Molding manufacturing method

Abstract

To provide a molding manufacturing method capable of easily forming a juncture while suppressing cracking of the juncture of two welded plates.SOLUTION: This molding manufacturing method comprises: stacking and welding an inner metal plate on an outer metal plate to form a first juncture; and bending, after the formation of the first juncture, the outer metal plate together with the inner metal plate in a first direction through first pressing to form a first surface, a second surface, and a bent part in the outer metal plate. The method further comprises bending, after the first pressing, the outer metal plate together with the inner metal plate in a second direction through second pressing to form a reverse bent part bent opposite to the bent part in the outer metal plate. The first juncture is a part in which the inner metal plate is welded to a region where the inner metal plate becomes a first surface of the outer metal plate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a molded article. [Background technology]

[0002] In the drawing and bending of metal sheets, a reinforcing plate (i.e., a patch) is welded to the base metal sheet to increase its strength, and then the sheet is pressed. In this type of processing, a difference in elongation occurs between the reinforcing plate, which is located on the inside of the bend, and the base metal, which is located on the outside. As a result, shear stress occurs in the welded part of the reinforcing plate, which may cause cracking.

[0003] Patent Document 1 discloses a method for manufacturing a molded product having a top plate portion, two vertical wall portions, and bent portions located between the top plate portion and each vertical wall portion by stacking and welding a main body blank and a reinforcing blank, and then pressing the stacked and welded main body blank and a reinforcing blank. In this manufacturing method, before pressing, joints are formed in the main body blank and the reinforcing blank at portions corresponding to each vertical wall portion. Furthermore, before welding, a convex shape is formed in the main body blank located on the outside of the bend to suppress cracking at the joint. Then, the molded product is manufactured so that bent portions are formed in the portions where the convex shape is formed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-102761 Summary of the Invention [Problem to be solved by the invention]

[0005] Another method for preventing cracks at the joint between two welded plates is, for example, to provide a joint only in the part of the two plates that corresponds to the top plate, rather than providing a joint in the part that corresponds to the vertical plate, and then press the two plates together and provide a joint in the vertical wall part.

[0006] However, in this method, a gap may be formed between the two plate materials in the vertical wall portion due to a difference in the amount of springback of the two plate materials after pressing. When this gap is formed, there is a problem in that it is difficult to weld the two plate materials in the vertical wall portion after pressing.

[0007] An object of one aspect of the present disclosure is to provide a method for manufacturing a molded product that can easily form a joint between two welded plate materials while suppressing cracks at the joint. [Means for solving the problem]

[0008] One aspect of the present disclosure is a method for manufacturing a molded product. The method includes overlapping an inner metal plate and an outer metal plate and welding them to form a first joint, and, after forming the first joint, bending the outer metal plate together with the inner metal plate in a first direction by a first press. The method also includes, after the first press, bending the outer metal plate together with the inner metal plate in a second direction opposite to the first direction by a second press. The second press forms a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first surface and the second surface and in which the inner metal plate is overlapped. The first press forms a reverse bent portion in the outer metal plate that bends in the opposite direction to the bent portion, in which the inner metal plate is overlapped. The reverse bent portion is formed in the outer metal plate so as to overlap a region of the outer metal plate that will become the bent portion. The inner metal plate is positioned outside the reverse bent portion after the first press and inside the bent portion after the second press. The first joint is a portion where the inner metal plate is welded to a region of the outer metal plate that will become the first surface.

[0009] With this configuration, even if the outer metal plate is bent together with the inner metal plate by the first and second presses, resulting in a difference in elongation length between the outer metal plate and the inner metal plate, stress is unlikely to concentrate at the first joint. Furthermore, because the outer metal plate and the inner metal plate are first bent in the first direction before being bent in the second direction, even if springback occurs in the outer metal plate and the inner metal plate due to bending in the second direction, the gap between the inner metal plate and the second surface of the outer metal plate after the second press is likely to be reduced. Therefore, it is possible to easily form a joint that can be formed between the inner metal plate and the second surface of the outer metal plate while suppressing cracks at the first joint between the two welded metal plates.

[0010] One aspect of the present disclosure may further include welding the outer metal plate and the inner metal plate together after the second pressing to form a second joint portion where the inner metal plate is welded to the second surface. According to this configuration, the second joint is formed in a state where it is less susceptible to the effect of the difference in elongation length between the outer metal plate and the inner metal plate due to the second pressing. This makes it possible to make the second joint less susceptible to cracking. Furthermore, the second joint is formed in a state where the gap between the inner metal plate and the second surface of the outer metal plate after the second pressing is reduced. This makes it easy to form the second joint.

[0011] In one embodiment of the present disclosure, the inner metal plate may have a preliminary cover portion that overlaps the reverse bent portion after a first press and a cover portion that overlaps the bent portion after a second press. The cover portion may have a first end portion located on the first surface side and a second end portion located on the second surface side. The reverse bent portion may be formed such that the length from a position on the inner metal plate that will become the first end portion to an end portion of the preliminary cover portion that will become the second surface side of the outer metal plate is longer than the length from the first end portion to the second end portion of the cover portion.

[0012] In this configuration, the portion of the outer metal plate of the preliminary cover part near the end portion located on the side of the region that will become the second surface, which has been curved and deformed in the first direction by the first press, extends in a substantially straight line after the second press. This makes it easier for springback to occur, pressing the inner metal member against the second surface of the outer metal plate. This makes it possible to further reduce the gap between the inner metal plate and the second surface of the outer metal plate after the second press.

