air-conditioning apparatus according to Embodiment 1.

[Fig. 2] Fig. 2 is a functional block diagram illustrating an example of the configuration of a controller as illustrated in Fig. 1.

[Fig. 3] Fig. 3 is a flowchart illustrating an example of the flow of a refrigerant leak detection process for an indoor unit in Embodiment 1.

[Fig. 4] Fig. 4 is a functional block diagram illustrating an example of the configuration of a controller in Embodiment 2.

[Fig. 5] Fig. 5 is a flowchart illustrating an example of the flow of a refrigerant leak detection process for an indoor unit in Embodiment 2.

[Fig. 6] Fig. 6 is a flowchart illustrating an example of the flow of a refrigerant leak detection process for an indoor unit in Embodiment 3.

[Fig. 7] Fig. 7 is a schematic diagram illustrating another example of the configuration of the indoor unit as illustrated in Fig. 1. Description of Embodiments [0011] Embodiment 1 An air-conditioning apparatus according to Embodiment 1 of the present invention will be described. Fig. 1 is a schematic diagram illustrating an example of the configuration of an air-conditioning apparatus 100 according to Embodiment 1. As illustrated in Fig. 1, the air-conditioning apparatus 100 includes an outdoor unit 1, an indoor unit 2, and a controller 3.

[0012] <Configuration of Air-Conditioning Apparatus 100> (Outdoor Unit 1) The outdoor unit 1 includes a compressor 11, a condenser 12, an outdoor-unit fan 12a, and an accumulator 13. The compressor 11 sucks low-temperature, low-pressure refrigerant, compresses the sucked refrigerant into high-temperature, high-pressure refrigerant, and discharges the high-temperature, high-pressure refrigerant. For example, the compressor 11 is an inverter compressor whose capacity is controlled by changing its compressor frequency. The capacity corresponds to the discharge rate of refrigerant per unit time. The compressor frequency of the compressor 11 is controlled by the controller 3.

[0013] The condenser 12 causes heat exchange to be performed between outside air supplied from the outdoor-unit fan 12a and the refrigerant discharged from the compressor 11, thereby transferring heat of the refrigerant to the outside air, and condensing the refrigerant. The outdoor-unit fan 12a supplies the outside air to the condenser 12. A rotation speed of the outdoor-unit fan 12a is controlled by the controller 3. By controlling the rotation speed, the supply rate of air to the condenser 12 is adjusted.

[0014] The accumulator 13 is provided on a low-pressure side that is a suction side of the compressor 11. The accumulator 13 stores, for example, surplus refrigerant that remains because of the difference in operation state between a cooling operation and a heating operation, or surplus refrigerant that remains because of a transient change of the operation.

[0015] (Indoor Unit 2) The indoor unit 2 includes a first open/close valve 21, an expansion valve 22, an evaporator 23, and a refrigerant leak detection unit 24. The first open/close valve 21 is provided on a refrigerant inlet side of the indoor unit 2, and is opened or closed to control the flow of refrigerant. Opening and closing of the first open/close valve 21 are controlled by the controller 3. For example, the first open/close valve 21 is a diaphragm valve in which there is a small possibility that valve leakage in which fluid leaks from the valve will occur [0016] For example, the expansion valve 22 is a valve whose opening degree can be controlled, such as an electronic expansion valve, or a capillary. Also, the expansion valve 22 expands refrigerant. The opening degree of the expansion valve 22 is controlled by the controller 3 such that an evaporating temperature at the evaporator 23 reaches a target evaporating temperature.

[0017] The evaporator 23 causes heat exchange to be performed between indoor air supplied from an indoor-unit fan 23a and refrigerant that flows out from the expansion valve 22. Thereby, air for cooling that is to be supplied to an indoor space is obtained.

The indoor-unit fan 23a supplies air to the evaporator 23. A rotation speed of the indoor-unit fan 23a is controlled by the controller 3. By controlling the rotation speed, the supply rate of air to the evaporator 23 is adjusted.

[0018] The refrigerant leak detection unit 24 is provided downstream of the evaporator 23, and includes a pressure sensor 24a, a check joint 24b, and a second open/close valve 24c. The pressure sensor 24a is a state detection unit that detects a state of the inside of a refrigerant pipe. The pressure sensor 24a is provided upstream of the second open/close valve 24c, and detects a pressure P of the inside of the refrigerant pipe. The check joint 24b is an opening portion that branches off from the refrigerant pipe, and is provided to allow refrigerant to flow into the refrigerant pipe or flow out from the refrigerant pipe, and allow air to flow out from the refrigerant pipe.

