Molding manufacturing device, molding device, and press line

Abstract

To provide a molding manufacturing device, a molding device, and a press line capable of suppressing generation of wrinkles at the base of a burring part.SOLUTION: For manufacturing a molding 100a having a burring part 106 from a metal material 100, a preliminary molding part 104 is formed in a plate-like part 102 of the metal material 100 prior to formation of the burring part 106. In a state where the plate-like part 102 is supported by a R surface 42b of a die 14, a part of the first support surface 20 of a punch 12 outside the R surface 42b in the radial direction Y of an inner peripheral edge 20a and a part of the second support surface 22 of the punch 12 inside the R surface 42b in the radial direction Y, the punch 12 and the die 14 are brought close to each other to form the preliminary molding part 104.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a molded product, a molding device, and a press line. [Background technology]

[0002] Burring is often performed on various press-formed parts, such as automobile parts. Burring is generally performed by drilling a pilot hole in a material and then extruding the peripheral edge of the pilot hole into a cylindrical shape.

[0003] The burred portion is required to have fatigue strength. Therefore, as disclosed in Patent Document 1, for example, a technique is used in which compressive stress is applied to the end of the burred portion by coining, thereby alleviating the tensile residual stress at the end. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-051609 Summary of the Invention [Problem to be solved by the invention]

[0005] When burring is performed, a compressive force acts on the inside of the curved portion (root portion) of the burred part. This compressive force tends to cause uneven compressive deformation on the inside of the bent portion. As a result, minute wrinkles may occur.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a molded product, a molding device, and a press line that can prevent wrinkles from occurring at the base of a burred portion. [Means for solving the problem]

[0007] (1) A method for manufacturing a molded product according to an embodiment of the present invention includes: A method for manufacturing a molded product by performing burring on a plate-shaped portion of a metal material, comprising: The thickness direction of the plate-shaped portion is the pressing direction, a first die disposed on one side of the plate-like portion in the press direction and a first punch disposed on the other side of the plate-like portion in the press direction to form a cylindrical preformed portion that protrudes from the plate-like portion to the one side in the press direction and has a smaller diameter toward the one side in the press direction, and then the burring process is performed on the preformed portion; the first punch includes a first support surface facing the one side in the pressing direction and having an annular first inner circumferential edge, and a second support surface provided inside the first inner circumferential edge and protruding from the first support surface toward the one side in the pressing direction, the first die includes: a third support surface facing the first support surface in the pressing direction and having an annular second inner circumferential edge; and a fourth support surface provided inside the second inner circumferential edge and recessed from the third support surface to the one side in the pressing direction, the second support surface includes a first tapered surface that faces radially outward from the first inner circumferential edge and has a diameter that decreases toward the one side in the pressing direction, an end portion of the fourth support surface on the second inner peripheral edge side is an R surface, When forming the preformed portion, The method is characterized in that, while the plate-shaped portion is supported by the R surface, a portion of the first support surface that is radially outer than the R surface, and a portion of the second support surface that is radially inner than the R surface, the first punch and the first die are brought closer in the pressing direction to sandwich the plate-shaped portion between the first support surface and the third support surface, and a portion of the plate-shaped portion is pressed toward the fourth support surface by the first tapered surface, thereby forming the pre-formed portion.

[0008] (2) In the method for manufacturing the molded product, the fourth support surface includes a second tapered surface that faces inward in the radial direction and has a diameter that becomes smaller toward the one side in the pressing direction, The preformed portion may be formed by sandwiching a part of the plate-like portion between the first tapered surface and the second tapered surface.

[0009] (3) In the method for producing the molded product, The second support surface further includes a third tapered surface facing inward in the radial direction and having a diameter that decreases toward the other side in the pressing direction, The fourth support surface further includes a fourth tapered surface that faces outward in the radial direction and has a diameter that decreases toward the other side in the pressing direction, When forming the preformed portion, a part of the plate-like portion may be further sandwiched between the third tapered surface and the fourth tapered surface.

[0010] (4) In the method for producing the molded article, After a pilot hole is formed in the plate-like portion, the preformed portion may be formed by pressing a peripheral portion of the pilot hole in the plate-like portion toward the fourth support surface using the first tapered surface.

[0011] (5) In the method for producing the molded article, The burring process may be performed after a pilot hole is formed in the center of the preformed portion.

[0012] (6) A molding device according to an embodiment of the present invention is A forming apparatus for forming a preformed portion on a plate-shaped portion of a metal material before performing burring on the plate-shaped portion, a first die disposed on one side in the pressing direction and a first punch disposed on the other side in the pressing direction so as to face each other in the pressing direction; the first punch includes a first support surface facing the one side in the pressing direction and having an annular first inner circumferential edge, and a second support surface provided inside the first inner circumferential edge and protruding from the first support surface toward the one side in the pressing direction, the first die includes: a third support surface facing the first support surface in the pressing direction and having an annular second inner circumferential edge; and a fourth support surface provided inside the second inner circumferential edge and recessed from the third support surface to the one side in the pressing direction, the second support surface includes a first tapered surface that faces radially outward from the first inner circumferential edge and has a diameter that decreases toward the one side in the pressing direction, an end portion of the fourth support surface on the second inner peripheral edge side is an R surface, The plate-shaped portion is supported by the R-surface, a portion of the first support surface that is radially outer than the R-surface, and a portion of the second support surface that is radially inner than the R-surface, and the first punch and the first die are brought closer in the pressing direction to sandwich the plate-shaped portion between the first support surface and the third support surface, and a portion of the plate-shaped portion is pressed toward the fourth support surface by the first tapered surface, thereby forming the cylindrical pre-formed portion that protrudes from the plate-shaped portion to one side in the pressing direction and has a smaller diameter toward the one side in the pressing direction.

[0013] (7) The press line according to the embodiment of the present invention is The method comprises: a first die for forming a preformed portion on a plate-shaped portion of a metal material; and a second die for performing burring on the preformed portion; the first mold includes a first die arranged on one side in the press direction and a first punch arranged on the other side in the press direction so as to face each other in the press direction, the second mold includes a second die arranged on the one side in the press direction and a second punch arranged on the other side in the press direction so as to face each other in the press direction, the first punch includes a first support surface facing the one side in the pressing direction and having an annular first inner circumferential edge, and a second support surface provided inside the first inner circumferential edge and protruding from the first support surface toward the one side in the pressing direction, the first die includes: a third support surface facing the first support surface in the pressing direction and having an annular second inner circumferential edge; and a fourth support surface provided inside the second inner circumferential edge and recessed from the third support surface to the one side in the pressing direction, the second support surface includes a first tapered surface that faces radially outward from the first inner circumferential edge and has a diameter that decreases toward the one side in the pressing direction, an end portion of the fourth support surface on the second inner peripheral edge side is an R surface, the second die has a hole into which the second punch can be inserted and a fifth support surface provided around the hole; in the first die, in a state in which the plate-like portion is supported by the R-surface, a portion of the first support surface that is outer than the R-surface in the radial direction, and a portion of the second support surface that is inner than the R-surface in the radial direction, the first punch and the first die are brought closer in the pressing direction, and the plate-like portion is sandwiched between the first support surface and the third support surface, and a part of the plate-like portion is pressed toward the fourth support surface by the first tapered surface, thereby forming the cylindrical preformed portion that protrudes from the plate-like portion to the one side in the pressing direction and has a diameter that is smaller toward the one side in the pressing direction, In the second mold, the periphery of the preformed portion of the plate-shaped portion is supported by the fifth support surface of the second die so that the preformed portion is positioned within the hole portion, and the burring process is performed by pushing the preformed portion into the hole portion with the second punch. [Effects of the Invention]

[0014] According to the present invention, it is possible to prevent wrinkles from occurring at the base of the burred portion. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram for explaining an example of a conventional burring method. [Figure 2]FIG. 2 is a diagram for explaining an example of a conventional burring method. [Figure 3] FIG. 3 is a diagram showing steps of a method for producing a molded product according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a molding device used in the pre-molding step. [Figure 5] FIG. 5 is a diagram for explaining the preforming step. [Figure 6] FIG. 6 is a diagram for explaining the burring process. [Figure 7] FIG. 7 is a diagram showing a modified example of the molding device. [Figure 8] FIG. 8 is a diagram showing steps of a method for producing a molded product according to a second embodiment of the present invention. [Figure 9] FIG. 9 is a diagram for explaining the preforming step. [Figure 10] FIG. 10 is a diagram for explaining the burring process. [Figure 11] FIG. 11 is a diagram showing a modified example of the molding device. [Figure 12] FIG. 12 is a schematic view showing a molding apparatus used in a method for manufacturing a molded product according to a third embodiment of the present invention. [Figure 13] FIG. 13 is a diagram for explaining the preforming step. [Figure 14] FIG. 14 is a diagram for explaining the burring process. [Figure 15] FIG. 15 is a diagram for explaining a modified example of the preforming step. [Figure 16] FIG. 16 is a diagram for explaining a modified example of the molding device. [Figure 17] FIG. 17 is a diagram showing the lower arm. [Figure 18] FIG. 18 is a schematic diagram showing a press line. [Figure 19] FIG. 19 is a diagram showing an example of a process carried out by a press line. [Figure 20] FIG. 20 is a diagram showing an example of a process carried out by a press line. [Figure 21] FIG. 21 is a diagram showing an example of a process carried out by a press line. [Figure 22] FIG. 22 is a diagram showing an example of a process carried out by a press line. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1 and 2 are diagrams illustrating an example of a conventional burring method. In Fig. 1, a case where burring is performed on a plate-shaped portion 202 of a metal material 200 using a forming device 1 equipped with a hollow die 2, a hollow pad 3, and a cylindrical punch 4 is described.

