JP2010230361A - Method and apparatus for inspecting defect of structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for determining the presence of communication between a closed space provided in a structure, such as a ceramic device, and an external space, by a simple method. <P>SOLUTION: After a permeable liquid that has an impregnation property to defects and shows color differing from that of the structure is adhered to an outer surface of the structure that has diffusion/transmission properties and has, in the inside, a closed space not visible from the outside, a surplus permeable liquid adhered to the outer surface is removed and then a transmission image of the structure is observed while the structure is being irradiated with illumination light. The presence of communication defects for allowing the external space to communicate with the closed space in the structure is determined, based on a color state that is identified by the observation and is at a part corresponding to the closed space, namely a part corresponding to a formation region of the closed space. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a defect inspection method for a structure such as a ceramic device having a closed space inside, and more particularly to a defect inspection method using a penetrating flaw detection method.

  As a technique for detecting defects (surface defects) such as minute scratches and cracks existing on the surface of an object, a penetrating flaw detection method has been conventionally known (see, for example, Patent Document 1). The penetration flaw detection method is generally performed according to the following procedure. First, a penetrating liquid colored in red or other colors or having fluorescence and having strong penetrability is attached to the surface of an object to be examined by coating or dipping. Thereafter, excess permeate is removed, and the object is washed and dried. Subsequently, a developer, a developer, or the like is attached to the test object. At this time, if a surface defect such as a crack is present in the test object, the permeated liquid that has permeated the defect portion oozes out, and an indication pattern such as red or fluorescence is displayed on the surface of the test object. The presence or absence of a defect can be determined by the presence or absence of such an instruction pattern.

JP-A-10-332604

For example, in a structure such as a device in which ceramics such as zirconia is used as a constituent material (hereinafter also referred to as a ceramic device), in order to ensure a predetermined function, the structure is isolated from the external space. In some cases, a closed space or a space filled with a porous body (hereinafter referred to as a closed space without being distinguished) is provided. In such a structure, it is necessary to ensure that the closed space is isolated from the external space in order to exert its function. In other words, such a structure is required to have no defect that allows communication between the external space and the internal closed space.

  However, for example, in the case of a ceramic device, it is usually produced by laminating a plurality of ceramic green sheets each printed with a predetermined circuit pattern or the like to form a laminate and firing the laminate. In some cases, it is produced including minute defects that cause communication with the outside due to contamination of foreign matter before lamination or before firing or poor lamination. Since the presence of such a micro defect is one of the factors that cause the device to deteriorate, the device having such a defect needs to be excluded as a rejected product in the inspection process.

  Conventionally, such ceramic devices have been subjected to defect inspection using the penetrating flaw detection method as described above. However, with such a method, micro defects such as cracks penetrate from the external space to the internal closed space. However, it was not possible to determine whether or not both were communicated.

  The present invention has been made in view of the above problems, and provides a technique capable of determining whether or not there is communication between a closed space provided inside a structure such as a ceramic device and an external space by a simple technique. For the purpose.

  In order to solve the above-mentioned problem, the invention of claim 1 is a method for inspecting a defect of a structure having a closed space that has a diffuse transmission ability and is not visible from the outside, and is provided on the outer surface of the structure with respect to the defect. An attachment step of attaching an permeable liquid having impregnation ability and a color different from that of the structure, a removal step of removing the permeable liquid attached to an outer surface of the structure in the attachment step, and the removal step The structure that has undergone the observation is observed with the illumination light irradiated by illumination means, and the coloration in the portion corresponding to the closed space, which is a portion corresponding to the formation region of the closed space, specified by the observation And a determination step of determining the presence or absence of a communication defect in the structure that allows the external space and the closed space to communicate with each other based on the state.

  The invention according to claim 2 is the structure defect inspection method according to claim 1, wherein in the determination step, an observation position is set on the opposite side of the illumination unit with respect to the structure, and the illumination is irradiated. The observation is performed on a transmission image obtained by diffused transmission light.

  A third aspect of the present invention is the structure defect inspection method according to the first aspect, wherein, in the determination step, an observation position is set on the same side as the illuminating means with respect to the structure, and the structure is irradiated. The observation is performed on a reflected image of reflected illumination light from the outer surface and the inside of the structure body of the illumination light.

  A fourth aspect of the present invention is the defect inspection method for a structure according to any one of the first to third aspects, wherein in the observation step, the colored state different from other portions is provided in the portion corresponding to the closed space. It is characterized in that it is determined that the communication defect exists when there is a portion having the same.

