Structural member and method for manufacturing the same

Abstract

This method for manufacturing a structural member (10) is provided with a step for preparing a blank (30) and a step for shaping the blank (30) into the structural member (10). The blank (30) includes a first portion (31) and a second portion (32) continuous with the first portion (31). The structural member (10) includes a first member (11) and a second member (12). In the shaping step, in the state in which a mold (40) is restraining the first member (11) from a first direction (D1) and is restraining flanges (123, 123a, 123b) of the second member (12) from a second direction (D2), a top plate (121) and vertical walls (122, 122a, 122b) of the second member (12) are shaped by the mold (40) from the second direction (D2).

Description

Technical Field

[0001] The present disclosure relates to a structural member and a method for manufacturing the same.

Background Art

[0002] Structures such as automobile bodies are composed of a plurality of structural members. Each of the structural members is produced, for example, by processing a blank with a die. The structure is formed by joining the molded structural members by welding.

[0003] In recent years, in the automotive field, the trend to integrate structural members for vehicle bodies at the blank stage has been accelerating. When a module composed of a plurality of structural members is molded from a single blank, the number of parts of the vehicle body can be reduced compared to the case where a plurality of structural members are joined after molding. As a result, steps in manufacturing the vehicle body can be omitted, and emissions of greenhouse gases (life cycle GHG) over the entire life cycle of the vehicle body can be reduced.

[0004] However, when a module that has conventionally been composed of a plurality of structural members is molded as a single structural member, a portion with a negative angle relative to the working direction of the die may occur in this structural member. If there is a portion with a negative angle relative to the working direction, molding of the structural member becomes difficult.

[0005] Patent Document 1 discloses a technique of forming negative angle portions (groove-shaped bead portions) on the left and right vertical walls of a structural member having a hat-shaped cross section. In Patent Document 1, a die including an upper die, a lower die, and a pair of slide dies attached to both side surfaces of the upper die via cam mechanisms is used. The lower die includes a central die and a pair of split dies attached to both side surfaces of the central die via cam mechanisms. In Patent Document 1, the pair of split dies are separated in the width direction of the die as the die clamping operation of the die proceeds. Further, the pair of slide dies approach each other in the width direction of the die as the die clamping operation proceeds. Then, each vertical wall is sandwiched between the split die and the slide die, and the bead portion is formed on the vertical wall.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-83807 [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, when multiple components are molded together as a single structural component, portions of this component may have negative angles relative to the die's machining direction. Furthermore, when multiple components are molded together as a single structural component, it may be necessary to mold flanges parallel to the die's machining direction. For example, when multiple components, each having a hat shape in cross-section, are molded together as a single structural component, if the top plate of one adjacent component is bent relative to the top plate of the other, the top plate of one of the components may have a negative angle relative to the die's machining direction. Also, if the top plate of one adjacent component is bent relative to the top plate of the other, it is possible that the flange of one of the components may be substantially parallel to the die's machining direction. Therefore, it is difficult to mold such components together from a single blank. When the top plates of one component and the top plate of the other component are bent at an angle of 150° or less, it becomes even more difficult to mold these components together as a single structural component.

[0008] The object of this disclosure is to provide a method for manufacturing a structural member that allows the first member and the second member to be integrally molded as a single structural member, even when the top plate of the first member and the top plate of the second member are bent at an angle of 150° or less. [Means for solving the problem]

[0009] A method for manufacturing a structural member according to this disclosure comprises the steps of preparing a blank and forming the blank into a structural member using a mold. The blank includes a first portion and a second portion continuous with the first portion. The structural member includes a first member and a second member. The first member includes a first top plate, a pair of first vertical walls, and a pair of first flanges. The first vertical walls are connected to both side edges of the first top plate. The first flanges are connected to the first vertical walls on the opposite side of the first top plate. The first flanges protrude outward from the first vertical walls. The second member includes a second top plate, a pair of second vertical walls, and a pair of second flanges. The second top plate is bent relative to the first top plate at an angle of 150° or less. The second vertical walls are connected to both side edges of the second top plate. The second flanges are connected to the second vertical walls on the opposite side of the second top plate. The second flanges protrude outward from the second vertical walls. In the molding process, the first part is molded into the first member and the second part is molded into the second member. In the molding process, the first member is restrained from the first direction by the mold, and the second flange is restrained from the second direction perpendicular to the first direction, while the second top plate and the second vertical wall are molded from the second direction by the mold. [Effects of the Invention]

[0010] According to the manufacturing method of the structural member described herein, even when the top plate of the first member and the top plate of the second member are bent at an angle of 150° or less, the first member and the second member can be integrally molded as a single structural member. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view of a structural member according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view of the first member included in the structural member shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the second member included in the structural member shown in Figure 1. [Figure 4] Figure 4 is a longitudinal cross-sectional view of the structural member shown in Figure 1. [Figure 5A] Figure 5A is a schematic diagram illustrating the manufacturing method of a structural member according to the embodiment. [Figure 5B] Figure 5B is a schematic diagram illustrating the manufacturing method of a structural member according to the embodiment. [Figure 5C] Figure 5C is a schematic diagram illustrating the manufacturing method of a structural member according to the embodiment. [Figure 5D] Figure 5D is a schematic diagram illustrating the manufacturing method of a structural member according to the embodiment. [Figure 5E] Figure 5E is a schematic diagram illustrating the manufacturing method of a structural member according to the embodiment. [Figure 5F] Figure 5F is a schematic diagram illustrating the manufacturing method of a structural member according to the embodiment. [Figure 6] Figure 6 is a perspective view of a structural member according to a modified example of the embodiment. [Figure 7] Figure 7 is a perspective view of a structural member relating to another modified embodiment. [Modes for carrying out the invention]

[0012] A method for manufacturing a structural member according to an embodiment comprises the steps of preparing a blank and forming the blank into a structural member using a mold. The blank includes a first portion and a second portion continuous with the first portion. The structural member includes a first member and a second member. The first member includes a first top plate, a pair of first vertical walls, and a pair of first flanges. The first vertical walls are connected to both side edges of the first top plate. The first flanges are connected to the first vertical walls on the opposite side of the first top plate. The first flanges protrude outward from the first vertical walls. The second member includes a second top plate, a pair of second vertical walls, and a pair of second flanges. The second top plate is bent relative to the first top plate at an angle of 150° or less. The second vertical walls are connected to both side edges of the second top plate. The second flanges are connected to the second vertical walls on the opposite side of the second top plate. The second flanges protrude outward from the second vertical walls. In the molding process, the first part is molded into the first member and the second part is molded into the second member. In the molding process, the first member is restrained from the first direction by the mold, and the second flange is restrained from the second direction perpendicular to the first direction, while the second top plate and the second vertical wall are molded from the second direction by the mold (first configuration).

