Automotive collision energy absorption components

Abstract

The present invention provides an automotive collision energy absorbing component that efficiently absorbs collision energy by axially collapsing when a collision load is applied from the front or rear of the vehicle. [Solution] The collision energy absorbing component 1 for automobiles according to the present invention absorbs collision energy by axially crushing a rectangular tube portion 10 when a collision load is input from the front or rear of the automobile. The rectangular tube portion 10 is formed in a cylindrical shape with a substantially rectangular cross-section by two first planar portions 11-1 that are parallel to each other, two second planar portions 11-2 that are perpendicular to the first planar portions 11-1 and parallel to each other, and four curved portions 13 that connect the first planar portions 11-1 and the second planar portions 11-2. The width W1 of the first planar portions 11-1 and the width W2 of the second planar portions 11-2 are both 20 mm or more, and the plate thickness t1 and width W2 of the first planar portion 11-1, the plate thickness t2 and width W2 of the second planar portion 11-2, and the plate thickness t3 and radius of curvature R3 of the curved portion 13 satisfy the following relationship. 0.23×(R3 / t3)≦((W1 / t1)+(W2 / t2)) / 2≦3.60×(R3 / t3)

Description

Technical Field

[0001] The present invention relates to a vehicle collision energy absorption component provided at the front or rear of a vehicle body, which absorbs collision energy when a collision load is input from the front or rear of the vehicle.

Background Art

[0002] Structural components of vehicles are required to be lightweight for fuel efficiency improvement and to have improved collision safety. In electric vehicles, increasing the battery loading capacity is effective for extending the cruising range, but this increases the vehicle body weight and becomes a factor in increasing the impact (collision energy) during vehicle collisions. Therefore, in electric vehicles, structural components that can sufficiently absorb collision energy are required.

[0003] As a structural component that absorbs collision energy during vehicle collisions, there are vehicle collision absorption components such as a crash box that is attached to the front or rear of the vehicle body and absorbs collision energy during a frontal collision or a rear collision of the vehicle to suppress deformation inside the vehicle cabin and protect the occupants. The crash box is provided, for example, between the front side member and the front bumper beam at the front of the vehicle, and is a structural component that absorbs collision energy by axial crushing when a compressive force in the front-rear direction acts during a vehicle collision.

[0004] Many vehicle collision energy absorption components have been proposed so far. For example, Patent Document 1 discloses a crash box that has a structure in which performance such as energy absorption amount, maximum resistance force, and remaining crushed amount can be set to target performance, and the box body can be easily set to a desired shape. Patent Document 2 discloses a crash can (corresponding to a "crash box") that can achieve both suppression of the transmission amount of the initial load during vehicle collision to the front frame and ensuring of the energy absorption amount. Patent Document 3 discloses a cylindrical impact absorbing member having a roughly cross-shaped closed cross section with 12 vertices perpendicular to the axial direction, which absorbs impact energy (collision energy) by plastically deforming in a bellows-like manner when subjected to an axial compressive load. Patent Document 4 discloses an impact-absorbing member having a closed cross-section with four or more vertices, wherein each surface is provided with bead-shaped portions that serve as the starting point for bellows-like plastic deformation, arranged alternately so that the direction of the irregularities is in the opposite direction. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-234377 [Patent Document 2] Japanese Patent Publication No. 2022-12132 [Patent Document 3] International Publication No. 2014 / 073084 [Patent Document 4] Japanese Patent Publication No. 2011-179579 [Overview of the project] [Problems that the invention aims to solve]

[0006] Until now, collision energy absorption components such as crash boxes have used relatively low-strength steel plates to allow for sufficient compressive deformation. However, in response to the demand for increased energy absorption during electric vehicle collisions, there is growing consideration to using thicker steel plates with a tensile strength of 590 MPa or higher, or even steel plates with a tensile strength of 980 MPa or higher.

[0007] These collision energy absorbing components, made from steel plates, increase the resistance to compressive loads caused by collisions when another vehicle collides with the front (or rear) of a vehicle. This prevents excessive crushing and reduces deformation inside the vehicle's interior. However, because the collision energy is absorbed by the deformation of the other vehicle, this could potentially increase the harm to the occupants of the other vehicle. Therefore, it is important that collision energy absorbing components not only absorb sufficient collision energy but also do not have excessively high maximum loads (resistance) to reduce harm to the other vehicle.

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

[0009] The technology described in Patent Document 2 is designed so 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 decrease in the later stages of the collision without stable collapse, and the collision energy cannot be sufficiently absorbed.

