Automotive crash energy absorption part

Abstract

A crash energy absorption part 1 according to the present invention is provided at a front portion or a rear portion of a vehicle body, extends in the vehicle body longitudinal direction, and absorbs crash energy by axial crushing when a crash load is input from the front or rear of the vehicle body. The crash energy absorption part 1 has a cylindrical portion 10 including four or more surface portions 11, and the cross-sectional shape of the cylindrical portion 10 orthogonal to the vehicle body longitudinal direction is a polygonal shape having four or more sides. Each surface portion 11 has a plurality of beads 20 extending in a direction substantially orthogonal to the vehicle body longitudinal direction and formed at a depth equal to or greater than the plate thickness of the surface portion 11. The plurality of beads 20 are not formed on the surface portion 11 corresponding to the shortest side of the polygon, but at least three beads 20 are formed at equal intervals in the vehicle body longitudinal direction on the surface portion 11 corresponding to the longest side of the polygon.

Description

Automotive collision energy absorption parts

[0001] The present invention relates to a crashworthiness energy absorption part for an automobile that is provided at the front or rear of a vehicle body and absorbs crash energy by undergoing axial crash when a crash load is input from the front or rear of the vehicle body.

[0002] Automotive structural components are required to be lighter in weight to improve fuel economy and crash safety. In electric vehicles, increasing the battery load is effective in extending the driving range, but this increases the vehicle weight, which in turn increases the impact (collision energy) in the event of a vehicle collision. Therefore, electric vehicles require structural components that can adequately absorb collision energy.

[0003] Crash boxes are automobile collision energy absorption components that absorb collision energy during a vehicle collision. They are attached to the front or rear of the vehicle and protect occupants by absorbing collision energy during a collision, thereby suppressing deformation inside the vehicle cabin. The crash boxes are installed, for example, between the front side members and the front bumper beam at the front of the vehicle, and when compressive force acts in the fore-and-aft direction of the vehicle during a vehicle collision, they undergo axial collapse to absorb the collision energy.

[0004] Many automobile collision energy absorption parts have been proposed. For example, Patent Document 1 discloses a crash box that has a structure that allows performance such as energy absorption amount, maximum load, and residual part length to be set to target performance, while the box body can be easily set to a desired shape. Furthermore, Patent Document 2 discloses a crash can (corresponding to a "crash box") that can simultaneously suppress the amount of initial load transmitted to the front frame during a vehicle collision and ensure energy absorption.

[0005] JP 2009-234377 A JP 2022-12132 A

[0006] Until now, crash boxes have been made of steel plates with a relatively low strength, around 440 MPa, to ensure sufficient compressive deformation. However, in response to demands for increased collision energy absorption in the event of an electric vehicle collision, the use of thicker steel plates with a tensile strength of 590 MPa or steel plates with a tensile strength of 980 MPa or higher is being considered.

[0007] Crash boxes made of these steel plates do not collapse properly when another vehicle collides with the front of the vehicle due to their increased resistance to the compressive load of the collision. This means that the collision energy is absorbed by the deformation of the other vehicle, which may increase the risk of injury to the occupants of the other vehicle. Therefore, it is important that the crash box not only reduces the amount of collision energy absorption, but also ensures that the maximum load (resistance) is not too high in order to reduce the risk of injury to the other vehicle.

[0008] However, the crash box of Patent Document 1 has a structure in which reinforcement is provided to connect a pair of opposing walls of the box body, which makes it impossible to avoid an increase in maximum load. Furthermore, in the crash box of Patent Document 1, because the reinforcement is provided inside the tube-like box body, the number of parts and weight increase compared to a crash box that only has a tube-like box body.

[0009] The crash can in Patent Document 2 is configured so that when a collision load directed toward the rear of the vehicle is input, a first weak point formed at a corner between the upper or lower surface and the side surface deforms before a second weak point provided on the pair of side surfaces deforms. As a result, while it is possible to reduce the collision load at the early stage of the collision, the crash can does not collapse stably at the later stage of the collision, reducing the collision load and failing to sufficiently absorb the collision energy.

[0010] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a collision energy absorption component for an automobile that can keep the collision load low in the early stages of a collision when a collision load is input from the front or rear of the vehicle, and can obtain a sufficient collision energy absorption effect in the later stages of the collision.

[0011] The automobile collision energy absorption component of the present invention is mounted on the front or rear of the vehicle body, extends in the fore-and-aft direction of the vehicle body, and axially collapses to absorb collision energy when a collision load is input from the front or rear of the vehicle body. The component has a cylindrical portion with four or more face portions, the cross-sectional shape of the cylindrical portion perpendicular to the axial collapse direction of axial collapse being a polygon with more than one side, and any of the face portions has a plurality of beads extending in a direction approximately perpendicular to the axial collapse direction and formed to a depth equal to or greater than the plate thickness of the face portion, the plurality of beads being not formed on face portions corresponding to the sides of the polygon with the shortest length, and three or more of the beads are formed at equal intervals in the axial collapse direction on at least face portions corresponding to the sides of the polygon with the longest length.

