JP2013160745A - Method and device for inspecting porous carbon fiber sheet-like material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for automatically inspecting appearance defects of a porous carbon fiber sheet-like material comprising short carbon fiber and carbonized resin and traveling continuously in an optical approach and detecting plural types of defects different in feature quantitatively and accurately.SOLUTION: The method for inspecting a porous carbon fiber sheet-like material comprising short carbon fiber and carbonized resin and traveling continuously comprises at least (a) lighting means irradiating the sheet-like material with light, (b) imaging means receiving reflected light from the lighting means, (c) data processing means for processing image data obtained by the imaging means, and (d) data classifying means extracting and classifying defects according to feature amount comprising at least one of minimum luminance value and maximum luminance value obtained by the data processing means.

Description

  The present invention relates to a method and an apparatus for automatically inspecting appearance defects of a porous carbon fiber sheet-like material composed of short carbon fibers and carbonized resin and continuously running by an optical method.

In recent years, various developments have been made on environmental issues and energy issues. Among them, fuel cells that take advantage of features such as CO ₂ reduction due to high power generation efficiency and the fact that the only waste is water are attracting attention.

  A fuel cell is mainly composed of an electrolyte membrane, a catalyst, an electrode, and a separator, and a porous carbon fiber sheet is used as an electrode substrate.

  In the porous carbon fiber sheet-like material used for these electrode base materials, various defects that occur during production have an adverse effect when used as an electrode base material, and the problem that the originally required function cannot be fully exhibited There is. The defects mentioned here are caused, for example, by adhesion of floating impurities in the manufacturing process, non-uniform impregnation of carbonized resin, or short bundles of carbon fibers that are not dispersed but solidified. To do.

  Therefore, an appearance inspection is performed to detect various defects generated in the porous carbon fiber sheet. However, in the past, inspections repeatedly performed in the manufacturing process of porous carbon fiber sheet-like materials have been performed by human visual inspection, and the burden on the inspector is large and there are individual differences depending on the inspector. There is a problem that the appearance inspection cannot be performed quantitatively and accurately.

  For this reason, there is a need to introduce automatic appearance inspection technology for the purpose of saving labor, improving accuracy, and preventing defects from leaking out. For example, Patent Document 1 proposes an automatic appearance inspection using an optical technique for a continuous porous electrode substrate. This technology irradiates the surface of the porous electrode substrate with light by an illuminating means, images the transmitted light, specularly reflected light and scattered light with an imaging means, and analyzes the imaged data with an image processing unit, The main feature is to determine the type, location and size of the defect.

  However, in the method described in Patent Document 1, in order to detect all of a plurality of types of defects having different characteristics, at least three imaging units and illumination units are required to receive transmitted light, specularly reflected light, and scattered light. There are problems such as an increase in the cost of the inspection apparatus and an increase in the installation space of the inspection apparatus.

  For the image processing means for analyzing the imaging data, the integrated value is calculated by integrating the density value of each pixel in the defect detection block constituted by a plurality of adjacent pixels, and the integrated value and a predetermined threshold value are calculated. The defect is detected by comparing with the above. However, for a plurality of types of defects having different characteristics, the defect detection is discriminated by only one characteristic of the gray value, so that there is a problem that the detection accuracy is lowered. It was.

JP 2010-272250 A

  The present invention has been made to solve the above-mentioned problems of the prior art, and automatically detects the appearance defects of a porous carbon fiber sheet made of short carbon fibers and carbonized resin by an optical method. It is an object of the present invention to provide a method and apparatus for quantitatively and accurately detecting a plurality of types of defects with different characteristics.

In order to achieve the above object, the inspection apparatus according to the present invention employs the following configuration. That is, a porous carbon fiber sheet-like inspection method comprising carbon short fibers and carbonized resin and continuously running, comprising at least the following means (a) to (d): This is an inspection method for a carbon fiber sheet.
(A) illuminating means for irradiating the sheet-like material with light;
(B) imaging means for receiving reflected light from the illumination means;
(C) data processing means for processing image data obtained by the imaging means;
(D) Data sorting means for extracting and sorting out defects based on a feature quantity consisting of at least one of the minimum brightness value and the maximum brightness value obtained by the data processing means.

