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

Abstract

To provide a skeleton member for an automobile body, a joint structure, and a manufacturing method of the skeleton member capable of reducing occurrence of dimensional accuracy failure after molding, securing connection performance with other components, and preventing deterioration of collision resistance performance.SOLUTION: A framework member 1 for an automobile vehicle body including a vertical side portion 11, a horizontal side portion 12, and a curved portion 13, the framework member 1 including a top plate 21 formed continuously with the vertical side portion 11, the horizontal side portion 12, and the curved portion 13, a vertical wall 22 formed continuously with an end portion of the top plate 21 on a side where the curved portion 13 of the vertical side portion in a vehicle body front-rear direction is formed, and a bead 5 formed on the top plate 21, having a concave shape when viewed from an outer surface side of the vehicle body, and extending in the vehicle body front-rear direction, the bead 5 is formed in a region excluding a first line L1 obtained by extending a center axis of a ridge line 3 between the top plate 21 and the vertical wall 22 in the lateral side portion 12 in the vehicle body front-rear direction.SELECTED DRAWING: Figure 9

Description

[Technical Field]

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

[0002] When steel sheets are press-formed and removed from the mold, springback can cause defects, resulting in poor dimensional accuracy. In particular, L-shaped and T-shaped parts suffer from uneven undulations in the curved portion of the top plate. Here, L-shaped and T-shaped parts include 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, L-shaped and T-shaped parts include a top plate formed continuously with the vertical side, horizontal side, and 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 L-shaped and T-shaped parts are used as frame components for automobile bodies, the L-shaped and T-shaped parts include the lower A-pillar shown in FIG. 1(A), the lower B-pillar shown in FIG. 1(B), and the upper B-pillar shown in FIG. 1(C).

[0003] The above-mentioned defects in L-shaped and T-shaped parts are caused by stress that occurs when forming the flanges of the curved parts. Tensile stress is 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 of the top plate to the horizontal side, which has lower rigidity than the ridge line with the vertical wall part, undergoes concentrated elastic deformation, resulting in wavy, uneven shape defects.

[0004] Conventionally, methods for reducing such poor dimensional accuracy have generally been used to increase the rigidity of molded products. For example, Patent Document 1 discloses a method of placing 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 an uneven portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-125951 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-212148 Summary of the Invention [Problem to be solved by the invention]

[0006] The curved portions of L-shaped or T-shaped parts primarily serve as joints for joining with other parts (also called mating parts). When the L-shaped or T-shaped part is the lower A-pillar, lower B-pillar, or upper B-pillar shown in Figure 1, the top panels of the horizontal sides of each part are spot-welded to a straight part such as a side sill or roof rail as the mating part. When joining an L-shaped or T-shaped part to a mating part, a gap of several millimeters must be left so that the two parts do not interfere with each other except at the spot welding points.

[0007] For example, the top plate of the horizontal part of an automobile's A-pillar lower, which is an L-shaped part, is spot welded to the side sill, a straight part with an M-shaped cross section, 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 part is often straight, this gap exists extending in the same direction as the longitudinal direction of the mating part. Therefore, interference with the mating part becomes an issue, making it difficult to arrange the bead so that it crosses the extension direction of the horizontal side, 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, 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, when a recess extending parallel to the direction of extension of the vertical side is formed in the horizontal side of the B-pillar, the bead becomes a breakage point when the vehicle is hit head-on, which reduces 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 parts, and prevent a decrease in collision resistance performance. [Means for solving the problem]

[0011] (1) According to one aspect of the present invention, there is provided a frame 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 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 a 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, 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 portion of the top plate on a side where the curved portion of the vertical side portion in the vehicle body front-rear direction is formed; 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 front-rear direction of the vehicle body; Equipped with A frame 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 side portion.

[0012] (2) In the skeletal member for an automobile body of (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.

