Manufacturing method for molded products

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 product.

Background Art

[0002] In the drawing or bending of a metal plate, in order to increase the strength, a reinforcing plate (that is, a patch) is overlapped and welded to the base material of the metal plate, and then pressing is performed. In such processing, a difference in elongation length due to pressing occurs between the reinforcing plate disposed on the inner side of the bending and the base material disposed on the outer side. As a result, shear stress is generated at the welded portion of the reinforcing plate, and there is a risk of cracking.

[0003] Here, Patent Document 1 discloses a method for manufacturing a molded product having a top plate portion, two vertical wall portions, and a bending portion located between the top plate portion and each vertical wall portion, after overlapping and welding a main body blank material and a reinforcing blank material and then pressing. In this manufacturing method, before pressing, a joint portion is provided at a portion corresponding to each vertical wall portion in the main body blank material and the reinforcing blank material. Further, before welding, a convex shape for suppressing cracking of the joint portion is formed on the main body blank material disposed on the outer side of the bending. Then, the molded product is manufactured such that a bending portion is formed at the portion where the convex shape is provided.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As another method for suppressing cracking of the joint portion in two welded plate materials, for example, in two plate materials, a joint portion is not provided in a portion corresponding to the vertical plate portion in advance, and a joint portion is provided only in a portion corresponding to the top plate portion, and then after pressing the two plate materials, a joint portion is provided in the vertical wall portion.

[0006] However, with this alternative method, a gap may form between the two plates in the vertical wall section due to the difference in the amount of springback between the two plates after pressing. When such a gap forms, welding the two plates in the vertical wall section after pressing tends to become difficult.

[0007] One aspect of this disclosure is to provide a method for manufacturing a molded product that can suppress cracking at the joint between two welded plate materials while facilitating the formation of the joint. [Means for solving the problem]

[0008] One aspect of this disclosure is a method for manufacturing a molded product. The method comprises: overlapping an inner metal plate with an outer metal plate and welding them together to form a first joint; and, after the formation of 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 comprises, 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. In the second press, a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first and second surfaces and overlapping with the inner metal plate are formed on the outer metal plate. In the first press, a reverse bent portion, which bends in the opposite direction to the bent portion and overlaps with the inner metal plate, is formed on the outer metal plate. The reverse bent portion is formed on the outer metal plate so as to overlap with the region 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 the area where the inner metal plate is welded to the first surface region of the outer metal plate.

[0009] In this configuration, even if the outer metal plate is bent together with the inner metal plate by the first and second pressings, and a difference in elongation length occurs between the outer and inner metal plates, stress is less likely to concentrate at the first joint. Furthermore, since the outer and inner metal plates are first bent in the first direction before being bent in the second direction, even if springback occurs in the outer and inner metal plates 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 pressing is easily reduced. Therefore, it is possible to suppress cracking at the first joint in the two welded metal plates while facilitating the formation of the joint that can be formed between the second surface of the inner and outer metal plates.

[0010] One aspect of the present disclosure may further include welding the outer metal plate and the inner metal plate after the second pressing to form a second joint, which is the portion of the inner metal plate that is welded to the second surface. With this configuration, the second joint is formed in a state that is less affected by the difference in elongation length between the outer and inner metal plates due to the second pressing. Therefore, cracks are less likely to occur in the second joint. In addition, the second joint is formed with a reduced gap between the second surface of the inner and outer metal plates after the second pressing. Therefore, the formation of the second joint is easier.

[0011] In one aspect of this disclosure, the inner metal plate may have a pre-cover portion that overlaps the reverse bend portion after the first press, and a cover portion that overlaps the bend portion after the second press. The cover portion may have a first end located on the first surface side and a second end located on the second surface side. The reverse bend portion may be formed such that the length from the position of the first end of the inner metal plate to the end of the pre-cover portion located on the side of the second surface of the outer metal plate is longer than the length from the first end to the second end of the cover portion.

[0012] In this configuration, the portion of the outer metal plate in the pre-cover section that is located near the end on the side that will become the second surface, which has undergone curvature deformation in the first direction due to the first press, extends in a nearly straight line after the second press. This makes it easier for springback to occur, causing the inner metal member to be pressed against the second surface of the outer metal plate. Therefore, the gap between the inner metal plate and the second surface of the outer metal plate after the second press can be further reduced.

