Framework member for automobile body, joint structure, and method for manufacturing framework member

Abstract

The present invention addresses the problem of providing a framework member for an automobile body, a joint structure, and a manufacturing method for a framework member, capable of reducing the occurrence of poor dimensional accuracy after shaping, ensuring connection performance with other members, and preventing a deterioration in collision resistance performance. A framework member (1) for an automobile body comprises a vertical side portion (11), a horizontal side portion (12), and a curved portion (13), and is provided with a top plate (21) that is formed continuously with the vertical side portion (11), the horizontal side portion (12) and the curved portion (13), a vertical wall (22) that is formed continuously with an end portion of the top plate (21) on the side of the vertical side portion on which the curved portion (13) is formed, in a vehicle body front-rear direction, and a bead (5) that is formed in the top plate (21), has a recessed shape when viewed from the outer surface side of the vehicle body, and extends in the vehicle body front-rear direction, wherein the bead (5) is formed in a region excluding a first line (L1) obtained by extending the central axis line of a ridge line (3) in the horizontal side portion (12) between the top plate (21) and the vertical wall (22) in the vehicle body front-rear direction.

Description

Frame member for automobile body, joint structure, and method for manufacturing frame member

[0001] The present invention relates to a frame member for an automobile body, a joint structure, and a method for manufacturing the frame member.

[0002] When a steel sheet is press-formed and removed from a mold, springback can cause defects, resulting in a deterioration in the dimensional accuracy of the press-formed component. In particular, in the case of L-shaped or T-shaped components, uneven undulations occurring at the curved portion of the top plate are a problem. Here, the L-shaped or T-shaped component comprises a vertical side extending in one direction, a horizontal side connected to one end of the vertical side and extending in a direction different from the vertical side, and a curved portion formed at the connection between the vertical side and the horizontal side. Furthermore, the L-shaped or T-shaped component comprises a top plate formed continuously with the vertical side, the horizontal side, and the curved portion, a vertical wall formed continuously with the end of the top plate, and a flange formed continuously with the end of the vertical wall opposite the end connected to the top plate. When the L-shaped or T-shaped component is a frame component for an automobile body, the components in the A-pillar lower shown in FIG. 1(A), the B-pillar lower shown in FIG. 1(B), and the B-pillar upper shown in FIG. 1(C) are L-shaped or T-shaped components.

[0003] The above-mentioned defects in L-shaped and T-shaped components are caused by stresses that occur when forming the flanges of the curved parts. Tensile stresses are generated in the flanges of the curved parts due to stretch flange deformation. At this time, a reverse compressive stress occurs in the top plate as a reaction force to the generated tensile stress. When this compressive stress is released during springback, the area from the curved part to the horizontal side of the top plate, which has lower rigidity than the ridge line with the vertical wall part, undergoes concentrated elastic deformation, resulting in undulating, uneven shape defects.

[0004] Conventionally, methods for reducing such dimensional accuracy defects have generally been used to increase the rigidity of molded products. For example, Patent Document 1 discloses a method of arranging a bead at an angle on the curved portion of the top plate of a front pillar (A-pillar). Also, Patent Document 2 discloses a structure for the upper part of a center pillar (B-pillar) having a concave-convex portion.

[0005] JP 2007-125951 A JP 2003-212148 A

[0006] The curved portion of an L-shaped or T-shaped member primarily serves as a joint to join another member (also called the mating member). When the L-shaped or T-shaped member is the lower A-pillar, lower B-pillar, or upper B-pillar shown in Figure 1, the top panel of the horizontal edge of each member is spot-welded to a straight member such as a side sill or roof rail as the mating member. When joining an L-shaped or T-shaped member to a mating member, a gap of several millimeters must be left so that the two members do not interfere with each other except at the spot welding points.

[0007] For example, in the case of an automobile A-pillar lower, which is an L-shaped component, the top plate of the horizontal side is spot welded to a straight component with an M-shaped cross section called a side sill, as shown in Figure 2. At this time, it is necessary to leave a gap other than the spot welding points indicated by "X" in Figure 2(B).

[0008] Since the mating joint member is often straight, this gap exists extending in the same direction as the longitudinal direction of the mating joint member. Therefore, interference with the mating joint member becomes an issue, making it difficult to arrange the bead so that it crosses the extension direction of the horizontal side portion as in Patent Document 1. Furthermore, if the bead shape overlaps with the punch shoulder ridge as in Patent Document 1, that is, if the extension direction of the bead is inclined to the extension direction of the vertical side portion, the bead can become a break point in the event of a head-on collision of the automobile, causing a decrease in collision performance.

