Method for manufacturing battery case

Abstract

To provide a method for manufacturing a battery case, capable of reducing solidification cracking at a joint, in a battery case including a case body that is made of an aluminum material and joined by laser welding.SOLUTION: There is provided a method for manufacturing a battery case 1 that includes: a cylindrical case body 11 made of an aluminum material, having an opening 11K, into which an electrode body 2 is inserted, at least at one axial end 111 and having a joint 11S which intersects with the opening and butt-joins ends 112 in a width direction together; and a sealing body 12 sealing the opening. The method includes: a projection formation step S1 of forming a projection 11T projecting to the outer surface side of the case body along the end in a width direction; and a welding step S2 of, after butt-joining the projections together, forming, at the joint, a welded metal part 11Y from a molten metal 11YK that is melted by irradiating the projection with laser light LS from the outer surface side of the case body, the welded metal part being raised in a curved shape to the outer surface side of the case body.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a battery case. [Background technology]

[0002] For example, Patent Document 1 discloses a rectangular battery can (battery case) formed by laser welding at least two members made of steel plates, characterized in that a first linear joint is formed at the bottom and reaches the lower ends of the opposing side wall portions (case main body), and that a second linear joint and a third linear joint are formed on the opposing side wall portions, respectively, which are connected to the first joint and reach the openings at the upper ends of the respective side wall portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-59954 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the prismatic battery cans have the advantage of being easily adaptable to larger batteries, they have issues with corrosion resistance to electrolyte because they are made of steel plate. Furthermore, because they are made of steel plate, they have issues with not being able to meet the need for weight reduction. In this regard, forming the prismatic battery cans from aluminum offers a potential solution to the issues of corrosion resistance and weight reduction.

[0005] However, since aluminum has a linear expansion coefficient that is about twice as large as that of steel plates, there was a problem in that cracks (solidification cracking) were likely to occur at each joint due to thermal stress when the molten metal from laser welding solidified.

[0006] The disclosed technology has been made in consideration of such problems, and aims to provide a manufacturing method for a battery case in which the case body made of aluminum material is joined by laser welding, and which can reduce solidification cracking at the joint. [Means for solving the problem]

[0007] (1) One aspect of the disclosed technology for solving the above-described problems is a method for manufacturing a battery case including: a cylindrical case body made of aluminum, the case body having an opening at at least one axial end for inserting an electrode body, and a joint that intersects with the opening and butt-joins the widthwise ends; and a sealing body that seals the opening, the method comprising: a convexity forming step of forming convexities that protrude toward the outer surface of the case body along the widthwise ends; and a welding step of butting the convexities together and then irradiating the convexities from the outer surface of the case body with laser light to melt the molten metal, thereby forming a weld metal part that curves up toward the outer surface of the case body at the joint.

[0008] (2) In the manufacturing method of the battery case described in (1), it is preferable that the convex portion is formed at a widthwise end portion displaced toward the inner surface side relative to the general portion while maintaining the plate thickness of the case body.

[0009] (3) In the manufacturing method of the battery case described in (1), it is preferable that the convex portion protrudes from a groove surface to the outer surface at a widthwise end portion where a groove surface that is recessed toward the inner surface of the outer surface of the case body is formed.

