Press forming method

Abstract

A press forming method is through a draw forming step and a trimming forming step, and a formed product is a hat-shaped formed product including a top surface portion, an outer corner portion, a vertical wall portion, an inner corner portion, and a flange portion. In the draw forming step, an intermediate formed product (8) including a convex portion (81) corresponding to the outer corner portion and a concave portion (83) corresponding to the inner corner portion is formed. The curvature radii of the convex portion (81) and the concave portion (83) are made larger than those of the outer corner portion and the inner corner portion, and the cross-sectional shape of the convex portion (81) is made more bulged toward the top surface portion side along a press direction F than that of the outer corner portion. In the trimming forming step, by pressing a position inside the intermediate formed product (8) more than the convex portion (81) and a position outside more than the concave portion (83), material outflow from the inside to the outside and material inflow from the outside to the inside are suppressed, and at the same time, the convex portion (81) is pressed toward the concave portion (83) side along the press direction F, whereby the outer corner portion and the inner corner portion are formed.

Description

Technical Field

[0001] This invention relates to a stamping forming method. More specifically, it relates to a stamping forming method that forms a workpiece into a hat-shaped article in cross-section by means of a drawforming step and a restrike forming step. Background Technology

[0002] In recent years, the electrification of automobiles has been developing. Most electric vehicles are driven by motors powered by electricity supplied by batteries. The batteries are housed in the vehicle body in a box-shaped battery casing. In order to accommodate as many battery cells as possible in the battery casing, the volume of the battery casing is preferably large.

[0003] Furthermore, cap-shaped containers with bottoms used in battery casings are sometimes formed, for example, by drawing. Patent Document 1 discloses a stamping method that uses a pressure ring to suppress wrinkling while drawing to form a cap-shaped article.

[0004] [Previous Technical Documents]

[0005] (Patent Documents)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-24837 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] However, in order to maximize the volume of the battery casing as described above, it is necessary to minimize the radii of curvature of the outer and inner corners of the casing in cross-section. However, if this shape is to be formed using drawing, a portion of the material will be dragged by the punch, which can easily lead to cracking.

[0009] Furthermore, to prevent crack formation, it is considered to perform a two-step drawing process to achieve the optimal radii of curvature for the outer and inner corners. However, this can sometimes lead to wrinkles at the flange. When the molded article is used as a battery casing, the flange sometimes serves as a sealing surface, thus it is necessary to suppress wrinkles at the flange.

[0010] The purpose of this invention is to provide a stamping forming method that uses stamping forming to form a molded article with a hat-shaped cross-section, which can reduce the radius of curvature of the outer and inner corners while suppressing the generation of wrinkles and cracks.

[0011] [Technical means to solve the problem]

[0012] (1) The stamping forming method of the present invention includes a drawing forming step (e.g., described later). Figure 2 S1) and finishing and shaping steps (e.g., as described later) Figure 2 S2), and a shaped article (e.g., shaped article 9) is formed from the workpiece (e.g., workpiece W described later), the shaped article being cap-shaped in cross-section and including a top portion (e.g., top portion 90 described later) orthogonal to the stamping direction (e.g., stamping direction F described later), a longitudinal wall portion (e.g., longitudinal wall portion 92 described later) extending along the aforementioned stamping direction from the edge of the top portion, a flange portion (e.g., flange portion 94 described later) orthogonal to the aforementioned stamping direction from the edge of the longitudinal wall portion, an outer corner portion (e.g., outer corner portion 91 described later) between the aforementioned top portion and the aforementioned longitudinal wall portion, and an inner corner portion (e.g., inner corner portion 93 described later) between the aforementioned longitudinal wall portion and the aforementioned flange portion, the stamping forming method is characterized in that, in the aforementioned drawing forming step, a protrusion (e.g., shaped article 93 described later) corresponding to the aforementioned outer corner portion is formed from the aforementioned workpiece. An intermediate molded article (e.g., intermediate molded article 8) consisting of a protrusion 81 and a recess corresponding to the aforementioned inner corner (e.g., recess 83 described later), wherein the radius of curvature of the aforementioned protrusion and the aforementioned recess in cross-section is greater than that of the aforementioned outer corner and the aforementioned inner corner, and the cross-sectional shape of the aforementioned protrusion bulges outward toward the aforementioned top surface side along the aforementioned stamping direction compared to the aforementioned outer corner. In the aforementioned finishing molding step, by pressing the position of the intermediate molded article that is more inward than the aforementioned protrusion (e.g., the first intermediate plane portion 87 described later) and the position that is more outward than the aforementioned recess (e.g., the outer peripheral edge portion of the intermediate flange portion 84 described later), the material is suppressed from flowing outward from the aforementioned inner side and from flowing inward from the aforementioned outer side. At the same time, the aforementioned protrusion is pressed toward the aforementioned recess side along the aforementioned stamping direction, thereby forming the aforementioned outer corner and the aforementioned inner corner.

