Welding quality inspection system and battery

Abstract

To provide a battery welding quality inspection system capable of inspecting welding quality with high accuracy. [Solution] The welding quality inspection system includes an imaging device that images a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by welding, and an evaluation processing unit that evaluates the quality of the welding based on the image obtained by imaging.

Description

[Technical field]

[0001] The present disclosure relates to a weld quality inspection system, a weld quality inspection method, and a battery. [Background technology]

[0002] Batteries used in electric vehicles and the like are generally embodied in the form of a battery pack. In the battery pack, a large number of battery cells are connected in series and / or parallel by welding the battery cells to a bus bar via metal wires or metal tabs. As a result, a high-voltage and high-capacity battery pack is realized. Such a battery pack is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-45155 Summary of the Invention [Problem to be solved by the invention]

[0004] However, welding quality affects the performance of a battery pack, so there is a need to inspect the welding quality with high accuracy. For example, there is a need to reliably detect any defects or insufficient welding strength.

[0005] The present disclosure has been made in consideration of the above points, and provides a welding quality inspection system, a welding quality inspection method, and a battery that can inspect welding quality with high accuracy. [Means for solving the problem]

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

[0007] One aspect of the weld quality inspection method of the present disclosure includes: Taking an image of a thermally sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by welding; determining a quality of the weld based on the image captured in the step; Includes.

[0008] One aspect of the battery of the present disclosure is A battery cell; A conductive member electrically connected to the battery cell by welding; A heat-sensitive paint applied to the conductive member; Equipped with. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a welding quality inspection system, a welding quality inspection method, and a battery capable of inspecting welding quality with high accuracy. [Brief description of the drawings]

[0010] [Figure 1] A diagram showing the welded points between the battery cells and bus bars in a battery. [Figure 2A] Diagram showing application of heat-sensitive paint to busbars [Figure 2B] A diagram showing the discoloration of the heat-sensitive paint when welding is performed normally. [Figure 2C] A diagram showing the discoloration of heat-sensitive paint when a welding defect occurs [Diagram 3] FIG. 1 is a schematic diagram showing a schematic configuration of a battery welding quality inspection system according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The inventors of the present invention noticed that in conventional laser welding machines, the welding quality is detected based on the reflected light of the laser, temperature, generation of fumes, etc., but the detection accuracy is not sufficiently high. One reason for this is thought to be that the temperature is detected based on infrared light. More specifically, infrared light includes the reflected light of the laser, which is difficult to separate.

[0012] The inventor of the present invention discovered a configuration for inspecting the quality of welding without relying on infrared light, and came up with the present disclosure. One feature of the present disclosure is that a heat-sensitive paint is applied to a conductive member, the heat-sensitive paint is photographed by a camera, and the quality of welding is judged based on the image obtained by the camera. This allows the welding quality to be inspected with high accuracy.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] Fig. 1 is a diagram showing the state of welded points between a battery cell 11 and a bus bar 12 in a battery 10. Figs. 2A to 2C are diagrams provided for explaining an embodiment. Fig. 1 and Figs. 2A to 2C are each a top view showing the state of welding in one battery cell 11. In an actual battery, several thousand battery cells 11 shown in Figs. 1 and 2A to 2C are connected in series and in parallel via bus bars 12.

[0015] 1, the battery cell 11 is welded to the bus bar 12 at a positive electrode welded portion 12a and a negative electrode welded portion 12b. Specifically, the bus bar 12 is heated by irradiating it with a laser beam from the front side of the page, whereby the back side of the bus bar 12 melts and the bus bar 12 and the battery cell 11 are welded together. The battery cell 11 is a cylindrical lithium ion battery.

[0016] Next, the configuration of the embodiment will be described with reference to Fig. 2A to Fig. 2C. As shown in Fig. 2A, in the battery 100 of the embodiment, 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 periphery of the welded parts. Specifically, the heat-sensitive paint 111 is applied to the area including the positive electrode welded part 12a and the surrounding area, and the heat-sensitive paint 112 is applied to the area including the negative electrode welded part 12b and the surrounding area.

