Method of forming sheet material, method of forming can lid, and method of forming can bottom

Abstract

To increase the plate thickness of an annular projecting part in a wide range including a necessary range by a simple manufacturing process while preventing unintended deformation of a material due to relative pushing.SOLUTION: A method of forming a plate material according to the present invention includes a step of forming a center plate portion and forming an outer peripheral plate portion via a side wall portion rising upward on an outer peripheral side of the center plate portion, a step of forming an annular curved portion on an inner peripheral side of the side wall portion, and a step of deforming at least the annular curved portion to selectively form an annular protruding portion having an increased plate thickness. In the step of forming the annular protruding portion, while the annular curved portion is supported by a support member that is relatively movable in a second direction opposite to a first direction in which the annular protruding portion to be formed protrudes, a pressing force in the first direction is applied to the outer peripheral plate portion to generate a compressive stress in the second direction in the side wall portion, and at least a part of the plate material constituting the side wall portion is moved on a support surface of the support member to form the annular protruding portion having a selectively increased plate thickness.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for forming a plate material, a method for forming a can lid, and a method for forming a can bottom. [Background technology]

[0002] Metal can containers (metal cans) are required to have as small a thickness as possible while still maintaining pressure resistance in order to conserve material resources, reduce weight, etc. For example, in the can lid and can bottom, so-called buckling can occur due to an increase in internal pressure, so there is a strong demand for innovations to maintain pressure resistance.

[0003] For example, in order to reduce the thickness of the plate material that will become the can lid or bottom while maintaining its pressure resistance, it is known to form an annular protrusion consisting of an inner wall portion, a curved convex portion, and a part of the outer wall portion on the outer side of the central plate portion that will become the lid surface or bottom surface, and to increase the plate thickness of the curved convex portion.

[0004] For example, Patent Document 1 describes that in a can lid having a center panel portion (central plate portion), a panel wall portion (inner peripheral wall portion), a chuck wall radius portion (curved convex portion), a chuck wall portion (outer peripheral wall portion), and a curl portion, by making the plate thickness t2 of the lower end of the panel wall portion greater than the plate thickness t1 of the center panel portion (t2>t1), the pressure resistance strength is improved while the plate thickness of the plate material is reduced. Patent Document 1 also describes making the plate thickness t3 of the chuck wall radius portion greater than the plate thickness t1 of the center panel portion (t3>t1), and indicates the range within which the pressure resistance strength needs to be improved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-16093 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when forming an annular protrusion on a sheet material using a conventional method, such as the can lid manufacturing method described in Patent Document 1, if the annular protrusion is formed in a single stroke using upper and lower dies, the sheet thickness on only one side of the annular protrusion increases significantly, and it is not possible to increase the sheet thickness in the range necessary to improve the pressure resistance of the annular protrusion (also referred to as the "required range"). To increase the sheet thickness over a wide range, including the required range of the annular protrusion, using the conventional method requires relative pressing (pressing) of the central sheet portion in multiple stages, and each stage requires the use of a die with a different shape, which makes the manufacturing process complicated.

[0007] Furthermore, the relative pressing (pressing) of the sheet material not only increases its thickness but also attempts to release stress through deformation and material flow, but with conventional methods, the sheet material tends to flow toward the outer wall, making it difficult to maintain the required shape for, for example, a can lid or can bottom. In other words, the range in which relative pressing can be performed while maintaining the shape is narrow, and depending on the required performance, there are cases in which a sufficient increase in sheet thickness cannot be achieved.

[0008] The present invention addresses these circumstances by providing a method for forming a sheet material, a method for forming a can lid, and a method for forming a can bottom that are capable of increasing the sheet thickness of the annular protrusion over a wide range, including the required range, through a simple manufacturing process while preventing unintended deformation of the material due to relative pressing (pressing). [Means for solving the problem]

[0009] In order to solve such problems, the method for forming a sheet material of the present invention includes the steps of forming a central sheet portion and forming an outer peripheral sheet portion via side wall portions that rise upward on the outer peripheral side of the central sheet portion, forming an annular curved portion on the inner peripheral side of the side wall portions, and deforming at least the annular curved portion to form an annular protrusion having a selectively increased sheet thickness. In the step of forming the annular protrusion, the annular curved portion is supported by a support member that is relatively movable in a second direction opposite to a first direction in which the annular protrusion to be formed protrudes, and a pressing force in the first direction is applied to the outer peripheral sheet portion, thereby generating a compressive stress in the second direction in the side wall portions, and at least a portion of the sheet material that constituted the side wall portions is moved on the support surface of the support member, thereby forming the annular protrusion having a selectively increased sheet thickness.

[0010] The can lid forming method of the present invention is characterized in that it includes the sheet material forming method of the present invention as part of all steps. The can bottom forming method of the present invention is characterized in that it includes the sheet material forming method of the present invention as part of all steps. [Effects of the Invention]

[0011] According to the present invention having such characteristics, it is possible to increase the plate thickness of the annular protrusion over a wide range, including the required range, using a simple manufacturing process while preventing unintended deformation of the material due to relative pressing (pressing). [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a side view of a plate having an annular protrusion in schematic form; FIG. [Figure 2] FIG. 1 is a flow diagram illustrating a process for forming a plate material having an annular protrusion in a schematic form. [Figure 3] FIG. 1 is a first explanatory diagram of a forming process for a plate material having an annular protrusion in a schematic form. [Figure 4] FIG. 10 is a second explanatory diagram of the forming process of the plate material having the annular protrusion in a schematic form. [Figure 5]FIG. 2 is a side view of the can lid in the first embodiment. [Figure 6] FIG. 2 is a flow chart showing the can lid forming process in the first embodiment. [Figure 7] FIG. 2 is a first explanatory view of a can lid forming process according to the first embodiment. [Figure 8] FIG. 4 is a second explanatory view of the can lid forming step in the first embodiment. [Figure 9] FIG. 10 is a third explanatory view of the can lid forming process in the first embodiment. [Figure 10] 1 is a side cross-sectional view showing a schematic configuration of a forming device used in a can lid forming step in a first embodiment. [Figure 11] 1A and 1B are partial end views showing the intermediate formed body used in Examples 1 to 5 of the first embodiment, illustrating measurement points a to v for the plate thickness [mm]. (a) shows measurement points a to e and p to v. (b) is an enlarged view of a partial region (region surrounded by a square frame) including the chuck wall radius portion shown in (a), illustrating measurement points f to o. [Figure 12] FIG. 1 is a diagram showing the plate thickness [mm] measured at measurement points a to v for each bearing force (countersink holding force) [kgf] in Examples 1 to 5. [Figure 13] 1 is a table showing the values ​​of the lid diameter, shape, original plate thickness [mm], support force (countersink holding force) [kgf], UD [mm], PH [mm], and pressure resistance value [MPa] for the formed cans formed in Examples 6 to 8 of the first embodiment and Comparative Example 1. [Figure 14] FIG. 1 is a diagram illustrating measurement points of UD [mm] and PH [mm] for formed cans formed in Examples 6 to 8 of the first embodiment and Comparative Example 1. [Figure 15] FIG. 10 is a first explanatory view of a can lid forming process according to the second embodiment. [Figure 16] FIG. 10 is a second explanatory view of the can lid forming process in the second embodiment. [Figure 17] FIG. 10 is a third explanatory view of the can lid forming step in the second embodiment. [Figure 18] FIG. 10 is a first explanatory view of the can bottom forming step in the third embodiment. [Figure 19]FIG. 10 is a second explanatory view of the can bottom forming step in the third embodiment. [Figure 20] FIG. 10 is a partial end view showing a part of the intermediate formed body for the can bottom used in Example 9 of the third embodiment. [Figure 21] FIG. 10 is a partial end view showing a part of the final formed product of the can bottom used in Example 9 of the third embodiment, showing measurement points w1 to w7 of the plate thickness [mm]. [Figure 22] 10 is a table showing measurement results in Example 9 of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts with the same function, and duplicate explanations in each drawing will be omitted as appropriate. In the following description, "almost..." means "substantially...". For example, "almost circular" means not only a "circular" (perfect circle), but also an elliptical shape or the like that is similar to a circle.

[0014] [Summary form] A method for forming a plate material according to a general embodiment (overview) of the present invention forms a formed material 1E, as shown in Fig. 1. The formed material 1E is formed from a substantially disk-shaped plate material 11E. The formed material 1E has a center panel portion (center plate portion) 12E, which is a substantially circular, substantially flat surface located approximately in the center of the plate material 11E, an annular protrusion portion 13E located on the outer periphery of the center panel portion 12E, and an outer periphery panel portion (outer periphery plate portion) 14E located further on the outer periphery of the center panel portion 12E.

[0015] The plate material 11E is made of a material mainly made of metal. The material mainly made of metal is not particularly limited, but may be, for example, a single metal material such as aluminum, aluminum alloy, or steel, or a clad material of these metals, or a composite metal material in which one or both sides of these metals are subjected to surface treatment, painting (paint containing lubricant, etc.), lamination, etc.