  A fifth aspect of the present invention is the structure defect inspection method according to any one of the first to third aspects, wherein in the observation step, the portion corresponding to the closed space corresponds to a color of the permeable liquid. When there is a portion having a coloration state, it is determined that the communication defect exists.

  A sixth aspect of the present invention is the structure defect inspection method according to any one of the first to fifth aspects, wherein the observation step is performed by imaging the structure by an imaging unit disposed at the observation position. An imaging step of acquiring an appearance image of the structure, and an image determination step of determining the presence or absence of the communication defect in the structure by specifying the coloration state from the appearance image. It is characterized by.

  A seventh aspect of the invention is the structure defect inspection method according to the sixth aspect, wherein in the image determination step, the coloration state is specified from a hue distribution in the appearance image, and the closed space corresponding portion In addition, it is determined that the communication defect exists when there is a portion having a hue difference that exceeds a predetermined threshold with the surroundings.

  The invention according to claim 8 is the structure defect inspection method according to any one of claims 1 to 7, wherein the closed space is formed as a porous space filled with a porous body. It is characterized by that.

  A ninth aspect of the present invention is the structure defect inspection method according to any one of the first to eighth aspects, wherein the structural body is a flat plate member, and the illumination light is used in the determination step. It irradiates with respect to one main surface of the said flat member.

  A tenth aspect of the present invention is the structure defect inspection method according to any one of the first to ninth aspects, wherein the structural body is a ceramic device.

  The invention of claim 11 is the structure defect inspection method according to claim 10, wherein the ceramic device is formed by laminating a plurality of ceramic green sheets each having a predetermined circuit pattern printed thereon. It is formed by baking, It is characterized by the above-mentioned.

  A twelfth aspect of the present invention is the structure defect inspection method according to any one of the first to eleventh aspects, wherein the structure is a sensor element of a gas sensor.

  The invention according to claim 13 is an apparatus for inspecting a defect of a structure having a diffuse transmission ability and having a closed space inside which is not visible from the outside. A stage on which a structure in which the permeable liquid is removed from the outer surface after the permeable liquid having a different color is once attached to the outer surface is mounted, and the structure mounted on the stage is illuminated Illuminating means for irradiating light, imaging means for imaging the structure mounted on the stage and generating an appearance image of the structure, and imaging means in a state irradiated with illumination light by the illuminating means In the obtained appearance image, the external space and the closed space in the structure are communicated based on the coloration state of the closed space corresponding portion that is a portion corresponding to the formation region of the closed space. Determining means for determining whether the communication defect that, characterized in that it comprises a.

  A fifteenth aspect of the invention is the structure defect inspection apparatus according to the thirteenth aspect of the invention, wherein the illuminating means and the imaging means are positioned on the opposite sides with respect to the structure placed on the stage. The appearance image is generated as a transmission image by diffused transmission light of the illumination light that is arranged and irradiated.

  A fifteenth aspect of the invention is the structure defect inspection apparatus according to the thirteenth aspect, wherein the illumination unit and the imaging unit are located on the same side with respect to the structure mounted on the stage. The appearance image is generated as a reflected image by reflected light from the outer surface and the inside of the structure.

  A sixteenth aspect of the present invention is the structure defect inspection apparatus according to any one of the thirteenth to fifteenth aspects, wherein the determination means includes a hue distribution specifying means for specifying a hue distribution in the appearance image. Based on the hue distribution, it is determined whether or not there is a portion having a hue difference exceeding a predetermined threshold with the surroundings in the portion corresponding to the closed space, and there is a portion exceeding the threshold And determining that the communication defect exists.

  According to the first to sixteenth aspects of the present invention, the closed space is communicated with the outside in the structure having the closed space that cannot be visually recognized from the outside by utilizing the impregnation ability of the permeable liquid into the defect. The presence or absence of a communication defect can be reliably determined by the coloration state of the portion corresponding to the closed space on the outer surface of the structure.

  In particular, according to the invention of claim 2 and claim 14, since the transmission image by the diffuse transmission light of the illumination light irradiated to the structure is observed, when the permeable liquid has entered the closed space, Light incident on the inside of the structure and transmitted through the permeable liquid is observed relatively strongly. Thereby, the presence of the communication defect can be detected with higher sensitivity.