[0013] In the manufacturing method according to the first configuration, the first member of the structural member is formed from the first portion of the blank, and the second member of the structural member is formed from the second portion of the blank that is continuous with the first portion. In the step of forming the structural member from the blank, while the first member is restrained from the first direction by a die, and the flange (second flange) of the second member is restrained from the second direction perpendicular to the first direction, the top plate (second top plate) and the vertical wall (second vertical wall) of the second member are formed from the second direction by the die. By forming the second top plate from the second direction different from the first direction in this manner, even if the second top plate is bent relative to the top plate (first top plate) of the first member so that a portion forming a negative angle with respect to the first direction exists on the second top plate, the second top plate can be formed. Further, since the second member is formed from the side with respect to the first direction, even if the second top plate is bent relative to the first top plate so that the second flange includes a portion substantially parallel to the first direction, the second flange can be formed. Therefore, even when the first top plate and the second top plate are bent at an angle of 150° or less, the first member and the second member can be integrally formed as a single structural member. As a result, compared with the case where the first member and the second member are separately formed as different members, the number of components in a structure such as a vehicle body can be reduced. Consequently, the manufacturing process of the structure can be omitted, and the life cycle GHG emissions can be reduced.

[0014] When the second top plate is bent at an angle of 150° or less relative to the first top plate, wrinkles are likely to occur during forming at the bent portions and the like of these top plates. In contrast, in the manufacturing method according to the first configuration, the second top plate is formed from the second direction in a state where the first member is restrained from the first direction and the second flange is restrained from the second direction perpendicular to the first direction. Thereby, during forming of the structural member, the occurrence of wrinkles at the bent portions and the like of the first top plate and the second top plate can be suppressed.

[0015] In the manufacturing method according to the first configuration, the mold may include two movable dies. In this case, in the forming step, one of the two movable dies moving along the second direction may form a part of the second portion into the second flange and restrain the second flange, and the other of the two movable dies moving along the second direction may form the remaining part of the second portion into the second top plate and the second vertical wall (second configuration).

[0016] In the manufacturing method according to the second configuration, the mold may further include an upper die and a lower die. In this case, in the forming step, while the first member is sandwiched and restrained from the first direction by the upper die and the lower die, and the second flange is sandwiched and restrained by the upper die and one of the movable dies, the second top plate and the second vertical wall may be formed by the other movable die (third configuration).

[0017] A structural member according to an embodiment includes a first member and a second member. The first member includes a first top plate, a pair of first vertical walls, and a pair of first flanges. The first vertical walls are connected to both side edges of the first top plate. The first flanges are connected to the first vertical walls on the side opposite to the first top plate. The first flanges protrude outward from the first vertical walls. The second member includes a second top plate, a pair of second vertical walls, and a pair of second flanges. The second top plate is bent relative to the first top plate so as to form an angle of 150° or less with the first top plate. The second vertical walls are connected to both side edges of the second top plate. The second flanges are connected to the second vertical walls on the side opposite to the second top plate. The second flanges protrude outward from the second vertical walls. The second member is provided continuously with the first member (fourth configuration).

[0018] In the structural member according to the fourth configuration, the second member is provided continuously with the first member. That is, there is no joint portion such as a welded portion at the boundary between the first member and the second member, and for example, there is no overlapping portion for arranging the joint portion. Therefore, the structural member can be reduced in weight as compared with the case where a joint portion exists at the boundary between the first member and the second member.

[0019] In the structural member relating to the fourth configuration, the total extended length of the first and second top plates, measured along the first and second top plates, may be 400 mm or more (fifth configuration).

[0020] Embodiments of this disclosure will be described below with reference to the drawings. In these drawings, the same or equivalent components are denoted by the same reference numerals, and the same description will not be repeated.

[0021] [Structural Member Composition] Figure 1 is a perspective view of the structural member 10 according to this embodiment. The structural member 10 comprises a first member 11 and a second member 12.

[0022] Referring to Figure 1, the first member 11 includes a top plate 111, a pair of vertical walls 112a, 112b, and a pair of flanges 113a, 113b.

[0023] The top plate 111 extends in the longitudinal direction of the first member 11. The vertical walls 112a and 112b are connected to both side edges of the top plate 111. One vertical wall 112a is provided on the side opposite to the other vertical wall 112b relative to the top plate 111. The flanges 113a and 113b are connected to the vertical walls 112a and 112b, respectively, on the opposite side of the top plate 111. The flanges 113a and 113b protrude outward from the vertical walls 112a and 112b.

[0024] The vertical walls 112a and 112b extend along the top plate 111 in the longitudinal direction of the first member 11. The flanges 113a and 113b each extend along the vertical walls 112a and 112b in the longitudinal direction of the first member 11. The height of the vertical walls 112a and 112b may be constant along the entire length of the first member 11 in the longitudinal direction, or it may vary along the longitudinal direction of the first member 11. For example, in a part of the longitudinal direction of the first member 11, the vertical walls 112a and 112b may substantially disappear, and the top plate 111 and flanges 113a and 113b may be flat.

