JP2022179852A - Device and method for detecting coolant leakage - Google Patents

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 The present disclosure relates to a refrigerant leakage detection device and a refrigerant leakage detection method for detecting refrigerant leakage from a refrigerant pipe.

In recent years, amidst strong concerns about the effects of global warming, there is a movement to suppress the leakage of refrigerants such as CFCs, which have a high greenhouse effect, into the atmosphere. Refrigerant leakage into the atmosphere occurs when the refrigerant enclosed in refrigerators and air conditioners leaks into the atmosphere because it is not recovered at the time of disposal, and when the refrigerant pipes of equipment, etc., are in use. may be damaged and leak. Of the amount of refrigerant that leaks into the atmosphere, the amount of refrigerant that leaks while the device is in use is greater than the amount of refrigerant that leaks at the time of disposal, and it is necessary to suppress this. For this purpose, a technique for detecting refrigerant leakage simply and accurately during use of equipment is required. In addition, if a refrigerant pipe or the like is damaged and refrigerant leaks, the device cannot be used again unless the corresponding portion is repaired. Therefore, there is a demand for a technique that can detect refrigerant leakage and at the same time specify the location of refrigerant leakage.

In Patent Document 1, as means for detecting refrigerant leakage from a refrigerant pipe, an electrode is attached to the outer periphery of a heat insulating material that covers the outer surface of the refrigerant pipe, and the capacitance between the refrigerant pipe and the electrode is measured. A measuring refrigerant leak detection device is disclosed. In the refrigerant leakage detection device of Patent Literature 1, leakage of the refrigerant is detected when the capacitance increased due to the leakage of the refrigerant exceeds a threshold value.

In addition, two sensors are placed near the refrigerant pipe, and the fluid containing the refrigerant caused by the leakage of the refrigerant is captured between the two plate electrodes that make up the sensor. Techniques for detecting leaks are also known.

JP 2018-173259 A

In the technique disclosed in Patent Document 1, the leakage of the refrigerant is detected by detecting the change in the electrostatic capacitance caused by the leakage of the refrigerant. When installed indoors, the refrigerant leakage detection device described in Patent Document 1 is exposed to changes in temperature and humidity due to operating conditions of air conditioners 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, but in this case, it will be 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. Also, temperature changes cause humidity fluctuations. Changes in these environmental factors can result in minute increases or decreases in component dimensions, variations in dielectric constants, or variations in electrical equipment properties, resulting in variations in measured capacitance values. Since the change in capacitance due to leakage of the refrigerant is very small, the method described in Patent Document 1 may erroneously detect leakage of the refrigerant due to the change in capacitance due to environmental factors.

Therefore, an object of the present disclosure is to provide a refrigerant leakage detection device and a refrigerant leakage detection method that can reduce the influence of environmental factors and prevent erroneous detection.

A refrigerant leakage detection device disclosed in the present application includes a first electrode disposed on the outer circumference of a heat insulating material provided on the outer circumference of a refrigerant pipe extending along the refrigerant circulation direction, and the first electrode and the refrigerant circulation direction. a second electrode disposed on the outer periphery of the heat insulating material, a first electrode capacitance between the first electrode and the refrigerant pipe, and a capacitance between the second electrode and the refrigerant pipe; and a detection unit that detects leakage of the coolant based on the second electrode capacitance between the two electrodes.

Further, in the refrigerant leakage detection method disclosed in the present application, a first electrode disposed on the outer circumference of a heat insulating material provided on the outer circumference of a refrigerant pipe extending along the refrigerant flow direction and a first electrode between the refrigerant pipe. Based on the first electrode capacitance and the second electrode capacitance between the refrigerant pipe and a second electrode separated from the first electrode in the flow direction and arranged on the outer periphery of the heat insulating material and a detection step of detecting leakage of the refrigerant flowing through the refrigerant pipe.

According to the refrigerant leakage detection device according to the present disclosure, the first electrode disposed in the heat insulating material covering the refrigerant pipe and the first electrode electrostatic capacitance between the refrigerant pipe and the second electrode capacitance disposed in the heat insulating material covering the refrigerant pipe a detection unit that detects refrigerant leakage based on the second electrode capacitance between the electrode and the refrigerant pipe; Therefore, it is possible to suppress the influence of environmental factors on the detection of refrigerant leakage.

1 is a configuration diagram showing a refrigerant leakage detection device according to Embodiment 1; FIG. FIG. 5 is a schematic diagram showing a modification 1 of installation of the refrigerant leakage detection device according to the first embodiment; FIG. 9 is a schematic diagram showing a modification 2 of installation of the refrigerant leakage detection device according to the first embodiment; FIG. 2 is a schematic diagram showing a plane perpendicular to the longitudinal direction of the refrigerant pipe of the refrigerant leakage detection device according to Embodiment 1; FIG. 2 is a circuit diagram showing the circuit configuration of the capacitance measurement unit of the refrigerant leakage detection device according to Embodiment 1; 4 is a flow chart of a refrigerant leakage detection method using the refrigerant leakage detection device according to Embodiment 1; 5 is a graph showing an example of measured values of the first electrode capacitance and the second electrode capacitance obtained from the capacitance measurement unit of the refrigerant leakage detection device according to Embodiment 1; FIG. 6 is a configuration diagram showing a refrigerant leakage detection device according to Embodiment 2; 8 is a flow chart of a refrigerant leakage detection method by the refrigerant leakage detection device according to Embodiment 2; 9 is a graph showing an example of 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 Embodiment 2; 11 is a graph showing calculated values obtained by calculating the measured values of FIG. 10 in a capacitance calculator. FIG. 9 is a schematic diagram showing a configuration in which a capacitance measurement unit, a capacitance calculation unit, and a detection unit are integrated in the refrigerant leakage detection device according to Embodiment 2;

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, embodiment of the refrigerant|coolant leak detection apparatus which this application discloses is described in detail. In addition, the embodiment shown below is an example, and the present invention is not limited by these embodiments.

