JP2008139052A - Method and device for inspecting crack of honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crack inspection method of a honeycomb structure capable of detecting even a fine crack of a partition wall. <P>SOLUTION: The honeycomb structure 20 is irradiated with light from the side of its first opening end surface 23 by an illumination device 40 and, in this light irradiation state, the honeycomb structure 20 is imaged from the side of its second opening end surface 24 using a camera of which the optical axis is inclined with respect to the axial direction of a through-hole 22. The light and dark of the image data acquired by the camera are discriminated to detect the crack 25 of each of the partition walls 21 of the honeycomb structure 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crack inspection method and an inspection apparatus for a honeycomb structure.

  For example, a diesel engine employs a filter (DPF) that collects PM (particulate matter) in exhaust gas. As a ceramic honeycomb structure constituting the DPF, FIGS. ) Is known. The honeycomb structure 20 is provided with a large number of through holes 22 partitioned by partition walls 21.

  The honeycomb structure 20 becomes a product through processes such as drying and firing after extrusion molding of a clay-like molding material. However, a crack (crack) may occur in the partition wall 21 due to a partial shrinkage difference of the partition wall 21 in the drying process or the firing process. Since the molded body in which the partition wall 21 is cracked may affect the function and durability of the product, it is necessary to inspect the presence or absence of the crack.

As a method for inspecting the presence or absence of cracks in the partition wall 21, for example, a method described in Patent Document 1 is known. In this method, a parallel light beam oblique to the axis of the through hole 22 is irradiated from one end surface side of the honeycomb structure 20. And the light which passed through the crack which exists in the partition 21 and entered into the adjacent through-hole 22 is detected on the other end surface side of the honeycomb structure 20 to detect the presence of the crack.
JP 58-155343 A

  In the inspection method described in Patent Document 1, it is possible to inspect a relatively large crack that allows light in the above-described oblique direction to pass through, but inspects a fine crack that does not pass light at the above-described angle. Was difficult.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a honeycomb structure crack inspection method and inspection apparatus capable of detecting even fine partition wall cracks.

  Hereinafter, means and the like effective for solving the above-described problems will be described while showing functions and effects as necessary.

  The invention described in claim 1 relates to a crack inspection method for inspecting cracks in the partition walls in a honeycomb structure having a large number of through holes formed in parallel and linearly by the partition walls. Then, light is irradiated by light irradiation means from one end surface side of the honeycomb structure, and in this light irradiation state, the imaging means is used in which the optical axis is substantially inclined with respect to the axial direction of the through hole. An image of the honeycomb structure is taken from the other end surface side, and cracks in the partition walls in the honeycomb structure are detected by identifying brightness and darkness in image data obtained by the imaging means.

  By using an image pickup means in which the optical axis is substantially inclined with respect to the axial direction of the through hole, the inside of the partition wall can be imaged from the other end face side of the honeycomb structure. Here, the light irradiated by the light irradiating means includes components that skew in various directions. Each skew component enters the through hole from one end surface side of the honeycomb structure, and passes through the through hole while being reflected by the partition walls. The light emitted from the other end surface also includes components that are skewed in various directions, but what actually contributes to the imaging of the imaging means is light that exits in parallel with the optical axis of the imaging means from the other end surface side. is there. That is, only light that is incident at a predetermined angle with respect to the partition wall from one end surface side, is reflected at a predetermined angle with respect to the partition wall, and exits in parallel with the optical axis of the imaging unit contributes to the imaging of the imaging unit. Become.

  When the light incident on the through hole from the one end surface side is reflected by the partition wall without cracks and exits from the other end surface side, the image of the partition wall obtained by the imaging means has almost uniform brightness. On the other hand, when light incident on the through-hole from one end surface is reflected by a cracked partition wall, light is scattered at the cracked portion, so reflected light parallel to the optical axis of the imaging means is weakened. This is true not only for relatively large cracks but also for fine cracks. Therefore, in the image data picked up by the image pickup means, the portion corresponding to the crack is relatively darker than the other partition wall portions. For this reason, it is possible to detect a crack in the partition wall by identifying the brightness and darkness in the image data obtained by the imaging means.

