JP2009115655A - Inspection method and inspection device for filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means capable of detecting with high sensitivity and ease defects in a filter, without having to apply a load to the filter, and without having to require the time and the labor for pretreatment and after-treatment. <P>SOLUTION: In this inspection method for the filter, fine particles are generated, the fine particles are introduced from one side of the filter into the filter, an intensified directivity of light is generated, the light is transmitted through the other side of the filter, vibration of the air is generated further in the other side of the filter, and the fine particles are irradiated with the light to have the fine particles visualized, while being moved, discharged from the other side of the filter by the vibration of the air. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for detecting a filter defect and an apparatus used for detecting a filter defect.

  In consideration of environmental impact, there is an increasing need to remove particulate matter contained in exhaust gas discharged from automobile engines and the like from the exhaust gas. In particular, regulations regarding the removal of particulate matter (particulate matter (also referred to as PM)) discharged from diesel engines tend to be strengthened worldwide. Under such circumstances, DPF (diesel particulate filter) for collecting and removing PM has been attracting attention.

  As an embodiment of the DPF, a plugged filter having a honeycomb structure (honeycomb filter) can be given. The honeycomb filter includes a porous partition wall that partitions and forms a plurality of cells serving as a fluid flow path, and has one end opened and the other end plugged, and one cell The remaining cells whose end portions are plugged and whose other end portions are opened are alternately arranged. According to this honeycomb filter, the fluid (exhaust gas) flowing in from one end where a predetermined cell opens passes through the partition wall and flows out as a permeating fluid to the remaining cell side, and the remaining cell opens. By flowing out from the other end, the effect of collecting and removing PM in the exhaust gas can be obtained.

  A filter having a structure in which exhaust gas permeates through porous partition walls (wall flow type filter), such as the above honeycomb filter, can reduce the filtration flow rate (partition wall permeation flow rate) because the filtration area can be increased. The pressure loss is small, and the PM collection efficiency is relatively good. However, this is based on the premise that there is no defect such as an unintended hole in the partition wall. If there is a defect, PM passes through the defect, and the PM collection capability itself as a DPF is lowered before the efficiency. For that reason, defect inspection during filter manufacturing is a very important process.

As related prior art documents, for example, Patent Documents 1 to 5 can be cited.
Japanese Patent No. 3904933 JP-A-6-134268 Japanese Patent Laid-Open No. 4-104038 JP-A-7-174660 JP 2000-193582 A

  The simplest method for inspecting filter defects is by visual observation. However, it is usually impossible to observe defects from the outside due to the structure of the filter. In addition, a method (soot printing method) is known in which soot is allowed to flow into a filter, discharged soot is adhered to a white cloth, and a defect is detected depending on the degree of adhesion. However, the load is once applied to the filter, and in addition, it takes time and labor to remove the soot before shipping (after the inspection), which is not a preferable means. Furthermore, the presence or absence of defects can be inspected by placing the filter in water and applying air pressure from the fluid inflow side and checking the foaming phenomenon on the fluid permeation and outflow side. Although the filter is not loaded, it is not a desirable means because it requires defoaming before inspection and drying after inspection.

  The present invention has been made under such circumstances, the present invention does not apply a filter defect, load on the filter, time and labor for pre-processing and post-processing, high sensitivity, It is an object to provide a means that can be easily detected. As a result of repeated research to solve this problem, the following means have been conceived.

  That is, first, according to the present invention, fine particles are generated, the fine particles are introduced into the filter from one side of the filter, light having strong directivity is generated, and the light is transmitted to the other side of the filter. Passing through the filter and generating air vibrations on the other side of the filter. The fine particles discharged from the other side of the filter are moved laterally by the vibration of the air. A method for inspecting a filter for visualizing the above is provided.

  The filter is capable of exhibiting a filtration (filtering) action. In this specification, one side of the filter, the other side is based on a member that exhibits the filtering action, and one side thereof, It means the other side. The most important part that should not have defects is a member that exhibits its filtering action (for example, a porous partition corresponds to a honeycomb filter), so that fine particles are introduced into the filter from one side of the filter, By checking whether or not fine particles are uniformly discharged from the other side of the filter, it is possible to inspect whether or not the filter is defective.