[0017] As shown in Fig. 1(a), when burring is performed by a forming device 1, a plate-shaped portion 202 of a metal material 200 having a pilot hole 202a formed therein is clamped. In this state, as shown in Fig. 1(b), a punch 4 pushes the peripheral portion of the pilot hole 202a toward the die 2. This forms a cylindrical burred portion 210 as shown in Fig. 2.

[0018] Here, in the process of forming the burred portion 210, as shown in FIG. 1(b), the metal material 200 is bent and deformed while contacting the die shoulder 2a. At this time, a compressive force acts on the inside of the bent portion 204 of the metal material 200 (hereinafter referred to as the bent portion 204) as shown by the arrow in FIG. 1(b). This compressive force tends to cause non-uniform compressive deformation inside the bent portion. As a result, as shown in FIG. 2, minute wrinkles 212 may occur at the base of the burred portion 210 (the bent portion 204).

[0019] In order to prevent the occurrence of wrinkles as described above, the inventors focused on the fact that the deformation in the thickness direction of the bent deformation portion 204 of the metal material 200 that comes into contact with the die shoulder 2a is restricted. They then considered that by increasing the contact area between the bent deformation portion 204 and the die shoulder 2a and restricting the deformation in the thickness direction of the bent deformation portion 204, it would be possible to prevent wrinkles from occurring at the base portion (bent deformation portion 204) of the burring processing portion 210. However, they found that the conventional processing method shown in Fig. 1 cannot sufficiently prevent the occurrence of wrinkles in the early stages of forming because it is not possible to ensure a sufficient contact area between the bent deformation portion 204 and the die shoulder 2a.

[0020] Therefore, the inventors further investigated the possibility of forming a preformed portion before burring, and found that the occurrence of wrinkles at the base of the burred portion can be suppressed by devising the shape of the mold (punch, die) that forms the preformed portion.

[0021] Hereinafter, a method for manufacturing a molded product, a molding apparatus, and a press line according to an embodiment of the present invention will be described with reference to the drawings.

[0022] (First embodiment) Fig. 3 is a diagram showing steps in a method for manufacturing a molded product according to a first embodiment of the present invention. As shown in Fig. 3, in the method for manufacturing a molded product according to this embodiment, a pilot hole 102a (see Fig. 5) is formed in a plate-like portion 102 (see Fig. 5) of a metal material 100 (see Fig. 5 described later) (step S1), a preformed portion is then formed around the pilot hole 102a (step S2), and then burring is performed on the preformed portion (step S3). The step of forming the pilot hole 102a in step S1 is the same as the step of forming a pilot hole in a conventional burring method, so a description thereof will be omitted.

[0023] Fig. 4 is a schematic diagram showing a forming device used in the preforming step of step S2. Fig. 5 is a diagram for explaining the preforming step. As shown in Fig. 4, a forming device 10 includes a punch 12 and a die 14 that are arranged to face each other in a pressing direction X. As shown in Fig. 5, the pressing direction X coincides with the thickness direction of a plate-shaped portion 102 of a metal material 100 to be processed.

[0024] 4 and 5, the punch 12 and the die 14 are provided so as to be able to move relative to each other in the press direction X. Note that the means for moving the punch 12 and the die 14 relative to each other in the press direction X can be configured in the same way as a drive mechanism of a known press device (electric cylinder, hydraulic cylinder, gas cushion device), and therefore a description thereof will be omitted.

[0025] In the following, for ease of explanation, the side where the punch 12 is located in the pressing direction X will be referred to as the upper side, and the side where the die 14 is located will be referred to as the lower side, but the vertical positional relationship between the punch 12 and the die 14 may be reversed. In this embodiment, the punch 12 corresponds to the first punch, and the die 14 corresponds to the first die.

[0026] As shown in FIG. 4 , the punch 12 has a first support surface 20 facing downward (to one side in the pressing direction X) and a second support surface 22 protruding downward from the first support surface 20. In this embodiment, the first support surface 20 is formed as a plane extending in a direction perpendicular to the pressing direction X. The first support surface 20 has an inner peripheral edge 20a that is annular when viewed from the pressing direction X. When viewed from the pressing direction X, the second support surface 22 is provided inside the inner peripheral edge 20a of the first support surface 20. Note that in FIG. 4 , an imaginary line that passes through the center of the inner peripheral edge 20a and extends in the pressing direction X is indicated by a dashed dotted line. In this specification, the term "annular" includes not only a strictly circular ring but also a ring that has a shape that can be recognized as a circle or an ellipse as a whole. Therefore, an annular inner peripheral edge includes not only a circular inner peripheral edge but also an elliptical inner peripheral edge. In this embodiment, the inner peripheral edge 20a and an inner peripheral edge 40a, which will be described later, have a circular shape when viewed from the pressing direction X. In this embodiment, the inner peripheral edge 20a corresponds to a first inner peripheral edge.

[0027] The second support surface 22 has a first tapered surface 22a that faces outward in the radial direction Y of the inner circumferential edge 20a and has a diameter that decreases downward (toward the die 14). Hereinafter, the radial direction Y simply refers to the radial direction of the inner circumferential edge 20a. In this embodiment, the end of the second support surface 22 on the inner circumferential edge 20a side is an R-surface 22b that curves concavely upward (toward the other side in the pressing direction X) and inward in the radial direction Y. In this embodiment, the second support surface 22 is formed in a truncated cone shape whose diameter decreases downward. When viewed from the pressing direction, a circular flat surface 22c is formed at the center of the second support surface 22. Furthermore, the boundary between the first tapered surface 22a and the flat surface 22c of the second support surface 22 is an R-surface 22d that curves convexly downward (toward one side in the pressing direction X) and outward in the radial direction Y. In this embodiment, the cross-sectional shape of the second support surface 22 (first tapered surface 22a) perpendicular to the pressing direction X is circular, but the cross-sectional shape does not have to be a perfect circle. For example, when forming a burred portion having an elliptical shape when viewed from the pressing direction X, the cross-sectional shape of the second support surface 22 (first tapered surface 22a) perpendicular to the pressing direction X may be elliptical. In this specification, "the diameter is smaller toward one side (or the other side) in the pressing direction" means "the radial dimension is smaller toward one side (or the other side) in the pressing direction."

[0028] The die 14 has a third support surface 40 facing the first support surface 20 in the press direction X, and a fourth support surface 42 recessed downward from the third support surface 40. In this embodiment, the third support surface 40 is formed in a planar shape extending in a direction perpendicular to the press direction X. The third support surface 40 has an inner peripheral edge 40a that has a circular ring shape when viewed from the press direction X. When viewed from the press direction X, the fourth support surface 42 is provided inside the inner peripheral edge 40a of the third support surface 40. In this embodiment, the inner peripheral edge 40a corresponds to the second inner peripheral edge.

[0029] The fourth support surface 42 has a second tapered surface 42a that faces inward in the radial direction Y and has a diameter that decreases toward the lower side. The end of the fourth support surface 42 on the inner peripheral edge 40a side is a rounded surface 42b that convex upward and inward in the radial direction Y. The fourth support surface 42 is provided below the second support surface 22 so as to face the second support surface 22 in the pressing direction X. In this embodiment, the center of the fourth support surface 42 coincides with the center of the second support surface 22 as viewed from the pressing direction X. Furthermore, in this embodiment, the fourth support surface 42 has a shape that corresponds to the second support surface 22 of the punch 12 and is formed in a truncated cone shape with a diameter that decreases toward the lower side. A circular flat surface 42c is formed at the center of the fourth support surface 42 as viewed from the pressing direction. In addition, in the fourth support surface 42, the boundary between the second tapered surface 42a and the flat surface 42c is an R-surface 42d that curves downward (to one side in the pressing direction X) and outward in the radial direction Y.

[0030] 5(a), in the preforming step, first, the plate-shaped portion 102 of the metal material 100 is placed between the punch 12 and the die 14. In this embodiment, the plate-shaped portion 102 is supported by the third support surface 40 of the die 14 so that the center of the pilot hole 102a coincides or approximately coincides with the center of the fourth support surface 42 (second support surface 22) when viewed from the pressing direction X.

[0031] Next, as shown in Figure 5(b), the punch 12 and the die 14 are brought closer to each other in the press direction X, and the plate-shaped portion 102 of the metal material 100 is supported by the R surface 42b of the die 14, the portion of the first support surface 20 that is outer than the R surface 42b in the radial direction Y, and the portion of the second support surface 22 that is inner than the R surface 42b in the radial direction Y (in this embodiment, the first tapered surface 22a).