[0019] The second open/close valve 24c is provided downstream of the pressure sensor 24a and on a refrigerant outlet side of the indoor unit 2. The second open/close valve 24c is opened or closed to control the flow of refrigerant. Opening and closing of the second open/close valve 24c are controlled by the controller 3. For example, the second open/close valve 24c is a diaphragm valve in which there is a small possibility that valve leakage will occur.

[0020] In the air-conditioning apparatus 100 according to Embodiment 1, the compressor 11, the condenser 12, the first open/close valve 21, the expansion valve 22, the evaporator 23, and the accumulator 13 are successively connected by refrigerant pipes, whereby a refrigerant circuit is provided. In general, R410A, which is an inflammable refrigerant, is used as refrigerant that is circulated in the refrigerant circuit. In Embodiment 1, slightly flammable refrigerant such as R32 or R1234yf can also be used in addition to inflammable refrigerants.

[0021] <Operation of Air-Conditioning Apparatus 100> An operation of the air-conditioning apparatus 100 during the cooling operation will be described. The low-temperature, low-pressure refrigerant is compressed by the compressor 11 to change into high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant is discharged from the compressor 11, and then flows into the condenser 12. The high-temperature, high-pressure gas refrigerant having flowed into the condenser 12 exchanges heat with outside air, and is thus condensed to change into high-pressure liquid refrigerant, and the high-pressure liquid refrigerant then flows out from the condenser 12.

[0022] The high-pressure liquid refrigerant having flowed out from the condenser 12 flows out from the outdoor unit 1, and flows into the indoor unit 2. The high-pressure liquid refrigerant having flowed into the indoor unit 2 flows into the expansion valve 22 through the first open/close valve 21. The refrigerant having flowed into the expansion valve 22 is reduced in pressure by the expansion valve 22 to change into low temperature, low pressure two-phase gas-liquid refrigerant. The low-temperature, low-pressure two-phase gas-liquid refrigerant flows into the evaporator 23.

[0023] The low-temperature, low-pressure two-phase gas-liquid refrigerant having flowed into the evaporator 23 exchanges heat with indoor air to receive heat from the indoor air and evaporate, thus changing into low-temperature, low-pressure gas refrigerant, and the low-temperature, low-pressure gas refrigerant then flows out from the evaporator 23. The low-temperature, low-pressure gas refrigerant having flowed out from the evaporator 23 flows out from the indoor unit 2 through the refrigerant leak detection unit 24. The low-temperature, low-pressure gas refrigerant having flowed out from the indoor unit 2 flows into the outdoor unit 1, and is sucked into the compressor 11.

[0024] (Controller 3) The controller 3 controls the compressor frequency of the compressor 11, the opening degree of the expansion valve 22, etc., on the basis of the result of detection by various sensors not illustrated that are provided in respective associated units of the air-conditioning apparatus 100. In particular, it should be noted that the controller 3 performs a refrigerant leak detection process of determining whether a refrigerant leak occurs in the indoor unit 2 or not on the basis of the result of detection by the pressure sensor 24a, and controls an operation of the air-conditioning apparatus 100 on the basis of the result of the determination of whether a refrigerant leak occurs or not.

[0025] Fig. 2 is a functional block diagram illustrating an example of the configuration of the controller 3 as illustrated in Fig. 1. The controller 3 executes software on an arithmetic device such as a microcomputer to perform various functions. Alternatively, the controller 3 is, for example, hardware that performs various functions, such as a circuit device. It should be noted that in the above example, the controller 3 is provided outside the outdoor unit 1 and the indoor unit 2; however, this is not!imitative. That is, the controller 3 may be provided in either the outdoor unit 1 or the indoor unit 2. [0026] As illustrated in Fig. 2, the controller 3 includes an operation control unit 31, a leak determination unit 32, a storage unit 33, and a refrigerant insufficiency detection unit 34.

