Refrigerant leak detection device and refrigerant leak detection method

Abstract

To provide a device and a method for detecting a coolant leakage that can prevent a wrong detection by reducing influence of an environmental factor.SOLUTION: A device for detecting a coolant leakage includes: a first electrode arranged in the outer periphery of a heat insulating material provided in the outer periphery of a coolant pipe extending along the direction of circulation of the coolant; a second electrode arranged in the outer periphery of the heat insulating material to be distant from the first electrode in the direction of circulation of the coolant; and a detection unit for detecting a leakage of the coolant on the basis of a first electrode capacitance between the first electrode and the coolant pipe and a second electrode capacitance between the second electrode and the coolant pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a refrigerant leak detection device and a refrigerant leak detection method for detecting a refrigerant leak from a refrigerant pipe. [Background technology]

[0002] In recent years, amid strong concerns about the effects of global warming, there has been a movement to suppress the leakage of refrigerants such as fluorocarbons, which have a high greenhouse effect, into the atmosphere. The leakage of refrigerants into the atmosphere can occur when the refrigerants sealed in refrigerators and air conditioners are not collected when they are disposed of, or when the refrigerant pipes of the refrigerators and air conditioners are damaged during use. The amount of refrigerant that leaks into the atmosphere while the equipment is in use is greater than the amount of refrigerant that leaks when the equipment is disposed of, and this must be suppressed. To achieve this, a technology is required that can easily and accurately detect the leakage of refrigerant while the equipment is in use. In addition, if the refrigerant pipes are damaged and the refrigerant leaks, the equipment cannot be used again unless the affected area is repaired. Therefore, there is a demand for a technology that can detect the leakage of refrigerant and identify the location of the leakage at the same time.

[0003] Patent Document 1 discloses a refrigerant leakage detection device that, as a means for detecting refrigerant leakage from a refrigerant pipe, attaches electrodes to the outer periphery of the insulation covering the outer surface of the refrigerant pipe and measures the capacitance between the refrigerant pipe and the electrodes. The refrigerant leakage detection device of Patent Document 1 detects refrigerant leakage when the capacitance that increases with refrigerant leakage exceeds a threshold value.

[0004] Another known technology involves placing two sensors near a refrigerant pipe, capturing refrigerant-containing fluid caused by a refrigerant leak between two plate electrodes that make up the sensor, and detecting a refrigerant leak from a change in capacitance or impedance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-173259 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology of Patent Document 1, the change in capacitance due to the leakage of the refrigerant is detected by capturing the change in capacitance. When the refrigerant leakage detection device described in Patent Document 1 is installed indoors, it is exposed to changes in temperature and humidity due to the operating conditions of the air conditioner or seasonal changes. In addition, the refrigerant leakage detection device described in Patent Document 1 is assumed to be installed not only indoors but also outdoors, in which case it is exposed to changes in environmental factors such as temperature and humidity more than indoors. In addition, since the temperature of the refrigerant flowing through the refrigerant pipe is different from the outside air temperature, the temperature of the refrigerant varies depending on the operating conditions of the equipment. In addition, humidity fluctuations occur due to temperature changes. These changes in environmental factors cause slight increases and decreases in the dimensions of the components, changes in the dielectric constant, or changes in the characteristics of the electrical equipment, which causes the measured capacitance value to fluctuate. Since the change in capacitance due to the leakage of the refrigerant is minute, the method described in Patent Document 1 may erroneously detect the leakage of the refrigerant due to changes in capacitance caused by environmental factors.

[0007] Therefore, an object of the present disclosure is to provide a refrigerant leak detection device and a refrigerant leak detection method that can reduce the influence of environmental factors and prevent erroneous detection. [Means for solving the problem]

[0008] The refrigerant leakage detection device disclosed in the present application includes a first electrode arranged on the outer periphery of a thermal insulation material provided on the outer periphery of a refrigerant pipe extending in the flow direction of the refrigerant, a second electrode arranged on the outer periphery of the thermal insulation material and spaced apart from the first electrode in the flow direction of the refrigerant, and a detection unit that detects leakage of the refrigerant based on a first electrode capacitance between the first electrode and the refrigerant pipe and a second electrode capacitance between the second electrode and the refrigerant pipe; a capacitance measuring unit that measures the first electrode capacitance and the second electrode capacitance, and a capacitance calculation unit that is connected to the capacitance measuring unit and has a memory that stores measured values ​​of the first electrode capacitance and the second electrode capacitance, wherein the capacitance calculation unit calculates a relationship between the measured values ​​of the first electrode capacitance and the second electrode capacitance, and the detection unit identifies the electrode from which the refrigerant has leaked based on an increase or decrease in a calculated value obtained by calculating the relationship between the first electrode capacitance and the second electrode capacitance. It is something.

[0009] The refrigerant leakage detection method disclosed in the present application includes a first electrode disposed on the outer periphery of a heat insulating material provided on the outer periphery of a refrigerant pipe extending in the flow direction of the refrigerant; ,before A second electrode disposed on an outer periphery of the thermal insulating material and spaced apart from the first electrode in the flow direction; a first electrode capacitance between the refrigerant tube and the ... The cooling system further includes a detection step of detecting leakage of the refrigerant flowing through the refrigerant pipe based on a second electrode capacitance between the refrigerant pipe and the second electrode. The detection step includes a measurement step of measuring the first electrode capacitance and the second electrode capacitance, a calculation step of calculating a relationship between the measured values ​​of the first electrode capacitance and the second electrode capacitance, and a determination step of identifying the electrode from which the refrigerant has leaked based on an increase or decrease in a calculated value obtained by calculating the relationship between the first electrode capacitance and the second electrode capacitance. . Effect of the Invention

[0010] The refrigerant leak detection device according to the present disclosure includes a detection unit that detects refrigerant leaks based on a first electrode capacitance between the refrigerant pipe and a first electrode disposed in a thermal insulating material covering the refrigerant pipe, and a second electrode capacitance between the refrigerant pipe and a second electrode disposed in a thermal insulating material covering the refrigerant pipe, thereby making it possible to suppress the effects of environmental factors on the detection of refrigerant leaks. [Brief description of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing a refrigerant leakage detection device according to a first embodiment. [Diagram 2] FIG. 4 is a schematic diagram showing a first modified example of the installation of the refrigerant leakage detection device according to the first embodiment. [Diagram 3] 4 is a schematic diagram showing a second modified example of the installation of the refrigerant leakage detection device according to the first embodiment. FIG. [Figure 4] 1 is a schematic diagram showing a surface perpendicular to the longitudinal direction of a refrigerant pipe of a refrigerant leakage detection device according to a first embodiment. FIG. [Diagram 5] 2 is a circuit diagram showing a circuit configuration of a capacitance measurement unit of the refrigerant leakage detection device according to the first embodiment. FIG. [Figure 6] 3 is a flowchart of a refrigerant leakage detection method performed by the refrigerant leakage detection device according to the first embodiment. [Figure 7] 4 is a graph showing an example of the measured values ​​of the first electrode capacitance and the second electrode capacitance acquired from the capacitance measurement unit of the refrigerant leakage detection device according to the first embodiment. [Figure 8]FIG. 11 is a configuration diagram showing a refrigerant leakage detection device according to a second embodiment. [Figure 9] 6 is a flowchart of a refrigerant leakage detection method performed by the refrigerant leakage detection device according to the second embodiment. [Figure 10] 10 is a graph showing an example of the measured values ​​of the first electrode capacitance and the second electrode capacitance acquired from the capacitance measurement unit 5 of the refrigerant leakage detection device according to the second embodiment. [Figure 11] 11 is a graph showing values ​​calculated by a capacitance calculation unit based on the measured values ​​in FIG. 10 . [Figure 12] 10 is a schematic diagram showing a configuration in which a capacitance measurement unit, a capacitance calculation unit, and a detection unit are integrated in a refrigerant leakage detection device according to a second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the refrigerant leakage detection device disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the embodiments described below are merely examples, and the present invention is not limited to these embodiments.

