Crashworthiness energy absorption part for vehicle

Abstract

A crashworthiness energy absorption part 1 according to the present invention absorbs crash energy by undergoing axial crash when a crash load is input from the front or the rear of a vehicle body, and comprises: a cylindrical part 10 including eight surface parts 11 and having an octagonal cross-sectional shape orthogonal to an axial crash direction; and a plurality of slits 20 formed in any of the surface parts 11 in a shape extending in a direction substantially orthogonal to the axial crash direction. The plurality of slits 20 are not formed in inclined surface parts 11d corresponding to the sides of the minimum length of the octagonal shape, but instead three or more slits are formed at equal intervals along the axial crash direction in side surface parts 11c corresponding to the sides of the maximum length of the octagonal shape. The length of each slit 20 is 10% or more of the length of the side of the side surface parts 11c, and the width of each slit 20 is 1.0 times or more of the plate thickness of the side surface parts 11c.

Description

Automotive collision energy absorption components

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

[0002] Automotive structural components are required to be lightweight to improve fuel efficiency and to have improved crash safety. In electric vehicles, increasing the battery capacity is effective in extending the driving range, but this increases the vehicle's weight, which in turn increases the impact (crash energy) during a collision. Therefore, electric vehicles require structural components that can adequately absorb crash energy.

[0003] One type of automotive collision energy absorbing component that absorbs collision energy during a vehicle collision is the crash box, which is installed at the front or rear of the vehicle. By absorbing collision energy during a collision, it suppresses deformation inside the vehicle's interior and protects the occupants. For example, a crash box is installed between the front side member and the front bumper beam at the front of the vehicle. When a compressive force acts in the longitudinal direction of the vehicle during a collision, it axially collapses to absorb the collision energy.

[0004] So far, many automotive collision energy absorption components have been proposed. For example, Patent Document 1 discloses a crush box that can be set to a desired shape of the box body while setting performance such as energy absorption amount, maximum resistance (maximum load), and residual part length (residual part length) to target performance. In addition, Patent Document 2 discloses a crash can (corresponding to "crash box") that can achieve both suppression of the amount of initial load transmitted to the front frame during vehicle collision and ensuring of energy absorption amount.

[0005] Japanese Patent Application Laid-Open No. 2009-234377 Japanese Patent Application Laid-Open No. 2022-12132

[0006] So far, for the crush box, a steel plate with a relatively low strength of about 440 MPa tensile strength has been used to be sufficiently compressed and deformed. However, in response to the demand for increasing the collision energy absorption amount during the collision of electric vehicles, it has been considered to use a steel plate with a tensile strength of 590 MPa grade and a thick plate thickness, or a steel plate with a tensile strength of 980 MPa grade or more.

[0007] The crush box using these steel plates has a high yield strength against the compressive load (compressive load) due to the collision, so it will not collapse appropriately when another vehicle collides. As a result, since the collision energy is absorbed by the deformation of the vehicle on the other side, there is a possibility of increasing the harmfulness to the occupants of the vehicle on the other side. Therefore, it is also important that the crush box does not have too high a maximum load (yield strength) in order to reduce the harmfulness to the collision opponent as well as not to impair the collision energy absorption amount.

[0008] However, the crash box described in Patent Document 1 has a structure in which reinforcement is provided to connect a pair of opposing walls of the box body, which inevitably increases the maximum load. Furthermore, in the crash box described in Patent Document 1, since the reinforcement is provided inside the cylindrical box body, the number of parts and weight are increased compared to a crash box that only has a cylindrical box body.

[0009] The crash box described in Patent Document 2 is designed such that when a collision load is applied in the rearward direction of the vehicle, a first weak point formed at the corner between the upper or lower surface and the side surface deforms before a second weak point provided on a pair of side surfaces. Therefore, although it is possible to reduce the collision load in the initial stages of the collision, the collision load does not collapse stably in the later stages of the collision, and the collision energy cannot be sufficiently absorbed.

[0010] The present invention was made to solve the above problems, and its objective is to provide an automotive collision energy absorbing component that can suppress the collision load in the initial stages of a collision when a collision load is applied from the front or rear of the vehicle, and can also obtain a sufficient collision energy absorption effect in the later stages of the collision.