[0027] The refrigerant insufficiency detection unit 34 determines whether the refrigerant in the refrigerant circuit is insufficient or not on the basis of detection information from the various sensors, etc., provided in the air-conditioning apparatus 100. When it is determined that the refrigerant is insufficient, the refrigerant insufficiency detection unit 34 determines that insufficiency of the refrigerant is caused by a refrigerant leak, and supplies refrigerant leak information indicating the refrigerant leak to the operation control unit 31. It should be noted that it is possible to detect whether refrigerant is insufficient or not by a generally used method, for example, based on the degree of subcooling.

[0028] The operation control unit 31 controls the first open/close valve 21 and the second open/close valve 24c in the refrigerant leak detection process, on the basis of the refrigerant leak information from the refrigerant insufficiency detection unit 34. Furthermore, the operation control unit 31 controls a pump-down operation on the basis of the result of the following pressure comparison by the leak determination unit 32. [0029] The leak determination unit 32 compares the pressure P detected by the pressure sensor 24a with a target pressure Pm stored in the storage unit 33. Then, the leak determination unit 32 determines whether a refrigerant leak occurs in the indoor unit 2 or not on the basis of the result of the comparison. To be more specific, in the case where the pressure P is higher than the target pressure Pm, the leak determination unit 32 determines that a refrigerant leak occurs in the indoor unit 2.

[0030] The storage unit 33 stores, for example, parameters for use in an associated process by an associated one of the units provided in the controller 3. For example, the storage unit 33 stores the target pressure Pm to be referred to by the leak determination unit 32. The target pressure Pm is a pressure to be referred to as a reference in detection of whether a refrigerant leak occurs between the first open/close valve 21 and the second open/close valve 24c. For example, the target pressure Pm is set less than or equal to an atmospheric pressure.

[0031] <Refrigerant leak Detection Process> Fig. 3 is a flowchart illustrating an example of the flow of the refrigerant leak detection process for the indoor unit 2 according to Embodiment 1. The refrigerant leak detection process in Embodiment 1 will be described with reference to Fig. 3. [0032] In step S1, the refrigerant insufficiency detection unit 34 determines whether refrigerant leaks in the refrigerant circuit or not on the basis of detection information from the various sensors, etc. When determining that refrigerant leaks (Yes in step Si), the refrigerant insufficiency detection unit 34 sends the refrigerant leak information to the operation control unit 31.

[0033] In step S2, the operation control unit 31 closes the first open/close valve 21 on the basis of the refrigerant leak information from the refrigerant insufficiency detection unit 34, thereby shutting out the inflow of refrigerant from the outdoor unit 1. By contrast, when it is determined that refrigerant does not leak (No in step Si), the process returns to step 51, and the process of step 51 is repeatedly performed until it is determined that refrigerant leaks.

[0034] When refrigerant leaks in the refrigerant circuit, in step S3, the operation control unit 31 starts the pump-down operation, and causes refrigerant in the refrigerant pipe in the indoor unit 2 to move to the outside of the indoor unit 2, and decreases the pressure in the refrigerant pipe in the indoor unit 2 such that the pressure reaches or falls below the atmospheric pressure. At this time, the operation control unit 31 reduces a low-pressure cut value of the compressor 11 that is referred to in determination of whether an abnormality occurs on the suction side of the compressor 11, to a value below a normal value, thereby to cause the inside of the refrigerant pipe in the indoor unit 2 to be in a negative pressure state.

[0035] In step S4, the leak determination unit 32 compares the pressure P in the refrigerant pipe in the indoor unit 2 that is detected by the pressure sensor 24a, with the target pressure Pm stored in the storage unit 33. As the result of the comparison, when it is determined that the pressure P is higher than or equal to the target pressure Pm (No in step S4), the process returns to step S4, and the process of step S4 is repeatedly performed until the pressure P falls below the target pressure Pm.

[0036] When the pressure P is lower than the target pressure Pm (Yes in step S4), in step S5, the operation control unit 31 closes the second open/close valve 24c, and shuts out the inflow of refrigerant from the outdoor unit 1 to the indoor unit 2. Furthermore, the operation control unit 31 stops the operation of the compressor 11, thereby stopping the pump-down operation.

[0037] After the elapse of a set time from the process of step S5, in step S6, the leak determination unit 32 compares the pressure P in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c with the target pressure Pm. At this time, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is negative pressure. Thus, in the case where a leakage point is present in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c, when the first open/close valve 21 and the second open/close valve 24c are in the closed state, air flows into the refrigerant pipe. As a result, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is raised from the negative pressure to the atmospheric pressure. It is therefore possible to determine whether a refrigerant leak occurs or not on the basis of the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c.