[0013] Embodiment 1 FIG. 1 is a configuration diagram showing a refrigerant leakage detection device 100 according to the first embodiment. As shown in FIG. 1, the refrigerant leakage detection device 100 according to the first embodiment has a detection unit 3, a capacitance measurement unit 5, and a detection unit 6. The detection unit 3 has a first electrode 4a arranged on the outer surface of a thermal insulation material 2 covering a refrigerant tube 1, and a second electrode 4b arranged on the outer surface of the thermal insulation material 2 independently of the first electrode 4a. The capacitance measurement unit 5 measures the capacitance between the refrigerant tube 1 and the detection unit 3. The detection unit 6 detects a refrigerant leakage based on the capacitance between the first electrode 4a and the refrigerant tube 1 and the capacitance between the second electrode 4b and the refrigerant tube 1. Hereinafter, the first electrode 4a and the second electrode 4b may be collectively referred to simply as the electrode 4.

[0014] The refrigerant leak detection device 100 is attached to a refrigerant pipe 1 provided in a refrigeration cycle device such as a refrigerator or an air conditioner. A refrigerant flows through the refrigerant pipe 1. The refrigerant pipe 1 is made of a metal circular pipe. A heat insulating material 2 is provided around the refrigerant pipe 1 to cover the outer surface of the refrigerant pipe 1. The metal constituting the refrigerant pipe 1 is, for example, copper. A temperature difference occurs between the refrigerant flowing inside the refrigerant pipe 1 and the air temperature around the refrigerant pipe 1. In particular, when the refrigerant pipe 1 is placed outdoors, the temperature difference between the refrigerant flowing inside the refrigerant pipe 1 and the air temperature around the refrigerant pipe 1 is larger than when the refrigerant pipe 1 is placed indoors. The heat insulating material 2 covering the refrigerant pipe 1 is provided in consideration of the temperature difference, in order to suppress the temperature of the refrigerant in the refrigerant pipe 1 from changing depending on the air temperature around the refrigerant pipe 1. The refrigerant pipe 1 may be commercially available in a state where it is covered with the heat insulating material 2 in advance. The material constituting the heat insulating material 2 is, for example, foamed polyethylene. In the following description, as shown in FIG. 1, the direction in which the refrigerant pipe 1 extends will be referred to as the "longitudinal direction L" and the radial direction R of the refrigerant pipe 1 perpendicular to the "longitudinal direction L" will be referred to as the "radial direction R" for other components as well.

[0015] The electrodes 4 are attached to the outer periphery of the refrigerant tube 1 through which the refrigerant flows and the insulating material 2 covering the outer surface of the refrigerant tube 1. The electrodes 4 are conductors. Each electrode 4 is configured to sandwich the insulating material 2, which is a dielectric, between the refrigerant tube 1 made of metal, thereby forming a capacitor between the refrigerant tube 1. When the refrigerant leaks from the refrigerant tube 1, the liquid refrigerant or a mixed fluid of the refrigerant and refrigeration oil enters the space between the electrodes 4 and the refrigerant tube 1. The electrodes 4 detect a change in the electrostatic capacitance between the electrodes 4 and the refrigerant tube 1 due to the refrigerant that has entered the space between the electrodes 4 and the refrigerant tube 1.

[0016] The electrode 4 can be selected from, for example, an aluminum thin plate, a stainless steel thin plate, or a copper thin plate. When aluminum is used as the electrode 4, the refrigerant leakage detection device 100 is light, inexpensive, and has good workability. When stainless steel is used as the electrode 4, the refrigerant leakage detection device 100 has good corrosion resistance. When copper is used as the electrode 4, the electrode 4 has good conductivity, so that the change in capacitance is accurately detected. In addition, the shape and the method of attachment of the electrode 4 are not important as long as it can be placed on the surface of the insulating material 2. The electrode 4 may be a metal plate wrapped around the surface of the insulating material 2. In this case, the electrode 4 has a ring or arc shape when viewed in the axial direction of the refrigerant tube 1. The electrode 4 may be, for example, a conductive paste directly applied to the insulating material 2 and hardened. In this case, the electrode 4 is not affected by the dimensions of the refrigerant tube 1 or the insulating material 2, and can be easily attached. The electrode 4 may have, for example, a conductive layer attached to an insulator, or a conductive layer deposited or applied on an insulator. For example, when the electrode 4 is made of a metal foil attached onto a thin insulating film, it is softer than the electrode 4 made of a thin metal plate, and the attachment can be improved. In addition, the insulating film is expected to have an effect of protecting the metal foil, and an electrode 4 that does not deteriorate for a long period of time can be realized. However, it is preferable that there is no gap between the electrode 4 and the surface of the insulating material 2. It is preferable that the electrode 4 is attached so as to go around the outer peripheral surface of the insulating material 2. This is because, in principle, the refrigerant leakage detection device 100 detects an increase in capacitance due to the refrigerant that has entered the space between the electrode 4 and the refrigerant tube 1 when the refrigerant leaks, and therefore, by arranging the electrode 4 so as to go around the refrigerant tube 1, the change in capacitance can be reliably detected.

[0017] The electrode 4 may be made of, for example, a flexible thin metal plate. In this case, the electrode 4 may be wrapped around the insulating material 2 without any gaps and fixed with a conductive tape or adhesive so that the electrode 4 is placed in close contact with the surface of the insulating material. By eliminating the gap between the electrode 4 and the insulating material 2, the distance between the electrode 4 and the refrigerant tube 1 is less likely to change even if the electrode 4 vibrates in accordance with the vibration of the refrigerant tube 1 during operation of the air conditioner, so that fluctuations in capacitance that are a cause of noise are suppressed and false detection is prevented.