  The invention according to claim 2 is characterized in that the presence of a crack in a relatively dark portion is detected by identifying a relative brightness difference in the image data obtained by the imaging means. As described above, in the image data picked up by the image pickup means, the portion corresponding to the crack is relatively darker than the other partition wall portions. Therefore, it is possible to detect a crack in a relatively dark part by identifying a relative brightness difference (brightness / darkness difference) in the image data.

  According to a third aspect of the present invention, the brightness in the image data for the partition without cracks is defined in advance as a reference brightness, and in the image data obtained by the imaging means, the brightness is compared with the reference brightness. And cracks in the partition walls in the honeycomb structure are detected. If the lightness in the image data of the partition wall having no crack is used as the reference lightness, it is possible to easily detect a crack in the partition wall by discriminating the brightness from the reference lightness.

  In the invention according to claim 4, when the length of the honeycomb structure is L and the diameter of the through hole is a, the substantial inclination angle between the optical axis of the imaging means and the axis of the through hole It is characterized in that θ is set such that θ = arctan (a / L). Thereby, the full length of the partition from the one end surface side to the other end surface side can be imaged. As a result, the presence or absence of cracks in the entire length of the partition wall can be inspected at a time, and the efficiency of crack inspection is improved.

  The invention according to claim 5 is characterized in that the light emitted from the plurality of through-holes is condensed on the imaging surface of the imaging means using a telecentric optical system. As a result, it is possible to condense light that emerges in parallel with the optical axis of the telecentric optical system from the other end surface side of the through hole onto the imaging surface of the imaging means. As a result, it is possible to inspect collectively for the presence or absence of cracks in the plurality of partition walls, thereby improving the inspection efficiency.

  The invention described in claim 6 is characterized in that the light emitted from all the through-holes is condensed on the imaging plane of the imaging means using the telecentric optical system. Thereby, it is possible to inspect collectively for the presence or absence of cracks in the partition walls in all the through holes, and the efficiency of the inspection is improved.

  In the invention according to claim 7, by substantially moving the optical axis of the convex lens disposed between the honeycomb structure and the imaging means and the optical axis of the imaging means, the imaging is substantially performed. The optical axis of the means and the axis of the through hole are inclined. When the optical axis of the convex lens is shifted with respect to the optical axis of the imaging unit, light incident at a predetermined angle with respect to the optical axis of the convex lens is collected on the optical axis of the imaging unit. That is, it is possible to create a state in which the optical axis of the imaging means is substantially inclined with respect to the axis of the through hole.

  The invention according to claim 8 is characterized in that a Fresnel convex lens is used as the convex lens. By using a Fresnel convex lens, the lens can be made thin and light, and the apparatus used in the present invention can be reduced in size and weight.

  The invention according to claim 9 relates to a crack inspection apparatus for partition walls in a honeycomb structure having a plurality of through holes partitioned from each other by partition walls. And a light irradiating means for irradiating light from one end face side of the honeycomb structure, and the other end face side of the honeycomb structure with the optical axis inclined substantially with respect to the axial direction of the through-hole. It is characterized by comprising an arranged image pickup means and a display means for displaying the image data acquired by the image pickup means.

  By using such an apparatus, the above-described inspection method can be suitably realized.

[First Embodiment]
Hereinafter, a first embodiment of a crack inspection apparatus for a honeycomb structure according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an overall configuration of a crack inspection apparatus. The honeycomb structure 20 of the present embodiment is made of ceramic, and is used for a filter or the like of an automobile exhaust gas purification device. The honeycomb structure 20 has a cylindrical shape, and is provided with a large number of through holes 22 partitioned by partition walls 21 as shown in FIGS. 9 (a) and 9 (b). Each through hole 22 extends linearly between the first opening end face 23 and the second opening end face 24 in the honeycomb structure 20 and penetrates between both end faces 23, 24. Each through hole 22 is formed so that its axis is parallel to the axis H of the honeycomb structure. The through hole 22 has a square cross section, and the length a of one side thereof is about 1 mm. The length L of the through hole 22 (honeycomb structure 20), that is, the distance from the first opening end face 23 to the second opening end face 24 is about 100 mm. The maximum diameter d of the cross section perpendicular to the penetration direction of the honeycomb structure 20 is about 150 mm.

