Air conditioner

Abstract

This air conditioner comprises: a housing (10A) (20A); a blower (15) (23) that takes in air from the outside of the housing (10A) (20A) to the inside thereof; a heat exchanger (13) (21) that exchanges heat between the air taken to the inside of the housing (10A) (20A) and a refrigerant; a pipe (31, 32) that is connected to the heat exchanger (13) (21) and forms a refrigerant circuit in which the refrigerant circulates; an ambient temperature sensor (42) (44) that detects an ambient temperature inside the housing (10A) (20A); and a control unit (16) (24) that determines that refrigerant leakage has occurred when, with the blower (15) (23) stopped, an amount of decrease per unit time of a detected value of the ambient temperature sensor (42) (44) becomes equal to or greater than a predetermined value, and executes processing for suppressing ignition of the refrigerant.

Description

Air conditioner

[0001] The present invention relates to an air conditioner.

[0002] As alternative refrigerants for a room air conditioner of a type in which an indoor unit and an outdoor unit are separated, a packaged air conditioner, and a low-temperature refrigeration device, refrigerants such as R290 refrigerant having a low global warming potential (GWP) have been proposed.

[0003] By the way, R290 refrigerant is a flammable gas. When the flammable gas diffuses into the room or the outdoors at a slow leakage rate from a pinhole of a heat exchanger or a flare connection part and the gas concentration does not increase, the ignition risk is small. Also, during operation, for example, even if the refrigerant leaks, the indoor air flow is agitated and the air flow speed is relatively large, so it is difficult for the leaked refrigerant to diffuse and increase to a gas concentration that can catch fire.

[0004] However, when a crack occurs in the pipe due to an external force or when the flare connection part comes off, rapid refrigerant leakage occurs outside the refrigerant circuit. When such rapid refrigerant leakage occurs, almost all of the refrigerant in the refrigerant circuit leaks, and the increase in the refrigerant concentration near the leakage point becomes large. When the increase in the refrigerant concentration is large and there is an ignition source in the indoor atmosphere when the air conditioner is stopped and the indoor air flow is stagnant, there is a possibility that the refrigerant will catch fire.

[0005] The technique described in Patent Document 1 below utilizes the fact that when refrigerant leakage occurs, the pressure of the refrigerant in the refrigerant circuit decreases, so the temperature of the refrigerant decreases. When the refrigerant temperature detected by a temperature sensor arranged at a place where the liquid-phase refrigerant accumulates when the compressor stops drops below a predetermined speed, it is determined that there is a leakage. According to the technique described in Patent Document 1, by detecting the difference between the refrigerant temperature and the ambient temperature and the temperature changes of the indoor and outdoor heat exchangers, it is possible to prevent misjudging that refrigerant leakage has occurred due to external disturbances or the pressure equalization operation immediately after the compressor stops.

[0006] Japanese Unexamined Patent Application Publication No. 2000-81258

[0007] However, the technology described in Patent Document 1 is based on the premise of detecting the temperature of the refrigerant in liquid phase. The location where the liquid phase refrigerant accumulates changes depending on the external environment, such as the ambient temperature. Therefore, if the liquid phase refrigerant does not accumulate at the location where the temperature sensor is placed, the leak may not be detected, and the refrigerant concentration near the leak location may rise. When the refrigerant concentration rises, there is a risk of the refrigerant igniting.

[0008] This invention addresses these conventional unresolved problems and aims to provide an air conditioner that can reliably detect refrigerant leakage while the unit is stopped and suppress ignition of the refrigerant.

[0009] To achieve the above objective, an air conditioner according to one aspect of the present invention comprises a housing, a blower that takes in air from the outside to the inside of the housing, a heat exchanger that exchanges heat between the air taken in to the inside of the housing and a refrigerant, piping connected to the heat exchanger and forming a refrigerant circuit through which the refrigerant circulates, an ambient temperature sensor that detects the ambient temperature inside the housing, and a control unit that, when the blower is stopped, determines that there is a refrigerant leak when the amount of decrease per unit time of the ambient temperature sensor's detected value exceeds a predetermined value, and executes a process to suppress ignition of the refrigerant.