[0013] In one aspect of the present disclosure, the reverse bent portion may be formed such that a first bending angle of the reverse bent portion is greater than a second bending angle of the bent portion. The first bending angle may be an angle formed by a first inclined line along a preliminary opposite surface constituting a region of the outer metal plate opposite to the region that will become the second surface, with respect to an intersection line that intersects the region that will become the first surface of the outer metal plate approximately perpendicularly, in a cross section along the direction in which the first surface, the bent portion, and the second surface are aligned. The second bending angle may be an angle formed by a second inclined line along an opposite surface of the outer metal plate opposite to the second surface, with respect to the intersection line, in the cross section.

[0014] With this configuration, during the second press, interference between the portion of the outer metal plate having the area that will become the second surface after the first press and the mold used for the second press can be suppressed.

[0015] In one aspect of the present disclosure, the reverse bend portion may be formed so that the end portion of the reverse bend portion located on the side of the region that will become the first surface of the outer metal plate is located closer to the side of the region that will become the second surface of the outer metal plate than the position of the end portion of the outer metal plate on the first surface side of the bent portion.

[0016] With this configuration, the first press makes it difficult for the outer metal plate to bend and deform in the area that will become the first surface, thereby preventing the first surface from retaining a bending tendency in the first direction during the second press. [Brief explanation of the drawings]

[0017] [Figure 1]FIG. 2 is a perspective view schematically showing a molded product. [Figure 2] FIG. 2 is a side view schematically showing the molded product. [Figure 3] Fig. 3A is a schematic cross-sectional view along the short side at the position of the first joint of the blank after the pre-welding step. Fig. 3B is a schematic cross-sectional view along the short side at the position of the first joint of the blank after the first bending step. Fig. 3C is a schematic cross-sectional view along the short side at the position of the first joint of the blank after the second bending step. Fig. 3D is a schematic cross-sectional view along the short side at the positions of the first and second joints of the molded product completed after the post-welding step. [Figure 4] FIG. 1 is a flow chart showing a method for manufacturing a molded product. [Figure 5] FIG. 10 is a diagram illustrating a first bending step. [Figure 6] FIG. 10 is a diagram illustrating a second bending step. [Figure 7] 10A and 10B are diagrams illustrating the relationship between a bent portion and a reverse bent portion. [Figure 8] 10A and 10B are diagrams illustrating a reverse bent portion of a first comparative example. [Figure 9] 10A and 10B are diagrams illustrating a reverse bent portion of a second comparative example. [Figure 10] FIG. 10 is a schematic side view of a molded product of a first modified example taken along the short side direction. [Figure 11] FIG. 10 is a schematic side view of a molded product of a second modified example taken along the short side direction. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Composition of molded product] The molded product 100 shown in Figures 1 and 2 is formed by welding and pressing a blank material (hereinafter simply referred to as blank material), which is a plate material made by overlapping a first metal plate 1 and a second metal plate 2.

[0019] The molded product 100 is a plate-like part extending in the longitudinal direction L and has multiple corners 10. The corners 10 are formed by pressing a blank material in the thickness direction. In this embodiment, the molded product 100 has a hat-shaped cross-sectional shape along the short-side direction S, which is perpendicular to the longitudinal direction L (hereinafter simply referred to as the cross-sectional shape). The hat shape is a shape including two opposing side walls, a top wall connecting the two side walls at first ends, and two flange portions extending away from each other from second ends of the side walls opposite the first ends. Note that the cross-section along the short-side direction S can also be referred to as a cross-section along the direction in which a first surface 111, a bent portion 13, and a second surface 121, which will be described later, are aligned.

[0020] The molded product 100 is used, for example, as a component part of an automobile body. In this embodiment, the molded product 100 is a rocker provided at the bottom of the side of the automobile. The molded product may also be, for example, a front pillar or a center pillar. The molded product 100 includes a first metal plate 1, a second metal plate 2, a plurality of first joints 3, and a plurality of second joints 4.

[0021] <First metal plate> The first metal plate 1 is made of, for example, a steel plate. In this embodiment, the first metal plate 1 has a hat-shaped cross section. The first metal plate 1 has a top wall 11, two side walls 12, two bent portions 13, and two flange portions 14.

[0022] The plate surface of the top wall 11 extends in a direction intersecting with the plate surfaces of the two side walls 12 that face each other with a gap between them. The top wall 11 has a first surface 111. The side walls 12 have second surfaces 121 that extend in a direction intersecting with the first surface 111. The first surface 111 is a surface of the plate surface of the top wall 11 that continues to the inner surface of a bending portion 13, which will be described later. The second surface 121 is a surface of the plate surface of the side walls 12 that continues to the inner surface of a bending portion 13, which will be described later.

[0023] The bent portion 13 is a portion between the top wall 11 and the side wall 12, and is bent by bending the first metal plate 1. The bent portion 13 forms a corner portion 10 of the molded product 100. The bent portion 13 connects the first surface 111 of the top wall 11 and the second surface 121 of the side wall 12.

[0024] The flange portion 14 is formed by bending the end portion of the side wall 12 opposite to the top wall 11 by bending the first metal plate 1. The plate surface of the flange portion 14 extends in a direction intersecting with the plate surface of the side wall 12.

[0025] <Second metal plate> The second metal plate 2 is made of, for example, a steel plate, similar to the first metal plate 1. The materials of the first metal plate and the second metal plate are not particularly limited. The first metal plate and the second metal plate may be made of different materials. In this embodiment, the second metal plate 2 has a U-shaped cross section.

