Plate material forming method, can lid forming method, and can bottom forming method

Abstract

Provided is a plate material forming method with which it is possible to increase the plate thickness of an annular projecting portion over a wide range, including a required range, using a simple manufacturing process, while preventing unintended deformation of the material through relative pressing. The plate material forming method according to the present invention includes a step for forming a specific plate portion and a side wall portion, a step for forming an annular curved portion connected to the side wall portion, and a step for deforming at least the annular curved portion to form an annular projecting portion having a selectively increased plate thickness, wherein, in the step for forming the annular projecting portion, the annular projecting portion having a selectively increased plate thickness is formed by applying a pressing force to the specific plate portion in a first direction in which the annular projecting portion to be formed projects, while supporting the annular curved portion using a supporting member that can move relatively in a second direction opposite to the first direction, to thereby cause at least a part of the plate material that constituted the side wall portion to move along a supporting surface of the supporting member while generating compressive stress in the second direction in the side wall portion.

Description

Technical Field

[0001] The present invention relates to a method for forming a plate material that becomes, for example, a can lid, a can bottom, or the like, a method for forming a can lid, and a method for forming a can bottom.Background Art

[0002] A can container made of metal (metal can) is required to reduce a plate thickness as much as possible for saving material resources and for achieving weight reduction while maintaining pressure resistance strength. For example, in a can lid and a can bottom, since so-called buckling may occur due to an increase in internal pressure of the can, measures for maintaining the pressure resistance strength thereof are strongly required.

[0003] To reduce a plate thickness of a plate material that becomes, for example, a can lid, a can bottom, and the like while maintaining pressure resistance strength thereof, it is known to form, on an outer peripheral side relative to a center plate part that becomes a lid surface, a bottom surface, and the like, an annular projecting part including an inner peripheral wall part, a curved convex part, and a part of an outer peripheral wall part, and to increase a plate thickness of the curved convex part.

[0004] For example, Patent Literature 1 describes that, in a can lid including a center panel part (center plate part), a panel wall part (inner peripheral wall part), a chuck wall radius part (curved convex part), a chuck wall part (outer peripheral wall part), and a curl part, pressure resistance strength is improved while reducing a plate thickness of a plate material by making a plate thickness t2 at a lower end of the panel wall part larger than a plate thickness t1 of the center panel part (t2 > t1). Patent Literature 1 also describes that a plate thickness t3 of the chuck wall radius part is made larger than the plate thickness t1 of the center panel part (t3 > t1), and shows a required range for improving pressure resistance strength.Citation ListPatent Literature

[0005] PTL1: Japanese Patent Laid-Open No. 2022-16093Summary of InventionTechnical Problem

[0006] However, as in the method for manufacturing the can lid described in Patent Literature 1, when an annular projecting part is formed on a plate material by a conventional method, if the annular projecting part is formed in one stroke using upper and lower dies, only a plate thickness on an inner peripheral side of the annular projecting part is significantly increased, and the plate thickness of the annular projecting part cannot be increased over a wide range. To increase the plate thickness of the annular projecting part over a wide range by a conventional method, relative pushing (pressing) with respect to the center plate part needs to be performed in a plurality of stages, and dies having different shapes need to be used each time, so that a manufacturing process is complicated.

[0007] In addition, due to relative pushing (pressing), the plate material tends not only to increase the plate thickness thereof but also to release stress by deformation or material flow; however, in a conventional method, a material of the plate material easily flows toward the outer peripheral wall part side, and thus it is difficult to maintain a shape required as, for example, a can lid, a can bottom, and the like. That is, a range in which relative pushing can be performed while maintaining the shape is narrow, and sufficient increase in plate thickness cannot be achieved in some cases depending on required performance.

[0008] The present invention aims to address such circumstances. That is, an object of the present invention is to provide a method for forming a plate material, a method for forming a can lid, and a method for forming a can bottom, which are capable of increasing a plate thickness of an annular projecting part over a wide range including a required range with a simple manufacturing process, while preventing unintended deformation of a material due to relative pushing (pressing).Solution to Problem

[0009] A method for forming a plate material of the present invention includes: a step of forming a specific plate part and a side wall part; a step of forming an annular curved part connected to the side wall part; and a step of deforming at least the annular curved part to form the annular projecting part in which a plate thickness is selectively increased, wherein, in the step of forming the annular projecting part, a pressing force in a first direction is applied to the specific plate part while supporting the annular curved part by a support member that is relatively movable in a second direction opposite to the first direction in which the annular projecting part to be formed projects, thereby generating compressive stress in the second direction in the side wall part while moving at least a portion of a plate material constituting the side wall part on a support surface of the support member, whereby the annular projecting part is formed such that a plate thickness is selectively increased.

[0010] The method for forming the plate material of the present invention includes: a step of forming, in a plate-like portion of the plate material, a center projecting part constituted of a center plate part and a side wall part on an outer peripheral side thereof; a step of forming an outer peripheral curved part on an outer peripheral side of the side wall part; and a step of deforming at least the outer peripheral curved part to form the annular projecting part in which a plate thickness is selectively increased, wherein, in the step of forming the annular projecting part, a pressing force in a direction opposite to the projecting direction is applied to the center projecting part while supporting the outer peripheral curved part by a support member that is relatively movable in a projecting direction of the center projecting part, thereby generating compressive stress in the projecting direction in the side wall part while moving at least a portion constituting the side wall part on a support surface of the support member, whereby the annular projecting part is formed such that a plate thickness is selectively increased. A method for forming a can lid of the present invention includes, as a part of the entire process, the method for forming the plate material of the present invention having such characteristics. A method for forming a can bottom of the present invention includes, as a part of the entire process, the method for forming the plate material of the present invention having such characteristics.

[0011] The method for forming the plate material of the present invention includes: a step of forming a center plate part and forming an outer peripheral plate part via a side wall part that rises upward on an outer peripheral side relative to the center plate part; a step of forming an annular curved part on an inner peripheral side of the side wall part; and a step of deforming at least the annular curved part to form the annular projecting part in which a plate thickness is selectively increased, wherein, in the step of forming the annular projecting part, a pressing force in a first direction is applied to the outer peripheral plate part while supporting the annular curved part by a support member that is relatively movable in a second direction opposite to the first direction in which the annular projecting part to be formed projects, thereby generating compressive stress in the second direction in the side wall part while moving at least a portion of a plate material constituting the side wall part on a support surface of the support member, whereby the annular projecting part is formed such that a plate thickness is selectively increased. A method for forming a can lid of the present invention includes, as a part of the entire process, the method for forming the plate material of the present invention having such characteristics. A method for forming a can bottom of the present invention includes, as a part of the entire process, the method for forming the plate material of the present invention having such characteristics.Advantageous Effects of Invention

[0012] According to the present invention, it is possible to increase the plate thickness of the annular projecting part over a wide range including a required range with a simple manufacturing process, while preventing unintended deformation of the material due to relative pushing (pressing).Brief Description of Drawings

[0013] FIG. 1 is a side view of a plate material having an annular projecting part in a first schematic embodiment. FIG. 2 is a flowchart illustrating the forming process of a plate material having an annular projecting part in the first schematic embodiment. FIG. 3 is an explanatory diagram of the forming process of a plate material having an annular projecting part in the first schematic embodiment. FIG. 4 is a side view of a can lid in a first embodiment. FIG. 5 is a flowchart illustrating the forming process of a can lid in the first embodiment. FIG. 6 is a first explanatory diagram of the forming process of a can lid in the first embodiment. FIG. 7 is a second explanatory diagram of the forming process of a can lid in the first embodiment. FIG. 8 is a side cross-sectional view illustrating a schematic configuration of a forming device used in the forming process of a can lid in the first embodiment. FIG. 9 is an explanatory diagram of an annular projecting part forming (plate-thickness increasing forming) step and a shape forming step for a can lid in the forming process of a can lid in the first embodiment. FIG. 10A is a first explanatory diagram of an annular projecting part forming (plate-thickness increasing forming) step in the forming process of a can lid in the first embodiment. FIG. 10B is a second explanatory diagram of an annular projecting part forming (plate-thickness increasing forming) step in the forming process of a can lid in the first embodiment. FIG. 11A is a partial end face view partially illustrating a side end face of a preform for the can lid in the first embodiment. FIG. 11B is a partial end face view partially illustrating a side end face of the preform for the can lid after an annular projecting part forming (plate-thickness increasing forming) step in the first embodiment. FIG. 12 is an explanatory diagram of an annular projecting part forming (plate-thickness increasing forming) step in an example of the first embodiment. FIG. 13 is a diagram illustrating a lip height [mm] with respect to a supporting force [kN] in the example of the first embodiment. FIG. 14A is a partial end face view partially illustrating a side end face of the preform for the can lid after an annular projecting part forming (plate-thickness increasing forming) step in the example of the first embodiment. FIG. 14B is a partial enlarged view illustrating a part of FIG. 14A in an enlarged manner. FIG. 15 is a diagram illustrating plate thicknesses [mm] at measurement points A to F of the annular projecting part with respect to a supporting force [kN] during the steps of forming the annular projecting part (forming steps of increasing a plate thickness) in the example of the first embodiment. FIG. 16 is an explanatory diagram of the forming process of a can bottom in a second embodiment. FIG. 17 is a side view of a plate material having an annular projecting part in a second schematic embodiment. FIG. 18 is a flowchart illustrating the forming process of a plate material having an annular projecting part in the second schematic embodiment. FIG. 19 is a first explanatory diagram of the forming process of a plate material having an annular projecting part in the second schematic embodiment. FIG. 20 is a second explanatory diagram of the forming process of a plate material having an annular projecting part in the second schematic embodiment. FIG. 21 is a side view of a can lid in a third embodiment. FIG. 22 is a flowchart illustrating the forming process of a can lid in the third embodiment. FIG. 23 is a first explanatory diagram of the forming process of a can lid in the third embodiment. FIG. 24 is a second explanatory diagram of the forming process of a can lid in the third embodiment. FIG. 25 is a third explanatory diagram of the forming process of a can lid in the third embodiment. FIG. 26 is a side cross-sectional view illustrating a schematic configuration of a forming device used in the steps of forming the can lid in the third embodiment. FIG. 27 is a partial end face view partially illustrating an intermediate formed body used in Examples 1 to 5 of the third embodiment, and is a diagram illustrating measurement points a to v of a plate thickness [mm]. In (a), the measurement points a to e and p to v are illustrated. (b) is an enlarged view of a partial region including a chuck wall radius part (a region surrounded by a rectangular frame) illustrated in (a), and illustrates the measurement points f to o. FIG. 28 is a diagram illustrating plate thicknesses [mm] measured at the measurement points a to v for each supporting force (countersink holding force) [kgf] in Examples 1 to 5. FIG. 29 is a table indicating respective values of a lid diameter, a shape, an original plate thickness [mm], a supporting force (countersink holding force) [kgf], UD [mm], PH [mm], and a pressure resistance value [MPa] for formed cans formed in Examples 6 to 8 of the third embodiment and Comparative Example 1. FIG. 30 is a diagram for explaining measurement positions of UD [mm] and PH [mm] for formed cans formed in Examples 6 to 8 of the third embodiment and Comparative Example 1. FIG. 31 is a first explanatory diagram of the forming process of a can lid in a fourth embodiment. FIG. 32 is a second explanatory diagram of the forming process of a can lid in the fourth embodiment. FIG. 33 is a third explanatory diagram of the forming process of a can lid in the fourth embodiment. FIG. 34 is a first explanatory diagram of the forming process of a can bottom in a fifth embodiment. FIG. 35 is a second explanatory diagram of the forming process of a can bottom in the fifth embodiment. FIG. 36 is a partial end face view partially illustrating an intermediate formed body of the can bottom used in Example 9 of the fifth embodiment. FIG. 37 is a partial end face view partially illustrating a final formed body of the can bottom used in Example 9 of the fifth embodiment, and is a diagram illustrating measurement points w1 to w7 of a plate thickness [mm]. FIG. 38 is a table indicating measurement results in Example 9 of the fifth embodiment. Description of Embodiments

[0014] The following describes embodiments of the present invention (present embodiment) with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts having the same functions, and redundant description for each drawing will be omitted as appropriate. Additionally, in the following description, the term "substantially... " indicates that something is approximately or nearly in that state or shape. For example, the term "substantially circular shape" means not only a "circular shape" (perfect circle) but also encompasses an elliptical shape and the like similar to the circular shape.[Main embodiment]

[0015] A method for forming a plate material according to a main embodiment of the present invention is a method for forming a plate material that becomes, for example, a can lid, a can bottom, or the like. The method for forming the plate material includes: a step of forming a specific plate part to which a pressing force is applied in a first direction (downward direction) (described later) by an upper tool for the specific plate part, and a side wall part connected to the specific plate part; a step of forming an annular curved part connected to the side wall part; and a step of deforming at least the annular curved part to form an annular projecting part in which a plate thickness is selectively increased.

[0016] In the step of forming the annular projecting part, the annular curved part is supported by a support member (support tool for the annular curved part) that is relatively movable in a second direction (upward direction) opposite to the first direction (downward direction) in which the annular projecting part to be formed projects. In this state, the upper tool for the specific plate part is lowered to apply a pressing force in the first direction to the specific plate part.

[0017] Accordingly, while generating compressive stress in the second direction in the side wall part, at least a portion of the plate material constituting the side wall part is moved on a support surface of the support member (support tool for the annular curved part). As a result, in the method for forming the plate material according to the main embodiment, the annular projecting part is formed such that the plate thickness is selectively increased based on the moved portion.

[0018] In the method for forming the plate material according to the main embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to increase the plate thickness of the annular projecting part over a wide range including a required range while preventing unintended deformation of material due to relative pushing (pressing) with such a simple manufacturing process.[First schematic embodiment]

[0019] The method for forming the plate material according to a first schematic embodiment of the present invention is a method for forming a formed material 1 illustrated in FIG. 1. The formed material 1 includes a center panel part (center plate part) 12 that is a substantially flat surface having a substantially circular shape positioned substantially at the center of a plate material 11 having a substantially disk shape, an annular projecting part 13 positioned on an outer peripheral side thereof, and an outer peripheral panel part (outer peripheral plate part) 14 positioned on a further outer peripheral side thereof.

[0020] The plate material 11 is made of a material mainly containing metal. The material mainly containing metal is not particularly limited, and may be, for example, a single metal material such as aluminum, an aluminum alloy, steel, or the like, a clad material of these metals, or a composite metal material obtained by applying surface treatment, coating, lamination, or the like to one surface or both surfaces of these metals.

[0021] A curved part (curved end part) 121 is formed at an outer edge (an end part on a radially outer side) of the center panel part (center plate part) 12, and an inner peripheral wall part 131 is formed to extend downward in a substantially linear shape from a terminal end (outer end) of the curved part 121. A curved convex part 132 is a curved portion formed such that an end part (inner end) on an inner peripheral side thereof is connected to a lower end of the inner peripheral wall part 131, and an end part (outer end) on an outer peripheral side thereof is connected to an outer peripheral wall part 133. The outer peripheral wall part 133 is formed to extend upward in a substantially linear shape from an upper end (outer end) on an outer peripheral side of the curved convex part 132, and to be connected to a curved part (curved end part) 141 of the outer peripheral panel part (outer peripheral plate part) 14. The annular projecting part 13 is constituted of the inner peripheral wall part 131, the curved convex part 132, and the outer peripheral wall part 133 as described above.

[0022] A forming process of the formed material 1 (forming method) includes, as illustrated in FIG. 2, a blank punching step S1, a center projecting part forming step S2, an outer peripheral curved part forming step S3, and an annular projecting part forming (plate-thickness increasing forming) step S4. In the forming process (S1 to S4), a shape of the plate material 11 is changed as shown in states a1 to a5 in FIG. 3 to form the formed material 1 in state a6.

[0023] In the blank punching step S1, the plate material 11 is formed into a substantially disk shape by using upper and lower punching tools (not illustrated) (state a1 in FIG. 3). The shape may vary depending on the target formed product (for example, an elliptical shape, a polygonal shape, or the like).

[0024] In the center projecting part forming step S2, for example, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate material 11 having a substantially disk shape, while fixing an outer peripheral panel part (outer peripheral plate part) 25 of the plate material 11 having a substantially disk shape, drawing processing is performed on an inner peripheral side thereof, thereby forming, as shown in state a2 in FIG. 3, a center projecting part 22 including a center panel part (center plate part) 23 corresponding to the "specific plate part" described in the above main embodiment, and a side wall part 24 on an outer peripheral side thereof.

