JP2007071574A - Airtightness inspection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a leakage unable to be coped with by a conventional airtightness inspection device, because, for example, a defect hole is extremely fine, or bubbles generated by pressurization leakage of internal gas is too small to be separated and raised from an inspection object in the case of an airtight container or the like formed of a material endurable only to a low pressure such as a resin or a thin plate. <P>SOLUTION: In the airtightness inspection, the inspection object 40 is immersed into an inspection liquid vessel 10, and air is supplied into the inspection object 40, and bubbles generated from a defect part of the pressurized inspection object 40 are detected, to thereby inspect airtightness. In the inspection, an ultrasonic transmission part 20 and an ultrasonic reception part 30 are arranged on optional different positions in the inspection liquid vessel 10, and a standing sound field is generated by a periodical ultrasonic wave wherein a fixed pattern waveform is transmitted repeatedly from the ultrasonic transmission part in the inspection liquid vessel, and each received waveform before pressurization and after pressurization is compared each other by the ultrasonic reception part 30, and hereby a change of the standing sound field caused by the bubbles generated from the defect part of the inspection object is detected as a change of a standing waveform, to thereby inspect airtightness of the inspection object. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for performing an airtight inspection of a steel pipe material, a sealed container body, and the like in a liquid using ultrasonic waves.

  In many fields where airtight parts are manufactured, airtight inspection using an air leak inspection apparatus as shown in Patent Document 1 is performed. The air tightness inspection device immerses the inspection object in the liquid tank, then fills the inspection object with gas and pressurizes it to cause gas leakage from the defect of the inspection object in the water tank. It is an apparatus for confirming pass / fail by checking, and is generally called a submerged airtight inspection apparatus. The submerged airtight inspection device is put into practical use in various fields such as automobile parts, gas appliances, and medical appliances. In particular, 100% inspection is performed in the airtight inspection of steel pipe materials and airtight containers where airtightness such as flammability, solubility, high temperature, and low temperature is extremely important, and the ambiguity of judgment based on skill level of visual inspection and labor cost Was a problem at the manufacturing site. The device of Patent Document 1 also has a rocking mechanism for facilitating the separation of bubbles into water, and is still generally used in a wide field.

  Currently, due to the flow of inspection automation, industries such as electrical machinery, oil and gas equipment, automobiles, and food machinery that manufacture airtight parts are trying to automate a number of inspection devices. Currently, helium and hydrogen gas A differential pressure type automatic inspection apparatus as shown in Patent Document 3 using a gas diffusion type and an airtight differential pressure as shown in Patent Document 2 using a gas is put into practical use.

  However, in the differential pressure type automatic inspection device, when the inspection object is at a high temperature due to the residual heat after welding, the accuracy is not good due to the influence of pressure fluctuation due to gas expansion or the influence of environmental temperature or atmospheric pressure fluctuation. There is a drawback. On the other hand, gas diffusion type requires an expensive chamber tank, helium gas is expensive, and hydrogen gas is a reinforced and lightweight component using hydrogen-absorbing materials such as composite materials such as carbon fiber and new materials However, the scope of application is limited.

  In addition to the above inspection apparatuses, an airtight inspection method using ultrasonic waves has also been proposed. As an example, the method disclosed in Patent Document 4 will be described in detail with reference to FIG. Both ends of the steel pipe 71 as an object are held by a holding device 72 and placed in a water tank 76 filled with water. Next, the steel pipe 71 is filled with compressed air from the pneumatic feeder 73. At this time, if the steel pipe 71 has a through hole 74 penetrating the inner and outer surfaces, the air filled in the steel pipe 71 leaks out of the steel pipe 71 through the through hole 74 and rises as bubbles in the water, Ascend to and burst. This is a method of detecting the presence or absence of a through hole by detecting the ultrasonic wave generated at the time of rupture with a microphone or a detection device 75.