[0013] (2) Preferably, in the aforementioned trimming and forming step, by pressing the outer peripheral edge of the intermediate molded article that is further outward than the aforementioned recess, a step-shaped bend (e.g., the bend 96 described later) is formed while suppressing the material from flowing inward from the aforementioned outer side. In the aforementioned molded article, the radius of curvature of the curved outer corner portion (e.g., the first curved outer corner portion 91a and the second curved outer corner portion 91b described later) that is the curved portion in the aforementioned outer corner portion in the top view along the aforementioned stamping direction is greater than the radius of curvature of the portion of the aforementioned bend portion that is circumferentially outside the aforementioned curved outer corner portion in the aforementioned top view.

[0014] (3) Preferably, in the aforementioned finishing and forming step, a first intermediate plane portion (e.g., the first intermediate plane portion 87 described later) that is more inner than the aforementioned protrusion in the aforementioned intermediate molded article is pressed by using a pad mold (e.g., the pad mold 42 described later) to form a first plane portion (e.g., the first plane portion 97 described later) on the aforementioned top surface of the aforementioned molded article. In the aforementioned molded article, a step portion (e.g., the step portion 95 described later) is formed between the aforementioned first plane portion in the aforementioned top surface and a second plane portion (e.g., the second plane portion 98 described later) that is more outer than the first plane portion in the aforementioned stamping direction.

[0015] (4) In this case, it is preferred that the aforementioned workpiece is an aluminum or aluminum alloy sheet.

[0016] (The effect of the invention)

[0017] (1) In the stamping forming method of the present invention, a formed article, which is cap-shaped in cross-section and includes a top surface, outer corner, longitudinal wall, inner corner, and flange, is formed by a drawing forming step and a finishing forming step. Here, in the drawing forming step, an intermediate formed article is formed from the workpiece including a convex portion corresponding to the outer corner and a concave portion corresponding to the inner corner. In addition, in the drawing forming step, the radii of curvature of these convex and concave portions in cross-section are made larger than those of the outer corner and inner corner in the formed article, respectively, so that the cross-sectional shape of the convex portion bulges towards the top surface side along the stamping direction more than that of the outer corner. As a result, cracks are suppressed in the convex and concave portions that become the outer and inner corners, and the material required for forming the outer and inner corners in the subsequent finishing forming step can be ensured. Furthermore, in the finishing forming step, by pressing the positions in the intermediate molded part that are more inward than the protrusions and more outward than the concave parts, material outflow from the positions more inward than the protrusions and inflow from the positions more outward than the concave parts are suppressed. At the same time, the protrusions are pressed towards the concave parts along the stamping direction, thereby forming the outer and inner corners. As a result, while the material of the protrusions formed in the drawing forming step is moved towards the longitudinal wall, the longitudinal wall is extended towards the inner corners along the stamping direction. Therefore, while suppressing wrinkles and cracks in the top surface, outer corners, longitudinal walls, inner corners, and flanges, outer and inner corners with smaller radii of curvature can be formed.

[0018] (2) In the finishing molding step, by pressing the outer peripheral edge of the intermediate molded part, which is further outward than the concave part, a stepped bend is formed while preventing material from flowing inward from the outer peripheral edge. Furthermore, in the molded part obtained after the finishing molding step, the radius of curvature of the curved outer corner portion, which is the curved portion in top view, is greater than the radius of curvature of the portion of the bend that is circumferentially outward relative to the curved outer corner portion. Therefore, wrinkles can be prevented from forming in the portion of the flange portion of the molded part that is further inward than the bend, so when the molded part is used as a battery casing, the flange portion can be used as a sealing surface.

[0019] (3) In the finishing forming step, a first flat portion is formed on the top surface of the molded article by pressing a first intermediate flat portion, which is further inward than the protrusion, using a die. Furthermore, in the molded article obtained after the finishing forming step, a step is formed between the first flat portion on the top surface and a second flat portion, which is further outward than the first flat portion, such that the second flat portion is closer to the flange side in the stamping direction than the first flat portion. By forming this step, wrinkles between the first flat portion and the outer corner portion that may occur when the protrusion is pressed towards the flange side in the stamping direction during the finishing forming step can be reduced.

[0020] (4) Generally speaking, if aluminum or aluminum alloy sheets are formed by deep drawing, cracks are easily generated due to local stretching. In contrast, in this invention, by forming a shaped article from an aluminum or aluminum alloy workpiece through the drawing and finishing forming steps described above, it is possible to suppress the generation of cracks while forming outer and inner corners with smaller radii of curvature. Attached Figure Description

[0021] Figure 1A This is a plan view of a molded article formed using a stamping method according to an embodiment of the present invention, viewed from the outside.