[0010] The technologies described in Patent Documents 3 and 4 are said to undergo stable bellows-like plastic deformation when subjected to axial compressive load, and to have a high amount of impact energy absorption when crushed by a predetermined amount of deformation. However, securing the required amount of impact energy absorption (absorbed energy) tends to increase the weight, and there was room for improvement in improving the absorbed energy per unit weight (weight efficiency) by optimizing the cross-sectional shape such as the length of the sides and the thickness of the plates.

[0011] The present invention was made to solve the above-mentioned problems, and aims to provide an automotive collision energy absorbing component that sufficiently absorbs collision energy when a collision load is applied from the front or rear of the vehicle, and that has excellent weight efficiency of absorbed energy. [Means for solving the problem]

[0012] (1) The collision energy absorbing component for automobiles according to the present invention comprises a rectangular tubular portion extending in the longitudinal direction at the front or rear of the vehicle body, and when a collision load is applied from the front or rear of the automobile, the rectangular tubular portion axially collapses to absorb the collision energy. The rectangular tube portion is formed into a cylindrical shape with a substantially rectangular cross-sectional shape perpendicular to the axial crushing direction, by two first planar portions parallel to each other, two second planar portions perpendicular to the first planar portions and parallel to each other, and four curved portions connecting the first planar portions and the second planar portions. The width W1 of the first flat portion and the width W2 of the second flat portion are both 20 mm or more, and the plate thickness t1 and width W2 of the first flat portion, the plate thickness t2 and width W2 of the second flat portion, and the plate thickness t3 and radius of curvature R3 of the curved portion satisfy the following relationship. 0.23×(R3 / t3)≦((W1 / t1)+(W2 / t2)) / 2≦3.60×(R3 / t3) [Effects of the Invention]

[0013] According to the present invention, when an automobile collides, the rectangular tubular section deforms into a bellows shape and collapses axially, thereby sufficiently absorbing collision energy and increasing the weight efficiency of the absorbed energy. [Brief explanation of the drawing]

[0014] [Figure 1] This figure illustrates the configuration of an automobile collision energy absorbing component according to an embodiment of the present invention. [Figure 2]In the embodiment, it is a diagram showing a specific example of a square tube portion of a vehicle collision energy absorption component that is an analysis target of a collision simulation ((a) invention example, (b) comparative example). [Figure 3] In the embodiment, it is a diagram showing a deformed state in the axial crushing process of a square tube portion of a vehicle collision energy absorption component that is an analysis target of a collision simulation ((a) invention example, (b) comparative example). [Figure 4] In the embodiment, it is a load-stroke curve obtained by a collision simulation with the square tube portion as an analysis target. [Figure 5] In the embodiment, it is a graph plotting the relationship between the width plate thickness ratio / curvature radius plate thickness ratio of a square tube portion in which the widths and plate thicknesses of the first flat portion and the second flat portion and the curvature radius and plate thickness of the curved portion are variously changed, and the absorption energy efficiency obtained by a collision simulation.

Mode for Carrying Out the Invention

[0015] The vehicle collision energy absorption component 1 according to an embodiment of the present invention (hereinafter, simply referred to as "collision energy absorption component 1") is provided with a square tube portion 10 extending in the front-rear direction at the front or rear of the vehicle body, as shown in FIG. 1 as an example. And when a collision load is input from the front or rear of the vehicle body, the square tube portion 10 is axially crushed to absorb the collision energy in the collision energy absorption component 1.

[0016] Hereinafter, the collision energy absorption component 1 according to the present embodiment will be described. In the following description, based on the state in which the collision energy absorption component 1 is provided on the vehicle body such that the direction in which the square tube portion 10 is axially crushed (axial crushing direction) coincides with the front-rear direction of the vehicle, the relative positions and directions of each component are represented. In the drawings of the present application, the x-axis direction, y-axis direction, and z-axis direction respectively indicate the front-rear direction, width direction, and up-down direction of the vehicle. Also, the drawings of the present application clearly illustrate the features of the present invention, and the dimensions, ratios, arrangements, etc. of each component are not necessarily the same as those in reality.

[0017] As shown in Figure 1, the rectangular tube portion 10 has two first planar portions 11-1 that are parallel to each other, two second planar portions 11-2 that are perpendicular to the first planar portions 11-1 and parallel to each other, and a curved portion 13 that connects the first planar portions 11-1 and the second planar portions 11-2. The first planar portions 11-1, the second planar portions 11-2, and the curved portion 13 form a cylindrical shape with a cross-sectional shape perpendicular to the direction of axial crushing. Here, the first planar portions 11-1 and the second planar portions 11-2 correspond to the sides of the approximate rectangle, and the curved portion 13 corresponds to the rounded corners that are curved in an arc shape of the approximate rectangle.

