JP2019174455A - Automatic leaked air bubble detection system and automatic leaked air bubble detection method - Google Patents

Abstract

To inexpensively and efficiently perform leak inspection for an inspection object.SOLUTION: A surfactant is mixed with solution in which an inspection object is sunk so that a leaked air bubble is easy to peel off from the inspection object when the leaked air bubble occur from the inspection object. The inspection object is pressurized so that the leaked air bubble is easy to get out when the inspection object is defective. It is mechanically and automatically determined whether there is the leaked air bubble by creating an area where it is easy to photograph the leaked air bubble, guiding the leaked air bubble to the area, photographing the area with a photographing device, and analyzing an image obtained by photographing the area with the determination device.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a leak bubble automatic detection system and a leak bubble automatic detection method, and can be suitably used for, for example, a leak bubble automatic detection system and a leak bubble automatic detection method based on a non-destructive inspection.

  The leak inspection of an industrial product is an important nondestructive inspection for determining the presence or absence of defects penetrating from the inside to the outside of the industrial product. An inspection method using helium gas having a small molecular weight is known as a highly accurate leak inspection. However, the conventional leak inspection apparatus using helium gas as a search gas is relatively large in scale and relatively expensive. Also, the concentration of helium gas present in the atmosphere is inherently very low. Therefore, in the conventional technology, it is relatively difficult to restore the inspection environment in which helium gas has once leaked to the original state before the next inspection, and it is relatively difficult, and it takes time and effort for the conversion work. Is complicated and inefficient. Also, the economic cost of helium gas is relatively high.

  A leak inspection using air in the atmosphere instead of helium gas is also known as a simpler and less expensive inspection method. That is, as in the so-called tire puncture inspection, the inspection object is submerged in the liquid, pressure is applied to the inspection object as necessary, and it is detected whether air existing inside the inspection object leaks outside as bubbles. . However, in this inspection method, the presence or absence of bubbles in the liquid is determined by visual observation by an operator. For this reason, the burden on workers who perform visual determination continuously is heavy, and the determination criteria are not necessarily the same for each worker.

  In relation to the above, Patent Document 1 (Japanese Patent Laid-Open No. 2006-205988) discloses a description relating to a leak test method and an apparatus therefor. In this leak test method, a test specimen is immersed in a liquid in a container, and a leak is detected by bubbles emerging from the inside of the test specimen. This leak test method is characterized in that an ultrasonic detector is disposed above the liquid level of the container, and the ultrasonic wave generated when bubbles burst on the liquid level is detected by the ultrasonic detector. This liquid is a mixed liquid of water and a fine foam agent. Here, the micro-foaming agent is to make the foam generated in the liquid finer than the foam generated in the liquid consisting only of water.

  In the leak test method of Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-205988), bubbles are leaked from a test body submerged in a liquid in order to inspect the presence or absence of a hole or the like through which air leaks from the inside of the test body. Determine whether or not. The presence of bubbles is detected as ultrasonic waves generated when the bubbles burst on the liquid surface. Here, a fine foam with a diameter of less than 1 mm is easier to detect than a larger foam, and a fine foam agent that easily generates a fine foam is incorporated in a liquid environment that submerges the specimen. Has been. As the fine foam agent, in addition to methanol and ethanol, a lower alcohol such as isopropanol (isopropyl alcohol) or a higher alcohol having 6 or more carbon atoms may be used. However, surfactants added for the purpose of allowing easy visual observation by generating large bubbles are also inappropriate as fine foam agents. Further, there is no disclosure or suggestion about optically detecting bubbles with a camera or the like.

  Further, Non-Patent Document 1 discloses an experimental result indicating that, in bubbles generated in a liquid, the bubble diameter of a gas having a higher gas density is smaller.

  Non-Patent Document 2 discloses an approximate expression for obtaining the diameter of a bubble derived from a gas discharged from a minute hole opened at an end of a cylinder submerged in a liquid.

Japanese Patent Laid-Open No. 2006-205988

Kiyoshi Idokawa, Kouji Ikeda, Takashi Fukuda, Naruji Morooka, "Effects of fluid properties on bubble characteristics in a high-pressure bubble column", Chemical Engineering, 1985, 11, 4, 432-437 HASAN N. OGUZ and ANDREA PROSPERETTI, "Dynamics of bubble growth and detection from a needle", Journal of Fluid Mechanics, 1993, vol. 257, 111-145

  Perform leak inspection for inspection objects at low cost and efficiency. Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  The means for solving the problem will be described below using the numbers used in the (DETAILED DESCRIPTION). These numbers are added to clarify the correspondence between the description of (Claims) and (Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  According to one embodiment, the automatic air bubble detection system includes a container (2), a screen (3), a decompression device (4), a pressurization device (5), and an imaging device (6). A device (7) and a control device (8) are provided. Here, the container (2) stores the inspection object (9) and the solution (21) in which the inspection object (9) is submerged. The screen (3) is disposed immediately above the inspection object (9) and has an internal space (31) for sandwiching the solution (21). The decompression device (4) depressurizes the internal space (31) of the screen (3), the water level (33) of the solution (21) in the internal space (31) of the screen (3), and the solution in the container (2). Raise higher than (21) water level (23). The pressurizing device (5) pressurizes the inspection object (9). The photographing device (6) photographs the screen (3) and generates an image. The determination device (7) analyzes the captured image and determines the presence or absence of leaking bubbles originating from the inspection target (9). The control device (8) automatically controls operations of the decompression device (4), the pressurization device (5), and the determination device (7).

