JP7484082B2 - Air conditioners - Google Patents

Description

The present invention relates to an air conditioner equipped with a refrigerant sensor.

Conventionally, air conditioners use mildly flammable refrigerants (e.g., R32) or flammable refrigerants that are heavier than air as refrigerants. In the event that a refrigerant leaks from an air conditioner, a refrigerant sensor is installed to detect the leaked refrigerant to ensure the safety of users. For example, in a typical indoor unit, the refrigerant sensor is usually placed under the weld or connection between the indoor heat exchanger and the refrigerant piping from the outdoor unit, which is a position where there is a high risk of refrigerant leakage. The refrigerant sensor is also placed at a lower position than the heat exchanger in which the refrigerant circulates to monitor leakage. The refrigerant sensor monitors at a similar position even when the air conditioner is in operation. In many cases, inexpensive semiconductor-type refrigerant sensors are used, but in this case, the refrigerant sensor does not react to a specific refrigerant, but also reacts to non-flammable refrigerants containing the same components, LP gas, other gases such as alcohols (hereinafter referred to as external gases).

As a safety measure after a refrigerant leaks during operation of an air conditioner, a method has been disclosed (for example, Patent Document 1) in which, when it is determined that a refrigerant leak has occurred inside the indoor unit, the indoor fan (hereinafter, when not distinguished from the outdoor fan of the outdoor unit, it may be referred to as the blower fan) is controlled to stir the leaked refrigerant and dilute the leaked refrigerant to prevent ignition. In this method, if a refrigerant gas leak is detected by the refrigerant sensor during operation, an operation is performed to stir the refrigerant, but for monitoring during operation, air from the room in which the indoor unit is located is taken in through the suction port of the indoor unit. Therefore, if external gas is generated inside the room, the external gas will be taken in. As a result, the external gas may also flow into the internal space of the indoor unit where the refrigerant sensor is located, and it may be determined that a refrigerant leak is occurring even though no refrigerant is leaking inside the indoor unit.

In addition, inside the indoor unit, a refrigerant sensor is provided near the discharge part of the drain pan located below the indoor heat exchanger, and as a countermeasure in the case where the refrigerant leakage point inside the indoor unit and the installation position of the refrigerant sensor, i.e., the detection position, are separated, a method is disclosed (for example, Patent Document 2) in which the air outlet of the indoor unit is closed and the indoor fan is rotated at or below the minimum rotation speed for normal operation, and the refrigerant leaked inside the indoor unit is carried by the air flow and guided to the refrigerant sensor. Here, the minimum rotation speed for normal operation is the rotation speed at which the wind speed or air volume that can circulate air inside the indoor unit is obtained. However, since the indoor fan rotates to take in indoor air from the suction port, the refrigerant leaked inside the indoor unit is diluted, and since the air outlet of the indoor unit is not a sealed structure, the leaked refrigerant is exhausted outside the indoor unit, and the concentration of the refrigerant gradually decreases. As a result, it may be determined that the refrigerant is not leaking even though it is actually leaking.

In addition, there are also cases where, when the refrigerant sensor reacts while the air conditioner is operating, the indoor fan is stopped or its speed is reduced, and then the change in gas concentration before and after the indoor fan is stopped or before and after the speed is reduced is compared to determine whether the refrigerant sensor reacted due to external gas or a refrigerant leak. However, neither method takes into account the determination when the air conditioner is not operating.

JP 2016-090110 A JP 2017-015324 A

The present invention aims to solve the problems mentioned above, and to provide an air conditioner that can accurately determine whether or not a refrigerant leaks while the air conditioner is not in operation.

In order to achieve the above object, the present invention is understood as follows.
(1) An air conditioner comprising a housing, a refrigerant sensor that detects leaked refrigerant, a blower fan that circulates air inside and outside the housing inside the housing, and a control means for controlling the operation of the refrigerant sensor and the blower fan, wherein when the refrigerant sensor detects a gas concentration equal to or higher than a predetermined level while the air conditioner is not in operation, the control means operates the blower fan at a first rotation speed and performs a primary determination to determine whether refrigerant has leaked inside the indoor unit or whether external gas has been detected by comparing the change in gas concentration per unit time before and after the operation of the blower fan, and if it is determined by the primary determination that external gas has been detected , no safety measures are taken.

(2) In the above (1), in the primary determination, if the change in gas concentration after the blower fan is operated is greater than before the blower fan is operated, it is determined that the refrigerant is not leaking, and if the change in gas concentration after the blower fan is operated is smaller than before the blower fan is operated, it is determined that the refrigerant is leaking.

(3) In the above (1) or (2), the control means further operates the blower fan at a second rotation speed lower than the first rotation speed, or stops the blower fan, and performs a secondary determination to determine whether or not refrigerant has leaked inside the indoor unit by comparing the change in gas concentration per unit time before and after the reduction in the rotation speed of the blower fan or before and after the fan is stopped.

