Manufacturing method of metal can and die set

Abstract

To provide a manufacturing method of a metal can which can obtain metal cans having a small curvature radius of each corner part between side walls while inhibiting reduction of a plate thickness.SOLUTION: A manufacturing method includes: a step in which an untreated can (20) is prepared; and a step in which the untreated can (20) is corrected by using a die set (10, 10A) to obtain a metal can (30). The untreated can (20) includes: a pair of first side walls (21); corner parts (23); and a pair of second side walls (22). The die set (10, 10A) includes: a pair of first dies (11); a pair of second dies (12); and a core (13, 13A). In the step in which the untreated can (20) is corrected, the first side walls (21) and the corner parts (23) are pressed against the core (13, 13A) by the first dies (11) in a state where the second side walls (22) are supported by the second dies (12) and the core (13, 13A).SELECTED DRAWING: Figure 2B

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a metal can and a mold set.

Background Art

[0002] In recent years, the popularization of electric vehicles including battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs) has been promoted. In electric vehicles, for example, non-aqueous electrolyte secondary batteries are used. In electric vehicles, in general, a plurality of batteries connected to each other are mounted in order to ensure high output and high capacity.

[0003] In electric vehicles and the like, an increase in the size and energy density of batteries is required. By increasing the size of the battery, the number of batteries (number of mounted cells) mounted on an electric vehicle or the like can be reduced. As a result, since the area of the battery case per unit area in the battery mounting space is reduced, an increase in energy density can be expected. For example, when a rectangular tubular metal can is used as the battery case, the smaller the radius of curvature of the corner portion between the side walls of the metal can, the more closely the batteries can be arranged, and the loss of the battery mounting space can be reduced.

[0004] A rectangular tubular metal can is generally manufactured by deep drawing of a metal plate. For example, as described in Patent Document 1, when manufacturing a metal can, multi-stage deep drawing is performed on a metal plate as a material. In Patent Document 1, a first intermediate cup body having a substantially elliptical cross section is formed from the metal plate by deep drawing. Next, a second intermediate cup body is formed from the first intermediate cup body by multi-stage redrawing. The second intermediate cup body has a substantially elliptical cross section in which the ratio of the minor axis to the major axis (minor axis / major axis) is smaller than that of the first intermediate cup body. Thereafter, redrawing and multi-stage ironing are performed on the second intermediate cup body to manufacture a rectangular tubular metal can.

[0005] In addition to the side walls of the metal can being thinned by ironing during deep drawing, the corners between the side walls on the outer surface of the metal can may be reduced in diameter. However, it is difficult to apply ironing to the manufacture of thin-walled metal cans. Specifically, in ironing, the clearance between the dies is set smaller than the thickness of the metal sheet that is the material. Then, using these dies, a metal can with a thinner wall than the original metal sheet is formed. When the thickness of the original metal sheet is small, the load applied to the metal sheet in the thickness direction from the die in ironing becomes large, and deformation or damage of the die may occur. Even when manufacturing a large metal can, a large load is likely to occur on the die, and it may be difficult to apply ironing. When forming a metal can by only deep drawing without performing ironing, it is difficult to reduce the diameter of the corner portion between the side walls.

[0006] On the other hand, for example, Patent Document 2 discloses a method of manufacturing a three-dimensional molded product by subjecting an aluminum resin composite laminate to drawing. In Patent Document 2, a corner portion is pressed from the inside to the outside of the three-dimensional molded product by a pressing jig. Patent Document 2 describes that thereby, the radius of curvature of the corner portion can be reduced to less than the thickness of the aluminum resin composite laminate.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In Patent Document 2, the diameter of the corner portion is reduced by pressing the corner portion from the inside to the outside of the three-dimensional molded product with a pressing jig. However, in this method, there is a possibility that the plate thickness may decrease at the corner portion. In particular, when the three-dimensional molded product is thin, there is a risk of cracking at the corner portion due to the decrease in plate thickness.

[0009] An object of the present disclosure is to provide a method for manufacturing a metal can that can obtain a metal can with a small radius of curvature at the corner portion between the side walls while suppressing a decrease in plate thickness.

Means for Solving the Problems

[0010] The method for manufacturing a metal can according to the present disclosure includes a step of preparing a blank can and a step of using a mold set to correct the blank can to obtain a metal can. The blank can includes a pair of first side walls, a corner portion, and a pair of second side walls. The pair of first side walls are arranged to face each other. The corner portion is provided on both sides of each of the first side walls. The pair of second side walls are each connected to both of the first side walls via the corner portion. The mold set includes a pair of first molds, a pair of second molds, and a core. The pair of first molds are arranged outside the blank can and face the first side walls respectively. The pair of second molds are arranged outside the blank can and face the second side walls respectively. The core is arranged inside the blank can in contact with the second side wall and with a gap formed between each of the core and the first side walls. In the step of correcting the blank can, with the second side wall supported by the second mold and the core, the first side wall and the corner portion are pressed toward the core side by the first mold.

Effects of the Invention

[0011] According to the method for manufacturing a metal can according to the present disclosure, it is possible to obtain a metal can with a small radius of curvature at the corner portion between the side walls while suppressing a decrease in plate thickness.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 2E

Figure 2F

Figure 3

Figure 4

Figure 5

Figure 6

MODE FOR CARRYING OUT THE INVENTION

[0013] The manufacturing method of a metal can according to the embodiment includes a step of preparing a blank can, and a step of using a mold set to correct the blank can to obtain a metal can. The blank can includes a pair of first side walls, a corner portion, and a pair of second side walls. The pair of first side walls are arranged to face each other. The corner portion is provided on both sides of each of the first side walls. The pair of second side walls are each connected to both of the first side walls via the corner portion. The mold set includes a pair of first molds, a pair of second molds, and a core. The pair of first molds are arranged outside the blank can and face the first side walls respectively. The pair of second molds are arranged outside the blank can and face the second side walls respectively. The core is arranged inside the blank can so as to contact the second side wall and form a gap between each of the core and the first side walls. In the step of correcting the blank can, with the second side wall supported by the second mold and the core, the first side wall and the corner portion are pressed toward the core side by the first mold (first configuration).

