Air conditioner

Abstract

To provide an air conditioner that secures safety.SOLUTION: An air conditioner includes: a casing; a heat exchanger and a fan that are accommodated in the casing and in which a refrigerant flows; a sensor that detects a concentration of the refrigerant in the casing; and a control section that controls rotational frequency of the fan. The control section measures the concentration of the refrigerant in the casing for a predetermined time after the concentration of the refrigerant that is a detection value obtained by the sensor reaches a concentration reference value, calculates concentration rise speed within the predetermined time on the basis of the concentration for the predetermined time, and controls rotational frequency of the fan on the basis of the calculated concentration rise speed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an air conditioning apparatus. [Background technology]

[0002] An air conditioner consists of an indoor unit and an outdoor unit. The indoor and outdoor units are connected by refrigerant piping through which the refrigerant circulates. Each indoor and outdoor unit is equipped with a blower, which, when driven, generates airflow to exchange heat between the surrounding air and the refrigerant.

[0003] Conventionally, there is a technology in which a sensor is installed in the indoor unit to detect the concentration of refrigerant in the air that has leaked around the indoor unit, and when refrigerant leaks from the indoor unit, the indoor unit's fan is driven to agitate the indoor air containing the leaked refrigerant. This prevents the occurrence of a region in which the refrigerant concentration in the indoor air falls within the flammable concentration range (hereinafter referred to as the flammable concentration region).

[0004] In recent years, refrigerants with low GWP (Global Warming Potential) have been increasingly adopted to prevent global warming, such as R32 refrigerant or refrigerants with lower upper and lower limits of the flammable concentration range than R32 refrigerant. Examples of such refrigerants include R290, R600a, R1270, R717, R1132E, R152a, and R1234yf. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-166680 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional air conditioners, when a refrigerant leak is detected, the blower is immediately activated to agitate the indoor air containing the leaked refrigerant. However, if the leakage rate is large and the refrigerant concentration around the indoor unit exceeds the upper limit of the flammable concentration range, agitating the air with the blower expands the flammable concentration range and increases the risk of ignition. Furthermore, if the amount of leaked refrigerant supplied to the space inside the indoor unit due to the leak balances with the amount of leaked refrigerant discharged from the space inside the indoor unit due to agitation by the blower, a certain concentration is maintained inside the indoor unit, prolonging the time the flammable concentration range exists.

[0007] Furthermore, when using refrigerants such as the hydrocarbon refrigerant R290 or the fluorine refrigerant R1234yf, the upper and lower limits of the flammable concentration range are lower than those of R32 refrigerant, so the probability that the concentration will remain within the flammable concentration range increases, and the probability of the flammable concentration range remaining in the indoor space increases for a longer period of time, increasing the risk of ignition within the indoor space.

[0008] Therefore, there is a demand for an air conditioning device that can ensure safety by reducing the risk of ignition within the space.

[0009] In one aspect, an object is to provide an air conditioner that ensures safety. [Means for solving the problem]

[0010] An air conditioning apparatus according to one embodiment includes a housing, a heat exchanger and a fan through which a refrigerant contained in the housing flows, a sensor for detecting the concentration of the refrigerant within the housing, and a control unit for controlling the rotation speed of the fan. The control unit measures the concentration of the refrigerant within the housing for a predetermined time after the refrigerant concentration detected by the sensor reaches a concentration reference value, calculates a concentration increase rate within the predetermined time based on the concentration during the predetermined time, and controls the rotation speed of the fan based on the calculated concentration increase rate. [Effects of the Invention]

[0011] According to one aspect, safety can be ensured. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram showing an example of the configuration of an air conditioning apparatus according to this embodiment. [Figure 2] FIG. 2 is a block diagram illustrating an example of the configuration of the first control unit according to the first embodiment. [Figure 3] FIG. 3 is a block diagram illustrating an example of the configuration of the second control unit according to the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of the flammable concentration range. [Figure 5] FIG. 5 is an explanatory diagram showing an example of the first rotation speed table. [Figure 6] FIG. 6 is a flowchart illustrating an example of a processing operation of the first control unit related to the outdoor fan control process according to the first embodiment. [Figure 7] FIG. 7 is a flowchart illustrating an example of a processing operation of the second control unit related to the indoor fan control processing of the first embodiment. [Figure 8] FIG. 8 is a block diagram illustrating an example of the configuration of the first control unit according to the second embodiment. [Figure 9] FIG. 9 is a block diagram illustrating an example of the configuration of the second control unit according to the second embodiment. [Figure 10] FIG. 10 is a flowchart illustrating an example of a processing operation of the first control unit related to the outdoor fan control process of the second embodiment. [Figure 11] FIG. 11 is a block diagram illustrating an example of the configuration of the first control unit according to the third embodiment. [Figure 12] FIG. 12 is a block diagram illustrating an example of the configuration of the second control unit according to the third embodiment. [Figure 13] FIG. 13 is a flowchart illustrating an example of a processing operation of the first control unit related to the outdoor fan control processing of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of an air conditioning apparatus disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the following examples may be combined as appropriate within the scope of not causing any contradiction. [Example]

[0014] Fig. 1 is an explanatory diagram showing an example of the configuration of an air conditioner 1 of this embodiment. The air conditioner 1 shown in Fig. 1 has an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 is, for example, a device installed outdoors. The indoor unit 20 is, for example, a device installed in an indoor space.

[0015] The outdoor unit 10 has a first casing 10A, a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor expansion valve 14, an outdoor fan 15, a first sensor 31A, and a first control unit 16. The first casing 10A houses the compressor 11, the four-way valve 12, the outdoor heat exchanger 13, the outdoor expansion valve 14, the outdoor fan 15, the first sensor 31A, and the first control unit 16. The indoor unit 20 has a second casing 20A, an indoor heat exchanger 21, an indoor fan 23, a second sensor 31B, and a second control unit 24. The second casing 20A houses the indoor heat exchanger 21, the indoor fan 23, the second sensor 31B, and the second control unit 24.

[0016] The outdoor unit 10 and the indoor unit 20 are connected to each other so that a refrigerant circulates through a liquid pipe 32 and a gas pipe 33. The air conditioner 1 has a refrigerant circuit. The refrigerant circuit has a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor expansion valve 14, an indoor heat exchanger 21, the liquid pipe 32, and the gas pipe 33.

[0017] Compressor 11 is a variable capacity compressor whose operating capacity can be varied by being driven by a motor (not shown) whose rotation speed is controlled by an inverter. Four-way valve 12 has a first port a, a second port b, a third port c, and a fourth port d. First port a is connected to a discharge port of compressor 11 via refrigerant piping 17a. Second port b is connected to one refrigerant inlet / outlet of outdoor heat exchanger 13 via refrigerant piping 17b. Third port c is connected to a suction port of compressor 11 via refrigerant piping 17c. Fourth port d is connected to shut-off valve 18, which is connected to gas pipe 33 via refrigerant piping 17d.