[0032] As shown in FIG. 5(c), the punch 12 and the die 14 are brought even closer together, and the plate-like portion 102 is sandwiched between the first support surface 20 and the third support surface 40. A portion of the plate-like portion 102 (in this embodiment, the peripheral portion of the pilot hole 102a) is pressed toward the fourth support surface 42 by the first tapered surface 22a. This forms a cylindrical preformed portion (cylindrical portion) 104 that protrudes downward from the plate-like portion 102 and has a smaller diameter toward the bottom. In this embodiment, by sandwiching a portion of the plate-like portion 102 between the first tapered surface 22a and the second tapered surface 42a, it is pressed against the R-surface 42b. This allows the preformed portion 104 to be precisely formed into a desired shape. Desirably, a portion of the plate-like portion 102 is sandwiched between the first tapered surface 22a and the second tapered surface 42a, and also between the R-surface 22b and the R-surface 42b, thereby enabling the preformed portion 104 to be molded into the desired shape with even greater precision.

[0033] As described above, in this embodiment, the preformed portion 104 is formed while a portion of the plate-shaped portion 102 (the peripheral edge of the pilot hole 102a) is supported by the rounded surface 42b of the die 14. As a result, the root portion 104a of the preformed portion 104 becomes a curved portion that is curved in an arc shape in a cross section that passes through the center of the pilot hole 102a and is parallel to the thickness direction (press direction X) of the plate-shaped portion 102. Hereinafter, the root portion 104a of the preformed portion 104 will also be referred to as the curved portion 104a.

[0034] 6 is a diagram for explaining the burring process. The forming device 5 used in the burring process can be configured in the same way as a conventional forming device used in burring, so the forming device 5 will only be briefly described.

[0035] 6(a), the molding device 5 includes a hollow die 6, a hollow pad 7, and a cylindrical punch 8. In the description of the burring process, the side where the pad 7 is located in the press direction X is referred to as the upper side, and the side where the die 6 is located is referred to as the lower side, but the vertical positional relationship between the pad 7 and the die 6 may be reversed.

[0036] The die 6 has a hole 6a into which the punch 8 can be inserted and a support surface 6b provided around the hole 6a. The hole 6a has a circular shape in a cross section perpendicular to the pressing direction X. A shoulder 6c of the die 6 (the boundary between the inner peripheral surface of the hole 6a and the support surface 6b) is a rounded surface that is convex upward and radially inward of the hole 6a. The radius of curvature of the shoulder 6c in a cross section of the die 6 that passes through the center of the hole 6a and is parallel to the pressing direction X (hereinafter simply referred to as the radius of curvature of the shoulder 6c) may be larger, smaller, or the same as the radius of curvature of the rounded surface 42b in a cross section of the die 14 that passes through the center of the inner peripheral edge 40a (see FIG. 4) and is parallel to the pressing direction X (hereinafter simply referred to as the radius of curvature of the rounded surface 42b). In this embodiment, the support surface 6b corresponds to the fifth support surface. When forming a burred portion having an elliptical shape when viewed from the pressing direction X, the hole 6a is formed so as to have an elliptical shape in a cross section perpendicular to the pressing direction X.

[0037] As shown in FIG. 6(a), when performing burring, first, the periphery of the preformed portion 104 of the plate-like portion 102 is supported by the support surface 6b of the die 6 so that the preformed portion 104 is positioned within the hole 6a of the die 6. In this state, as shown in FIG. 6(b), the preformed portion 104 is pressed into the hole 6a by the punch 8. As a result, the curved portion 104a of the preformed portion 104 is curved while contacting the shoulder portion 6c of the die 6, thereby forming a tubular (cylindrical in this embodiment) burred portion 106. In this manner, a molded product 100a having the burred portion 106 is manufactured. The height (length in the pressing direction X) of the burred portion 106 is greater than the height (length in the pressing direction X) of the preformed portion 104. The tip (diameter of the opening) of the burred portion 106 is, for example, 20 to 100 mm. This also applies to the embodiments described below.

[0038] In this embodiment, the molded article 100a (metal material 100) is typically made of a steel member having a tensile strength of 780 MPa or more, preferably 980 MPa or more, and more preferably 1180 MPa or more. In this embodiment, the molded article 100a (metal material 100) is typically made of a steel member having a Vickers hardness (HV1) of 240 or more, preferably 300 or more, and more preferably 340 or more. "HV1" refers to the "hardness symbol" used when a Vickers hardness test is performed with a test force of 1 kgf (9.807 N) (see JIS Z 2244-1:2020). The Vickers hardness of the molded article 100a (metal material 100) is measured as follows. First, a measurement sample is cut from a flat portion of the molded article 100a (a portion that has not been subjected to drilling, bending, or other processes), embedded in resin, and the cut surface is polished. Then, measurements were taken at 10 points at 0.5 mm intervals from the surface of the measurement sample (the surface of the molded article 100a) to a depth of 1 / 4 of the plate thickness with a test force of 1 kgf (9.807 N), and the average was calculated. The thickness of the molded article 100a (metal material 100) is, for example, 1.8 to 4.2 mm, more preferably 2.0 to 3.9 mm, and even more preferably 2.3 to 3.2 mm. If the surface of the molded article 100a (metal material 100) is plated, the thickness measured here includes the plating. By keeping the thickness of the molded article 100a (metal material 100) within the above range, desired rigidity and light weight can be achieved. The thickness of the molded article 100a (metal material 100) is calculated by measuring the thickness at five points on a flat portion (a portion not subjected to drilling, bending, etc.) using a micrometer, and the average value of the measurements is calculated. The same applies to the embodiments described below regarding the tensile strength, hardness, and thickness of the molded article (metal material).

[0039] (Action and effect) 5, preforming is performed on the plate-shaped portion 102 of the metal material 100 in a state in which the plate-shaped portion 102 is supported by the rounded surface 42b of the die 14, a portion of the first support surface 20 of the punch 12 on the inner peripheral edge 20a that is outer than the rounded surface 42b in the radial direction Y, and a portion of the second support surface 22 of the punch 12 that is inner than the rounded surface 42b in the radial direction Y. The second support surface 22 is provided to protrude from the first support surface 20 to one side (the die 14 side) in the pressing direction X. As a result, as shown in FIG. 5(b), the plate-shaped portion 102 is supported by the first support surface 20 and the second support surface 22, and thereby the plate-shaped portion 102 can be inclined with respect to the first support surface 20. That is, in this embodiment, the plate-shaped portion 102 is supported at two points on the punch 12 side, and the plate-shaped portion 102 is tilted relative to the first support surface 20 of the punch 12. Then, the portion of the plate-shaped portion 102 between the two points is pressed against the rounded surface 42b of the die 14, thereby performing preforming. In this case, when preforming the plate-shaped portion 102, the contact area between the portion of the plate-shaped portion 102 to be bent (the curved portion 104a forming the base of the preformed portion 104) and the rounded surface 42b can be sufficiently increased. This restricts deformation of the base portion 104a of the preformed portion 104 in the thickness direction during the formation of the preformed portion 104, thereby preventing uneven compressive deformation of the base portion 104a. As a result, the generation of minute wrinkles on the inside of the bent portion of the base portion 104a of the preformed portion 104 can be prevented.

[0040] Furthermore, in the burring process, bending can be performed by pressing the shoulder portion 6c of the die 6 against the root portion 104a of the preformed portion 104, which has been curved in advance in the preforming process. In this case, since the root portion 104a (part of the root portion of the burred portion 106) has already been formed, the contact area between the shoulder portion 6c and the root portion 104a can be sufficiently large. As a result, deformation in the thickness direction is constrained, and the occurrence of wrinkles in the root portion of the burred portion 106 can be suppressed compared to when forming from a flat material as shown in FIG. 1. Furthermore, in this embodiment, as described above, the occurrence of wrinkles in the root portion 104a of the preformed portion 104 is suppressed. This sufficiently suppresses the occurrence of wrinkles in the root portion of the burred portion 106.

[0041] From the viewpoint of sufficiently increasing the contact area between the shoulder portion 6c and the base portion 104a in the burring process, it is preferable that the rounded surface 42b and the shoulder portion 6c of the die 6 are provided so that the shoulder portion 6c of the die 6 is pressed against a portion of the metal material 100 against which the rounded surface 42b of the die 14 is pressed. Specifically, for example, the size of the circle formed by the inner edge of the rounded surface 42b as viewed from the press direction X of the forming apparatus 10 (diameter D1a in FIG. 4) is set to be equal to or smaller than the size of the circle formed by the outer edge of the shoulder portion 6c as viewed from the press direction X of the forming apparatus 5 (diameter D2b in FIG. 6), and the size of the circle formed by the outer edge of the rounded surface 42b as viewed from the press direction X of the forming apparatus 10 (diameter D1b in FIG. 4) is set to be equal to or larger than the size of the circle formed by the inner edge of the shoulder portion 6c as viewed from the press direction X of the forming apparatus 5 (diameter D2a in FIG. 6).

[0042] When the radius of curvature of the shoulder 6c of the die 6 is set larger than the radius of curvature of the rounded surface 42b of the die 14, the root portion 104a of the preformed portion 104 formed by the rounded surface 42b is pushed open by the shoulder 6c of the die 6. In this case, a tensile force, rather than a compressive force, can be applied to the inside of the bent portion of the root portion 104a. As a result, uneven compressive deformation can be prevented from occurring at the root portion of the burred portion 106, and the occurrence of minute wrinkles can be sufficiently suppressed. From the viewpoint of achieving this effect, it is preferable to set the radius of curvature of the shoulder 6c of the die 6 larger than the radius of curvature of the rounded surface 42b of the die 14.

