Welding quality inspection system, welding quality inspection method and battery

Abstract

The invention provides a welding quality inspection system, a welding quality inspection method and a battery capable of inspecting welding quality with high precision. This welding quality inspection system is provided with: an image pickup device that picks up an image of a heat-sensitive coating material applied to a conductive member electrically connected to a plurality of battery cells by welding; and a determination processing unit that determines the quality of the welding on the basis of the image obtained by the imaging device.

Description

Technical Field

[0001] The invention relates to a welding quality inspection system, a welding quality inspection method and a battery. Background Art

[0002] Batteries used in electric vehicles and the like are usually embodied in the form of battery packs. The battery pack is a battery pack in which a plurality of battery cells are welded to a bus bar by metal wires or metal tabs, thereby connecting the plurality of battery cells in series and / or in parallel. As a result, a high-voltage and high-capacity battery pack is realized. Such a battery pack is described, for example, in Patent Document 1.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2023-45155 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, welding quality affects the performance of the battery pack, so it is required to inspect welding quality with high accuracy. For example, if there are defects in welding or insufficient welding strength, it is required to reliably detect them.

[0008] The present invention has been made in view of the above-mentioned problems, and provides a welding quality inspection system, a welding quality inspection method, and a battery capable of inspecting welding quality with high accuracy.

[0009] Solutions to the problem

[0010] One embodiment of the welding quality inspection system of the present invention comprises:

[0011] a camera device for photographing a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by welding; and

[0012] The determination processing unit determines the quality of the welding based on the image obtained by the imaging device.

[0013] One embodiment of the welding quality inspection method of the present invention includes:

[0014] a step of photographing a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by welding; and

[0015] A step of determining the quality of the welding based on the image captured in the step of capturing images.

[0016] One embodiment of the battery of the present invention comprises:

[0017] Battery cells;

[0018] A conductive member electrically connected to the battery cell by welding; and

[0019] A heat-sensitive paint is coated on the conductive component.

[0020] Effects of the Invention

[0021] According to the present invention, 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

[0022] Figure 1 The figure shows the welding positions of the battery cells and the bus bars in the battery.

[0023] Figure 2A This is a diagram showing a state of applying heat-sensitive paint to a busbar.

[0024] Figure 2B This is a diagram showing how the heat-sensitive paint changes color when normal welding is performed.

[0025] Figure 2C This is a diagram showing how the heat-sensitive paint changes color when a welding defect occurs.

[0026] Figure 3 It is a schematic diagram showing a schematic configuration of a battery welding quality inspection system according to an embodiment.

[0027] Description of Reference Numerals

[0028] 10, 100: battery;

[0029] 11: Battery cell;

[0030] 12: Busbar;

[0031] 12a: positive electrode welding part;

[0032] 12b: negative electrode welding part;

[0033] 111, 112: Thermosensitive coating;

[0034] 200: welding quality inspection system;

[0035] 300: Camera;

[0036] 400: determination processing unit;

[0037] 500: Laser welding machine. DETAILED DESCRIPTION

[0038] In conventional laser welding machines, welding quality is detected based on reflected light of the laser, temperature, or smoke generation, but the detection accuracy is not high enough, which has attracted the attention of the inventors. It is believed that one of the causes of this problem is that temperature detection is based on infrared light. More specifically, since infrared light also contains reflected light of the laser, it is difficult to separate them.

[0039] The inventor of the present invention has found a structure that can inspect the quality of welding without relying on infrared light, and has obtained the present invention. One feature of the present invention is that a heat-sensitive paint is applied to the conductive member in advance, and the heat-sensitive paint is photographed by a camera, and the quality of welding is determined based on the image obtained by the camera. In this way, the quality of welding can be inspected with high accuracy.

[0040] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0041] Figure 1 The figure shows the welding positions of the battery cells 11 and the bus bars 12 in the battery 10 . Figure 2A-2C It is a figure for explaining embodiment. Figure 1 and Figure 2A-2C Each of the above diagrams shows a top view of a welding process in a battery cell 11. In an actual battery, there are about several thousand Figure 1 and Figure 2A-2C The battery cells 11 shown are connected in series and in parallel via bus bars 12 .