  In the filter inspection method according to the present invention, the fine particles are preferably water. The water is more preferably pure water with few impurities. When the fine particles are water, it is preferable that the fine particles are generated by a humidifying means that makes water fine particles by vibration of an ultrasonic vibrator. In addition, fine particles that are water can be generated by spraying from a nozzle.

  In addition, when the fine particles are not water, for example, burning standard incense such as incense, spraying glycols by heating, vaporizing, condensing, using solid carbon dioxide or liquid nitrogen, etc. It is possible to generate fine particles by using a device or by means of generating fine particles such as calcium carbonate using a vibration device or a blower.

  In the filter inspection method according to the present invention, it is preferable to generate air vibrations two-dimensionally.

  In the filter inspection method according to the present invention, it is preferable to generate vibration of the air by generating a longitudinal wave in the air. Alternatively, in the filter inspection method according to the present invention, it is preferable to generate vibration of the air by generating a longitudinal wave in the air. In these cases, if a longitudinal wave is generated in the air from two or more directions, or if air is sent, vibration of the air can be generated two-dimensionally.

  Longitudinal waves using air as a medium are dense waves in which vibration of air density propagates and are also called sound waves.

  In the filter inspection method according to the present invention, the filter has a surface on the other side, generates light in a planar shape, passes the light in parallel with the surface on the other side of the filter, and is two-dimensional. In particular, it is preferable to irradiate the fine particles with light.

  In the filter inspection method according to the present invention, it is preferable that a visualized image of fine particles is taken into a computer, recorded, and analyzed.

  In the filter inspection method according to the present invention, the particle diameter of the fine particles is preferably 0.3 μm or more and 200 μm or less.

  The filter inspection method according to the present invention is suitably used when the filter to be inspected is a porous honeycomb structure.

  The filter inspection method according to the present invention is suitably used when the filter to be inspected is a diesel particulate filter.

  In the filter inspection method according to the present invention, when the generated fine particles are introduced into the filter from one side of the filter, for example, the generated fine particles are collected in a tank, and a uniform pressure is applied after a uniform concentration. It is preferably introduced into the filter. Instead of applying pressure, fine particles may be introduced from the tank into the filter by suction from the other side of the filter with a fan or the like.

  In the filter inspection method according to the present invention, the concentration of the fine particles introduced into the filter is not particularly limited. It is possible to appropriately select a density that can be detected by light having strong directivity and that makes the contrast between the defective part and the other part clear.

  Next, according to the present invention, fine particle generating means for generating fine particles, fine particle introducing means for introducing the fine particles into the filter from one side of the filter, and directivity so as to pass through the other side of the filter. There is provided a filter inspection device comprising light generating means for generating strong light and longitudinal wave generating means for generating air vibration on the other side of the filter.

  In the filter inspection apparatus according to the present invention, the fine particles are preferably water (fine water droplets). Pure water is more preferable.

  In the filter inspection apparatus according to the present invention, it is preferable that the particulate generation means is an ultrasonic humidifier.

  In the filter inspection apparatus according to the present invention, it is preferable that two or more longitudinal wave generating means are provided.

  In the filter inspection apparatus according to the present invention, the longitudinal wave generating means is preferably at least one means selected from an electric signal manufacturing apparatus and a speaker, and a piezoelectric actuator and a diaphragm. Alternatively, in the filter inspection apparatus according to the present invention, the longitudinal wave generating means is preferably a vibrator, or a vibration motor and a diaphragm. As an example of a vibrator, a low frequency vibration motor can be given as an example of an air vibrator or a vibration motor.

  In the filter inspection apparatus according to the present invention, it is preferable that the light generating means is a means capable of generating light in a planar shape and allowing the light to pass in parallel to the surface on the other side of the filter.

  The filter inspection apparatus according to the present invention preferably includes a camera for imaging fine particles, and a computer that takes in and records and analyzes the captured image of the fine particles.

  As the camera, a camera having an image pickup element / medium such as a CCD or a film can be employed. As the computer, it is preferable to use a dedicated image analysis apparatus. In addition, it is preferable that the computer also serves as an image analysis device and the electrical signal manufacturing device.

  In the filter inspection apparatus according to the present invention, the particle diameter of the fine particles is preferably 0.3 μm or more and 200 μm or less.

