Impact-absorbing structure for automobile, and automobile skeleton

Abstract

This impact-absorbing structure for an automobile is provided with a first member and a second member. The first member is provided with a flange part, a side wall part, and a top plate part. A bead section, which has a flange bead extending in a direction intersecting the axial direction so as to divide the flange part in the axial direction, and a side wall bead extending in a direction intersecting the axial direction so as to divide the side wall part in the axial direction, is continuously formed on the first member. The flange bead is formed so as to protrude in a direction away from the top plate part of the first member, and the side wall bead is formed so as to protrude from the side wall part toward the inside of the hollow cross section.

Description

Automobile shock absorbing structure and automobile frame

[0001] This application claims priority to Japanese Patent Application No. 2024-059650, filed on April 2, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, in order to combat global warming, automobiles have been required to comply with greenhouse gas emission regulations. ２ While there is a demand for reduced emissions, collision safety regulations are becoming stricter. Therefore, automotive components are required to be lighter and have improved collision safety, making material selection and structural design important. Among automotive components, front side members, rear side members, crash boxes, and other components that receive loads in the longitudinal direction (axial direction) of the component are required to absorb collision energy by bending deformation or by bellows deformation along the axial direction.

[0003] For example, Patent Document 1 discloses an automobile body structure consisting of side members and cross members, in which a crushable deformation portion is provided in the side member and a deformation-allowing portion is provided in a reinforcing member, and the cross section of the deformation-allowing portion is set so that the deformation stroke of the deformation-allowing portion approximately matches the crushing stroke of the crushable deformation portion based on the crushing stroke of the crushable deformation portion.

[0004] Japanese Patent Application Publication No. 11-348824

[0005] According to the technology of Patent Document 1, the crushing stroke of the crushable portion and the deformation stroke of the deformable portion are the same, which is said to ensure that the side member is crushed into a bellows-like shape. However, the technology of Patent Document 1 is based on a structure in which a cross member is connected to the lower end of the side member via a reinforcing member, and therefore it is necessary to consider not only the crushable portion of the side member but also the cross section of the deformable portion of the reinforcing member. Therefore, further ingenuity is required to increase the amount of energy absorbed per member weight (energy absorption efficiency).

[0006] Therefore, an object of the present invention is to provide an energy absorbing structure and an automobile frame that can realize stable bellows deformation by the simple method of providing beads and exhibit excellent energy absorption efficiency.

[0007] In order to solve the above problems, the present invention proposes the following means: (1) A first aspect of the present invention is an impact absorbing structure for an automobile, comprising a first member and a second member extending in an axial direction and joined to each other to form a hollow cross section, the first member comprising a flange portion, a sidewall portion extending along a first ridge line formed on an edge of the flange portion, and a top plate portion extending along a second ridge line formed on an edge of the sidewall portion opposite to the first ridge line, the first member having a bead portion continuously formed thereon, the bead portion including a flange bead extending in a direction intersecting the axial direction so as to divide the flange portion in the axial direction, and a sidewall bead extending in a direction intersecting the axial direction so as to divide the sidewall portion in the axial direction, the flange bead being formed to protrude in a direction away from the top plate portion of the first member, and the sidewall bead being formed to protrude from the sidewall portion toward the inside of the hollow cross section. (2) In the automotive impact absorbing structure described in (1) above, the second member may have a bead portion formed in surface contact with at least a portion of the flange bead of the bead portion of the first member. (3) In the automotive impact absorbing structure described in (1) or (2) above, the bottom of the flange bead of the first member may be flat. (4) In the automotive impact absorbing structure described in (1) or (2) above, the bottom of the flange bead of the first member may be flat, and the bottom may be joined to the second member. (5) In the automotive impact absorbing structure described in (1) or (2) above, the bottom of the flange bead of the first member may be joined to the second member. (6) In the shock absorbing structure for an automobile described in any one of (1) to (5) above, the second member may include a flange portion, a side wall portion extending from a third ridge line formed on an edge of the flange portion, and a top plate portion extending from a fourth ridge line formed on an edge of the side wall portion opposite to the third ridge line. (7) In the shock absorbing structure for an automobile described in (6) above, a height H2 of the side wall portion of the second member may be smaller than a height H1 of the side wall portion of the first member.(8) In the vehicle impact absorption structure described in any one of (1) to (7) above, the first member may be a hat-shaped cross-section member having a pair of the flange portions and a pair of the side wall portions. (9) In the vehicle impact absorption structure described in (8) above, the pair of side wall portions may each have a side wall bead formed thereon, and the side wall beads formed on each of the pair of side wall portions may be formed at the same position in the axial direction. (10) In the vehicle impact absorption structure described in (8) or (9) above, the pair of side wall portions may each have a side wall bead formed thereon, and the side wall beads formed on each of the pair of side wall portions may have different depths. (11) In the vehicle impact absorption structure described in any one of (1) to (10) above, the hollow cross section may have a width direction length perpendicular to the axial direction and parallel to the top plate portion of the first member that is greater than a height direction length perpendicular to the width direction and the axial direction. (12) In the shock absorbing structure for an automobile according to any one of (1) to (11) above, the first member may be made of a metal material. (13) A second aspect of the present invention is an automobile frame having a pair of tubular parts to which the shock absorbing structure for an automobile according to any one of (1) to (12) above is applied, and the pair of tubular parts have the side wall portions formed on surfaces facing each other.