[0026] The second metal plate 2 is overlapped and welded to the first metal plate 1. The second metal plate 2 is disposed across the top wall 11, the two side walls 12, and the two bent portions 13 of the first metal plate 1. In this embodiment, the second metal plate 2 overlaps the first surface 111 of the first metal plate 1, the second surfaces 121 of each side wall 12, and the inner surfaces of each bent portion 13. That is, the second metal plate 2 is disposed inside each bent portion 13 of the first metal plate 1 and is welded to the first metal plate 1 so as to overlap each bent portion 13 from the inside. In this embodiment, the second metal plate 2 has a shorter length in the longitudinal direction L than the first metal plate 1 and overlaps only a portion of the first metal plate 1 along the longitudinal direction L. Note that the second metal plate may have approximately the same length as the first metal plate in the longitudinal direction L and overlap the entire range from end to end of the first metal plate along the longitudinal direction L.

[0027] The second metal plate 2 has a first cover portion 21, two second cover portions 22, and two third cover portions . The first cover portion 21 is a portion that overlaps the first surface 111 of the first metal plate 1.

[0028] Each second cover portion 22 is a portion that overlaps with each second surface 121 of the first metal plate 1. Each third cover portion 23 is a portion that overlaps the inner surface of each bent portion 13 of the first metal plate 1, and connects the first cover portion 21 and each second cover portion 22. The third cover portion 23, together with the bent portion 13 of the first metal plate 1, constitutes a corner portion 10 of the molded product 100.

[0029] In this embodiment, the molded product 100 is configured such that, for example, the first metal plate 1 has a tensile strength of 980 MPa or more, and the second metal plate 2 located on the inside of the bent portion 13 has a thickness greater than the thickness of the first metal plate 1. Note that the tensile strength of the first metal plate is not limited to the above-mentioned numerical value. Furthermore, the thicknesses of the first metal plate and the second metal plate are not particularly limited. The thicknesses of the first metal plate and the second metal plate may be the same or different.

[0030] <1st joint> As shown in FIG. 1, the first joint 3 is a portion of the molded product 100 where the first cover portion 21 of the second metal plate 2 is welded to the first surface 111 of the first metal plate 1. As will be described in detail later, in this embodiment, the first joint 3 is formed before the bending process of the blank. Therefore, as shown in FIG. 3A, the first joint 3 is a portion of the blank where a portion 21A of the second metal plate 2 that will become the first cover portion 21 is welded to a first region 111A that will become the first surface 111 of the first metal plate 1. A plurality of first joints 3 are provided. As shown in FIG. 1, the plurality of first joints 3 are arranged at intervals from each other in the longitudinal direction L. Note that a plurality of first joints may be provided so as to be aligned in the lateral direction S.

[0031] <Second joint> The second joints 4 are portions of the molded product 100 where the second cover portions 22 of the second metal plate 2 are welded to the second surfaces 121 of the first metal plate 1. Note that, as will be described in detail later, in this embodiment, the second joints 4 are formed after the bending process of the blank material, unlike the first joints 3. A plurality of second joints 4 are provided. The plurality of second joints 4 are arranged at intervals from each other in the longitudinal direction L. Note that a plurality of second joints may also be provided so as to be arranged in the lateral direction S.

[0032] The first joint 3 and the second joint 4 are each formed by, for example, a nugget formed at a welding point by spot welding. Note that each joint may penetrate the first metal plate or the second metal plate.

[0033] [2. Manufacturing method of molded products] Next, a method for manufacturing the above-mentioned molded product 100 will be described with reference to Figures 3A to 3D and 4 to 6. The method for manufacturing the molded product 100 includes a pre-welding step S10, a first bending step S20, a second bending step S30, and a post-welding step S40.

[0034] <Pre-welding process> 3A , a flat second metal plate 2 is overlapped on a flat first metal plate 1 and welded to form a first joint 3. Specifically, the second metal plate 2 is overlapped so as to straddle a first portion 11A that will become the top wall 11, a second portion 12A that will become the two side walls 12, and a third portion 13A that will become the two bent portions 13 of the first metal plate 1 before bending. Thereafter, the portion 21A that will become the first cover portion 21 of the second metal plate 2 before bending is spot-welded to a first region 111A that will become the first surface 111 of the first metal plate 1, for example, to form the first joint 3.

[0035] <First bending process> Next, as shown in FIG. 3B , after the first joint 3 is formed, the first metal plate 1 is bent together with the second metal plate 2 in a first direction D1 to form a preliminary corner 10B. The first direction D1 is the bending direction opposite to the second direction D2, which is the bending direction when performing the bending process to form the shape of the molded product 100 described above. As will be described in detail later, in the first bending process, the first metal plate 1 and the second metal plate 2 are bent in the first direction D1 to an extent that they are plastically deformed. The preliminary corner 10B is formed by pressing the blank material in the thickness direction, similar to the corner 10.

[0036] Specifically, the welded blank obtained in the pre-welding step S10 is subjected to a first cold press using a first mold 5A, a second mold 5B, and a third mold 5C shown in Fig. 5 to form preliminary corners 10B. The blank having preliminary corners 10B is also referred to as a preformed product 101.

[0037] As a result, the first metal plate 1 is press-formed to form a preliminary top wall portion 11B, two preliminary side wall portions 12B, and two reverse bent portions 13B on the first metal plate 1. The preliminary top wall portion 11B is a portion that will mostly become the top wall 11 of the molded product 100. The preliminary side wall portion 12B is a portion that will mostly become the side wall 12 of the molded product 100. The reverse bent portion 13B is a region between the preliminary top wall portion 11B and the preliminary side wall portion 12B, and bends in the opposite direction to the bent portion 13. The reverse bent portion 13B is formed so that it partially or entirely overlaps with the region of the first metal plate 1 that will become the bent portion 13 on the first metal plate 1 after bending in the first direction D1. The reverse bent portion 13B constitutes the preliminary corner portion 10B of the preformed product 101.