[0012] Of the plurality of beads, the first bead from one end side in the axial crushing direction to which the collision load is input in the automobile collision energy absorption component preferably has both ends extending to ridge sections on both side ends of the face portion on which the bead is formed, and is formed in a range from the one end side that is 20% or less of the total length of the automobile collision energy absorption component in the axial crushing direction.

[0013] The interval between the plurality of beads is preferably in the range of 2.0 to 3.0 times the minimum length of the side of the polygon.

[0014] The tubular portion is bonded by overlapping the ends of a bent metal plate or the ends of two or more parts to provide a non-bonded area, and the non-bonded area may be located within a band-shaped area along the circumferential surface of the tubular portion in a direction perpendicular to the axial crush direction in the center between adjacent beads.

[0015] According to the present invention, the collision load in the early stage of a collision can be kept low, and the collision energy can be sufficiently absorbed by stable axial crushing deformation in the later stage of the collision, thereby improving the collision performance of the vehicle and contributing to improving the marketability of the automobile.

[0016] FIG. 1 is a diagram illustrating an automobile collision energy absorption component according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the spacing and depth of multiple beads formed on the surface portion constituting the tubular portion in the automobile collision energy absorption component according to the present embodiment. FIG. 3 is a diagram illustrating an automobile collision energy absorption component according to another embodiment of the present invention and an example. FIG. 4 is a diagram illustrating a specific cross-sectional shape of the tubular portion in the automobile collision energy absorption component according to the present invention. FIG. 5 is a diagram illustrating an automobile collision energy absorption component used as a comparative example in the example. FIG. 5-1 is a diagram illustrating a tubular portion in an automobile collision energy absorption component according to the present invention, formed by overlapping and joining the ends of two components, with a non-joined region at the center between adjacent beads at the overlapped ends. FIG. 5-2 is a diagram illustrating a tubular portion in an automobile collision energy absorption component according to the present invention, where the overlapped ends of the two components are joined in different ways, and the bellows-like deformation of the tubular portion during axial crushing. ((a) No non-joined region, (b) With non-joined region). Fig. 5-3 is a diagram showing an example of a tubular portion in an automobile collision energy absorption component according to the present invention, in which the end of a hat-shaped cross-section component and the end of a back plate are overlapped and joined, and the overlapped and joined end is not located on a surface portion on which multiple beads are formed. Fig. 5-4 is a diagram showing a specific example of a tubular portion in an automobile collision energy absorption component according to the present invention, in which the end of three components are overlapped and joined. Fig. 6 is a graph showing an example of a load-stroke curve obtained by a collision simulation of an automobile collision energy absorption component according to an example of the invention in the examples. Fig. 7 is a diagram showing the state of deformation after the start of a collision obtained by a collision simulation of automobile collision energy absorption components according to an example of the invention and a comparative example in the examples ((a) Example of the invention, (b) Comparative example).

[0017] [Background to the Invention] As an example of a collision energy absorption component that absorbs collision energy by axial crushing, there is a collision energy absorption component 3 having eight face portions 11 and a tubular portion 10 whose cross section perpendicular to the axial crushing direction is an octagon, as shown in FIG. 5 .

[0018] As described above, such a collision energy absorbing component 3 is required to suppress the collision load at an early stage of the collision to a low level, and to obtain a sufficient collision energy absorption effect at a later stage of the collision.

[0019] Each surface 11 of the cylindrical portion 10 corresponds to each side of an octagon in the cross-sectional shape of the cylindrical portion 10, but the lengths of all sides of the octagon are not necessarily equal in the cylindrical portion 10. For example, in the cylindrical portion 10 shown in Fig. 5, the inclined surface 11d corresponds to the shortest side of the octagon, the side surface 11c corresponds to the longest side of the octagon, and the top surface 11a and bottom surface 11b correspond to sides of the octagon with lengths between the shortest and longest sides.

[0020] When a collision load is applied to a collision energy absorption component 3 having such a tubular portion 10, the tubular portion 10 undergoes axial collapse due to buckling of each surface portion 11, thereby absorbing the collision energy. However, the buckling period of the inclined surface portion 11d corresponding to the side with the shortest length of the octagon is shorter than the buckling period of the side portion 11c corresponding to the side with the longest length. Therefore, the collision energy absorption component 3 exhibits unstable buckling behavior during the axial collapse process of the tubular portion 10 due to non-uniform buckling of each surface portion 11. As a result, the collision load decreases in the later stages of the collision, and the collision energy cannot be sufficiently absorbed.

[0021] The inventors conducted extensive research into this issue. As a result, they came up with the idea of ​​forming multiple beads on the side surface portion 11c corresponding to the longest side without forming a bead on the inclined surface portion 11d corresponding to the shortest side, thereby making the buckling period of each surface portion 11 closer to, or more preferably, matching, the buckling period of the inclined surface portion 11d corresponding to the shortest side. They then discovered that a tubular portion having beads formed thereon undergoes stable axial crushing deformation in the later stages of a collision, resulting in bellows-like deformation and sufficient absorption of collision energy while suppressing a decrease in collision load. In particular, by aligning the buckling of each surface portion with the surface portion corresponding to the shortest side, the period of bellows-shaped buckling deformation can be shortened, enabling greater absorption of collision energy. They also discovered that forming beads on the side surface portion 11c can reduce collision loads in the early stages of a collision.

