Automobile frame member

Abstract

An automobile frame member formed of a steel material having a tensile strength of 900 MPa or more, said frame member comprising a top plate, two vertical walls, two first flanges, a first crease part interposed between the top plate and a vertical wall, a second crease part interposed between a vertical wall and a first flange, two second flanges extending respectively from the two vertical walls, and a third flange extending from the top plate, wherein: the first flanges and the second flanges are connected, and the second flanges and the third flange are connected; and the second crease part has a monotonically decreasing part of a distance n from an L0 cross section to an L1 cross section.

Description

Automobile frame components

[0001] The present invention relates to an automobile frame member.

[0002] In recent years, fuel economy regulations have become stricter around the world, requiring lighter vehicles. Furthermore, in response to fuel economy regulations in various countries and the trend toward carbon neutrality, the electrification of vehicle power sources is also progressing. This has led to the need to install heavy batteries in vehicles, further increasing the need for weight reduction. At the same time, there is also a demand for improved crashworthiness, and it is necessary to achieve both lightweight vehicles and crashworthiness.

[0003] Examples of structural components that contribute to collision safety include bumper beams, side sills, cross members, roof side rails, center pillars, and other components located around the cabin. These components are required to generate a high reaction force (deformation resistance) against external forces such as collision loads and absorb collision energy in order to improve occupant safety during a collision and to enhance the protection function of the battery located under the floor. Possible methods for improving energy absorption performance include improving the materials used, such as increasing the strength or thinning of the structural components or using different materials. However, improvements to the shape of each component that makes up the structural components and the joining structure between the components are also required.

[0004] As a technology relating to the shape or joining structure of a conventional automobile frame member, Patent Document 1 discloses a metal frame member having a groove bottom, two ridges, and two vertical walls, in which an outward continuous flange is formed over the groove bottom, ridges, and vertical walls. Patent Documents 2 to 4 also disclose members having an outward continuous flange, similar to Patent Document 1.

[0005] Patent Document 5 discloses a joint structure including a hat-shaped first member and a hat-shaped second member whose longitudinal end is connected to the first member. In this joint structure, a flange is formed on the top surface of the second member and extends toward the first member, and the flange is joined to a vertical wall of the first member. Patent Document 6 discloses a press-formed product having a T-shaped top plate portion, a wall portion continuous from the top plate portion, and a flange portion continuous from the wall portion, in which the ridge line connecting the vertical side portion and the horizontal side portion of the top plate portion is curved.

[0006] Patent Document 7 discloses a vehicle undercarriage structure including a pair of rockers extending in the fore-and-aft direction of the vehicle and a floor cross member extending in the vehicle width direction between the pair of rockers and having one end joined to the lower part of the rockers.Patent Document 8 discloses a vehicle floor structure including a pair of rockers arranged on both outer sides of a floor panel of the vehicle in the vehicle width direction and extending in the fore-and-aft direction of the vehicle, a tunnel arranged in the center of the floor panel in the vehicle width direction, and a cross member connecting the rockers and the tunnel in the vehicle width direction.

[0007] International Publication No. 2016 / 104078 Japanese Patent No. 6176046 International Publication No. 2013 / 154114 International Publication No. 2016 / 194963 Japanese Patent Application Publication No. 2020-142767 Japanese Patent No. 6690605 Japanese Patent Application Publication No. 2015-105033 Japanese Patent Application Publication No. 2017-081200

[0008] As mentioned above, the structure of automotive frame members has been studied for various purposes, but in order to achieve both weight reduction and collision safety at a higher level, it is desirable to further improve energy absorption performance without substantially increasing weight.

[0009] The present invention has been made in view of the above circumstances, and has as its object to improve the energy absorption performance of an automobile frame member without causing a substantial increase in weight.

[0010] One aspect of the present invention that solves the above-mentioned problems is an automobile frame member formed of steel having a tensile strength of 900 MPa or more, the automobile frame member having a top plate, two vertical walls facing each other, two first flanges extending from each of the two vertical walls in a cross section perpendicular to the top plate, a first ridge portion sandwiched between the top plate and the vertical walls, a second ridge portion sandwiched between the vertical walls and the first flanges, two second flanges extending from each of the two vertical walls, and a third flange extending from the top plate, wherein the first flange and the second flange, and the second flange and the third flange are respectively connected, and when a straight line extending from an intersection line of a vertical wall extension plane extending the vertical wall toward the first flange and a first flange extension plane extending the first flange toward the vertical wall is taken as a reference line, the second ridge portion has a monotonically decreasing portion of a distance n from the L0 cross section to the L1 cross section defined below. L0 cross section: end point O of the vertical wall extension surface on the second flange side on the reference straight line h and an end point O of the first flange extension surface on the second flange side on the reference straight line. f a cross section perpendicular to the reference line passing through a point farthest from the second flange. L1 cross section: a cross section perpendicular to the reference line located at a distance L1 in the extension direction of the reference line from the intersection of a plane including the second flange and the reference line. However, when the flange width of the first flange is F, F / 2≦L1≦3F is satisfied. Distance n: the distance in the N direction from the reference line to the second ridge line portion in the cross section perpendicular to the reference line. N direction: the direction in which the first flange extended surface is rotated by an angle θ / 2 around the reference line toward the vertical wall extended surface in the cross section perpendicular to the reference line. Angle θ: the angle between the vertical wall extended surface and the first flange extended surface in the cross section perpendicular to the reference line.