  The filter inspection apparatus according to the present invention is preferably used when the filter to be inspected is a porous honeycomb structure.

  The filter inspection apparatus according to the present invention is preferably used when the filter to be inspected is a diesel particulate filter.

  In the present specification, the light having strong directivity is not particularly limited as long as it is light having a wavelength that is diffracted and scattered by being irradiated on the fine particles. For example, laser light is preferable. A solid laser, gas laser, semiconductor laser, dye laser, excimer laser, free electron laser, or the like can be preferably used. The wavelength of the light is not particularly limited, and for example, a red laser beam of about 650 nm, a green laser beam of about 532 nm, a violet laser beam of about 400 nm, and the like can be suitably used.

  The method for inspecting a filter according to the present invention makes it easy to detect defects because the particles are visualized by irradiating the particles with light while moving the particles discharged from the other side of the filter by vibration of air. In addition, it is possible to detect defects with high sensitivity.

  This will be described more specifically. When fine particles are generated, the fine particles are introduced into the filter from one side of the filter, light having strong directivity is generated, and when the light passes through the other side of the filter, it is discharged from the other side of the filter. The fine particles to be visualized are diffracted and scattered by being irradiated with light. If there is a defect in the filter, a lot of large particles are discharged from it, so a lot of light is diffracted and scattered by the large number of particles, so even if the defect exists in a place where it can not be seen from the outside, Depending on the difference in brightness (brightness), it is possible to determine the presence or absence of a filter defect, and it is possible to specify the location of the defect. However, in the case where laser light that passes substantially parallel to the end face is generated in the vicinity of the end face on the other side of the honeycomb filter (particulate discharge side), the diffused light component of the laser light becomes the end face on the other side of the honeycomb filter. May be irradiated. In such a case, the diffused light component is reflected at the end face to generate reflected light (also referred to as end face reflected light), making it difficult to distinguish between the diffracted and scattered light from the fine particles and the end face reflected light. Therefore, it is impossible to accurately observe the visualized fine particles. That is, the defect cannot be detected with sufficient sensitivity. The filter inspection method according to the present invention can determine a difference in luminance at a place where it is easy to discriminate between diffracted and scattered light by the fine particles and end surface reflected light by moving fine particles that diffract and scatter light. Therefore, it is possible to detect the filter defect more sensitively and more easily than when the fine particles are not moved. In addition, depending on whether or not a relatively bright place (also called a bright spot) moves (whether it shakes or not), it is determined whether the high brightness is caused by fine particles or the filter itself. Since this is possible, the possibility of erroneously detecting defects can be suppressed from this point.

  In the preferred embodiment of the filter inspection method according to the present invention, the fine particles are water, and more preferably pure water. Therefore, no extra deposits are generated on the filter during the inspection. Therefore, it is not necessary to perform pre-processing and post-processing, and it is possible to reduce the time and labor required for them by the conventional means.

  In the preferred embodiment of the filter inspection method according to the present invention, the water fine particles are generated by the humidifying means using ultrasonic waves, so that the fine particles can be easily generated. In addition, in this specification, all the generated fine particles of water are also expressed as water smoke.

  In the preferred embodiment of the filter inspection method according to the present invention, air vibrations are generated two-dimensionally, so that the fine particles can be freely moved in the intended direction on one plane. Therefore, it is possible to reliably and quickly find a place where it is easy to discriminate between the diffracted scattered light and the end-surface reflected light by the fine particles and to easily determine the difference in luminance. Therefore, it is possible to further reduce the possibility of misjudgment of the presence or absence of a filter defect as compared with the case where air vibration is not generated two-dimensionally, and in addition, it is necessary to judge the difference in luminance. The time can be further shortened.

  In a preferred embodiment of the filter inspection method according to the present invention, the longitudinal wave is generated in the air, whereby the control of the movement of the fine particles is easy. Fine particles can be moved by an intended distance by adjusting the frequency and wavelength of the longitudinal wave. Therefore, it is easy to discriminate between the diffracted scattered light and the end face reflected light by the fine particles, and it is possible to surely find the place where the difference in luminance is easy to be determined, and the presence or absence of the filter defect can be determined with high sensitivity .