In the inspection method for a porous carbon fiber sheet according to the present invention, it is preferable that the data processing means further includes the following means.
(C-1) first data processing means for extracting defect candidates from the image data obtained by the imaging means;
(C-2) Second data processing means for calculating the feature amount from the defect candidate image data obtained by the first data processing means.

  In the method for inspecting a porous carbon fiber sheet according to the present invention, the imaging means is located on the same side as the illumination means with respect to the surface of the porous carbon fiber sheet, and the imaging means is the illumination. It is preferably provided at a position to receive specularly reflected light or scattered light generated on the surface of the porous carbon fiber sheet by means.

  In the method for inspecting a porous carbon fiber sheet according to the present invention, the angle θ1 from the vertical direction of the illumination means with respect to the surface of the porous carbon fiber sheet and the perpendicular of the imaging means with respect to the surface of the porous carbon fiber sheet. The angle θ2 from the direction is preferably 0 ° <θ1 ≦ 15 ° and 0 ° ≦ θ2 ≦ 15 °.

  In the method for inspecting a porous carbon fiber sheet of the present invention, it is preferable to further use an area and a circularity as the feature amount.

  In the method for inspecting a porous carbon fiber sheet according to the present invention, the defects of the sheet are due to insufficient resin, excessive resin, adhesion of foreign substances, adhesion of dirt, aggregation of short fibers, pinholes, tears, and missing edges. Preferably there is.

Moreover, the following structure is employ | adopted about the inspection apparatus in this invention. That is, a porous carbon fiber sheet-like inspection apparatus comprising carbon short fibers and carbonized resin and continuously running, comprising at least the following means (a) to (d): This is a carbon fiber sheet inspection device.
(A) illuminating means for irradiating the sheet-like material with light;
(B) imaging means for receiving reflected light from the illumination means;
(C) data processing means for processing image data obtained by the imaging means;
(D) Data sorting means for extracting and sorting out defects based on a feature quantity consisting of at least one of the minimum brightness value and the maximum brightness value obtained by the data processing means.

In the inspection apparatus for a porous carbon fiber sheet of the present invention, it is preferable that the data processing means further includes the following means.
(C-1) first data processing means for extracting defect candidates from the image data obtained by the imaging means;
(C-2) Second data processing means for calculating the feature amount from the defect candidate image data obtained by the first data processing means.

  In the inspection apparatus for a porous carbon fiber sheet according to the present invention, the imaging means is located on the same side as the illumination means with respect to the surface of the porous carbon fiber sheet, and the imaging means is the illumination. It is preferably provided at a position to receive specularly reflected light or scattered light generated on the surface of the porous carbon fiber sheet by means.

  In the inspection apparatus for a porous carbon fiber sheet of the present invention, the angle θ1 from the vertical direction of the illumination means with respect to the surface of the porous carbon fiber sheet, and the vertical of the imaging means with respect to the surface of the porous carbon fiber sheet. The angle θ2 from the direction is preferably 0 ° <θ1 ≦ 15 ° and 0 ° ≦ θ2 ≦ 15 °.

  In the inspection apparatus for a porous carbon fiber sheet of the present invention, it is preferable to further use an area and a circularity as the feature amount.

  In the inspection apparatus for a porous carbon fiber sheet of the present invention, the defects of the sheet are due to lack of resin, excessive resin, adhesion of foreign matter, adhesion of dirt, aggregation of short fibers, pinholes, tears, and missing edges. Preferably there is.

  According to the present invention, it is possible to quantitatively and accurately detect a plurality of types of defects having different characteristics in a porous carbon fiber sheet-like material composed of short carbon fibers and carbonized resin and continuously running.