[0010] (4) In the method for manufacturing a battery case described in (1), it is preferable that the convex portion protrudes toward both the outer surface side and the inner surface side at the widthwise end of the case body. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view of a sealed storage battery including a battery case according to a first example embodiment, which is manufactured by a method for manufacturing a battery case according to one aspect of the present embodiment. [Figure 2] 2 is a flowchart showing a method for manufacturing the battery case shown in FIG. 1. [Figure 3] 2 is a perspective view of a rectangular cylindrical intermediate product used in the case body of the battery case shown in FIG. 1. FIG. [Figure 4] 2 is a perspective view showing the state in the middle of laser welding the joints of two divided rectangular tubular intermediate products to form the case body of the battery case shown in FIG. 1. FIG. [Figure 5A] FIG. 5 is an enlarged cross-sectional view of part A shown in FIG. [Figure 5B] FIG. 5 is an enlarged cross-sectional view of part B shown in FIG. [Figure 6A] FIG. 5 is an enlarged cross-sectional view of a first modified example of a portion A shown in FIG. [Figure 6B] FIG. 5 is an enlarged cross-sectional view of a first modified example of a portion B shown in FIG. [Figure 7A] FIG. 5 is an enlarged cross-sectional view of a modified example 2 of the part A shown in FIG. [Figure 7B] FIG. 5 is an enlarged cross-sectional view of a modified example 2 of the portion B shown in FIG. [Figure 8A] FIG. 5 is an enlarged cross-sectional view of a third modified example of the part A shown in FIG. [Figure 8B] FIG. 5 is an enlarged cross-sectional view of a third modification of part B shown in FIG. [Figure 9A] FIG. 5 is a perspective view of a fourth modified example of the C portion shown in FIG. 4 before welding. [Figure 9B] FIG. 5 is a perspective view of a fourth modification of the C portion shown in FIG. 4 after welding. [Figure 10] FIG. 10 is a schematic perspective view of a sealed storage battery including a battery case according to a second example embodiment, which is manufactured by a method for manufacturing a battery case according to one aspect of the present embodiment. [Figure 11A] 11 is a cross-sectional view of a first intermediate product used in the case body of the battery case shown in FIG. [Figure 11B] 11 is a cross-sectional view of a second intermediate product used in the case body of the battery case shown in FIG. [Figure 11C] 11 is a cross-sectional view of a third intermediate product used in the case body of the battery case shown in FIG. [Figure 11D] 11 is a cross-sectional view of the case body of the battery case shown in FIG. [Figure 12A] 11 is a cross-sectional view of an intermediate product used in Modification 1 of the case body of the battery case shown in FIG. [Figure 12B] 11 is a cross-sectional view of a first modified example of the case body of the battery case shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Manufacturing method of the present battery case> Next, a method for manufacturing a battery case according to one aspect of the embodiment of the disclosed technology will be described in detail with reference to the drawings. Fig. 1 shows a schematic cross-sectional view of a sealed storage battery including a battery case according to a first example, which was manufactured by the method for manufacturing a battery case according to one aspect of the present embodiment. The X direction indicates the longitudinal direction of the case body, the Y direction indicates the width direction of the case body, and the Z direction indicates the axial direction of the case body.

[0013] (Battery case of the first embodiment) As shown in FIG. 1 , the battery case 1 of the first embodiment is made of aluminum and includes a cylindrical case body 11 having an opening 11K at at least one axial end 111 for inserting an electrode assembly 2, a joint 11S that intersects with the opening 11K and butt-joins widthwise ends 112 of the case body 11, and a sealing body 12 that seals the opening 11K. A welded metal portion 11Y that curves and protrudes toward the outer surface 11G is formed at the joint 11S between the widthwise ends 112 of the case body 11. The aluminum material is not limited to aluminum material and includes aluminum alloy material. Here, the case body 11 is formed in a rectangular tube shape, but it may also be formed in a cylindrical shape.

[0014] The electrode body 2 inserted through the opening 11K is formed by stacking a positive electrode body and a negative electrode body with a separator sandwiched between them. FIG. 1 illustrates a wound-type electrode body 2 in which long, stacked positive electrode bodies, negative electrode bodies, and a separator are wound flat. However, this is not a limitation. A laminated-type electrode body 2 in which rectangular positive electrode bodies and negative electrode bodies are stacked with a separator sandwiched between them may also be used. The current collector foils 21 on the positive and negative sides of the electrode body 2 are connected to current collector terminals 4 on the positive and negative sides, respectively. Each current collector terminal 4 includes an external terminal 41 protruding from the outer surface of the battery case 1 and an internal terminal 42 connected to the current collector foil 21 on the inner surface of the battery case 1. The external terminals 41 are fixed to the sealing body 12 via an insulating member 3.