[0009] Furthermore, as in Patent Document 2, if a recess extending parallel to the direction of extension of the vertical side is formed on the horizontal side of the B-pillar, the bead will become a breaking point when the vehicle is hit head-on, causing a decrease in collision performance.

[0010] Therefore, the present invention has been made with a focus on the above-mentioned problems, and aims to provide a frame member for an automobile body, a joint structure, and a method for manufacturing a frame member that can reduce the occurrence of poor dimensional accuracy after molding, ensure connection performance with other members, and prevent a decrease in collision resistance performance.

[0011] (1) According to one aspect of the present invention, there is provided a skeletal member for an automobile body comprising: a vertical side portion extending in the vertical direction of the vehicle body; a horizontal side portion connected to one end of the vertical side portion in the vertical direction of the vehicle body, extending in the fore-and-aft direction of the vehicle body, and protruding in at least one direction in the fore-and-aft direction relative to the vertical side portion; and a curved portion at the connection between the horizontal side portion and the vertical side portion, formed on the side of the horizontal side portion protruding in the fore-and-aft direction of the vehicle body, wherein the skeletal member for an automobile body comprises: a top plate formed continuously with the vertical side portion, the horizontal side portion, and the curved portion; a vertical wall formed continuously with the end of the top plate on the side of the vertical side portion in the fore-and-aft direction of the vehicle body where the curved portion is formed; and a bead formed on the top plate, having a concave shape when viewed from the outer surface side of the vehicle body, and extending in the fore-and-aft direction of the vehicle body, wherein the bead is formed in an area excluding a first line extending in the fore-and-aft direction of the vehicle body from the central axis of the ridge line between the top plate and the vertical wall at the horizontal side portion.

[0012] (2) In the skeletal member for an automobile body described in (1) above, the bead is formed in both the front and rear regions in the fore-and-aft direction of the vehicle body, with a second line extending in the vertical direction of the vehicle body from the central axis of the ridge line between the top plate and the vertical wall at the vertical side portion as the boundary.

[0013] (3) In the frame member for an automobile body of (1) or (2) above, the beads are formed in both upper and lower regions in the vertical direction of the vehicle body, with the first line as the boundary.

[0014] (4) In the frame member for an automobile body according to any one of (1) to (3) above, a plurality of the beads are formed in the vertical direction of the vehicle body.

[0015] (5) In any one of (1) to (4) above, the skeletal member for an automobile body further comprises a convex portion formed on the vertical side portion and having a convex shape when viewed from the outer surface side of the vehicle body, and the bead is formed closer to the horizontal side portion than the convex portion.

[0016] (6) According to one aspect of the present invention, there is provided a joint structure for an automobile body, comprising a first skeletal member and a second skeletal member joined to the first skeletal member, wherein the first skeletal member is a skeletal member for an automobile body described in any one of (1) to (5) above, the second skeletal member has a top plate that is at least partially overlapping the top plate of the first skeletal member, and a recess formed in the top plate, which has a concave shape when viewed from the outer surface side of the vehicle body and extends in the fore-and-aft direction of the vehicle body, and the bead is fitted into the recess.

[0017] (7) According to one aspect of the present invention, there is provided a method for manufacturing a skeletal member for an automobile body, the skeletal member comprising: a vertical side portion extending in the vertical direction of the vehicle body; a horizontal side portion connected to one end of the vertical side portion in the vertical direction of the vehicle body, extending in the longitudinal direction of the vehicle body, and protruding in at least one direction in the longitudinal direction of the vehicle body relative to the vertical side portion; and a curved portion at the connection portion between the horizontal side portion and the vertical side portion, the curved portion being formed on the side of the horizontal side portion protruding in the longitudinal direction of the vehicle body, the skeletal member being manufactured by press-forming a metal plate; the skeletal member comprising: a top plate formed continuously with the vertical side portion, the horizontal side portion, and the curved portion; a vertical wall formed continuously with an end of the top plate on the side of the vertical side portion in the longitudinal direction of the vehicle body where the curved portion is formed; and a bead formed on the top plate, having a concave shape when viewed from the outer surface side of the vehicle body, and extending in the longitudinal direction of the vehicle body; A method for manufacturing a skeletal member for an automobile body is provided, in which the bead is formed in an area excluding a first line extending in the fore-and-aft direction of the vehicle body from the central axis of the ridge line between the top plate and the vertical wall at the horizontal edge portion.