  According to one embodiment, in the method for automatically detecting leaked bubbles, the solution (21) is applied to the container (2) (S01), and the inspection target (9) is immersed in the solution (21) (S02). And placing the screen (3) immediately above the inspection object (9), sandwiching the solution (21) in the internal space (31) of the screen (3) (S03), and the internal space of the screen (3) (31 ) Is decompressed by the decompression device (4), and the water level (33) of the solution (21) in the internal space (31) of the screen (3) is set to be higher than the water level (23) of the solution (21) in the container (2). Raising the height (S05), pressurizing the inspection object (9) with the pressurizing device (5) (S06), and photographing the screen (3) with the photographing device (6) to generate an image (S07). ) And analyzing the shot image 9) Determining the presence or absence of leaking bubbles originating from (S08), depressurizing by depressurizing device (4) (S05), pressurizing by pressurizing device (5) (S06), and determinating device (7) (S08) is automatically controlled by the control device (8) (S04).

  According to the above-described embodiment, an area in which leaking bubbles can be easily photographed is created, the leaking bubbles are induced therein, the area is photographed by the photographing device, and an image obtained by photographing is analyzed by the determination device. Thus, it is possible to mechanically and automatically determine the presence or absence of leaking bubbles.

FIG. 1A is a partial cross-sectional view illustrating a configuration example of a leaky bubble automatic detection system according to an embodiment. FIG. 1B is a block circuit diagram illustrating a configuration example of a determination apparatus according to an embodiment. FIG. 1C is a plan view showing another configuration example of the automatic leak bubble detection system according to one embodiment. FIG. 1D is a partial cross-sectional view showing a modified example of the leaked bubble automatic detection system shown in FIG. 1A. FIG. 2 is a flowchart illustrating an example of a configuration of a method for automatically detecting leaked bubbles according to an embodiment. FIG. 3 is a graph showing an example of the relationship between the concentration of ethanol in the solution used in the automatic leak bubble detection system and the automatic leak bubble detection method according to an embodiment and the time until the leak bubble is generated from the inspection target and separated. It is.

  With reference to the attached drawings, a mode for carrying out an automatic leak bubble detection system and an automatic leak bubble detection method according to the present invention will be described below.

(First embodiment)
With reference to FIG. 1A, the structure of the automatic air bubble detection system 1 according to the present embodiment will be described. FIG. 1A is a partial cross-sectional view showing a configuration example of an automatic leak bubble detection system 1 according to an embodiment.

(Component)
The components of the leaked bubble automatic detection system 1 in FIG. 1A will be described. 1A includes a container 2, a screen 3, a decompression device 4, an airtight hose 41, a pressurization device 5, an airtight hose 51, an imaging device 6, a determination device 7, And a control device 8.

  The screen 3 includes an internal space 31, a water level gauge 34, a slope portion 35, a first plane portion 361, a second plane portion 362, a connection port 37, a frame portion 38, and a crosspiece 39. As will be described later, the inclined surface portion 35 of the screen 3 is also configured to collect leaked bubbles 91 generated inside thereof in a specific region, and is also called a hopper jig.

  The container 2 is configured such that a solution 21 is applied to the inside thereof, the inspection object 9 is submerged in the solution 21, and the screen 3 is disposed above the inspection object 9. Therefore, it is preferable that the container 2 is made of a material that does not leak even if the solution 21 is stretched and that does not deteriorate even if it contacts the solution 21. The solution 21 is, for example, an aqueous solution in which a surfactant is mixed with water at a predetermined ratio. As the surfactant, it is preferable to select a surfactant that quickly leaks from the surface of the inspection target 9 when the leakage bubble 91 is generated from the inspection target 9. For example, ethanol may be used. However, the solvent and the surfactant in the solution 21 and the mixing ratio of both are preferably selected so as not to adversely affect the submerged inspection object 9.

  The shape of the container 2 is preferably, for example, that the top surface is open and the bottom surface is flat so that the inspection object 9 and the screen 3 can be stably disposed, but this is only an example, The configuration of the container 2 according to the present embodiment is not limited. The bottom surface of the container 2 may have a curved surface that is complementary to the shapes of the inspection object 9 and the screen 3, for example.

  In the solution 21 stretched on the container 2, a lid (not shown) may be put on the container 2 so that foreign matter in the air does not enter from the open upper surface. At this time, the lid is preferably provided with a hole for preventing interference with the screen 3.

  The screen 3 is configured to make it easier for the photographing device 6 to photograph the state in which the leaked bubbles 91 generated from the inspection object 9 float in the solution 21. It is necessary that at least a part of the screen 3, particularly the inner surface, is in contact with the solution 21. Moreover, it is preferable that the screen 3 is transparent to the extent that there is no hindrance to photographing the leaking bubbles 91. The screen 3 may be made of, for example, a transparent acrylic material or a PET (polyethylene terephthalate) material. In addition, a dark curtain (not shown) may be arranged near the screen 3 so that the leaked bubbles 91 can be easily distinguished from the solution 21 when viewed from the photographing device 6. As will be described later, a plurality of screens 3 may be used side by side in accordance with the size of the inspection object 9.

  The water level gauge 34 is configured to measure the water level 33 of the solution 21 in the internal space 31 of the screen 3 and determine whether the water level 33 is included in the range defined by the upper limit water level 331 and the lower limit water level 332. Yes. In the configuration example of FIG. 1A, the water level gauge 34 is configured as a digital camera different from the imaging device 6. However, this configuration is merely an example and does not limit the present embodiment. As another example, the water level gauge 34 is a mechanical water level gauge 34 that is a float disposed in the internal space 31 of the screen 3 and moves in accordance with the movement of the water surface 32 of the solution 21 in the internal space 31. Also good. As yet another example, the imaging device 6 may function as the water level gauge 34.