[0025] Figure 2 is a cross-sectional view of the first member 11 shown in Figure 1, along line II-II. Figure 2 shows the cross-section (transverse plane) obtained when the first member 11 is cut by a plane perpendicular to its longitudinal direction.

[0026] Referring to Figure 2, the first member 11 has a hat-shaped cross-section in at least a portion of its longitudinal direction. That is, the first member 11 includes four ridges 114a, 114b, 115a, and 115b in a cross-sectional view in at least a portion of its longitudinal direction.

[0027] The ridge sections 114a and 114b are provided continuously with the top plate 111. The ridge section 114a connects one vertical wall 112a to the top plate 111. The ridge section 114a is the corner between the top plate 111 and the vertical wall 112a. The ridge section 114b is on the opposite side of the vertical wall 112a and connects the other vertical wall 112b to the top plate 111. The ridge section 114b is the corner between the top plate 111 and the vertical wall 112b. The ridge sections 114a and 114b may each have an arc shape in a cross-sectional view of the first member 11.

[0028] The ridge sections 115a and 115b are provided on the opposite side of the top plate 111, continuously attached to the vertical walls 112a and 112b, respectively. Ridge section 115a connects one vertical wall 112a to the flange 113a. Ridge section 115a is the corner between the vertical wall 112a and the flange 113a. Ridge section 115b connects the other vertical wall 112b to the flange 113b. Ridge section 115b is the corner between the vertical wall 112b and the flange 113b. Ridge sections 115a and 115b may each have an arc shape in a cross-sectional view of the first member 11.

[0029] The vertical walls 112a and 112b may be arranged symmetrically or asymmetrically in a cross-sectional view of the first member 11. For example, in a cross-sectional view of the first member 11, the heights of the vertical walls 112a and 112b may be equal or different. Also, the vertical walls 112a and 112b may be arranged parallel or non-parallel in a cross-sectional view of the first member 11. For example, the vertical walls 112a and 112b may be spaced further apart from each other as they move away from the top plate 111 in a cross-sectional view of the first member 11.

[0030] Similarly, the flanges 113a and 113b may be arranged symmetrically or asymmetrically in a cross-sectional view of the first member 11. For example, in a cross-sectional view of the first member 11, the lengths of the flanges 113a and 113b may be equal or different. Also, the flanges 113a and 113b may be parallel or non-parallel in a cross-sectional view of the first member 11.

[0031] Returning to Figure 1, the second member 12 is adjacent to the first member 11 in its longitudinal direction. The second member 12 is provided continuously with the first member 11. The statement that the second member 12 is continuous with the first member 11 means that there is no joint between the first member 11 and the second member 12, and that the first member 11 and the second member 12 are formed from a common metal plate.

[0032] Referring to Figure 1, the second member 12 includes a top plate 121, a pair of vertical walls 122a, 122b, and a pair of flanges 123a, 123b.

[0033] The top plate 121 extends in the longitudinal direction of the second member 12. The top plate 121 bends relative to the top plate 111 of the first member 11. The second member 12 may be arranged so as a whole bend relative to the first member 11. The vertical walls 122a and 122b are connected to both side edges of the top plate 121. One vertical wall 122a is provided on the opposite side of the top plate 121 from the other vertical wall 122b. The flanges 123a and 123b are connected to the vertical walls 122a and 122b, respectively, on the opposite side of the top plate 121. The flanges 123a and 123b project outward from the vertical walls 122a and 122b.

[0034] The vertical walls 122a and 122b extend along the top plate 121 in the longitudinal direction of the second member 12. The flanges 123a and 123b each extend along the vertical walls 122a and 122b in the longitudinal direction of the second member 12. The height of the vertical walls 122a and 122b may be constant along the entire length of the second member 12, or it may vary along the longitudinal direction of the second member 12. For example, in a part of the longitudinal direction of the second member 12, the vertical walls 122a and 122b may substantially disappear, and the top plate 121 and flanges 123a and 123b may be flat. The flanges 123a and 123b may be connected and integrated at both ends of the longitudinal direction of the second member 12, at the end opposite to the first member 11.

[0035] Figure 3 is a cross-sectional view of the second member 12 shown in Figure 1, taken along line III-III. Figure 3 shows the cross-section (transverse plane) of the second member 12 when it is cut by a plane perpendicular to its longitudinal direction.

[0036] Referring to Figure 3, the second member 12 has a hat-shaped cross-section in at least a portion of its longitudinal direction. That is, the second member 12 includes four ridges 124a, 124b, 125a, and 125b in a cross-sectional view in at least a portion of its longitudinal direction.

[0037] The ridge sections 124a and 124b are provided continuously with the top plate 121. The ridge section 124a connects one vertical wall 122a to the top plate 121. The ridge section 124a is the corner between the top plate 121 and the vertical wall 122a. The ridge section 124b is on the opposite side of the vertical wall 122a and connects the other vertical wall 122b to the top plate 121. The ridge section 124b is the corner between the top plate 121 and the vertical wall 122b. The ridge sections 124a and 124b may each have an arc shape in a cross-sectional view of the second member 12.

[0038] The ridge sections 125a and 125b are provided on the opposite side of the top plate 121, continuously attached to the vertical walls 122a and 122b, respectively. Ridge section 125a connects one vertical wall 122a to the flange 123a. Ridge section 125a is the corner between the vertical wall 122a and the flange 123a. Ridge section 125b connects the other vertical wall 122b to the flange 123b. Ridge section 125b is the corner between the vertical wall 122b and the flange 123b. Ridge sections 125a and 125b may each have an arc shape in a cross-sectional view of the second member 12.

[0039] The vertical walls 122a and 122b may be arranged symmetrically or asymmetrically in a cross-sectional view of the second member 12. For example, in a cross-sectional view of the second member 12, the heights of the vertical walls 122a and 122b may be equal or different. Also, the vertical walls 122a and 122b may be arranged parallel or non-parallel in a cross-sectional view of the second member 12. For example, the vertical walls 122a and 122b may be spaced further apart from each other as they move away from the top plate 121 in a cross-sectional view of the second member 12.