[0025] In the outer peripheral curved part forming step S3 and an annular projecting part forming (plate-thickness increasing forming) step S4, for example, forming is performed on the plate material 11 on which the center projecting part 22 has been formed by using an upper tool U1 and a lower tool L1. The upper tool U1 includes an annular upper outer tool U11, an upper center tool (upper tool for the specific plate part) U12, and an annular side wall part guide tool U13 positioned therebetween. The lower tool L1 includes an annular lower outer tool L11, a lower center tool L12, and an annular curved part support tool (support member) L13 positioned therebetween.

[0026] In the outer peripheral curved part forming step S3, for example, as shown in state a3 in FIG. 3, after the plate material 11 in which the center projecting part 22 including the center panel part 23 and the side wall part 24 has been formed is placed on the lower tool L1, the upper outer tool U11 is lowered. Accordingly, the outer peripheral panel part (outer peripheral plate part) 25 of the plate material 11 is fixed by being sandwiched between an abutting surface U11a of the upper outer tool U11 and an abutting surface L11a of the lower outer tool L11. This fixing of the outer peripheral panel part (outer peripheral plate part) 25 is continued thereafter until an annular projecting part forming (plate-thickness increasing forming) step S4 is ended.

[0027] In this state, in the outer peripheral curved part forming step S3, as shown in state a3 and state a4 in FIG. 3, the upper center tool U12 and the side wall part guide tool U13 are lowered. At this time, by lowering the upper center tool U12, the lower center tool L12 is pushed downward such that the center panel part 23 is sandwiched between an abutting surface U12a of the upper center tool U12 and an abutting surface L12a of the lower center tool L12 (state a4 in FIG. 3). In addition, by lowering the side wall part guide tool U13, the side wall part 24 inclined outward and downward comes to be positioned between an inner guide surface U13a of the side wall part guide tool U13 and an outer guide surface L12b of the lower center tool L12. By positioning the side wall part guide tool U13 and the lower center tool L12 around the side wall part 24, when compressive stress is applied to the side wall part 24 in the subsequent annular projecting part forming (plate-thickness increasing forming) step S4, it is possible to prevent buckling of the side wall part 24 due to the compressive stress.

[0028] The upper center tool U12 is lowered such that a height position of the abutting surface U12a thereof approaches a height position of an abutting surface (support surface) L13a of the curved part support tool (support member) L13. That is, the curved part support tool (support member) L13 is relatively movable in a projecting direction of the center projecting part 22 (upward direction, which is a second direction opposite to a first direction in which the annular projecting part 13 to be formed later (state a5 in FIG. 3) projects). The curved part support tool L13 applies a supporting force toward the projecting direction (second direction) to the plate material 11 on the abutting surface (support surface) L13a of the curved part support tool L13. Therefore, by lowering the upper center tool U12 and the side wall part guide tool U13, an outer peripheral curved part (annular curved part) 26 having a curved shape along a shape of the abutting surface L13a of the curved part support tool L13 is formed on an outer peripheral side of the side wall part 24 by being supported by the curved part support tool L13 that applies the supporting force. In this manner, a preform 11a having the outer peripheral curved part (annular curved part) 26 is formed from the plate material 11 (state a4 in FIG. 3).

[0029] In an annular projecting part forming (plate-thickness increasing forming) step S4, for example, as shown in state a4 and state a5 in FIG. 3, while supporting the outer peripheral curved part (annular curved part) 26 of the formed preform 11a by the abutting surface (support surface) L13a of the curved part support tool (support member) L13, a pressing force is applied to the center projecting part 22 in a direction (a downward direction, which is the first direction in which the annular projecting part 13 (state a5 in FIG. 3) to be formed later projects) opposite to the projecting direction thereof (second direction).

[0030] At this time, the upper center tool U12 is continuously lowered to push down the lower center tool L12 with the abutting surface U12a thereof. As a result, a pressing force is applied to the center panel part (specific plate part) 23 sandwiched between the abutting surface U12a and the abutting surface L12a of the lower center tool L12, and the center panel part 23 is pushed in the downward direction (first direction). At the same time, the side wall part guide tool U13 prevents the side wall part 24 from buckling due to compressive stress applied to the side wall part 24 by positioning the side wall part 24 between the inner guide surface U13a of the side wall part guide tool U13 and the abutting surface L12b of the lower center tool L12. Accordingly, the upper center tool U12 applies a pressing force larger than the supporting force of the curved part support tool L13 to the outer peripheral curved part (annular curved part) 26 via the side wall part 24.

[0031] By such an annular projecting part forming (plate-thickness increasing forming) step due to continuous lowering of the upper center tool U12 and the side wall part guide tool U13, the outer peripheral curved part (annular curved part) 26 is deformed, and at least a portion constituting the side wall part 24 is moved toward an outer side of the center projecting part 22 on the abutting surface L13a of the curved part support tool L13 while generating compressive stress in the projecting direction (second direction) in the side wall part 24. As a result, the annular projecting part 13 is formed such that the plate thickness is selectively increased based on the moved portion (state a5 in FIG. 3).

[0032] After forming the formed material 1 having the annular projecting part 13, the formed material 1 is removed from the upper tool U1 and the lower tool L1, thereby obtaining the formed material 1 in state a6 in FIG. 3. In the formed material 1, the annular projecting part 13 has an increased plate thickness over a wide range including the curved convex part 132 between the inner peripheral wall part 131 and the outer peripheral wall part 133. In the example of state a6 in FIG. 3, the outer peripheral panel part (outer peripheral plate part) 25 and the center panel part (center plate part) 23 are illustrated as being located at substantially the same height position, but the embodiment is not limited to such an example. The height position of the outer peripheral panel part 25 and the height position of the center panel part 23 may be different from each other as needed; for example, the height position of the outer peripheral panel part 25 may be lower than the height position of the center panel part 23.

[0033] As described above, in the method for forming the plate material 11 according to the first schematic embodiment, relative pushing (pressing) with respect to the center panel part (specific plate part) 23 is continuously performed (in one stroke) by using the same device (upper and lower dies) including the upper tool U1 and the lower tool L1. That is, in the forming method of the first schematic embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to form the annular projecting part 13 having an increased plate thickness over a wide range including a required range with such a simple manufacturing process.

[0034] In the forming process of the formed material 1, instead of the example described herein, the same device (upper and lower dies) may be consistently used from the blank punching step S1 to an annular projecting part forming (plate-thickness increasing forming) step S4. Alternatively, in the step of forming the formed material 1, from the blank punching step S1 to the outer peripheral curved part forming step S3, a device (upper and lower dies) different from the device (device including the upper tool U1 and the lower tool L1) used in an annular projecting part forming (plate-thickness increasing forming) step S4 may be used. In this case, the preform 11a is prepared in advance by the different device, and the preform 11a is successively placed between the upper tool U1 and the lower tool L1 described above.

[0035] In the first schematic embodiment, the example has been described in which the upper center tool U12 is lowered, with respect to the curved part support tool (support member) L13, so as to approach the curved part support tool (support member) L13, but the embodiment is not limited thereto. The curved part support tool (support member) L13 is relatively movable in the projecting direction (upward direction, which is the second direction) of the center projecting part 22. Therefore, instead of the example described herein, the curved part support tool (support member) L13 may be raised, with respect to the upper center tool U12, so as to approach the upper center tool U12, thereby applying a pressing force toward the projecting direction (second direction) to the plate material 11 on the abutting surface (support surface) L13a.

[0036] In this case, the center panel part 23 is sandwiched and fixed between the upper center tool U12 and the lower center tool L12, and, in this state, the lower outer tool L11 and the curved part support tool (support member) L13 are raised so as to push up the upper outer tool U11 and the side wall part guide tool U13. As a result, the outer peripheral curved part (annular curved part) 26 having a curved shape along a shape of the abutting surface L13a of the curved part support tool L13 is formed on an outer peripheral side of the side wall part 24, and subsequently, the annular projecting part 13 is formed.

[0037] Next, the following describes first and second embodiments as specific embodiments of the present invention. In the first and the second embodiments, configurations that are the same as those in the above-described first schematic embodiment, or configurations that are the same as each other, will not be described.[First embodiment]

[0038] A method for forming a plate material in the first embodiment is a method for forming a can lid 3 exemplified in FIG. 4 as a formed material. The can lid 3 includes a center panel part (center plate part) 31, a panel wall part (inner peripheral wall part) 321, a chuck wall radius part (curved convex part) 322, a chuck wall part including a first chuck wall part (first outer peripheral wall part) 323 and a second chuck wall part (second outer peripheral wall part) 33, and a curl part 34. Here, an annular projecting part 32 is constituted of the panel wall part 321, the chuck wall radius part 322, and the first chuck wall part 323.

[0039] The center panel part (center plate part) 31 is positioned substantially at the center of the can lid 3, and is constituted of a substantially flat surface having a substantially circular shape. In a case where the can lid 3 is a stay-on-tab type, a tab for an opening, a score, and the like are disposed on the center panel part 31.

[0040] A curved part (curved end part) 311 is formed at an outer edge (an end part on a radially outer side) of the center panel part 31, and the panel wall part (inner peripheral wall part) 321 is formed to extend downward in a substantially linear shape from a terminal end (outer end) of the curved part 311. The chuck wall radius part (curved convex part) 322 is a curved portion formed such that an end part (inner end) on an inner peripheral side thereof is connected to a lower end of the panel wall part 321, and an end part (outer end) on an outer peripheral side thereof is connected to the first chuck wall part (first outer peripheral wall part) 323.

[0041] The first chuck wall part (first outer peripheral wall part) 323 extends upward in a substantially linear shape from an upper end (outer end) on an outer peripheral side of the chuck wall radius part (curved convex part) 322. The second chuck wall part (second outer peripheral wall part) 33 is formed to extend in a substantially linear shape so as to be inclined outward and upward from an upper end (outer end) on an outer peripheral side of the first chuck wall part 323, and is formed such that an upper end thereof is connected to a curved portion of the curl part 34.

[0042] The method for forming the can lid 3 includes, as a part of the entire process, the method for forming the plate material 11 according to the above-described first schematic embodiment. That is, the method for forming the can lid 3 includes, as illustrated in FIG. 5, a blank punching step S11, an outer peripheral part drawing step S12, a center projecting part forming step S13, an outer peripheral curved part forming step S14, an annular projecting part forming (plate-thickness increasing forming) step S15, and a shape forming step S16 for a can lid. In the forming process (S11 to S16), a shape of a plate material 41 is changed as shown in states a11 to a18 in FIG. 6 and FIG. 7 to form the can lid 3 in state a19 in FIG. 7.

[0043] In the blank punching step S11, for example, the plate material 41 is formed into a substantially disk shape by using upper and lower punching tools (not illustrated) for punching the plate material 41 to be processed to have a substantially disk shape (state a11 in FIG. 6).

[0044] The plate material 41 is made of a material mainly containing metal. The metal material is not particularly limited, and may be, for example, a single metal material such as aluminum, an aluminum alloy, steel, or the like, a clad material of these metals, or a composite metal material obtained by applying surface treatment, coating, lamination, or the like to one surface or both surfaces of these metals.

[0045] In the outer peripheral part drawing step S12, for example, by using upper and lower tools for outer peripheral drawing (not illustrated) for performing drawing processing on an outer peripheral portion of the plate material 41 having a substantially disk shape, drawing processing is performed on the outer peripheral portion while fixing a plate-like portion on an inner peripheral side relative to the outer peripheral portion of the plate material 41 having a substantially disk shape shown in state a11 in FIG. 6. Accordingly, as shown in state a12 in FIG. 6, an outer peripheral part (side surface) 43 extending in a substantially vertical direction (downward direction) with respect to a plate-like portion 42 is formed on an outer peripheral side of the plate-like portion 42 of the plate material 41.

[0046] In the center projecting part forming step S13, for example, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate-like portion 42 of the plate material 41 in state a12 in FIG. 6, an outer panel part 420, which is an outer peripheral portion of the plate-like portion 42, is fixed while drawing processing is performed on an inner peripheral side thereof. Accordingly, as shown in state a13 in FIG. 6, a center projecting part 44 including a center panel part (center plate part) 45 corresponding to the "specific plate part" described in the above main embodiment, and a side wall part 46 on an outer peripheral side thereof, is formed on an inner peripheral side relative to an outer peripheral panel part (outer peripheral plate part) 421 of the plate material 41. A shape of the center panel part (center plate part) 45 is not particularly limited; however, as exemplified in FIG. 6, the center panel part (center plate part) 45 may have a curved (dome) shape that gently projects in a projecting direction of the center projecting part 44 (the second direction opposite to the first direction in which an annular projecting part 32a to be formed later (state a16 in FIG. 6) projects).

[0047] In the outer peripheral curved part forming step S14 and an annular projecting part forming (plate-thickness increasing forming) step S15, forming is performed on the plate material 41 in which the center projecting part 44 is formed (state a13 in FIG. 6) by using, for example, a forming device M1 including an upper tool U2 and a lower tool L2 illustrated in FIG. 8. As illustrated in FIG. 8 and state a14 in FIG. 6, for example, the upper tool U2 includes an annular upper outer tool U21, an upper center tool (upper tool for the specific plate part) U22, and an annular side wall part guide tool U23 positioned therebetween. The lower tool L2 includes an annular lower outer tool L21, a lower center tool L22, and an annular curved part support tool (support member) L23 positioned therebetween.

[0048] As illustrated in FIG. 8, in the forming device M1, the upper tool U2 includes cushion pins Ua1 and Ua2 connected to an air cylinder, and the lower tool L2 includes cushion pins La1 and La2 connected to the air cylinder. In the upper tool U2, the upper center tool U22 and the side wall part guide tool U23 are movable in upward and downward directions by the cushion pin Ua1 connected to the air cylinder, and the upper outer tool U21 is movable in the upward and downward directions by the cushion pin Ua2 connected to the air cylinder.

[0049] In the lower tool L2, the lower center tool L22 and the curved part support tool (support member) L23 are movable in the upward and downward directions by the cushion pin La1 connected to the air cylinder, and the lower outer tool L21 is movable in the upward and downward directions by the cushion pin La2 connected to the air cylinder. Alternatively, the forming device M1 may include elastic members such as a spring members instead of the cushion pins Ua1, Ua2, La1, and La2 connected to the air cylinder as described above.

[0050] In the outer peripheral curved part forming step S14, for example, as shown in state a14 in FIG. 6, after the plate material 41 in which the center projecting part 44 has been formed is placed on the lower tool L2, the upper outer tool U21 is lowered. Accordingly, the outer peripheral panel part (outer peripheral plate part) 421 of the plate material 41 is fixed by being sandwiched between an abutting surface U21a of the upper outer tool U21 and an abutting surface L21a of the lower outer tool L21. This fixing of the outer peripheral panel part (outer peripheral plate part) 421 is continued thereafter until an annular projecting part forming (plate-thickness increasing forming) step S15 is ended.

[0051] In this state, in the outer peripheral curved part forming step S14, the upper center tool U22 and the side wall part guide tool U23 are lowered. At this time, as shown in state a14 and state a15 in FIG. 6, by lowering the upper center tool U22, the lower center tool L22 is pushed downward such that the center panel part 45 is sandwiched between an abutting surface U22a of the upper center tool U22 and an abutting surface L22a.

[0052] The upper center tool U22 is lowered such that a height position of the abutting surface U22a thereof approaches a height position of an abutting surface (support surface) L23a of the curved part support tool (support member) L23. That is, the curved part support tool (support member) L23 is relatively movable in the projecting direction (upward direction, which is the second direction) of the center projecting part 44. The curved part support tool L23 applies a supporting force toward the projecting direction (second direction) to the plate material 41 on the abutting surface (support surface) L23a thereof. Therefore, by lowering the upper center tool U22 and the side wall part guide tool U23, an outer peripheral curved part (annular curved part) 47 having a curved shape along a shape of the abutting surface L23a of the curved part support tool L23 is formed on an outer peripheral side of the side wall part 46 by being supported by the curved part support tool L23 that applies the supporting force. In this manner, a preform 41a having the outer peripheral curved part (annular curved part) 47 is formed from the plate material 41 (state a15 in FIG. 6).

[0053] In the annular projecting part forming step (plate thickness increasing step) S15 (state a15 and state a16 in FIG. 6), for example, while supporting the outer peripheral curved part (annular curved part) 47 of the formed preform 41a by the abutting surface (support surface) L23a of the curved part support tool (support member) L23, a pressing force is applied to the center projecting part 44 in a direction opposite to the projecting direction thereof (the downward direction, which is the first direction in which the annular projecting part 32a to be formed (state a16 in FIG. 6) projects).