It is the schematic of the test | inspection apparatus used for implementation of the test | inspection method of the porous carbon fiber sheet-like material of this invention. It is a side view of the test | inspection apparatus used for implementation of the test | inspection method of the porous carbon fiber sheet-like material of this invention. (A) is image data of a porous carbon fiber sheet-like material, and (b) is a diagram showing the relationship between the angle of the illumination means and the imaging means and the luminance variation. It is a schematic diagram of the surface state when light is irradiated from the illumination means to the surface of the porous carbon fiber sheet-like material. (A) is image data of a porous carbon fiber sheet-like material, and (b) is a diagram showing the relationship between the angle of the illumination means and the imaging means and the luminance variation. It is the schematic of the data processing means and data classification means used for implementation of the inspection method of the porous carbon fiber sheet-like material of this invention. It is the image data of each fault used as the detection object of the present invention. Here, (a) is resin shortage, (b) is excessive resin, (c) is foreign matter adhering, (d) is dirt adhering, (e) is short fiber aggregation, (f) is pinhole, (g) is It is torn and (h) is a missing edge.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  First, the porous carbon fiber sheet-like material that is the inspection object of the present invention will be described. Examples of the porous carbon fiber sheet-like material include a sheet-like material made from short fibers including short carbon fibers, a woven or knitted fabric or non-woven fabric containing carbon fibers, or a sheet-like material obtained by aligning carbon fibers in one or more directions. Examples thereof include a carbon fiber sheet-like material bound with a matrix resin and / or an organic carbide. Furthermore, examples include porous carbon sheet-like materials obtained by carbonizing the carbon fiber sheet-like material in an inert atmosphere, sheets of fiber-reinforced plastic other than carbon fibers, films, woven fabrics, nonwoven fabrics, There are no particular restrictions on the material of the porous carbon fiber sheet such as paper. In particular, a carbon fiber sheet-like product in which dispersed carbon short fibers are bound with resin and / or organic carbide has a high flexural modulus, a high coefficient of static friction, and a brittle nature. It is preferable to apply the method for manufacturing the wound body. Here, the dispersed state is often a state in which the short carbon fibers do not have a remarkable orientation in the sheet surface and are present almost randomly, for example, in a random direction. The fiber length of the short carbon fiber is preferably 3 to 20 mm, more preferably 5 to 15 mm. By setting the fiber length of the short carbon fiber within the above range, when the short carbon fiber is dispersed and paper is obtained to obtain a carbon fiber sheet, the dispersibility of the short carbon fiber can be improved and the basis weight variation can be suppressed.

  In addition, the types of defects that occur in the porous carbon fiber sheet to be inspected include resin shortage, excessive resin, foreign matter adhesion, dirt adhesion, short fiber agglomeration, pinholes, tears, and missing edges. Can be mentioned. Here, each defect will be briefly described.

  The resin shortage is a portion where the carbonized resin impregnation amount is smaller than the normal portion of the porous carbon fiber sheet-like material, and appears black.

  The excessive resin is a portion where the amount of impregnation of the carbonized resin is larger than the normal part of the porous carbon fiber sheet-like material, and appears white.

  The adhesion of foreign matter and dirt are spots where impurities floating in the manufacturing process are attached and appear black.

  The short fiber agglomeration is a portion where the short carbon fibers are not sufficiently dispersed in the process of making the short carbon fibers and are bundled together and appear white.

  A pinhole is a portion where impurities floating in the manufacturing process adhere and react to cause a hole.

  The tear is a portion that has been torn due to a change in tension when the porous carbon fiber sheet is conveyed.

  The lack of the end is a portion where the end of the porous carbon fiber sheet is missing.

  Moreover, since these defects have different defect detection priorities due to differences in the occurrence situation and influence on subsequent processes, it is preferable to detect each defect separately. In particular, with regard to the defects that have occurred through the porous carbon fiber sheet such as pinholes, tears, and missing edges, when the porous carbon fiber sheet is transported, There is a risk of the porous carbon layer fiber sheet material breaking, which has a large effect on production efficiency, and since the priority of defect detection is higher than other defects, these are detected separately from other defects It is preferable.

  From here, the inspection method and apparatus according to the present invention will be described. FIG. 1 and FIG. 2 show an outline of an inspection apparatus suitably used for the inspection method of the porous carbon fiber sheet-like product 6. The porous carbon fiber sheet 6 is conveyed along the longitudinal direction MD of the porous carbon fiber sheet 6 indicated by an arrow A. Illumination means 1 is provided at a predetermined position above the porous carbon fiber sheet 6 so that light is irradiated to the surface of the porous carbon fiber sheet 6 at a predetermined angle with respect to the porous carbon fiber sheet 6. Is arranged. Further, the imaging means 2 is arranged on the same side as the illumination means 1 so as to receive the reflected light generated on the surface of the porous carbon fiber sheet-like material 6. The image picked up by the image pickup means 2 is input to the image input means 3, and further, analysis and defect determination are performed by the image analysis means 4. The results analyzed and determined by the image analysis unit 4 are stored in the image storage unit 5.