Embodiment 1.
FIG. 1 is a configuration diagram showing a refrigerant leakage detection device 100 according to Embodiment 1. As shown in FIG. As shown in FIG. 1 , the coolant leakage detection device 100 of Embodiment 1 has a detection section 3 , a capacitance measurement section 5 and a detection section 6 . The detection unit 3 includes a first electrode 4a arranged on the outer surface of the heat insulating material 2 covering the refrigerant pipe 1 and a second electrode 4b arranged on the outer surface of the heat insulating material 2 independently of the first electrode 4a. I have. The capacitance measurement unit 5 measures capacitance between the refrigerant pipe 1 and the detection unit 3 . The detection unit 6 detects refrigerant leakage based on the capacitance between the first electrode 4 a and the refrigerant pipe 1 and the capacitance between the second electrode 4 b and the refrigerant pipe 1 . Hereinafter, the first electrode 4a and the second electrode 4b may be simply referred to as the electrode 4 when collectively referred to.

A refrigerant leakage 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 inside the refrigerant pipe 1 . Refrigerant pipe 1 is composed of a circular pipe made of metal. A heat insulating material 2 covering the outer surface of the refrigerant pipe 1 is provided around the outer circumference of the refrigerant pipe 1 . Copper, for example, is used as the metal forming the refrigerant pipe 1 . A temperature difference occurs between the refrigerant flowing inside the refrigerant pipe 1 and the temperature around the refrigerant pipe 1 . In particular, when the refrigerant pipe 1 is arranged outdoors, the difference between the refrigerant flowing inside the refrigerant pipe 1 and the temperature around the refrigerant pipe 1 is greater than when the refrigerant pipe 1 is arranged indoors. Temperature difference increases. The heat insulating material 2 covering the refrigerant pipe 1 is provided for the purpose of suppressing the change in the temperature of the refrigerant in the refrigerant pipe 1 due to the ambient air temperature in consideration of the temperature difference. Refrigerant pipe 1 may be commercially available in a state covered with heat insulating material 2 in advance. For example, foamed polyethylene is used as a material for forming the heat insulating material 2 . 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" for other members, and the direction in which the refrigerant pipe 1 extends will be referred to as the "longitudinal direction L". The radial direction R of the refrigerant pipes 1 that intersect at right angles is called "radial direction R".

The electrodes 4 are attached to the outer periphery of the refrigerant pipe 1 through which the refrigerant flows and the heat insulating material 2 covering the outer surface of the refrigerant pipe 1 . Electrode 4 is a conductor. Each of the electrodes 4 has a configuration in which a heat insulating material 2 that is a dielectric is sandwiched between the electrodes 4 and the refrigerant pipe 1 made of metal, thereby forming a capacitor with the refrigerant pipe 1 . When the refrigerant leaks from the refrigerant pipe 1 , liquid refrigerant or a mixed fluid of refrigerant and refrigerating machine oil enters the space between the electrode 4 and the refrigerant pipe 1 . The electrode 4 detects a change in capacitance between the electrode 4 and the refrigerant pipe 1 due to refrigerant that has entered the space between the electrode 4 and the refrigerant pipe 1 .

For the electrode 4, for example, an aluminum thin plate, a stainless steel thin plate, a copper thin plate, or the like can be selected. When aluminum is used as the electrode 4, the refrigerant leakage detection device 100 is lightweight, inexpensive, and easy to work. When stainless steel is used for the electrodes 4, the corrosion resistance of the refrigerant leakage detection device 100 is improved. When copper is used as the electrode 4, the electrical conductivity is good, so the change in capacitance can be accurately detected. Moreover, the electrode 4 may be of any shape and mounting method as long as it can be placed on the surface of the heat insulating material 2 . The electrode 4 may be formed by wrapping a single metal plate around the surface of the heat insulating material 2 . In this case, the electrode 4 has an annular or arc shape when viewed in the axial direction of the refrigerant pipe 1 . The electrode 4 may be, for example, a conductive paste that is directly applied onto the heat insulating material 2 and cured. In this case, the electrodes 4 are not affected by the dimensions of the refrigerant pipe 1 or the heat insulating material 2, and can be installed easily. The electrode 4 may have, for example, a conductive layer attached on an insulator, or a conductive layer deposited or coated on an insulator. For the electrode 4, for example, when a metal foil is stuck on a thin insulating film, the electrode 4 is softer than the electrode 4 formed of a thin metal plate, and can be easily attached. Moreover, the insulator film can be expected to have the effect of protecting the metal foil, and the electrode 4 that does not deteriorate for a longer period of time can be realized. However, it is preferable that there is no gap between the electrode 4 and the surface of the heat insulating material 2 . It is preferable that the electrode 4 is attached so as to encircle the outer peripheral surface of the heat insulating material 2 . This is because, in principle, the refrigerant leakage detection device 100 detects an increase in capacitance due to refrigerant entering the space between the electrode 4 and the refrigerant pipe 1 when the refrigerant leaks. This is because by arranging the electrodes 4 so as to encircle 1, the change in capacitance can be reliably detected.

The electrode 4 may be composed of, for example, a flexible thin-film metal plate. In this case, the electrode 4 may be wound around the heat insulating material 2 without any gaps and fixed with a conductive tape or an adhesive material so that the electrode 4 is placed in close contact with the surface of the heat insulating material. By eliminating the gap between the electrode 4 and the heat insulating material 2, the distance between the electrode 4 and the refrigerant pipe 1 changes even if the electrode 4 vibrates with the vibration of the refrigerant pipe 1 in the operating state of the air conditioner. As a result, fluctuations in capacitance, which cause noise, are suppressed, and erroneous detection is prevented.

A first electrode 4 a and a second electrode 4 b that constitute the electrode 4 are arranged on the surface of the heat insulating material 2 that covers the refrigerant pipe 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 have a gap and are arranged independently. The first electrode 4a and the second electrode 4b are alternately charged, and the capacitance between the first electrode 4a and the refrigerant pipe 1 and the capacitance between the second electrode 4b and the refrigerant pipe 1 are independent. measured by The first electrode 4a and the second electrode 4b are arranged along the direction in which the refrigerant pipe 1 extends. The first electrode 4a and the second electrode 4b are arranged in the longitudinal direction L of the refrigerant pipe 1, for example, when the refrigerant pipe 1 extends straight.