[0008] According to the above-described aspect of the present invention, the highly rigid first ridgeline is separated by the bead portion, thereby reducing deformation resistance on the flange side when subjected to an axial compressive load (rigidity reduction effect). Furthermore, the ridgeline between the flange bead and the sidewall bead (the bead portion first ridgeline) is located farther from the top plate portion of the first member (toward the second member) than the first ridgeline. Therefore, the space near the bead portion first ridgeline functions as a material inflow space during bellows deformation, preventing interference between deformation points within the bead (interference avoidance effect). Therefore, when an axial compressive load is applied to the shock absorbing structure, bellows deformation in the axial collapse mode can be more stably achieved. This allows for stable bellows deformation and excellent energy absorption efficiency through the simple technique of adding a bead.

[0009] 5 is a perspective view of a shock absorbing structure according to one embodiment of the present invention. FIG. 1 is a cross-sectional end view taken along the cross-sectional line I-I in FIG. 1. FIG. 2 is a cross-sectional view of a portion of a first member where a bead portion is formed. FIG. 3 is a cross-sectional end view of a portion of a second member where a bead portion is formed. FIG. 5 is an enlarged view of part A in FIG. 1. FIG. 6 is a cross-sectional end view taken along the cross-sectional line II-II in FIG. 5. FIG. 7 is a plan view of a structure to which the shock absorbing structure according to this embodiment is applied. FIG. 8 is a cross-sectional view of a portion of a shock absorbing structure according to a first modified example where a bead portion is formed. FIG. 9 is a cross-sectional view of a second member in the shock absorbing structure according to the first modified example. FIG. 10 is a cross-sectional view of a portion of a shock absorbing structure according to a second modified example where a bead portion is formed. FIG. 11 is a cross-sectional view of a first member in the shock absorbing structure according to the second modified example. FIG. 12 is a cross-sectional view of a second member in the shock absorbing structure according to the second modified example. FIG. 13 is a cross-sectional view of a portion of a shock absorbing structure according to a third modified example where a bead portion is formed. FIG. 14 is a cross-sectional view of a portion of a shock absorbing structure according to a fourth modified example where a bead portion is formed. FIG. 15 is a cross-sectional view of a portion of a shock absorbing structure according to a fifth modified example. 1 is a perspective view showing deformation of the shock absorbing structure according to the invention, and a graph showing the relationship between the amount of crushing (mm) and the energy absorption efficiency (kJ / kg) for Comparative Example 1, Comparative Example 2, and the invention example.

[0010] Hereinafter, an impact absorbing structure for an automobile according to one embodiment of the present invention (hereinafter referred to as the impact absorbing structure according to this embodiment) will be described with reference to the drawings. Note that the impact absorbing structure according to this embodiment aims to absorb collision energy by bellows deformation in axial collapse mode, and therefore is applied to the automobile frame in an orientation in which the central axis of the impact absorbing structure is substantially aligned with the fore-and-aft directions (the forward and backward directions) of the automobile.

[0011] In this specification, the direction parallel to the central axis of the impact absorbing structure is referred to as the axial direction x, any one of the directions perpendicular to the axial direction x (for example, a direction coinciding with the vehicle height direction) is referred to as the height direction z, and the direction perpendicular to the axial direction x that is perpendicular to the height direction z (for example, a direction coinciding with the vehicle width direction or a direction parallel to the top plate portion of the first member described later when viewed in the axial direction) is referred to as the width direction y. Note that, for convenience of explanation, the height direction z and the width direction y correspond to the height direction z and width direction y of the vehicle, but for example, the height direction z may correspond to the left-right direction of the vehicle and the width direction y may correspond to the up-down direction of the vehicle.

[0012] (Automobile Impact Absorption Structure 1) Fig. 1 is a perspective view of an impact absorption structure 1 according to one embodiment of the present invention. As shown in Fig. 1, the impact absorption structure 1 according to this embodiment has a hollow tubular shape extending in the axial direction x. The impact absorption structure 1 is configured by spot welding a first member 10 having a bead portion 110 formed therein and a second member 20 having a bead portion 210 formed therein to each other at joints P1 and P2.

[0013] 2 is an end view of a cross section taken along the cross section line I-I in FIG. 1, showing a cross section perpendicular to the axial direction x of the region where the bead portion 110 and the bead portion 210 are formed in the shock absorbing structure 1. As shown in FIG. 2, the shock absorbing structure 1 is configured to have a substantially rectangular hollow cross section by joining together a first member 10, which is a hat-shaped cross section member, and a second member 20, which is a flat cross section member. Note that other members such as reinforcements may be attached inside the hollow cross section of the shock absorbing structure 1.