[0022] Figure 1B This is a front view of the finished product.

[0023] Figure 1C It is along the shaped product Figure 1A The cross-sectional view of line II in the diagram.

[0024] Figure 1D It is a partial 3D view of the finished product.

[0025] Figure 2 It is a flowchart illustrating the specific sequence of the stamping forming process.

[0026] Figure 3 This is a diagram illustrating the structure of the first stamping device used in the drawing process.

[0027] Figure 4 It is a diagram comparing the cross-sectional shape of an intermediate molded product formed through the drawing process with the cross-sectional shape of the finished product.

[0028] Figure 5 This is a diagram illustrating the structure of the second stamping device used in the finishing and forming process.

[0029] Figure 6 It is a cross-sectional view of an intermediate molded product, used to illustrate the movement of material during the finishing and forming process.

[0030] Figure 7A It is a perspective view of the part corresponding to the first curved outer corner of the molded part in the intermediate molded part, and is a diagram used to illustrate the stretching of material in the drawing and finishing steps.

[0031] Figure 7B It is a plan view of the part corresponding to the first curved outer corner of the molded part in the intermediate molded part, and is a diagram used to illustrate the stretching of material in the drawing and finishing steps.

[0032] Figure 8 It is a diagram obtained by drawing the strain state of the drawing and finishing forming steps of the part that becomes the first curved outer corner of the molded article as a forming limit line diagram.

[0033] Figure 9 It is a plan view showing the structure near the first curved outer corner and the second curved outer corner of the molded article. Detailed Implementation

[0034] Hereinafter, a stamping forming method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0035] Figure 1A This is a plan view of the molded article 9 formed using the stamping method of this embodiment, viewed from the outside. Figure 1B This is a front view of the molded product 9 viewed along its long side. Figure 1C It is along the 9th molded part Figure 1A A cross-sectional view of line II in the middle. Figure 1D This is a partial 3D view of the molded product 9.

[0036] like Figures 1A to 1C As shown, the molded article 9 is a rectangular cylindrical shape with a base when viewed from above. Furthermore, the molded article 9 is cap-shaped when viewed in cross-section, and is formed from a sheet metal workpiece using the stamping method described later. Hereinafter, the molded article 9 will be described as a battery casing for housing multiple battery cells mounted on an electric vehicle, but the present invention is not limited thereto.

[0037] The molded article 9 includes: a top surface 90, along the stamping direction F in the stamping method (see reference). Figure 1C The top surface 90 extends in a roughly orthogonal direction and is rectangular in shape when viewed from above; the longitudinal wall portion 92 extends from the periphery of the four sides of the top surface portion 90 along the stamping direction F; and the flange portion 94 extends outward from the edge of the longitudinal wall portion 92 along a surface that is roughly orthogonal to the stamping direction F (i.e., a surface that is roughly parallel to the top surface portion 90).

[0038] The longitudinal wall portion 92 is a cylindrical section connecting the top portion 90 and the flange portion 94, and appears rectangular when viewed from above. For example... Figure 1C As shown, the longitudinal wall portion 92 slopes slightly outward from the top portion 90 towards the flange portion 94. The top portion 90 is approximately orthogonal to the longitudinal wall portion 92, and the longitudinal wall portion 92 is approximately orthogonal to the flange portion 94. Hereinafter, the portion between the top portion 90 and the longitudinal wall portion 92 that curves outward in cross-section is referred to as the outer corner portion 91, and the portion between the longitudinal wall portion 92 and the flange portion 94 that curves inward in cross-section is referred to as the inner corner portion 93. These outer corner portions 91 and inner corner portions 93 are rectangular in shape when viewed from above. Furthermore, hereinafter, the outer corner portions 91 with a predetermined radius of curvature R (refer to the following description) in top view will be referred to as... Figure 9 The curved portions are referred to as the first curved outer corner portion 91a and the second curved outer corner portion 91b. Additionally, as... Figure 1C As shown, the following description addresses the case where the radius of curvature of the outer corner 91 in cross-section is smaller than that of the inner corner 93 in cross-section, but the present invention is not limited thereto.

[0039] A stepped portion 95, which appears rectangular when viewed from above, is formed in a position further inward than the outer corner 91 within the top portion 90. The stepped portion 95 is as follows... Figure 1C As shown, it has a stepped shape in cross-section. Hereinafter, the portion of the top surface 90 that is further inward than the step portion 95 will be referred to as the first flat portion 97, and the portion that is further outward than the step portion 95 will be referred to as the second flat portion 98. Compared to the first flat portion 97, the second flat portion 98 is closer to the flange portion 94 side along the stamping direction F. That is, the second flat portion 98 is lower than the first flat portion 97.

