Automotive structural components

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

TECHNICAL FIELD

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

BACKGROUND ART

[0002] In recent years, fuel efficiency regulations have been tightened worldwide, and weight reduction of automobiles has been required. In addition, along with the trend of complying with fuel efficiency regulations in various countries and the move toward carbon neutrality, electrification of automobile power sources is also progressing. Along with this, it is required to mount heavy batteries on vehicles, and the need for weight reduction is increasing more and more. On the other hand, improvement of collision safety is also required, and both weight reduction and collision safety of automobiles are demanded to be achieved.

[0003] As an example of skeleton members that contribute to collision safety, there are members disposed around the cabin such as bumper beams, side sills, cross members, roof side rails, and center pillars. For these members, in order to improve the safety of occupants in the event of a collision and enhance the protection function of the battery arranged under the floor, a high reaction force (deformation resistance force) is generated against external forces such as collision loads, for example, so as to achieve the performance of absorbing collision energy. As means for improving energy absorption performance, for example, improvements in material aspects such as increasing the strength of the material of the skeleton member, reducing the wall thickness, or applying different materials can be considered, but improvements to the shape of each component constituting the skeleton member and the joining structure between the components are also required.

[0004] As a conventional technique related to the shape or joining structure of automobile skeleton members, Patent Document 1 discloses that in a metal skeleton member having a groove bottom portion, two ridge line portions, and two vertical wall portions, outward continuous flanges are formed extending across the groove bottom portion, the ridge line portions and the vertical wall portions. Similarly to Patent Document 1, Patent Documents 2 to 4 also disclose members having outward continuous flanges.

[0005] Patent Document 5 discloses a joint structure comprising 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 extending from the top surface of the second member toward the first member, and the flange and the vertical wall of the first member are joined. Patent Document 6 discloses a press-formed product having a T-shaped top plate portion, a wall portion continuous with the top plate portion, and a flange portion continuous with the wall portion, wherein the ridge connecting the vertical and horizontal sides of the top plate portion is curved.

[0006] Patent Document 7 discloses a vehicle understructure in which a pair of rockers extending in the longitudinal direction of the vehicle and a floor cross member extending in the vehicle width direction between the pair of rockers, with one end joined to the lower part of the rockers, are joined together. Patent Document 8 discloses a vehicle floor structure having a pair of rockers disposed on both outer sides in the vehicle width direction of the vehicle floor panel and extending in the longitudinal direction of the vehicle, a tunnel disposed 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. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2016 / 104078 [Patent Document 2] Japanese Patent No. 6176046 [Patent Document 3] International Publication No. 2013 / 154114 [Patent Document 4] International Publication No. 2016 / 194963 [Patent Document 5] Japanese Patent Application Publication No. 2020-142767 [Patent Document 6] Japanese Patent No. 6690605 [Patent Document 7] Japanese Patent Application Publication No. 2015-105033 [Patent Document 8] Japanese Patent Application Publication No. 2017-081200 [Overview of the project] [Problems that the invention aims to solve]

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

[0009] This invention has been made in view of the above circumstances, and aims to improve the energy absorption performance of an automobile frame member without substantially increasing its weight. [Means for solving the problem]