It is a figure which shows typically the structure 1 used as the application object of the defect inspection method which concerns on this Embodiment. It is a figure which illustrates the case where the defect 4 exists in the structure 1. It is a figure which illustrates the structure 1 which equips the inside with the porous space 2a with which the porous body was filled. It is a figure which shows the procedure of the process in the defect inspection method which concerns on this Embodiment. It is a figure which shows a 1st observation aspect. It is a figure which shows a 2nd observation aspect. It is a figure which shows typically the structure of the defect inspection apparatus 100 corresponding to a 1st observation aspect. It is a figure which shows typically the structure of the defect inspection apparatus 200 corresponding to a 2nd observation aspect. It is a figure which shows the procedure of the process in the defect inspection method performed using the defect inspection apparatus 100 and 200. FIG. It is a schematic cross section which illustrates the structure of the sensor element 101 which is the structure 1 made into the object of a defect inspection in an Example. FIG. 4 is a diagram illustrating a captured image of an outer surface 101s with respect to a sensor element 101. It is the figure which binarized the picked-up image shown in FIG. 11 into the red area | region and the area | region other than that. It is a figure which shows the hue distribution obtained from the captured image shown in FIG.

<Applicability of defect inspection method>
First, the structure of the structure to which the defect inspection method according to the embodiment of the present invention is applied and the defects existing in the structure will be described. In the present embodiment, the defect refers to a minute defect that is difficult to visually recognize with the naked eye, such as a scratch or a crack starting from the outer surface of the structure. Further, as will be described later, the defect inspection method is a method for inspecting the presence or absence of defects in the structure using the light diffusion transmission ability of the structure, and therefore has the light diffusion transmission ability. An object that does not (not substantially transmit light) does not correspond to the structure in this embodiment.

  FIG. 1 is a diagram schematically showing a structure 1 to which a defect inspection method according to this embodiment is applied. FIG. 1A is a schematic cross-sectional view of the structure 1, and FIG. 1B is a top view. As shown in FIG. 1, a structure 1 to which the defect inspection method is applied includes a closed space 2 that is isolated from the outside and cannot be visually recognized from the outside. Moreover, the structure 1 has a diffuse transmission capability with respect to light of a predetermined wavelength. In addition, there may be a non-transmissive portion 3 that does not have such diffuse transmission capability inside the structure 1. Note that the shape, size, number, and magnitude relationship of the structure 1, the closed space 2, and the non-transmissive portion 3 illustrated in the present embodiment are not limited to those illustrated. .

  On the other hand, FIG. 2 is a diagram illustrating a case where the defect 4 exists in the structure 1. FIG. 2A illustrates a case where there is a defect 4 (non-communication defect 4a) that starts from the outer surface 1s and does not reach the closed space 2. On the other hand, FIG. 2B illustrates a case where the defect 4 (communication defect 4b) that reaches the closed space 2 from the outer surface 1s is present. In the case shown in FIG. 2B, the space called the closed space 2 is not strictly isolated from the outside, but in view of the gist of the present invention, in the present embodiment, In this case, the space is referred to as a closed space 2.

  In the defect inspection method according to the present embodiment, which will be described in detail below, the structure 1 in which the communication defect 4b shown in FIG. 2B is present can be distinguished from the structure 1 in another state. This is a detection method.

  Moreover, FIG. 3 is a figure which illustrates the structure 1 which equips the inside with the porous space 2a with which the porous body was filled. The porous space 2a can be regarded as a portion where the minute closed space 2 is formed because a large number of minute voids are continuously formed in a three-dimensional network. Therefore, the structure 1 having such a porous space 2a is also an application target of the defect inspection method according to the present embodiment. Therefore, in the following, when the closed space 2 is simply referred to, the porous space 2a is included.

  Specifically, a ceramic device or the like formed by firing a laminated body in which a plurality of ceramic green sheets each having a predetermined circuit pattern printed thereon is fired is a suitable example of the structure 1. In such ceramic devices, there are those having a cavity structure inside, those having a porous film or a porous layer formed by printing, and if there is a communication defect 4b reaching these cavities and porous film, The device may not exhibit the desired characteristics. For this reason, it is important to inspect the presence or absence of the communication defect 4b in the manufacturing process. More specifically, the ceramic device corresponds to a sensor element used for a gas sensor for measuring a gas such as NOx.

<Defect inspection method>
Next, the principle and procedure of the defect inspection method according to the present embodiment will be described. FIG. 4 is a diagram showing a processing procedure in the defect inspection method according to the present embodiment.

  First, a penetrating liquid that has the ability to impregnate the defect 4 and has a different color from the structure 1 is attached to the outer surface 1s of the structure 1 to be inspected (step S1). There are various methods for attaching the structure 1 depending on the structure and size of the structure 1, but this is simply realized by immersing the structure 1 in the permeable liquid. Alternatively, a mode in which a permeable liquid is applied to the outer surface 1s of the structure 1 or spray irradiation is also possible.