[0014] In the manufacturing method according to the first configuration, the blank can is corrected using a mold set including a pair of first molds, a pair of second molds, and a core. When correcting the blank can, the core is arranged inside the blank can in a state of contacting the second side wall of the blank can and forming a gap between each of the core and the first side walls of the blank can. In the step of correcting the blank can, with the second side wall of the blank can supported by the second mold and the core, the first side wall of the blank can and the corner portions provided on both sides of each first side wall are pressed toward the core side by the first mold. As a result, the corner portions of the blank can are each crushed by the first mold, deformed so as to have a sharp corner, and reduced in diameter. Therefore, a metal can with a small radius of curvature of the corner portion between the first side wall and the second side wall can be obtained.

[0015] In the manufacturing method according to the first configuration, when reducing the diameter of the corner portion between the first side wall and the second side wall, the first mold is pressed against the blank can from the outside, and the first side wall and the corner portion are compressed inside the blank can. In this case, an increase in the cross-sectional line length of the first side wall and the corner portion is less likely to occur. Therefore, a reduction in the plate thickness due to correction can be suppressed in the first side wall and the corner portion.

[0016] In the manufacturing method according to the first configuration, when the radius of curvature of the corner portion before correction is R0 (mm), the radius of curvature of the corner portion after correction is R1 (mm), and the displacement amount of the first side wall due to correction is ΔX (mm), R0, R1, and ΔX may satisfy the following formula (second configuration). ΔX≦(R0 - 0.5708R0) - (R1 - 0.5708R1) + 2.0

[0017] According to the second configuration, the linear length of the portion of the material can that is deformed by the first mold, that is, the first side wall and the corner portions provided on both sides thereof, does not substantially change before and after correction. In this case, not only can the reduction in plate thickness due to correction be suppressed, but also the occurrence of flash due to correction and wrinkles resulting therefrom can be suppressed.

[0018] In the manufacturing method according to the first or second configuration, the corner portion before correction may have a radius of curvature of 20.0 mm or less (third configuration).

[0019] In the manufacturing method according to any one of the first to third configurations, the first side wall may be formed of a steel plate. In this case, the first side wall can have a plate thickness of 0.1 mm or more and 2.0 mm or less (fourth configuration).

[0020] Since the steel plate is high-strength, when ironing is applied to a material can formed of a steel plate, the load on the mold is large and the mold is likely to deform or be damaged. Therefore, when the material can is formed of a steel plate, it is difficult to apply ironing to the material can. When the steel plate is thin, it becomes even more difficult to apply ironing, and it is difficult to reduce the diameter of the corner portion by ironing. However, in the manufacturing method according to the embodiment, the diameter of the corner portion between the side walls of the material can can be reduced without applying ironing. That is, when the first side wall and the corner portion of the material can are pressed against the core side by the first mold, the corner portion is deformed and its radius of curvature becomes smaller. Therefore, even when the first side wall continuous with the corner portion is formed of a steel plate and is as thin as 0.1 mm or more and 2.0 mm or less, it is possible to easily reduce the diameter of the corner portion.

[0021] The mold set according to the embodiment is for correcting a stock can. The stock can includes a pair of first side walls, a corner portion, and a pair of second side walls. The pair of first side walls are arranged to face each other. The corner portion is provided on both sides of each of the first side walls. The pair of second side walls are each connected to both of the first side walls via the corner portion. The mold set includes a core, a pair of first molds, and a pair of second molds. The core includes a pair of first side surfaces and a pair of second side surfaces. The pair of second side surfaces connect the first side surfaces to each other. The core is disposed inside the stock can when the mold set is in use. The pair of first molds respectively correspond to the first side surfaces. The pair of first molds are disposed outside the stock can when the mold set is in use. The pair of second molds respectively correspond to the second side surfaces. The pair of second molds are disposed outside the stock can when the mold set is in use. The first mold is configured to crush the first side wall and the corner portion of the stock can toward the first side surface side. The second mold is configured to support the second side wall of the stock can together with the second side surface (fifth configuration).

[0022] The method for manufacturing a metal can according to another embodiment includes a step of preparing a stock can and a step of using a mold set to correct the stock can to obtain a metal can. The stock can includes a pair of first side walls, a corner portion, and a pair of second side walls. The pair of first side walls are arranged to face each other. The corner portion is provided on both sides of each of the first side walls. The pair of second side walls are each connected to both of the first side walls via the corner portion. The mold set includes a pair of first molds, a pair of second molds, and a core. The pair of first molds are disposed outside the stock can. The pair of second molds are disposed outside the stock can. The core is disposed inside the stock can such that it contacts the second side wall and a gap is formed between the core and each of the first side walls. In the step of correcting the stock can, with the second side wall supported by the second mold and the core, the first side wall and the corner portion are pressed against the core side by the first mold.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In these drawings, the same or corresponding components are denoted by the same reference numerals, and the same description will not be repeated.