  The crack inspection apparatus 10 includes a placement unit 30, an illumination device 40, a telecentric optical system 50, a camera 60, an imaging control unit 70, and a monitor 80.

  A cylindrical honeycomb structure 20 is placed on the placement portion 30 with its axis line oriented in the horizontal direction. The mounting portion 30 is provided with a holding portion 31 for sandwiching the honeycomb structure 20 and fixing it at a predetermined position on the mounting portion 30.

  The lighting device 40 is a surface light source, and irradiates light from the first opening end face 23 side of the honeycomb structure 20 placed on the placement unit 30 toward the honeycomb structure 20. The illumination device 40 emits light including a component that is skewed with respect to the through hole 22 in addition to a component parallel to the through hole 22 of the honeycomb structure 20.

  The telecentric optical system 50 is for condensing light emitted from the second opening end face 24 side of the plurality of through holes 22. The telecentric optical system 50 is an optical system configured such that light rays incident parallel to the optical axis of the lens pass through the focal point of the lens, but light rays incident obliquely with respect to the optical axis do not pass through the focal point. . That is, as shown in FIG. 2, only the light parallel to the optical axis T of the lens 51 out of the light passing through the through-hole 22 of the honeycomb structure 20 passes through the aperture stop 52 provided at the focal position f of the lens 51. . Therefore, by using the telecentric optical system 50, even if the light is parallel to the optical axis T of the telecentric optical system 50, even the light away from the optical axis T is condensed on the imaging surface 61 of the camera 60. be able to.

  As shown in FIGS. 1 and 2, in this embodiment, the telecentric optical system 50 is arranged such that the optical axis T forms an angle θ (= arctan (a / L)) with the axis H of the honeycomb structure 20. The As shown in FIG. 1, the telecentric optical system 50 is configured to collect light emitted from all the through holes 22 of the honeycomb structure 20. The inspection image 81 is formed corresponding to all the through holes 22 of the honeycomb structure 20.

  The camera 60 is connected with its optical axis C aligned with the optical axis T of the telecentric optical system 50. That is, the optical axis C of the camera 60 is also arranged so as to form an angle θ with the axis H of the honeycomb structure 20. Thereby, the camera 60 can image the partition wall 21 from the direction of the angle θ with respect to the axis H of the honeycomb structure 20. As the camera 60, for example, a CCD camera, a CMOS camera, a line sensor, or the like can be used. The camera 60 performs imaging in accordance with an imaging command signal from the imaging control unit 70 and transmits obtained image data to the imaging control unit 70.

  The imaging control unit 70 outputs an imaging command signal to the camera 60 and receives image data captured by the camera 60. The received image data is output to the monitor 80. As a result, the inspection image 81 acquired by the camera 60 is displayed on the monitor 80.

  Next, a crack inspection method using the crack inspection apparatus 10 of this embodiment will be described.

  First, the honeycomb structure 20 is mounted on the mounting unit 30 and fixed to a predetermined position on the mounting unit 30 by the holding unit 31. Next, the illumination device 40 irradiates the entire surface of the first opening end surface 23 of the honeycomb structure 20 with light. Then, the light emitted from the second opening end face 24 of the honeycomb structure 20 is received by the telecentric optical system 50. The telecentric optical system 50 focuses only the light parallel to the optical axis T on the imaging surface 61 of the camera 60.