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

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

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

[0016] With this configuration, the first pressing is less likely to cause curvature deformation in the first surface region of the outer metal plate, thus suppressing the retention of a bending curvature in the first direction on the first surface during the second pressing. [Brief explanation of the drawing]

[0017] [Figure 1]It is a perspective view schematically showing a molded product. [Figure 2] It is a side view schematically showing a molded product. [Figure 3] FIG. 3A is a schematic cross-sectional view along the short side direction at the position of the first joint of the blank material after the pre-welding process. FIG. 3B is a schematic cross-sectional view along the short side direction at the position of the first joint of the blank material after the first bending process. FIG. 3C is a schematic cross-sectional view along the short side direction at the position of the first joint of the blank material after the second bending process. FIG. 3D is a schematic cross-sectional view along the short side direction at the positions of the first joint and the second joint of the molded product completed after the post-welding process. [Figure 4] It is a flowchart showing a method for manufacturing a molded product. [Figure 5] It is a figure for explaining the first bending process. [Figure 6] It is a figure for explaining the second bending process. [Figure 7] It is a figure for explaining the relationship between the bent portion and the reverse bent portion. [Figure 8] It is a figure for explaining the reverse bent portion of the first comparative example. [Figure 9] It is a figure for explaining the reverse bent portion of the second comparative example. [Figure 10] It is a schematic side view along the short side direction of the molded product of the first modified example. [Figure 11] It is a schematic side view along the short side direction of the molded product of the second modified example.

Embodiments for Carrying Out the Invention

[0018] [[ID=3b7]] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration of Molded Product] The molded product 100 shown in FIGS. 1 and 2 is formed by bending a blank material (hereinafter simply referred to as a blank material), which is a plate material obtained by overlapping a first metal plate 1 and a second metal plate 2, by welding and pressing.

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

[0020] The molded product 100 is used, for example, as a component of the body of an automobile. In this embodiment, the molded product 100 is a rocker provided on the lower part 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 comprises 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 surface of the top wall 11 extends in directions that intersect with the surfaces of the two side walls 12, which are spaced apart from each other. The top wall 11 has a first surface 111. The side walls 12 have a second surface 121 that extends in a direction intersecting with the first surface 111. The first surface 111 is the surface of the top wall 11 that is continuous with the inner surface of the bent portion 13, which will be described later. The second surface 121 is the surface of the side walls 12 that is continuous with the inner surface of the bent portion 13, which will be described later.

[0023] The bent portion 13 is the part between the top wall 11 and the side wall 12, and is bent by the bending process of the first metal plate 1. The bent portion 13 constitutes the 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 of the side wall 12 opposite to the top wall 11 through a bending process of the first metal plate 1. The plate surface of the flange portion 14 widens in a direction that intersects with the plate surface of the side wall 12.

[0025] <Second metal plate> The second metal plate 2, like the first metal plate 1, is made of, for example, a steel plate. The materials of the first and second metal plates are not particularly limited. Furthermore, the first and second metal plates 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 welded to the first metal plate 1 by overlapping it. The second metal plate 2 is positioned to straddle 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. In other words, the second metal plate 2 is positioned 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 length L of the second metal plate 2 is shorter than that of the first metal plate 1, and it overlaps only a portion of the first metal plate 1 along its longitudinal direction L. Alternatively, the second metal plate may have approximately the same length L as the first metal plate and overlap the first metal plate over its entire length from end to end along its 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 23. The first cover portion 21 is the part that overlaps the first surface 111 of the first metal plate 1.

[0028] Each second cover portion 22 is a part that overlaps each second surface 121 of the first metal plate 1. Each third cover portion 23 is a part 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. Together with the bent portions 13 of the first metal plate 1, the third cover portion 23 constitutes the corner portion 10 of the molded product 100.

[0029] In this embodiment, the molded product 100 is configured such that, for example, 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 greater than the thickness of the first metal plate 1. The tensile strength of the first metal plate is not limited to the above value. Furthermore, the thicknesses of the first and second metal plates are not particularly limited. The thicknesses of the first and second metal plates may be the same or different.

[0030] <1st joint> As shown in Figure 1, the first joint 3 is the portion in 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 of the blank material. Therefore, as shown in Figure 3A, the first joint 3 is the portion in the blank material where the portion 21A that becomes the first cover portion 21 of the second metal plate 2 is welded to the first region 111A that becomes the first surface 111 of the first metal plate 1. Multiple first joints 3 are provided. As shown in Figure 1, multiple first joints 3 are arranged in the longitudinal direction L with spaces between them. Note that multiple first joints may be provided arranged in the short direction S.