[0011] In an automobile frame member, the energy absorption performance can be improved without a substantial increase in weight.

[0012] 6 is a diagram showing a schematic configuration of a joining structure using an automobile frame member according to one embodiment of the present invention. FIG. 6 is a diagram showing the A-A cross section in FIG. 1. FIG. 6 is a diagram for explaining the shape of a second ridge line portion at a corner portion. FIG. 6 is a cross section perpendicular to a reference straight line at a corner portion. FIG. 6 illustrates an example of change in distance n between the L0 cross section and the L1 cross section. FIG. 6 is a diagram for explaining the outer edge shape of a second ridge line portion at a connection point between the second ridge line portion and the third ridge line portion. FIG. 6 is a diagram showing a connection point between the second ridge line portion and the third ridge line portion as viewed from a direction perpendicular to the first flange in FIG. 6. FIG. 6 is a diagram showing the distance m from the reference straight line to the end point of the second ridge line portion. A , m B 1 is a diagram for explaining an example of the shape of a second ridge line portion at a corner portion. FIG. 2 is a diagram for explaining an example of the shape of an automobile frame member. FIG. 3 is a diagram for explaining an analytical model in collision simulation (1). FIG. 4 is a diagram for explaining conditions for collision simulation (1). FIG. 5 is a diagram for explaining dimensions of the analytical model. FIG. 6 is a diagram for explaining results of collision simulation (1). FIG. 7 is a diagram for explaining results of collision simulation (1). FIG. 8 is a diagram for explaining an analytical model in collision simulation (2). FIG. 9 is a diagram for explaining results of collision simulation (2). FIG. 10 is a diagram for explaining an analytical model in collision simulation (3). FIG. 11 is a diagram for explaining results of collision simulation (3). FIG. 12 is a diagram for explaining an analytical model in collision simulation (4). FIG. 13 is a diagram for explaining results of collision simulation (4). FIG. 14 is a diagram for explaining results of collision simulation (5).

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals, and redundant description will be omitted.

[0014] Fig. 1 is a diagram showing a schematic configuration of a joint structure 1 using an automobile frame member according to this embodiment. It is a diagram showing a cross section taken along the line A-A in Fig. 2. Note that the x-direction, y-direction, and z-direction in this specification and drawings are perpendicular to each other.

[0015] The joining structure 1 includes a first member 10, a second member 20, and a third member 30. In this embodiment, the first member 10 is an automobile frame member to which the third member 30 is joined, and the second member 20 corresponds to another automobile frame member to be joined to the automobile frame member.

[0016] The first member 10 and the second member 20 are members that extend in different directions, and the axial end of the first member 10 is joined to the second member 20. The first member 10 is a member that has a hat-shaped cross section perpendicular to the axial direction (x direction). A detailed description of the shape of the first member 10 will be given later. The second member 20 has a first wall surface 21 that extends parallel to the y-z plane or inclined at, for example, ±10 degrees so as to face the axial end of the first member 10, and a second wall surface 22 that extends from the z-direction end of the first wall surface 21 toward the opposite side from the first member 10 (the positive side in the x direction).

[0017] The joining structure 1 including the first member 10 and the second member 20 is applied to a location where the members 10, 20 are joined in a T-shape. Specific application examples include a joining location between a floor cross member and a side sill, a joining location between a roof cross member and a roof side rail, a joining location between a center pillar and a side sill or a roof side rail, a joining location between a front side member and a front bumper beam, and a joining location between a rear side member and a rear bumper beam.

[0018] For example, if the first member 10 is a cross member (a floor cross member or a roof cross member), the second member 20 is a side sill or a roof side rail. Also, if the first member 10 is a center pillar, the second member 20 is a side sill or a roof side rail. Also, if the first member 10 is a side member (a front side member or a rear side member), the second member 20 is a bumper beam (a front bumper beam or a rear bumper beam).

[0019] In addition, when the joining structure 1 is one of the following joining structures, the x direction, y direction, and z direction in the drawings respectively indicate the following directions: Joining structure between a cross member and a side sill or a roof side rail: x direction: vehicle width direction, y direction: vehicle length direction, z direction: vehicle height direction Joining structure between a center pillar and a side sill or a roof side rail: x direction: vehicle height direction, y direction: vehicle length direction, z direction: vehicle width direction Joining structure between a side member and a bumper beam: x direction: vehicle length direction, y direction: vehicle width direction, z direction: vehicle height direction

[0020] For example, if the first member 10 is a floor cross member and the second member 20 is a side sill, the first wall surface 21 of the second member 20 is the wall surface of the side sill on the vehicle interior side (cabin side) in the vehicle width direction. In this case, the second wall surface 22 is a wall surface extending toward the vehicle exterior side (opposite the cabin side) in the vehicle width direction, and corresponds to the upper or lower surface of the side sill.

[0021] When the first member 10 is a roof cross member and the second member 20 is a roof side rail, the first wall surface 21 of the second member 20 is the wall surface of the roof side rail on the vehicle interior side (cabin side) in the vehicle width direction. In this case, the second wall surface 22 is a wall surface extending toward the vehicle exterior side (opposite the cabin side) in the vehicle width direction, and corresponds to the upper or lower surface of the roof side rail.

[0022] When the first member 10 is a center pillar and the second member 20 is a side sill, the first wall surface 21 of the second member 20 is the upper surface of the side sill. In this case, the second wall surface 22 is a wall surface extending downward from the upper surface of the side sill, and corresponds to the wall surface of the side sill on the vehicle inner side (cabin side) or the vehicle outer side (opposite the cabin side) in the vehicle width direction.