  In order to raise the water level 33 of the water surface 32 of the solution 21 in the internal space 31 of the screen 3 to a position higher than the water level 23 of the water surface 22 of the solution 21 in the container 2, the decompression device 4 has a pressure in the internal space 31 of the screen 3. It is configured to lower. The decompression device 4 may be, for example, a vacuum pump that extracts air from the internal space 31 of the screen 3.

  The pressurization device 5 is used to make it easy for gas such as air existing in the internal space of the inspection object 9 to leak out of the inspection object 9 through this defect when the inspection object 9 is defective. The pressure in the internal space of the inspection object 9 is increased. The pressurizing device 5 may be, for example, a compressor that sends compressed air into the internal space of the inspection object 9.

  The imaging device 6 captures the appearance of the leaking bubbles 91 floating in the solution 21 existing in the internal space 31 of the screen 3 and transmits the resulting image data as a digital signal to the determination device 7. It is configured. The imaging device 6 is, for example, a digital camera.

  The determination device 7 is configured to determine whether or not a leaking bubble 91 is reflected in the image data received from the imaging device 6. The determination device 7 may be, for example, a computer that executes a predetermined program. As illustrated in FIG. 1D, the determination device 7 may further control the photographing device 6 or may transmit an arbitrary signal to the control device 8. FIG. 1D is a partial cross-sectional view showing a modified example of the leaked bubble automatic detection system 1 shown in FIG. 1A.

  With reference to FIG. 1B, the component of the determination apparatus 7 by this embodiment is demonstrated. FIG. 1B is a block diagram illustrating a configuration example of the determination device 7 according to an embodiment. The determination device 7 in FIG. 1B includes a bus 71, an input / output interface 72, a calculation device 73, a storage device 74, and an external storage device 75. The storage device 74 stores a program 741 and data 742.

  The control device 8 is configured to automatically control the decompression device 4, the pressurization device 5, the imaging device 6, the determination device 7, and the water level gauge 34. For example, the control device 8 may be a computer that executes a predetermined program. The control device 8 may be configured similarly to the determination device 7. Also, the control device 8 and the determination device 7 may have two functions provided by the same computer executing a predetermined program. Note that, as illustrated in FIG. 1D, the imaging device 6 may be controlled by the determination device 7 instead of the control device 8. The configuration of FIG. 1D is obtained by changing the main body that controls the imaging device 6 from the control device 8 to the determination device 7 as compared to the configuration of FIG. 1A. The other configuration in FIG. 1D is the same as that in FIG. 1A, and thus further detailed description is omitted.

(Connection)
The positional relationship and connection relationship of the components of the automatic leak bubble detection system 1 in FIG. 1A will be described.

  First, the solution 21 is stretched inside the container 2. The entire inspection object 9 is immersed in the solution 21. When the screen 3 is viewed from above in the vertical direction perpendicular to the water surface 22 of the solution 21, that is, when viewed from the direction in which the leaking bubbles 91 float in the direction opposite to gravity in the solution 21, It arrange | positions so that the whole test object 9 may be covered. Similarly, the screen 3 is disposed inside the container 2 when viewed from above. On the other hand, when viewed from the side in the horizontal direction with respect to the water surface 22, the lower part of the screen 3 including the slope 35 is in the solution 21, and the remaining upper part is from the water surface 22 of the solution 21. Out.

  A portion of the screen 3 that protrudes from the water surface 22 is mainly composed of a first plane portion 361, a second plane portion 362, and a frame portion 38. In the configuration example shown in FIG. 1A, the first plane portion 361 and the second plane portion 362 have the same shape and are arranged in parallel to each other. Further, the frame portion 38 is disposed so as to be sandwiched between the first plane portion 361 and the second plane portion 362 and along the flanges of the first plane portion 361 and the second plane portion 362. Here, it is preferable that the first plane portion 361 and the second plane portion 362 are integrated in a watertight manner via the frame portion 38. Further, a crosspiece 39 may be disposed between the first plane portion 361 and the second plane portion 362 so as not to be deformed in a direction in which both approach each other.

  In other words, the internal space 31 sandwiched between the first plane portion 361 and the second plane portion 362 is defined by the first plane portion 361, the second plane portion 362, and the frame portion 38. It is preferable that the solution 21 existing inside does not leak out of the screen 3 from anywhere other than the connection port 37. The connection port 37 is provided in the second plane part 362 in the configuration example of FIG. 1A, but may be provided in the first plane part 361 or may be provided in the frame part 38.

  The connection port 37 of the screen 3 is connected to the decompression device 4 disposed outside the solution 21 via an airtight hose 41. In other words, the decompression device 4 can extract air present in the internal space 31 of the screen 3 through the airtight hose 41 and the connection port 37.

  The decompression device 4 is preferably electrically connected to the control device 8. In other words, the decompression device 4 is configured to operate in accordance with a control signal electrically transmitted from the control device 8. The decompression device 4 is supplied with power from a power source (not shown). As an example, the control device 8 may control the operation of the decompression device 4 by turning on or off the power supply between the decompression device 4 and its power source.

  The pressurizing device 5 is disposed outside the solution 21 and is connected to the internal space of the inspection object 9 via an airtight hose 51. In other words, the pressurizing device 5 can send compressed air toward the internal space of the inspection object 9 via the airtight hose 51. The airtight hose 51 may pass through a gap between the container 2 and the screen 3 in order to connect the pressurizing device 5 and the inspection object 9 disposed immediately below the screen 3.