[0014] (First member 10) FIG. 3 is a cross-sectional view of a portion of the first member 10 where the bead portion 110 is formed. More specifically, FIG. 3 is a view of a cross section of the portion perpendicular to the axial direction x, as viewed from the axial direction x. As shown in FIG. 3 , the first member 10 has a pair of flange portions 11, a pair of side wall portions 13, and a top plate portion 15. The flange portions 11 and the side wall portions 13 are connected to each other across a first ridge line L1a extending in the axial direction x. The side wall portions 13 and the top plate portion 15 are connected to each other across a second ridge line L2a extending in the axial direction x. That is, the first member 10 includes the flange portion 11, the side wall portions 13 extending via the first ridge line L1a formed on the edge of the flange portion 11, and the top plate portion 15 extending via the second ridge line L2a formed on the edge of the side wall portions 13 opposite to the first ridge line L1a.

[0015] (Second member 20) Fig. 4 is a cross-sectional view of a portion of the second member 20 where the bead portion 210 is formed. More specifically, Fig. 4 is a view of a cut surface of the portion perpendicular to the axial direction x as viewed from the axial direction x. As shown in Fig. 4, the second member 20 has a flat portion 21. As shown in Fig. 1, a surface of the flat portion 21 near an edge in the width direction y is overlapped with the flange portion 11 of the first member 10 and spot-welded to it at a joint P1.

[0016] The first member 10 (and the second member 20) are preferably members made of a metal material, and can be obtained, for example, by forming a steel plate (blank) by cold pressing or hot stamping. The thickness of the steel plate (blank) may be 0.3 mm or more and 2.3 mm or less. The hot stamping method refers to a method in which a blank is heated, and the heated blank is formed in a forming die and rapidly cooled in the die to process the blank into a desired shape and strength. The heating temperature of the blank is Ac ３ It is recommended to set it to 1 point or more. ３ The temperature at which ferrite disappears from the metal structure of the blank is the temperature at which the metal structure after hot stamping becomes mainly martensite.

[0017] 1, a flat bracket 50 is attached to the ends of the first member 10 and the second member 20 in the axial direction x. The impact absorbing structure 1 according to this embodiment is connected to a bumper 60 (not shown in FIG. 1) via this bracket 50.

[0018] (Bead Portion 110 of First Member 10) Returning to FIG. 3 , the bead portion 110 of the first member 10 is continuously formed so as to divide the flange portion 11, the first ridge line L1a, the side wall portion 13, and the second ridge line L2a in the axial direction x. As shown in FIG. 3 , the bead portion 110 is not formed in the central portion of the top plate portion 15 in the width direction y. In the shock absorbing structure 1 according to this embodiment, one bead portion 110 is formed on each side of the first member 10 in the width direction y. The bead portions 110 on both sides are formed at the same position in the axial direction x, i.e., facing each other. This makes it possible to more stably achieve bellows deformation in the collapse mode. However, the bead portion 110 may be formed on only one of both sides of the first member 10 in the width direction y. Furthermore, the bead portions 110 on both sides may be formed at different positions in the axial direction x.

[0019] (Bead portion 110) Figure 5 is an enlarged view of portion A in Figure 1. As shown in Figure 5, the bead portion 110 has a flange bead 111 extending in a direction intersecting the axial direction x so as to divide the flange portion 11 in the axial direction x, and a sidewall bead 113 extending in a direction intersecting the axial direction x so as to divide the sidewall portion 13 in the axial direction x. As shown in Figures 1 and 5, a bead portion first ridge line L1b exists between the flange bead 111 and the sidewall bead 113. Furthermore, as shown in Figure 1, a bead portion second ridge line L2b exists between the sidewall bead 113 and the top plate portion 15.

[0020] 5, the flange bead 111 of the bead portion 110 has a groove shape formed by a bottom portion 111a and a pair of wall portions 111b connected to the edge of the bottom portion 111a in the axial direction x. Similarly, the side wall bead 113 of the bead portion 110 has a groove shape formed by a bottom portion 113a and a pair of wall portions 113b connected to the edge of the bottom portion 113a in the axial direction x.

[0021] (Rigidity Reduction Effect) Typically, in a hollow tubular member formed by joining multiple components with flanges, the multiple components are overlapped at the flange, and a ridgeline extends axially near the flange. Therefore, in a cross section perpendicular to the axial direction of the hollow tubular member, the flange-side portion experiences greater deformation resistance when subjected to an axial compressive load than the portion opposite the flange (the top plate in the case of a hat-shaped cross-section member). Therefore, in order to achieve stable energy absorption, it was necessary to employ a complex structure that induces a bending deformation mode at multiple locations, allowing for relatively stable control of the deformation mode. On the other hand, in the shock absorbing structure 1 according to this embodiment, the bead portion 110 is formed continuously not only at the sidewall bead 113 but also at the flange bead 111. Therefore, the first ridgeline L1a, which has high rigidity, is interrupted by the bead portion 110. Therefore, deformation resistance on the flange side when subjected to an axial compressive load can be reduced. Therefore, by using the simple technique of providing a bead, the difference in rigidity between the flange-side ridgeline and the top-plate-side ridgeline can be reduced, and high energy absorption can be achieved through stable bellows deformation.

[0022] Returning to Fig. 3 , it is preferable that the width W1 of the hollow cross section in the width direction y is greater than the height H1 in the height direction z of the shock absorbing structure 1 according to this embodiment. More specifically, the width W1 is the distance in the width direction y between the pair of side wall portions 13 of the first member 10, and the height H1 is the distance in the height direction z between the flange portion 11 and the top plate portion 15 of the first member 10. As shown in Fig. 3 , the width W1 and the height H1 are dimensions based on the center of the plate thickness of each portion. If the width W1 of the hollow cross section is greater than the height H1, the effect of reducing deformation resistance on the flange side when subjected to an axial compressive load can be more reliably obtained, which is preferable.