[0011] The collision energy absorbing component for automobiles according to the present invention is provided at the front or rear of a vehicle body and extends in the longitudinal direction of the vehicle body, and absorbs collision energy by axially collapsing when a collision load is input from the front or rear of the vehicle body, and has a cylindrical part (section) having four or more surfaces, the cross-sectional shape of the cylindrical part perpendicular to the direction of axial collapse is a polygon with four or more sides, and has a plurality of slits formed in one of the surfaces in a shape that extends in a direction substantially perpendicular to the direction of axial collapse, the plurality of slits are not formed in the surface corresponding to the side with the shortest length of the polygon, and three or more are formed at equal intervals in the direction of axial collapse in the surface corresponding to the side with the longest length of the polygon, the length of each slit is 10% or more of the length of the side of the polygon corresponding to the surface on which the slit is formed, and the width of each slit is 1.0 times or more the plate thickness of the surface on which the slit is formed.

[0012] The length of the slit is preferably 85% or less of the length of the side of the polygon corresponding to the surface portion on which the slit is formed, and the width of the slit is preferably 5.0 times or less the thickness of the surface portion on which the slit is formed.

[0013] The spacing between the multiple slits is preferably between 1.0 and 1.5 times the minimum side length of the polygon.

[0014] According to the present invention, when a collision load is applied from the front or rear of the vehicle body, the collision load in the initial stages of the collision is kept low, and the collision energy can be sufficiently absorbed by undergoing stable axial crushing deformation in the later stages of the collision. This improves the collision performance of the vehicle and contributes to improving the marketability of the automobile.

[0015] Figure 1 is a diagram illustrating an automotive collision energy absorbing component according to an embodiment of the present invention. Figure 2 is a diagram illustrating the length and width of multiple slits formed on the surface constituting the cylindrical portion of the automotive collision energy absorbing component according to this embodiment, and the spacing between the slits ((a) rectangular slit, (b) elliptical slit). Figure 3 is a diagram showing the specific cross-sectional shape of the cylindrical portion in the automotive collision energy absorbing component according to the present invention. Figure 4 is a diagram illustrating an automotive collision energy absorbing component used as a comparative example in the embodiment. Figure 5 is a diagram showing the deformation after the start of a collision, as determined by a collision simulation of the automotive collision energy absorbing component in the embodiment ((a) multiple slits formed on the side corresponding to the longest side of the cylindrical portion, (b) no slits formed).

[0016] [Background to the Invention] As an example of a collision energy absorbing component that absorbs collision energy by axial crushing, a collision energy absorbing component 3 is provided, as shown in Figure 4, which has eight surface portions 11 and a cylindrical portion 10 with an octagonal cross-sectional shape perpendicular to the direction of axial crushing.

[0017] In such collision energy absorbing components 3, as described above, it is required to keep the collision load low in the initial stages of the collision and to obtain a sufficient collision energy absorption effect in the later stages of the collision.

[0018] 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, however, the lengths of all sides of the octagon in the cylindrical portion 10 are not necessarily equal. For example, in the cylindrical portion 10 shown in Figure 4, the slope section 11d corresponds to the side with the shortest length of the octagon, the side surface 11c corresponds to the side with the longest length of the octagon, and the top surface 11a and bottom surface 11b correspond to sides with lengths between the shortest and longest sides of the octagon.

[0019] When an impact load is applied to the impact energy absorbing component 3 having such a cylindrical portion 10, the cylindrical portion 10 axially collapses due to buckling of each surface portion 11, absorbing the impact energy. However, the buckling period of the inclined surface portion 11d corresponding to the shortest side of the octagon is shorter than the buckling period of the side portion 11c corresponding to the longest side. Therefore, the impact energy absorbing component 3 exhibits unstable buckling behavior in the axial collapse process of the cylindrical portion 10, with the buckling of each surface portion 11 not being uniform. As a result, the impact load decreases in the later stages of the collision, and the impact energy cannot be sufficiently absorbed.

[0020] The inventors diligently considered these problems. As a result, they conceived the idea of ​​forming a slit (hole) in the side portion 11c corresponding to the longest side, which serves as the starting point for bending during the axial crushing process, while not forming a slit in the inclined surface portion 11d corresponding to the shortest side. This idea aims to bring the buckling period of each surface portion 11 closer to, or more preferably, match to, the buckling period of the inclined surface portion 11d corresponding to the shortest side.

