Method for manufacturing automotive structural members and molding die system for automotive structural members

Abstract

The objective is to provide a method for manufacturing automotive structural members and a molding die system for automotive structural members that can produce automotive structural members without causing molding defects. [Solution] The method for manufacturing this automotive structural member includes a second step in which, from the start to the end of the press working process, the area of ​​the protrusion 10, including the pair of vertical wall portions 13, is pressed with a second pad 180, and then the intermediate part Ma is press-formed with a second die 170 to form a protrusion 20 next to the protrusion 10. Furthermore, the molding die system for the automotive structural member is configured such that the second pad 180 matches the entire area of ​​the convex surface of the protrusion 10, including the pair of vertical wall portions 13, and has a second concave surface 181 that is positioned opposite the first convex surface 171a.

Description

【Technical Field】 【0001】 The present invention relates to a method for manufacturing an automotive structural member and a molding die system for an automotive structural member. 【Background Art】 【0002】 In recent years, automobiles equipped with shock-absorbing members for absorbing impacts caused by collision accidents or the like on the frame have become widely popular. The locations of this type of shock-absorbing member within the vehicle body vary. For example, in Patent Document 1 below, a structure in which a shock-absorbing member having a corrugated shape is joined to the side portion of a battery tray is disclosed. This shock-absorbing member includes a corrugated portion having a plurality of bottom surfaces and a plurality of convex portions. When a collision load is applied from the vehicle width direction, the plurality of convex portions are crushed at short intervals, and the entire body of each convex portion undergoes an axial crushing mode of deformation in a bellows shape to absorb collision energy. As a result, it is possible to improve the energy absorption performance of the battery tray. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent No. 75,13,919 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 Incidentally, because the aforementioned wave-shaped portion has a complex shape with alternating bumps and dips along the longitudinal direction of the part, transfer press forming is more suitable for its manufacture than progressive press forming. In this transfer press forming, multiple single-step dies are prepared, and the press forming is carried out while changing the die used for each step, making it possible to manufacture products with complex shapes with higher precision than in the case of progressive press forming. However, when manufacturing corrugated molded products with the aforementioned wave-shaped portion as automotive structural components, the molding process is not easy due to the complexity of the shape, and molding defects such as reduction in plate thickness and cracking are particularly likely to occur at the edges of the corrugations. This problem is especially pronounced when high-strength materials are used as the material for automotive structural components. 【0005】 This invention has been made in view of the above circumstances, and aims to provide a method for manufacturing automotive structural members and a molding die system for automotive structural members, which will enable the production of automotive structural members without causing molding defects. [Means for solving the problem] 【0006】 In order to solve the above problems and achieve the above objectives, the present invention employs the following embodiments. (1) A method for manufacturing an automobile structural member according to one aspect of the present invention is: A method for manufacturing an automotive structural member by pressing a metal sheet, wherein the cross-sectional shape along one direction is such that multiple convex portions, each having a pair of vertical walls, are arranged in a row, The first step is to press the metal plate with a first die to form a first protrusion, which is one of the aforementioned protrusions, Following the first step, the second step involves pressing the area of ​​the first protrusion, including the pair of vertical wall portions, with a pad from the start to the end of the press working process, and then pressing the metal plate with a second die, which is different from the first die, to form at least a part of the second protrusion next to the first protrusion. It has. 【0007】 According to the method for manufacturing automotive structural members described in (1) above, in the first step, the first protrusion is first formed by press working using the first die. In the subsequent second step, at least a portion of the second protrusion is formed next to the first protrusion by press working. From the start to the end of the press working, the area of ​​the first protrusion, including a pair of vertical wall portions, is continuously pressed with a pad to maintain the shape of the first protrusion and at the same time maintain the proper positioning of the metal plate relative to the second die. Therefore, the second die can be accurately applied to the portion of the metal plate where at least a portion of the second protrusion is to be formed by the second die, and press working can be performed. Thus, in the second step, the first protrusion that has already been formed on the metal sheet is pressed down with a pad, thereby maintaining the proper positioning of the metal sheet from the start to the end of the press work, and forming at least a part of a new protrusion (second protrusion). By repeatedly performing this second step sequentially, it becomes possible to manufacture automotive structural members having multiple protrusions without molding defects. In the second step, either the entire range of the second protrusion, including both of the pair of vertical wall sections, may be formed in a single press operation, or a molding process that includes only one of the pair of vertical wall sections but not the other (forming a part of the second protrusion) may be performed in a single press operation. Furthermore, during the second process, the area outside the area held down by the pad may be lightly restrained with a holder (not shown) or the like, or it may be left completely unrestrained. 【0008】 (2) In the method for manufacturing an automobile structural member described in (1) above, the following may be used: The aforementioned automobile structural member further comprises a top wall portion connecting the upper edges of the pair of vertical wall portions, and a bottom wall portion connecting the adjacent protrusions, In the first step, in addition to the pair of vertical wall portions, the top wall portion is formed as part of the first protrusion. In the second step, the bottom wall portion is formed between the first and second protrusions, in addition to at least a portion of the second protrusion. In the method for manufacturing an automobile structural member described in (2) above, a corrugated automobile structural member can be manufactured by connecting multiple protrusions, each consisting of a top wall and a pair of side walls, via a bottom wall. 【0009】 (3) In the method for manufacturing an automobile structural member described in (1) or (2) above, the following may be used: In the first step described above, Simultaneously with the press working of the first protrusion, From the start to the end of the press working process, the portion of the metal plate where the second protrusion is to be formed is press-formed in a direction along the one direction, thereby obtaining a pre-formed portion that is bent in the same direction as the second protrusion. In the case of the manufacturing method for automotive structural members described in (3) above, by pre-forming a pre-formed portion that bends in the same direction as the second protrusion in the metal sheet before the second step, material can be pre-filled into the position that will become the second protrusion before the second step. This makes it possible to more reliably prevent molding defects in areas where thinning or cracking is likely to occur in conventional methods (for example, the ridge connecting the top wall and the vertical wall) when forming at least a part of the second protrusion by press working in the second step. 【0010】 (4) In the method for manufacturing automotive structural members described in (3) above, the following may be used: When the aforementioned automobile structural member is viewed in a cross-section along the aforementioned direction, each of the aforementioned protrusions further has a top wall portion that is connected to each of the pair of vertical wall portions via a ridge portion, When forming the preformed portion in the first step, a chamfered portion or an arc portion is formed in the portion of the preformed portion corresponding to each of the ridges. In the manufacturing method of the automotive structural member described in (4) above, by pre-forming chamfered or arc-shaped portions at positions corresponding to each ridge, which were areas prone to thinning or cracking in conventional methods, material can be pre-filled into these positions. This makes it possible to more reliably prevent molding defects in each ridge formed in the second step. 【0011】 (5) In the method for manufacturing an automobile structural member described in (3) above, The pre-formed portion may be formed such that its height is greater than the height of the second protrusion that is to be formed at the position of the pre-formed portion. In the method for manufacturing automotive structural members described in (5) above, by making the height of the preformed portion greater than that of the second protrusion, the length of the line along the cross-section of the preformed portion when the metal sheet after the first process is viewed in a cross-section along the one direction can be made longer in advance before the second process. This allows the material necessary for forming the ridge to be introduced in advance when forming at least a part of the second protrusion by press working in the second process. As a result, when forming at least a part of the second protrusion by press working in the second process, it is possible to more reliably prevent molding defects in areas where thinning or cracking was likely to occur in conventional methods (for example, the ridge connecting the top wall and the vertical wall). 