  The camera 60 receives an imaging command signal from the imaging control unit 70 and performs imaging, and transmits acquired image data to the imaging control unit 70. The imaging control unit 70 transmits image data to the monitor 80, and displays an inspection image 81 on the monitor 80 as shown in FIG. The inspection image 81 displayed on the monitor 80 is visually confirmed by an inspector. Then, when a portion of the inspection image 81 displayed on the monitor 80 corresponding to the partition wall 21 is darker than the other partition wall 21 is detected, it is detected that a crack exists. The

  This point will be described in detail with reference to FIG. FIG. 4 is a schematic diagram for explaining the principle of crack detection. The light irradiated by the illuminating device 40 includes components that skew in various directions. Each of the skew components enters the through hole 22 from the first opening end face 23 of the honeycomb structure 20, and passes through the through hole 22 while being reflected by the partition wall 21. The light emitted from the second opening end face 24 also includes components that are skewed in various directions, but the light passing through the aperture stop 52 of the telecentric optical system 50 is in a direction parallel to the optical axis T of the telecentric optical system 50. Only ingredients. That is, only the light incident on the telecentric optical system 50 in parallel with the optical axis T contributes to imaging by the camera 60.

  When the light incident on the through hole 22 from the first opening end face 23 side is reflected by the partition wall 21 without the crack 25 and exits from the second opening end face 24, the portion corresponding to the partition wall 21 in the inspection image 81 is substantially uniform. Brightness. On the other hand, when the light incident on the through hole 22 from the first opening end face 23 side is reflected by the partition wall 21 having the fine crack 25, the light is scattered at the portion of the crack 25 and reflected parallel to the optical axis T. The light is weakened. Therefore, in the inspection image 81 obtained by condensing light parallel to the optical axis T, the portion corresponding to the crack 25 is darker than the partition 21 portion without the crack 25. For this reason, when there is a partition wall 21 including a darker portion than the others in the inspection image 81, it can be seen that the crack 25 exists in the partition wall 21.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  In the crack 25 portion of the partition wall 21, light is scattered without being reflected at the same angle as the incident angle. That is, when the light reflected by the partition wall 21 in which the crack 25 exists is collected, the reflected light parallel to the light reflected by the portion without the crack 25 is weakened at the crack 25 portion. As a result, the partition wall 21 is imaged in a state where the optical axis T of the telecentric optical system 50 (the optical axis C of the camera 60) and the axis H of the honeycomb structure 20 are tilted. By detecting the part of the partition wall 21 that appears darker than that, it is possible to easily inspect the fine crack 25.

  In other words, in the present embodiment, the inspection image formed by the light reflected by the partition walls 21 by inclining the optical axis T of the telecentric optical system 50 (the optical axis C of the camera 60) and the axis H of the honeycomb structure 20. 81 is acquired. Even a fine crack affects the intensity of reflected light, and therefore, unlike an inspection method in which a crack is detected by light penetrating the partition wall 21 in an oblique direction, a fine crack can be suitably detected.

  In the present embodiment, the reference brightness for determining the presence or absence of the crack 25 is the brightness of the part of the partition wall 21 without the crack 25 in the inspection image 81. If this brightness is used as a reference, the crack 25 of the partition wall 21 can be easily detected by detecting a darker portion.

  In the present embodiment, the axis H of the honeycomb structure 20 (that is, the axis of the through hole 22) and the optical axis T of the telecentric optical system 50 are inclined by an angle arctan (a / L). Thereby, the inspection image 81 in the full length of the partition 21 from the 1st opening end surface 23 side to the 2nd opening end surface 24 side can be obtained. As a result, the presence or absence of the crack 25 in the entire length of the partition wall 21 can be inspected at a time, and the efficiency of the crack inspection is improved.

  In the present embodiment, the light emitted from the second opening end face 24 of the honeycomb structure 20 is collected using the telecentric optical system 50. As a result, the light emitted from the second opening end face 24 in parallel with the optical axis T of the telecentric optical system 50 can be condensed almost uniformly on the imaging surface 61 of the camera 60. As a result, the inspection image 81 is formed corresponding to the plurality of partition walls 21 of the honeycomb structure 20. By using the inspection image 81, it is possible to inspect collectively for the presence or absence of the crack 25 in the plurality of partition walls 21, and the inspection efficiency is improved.