[0040] A bent portion 96, which is rectangular in shape when viewed from above, is formed on the outer periphery of the flange portion 94. The bent portion 96 is as follows... Figure 1C As shown, it is stepped. The portion of the flange 94 that is more inner than the bent portion 96 is closer to the top surface 90 side along the stamping direction F compared to the portion that is more outer. That is, the portion of the flange 94 that is more outer than the bent portion 96 is lower than the portion that is more inner.

[0041] Generally, if a molded article 9, including the outer corner portion 91, longitudinal wall portion 92, and inner corner portion 93 as described above, is to be formed from a flat workpiece using only one drawing step, cracks are likely to occur in these outer corner portions 91, longitudinal wall portions 92, and inner corner portions 93. In addition, cracks are particularly likely to occur in these outer corner portions 91, longitudinal wall portions 92, and inner corner portions 93, especially in the first curved outer corner portion 91a and the second curved outer corner portion 91b.

[0042] Furthermore, in order to suppress the generation of cracks as described above, it is considered to form the molded article 9 from the flat workpiece using a two-step drawing process. However, if the molded article 9 is formed using a two-step drawing process, wrinkles may sometimes occur in the flange portion 94. In particular, wrinkles tend to occur in the outer circumferential direction of the first curved outer corner portion 91a and the second curved outer corner portion 91b in the flange portion 94 when viewed from above. Hereinafter, a stamping forming method for suppressing wrinkles or cracks in such molded articles 9 will be described.

[0043] Furthermore, the following description addresses the use of aluminum or aluminum alloy sheets, which are suitable materials for battery casings and are prone to cracking, as workpieces, but the present invention is not limited thereto.

[0044] Figure 2 This is a flowchart illustrating the specific sequence of the stamping forming method according to this embodiment. For example... Figure 2 As shown, the formed article 9 shown in FIG1 is formed from a workpiece through a drawing forming step (S1) and a trimming forming step (S2). The specific sequence of these drawing forming steps and trimming forming steps will be explained below.

[0045] Figure 3 This is a diagram illustrating the structure of the first stamping apparatus 1 used in the drawing process. The first stamping apparatus 1 includes: a lower die mechanism 20 having a lower die 21 disposed on the lower side of the plate-shaped workpiece W; and an upper die mechanism 30 that causes the upper die 31 to approach or move away from the lower die 21 along the stamping direction F.

[0046] The upper die mechanism 30, for example, uses a servo motor to move the upper die 31 closer to or further away from the lower die 21. The upper die 31 and lower die 21 together clamp the workpiece W for stamping, forming a die surface 31a on its lower surface for abutting against the upper surface of the workpiece W. The die surface 31a is concave towards the lower die 21. An annular retainer 32 is provided around the periphery of the upper die 31. The front end face of the retainer 32 is horizontal and protrudes slightly towards the lower die 21 than the die surface 31a. Therefore, when the upper die 31 is moved closer to the lower die 21 using the upper die mechanism 30, the retainer 32 abuts against the workpiece W before the die surface 31a.

[0047] The lower die mechanism 20 includes: a lower die 21; a base 22 for supporting the lower die 21; an annular pressure ring 23 for supporting the portion of the workpiece W that becomes the flange portion 94 in the molded article 9; and a die buffer mechanism 24 for raising and lowering the pressure ring 23.

[0048] The lower die 21 is disposed on the upper part of the base 22, and together with the upper die 31, clamps the workpiece W for stamping. A die surface 21a is formed on the upper surface of the lower die 21 for abutting against the lower surface of the workpiece W. The die surface 21a is convex towards the upper die 31.

[0049] The blank holder 23 is positioned opposite the retainer 32 along the stamping direction F. To prevent wrinkles and positional shifts during stamping of the workpiece W, it clamps the outer periphery of the workpiece W together with the retainer 32. The die buffer mechanism 24 uses a lifting mechanism (not shown) to move the blank holder 23 up and down along the stamping direction F.

[0050] In the drawing process, the workpiece W is formed using the first stamping apparatus 1 in the following sequence: First, the blank holder 23 is raised to a position higher than the lower die 21, and the workpiece W is placed on the blank holder 23. Next, the upper die 31 is brought close to the lower die 21. As described above, when the upper die 31 approaches the lower die 21, the retainer 32 abuts against the workpiece W before the die surface 31a, thereby clamping the outer periphery of the workpiece W by the retainer 32 and the blank holder 23. Furthermore, when the upper die 31 is brought closer to the lower die 21, the die surface 31a of the upper die 31 and the die surface 21a of the lower die 21 come into contact with both sides of the workpiece W. Thus, the workpiece W is formed to mimic the shape of the die surface 21a. Hereinafter, the formed article formed from the workpiece W using the drawing process will be referred to as an intermediate formed article.