(4) In the above (3), in the secondary judgment, if the change in gas concentration after the rotation speed of the blower fan has decreased or been stopped is smaller than before the rotation speed of the blower fan has decreased or been stopped, it is judged that refrigerant has leaked. Conversely, if the change in gas concentration after the rotation speed of the blower fan has decreased or been stopped is greater than before the rotation speed of the blower fan has decreased or been stopped, it is judged that refrigerant has leaked.

(5) In any one of (1) to (4) above, the air conditioner is a floor-standing indoor unit.

The present invention provides an air conditioner that can accurately determine whether or not a refrigerant leaks while the air conditioner is not in operation.

1A and 1B are diagrams for explaining an air conditioner according to an embodiment of the present invention, in which FIG. 1A is a refrigerant circuit diagram, and FIG. 1B is a block diagram of a control means of the air conditioner. 1 is a perspective view showing an indoor unit of an air conditioner according to an embodiment of the present invention. 1 is an exploded perspective view showing an indoor unit of an air conditioner according to an embodiment of the present invention. FIG. 2 is a block diagram showing a control configuration of an indoor unit of the air conditioner according to the embodiment of the present invention. 11A and 11B are diagrams illustrating a primary determination by controlling a blower fan according to an embodiment of the present invention. 11A and 11B are diagrams illustrating a secondary determination by controlling a blower fan according to an embodiment of the present invention. 5 is a flowchart illustrating a procedure of determination by controlling a blower fan according to the embodiment of the present invention.

(Embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiment, and various modifications can be made without departing from the spirit of the present invention.

<Air conditioner configuration>
First, with reference to Fig. 1 (A), a refrigerant circuit of an air conditioner 1 including an outdoor unit 2 will be described. As shown in Fig. 1 (A), the air conditioner 1 in this embodiment includes an outdoor unit 2 installed outdoors, and an indoor unit 3 installed indoors and connected to the outdoor unit 2 by a liquid pipe 4 and a gas pipe 5. In detail, a liquid side shutoff valve 25 of the outdoor unit 2 and a liquid pipe connection part 33 of the indoor unit 3 are connected by the liquid pipe 4. In addition, a gas side shutoff valve 26 of the outdoor unit 2 and a gas pipe connection part 34 of the indoor unit 3 are connected by the gas pipe 5. The refrigerant circuit 10 of the air conditioner 1 is configured as described above.

<<Outdoor unit refrigerant circuit>>
First, the outdoor unit 2 will be described. The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an expansion valve 24, a liquid side shut-off valve 25 connected to a liquid pipe 4, a gas side shut-off valve 26 connected to a gas pipe 5, and an outdoor fan 27. These elements except for the outdoor fan 27 are connected to each other by refrigerant pipes described in detail below, and constitute an outdoor unit refrigerant circuit 10a that is a part of the refrigerant circuit 10. An accumulator (not shown) may be provided on the refrigerant suction side of the compressor 21.

The compressor 21 is a variable-capacity compressor whose operating capacity can be changed by controlling the rotation speed with an inverter (not shown). The refrigerant discharge side of the compressor 21 is connected to port a of the four-way valve 22 via a discharge pipe 61. The refrigerant suction side of the compressor 21 is connected to port c of the four-way valve 22 via a suction pipe 66.

The four-way valve 22 is a valve for switching the direction of refrigerant flow, and has four ports a, b, c, and d. As described above, port a is connected to the refrigerant discharge side of the compressor 21 by a discharge pipe 61. Port b is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 23 by a refrigerant piping 62. As described above, port c is connected to the refrigerant suction side of the compressor 21 by a suction pipe 66. And port d is connected to the gas side shutoff valve 26 by an outdoor unit gas pipe 64. The four-way valve 22 is the flow path switching means of the present invention.

The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27 described later. As described above, one refrigerant inlet/outlet of the outdoor heat exchanger 23 is connected to port b of the four-way valve 22 by a refrigerant piping 62, and the other refrigerant inlet/outlet is connected to the liquid side shutoff valve 25 by an outdoor unit liquid pipe 63. The outdoor heat exchanger 23 functions as a condenser during cooling operation and as an evaporator during heating operation by switching the four-way valve 22 described later.

The expansion valve 24 is an electronic expansion valve driven by a pulse motor (not shown). Specifically, its opening is adjusted by the number of pulses applied to the pulse motor. During heating operation, the opening of the expansion valve 24 is adjusted so that the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 21, becomes a predetermined target temperature.

The outdoor fan 27 is made of a resin material and is disposed near the outdoor heat exchanger 23. The center of the outdoor fan 27 is connected to the rotating shaft of a fan motor (not shown). The outdoor fan 27 rotates as the fan motor rotates. As the outdoor fan 27 rotates, outside air is taken into the outdoor unit 2 from an intake port (not shown) of the outdoor unit 2, and the outside air that has exchanged heat with the refrigerant in the outdoor heat exchanger 23 is discharged to the outside of the outdoor unit 2 from an outlet port (not shown) of the outdoor unit 2.

