Welding method and welded structure
By using a laser welding method that rotates and scans the laser from the inside out, the problem of intermetallic compound formation during the welding process is solved, thus maintaining welding strength and ensuring welding quality.
Patent Information
- Application Number
- CN202510972576.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-07-23
- Filing Date
- 2025-07-15
- Publication Date
- 2026-01-23
AI Technical Summary
During the welding process, when the same type of metal layer comes into contact with different types of metal layers, intermetallic compounds are easily formed, which leads to a decrease in welding strength. Especially in the latter half of the welding process, the heat-affected zone causes the welding depth to increase, affecting the welding quality of different types of metal layers.
Using laser welding, layers of the same type of metal and layers of different types of metal are sequentially arranged from the top. The same type of metal layers are joined together by laser welding. The laser rotates and scans along the rectangular shape from the inside to the outside to avoid the heat affecting the penetration of different types of metal layers.
It effectively suppresses the thermal effects of different types of metal layers, reduces the formation of intermetallic compounds, maintains welding strength, and ensures welding quality.
Smart Images
Figure CN121373751A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a welding method and a welded structure. BACKGROUND
[0002] In International Publication No. 2015 / 129231, a technique related to a laser welding method in which a laser is irradiated in a spiral shape to a laminated joint workpiece is disclosed. According to the laser welding disclosed in International Publication No. 2015 / 129231, in order to avoid re-irradiation of a laser to a liquid phase portion that has been melted by the laser, the laser is irradiated while moving in a spiral-shaped orbit.
[0003] Here, in a battery pack, there is a case in which, for a bus bar, aluminum is used, and for an electrode terminal provided to a battery cell, a terminal of a double-layer structure in which an aluminum layer is provided on the outside and a copper layer is provided on the inside is used. In this case, the bus bar is fixed to the aluminum layer on the outside of the electrode terminal by laser welding.
[0004] At the welding site, from the outside, an aluminum layer is laminated at the first layer, an aluminum layer is laminated at the second layer, and a copper layer is laminated at the third layer. In this case, the first layer and the second layer are the same kind of metal material, and the third layer is a different kind of metal material from the first layer and the second layer.
[0005] It is considered that, in the case of laser welding of a laminated structure of such metals, when the same kind of metal of the upper two layers is laser welded, the welding portion reaches the different kind of metal of the third layer, and the different kind of metal of the third layer is melted. As a result, an intermetallic compound can be generated, and the welding strength of the upper two layers can be reduced.
[0006] In laser welding for fixing an existing bus bar to an electrode terminal, although welding is performed while rotating from the outside toward the inside, in the latter half of the welding, there is a tendency that the welding is deepened. This is because, in the latter half of the welding, the welding sites are close to each other, the welding (melted pool) is further deepened due to the heat influence of each other, and the welding portion reaches the different kind of metal of the third layer and melts it. SUMMARY
[0007] The present disclosure is achieved to solve the above-described problem, and aims to provide a welding method and a welded structure that can suppress the influence on the welding strength of the upper two layers even in welding in which a different kind of metal is present in the lower layer. [1]
[0009] The welding method of the present disclosure is as follows: a welding method in which a first metal layer, a second metal layer, and a third metal layer are sequentially arranged from the upper side, and the first metal layer and the second metal layer are joined by laser welding, wherein the first metal layer and the second metal layer are the same first metal material, and the third metal layer is a second metal material different from the first metal material, and when the first metal layer and the second metal layer are joined by laser welding by irradiating and scanning laser light from the side on which the first metal layer is present, the laser light is rotated from the inside to the outside while being irradiated to the first metal layer. [2]
[0011] In the welding method described in [1], in the scanning of the laser light, the laser light is rotated from the inside to the outside in a rectangular shape to irradiate the laser light. [3]
[0013] In the welding method described in [1] or [2], the first metal material is aluminum, and the second metal material is copper. [4]
[0015] In the welding method described in any one of [1] to [3], the first metal layer is a bus bar for a battery pack, the second metal layer and the third metal layer are electrode terminals that constitute the battery pack, and the bus bar is welded to the electrode terminals using the laser light. [5]
[0017] The welding structure of the present disclosure is as follows: a welding structure in which a first metal layer, a second metal layer, and a third metal layer are sequentially arranged from the upper side, and the first metal layer and the second metal layer are joined by laser welding, wherein the first metal layer and the second metal layer are the same first metal material, and the third metal layer is a second metal material different from the first metal material, and when the first metal layer and the second metal layer are joined by laser welding by irradiating and scanning laser light from the side on which the first metal layer is present, the laser light is rotated from the inside to the outside while being irradiated to the first metal layer, and in the case where the cross section along the irradiation direction of the laser light after the laser welding is observed, the welding depth of the welded portion of the first metal layer and the second metal layer is set to be shallower on the inside than on the outside. [6]
[0019] In the welding structure described in [5], in the scanning of the laser light, the laser light is rotated from the inside to the outside in a rectangular shape to irradiate the laser light. [7]
[0021] In the welded structure described in [5] and [6], the first metal material is aluminum, and the second metal material is copper. [8]
[0023] In the welded structure described in any one of [5] to [7], the first metal layer is a bus bar for a battery pack, and the second metal layer and the third metal layer are electrode terminals constituting the battery pack.