[0023] (Interference Avoidance Effect) The flange bead 111 of the bead portion 110 is formed to protrude away from the top plate portion 15 of the first member 10 (i.e., convex in a direction away from the central axis). On the other hand, the sidewall bead 113 connected to the flange bead 111 is formed to protrude from the sidewall portion 13 toward the inside of the hollow cross section (i.e., toward the central axis). Therefore, the flange bead 111 and the sidewall bead 113 form a groove that is bent in a substantially L-shape when viewed in the axial direction. Therefore, the bead portion first ridge line L1b is located at a position spaced apart from the first ridge line L1a not only in the width direction y but also in the height direction z. If the bead were formed only on the sidewall, the ridge line of the portion where the bead is formed (the ridge line between the flange and the sidewall) would be located at a position spaced apart only in the width direction y from the ridge line of the portion where the bead is not formed (the ridge line between the flange and the sidewall). In this case, as the bellows-like deformation progresses, the deformed portions may interfere with each other within the bead, increasing the deformation resistance on the flange side. On the other hand, with the shock absorbing structure 1 according to this embodiment, the bead portion first ridge line L1b is located at a distance from the first ridge line L1a not only in the width direction y but also in the height direction z. This allows the area near the bead portion first ridge line L1b to function as a material inflow space as the bellows-like deformation progresses. This prevents the deformed portions from interfering with each other within the bead (interference avoidance effect). Therefore, bellows-like deformation in the axial crushing mode can be achieved more stably.

[0024] (Radius of curvature of ridge line) The radius of curvature Ra of the first ridge line L1a in a cross section perpendicular to the axial direction x may be 3 mm to 20 mm. The radius of curvature Rb of the bead portion first ridge line L1b in a cross section perpendicular to the axial direction x may be 3 mm to 100 mm. The radius of curvature Ra is the radius of curvature of the first ridge line L1a measured at a position 10 mm away in the axial direction x from the position where the bead portion 110 is formed. The radius of curvature Rb is the radius of curvature of the bead portion first ridge line L1b measured at the center position of the bead portion 110 in the axial direction x.

[0025] Here, to effectively achieve the rigidity reduction effect, it is preferable to satisfy the relationship Rb>Ra. Because axially extending ridgelines contribute to high rigidity, it is preferable that the radius of curvature Ra be small at the first ridgeline L1a where no bead is formed. On the other hand, it is preferable to reduce rigidity at the first ridgeline L1b of the bead portion by increasing the radius of curvature Rb. Therefore, by satisfying the relationship Rb>Ra, it is possible to reduce the deformation resistance on the flange side (flange bead 111) when subjected to an axial compressive load while maintaining high rigidity at the portion where no bead is formed. Therefore, it is possible to more stably achieve bellows deformation in the axial crush mode. The relationship Rb>Ra×1.05 or Rb>Ra×1.10 may also be satisfied.

[0026] On the other hand, to obtain an effective interference avoidance effect, it is preferable that the relationship Rb<Ra be satisfied. The smaller the radius of curvature of the bead portion first ridge line L1b, the further the bead portion first ridge line L1b can be positioned in a position farther away from the first ridge line L1a in the width direction y and the height direction z, thereby ensuring a larger material flow space and enhancing the interference avoidance effect. The bead portion first ridge line L1b can be formed, for example, using a press mold with protrusions shaped to correspond to the bead shape. In this case, due to reasons related to press molding technology, such as low shape fixability during press molding, the radius of curvature Rb of the bead portion first ridge line L1b becomes larger than the radius of curvature Ra of the first ridge line L1a. This makes it difficult to ensure a sufficient distance between the bead portion first ridge line L1b and the first ridge line L1a in the width direction y and the height direction z, which may result in an insufficient interference avoidance effect at the bead portion first ridge line L1b. Therefore, when forming the bead portion 110, it is preferable to perform press molding so that the bead portion first ridge line L1b is located further away from the top plate portion 15. Only one bead portion first ridge line L1b is formed in one bead portion 110, but two or more bead portion first ridge lines L1b may be formed.

[0027] (Shape of the bottom 111a of the bead portion 110) In the bead portion 110, the bottom 111a of the flange bead 111 and the bottom 113a of the sidewall bead 113 are preferably flat. In this case, the bead portion first ridge line L1b can be positioned further away from the first ridge line L1a in the width direction y and the height direction z, thereby enhancing the above-mentioned interference avoidance effect. Furthermore, when the flange bead 111 includes a joint P2 for joining to the second member 20, the flat bottom 111a of the flange bead 111 can improve workability during joining to the second member 20 (specifically, the flat bottom 211a of the flange bead 211 described below). In particular, when the joint P2 for joining to the second member 20 in the flange bead 111 is a spot-welded or laser-welded joint, the flat bottom 111a can further improve workability during spot welding or laser welding. Here, "the bottom 111a of the flange bead 111 is flat" means that the radius of curvature in a cross section perpendicular to the axial direction x and height direction z at the center position of the flange bead 111 in the width direction y and axial direction x is 50 mm or more. Also, "the bottom 113a of the side wall bead 113 is flat" means that the radius of curvature in a cross section perpendicular to the axial direction x and width direction y at the center position of the side wall bead 113 in the height direction z and axial direction x is 50 mm or more.