【0012】 (6) In the method for manufacturing an automobile structural member described in (1) above, The second step and subsequent steps may further include a third step in which, after pressing down the molded area formed into the final shape by the press working up to the previous step with another pad, press working is repeatedly performed on the area outside the molded area to form the plurality of protrusions. In the manufacturing method of automotive structural members described in (6) above, the arrangement of the metal sheets can be properly maintained from the start to the end of the press working process by pressing down the molded area up to the previous process with a pad. Therefore, a corrugated molded product in which multiple protrusions without molding defects are aligned in one direction can be manufactured as an automotive structural member. 【0013】 (7) In the method for manufacturing an automobile structural member described in (1) above, The tensile strength of the aforementioned automobile structural member may be 980 MPa or higher. In the case of the manufacturing method for automotive structural members described in (7) above, even when using high-strength steel plates with a tensile strength of 980 MPa or more, molding defects can be suppressed. 【0014】 (8) The mold system for an automotive structural member according to one aspect of the present invention is a mold system for an automotive structural member used in the manufacturing method of an automotive structural member according to any one of the above (1) to (7), comprising the first mold, the second mold, and the pad, where the second mold has a first split mold having a first convex surface that matches the concave surface of the first convex portion and a second convex surface that matches at least a part of the concave surface of the second convex portion, and a second split mold having a first concave surface disposed opposite to the second convex surface, and the pad has a second concave surface that matches the entire range of the convex surface of the first convex portion including the pair of vertical wall portions and is disposed opposite to the first convex surface. 【0015】 According to the mold system for an automotive structural member described in (8) above, when performing the second step, first, by sandwiching the first convex portion between the first convex surface of the second mold and the second concave surface of the pad, the arrangement state of the metal plate with respect to the second mold can be properly maintained. Then, the first split mold and the second split mold are relatively approximated to sandwich the metal plate and perform press working. Specifically, the metal plate is sandwiched between the second convex surface and the first concave surface to form part or all of the second convex portion. During this time, since the arrangement state of the metal plate with respect to the second mold is properly maintained by pressing the first convex portion with the pad, the second convex surface and the first concave surface can be accurately applied to the portion of the metal plate where the second convex portion is to be formed, and press working can be performed. Note that the first split mold and the second split mold of the second mold may be either a case including a shape corresponding to the molding of the entire range of the second convex portion including both of the pair of vertical wall portions or a case including only one of the pair of vertical wall portions but not the other (having a shape corresponding to a part of the second convex portion). Also, during the second step, the portion outside the range pressed by the pad may be lightly pressed with a holder or the like (not shown), or may be completely unconstrained. 【Advantages of the Invention】 【0016】 According to each of the above embodiments, a method for manufacturing an automotive structural member that can be obtained without producing molding defects, and a molding die system for automotive structural members can be provided. [Brief explanation of the drawing] 【0017】 [Figure 1] This is a perspective view showing an example of the arrangement of an automobile structural member manufactured by the manufacturing method for automobile structural members according to the first embodiment of the present invention. [Figure 2] This is a perspective view of the automotive structural component (corrugated molded product). [Figure 3] This is an explanatory diagram illustrating the general process of manufacturing the automotive structural member (transfer press processing). Here, (a) is a side view of the molding die system used in this manufacturing method, and (b) is a perspective view showing the shape of the intermediate parts after each process of press processing by the molding die system. [Figure 4] This diagram shows the manufacturing method for an automobile structural member and the main parts of the molding die system in the same embodiment, and is an explanatory diagram showing the first step when preforming is not performed. Here, each step is carried out in chronological order according to (a), (b), and (c). [Figure 5] This diagram shows the second step following the first step in Figure 4, with each step proceeding in chronological order according to (a), (b), and (c). [Figure 6] This is a side view showing the intermediate parts after the second manufacturing process. [Figure 7] This diagram shows a method for manufacturing an automobile structural member and a manufacturing apparatus according to a second embodiment of the present invention, and is an explanatory diagram showing the first step when preforming is performed. Here, each step is carried out in chronological order according to (a), (b), and (c). [Figure 8] This diagram shows the second step following the first step in Figure 7, with each step proceeding in chronological order according to (a), (b), and (c). [Figure 9] This is a side view showing the intermediate parts after the second manufacturing process. [Figure 10]This figure shows a modified example of the second embodiment described above, and is a partially enlarged cross-sectional view of the intermediate part after the first step and before the second step, viewed in a cross-section along the direction of the arrangement of the bumps and grooves. Here, (a) shows the case in which a chamfer is formed on the part that will become the ridge after the first step. (b) shows the case in which the height dimension of the preformed part after the first step is greater than the height dimension of the first protrusion. (c) shows the case in which a bead is further added to the preformed part in (b). [Figure 11] The figures show modified examples of the automobile structural members manufactured according to the first and second embodiments described above, and are partially enlarged cross-sectional views taken in a cross-section along the direction of the arrangement of the irregularities. Here, (a) shows a form having only vertical wall portions with a straight cross-sectional shape, without including a top wall portion and a bottom wall portion. (b) shows a form in which the cross-sectional shape of each edge portion is curved. (c) shows a form in which the irregularities are composed only of wall portions with a curved cross-sectional shape. (d) shows a form combining relatively large and small irregularity heights. (e) shows a form combining different irregularity shapes. [Figure 12] This is a perspective view showing other variations of the automotive structural member manufactured according to the first and second embodiments described above. Figure 12 shows a form in which the height and width dimensions of each protrusion are changed in the short-side direction of the automotive structural member (from the front of the page to the back of the page). [Figure 13] The figures show yet another modification of the automotive structural member manufactured according to the first and second embodiments described above, and are partially enlarged cross-sectional views taken in a cross-section along the direction of the arrangement of the irregularities. Here, (a) shows a form in which the automotive structural member does not have a flange at the longitudinal end. (b) shows a form in which there is a flange with one bend at the right edge of the paper. (c) shows a form in which there is a flange with two bends at the right edge of the paper. [Figure 14] This figure shows another example of an application of an automotive structural component, specifically a perspective view showing its application as an energy-absorbing component positioned on the side of a battery tray. [Figure 15]This figure, among the examples, shows the numerical calculation results of the inventive example, and is a perspective view showing the plate thickness reduction distribution of an automobile structural member manufactured by the manufacturing method of the second embodiment described above. [Figure 16] This figure shows the numerical calculation results of a comparative example among the examples, and is a perspective view showing the plate thickness reduction distribution of an automobile structural member manufactured by a conventional manufacturing method. [Figure 17] This figure shows the results of numerical calculations verifying the process by which molding defects occur in conventional manufacturing methods, where (a) shows the start of the process corresponding to the second step, and (b) shows the end of the same step. [Modes for carrying out the invention] 【0018】 The following describes, with reference to the drawings, the manufacturing method for automotive structural members and the molding die system for automotive structural members according to each embodiment and various modifications of the present invention. In the following description, the case in which the automotive structural member manufactured according to the present invention is an impact absorbing member placed in the side sill of an automobile will be used as an example. Furthermore, in the following description, both cold pressing and hot pressing can be used for "pressing". 