[0015] The electrode assembly 2, connected to the current collecting terminal 4 and fixed to the sealing body 12, is housed in the case body 11 through the opening 11K. After the electrode assembly 2 is housed in the opening 11K of the case body 11, it is sealed with the sealing body 12. A joint 12S between the opening 11K of the case body 11 and the sealing body 12 is joined by, for example, laser welding. The case body 11 is formed as a bottomed rectangular cylinder having a pair of long side walls 11a, 11a extending in the longitudinal direction (X direction), a pair of short side walls 11b, 11b extending in the width direction (Y direction), and a bottom wall 11c forming the cylinder bottom. A rectangular opening 11K is formed in one axial end 111 of the case body 11. The electrode body 2 is placed inside the case body 11 through the opening 11K, and after the opening 11K and the sealing body 12 are joined, the electrolyte 5 is injected through an injection port (not shown), and the sealed storage battery 10 is completed after initial charging, aging, etc.

[0016] (Manufacturing method of the battery case of the first embodiment) Fig. 2 shows a flowchart illustrating a method for manufacturing the battery case shown in Fig. 1. Fig. 3 shows a perspective view of a rectangular tubular intermediate product used for the case body of the battery case shown in Fig. 1. Fig. 4 shows a perspective view of two divided rectangular tubular intermediate products in the middle of being laser-welded at their joints to form the case body of the battery case shown in Fig. 1.

[0017] 1 to 4, this method for manufacturing a battery case 1 includes a cylindrical case body 11 made of aluminum, the case body 11 having an opening 11K at at least one axial end 111 through which an electrode assembly 2 is inserted, and a joint 11S that intersects with the opening 11K and butt-joins widthwise ends 112, and a sealing body 12 that seals the opening 11K. The method includes a convex portion forming step S1 and a welding step S2. The convex portion forming step S1 is a step of forming a convex portion 11T that protrudes toward the outer surface 11G of the case body 11 along the widthwise end 112 of the case body 11. The welding step S2 is a step of butting the convex portions 11T together and then irradiating the convex portions 11T with laser light LS from the outer surface 11G side of the case body 11 to melt the convex portions 11T, thereby forming a weld metal portion 11Y that curves up toward the outer surface 11G of the case body 11 at the joint 11S.

[0018] In the convex portion forming step S1, for example, as shown in FIG. 3, a rectangular tubular intermediate product 11X having a hat-shaped cross section is drawn from a flat aluminum plate by press forming. The rectangular tubular intermediate product 11X has a flange corresponding to the convex portion 11T on its outer periphery (widthwise end 112), a short side wall 11b and a bottom wall 11c extending from the flange, and a long side wall 11a forming a top plate. The rectangular tubular intermediate product 11X is then divided into two pieces along a parting line that divides the rectangular tubular intermediate product 11X into two equal parts along the longitudinal direction (X direction). The parting line is formed at the position of the opening 11K of the case body 11. The convex portion 11T is bent at a right angle relative to the widthwise end 112 of the short side wall 11b and the bottom wall 11c, and protrudes toward the outer surface 11G. The convex portion forming step S1 does not have to be limited to a press forming method in which the rectangular cylindrical intermediate product 11X is drawn from a flat aluminum plate by a press, but may be formed by a die casting method, a cold or warm forging method, etc. Furthermore, cutting, electric discharge machining, etc. may be combined with these forming methods.

[0019] In the welding step S2, for example, as shown in FIG. 4 , the protrusions 11T of the two divided rectangular tubular intermediate products 11X are butted against each other and abutted against each other, and a laser beam LS is irradiated onto the protrusions 11T from the outer surface 11G side of the case body 11. Here, the laser beam LS is moved relatively along the protrusions 11T, but the protrusions 11T may also be moved relative to the laser beam LS. The laser beam LS may be a single beam with a narrow beam width, but a multi-beam or annular beam with a wide beam width is preferable. When the laser beam LS is a single beam, it is preferable to move the beam tip relatively along the protrusions 11T while slightly vibrating it in the width direction (Y direction) of the protrusions 11T. Then, the molten metal 11YK of the protrusions 11T irradiated with the laser beam LS melts the protrusions 11T, forming a weld metal portion 11Y at the joint 11S, which protrudes in a curved shape toward the outer surface 11G side of the case body 11. This forms a cylindrical case body 11 having a joint portion 11S that intersects with the opening portion 11K and butt-joins the widthwise ends 112 together.