  In the preferred embodiment of the filter inspection method according to the present invention, fine particles can be moved quickly by generating a longitudinal wave in the air using, for example, a vibrator. By adjusting the frequency, amplitude, and waveform of the longitudinal wave to be generated, the fine particles can be moved quickly by the intended distance. Therefore, it is possible to quickly find a place where it is easy to discriminate between the diffracted scattered light and the end face reflected light due to the fine particles, and to easily determine the difference in luminance, and it is possible to quickly determine whether there is a filter defect.

  In a preferred embodiment of the filter inspection method according to the present invention, the filter has a surface on the other side, generates light in a planar shape, and passes the light parallel to the surface on the other side of the filter. Since the fine particles are irradiated two-dimensionally, the location of the defect can be easily specified, and in addition, the defect can be detected with high sensitivity.

  In the preferred embodiment of the filter inspection method according to the present invention, the visualized fine particle image is taken into a computer, recorded, and analyzed, so that the presence or absence of the filter defect and the location of the defect can be recorded reliably. Is possible. In addition, since it is possible to construct a database of places where defects are likely to occur, it is useful for improving the manufacturing method by feeding back to the filter manufacturing method.

  In a preferred embodiment of the filter inspection method according to the present invention, since the particle diameter of the fine particles is 0.3 μm or more and 200 μm or less, defects can be detected with high sensitivity.

  The filter inspection apparatus according to the present invention is an apparatus capable of implementing the above-described filter inspection method according to the present invention, and exhibits the above-described effects through the implementation of the filter inspection method according to the present invention.

  Specifically, in the filter inspection apparatus according to the present invention, water fine particles can be easily generated with a commercially available ultrasonic humidifier. Further, by providing two or more longitudinal wave generating means (preferably located on one plane), it is possible to generate air vibrations two-dimensionally. By producing a desired electric signal with an electric signal manufacturing apparatus, converting it into vibration with a speaker and propagating it into the air, it is possible to generate a longitudinal wave in the air and generate vibration of the air. Similarly, by vibrating the diaphragm by the displacement of the piezoelectric actuator or the displacement of the vibrator, a longitudinal wave can be generated in the air and the vibration of the air can be generated.

  Hereinafter, embodiments of the present invention will be described with appropriate reference to the drawings, but the present invention should not be construed as being limited thereto. Various changes, modifications, improvements, and substitutions can be added based on the knowledge of those skilled in the art without departing from the scope of the present invention. For example, the drawings show preferred embodiments according to the present invention, but the present invention is not limited by the modes shown in the drawings or the information shown in the drawings. In practicing or verifying the present invention, the same means as described in this specification or equivalent means can be applied, but preferred means are those described below.

  First, with reference to FIG. 2 to FIG. 5, taking a case of inspecting a honeycomb filter as an example, a honeycomb filter to be inspected, a principle for detecting a filter defect, and preferable conditions in the filter inspection method will be described.

  The honeycomb filter will be described. FIG. 2 is a perspective view schematically illustrating an example of a honeycomb filter that is an inspection target (subject), and FIG. 3 is a cross-sectional view schematically illustrating an example of the honeycomb filter. For easier understanding, the structure is simplified in FIG. 3 as compared to FIG.

  The honeycomb filter 1 shown in FIG. 2 and FIG. 3 is a honeycomb structure including a porous partition wall 4 in which a plurality of cells 3 serving as fluid flow paths are defined in an interior surrounded by an outer peripheral wall 8. A plugged portion 10 for plugging the end portion of the cell 3 is formed. The partition wall 4 is arranged so as to form a plurality of cells 3 communicating between the two end faces 2a and 2b, and the plugging portion 10 plugs the cells 3 at any of the end faces 2a and 2b. Is arranged. The plugged portions 10 exist so that adjacent cells 3 are plugged at opposite ends (ends on either side of the end surfaces 2a and 2b). As a result, the end surfaces of the honeycomb filter 1 are present. Exhibits a checkered pattern (see Figure 2).

  The principle of detecting a filter defect will be described. FIG. 4 is a diagram illustrating the defect detection principle, and is a cross-sectional view schematically illustrating an example of a honeycomb filter. FIG. 5 is a diagram showing a state in which fine particles are moved by vibration of air, and is an enlarged view (corresponding to an enlarged view seen from above in FIG. 2) showing an end face of the honeycomb filter.