[0043] In this embodiment, the second tapered surface 42a extends linearly in a cross section of the die 14 that passes through the center of the inner peripheral edge 40a and is parallel to the pressing direction X. To prevent the area of ​​the metal material 100 that is bent and deformed without contacting the rounded surface 42b of the die 14 during preforming from increasing, the inclination angle θ42 (see FIG. 4 ) of the second tapered surface 42a relative to the third support surface 40 in the cross section of the die 14 is preferably set to 30° or greater, and more preferably set to 40° or greater. Furthermore, to increase the contact area between the shoulder portion 6c of the die 6 and the base portion 104a of the preformed portion 104 during burring, the inclination angle θ42 is preferably set to 65° or less, and more preferably set to 50° or less. That is, the inclination angle θ42 is preferably set to 30 to 65°, and more preferably set to 40 to 50°. In this embodiment, the first tapered surface 22a is also formed so as to extend linearly in a cross section of the punch 12 that passes through the center of the inner peripheral edge 20a and is parallel to the pressing direction X. As with the inclination angle θ42, the inclination angle θ22 of the first tapered surface 22a with respect to the first support surface 20 in the above cross section of the punch 12 is preferably set to, for example, 30 to 65°, and more preferably 40 to 50°.

[0044] As in the second embodiment described below, it is also possible to form the pilot hole after forming the preformed portion. However, when forming the pilot hole after forming the preformed portion, it may be difficult to ensure a sufficient flat plate-like portion around the pilot hole. In this case, the diameter of the pilot hole is limited. In contrast, in this embodiment, the preformed portion 104 is formed after forming the pilot hole 102a in the plate-like portion 102, so that the diameter of the pilot hole 102a can be sufficiently ensured.

[0045] (Variation) The wrinkle suppression effect described above can be achieved by preforming the plate-shaped portion 102 while supporting it at three points: the rounded surface 42b of the die 14; a portion of the first support surface 20 of the punch 12 that is outer than the rounded surface 42b in the radial direction Y of the inner peripheral edge 20a; and a portion of the second support surface 22 of the punch 12 that is inner than the rounded surface 42b in the radial direction Y. Therefore, as long as the plate-shaped portion 102 can be supported at three points as described above, the shape of each part of the forming apparatus 10 is not limited to the shape shown in FIG. 4 . For example, as shown in FIG. 7 , the die 14 may be formed with a hole 42e that opens at the center of the fourth support surface 42 as viewed from the pressing direction X. Furthermore, as shown in FIG. 7( b ), the punch 12 may be formed with a hole 22e that opens at the center of the second support surface 22 as viewed from the pressing direction X. Furthermore, as shown in FIG. 7( c ), the height of the second support surface 22 in the pressing direction X may be smaller than the height of the preformed portion 104. In the forming apparatus 10 of Figures 7(a) and (b), the tip of the preforming portion 104 is not supported by the fourth support surface 42. Moreover, in the forming apparatus 10 of Figure 7(c), the tip of the preforming portion 104 is not supported by the second support surface 22 and the fourth support surface 42. Even in these cases, the plate-like portion 102 can be supported at three points during preforming as in the above-mentioned embodiment, and therefore the same effect can be obtained.

[0046] In the above-described embodiment, the first tapered surface 22a is formed to extend linearly in a cross section of the punch 12 that passes through the center of the inner peripheral edge 20a and is parallel to the pressing direction X. However, the first tapered surface 22a may be curved in an arcuate shape in the cross section. The same applies to the second tapered surface 42a. Note that, when the first tapered surface 22a is curved in an arcuate shape in the cross section of the punch 12, the radius of curvature of the first tapered surface 22a is set to be larger than the radius of curvature of the rounded surface 22b. Similarly, the radius of curvature of the second tapered surface 42a is set to be larger than the radius of curvature of the rounded surface 42b. For example, the radius of curvature of the first tapered surface 22a is set to be 10 times or more the radius of curvature of the rounded surface 22b, and the radius of curvature of the second tapered surface 42a is set to be 10 times or more the radius of curvature of the rounded surface 42b. Similarly, the tapered surfaces in the embodiments described below may be formed to extend linearly or curved in an arcuate shape.

[0047] As in the case where the second tapered surface 42a is formed to extend linearly, when the second tapered surface 42a is formed to be curved in an arc, the inclination angle of the second tapered surface 42a with respect to the third support surface 40 in a cross section of the die 14 that passes through the center of the inner peripheral edge 40a and is parallel to the pressing direction X is preferably set to 30 to 65°, more preferably 40 to 50°. When the second tapered surface 42a is formed to be curved in the cross section of the die 14, the inclination angle is determined as follows. First, the boundary between the rounded surface 42b and the second tapered surface 42a is identified. In this embodiment, as described above, the radius of curvature of the second tapered surface 42a is set to be larger than the radius of curvature of the rounded surface 42b. Therefore, in this embodiment, when the curvature is calculated from the rounded surface 42b toward the second tapered surface 42a in the cross section of the die 14, the point where the curvature clearly changes is identified as the boundary. The angle formed by the tangent to the fourth support surface 42 at the identified boundary and the third support surface 40 is defined as the inclination angle of the second tapered surface 42a with respect to the third support surface 40. Similarly, when the first tapered surface 22a is curved, the curvature is calculated from the rounded surface 22b toward the first tapered surface 22a, and the point where the curvature clearly changes is identified as the boundary between the rounded surface 22b and the first tapered surface 22a. The angle formed by the tangent to the second support surface 22 at the identified boundary and the first support surface 20 is defined as the inclination angle of the first tapered surface 22a with respect to the first support surface 20. In this case as well, the inclination angle of the first tapered surface 22a with respect to the first support surface 20 is preferably set to 30 to 65°, and more preferably 40 to 50°.

[0048] (Second embodiment) Fig. 8 is a diagram showing steps in a method for manufacturing a formed product according to a second embodiment of the present invention. As shown in Fig. 8, in the method for manufacturing a formed product according to this embodiment, a preformed portion is formed in a plate-like portion of a metal material 100 (see Fig. 9 described later) (step S1), then a pilot hole is formed in the preformed portion (step S2), and then burring is performed on the preformed portion (step S3). Fig. 9 is a diagram for explaining the preformed step. Note that in this embodiment as well, the preformed step is performed using the forming apparatus 10 described in Fig. 4.

[0049] 9(a), in the preforming step, first, the plate-shaped portion 102 of the metal material 100 is placed between the punch 12 and the die 14. In this embodiment, the plate-shaped portion 102 is supported by the third support surface 40 of the die 14.

[0050] Next, as shown in Figure 9(b), the punch 12 and the die 14 are brought closer to each other in the press direction X, and the plate-shaped portion 102 is supported by the R-surface 42b of the die 14, the portion of the first support surface 20 on the inner peripheral edge 20a that is outer than the R-surface 42b in the radial direction Y, and the portion of the second support surface 22 that is inner than the R-surface 42b in the radial direction Y (in this embodiment, the R-surface 22d).

[0051] As shown in FIG. 9(c), the punch 12 and the die 14 are brought even closer together, and the plate-shaped portion 102 is sandwiched between the first support surface 20 and the third support surface 40, while a portion of the plate-shaped portion 102 is pressed toward the fourth support surface 42 by the second support surface 22. This forms a cylindrical preformed portion (cylindrical portion) 108 whose diameter decreases toward the bottom. In this embodiment, a portion of the plate-shaped portion 102 is sandwiched between the first tapered surface 22a and the second tapered surface 42a, and also between the flat surface 22c and the flat surface 42c, and is pressed against the R-surface 42b. This allows the preformed portion 108 to be precisely formed into the desired shape. Desirably, a portion of the plate-like portion 102 is sandwiched between the first tapered surface 22a and the second tapered surface 42a, between the flat surface 22c and the flat surface 42c, and further between the R-surface 22d and the R-surface 42d, thereby enabling the preformed portion 108 to be molded into the desired shape with even greater precision.

[0052] As described above, in this embodiment as well, the preformed portion 108 is formed while a portion of the plate-like portion 102 is supported by the R surface 42b of the die 14. Therefore, the root portion 108a of the preformed portion 108 becomes a curved portion that is curved in an arc shape, similar to the root portion 104a of the preformed portion 104 described above (see FIG. 5(c)).

[0053] Next, in a pilot hole forming process in step S2, a pilot hole 108b (see FIG. 10 described later) is formed in the center of the preformed portion 108. Note that the pilot hole forming process in step S2 is the same as the process of forming a pilot hole in a conventional burring method, and therefore a description thereof will be omitted.

[0054] 10 is a diagram for explaining the burring process. In this embodiment, the burring process is also carried out using the forming device 5 described with reference to FIG.