[0020] FIG. 5A shows an enlarged cross-sectional view of portion A shown in FIG. 4 . FIG. 5B shows an enlarged cross-sectional view of portion B shown in FIG. 4 . As shown in FIG. 5A , the protrusion 11T protrudes from the outer surface 11G of the case body 11 toward the outer surface 11G by a predetermined protrusion amount d1. The thickness t1 of the protrusion 11T is formed to be substantially the same as the thickness t1 of the case body 11, although some thickness variation occurs due to drawing. The outer peripheral edges 11TG of the widthwise ends 112 of the protrusion 11T, which are continuous with the inner surface 11N, abut against each other. Furthermore, as shown in FIG. 5B , the protrusion amount d1 of the protrusion 11T correlates with the protrusion amount d2 of the weld metal portion 11Y, which protrudes in a curved manner toward the outer surface 11G of the case body 11. That is, increasing the protrusion amount d1 of the protrusion 11T also increases the protrusion amount d2 of the weld metal portion 11Y.

[0021] In this way, in the protrusion forming step S1, protrusions 11T are formed along the widthwise end portions 112 so as to protrude toward the outer surface 11G of the case body 11. This increases the volume of molten metal 11YK that can be melted in the welding step S2 by the volume of the protrusions 11T. Furthermore, in the welding step S2, after the protrusions 11T are butted against each other, laser light LS is irradiated onto the protrusions 11T from the outer surface 11G side of the case body 11 to melt the molten metal 11YK, forming a weld metal portion 11Y that protrudes in a curved shape toward the outer surface 11G of the case body 11 at the joint 11S. Therefore, thermal contraction during solidification of the curved protrusion of the weld metal portion 11Y is dispersed by the curved protrusion of the weld surface 11YM. This suppresses thermal stress during solidification in the weld metal portion 11Y, thereby reducing solidification cracking at the joint 11S in the case body 11 made of aluminum, which has a high thermal expansion coefficient. Therefore, it is possible to provide a method for manufacturing a battery case that can reduce solidification cracks at the joint 11S in a battery case 1 in which the case body 11 made of aluminum material is joined by laser welding.

[0022] 5B, the weld metal portion 11Y preferably has a weld surface 11YM formed in an arc shape with a constant radius of curvature 115. This is because the thermal contraction of the weld metal portion 11Y during solidification is more evenly distributed by the arc-shaped protruding weld surface 11YM, reducing the thermal stress on the weld metal portion 11Y during solidification. Furthermore, the weld metal portion 11Y preferably has not only a front bead portion 11Y1 protruding toward the outer surface 11G, but also a back bead portion 11Y2 protruding toward the inner surface 11N by a smaller amount than the front bead portion 11Y1. The presence of the back bead portion 11Y2 prevents insufficient penetration due to unmelted metal on the inner surface 11N side, thereby increasing the joining strength of the joint 11S.

[0023] Moreover, Fig. 6A shows an enlarged cross-sectional view of Modification 1 of portion A shown in Fig. 4. Fig. 6B shows an enlarged cross-sectional view of Modification 1 of portion B shown in Fig. 4. As shown in Figs. 6A and 6B, convex portion 11T may be formed on widthwise end portion 112B displaced toward inner surface 11N with respect to general portion 113, while maintaining plate thickness t1 of case body 11.

[0024] In this case, the protrusion amount d1 of the protrusion 11T shown in FIG. 6A is the same as the protrusion amount d1 of the protrusion 11T shown in FIG. 5A. However, the protrusion amount d3 of the protrusion 11T relative to the general portion 113 can be reduced by the amount that the widthwise end 112B is displaced toward the inner surface 11N relative to the general portion 113. Furthermore, the thickness t1 of the case body 11 can be maintained. Therefore, the protrusion amount d2 of the weld metal portion 11Y toward the outer surface 11G shown in FIG. 6B can be maintained while the displacement amount d4 of the case body 11 relative to the general portion 113 can be reduced, thereby suppressing expansion of the case body 11. Furthermore, the first joint portion 11S can be formed at the widthwise end 112B while maintaining the thickness t1 of the case body 11, thereby preventing a decrease in strength of the case body 11. Therefore, solidification cracking at the joint portion 11S in the case body 11 can be reduced while suppressing expansion of the case body 11 and avoiding a decrease in strength. In this case as well, the weld metal portion 11Y preferably has not only a front bead portion 11Y1 protruding toward the outer surface 11G, but also a back bead portion 11Y2 protruding toward the inner surface 11N by a smaller amount than the front bead portion 11Y1.