In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1(A), the discharge pipe 61 is provided with a discharge pressure sensor 71 that detects the pressure of the refrigerant discharged from the compressor 21, and a discharge temperature sensor 73 that detects the temperature of the refrigerant discharged from the compressor 21 (the discharge temperature described above). The suction pipe 66 is provided with a suction pressure sensor 72 that detects the pressure of the refrigerant sucked into the compressor 21, and a suction temperature sensor 74 that detects the temperature of the refrigerant sucked into the compressor 21.

A heat exchanger temperature sensor 75 is provided in the approximate middle of the refrigerant path (not shown) of the outdoor heat exchanger 23 to detect the outdoor heat exchanger temperature, which is the temperature of the outdoor heat exchanger 23. An outdoor air temperature sensor 76 is provided near the air intake (not shown) of the outdoor unit 2 to detect the temperature of the outdoor air flowing into the outdoor unit 2, i.e., the outdoor air temperature.

The outdoor unit 2 is also equipped with an outdoor unit control means 200. The outdoor unit control means 200 is mounted on a control board stored in an electrical equipment box (not shown) of the outdoor unit 2. As shown in FIG. 1(B), the outdoor unit control means 200 includes a CPU 210, a memory unit 220, a communication unit 230, and a sensor input unit 240.

The storage unit 220 is composed of a flash memory, and stores the control program for the outdoor unit 2, detection values corresponding to detection signals from various sensors, the control states of the compressor 21 and the outdoor fan 27, etc. Also, although not shown, the storage unit 220 stores in advance a rotation speed table that determines the rotation speed of the compressor 21 according to the required capacity received from the indoor unit 3.

The communication unit 230 is an interface that communicates with the indoor unit 3. The sensor input unit 240 receives detection results from various sensors in the outdoor unit 2 and outputs them to the CPU 210.

The CPU 210 takes in the detection results of each sensor of the outdoor unit 2 described above via the sensor input unit 240. Furthermore, the CPU 210 takes in the control signal transmitted from the indoor unit 3 via the communication unit 230. The CPU 210 controls the drive of the compressor 21 and the outdoor fan 27 based on the taken-in detection results and control signals. The CPU 210 also controls the switching of the four-way valve 22 based on the taken-in detection results and control signals. Furthermore, the CPU 210 adjusts the opening degree of the expansion valve 24 based on the taken-in detection results and control signals.

<<Indoor unit refrigerant circuit>>
Next, the indoor unit 3 will be described with reference to Fig. 1 (A). The indoor unit 3 includes an indoor heat exchanger 31, an indoor fan 32, a liquid pipe connection part 33 to which the other end of the liquid pipe 4 is connected, and a gas pipe connection part 34 to which the other end of the gas pipe 5 is connected. Each of these devices except for the indoor fan 32 is connected to each other by each refrigerant pipe described in detail below, and constitutes an indoor unit refrigerant circuit 10b that is a part of the refrigerant circuit 10.

The indoor heat exchanger 31 exchanges heat between the refrigerant and indoor air taken into the indoor unit 3 from an intake port (not shown) of the indoor unit 3 by the rotation of the indoor fan 32 described below. One refrigerant inlet/outlet of the indoor heat exchanger 31 is connected to the liquid pipe connection part 33 and the indoor unit liquid pipe 67. The other refrigerant inlet/outlet of the indoor heat exchanger 31 is connected to the gas pipe connection part 34 and the indoor unit gas pipe 68. The indoor heat exchanger 31 functions as an evaporator when the indoor unit 3 is performing cooling operation, and functions as a condenser when the indoor unit 3 is performing heating operation.

The indoor fan 32 is made of a resin material and is located near the indoor heat exchanger 31. The indoor fan 32 is rotated by a fan motor (not shown) to draw indoor air into the indoor unit 3 from an intake port (not shown) of the indoor unit 3, and blows the indoor air that has exchanged heat with the refrigerant in the indoor heat exchanger 31 out into the room from an outlet port (not shown) of the indoor unit 3.

In addition to the elements described above, the indoor unit 3 is provided with various sensors. The indoor unit liquid pipe 67 is provided with a liquid-side temperature sensor 77 that detects the temperature of the refrigerant flowing into or out of the indoor heat exchanger 31. The indoor unit gas pipe 68 is provided with a gas-side temperature sensor 78 that detects the temperature of the refrigerant flowing out or into the indoor heat exchanger 31. A room temperature sensor 79 is provided near the suction port (not shown) of the indoor unit 3 to detect the temperature of the indoor air flowing into the indoor unit 3, i.e., the room temperature.

The indoor unit 3 is also equipped with an indoor unit control means 300. The indoor unit control means 300 is mounted on a control board stored in an electrical component box 301 (see FIG. 3) of the indoor unit 3. As shown in FIG. 1(B), the indoor unit control means 300 includes a CPU 310, a memory unit 320, a communication unit 330, and a sensor input unit 340 (note that in this specification, the indoor unit control means 300 may be simply referred to as the control means).