  As shown in FIG. 3, when the honeycomb filter 1 is used as a DPF, the exhaust gas (fluid) flows into the cell 3 (predetermined cell 3) from the one end face 2a side, and is filtered. Passes through the partition wall 4 and flows out to the cell 3 (remaining cell 3) opened on the other end face 2b side as permeate fluid, and further flows out from the other end face 2b side to the outside. When passing through the partition walls 4, PM contained in the exhaust gas is collected by the partition walls 4. However, if there is a defect such as an unintended hole in the partition wall 4, PM passes through the partition wall 4, and the PM collecting ability as the DPF is lowered. Therefore, inspection of the defect is required at the time of shipment.

  As shown in FIG. 4, in the honeycomb filter 1, when the fine particles 7 are introduced into the cells 3 from the end surface 2a side (for example), the fine particles 7 pass through the partition walls 4 and are discharged from the end surface 2b side. When the laser device 51 generates laser light and diffuses it with a lens (or scans) in the vicinity of the end face 2b in the vicinity of the end face 2b and irradiates the laser light in a planar shape, the discharged fine particles 7 Is diffracted and scattered by light and visualized. At this time, if there are defects 6 in the partition walls 4, more fine particles 7 having a larger particle diameter are discharged from there as compared with the case where there are no defects 6. Since the larger fine particle 7 diffracts and scatters more light, the laser beam is emitted above the cell 3 (part A circled in FIG. 4) formed by the partition 4 having a larger defect (defect 6). More diffraction scattering. Therefore, it is possible to detect the cell 3 formed by the partition wall 4 having the defect 6 based on the difference in luminance in the vicinity of the end face 2b (for example) of the honeycomb filter 1. Similarly, when there is a defect in the plugged portion 10, a larger number of fine particles having a larger particle diameter are discharged therefrom, so that the cell 3 having a defect in the plugged portion 10 is detected. I can do it.

  In addition to the diffused light component of the laser light, the light irradiated onto the end face 2b of the honeycomb filter 1 includes a part of diffraction scattered light generated by irradiating fine particles with the laser light. When a defect is detected using fine particles having a particle diameter of about 5 μm, the diffracted scattered light becomes light traveling in the same direction as the traveling direction of the laser light, and a part of the diffracted scattered light becomes end face irradiation light, It becomes difficult to discriminate between diffracted and scattered light and end face reflected light. Therefore, it is impossible to accurately observe the visualized fine particles. That is, the defect cannot be detected with sufficient sensitivity. When a large number of fine particles having a particle diameter of about 5 μm are used, the diffracted scattered light is mainly light that travels in the same direction as the traveling direction of the laser light, so that the amount of light incident on the imaging device that captures an image of the fine particles is reduced. Therefore, the obtained fine particle image tends to be dark. In addition, since the end surface reflected light is conventionally detected as a defect, sufficient detection sensitivity cannot be obtained.

  On the other hand, on the end face 2b side of the honeycomb filter 1, sound waves are generated by an electric signal manufacturing apparatus and a speaker (for example, not shown in FIG. 4), and the fine particles 7 are moved by the sound waves, and diffraction scattering by the fine particles. If a difference in luminance is observed and analyzed in a place where it is easy to discriminate between light and end-surface reflected light, erroneous detection can be avoided. Further, since it is possible to determine whether the brightness is a fine particle or the filter itself depending on whether the bright spot moves (whether it shakes or not), the partition 4 or the plugging portion 10 The risk of making a mistake when there is a defect is reduced.

  When moving the microparticles 7 by sound waves, as shown in FIG. 5, the two speakers 21a and 21b, which are sound wave generation sources, are, for example, 90 ° (θ = 90 ° in FIG. 5) with respect to the cell 3. The fine particles can be rotated and moved on the track 42 by adjusting the waveforms of the speakers 21a and 21b. If the bright spot 41 moves on the track 42, the bright spot is caused by the fine particles, and it can be determined that the partition wall 4 (the plugged portion 10 if there is the plugged portion 10) is defective. I can do it.