[0038] Furthermore, the second metal plate 2 is bent along the auxiliary top wall portion 11B, the auxiliary side wall portion 12B, and the reverse bent portion 13B. As a result, the auxiliary first cover portion 21B, two auxiliary second cover portions 22B, and two auxiliary third cover portions 23B are formed on the second metal plate 2. The auxiliary first cover portion 21B is a portion that overlaps the auxiliary top wall portion 11B. Each auxiliary second cover portion 22B is a portion that overlaps each auxiliary side wall portion 12B. Each auxiliary third cover portion 23B is a portion that overlaps the outer surface of each reverse bent portion 13B and connects the auxiliary first cover portion 21B and each auxiliary second cover portion 22B. That is, in the preformed product 101, the second metal plate 2 is arranged outside the reverse bent portions 13B of the first metal plate 1 and overlaps the first metal plate 1 so as to overlap each reverse bent portion 13B from the outside. The preliminary third cover portion 23B constitutes the preliminary corner portion 10B of the preform 101 together with the reverse bent portion 13B.

[0039] As shown in FIG. 5, the first mold 5A is disposed above the second mold 5B so as to face the second mold 5B. The first mold 5A has a protruding portion 51A at its approximate center that protrudes toward the second mold 5B. The protruding portion 51A has surfaces that can mold the preliminary top wall portion 11B, two preliminary side wall portions 12B, and two reverse bent portions 13B of the preform 101. The second mold 5B has a recessed portion 51B, facing the protruding portion 51A of the first mold 5A, into which the protruding portion 51A can be fitted. The recessed portion 51B has surfaces that can mold the preliminary first cover portion 21B, two preliminary second cover portions 22B, and two preliminary third cover portions 23B of the preform 101. The second mold 5B has a through-hole 52B, into which the third mold 5C is inserted, facing the surface of the protruding portion 51A that molds the preliminary top wall portion 11B. That is, the through hole 52B is located approximately in the center of the recess 51 B. The third mold 5C is inserted into the through hole 52B of the second mold 5B and is disposed so as to be movable relative to the second mold 5B.

[0040] In this embodiment, the welded blank is placed between the second mold 5B and the first mold 5A, with the third mold 5C inserted into the through hole 52B. The first mold 5A and the second mold 5B are then brought close to each other, and the protrusions 51A are fitted into the recesses 51B, thereby molding the preform 101. At this time, the third mold 5C is pushed downward by the protrusions 51A.

[0041] <Second bending process> Next, as shown in Fig. 3C, after the bending process in the first direction D1 by the above-mentioned first cold press, the first metal plate 1 is bent together with the second metal plate 2 in the second direction D2 to form the corner portion 10. Specifically, the blank material (i.e., the preform 101) after the bending process obtained in the first bending step S20 is subjected to a second cold press using a fourth mold 6A, a fifth mold 6B, and a sixth mold 6C shown in Fig. 6 to form the corner portion 10.

[0042] As a result, the first metal plate 1 after bending in the first direction D1 is pressed, and a top wall 11 (i.e., the first surface 111), two side walls 12 (i.e., the two second surfaces 121), two bent portions 13, and two flange portions 14 are formed on the first metal plate 1.

[0043] Furthermore, the second metal plate 2 after bending in the first direction D1 is bent along the top wall 11, the two side walls 12, and the two bent portions 13. As a result, the first cover portion 21, two second cover portions 22, and two third cover portions 23 are formed on the second metal plate 2.

[0044] As shown in FIG. 6 , the fourth mold 6A is disposed above the fifth mold 6B so as to face the fifth mold 6B. The fifth mold 6B has a protruding portion 61B protruding toward the fourth mold 6A at approximately its center. The protruding portion 61B has surfaces capable of molding the first cover portion 21, two second cover portions 22, and two third cover portions 23 of the molded product 100. The fourth mold 6A has a recessed portion 61A, at a position facing the protruding portion 61B of the fifth mold 6B, into which the protruding portion 61B can be fitted. The recessed portion 61A has surfaces capable of molding the top wall 11, two side walls 12, two bent portions 13, and two flange portions 14. The fourth mold 6A has a through hole 62A, through which the sixth mold 6C is inserted, at a position facing the surface of the protruding portion 61B that molds the first cover portion 21. That is, the through hole 62A is located approximately in the center of the recessed portion 61A. The sixth mold 6C is inserted into the through-hole 62A of the fourth mold 6A and is arranged so as to be movable relative to the fourth mold 6A.

[0045] In this embodiment, the preformed product 101 is placed between the fourth mold 6A and the fifth mold 6B, with the sixth mold 6C inserted into the through-hole 62A, so that the auxiliary top wall portion 11B and the auxiliary first cover portion 21B are sandwiched between the sixth mold 6C and the protruding portion 61B of the fifth mold 6B. At this time, the fourth mold 6A is placed above and spaced apart from the fifth mold 6B so as not to interfere with the auxiliary side wall portion 12B of the preformed product 101. Then, the fourth mold 6A and the fifth mold 6B are brought close to each other, and the protruding portion 61B is fitted into the recessed portion 61A, thereby molding a blank having the above-mentioned corner portion 10.

[0046] That is, in this embodiment, when a blank is bent in the first direction D1, only the plate surface located on the first side (the inner surface of the preliminary top wall portion 11B) based on the ridge line R0 of the reverse bent portion 13B of the first metal plate 1 formed by the bending is joined to the second metal plate 2 by the first joint portion 3. On the other hand, the plate surface located on the second side opposite the first side based on the ridge line R0 of the reverse bent portion 13B (the inner surface of the preliminary side wall portion 12B) is not joined to the second metal plate 2. Furthermore, when a blank having the preliminary corner portion 10B is bent in the second direction D2, only the plate surface located on the first side (i.e., the first surface 111) based on the ridge line R of the bent portion 13 of the first metal plate 1 formed by the bending is joined to the second metal plate 2 by the first joint portion 3. On the other hand, the plate surface (ie, second surface 121) located on the second side opposite to the first side with respect to the ridge line R of bent portion 13 is not joined to second metal plate 2.