The storage unit 320 is made up of a flash memory, and stores the control program for the indoor unit 3, detection values corresponding to detection signals from various sensors, the control state of the indoor fan 32, etc. Also, although not shown, the storage unit 320 stores in advance a rotation speed table that determines the rotation speed of the indoor fan 32, including the rotation speed for monitoring refrigerant leakage during operation stoppage, which will be described later.

The communication unit 330 is an interface that communicates with the outdoor unit 2. The sensor input unit 340 receives the detection results from various sensors in the indoor unit 3 and outputs them to the CPU 310.

The CPU 310 takes in the detection results of each sensor of the indoor unit 3 described above via the sensor input unit 340. Furthermore, the CPU 310 takes in the control signal transmitted from the outdoor unit 2 via the communication unit 330. Based on the taken-in detection results and control signal, the CPU 310 controls the drive of the indoor fan 32, including the drive for monitoring refrigerant leakage during operation stoppage, which will be described later. The CPU 310 also calculates the temperature difference between the set temperature set by the user by operating a remote control (not shown) and the room temperature detected by the room temperature sensor 79, and transmits the required capacity based on the calculated temperature difference to the outdoor unit control means 200 of the outdoor unit 2 via the communication unit 330.

<Air conditioner operation>
Next, the flow of refrigerant in the refrigerant circuit 10 and the operation of each part during air conditioning operation of the air conditioner 1 in this embodiment will be described with reference to Fig. 1 (A). Below, a case where the indoor unit 3 performs heating operation will be described based on the refrigerant flow shown by the solid line in the figure. Note that the refrigerant flow shown by the dashed line indicates cooling operation.

When the indoor unit 3 performs heating operation, the CPU 210 switches the four-way valve 22 to the state shown by the solid lines in FIG. 1(A), that is, so that ports a and d of the four-way valve 22 communicate with each other, and so that ports b and c of the four-way valve 22 communicate with each other. This causes the refrigerant to circulate in the direction shown by the solid arrows in the refrigerant circuit 10, resulting in a heating cycle in which the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchanger 31 functions as a condenser.

The high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 61 and into the four-way valve 22. The refrigerant that flows into port a of the four-way valve 22 flows through the outdoor unit gas pipe 64 from port d of the four-way valve 22 and flows into the gas pipe 5 via the gas side shutoff valve 26. The refrigerant flowing through the gas pipe 5 flows into the indoor unit 3 via the gas pipe connection part 34.

The refrigerant that flows into the indoor unit 3 flows through the indoor unit gas pipe 68 into the indoor heat exchanger 31, where it exchanges heat with the indoor air drawn into the indoor unit 3 by the rotation of the indoor fan 32, and is condensed. In this way, the indoor heat exchanger 31 functions as a condenser, and the indoor air that has been warmed by heat exchange with the refrigerant in the indoor heat exchanger 31 is blown out into the room from an air outlet (not shown), heating the room in which the indoor unit 3 is installed.

The refrigerant flowing out from the indoor heat exchanger 31 flows through the indoor unit liquid pipe 67 and enters the liquid pipe 4 via the liquid pipe connection part 33. The refrigerant flowing through the liquid pipe 4 and entering the outdoor unit 2 via the liquid side closing valve 25 is reduced in pressure as it flows through the outdoor unit liquid pipe 63 and passes through the expansion valve 24. As described above, the opening degree of the expansion valve 24 during heating operation is adjusted so that the discharge temperature of the compressor 21 becomes a predetermined target temperature.

The refrigerant that passes through the expansion valve 24 and flows into the outdoor heat exchanger 23 evaporates through heat exchange with the outside air drawn into the outdoor unit 2 by the rotation of the outdoor fan 27. The refrigerant that flows out of the outdoor heat exchanger 23 into the refrigerant piping 62 flows through ports b and c of the four-way valve 22 and the suction pipe 66, is sucked into the compressor 21, and is compressed again.

<Indoor unit structure>
Next, an example of the structure of a floor-standing indoor unit 3 according to this embodiment will be described with reference to Figures 2 and 3. Figure 2 is a perspective view showing the exterior of the indoor unit 3, Figure 3 is an exploded perspective view showing the internal structure of the indoor unit 3, and Figure 4 is a block diagram showing the control configuration of the indoor unit 3. The air conditioner 1 exchanges heat between the air and a refrigerant (e.g., R32 refrigerant) circulating between the outdoor unit 2 and the indoor unit 3, and blows cold air or hot air from the indoor unit 3 into the room to perform cooling, heating, dehumidification, etc. of the room.

As shown in FIG. 2, the indoor unit 3 is a floor-standing type that is installed on the floor surface, and includes a housing 6, an intake port 36 provided on the front side of the housing 6, and an upper outlet 35x (outlet 35) and a lower outlet 35y (outlet 35) provided above and below the intake port 36. As shown in FIG. 3, a heat exchanger 31 is provided inside the indoor unit 3 in the air passage connecting the intake port 36 and the two outlets 35. In this embodiment, the distinction between the top and bottom of each element is represented by a code subnumber x/y (x is top, y is bottom), and when there is no distinction between the top and bottom, the code subnumber x/y is omitted.