[0010] One aspect of the present invention, which solves the above problems, is an automobile frame member made of steel with a tensile strength of 900 MPa or more, comprising: a top plate; two opposing vertical walls; two first flanges extending from each of the two vertical walls in a cross section perpendicular to the top plate; a first ridge line portion sandwiched between the top plate and the vertical walls; a second ridge line 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 flanges and the second flanges, and the second flanges and the third flanges are connected, and when the straight line obtained by extending the intersection of the vertical wall extension surface obtained by extending the vertical wall toward the first flange and the first flange extension surface obtained by extending the first flange toward the vertical wall is taken as a reference straight line, the second ridge line portion has a monotonically decreasing portion of distance n between the L0 cross section and the L1 cross section as defined below. m defined below 0A 、m 1A 、m 0B 、m 1B However, 2.4≦m 0A / m 1A ≤5.4 and 2.4 ≤m 0B / m 1B Satisfying one or both of the conditions ≤ 5.4, Automotive skeleton member. L0 cross section: A cross section perpendicular to the reference straight line, passing through the end point O on the second flange side of the vertical wall extension surface on the reference straight line h and the end point O on the second flange side of the first flange extension surface on the reference straight line f that is farther from the second flange among the above points. L1 cross section: A cross section perpendicular to the reference straight line, located at a position with a distance L1 in the extending direction of the reference straight line from the intersection of the plane including the second flange and the reference straight line, provided that F / 2≦L1≦3F is satisfied, where F is the flange width of the first flange. Distance n: The distance in the N direction from the reference straight line to the second ridge portion in the cross section perpendicular to the reference straight line. N direction: A direction obtained by rotating the first flange extension surface around the reference straight line toward the vertical wall extension surface by an angle of θ / 2 in the cross section perpendicular to the reference straight line. Angle θ: The angle formed by the vertical wall extension surface and the first flange extension surface in the cross section perpendicular to the reference straight line. m 0A : Said L 0 The distance from the reference line in the cross-section to the endpoint on the vertical wall side of the second ridge line. m 1A : 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 line. m 0B : 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 portion. m 1B : 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 portion. [Advantageous Effects of the Invention]

[0011] In the automotive skeleton member, it is possible to improve energy absorption performance without a substantial increase in weight. [Brief Description of the Drawings]

[0012] [Figure 1]This figure shows a schematic configuration of a joint structure using an automotive frame member according to one embodiment of the present invention. [Figure 2] This figure shows the AA section in Figure 1. [Figure 3] This diagram illustrates the shape of the second ridge at the corner. [Figure 4] This is a cross-sectional view perpendicular to the reference line at the corner. [Figure 5] This figure illustrates the change in distance n between cross-sections L0 and L1. [Figure 6] This diagram illustrates the shape of the outer edge of the second ridge section at the connection point between the second and third ridge sections. [Figure 7] This figure shows the connection point between the second and third ridge sections, viewed from a direction perpendicular to the first flange in Figure 6. [Figure 8] This diagram illustrates the distances mA and mB from the reference line to the endpoint of the second ridge. [Figure 9] This diagram illustrates an example of the shape of the second ridge at a corner. [Figure 10] This figure shows examples of shapes for automotive structural components. [Figure 11] This is a diagram illustrating the analysis model in collision simulation (1). [Figure 12] This is a diagram illustrating the conditions for collision simulation (1). [Figure 13] This is a diagram showing the dimensions of the analysis model. [Figure 14] This is a diagram illustrating the results of the collision simulation (1). [Figure 15] This is a diagram illustrating the results of the collision simulation (1). [Figure 16] This is a diagram illustrating the analysis model used in collision simulation (2). [Figure 17] This is a diagram illustrating the results of the collision simulation (2). [Figure 18] This is a diagram illustrating the analysis model used in collision simulation (3). [Figure 19] This is a diagram illustrating the results of the collision simulation (3). [Figure 20] This is a diagram illustrating the analysis model used in collision simulation (4). [Figure 21] This is a diagram illustrating the results of the collision simulation (4). [Figure 22] This is a diagram illustrating the results of the collision simulation (5). [Modes for carrying out the invention]

[0013] Hereinafter, one 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 denoted by the same reference numerals, and redundant explanations will be omitted.

[0014] Figure 1 is a schematic diagram of the joint structure 1 using the automotive frame member according to this embodiment. Figure 2 is a diagram of the AA cross section. Note that the x, y, and z directions in this specification and drawings are perpendicular to each other.

[0015] The joint structure 1 comprises 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 which the automobile frame member is joined.

