Metal can, method for manufacturing metal can, battery, and method for manufacturing battery

Abstract

To provide a method for manufacturing a metal can capable of reducing the twist of the metal can.SOLUTION: A method for manufacturing a metallic can (10, side 10A) includes a first step, a second step, and a third step. In the first step, a metal plate (40) is prepared. In the second step, the metal sheet (40) is drawn to obtain an intermediate formed product (102). The intermediate molded product (102) includes a peripheral wall (11) having a rectangular tube shape and a bottom plate (12). The bottom plate (12) closes one axial end of the peripheral wall (11). In a third step, a recess (123) is formed in the bottom plate (12). The recessed portion (123) has a shape recessed toward the inside of the intermediate molded product (102).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a metal can and a method for manufacturing the same, and also to a battery and a method for manufacturing the same. [Background technology]

[0002] For example, large batteries for vehicle or stationary use employ a rectangular metal can as a battery case. The metal can includes, for example, a substantially rectangular cylindrical peripheral wall and a bottom plate. The metal can has an opening on the opposite side of the bottom plate. A lid is joined to the metal can to close the opening.

[0003] Such metal cans are generally formed by drawing a metal plate. For example, as described in Patent Document 1, when manufacturing a metal can, a metal plate as a raw material is subjected to a multi-stage deep drawing process. In Patent Document 1, a first intermediate cup-shaped body having a substantially elliptical cross section is formed from a metal plate by deep drawing. Next, a second intermediate cup-shaped body is formed from the first intermediate cup-shaped body by multi-stage re-drawing. The second intermediate cup-shaped body has a substantially elliptical cross section with a smaller ratio of minor axis to major axis (minor axis / major axis) than the first intermediate cup-shaped body. Thereafter, the second intermediate cup-shaped body is subjected to re-drawing and multi-stage ironing to produce a metal can in the shape of a rectangular cylinder with a bottom. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4119612 Summary of the Invention [Problem to be solved by the invention]

[0005] When a metal can having a bottomed rectangular cylindrical shape is formed by drawing a metal sheet as in Patent Document 1, the resulting metal can may become twisted. In particular, when forming a metal can with a relatively large aspect ratio, the flow of material from the bottom plate to the peripheral wall is likely to differ between the short and long sides during the drawing process. As a result, the stress balance in the metal can after drawing is likely to be disrupted, making the metal can prone to twisting. If the metal can is significantly twisted, it is difficult to join a lid to the metal can.

[0006] An object of the present disclosure is to provide a method for manufacturing metal cans that can reduce twisting of the metal cans. [Means for solving the problem]

[0007] The method for manufacturing a metal can according to the present disclosure includes a first step, a second step, and a third step. In the first step, a metal plate is prepared. In the second step, the metal plate is subjected to drawing to obtain an intermediate formed product. The intermediate formed product includes a rectangular cylindrical peripheral wall and a bottom plate. The bottom plate seals one axial end of the peripheral wall. In the third step, a recess is formed in the bottom plate. The recess has a shape recessed toward the inside of the intermediate formed product. [Effects of the Invention]

[0008] According to the method for manufacturing a metal can according to the present disclosure, twisting of the metal can can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a metal can according to the first embodiment. [Figure 2] FIG. 2 is another perspective view of the metal can according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the metal can shown in FIG. [Figure 4] FIG. 4 is a vertical cross-sectional view of the metal can shown in FIG. [Figure 5] FIG. 5 is a bottom view of the metal can shown in FIG. [Figure 6] FIG. 6 is a perspective view of the battery according to the first embodiment. [Figure 7A] FIG. 7A is a schematic diagram illustrating the method for manufacturing a metal can according to the first embodiment. [Figure 7B] FIG. 7B is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7C] FIG. 7C is a schematic view for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7D] FIG. 7D is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7E] FIG. 7E is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7F] FIG. 7F is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7G] FIG. 7G is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7H] FIG. 7H is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7I] FIG. 7I is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 7J] FIG. 7J is a schematic diagram for explaining the method for manufacturing a metal can according to the first embodiment. [Figure 8] FIG. 8 is a schematic view for explaining the method for manufacturing the battery according to the first embodiment. [Figure 9A] FIG. 9A is a schematic diagram illustrating a method for manufacturing a metal can according to the second embodiment. [Figure 9B] FIG. 9B is a schematic diagram for explaining the method for manufacturing a metal can according to the second embodiment. [Figure 10] FIG. 10 is a bottom view of the metal can according to the second embodiment. [Figure 11] FIG. 11 is a vertical cross-sectional view of a metal can according to the second embodiment. [Figure 12A] FIG. 12A is a schematic diagram illustrating a method for manufacturing a metal can according to the third embodiment. [Figure 12B]FIG. 12B is a schematic diagram for explaining the method for manufacturing a metal can according to the third embodiment. [Figure 13] FIG. 13 is a bottom view of a metal can according to a modified example of the first embodiment. [Figure 14] FIG. 14 is a bottom view of a metal can according to another modified example of the first embodiment. [Figure 15] FIG. 15 is a bottom view of a metal can according to yet another modified example of the first embodiment. [Figure 16] FIG. 16 is a diagram showing the shape of the analytical model (bottom plate of the metal can) used in the first example. [Figure 17] FIG. 17 is a diagram showing the shape of another analytical model (bottom plate of a metal can) used in the first example. [Figure 18] FIG. 18 is a diagram showing the shape of yet another analytical model (bottom plate of a metal can) used in the first example. [Figure 19] FIG. 19 is a graph showing the torsion angle of each analytical model in the first example. [Figure 20] FIG. 20 is a graph showing the stress difference between the analysis models in the first example. [Figure 21] FIG. 21 is a graph showing the relationship between the stress difference and the torsion angle for each analytical model in the first example. [Figure 22] FIG. 22 is a graph showing the distribution of Vickers hardness in the bottom plate for the analysis model of the second example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for manufacturing a metal can according to the embodiment includes a first step, a second step, and a third step. In the first step, a metal plate is prepared. In the second step, the metal plate is drawn to obtain an intermediate product. The intermediate product includes a rectangular cylindrical peripheral wall and a bottom plate. The bottom plate closes one axial end of the peripheral wall. In the third step, a recess is formed in the bottom plate. The recess has a shape recessed toward the inside of the intermediate product (first configuration).