[0040] Similarly, the flanges 123a and 123b may be arranged symmetrically or asymmetrically in a cross-sectional view of the second member 12. For example, in a cross-sectional view of the second member 12, the lengths of the flanges 123a and 123b may be equal or different. Also, the flanges 123a and 123b may be parallel or non-parallel in a cross-sectional view of the second member 12.

[0041] Figure 4 is a cross-sectional view of the structural member 10 shown in Figure 1, taken along the line IV-IV. Figure 4 shows the cross-sections (longitudinal sections) of the structural member 10 when it is cut along the longitudinal directions of the first member 11 and the second member 12, and along the thickness direction of the top plates 111 and 121.

[0042] Referring to Figure 4, the top plate 111 of the first member 11 includes at least one flat portion 141. The top plate 121 of the second member 12 includes at least one flat portion 142. The flat portions 141 and 142 are substantially straight (flat) in a longitudinal cross-sectional view of the structural member 10.

[0043] In the top plates 111 and 121, a curved portion 143 may be provided between adjacent flat portions 141 and 142. If the top plate 121 includes a plurality of flat portions 142, as in the example of this embodiment, a curved portion 143 may also be provided between adjacent flat portions 142. In a longitudinal cross-sectional view of the structural member 10, the curved portion 143 has a concave arc shape directed inward toward the structural member 10. The flat portion 141 of the top plate 111 can be smoothly connected to the flat portion 142 of the top plate 121 via the curved portion 143.

[0044] The top plate 121 of the second member 12 is bent relative to the top plate 111 of the first member 11 so as to form an angle θ with the top plate 111. The angle θ is the angle formed by the flat portion 141 of the top plate 111 and the flat portion 142 of the top plate 121 in a longitudinal cross-sectional view of the structural member 10. More specifically, the angle θ is the angle between the extension lines (dash-dot lines) of the outer surfaces of the flat portions 141 and 142 in the longitudinal cross-section of the structural member 10, and the angle formed by these extension lines on the first member 11 side in the longitudinal direction of the structural member 10 and on the top plate 111 and 121 side in the height direction of the structural member 10. If at least one of the top plates 111 and 121 contains multiple flat portions, the angle θ is the smallest angle formed by the combination of flat portions 141 and 142 selected from the top plates 111 and 121, respectively. The angle θ is 150° or less, preferably 135° or less, and more preferably 120° or less. The angle θ may also be 110° or less, or 100° or less. The angle θ may also be 90° or more.

[0045] The structural member 10 is a relatively long member. In the structural member 10, the extended length L of the top plates 111 and 121 is, for example, 400 mm or more. The extended length L may be 600 mm or more, or 800 mm or more. The extended length L is, for example, 1500 mm or less. The extended length L is the total extended length of the top plates 111 and 121 in the longitudinal direction of the structural member 10, measured along the top plate 111 of the first member 11 and the top plate 121 of the second member 12. The extended length L is measured, for example, along the outer surface of the top plates 111 and 121 in the longitudinal section of the structural member 10 at the center of the width of the top plate 111 or 121.

[0046] Returning to Figure 1, the first member 11 and the second member 12 are formed from metal plates. The first member 11 and the second member 12 may also be formed from steel plates. The structural member 10 can have a tensile strength of 440 MPa or more in the first member 11 and the second member 12. The tensile strength of the structural member 10 may be 590 MPa or more, 780 MPa or more, or 980 MPa or more.

[0047] The tensile strength of the structural member 10 is determined in accordance with JIS Z 2241:2011 by taking a No. 5 test specimen of the full thickness from the flat part of the top plate 111 near the center in the longitudinal and width directions of the first member 11 and performing a tensile test. If only one test specimen for tensile strength testing can be taken from the top plate 111, the tensile strength is determined by performing a tensile strength test on that one test specimen. If two or more test specimens can be taken, up to three test specimens are taken and tensile strength tests are performed, and the tensile strength of the structural member 10 is determined by taking the average value of the measured tensile strengths.

[0048] If it is difficult to obtain a test specimen for tensile testing from the top plate 111 of the first member 11, the tensile strength of the structural member 10 can be determined based on its Vickers hardness. The Vickers hardness of the structural member 10 can be determined in accordance with JIS Z 2244-1:2024 by preparing an optical microscope microscopy specimen of the entire thickness of the vertical cross-section of the flat part of the top plate 111 near the center in the longitudinal and width directions of the first member 11, measuring the Vickers hardness at five points in the 1 / 4 t portion (1 / 4 plate thickness portion) of the specimen with a test load of 1.961 N (200 gf), and taking the average value of these measurements. If the determined Vickers hardness is Hv138 or higher, the tensile strength of the structural member 10 is 440 MPa or higher. If the Vickers hardness is Hv184 or higher, the tensile strength of the structural member 10 is 590 MPa or higher. If the Vickers hardness is Hv243 or higher, the tensile strength of the structural member 10 is 780 MPa or higher. If the Vickers hardness is Hv305 or higher, the tensile strength of the structural member 10 is 980 MPa or higher.

[0049] For example, a tensile strength of 440 MPa corresponds to Hv138. In this case, if a Vickers hardness test is performed with a test load of 1.961 N (200 gf) in accordance with JIS Z 2244-1:2024, the diagonal length d of the indentation will be 51.8 μm. If the plate thickness is 0.6 mm, the 1 / 4t portion is located 0.15 mm from the sample surface, but 2.5 times the diagonal length d is 0.1295 mm, which satisfies the provision in JIS Z 2244-1:2024 that the Vickers hardness test must be performed at a distance of at least 2.5 times the diagonal length d from the surface edge to avoid the influence of the surface edge. Also, for example, a tensile strength of 1180 MPa corresponds to Hv367. In this case, when a Vickers hardness test is performed with a test load of 1.961 N (200 gf), the diagonal length d of the indentation is 31.8 μm, and it is possible to measure the Vickers hardness in accordance with JIS Z 2244-1:2024.