  Preferred conditions in the filter inspection method will be described. From the viewpoint of preventing the fine particles 7 from diffusing and lowering the sensitivity, it is preferable that light with high directivity is allowed to pass through a range from directly above the end face 2b from which the fine particles 7 are discharged to 5 mm. More preferably, it is in the range from directly above the end face 2b to 3 mm.

  The particle diameter of the fine particles 7 is preferably 0.3 μm or more and 200 μm or less, more preferably 0.5 μm or more and 50 μm or less, and even more preferably 1 μm or more and 10 μm or less. However, this is a range selected from the viewpoint of detection sensitivity, and the particle diameter of the fine particles 7 is selected appropriately depending on the shape of the filter to be inspected, the pore diameter in the case of a porous body, and the like. I can do it. For example, by examining the relationship between the type of defect and the particle size distribution of the discharged fine particles, it is possible to select an appropriate particle size suitable for the inspection object.

  Next, a filter inspection apparatus and a filter inspection method will be described with reference to FIG. 1 taking a case of inspecting a honeycomb filter as an example.

  The filter inspection apparatus will be described. FIG. 1 is a view showing an embodiment of a filter inspection apparatus according to the present invention, and is a side view seen through the inside. 1 includes a water tank 12 housed in a housing 19, a laser device 51, two cameras 15 (CCD camera), a plurality of lights 16 (LED lights), a single speaker 21, And the mounting table 25, the two ultrasonic humidifiers 11 outside the housing 19, the electric signal manufacturing device 22, and the image analysis device 17.

  The image analysis device 17 also serves as the electrical signal manufacturing device 22. In the laser device 51, the lens is attached at a position where the laser beam passes. The laser device 51 is attached to the elevator 14 and freely moves up and down. The camera 15 and the illumination 16 are attached to the elevator 14 via the arm 24 and similarly move up and down freely. The smoke tank 12 is provided with a pressure gauge 27 and a fine particle concentration meter 28, and the pressure and fine particle concentration in the smoke tank 12 can be managed.

  A filter inspection method will be described. In the inspection, first, the honeycomb filter 1 as the subject is placed on the slide mounting table 25 and enters the housing 19. The honeycomb filter 1 is loaded (unloaded) by opening and closing (for example, automatically) the door 18 provided in the housing 19. During the inspection, the door 18 is closed, and the inside of the housing 19 becomes a closed space. Therefore, the movement of the fine particles (smoke) is not disturbed by the disturbance. Moreover, the illumination 16 is installed in order to photograph the state of the honeycomb filter 1 when water smoke is not emitted. The mounting table 25 is open at a portion facing the end face 2 b of the honeycomb filter 1, but in a state of entering the housing 19, the mounting table 25 is in close contact with the water tank 12 through a synthetic resin packing or the like.

  Next, fine particles are introduced into the cell 3 from the end face 2 a side of the honeycomb filter 1. Specifically, the ultrasonic humidifier 11 corresponding to the fine particle generating means generates water smoke 20 in which fine water droplets (corresponding to fine particles) of about 5 μm are suspended using water and air as raw materials. The ultrasonic humidifier 11 is a device including a blower fan, and communicates with the water smoke tank 12 through the duct 13 (the duct 13 and the water smoke tank 12 correspond to the particle introduction means). The generated smoke 20 is stored in the smoke tank 12 and further enters the cell 3 from the end face 2a of the honeycomb filter 1 through the opening of the mounting table 25 and contacts the partition wall 4 in a pressurized state. Then, it passes through the pores of the partition walls 4, which are porous, to the end face 2 b side of the honeycomb filter 1 and is opened in the housing 19. Note that the pressure in the smoke tank 12 in a pressurized state varies depending on the subject. When the specimen is a porous honeycomb filter 1, the pressure is about 1 to 150 Pa.

  The presence or absence of a defect in the honeycomb filter 1 or the defect location is specified by irradiating the smoke 20 released on the end face 2b side of the honeycomb filter 1 with laser light and observing or analyzing the difference in luminance.

  When irradiating the laser light, the elevator 14 adjusts the laser device 51, which is a light generating means, to an appropriate position so that the laser light, which is highly directional light, is parallel to the end face 2b of the honeycomb filter 1, and , To pass through an appropriate position on the end face 2b.