【0019】 [First Embodiment] First, we will explain the automotive structural components, followed by a description of the molding die system and manufacturing method for these components. Figure 1 is a perspective view showing an example of the arrangement of automotive structural members manufactured by the manufacturing method of automotive structural members according to this embodiment. In the following description, the direction along the direction of movement of the vehicle body 1 will be referred to as the front-rear direction or X direction, the direction of travel of the vehicle body will be referred to as the front direction, its backward direction will be referred to as the rear direction, the vertical direction along the direction of gravity will be referred to as the up-down direction or Z direction, upward along the vertical direction will be referred to as the up direction, downward along the vertical direction will be referred to as the down direction, the horizontal direction when viewed along the direction of travel of the vehicle body 1 will be referred to as the left-right direction or Y direction, the horizontal leftward direction along the direction of travel of the vehicle body will be referred to as the left direction, and the horizontal rightward direction along the direction of travel of the vehicle body will be referred to as the right direction. 【0020】 As shown in Figure 1, the vehicle body 1 includes a side sill 2 which forms part of the frame that constitutes the skeleton of the vehicle body 1, and a battery tray 3 which houses a battery pack (not shown) such as a lithium-ion battery. Here, the vehicle body 1 of an electric vehicle that runs on motor drive is shown as an example, but it may also be the vehicle body of an automobile with an internal combustion engine. The side sills 2 are positioned below the doors of the side openings so as to extend along the longitudinal direction of the vehicle body 1. The side sills 2 are cylindrical bodies having a central axis along the longitudinal direction, and energy absorbing members (automotive structural members) 5 are fixed inside them by welding or the like so as to extend along the longitudinal direction. There are a total of two side sills 2, one on each side of the vehicle body 1. 【0021】 Similarly, the energy absorbing members 5 are also positioned at two locations on the vehicle body 1, one on the left and one on the right. Each energy absorbing member 5 is positioned to the left of the battery tray 3 and to the right of the battery tray 3, respectively, to protect the occupants and the battery tray 3 from the impact force of a side collision with the vehicle body 1. When an impact force is applied to the vehicle body 1 in the rightward direction (-Y direction) of the energy absorbing member 5, the energy absorbing member 5 is compressed and plastically deformed in the rightward direction (-Y direction) to absorb the collision energy. Similarly, when an impact force is applied to the vehicle body 1 in the leftward direction (+Y direction) of the energy absorbing member 5, the energy absorbing member 5 is compressed and plastically deformed in the leftward direction (+Y direction) to absorb the collision energy. 【0022】 Since the pair of energy absorbing members 5 have the same shape, Figure 2 illustrates the energy absorbing member 5 located on the left side when viewed in the direction of travel, and continues the explanation. Figure 2 is a perspective view of the energy absorbing member 5, which is a corrugated molded product, and the symbol F in the figure indicates the impact force applied in a direction perpendicular to the extending direction of the energy absorbing member 5 (the -Y direction). Furthermore, in the following explanation, "one direction" means the longitudinal direction of the energy absorbing member 5, and "a section along one direction" means the longitudinal section along that longitudinal direction. 【0023】 As shown in Figure 2, the energy absorbing member 5 is a single-piece component formed by press-forming a long, strip-shaped metal plate in one direction to create multiple protrusions and indentations. A flange f is formed at each of its front and rear ends, which is welded and fixed to the inside of the cylindrical body of the side sill 2. As the material of the energy absorbing member 5, metal materials such as steel, aluminum alloy, or magnesium alloy with a tensile strength of 440 to 2500 MPa can be used. When applying the present invention to automotive structural members other than the energy absorbing member 5, other metal materials may be used as the material. 【0024】 The energy absorbing member 5 is a corrugated molded product in which multiple protrusions 10, 20 having the same shape as each other are integrally connected with a bottom wall portion 14 in between, and is long in the front-to-back direction (X direction). Hereafter, in order to distinguish them in the manufacturing method described later, the first protrusion formed at the central position of the energy absorbing member 5 (first protrusion) will be assigned the reference numeral 10, and the other protrusions (second protrusions) will be assigned the reference numeral 20. However, as described above, the protrusion 10 and each of the protrusions 20 have the same shape as each other. 【0025】 As shown in Figure 4(c) described later, the protrusion 10 has a top wall portion 11 and a pair of vertical wall portions 13 connected to both sides of the top wall portion 11 via a pair of ridge portions 12a. The top wall portion 11 is a flat plate having an upper and lower surface parallel to the front-to-back and left-to-right directions. In plan view, the top wall portion 11 has a rectangle that is long in the left-to-right direction, and the plate thickness is the same at all positions in the plane. Ridge portions 12a extending along the left-to-right direction are formed on both the front and rear edges of the top wall portion 11. Each vertical wall section 13 is a flat plate integrally connected to the top wall section 11 via a ridge section 12a. When viewed from the side along the -Y direction, the pair of vertical wall sections 13 are inclined such that the distance between them gradually widens from the upper end connected to the ridge section 12a to the lower end. Therefore, when viewing the pair of vertical wall sections 13, both their outer and inner surfaces are also inclined such that the distance between them gradually widens from the upper end connected to the ridge section 12a to the lower end. Consequently, the lower surface of the convex section 10, in combination with the lower surface of the top wall section 11 and the inner surfaces of the pair of vertical wall sections 13, forms a concave surface that opens downwards when viewed from the side. Furthermore, the upper surface of the convex section 10, in combination with the upper surface of the top wall section 11 and the outer surfaces of the pair of vertical wall sections 13, forms a trapezoidal convex surface when viewed from the side. 【0026】 As shown in Figure 6, which will be described later, the protrusion 20 has a top wall portion 21 and a pair of vertical wall portions 23 that are connected to both sides of the top wall portion 21 via a pair of ridge portions 22a. The top wall portion 21 is a flat plate having an upper and lower surface parallel to the front-rear and left-right directions. In plan view, the top wall portion 21 has a rectangle that is elongated in the left-right direction, and the plate thickness is the same at all positions in the plane. Ridge portions 22a extending along the left-right direction are formed on both the front and rear edges of the top wall portion 21. Each vertical wall section 23 is a flat plate integrally connected to the top wall section 21 via a ridge section 22a, and is inclined such that, when viewed from the side along the -Y direction, the distance between the pair of vertical wall sections 23 gradually widens from the upper end connected to the ridge section 22a to the lower end. Therefore, when viewing the pair of vertical wall sections 23, both their outer and inner surfaces are also inclined such that the distance between them gradually widens from the upper end connected to the ridge section 22a to the lower end. Consequently, the lower surface of the convex section 20, when viewed from the side, forms a trapezoidal concave surface due to the combination of the lower surface of the top wall section 21 and the inner surfaces of the pair of vertical wall sections 23. Furthermore, the upper surface of the convex section 20, when viewed from the side, forms a trapezoidal convex surface due to the combination of the upper surface of the top wall section 21 and the outer surfaces of the pair of vertical wall sections 23. 【0027】 Returning to Figure 2, the bottom wall portion 14 is a flat plate having an upper and lower surface parallel to the front-to-back and left-to-right directions. In plan view, the bottom wall portion 14 has a rectangle that is elongated in the left-to-right direction, and the plate thickness is the same at each position in the plane. The front and rear edges of the bottom wall portion 14 are connected to the lower ends of the vertical wall portion 13 via ridge portions 12b that extend along the left-to-right direction. 【0028】 Each protrusion 10 has a total of four bent lines formed by a pair of ridge sections 12a and a pair of ridge sections 12b. These bent sections are formed by bending by press processing, which will be described later. Looking at the details, the top wall section 11 and each vertical wall section 13 are connected by curved inner and outer surfaces. Similarly, each vertical wall section 13 and the bottom wall section 14 are also connected by curved inner and outer surfaces. When the impact force F shown in Figure 2 is applied to the energy absorbing member 5, the smaller the radius of curvature of each of the curved surfaces described above, the longer the uneven shape and function of the energy absorbing member 5 can be maintained. Therefore, a smaller radius of curvature of the curved surfaces described above is preferable from the viewpoint of increasing the amount of energy absorbed, as it allows the impact force F to be absorbed more effectively. However, when press-forming is performed using conventional manufacturing methods to reduce the radius of curvature of each ridge portion 12a, 12b, molding defects such as insufficient plate thickness and cracking are likely to occur in each curved surface due to (a) insufficient material inflow and (b) localized stretching of the material due to the small radius of the die. Therefore, in this embodiment, a manufacturing method using a new molding die system shown in Figures 3 to 6 has been adopted for the production of the energy absorbing member 5 described above. 