[0050] The thickness of the structural member 10 may be 2.3 mm or less. The thickness of the structural member 10 may be, for example, 2.0 mm or less, preferably 1.5 mm or less, and more preferably 1.0 mm or less. The thickness of the structural member 10 may be 0.7 mm or more. The thickness of the structural member 10 can be measured at the same location as the measurement location for tensile strength or Vickers hardness.

[0051] Such structural members 10 are used, for example, in the body of an automobile. One of the first member 11 and the second member 12 may be, for example, a front side member for the body. In this case, the other of the first member 11 and the second member 12 may be a joint member for connecting the front side member to another member, for example, an A-pillar post. Alternatively, one of the first member 11 and the second member 12 may be a cross member for the body. In this case, the other of the first member 11 and the second member 12 may be a joint member for connecting the cross member to another member, for example, a wheel well. However, the applications of the structural member 10 are not limited to these examples.

[0052] [Method for manufacturing structural members] Next, the manufacturing method for the structural member 10 will be described with reference to Figures 5A to 5F. The manufacturing method for the structural member 10 according to this embodiment comprises a preparation step and a molding step. The manufacturing method may further include a heating step.

[0053] (preparation process) Referring to Figure 5A, the preparation step involves preparing a blank 30. The blank 30 includes a first portion 31 and a second portion 32. The second portion 32 is continuous with the first portion 31. That is, the first portion 31 and the second portion 32 are contained within a single metal sheet 33, and there are no joints such as welds between the first portion 31 and the second portion 32. The metal sheet 33 may be a steel sheet.

[0054] (Heating process) In this embodiment, the structural member 10 (Figures 1 to 4) may be manufactured by cold working or by hot working (hot stamping). When the structural member 10 is manufactured by hot stamping, a heating step is performed before the forming step. In the heating step, the blank 30 is heated, for example, in a heating furnace. If the metal sheet 33 including the first part 31 and the second part 32 is a steel sheet, the metal sheet 33 is heated to an austenite transformation completion temperature (A c3 It is preferable to heat it to a temperature of 1.5°C or higher.

[0055] (molding process) Referring to Figures 5B to 5F, in the molding process, the blank 30 is molded into a structural member 10 (Figures 1 to 4) using a mold 40. In the molding process, the first part 31 of the blank 30 is molded into the first member 11 (Figure 1), and the second part 32 of the blank 30 is molded into the second member 12 (Figure 1). In the molding process, the first member 11 is constrained from the first direction D1 by the mold 40, and the flanges 123a and 123b (Figure 1) of the second member 12 are constrained from the second direction D2, while the top plate 121 and vertical walls 122a and 122b (Figure 1) of the second member 12 are molded from the second direction D2 by the mold 40. Hereafter, unless otherwise necessary, the vertical walls 122a and 122b of the second member 12 will be collectively referred to as vertical wall 122, and the flanges 123a and 123b will be collectively referred to as flange 123. Similarly, when there is no particular need to distinguish between them, the vertical walls 112a and 112b of the first member 11 are collectively referred to as vertical wall 112, and the flanges 113a and 113b are collectively referred to as flange 113.

[0056] Figure 5B is a perspective view of the blank 30 and the mold 40. Figures 5C to 5F show cross-sections (longitudinal sections) of the blank 30 and the mold 40 when they are cut along the longitudinal and thickness directions of the blank 30 at the position where the top plates 111 and 121 (Figure 1) of the structural member 10 are formed.

[0057] First, the configuration of the mold 40 will be described with reference to Figures 5B and 5C. In this embodiment, the mold 40 includes an upper mold 41, a lower mold 42, and movable molds 43 and 44.

[0058] The upper die 41 and the lower die 42 are positioned opposite each other in a first direction D1. The upper die 41 and the lower die 42 are configured to be able to move closer to and further apart relative to each other in the first direction D1. The first direction D1 is the pressing direction of the upper die 41 and the lower die 42, and is, for example, the vertical direction.

[0059] The lower die 42 is the part of the mold 40 that is mainly used to process the first portion 31 of the blank 30 to form the first member 11 (Figure 1). The lower die 42 can process the first portion 31 together with the upper die 41. The molding surface 411 of the upper die 41 has a shape that corresponds to at least the first member 11. The molding surface 421 of the lower die 42 has a shape that corresponds to at least the top plate 111 and vertical wall 112 (Figure 1) of the first member 11. In this embodiment, the lower die 42 is supported from the opposite side of the upper die 41 by an elastic member 45. The elastic member 45 is a member that can expand and contract in a first direction D1, and includes, for example, a spring or a fluid pressure cylinder. The expansion and contraction of the elastic member 45 causes the lower die 42 to move in the first direction D1.

[0060] The movable molds 43 and 44 are positioned, for example, to the side of the lower mold 42. The movable molds 43 and 44 are the parts of the mold 40 that are mainly used to process the second portion 32 of the blank 30 to form the second member 12 (Figure 1). The movable molds 43 and 44 can process the second portion 32 together with the upper mold 41. The molding surface 431 of the movable mold 43 has a shape that corresponds to at least a part of the flange 123 (Figure 1) of the second member 12. The molding surface 441 of the movable mold 44 has a shape that corresponds to at least a part of the top plate 121 and vertical wall 122 (Figure 1) of the second member 12. Since the movable mold 44 is used to form the top plate 121 and vertical wall 122, it is positioned inside the movable mold 43 which is used to form the flange 123. In a vertical cross-sectional view of the mold 40 (Figure 5C), the movable molds 43 and 44 may be arranged side by side in the first direction D1. The molding surfaces 412 and 413 of the upper mold 41 correspond to the molding surface 431 of the movable mold 43 and the molding surface 441 of the movable mold 44, respectively.

[0061] The movable molds 43 and 44 are each configured to be movable in a second direction D2. The second direction D2 is substantially perpendicular to the first direction D1 in a longitudinal cross-sectional view of the mold 40. The second direction D2 is, for example, the horizontal direction.