  Here, the color different from the structure 1 is not necessarily discernible with the naked eye, and can be discriminated as a different color when irradiated with light of a predetermined wavelength including other than fluorescence and visible light. If it is. For example, in the case where the structure 1 is a white element having zirconia as a main component material, it is used in a conventional penetrant flaw detection method (for example, disclosed in Patent Document 1). It is possible to use a red dye penetrant flaw detector.

  When the permeable liquid is attached to the outer surface 1s of the structure 1 in this manner, if the defect 4 exists in the structure 1, the permeable liquid penetrates from the outer surface 1s to the defect 4 due to its impregnation ability. I will do it. In this case, in the case where the communication defect 4b exists in the structure 1, the permeable liquid enters the closed space 2 through the communication defect 4b. In addition, when the porous space 2a exists inside the structure 1 as shown in FIG. 3, if there is a communication defect 4b that reaches the porous space 2a, the porous space 2a is permeable. Liquid will enter.

  After attaching the permeable liquid in this way, the excess permeable liquid adhering to the outer surface 1s is removed (step S2). The permeable liquid is removed by, for example, wiping with a wiping member such as a waste cloth or washing the structure 1 with water. When the non-communication defect 4a and the communication defect 4b are present in the structure 1, the permeable liquid that has entered the inside or further into the closed space 2 is not removed by the removal process and remains in the place. To do. Although not indispensable in the present embodiment, for the purpose of using the inspection by the conventional penetrant flaw detection method, a predetermined solvent may be applied or removed during the removal process, for example, after the structure 1 is washed with water. You may make it perform the image development process by immersion in this solvent.

  The appearance of the structure 1 is observed with the excess permeable liquid removed in this way (step S3). And the presence or absence of the communication defect 4b is determined based on the presence or absence of coloration in the closed space corresponding part RE (steps S4 to S6).

  The observation of the structure 1 in step S3 is performed by irradiating the structure 1 with illumination light that can be diffused and transmitted through the structure 1 (hereinafter simply referred to as illumination light). The method of observation depends on the position of the illumination light source and the observation position. It is roughly divided into two according to the arrangement relationship. Hereinafter, these are referred to as a first observation mode and a second observation mode. In both of the first observation mode and the second observation mode, illumination light with sufficient intensity is irradiated for observation.

  FIG. 5 is a diagram showing a first observation mode. In the first observation mode, observation is performed with the observation position 13 set on the same side of the structure 1 as the illumination unit 11 (first illumination unit 11a). In this case, at the observation position 13, a reflected image of the illumination light 12 (first illumination light 12 a) irradiated to the structure 1 by the outer surface 1 s of the structure 1 and the reflected light L1 or reflected light L2 from the inside is observed. It will be. However, the reflected light L1 is obtained from the part (closed space corresponding part) RE corresponding to the formation region of the closed space 2 in the outer surface 1s irradiated with the first illumination light 12a, and the closed space corresponding part RE in the outer surface 1s. It is assumed that the reflected light L2 is obtained from a portion other than.

  Since the first illumination light 12a can be diffused and transmitted through the structure 1 as described above, as shown in FIG. 5, when the permeable liquid 5 enters the closed space 2 through the communication defect 4b, the first illumination light 12a is closed. The reflected light L2 from the space corresponding part RE includes a wavelength component reflected by the permeable liquid 5 entering the closed space 2 in the first illumination light 12a incident on the structure 1. Become. That is, a state in which the closed space corresponding part RE exhibits a color derived from the permeable liquid 5 is observed. For example, if the permeable liquid 5 is red, the reflected image by the reflected light L2 is red. That is, when the closed space corresponding part RE of the outer surface 1s of the structure 1 is colored by the permeable liquid 5 different from other parts (YES in step 4), the structure 1 has the communication defect 4b. Then, it can be determined that it is determined (step S5).

  On the other hand, when the permeable liquid 5 does not enter, the reflected light L2 from the closed space corresponding part RE does not include a component reflected by the permeable liquid 5, and thus the reflected light L1 from other than the closed space corresponding part RE. There is no significant difference. That is, a state in which the closed space corresponding part RE exhibits a color derived from the permeable liquid 5 is not observed. Therefore, when the closed space corresponding part RE of the outer surface 1s of the structure 1 is not colored by the permeable liquid 5 different from other parts (NO in step 4), the structure 1 has the communication defect 4b. It can be determined not to be performed (step S6).