[0025] Moreover, Fig. 7A shows an enlarged cross-sectional view of Modification 2 of portion A shown in Fig. 4. Fig. 7B shows an enlarged cross-sectional view of Modification 2 of portion B shown in Fig. 4. As shown in Figs. 7A and 7B, convex portion 11T may be formed on widthwise end portion 112C where concave groove surface 114 recessed toward inner surface 11N with respect to outer surface 11G of case body 11 is formed, so as to protrude from concave groove surface 114 to outer surface 11G.

[0026] In this case, the protrusion 11T shown in FIG. 7A protrudes from the groove surface 114 to the outer surface 11G, so the protrusion amount d5 of the protrusion 11T is smaller than the thickness t1 of the case body 11. Therefore, as shown in FIG. 7B, the protruding amount d6 of the curved weld metal portion 11Y is also reduced, making it less likely to protrude from the outer surface 11G of the case body 11. Furthermore, by making the width w1 of the protrusion 11T larger than the protrusion amount d5, the weld surface 11YM of the weld metal portion 11Y can be formed into a more gently curved surface (an arcuate surface with a large radius of curvature 115C). This distributes the thermal contraction of the weld metal portion 11Y during solidification over a wider area, thereby reducing the thermal stress on the weld metal portion 11Y during solidification. Furthermore, the widthwise end 112C, whose thickness t2 is reduced by the groove surface 114, expands and contracts in the region of the groove surface 114, thereby absorbing the thermal contraction of the weld metal portion 11Y during solidification. Therefore, solidification cracking at the joint 11S can be further reduced while compacting the external dimensions of the case body 11. In this case as well, it is preferable that the weld metal portion 11Y has not only a front bead portion 11Y1 protruding toward the outer surface 11G, but also a back bead portion 11Y2 protruding toward the inner surface 11N by a smaller amount than the front bead portion 11Y1.

[0027] Moreover, Fig. 8A shows an enlarged cross-sectional view of Modification 3 of part A shown in Fig. 4. Fig. 8B shows an enlarged cross-sectional view of Modification 3 of part B shown in Fig. 4. As shown in Figs. 8A and 8B, protrusion 11T may be formed at widthwise end 112D of case body 11 so as to protrude toward both outer surface 11G and inner surface 11N.

[0028] In this case, the protrusion 11T is formed at the widthwise end 112 of the case body 11 by an outer protrusion 11T1 protruding toward the outer surface 11G and an inner protrusion 11T2 protruding toward the inner surface 11N. Therefore, the protrusion amount d10 of the back bead 11Y2 protruding in a curved shape toward the inner surface 11N can be increased while ensuring the protrusion amount d9 of the front bead 11Y1 protruding toward the outer surface 11G of the widthwise end 112 of the weld metal portion 11Y. Therefore, the back bead 11Y2 protruding in a curved shape can also disperse thermal stress during solidification of the molten metal 11YK, further reducing solidification cracking at the joint 11S of the case body 11. It is preferable that the protrusion amount d8 of the inner protrusion 11T2 be smaller than the protrusion amount d7 of the outer protrusion 11T1, and that the outer protrusion 11T1 and the inner protrusion 11T2 each have a narrower tip end than a base end. This is because it is possible to avoid an excessively large cross-sectional area of ​​the weld metal portion 11Y, which would otherwise cause an increase in thermal stress during solidification.

[0029] 9A shows a perspective view of Variation 4 of portion C shown in FIG. 4 before welding. FIG. 9B shows a perspective view of Variation 4 of portion C shown in FIG. 4 after welding. As shown in FIG. 9A, the protrusion 11T may be formed so that its protrusion amount increases at the opening 11K where the axial end 111 and the widthwise end 112 of the case body 11 intersect. That is, the protrusion 11T may include a protrusion 11T3 having a constant protrusion amount and a protrusion 11T4 whose protrusion amount gradually increases toward the opening 11K. In this case, as shown in FIG. 9B, a weld metal portion 11Y3 having a constant protrusion amount of the weld metal portion 11Y and a weld metal portion 11Y4 whose protrusion amount gradually increases toward the opening 11K can be formed at the joint 11S.