  The angle at which the illumination means 1 in the present invention irradiates light on the surface of the porous carbon fiber sheet-like material 6 is to irradiate light at an angle at which it is regularly reflected or scattered to the imaging means 2 described later, as shown in FIG. Is preferred. In particular, the angle θ1 from the vertical direction of the illumination means 1 with respect to the surface of the porous carbon fiber sheet-like material 6 is preferably 0 ° to 15 °, as will be described later.

  Moreover, the illumination means 1 has an irradiation surface having a line shape or a planar shape and is at a position orthogonal to the longitudinal direction MD of the porous carbon fiber sheet-like material 6, or the porous carbon fiber sheet-like material 6. It is preferable that it is arrange | positioned in the position which covers the width direction TD. This is because, when the width direction TD of the porous carbon fiber sheet 6 is inspected at the same time, the irradiation with the irradiation surface having a line shape or plane shape is more porous than the arrangement in which the spot-shaped illumination is arranged in the width direction TD. It is possible to uniformly irradiate the surface of the porous carbon fiber sheet 6 with light arranged at a position orthogonal to the longitudinal direction MD of the fiber sheet 6 and prevent deterioration in detection accuracy due to illumination unevenness. It is because it can do.

  The imaging means 2 in the present invention receives specularly reflected light or scattered light generated on the surface of the porous carbon fiber sheet 6 on the same side as the illumination means 1 with respect to the porous carbon fiber sheet 6. Has been placed. In this inspection method, light is irradiated from the illumination means 1 to the surface of the porous carbon fiber sheet-like material 6, and the porous carbon fiber is scattered by specularly reflected light or scattered light generated on the surface of the porous carbon fiber sheet-like material 6. The surface image of the fiber sheet 6 is picked up by the image pickup means 2. Thereby, the image data of the predetermined range of the porous carbon fiber sheet-like article 6 can be obtained. For example, a CCD line sensor camera or the like is preferably used as the imaging unit 2. Moreover, it is preferable that angle (theta) 2 from the orthogonal | vertical direction of the imaging means 2 with respect to the surface of the porous carbon fiber sheet-like material 6 is 0 degree-15 degrees so that it may mention later.

  Here, the range of the angle θ1 from the vertical direction of the illumination means 1 to the surface of the porous carbon fiber sheet 6 and the angle θ2 from the vertical direction of the imaging means 2 to the surface of the porous carbon fiber sheet 6 are described in detail. explain.

  FIG. 3A shows an angle θ1 from the vertical direction of the illumination unit 1 with respect to the surface of the porous carbon fiber sheet 6 and an angle θ2 from the vertical direction of the imaging unit with respect to the surface of the porous carbon fiber sheet 6. Image data obtained by imaging the normal part of the porous carbon fiber sheet-like material 6 by providing several levels is shown in FIG. The image data 31a has an angle θ1 = angle θ2 = 15 °, the image data 32a has an angle θ1 = angle θ2 = 30 °, and the image data 33a has an angle θ1 = angle θ2 = 45 °. The image data 34a is image data of a normal part when the angle θ1 = the angle θ2 = 60 °. In addition, the luminance variation values at the respective plot points in FIG. 3B are 31a = 14.0, 32b = 22.2, 33b = 23.6, and 34b = 23.7.

  Here, the luminance variation is a standard deviation of the luminance value of each pixel in the entire image data, and the larger this is, the larger the luminance unevenness of the normal part is. That is, the smaller the variation in luminance, the more the porous carbon fiber sheet-like material 6 can be imaged without being affected by the luminance unevenness of the normal portion. In the data processing means and data sorting means described later, the normal part It is possible to detect defects with high accuracy without requiring complicated processing for suppressing uneven brightness. Further, since complicated processing is not required, the processing time of the data processing means and the data sorting means can be shortened.