  In the case of the first observation mode, when the non-transmissive part 3 is present in the structure 1, the reflected light L3 from the non-transmissive part 3 is also observed. For this reason, it is necessary to prevent erroneous determination such as misidentifying the coloration of the portion corresponding to the non-transmissive portion 3 in the reflected image as the coloration in the closed space corresponding portion RE.

  FIG. 6 is a diagram showing a second observation mode. In the second mode, observation is performed with the observation position 13 set on the opposite side of the illuminating means 11 (second illuminating means 11b) with respect to the structure 1. In this case, at the observation position 13, a transmission image of the diffused light L4 or the diffused light L5 of the illumination light 12 (second illumination light 12b) irradiated on the structure 1 is observed. However, in the outer surface 1s irradiated with the second illumination light 12b, the diffuse transmitted light L4 is obtained from the portion RE corresponding to the formation region of the closed space 2 (closed space corresponding portion) RE, and the outer space 1s corresponding to the closed space corresponding portion. It is assumed that diffuse transmitted light L5 is obtained from a portion other than RE.

  Since the second illumination light 12b is light that can be diffused and transmitted through the structure 1 as described above, when the permeable liquid 5 has entered the closed space 2 through the communication defect 4b as shown in FIG. The diffused transmission light L5 from the closed space corresponding part RE includes a wavelength component transmitted through the permeable liquid 5 entering the closed space 2 out of the first illumination light 12a incident on the structure 1. It will be. That is, a state in which the closed space corresponding part RE exhibits a color derived from the permeable liquid 5 is observed (step S5). Therefore, also in the second observation mode, as in the first observation mode, the closed space corresponding part RE of the outer surface 1s of the structure 1 is different from the other parts derived from the permeable liquid 5. If there is a color (YES in step 4), the structure 1 has the communication defect 4b (step S5). If there is no such coloration (NO in step 4), the structure 1 has the communication defect 4b. Can be determined not to exist (step S6).

  In the case of the second observation mode, even if the non-transmission part 3 exists in the structure 1, the second illumination light 12b is reflected by the non-transmission part 3, so that the reflected light L6 is observed at the observation position 13. In addition, the transmitted light L6 ′ that passes through the non-transmissive portion 3 is not observed. Therefore, the transmission image obtained at the observation position 13 does not show the coloration of the part corresponding to the non-transmission part 3. That is, it can be said that the second observation mode is more preferable than the first observation mode in that the erroneous determination as described above does not occur.

  Furthermore, in the case of the first observation mode, the reflected light L2 from the closed space corresponding part RE is reflected by the reflected light from the outer surface 1s of the structure 1 and the inside (if the non-transmissive part 3 exists, the non-transmissive part 3). And the former component which is obtained as a superposition with the reflected light from (including the above) and which is not related to the detection becomes very large. Therefore, even if the permeable liquid 5 has entered the closed space 2, the reflected light from the permeable liquid 5 can be obtained only with a relatively weak intensity. However, in the case of the second observation mode, the reflected light from the outer surface 1s of the structure 1 is not observed. On the other hand, if the permeable liquid 5 has entered the closed space 2, the structure RE The light incident on the inside of 1 and transmitted through the permeable liquid 5 maintains its color and reaches the outside. As a result, when the permeable liquid 5 has entered the closed space 2, the light transmitted through the permeable liquid 5 is relatively mixed in the closed space corresponding part RE, although the diffuse transmitted light from other parts is mixed somewhat. Strongly observed. Therefore, the second observation mode can detect the presence of the communication defect 4b with higher sensitivity than the first observation mode. For example, in the case of the second observation mode, it is possible to sufficiently specify the coloration state corresponding to the presence of the communication defect 4b even by visual observation.

<Decision based on captured image>
The direct observation of the structure 1 according to the above-described aspect and the determination of the presence or absence of the communication defect 4b based on the observation are performed while directly observing the structure 1, and the outer surface 1s is imaged and based on the obtained captured image. It can also be done. The simplest method is to output a captured image to an output product of some recording medium (photo paper, etc.) or a display medium (display, etc.), and the coloration state of the closed space corresponding part RE in the image represented by the output product A method for judging the above can be considered. However, this is only a difference between whether or not in-situ observation is performed, and is a method substantially equivalent to direct observation in that it is finally determined by visual observation.