[0010] According to one aspect of the present invention, an air conditioner can be obtained that can reliably detect refrigerant leakage while the unit is stopped and suppress ignition of the refrigerant.

[0011] Figure 1 is a block diagram showing an example of the configuration of an air conditioner according to the first embodiment of this disclosure. Figure 2 is a diagram showing the schematic configuration of the indoor unit of the air conditioner according to the first embodiment of this disclosure. Figure 3 is a perspective view showing the main part of the indoor unit according to the first embodiment of this disclosure from below. Figure 4 is a flowchart showing the control processing procedure of the second control unit according to the first embodiment of this disclosure. Figure 5 is a perspective view showing the outdoor unit of the air conditioner according to the second embodiment of this disclosure. Figure 6 is an exploded perspective view showing the outdoor unit of the air conditioner according to the second embodiment of this disclosure. Figure 7 is a flowchart showing the control processing procedure of the first control unit according to the second embodiment of this disclosure.

[0012] Next, embodiments of the present invention will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Furthermore, the embodiments shown below are illustrative examples of devices and methods for realizing the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the structure, arrangement, etc. of the components described below. Various modifications can be made to the technical idea of ​​the present invention within the technical scope defined by the claims described in the patent claims.

[0013] <First Embodiment> Figure 1 is a block diagram showing an example of the configuration of an air conditioner 1 according to the first embodiment of the present disclosure. The air conditioner 1 shown in Figure 1 has an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 is a device installed outdoors. The indoor unit 20 is a device installed in an indoor space.

[0014] The outdoor unit 10 includes a first housing 10A, a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor expansion valve 14, an outdoor fan 15, an outdoor temperature sensor 41, a first ambient temperature sensor 42, and a first control unit 16 (an example of a control unit). The first housing 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 outdoor temperature sensor 41, the first ambient temperature sensor 42, and the first control unit 16. The indoor unit 20 includes a second housing 20A, an indoor heat exchanger 21, an indoor fan 23, an indoor temperature sensor 43, a second ambient temperature sensor 44, and a second control unit 24 (an example of a control unit). The second enclosure 20A houses the indoor heat exchanger 21, the indoor fan 23, the indoor temperature sensor 43, the second ambient temperature sensor 44, and the second control unit 24.

[0015] The outdoor unit 10 and the indoor unit 20 are connected by a liquid pipe 31 (an example of piping) and a gas pipe 32 (an example of piping). The air conditioner 1 has a refrigerant circuit. The refrigerant circuit includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor expansion valve 14, an indoor heat exchanger 21, a liquid pipe 31, and a gas pipe 32, through which the refrigerant circulates. A flammable refrigerant (for example, R290 refrigerant) is used as the refrigerant circulating in the refrigerant circuit. The refrigerant may also contain an odorant (such as sulfur-based, cyclohexane, or ethyl acrylate).

[0016] The compressor 11 is a variable-capacity compressor whose operating capacity can be varied by being driven by a motor (not shown) whose rotational speed is controlled by an inverter. The four-way valve 12 has a first port a, a second port b, a third port c, and a fourth port d. The first port a is connected to the discharge port of the compressor 11 by refrigerant piping 17a. The second port b is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 13 by refrigerant piping 17b. The third port c is connected to the suction port of the compressor 11 by refrigerant piping 17c. The fourth port d is connected to a shut-off valve 18 which is connected to the gas pipe 32 by refrigerant piping 17d.

[0017] 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 the refrigerant flowing through the refrigerant piping. One refrigerant inlet / outlet of the outdoor heat exchanger 13 is connected to the second port b of the four-way valve 12 by refrigerant piping 17b. The other refrigerant inlet / outlet of the outdoor heat exchanger 13 is connected to the shut-off valve 19 by refrigerant piping 17e. An outdoor expansion valve 14 is provided in the refrigerant piping 17e that connects the other refrigerant inlet / outlet to the shut-off valve 19.