In another airtight inspection technique using ultrasonic waves, a bubble collecting funnel is provided on the object to be inspected, and bubbles are detected by a detector using an ultrasonic echo method or an ultrasonic Doppler method in the bubble collection tube or the bubble accumulation tube. For detecting the presence or absence of air and the amount of air (for example, see Patent Documents 5 and 6), and for detecting sound generated when gas leaks from an inspection object due to a whistling effect as an audible sound or an ultrasonic wave (for example, In addition to a sensor directly attached to an inspection object and detecting mechanical vibration or vibration sound generated when gas leaks from the inspection object as an ultrasonic wave (see Patent Document 7) (for example, patent) Document 8) is known.
Japanese Utility Model Publication No. 03-27334 JP 2004-163223 A Japanese Utility Model Publication No. 63-63742 Japanese Patent Laid-Open No. 50-43988 Japanese Patent Laid-Open No. 03-180734 No. 3044473 gazette JP-A 63-249033 Japanese Patent Laid-Open No. 62-133334

However, in these airtight inspection devices, the amount of leakage can be increased when the defect hole is relatively large and the amount of leakage is large, or the object to be inspected is strong and the pressure of compressed air supplied to the object to be inspected is increased. Although it is effective in some cases, it is a material that can only be pressed at low pressure because the defect hole is extremely fine due to recent quality improvement, or it is easily deformed by internal pressure, such as resin, and leaks due to pressure deformation. Airtight containers where airtightness is particularly important, such as in the case of airtight containers made, or in the case of airtight containers made with a structure that can only be pressed under low pressure because internal deformation causes deformation and fracture. In this case, even if there is a leak, it is extremely small and does not cause a vibration or whistling effect. Can not The present invention a new problem occurs that mention has been made in view of recent such problems. The main object of the present invention is to create a standing sound field in an aquarium using ultrasonic waves, and the standing sound field is a reproducible standing sound field that is uniquely generated by the ultrasonic reflection environment in the aquarium. Focusing on a certain thing, by detecting the change of the standing sound field accompanying the change of the ultrasonic reflection environment due to the leakage in the aquarium from the received waveform, it detects the minute leakage that cannot be handled by the conventional airtightness inspection device, It is another object of the present invention to provide a high-performance airtight inspection apparatus capable of estimating the leakage position by performing operational analysis on a received waveform.

  That is, the feature of the present invention that meets the above-described purpose is that the object to be inspected is immersed in the inspection liquid in the inspection liquid tank, and gas is supplied into the inspection object from the pipe connected to the object to be inspected. In an airtight inspection method for inspecting the airtightness of an inspection object by detecting bubbles generated from a defective part of the pressed inspection object, a predetermined pattern waveform is repeatedly transmitted from the ultrasonic transmission unit into the inspection liquid tank By creating a standing sound field with periodic ultrasonic waves, and comparing the received waveform before and after pressurization in the ultrasonic receiver, the standing by the bubbles generated from the defective part of the inspection object The object is to inspect the airtightness of the inspection object by detecting the change in the sound field as the change in the standing waveform.

  According to a second aspect of the present invention, in the above airtightness inspection method, a detection calculation unit is provided outside the test solution tank, and ultrasonic receiving units are arranged at two or more arbitrarily different locations in the test solution tank. By comparing the changes in the standing waveform due to the bubbles generated from the defective part of the inspection object received by each of the receiving parts, the generation position of the bubbles generated from the defective part of the inspection object is calculated by processing. It is characterized by estimating. Furthermore, the present invention is characterized by an apparatus for carrying out the above airtightness inspection method.

  Hereinafter, more specifically, in a state where the object to be inspected is immersed in the inspection liquid in the inspection liquid tank, from an ultrasonic transmission unit arranged at one arbitrary position in the inspection liquid at regular intervals. When periodic ultrasonic waves that repeatedly transmit a predetermined pattern waveform are transmitted into the test liquid tank, the transmitted ultrasonic waves travel straight while diffusing, and the inner wall of the test liquid tank, the structure inside the test liquid tank, the object to be inspected Reflects on objects. The reflected ultrasonic wave repeatedly attenuates and extinguishes in various ways while hitting the inner wall of the test liquid tank, the structure inside the test liquid tank, the object to be inspected, etc. while being diffused and attenuated. At this time, when the sound pressure of various reflected ultrasonic waves is received at an arbitrary position in the test solution tank, a standing waveform that repeats a predetermined pattern waveform at a certain period is received as a result of superimposing a transmitted wave and a reflected wave. Will come to be. This standing waveform is different when the receiving position and receiving direction in the test liquid tank are different, and the material and shape of the inner wall of the test liquid tank and the structure in the test liquid tank are changed. In some cases, a change corresponding to the change is shown. In this way, the transmitted wave transmitted into the test liquid tank is reflected variously by the reflector in the test liquid tank, and as a result, the sound pressure distribution of the ultrasonic waves formed in the test tank by the superposition of the waves This is generally called a standing sound field, and the standing sound field does not change unless the acoustic environment in the test solution tank changes, and the periodicity is maintained.