[0024] The above and other objects, features, aspects and advantages of the present application will become more apparent from the following detailed description of the present application when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0025] Figure 1 is a view showing a basic structure of a battery pack.
[0026] Figure 2 is a view showing Figure 1 a battery cell and an end plate in the battery pack shown in FIG. 1.
[0027] Figure 3 is a view showing Figure 1 a battery cell in the battery pack shown in FIG. 1.
[0028] Figure 4 is a view showing a configuration of a bus bar in the battery pack.
[0029] Figure 5 is Figure 4 a partial cross-sectional view in the arrow V direction in FIG. 1.
[0030] Figure 6 is a schematic view showing a welding method of an electrode terminal and a bus bar.
[0031] Figure 7 is Figure 6 a VII-VII line cross-sectional view in FIG. 1.
[0032] Figure 8 is a cross-sectional view corresponding to the VII-VII line cross-sectional view in FIG. 1 in the related art. Figure 6
[0033] Figure 9 is a schematic view showing a welding method of another electrode terminal and a bus bar.DETAILED DESCRIPTION
[0034] Hereinafter, an embodiment of the present technology will be described. The same reference numerals are sometimes attached to the same or equivalent portions, and the description thereof is not repeated.
[0035] In the following embodiments, in the case where a number, a quantity, or the like is mentioned, the scope of the present technology is not necessarily limited to the number, the quantity, or the like, unless otherwise specifically described. In the following embodiments, each of the constituent elements is not necessarily essential to the present technology, unless otherwise specifically described. The present technology is not limited to a technology that necessarily functions to achieve all the effects mentioned in the present embodiments.
[0036] In the present specification, the description of "comprise" and "include", "have" is in an open form. That is, in the case of including a certain structure, other structures than the structure can be included, or the above other structures can not be included.
[0037] In the present specification, in the case where geometric words and words indicating positional and directional relationships, such as "parallel", "orthogonal", "inclined by 45°", "coaxial", "along", and the like are used, these words allow for manufacturing errors or variations. In the present specification, in the case where words indicating relative positional relationships, such as "upper side", "lower side", and the like are used, these words are used as words indicating relative positional relationships in one state, and the relative positional relationships can be reversed or rotated to an arbitrary angle depending on the setting direction of each mechanism (for example, reversing the entire mechanism upside down, or the like).
[0038] The battery pack 1 shown below can be mounted on a battery electric vehicle (BEV), a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and the like. However, the use of the battery pack 1 is not limited to vehicle-mounted use.
[0039] (Battery pack 1)
[0040] Figure 1 is a view that shows the basic structure of the battery pack 1. Figure 2 is a view that shows the battery cell 100 and the end plate 200 included in the battery pack 1. Figure 3 is a view that shows the battery cell 100 in the battery pack 1.
[0041] As shown in Figure 1 , Figure 2 , the battery pack 1, which is one example of an "electricity storage module", includes the battery cell 100, the end plate 200, and the restraint member 300.
[0042] The battery cell 100 is a lithium ion battery as one example, but the battery cell 100 can be another battery, such as a nickel-hydrogen battery.