[0018] The outdoor fan 15 is driven by a motor (not shown) to draw outside air into the outdoor unit 10 and generate an airflow to release the outside air, which has exchanged heat with the refrigerant in the outdoor heat exchanger 13, to the outside of the outdoor unit 10. In addition, the outdoor fan 15 also generates an airflow inside the first housing 10A, so that it can agitate the air containing refrigerant that has leaked inside the first housing 10A.

[0019] The first control unit 16 is a control unit that performs actions such as starting, stopping, and controlling the rotation speed of the compressor 11, switching control of the four-way valve 12, opening degree control of the outdoor expansion valve 14, and drive control of the outdoor fan 15. In addition, the first control unit 16 receives start and stop requests from the air conditioner 1 and controls at least the start and stop of the compressor 11.

[0020] The indoor heat exchanger 21 is a heat exchanger that exchanges heat between indoor air drawn into the indoor unit 20 by the indoor fan 23 and refrigerant flowing through the refrigerant piping. One refrigerant inlet / outlet and connection port 26 of the indoor heat exchanger 21 are connected by refrigerant piping 28a. The other refrigerant inlet / outlet and connection port 27 of the indoor heat exchanger 21 are connected by refrigerant piping 28b. The shut-off valve 19 of the outdoor unit 10 and the connection port 27 of the indoor unit 20 are connected by a liquid pipe 31, and the shut-off valve 18 of the outdoor unit 10 and the connection port 26 of the indoor unit 20 are connected by a gas pipe 32.

[0021] The indoor fan 23, driven by a motor (not shown), draws outside air into the indoor unit 20 and generates an airflow to release the outside air, which has exchanged heat with the refrigerant in the indoor heat exchanger 21, to the outside of the indoor unit 20. In addition, the indoor fan 23 also generates an airflow within the second housing 20A, so that it can agitate the refrigerant-containing air that has leaked within the second housing 20A.

[0022] The outdoor unit 10 has, for example, an outdoor temperature sensor 41, a first ambient temperature sensor 42, and a first control unit 16 arranged inside the first housing 10A. The outdoor temperature sensor 41 uses, for example, a thermistor and outputs a voltage value that changes according to the outdoor temperature to the first control unit 16 as an outdoor temperature detection value. The first ambient temperature sensor 42 uses, for example, a thermistor and outputs a voltage value that changes according to the ambient temperature inside the first housing 10A to the first control unit 16 as an ambient temperature detection value.

[0023] The first control unit 16 includes a communication unit that communicates with the second control unit 24 and a storage unit that stores a control program. When the heating operation of the air conditioner 1 ends, or when the cooling operation ends, the first control unit 16 executes a process to suppress ignition of the refrigerant based on the ambient temperature detected by the first ambient temperature sensor 42, in accordance with the control program stored in the storage unit.

[0024] The indoor unit 20 has, for example, an indoor temperature sensor 43, a second ambient temperature sensor 44, and a second control unit 24 arranged inside the second housing 20A. The indoor temperature sensor 43 uses, for example, a thermistor and outputs a voltage value that changes according to the indoor temperature to the second control unit 24 as an indoor temperature detection value. The second ambient temperature sensor 44 uses, for example, a thermistor and outputs a voltage value that changes according to the ambient temperature inside the second housing 20A to the second control unit 24 as an ambient temperature detection value.

[0025] The second control unit 24 includes a communication unit that communicates with the first control unit 16 and a storage unit that stores a control program. When the heating operation of the air conditioner 1 ends, or when the cooling operation ends, the second control unit 24 performs processing to reduce the risk of ignition of the refrigerant based on the ambient temperature detected by the second ambient temperature sensor 44, in accordance with the control program stored in the storage unit.

[0026] (Structure of the indoor unit of the first embodiment) Next, the structure of the indoor unit 20 constituting the air conditioner 1 according to the first embodiment will be described with reference to Figures 2 and 3. In the figures, the straight lines indicated by "up" and "down" are vertical directions, the straight lines indicated by "front" and "back" are horizontal directions perpendicular to the vertical direction, and the straight lines indicated by "left" and "right" are horizontal directions perpendicular to a virtual plane that includes the vertical and front-back directions.