  The pressurizing device 5 is preferably electrically connected to the control device 8. In other words, the pressurizing device 5 is configured to be able to operate according to a control signal electrically transmitted from the control device 8. The pressurizing device 5 is supplied with power from a power source (not shown). As an example, the control device 8 may control the operation of the decompression device 4 by turning on or off the power supply between the pressurization device 5 and its power source.

  The imaging device 6 is disposed outside the solution 21. The imaging device 6 is configured such that the thickness of the internal space 31 is within the range of the depth of field of the imaging device 6 so that the leaked bubbles 91 floating in the solution 21 of the internal space 31 can be captured more reliably. It is preferable that they are arranged at various positions. The depth of field is a range of a distance between the subject that appears to be in focus and the photographing apparatus 6. In other words, the distance between the first plane part 361 and the second plane part 362 is preferably within the range of the depth of field of the imaging device 6.

  In general, of the performance of the optical system, the depth of field and the desired high image quality are in a trade-off relationship. In other words, if the range of the depth of field is expanded, the image quality in terms of detecting the leaking bubble 91 is lowered, and if the desired image quality is increased, the range of the depth of field is narrowed. In the present embodiment, in order to improve the image quality of the photographing device 6, the option of shortening the distance between the first plane part 361 and the second plane part 362, that is, reducing the thickness of the internal space 31 of the screen 3. Is adopted. Specifically, in the present embodiment, the thickness of the internal space 31 is 5 millimeters, but may be included in a range of 3 to 15 millimeters, for example. However, this numerical value is only an example, and does not limit the configuration of the automatic leakage bubble detection system 1 according to the present embodiment. Desirable image quality and depth of field in the imaging device 6 are preferably selected as appropriate according to the size of defects that may occur in the inspection object 9, the type and concentration of the surfactant contained in the solution 21, and the like. The upper limit of the thickness of the internal space 31 may be determined according to the depth of field. The lower limit of the thickness of the internal space 31 may be determined according to the deformation of the screen 3 that occurs when the water level 33 is raised to a desired height by the decompression device 4 and the rigidity of the screen 3. In other words, even if the lower limit of the thickness of the internal space 31 is set so that the rise of the leaking bubbles 91 is not hindered as a result of the first flat surface portion 361 and the second flat surface portion 362 being deformed in a direction approaching each other. good. Or you may arrange | position the crosspiece 39 between both in order to prevent the deformation | transformation of the 1st plane part 361 and the 2nd plane part 362.

  The photographing device 6 is electrically connected to the control device 8. The imaging device 6 captures the screen 3 in accordance with the control signal transmitted from the control device 8, and transmits image data obtained as a result of the capturing to the control device 8.

  The water level gauge 34 according to the present embodiment is disposed outside the solution 21 and is disposed at a position where the water surface 32 of the solution 21 in the internal space 31 can be reliably photographed, similarly to the photographing device 6. It is preferable. More specifically, it is preferable that the water level gauge 34 is arranged at a position where the water surface 32 should be, that is, a region where the region between the upper limit water level 331 and the lower limit water level 332 can be photographed.

  The water level gauge 34 is electrically connected to the control device 8. The water level gauge 34 shoots the water surface 32 in accordance with a control signal transmitted from the control device 8, and transmits image data obtained as a result of the photographing to the control device 8.

  The determination device 7 is disposed outside the solution 21. With reference to FIG. 1B, the connection relationship of the component of the determination apparatus 7 is demonstrated. The bus 71 is connected to each of the input / output interface 72, the arithmetic device 73, the storage device 74, and the external storage device 75. In other words, each of the input / output interface 72, the arithmetic device 73, the storage device 74, and the external storage device 75 can perform electrical communication with each other via the bus 71.

  The input / output interface 72 may be connected to the imaging device 6 and receive image data from the imaging device 6. Further, the input / output interface 72 may be connected to the control device 8 and receive a control signal from the control device 8.

  The storage device 74 may store a program 741 and data 742. Here, the arithmetic device 73 may read the program 741 and the data 742 from the storage device 74 via the bus 71, execute the program 741, and use the contents of the data 742 during the execution of the program 741, or the data 742. May be written in the storage device 74.

  In addition, the external storage device 75 may be connected to an external recording medium 751. The external storage device 75 may read other programs and data from the connected recording medium 751 and store them in the storage device 74.

  The control device 8 is disposed outside the solution 21. The control device 8 may be configured as one of functions obtained by the determination device 7 executing the program 741, or may be configured as a computer different from the determination device 7. In any case, the more detailed configuration of the control device 8 is the same as the configuration example of the determination device 7 shown in FIG. 1B, and thus further detailed description is omitted. However, the control device 8 may be part or all of the decompression device 4, the pressurization device 5, the imaging device 6, the determination device 7, and the water level gauge 34 via the input / output interface 72 or another device corresponding thereto. It is connected to the.

  As described above, a plurality of screens 3 may be used side by side in accordance with the size of the inspection object 9. This will be described with reference to FIG. 1C. FIG. 1C is a plan view showing another configuration example of the automatic leak bubble detection system 1 according to an embodiment.

  In FIG. 1C, a total of three screens 3 of the first screen 3A to the third screen 3C are arranged side by side in the longitudinal direction of the inspection object 9. Each of the first screen 3A to the third screen 3C is similar to the case of the screen 3 in FIG. 1A. The slope portions 35A to 35C, the first plane portions 361A to 361C, the second plane portions 362A to 362C, and the frame Parts 38A to 38C. Here, the total number of screens 3 is only an example, and does not limit the present embodiment. Hereinafter, when the first screen 3A to the third screen 3C are not distinguished, they are simply referred to as “screen 3”.