[0011] As a result of investigations by the present inventors, it is presumed that the driving force for the twisting of a metal can that occurs after drawing is stress in the bottom plate. More specifically, immediately after forming, compressive stress may occur in the center of the bottom plate of the metal can, and tensile stress may occur on both ends. In this case, when the stress is released by demolding, the center of the bottom plate elongates, while both ends of the bottom plate contract. As a result, the balance of stress in the bottom plate is lost, and the peripheral wall connected to the bottom plate partially collapses inward or outward of the metal can, causing twisting of the metal can.

[0012] In contrast, in the manufacturing method according to the first aspect, a recess is formed in the bottom plate of the intermediate product obtained by drawing. By processing the bottom plate to form a recess in this manner, the tensile or compressive stress generated in the bottom plate by drawing can be reduced and the stress in the bottom plate can be made uniform. Therefore, even when a bottomed rectangular tubular metal can is manufactured through drawing, twisting of the metal can can be reduced.

[0013] In the manufacturing method according to the first configuration, the projected area of ​​the recess in the axial direction may be 1.0% or more of the projected area of ​​the bottom plate in the axial direction (second configuration).

[0014] In the manufacturing method according to the first or second configuration, the peripheral wall can have an aspect ratio of 5.0 or more and 15.0 or less when viewed in a cross section perpendicular to the axial direction (third configuration).

[0015] As described above, in the manufacturing method according to the embodiment, the stress generated in the bottom plate can be made uniform by forming a recess in the bottom plate, and therefore, even in the case of a metal can having a relatively large aspect ratio as in the third configuration, in which the flow of material from the bottom plate to the peripheral wall during drawing tends to be uneven, it is possible to manufacture the can with reduced twisting.

[0016] In the manufacturing method according to any one of the first to third configurations, the third step may be carried out in the second step together with molding of the intermediate molded product (fourth configuration).

[0017] In the fourth configuration, the recesses are formed in the bottom plate in conjunction with the forming of the intermediate product by drawing, which reduces the number of steps in the manufacture of metal cans compared to when the recesses are formed in a separate step from the forming of the intermediate product.

[0018] The manufacturing method according to any one of the first to fourth configurations may further include a fourth step of crushing at least a portion of the recess in the axial direction (fifth configuration).

[0019] In the manufacturing method according to any one of the first to fifth configurations, the metal plate may have a thickness of 0.1 mm or more and 0.8 mm or less (sixth configuration).

[0020] When a metal plate used as a raw material is thin, twisting tends to occur in the metal can when the metal can is manufactured by drawing the metal plate. However, in the manufacturing method according to the embodiment, by forming a recess in the bottom plate, stress generated in the bottom plate can be made uniform, making the metal can less likely to twist. Therefore, even when a relatively thin metal plate is drawn as in the sixth configuration, twisting can be made less likely to occur in the manufactured metal can.

[0021] A metal can according to an embodiment includes a rectangular cylindrical peripheral wall and a bottom plate. The bottom plate closes one axial end of the peripheral wall. A recess is formed in the bottom plate. The recess has a shape recessed toward the inside of the metal can (seventh configuration).

[0022] In the metal can according to the seventh configuration, a recess is formed in the bottom plate. This increases the rigidity of the bottom plate, thereby suppressing deformation of the bottom plate. Furthermore, by forming the recess in the bottom plate, stress in the bottom plate is reduced, resulting in a metal can with improved stress balance.

[0023] In the metal can according to the seventh configuration, the projected area of ​​the recess in the axial direction may be 1.0% or more of the projected area of ​​the bottom plate in the axial direction (eighth configuration).

[0024] A metal can according to another embodiment includes a rectangular cylindrical peripheral wall and a bottom plate. The bottom plate closes one axial end of the peripheral wall. The bottom plate includes a high-hardness portion. The high-hardness portion has a Vickers hardness that is 10 HV or more higher than that of other portions of the bottom plate (ninth configuration).

[0025] In the metal can according to the ninth configuration, the bottom plate is provided with a high-hardness portion, which makes it easier to suppress deformation of the bottom plate.

[0026] A method for manufacturing a battery according to the embodiment includes the steps of preparing a metal can as a battery case and a lid according to any one of the seventh to ninth configurations, and joining the lid to the metal can to seal the metal can (tenth configuration).

[0027] A battery according to an embodiment includes a metal can as a battery case according to any one of the seventh to ninth configurations, and a lid. The lid is joined to the metal can to seal the metal can (eleventh configuration).