[0062] The movable molds 43 and 44 can be moved in a second direction D2, for example, by a cam mechanism. In this case, the mold 40 may include a cam driver 46. The cam driver 46 is able to move relative to and away from the movable molds 43 and 44 in a first direction D1. The movable molds 43 and 44 can function as sliding cams actuated by the cam driver 46.

[0063] The movable molds 43 and 44 each have sliding surfaces 432 and 442 opposite to the molding surfaces 431 and 441, respectively. The sliding surfaces 432 and 442 are inclined with respect to a first direction D1 in a longitudinal cross-sectional view of the mold 40, for example. The cam driver 46 has a sliding surface 461 corresponding to the sliding surfaces 432 and 442 of the movable molds 43 and 44.

[0064] As shown in Figure 5C, before the start of the molding process, the upper mold 41 and the lower mold 42 are separated in the first direction D1. Also, the cam driver 46 is separated from the movable molds 43 and 44 in the first direction D1. At the start of the molding process, the blank 30 is placed between the upper mold 41 and the lower mold 42 and movable molds 43 and 44.

[0065] Next, the upper mold 41 is brought relatively closer to the lower mold 42 in the first direction D1. Also, the cam driver 46 is brought relatively closer to the movable molds 43 and 44 in the first direction D1. For example, the upper mold 41 is moved towards the lower mold 42 along the first direction D1. Also, the cam driver 46 is moved towards the movable molds 43 and 44 along the first direction D1. In this embodiment, as shown in Figure 5D, the first portion 31 of the blank 30 is clamped between the upper mold 41 and the lower mold 42 from the first direction D1, and the molding of the first member 11 begins. The upper mold 41 and the lower mold 42 form, for example, the top plate 111 and the vertical wall 112 (Figure 1) before the flange 113.

[0066] As shown in Figure 5E, after the first portion 31 of the blank 30 is clamped between the upper mold 41 and the lower mold 42, as the upper mold 41 moves further, the lower mold 42 is pushed in the first direction D1 by the upper mold 41, and the elastic member 45 contracts. Also, as the cam driver 46 and the movable mold 43 move closer together, the sliding surface 461 of the cam driver 46 comes into contact with the sliding surface 432 of the movable mold 43 and slides on the sliding surface 432. As a result, the movable mold 43 moves along the second direction D2. The movable mold 43 is pushed towards the upper mold 41 by the cam driver 46, forming a part (end) of the second portion 32 of the blank 30 into the flange 123. More specifically, the forming surface 431 of the movable mold 43 and the forming surface 412 of the upper mold 41 clamp a part of the second portion 32, and a part of the second portion 32 is formed into the flange 123.

[0067] Referring to Figure 5F, in the molding process, a portion (end) of the second part 32 is molded into a flange 123 by the movable mold 43 and the flange 123 is restrained, while the remaining portion of the second part 32 is molded into a top plate 121 and a vertical wall 122 by the movable mold 44. More specifically, the first member 11 is clamped and restrained from the first direction D1 by the upper mold 41 and the lower mold 42, and the flange 123 is clamped and restrained by the upper mold 41 and the movable mold 43, while the top plate 121 and the vertical wall 122 are molded by the movable mold 44.

[0068] In this embodiment, as the cam driver 46 and the movable mold 44 approach each other, the sliding surface 461 of the cam driver 46 contacts the sliding surface 442 of the movable mold 44 and slides along the sliding surface 442. This causes the movable mold 44 to move along the second direction D2. The movable mold 44 is pushed out toward the upper mold 41 by the cam driver 46, forming the portion of the second part 32 that is not constrained by the movable mold 43. More specifically, the forming surface 441 of the movable mold 44 and the forming surface 413 of the upper mold 41 clamp the second part 32, and the second part 32 is formed into the top plate 121 and the vertical wall 122. This forms the structural member 10 from the blank 30.

[0069] If a heating process is performed before the molding process, the structural member 10 may be held within the mold 40. This allows the structural member 10 to be deheated (quenched) by the mold 40.

[0070] In this embodiment, the height of the portion of the lower mold 42 on the side of the movable mold 44 is greater than the height of the portion on the opposite side of the movable mold 44. Therefore, when the top plate 111 or 112 of the structural member 10 rises in the first direction D1 from the lower mold 42 to the movable mold 44, the rising portion of the top plate 111 or 112 can be supported by the lower mold 42. This prevents the top plate 111 or 112 from partially dropping due to gravity when the movable mold 44 is separated from the lower mold 42 in the second direction D2 during demolding.

[0071] [effect] In the manufacturing method according to this embodiment, a structural member 10 including a first member 11 and a second member 12 is formed from a blank 30 including a first part 31 and a second part 32. In the molding process, the first member 11 is restrained by the mold 40 from a first direction D1, and the flange 123 of the second member 12 is restrained from a second direction D2 perpendicular to the first direction D1, while the top plate 121 and vertical wall 122 of the second member 12 are formed by the mold 40 from the second direction D2. In this case, even if the top plate 121 of the second member 12 is bent relative to the top plate 111 of the first member 11, and there is a portion of the top plate 121 that intrudes into the first member 11 side in a longitudinal cross-sectional view of the structural member 10, that is, a portion that is at a negative angle with respect to the first direction D1, the top plate 121 can still be formed by the mold 40. Furthermore, since the second member 12 is formed from the side with respect to the first direction D1, even if the flange 123 of the second member 12 includes a portion substantially parallel to the first direction D1 due to the bending of the top plate 121 relative to the top plate 111, the flange 123 can be formed in the mold 40. Therefore, even if the top plate 121 is bent at an angle θ of 150° or less relative to the top plate 111, which is generally difficult to form, the first member 11 and the second member 12 can be integrated at the blank 30 stage and formed as a single structural member 10.