[0018] The outdoor heat exchanger 13 is a heat exchanger that exchanges heat between outside air taken into the outdoor unit 10 by the outdoor fan 15 and refrigerant flowing through a refrigerant pipe. One refrigerant inlet / outlet of the outdoor heat exchanger 13 is connected to the second port b of the four-way valve 12 by a refrigerant pipe 17b. The other refrigerant inlet / outlet of the outdoor heat exchanger 13 is connected to a stop valve 19 by a refrigerant pipe 17e. An outdoor expansion valve 14 is provided in the refrigerant pipe 17e that connects the other refrigerant inlet / outlet and the stop valve 19.

[0019] The outdoor fan 15 is driven by a motor (not shown) to take in outside air into the outdoor unit 10 and generate an air flow for discharging the outside air that has exchanged heat with the refrigerant in the outdoor heat exchanger 13 to the outside of the outdoor unit 10. The outdoor fan 15 also generates an air flow within the first housing 10A, and therefore can agitate air containing refrigerant that has leaked within the first housing 10A.

[0020] The first control unit 16 is a control unit that executes control of the start, stop, and rotation speed of the compressor 11, switching control of the four-way valve 12, control of the opening degree of the outdoor expansion valve 14, and drive control of the outdoor fan 15. Furthermore, the first control unit 16 receives a start request or stop request from the air conditioner 1 and controls at least the start and stop of the compressor 11.

[0021] The indoor heat exchanger 21 is a heat exchanger that exchanges heat between the indoor air taken into the indoor unit 20 by the indoor fan 23 and the refrigerant flowing through the refrigerant piping. One refrigerant inlet and outlet of the indoor heat exchanger 22 is connected to refrigerant piping 28a, which is connected to the shut-off valve 26. The other refrigerant inlet and outlet of the indoor heat exchanger 21 is connected to refrigerant piping 28b, which is connected to the shut-off valve 27. The shut-off valve 19 of the outdoor unit 10 and the shut-off valve 27 of the indoor unit 20 are connected by a liquid pipe 32, and the shut-off valve 18 of the outdoor unit 10 and the shut-off valve 26 of the indoor unit 20 are connected by a gas pipe 33.

[0022] The indoor fan 23 is driven by a motor (not shown) to draw in outside air into the indoor unit 20 and generate an air flow for discharging the outside air that has exchanged heat with the refrigerant in the indoor heat exchanger 21 to the outside of the indoor unit 20. The indoor fan 23 also generates an air flow within the second housing 20A, and therefore can agitate air containing refrigerant that has leaked within the second housing 20A.

[0023] The outdoor unit 10 has, for example, a first sensor 31A and a first control unit 16 arranged in a first housing 10A. The first sensor 31A is an infrared sensor that can detect the concentration of refrigerant contained in the air. The first sensor 31A measures the concentration of refrigerant that has leaked into the first housing 10A of the outdoor unit 10 and outputs the measurement result of the refrigerant concentration in the first housing 10A to the first control unit 16.

[0024] The indoor unit 20 has, for example, a second sensor 31B and a second control unit 24 arranged in the second housing 20A. The second sensor 31B is an infrared sensor that can detect the concentration of refrigerant contained in the air. The second sensor 31B measures the concentration of refrigerant that has leaked into the second housing 20A of the indoor unit 20 and outputs the measurement result of the refrigerant concentration in the second housing 20A to the second control unit 24.

[0025] FIG. 2 is a block diagram showing an example of the configuration of the first control unit 16 according to the first embodiment. The first control unit 16 shown in FIG. 2 includes a first communication unit 41, a first memory 43, and a first control unit 44. The first communication unit 41 is a communication unit on the outdoor unit 10 side that communicates with the second control unit 24. The first memory 43 stores various information. The first memory 43 includes, for example, a first threshold memory 43A that stores various thresholds, a first concentration memory 43B that temporarily stores the refrigerant concentration in the first housing 10A as a measurement result, a first rotation speed table 43C that pre-stores the rotation speed of the outdoor fan 15 set for each range of refrigerant concentration, and a first speed memory 43D that stores the concentration increase rate (described later). The first control unit 44 controls the entire first control unit 16.

[0026] The first threshold memory 43A stores a concentration reference value and a rate reference value in advance. The concentration reference value is a threshold value for determining whether a refrigerant leak has occurred in the first casing 10A, and is set to, for example, a value within a range from the lower limit of the concentration measurable by the sensor to a concentration of ¼ of the LFL (later described). The rate reference value is a reference value for the rate of increase in concentration in the first casing 10A for determining that the rate of increase in the refrigerant concentration over a predetermined period of time in the first casing 10A is fast and that there is a high possibility that the concentration will exceed the flammable concentration range (explosive range).

[0027] FIG. 4 is an explanatory diagram showing an example of a flammable concentration range. The flammable concentration range shown in FIG. 4 is the concentration range in which a refrigerant will burn. The UFL (Upper Flammability Limit) is the upper limit of the flammable concentration range of a refrigerant. The LFL (Lower Flammability Limit) is the lower limit of the flammable concentration range of a refrigerant. The flammable concentration range differs depending on the type of refrigerant. The refrigerant used in the air conditioner 1 is, for example, a flammable refrigerant whose upper limit concentration (UFL) of the flammable concentration range is less than 29.3 Vol%. Examples of such refrigerants include R290, R600a, R1270, R717, R1132E, R152a, and R1234yf. Among these, the flammable concentration ranges (UFL-LFL) of R290 and R1234yf are smaller than that of R32 (R290: 2.1-9.5 Vol%, R1234yf: 6.2-14.0 Vol%, R32: 13.3-29.3 Vol%). However, as the concentration gradually approaches 0% during agitation, the rate of decrease per unit time decreases as the concentration approaches 0%. As a result, R290 and R1234yf, which have low flammable concentration ranges, spend more time in the flammable concentration range. This means that the concentration remains within the flammable concentration range, and the flammable concentration area exists for a longer period of time, prolonging the risk of ignition.

[0028] FIG. 5 is an explanatory diagram showing an example of the first rotation speed table 43C. The first rotation speed table 43C shown in FIG. 5 is a table that stores in advance the fan rotation speeds of the outdoor fan 15 that are set when the rate of increase in concentration of the refrigerant in the first housing 10A is equal to or greater than a reference speed value and when it is less than the reference speed value. The concentration increase rate is the concentration increase value per unit time, i.e., indicates the amount of leakage per unit time. The reference speed value is set in advance through testing or the like. When the concentration increase rate is equal to or greater than the reference speed value, the outdoor fan 15 has a lower rotation speed, e.g., a minimum rotation speed, than the outdoor fan 15 has when the concentration increase rate is less than the reference speed value. When the concentration increase rate is less than the reference speed value, the outdoor fan 15 has a higher rotation speed, e.g., a maximum rotation speed, than the outdoor fan 15 has when the concentration increase rate is equal to or greater than the reference speed value.

