A method and device for detecting the surface finish of a fuel cell graphite plate

Abstract

The present invention relates to a method and device for detecting the surface forming smoothness of a fuel cell graphite plate. The method comprises the following steps: S1, placing the graphite plate in a dark room, irradiating the surface area of the graphite plate with a fixed light source, and a camera capturing an image of the graphite plate surface; S2, intercepting an image of the area to be analyzed from the graphite plate surface image; S3, converting the image of the area to be analyzed into a grayscale image; S4, obtaining the grayscale values of each pixel point in the grayscale image; S5, calculating the grayscale value distribution in the grayscale image, and determining the smoothness of the area to be analyzed according to the grayscale value distribution. Compared with the prior art, the present invention realizes quantitative analysis of the surface forming smoothness of the graphite plate, and avoids misjudgment caused by physiological and cognitive differences between people.

Description

Technical Field

[0001] The invention relates to a fuel cell graphite plate detection technology, and in particular to a fuel cell graphite plate surface molding smoothness detection method and device. Background Art

[0002] The bipolar plate is the core component of the fuel cell stack. Whether it is a metal bipolar plate or a graphite bipolar plate, the smoothness of the ridges and grooves in the flow field is crucial. Its defects may have a fatal impact on corrosion resistance, high and low temperature, hydrophilicity, drainage effect, etc.

[0003] Currently, there is no instrument for detecting the surface smoothness of graphite plates for battery materials. The detection of the surface smoothness of graphite plates for battery materials is mostly done by manual visual inspection, which leads to problems of non-quantification and inconsistent evaluation standards. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a method and device for detecting the surface finish of a fuel cell graphite plate.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for detecting the surface finish of a fuel cell graphite plate, the method comprising the following steps:

[0007] S1. Place the graphite plate in a dark room, illuminate the surface area of the graphite plate with a fixed light source, and use a camera to capture the surface image of the graphite plate;

[0008] S2, intercepting the image of the area to be analyzed from the surface image of the graphite plate;

[0009] S3, converting the image of the area to be analyzed into a grayscale image;

[0010] S4, obtaining the gray value of each pixel in the gray image;

[0011] S5. Calculate the grayscale value distribution in the grayscale image, and determine the smoothness of the area to be analyzed according to the grayscale value distribution.

[0012] Preferably, step S5 is specifically as follows: determining a first value and a second value of the grayscale image according to the grayscale value, wherein the first value is the ratio of the area of the black shadow area to the total area in the grayscale image, and the second value is the ratio of the standard deviation of the grayscale values of all pixels except the black shadow area in the grayscale image to the mean. The smaller the first value and the second value are, the higher the smoothness of the area to be analyzed is.

[0013] Preferably, the black shadow area is determined as pixel points with grayscale values in the range of 0 to 30.

[0014] A device for detecting the surface finish of a graphite plate of a fuel cell, the device comprising a darkroom, a fixed light source and a camera. The darkroom is used to cover the graphite plate to be detected. The fixed light source is fixed on the top of the darkroom and irradiates the surface area of the graphite plate. The camera is fixed on the top of the darkroom, and the camera lens is located inside the darkroom and aligned with the graphite plate;

[0015] The device further comprises a memory and a processor. The memory is used to store a computer program, and the processor is used to implement steps S2 - S5 in the method when executing the computer program.

[0016] Preferably, the darkroom comprises a darkroom cover and a darkroom cover fixing tooling. The bottom of the darkroom cover is fixed on the detection plane through the darkroom cover fixing tooling.

[0017] Preferably, the darkroom cover is in the shape of a trapezoidal table. The center point of the top surface of the darkroom cover and the center point of the graphite plate are on the same vertical line, and the camera is fixed at the center point position of the top surface of the darkroom cover.

[0018] Preferably, the darkroom cover fixing tooling comprises four first right - angle fixing blocks. The four corners of the bottom of the darkroom cover are respectively fixed on the detection plane through a first right - angle fixing block.

[0019] Preferably, the graphite plate is fixed on the detection plane through a plate fixing tooling.

[0020] Preferably, the plate fixing tooling comprises a horizontal fixing block and a second right - angle fixing block. The second right - angle fixing block is used to limit the position of the right angle formed by the first long side and the first short side on the graphite plate, and the first horizontal fixing block is used to limit the position of the first long side on the graphite plate.

