WELDING QUALITY TESTING SYSTEM, WELDING QUALITY TESTING PROCEDURE AND BATTERY

Abstract

The present application provides a weld quality inspection system, a weld quality inspection method, and a battery, each capable of inspecting weld quality with high accuracy. The weld quality inspection system of the present application comprises: an imaging device that images a heat-sensitive varnish applied to a conductive element electrically connected by a weld to a plurality of battery cells; and a determining processing element that determines the quality of the weld based on an image obtained from the imaging device.

Description

Technical area

[0001] The present application relates to a welding quality inspection system, a welding quality inspection method and a battery. State of the art

[0002] A battery used in an electric vehicle or the like is generally implemented in the form of a battery pack. In the battery pack, a number of battery cells are welded to a bus bar via a metal wire or metal tab, so that a number of battery cells are connected in series and / or parallel. This forms a high-voltage, high-capacity battery pack. Such a battery pack is described, for example, in Patent Literature (hereinafter "PTL") 1. ReferencesPatent literature

[0003] PTL 1 Japanese Patent Publication No. 2023-45155 Summary of the inventionTechnical problem

[0004] Weld quality also affects the performance of a battery pack. Accordingly, it is necessary to inspect weld quality with high precision. For example, if there is a weld defect or insufficient weld strength, the weld defect or insufficient weld strength must be reliably detected.

[0005] The present application has been made in consideration of the above points and provides a welding quality inspection system, a welding quality inspection method and a battery each capable of inspecting welding quality with high accuracy. Solution to the problem

[0006] One aspect of a welding quality inspection system of the present application includes: an imaging device that images a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells through a weld; and a determination processing element that determines a welding quality based on an image obtained by the imaging device.

[0007] One aspect of a method for inspecting weld quality according to the present application includes: imaging a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by a weld; and determining a quality of the weld based on an image imaged during the imaging.

[0008] One aspect of a battery of the present application comprises: a battery cell; a conductive member electrically connected to the battery cell by a weld; and a heat-sensitive paint applied to the conductive member. Advantageous effects of the invention

[0009] According to the present application, it is possible to provide a welding quality inspection system, a welding quality inspection method, and a battery each capable of inspecting welding quality with high accuracy. Brief description of the drawings Fig. shows what welded sections look like between a battery cell and a busbar in a battery; Fig. shows how heat-sensitive paints are applied to the busbar; Fig. shows how the heat-sensitive paints discolor during normal welding; Fig. shows how the heat-sensitive paints change color when a welding defect occurs; and Fig. is a schematic diagram showing a schematic configuration of a welding quality inspection system for a battery according to an embodiment. Description of the embodiments

[0010] The inventor of the present invention has focused on the fact that a conventional laser welding machine detects welding quality based on the reflected light of the laser, the temperature of the laser, the smoke emission, and / or the like, but the detection accuracy of this cannot be said to be high enough. It is suspected that one of the causes is the implementation of temperature detection based on infrared light. More specifically, it is because the infrared light also contains the reflected light of the laser, and it is difficult to separate the reflected light.

[0011] The inventor of the present invention has found a system for inspecting welding quality without relying on infrared light, thus achieving the present application. A feature of the present application is that a heat-sensitive paint is applied to a conductive member, the heat-sensitive paint is imaged by a camera, and the welding quality is determined based on the image obtained by the camera. This makes it possible to inspect the welding quality with high accuracy.

[0012] An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0013] Fig. shows what the welded parts between the battery cell 11 and the busbar 12 in the battery 10 look like. Fig. are diagrams used to describe the embodiment. Each of the Fig. is a top view showing what welds look like in a battery cell 11. In the actual battery, there are about several thousand battery cells 11, for which Fig. a battery cell 11 is shown, connected in series and parallel via the busbar 12.

[0014] As in Fig. As shown, the battery cell 11 is welded to the bus bar 12 at the positive electrode welding point 12a and the negative electrode welding point 12b. Specifically, laser light is emitted from the front side of the paper surface of the bus bar 12 to heat the bus bar 12, thereby melting the back side of the bus bar 12 and welding the bus bar 12 and the battery cell 11. The battery cell 11 is a lithium-ion battery with a cylindrical shape.