[0018] (8) A manufacturing method of a frame member for an automobile body as described in (7) above, comprising: a first press process in which the metal plate is press-molded to form an intermediate member having the top plate, in which the area where the bead is formed is flat, and the vertical wall; and a second press process in which the intermediate member is press-molded to form a bead on the top plate.

[0019] According to one aspect of the present invention, there are provided a frame member for an automobile body, a joint structure, and a method for manufacturing a frame member, which can reduce the occurrence of poor dimensional accuracy after molding, ensure connection performance with other components, and prevent a decrease in collision resistance performance.

[0020] 9A and 9B are schematic diagrams showing examples of a skeletal member and a mating joint member for an automobile body, where (A) shows a case where the skeletal member is an A-pillar lower, (B) shows a case where the skeletal member is a B-pillar lower, and (C) shows a case where the skeletal member is a B-pillar upper.

[0023] Fig. 9A is an explanatory diagram showing a joint structure in which an A-pillar lower and a mating joint member are joined, where (A) is a plan view of the skeletal member, and (B) is a cross-sectional view of the joint structure taken along the II-I' section of (A).

[0024] Fig. 9B is a perspective view of a skeletal member.

[0025] Fig. 9C is a schematic diagram showing a skeletal member in which a shape defect has occurred.

[0026] Fig. 9D is an explanatory diagram showing the cause of the shape defect.

[0027] Fig. 9E is a plan view of a T-shaped skeletal member.

[0028] Fig. 9F is a cross-sectional view of a T-shaped skeletal member having a convex portion. FIG. 1 is a plan view showing an example of a T-shaped skeletal member in a modified example. FIG. 2 is a plan view showing an example of a T-shaped skeletal member in a modified example. FIG. 3 is a plan view showing an example of a T-shaped skeletal member in a modified example. FIG. 4 is a plan view showing the dimensions of a skeletal member in an example. FIG. 5 is a cross-sectional view showing the dimensions of a skeletal member in an example. FIG. 6 is an enlarged plan view showing a bead portion in an example. FIG. 7 is a plan view showing the arrangement of beads in a skeletal member in an example. FIG. 8 is a contour diagram showing the results in the examples, where (A) shows the results of Comparative Example 1, (B) shows the results of Example 4, (C) shows the results of Example 5, and (D) shows the results of Example 6.

[0021] In the following detailed description, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. The drawings are schematic and may differ from the actual product. Furthermore, the embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not specify the materials, structure, arrangement, etc. of component parts as described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0022] A skeleton member for an automobile body according to one embodiment of the present invention will be described. The skeleton member in this embodiment is an L-shaped or T-shaped metal member used for an automobile body. Such a skeleton member is used, for example, in an A-pillar lower, a B-pillar lower part, or a B-pillar lower part as shown in FIG. 1 . In this embodiment, a case where the skeleton member is an A-pillar lower will be described as an example.

[0023] The A-pillar lower skeletal member 1 is a metal member that has an L-shape when viewed from the exterior of the vehicle body, as shown in Fig. 3. In the following description, in relation to a skeletal member for an automobile body, the up-down direction of the automobile body is referred to as the vehicle body up-down direction (the up-down direction in Fig. 3), and the front-to-rear direction of the automobile body is referred to as the vehicle body front-to-rear direction (the left-to-right direction in Fig. 3). Furthermore, the upper and lower sides in the up-to-down direction in Fig. 3 correspond to the upper and lower sides of the vehicle body, respectively, the right and left sides in the left-to-right direction in Fig. 3 correspond to the front and rear sides of the vehicle body, respectively, and the front and rear sides in the front-to-rear direction relative to the plane of Fig. 3 correspond to the outer and inner sides of the vehicle body, respectively.

[0024] The frame member 1 includes a vertical side portion 11, a horizontal side portion 12, and a curved portion 13, which are portions separated by dotted lines in Fig. 3. The vertical side portion 11 is a portion extending in the up-down direction of the vehicle body. The horizontal side portion 12 is connected to the lower end of the vertical side portion 11, which is one end of the vertical side portion in the vehicle body up-down direction, extends in the fore-aft direction of the vehicle body, and is a portion protruding rearward, which is one side of the fore-aft direction of the vehicle body, from the vertical side portion 11. The curved portion 13 is a connection portion between the horizontal side portion 12 and the vertical side portion 11, is formed on the rear side, which is the side of the horizontal side portion 12 that protrudes in the fore-aft direction of the vehicle body, and is a portion that is curved concavely when viewed from the outside of the vehicle body.