[0018] The first electrode 4a and the second electrode 4b constituting the electrode 4 are arranged on the surface of the insulating material 2 covering the refrigerant tube 1. The first electrode 4a and the second electrode 4b are arranged independently. That is, the first electrode 4a and the second electrode 4b are not electrically connected to each other and are insulated. The first electrode 4a and the second electrode 4b are arranged independently with a gap. The first electrode 4a and the second electrode 4b are alternately charged, and the capacitance between the first electrode 4a and the refrigerant tube 1 and the capacitance between the second electrode 4b and the refrigerant tube 1 are measured independently. The first electrode 4a and the second electrode 4b are arranged along the direction in which the refrigerant tube 1 extends. For example, when the refrigerant tube 1 extends in a straight line, the first electrode 4a and the second electrode 4b are arranged in the longitudinal direction L of the refrigerant tube 1.

[0019] Fig. 2 is a schematic diagram showing a first modification of the installation of the refrigerant leak detection device 100 according to the embodiment 1. As shown in Fig. 2, in the first modification of the installation of the refrigerant leak detection device 100, the first electrode 4a and the second electrode 4b are attached to an L-shaped refrigerant pipe 1, and the longitudinal directions L of the first electrode 4a and the second electrode 4b are arranged in directions perpendicular to each other.

[0020] Fig. 3 is a schematic diagram showing a second modification of the installation of the refrigerant leak detection device 100 according to the first embodiment. As shown in Fig. 3, in the second modification of the installation of the refrigerant leak detection device 100, the first electrode 4a and the second electrode 4b are attached to a U-shaped refrigerant pipe 1 and are arranged to face each other. The longitudinal directions L of the first electrode 4a and the second electrode 4b extend parallel to each other. The arrangement of the first electrode 4a and the second electrode 4b is not limited to the arrangement shown in Figs. 1 to 3, and can be changed as appropriate to suit the shape of the refrigerant pipe 1.

[0021] The capacitance measuring unit 5 and the detection unit 6 are provided in, for example, a control device 50. The control device 50 is configured with, for example, a CPU (Central Processing Unit, also called a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)). The control device 50 has a memory configured with, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk), or the like. The control device 50 realizes processing by a program stored in the memory.

[0022] The capacitance measurement unit 5 is electrically connected to the refrigerant tube 1 and the electrode 4 by a pair of terminals 5a. Each terminal is formed of, for example, a pin. The capacitance measurement unit 5 measures the capacitance between the electrode 4 and the refrigerant tube 1 connected by the terminals 5a. The capacitance measurement unit 5 is disposed in a position close to the electrode 4.

[0023] It is desirable that the wiring extending from the terminal 5a connecting the capacitance measurement unit 5 and the refrigerant pipe 1, and the wiring extending from the terminal 5a connecting the capacitance measurement unit 5 and the electrode 4 are as short as possible. The capacitance measured by the capacitance measurement unit 5 includes the stray capacitance of the wiring, but the stray capacitance of the wiring is unnecessary for detecting refrigerant leakage. In addition, if the wiring is long, it is easily affected by electromagnetic noise through the wiring. By arranging the capacitance measurement unit 5 and the electrode 4 at a position where the wiring can be shortened, the stray capacitance and electromagnetic noise of the wiring, which are factors in false detection, can be reduced. However, the capacitance measurement unit 5 and the electrode 4 are arranged at a distance so that the capacitance measurement unit 5 and the electrode 4 do not come into direct contact with each other. By separating the main body of the capacitance measurement unit 5 from the electrode 4, the effect on the capacitance due to the conduction between the main body of the capacitance measurement unit 5 and the electrode 4 is prevented, and false detection of refrigerant leakage is reduced.

[0024] The capacitance measuring unit 5 may be disposed at a position shifted either upstream or downstream in the refrigerant flow direction from the installation position of the electrode 4 along the longitudinal direction L of the refrigerant pipe 1 so that the capacitance measuring unit 5 and the electrode 4 do not overlap. Also, the capacitance measuring unit 5 is preferably disposed and attached from above the insulating material 2 so as to be fixed to the refrigerant pipe 1 and the insulating material 2. By disposing the capacitance measuring unit 5 on the outer surface of the insulating material 2, it is possible to detect a refrigerant leak without the need to remove the insulating material 2.

[0025] The detection unit 6 is electrically connected to the capacitance measurement unit 5. The detection unit 6 compares the capacitance between the first electrode 4a and the refrigerant pipe 1 obtained by the capacitance measurement unit 5 with the capacitance between the second electrode 4b and the refrigerant pipe 1 to detect refrigerant leakage.

[0026] Next, the operating principle of the refrigerant leak detection device 100 according to the first embodiment for detecting a refrigerant leak will be described with reference to Fig. 4. Fig. 4 is a schematic diagram showing a surface perpendicular to the longitudinal direction L of the refrigerant tube 1 of the refrigerant leak detection device 100 according to the first embodiment. A mixed fluid of refrigerant and refrigeration oil flows inside the metal refrigerant tube 1. The refrigerant tube 1, the insulating material 2, and the electrode 4 form a capacitor. That is, the refrigerant tube 1, the insulating material 2, and the first electrode 4a form a first capacitor C1, and the refrigerant tube 1, the insulating material 2, and the second electrode 4b form a second capacitor C2.

[0027] As shown in Fig. 4, a small gap 14 is formed between the refrigerant pipe 1 and the insulating material 2. Therefore, a capacitor is formed between the electrode 4 and the gap 14, and between the gap 14 and the refrigerant pipe 1, and these two capacitors can be considered as being connected in series. In this case, if we assume that the width g of the gap 14 in the radial direction R is uniform over the entire circumference of the refrigerant pipe 1, the capacitance C of the capacitor is the capacitance C between the electrode 4 and the gap 14. ins and the capacitance C between the gap 14 and the refrigerant pipe 1 gap Therefore, the capacitance is expressed by the following equations 1 to 3.

[0028]

number

number

number

[0029] where ε0 is the dielectric constant of air, ε ins is the relative dielectric constant of the insulating material 2, L is the width in the longitudinal direction L of the electrode 4, D1 is the outer diameter of the refrigerant tube 1, D2 is the inner diameter of the electrode 4, and g is the width in the radial direction R of the gap 14.

[0030] When a pinhole or crack occurs in the refrigerant pipe 1 due to aging or other factors, causing a refrigerant leak, a fluid such as a refrigerant or refrigeration oil flows out of the refrigerant pipe 1 and flows into the gap between the refrigerant pipe 1 and the electrode 4. The relative dielectric constant of the fluid such as a refrigerant or refrigeration oil that flows into the gap between the refrigerant pipe 1 and the electrode 4 is greater than the dielectric constant of air. Therefore, when this fluid accumulates in the gap 14 between the refrigerant pipe 1 and the insulation material 2, the capacitance C between the refrigerant pipe 1 and the gap 14 increases. gap increases, and accordingly, the capacitance C between the refrigerant pipe 1, the insulating material 2, and the electrode 4 increases. Then, in the detection unit 6, the presence or absence of a refrigerant leak is determined based on the capacitance C obtained by the capacitance measurement unit 5.