  Instead of such visual observation, a defect inspection apparatus that can automatically determine the presence or absence of a communication defect may be used. FIG. 7 is a diagram schematically showing the configuration of the defect inspection apparatus 100 corresponding to the first observation mode. FIG. 8 is a diagram schematically showing the configuration of the defect inspection apparatus 200 corresponding to the second observation mode.

  Both the defect inspection apparatuses 100 and 200 are provided at a position corresponding to the illumination unit 11 (the first illumination unit 11a or the second illumination unit 11b), the stage 14 for placing the structure 1, and the observation position 13. The image pickup means 15 and the image processing device 16 that performs image processing on the picked-up image obtained by the image pickup means 15 and determines the presence or absence of the communication defect 4b.

  As the imaging unit 15, a known imaging device (CCD camera or the like) can be used. The image processing device 16 may be a general-purpose personal computer in which a program for executing processing to be described later is installed, or a circuit element including a dedicated arithmetic processing circuit is used. Also good. Further, the components of the defect inspection apparatuses 100 and 200 do not necessarily have to be provided as a single unit.

  FIG. 9 is a diagram illustrating a processing procedure in the defect inspection method performed using the defect inspection apparatuses 100 and 200. In such a process, first, the structure 1 is subjected in advance to the structure 1 in steps S1 and S2 (steps S11 and S12). Thereafter, it is placed on the stage 14.

  As a process corresponding to step S3 in a state where the illumination light (first illumination light 12a or second illumination light 12b) is irradiated from each illumination means 11 (first illumination means 11a or second illumination means 11b), The imaging unit 15 images the outer surface 1s of the structure 1 (step S13), and the image processing device 16 extracts the hue distribution on the outer surface 1s from the obtained captured image (step S14). More specifically, the RGB image data representing the captured image (image conversion processing to data representing the hue distribution is performed. The hue distribution is a distribution (two-dimensional distribution) for a two-dimensional region on the outer surface 1s. It may be an aspect of obtaining, or may be an aspect of obtaining a distribution (that is, a one-dimensional distribution) in a predetermined direction on the outer surface 1s, and a known technique can be applied to the above-described image conversion processing. Therefore, detailed description thereof is omitted.

  In the obtained hue distribution, it is determined whether or not there is a portion having a hue difference exceeding a predetermined threshold in the closed space corresponding part RE (step S15). Note that the determination based on the hue is only that the intensity of light from the permeable liquid 5 is reduced even if a shield such as an electrode exists between the permeable liquid 5 and the outer surface 1s. Because the hue value does not change, the certainty of detection is high. Further, when the defect inspection apparatus 200 is used (when observation is performed according to the second observation mode), the second illumination light 12b does not pass through the non-transmissive part 3 although there is wraparound due to diffusion. 3 may be observed as a dark part (dark color part), but by making a determination based on the hue, such a dark part and a colored part by the permeable liquid 5 are preferably used. Can be identified.

  Specifically, first, a portion where the change rate of the hue value is almost zero in the hue distribution is specified in the image processing device 16. Such a location represents a location where the permeable liquid 5 does not enter in the structure 1, and the image processing device 16 treats the hue value at that location as a reference value for determining the coloration state. . Alternatively, if the types of the structures 1 to be measured are always the same, a specific hue value may be specified as a reference value in advance and stored in the image processing device 16. Next, the image processing device 16 determines whether or not there is a portion that takes a hue value different from the reference value beyond the threshold value stored in advance. The threshold value is appropriately determined according to the type of the structure 1 or the permeable liquid 5 or the type of the defect processing apparatus.

  If such a location exists (YES in step S15), it can be determined that the communication body 4 has the communication defect 4b (step S16). If such a location does not exist (NO in step S15), it can be determined that there is no communication defect 4b in the structure 1 (step S17). The reason why such a determination can be made is that the hue difference between the part and another part is caused by the penetration of the permeable liquid 5 into the closed space 2.

  As described above, according to the present embodiment, the closed space is communicated with the outside in a structure having a closed space that cannot be visually recognized from the outside by using the impregnation ability of the permeable liquid into the defect. The presence or absence of a communication defect can be determined by the coloration state of the portion corresponding to the closed space on the outer surface of the structure. In addition, by observing a diffusion image due to diffused transmission light from the structure, the presence or absence of a communication defect can be more reliably determined.

  Hereinafter, an example in which defect inspection is performed using the defect inspection apparatus 200 will be described. FIG. 10 is a schematic cross-sectional view illustrating the structure of the sensor element 101 that is the structure 1 to be subjected to defect inspection in the present embodiment.