  Since each of the first screen 3A to the third screen 3C is configured in the same manner as the screen 3 shown in FIG. 1A, further detailed description is omitted. In addition to the first screen 3A to the third screen 3C, the leaked bubble automatic detection system 1 shown in FIG. 1C includes three water level gauges 34 (not shown), three decompression devices 4 (not shown), and three units. It is preferable that the imaging devices 6A to 6C are provided. Hereinafter, when the first imaging device 6A to the third imaging device 6C are not distinguished, they are simply referred to as “imaging device 6”.

  In other words, in the leaked bubble automatic detection system 1 shown in FIG. 1C, the same number of water level gauges 34, decompression devices 4, and imaging devices 6 as the screen 3 are used. About the pressurization apparatus 5, the determination apparatus 7, and the control apparatus 8 which remain | survive, you may increase to the same number as the screen 3, and you may operate | move independently if possible.

  The positional relationship between the first screen 3A to the third screen 3C will be described. The leaking bubbles 91 generated from the inspection object 9 can be reliably guided to the internal space 31 sandwiched between the first flat surface portion 361 and the second flat surface portion 362 of any of the screens 3. It is preferable that the slope 35 is in close contact.

  The positional relationship between the first screen 3A to the third screen 3C and the first imaging device 6A to the third imaging device 6C will be described. The first photographing device 6A to the third photographing device 6C photograph the first screen 3A to the third screen 3C, respectively. Therefore, in the configuration example of FIG. 1C, it is possible to photograph a range that is three times as simple as the case of FIG. 1A. In addition, it is preferable that the dimension in the width direction of each screen 3 is appropriately set based on various parameters such as the focal length and the angle of view of each photographing device 6.

(Operation)
With reference to FIG. 2, the operation of the automatic leak bubble detection system 1 according to the present embodiment, that is, the automatic leak bubble detection method according to the present embodiment will be described. FIG. 2 is a flowchart illustrating an example of a configuration of a method for automatically detecting leaked bubbles according to an embodiment. Note that the method for automatically detecting leaked bubbles according to the present embodiment is the same regardless of the total number of screens 3, and hence the case where the total number of screens 3 is 1 will be described below.

  The flowchart of FIG. 2 includes a total of 12 processes, ie, 0th step S00 to 11th step S11. The flowchart of FIG. 2 starts from the 0th step S00. After the 0th step S00, the first step S01 is executed.

  In the first step S01, the solution 21 is put on the container 2. Here, with reference to FIG. 3, the relationship between the concentration of the surfactant contained in the solution 21 and the time until the leaked bubbles 91 generated from the inspection object 9 are peeled off from the surface of the inspection object 9 will be described. FIG. 3 shows the relationship between the concentration of ethanol in the solution 21 used in the automatic leak bubble detection system 1 and the automatic leak bubble detection method according to an embodiment and the time until the leak bubble 91 is generated from the inspection object 9 and is detached. It is a graph which shows an example.

  In the example of FIG. 3, when the solution 21 does not contain ethanol, it took 60 seconds or longer to peel, but in the case of the solution 21 mixed with 40% by weight of ethanol, the peeling was realized within 10 seconds. . This indicates that the efficiency of the leaked bubble automatic detection system 1 and the leaked bubble automatic detection method according to the present embodiment is greatly improved as compared with the conventional method. Depending on the type of surfactant contained in the solution 21, even when the concentration is 1% or less, peeling may be achieved at a speed equivalent to or faster than when ethanol is contained.

  In the example of FIG. 3, even when 50% by weight of ethanol is mixed with the solution 21, the time until peeling is not significantly shortened. This indicates that increasing the ethanol concentration above 40% by weight does not necessarily lead to further efficiency improvements.

  Therefore, in this embodiment, the ethanol concentration in the solution 21 is set to about 40% by weight. However, this value is merely an example and does not limit the present embodiment. The concentration of ethanol as a surfactant with respect to the solution 21 may be within a range of 40 to 45% by weight, for example. Following the first step S01, a second step S02 is executed.

  In the second step S02, the inspection object 9 is immersed in the solution 21 in the container 2. The entire inspection object 9 is preferably located below the water surface 22 of the solution 21. Moreover, it is preferable that the test object 9 is connected to the pressurization device 5 via the airtight hose 51 in advance. Following the second step S02, a third step S03 is executed.

  In the third step S <b> 03, the screen 3 is disposed immediately above the inspection object 9 submerged in the solution 21 in the container 2. At this time, it is preferable that the lower portion of the screen 3, particularly the slope portion 35, is immersed in the solution 21 in the container 2. On the other hand, it is preferable that at least a portion of the upper portion of the screen 3, particularly the flat portion 361 and the flat portion 362, which is photographed by the photographing device 6, protrudes upward from the water surface 22 of the solution 21 in the container 2. At this time, the water level 33 of the water surface 32 of the solution 21 in the internal space 31 of the screen 3 may be the same as the water level 23 of the water surface 22 of the solution 21 in the container 2. Following the third step S03, a fourth step S04 is executed.

  In the fourth step S04, the control device 8 controls the decompression device 4, the pressurization device 5, the photographing device 6, and the determination device 7. It is preferable that the subsequent operation of the automatic leak bubble detection system 1 is automatically performed under the control of the control device 8. In other words, each process of the first step S01 to the third step S03 may be performed manually by an operator. Following the fourth step S04, a fifth step S05 is executed.