[0024] <First Embodiment> [Configuration of Mold Set] FIG. 1 is a perspective view schematically showing a mold set 10 according to this embodiment. Referring to FIG. 1, the mold set 10 is used to correct a rectangular tube-shaped material can 20. The mold set 10 includes a pair of first molds 11, a pair of second molds 12, and a core 13. The first mold 11 and the second mold 12 are arranged outside the material can 20 when the mold set 10 is in use. The core 13 is arranged inside the material can 20 when the mold set 10 is in use.

[0025] The core 13 has, for example, a substantially rectangular parallelepiped shape or a substantially cubic shape. The core 13 includes a pair of first side surfaces 131 and a pair of second side surfaces 132. The core 13 can further include four corner portions 133.

[0026] In the core 13, one first side surface 131 is arranged on the opposite side of the other first side surface 131. Corner portions 133 are continuously provided on both sides of each first side surface 131. One second side surface 132 is arranged on the opposite side of the other second side surface 132. Each of the second side surfaces 132 connects the first side surfaces 131 to each other. More specifically, each of the second side surfaces 132 is connected to both of the first side surfaces 131 via the corner portions 133.

[0027] In this embodiment, the length between the first side surfaces 131 is greater than the length between the second side surfaces 132. However, the length between the first side surfaces 131 may be less than or equal to the length between the second side surfaces 132. Hereinafter, for the sake of convenience of explanation, regarding the mold set 10 and the material can 20, the direction in which the first side surfaces 131 are arranged may be referred to as the width direction, and the direction in which the second side surfaces 132 are arranged may be referred to as the depth direction. Also, regarding the mold set 10 and the material can 20, the direction perpendicular to the width direction and the depth direction may be referred to as the height direction.

[0028] In the example shown in FIG. 1, the core 13 further includes a top surface 134 and a bottom surface 135. The top surface 134 is connected to the side surfaces 131 and 132 at one end side in the height direction. The bottom surface 135 is connected to the side surfaces 131 and 132 at the other end side in the height direction. Chamfering such as R chamfering or C chamfering may be applied to the corners between the top surface 134 and the side surfaces 131 and 132. Similarly, chamfering such as R chamfering or C chamfering may be applied to the corners between the bottom surface 135 and the side surfaces 131 and 132.

[0029] A pair of first molds 11 are arranged on both sides of the core 13 in the width direction. The first molds 11 respectively correspond to the first side surface 131 of the core 13. Each of the first molds 11 includes a pressing surface 111. The pressing surface 111 is provided on the surface on the core 13 side in each of the first molds 11.

[0030] A pair of second molds 12 are arranged on both sides of the core 13 in the depth direction. The second molds 12 respectively correspond to the second side surface 132 of the core 13. Each of the second molds 12 includes a supporting surface 121. The supporting surface 121 is provided on the surface on the core 13 side in each of the second molds 12.

[0031] [Method for manufacturing a metal can] Next, a method for manufacturing a metal can using the mold set 10 will be described with reference to FIGS. 2A to 2F. Although not particularly limited, the metal can to be manufactured is, for example, a battery case. The method for manufacturing a metal can according to the present embodiment includes a preparation step and a correction step.

[0032] (Preparation step) Referring to FIG. 2A, in the preparation step, a blank can 20 is prepared. The blank can 20 typically has a bottomed rectangular tube shape. The blank can 20 includes a pair of first side walls 21, a pair of second side walls 22, and four corner portions 23. In the example of FIG. 2A, the blank can 20 further includes a bottom plate 24.

[0033] A pair of first side walls 21 are arranged to face each other. Corner portions 23 are provided on both sides of each of the first side walls 21. The corner portions 23 are provided continuously with each of the first side walls 21. A pair of second side walls 22 are arranged to face each other and connect the first side walls 21 to each other. The second side walls 22 are each connected to both of the first side walls 21 via the corner portions 23.

[0034] The side walls 21, 22 each have a substantially flat shape. The side walls 21, 22 have, for example, a substantially or approximately rectangular shape. Each of the corner portions 23 extends along the side walls 21, 22 between the side walls 21, 22. Each of the corner portions 23 can have a substantially arc shape when viewed in a cross section (transverse cross section) perpendicular to its extending direction. The side walls 21, 22 and the corner portions 23 form a substantially rectangular tube-shaped peripheral wall in the material can 20.

[0035] The bottom plate 24 seals one axial end of the substantially rectangular tube-shaped peripheral wall. The material can 20 has an opening 25 at the other axial end of the peripheral wall.

[0036] The material can 20 is formed of a metal plate. The material can 20 is typically formed by deep drawing of a metal plate. The material can 20 may be formed, for example, by performing multiple drawing processes (multi-stage drawing processes) on a metal plate.

[0037] The metal plate forming the material can 20 may be an aluminum alloy plate or a steel plate. The steel plate includes, for example, a stainless steel plate or a plated steel plate. Alternatively, the material can 20 may be formed of a metal plate made of titanium or copper, or an alloy thereof. The material can 20 only needs to be formed of a metal plate, and its material is not particularly limited. However, when the manufactured metal can is a battery case, the material can 20 is preferably formed of a nickel-plated steel plate or a stainless steel plate.

[0038] The thickness of the blank can 20 is not particularly limited. The thickness of the blank can 20 can be appropriately selected according to, for example, the use of the metal can to be manufactured. When the metal can to be manufactured is a battery case, the thickness of the side walls 21, 22 of the blank can 20 is, for example, 0.1 mm or more and 3.0 mm or less. When the metal can to be manufactured is a battery case and the blank can 20 is formed of a steel plate, the thickness of the side walls 21, 22 is, for example, 0.1 mm or more and 2.0 mm or less. The thickness of the bottom plate 24 may be the same as that of the side walls 21, 22 or different from that of the side walls 21, 22.