[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) The framework member for an automobile body according to any one of (1) to (4) above 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, 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 of an automobile body, comprising a first frame member and a second frame member joined to the first frame member, The first frame member is a frame member for an automobile body according to any one of (1) to (5) above, the second framework member has a top plate at least partially overlapping the top plate of the first framework member, and a recess formed in the top plate, 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 is fitted into the recess, thereby providing a joint structure for an automobile body.

[0017] (7) According to one aspect of the present invention, there is provided a method for manufacturing a frame member for an automobile body, the frame 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 a 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 framework member is manufactured by press-forming a metal plate; The framework member includes 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 portion of the top plate on the side of the vertical side portion in the vehicle body longitudinal direction 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 vehicle body longitudinal direction, 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 side portion.

[0018] (8) A method for manufacturing a frame member for an automobile body according to (7) above, comprising: a first press process for press-forming the metal plate to form an intermediate member having the top plate, the region where the bead is to be formed, flat, and the vertical wall; and a second pressing step of press-molding the intermediate member to form a bead on the top plate. [Effects of the Invention]

[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 parts, and prevent a decrease in collision resistance performance. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are schematic diagrams showing examples of a skeletal member for an automobile body and a mating part of the joint, where (A) shows the case where the skeletal member is an A-pillar lower, (B) shows the case where the skeletal member is a B-pillar lower part, and (C) shows the case where the skeletal member is a B-pillar upper part. [Figure 2] 1A and 1B are explanatory diagrams showing a joint structure in which an A-pillar lower and a mating part are joined, in which (A) is a plan view of a skeletal member, and (B) is a cross-sectional view of the joint structure at the II' section of (A). [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 2 is a plan view showing four regions of the top plate of the framework member. [Figure 6] FIG. 10 is a schematic diagram showing a skeletal member in which a shape defect occurs. [Figure 7] FIG. 10 is an explanatory diagram showing the cause of defective shape. [Figure 8] FIG. 10 is a plan view showing a conventional framework member. [Figure 9] FIG. 2 is a plan view showing a framework member according to an embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view of the joint structure taken along the line II-II′ in FIG. 9. [Figure 11] FIG. 10 is a cross-sectional view of the joint structure taken along the line III-III′ in FIG. 9. [Figure 12] FIG. 10 is a plan view showing a T-shaped skeletal member. [Figure 13] FIG. 10 is a plan view showing a T-shaped skeletal member having a convex portion. [Figure 14] FIG. 10 is a plan view showing an example of a T-shaped framework member in a modified example. [Figure 15] FIG. 10 is a plan view showing an example of a T-shaped framework member in a modified example. [Figure 16] FIG. 10 is a plan view showing an example of a T-shaped framework member in a modified example. [Figure 17] FIG. 10 is a plan view showing dimensions of a skeletal member in the embodiment. [Figure 18] FIG. 4 is a cross-sectional view showing dimensions of a skeletal member in an example. [Figure 19] FIG. 4 is an enlarged plan view showing a bead portion in the embodiment. [Figure 20] FIG. 2 is a plan view showing the arrangement of beads of a framework member according to an embodiment. [Figure 21] FIG. 2 is a plan view showing the arrangement of beads of a framework member according to an embodiment. [Figure 22] 1A and 1B are contour diagrams showing the results of 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. DETAILED DESCRIPTION OF THE INVENTION

[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] As shown in Fig. 3, the skeletal member 1, which is the A-pillar lower, is a metal member that has an L-shape when viewed from the exterior side of the vehicle body. In the following description, in the 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 are the upper and lower sides of the vehicle body, respectively, the right and left sides in the left-to-right direction in Fig. 3 are 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 are the outer and inner sides of the vehicle body, respectively.