As shown in FIG. 3, the upper air passage 37x (air passage 37) is provided with an upper indoor fan 32x (indoor fan 32) rotated by an upper motor 38x (motor 38), and the upper indoor fan 37x is covered by an upper casing 39x (casing 39) that constitutes the upper air outlet 35x. Similarly, the lower air passage 37y (air passage 37) is provided with a lower indoor fan 32y (indoor fan 32) rotated by a lower motor 38y (motor 38), and the lower indoor fan 32y is covered by a lower casing 39y (casing 39) that constitutes the lower air outlet 35y. In addition, the indoor unit 3 is provided with an electrical equipment box 301 that houses the indoor unit control means 300 described above, a display unit 302 that displays the operating state of the indoor unit 3, and a room temperature sensor 79.

In general, in an air conditioner 1 that circulates refrigerant between the indoor unit 3 and the outdoor unit 2, if refrigerant leaks from the indoor unit 3, the leaked refrigerant will accumulate near the floor surface, increasing the refrigerant concentration near the floor surface. In particular, when using a flammable refrigerant or a slightly flammable refrigerant such as the R32 refrigerant used in this embodiment, the concentration of the leaked refrigerant may reach a flammable concentration. However, with the floor-standing indoor unit 3 of this embodiment, the air blown out by the operation of the indoor fan 32 flows near the floor surface, making it easier to diffuse the leaked refrigerant throughout the room.

(Control Unit)
As shown in Fig. 4, the air conditioner 1 is provided with an indoor unit control means 300 that controls the outdoor unit 2, the indoor fan 32 of the indoor unit 3, etc., in response to settings on an operation unit 303 having an infrared remote control, an infrared receiver, etc. Furthermore, a refrigerant sensor 304 that detects refrigerant leakage, and an alarm 305 that outputs an alarm sound are connected to the indoor unit control means 300. Based on the detection of refrigerant leakage by the refrigerant sensor 304, safety measures such as notifying the user of the refrigerant leakage by the alarm 305, diffusing the leaked refrigerant indoors by the indoor fan 32, and cutting off the circulation of the refrigerant by a shutoff valve (not shown) are performed.

The refrigerant sensor 304 is a semiconductor-type refrigerant sensor that can accurately detect low concentrations of refrigerant.

The semiconductor refrigerant sensor 304 is equipped with a detection unit 304a that detects refrigerant leakage in a heated state (e.g., 300-400°C) and a heater 304b that heats the detection unit 304a. The detection unit 304a detects refrigerant leakage by utilizing the fact that the electrical resistance of the sensor element decreases in the presence of a flammable refrigerant, and the amount of decrease in electrical resistance depends on the refrigerant concentration. The sensor element is formed from a sintered body of a metal oxide (e.g., tin oxide) that has semiconductor properties.

When the sensor element of the detection unit 304a is heated to 300-400°C by the heat of the heater 304b, in the atmosphere that does not contain reducing gases such as refrigerants, a certain amount of oxygen in the air is negatively charged and adsorbed to the surface (oxygen captures electrons of tin oxide and adsorbs to the surface), resulting in a high resistance value. When a reducing gas such as a refrigerant comes into contact with the surface of this sensor element, a reaction occurs with the adsorbed oxygen, which is desorbed, and the captured electrons are released, decreasing the resistance value. Based on this change in resistance value, it is possible to detect refrigerant leaks and the concentration of leaked refrigerant.

<Detection of refrigerant leakage>
With the above-described configuration, the air conditioner 1 determines whether or not there is a refrigerant leak as follows: The determination of whether or not there is a refrigerant leak according to this embodiment can be applied to both the outdoor unit 2 and the indoor unit 3, but the following describes the case where it is applied to the indoor unit 3.

As described above, the indoor unit 3 includes a refrigerant sensor 304 that detects the concentration of the leaked refrigerant, an indoor fan 32 that circulates air inside and outside the housing inside the housing, and an indoor unit control means 300 that controls the operation of the refrigerant sensor 304 and the indoor fan 32. When the refrigerant sensor 304 detects a gas concentration equal to or higher than a predetermined level while the air conditioner 1 is not in operation, the indoor unit control means 300 operates the indoor fan 32 at a first rotation speed, compares the change in gas concentration per unit time before and after the operation of the indoor fan 32, and performs a primary determination as to whether or not refrigerant has leaked inside the indoor unit 3. If the change in gas concentration per unit time before and after the operation of the indoor fan 32 is greater after the operation of the indoor fan 32 than before the operation of the indoor fan 32, it is estimated that the detected gas concentration is the concentration of the external gas and that no refrigerant has leaked, and if the change in gas concentration after the operation of the indoor fan 32 is smaller than before the operation of the indoor fan 32, it is estimated that a refrigerant has leaked. In this way, it is possible to distinguish whether the increase in gas concentration is due to external gas flowing into the indoor unit 3 or due to a refrigerant leak inside the indoor unit 3, and accurately determine whether a refrigerant leak has occurred.