[0022] The present invention has been made based on these findings, and the specific configuration thereof will be described below.

[0023] [Embodiment] An automobile collision energy absorption component (hereinafter simply referred to as "collision energy absorption component") according to an embodiment of the present invention is provided at the front or rear of a vehicle body and extends in the fore-and-aft direction of the vehicle body. The collision energy absorption component absorbs collision energy by axially collapsing when a collision load is input from the front or rear of the vehicle body. As shown in FIG. 1 , the collision energy absorption component 1 according to this embodiment has a tubular portion 10 and a plurality of beads 20. The following description describes the relative positions and directions of each component, based on the assumption that the collision energy absorption component 1 is provided on the vehicle body so that the direction in which the collision energy absorption component 1 axially collapses (axial collapse direction) coincides with the fore-and-aft direction of the vehicle. Furthermore, in this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted or simplified.

[0024] <Cylindrical portion> As shown in Fig. 1 , the cylindrical portion 10 has eight surface portions 11: an upper surface portion 11a, a lower surface portion 11b, a pair of side surface portions 11c, and an inclined surface portion 11d connecting the upper surface portion 11a or the lower surface portion 11b to the side surface portion 11c. When the collision energy absorption component 1 is installed on the vehicle body, the upper surface portion 11a and the lower surface portion 11b face each other in the vertical direction of the vehicle, and the pair of side surface portions 11c face each other in the left-right direction of the vehicle. The cylindrical portion 10 has an octagonal cross section perpendicular to the axial collapse direction, and has rounded ridges 13 connecting the side ends of the surface portions 11 in the direction perpendicular to the axial collapse direction. In the cross section of the cylindrical portion 10 perpendicular to the axial collapse direction, each surface portion 11 corresponds to a side of the octagon, and each rounded ridge 13 corresponds to a corner of the octagon. In this embodiment, the inclined surface portion 11d corresponds to the side with the shortest length of the octagonal cross-sectional shape of the cylindrical portion 10, and the side surface portion 11c corresponds to the side with the longest length of the octagon.

[0025] 1, the plurality of beads 20 are not formed on the inclined surface portion 11d corresponding to the side with the shortest length of the octagonal cross-sectional shape of the tubular portion 10, but are formed in threes at equal intervals in the axial collapse direction on the side surface portion 11c corresponding to the side with the longest length. Furthermore, in the collision energy absorption component 1, three beads 20 are also formed on the upper surface portion 11a and the lower surface portion 11b at equal intervals in the axial collapse direction, similar to the side surface portion 11c.

[0026] The bead 20 formed on the side surface portion 11c extends in a direction substantially perpendicular to the axial collapse direction of the tubular portion 10, and has a depth equal to or greater than the thickness of the side surface portion 11c. The direction in which the bead 20 extends is substantially perpendicular to the axial direction in order to allow for manufacturing errors and variations, but it is preferable that the direction be perpendicular to the axial collapse direction. The allowable range for the bead extension direction due to manufacturing errors and variations is preferably within ±5° of the direction perpendicular to the axial collapse direction.

[0027] As shown in Figure 2(b), the depth of the bead 20 (bead depth) is the distance from the surface 15 of the portion of the surface 11 (side surface 11c) on which each bead 20 is formed, where the bead 20 is not formed, to the bottom of the bead 20 in the thickness direction. The width of each bead 20 is preferably 5 mm or more and 30 mm or less. The length of each bead 20 is preferably 1.2 times or more the width and less than the width of the surface 11 on which each bead 20 is formed.

[0028] The interval between the beads 20 is the distance between the central axes of adjacent beads 20 in the axial crushing direction of the collision energy absorbing component 1 (cylindrical portion 10), as shown in FIG. 2(a).

[0029] In the collision energy absorption component 1 according to this embodiment, a bead 20 having a depth equal to or greater than the plate thickness is formed on the side surface portion 11c corresponding to the longest side of the octagonal cross-sectional shape of the tubular portion 10. As a result, when a collision load is input to the front end of the collision energy absorption component 1 in the vehicle body longitudinal direction, the bead 20 acts as an effective starting point for bending deformation in the early stage of the collision, thereby keeping the maximum collision load in the early stage of the collision low and reducing the damage to the other side in the collision.

[0030] Furthermore, the collision energy absorption component 1 can make the buckling period of each surface portion 11 of the tubular portion 10 approach, or more preferably match, the inclined surface portion 11d corresponding to the side with the shortest length and having the shortest buckling period. This allows the tubular portion 10 to undergo stable axial collapse and deform into an accordion-like shape while suppressing a decrease in collision load in the later stages of the collision, allowing the collision energy absorption component 1 to sufficiently absorb the collision energy.

[0031] As described above, the collision energy absorption component 1 according to this embodiment can reduce the collision load in the early stages of a collision and sufficiently absorb the collision energy while suppressing a decrease in the collision load in the later stages of the collision, thereby improving the collision performance of automobiles and contributing to improved marketability.