[0016] The first member 10 and the second member 20 are members that extend in different directions from each other, and the axial end of the first member 10 is joined to the second member 20. The first member 10 is a member whose cross-section perpendicular to the axial direction (x direction) is hat-shaped. A detailed explanation 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 yz 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 (positive x-direction side).

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

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

[0019] Furthermore, if the joint structure 1 is the following joint structure, the x, y, and z directions in the figure represent the following directions, respectively. • Joint structure between the cross member and the side sill or roof side rail x direction: vehicle width direction, y direction: vehicle length direction, z direction: vehicle height direction • Joint structure between the center pillar and the side sill or roof side rail x direction: vehicle height direction, y direction: vehicle length direction, z direction: vehicle width direction • Joint structure between side member and 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, then the first wall surface 21 of the second member 20 is the side sill's inner (cabin side) wall surface in the vehicle width direction. In this case, the second wall surface 22 is the wall surface extending outward in the vehicle width direction (opposite side from the cabin side), 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 on the vehicle side (cabin side) in the vehicle width direction of the roof side rail. In this case, the second wall surface 22 is the wall surface that extends toward the vehicle side (opposite side from 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 the center pillar and the second member 20 is the 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 that extends downward from the upper surface of the side sill and corresponds to the inner (cabin side) or outer (opposite side from the cabin side) wall surface of the side sill 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 lower surface of the roof side rail. In this case, the second wall surface 22 is a wall surface that extends upward from the lower surface of the roof side rail and corresponds to the inner (cabin side) or outer (opposite side from the cabin side) wall surface of the roof side rail 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 on the vehicle side (cabin side) in the vehicle length direction of the bumper beam. In this case, the second wall surface 22 is the wall surface that extends toward the vehicle side (opposite side from the cabin side) in the vehicle length direction, and corresponds to the upper or lower surface of the bumper beam.

[0025] The total length of the first member 10 and the total length of the second member are appropriately changed according to the application location of the joint structure 1 to 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 appropriately changed according to the application location of the joint structure 1 to 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 and 20 may be, for example 0.8 mm or more, or 1.0 mm or more. Also, the plate thickness of each member 10 and 20 may be, for example 4.0 mm or less, or 3.0 mm or less. The plate thicknesses of each member 10 and 20 may be different from each other.

[0026] The materials used for the first member 10 and the second member 20 include, for example, steel with a tensile strength of 590 MPa or more, or metallic materials such as aluminum alloy or magnesium alloy. Furthermore, the materials of each member 10 and 20 may be different metallic materials.

[0027] Furthermore, if the material of the first member 10 is steel, it is preferable that the tensile strength of the steel be 900 MPa or higher. As will be shown in the embodiments described later, using 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 higher. The tensile strength of the steel is preferably 980 MPa or higher, more preferably 1180 MPa or higher, and even more preferably 1470 MPa or higher.

[0028] The third member 30 is a mating member that is joined to the first member 10, which has a hat-shaped cross-section. By joining the third member 30 to the first member 10, a hollow portion 35 extending in the x-direction is formed between the third member 30 and the first member 10. More specifically, the hollow portion 35 is formed by the third member 30 surrounding the top plate 11 and two vertical walls 12 and 13 of the first member 10, as described later. The cross-sectional shape perpendicular to the top plate 11 of the automobile frame member to which the first member 10 and the third member 30 are joined is a closed cross-sectional shape. In this embodiment, the third member 30 is a closing plate made of a flat plate, but the third member 30 may be, for example, a hat-shaped member, or another part such as a floor panel. Furthermore, as the material for the third member 30, for example, a metal material such as steel with a tensile strength of 270 MPa or more, or an aluminum alloy or magnesium alloy can be used.