[0051] Figure 4 This diagram compares the cross-sectional shape of the intermediate molded product 8, formed through a drawing process, with the cross-sectional shape of the finished product 9. Figure 4 In the drawing process, the die surface 21a of the lower die used in the drawing process is shown with a thick solid line, and the die surface of the lower die used in the finishing process, which is described later, is shown with a dashed line, i.e., the inner surface of the molded article 9.

[0052] The die surface 21a of the lower die used in the drawing process has, from the inside to the outside, a top surface 211, a stepped surface 212, a convex surface 213, a longitudinal wall surface 214, a concave surface 215, and a flange surface 216. For example... Figure 4As shown, in the intermediate molded article 8, the first intermediate flat part 87 corresponding to the first flat part 97 in the molded article 9 is formed by the top surface 211, the intermediate step part 85 corresponding to the step part 95 in the molded article 9 is formed by the step surface 212, the convex part 81 corresponding to the second flat part 98 and the outer corner part 91 in the molded article 9 is formed by the convex surface 213, the intermediate longitudinal wall part 82 corresponding to the longitudinal wall part 92 in the molded article 9 is formed by the longitudinal wall surface 214, the concave part 83 corresponding to the inner corner part 93 in the molded article 9 is formed by the concave surface 215, and the intermediate flange part 84 corresponding to the flange part 94 in the molded article 9 is formed by the flange surface 216.

[0053] like Figure 4 As shown, in the die surface 21a of the lower die used in the drawing process, the top surface 211, the step surface 212, the longitudinal wall surface 214, and the flange surface 216 have shapes that are almost identical to the inner surface of the molded article 9, while the shapes of the convex surface 213 and the concave surface 215 are different from the inner surface of the molded article 9. More specifically, the radii of curvature of the convex surface 213 and the concave surface 215 in cross-section are larger than the radii of curvature of the inner surface of the molded article 9 in cross-section. In addition, the convex surface 213 bulges out more convexly towards the top surface 211 in cross-section compared to the inner surface of the molded article 9 along the stamping direction F.

[0054] Therefore, in the intermediate molded article 8 formed by the drawing forming step described above, the radii of curvature of the protrusion 81 and the concave part 83 in cross-section are greater than the radii of curvature of the outer corner part 91 and the inner corner part 93 in cross-section in the molded article 9, and the cross-sectional shape of the protrusion 81 bulges out towards the top part 90 along the stamping direction F compared with the second flat part 98 and the outer corner part 91.

[0055] In addition, such as Figure 4 As shown, the height along the stamping direction F from the intermediate flange portion 84 to the first intermediate plane portion 87 in the intermediate molded article 8 is equal to the height along the stamping direction F from the flange portion 94 to the first plane portion 97 in the molded article 9.

[0056] Figure 5 This illustrates the shaping and finishing steps (see reference). Figure 2 A diagram showing the structure of the second stamping device 4 used in S2). Figure 5 The image shows the state in which the intermediate formed product 8, which has been formed by the above-mentioned drawing process, is placed on the second stamping processing device 4.

[0057] The second stamping device 4 includes: a lower die 41; a pad actuator (not shown) for bringing a pad die 42 closer to or away from the lower die 41; and a movable die actuator (not shown) for bringing a movable die 43 closer to or away from the lower die 41.

[0058] The shape of the die surface 41a of the lower die 41 mimics the shape of the portion of the molded article 9 that is further inward than the bent portion 96. More specifically, the die surface 41a of the lower die 41 has, from the inside to the outside, a top surface 412, a convex surface 413, a longitudinal wall surface 414, a concave surface 415, and a flange surface 416. The surface of the pad die 42 is generally flat and has a shape that is approximately the same as the first flat portion 97 of the molded article 9 when viewed from above along the stamping direction F. Therefore, by pressing the pad die 42 against the first intermediate flat portion 87 of the intermediate molded article 8 using a pad actuator, material outflow from the first intermediate flat portion 87 side can be prevented.

[0059] The shape of the mold surface 43a of the movable mold 43 mimics the shape of the portion of the molded article 9 that is further outward than the first flat portion 97. More specifically, the mold surface 43a of the movable mold 43 has, from the inside to the outside, a top surface 432, a concave surface 433, a longitudinal wall surface 434, a convex surface 435, and a flange surface 436. In addition, on the movable mold 43, at a position further outward than the flange surface 436, a fixing portion 437 is provided that protrudes further towards the lower mold 41 in the stamping direction F than the flange surface 436. Therefore, when the movable mold 43 is brought closer to the lower mold 41 in the stamping direction F using the movable mold actuator, the fixing portion 437 abuts against the intermediate molded article 8 before the mold surface 43a.