[0023] When the first member 10 is a center pillar and the second member 20 is a roof side rail, the first wall surface 21 of the second member 20 is the underside of the roof side rail. In this case, the second wall surface 22 is a wall surface extending upward from the underside of the roof side rail, and corresponds to the wall surface of the roof side rail on the inside (cabin side) or outside (opposite the cabin side) in the vehicle width direction.

[0024] When the first member 10 is a side member and the second member 20 is a bumper beam, the first wall surface 21 of the second member 20 is the wall surface of the bumper beam on the vehicle interior side (cabin side) in the vehicle length direction. In this case, the second wall surface 22 is a wall surface extending toward the vehicle exterior side (opposite the cabin side) in the vehicle length direction, and corresponds to the upper or lower surface of the bumper beam.

[0025] The overall length of the first member 10 and the overall length of the second member are each changed as appropriate depending on the application location of the joining structure 1 on the vehicle body, etc., but are, for example, 100 to 3000 mm. The plate thickness of the first member 10 and the plate thickness of the second member 20 are each changed as appropriate depending on the application location of the joining structure 1 on the vehicle body, the required energy absorption performance, etc., but are, for example, 0.5 to 6.0 mm. The plate thickness of each member 10, 20 may be, for example, 0.8 mm or more, or 1.0 mm or more. Furthermore, the plate thickness of each member 10, 20 may be, for example, 4.0 mm or less, or 3.0 mm or less. The plate thicknesses of each member 10, 20 may be different from each other.

[0026] The first member 10 and the second member 20 may be made of a metal material such as steel having a tensile strength of 590 MPa or more, or an aluminum alloy or a magnesium alloy. The first member 10 and the second member 20 may be made of different metal materials.

[0027] When the material of the first member 10 is steel, the tensile strength of the steel is preferably 900 MPa or more. As will be shown in the examples described later, the use of the first member 10 according to this embodiment can improve energy absorption performance compared to conventional members, and this effect is significantly greater when the tensile strength is 900 MPa or more. The tensile strength of the steel is preferably 980 MPa or more, more preferably 1180 MPa or more, and even more preferably 1470 MPa or more.

[0028] The third member 30 is a mating member to be joined to the first member 10, which has a hat-shaped cross section. Joining the third member 30 and the first member 10 forms a hollow portion 35 extending in the x-direction between the first member 10 and the third member 30. Specifically, the hollow portion 35 is formed by the third member 30 and the top plate 11 and two vertical walls 12 and 13 (described later) of the first member 10. The cross-sectional shape perpendicular to the top plate 11 of the automobile frame member in which the first member 10 and the third member 30 are joined together is a closed cross-sectional shape. In this embodiment, the third member 30 is a flat closing plate. However, the third member 30 may also be, for example, a hat-shaped member or another component such as a floor panel. The third member 30 may be made of a metal material, such as steel having a tensile strength of 270 MPa or more, or an aluminum alloy or magnesium alloy.

[0029] (Shape of First Member) Next, the shape of the first member 10 as an automobile frame member will be described in detail. The first member 10 is a member having a hat-shaped cross section perpendicular to the axial direction (x direction), and has a top plate 11, two vertical walls 12, 13, and two first flanges 14a, 15a.

[0030] The top plate 11 extends in the longitudinal direction of the first member 10 and has a flat portion that extends parallel to the x-y plane or inclined at, for example, ±30 degrees relative to the x-y plane. The two vertical walls 12, 13 face each other, with one vertical wall 12 located between the top plate 11 and the first flange 14a and the other vertical wall 13 located between the top plate 11 and the first flange 15a. The opening angle between the two vertical walls 12, 13, i.e., the angle α between each of the two vertical walls 12, 13 and a plane perpendicular to the top plate 11 in a cross section perpendicular to the axial direction (x direction) of the first member 10, is, for example, 0 to 20°. The angle between the top plate 11 and one vertical wall 12 and the angle between the top plate 11 and the other vertical wall 13 may be different from each other. The first flange 14a extends outward (toward the negative y direction) from the end of the vertical wall 12 on the negative z-direction side (opposite the top plate 11 side), and the first flange 15a extends outward (toward the positive y direction) from the end of the vertical wall 13 on the negative z-direction side (opposite the top plate 11 side).

[0031] The first member 10, which includes the top plate 11, the two vertical walls 12, 13, and the two first flanges 14a, 15a, is formed by, for example, press working, and the top plate 11 is connected to the two vertical walls 12, 13, and the two vertical walls 12, 13 are further connected to the two first flanges 14a, 15a, respectively. In other words, the first member 10 is composed of a single part, and the top plate 11, the two vertical walls 12, 13, and the two first flanges 14a, 15a are members made of a continuous material.

[0032] Therefore, two first ridge portions 16, 17 are formed between the top plate 11 and each of the two vertical walls 12, 13. In addition, a second ridge portion 18 is formed between the vertical wall 12 and the first flange 14a, and a second ridge portion 19 is formed between the vertical wall 13 and the first flange 15a. The first ridge portions 16, 17 and the second ridge portions 18, 19 each extend along the axial direction (x direction) of the first member 10.