[0021] Preferably, a plurality of fixed light sources are provided and evenly distributed on the top of the darkroom.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The present invention realizes the quantitative analysis of the surface finish of the graphite plate through image analysis, avoiding misjudgment caused by physiological and cognitive differences between people;

[0024] (2) The principle of the present invention for quantitatively analyzing the surface forming smoothness of the graphite plate is as follows: The particles used for forming the graphite plate are generally small expanded graphite flakes or graphite particles, which are smooth on the surface during extrusion and leveling and can effectively reflect light. When the flakes or particles are not in the same plane, or even in a powder state, they cannot emit light, or have a different light reflection direction from the overall plane. Therefore, if the surface forming smoothness of the graphite plate is poor, the corresponding area in the captured image appears black (that is, after converting to a grayscale image, the gray value of the pixel points tends to be 0, and the present invention determines the area with a gray value in the range of 0-30 as the black shadow area). Thus, through the quantitative analysis of the gray value, a method for efficiently quantitatively analyzing the surface forming smoothness of the graphite plate is provided;

[0025] (3) The present invention can adopt a fully computerized and fully automated process for processing, which can finely analyze each specific area, especially the numerous bipolar plate ridge areas, effectively reducing manual consumption;

[0026] (4) The data analysis part of the present invention can effectively adapt to different plates and photographing lights, and the method has universality and can be widely applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of the method for detecting the surface forming smoothness of the fuel cell graphite plate of the present invention;

[0028] Figure 2 is the grayscale image to be analyzed in Example 1;

[0029] Figure 3 is a schematic structural diagram of the photographing tooling in the device for detecting the surface forming smoothness of the fuel cell graphite plate of the present invention;

[0030] In the figure, 1 is a darkroom cover, 2 is a darkroom cover fixing tooling, 3 is a graphite plate, 4 is a plate fixing tooling, 5 is a fixed light source, and 6 is a camera. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Note that the following description of the embodiments is only illustrative in nature, and the present invention is not intended to limit the objects to which it is applicable or its uses, and the present invention is not limited to the following embodiments.

[0032] Example 1

[0033] As Figure 1 shown, this embodiment provides a method for detecting the surface forming smoothness of a fuel cell graphite plate, and the method includes the following steps:

[0034] S1. Place the graphite plate 3 in a dark room, irradiate the surface area of the graphite plate 3 with a fixed light source 5, and use a camera 6 to capture the surface image of the graphite plate 3. When conducting batch analysis, it is necessary to use the same camera 6 settings to obtain photos with the same properties, including: the pixel size of the photo, the magnification factor, the relative position of the target in the photo, etc., to facilitate subsequent batch process analysis;

[0035] S2. In order to obtain a fine analysis of a certain area of the bipolar plate, such as grooves, ridges, or other areas to be analyzed, software can be used to intercept this area and store it as a picture file for subsequent analysis;

[0036] S3. Convert the image of the area to be analyzed into a grayscale image;

[0037] S4. Obtain the grayscale values of each pixel point in the grayscale image;

[0038] S5. Calculate the distribution of grayscale values in the grayscale image, and determine the smoothness of the area to be analyzed according to the distribution of grayscale values.

[0039] Step S5 is specifically as follows: Determine the first value and the second value of the grayscale image according to the grayscale value. The first value is the ratio of the area of the black shadow area to the total area in the grayscale image, and the second value is the ratio of the standard deviation to the mean of the grayscale values of all pixel points other than the black shadow area in the grayscale image. The smaller the first value and the second value, the higher the smoothness of the area to be analyzed. Among them, the black shadow area is determined as the pixel points with grayscale values in the range of 0-30.

[0040] In this embodiment, specifically:

[0041] First, use a digital camera 6 to take pictures of the graphite bipolar plate sample, use the photoshop software to intercept the image of the area to be analyzed, and save it as a JPG format picture. The obtained pictures have the same size and the same pixel ratio.

[0042] Furthermore, import the above-obtained pictures into the software Matlab and generate a data file. Use the rbg2gray command to convert the data into grayscale mode. As known from the MATLAB description, this data is 8-bit integer (uint8) data, where the minimum value 0 represents black and the maximum value 255 represents white. The data between 0-255 is an integer value that linearly reflects the grayscale.

[0043] Data analysis mainly consists of two parts: the first value and the second value. The first value is the ratio of the area of the black shadow area to the total area in the grayscale image, and the second value is the ratio of the standard deviation to the mean of the grayscale values of all pixel points other than the black shadow area in the grayscale image. Generally, it is considered that the smaller the first value and the second value, the better the forming effect. The black area can be defined as the grayscale value ranging from 0 to 30, and the first value D is obtained by counting the proportion of the number of grayscale values within this range.