[0027] The indoor unit 20 is a wall-mounted indoor unit fixed to the wall surface, and as shown in Figure 2, it comprises a box-shaped second housing 20A having a rear panel 50, a ceiling panel 51, a front panel 52, a bottom panel 53, and left and right side panels (not shown).

[0028] Multiple intake ports 56 are formed in the ceiling panel 51, and an outlet port 57 is formed in the bottom panel 53, which is a long rectangular opening in the left-right direction. The internal space of the second housing 20A between the intake ports 56 and the outlet port 57 is used as a ventilation passage 58.

[0029] A wind deflector 59 for opening and closing the air outlet 57 is positioned on the bottom panel 53. The wind deflector 59 has a rectangular shape that is substantially the same as the opening shape of the air outlet 57, and the wind deflector drive unit (not shown) drives the air outlet 57 to open (shown by the dashed line in Figure 2) or to close (shown by the dashed line in Figure 2).

[0030] In the ventilation passage 58, the cylindrical impeller 23a of the indoor fan 23 is positioned with its rotating shaft 23p extending in the left-right direction, and a fan motor 23b that rotates the impeller 23a in the forward or reverse direction is connected to the right end of the rotating shaft 23p.

[0031] As shown in Figure 2, an indoor heat exchanger 21 is positioned between the intake port 56 of the ventilation passage 58 and the indoor fan 23. The indoor heat exchanger 21 is composed of first to fourth divided heat exchangers 21a to 21d that surround the indoor fan 23 from above. The first to fourth divided heat exchangers 21a to 21d have a plurality of tubes 61 arranged parallel to each other and a plurality of fins (not shown) made of thin metal plates, the plurality of fins are arranged at equal intervals from each other, and the tubes 61 are inserted perpendicular to the plurality of fins.

[0032] As shown in Figure 3, a piping connection section 62 is provided at the right end of the indoor heat exchanger 21. The piping connection section 62 consists of pipes that connect adjacent tubes 61 of each of the first to fourth divided heat exchangers 21a to 21d, and pipes that connect the ends and start points of adjacent divided heat exchangers (for example, the first divided heat exchanger 21a and the second divided heat exchanger 21b), and serves as a flow path for the flammable refrigerant.

[0033] A drain pan 63 is positioned below the fourth divided heat exchanger 21d that constitutes the indoor heat exchanger 21. The drain pan 63 is a gutter-shaped member comprising a long bottom plate extending in the left-right direction, a front plate rising from the front side in the short direction of the bottom plate, a back plate rising from the rear side in the short direction of the bottom plate, and side plates rising from both ends in the longitudinal direction (left-right direction) of the bottom plate. A drain outlet (not shown) is formed in the drain pan 63. A cylindrical connection part 65 communicating with the drain outlet is formed on the outside of the back plate. A drain hose (not shown) is connected to the connection part 65 for discharging condensed water accumulated in the drain pan 63 to the outside through the drain outlet. In other words, the drain pan 63 receives the drain water dripping from the indoor heat exchanger 21.

[0034] By the way, the second ambient temperature sensor 44 according to the first embodiment is provided below the upper end of the indoor heat exchanger 21 and above the lower end of the drain pan 63, that is, above the bottom plate. The indoor temperature sensor 43 is provided above the second ambient temperature sensor 44. The second ambient temperature sensor 44 does not detect the temperature of the refrigerant in liquid phase itself, but rather detects the ambient temperature of the air where refrigerant leakage is occurring. When refrigerant leaks into the air from the refrigerant piping, it expands and the ambient temperature decreases. Therefore, if the decrease in the detected value of the second ambient temperature sensor 44 per unit time exceeds a predetermined value, it can be determined that refrigerant leakage is occurring. Also, since refrigerant is denser than air, by providing the second ambient temperature sensor 44 at the above position, it is easy to detect changes in ambient temperature when refrigerant leaks from the piping connection 62, etc.

[0035] (Control of the air conditioner in the first embodiment) Next, the process of suppressing ignition of the refrigerant by the second control unit 24 in the first embodiment will be described with reference to the flowchart in Figure 4.