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In these drawings, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0029] First Embodiment [Metal can composition] 1 and 2 are perspective views of a metal can 10 according to this embodiment. The metal can 10 is used, for example, as a battery case. The metal can 10 includes a peripheral wall 11, a bottom plate 12, and an opening 13.

[0030] 1, peripheral wall 11 has a substantially rectangular cylindrical shape. A bottom plate 12 is provided at one axial end of peripheral wall 11. An opening 13 is provided at the other axial end of peripheral wall 11.

[0031] The peripheral wall 11 includes a pair of first side walls 111a and 111b, a pair of second side walls 112a and 112b, and four corner portions 113.

[0032] Each of the first side walls 111a and 111b has a substantially rectangular flat plate shape. The first side walls 111a and 111b are arranged to face each other. The first side walls 111a and 111b face each other in the short side direction of the peripheral wall 11 when viewed along the axial direction of the peripheral wall 11.

[0033] Each of the second side walls 112a and 112b has a substantially rectangular flat plate shape. The second side walls 112a and 112b are arranged to face each other. When viewed along the axial direction of the peripheral wall 11, the second side walls 112a and 112b face each other in the longitudinal direction of the peripheral wall 11.

[0034] The second side walls 112a and 112b are connected to the first side walls 111a and 111b, respectively, via corner portions 113. The second side wall 112a is connected to the first side wall 111a via one of the corner portions 113 and is connected to the first side wall 111b via the other corner portion 113. The second side wall 112b is connected to the first side wall 111a via one of the corner portions 113 on the opposite side from the second side wall 112a and is connected to the first side wall 111b via the other corner portion 113.

[0035] 2 , the bottom plate 12 closes one axial end of the peripheral wall 11. The bottom plate 12 may include a main body portion 121 and a corner portion 122. The corner portion 122 is provided to surround the main body portion 121. The main body portion 121 is connected to the peripheral wall 11 via the corner portion 122.

[0036] At least one recess 123 is formed in the bottom plate 12. The recess 123 is typically provided in the main body 121 of the bottom plate 12. Compared to other parts of the bottom plate 12, the recess 123 has a shape that is recessed toward the inside of the metal can 10.

[0037] Fig. 3 is a diagram (transverse cross-sectional view) showing a cross section of the metal can 10 perpendicular to the axial direction of the peripheral wall 11. Fig. 4 is a diagram (longitudinal cross-sectional view) showing a cross section of the metal can 10 along the axial direction of the peripheral wall 11.

[0038] Referring to FIG. 3, the peripheral wall 11 has, for example, a substantially rectangular shape when viewed in a cross section (transverse cross section) perpendicular to its axial direction. In this case, the peripheral wall 11 may have an aspect ratio of 5.0 or more when viewed in its transverse cross section. The aspect ratio of the peripheral wall 11 may be 15.0 or less. The aspect ratio is the ratio (WL / WS) of the longitudinal width WL of the peripheral wall 11 to the lateral width WS of the peripheral wall 11. The lateral width WS of the peripheral wall 11 is the shortest distance from the outer surface of one first side wall 111a to the outer surface of the other first side wall 111b when viewed in the transverse cross section of the peripheral wall 11. The longitudinal width WL of the peripheral wall 11 is the shortest distance from the outer surface of one second side wall 112a to the outer surface of the other second side wall 112b when viewed in the transverse cross section of the peripheral wall 11.

[0039] The widths WS and WL can be determined, for example, depending on the application of the metal can 10. When the metal can 10 is a battery case, the width WL may be 100.0 mm or more. When the metal can 10 is a battery case, the width WL may be 400.0 mm or less. The widths WS and WL can be measured, for example, in a cross section of the peripheral wall 11 at a position 5.0 mm axially from the opening 13 (FIG. 1).

[0040] 4, metal can 10 has height H. Height H is the maximum distance along the axial direction of peripheral wall 11 from the outer surface of the portion of bottom plate 12 other than recess 123 to the edge of peripheral wall 11 on the opening 13 side. Height H may be 2.0 times or more the width WS (FIG. 3) in the short side direction of peripheral wall 11. Height H may be 7.0 times or less the width WS.

[0041] In the bottom plate 12, the recess 123 has a depth D. The depth D is the maximum distance along the axial direction of the peripheral wall 11 from the outer surface of the portion of the bottom plate 12 other than the recess 123 to the bottom of the recess 123. The depth D of the recess 123 may be equal to or greater than the thickness of the bottom plate 12. The thickness of the bottom plate 12 is measured, for example, at the main body portion 121. The depth D is, for example, equal to or greater than 0.1 mm. The depth D may be equal to or less than 10.0 mm.

[0042] 5 is a diagram (bottom view) of the metal can 10 as seen from the bottom plate 12 side. In other words, FIG. 5 shows the outer surface of the bottom plate 12 when projected onto a plane perpendicular to the axial direction of the peripheral wall 11.

[0043] The bottom plate 12 corresponds to the peripheral wall 11 (FIG. 3) and can have a substantially rectangular shape when viewed from the bottom of the metal can 10. In this embodiment, the recess 123 also has a substantially rectangular shape when viewed from the bottom of the metal can 10. The recess 123 is preferably provided substantially symmetrically with respect to a width center line CL in the longitudinal direction of the bottom plate 12 when viewed from the bottom of the metal can 10. The recess 123 may also be provided substantially symmetrically with respect to a width center line CS in the lateral direction of the bottom plate 12 when viewed from the bottom of the metal can 10.