[0038] That is, when the pressure P is higher than the target pressure Pm (Yes in step S6), it is assumed that the pressure P is raised because of an inflow of air from a leakage point, and in step S7, the leak determination unit 32 thus determines that a refrigerant leak occurs in the indoor unit 2.

[0039] By contrast, when the pressure P is lower than or equal to the target pressure Pm (No in step S6), it is assumed that no leakage point is present. Therefore, air does not flow into the refrigerant pipe, and the leak determination unit 32 thus determines that refrigerant does not leak in the indoor unit 2, and the process returns to step S1.

[0040] In such a manner, in Embodiment 1, it is detected whether a refrigerant leak occurs or not on the basis of a change in the pressure P that occurs when the pressure in the refrigerant pipe is set to negative pressure by performing the pump-down operation. When a refrigerant leak in the indoor unit 2 is detected, the refrigerant in the indoor unit 2 is moved to the outside of the indoor unit 2. Therefore, even if a leakage point is present in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c, it is possible to ensure safety since the leakage of refrigerant from the indoor unit 2 into a room is reduced.

[0041] It should be noted that in the case where a refrigerant leak occurs, air enters the refrigerant circuit because of the negative pressure. Therefore, even after the leakage point is simply repaired by, for example, brazing, air remains in the refrigerant pipe. In the case where air and the refrigerant are present in the refrigerant circuit, the entire refrigerant circuit needs to be subjected to vacuuming in order to prevent, for example, occurrence of a failure in the compressor 11. In this case, vacuuming is performed only in the indoor unit 2 using the check joint 24b, with the first open/close valve 21 and the second open/close valve 24c closed. It is therefore possible to reduce the time required for restoration to normal conditions, and thus facilitate the restoration after simply repairing the leakage point.

[0042] As described above, in the air-conditioning apparatus 100 according to Embodiment 1, the first open/close valve 21 provided on the refrigerant inlet side of the indoor unit 2 and the second open/close valve 24c provided on the refrigerant outlet side of the indoor unit 2 are closed; and then, based on the result of detection by the pressure sensor 24a at this time, it is detected whether a refrigerant leak occurs or not in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c. Thereby, it is possible to detect whether a refrigerant leak occurs in the indoor unit 2 or not.

[0043] Furthermore, in the air-conditioning apparatus 100, the operation control unit 31 closes the first open/close valve 21 to cause the inside of the refrigerant pipe to be in a negative pressure state, and when the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c falls below the target pressure, the operation control unit 31 closes the second open/close valve 24c. When the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is higher than the target pressure after a set time elapses from the time when the second open/close valve 24c is closed, the leak determination unit 32 determines that a refrigerant leak occurs. If a leakage point is present in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c, air flows into the refrigerant pipe that is in the negative pressure state, and the pressure in the refrigerant pipe is thus raised. In such a manner, it is possible to promptly detect whether a refrigerant leak in the indoor unit 2 or not.

[0044] Embodiment 2 An air-conditioning apparatus according to Embodiment 2 of the present invention will be described. With respect to Embodiment 1, it is described above that diaphragm valves in which valve leakage will not occur are used as the first open/close valve 21 and the second open/close valve 24c. By contrast, in Embodiment 2, valves such as needle valves or butterfly valves may also be used as the first open/close valve 21 and the second open/close valve 24c. In each of the needle valves or butterfly valves, there is a possibility that a foreign matter will be caught between the valve and a valve seat, and the valve will not be normally closed, as a result of which valve leakage will occur at the valve.

[0045] If a valve that may cause valve leakage is used, it can be assumed that if valve leakage occurs at the valve, even when the valve is in the closed state, refrigerant prevented by the valve from entering the refrigerant pipe flows into the refrigerant pipe, and as a result the pressure in the refrigerant pipe is raised. That is, in the case of using the valve that may cause valve leakage, it is not possible to determine whether the pressure in the refrigerant pipe is raised because of the inflow of air into the refrigerant pipe or because of the inflow of refrigerant into the refrigerant pipe, which is caused by occurrence of valve leakage at the valve. In view of this point, in Embodiment 2, in the case where it is detected whether a refrigerant leak occurs in the indoor unit 2 or not, it is determined whether or not valve leakage occurs at the first open/close valve 21 or the second open/close valve 24c.