  In addition, reflection of sound including ultrasonic waves generally occurs at the interface between two different materials, and almost at the interface between two materials where there is a large difference in specific acoustic resistance expressed by the product of the sound speed and density inherent in the material. Is reflected. For example, the difference between air is about 400, water is about 1.4 million, and metal is about 10 million, and the double difference between liquid and gas is particularly larger than the double difference between liquid and solid. From this, rather than the change in the acoustic environment in the inspection liquid tank generated in the inspection object itself by pressurizing the gas in the inspection object immersed in the inspection liquid, the inspection by the pressurization The change in the acoustic environment caused by the bubbles formed by leaking from the defect of the object gives a larger change to the standing sound field in the inspection liquid tank.

  The invention according to claim 1 of the present invention utilizes this fact to provide at least one ultrasonic transmission unit and an ultrasonic reception unit arranged at a position different from the position where the ultrasonic transmission unit is arranged. One by one in the inspection liquid in the inspection tank, and by ultrasonic waves formed in the inspection tank by transmitting periodic ultrasonic waves that repeat a predetermined pattern waveform from the ultrasonic transmission unit When a standing sound field is received by the ultrasonic receiving unit, a periodic reception waveform corresponding to the arrangement position of the ultrasonic receiving unit in the inspection tank can be obtained, and the inspection object immersed in the inspection liquid When the gas inside is pressurized and, as a result, a change occurs in which bubbles are formed due to gas leakage from the defective portion on the surface of the object to be inspected, the acoustic environment in the inspection liquid tank has changed. It will be received by the ultrasonic receiver Changes in the previous year periodicity receiving waveform occurs. As a result, it is possible to realize a high-performance airtight inspection apparatus that can detect a minute leak that cannot be handled by a conventional airtight inspection apparatus.

  According to a second aspect of the present invention, in the method, a detection calculation unit and an ultrasonic wave receiving unit are disposed at two or more different locations in the test liquid tank outside the test liquid tank. Receiving waveforms received by the sound wave receiving unit are different waveforms based on the relative positional relationship between the inner wall of the test liquid tank in the test liquid tank or the structure inside the test liquid tank and the receiving unit arranged. Become. Therefore, when the gas in the inspection object immersed in the inspection liquid is pressurized, and as a result, a change occurs such that bubbles are formed on the surface of the inspection object due to gas leakage from the defective portion. The generation of bubbles generated from the defective part of the object to be inspected is performed by comparing the waveform changes after pressurization received by the ultrasonic wave receiving parts arranged at two or more different places with each other by the arithmetic processing part. The position can be estimated.

  Claims 3 and 4 are apparatuses for carrying out each of the above airtightness inspection methods, and can effectively carry out the airtightness inspection.

The hermetic inspection method and apparatus of the present invention has a very small amount of leakage from the defect of the object to be inspected, so it cannot be detected by a conventional airtight inspection apparatus, and even if it relies on visual inspection, it is highly accurate regardless of visual inspection. It is possible to improve the reliability and accuracy of airtight inspection by detecting the occurrence and leakage of bubbles.

  In particular, it is difficult to apply excessive inspection pressure such as thin objects or inspection objects that are easily deformed by internal pressure, or contain harmful or highly flammable substances that require high airtightness. It can be suitably applied to an airtight inspection of parts to be made. Inspection targets include automotive parts such as aluminum wheels, fuel pipes and fuel tanks, catalyst piping such as air conditioners and heat exchangers, electrical and electronic equipment parts such as fuel cell cases, flammable and harmful gases or chemicals, cells and microorganisms. It is effective for airtight inspection of medical instruments and food containers.

  Furthermore, the ultrasonic standing sound field that is uniquely generated by the reflection environment in the inspection liquid tank causes the leakage of bubbles from the object to be inspected to the inspection liquid, that is, the formation of a boundary between liquid and gas having very different specific acoustic resistance. Therefore, it is possible to simultaneously inspect shadow portions that cannot be visually confirmed, such as the opposite side or the lower side of the object to be inspected. In addition, due to analysis and estimation of leakage position using multiple ultrasonic transmitters or receivers, erroneous detection due to floating dust floating in the test liquid tank and the flow of the test liquid, the specific acoustic resistance is close to that of the test liquid, and the test target It is also possible to prevent erroneous detection due to the presence of bubbles preliminarily attached to the object and the rising of the bubbles adhering to the object from the object to be inspected.