【0029】 Figure 3 is an explanatory diagram illustrating the schematic steps of the manufacturing method (transfer press working) for automotive structural members according to this embodiment. Specifically, (a) is a side view of the molding die system used in the manufacturing method, and (b) is a perspective view showing the shape of the intermediate part Ma after each step of the press working process by the molding die system. In this manufacturing method, the first step involves using the first mold 50 located on the left side of Figure 3(a) to form the intermediate part Ma shown on the left side of Figure 3(b). Subsequently, the intermediate part Ma shown on the left side of Figure 3(b) is transferred to the second mold 70 located in the center of Figure 3(a) to perform the second step, thereby forming the intermediate part Ma shown in the center of Figure 3(b). Subsequently, the intermediate part Ma shown in the center of Figure 3(b) is transferred to the third mold 90 located on the right side of Figure 3(a) to perform the third step, thereby forming the intermediate part Ma shown on the right side of Figure 3(b). 【0030】 The molding die system of this embodiment shown in Figure 3 is a device used to manufacture the energy absorbing member 5 shown in Figure 2, and comprises a first mold 50, a first pad 60, a second mold 70, a second pad 80, a third mold 90, a third pad 100, a first base B1, a second base B2, and a drive mechanism (not shown). In Figure 3, for the sake of clarity, the number of molds and pads is shown as three each, but in reality, many more molds and pads are provided between the first base B1 and the second base B2, depending on the number of protrusions 20 to be formed on the energy absorbing member 5. 【0031】 The first base B1 is a pedestal that is installed in a fixed position, and the lower mold 51 of the first mold 50, the lower mold 71 of the second mold 70, and the lower mold 91 of the third mold 90 are fixed to its upper surface. The second base B2 is a base positioned directly above the first base B1, and the upper mold 52 of the first mold 50, the upper mold 72 of the second mold 70, and the upper mold 92 of the third mold 90 are fixed to its lower surface. The second base B2 is supported so as to be movable toward and toward the first base B1. Furthermore, the second base B2 moves toward and toward the first base B1 by receiving the driving force of the drive mechanism. Therefore, when the second base B2 is raised by the drive mechanism, mold opening occurs in the first mold 50, separating the upper mold 52 from the lower mold 51; in the second mold 70, separating the upper mold 72 from the lower mold 71; and in the third mold 90, separating the upper mold 92 from the lower mold 91. By performing this mold opening, the blank (metal plate) can be placed on the lower mold 51, and the intermediate parts Ma can be placed on the lower molds 71 ​​and 91, respectively. 【0032】 The first mold 50 has a lower mold 51 and an upper mold 52, as shown in Figure 4(a). The lower mold 51 has a first convex surface 51a formed on its upper surface, which has a convex shape that matches the concave surface formed on the lower surface of the convex portion (first convex portion) 10 described above. This first convex surface 51a has a trapezoidal shape consisting of an upper surface that matches the lower surface of the top wall portion 11 of the convex portion 10 and two side surfaces that match the inner surfaces of the pair of vertical wall portions 13. In Figure 4(a), the first convex surface 51a is shown in a vertical cross-section, but it forms a ridge with the same trapezoidal cross-section at each position from the front of the paper to the back of the paper. The upper mold 52 has a first concave surface 52a formed on its lower surface, which has a concave shape that matches the convex surface formed on the upper surface of the convex portion 10 described above. That is, it has an inner surface that matches the outer surfaces of the pair of vertical wall portions 13 of the convex portion 10. On the other hand, the lower surface of the first pad 60 has a shape that matches the upper surface of the top wall portion 11 of the convex portion 10. The first concave surface 52a, in combination with the flat surface 61 which is the lower surface of the first pad 60, forms a concave groove with the same trapezoidal cross-section at each position from the front to the back of the paper in Figure 4(b). 【0033】 The first pad 60 is positioned in the upper mold 52 so as to pass vertically through the first concave surface 52a, and can move up and down independently of the upper mold 52 by obtaining driving force from the drive mechanism. The lower end of the first pad 60 has a flat surface 61 that matches the upper surface of the top wall portion 11 of the convex portion 10. When forming the convex portion 10 with the first mold 50, the flat surface 61 of the first pad 60 can be pressed against the upper surface of the blank M placed on the lower mold 51 before lowering the upper mold 52, thereby fixing the blank M to the lower mold 51. 【0034】 The second mold 70 has a lower mold 71 and an upper mold 72, as shown in Figure 5(a). The lower mold 71 has a first convex surface 71a formed on its upper surface, which has the same shape as the first convex surface 51a of the lower mold 51 shown in Figure 4(a). However, while the first convex surface 51a was formed to protrude upward from the upper surface of the lower mold 51, this first convex surface 71a is formed to protrude upward from within a groove formed on the upper surface of the lower mold 71. In other words, the first convex surface 71a is formed to be sandwiched between a pair of parallel grooves formed on the upper surface of the lower mold 71, and the upper surface of the first convex surface 71a is at the same height as the upper surface of the second mold 70. In Figure 5(a), the first convex surface 71a forms a ridge with a trapezoidal cross-section that is the same at each position from the front side of the paper to the back side of the paper. Furthermore, on both sides of the first convex surface 71a of the lower mold 71, bottom surfaces 71b are formed that have a shape matching the lower surface of the bottom wall portion 14. In addition, next to each bottom surface 71b, a second convex surface 71c is formed that protrudes upward relative to these bottom surfaces 71b. These second convex surfaces 71c have a shape that matches a part of the concave surface formed on the lower surface of the convex portion (second convex portion) 20, specifically, the lower surface of the top wall portion 21 of the convex portion 20 and the inner surface of one of the pair of vertical wall portions 23. Note that although the first convex surface 71a is shown in a vertical cross-section in Figure 5(a), it has the same cross-sectional shape at each position from the front side of the paper to the back side of the paper. 【0035】 As shown in Figure 5(a), the lower surface of the upper mold 72 has a bottom surface 72a that matches the shape of the upper surface of the bottom wall portion 14, and a first concave surface 72b that is recessed upward with respect to the bottom surface 72a. This first concave surface 72b has a shape that matches a part of the convex surface formed on the upper surface of the convex portion (second convex portion) 20, specifically, the upper surface of the top wall portion 21 of the convex portion 20 and the outer surface of one of the pair of vertical wall portions 23. Here, if we look only at Figure 5(a), instead of saying that the first concave surface 72b is formed on the lower surface of the upper mold 72, we can also say that a convex surface including the bottom surface 72a is formed. However, as can be seen from the state when the mold is actually closed and formed, as shown in Figure 5(c), the surface indicated by reference numeral 72b is the surface to which the convex surface of the convex portion 20 fits in and matches, and even when viewed with reference to the bottom surface 72a, it is a surface that is recessed towards the back (upper) side, so the surface indicated by reference numeral 72b is uniformly referred to as the first concave surface. Note that although the vertical cross-section of this first concave surface 72b is shown in Figure 5(a), it has the same cross-sectional shape at each position from the front side of the paper to the back side of the paper. 【0036】 As shown in Figure 5(a), a second concave surface 81 is formed at the lower end of the second pad 80, which matches the convex surface that is the upper surface of the protrusion 10. This second concave surface 81 has a surface that matches the upper surface of the top wall portion 11 of the protrusion 10, and a pair of inclined surfaces that match the outer surfaces of both of the pair of vertical wall portions 13. The combination of these three surfaces within the second concave surface 81 forms a concave groove with the same trapezoidal cross-section at each position from the front to the back of the paper in Figure 5(a). The second pad 80 is positioned to pass vertically through the upper mold 72 and can move up and down independently of the upper mold 72 by obtaining driving force from the drive mechanism. A second concave surface 81 is formed at the lower end of the second pad 80, which matches the upper surface of the top wall portion 11 of the convex portion 10. Therefore, when forming the convex portion 20 with the second mold 70, as shown in Figure 5(b), the second pad 80 is lowered before lowering the upper mold 72, and the convex portion 10 of the blank M is sandwiched and fixed between the second concave surface 81 and the first convex surface 71a. This allows the intermediate component Ma to be fixed in the correct position relative to the concave and convex surfaces on the lower mold 71. 【0037】 Returning to Figure 3, the third mold 90 has a lower mold 91 and an upper mold 92. These lower mold 91 and upper mold 92 have molding surfaces with uneven surfaces similar to those of the second mold 70 described above. Similarly, the third pad 100 also has an uneven surface similar to the second concave surface 81 of the second pad 80 described above. However, the third mold 90 differs from the second mold 70 in that uneven surfaces that enclose the entire area molded in the second step are formed on the upper surface of the lower mold 91 and the lower end of the third pad 100, respectively, and uneven surfaces for forming new protrusions 20 are formed on the upper surface of the lower mold 91 and the lower surface of the upper mold 92, respectively. These will be explained with reference to Figure 3(b). 