FIG. 2 is a schematic diagram showing Modification 1 of installation of refrigerant leakage detection device 100 according to Embodiment 1. As shown in FIG. As shown in FIG. 2, in Modified Example 1 of installing the refrigerant leakage detection device 100, the first electrode 4a and the second electrode 4b are attached to the L-shaped refrigerant pipe 1, and the first electrode 4a and the second electrode 4b are attached to the L-shaped refrigerant pipe 1. The two electrodes 4b are arranged so that their longitudinal directions L are perpendicular to each other.

FIG. 3 is a schematic diagram showing a modification 2 of installation of the refrigerant leakage detection device 100 according to the first embodiment. As shown in FIG. 3, in Modified Example 2 of installation of the refrigerant leakage detection device 100, the first electrode 4a and the second electrode 4b are attached to the U-shaped refrigerant pipe 1 and arranged to face each other. It is 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.

The capacitance measurement unit 5 and the detection unit 6 are provided in the control device 50, for example. The control device 50 is configured by, for example, a CPU (Central Processing Unit, also referred to as a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor)). The control device 50 is, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a nonvolatile memory such as a volatile memory or a 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.

The capacitance measuring unit 5 is electrically connected to the refrigerant pipe 1 and the electrode 4 through a pair of terminals 5a. Each terminal is composed of, for example, a pin. The capacitance measuring unit 5 measures the capacitance between the electrode 4 and the refrigerant pipe 1 connected by the terminal 5a. The capacitance measurement unit 5 is arranged at a position close to the electrode 4 .

It is desirable that the wiring extending from the terminal 5a connecting the capacitance measuring section 5 and the refrigerant pipe 1 and the wiring extending from the terminal 5a connecting the capacitance measuring section 5 and the electrode 4 are as short as possible. This is because the capacitance measured by the capacitance measuring unit 5 includes the stray capacitance of the wiring, but the stray capacitance of the wiring is not necessary for detection of coolant leakage. Also, if the wiring is long, it is likely to be affected by electromagnetic noise or the like through the wiring. By arranging the capacitance measuring unit 5 and the electrode 4 at a position where the wiring can be shortened, it is possible to reduce the stray capacitance of the wiring and the electromagnetic noise that cause erroneous detection. However, the capacitance measurement unit 5 and the electrode 4 are arranged apart from each other 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 and the electrode 4, the influence on the capacitance due to the conduction between the main body of the capacitance measurement unit 5 and the electrode 4 is prevented, and the leakage of the refrigerant is prevented. Detection is reduced.

The capacitance measurement unit 5 is arranged, for example, along the longitudinal direction L of the refrigerant pipe 1 so that the capacitance measurement unit 5 and the electrode 4 do not overlap, from the installation position of the electrode 4 in the upstream direction of the coolant flow direction. or in a position shifted in the downstream direction. Moreover, it is preferable that the capacitance measuring unit 5 is arranged and attached so as to be fixed to the refrigerant pipe 1 and the heat insulating material 2 from above the heat insulating material 2 . By arranging the capacitance measuring part 5 on the outer surface of the heat insulating material 2 , coolant leakage can be detected without removing the heat insulating material 2 .

The detection unit 6 is electrically connected to the capacitance measurement unit 5 . The detection unit 6 measures the capacitance between the first electrode 4a and the refrigerant pipe 1 obtained from the capacitance measurement unit 5 and the capacitance between the second electrode 4b and the refrigerant pipe 1. Compare and detect refrigerant leaks.

Next, the operating principle of refrigerant leakage detection by the refrigerant leakage detection device 100 according to Embodiment 1 will be described with reference to FIG. 4 . FIG. 4 is a schematic diagram showing a plane perpendicular to the longitudinal direction L of the refrigerant pipe 1 of the refrigerant leakage detection device 100 according to the first embodiment. Inside the metal refrigerant pipe 1, a fluid in which refrigerant and refrigerating machine oil are mixed flows. The refrigerant pipe 1, the heat insulator 2 and the electrodes 4 form a capacitor. That is, the refrigerant pipe 1, the heat insulating material 2, and the first electrode 4a form the first capacitor C1, and the refrigerant pipe 1, the heat insulating material 2, and the second electrode 4b form the second capacitor C2.

As shown in FIG. 4, a slight gap 14 is formed between the refrigerant pipe 1 and the heat insulator 2 . Therefore, capacitors are formed between the electrode 4 and the air gap 14 and between the air gap 14 and the refrigerant tube 1, and these two capacitors can be considered as being connected in series. At this time, assuming that the width g of the air 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 air gap 14. _Ins , the capacitance _Cgap between the air gap 14 and the refrigerant pipe 1 is combined. Therefore, the capacitance is represented by the following Equations 1 to 3.

where _ε0 is the dielectric constant of air, _εins is the relative dielectric constant of the heat insulating material 2, L is the width of the electrode 4 in the longitudinal direction L, _D1 is the outer diameter of the refrigerant pipe 1, and _D2 is the inner diameter of the electrode 4. , g are the widths of the air gaps 14 in the radial direction R;

When a pinhole or crack occurs in the refrigerant pipe 1 due to factors such as deterioration over time and leakage of refrigerant occurs, a fluid such as refrigerant or refrigerating machine oil flows out of the refrigerant pipe 1 and flows between the refrigerant pipe 1 and the electrode 4. do. The dielectric constant of fluid such as refrigerant or refrigerator oil flowing between the refrigerant pipe 1 and the electrode 4 is higher than that of air. Therefore, when this fluid accumulates in the gap 14 between the refrigerant pipe 1 and the heat insulating material 2, the capacitance C _gap between the refrigerant pipe 1 and the gap 14 increases, and accordingly the refrigerant pipe 1 and the heat insulating material 2 and the electrode 4 increases. Then, based on the capacitance C obtained from the capacitance measurement unit 5, the detection unit 6 determines whether or not the refrigerant leaks.