[0031] <Second joint> The second joint 4 is a portion of the molded product 100 where each second cover portion 22 of the second metal plate 2 is welded to each second surface 121 of the first metal plate 1. As will be described in detail later, in this embodiment, unlike the first joint 3, the second joint 4 is formed after the bending of the blank material. Multiple second joints 4 are provided. Multiple second joints 4 are arranged at intervals from each other in the longitudinal direction L. Multiple second joints may also be provided arranged in the short direction S.

[0032] The first joint 3 and the second joint 4 are each composed of, for example, nuggets formed at the welding points of spot welding. Each joint may penetrate either the first or second metal plate.

[0033] [2. Method for manufacturing molded products] Next, a method for manufacturing the molded product 100 described above will be explained using Figures 3A to 3D and Figures 4 to 6. The manufacturing method for 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> First, as shown in Figure 3A, a flat second metal plate 2 is overlapped and welded onto a flat first metal plate 1 to form a first joint 3. Specifically, the second metal plate 2 is overlapped so as to span the first portion 11A which will become the top wall 11, the second portion 12A which will become the two side walls 12, and the third portion 13A which will become the two bent portions 13 of the first metal plate 1 before bending. Then, the first joint 3 is formed by, for example, spot welding the portion 21A of the second metal plate 2 which will become the first cover portion 21 to the first region 111A which will become the first surface 111 of the first metal plate 1.

[0035] <First bending process> Next, as shown in Figure 3B, after the formation of the first joint 3 described above, the first metal plate 1 is bent in the first direction D1 together with the second metal plate 2 to form the preliminary corner 10B. The first direction D1 is the opposite bending direction to the second direction D2, which is the bending direction used when bending 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 the extent that they undergo plastic deformation. The preliminary corner 10B is formed by pressing the blank material in the thickness direction, similar to the corner 10.

[0036] Specifically, the blank material obtained in the pre-welding process S10 is subjected to a first cold press to form a preliminary corner portion 10B using the first mold 5A, second mold 5B, and third mold 5C shown in Figure 5. The blank material having the preliminary corner portion 10B is also referred to as a preliminary molded product 101.

[0037] As a result, the first metal sheet 1 is press-formed, and a preliminary top wall portion 11B, two preliminary side wall portions 12B, and two reverse bend portions 13B are formed on the first metal sheet 1. The preliminary top wall portion 11B is the portion that will mostly become the top wall 11 of the molded product 100. The preliminary side wall portion 12B is the portion that will mostly become the side wall 12 of the molded product 100. The reverse bend portions 13B are the portions between the preliminary top wall portion 11B and the preliminary side wall portions 12B, and are bent in the opposite direction to the bend portion 13. The reverse bend portions 13B are formed in the first metal sheet 1 after bending in the first direction D1 such that they partially or completely overlap with the region that will become the bend portion 13 in the first metal sheet 1. The reverse bend portions 13B constitute the preliminary corner portion 10B of the preliminary molded product 101.

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

[0039] As shown in Figure 5, the first mold 5A is positioned above the second mold 5B and facing the second mold 5B. The first mold 5A has a projection 51A projecting toward the second mold 5B in its approximate center. The projection 51A has surfaces capable of forming a spare top wall portion 11B, two spare side wall portions 12B, and two reverse bend portions 13B of the pre-molded product 101. The second mold 5B has a recess 51B in a position facing the projection 51A of the first mold 5A into which the projection 51A can be fitted. The recess 51B has surfaces capable of forming a spare first cover portion 21B, two spare second cover portions 22B, and two spare third cover portions 23B of the pre-molded product 101. The second mold 5B has a through hole 52B into which the third mold 5C is inserted, in a position facing the surface of the projection 51A that forms the spare top wall portion 11B. In other words, the through hole 52B is located approximately in the center of the recess 51B. The third mold 5C is inserted into the through hole 52B of the second mold 5B and is positioned to be movable relative to the second mold 5B.

[0040] In this embodiment, a welded blank material is placed between the second mold 5B, in which the third mold 5C is inserted into the through hole 52B, and the first mold 5A. Then, the first mold 5A and the second mold 5B are brought closer together, and the protruding portion 51A is fitted into the recess 51B, thereby forming the aforementioned pre-molded product 101. At this time, the third mold 5C is pushed downward by the protruding portion 51A.