[0025] The frame member 1 also includes a top plate 21, a vertical wall 22, and a flange 23. The top plate 21 is formed in an L-shape, continuing from the vertical side portion 11, the horizontal side portion 12, and the curved portion 13, and is parallel to the vehicle body up-down direction and the vehicle body fore-and-aft direction. The vertical wall 22 is formed continuous with at least the end of the top plate 21 on the side where the curved portion 13 of the vertical side portion 11 is formed in the vehicle body fore-and-aft direction (the rear side in the vehicle body fore-and-aft direction in FIG. 3 ). In this embodiment, as shown in FIG. 3 , the vertical wall 22 is formed at least on the end of the top plate 21 on the front and rear sides in the vehicle body fore-and-aft direction. As shown in FIG. 4 , the vertical wall 22 is formed by bending at a predetermined angle in the height direction from the top plate 21. The height direction is parallel to the thickness direction of the top plate 21. Furthermore, a ridge line 3 is formed at the connection between the top plate 21 and the vertical wall 22. The flange 23 is a flat surface parallel to the top plate 21 and is formed continuously with the end of the vertical wall 22 opposite the end connected to the top plate 21 .

[0026] The vertical side portion 11, the horizontal side portion 12, and the curved portion 13 of the top plate 21 are divided according to the ridge line 3. Here, for the ridge line 3 on the side where the curved portion 13 is formed, a line extending from the central axis of the ridge line 3 of the horizontal side portion 12 in the front-rear direction of the vehicle body is defined as a first line L １ The line extending from the center axis of the ridge line 3 in the vertical side portion 11 in the vertical direction of the vehicle body is called the second line L ２ Then, the first line L １ The area below the first line L in the vertical direction of the vehicle body is the horizontal side portion 12 of the top plate 21. １ In the region above the second line L ２ The curved area of ​​the tabletop 21 is the curved portion 13 of the tabletop 21, and the curved area of ​​the tabletop 21 is the curved area of ​​the tabletop 21. ２ The area on the anti-curved side of the second line L is the vertical side 11 of the tabletop 21. ２ The curved side is the second line L ２ The anti-curved side is the direction opposite to the curved side (the front side in the longitudinal direction of the vehicle body in FIG. 3).

[0027] Furthermore, the frame member 1, which is an A-pillar lower, further includes a convex portion 4, which has a convex shape when viewed from the exterior of the vehicle body, on the vertical side portion 11 of the top panel 21. In the case of an A-pillar lower, the convex portion 4 is a hinge portion used for connecting with the door. Such a convex portion 4 also exists when the frame member is, for example, the lower portion of a B-pillar.

[0028] 5, the top plate 21 of the frame member 1 has four regions, a first region A to a fourth region D, which are divided in the vertical direction and the longitudinal direction of the vehicle body. １ and the second line L ２ In addition, the third line L ３ and the fourth line L ４ The third line L ３ is a line extending from the lower end of the convex portion 4 in the front-rear direction of the vehicle body. ４ is a line that passes through the point where the ridge line 3 of the horizontal side portion 12 starts to curve and extends in the vertical direction of the vehicle body. The first area A to the fourth area D are defined by the first line L １ ~Fourth line L ４ Specifically, the first area A to the fourth area D are divided by the third line L. ３ and below the fourth line L ４ The area to the right of the first line L １ The first region A and the second region B are formed above the first line L １ The third region C and the fourth region D are formed below the second line L. ２ The first area A and the third area C are formed on the curved side of the second line L. ２ A second region B and a fourth region D are formed on the right side of the first region B.

[0029] When a skeletal member 1 having such a shape is manufactured by press molding, irregular shape defects may occur in the region from the curved portion 13 of the top plate 21 to the horizontal side portion 12. Figure 6 shows an example of an irregular shape defect in the top plate 21 that occurs when molding the skeletal member 1. In Figure 6, the dotted lines on the top plate 21 indicate the contour lines of the irregularities. As shown in Figure 6, such shape defects occur in the region from the curved portion 13 of the top plate 21 to the horizontal side portion 12, mainly in the first region A to the fourth region D shown in Figure 5. As shown in Figure 7, such shape defects are caused by compressive stress that occurs in the region surrounded by the dashed line on the top plate 21 as a reaction force to tensile stress generated by stretch flange deformation in the flange 23 of the curved portion 13.