  In the fifth step S05, the decompression device 4 decompresses the internal space 31 of the screen 3, and raises the water level 33 of the solution 21 in the internal space 31 of the screen 3. At this time, the water level 33 is preferably lower than the upper limit water level 331 and higher than the lower limit water level 332. The upper limit water level 331 is preferably provided with an appropriate margin as a guideline for the solution 21 not to enter the decompression device 4 via the connection port 37 and the airtight hose 41. The lower limit water level 332 is provided with an appropriate margin as an indication that the water surface 32 does not interfere with the imaging of the leaked bubble 91 by the imaging device 6 and the image processing and determination of the image data by the determination device 7. Is preferred. In other words, the lower limit water level 332 is preferably above the upper boundary of the range in which the imaging device 6 captures the leaking bubble 91. However, as described above, when the photographing apparatus 6 also serves as the water level gauge 34, on the contrary, both the upper limit water level 331 and the lower limit water level 332 may be included in the photographing range of the photographing apparatus 6. In any case, the water level gauge 34 measures the water surface 32, and the control device 8 controls the decompression device 4 according to the result of the measurement, so that the water level 33 is maintained between the upper limit water level 331 and the lower limit water level 332. It is preferable. Following the fifth step S05, a sixth step S06 is executed.

One feature of the present apparatus is that a leaking bubble 91 passing through the inside of the screen 3 can be photographed by the photographing apparatus 6 disposed outside the screen 3. From this, the following merits are obtained.
1) There is little adverse effect on photographing due to dirt contained in the solution 21, and the photographing parameters (focal distance, distance from the photographing device 6 to the leaking bubble 91, etc.) for photographing the leaking bubble 91 with high accuracy can be freely selected. High degree.
2) Since the leaking bubble 91 that is the subject of imaging floats inside the screen 3, it is easy to distinguish it from the suspended matter floating inside the screen 3.
3) Since the appearance of the leaking bubble 91 to be photographed tends to increase while the pressure is reduced, there are few oversights.
4) When continuously measuring a plurality of inspection objects 9, even if the leaked bubbles 91 generated in the previous measurement remain on the water surface 32, the next measurement is not affected.

  In the sixth step S06, the pressurizing device 5 pressurizes the inspection object 9. That is, the pressurizing device 5 generates compressed air and sends the compressed air into the internal space of the inspection object 9 through the airtight hose 51. As a result, if there is a defect reaching the outside from the internal space in the inspection object 9, the air in the internal space of the inspection object 9 becomes a leaking bubble 91 and is generated on the surface of the inspection object 9. The leaking bubbles 91 generated on the surface of the inspection object 9 are rapidly peeled off from the surface of the inspection object 9 by the action of the surrounding solution 21, particularly the surfactant. The leaking bubbles 91 peeled off from the surface of the inspection object 9 starts to float in the vertical direction in the solution 21. In the case where the slope portion 35 exists directly above the leaking bubble 91, the leakage bubble 91 floats obliquely along the surface of the slope portion 35, and the internal space is sandwiched between the two flat portions 361 and 362. It is guided to 31 and resumes vertical ascent.

  Here, if the leaky bubble 91 adheres to the slope portion 35, the rise of the leaky bubble 91 is hindered, which may cause an erroneous determination. In order to prevent leaking bubbles 91 from adhering to the slope portion 35, it is preferable to set the angle of the inner surface of the slope portion 35 with respect to the direction of gravity to an appropriate value. In addition, it is preferable to select a material to which the leaky bubbles 91 are difficult to adhere as a material constituting the slope portion 35. Here, the fact that the leaked bubbles 91 are easily peeled off from the surface of the slope portion 35 means that the surface of the slope portion 35 is easily wetted by the solution 21 present around the leaked bubble 91. Therefore, it is preferable to select a material having high hydrophilicity as a material constituting the slope portion 35. Further, the ease of peeling of the leaking bubbles 91 on the surface of the slope portion 35 and the ease of wetting by the solution 21 are also affected by the type and concentration of the surfactant contained in the solution 21. Further, an appropriate coating agent may be applied to the inner surface of the slope portion 35 in order to further increase the hydrophilicity. The design of the slope portion 35, in other words, the design of the hopper jig is preferably performed in consideration of a combination of these conditions.

  In addition, if the inspection object 9 is a non-defective product that does not have a defect, naturally the leaking bubble 91 does not occur. After the sixth step S06, a seventh step S07 is executed.

  In the seventh step S07, the photographing device 6 photographs the screen 3. Various parameters relating to the photographing are appropriately adjusted according to the frequency with which the leaking bubble 91 can be generated, the size of the leaking bubble 91 that can be generated, the speed at which the leaking bubble 91 rises in the solution 21, and the like. Is preferred. Note that various parameters adjusted as appropriate may be transmitted to the imaging device 6 as a control signal generated by the control device 8, or may be manually reflected in the imaging device 6 by an operator. If necessary, it may be replaced with another imaging device 6 capable of imaging with desired parameters.

  The imaging device 6 may generate a plurality of image data by continuously performing imaging a plurality of times at a time. In other words, the imaging device 6 may perform so-called continuous shooting. Various parameters such as the number of image data to be continuously shot at a time and the period of continuous shooting can be set in advance via the control device 8, for example.

  In addition, the imaging device 6 may sequentially transmit a plurality of image data generated by continuous imaging to the determination device 7. In this case, the determination device 7 may continuously display data with a plurality of received images on a display device (not shown). In other words, by displaying the state of the screen 3 viewed from the photographing device 6 with a minimum time lag, so-called live display becomes possible.