[0041] <Second bending process> Next, as shown in Figure 3C, after the first cold press bending in the first direction D1 described above, 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 corner portion 10 is formed on the blank material obtained after bending in the first bending process S20 (i.e., the pre-formed product 101) by a second cold press using the fourth die 6A, fifth die 6B, and sixth die 6C shown in Figure 6.

[0042] As a result, the first metal plate 1, after being bent in the first direction D1, is press-formed, and a top wall 11 (i.e., a first surface 111), two side walls 12 (i.e., 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 being bent in the first direction D1, is bent along the top wall 11, the two side walls 12, and the two bent sections 13. As a result, a first cover section 21, two second cover sections 22, and two third cover sections 23 are formed on the second metal plate 2.

[0044] As shown in Figure 6, the fourth mold 6A is positioned above the fifth mold 6B and opposite the fifth mold 6B. The fifth mold 6B has a projection 61B projecting toward the fourth mold 6A in its approximate center. The projection 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 recess 61A in a position opposite to the projection 61B of the fifth mold 6B into which the projection 61B can be fitted. The recess 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 into which the sixth mold 6C is inserted, in a position opposite to the surface of the projection 61B that molds the first cover portion 21. That is, the through hole 62A is located approximately in the center of the recess 61A. The sixth mold 6C is inserted into the through hole 62A of the fourth mold 6A and is positioned to be movable relative to the fourth mold 6A.

[0045] In this embodiment, the spare molded product 101 is positioned between the fourth mold 6A and the fifth mold 6B, with the sixth mold 6C inserted into the through hole 62A, such that the spare top wall portion 11B and the spare 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 positioned above the fifth mold 6B so as not to interfere with the spare side wall portion 12B of the spare molded product 101. Then, the fourth mold 6A and the fifth mold 6B are brought closer together, and the protruding portion 61B is fitted into the recess 61A, thereby forming the blank material having the corner portion 10 described above.

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

[0047] <Post-welding process> Next, as shown in Figure 3D, after the second cold pressing process in the second direction D2 described above, the first metal plate 1 and the second metal plate 2 are further welded together to form a second joint 4. That is, the second joint 4 is formed on the blank material obtained after bending in the second bending process S30. Specifically, the second joint 4 is formed by spot welding, for example, 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 pre-welding process S10, first bending process S20, second bending process S30, and post-welding process S40.

[0049] [3. Relationship between the bent section and the reverse bent section] Next, the relationship between the bent portion 13 and the reverse bent portion 13B will be explained using Figure 7.

[0050] As shown in Figure 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, which overlaps 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] Furthermore, the reverse-bent portion 13B has a first end 131B located on the side of the spare top wall portion 11B and a second end 132B located on the side of the spare side wall portion 12B. Also, the spare third cover portion 23B that overlaps the reverse-bent portion 13B has a first end 231B located on the side of the spare first cover portion 21B (i.e., the side of the region that will become the first surface 111 of the first metal plate 1) and a second end 232B located on the side of the spare second cover portion 22B (i.e., the side of the region that will become the second surface 121 of the first metal plate 1).

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

[0053] In this embodiment, the center points in the thickness direction of each end 231, 232 of the third cover portion 23 are defined as midpoints P1 and P2, and the center point in the thickness direction of the second end 232B of the spare third cover portion 23B is defined as midpoint P3. In this case, the reverse bend portion 13B is formed such that the length from midpoint P1 to midpoint P3 in the spare molded product 101 is longer than the length from midpoint P1 to midpoint P2 in the molded product 100. As an example of satisfying the above condition (A), if the radius of curvature of the bend portion 13 in the molded product 100 is approximately 5 mm, it is preferable that the radius of curvature of the reverse bend portion 13B in the spare molded product 101 is approximately 7 mm or more.

[0054] (B) The first bending angle θ1 of the reverse bending portion 13B is greater than the second bending angle θ2 of the bending portion 13. The first bending angle θ1 is the angle that the first inclined line L2 makes with respect to the intersecting line L1 in a cross section along the shorter direction S. The intersecting line L1 is a line that intersects the region of the first metal plate 1 that becomes the first surface 111 approximately perpendicular to it (in other words, approximately perpendicular to the preliminary top wall portion 11B) in the said cross section. The first inclined line L2 is a line that follows the preliminary opposite surface 122B (in other words, the plate surface of the preliminary side wall portion 12B) which constitutes the region opposite to the region of the first metal plate 1 that becomes the second surface 121 in the said cross section.