[0060] right Figure 5 and Figure 1D By comparison, it can be seen that in the molded article 9, the first flat part 97 is formed by the pad mold 42, the step part 95 and the second flat part 98 are formed by the top surface 432, the outer corner part 91 is formed by the convex surface 413, the longitudinal wall part 92 is formed by the longitudinal wall surfaces 414 and 434, the inner corner part 93 is formed by the convex surface 435, the part of the flange part 94 that is more inner than the bent part 96 is formed by the flange surface 436, and the bent part 96 and the part of the flange part 94 that is more outer than the bent part 96 are formed by the fixing part 437.

[0061] In the finishing and forming step, the intermediate molded article 9 is formed from the intermediate molded article 8 by using the second stamping processing device 4 in the following sequence. First, the pad die 42 is pressed against the first intermediate plane portion 87 of the intermediate molded article 8 using the pad actuator. This prevents material from flowing outward from the first intermediate plane portion 87 in the intermediate molded article 8. Next, the movable die 43 is brought close to the lower die 41. As described above, when the movable die 43 is brought close to the lower die 41, the fixing portion 437 abuts against the intermediate flange portion 84 of the intermediate molded article 8 before the die surface 43a. Subsequently, when the movable die 43 is brought closer to the lower die 41, the outer peripheral portion of the intermediate flange portion 84 is bent by the fixing portion 437 and pressed into the space between the fixing portion 437 and the side surface 41b of the lower die 41 that is further outward than the die surface 41a. This prevents material from flowing inward from the outer peripheral portion of the intermediate flange portion 84 in the intermediate molded article 8, while forming the bent portion 96. In the finishing and forming step, while suppressing the material from flowing outward from the first intermediate plane portion 87 and the material from flowing inward from the outer periphery of the intermediate flange portion 84 in the manner described above, the movable mold 43 is lowered to the bottom dead center, and the protrusion 81 of the intermediate molded product 8 is pressed towards the concave portion 83 along the stamping direction F, thereby forming the molded product 9.

[0062] Figure 6 This is a cross-sectional view of intermediate molded part 8, used to illustrate the movement of material during the finishing and molding process. Figure 6 In the middle, the molded product 9, which has been formed from the intermediate molded product 8 after the finishing and shaping steps, is drawn with a dashed line.

[0063] During the finishing and forming step, while using the pad mold 42 and the fixing part 437 to suppress the outward flow of material from the first intermediate plane part 87 and the inward flow of material from the outer periphery of the intermediate flange part 84, the movable mold 43 is brought close to the lower mold 41, such as Figure 6 As shown, the convex surface 435 abuts against the concave portion 83, and the longitudinal wall surface 434 slides into contact with the intermediate longitudinal wall portion 82. Therefore, the material of the convex portion 81 moves outward in the circumferential direction by being drawn between the die surface 41a and the longitudinal wall surface 434. Furthermore, the materials of the intermediate longitudinal wall portion 82 and the convex portion 81 move towards the flange surface 436 along the stamping direction F by being drawn between the longitudinal wall surface 434 and the convex surface 413. Here, when the movable die 43 is further brought closer to the lower die 41 along the stamping direction F, near the bottom dead center, the top surface 432 contacts the convex portion 81, thereby reducing the radius of curvature of the convex portion 81 and the concave portion 83 of the intermediate molded article 8, and forming the outer corner portion 91 and the inner corner portion 93.

[0064] Figure 7A This is a perspective view of the portion of the intermediate molded article 8 corresponding to the first curved outer corner 91a in the molded article 9, used to illustrate the stretching of material during the drawing and finishing processes. Additionally, Figure 7BIs with Figure 7A The plan view of the same part is used to illustrate the stretching of material during the drawing and finishing processes. As described above, the first curved outer corner 91a and the second curved outer corner 91b are parts of the molded article 9 that are prone to cracking. Figure 7A In the diagram, arrow 71 indicates the stretching of material during the drawing process, and arrow 73 indicates the stretching of material during the finishing process. Furthermore, the stretching of the portion corresponding to the second curved outer corner 91b is qualitatively the same as the stretching of the portion corresponding to the first curved outer corner 91a, so its description is omitted.

[0065] like Figure 7A As shown, the extension of the portion forming the first curved outer corner 91a in the molded article 9 is mainly along the stamping direction F during the drawing process. In contrast, the portion of the protrusion 81 in the intermediate molded article 8, indicated by the thick solid line 75, moves to the portion indicated by the thick dashed line 76 after the finishing process (see reference). Figure 7A and Figure 7B Thus, the extension of the portion that becomes the first curved outer corner 91a in the molded article 9 is mainly an extension in a plane direction orthogonal to the stamping direction F during the finishing forming step.

[0066] Figure 8 This diagram is obtained by plotting the strain state during the drawing and finishing processes of the portion forming the first curved outer corner 91a in the molded article 9 as a forming limit line diagram with the maximum principal strain εx on the horizontal axis and the minimum principal strain εy on the vertical axis. Figure 8 In the diagram, the thick solid line represents the forming limit line FL. That is, when the strain exceeds this forming limit line FL, cracks or necking will appear in the molded product.