Next, the configuration and operation of the capacitance measuring section 5 will be described.

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

The charging/discharging circuit 11 has a power source 9, a first switch 10a, and a second switch 10b. The power supply 9 is a constant current source. One end of the first switch 10a is connected to the power supply 9, and the other end is connected to the first electrode 4a. A first capacitor C1 is formed on the side of the first switch 10a and has a first electrode capacitance 8a. One end of the second switch 10b is connected to the power supply 9, and the other end is connected to the second electrode 4b. A second capacitor C2 is formed on the side of the second switch 10b to generate a second electrode capacitance 8b. 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 pipe 1 via a first capacitor C1 and a second capacitor C2. The refrigerant pipe 1 is grounded.

The charging/discharging circuit 11 operates so that one of the first switch 10a and the second switch 10b is turned on and the other is turned off according to the voltage value of the electrode 4. FIG. When the first switch 10a is ON and the second switch 10b is OFF, the current output from the power supply 9 charges the first capacitor C1 and increases the voltage of the first electrode 4a. 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 current output from the power supply 9 charges the second capacitor C2 and increases the voltage of the second electrode 4b. This state is called a second state. In the charging/discharging circuit 11, the voltage of the electrode 4 is maintained within a preset range by alternately switching between the first state and the second state. Also, it is desirable that the time for switching between the first state and the second state be shorter than the time for environmental factors affecting the capacitance to change.

The time required for the environmental factor to change is, for example, the time required for the change when the environmental factor, which will be described later, changes beyond a certain fluctuation range. The time at which the environmental factors change includes the operating conditions of refrigeration cycle devices such as refrigerators or air conditioners, seasonal fluctuations in temperature and humidity, the temperature difference between the refrigerant flowing through the refrigerant pipe 1 and the outside air, and changes in the operating conditions of equipment. It is determined from the temperature difference of the refrigerant due to the temperature difference, the humidity fluctuation due to the temperature change of the outside air, and the like.

The counter circuit 12 counts the number of times the first switch 10a is turned on during a predetermined period of time. The fixed period is a period longer than at least the time during which the environmental factor changes. The number of counts counted by the counter circuit 12 changes according to the capacitance C of the capacitor generated between the refrigerant pipe 1 and the electrode 4 . Specifically, when the capacitance C of the capacitor increases, the number of counts decreases, and when the capacitance C of the capacitor decreases, the number of counts increases.

The count number from the counter circuit 12 is input to the count measurement unit 13 as a count signal. The count measurement unit 13 stores a conversion formula for converting the count number into the capacitance of the capacitor. The conversion formula is represented, for example, by Equation 4 below. The count measurement unit 13 uses a conversion formula to calculate the capacitance of the capacitor from the number of counts.

Here, C is the capacitance of the capacitor, A and B are correction coefficients determined by the operating conditions of the charging/discharging circuit 11, and Counts is the number of counts.

In this way, the capacitance C of the capacitor is calculated by the count measurement unit 13, and the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b measured by the capacitance measurement unit 5 are Become.

Although the counter circuit 12 counts the number of times the first switch 10a is turned on, the present invention is not limited to this case. The counter circuit 12 may count the number of times the second switch 10b is turned on.

Furthermore, the 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, the counter circuit 12 has a configuration in which the fluctuation range of the voltage of the capacitor, that is, the voltage at the connection point is determined by experiments or the like, and the median value between the maximum value and the minimum value of the fluctuation range is set as the threshold value. good too. In this case, the counter circuit 12 counts the number of times the voltage at the connection point exceeds the threshold during a predetermined period.

Note that 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, which constitute the capacitance measurement unit 5, can be configured by one microcontroller. Since the microcontroller is an inexpensive and small component, the capacitance measurement unit 5 can be configured compactly and at low cost.

Also, the capacitance measurement unit 5 may be entirely composed of one microcontroller, but is not limited to this configuration. In other words, the capacitance measurement unit 5 may be partially composed of one microcontroller and the other part may be composed of different components.

Also, although the capacitance measurement unit 5 has been described as using the count measurement unit 13 to calculate the capacitance C of the capacitor, the capacitance measurement unit 5 does not necessarily need to perform this processing. For example, without providing the count measurement unit 13 in the capacitance measurement unit 5 , the capacitance measurement unit 5 may transmit the count value counted by the counter circuit 12 to the detection unit 6 . That is, the detection unit 6 may have the function of the count measurement unit 13 . In this case, instead of the count measurement unit 13, the detection unit 6 calculates the capacitance C of the capacitor based on the count value, and determines leakage of the refrigerant based on the capacitance C.

The capacitance may be calculated using, for example, a conversion formula such as Equation 4 above. The detection unit 6 may directly read the count value transmitted from the capacitance measurement unit 5 as a signal that changes according to the capacitance C without obtaining the capacitance C, and detect refrigerant leakage. I do not care. 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 leakage detection device 100 can be reduced, and the manufacturing cost of the refrigerant leakage detection device 100 can be reduced. can do. Moreover, 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 .

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 substrate. When the capacitance measurement unit 5 and the detection unit 6 are integrated, the capacitance measurement unit 5 or the detection unit 6 may share a part of the components between the capacitance measurement unit 5 and the detection unit 6. be. Therefore, it is possible to reduce the number of parts required for the configuration of the refrigerant leakage detection device 100, and it is possible to reduce the manufacturing cost and make the refrigerant leakage detection device 100 compact.

Also, the capacitance measurement unit 5 is not limited to the configuration of FIG. The capacitance measurement unit 5 may be configured by, for example, an auto-balancing bridge circuit or a circuit using a Wheatstone bridge.

FIG. 6 is a flow chart 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 the control device 50, for example. In the detection step S01, the control device 50 detects refrigerant leakage based on the first electrode capacitance 8a and the second electrode capacitance 8b.