  Therefore, in the detection by visual inspection, there is a drawback that the inspectable range of the inspection object is limited or the water flow or transparency of the inspection liquid influences the judgment, but according to the present invention, those problems are also caused. It is possible to automate and reduce the labor cost and achieve high-precision detection. Compared with the conventional differential pressure type and gas diffusion type inspection methods, this device has a wider range of applications such as pressure resistance strength of objects to be inspected, detection of minute leaks, and the degree of freedom of the inspection gas used, and the running cost is low. Has the advantage of.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the embodiment shown below is an example of an airtight inspection apparatus for embodying the technical idea of the present invention, and the airtight inspection apparatus of the present invention is of course not limited to the following. Further, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the embodiments are not intended to limit the scope of the present invention only to the specific description unless otherwise specified. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation.

  FIG. 1 is a perspective view showing a schematic configuration of a test liquid tank of an airtight inspection apparatus for carrying out the airtight inspection method of the present invention. First, the airtightness inspection apparatus does not cause a change in shape as much as possible even when the inspection object 40 is immersed in the inspection liquid tank 10 in the state where the inspection liquid 13 is stored in the inspection liquid tank 10 and pressurized in the inspection object 40. To fix. The inspection liquid tank 10 has an arbitrary liquid level in the inspection liquid tank 10 in the same manner as the ultrasonic transmitter 20 disposed in advance in the liquid tank below an arbitrary liquid level in the inspection liquid tank 10. An ultrasonic receiving unit 30 disposed in a different position from the lower ultrasonic transmitting unit 20 is provided, and the ultrasonic transmitting unit 20 and the ultrasonic receiving unit 30 convert voltage changes into ultrasonic waves. Or vice versa. Further, although not shown, the inspection object 40 is supplied, immersed, and discharged by a handling device for carrying and a lifting device for raising and lowering.

  While the inspection object 40 is immersed, periodic ultrasonic waves that repeatedly transmit a predetermined pattern waveform are constantly radiated from the ultrasonic transmission unit 20. The ultrasonic receiving unit 30 receives a voltage waveform converted by sound pressure that can be received on the receiving surface at the position where the ultrasonic receiving unit 30 is disposed. For periodic ultrasonic waves radiated from the ultrasonic transmitter 20 and repeatedly transmitting a predetermined pattern waveform, a sine wave continuous wave as illustrated in FIG. Such as a burst sine wave, a rectangular wave having a different duty ratio as exemplified in (c), a periodic pulse wave as exemplified in (d), or a coded code signal as exemplified in (e). Used.

  Since the sine wave continuous wave of (a) has continuity, it is easy to create a standing sound field in the detection of leak and estimation of the leak position, and it has excellent responsiveness and periodicity of change, but it is noise resistant. There is a difficulty in sex and ease of detection. Since (c) and (d) are intermittent waveforms, it takes time to form a standing sound field and detect the periodicity of the received waveform in the detection of leakage and estimation of the leakage position. Excellent ease. (B) has a feature located between (a) and (c) above. (E) has both continuity of waveform and changes over time such as waveform amplitude, so it is easy to create a standing sound field, and it has excellent responsiveness and periodicity of change, and has changes over time of waveform. Therefore, there are many advantages such as noise resistance and ease of false detection and correction.

  FIG. 2 is a schematic configuration diagram of an airtight inspection apparatus when the inspection liquid tank is viewed from above. An air supply pipe 45 for pressurizing and supplying gas is connected to the object to be inspected 40, and the air supply pipe 45 is connected to a pressurized air supply apparatus 50 outside the test liquid tank 10. The ultrasonic transmission unit 20 is connected to a transmitter 25 provided outside the test liquid tank 10, while the ultrasonic reception unit 30 is connected to a receiver 35, and these are connected to a controller 60 including a calculation unit 65. Yes.

  Here, the air supply pipe 45 is detachable with respect to the inspection object 40 and has a flexible structure so that it can be interlocked with the ascent and descent of the inspection object 40 into the inspection liquid tank. The transmitter 25 includes a programmable periodic signal source generator and an amplifier for driving an electrostrictive element used in the ultrasonic transmitter 20. The receiver 35 has a low noise amplification circuit for accurately amplifying a weak voltage signal from the electrostrictive element used in the ultrasonic receiving unit 30 and a switch circuit for switching reception as necessary. .