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

[0056] For example, if 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 relative to the first bending angle θ1 of the reverse bent portion 13B will be as follows. The gap is measured at approximately the midpoint between the end of each second cover portion 22 on the third cover portion 23 side and the end on the opposite side of that end. This midpoint is the position where the second joint portion 4 is assumed 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 bending in the first direction D1 is not 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 bend 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 is 25° or more and less than 50°.

[0058] (C) The first end portion 131B of the reverse bend portion 13B is located on the side of the reserve side wall portion 12B than the position of the first end portion 131 of the bend portion 13 of the first metal plate 1.

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

[0060] (4a) In this embodiment, when the blank material 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, with respect to the ridge line R0 of the reverse bend portion 13B of the first metal plate 1 formed by the bending process. 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, with respect to the ridge line R0 of the reverse bend portion 13B.

[0061] Furthermore, when bending is performed in the second direction D2 on a blank material having a pre-corner 10B, only the first surface 111 located on the first side, relative to the edge radius 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 3. On the other hand, the second surface 121 located on the second side, relative to the edge radius R of the bent portion 13, is not joined to the second metal plate 2. Thus, in any bending process, the blank material does not have a second joint 4.

[0062] As a result, even if the first metal sheet 1 is bent together with the second metal sheet 2 by the first cold press, and a difference in elongation length along the reverse bend portion 13B occurs between the first metal sheet 1 and the second metal sheet 2, the second metal sheet 2 is less likely to be constrained in the region that becomes the second surface 121 of the first metal sheet 1. Similarly, even if the first metal sheet 1 is bent together with the second metal sheet 2 by the second cold press, and a difference in elongation length along the bend portion 13 occurs between the first metal sheet 1 and the second metal sheet 2, the second metal sheet 2 is less likely to be constrained in the second surface 121 of the first metal sheet 1. Therefore, stress is less likely 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 reduces the gap even if springback occurs in each metal plate 1 and 2 due to bending in the second direction D2, regardless of the combination of material strength and thickness of the first metal plate 1 and the second metal plate 2. As a result, the formation of the second joint 4 becomes easier.

[0064] Furthermore, 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 affected by the difference in elongation length along the bent portion 13 between the first metal sheet 1 and the second metal sheet 2 due to the second cold pressing. Therefore, it is possible to suppress cracking at the joints 3 and 4 in the welded first metal plate 1 and second metal plate 2 while facilitating the formation of the second joint 4.

[0065] (4b) In this embodiment, the reverse bend portion 13B is formed such 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. That is, the reverse bend portion 13B is formed to satisfy the above-described condition (A). As a result, the portion near the second end 232B of the preformed third cover portion 23B, which underwent curvature deformation in the first direction D1 by the first cold press, extends in a substantially straight line after the second cold press. Specifically, as shown in Figure 7, the midpoint P3 in the preformed product 101 is located at the midpoint P4 in the molded product 100 after the second cold press. Since the midpoint P4 is located at the side wall 12 which extends in a substantially straight line, the distance from midpoint P2 to midpoint P4 in the molded product 100 extends in a substantially straight line. This makes it easy for springback to occur, such that the second metal plate 2 is pressed against the second surface 121 of the first metal plate 1. Therefore, gaps can be further reduced.

[0066] (4c) For example, if the first bending angle of the reverse bend is smaller than or equal to the second bending angle of the bend, the warping of the spare side wall relative to the spare top wall tends to be larger in the preformed product. As a result, the spare side wall 12B and the fourth die 6A used for the second cold press tend to interfere with each other. On the other hand, in this embodiment, the reverse bend 13B is formed such that the first bending angle θ1 of the reverse bend 13B is larger than the second bending angle θ2 of the bend 13. That is, the reverse bend 13B is formed to satisfy the above-described condition (B). As a result, the warping of the spare side wall 12B relative to the spare top wall 11B in the preformed product 101 is reduced. As a result, interference between the spare side wall 12B in the preformed product 101 after the first cold press and the fourth die 6A used for the second cold press can be suppressed during the second cold press.

[0067] (4d) In this embodiment, the first end portion 131B of the reverse bend portion 13B is located on the side of the reserve sidewall portion 12B than the position of the first end portion 131 of the bend portion 13 in the first metal plate 1. That is, the reverse bend portion 13B is formed to satisfy the above-described condition (C). As a result, the first cold press makes it less likely for a curved deformation to occur in the first region 111A of the first metal plate 1. Therefore, in this embodiment, it is possible to suppress the retention of a bending tendency in the first direction D1 on the first surface 111 (i.e., the top wall 11) during the second cold press.