[0039] (Straightening process) In the straightening process, the blank can 20 is straightened using the mold set 10 to obtain a metal can. FIGS. 2B and 2C are diagrams (cross-sectional views) showing cross-sections of the mold set 10 and the blank can 20 in the straightening process cut by a plane perpendicular to the height direction.

[0040] Referring to FIG. 2B, when starting the straightening process, the core 13 of the mold set 10 is disposed inside the blank can 20. The core 13 is disposed inside the blank can 20 so as to be in contact with the second side wall 22 of the blank can 20 and to form a gap between each of the core 13 and the first side wall 21. Before the start of the straightening process, the second side surfaces 132 of the core 13 are in contact with the inner surfaces of the second side wall 22 of the blank can 20, respectively. The second side surfaces 132 of the core 13 preferably contact the entire or substantially the entire second side wall 22 of the blank can 20.

[0041] On one hand, the first side surfaces 131 of the cores 13 are respectively opposed to the inner surface of the first side walls 21 of the material can 20 with a gap therebetween. That is, when the distance between the first side surfaces 131 of the cores 13 is the width W0 and the distance between the outer surfaces of the first side walls 21 of the material can 20 is the width W1, the width W1 of the material can 20 is larger than the width W0 of the cores 13 even when subtracting the plate thicknesses of both first side walls 21. The first side surfaces 131 of the cores 13 preferably oppose the whole or substantially the whole of the first side walls 21 of the material can 20. The first side surfaces 131 of the cores 13 are arranged, for example, outside the boundary between the second side wall 22 and the corner portion 23 of the material can 20 in the width direction of the mold set 10. However, at the start point of the correction process, the first side surfaces 131 of the cores do not contact the first side walls 21 of the material can 20. The distance (clearance) between the first side surfaces 131 of the cores and the first side walls 21 of the material can 20 may be, for example, 100% or more and 150% or less of the plate thickness of the first side walls 21.

[0042] When the metal can to be manufactured is a battery case, the width W1 of the material can 20 is, for example, 100.0 mm or more and 400.0 mm or less. However, in the material can 20, when the distance between the first side walls 21 is shorter than the distance between the second side walls 22, the width W1 may be 10.0 mm or more and 50.0 mm or less. When the distance between the second side walls 22 is the depth D1, when the distance between the first side walls 21 is shorter than the distance between the second side walls 22, the depth D1 may be 100.0 mm or more and 400.0 mm or less. When the distance between the first side walls 21 is longer than the distance between the second side walls 22, the depth D1 may be 10.0 mm or more and 50.0 mm or less. The length of the material can 20 in the height direction is, for example, 80.0 mm or more and 130.0 mm or less. However, the dimensions of the material can 20 are not limited to these.

[0043] In the correction process, the bottom surface 135 (FIG. 1) of the core 13 may contact the bottom plate 24 (FIG. 2A) of the material can 20 from the inside. The top surface 134 (FIG. 1) of the core 13 may protrude outward in the height direction from the opening 25 (FIG. 2A) of the material can 20.

[0044] When starting the correction process, the first die 11 of the die set 10 is arranged outside the material can 20. The first dies 11 face the first side wall 21 of the material can 20 respectively. Before the start of the correction process, the first dies 11 face the outer surface of the first side wall 21 of the material can 20 with a gap therebetween. More specifically, each of the first dies 11 faces the first side wall 21 of the material can 20 by means of the pressing surface 111. Each of the first dies 11 preferably faces the entire or substantially the entire corresponding first side wall 21.

[0045] When starting the correction process, the second die 12 of the die set 10 is arranged outside the material can 20. The length of the second die 12 in the width direction of the die set 10 is preferably equal to or greater than the width W1 of the material can 20. The second dies 12 face the second side wall 22 of the material can 20 respectively. The second dies 12 are in contact with the outer surface of the second side wall 22 of the material can 20 respectively. More specifically, each of the second dies 12 contacts the second side wall 22 of the material can 20 by means of the support surface 121. The second side wall 22 of the material can 20 is supported from the inside and outside by the second side surface 132 of the core 13 and the support surface 121 of the second die 12 respectively. Each of the second dies 12 preferably supports the entire or substantially the entire corresponding second side wall 22 together with the core 13.

[0046] Referring to FIGS. 2B and 2C, in the correction process, with the second side wall 22 of the material can 20 supported by the second mold 12 and the ejector pin 13, the first mold 11 presses the first side wall 21 and the corner portion 23 of the material can 20 toward the ejector pin 13 side. More specifically, by moving the first mold 11 closer to the ejector pin 13 respectively, the corresponding first side wall 21 and the corner portion 23 are pressed and deformed inside the material can 20 by the respective pressing surfaces 111 of the first mold 11. The first side wall 21 and the corner portion 23 of the material can 20 are deformed so as to be crushed by the first mold 11 and are clamped between the first mold 11 and the ejector pin 13. At this time, the support surface 121 of the second mold 12 and the second side surface 132 of the ejector pin 13 support the entire second side wall 22 so that the second side wall 22 of the material can 20 does not move in the depth direction of the mold set 10. The first mold 11 compresses the entire first side wall 21 and the corner portion 23 of the material can 20 inward in the width direction of the mold set 10. As a result, the material can 20 is corrected and becomes a bottomed square cylindrical metal can 30 as shown in FIG. 2D.

[0047] FIG. 2E is a cross-sectional view of the material can 20 before correction, and is a view showing an enlarged part to be deformed by correction. FIG. 2F is a cross-sectional view of the metal can 30 after correction, and is a view showing an enlarged part deformed by correction. In FIG. 2F, the material can 20 before correction is also shown by a two-dot chain line.