[0016] A curved end 121E is formed as the radially outer end (outer edge) of the center panel portion (central plate portion) 12E, and an inner circumferential wall portion 131E is formed so as to extend downward in a substantially linear fashion from the outer end (terminal end) of the curved end 121E. The curved convex portion 132E is a curved portion formed so that its inner end (inner circumferential end) is connected to the lower end of the inner circumferential wall portion 131E and its outer end (outer circumferential end) is connected to the lower end of the outer circumferential wall portion 133E. The outer circumferential wall portion 133E extends upward in a substantially linear fashion from the outer end of the curved convex portion 132E and is formed so as to connect to a curved end (curved portion) 141E formed as the radially inner end of the outer panel portion 14E. The annular protrusion 13E is composed of the inner circumferential wall portion 131E, the curved convex portion 132E, and the outer circumferential wall portion 133E.

[0017] The forming process (forming method) of the plate material 11E for forming this formed material 1E includes, for example, a blank punching process S31, a central-peripheral plate portion forming process S32, an annular curved portion forming process S33, and an annular protruding portion forming (plate thickness increasing forming) process S34, as shown in Fig. 2. In these forming processes (S31 to S34), the shape of the plate material 11E is changed as shown in states m1 to m6 in Figs. 3 and 4 to form the formed material 1E in state m7 in Fig. 4.

[0018] In the blank punching process S31, the shape varies depending on the target molded product (for example, it may be elliptical, polygonal, etc.), but for example, the plate material 11E to be processed is formed into an approximately disk shape using upper and lower punching tools (not shown) for punching the plate material 11E into an approximately disk shape (state m1 in Figure 3).

[0019] In the center-to-peripheral plate forming step S32, for example, using upper and lower center drawing tools (not shown) for drawing the approximately central portion of the approximately disk-shaped plate material 11E, a blank-holding force is applied to the outer peripheral portion of the approximately disk-shaped plate material 11E (the later outer peripheral panel portion (outer peripheral plate portion) 21E), while drawing is performed on the inner peripheral side. As a result, as shown in state m2 in Figure 3, the center panel portion (center plate portion) 22E is formed, and the outer peripheral panel portion (outer peripheral plate portion) 21E is formed via the side wall portion 23E that rises upward on the outer peripheral side of the center panel portion 22E.

[0020] In the annular curved portion forming process S33 and the annular protrusion forming (thickening forming) process S34, the plate material 11E (state m3 in Figure 3) on which the center panel portion (central plate portion) 22E and the outer peripheral panel portion (outer peripheral plate portion) 21E have been formed is formed using an upper tool U5 located above it and a lower tool L5 located below it. The upper tool U5 includes an annular upper outer tool U51, an upper central tool U52, and an annular guide tool U53 located between them. The lower tool L5 includes an annular lower outer tool L51, a lower central tool L52, and an annular support tool (support member) L53 located between them.

[0021] In the annular curved portion forming step S33, the sheet material 11E on which the center panel portion 22E and the outer peripheral panel portion 21E have been formed is placed on the lower tool L5 (state m3 in FIG. 3). Then, the center panel portion (central plate portion) 22E of the sheet material 11E is sandwiched and fixed between the contact surfaces U52a of the upper central tool U52 and L52a of the lower central tool L52 (state m4 in FIG. 3). This fixing of the center panel portion 22E continues thereafter until the annular protrusion forming (plate thickness increasing forming) step S34 is completed.

[0022] In this state, in the annular curved portion forming step S33, as shown in state m4 in Fig. 3 and state m5 in Fig. 4, the upper outer tool U51 applies a pressing force in a first direction (downward), which is a direction in which the annular protrusion 13E (state m6 in Fig. 4) to be formed later will protrude. At this time, the upper outer tool U51 presses down the lower outer tool L51 while sandwiching the outer peripheral panel portion (outer peripheral plate portion) 21E between the abutment surface U51a of the upper outer tool U51 and the abutment surface L51a of the lower outer tool L51.

[0023] The guide tool U53 may or may not descend, as shown in state m4 in Fig. 3 and states m5 and m6 in Fig. 4. In either case, the guide tool U53 and the lower outer tool L51 are positioned around the side wall portion 23E. This prevents buckling of the side wall portion 23E due to compressive stress when the side wall portion 23E is subjected to compressive stress in the subsequent annular protrusion forming (thickness increasing) process S34.

[0024] In this annular curved portion forming step S33, the upper outer tool U51 presses down the lower outer tool L51 so that the height position of its contact surface U51a approaches the height position of the contact surface (support surface) L53a of the support tool (support member) L53. That is, the support tool L53 is relatively movable in a second direction (upward), which is the opposite direction to the first direction (downward). The support tool L53 applies a support force in the second direction (upward) to the sheet material 11E on its contact surface (support surface) L53a. Therefore, when the upper outer tool U51 presses down the lower outer tool L51, the inner periphery of the side wall portion 23E is supported by the support tool L53 that applies this support force, forming an annular curved portion 24E that curves along the shape of the contact surface L53a. The sheet material 11E having such an annular curved portion 24E formed therein is referred to as a preform 11Ea (state m5 in FIG. 4).

[0025] In the annular protrusion molding (plate thickness increasing molding) process S34, for example, as shown in states m5 and m6 in Figure 4, the annular curved portion 24E of the molded preform 11Ea is supported by the abutment surface (support surface) L53a of the support tool (support member) L53 (by a support force directed in the second direction (upward)), while a pressing force is applied in the first direction (downward) to the outer panel portion (outer plate portion) 21E.

[0026] At this time, the upper outer tool U51 continuously applies a pressing force in the first direction (downward) so as to press down the lower outer tool L51 with its contact surface U51a. That is, the upper outer tool U51 continuously applies a pressing force to the outer peripheral panel portion (outer peripheral plate portion) 21E sandwiched between the contact surface U51a and the contact surface L51a of the lower outer tool L51, thereby pressing the outer peripheral panel portion 21E in the first direction (downward). At the same time, the guide tool U53 positions the side wall portion 23E between its outer guide surface U53a and the contact surface L51b of the lower outer tool L51, thereby preventing the side wall portion 23E from buckling due to the compressive stress applied to the side wall portion 23E. As a result, the support force of the support tool (support member) L53 can apply a greater pressing force to the annular curved portion 24E via the side wall portion 23E than the upper outer tool U51.

[0027] In this way, the support tool L53 applies a support force in a second direction (upward) opposite to the first direction (downward) in which the annular protrusion 13E (state m6 in FIG. 4) to be formed protrudes, while the upper outer tool U51 presses in. This deforms the annular curved portion 24E and generates compressive stress in the second direction (upward) in the side wall portion 23E, moving at least a portion of the plate material that constitutes the side wall portion 23E on the contact surface L53a of the support tool L53 toward the inside of the outer peripheral panel portion (outer peripheral plate portion) 21E. As a result, unintended deformation of the material due to relative pressing (pressing) is prevented, and the plate thickness of the moved portion is selectively increased to form the annular protrusion 13E (state m6 in FIG. 4).

[0028] After molding the formed material 1E having this annular protrusion 13E, the formed material 1E is removed from the upper tool U5 and the lower tool L5 to obtain the formed material 1E in state m7 of FIG. 4. In the formed material 1E, the annular protrusion 13E has an increased thickness over a wide area, including the area required to improve the pressure resistance of the curved convex portion 132E between the inner peripheral wall portion 131E and the outer peripheral wall portion 133E. Note that the example of state m7 in FIG. 4 shows the outer peripheral panel portion (outer peripheral plate portion) 21E and the center panel portion (center plate portion) 22E at approximately the same height, but this is not limited to this example. The height positions of the outer peripheral panel portion 21E and the center panel portion 22E may differ as necessary. For example, the height position of the outer peripheral panel portion 21E may be lower than the height position of the center panel portion 22E.

[0029] In this manner, in the molding method for the plate material 11E according to the general embodiment, the outer peripheral panel portion (outer peripheral plate portion) 21E is continuously (in one stroke) pressed relative to one another using the same device (upper and lower dies) having an upper tool U5 and a lower tool L5. In other words, the molding method according to this general embodiment does not perform this pressing in multiple stages using dies of different shapes each time, but rather, with this simple manufacturing process, it is possible to form the annular protrusion 13E in which the plate thickness is increased within the range required to improve pressure resistance while preventing unintended deformation of the material due to the relative pressing.

[0030] Instead of the example described here, the forming process of the formed material 1E may use the same apparatus (upper and lower dies) consistently from the blank punching process S31 to the annular protrusion forming (thickness increasing) process S34. Alternatively, the forming process of the formed material 1E may use an apparatus (upper and lower dies) different from the apparatus (apparatus having an upper tool U5 and a lower tool L5) used in the annular protrusion forming (thickness increasing) process S34 from the blank punching process S31 to the annular curved portion forming process S33. In this case, the preform 11Ea is prepared in advance in this different apparatus, and the preform 11Ea is sequentially placed between the upper tool U5 and the lower tool L5.

[0031] In addition, in this overview, an example has been described in which the upper outer tool U51 applies a pressing force in a first direction (downward) to the plate material 11E on the contact surface (support surface) L53a so that the upper outer tool U51 approaches the support tool (support member) L53, but this is not limiting. The support tool (support member) L53 is relatively movable in a second direction (upward). Therefore, instead of the example described here, the support tool (support member) L53 may apply a pressing force in the second direction (upward) to the plate material 11E on the contact surface (support surface) L53a so that the support tool (support member) L53 approaches the upper outer tool U51.

[0032] In this case, the outer peripheral panel portion 21E is sandwiched and fixed between the upper outer tool U51 and the lower outer tool L51, and in this state, the support tool (support member) L53 pushes up the guide tool U53. As a result, an annular curved portion 24E having a curved shape that follows the shape of the contact surface L53a of the support tool L53 is formed on the inner peripheral side of the side wall portion 23E, and then an annular protrusion 13E is formed.