[0029] The first control unit 44 determines whether the refrigerant concentration in the first housing 10A has reached the concentration reference value. When the refrigerant concentration in the first housing 10A has reached the concentration reference value, the first control unit 44 measures the refrigerant concentration in the first housing 10A multiple times over a predetermined time period using the first sensor 31A. The first control unit 44 calculates the concentration increase rate over the predetermined time period in the first housing 10A based on the refrigerant concentration obtained through the measurement. Note that the predetermined time period can be changed as appropriate. The concentration increase rate is the rate at which the refrigerant concentration in the first housing 10A increases over the predetermined time period. The first control unit 44 calculates the concentration increase rate over the predetermined time period in the first housing 10A based on, for example, the refrigerant concentration measured at the start of the predetermined time period during which the measurement is performed, the amount of change in the refrigerant concentration measured at the end of the predetermined time period, and the predetermined time period.

[0030] The first control unit 44 controls the rotation speed of the outdoor fan 15 based on the calculated rate of increase in concentration. The first control unit 44 determines whether the calculated rate of increase in concentration is equal to or greater than the reference speed value stored in the first threshold memory 43A. If the rate of increase in concentration is equal to or greater than the reference speed value, the first control unit 44 determines whether the refrigerant concentration measured in the first housing 10A has exceeded a predetermined value.

[0031] When the refrigerant concentration exceeds a predetermined value, the first control unit 44 references the first rotation speed table 43C, extracts the minimum rotation speed according to the range of refrigerant concentration, and sets the rotation speed of the outdoor fan 15 to the minimum rotation speed. Instead of driving the outdoor fan 15 when it is determined that the rate of increase in refrigerant concentration is equal to or greater than the speed reference value, the first control unit 44 waits until the refrigerant concentration exceeds a predetermined value higher than the UFL before starting to drive the outdoor fan 15, thereby enabling the refrigerant concentration to quickly escape the flammable concentration range.

[0032] If the rate of increase in concentration is equal to or greater than the reference rate and the refrigerant concentration is equal to or less than a predetermined value, the first control unit 44 repeats the same determination until the refrigerant concentration exceeds the predetermined value. If the rate of increase in concentration is less than the reference rate and the refrigerant concentration is equal to or less than the predetermined value, the first control unit 44 references the first rotation speed table 43C, extracts a high rotation speed according to the range of refrigerant concentration, and sets the rotation speed of the outdoor fan 15 to the high rotation speed. Specifically, the rotation speed of the outdoor fan 15 is set to the maximum rotation speed.

[0033] FIG. 3 is a block diagram showing an example of the configuration of the second control unit 24 according to the first embodiment. The second control unit 24 shown in FIG. 2 includes a second communication unit 51, a second memory 53, and a second control unit 54. The second communication unit 51 is a communication unit on the indoor unit 20 side that communicates with the first control unit 16. The second memory 53 stores various information. The second memory 53 includes, for example, a second threshold memory 53A that stores various thresholds, a second concentration memory 53B that temporarily stores the refrigerant concentration in the second housing 20A as a measurement result, a second rotation speed table 53C that pre-stores the rotation speed of the indoor fan 23 to be set for each range of refrigerant concentration, and a second speed memory 53D that stores the calculated rate of increase in concentration. The second control unit 54 controls the entire second control unit 24.

[0034] The second threshold memory 53A stores a concentration reference value and a rate reference value in advance. The concentration reference value is a threshold value for determining whether a refrigerant leak has occurred in the second casing 20A, and is set to, for example, a value within a range from the lower limit of the concentration measurable by the sensor to a concentration of ¼ of the LFL (Long-Term Fluid Level), which will be described later. The rate reference value is a reference value for the rate of increase in concentration in the second casing 20A, for determining that the rate of increase in the refrigerant concentration over a predetermined period of time in the second casing 20A is fast and that there is a high possibility that the concentration will exceed the flammable concentration range (explosive range).

[0035] The second rotation speed table 53C also stores in advance fan rotation speeds of the indoor fan 23 that are set when the rate of increase in concentration of the refrigerant in the second housing 20A is equal to or greater than the reference speed value and when it is less than the reference speed value. The concentration increase rate is the concentration increase value per unit time, and in other words, indicates the amount of leakage per unit time. When the concentration increase rate is equal to or greater than the reference speed value, the rotation speed of the indoor fan 23 is lower, for example, the minimum rotation speed, than the rotation speed of the indoor fan 23 when the concentration increase rate is less than the reference speed value. When the concentration increase rate is less than the reference speed value, the rotation speed of the indoor fan 23 is higher, for example, the maximum rotation speed, than the rotation speed of the indoor fan 23 when the concentration increase rate is equal to or greater than the reference speed value.

[0036] The second control unit 54 determines whether the refrigerant concentration in the second housing 20A has reached the concentration reference value. When the refrigerant concentration in the second housing 20A has reached the concentration reference value, the second control unit 54 measures the refrigerant concentration in the second housing 20A multiple times over a predetermined time period using the second sensor 31B. The second control unit 54 calculates the concentration increase rate over the predetermined time period in the second housing 20A based on the refrigerant concentration obtained through the measurement. Note that the predetermined time period can be changed as appropriate. The concentration increase rate is the rate at which the refrigerant concentration in the second housing 20A increases over the predetermined time period. The second control unit 54 calculates the concentration increase rate over the predetermined time period in the second housing 20A based on, for example, the refrigerant concentration measured at the start of the predetermined time period during which the measurement is performed, the amount of change in the refrigerant concentration measured at the end of the predetermined time period, and the predetermined time period.

[0037] Based on the calculated rate of increase in concentration, the second control unit 54 controls the indoor fan 23 to change the rotation speed of the indoor fan 23. The second control unit 54 determines whether the calculated rate of increase in concentration is equal to or greater than the speed reference value stored in the second threshold memory 53A.

[0038] When the rate of increase in concentration is equal to or greater than the reference rate, the second control unit 54 refers to the second rotation speed table 53C, extracts the minimum rotation speed according to the range of the refrigerant concentration, and sets the rotation speed of the indoor fan 23 to the minimum rotation speed.

[0039] If the rate of increase in concentration is equal to or greater than the reference rate and the refrigerant concentration is equal to or less than a predetermined value, the second control unit 54 repeats the same determination until the refrigerant concentration exceeds the predetermined value. If the rate of increase in concentration is less than the reference rate and the refrigerant concentration is equal to or less than the predetermined value, the second control unit 54 references the second rotation speed table 53C, extracts a high rotation speed corresponding to the range of refrigerant concentration, and sets the rotation speed of the indoor fan 23 to the high rotation speed. Specifically, the rotation speed of the indoor fan 23 is set to the maximum rotation speed.