[0048] As shown in FIG. 2E, in the material can 20 before correction, each of the corner portions 23 continuous with the first side wall 21 has a radius of curvature R0. The radius of curvature R0 is the radius of curvature of the corner portion 23 on the outer surface of the material can 20. The radius of curvature R0 is defined as the radius of a circle passing through three points, namely, both R stops of the corner portion 23 and the midpoint between them. The radius of curvature R0 can be measured, for example, at a position 5.0 mm in the height direction from the opening 25 (FIG. 2A) of the material can 20.

[0049] When the radius of curvature R0 is too large, the material can 20 may be, for example, oblong in plan view. From the viewpoint of ensuring the rectangular shape of the material can 20, the radius of curvature R0 is preferably 20.0 mm or less. The radius of curvature R0 is preferably 15.0 mm or less. When the radius of curvature R0 is small, the necessity of reducing the diameter of the corner portion 23 by correction is reduced. Therefore, the radius of curvature R0 is, for example, 3.0 mm or more, and preferably 5.0 mm or more.

[0050] Regarding each first side wall 21 and the corner portions 23 on both sides thereof, the linear length from the R stop of one corner portion 23 (on the second side wall 22 side) to the R stop of the other corner portion 23 (on the second side wall 22 side) is defined as L1. The linear length L1 is the length measured along the outer surface of the material can 20 from the R stop of one corner portion 23 to the R stop of the other corner portion 23 in the cross section of the material can 20 at the measurement position of the radius of curvature R0. The linear length L1 can be divided into the linear lengths L of both corner portions 23 1-1 and the linear length L of the first side wall 21 1-2 as described above.

[0051] The first side wall 21 and the corner portions 23 on both sides thereof are deformed so as to be crushed in the correction process. As a result, the diameter of the corner portion 23 is reduced. When the correction process is performed, the first side wall 21 and the corner portions 23 on both sides thereof become the straight portions 31, 32 and the corner portion 33 in the corrected metal can 30 as shown in FIG. 2F.

[0052] The straight portions 31 and the corner portion 33 are arranged on both sides of the straight portion 32. The straight portion 31 is connected to the straight portion 32 via each of the corner portions 33. In the metal can 30, each of the corner portions 33 has a radius of curvature R1. The radius of curvature R1 is the radius of curvature of the corner portion 33 on the outer surface of the metal can 30. The corner portion 33 may be an arc shape having a curvature, or may be a pin angle shape having a curvature of 0.

[0053] When the corner portion 33 has a curvature (curvature ≠ 0), the radius of curvature R1 is the radius of a circle passing through the two R stops of the corner portion 33 and the midpoint of these two points. This radius of curvature R1 can be measured, for example, at a position 5.0 mm in the height direction from the opening of the metal can 30. The radius of curvature R1 is, for example, 0 mm or more and 10.0 mm or less. When the corner portion 33 is pin-angled, the radius of curvature R1 is defined as 0.

[0054] Regarding the straight portions 31, 32 and the corner portion 33, let the line length from the end of one straight portion 31 (on the second side wall 22 side) to the end of the other straight portion 31 (on the second side wall 22 side) be L2. The end of the straight portion 31 is the portion that was the R stop of the corner portion 23 in the raw material can 20 before correction (Fig. 2E). The line length L2 is the length measured along the outer surface of the metal can 30 from the end of one straight portion 31 to the end of the other straight portion 31 in the cross section of the metal can 30 at the measurement position of the radius of curvature R1. The line length L2 can be divided into the line length L of the straight portion 31 2-1 , the line length L of the corner portion 33 2-2 , and the line length L of the straight portion 32 2-3 . It is preferable that the line length L2 is substantially or almost equal to the line length L1 (Fig. 2E) of the portion to be deformed in the raw material can 20 before correction.

[0055] In the correction process, each of the first side wall 21 and the corner portion 23 is compressed in the width direction by the first mold 11 (Figs. 2B and 2C), so that the width W1 (Fig. 2B) of the raw material can 20 becomes shorter. As shown in Fig. 2F, when the displacement amount of the first side wall 21 due to correction is ΔX, ΔX can be expressed by the following formula (1). When the cross section of the raw material can 20 before correction and the cross section of the metal can 30 after correction are overlapped so that their centers coincide, ΔX is the distance from the first side wall 21 of the raw material can 20 to the straight portion 32 of the metal can 30. The width W0 (Fig. 2B) of the core 13 corresponds to the width W1 (Fig. 2B) of the raw material can 20 before correction minus 2ΔX and the plate thicknesses of both first side walls 21. ΔX = R0 - (L 2-1 + R1) ···(1)

[0056] Referring again to FIG. 2E, in the raw material can 20 before correction, the wire length L of each corner portion 23 1-1 can be calculated as 1 / 4×2πR0. Also, in the raw material can 20 before correction, the wire length L of the first side wall 21 1-2 can be calculated by subtracting 2R0 from the depth D1, which is the distance between the second side walls 22. Therefore, the wire length L1 of the portion to be deformed in the raw material can 20 before correction is represented by the following formula (2). L1 = 2L 1-1 + L 1-2 = 2(1 / 4×2πR0)+(D1 - 2R0) = D1 + 1.1416R0 ···(2)

[0057] On the other hand, referring to FIG. 2F, in the metal can 30 after correction, the wire length L of each corner portion 33 2-2 can be calculated as 1 / 4×2πR1. Since the depth D1 (FIG. 2E), which is the distance between the second side walls 22, does not substantially change before and after correction, the wire length L of the straight portion 32 2-3 can be calculated by subtracting 2R1 from D1. Therefore, the wire length L2 of the portion after deformation in the metal can 30 is represented by the following formula (3). L2 = 2L 2-1 + 2L 2-2 + L 2-3 = 2L 2-1 + 2(1 / 4×2πR1)+(D1 - 2R1) = 2L 2-1 + D1 + 1.1416R1 ···(3)