  In the present embodiment, the telecentric optical system 50 is configured so as to be able to focus the light emitted from all the through holes 22 of the honeycomb structure 20 on the imaging surface 61 of the camera 60, so that an inspection image is obtained. 81 is formed corresponding to all the partition walls 21 of the honeycomb structure 20 (FIG. 3). Thereby, the crack inspection can be performed collectively for all the through holes 22 of the honeycomb structure 20. Therefore, the efficiency of crack inspection is further improved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 5, the crack inspection apparatus 110 of this embodiment includes an illumination device 140, a Fresnel convex lens 150, a lens moving unit 151, a camera 160, an imaging control unit 170, a monitor 180, a controller 190, and an operation unit 191. It is configured.

  The illumination device 140 is a surface light source. The illuminating device 140 is installed with the light emitting surface facing vertically upward, and the honeycomb structure 20 with the first opening end surface 23 facing down is placed on the illuminating device 140. From the lighting device 140, light including a component that is skewed with respect to the through hole 22 in addition to a component parallel to the through hole 22 of the honeycomb structure 20 is irradiated upward.

  The Fresnel convex lens 150 is provided above the lighting device 140. And it is comprised so that the signal from the lens moving means 151 can be received, and it can move to two directions (x, y-axis direction) orthogonal in a horizontal surface. The lens moving means 151 receives the signal from the controller 190 and moves the Fresnel convex lens 150 in the x and y directions.

  The camera 160 is the same as the camera 60 of the first embodiment except that the wide-angle lens 161 is mounted, and the imaging control unit 170 operates in response to a signal from the controller 190, in the first embodiment. This is the same as the imaging control unit 70 of FIG. The monitor 180 is the same as the monitor 80 of the first embodiment.

  When the inspector operates the operation means 191, an operation input signal is input to the controller 190. In response to the operation input signal, the controller 190 outputs a control command signal to the lens moving unit 151 and the imaging control unit 170 as described above.

  Here, an operation when the Fresnel convex lens 150 is moved in a horizontal plane will be described. When the optical axis F of the Fresnel convex lens 150 is coincident with the optical axis C of the camera 160, as shown in FIG. They are collected at the focal point of the Fresnel convex lens 150 existing on F (the focal position in this case is assumed to be f0). Next, consider a case where the Fresnel convex lens 150 is moved by a distance x0 in the x-axis direction as shown in FIG. In this case, the light condensed at the position f0 is light that enters the lower surface of the Fresnel convex lens 150 in parallel at a predetermined angle. That is, by moving the Fresnel convex lens 150 in the xy plane, the honeycomb structure 20 is substantially tilted with respect to the axis H of the honeycomb structure 20 (inclination direction of the two-dot chain line in FIG. 8B). You can get the same effect that you saw. Therefore, by appropriately setting the moving distance of the Fresnel convex lens 150, the angle θ (= arctan (a / L)) is inclined with respect to the axis H of the honeycomb structure 20 as in the first embodiment. An inspection image similar to that captured by the camera 160 can be obtained.

  Next, a crack inspection method using the crack inspection apparatus 110 of this embodiment will be described. First, with the Fresnel convex lens 150 retracted from the lighting device 140, the honeycomb structure 20 with the first opening end face 23 facing down is placed on the lighting device 140. At this time, the axis H of the honeycomb structure 20 and the optical axis C of the lens of the camera 160 are matched. In order to make the axis H of the honeycomb structure 20 coincide with the optical axis C of the lens of the camera 160, the mounting position of the honeycomb structure 20 is checked while checking the inspection image 181 captured by the camera 160 on the monitor 180. Adjust it.

  Next, the operating means 191 is operated to move the Fresnel convex lens 150 onto the honeycomb structure 20 so that the optical axis C of the camera 160 and the optical axis F of the Fresnel convex lens 150 are aligned. In a state in which both optical axes C and F coincide with each other, light perpendicularly incident on the lower surface of the Fresnel convex lens 150 is collected on the optical axis C of the camera 160. That is, the inspection image 181 in a state where the optical axes C and F coincide with each other is a view of each through hole 22 of the honeycomb structure 20 as viewed from directly above the second opening end face 24 side. Then, since light that has traveled straight through the through hole 22 without being reflected by the partition wall 21 is reflected at a position corresponding to the through hole 22 in the inspection image 181, as shown in FIG. This is the state in which the difference in brightness is the clearest. This state can also be confirmed while looking at the monitor 180.