[0024] The frame member 1 has a vertical side portion 11, a horizontal side portion 12, and a curved portion 13, which are portions separated by dotted lines in Figure 3. The vertical side portion 11 is a portion that extends 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-and-aft direction of the vehicle body, and is a portion that protrudes rearward, which is one side of the fore-and-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-and-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 a portion parallel to the up-down direction and the fore-and-aft direction of the vehicle body. 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 fore-and-aft direction of the vehicle body (the rear side in the fore-and-aft direction of the vehicle body 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 side and the rear side in the fore-and-aft direction of the vehicle body. 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 a direction parallel to the thickness direction of the top plate 21. Furthermore, a ridge line 3 is formed at the connection portion 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 to the end connected to the top plate 21.

[0026] The vertical side portion 11, horizontal side portion 12, and 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 at the horizontal side portion 12 in the fore-and-aft direction of the vehicle body is referred to as a first line L1, and a line extending from the central axis of the ridge line 3 at the vertical side portion 11 in the up-and-down direction of the vehicle body is referred to as a second line L2. The region below the first line L1 in the up-and-down direction of the vehicle body is the horizontal side portion 12 of the top plate 21. Furthermore, in the region above the first line L1 in the up-and-down direction of the vehicle body, the region on the curved side of the second line L2 is the curved portion 13 of the top plate 21, and the region on the anti-curved side of the second line L2 is the vertical side portion 11 of the top plate 21. The curved side and the anti-curved side indicate one side of the fore-and-aft direction of the vehicle body relative to the second line L2, where the curved side is the direction in which the ridge line 3 curves relative to the second line L2 (the rear side of the fore-and-aft direction of the vehicle body in Figure 3), and the anti-curved side is the direction opposite to the curved side (the front side of the fore-and-aft direction of the vehicle body in Figure 3).

[0027] Furthermore, the framework member 1, which is an A-pillar lower, further includes a convex portion 4 on the vertical side 11 of the top panel 21, which has a convex shape when viewed from the exterior of the vehicle body. 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 framework member is, for example, the lower part of a B-pillar.

[0028] As shown in FIG. 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. These regions are divided by a first line L1, a second line L2, a third line L3, and a fourth line L4. The third line L3 is a line extending from the lower end of the convex portion 4 in the longitudinal direction of the vehicle body. The fourth line L4 is a line passing through the point where the ridge line 3 of the horizontal side portion 12 begins to curve and extending in the vertical direction of the vehicle body. The first region A to the fourth region D are divided by the four lines, the first line L1 to the fourth line L4. Specifically, the first region A to the fourth region D are regions below the third line L3 and to the right of the fourth line L4. Also, a first region A and a second region B are formed above the first line L1, and a third region C and a fourth region D are formed below the first line L1. Furthermore, the first region A and the third region C are formed on the curved side of the second line L2, and the second region B and the fourth region D are formed to the right of the second line L2.

[0029] When a frame member 1 having such a shape is manufactured by press molding, irregular shape defects may occur in the region from the curved portion 13 to the horizontal side portion 12 of the top plate 21. FIG. 6 shows an example of an irregular shape defect in the top plate 21 that occurs when molding the frame member 1. In FIG. 6, the dotted lines on the top plate 21 indicate the contour lines of the irregularities. As shown in FIG. 6, such shape defects occur in the region from the curved portion 13 to the horizontal side portion 12 of the top plate 21, mainly in the first region A to the fourth region D shown in FIG. 5. As shown in FIG. 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 that occurs due to 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, to increase the rigidity of the top plate 21 (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. Also, as shown in FIG. 2, the frame member 1 is joined to the mating part 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 part. Therefore, there is a demand for a frame member for an automobile body that can reduce the occurrence of dimensional accuracy defects after molding, ensure connection performance with other parts, 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. Furthermore, 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] As shown in FIG. 9, the frame member 1 further includes a bead 5 formed on the top plate 21, which has a concave shape when viewed from the exterior of the vehicle body and extends in the fore-and-aft direction of the vehicle body. The bead 5 is formed in an area excluding the first line L1. By forming the bead 5 in an area excluding the first line L1, 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 part of the joint often has a straight shape extending in the fore-and-aft direction of the vehicle body, the shape of the mating part of the joint can also be easily changed 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 part when the frame member 1 is joined to the mating joint part as viewed from the exterior side of the vehicle body. 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 poor dimensional accuracy 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 direction in which the bead 5 extends) 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 of manufacturing frame members) The skeletal 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. Although the tensile strength may be less than 270 MPa and the plate thickness less than 0.6 mm, there are few metal parts for 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 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 forming in multiple presses is preferable. 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, vertical walls 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 walls 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 walls 22.