[0058] If the wire lengths L1 and L2 before and after correction are in the relationship of L1 = L2 + α or L1 = L2 - β (α and β are constants of 0 or more (mm)), the wire length L of the straight portion 31 2-1 can be expressed by the following formula (4-1) or formula (4-2) using formulas (2) and (3). D1 + 1.1416R0 = (2L 2-1 + D1 + 1.1416R1)+α L 2-1 = 0.5708(R0 - R1)-α / 2 ···(4-1) D1 + 1.1416R0 = (2L 2-1 + D1 + 1.1416R1) - β L 2-1 = 0.5708(R0 - R1) + β / 2 ···(4 - 2)

[0059] Substituting Equation (4 - 1) into Equation (1), the displacement amount ΔX in the width direction of the first side wall 21 in the correction process is represented by the following Equation (5). ΔX = R0 - (0.5708(R0 - R1) - α / 2 + R1) = (R0 - 0.5708R0) - (R1 - 0.5708R1) + α / 2 ···(5)

[0060] α is the difference between the wire length L1 before correction and the wire length L2 after correction. When L1 = L2 + α, the wire length L2 after correction is less than or equal to the wire length L1 before correction. When α is too large, burrs are likely to occur due to correction. From the perspective of suppressing the generation of wrinkles caused by burrs, α is preferably, for example, 4.0 mm or less. In this case, from Equation (5), the displacement amount ΔX in the width direction of the first side wall 21 in the correction process can satisfy the following Equation (6). However, the units of ΔX, R0, and R1 in Equation (6) are all mm. ΔX ≤ (R0 - 0.5708R0) - (R1 - 0.5708R1) + 2.0 ···(6)

[0061] To make it easier to further suppress the generation of wrinkles caused by burrs, α is more preferably 2.0 mm or less. That is, the constant 2.0 on the right side of the above Equation (6) can be replaced with 1.0.

[0062] Substituting Equation (4 - 2) into Equation (1), the displacement amount ΔX in the width direction of the first side wall 21 in the correction process is represented by the following Equation (7). ΔX = R0 - (0.5708(R0 - R1) + β / 2 + R1) = (R0 - 0.5708R0) - (R1 - 0.5708R1) - β / 2 ···(7)

[0063] β is the difference between the wire length L1 before correction and the wire length L2 after correction. When L1 = L2 - β, the wire length L2 after correction is equal to or greater than the wire length L1 before correction. The larger β is, the more likely it is that the plate thickness will decrease due to correction. From the perspective of suppressing the decrease in plate thickness, β is preferably, for example, 2.0 mm or less. In this case, from Equation (7), the displacement amount ΔX in the width direction of the first side wall 21 in the correction process can satisfy the following Equation (8). However, the units of ΔX, R0, and R1 in Equation (8) are all in mm. ΔX≧(R0 - 0.5708R0)-(R1 - 0.5708R1)-1.0 ···(8)

[0064] More preferably, β is 1.0 mm or less. That is, the constant 1.0 on the right side of the above Equation (8) can be replaced with 0.5.

[0065] [Effect] In this embodiment, the blank can 20 is corrected using the mold set 10. When correcting the blank can 20, the core 13 of the mold set 10 is disposed inside the blank can 20 in a state where it is in contact with the second side wall 22 of the blank can 20 and a gap is formed between each of the first side walls 21 of the blank can 20. The pair of first molds 11 of the mold set 10 are configured to crush the first side wall 21 and the corner portion 23 of the blank can 20 toward the first side surface 131 side of the core 13. Further, the pair of second molds 12 of the mold set 10 are configured to support the second side wall 22 of the blank can 20 together with the second side surface 132 of the core 13. Therefore, in the correction process of the blank can 20, with the second side wall 22 of the blank can 20 supported by the second mold 12 and the core 13, the first side wall 21 and the corner portion 23 of the blank can 20 can be pressed against the core 13 side by the first mold 11. As a result, each of the corner portions 23 of the blank can 20 is crushed, deformed so that the corners stand up, and the diameter is reduced. As a result, a metal can 30 having a corner portion 33 with a curvature radius R1 smaller than the original curvature radius R0 can be obtained.

[0066] Since the corner portion 33 of the metal can 30 is thus reduced in diameter, in, for example, an electric vehicle, the metal cans 30 serving as battery cases can be arranged relatively densely. That is, since the radius of curvature R1 of the corner portion 33 of the metal can 30 obtained by correction is smaller than the radius of curvature R0 of the original stock can 20, the voids generated between the arranged batteries can be reduced as compared with the case where a metal can manufactured only by drawing is used as a battery case. Thereby, it is possible to increase the energy density of the battery in an electric vehicle or the like.

[0067] In the present embodiment, when reducing the diameter of the corner portion 23 in the correction process, the first mold 11 is pressed against the stock can 20 from the outside, and the first side wall 21 and the corner portion 23 are compressed. Therefore, in the correction process, an increase in the linear length L1 (surface area) of the first side wall 21 and the corner portion 23 can be suppressed, and a decrease in the plate thickness due to correction can be suppressed. Therefore, even when the plate thickness of the stock can 20 is small, the stock can 20 can be corrected to reduce the diameter of the corner portion 23.