[0033] The top plate 11 sandwiched between the two first ridge lines 16, 17 is a flat area located between the end of the R of one first ridge line 16 (in other words, the boundary between the curved surface and the flat surface) and the end of the R of the other first ridge line 17. The vertical wall 12 sandwiched between the first ridge line 16 and the second ridge line 18 is a flat area located between the end of the R of the first ridge line 16 and the end of the R of the second ridge line 18. The vertical wall 13 sandwiched between the first ridge line 17 and the second ridge line 19 is a flat area located between the end of the R of the first ridge line 17 and the end of the R of the second ridge line 19. In addition, the first flange 14a corresponds to the flat area located outside (negative side in the y direction) from the R end of the second ridge portion 18, and the first flange 15a corresponds to the flat area located outside (positive side in the y direction) from the R end of the second ridge portion 19.

[0034] As shown in FIG. 1, the first member 10 further has two second flanges 14b, 15b and a third flange 15c in addition to the first flanges 14a, 15a described above.

[0035] The second flange 14b is a flange extending from both the vertical wall 12 and the top plate 11 at the end of the vertical wall 12 on the second member 20 side. The second flange 15b is a flange extending from both the vertical wall 13 and the top plate 11 at the end of the vertical wall 13 on the second member 20 side. The third flange 15c is a flange extending from the top plate 11 at the end of the top plate 11 on the second member 20 side.

[0036] The first flanges 14a, 15a are connected to the second flanges 14b, 15b, respectively, and the second flanges 14b, 15b are also connected to the third flange 15c. These flanges formed from a single piece of material, which are comprised of the first flanges 14a, 15a, the second flanges 14b, 15b, and the third flange 15c, are referred to as continuous flanges in this specification.

[0037] A third ridge portion 60 is formed between the vertical wall 13 and the second flange 15b and between the first flange 15a and the second flange 15b. The vertical wall 13 and the second flange 15b are connected to each other and the first flange 15a and the second flange 15b are connected to each other via the third ridge portion 60. The third ridge portion 60 between the vertical wall 13 and the second flange 15b is curved when viewed from a direction perpendicular to the first flange 15a (the z direction) and is formed in a curved shape so as to connect the flat portion of the vertical wall 13 and the flat portion of the second flange 15b. Although hidden by the top plate 11 and the vertical wall 12 and not shown in FIG. 1 , third ridge portions are also formed between the vertical wall 12 and the second flange 14b and between the first flange 14a and the second flange 15b.

[0038] In the first member 10 having such a continuous flange, when an external force such as a collision load is applied from the second member 20 side, the load transmission efficiency to the first ridge portions 16, 17 and the second ridge portions 18, 19 is improved, and the energy absorption performance can be improved compared to a member without a continuous flange.

[0039] It is preferable that no curved notches that convex inward are formed, for example, between the first flanges 14a, 15a and the second flanges 14b, 15b, or between the second flanges 14b, 15b and the third flange 15c.

[0040] Of the flanges that make up the continuous flange, the first flanges 14a and 15a are joined to the third member 30, the second flanges 14b and 15b are joined to the first wall surface 21 of the second member 20, and the third flange 15c is joined to the second wall surface 22 of the second member 20. The joining means is not particularly limited, and for example, welding means such as spot welding, laser welding, or plasma welding, or known joining means using an industrial adhesive can be applied.

[0041] In the first member 10 having the continuous flanges as described above, the shape of the second ridge portions 18, 19 near the ends of the second flanges 14b, 15b is different from the shape of the second ridge portions 18, 19 in areas sufficiently distant from the second flanges 14b, 15b. In this specification, for convenience of explanation, such ends of the second ridge portions 18, 19 are referred to as corner portions 40. The corner portions 40 are surrounded by the vertical wall 13, the first flanges 15a, and the third ridge portion 60, and are portions that mitigate sudden changes in shape.

[0042] In Figure 1, the corner portion on the side of one of the two second ridge portions 18, 19, the second ridge portion 18, is hidden by the top plate 11 and is not shown, but the shape of the corner portion on the side of the second ridge portion 18 is a left-right inverted shape when viewed from the x direction of the shape of the corner portion 40 on the side of the second ridge portion 19, which will be described below.

[0043] 3 is a diagram illustrating the shape of the second ridge line portion 19 at the corner portion 40. FIG. 4 is a cross-sectional view perpendicular to the reference line L at the corner portion 40. The second ridge line portion 19 at the corner portion 40 has a monotonically decreasing portion of distance n between the L0 cross section and the L1 cross section, as defined below. In explaining the shape of such second ridge line portion 19, the reference line L, the L0 cross section, the L1 cross section, and the distance n will first be explained.

[0044] The "reference line L" is the vertical wall extension plane P shown in FIG. A and the first flange extension surface P B The line extending from the line of intersection with the vertical wall extension plane P A is an imaginary plane formed by extending the vertical wall 13 toward the first flange 15a side between the top plate 11 side and the first flange 15a side. Bis an imaginary plane extending from the first flange 15a toward the vertical wall 13 (negative side in the y direction).

[0045] The "L0 cross section" is the point O shown in FIG. h and point O f The cross section is perpendicular to the reference line L and passes through a point far from the second flange 15b (in other words, a point far from the point O on the reference line L). h is the end point of the vertical wall extension surface on the reference line L on the second flange 15b side. f is the end point of the first flange extension surface on the second flange 15b side on the reference line L. Furthermore, the point O is the intersection point between the reference line L and the second flange extension surface obtained by extending the second flange 15b toward the reference line L.