[0055] As shown in FIG. 10(a), when performing burring, first, the periphery of the preforming portion 108 of the plate-like portion 102 is supported by the support surface 6b of the die 6 so that the preforming portion 108 with the pilot hole 108b formed therein is positioned within the hole portion 6a of the die 6. In this state, as shown in FIG. 10(b), the preforming portion 108 is pressed into the hole portion 6a by the punch 8. As a result, the base portion 108a of the preforming portion 108 is curved while contacting the shoulder portion 6c of the die 6, thereby forming a tubular (cylindrical in this embodiment) burring-processed portion 110. In this manner, a molded product 100a having the burring-processed portion 110 is manufactured. In this embodiment, too, the height (length in the pressing direction X) of the burring-processed portion 110 is greater than the height (length in the pressing direction X) of the preforming portion 108.

[0056] (Action and effect) In the present embodiment as well, in the preforming step, the plate-shaped portion 102 is preformed while being supported at three points: the rounded surface 42b of the die 14; a portion of the first support surface 20 of the punch 12 that is outer than the rounded surface 42b in the radial direction Y of the inner peripheral edge 20a; and a portion of the second support surface 22 of the punch 12 that is inner than the rounded surface 42b in the radial direction Y. This makes it possible to prevent minute wrinkles from occurring on the inside of the bend of the base portion 108a of the preformed portion 108, as in the first embodiment described above, and to sufficiently prevent wrinkles from occurring at the base portion of the burred processed portion 110.

[0057] Furthermore, in this embodiment, the preformed portion 108 is formed before the pilot hole 108b is formed. In this case, when the preformed portion 108 is formed, a larger tension can be applied to the portion of the plate-shaped portion 102 that is sandwiched between the second support surface 22 and the fourth support surface 42. This allows the plate-shaped portion 102 to be pressed against the R-surface 42b of the die 14 with sufficient force, further suppressing the occurrence of wrinkles.

[0058] When the present invention is used in manufacturing automobile parts or the like, the preformed portion 108 is formed when forming the portion other than the burred portion 110, and then the pilot hole 108b is formed, thereby preventing misalignment of the pilot hole 108b that occurs during forming or transport between processes. Furthermore, by forming the pilot hole 108b after preforming, it is possible to prevent the edge of the pilot hole 108b from being damaged by processing during preforming.

[0059] As in the first embodiment described above, in this embodiment, the shape of the forming apparatus 10 is not limited to the shape shown in Fig. 4. For example, as shown in Fig. 11(a), a hole 42f opening at the center of the fourth support surface 42 (flat surface 42c) may be formed in the die 14, or as shown in Fig. 11(b), a hole 22f opening at the center of the second support surface 22 (flat surface 22c) may be formed in the punch 12, or the hole 22f may be formed in the punch 12 and the hole 42f may be formed in the die 14. Even in these cases, the plate-like portion 102 can be supported at three points during preforming as in the above-described embodiment, and therefore the same effect can be obtained.

[0060] (Third embodiment) In the above-described embodiment, a preformed portion is formed using a punch 12 having a truncated cone-shaped second support surface 22 and a die 14 having a truncated cone-shaped fourth support surface 42, but the shapes of the second support surface and the fourth support surface are not limited to truncated cones.

[0061] Fig. 12 is a schematic diagram showing a molding apparatus used in a manufacturing method for a molded product according to a third embodiment of the present invention. The molding apparatus 10a shown in Fig. 12 differs from the molding apparatus 10 shown in Fig. 4 in the shapes of the punch 12 and the die 14. The punch 12 of the molding apparatus 10a has a second support surface 24 and a flat surface 26 instead of the second support surface 22 (see Fig. 4). The die 14 of the molding apparatus 10a has a fourth support surface 44 and a flat surface 46 instead of the fourth support surface 42 (see Fig. 4). The following mainly describes the configuration of the molding apparatus 10a that differs from the molding apparatus 10 shown in Fig. 4, and omits a description of the configuration common to the molding apparatus 10 shown in Fig. 4.

[0062] 12, the punch 12 has a first support surface 20, a second support surface 24 that protrudes downward from the first support surface 20 and is formed in an annular shape when viewed from the pressing direction X, and a flat surface 26 that is provided inside the second support surface 24 in the radial direction Y of the inner peripheral edge 20a of the first support surface 20. The flat surface 26 is formed in a planar shape so as to extend in a direction perpendicular to the pressing direction X.

[0063] The second support surface 24 has a first tapered surface 24a that faces outward in the radial direction Y and whose diameter decreases downward (one side in the press direction X: the die 14 side), and a third tapered surface 24b that faces inward in the radial direction Y and whose diameter decreases upward (the other side in the press direction X). In this embodiment, the end of the second support surface 24 on the inner circumferential edge 20a side is an R-surface 24c that is curved so as to be concave upward and inward in the radial direction Y. Note that, although the second support surface 24 is formed in an annular shape when viewed from the press direction X in this embodiment, the shape of the second support surface 24 when viewed from the press direction X does not have to be a perfect annular shape.

[0064] The die 14 has a third support surface 40, a fourth support surface 44 that is recessed downward from the third support surface 40 and has an annular shape when viewed from the pressing direction X, and a flat surface 46 that is provided on the inside of the fourth support surface 44 in the radial direction Y. The flat surface 46 is formed in a planar shape so as to extend in a direction perpendicular to the pressing direction X. In this embodiment, the second support surface 24 and the fourth support surface 44 face each other, and the flat surface 26 and the flat surface 46 face each other in the pressing direction X.

[0065] The fourth support surface 44 has a second tapered surface 44a that faces inward in the radial direction Y and has a diameter that decreases toward the bottom, and a fourth tapered surface 44b that faces outward in the radial direction Y and has a diameter that decreases toward the top. In this embodiment, the end of the fourth support surface 44 on the inner circumferential edge 40a side is an R-surface 44c that curves upward and inward in the radial direction Y, and the edge on the flat surface 46 side is an R-surface 44d that curves upward and outward in the radial direction Y.

[0066] Fig. 13 is a diagram for explaining the preforming step in this embodiment. Note that Fig. 13 explains the case where a pilot hole is formed after a preformed portion is formed, as in the second embodiment.

[0067] 13(a), in the preforming step, first, the plate-shaped portion 102 of the metal material 100 is placed between the punch 12 and the die 14. In this embodiment, the plate-shaped portion 102 is supported by the third support surface 40 of the die 14.

[0068] 13(b), the punch 12 and the die 14 are moved closer to each other in the pressing direction X, and the plate-like portion 102 is supported by the rounded surface 44c of the die 14, a portion of the first support surface 20 at the inner peripheral edge 20a that is outer than the rounded surface 44c in the radial direction Y, and a portion of the second support surface 24 that is inner than the rounded surface 44c in the radial direction Y (in this embodiment, the boundary between the first tapered surface 24a and the third tapered surface 24b: the lower end of the second support surface 24). Note that in this embodiment, a portion of the plate-like portion 102 is also supported by the flat surface 26 of the punch 12 and the rounded surface 44d of the die 14.

[0069] 13(c), the punch 12 and the die 14 are brought even closer together, and the plate-like portion 102 is sandwiched between the first support surface 20 and the third support surface 40, while a portion of the plate-like portion 102 is pressed toward the fourth support surface 44 and the flat surface 46 by the second support surface 24 and the flat surface 26. This forms the pre-formed portion 112. In this embodiment, the pre-formed portion 112 includes a cylindrical portion 112a whose diameter decreases toward the bottom, a cylindrical portion 112b whose diameter decreases toward the top, and a disk portion 112c provided inside the cylindrical portion 112b. The cylindrical portion 112a is a portion formed by being sandwiched between the first tapered surface 24a and the second tapered surface 44a, the cylindrical portion 112b is a portion formed by being sandwiched between the third tapered surface 24b and the fourth tapered surface 44b, and the disc portion 112c is a portion formed by being sandwiched between the flat surface 26 and the flat surface 46.

[0070] As described above, in this embodiment as well, the preformed portion 112 is formed while a portion of the plate-like portion 102 is supported by the rounded surface 44c of the die 14. Therefore, the base portion 112d of the preformed portion 112 (the portion rising from the plate-like portion 102) becomes an arc-shaped curved portion, similar to the base portion 104a of the preformed portion 104 described above (see FIG. 5(c)).

[0071] Next, a pilot hole 112e (see FIG. 14 described later) is formed in the center of the preformed portion 112. The pilot hole forming step is the same as the step of forming a pilot hole in a conventional burring method, and therefore a description thereof will be omitted.

[0072] FIG. 14 is a diagram illustrating the burring process. In this embodiment, the burring process is also performed using the molding apparatus 5 described in FIG. 6. As shown in FIG. 14(a), when performing burring, the periphery of the preformed portion 112 of the plate-like portion 102 is first supported by the support surface 6b of the die 6 so that the preformed portion 112 with the pilot hole 112e formed therein is positioned within the hole 6a of the die 6. In this state, as shown in FIG. 14(b), the preformed portion 112 is pushed into the hole 6a by the punch 8. As a result, the base portion 112d of the preformed portion 112 is curved while contacting the shoulder portion 6c of the die 6, and the cylindrical portions 112a and 112b are also stretched, forming a tubular (cylindrical in this embodiment) burred portion 114. In this manner, a molded product 100a having the burred portion 114 is manufactured. In this embodiment as well, the height (length in the pressing direction X) of the burring processed portion 114 is greater than the height (length in the pressing direction X) of the preformed portion 112.