  FIG. 4 is a conceptual diagram showing a situation in which ultrasonic waves radiated from the ultrasonic transmission unit 20 are reflected in a complex manner in the test liquid tank. The ultrasonic receiver 30 attenuates the ultrasonic wave radiated from the ultrasonic transmitter 20 into the liquid tank by reflection / diffusion on the tank wall or the acoustic boundary surface such as the boundary surface between the inspection object 40 and the test liquid 13. I will do it. Since the diffusion energy of the sound wave has a direction vector, it shows an arbitrary sound pressure change with time with respect to an arbitrary direction at an arbitrary position in the test liquid tank 10, that is, an arrangement position of the ultrasonic receiving unit 30 Change in sound pressure with time, and even with the same position, the sound pressure change with time will be different if the direction of the receiving surface is different. In addition, the arrangement positions of the ultrasonic transmission unit 20 and the ultrasonic reception unit 30 are not necessarily in the test liquid tank 10 and may be outside the test liquid tank in contact with the test liquid tank 10. When the influence of ultrasonic waves propagating in the material to be measured is large, the difficulty of the inspection becomes high, and substances such as air that have remarkably different acoustic resistance are outside the inspection liquid tank 10 that does not come into contact with the inspection liquid tank 10 or the liquid surface 14. Inspection is difficult because of the interposition.

  5 and 6 are conceptual diagrams showing that the ultrasonic wave radiated from the ultrasonic transmission unit 20 is diffusely reflected in a complex manner in the test liquid tank, resulting in a standing sound field. That is, FIG. 5 is a conceptual diagram of the test liquid tank as viewed from above, and FIG. 6 is a conceptual diagram of the test liquid tank as viewed from the side.

  As shown in these figures, periodic ultrasonic waves that repeatedly transmit a predetermined pattern waveform radiated from the ultrasonic transmission unit 20 are reflected and diffused in a complicated manner on the acoustic boundary surface in the test liquid tank, and as a result, A stationary sound field, which is a periodic change in sound pressure over time due to superposition of ultrasonic waves in the test liquid tank 10, is shown. In the standing sound field, the periodic ultrasonic wave is constantly transmitted from the ultrasonic transmission unit 20, and the acoustic boundary surface where the ultrasonic wave radiated in the test liquid tank 10 is reflected and diffused and the test liquid 13 are acoustically related. A predetermined standing sound field is generated when there is no change over time. The change in the standing sound field is also caused by the flow, temperature distribution, and suspended matter generated in the test solution 13, but the change due to the temperature distribution is smaller than the change due to the flow, and the change due to the flow is small and has a large effect on the standing sound field. Not so much. There are various types of changes due to suspended matter, but most of them are hydrophilic, so changes are negligible. The standing sound field generated in the inspection liquid tank 10 is observed at all locations of the inspection liquid 13 surrounding the inspection object 40. However, depending on the shape of the test liquid tank 10 and the object to be inspected 40, there may be a significantly dilute portion of the standing sound field in a few regions. It is also considered that the arrangement of the ultrasonic transmission unit 20 is taken into consideration, or that a plurality of ultrasonic transmission units are arranged.

  FIG. 7 shows an enlarged conceptual diagram of the vicinity of the defect portion 41 before and after pressurizing the inspection gas when the inspection object 40 has the defect portion 41. Since the defect part 41 of the inspection object 40 immersed in the inspection liquid 13 is an extremely small gap, the surface tension of the inspection liquid 13 and the atmospheric pressure of the gas preliminarily in the inspection object 40 are balanced only by immersion. Neither gas leakage into the inspection liquid 13 nor penetration of the inspection liquid 13 into the inspection object 40 occurs. For this reason, the ultrasonic wave reflected in the vicinity of the defective portion 41 of the inspection object is simple depending on the shape of the inspection object 40. When the inspection gas 16 is pumped and supplied into the inspection object 40 from the supply pipe 45 connected to the inspection object 40, the equilibrium is lost, and the inspection gas 16 extends from the defect portion 41 along the surface of the inspection object 40. Leakage occurs, and bubbles 17 are generated on the test solution 13 side. Since the defective portion 41 is extremely small, the bubbles 17 generated by the pressurization are rarely detached into the inspection liquid 13 while remaining attached to the surface of the inspection object 40. Alternatively, in the case where the inspection object 40 has a fragile material structure such as a thin metal plate or resin, if the pressure of the inspection gas 16 supplied under pressure is excessively large, the material of the inspection object 40 is deformed, and other than the defective portion. Also, there is a possibility that peeling or cracking may occur due to pressurization, so that the pressurizing force cannot be increased too much and only pressurization of 1.1 to 1.2 times can be performed. Even in such a case, the bubbles 17 generated by the pressurization are less likely to leave the test liquid 13 while remaining attached to the surface of the test object 40.