[0054] At this time, the upper center tool U22 is continuously lowered to push down the lower center tool L22 with the abutting surface U22a thereof. As a result, a pressing force is applied to the center panel part (specific plate part) 45 sandwiched between the abutting surface U22a and the abutting surface L22a of the lower center tool L22, and the center panel part 45 is pushed in the downward direction (first direction). At the same time, the side wall part guide tool U23 prevents the side wall part 24 from buckling due to compressive stress applied to the side wall part 46 by positioning the side wall part 46 between the inner guide surface U23a of the side wall part guide tool U23 and the outer guide surface L22b of the lower center tool L22. Accordingly, the upper center tool U22 applies a pressing force to the outer peripheral curved part (annular curved part) 47 via the side wall part 46.

[0055] By such pressing (plate-thickness increasing forming) due to continuous lowering of the upper center tool U22 and the side wall part guide tool U23, the center panel part 45 is pushed in the downward direction, and the outer peripheral curved part (annular curved part) 47 is deformed. Additionally, by this forming step for increasing a plate thickness, while generating compressive stress in the projecting direction (second direction) of the center projecting part 44 in the side wall part 46, at least a portion constituting the side wall part 46 is moved toward an outer side of the center projecting part 44 on the abutting surface L23a of the curved part support tool L23.

[0056] By an annular projecting part forming (plate-thickness increasing forming) step S15, an intermediate formed body 30 of the can lid (before shape forming of the can lid) (state a16 in FIG. 6), which has the annular projecting part 32a formed by selectively increasing a plate thickness based on the moved portion, is formed. This annular projecting part 32a has an increased plate thickness over a wide range including a chuck wall radius part (curved convex part) 322a.

[0057] As described above, in the method for forming the plate material 41 according to the first embodiment, relative pushing (pressing) with respect to the center panel part 45 is continuously performed (in one stroke) by using the same device (upper and lower dies) including the upper tool U2 and the lower tool L2. That is, in the forming method of the first embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to form the annular projecting part 32a having an increased plate thickness over a wide range including a required range with such a simple manufacturing process.

[0058] In this manner, after forming the intermediate formed body 30 of the can lid (before shape forming of the can lid) having the annular projecting part 32a, the intermediate formed body 30 of the can lid is removed from the upper tool U2 and the lower tool L2.

[0059] The shape forming step S16 for the can lid is a step of reforming a shape of the intermediate formed body 30 of the can lid to form the shape of the can lid. This shape forming step S16 for the can lid includes a step of forming a chuck wall part including the first chuck wall part (first outer peripheral wall part) 323 and the second chuck wall part (second outer peripheral wall part) 33 shown in the subsequent state a19.

[0060] The shape forming step S16 for the can lid may further include at least one or both of a known step (not illustrated) of forming the curl part 34 on an outer peripheral side relative to the annular projecting part 32a (or the annular projecting part 32 after forming), and a step of forming the center panel part (center plate part) 45 into a desired shape, for example, a substantially flat surface, in any order relative to, or simultaneously with, the above-described step of forming the chuck wall part.

[0061] In the shape forming step S16 for the can lid, for example, as shown in state a17 in FIG. 7, the shape of the intermediate formed body 30 of the can lid is reformed by using a can lid shape forming device M2 including an upper tool U3 and a lower tool L3. The upper tool U3 includes an upper outer tool U31, an upper center tool U32, and an annular processing tool U33 positioned therebetween. The lower tool L3 includes an annular lower outer tool L31 and a lower center tool L32. The lower tool L3 also includes an annular projecting part support tool L33 positioned between the lower outer tool L31 and the lower center tool L32.

[0062] In this shape forming step S16 for the can lid, as shown in state a17 in FIG. 7, after the intermediate formed body 30 of the can lid (before shape forming of the can lid) is placed on the lower tool L3, the shape forming step S16 for the can lid may be performed by, for example, lowering the upper outer tool U31, the upper center tool U32, and the processing tool U33 simultaneously. Alternatively, depending on the shape of the can lid, a timing of lowering of the upper outer tool U31, the upper center tool U32, and the processing tool U33 may be appropriately changed.

[0063] At this time, when the upper center tool U32 is lowered, the annular projecting part 32a is supported on an abutting surface (support surface) L33a of the annular projecting part support tool L33, and the annular projecting part 32a located between the lower center tool L32 and the lower outer tool L31 is formed into the annular projecting part 32 (state a18 in FIG. 7) having a shape along the abutting surface (support surface) L33a of the annular projecting part support tool L33. That is, at this time, the first chuck wall part (first outer peripheral wall part) 323 in the chuck wall part (refer to state a19) is formed.

[0064] At this time, when the upper outer tool U31 is lowered, an abutting surface U31a thereof abuts on the outer peripheral panel part (outer peripheral plate part) 421 on an abutting surface (support surface) L31b of the lower outer tool L31, thereby fixing the outer peripheral panel part (outer peripheral plate part) 421. In this state, when the processing tool U33 is lowered, the outer peripheral panel part (outer peripheral plate part) 421 is sandwiched between an abutting surface U33a of the processing tool U33 and an abutting surface L31a, thereby forming the second chuck wall part (second outer peripheral wall part) 33 (refer to state a19) having a shape along shapes of the lower outer tool L31 and the processing tool U33. In this manner, the chuck wall part (refer to state a19) including the first chuck wall part (first outer peripheral wall part) 323 and the second chuck wall part (second outer peripheral wall part) 33 on an outer peripheral side thereof is formed.

[0065] At this time, the curl part 34 can also be formed on an outer peripheral side of the lid. In this case, the lower tool L3 may include a tool for curling (not illustrated) on an outer peripheral side of the lower outer tool L31. As described above, when the processing tool U33 is lowered in a state in which the outer peripheral panel part (outer peripheral plate part) 421 is fixed, the outer peripheral panel part (outer peripheral plate part) 421 sandwiched between the abutting surface U33a of the processing tool U33 and the abutting surface L31a flows toward an outer peripheral side. In this state, when the tool for curling (not illustrated) is lowered, the curl part 34 having a shape along the abutting surface U31a of the upper outer tool U31 and an abutting surface (not illustrated) of the tool for curling (not illustrated) is formed (state a18 in FIG. 7).

[0066] At this time, the center panel part (center plate part) 45 may be formed into a desired shape, for example, a substantially flat surface. That is, the upper center tool U32 is lowered such that an abutting surface U32a thereof pushes down the lower center tool L32, whereby the center panel part (center plate part) 45 sandwiched between the abutting surface U32a and an abutting surface L32a of the lower center tool L32 is formed into the center panel part (center plate part) 31 having a substantially flat surface (state a18 in FIG. 7).

[0067] By removing the can lid 3 reformed in this manner from the can lid shape forming device M2, the can lid 3 shown in state a19 in FIG. 7 is obtained. The reformed can lid 3 in this state a19 has a shape in which the annular projecting part 32 including the panel wall part (inner peripheral wall part) 321, the chuck wall radius part (curved convex part) 322, and the first chuck wall part (first outer peripheral wall part) 323 projects substantially perpendicularly to an extending direction of the center panel part 31 shaped into a substantially flat surface.

[0068] Herein, the shape forming step S16 for the can lid in FIG. 7 has been described as including, at the same time, the step of forming the chuck wall part and the step of forming the center panel part (center plate part) 45 into a substantially flat surface; however, these steps may be included as steps at different stages in any order.

[0069] The following further describes an annular projecting part forming (plate-thickness increasing forming) step S15 and the shape forming step S16 for the can lid. In FIG. 9 in which the upper tool is omitted, a state b1 shows a shape of a part of the preform 41a formed in the outer peripheral curved part forming step S14. In this state b1, the center panel part 45 is positioned on an upper side relative to an uppermost position H at which a vertical height of the outer peripheral panel part (outer peripheral plate part) 421 is highest.

[0070] In this annular projecting part forming (plate-thickness increasing forming) step S15, as illustrated in FIG. 10A, the outer peripheral panel part (outer peripheral plate part) 421 of the preform 41a is sandwiched between the upper outer tool U21 and the lower outer tool L21, thereby generating a constrained portion K1 to fix the outer peripheral panel part (outer peripheral plate part) 421. In this state, a supporting force in the upward direction indicated by an arrow Y101 is applied to the outer peripheral curved part (annular curved part) 47 by the abutting surface (support surface) L23a of the curved part support tool L23. At this point, the preform 41a including this outer peripheral curved part (annular curved part) 47 has a shape illustrated in FIG. 11A.

[0071] In this state, the upper center tool U22 and the side wall part guide tool U23 are lowered. At this time, as indicated by an arrow Y91 in a state b2 in FIG. 9, the outer peripheral curved part (annular curved part) 47 of the preform 41a is supported by a supporting force from the downward direction thereof, and a pressing force is applied to the center panel part 45 of the preform 41a from the upward direction thereof, as indicated by an arrow Y92. Due to the pressing forces from the upward and downward directions, compressive stress is generated in the outer peripheral curved part (annular curved part) 47.

[0072] In this annular projecting part forming (plate-thickness increasing forming) step S15, the upper center tool U22 and the side wall part guide tool U23 are further lowered. Due to such continuous lowering, as shown in the state b2 and a state b3 in FIG. 9, a pressing force in the downward direction (first direction) indicated by the arrow Y92 (by the upper center tool U22) becomes larger than a supporting force in the upward direction (second direction) indicated by the arrow Y91 (by the curved part support tool L23). Accordingly, the curved part support tool L23 is pushed down.

[0073] At this time, as a pressing force in the downward direction indicated by an arrow Y102 by the upper center tool U22 is further applied to the center panel part 45 of the preform 41a, the center panel part 45 is pushed down further in the downward direction, as illustrated in FIG. 10B. Accordingly, the outer peripheral curved part (annular curved part) 47 illustrated in FIG. 10A is deformed.

[0074] As illustrated in FIG. 10B, due to a pressing force in the downward direction indicated by an arrow Y103 by the upper center tool U22 and a supporting force in the upward direction indicated by an arrow Y104 by the curved part support tool L23, compressive stress in a projecting direction (upward direction, which is the second direction) of the center projecting part 44 is applied to the side wall part 46 (FIG. 10A). Accordingly, as illustrated in FIG. 10B, while generating a compressed portion K2 due to this compressive stress, at least a portion constituting the side wall part 46 (FIG. 10A) moves toward an outer side of the center projecting part 44 on the abutting surface L23a of the curved part support tool L23, as indicated by an arrow Y105.

[0075] At this point, a formed body 30a-1 illustrated in FIG. 11B is formed. The formed body 30a-1 includes the annular projecting part 32a including a panel wall part (inner peripheral wall part) 321a, a chuck wall radius part (curved convex part) 322a, and a first chuck wall part (first outer peripheral wall part) 323a, and a plate thickness is increased in a wide range including the chuck wall radius part 322a.

[0076] In this manner, the intermediate formed body 30 of the can lid (before shape forming of the can lid) shown in the state b3 in FIG. 9 is formed. As shown in the state b3, in the intermediate formed body 30 of the can lid, an uppermost position of the center panel part 45 is positioned on a lower side relative to the uppermost position H of the outer peripheral panel part (outer peripheral plate part) 421.

[0077] Thereafter, in the shape forming step S16 for the can lid, the intermediate formed body 30 of the can lid is reformed by applying pressing forces thereto in the downward direction indicated by an arrow Y93 and an arrow Y94, as shown in a state b4 in FIG. 9. Accordingly, as shown in the state b4, the can lid 3 including the formed annular projecting part 32, the chuck wall part, and the center panel part (center plate part) 31 constituted of a substantially flat surface is obtained. In the can lid 3, the formed annular projecting part 32 has an increased plate thickness over a required range including the chuck wall radius part 322.

[0078] In the forming process of the can lid 3, instead of the example described herein, the same device (upper and lower dies) may be consistently used from the blank punching step S11 to an annular projecting part forming (plate-thickness increasing forming) step S15. Alternatively, in the forming process of the can lid 3, from the blank punching step S11 to the outer peripheral curved part forming step S14, a device (upper and lower dies) different from the device (device including the upper tool U2 and the lower tool L2 described above) used in an annular projecting part forming (plate-thickness increasing forming) step S15 may be used. In this case, the preform 41a is prepared in advance by the different device, and the preform 41a is placed between the upper tool U2 and the lower tool L2.[Example of first embodiment]

[0079] Next, the following describes an example of the first embodiment. In this example, as illustrated in FIG. 12, an intermediate formed body 30A of the can lid was formed by using a forming device M3 and a preform formed in advance (not illustrated). The preform was formed from a plate material made of an aluminum alloy (A5182P-H19, material plate thickness: 0.235 mm) having coating films formed on both surfaces.

[0080] The forming device M3 in FIG. 12 has the same configuration as that of the forming device M1 described above. That is, in the forming device M3, an upper tool U2A corresponds to the upper tool U2 described above, and a lower tool L2A corresponds to the lower tool L2 described above. Accordingly, an upper outer tool U21A, an upper center tool U22A, and a side wall part guide tool U23A correspond to the upper outer tool U21, the upper center tool U22, and the side wall part guide tool U23 described above. Additionally, a lower outer tool L21A, a lower center tool L22A, and a curved part support tool (support member) L23A correspond to the lower outer tool L21, the lower center tool L22, and the curved part support tool (support member) L23 described above.

[0081] By using this forming device M3, processing similar to that in an annular projecting part forming (plate-thickness increasing forming) step S15 was performed. That is, as illustrated in FIG. 12, a pressing force (8.0 kN) in the downward direction indicated by an arrow Y202 was applied to the lower outer tool L21A by the upper outer tool U21A, thereby fixing an outer peripheral panel part (outer peripheral plate part) 421A sandwiched between the lower outer tool L21A and the upper outer tool U21A.

[0082] In this state, while supporting, by the lower center tool L22A and the curved part support tool (support member) L23A, a portion to be the annular projecting part 32A together with the center panel part 45A corresponding to the "specific plate part" described in the above main embodiment, with supporting forces in the upward direction (second direction) indicated by arrows Y203 and Y204, the upper center tool U22A and the side wall part guide tool U23A were continuously lowered, and a pressing force in the downward direction (first direction) indicated by an arrow Y201 was continuously applied (plate-thickness increasing forming). The center panel part 45A and the annular projecting part 32A were formed by the plate-thickness increasing forming as described above.

[0083] In this manner, the intermediate formed body 30A of the can lid (before shape forming of the can lid) was obtained, the intermediate formed body 30A including the center panel part 45A and the annular projecting part 32A having the chuck wall radius part (curved convex part) 322A on an outer peripheral side of the center panel part 45A. In FIG. 12, a Lip Height (LH) is a length [mm] in a vertical direction from an uppermost position of the outer peripheral panel part (outer peripheral plate part) 421A to an outer side distal end.

[0084] In this example, the plate-thickness increasing forming was performed by varying a supporting force [kN] in the upward direction (second direction) indicated by the arrow Y204 by the curved part support tool (support member) L23A. FIG. 13 shows measurement values of the Lip Height (LH in FIG. 12) [mm] at respective values of the supporting force [kN].

[0085] In FIG. 13, a black circular plot indicates a value of the Lip Height [mm]. As illustrated in FIG. 13, even when the supporting force [kN] was increased, no large change was observed in the value of the Lip Height [mm]. This result means that the plate-thickness increasing forming does not affect the shape of the outer peripheral panel part (outer peripheral plate part) 421A.

[0086] FIG. 14A illustrates a part of the can lid formed in this example. FIG. 14B is an enlarged view of the annular projecting part 32A in FIG. 14A, and illustrates the panel wall part (inner peripheral wall part) 321A, the chuck wall radius part (curved convex part) 322A, and the first chuck wall part (first outer peripheral wall part) 323A that constitute the annular projecting part 32A. In FIG. 14B, measurement points of the plate thickness [mm] in the annular projecting part 32A are indicated by A to F.

[0087] In this example, for each value of the supporting force [kN] in the upward direction indicated by the arrow Y204 (FIG. 12) by the curved part support tool (support member) L23A during the plate-thickness increasing forming, the plate thickness [mm] was measured at the measurement points A to F (FIG. 14B) of the annular projecting part 32A in the can lid formed as illustrated in FIG. 14. FIG. 15 shows measurement results thereof.