[0021] Furthermore, it was found that the cylindrical portion with the slit formed in this way undergoes stable axial crushing deformation in the later stages of the collision, deforming into a bellows-shaped form, thereby absorbing sufficient collision energy while suppressing a decrease in the collision load. In particular, by aligning the buckling of each surface with the surface corresponding to the shortest length side, the period of bellows-shaped buckling deformation can be shortened, making it possible to absorb more collision energy. It was also found that forming slits in the side portion 11c makes it possible to keep the collision load low in the initial stages of the collision.

[0022] This invention is based on these findings, and its specific configuration is described below.

[0023] [Embodiment] Figure 1 shows an automobile collision energy absorbing component (hereinafter referred to as "collision energy absorbing component 1") according to an embodiment of the present invention as an example. The collision energy absorbing component 1 is provided on the front or rear of the vehicle body and extends in the longitudinal direction of the vehicle body, and absorbs collision energy by axially collapsing when a collision load is input from the front or rear of the vehicle body. As shown in Figure 1, the collision energy absorbing component 1 has a cylindrical portion 10 and a plurality of slits 20. The collision energy absorbing component 1 according to this embodiment will be described below. In the following description, the relative position and direction of each component are described based on the state in which the collision energy absorbing component 1 is provided on the vehicle body such that the direction in which the collision energy absorbing component 1 axially collapses (axial collapse direction) coincides with the longitudinal direction of the vehicle.

[0024] As shown in Figure 1, the cylindrical portion 10 has eight surfaces 11, including an upper surface 11a and a lower surface 11b, a pair of side surfaces 11c, and an inclined surface 11d connecting the upper surface 11a or lower surface 11b to the side surfaces 11c. When the collision energy absorbing component 1 is installed on the vehicle body, the upper surface 11a and the lower surface 11b face each other in the vertical direction of the vehicle, and the pair of side surfaces 11c face each other in the left-right direction of the vehicle.

[0025] The cylindrical portion 10 has an octagonal cross-sectional shape perpendicular to the axial crushing direction, and has a ridge line R portion 13 connecting the side ends of each surface portion 11 in the direction perpendicular to the axial crushing direction. In the cross-sectional shape of the cylindrical portion 10 perpendicular to the axial crushing direction, each surface portion 11 corresponds to each side of the octagon, and each ridge line R portion 13 corresponds to each corner of the octagon. In this embodiment, the inclined surface portion 11d corresponds to the side with the shortest length of the octagon in the cross-sectional shape of the cylindrical portion 10, and the side portion 11c corresponds to the side with the longest length of the octagon.

[0026] As shown in Figure 1, the multiple slits 20 are not formed on the inclined surface portion 11d corresponding to the shortest side of the octagon, but are formed at equal intervals in the axial crushing direction on the side portion 11c corresponding to the longest side of the octagon.

[0027] The direction in which the multiple slits 20 extend is set to be approximately perpendicular to the axial direction in order to allow for manufacturing errors and variations, but it is preferable that it be perpendicular to the direction of axial crushing. The range of the direction in which the slits 20 extend, due to manufacturing errors and variations, should be within ±5° of the direction perpendicular to the direction of axial crushing.

[0028] The length of each slit 20 is 10% or more of the length of the side of the octagon corresponding to the side portion 11c in which the slit 20 is formed. Also, the width of each slit 20 is 1.0 times or more the thickness of the plate portion 11c in which the slit 20 is formed.

[0029] As described above, in the collision energy absorbing component 1 according to this embodiment, a plurality of slits 20 are formed at equal intervals in the axial crushing direction on the side portion 11c of the surface portion 11, which corresponds to the longest side of the octagonal cross-sectional shape of the cylindrical portion 10. As a result, when a collision load is applied to the front end of the collision energy absorbing component 1 in the longitudinal direction of the vehicle body, the slits 20 act as effective starting points for bending deformation in the initial stages of the collision, thereby keeping the maximum collision load in the initial stages of the collision low and reducing the potential harm to the other party in the collision.