  FIG. 8 shows a schematic received waveform at the ultrasonic receiving unit 30 installed near the defective portion 41 before and after the inspection gas pressurization when the inspection object 40 has the defective portion 41, where (B) is after pressurization. The 2 MHz continuous wave ultrasonic wave radiated into the inspection liquid 13 from the ultrasonic transmitter 20 toward the defective portion 41 of the inspection object 40 travels in the inspection liquid 13 while diffusing and attenuating. Reflected at the boundary surface with the test liquid 13. Before pressurizing and supplying the inspection gas to the inspection object 40, the ultrasonic waves cause a relatively simple reflection at the boundary surface between the inspection object 40 and the inspection liquid 13 as shown in FIG. A simple sinusoidal continuous wave including many frequency components near 2 MHz is also received by the ultrasonic receiving unit 30 disposed in the vicinity.

  On the other hand, when the inspection gas 16 is supplied to the inspection object 40 under pressure, the inspection gas 16 leaks from the defect portion 41 along the surface of the inspection object 40 as shown in FIG. 17 occurs, the 2 MHz continuous wave ultrasonic wave radiated from the ultrasonic transmission unit 20 causes the boundary surface between the bubble 17 and the inspection liquid 13 generated in the defect portion 41 and the boundary surface between the inspection object 40 and the inspection liquid 13. Therefore, the voltage waveform received by the ultrasonic wave receiving unit 30 loses periodicity and has a waveform different from that before pressurization. Further, in most cases, the minute leakage of the inspection gas 16 from the defect portion 41 continues due to the pressurized supply, so that the state of reflection of the ultrasonic wave at the boundary surface between the bubble 17 generated in the defect portion 41 and the inspection liquid 13. Indicates a change with time, and the periodicity of the voltage waveform received by the ultrasonic wave receiver 30 is also lost.

  The frequency of the waveform before and after pressurization is obtained by storing and calculating the voltage waveform received by the ultrasonic wave receiving unit 30 through the receiver 35 by the controller 60 and the calculation unit 65 by a calculation analysis method such as a filter, FFT, or wavelet. A change in the received waveform before and after pressurization can be detected by obtaining and comparing the characteristic amount and periodicity related to the power spectrum. Thus, it is possible to detect a change in the acoustic environment in the inspection tank 10, that is, the presence or absence of a very small leakage of the inspection gas 16 from the defective portion 41 of the inspection object 40.

  FIG. 9 shows a schematic view when the ultrasonic wave receiving units are arranged at two different places as the second embodiment of the present invention. In this case, the ultrasonic transmitter 20 at an arbitrary position in the test liquid 13 filled in the test liquid tank 10 and the first ultrasonic receiver 30A at an arbitrary position in the test liquid 13 different from these. The second ultrasonic receiving unit 30B is disposed at an arbitrary position in the inspection liquid 13 different from that of the inspection object 13, and the inspection object 40 is immersed therein. From the ultrasonic transmitter 20, periodic ultrasonic waves that repeatedly transmit a predetermined pattern waveform are constantly radiated to the test liquid 13 in the test liquid tank 10. The emitted ultrasonic waves are reflected and diffused and attenuated on the tank wall and the acoustic boundary surface such as the boundary surface between the object to be inspected 40 and the test liquid 13 to form a standing sound field in the test liquid tank 10. To do. At this time, the acoustic environment when the inside of the test liquid tank 10 is viewed from the receiving surface of the first ultrasonic receiver 30A and the inside of the test liquid tank 10 is viewed from the receiving surface of the second ultrasonic receiver 30B. Since the acoustic environment differs from the case, the voltage waveforms received on the receiving surface of the first ultrasonic receiving unit 30A and the receiving surface of the second ultrasonic receiving unit 30B are different.

  10 (a) and 10 (b), a comparison of received waveforms at the first ultrasonic receiver 30A before and after the test gas pressurization when the inspection object 40 has a defective portion 41, and FIG. (B) and (b) show comparison of received waveforms at the second ultrasonic receiving unit 30B before and after pressurizing the inspection gas when the inspection object 40 has a defective portion 41. The reception waveform received by the first ultrasonic receiving unit 30A before pressurization and the reception waveform received by the second ultrasonic receiving unit 30B reflect the acoustic environment viewed from the receiving surface of each receiving unit. Therefore, the received voltage waveform is stored and calculated by the calculation unit 65 in the controller 60 in FIG. 2 via the receiver 35 by a calculation analysis method such as a filter, FFT, or wavelet. The features of the acoustic environment in the first ultrasonic receiving unit 30A before compression and the acoustic environment in the second ultrasonic receiving unit 30B can be obtained as feature quantities related to the frequency power spectrum of the waveform. The difference in the received waveform is caused by the difference in the propagation state of the ultrasonic wave from the ultrasonic transmitter 20 to the first ultrasonic receiver 30A or the second ultrasonic receiver 30B. Is an index indicating the propagation state of ultrasonic waves from the ultrasonic transmitter 20 to the first ultrasonic receiver 30A or the second ultrasonic receiver 30B. Similarly, the characteristic amount of periodicity obtained by the calculation unit 65 indicates that the acoustic environment in the test liquid tank 10 is stable and a standing sound field is formed as described above.