[0040] FIG. 6 is a flowchart illustrating an example of the processing operation of the first control unit 16 related to the outdoor fan control process of the first embodiment. The control illustrated in this flowchart is repeatedly executed while the air conditioning apparatus 1 is stopped. In FIG. 6, the first control unit 44 in the first control unit 16 determines whether the refrigerant concentration in the first casing 10A measured via the first sensor 31A has reached a concentration reference value (step S11). If the refrigerant concentration in the first casing 10A has reached the concentration reference value (step S11: Yes), the first control unit 44 measures the refrigerant concentration in the first casing 10A via the first sensor 31A multiple times over a predetermined time period (step S12). Next, the first control unit 44 calculates the rate of increase in concentration in the first casing 10A over the predetermined time period based on the measured refrigerant concentration in the first casing 10A (step S13). The rate of increase in concentration is calculated based on, for example, the amount of change between the refrigerant concentration measured at the start of the predetermined time period and the refrigerant concentration measured at the end of the predetermined time period, and the predetermined time period.

[0041] Next, the first control unit 44 determines whether the calculated concentration increase rate is equal to or greater than a reference rate (step S14). If the concentration increase rate is equal to or greater than the reference rate (step S14: Yes), the first control unit 44 determines that the rate at which the refrigerant concentration in the first housing 10A is increasing is fast, and determines whether the refrigerant concentration in the first housing 10A exceeds a predetermined value (step S15). The concentration increase rate is the concentration increase value per unit time, i.e., indicates the amount of leakage per unit time. Note that the predetermined value is preferably set to a value sufficiently higher than the UFL in order to maintain a state outside the flammable concentration range for a long period of time. For example, the predetermined value is set to a value approximately 10 Vol% higher than the UFL of the flammable concentration range of the refrigerant. In the case of R290, the predetermined value is set to 19.5 Vol%, which is 10 Vol% higher than the UFL (9.5 Vol%).

[0042] If the refrigerant concentration in first casing 10A exceeds the predetermined value (step S15: Yes), first control unit 44 references first rotation speed table 43C and sets the rotation speed of outdoor fan 15 to the minimum rotation speed (step S16). As a result, in an environment where the concentration in first casing 10A is increasing at a high rate and the refrigerant concentration in first casing 10A exceeds the UFL, the rotation speed of outdoor fan 15 is reduced to prevent the refrigerant concentration from falling into the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in first casing 10A.

[0043] Next, the first control unit 44 determines whether the refrigerant concentration in the first casing 10A is equal to or lower than the UFL (step S17). If the refrigerant concentration in the first casing 10A is equal to or lower than the UFL (step S17: Yes), the first control unit 44 references the first rotation speed table 43C and sets the rotation speed of the outdoor fan 15 to a high rotation speed (step S18). The first control unit 44 then returns to the process of step S11, in which the first control unit 44 determines whether the refrigerant concentration in the first casing 10A has reached the concentration reference value. As a result, in an environment where the refrigerant concentration in the first casing 10A is equal to or lower than the UFL, the rotation speed of the outdoor fan 15 is increased to immediately move the refrigerant concentration out of the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in the first casing 10A. On the other hand, if the refrigerant concentration in the first casing 10A exceeds the UFL (step S17: No), the first control unit 44 maintains the rotation speed of the outdoor fan 15 and returns to the processing of step S11 to determine whether the refrigerant concentration in the first casing 10A has reached the concentration reference value.

[0044] If the refrigerant concentration in first casing 10A has not reached the concentration reference value (step S11: No), first control unit 44 determines that a refrigerant leak has not occurred in first casing 10A, and ends the processing operation shown in Fig. 6. Furthermore, if the rate of increase in concentration is not equal to or greater than the rate reference value (step S14: No), first control unit 44 executes the processing of step S17, which determines whether the refrigerant concentration in first casing 10A is equal to or less than the UFL.

[0045] Furthermore, if the refrigerant concentration in first housing 10A does not exceed the predetermined value (step S15: No), first control unit 44 returns to the process of step S12. As a result, if the rate of increase in concentration is equal to or greater than the speed reference value, first control unit 44 does not drive outdoor fan 15 until the refrigerant concentration exceeds the predetermined value. This makes it easier to maintain an environment outside the flammable concentration range by preventing the refrigerant concentration from entering the flammable concentration range, and reduces the risk of ignition in first housing 10A.

[0046] FIG. 7 is a flowchart illustrating an example of the processing operation of the second control unit 24 related to the indoor fan control process of the first embodiment. The control illustrated in this flowchart is repeatedly executed while the air conditioning apparatus 1 is stopped. In FIG. 7, the second control unit 54 in the second control unit 24 determines whether the refrigerant concentration in the second casing 20A measured via the second sensor 31B has reached a concentration reference value (step S11A). If the refrigerant concentration in the second casing 20A has reached the concentration reference value (step S11A: Yes), the second control unit 54 measures the refrigerant concentration in the second casing 20A via the second sensor 31B multiple times over a predetermined time period (step S12A). Next, the second control unit 54 calculates the rate of increase in concentration in the second casing 20A over a predetermined time period based on the measured refrigerant concentration in the second casing 20A (step S13A). The rate of increase in concentration is calculated based on, for example, the amount of change between the refrigerant concentration measured at the start of the predetermined time period during which the measurement is performed and the refrigerant concentration measured at the end of the predetermined time period, and the predetermined time period.

[0047] Next, the second control unit 54 determines whether the calculated concentration increase rate is equal to or greater than a reference rate (step S14A). If the concentration increase rate is equal to or greater than the reference rate (step S14A: Yes), the second control unit 54 determines that the rate at which the refrigerant concentration in the second housing 20A is increasing is fast, and determines whether the refrigerant concentration in the second housing 20A exceeds a predetermined value (step S15A). The concentration increase rate is the concentration increase value per unit time, i.e., indicates the amount of leakage per unit time. Note that the predetermined value is preferably set to a value sufficiently higher than the UFL in order to maintain a state outside the flammable concentration range for a long period of time. For example, it may be set to a value approximately 10 Vol% higher than the UFL of the flammable concentration range of the refrigerant. In the case of R290, the predetermined value is set to 19.5 Vol%, which is 10 Vol% higher than the UFL (9.5 Vol%).

[0048] If the refrigerant concentration in second casing 20A exceeds the predetermined value (step S15A: Yes), second control unit 54 references second rotation speed table 53C and sets the rotation speed of indoor fan 23 to the minimum rotation speed (step S16A). As a result, in an environment where the concentration in second casing 20A is increasing at a high rate and the refrigerant concentration in second casing 20A exceeds the UFL, the rotation speed of indoor fan 23 is reduced to prevent the refrigerant concentration from falling within the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in second casing 20A.

[0049] Next, the second control unit 54 determines whether the refrigerant concentration in the second casing 20A is equal to or lower than the UFL (step S17A). If the refrigerant concentration in the second casing 20A is equal to or lower than the UFL (step S17A: Yes), the second control unit 54 references the second rotation speed table 53C and sets the rotation speed of the indoor fan 23 to a high rotation speed (step S18A). The second control unit 54 then returns to the process of step S11A, in which the second control unit 54 determines whether the refrigerant concentration in the second casing 20A has reached the concentration reference value. As a result, in an environment where the refrigerant concentration in the second casing 20A is equal to or lower than the UFL, the rotation speed of the indoor fan 23 is increased to immediately move the refrigerant concentration out of the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in the second casing 20A. On the other hand, if the refrigerant concentration in the second housing 20A exceeds the UFL (step S17A: No), the first control unit 44 maintains the rotation speed of the indoor fan 23 and returns to the processing of step S11A to determine whether the refrigerant concentration in the second housing 20A has reached the concentration reference value.