[0042] like Figure 1 As shown, the battery cell 11 is welded to the bus bar 12 at the positive electrode welding portion 12a and the negative electrode welding portion 12b. Specifically, the bus bar 12 is heated by irradiating the laser from the front side of the paper surface of the bus bar 12, so that the back side of the bus bar 12 is melted and the bus bar 12 and the battery cell 11 are welded. The battery cell 11 is a cylindrical lithium ion battery.

[0043] Next, use Figure 2A-2C The structure of the implementation method is described. Figure 2A As shown, in the battery 100 of this embodiment, the busbar 12 is coated with heat-sensitive paints 111 and 112. The heat-sensitive paints 111 and 112 are at least coated around the welding portion. Specifically, the heat-sensitive paint 111 is coated on the positive electrode welding portion 12a and the surrounding area, and the heat-sensitive paint 112 is coated on the negative electrode welding portion 12b and the surrounding area.

[0044] The heat-sensitive paints 111 and 112 change color according to temperature. When heat is applied to at least the positive electrode welding portion 12a or the negative electrode welding portion 12b, the heat-sensitive paints 111 and 112 change color according to the heat.

[0045] Figure 2B and Figure 2C This is a diagram showing how the heat-sensitive paint 111, 112 changes color due to welding. The shaded area is the area that changes color. Figure 2B The figure shows the color change of the thermosensitive paints 111 and 112 when normal welding is performed. The thermosensitive paint 111 around the positive electrode welding part 12a changes color uniformly, and the thermosensitive paint 112 around the negative electrode welding part 12b changes color uniformly.

[0046] Figure 2C The figure shows the discoloration of the thermosensitive paints 111 and 112 when abnormal welding is performed (when welding failure occurs), and the thermosensitive paint 111 around the positive electrode welding part 12a has uneven discoloration, and the thermosensitive paint 112 around the negative electrode welding part 12b has uneven discoloration.

[0047] Figure 3 Schematic diagram showing a schematic configuration of a battery welding quality inspection system 200 according to this embodiment. The welding quality inspection system 200 includes a camera 300 for photographing the heat-sensitive paints 111 and 112 , and a determination processing unit 400 for determining welding quality based on images obtained by the camera 300 .

[0048] Specifically, the camera 300 takes a picture of the heat-sensitive paint 111 and 112 after welding. Figure 3 In the example of FIG. 1 , the camera 300 is connected to the head of the laser welding machine 500 to photograph the heat-sensitive coatings 111 and 112 of the battery 100 after being welded by the laser welding machine 500 .

[0049] The determination processing unit 400 analyzes the discoloration of the heat-sensitive paints 111 and 112 by image processing, and determines the quality of welding based on the discoloration. This determination is performed based on, for example, the following determination criteria (i) to (v).

[0050] (i) It is determined whether the discolored area completely covers the area around the weld. If it does not completely cover the area, it is determined to be a poor weld. Figure 2C In the example, the discolored region of the thermosensitive paint 112 does not completely cover the negative electrode welding portion 12 b, so the determination processing unit 400 determines that the welding is defective.

[0051] (ii) It is determined whether the width of the discolored area surrounding the weld is larger than a predetermined value. If there is a discolored area with a width smaller than the predetermined value, it is determined that the weld is defective. Figure 2C In the example, the width of a portion of the discolored region of the thermosensitive paint 111 around the positive electrode welding portion 12a is smaller than a predetermined value, and therefore the determination processing unit 400 determines that the welding is defective.

[0052] (iii) When the color becomes lighter, the determination processing unit 400 determines that the welding is defective.

[0053] (iv) When color unevenness occurs in the discolored region, the determination processing unit 400 determines that the welding is defective.

[0054] (v) When the area of ​​the discolored region is smaller than a predetermined value, the determination processing unit 400 determines that the welding is defective.

[0055] The above-mentioned criteria (i) to (v) may be used alone or in combination of two or more. In addition, criteria other than the above-mentioned criteria (i) to (v) may be used.

[0056] In fact, the determination processing unit 400 has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. as main components. The CPU reads a program corresponding to the processing content from the ROM and expands it in the RAM, and performs the above-mentioned determination processing in cooperation with the expanded program. It should be noted that the determination processing unit 400 may also be formed entirely or partially by a hard-wired circuit such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field-Programmable Gate Array).

[0057] The determination result of the determination processing unit 400 is presented to the user via a display unit or a speaker (not shown).