[0028] (Dimensions of the bead portion) The depth d of the bead portion 110 may be 3 mm or more. If the depth d is 3 mm or more, buckling can be stably generated. From the viewpoint of workability, the depth d may be 20 mm or less. It is preferable that the depth d1 of the flange bead 111 is greater than the radius of curvature Ra of the first ridge line L1a. In this case, since the depth of the flange bead 111 is ensured, the bead portion first ridge line L1b can be positioned sufficiently spaced apart from the first ridge line L1a in the width direction y and the height direction z, thereby further enhancing the above-mentioned interference avoidance effect.

[0029] When the bead portions 110 are formed on both sides in the width direction, it is preferable that the depth d1 of the bead portions be different from each other. This is because, when the impact absorbing structure 1 according to this embodiment is applied to an automobile, deformation tends to occur in a manner that bends to either the left or right direction of the vehicle when an axial compressive load is applied. Designing the depths d1 of the bead portions 110 to be different from each other allows for stable bellows deformation.

[0030] (Bead Portion 210 of Second Member 20) In the shock absorbing structure 1 according to this embodiment, the bead portion 210 of the second member 20 has a shape corresponding to the bead portion 110 of the first member 10. FIG. 6 is an end view of a cross section taken along the cross section line II-II in FIG. 5 , showing a cross section perpendicular to the width direction y of the region where the bead portion 110 of the first member 10 and the bead portion 210 of the second member 20 are formed. As shown in FIGS. 5 and 6 , the flange bead 111 of the bead portion 110 has a trapezoidal cross section formed by a bottom portion 111a and a pair of wall portions 111b connected to the edge of the bottom portion 111a in the axial direction x. Similarly, the flange bead 211 of the bead portion 210 of the second member 20 has a trapezoidal cross section formed by a bottom portion 211a overlapping the bottom portion 111a of the first member 10 and a pair of wall portions 211b connected to the edge of the bottom portion 211a in the axial direction x. According to this configuration, even if the first member 10 has the bead portion 110 that protrudes in the height direction z, at least a portion of the bead portion 210 of the second member 20 can be in surface contact with at least a portion of the flange bead 111 of the bead portion 110 of the first member 10. Therefore, the joining strength between the first member 10 and the second member 20 can be increased.

[0031] (Joint P2 in Bead Portion) Furthermore, in the shock absorbing structure 1 according to this embodiment, the first member 10 is joined to the second member 20 not only at the joint P1 of the flange portion 11 but also at the joint P2 of the bead portion 110. This further increases the bonding strength between the first member 10 and the second member 20, which is preferable because it makes it easier for the second member 20 to follow the deformation of the first member 10. Note that even in a configuration in which the joint P2 is not provided in the bead portion 110, the bottom 111a of the bead portion 110 of the first member 10 is disposed opposite the bottom 211a of the bead portion 210 of the second member 20. Therefore, during shock absorption, the bottom 111a of the bead portion 110 of the first member 10 deforms toward the bottom 211a of the bead portion 210 of the second member 20. This is preferable because it is possible to easily obtain the effect of causing the second member 20 to follow the deformation of the first member 10.

[0032] FIG. 7 is a plan view of an automobile frame 1000 having a pair of tubular portions 1001 to which the impact absorbing structure 1 according to this embodiment is applied. In this automobile frame 1000, each end of the pair of tubular portions 1001 is connected to the bumper 60 via a bracket 50. As shown in FIG. 7 , when the impact absorbing structure 1 is applied to a pair of parallel tubular portions 1001, sidewall portions 13 on which sidewall beads 113 of the first members 10 of each impact absorbing structure 1 are formed are disposed on the opposing surfaces of the pair of impact absorbing structures 1 and on the opposite surface. Here, when a load is input from the bumper 60, the tubular portions 1001 tend to bias the load in the axial direction x outward in the width direction y. Therefore, stress is less likely to concentrate on the inner sides (facing surfaces) of the pair of tubular portions 1001 than on the outer sides. Therefore, a configuration may be adopted in which the sidewall portions 13 on which the sidewall beads 113 of the first members 10 of each impact absorbing structure 1 are formed are disposed only on the opposing surfaces. Furthermore, it is preferable that the depth of the bead portions 110 formed on the side wall portions 13 on opposing surfaces is greater than the depth of the bead portions 110 formed on the side wall portions 13 on the opposite surfaces. The shape of the bracket 50 is preferably designed so that the direction of load input to the impact absorption structure 1 during a collision coincides with the axial direction x of the impact absorption structure 1. This prevents the first member 10 and the second member 20 from spreading outward relative to each other when an axial compressive load is applied, making it possible to improve energy absorption efficiency.

[0033] (Modifications) The invention has been described above based on the present embodiment, but should not be limited to this. For example, the following modifications can be applied. Note that the same reference numerals are used for components that are substantially the same as those described in the shock absorbing structure 1 according to the above embodiment, and duplicated descriptions will be omitted.