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

[0030] The top plate 11 extends in the longitudinal direction of the first member 10 and has a planar portion that extends parallel to the xy plane or inclined at, for example, ±30 degrees. The two vertical walls 12 and 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 of the two vertical walls 12 and 13, that is, the angle α between the plane perpendicular to the top plate 11 in a cross section perpendicular to the axial direction (x direction) of the first member 10 and each of the two vertical walls 12 and 13, 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 (to the negative y-direction) from the z-side end (opposite to the top plate 11 side) of the vertical wall 12, and the first flange 15a extends outward (to the positive y-direction) from the z-side end (opposite to the top plate 11 side) of the vertical wall 13.

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

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

[0033] Furthermore, the top plate 11 sandwiched between the two first ridge sections 16 and 17 is a planar region located between the R-end of one first ridge section 16 (in other words, the boundary line between the curved surface and the plane) and the R-end of the other first ridge section 17. Also, the vertical wall 12 sandwiched between the first ridge section 16 and the second ridge section 18 is a planar region located between the R-end of the first ridge section 16 and the R-end of the second ridge section 18. Furthermore, the vertical wall 13 sandwiched between the first ridge section 17 and the second ridge section 19 is a planar region located between the R-end of the first ridge section 17 and the R-end of the second ridge section 19. Furthermore, the first flange 14a corresponds to the planar region located outward (negative side in the y-direction) from the end of the radius curve of the second ridge section 18, and the first flange 15a corresponds to the planar region located outward (positive side in the y-direction) from the end of the radius curve of the second ridge section 19.

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

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

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

[0037] A third ridge section 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 via this third ridge section 60, and the first flange 15a and the second flange 15b are connected to each other. Furthermore, the third ridge section 60 between the vertical wall 13 and the second flange 15b is curved when viewed from a direction perpendicular to the first flange 15a (z-direction), and is formed in a curved shape to connect the flat portion of the vertical wall 13 and the flat portion of the second flange 15b. In Figure 1, although not shown because it is hidden by the top plate 11 and the vertical wall 12, a third ridge section is 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] Furthermore, it is preferable that, for example, no curved notches that protrude inward are formed 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 constituting 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 are not particularly limited, and welding methods such as spot welding, laser welding, plasma welding, or known joining methods using industrial adhesives may be applied.

[0041] In the first member 10 having a continuous flange as described above, the shape of the second ridge sections 18 and 19 near the ends on the second flange 14b and 15b side differs from the shape of the second ridge sections 18 and 19 in areas sufficiently far from the second flange 14b and 15b. For the convenience of explanation, in this specification, such ends of the second ridge sections 18 and 19 are referred to as corner sections 40. The corner section 40 is surrounded by the vertical wall 13, the first flange 15a, and the third ridge section 60, and is a part that mitigates abrupt changes in shape.

[0042] In Figure 1, one of the two second ridge sections 18 and 19, the corner on the second ridge section 18 side, is hidden by the top plate 11 and is not shown. However, the shape of the corner on the second ridge section 18 side is the same as the shape of the corner section 40 on the second ridge section 19 side, which will be described below, when viewed from the x direction.

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

[0044] The "reference line L" is the vertical wall extension surface P shown in Figure 4. A and the first flange extension surface P B This is a straight line extending the intersection with [the other line]. Vertical wall extension surface P A This is a virtual plane formed by extending the vertical wall 13 towards the first flange 15a side, rather than the side facing the top plate 11. First flange extension plane P B This is a virtual plane obtained by extending the first flange 15a toward the vertical wall 13 side (negative side in the y direction).

[0045] The "L0 section" is point O shown in Figure 3. h and point O f This is a cross-section perpendicular to the reference line L, passing through a point that is farther from the second flange 15b (in other words, a point that is farther from point O on the reference line L). h The above point O is the endpoint on the second flange 15b side of the vertical wall extension surface on the reference line L. f Point O is the endpoint on the second flange 15b side of the first flange extension surface on the reference line L. Point O is the intersection of the second flange extension surface, obtained by extending the second flange 15b toward the reference line L, and the reference line L.