[0046] The "L1 cross section" is a cross section perpendicular to the reference line L at a position a distance L1 from a plane including the second flange 15b in the extension direction of the reference line L (in other words, a position a distance L1 from point O on the reference line L). The distance L1 is also the position where the monotonous decrease of the distance n ends.

[0047] When the flange width of the first flange 15a is F, it is necessary to satisfy the relationship F / 2≦L≦3F. If the distance L is less than F / 2, the benefits of providing the corner portions 40 are not fully realized, and the improvement in energy absorption performance is small. On the other hand, if the distance L exceeds 3F, the joint area between the first flange 15a and the third member 30 is reduced. For example, if the first flange 15a and the third member 30 are spot-welded, the number of spot-welded points will be reduced. In this case, as will be shown in the examples described later, the improvement in energy absorption performance is not fully realized even if the corner portions 40 are provided.

[0048] The "flange width F of the first flange 15a" is the maximum width of the first flange 15a within the range of L1 to 2×L1 on the side opposite to the second flange 15b side (negative side in the x direction) from the aforementioned L0 cross section.

[0049] The "distance n" is the distance from the reference line L to the second ridge line 19 in the N direction shown in FIG. 4. Here, the "N direction" refers to the distance from the first flange extension plane PB The vertical wall extension plane P A The angle θ is the direction of rotation of the vertical wall extension plane P in the cross section perpendicular to the reference line L. A and the first flange extension surface P B is the obtuse angle formed by

[0050] 5, in the second ridge portion 19 according to this embodiment, the distance n in the L0 cross section is longer than the distance n in the L1 cross section, and the second ridge portion 19 has a monotonically decreasing portion of the distance n from the L0 cross section to the L1 cross section. The above-mentioned corner portion 40 is a portion of the second ridge portion 19 near the end portion on the second flange 15b side, which includes this monotonically decreasing portion. In the first member 10 having such a second ridge portion 19, deformation of the vertical wall 13 and the first flange 15a is promoted when a collision load is input from the second flange 15b side.

[0051] Typically, when a collision load is applied to a member, a reaction force (deformation resistance force) is generated against the input. This reaction force increases as the member deforms, then decreases, and the fluctuations in the reaction force converge. On the other hand, as will be shown in the examples described later, when the corner portions 40 described above are present, the reaction force reaches a maximum and then decreases, after which it increases again, and then decreases again. In other words, a member equipped with a continuous flange having corner portions 40 deforms so that the reaction force in response to the collision load peaks multiple times. This lengthens the time during which a high reaction force is generated, resulting in improved energy absorption performance compared to a member equipped with a continuous flange without corner portions 40.

[0052] 6 is a diagram illustrating the outer edge shape of the second ridge line portion 19 at the connection point between the second ridge line portion 19 and the third ridge line portion 60. Fig. 7 is a diagram illustrating the connection point between the second ridge line portion 19 and the third ridge line portion 60 as viewed from a direction perpendicular to the first flange 15a in Fig. 6.

[0053] As shown in Fig. 7(a), the outer edge 19a' of the second ridge 19 at the end on the third ridge 60 side when viewed from a direction perpendicular to the first flange 15a may be curved convexly toward the opposite side from the first flange 15a. However, as shown in Fig. 7(b), the outer edge 19a of the second ridge 19 at the end on the third ridge 60 side is curved convexly toward the opposite side from the first flange 15a. P and the inflection point I P and the third ridge portion 60, it is preferable that the portion be curved convexly toward the first flange 15a side.

[0054] The closer the direction of the collision load input and the extension direction of the ridgeline are to being parallel, the greater the deformation resistance of the ridgeline against the input collision load. Therefore, when the outer edge 19a of the second ridgeline 19 is curved convexly toward the first flange 15a as shown in Figure 7(b), the deformation resistance of the end of the second ridgeline 19 against the collision load is greater than in the case of Figure 7(a), thereby improving the energy absorption performance.

[0055] The first member 10 according to this embodiment has been described above. The first member 10 according to this embodiment has a continuous flange consisting of first flanges 14a, 15a, second flanges 14b, 15b, and third flange 15c, and the second ridge portions 18, 19 have corner portions 40. With this first member 10, local buckling of the top plate 11, vertical walls 12, 13, and first flanges 14a, 15a due to axial loads is less likely to occur, and deformation of each portion is promoted. As a result, energy absorption performance can be improved.

[0056] Although a component with a continuous flange is slightly heavier than a component without a continuous flange, the weight increase due to the provision of the continuous flange is slight compared to the weight of the entire portion other than the continuous flange. In other words, it can be said that there is no substantial weight increase due to the provision of the continuous flange. Furthermore, since the amount of material used remains substantially the same even when the corner portion 40 is provided, it can be said that there is no substantial weight increase due to the provision of the corner portion 40. Furthermore, since the thickness of the component can be reduced to a degree that still achieves an improvement in energy absorption performance, it is possible to improve energy absorption performance while suppressing weight increase. In other words, by using the first member 10, it is possible to improve energy absorption performance without a substantial increase in weight.

[0057] (m A and m B Next, a preferred embodiment of the first member 10 will be described. FIG. 8 shows the ratio m A , m B 10 is a diagram for explaining the above and shows a cross section perpendicular to the reference line L.