  Note that various parameters relating to shooting preferably include, for example, focal length, shutter speed, aperture, and the like. These parameters are considered to have the following effects on the performance of the automatic leak bubble detection system 1 according to the present embodiment. That is, if the aperture is adjusted widely, the image quality in terms of detecting the leaking bubble 91 is improved, but the depth of field is narrowed. On the other hand, if the aperture is adjusted narrower, the depth of field is increased, but the image quality is lowered. If the shutter speed is adjusted to be short, the image quality is improved, but the length of movement of the leaking bubbles 91 in one image is shortened. On the contrary, if the shutter speed is adjusted to be long, the length that the leaking bubble 91 moves in one image becomes longer, but the image quality is lowered. If the focal length is adjusted to be short, the range of the screen 3 that appears in one image is widened, but the image quality is lowered. On the contrary, if the focal length is adjusted to be long, the image quality is improved, but the range of the screen 3 that appears in one image is narrowed.

  Image data obtained by photographing is transmitted to the determination device 7. Following the seventh step S07, an eighth step S08 is executed.

  In 8th step S08, the determination apparatus 7 analyzes image data, and determines the presence or absence of the leaking bubble 91 originating in the test object 9. FIG. Here, the determination device 7 first performs, for example, the following image processing on the image data received from the imaging device 6.

  First, if color information is included in the image data, so-called “grayscale processing” is performed on the image data. That is, the information corresponding to each pixel constituting the image data is converted into luminance data indicating how bright the image data is. If the photographing apparatus 6 has the setting, grayscale image data may be generated at the time of photographing.

  Next, a so-called “binarization” process is performed on the image data. That is, a desired threshold value is set for luminance, and information corresponding to each of the pixels constituting the image data is displayed as “black” data if the luminance is less than the threshold value, and “white” if the luminance value is equal to or higher than the threshold value. Is converted into data indicating "." It is preferable to set the threshold appropriately so that the pixel representing the leaking bubble 91 is converted to “white” and the other pixels are converted to “black”.

  In connection with the above processing, it is possible to make it easier to identify the leaking bubble 91 on the image data by using the above-mentioned dark curtain as the background of the screen 3 viewed from the photographing device 6.

  The image data obtained in this way is further subjected to filter processing. That is, a desired threshold value is set in order to distinguish the leaked bubble 91 and noises such as foreign matters other than the leaked bubble 91 on the image data, and “white” data that occupies the number of pixels equal to or greater than this threshold value adjacently. The “white” data that is recognized as a leaking bubble 91 and that occupies only the number of pixels less than this threshold adjacently is treated as unnecessary noise.

  In order to distinguish between the leaking bubble 91 and the noise, not only the number of pixels occupied by the adjacent “white” data but also its shape may be noted. For example, a square having the same number of vertical and horizontal pixels as this threshold may be cut out from an arbitrary position of the image data using another threshold, and the above-described filtering process may be performed in the cut out square.

  Furthermore, by comparing a plurality of image data generated by continuous shooting in the order of time series, it is possible to further improve the accuracy of determining the presence or absence of the leak bubble 91. For example, by comparing arbitrary image data with image data taken immediately before, image data taken immediately thereafter, or both image data, noise mixed in continuous shooting and real In some cases, the leaked bubble 91 can be distinguished.

  The result of determining whether or not the leaking bubble 91 has been detected from the captured image data may be output in an easy-to-understand manner to surrounding workers, for example. For example, you may display two types of images which distinguish the presence or absence of the leak bubble 91 with the display apparatus which is not illustrated. Further, two types of sound for distinguishing the presence or absence of the leaking bubble 91 may be played by a speaker (not shown).

  As illustrated in FIG. 1D, the determination device 7 may generate a signal notifying that the determination has been completed and transmit the signal to the control device 8. Following the eighth step S08, a ninth step S09 is executed.

  In the ninth step S09, the decompressed state of the internal space 31 of the screen 3 is released. At this time, the control device 8 may stop the decompression operation of the decompression device 4. By releasing the reduced pressure state, the water level 33 in the internal space 31 of the screen 3 is restored. Following the ninth step S09, a tenth step S10 is executed.

  In the tenth step S10, the screen 3 is raised. By doing so, the inspection object 9 can be taken out of the container 2. This operation may be performed manually by an operator or automatically by an appropriate mechanism. Following the tenth step S10, an eleventh step S11 is executed.

  In the eleventh step S11, a series of operations of the automatic leak bubble detection system 1 according to the present embodiment, that is, each process of the automatic leak bubble detection method according to the present embodiment is completed. Here, the inspection object 9 is taken out of the container 2 and disconnected from the airtight hose 51. If the leaking bubble 91 is out, it is treated as a defective product. On the contrary, the leaking bubble 91 is not out. Then, it is preferable that it is treated as a non-defective product at least in this standard. Thereafter, when a leak inspection is performed on another inspection object 9 in the same manner, the first step S01 may be omitted and the process may start from the second step S02.

(Second Embodiment)
In the present embodiment, the following changes are added to the first embodiment described above. That is, the pressurization device 5 pressurizes the inspection object 9 by sending helium gas having a higher atmospheric pressure than the outside air into the internal space of the inspection object 9. The pressurizing device 5 may include, for example, a helium gas cylinder. The other configurations of the leaky bubble automatic detection system 1 and the leaky bubble automatic detection method according to the present embodiment are the same as those of the first embodiment described above, and thus further detailed description thereof is omitted.

By using helium gas instead of compressed air, the following excellent effects can be obtained. That is, when helium gas is used, the inspection accuracy is improved as compared with the case where compressed air is used. In other words, a finer leak can be detected. The main reason is that helium molecules (He) constituting helium gas are smaller than nitrogen molecules (N ₂ ) and oxygen molecules (O ₂ ) which are the main components of air. That is, even if the defect present in the inspection object 9 is so fine that compressed air cannot pass, the same defect may pass through helium gas. As a result, according to the present embodiment, the inventors have confirmed through experiments that an accuracy comparable to that of a conventional leak test using helium gas as a search gas is achieved.