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

[0047] Furthermore, when the flange width of the first flange 15a is F, the condition F / 2 ≤ L1 ≤ 3F must be satisfied. If the distance L1 is less than F / 2, the advantages of providing the corner portion 40 are not fully realized, and the effect of improving energy absorption performance is small. On the other hand, if the distance L1 exceeds 3F, the joint area between the first flange 15a and the third member 30 decreases. For example, when spot welding the first flange 15a and the third member 30, the number of spot welding points decreases. In this case, as will be shown in the embodiment described later, even if the corner portion 40 is provided, the effect of improving energy absorption performance is not fully realized.

[0048] Furthermore, the "flange width F of the first flange 15a" is the maximum width of the first flange 15a within the range L1 to 2 × L1 on the opposite side (negative side in the x direction) from the L0 cross-section mentioned above.

[0049] "Distance n" is the distance from the reference line L in the N direction shown in Figure 4 to the second ridge section 19. Here, "N direction" refers to the first flange extension surface P B The vertical wall extension surface P is centered on the reference line L. A This is the direction rotated by an angle θ / 2 to the side. Furthermore, "angle θ" refers to the vertical wall extension plane P in a cross-section perpendicular to the reference line L. A and the first flange extension surface P B This is the obtuse angle formed by the two.

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

[0051] Normally, when a collision load is applied to a member, a reaction force (deformation resistance force) is generated in response to the input. This reaction force increases as the member deforms, then decreases, and the fluctuation in the increase and decrease of the reaction force converges. On the other hand, as will be shown in the embodiment described later, when the corner portion 40 described above is present, the reaction force, which has reached its maximum, tends to decrease, then tends to increase again, and then tends to decrease again. In other words, a member equipped with a continuous flange having a corner portion 40 deforms in such a way that the peak of the reaction force to the collision load appears multiple times. This makes it possible to extend the time during which a high reaction force is generated, and improves the energy absorption performance compared to a member equipped with a continuous flange without a corner portion 40.

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

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

[0054] The closer the direction of the impact load input and the direction of the ridge extension are to parallel, the greater the deformation resistance of the ridge to the impact load input. Therefore, when the outer edge 19a of the second ridge 19 is curved convexly toward the first flange 15a side as shown in Figure 7(b), the deformation resistance to the impact load at the end of the second ridge 19 increases compared to the case in Figure 7(a), thereby enhancing the effect of improving 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 and 19 have corner portions 40. With such a first member 10, local buckling of the top plate 11, vertical walls 12 and 13 and the first flanges 14a and 15a under axial load is less likely to occur, and deformation of each part is promoted. As a result, energy absorption performance can be improved.

[0056] Although members with continuous flanges are slightly heavier than members without continuous flanges, the weight increase due to the addition of continuous flanges is negligible compared to the weight of the entire structure excluding the continuous flanges. In other words, there is virtually no weight increase due to the addition of continuous flanges. Furthermore, since the amount of material used does not substantially change even when corner sections 40 are provided, there is virtually no weight increase due to the provision of corner sections 40. In addition, it is possible to reduce the weight by thinning the plate thickness of the members within a range where the effect of improving energy absorption performance is obtained, thus making it possible to improve energy absorption performance while suppressing weight increase. In other words, by using the first member 10, energy absorption performance can be improved without any substantial weight increase.

[0057] (m A and m B (ratio) Next, a preferred form of the first member 10 will be described. Figure 8 shows the distance m from the reference line L to the endpoint of the second ridge section. A , m B This is a diagram to explain the concept, and it shows a cross-section perpendicular to the reference line L.

[0058] Point R shown in Figure 8 A and point R B This is the endpoint (the point where R ends) of the second ridge section 19, and point R A Point R is the endpoint on the vertical wall 13 side. B This is the endpoint on the first flange 15a side. From the reference line L at this time, point R A The distance to m A Let's assume that point R is reached from the reference line L. B The distance to m B These are defined as follows: the distance m A and distance m B This represents the distance in an arbitrary cross-section perpendicular to the reference line L. And the distance m in the aforementioned cross-section L0. A and distance m B Each at a distance m 0A and distance m 0B Defined as such, the distance m in the L1 section. A and distance m BEach at a distance m 1A and distance m 1B This is how it is defined.