[0058] Point R shown in FIG. A and point R B is the end point of the second ridge line portion 19 (the point where R ends), and point R A is the end point on the vertical wall 13 side, point R B is the end point on the first flange 15a side. A Distance to m A From the reference line L to point R B Distance to m B These distances m A and the distance m B means the distance in an arbitrary cross section perpendicular to the reference line L. And the distance m A and the distance m B and distance m 0A and the distance m 0B and the distance m A and the distance m B and distance m 1A and the distance m 1BIt is defined as:

[0059] In this case, 2.4≦m 0A / m 1A ≦5.4 and 2.4≦m 0B / m 1B It is preferable to satisfy one or both of the conditions of m≦5.4. When the area where the corner portion 40 is formed increases, the joint area between the members may relatively decrease. However, in the first member 10 that satisfies the above conditions, it is possible to ensure a size of the joint area that can effectively improve the energy absorption performance. 0A / m1 or m 0B / m 1B is preferably 3.0 or more, more preferably 3.4 or more. 0A / m 1A or m 0B / m 1B is preferably 5.0 or less, more preferably 4.6 or less.

[0060] (Examples of shapes of second ridge line portion) Next, other preferred embodiments of the first member 10 will be described. Fig. 9 is a diagram for explaining examples of the shape of the second ridge line portion 19, and is a diagram showing a cross section perpendicular to the reference line L. Each of the two-dot chain lines shown in Fig. 9 exemplifies the shape of the second ridge line portion 19 at the corner portion 40, and the second ridge line portion 19 may have a shape that is convex upward or downward, for example.

[0061] 9, when the extension direction of first flange 15a in a cross section perpendicular to reference line L is defined as the y-axis positive direction, and the direction perpendicular to the y-axis and toward top plate 11 is defined as the z-axis positive direction, the shape of second ridge portion 19 can be expressed by a function z = f(y). In this case, in the monotonically decreasing portion of distance n shown in FIG. 5, the second derivative f"(y) of f(y) is preferably 0 or greater. This makes it possible to increase the joint area between second flange 15b and first wall surface 21 of second member 20 shown in FIG. 1, and, as will be shown in the examples described later, improve energy absorption performance compared to when the second derivative is less than 0 (when the joint is convex upward).

[0062] The example shown in FIG. 9 where the second derivative f"(y) = 0 is an example where the second ridge portion 19 is formed linearly in a cross section perpendicular to the reference line L, and is an example where the second ridge portion 19 is chamfered at an angle of 30° or 45°. Even in such a case, the joining area between the second flange 15b and the first wall surface 21 of the second member 20 is increased compared to a shape where the second ridge portion 19 is convex upward, thereby improving the energy absorption performance.

[0063] (Examples of Shape of First Member) The first member 10 having a continuous flange and a corner portion has been described above, but other shapes of such a first member 10 are shown as examples in FIG.

[0064] FIG. 10( a) shows an example in which the angle β between the plane extending from the first flange 15a toward the second flange 15b and the second flange 15b is not 90°, and the second flange 15b is inclined. FIG. 10( b) shows an example in which the third flange 15c extends in a direction parallel to the second flange 15b. As shown in this example, the third flange 15c may extend in a direction that is not parallel to the top plate 11. FIG. 10( c) shows an example in which the top plate 11 is composed of a flat portion 11a and an inclined portion 11b. FIG. 10( d) shows an example in which the top plate 11 has a convex portion 11c formed on the flat portion 11a. FIG. 10( e) shows an example in which the top plate 11 is formed in a stepped shape, composed of a lower step portion 11d and a higher step portion 11e. FIG. 10( f) shows an example in which multiple recesses 50 are formed in the vertical wall 13.

[0065] While the embodiments of the present invention have been described above, the present invention is not limited to these examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these modifications also fall within the technical scope of the present invention.

[0066] For example, the components of the above-described embodiments can be combined in any manner, and such combinations will naturally provide the functions and advantages of the individual components involved in the combination, as well as other functions and advantages that will be apparent to those skilled in the art from the description herein.

[0067] <Collision Simulation (1)> A collision simulation was performed using the analytical model shown in FIG. 11 . The model of Comparative Example 1 is a model of a joint structure using a first member 90 that does not have a continuous flange and a corner portion 40. The model of Comparative Example 2 is a model of a joint structure using a first member 91 that has a continuous flange but does not have a corner portion 40. The model of Comparative Example 3 is a model of a joint structure using a first member 92 that has a corner portion 40 but does not have a continuous flange. The model of Example 1 is a model of a joint structure 1 that uses a first member 10 that has a continuous flange and a corner portion 40, and corresponds to the joint structure 1 of FIG. 1 described in the above-mentioned embodiment. Note that the corner portion 40 in each model of Comparative Example 3 and Example 1 is provided not only at the second ridge portion 19 but also at the second ridge portion 18 on the opposite side.

[0068] 12 and 13 are diagrams for explaining the simulation conditions. In this simulation, the flange of the first member 10 is spot-welded to the second member 20 and the third member 30, respectively, and the condition is set such that the end face of the first member 10 on the axial side opposite to the second member 20 side (the negative side in the x-direction) is completely constrained. Furthermore, the first member 10 and the third member 30 are made of steel with a thickness of 1.4 mm and a tensile strength of 1470 MPa, and the second member 20 is set as a rigid body. The main dimensions of each member are as shown in FIGS. 12 and 13 .

[0069] Under the above conditions, the second member 20 was forcibly displaced 100 mm in the negative x-direction, and the energy absorption performance at this time was evaluated. The collision simulations for Comparative Examples 1 to 3 were conducted under the same conditions as in Example 1, except that the shape of the first member was different from that in Example 1.