[0031] Next, the configuration and operation of the capacitance measuring unit 5 will be described.

[0032] 5 is a circuit diagram showing a circuit configuration of the capacitance measurement unit 5 of the refrigerant leakage detection device 100 according to embodiment 1. As shown in FIG. 5, the capacitance measurement unit 5 includes a charge / discharge circuit 11, a counter circuit 12, and a count measurement unit 13.

[0033] The charge / discharge circuit 11 includes a power source 9, a first switch 10a, and a second switch 10b. The power source 9 is a constant current source. One end of the first switch 10a is connected to the power source 9, and the other end is connected to the first electrode 4a. A first capacitor C1 is formed on the first switch 10a side, and has a first electrode capacitance 8a. One end of the second switch 10b is connected to the power source 9, and the other end is connected to the second electrode 4b. A second capacitor C2 is formed on the second switch 10b side, and a second electrode capacitance 8b is generated. The first switch 10a and the second switch 10b are connected at a connection point. The other ends of the first electrode 4a and the second electrode 4b are connected to the refrigerant tube 1 via the first capacitor C1 and the second capacitor C2. The refrigerant tube 1 is grounded.

[0034] The charge / discharge circuit 11 operates so that either the first switch 10a or the second switch 10b is turned ON and the other is turned OFF according to the voltage value of the electrode 4. When the first switch 10a is ON and the second switch 10b is OFF, the first capacitor C1 is charged by the current output from the power source 9, and the voltage of the first electrode 4a increases. This state is called the first state. On the other hand, when the first switch 10a is OFF and the second switch 10b is ON, the second capacitor C2 is charged by the current output from the power source 9, and the voltage of the second electrode 4b increases. This state is called the second state. In the charge / discharge circuit 11, the first state and the second state are alternately switched to maintain the voltage of the electrode 4 within a preset range. In addition, it is desirable that the time required for switching between the first state and the second state is shorter than the time required for an environmental factor that affects the capacitance to change.

[0035] The time for an environmental factor to change is, for example, the time that is considered to be required for an environmental factor to change beyond a certain fluctuation range, as described below. The time for an environmental factor to change is determined by the operating conditions of a refrigeration cycle device such as a refrigerator or air conditioner, seasonal temperature and humidity fluctuations, the temperature difference between the refrigerant flowing through the refrigerant pipe 1 and the outside air, the temperature difference of the refrigerant due to changes in the operating conditions of the device, and humidity fluctuations due to changes in the outside air temperature.

[0036] The counter circuit 12 counts the number of times the first switch 10a is turned ON within a preset fixed period of time. The fixed period is at least longer than the time it takes for the environmental factors to change. The number counted by the counter circuit 12 changes depending on the capacitance C of the capacitor generated between the refrigerant tube 1 and the electrode 4. Specifically, when the capacitance C of the capacitor increases, the count decreases, and when the capacitance C of the capacitor decreases, the count increases.

[0037] The count number is input from the counter circuit 12 to the count measurement unit 13 as a count signal. A conversion formula for converting the count number into the capacitance of a capacitor is stored in the count measurement unit 13. The conversion formula is expressed by, for example, the following Equation 4. The count measurement unit 13 calculates the capacitance of the capacitor from the count number using the conversion formula.

[0038]

number

[0039] Here, C is the capacitance of the capacitor, A and B are correction coefficients determined by the operating conditions of the charge / discharge circuit 11, and Counts is the number of counts.

[0040] In this manner, the capacitance C of the capacitor is calculated by the count measurement unit 13, and becomes the measurement value of the first electrode capacitance 8a and the second electrode capacitance 8b measured by the capacitance measurement unit 5.

[0041] Although the counter circuit 12 has been described as counting the number of times the first switch 10a is turned ON, the present invention is not limited to this case, and the counter circuit 12 may count the number of times the second switch 10b is turned ON.

[0042] Furthermore, counter circuit 12 may count other things as long as the number of counts varies according to the capacitance C of the capacitor. For example, counter circuit 12 may be configured to obtain the fluctuation range of the capacitor voltage, i.e., the voltage at the connection point, by experiment or the like, and set the median between the maximum and minimum values ​​of the fluctuation range as the threshold. In this case, counter circuit 12 counts the number of times the voltage at the connection point exceeds the threshold during a preset fixed period.

[0043] The capacitance measurement unit 5 can be configured using, for example, a microcontroller. That is, the count measurement unit 13, the counter circuit 12, and the charge / discharge circuit 11 that configure the capacitance measurement unit 5 can be configured with one microcontroller. Since the microcontroller is an inexpensive and small component, the capacitance measurement unit 5 can be configured compactly and at low cost.

[0044] The capacitance measuring unit 5 may be configured as a whole by one microcontroller, but is not limited to this configuration. That is, the capacitance measuring unit 5 may be configured as a part by one microcontroller, and the other part by other parts.

[0045] Also, in the above description, the capacitance measurement unit 5 calculates the capacitance C of the capacitor using the count measurement unit 13, but this process does not necessarily have to be performed in the capacitance measurement unit 5. For example, the count measurement unit 13 may not be provided in the capacitance measurement unit 5, and the capacitance measurement unit 5 may transmit the count value counted by the counter circuit 12 to the detection unit 6. In other words, the detection unit 6 may take on the function of the count measurement unit 13. In this case, the detection unit 6 calculates the capacitance C of the capacitor based on the count value instead of the count measurement unit 13, and determines whether or not there is a refrigerant leak based on the calculated capacitance C.

[0046] The capacitance may be calculated using a conversion formula such as the above-mentioned equation 4, for example. The detection unit 6 may be configured to directly read the count value transmitted from the capacitance measurement unit 5 as a signal that changes according to the capacitance C, without calculating the capacitance C, and detect a refrigerant leak. If the capacitance measurement unit 5 is configured without the count measurement unit 13, the number of parts used as the count measurement unit 13 in the refrigerant leak detection device 100 can be reduced, and the manufacturing cost of the refrigerant leak detection device 100 can be reduced. Furthermore, not only the count measurement unit 13, but also other members constituting the capacitance measurement unit 5 may be shared with the detection unit 6.

[0047] Furthermore, the capacitance measurement unit 5 and the detection unit 6 may be integrated. In that case, the capacitance measurement unit 5 and the detection unit 6 are formed of the same circuit and arranged on the same board. When the capacitance measurement unit 5 and the detection unit 6 are integrated, some of the components of the capacitance measurement unit 5 or the detection unit 6 are shared between the capacitance measurement unit 5 and the detection unit 6. This makes it possible to reduce the number of components required to configure the refrigerant leak detection device 100, thereby reducing the manufacturing cost of the refrigerant leak detection device 100 and making it more compact.