  As shown in FIG. 3B, it can be seen that the luminance variation increases as the angle increases from the plot point 31b (the image data at this time corresponds to the image data 31a in FIG. 3A). . This is deeply related to the surface state of the porous carbon fiber sheet 6. FIG. 4 is a schematic view showing the surface of the porous carbon fiber sheet-like material 6 when light is irradiated from the illumination means 1. As shown in FIG. 4A, when the angle θ1 of the illumination means 1 is large, a shadow 43a of the fiber 42a is generated on the surface of the porous carbon fiber sheet-like material 6 by the irradiation light 41a from the illumination means 1. On the other hand, as shown in FIG. 4B, when the angle θ1 of the illumination means 1 is small, the shadow 43b of the fiber 42b is formed on the surface of the porous carbon fiber sheet 6 by the irradiation light 41b from the illumination means 1. Arise. Here, attention is paid to the shadows 43a and 43b in FIGS. 4 (a) and 4 (b). In FIG. 4A, the shadow 43a of the fiber 42a tends to be large. As a result, the luminance contrast increases between the fibers 42a and the shadow 43a, so that the luminance variation in the normal portion increases and the luminance unevenness in the normal portion also increases. On the other hand, in FIG. 4B, the shadow 43b of the fiber 42b is less likely to occur. As a result, the luminance contrast between the fiber 42b and the shadow 43b is reduced, so that the luminance variation in the normal portion is reduced and the luminance unevenness in the normal portion is also reduced. Therefore, it is preferable to provide the illumination unit 1 and the imaging unit 2 so that the angle θ1 of the illumination unit 1 and the angle θ2 of the imaging unit 2 are reduced.

  Furthermore, the scattered light in the range where θ is small is also examined. FIG. 5 shows image data when the angle θ1 = 10 ° of the illumination unit 1 and the angle θ2 = 0 ° of the imaging unit 2. The luminance variation in the image data 51a is a plot point 51b = 9.4, which is smaller than the plot point 31b in FIG. 3B, and matches the tendency in FIG. Therefore, when the angle θ1 of the illumination unit 1 and the angle θ2 of the imaging unit 2 are in the range of 0 to 15 °, the scattered light is sampled as light generated on the surface of the porous carbon fiber sheet 6 received by the imaging unit 2. However, the luminance variation obtained from the image data can be used as a determination index similarly to the regular reflection light.

  From these results, the angle θ1 of the illumination unit 1 and the angle θ2 of the image pickup unit 2 are preferably 0 to 15 °, and more preferably 0 to 10 °.

  In describing the data processing means and data sorting means in the present invention, the flow of image input, image analysis, and image storage will be briefly described.

  The image input means 3 sequentially inputs image data obtained by imaging the porous carbon fiber sheet-like material 6 illuminated by the illumination means 1 with the imaging means 2.

  The image data input to the image input means 3 is supplied to the image analysis means 4 and analyzed in time series (the data processing means and data sorting means of the present invention are applied to this analysis processing). Then, the analysis result in the image analysis means 4, the presence / absence of a defect based on the analysis result, the type of the defect, and the occurrence position thereof are detected, and the analysis is completed.

  When the analysis is completed, information input to the image storage unit 5 and analyzed and determined by the image analysis unit 4 is stored. An analysis (detection) processing method and a result determination method will be described later.

  As described above, a series of inspections of illumination, imaging, analysis, result determination, and storage are repeated, and a continuous automatic inspection is performed on the longitudinal direction MD of the porous carbon fiber sheet-like material 6. In addition, in this inspection method, the surface of the porous carbon fiber sheet 6 to be inspected includes insufficient resin, excessive resin, adhesion of foreign substances, adhesion of dirt, aggregation of short fibers, pinholes, tears, and missing edges. At least one or more of the defects can be detected.

  As shown in FIG. 6, the image analysis unit 4 in the present invention includes a first data processing unit 61, a second data processing unit 62, and a data sorting unit 63.

  The first data processing unit 61 is a data processing unit that extracts defect candidates from the image data obtained by the imaging unit 2.

  The second data processing unit 62 is a data processing unit that calculates the feature amount of the defect candidate from the image data of the defect candidate obtained by the first data processing unit.