[0034] (First Modification) Fig. 8 shows a shock absorbing structure 1A according to a first modification. In the shock absorbing structure 1 according to the above embodiment, the second member 20 is a member with a flat cross section that does not have a side wall portion, but the shock absorbing structure 1A shown in Fig. 8 uses a second member 20A that is a member with a hat-shaped cross section.

[0035] (Second member 20A) Figure 9 is a cross-sectional view of the second member 20A, taken perpendicular to the axial direction x, of a portion where the bead portion 210A is formed. As shown in Figure 9, the second member 20A is a hat-shaped cross-section member having a pair of flange portions 21A, a pair of side wall portions 23A, and a top plate portion 25A. The flange portions 21A and the side wall portions 23A are connected across a third ridge line L3a extending in the axial direction x. The side wall portions 23A and the top plate portion 25A are connected across a fourth ridge line L4a extending in the axial direction x. The second member 20A has a bead portion 210A formed therein that has a shape corresponding to the bead portion 110 of the first member 10.

[0036] (Bead portion 210A) The bead portion 210A of the second member 20A is formed continuously from the outer end of the flange portion 21A to the bead portion third ridge line L3b. The bead portion 210A is formed to be convex in the same direction as the protruding direction of the bead portion 110 of the first member 10. The bead portion 210A is formed continuously from the outer end of the flange portion 21A to the bead portion third ridge line L3b, but may also be formed continuously on the side wall portion 23A to the fourth ridge line L4a.

[0037] In this first modified example, the first member 10 and the second member 20A are joined to each other by joining (e.g., spot welding) the flange portion 21A of the second member 20A to the flange portion 11 of the first member 10. With this configuration, the position of the flange can be closer to the central axis than in the shock absorbing structure 1 according to the above-described embodiment, and superior energy absorption efficiency can be achieved.

[0038] In this first modified example, the height H1 of the first member 10 is preferably greater than the height H2 of the second member 20A (H1 > H2). As described with reference to FIG. 3 , the height H1 is the distance in the height direction z between the flange portion 11 of the first member 10 and the top plate portion 15. As shown in FIG. 9 , the height H2 is the distance in the height direction z between the flange portion 21A of the second member 20A and the top plate portion 25A. As shown in FIGS. 3 and 9 , the heights H1 and H2 are dimensions based on the center of the plate thickness of each portion. When subjected to an axial compressive load, the first member 10 deforms starting from the side wall bead 113, and the second member 20A deforms in response to this deformation. If the height H2 of the second member 20A is greater than or equal to the height H1, the deformation resistance of the second member 20A increases, making it more difficult for bellows deformation to occur. Therefore, a configuration in which H1 > H2 allows for stable bellows deformation and achieves superior energy absorption efficiency.

[0039] (Second Modification) Figure 10 shows a shock absorbing structure 1B according to a second modification. In the shock absorbing structure 1 according to the present embodiment described above, the first member 10 is a hat-shaped cross-section member having a pair of flange portions 11. On the other hand, in the shock absorbing structure 1B according to the second modification, the first member 10B has a flange portion 11B on only one side.

[0040] (First Member 10B) As shown in FIG. 10, the shock absorbing structure 1B is configured such that a first member 10B and a second member 20B are joined together to form a substantially rectangular hollow cross section.

[0041] 11 is a cross-sectional view of a portion of the first member 10B where the bead portion 110B is formed, the cross-section being perpendicular to the axial direction x, as viewed from the axial direction x. As shown in FIG. 11, the first member 10B has a flange portion 11B, a first side wall portion 13-1B connected to the flange portion 11B across a first ridge line L1a, a top plate portion 15B connected to the first side wall portion 13-1B across a second ridge line L2a, and a second side wall portion 13-2B connected to the top plate portion 15B across another second ridge line L2a.

[0042] (Bead portion 110B) The bead portion 110B has substantially the same configuration as the bead portion 110 of the shock absorbing structure 1 according to the above-described embodiment, and includes a flange bead 111B extending in a direction intersecting the axial direction x so as to divide the flange portion 11B in the axial direction x, and a sidewall bead 113B extending in a direction intersecting the axial direction x so as to divide the first sidewall portion 13-1B in the axial direction x. As shown in FIG. 11 , a bead portion first ridge line L1b exists between the flange bead 111B and the sidewall bead 113B. Furthermore, as shown in FIG. 11 , a bead portion second ridge line L2b exists between the sidewall bead 113B and the top plate portion 15B.

[0043] In the example shown in FIG. 11, no side wall bead is formed on the second side wall portion 13-2B facing the first side wall portion 13-1B, but a side wall bead may also be formed on the second side wall portion 13-2B.

[0044] 12 is a cross-sectional view of the second member 20B, taken along a line perpendicular to the axial direction x, of a portion of the second member 20B where the bead portion 210B is formed. As shown in FIG. 12, the second member 20B has a flat portion 21B and a side wall portion 23B connected to the flat portion 21B via a third ridge line L3a.

[0045] (Bead Portion 210B) The bead portion 210B of the second member 20B is formed in a convex shape in the same direction as the protruding direction of the flange bead 111B of the first member 10B.