[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 ≤ 5.4. While increasing the formation area of ​​the corner portion 40 may relatively decrease the joining area between members, in the first member 10 that satisfies the above conditions, a joining area size that effectively enhances energy absorption performance can be secured. Note that m 0A / m1 or m 0B / m 1B It is preferably 3.0 or higher, and more preferably 3.4 or higher. Also, m 0A / m 1A or m 0B / m 1B Preferably, it is 5.0 or less, and more preferably 4.6 or less.

[0060] (Example of the shape of the second ridge) Next, other preferred forms of the first member 10 will be described. Figure 9 is a diagram illustrating an example of the shape of the second ridge portion 19, and shows a cross section perpendicular to the reference line L. Each of the dashed lines shown in Figure 9 illustrates the shape of the second ridge portion 19 at the corner portion 40, and the second ridge portion 19 may be a shape that is convex upwards or convex downwards, etc.

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

[0062] In addition, the example in Figure 9 where the second derivative f″(y)=0 is an example in which the second ridge portion 19 is formed in a straight line in a cross section perpendicular to the reference line L, and the second ridge portion 19 is chamfered, such as by a 30° chamfer or a 45° chamfer. Even in such cases, compared to a shape in which the second ridge portion 19 is convex upward, the joining area between the second flange 15b and the first wall surface 21 of the second member 20 is increased, thereby improving the energy absorption performance.

[0063] (Example of the shape of the first component) The first member 10 having a continuous flange and a corner section has been described above, but other shapes of such a first member 10 are illustrated in Figure 10.

[0064] Figure 10(a) shows an example where the angle β between the plane extending the first flange 15a toward the second flange 15b and the second flange 15b is not 90°, and the second flange 15b is inclined. Figure 10(b) shows an example where 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 not parallel to the top plate 11. Figure 10(c) shows an example where the top plate 11 is composed of a flat portion 11a and an inclined portion 11b. Figure 10(d) shows an example where the top plate 11 has a protrusion 11c formed on the flat portion 11a. Figure 10(e) shows an example where the top plate 11 is formed in a stepped shape and is composed of a lower step portion 11d and a higher step portion 11e. Figure 10(f) shows an example where multiple recesses 50 are formed in the vertical wall 13.

[0065] Although embodiments of the present invention have been illustrated above, the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these will naturally also fall within the technical scope of the present invention.

[0066] For example, the constituent elements of the above embodiments can be combined in any way. From such any combination, the functions and effects of each constituent element in the combination will naturally be obtained, as well as other functions and effects that will be obvious to those skilled in the art from the description herein. [Examples]

[0067] <Collision Simulation (1)> Collision simulations were performed using the analysis model shown in Figure 11. The model for 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 for 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 for 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 for Example 1 is a model of a joint structure 1 using a first member 10 that has a continuous flange and a corner portion 40, and corresponds to the joint structure 1 in Figure 1 described in the above embodiment. Note that in the models for Comparative Example 3 and Example 1, the corner portion 40 is provided not only on the second ridge portion 19 but also on the second ridge portion 18 on the opposite side.

[0068] Figures 12 and 13 are diagrams illustrating 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, and the end face of the first member 10 on the side opposite to the second member 20 in the axial direction (negative x-direction) is fully constrained. The material for the first member 10 and the third member 30 is steel with a plate 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 shown in Figures 12 and 13.

[0069] Under the above conditions, the second member 20 was forcibly displaced 100 mm to the negative side in the x-direction, and its energy absorption performance 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 of Example 1.