[0036] First, the second control unit 24 determines whether the air conditioner 1 is in heating operation or cooling operation (step ST4a). If it determines that the air conditioner 1 is in heating operation or cooling operation (step ST4a: Yes), the second control unit 24 continues the process of determining whether it is in heating operation or cooling operation in step ST4a.

[0037] On the other hand, if the air conditioner 1 is determined to have stopped heating operation or cooling operation (step ST4a: No), the second control unit 24 determines whether the indoor fan 23 is stopped or not (step ST4b). If the second control unit 24 determines that the indoor fan 23 is running (step ST4b: No), the second control unit 24 continues the process of determining whether the indoor fan 23 is stopped or not in the process of step ST4b.

[0038] On the other hand, if it is determined that the indoor fan 23 is stopped (step ST4b: Yes), the second control unit 24 reads the ambient temperature detected value output from the second ambient temperature sensor 44 (step ST4c). In this flowchart, for convenience, it is stated that the process of reading the ambient temperature detected value is performed in step ST4c, but while the indoor fan 23 is stopped, the second control unit 24 acquires the ambient temperature detected value from the second ambient temperature sensor 44 at predetermined intervals (for example, 5 seconds). The acquired ambient temperature detected value is stored in the memory unit in association with the detection time. The second control unit 24 then calculates the amount of decrease M1 of the ambient temperature detected value per unit time (step ST4d) and determines whether the decrease amount M1 is greater than or equal to a predetermined value Th1 (for example, 0.4°C / sec) (step ST4e). The amount of decrease M1 of the ambient temperature detected value per unit time is calculated using the current ambient temperature detected value and the past (5 seconds ago) ambient temperature detected value stored in the memory unit.

[0039] If the second control unit 24 determines that the decrease amount M1 is greater than or equal to a predetermined value Th1 (step ST4e: Yes), it determines that there is a refrigerant leak and drives the indoor fan 23 to agitate the air inside the housing of the indoor unit 20 (inside the second housing 20A) containing the leaked refrigerant in order to reduce the risk of the leaked refrigerant igniting (step ST4f). This reduces the risk of the leaked refrigerant igniting. On the other hand, if the second control unit 24 determines that there is no refrigerant leak (step ST4e: No), it determines that there is no refrigerant leak and terminates the process, returning to step ST4a, and repeats the above refrigerant leak determination control.

[0040] <Effects of the First Embodiment> As described above, according to the first embodiment, by focusing on the fact that refrigerant expands when it leaks into the air, causing the ambient temperature to drop, the indoor unit 20 detects the temperature change of the ambient temperature inside the second housing 20A with the second ambient temperature sensor 44. This allows for the detection of refrigerant leakage without using an expensive refrigerant sensor, and even in locations where liquid phase refrigerant is not present. If the second control unit 24 determines that refrigerant leakage has occurred, the indoor fan 23 is driven to agitate the air inside the second housing 20A containing the leaked refrigerant, thereby reducing the risk of refrigerant ignition. Therefore, the process to suppress refrigerant ignition can be carried out at low cost.

[0041] Furthermore, according to the first embodiment, in the indoor unit 20, by providing the second ambient temperature sensor 44 below the upper end of the indoor heat exchanger 21 and above the lower end of the drain pan 63, temperature changes can be detected with higher accuracy in the vicinity of the drain pan 63, which is located below the indoor heat exchanger 21 where there is a risk of leakage.

[0042] <Second Embodiment> The air conditioner 1 according to the first embodiment is applicable to the air conditioner according to the second embodiment. Below, an example of the outdoor unit of the air conditioner according to the second embodiment to which the air conditioner 1 according to the first embodiment is applied will be described.

[0043] FIG. 5 is a perspective view showing the outdoor unit 10 according to the second embodiment. The outdoor unit 10 includes a first housing 10A. The first housing 10A is generally formed in a rectangular parallelepiped shape. The first housing 10A includes a cover 73 formed to be detachable.

[0044] FIG. 6 is an exploded perspective view showing the outdoor unit 10 according to the second embodiment. In addition to the cover 73 described later, the first housing 10A includes a bottom plate 75, a top plate 76, a front grill 77, and side grills 78. The bottom plate 75 is generally formed in a plate shape and is placed on the installation surface on which the outdoor unit 10 is installed. The top plate 76 is generally formed in a plate shape.

[0045] The top plate 76 is arranged along another plane parallel to the plane along which the bottom plate 75 extends. The front grill 77 is generally formed in a plate shape and has openings through which air passes. The front grill 77 is arranged between the bottom plate 75 and the top plate 76 along another plane perpendicular to the plane along which the bottom plate 75 extends and is fixed to the bottom plate 75. The side grills 78 are generally formed in a plate shape and have openings through which air passes. The side grills 78 are arranged between the bottom plate 75 and the top plate 76 along another plane perpendicular to the plane along which the bottom plate 75 extends and perpendicular to the plane along which the front grill 77 extends, and are fixed to the bottom plate 75.

[0046] The cover 73 includes a front cover 81, side covers 82, and a rear cover 83. The front cover 81 is generally formed in a plate shape. The side covers 82 are generally formed in a plate shape. The rear cover 83 is generally formed in a plate shape. The front cover 81 is arranged between the bottom plate 75 and the top plate 76 along the plane along which the front grill 77 extends and is fixed to the bottom plate 75.

[0047] The side covers 82 are arranged between the bottom plate 75 and the top plate 76 along another plane parallel to the plane along which the side grills 78 extend and are fixed to the bottom plate 75. The rear cover 83 is arranged between the bottom plate 75 and the top plate 76 along another plane parallel to the plane along which the front cover 81 extends and is fixed to the bottom plate 75.

[0048] The outdoor unit 10 further includes a partition plate 84. The partition plate 84 is formed in a plate shape. The partition plate 84 is disposed between the side grille 78 and the side cover 82 along another plane parallel to the plane along which the side grille 78 extends, and is fixed to the bottom plate 75. The partition plate 84 divides the space formed inside the first housing 10A into a main chamber 79 (an example of the first chamber) for housing the outdoor heat exchanger 13 and a machine chamber 88 (an example of the second chamber).

[0049] The main chamber 79 is surrounded by the bottom plate 75, the top plate 76, the front grille 77, the side grille 78, and the partition plate 84. The machine chamber 88 is surrounded by the bottom plate 75, the top plate 76, the cover 73, and the partition plate 84. And when the cover 73 is removed from the bottom plate 75, the machine chamber 88 is connected to the outside of the first housing 10A through the opening 94. That is, the opening 94 is formed on the side of the front cover 81, the side cover 82, and the rear cover 83 of the machine chamber 88.

[0050] The outdoor fan 15 and the outdoor heat exchanger 13 are disposed in the main chamber 79. The outdoor fan 15 blows outside air so that the air passing through the back of the first housing 10A and the opening of the side grille 78 passes through the outdoor heat exchanger 13, and the air passing through the outdoor heat exchanger 13 is discharged to the outside of the first housing 10A through the opening of the front grille 77.

[0051] The first control unit ͵16 has a plurality of electrical components and includes a power supply circuit 86. The power supply circuit 86 does not supply power to the outdoor expansion valve 14 when power is not supplied to the air conditioner 1, and supplies power to the outdoor expansion valve 14 when power is supplied to the air conditioner 1. The first control unit 16 controls the compressor 11, the four-way valve 12, the outdoor expansion valve 14, the outdoor heat exchanger 13, and the outdoor fan 15 using the power supplied to the air conditioner 1. The first control unit 16 is disposed in the electrical component storage space 89 on the side of the top plate 76 in the machine chamber 88.

[0052] Other refrigerant circuit components 91, distinct from the outdoor heat exchanger 13, are located in the refrigerant piping storage space 92 on the bottom plate 75 side of the machine room 88. These other refrigerant circuit components 91 include a compressor 11, a four-way valve 12, an outdoor expansion valve 14, and shut-off valves 18, 19, etc. (not shown).