[0047] <Post-welding process> 3D , after the bending in the second direction D2 by the second cold press described above, the first metal plate 1 and the second metal plate 2 are further welded together to form the second joint 4. That is, the second joint 4 is formed on the blank material after bending obtained in the second bending step S30. Specifically, the second joint 4 is formed by, for example, spot welding each second cover portion 22 of the second metal plate 2 after bending in the second direction D2 to each second surface 121 of the first metal plate 1.

[0048] As described above, in this embodiment, the molded product 100 is obtained by manufacturing in the order of the pre-welding step S10, the first bending step S20, the second bending step S30, and the post-welding step S40.

[0049] [3. Relationship between bent section and reverse bent section] Next, the relationship between the bent portion 13 and the reverse bent portion 13B will be described with reference to FIG.

[0050] 7, the bent portion 13 has a first end 131 located on the top wall 11 side and a second end 132 located on the side wall 12 side. The third cover portion 23 overlapping the bent portion 13 has a first end 231 located on the first cover portion 21 side (i.e., the first surface 111 side) and a second end 232 located on the second cover portion 22 side (i.e., the second surface 121 side).

[0051] The reverse bent portion 13B has a first end 131B located on the side of the auxiliary top wall portion 11B and a second end 132B located on the side of the auxiliary side wall portion 12B. The auxiliary third cover portion 23B overlapping the reverse bent portion 13B has a first end 231B located on the side of the auxiliary first cover portion 21B (i.e., the side of the area that will become the first surface 111 of the first metal plate 1) and a second end 232B located on the side of the auxiliary second cover portion 22B (i.e., the side of the area that will later become the second surface 121 of the first metal plate 1).

[0052] In this embodiment, the reverse bent portion 13B is formed with respect to the bent portion 13 so as to satisfy the following conditions (A) to (C). (A) The length from the position of the second metal plate 2 that will become the first end 231 of the third cover part 23 to the second end 232B of the spare third cover part 23B is longer than the length from the first end 231 of the third cover part 23 to the second end 232 of the third cover part 23.

[0053] In this embodiment, the center points in the thickness direction of the end portions 231, 232 of the third cover portion 23 are designated as midpoints P1 and P2, and the center point in the thickness direction of the second end portion 232B of the spare third cover portion 23B is designated as midpoint P3. In this case, the reverse bent portion 13B is formed so that the length from midpoint P1 to midpoint P3 in the preformed product 101 is longer than the length from midpoint P1 to midpoint P2 in the molded product 100. As an example that satisfies the above-mentioned condition (A), when the radius of curvature of the bent portion 13 in the molded product 100 is approximately 5 mm, the radius of curvature of the reverse bent portion 13B in the preformed product 101 is preferably approximately 7 mm or more.

[0054] (B) The first bending angle θ1 of the reverse bent portion 13B is larger than the second bending angle θ2 of the bent portion 13. The first bending angle θ1 is the angle formed by the first inclined line L2 with respect to the intersection line L1 in a cross section taken along the short-side direction S. The intersection line L1 is a line that intersects the region of the first metal plate 1 that will become the first surface 111 in the cross section (in other words, approximately perpendicular to the preliminary top wall portion 11B). The first inclined line L2 is a line that runs along the preliminary opposite surface 122B (in other words, the plate surface of the preliminary side wall portion 12B) that constitutes the region of the first metal plate 1 opposite to the region that will become the second surface 121 in the cross section.

[0055] The second bending angle θ2 is the angle that the second inclined line L3 makes with respect to the intersection line L1 in the cross section. The second inclined line L3 is a line that runs along the opposite surface 122 of the first metal plate 1 opposite to the second surface 121 (in other words, the plate surface of the side wall 12) in the cross section.

[0056] For example, when the second bending angle θ2 of the bent portion 13 is approximately 10°, the gap (hereinafter simply referred to as the gap) formed between the outer surface of each second cover portion 22 and the second surface 121 of each side wall 12 after bending in the second direction D2 with respect to the first bending angle θ1 of the reverse bent portion 13B is as follows: The gap is measured at approximately the midpoint from the end of each second cover portion 22 on the third cover portion 23 side to the end on the opposite side. This midpoint is the position where the second joint 4 is expected to be formed.

[0057] When the first bending angle θ1 is approximately 25°, the gap is approximately 1.86 mm. When the first bending angle θ1 is approximately 45°, the gap is approximately 1.63 mm. When the first bending angle θ1 is approximately 65°, the gap is approximately 2.17 mm. When the first bending angle θ1 is approximately 85°, the gap is approximately 2.61 mm. When the first bending angle θ1 is approximately 0°, i.e., when no bending in the first direction D1 is performed, the gap is approximately 3.15 mm. Therefore, when the second bending angle θ2 is 10°, the gap can be reduced by forming the reverse bent portion 13B so that the first bending angle θ1 is 10° or more. When the second bending angle θ2 is approximately 10°, it is more preferable that the first bending angle θ1 be 25° or more and less than 50°.

[0058] (C) The first end 131B of the reverse bent portion 13B is located closer to the preliminary side wall portion 12B than the position of the first metal plate 1 that will become the first end 131 of the bent portion 13.

[0059] [4. Effects] According to the embodiment described above in detail, the following effects can be obtained.