[0030] Furthermore, the collision energy absorbing component 1 can more preferably adjust the buckling period of each surface portion 11 in the cylindrical portion 10 to be closer to that of the inclined surface portion 11d corresponding to the side with the shortest buckling period. As a result, in the later stages of the collision, the cylindrical portion 10 deforms into a bellows shape by stable axial crushing while suppressing a decrease in the collision load, and the collision energy absorbing component 1 can sufficiently absorb the collision energy.

[0031] As described above, the collision energy absorbing component 1 according to this embodiment can suppress the collision load to a low level in the initial stages of a collision and suppress the decrease in the collision load in the later stages of the collision while absorbing sufficient collision energy. Therefore, it can improve the collision performance of an automobile and contribute to improving its marketability.

[0032] The present invention achieves the above effect by having a slit formed on the surface of the cylindrical part act as a breaking point, and the role of such a slit is particularly pronounced in the initial stages of impact. Specifically, in the initial stages of impact or in the mid-stage of impact when the cylindrical part undergoes axial crush deformation, stress concentrates at the ends of the slit due to the impact load, causing buckling. After the ends of the slit buckle and become the breaking point in the cylindrical part, the surrounding portion of the surface where the slit was formed deforms out of the plane, becoming a new breaking point.

[0033] Furthermore, the dimensions of the slits are important for them to function as the starting point for bending. As mentioned above, the length of the slit should be 10% or more of the side length of the polygon corresponding to the surface on which the slit is formed, but preferably the upper limit should be 85% or less of the side length of the polygon corresponding to the surface on which the slit is formed. Also, as mentioned above, the width of each slit should be 1.0 times or more of the plate thickness of the surface on which the slit is formed, but preferably the upper limit should be 5.0 times or less of the plate thickness of the surface on which the slit is formed. If the length and width of the slits exceed these upper limits, the collision load in the initial stages of the collision will be lower, but the collision load in the later stages of the collision will also be lower, and the effect of improving the amount of collision energy absorbed will decrease.

[0034] The spacing between the slits is preferably in the range of 1.0 to 1.5 times the minimum side length of the polygon in the cross-sectional shape of the cylindrical part. The spacing between the slits is the distance between the tips of each slit 20 in the direction of axial crushing, as shown in Figure 2(a).

[0035] The reason for setting the spacing of the multiple slits 20 within the above range is to bring the buckling period of the face corresponding to the longest side of the polygon closer to, or to match, the buckling period of the face corresponding to the shortest side of the polygon, which has a shorter buckling period. As a result, the collision energy absorbing component according to the present invention collapses stably (buckles) in the later stages of the collision, thus providing a stable and high collision energy absorption effect. Furthermore, by bringing the buckling period of each face closer to, or more preferably matching, the buckling period of the face corresponding to the shortest side, it is possible to suppress fluctuations in the collision load during the axial collapse process and reduce the decrease in the collision load.

[0036] In Figure 1, seven slits are formed on the side portion 11c, but in the present invention, it is sufficient to have three or more slits formed on the surface portion corresponding to the longest side (each side portion 11c in Figure 1). This promotes axial crushing by acting as the starting point for buckling of the cylindrical portion, thereby allowing for stable axial crushing and deformation of the cylindrical portion into a bellows shape while suppressing the decrease in impact load in the later stages of impact.

[0037] In the present invention, the slit serves as the starting point for buckling and promotes axial crushing of the cylindrical portion 10. Therefore, the present invention is not limited to the rectangular slit 20 shown in Figures 1 and 2(a), but may also be an elliptical slit 20A, as shown in Figure 2(b). In the case of a slit other than a rectangular shape, as shown in Figure 2(b), the length of the slit should be the maximum length in the direction perpendicular to the axial crushing direction, and the width of the slit should be the maximum length in the axial crushing direction.

[0038] Furthermore, the present invention is sufficient if the multiple slits are not formed on the surface portion corresponding to the shortest length side of the polygonal cross-sectional shape of the cylindrical portion (the inclined surface portion 11d shown in Figure 1), but at least on the surface portion corresponding to the shortest length side of the polygon (the side portion 11c shown in Figure 1). For this reason, the present invention includes cases in which the multiple slits are formed on a surface portion that does not correspond to either the longest length side or the shortest length side, as shown in Figure 1, such as the upper surface portion 11a and the lower surface portion 11b.