[0018] Furthermore, the collision energy absorbing component 1 has a width W1 of the first flat portion 11-1 and a width W2 of the second flat portion 11-2 that are both 20 mm or more, and the plate thickness t1 and width W1 of the first flat portion 11-1, the plate thickness t2 and width W2 of the second flat portion 11-2, and the plate thickness t3 and radius of curvature R3 of the curved portion 13 satisfy the following relationship (1). 0.23×(R3 / t3)≦((W1 / t1)+(W2 / t2)) / 2≦3.60×(R3 / t3) ···(1)

[0019] The widths W1 of the first planar section 11-1 and W2 of the second planar section 11-2 are the lengths of the sides of the corresponding approximate quadrilaterals. The radius of curvature R3 of the curved surface section 13 is the radius of curvature of the corners of the approximate quadrilateral.

[0020] The reason why the collision energy absorbing component 1 according to this embodiment is equipped with a rectangular tube portion 10 having a substantially square cross-sectional shape will be explained below.Hereafter, the first flat portion 11-1 and the second flat portion 11-2 will be collectively referred to as the flat portion 11.

[0021] During a frontal or rear-end collision of an automobile, collision energy absorbing components absorb collision energy by axially collapsing due to the collision load applied through the bumper. In this case, depending on the deformation state of the bumper, a load (eccentric load) may be applied to the collision energy absorbing component in a direction inclined from the direction of axial collapse.

[0022] When such an uneven load is applied to, for example, a collision energy absorbing component with a cylindrical section having a circular cross-section, bending deformation occurs, causing the cylindrical section to bend and potentially reducing the absorbed energy because the cylindrical section does not adequately collapse axially. Therefore, collision energy absorbing components are required to be robust enough to absorb collision energy sufficiently without bending deformation, even when an uneven load is applied.

[0023] In this embodiment, the rectangular tube portion 10 of the collision energy absorbing component 1 can have one of its four flat portions 11 bear the load even when an uneven load is applied, thus suppressing bending (bending deformation) like that of a cylindrical portion. Therefore, even when an uneven load is applied, the rectangular tube portion 10 deforms in a bellows-like manner in the direction of axial crushing, and can absorb sufficient collision energy, thus exhibiting high robustness against uneven loads.

[0024] Furthermore, in this embodiment, the width W1 of the first flat section 11-1 and the width W2 of the second flat section 11-2 are both 20 mm or less. This is because if the widths W1 and W2 are less than 20 mm, the overall size of the rectangular tube section 10 becomes too small, making it impossible to secure the necessary absorption energy during a vehicle collision. Furthermore, there are no particular restrictions on the upper limits of widths W1 and W2, but for practical purposes, it is preferable that they be 250 mm or less.

[0025] Furthermore, in this embodiment, the width W1 and thickness t1 of the first flat portion 11-1, the width W2 and thickness t2 of the second flat portion 11-2, and the radius of curvature R3 and thickness t3 of the curved portion 13 satisfy the relationship of equation (1) described above. This is based on the inventor's technical idea that by balancing the deformability of the first flat portion 11-1, the second flat portion 11-2, and the curved portion 13, the rectangular tube portion 10 can be deformed into a bellows shape during axial collapse to efficiently absorb impact energy.

[0026] The ease with which the flat section 11 deforms is influenced by its width W and thickness t. This is because the width W and thickness t of the flat section 11 affect its rigidity. A flat section 11 with a small width W and a thick thickness t, that is, a small ratio of width W to thickness t (width / thickness ratio), has high rigidity and is therefore less prone to buckling.

[0027] Furthermore, the ease with which the curved surface 13 deforms is influenced by its radius of curvature R3 and plate thickness t3. This is because the radius of curvature R3 and plate thickness of the curved surface 13 affect its rigidity. A curved surface 13 with a small radius of curvature R3 and a thick plate thickness t3, that is, a small ratio of radius of curvature R3 to plate thickness t3 (radius of curvature / plate thickness ratio) R3 / t3, has high rigidity and is therefore less prone to buckling.

[0028] Therefore, the ratio of the width-to-thickness ratio of the flat section 11 to the radius-to-thickness ratio of the curved section 13 (width-to-thickness ratio / radius-to-thickness ratio) is an important shape factor for balancing the ease of deformation of the flat section 11 and the curved section 13, and for efficiently absorbing collision energy by deforming the rectangular tube section 10 into a bellows shape when it is axially crushed. Here, the width-to-thickness ratio W / t of the flat section 11 is the average value of the width-to-thickness ratios calculated for the first flat section 11-1 and the second flat section 11-2, respectively (=((W1 / t1)+(W2 / t2)) / 2).