[0088] According to this example, as illustrated in FIG. 15, by applying and increasing the supporting force [kN], it was possible to increase the plate thickness [mm] relative to an original plate thickness of 0.235 mm over a wide range of the measurement points A to F in the annular projecting part 32A. In this example, particularly when the supporting force was the largest, that is, 8.9 kN, the plate thickness was significantly increased relative to the original plate thickness over a wide range of the measurement points A to F. Additionally, as illustrated in FIG. 15, it was possible to sufficiently increase the plate thickness at the measurement points B to E within a range of the chuck wall radius part (curved convex part) 322A. In this manner, in this example, by the plate-thickness increasing forming as a single step, it was possible to increase not only a plate thickness on an inner peripheral side of the annular projecting part but also a plate thickness over a required range including an outer peripheral side of the annular projecting part.[Second embodiment]

[0089] A method for forming a plate material in the second embodiment is a method for forming a can bottom 6 shown in state a27 in FIG. 16 as a formed material. The method for forming the can bottom 6 includes, as a part of the entire process, the method for forming the plate material 11 according to the above-described first schematic embodiment.

[0090] The method for forming the can bottom 6 includes steps similar to those in FIG. 5 described above, that is, the blank punching step S11, the outer peripheral part drawing step S12, the center projecting part forming step S13, the outer peripheral curved part forming step S14, an annular projecting part forming (plate-thickness increasing forming) step S15, and the shape forming step S16 for the can bottom, which are illustrated in FIG. 5. In the forming process (S11 to S16), after changing a shape of a plate material 51 as shown in states a21 to a26 in FIG. 16, reforming is performed to form the can bottom 6 in state a27.

[0091] In the blank punching step S11 in the forming process of the can bottom 6, for example, the plate material 51 is formed into a substantially disk shape by using upper and lower punching tools (not illustrated) for punching the plate material 51 to be processed to have a substantially disk shape (state a21 in FIG. 16).

[0092] In the outer peripheral part drawing step S12 in the forming process of the can bottom 6, for example, by using upper and lower tools for outer peripheral drawing (not illustrated) for performing drawing processing on an outer peripheral portion of the plate material 51 having a substantially disk shape, drawing processing is performed on the outer peripheral portion while fixing a plate-like portion on an inner side relative to the outer peripheral portion of the plate material 51 having a substantially disk shape shown in state a21 in FIG. 16. Accordingly, as shown in state a22 in FIG. 16, an outer peripheral part (side surface) 53 extending in a substantially vertical direction (upward direction) with respect to a plate-like portion 52 is formed on an outer peripheral side of the plate-like portion 52 of the plate material 51.

[0093] In the center projecting part forming step S13 in the forming process of the can bottom 6, for example, with respect to the plate material 51 in state a22 in FIG. 16, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate-like portion 52, an outer panel part (outer plate part) 521 of the plate-like portion 52 is fixed while being formed into an annular curved bottom part 522 that gently projects in a substantially vertical direction (downward direction), and drawing processing is performed on an inner peripheral side thereof in this state. Accordingly, as shown in state a23 in FIG. 16, a center projecting part 54 including a dome panel part (center plate part) 55 corresponding to the "specific plate part" described in the above main embodiment, and a side wall part 56 on an outer peripheral side thereof, is formed. The dome panel part (center plate part) 55 has a dome shape gently projecting in a projecting direction of the center projecting part 54 (upward direction, which is the second direction opposite to the first direction in which an annular projecting part 62a to be formed later (state a26 in FIG. 16) projects).

[0094] In the outer peripheral curved part forming step S14 and an annular projecting part forming (plate-thickness increasing forming) step S15, for example, forming is performed on the plate material 51 in which the center projecting part 54 is formed (state a23 in FIG. 16) by using a forming device including an upper tool U4 and a lower tool L4. As shown in state a24 in FIG. 16, for example, the upper tool U4 includes an annular upper outer tool U41, an upper center tool (upper tool for the specific plate part) U42, and an annular side wall part guide tool U43 positioned therebetween. The lower tool L4 includes an annular lower outer tool L41, and an annular curved part support tool (support member) L42 positioned on an inner peripheral side relative to the lower outer tool L41.

[0095] In the outer peripheral curved part forming step S14, for example, as shown in state a24 in FIG. 16, after the plate material 51 in which the center projecting part 54 has been formed is placed on the lower tool L4, the upper outer tool U41 is lowered. Accordingly, the annular curved bottom part (corresponding to the outer peripheral panel part) 522 of the plate material 51 is fixed by being sandwiched between an abutting surface U41a of the upper outer tool U41 and an abutting surface L41a of the lower outer tool L41. This fixing of the annular curved bottom part 522 is continued thereafter until an annular projecting part forming (plate-thickness increasing forming) step S15 is ended.

[0096] At the same time, in the outer peripheral curved part forming step S14, the upper center tool U42 and the side wall part guide tool U43 are lowered. At this time, as shown in state a24 in FIG. 16, due to lowering of the upper center tool U42, an abutting surface U42a thereof is caused to abut on the dome panel part 55.

[0097] The upper center tool U42 is lowered such that a height position of the abutting surface U42a thereof approaches a height position of the abutting surface (support surface) L42a of the curved part support tool (support member) L42. That is, the curved part support tool (support member) L42 is relatively movable in a projecting direction (upward direction, which is the second direction) of the center projecting part 54. The curved part support tool L42 applies, when the plate material 51 is positioned on an abutting surface L42a thereof, a supporting force toward the projecting direction (second direction) to the plate material 51. Therefore, by lowering the upper center tool U42 and the side wall part guide tool U43, an outer peripheral curved part (annular curved part) 57 having a curved shape along a shape of the abutting surface L42a of the curved part support tool L42 is formed on an outer peripheral side of the side wall part 56 by being supported by the curved part support tool L42 that applies the supporting force. In this manner, a preform 51a having the outer peripheral curved part (annular curved part) 57 is formed from the plate material 51 (state a25 in FIG. 16).

[0098] In an annular projecting part forming (plate-thickness increasing forming) step S15 (state a25 and state a26 in FIG. 16), for example, while supporting the outer peripheral curved part (annular curved part) 57 of the formed preform 51a by the abutting surface (support surface) L42a of the curved part support tool (support member) L42, a pressing force is applied to the center projecting part 54 constituted of the dome panel part 55 and the side wall part 56 in a direction opposite to the projecting direction thereof (downward direction, which is the first direction).

[0099] At this time, as the upper center tool U42 is continuously lowered so that the abutting surface U42a thereof pushes down the dome panel part 55, a pressing force is applied to the dome panel part (specific plate part) 55, the dome panel part 55 is lowered, and a pressing force is applied to the outer peripheral curved part (annular curved part) 57 positioned between a distal end abutting part U43a and the abutting surface L42a.

[0100] By such pressing (plate-thickness increasing forming) due to continuous lowering of the upper center tool U42 and the side wall part guide tool U43, the dome panel part 55 is pushed in the downward direction, and the outer peripheral curved part (annular curved part) 57 is deformed. Additionally, by this plate-thickness increasing forming, while generating compressive stress in the projecting direction (second direction) of the center projecting part 54 in the side wall part 56, at least a portion constituting the side wall part 56 is moved toward an outer side of the center projecting part 54 on the abutting surface L42a of the curved part support tool L42.

[0101] By an annular projecting part forming (plate-thickness increasing forming) step S15, an intermediate formed body 60 of the can bottom (before shape forming of the can bottom) (state a26 in FIG. 16), which has the annular projecting part 62a formed by selectively increasing a plate thickness based on the moved portion, is formed. This annular projecting part 62a has an increased plate thickness over a wide range including a so-called bottom radius part 622a. Thereafter, the formed intermediate formed body 60 of the can bottom (before shape forming of the can bottom) is removed from the upper tool U4 and the lower tool L4.

[0102] As described above, also in the method for forming the plate material 51 according to the second embodiment, relative pushing (pressing) with respect to the dome panel part (specific plate part) 55 is continuously performed (in one stroke) by using the same device (upper and lower dies) including the upper tool U4 and the lower tool L4. That is, also in the forming method of the second embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to form the annular projecting part 62a having an increased plate thickness over a required range with such a simple manufacturing process.

[0103] The shape forming step S16 for the can bottom is a step of reforming a shape of the intermediate formed body 60 of the can bottom as needed to form a shape of the can bottom, and includes, as this step, a step of forming a shape of a can bottom annular projecting part 62. After reforming in the shape forming step S16 for the can bottom, the can bottom 6 removed from a reforming device (not illustrated) is obtained (state a27 in FIG. 16).

[0104] The shape forming step S16 for the can bottom can be performed by a conventionally known method, and may be performed by a method using a rotating roll or a method using press forming, for example.

[0105] Furthermore, in the second embodiment, particularly in a case where an inner surface coating step is required, it is desirably performed at a stage prior to the shape forming step S16 for the can lid.

[0106] The can bottom 6 in state a27 includes a dome panel part (center plate part) 61, a dome panel wall part (inner peripheral wall part) 621, a bottom radius part (curved convex part) 622, a chime lower part (first outer peripheral wall part) 623, and a chime part (second outer peripheral wall part) 63. Here, the can bottom annular projecting part 62 is constituted of the dome panel wall part 621, the bottom radius part 622, and the chime lower part 623. The can bottom annular projecting part 62 has a shape slightly inclined inward by reforming, and has an increased plate thickness over a required range including the bottom radius part 622.

[0107] The shape forming step S16 for the can bottom may further include, as needed, a step of forming the dome panel part (center plate part) 55 into a desired shape, for example, a shape other than a spherical surface such as a substantially spheroidal surface, a substantially conical surface, or a substantially flat surface. In this case, the shape forming step S16 for the can bottom may include, as a step of reforming the shape of the intermediate formed body 60 of the can bottom in state a26 in FIG. 16, a step of forming a shape of the can bottom annular projecting part 62 and a step of forming the dome panel part (center plate part) 55 into, for example, a substantially flat surface, simultaneously or in any order.[Second schematic embodiment]

[0108] The method for forming the plate material according to a second schematic embodiment of the present invention is a method for forming a formed material 1E as illustrated in FIG. 17. The formed material 1E is formed from a plate material 11E having a substantially disk shape. The formed material 1E includes a center panel part (center plate part) 12E that is a substantially flat surface having a substantially circular shape positioned substantially at the center of a plate material 11E, an annular projecting part 13E positioned on an outer peripheral side thereof, and an outer peripheral panel part (outer peripheral plate part) 14E positioned on a further outer peripheral side thereof.

[0109] The plate material 11E is made of a material mainly containing metal. The material mainly containing metal is not particularly limited, and may be, for example, a single metal material such as aluminum, an aluminum alloy, steel, or the like, a clad material of these metals, or a composite metal material obtained by applying surface treatment, coating (including a coating material containing a lubricant), lamination, or the like to one surface or both surfaces of these metals.

[0110] A curved end part 121E is formed as an end part (outer edge) on a radially outer side of the center panel part (center plate part) 12E, and an inner peripheral wall part 131E is formed to extend downward in a substantially linear shape from an outer end (terminal end) of the curved end part 121E. The curved convex part 132E is a curved portion formed such that an inner end (end part on an inner peripheral side) thereof is connected to a lower end of the inner peripheral wall part 131E, and an outer end (end part on an outer peripheral side) thereof is connected to a lower end of an outer peripheral wall part 133E. The outer peripheral wall part 133E is formed to extend upward in a substantially linear shape from an outer end (upper end on an outer peripheral side) of the curved convex part 132E, and to be connected to a curved end part (curved part) 141E formed as an end part on a radially inner side of the outer peripheral panel part (outer peripheral plate part) 14E. The annular projecting part 13E is constituted of the inner peripheral wall part 131E, the curved convex part 132E, and the outer peripheral wall part 133E as described above.

[0111] A forming process (forming method) of the plate material 11E for forming the formed material 1E includes, for example, as illustrated in FIG. 18, a blank punching step S31, a center-outer peripheral plate part forming step S32, an annular curved part forming step S33, and an annular projecting part forming (plate-thickness increasing forming) step S34. In the forming process (S31 to S34), a shape of the plate material 11E is changed as shown in a state m1 to a state m6 in FIG. 19 and FIG. 20 to form the formed material 1E in a state m7 in FIG. 20.

[0112] In the blank punching step S31, although shapes are different depending on a target formed product (for example, the shape may be an elliptical shape, a polygonal shape, or the like), for example, the plate material 11E is formed into a substantially disk shape by using upper and lower punching tools (not illustrated) for punching the plate material 11E to be processed to have a substantially disk shape (the state m1 in FIG. 19).

[0113] In the center-outer peripheral plate part forming step S32, for example, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate material 11E having a substantially disk shape, while applying a wrinkle pressing force to a portion on an outer peripheral side (an outer peripheral panel part (becoming an outer peripheral plate part) 21E later) of the plate material 11E having a substantially disk shape, drawing processing is performed on an inner peripheral side thereof in that state. Accordingly, as shown in the state m2 in FIG. 19, a center panel part (center plate part) 22E is formed, and, via a side wall part 23E that rises upward on an outer peripheral side relative to the center panel part 22E, the outer peripheral panel part (outer peripheral plate part) 21E corresponding to the "specific plate part" described in the above main embodiment is formed.

[0114] In the annular curved part forming step S33 and an annular projecting part forming (plate-thickness increasing forming) step S34, forming is performed on the plate material 11E (the state m3 in FIG. 19), in which the center panel part (center plate part) 22E and the outer peripheral panel part (outer peripheral plate part) 21E have been formed, by using an upper tool U5 positioned on an upper side thereof and a lower tool L5 positioned on a lower side thereof. The upper tool U5 includes an annular upper outer tool (upper tool for the specific plate part) U51, an upper center tool U52, and an annular guide tool U53 positioned therebetween. The lower tool L5 includes an annular lower outer tool L51, a lower center tool L52, and an annular support tool (support member) L53 positioned therebetween.

[0115] In the annular curved part forming step S33, the plate material 11E in which the center panel part 22E and the outer peripheral panel part 21E have been formed is placed on the lower tool L5 (the state m3 in FIG. 19). Then, the center panel part (center plate part) 22E of the plate material 11E is sandwiched and fixed between an abutting surface U52a of the upper center tool U52 and an abutting surface L52a of the lower center tool L52 (the state m4 in FIG. 19). This fixing of the center panel part 22E is continued thereafter until an annular projecting part forming (plate-thickness increasing forming) step S34 is ended.

[0116] In this state, in the annular curved part forming step S33, as shown in the state m4 in FIG. 19 and the state m5 in FIG. 20, a pressing force in the first direction (downward direction), which is a direction in which the annular projecting part 13E to be formed later (the state m6 in FIG. 20) projects, is applied by the upper outer tool U51. At this time, while sandwiching the outer peripheral panel part (outer peripheral plate part) 21E between an abutting surface U51a of the upper outer tool U51 and an abutting surface L51a of the lower outer tool L51, the upper outer tool U51 pushes down the lower outer tool L51.

[0117] The guide tool U53 may be either one that is lowered as shown in the state m4 in FIG. 19 and the state m5 and the state m6 in FIG. 20, or one that is not lowered. In either case, the guide tool U53 and the lower outer tool L51 are positioned around the side wall part 23E. Accordingly, when compressive stress is applied to the side wall part 23E in the subsequent annular projecting part forming (plate-thickness increasing forming) step S34, it is possible to prevent buckling of the side wall part 23E due to the compressive stress.

[0118] In the annular curved part forming step S33, the upper outer tool U51 pushes down the lower outer tool L51 such that a height position of the abutting surface U51a of the upper outer tool U51 approaches a height position of an abutting surface (support surface) L53a of the support tool (support member) L53. That is, the support tool L53 is relatively movable in the second direction (upward direction), which is a direction opposite to the first direction (downward direction). The support tool L53 applies a supporting force toward the second direction (upward direction) to the plate material 11E on the abutting surface (support surface) L53a thereof. Accordingly, by pushing down the lower outer tool L51 by the upper outer tool U51, an annular curved part 24E having a curved shape along a shape of the abutting surface L53a of the support tool L53 is formed on an inner peripheral side of the side wall part 23E by being supported by the support tool L53 that applies the supporting force. The plate material 11E in which the annular curved part 24E as described above has been formed is referred to as a preform 11Ea (the state m5 in FIG. 20).

[0119] In an annular projecting part forming (plate-thickness increasing forming) step S34, for example, as shown in the state m5 and the state m6 in FIG. 20, while supporting the annular curved part 24E of the formed preform 11Ea by the abutting surface (support surface) L53a of the support tool (support member) L53 (with a supporting force toward the second direction (upward direction)), a pressing force is applied in the first direction (downward direction) to the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 21E.