[0033] First to third embodiments, which are specific embodiments of the present invention, will be described below. In the first to third embodiments, descriptions of the same configurations as those in the above-described general embodiment or the same configurations as each other will be omitted.

[0034] [First embodiment] The sheet material forming method according to the first embodiment forms a can lid 3E, as shown in Fig. 5, as a formed material. The can lid 3E has a center panel portion (central plate portion) 31E, a panel wall portion (inner peripheral wall portion) 321E, a chuck wall radius portion (curved convex portion) 322E, a chuck wall portion consisting of a first chuck wall portion (first outer peripheral wall portion) 323E and a second chuck wall portion (second outer peripheral wall portion) 33E, and a curl portion 34E. Here, the panel wall portion 321E, the chuck wall radius portion 322E, and the first chuck wall portion 323E form an annular protrusion portion 32E.

[0035] The center panel portion (central plate portion) 31E is located approximately in the center of the can lid 3E and consists of a substantially circular, substantially flat surface. If the can lid 3E is a stay-on tab type, the center panel portion 31E is provided with a tab, score, etc. for opening.

[0036] A curved end portion 311E is formed as the radially outer end portion of the center panel portion 31E, and a panel wall portion (inner peripheral wall portion) 321E is formed so as to extend downward in a substantially straight line from the outer end of the curved end portion 311E. The chuck wall radius portion (curved convex portion) 322E is a curved portion formed so that its inner end is connected to the lower end of the panel wall portion 321E and its outer end is connected to the lower end of a first chuck wall portion (first outer peripheral wall portion) 323E.

[0037] The first chuck wall portion (first outer peripheral wall portion) 323E extends upward in a substantially linear manner from the outer end of the chuck wall radius portion (curved convex portion) 322E. The second chuck wall portion (second outer peripheral wall portion) 33E extends in a substantially linear manner from the upper end of the first chuck wall portion 323E so as to be inclined upward and outward, and its upper end is formed so as to connect to the curved portion of the curl portion 34E.

[0038] The method for forming the can lid 3E includes, as part of its overall steps, the method for forming the sheet material 11E according to the above-described general embodiment. That is, as shown in Fig. 6, the method for forming the can lid 3E includes a blank punching step S41, a peripheral drawing step S42, a central-peripheral sheet portion forming step S43, an annular curved portion forming step S44, an annular protrusion forming (sheet thickness increasing forming) step S45, and a (can lid) shape forming step S46. In these forming steps (S41 to S46), the shape of the sheet material 41E is changed as shown in states m11 to m18 in Figs. 7 to 9, and the can lid 3E in state m19 in Fig. 9 is formed.

[0039] In the blank punching step S41, for example, upper and lower punching tools (not shown) for punching the plate material 41E to be processed into a substantially disk shape are used to form the plate material 41E into a substantially disk shape (state m11 in FIG. 7).

[0040] The plate material 41E is made of a material mainly composed of metal. The metal material is not particularly limited, but may be, for example, a single metal material such as aluminum, aluminum alloy, or steel, or a clad material of these metals, or a composite metal material in which one or both sides of these metals are subjected to surface treatment, painting (paint containing lubricant, etc.), lamination, etc.

[0041] In the outer periphery drawing step S42, for example, using an upper and lower outer periphery drawing tool (not shown) for drawing the outer periphery of the substantially disk-shaped plate material 41E, the plate-like portion on the inner periphery side of the outer periphery of the substantially disk-shaped plate material 41E shown in state m11 in Fig. 7 is fixed and the outer periphery is drawn. As a result, an outer periphery side portion 43E is formed on the outer periphery side of the plate-like portion 42E of the plate material 41E, which hangs down via a curved corner (extending in a direction substantially perpendicular (downward) to the plate-like portion 42E), as shown in state m12 in Fig. 7.

[0042] In the center-periphery plate portion forming step S43, for example, for a plate material 41E in state m12 of FIG. 7, upper and lower center drawing tools (not shown) for drawing the approximately central portion of the plate-shaped portion 42E are used to draw the inner periphery of the outer panel portion (outer plate portion) 420E, which is the outer peripheral portion of the plate-shaped portion 42E, while applying a blank holding force to the outer panel portion (outer plate portion) 420E. As a result, as shown in state m13 of FIG. 7, a center panel portion (center plate portion) 45E is formed, and an outer peripheral panel portion (outer peripheral plate portion) 421E is formed via a side wall portion 46E that rises on the outer peripheral side of the center panel portion 45E. Note that the shape of the center panel portion (center plate portion) 45E may be, for example, a substantially flat surface as exemplified in FIG. 7, but is not limited to such a substantially flat surface and may be other shapes. The shape of the center panel portion 45E may be a curved (dome) shape (not shown) that gently protrudes in a first direction (downward) in which the annular protrusion 32Ea (state m16 in Figure 8) to be molded later protrudes, or in the opposite second direction (upward).

[0043] In the annular curved portion forming step S44 and the annular protrusion forming (thickening forming) step S45, the sheet material 41E (state m13 in FIG. 7) having the center panel portion (central plate portion) 45E and the outer peripheral panel portion (outer peripheral plate portion) 421E formed therein is formed using a forming device M4 having an upper tool U6 and a lower tool L6, for example, as shown in FIG. 10. As shown in FIG. 10 and state m14 in FIG. 8, for example, the upper tool U6 includes an annular upper outer tool U61, an upper central tool U62, and an annular guide tool U63 positioned therebetween. The lower tool L6 includes an annular lower outer tool L61, a lower central tool L62, and an annular support tool (support member) L63 positioned therebetween.

[0044] 10, the forming device M4 has an upper tool U6 equipped with cushion pins Ua11 and Ua12 connected to an air cylinder, and a lower tool L6 equipped with cushion pins La11 and La12 connected to an air cylinder. In the upper tool U6, the upper central tool U62 can be moved up and down by the cushion pins Ua11 and Ua12 connected to the air cylinder, and the guide tool U63 can be moved up and down by the cushion pin Ua12 connected to the air cylinder.

[0045] In the lower tool L6, the support tool (support member) L63 can be moved up and down by cushion pins La11 connected to an air cylinder, and the lower outer tool L61 can be moved up and down by cushion pins La12 connected to an air cylinder. Note that the molding device M4 may be provided with elastic members such as spring members, or hydraulic cylinders (for example, oil pressure cylinders) instead of the cushion pins Ua11, Ua12, La11, and La12 connected to such air cylinders.

[0046] In the annular curved portion forming step S44, for example, as shown in state m14 in Figure 8, the sheet material 41E on which the center panel portion (central plate portion) 45E and the outer peripheral panel portion (outer peripheral plate portion) 421E have been formed is sandwiched between the upper tool U6 and the lower tool L6. At this time, the center panel portion 45E of the sheet material 41E is sandwiched and fixed between the contact surface U62a of the upper central tool U62 and the contact surface L62a of the lower central tool L62. This fixation of the center panel portion 45E continues until the annular protrusion forming (plate thickness increasing) step S45 is completed.

[0047] In this state, in the annular curved portion forming process S44, the upper outer tool U61 applies a pressing force in the first direction (downward) as shown in states m14 and m15 in Fig. 8. At this time, the upper outer tool U61 presses down the lower outer tool L61 while sandwiching the outer peripheral panel portion (outer peripheral plate portion) 421E between the contact surface U61a of the upper outer tool U61 and the contact surface L61a of the lower outer tool L61.

[0048] The guide tool U63 may be either one that does not descend, as shown in states m14 to m16 in Figure 8, or one that descends. In either case, the guide tool U63 and the lower outer tool L61 are positioned around the side wall portion 46E. This makes it possible to prevent buckling of the side wall portion 46E due to compressive stress when the side wall portion 46E is subjected to compressive stress in the subsequent annular protrusion forming (thickness increasing forming) step S45.

[0049] In this annular curved portion forming step S44, the upper outer tool U61 presses down the lower outer tool L61 so that the height position of its contact surface U61a approaches the height position of the contact surface (support surface) L63a of the support tool (support member) L63. That is, the support tool L63 is relatively movable in the second direction (upward). This support tool L63 applies a support force in the second direction (upward) to the plate material 41E on its contact surface (support surface) L63a. Therefore, by pressing down the lower outer tool L61 with the upper outer tool U61, an annular curved portion 47E is formed on the inner periphery of the side wall portion 46E, supported by the support tool L63 that applies this support force, and the annular curved portion 47E is curved along the shape of the contact surface L63a. The plate material 41E with such an annular curved portion 47E formed therein is referred to as a preform 41Ea (state m15 in FIG. 8 ).

[0050] In the annular protrusion molding (plate thickness increasing molding) process S45, for example, as shown in states m15 and m16 in Figure 8, the annular curved portion 47E of the molded preform 41Ea is supported by the abutment surface (support surface) L63a of the support tool (support member) L63 (by a support force directed in the second direction (upward)), while a pressing force is applied in the first direction (downward) to the outer panel portion (outer plate portion) 421E.