[0044] If the area of ​​the bottom plate 12 when projected onto a plane perpendicular to the axial direction of the peripheral wall 11 is defined as the projected area A0 in the axial direction, and the area of ​​the recess 123 when projected onto the same plane is defined as the projected area A in the axial direction, the projected area A of the recess 123 in the axial direction is, for example, 1.0% or more of the projected area A0 of the bottom plate 12. The projected area A of the recess 123 in the axial direction is preferably 10.0% or more, and more preferably 20.0% or more, of the projected area A0 of the bottom plate 12. The projected area A of the recess 123 in the axial direction may be 80.0% or less of the projected area A0 of the bottom plate 12.

[0045] [Battery configuration] 6 is a perspective view of a battery 20 that uses the metal can 10 as a battery case. The battery 20 may be, for example, a lithium ion secondary battery. The battery 20 includes the metal can 10 and a lid 30.

[0046] The metal can 10 contains an electrode assembly, an electrolyte solution, etc. (not shown). The lid 30 is joined to the metal can 10 to seal the metal can 10. The lid 30 is attached to the metal can 10 so as to close the opening 13. The lid 30 is made of metal. The material of the lid 30 may be the same as that of the metal can 10, or may be different from that of the metal can 10.

[0047] [Metal can manufacturing method] Next, a method for manufacturing the metal can 10 will be described with reference to Figures 7A to 7J. The method for manufacturing the metal can 10 according to this embodiment includes a first step, a second step, and a third step.

[0048] (1st step) Referring to FIG. 7A, in the first step, a metal plate 40 is prepared as a material for the metal can 10 (FIGS. 1 and 2).

[0049] The metal plate 40 is, for example, a steel plate. The metal plate 40 may be a stainless steel plate or a surface-treated steel plate. Surface-treated steel plates include plated steel plates. When the metal can 10 (FIGS. 1 and 2) to be manufactured is a battery case, the surface-treated steel plate is preferably a nickel-plated steel plate. Alternatively, when the metal can 10 is a battery case, the metal plate 40 is preferably a stainless steel plate. However, the metal plate 40 may also be a plate material made of aluminum, titanium, copper, or an alloy thereof.

[0050] The thickness of the metal plate 40 can be determined appropriately depending on, for example, the application of the metal can 10 (FIGS. 1 and 2). When the metal can 10 to be manufactured is a battery case, the thickness of the metal plate 40 is, for example, 0.1 mm or more. In this case, the thickness of the metal plate 40 may be 0.8 mm or less.

[0051] (2nd process) 7B to 7G, in the second step, the metal plate 40 is drawn to obtain the intermediate product 102. In the second step, it is sufficient that the metal plate 40 is drawn at least once. In this embodiment, the metal plate 40 is drawn multiple times to form the intermediate product 102.

[0052] 7B, in the first drawing, for example, a die 50 can be used. The die 50 may be a known die for drawing. In this embodiment, the die 50 includes a punch 51, a die 52, and blank holders 53 and 54.

[0053] During drawing, the metal sheet 40 is placed between the punch 51 and the die 52. Next, the outer peripheral portion of the metal sheet 40 is clamped between the die 52 and the blank holder 53, and the punch 51 presses the metal sheet 40 into the die 52 as shown in FIG. 7C . At this time, the metal sheet 40 may be pressed into the die 52 by moving the die 52 toward the punch 51, or the metal sheet 40 may be pressed into the die 52 by moving the punch 51 toward the die 52. The blank holder 54 comes into contact with the metal sheet 40 later than the blank holder 53. The blank holder 54 can support the metal sheet 40 on the inner peripheral side of the blank holder 53.

[0054] The metal sheet 40 is pressed into the die 52 by the punch 51, thereby subjecting the metal sheet 40 to a drawing process. As shown in Fig. 7D, when the metal sheet 40 is completely pressed into the die 52, the metal sheet 40 becomes a cylindrical intermediate product 101 with a bottom.

[0055] Referring to FIG. 7E, the intermediate formed product 101 (metal plate 40) is further subjected to drawing. In the second and subsequent drawing processes, for example, a die 60 can be used. The die 60 may be a known die for drawing. In this embodiment, the die 60 includes a punch 61, a die 62, and a blank holder 63.

[0056] During the drawing process, the intermediate formed product 101 is supported by a punch 61 and a blank holder 63 arranged on the outer periphery of the punch 61. As shown in FIG. 7F , the intermediate formed product 101 is pressed into a die 62 by the punch 61. At this time, the intermediate formed product 101 may be pressed into the die 62 by moving the die 62 toward the punch 61 and the blank holder 63, or the intermediate formed product 101 may be pressed into the die 62 by moving the punch 61 and the blank holder 63 toward the die 62. As shown in FIGS. 7F and 7G , as the intermediate formed product 101 is pressed into the die 62, the blank holder 63 is pressed down relative to the punch 61 by the die 62. In this way, the intermediate formed product 101 is subjected to the drawing process.

[0057] The intermediate molded product 101 is subjected to drawing at least once as shown in Figures 7E to 7G. The intermediate molded product 101 may be subjected to drawing two or more times. By drawing the intermediate molded product 101, an intermediate molded product 102 having a final shape is formed.

[0058] (3rd step) As shown in Fig. 7H, the intermediate molded product 102 obtained in the second step includes a peripheral wall 11 and a bottom plate 12 similar to those of the finished metal can 10 (Figs. 1 and 2). However, in the intermediate molded product 102, the bottom plate 12 does not have the recess 123 (Fig. 2). In the third step, the recess 123 is formed in the bottom plate 12.