[0017] The heat-sensitive paints 111 and 112 change color in response to temperature. When heat is applied to at least the positive electrode welded portion 12a and the negative electrode welded portion 12b, the heat-sensitive paints 111 and 112 change color in response to the heat.

[0018] 2B and 2C are diagrams showing discoloration of the heat-sensitive paints 111, 112 due to welding. The shaded areas are discolored areas. Fig. 2B is a diagram showing discoloration of the heat-sensitive paints 111, 112 when normal welding has been performed, where the heat-sensitive paint 111 around the positive electrode welded portion 12a has discolored evenly, and the heat-sensitive paint 112 around the negative electrode welded portion 12b has discolored evenly.

[0019] FIG. 2C shows the discoloration of heat-sensitive paints 111, 112 when abnormal welding is performed (when poor welding occurs), with heat-sensitive paint 111 around positive electrode weld 12a showing uneven discoloration, and heat-sensitive paint 112 around negative electrode weld 12b showing uneven discoloration.

[0020] 3 is a schematic diagram showing a schematic configuration of a battery welding quality inspection system 200 according to this embodiment. The welding quality inspection system 200 has a camera 300 that captures images of the heat-sensitive paints 111 and 112, and a judgment processing unit 400 that judges the quality of the welding based on the image obtained by the camera 300.

[0021] Specifically, the camera 300 captures an image of the heat-sensitive paints 111, 112 after welding. In the example of Fig. 3, the camera 300 is connected to the head of the laser welding machine 500, and captures an image of the heat-sensitive paints 111, 112 of the battery 100 after welding by the laser welding machine 500.

[0022] The judgment processing unit 400 analyzes the discoloration of the heat-sensitive paints 111, 112 by image processing, and judges the quality of the welding based on the state of the discoloration. This judgment is made based on, for example, the following judgment criteria (i) to (v).

[0023] (i) Determine whether the discolored area completely covers the periphery of the welded part, and if not, determine that the weld is defective. For example, in FIG. 2C, the discolored area of ​​the heat-sensitive paint 112 does not completely cover the negative electrode welded part 12b, so the determination processing unit 400 determines that the weld is defective.

[0024] (ii) Determine whether the width of the discolored area surrounding the weld is greater than a predetermined value, and if there is a discolored portion with a width smaller than the predetermined value, determine that the weld is defective. For example, in Fig. 2C, the width of a part of the discolored area of ​​the heat-sensitive paint 111 surrounding the positive electrode weld 12 is smaller than the predetermined value, so the determination processing unit 400 determines that the weld is defective.

[0025] (iii) If the discoloration is light, the judgment processing unit 400 judges the welding to be defective.

[0026] (iv) If color unevenness occurs in the discolored area, the judgment processing unit 400 judges the welding to be defective.

[0027] (v) If the area of ​​the discolored region is smaller than a predetermined value, the judgment processing unit 400 judges the welding to be defective.

[0028] The above criteria (i) to (v) may be used alone or in combination of two or more. Criteria other than the above criteria (i) to (v) may also be used.

[0029] In practice, the determination processing unit 400 includes, as its main components, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU reads out a program corresponding to the processing contents from the ROM, loads it in the RAM, and performs the above-mentioned determination processing in cooperation with the loaded program. Note that all or a part of the determination processing unit 400 may be formed by a hardwired circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0030] The result of the determination by the determination processing unit 400 is presented to the user by a display unit, a speaker, etc. (not shown).

[0031] As described above, according to this embodiment, the welding quality inspection system 200 includes an imaging device (camera 300) that images the heat-sensitive paints 111, 112 applied to a conductive member (bus bar 12) electrically connected to a plurality of battery cells 11 by welding, and a judgment processing unit 400 that judges the quality of the welding based on the image obtained by the imaging device (camera 300).

[0032] This makes it possible to realize a welding quality inspection system 400 that can inspect welding quality with high accuracy.