[0120] At this time, the upper outer tool U51 continuously applies a pressing force in the first direction (downward direction) so that the abutting surface U51a thereof pushes down the lower outer tool L51. That is, the upper outer tool U51 continuously applies a pressing force to the outer peripheral panel part (outer peripheral plate part) 21E sandwiched between the abutting surface U51a and the abutting surface L51a of the lower outer tool L51, and pushes the outer peripheral panel part 21E in the first direction (downward direction). At the same time, the guide tool U53 prevents the side wall part 23E from buckling due to compressive stress applied to the side wall part 23E by positioning the side wall part 23E between the outer guide surface U53a of the guide tool U53 and the abutting surface L51b of the lower outer tool L51. Accordingly, the supporting force of the support tool (support member) L53 can apply a pressing force larger than that of the upper outer tool U51 to the annular curved part 24E via the side wall part 23E.

[0121] In this manner, pushing is performed by the upper outer tool U51 while applying, by the support tool L53, a supporting force in the second direction (upward direction) opposite to the first direction (downward direction) in which the annular projecting part 13E to be formed (the state m6 in FIG. 20) projects. Accordingly, while deforming the annular curved part 24E and generating compressive stress in the second direction (upward direction) in the side wall part 23E, at least a portion of the plate material constituting the side wall part 23E is moved toward an inner side of the outer peripheral panel part (outer peripheral plate part) 21E on the abutting surface L53a of the support tool L53. As a result, the annular projecting part 13E is formed such that the plate thickness is selectively increased based on the moved portion (the state m6 in FIG. 20).

[0122] After forming the formed material 1E having the annular projecting part 13E, the formed material 1E is removed from the upper tool U5 and the lower tool L5, thereby obtaining the formed material 1E in the state m7 in FIG. 20. In the formed material 1E, the annular projecting part 13E has an increased plate thickness over a wide range including a required range for improving pressure resistance strength in the curved convex part 132E located between the inner peripheral wall part 131E and the outer peripheral wall part 133E. In the example of the state m7 in FIG. 20, the outer peripheral panel part (outer peripheral plate part) 21E and the center panel part (center plate part) 22E are illustrated as being located at substantially the same height position, but the embodiment is not limited to such an example. The height position of the outer peripheral panel part 21E and the height position of the center panel part 22E may be different from each other as needed; for example, the height position of the outer peripheral panel part 21E may be lower than the height position of the center panel part 22E.

[0123] As described above, in the method for forming the plate material 11E according to the second schematic embodiment, relative pushing (pressing) with respect to the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 21E is continuously performed (in one stroke) by using the same device (upper and lower dies) including the upper tool U5 and the lower tool L5. That is, in the forming method according to the second schematic embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to form the annular projecting part 13E having an increased plate thickness over a required range for improving pressure resistance strength with such a simple manufacturing process.

[0124] In the forming process of the formed material 1E, instead of the example described herein, the same device (upper and lower dies) may be consistently used from the blank punching step S31 to an annular projecting part forming (plate-thickness increasing forming) step S34. Alternatively, in the forming process of the formed material 1E, from the blank punching step S31 to the annular curved part forming step S33, a device (upper and lower dies) different from the device (device including the upper tool U5 and the lower tool L5) used in an annular projecting part forming (plate-thickness increasing forming) step S34 may be used. In this case, the preform 11Ea is prepared in advance by the different device, and the preform 11Ea is successively placed between the upper tool U5 and the lower tool L5 described above.

[0125] In the second schematic embodiment, an example has been described in which the upper outer tool U51 applies a pressing force in the first direction (downward direction) to the plate material 11E on the abutting surface (support surface) L53a so that the upper outer tool U51 approaches the support tool (support member) L53, but the embodiment is not limited thereto. The support tool (support member) L53 is relatively movable in the second direction (upward direction). Thus, instead of the example described herein, the support tool (support member) L53 may apply a pressing force in the second direction (upward direction) to the plate material 11E on the abutting surface (support surface) L53a so that the support tool (support member) L53 approaches the upper outer tool U51.

[0126] In this case, the outer peripheral panel part 21E is sandwiched and fixed between the upper outer tool U51 and the lower outer tool L51, and the support tool (support member) L53 pushes up the guide tool U53 in this state. Accordingly, the annular curved part 24E having a curved shape along a shape of the abutting surface L53a of the support tool L53 is formed on an inner peripheral side of the side wall part 23E, and subsequently, the annular projecting part 13E is formed.

[0127] Next, the following describes third to fifth embodiments as specific embodiments of the present invention. In the third to the fifth embodiments, configurations that are the same as those in the above-described second schematic embodiment, or configurations that are the same as each other, will not be described.[Third embodiment]

[0128] A method for forming a plate material according to the third embodiment is a method for forming a can lid 3E exemplified in FIG. 21 as a formed material. The can lid 3E includes a center panel part (center plate part) 31E, a panel wall part (inner peripheral wall part) 321E, a chuck wall radius part (curved convex part) 322E, a chuck wall part including a first chuck wall part (first outer peripheral wall part) 323E and a second chuck wall part (second outer peripheral wall part) 33E, and a curl part 34E. Here, an annular projecting part 32E is constituted of the panel wall part 321E, the chuck wall radius part 322E, and the first chuck wall part 323E.

[0129] The center panel part (center plate part) 31E is positioned substantially at the center of the can lid 3E, and is constituted of a substantially flat surface having a substantially circular shape. In a case where the can lid 3E is a stay-on-tab type, a tab for an opening, a score, and the like are disposed on the center panel part 31E.

[0130] A curved end part (curved part) 311E is formed as an end part (outer edge) on a radially outer side of the center panel part 31E, and the panel wall part (inner peripheral wall part) 321E is formed to extend downward in a substantially linear shape from an outer end (terminal end) of the curved end part 311E. The chuck wall radius part (curved convex part) 322E is a curved portion formed such that an inner end thereof (end part on an inner peripheral side) is connected to a lower end of the panel wall part 321E, and an outer end thereof (end part on an outer peripheral side) is connected to a lower end of the first chuck wall part (first outer peripheral wall part) 323E.

[0131] The first chuck wall part (first outer peripheral wall part) 323E extends upward in a substantially linear shape from an outer end (upper end on an outer peripheral side) of the chuck wall radius part (curved convex part) 322E. The second chuck wall part (second outer peripheral wall part) 33E is formed to extend in a substantially linear shape so as to be inclined outward and upward from an upper end (upper end on an outer peripheral side) of the first chuck wall part 323E, and is formed such that an upper end thereof is connected to a curved portion of the curl part 34E.

[0132] The method for forming the can lid 3E includes, as a part of the entire process, the method for forming the plate material 11E according to the above-described second schematic embodiment. That is, the method for forming the can lid 3E includes, as illustrated in FIG. 22, a blank punching step S41, an outer peripheral drawing step S42, a center-outer peripheral plate part forming step S43, an annular curved part forming step S44, an annular projecting part forming (plate-thickness increasing forming) step S45, and a shape forming step S46 (for the can lid). In the forming process (S41 to S46), a shape of a plate material 41E is changed as shown in a state m11 to a state m18 in FIG. 23 to FIG. 25 to form the can lid 3E in a state m19 in FIG. 25.

[0133] In the blank punching step S41, for example, the plate material 41E is formed into a substantially disk shape by using upper and lower punching tools (not illustrated) for punching the plate material 41E to be processed to have a substantially disk shape (the state m11 in FIG. 23).

[0134] The plate material 41E is made of a material mainly containing metal. The metal material is not particularly limited, and may be, for example, a single metal material such as aluminum, an aluminum alloy, steel, or the like, a clad material of these metals, or a composite metal material obtained by applying surface treatment, coating (including a coating material containing a lubricant), lamination, or the like to one surface or both surfaces of these metals.

[0135] In the outer peripheral drawing step S42, for example, by using upper and lower tools for outer peripheral drawing (not illustrated) for performing drawing processing on an outer peripheral portion of the plate material 41E having a substantially disk shape, drawing processing is performed on the outer peripheral portion while fixing a plate-like portion on an inner peripheral side relative to the outer peripheral portion of the plate material 41E having a substantially disk shape shown in the state m11 in FIG. 23. Accordingly, as shown in the state m12 in FIG. 23, an outer peripheral side part 43E is formed on an outer peripheral side of a plate-like portion 42E of the plate material 41E so as to hang downward via a curved corner part (extend in a substantially vertical direction (downward direction) with respect to the plate-like portion 42E).

[0136] In the center-outer peripheral plate part forming step S43, for example, with respect to the plate material 41E in the state m12 in FIG. 23, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate-like portion 42E, while applying a wrinkle pressing force to an outer panel part (outer plate part) 420E that is an outer peripheral portion of the plate-like portion 42E, drawing processing is performed on an inner peripheral side thereof. Accordingly, as shown in the state m13 in FIG. 23, a center panel part (center plate part) 45E is formed, and, via a side wall part 46E that rises upward on an outer peripheral side relative to the center panel part 45E, the outer peripheral panel part (outer peripheral plate part) 421E corresponding to the "specific plate part" described in the above main embodiment is formed. A shape of the center panel part (center plate part) 45E may be, for example, a substantially flat surface as exemplified in FIG. 23, but the shape is not limited to such a substantially flat surface and may be another shape. The shape of the center panel part 45E may be, for example, a curved (dome) shape (not illustrated) that gently projects in the first direction (downward direction) in which an annular projecting part 32Ea to be formed later (the state m16 in FIG. 24) projects, or in the second direction (upward direction) opposite thereto.

[0137] In the annular curved part forming step S44 and an annular projecting part forming (plate-thickness increasing forming) step S45, forming is performed on the plate material 41E (the state m13 in FIG. 23), in which the center panel part (center plate part) 45E and the outer peripheral panel part (outer peripheral plate part) 421E have been formed, by using a forming device M4 including, for example, an upper tool U6 and a lower tool L6 illustrated in FIG. 26. As shown in FIG. 26 and in, for example, the state m14 in FIG. 24, the upper tool U6 includes an annular upper outer tool (upper tool for the specific plate part) U61, an upper center tool U62, and an annular guide tool U63 positioned therebetween. The lower tool L6 includes an annular lower outer tool L61, a lower center tool L62, and an annular support tool (support member) L63 positioned therebetween.

[0138] As illustrated in FIG. 26, in the forming device M4, the upper tool U6 includes cushion pins Ua11 and Ua12 connected to an air cylinder, and the lower tool L6 includes cushion pins La11 and La12 connected to the air cylinder. In the upper tool U6, the upper center tool U62 is movable in upward and downward directions by the cushion pins Ua11 and Ua12 connected to the air cylinder, and the guide tool U63 is movable in the upward and downward directions by the cushion pin Ua12 connected to the air cylinder.

[0139] In the lower tool L6, the support tool (support member) L63 is movable in the upward and downward directions by the cushion pin La11 connected to the air cylinder, and the lower outer tool L61 is movable in the upward and downward directions by the cushion pin La12 connected to the air cylinder. Alternatively, the forming device M4 may include elastic members such as a spring member, a hydraulic cylinder (for example, an oil hydraulic cylinder), or the like instead of the cushion pins Ua11, Ua12, La11, and La12 connected to the air cylinder as described above.

[0140] In the annular curved part forming step S44, for example, as shown in the state m14 in FIG. 24, the plate material 41E in which the center panel part (center plate part) 45E and the outer peripheral panel part (outer peripheral plate part) 421E have been formed is sandwiched between the upper tool U6 and the lower tool L6. At this time, the center panel part 45E of the plate material 41E is sandwiched and fixed between an abutting surface U62a of the upper center tool U62 and an abutting surface L62a of the lower center tool L62. This fixing of the center panel part 45E is continued thereafter until an annular projecting part forming (plate-thickness increasing forming) step S45 is ended. In that state, in the annular curved part forming step S44, as shown in the state m14 and the state m15 in FIG. 24, a pressing force is applied in the first direction (downward direction) by the upper outer tool U61. At this time, while sandwiching the outer peripheral panel part (outer peripheral plate part) 421E between an abutting surface U61a of the upper outer tool U61 and an abutting surface L61a of the lower outer tool L61, the upper outer tool U61 pushes down the lower outer tool L61.

[0141] The guide tool U63 may be either one that is not lowered as shown in the state m14 to the state m16 in FIG. 24, or one that is lowered. In either case, the guide tool U63 and the lower outer tool L61 are positioned around the side wall part 46E. Accordingly, when compressive stress is applied to the side wall part 46E in the subsequent annular projecting part forming (plate-thickness increasing forming) step S45, it is possible to prevent buckling of the side wall part 46E due to the compressive stress.

[0142] In the annular curved part forming step S44, the upper outer tool U61 pushes down the lower outer tool L61 such that a height position of the abutting surface U61a of the upper outer tool U61 approaches a height position of an abutting 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 direction). The support tool L63 applies a supporting force toward the second direction (upward direction) to the plate material 41E on the abutting surface (support surface) L63a thereof. Accordingly, by pushing down the lower outer tool L61 by the upper outer tool U61, an annular curved part 47E having a curved shape along a shape of the abutting surface L63a of the support tool L63 is formed on an inner peripheral side of the side wall part 46E by being supported by the support tool L63 that applies the supporting force. The plate material 41E in which the annular curved part 47E as described above has been formed is referred to as a preform 41Ea (the state m15 in FIG. 24).

[0143] In an annular projecting part forming (plate-thickness increasing forming) step S45, for example, as shown in the state m15 and the state m16 in FIG. 24, while supporting the annular curved part 47E of the formed preform 41Ea by the abutting surface (support surface) L63a of the support tool (support member) L63 (with a supporting force toward the second direction (upward direction)), a pressing force is applied in the first direction (downward direction) to the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 421E.

[0144] At this time, the upper outer tool U61 continuously applies a pressing force in the first direction (downward direction) so that the abutting surface U61a thereof pushes down the lower outer tool L61. That is, the upper outer tool U61 continuously applies a pressing force to the outer peripheral panel part (outer peripheral plate part) 421E sandwiched between the abutting surface U61a and the abutting surface L61a of the lower outer tool L61, and pushes the outer peripheral panel part 421E in the first direction (downward direction). At the same time, the guide tool U63 prevents the side wall part 46E from buckling due to compressive stress applied to the side wall part 46E by positioning the side wall part 46E between the outer guide surface U63a of the guide tool U63 and the abutting surface L61b of the lower outer tool L61. Accordingly, the supporting force of the support tool (support member) L63 can apply a pressing force larger than that of the upper outer tool U61 to the annular curved part 47E via the side wall part 46E.

[0145] In this manner, pushing is performed by the upper outer tool U61 while applying, by the support tool L63, a supporting force in the second direction (upward direction). Accordingly, while deforming the annular curved part 47E and generating compressive stress in the second direction (upward direction) in the side wall part 46E, at least a portion of the plate material constituting the side wall part 46E is moved toward an inner side of the outer peripheral panel part (outer peripheral plate part) 421E on the abutting surface L63a of the support tool L63.

[0146] By an annular projecting part forming (plate-thickness increasing forming) step S45 as described above, an intermediate formed body 30E of the can lid (before shape forming (reforming)) (the state m16 in FIG. 24), which has the annular projecting part 32Ea formed by selectively increasing a plate thickness based on the moved portion, is formed. In the intermediate formed body 30E, the annular projecting part 32Ea has an increased plate thickness over a wide range including a required range for improving pressure resistance strength in a chuck wall radius part (curved convex part) 322Ea.

[0147] As described above, in the method for forming the plate material 41E according to the third embodiment, relative pushing (pressing) with respect to the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 421E is continuously performed (in one stroke) by using the same device (upper and lower dies) including the upper tool U6 and the lower tool L6. That is, in the forming method according to the third embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to form the annular projecting part 32Ea having an increased plate thickness over a wide range with such a simple manufacturing process.

[0148] In this manner, after forming the intermediate formed body 30E of the can lid (before shape forming) having the annular projecting part 32Ea, the intermediate formed body 30E of the can lid is removed from the upper tool U6 and the lower tool L6.

[0149] The shape forming step S46 for the can lid is a step of reforming a shape of the intermediate formed body 30E of the can lid to form the shape of the can lid. This shape forming step S46 for the can lid includes a step of forming a chuck wall part including the first chuck wall part (first outer peripheral wall part) 323E and the second chuck wall part (second outer peripheral wall part) 33E shown in the state m19 in FIG. 25.