[0059] 7I, in the third step, for example, a mold 70 can be used. The mold 70 includes a punch 71 and a die 72. A convex portion 711 corresponding to the concave portion 123 (FIG. 2) is formed on the surface of the punch 71 facing the die 72. A concave portion 721 corresponding to the convex portion 711 of the punch 71 is formed on the surface of the die 72 facing the punch 71.

[0060] In the third step, with the die 72 disposed within the intermediate molded product 102, the bottom plate 12 of the intermediate molded product 102 is clamped between the punch 71 and the die 72 as shown in Fig. 7J. At this time, the convex portion 711 of the punch 71 presses a part of the bottom plate 12 into the inside of the intermediate molded product 102, forming a concave portion 123. In this way, the metal can 10 can be manufactured.

[0061] [Battery manufacturing method] Next, a description will be given of a method for manufacturing a battery 20 (FIG. 6) using the metal can 10. The method for manufacturing the battery 20 according to this embodiment includes a preparation step and a joining step.

[0062] 8, in the preparation step, a metal can 10 as a battery case and a lid 30 are prepared. In the joining step, the lid 30 is joined to the metal can 10 to seal the metal can 10. The lid 30 is joined to the metal can 10 in a state in which necessary contents, such as an electrode assembly and an electrolyte, are housed. The lid 30 is joined to the metal can 10 by, for example, welding.

[0063] [effect] In this embodiment, the bottom plate 12 of the intermediate product 102 obtained by one or more drawing processes is processed to form recesses 123 in the bottom plate 12. This reduces the tensile or compressive stress generated in the bottom plate 12 by the drawing process, and makes it possible to uniformize the stress in the bottom plate 12. As a result, it is possible to reduce twisting of the metal can 10.

[0064] In this embodiment, the peripheral wall 11 of the metal can 10 can have an aspect ratio of 5.0 or more and 15.0 or less in cross section. When the aspect ratio is relatively large, the flow of material into the peripheral wall 11 is likely to differ between the short and long sides during drawing, which can lead to imbalance of stress in the bottom plate 12. However, in this embodiment, the bottom plate 12 of the intermediate product 102 after drawing is processed to form a recess 123. This process reduces the stress generated in the bottom plate 12 and the driving force for twisting the metal can 10. Therefore, even when manufacturing a metal can 10 with an aspect ratio of the peripheral wall 11 of 5.0 or more, twisting of the metal can 10 can be made less likely.

[0065] In this embodiment, the metal plate 40 used as the raw material may have a thickness of 0.1 mm or more and 0.8 mm or less. When the thickness of the metal plate 40 is relatively small, the rigidity of the manufactured metal can 10 is also low, and the metal can 10 is prone to twisting. However, in this embodiment, by forming the recess 123 in the bottom plate 12, the stress in the bottom plate 12 can be reduced and made uniform. Therefore, even a relatively thin-walled metal can 10 can be manufactured while suppressing twisting.

[0066] Aluminum alloy sheets have a lower specific gravity than steel sheets. Therefore, when metal cans are manufactured by drawing aluminum alloy sheets, relatively thick aluminum alloy sheets are often used as the raw material. In this case, applying an ironing process to the peripheral wall of the metal can after drawing to thin the peripheral wall can alleviate uneven stress caused by differences in material flow between the short and long sides, thereby reducing twisting of the metal can.

[0067] On the other hand, when steel sheet is used as the material for metal cans, it is difficult to apply ironing. For example, when it is necessary to reduce the weight of metal cans, thin-walled metal cans are formed from relatively thin steel sheets. When such thin-walled metal cans are subjected to ironing, the load imposed on the metal can from the ironing mold increases, which may cause deformation or damage to the mold. Furthermore, when the steel sheet is a surface-treated steel sheet, the ironing process may damage the surface treatment layer, thereby reducing the corrosion resistance of the steel sheet.

[0068] However, in this embodiment, it is possible to reduce twisting of the metal can 10 without performing ironing. Therefore, it is possible to manufacture a thin-walled metal can 10 from a metal plate 40 having a thickness of, for example, 0.8 mm or less while suppressing twisting of the metal can 10.

[0069] In this embodiment, it is preferable that a recess 123 having a depth D equal to or greater than the thickness of the bottom plate 12 is formed in the bottom plate 12 of the intermediate molded product 102. This more effectively relieves the stress state generated in the bottom plate 12 by the drawing process.

[0070] In the metal can 10 according to this embodiment, the bottom plate 12 has the recess 123, which increases the rigidity of the bottom plate 12. This makes it possible to suppress deformation of the bottom plate 12.

[0071] For example, when the battery 20 is charged and discharged, the battery 20 may expand and contract. When multiple batteries 20 are modularized, pressure acts on each battery 20 from the other batteries 20 to suppress expansion. When the contents of the battery 20 do not reach the bottom plate 12 of the metal can 10 serving as the battery case, this pressure is likely to cause deformation of the bottom plate 12. However, in this embodiment, the recess 123 is formed in the bottom plate 12, increasing the rigidity of the bottom plate 12, and therefore deformation of the bottom plate 12 can be suppressed.

[0072] Second Embodiment 9A and 9B are schematic diagrams illustrating a method for manufacturing a metal can 10A according to this embodiment. The method for manufacturing a metal can 10A according to this embodiment includes a fourth step in addition to the first, second, and third steps similar to those of the first embodiment.