[0046] According to the configurations of the first and second modified examples, similar to the shock absorbing structure 1 according to the above-described embodiment, a stable bellows-like deformation can be achieved due to the effect of reducing rigidity and the effect of avoiding interference, thereby making it possible to improve the energy absorption efficiency.

[0047] Moreover, various modifications can be applied to the bead portion 110 of the first member 10. Hereinafter, a description will be given with reference to Figs.

[0048] In a shock absorbing structure 1C that is a third modified example of the shock absorbing structure, a notch Q is formed in a flange portion 21C of a second member 20C. The first member 10 has the same configuration as the first member 10 of the shock absorbing structure 1 according to the present embodiment described above.

[0049] FIG. 13 is a cross-sectional view of the bead portion 110 of the first member 10. More specifically, FIG. 13 is a cross-section perpendicular to the width direction y at a portion where the flange bead 111 is formed. In this third modified example, a notch Q is formed in the second member 20C at a portion corresponding to the bead portion 110 of the first member 10. That is, the second member 20C does not have a portion corresponding to the bead portion 210 formed in the second member 20 of the shock absorbing structure 1 shown in FIGS. 1 and 4 . In this configuration, the bottom 111a of the flange bead 111 of the first member 10 is not joined to the second member 20C, and the flange portion 11 of the first member 10 is joined to the flange portion 21C of the second member 20, thereby joining the first member 10 and the second member 20C. Note that the flange bead 111 of the first member 10 may be joined to the flange portion 21C of the second member 20C by arc welding.

[0050] (Fourth Modification) In a shock absorbing structure 1D, which is a fourth modification of the shock absorbing structure, a first member 10D has a bead portion 110D having an arc-shaped cross-sectional shape. FIG. 14 is a cross-sectional view of the bead portion 110D of the first member 10D. More specifically, FIG. 14 is a cross-section perpendicular to the width direction y at a portion where a flange bead 111D is formed. In this fourth modification, the flange bead 111D has an arc-shaped cross-sectional shape formed by a bottom portion 111aD and a pair of wall portions 111bD. In this configuration, the bottom portion 111aD of the flange bead 111D of the first member 10D may be joined to a second member 20D having a bead portion 210D having an arc-shaped cross-sectional shape.

[0051] (Fifth Modification) In a shock absorbing structure 1E, which is a fifth modification of the shock absorbing structure, a first member 10E has a bead portion 110E with a triangular cross section. FIG. 15 is a cross-sectional view of the bead portion 110E. More specifically, FIG. 15 is a cross-section perpendicular to the width direction y at a portion where a flange bead 111E is formed. In this fifth modification, the flange bead 111E has a triangular cross-sectional shape formed by a bottom portion 111aE and a pair of wall portions 111bE. In this configuration, the bottom portion 111aE of the flange bead 111E of the first member 10E may be joined to a second member 20E having a bead portion 210E with a triangular cross-sectional shape.

[0052] (Other Modifications) The shock absorbing structures 1A to 1E according to the above-described modifications can achieve the same effects as the shock absorbing structure according to the embodiment. Other modifications include the following configurations. For example, the bead portion 110 of the first member 10 and the bead portion 210 of the second member 20 may be formed in multiple locations spaced apart in the axial direction x. The bead portion 210 of the second member 20 may be formed at one location on each end of the second member 20 in the width direction y, or may be formed linearly to connect both ends in the width direction y. Furthermore, a bead formed to protrude outward (i.e., protrude in a direction away from the central axis) may be formed on the top plate portion 15 of the first member 10. Furthermore, when the second member 20A, which is a hat-shaped cross-section member as in the first modification, is used as the second member, a bead formed to protrude outward (i.e., protrude in a direction away from the central axis) may be formed on the top plate portion 25 thereof. The shock absorbing structure 1 is configured by joining the first member 10 and the second member 20 to each other by spot welding at joints P1 and P2, but instead of spot welding, the first member 10 and the second member 20 may be joined by laser welding, arc welding, or plasma welding. The first member 10 and the second member 20 may also be joined by mechanical fastening. Furthermore, the above-mentioned joining modes may be combined.

[0053] (Example) In an experiment to confirm the effects of the present invention, a hollow tubular member (length = 600 mm, width = 150 mm, height = 70 mm) obtained by press-forming from the same type of steel plate material was prepared. One end in the axial direction x was fixed, and an impactor was caused to collide with the other end in the axial direction x at a speed of 80 km / h. This applied a compressive load in the axial direction x, and the amount of crushing in the axial direction x and the load were measured.

[0054] FIG. 16 is a perspective view showing deformation of the shock absorbing structure according to Comparative Example 1. In Comparative Example 1, a configuration was adopted in which bead portions were not provided on either the side walls or the flange. FIG. 17 is a perspective view showing deformation of the shock absorbing structure according to Comparative Example 2. In Comparative Example 2, a configuration was adopted in which bead portions were provided only on the side walls (including the ridge lines of the top plate and side walls). FIG. 18 is a perspective view showing deformation of the shock absorbing structure according to an example of the invention. Example 1 of the invention is based on the configuration of the shock absorbing structure 1 according to the embodiment shown in FIG. 1. In other words, bead portions were provided on the side walls and the flange.