[0068] In the present embodiment, the displacement amount ΔX of the first side wall 21 in the correction process preferably satisfies the above-described formula (6) in relation to the radius of curvature R0 of the corner portion 23 of the stock can 20 before correction and the radius of curvature R1 of the corner portion 33 of the metal can 30 after correction. In this case, the linear length L2 of the deformation completion portion in the metal can 30 after correction does not become too small with respect to the linear length L1 of the deformation planned portion in the stock can 20 before correction. Therefore, it is difficult for excess material to occur due to correction, and the occurrence of wrinkles in the metal can 30 can be suppressed.

[0069] In this embodiment, it is preferable that the displacement amount ΔX of the first side wall 21 in the correction process satisfies the above-described formula (8) in relation to the radius of curvature R0 of the corner portion 23 of the raw material can 20 before correction and the radius of curvature R1 of the corner portion 33 of the metal can 30 after correction. In this case, the line length L2 of the deformation completion portion in the metal can 30 after correction does not become too large with respect to the line length L1 of the deformation planned portion in the raw material can 20 before correction. Therefore, a reduction in plate thickness due to correction is less likely to occur, and the occurrence of cracks in the metal can 30 can be suppressed.

[0070] However, since the first side wall 21 and the corner portion 23 are crushed inside the raw material can 20 by the first mold 11, the line length L2 after correction is often approximately the same as or less than the line length L1 before correction. That is, since the first side wall 21 and the corner portion 23 of the raw material can 20 are crushed and it is difficult to apply circumferential tension, a reduction in plate thickness due to correction is unlikely to occur in the first place. Therefore, in the manufacturing method according to this embodiment, it is preferable to satisfy at least formula (6) among formula (6) regarding the excess thickness and formula (8) regarding the reduction in plate thickness.

[0071] Generally, an aluminum alloy plate is used for the battery case. When aiming to improve the space efficiency of the battery, it is conceivable to adopt a higher-strength steel plate as the material for the battery case instead of the aluminum alloy plate, and make the battery case smaller and thinner than before. On the other hand, since the specific gravity of steel is larger than that of the aluminum alloy, when it is necessary to avoid an increase in the weight of the battery due to the application of the steel plate, a considerable reduction in thickness is required for the battery case. More specifically, since the specific gravity of steel is about three times that of the aluminum alloy, the thickness of the battery case formed of the steel plate is required to be about 1 / 3 or less of the thickness of the battery case formed of the aluminum alloy plate. However, when the steel plate is thin, it is difficult to reduce the diameter of the corner portion by ironing as in the conventional method due to the load on the mold. Also, since the steel plate has high strength, the load on the mold is large, and the application of ironing is difficult.

[0072] In contrast, in the present embodiment, without applying ironing, the corner portion 23 between the side walls 21 and 22 of the material can 20 can be reduced in diameter. That is, when the first side wall 21 and the corner portion 23 of the material can 20 are crushed by the first mold 11, the radius of curvature R0 of the corner portions 23 on both sides of each first side wall 21 becomes smaller. Therefore, even if the first side wall 21 continuous with the corner portion 23 is formed of a steel plate and the first side wall 21 is as thin as 0.1 mm or more and 2.0 mm or less, the corner portion 23 can be relatively easily reduced in diameter. Further, even when it is difficult to apply ironing due to the large size of the material can 20, the corner portion 23 can be reduced in diameter.

[0073] In the present embodiment, the metal can 30 can be formed of a steel plate. Since the steel plate has higher strength than an aluminum alloy plate, by adopting the steel plate, the metal can 30 can be made thinner. The side wall of the metal can 30 after correction can also have a plate thickness of, for example, 0.1 mm or more and 2.0 mm or less. Thereby, for example, in an electric vehicle, when arranging batteries using the metal can 30 as a battery case, compared with the case of using a battery case of a general aluminum alloy plate, the ratio of the battery case to the battery mounting space becomes smaller. Therefore, the space efficiency of the battery can be improved.

[0074] However, the use of the metal can 30 is not limited to the case of an in-vehicle battery case. The metal can 30 may be used as a case for a stationary battery. The metal can 30 may be used for other purposes than a battery case.

[0075] <Second Embodiment> FIGS. 3 and 4 are cross-sectional views schematically showing a mold set 10A according to the present embodiment. The mold set 10A has substantially the same configuration as the mold set 10 according to the first embodiment. However, the mold set 10A is different from the mold set 10 according to the first embodiment in the shape of the core 13A.

[0076] In the mold set 10 according to the first embodiment, the corner portions 133 of the cores 13 each have a shape generally following the corner portions 33 of the metal can 30 after correction. That is, the corner portions 133 of the cores 13 each have a radius of curvature corresponding to the radius of curvature R1 of the corner portions 33 after correction. On the other hand, as shown in FIG. 3, in the mold set 10A according to the present embodiment, the corner portions 133A of the cores 13A each have a shape following a part of the corner portions 23 of the raw material can 20 before correction. At the start of the correction process, the corner portions 133A of the cores 13A are each provided along the portion of the corner portions 23 of the raw material can 20 that is continuous with the second side wall 22. However, the corner portions 133A of the cores 13A are not arranged in the portion of the corner portions 23 of the raw material can 20 that is continuous with the first side wall 21. Each of the corner portions 133A has a radius of curvature corresponding to the radius of curvature R0 (FIG. 2E) of the corner portions 23 before correction.

[0077] Alternatively, as shown in FIG. 4, the corner portions 133A of the cores 13A may each be a chamfered portion C between the first side surface 131 and the second side surface 132. In this case, each of the corner portions 133A is an inclined surface inclined with respect to the side surfaces 131 and 132. The inclination angle of the corner portions 133A with respect to the side surfaces 131 and 132 is not particularly limited. An R-chamfering process may be performed on the boundary portion between the corner portion 133A and the first side surface 131. Similarly, an R-chamfering process may be performed on the boundary portion between the corner portion 133A and the second side surface 132.