[0073] The fourth step is carried out after the third step. The metal can 10 obtained in the third step undergoes the fourth step to become a metal can 10A. In the fourth step, at least a portion of the recess 123 is crushed in the axial direction of the peripheral wall 11. As shown in FIG. 9A, a mold 80 can be used in the fourth step. The mold 80 includes a punch 81 and a die 82.

[0074] In the fourth step, with the die 82 placed inside the metal can 10 after the third step, the bottom plate 12 is clamped between the punch 81 and the die 82 as shown in FIG. 9B. As a result, at least a portion of the recess 123 in the bottom plate 12 is crushed in the axial direction of the peripheral wall 11 between the punch 81 and the die 82, and the metal can 10 (FIG. 9A) obtained in the third step becomes the metal can 10A. In this embodiment, the entire recess 123 is crushed in the axial direction of the peripheral wall 11. As a result, the outer and inner surfaces of the bottom plate 12 are generally flattened.

[0075] Fig. 10 is a view (bottom view) of the metal can 10A as seen from the bottom plate 12 side. Fig. 11 is a view (cross-sectional view taken along line XI-XI in Fig. 10) showing a cross section of the metal can 10A taken along the axial direction of the peripheral wall 11. Fig. 11 shows an enlarged view of a portion of the bottom plate 12.

[0076] As shown in FIG. 10 , the bottom plate 12 of the metal can 10A includes a high-hardness portion 124. The high-hardness portion 124 is a portion that has undergone work hardening due to the crushing of the recess 123 ( FIG. 9A ). Because the crushing of the recess 123 leaves a processing mark, the high-hardness portion 124 can be visually confirmed. The high-hardness portion 124 is formed corresponding to the position of the peripheral edge (ridge portion) of the recess 123. In this embodiment, the entire recess 123 is crushed, so that the high-hardness portion 124 has a frame shape when viewed along the axial direction of the peripheral wall 11. The high-hardness portion 124 can have, for example, a rectangular frame shape when viewed along the axial direction of the peripheral wall 11. In the example of FIG. 10 , the high-hardness portion 124 is formed substantially symmetrically with respect to a width center line CL in the longitudinal direction of the bottom plate 12 when viewed from the bottom of the metal can 10A.

[0077] 11 , the high-hardness portion 124 has a Vickers hardness HV1 that is 10 HV or more higher than that of the other portion 125 of the bottom plate 12. The Vickers hardness HV1 of the high-hardness portion 124 and the Vickers hardness HV2 of the other portion 125 of the bottom plate 12 can be measured as follows: The metal can 10A is cut at the position of the bottom plate 12 to prepare five test pieces for hardness measurement. Each test piece is prepared so that the cross section of the bottom plate 12, including the high-hardness portion 124 and the other portion 125, is exposed on the surface. Then, a Vickers hardness test in accordance with JIS Z 2244 (2009) is performed on each test piece with a test force of 0.5 N, and the Vickers hardness of the high-hardness portion 124 and the other portion 125 is measured at the center of the thickness of the bottom plate 12. The average value of the Vickers hardness of the high hardness portion 124 obtained for the five test pieces is defined as the Vickers hardness HV1 of the high hardness portion 124. The average value of the Vickers hardness of the other portion 125 obtained for the five test pieces is defined as the Vickers hardness HV2 of the other portion 125.

[0078] The other portion 125 of the bottom plate 12 is a portion of the main body portion 121 other than the high hardness portion 124, and is a substantially flat portion. For example, if a sufficiently large flat portion exists on the peripheral wall 11 side of the high hardness portion 124 of the main body portion 121, the Vickers hardness HV2 may be measured using the flat portion as the other portion 125. On the other hand, if a sufficiently large flat portion does not exist on the peripheral wall 11 side of the high hardness portion 124 of the main body portion 121, the Vickers hardness HV2 may be measured using the flat portion on the opposite side of the high hardness portion 124 of the main body portion 121 from the peripheral wall 11 as the other portion 125.

[0079] In this embodiment, after the recess 123 is formed in the bottom plate 12, the recess 123 is crushed. However, by forming the recess 123 once in the bottom plate 12, the tensile or compressive stress generated in the bottom plate 12 by the drawing process is reduced, as in the first embodiment, and the stress in the bottom plate 12 can be made uniform. Therefore, the twisting of the metal can 10A can be reduced.

[0080] The metal can 10A according to this embodiment can be used in place of the metal can 10 according to the first embodiment for the battery 20 and for manufacturing the battery 20. The bottom plate 12 of the metal can 10A is provided with a high-hardness portion 124. This makes it easier to suppress deformation of the bottom plate 12 when pressure from other batteries 20 acts upon the battery 20 during expansion, for example.

[0081] In this embodiment, after the recess 123 is formed in the bottom plate 12, the recess 123 is crushed. As a result, when the metal can 10A is used for the battery 20, for example, the volume of the battery 20 can be increased compared to when the recess 123 is maintained.

[0082] Third Embodiment In the first and second embodiments, the third step of forming the recess 123 in the bottom plate 12 is carried out after the second step of forming the metal plate 40 into the intermediate product 102 by drawing. However, the third step may be carried out in conjunction with the formation of the intermediate product 102 in the second step. If the intermediate product 102 is formed by multiple drawing steps in the second step, the third step is carried out in conjunction with the final drawing step. On the other hand, if the intermediate product 102 is formed by only one drawing step in the second step, the third step is carried out in conjunction with this drawing step.