[0055] 19 is a graph showing the relationship between the collapse amount (mm) and the energy absorption efficiency (kJ / kg) for Comparative Example 1, Comparative Example 2, and the invention example. In the impact absorbing structure of Comparative Example 1, the rigidity of the flange side was higher than the rigidity of the top plate side due to the absence of a bead portion, resulting in a deformation mode in which the structure bends in the direction from the flange side toward the top plate side. Therefore, the impact absorbing structure of Comparative Example 1 did not achieve desirable deformation due to bellows deformation, and the energy absorption efficiency at the time when the collapse amount reached 200 mm was 2.1 kJ / kg.

[0056] In the impact absorbing structure of Comparative Example 2, by providing the bead portion only to the side wall (including the ridge line between the top plate and the side wall), bellows deformation was induced in the early stages of collapse, but as the bellows deformation progressed, the end of the side wall bead (the end near the ridge line between the side wall and the flange) was not sufficiently deformed, and a deformation mode occurred in which the bead bent in a direction from the flange side toward the top plate side. Therefore, the impact absorbing structure of Comparative Example 2 did not achieve desirable bellows deformation, and the energy absorption efficiency at the time when the collapse amount reached 200 mm was 2.3 kJ / kg (110% of Comparative Example 1).

[0057] On the other hand, with the impact absorbing structure according to the example of the present invention, by providing a bead on the flange portion so that the high-rigidity portion such as the flange-side ridgeline is removed from the side wall bead, it was possible to achieve a more stable bellows-like deformation. Therefore, with the impact absorbing structure according to the example of the present invention, the energy absorption efficiency at the time when the collapse amount reached 200 mm was 2.8 kJ / kg (133% of that of Comparative Example 1).

[0058] According to the present disclosure, an energy absorbing structure and an automobile frame are provided that realize stable bellows deformation by the simple method of providing beads and are capable of exhibiting excellent energy absorption efficiency.

[0059] DESCRIPTION OF SYMBOLS 1 Impact absorbing structure 10 First member 11 Flange portion 13 Side wall portion 15 Top plate portion 110 Bead portion 111 Flange bead 111a Bottom portion 111b Wall portion 113 Side wall bead 20 Second member 21 Flat portion 210 Bead portion 211 Flange bead 211a Bottom portion 211b Wall portion 50 Bracket L1a First ridge line L1b Bead portion first ridge line L2a Second ridge line L2b Bead portion second ridge line P1, P2 Joint portion y Width direction z Height direction x Axial direction

Claims

1. An impact absorption structure for an automobile comprising a first member and a second member extending in an axial direction and joined to each other to form a hollow cross section, wherein the first member comprises: a flange portion; a side wall portion extending along a first ridge line formed on an edge of the flange portion; and a top plate portion extending along a second ridge line formed on an edge of the side wall portion opposite to the first ridge line, wherein the first member is continuously formed with bead portions having: a flange bead extending in a direction intersecting the axial direction so as to divide the flange portion in the axial direction; and a side wall bead extending in a direction intersecting the axial direction so as to divide the side wall portion in the axial direction, wherein the flange bead is formed to protrude in a direction away from the top plate portion of the first member, and the side wall bead is formed to protrude from the side wall portion towards the inside of the hollow cross section.

2. The automobile impact absorbing structure according to claim 1, wherein the second member is formed with a bead portion that comes into surface contact with at least a portion of the flange bead of the bead portion of the first member.

3. The automobile shock absorbing structure according to claim 1, wherein the bottom of the flange bead of the first member is flat.

4. The automobile impact absorbing structure according to claim 1, wherein the bottom of the flange bead of the first member is flat, and the bottom is joined to the second member.

5. The automobile impact absorbing structure according to claim 1, wherein the bottom of the flange bead of the first member is joined to the second member.

6. The automobile impact absorbing structure described in claim 1, characterized in that the second member comprises: a flange portion; a side wall portion extending across a third ridge line formed on the edge of the flange portion; and a top plate portion extending across a fourth ridge line formed on the edge of the side wall portion opposite the third ridge line.

7. The automobile impact absorbing structure according to claim 6, wherein the height H2 of the side wall portion of the second member is smaller than the height H1 of the side wall portion of the first member.

8. The automobile impact absorbing structure according to claim 1, wherein the first member is a hat-shaped cross-section member having a pair of the flange portions and a pair of the side wall portions.

9. The automobile impact absorbing structure according to claim 8, characterized in that the side wall beads are formed on each of the pair of side wall portions, and the side wall beads formed on each of the pair of side wall portions are formed at the same position in the axial direction.

10. The automobile impact absorbing structure according to claim 8, wherein the side wall beads are formed on each of the pair of side wall portions, and the side wall beads formed on each of the pair of side wall portions have different depths.

11. The automobile impact absorbing structure described in claim 1, characterized in that the width of the hollow cross section, which is perpendicular to the axial direction and parallel to the top plate portion of the first member, is greater than the height of the hollow cross section, which is perpendicular to the width and axial directions.

12. The automobile impact absorbing structure according to claim 1, wherein the first member is made of a metal material.

13. An automobile frame comprising a pair of tubular sections to which the automobile shock absorbing structure according to any one of claims 1 to 12 is applied, wherein the pair of tubular sections have the side wall sections formed on the surfaces facing each other.

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