[0050] If the refrigerant concentration in second casing 20A has not reached the concentration reference value (step S11A: No), second control unit 54 determines that a refrigerant leak has not occurred in second casing 20A, and ends the processing operation shown in Fig. 7. If the rate of increase in concentration is not equal to or greater than the rate reference value (step S14A: No), second control unit 54 executes the processing of step S17A to determine whether the refrigerant concentration in second casing 20A is equal to or less than the UFL.

[0051] Furthermore, if the refrigerant concentration in second housing 20A does not exceed the predetermined value (step S15A: No), second control unit 54 returns to the process of step S12A. As a result, if the rate of increase in concentration is equal to or greater than the speed reference value, first control unit 44 does not drive outdoor fan 15 until the refrigerant concentration exceeds the predetermined value. This makes it easier to maintain an environment outside the flammable concentration range by preventing the refrigerant concentration from entering the flammable concentration range, and reduces the risk of ignition in second housing 20A.

[0052] In the first control unit 16 in the air conditioning apparatus 1 of the first embodiment, when the rate of increase in concentration in the first casing 10A is equal to or greater than the reference rate, it can determine that the refrigerant concentration in the first casing 10A is likely to exceed the UFL of the flammable concentration range, and therefore the rotation speed of the outdoor fan 15 is reduced to make it easier to maintain an environment in which the refrigerant concentration in the first casing 10A exceeds the UFL and falls outside the flammable concentration range. As a result, the risk of ignition in the first casing 10A can be reduced.

[0053] Furthermore, when the rate of increase in concentration inside first housing 10A is less than the reference rate, first control unit 16 can also determine that the flammable concentration range will remain in first housing 10A for a long time, and therefore increases the rotation speed of outdoor fan 15 so that the concentration inside first housing 10A quickly falls below the LFL of the flammable concentration range, creating an environment where the concentration inside first housing 10A falls outside the flammable concentration range. As a result, the risk of ignition inside first housing 10A can be reduced while also stirring the refrigerant accumulating around outdoor unit 10 outside first housing 10A.

[0054] If the rate of increase in concentration in second housing 20A is equal to or greater than the reference rate, second control unit 24 in air conditioning apparatus 1 can determine that the refrigerant concentration in second housing 20A is likely to exceed the UFL, the flammable concentration range, and therefore reduces the rotation speed of indoor fan 23 to make it easier to maintain an environment in which the refrigerant concentration in second housing 20A exceeds the UFL and falls outside the flammable concentration range. As a result, the risk of ignition in second housing 20A can be reduced.

[0055] Furthermore, when the rate of increase in concentration inside the second housing 20A is slow and less than the reference rate, the second control unit 24 can also determine that the flammable concentration range will remain in the second housing 20A for a long time, and therefore increases the rotation speed of the indoor fan 23 so that the concentration inside the second housing 20A quickly becomes less than the LFL of the flammable concentration range, thereby creating an environment in which the concentration inside the second housing 20A falls outside the flammable concentration range. As a result, the risk of ignition inside the second housing 20A can be reduced while also stirring the refrigerant accumulating around the indoor unit 20 outside the second housing 20A.

[0056] For ease of explanation, the example has been given in which the first control unit 44 in the first control unit 16 of the outdoor unit 10 is used to perform threshold determination of the refrigerant concentration and concentration increase rate in the first casing 10A. Also, the example has been given in which the second control unit 54 in the second control unit 24 of the indoor unit 20 is used to perform threshold determination of the refrigerant concentration and concentration increase rate in the second casing 20A. However, the threshold determination of the refrigerant concentration and concentration increase rate in the first casing 10A and the second casing 20A may be performed by either the first control unit 16 or the second control unit 24, and this can be changed as appropriate.

[0057] For example, the second control unit 24 obtains the refrigerant concentration in the first casing 10A from the first control unit 16, and extracts the rotation speed of the outdoor fan 15 from the first rotation speed table 43C based on the refrigerant concentration in the first casing 10A. The second control unit 24 then transmits the extracted rotation speed of the outdoor fan 15 to the first control unit 16. The first control unit 16 may then set the rotation speed of the outdoor fan 15 obtained from the second control unit 24 to the outdoor fan 15.

[0058] Furthermore, for example, the first control unit 16 obtains the refrigerant concentration in the second casing 20A from the second control unit 24, and extracts the rotation speed of the indoor fan 23 from the second rotation speed table 53C based on the refrigerant concentration in the second casing 20A. Then, the first control unit 16 transmits the extracted rotation speed of the indoor fan 23 to the second control unit 24. Then, the second control unit 24 may set the rotation speed of the indoor fan 23 obtained from the first control unit 16 to the indoor fan 23.

[0059] Furthermore, the predetermined value is set to a value approximately 10 Vol % higher than the UFL, which is the upper limit of the flammable concentration range of the refrigerant, but is not limited to this and can be changed as appropriate.

[0060] In the air conditioner 1 of Example 1, for example, a case has been illustrated in which the rotation speed of the outdoor fan 15 is set to the minimum rotation speed when the rate of increase in concentration in the first casing 10A of the outdoor unit 10 is equal to or greater than the speed reference value. However, the present invention is not limited to this, and an embodiment thereof will be described below as Example 2. 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. [Example]

[0061] FIG. 8 is a block diagram illustrating an example of the configuration of a first control unit 16A according to a second embodiment. The first control unit 16A according to the second embodiment shown in FIG. 8 differs from the first control unit 16 according to the first embodiment in that it includes a first airflow speed measurement unit 45 that measures the outdoor airflow speed, which is the wind speed of the outdoor air around the outdoor unit 10. The first control unit 44A determines whether the outdoor airflow speed measured by the first airflow speed measurement unit 45 exceeds a reference airflow speed. The first threshold memory 43A1 pre-stores a reference airflow speed value that indicates the airflow speed outside the housing when the outdoor fan 15 is driven at the minimum rotation speed. If the outdoor airflow speed exceeds the reference airflow speed, the first control unit 44A stops the outdoor fan 15 to use the outdoor air to agitate the refrigerant-containing air in the first housing 10A. In other words, the outdoor air is used to create an environment in which the refrigerant concentration in the first housing 10A is below the UFL, i.e., outside the flammable concentration range. When the outdoor air wind speed value does not exceed the reference wind speed value, the first control unit 44A refers to the first rotation speed table 43C, extracts the minimum rotation speed, which is the rotation speed of the outdoor fan 15 corresponding to the range of refrigerant concentration, and sets the rotation speed of the outdoor fan 15 to the minimum rotation speed.