[0060] (4a) In this embodiment, when the blank is bent in the first direction D1, only the inner surface of the preliminary top wall portion 11B located on the first side is joined to the second metal plate 2 by the first joint portion 3, based on the ridge line R0 of the reverse bent portion 13B of the first metal plate 1 formed by the bending. On the other hand, the inner surface of the preliminary side wall portion 12B located on the second side is not joined to the second metal plate 2, based on the ridge line R0 of the reverse bent portion 13B.

[0061] Furthermore, when a blank having preliminary corner portion 10B is bent in second direction D2, only the first surface 111 located on the first side of ridge line R of bent portion 13 of first metal plate 1 formed by the bending is joined to second metal plate 2 by first joint portion 3. On the other hand, the second surface 121 located on the second side of ridge line R of bent portion 13 is not joined to second metal plate 2. In this way, when either bending process is performed, the second joint portion 4 is not provided on the blank.

[0062] As a result, even if the first metal plate 1 is bent together with the second metal plate 2 by the first cold press and a difference in elongation length along the reverse bend portion 13B occurs between the first metal plate 1 and the second metal plate 2, the second metal plate 2 is unlikely to be constrained in the region that will become the second surface 121 of the first metal plate 1. Furthermore, even if the second cold press bends the first metal plate 1 together with the second metal plate 2 and a difference in elongation length along the bent portion 13 occurs between the first metal plate 1 and the second metal plate 2, the second metal plate 2 is unlikely to be constrained by the second surface 121 of the first metal plate 1. Therefore, stress is unlikely to concentrate at the first joint portion 3 during either cold press.

[0063] Furthermore, in this embodiment, the first metal plate 1 and the second metal plate 2 are first bent in the first direction D1 before being bent in the second direction D2. This makes it easy to reduce gaps even if springback occurs in the metal plates 1 and 2 due to bending in the second direction D2, regardless of the combination of material strength and plate thickness of the first metal plate 1 and the second metal plate 2. As a result, it becomes easier to form the second joint 4.

[0064] In this embodiment, the second joint 4 is formed on the blank material after bending. Therefore, the second joint 4 is formed in a state that is less susceptible to the influence of the difference in elongation length along the bent portion 13 between the first metal plate 1 and the second metal plate 2 due to the second cold pressing. Therefore, cracks at the joints 3, 4 of the welded first metal plate 1 and second metal plate 2 can be suppressed, and the second joint 4 can be easily formed.

[0065] (4b) In this embodiment, the reverse bent portion 13B is formed so that the length from the midpoint P1 to the midpoint P3 in the preform 101 is longer than the length from the midpoint P1 to the midpoint P2 in the molded product 100. That is, the reverse bent portion 13B is formed so as to satisfy the above-described condition (A). Therefore, a portion of the preliminary third cover portion 23B near the second end 232B, which has been subjected to bending deformation in the first direction D1 by the first cold pressing, extends in a substantially straight line after the second cold pressing. Specifically, as shown in FIG. 7 , the midpoint P3 in the preform 101 is located at the midpoint P4 in the molded product 100 after the second cold pressing. Because the midpoint P4 is located on the side wall 12 that extends in a substantially straight line, the molded product 100 extends in a substantially straight line from the midpoint P2 to the midpoint P4. This makes it easy for springback to occur, in which the second metal plate 2 is pressed against the second surface 121 of the first metal plate 1. This allows the gap to be further reduced.

[0066] (4c) For example, if the first bending angle of the reverse bent portion is smaller than or equal to the second bending angle of the bent portion, the preliminary side wall portion in the preform is likely to warp upward relative to the preliminary top wall portion. This increases the likelihood of interference between the preliminary side wall portion 12B and the fourth mold 6A used in the second cold pressing. In contrast, in this embodiment, the reverse bent portion 13B is formed so that the first bending angle θ1 of the reverse bent portion 13B is larger than the second bending angle θ2 of the bent portion 13B. That is, the reverse bent portion 13B is formed to satisfy the above-described condition (B). This reduces warping of the preliminary side wall portion 12B relative to the preliminary top wall portion 11B in the preform 101. This reduces interference between the preliminary side wall portion 12B of the preform 101 after the first cold pressing and the fourth mold 6A used in the second cold pressing.

[0067] (4d) In this embodiment, the first end 131B of the reverse bent portion 13B is located closer to the preliminary side wall portion 12B than the position of the first metal plate 1 that will become the first end 131 of the bent portion 13. In other words, the reverse bent portion 13B is formed to satisfy the above-mentioned condition (C). This makes it difficult for a portion to be curved and deformed in the first region 111A of the first metal plate 1 by the first cold pressing. Therefore, in this embodiment, it is possible to prevent a bending tendency in the first direction D1 from remaining on the first surface 111 (i.e., the top wall 11) during the second cold pressing.

[0068] 8 and 9, when the condition (B) described above is satisfied but the condition (C) is not satisfied, as in the case of the reverse bent portion 13C of the first comparative example and the reverse bent portion 13D of the second comparative example, the first cold pressing is likely to cause a curved portion in the first region 111A of the first metal plate 1. As shown in FIGS. 8 and 9, the first end 131C of the reverse bent portion 13C and the first end 131D of the reverse bent portion 13D are located closer to the first region 111A of the first metal plate 1, which is the first surface 111 of the bent portion 13, than the position of the first metal plate 1 that is the first end 131 of the bent portion 13. Therefore, when the reverse bent portions 13B and 13C shown in FIGS. 8 and 9 are formed, a bending tendency in the first direction is likely to remain on the first surface 111 (i.e., the top wall 11) during the second cold pressing.

[0069] (4e) In the present embodiment, the molded product 100 is configured, for example, such that the tensile strength of the first metal plate 1 is 980 MPa or more, and the thickness of the second metal plate 2 located inside the bent portion 13 is thicker than the thickness of the first metal plate 1. In such a configuration, if the first bending step S20 is not performed before the second bending step S30, gaps are likely to become large. However, in the present embodiment, the first bending step S20 is performed before the second bending step S30, so gaps are more likely to be reduced.