【0038】 As shown in the center of Figure 3(b), when molding with the second mold 70, the portion of area R1 that was completed molding in the first step is pressed down by the second concave surface 81 of the second pad 80, and then the convex portion 20 is formed next to it. Subsequently, when molding using the third mold 90, the portion of area R2 that was completed molding in the second step is pressed down by the third pad 100, and then one new convex portion 20 is formed on each side of it. Furthermore, to form new protrusions 20, the area R3 that was molded in the third step, as shown on the right side of Figure 3(b), is pressed down with a pad (not shown), and then new protrusions 20 are formed one on each side of it using a separate mold (not shown). In this way, by repeatedly pressing down the area that was molded in the previous step and then forming new protrusions 20 next to it, the energy absorbing member 5 shown in Figure 2 can be manufactured. The details of this manufacturing process will be explained below. Furthermore, when clamping or holding the workpiece in the blank M or intermediate part Ma as described above, it is sufficient to fix the workpiece so that it does not shift significantly within the mold. Alternatively, the workpiece area may be completely constrained within the mold. This point will also be the case in the following explanation. 【0039】 In the manufacturing method of the automotive structural member according to this embodiment, first, the first step shown in Figures 4(a) and (b) is performed to form the intermediate part Ma shown in Figure 4(c), and then, the second step shown in Figures 5(a) to (c) is performed to form the intermediate part Ma shown in Figure 6. Then, by repeating the press working corresponding to the second step, the energy absorbing member 5 shown in Figure 2 is manufactured. 【0040】 In other words, in the first step, as shown in Figure 4(a), the blank M is first placed on the opened lower mold 51, and then the first pad 60 is lowered. As a result, the blank M is sandwiched between the flat surface 61 of the first pad 60 and the first convex mold surface 51a of the lower mold 51, thus completing the positioning of the blank M relative to the lower mold 51. In Figure 4(b), following Figure 4(a), the upper mold 52 is lowered while the blank M is held down by the first pad 60. As a result, the blank M is sandwiched between the first convex surface 51a and the first concave surface 52a, and the convex portion 10 is formed. During this time, the portion of the blank M sandwiched between the flat surface 61 of the first pad 60 and the top surface of the first convex surface 51a may be restrained. On the other hand, the portion of the blank M other than the portion sandwiched between the flat surface 61 of the first pad 60 and the top surface of the first convex surface 51a may be lightly restrained by a holder or the like (not shown), or it may be left completely unrestrained. In this case, if it is left unrestrained, the flow of material necessary for forming the convex portion 10 can be made smoother. After forming the protrusion 10, the upper mold 52 is raised and the mold is opened to obtain the intermediate part Ma shown in Figure 4(c). This intermediate part Ma has a protrusion 10 formed thereon, which has a pair of ridge sections 12a and a pair of ridge sections 12b with small radii of curvature. Since these are formed with sufficient material flow, there are no cracks or excessive reduction in plate thickness at each ridge section 12a, 12b. 【0041】 In the second step, following the first step, the intermediate part Ma is first placed on the open lower mold 71, as shown in Figure 5(a), and then the second pad 80 is lowered. The convex portion 10, which was completed in the first step, then fits into the second concave surface 81 of the second pad 80. By continuing to push down the second pad 80, the convex portion 10 is sandwiched between the second concave surface 81 and the first convex surface 71a, as shown in Figure 5(b). Specifically, the entire range of the convex portion 10, which was completed in the preceding first step, including the top wall portion 11 and the pair of vertical wall portions 13, is positioned. On the other hand, the parts of the intermediate component Ma other than the protrusion 10 may be lightly restrained by a holder or the like (not shown), or they may be left completely unrestrained. Here, as shown in Figure 5(b), if the parts of the intermediate component Ma other than the protrusion 10 are left unrestrained, the material flow along the left-right direction of the paper can be prevented from being obstructed by the second pad 80 in both the left and right portions of the intermediate component Ma relative to the protrusion 10. As a result, the intermediate component Ma is properly positioned relative to the lower mold 71. 【0042】 In Figure 5(c), following Figure 5(b), the upper mold 72 is lowered while maintaining the positioning of the intermediate part Ma by the second pad 80. As a result, the intermediate part Ma is sandwiched between the second convex surface 71c and the first concave surface 72b, and a portion of the convex portion 20 is formed on both sides of the convex portion 10. During this time, the portion of the intermediate part Ma that is sandwiched between the second concave surface 81 of the second pad 80 and the first convex surface 71a of the lower mold 71 is positioned. If the portion other than the portion sandwiched between the second concave surface 81 and the first convex surface 71a is not restrained, the flow of material necessary for forming the convex portion 20 can be made smoother. After forming the protrusion 20, the upper mold 72 is raised and the mold is opened to obtain the intermediate part Ma shown in Figure 6. This intermediate part Ma has a protrusion 10 having a pair of ridge sections 12a and a pair of ridge sections 12b with small radii of curvature, as well as a protrusion 20 having ridge sections 22a and 22b with similarly small radii of curvature. However, since these are formed with sufficient material flow, there are no cracks or excessive reduction in plate thickness at each of the ridge sections 12a, 12b, 22a, and 22b. 【0043】 The basics of the manufacturing method and manufacturing apparatus for automotive structural members according to the above embodiment are summarized below. A method for manufacturing an automobile structural member according to one aspect of the present invention is: A method for manufacturing an energy absorbing member (automotive structural member) 5 by pressing a blank (metal plate) M, wherein the cross-sectional shape along one direction is a corrugated molded product in which multiple convex portions 10, 20 having a pair of vertical wall portions 13, 23 are arranged in a row, As shown in Figure 4, the first step is to press-form the blank M with the first mold 50 to form one of the protrusions, which is a protrusion (first protrusion) 10, As shown in Figure 5, following the first step, the second step involves pressing the entire area of ​​the protrusion 10, including the pair of vertical wall portions 13, with the second pad 80 from the start to the end of the press working process, and then press working the intermediate part Ma with a second mold 70, which is different from the first mold 50, to form a portion of the protrusion 20 on both sides of the protrusion 10. It has. 【0044】 As shown in Figure 6, in the second step of this embodiment, molding is performed that includes only one of the pair of vertical wall portions 23 but not the other (molding that forms only a part of the protrusion 20). However, it is not limited to this, and the entire range including both of the pair of vertical wall portions 23 may be formed in one step in the second step. Furthermore, in the above-described method for manufacturing automotive structural members, as shown in Figure 3, a third step may be further included in which, after the second step, the area that has been formed by the press working up to the previous step is pressed down with a third pad (another pad) 100, and then press working is repeatedly performed on the area outside the formed area to form multiple new protrusions 20. 【0045】 The molding die system for automotive structural members according to this embodiment is This is used in the above-mentioned method for manufacturing automotive structural members, It comprises a first mold 50, a second mold 70, a first pad 60, and a second pad 80. As shown in Figure 5, the second mold 70 is A lower mold (first split mold) 71 having a first convex mold surface 71a that matches the concave surface of the convex portion (first convex portion) 10, and a second convex mold surface 71c that matches at least a part of the concave surface of the convex portion 20, The upper mold (second split mold) 72 has a first concave surface 72b positioned opposite to the second convex surface 71c, The second pad 80 has a second concave surface 81 that matches the entire convex surface of the convex portion 10, including the pair of vertical wall portions 13, and is positioned opposite the first convex surface 71a. 【0046】 According to the manufacturing method using the molding die system for automotive structural members of this embodiment, when performing the second step, first, the convex portion 10 is sandwiched between the first convex surface 71a of the second die 70 and the second concave surface 81 of the second pad 80, thereby properly maintaining the position of the intermediate part Ma relative to the lower die 71 of the second die 70. Then, the upper die 72 and the lower die 71 are brought relatively close together to sandwich the intermediate part Ma and perform press working. Specifically, the intermediate part Ma is sandwiched between the second convex surface 71c and the first concave surface 72b to form at least a part of the convex portion 20. During this time, the entire area of ​​the convex portion 10 is pressed down by the second pad 80, so the position of the intermediate part Ma relative to the lower die 71 of the second die 70 is properly maintained, and the second convex surface 71c and the first concave surface 72b can be accurately applied to the part of the intermediate part Ma where the convex portion 20 is to be formed, and press working can be performed. In this case, if the area outside the range held down by the second pad 80 is left unrestrained, the material flow necessary to form at least a portion of the protrusion 20 can be made smoother. Therefore, the energy absorbing member 5 shown in Figure 2 can be obtained without causing molding defects. 【0047】 [Second Embodiment] A method for manufacturing an automotive structural member and a molding die system according to a second embodiment of the present invention will be described below with reference to Figures 7 to 9. In this second embodiment, a corrugated molded product is manufactured as an energy absorbing member 5, similar to the first embodiment. However, in the first step of the manufacturing process, the pre-formed portions 20A and 20B are formed simultaneously with the formation of the convex portion 10, which is a key difference from the first embodiment. The following description will focus particularly on the differences from the first embodiment. 