  When the optical axis C of the camera 160 coincides with the optical axis F of the Fresnel convex lens 150, the Fresnel convex lens 150 is moved in the x-axis direction from this state. The movement of the Fresnel convex lens 150 is performed while viewing the inspection image 181 output to the monitor 180, and the light that has passed through the through hole 22 without being reflected by the partition wall 21 does not appear in the inspection image 181 (state of FIG. 5). The movement of the Fresnel convex lens 150 is stopped. This state is a state in which the axis H of the honeycomb structure 20 and the optical axis C of the lens of the camera 160 are substantially inclined by an angle θ (= arctan (a / L)). In this state, the inspection image 181 displayed on the monitor 180 is visually confirmed by the inspector. When there is a portion that is darker than the other partition walls 21 in the portion corresponding to the partition wall 21 of the inspection image 81 displayed on the monitor 80, it can be seen that the crack 25 exists in the partition wall 21. .

  Thereafter, the optical axis C of the camera 160 and the optical axis F of the Fresnel convex lens 150 are made to coincide again, and the Fresnel convex lens 150 is moved in the same manner in the opposite direction of the x axis and in the positive and negative directions of the y axis. Thereby, the presence or absence of the crack 25 in the four partition walls 21 forming each through hole 22 can be inspected. Moreover, you may inspect from the 1st opening end surface 23 side of the honeycomb structure 20 as needed.

  Also in this embodiment, the Fresnel convex lens 150 is moved to create a state in which the optical axis C of the lens of the camera 160 and the axis H of the honeycomb structure 20 are substantially inclined. Thereby, as in the first embodiment, the partition wall 21 inside the through hole 22 can be imaged in a state where the optical axis C of the lens of the camera 160 is substantially inclined with respect to the axis H of the honeycomb structure 20. Then, by detecting a portion of the inspection image 181 of the partition wall 21 that is darker than the reference brightness, the minute crack 25 can be easily inspected.

  In this embodiment, it is possible to easily finely adjust the substantial inclination angle between the axis H of the honeycomb structure 20 and the optical axis C of the lens of the camera 160 by adopting a configuration in which the Fresnel convex lens 150 is moved. It becomes. Further, by using the Fresnel convex lens 150, the lens can be made thin and light.

[Other Embodiments]
In the above embodiment, the case where the partition wall 21 has the fine crack 25 has been described. However, the present invention can be applied not only to inspection of the fine crack 25 but also to a relatively large crack 25. FIG. 8 is a schematic diagram for explaining the principle of detecting a relatively large crack. As shown in FIG. 8, when a relatively large crack 25 exists, light enters the through hole 22 from the adjacent through hole 22, but the shadow corresponding to the thickness of the partition wall 21 (see FIG. 8). 8). Therefore, even in the case of a relatively large crack 25, it is possible to inspect the crack 25 by the configuration and method of each of the above embodiments by detecting a darker part than the other.

  In each of the above-described embodiments, the inspection images 81 and 181 displayed on the monitors 80 and 180 are visually observed. However, instead of this, the image processing apparatus may automatically determine them. That is, the crack 25 existing in the partition wall 21 appears as a difference in brightness between the inspection images 81 and 181. Therefore, automatic determination of the presence or absence of the crack 25 by the image processing apparatus can be easily realized by using the image brightness as an index.

  In the first embodiment, the light emitted from all the through holes 22 of the honeycomb structure 20 is collected using the telecentric optical system 50. However, the light collection by the telecentric optical system is not limited to this. For example, the through holes 22 included in the honeycomb structure 20 may be divided into a plurality of groups, and the light emitted from the through holes 22 may be collected for each group. Also by this, since the crack inspection can be performed collectively for the plurality of through holes 22, the crack inspection can be performed efficiently. Further, it is possible to inspect the cracks 25 of the respective partition walls 21 while moving the camera 60 without using the telecentric optical system 50.