The detection step S01 includes, for example, a measurement step S11 and a determination step S12. In the measurement step S11, the controller 50 uses the capacitance measurement unit 5 to measure and acquire the first electrode capacitance 8a and the second electrode capacitance 8b at regular intervals. In determination step S12, the control device 50 uses the detection unit 6 to determine refrigerant leakage based on the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b obtained in the measurement step S11. . Note that the detection step S01 may be periodically and repeatedly performed, for example, when a refrigeration cycle device such as a refrigerator or an air conditioner to which the refrigerant leakage detection device 100 is attached is in operation or stopped.

FIG. 7 is a graph showing an example of measured values of the first electrode capacitance 8a and the second electrode capacitance 8b obtained from the capacitance measurement unit 5 of the refrigerant leakage detection device 100 according to Embodiment 1. is. In FIG. 7, the horizontal axis indicates time, and the vertical axis indicates capacitance.

As shown in FIG. 7, when no refrigerant leakage occurs between the first electrode 4a and the refrigerant pipe 1 and between the second electrode 4b and the refrigerant pipe 1, the first electrode capacitance 8a and the second electrode capacitance 8b exhibit similar variations as they are affected by similar environmental factors. On the other hand, when refrigerant leakage occurs between the first electrode 4a and the refrigerant pipe 1, the first electrode capacitance 8a increases. Since the relative permittivity of the refrigerant or refrigerating machine oil is greater than the permittivity of air, the first electrode capacitance 8a affected by the leakage of the refrigerant is affected by the leakage of the refrigerant, and the first electrode affected by the leakage of the refrigerant A difference occurs between the capacitance 8a and the second electrode capacitance 8b, which is not affected by refrigerant leakage. Therefore, the detection unit 6 determines leakage of the coolant based on the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b. That is, when the first electrode capacitance 8a and the second electrode capacitance 8b have a certain magnitude relationship, the detection unit 6 can determine that there is refrigerant leakage.

Note that the detection unit 6 immediately determines that there is leakage of the refrigerant from the refrigerant pipe 1 based on the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b. A configuration that In addition, when the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b, which is determined by the detection unit 6 to determine that the refrigerant is leaking, continues for a predetermined period of time Alternatively, it may be determined that there is refrigerant leakage from the refrigerant pipe 1 . Capacitance is easily affected by noise, so if a large instantaneous change in capacitance is detected due to the influence of noise, the presence or absence of refrigerant leakage can be detected from the transient capacitance measurement value. If judged, there is a possibility that it will be an erroneous detection. Therefore, even if the detection unit 6 detects the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b, the state continues for a certain period of time without judging refrigerant leakage immediately. Monitor whether or not With such a configuration, the detection unit 6 can suppress erroneous detection due to noise and detect refrigerant leakage more accurately.

The influence of environmental factors that hinder the detection accuracy of the refrigerant leak detection device 100 will be described below. When the refrigerant leakage detection device 100 is attached to an indoor air conditioner, it is exposed to changes in temperature and humidity due to changes in operating conditions and seasons of the air conditioner. In addition, the refrigerant leakage detection device 100 can be attached not only to indoor air conditioners but also to outdoor air conditioners. It will happen.

As mentioned above, capacitance occurs when two or more conductors are placed insulated with a dielectric sandwiched between them, and the value of capacitance in this case is the dielectric constant and the geometry of the conductor. The refrigerant leakage detection device 100 has a configuration in which a refrigerant pipe 1 and an electrode 4, which are two conductors, are arranged to be insulated with a heat insulating material 2, which is a dielectric, sandwiched therebetween. Therefore, the capacitance between the coolant tube 1 and the electrode 4 varies with the dielectric constant of the heat insulating material 2 and the geometry of the coolant tube 1 and the electrode 4 .

The dielectric constant of the heat insulating material 2, which is a dielectric, varies depending on changes in the amount of water that the heat insulating material 2 can hold due to changes in ambient humidity, or the gap 14 between the refrigerant pipe 1 and the heat insulating material 2 due to changes in ambient humidity. changes due to changes in the amount of water contained in In addition, when the ambient temperature changes, at least one of the electrode 4 and the refrigerant pipe 1, which are conductors, expands or contracts, and changes in size or shape, resulting in a change in geometry. Therefore, in the configuration in which the refrigerant pipe 1 and the electrode 4, which are two conductors, sandwich the heat insulating material 2, which is a dielectric, the refrigerant pipe 1, the electrode 4, and the heat insulating material 2 are connected even when there is no refrigerant leakage. , the capacitance between the refrigerant pipe 1 and the electrode 4 fluctuates due to minute changes caused by the influence of environmental factors.

It is considered that the first electrode 4a and the second electrode 4b in the coolant leakage detection device 100 are affected by similar environmental factors. Therefore, in a steady state in which no refrigerant leaks, the first electrode capacitance 8a and the second electrode capacitance 8b exhibit similar fluctuations caused by similar environmental factors. On the other hand, for example, when the refrigerant leaks between the first electrode 4a and the refrigerant pipe 1, the first electrode capacitance 8a fluctuates under the influence of the leakage of the refrigerant in addition to the influence of environmental factors. It shows a variation different from the second electrode capacitance 8b which is not affected by refrigerant leakage.

Therefore, in Embodiment 1, by comparing the first electrode capacitance 8a and the second electrode capacitance 8b, it is possible to derive the change in capacitance caused by refrigerant leakage. By observing the variation of the first electrode capacitance 8a and the second electrode capacitance 8b, the variation of the capacitance due to environmental factors is removed, and the change of the capacitance due to the leakage of the coolant is used. A leak is detected.