[0032] 1 has a plurality of beads 20 formed on the side surface portion 11c, the top surface portion 11a, and the bottom surface portion 11b. However, in the present invention, it is sufficient that the plurality of beads 20 are not formed on the surface portion 11 corresponding to the side with the shortest length of the polygonal cross-sectional shape of the tubular portion 10, but are formed at least on the surface portion 11 (side surface portion 11c) corresponding to the side with the shortest length of the polygonal cross-sectional shape of the tubular portion 10. Therefore, the present invention also includes a case in which the beads 20 are not formed on the top surface portion 11a and the bottom surface portion 11b that do not correspond to the side with the longest length of the polygon.

[0033] As shown in Figure 1, when multiple beads 20 are formed on a surface portion 11 other than the surface portion 11 corresponding to the longest side of the polygonal cross-sectional shape of the tubular portion 10, the spacing and depth of the beads 20 should be set to the same as those of the multiple beads 20 formed on the surface portion 11 corresponding to the longest side.

[0034] 3 is preferably formed as the first bead 20 from one end in the axial crushing direction in which the collision load is input to the collision energy absorption component 1A. Both end portions 21a of the first bead 21 extend to the ridge lines R-portions 13 on both side ends of the surface portions (side surface portions 11c, upper surface portion 11a, and lower surface portion 11b) on which the bead 20 is formed. Furthermore, the first bead 21 is formed in a range of 20% or less from the one end side in which the collision load is input with respect to the entire length of the collision energy absorption component 1 in the axial crushing direction.

[0035] By forming the first bead 21 in this manner, in the early stage of a collision, bending deformation is reliably induced starting from the first bead 21, and the collision load can be effectively kept low.

[0036] Furthermore, the spacing between the multiple beads 20 is preferably in the range of 2.0 to 3.0 times the minimum length of the side of the polygon of the cross-sectional shape of the tubular portion 10. This is to make the buckling period of the face portion corresponding to the longest side of the polygon approach or match the buckling period of the face portion corresponding to the shortest side of the polygon with a short buckling period. This allows the collision energy absorption component 1 to stably collapse (cross-section collapsing) (buckling deformation) in the later stages of the collision, thereby achieving a stable and high collision energy absorption effect. Furthermore, by making the buckling period of each face portion 11 approach, or more preferably match, the buckling period of the inclined face portion 11d, which is the face portion corresponding to the shortest side, it is possible to suppress fluctuations in collision load during the axial collapse process and reduce a decrease in collision load.

[0037] In the present invention, the cylindrical portion 10 is not limited to the cylindrical portion 10 shown in Fig. 4(a) formed by joining (e.g., electric arc welding) two parts 10A formed by press-forming metal plates with their opening sides facing each other to form an octagonal cross-sectional shape. Fig. 4(b) shows a cylindrical portion 10 formed by roll-forming a single metal plate and joining (e.g., laser beam welding) its end portions 17 to form an octagonal cross-sectional shape.

[0038] The cross-sectional shape of the cylindrical portion 10 is not limited to an octagonal shape, and may be any polygon having four or more sides 11 and a cross-sectional shape greater than or equal to a square. Fig. 4( c) shows a cylindrical portion 10 having four sides formed by joining two U-shaped cross-section parts 10B formed by press-forming a metal plate into a U-shaped cross section with their opening sides facing each other, forming a rectangular cross-sectional shape. Fig. 4( d) shows a cylindrical portion 10 having four sides formed by joining (e.g., by spot welding) a flange portion 19 of a hat-shaped cross-section part 10C formed by press-forming a metal plate into a hat-shaped cross section to a back plate 10D. Figure 4(e) shows a cylindrical portion 10 having six faces and a hexagonal cross-sectional shape, formed by joining flanges 19 of parts 10E, which are made by pressing a metal plate into a hat-shaped cross-sectional shape, with the opening sides facing each other.

[0039] 1 and 3, the length of the beads 20 in the direction substantially perpendicular to the axial crushing direction is preferably made longer as they are disposed closer to one end of the tubular portion 10 where the collision load is input. This makes it easier for the beads 20 to buckle at the initial stage of the collision, and effectively reduces the maximum collision load at the initial stage of the collision.

[0040] 1 and 4(a), (c), and (e) are formed by joining (for example, by arc welding or laser welding) two components 10A with their openings facing each other. In such a cylindrical portion 10, the end portions 10A1 of the two components 10A are overlapped and joined by a joining portion 31 so as to provide a non-jointed region 33, as in the cylindrical portion 10-1 illustrated in FIG.

[0041] The non-bonded region 33 is preferably provided in the center between adjacent beads 20. The center between adjacent beads 20 is a portion between the beads 20 that has a width in the axial collapse direction.

[0042] The reason why the cylindrical portion 10-1 shown in Fig. 5-1 is preferred will be explained with reference to Fig. 5-2. In Fig. 5-2(a), the cylindrical portion 40 has overlapping end portions 10A1 between adjacent beads 20 continuously joined by a weld line 41.

[0043] In the process of axial collapse, the tubular portion 40 is deformed into an accordion shape, with the multiple beads 20 formed on the side surface portion 11c becoming the starting points for buckling. However, because the tubular portion 40 is continuously joined between adjacent beads 20 by weld lines 41, as shown in the A-A cross section, when the buckled valleys starting from the beads 20 deform into a mountain shape, the position of the peak of the mountain is not fixed, resulting in a non-uniform accordion-like deformation.