[0048] 5 as long as it can measure the capacitance C of the capacitor or a physical quantity that varies according to the capacitance C. The capacitance measuring unit 5 may be configured, for example, with an auto-balancing bridge circuit or a circuit using a Wheatstone bridge.

[0049] Fig. 6 is a flowchart of a refrigerant leakage detection method by the refrigerant leakage detection device 100 according to the first embodiment. As shown in Fig. 6, the refrigerant leakage detection method has a detection step S01. The detection step S01 is performed by, for example, the control device 50. In the detection step S01, the control device 50 detects a refrigerant leakage based on the first electrode capacitance 8a and the second electrode capacitance 8b.

[0050] The detection step S01 includes, for example, a measurement step S11 and a determination step S12. In the measurement step S11, the control device 50 measures and acquires the first electrode capacitance 8a and the second electrode capacitance 8b at regular time intervals using the capacitance measurement unit 5. In the determination step S12, the control device 50 determines whether or not there is a refrigerant leak based on the measurement values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b acquired in the measurement step S11 using the detection unit 6. Note that the detection step S01 may be periodically repeated, for example, when a refrigeration cycle device such as a refrigerator or air conditioner to which the refrigerant leakage detection device 100 is attached is operating or stopped.

[0051] Fig. 7 is a graph showing an example of the measured values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b acquired from the capacitance measurement unit 5 of the refrigerant leakage detection device 100 according to embodiment 1. In Fig. 7, the horizontal axis represents time, and the vertical axis represents capacitance.

[0052] As shown in FIG. 7, when there is no refrigerant leakage between the first electrode 4a and the refrigerant tube 1 and between the second electrode 4b and the refrigerant tube 1, the first electrode capacitance 8a and the second electrode capacitance 8b show similar fluctuations because they are affected by similar environmental factors. On the other hand, when there is refrigerant leakage between the first electrode 4a and the refrigerant tube 1, the first electrode capacitance 8a increases. Since the relative dielectric constant of the refrigerant or the refrigeration oil is larger than the dielectric constant of air, the first electrode capacitance 8a where there is refrigerant leakage is affected by the refrigerant leakage, and a difference occurs between the first electrode capacitance 8a affected by the refrigerant leakage and the second electrode capacitance 8b not affected by the refrigerant leakage. Therefore, the detection unit 6 determines the leakage of the refrigerant based on the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b. That is, the detection unit 6 can determine that there is a refrigerant leakage when the first electrode capacitance 8a and the second electrode capacitance 8b have a certain magnitude relationship.

[0053] In addition, the detection unit 6 may be configured to immediately determine that there is a refrigerant leak from the refrigerant tube 1 based on the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b in determining whether or not there is a refrigerant leak. The detection unit 6 may also be configured to determine that there is a refrigerant leak from the refrigerant tube 1 when the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b, which determines that there is a refrigerant leak, continues for a preset certain period of time. Since capacitance is easily affected by noise, if a large change in capacitance is detected instantaneously due to the influence of noise, there is a possibility of erroneous detection if the presence or absence of a refrigerant leak is determined based on the measured value of the transient capacitance. Therefore, even if the detection unit 6 detects the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b, it does not immediately determine that there is a refrigerant leak, but monitors whether the state continues for a certain period of time. With this configuration, the detection unit 6 can suppress erroneous detection due to noise and more accurately detect the refrigerant leak.

[0054] Below is a description of the influence of environmental factors that may impair the detection accuracy of the refrigerant leak detection device 100. When the refrigerant leak detection device 100 is attached to an indoor air conditioner, it is exposed to changes in temperature and humidity due to the operating status of the air conditioner and seasonal changes. The refrigerant leak detection device 100 can also be attached to an outdoor air conditioner, not just an indoor air conditioner, in which case it is exposed to even more changes in environmental factors such as temperature and humidity than an indoor air conditioner.

[0055] As described above, capacitance occurs when two or more conductors are arranged insulated with a dielectric between them, and the value of the capacitance in this case is determined by the dielectric constant of the dielectric and the geometric shape of the conductors. The refrigerant leak detection device 100 is configured such that two conductors, a refrigerant tube 1 and an electrode 4, are arranged insulated with a dielectric insulating material 2 between them. Therefore, the capacitance between the refrigerant tube 1 and the electrode 4 varies depending on the dielectric constant of the insulating material 2 and the geometric shape of the refrigerant tube 1 and the electrode 4.

[0056] The dielectric constant of the insulating material 2, which is a dielectric, changes due to a change in the amount of moisture that the insulating material 2 can hold due to a change in the surrounding humidity, or due to a change in the amount of moisture contained in the gap 14 between the refrigerant tube 1 and the insulating material 2 due to a change in the surrounding humidity. In addition, when the surrounding air temperature changes, at least one of the electrode 4 and the refrigerant tube 1, which are conductors, expands or contracts, changing the dimensions or shape, and thus changing their geometric shape. Therefore, in a configuration in which the refrigerant tube 1 and the electrode 4, which are two conductors, sandwich the insulating material 2, which is a dielectric, even if there is no refrigerant leakage, the capacitance between the refrigerant tube 1 and the electrode 4 will fluctuate due to minute changes caused by the influence of environmental factors between the refrigerant tube 1, the electrode 4, and the insulating material 2.

[0057] It is considered that the first electrode 4a and the second electrode 4b in the refrigerant leak detection device 100 are affected by similar environmental factors. Therefore, in a steady state where there is no refrigerant leakage, the first electrode capacitance 8a and the second electrode capacitance 8b show similar fluctuations caused by the influence of similar environmental factors. On the other hand, for example, when refrigerant leaks between the first electrode 4a and the refrigerant tube 1, the first electrode capacitance 8a fluctuates due to the influence of the refrigerant leakage in addition to the influence of the environmental factors, and therefore shows a different fluctuation from the second electrode capacitance 8b that is not affected by the refrigerant leakage.

[0058] Therefore, in the first embodiment, by comparing the first electrode capacitance 8a and the second electrode capacitance 8b, it is possible to derive the change in capacitance caused by the refrigerant leakage. By observing the fluctuations in the first electrode capacitance 8a and the second electrode capacitance 8b, the fluctuations in capacitance caused by environmental factors are eliminated, and the leakage of the refrigerant is detected based on the change in capacitance caused by the leakage of the refrigerant.