[0073] From the same viewpoint as in the first embodiment, for example, the size (diameter D3a in FIG. 12) of the circle formed by the inner edge of the rounded surface 44c as viewed from the press direction X of the molding apparatus 10a (see FIG. 12) is set to be equal to or smaller than the size (diameter D2b in FIG. 6) of the circle formed by the outer edge of the shoulder 6c as viewed from the press direction X of the molding apparatus 5, and the size (diameter D3b in FIG. 12) of the circle formed by the outer edge of the rounded surface 44c as viewed from the press direction X of the molding apparatus 10a is set to be equal to or larger than the size (diameter D2a in FIG. 6) of the circle formed by the inner edge of the shoulder 6c as viewed from the press direction X of the molding apparatus 5. Furthermore, the radius of curvature of the shoulder 6c of the die 6 may be larger, smaller, or the same as the radius of curvature of the rounded surface 44c in a cross section of the die 14 that passes through the center of the inner peripheral edge 40a (see FIG. 12) and is parallel to the press direction X (hereinafter simply referred to as the radius of curvature of the rounded surface 44c). However, from the same viewpoint as in the first embodiment, it is preferable that the radius of curvature of the shoulder portion 6c of the die 6 is larger than the radius of curvature of the rounded surface 44c of the die .

[0074] From the same viewpoint as in the first embodiment, in a cross section of the die 14 that passes through the center of the inner peripheral edge 40a and is parallel to the pressing direction X, the inclination angle θ44 (see FIG. 12) of the second tapered surface 44a with respect to the third support surface 40 is preferably set to 30 to 65°, and more preferably set to 40 to 50°. In this embodiment, the second tapered surface 44a is formed in a curved shape rather than a straight shape in the cross section of the die 14. In this embodiment, when the curvature is calculated from the rounded surface 44c toward the second tapered surface 44a in the cross section of the die 14, the angle formed by the tangent to the fourth support surface 44 (shown by a two-dot chain line in FIG. 12) at the point where the curvature clearly changes (i.e., the boundary between the rounded surface 44c and the second tapered surface 44a) and the third support surface 40 is defined as the inclination angle θ44. Similarly, in a cross section of the punch 12 that passes through the center of the inner peripheral edge 20a and is parallel to the pressing direction X, the first tapered surface 24a is formed in a curved shape. When the curvature is calculated from the rounded surface 24c toward the first tapered surface 24a in the cross section of the punch 12, the angle formed by the tangent to the second support surface 24 at the point where the curvature clearly changes (the line shown by the two-dot chain line in FIG. 12) and the first support surface 20 is defined as the inclination angle θ24 of the first tapered surface 24a with respect to the first support surface 20. The inclination angle θ24 is preferably set to 30 to 65°, and more preferably 40 to 50°.

[0075] (Action and effect) In the present embodiment as well, in the preforming step, the plate-shaped portion 102 is preformed while being supported by at least three points: the rounded surface 44c of the die 14; a portion of the first support surface 20 of the punch 12 that is outer than the rounded surface 44c in the radial direction Y of the inner peripheral edge 20a; and a portion of the second support surface 24 of the punch 12 that is inner than the rounded surface 44c in the radial direction Y (in the present embodiment, the boundary between the first tapered surface 24a and the third tapered surface 24b). As a result, as in the first embodiment described above, it is possible to prevent minute wrinkles from occurring on the inside of the bend of the base portion 112d of the preformed portion 112, and it is possible to sufficiently prevent wrinkles from occurring in the base portion of the burred processed portion 114.

[0076] Furthermore, in this embodiment, by sandwiching the plate-shaped portion 102 not only between the first tapered surface 24a and the second tapered surface 44a but also between the third tapered surface 24b and the fourth tapered surface 44b, a greater tension can be applied to the die 14 side of the plate-shaped portion 102. This allows the plate-shaped portion 102 to be pressed against the R-surface 44c of the die 14 with sufficient force, further suppressing the occurrence of wrinkles.

[0077] Also in this embodiment, similarly to the second embodiment, the preformed portion 112 is formed before the pilot hole 112e is formed, so that a greater tension can be applied to the plate-like portion 102 when forming the preformed portion 112. This can further suppress the occurrence of wrinkles.

[0078] (Variation 1) 15(a), when using the molding apparatus 10a, the pilot hole 112e may be formed and then the preformed portion 112 may be formed, as in the first embodiment described above. As described above, forming the pilot hole after forming the preformed portion can prevent misalignment of the pilot hole that may occur during molding or transport between processes, and can also prevent damage to the edge of the pilot hole due to processing during preforming.

[0079] (Variation 2) In the above-described forming apparatus 10a, the first support surface 20 and the flat surface 26 are positioned at the same position in the press direction X, and the third support surface 40 and the flat surface 46 are positioned at the same position, but as shown in Fig. 15(b), the flat surface 26 may protrude downward relative to the first support surface 20, and the flat surface 46 may be recessed downward relative to the third support surface 40. Furthermore, although not shown, a hole opening at the flat surface 26 may be formed in the punch 12, and a hole opening at the flat surface 46 may be formed in the die 14, similar to the forming apparatus 10 shown in Fig. 11.

[0080] (Variation 3) In the above-described embodiment, the lower end of the second support surface 24 is curved in an arcuate shape that is convex downward, and the lower end of the fourth support surface 44 is curved in an arcuate shape that is concave downward, but the shapes of the second support surface 24 and the fourth support surface 44 are not limited to the above-described examples. For example, as shown in FIG. 16 , the lower end of the second support surface 24 may be provided with a flat surface 24d that is annular when viewed from the pressing direction X, and the lower end of the fourth support surface 44 may be provided with a flat surface 44e that is annular when viewed from the pressing direction X. Note that, in the second support surface 24, the boundary between the first tapered surface 24a and the flat surface 24d is an R-surface 24e that is curved downward and convex outward in the radial direction Y, and the boundary between the third tapered surface 24b and the flat surface 24d is an R-surface 24f that is curved downward and convex inward in the radial direction Y.

[0081] In this embodiment, when forming the preformed portion, as shown in FIG. 16 , the plate-like portion 102 can be supported at at least three points: the rounded surface 44c of the die 14; a portion of the first support surface 20 that is outer than the rounded surface 44c in the radial direction Y of the inner peripheral edge 20a; and a portion of the second support surface 24 that is inner than the rounded surface 44c in the radial direction Y (the rounded surface 24e in this embodiment). This prevents minute wrinkles from forming on the inside of the bent portion at the base of the preformed portion, as in the above-described embodiment, and sufficiently prevents wrinkles from forming at the base of the burred portion. In this embodiment, a portion of the plate-like portion 102 is supported by the rounded surface 24f in addition to the flat surface 26 of the punch 12 and the rounded surface 44d of the die 14.

[0082] (Usage example) The method for manufacturing a molded product according to the present invention can be used, for example, when manufacturing automobile parts. Hereinafter, a case where a lower arm is manufactured using a press line will be described. Figure 17 is a schematic diagram showing a lower arm, where (a) is a plan view showing the lower arm, and (b) is an end view showing part AB of (a).

[0083] The lower arm 300 shown in Fig. 17 has a top plate portion 302, burred portions 304, 306 formed to rise in the thickness direction of the top plate portion 302, a groove portion 308 formed in the center of the top plate portion 302, and a wall portion 310 formed to rise from the edge of the top plate portion 302 in the thickness direction of the top plate portion 302. Note that the shape of the lower arm 300 shown in Fig. 17 is simplified to explain an example of how the present invention is used. Automotive parts manufactured using the present invention are not limited to the lower arm shown in Fig. 17, and the present invention can be used when manufacturing automotive parts of various shapes having burred portions.

[0084] 18 is a schematic diagram showing a press line 500 for manufacturing the lower arm 300. The press line 500 has five dies 50, 52, 54, 56, and 58 arranged along the conveyance direction of the metal material 100. The dies 50, 52, 54, 56, and 58 have upper dies 50a, 52a, 54a, 56a, and 58a fixed to a slide 60 and lower dies 50b, 52b, 54b, 56b, and 58b fixed to a bolster 62. The slide 60 is provided so as to be movable in the press direction X relative to the bolster 62. In the press line 500, a drive mechanism (not shown) reciprocates the slide 60 relative to the bolster 62, while a conveying mechanism (not shown) conveys the metal material 100 through the dies 50, 52, 54, 56, and 58 in this order, thereby carrying out five processes, steps S11 to S15, thereby manufacturing the lower arm 300.

[0085] Fig. 19 is a diagram illustrating an example of a process carried out by a press line 500. In the example shown in Fig. 19, first, in step S11, groove portion 308 is formed by clamping between upper mold 50a and lower mold 50b of mold 50. As upper mold 50a and lower mold 50b, a punch 501 and a die 502 similar to known punches and dies can be used.

[0086] Next, in step S12, the pad is bent using the mold 52. Specifically, while the groove portion 308 is pressed by the pad 521 of the upper mold 52a, the wall portion 310 is formed by the punch 522 of the upper mold 52a. As the upper mold 52a, a pad 521 and a punch 522 similar to known pads and punches can be used, and as the lower mold 52b, a die 523 similar to known dies can be used. Although a detailed description will be omitted, a trimming step for removing a portion of the metal material 100 may be performed between step S11 and step S12. In this case, a die for performing the trimming step is disposed between the mold 50 and the mold 52.