[0078] Even when the correction process of the raw material can 20 is performed using the mold set 10A according to the present embodiment, the same effects as those of the first embodiment can be achieved. Also, in the case of the mold set 10A according to the present embodiment, for example, even when the radius of curvature R0 (FIG. 2E) of each corner portion 23 of the raw material can 20 before correction is large, it becomes easier to arrange the core 13 inside the raw material can 20.

[0079] As described above, the embodiments according to the present disclosure have been described. However, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof.

Example

[0080] Hereinafter, the present disclosure will be described in more detail by way of examples. However, the present disclosure is not limited to the following examples.

[0081] To confirm the effect of the present disclosure, for the correction of the material can 20 using the mold set 10 according to the first embodiment, CAE analysis was performed using commercially available analysis software (LS-DYNA, manufactured by JSOL Corporation), and the sheet thickness reduction rate of the metal can 30 after correction was investigated.

[0082] The dimensions of the material can 20 before correction and the metal can 30 after correction are as follows. · Before correction: D26.5×W148.0×H100.0, R0 = 5.0, [mm] · After correction (target value): D26.5×W144.5×H100.0, R1 = 1.5, ΔX = 1.75, [mm]

[0083] The sheet thickness reduction rate of the metal can 30 after correction is shown in FIG. 5 (Example). FIG. 5 also shows the sheet thickness reduction rate of the material can 20 (deep drawing product) before correction as a comparative example. The sheet thickness reduction rate is obtained by ((sheet thickness of the material) - (sheet thickness of each part after forming)) / (sheet thickness of the material). The sheet thickness of the material is the sheet thickness of the metal sheet before deep drawing. In this analysis, the sheet thickness of the material was 0.3 mm. The sheet thickness of each part after forming is, in the case of the comparative example, the sheet thickness of each part of the material can 20 after deep drawing, and in the case of the example, the sheet thickness of each part of the metal can 30 obtained by correcting the material can 20. In FIG. 5, for each of the comparative example and the example, the maximum value of the measured sheet thickness reduction rate (sheet thickness reduction rate of the thinnest part) is shown. As shown in FIG. 5, the sheet thickness reduction rate of the example differed from that of the comparative example by only about 2.0%.

[0084] Regarding the control example, the radius of curvature R0 of the corner portion 23 between the side walls of the material can 20 is shown in FIG. 6 as the radius of curvature R1 of the corner portion 33 between the side walls of the metal can 30 after correction for the example. FIG. 6 also shows the radius of curvature of the corner portion on the bottom plate side for each of the control example and the example. As shown in FIG. 6, in the example, the radius of curvature R1 of the corner portion 33 between the side walls has clearly become smaller compared to the radius of curvature R0 before correction. In the example, the corner portion between the longitudinal side wall and the bottom plate, that is, the corner portion on the bottom plate side that is continuous with the side wall deformed by the correction, has also deformed and become smaller in diameter. Also, in the example, the corner portion between the short side wall and the bottom plate has also become smaller in diameter.

[0085] As described above, according to the manufacturing method according to the present disclosure, it has been confirmed that at least the corner portion 33 between the side walls can be made smaller in diameter while suppressing a reduction in plate thickness. Furthermore, it has been confirmed that the corner portion on the bottom plate side that is continuous with the side wall deformed by the correction can also be made smaller in diameter.

Explanation of Signs

[0086] 10, 10A: Die set 11: First die 12: Second die 13, 13A: Core 20: Material can 21: First side wall 22: Second side wall 23: Corner portion 30: Metal can 33: Corner portion

Claims

1. A method for manufacturing a metal can, comprising: preparing a blank can including a pair of first side walls arranged to face each other, corner portions provided on both sides of each of the first side walls, and a pair of second side walls each connected to both of the first side walls via the corner portions; using a mold set including a pair of first molds arranged outside the blank can and facing the first side walls respectively, a pair of second molds arranged outside the blank can and facing the second side walls respectively, and cores arranged inside the blank can in contact with the second side walls and having a gap formed between each of the first side walls, and correcting the blank can to obtain a metal can; and in the step of correcting the blank can, the first side walls and the corner portions are pressed against the core side by the first molds while the second side walls are supported by the second molds and the cores.

2. The manufacturing method according to claim 1, Let the radius of curvature of the corner part before correction be R ０ (mm), and the radius of curvature of the corner part after correction be R １ (mm). When the displacement amount of the first side wall due to correction is ΔX (mm), R ０ , R １ , and ΔX satisfy the following formula, manufacturing method. ΔX ≤ (R ０ −0.5708R ０ ) − (R １ −0.5708R １ ) + 2.0

3. The manufacturing method according to claim 1, wherein the corner portion before correction has a radius of curvature of 20.0 mm or less.

4. The manufacturing method according to claim 1, wherein the first side walls are formed of a steel plate and have a plate thickness of 0.1 mm or more and 2.0 mm or less.

5. A mold set for correcting a blank can including a pair of first side walls arranged to face each other, corner portions provided on both sides of each of the first side walls, and a pair of second side walls each connected to both of the first side walls via the corner portions, the mold set comprising: a pair of first side surfaces and a pair of second side surfaces connecting the first side surfaces to each other, cores arranged inside the blank can when the mold set is in use, a pair of first molds corresponding to the first side surfaces respectively and arranged outside the blank can when the mold set is in use, a pair of second molds corresponding to the second side surfaces respectively and arranged outside the blank can when the mold set is in use; and the first molds are configured to crush the first side walls and the corner portions of the blank can toward the first side surface side, and the second molds are configured to support the second side walls of the blank can together with the second side surfaces.

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