[0067] As mentioned above, the stretching of the material in the drawing process is mainly along the stamping direction. Therefore, the strain state deformation after the drawing process is as follows: Figure 8 The state shown at point P1. Furthermore, the material stretching during the finishing and forming step is primarily in the plane direction orthogonal to the stamping direction. Therefore, after the finishing and forming step, the strain state deformation of the formed article 9 is as follows: Figure 8 The state shown at point P2 in the diagram. As described above, in the stamping forming method of this embodiment, by forming the molded article 9 through two steps—drawing and finishing—the occurrence of cracks or necking can be suppressed.

[0068] Figure 9This is a plan view showing the structure near the first curved outer corner 91a and the second curved outer corner 91b in the molded article 9. As described above, the bent portion 96 in the molded article 9 is formed by the fixing portion 437 of the movable mold 43 during the finishing molding step. Here, in the finishing molding step, it is preferable to... Figure 9 As shown, the bending portion 96 is formed such that the radius of curvature R of the first curved outer corner portion 91a and the second curved outer corner portion 91b in top view is greater than the radius of curvature r of the portion of the bending portion 96 that is circumferentially outer relative to the first curved outer corner portion 91a and the second curved outer corner portion 91b in top view. This suppresses wrinkles from forming in the portion of the flange portion 94 that is further inward than the bending portion 96.

[0069] The stamping method according to this embodiment has the following effects.

[0070] (1) In the stamping forming method, a formed article 9 is formed by a drawing forming step and a finishing forming step, which is hat-shaped in cross-section and includes a top surface 90, an outer corner 91, a longitudinal wall 92, an inner corner 93, and a flange 94. Here, in the drawing forming step, an intermediate formed article 8 is formed from the workpiece W, including a protrusion 81 corresponding to the outer corner 91 and a concave portion 83 corresponding to the inner corner 93. In addition, in the drawing forming step, the radii of curvature of these protrusions 81 and concave portions 83 in cross-section are made larger than those of the outer corner 91 and the inner corner 93, respectively, so that the cross-sectional shape of the protrusion 81 bulges towards the top surface 90 side along the stamping direction F more than that of the outer corner 91. As a result, cracks are suppressed in the protrusions 81 and concave portions 83 that become the outer corner 91 and the inner corner 93, and the material required for forming the outer corner 91 and the inner corner 93 in the subsequent finishing forming step can be ensured. Furthermore, in the finishing and forming step, by pressing the positions in the intermediate molded part 8 that are more inward than the protrusion 81 and more outward than the concave part 83, material outflow from the position more inward than the protrusion 81 and inflow from the position more outward than the concave part 83 are suppressed. At the same time, the protrusion 81 is pressed towards the concave part 83 along the stamping direction F, thereby forming the outer corner 91 and the inner corner 93. Thus, while the material of the protrusion 81 formed in the drawing step is moved towards the longitudinal wall 92, the longitudinal wall 92 is extended towards the inner corner 93 along the stamping direction F. Therefore, while suppressing wrinkles or cracks in the top surface 90, the outer corner 91, the longitudinal wall 92, the inner corner 93, and the flange 94, the outer corner 91 and the inner corner 93 with smaller radii of curvature are formed.

[0071] (2) In the finishing molding step, by pressing the outer peripheral edge of the intermediate molded part 8, which is further outward than the concave part 83, a stepped bend 96 is formed while suppressing the inflow of material from the outer peripheral edge. Furthermore, in the molded part 9 obtained after the finishing molding step, the radius of curvature R of the first curved outer corner 91a and the second curved outer corner 91b, which are curved portions in plan view, is greater than the radius of curvature r of the portion of the bend 96 that is circumferentially outer relative to the curved outer corners 91a and 91b. Therefore, wrinkles can be suppressed in the portion of the flange 94 of the molded part 9 that is further inward than the bend 96, so that when the molded part 9 is used as a battery casing, the flange 94 can be used as a sealing surface.

[0072] (3) In the finishing forming step, the first intermediate flat portion 87, which is more inward than the protrusion 81, is pressed in the intermediate molded part 8 by the pad mold 42, and the first flat portion 97 is formed on the top surface 90 of the molded part 9. In addition, in the molded part 9 obtained after the finishing forming step, a step portion 95 is formed between the first flat portion 97 and the second flat portion 98, which is more outward than the first flat portion 97, such that the second flat portion 98 is closer to the flange portion 94 side along the stamping direction F than the first flat portion 97. By forming this step portion 95, wrinkles between the first flat portion 97 and the outer corner portion 91 that may occur when the protrusion 81 is pressed towards the flange portion 94 side along the stamping direction F in the finishing forming step can be reduced.