[0038] (Automobile body joint structure) 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 part 6 to a skeletal member 1. The skeletal member 1 is also referred to as the first skeletal member, and the mating joint part 6 is also referred to as the second skeletal member. In this embodiment, the skeletal member 1 is an A-pillar lower, and the mating joint part 6 is a side sill.

[0039] The mating joint part 6 is a straight part extending in the longitudinal direction of the vehicle body. As shown in FIGS. 10 and 11 , in a cross section perpendicular to the extending direction (the longitudinal direction of the vehicle body), the mating joint part 6 includes 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 side 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 part 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 a 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] <Modification> 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 set forth 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 longitudinal direction of the vehicle body, or a plurality of beads 5 may be formed in the vertical direction of the vehicle body. For example, the beads 5 may be formed in the front and rear regions of the vehicle body, with the second line L2 as the boundary. Furthermore, the beads 5 may be formed in the upper and lower regions of the vehicle body, with the first line L1 as the boundary. Providing a plurality of beads 5, or providing beads 5 in multiple regions from the first region A to the fourth region D, improves rigidity and further reduces the occurrence of poor dimensional accuracy after molding. 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 a single bead 5 may be provided across the multiple regions.

[0043] 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 part such as a lower B-pillar or an upper B-pillar. FIGS. 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 longitudinal direction of the vehicle body (left-right direction in FIGS. 12 and 13). Note that FIG. 12 shows a skeletal member 1 without a convex portion 4 on the vertical side portion 11, while FIG. 13 shows a skeletal member 1 with a convex portion 4 on the vertical side portion 11. The third line L3 may be a line extending in the longitudinal direction of the vehicle body from a point where the ridge line 3 of the vertical side portion 11 begins to curve. Alternatively, as shown in FIG. 12, the third line L3 may be a line extending in the longitudinal direction of the vehicle body slightly below a point where the ridge line 3 of the vertical side portion 11 begins to curve. In the case of FIG. 13, the definition is the same as in the above embodiment. 12 and 13, the first line L1, the second line L2, and the fourth line L4 are defined in the same manner as in the above embodiment, and two fourth lines L4 are set. Furthermore, when the frame member 1 is T-shaped, the horizontal side portions 12 do not have to be completely straight. For example, the horizontal side portions 12 may be bent in a V-shape or a U-shape around the center of the vertical side portions 11 in the vehicle front-rear direction.

[0044] As an example of providing beads 5 when the skeletal member 1 is T-shaped, an example in which beads 5 are provided on the skeletal member 1 of FIG. 12 is shown in FIGS. 14 to 16. In the examples shown in FIGS. 14 to 16, at least one bead 5 similar to that of the above embodiment is provided in the first region A to fourth region D, which are separated by the first line L1 to fourth line L4. Note that in the examples shown in FIGS. 14 to 16, since the skeletal member 1 is T-shaped, 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 to the third region C on the right. In the example shown in FIG. 16, beads 5 are provided in the second region B, from the third region C to the fourth region D on the left side, and from the fourth region D to the third region C on the right side. [Example]

[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. The example in Fig. 17 shows a state in which the bead 5 has been removed. To prevent cracks in 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] [Table 1]

[0048] In the process of forming the frame member 1, the metal plate was molded into the frame member 1 by using form molding to form the flange 23 from the vertical wall 22 while the top plate 21 was held down with a pad. In addition, when forming the flange 23 from the vertical wall 22, the bead 5 was also formed.