[0059] According to the refrigerant leakage detection device 100 according to the first embodiment described above, the detection unit 6 determines whether or not a refrigerant is leaking based on the first electrode capacitance 8a between the first electrode 4a and the refrigerant tube 1 and the second electrode capacitance 8b between the second electrode 4b and the refrigerant tube 1. As shown in Figs. 1 to 3, the first electrode 4a and the second electrode 4b are arranged in pairs and are independent of each other with a space therebetween, and are therefore affected by similar environmental factors. In addition, the first electrode 4a and the second electrode 4b are not electrically connected and are independent of each other. In a steady state in which no refrigerant is leaking, the first electrode capacitance 8a between the first electrode 4a and the refrigerant tube 1 and the second electrode capacitance 8b between the second electrode 4b and the refrigerant tube 1 show similar fluctuations. Therefore, the amount of change in capacitance due to the influence of environmental factors is eliminated by comparing the first electrode capacitance 8a and the second electrode capacitance 8b. Therefore, the refrigerant leak detection device 100 detects refrigerant leaks by extracting only the change in capacitance caused by refrigerant leakage from a comparison of the first electrode capacitance 8a and the second electrode capacitance 8b, thereby preventing erroneous detection and contributing to more accurate and precise detection of refrigerant leaks.

[0060] Moreover, by evaluating the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b, it is possible to identify the electrode 4 in which the refrigerant is leaking.

[0061] Furthermore, the number of electrodes 4 installed in the entire refrigerant pipe 1 can be reduced, reducing the cost of the refrigerant leakage detection device 100, and also allowing for some degree of likelihood in the placement locations.

[0062] Furthermore, in the refrigerant leak detection device 100, the electrode 4 is arranged on the outer surface of the insulating material 2 that covers the outer surface of the refrigerant pipe 1, making it easy to attach the electrode 4 to the refrigerant pipe 1. Furthermore, because the electrode 4 is arranged on the outer surface of the insulating material 2, there is no need to destroy the insulating material 2 in order to forcibly attach the electrode 4 directly to the refrigerant pipe 1. Furthermore, since the capacitance measurement unit 5 is arranged opposite the outer surface of the electrode 4, the capacitance measurement unit 5 is arranged adjacent to the outer surface of the electrode 4, making it easy to attach the capacitance measurement unit 5 to the refrigerant pipe 1.

[0063] In particular, when the first electrode 4a and the second electrode 4b are configured in the form of a flexible thin film, the first electrode 4a and the second electrode 4b can be easily attached to existing piping.

[0064] Furthermore, the detection unit 3 is composed of two independent electrodes, the first electrode 4a and the second electrode 4b, which are arranged with a gap between them. This allows the distance between the first electrode 4a and the second electrode 4b to be set arbitrarily, and also makes it possible to make the effects of environmental factors on the first electrode 4a and the second electrode 4b similar, thereby making it possible to suppress the effects of environmental factors.

[0065] In addition, the first electrode 4a and the second electrode 4b are connected to a capacitance measuring unit 5, and the first electrode capacitance 8a and the second electrode capacitance 8b are alternately measured. By alternately measuring the two first electrodes 4a and the second electrodes 4b using one capacitance measuring unit 5, the amount of variation in capacitance value caused by the influence of environmental factors can be made equal for the two first electrodes 4a and the second electrodes 4b.

[0066] Furthermore, the time required to measure the first electrode capacitance 8a and the second electrode capacitance 8b is shorter than the time required for the environmental factors to change, so that the first electrode capacitance 8a and the second electrode capacitance 8b can be measured with the influence of the environmental factors suppressed.

[0067] It is also advisable to shorten as much as possible the length of the wiring between the capacitance measurement unit 5 and the electrode 4, and the wiring between the capacitance measurement unit 5 and the refrigerant pipe 1. This reduces the effect of stray capacitance of the wiring and electromagnetic noise on the detection value, improving the accuracy of refrigerant leakage detection.

[0068] Embodiment 2 8 is a configuration diagram showing a refrigerant leakage detection device 200 according to embodiment 2. The refrigerant leakage detection device 200 according to embodiment 2 differs from embodiment 1 in that it has a capacitance calculation unit 7 that calculates the ratio between a first electrode capacitance 8a and a second electrode capacitance 8b. The other configuration is the same as embodiment 1, so detailed description of components that correspond to or are equivalent to those in embodiment 1 will be omitted.

[0069] 8, refrigerant leakage detection device 200 of embodiment 2 has a detection unit 3, a capacitance measurement unit 5, a capacitance calculation unit 7, and a detection unit 6. As in embodiment 1, detection unit 3 has a first electrode 4a arranged on the outer surface of insulation material 2 covering refrigerant pipe 1, and a second electrode 4b arranged independently of the first electrode 4a on the outer surface of insulation material 2. As in embodiment 1, capacitance measurement unit 5 measures a first electrode capacitance 8a between the first electrode 4a and refrigerant pipe 1, and a second electrode capacitance 8b between the second electrode 4b and refrigerant pipe 1.

[0070] The capacitance calculation unit 7 acquires the measurement values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b from the capacitance measurement unit 5, and calculates the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b. The capacitance calculation unit 7 is connected to the capacitance measurement unit 5, and includes a memory that stores the measurement values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b acquired by the capacitance measurement unit 5. The capacitance calculation unit 7 calculates the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b from the measurement values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b stored in the memory, and outputs the calculated value to the detection unit 6.

[0071] A threshold value for the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b is set in advance and stored in the detection unit 6. The detection unit 6 determines the presence or absence of a refrigerant leak based on the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b output from the capacitance calculation unit 7. The detection unit 6 determines that a refrigerant leak has occurred from the refrigerant pipe 1 when the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b obtained from the capacitance calculation unit 7 exceeds a threshold value q.

[0072] Fig. 9 is a flowchart of a refrigerant leakage detection method by the refrigerant leakage detection device 200 according to the second embodiment. As shown in Fig. 9, the refrigerant leakage detection method has a detection step S02. The detection step S02 is performed by, for example, the control device 50. In the detection step S02, the control device 50 detects a refrigerant leakage based on the first electrode capacitance 8a and the second electrode capacitance 8b.

[0073] The detection step S02 includes, for example, a measurement step S21, a calculation step S22, and a determination step S23. In the measurement step S21, the control device 50 measures the first electrode capacitance 8a and the second electrode capacitance 8b at regular time intervals using the capacitance measurement unit 5. In the calculation step S22, the control device 50 calculates a ratio between the first electrode capacitance 8a and the second electrode capacitance 8b measured in the measurement step S21 using the capacitance calculation unit 7. In the determination step S23, the control device 50 determines whether or not there is a refrigerant leak based on a comparison between the ratio calculated in the calculation step S22 and a pre-stored threshold value using the detection unit 6.

[0074] Fig. 10 is a graph showing an example of the measured values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b acquired from the capacitance measurement unit 5 of the refrigerant leakage detection device 200 according to the second embodiment. In Fig. 10, the horizontal axis indicates time, and the vertical axis indicates capacitance. As shown in Fig. 10, for example, when a refrigerant leak occurs at the first electrode 4a, the relative dielectric constant of the refrigerant or refrigeration oil is greater than the dielectric constant of air, so the first electrode capacitance 8a increases. The measured values ​​by the capacitance measurement unit 5 show a difference between the first electrode capacitance 8a when there is a refrigerant leak and the second electrode capacitance 8b when there is no refrigerant leak.