[0073] (4) Generally speaking, if aluminum or aluminum alloy sheets are formed by deep drawing, cracks are easily generated due to local stretching. In contrast, in this embodiment, by forming the molded article 9 from the aluminum or aluminum alloy workpiece W through the drawing and finishing forming steps described above, the generation of cracks can be suppressed while forming the outer corner 91 and inner corner 93 with smaller radii of curvature.

[0074] The above description illustrates one embodiment of the present invention, but the invention is not limited thereto. Appropriate modifications to the details can be made within the scope of the invention's intent.

[0075] Figure Labels

[0076] W: Workpiece

[0077] 1: First stamping processing device

[0078] 21: Lower mold

[0079] 21a: Mold surface

[0080] 211: Top surface

[0081] 212: Step difference surface

[0082] 213: Convex surface

[0083] 214: Longitudinal wall

[0084] 215: Concave surface

[0085] 216: Flange surface

[0086] 4: Second stamping processing device

[0087] 41: Lower mold

[0088] 41a: Mold surface

[0089] 412: Top surface

[0090] 413: Convex surface

[0091] 414: Longitudinal wall

[0092] 415: Concave surface

[0093] 416: Flange surface

[0094] 42: Molding pad

[0095] 43: Movable model

[0096] 43a: Mold surface

[0097] 432: Top surface

[0098] 433: Concave surface

[0099] 434: Longitudinal wall

[0100] 435: Convex surface

[0101] 436: Flange surface

[0102] 437: Fixing part

[0103] 8: Intermediate molded products

[0104] 81: convex part

[0105] 82: Middle longitudinal wall section

[0106] 83: Concave

[0107] 84: Middle flange portion

[0108] 85: Intermediate step difference

[0109] 87: First intermediate plane section

[0110] 9: Molded products

[0111] 90: Top face

[0112] 91: Outer corner

[0113] 91a: First curved outer corner (curved outer corner)

[0114] 91b: Second curved outer corner (curved outer corner)

[0115] 92: Longitudinal wall section

[0116] 93: Inner corner

[0117] 94: Flange portion

[0118] 95: Step Difference Part

[0119] 96: Bending section

[0120] 97: First planar part

[0121] 98: Second Plane Section

Claims

1. A stamping forming method, comprising a drawing forming step and a finishing forming step, wherein a formed article is hat-shaped in cross-section and includes a top portion orthogonal to the stamping direction, a longitudinal wall portion extending along the stamping direction from an edge of the top portion, a flange portion orthogonal to the stamping direction from an edge of the longitudinal wall portion, an outer corner portion between the top portion and the longitudinal wall portion, and an inner corner portion between the longitudinal wall portion and the flange portion, characterized in that... In the aforementioned drawing forming step, an intermediate formed product is formed from the aforementioned workpiece, including a convex portion corresponding to the aforementioned outer corner portion and a concave portion corresponding to the aforementioned inner corner portion. Furthermore, the radii of curvature of the aforementioned convex portion and the aforementioned concave portion in cross-section are made larger than those of the aforementioned outer corner portion and the aforementioned inner corner portion, and the cross-sectional shape of the aforementioned convex portion bulges more towards the aforementioned top surface side along the aforementioned stamping direction compared to the aforementioned outer corner portion. In the aforementioned finishing and forming step, by pressing the portion of the intermediate molded article that is further inward than the aforementioned protrusion and the portion that is further outward than the aforementioned concave, material outflow from the aforementioned inner side and material inflow from the aforementioned outer side are suppressed. At the same time, the aforementioned protrusion is pressed towards the aforementioned concave side along the aforementioned stamping direction, thereby forming the aforementioned outer corner, the aforementioned inner corner, and the stepped bend. In the aforementioned molded article, the radius of curvature of the curved outer corner portion, which is a curved portion in a top view along the aforementioned stamping direction, is greater than the radius of curvature of the portion of the aforementioned bent portion that is circumferentially outside the aforementioned curved outer corner portion in a top view.

2. The stamping forming method according to claim 1, wherein, In the aforementioned finishing and shaping step, the first intermediate flat portion, which is further inward than the aforementioned protrusion, is formed on the aforementioned top surface of the aforementioned molded article by pressing it with a pad mold. In the aforementioned molded article, a stepped portion is formed between the aforementioned first planar portion and the second planar portion which is further outward than the first planar portion in the aforementioned top surface, such that the second planar portion is closer to the aforementioned flange portion side along the aforementioned stamping direction than the aforementioned first planar portion.

3. The stamping forming method according to claim 1, wherein, The aforementioned workpiece is an aluminum or aluminum alloy sheet.

4. The stamping forming method according to claim 2, wherein, The aforementioned workpiece is an aluminum or aluminum alloy sheet.

Images