[0030] One method for reducing irregular shape defects is to provide a bead 5' on the top plate 21 that extends at an angle relative to the longitudinal direction of the vehicle body, as shown in FIG. 8 (Patent Document 1). With this method, as shown by the arrow in FIG. 8, when a load is applied during a frontal collision, the bead 5' may become a fracture point, potentially reducing crashworthiness. Furthermore, as shown in FIG. 2, the frame member 1 is joined to the mating joint member by spot welding. In this case, if a bead 5' like that shown in FIG. 8 is present, the bead 5' will interfere with the mating joint member. Therefore, there is a need for a frame member for an automobile body that can reduce the occurrence of dimensional inaccuracies after molding, ensure connection performance with other members, and prevent a decrease in crashworthiness.

[0031] A skeleton member 1 for an automobile body according to this embodiment is shown in Figure 9. The skeleton member 1 shown in Figure 9 is the same as the skeleton member 1 described with reference to Figures 3 to 5, except that beads 5, which will be described later, are formed therein. That is, as shown in Figure 3, the skeleton member 1 includes vertical side portions 11, horizontal side portions 12, and curved portions 13. Also, as shown in Figures 3 and 9, the skeleton member 1 includes a top plate 21, vertical walls 22, flanges 23, and convex portions 4. These configurations are the same as those described above, and therefore will not be described further.

[0032] 9, the frame member 1 further includes a bead 5 formed on the top plate 21, having a concave shape when viewed from the outer surface side of the vehicle body, and extending in the front-rear direction of the vehicle body. The bead 5 is aligned along the first line L１ The first line L is formed in the region excluding the upper portion. １ By forming the bead 5 in the region excluding the upper portion, it is possible to prevent the bead 5 from becoming a breaking point in the event of a frontal collision of the vehicle. Furthermore, since the mating joint member often has a straight shape extending in the fore-and-aft direction of the vehicle body, the mating joint member can also easily change its shape to match the bead 5, making it easier to ensure a gap.

[0033] Furthermore, the bead 5 is preferably formed in the joint structure portion, which is the region of the top plate 21 surrounded by a dashed line as shown in FIG. 9 . The joint structure portion is a region including the first region A to the fourth region D, and is a region that overlaps with the mating joint member when viewed from the exterior of the vehicle body when the frame member 1 is joined to the mating joint member. By doing so, the bead 5 is formed in the region of the joint structure portion where shape defects are likely to occur, improving the rigidity of the region of the joint structure portion and reducing the occurrence of dimensional accuracy defects after molding. Furthermore, the bead 5 is preferably formed in at least one of the first region A to the fourth region D.

[0034] The cross-sectional shape of the bead 5 (the shape of the bead 5 in a cross section perpendicular to the extension direction of the bead 5) is not particularly limited, and may be, for example, V-shaped or U-shaped. The protruding direction of the bead 5 is preferably a direction that makes the automobile body concave when viewed from the exterior. If the protruding direction of the bead 5 is a direction that makes the automobile body convex when viewed from the exterior, the bead 5 will protrude to the outside of the vehicle, which is undesirable as it will affect the appearance of the vehicle. In addition, the bottom of the bead 5 is preferably flat. By making the bottom of the bead 5 flat, the flat bottom can be used as a spot welding point.

[0035] Furthermore, when the framework member 1 has a convex portion 4 like an A-pillar lower, it is preferable that the bead 5 be formed closer to the horizontal side portion 12 than the convex portion 4. By doing so, as shown by the arrows in Figure 9, tensile stress is generated between the convex portion 4 and the bead 5 when the framework member 1 is formed. Because the top plate 21 is curved, tension is also generated in the circumferential direction, which can offset the compressive stress that causes the top plate 21 to undulate.

[0036] (Method for Manufacturing Skeleton Member) The skeleton member 1 according to this embodiment is manufactured by press-forming a metal plate. The metal plate preferably has a tensile strength of 270 MPa or more and 1800 MPa or less and a plate thickness of 0.6 mm or more and 4.0 mm or less. While the tensile strength may be less than 270 MPa and the plate thickness less than 0.6 mm, there are few metal members in general automobiles, home appliances, etc. whose tensile strength and plate thickness are below these values. Metal plates with a tensile strength exceeding 1800 MPa have poor ductility and are therefore prone to cracking when forming the bead 5. Metal plates with a plate thickness exceeding 4.0 mm may be subject to a high processing load in the second press process described below, which may result in damage such as denting of the mold. Furthermore, the metal plate is preferably a steel plate.