[0062] FIG. 9 is a block diagram illustrating an example of the functional configuration of a second control unit 24A according to a second embodiment. The second control unit 24A according to the second embodiment illustrated in FIG. 9 differs from the second control unit 24 according to the first embodiment in that it includes a second airflow speed measurement unit 55 that measures the outdoor airflow speed, which is the wind speed of the outdoor air around the indoor unit 20. The second control unit 54A determines whether the outdoor airflow speed measured by the second airflow speed measurement unit 55 exceeds a reference airflow speed. The second threshold memory 53A1 pre-stores a reference airflow speed value that indicates the airflow speed corresponding to the minimum rotation speed of the indoor fan 23. If the outdoor airflow speed exceeds the reference airflow speed, the second control unit 54A stops the indoor fan 23 to use the outdoor airflow to agitate the refrigerant-containing air in the second housing 20A. In other words, the outdoor airflow is used to create an environment in which the refrigerant concentration in the second housing 20A is below the UFL, i.e., outside the flammable concentration range. When the outside air wind speed value does not exceed the reference wind speed value, the second control unit 54A refers to the second rotation speed table 53C, extracts the minimum rotation speed, which is the rotation speed of the indoor fan 23 corresponding to the range of refrigerant concentration, and sets the rotation speed of the indoor fan 23 to the minimum rotation speed.

[0063] Fig. 10 is a flowchart showing an example of the processing operation of the first control unit 16A related to the outdoor fan control process of Example 2. The control shown in this flowchart is repeatedly executed while the air conditioner 1 is stopped. In Fig. 10, the first control unit 44A determines whether the concentration increase rate calculated in step S13 is equal to or greater than a speed reference value (step S21). If the concentration increase rate is equal to or greater than the speed reference value (step S21: Yes), the first control unit 44A determines that the rate at which the refrigerant concentration in the first casing 10A is increasing is fast, and determines whether the refrigerant concentration in the first casing 10A exceeds a predetermined value (step S22).

[0064] If the refrigerant concentration in the first casing 10A exceeds a predetermined value (step S22: Yes), the first control unit 44A determines whether the outside air velocity exceeds a reference velocity (step S23). If the outside air velocity does not exceed the reference velocity (step S23: No), the first control unit 44A references the first rotation speed table 43C and sets the rotation speed of the outdoor fan 15 to the minimum rotation speed (step S24). As a result, in an environment where the concentration in the first casing 10A is increasing rapidly, the refrigerant concentration in the first casing 10A exceeds the UFL, and the outside air velocity does not exceed the reference velocity, the rotation speed of the outdoor fan 15 is reduced to prevent the refrigerant concentration from falling within the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in the first casing 10A.

[0065] The first control unit 44A determines whether the refrigerant concentration in the first casing 10A is equal to or lower than the UFL (step S25). If the refrigerant concentration in the first casing 10A is equal to or lower than the UFL (step S25: Yes), the first control unit 44A references the first rotation speed table 43C and sets the rotation speed of the outdoor fan 15 to a high rotation speed (step S26). The first control unit 44A then returns to the process of step S11, in which the first control unit 44A determines whether the refrigerant concentration in the first casing 10A has reached the concentration reference value. As a result, in an environment where the refrigerant concentration in the first casing 10A is equal to or lower than the UFL, the rotation speed of the outdoor fan 15 is increased to immediately move the refrigerant concentration out of the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in the first casing 10A.

[0066] Furthermore, if the concentration increase rate is not equal to or greater than the rate reference value (step S21: No), first control unit 44A executes the process of step S25 to determine whether the refrigerant concentration in first casing 10A is equal to or less than a predetermined value.

[0067] Furthermore, if the refrigerant concentration in first housing 10A does not exceed UFL (step S22: No), first control unit 44A returns to the processing of step S12. As a result, if the rate of increase in concentration is equal to or greater than the reference rate, first control unit 44 does not drive outdoor fan 15 until the refrigerant concentration exceeds a predetermined value. This makes it easier to maintain an environment outside the flammable concentration range by preventing the refrigerant concentration from entering the flammable concentration range, and reduces the risk of ignition in first housing 10A.

[0068] If the outside air velocity exceeds the reference velocity (step S23: Yes), first control unit 44A stops outdoor fan 15 (step S27) and executes the process of step S25, which determines whether the refrigerant concentration in first casing 10A is equal to or lower than the UFL. If the refrigerant concentration in first casing 10A is equal to or lower than the UFL (step S25: Yes), first control unit 44A references first rotation speed table 43C and sets the rotation speed of outdoor fan 15 to a high rotation speed (step S26). As a result, in an environment where the concentration in first casing 10A is increasing at a high rate, the refrigerant concentration in first casing 10A exceeds the UFL, and the outside air velocity exceeds the reference velocity, outdoor fan 15 is not used, thereby preventing the refrigerant concentration from falling within the flammable concentration range. This makes it easier to maintain an environment outside the flammable concentration range and reduces the risk of ignition in first casing 10A.

[0069] Furthermore, if the refrigerant concentration in the first housing 10A is not below UFL (step S25: No), the first control unit 44A determines that the refrigerant concentration in the first housing 10A is outside the flammable concentration range, and returns to the processing of step S11, which determines whether the refrigerant concentration in the first housing 10A has reached the concentration reference value.

[0070] 10 illustrates an example of controlling the outdoor fan 15 based on the refrigerant concentration, refrigerant rising speed, and outside air speed in the first casing 10A of the outdoor unit 10. However, the indoor fan 23 may also be controlled based on the refrigerant concentration, refrigerant rising speed, and outside air speed in the second casing 20A of the indoor unit 20, and this can be changed as appropriate.

[0071] When the wind speed value of the outdoor air around the outdoor unit 10 exceeds the reference wind speed value, the first control unit 16A of the second embodiment can agitate the refrigerant accumulating around the outdoor unit 10 without using the outdoor fan 15, because the refrigerant concentration in the first housing 10A exceeds the UFL, making it easier to maintain an environment in the outdoor air outside the flammable concentration range and reducing the risk of ignition.

[0072] When the wind speed value of the outside air around the indoor unit 20 exceeds the reference wind speed value, the second control unit 24A can agitate the refrigerant accumulating around the indoor unit 20 without using the indoor fan 23, because the refrigerant concentration in the second housing 20A exceeds the UFL, making it easier to maintain an environment in the outside air outside the flammable concentration range and reducing the risk of ignition.

[0073] For ease of explanation, the example has been given in which the first control unit 44A in the first control unit 16A of the outdoor unit 10 is used to perform threshold determination of the refrigerant concentration, concentration increase rate, and outdoor air velocity value in the first casing 10A. Also, the example has been given in which the second control unit 54A in the second control unit 24A of the indoor unit 20 is used to perform threshold determination of the refrigerant concentration, concentration increase rate, and outdoor air velocity value in the second casing 20A. However, the threshold determination of the refrigerant concentration, concentration increase rate, and outdoor air velocity value in the first casing 10A and the second casing 20A may be performed by either the first control unit 16A or the second control unit 24A, and this can be changed as appropriate.