[0070] Figure 14 shows the simulation results for each model. As shown in Figure 14, the model of Example 1, which has a continuous flange and a corner section, showed increased energy absorption compared to the models of Comparative Examples 1 to 3, which do not have one or both of the continuous flange and the corner section.

[0071] Figure 15 shows the magnitude of the reaction force (deformation resistance force) generated in the structures of Example 1 and Comparative Example 2 with respect to the displacement of the second member 20. As shown in Figure 15, in the model of Example 1, the reaction force, which was maximum in the initial stage when the displacement of the second member 20 began (in other words, the initial stage of collision), tends to decrease, and then tends to increase again. As a result, the time during which a high reaction force is generated is longer than before, and as shown in Figure 14, it exhibits higher energy absorption performance than the other models.

[0072] <Collision Simulation (2)> Next, a collision simulation was performed using the model of Comparative Example 4 shown in Figure 16, which has a modified area of ​​the corner portion 40 in the extension direction of the second ridge portion 19. In the model of Comparative Example 4, the area of ​​the corner portion 40 is different from that of the model of Example 1, but the simulation conditions such as constraint conditions and forced displacement conditions are the same as in collision simulation (1). In all models, the flange width F of the first flange 15a is 29 mm, the value of F / 2 is 14.5 mm, and the value of 3F is 87 mm. Therefore, the model of Example 1 with L1 = 40 mm satisfies the condition F / 2 ≤ L1 ≤ 3F, but the model of Comparative Example 4 with L1 = 120 mm does not satisfy the condition F / 2 ≤ L1 ≤ 3F. In addition, the corner portion 40 of each model shown in Figure 16 is provided not only on the second ridge portion 19 but also on the second ridge portion 18 on the opposite side.

[0073] Figure 17 shows the simulation results for each model. As shown in Figure 17, the model of Example 1, which satisfies F / 2 ≤ L1 ≤ 3F, showed increased energy absorption compared to the model of Comparative Example 4, which does not satisfy F / 2 ≤ L1 ≤ 3F. Furthermore, the model of Comparative Example 4, which does not satisfy F / 2 ≤ L1 ≤ 3F, showed decreased energy absorption compared to the models of Comparative Examples 1 to 3, which lacked either a continuous flange or a corner section, or both.

[0074] <Collision Simulation (3)> Next, as shown in Figure 18, the distance m from the reference straight line L at the corner section 40 to the endpoint of the second ridge section 19. A , m BCollision simulations were conducted using multiple different embodiment models. In these collision simulations, the distance m in each model was... A , m B Although they differ from one another, the simulation conditions such as constraints and forced displacement conditions are the same as in the collision simulation (1). Note that in this simulation, m in one model 0A / m 1A The value and m 0B / m 1B The values ​​of are the same, for example m 0A / m 1A In models where the value of is 4.0, m 0B / m 1B The value of is also 4.0. Furthermore, the corner sections 40 of each model shown in Figure 18 are provided not only on the second ridge section 19 but also on the second ridge section on the opposite side.

[0075] Figure 19 shows the simulation results for each model. The rate of increase in energy absorption (EA increase rate), shown on the vertical axis of Figure 19, is calculated using the following formula. EA growth 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 of Comparative Example 1 model As shown in Figure 19, 2.4 ≤ m 0A / m 1A ≤5.4 and 2.4 ≤m 0B / m 1B When the value is ≤5.4, the rate of increase in energy absorption is better than when it falls outside these numerical ranges.

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

[0077] Figure 21 shows the simulation results for each model. As shown in Figure 21, in the model of Example 1, where the second ridge portion 19 is convex downwards at the corner portion 40, the amount of energy absorbed increased compared to the model of Example 2, where it is convex upwards. That is, it is preferable that the second derivative when the second ridge portion 19 is expressed as a function of Z=f(y) is 0 or greater.