[0058] As described above, according to the present embodiment, the welding quality inspection system 200 comprises: an imaging device (camera 300) for photographing the heat-sensitive paint 111, 112 applied on the conductive component (bus bar 12) electrically connected to the plurality of battery cells 11 by welding; and a determination processing unit 400 for determining the quality of the welding based on the image obtained by the imaging device (camera 300).

[0059] Thus, it is possible to realize welding quality inspection system 400 that can inspect welding quality with high accuracy.

[0060] The above-mentioned embodiment is only an example of implementing the present invention, and the technical scope of the present invention should not be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from the gist or main features thereof.

[0061] In addition to the above-mentioned embodiments, thermosensitive paints having different thermal sensitivities depending on the distance from the welding portion (positive electrode welding portion 12a, negative electrode welding portion 12b) may be used as the thermosensitive paints 111 and 112. For example, the thermosensitive paint 111 may be a thermosensitive paint having a higher thermal sensitivity as the distance from the positive electrode welding portion 12a increases, and the thermosensitive paint 112 may be a thermosensitive paint having a higher thermal sensitivity as the distance from the negative electrode welding portion 12b increases.

[0062] Here, the farther the distance from the welding part (positive electrode welding part 12a, negative electrode welding part 12b), the smaller the temperature rise caused by welding. Therefore, when using thermosensitive paints 111 and 112 with no difference in thermal sensitivity, the farther the distance from the welding part (positive electrode welding part 12a, negative electrode welding part 12b), the smaller the degree of discoloration. Therefore, when using thermosensitive paints 111 and 112 with no difference in thermal sensitivity, it is necessary to perform determination processing based on this situation. In contrast, if the thermosensitive paint 111 is set to a thermosensitive paint with higher thermal sensitivity as the distance from the positive electrode welding part 12a is longer, and the thermosensitive paint 112 is set to a thermosensitive paint with higher thermal sensitivity as the distance from the negative electrode welding part 12b is longer, the reduction of discoloration caused by distance can be suppressed, so the processing of the determination processing unit 400 can be simplified.

[0063] Although in the above-mentioned embodiment, the conductive component electrically connected to the battery cell 11 by welding is the bus bar 12, and the case where the heat-sensitive paint 111, 112 is applied to the bus bar 12 is described, but it is not limited to this. For example, the conductive component may include the bus bar 12 and the wire (not shown) connecting the battery cell 11 and the bus bar 12, and the heat-sensitive paint is applied to the bus bar 12 and the battery cell 11. In this way, the quality of the welding between the bus bar 12 and the wire (not shown) and the quality of the welding between the battery cell 11 and the wire (not shown) can be inspected based on the discoloration of the heat-sensitive paint.

[0064] Industrial Applicability

[0065] The present invention can be applied to a system for inspecting welding quality of batteries used in electric vehicles and the like, for example.

Claims

1. A welding quality inspection system, characterized in that: have: a camera device for photographing a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by welding; and The determination processing unit determines the quality of the welding based on the image obtained by the imaging device.

2. The welding quality inspection system according to claim 1, wherein: The heat-sensitive paint is applied at least around the welding part.

3. The welding quality inspection system according to claim 1, wherein: The thermal sensitivity of the thermal paint varies depending on the distance between the thermal paint and the welding portion.

4. The welding quality inspection system according to claim 1, wherein: The conductive component is a busbar, The heat-sensitive paint is at least applied to the busbar.

5. The welding quality inspection system according to claim 1, wherein: The conductive component includes a bus bar and a wire connecting the battery cell to the bus bar. The heat-sensitive paint is applied to the bus bar and the battery cell.

6. A welding quality inspection method, characterized in that: include: The step of photographing a heat-sensitive paint applied to a conductive member electrically connected to a plurality of battery cells by welding; as well as A step of determining the quality of the welding based on the image captured in the step of capturing images.

7. A battery, characterized in that: have: Battery cells; A conductive member electrically connected to the battery cell by welding; and A heat-sensitive paint is applied on the conductive component.

8. The battery according to claim 7, wherein The heat-sensitive paint is applied at least around the welding part.

9. The battery according to claim 7, wherein The thermal sensitivity of the thermal paint varies depending on the distance between the thermal paint and the welding portion.

10. The battery according to claim 7, wherein The conductive component is a busbar, The heat-sensitive paint is at least applied to the busbar.

11. The battery according to claim 7, wherein The conductive component includes a bus bar and a wire connecting the battery cell to the bus bar. The heat-sensitive paint is applied to the bus bar and the battery cell.

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