[0083] 12A and 12B, when the third step is performed within the second step, the drawing die 60 may further include a pad 64. A convex portion 641 corresponding to the concave portion 123 of the metal can 10 is formed on the surface of the pad 64 facing the punch 61. A concave portion 611 corresponding to the convex portion 641 of the pad 64 is formed on the surface of the punch 61 facing the pad 64.

[0084] For example, as the intermediate molded product 101 is pressed into the die 62, the pad 64 approaches the punch 61 and, together with the punch 61, holds the bottom plate 12. The bottom plate 12 is held between the convex portion 641 of the pad 64 and the concave portion 611 of the punch 61. As a result, the intermediate molded product 101 is molded into the final intermediate molded product 102, and the concave portion 123 of the bottom plate 12 is formed, thereby producing the metal can 10.

[0085] The metal can 10 may be subjected to a fourth step, similar to the second embodiment. That is, the recess 123 of the bottom plate 12 may be crushed in the axial direction of the peripheral wall 11.

[0086] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0087] In each of the above embodiments, a single recess 123 occupying most of the bottom plate 12 is formed in the bottom plate 12 of the metal can 10. However, as shown in Fig. 13, a recess 123 having a relatively small projected area A in the axial direction may be formed in the bottom plate 12, or as shown in Fig. 14, multiple recesses 123 may be formed in the bottom plate 12. When multiple recesses 123 are formed in the bottom plate 12, the depths D of the recesses 123 may be the same or different. When multiple recesses 123 are formed in the bottom plate 12, the total projected area of ​​these recesses 123 is defined as A, and the ratio of the projected area A of the recess 123 to the projected area A0 of the bottom plate 12 is measured.

[0088] In each of the above embodiments and the examples shown in FIGS. 13 and 14 , the recess 123 has a rectangular shape when viewed from the bottom of the metal can 10, and the longitudinal direction of the recess 123 coincides with the longitudinal direction of the rectangular cylindrical peripheral wall 11. However, the shape of the recess 123 when viewed from the bottom of the metal can 10 is not limited to this. For example, as shown in FIG. 15 , the recess 123 may extend in the short direction of the peripheral wall 11 when viewed from the bottom of the metal can 10. In this case, multiple recesses 123 or a single recess 123 may be formed in the bottom plate 12.

[0089] 13 to 15, the recesses 123 are formed in the bottom plate 12 so as to be substantially symmetrical with respect to the width center line CL in the longitudinal direction of the bottom plate 12 when viewed from the bottom of the metal can 10. However, the recesses 123 may also be formed so as to be asymmetrical with respect to the width center line CL when viewed from the bottom of the metal can 10.

[0090] 13 to 15, as in the second embodiment, after forming the recess 123 in the bottom plate 12, the recess 123 may be crushed in the axial direction of the peripheral wall 11 to form the high hardness portion 124. In this case, the entire recess 123 may be crushed, or only a part of the recess 123 may be crushed. Furthermore, at the position where the recess 123 is crushed, the bottom plate 12 may be generally flat, or a step may remain.

[0091] In each of the above-described embodiments, the bottom surface of the recess 123 formed in the bottom plate 12 is substantially flat in a vertical cross-sectional view of the metal can 10. However, the shape of the recess 123 in a vertical cross-sectional view of the metal can 10 is not limited to this. For example, the recess 123 may be entirely arc-shaped in a vertical cross-sectional view of the metal can 10. [Example]

[0092] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0093] [First Example] In order to confirm the effects of the present disclosure, analysis was performed using general-purpose analysis software (LS-DYNA, manufactured by JSOL Corporation). Specifically, for the shapes shown in Figures 5, 13, 14, and 16 to 18, recesses were formed in the bottom plates of metal cans formed by drawing, and then springback analysis was performed to evaluate the effect of reducing twist in the metal cans.

[0094] The common conditions are as follows: Metal plate (material) thickness: 0.3 mm -Dimensions of metal can after drawing Width in short direction WS: 26.5 mm x Width in long direction WL: 148.0 mm x Height H: 95.0 mm Aspect ratio: 5.6

[0095] The conditions for each analysis model are shown in Table 1. In Table 1, "symmetric" means that one or more recesses are provided in the bottom plate so as to be symmetrical with respect to the longitudinal width center line CL, and "asymmetric" means that one or more recesses are provided in the bottom plate so as to be asymmetrical with respect to the longitudinal width center line CL.

[0096] [Table 1]

[0097] The effect of reducing twisting of the metal can was evaluated using the twist angle and stress difference.

[0098] The twist angle was calculated by performing a springback analysis on each analytical model (after recess formation) using the following procedure. Specifically, for the wide first side wall, the springback amount was measured at three axially aligned measurement points (the edge on the opening side, a point 40 mm axially away from the opening, and a point 80 mm axially away from the opening) at position P1, 50 mm from the center of the longitudinal width toward one of the second side walls, and position P2, 50 mm from the center of the longitudinal width toward the other second side wall. For each of positions P1 and P2, an approximation line for the springback amount at the three measurement points was created. The difference between the slope of the approximation line for the springback amount at position P1 and the slope of the approximation line for the springback amount at position P2 was determined to be the twist angle. It can be determined that the smaller the twist angle, the more the twist of the metal can is reduced.