[0070] In this embodiment, the first metal plate 1 corresponds to an example of an outer metal plate, and the second metal plate 2 corresponds to an example of an inner metal plate. The first surface 111 of the top wall 11 corresponds to an example of a first surface, the second surface 121 of the side wall 12 corresponds to an example of a second surface, and the first region 111A of the first metal plate 1 corresponds to an example of a region of the outer metal plate that will become the first surface. The spare third cover portion 23B corresponds to an example of a spare cover portion, and the third cover portion 23 corresponds to an example of a cover portion. The first end portion 231 of the third cover portion 23 corresponds to an example of a first end portion of a cover portion, and the second end portion 232 of the third cover portion 23 corresponds to an example of a second end portion of a cover portion. The second end portion 232B of the spare third cover portion 23B corresponds to an example of an end portion of the spare cover portion located on the side of the region of the outer metal plate that will become the second surface. Moreover, the first end 131B of the reverse bent portion 13B corresponds to an example of an end located on the side of the region that becomes the first surface of the outer metal plate in the reverse bent portion.

[0071] 5. Other Embodiments Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take on various forms.

[0072] (5a) In the above embodiment, the cross-sectional shape of the second metal plate 2a is U-shaped. However, for example, as in the molded product 100a of the first modified example shown in FIG. 10, the cross-sectional shape of the second metal plate 2a may be L-shaped. In this case, in the first bending step, bending in the first direction D1 is performed only on the portion of the welded blank where the second metal plate 2a overlaps. Although not shown, a reverse bent portion may be formed in the first metal plate 1a and a third cover portion may be formed in the second metal plate 2a. In other words, bending in the first direction D1 may not be performed on the portion of the welded blank where the second metal plate 2a does not overlap. In such a case, the same effects as those of (4a) to (4d) of the above embodiment can be obtained.

[0073] (5b) In the above embodiment, the second metal plate 2 is disposed inside the bent portion 13 of the first metal plate 1 and welded to the first metal plate 1 so as to overlap the bent portion 13 from the inside. However, for example, as in a molded product 100b of a second modified example shown in FIG. 11 , the second metal plate 2b may be disposed outside the bent portion 13 of the first metal plate 1 and welded to the first metal plate 1 so as to overlap the bent portion 13 from the outside. In other words, the second metal plate 2b may be overlapped on the outer surface of the bent portion 13. In the case of the molded product 100b shown in FIG. 11 , the first metal plate 1 corresponds to an example of an inner metal plate, and the second metal plate 2b corresponds to an example of an outer metal plate. Furthermore, the inner surface of the first cover portion 21b corresponds to an example of the first surface, the inner surface of the second cover portion 22b corresponds to an example of the second surface, the third cover portion 23b corresponds to an example of a bent portion, and the area of ​​the second metal plate 2b that forms the inner surface of the first cover portion 21b corresponds to an example of the area of ​​the outer metal plate that forms the first surface.

[0074] (5c) In the above embodiment, in the pre-welding step, the portion 21A of the second metal plate 2 before bending, which will become the first cover portion 21, is welded to the first region 111A that will become the first surface 111 of the first metal plate 1, thereby forming the first joint 3. Then, in the post-welding step, the second cover portion 22 of the second metal plate 2 after bending is welded to the second surface 121 of the first metal plate 1, thereby forming the second joint 4. However, the welds formed in the pre-welding step and the post-welding step are not limited to this. For example, in the pre-welding step, the portion of the second metal plate 2 before bending, which will become one of the second cover portions 22, may be welded to the region that will become the second surface of the first metal plate 1, thereby forming the first joint. Then, in the post-welding step, the first cover portion 21 of the second metal plate 2 after bending may be welded to the first surface 111 of the first metal plate 1, and the other second cover portion 22 may be welded to the second surface 121 of the first metal plate 1 that overlaps the other second cover portion 22. In such a case, the same effects as those of (4a) to (4d) of the above embodiment can be obtained.

[0075] (5d) In the above embodiment, the molded product 100 has a hat-shaped cross section. However, for example, the molded product may have a U-shaped or L-shaped cross section.

[0076] (5e) In the above embodiment, the reverse bent portion 13B is formed to satisfy all of the above conditions (A) to (C), but for example, the reverse bent portion may be formed to satisfy at least one of the conditions (A) to (C). In such a case, the same effect as at least the effect (4a) of the above embodiment can be obtained.

[0077] (5f) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0078] [6. Technical Ideas Disclosed in the Present Specification] [Item 1] A method for manufacturing a molded product, comprising: overlapping and welding the inner metal plate to the outer metal plate to form a first joint; After forming the first joint portion, bending the outer metal plate together with the inner metal plate in a first direction by a first press; After the first pressing, by a second pressing, bending the outer metal plate together with the inner metal plate in a second direction opposite to the first direction; Equipped with In the second pressing, a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first surface and the second surface and overlapping the inner metal plate are formed in the outer metal plate, In the first pressing, a reverse bent portion that bends in the opposite direction to the bent portion, and in which the inner metal plate is overlapped, is formed in the outer metal plate, The reverse bent portion is formed so as to overlap a region of the outer metal plate that will become the bent portion, the inner metal plate is disposed outside the reverse bent portion after the first pressing, and is disposed inside the bent portion after the second pressing; A method for manufacturing a molded product, wherein the first joint is a portion where the inner metal plate is welded to a region of the outer metal plate that becomes the first surface.

[0079] [Item 2] A method for producing a molded product according to item 1, The method for manufacturing a molded product further comprises welding the outer metal plate and the inner metal plate together after the second pressing to form a second joint portion where the inner metal plate is welded to the second surface.