[0043] A plurality of battery cells 100 are arranged in a manner of being arranged in the Y-axis direction. The battery cell 100 includes an electrode terminal 110. Between the plurality of battery cells 100, a separator (not shown) can also be sandwiched. The plurality of battery cells 100 sandwiched by the two end plates 200 are pressed by the end plates 200, and thereby are constrained between the two end plates 200.
[0044] The end plate 200 is arranged at both ends of the battery pack 1 in the Y-axis direction (arrangement direction). The end plate 200 is fixed to a base such as a housing that accommodates the battery pack 1.
[0045] The constraint member 300 connects the two end plates 200 to each other. The constraint member 300 is attached to the two end plates 200.
[0046] By engaging the constraint member 300 with the end plates 200 in a state where the stacked body of the plurality of battery cells 100 and the end plates 200 is subjected to a compressive force in the Y-axis direction, and then releasing the compressive force, a tensile force is applied to the constraint member 300 that connects the two end plates 200. As a reaction to this tensile force, the constraint member 300 presses the two end plates 200 in a direction in which the two end plates 200 are brought closer to each other.
[0047] As shown in Figure 3 The battery cell 100 is formed in a flat-surfaced rectangular parallelepiped shape. The electrode terminal 110 includes a positive electrode terminal 111 and a negative electrode terminal 112. The electrode terminal 110 is formed on the upper surface of a square-shaped housing 120. In the housing 120, an electrode body and an electrolyte solution, which are not shown, are accommodated. In order to facilitate the explanation of the configuration of the battery cell 100, in the following explanation, the X direction will be referred to as the width direction, the Y direction will be referred to as the thickness direction, and the Z direction will be referred to as the height direction.
[0048] Figure 4 is a view that shows the arrangement of the bus bar 400 in the battery pack 1. In the example of Figure 4 , the positive electrode terminal 111 and the negative electrode terminal 112 of the battery cells 100 that are adjacent to each other are electrically connected by the bus bar 400, and thereby the plurality of battery cells 100 are electrically connected in series.
[0049] That is, the battery pack 1 includes: a plurality of battery cells 100 each having an electrode terminal 110 and arranged in a predetermined direction; and a bus bar 400 that connects the electrode terminals 110 of the plurality of battery cells 100 to each other.
[0050] (Welding method and welded structure)
[0051] Next, referring to Figures 5-6The welding method and welding structure between the electrode terminal 110 and the busbar 400 will be described. As an example of the electrode terminal 110, the case of welding the negative terminal 112 to the busbar 400 will be described.
[0052] The busbar 400 (first metal layer) is made of aluminum. The negative terminal 112 has a first electrode component 112a connected to a battery element (not shown) disposed inside the battery cell 100, and a second electrode component 112b covering the first electrode component 112a and disposed integrally with the first electrode component 112a. Because the busbar 400 is fixed to the second electrode component 112b by welding, the second electrode component 112b is made of aluminum (second metal layer). In order to ensure good electrical connection with the battery element (not shown) disposed inside the battery cell 100, the first electrode component 112a is made of copper (third metal layer).
[0053] Busbar 400 and negative terminal 112 are sequentially provided with a first metal layer, a second metal layer, and a third metal layer from top to bottom, and the first metal layer and the second metal layer are joined by laser welding. The first metal layer and the second metal layer are made of the same type of first metal material (aluminum), and the third metal layer is made of a different second metal material (copper).
[0054] like Figure 6 As shown, the busbar 400 and the second electrode component 112b are fixed by welding using a laser (L11). In this embodiment, when the busbar 400 and the second electrode component 112b are joined by laser welding by irradiating the laser (L11) from the side where the busbar 400 is located, the laser (L11) is rotated from the inside to the outside while scanning the busbar 400.
[0055] In this embodiment, during laser (L11) scanning, the laser (L11) is rotated from the inside to the outside along a rectangular shape to irradiate the cells. Preferably, the rectangular shape is one in which the width direction (X direction) of the battery cell 100 is the longer side and the thickness direction (Y direction) is the shorter side.
[0056] For example, as one example, the thickness of the busbar 400 is about 0.8 mm, the thickness of the first electrode component 112a is about 0.7 mm, the thickness of the welded part of the second electrode component 112b is about 0.7 mm, the output of the laser (L11) is 1500W, the scanning speed is 400 mm / s, and the long side (L1) of the rectangular shape after laser (L11) irradiation is about 5 mm, and the short side (L2) is about 1 mm.