[0074] For example, the second control unit 24A acquires the refrigerant concentration in the first casing 10A and the outside air velocity value from the first control unit 16A, and extracts the rotation speed of the outdoor fan 15 from the first rotation speed table 43C based on the refrigerant concentration in the first casing 10A, the rate of increase in concentration, and the outside air velocity value. The second control unit 24A then transmits the extracted rotation speed of the outdoor fan 15 to the first control unit 16A. The first control unit 16A may then set the rotation speed of the outdoor fan 15 acquired from the second control unit 24A in the outdoor fan 15.

[0075] For example, the first control unit 16A acquires the refrigerant concentration in the second casing 20A and the outside air velocity value from the second control unit 24A, and extracts the rotation speed of the indoor fan 23 from the second rotation speed table 53C based on the refrigerant concentration, the rate of increase in concentration, and the outside air velocity value in the second casing 20A. The first control unit 16A then transmits the extracted rotation speed of the indoor fan 23 to the second control unit 24A. The second control unit 24A may then set the rotation speed of the indoor fan 23 acquired from the first control unit 16A to the indoor fan 23.

[0076] In the air conditioner 1 of Example 1, for example, the case where the outdoor fan 15 is controlled by using the rate of increase in concentration in the first housing 10A in the outdoor unit 10 is exemplified, but the rate of increase in concentration does not have to be used, and such an embodiment will be described below 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. [Example]

[0077] Fig. 11 is a block diagram showing an example of the configuration of a first control unit 16B according to a third embodiment. The first control unit 16B according to the third embodiment shown in Fig. 11 differs from the first control unit 16 according to the first embodiment in that the first control unit 16B controls the driving of the outdoor fan 15 using only the refrigerant concentration in the first casing 10A. The first control unit 44B does not have a function of calculating the rate of increase in concentration in the first casing 10A.

[0078] When the refrigerant concentration in the first casing 10A exceeds a predetermined value, the first control unit 44B refers to the first rotation speed table 43C and sets the rotation speed of the outdoor fan 15 to the minimum rotation speed. When the refrigerant concentration in the first casing 10A is equal to or lower than a predetermined value, the first control unit 44B refers to the first rotation speed table 43C and sets the rotation speed of the outdoor fan 15 to a high rotation speed.

[0079] Fig. 12 is a block diagram showing an example of the configuration of a second control unit 24B of Example 3. The second control unit 24B of Example 3 shown in Fig. 12 differs from the second control unit 24 of Example 1 in that the second control unit 24B controls the driving of the indoor fan 23 using only the refrigerant concentration in the second casing 20A. In other words, the second control unit 54B does not have a function of calculating the rate of increase in concentration in the second casing 20A.

[0080] When the refrigerant concentration in the second casing 20A exceeds a predetermined value, the second control unit 54B refers to the second rotation speed table 53C and sets the rotation speed of the indoor fan 23 to the minimum rotation speed. When the refrigerant concentration in the second casing 20A is equal to or lower than a predetermined value, the second control unit 54B refers to the second rotation speed table 53C and sets the rotation speed of the indoor fan 23 to a high rotation speed.

[0081] Fig. 13 is a flowchart showing an example of the processing operation of the first control unit 16B related to the outdoor fan control process of Example 3. The control shown in this flowchart is repeatedly executed while the air conditioning apparatus 1 is not operating. In Fig. 13, the first control unit 44B in the first control unit 16B determines whether the refrigerant concentration in the first casing 10A measured via the first sensor 31A has reached the concentration reference value (step S31). If the refrigerant concentration in the first casing 10A has reached the concentration reference value (step S31: Yes), the first control unit 44B proceeds to the processing of step S33.

[0082] Next, after a predetermined time has elapsed, the first control unit 44B measures the refrigerant concentration in the first casing 10A via the first sensor 31A (step S33). The first control unit 44B determines whether the refrigerant concentration in the first casing 10A exceeds a predetermined value (step S34). The predetermined value is preferably set to a value sufficiently higher than the UFL in order to maintain a state outside the flammable concentration range for a long period of time. For example, the predetermined value is set to 19.5 Vol%, which is 10 Vol% higher than the UFL (9.5 Vol%).

[0083] If the refrigerant concentration in first casing 10A exceeds the predetermined value (step S34: Yes), first control unit 44B references first rotation speed table 43C and sets the rotation speed of outdoor fan 15 to the minimum rotation speed (step S35). As a result, in an environment where the refrigerant concentration in first casing 10A exceeds the UFL, the rotation speed of outdoor fan 15 is reduced to prevent the refrigerant concentration from falling into the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in first casing 10A.

[0084] Next, the first control unit 44B determines whether the refrigerant concentration in the first casing 10A is equal to or lower than the UFL (step S36). If the refrigerant concentration in the first casing 10A is equal to or lower than the UFL (step S36: Yes), the first control unit 44B references the first rotation speed table 43C and sets the rotation speed of the outdoor fan 15 to a high rotation speed (step S37). The first control unit 44B then returns to the process of step S31, in which the first control unit 44B determines whether the refrigerant concentration in the first casing 10A has reached the concentration reference value. As a result, in an environment where the refrigerant concentration in the first casing 10A is equal to or lower than the UFL, the rotation speed of the outdoor fan 15 is increased to immediately move the refrigerant concentration out of the flammable concentration range, making it easier to maintain an environment outside the flammable concentration range and reducing the risk of ignition in the first casing 10A. On the other hand, if the refrigerant concentration in the first housing 10A exceeds the UFL (step S36: No), the first control unit 44 maintains the rotation speed of the outdoor fan 15 and returns to the processing of step S31 to determine whether the refrigerant concentration in the first housing 10A has reached the concentration reference value.

[0085] 13. If the refrigerant concentration in first casing 10A has not reached the concentration reference value (step S31: No), first control unit 44B ends the processing operation shown in Fig. 13. If the refrigerant concentration in first casing 10A has not exceeded the predetermined value (step S34: No), first control unit 44B returns to the processing of step S33. As a result, if the rate of increase in concentration is equal to or greater than the rate reference value, first control unit 44 does not drive outdoor fan 15 until the refrigerant concentration exceeds the predetermined value. This makes it easier to maintain an environment outside the flammable concentration range by preventing the refrigerant concentration from falling within the flammable concentration range, and reduces the risk of ignition within first casing 10A.

[0086] In the outdoor unit 10 of the third embodiment, in an environment where the refrigerant concentration in the first casing 10A exceeds the UFL, the outdoor fan 15 is rotated at a slower speed to create an environment where the concentration in the first casing 10A falls outside the flammable concentration range. As a result, the risk of ignition in the first casing 10A can be reduced.

[0087] The outdoor unit 10 can determine that an environment in which the refrigerant concentration in the first housing 10A is below the UFL is also an environment in which the flammable concentration range will remain in the first housing 10A for a long time, and therefore sets the rotation speed of the outdoor fan 15 to a high rotation speed so that the refrigerant concentration in the first housing 10A is below the LFL, thereby keeping the refrigerant concentration in the first housing 10A out of the flammable concentration range. As a result, the risk of ignition in the first housing 10A can be reduced.