[0039] When forming slits on surfaces other than those corresponding to the longest or shortest side (such as the top surface 11a or bottom surface 11b in Figure 1), the length and width of each slit, as well as the spacing between slits, should be the same as those formed on the surface corresponding to the longest side (such as the side surface 11c in Figure 1).

[0040] Furthermore, the method for forming slits on these surfaces can be, for example, punching by shearing or laser processing, and can be done either before or after the forming process of the cylindrical part, or during the forming process of the cylindrical part.

[0041] In the present invention, the cylindrical portion 10 is not limited to one formed by joining two parts 10A, which are press-formed from metal plates, with their openings facing each other (for example, by electric arc welding), as shown in Figure 3(a), to form an octagonal cross-sectional shape. Figure 3(b) shows a cylindrical portion 10 formed by roll-forming a single metal plate and joining its ends 17 (for example, by laser beam welding), to form an octagonal cross-sectional shape.

[0042] The cylindrical portion 10 shown in Figure 1 had eight facets 11 and an octagonal cross-sectional shape. However, the present invention is not limited to this, and any cylindrical portion with four or more facets and a polygonal cross-sectional shape of four or more sides is acceptable. Figure 3(c) shows a cylindrical portion 10 formed by joining two U-shaped cross-sectional parts 10B, each press-formed from a metal plate into a U-shaped cross-section, with their openings facing each other, and having four facets and a square cross-sectional shape.

[0043] We conducted an analysis to confirm the effects of the collision energy absorbing component for automobiles according to the present invention, and the results are described below.

[0044] As an example of the invention, the analysis targets the collision energy absorption component 1 (Fig. 1) described in the embodiment, and performs a collision simulation in which a punch is collided with one end side in the axial crushing direction to input a collision load. Then, through the collision simulation, the deformation state of the collision energy absorption component 1 in the axial crushing process, and the relationship between the collision load input to the collision energy absorption component 1 and the deformation amount in the axial crushing direction (load-stroke curve) were obtained.

[0045] The collision energy absorption component 1 is made of a steel plate with a tensile strength of 980 MPa and a plate thickness of 1.2 mm. As shown in Fig. 3(a), the cylindrical portion 10 is formed by arc-welding two parts 10A formed by press-forming a steel plate to form an octagonal cross-sectional shape. In the octagon of the cross-sectional shape of the cylindrical portion 10, the length of the side corresponding to the upper surface portion 11a and the lower surface portion 11b is 42 mm, the length of the side corresponding to the side surface portion 11c is 66 mm, and the length of the side corresponding to the inclined surface portion 11d is 22 mm. That is, the side corresponding to the inclined surface portion 11d has the minimum length, and the side corresponding to the side surface portion 11c has the maximum length.

[0046] In the collision energy absorption component 1, the slits 20 are not formed on the inclined surface portion 11d corresponding to the side with the minimum length, but seven slits 20 are formed at equal intervals in the axial crushing direction on the side surface portion 11c corresponding to the side with the maximum length. Then, collision simulations were performed for each of the collision energy absorption components 1 in which the length, width, and interval of the slits 20 were variously changed as shown in No. 2 to No. 12 in Table 1 below. Also, as shown in Fig. 4, as a comparison target, a collision simulation was also performed for the collision energy absorption component 3 in which no slit was formed on any of the surface portions 11 constituting the cylindrical portion 10 (No. 1 in Table 1).

[0047]

[0048] Fig. 5 shows the state of deformation after the collision obtained by performing a collision simulation for each of the collision energy absorption component 1 (invention example) in which a plurality of slits 20 with the length, width, and interval shown in No. 2 of Table 1 are formed on the side surface portion 11c, and the collision energy absorption component 3 (comparative example) in which no slit shown in No. 1 of Table 1 is formed.

[0049] As shown in Figure 5(a), in the collision energy absorbing component 1 according to the invention example, the inclined surface portion 11d corresponding to the longest side buckles starting from the slit 20, and this buckling occurs at approximately the same position in the axial crushing direction as the buckling of the inclined surface portion 11d corresponding to the shortest side. This indicates that the buckling deformation of the cylindrical portion 10 is progressing in a bellows-like manner.

[0050] In contrast, in the impact energy absorbing component 3, which does not have a slit, as shown in Figure 5(b), the buckling of the inclined surface portion 11d and the buckling of the side portion 11c do not align in the direction of axial crushing. As a result, deformation of the cylindrical portion progresses while buckling occurs at an unintended position. Such unstable buckling behavior is thought to lead to fracture of the welded joint or base material, resulting in a decrease in absorbed energy.