[0068] Furthermore, as shown in the simplified reverse-bent portion 13C of the first comparative example and the reverse-bent portion 13D of the second comparative example in Figures 8 and 9, if the above-mentioned condition (B) is satisfied but condition (C) is not, a portion that undergoes curvature deformation is likely to occur in the first region 111A of the first metal sheet 1 after the first cold press. As shown in Figures 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 on the side of the first region 111A, which is the first surface 111 of the bent portion 13, rather than the position that becomes the first end 131 of the bent portion 13 in the first metal sheet 1. For this reason, when the reverse-bent portions 13B and 13C shown in Figures 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) after the second cold press.

[0069] (4e) In this embodiment, the molded product 100 is configured such that, for example, 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 greater than the thickness of the first metal plate 1. In such a configuration, if the first bending process S20 is not performed before the second bending process S30, the gap tends to be large. However, in this embodiment, since the first bending process S20 is performed before the second bending process S30, the gap tends to be reduced more easily.

[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. Also, 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 that becomes the first surface of the outer metal plate. Also, 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. Also, 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. Also, the second end portion 232B of the spare third cover portion 23B corresponds to an example of an end portion located on the side of the region that becomes the second surface of the outer metal plate in the spare cover portion. Furthermore, the first end portion 131B of the reverse-bent portion 13B corresponds to an example of an end portion located on the side of the outer metal plate in the reverse-bent portion that becomes the first surface.

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

[0072] (5a) In the above embodiment, the cross-sectional shape of the second metal plate 2 was U-shaped, but the cross-sectional shape of the second metal plate 2a may be L-shaped, for example, as shown in the molded product 100a of the first modified example in Figure 10. In this case, in the first bending process, bending in the first direction D1 is performed only on the portion of the blank material after welding in which the second metal plate 2a overlaps, and although not shown, a reverse bend portion may be formed on the first metal plate 1 and a third cover portion on the second metal plate 2a. That is, bending in the first direction D1 is not required on the portion of the blank material after welding in which the second metal plate 2a does not overlap. In this case as well, the same effects as those of (4a) to (4d) in the above embodiment can be obtained.

[0073] (5b) In the above embodiment, the second metal plate 2 is positioned inside the bent portion 13 of the first metal plate 1 and is welded to the first metal plate 1 so as to overlap the bent portion 13 from the inside. However, for example, as shown in the molded product 100b of the second modified example in Figure 11, the second metal plate 2b may be positioned 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 superimposed on the outer surface of the bent portion 13. In the case of the molded product 100b shown in Figure 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 the bent portion, and the region of the second metal plate 2b that becomes the inner surface of the first cover portion 21b corresponds to an example of the region of the outer metal plate that becomes the first surface.

[0074] (5c) In the above embodiment, in the pre-welding process, the portion 21A of the second metal plate 2 before bending that 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 to form the first joint portion 3. Then, in the post-welding process, 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 to form the second joint portion 4. However, the welds formed in the pre-welding and post-welding processes are not limited to these. For example, in the pre-welding process, one portion of the second metal plate 2 before bending that will become the second cover portion 22 may be welded to the region that will become the second surface of the first metal plate 1 to form the first joint portion. Furthermore, in the post-welding process, 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 with the other second cover portion 22 to form a second joint. In this case as well, 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 had a hat-shaped cross-section, but for example, the molded product may have a U-shaped or L-shaped cross-section.

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

[0077] (5f) The functions of one component in the above embodiment may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, some parts of the configuration of the above embodiment may be omitted. Also, at least some parts of the configuration of the above embodiment may be added to, replaced with, or otherwise adapted to the configuration of other above embodiments.

[0078] [6. The technical concept disclosed herein] [Item 1] A method for manufacturing molded products, The inner metal plate is overlapped and welded to the outer metal plate to form the first joint, After the formation of the first joint, the outer metal plate is bent in the first direction together with the inner metal plate by a first press, After the first press, a second press is performed to bend 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 and second surfaces and where the inner metal plates are overlapped are formed on the outer metal plate. In the first pressing, a reverse bend portion is formed on the outer metal plate, which bends in the opposite direction to the bend portion, and the inner metal plates are overlapped in this reverse bend portion. The reverse bend portion is formed in the outer metal plate so as to overlap with the region that will become the bend portion. The inner metal plate is positioned outside the reverse bend after the first press, and inside the bend after the second press. A method for manufacturing a molded product, wherein the first joint is a portion in which the inner metal plate is welded to the region of the outer metal plate that becomes the first surface.