  The data disposition classification unit 63 is a data classification unit that extracts defects from the defect candidate feature quantities obtained by the second data processing unit and classifies them.

  Here, each data processing means and data separation in the image analysis means 4 will be described in detail.

  First, the first data processing unit 61 extracts defect candidates from the image data obtained by the imaging unit 2. Since the image data obtained by the imaging unit 2 here may include a defect candidate other than the defect candidate to be detected (for example, the background of the imaging region), the detection target is detected from this image data. The process which extracts only the defect candidate which becomes becomes is implemented. Such extraction processing is generally binarized, and if the pixel in the image data is brighter than a preset brightness (threshold), it is extracted as bright portion data, and if dark, it is extracted as dark portion data.

  In the method for inspecting a porous carbon fiber sheet 6 according to the present invention, the defect candidate is imaged brighter or darker than the background by receiving the light emitted from the illumination unit 1 as reflected light by the imaging unit 2. Therefore, binarization processing can be applied. By executing such processing on all the pixels in the image data, the defect candidates are extracted as bright part data or dark part data.

  In addition, when the image data includes noise (for example, tumbling noise called sesame salt noise), before performing the above extraction process, an averaging filter, a Gaussian filter, It is preferable to perform a filtering process such as a median filter to reduce noise so that a defect candidate can be easily extracted as bright part data or dark part data.

The second data processing unit 62 calculates the feature amount of the defect candidate from the defect candidate image data obtained by the first data processing unit 61. Typical features here include a center of gravity, a circumscribed rectangle, an area, a perimeter, and a circularity. Each feature amount will be briefly described. The center of gravity is the center of the weight of the entire region when it is assumed that the pixels in the extracted region have an equal weight. The circumscribed rectangle is the smallest rectangle that touches the extracted area, and is used to know the approximate size of the area. The area is the number of pixels constituting the extracted region. The perimeter is the number of pixels around the extracted area. The circularity represents how close the extracted region is to a circle, and is obtained by 4πS / L ² where S is the area and L is the perimeter. When the object is a circle, the maximum circularity is 1, and the further away from the circle, the smaller the value. Such feature amounts are calculated and used for extraction and separation processing by a data separation means described later. In the present invention, the defects generated in the porous carbon fiber sheet 6 have different characteristics. Therefore, by applying one or more kinds of feature quantities suitable for each defect, the defect detection accuracy can be improved. It becomes possible to improve.

  In addition, the above-mentioned feature amount is focused on the shape feature of the pixels constituting the extracted region, but there is also a feature amount focused on the luminance value of the pixels constituting the extracted region. It can also be applied. Typical examples include a minimum luminance value and a maximum luminance value. The minimum luminance value is the value with the lowest luminance among the pixels constituting the extracted region, and the maximum luminance value is the value with the highest luminance among the pixels constituting the extracted region. For example, regarding the shortage of resin, this defect is a portion where the amount of impregnation of the carbonized resin is smaller than the normal portion of the porous carbon fiber sheet-like material 6 and appears black. Therefore, the luminance value of the pixels constituting the defect portion Should be smaller than the luminance value of the pixels constituting the normal part. Therefore, in this case, the minimum luminance value can be applied. In this way, the luminance feature amount can be applied, and by applying these in combination with the shape feature amount described above, it is possible to further improve the defect detection accuracy.

  The data classification means 63 extracts defects from the defect candidate feature quantities obtained by the second data processing means 62 and classifies them. The feature amount calculated by the second data processing means 62 is compared with a preset threshold value, and if the feature amount is equal to or greater than the threshold value or less than the threshold value, it is extracted as a defect. In addition, since the shape characteristics and luminance characteristics are different for each defect, the optimal feature amount is selected in advance according to the defect feature to be detected, and a threshold is set to compare the defect candidates for each defect. It becomes possible to do. For example, in the case of a pinhole, since it has a rounder shape than other defects, the degree of circularity is selected as a feature quantity, and the threshold value is closer to 1 (closer to a circle, the closer to 1) Therefore, it is possible to accurately distinguish from other defects.