[0051] At this time, the upper outer tool U61 continuously applies a pressing force in the first direction (downward) so as to press down the lower outer tool L61 with its contact surface U61a. That is, the upper outer tool U61 continuously applies a pressing force to the outer peripheral panel portion (outer peripheral plate portion) 421E sandwiched between the contact surface U61a and the contact surface L61a of the lower outer tool L61, thereby pressing the outer peripheral panel portion 421E in the first direction (downward). At the same time, the guide tool U63 positions the side wall portion 46E between its outer guide surface U63a and the contact surface L61b of the lower outer tool L61, thereby preventing the side wall portion 46E from buckling due to the compressive stress applied to the side wall portion 46E. As a result, the support force of the support tool (support member) L63 can apply a greater pressing force to the annular curved portion 47E via the side wall portion 46E than the upper outer tool U61.

[0052] In this way, the upper outer tool U61 presses the side wall 46E while applying a supporting force in the second direction (upward) with the support tool L63. This deforms the annular curved portion 47E and generates a compressive stress in the second direction (upward) in the side wall 46E, moving at least a portion of the plate material that constitutes the side wall 46E on the contact surface L63a of the support tool L63 toward the inside of the outer peripheral panel portion (outer peripheral plate portion) 421E.

[0053] This annular protrusion forming (thickness increasing forming) step S45 prevents unintended deformation of the material due to relative pushing (pressing), and forms an intermediate formed body 30E (state m16 in Figure 8) of a can lid (before shape forming (reforming)) having an annular protrusion 32Ea whose thickness is selectively increased based on the moved portion. In the intermediate formed body 30E, the annular protrusion 32Ea has an increased thickness over a wide range, including the range required to improve the pressure resistance of the chuck wall radius portion (curved convex portion) 322Ea.

[0054] As described above, in the method for forming the plate material 41E according to the first embodiment, the outer peripheral panel portion (outer peripheral plate portion) 421E is pressed (pressed) relative to the outer peripheral panel portion (outer peripheral plate portion) continuously (in one stroke) using the same device (upper and lower dies) having the upper tool U6 and the lower tool L6. In other words, the forming method according to the first embodiment does not perform this pressing in multiple stages using dies of different shapes each time, but can form the annular protrusion 32Ea with an increased plate thickness over a wide range in this simple manufacturing process.

[0055] After the intermediate can lid formed body 30E (before shape forming) having the annular protrusion 32Ea is formed in this manner, the intermediate can lid formed body 30E is removed from the upper tool U6 and the lower tool L6.

[0056] The can lid shape forming step S46 is a step of reforming the shape of the can lid intermediate formed body 30E to form it into the shape of a can lid. This can lid shape forming step S46 includes a step of forming a chuck wall portion consisting of a first chuck wall portion (first outer peripheral wall portion) 323E and a second chuck wall portion (second outer peripheral wall portion) 33E shown in state m19 in Figure 9.

[0057] This can lid shape forming process S46 may further include a known process (not shown) of forming a curled portion 34E (state m18 in Figure 9) on the outer side of the annular protrusion 32Ea (or the annular protrusion 32E after forming), in any order or simultaneously with the process of forming the above-mentioned chuck wall portion.

[0058] The center panel portion 45E of the intermediate formed body 30E may have another shape other than a substantially flat surface as shown in state m16 in Fig. 8, for example, a curved (dome) shape (not shown) that gently protrudes in the second direction (upward). In this case, the can lid shape forming step S46 may further include at least one or both of a known step of forming the center panel portion 45E into a desired shape (for example, a step of forming a substantially flat surface) and a step of forming the curled portion 34E, in any order or simultaneously with the step of forming the chuck wall portion.

[0059] In the can lid shaping step S46, as shown in state m17 in Figure 9, the shape of the can lid intermediate formed body 30E is reformed using a can lid shaping device M5 having an upper tool U7 and a lower tool L7. The upper tool U7 has an annular upper outer tool U71, an upper central tool U72, and an annular processing tool U73 located therebetween. The lower tool L7 has an annular lower outer tool L71, a lower central tool L72, and an annular protrusion support tool L73 located therebetween.

[0060] In this can lid shape forming step S46, as shown in state m17 in Fig. 9, after placing the intermediate formed body 30E of the can lid (before shape forming) on ​​the lower tool L7, the upper outer tool U71, the upper central tool U72, and the processing tool U73 may be lowered, for example, simultaneously to perform the can lid shape forming step S46. Alternatively, depending on the shape of the can lid, the timing of the descent of the upper outer tool U71, the upper central tool U72, and the processing tool U73 may be changed as appropriate.

[0061] At this time, as the upper central tool U72 descends, the annular protrusion 32Ea is supported by the contact surface (support surface) L73a of the annular protrusion support tool L73, and the annular protrusion 32Ea between the lower central tool L72 and the lower outer tool L71 is formed into an annular protrusion 32E (state m18 in FIG. 9) shaped along the contact end U72b of the upper central tool U72 and the contact surface (support surface) L73a of the annular protrusion support tool L73. That is, at this time, a first chuck wall portion (first outer peripheral wall portion) 323E (state m19 in FIG. 9) of the chuck wall portion is formed.

[0062] At this time, the upper outer tool U71 descends, causing its contact surface U71a to come into contact with the outer peripheral panel portion (outer peripheral plate portion) 421E on the contact surface (support surface) L71b of the lower outer tool L71, thereby fixing the outer peripheral panel portion 421E. In this state, the processing tool U73 descends, and the outer peripheral panel portion 421E is sandwiched between the contact surface U73a and the contact surface L71a, thereby forming a second chuck wall portion (second outer peripheral wall portion) 33E (state m19 in FIG. 9) that conforms to the shapes of the lower outer tool L71 and the processing tool U73. In this way, a chuck wall portion (state m19 in FIG. 9) consisting of the first chuck wall portion (first outer peripheral wall portion) 323E and the second chuck wall portion (second outer peripheral wall portion) 33E on its outer periphery is formed.

[0063] At this time, a curled portion 34E can also be formed on the outer periphery of the lid. In this case, the lower tool L7 may be provided with a curling tool (not shown) on the outer periphery of the lower outer tool L71. As described above, when the processing tool U73 is lowered with the outer periphery panel portion 421E fixed, the outer periphery panel portion 421E sandwiched between the abutment surface U73a and the abutment surface L71a of the processing tool U73 flows toward the outer periphery. In this state, when the curling tool (not shown) is lowered, the curled portion 34E is formed in a shape that conforms to the abutment surface U71a of the upper outer tool U71 and the abutment surface (not shown) of the curling tool (state m18 in FIG. 9).

[0064] Furthermore, at this time, if the shape of the center panel portion (central plate portion) 45E is another shape (for example, a curved (dome) shape that gently protrudes in the second direction (upward) (not shown)), the shape can be formed into a desired shape, for example, a substantially flat surface. In this case, the upper central tool U72 descends so that its abutment surface U72a presses down on the lower central tool L72, thereby forming the center panel portion (central plate portion) 45E of another shape (for example, a curved (dome) shape that gently protrudes in the second direction) sandwiched between the abutment surface U72a and the abutment surface L72a of the lower central tool L72 into a substantially flat center panel portion (central plate portion) 31E (state m18 in FIG. 9).

[0065] In this case, in the can lid shape forming process S46 in Figure 6, the process of forming the chuck wall portion and the process of forming the center panel portion (central plate portion) 45E into an approximately flat surface are carried out simultaneously, but these processes may also be carried out in any order as separate steps.

[0066] The can lid 3E reformed in this way is removed from the can lid shape forming device M5 to obtain the can lid 3E shown in state m19 in Fig. 9. The reformed can lid 3E in state m19 has a shape in which an annular protruding portion 32E consisting of a panel wall portion (inner peripheral wall portion) 321E, a chuck wall radius portion (curved convex portion) 322E, and a first chuck wall portion (first outer peripheral wall portion) 323E protrudes downward approximately perpendicularly to the extension direction of the center panel portion 31E.

[0067] Instead of the example described here, the can lid 3E forming process may use the same apparatus (upper and lower dies) consistently from the blank punching process S41 to the annular protrusion forming (thickness increasing) process S45. Alternatively, the can lid 3E forming process may use an apparatus (upper and lower dies) different from the apparatus (the apparatus having the above-mentioned upper tool U6 and lower tool L6) used in the annular protrusion forming (thickness increasing) process S45 from the blank punching process S41 to the annular curved portion forming process S44. In this case, the preform 41Ea is prepared in advance in this different apparatus, and the preform 41Ea is placed between the upper tool U6 and the lower tool L6.

[0068] [Examples of the first embodiment (Examples 1 to 5)] Examples (Examples 1 to 5) of the first embodiment will be described. In Examples 1 to 5, an intermediate formed body 40Eb (FIG. 11(a)) before shaping (reforming) the can lid was formed from a sheet material by the blank punching step S41 to the annular protrusion forming (sheet thickness increasing) step S45 described above in the first embodiment. The sheet material used was an aluminum alloy (A5182) (metal portion) with an original thickness of 0.218 mm, with a lubricant-containing paint applied to both sides. As shown in FIG. 11(a), the intermediate formed body 40Eb has a curved (dome-shaped) center panel portion (central plate portion) 45Eb, an outer peripheral panel portion (outer peripheral plate portion) 421Eb corresponding to the outer peripheral panel portion 421E described above, and an annular protrusion portion 32Eb.