[0070] The simulation results for each model are shown in Figure 14. As shown in Figure 14, the model of Example 1, which has a continuous flange and a corner portion, exhibited a higher energy absorption amount than the models of Comparative Examples 1 to 3, which did not have either or both of the continuous flange and the corner portion.

[0071] 15 is a diagram showing the magnitude of the reaction force (deformation resistance force) generated in the structures of Example 1 and Comparative Example 2 relative to the amount of displacement of the second member 20. As shown in Fig. 15, in the model of Example 1, the reaction force reaches a maximum in the initial stage when the displacement of the second member 20 starts (in other words, in the initial stage of the collision), and then begins to decrease, and then begins to increase again. As a result, the time during which a high reaction force is generated becomes longer than before, and as shown in Fig. 14, the model exhibits higher energy absorption performance than the other models.

[0072] <Collision Simulation (2)> Next, a collision simulation was performed using a model of Comparative Example 4 shown in FIG. 16 , in which the area of ​​the corner portion 40 in the extension direction of the second ridge line portion 19 was changed. The model of Comparative Example 4 differed from the model of Example 1 in the area where the corner portion 40 was formed, but the simulation conditions, such as the constraint conditions and forced displacement conditions, were the same as those in Collision Simulation (1). In both models, the flange width F of the first flange 15a was 29 mm, the value of F / 2 was 14.5 mm, and the value of 3F was 87 mm. Therefore, the model of Example 1, in which L1 = 40 mm, satisfied the condition F / 2 ≦ L1 ≦ 3F, while the model of Comparative Example 4, in which L1 = 120 mm, did not. Furthermore, the corner portion 40 in each model shown in FIG. 16 was provided not only on the second ridge line portion 19 but also on the opposite second ridge line portion 18.

[0073] 17 shows the simulation results for each model. As shown in FIG. 17, the model of Example 1, which satisfies F / 2≦L1≦3F, absorbed more energy than the model of Comparative Example 4, which did not satisfy F / 2≦L1≦3F. Furthermore, the model of Comparative Example 4, which did not satisfy F / 2≦L1≦3F, absorbed less energy than the models of Comparative Examples 1 to 3, which did not have either or both of the continuous flange and the corner portion.

[0074] <Collision Simulation (3)> Next, as shown in FIG. 18, the distance m from the reference line L at the corner portion 40 to the end point of the second ridge portion 19 is calculated. A , m B A collision simulation was carried out using a plurality of example models with different distances mA , m B However, the simulation conditions such as constraint conditions and forced displacement conditions are the same as those in the collision simulation (1). 0A / m 1A The value of m 0B / m 1B The values ​​of m 0A / m 1A In the model with a value of 4.0, m 0B / m 1B The value of is also 4.0. In addition, the corner portion 40 of each model shown in Fig. 18 is provided not only on the second ridge line portion 19 but also on the second ridge line portion on the opposite side.

[0075] Fig. 19 shows the simulation results for each model. The rate of increase in the amount of energy absorption (EA increase rate) shown on the vertical axis of Fig. 19 is calculated by the following formula: EA increase rate = (EA @ each Example - EA @ Comparative Example 1) / (EA @ Comparative Example 1) EA @ each Example: energy absorption amount of each Example model in this simulation EA @ Comparative Example 1: energy absorption amount of the Comparative Example 1 model As shown in Fig. 19, 2.4 ≤ m 0A / m 1A ≦5.4 and 2.4≦m 0B / m 1B When the value satisfies the range ≦5.4, the rate of increase in the amount of energy absorption is improved compared to when the value is outside these ranges.

[0076] <Collision Simulation (4)> Next, a collision simulation was performed using the model of Example 2 in which the shape of the second ridge line portion 19 at the corner portion 40 is convex upward, as shown in Fig. 20 . The model of Example 2 differs from the model of Example 1 in that the second ridge line portion 19 at the corner portion 40 is convex upward or downward, but the simulation conditions, such as the constraint conditions and forced displacement conditions, are the same as those in Collision Simulation (1). Note that the corner portion 40 of each model shown in Fig. 20 is provided not only on the second ridge line portion 19 but also on the second ridge line portion on the opposite side.

[0077] 21 is a diagram showing the simulation results for each model. As shown in Fig. 21, the model of Example 1, in which the second ridge 19 at the corner 40 is convex downward, exhibits a greater amount of energy absorption than the model of Example 2, in which the second ridge 19 is convex upward. In other words, when the second ridge 19 is expressed as a function Z = f(y), the second derivative is preferably 0 or greater.

[0078] <Collision Simulation (5)> Next, a plurality of models with different tensile strengths were created based on the models of Example 1 and Comparative Example 2 shown in Fig. 11, and a collision simulation was performed using these models. The simulation conditions, such as the constraint conditions and forced displacement conditions, were the same as those in Collision Simulation (1).

[0079] Fig. 22 shows the simulation results for each model. The black dots in Fig. 22 indicate the results for an example model in which the tensile strength was changed based on the model of Example 1 shown in Fig. 11, and the white dots in Fig. 22 indicate the results for a comparative example model in which the tensile strength was changed based on the model of Comparative Example 2 shown in Fig. 11. As shown in Fig. 22, when the tensile strength of the material was 900 MPa or higher, the difference in the energy absorption amount between the example model having corner portions 40 and the comparative example model not having corner portions 40 increased.