[0072] More specifically, in the manufacturing method according to this embodiment, the mold 40 includes two movable molds 43 and 44 that move independently in the second direction D2. In the molding process, the end of the second portion 32 can be formed into a flange 123 by the movable mold 43 that moves along the second direction D2. In this way, by forming the flange 123 from the side with respect to the first direction D1 using the movable mold 43, the flange 123 can be formed even if the flange 123 includes a portion that is parallel or nearly parallel to the first direction D1.

[0073] Furthermore, in the molding process, the remaining portion of the second part 32 can be molded into the top plate 121 and vertical wall 122 by another movable mold 44 that moves along the second direction D2. In this way, by molding the top plate 121 and vertical wall 122 from the side with respect to the first direction D1 by the movable mold 44, the top plate 121 and the vertical wall 122 connected thereto can be molded even if the top plate 121 includes a portion that is at a negative angle with respect to the first direction D1.

[0074] In this embodiment, the first member 11 and the second member 12 can be integrally molded as a single structural member 10. This reduces the number of parts in a structure such as a vehicle body compared to the case where the first member 11 and the second member 12 are separate members. As a result, the manufacturing process of the structure can be omitted, and life cycle GHG emissions can be reduced.

[0075] In the structural member 10 according to this embodiment, the first member 11 and the second member 12 are provided in a continuous manner. That is, the first member 11 and the second member 12 are formed from a common metal plate, and there are no joints such as welds at the boundary between the first member 11 and the second member 12. This makes it possible to lighten the structural member 10. In particular, compared to the case in which the first member 11 and the second member 12 are joined by overlapping welding, the overlapping portion for joining the first member 11 and the second member 12 is unnecessary, so the weight of the structural member 10 can be reduced.

[0076] In the structural member 10 according to this embodiment, the top plate 111 of the first member 11 and the top plate 121 of the second member 12 are bent at an angle θ of 150° or less. Even in this case, if the total extended length L of the top plates 111 and 121 is relatively short, it may be possible to form the structural member 10 by general press forming while suppressing the occurrence of wrinkles in the bent parts of the top plates 111 and 121, for example by rotating the pressing direction. However, if the total extended length L of the top plates 111 and 121 is long, it becomes difficult to rotate the pressing direction, making it difficult to prevent wrinkles by rotating the pressing direction. On the other hand, in this embodiment, the first member 11 and the second member 12 are formed from two directions, the first direction D1 and the second direction D2. More specifically, the top plate 121 of the second member 12 is formed from the second direction D2 while the first member 11 is restrained from the first direction D1 and the flange 123 of the second member 12 is restrained from the second direction D2. This makes it possible to suppress the occurrence of wrinkles on the top plates 111 and 121 without rotating the press direction. Therefore, even structural members 10 with a total extended length L of top plates 111 and 121 of 400 mm or more can be easily formed.

[0077] In general press forming, that is, press forming in a single direction, when integrally forming the first member 11 and the second member 12, the smaller the angle θ between the top plate 111 of the first member 11 and the top plate 121 of the second member 12, the more difficult the forming becomes. For example, if the angle θ is less than 120°, wrinkles will occur in the bent parts of the top plates 111 and 121 in general press forming, making it difficult to properly form the first member 11 and the second member 12. However, in this embodiment, the first member 11 and the second member 12 are formed from two directions, the first direction D1 and the second direction D2. More specifically, the top plate 121 of the second member 12 is raised from the second direction D2 while the first member 11 is restrained from the first direction D1 and the flange 123 of the second member 12 is restrained from the second direction D2. In this case, the occurrence of wrinkles in the top plates 111 and 121 can be suppressed. In the manufacturing method according to this embodiment, even when the angle θ is 110° or less or 100° or less, wrinkles are less likely to occur on the top plates 111 and 121, and the first member 11 and the second member 12 can be well integrally molded.

[0078] When the first member 11 and the second member 12 are integrally formed by general press forming, if the first member 11 and the second member 12 are thick, wrinkles in the top plates 111 and 121 are easily flattened during forming, and the degree of wrinkles that occur in the top plates 111 and 121 is relatively small. However, if the first member 11 and the second member 12 are thin, wrinkles in the top plates 111 and 121 are not easily flattened, and in general press forming, noticeable wrinkles occur in the bent parts of the top plates 111 and 121. On the other hand, in this embodiment, the first member 11 and the second member 12 are formed from two directions, the first direction D1 and the second direction D2. More specifically, with the first member 11 restrained from the first direction D1 and the flange 123 of the second member 12 restrained from the second direction D2, the top plate 121 of the second member 12 is raised from the second direction D2. In this case, even if the first member 11 and / or the second member 12 are thin, the occurrence of wrinkles on the top plates 111 and 121 can be suppressed. When using the manufacturing method according to this embodiment, even if the thickness of one or both of the first member 11 and the second member 12 is, for example, 2.0 mm or less, 1.5 mm or less, or 1.0 mm or less, wrinkles are less likely to occur on the top plates 111 and 121, and the first member 11 and the second member 12 can be well integrally molded. Furthermore, even if the first member 11 and / or the second member 12 are thin and the angle θ of the top plates 111 and 121 is relatively small, the occurrence of wrinkles on the top plates 111 and 121 can be suppressed.

[0079] While embodiments relating to this disclosure have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible as long as they do not deviate from its spirit.

[0080] In the above embodiment, the structural member 10 includes a first member 11 and a second member 12. The structural member 10 may further include other members. For example, as shown in Figure 6, the structural member 10 may include a third member 13 in addition to the first member 11 and the second member 12.

[0081] As shown in Figure 6, the third member 13 may be arranged in parallel with the second member 12. The third member 13, like the second member 12, may have a hat-shaped cross-section in at least a portion of its longitudinal direction. The third member 13 may be joined to the second member 12 by welding, for example, at the stage of the blank 30 (Figure 5A) before molding. Alternatively, the third member 13 may be provided continuously with the second member 12, and there may be no joint such as a weld at the boundary between the second member 12 and the third member 13. Even with such a structural member 10, the manufacturing method according to the above embodiment can be applied. However, the third member 13 may be joined to the second member 12 by welding, for example, after the molding of the first member 11 and the second member 12. Although not shown, the third member 13 may be arranged in parallel with the first member 11. In this case as well, the third member 13 may be joined to the first member 11 before molding by welding, for example, or it may be joined to the first member 11 after the molding of the first member 11 and the second member 12. Alternatively, the third member 13 may be provided continuously with the first member 11, and there may be no joint such as a weld at the boundary between the first member 11 and the third member 13.