  Although helium molecules are smaller than nitrogen molecules and oxygen molecules, the presence of helium gas that has become leaked bubbles 91 in the solution 21 can be detected by the determination device 7 as in the first embodiment. . That is, the helium gas that has passed through the defect of the inspection object 9 becomes a leaking bubble 91, which is separated from the surface of the inspection object 9 and floats in the solution 21. At this time, the leaking bubble 91 derived from helium gas expands to the same size as when compressed air is used in the first embodiment. Therefore, even if the leaking bubble 91 derived from helium gas is imaged by the imaging device 6 in the internal space 31 of the screen 3, the presence is determined by the determination device 7 as in the case of the first embodiment. In particular, the inventor has observed through experimentation that a helium gas leaking bubble 91 that has passed through a defect that cannot pass air tends to be larger than a leaking bubble 91 derived from air.

In relation to this, Non-Patent Document 1 discloses an experimental result indicating that a bubble having a higher gas density has a smaller bubble diameter in bubbles generated in a liquid. Non-Patent Document 2 discloses the following approximate expression (1).
R _F = (3σa / 2ρg) ^ (1/3) (1)
This approximate expression (1) represents the radius R _F of the bubble derived from the gas discharged from the minute hole opened at the end of the cylinder submerged in the liquid. Here, σ represents the surface tension coefficient of the liquid, a represents the inner radius of the cylinder, ρ represents the density of the liquid, and g represents the gravitational acceleration.

  As described above, the helium gas leak bubble 91 in the present embodiment can also be detected by using the same image processing as in the first embodiment.

  Further, the leaking bubbles 91 of the helium gas also peel off earlier from the surface of the inspection object 9 by the action of the surfactant. This effect is the same as in the case of the first embodiment.

  The invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say. In addition, the features described in the embodiments can be freely combined within a technically consistent range.

DESCRIPTION OF SYMBOLS 1 Leak bubble automatic detection system 2 Container 21 Solution 22 Water surface 23 Water level 3, 3A-3C Screen 31 Internal space 32 Water surface 33 Water level 331 Upper limit water level 332 Lower limit water level 34 Water level meter 35, 35A-35C Slope part 361, 361A-361C Plane part 362, 362A to 362C Plane portion 37 Connection port 38, 38A to 38C Frame portion 39 Cross 4 Depressurization device 41 Airtight hose 5 Pressurization device 51 Airtight hose 6, 6A to 6C Imaging device 7 Judgment device 71 Bus 72 Input / output interface 73 Operation Device 74 Storage device 741 Program 742 Data 75 External storage device 751 Recording medium 8 Control device 9 Inspection object 91 Leaked bubble

Claims (10)

A container for storing an inspection object and a solution in which the inspection object is immersed;
A screen disposed immediately above the inspection object and having an internal space for sandwiching the solution;
A pressure reducing device that depressurizes the internal space of the screen and raises the water level of the solution in the internal space of the screen higher than the water level of the solution in the container;
A pressurizing device for pressurizing the inspection object;
A photographing device for photographing the screen and generating an image;
A determination device that analyzes the captured image and determines the presence or absence of leaking bubbles derived from the inspection target;
A leak bubble automatic detection system comprising: a controller for automatically controlling operations of the decompressor, the pressurizer, and the determination device. In the automatic air leak detection system according to claim 1,
A water level meter for measuring the water level of the solution in the internal space of the screen;
The said control apparatus controls the said pressure reduction device so that the said water level may be settled in the predetermined range according to the measurement result of the said water level meter. The leak bubble automatic detection system according to claim 1 or 2,
The solution is an aqueous solution containing a surfactant. In the automatic air leak detection system according to claim 3,
The surfactant is
Including ethanol,
The concentration of the ethanol in the solution is included in a range of 40 wt% to 45 wt%. In the leaking bubble automatic detection system according to any one of claims 1 to 4,
The screen is
Two plane portions arranged perpendicular to the water surface of the solution and arranged parallel to each other;
A slope portion that guides the leaking bubble derived from the inspection object toward the internal space between the two flat portions;
The distance between the two flat portions is included in a range of 3 to 15 millimeters. In the automatic air bubble detection system according to claim 5,
The leak bubble automatic detection system further comprising a coating agent applied to the inner surface of the slope portion so as to enhance the hydrophilicity of the inner surface of the slope portion with respect to the solution. In the leaking bubble automatic detection system according to any one of claims 1 to 6,
The said pressurization apparatus pressurizes the said test object with the compressed air which compressed external air. Leaked bubble automatic detection system. In the leaking bubble automatic detection system according to any one of claims 1 to 6,
The said pressurization apparatus pressurizes the said test object with helium gas which has atmospheric pressure higher than external air. Leaked bubble automatic detection system. In the automatic air leak detection system according to any one of claims 1 to 8,
The determination apparatus controls an operation of the photographing apparatus. Filling the container with a solution,
Immersing the test object in the solution;
Placing a screen directly above the inspection object, sandwiching the solution in the internal space of the screen;
Reducing the internal space of the screen with a decompression device, and raising the water level of the solution in the internal space of the screen higher than the water level of the solution in the container;
Pressurizing the inspection object with a pressurizing device;
Photographing the screen with a photographing device to generate an image;
Analyzing the photographed image to determine the presence or absence of leaking bubbles derived from the inspection object by a determination device;
The control device automatically controls the decompression by the decompression device, the pressurization by the pressurization device, the photographing by the photographing device, and the detection by the determination device. Yes Leaked bubble automatic detection method.

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