  In the second embodiment, the Fresnel convex lens 150 is used. However, even if a simple convex lens is used, a state in which the optical axis C of the lens of the camera 160 is substantially inclined with respect to the axis H of the honeycomb structure 20 can be created. In the second embodiment, the wide-angle lens 161 is mounted on the camera 160, but the wide-angle lens 161 is not an essential requirement for the present invention.

The figure which shows the whole structure of the crack inspection apparatus which concerns on 1st Embodiment. Explanatory drawing of a telecentric optical system. The figure which shows the test | inspection image displayed on a monitor. The schematic diagram for demonstrating the detection principle of a crack. The figure which shows the whole structure of the crack inspection apparatus which concerns on 2nd Embodiment. The figure which shows an effect | action at the time of moving a Fresnel convex lens. The figure which shows the test | inspection image displayed on a monitor. The schematic diagram for demonstrating the detection principle of a crack. (A) is a perspective view of a honeycomb structure, (b) is an axial sectional view of the honeycomb structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Crack inspection apparatus, 20 ... Honeycomb structure, 21 ... Partition, 22 ... Through-hole, 23 ... 1st opening end surface, 24 ... 2nd opening end surface, 25 ... Crack, 30 ... Mounting part, 31 ... Holding part, 40 ... Illuminating device, 50 ... Telecentric optical system, 60 ... Camera, 70 ... Imaging control unit, 80 ... Monitor, 81 ... Inspection image.

Claims (9)

In the honeycomb structure having a large number of through-holes formed in parallel and linearly by the partition walls, a crack inspection method for inspecting cracks of the partition walls,
Irradiate light from the one end surface side of the honeycomb structure by light irradiation means,
In this light irradiation state, the honeycomb structure is imaged from the other end surface side using an imaging means having an optical axis substantially inclined with respect to the axial direction of the through hole,
A method for inspecting cracks in a honeycomb structure, wherein cracks in partition walls in the honeycomb structure are detected by identifying brightness and darkness in image data obtained by the imaging means.   The crack of the honeycomb structure according to claim 1, wherein a crack is detected in a relatively dark portion by identifying a relative brightness difference in image data obtained by the imaging means. Inspection method. The brightness in the image data for the partition without cracks is defined in advance as a reference brightness,
The crack inspection of the honeycomb structure according to claim 1, wherein in the image data obtained by the imaging means, light and darkness are identified by comparison with the reference lightness, and cracks in the partition walls in the honeycomb structure are detected. Method. When the length of the honeycomb structure is L and the diameter of the through hole is a, the substantial inclination angle θ between the optical axis of the imaging means and the axis of the through hole is θ = arctan (a / L )
The crack inspection method for a honeycomb structure according to any one of claims 1 to 3, wherein the crack inspection method is set so as to satisfy the following conditions.   The honeycomb structure according to any one of claims 1 to 4, wherein light emitted from a plurality of the through holes is condensed on an imaging surface of the imaging means using a telecentric optical system. Crack inspection method.   The honeycomb structure according to any one of claims 1 to 4, wherein light emitted from all of the through holes is condensed on an imaging surface of the imaging unit using a telecentric optical system. Crack inspection method.   By relatively moving the optical axis of the convex lens disposed between the honeycomb structure and the imaging unit and the optical axis of the imaging unit, the optical axis of the imaging unit and the through hole are substantially The crack inspection method for a honeycomb structure according to any one of claims 1 to 4, wherein the axis is inclined.   The method for inspecting cracks in a honeycomb structure according to claim 7, wherein a Fresnel convex lens is used as the convex lens. In the honeycomb structure having a large number of through-holes formed in parallel and linearly by the partition walls, a crack inspection apparatus for inspecting cracks in the partition walls,
A light irradiation means for irradiating light from one end surface side of the honeycomb structure;
In a state where the optical axis is substantially inclined with respect to the axial direction of the through hole, an imaging unit disposed on the other end surface side of the honeycomb structure;
A crack inspection apparatus for a honeycomb structure, comprising: display means for displaying image data acquired by the imaging means.

Images