【0048】 In the first step of this embodiment, a first mold 150 different from the first mold 50 used in the first embodiment is used to form the pre-formed parts 20A and 20B. As shown in Figure 7(a), the first mold 150 has a lower mold 151 and an upper mold 152. The lower mold 151 has a first convex surface 151a formed on its upper surface, which has a convex shape that matches the concave surface formed on the lower surface of the convex portion (first convex portion) 10 described above. This first convex surface 151a has a trapezoidal shape consisting of an upper surface that matches the lower surface of the top wall portion 11 of the convex portion 10 and two side surfaces that match the inner surfaces of the pair of vertical wall portions 13. 【0049】 Furthermore, the lower mold 151 has a pair of second convex mold surfaces 151b for forming the pre-formed portion 20A, with the first convex mold surface 151a interposed between them. In addition, the lower mold 151 has a pair of third convex mold surfaces 151d for forming the pre-formed portion 20B, with the first convex mold surface 151a and each of the second convex mold surfaces 151b interposed between them. In other words, as shown in Figure 7(a), when the upper surface of the lower mold 151 is viewed in a vertical cross-section along one direction, the bottom surface 151c, the second convex surface 151b, and the third convex surface 151d are integrally formed in this order on the left side of the paper of the trapezoidal first convex surface 151a. Similarly, the bottom surface 151c, the second convex surface 151b, and the third convex surface 151d are integrally formed in this order on the right side of the paper of the first convex surface 151a. Therefore, the upper surface of the lower mold 151 is symmetrical in shape with respect to the first convex surface 151a. 【0050】 The first convex surface 151a has a trapezoidal shape consisting of an upper surface that matches the lower surface of the top wall portion 11 of the convex portion 10 and two side surfaces that match the inner surfaces of the pair of vertical wall portions 13. The first convex surface 151a forms a projection with the same trapezoidal cross-section at each position from the front to the back of the paper in Figure 7(a). Each base surface 151c is a horizontal surface that is connected to the lower edge of the first convex surface 151a. Each second convex surface 151b has an arcuate surface formed at its apex and a pair of side surfaces extending from both sides of the arcuate surface. The second convex surface 151b is similar to the first convex surface 151a in that it has both side surfaces that slope from their upper end to their lower end, but it differs in that the apex of the first convex surface 151a is a flat surface, while the apex of the second convex surface 151b is an arcuate surface that is close to a semicircle. Because the cross-section of this second convex surface 151b does not contain any sharply curved parts, such as ridges, it does not obstruct the flow of material into the area where the preformed portion 20A shown in Figure 7(c) is formed when performing the press working shown in Figure 7(b). 【0051】 Each third convex surface 151d is a gently concave curved surface in the portion connected to the lower edge of the second convex surface 151b, while the portion away from the lower edge of the second convex surface 151b is a gently convex curved surface. Because this third convex surface 151d does not have any sharply curved portions, such as ridges, within its cross-section, and furthermore, its height is kept lower than that of the second convex surface 151b, it does not obstruct the flow of material into the area forming the preformed portion 20B shown in Figure 7(c) when performing the press working shown in Figure 7(b). The first convex surface 151a, each second convex surface 151b, each bottom surface 151c, and each third convex surface 151d described above have the same cross-sectional shape at each position in the lower mold 151, from the front side of the paper to the back side of the paper in Figure 7(a). 【0052】 The upper mold 152 has a first concave surface 152a formed on its lower surface, which has a concave shape that matches the convex surface formed on the upper surface of the convex portion 10 described above. That is, it has an inner surface that matches the outer surfaces of the pair of vertical wall portions 13 of the convex portion 10. On the other hand, the lower surface of the first pad 160 has a shape that matches the upper surface of the top wall portion 11 of the convex portion 10. The first concave surface 152a, when combined with the flat surface 161 which is the lower surface of the first pad 160, can form a concave groove with the same trapezoidal cross-section at each position from the front to the back of the paper in Figure 7(b). 【0053】 Furthermore, the upper mold 152 has a pair of second concave surfaces 152b for forming the pre-formed portion 20A, with a first concave surface 152a interposed between them. In addition, the upper mold 152 has a pair of third concave surfaces 152d for forming the pre-formed portion 20B, with a first concave surface 152a and each of the second concave surfaces 152b interposed between them. In other words, as shown in Figure 7(a), when the lower surface of the upper mold 152 is viewed in a vertical cross-section along one direction, on the left side of the paper of the first concave surface 152a, the bottom surface 152c, the second concave surface 152b, and the third concave surface 152d are formed integrally in this order. Similarly, on the right side of the paper of the first concave surface 152a, the bottom surface 152c, the second concave surface 152b, and the third concave surface 152d are also formed integrally in this order. Therefore, the lower surface of the upper mold 152 is symmetrical in shape with respect to the first concave surface 152a. 【0054】 Each bottom surface 152c is a horizontal surface that is connected to the lower edge of the first concave surface 152a. Each second concave surface 152b has an arcuate surface formed at its apex and a pair of side surfaces adjacent to both sides of the arcuate surface. The second concave surface 152b is similar to the first concave surface 152a in that it has both side surfaces that slope from the upper end to the lower end, but differs in that its apex is an arcuate surface. This second concave surface 152b is designed so as not to obstruct the flow of material into the area where the preformed portion 20A shown in Figure 7(c) is formed when performing the press working shown in Figure 7(b). 【0055】 Each third concave surface 152d is a gently convex curved surface in the portion connected to the lower edge of the second concave surface 152b, while the portion away from the lower edge of the second concave surface 152b is a gently concave curved surface. Because this third concave surface 152d does not have any sharply curved portions, such as ridges, within its cross-section, and furthermore, its height is kept lower than that of the second concave surface 152b, it does not obstruct the flow of material into the area forming the preformed portion 20B shown in Figure 7(c) when performing the press working shown in Figure 7(b). The first concave surface 152a, each second concave surface 152b, each bottom surface 152c, and each third concave surface 152d described above have the same cross-sectional shape in the upper mold 152 at each position from the front side to the back side of the paper in Figure 7(a). 【0056】 The first pad 160 is positioned in the upper mold 152 so as to pass vertically through the first concave surface 152a, and can move up and down independently of the upper mold 152 by obtaining driving force from the drive mechanism. The lower end of the first pad 160 has a flat surface 161 that matches the upper surface of the top wall portion 11 of the convex portion 10. When forming the convex portion 10 with the first mold 150, the flat surface 161 of the first pad 160 can be pressed against the upper surface of the blank M placed on the lower mold 151 before lowering the upper mold 152, thereby fixing the blank M to the lower mold 151. 【0057】 Furthermore, in the second step of this embodiment, a second mold 170 different from the second mold 70 used in the first embodiment is used. The second mold 170 has a lower mold 171 and an upper mold 172, as shown in Figure 8(a). The lower mold 171 has a first convex surface 171a formed on its upper surface, which has the same shape as the first convex surface 151a of the lower mold 151 shown in Figure 7(a). Furthermore, a second convex surface 171b, which has the same shape as the first convex surface 171a, is formed one to the left and one to the right of the first convex surface 171a, with a gap between them. In other words, the upper surface of the lower mold 171 has three convex surfaces, each having the same shape that matches the concave surfaces of the convex portions 10 and 20, arranged with gaps between them. These three convex surfaces form a ridge with a trapezoidal cross-section, which is the same shape at each position from the front to the back of the paper in Figure 8(a). 【0058】 The upper mold 172 has two second concave surfaces 172b formed on its lower surface, which match the convex surface of the convex portion 20, spaced apart with the second pad 180 interposed between them. Similarly, as shown in Figure 8(a), a second concave surface 181 is formed at the lower end of the second pad 180, which matches the convex surface that is the upper surface of the protrusion 10. This second concave surface 181 has a surface that matches the upper surface of the top wall portion 11 of the protrusion 10, and a pair of inclined surfaces that match the outer surfaces of the pair of vertical wall portions 13. The combination of these three surfaces within the second concave surface 181 forms a concave groove with the same trapezoidal cross-section at each position from the front to the back of the paper in Figure 8(a). The second pad 180 is positioned to pass vertically through the upper mold 172 and can move up and down independently of the upper mold 172 by obtaining driving force from the drive mechanism. A second concave surface 181 is formed at the lower end of the second pad 180, which matches the upper surface of the top wall portion 11 of the convex portion 10. Therefore, when forming the convex portion 20 with the second mold 170, as shown in Figure 8(b), the second pad 180 is lowered before lowering the upper mold 172, and the convex portion 10 of the blank M is sandwiched between the second concave surface 181 and the first convex surface 171a. This allows the intermediate part Ma to be positioned in the correct position relative to the concave and convex surfaces on the lower mold 171. 