  The sensor element 101 is a ceramic device that is white in appearance and has, for example, zirconia as a ceramic main component, which is used for measuring NOx concentration in a gas to be measured. The sensor element 101 includes an electrode pattern and a heater on one surface or both surfaces of the six ceramic layers of the first layer 101a, the second layer 101b, the third layer 101c, the fourth layer 101d, the fifth layer 101e, and the sixth layer 101f. It has a structure in which various circuit patterns such as patterns are formed. The sensor element 101 is produced by firing a laminate obtained by laminating a ceramic green sheet corresponding to the first to sixth layers 101a to 101f on which a corresponding print pattern is formed. It becomes. The thickness of each ceramic layer is preferably about 100 μm to 1500 μm, more preferably about 200 μm to 1000 μm, and still more preferably about 300 μm to 400 μm.

  In the sensor element 101, the heater insulating layer 102 provided between the fourth layer 101 d and the fifth layer 101 e corresponds to the closed space 2. More precisely, the heater insulating layer 102 is the porous space 2a. The heater insulating layer 102 is a layer provided to electrically insulate the heater 103, and is formed of porous alumina to a thickness of 10 μm to 200 μm. More preferably, it is about 20 micrometers-100 micrometers, More preferably, it is about 30 micrometers-60 micrometers.

  In the sensor element 101, voids 104 and 105 communicating with the outside are provided at positions where the second layer 101b and the third layer 101c are formed, respectively, but the permeable liquid has entered the voids 104 and 105. However, since the permeable liquid remains in the voids 104 and 105 because it is removed by washing with water, the presence of a communication defect is not mistaken.

  In the present embodiment, a plurality of sensor elements 101 having such a configuration are prepared, and the permeable liquid is attached and removed according to the procedure shown in FIG. As the penetrating liquid, dyeing penetrant R-3B (NT Plus) manufactured by Eishin Chemical was used. Such an osmotic liquid exhibits a red color.

  FIG. 11 shows three sensor elements 101 (sample A, sample B, and sample C) obtained by imaging by the imaging means 15 provided in the defect inspection apparatus 200 after attaching the permeable liquid and removing it with water. It is a figure which shows the picked-up image of 101s outer surface (upper surface in FIG. 10). FIG. 12 is a diagram obtained by binarizing the captured image obtained as shown in FIG. 11 into a red region (more strictly, a region exhibiting a color similar to the permeable liquid) and other regions. is there. Although FIG. 11 is originally a color image, it is shown in monochrome for convenience of illustration, and it is difficult to specify the actual color appearance in the sensor element 101 from FIG. FIG. 12 is shown. The region shown in light gray in FIG. 12 is a region that is generally red in FIG. That is, only the sample B and the sample C have a region exhibiting a color similar to the color of the permeable liquid.

  FIG. 13 is a diagram illustrating hue distributions obtained from the captured images of the three sensor elements 101 (sample A, sample B, and sample C) illustrated in FIG. 11 in the image processing apparatus 16. Here, a one-dimensional hue distribution along the broken line shown in FIG. 11 is shown. FIG. 13 also shows the distribution of lightness and saturation at the same position for comparison.

  According to FIG. 13, in the case of sample A, the hue is substantially constant, while in the case of sample B, in the position of arrow AR1, in the case of sample C, in the position of arrow AR2, the hue is compared with other locations. There are places with different values. These generally coincide with the reddish region in FIG. 11 (the region represented by light gray in FIG. 12). In addition, since correspondence with FIG. 11 is not seen about brightness and again, FIG. 13 also shows that it is difficult to determine the presence or absence of penetration of the permeable liquid using these as indices.

  The results shown in FIG. 13 indicate that the coloration region resulting from the infiltration of the permeable liquid can be suitably measured by making a determination based on the hue value. This means that the sensor element 101 can accurately determine the presence or absence of a communication defect from the hue distribution of the captured image.