In addition, after the operation at the first rotation speed, the indoor unit control means 300 may further operate (or stop) the indoor fan 32 at a second rotation speed lower than the first rotation speed, and compare the gas concentration change per unit time before and after the rotation speed of the indoor fan 32 is reduced (or before and after it is stopped) to perform a secondary judgment as to whether or not refrigerant has leaked inside the indoor unit 3. If the gas concentration change per unit time before and after the rotation speed of the indoor fan 32 is reduced (or before and after it is stopped) is greater than before the rotation speed of the indoor fan 32 is reduced (or before it is stopped), it is estimated that the detected gas concentration is the concentration of the external gas and that refrigerant has not leaked, and if the gas concentration change after the rotation speed of the indoor fan 32 is reduced (or after it is stopped) is smaller than before the rotation speed of the indoor fan 32 is reduced (or before it is stopped), it is estimated that refrigerant has leaked.

The primary and secondary judgments will be explained using Figs. 5 to 7. Figs. 5 and 6 show how the gas concentration changes with the operation of the indoor fan 32, with gas concentration C (%) on the vertical axis and time T (s) on the horizontal axis. Fig. 7 is a flowchart explaining the judgment procedure. In the following explanation, the leaked refrigerant is referred to as "refrigerant gas", gas generated from other gas sources in the room in which the indoor unit 3 is installed is referred to as "external gas", and gas when there is no distinction between refrigerant gas and external gas is simply referred to as "gas".

External gases include gases contained in insecticides, deodorants, and air fresheners that are temporarily dispersed in the room in which the indoor unit 3 is installed, as well as gases generated by any decaying matter.

When the refrigerant sensor 304 detects gas while the operation is stopped, and the detected gas concentration value is equal to or higher than a threshold value _C0 (predetermined gas concentration) lower than a set value _C1 at which a safety measure should be implemented, the indoor unit control means 300 operates the indoor fan 32 at a first rotation speed (rotation speed A rpm in Figs. 5 and 6).Then, the change in gas concentration before the operation of the indoor fan 32 is stored in the memory unit 320, and the change in gas concentration per unit time before and after the operation of the indoor fan 32 is compared.

A flammable refrigerant will ignite when its concentration is within a predetermined range. This concentration range is called the flammable concentration range, and the lower limit of this flammable concentration range is referred to as the LFL (Lower Flammable Limit). For example, the set value _C1 is set to 1/2 of the LFL, and the threshold value _C0 is set to 1/4 of the LFL. Incidentally, when R32 is used as the refrigerant, the LFL is 14.4%, and the permissible concentration regulation value is 3.6%, which is the LFL multiplied by the safety factor (1/4).

5 , if the gas concentration change ΔC _a /ΔT _a after the indoor fan 32 operates at the first rotation speed A rpm becomes larger than the gas concentration change ΔC/ΔT before the indoor fan 32 operates, it is determined (primary determination) that there is no refrigerant leakage. In other words, it is presumed that the increase in gas concentration is caused by external gas, and that the increase in gas concentration change detected by the refrigerant sensor 304 is due to the external gas being sucked into the indoor unit 3 by the indoor fan 32.

In contrast, as shown in Fig. 6, if the gas concentration change ΔC _a /ΔT _a after the indoor fan 32 operates at the first rotation speed Arpm becomes smaller than the gas concentration change ΔC/ΔT before the indoor fan 32 operates (Fig. 6 shows a case where the gas concentration change ΔC _a /ΔT _a after operation is negative), it is determined that refrigerant has leaked (primary determination). In other words, it is presumed that the cause of the increase in gas concentration is refrigerant gas, and that the gas concentration change detected by the refrigerant sensor 304 has decreased (become negative in Fig. 6) due to the refrigerant gas being blown out of the indoor unit 3 by the indoor fan 32.

Here, if the above-mentioned primary judgment results in a large gas concentration change ΔC _a /ΔT _a , it is not judged as a refrigerant leak, whereas if the gas concentration change ΔC _a /ΔT _a becomes small (for example, becomes negative), it is possible to judge as a refrigerant leak. However, since there may be cases where refrigerant leakage from the indoor unit 3 and the generation of external gas inside the room occur simultaneously, a secondary judgment may be made as follows.

That is, the indoor unit control means 300 operates the indoor fan 32 at the first rotation speed A rpm for a predetermined time (e.g., 30 seconds), and then operates it at a second rotation speed (represented by B rpm in Figs. 5 and 6) that is lower than the first rotation speed A rpm for another predetermined time (e.g., 30 seconds). Then, the change in gas concentration per unit time before and after the reduction in the rotation speed of the indoor fan 32 is compared.

As a result, when the gas concentration change ΔC _b /ΔT _b after the indoor fan 32 operates at the second rotation speed B rpm is smaller than the gas concentration change ΔC _a /ΔT _a when the indoor fan 32 operates at the first rotation speed A rpm, it can be more accurately determined (secondary determination) that there is no refrigerant leakage. In other words, it is presumed that the cause of the increase in gas concentration is external gas, and that the change in gas concentration detected by the refrigerant sensor 304 has become smaller due to the reduction in the amount of external gas sucked into the indoor unit 3 as the rotation speed of the indoor fan 32 has decreased.