  When the inspection gas 16 is pressurized and supplied to the inspection object 40, the inspection gas 16 leaks from the defect portion 41 along the surface of the inspection object 40, and bubbles 17 are generated on the inspection liquid 13 side. The ultrasonic wave radiated from 20 is reflected at the boundary surface between the bubble 17 and the inspection liquid 13 generated in the defect portion 41 and the boundary surface between the inspection object 40 and the inspection liquid 13, and is reflected differently from that before pressurization. The voltage waveform received by the first ultrasonic receiving unit 30A and the voltage waveform received by the second ultrasonic receiving unit 30B lose periodicity in order to generate a direction and reflectivity, and before pressurization. It becomes a different waveform. Moreover, the waveform change shows a different change between the voltage waveform received by the first ultrasonic receiving unit 30A and the voltage waveform received by the second ultrasonic receiving unit 30B. This difference in change stems from the fact that the relative positional relationship in which the bubbles 17 are generated is different in the propagation process of ultrasonic waves from the ultrasonic transmitter 20 to the first ultrasonic receiver 30A or the second ultrasonic receiver 30B. . From this, the voltage waveform received by the first ultrasonic receiving unit 30A after pressurization and the voltage waveform received by the second ultrasonic receiving unit 30B are stored in the controller 60 via the receiver 35. By calculating and storing by the calculation unit 65 using a calculation analysis method such as a filter, FFT, wavelet, etc., the frequency spectrum change tendency, the change in the characteristic amount related to the frequency spectrum, the change response time, the difference in periodicity loss tendency, etc. The change position of the acoustic environment can be estimated.

  Furthermore, the number of the ultrasonic receivers 30 to be arranged in the inspection liquid tank 10 is not limited to two, but more than that, and the positions of the defective parts 41 can be estimated more accurately by arranging them at different positions and orientations. be able to. However, if the number of ultrasonic receiving units is increased, more time is required for the analysis, so the balance between the inspection time and the position estimation accuracy becomes a problem. Theoretically, the same estimation is possible with a plurality of ultrasonic transmission units 20 and a single ultrasonic reception unit 30, but only one measurement data, that is, a reception waveform used for calculation analysis is obtained. Therefore, high accuracy is required for the receiver 35 and the calculation unit 65, which increases the difficulty, which is not preferable. Furthermore, a plurality of ultrasonic transmitters 20 and ultrasonic receivers 30 can be provided, which can be easily considered.

  If the object to be inspected has the same shape, such as a mass-produced product, prepare a simulated object in which a defective part is intentionally created at various positions of the inspected object in advance, and use this simulated object to remove from the defective part. Due to the leakage of the inspection gas, the change in the voltage waveform received by the ultrasonic wave receiving unit is calculated and analyzed by the calculation unit in the controller, and the characteristic amount necessary for the detection of the presence or absence of the leak and the position estimation is obtained in advance. By storing this in the controller and using it as a reference value for the presence / absence of leakage or the position estimation, the calculation analysis can be made fast and easy.