Examples of the present invention will be described below. The structure of the porous carbon fiber sheet-like inspection method and apparatus used in this example is shown below.
Illumination means: LED line illumination (length 900 mm, manufactured by CCS, HLND-900SW-R)
Imaging means: line sensor camera (7400 pixels, manufactured by Nippon Electro Sensory Devices, SuFi74)
Image analysis means: image processing library HALCON (Ver. 10.0.1, manufactured by MVTec)
Angle θ1: 10 ° from the vertical direction of the illumination means with respect to the surface of the porous carbon fiber sheet
Angle θ2: 0 ° from the vertical direction of the imaging means with respect to the surface of the porous carbon fiber sheet
Distance WD1: 1430 mm between the surface of the porous carbon fiber sheet and the illumination means
Distance WD2 between surface of porous carbon fiber sheet and imaging means: 100 mm
Conveying speed of porous carbon fiber sheet: 5 m / min

  With the above configuration, it can be obtained by imaging each defect of resin shortage, excess resin, foreign matter adhesion, dirt adhesion, short fiber aggregation, pinhole, tearing, end missing in porous carbon fiber sheet material. The data processing means and data sorting means of the present invention were implemented on the image data. FIG. 7 shows image data of each defect.

  As a first data processing means, binarization processing was performed. As shown in Table 1, threshold values for binarization processing for each defect were set in advance. For example, (a) the binarization threshold value for insufficient resin is 45 or less, which means that pixels having a luminance value of 45 or less in the image data are extracted as dark portion data. In addition, the binarization threshold value of (b) excessive resin is 90 or more, which means that pixels having a luminance value of 90 or more in the image data are extracted as bright portion data.

  Next, the second data processing unit was implemented, and the feature amount of the defect candidate obtained by the first data processing unit was calculated. The calculated feature amounts are four types of area, circularity, minimum luminance value, and maximum luminance value, and Table 2 shows the calculation results of the feature amounts of each defect candidate.

  Finally, a data classification unit is implemented, and defects are extracted from the defect candidate feature amounts obtained by the second data processing unit and classified. The feature amount to be applied and its threshold value are set with reference to Table 2. First, focusing on the area as the feature amount, (c) foreign matter adhesion and (g) tearing have the same value (682). Therefore, if the area is applied as the feature amount, the two cannot be separated. Therefore, focusing on the feature quantity other than the area, the circularity and the minimum luminance value are different in all defect candidates. Therefore, by applying one of these two feature amounts and setting the values shown in Table 2 as threshold values, it becomes possible to classify all defect candidates.

  In this example, all the defect candidates were separated by applying only one type of feature amount, but the inspection range (length in the longitudinal direction and width direction) of the porous carbon fiber sheet was widened, When the number of defects to be detected increases, it becomes difficult to accurately classify all defect candidates with only one type of feature amount. In such a case, it is possible to classify all defect candidates more accurately by applying a combination of a plurality of types of feature amounts.

  In this way, it is possible to sort all defect candidates quantitatively and accurately without requiring complicated processing as compared with the conventional method.

1: Illumination means 2: Imaging means 3: Image input means 4: Image analysis means 5: Image storage means 6: Porous carbon fiber sheet A: Transport direction of porous carbon fiber sheet MD: Porous carbon fiber Longitudinal direction of the sheet-like material TD: Width direction of the porous carbon fiber sheet-like material θ1: Angle from the vertical direction of the illumination means with respect to the surface of the porous carbon fiber sheet-like material θ2: With respect to the surface of the porous carbon fiber sheet-like material Angle from the vertical direction of the imaging means WD1: Distance between the surface of the porous carbon fiber sheet and the illumination means WD2: Distance between the surface of the porous carbon fiber sheet and the imaging means 31a, 32a, 33a, 34a: Image data of porous carbon fiber sheets 31b, 32b, 33b, 34b: plot points 41a, 41b: irradiation light 42a, 42b: fibers 43a, 43b: shadows 51a: many Image data of porous carbon fiber sheet 51b: plot point of graph 61: first data processing means 62: second data processing means 63: data sorting means

  According to the present invention, the appearance defect of a porous carbon fiber sheet made of short carbon fibers and carbonized resin is automatically inspected by an optical method, and a plurality of kinds of defects having different characteristics are quantitatively analyzed. In addition, since it has the property of being able to be detected with high accuracy, it can be suitably used for appearance inspection and quality control in the manufacturing process of porous carbon fiber sheet material, but its application range is limited to this. It is not something that can be done.