[0069] In Examples 1 to 5, in the annular protrusion forming (thickening forming) step S45, the annular curved portion (not shown) was supported by the contact surface (support surface) L63a of the support tool (support member) L63 (by a support force directed upward (the second direction)), while a downward (first direction) pressing force was applied to the outer peripheral panel portion (outer peripheral plate portion) 421Eb. At this time, the support force directed upward (the second direction) by the support tool L63 was applied to the plate portion (of the annular curved portion) on the contact surface (support surface) L63a of the support tool L63. The magnitude of the support force, i.e., the support force (countersink holding force) [kgf], was varied among Examples 1 to 5, and the plate thickness [mm] of the metal portion of the plate of the intermediate formed body 40Eb was measured at measurement points a to v (FIGS. 11(a) and 11(b)) for each different support force (FIG. 12).

[0070] In performing the above-described annular protrusion forming (plate thickness increasing forming) process S45, as shown in Fig. 12, the support force (countersink holding force) [kgf] applied by the support tool L63 was set to 200 kgf in Example 1, 400 kgf in Example 2, 600 kgf in Example 3, 800 kgf in Example 4, and 1000 kgf in Example 5. Graphs G1 to G5 in Fig. 12 are graphs showing the measured values ​​of plate thicknesses [mm] of the metal portion at measurement points a to v in the plate material after processing of step S45 in Example 1 (support force 200 kgf), Example 2 (support force 400 kgf), Example 3 (support force 600 kgf), Example 4 (support force 800 kgf), and Example 5 (support force 1000 kgf), respectively.

[0071] As shown in the measurement results in Fig. 12, in all of Examples 1 to 5 in which an upward (second direction) supporting force (countersink holding force) [kgf] was applied by the support tool L63, the thickness of the metal portion of the plate material could be made thicker than the original plate thickness (0.218 mm) over a wide range within the range of measurement points a to v. Furthermore, from the results of Examples 1 to 5 in Fig. 12, it can be seen that the thickness [mm] of the metal portion of the plate material can be made thicker as the supporting force [kgf] increases.

[0072] Here, it has been confirmed through various experiments, simulations, etc. conducted in advance that the range including measurement points f to i and the range including measurement points l to n on chuck wall radius portion (curved convex portion) 322Eb (FIG. 11(b)) of annular protrusion 32Eb are ranges particularly necessary for improving the pressure resistance of a can container (metal can) with a lid attached after shape forming (reforming) that is formed from intermediate formed body 40Eb. In chuck wall radius portion (curved convex portion) 322Eb shown in FIG. 11(b), the range between the dotted lines including measurement points f to i is referred to as the "main pressure-resistant range X1," and the range between the dotted lines including measurement points l to n is referred to as the "main pressure-resistant range X2." As shown in the measurement results in the main pressure-resistance ranges X1 and X2 in Figure 12, it can be seen that by applying a large value as the support force (countersink holding force) [kgf] in the second direction (upward) using the support tool L63, a sufficiently large plate thickness [mm] value can be obtained in both the main pressure-resistance ranges X1 and X2 (for example, Examples 4 and 5).

[0073] [Examples of the first embodiment (Examples 6 to 8, Comparative Example 1)] Next, examples of the first embodiment (Examples 6 to 8, Comparative Example 1) will be described. In Examples 6 to 8 and Comparative Example 1, the can lid 3Ec shown in Fig. 14 was formed from a plate material by the blank punching step S41 to the can lid shape forming step S46 described above in the first embodiment. The plate material used was an aluminum alloy (A5182) (Fig. 13) (metal part) with an original thickness of 0.218 mm, with both sides coated with a paint containing a lubricant.

[0074] In addition, when performing the above-mentioned annular protrusion forming (plate thickness increasing forming) process S45, the support force (countersink holding force) [kgf] applied by the support tool L63 was set to 700 kgf in Example 6, 800 kgf in Example 7, 900 kgf in Example 8, and 0 kgf in Comparative Example 1 (FIG. 13). As shown in FIG. 13, the can lids 3Ec formed in Examples 6 to 8 and Comparative Example 1 all had a lid diameter of 206 (2 6 / 16 inches), a can lid shape of a CDL (Container Development Ltd.) shape, a unit depth (UD) [mm] of 6.66 mm, and a panel height (PH) [mm] of 2.54 mm.

[0075] As shown by the double-headed arrow in Figure 14, the unit depth (UD) [mm] is the height distance [mm] from the lower end of the outer surface of the can lid 3Ec (i.e., the lower end of the outer surface of the chuck wall radius portion (curved convex portion) 322Ec of the annular protrusion 32Ec) to the upper end of the outer surface of the can lid 3Ec, and the panel height (PH) [mm] is the height distance from the lower end of the outer surface of the can lid 3Ec to the outer surface of the center panel portion (central plate portion) 31Ec.

[0076] In Examples 6 to 8 and Comparative Example 1, a pressure test was conducted in which the formed can lid 3Ec was wrapped around a can container (metal can) and subjected to water pressure inside. As a result, as shown in FIG. 13 , Example 6 exhibited a pressure resistance value (pressure strength) of 0.654 MPa, Example 7 exhibited a pressure resistance value of 0.656 MPa, and Example 8 exhibited a pressure resistance value of 0.696 MPa, all of which satisfied the required performance. On the other hand, Comparative Example 1 exhibited a pressure resistance value of 0.630 MPa, which was not a pressure resistance value that satisfied the required performance. These results demonstrate that the pressure resistance of the can lid can be increased by applying a supporting force (countersink holding force) [kgf] applied by the support tool L63, and that the pressure resistance of the can lid can be further increased as the supporting force increases.

[0077] [Second embodiment] In the sheet material forming method according to the second embodiment, a first stage of sheet thickness increasing forming is performed on the sheet material by the process shown in Fig. 15, a second stage of sheet thickness increasing forming is performed by the process shown in Fig. 16, and then a third stage of sheet thickness increasing forming is performed by the process shown in Fig. 17. Note that the height Ht indicated by the dotted line in Figs. 15 to 17 indicates the same height throughout.

[0078] (First stage of increasing thickness) 15, first, using upper and lower peripheral drawing tools (not shown) for drawing the outer peripheral portion of a plate material 51E formed into a substantially disk-like shape by blank punching, a blank-holding force is applied to a plate-like portion 52E located on the inner side of the outer peripheral portion of the substantially disk-like plate material 51E, and the outer peripheral portion is drawn while the blank-holding force is applied to the plate-like portion 52E. As a result, as shown in state m21 in FIG. 15, an outer peripheral side portion 53E is formed on the outer peripheral side of the plate-like portion 52E, which hangs down via a curved corner (extending in a substantially perpendicular direction (downward) to the plate-like portion 52E).

[0079] Next, for the sheet material 51E in state m21, upper and lower center drawing tools (not shown) for drawing the approximately central portion of the plate-shaped portion 52E are used to apply a blank-holding force to the outer periphery of the plate-shaped portion 52E while drawing the inner periphery. As a result, as shown in state m22 in Figure 15, an outer periphery panel portion (outer periphery plate portion) 521E of the sheet material 51E is formed, and a center panel portion (central plate portion) 54E is formed via side wall portions 55E that rise upward on the inner periphery side of the outer periphery panel portion 521E. Here, a central protrusion 56E is formed by the center panel portion (central plate portion) 54E and the side wall portions 55E.

[0080] Next, as shown in state m23 of FIG. 15, forming is performed using, for example, a forming device having an upper tool U8 and a lower tool L8. The upper tool U8 includes an annular upper outer tool U81, an upper central tool U82, and an annular guide tool U83 located therebetween. Note that the guide tool U83 shown in the examples of FIGS. 15 to 17 is integrally provided with the upper central tool U82 on the outer periphery of the upper central tool U82. However, the guide tool U83 is not limited to this configuration and may be provided separately from the upper central tool U82 on the outer periphery of the upper central tool U82. The lower tool L8 includes an annular lower outer tool L81, a lower central tool L82, and an annular support tool (support member) L83 located therebetween. As shown in state m23, the plate material 51E on which the center panel portion 54E and the side wall portion 55E (i.e., the central protrusion 56E) have been formed is placed between the upper tool U8 and the lower tool L8.

[0081] Then, the upper outer tool U81 and the lower outer tool L81 sandwich and fix the outer peripheral panel portion 521E of the plate material 51E (state m24 in FIG. 15). This fixation continues until state m26. With the outer peripheral panel portion 521E fixed in this manner, the upper central tool U82 presses down the lower central tool L82 while sandwiching the center panel portion 54E between the abutment surface U82a of the upper central tool U82 and the abutment surface L82a of the lower central tool L82 (state m24, state m25). Furthermore, the side wall portion 55E is positioned between the guide tool U83 and the lower central tool L82.

[0082] The upper central tool U82 presses down the lower central tool L82 so that the height position of its contact surface U82a approaches the height position of the contact surface (support surface) L83a of the support tool (support member) L83. That is, the support tool L83 is relatively movable in a second direction (upward) opposite to the first direction (downward) in which the annular protrusion 62Ea (state m26 in FIG. 15) to be formed later protrudes. The support tool L83 applies a support force in the second direction (upward) to the plate material 51E on its contact surface (support surface) L83a. Therefore, by pressing down the lower central tool L82 with the upper central tool U82, an annular curved portion 57E having a curved shape that conforms to the shape of the contact surface L83a is formed on the outer periphery of the side wall portion 55E by being supported by the support tool L83 that applies this support force (state m25 in FIG. 15).

[0083] Then, while supporting the annular curved portion 57E with the abutment surface (support surface) L83a of the support tool (support member) L83 (by a support force directed in the second direction (upward)), a pressing force is applied to the center panel portion 54E in a first direction (downward) opposite to the second direction.