In contrast, as shown in Fig. 6, when the gas concentration change _ΔCb / _ΔTb when the indoor fan 32 operates at the second rotation speed B rpm is larger than the gas concentration change ΔCa/ _ΔTa when the indoor fan 32 operates at the first rotation speed A rpm (Fig. 6 shows the case where the gas concentration change _{ΔCb / ΔTb} is positive), it can be more accurately determined that refrigerant has leaked (secondary determination). That is, it is presumed that the cause of the increase in gas concentration is refrigerant gas, and that despite the decrease in the rotation speed of the indoor fan 32 causing a decrease in the external gas sucked into the indoor unit 3, the refrigerant gas present inside the indoor unit 3 is being generated, causing the increase in the gas concentration change detected by the refrigerant sensor 304.

In Figures 5 and 6, the time (hereinafter referred to as the specified time) for operating the indoor fan 32 at the first rotation speed A rpm or the second rotation speed B rpm is preferably approximately 30 seconds. If it is shorter than this, the response time of the refrigerant sensor 304 will be insufficient and the accurate gas concentration inside the indoor unit 3 will not be able to be detected. Conversely, if it is longer than this, the gas concentration inside the indoor unit 3 and the room will become uniform, and no change in gas concentration will be observed. Note that, although the response time will change slightly, the same applies when the refrigerant sensor 304 is an infrared type or thermal conduction type other than a semiconductor type.

As shown in Fig. 6, if it is presumed that the cause of the increase in gas concentration is refrigerant gas, safety measures such as continuous rotation of the indoor fan 32, stirring, mechanical ventilation, and shutoff valves are implemented, and notification means such as an alarm 305 and a warning light (located on the display unit 302) are activated. Even if the above-mentioned primary or secondary judgment is being performed, safety measures are implemented when the gas concentration reaches the set value _C1 . On the other hand, if it is presumed that the cause of the increase in gas concentration is external gas, no safety measures are implemented.

The above-described judgment procedure is shown in a flow chart in FIG. 7. That is, the indoor unit control means 300 detects the gas concentration change ΔC/ΔT before the operation of the indoor fan 32 (step ST1), and when the gas concentration C becomes equal to or greater than the threshold value C ₀ (Yes in step ST2), the indoor fan 32 is operated at the first rotation speed Arpm (step ST3). On the other hand, when the gas concentration C is less than the threshold value C ₀ (No in step ST2), the detection of the gas concentration change ΔC/ΔT is continued. Here, in step ST1, the CPU 210 reads out the gas concentration detection value c0 from the storage unit 220, which is a storage means, and calculates the change amount ΔC/ΔT (=(c1-c0)/(t1-t0)) of the gas concentration detection value c per unit time (here, t1-t0) of the detection value c from the difference between the detection value c0 and the gas concentration detection value c1 at the current time t1.

After step ST3, the indoor unit control means 300 detects the gas concentration change ΔC _a /ΔT _a for 30 seconds after the indoor fan 32 is operated (step ST4), and if the gas concentration change ΔC _a /ΔT _a is greater than the gas concentration change ΔC/ΔT (Yes in step ST5), proceeds to step ST6. On the other hand, if the gas concentration change ΔC _a /ΔT _a is smaller than the gas concentration change ΔC/ΔT (No in step ST5), proceeds to step ST10. Step ST5 is the primary determination.

Then, if the gas concentration change ΔC _a /ΔT _a is greater than the gas concentration change ΔC / ΔT before the operation of the indoor fan 32 (Yes in step ST5), the indoor unit control means 300 operates (or stops) the indoor fan 32 at a second rotation speed B rpm lower than the first rotation speed A rpm (step ST6). The indoor unit control means 300 detects the gas concentration change ΔC _b / ΔT _b for 30 seconds after the indoor fan 32 is operated (or stopped) at the second rotation speed B rpm (step ST7), and if the gas concentration change ΔC _b / ΔT _b is smaller than the gas concentration change ΔC _a / ΔT _a (Yes in step ST8), the process proceeds to step ST9. On the other hand, if the gas concentration change ΔC _b / ΔT _b is greater than the gas concentration change ΔC _a / ΔT _a (No in step ST8), the process proceeds to step ST10. ST8 is the judgment of the secondary judgment.

In step ST9, it is presumed that the cause of the increase in gas concentration is an external gas, and no safety measures are taken. On the other hand, in step ST10, it is presumed that the cause of the increase in gas concentration is refrigerant gas, and safety measures such as continuous rotation of the indoor fan 32, stirring, mechanical ventilation, and shutoff valves are implemented, and notification means such as the alarm 305 and warning lights (located on the display unit 302) are activated.