[0150] The shape forming step S46 for the can lid may further include a known step (not illustrated) of forming the curl part 34E (the state m18 in FIG. 25) on an outer peripheral side relative to the annular projecting part 32Ea (or the annular projecting part 32E after forming), in any order relative to, or simultaneously with, the above-described step of forming the chuck wall part.

[0151] The center panel part 45E of the intermediate formed body 30E may have a shape other than a substantially flat surface as shown in the state m16 in FIG. 24, and may have, for example, a curved (dome) shape (not illustrated) that gently projects in the second direction (upward direction). In this case, the shape forming step S46 for the can lid may further include at least one or both of a step of forming the center panel part 45E into a desired shape (for example, into a substantially flat surface) and a known step of forming the above-described curl part 34E, in any order relative to, or simultaneously with, the above-described step of forming the chuck wall part.

[0152] In the shape forming step S46 for the can lid, for example, as shown in the state m17 in FIG. 25, the shape of the intermediate formed body 30E of the can lid is reformed by using a can lid shape forming device M5 including an upper tool U7 and a lower tool L7. The upper tool U7 includes an annular upper outer tool U71, an upper center tool U72, and an annular processing tool U73 positioned therebetween. The lower tool L7 includes an annular lower outer tool L71, a lower center tool L72, and an annular projecting part support tool L73 positioned therebetween.

[0153] In this shape forming step S46 for the can lid, as shown in the state m17 in FIG. 25, after the intermediate formed body 30E (before shape forming) of the can lid is placed on the lower tool L7, the shape forming step S46 for the can lid may be performed by, for example, lowering the upper outer tool U71, the upper center tool U72, and the processing tool U73 simultaneously. Alternatively, depending on the shape of the can lid, a timing of lowering of the upper outer tool U71, the upper center tool U72, and the processing tool U73 may be appropriately changed.

[0154] At this time, when the upper center tool U72 is lowered, the annular projecting part 32Ea is supported on an abutting surface (support surface) L73a of the annular projecting part support tool L73, and the annular projecting part 32Ea located between the lower center tool L72 and the lower outer tool L71 is formed into the annular projecting part 32E (the state m18 in FIG. 25) having a shape along an abutting end part U72b of the upper center tool U72 and the abutting surface (support surface) L73a of the annular projecting part support tool L73. That is, at this time, the first chuck wall part (first outer peripheral wall part) 323E (the state m19 in FIG. 25) in the chuck wall part is formed.

[0155] At this time, when the upper outer tool U71 is lowered, an abutting surface U71a thereof abuts on the outer peripheral panel part (outer peripheral plate part) 421E on an abutting surface (support surface) L71b of the lower outer tool L71, thereby fixing the outer peripheral panel part 421E. In this state, when the processing tool U73 is lowered, the outer peripheral panel part 421E is sandwiched between an abutting surface U73a of the processing tool U73 and the abutting surface L71a, thereby forming the second chuck wall part (second outer peripheral wall part) 33E (the state m19 in FIG. 25) having a shape along shapes of the lower outer tool L71 and the processing tool U73. In this manner, the chuck wall part (the state m19 in FIG. 25) including the first chuck wall part (first outer peripheral wall part) 323E and the second chuck wall part (second outer peripheral wall part) 33E on an outer peripheral side thereof is formed.

[0156] At this time, the curl part 34E can also be formed on an outer peripheral side of the lid. In this case, the lower tool L7 may include a tool for curling (not illustrated) on an outer peripheral side of the lower outer tool L71. As described above, when the processing tool U73 is lowered in a state in which the outer peripheral panel part 421E is fixed, the outer peripheral panel part 421E sandwiched between the abutting surface U73a of the processing tool U73 and the abutting surface L71a flows toward an outer peripheral side. In this state, when the tool for curling (not illustrated) is lowered, the curl part 34E having a shape along the abutting surface U71a of the upper outer tool U71 and an abutting surface (not illustrated) of the tool for curling is formed (the state m18 in FIG. 25).

[0157] At this time, in a case where the shape of the center panel part (center plate part) 45E is another shape (for example, a curved (dome) shape that gently projects in the second direction (upward direction) (not illustrated)), the shape thereof may also be formed into a desired shape, for example, a substantially flat surface. In this case, the upper center tool U72 is lowered such that an abutting surface U72a thereof pushes down the lower center tool L72, whereby the center panel part (center plate part) 45E having another shape (for example, a curved (dome) shape that gently projects in the second direction) and sandwiched between the abutting surface U72a and an abutting surface L72a of the lower center tool L72 is formed into the center panel part (center plate part) 31E having a substantially flat surface (the state m18 in FIG. 25).

[0158] In this case, the shape forming step S46 for the can lid in FIG. 22 includes the step of forming the chuck wall part and the step of forming the center panel part (center plate part) 45E into a substantially flat surface at the same time; however, these steps may be included as steps at different stages in any order.

[0159] By removing the can lid 3E reformed in this manner from the can lid shape forming device M5, the can lid 3E shown in the state m19 in FIG. 25 is obtained. The reformed can lid 3E in this state m19 has a shape in which the annular projecting part 32E including the panel wall part (inner peripheral wall part) 321E, the chuck wall radius part (curved convex part) 322E, and the first chuck wall part (first outer peripheral wall part) 323E projects downward substantially perpendicularly to an extending direction of the center panel part 31E.

[0160] In the forming process of the can lid 3E, instead of the example described herein, the same device (upper and lower dies) may be consistently used from the blank punching step S41 to an annular projecting part forming (plate-thickness increasing forming) step S45. Alternatively, in the forming process of the can lid 3E, from the blank punching step S41 to the annular curved part forming step S44, a device (upper and lower dies) different from the device (device including the upper tool U6 and the lower tool L6 described above) used in an annular projecting part forming (plate-thickness increasing forming) step S45 may be used. In this case, the preform 41Ea is prepared in advance by the different device, and the preform 41Ea is placed between the upper tool U6 and the lower tool L6.[Examples of third embodiment (Examples 1 to 5)]

[0161] The following describes examples of the third embodiment (Examples 1 to 5). In Examples 1 to 5, through the blank punching step S41 to an annular projecting part forming (plate-thickness increasing forming) step S45 described above in the third embodiment, an intermediate formed body 40Eb (FIG. 27(a)) before shape forming (reforming) of the can lid was formed from the plate material. As the plate material, a plate material was used that was formed by applying a coating material containing a lubricant to both surfaces of an aluminum alloy (A5182) (metal portion) having an original plate thickness of 0.218 mm. As illustrated in FIG. 27(a), the intermediate formed body 40Eb includes a center panel part (center plate part) 45Eb having a curved (dome) shape, an outer peripheral panel part (an outer peripheral plate part, a specific plate part) 421Eb corresponding to the outer peripheral panel part 421E described above, and an annular projecting part 32Eb.

[0162] In Examples 1 to 5, in an annular projecting part forming (plate-thickness increasing forming) step S45 described above, while supporting the annular curved part (not illustrated herein) by the abutting surface (support surface) L63a of the support tool (support member) L63 described above (with a supporting force toward the upward direction (the second direction described above)), a pressing force was applied in the downward direction (the first direction described above) to the outer peripheral panel part (outer peripheral plate part) 421Eb. At this time, a supporting force toward the upward direction (second direction) was applied, by the support tool L63, to a plate material portion (of the annular curved part) on the abutting surface (support surface) L63a of the support tool L63. At this time, the magnitude of the supporting force, that is, the supporting force (countersink holding force) [kgf], was varied among Examples 1 to 5, and for each different supporting force, a plate thickness [mm] of the metal portion at measurement points a to v (FIGS. 27(a) and 27(b)) in the plate material of the intermediate formed body 40Eb was measured (FIG. 28).

[0163] In performing the processing in an annular projecting part forming (plate-thickness increasing forming) step S45 described above, as illustrated in FIG. 28, the supporting 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. 28 are graphs indicating measured values of the plate thickness [mm] of the metal portion at the measurement points a to v in the plate material after the processing in step S45, respectively corresponding to Example 1 (supporting force: 200 kgf), Example 2 (supporting force: 400 kgf), Example 3 (supporting force: 600 kgf), Example 4 (supporting force: 800 kgf), and Example 5 (supporting force: 1000 kgf). As shown in the measurement results in FIG. 28, in any of Examples 1 to 5 in which the supporting force (countersink holding force) [kgf] in the upward direction (second direction) was applied by the support tool L63, it was possible to make the plate thickness of the metal portion in the plate material thicker than the original plate thickness (0.218 mm) over a wide range within a range of the measurement points a to v. From the results of Examples 1 to 5 in FIG. 28, it can be found that, as the supporting force [kgf] is increased, the plate thickness [mm] of the metal portion in the plate material can be made thicker.

[0164] Here, a range including the measurement points f to i and a range including the measurement points 1 to n of a chuck wall radius part (curved convex part) 322Eb (FIG. 27(b)) of the annular projecting part 32Eb are ranges that are particularly necessary for improving pressure resistance of the can container (metal can) to which the lid after shape forming (reforming) is attached, the can container being formed from the intermediate formed body 40Eb, as confirmed by various experiments, simulations, and the like that were previously conducted. In the chuck wall radius part (curved convex part) 322Eb illustrated in FIG. 27(b), a range between dotted lines including the measurement points f to i is defined as a "main pressure-resistance range X1", and a range between dotted lines including the measurement points 1 to n is defined as a "main pressure-resistance range X2". As shown in the measurement results in the main pressure-resistance ranges X1 and X2 in FIG. 28, it can be found that, by applying a large value as the supporting force (countersink holding force) [kgf] in the second direction (upward direction) described above by the support tool L63, sufficiently large values of the plate thickness [mm] can be obtained in both of the main pressure-resistance ranges X1 and X2 (for example, Examples 4 and 5).[Examples of third embodiment (Examples 6 to 8, Comparative Example 1)]

[0165] Next, the following describes examples of the third embodiment (Examples 6 to 8, Comparative Example 1). In Examples 6 to 8 and Comparative Example 1, a can lid 3Ec illustrated in FIG. 30 was formed from the plate material through the blank punching step S41 to the shape forming step S46 for the can lid described above in the third embodiment. As the plate material, a plate material was used that was formed by applying a coating material containing a lubricant to both surfaces of an aluminum alloy (A5182) (FIG. 29) (metal portion) having an original plate thickness of 0.218 mm.

[0166] In performing the processing in an annular projecting part forming (plate-thickness increasing forming) step S45 described above, the supporting 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. 29). As illustrated in FIG. 29, the can lids 3Ec formed in the examples 6 to 8 and Comparative Example 1 all had a lid diameter of 206 diameter (2 inches 6 / 16), 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.

[0167] As indicated by bidirectional arrows in FIG. 30, the unit depth (UD) [mm] is a distance [mm] in a height direction from a lower end of an outer surface of the can lid 3Ec (that is, a lower end of an outer surface of a chuck wall radius part (curved convex part) 322Ec of the annular projecting part 32Ec) to an upper end of the outer surface of the can lid 3Ec, and the panel height (PH) [mm] is a distance in the height direction from the lower end of the outer surface of the can lid 3Ec to an outer surface of a center panel part (center plate part) 31Ec.

[0168] In Examples 6 to 8 and Comparative Example 1, a pressure resistance test was conducted in which the formed can lid 3Ec was seamed onto a can container (metal can) and a water pressure was applied to an inner part. As a result, as illustrated in FIG. 29, a pressure resistance value (pressure resistance strength) was 0.654 MPa in Example 6, 0.656 MPa in Example 7, and 0.696 MPa in Example 8, all of which were pressure resistance values satisfying required performance. On the other hand, the pressure resistance value (pressure resistance strength) in Comparative Example 1 was 0.630 MPa, which was not a pressure resistance value satisfying required performance. From these results, it can be found that, by applying the supporting force (countersink holding force) [kgf] by the support tool L63, pressure resistance strength of the can lid can be increased, and that the pressure resistance strength of the can lid can be further increased as the supporting force is increased.[Fourth embodiment]

[0169] A method for forming the plate material according to a fourth embodiment is configured such that, after a plate-thickness increasing forming at the first stage is performed on the plate material by processing illustrated in FIG. 31, a plate-thickness increasing forming at the second stage is performed by processing illustrated in FIG. 32, and thereafter, a plate-thickness increasing forming at the third stage is performed by processing illustrated in FIG. 33. A height Ht indicated by a dotted line in FIG. 31 to FIG. 33 consistently indicates the same height.(Forming step of increasing plate thickness at first stage)

[0170] In the plate-thickness increasing forming at the first stage performed in the processing illustrated in FIG. 31, first, by using upper and lower tools for outer peripheral drawing (not illustrated) for performing drawing processing on an outer peripheral portion of a plate material 51E formed into a substantially disk shape by blank punching, drawing processing is performed on the outer peripheral portion while applying a wrinkle pressing force to a plate-like portion 52E on an inner peripheral side relative to the outer peripheral portion of the plate material 51E having a substantially disk shape. Accordingly, as shown in a state m21 in FIG. 31, an outer peripheral side part 53E is formed on an outer peripheral side of the plate-like portion 52E so as to hang downward via a curved corner part (extend in a substantially vertical direction (downward direction) with respect to the plate-like portion 52E).

[0171] Next, with respect to the plate material 51E in the state m21, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate-like portion 52E, while applying a wrinkle pressing force to an outer peripheral portion of the plate-like portion 52E, drawing processing is performed on an inner peripheral portion relative thereto. Accordingly, as shown in a state m22 in FIG. 31, an outer peripheral panel part (outer peripheral plate part) 521E is formed in the plate material 51E, and a center panel part (a center plate part, a specific plate part) 54E is formed via a side wall part 55E that rises upward on an inner peripheral side relative to the outer peripheral panel part 521E. Here, a center projecting part 56E is formed by the center panel part (center plate part) 54E and the side wall part 55E.

[0172] Next, as shown in a state m23 in FIG. 31, forming is performed by using a forming device including an upper tool U8 and a lower tool L8, for example. The upper tool U8 includes an annular upper outer tool U81, an upper center tool U82, and an annular guide tool U83 positioned therebetween. The guide tool U83 illustrated in examples of FIG. 31 to FIG. 33 is provided integrally with the upper center tool U82 on an outer peripheral side of the upper center tool U82. However, the guide tool U83 is not limited to such a configuration, and may be provided separately from the upper center tool U82 on an outer peripheral side of the upper center tool U82. The lower tool L8 includes an annular lower outer tool L81, a lower center tool L82, and an annular support tool (support member) L83 positioned therebetween. As shown in the state m23, the plate material 51E in which the center panel part 54E and the side wall part 55E (that is, the center projecting part 56E) are formed is placed between the upper tool U8 and the lower tool L8.

[0173] The outer peripheral panel part 521E of the plate material 51E is then sandwiched and fixed between the upper outer tool U81 and the lower outer tool L81 (a state m24 in FIG. 31). This fixing is continued until a state m26. In this manner, in a state where the outer peripheral panel part 521E is fixed, the upper center tool U82 pushes down the lower center tool L82 while the center panel part 54E is sandwiched between an abutting surface U82a of the upper center tool U82 and an abutting surface L82a of the lower center tool L82 (the state m24, a state m25). Additionally, the side wall part 55E is positioned between the guide tool U83 and the lower center tool L82.

[0174] The upper center tool U82 pushes down the lower center tool L82 such that a height position of the abutting surface U82a of the upper center tool U82 approaches a height position of an abutting surface (support surface) L83a of the support tool (support member) L83. That is, the support tool L83 is relatively movable in the second direction (upward direction) opposite to the first direction (downward direction) in which an annular projecting part 62Ea to be formed later (a state m26 in FIG. 31) projects. The support tool L83 applies a supporting force toward the second direction (upward direction) to the plate material 51E on the abutting surface (support surface) L83a thereof. Accordingly, by pushing down the lower outer tool L82 by the upper center tool U82, an annular curved part 57E having a curved shape along a shape of the abutting surface L83a of the support tool L83 is formed on an outer peripheral side of the side wall part 55E by being supported by the support tool L83 that applies the supporting force (the state m25 in FIG. 31).

[0175] Thereafter, furthermore, while supporting the annular curved part 57E by the abutting surface (support surface) L83a of the support tool (support member) L83 (with a supporting force toward the second direction (upward direction)), a pressing force is applied to the center panel part (specific plate part) 54E in the first direction (downward direction) opposite to the second direction.