Claims (12)

A method for inspecting a porous carbon fiber sheet comprising a carbon short fiber and a carbonized resin and continuously running, comprising at least the following means (a) to (d): Sheet inspection method.
(A) illuminating means for irradiating the sheet-like material with light;
(B) imaging means for receiving reflected light from the illumination means;
(C) data processing means for processing image data obtained by the imaging means;
(D) Data sorting means for extracting and sorting out defects based on a feature quantity consisting of at least one of the minimum brightness value and the maximum brightness value obtained by the data processing means. The method for inspecting a porous carbon fiber sheet according to claim 1, wherein the data processing means further comprises the following means.
(C-1) first data processing means for extracting defect candidates from the image data obtained by the imaging means;
(C-2) Second data processing means for calculating the feature amount from the defect candidate image data obtained by the first data processing means. The imaging means is located on the same side as the illuminating means with respect to the surface of the porous carbon fiber sheet-like material, and the imaging means causes regular reflection that occurs on the surface of the porous carbon fiber sheet-like material by the illuminating means. 3. The method for inspecting a porous carbon fiber sheet according to claim 1, wherein the inspection method is provided at a position for receiving light or scattered light. The angle θ1 from the vertical direction of the illumination means with respect to the surface of the porous carbon fiber sheet-like material and the angle θ2 from the vertical direction of the imaging means with respect to the surface of the porous carbon fiber sheet-like material are 0 ° <θ1 ≦ 15 °, The inspection method for a porous carbon fiber sheet according to any one of claims 1 to 3, wherein 0 ° ≤ θ2 ≤ 15 °. The inspection method for a porous carbon fiber sheet according to any one of claims 1 to 4, wherein an area and a circularity are further used as the feature amount. 6. The sheet according to any one of claims 1 to 5, wherein the defects of the sheet-like material are insufficient resin, excessive resin, adhesion of foreign matters, adhesion of dirt, aggregation of short fibers, pinholes, tears, and missing end portions. The inspection method of the porous carbon fiber sheet-like material of description. A porous carbon fiber sheet-like inspection apparatus comprising carbon short fibers and a carbonized resin and continuously running, comprising at least the following means (a) to (d): Sheet inspection device.
(A) illuminating means for irradiating the sheet-like material with light;
(B) imaging means for receiving reflected light from the illumination means;
(C) data processing means for processing image data obtained by the imaging means;
(D) Data sorting means for extracting and sorting out defects based on a feature quantity consisting of at least one of the minimum brightness value and the maximum brightness value obtained by the data processing means. The inspection apparatus for a porous carbon fiber sheet according to claim 7, wherein the data processing means further includes the following means.
(C-1) first data processing means for extracting defect candidates from the image data obtained by the imaging means;
(C-2) Second data processing means for calculating the feature amount from the defect candidate image data obtained by the first data processing means. The imaging means is located on the same side as the illuminating means with respect to the surface of the porous carbon fiber sheet-like material, and the imaging means causes regular reflection that occurs on the surface of the porous carbon fiber sheet-like material by the illuminating means. 9. The inspection apparatus for a porous carbon fiber sheet according to claim 7, wherein the inspection apparatus is provided at a position for receiving light or scattered light. The angle θ1 from the vertical direction of the illumination means with respect to the surface of the porous carbon fiber sheet-like material and the angle θ2 from the vertical direction of the imaging means with respect to the surface of the porous carbon fiber sheet-like material are 0 ° <θ1 ≦ 15 °, The inspection apparatus for a porous carbon fiber sheet according to claim 7, wherein 0 ° ≦ θ2 ≦ 15 °. The inspection apparatus for a porous carbon fiber sheet according to any one of claims 7 to 10, wherein an area and a circularity are further used as the feature amount. The defect of the sheet-like material is insufficient resin, excessive resin, adhesion of foreign matter, adhesion of dirt, agglomeration of short fibers, pinholes, tearing, and missing end portions. The inspection apparatus for a porous carbon fiber sheet according to the description.

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