[0053] Incidentally, the first ambient temperature sensor 42 according to the second embodiment is provided in the lower part of the machine room 88, that is, on the side of the bottom plate 75 of the refrigerant piping storage space 92. The outdoor temperature sensor 41 is provided in the upper part of the machine room 88, that is, on the side of the rear cover 83 of the electrical component storage space 89.

[0054] (Control of the air conditioner in the second embodiment) Next, the process of suppressing ignition of the refrigerant by the first control unit 16 in the second embodiment will be described with reference to the flowchart in Figure 7.

[0055] First, the first control unit 16 determines whether the air conditioner 1 is in heating operation or cooling operation (step ST7a). If it determines that the air conditioner 1 is in heating operation or cooling operation (step ST7a: Yes), the first control unit 16 continues the process of determining whether it is in heating operation or cooling operation in step ST7a.

[0056] On the other hand, if the air conditioner 1 is determined to have stopped heating operation or cooling operation (step ST7a: No), the first control unit 16 determines whether the outdoor fan 15 is stopped or not (step ST7b). If the first control unit 16 determines that the outdoor fan 15 is running (step ST7b: No), the first control unit 16 continues the process of determining whether the outdoor fan 15 is stopped or not in step ST7b.

[0057] On the other hand, if it is determined that the outdoor fan 15 is stopped (step ST7b: Yes), the first control unit 16 reads the ambient temperature detected value output from the first ambient temperature sensor 42 (step ST7c). In this flowchart, for convenience, it is stated that the process of reading the ambient temperature detected value is performed in step ST7c, but while the outdoor fan 15 is stopped, the first control unit 16 acquires the ambient temperature detected value from the first ambient temperature sensor 42 at predetermined intervals (for example, 5 seconds). The acquired ambient temperature detected value is stored in the memory unit in association with the detection time. The first control unit 16 then calculates the amount of decrease M2 of the ambient temperature detected value per unit time (step ST7d) and determines whether the decrease amount M2 is greater than or equal to a predetermined value Th2 (for example, 0.4°C / sec) (step ST7e). The amount of decrease M2 of the ambient temperature detected value per unit time is calculated using the current ambient temperature detected value and the past (5 seconds ago) ambient temperature detected value stored in the memory unit. Specifically, the decrease per unit time M2 is the value obtained by subtracting the detected value from n seconds ago from the current detected value and dividing the result by n.

[0058] If the first control unit 16 determines that the decrease amount M2 is equal to or greater than a predetermined value Th2 (step ST7e: Yes), it determines that there is a refrigerant leak and sends and displays information indicating the refrigerant leak to, for example, a remote control or terminal held by the user outside the device (step ST7f). This information indicating the refrigerant leak is designed to make it easy for the user to recognize the risk of ignition due to the refrigerant leak, and consists of, for example, a mark representing the refrigerant leak and a concise explanation. In addition to being visually displayed, the information indicating the refrigerant leak may also be conveyed as an audio message using voice synthesis.

[0059] On the other hand, if the first control unit 16 determines that the decrease amount M2 is less than a predetermined value Th2 (step ST7e: No), it determines that no refrigerant leakage has occurred, terminates the process, returns to step ST7a, and repeats the above refrigerant leakage determination control.

[0060] <Effects of the Second Embodiment> As described above, the second embodiment provides the same effects as the first embodiment, and when a refrigerant leak is detected, information indicating the refrigerant leak is notified to the outside, allowing external users to immediately become aware of the refrigerant leak and take prompt countermeasures such as preventing ignition of the refrigerant. Alternatively, instead of notifying the outside of information indicating a refrigerant leak, the outdoor fan 15 may be driven to agitate the air inside the housing of the outdoor unit 10 (inside the first housing 10A) containing the leaked refrigerant, as in the first embodiment, or these may be performed simultaneously.

[0061] Furthermore, according to the second embodiment, since the first ambient temperature sensor 42 is installed in the lower part of the machine room 88, temperature changes can be detected with higher accuracy within the machine room 88, where there is a risk of leakage.