[0082] In the structural member 10 according to the above embodiment, a single first member 11 and a single second member 12 are provided, and the first member 11 and the second member 12 are arranged to form a substantially L-shape. However, as shown in Figure 7, the structural member 10 may also include, for example, two second members 12. In the example in Figure 7, the second members 12 are arranged on both sides in the longitudinal direction of the first member 11. That is, the first member 11 and the two second members 12 are arranged to form a substantially U-shape. One second member 12 is arranged adjacent to the first member 11 in its longitudinal direction and is continuous with the first member 11. The other second member 12 may be arranged adjacent to the first member 11 on the opposite side of the first second member 12 and is continuous with the first member 11. Even with such a structural member 10, the manufacturing method according to the above embodiment can be applied. It is preferable that each of the second members 12 is provided continuously with the first member 11 and is molded integrally with the first member 11. However, if the structural member 10 includes two second members 12, it is sufficient that at least one of the second members 12 is provided continuously with the first member 11, and either of the second members 12 may be joined to the first member 11 by welding or the like before or after molding.

[0083] In the manufacturing method according to the above embodiment, the movable molds 43 and 44 move in the second direction D2 by a cam mechanism. More specifically, the movable molds 43 and 44 move in the second direction D2 by a common cam driver 46. However, it is also possible to provide a cam driver for each of the movable molds 43 and 44. For example, if the position of the sliding surface 432 of the movable mold 43 and the position of the sliding surface 442 of the movable mold 44 are different in directions perpendicular to the first direction D1 and the second direction D2 (directions perpendicular to the plane of the paper in Figures 5C to 5F), a cam driver can be provided for each of the movable molds 43 and 44. However, it is sufficient that the movable molds 43 and 44 are configured to be movable in the second direction D2. It is not necessarily required that a cam mechanism be used as a means to actuate the movable molds 43 and 44. For example, the movable molds 43 and 44 may be moved in the second direction D2 by an actuator such as a hydraulic cylinder. When the movable molds 43 and 44 are actuated by means other than a cam mechanism, the mold 40 is not provided with a cam driver 46.

[0084] In the above embodiment, the movable mold 44 is positioned inside the movable mold 43. However, the arrangement of the movable molds 43 and 44 is not limited to this. For example, the movable mold 43 may be housed within the movable mold 44 and configured to protrude from the movable mold 44 in the second direction D2.

[0085] In the above embodiment, the mold 40 includes an upper mold 41, a lower mold 42, and movable molds 43 and 44. However, the mold 40 does not necessarily have to adopt the configuration described in the above embodiment. The mold 40 is sufficient if it is configured to allow the top plate 121 and vertical wall 122 of the second member 12 to be molded from the second direction D2 while constraining the first member 11 from the first direction D1 and constraining the flange 123 of the second member 12 from the second direction D2.

[0086] In the above embodiment, the upper mold 41 is positioned above the lower mold 42. However, the positional relationship between the upper mold 41 and the lower mold 42 is not limited to this. For example, the lower mold 42 may be positioned above the upper mold 41, or the upper mold 41 and the lower mold 42 may not be positioned vertically.

[0087] In the above embodiment, a metal plate serving as a patch material may be provided on the blank 30 before the molding process. The patch material is overlapped on a part of the blank 30 and joined to the blank 30 by spot welding or laser welding. The blank 30 may be molded into a structural member 10 with the patch material joined to it. The patch material can be placed in the structural member 10 where reinforcement is required. [Explanation of Symbols]

[0088] 10: Structural members 11: First component 111: Top plate (first top plate) 112,112a,112b: Vertical wall (First vertical wall) 113, 113a, 113b: Flange (First flange) 12: Second component 121: Top plate (second top plate) 122, 122a, 122b: Vertical wall (second vertical wall) 123, 123a, 123b: Flange (second flange) 30: Blank 31: Part 1 32:Second part 40: Mold 41: Upper mold 42: Lower mold 43,44: Movable type

Claims

1. A method for manufacturing structural members, A step of preparing a blank including a first part and a second part continuous with the first part, A step of forming the blank into a structural member including a first member and a second member using a mold including an upper mold and a lower mold, Equipped with, The first member includes a first top plate, a pair of first vertical walls connected to both side edges of the first top plate, and a pair of first flanges connected to the first vertical walls on the opposite side of the first top plate and projecting outward from the first vertical walls. The second member includes a second top plate that is bent relative to the first top plate at an angle of 150° or less with the first top plate, a pair of second vertical walls connected to both side edges of the second top plate, and a pair of second flanges connected to the second vertical wall on the opposite side of the second top plate and projecting outward from the second vertical wall. A manufacturing method in which, in the molding step, the first portion is formed into the first member and the second portion is formed into the second member, and the first member is restrained by the mold from a first direction which is the pressing direction of the upper and lower molds, and the second flange is restrained from a second direction which is perpendicular to the first direction, and the second top plate and the second vertical wall are formed by the mold from the second direction.

2. A manufacturing method according to claim 1, The mold further includes two movable molds, A manufacturing method comprising the molding process, in which one of the two movable molds moves along the second direction to form a part of the second portion into the second flange and restrain the second flange, and the other of the two movable molds moves along the second direction to form the other portion of the second portion into the second top plate and the second vertical wall.

3. A manufacturing method according to claim 2, A manufacturing method comprising the molding process, in which the first member is clamped and restrained from a first direction by the upper mold and the lower mold, and the second flange is clamped and restrained by the upper mold and one of the movable molds, while the second top plate and the second vertical wall are molded by the other movable mold.

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