[0084] At this time, the upper central tool U82 continuously applies a pressing force in the first direction (downward) to press down the lower central tool L82 with its contact surface U82a. That is, the upper central tool U82 continuously applies a pressing force to the center panel portion (center plate portion) 54E sandwiched between the contact surface U82a and the contact surface L82a of the lower central tool L82, thereby pressing the center panel portion 54E in the first direction (downward). At the same time, the guide tool U83 positions the side wall portion 55E between itself and the lower central tool L82, thereby preventing the side wall portion 55E from buckling due to the compressive stress applied to the side wall portion 55E. As a result, the support force of the support tool (support member) L83 can apply a greater pressing force to the annular curved portion 57E via the side wall portion 55E than the upper central tool U82.

[0085] This pressing by the upper central tool U82 deforms the annular curved portion 57E and generates compressive stress in the second direction (upward) in the side wall portion 55E, moving at least a portion of the plate material that constitutes the side wall portion 55E on the abutment surface L83a of the support tool L83 toward the outside of the center panel portion 54E.

[0086] As a result, a can lid intermediate 60E having an annular protrusion 62Ea whose thickness is selectively increased based on the moved portion is formed (state m26). In the intermediate 60E, the annular protrusion 62Ea is connected to the outer peripheral panel portion (outer peripheral plate portion) 521E via the side wall portion 61E on its outer periphery. The annular protrusion 62Ea has an increased thickness over a wide range, including the area required to improve the pressure resistance of the chuck wall radius portion (curved convex portion).

[0087] Thereafter, as shown in state m27, the can lid intermediate formed body 60E is removed from the upper tool U8 and the lower tool L8. In this way, the intermediate formed body 60E (state m28) that has undergone the first stage of thickness increasing forming is obtained.

[0088] (Second stage thickness increase forming) 16, the intermediate formed body 60E (state m29 (i.e., state m28 in FIG. 15)) that has undergone the first stage of thickness increasing forming is subjected to a pressing force in a first direction (downward) by the upper outer tool U81, as in the first embodiment described above. That is, the intermediate formed body 60E is placed between the upper tool U8 and the lower tool L8 (state m30), and then the center panel portion 54E is sandwiched and fixed between the upper central tool U82 and the lower central tool L82 (state m31).

[0089] In this state, a pressing force is applied to the outer peripheral panel portion 521E sandwiched between the upper outer tool U81 and the lower outer tool L81, and the outer peripheral panel portion 521E is pressed in a first direction (downward). This deforms the annular protrusion 62Ea and generates a compressive stress in the side wall portion 61E in a second direction (upward), while moving at least a portion of the sheet material constituting the side wall portion 61E on the contact surface L83a of the support tool L83 toward the inside of the outer peripheral panel portion 521E. In this way, an intermediate formed body 70E (of a can lid) is formed, which has an annular curved portion 62Eb whose thickness is selectively further increased on the inner circumferential side of the outer peripheral panel portion 521E (state m32). The intermediate formed body 70E has a side wall portion 63E that rises upward on the inner circumferential side of the annular curved portion 62Eb, and the side wall portion 63E and a center panel portion (central plate portion) 54E form a central protrusion 64E.

[0090] Thereafter, as shown in state m33, the intermediate formed body 70E is removed from the upper tool U8 and the lower tool L8. In this way, the intermediate formed body 70E (state m34) that has undergone the second-stage thickness increasing forming is obtained.

[0091] (Third stage thickness increase forming) In the third stage of thickness increasing forming performed by the process shown in Figure 17, the intermediate formed body 70E (state m35 (i.e., state m34 in Figure 16)) that has undergone the second stage of thickness increasing forming is subjected to the same process as the first stage of thickness increasing forming described above. That is, the intermediate formed body 70E shown in state m35 in Figure 17 is placed between the upper tool U8 and the lower tool L8 as shown in state m36, and the outer peripheral panel portion 521E is sandwiched and fixed between the upper outer tool U81 and the lower outer tool L81 as shown in state m37.

[0092] In this state, while the center panel portion 54E is sandwiched between the upper central tool U82 and the lower central tool L82, the upper central tool U82 continuously applies a pressing force in the first direction (downward) so as to press down on the lower central tool L82 (state m37, state m38).

[0093] Specifically, while the annular curved portion 62Eb of the intermediate molded body 70E is supported by the contact surface L83a of the support tool L83 (by a supporting force in the second direction (upward)), a pressing force is continuously applied to the center panel portion 54E in a first direction (downward) opposite to the second direction (upward). At this time, the supporting force of the support tool (support member) L83 can apply a greater pressing force to the annular curved portion 62Eb via the side wall portion 63E than the upper central tool U82.

[0094] This pressing by the upper central tool U82 deforms the annular curved portion 62Eb and generates compressive stress in the second direction (upward) in the side wall portion 63E, moving at least a portion of the plate material that constitutes the side wall portion 63E on the abutment surface L83a of the support tool L83 toward the outside of the center panel portion 54E.

[0095] As a result, a can lid intermediate 80E having an annular protrusion 82Ea whose thickness is selectively increased further based on the moved portion is formed (state m38). In the intermediate 80E, the annular protrusion 82Ea is connected to the outer peripheral panel portion 521E on its outer periphery via the side wall portion 81E.

[0096] Thereafter, as shown in state m39, the can lid intermediate formed body 80E is removed from the upper tool U8 and the lower tool L8. In this way, the can lid intermediate formed body 80E (state m40) is obtained, which has undergone the third stage of thickness-increasing forming. The intermediate formed body 80E in state m40 has an even greater thickness increase over a wide range, including the range required to improve the pressure resistance of the chuck wall radius portion (curved convex portion) 822Ea of the annular protrusion 82Ea.

[0097] As described above, according to the sheet material shaping method of the second embodiment, the sheet material can be subjected to a multi-stage thickness increasing shaping process, such as the first to third stages shown in Figures 15 to 17, to further increase the sheet thickness over a wide range, including the required range for the annular protrusion 82Ea. As a result, a can lid with further improved pressure resistance can be formed from the intermediate formed body 80E formed by the sheet material shaping method of the second embodiment.

[0098] In the first to third stages of thickness increasing forming shown in Figures 15 to 17 described above, the same forming device having an upper tool U8 and a lower tool L8 was used consistently. However, this is not limited to this example. The forming device having the upper tool U8 and the lower tool L8 may have different configurations (particularly in cushion pins (not shown), air cylinders (not shown), etc.) between the one used in the first and third stages of thickness increasing forming and the one used in the second stage of thickness increasing forming.

[0099] [Third embodiment] The method for forming a plate material in the third embodiment forms a can bottom 10E as a formed material, as shown in state m48 in Fig. 19. The method for forming this can bottom 10E includes the method for forming a plate material 11E according to the above-described general embodiment as part of the overall process.

[0100] The method for forming this can bottom 10E includes the same steps as those shown in Fig. 6, namely, the blank punching step S41, the outer periphery drawing step S42, the central-outer periphery plate portion forming step S43, the annular curved portion forming step S44, the annular protrusion forming (plate thickness increasing forming) step S45, and the (can bottom) shape forming step S46, all of which are shown in Fig. 6. In these forming steps (S41 to S46), the shape of the plate material 91E is changed as shown in states m41 to m47 in Figs. 18 and 19, and then the can bottom is shaped (reformed) to form the can bottom 10E in state m48.

[0101] In the blank punching step S41 in the process of forming the can bottom 10E, for example, upper and lower punching tools (not shown) are used to punch the plate material 91E to be processed into an approximately disk shape, and the plate material 91E is formed into an approximately disk shape (state m41 in Figure 18).

[0102] In the peripheral drawing step S42 in the process of forming the can bottom 10E, for example, upper and lower peripheral drawing tools (not shown) for drawing the peripheral portion of a substantially disk-shaped sheet material 91E are used to draw the peripheral portion of the substantially disk-shaped sheet material 91E while applying a blank-holding force to a plate-like portion inside the peripheral portion of the substantially disk-shaped sheet material 91E shown in state m41 in Fig. 18 . As a result, as shown in state m42 in Fig. 18 , a peripheral side portion 93E is formed that rises upward via curved corners (extending in a direction substantially perpendicular (upward) to the plate-like portion 92E) on the outer periphery side of the sheet material 91E. If necessary, known ironing may be added to the peripheral side portion 93E.

[0103] In the center-periphery plate portion forming step S43 in the can bottom 10E forming process, for example, for a plate material 91E in state m42 of FIG. 18 , upper and lower center drawing tools (not shown) for drawing the approximately central portion of the plate-shaped portion 92E are used to apply a blank holding force to the outer panel portion (outer plate portion) 921E of the plate-shaped portion 92E, while drawing the inner peripheral side of the outer panel portion. As a result, as shown in state m43 of FIG. 18 , a center panel portion (center plate portion) 94Ea having a substantially flat surface is formed. At the same time, a peripheral panel portion (periphery plate portion) 922E is formed via a side wall portion 95E rising outward from the center panel portion 94Ea. The center panel portion 94Ea is to be formed into the dome panel portion 94E later.