  In observing or analyzing the difference in luminance, the electric signal manufacturing apparatus 22 and the speaker 21 which are longitudinal wave generating means are used. Specifically, the sound wave is emitted from the speaker 21 based on the electric signal produced by the electric signal manufacturing apparatus 22, the water smoke 20 is moved by the sound wave, and it moves while observing whether the bright spot moves. In this case, the brightness difference is observed and analyzed by moving the bright spot to an appropriate place where it is easy to discriminate between the diffracted scattered light from the fine particles and the end face reflected light, and to easily determine the brightness difference.

  The luminance distribution is collected in the image analysis device 17 as appropriate luminance information by adjusting the position of the camera 15. The difference in luminance is determined through human vision on the monitor of the image analysis device 17 or automatically analyzed by a program provided in the image analysis device 17, and through these, the presence or absence of a defect and the location of the defect are specified. When the inspection is completed, the honeycomb filter 1 as the subject is placed on the mounting table 25 that slides and goes out of the housing 19.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1 A honeycomb filter 1 shown in FIGS. 2 and 3 was prepared as an object to be measured. The honeycomb filter 1 used in this example had a diameter of 229 mm, a length of 279 mm, and a cell density of 46.5 cells / cm ² .

  About the prepared honey-comb filter 1, the detection of the defect was performed using the test | inspection apparatus 100 shown by FIG. The speaker 21 is disposed on the opposite side of the honeycomb filter 1 as viewed from the laser device 51 so that the center thereof is 4 mm from the end face 2 b of the honeycomb filter 1.

  First, fine particles having a particle diameter of 5 μm are generated by the ultrasonic humidifier 11, and the fine particles are introduced into the duct 13 by a fine particle supply fan (not shown) attached to the ultrasonic humidifier 11. After equalizing the concentration, the fine particles were introduced into the plurality of cells 3 from the end face 2a side of the honeycomb filter 1 and discharged to the end face 2b side. At the same time, the laser device 51 emits a planar He—Ne laser beam parallel to the end surface 2 b to a position where the height from the end surface 2 b is 4 mm, and the He—Ne laser beam irradiates fine particles. And visualized.

  Then, the speaker 21 is vibrated by the electric signal sent from the electric signal manufacturing apparatus 22 also serving as the image analysis device 17 to generate air vibration, and the visualized fine particles are moved by the air vibration, An image of the fine particles was picked up by the camera 15 and confirmed by the image analyzer 17 to inspect the honeycomb filter 1 for defects.

  (Comparative Example 1) Without using the electric signal manufacturing apparatus 22 and the speaker 21, the image of the fine particles discharged naturally is not captured on the end face 2b side without moving the visualized fine particles by the vibration of air. The image was picked up by 15 and confirmed by the image analysis device 17. Otherwise, the honeycomb filter 1 was inspected for defects in the same manner as in Example 1.

  (Test results and discussion) In Example 1, the detection rate increased by 7% (N number: 20) as compared with Comparative Example 1. Further, in Example 1, as compared with Comparative Example 1, the image of the fine particles discharged from the cell in which the defect was generated by the image analysis device 17 appeared clearly and brightly. Furthermore, in Example 1, it was confirmed that it was possible to determine whether or not the scattering was caused by fine particles depending on whether or not the portion where the light was diffracted and scattered was changed by the vibration of air.

  [Detection Rate] With respect to 20 honeycomb filters 1 having defects, the number of cells in which defects occurred (number of detected defects) was measured for each of Example 1 and Comparative Example 1. Then, from the result, {(number of defects detected in Example 1) / (number of defects detected in Comparative Example 1) × 100} −100 (%) was calculated and set as a detection number increase rate. For example, when the number of defects according to Example 1 is 11 and the number of defects according to Comparative Example 1 is 10, the rate of increase in the detection number is 10%. Thus, about the honeycomb filter (20 bodies), the detection number increase rate was obtained, and the average value of the obtained detection number increase rate was set as the detection rate.

  The filter inspection method and filter inspection apparatus according to the present invention can be used as means for inspecting the presence or absence of a filter defect. In particular, it is suitably used as a means for inspecting a porous honeycomb filter used as a DPF for removing particulate matter from exhaust gas.