[0087] Next, in step S13, a prepared hole 120 for forming a burred portion 304 (see FIG. 17) is formed by a mold 54. A pad 541 and a punch 542 similar to a known pad and punch can be used as the upper mold 54a, and a die 543 similar to a known die can be used as the lower mold 54b. Although not shown in the drawings, a prepared hole for forming a burred portion 306 (see FIG. 17) is also formed in step S13.

[0088] Next, in step S14, the mold 56 forms the preformed portion 130 around the periphery of the pilot hole 120. A pad similar to a known pad can be used as the pad 561 of the upper mold 56a, and the punch 562 of the upper mold 56a has the configuration of the punch 12 of the above-described embodiment. Furthermore, the die 563 of the lower mold 56b has the configuration of the die 14 of the above-described embodiment. Note that, for portions of the die 563 other than the portion for forming the preformed portion 130, a known die configuration can be used. In this embodiment, the mold 56 corresponds to the first mold, the punch 562 corresponds to the first punch, and the die 563 corresponds to the first die. Note that, although not shown, in step S14, a preformed portion for forming the burring processing portion 306 (see FIG. 17) is also formed.

[0089] Finally, in step S15, the burring processing portion 304 is formed by the mold 58. A pad 581 and a punch 582 similar to a known pad and punch can be used as the upper mold 58a, and a die 583 similar to a known die can be used as the lower mold 58b. The portion of the mold 58 that forms the burring processing portion 304 is configured in the same manner as the above-mentioned molding apparatus 5. Although not shown, the burring processing portion 306 (see FIG. 17) is also formed in step S15. This completes the lower arm 300. In this embodiment, the mold 58 corresponds to the second mold, the punch 582 corresponds to the second punch, and the die 583 corresponds to the second die.

[0090] FIG. 20 is a diagram illustrating another example of the process performed by the press line 500. In the example shown in FIG. 20 as well, first, the groove portion 308 is formed in step S11, and then the wall portion 310 is formed in step S12. Note that steps S11 and S12 in FIG. 20 are similar to steps S11 and S12 in FIG. 19, and therefore description thereof will be omitted. Also in this example, a trimming process for removing a portion of the metal material 100 may be performed between steps S11 and S12. In this case, a die for performing the trimming process is disposed between the die 50 and the die 52.

[0091] Next, in step S13, the mold 54 forms a preformed portion 130 for forming the burred portion 304 (see FIG. 17) in a part of the metal material 100. A pad similar to a known pad can be used as the pad 544 of the upper mold 54a, and the punch 545 of the upper mold 54a has the configuration of the punch 12 in the above-described embodiment. Furthermore, the die 546 of the lower mold 54b has the configuration of the die 14 in the above-described embodiment. Note that, for the portions of the die 546 other than the portion for forming the preformed portion 130, a known die configuration can be used. In this embodiment, the mold 54 corresponds to the first mold, the punch 545 corresponds to the first punch, and the die 546 corresponds to the first die. Note that, although not shown, in step S13, a preformed portion for forming the burred portion 306 (see FIG. 17) is also formed.

[0092] Next, in step S14, a pilot hole 120 is formed in the center of the preformed portion 130 by the mold 56. A pad 564 and a punch 565 similar to known pads and punches can be used as the upper mold 56a, and a die 566 similar to known dies can be used as the lower mold 56b. Although not shown in the drawings, a pilot hole for forming the burred portion 306 (see FIG. 17) is also formed in step S14.

[0093] Finally, in step S15, a burred portion 304 is formed by the mold 58. Although not shown, a burred portion 306 (see FIG. 17) is also formed in step S15. This completes the lower arm 300. Note that step S15 in FIG. 20 is similar to step S15 in FIG. 19, and therefore a detailed description thereof will be omitted.

[0094] In the example shown in Figures 19 and 20, five dies (six dies if a trimming process is performed) are installed on one press line 500, but the five dies (or six dies) may also be arranged across two press lines.

[0095] Fig. 21 is a diagram illustrating another example of a process performed by the press line 500. Note that, while the example illustrated in Fig. 19 and Fig. 20 describes a case in which the lower arm 300 is manufactured from the metal material 100 using five dies 50, 52, 54, 56, and 58, Fig. 21 and Fig. 22 described below describe a case in which the lower arm 300 is manufactured using four dies 50, 52, 54, and 56.

[0096] In the example shown in FIG. 21 , first, in step S11, a preformed portion 130 and a groove portion 308 for forming a burred portion 304 (see FIG. 17 ) are formed by clamping with a mold 50. The punch 503 of the upper mold 50a has the configuration of the punch 12 of the above-described embodiment, and the die 504 of the lower mold 50b has the configuration of the die 14 of the above-described embodiment. It should be noted that, for the portions of the punch 503 and the die 504 other than those for forming the preformed portion 130, known punch and die configurations can be used. In this embodiment, the mold 50 corresponds to the first mold, the punch 503 corresponds to the first punch, and the die 504 corresponds to the first die. It should be noted that, although not shown, a preformed portion for forming a burred portion 306 (see FIG. 17 ) is also formed in step S11.

[0097] Next, in step S12, the pad is bent using the mold 52. Specifically, while the groove portion 308 is pressed by the pad 524 of the upper mold 52a, the wall portion 310 is formed by the punch 525 of the upper mold 52a. As the upper mold 52a, a pad 524 and a punch 525 similar to known pads and punches can be used, and as the lower mold 52b, a die 526 similar to known dies can be used. Although a detailed description will be omitted, a trimming step for removing a portion of the metal material 100 may be performed between step S11 and step S12. In this case, a die for performing the trimming step is disposed between the mold 50 and the mold 52.

[0098] Next, in step S13, a pilot hole 120 is formed in the center of the preformed portion 130 by the mold 54. Although not shown, in step S13, a pilot hole for forming a burred portion 306 (see FIG. 17) is also formed. Note that step S13 in FIG. 21 is similar to step S14 in FIG. 20, and therefore a detailed description thereof will be omitted.

[0099] Finally, in step S14, a burred portion 304 is formed by the mold 56. Although not shown, a burred portion 306 (see FIG. 17) is also formed in step S14. This completes the lower arm 300. Note that step S14 in FIG. 21 is similar to step S15 in FIG. 20, and therefore a detailed description thereof will be omitted.

[0100] In the example shown in FIG. 21, the grooves 308 and the preformed portion 130 are formed in step S11, so the number of steps can be reduced compared to the examples shown in FIGS.

[0101] Fig. 22 is a diagram illustrating yet another example of the process performed by the press line 500. In the example shown in Fig. 22, first, in step S11, the groove portion 308 is formed by clamping with the mold 50. Note that step S11 in Fig. 22 is similar to step S11 in Fig. 19, and therefore description thereof will be omitted.

[0102] Next, in step S12, the mold 52 forms the preformed portion 130 and the wall portion 310 for forming the burred portion 304 (see FIG. 17). In this embodiment, the punch 527 for forming the preformed portion 130 in the upper mold 52a has the same configuration as the punch 12 in the above-described embodiment. Furthermore, the pad 528 and punch 529 for bending the pad in the upper mold 52a can have known pad and punch configurations. The die 530 of the lower mold 52b has the same configuration as the die 14 in the above-described embodiment. Note that, for portions of the die 530 other than the portion for forming the preformed portion 130, known die configurations can be used. Note that, although not shown, in step S12, a preformed portion for forming the burred portion 306 (see FIG. 17) is also formed.

[0103] Although detailed description will be omitted, a trimming step for removing a part of the metal material 100 may be performed between step S11 and step S12. In this case, a mold for performing the trimming step is disposed between the mold 50 and the mold 52.

[0104] Next, in step S13, the mold 54 forms a pilot hole 120 in the center of the preformed portion 130. Although not shown, in step S13, a pilot hole for forming the burred portion 306 (see FIG. 17) is also formed. Note that step S13 in FIG. 22 is similar to step S14 in FIG. 20, and therefore a detailed description thereof will be omitted.

[0105] Finally, in step S14, a burred portion 304 is formed by the mold 56. Although not shown, a burred portion 306 (see FIG. 17) is also formed in step S14. This completes the lower arm 300. Note that step S14 in FIG. 22 is similar to step S15 in FIG. 20, and therefore a detailed description thereof will be omitted.

[0106] In the example shown in FIG. 22, the wall portion 310 and the preformed portion 130 are formed in step S12, so the number of steps can be reduced compared to the examples shown in FIGS.

[0107] In the examples shown in Figures 21 and 22, four dies (five dies if a trimming process is performed) may be provided on one press line, or the four dies (or five dies) may be arranged across two press lines.

[0108] In the above embodiment, the case where the present invention is applied to a press line of a plurality of transfer types has been described, but the present invention may also be applied to a press line of a tandem type.