[0037] In the manufacturing method of the skeletal member 1 according to this embodiment, a metal plate is press-formed. In this case, forming may be performed in a single press, but multiple presses are preferred. When forming in multiple presses, a first press step and a second press step are performed. In the first press step, the metal plate is press-formed to form an intermediate member having a top plate 21 with a flat area where the bead 5 is to be formed, a vertical wall 22, and a flange 23. In other words, in the first step, the configuration other than the bead 5 is the same as the intended skeletal member 1. In this case, it is preferable to perform form-forming to form the flange 23 from the vertical wall 22 while the top plate 21 is held down by a pad. In the second step, the intermediate member formed in the first press step is press-formed to form the bead 5 on the top plate 21. Note that the first and second steps may each be performed in multiple presses. Furthermore, the bead 5 may also be formed when forming the flange 23 from the vertical wall 22.

[0038] (Joint Structure of Automobile Body) The joint structure of an automobile body in this embodiment will be described with reference to Figures 10 and 11. In this embodiment, the joint structure is formed by joining a mating joint member 6 to a skeleton member 1. The skeleton member 1 is also referred to as the first skeleton member, and the mating joint member 6 is also referred to as the second skeleton member. In this embodiment, the skeleton member 1 is an A-pillar lower, and the mating joint member 6 is a side sill.

[0039] The mating joint member 6 is a straight member extending in the longitudinal direction of the vehicle body. As shown in FIGS. 10 and 11 , the mating joint member 6 includes, in a cross section perpendicular to the extending direction (the longitudinal direction of the vehicle body), a top plate 61, vertical walls 62 formed continuously at both ends of the top plate 61, and a flange 63 formed continuously with the vertical wall 62. The top plate 61 also has at least one recess 64 extending in the longitudinal direction of the vehicle body and having a concave shape when viewed from the exterior of the vehicle body. In the example shown in FIGS. 10 and 11 , two recesses 64 are formed. Of these, one recess 64 (the upper recess 64 in FIGS. 10 and 11 , also referred to as the corresponding recess) is formed at a position corresponding to the bead 5 of the frame member 1 when the frame member 1 and the mating joint member 6 are joined, so that the bead 5 can be fitted into it. The corresponding recess preferably has a cross-sectional shape similar to that of the bead 5.

[0040] In the joint structure of the automobile body in this embodiment, the bead 5 is fitted into the corresponding recess. As shown in Fig. 10, the bead 5 and the corresponding recess are preferably joined by spot welding. In Fig. 10, the positions indicated by "X" are spot welding points.

[0041] <Modifications> Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention that include various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention described in the claims also encompass embodiments that include these modifications described herein, either alone or in combination.

[0042] For example, in the above embodiment, one bead 5 is formed on the frame member 1, but the present invention is not limited to this example. A plurality of beads 5 may be formed on the frame member 1. In this case, a plurality of beads 5 may be formed in the front-rear direction of the vehicle body, or a plurality of beads 5 may be formed in the up-down direction of the vehicle body. For example, the bead 5 may be formed on the frame member 1 along the second line L ２ The bead 5 may be formed in the front and rear regions in the vehicle longitudinal direction, with the first line L as the boundary. １The beads 5 may be formed in the upper and lower regions in the vertical direction of the vehicle body, with the boundary being the first region A to the fourth region D. By providing multiple beads 5 or providing beads 5 in multiple regions from the first region A to the fourth region D, rigidity is improved, and therefore the occurrence of poor dimensional accuracy after molding can be further reduced. Note that when beads 5 are provided in multiple regions from the first region A to the fourth region D, different beads 5 may be provided in each of the multiple regions, or one bead 5 may be provided across the multiple regions.

[0043] Furthermore, in the above embodiment, the skeletal member 1 is an L-shaped A-pillar lower, but the present invention is not limited to this example. The skeletal member 1 may be a T-shaped member such as a B-pillar lower part or a B-pillar upper part. Figures 12 and 13 show an example of a T-shaped skeletal member 1. When the skeletal member 1 is T-shaped, curved portions 13 are formed on both sides of the vertical side portion 11 in the fore-and-aft direction of the vehicle body (left-and-right direction in Figures 12 and 13). Note that Figure 12 shows a skeletal member 1 that does not have a convex portion 4 on the vertical side portion 11, while Figure 13 shows a skeletal member 1 that has a convex portion 4 on the vertical side portion 11. The third line L ３ The third line L may be a line extending in the front-rear direction of the vehicle body from the point where the ridge line 3 of the vertical side portion 11 begins to curve. Alternatively, as shown in FIG. 12, the third line L ３ The first line L may be a line extending in the front-rear direction of the vehicle body slightly below the point where the ridge line 3 of the vertical side portion 11 begins to curve. In the case of Fig. 13, it is defined in the same way as in the above embodiment. Also, in Figs. 12 and 13, the first line L １ , second line L ２ and the fourth line L ４ is defined in the same manner as in the above embodiment, and the fourth line L ４ Furthermore, when the frame member 1 is T-shaped, the horizontal side portion 12 does not have to be completely straight. For example, the horizontal side portion 12 may be bent in a V-shape or a U-shape around the center of the vertical side portion 11 in the fore-and-aft direction of the vehicle body.