[0080] As the tensile strength increases, elastic buckling tends to occur more easily in flat portions such as the vertical walls 12 and 13, the first flanges 14a and 15a, and the second flanges 14b and 15b. On the other hand, in the example model, corner portions 40 are present between the vertical walls 12 and 13 and the first flanges 14a and 15a and the second flanges 14b and 15b, and the flat portion area is smaller than that of the comparative example model. This suppresses elastic buckling that tends to occur in the flat portion area, and the higher the strength of the material, the more pronounced the difference in energy absorption performance between the example model and the comparative example model. In other words, the higher the strength of the material, the better the energy absorption performance of an automobile frame member having continuous flanges and corner portions.

[0081] The above describes the embodiments of the present invention. The effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology disclosed herein may achieve other effects that will be apparent to those skilled in the art from the description of this specification, in addition to or in place of the above effects.

[0082] The present invention can be applied to automobile frame members.

[0083] DESCRIPTION OF SYMBOLS 1 Joint structure 10 First member 11 Top plate 12, 13 Vertical wall 14a, 15a First flange 14b, 15b Second flange 15c Third flange 16, 17 First ridge portion 18, 19 Second ridge portion 19a Outer edge of second ridge portion 19a' Outer edge of second ridge portion 20 Second member 21 Wall surface 22 Wall surface 30 Third member 35 Hollow portion 40 Corner portion 50 Recessed portion 60 Third ridge portion I P Inflection point F Flange width of first flange L Reference line m A Distance from the reference line to the end point of the vertical wall of the second ridge line in a cross section perpendicular to the reference line (m) B Distance from the reference line to the end point of the second ridge line on the first flange side in a cross section perpendicular to the reference line n Distance from the reference line to the second ridge line in the N direction in a cross section perpendicular to the reference line O Intersection of the reference line and the extension plane of the second flange O f End point of the first flange extension surface on the second flange side on the reference straight line O h End point of the second flange side of the vertical wall extension plane on the reference line P A Vertical wall extension surface P B First flange extension surface R A End point of the second ridge on the vertical wall side in a cross section perpendicular to the reference line R B The end point of the second ridge line on the first flange side in a cross section perpendicular to the reference line. α The opening angle of the vertical wall with respect to the vertical plane. β The angle of the second flange with respect to the horizontal plane. θ The angle between the extension plane of the vertical wall and the extension plane of the first flange.

Claims

1. An automobile frame member made of steel with a tensile strength of 900 MPa or more, The tabletop and Two vertical walls facing each other, In a cross section perpendicular to the top plate, two first flanges extend from each of the two vertical walls, The first ridge portion sandwiched between the top plate and the vertical wall, The second ridge portion sandwiched between the vertical wall and the first flange, Two second flanges extending from each of the two aforementioned vertical walls, It has a third flange extending from the top plate, The first flange and the second flange, and the second flange and the third flange are connected, When the straight line obtained by extending the intersection line between the vertical wall extension plane, which extends the vertical wall toward the first flange, and the first flange extension plane, which extends the first flange toward the vertical wall, is taken as the reference straight line, the second ridge portion is defined as L as follows: 0 From the cross-section, L 1 An automotive frame member having a monotonically decreasing portion of distance n leading up to the cross-section. L 0 Cross-section: End point O on the second flange side of the vertical wall extension surface on the reference straight line. h And the endpoint O on the second flange side of the extended surface of the first flange on the aforementioned reference line. f A cross-section perpendicular to the reference line that passes through a point that is farther from the second flange. L 1 Cross-section: Distance L in the extension direction of the reference line from the intersection point of the plane including the second flange and the reference line. 1 A cross-section perpendicular to the aforementioned reference line at the position. However, when the flange width of the first flange is F, F / 2 ≤ L 1 The condition ≤ 3F is satisfied. Distance n: The distance in the N direction from the reference line to the second ridge portion in a cross section perpendicular to the reference line. N direction: The direction in which the extension surface of the first flange is rotated by an angle θ / 2 toward the extension surface of the vertical wall around the reference line in a cross section perpendicular to the reference line. Angle θ: The angle between the vertical wall extension plane and the first flange extension plane in a cross section perpendicular to the reference line.

2. the aforementioned L 0 Let m be the distance from the reference straight line in the cross section to the end point on the vertical wall side of the second ridge line portion 0A , Said L 1 The distance from the reference line in the cross-section to the endpoint on the vertical wall side of the second ridge is m 1A , Said L 0 The distance from the reference line in the cross-section to the endpoint on the first flange side of the second ridge is m 0B , Said L 1 The distance from the reference line in the cross-section to the endpoint on the first flange side of the second ridge is m 1B In that case, 2.4 ≤ m 0A / m 1A ≤5.4 and 2.4 ≤m 0B / m 1B An automobile frame member according to claim 1, satisfying one or both of the conditions ≤ 5.

4.

3. The automotive frame member according to claim 1 or 2, wherein the extension direction of the first flange in a cross section perpendicular to the reference line is the positive y-axis direction, the direction perpendicular to the y-axis and toward the top plate is the positive z-axis direction, and when the shape of the second ridge portion in the monotonic decreasing portion is expressed as a function z = f(y), the second derivative of f(y) is 0 or greater.

4. The device comprises mating members joined to the two first flanges, The automobile frame member according to claim 1 or 2, wherein a hollow portion is formed surrounded by the top plate, the two vertical walls, and the mating member.