[0015] Next, the configuration of the embodiment is based on the Fig. As described in Fig. As shown, in the battery 100 of the present embodiment, the heat-sensitive paints 111 and 112 are applied to the bus bar 12. The heat-sensitive paints 111 and 112 are applied at least to the edges of the welded parts. Specifically, the heat-sensitive paint 111 is applied to an area around the positive electrode weld 12a, and the heat-sensitive paint 112 is applied to an area around and including the negative electrode weld 12b.

[0016] The heat-sensitive varnishes 111 and 112 change their color depending on the temperature. When at least the positive electrode welding point 12a and the negative electrode welding point 12b are heated, the heat-sensitive varnishes 111 and 112 change their color depending on the heat.

[0017] The Fig. show how the heat-sensitive paints 111 and 112 change their color through weld seams. The shaded areas represent the areas where the heat-sensitive paints 111 and 112 change their color. Fig. shows how the heat-sensitive paints 111 and 112 change color during normal welding. The heat-sensitive paint 111 around the positive electrode welding point 12a changes color uniformly, and the heat-sensitive paint 112 around the negative electrode welding point 12b changes color uniformly.

[0018] Fig. shows how the heat-sensitive paints 111 and 112 change color when abnormal welding is performed (when a welding defect occurs), and the heat-sensitive paint 111 around the positive electrode welding site 12a changes color unevenly, and the heat-sensitive paint 112 around the negative electrode welding site 12b changes color unevenly.

[0019] Fig. 1 is a schematic diagram showing a schematic configuration of the welding quality inspection system 200 for a battery according to the present embodiment. The welding quality inspection system 200 includes: a camera 300 that images the heat-sensitive paints 111 and 112; and a determination processing element 400 that determines the welding quality based on an image obtained from the camera 300.

[0020] The camera 300 specifically captures the heat-sensitive coatings 111 and 112 after welding. In the example of Fig. the camera 300 is coupled to a head of the laser welding machine 500 and images the heat-sensitive lacquers 111 and 112 of the battery 100 after welding by the laser welding machine 500.

[0021] The determination processing element 400 analyzes color changes in the heat-sensitive paints 111 and 112 by image processing and determines the welding quality based on the color change of the heat-sensitive paints 111 and 112. This determination is performed, for example, based on the following determination criteria (i) to (v).

[0022] (i) The determination processing element 400 determines whether a color change area completely covers the circumference of a welded part, and in a case where the color change area does not completely cover the circumference of the welded part, the determination processing element 400 determines the case as a welding defect. In Fig. For example, the color change area on the heat-sensitive paint 112 does not completely cover the negative electrode welding point 12b, which the determination processing element 400 therefore determines as a welding defect.

[0023] (ii) The determination processing element 400 determines whether the width of a color change area surrounding a weld part is greater than a predetermined value, and in a case where there is a color change area having a width smaller than the predetermined value, the determination processing element 400 determines the case as a welding defect. For example, in Fig. the width of a part of the color change area on the heat-sensitive paint 111 around the positive electrode welding point 12a r smaller than the predetermined value, which the determination processing element 400 therefore determines as a welding defect.

[0024] (iii) The determination processing element 400 determines a slight color change as a welding defect.

[0025] (iv) The determination processing element 400 determines color irregularities occurring in a color change area as welding defects.

[0026] (v) The determination processing element 400 determines the area of ​​a color change region smaller than a predetermined value as a welding defect.

[0027] The determination criteria (i) to (v) described above may be used alone, or two or more of them may be used in combination. Furthermore, determination criteria other than those described above (i) to (v) may also be used.

[0028] In practice, the determination processing element 400 includes a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), and the like as main components. The CPU reads a program from the ROM according to a processing content, develops the program in the RAM, and cooperates with the developed program to perform the determination processing described above. Note that the determination processing element 400 may be entirely or partially constituted by a hard-wired circuit such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0029] The determination result of the determination processing element 400 is presented to the user through a display part (not shown), a speaker (not shown), and / or the like.

[0030] As described above, the welding quality inspection system 200 according to the present embodiment includes: an imaging device (camera 300) that images heat-sensitive paints 11 and 112 applied to a conductive member (bus bar 12) electrically connected to a plurality of battery cells 11 by welding; and a determination processing element 400 that determines a welding quality based on an image obtained by the imaging device (camera 300).

[0031] In this way, it is possible to implement a welding quality inspection system 200 capable of inspecting the welding quality with high accuracy.