[0044] As an example of providing beads 5 when the frame member 1 is T-shaped, examples in which beads 5 are provided on the frame member 1 of FIG. 12 are shown in FIGS. 14 to 16. In the examples shown in FIGS. 14 to 16, the first line L １ ~Fourth line L ４At least one bead 5 similar to that in the above embodiment is provided in each of the first region A to fourth region D, which are divided by the boundary. Note that in the examples shown in FIGS. 14 to 16, the skeleton member 1 has a T-shape, and therefore, unlike the above embodiment, two first regions A and two third regions C are formed. In the example shown in FIG. 14, a bead 5 is provided in each of the six first regions A to fourth regions D. In the example shown in FIG. 15, one bead 5 is provided from the third region C on the left side to the third region C on the right side. In the example shown in FIG. 16, a bead 5 is provided in the second region B, from the third region C on the left side to the fourth region D, and from the fourth region D to the third region C on the right side.

[0045] An example carried out by the present inventors will be described below. In the example, a simulation was carried out in which an L-shaped frame member 1 was formed by press-forming a metal plate, and the height of the irregularities on the top plate 21 was evaluated.

[0046] 17 and 18 show example dimensions of the skeletal member 1 used in the verification. Note that the example in Fig. 17 shows a state in which the bead 5 has been removed. To prevent cracking of the metal plate, the boundaries of the top plate 21, vertical wall 22, and flange 23 are curved with a radius of curvature of 5 mm for the convex boundaries facing the outside of the product and a radius of curvature of 6 mm for the concave boundaries (curvature of the curved portion in Fig. 18). The metal plate used in the verification is a steel plate with a thickness of 1.4 mm and a strength level of 590 MPa, and has the material properties shown in Table 1.

[0047]

[0048] In the process of forming the frame member 1, the frame member 1 was formed from a metal plate using foam molding to form the flanges 23 from the vertical walls 22 while the top plate 21 was held down with pads. In addition, the beads 5 were also formed when forming the flanges 23 from the vertical walls 22.

[0049] The cross-sectional shape of the bead 5 is a 2 mm deep U-shape as shown in Figure 19, with the boundary between the top surface and the bead and the curved portion within the bead 5 having a radius of curvature of 7 mm, and the bottom having a parallel portion of 10 mm. Note that the cross-sectional shape is not limited to this shape. Whatever the shape, the presence of a bead can generate tensile stress and suppress the cause of undulation. If you want to increase rigidity, it is better to make the cross-sectional shape deeper so that the quadratic section modulus of the cross-sectional shape is higher, make the curved portion have a smaller radius of curvature, and make it wider.

[0050] Table 2 shows the conditions for the examples and the measurement results of the irregularity height (size of irregularities) on the top plate 21. Figure 22 also shows the contour diagrams of the shapes of Comparative Example 1 and Examples 4, 5, and 6. For comparison, in the examples, a skeletal member 1 was molded without beads (Comparative Example 1). In Comparative Example 1, the skeletal member 1 shown in Figure 17 was molded. In the examples, the skeletal member 1 was molded under multiple conditions in which beads 5 were placed in various positions (Examples 1 to 7). The bead placement in Table 2 indicates the placement position of the beads 5, with A to D corresponding to the first region A to the fourth region D, respectively. A indicates that one bead 5 is formed in the first region A, B indicates that one bead 5 is formed in the second region B, C indicates that one bead 5 is formed in the third region C, and D indicates that one bead 5 is formed in the fourth region D. The beads 5 formed in each region were positioned and shaped as shown in Figure 20. Furthermore, the condition where multiple bead arrangements are described indicates that multiple beads 5a to 5d are formed in multiple regions. The CD connection condition in Example 4 is shown in Figure 21, where one bead 5e is provided across the third region C and the fourth region D.