[0075] FIG. 11 is a graph showing the calculated values ​​calculated by the capacitance calculation unit 7 from the measured values ​​of FIG. 10. In FIG. 11, the horizontal axis indicates time, and the vertical axis indicates the ratio of the first electrode capacitance 8a to the second electrode capacitance 8b. As shown in FIG. 11, the capacitance calculation unit 7 calculates the ratio of the first electrode capacitance 8a to the second electrode capacitance 8b from the measured values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b measured by the capacitance measurement unit 5. The ratio of the first electrode capacitance 8a to the second electrode capacitance 8b is compared with a pre-stored threshold value in the detection unit 6. When refrigerant leakage occurs in the first electrode capacitance 8a, the ratio of the first electrode capacitance 8a to the second electrode capacitance 8b without refrigerant leakage increases. The detection unit 6 determines the presence or absence of refrigerant leakage from the refrigerant pipe 1 by comparing the ratio of the first electrode capacitance 8a to the second electrode capacitance 8b without refrigerant leakage with a threshold value.

[0076] As in the first embodiment, the refrigerant leak detection device 200 is exposed to changes in environmental factors such as temperature or humidity, causing fluctuations in the capacitance between the refrigerant tube 1 and the electrode 4. For example, when the temperature changes, at least one of the electrode 4 and the refrigerant tube 1 expands or contracts, causing the dimensions or shapes of the electrode 4 and the refrigerant tube 1 to change. This causes the outer diameter D1 of the refrigerant tube 1, the inner diameter D2 of the electrode 4, and the width g of the radial direction R of the gap 14 in the above-mentioned mathematical expression 1 to change. Also, for example, when the ambient humidity changes, the amount of moisture held in the insulating material 2, which is a dielectric, or the amount of moisture contained in the gap 14 between the refrigerant tube 1 and the insulating material 2 changes, causing the relative dielectric constant ε of the insulating material 2 in the above-mentioned mathematical expression 1 to change. ins changes.

[0077] In this way, when there is a change in the environmental factors, the outer diameter D1 of the refrigerant pipe 1, the inner diameter D2 of the electrode 4, the width g of the gap 14 in the radial direction R, or the relative dielectric constant ε of the insulating material 2 in the formula 1 changes with the change in the environmental factors. ins Therefore, in a configuration in which the refrigerant pipe 1 and the electrode 4, which are two conductors, sandwich the insulating material 2, which is a dielectric, even if there is no refrigerant leakage, the capacitance will fluctuate due to minute changes that occur in the refrigerant pipe 1, the electrode 4, and the insulating material 2 due to the influence of environmental factors.

[0078] As shown in FIG. 10, the amount of change in the first electrode capacitance 8a and the second electrode capacitance 8b may change relative to the absolute value of the first electrode capacitance 8a and the second electrode capacitance 8b. For example, assume that the first electrode capacitance 8a between the first electrode 4a and the refrigerant pipe 1 is 10 pF, and the second electrode capacitance 8b between the second electrode 4b and the refrigerant pipe 1 is 20 pF. If it is assumed that the first electrode capacitance 8a and the second electrode capacitance 8b increase by 10% due to a change in the environmental factor, the first electrode capacitance 8a is 11 pF, and the second electrode capacitance 8b is 22 pF. The difference between the first electrode capacitance 8a and the second electrode capacitance 8b before the change in the environmental factor is 10 pF, whereas the difference between the first electrode capacitance 8a and the second electrode capacitance 8b after the change in the environmental factor is 11 pF. That is, before and after the change in the environmental factor, the change in the first electrode capacitance 8a is 1 pF and the change in the second electrode capacitance 8b is 2 pF, so that the change in each changes relatively, and the difference between the first electrode capacitance 8a and the second electrode capacitance 8b also changes. Therefore, even if there is no leakage of the refrigerant, the difference between the first electrode capacitance 8a and the second electrode capacitance 8b before and after the change in the environmental factor changes.

[0079] 11, when the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b is calculated, if there is no refrigerant leakage, the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b will be equal before and after the change in the environmental factor. Therefore, in the second embodiment, by calculating the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, it is possible to remove the change in capacitance due to the environmental factor and detect the change in the first electrode capacitance 8a and the second electrode capacitance 8b due to the leakage of the refrigerant.

[0080] In addition, the electrode from which the refrigerant is leaking can be identified by detecting an increase or decrease in the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b. For example, if the ratio is calculated by dividing the first electrode capacitance 8a by the second electrode capacitance 8b, it can be determined that the refrigerant is leaking from the first electrode 4a if the ratio increases, and that the refrigerant is leaking from the second electrode 4b if the ratio decreases.

[0081] In the above description, the capacitance calculation unit 7 outputs a calculated value obtained by calculating the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b obtained by the capacitance measurement unit 5 to the detection unit 6, and the detection unit 6 determines whether or not there is a refrigerant leak; however, this is not limiting. The capacitance calculation unit 7 may be configured to calculate, for example, a rate of change in the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, and the detection unit 6 may determine whether or not there is a refrigerant leak.

[0082] FIG. 12 is a schematic diagram showing a configuration in which the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 are integrated in the refrigerant leakage detection device 200 according to the second embodiment. As shown in FIG. 12, the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 may be integrated as the device main body 20. In that case, the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 may be formed in the same circuit and disposed on the same substrate. When the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 are integrated, some of the components can be shared by the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6. Therefore, the number of components required for the configuration of the refrigerant leakage detection device 200 can be reduced, and the manufacturing cost of the refrigerant leakage detection device 200 can be reduced and the device can be made compact.

[0083] According to the refrigerant leakage detection device 200 according to the second embodiment described above, the leakage of the refrigerant is detected using the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b. The first electrode 4a and the second electrode 4b are arranged independently with a space therebetween, and the first electrode capacitance 8a between the first electrode 4a and the refrigerant tube 1 and the second electrode capacitance 8b between the second electrode 4b and the refrigerant tube 1 vary due to the influence of similar environmental factors. Therefore, in the second embodiment, the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b is obtained to remove the variation in capacitance due to environmental factors, and the variation between the first electrode capacitance 8a and the second electrode capacitance 8b due to the leakage of the refrigerant can be detected. This prevents the refrigerant leakage detection device 200 from making a false detection, contributing to improved accuracy and precision.

[0084] Furthermore, the capacitance calculation unit 7 stores the measured values ​​of the first electrode capacitance 8a and the second electrode capacitance 8b, and calculates the relationship between the first electrode capacitance 8a and the first electrode capacitance 8b. Therefore, the first electrode capacitance 8a and the second electrode capacitance 8b can be compared with each other.

[0085] In addition, the detection unit 6 can determine whether a refrigerant leakage state has been detected from the first electrode 4a or the second electrode 4b based on an increase or decrease in the calculated value calculated in the capacitance calculation unit 7 based on relationships such as the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b.