[0176] At this time, the upper center tool (upper tool for the specific plate part) U82 continuously applies a pressing force in the first direction (downward direction) so that the abutting surface U82a thereof pushes down the lower center tool L82. That is, the upper center tool U82 continuously applies a pressing force to the center panel part (the center plate part, the specific plate part) 54E sandwiched between the abutting surface U82a and the abutting surface L82a of the lower center tool L82, and pushes the center panel part 54E in the first direction (downward direction). At the same time, the guide tool U83 prevents the side wall part 55E from buckling due to compressive stress applied to the side wall part 55E by positioning the side wall part 55E between the guide tool U83 and the lower center tool L82. Accordingly, the supporting force of the support tool (support member) L83 can apply a pressing force larger than that of the upper center tool U82 to the annular curved part 57E via the side wall part 55E.

[0177] By such pushing by the upper center tool U82, while deforming the annular curved part 57E and generating compressive stress in the second direction (upward direction) in the side wall part 55E, at least a portion of the plate material constituting the side wall part 55E is moved toward an outer side of the center panel part (specific plate part) 54E on the abutting surface L83a of the support tool L83.

[0178] As a result, an intermediate formed body 60E of the can lid including an annular projecting part 62Ea in which a plate thickness is selectively increased based on the moved portion is formed (state m26). In the intermediate formed body 60E, the annular projecting part 62Ea is connected, on an outer peripheral side thereof, to the outer peripheral panel part (outer peripheral plate part) 521E via a side wall part 61E. The annular projecting part 62Ea has an increased plate thickness over a wide range including a required range for improving pressure resistance strength in the chuck wall radius part (curved convex part).

[0179] Thereafter, as shown in a state m27, the intermediate formed body 60E of the can lid is removed from the upper tool U8 and the lower tool L8. In this manner, the intermediate formed body 60E (a state m28) on which the plate-thickness increasing forming at the first stage has been performed is obtained.(Forming step of increasing plate thickness at second stage)

[0180] In the plate-thickness increasing forming at the second stage performed in the processing illustrated in FIG. 32, to the intermediate formed body 60E (a state m29 (that is, the state m28 in FIG. 31)) on which the plate-thickness increasing forming at the first stage has been performed, a pressing force in the first direction (downward direction) is applied by the upper outer tool (upper tool for the specific plate part) U81, in the same manner as in the third embodiment described above. That is, the intermediate formed body 60E is placed between the upper tool U8 and the lower tool L8 (a state m30), and thereafter the center panel part 54E is sandwiched and fixed by the upper center tool U82 and the lower center tool L82 (a state m31).

[0181] In this state, a pressing force is applied to the outer peripheral panel part (specific plate part) 521E sandwiched between the upper outer tool U81 and the lower outer tool L81, and the outer peripheral panel part 521E is pushed in the first direction (downward direction). Accordingly, while deforming the annular projecting part 62Ea and generating compressive stress in the second direction (upward direction) in the side wall part 61E, at least a portion of the plate material constituting the side wall part 61E is moved toward an inner side of the outer peripheral panel part 521E on the abutting surface L83a of the support tool L83. In this manner, an intermediate formed body 70E (of the can lid) having an annular curved part 62Eb is formed on an inner peripheral side relative to the outer peripheral panel part 521E, the annular curved part 62Eb having a plate thickness that is further selectively increased based on the movement (a state m32). The intermediate formed body 70E has a side wall part 63E that rises upward on an inner peripheral side relative to the annular curved part 62Eb, and a center projecting part 64E is formed by the side wall part 63E and the center panel part (center plate part) 54E.

[0182] Thereafter, as shown in a state m33, the intermediate formed body 70E is removed from the upper tool U8 and the lower tool L8. In this manner, the intermediate formed body 70E (a state m34) on which the plate-thickness increasing forming at the second stage has been performed is obtained.(Forming step of increasing plate thickness at third stage)

[0183] In the plate-thickness increasing forming at the third stage performed in the processing illustrated in FIG. 33, to the intermediate formed body 70E (a state m35 (that is, the state m34 in FIG. 32)) on which the plate-thickness increasing forming at the second stage has been performed, processing similar to that of the plate-thickness increasing forming at the first stage described above is performed. That is, the intermediate formed body 70E shown in the state m35 in FIG. 33 is placed between the upper tool U8 and the lower tool L8 as shown in a state m36, and the outer peripheral panel part 521E is sandwiched and fixed by the upper outer tool U81 and the lower outer tool L81 as shown in a state m37.

[0184] In this state, while sandwiching the center panel part 54E between the upper center tool U82 and the lower center tool L82, the upper center tool (upper tool for the specific plate part) U82 continuously applies a pressing force in the first direction (downward direction) so as to push down the lower center tool L82 (the state m37, a state m38).

[0185] Specifically, while supporting the annular curved part 62Eb of the intermediate formed body 70E by the abutting surface L83a of the support tool L83 (with a supporting force toward the second direction (upward direction)), a pressing force is continuously applied to the center panel part (specific plate part) 54E in the first direction (downward direction) opposite to the second direction (upward direction). At this time, the supporting force of the support tool (support member) L83 can apply a pressing force larger than that of the upper center tool U82 to the annular curved part 62Eb via the side wall part 63E.

[0186] By such pushing by the upper center tool U82, while deforming the annular curved part 62Eb and generating compressive stress in the second direction (upward direction) in the side wall part 63E, at least a portion of the plate material constituting the side wall part 63E is moved toward an outer side of the center panel part 54E on the abutting surface L83a of the support tool L83.

[0187] As a result, an intermediate formed body 80E of the can lid including an annular projecting part 82Ea in which a plate thickness is further selectively increased based on the moved portion is formed (the state m38). In the intermediate formed body 80E, the annular projecting part 82Ea is connected, on an outer peripheral side thereof, to the outer peripheral panel part 521E via a side wall part 81E.

[0188] Thereafter, as shown in a state m39, the intermediate formed body 80E of the can lid is removed from the upper tool U8 and the lower tool L8. In this manner, the intermediate formed body 80E of the can lid (a state m40) on which the plate-thickness increasing forming at the third stage has been performed is obtained. In the intermediate formed body 80E in the state m40, a plate thickness is further increased over a wide range including a required range for improving pressure resistance strength in the chuck wall radius part (curved convex part) 822Ea of the annular projecting part 82Ea.

[0189] In this manner, with the method for forming the plate material according to the fourth embodiment, by performing forming steps of increasing a plate thickness in a plurality of stages including the first to the third stages illustrated in FIG. 31 to FIG. 33 on the plate material, the plate thickness can be further increased over a wide range including a required range in the annular projecting part 82Ea. Accordingly, a can lid having further improved pressure resistance strength can be formed from the intermediate formed body 80E formed by the method for forming the plate material according to the fourth embodiment.

[0190] In the forming steps of increasing a plate thickness at the first to the third stages illustrated in FIG. 31 to FIG. 33 described above, the same forming device including the upper tool U8 and the lower tool L8 was consistently used. However, the embodiment is not limited to such examples. A configuration of the forming device including the upper tool U8 and the lower tool L8 may be different between the forming device used in the forming steps of increasing a plate thickness at the first and the third stages and the forming device used in the plate-thickness increasing forming at the second stage (particularly in cushion pins (not illustrated), an air cylinder (not illustrated), and the like).[Fifth embodiment]

[0191] A method for forming a plate material in the fifth embodiment is a method for forming a can bottom 10E exemplified in a state m48 in FIG. 35 as a formed material. The method for forming the can bottom 10E includes, as a part of the entire process, the method for forming the plate material 11E according to the above-described second schematic embodiment.

[0192] The method for forming the can bottom 10E includes steps similar to those in FIG. 22 described above, that is, the blank punching step S41, the outer peripheral drawing step S42, the center-outer peripheral plate part forming step S43, the annular curved part forming step S44, an annular projecting part forming (plate-thickness increasing forming) step S45, and the shape forming step S46 (for the can bottom), which are illustrated in FIG. 22. In the forming process (S41 to S46), after changing a shape of a plate material 91E as shown in a state m41 to a state m47 in FIGS. 34 and 35, shape forming (reforming) of the can bottom is performed to form the can bottom 10E in the state m48.

[0193] In the blank punching step S41 in the forming process of the can bottom 10E, for example, the plate material 91E is formed into a substantially disk shape by using upper and lower punching tools (not illustrated) for punching the plate material 91E to be processed to have a substantially disk shape (the state m41 in FIG. 34).

[0194] In the outer peripheral drawing step S42 in the forming process of the can bottom 10E, for example, by using upper and lower tools for outer peripheral drawing (not illustrated) for performing drawing processing on an outer peripheral portion of the plate material 91E having a substantially disk shape, drawing processing is performed on the outer peripheral portion while applying a wrinkle pressing force to a plate-like portion on an inner side relative to the outer peripheral portion of the plate material 91E having a substantially disk shape shown in the state m41 in FIG. 34. Accordingly, as shown in the state m42 in FIG. 34, an outer peripheral side part 93E is formed so as to rise upward on an outer peripheral side relative to a plate-like portion 92E of the plate material 91E via a curved corner part (extend in a substantially vertical direction (upward direction) with respect to the plate-like portion 92E). Note that known ironing forming may be additionally applied to the outer peripheral side part 93E as needed.

[0195] In the center-outer peripheral plate part forming step S43 in the forming process of the can bottom 10E, for example, with respect to the plate material 91E in the state m42 in FIG. 34, by using upper and lower tools for center drawing (not illustrated) for performing drawing processing on a substantially central portion of the plate-like portion 92E, while applying a wrinkle pressing force to an outer panel part (outer plate part) 921E of the plate-like portion 92E, drawing processing is performed on an inner peripheral side thereof in this state. Accordingly, as shown in the state m43 in FIG. 34, a center panel part (center plate part) 94Ea having a substantially flat surface is formed. At the same time, an outer peripheral panel part (outer peripheral plate part) 922E corresponding to the "specific plate part" described in the above main embodiment is formed via a side wall part 95E that rises upward on an outer peripheral side relative to the center panel part 94Ea. The center panel part 94Ea is to be formed into a dome panel part 94E later.

[0196] In the annular curved part forming step S44 and an annular projecting part forming (plate-thickness increasing forming) step S45 in the forming process of the can bottom 10E, for example, forming is performed on the plate material 91E (the state m43 in FIG. 34), in which the center panel part 94Ea and the outer peripheral panel part 922E have been formed, by using a forming device including an upper tool U9 and a lower tool L9. As shown in, for example, the state m44 in FIG. 34, the upper tool U9 includes an annular upper outer tool (upper tool for the specific plate part) U91, an upper center tool U92, and an annular guide tool U93 positioned therebetween. The lower tool L9 includes an annular lower outer tool L91, a lower center tool L92, and an annular support tool (support member) L93 positioned therebetween. As shown in the state m44 in FIG. 34, the plate material 91E in which the center panel part 94Ea and the outer peripheral panel part 922E have been formed is placed between the upper tool U9 and the lower tool L9.

[0197] Thereafter, the center panel part 94Ea is sandwiched and fixed between an abutting surface U92a of the upper center tool U92 and an abutting surface L92a of the lower center tool L92. By being sandwiched and fixed in this manner, the center panel part 94Ea is formed into the dome panel part 94E having a dome shape that gently projects in the second direction (upward direction) opposite to the first direction (downward direction) in which an annular projecting part 102Ea to be formed later (the state m47 in FIG. 35) projects (the state m45 in FIG. 35). Such fixing of the dome panel part 94E by the upper center tool U92 and the lower center tool L92 is continued thereafter until an annular projecting part forming (plate-thickness increasing forming) step S45 is ended.

[0198] n that state, in the annular curved part forming step S44 in the forming process of the can bottom 10E, as shown in the state m45 and the state m46 in FIG. 35, a pressing force is applied in the first direction (downward direction) by the upper outer tool U91. At this time, while sandwiching the outer peripheral panel part (outer peripheral plate part) 922E between an abutting surface U91a of the upper outer tool U91 and an abutting surface L91a of the lower outer tool L91, the upper outer tool U91 pushes down the lower outer tool L91.

[0199] The guide tool U93 may be either one that is lowered as shown in the state m45 to the state m47 in FIG. 35, or one that is not lowered. In either case, the guide tool U93 and the lower outer tool L91 are positioned around the side wall part 95E. Accordingly, when compressive stress is applied to the side wall part 95E in the subsequent annular projecting part forming (plate-thickness increasing forming) step S45, it is possible to prevent buckling of the side wall part 95E due to the compressive stress.

[0200] In the annular curved part forming step S44 in the forming process of the can bottom 10E, the upper outer tool U91 pushes down the lower outer tool L91 such that a height position of the abutting surface U91a of the upper outer tool U91 approaches a height position of an abutting 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 direction). The support tool L93 applies a supporting force toward the second direction (upward direction) to the plate material 91E on the abutting surface (support surface) L93a thereof.

[0201] Accordingly, by pushing down the lower outer tool L91 by the upper outer tool U91, an annular curved part 96E having a curved shape along a shape of the abutting surface L93a of the support tool L93 is formed on an inner peripheral side of the side wall part 95E by being supported by the support tool L93 that applies the supporting force. The plate material 91E in which the annular curved part 96E as described above has been formed is referred to as a preform 91Ea (state m46 in FIG. 35).

[0202] In an annular projecting part forming (plate-thickness increasing forming) step S45 in the forming process of the can bottom 10E, for example, as shown in the state m46 and the state m47 in FIG. 35, while supporting the annular curved part 96E of the formed preform 91Ea by the abutting surface L93a of the support too L93 (with a supporting force toward the second direction (upward direction)), a pressing force is applied in the first direction (downward direction) to the outer peripheral panel part 922E.

[0203] At this time, the upper outer tool U91 continuously applies a pressing force in the first direction (downward direction) so that the abutting surface U91a thereof pushes down the lower outer tool L91. That is, the upper outer tool U91 continuously applies a pressing force to the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 922E sandwiched between the abutting surface U91a and the abutting surface L91a of the lower outer tool L91, and pushes the outer peripheral panel part 922E in the first direction (downward direction). At the same time, the guide tool U93 prevents the side wall part 95E from buckling due to compressive stress applied to the side wall part 95E by positioning the side wall part 95E between the outer guide surface U93a of the guide tool U93 and the abutting surface L91b of the lower outer tool L91. Accordingly, the supporting force of the support tool (support member) L93 can apply a pressing force larger than that of the upper outer tool U91 to the annular curved part 96E via the side wall part 95E.

[0204] In this manner, pushing is performed by the upper outer tool U91 while applying, by the support tool L93, a supporting force in the second direction (upward direction). Accordingly, while deforming the annular curved part 96E and generating compressive stress in the second direction (upward direction) in the side wall part 95E, at least a portion of the plate material constituting the side wall part 95E is moved toward an inner side of the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 922E on the abutting surface L93a of the support tool L93.

[0205] By an annular projecting part forming (plate-thickness increasing forming) step S45 as described above in the forming process of the can bottom 10E, an intermediate formed body 100E of the can bottom (before shape forming (reforming)) (the state m47 in FIG. 35), which has the annular projecting part 102Ea formed by selectively increasing a plate thickness based on the moved portion, is formed. In the intermediate formed body 100E, the annular projecting part 102Ea has an increased plate thickness over a wide range including a required range for improving pressure resistance strength in a bottom radius part (curved convex part) 112Ea. In this manner, after forming the intermediate formed body 100E of the can bottom (before shape forming) having the annular projecting part 102Ea, the intermediate formed body 100E of the can bottom is removed from the upper tool U9 and the lower tool L9.

[0206] As described above, also in the method for forming the plate material 91E according to the fifth embodiment, relative pushing (pressing) with respect to the outer peripheral panel part (the outer peripheral plate part, the specific plate part) 922E is continuously performed (in one stroke) by using the same device (upper and lower dies) including the upper tool U9 and the lower tool L9. That is, also in the forming method of the fifth embodiment, this pushing is not performed in a plurality of stages using dies having different shapes each time; instead, it is possible to form the annular projecting part 102Ea having an increased plate thickness over a required range with such a simple manufacturing process.

[0207] The shape forming step S46 for the can bottom is a step of reforming a shape of the intermediate formed body 100E of the can bottom as needed (bottom reforming) to form a shape of the can bottom, and includes, as this step, a step of forming a shape of a can bottom annular projecting part 102E. After reforming in the shape forming step S46 for the can bottom, the can bottom 10E removed from a reforming device (not illustrated) is obtained (the state m48 in FIG. 35).

[0208] The shape forming step S46 for the can bottom can be performed by a conventionally known method, and may be performed by a method using a rotating roll or a method using press forming, for example.