[0078] <Collision Simulation (5)> Next, based on the models of Example 1 and Comparative Example 2 shown in Figure 11, multiple models with modified tensile strengths were created, and collision simulations were performed. The simulation conditions, such as constraint conditions and forced displacement conditions, were the same as in collision simulation (1).

[0079] Figure 22 shows the simulation results for each model. The black circles in Figure 22 indicate the results for the example model, which is based on the model of Example 1 shown in Figure 11 but with a modified tensile strength, and the white circles in Figure 22 indicate the results for the comparative example model, which is based on the model of Comparative Example 2 shown in Figure 11 but with a modified tensile strength. As shown in Figure 22, when the tensile strength of the material is 900 MPa or higher, the difference in energy absorption between the example model with corners 40 and the comparative example model without corners 40 increases.

[0080] As tensile strength increases, elastic buckling tends to occur more easily in planar sections such as the vertical walls 12, 13, the first flanges 14a, 15a, and the second flanges 14b, 15b. On the other hand, in the embodiment model, a corner section 40 exists between the vertical walls 12, 13 and the first flanges 14a, 15a and the second flanges 14b, 15b, reducing the planar section area compared to the comparative example model. This suppresses elastic buckling that tends to occur in the planar section area, and the difference in energy absorption performance between the embodiment model and the comparative example model becomes more pronounced as the material strength increases. In other words, automotive frame members with continuous flanges and corner sections exhibit superior energy absorption performance as the material strength increases.

[0081] The embodiments of the present invention have been described above. The effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that will be apparent to those skilled in the art from the description herein, in addition to or in lieu of the effects described herein. [Industrial applicability]

[0082] This invention can be applied to automotive structural members. [Explanation of Symbols]

[0083] 1 Joint structure 10 First Member 11 Top plate 12, 13 Vertical walls 14a, 15a First flange 14b, 15b Second flange 15c Third flange 16, 17 First ridge section 18, 19 Second ridge section 19a Outer edge of the second ridge section 19a' Outer edge of the second ridge 20 Second Member 21 Wall surface 22 Wall surface 30 Third Member 35 Hollow part 40 Corner section 50 recesses 60 Third Ridge Section I P Inflection point F Flange width of the first flange L Reference straight line m A Distance from the reference line to the vertical wall end point of the second ridge in a cross section perpendicular to the reference line. m B Distance from the reference line to the first flange-side endpoint of the second ridge section in a cross section perpendicular to the reference line. n is the distance from the reference line to the second ridge 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 The second flange-side endpoint of the first flange extension plane on the reference straight line. O h Second flange side endpoint of the vertical wall extension surface on the reference line P A Vertical wall extension surface P B First flange extension surface R A The vertical wall-side endpoint of the second ridge section in a cross-section perpendicular to the reference line. R B The first flange-side endpoint of the second ridge section in a cross-section perpendicular to the reference line. α: Angle of the vertical wall relative to the vertical plane. β Angle of the second flange relative to the horizontal plane θ is the angle between the vertical wall extension plane and the first flange extension plane.

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 It has a monotonically decreasing section of distance n leading up to the cross-section, Automotive frame members such that m0A, m1A, m0B, and m1B, as defined below, satisfy either or both of the following conditions: 2.4 ≤ m0A / m1A ≤ 5.4 and 2.4 ≤ m0B / m1B ≤ 5.

4. 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 first flange extension surface, in a cross section perpendicular to the reference line, is rotated by an angle θ / 2 toward the vertical wall extension surface around 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. m 0A: The distance from the reference line in the L 0 cross section to the endpoint on the vertical wall side of the second ridge section. m 1A: The distance from the reference line in the L1 cross section to the endpoint on the vertical wall side of the second ridge section. m 0B: The distance from the reference straight line in the L 0 cross section to the endpoint on the first flange side of the second ridge section. m1B: The distance from the reference line in the L1 cross section to the endpoint on the first flange side of the second ridge section.

2. The automotive frame member according to claim 1, 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.

3. 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.

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