[0049] The cross-sectional shape of 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 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, if there is a bead, it will generate tensile stress and suppress the cause of swell. If you want to increase rigidity, it is better to make it 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 in the examples and the measurement results of the height of the unevenness of the top plate 21. FIG. 22 shows the shape appearance (contour diagram) of Comparative Example 1 and Examples 4, 5, and 6 of the present invention. In the examples, for comparison, a skeletal member 1 was molded under conditions in which no beads were provided (Comparative Example 1). That is, in Comparative Example 1, a skeletal member 1 like that shown in FIG. 17 was molded. In the examples, skeletal members 1 were molded under multiple conditions in which beads 5 were arranged in various positions (Examples 1 to 7 of the present invention). The bead arrangements in Table 2 indicate the arrangement positions of the beads 5, with A to D corresponding to the first region A to the fourth region D, respectively. That is, 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 provided in the positions and shapes shown in FIG. 20. Furthermore, conditions in which multiple bead arrangements are listed indicate that multiple beads 5a to 5d are formed in multiple regions, respectively. The CD connection conditions in Example 4 of the invention are as shown in FIG. 21, where one bead 5e is provided across the third region C and the fourth region D.

[0051] [Table 2]

[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 difference between the irregularities 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 difference between the irregularities exceeds 3.5 mm.

[0053] As a result of the examples, it was confirmed that the unevenness difference was reduced in invention examples 1 to 7 compared to comparative example 1. In other words, it was confirmed that by providing the beads 5, undulation of the top plate 21 could be suppressed. [Explanation of symbols]

[0054] 1. Skeletal member (first skeletal member) 11 Vertical side 12 Side part 13 Curved section 21 Top plate 22 Vertical Wall 23 flange 3 Ridgeline 4 Convex part 5.5' bead 6. Mating part (second frame member) 61 Top plate 62 Vertical Wall 63 flange 64 recess

Claims

1. A frame 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 front-rear direction of the vehicle body, and protruding in at least one direction in the front-rear direction of the vehicle body relative to the vertical side portion; and a curved portion at a 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 front-rear direction of the vehicle body, 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 portion of the top plate on a side where the curved portion of the vertical side portion in the vehicle body front-rear direction is formed; 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 front-rear direction of the vehicle body; Equipped with 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.

2. 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 up-and-down 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. 2. The automotive body frame member according to claim 1, wherein the beads are formed in both upper and lower regions of the vehicle body in the vertical direction, with the first line as a boundary.

4. 2. The automotive body frame member according to claim 1, wherein a plurality of the beads are formed in the vertical direction of the vehicle body.

5. The vehicle body further includes 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, 5. The automotive body frame member according to claim 1, wherein the bead is formed closer to the horizontal side portion than the convex portion.

6. A joint structure of an automobile body, comprising: a first frame member; and a second frame member joined to the first frame member, the first frame member is a frame member for an automobile body according to any one of claims 1 to 4, the second framework member has a top plate at least partially overlapping the top plate of the first framework member, and a recess formed in the top plate, 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 is fitted into the recess, forming a joint structure for an automobile body.

7. A method for manufacturing a frame member for an automobile body, the frame member comprising: a vertical side portion extending in a 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 a front-rear direction of the vehicle body, and protruding in at least one direction in the front-rear direction of the vehicle body relative to the vertical side portion; and a curved portion at a 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 front-rear direction of the vehicle body, The framework member is manufactured by press-forming a metal plate; The framework member includes: 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 portion of the top plate on the side of the vertical side portion in the vehicle body longitudinal direction 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 vehicle body longitudinal direction, 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 first press process for press-forming the metal plate to form an intermediate member having the top plate, the region where the bead is to be formed, flat, and the vertical wall; a second pressing step of press-molding the intermediate member to form a bead on the top plate; The method for manufacturing a frame member for an automobile body according to claim 7, comprising:

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