According to the refrigerant leakage detection device 100 according to Embodiment 1 described above, in the detection unit 6, the first electrode capacitance 8a between the first electrode 4a and the refrigerant pipe 1 and the second electrode 4b Refrigerant leakage is determined based on the second electrode capacitance 8b between the refrigerant pipe 1 and the second electrode capacitance 8b. As shown in FIGS. 1 to 3, the first electrode 4a and the second electrode 4b are arranged in pairs and independently with a space therebetween, so they are affected by similar environmental factors. . Also, the first electrode 4a and the second electrode 4b are not electrically connected and are independent. In a steady state where no refrigerant is leaking, the first electrode capacitance 8a between the first electrode 4a and the refrigerant pipe 1 and the second electrode capacitance 8a between the second electrode 4b and the refrigerant pipe 1 are 8b shows similar variation. Therefore, by comparing the first electrode capacitance 8a and the second electrode capacitance 8b, the amount of change in capacitance due to the influence of environmental factors is eliminated. Therefore, the refrigerant leakage detection device 100 detects the refrigerant leakage by extracting only the capacitance change caused by the refrigerant leakage from the comparison of the first electrode capacitance 8a and the second electrode capacitance 8b. By doing so, it is possible to prevent erroneous detection and contribute to the accuracy and precision of refrigerant leak detection.

Further, by evaluating the relationship between the first electrode capacitance 8a and the second electrode capacitance 8b, it is possible to identify the electrode 4 where the coolant leaks.

In addition, the number of electrodes 4 to be installed in the entire refrigerant pipe 1 can be reduced, the cost of the refrigerant leakage detection device 100 can be reduced, and the arrangement location can be given a certainty.

Further, in the refrigerant leakage detection device 100, the electrodes 4 are arranged on the outer surface of the heat insulating material 2 covering the outer surface of the refrigerant pipe 1, so that the electrodes 4 can be easily attached to the refrigerant pipe 1. Moreover, since the electrodes 4 are arranged on the outer surface of the heat insulating material 2, it is not necessary to destroy the heat insulating material 2 in order to forcibly attach the electrodes 4 directly to the refrigerant pipes 1. - 特許庁In addition, since the capacitance measurement unit 5 is arranged facing the outer surface of the electrode 4, the capacitance measurement unit 5 is arranged adjacent to the outer surface of the electrode 4, so that the capacitance can be measured. It is easy to attach the portion 5 to the refrigerant pipe 1 .

In particular, when the first electrode 4a and the second electrode 4b have a flexible thin-film configuration, it becomes easy to attach the first electrode 4a and the second electrode 4b to the existing pipe.

Further, the detection unit 3 is composed of two independent first electrodes 4a and second electrodes 4b, and the first electrodes 4a and the second electrodes 4b are arranged with an interval therebetween. Therefore, the distance between the first electrode 4a and the second electrode 4b can be arbitrarily set, and the influence of environmental factors on the first electrode 4a and the second electrode 4b can be made the same. can be suppressed.

Also, the first electrode 4a and the second electrode 4b are connected to the capacitance measurement section 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 measurement unit 5, the amount of change in the capacitance value due to the influence of environmental factors is 2 can be equal with one first electrode 4a and second electrode 4b.

Moreover, the time for measuring the first electrode capacitance 8a and the second electrode capacitance 8b is shorter than the change time of the environmental factor. Therefore, it is possible to measure the first electrode capacitance 8a and the second electrode capacitance 8b in which the influence of environmental factors is suppressed.

Moreover, it is preferable to shorten the length of the wiring between the capacitance measuring unit 5 and the electrode 4 and the length of the wiring between the capacitance measuring unit 5 and the refrigerant pipe 1 as much as possible. As a result, it is possible to reduce the influence of the stray capacitance of the wiring and the electromagnetic noise on the detected value, so that it is possible to improve the detection accuracy of refrigerant leakage.

Embodiment 2.
FIG. 8 is a configuration diagram showing a refrigerant leakage detection device 200 according to Embodiment 2. As shown in FIG. The refrigerant leakage detection device 200 according to Embodiment 2 has the capacitance calculation unit 7 that calculates the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, and is different from that of the embodiment. different from 1. Since the rest of the configuration is the same as that of the first embodiment, the detailed description of the components corresponding to or corresponding to those of the first embodiment will be omitted.

As shown in FIG. 8 , the refrigerant leakage detection device 200 of the second embodiment has a detection section 3 , a capacitance measurement section 5 , a capacitance calculation section 7 and a detection section 6 . As in the first embodiment, the detection unit 3 is arranged independently of the first electrode 4a arranged on the outer surface of the heat insulating material 2 covering the refrigerant pipe 1 and the first electrode 4a arranged on the outer surface of the heat insulating material 2. and a second electrode 4b. As in the first embodiment, the capacitance measurement unit 5 includes a first electrode capacitance 8a between the first electrode 4a and the refrigerant pipe 1 and a second electrode capacitance 8a between the second electrode 4b and the refrigerant pipe 1. Measure the capacitance 8b.

The capacitance calculation unit 7 acquires the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b from the capacitance measurement unit 5, and calculates the first electrode capacitance 8a and the second electrode capacitance 8b. A ratio between the electrode capacitance 8b and the electrode capacitance 8b is calculated. The capacitance calculation unit 7 is connected to the capacitance measurement unit 5, and calculates the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b obtained by the capacitance measurement unit 5. It has memory to store. The capacitance calculator 7 calculates the first electrode capacitance 8a and the second electrode capacitance 8b from the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b stored in the memory. 8b and , and outputs the calculated value to the detection unit 6 .

A threshold value of the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b is preset and stored in the detection unit 6 . The detection unit 6 determines presence or absence of refrigerant leakage based on the ratio between the first electrode capacitance 8a output from the capacitance calculation unit 7 and the second electrode capacitance 8b. The detection unit 6 determines that the refrigerant leaks 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. I judge.

FIG. 9 is a flow chart 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 the control device 50, for example. In the detection step S02, the control device 50 detects refrigerant leakage based on the first electrode capacitance 8a and the second electrode capacitance 8b.