[0046] <Configuration of Air-Conditioning Apparatus 100> A configuration of the air-conditioning apparatus 100 according to Embodiment 2 will be described. It should be noted that in the air-conditioning apparatus 100 according to Embodiment 2, the function of a controller 203 is different from that of the controller 3 of Embodiment 1, and only the controller 203 will thus be described.

[0047] (Controller 3) Fig. 4 is a functional block diagram illustrating an example of the configuration of the controller 203 according to Embodiment 2. As illustrated in Fig. 4, the controller 203 includes the operation control unit 31, the refrigerant insufficiency detection unit 34, a leak determination unit 232, a storage unit 233, and a pressure change measurement unit 235. It should be noted that in the following description of Embodiment 2, components that are the same as those in Embodiment 1 will be denoted by the same reference signs, and their detailed descriptions will thus be omitted.

[0048] The pressure change measurement unit 235 measures an increasing amount AP that is the amount of change of the pressure P that is made until the pressure P exceeds the target pressure Pm from the time when the second open/close valve 24c is closed, and a rise time Atp that is time which elapses until the increasing amount AP is reached. That is, the pressure change measurement unit 235 measures, in the case where the first open/close valve 21 and the second open/close valve 24c are closed, the amount of change of the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c and the elapsed time.

[0049] The leak determination unit 232 compares the pressure P detected by the pressure sensor 24a with the target pressure Pm stored in the storage unit 33. Then, the leak determination unit 232 determines whether a refrigerant leak occurs in the indoor unit 2 or not on the basis of the result of the comparison. Furthermore, the leak determination unit 232 determines whether valve leakage occurs at the first open/close valve 21 or the second open/close valve 24c or not on the basis of the result of the comparison and the result of the measurement by the pressure change measurement unit 235.

[0050] The storage unit 233 stores the target pressure Pm that is referred to by the leak determination unit 32. Furthermore, the increasing amount AP in the pressure P measured by the pressure change measurement unit 235 and the rise time Atp measured thereby are stored in the storage unit 233 in association with each other. [0051] <Refrigerant Leak Detection Process> Fig. 5 is a flowchart illustrating an example of the flow of a refrigerant leak detection process for the indoor unit 2 in Embodiment 2. The refrigerant leak detection process in Embodiment 2 will be described with reference to Fig. 5.

[0052] In step S10, the refrigerant leak detection process is performed. In step S10, processes of steps S1 to S5 in Embodiment 1 as indicated in Fig. 3 are performed. To be more specific, when the refrigerant insufficiency detection unit 34 detects a refrigerant leak in the refrigerant circuit, the operation control unit 31 closes the first open/close valve 21 and cause the pump-down operation to start, and then closes the second open/close valve 24c and causes the pump-down operation to end. Thereby, the pressure in the refrigerant pipe in the indoor unit 2 reaches or falls below the atmospheric pressure. When the second open/close valve 24c is closed, the pressure change measurement unit 235 starts to measure the increasing amount AP and the rise time Atp in the pressure P. [0053] After a set time elapses from the process of step 510, in step S11, the leak determination unit 232 compares the pressure P in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c with the target pressure Pm. As the result of the comparison, when the pressure P is higher than the target pressure Pm (Yes in step S11), in step S12, the pressure change measurement unit 235 outputs the result of measurement of the increasing amount AP and the rise time Atp in the pressure P. By contrast, when the pressure P is lower than or equal to the target pressure Pm (No in step S11), the process returns to step S10.

[0054] In step S13, the operation control unit 31 opens the first open/close valve 21.

Next, in step S14, the operation control unit 31 opens the second open/close valve 24c.

Thereby, refrigerant flows into the refrigerant pipe in the indoor unit 2, and in the case where a foreign matter is caught at the first open/close valve 21 or the second open/close valve 24c, it is removed. It should be noted that in steps S13 and S14, the first open/close valve 21 and the second open/close valve 24c are opened in this order in order to prevent the backflow of refrigerant.