[0209] Furthermore, in the fifth embodiment, particularly in a case where an inner surface coating step is required, it is desirably performed at a stage prior to the shape forming step S46 for the can bottom.

[0210] The can bottom 10E in the state m48 in FIG. 35 includes a dome panel part (center plate part) 101E, a dome panel wall part (inner peripheral wall part) 151E, a bottom radius part (curved convex part) 152E, a chime lower part (first outer peripheral wall part) 153E, and a chime part (second outer peripheral wall part) 103E. Here, the can bottom annular projecting part 102E is constituted of the dome panel wall part 151E, the bottom radius part 152E, and the chime lower part 153E. The can bottom annular projecting part 102E has a shape slightly inclined inward by reforming, and has an increased plate thickness over a wide range including a required range in the bottom radius part 152E.

[0211] The shape forming step S46 for the can bottom may further include, as needed, a step of forming the dome panel part (center plate part) 94E into a desired shape, for example, a shape other than a spherical surface such as a substantially spheroidal surface, a substantially conical surface, or a substantially flat surface. In this case, the shape forming step S46 for the can bottom may include, as a step of reforming the shape of the intermediate formed body 100E of the can bottom in the state m47 in FIG. 35, a step of forming a shape of the can bottom annular projecting part 102E and a step of forming the dome panel part (center plate part) 94E into, for example, a substantially flat surface, simultaneously or in any order.[Example of fifth embodiment (Example 9)]

[0212] Next, the following describes an example of the fifth embodiment (Example 9). In Example 9, a drawn and ironed can (DI can) having an internal volume of 350 mL (after shape forming (reforming) of the can bottom) was manufactured by a method described below. First, as a plate material (blank) to be processed, an aluminum alloy plate (JIS H 4000 A3104-H19 material, 0.220 mm (original plate thickness)) was prepared. Next, a predetermined amount of known cupping oil was applied to both surfaces of the aluminum alloy plate (plate material) as a lubricant during drawing processing.

[0213] Next, the aluminum alloy plate to which the lubricant had been applied was punched into a disk shape (not illustrated) having a diameter of 160 mm by using a drawing forming machine (upper and lower punching tools) (not illustrated) (a processing step corresponding to the blank punching step S41 in the forming process of the can bottom 10E described above). Thereafter, draw forming was performed on an outer peripheral portion of the disk-shaped plate material by using upper and lower tools for outer peripheral drawing (not illustrated), while applying a wrinkle pressing force to a plate-like portion located on an inner side relative to the outer peripheral portion. Accordingly, a drawn cup (not illustrated) having a diameter of 90 mm was formed.

[0214] The drawn cup (not illustrated) was conveyed to a body maker (can body manufacturing machine), and after redraw forming was performed so as to obtain a shape having a diameter of 66 mm, a processing step corresponding to the outer peripheral drawing step S42 in the forming process of the can bottom 10E described above was performed by using a coolant. Accordingly, a cup body having a bottom part with a shape as shown in the state m42 in FIG. 34, and having a diameter of 66 mm, a height of 130 mm, and a minimum thickness of a body part of 0.105 mm was formed.

[0215] Next, a processing step corresponding to the center-outer peripheral plate part forming step S43 in the forming process of the can bottom 10E described above was performed on the formed cup body by using upper and lower tools for center drawing (not illustrated). Accordingly, a first precursor (not illustrated) of the DI can was formed, the first precursor including a can bottom (corresponding to the state m43 in FIG. 34) formed by forming a center panel part (center plate part) having a flat surface and forming an outer peripheral panel part (an outer peripheral plate part, a specific plate part) via a side wall part that rises upward on an outer peripheral side relative to the center panel part.

[0216] Next, the first precursor was placed between the upper tool U9 and the lower tool L9 described above as shown in the state m44 in FIG. 34. Then, the center panel part was sandwiched and fixed between the upper center tool U92 and the lower center tool L92, and the center panel part was deformed into a shape of a dome panel part as shown in the state m45 in FIG. 35. In this state, as a pressing process in which a pressing force is applied in the above-described first direction (downward direction) by the upper outer tool U91, a processing step corresponding to the annular curved part forming step S44 and a subsequent processing step corresponding to an annular projecting part forming (plate-thickness increasing forming) step S45 in the forming process of the can bottom 10E described above were performed.

[0217] First, in the processing step corresponding to the annular curved part forming step S44 in the forming process of the can bottom 10E described above, the upper outer tool U91 pushed down the lower outer tool L91 while sandwiching an outer peripheral panel part (outer peripheral plate part) between the upper outer tool U91 and the lower outer tool L91. Accordingly, a second precursor of the DI can including a preform of a can bottom having an annular curved part as shown in the state m46 in FIG. 35 was formed.

[0218] Subsequently, in the processing step corresponding to an annular projecting part forming (plate-thickness increasing forming) step S45 in the forming process of the can bottom 10E described above, while supporting the annular curved part of the formed preform by the support tool L93 (with a supporting force toward the second direction (upward direction) described above), a pressing force was applied in the first direction (downward direction) to the outer peripheral panel part (specific plate part). Accordingly, a drawn and ironed can (DI can) (before shape forming (reforming) of the can bottom) having a shape corresponding to the state m47 in FIG. 35, that is, including an intermediate formed body 510E of the can bottom having an annular projecting part 512E illustrated in FIG. 36, was formed. The annular projecting part 512E includes a dome panel wall part 513E, a bottom radius part 514E (before reforming), and a chime lower part 515E (before reforming). Additionally, a chime part 516E (before reforming) was formed on an outer side of the chime lower part 515E.

[0219] By subjecting the intermediate formed body 510E of the can bottom illustrated in FIG. 36 to a trimming process for cutting an open end part to a required can height by a conventional method, and to a bottom reforming process (a processing step corresponding to the shape forming step S46 for the can bottom in the forming process of the can bottom 10E described above), a final formed body 520E (after reforming) of the can bottom illustrated in FIG. 37 was obtained.

[0220] A plate thickness [mm] of a metal portion at each point in the final formed body 520E (after reforming) illustrated in FIG. 37 was measured. FIG. 37 illustrates measurement points w1 to w7 at which measurement was performed. The plate thickness [mm] was measured as follows. After the formed drawn and ironed can (DI can) (as a final formed body) was embedded in an epoxy resin, the DI can including the epoxy resin was cut along a vertical axis (Z-axis) of the DI can. After exposing a center cross section by cutting and careful polishing, a plate thickness [mm] of the metal portion at each of the measurement points w1 to w7 was measured using a measuring microscope.

[0221] As indicated by the table in FIG. 38, in Example 9, a height Hp of a dome panel part 522E (FIG. 37) in the drawn and ironed can (DI can) (as a final formed body) was 12.3 mm. In the final formed body 520E, a diameter (d1) (FIG. 37) between boundary portion of the dome panel part 522E and a can bottom annular projecting part 523E (after reforming) was 47.0 mm, and a diameter (d2) (FIG. 37) of a grounding part of the can bottom annular projecting part 523E was 48.0 mm. The plate thickness [mm] of the metal portion at the measurement points w1 to w7 (FIG. 37) was as indicated in the table in FIG. 38.[Pressure resistance test evaluation]

[0222] For the obtained drawn and ironed can (DI can) (as a final formed body), a pressure resistance test evaluation was performed by the following pressure resistance test method. Evaluation results thereof are indicated in the table in FIG. 38.[Pressure resistance test method]

[0223] In a state in which a cup-like container is filled with water, an opening end is sealed with a plug provided with a water supply pipe. Next, pressurized water is fed into the cup-like container from a water supply pump through the water supply pipe. An internal pressure of the cup-like container increases, and at a certain point in time, the dome panel part is instantaneously deformed to be inverted outward (buckling). Normally, simultaneously with this deformation, the internal pressure of the can (DI can) (can internal pressure) abruptly decreases. The highest value of the can internal pressure during this period is defined as the pressure resistance value (pressure resistance force) [MPa].

[0224] As indicated by the evaluation results in the table in FIG. 38, the drawn and ironed can (DI can) (as a final formed body) formed in Example 9 corresponds to a 350 mL can, and a can weight [g] thereof was 9.9 g (as a weight of the metal portion after the rimming process). As is clear from the evaluation results in FIG. 38, the plate thickness [mm] of the metal portion was increased over a wide range including a required range for improving pressure resistance strength in the annular projecting part (after reforming) of the can bottom. Accordingly, with this DI can, preferred pressure resistance force (pressure resistance value [MPa]) was obtained. In addition, by adopting the method shown in Example 9, which yielded such results, as a part of a series of can manufacturing processes, it is possible to manufacture a can body that maintains pressure resistance strength while reducing an original plate thickness for saving material resources and for achieving weight reduction.

[0225] The embodiments of the present invention have been described in detail with reference to the drawings; however, specific configurations are not limited to these embodiments, and design changes and the like within a scope not departing from the gist of the present invention are also encompassed by the present invention. In addition, the above-described examples can be combined by utilizing each other's technologies, as long as there is no particular inconsistency or problem in their purposes and configurations.Reference Signs List

[0226] 1: formed material; 3: can lid; 6: can bottom; 11, 41, 51: plate material; 11a, 41a, 51a: preform; 12, 23, 31, 45, 45A: center panel part (center plate part); 13, 32, 32a, 32A, 62a: annular projecting part; 14, 25, 421, 421A: outer peripheral panel part (outer peripheral plate part); 420, 521: outer panel part (outer plate part); 22, 44, 54: center projecting part; 24, 46, 56: side wall part; 26, 47, 57: outer peripheral curved part (annular curved part); 30, 30A: intermediate formed body of can lid (before shape forming of can lid); 30a-1: formed body; 33: second chuck wall part (second outer peripheral wall part); 34: curl part; 42, 52: plate-like portion; 43, 53: outer peripheral part (side surface); 60: intermediate formed body of can bottom (before shape forming of can bottom); 121, 141, 311: curved part; 131: inner peripheral wall part; 132: curved convex part; 133: outer peripheral wall part; 321, 321a, 321A: panel wall part (inner peripheral wall part); 322, 322a, 322A: chuck wall radius part (curved convex part); 323, 323a, 323A: first chuck wall part (first outer peripheral wall part); 522: annular curved bottom part; 55, 61: dome panel part (center plate part); 62: can bottom annular projecting part; 63: chime part (second outer peripheral wall part; 621: dome panel wall part (inner peripheral wall part); 622, 622a: bottom radius part (curved convex part); 623: chime lower part (first outer peripheral wall part) 1E: formed material; 11E, 41E, 51E: plate material; 11Ea, 41Ea: preform; 12E, 22E, 31E, 31Ec, 45E, 45Eb, 54E: center panel part (center plate part); 121E, 141E, 311E: curved end part; 13E, 32E, 32Ea, 32Eb, 32Ec, 62Ea, 82Ea: annular projecting part; 131E: inner peripheral wall part; 132E: curved convex part; 133E: outer peripheral wall part; 14E, 21E, 421E, 421Eb, 521E: outer peripheral panel part (outer peripheral plate part); 23E, 46E, 55E, 61E, 63E, 81E: side wall part; 24E, 47E, 57E, 62Eb: annular curved part; 3E, 3Ec: can lid; 30E, 40Eb: intermediate formed body of can lid; 321E: panel wall part (inner peripheral wall part); 322E, 322Ea, 322Eb, 322Ec, 822Ea: chuck wall radius part (curved convex part); 323E: first chuck wall part (first outer peripheral wall part); 33E: second chuck wall part (second outer peripheral wall part); 34E: curl part; 42E: plate-like portion; 420E: outer panel part (outer plate part); 43E: outer peripheral side part; 52E: plate-like portion; 53E: outer peripheral side part; 56E, 64E: center projecting part; 10E: can bottom; 91E: plate material; 91Ea: preform; 92E: plate-like portion; 921E: outer panel part (outer plate part); 922E: outer peripheral panel part (outer peripheral plate part); 93E: outer peripheral side part; 94E: dome panel part (center plate part); 94Ea: center panel part (center plate part); 95E: side wall part; 96E: annular curved part; 100E: intermediate formed body of can bottom; 101E: dome panel part (center plate part); 102E: can bottom annular projecting part; 102Ea: annular projecting part; 112Ea: bottom radius part (curved convex part); 103E: chime part (second outer peripheral wall part); 151E: dome panel wall part (inner peripheral wall part); 152E: bottom radius part (curved convex part); 153E: chime lower part (first outer peripheral wall part); 921E: outer panel part (outer plate part); 922E: outer peripheral panel part (outer peripheral plate part); 510E: intermediate formed body of can bottom (before reforming); 511E: dome panel part (of intermediate formed body); 512E: annular projecting part (of intermediate formed body); 513E: dome panel wall part (of intermediate formed body); 514E: bottom radius part (of intermediate formed body); 515E: chime lower part (of intermediate formed body); 516E: chime part (of intermediate formed body); 520E: final formed body of can bottom (after reforming); 522E: dome panel part (of final formed body); 523E: can bottom annular projecting part (of final formed body)

Claims

1. A method for forming a plate material, comprising: a step of forming a specific plate part and a side wall part; a step of forming an annular curved part connected to the side wall part; and a step of deforming at least the annular curved part to form an annular projecting part in which a plate thickness is selectively increased, wherein, in the step of forming the annular projecting part, a pressing force in a first direction is applied to the specific plate part while supporting the annular curved part by a support member that is relatively movable in a second direction opposite to the first direction in which the annular projecting part to be formed projects, thereby generating compressive stress in the second direction in the side wall part while moving at least a portion of a plate material constituting the side wall part on a support surface of the support member, whereby the annular projecting part is formed such that a plate thickness is selectively increased.

2. A method for forming a plate material, comprising: a step of forming a center projecting part constituted of a center plate part and a side wall part on an outer peripheral side of the center plate part in a plate-like portion of the plate material; a step of forming an outer peripheral curved part on an outer periphery of the side wall part; and a step of deforming at least the outer peripheral curved part to form an annular projecting part in which a plate thickness is selectively increased, wherein, in the step of forming the annular projecting part, a pressing force in a direction opposite to the projecting direction is applied to the center projecting part while supporting the outer peripheral curved part by a support member that is relatively movable in a projecting direction of the center projecting part, thereby generating compressive stress in the projecting direction in the side wall part while moving at least a portion constituting the side wall part on a support surface of the support member, whereby the annular projecting part is formed such that a plate thickness is selectively increased.

3. The forming method according to claim 2, wherein in the step of forming the annular projecting part, at least a portion constituting the side wall part is moved toward an outer side of the center projecting part on the support surface of the support member.

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

5. A method for forming a can lid, comprising the forming method according to claim 2 as a part of an entire process.

6. The method for forming the can lid according to claim 5, comprising a step of forming a chuck wall part as a step of forming a shape of the can lid, after the step of forming the annular projecting part.

7. A method for forming a can bottom, comprising the forming method according to claim 2 as a part of an entire process.

8. The method for forming the can bottom according to claim 7, at least comprising a step of forming a shape of a can bottom annular projecting part as a step of forming a shape of the can bottom, after the step of forming the annular projecting part.

9. A method for forming a plate material, comprising: a step of forming a center plate part and forming an outer peripheral plate part via a side wall part that rises upward on an outer peripheral side relative to the center plate part; a step of forming an annular curved part on an inner peripheral side of the side wall part; and a step of deforming at least the annular curved part to form an annular projecting part in which a plate thickness is selectively increased, wherein, in the step of forming the annular projecting part, a pressing force in a first direction is applied to the outer peripheral plate part while supporting the annular curved part by a support member that is relatively movable in a second direction opposite to the first direction in which the annular projecting part to be formed projects, thereby generating compressive stress in the second direction in the side wall part while moving at least a portion of a plate material constituting the side wall part on a support surface of the support member, whereby the annular projecting part is formed such that a plate thickness is selectively increased.

10. The forming method according to claim 9, wherein in the step of forming the annular projecting part, at least a portion of the plate material constituting the side wall part is moved toward an inner side of the outer peripheral plate part on the support surface of the support member.

11. The forming method according to claim 9, wherein the plate material is made of a material mainly containing metal.

12. A method for forming a can lid, comprising the forming method according to claim 9 as a part of an entire process.

13. The method for forming a can lid according to claim 12, comprising a step of forming a chuck wall part as a step of forming a shape of the can lid, after the step of forming the annular projecting part.

14. A method for forming a can bottom, comprising the forming method according to claim 9 as a part of an entire process.

15. The method for forming the can bottom according to claim 14, at least comprising a step of forming a shape of a can bottom annular projecting part as a step of forming a shape of the can bottom, after the step of forming the annular projecting part.

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