(Effects of the embodiment)
As described above, in the air conditioner 1 that uses a flammable or slightly flammable refrigerant that has a higher specific gravity than air, if there is a change in the detection value of the refrigerant sensor 304 while the unit is not operating, the rotation speed of the indoor fan 32 in the indoor unit 3 is controlled to detect the change in gas concentration, thereby making it possible to accurately determine whether a refrigerant leak has occurred by distinguishing whether the increase in gas concentration is due to external gas flowing into the indoor unit 3 or due to refrigerant leakage inside the indoor unit 3.

The above describes in detail preferred embodiments of the present invention, but the present invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

For example, the above embodiment has been described using a floor-standing indoor unit 3 as an example, but the present invention can also be implemented with a wall-mounted indoor unit or outdoor unit.

In addition, in the above embodiment, it is assumed that the refrigerant sensor 304 is disposed inside the indoor unit 3, but it may be disposed outside the indoor unit 3. However, if it is disposed outside the indoor unit 3, it is necessary to provide a space inside the housing that can circulate air inside and outside the housing by operating the indoor fan 32.

In addition, although the above-mentioned embodiment uses R32 as the refrigerant, the air conditioner may use other refrigerants. However, since the LFL differs depending on the type of refrigerant, the standard value (LFL * 1/4) must be changed according to the type of refrigerant. For example, the LFL of R32 is 14.4%, while that of R1234yf is 6.2% and that of R1234ze is 6.5%.

In the above embodiment, the indoor fan 32 is operated at a second rotation speed B rpm, which is lower than the first rotation speed A rpm, in the secondary determination. However, instead of operating at the second rotation speed B rpm, the indoor fan 32 may be stopped to detect the change in gas concentration. When the indoor fan 32 is stopped, air does not circulate inside the housing, so that the determination of refrigerant gas leakage can be made earlier. Note that after the second rotation speed B rpm, the indoor fan 32 may be stopped to detect the change in gas concentration.

REFERENCE SIGNS LIST 1 air conditioner 2 outdoor unit 3 indoor unit 4 liquid pipe 5 gas pipe 6 housing 10 refrigerant circuit 10a outdoor unit refrigerant circuit 10b indoor unit refrigerant circuit 21 compressor 22 four-way valve 23 outdoor heat exchanger 24 expansion valve 25 liquid side shut-off valve 26 gas side shut-off valve 27 outdoor fan 31 indoor heat exchanger 32 indoor fan 33 liquid pipe connection part 34 gas pipe connection part 35 outlet 36 suction port 37 air passage 38 motor 39 casing 61 discharge pipe 62 refrigerant piping 63 outdoor unit liquid pipe 64 outdoor unit gas pipe 66 suction pipe 67 indoor unit liquid pipe 68 indoor unit gas pipe 71 discharge pressure sensor 72 suction pressure sensor 73 discharge temperature sensor 74 suction temperature sensor 75 Heat exchange temperature sensor 76 Outdoor air temperature sensor 77 Liquid side temperature sensor 78 Gas side temperature sensor 79 Room temperature sensor 200 Outdoor unit control means 210 CPU
220 Memory section 230 Communication section 240 Sensor input section 300 Indoor unit control means 301 Electrical equipment box 302 Display section 303 Operation section 304 Refrigerant sensor 305 Alarm 310 CPU
320 Storage unit 330 Communication unit 340 Sensor input unit

Claims (4)

A housing and
A refrigerant sensor that detects leaked refrigerant;
a blower fan for circulating air between inside and outside the housing inside the housing;
A control means for controlling the operation of the refrigerant sensor and the blower fan,
The control means performs a primary determination when the refrigerant sensor detects a gas concentration equal to or higher than a predetermined level while the air conditioner is stopped, operates the blower fan at a first rotation speed, compares the change in gas concentration per unit time before and after the operation of the blower fan, and determines that external gas has been detected if the change in gas concentration after the operation of the blower fan is greater than before the operation of the blower fan, and determines that refrigerant has leaked inside the indoor unit if the change in gas concentration after the operation of the blower fan is smaller than before the operation of the blower fan, and performs a primary determination that external gas has been detected , and does not take any safety measures if it is determined that external gas has been detected by the primary determination. The air conditioner described in claim 1, characterized in that the control means further operates the blower fan at a second rotation speed lower than the first rotation speed, or stops the blower fan, and performs a secondary determination to determine whether or not refrigerant has leaked inside the indoor unit by comparing the change in gas concentration per unit time before and after the reduction in the rotation speed of the blower fan or before and after the fan is stopped. The air conditioner according to claim 2, characterized in that in the secondary judgment, if the change in gas concentration after the rotation speed of the blower fan has decreased or been stopped is smaller than before the rotation speed of the blower fan has decreased or been stopped, it is judged that refrigerant has leaked, and if the change in gas concentration after the rotation speed of the blower fan has decreased or been stopped is greater than before the rotation speed of the blower fan has decreased or been stopped . The air conditioner according to any one of claims 1 to 3 , wherein the air conditioner is a floor-standing indoor unit.

Images