[0055] In step S15, the refrigerant leak detection process is performed. In step S15, processes of steps S2 to S5 as illustrated in Fig. 3 are performed. To be more specific, the operation control unit 31 closes the first open/close valve 21 and causes the pump-down operation to start, and then closes the second open/close valve 24c and causes the compressor 11 to stop. Thereby, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c reaches or falls below the atmospheric pressure.

[0056] After a set time elapses from the process of step S15, in step S16, the leak determination unit 232 compares the pressure P in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c with the target pressure Pm. As the result of the comparison, when the pressure P is lower than or equal to the target pressure Pm (No in step S16), the leak determination unit 232 determines that a foreign matter caught at the first open/close valve 21 or the second open/close valve 24c are removed by the processes of steps S13 and S14. Then, the process returns to step S10.

[0057] By contrast, when the pressure P is higher than the target pressure Pm (Yes in step S16), in step S17, the leak determination unit 232 determines whether the processes of steps S12 to S16 are performed a set number of times or not. When the processes of steps S12 to S16 are not performed the set number of times (No in step S17), the process returns to step S12.

[0058] When the processes of steps S12 to S16 are performed the set number of times (Yes in step S17), in step S18, the leak determination unit 232 reads out from the storage unit 233, a set number of information items regarding a set number of values regarding each of the increasing amount AP of the pressure P and the rise time Atp. Then, the leak determination unit 232 determines whether the read-out information items vary or not.

[0059] It should be noted that why the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is raised can be determined on the basis of whether the set number of information items vary or not. In the case where a leakage point is present in the refrigerant pipe, even when the refrigerant leak detection process is repeatedly performed such that the pressure in the refrigerant pipe becomes constant, the inflow of air that flows into the refrigerant pipe and time that elapses until the inflow of air is reached are constant. That is, in the case where a leakage point is present in the refrigerant pipe, the set of number of information items do not vary even after a process of removing a foreign matter caught from the first open/close valve 21 or the second open/close valve 24c is performed.

[0060] By contrast, in the case where valve leakage occurs at the first open/close valve 21 or the second open/close valve 24c, it can be assumed that the flow rate of refrigerant that flows into the refrigerant pipe and the time in which refrigerant flows in the refrigerant pipe vary in accordance with the state of a foreign matter caught in the pipe. That is, in the case where valve leakage occurs at the first open/close valve 21 or the second open/close valve 24c, the state of a foreign matter is changed by performing the process of removing the foreign matter caught at the first open/close valve 21 or the second open/close valve 24c. Thus, the set number of information items vary.

[0061] It can be determined from the above that in the case where the set number of information items do not vary, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is raised because of presence of a leakage point in the refrigerant pipe. Also, it can be determined that in the case where the set number of information items vary, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is raised because of occurrence of valve leakage at the first open/close valve 21 or the second open/close valve 24c.

[0062] Therefore, when the set number of information items vary (Yes in step S18), the leak determination unit 232 determines that the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is raised because of occurrence of valve leakage at the first open/close valve 21 or the second open/close valve 24c. Then, the process returns to step S10. By contrast, when the set number of information items do not vary (No in step S18), in step S19, the leak determination unit 232 determines that the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is raised because of occurrence of a refrigerant leak.

[0063] As described above, in Embodiment 2, it is determined whether valve leakage occurs at the first open/close valve 21 or the second open/close valve 24c or not, after performing a process of opening the first open/close valve 21 and the second open/close valve 24c and causing refrigerant to flow in the refrigerant pipe. It is possible to reduce the frequency with which occurrence of valve leakage at the first open/close valve 21 or the second open/close valve 24c is determined by mistake as occurrence of a refrigerant leak, and thus accurately detect whether a refrigerant leak occurs or not.

[0064] Embodiment 3 An air-conditioning apparatus according to Embodiment 3 of the present invention will be described. In Embodiment 3, when insufficiency of refrigerant is detected, the inside of the refrigerant pipe in the indoor unit 2 is made to be in a high-pressure state, and it is then detected whether a refrigerant leak occurs or not. In this regard, Embodiment 3 is different from Embodiments 1 and 2. It should be noted that the configuration of the air-conditioning apparatus 100 according to Embodiment 3 is the same as that of Embodiment 1, and its description will thus be omitted.

[0065] <Refrigerant Leak Detection Process> Fig. 6 is a flowchart illustrating an example of the flow of a refrigerant leak detection process for the indoor unit 2 in Embodiment 3. The refrigerant leak detection process of Embodiment 3 will be described with reference to Fig. 6.