[0057] In Figure 7When the cross section of the welding portion along the irradiation direction of the laser after laser welding is observed, when the above welding method is used, since the laser (L11) is scanned while rotating from the inside to the outside, the welding depth of the molten pool (W1) on the outside is deeper than that on the inside, but the welding position of the laser (L11) is more on the outside, the longer the welding interval, and thus it is difficult to be affected by heat. Also, since heat can be dissipated to the outside, the heat influence of each other can be minimized.
[0058] As a result, even when the welding depth of the molten pool (W1) on the outside reaches the second electrode member 112b of the third metal layer, the depth (D1) is suppressed to a minimum depth, and thus the generation of intermetallic compounds can be suppressed.
[0059] On the other hand, for the cross-sectional configuration of the welding portion of Figure 8 , it is indicated that the laser (L11) is scanned while rotating from the outside to the inside under the same conditions as above. In this case, the welding position of the laser (L11) is more on the inside, the shorter the welding interval, and thus it is greatly affected by heat. Also, heat is difficult to dissipate to the outside, and heat is accumulated on the inside, and as a result, the inside becomes a higher temperature state.
[0060] As a result, the depth (D2) of the molten pool (W1) is deep on the inside (center), the third metal layer reaches the second electrode member 112b more deeply, and the generation of intermetallic compounds is promoted.
[0061] Further, it is illustrated that in Figure 6 , the laser (L11) is irradiated in the counterclockwise rotation direction, but as Figure 9 indicates, the laser (L11) can also be irradiated in the clockwise rotation direction.
[0062] Further, in the above description, the case where the bus bar 400 is welded to the electrode terminal 110 provided to the battery cell 100 is described, but it is not limited to this application example, and can be applied to a connection site having the same structure.
[0063] The embodiments of the present application have been described, but the embodiments disclosed herein should be considered to be illustrative rather than restrictive in all aspects. The scope of the present application is shown by the claims, and is intended to include all modifications within the meaning and range equivalent to the claims.
Claims
1. A welding method comprising, from top to bottom, a first metal layer, a second metal layer, and a third metal layer, wherein the first metal layer and the second metal layer are joined by laser welding. The welding method is characterized in that... The first metal layer and the second metal layer are made of the same first metal material. The third metal layer is a second metal material that is different from the first metal material. When a laser is irradiated and scanned from the side containing the first metal layer to join the first metal layer and the second metal layer by laser welding, While rotating the laser from the inside to the outside, the laser is irradiated onto the first metal layer.
2. The welding method according to claim 1, characterized in that, In the laser scanning, the laser is rotated along a rectangular shape from the inside to the outside to illuminate the laser.
3. The welding method according to claim 1, characterized in that, The first metallic material is aluminum. The second metallic material is copper.
4. The welding method according to claim 1, characterized in that, The first metal layer is used for the busbar of the battery pack. The second metal layer and the third metal layer are the electrode terminals constituting the battery pack. The busbar is welded to the electrode terminal using the laser.
5. A welding structure comprising a first metal layer, a second metal layer, and a third metal layer sequentially disposed from top to bottom, wherein the first metal layer and the second metal layer are joined by laser welding. The welded structure is characterized in that... The first metal layer and the second metal layer are made of the same first metal material. The third metal layer is a second metal material that is different from the first metal material. When laser welding is used to join the first metal layer and the second metal layer by irradiating and scanning the first metal layer from the side where the first metal layer is located, the laser is irradiated onto the first metal layer while rotating from the inside to the outside. When observing a cross-section along the direction of laser irradiation after laser welding, The welding depth of the welded portion of the first metal layer and the second metal layer is set such that the inner side is shallower than the outer side.
6. The welded structure according to claim 5, characterized in that, In the laser scanning, the laser is rotated along a rectangular shape from the inside to the outside to illuminate the laser.
7. The welded structure according to claim 5, characterized in that, The first metallic material is aluminum. The second metallic material is copper.
8. The welded structure according to any one of claims 5 to 7, characterized in that, The first metal layer is used for the busbar of the battery pack. The second metal layer and the third metal layer are the electrode terminals constituting the battery pack.