[0080] [Item 3] A method for producing a molded product according to item 1 or 2, the inner metal plate has a preliminary cover portion that overlaps the reverse bent portion after the first pressing, and a cover portion that overlaps the bent portion after the second pressing, the cover portion has a first end portion located on the first surface side and a second end portion located on the second surface side, a method for manufacturing a molded product, wherein the reverse bent portion is formed so that a length from a position that becomes the first end of the inner metal plate to an end of the outer metal plate in the preliminary cover portion that is located on the side of a region that becomes the second surface is longer than a length from the first end to the second end of the cover portion.

[0081] [Item 4] A method for producing a molded product according to any one of items 1 to 3, The reverse bend portion is formed such that a first bend angle of the reverse bend portion is greater than a second bend angle of the bend portion, the first bending angle is an angle formed by a first inclined line along a preliminary opposite surface constituting a region of the outer metal plate opposite to the region of the outer metal plate that will become the second surface, with respect to an intersection line that intersects the region of the outer metal plate that will become the first surface substantially perpendicularly, in a cross section along a direction in which the first surface, the bent portion, and the second surface are aligned, A method for manufacturing a molded product, wherein the second bending angle is the angle formed by a second inclined line along the opposite surface of the outer metal plate opposite the second surface with respect to the intersection line in the cross section.

[0082] [Item 5] A method for producing a molded product according to any one of items 1 to 4, A method for manufacturing a molded product, wherein the reverse bent portion is formed so that the end portion of the reverse bent portion located on the side of the region that will become the first surface of the outer metal plate is located closer to the side of the region that will become the second surface of the outer metal plate than the position of the end portion of the outer metal plate on the side of the first surface of the bent portion. [Explanation of symbols]

[0083] 1...first metal plate, 2, 2a, 2b...second metal plate, 3...first joint portion, 4...second joint portion, 5A to 5C...first to third molds, 6A to 6C...fourth to sixth molds, 10...corner portion, 10B...preliminary corner portion, 11...top wall, 11B...preliminary top wall portion, 12...side wall, 12B...preliminary side wall portion, 13...bent portion, 13B to 13D...reverse bent portion, 14...flange portion, 21, 21b...first cover portion, 21B...preliminary first cover portion, 22, 22b...second cover portion, 22B...preliminary second cover portion, 23, 23b...third cover portion, 23 B...spare third cover part, 51A, 61B...protrusion, 51B, 61A...recess, 52B, 62A...through hole, 100, 100a, 100b...molded product, 101...preliminary molded product, 111...first surface, 111A...first region, 121...second surface, 122...opposite surface, 122B...spare opposite surface, 131, 131B-131D, 231, 231B...first end, 132, 132B, 232, 232B...second end, L1...intersection line, L2...first inclined line, L3...second inclined line, P1-P4...midpoint, R, R0...ridge line.

Claims

1. A method for manufacturing a molded product, comprising: overlapping and welding the inner metal plate to the outer metal plate to form a first joint; bending the outer metal plate together with the inner metal plate in a first direction by a first press after forming the first joint portion; After the first pressing, by a second pressing, bending the outer metal plate together with the inner metal plate in a second direction opposite to the first direction; Equipped with In the second pressing, a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first surface and the second surface and overlapping the inner metal plate are formed in the outer metal plate, In the first pressing, a reverse bent portion that is bent in the opposite direction to the bent portion and in which the inner metal plate is overlapped is formed in the outer metal plate, The reverse bent portion is formed so as to overlap a region of the outer metal plate that will become the bent portion, the inner metal plate is disposed on the outside of the reverse bent portion after the first pressing, and is disposed on the inside of the bent portion after the second pressing, A method for manufacturing a molded product, wherein the first joint is a portion where the inner metal plate is welded to a region of the outer metal plate that becomes the first surface.

2. A method for manufacturing a molded product according to claim 1, The method for manufacturing a molded product further comprises welding the outer metal plate and the inner metal plate together after the second pressing to form a second joint portion where the inner metal plate is welded to the second surface.

3. A method for manufacturing a molded product according to claim 1 or claim 2, the inner metal plate has a preliminary cover portion that overlaps the reverse bent portion after the first pressing, and a cover portion that overlaps the bent portion after the second pressing, the cover portion has a first end portion located on the first surface side and a second end portion located on the second surface side, a method for manufacturing a molded product, wherein the reverse bent portion is formed so that a length from a position that becomes the first end of the inner metal plate to an end of the outer metal plate in the spare cover portion that is located on the side of a region that becomes the second surface is longer than a length from the first end to the second end of the cover portion.

4. A method for manufacturing a molded product according to claim 1 or claim 2, The reverse bend portion is formed such that a first bend angle of the reverse bend portion is greater than a second bend angle of the bend portion, the first bending angle is an angle formed by a first inclined line along a preliminary opposite surface constituting a region of the outer metal plate opposite to the region of the outer metal plate that will become the second surface, with respect to an intersection line that intersects the region of the outer metal plate that will become the first surface substantially perpendicularly, in a cross section along a direction in which the first surface, the bent portion, and the second surface are aligned, A method for manufacturing a molded product, wherein the second bending angle is an angle formed by a second inclined line along an opposite surface of the outer metal plate opposite the second surface with respect to the intersection line in the cross section.

5. A method for manufacturing a molded product according to claim 1 or claim 2, A method for manufacturing a molded product, wherein the reverse bent portion is formed so that the end portion of the outer metal plate located on the side of the region that will become the first surface is located closer to the region that will become the second surface of the outer metal plate than the position of the end portion of the outer metal plate on the first surface side of the bent portion.

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