[0086] Furthermore, the capacitance calculation unit 7 may be configured to calculate the rate of change of the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b. This cancels the amount of capacitance fluctuation caused by the influence of environmental factors, prevents erroneous detection by the refrigerant leak detection device 200, and contributes to improving the accuracy and precision of the refrigerant leak detection device 200.

[0087] Furthermore, the detection unit 6 may be configured to set a threshold value for the ratio of the first electrode capacitance 8a to the second electrode capacitance 8b, and detect a refrigerant leak when the threshold value is exceeded. This prevents erroneous detection by the refrigerant leak detection device 200, contributing to improved accuracy and precision of the refrigerant leak detection device 200.

[0088] Furthermore, the detection unit 6 may be configured to set a threshold value for the rate of change of the ratio of the first electrode capacitance 8a to the second electrode capacitance 8b, and detect a refrigerant leak when the threshold value is exceeded. This prevents erroneous detection by the refrigerant leak detection device 200, contributing to improved accuracy and precision of the refrigerant leak detection device 200.

[0089] In addition, the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 are disposed close to the detection unit 3. Therefore, the wiring connecting the detection unit 3, the capacitance calculation unit 7, and the detection unit 6 can be shortened, and the influence of the capacitance value of the wiring can be reduced.

[0090] Furthermore, the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 may be integrated into a refrigerant leakage detection circuit, thereby reducing the volume of the refrigerant leakage detection device 200 and enabling space saving.

[0091] The other effects are the same as those of the refrigerant leak detection device 100 of the first embodiment, so detailed explanations of components that correspond to or are equivalent to those of the first embodiment will be omitted here. [Explanation of symbols]

[0092] 1 Refrigerant pipe, 2 insulation material, 3 detection unit, 4 electrode, 4a first electrode, 4b second electrode, 5 capacitance measurement unit, 5a terminal, 6 detection unit, 7 capacitance calculation unit, 8a first electrode capacitance, 8b second electrode capacitance, 9 power supply, 10a first switch, 10b second switch, 11 charge / discharge circuit, 12 counter circuit, 13 count measurement unit, 14 gap, 20 device main body, 50 control device, 100 refrigerant leak detection device, 200 refrigerant leak detection device.

Claims

1. a first electrode disposed on an outer periphery of a heat insulating material provided on an outer periphery of a refrigerant pipe extending in a flow direction of the refrigerant; a second electrode disposed on an outer periphery of the thermal insulation material and spaced apart from the first electrode in a flow direction of the refrigerant; a detection unit that detects leakage of the refrigerant based on a first electrode capacitance between the first electrode and the refrigerant pipe and a second electrode capacitance between the second electrode and the refrigerant pipe; a capacitance measuring unit for measuring the first electrode capacitance and the second electrode capacitance; a capacitance calculation unit connected to the capacitance measurement unit and including a memory for storing measured values ​​of the first electrode capacitance and the second electrode capacitance; the capacitance calculation unit calculates a relationship between the measured values ​​of the first electrode capacitance and the second electrode capacitance, The detection unit identifies the electrode from which the refrigerant has leaked based on an increase or decrease in a calculated value obtained by calculating a relationship between the first electrode capacitance and the second electrode capacitance. Refrigerant leak detection device.

2. 2. The refrigerant leakage detection device according to claim 1, wherein the first electrode and the second electrode are connected to the capacitance measuring unit, and the capacitance between the first electrode and the refrigerant pipe and the capacitance between the second electrode and the refrigerant pipe are alternately measured.

3. 3. The refrigerant leakage detection device according to claim 1, wherein the capacitance measuring unit measures the first electrode capacitance and the second electrode capacitance in a time shorter than a time for which an environmental factor affecting the capacitance changes.

4. 4. The refrigerant leakage detection device according to claim 1, wherein the capacitance calculation unit calculates a ratio between the first electrode capacitance and the second electrode capacitance.

5. The refrigerant leakage detection device according to any one of claims 1 to 4, wherein the capacitance calculation unit calculates a rate of change of a ratio between the first electrode capacitance and the second electrode capacitance.

6. a threshold value of the ratio between the first electrode capacitance and the second electrode capacitance is stored in the detection unit, 5. The refrigerant leakage detection device according to claim 4, wherein the detection unit detects a refrigerant leakage when the ratio between the first electrode capacitance and the second electrode capacitance calculated by the capacitance calculation unit exceeds a threshold value of the ratio.

7. the detection unit sets a threshold value for a rate of change of the ratio between the first electrode capacitance and the second electrode capacitance, 6. The refrigerant leakage detection device according to claim 5, wherein a refrigerant leakage is detected when a rate of change of the ratio between the first electrode capacitance and the second electrode capacitance calculated by the capacitance calculation unit exceeds a threshold value of the rate of change of the ratio.

8. The refrigerant leakage detection device according to any one of claims 1 to 7, wherein the capacitance measurement unit, the capacitance calculation unit, and the detection unit are arranged in close proximity to the first electrode and the second electrode.

9. The refrigerant leakage detection device according to any one of claims 1 to 8, further comprising a refrigerant leakage detection circuit in which the capacitance measurement unit, the capacitance calculation unit, and the detection unit are integrated.

10. The first electrode and the second electrode are The refrigerant leakage detection device according to any one of claims 1 to 9, which is independently arranged on an outer surface of the insulation material.

11. The refrigerant leakage detection device according to any one of claims 1 to 10, wherein the first electrode and the second electrode are paired to form a detection section.

12. The refrigerant leakage detection device according to any one of claims 1 to 11, wherein the first electrode and the second electrode are wound around the outer surface of the insulation material and are configured as annular or arc-shaped electrodes when viewed in the axial direction of the refrigerant pipe.

13. 13. The refrigerant leakage detection device according to claim 1, wherein the first electrode and the second electrode are formed of flexible thin-film conductive electrodes.

14. The refrigerant leakage detection device according to any one of claims 1 to 13, further comprising a gap between the first electrode and the second electrode.

15. a detection step of detecting leakage of the refrigerant flowing through the refrigerant pipe based on a first electrode disposed on the outer periphery of a thermal insulation material provided on the outer periphery of a refrigerant pipe extending in a flow direction of the refrigerant, a second electrode disposed on the outer periphery of the thermal insulation material and spaced apart from the first electrode in the flow direction, and a first electrode capacitance between the first electrode and the refrigerant pipe, and a second electrode capacitance between the first electrode and the refrigerant pipe, The detection step includes: a measuring step of measuring the first electrode capacitance and the second electrode capacitance; a calculation step of calculating a relationship between the measured values ​​of the first electrode capacitance and the second electrode capacitance; a determination step of identifying the electrode from which the refrigerant has leaked based on an increase or decrease in a calculated value obtained by calculating a relationship between the first electrode capacitance and the second electrode capacitance; A refrigerant leak detection method comprising:

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