[0033] The above-described embodiments are merely examples of the implementation of the present disclosure, and the technical scope of the present disclosure should not be interpreted as being limited by these embodiments. In other words, the present disclosure can be implemented in various forms without departing from the gist or main characteristics of the disclosure.

[0034] In addition to the above-described embodiment, heat-sensitive paints having different heat sensitivity depending on the distance from the welded parts (positive electrode welded part 12a, negative electrode welded part 12b) may be used as heat-sensitive paints 111 and 112. For example, heat-sensitive paint 111 may have a higher heat sensitivity the farther it is from positive electrode welded part 12a, and heat-sensitive paint 112 may have a higher heat sensitivity the farther it is from negative electrode welded part 12b.

[0035] Here, the greater the distance from the welded portion (positive electrode welded portion 12a, negative electrode welded portion 12b), the smaller the temperature rise due to welding. Therefore, when heat-sensitive paints 111 and 112 with uniform heat sensitivity are used, the greater the distance from the welded portion (positive electrode welded portion 12a, negative electrode welded portion 12b), the smaller the degree of discoloration. Therefore, when heat-sensitive paints 111 and 112 with uniform heat sensitivity are used, it is necessary to perform a judgment process that takes this into account. In contrast, if heat-sensitive paint 111 is made to have a higher heat sensitivity the greater the distance from positive electrode welded portion 12a, and heat-sensitive paint 112 is made to have a higher heat sensitivity the greater the distance from negative electrode welded portion 12b, the decrease in discoloration due to distance is suppressed, and the processing in judgment processing portion 400 can be simplified.

[0036] In the above embodiment, the conductive member electrically connected to the battery cell 11 by welding is the bus bar 12, and the heat-sensitive paints 111, 112 are applied to the bus bar 12, but this is not limiting. For example, the conductive member may include the bus bar 12 and a wire (not shown) that connects the battery cell 11 and the bus bar 12, and the heat-sensitive paint may be applied to the bus bar 12 and the battery cell 11. This makes it possible to inspect the quality of the welding between the bus bar 12 and the wire (not shown) and the welding between the battery cell 11 and the wire (not shown) based on the discoloration of the heat-sensitive paint. [Industrial Applicability]

[0037] The present disclosure may be applied to a system for inspecting the welding quality of batteries used in, for example, electric vehicles. [Explanation of symbols]

[0038] 10, 100 Battery 11 Battery Cells 12 Busbar 12a Positive electrode weld 12b Negative electrode weld 111, 112 Heat-sensitive paint 200 Welding quality inspection system 300 Camera 400 Judgment processing unit

Claims

1. an imaging device that images a heat-sensitive paint applied to a conductive member that is electrically connected to a plurality of battery cells by welding; a determination processing unit that determines the quality of the welding based on the image obtained by the imaging device; Equipped with The heat-sensitive paint has a different heat sensitivity depending on the distance from the welded part. Welding quality inspection system.

2. The heat-sensitive paint is applied at least around the welded portion. The weld quality inspection system of claim 1 .

3. the conductive member is a bus bar, The heat-sensitive paint is applied to at least the bus bar. The weld quality inspection system of claim 1 .

4. The conductive member includes a bus bar and a wire connecting the battery cell and the bus bar, The heat-sensitive paint is applied to the bus bar and the battery cell. The weld quality inspection system of claim 1 .

5. A battery cell; A conductive member electrically connected to the battery cell by welding; A heat-sensitive paint applied to the conductive member; Equipped with The heat-sensitive paint has a different heat sensitivity depending on the distance from the welded part. battery.

6. The heat-sensitive paint is applied at least around the welded portion.

6. The battery of claim 5.

7. the conductive member is a bus bar, The heat-sensitive paint is applied to at least the bus bar.

6. The battery of claim 5.

8. The conductive member includes a bus bar and a wire connecting the battery cell and the bus bar, The heat-sensitive paint is applied to the bus bar and the battery cell.

6. The battery of claim 5.

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