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 uses the capacitance measurement unit 5 to measure the first electrode capacitance 8a and the second electrode capacitance 8b at regular time intervals. In the calculation step S22, the controller 50 causes the capacitance calculator 7 to calculate the ratio of the first electrode capacitance 8a and the second electrode capacitance 8b measured in the measurement step S21. In determination step S23, the control device 50 uses the detection unit 6 to determine refrigerant leakage based on comparison between the ratio calculated in the calculation step S22 and a pre-stored threshold value.

FIG. 10 is a graph showing an example of the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b obtained from the capacitance measurement unit 5 of the refrigerant leakage detection device 200 according to Embodiment 2. . In FIG. 10, the horizontal axis indicates time, and the vertical axis indicates capacitance. As shown in FIG. 10, for example, when refrigerant leakage occurs at the first electrode 4a, the first electrode capacitance 8a increases because the relative permittivity of the refrigerant or refrigerating machine oil is greater than the permittivity of air. do. There is a difference in the measured value of the capacitance measurement unit 5 between the first electrode capacitance 8a with refrigerant leakage and the second electrode capacitance 8b without refrigerant leakage.

FIG. 11 is a graph showing calculated values obtained by calculating the measured values of FIG. 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 first electrode capacitance from the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b measured by the capacitance measurement unit 5. A ratio between the capacitance 8a and the second electrode capacitance 8b is calculated. The ratio between the first electrode capacitance 8a and the second electrode capacitance 8b is compared with a pre-stored threshold in the detector 6 . When refrigerant leakage occurs in the first electrode capacitance 8a, the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b without refrigerant leakage increases. The detector 6 compares the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b without refrigerant leakage with a threshold to determine whether or not the refrigerant is leaking from the refrigerant pipe 1. .

As in the first embodiment, refrigerant leakage detection device 200 is exposed to changes in environmental factors such as temperature and humidity, and variations occur in the capacitance between refrigerant pipe 1 and electrode 4 . For example, when the temperature changes, at least one of the electrodes 4 and the coolant tube 1 expands or contracts, changing the size or shape of the electrode 4 and the coolant tube 1 . Therefore, the outer diameter D ₁ of the refrigerant pipe 1, the inner diameter D ₂ of the electrode 4, and the width g of the gap 14 in the radial direction R in Equation 1 change. Further, for example, when the ambient humidity changes, the amount of water retained in the heat insulating material 2, which is a dielectric, or the amount of water contained in the gap 14 between the refrigerant pipe 1 and the heat insulating material 2 changes. , the dielectric constant ε _ins of the heat insulating material 2 in Equation 1 changes.

In this way, when there is a change in the environmental factor, the outer diameter D ₁ of the refrigerant pipe 1, the inner diameter D ₂ of the electrode 4, the width g of the gap 14 in the radial direction R, or The dielectric constant ε _ins of the heat insulating material 2 changes. Therefore, in the configuration in which the refrigerant pipe 1 and the electrode 4, which are two conductors, sandwich the heat insulating material 2, which is a dielectric, even if there is no leakage of the refrigerant, the refrigerant pipe 1 may be affected by environmental factors. , the electrode 4, and the heat insulating material 2, the electrostatic capacitance fluctuates.

As shown in FIG. 10, the amount of change in the first electrode capacitance 8a and the second electrode capacitance 8b is relative to the absolute values of the first electrode capacitance 8a and the second electrode capacitance 8b. may change to 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. . Assuming that the first electrode capacitance 8a and the second electrode capacitance 8b increase by 10% due to changes in environmental factors, 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 10 pF. The difference from the capacitance 8b is 11 pF. That is, the amount of change in the first electrode capacitance 8a is 1 pF and the amount of change in the second electrode capacitance 8b is 2 pF before and after the change in environmental factors. , and the difference between the first electrode capacitance 8a and the second electrode capacitance 8b also fluctuates. Therefore, even if there is no refrigerant leakage, the difference between the first electrode capacitance 8a and the second electrode capacitance 8b before and after the change in the environmental factor fluctuates.

On the other hand, as shown in FIG. 11, when the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b is obtained, if there is no refrigerant leakage, the first electrode capacitance 8a and the second The ratio with the electrode capacitance 8b becomes equal before and after the change in the environmental factor. Therefore, in the second embodiment, by obtaining the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, the fluctuation of the capacitance due to environmental factors is eliminated, and the second electrode caused by the refrigerant leakage is eliminated. Variations in the one-electrode capacitance 8a and the second-electrode capacitance 8b can be detected.

Further, by detecting an increase or decrease in the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, it is possible to identify the electrode where the coolant is leaking. For example, when the ratio is the value obtained by dividing the first electrode capacitance 8a by the second electrode capacitance 8b, if the ratio increases, the refrigerant is leaking from the first electrode 4a, and if the ratio decreases, It is possible to identify that the coolant is leaking from the second electrode 4b.

In the above description, the capacitance calculation unit 7 outputs to the detection unit 6 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. Although the configuration in which the detection unit 6 determines the leakage of the refrigerant is taken as an example, it is not limited to this. The capacitance calculation unit 7 calculates, for example, the rate of change in the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, and the detection unit 6 determines leakage of the coolant. good too.

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 coolant 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 a device 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 arranged on the same substrate. When the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 are integrated, a part of the components is the capacitance measurement unit 5, the capacitance calculation unit 7, It can be shared with the detection unit 6 . Therefore, it is possible to reduce the number of parts required for the configuration of the refrigerant leakage detection device 200, and it is possible to reduce the manufacturing cost and make the refrigerant leakage detection device 200 compact.

According to the coolant leakage detection device 200 according to the second embodiment described above, coolant leakage 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. The second electrode capacitance 8b with the refrigerant pipe 1 fluctuates under the influence of similar environmental factors. Therefore, in the second embodiment, by obtaining the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, fluctuations in capacitance due to environmental factors are removed, and A change in the first electrode capacitance 8a and the second electrode capacitance 8b can be detected. As a result, erroneous detection by the refrigerant leak detection device 200 can be prevented, contributing to accuracy and precision.

In addition, in the capacitance calculator 7, the measured values of the first electrode capacitance 8a and the second electrode capacitance 8b are stored, and the values of the first electrode capacitance 8a and the first electrode capacitance 8a A relationship is computed. Therefore, the first electrode capacitance 8a and the second electrode capacitance 8b can be compared with each other.

Further, the detection unit 6 detects the first electrode 4a by increasing or decreasing the calculated value obtained by the capacitance calculation unit 7 based on the relationship such as the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b. Alternatively, it is possible to identify from which of the second electrodes 4b the refrigerant leak state has been detected.

Further, 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 variation due to the influence of environmental factors, prevents erroneous detection by the refrigerant leakage detection device 200 , and contributes to the accuracy and precision of the refrigerant leakage detection device 200 .

Further, the detection unit 6 may be configured to set a threshold of the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b and detect coolant leakage when the threshold is exceeded. As a result, erroneous detection by the refrigerant leakage detection device 200 can be prevented, and the accuracy and precision of the refrigerant leakage detection device 200 can be improved.

Further, the detection unit 6 may be configured to set a threshold for the rate of change of the ratio between the first electrode capacitance 8a and the second electrode capacitance 8b, and detect coolant leakage when the threshold is exceeded. . As a result, erroneous detection by the refrigerant leakage detection device 200 can be prevented, and the accuracy and precision of the refrigerant leakage detection device 200 can be improved.

Also, the capacitance measurement unit 5 , the capacitance calculation unit 7 , and the detection unit 6 are arranged 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 wiring capacitance value can be reduced.

Moreover, the capacitance measurement unit 5, the capacitance calculation unit 7, and the detection unit 6 may constitute an integrated refrigerant leakage detection circuit. As a result, the volume of the refrigerant leakage detection device 200 can be reduced and the space can be saved.

Other effects are the same as in the case of the refrigerant leakage detection device 100 of the first embodiment, so detailed descriptions of components corresponding to or corresponding to those of the first embodiment are omitted here.

REFERENCE SIGNS LIST 1 refrigerant pipe 2 heat insulating 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 Air gap 20 Device main body 50 Control device, 100 Refrigerant Leak Detection Device, 200 Refrigerant Leak Detection Device.

Claims (18)

a first electrode disposed on the outer circumference of a heat insulating material provided on the outer circumference of the refrigerant pipe extending along the direction of flow of the refrigerant;
a second electrode arranged on the outer periphery of the heat insulating material, separated from the first electrode in the flow direction of the coolant;
The refrigerant leakage is detected 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 detection unit;
Refrigerant leakage detection device. 2. The coolant leakage detection device according to claim 1, further comprising a capacitance measuring unit that measures the capacitance of the first electrode and the capacitance of the second electrode. The first electrode and the second electrode are connected to the capacitance measurement unit, and the capacitance between the first electrode and the refrigerant pipe and the capacitance between the second electrode and the refrigerant pipe 3. The refrigerant leakage detection device according to claim 2, wherein the capacitance between and is alternately measured. 3. The capacitance measuring unit measures the first electrode capacitance and the second electrode capacitance in a time shorter than a change time of an environmental factor affecting the capacitance. Or the refrigerant leak detection device according to claim 3. 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;
5. The capacitance calculator according to any one of claims 2 to 4, wherein the capacitance calculator calculates the relationship between the measured values of the first electrode capacitance and the second electrode capacitance. Refrigerant leak detector. 6. The detector according to claim 5, wherein the detection unit identifies the electrode from which the coolant 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. Refrigerant leak detector. 7. The refrigerant leakage detection device according to claim 5, wherein the capacitance calculation unit calculates a ratio between the first electrode capacitance and the second electrode capacitance. The refrigerant according to any one of claims 5 to 7, wherein the capacitance calculation unit calculates a change speed of a ratio between the first electrode capacitance and the second electrode capacitance. Leak detection device. The detection unit stores a threshold value of the ratio between the first electrode capacitance and the second electrode capacitance,
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, the detection unit detects refrigerant leakage. 8. The refrigerant leakage detection device according to claim 7. The detection unit sets a threshold for a change speed of the ratio between the first electrode capacitance and the second electrode capacitance,
When the change speed of the ratio of the first electrode capacitance and the second electrode capacitance calculated by the capacitance calculation unit exceeds a threshold of the change speed of the ratio, the refrigerant leaks. 9. The refrigerant leakage detection device according to claim 8, which detects the The capacitance measurement unit, the capacitance calculation unit, and the detection unit are arranged in proximity to the first electrode and the second electrode, according to any one of claims 5 to 10. Refrigerant leak detection device described. The refrigerant leakage detection device according to any one of claims 6 to 11, further comprising a refrigerant leakage detection circuit in which the capacitance measurement section, the capacitance calculation section, and the detection section are integrated. The first electrode and the second electrode are
The refrigerant leakage detection device according to any one of claims 1 to 12, wherein the refrigerant leakage detection device is independently arranged on the outer surface of the heat insulating material covering the outer surface of the refrigerant pipe through which the refrigerant flows. The refrigerant leakage detection device according to any one of claims 1 to 13, wherein the first electrode and the second electrode constitute a detection unit in pairs. The first electrode and the second electrode are wound around the outer surface of the heat insulating material, and are formed of annular or arc-shaped electrodes when viewed in the axial direction of the refrigerant pipe. 15. The refrigerant leakage detection device according to any one of 14. 16. The coolant leakage detection device according to claim 1, wherein the first electrode and the second electrode are composed of flexible thin-film conductive electrodes. 17. The refrigerant leakage detection device according to any one of claims 1 to 16, further comprising a gap between the first electrode and the second electrode. A first electrode disposed on the outer circumference of a heat insulating material provided on the outer circumference of a refrigerant pipe extending along the flow direction of the refrigerant, a first electrode electrostatic capacitance between the refrigerant pipe, and the first electrode Detection of leakage of the refrigerant flowing through the refrigerant pipe based on a second electrode capacitance between the refrigerant pipe and a second electrode spaced apart in the flow direction and arranged on the outer periphery of the heat insulating material A refrigerant leakage detection method having a detection step of performing

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