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

[0080] [Item 3] A method for manufacturing a molded article as described in item 1 or item 2, The inner metal plate has a preliminary cover portion that overlaps the reverse bend portion after the first press, and a cover portion that overlaps the bend portion after the second press. The cover portion has a first end located on the first surface side and a second end located on the second surface side. A method for manufacturing a molded product, wherein the reverse-bent portion is formed such that the length from the position of the first end of the inner metal plate to the end of the outer metal plate in the spare cover portion that is located on the side of the second surface is longer than the length from the first end to the second end of the cover portion.

[0081] [Item 4] A method for manufacturing a molded article as described in any one of items 1 to 3, The reverse-bent portion is formed such that the first bending angle of the reverse-bent portion is greater than the second bending angle of the bent portion. The first bending angle is the angle formed by a first inclined line along the preliminary opposite surface that constitutes the region opposite to the region that becomes the second surface of the outer metal plate, with respect to an intersection line that intersects substantially perpendicularly with the region that becomes the first surface of the outer metal plate, in a cross section along the 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 in the cross section by a second inclined line along the opposite side of the second surface of the outer metal plate with respect to the intersecting line.

[0082] [Item 5] A method for manufacturing a molded article as described in any one of items 1 to 4, A method for manufacturing a molded product, wherein the reverse bend portion is formed such that the end of the outer metal plate located on the side of the first surface region in the reverse bend portion is located on the side of the outer metal plate that will become the second surface region, rather than the position of the end of the outer metal plate located on the first surface side of the bend portion. [Explanation of Symbols]

[0083] 1...First metal plate, 2,2a,2b...Second metal plate, 3...First joint, 4...Second joint, 5A~5C...First to third molds, 6A~6C...Fourth to sixth molds, 10...Corner, 10B...Reserve corner, 11...Top wall, 11B...Reserve top wall, 12...Side wall, 12B...Reserve side wall, 13...Bent section, 13B~13D...Reverse bent section, 14...Flange section, 21,21b...First cover section, 21B...Reserve first cover section, 22,22b...Second cover section, 22B...Reserve second cover section, 23,23b...Third cover section, 23 B... Spare third cover section, 51A, 61B... Protruding section, 51B, 61A... Recessed section, 52B, 62A... Through hole, 100, 100a, 100b... Molded product, 101... Spare 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 section, 132, 132B, 232, 232B... Second end section, L1... Intersecting line, L2... First inclined line, L3... Second inclined line, P1~P4... Midpoint, R, R0... Ridge line.

Claims

1. A method for manufacturing molded products, The inner metal plate is overlapped and welded to the outer metal plate to form the first joint, After the formation of the first joint, the outer metal plate is bent in the first direction together with the inner metal plate by a first press, After the first press, a second press is performed to bend 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 and second surfaces and where the inner metal plates are overlapped are formed on the outer metal plate. In the first pressing, a reverse bend portion is formed on the outer metal plate, which bends in the opposite direction to the bend portion, and the inner metal plates are overlapped in this reverse bend portion. The reverse bend portion is formed in the outer metal plate so as to overlap with the region that will become the bend portion. The inner metal plate is positioned outside the reverse bend after the first press, and inside the bend after the second press. A method for manufacturing a molded product, wherein the first joint is a portion in which 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 article according to claim 1, A method for manufacturing a molded product, further comprising welding the outer metal plate and the inner metal plate after the second pressing to form a second joint, which is the portion where the inner metal plate is welded to the second surface.

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

4. A method for manufacturing a molded article according to claim 1 or claim 2, The reverse-bent portion is formed such that the first bending angle of the reverse-bent portion is greater than the second bending angle of the bent portion. The first bending angle is the angle formed by a first inclined line along the preliminary opposite surface that constitutes the region opposite to the region that becomes the second surface of the outer metal plate, with respect to an intersection line that intersects substantially perpendicularly with the region that becomes the first surface of the outer metal plate, in a cross section along the 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 in the cross section by a second inclined line along the opposite side of the second surface of the outer metal plate with respect to the intersecting line.

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

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