[0051] For each of the conditions No. 1 to No. 2 in Table 1, the maximum value of the collision load at the beginning of the collision (hereinafter referred to as "initial maximum load") was determined from the load-stroke curve obtained by collision simulation, as the initial maximum load indicating the performance of collision energy absorption component 1. Furthermore, the amount of collision energy absorbed (hereinafter referred to as "absorbed energy") was determined by the cumulative value of the collision load up to a deformation amount (stroke) of 130 mm in the axial crushing direction. The initial maximum load and absorbed energy obtained for each of No. 1 to No. 12 are shown in Table 1 above.

[0052] No. 1 is a comparative example in which no slits are formed on any of the surfaces 11, as shown in Figure 4. The initial maximum load was 366 kN and the absorbed energy was 7.4 kJ.

[0053] In No. 2, the length of the slit 20 (=35mm) is 53% of the width of the side portion 11c (=66mm, the length of the side portion 11c), and the width of the slit 20 (=4.0mm) is 3.3 times the plate thickness of the side portion 11c (1.2mm), both of which are within the scope of the present invention. Furthermore, in No. 2, the spacing of the slits 20 (=28mm) is 1.3 times the minimum side length of the octagonal cross-sectional shape of the cylindrical portion 10 (=22mm, the length of the side corresponding to the inclined surface portion 11d), which is within the preferred range of the present invention. In No. 2, the initial maximum load was 272kN, which was significantly lower than in No. 1, which does not have slits. Also, the absorbed energy was 15.7kJ, which was significantly higher than in No. 1. The reason why the impact load at the beginning of the collision was lower in No. 2 is thought to be that the vicinity of the slit 20 buckled first at the beginning of the collision, followed by buckling of the ridge section R near the slit 20.

[0054] In No. 3, the length of the slit 20 is 59 mm, which is 89% of the width of the side portion 11c, and is larger than the preferred range of the present invention (85% or less of the side length of the side portion 11c, which is 66 mm). The initial maximum load was 206 kN, which was significantly lower than in No. 1 because the slit 20 was longer than in No. 2. The absorbed energy was 11.7 kJ, which was lower than in No. 2 but higher than in No. 1. The reason why the absorbed energy was lower than in No. 2 is thought to be that the ratio of the opening area of ​​the slit 20 to the area of ​​the side portion 11c increased, which reduced the impact load during deformation.

[0055] In No. 4, the width of the slit 20 was set to 2.0 mm, and the thickness of the side portion 11c (1.2 mm) was greater than or equal to that of the present invention. The initial maximum load was 272 kN, similar to No. 2, and lower than No. 1. The absorbed energy was 13.7 kJ, which was lower than No. 2 but higher than No. 1.

[0056] In No. 5, the length of the slit 20 was set to 7 mm, which is within the scope of the present invention (more than 10% of the side length of the side portion 11c, which is 66 mm). The initial maximum load was 296 kN, which increased compared to No. 2 due to the shorter length of the slit 20, but was lower than that of No. 1. The absorbed energy was 13.4 kJ, which was lower than that of No. 2, but increased compared to No. 1.

[0057] In No. 6, the length of the slit 20 was set to 3 mm, which is outside the scope of the present invention (less than 10% of the width of the side portion 11c, which is 66 mm). The initial maximum load was 362 kN, which was about the same as in No. 1, where no slit was formed. This is thought to be because, with a slit length of less than 10%, sufficient out-of-plane deformation occurred at the end of the slit 20, and was insufficient to induce buckling of the ridge radius portion 13 of the cylindrical portion 10. The absorbed energy was also about the same as in No. 1, at 7.2 kJ. This is thought to be because, if the length of the slit 20 is too short, the effect as a starting point for buckling is not obtained, and the cylindrical portion 10 does not stably deform into a bellows shape during the collision process.