It is a side view which shows one Embodiment of the inspection apparatus of the filter which concerns on this invention (the inside was seen through). It is a perspective view which shows typically an example of the honey-comb filter which is a test object. It is sectional drawing which shows typically an example of the honey-comb filter which is a test object. It is a figure which shows the defect detection principle of the inspection method of the filter which concerns on this invention, Comprising: It is sectional drawing which shows typically an example of a honey-comb filter. It is a figure which shows a mode that microparticles | fine-particles are moved by the vibration of the air in the inspection method of the filter which concerns on this invention, Comprising: It is an enlarged view which shows the end surface of a honeycomb filter.

Explanation of symbols

1: honeycomb filter, 2a, 2b: end face, 3: cell, 4: partition, 6: defect, 7: fine particle, 8: outer peripheral wall, 10: plugged portion, 11: ultrasonic humidifier, 12: water smoke tank , 13: Duct, 14: Elevator, 15: Camera, 16: Illumination, 17: Image analysis device, 18: Door, 19: Housing, 20: Smoke, 21, 21a, 21b: Speaker, 22: Electric signal manufacturing device , 24: arm, 25: mounting table, 27: pressure gauge, 28: fine particle concentration meter, 51: laser device, 100: inspection device.

Claims (22)

  Generate fine particles, introduce the fine particles into the filter from one side of the filter, generate highly directional light, pass the light through the other side of the filter, and A method for inspecting a filter in which air vibration is generated on the side of the filter and the fine particles discharged from the other side of the filter are moved by the vibration of the air, and the light is irradiated to the fine particles to visualize the fine particles.   The filter inspection method according to claim 1, wherein the fine particles are water.   The filter inspection method according to claim 2, wherein the fine particles are generated by a humidifying means using ultrasonic waves.   The filter inspection method according to claim 1, wherein the vibration of the air is generated two-dimensionally.   The filter inspection method according to claim 1, wherein a vibration of the air is generated by generating a longitudinal wave in the air.   The filter inspection method according to claim 1, wherein vibration of the air is generated by generating a longitudinal wave in the air. The filter has a surface on the other side,
7. The light according to claim 1, wherein the light is generated in a planar shape, the light is passed in parallel with the surface on the other side of the filter, and the fine particles are irradiated two-dimensionally. Filter inspection method.   The filter inspection method according to claim 1, wherein the visualized image of the fine particles is taken into a computer, recorded, and analyzed.   The filter inspection method according to claim 1, wherein a particle diameter of the fine particles is 0.3 μm or more and 200 μm or less.   The filter inspection method according to claim 1, wherein the filter to be inspected is a porous honeycomb structure.   The filter inspection method according to claim 1, wherein the filter to be inspected is a diesel particulate filter.   Fine particle generating means for generating fine particles, fine particle introducing means for introducing the fine particles into the filter from one side of the filter, and light generation for generating highly directional light so as to pass through the other side of the filter And a longitudinal wave generating means for generating vibration of air on the other side of the filter.   The filter inspection apparatus according to claim 12, wherein the fine particles are water.   The filter inspection apparatus according to claim 13, wherein the fine particle generation means is an ultrasonic humidifier.   The filter inspection apparatus according to any one of claims 12 to 14, wherein the longitudinal wave generating means includes two or three or more.   The filter inspection apparatus according to any one of claims 12 to 15, wherein the longitudinal wave generating means is at least one means selected from an electric signal manufacturing apparatus and a speaker, and a piezoelectric actuator and a diaphragm.   The filter inspection apparatus according to any one of claims 12 to 15, wherein the longitudinal wave generating means is a vibrator or a vibration motor and a diaphragm.   The filter inspection according to any one of claims 12 to 17, wherein the light generating means is means for generating the light in a planar shape and allowing the light to pass in parallel with the surface on the other side of the filter. apparatus.   The filter inspection apparatus according to any one of claims 12 to 18, further comprising a camera that captures the fine particles, and a computer that takes in and records and analyzes the captured image of the fine particles.   The filter inspection apparatus according to any one of claims 12 to 19, wherein a particle diameter of the fine particles is 0.3 µm or more and 200 µm or less.   The filter inspection apparatus according to any one of claims 12 to 20, wherein the filter to be inspected is a porous honeycomb structure.   The filter inspection apparatus according to any one of claims 12 to 21, wherein the filter to be inspected is a diesel particulate filter.

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