[0044] In contrast, in the tubular portion 10-1 shown in FIG. 5-2(b), the non-bonded region 33 at the overlapping end portion 10A1 has lower bending rigidity than the bonded region 31, and therefore, in the process of axial collapse of the tubular portion 10-1, the non-bonded region 33 as well as the multiple beads 20 become the starting point of buckling. Therefore, as shown in the B-B cross-sectional view, when the tubular portion 10-1 deforms in a mountain-like shape between the buckled valleys starting from the bead 20, the non-bonded region 33 provided in the center between the beads 20 becomes the peak of the mountain, resulting in a uniform bellows-like deformation. As a result, when a collision load is input to a collision energy absorption component including the tubular portion 10-1, the tubular portion 10-1 more preferably deforms in a bellows-like shape, allowing for better absorption of the collision energy.

[0045] In the tubular portion 10-1 shown in Figures 5-1 and 5-2(b), the overlapping and joined end portion 10A1 is located on the side portion 11c on which multiple beads 20 are formed, and a non-joined region 33 is provided in the center between adjacent beads 20.

[0046] In contrast, as shown in Figure 5-3, in the tubular portion 10-2 in which the end portion 10C1 (flange 19) of the hat-shaped cross-sectional part 10C and the end portion 10D1 of the back plate 10D are overlapped and joined (for example, by spot welding, etc.), the overlapping and joined ends 10C1, 10D1 (and the joint portion 31) are not located on the side portion 11c on which multiple beads 20 are formed.

[0047] In this type of tubular portion 10-2, the non-bonded region 33 at the overlapping ends 10C1, 10D1 may also be located within a band-shaped region 35 (within the area surrounded by the dashed line in FIG. 5-3) along the circumferential surface of the tubular portion 10-2, perpendicular to the axial collapse direction, in the center between adjacent beads 20 on the side surface portion 11c. In other words, the non-bonded region 33 of the tubular portion 10-2 is located at a position equidistant from the center between the beads 20 and from one end of the tubular portion 10-2 in the axial collapse direction where the collision load is input.

[0048] During the axial crushing process, the cylindrical portion 10-2 undergoes a uniform bellows-like deformation, and the non-bonded regions 33 at the overlapping ends 10C1 and 10D1, as well as the multiple beads 20 formed on the side portion 11c, also become the starting points for buckling, thereby enabling the cylindrical portion 10-2 to absorb more of the collision energy.

[0049] An embodiment in which the overlapping end portion of two components is not part of the surface portion on which multiple beads are formed is not limited to the tubular portion 10-2 shown in Fig. 5-3, but also includes, for example, the tubular portion 10 shown in Fig. 4(e). Even in the tubular portion 10 shown in Fig. 4(a), multiple beads are not necessarily formed on the surface portion including the overlapping end portions of the two components 10A. Even in such a case, as with the tubular portion 10-2 in Fig. 5-3, it is preferable that the non-bonded region at the overlapping end portion be within a band-shaped region along the circumferential surface of the tubular portion 10, perpendicular to the axial collapse direction, in the center between adjacent beads.

[0050] In the tubular portion 10-1 shown in Fig. 5-1, the non-bonded region 33 is provided in the center between adjacent beads 20. In this case, similar to the tubular portion 10-2 in Fig. 5-3 described above, the non-bonded region 33 is synonymous with being located within a band-shaped region along the circumferential surface of the tubular portion 10-1, perpendicular to the axial collapse direction, in the center between adjacent beads 20.

[0051] 5-1 to 5-3, the cylindrical portion is formed by two parts press-formed from metal plates. However, in the present invention, the cylindrical portion may be a cylindrical portion 10 formed by bending a single metal plate by any method such as roll forming or press working, as shown in FIG.

[0052] Alternatively, as shown in Figure 5-4, the cylindrical portion 10-3 may be formed by overlapping and joining the end portions 10E1 of three components 10E. In the case of the cylindrical portion 10-3, the non-joined region of the overlapping and joined end portions 10E1 is preferably located within a band-like region along the circumferential surface of the cylindrical portion 10-3, perpendicular to the axial collapse direction, at the center of adjacent beads formed on the side surface portion 11c. Furthermore, because it is ideal for deformation of the cylindrical portion 10-3 to progress evenly on a plane perpendicular to the axial collapse direction, it is preferable that a non-joined region be provided at all three overlapping and joined end portions 10E1.

[0053] If the width (length in the axial crushing direction) of the non-bonded region is less than four times the thickness of the metal plate forming the tubular portion, bending deformation is unlikely to occur during the axial crushing process of the tubular portion, and the non-bonded region is unlikely to become a buckling initiation point. Therefore, it is preferable that the width of the non-bonded region is four times or more the thickness of the metal plate. This allows the non-bonded region to stably become a buckling initiation point, resulting in uniform bellows-like deformation and improved energy absorption.

[0054] An analysis was carried out to confirm the effects of the automobile collision energy absorbing component according to the present invention, and the results will be described below.