[0044]

[0045] Among them, N1 is the number of pixel points with grayscale values ranging from 0 to 30 in the grayscale image, N2 is the number of pixel points with grayscale values greater than 30 in the grayscale image, and N1 + N2 is the total number of pixel points in the grayscale image;

[0046] The second value is obtained by the following formula:

[0047]

[0048]

[0049]

[0050] Among them, v is the second value, s is the standard deviation of the grayscale values of all pixel points other than the black shadow area in the grayscale image, μ is the pixel mean of all pixel points other than the black shadow area in the grayscale image, and A i is the grayscale value of the i-th pixel point.

[0051] The principle of the quantitative analysis of the surface forming smoothness of the graphite plate in the present invention is as follows: The particles used for the forming of the graphite plate are generally small expanded graphite flakes or graphite particles, which are smooth on the surface during extrusion and leveling and can effectively reflect light. When the flakes or particles are not in the same plane, or even in a powder state, they cannot emit light, or the light reflection direction is different from that of the overall plane. Therefore, if the surface forming smoothness of the graphite plate is poor, the corresponding area of the captured image will be black (that is, after being converted into a grayscale image, the grayscale value of the pixel points tends to be 0, and the present invention determines the area with grayscale values in the range of 0 to 30 as the black shadow area). Thus, through the quantitative analysis of the grayscale values, a method for efficiently quantitatively analyzing the surface forming smoothness of the graphite plate is provided.

[0052] In this embodiment, 3 regions are intercepted simultaneously, such as Figure 2 the three regions of channel1, Rib2, and Rib3 in it. Among them, channel1 is the smooth comparison region, and Rib2 and Rib3 are the two target forming regions. The analysis results shown in Table 1 are obtained through analysis:

[0053] Table 1 Analysis and comparison table of the smoothness of different regions of the graphite plate 3

[0054] Analysis area First value Second value Description Channel1 0.2％ 21.62％ Smooth comparison area Rib2 28.49％ 42.12％ Target forming area Rib3 35.69％ 45.59％ Target forming area

[0055] Therefore, it can be seen that, compared with the smooth comparison region channel1, the first values obtained from the analysis of the target forming regions Rib2 and Rib3 are significantly greater than the first value of channel1, and the second values corresponding to Rib2 and Rib3 are also greater than the second value of channel1. Thus, it can be seen that the surface finish of Rib2 and Rib3 is not as good as that of the Channel1 region, and the surface finish of the Rib2 region is lower than that of the Rib3 region.

[0056] Embodiment 2

[0057] This embodiment provides a device for detecting the surface finish of a fuel cell graphite plate. The device includes a photographing tooling, a memory, and a processor. The memory is used to store a computer program, and the processor is used to implement steps S2 to S5 in the surface finish detection method in Embodiment 1 when executing the computer program. The surface finish detection method is not described in detail here.

[0058] As Figure 3 shown, the photographing tooling includes a darkroom, a fixed light source 5, and a camera 6. The darkroom is used to cover the graphite plate 3 to be detected. The fixed light source 5 is fixed on the top of the darkroom and irradiates the surface area of the graphite plate 3. The camera 6 is fixed on the top of the darkroom, and the camera 6 lens is located inside the darkroom and aligned with the graphite plate 3;

[0059] The darkroom includes a darkroom cover 1 and a darkroom cover fixing tooling 2. The bottom of the darkroom cover 1 is fixed on the detection plane through the darkroom cover fixing tooling 2. The darkroom cover 1 is in the shape of a trapezoidal table. The center point of the top surface of the darkroom cover 1 and the center point of the graphite plate 3 are located on the same vertical line. The camera 6 is fixed at the center point position of the top surface of the darkroom cover 1. The darkroom cover fixing tooling 2 includes four first right-angle fixing blocks, and the four corners of the bottom of the darkroom cover 1 are respectively fixed on the detection plane through a first right-angle fixing block.

[0060] The graphite plate 3 is fixed on the detection plane through a plate fixing tooling 4. The plate fixing tooling 4 includes a horizontal fixing block and a second right-angle fixing block. The second right-angle fixing block is used to limit the position of the right angle formed by the first long side and the first short side on the graphite plate 3, and the first horizontal fixing block is used to limit the position of the first long side on the graphite plate 3.

[0061] A plurality of fixed light sources 5 are provided and evenly distributed on the top of the darkroom. In this embodiment, 6 fixed light sources 5 are provided and distributed on both sides of the camera 6, with 3 provided on each side.