【0059】 In the manufacturing method of the automotive structural member according to this embodiment, first, the first step shown in Figures 7(a) and (b) is performed to form the intermediate part Ma shown in Figure 7(c), and then, the second step shown in Figures 8(a) to (c) is performed to form the intermediate part Ma shown in Figure 9. Then, by repeating the press working corresponding to the second step, the energy absorbing member 5 shown in Figure 2 is manufactured. 【0060】 In other words, in the first step, as shown in Figure 7(a), the blank M is first placed on the open lower mold 151, and then the first pad 160 is lowered. As a result, the blank (metal plate) M is sandwiched between the flat surface 161 of the first pad 160 and the first convex mold surface 151a of the lower mold 151, thus completing the positioning of the blank M relative to the lower mold 151. 【0061】 In Figure 7(b), following Figure 7(a), the upper die 152 is lowered while maintaining the fixation of the blank M by the first pad 160. As a result, the blank M is sandwiched between the first convex surface 151a and the first concave surface 152a, and the convex portion 10 is formed. At the same time, the blank M is sandwiched between the second convex surface 151b and the second concave surface 152b to form a pair of preformed portions 20A. During this time, the portion of the blank M sandwiched between the flat surface 161 of the first pad 160 and the top surface of the first convex surface 151a may be restrained. In both the lower die 151 and the upper die 152, there are no sharply curved portions, such as ridges, in the area where the preformed portions 20A are formed, so the inflow of metal material for forming the preformed portions 20A is not obstructed. Thus, the convex portion 10 and each of the preformed portions 20A can be formed without causing a reduction in plate thickness or cracking. Furthermore, if the portion other than the area sandwiched between the flat surface 161 and the top surface of the first convex surface 151a is left unrestrained, the flow of material necessary for forming the convex portion 10 can be made smoother. 【0062】 After forming the protrusion 10 and each preformed section 20A, the upper mold 152 is raised and the mold is opened to obtain the intermediate part Ma shown in Figure 7(c). This intermediate part Ma has a protrusion 10 formed thereon, which has a pair of ridge sections 12a and a pair of ridge sections 12b with small radii of curvature. As described above, these are formed with sufficient material flow, so there are no cracks or excessive reduction in plate thickness at each ridge section 12a, 12b. 【0063】 In the second step, following the first step, the intermediate part Ma is first placed on the open lower mold 171, as shown in Figure 8(a), and then the second pad 180 is lowered. As a result, the convex portion 10, which was completed in the first step, fits into the second concave surface 181 of the second pad 180. By continuing to push down the second pad 180, the convex portion 10 is sandwiched between the second concave surface 181 and the first convex surface 171a, as shown in Figure 8(b). Specifically, the shape of the entire area of ​​the convex portion 10, which was completed in the preceding first step, including the top wall portion 11 and the pair of vertical wall portions 13, is maintained. In addition, each of the pair of pre-formed portions 20A formed in the first step can be placed on top of each second convex surface 171b. In this way, the intermediate part Ma is properly positioned relative to the lower mold 171. On the other hand, as shown in Figure 8(b), the parts of the intermediate component Ma other than the protruding portion 10 may be left unconstrained. 【0064】 In Figure 8(c), following Figure 8(b), the upper mold 172 is lowered while the intermediate part Ma is held in place by the second pad 180. As a result, the intermediate part Ma is sandwiched between each second convex surface 171b and each second concave surface 172b, so that convex parts 20 are formed on both sides of the convex part 10. During this time, the portion of the intermediate part Ma sandwiched between the second concave surface 181 of the second pad 180 and the first convex surface 171a of the lower mold 171 may be completely restrained. The portion other than the portion sandwiched between the second concave surface 181 and the first convex surface 171a may be lightly restrained by a holder or the like (not shown), or it may be completely unrestrained. In this case, if it is unrestrained, the flow of material necessary for forming the convex parts 20 can be made smoother. After forming each of the protrusions 20, the upper mold 172 is raised and the mold is opened to obtain the intermediate part Ma shown in Figure 9. This intermediate part Ma has a pair of protrusions 20, each having a pair of ridge sections 12a and 22b with small radii of curvature, in addition to the protrusion 10 having a pair of ridge sections 12a and 22b with small radii of curvature. As described above, these are formed with sufficient material flow, so there are no cracks or excessive reduction in plate thickness in each of the ridge sections 12a, 12b, 22a, and 22b. 【0065】 The basics of the manufacturing method and manufacturing apparatus for automotive structural members according to the above embodiment are summarized below. A method for manufacturing an automobile structural member according to one aspect of the present invention is: As shown in Figure 3, this is a method for manufacturing an automobile structural member in which a blank (metal plate) M has a cross-sectional shape in one direction in which multiple protrusions 10, 20 having a pair of vertical wall portions 13, 23 are arranged in a row, As shown in Figure 7, the first step involves press-forming the blank M with the first mold 150 to form one of the protrusions, which is a protrusion (first protrusion) 10. As shown in Figure 8, following the first step, the second step involves pressing the area of ​​the protrusion 10, including the pair of vertical wall portions 13, with the second pad (pad) 180 from the start to the end of the press working, and then press working the intermediate part Ma with a second mold 170, which is different from the first mold 150, to form a protrusion 20 next to the protrusion 10. It has. 【0066】 In the above method for manufacturing automotive structural members, As shown in Figure 7, in the first step, Simultaneously with the press processing of the protrusion 10, From the start to the end of the press working process, the portion of the blank M intended to form the convex portion 20 may be press-worked to obtain a pre-formed portion 20A that bends in the same direction as the convex portion 20. 【0067】 In the above method for manufacturing automotive structural members, As shown in Figure 3, in the third step, the molded area formed into the final shape by the press working up to the previous step is pressed down by other pads such as the third pad 100, and then the press working outside the molded area is repeatedly performed to form the multiple protrusions. You may do this further. 【0068】 The molding die system for automotive structural members according to this embodiment is This is used in the above-mentioned method for manufacturing automotive structural members, It comprises a first mold 150, a second mold 170, a first pad 160, and a second pad 180. As shown in Figure 8, the second mold 170 is A lower mold (first split mold) 171 having a first convex mold surface 171a that matches the concave surface of the convex portion (first convex portion) 10, and a second convex mold surface 171b that matches the entire area of ​​the concave surface of the convex portion (second convex portion) 20, The upper mold (second split mold) 172 has a second concave surface 172b positioned opposite to the second convex surface 171b, The second pad 180 has a second concave surface 181 that matches the entire convex surface of the convex portion 10, including the pair of vertical wall portions 13, and is positioned opposite the first convex surface 171a. 【0069】 According to the manufacturing method using the molding die system for automotive structural members of this embodiment, when performing the second step, first, the convex portion 10 is sandwiched between the first convex surface 171a of the second mold 170 and the second concave surface 181 of the second pad 180, thereby properly maintaining the position of the intermediate part Ma relative to the lower mold 171 of the second mold 170. Then, the upper mold 172 and the lower mold 171 are brought relatively close together to sandwich the intermediate part Ma and perform press working. Specifically, the intermediate part Ma is sandwiched between the second convex surface 171b and the second concave surface 172b to form a convex portion 20. During this time, the convex portion 10 is pressed down by the second pad 180, which properly maintains the position of the intermediate part Ma relative to the lower mold 171 of the second mold 170. Therefore, the second concave surface 172b can be accurately applied to the part of the intermediate part Ma where the convex portion 20 is to be formed, and press working can be performed. Furthermore, during this pressing process, the area outside the range pressed by the second pad 180 may be left unrestrained. In this case, the material flow necessary to form at least a portion of the protrusion 20 can be made smoother. Therefore, the energy absorbing member 5 shown in Figure 2 can be obtained without causing molding defects. 【0070】 [Differentiation] Hereinafter, modifications of the first and second embodiments described above will be explained with reference to Figures 10 to 14. First, a modified example of the second embodiment described above will be explained with reference to Figure 10. In the second embodiment described above, an example was shown in which a preformed portion 20A with an arc-shaped top was formed, as shown in Figure 7(c). However, a preformed portion 20A with a top of any other shape, as shown in Figure 10, may also be used. Specifically, Figure 10(a) shows the case where chamfers are formed on the parts that become the ridges 22a and 22b after the first step. Figure 10(b) shows the case where the height dimension of the preformed part after the first step is greater than the height dimension of the first protrusion. Figure 10(c) shows the case where a bead is further added to the preformed part in Figure 10(b). As illustrated above, in a cross-section of the energy absorbing member 5 viewed along one direction, chamfered portions or arc portions may be formed in the pre-formed portion 20A formed in the first step, at the locations corresponding to each ridge. Furthermore, as illustrated in Figures 10(b) and 10(c), the pre-formed portion 20A may be formed such that its height is greater than the height of the protrusion 20 that is to be formed at the location of the pre-formed portion 20A. 