[0062] <Other Embodiments> As described above, the present invention has been described by the first and second embodiments, but the descriptions and drawings that constitute part of this disclosure should not be understood as limiting the present invention. If the spirit of the technical content disclosed by the above embodiments is understood, it will be clear to those skilled in the art that various alternative embodiments, examples, and operational techniques can be included in the present invention. Furthermore, the configurations disclosed by the first and second embodiments can be combined as appropriate to the extent that they do not cause contradictions. For example, configurations disclosed by multiple different embodiments may be combined, or configurations disclosed by multiple different modifications of the same embodiment may be combined.

[0063] 1 Air conditioner 10 Outdoor unit 10A First housing 11 Compressor 12 Four-way valve 13 Outdoor heat exchanger 14 Outdoor expansion valve 15 Outdoor fan 16 First control unit 17a-17e Refrigerant piping 18, 19 Shut-off valve 20 Indoor unit 20A Second housing 21 Indoor heat exchanger 21a First divided heat exchanger 21b Second divided heat exchanger 21c Third divided heat exchanger 21d Fourth divided heat exchanger 23 Indoor fan 23a Impeller 23b Fan motor 23p Rotating shaft 24 Second control unit 26, 27 Connection ports 28a, 28b Refrigerant piping 31 Liquid pipe 32 Gas pipe 41 Outdoor temperature sensor 42 First ambient temperature sensor 43 Indoor temperature sensor 44 Second ambient temperature sensor 50 Rear panel 51 Ceiling panel 52 Front panel 53 Bottom panel 56 Intake port 57 Outlet port 58 Ventilation path 59 Air deflector 61 Tube 62 Pipe connection 63 Drain pan 65 Connection 73 Cover 75 Bottom plate 76 Top plate 77 Front grille 78 Side grille 79 Main compartment 81 Front cover 82 Side cover 83 Rear cover 84 Partition plate 86 Power circuit 88 Machine room 89 Space for storing electrical components 92 Space for storing refrigerant piping a First port b Second port c Third port d Fourth port

Claims

1. An air conditioner comprising: a housing; a blower that draws air from the outside to the inside of the housing; a heat exchanger that exchanges heat between the air drawn into the inside of the housing and a refrigerant; piping connected to the heat exchanger and forming a refrigerant circuit through which the refrigerant circulates; an ambient temperature sensor that detects the ambient temperature inside the housing; and a control unit that, when the blower is stopped, determines that there is a refrigerant leak when the rate of decrease per unit time of the ambient temperature sensor's detection value exceeds a predetermined value, and executes a process to suppress ignition of the refrigerant.

2. The air conditioner according to claim 1, wherein the control unit performs at least one of the following as a process to suppress ignition of the refrigerant: drive control of the blower and notification to the outside of information indicating refrigerant leakage.

3. The air conditioner according to claim 1, wherein the housing, the heat exchanger, and the blower are provided in an indoor unit and an outdoor unit, respectively, the indoor unit and the outdoor unit are connected via the piping, and the ambient temperature sensor is provided in the indoor unit to detect the ambient temperature inside the housing of the indoor unit.

4. The air conditioner according to claim 3, comprising a drain pan provided below the heat exchanger to receive drain water dripping from the heat exchanger, wherein the ambient temperature sensor is provided below the upper end of the heat exchanger and above the lower end of the drain pan.

5. The air conditioner according to claim 1, wherein the housing, the heat exchanger, and the blower are provided in an indoor unit and an outdoor unit, respectively, the indoor unit and the outdoor unit are connected via the piping, and the ambient temperature sensor is provided in the outdoor unit to detect the ambient temperature inside the housing of the outdoor unit.

6. The air conditioner according to claim 5, wherein the outdoor unit comprises a first chamber in which the blower and the heat exchanger are provided and a second chamber in which the piping is provided, and the ambient temperature sensor is provided in the lower part of the second chamber.

7. The air conditioner according to claim 6, wherein the second room is a machine room.

8. The air conditioner according to any one of claims 1 to 7, wherein a flammable refrigerant is used as the refrigerant.

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