DESCRIPTION OF SYMBOLS 1 Structure 1s Exterior surface (of structure 1) 2 Closed space 2a Porous space 3 Non-permeable part 4 Defect 4a Non-communication defect 4b Communication defect 5 Penetration liquid 11 (11a, 11b) Illumination means (1st illumination means, 1st illumination means) (2 lighting means)
12 (12a, 12b) Illumination light (first illumination light, second illumination light)
DESCRIPTION OF SYMBOLS 13 Observation position 14 Stage 15 Imaging means 16 Image processing apparatus 100, 200 Defect inspection apparatus 101 Sensor element 101 s (Sensor element 101) outer surface 102 Heater insulating layer 103 Heater L1-L3, L6 Reflected light L4, L5 Diffuse transmitted light RE ( Closed space corresponding part (outside surface 1s)

Claims (16)

A method for inspecting defects in a structure having a closed space that has diffuse permeability and is invisible from the outside,
An adhesion step of adhering a penetrating liquid having an impregnation ability for defects and a color different from that of the structure to the outer surface of the structure;
A removing step of removing the permeable liquid attached to the outer surface of the structure in the attaching step;
Closed space corresponding part, which is a part corresponding to the formation area of the closed space, which is identified by the observation by observing the structure in a state in which illumination light is irradiated to the structure after the removing step by illumination means A determination step of determining the presence or absence of a communication defect that communicates the external space and the closed space in the structure based on the coloration state in
A defect inspection method for a structure, comprising: A defect inspection method for a structure according to claim 1,
In the determination step, an observation position is set on the opposite side of the illuminating unit with respect to the structure, and the observation is performed on a transmission image of diffused transmitted light of the irradiated illumination light.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to claim 1,
In the determination step, an observation position is set on the same side as the illuminating unit with respect to the structure, and a reflected image of reflected light from the outer surface and the inside of the structure of the illumination light irradiated on the structure is targeted. Make the observation,
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 3,
In the observation step, it is determined that the communication defect exists when there is a portion having a different color state from the other portion in the closed space corresponding part.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 3,
In the observation step, it is determined that the communication defect exists when there is a portion having a coloration state corresponding to the color of the permeable liquid in the portion corresponding to the closed space.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 5,
The observation step is
An imaging step of acquiring an appearance image of the structure by imaging the structure by an imaging unit disposed at the observation position;
An image determination step for determining the presence or absence of the communication defect in the structure by specifying the coloration state from the appearance image;
A defect inspection method for a structure, comprising: A defect inspection method for a structure according to claim 6,
In the image determination step, the coloration state is specified from the hue distribution in the appearance image, and the portion corresponding to the closed space has a hue difference that exceeds a predetermined threshold with the surroundings. It is determined that the communication defect exists.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 7,
The closed space is formed as a porous space filled with a porous body.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 8,
The structure is a flat plate member;
In the determination step, the illumination light is applied to one main surface of the flat plate member.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 9,
The structure is a ceramic device;
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to claim 10,
The ceramic device is formed by firing a laminate formed by laminating a plurality of ceramic green sheets each having a predetermined circuit pattern printed thereon.
A defect inspection method for a structure characterized by the above. A defect inspection method for a structure according to any one of claims 1 to 11,
The structure is a sensor element of a gas sensor;
A defect inspection method for a structure characterized by the above. An apparatus for inspecting a defect of a structure having a closed space inside which has a diffuse permeability and is invisible from the outside,
A stage on which the structure from which the permeable liquid has been removed from the outer surface is placed after the permeable liquid having an impregnation ability for defects and a color different from that of the structure is once attached to the outer surface;
Illuminating means for illuminating the structure placed on the stage with illumination light;
Imaging means for imaging the structure placed on the stage and generating an appearance image of the structure;
In the structure, based on a coloration state of a portion corresponding to a closed space, which is a portion corresponding to a formation region of the closed space, in the appearance image obtained by the imaging unit in a state where illumination light is irradiated by an illuminating unit. Determining means for determining the presence or absence of a communication defect that allows communication between the external space and the closed space;
A defect inspection apparatus comprising: A defect inspection apparatus for a structure according to claim 13,
The illumination means and the imaging means are arranged so as to be positioned on the opposite sides with respect to the structure mounted on the stage, and the appearance image is generated as a transmission image by the diffuse transmission light of the irradiated illumination light To
A structure defect inspection apparatus characterized by the above. A defect inspection apparatus for a structure according to claim 13,
The illumination means and the imaging means are arranged so as to be positioned on the same side with respect to the structure mounted on the stage, and the appearance image is reflected as a reflection image by reflected light from the outer surface and the inside of the structure. Generate,
A structure defect inspection apparatus characterized by the above. A defect inspection apparatus for a structure according to any one of claims 13 to 15,
The determination means is
Hue distribution specifying means for specifying the hue distribution in the appearance image;
With
Based on the hue distribution, in the portion corresponding to the closed space, it is determined whether there is a hue difference that exceeds a predetermined threshold with the surroundings, and when there is a portion that exceeds the threshold, Determining that the communication defect exists;
A defect inspection apparatus for a structure, comprising: