Leak inspection method and leak inspection apparatus

Abstract

To provide a leak inspection method and leak inspection device capable of accurately inspecting an air leak in an inspection object in a short time.SOLUTION: A leak inspection method for inspecting an air leak in an inspection object that has an internal space which is depressurized to a prescribed vacuum level and sealed airtightly, includes: a light projection step of projecting excitation light from the outside of the internal space onto a pressure-sensitive paint whose light emission intensity changes due to a change in the oxygen concentration in the internal space; a measurement step of measuring the attenuation speed of the light emission intensity; and a determination step of determining the presence of an air leak when the attenuation speed exceeds a predetermined threshold.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a leak inspection method and a leak inspection device.

Background Art

[0002] There is known an optical oxygen concentration measurement method that combines a light-emitting layer that emits light upon receiving excitation light and an absorption dye layer whose light absorption spectrum changes depending on the degree of binding with oxygen molecules that change according to the oxygen concentration, and detects the light intensity of output light that changes based on the fact that when incident light for causing the light-emitting layer to emit light or light emitted from the light-emitting layer passes through the absorption dye layer, a part of it is absorbed (Patent Document 1).

[0003] A pressure field measurement step of optically measuring the pressure distribution on the surface of an object in contact with a fluid using a pressure-sensitive paint and a velocity field measurement step of optically measuring the spatial behavior of the fluid by scattering visible particles in the fluid are performed simultaneously, and information on the pressure field and the velocity field for the same event is used as information correlated in the time direction to obtain a fluid measurement method that is also known (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a leak inspection method and a leak inspection device that can accurately inspect air leaks in a test object in a short time.

Means for Solving the Problems

[0006] To solve the aforementioned problem, the leak inspection method described in claim 4 is: A leak inspection method for inspecting air leaks in an object under inspection, which has an internal space that is reduced to a predetermined vacuum and airtightly sealed, in a bright environment, A light projection step involves projecting excitation light from outside the internal space onto a pressure-sensitive paint, which is applied to a white plate and placed within the internal space, and whose luminescence intensity changes with changes in the oxygen concentration within the internal space. A light receiving step that receives light emitted from the pressure-sensitive paint, The time waveform of the emission intensity of the received light shows attenuation. time A measurement step to measure, The damping time In this case, the time at which the luminescence intensity represented by equation (1) decreases to 37% of its maximum value is a predetermined threshold. Less than This includes a notification step in which an air leak is detected and a notification is issued accordingly. It is characterized by the following: I(t) = I0 × exp(-t / τ) (1) Here, I(t) is the emission intensity at time t, I0 is the emission intensity when the excitation light disappears, and τ is the emission lifetime.

[0010] To solve the above problem, the leak inspection device according to claim 1 is: A leak inspection device for inspecting air leaks in an object under inspection, which has an internal space that is reduced to a predetermined vacuum and airtightly sealed, in a bright environment, An excitation light source is provided that projects excitation light from outside the internal space onto a pressure-sensitive paint, which is applied to a white plate and placed within the internal space, and whose luminescence intensity changes with changes in the oxygen concentration within the internal space. A light receiving means for receiving light emitted from the pressure-sensitive paint, The time waveform of the emission intensity of the received light shows attenuation. time A measuring means for measuring, The damping time In this case, the time at which the luminescence intensity represented by equation (1) decreases to 37% of its maximum value is a predetermined threshold. Less than It includes a notification means that determines if an air leak is present and notifies the system accordingly. It is characterized by the following: I(t)=I0×exp(-t / τ) (1) Here, I(t) is the light emission intensity at time t, I0 is the light emission intensity when the excitation light disappears, and τ is the luminescence lifetime.

[0011] Claim 2 The invention described in claim 1 In the leak inspection device described in claim said The excitation light is pulsed and the excitation wavelength of the pressure-sensitive paint includes a wavelength range of 400 nm to 700 nm. , which is characterized in that.

[0012] Claim 3 The invention described in claim 1 or 2 In the leak inspection device described in claim the pressure-sensitive paint contains a ruthenium complex,[[]]<( which is characterized in that.

Effect of the Invention

[0013] According to the invention described in claim 1,[[]] In a bright environment the air leak of the test object can be accurately inspected in a short time.

[0015] Claim 2 According to the invention described in claim

[0016] Claim 3 According to the invention described in claim

[0017] Claim 4 According to the invention described in claim In a bright environment the air leak of the test object can be accurately inspected in a short time.

Brief Description of the Drawings

[0020] [Figure 1] It is a block diagram showing the functional configuration of the leak inspection device according to the present embodiment. [Figure 2]This is a schematic diagram illustrating an example of a leak inspection device according to this embodiment. [Figure 3] This flowchart schematically illustrates the leak testing procedure according to this embodiment. [Figure 4] This diagram conceptually illustrates the attenuation of luminescence intensity. [Figure 5] This figure shows an example of measurement results for luminescence lifetime under vacuum and atmospheric pressure. [Figure 6] This figure shows an example of measurement results for the luminescence lifetime of an excitation light source under atmospheric pressure, with varying luminescence intensity. [Figure 7] This figure shows an example of measurement results for the luminescence lifetime of an excitation light source under vacuum conditions, with varying luminescence intensity. [Figure 8] This is a schematic cross-sectional view showing the configuration of a water meter as an example of an object under inspection. [Modes for carrying out the invention]

[0021] The present invention will now be described in more detail with reference to the drawings, with examples of embodiments and specific examples provided below, but the present invention is not limited to these embodiments and specific examples. Furthermore, it should be noted that the following diagrams used in the explanation are schematic, and the proportions of the dimensions may differ from those of reality. For ease of understanding, diagrams of components other than those necessary for the explanation have been omitted as appropriate.

[0022] The leak inspection method according to this embodiment is a leak inspection method for inspecting air leaks in an object to be inspected which has an internal space that is depressurized to a predetermined degree of vacuum and airtightly sealed, and comprises a light projection step of projecting excitation light from outside the internal space onto a pressure-sensitive paint P whose luminescence intensity changes with changes in the oxygen concentration inside the internal space, and the attenuation of luminescence intensity time A measurement step to measure the decay time a predetermined threshold Less than The procedure includes a determination step that determines if an air leak is present in certain cases.

[0023] The leak inspection apparatus 1 for implementing the leak inspection method according to this embodiment includes a light-emitting unit 10 that projects excitation light from outside the internal space onto a pressure-sensitive paint P whose light emission intensity changes with changes in the oxygen concentration inside the internal space, a light-receiving unit 20 as a light-receiving means for receiving the light emitted from the pressure-sensitive paint P, and a light-receiving device for attenuating the light emission intensity of the received light. time A measuring unit 30 as a measuring means for measuring attenuation time a predetermined threshold Less than It is equipped with a notification unit 40, which serves as a notification means to notify the user if such a situation occurs.

[0024] First, a leak inspection device 1 for implementing the leak inspection method according to this embodiment and a water meter 100 as an example of an object to be inspected will be described with reference to the drawings. Figure 1 is a block diagram showing the functional configuration of the leak inspection device 1 according to this embodiment, Figure 2 is a schematic diagram showing an example of the leak inspection device 1 according to this embodiment, and Figure 8 is a schematic cross-sectional diagram showing the configuration of a water meter 100 as an example of an object to be inspected.

[0025] (Water meter) As an example of an object to be inspected, the water meter 100 has a lower case 110 with an inlet 111 and an outlet 112 formed at both ends, as shown in Figure 8, and an inner case 120 is housed inside the lower case 110. The inner case 120 is provided with a plurality of inlet nozzles 121 and outlet nozzles 122, and an impeller support member 123 is erected at the center of the inner bottom of the inner case 120. An impeller 124 having a magnet M1 on the upper part of its shaft is rotatably supported on the impeller support member 123.

[0026] An indicator unit 130 is provided above the impeller 124 via a gasket G1. The indicator unit 130 consists of a register box 131, a lower base plate 132, an upper base plate 133, a magnetic gear 134 with a magnet M2 attached, a gear train 135, a pointer (not shown), a numeral wheel 136, and a glass plate 137 attached via an O-ring S1. Furthermore, the magnet M2 of the magnetic gear 134 and the magnet M1 of the impeller 124 face each other across the bottom wall of the register box 131 and are magnetically coupled. The indicator unit 130 configured in this way is depressurized to a predetermined degree of vacuum and airtightly sealed. In this embodiment, the leak inspection device 1 uses the indicator unit 130, which has been sealed by vacuuming with pressure-sensitive paint P applied to the upper base plate 133, as the object to be inspected for leak inspection.

[0027] (Overall configuration of the leak detection system) The leak inspection apparatus 1 that implements the leak inspection method according to this embodiment, as shown in Figure 1, includes a light-emitting unit 10 that projects excitation light from outside the internal space onto a pressure-sensitive paint P whose light emission intensity changes with changes in the oxygen concentration inside the internal space, a light-receiving unit 20 as a light-receiving means that receives the light emitted from the pressure-sensitive paint P, and a light-receiving unit that measures the attenuation of the light emission intensity of the received light. time A measuring unit 30 as a measuring means for measuring attenuation time The leak inspection device 1 includes a notification unit 40 which serves as a notification means for notifying when the value is below a predetermined threshold. The processing of the light-emitting unit 10, light-receiving unit 20, measurement unit 30, and notification unit 40 in the leak inspection device 1 is implemented, for example, by a general computer in which a processor consisting of a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory) executes a predetermined program.

[0028] (Light-emitting part) The light-emitting unit 10 consists of an excitation light source 11 and a drive unit 12 that controls the emission of light from the excitation light source 11. The excitation light source 11 is an LED (light-emitting diode) with an emission wavelength of 400 nm to 700 nm, and emits light in a pulsed manner at the drive unit 12. The emission intensity of the excitation light source 11 should be equal to the light intensity emitted by the pressure-sensitive paint P when pressure is applied, and as will be described later, the decay rate of the emission intensity of the pressure-sensitive paint P does not depend on the emission intensity of the excitation light source 11.

[0029] (Light receiving part) The light-receiving unit 20 consists of a photodiode 21 that receives light emitted from the pressure-sensitive paint P and a trans-impedance amplifier (TIA) 22. When light is shone on the photodiode 21, an electric charge is generated in the photodiode 21 by photoelectric conversion. The amount of charge generated depends on the amount of light shone on the photodiode 21. In the light-receiving unit 20, the charge generated in the photodiode 21 is converted into a voltage signal by the TIA 22.

[0030] (Measurement part) The measurement unit 30 includes an oscilloscope 31, which reads out the voltage signal converted by the TIA 22 and measures the attenuation of the light emission intensity of the light received by the photodiode 21. time The measurement unit 30 measures the attenuation of the light emission intensity of the light received by the photodiode 21. Specifically, the oscilloscope 31 reads the voltage signal converted by the TIA 22 and obtains the time waveform of the light emission intensity from the photodiode 21. The measurement unit 30 performs signal processing on the digitized time waveform information of the light emission intensity from the oscilloscope 31 to measure the attenuation of the light emission intensity of the light received by the photodiode 21. time Calculate.

[0031] (News Department) The notification unit 40 detects the attenuation detected by the measurement unit 30. time The predetermined threshold Th Less than In certain cases, it will detect an air leak and issue an alert. Here, the decay of the light emission intensity is detected from the time waveform information of the light emission intensity. time It is known that this depends on the number of collisions with oxygen. The relationship between the luminescence lifetime τ and the luminescence intensity I(t) at a certain time t is given by equation (1). I(t) = I0 × exp(-t / τ) (1) I0 is the emission intensity (maximum value) when the excitation light disappears. It is expressed as follows, and when t=τ, the luminescence intensity I(τ) is, I(τ) = (1 / e)I0 ~ 0.37I0, which is the time (attenuation) during which the luminescence intensity decreases to 37% of its maximum value (I0). time The presence or absence of an air leak is determined by measuring the following.

[0032] The notification unit 40 may consist of, for example, a speaker that notifies information by sound, a vibrator that notifies information by vibration, a lamp that notifies information by lighting up or flashing, etc. Alternatively, notification may be provided by displaying information on the display of the computer that performs processing on the leak inspection device 1. The notification unit 40 is not limited to the example shown herein and may consist of other mechanisms capable of notifying information, or may be composed of multiple combinations thereof. Furthermore, these notification units 40 may be provided independently of the computer constituting the leak inspection device 1 and controlled by communication.

[0033] (Leak detection method) The leak inspection method according to this embodiment includes a light projection step in which excitation light is projected from outside the internal space onto a pressure-sensitive paint P whose luminescence intensity changes with changes in oxygen concentration within an internal space that is reduced to a predetermined vacuum and airtightly sealed, and the attenuation of luminescence intensity. time A measurement step to measure the decay time The predetermined threshold Th Less than The system includes a notification step that determines if an air leak is present and notifies the system accordingly.

[0034] Figure 3 is a flowchart illustrating the flow of the leak test according to this embodiment. In this embodiment, the indicator unit 130 of a water meter 100 is used as the object to be inspected for air leak testing as an example of an internal space that is reduced to a predetermined vacuum and airtightly sealed. First, a pressure-sensitive coating P is inserted into the indicator unit 130, which will be the object to be measured (S101). Examples of pressure-sensitive coatings P include platinum-porphyrin complexes such as PtTFPP and PtOEPP, palladium-porphyrin complexes such as PdTFPP, ruthenium complexes, and polycyclic aromatic hydrocarbons such as pyrene.

[0035] In this embodiment, the pressure-sensitive coating P was obtained by coating a white plate with a ruthenium complex, such as Ru(dpp)3, which is less expensive than a platinum-porphyrin complex. By coating the white plate with the pressure-sensitive coating P, the reflection of the excitation light source can be improved. Pressure-sensitive paint P is a paint whose luminescence intensity and luminescence lifetime change according to the partial pressure of oxygen, and the luminescence intensity gradually decreases when it is extinguished. time It is known that this depends on the number of collisions with oxygen, and the attenuation of luminescence intensity. time By evaluating this, it becomes possible to determine the amount of oxygen partial pressure, i.e., the state of reduced pressure.

[0036] Next, unit 130 is connected to a vacuum pump and the inside of unit 130 is depressurized to a predetermined vacuum level by evacuating it (S102). At this time, it is desirable to connect a pressure gauge to check the depressurized state of unit 130. Then, the excitation light source 11 is made to emit light, irradiating the pressure-sensitive paint P inside the unit 130, which has been reduced to a predetermined vacuum level (S103). In this embodiment, the excitation light source 11 is an LED (light-emitting diode) with an emission wavelength of 440 nm, and emits light in a pulsed manner with a driving current of 20 A (A: Ampere).

[0037] The excitation light source 11 is made to emit light, and the pressure-sensitive paint P is irradiated with light while the photodiode 21 of the light-receiving unit 20 receives the light emitted from the pressure-sensitive paint P (S104). The photodiode 21 generates an electric charge in proportion to the amount of light received. In the light-receiving unit 20, the electric charge generated by the photodiode 21 is converted into a voltage signal by the TIA 22 (S105). TIA22 amplifies the charge signal generated by the photodiode 21, converts it into a digital signal using an A / D converter (not shown), and outputs it as a voltage signal to the measurement unit 30.

[0038] In the measurement unit 30, the voltage signal converted by the TIA 22 is read out by the oscilloscope 31, and the decay time of the light emission intensity received by the photodiode 21 is measured (S106). Specifically, the oscilloscope 31 reads out the voltage converted by the TIA 22, and obtains the time waveform of the light emission intensity from the light emission intensity information from the photodiode 21. The measurement unit 30 performs signal processing on the digitized time waveform information of the light emission intensity from the oscilloscope 31 to measure the decay time of the light emission intensity received by the photodiode 21. time Calculate. In other words, if I0 is the emission intensity (maximum value) when the excitation light disappears, then the time it takes for the emission intensity I to decrease to 37% of the maximum value (I0) is called decay. time It is calculated as follows.

[0039] Figure 4 conceptually illustrates the attenuation of luminescence intensity. As shown in Figure 4, the luminescence of the pressure-sensitive paint P is emitted while it is being irradiated with excitation light from the excitation light source 11 (excitation light source ON), and then attenuates when the excitation light irradiation stops. This attenuation time This changes in response to the partial pressure of oxygen in the internal space, and the higher the partial pressure of oxygen, the more it decays. time The time is shortened, and in a vacuum it is lengthened. In this embodiment, the time it takes for the luminescence intensity I to decrease to 37% of the maximum value (I0) is attenuated. time It is calculated as a predetermined threshold Th Less than In this case, it is determined that there is a constant partial pressure of oxygen, meaning that an air leak is occurring rather than a vacuum (S107; Yes).

[0040] If an air leak is detected in step S107, the notification unit 40 notifies the user of this fact (S108). If no air leak is detected in step 107 (S107; No), the process returns to step S101, and an air leak test is performed on the next object to be inspected. [Examples]

[0041] An air leak test was performed on the indicator unit 130 of the water meter 100 shown in Figure 8 using the leak testing device 1 shown in Figure 2.

[0042] "Example 1" A ruthenium complex is applied as a pressure-sensitive paint P to the upper base plate 133 of the indicator unit 130, and the time it takes for the luminescence intensity to decrease to 37% of its maximum value in both a vacuum state (under vacuum) and a state with the valve open (under atmospheric pressure) is measured as the decay time of luminescence intensity. time They were measured as follows: As shown in Figure 5, the luminescence intensity decreases under vacuum and atmospheric pressure. time The results showed a difference. In a vacuum, the luminescence intensity is attenuated. time While the time is 1.01 μs, the luminescence intensity decreases at atmospheric pressure. time The duration was 0.60 μs. Thus, the internal space of the indicator unit 130 exhibits a decrease in light emission intensity compared to a vacuum state when under atmospheric pressure. time This shortens the time required for the indicator unit 130 to emit light, and by measuring the change in luminescence lifetime due to oxygen quenching, it becomes possible to accurately and quickly determine whether or not there is an air leak.

[0043] Example 2 A ruthenium complex is applied as a pressure-sensitive paint P to the upper base plate 133 of the indicator unit 130, and the attenuation of luminescence intensity in a vacuum state (under vacuum) and with the valve open (under atmospheric pressure) is observed. time The measurements were taken in both a dark room and a brightly lit room.

[0044] Figure 6 shows the attenuation of luminescence intensity under atmospheric pressure. time The results shown are obtained by varying the emission intensity of the excitation light source 11 to 20A, 40A, and 80A (drive current of the drive unit 12) in a dark room, and by measuring the emission intensity of the excitation light source 11 at 40A in a bright room. As shown in Figure 6, even when the emission intensity of the excitation light source 11 is varied to 20A, 40A, and 80A in a dark room, the emission intensity does not decrease. time The attenuation times were 0.68 μs, 0.60 μs, and 0.60 μs, respectively, and the results were independent of the emission intensity of the excitation light source 11. Furthermore, the attenuation of emission intensity when the emission intensity of the excitation light source 11 was set to 40 A in a brightly lit room was also observed. time The response time was 0.60 μs, indicating that the result was independent of the brightness of the testing environment.

[0045] Figure 7 shows the attenuation of light emission intensity under vacuum. time The following shows the results of measuring the emission intensity of the excitation light source 11 in a dark room, changing it to 20A, 40A, and 80A (drive current of the drive unit 12), and in a bright room with the emission intensity of the excitation light source 11 set to 40A. As shown in Figure 7, even when the emission intensity of the excitation light source 11 is changed to 20A, 40A, and 80A in a dark room, the emission intensity does not decrease. time The attenuation times were 1.05 μs, 1.02 μs, and 0.97 μs, respectively, and were independent of the emission intensity of the excitation light source 11. Furthermore, the attenuation of emission intensity when the emission intensity of the excitation light source 11 was set to 40 A in a brightly lit room was also observed. time The response time was 0.92 μs, indicating that the result was independent of the brightness of the testing environment.

[0046] Thus, the attenuation of luminescence intensity occurs in both vacuum and atmospheric pressure. time The results were independent of the emission intensity of the excitation light source 11 and also independent of the brightness of the inspection environment. This prevents attenuation of light emission intensity, regardless of the light emission intensity of the excitation light source 11 or the brightness of the inspection environment. time By measuring this, it becomes possible to determine whether or not there is an air leak in the indicator unit 130. In other words, it can be measured in a brightly lit room, and for example, air leak inspection of the indicator unit 130 can be performed at the production site of a water meter 100.

[0047] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention as described in the claims. For example, as the pressure-sensitive coating P, platinum-porphyrin complexes such as PtTFPP and PtOEPP, which have a longer luminescence lifetime due to oxygen quenching compared to ruthenium complexes, may be used. As the excitation light source 11, an excitation light source composed of a laser diode with an emission wavelength of 400 nm to 700 nm may be used. [Explanation of symbols]

[0048] 1. Leak detection device 10. Light-emitting part 11...Excitation light source, 12...Drive unit 20... Light receiving section 21...Photodiode, 22...Transimpedance amplifier (TIA) 30...Measuring section 31. Oscilloscope 40... News Department 100...water meter 130... Instruction Unit 131... Register box, 132... Lower base plate, 133... Upper base plate

Claims

1. A leak inspection device for inspecting air leaks in an object under inspection, which has an internal space that is reduced to a predetermined vacuum and airtightly sealed, in a bright environment, An excitation light source is provided that projects excitation light from outside the internal space onto a pressure-sensitive paint, which is applied to a white plate and placed within the internal space, and whose luminescence intensity changes with changes in the oxygen concentration within the internal space. A light receiving means for receiving light emitted from the pressure-sensitive paint, A measuring means for measuring decay time from the time waveform of the emission intensity of the received light, The system includes a notification means that determines that there is an air leak and notifies the system if the time it takes for the luminescence intensity represented by equation (1) to decrease to 37% of the maximum value during the decay time is less than a predetermined threshold, A leak detection device characterized by the following features. I(t)=I ０ ×exp(-t / τ) (1) Here, I(t) is the luminescence intensity at time t, I ０ τ is the emission intensity when the excitation light disappears, and τ is the emission lifetime.

2. The excitation light is pulsed and the excitation wavelength of the pressure-sensitive paint includes a wavelength range of 400 nm to 700 nm. The leak inspection device according to feature 1.

3. The pressure-sensitive paint contains a ruthenium complex. The leak inspection device according to claim 1 or 2.

4. A leak inspection method for inspecting air leaks in an object under inspection, which has an internal space that is reduced to a predetermined vacuum and airtightly sealed, in a bright environment, A light projection step involves projecting excitation light from outside the internal space onto a pressure-sensitive paint, which is applied to a white plate and placed within the internal space, and whose luminescence intensity changes with changes in the oxygen concentration within the internal space. A light receiving step that receives light emitted from the pressure-sensitive paint, A measurement step of measuring the decay time from the time waveform of the emission intensity of the received light, The notification step includes determining that there is an air leak and notifying the relevant party if the time it takes for the luminescence intensity represented by equation (1) to decrease to 37% of the maximum value during the decay time is less than a predetermined threshold, A leak testing method characterized by the following: I(t)=I ０ ×exp(-t / τ) (1) Here, I(t) is the luminescence intensity at time t, I ０ τ is the emission intensity when the excitation light disappears, and τ is the emission lifetime.

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