[0032] The above-described embodiment is merely an illustration of an exemplary embodiment for implementing the present application, and the technical scope of the present invention is not limited thereby. That is, the present application can be implemented in various forms without deviating from the gist or main features thereof.

[0033] In addition to the embodiment described above, heat-sensitive paints 111 and 112 with heat sensitivity that varies depending on the distance to the welding part (positive electrode welding point 12a or negative electrode welding point 12b) may be used. For example, heat-sensitive paint 111 may be designed to have higher heat sensitivity as the distance to the positive electrode welding point 12a increases, and heat-sensitive paint 112 may be designed to have higher heat sensitivity as the distance to the negative electrode welding point 12b increases.

[0034] As the distance from the welding part (positive electrode welding point 12a or negative electrode welding point 12b) increases, the temperature increase caused by welding decreases. Accordingly, in a case where heat-sensitive paints 111 and 112 with uniform heat sensitivity are used, the degree of color change becomes smaller as the distance from the welding part (positive electrode welding point 12a or negative electrode welding point 12b) increases. For this reason, in a case where heat-sensitive paints 111 and 112 with uniform heat sensitivity are used, it is necessary to perform determination processing in advance.In contrast, when the heat-sensitive paint 111 is configured to have higher heat sensitivity as the distance to the positive electrode welding point 12a increases, and the heat-sensitive paint 112 is configured to have higher heat sensitivity as the distance to the negative electrode welding point 12b increases, a decrease in color change due to the distance is suppressed, and thus it is possible to simplify the processing in the determination processing element 400.

[0035] In the above-described embodiment, a case was described where the conductive member electrically connected to the battery cell 11 by welding is the bus bar 12, and heat-sensitive paints 111 and 112 are applied to the bus bar 12, but the present application is not limited to this. For example, the conductive member may include the bus bar 12 and a wire (not shown) connecting the battery cell 11 to the bus bar 12, and the heat-sensitive paint may be applied to the bus bar 12 of the battery cell 11. Thus, it is possible to check the welding quality between the bus bar 12 and the wire (not shown) and the welding quality between the battery cell 11 and the wire (not shown) based on a color change of the heat-sensitive paint. Industrial applicability

[0036] The present application can be applied to a system that checks the welding quality for a battery used, for example, in an electric vehicle or the like. List of reference symbols 10, 100 battery 11 battery cells 12 Busbar 12a Positive electrode welding point 12b Negative electrode welding point 111, 112 Heat-sensitive paints 200 welding quality testing system 300 Camera 400 Determination processing element QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-45155

[0003]

Claims

[1] Welding quality testing system, comprising: an imaging device that images a heat-sensitive paint, wherein the heat-sensitive paint is applied to a conductive element that is electrically connected to a plurality of battery cells by a weld; and a determination processing element that determines a welding quality based on an image obtained from the imaging device. [2] The welding quality inspection system according to claim 1, wherein the heat-sensitive paint is applied to at least an edge portion of a weldment. [3] The welding quality inspection system according to claim 1, wherein the heat-sensitive paint has a heat sensitivity which varies depending on the distance from the welding part. [4] Welding quality inspection system according to claim 1, wherein: the conductive element is a busbar, and the heat-sensitive paint is applied at least to the busbar. [5] Welding quality inspection system according to claim 1, wherein: the conductive element comprises a bus bar and a wire connecting the plurality of battery cells to the bus bar, and the heat-sensitive paint is applied to the busbar and the multiple battery cells. [6] Welding quality testing procedures including: Imaging a heat-sensitive paint, wherein the heat-sensitive paint is applied to a conductive element that is electrically connected to a plurality of battery cells by a weld; and Determination of weld quality based on an image taken during imaging. [7] A battery comprising: a battery cell; a conductive element electrically connected to the battery cell by a weld; and a heat-sensitive varnish that is applied to the conductive element. [8] A battery according to claim 7, wherein the heat-sensitive paint is applied to at least an edge region of a weld part. [9] The battery according to claim 7, wherein the heat-sensitive paint has a heat sensitivity that varies depending on the distance from the welding part. [10] The battery of claim 7, wherein: the conductive element is a busbar, and the heat-sensitive varnish is applied at least to the busbar. [11] The battery of claim 7, wherein: the conductive element comprises a busbar and a wire connecting the battery cell to the busbar, and the heat-sensitive paint is applied to the busbar and the battery cell.

Images