[0099] The stress difference was measured for each analytical model (after recess formation) before springback analysis. Specifically, the longitudinal stress in each of the regions R1, located in the center of the bottom plate in the longitudinal direction, and regions R2 and R3, located at both ends in the longitudinal direction, was measured, and the average stress value was calculated. The average of the average stress value in region R2 and the average stress value in region R3 was then calculated, and the absolute value of the difference between this average stress value and the average stress value in the center region R1 was determined as the stress difference. It can be concluded that the smaller the stress difference, the more uniform the stress in the bottom plate and the greater the reduction in twisting of the metal can.

[0100] The twist angle and stress difference for each analysis model are shown in Figures 19 and 20. As shown in Figures 19 and 20, when a recess is provided on the bottom surface, the twist angle and stress difference are significantly smaller than when no recess is provided. Therefore, it can be said that providing a recess on the bottom surface can reduce twisting of metal cans.

[0101] Figure 19 shows the relationship between the ratio of the projected area of ​​the recess to the bottom plate: A / A0 and the twist angle. As shown in Figure 19, when recesses are formed in the bottom plate so as to be symmetrical with respect to the longitudinal width center line CL, it was confirmed that the twist angle is almost 0° regardless of A / A0. On the other hand, when recesses are formed in the bottom plate so as to be asymmetrical with respect to the longitudinal width center line CL, the twist angle is reduced compared to when no recesses are formed, but the twist angle is slightly larger compared to when recesses are formed in the bottom plate so as to be symmetrical with respect to the longitudinal width center line CL.

[0102] Figure 20 shows the relationship between the ratio of the projected area of ​​the recess to the bottom plate: A / A0, and the stress difference. Figure 21 shows the relationship between the stress difference and the torsion angle. There was almost no difference in the stress difference between when the recess was formed in the bottom plate so as to be asymmetric with respect to the longitudinal width center line CL and when the recess was formed in the bottom plate so as to be asymmetric with respect to the longitudinal width center line CL.

[0103] This analysis confirmed that by providing a recess in the bottom plate, the stress in the bottom plate can be made uniform, and twisting of the metal can can be reduced.

[0104] [Second Example] For an analytical model with a recess similar to that of No. 1 in Table 1, an analysis was conducted in which the recess in the bottom plate was crushed with a flat tool to evaluate the effect of reducing twisting of the metal can. It was confirmed that even when the recess in the bottom plate was crushed, the same effect as No. 1 was obtained in reducing twisting of the metal can.

[0105] For the analytical model of this example, the Vickers hardness of the bottom plate was measured after the recess was crushed. In this example, the test force was 0.5 N, and the Vickers hardness was measured at 1 mm intervals on the cross section of the bottom plate from the main body toward the corners. The Vickers hardness measurement results are shown in Figure 22.

[0106] As shown in Figure 22, when a recess was formed in the bottom plate and then crushed (with bottom plate correction), it was confirmed that a high-hardness portion with a Vickers hardness greater than that of other portions of the bottom plate was formed at the position where the recess was crushed. The Vickers hardness of the high-hardness portion was 10 HV or more greater than that of other portions of the bottom plate. On the other hand, when a recess was not formed in the bottom plate (without bottom plate correction), the bottom plate did not include a high-hardness portion with a Vickers hardness greater than that of other portions by 10 HV or more. [Explanation of symbols]

[0107] 10, 10A: Metal can 11: Peripheral wall 12: Bottom plate 123: Recess 124: High hardness part 20:Battery 30: Lid 40:Metal plate 101,102: Intermediate molded product

Claims

1. A method for manufacturing a metal can, comprising: A first step of preparing a metal plate; a second step of drawing the metal plate to obtain an intermediate formed product including a rectangular cylindrical peripheral wall and a bottom plate closing one axial end of the peripheral wall; a third step of forming a recess in the bottom plate, the recess having a shape recessed toward the inside of the intermediate molded product; A manufacturing method comprising:

2. The method of claim 1, A manufacturing method in which a projected area of ​​the recess in the axial direction is 1.0% or more of a projected area of ​​the bottom plate in the axial direction.

3. The method of claim 1, The manufacturing method, wherein the peripheral wall has an aspect ratio of 5.0 or more and 15.0 or less when viewed in a cross section perpendicular to the axial direction.

4. The method of claim 1, The third step is carried out in conjunction with molding of the intermediate molded product within the second step.

5. The method of claim 1 further comprising: a fourth step of crushing at least a portion of the recess in the axial direction; A manufacturing method comprising:

6. The method of claim 1, The manufacturing method, wherein the metal plate has a thickness of 0.1 mm or more and 0.8 mm or less.

7. A metal can, A rectangular cylindrical peripheral wall, a bottom plate that closes one axial end of the peripheral wall and has a recess formed therein that is recessed toward the inside of the metal can; A metal can comprising:

8. The metal can according to claim 7, A metal can, wherein a projected area of ​​the recess in the axial direction is 1.0% or more of a projected area of ​​the bottom plate in the axial direction.

9. A metal can, A rectangular cylindrical peripheral wall, a bottom plate that closes one axial end of the peripheral wall; Equipped with The bottom plate includes a high-hardness portion having a Vickers hardness that is 10 HV or more higher than that of other portions of the bottom plate.

10. A method for manufacturing a battery, comprising: a step of preparing the metal can according to any one of claims 7 to 9 as a battery case and a lid; a step of joining the lid to the metal can to seal the metal can; A manufacturing method comprising:

11. A battery, The metal can according to any one of claims 7 to 9 as a battery case; a lid body joined to the metal can to seal the metal can; A battery.

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