[0104] In the annular curved portion forming step S44 and the annular protrusion forming (thickening forming) step S45 in the can bottom 10E forming process, for example, a sheet material 91E on which a center panel portion 94Ea and an outer peripheral panel portion 922E have been formed (state m43 in FIG. 18 ) is formed using a forming device having an upper tool U9 and a lower tool L9. As shown in state m44 in FIG. 18 , for example, the upper tool U9 includes an annular upper outer tool U91, an upper central tool U92, and an annular guide tool U93 positioned therebetween. The lower tool L9 includes an annular lower outer tool L91, a lower central tool L92, and an annular support tool (support member) L93 positioned therebetween. As shown in state m44 in FIG. 18 , the sheet material 91E on which a center panel portion 94Ea and an outer peripheral panel portion 922E have been formed is placed between the upper tool U9 and the lower tool L9.

[0105] Thereafter, the center panel portion 94Ea is sandwiched and fixed between the contact surfaces U92a of the upper central tool U92 and L92a of the lower central tool L92. By being sandwiched and fixed in this manner, the center panel portion 94Ea is formed into the dome panel portion 94E (state m45 in FIG. 19) having a dome shape that gently protrudes in a second direction (upward) opposite to the first direction (downward) in which the annular protrusion 102Ea (state m47 in FIG. 19) to be formed later protrudes. This fixing of the dome panel portion 94E by the upper central tool U92 and the lower central tool L92 continues thereafter until the annular protrusion forming (plate thickness increasing forming) process S45 is completed.

[0106] In this state, in the annular curved portion forming step S44 in the process of forming the can bottom 10E, the upper outer tool U91 applies a pressing force in the first direction (downward) as shown in states m45 and m46 in Fig. 19. At this time, the upper outer tool U91 presses down the lower outer tool L91 while sandwiching the outer peripheral panel portion (outer peripheral plate portion) 922E between the abutment surface U91a of the upper outer tool U91 and the abutment surface L91a of the lower outer tool L91.

[0107] The guide tool U93 may or may not descend, as shown in states m45 to m47 in Fig. 19. In either case, the guide tool U93 and the lower outer tool L91 are positioned around the side wall portion 95E. This prevents buckling of the side wall portion 95E due to compressive stress when the side wall portion 95E is subjected to compressive stress in the subsequent annular protrusion forming (thickness increasing) step S45.

[0108] In the annular curved portion forming step S44 in the process of forming the can bottom 10E, the upper outer tool U91 presses down the lower outer tool L91 so that the height position of its contact surface U91a approaches the height position of the contact surface (support surface) L93a of the support tool (support member) L93. That is, the support tool L93 is relatively movable in the second direction (upward). The support tool L93 applies a supporting force in the second direction (upward) to the plate material 91E on its contact surface (support surface) L93a.

[0109] Therefore, when the upper outer tool U91 presses down the lower outer tool L91, an annular curved portion 96E having a curved shape that follows the shape of the contact surface L93a of the side wall portion 95E is formed on the inner periphery of the side wall portion 95E by being supported by the support tool L93 that applies this supporting force. Note that the plate material 91E having such an annular curved portion 96E formed therein is referred to as a preform 91Ea (state m46 in FIG. 19 ).

[0110] In the annular protrusion forming (plate thickness increasing forming) process S45 in the can bottom 10E forming process, for example, as shown in states m46 and m47 in Figure 19, the annular curved portion 96E of the formed preform 91Ea is supported by the abutment surface L93a of the support tool L93 (by a supporting force in the second direction (upward)), while a pressing force is applied in the first direction (downward) to the outer peripheral panel portion 922E.

[0111] At this time, the upper outer tool U91 continuously applies a pressing force in a first direction (downward) so as to press down the lower outer tool L91 with its contact surface U91a. That is, the upper outer tool U91 continuously applies a pressing force to the outer peripheral panel portion (outer peripheral plate portion) 922E sandwiched between the contact surface U91a and the contact surface L91a of the lower outer tool L91, thereby pressing the outer peripheral panel portion 922E in the first direction (downward). At the same time, the guide tool U93 positions the side wall portion 95E between its outer guide surface U93a and the contact surface L91b of the lower outer tool L91, thereby preventing the side wall portion 95E from buckling due to the compressive stress applied to the side wall portion 95E. As a result, the support force of the support tool (support member) L93 can apply a greater pressing force to the annular curved portion 96E via the side wall portion 95E than the upper outer tool U91.

[0112] In this manner, the upper outer tool U91 is pressed in while the support tool L93 applies a support force in the second direction (upward), thereby deforming the annular curved portion 96E and generating a compressive stress in the second direction (upward) in the side wall portion 95E, and at least a portion of the plate material constituting the side wall portion 95E on the contact surface L93a of the support tool L93 is moved toward the inside of the outer peripheral panel portion (outer peripheral plate portion) 922E.

[0113] This annular protrusion forming (thickening forming) step S45 in the can bottom 10E forming process prevents unintended deformation of the material due to relative pressing (pressing), and forms a can bottom intermediate formed body 100E (state m47 in Figure 19) having an annular protrusion 102Ea whose thickness is selectively increased based on the moved portion. In the intermediate formed body 100E, the annular protrusion 102Ea has an increased thickness over a wide range, including the area required to improve the pressure resistance of the bottom radius portion (curved convex portion) 112Ea. After forming the can bottom intermediate formed body 100E (before shape forming) having the annular protrusion 102Ea in this manner, the can bottom intermediate formed body 100E is removed from the upper tool U9 and the lower tool L9.

[0114] In this way, in the molding method for the plate material 91E of the third embodiment, the dome panel portion 94E is pressed (pressed) relative to the plate material 91E continuously (in one stroke) using the same device (upper and lower dies) having the upper tool U9 and the lower tool L9. In other words, the molding method of the third embodiment does not perform this pressing in multiple stages using dies of different shapes each time, but rather can mold the annular protrusion 102Ea with an increased plate thickness within the required range using this simple manufacturing process.

[0115] The can bottom shape forming step S46 is a step of reforming the shape of the can bottom intermediate formed body 100E as necessary (bottom reform) to form it into the shape of the can bottom, and this step includes a step of forming the shape of the can bottom annular protrusion 102E. After reforming in this can bottom shape forming step S46, the can bottom 10E is obtained by removing it from the reforming device (not shown) (state m48 in Figure 19).

[0116] The can bottom shaping step S46 can be carried out by a conventionally known method, for example, a method using a rotating roll or a method using press molding.

[0117] In the third embodiment, if an inner surface painting step is particularly required, it is desirable to perform this step before the can bottom shape forming step S46.

[0118] The can bottom 10E in state m48 of Figure 19 includes a dome panel portion (center plate portion) 101E, a dome panel wall portion (inner peripheral wall portion) 151E, a bottom radius portion (curved convex portion) 152E, a chime lower portion (first outer peripheral wall portion) 153E, and a chime portion (second outer peripheral wall portion) 103E. The dome panel wall portion 151E, the bottom radius portion 152E, and the chime lower portion 153E form the can bottom annular protrusion 102E. The can bottom annular protrusion 102E has a shape that is slightly inwardly inclined due to reforming, and the plate thickness is increased over a wide area, including the required range, of the bottom radius portion 152E.

[0119] Note that the can bottom shape forming step S46 may further include a step of forming the dome panel portion (central plate portion) 94E into a desired shape, such as a shape other than a spherical surface, such as a substantially spheroidal surface, a substantially conical surface, a substantially flat surface, etc. In this case, the can bottom shape forming step S46 may include, simultaneously or in any order, a step of forming the shape of the can bottom annular protrusion 102E and a step of forming the dome panel portion (central plate portion) 94E into, for example, a substantially flat surface, as a step of reforming the shape of the can bottom intermediate formed body 100E in state m47 of Figure 19 .

[0120] [Example of the third embodiment (Example 9)] Next, an example (Example 9) of the third embodiment will be described. In Example 9, a drawn and ironed can (DI can) with an internal volume of 350 mL (after the can bottom was reshaped (reformed)) was manufactured by the following method. First, an aluminum alloy plate (JIS H 4000 A3104-H19 material, 0.220 mm (original plate thickness)) was prepared as a plate material (base plate) to be processed. Next, a predetermined amount of known cupping oil was applied to both sides of this aluminum alloy plate (plate material) as a lubricant during the drawing process.

[0121] Next, the lubricant-coated aluminum alloy plate was punched out into a disk shape (not shown) with a diameter of 160 mm using a drawing machine (upper and lower punching tools) (not shown) (a process corresponding to the blank punching step S41 in the forming process of the can bottom 10E described above). Thereafter, the peripheral portion of the disk-shaped plate material was drawn using the upper and lower peripheral drawing tools (not shown) while applying a blank holding force to the plate-shaped portion inside the peripheral portion. This resulted in the formation of a drawn cup (not shown) with a diameter of 90 mm.

[0122] This drawn cup (not shown) was transported to a body maker (can body manufacturing machine) and re-drawn to a shape with a diameter of 66 mm, after which a process equivalent to the peripheral drawing step S42 in the process of forming the can bottom 10E described above was carried out using coolant. As a result, a cup body was formed having a bottom shape as shown in state m42 in Fig. 18, a diameter of 66 mm, a height of 130 mm, and a minimum body thickness of 0.105 mm.

[0123] Next, this formed cup body was subjected to a process equivalent to the center-peripheral plate portion forming step S43 in the above-mentioned process for forming the can bottom 10E using upper and lower center drawing tools (not shown). This formed a center panel portion (center plate portion) consisting of a flat surface, and also formed a can bottom (corresponding to state m43 in FIG. 18 ) formed by forming the peripheral panel portion (peripheral plate portion) via sidewall portions rising on the outer peripheral side of the center panel portion, thereby forming a first precursor of a DI can (not shown).