It is a perspective schematic diagram of the inspection liquid tank part of the airtight inspection device concerning one embodiment of the present invention. It is a schematic block diagram of the airtight inspection apparatus which looked at the test | inspection liquid tank shown in FIG. 1 from the upper surface. (A), (b), (c), (d), and (e) are waveform diagrams showing waveform examples of periodic ultrasonic waves that repeatedly transmit a predetermined pattern waveform. FIG. 2 is a horizontal cross-sectional view of the test liquid tank shown in FIG. 1 as viewed from above, and is a conceptual diagram illustrating a state in which emitted ultrasonic waves are reflected and diffused in the test liquid tank. It is the horizontal sectional view which looked at the inspection liquid tank shown in Drawing 1 from the upper surface, and is a key map explaining the standing sound field which arose in the inspection liquid tank. It is the vertical sectional view which looked at the test liquid tank shown in Drawing 1 from the side, and is a key map explaining the standing sound field which arose in the test liquid tank. An enlarged conceptual diagram of the vicinity of the defective part for explaining that the state of reflection of ultrasonic waves changes when bubbles are leaked from the defective part due to the pressurized supply of the inspection gas. ) Is after pressurization. FIG. 8A is a schematic waveform diagram of a reception waveform at an ultrasonic receiving unit based on the conceptual diagram shown in FIG. 7, where FIG. 7A is a reception waveform before pressurization and FIG. 7B is a reception waveform after pressurization. It is the schematic which looked at the test liquid tank of the airtight test | inspection apparatus concerning the 2nd Embodiment of this invention from the upper surface, (A) is. FIG. 8 is a comparative waveform diagram showing changes in the received waveform accompanying bubble leakage in the first ultrasonic receiving unit based on the conceptual diagram shown in FIG. 7, (A) before pressurization, (B) after pressurization. It is. FIGS. 7A and 7B are comparative waveform diagrams showing changes in the received waveform due to bubble leakage in the second ultrasonic receiving unit based on the conceptual diagram shown in FIG. 7. is there. It is the schematic which shows an example of the conventional airtight test | inspection.

Explanation of symbols

10: Test liquid tank 13: Test liquid 14: Liquid surface 16: Test gas 17: Ultrasonic transmitter 25: Transmitter 30: Ultrasonic receiver 30A: First ultrasonic receiver 30B: Second ultrasonic receiver Part 35: Receiver 40: Inspected object 41: Defect part 45: Air supply pipe 50: Pressurized air supply apparatus 60: Controller 65: Calculation part 70: Filter 71: Steel pipe 72: Holding apparatus 73: Pneumatic feeder 74: Penetration Hole 75: Detection device 76: Water tank 77: Recorder

Claims (4)

Bubbles generated from defective parts of the pressurized test object by immersing the test object in the test liquid in the test liquid tank, supplying gas from the pipe connected to the test object into the test object In the airtight inspection method for inspecting the airtightness of the object to be inspected by detecting
An ultrasonic transmission unit and an ultrasonic reception unit are arranged at different arbitrary positions in the inspection liquid tank,
A standing sound field is created by periodic ultrasonic waves such that a predetermined pattern waveform is repeatedly transmitted from the ultrasonic transmitter to the test liquid tank, and the received waveform after pressurization is compared in the ultrasonic receiver. The airtightness of the inspection object is inspected by detecting the change of the standing sound field due to the bubbles generated from the defective part of the inspection object as the change of the frequency power spectrum of the standing waveform. Airtight inspection method.   A detection operation unit is provided outside the inspection liquid tank, ultrasonic reception units are arranged at two or more arbitrarily different locations in the inspection liquid tank, and received by each of the arranged ultrasonic reception units. By comparing the changes in the frequency power spectrum of the standing waveform due to the bubbles generated from the defective portion of the object with each other, the generation position of the bubbles generated from the defective portion of the inspection object is estimated by a calculation process. The airtight inspection method according to claim 1. Bubbles generated from defective parts of the pressurized test object by immersing the test object in the test liquid in the test liquid tank, supplying gas from the pipe connected to the test object into the test object An airtight inspection device that inspects the airtightness of an object to be inspected by detecting
In order to transmit an ultrasonic wave to the test liquid in the test liquid tank and create a standing wave in the test liquid tank without a gap, an ultrasonic transmitter is disposed at an arbitrary position in the test liquid tank. With
Arrange the ultrasonic receiver at any different position in the test liquid tank,
While creating a standing sound field by periodic ultrasonic waves such that a predetermined pattern waveform is repeatedly transmitted from the ultrasonic transmission unit into the inspection liquid tank, reception before and after pressurization in the ultrasonic reception unit By comparing the waveforms, the change in the standing sound field due to the bubbles generated from the defective part of the inspection object is detected as the change in the frequency power spectrum of the standing waveform so as to inspect the airtightness of the inspection object. An airtight inspection device characterized by   A detection calculation unit is provided outside the test liquid tank, and ultrasonic reception units are arranged at two or more arbitrarily different locations in the test liquid tank, and received by each of the arranged ultrasonic reception units. Computation processing of the generation position of the bubble generated from the defective part of the inspection object is performed by comparing the change of the frequency power spectrum of the standing waveform due to the bubble generated from the defective part of the inspection object. The airtightness inspection apparatus according to claim 3, wherein the airtightness inspection apparatus according to claim 3 can be estimated.

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