[0062] Place the graphite plate 3 sample to be photographed on the electrode plate fixing tooling 4, install the darkroom cover 1 to the darkroom cover fixing tooling 2, place the digital camera 6 on the shooting base, turn on the fixed light source 5, and take a photo. Import the obtained pictures into the software Matlab and generate a data file. Use the rbg2gray function to convert the RBG to grayscale mode, and change the three-dimensional data to two-dimensional data. Since the photos are taken using the tooling with accurate positioning, the positioning dimensions can be directly converted to data positions through the image resolution.

[0063] α = βγ

[0064] Among them, α is the position of the data matrix, β is the positioning geometric dimension, and γ is the image precision, generally with the unit of dpi, that is, the number of pixels per inch. If the distance from the measurement point to the target point is β, then the number of its pixels is βγ, which is also the position of the corresponding data in the matrix.

[0065] In Matlab, the area of the target data can be located and selected in the above way and saved as an independent data variable. Screen out the quantity and total proportion of the data within the range of 0 - 30 to obtain the first value, and the ratio of the standard deviation value to the average value within the range of 30 - 255 to obtain the second value. Then, judge the surface smoothness of the graphite plate 3 based on the magnitudes of the first value and the second value.

[0066] The above embodiments are only examples and do not represent the limitation of the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical idea of the present invention.

Claims

1. A method for detecting the surface finish of a graphite plate of a fuel cell, characterized in that, The method comprises the following steps: S1, placing the graphite plate (3) in a dark room, using a fixed light source (5) to illuminate the surface area of the graphite plate (3), and using a camera (6) to capture an image of the surface of the graphite plate (3); S2, intercepting an image of the area to be analyzed from the surface image of the graphite plate (3); S3, converting the image of the area to be analyzed into a grayscale image; S4, obtaining the gray value of each pixel in the gray image; S5, calculating the gray value distribution in the gray image, and determining the smoothness of the area to be analyzed according to the gray value distribution. Step S5 is specifically as follows: determining the first value and the second value of the grayscale image according to the grayscale value, wherein the first value is the ratio of the area of the black shadow area to the total area in the grayscale image, and the second value is the ratio of the standard deviation of the grayscale values of all pixels except the black shadow area in the grayscale image to the mean. The smaller the first value and the second value are, the higher the smoothness of the area to be analyzed is.

2. The surface forming smoothness detection method of a fuel cell graphite plate according to claim 1, characterized in that The black shadow area is determined as pixels with grayscale values in the range of 0 to 30.

3. A device for detecting the surface finish of a graphite plate of a fuel cell, characterized in that, The device comprises a darkroom, a fixed light source (5) and a camera (6); the darkroom is used to cover the graphite plate (3) to be tested; the fixed light source (5) is fixed on the top of the darkroom and illuminates the surface area of the graphite plate (3); the camera (6) is fixed on the top of the darkroom; the camera (6) lens is located in the darkroom and is aimed at the graphite plate (3); The device also includes a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to implement steps S2 to S5 in the method according to any one of claims 1 to 2 when executing the computer program.

4. The surface forming smoothness detection device for a fuel cell graphite plate according to claim 3, wherein, The darkroom comprises a darkroom cover (1) and a darkroom cover fixing tool (2), and the bottom of the darkroom cover (1) is fixed on a detection plane by the darkroom cover fixing tool (2).

5. The surface finish detection device for a fuel cell graphite plate according to claim 4, characterized in that, The darkroom cover (1) is in the shape of a trapezoid, the center point of the top surface of the darkroom cover (1) and the center point of the graphite plate (3) are located on the same vertical line, and the camera (6) is fixed at the center point of the top surface of the darkroom cover (1).

6. The surface finish detection device for a fuel cell graphite plate according to claim 5, wherein, The darkroom cover fixing tool (2) comprises four first right-angle fixing blocks, and the four bottom corners of the darkroom cover (1) are respectively fixed on the detection plane via a first right-angle fixing block.

7. A device for detecting the surface finish of a graphite plate of a fuel cell according to claim 3, characterized in that, The graphite plate (3) is fixed on the detection plane by means of a plate fixing fixture (4).

8. The surface finish detection device for a fuel cell graphite plate according to claim 7, wherein, The electrode plate fixing tool (4) comprises a first horizontal fixing block and a second right-angle fixing block, the second right-angle fixing block is used to limit the position of the right angle formed by the first long side and the first short side on the graphite plate (3), and the first horizontal fixing block is used to limit the position of the first long side on the graphite plate (3).

9. The surface finish detection device for a fuel cell graphite plate according to claim 3, wherein, The fixed light sources (5) are arranged in plurality and evenly distributed on the top of the darkroom.

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