[0030] Generally, welding heat of the joint 11S accumulates at the opening 11K where the axial end 111 and the widthwise end 112 of the case body 11 intersect, and melting of the molten metal is likely to occur. For this reason, it is often necessary to adopt a control method in which the output of the laser beam LS is reduced as it approaches the opening 11K.

[0031] However, by providing the protrusion 11T4, whose protrusion amount gradually increases toward the opening 11K, it is not necessary to reduce the output of the laser beam LS as the opening 11K is approached, and the weld metal portion 11Y4 gradually increases in protrusion amount toward the opening 11K, thereby increasing its resistance to burn-through. Therefore, the weld metal portion 11Y of the joint 11S can be more stably formed at the opening 11K where the axial end 111 and the widthwise end 112 of the case body 11 intersect. Furthermore, the curved protrusion of the weld metal portion 11Y reduces solidification cracking at the joint 11S.

[0032] (Battery case of the second embodiment) Fig. 10 is a schematic perspective view of a sealed storage battery including a battery case according to a second embodiment of the present invention, manufactured by a method for manufacturing a battery case according to one aspect of the present invention. As shown in Fig. 10, the battery case 1B according to the second embodiment is made of aluminum and includes a cylindrical case body 11B having openings 11BK at both axial ends 111B through which electrode bodies 2 are inserted, and a joint 11S that intersects with the openings 11BK and butt-joins the widthwise ends 112 of the case body 11B, and two sealing bodies 12B that seal the openings 11BK. A welded metal portion 11Y that curves toward the outer surface 11G is formed at the joint 11S between the widthwise ends 112 of the case body 11B.

[0033] The electrode assembly 2, connected to the current collector terminal 4 (41) and fixed to the sealing body 12B, is housed in the case body 11B through the opening 11BK. After the electrode assembly 2 is housed in the opening 11BK of the case body 11B, it is sealed with the sealing body 12B. The joint 12BS between the opening 11BK of the case body 11B and the sealing body 12B is joined by, for example, laser welding. The case body 11B is formed as a bottomless rectangular cylinder having a pair of long side walls 11Ba, 11Ba extending in the longitudinal direction (X direction) and a pair of short side walls 11Bb, 11Bc extending in the width direction (Y direction). After the electrode assembly 2 is housed in the case body 11B through the opening 11BK and the opening 11BK is joined to the sealing body 12B, the electrolyte 5 is injected through an inlet (not shown). Initial charging, aging, and other processes are performed to complete the sealed storage battery 10B.

[0034] (Method of manufacturing the battery case of the second embodiment) 11A shows a cross-sectional view of a first intermediate product used in the case body of the battery case shown in FIG. 10. FIG. 11B shows a cross-sectional view of a second intermediate product used in the case body of the battery case shown in FIG. 10. FIG. 11C shows a cross-sectional view of a third intermediate product used in the case body of the battery case shown in FIG. 10. FIG. 11D shows a cross-sectional view of the case body of the battery case shown in FIG. 10.

[0035] 2, 10, and 11A-11D, the method for manufacturing a battery case 1B of the second embodiment, similar to the method for manufacturing the battery case 1 of the first embodiment described above, is a method for manufacturing a battery case 1B including a cylindrical case body 11B made of aluminum, the case body 11B having an opening 11BK at at least one axial end 111B for inserting an electrode assembly 2, and a joint 11S that intersects with the opening 11BK and butt-joins the widthwise ends 112 of the case body 11B, and a sealing body 12B that seals the opening 11BK, and includes a protrusion-forming step S1 and a welding step S2. The protrusion-forming step S1 is a step for forming a protrusion 11T that protrudes toward the outer surface 11G of the case body 11B along the widthwise end 112 of the case body 11B. In the welding step S2, the protrusions 11T are butted together, and then laser light LS is applied to the protrusions 11T from the outer surface 11G side of the case body 11B to melt the protrusions 11T, thereby forming a weld metal portion 11Y that curves and protrudes toward the outer surface 11G side of the case body 11B at the joint 11S with molten metal 11YK. Here, the method for manufacturing the battery case 1B of the second embodiment will be described, focusing on the differences from the method for manufacturing the battery case 1 of the first embodiment.