[0066] In step S21, the refrigerant insufficiency detection unit 34 determines whether the refrigerant leaks in the refrigerant circuit or not on the basis of detection information from various sensors, etc. When it is determined that the refrigerant does not leak (No in step S21), the process returns to step S21, and the process of step S21 is repeatedly performed until it is determined that the refrigerant leaks in the refrigerant circuit.

[0067] When it is determined that the refrigerant leaks in the refrigerant circuit (Yes in step S21), the refrigerant insufficiency detection unit 34 supplies refrigerant leak information to the operation control unit 31. In step S22, the operation control unit 31 closes the second open/close valve 24c on the basis of the refrigerant leak information from the refrigerant insufficiency detection unit 34. In step S23, the operation control unit 31 causes the compressor 11 to start to operate, and causes the refrigerant to stay in the refrigerant pipe such that the inside of the refrigerant pipe in the indoor unit 2 is made to be in a high-pressure state.

[0068] In step S24, the leak determination unit 32 compares the pressure P in the refrigerant pipe in the indoor unit 2 that is detected by the pressure sensor 24a with the target pressure Pm stored in the storage unit 33. The target pressure PM is a reference pressure to be referred to at the time of detecting whether a leak occurs at the refrigerant pipe in the indoor unit 2. For example, the target pressure Pm is set higher than or equal to the atmospheric pressure and less than or equal to a withstanding pressure of the refrigerant pipe.

[0069] In the result of the comparison, when the pressure P is lower than the target pressure Pm (No in step S24), the process returns to step S24, and the process of step S24 is repeatedly performed until the pressure P reaches or exceeds the target pressure Pm. By contrast, when the pressure P is higher than or equal to the target pressure Pm (Yes in step S24), in step S25, the operation control unit 31 closes the first open/close valve 21 to prevent the refrigerant from flowing out toward the outdoor unit 1. Furthermore, the operation control unit 31 stops the operation of the compressor 11.

[0070] After a set time elapses from the process of step S25, in step S26, the leak determination unit 32 compares the pressure P in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c with the target pressure Pm. At this time, the inside of the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is in a high-pressure state. In the case where a leakage point is present in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c, when the first open/close valve 21 and the second open/close valve 24c are in the closed state, the refrigerant flows out from the refrigerant pipe, and the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is thus reduced. Therefore, based on the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c, it is possible to determine whether a refrigerant leak occurs or not.

[0071] That is, when the pressure P is lower than the target pressure Pm (Yes in step S26), it can be assumed that the refrigerant flows out from the leakage point and as a result the pressure P is reduced. Therefore, the leak determination unit 32 determines that a refrigerant leak occurs in the indoor unit 2. Then, in step S27, the operation control unit 31 opens the second open/close valve 24c and causes the compressor 11 to operate.

[0072] By contrast, when the pressure P is higher than or equal to the target pressure Pm (No in step S26), it can be assumed that a refrigerant leak does not occur.

Therefore, the leak determination unit 32 determines that a refrigerant leak does not occur in the indoor unit 2, and the process returns to step S21.

[0073] In step S28, the leak determination unit 32 determines whether the pressure P in the refrigerant pipe in the indoor unit 2 is negative pressure or not. In the case where the pressure P is not negative pressure (No in step S28), the process returns to step S28, and the process of step S28 is repeatedly performed until the pressure P reaches negative pressure.

[0074] When the pressure P is negative pressure (step S28: Yes), the operation control unit 31 closes the second open/close valve 24c and causes the pump-down operation to start. Thereby, the refrigerant in the refrigerant pipe in the indoor unit 2 flows out from the indoor unit 2 to the outside thereof. Furthermore, since the second open/close valve 24c is closed, and the pressure in the refrigerant pipe is thus negative pressure, air having flowed from the leakage point is prevented from flowing out from the indoor unit 2 to the outside thereof.