[0088] In an environment where the refrigerant concentration in the second casing 20A exceeds the UFL, the indoor unit 20 reduces the rotation speed of the indoor fan 23 to create an environment where the concentration in the second casing 20A falls outside the flammable concentration range. As a result, the risk of ignition in the second casing 20A can be reduced.

[0089] The indoor unit 20 can determine that an environment in which the refrigerant concentration in the second casing 20A is below the UFL is also an environment in which the flammable concentration range will remain in the second casing 20A for a long time, and therefore sets the rotation speed of the indoor fan 23 to a high rotation speed so that the refrigerant concentration in the second casing 20A is below the LFL, thereby keeping the refrigerant concentration in the second casing 20A out of the flammable concentration range. As a result, the risk of ignition in the second casing 20A can be reduced.

[0090] 13 illustrates an example in which the outdoor fan 15 is controlled based on the refrigerant concentration in the first casing 10A of the outdoor unit 10. However, the indoor fan 23 may also be controlled based on the refrigerant concentration in the second casing 20A of the indoor unit 20, and this can be modified as appropriate.

[0091] For ease of explanation, the example has been given in which the first control unit 44B in the first control unit 16B of the outdoor unit 10 is used to perform threshold determination of the refrigerant concentration in the first casing 10A. Also, the example has been given in which the second control unit 54B in the second control unit 24B of the indoor unit 20 is used to perform threshold determination of the refrigerant concentration in the second casing 20A. However, threshold determination of the refrigerant concentrations in the first casing 10A and the second casing 20A may be performed by either the first control unit 16B or the second control unit 24B, and this can be changed as appropriate.

[0092] For example, the second control unit 24B obtains the refrigerant concentration in the first casing 10A from the first control unit 16B, and extracts the rotation speed of the outdoor fan 15 from the first rotation speed table 43C based on the refrigerant concentration in the first casing 10A. The second control unit 24B then transmits the extracted rotation speed of the outdoor fan 15 to the first control unit 16B. The first control unit 16B may then set the rotation speed of the outdoor fan 15 obtained from the second control unit 24B in the outdoor fan 15.

[0093] For example, the first control unit 16B obtains the refrigerant concentration in the second casing 20A from the second control unit 24B, and extracts the rotation speed of the indoor fan 23 from the second rotation speed table 53C based on the refrigerant concentration in the second casing 20A. The first control unit 16B then transmits the extracted rotation speed of the indoor fan 23 to the second control unit 24B. The second control unit 24B may then set the rotation speed of the indoor fan 23 obtained from the first control unit 16B to the indoor fan 23. [Explanation of symbols]

[0094] 1. Air conditioning equipment 10 Outdoor unit 10A First enclosure 15 Outdoor fan 20 Indoor unit 20A second enclosure 23 Indoor fan 31A First Sensor 31B Second Sensor 44 First control section 45 First wind speed measurement section 54 Second control section 55 Second wind speed measurement section

Claims

1. An air conditioning apparatus having a housing, a heat exchanger and a fan through which a refrigerant accommodated in the housing flows, a sensor for detecting the concentration of the refrigerant within the housing, and a control unit for controlling the rotation speed of the fan, The control unit measuring the concentration of the refrigerant in the housing for a predetermined time after the concentration of the refrigerant detected by the sensor reaches a concentration reference value; calculating a rate of increase in concentration within the predetermined time based on the concentration during the predetermined time; The air conditioning apparatus is characterized in that the rotation speed of the fan is controlled based on the calculated rate of increase in concentration.

2. The control unit 2. The air conditioning apparatus according to claim 1, wherein, when the rate of increase in concentration is equal to or greater than a predetermined reference speed value, the rotation speed of the fan is set to a lower value than the rotation speed of the fan set when the rate of increase in concentration is less than the reference speed value.

3. The control unit 3. The air conditioner according to claim 2, wherein the rotational speed of the fan is set to a minimum rotational speed when the rate of increase in concentration is equal to or greater than the reference speed value.

4. Further, a wind speed measuring unit is provided to measure the wind speed around the air conditioning device, The control unit 3. The air conditioning apparatus according to claim 2, wherein the fan stops rotating when the concentration increase rate is equal to or greater than the reference rate and the outdoor air speed measured by the air speed measuring unit exceeds the reference air speed.

5. The control unit The air conditioning apparatus according to claim 3, characterized in that, when the concentration inside the housing decreases and becomes equal to or lower than a predetermined value, the rotation speed of the fan is set to a higher rotation speed than the rotation speed of the fan set when the rate of increase in concentration is equal to or higher than the speed reference value.

6. The control unit 3. The air conditioning apparatus according to claim 2, wherein when the rate of increase in concentration is less than the reference speed value, the rotation speed of the fan is set to a higher rotation speed than the rotation speed of the fan set when the rate of increase in concentration is equal to or greater than the reference speed value.

7. An air conditioning apparatus having a housing, a heat exchanger and a fan through which a refrigerant accommodated in the housing flows, a sensor for detecting the concentration of the refrigerant within the housing, and a control unit for controlling the rotation speed of the fan, The control unit measuring the concentration of the refrigerant, which is the detected value of the sensor; An air conditioning apparatus characterized in that the concentration is measured a predetermined time after the refrigerant concentration reaches a concentration reference value, and the rotation speed of the fan is controlled based on the measured concentration.

8. The control unit The air conditioning apparatus according to claim 7, characterized in that, when the concentration measured after the specified time has elapsed exceeds a predetermined value, the rotation speed of the fan is set to a lower speed than the rotation speed of the fan set when the concentration is less than the predetermined value.

9. The control unit 9. The air conditioning apparatus according to claim 8, wherein the rotation speed of the fan is set to a minimum rotation speed when the concentration measured after the predetermined time has elapsed exceeds the predetermined value.

10. Further, a wind speed measuring unit is provided to measure the wind speed around the air conditioning device, The control unit An air conditioning device as described in any one of claims 7 to 9, characterized in that the rotation of the fan is stopped when the concentration measured after the specified time has elapsed exceeds a specified value and the outdoor air wind speed value measured by the wind speed measurement unit exceeds a reference wind speed value.

11. The control unit The air conditioning apparatus according to claim 9, characterized in that, when the concentration inside the housing decreases to below the predetermined value, the rotation speed of the fan is set to a higher speed than the rotation speed of the fan set when the concentration exceeds the predetermined value.

12. The control unit An air conditioning device as described in any one of claims 7 to 9, characterized in that when the concentration measured after the predetermined time has elapsed is equal to or lower than a predetermined value, the rotation speed of the fan is set to a higher speed than the rotation speed of the fan set when the concentration exceeds the predetermined value.

13. The refrigerant is 8. The air conditioning apparatus according to claim 1, wherein the upper limit of the flammable concentration range is less than 29.3 Vol %.

Images