[0051]

[0052] In Table 2, the condition for a good shape is when the absolute value of the irregularities is within 3.0 mm and the irregularity difference is 3.5 mm or less. The condition for a poor shape is when the absolute value of the irregularities exceeds 3.0 mm or the irregularity difference exceeds 3.5 mm.

[0053] As a result of the examples, it was confirmed that the unevenness difference was reduced in Examples 1 to 7 compared to Comparative Example 1. In other words, it was confirmed that the provision of the bead 5 can suppress undulation of the top plate 21.

[0054] REFERENCE SIGNS LIST 1 skeletal member (first skeletal member) 11 vertical side portion 12 horizontal side portion 13 curved portion 21 top plate 22 vertical wall 23 flange 3 ridge line 4 convex portion 5, 5' bead 6 mating member (second skeletal member) 61 top plate 62 vertical wall 63 flange 64 recessed portion

Claims

1. A skeletal member for an automobile body comprising: a vertical side portion extending in the vertical direction of the vehicle body; a horizontal side portion connected to one end of the vertical side portion in the vertical direction of the vehicle body, extending in the fore-and-aft direction of the vehicle body, and protruding in at least one direction in the fore-and-aft direction relative to the vertical side portion; and a curved portion at the connection between the horizontal side portion and the vertical side portion, formed on the side of the horizontal side portion protruding in the fore-and-aft direction of the vehicle body; wherein the skeletal member for an automobile body comprises: a top plate formed continuously with the vertical side portion, the horizontal side portion, and the curved portion; a vertical wall formed continuously with the end of the top plate on the side in the fore-and-aft direction of the vehicle body where the curved portion of the vertical side portion is formed; and a bead formed on the top plate, which has a concave shape when viewed from the outer surface side of the vehicle body and extends in the fore-and-aft direction of the vehicle body; 2. A skeletal member for an automobile body as described in claim 1, wherein the bead is formed in both the front and rear regions in the fore-and-aft direction of the vehicle body, with a second line extending in the vertical direction of the vehicle body from the central axis of the ridge line between the top plate and the vertical wall at the vertical side portion as the boundary.

3. A frame member for an automobile body as set forth in claim 1 or 2, wherein the beads are formed in both the upper and lower regions of the vehicle body in the vertical direction, with the first line as the boundary.

4. A frame member for an automobile body according to any one of claims 1 to 3, wherein a plurality of the beads are formed in the vertical direction of the vehicle body.

5. A skeletal member for an automobile body as set forth in any one of claims 1 to 4, further comprising a convex portion formed on the vertical side and having a convex shape when viewed from the outer surface side of the vehicle body, and the bead is formed closer to the horizontal side than the convex portion.

6. A joint structure for an automobile body comprising a first skeletal member and a second skeletal member joined to the first skeletal member, wherein the first skeletal member is a skeletal member for an automobile body as defined in any one of claims 1 to 5, and the second skeletal member has a top plate that is at least partially overlapping the top plate of the first skeletal member, and a recess formed in the top plate that has a concave shape when viewed from the outer surface of the body and extends in the fore-and-aft direction of the body, and the bead is fitted into the recess.

7. A method for manufacturing a skeletal member for an automobile body, the skeletal member comprising: a vertical side portion extending in the vertical direction of the vehicle body; a horizontal side portion connected to one end of the vertical side portion in the vertical direction of the vehicle body, extending in the longitudinal direction of the vehicle body, and protruding in at least one direction in the longitudinal direction of the vehicle body relative to the vertical side portion; and a curved portion at the connection between the horizontal side portion and the vertical side portion, formed on the side of the horizontal side portion protruding in the longitudinal direction of the vehicle body, wherein the skeletal member is manufactured by press-forming a metal plate; and the skeletal member comprises: a top plate formed continuously with the vertical side portion, the horizontal side portion, and the curved portion; a vertical wall formed continuously with the end of the top plate on the side of the vertical side portion in the longitudinal direction of the vehicle body where the curved portion is formed; and a bead formed on the top plate, having a concave shape when viewed from the outer surface side of the vehicle body, and extending in the longitudinal direction of the vehicle body; A method for manufacturing a skeletal member for an automobile body, wherein the bead is formed in an area excluding a first line extending in the fore-and-aft direction of the vehicle body from the central axis of the ridge line between the top plate and the vertical wall at the horizontal side portion.

8. A method for manufacturing a frame member for an automobile body as described in claim 7, comprising: a first press process in which the metal plate is press-formed to form an intermediate member having the top plate, the area where the bead is to be formed, flat, and the vertical wall; and a second press process in which the intermediate member is press-formed to form a bead on the top plate.

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