[0075] As described above, in Embodiment 3, it is detected whether a refrigerant leak occurs or not on the basis of change in the pressure P that is made when the pressure in the refrigerant pipe between first open/close valve 21 and the second open/close valve 24c is made high. In the case where a leakage point is present in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c, the refrigerant flows out from the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c that is in a high-pressure state, and the pressure in the refrigerant pipe is reduced. In such a manner, in Embodiment 3, it is detected whether a refrigerant leak occurs or not, using refrigerant that is compressed by the compressor 11 and made to be is made to in a high-pressure state. It is therefore possible to detect a refrigerant leak even if the degree of the leak is small as in a slow leak. [0076] Although Embodiments 1 to 3 of the present invention are described above, the present invention is not limited to Embodiments 1 to 3, and various modifications and applications can be applied within the scope of the present invention. For example, Embodiments 1 to 3 of the present invention can be combined. To be more specific, the operation to detect whether a leak occurs in a valve as described regarding Embodiment 2 may be applied to Embodiment 3.

[0077] Furthermore, it should be noted that in Embodiment 1 and 2, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is set to negative pressure, and in this state, it is detected whether a refrigerant leak occurs or not, whereas in Embodiment 3, the pressure in the refrigerant pipe between the first open/close valve 21 and the second open/close valve 24c is made high, and in this state, it is detected whether a refrigerant leak occurs or not. The above technique of Embodiment 1 or 2 may be combined with the above technique of Embodiment 3. Because of such a combination of those techniques, it is possible to detect whether a refrigerant leak occurs in the indoor unit 2 or not with a high accuracy.

[0078] Moreover, in Embodiment 2, it is determined whether valve leakage occurs at the first open/close valve 21 or the second open/close valve 24c or not by the way of performing a process of causing refrigerant to flow into the refrigerant pipe in the indoor unit 2. This, however, is not!imitative. For example, the following method may be applied: gas in the refrigerant pipe is taken from the check joint 24b or a gas detection device that serves as a state detection unit is connected to the check joint 2, and it is then determined whether valve leakage occurs in the valve or not on the basis of components of the gas in the refrigerant pipe. More specifically, in the case where the gas in the refrigerant pipe contains gas in the air, such as nitrogen, oxygen or carbon dioxide, it is determined that the refrigerant leaks at the first open/close valve 21 or the second open/close valve 24c.

[0079] Fig. 7 is a schematic diagram illustrating another example of the configuration of the indoor unit 2 as illustrated in Fig. 1. As illustrated in Fig. 7, the refrigerant leak detection unit 24 of the indoor unit 2 includes the pressure sensor 24a, the second open/close valve 24c, and a gas detection device 24d. In such a manner, the refrigerant leak detection unit 24 may be formed to include the gas detection device 24d, and detect components of gas in the refrigerant pipe in the above manner to determine whether valve leakage occurs at the valve or not.

[0080] With respect to Embodiments 1 to 3, it is described above that the refrigerant leak detection unit 24 is provided in the indoor unit 2. This, however, is not!imitative. For example, the refrigerant leak detection unit 24 may be provided as a refrigerant leak detection device; that is, the refrigerant leak detection unit 24 and the indoor unit 2 may be provided as separate units. In this case, by attaching the above refrigerant leak detection device to an existing indoor unit, it is possible to perform the same refrigerant leak process as describe above regarding Embodiments 1 to 3.

[0081] Furthermore, in the case where a further open/close valve is provided in addition to the first open/close valve 21 and the second open/close valve 24c as described regarding Embodiments 1 to 3, it is possible to more accurately detect a leakage point in the indoor unit 2 and a leakage point at an extension pipe, etc., that connects the outdoor unit 1 and the indoor unit 2. For example, in the case where a third open/close valve is provided upstream of the first open/close valve 21, and a fourth open/close valve is provided downstream of the second open/close valve 24c, it is possible to detect whether a refrigerant leak occurs between one of the first open/close valve 21 and the third open/close valve and one of the second open/close valve 24c and the fourth open/close valve or not.

Reference Signs List [0082] 1 outdoor unit, 2 indoor unit, 3, 203 controller, 11 compressor, 12 condenser, 12a outdoor-unit fan, 13 accumulator, 21 first open/close valve, 22 expansion valve, 23 evaporator, 23a indoor-unit fan, 24 refrigerant leak detection unit, 24a pressure sensor, 24b check joint, 24c second open/close valve, 24d gas detection device, 31 operation control unit, 32, 232 leak determination unit, 33, 233 storage unit, 34 refrigerant insufficiency detection unit, 100 air-conditioning apparatus, 235 pressure change measurement unit