[0055] The analysis was performed using the collision energy absorption component 1 (see FIG. 1) and collision energy absorption component 1A (see FIG. 3) described in the embodiment as examples of the invention as analysis targets, and a collision simulation was performed in which a punch was struck on one end side in the axial crushing direction to input a collision load. The collision simulation then determined the deformation state of the collision energy absorption components 1 and 1A during the axial crushing process, and the relationship between the collision load input to the collision energy absorption components 1 and 1A and the deformation amount (stroke) in the axial crushing direction.

[0056] As described above, the collision energy absorption components 1 and 1A have a cylindrical portion 10 having an octagonal cross section perpendicular to the axial crushing direction, and a plurality of beads 20 extending in a direction perpendicular to the axial crushing direction on one of the surface portions 11 that make up the cylindrical portion 10. The collision energy absorption components 1 and 1A were made using steel plate with a tensile strength of 590 MPa and a plate thickness of 2.0 mm, or a tensile strength of 980 MPa and a plate thickness of 1.2 mm, and had a total length of 188 mm in the axial crushing direction.

[0057] The cylindrical portion 10 has eight surfaces 11, namely, an upper surface 11a, a lower surface 11b, a side surface 11c, and an inclined surface 11d, and a ridge line R portion 13 connecting the surfaces 11, forming an octagonal cross section. In the octagonal cross section of the cylindrical portion 10, the lengths of the sides corresponding to the upper surface 11a and the lower surface 11b are 42 mm, the length of the side corresponding to the side surface 11c is 66 mm, and the length of the side corresponding to the inclined surface 11d is 22 mm. In other words, the side corresponding to the inclined surface 11d is the shortest length, and the side corresponding to the side surface 11c is the longest length.

[0058] The beads 20 were not formed on the inclined surface portion 11d corresponding to the side with the shortest length, but three were formed at equal intervals in the axial crush direction on each of the upper surface portion 11a, the lower surface portion 11b, and the side surface portion 11c of the surface portion 11. The depth of each bead 20 was set to be equal to or greater than the plate thickness of the surface portion 11 on which the bead 20 was formed. The width of each bead 20 was set to 15 mm, and the length was set to 21 mm to 53 mm, and the length of the beads 20 was varied within the above ranges so that the longer the beads 20 were, the closer they were to one end of the tubular portion 10 where the collision load was input.

[0059] As described above, the collision energy absorption component 1A is formed so that the first bead 20 (first bead 21) from one end side in the axial crushing direction where the collision load is input extends to the ridge R portion 13 at both ends in the direction perpendicular to the axial crushing direction.

[0060] In the examples, collision simulations were performed by variously changing the depth (bead depth) of the beads 20 and the spacing (bead spacing) of the beads 20 in the collision energy absorption components 1 and 1A. Furthermore, for the collision energy absorption component 1A, the position of the first bead 20 from one end in the axial crushing direction where the collision load is input (the position of the first bead 21) was variously changed.

[0061] As a comparison, a collision simulation was also performed on a collision energy absorbing component 3 in which no beads 20 were formed on any of the surface portions 11 that constitute the cylindrical portion 10, as shown in FIG.

[0062] (Load-Stroke Curve) Figure 6 shows an example of a load-stroke curve obtained by a collision simulation of the collision energy absorption component 1 according to the example. The collision energy absorption component 1 is deformed by the movement of the punch, and during the collision process, the collision load increases and decreases because the deformation resistance due to the deformation of the cylindrical portion is repeatedly increased and buckled. Then, when the deformation of the collision energy absorption component 1 bottoms out, the collision load increases monotonically and the deformation ends.

[0063] From the load-stroke curve shown in Figure 6, the maximum value shown at the beginning of the collision was determined as the initial maximum load that indicates the performance of the collision energy absorption component 1. Furthermore, the integrated value of the collision load up to a stroke of 130 mm was determined as the amount of collision energy absorbed (hereinafter referred to as "absorbed energy").

[0064] 7A and 7B show the deformation of the collision energy absorption component 1 according to the example of the present invention and the collision energy absorption component 3 according to the comparative example, as determined by a collision simulation. In the example of the present invention, as shown in Fig. 7A, starting from the bead 20, each surface portion 11 on which the bead 20 is formed and the inclined surface portion 11d on which the bead 20 is not formed buckle at positions close to each other in the axial crushing direction, and the tubular portion 10 is deformed like an accordion.

[0065] In contrast, in the comparative example, as shown in Figure 7(b), deformation progresses with the buckling occurring at a different position between the inclined surface portion 11d corresponding to the side with the shortest length and the side surface portion 11c corresponding to the side with the longest length, and the tubular portion 10 does not deform like an accordion. Furthermore, in the comparative example, buckling occurs not only in a region near the one end where the collision load is input, but also at the other end. This type of deformation is unstable buckling behavior in which the collision load fluctuates greatly, leading to fracture of the welds and base material in the tubular portion 10, resulting in a significant decrease in the collision load and a decrease in absorbed energy.

[0066] Table 1 shows the results of the initial maximum load and absorbed energy when the bead depth of the collision energy absorption component 1A made from a steel plate with a tensile strength of 980 MPa and a plate thickness of 1.2 mm is changed.