[0058] For Nos. 7 to 10, the width of the slit 20 was set to 0.8 mm, 1.2 mm, 6.0 mm, and 8.0 mm. For No. 7, where the width of the slit 20 was outside the range of the present invention (less than 1.0 times the plate thickness of the side portion 11c, which is 1.2 mm), the initial maximum load was 363 kN and the absorbed energy was 7.8 kN, both of which were about the same as No. 1. This is thought to be because the opening width of the slit 20 was too narrow, causing the opening edge of the slit 20 to abut in the direction of axial crushing during impact, thus preventing it from acting as a starting point for buckling. For Nos. 8 to 10, where the width of the slit 20 was within the range of the present invention (1.0 times or more the plate thickness of the side portion 11c, which is 1.2 mm), the initial maximum loads were 297 kN, 264 kN, and 221 kN, respectively, all of which were lower than No. 1, which did not have a slit. Furthermore, for No. 8 to No. 10, the absorbed energy was 13.6 kJ, 14.0 kJ, and 11.5 kJ, respectively, all of which were increased compared to No. 1, which did not have a slit. For No. 10, where the width of the slit 20 was outside the preferred range of the present invention (more than 5.0 times the plate thickness of the side portion 11c, which is 1.2 mm), the initial maximum load and absorbed energy decreased compared to No. 2. The decrease in the initial maximum load is thought to be due to the wider width of the slit 20, which reduced the cross-sectional area receiving the impact load.

[0059] In No. 11 and No. 12, the length and width of the slits 20 are within the preferred range of the present invention, while the spacing of the slits 20 is outside the preferred range of the present invention (less than 1.0 times or more than 1.5 times the length of the side of the inclined surface portion 11d corresponding to the side of the shortest length, which is 22m). The initial maximum loads for No. 11 and No. 12 were 287kN and 288kN, respectively, which were lower than No. 1, which did not have slits, and there was no significant difference from No. 2 and No. 4. The absorbed energy was 12.1kJ and 12.2kJ, which was slightly lower than No. 2, No. 4, No. 5, No. 8, and No. 9, in which the length, width, and spacing of the slits 20 were within the preferred range of the present invention. This indicates that by setting the spacing of the slits 20 within the preferred range of the present invention based on the length of the side of the shortest length, the buckling wavelength of the side portion 11c can be matched to the inclined surface portion 11d, which has a short buckling period, and more stable bellows deformation can be obtained.

[0060] In summary, the collision energy absorbing component according to the present invention reduces the collision load in the initial stages of a collision and improves collision energy by causing stable buckling deformation in a bellows-like manner in the later stages of the collision.

[0061] According to the present invention, it is possible to provide an automotive collision energy absorbing component that can suppress the collision load in the initial stages of a collision and obtain a sufficient collision energy absorption effect in the later stages of a collision when a collision load is input from the front or rear of the vehicle.

[0062] 1 Collision energy absorbing component 3 Collision energy absorbing component 10 Cylindrical part 10A Component 10B U-shaped cross section component 11 Surface part 11a Top surface part 11b Bottom surface part 11c Side part 11d Inclined surface part 13 Ridge radius part 15 Surface 17 End part 19 Flange portion 20, 20A Slit

Claims

1. An automotive collision energy absorbing component provided at the front or rear of a vehicle body and extending in the longitudinal direction of the vehicle body, which absorbs collision energy by axially collapsing when a collision load is applied from the front or rear of the vehicle body, comprising: a cylindrical portion having four or more surface surfaces, the cylindrical portion having a polygonal cross-sectional shape perpendicular to the direction of axial collapse where it axially collapses, and having a plurality of slits formed in one of the surface surfaces in a shape extending in a direction substantially perpendicular to the direction of axial collapse, the plurality of slits not formed in the surface surface corresponding to the side with the shortest length of the polygon, but three or more slits formed at equal intervals in the direction of axial collapse on the surface surface corresponding to the side with the longest length of the polygon, the length of each slit being 10% or more of the length of the side of the polygon corresponding to the surface surface on which the slit is formed, and the width of each slit being 1.0 times or more the plate thickness of the surface surface on which the slit is formed.

2. The collision energy absorbing component for automobiles according to claim 1, wherein the length of the slit is 85% or less of the length of the side of the polygon corresponding to the surface portion on which the slit is formed, and the width of the slit is 5.0 times or less the thickness of the surface portion on which the slit is formed.

3. The collision energy absorbing component for automobiles according to claim 1 or 2, wherein the spacing between the plurality of slits is 1.0 to 1.5 times the minimum side length of the polygon.

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