[0124] Next, the first precursor was placed between the upper tool U9 and the lower tool L9, as shown in state m44 in Figure 18. The center panel portion was then sandwiched and fixed between the upper central tool U92 and the lower central tool L92, and this center panel portion was deformed into the shape of the dome panel portion, as shown in state m45 in Figure 19. In this state, a pressing process was performed in which the upper outer tool U91 applied a pressing force in the first direction (downward) as described above, which was a process corresponding to the annular curved portion forming step S44 and the subsequent annular protrusion forming (plate thickness increasing forming) step S45 in the can bottom 10E forming process described above.

[0125] First, in a process corresponding to the annular curved portion forming step S44 in the above-described can bottom 10E forming step, the upper outer tool U91 pressed down the lower outer tool L91 while sandwiching the outer peripheral panel portion (outer peripheral plate portion) between the upper outer tool U91 and the lower outer tool L91. This formed a second precursor of a DI can, including a can bottom preform having an annular curved portion as shown in state m46 in Fig. 19 .

[0126] Next, in a process corresponding to the annular protrusion forming (thickening forming) step S45 in the can bottom 10E forming process described above, the annular curved portion of the formed preform was supported by the support tool L93 (by the support force in the second direction (upward) described above), while a pressing force was applied in the first direction (downward) to the outer peripheral panel portion. This resulted in a drawn and ironed can (DI can) (before the can bottom shape forming (reforming)) including a can bottom intermediate formed body 510E having a shape corresponding to state m47 in FIG. 19, i.e., the annular protrusion 512E shown in FIG. 20. This annular protrusion 512E has a dome panel wall portion 513E, a bottom radius portion 514E (before the reforming), and a chime lower portion 515E (before the reforming). Furthermore, a chime portion 516E (before the reforming) was formed outside the chime lower portion 515E.

[0127] This intermediate can bottom formed body 510E shown in Figure 20 was subjected to trimming processing to cut the mouth edge to the required can height and bottom reforming processing (a process equivalent to the can bottom shape forming process S46 in the can bottom 10E forming process described above) using conventional methods, to obtain the final can bottom formed body 520E (after reforming) shown in Figure 21.

[0128] The thickness [mm] of the metal portion at each location in the final molded body 520E (after reforming) shown in Figure 21 was measured. Figure 21 shows the measurement points w1 to w7. The thickness [mm] was measured as follows. That is, the molded (final molded body) drawn and ironed can (DI can) was embedded in epoxy resin, and then cut along the vertical axis (Z axis) of the DI can together with the epoxy resin. After exposing the central cross section by cutting and careful polishing, the thickness [mm] of the metal portion at each of the measurement points w1 to w7 was measured using a measuring microscope.

[0129] As shown in the table of Fig. 22, in Example 9, the height Hp of the dome panel portion 522E (Fig. 21) in the drawn and ironed can (DI can) (the final formed body) was 12.3 mm. In the final formed body 520E, the diameter (d1) (Fig. 21) between the boundary between the dome panel portion 522E and the (post-reformed) can bottom annular protrusion 523E was 47.0 mm, and the diameter (d2) (Fig. 21) of the ground contact portion of the can bottom annular protrusion 523E was 48.0 mm. The thicknesses [mm] of the metal portions at measurement points w1 to w7 (Fig. 21) were as shown in the table of Fig. 22.

[0130] [Pressure resistance test evaluation] The drawn and ironed cans (DI cans) obtained (as final formed bodies) were subjected to a pressure resistance test evaluation using the following pressure resistance test method. The evaluation results are shown in the table of FIG.

[0131] [Pressure resistance test method] With the cup-shaped container filled with water, the open end is sealed with a plug equipped with a water pipe. Next, pressurized water is sent into the cup-shaped container from a water pump through the water pipe. The internal pressure of the cup-shaped container rises, and at a certain point the dome panel instantly deforms, inverting outward (buckling). Normally, at the same time as this deformation, the internal pressure of the can (DI can) drops suddenly. The maximum internal pressure of the can during this period is the withstand pressure value (withstand pressure) [MPa].

[0132] As shown in the evaluation results in the table of Figure 22, the drawn and ironed can (DI can) (the final product) formed in Example 9 corresponds to a 350 mL can, and its can weight [g] (as the weight of the metal part after trimming) was 9.9 g. As can be seen from the evaluation results in Figure 22, the thickness [mm] of the metal part increased over a wide range, including the range required to improve the pressure resistance of the annular protrusion (after reforming) on ​​the can bottom. As a result, this DI can achieved a desirable pressure resistance (pressure resistance value [MPa]).

[0133] Furthermore, by adopting the method shown in Example 9, which provided these results, in part of the can-making process, it became possible to manufacture can bodies that were thinner in original thickness to save material resources and reduce weight, while still maintaining pressure strength.

[0134] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and the present invention also includes design changes within the scope of the present invention. Furthermore, the above-mentioned examples can be combined by utilizing each other's technologies as long as there are no particular contradictions or problems in the purpose, configuration, etc. [Explanation of symbols]

[0135] 1E: molding material, 11E, 41E, 51E: plate material, 11Ea, 41Ea: preform, 12E, 22E, 31E, 31Ec, 45E, 45Eb, 54E: center panel portion (center plate portion), 121E, 141E, 311E: curved end portion, 13E, 32E, 32Ea, 32Eb, 32Ec, 62Ea, 82Ea: annular protrusion portion, 131E: inner peripheral wall portion, 132E: curved convex portion, 133E: outer peripheral wall portion, 14E, 21E, 421E, 421Eb, 521E: outer peripheral panel portion (outer peripheral plate portion), 23E, 46E, 55E, 61E, 63E, 81E: side wall portion , 24E, 47E, 57E, 62Eb: annular curved portion, 3E, 3Ec: can lid, 30E, 40Eb: can lid intermediate formed body, 321E: panel wall portion (inner peripheral wall portion), 322E, 322Ea, 322Eb, 322Ec, 822Ea: chuck wall radius portion (curved convex portion), 323E: first chuck wall portion (first outer peripheral wall portion), 33E: second chuck wall portion (second outer peripheral wall portion), 34E: curl portion, 42E: plate-shaped portion, 420E: outer panel portion (outer plate portion), 43E: outer peripheral side portion, 52E: plate-shaped portion, 53E: outer peripheral side portion, 56E,64E: central protrusion, 10E: can bottom, 91E: plate material, 91Ea: preform, 92E: plate-shaped portion, 921E: outer panel portion (outer plate portion), 922E: outer peripheral panel portion (outer plate portion), 93E: outer peripheral side portion, 94E: dome panel portion (central plate portion), 94Ea: center panel portion (central plate portion), 95E: side wall portion, 96E: annular curved portion, 100E: can bottom intermediate formed body, 101E: dome panel portion (central plate portion), 102E: can bottom annular protrusion, 102Ea: annular protrusion, 112Ea: bottom radius portion (curved convex portion), 103E: chime portion (second outer peripheral wall portion), 151E: dome panel wall portion (inner peripheral wall portion), 152E: bottom radius (curved convex portion), 153E: chime lower portion (first outer peripheral wall portion), 921E: outer panel portion (outer plate portion), 922E: outer peripheral panel portion (outer plate portion), 510E: can bottom intermediate formed body (before reforming), 511E: dome panel portion (of intermediate formed body), 512E: annular protrusion portion (of intermediate formed body), 513E: dome panel wall portion (of intermediate formed body), 514E: bottom radius portion (of intermediate formed body), 515E: chime lower portion (of intermediate formed body), 516E: chime portion (of intermediate formed body), 520E: can bottom final formed body (after reforming), 522E: dome panel portion (of final formed body), 523E: can bottom annular protrusion portion (of final formed body),

Claims

1. A method for forming a plate material, comprising: a step of forming a central plate portion and forming an outer peripheral plate portion via a side wall portion rising upward on the outer peripheral side of the central plate portion; forming an annular curved portion on an inner circumferential side of the side wall portion; and a step of deforming at least the annular curved portion to selectively form an annular protruding portion having an increased thickness, In the step of forming the annular protrusion, The annular curved portion is supported by a support member that is relatively movable in a second direction opposite to a first direction in which the annular protrusion to be formed protrudes, and a pressing force is applied to the outer peripheral plate portion in the first direction, thereby generating a compressive stress in the second direction in the side wall portion, and at least a portion of the plate material that constitutes the side wall portion is moved on the support surface of the support member, thereby forming the annular protrusion with a selectively increased plate thickness. A molding method characterized by:

2. The forming method according to claim 1, characterized in that in the process of forming the annular protrusion, at least a portion of the plate material that constituted the side wall portion on the support surface of the support member is moved toward the inside of the outer peripheral plate portion.

3. 2. The molding method according to claim 1, wherein the plate material is made of a material mainly containing metal.

4. A method for forming can lids, comprising the method according to claim 1 as part of the entire process.

5. After the step of forming the annular protrusion, The process of forming the can lid is as follows:

5. The method for forming a can lid according to claim 4, further comprising a step of forming a chuck wall portion.

6. A method for forming a can bottom, comprising the method according to claim 1 as part of the entire process.

7. After the step of forming the annular protrusion, The step of forming into the shape of the can bottom includes:

7. The method for forming a can bottom according to claim 6, further comprising at least a step of forming the shape of the can bottom annular protrusion.

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