[0067]

[0068] In Table 1, No. 1 represents the results for a collision energy absorption component 3 in which no bead 20 is formed on the surface portion 11, as shown in Figure 5 (comparative example). In contrast, Nos. 2 to 4 represent the results for cases in which multiple beads 20 are formed on the surface portion 11 other than the inclined surface portion 11d corresponding to the side with the shortest length. Nos. 2 and 3 have bead depths of 3.2 mm and 1.4 mm, respectively, which are greater than the plate thickness of the surface portion 11 and fall within the range of the present invention. No. 4 has a bead depth of 0.8 mm, which is less than the plate thickness of the surface portion 11 and falls outside the range of the present invention.

[0069] No. 1 has a higher initial maximum load and reduced absorbed energy than No. 2, which has a bead depth of 3.2 mm. The initial maximum load in No. 2 is lower than that in No. 1. This is thought to be due to stress concentration in the bead 20 at the beginning of the collision, causing buckling of the ridge R portion 13 where the end 21 a of the bead 20 is located.

[0070] Comparing No. 3 and No. 4, No. 4, in which the bead depth was less than the plate thickness of the face portion 11, had a high initial maximum load and reduced absorbed energy. This is because No. 4, in which the bead depth was shallow, did not experience stress concentration in the bead 20, and buckling did not occur starting from the bead 20. On the other hand, No. 3, in which the bead depth was equal to or greater than the plate thickness of the face portion 11, had a reduced initial maximum load and increased absorbed energy.

[0071] In this way, by making the bead depth of the bead 20 formed on the surface portion 11 equal to or greater than the plate thickness, it is possible to obtain the effect of the bead 20 acting as a starting point for buckling in the early stage of a collision. However, even if the bead depth is further increased, it is thought that the decrease in the initial maximum load and the increase in absorbed energy will reach a saturation point.

[0072] Table 2 shows the results of the initial maximum load and absorbed energy when the position of the first bead 21 is changed in the collision energy absorption component 1A, which is formed so that both ends of the first bead 21 counting from the end where the collision load is input are placed on the ridge R portion 13, as shown in Figure 3. The collision energy absorption component 1A was made using a steel plate with a tensile strength of 980 MPa and a plate thickness of 1.2 mm, and the bead depth of each bead 20 was 3.2 mm.

[0073]

[0074] In Table 2, No. 2 is the same as No. 2 in Table 1, and is the result of the collision energy absorption component 1 in which the first bead 21 is formed so that both ends do not overlap the ridgeline R portion 13. Nos. 5 to 7 are cases in which the distance from the one end where the collision load is input to the first bead 20 is changed to 4%, 16%, and 21% of the total length (=188 mm) of the collision energy absorption component 1A, and Nos. 5 and 6 are within the preferred range of the present invention, while No. 7 is outside the preferred range of the present invention.

[0075] It can be seen that the maximum load at the initial stage of collision is lower in Nos. 5 and 6 compared to No. 2. This is thought to be because in Nos. 5 and 6, both ends of the first bead 21 are located on the ridgeline R portion 13, making buckling more likely to occur in the ridgeline R portion 13.

[0076] In No. 7, in which the position of the first bead 21 was set to 21% of the total length of the collision energy absorption component 1A, buckling began from the second bead 20, so the maximum load at the initial stage of the collision was approximately the same as that of No. 2. This shows that in order to reduce the initial maximum load, it is preferable to form the first bead 21 within a range of 20% or less from the one end side where the collision load is input.

[0077] Table 3 shows the results of the initial maximum load and absorbed energy when the spacing of the beads 20 of the collision energy absorption component 1A shown in Figure 3 is changed. The collision energy absorption component 1A was made using a steel plate with a tensile strength of 980 MPa and a plate thickness of 1.2 mm, and the bead depth was set to 3.2 mm.

[0078]

[0079] In Table 3, No. 5 is the same as that shown in Table 2, and the bead spacing is 2.5 times the length of the side with the smallest length. Nos. 8 to 11 are cases where the bead spacing is 1.8 times, 2.0 times, 3.0 times, and 3.2 times the length of the side with the smallest length, respectively. Nos. 8 to 10 are within the preferred range of the present invention, while No. 11 is outside the preferred range of the present invention.

[0080] The initial collision loads for Nos. 8 to 11 were all similar to No. 5, and lower than No. 2. These results show that in order to reduce the initial maximum load, it is more effective to form both end portions 21a of the first bead 21 to extend to the ridge R portion 13 than to change the bead spacing.

[0081] Furthermore, the absorbed energy was highest for No. 5, in which the bead spacing was 2.5 times the minimum length. It decreased as the bead spacing decreased (No. 8, No. 9) or increased (No. 10, No. 11) from this value. When a collision load is applied to a tubular portion 10 with polygonal cross-sectional shapes of different side lengths, the buckling period of each surface portion 11 differs, with the surface portion 11 with the shortest side length having a shorter buckling period than the other surface portions 11. However, by forming beads 20 on surface portions 11 other than the surface portion 11 corresponding to the side with the minimum length, the buckling period can be made closer to the buckling period of the surface portion 11 corresponding to the side with the minimum length, resulting in stable bellows-like buckling deformation. The results shown in Table 3 indicate that, to improve absorbed energy, it is preferable to set the spacing between multiple beads 20 formed on a surface portion 11 to be 2.0 to 3.0 times the minimum length.