[0109] In the above embodiment, the case where the preformed portion (burred portion) is formed in a part of the flat plate-like portion has been described, but the part where the preformed portion is formed does not have to be completely flat, and may be gently curved. In this case, for example, the thickness direction of the part of the metal material that will be the center of the burred portion becomes the pressing direction. [Example]

[0110] The preforming step and burring step described with reference to FIGS. 4 to 6 were performed using the forming apparatus 10 and the forming apparatus 5 to confirm the effects of the present invention. As shown in Table 1 below, in Examples (Nos. 1 to 14), a steel plate having a thickness of 2.9 mm and a Vickers hardness (HV1) of 250 or 350 was used as the metal material 100. The Vickers hardness (HV1) of the metal material 100 was measured according to the Vickers hardness measurement method described above. For the forming apparatus 10 in the preforming step, the inclination angle θ42 of the second tapered surface 42a relative to the third support surface 40 (see FIG. 4), the radius of curvature of the rounded surface 42b of the die 14 (see FIG. 4), the diameter D1a of the inner edge of the rounded surface 42b, and the diameter D1b of the outer edge of the rounded surface 42b were set as shown in Table 1. The height H (see FIG. 4) of the fourth support surface 42 in the pressing direction X was 20 mm, and the radius of curvature of the rounded surface 22d of the punch 12 was 3.0 mm. The inclination angle θ22 (see FIG. 4) of the first tapered surface 22a relative to the first support surface 20 was equal to the inclination angle θ42. Regarding the forming device 5 for the burring process, the diameter D2a (see FIG. 6) of the inner edge of the shoulder 6c was 50 mm, the diameter D2b (see FIG. 6) of the outer edge of the shoulder 6c was 52 mm, the radius of curvature of the shoulder 6c of the die 6 was 1.0 mm, and the radius of curvature of the shoulder 8a of the punch 8 was 5.0 mm. The pad load of the pad 7 in the burring process was 150 kN. In the comparative examples (Nos. 15 and 16), burring was performed using the forming device 5 without performing the preforming process. In the comparative examples (Nos. 15 and 16), a steel plate having a thickness of 2.9 mm and a Vickers hardness (HV1) of 250 or 350 was used as the metallic material 100.

[0111] [Table 1]

[0112] For the Examples (Nos. 1 to 14) and Comparative Examples (Nos. 15 and 16), after burring, the base of the burred portion (the portion corresponding to the bent portion 204 in FIG. 2) was cut out, embedded in resin, the cut surface was polished, carbon deposition was performed, and the base portion was observed by SEM. In the results column of Table 1, "C" means that the number of wrinkles that occurred in the base portion was 15 or more, "B" means that the number of wrinkles was 5 to 14, and "A" means that the number of wrinkles was 4 or less.

[0113] From the results shown in Table 1, it was confirmed that the present invention can suppress the occurrence of wrinkles at the base of the burred portion. [Industrial Applicability]

[0114] According to the present invention, a method for manufacturing a molded product, a molding device, and a press line can be provided that can suppress the occurrence of wrinkles at the base of a burred portion. The present invention can be particularly effectively used when performing burring on high-strength metal materials that are prone to wrinkles at the base of a burred portion. [Explanation of symbols]

[0115] 6b Support surface (5th support surface) 10,10a Molding equipment 12 Punch 14 Die 20 1st support surface 20a, 40a inner edge 22,24 Second support surface 22a, 24a First tapered surface 24b Third tapered surface 40 Third support surface 42,44 4th support surface 42a, 44a Second tapered surface 42b,44c R side 44b 4th tapered surface 100 Metallic Materials 102 Plate-shaped part 104,108,112,130 Preformed part 106,110,114,304,306 Burring processing section 500 Press Line

Claims

1. A method for manufacturing a molded product by performing burring on a plate-shaped portion of a metal material, comprising: The thickness direction of the plate-shaped portion is the pressing direction, a preformed portion having a cylindrical portion that protrudes from the plate-like portion to one side in the press direction and has a diameter that is smaller toward the one side in the press direction, is formed by a first die that is arranged on one side of the plate-like portion in the press direction and a first punch that is arranged on the other side in the press direction, and then the burring process is performed on the preformed portion; the first punch includes a first support surface facing the one side in the pressing direction and having an annular first inner circumferential edge, and a second support surface provided inside the first inner circumferential edge and protruding from the first support surface toward the one side in the pressing direction, the first die includes: a third support surface facing the first support surface in the pressing direction and having an annular second inner peripheral edge; and a fourth support surface provided inside the second inner peripheral edge and recessed from the third support surface to the one side in the pressing direction, the second support surface includes a first tapered surface that faces outward in the radial direction of the first inner circumferential edge and has a diameter that decreases toward the one side in the pressing direction, an end portion of the fourth support surface on the second inner peripheral edge side is an R surface, When forming the preformed portion, a first punch and a first die are moved closer to each other in the pressing direction while supporting the plate-like portion by the R-surface, a portion of the first support surface that is radially outer than the R-surface, and a portion of the second support surface that is radially inner than the R-surface, and the plate-like portion is sandwiched between the first support surface and the third support surface, and a portion of the plate-like portion is pressed toward the fourth support surface by the first tapered surface, thereby forming the pre-formed portion.

2. the fourth support surface includes a second tapered surface that faces inward in the radial direction and has a diameter that decreases toward the one side in the pressing direction, The method for manufacturing a molded product according to claim 1 , wherein the preformed portion is formed by sandwiching a part of the plate-like portion between the first tapered surface and the second tapered surface.

3. the second support surface further includes a third tapered surface that faces inward in the radial direction and has a diameter that decreases toward the other side in the pressing direction, the fourth support surface further includes a fourth tapered surface that faces outward in the radial direction and has a diameter that decreases toward the other side in the pressing direction, The method for manufacturing a molded product according to claim 2 , wherein when forming the preformed portion, a part of the plate-like portion is further sandwiched between the third tapered surface and the fourth tapered surface.

4. 2. The method for manufacturing a molded product according to claim 1, wherein after a pilot hole is formed in the plate-like portion, the preformed portion is formed by pushing the peripheral portion of the pilot hole in the plate-like portion toward the fourth support surface using the first tapered surface.

5. The method for manufacturing a molded product according to claim 1 , wherein the burring is performed after a pilot hole is formed in the center of the preformed portion.

6. A forming apparatus for forming a preformed portion on a plate-shaped portion of a metal material before performing burring on the plate-shaped portion, a first die disposed on one side in the pressing direction and a first punch disposed on the other side in the pressing direction so as to face each other in the pressing direction, the first punch includes a first support surface facing the one side in the pressing direction and having an annular first inner circumferential edge, and a second support surface provided inside the first inner circumferential edge and protruding from the first support surface toward the one side in the pressing direction, the first die includes: a third support surface facing the first support surface in the pressing direction and having an annular second inner peripheral edge; and a fourth support surface provided inside the second inner peripheral edge and recessed from the third support surface to the one side in the pressing direction, the second support surface includes a first tapered surface that faces outward in the radial direction of the first inner circumferential edge and has a diameter that decreases toward the one side in the pressing direction, an end portion of the fourth support surface on the second inner peripheral edge side is an R surface, a forming device that supports the plate-shaped portion by the R-surface, a portion of the first support surface that is radially outer than the R-surface, and a portion of the second support surface that is radially inner than the R-surface, and then moves the first punch and the first die closer in the press direction to sandwich the plate-shaped portion between the first support surface and the third support surface, and presses a portion of the plate-shaped portion toward the fourth support surface with the first tapered surface, thereby forming the pre-formed portion that protrudes from the plate-shaped portion to one side in the press direction and has a cylindrical portion whose diameter is smaller toward the one side in the press direction.

7. The method includes: a first die for forming a preformed portion on a plate-shaped portion of a metal material; and a second die for performing burring on the preformed portion. the first mold includes a first die arranged on one side in the press direction and a first punch arranged on the other side in the press direction so as to face each other in the press direction, the second mold includes a second die arranged on the one side in the press direction and a second punch arranged on the other side in the press direction so as to face each other in the press direction, the first punch includes a first support surface facing the one side in the pressing direction and having an annular first inner circumferential edge, and a second support surface provided inside the first inner circumferential edge and protruding from the first support surface toward the one side in the pressing direction, the first die includes a third support surface facing the first support surface in the pressing direction and having an annular second inner peripheral edge, and a fourth support surface provided inside the second inner peripheral edge and recessed from the third support surface to the one side in the pressing direction, the second support surface includes a first tapered surface that faces outward in the radial direction of the first inner circumferential edge and has a diameter that decreases toward the one side in the pressing direction, an end portion of the fourth support surface on the second inner peripheral edge side is an R surface, the second die has a hole into which the second punch can be inserted and a fifth support surface provided around the hole; in the first die, the plate-like portion is supported by the R-surface, a portion of the first support surface that is outer than the R-surface in the radial direction, and a portion of the second support surface that is inner than the R-surface in the radial direction, and the first punch and the first die are brought closer in the pressing direction to sandwich the plate-like portion between the first support surface and the third support surface, and a part of the plate-like portion is pressed toward the fourth support surface by the first tapered surface, thereby forming the preformed portion which protrudes from the plate-like portion to one side in the pressing direction and has a cylindrical portion whose diameter is smaller toward the one side in the pressing direction, A press line in which, in the second mold, burring is performed by pushing the preformed portion into the hole portion with the second punch while the periphery of the preformed portion of the plate-shaped portion is supported by the fifth support surface of the second die so that the preformed portion is positioned within the hole portion.

Images