【0071】 Next, Figure 11 shows a modified example of the uneven shape of the protrusions 10 and 20. Specifically, Figure 11(a) shows a configuration having a cross-sectional shape consisting only of straight sections, excluding the top wall sections 11, 21 and the bottom wall section 14. Figure 10(b) shows a configuration where the cross-sectional shape of each edge section is curved. Figure 10(c) shows a configuration in which the unevenness is composed only of walls with curved cross-sectional shapes. Figure 10(d) shows a configuration combining relatively large and small unevenness heights. Figure 10(e) shows a configuration combining different unevenness shapes. 【0072】 Next, Figure 12 shows a modified example in which the height and width dimensions of each protrusion change in the short-side direction of the automobile structural member (from the front of the page to the back of the page). In other words, Figure 12 shows the case where the wavy arrangement differs between the front and back of the page. 【0073】 Next, Figure 13 shows a modified example relating to flange f. Specifically, Figure 13(a) shows a configuration without flanges at the longitudinal ends. Figure 13(b) shows a configuration with a flange f having one bend at the right edge of the page. Figure 13(c) shows a configuration with a flange f having two bends at the right edge of the page. 【0074】 Next, Figure 14 shows a modified example of the application location of the energy absorbing member 5. In other words, while the first and second embodiments described above illustrate the application of the present invention to the manufacture of the energy absorbing member 5 in the side sill 2, the invention is not limited to these examples and may also be applied to energy absorbing members 5 arranged on both sides of the battery tray 3 as shown in Figure 14. In this case, the energy absorbing member 5 is fixed to the left side of the battery tray 3 by welding or the like so as to be aligned in the front-rear direction, and the energy absorbing member 5 is also fixed to the right side of the battery tray 3 by welding or the like so as to be aligned in the front-rear direction. Furthermore, the energy absorbing member 5 may be applied to locations other than the side sill 2 and the battery tray 3. [Examples] 【0075】 Figure 15 shows an example of numerical calculation results when the corrugated energy-absorbing member 5 is manufactured using the manufacturing method described in the second embodiment above. Figure 16 shows an example of numerical calculation results when manufactured using a conventional manufacturing method. In each figure, the hatching density increases as the plate thickness reduction rate increases. The same preconditions were used for these numerical calculations. Specifically, the calculation conditions were that the material had a tensile strength of 980 MPa and a plate thickness of 1.6 mm. As can be seen by comparing Figure 15 and Figure 16, a higher localized rate of plate thickness reduction is observed in Figure 16, which is the conventional example, compared to Figure 15, which is the inventive example. Cracks were confirmed to have occurred at the bent area, which is particularly darkened at the right edge of the page in Figure 16. 【0076】 Therefore, in order to investigate the cause of the high plate thickness reduction rate and cracking in the conventional example shown in Figure 16, the behavior of the intermediate component Ma within the mold was confirmed by numerical calculation. The results are shown in Figure 17. As shown in Figure 17(a), when manufactured using the conventional manufacturing method, in the second step, only the upper surface of the top wall portion 11 of the protrusion 10 is pressed down with a pad, but the sides are not pressed down. As a result, as can be seen from Figure 17(a), the intermediate part Ma was not properly positioned and fixed in the mold, especially with respect to the lower die, and there were parts that were tilted. Then, as the upper die was lowered without the intermediate part Ma being properly positioned, as shown in Figure 17(b), the uneven edges of the mold and the uneven edges of the intermediate part Ma did not make proper contact with each other, and proper press processing was not achieved. On the other hand, in the example of the invention shown in Figure 15, the convex portion 10 formed in the first step is pressed against the lower die in the second step, including the vertical wall portion 13 in addition to the top wall portion 11. As a result, the intermediate part Ma does not tilt within the die, and press working is performed on it. Thus, in the example of the invention, the placement of the intermediate part Ma relative to the lower die is made appropriate before press working, and it has been confirmed that the high rate of plate thickness reduction and cracking that occur in the conventional example do not occur. [Explanation of symbols] 【0077】 5. Energy absorbing members (automotive structural members) 10. Convex part (first convex part) 11,21 Top wall section 12a,12b,22a,22b Ridge line part 13,23 Vertical wall section 14 Bottom wall section 20. Convex section (second convex section) 20A,20B Preformed part 50 First mold 51 Lower mold 51a First convex surface 52 Upper mold 52a 1st concave surface 60 First pad 70 Second mold 71 Lower mold 71a First convex surface 71c Second convex surface 72 Upper mold 72a Bottom 72b 1st concave surface 80 Second pad (pad) 81 Second concave surface 90 Third mold 91 Lower mold 92 Upper mold 100 Third pad (pad) 150 First mold 151 Lower mold 151a First convex surface 151b Second convex surface 152 Upper mold 152a First concave surface 152b 2nd concave surface 160 First Pad 170 Second mold 171 First part mold 171a First convex surface 171b Second convex surface 172 Second part mold 172a 1st concave surface 172b 2nd concave surface 180 Second pad (pad) 181 Second concave surface M Blank (metal plate) Ma Intermediate component (metal plate)

Claims

[Claim 1] A method for manufacturing an automotive structural member by pressing a metal sheet, wherein the cross-sectional shape along one direction is such that multiple convex portions, each having a pair of vertical walls, are arranged in a row, The first step is to press the metal plate with a first die to form a first protrusion, which is one of the aforementioned protrusions, Following the first step, the second step involves pressing the area of ​​the first protrusion, including the pair of vertical wall portions, with a pad from the start to the end of the press working process, and then press working the metal plate with a second die, which is different from the first die, to form at least a part of the second protrusion next to the first protrusion. A method for manufacturing an automobile structural member, characterized by having the following features. [Claim 2] The aforementioned automobile structural member further comprises a top wall portion connecting the upper edges of the pair of vertical wall portions, and a bottom wall portion connecting the adjacent protrusions, In the first step, in addition to the pair of vertical wall portions, the top wall portion is formed as part of the first protrusion. In the second step, the bottom wall portion is formed between the first and second protrusions, in addition to at least a portion of the second protrusion. A method for manufacturing an automobile structural member according to claim 1. [Claim 3] In the first step described above, Simultaneously with the press working of the first protrusion, From the start to the end of the press working process, the portion of the metal plate intended to form the second protrusion is press-formed in a direction along the aforementioned one direction, thereby obtaining a pre-formed portion that bends in the same direction as the second protrusion. A method for manufacturing an automobile structural member according to claim 1. [Claim 4] When the aforementioned automobile structural member is viewed in a cross-section along the aforementioned direction, each of the aforementioned protrusions further has a top wall portion that is connected to each of the pair of vertical wall portions via a ridge portion, When forming the preformed portion in the first step, a chamfered portion or an arc portion is formed in the portion of the preformed portion corresponding to each of the ridges. The method for manufacturing an automobile structural member according to claim 3. [Claim 5] The preformed portion is formed such that its height is greater than the height of the second protrusion which is to be formed at the location of the preformed portion. The method for manufacturing an automobile structural member according to claim 3. [Claim 6] In the third step, the molded area formed into the final shape by the press working up to the previous step is held down by another pad, and the press working outside the molded area is repeatedly performed to form the multiple protrusions. A method for manufacturing an automobile structural member according to claim 1, further comprising the above. [Claim 7] The tensile strength of the aforementioned automobile structural member is 980 MPa or more. A method for manufacturing an automobile structural member according to claim 1. [Claim 8] A molding die system for an automobile structural member, used in a method for manufacturing an automobile structural member according to any one of claims 1 to 7, The invention comprises the first mold, the second mold, and the pad, The second mold, A first split mold having a first convex mold surface that matches the concave surface of the first convex portion, and a second convex mold surface that matches at least a part of the concave surface of the second convex portion, A second split mold having a first concave surface positioned opposite the second convex surface, It has, The pad, including the pair of vertical wall portions, matches the entire area of ​​the convex surface of the first protrusion and has a second concave surface positioned opposite the first convex surface. A molding die system for automotive structural members, characterized by the following features.

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