[0082] Furthermore, as shown in Fig. 5-1, a collision simulation was performed on a collision energy absorption component having a tubular portion 10-1 formed by overlapping and joining the end portions 10A1 of two components 10A. The simulation involved impacting one end in the axial crushing direction with a punch to input a collision load. The effect of the non-bonded region 33 provided on the overlapping and joined end portions 10A1 was then verified.

[0083] The tubular portion 10-1 analyzed in the collision simulation had the same shape and bead 20 arrangement as the tubular portion 10 shown in No. 5 of Table 2. Furthermore, a non-bonded region 33 was provided in the center between adjacent beads 20 in the overlapping and bonded end portion 10A1.

[0084] A similar collision simulation was also performed on the tubular portion 40 (see FIG. 5-2(a)) that does not have the non-bonded region 33, and the absorbed energy was compared when the non-bonded region 33 was present and when the width (length in the axial crushing direction) of the non-bonded region 33 was changed. The joint 31 and weld line 41 of the overlapping end portion 10A1 were joined using arc welding.

[0085] Table 4 shows the results of the initial maximum load and the absorbed energy when the length of the non-bonded region 33 in the cylindrical portion 10-1 is changed.

[0086]

[0087] In Table 4, No. 5 is the same as No. 5 shown in Tables 2 and 3, and the width of the non-bonded region 33 is 15 mm. No. 12 is a tubular portion 40 without a non-bonded region 33, and adjacent beads 20 are continuously bonded by a weld line 41. No. 13 has a non-bonded region 33 with a width of 5 mm, which is slightly larger than four times the thickness (1.2 mm) of the steel plate used for the tubular portion 10-1.

[0088] As shown in Table 4, although the initial maximum loads of No. 5, No. 12, and No. 13 are all approximately the same, it can be seen that the absorbed energy of No. 5 and No. 13, which have the non-bonded region 33, is higher than that of No. 12, which does not have the non-bonded region 33. This is thought to be because in No. 5 and No. 13, which have the non-bonded region 33, the non-bonded region 33 becomes the starting point of buckling, causing the tubular portion 10-1 to deform more uniformly into an accordion shape.

[0089] As described above, it has been demonstrated that the collision energy absorption component according to the present invention reduces the collision load in the early stage of a collision and improves collision energy by stably buckling in the later stage of the collision. Furthermore, it has been demonstrated that the absorption of energy is improved by joining the ends of a cylindrical part made of two parts so as to overlap each other and provide a non-joined region.

[0090] According to the present invention, it is possible to provide a collision energy absorption component for an automobile that can keep the collision load low in the early stages of a collision when a collision load is input from the front or rear of the vehicle, and can obtain a sufficient collision energy absorption effect in the later stages of the collision.

[0091] 1 Collision energy absorption part 1A Collision energy absorption part 3 Collision energy absorption part 10, 10-1, 10-2, 10-3 Cylindrical part 10A Part 10A1 End 10B U-shaped cross-sectional part 10C Hat-shaped cross-sectional part 10C1 End 10D Back plate 10D1 End 10E Part 10E1 End 11 Surface part 11a Upper surface part 11b Lower surface part 11c Side part 11d Inclined surface part 13 Ridge line R part 15 Surface 17 End 19 Flange 20 Bead 21 First bead 21a End 31 Joint part 33 Non-jointed region 35 Region 40 Cylindrical part 41 Weld line

Claims

1. An automobile collision energy absorption component that is mounted on the front or rear of a vehicle body, extends in the fore-and-aft direction of the vehicle body, and absorbs collision energy by undergoing axial collapse when a collision load is input from the front or rear of the vehicle body, the automobile collision energy absorption component having a tubular portion with four or more face portions, the cross section of the tubular portion perpendicular to the axial collapse direction of axial collapse being a polygon with four or more sides, any of the face portions having a plurality of beads that extend in a direction approximately perpendicular to the axial collapse direction and are formed to a depth equal to or greater than the plate thickness of the face portion, the plurality of beads are not formed on the face portion corresponding to the side with the shortest length of the polygon, and three or more of the beads are formed at equal intervals in the axial collapse direction on at least the face portion corresponding to the side with the longest length of the polygon.

2. An automobile collision energy absorption component as described in claim 1, wherein, of the plurality of beads, the first bead from one end side in the axial crushing direction where the collision load is input in the automobile collision energy absorption component has both ends extending to the ridge R portions on both sides of the face portion on which the bead is formed, and is formed in a range from the one end side that is 20% or less of the overall length of the automobile collision energy absorption component in the axial crushing direction.

3. An automobile collision energy absorption component according to claim 1 or 2, wherein the spacing between the plurality of beads is in the range of 2.0 to 3.0 times the minimum length of the side of the polygon.

4. An automobile collision energy absorption component as set forth in claim 1 or 2, wherein the tubular portion is joined by overlapping the ends of a single bent metal plate or the ends of two or more parts to provide a non-bonded region, and the non-bonded region is located within a band-shaped region along the circumferential surface of the tubular portion, perpendicular to the axial crushing direction, in the center between adjacent beads.

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