[0036] In the convex portion forming step S1 of the second embodiment, first, as shown in FIG. 11A, a first intermediate product 11BX is produced by bending a flat aluminum plate to form convex portions 11T protruding toward the outer surface 11G at both widthwise ends 112. Next, as shown in FIG. 11B, a second intermediate product 11BY is produced by bending the short side wall portion 11Bb on which the convex portions 11T are formed toward the inner surface 11N relative to the long side wall portion 11Ba. Next, as shown in FIG. 11C, a third intermediate product 11BZ is produced by bending the long side wall portion 11Ba toward the inner surface 11N relative to the short side wall portion 11Bc opposite the short side wall portion 11Bb on which the convex portions 11T are formed. In the third intermediate product 11BZ, the convex portions 11T abut against each other. 11D, in a welding step S2, a laser beam LS is irradiated onto the protrusion 11T from the outer surface 11G side of the case body 11B to melt the protrusion 11T, and the molten metal 11YK forms a welded metal portion 11Y that curves and protrudes toward the outer surface 11G side of the case body 11B at the joint 11S. This completes the production of the case body 11B of the battery case 1B of the second embodiment.

[0037] FIG. 12A shows a cross-sectional view of an intermediate product used in Variation 1 of the case body of the battery case shown in FIG. 10 . FIG. 12B shows a cross-sectional view of Variation 1 of the case body of the battery case shown in FIG. 10 . In the third intermediate product 11BZ shown in FIG. 11C , the protrusion 11T is formed at the widthwise end 112 located at the widthwise center of the short side wall 11Bb. However, the location of the protrusion 11T is not limited thereto. For example, as shown in FIG. 12A , the protrusion 11T may be formed at the widthwise end 112 located at the intersection of the short side wall 11Bb and the long side wall 11Ba. In this case, as shown in FIG. 12B , the weld metal portion 11Y of the joint 11S is located at the intersection of the short side wall 11Bb and the long side wall 11Ba. Since the weld metal portion 11Y of the joint 11S is not located at the widthwise center of the short side wall 11Bb, it is advantageous in that it is easier to form an electrolyte inlet, a safety valve, etc. It goes without saying that modifications 1 to 4 shown in FIGS. 6A to 9B can be applied to the protrusion 11T shown in FIGS. 11C and 12A and the welded metal portion 11Y shown in FIGS. 11D and 12B. [Explanation of symbols]

[0038] 1. 1B battery case 2 Electrode body 10, 10B sealed storage battery 11, 11B case body 11G External surface 11K aperture 11N inner surface 11S joint 11T convex part 11Y Welded metal part 11YK Molten Metal 12, 12B Sealing body 111 Axial end 112, 112B, 112C Width end 112D Width end 113 General section 114 Concave groove surface LS laser light S1 Convex part forming process S2 Welding process

Claims

1. a cylindrical case body made of aluminum, having an opening at at least one axial end portion for inserting an electrode body, and a joint portion that intersects with the opening portion and butt-joins widthwise ends of the case body; a sealing body that seals the opening, a convex portion forming step of forming a convex portion that protrudes toward an outer surface of the case body along the width direction end portion; a welding process in which, after the protrusions are butted together, a laser beam is irradiated onto the protrusions from the outer surface side of the case body to melt the protrusions, thereby forming a weld metal portion that protrudes in a curved shape toward the outer surface side of the case body at the joint portion with molten metal; A method for manufacturing a battery case comprising:

2. The method for manufacturing a battery case according to claim 1, The convex portion is formed at a widthwise end portion displaced toward the inner surface side relative to the general portion while maintaining the plate thickness of the case body. A method for manufacturing a battery case.

3. The method for manufacturing a battery case according to claim 1, The convex portion is formed at a widthwise end portion of the case body on which a concave groove surface recessed toward the inner surface with respect to the outer surface of the case body is formed, and the convex portion protrudes from the concave groove surface to the outer surface. A method for manufacturing a battery case.

4. The method for manufacturing a battery case according to claim 1, The protrusions protrude toward both the outer surface side and the inner surface side at the widthwise end of the case body. A method for manufacturing a battery case.

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