[0029] Furthermore, the ratio of the width of the flat section 11 to the thickness of the curvature radius of the curved section 13, which can balance the ease of deformation of the flat section 11 and the curved section 13, was determined to satisfy the relationship given by equation (1), based on the results of collision simulations described in the embodiments below.

[0030] In other words, if the width-to-thickness ratio of the flat section 11 and the radius-to-thickness ratio of the curved section 13 satisfy the relationship given by equation (1), the ease of deformation of the flat section 11 and the curved section 13 can be balanced. As a result, when the rectangular tube section 10 is axially crushed, the buckling pitch of the flat section 11 (first flat section 11-1, second flat section 11-2) and the curved section 13 deforms in a bellows-like manner in the out-of-plane direction, thus efficiently absorbing impact energy.

[0031] However, if the ratio of the width-to-thickness ratio of the flat section 11 to the radius-to-thickness ratio of the curved section 13 (width-to-thickness ratio / radius-to-thickness ratio) is less than 0.23 (0.23 × (R3 / t3) ≤ ((W1 / t1) + (W2 / t2)) / 2), the rigidity of the curved section 13 is low relative to the flat section 11, resulting in uneven deformation with non-uniform buckling pitches between the flat section 11 and the curved section 13, and a decrease in absorbed energy.

[0032] Furthermore, if the ratio of the width-to-thickness ratio of the flat section 11 to the radius-to-thickness ratio of the curved section 13 (width-to-thickness ratio / radius-to-thickness ratio) exceeds 3.6 (((W1 / t1)+(W2 / t2)) / 2≦3.60×(R3 / t3)), the rigidity of the curved section 13 is higher than that of the flat section 11. As a result, the buckling pitch of the curved section 13 becomes longer than that of the flat section 11, preventing the desired bellows-like deformation from being obtained and reducing the absorbed energy.

[0033] The critical value of the shape factor (width-to-thickness ratio / radius-to-thickness ratio) of the rectangular tube section 10 will be demonstrated in the example described later.

[0034] As described above, in the collision energy absorbing component 1 according to this embodiment, by balancing the ease of deformation between the flat portion 11 (first flat portion 11-1 and second flat portion 11-2) and the curved portion 13 of the rectangular tube portion 10, the rectangular tube portion 10 can be deformed into a bellows shape during a vehicle collision. This allows for sufficient absorption of collision energy and improves weight efficiency.

[0035] In this invention, there are no particular limitations on the radius of curvature of the curved portion. However, if the radius of curvature is less than 10 mm, the bending rigidity of the curved portion increases, making it difficult to deform in the out-of-plane direction. Therefore, the desired bellows deformation is less likely to occur during the axial crushing process of the rectangular tube portion. For this reason, in this invention, the radius of curvature of the curved portion is preferably 10 mm or more. Furthermore, there are no particular limitations on the upper limit of the radius of curvature of the curved portion, but for practical purposes, it is preferably 30 mm or less.

[0036] In the present invention, the rectangular tube portion can be manufactured, for example, by forming a metal pipe into a substantially rectangular cross-sectional shape. However, the present invention is not limited to this method for manufacturing the rectangular tube portion. For example, the rectangular tube section may be formed by bending a single metal sheet of uniform thickness (e.g., steel sheet) into a cylindrical shape, or by bending a single metal sheet with gradually changing thickness, such as a Tailor Rolled Blank, into a cylindrical shape. Alternatively, it may be formed by welding multiple metal sheets of different thicknesses together to form a single sheet, such as a Tailor Welded Blank, and then bending it into a cylindrical shape. The ends of the rectangular tube section formed by bending a single sheet can be joined by laser welding or arc welding, or by overlapping and joining by spot welding.

[0037] Furthermore, while metal pipes or metal plates with a thickness of 0.8 mm to 2.3 mm can be used as the material for the rectangular tube section, the present invention is not limited to these materials or thicknesses. [Examples]

[0038] We have conducted an analysis to demonstrate the effects of the collision energy absorbing component for automobiles according to the present invention, and will describe it below.

[0039] The analysis involved performing a collision simulation by impacting one end of the rectangular tube sections 10 and 20 in the direction of axial crushing with a punch and inputting a collision load. The collision simulation then determined the deformation state of the rectangular tube sections 10 and 20 during the axial crushing process, and the relationship between the collision load input to the rectangular tube sections 10 and 20 and the amount of punch movement (stroke).

[0040] The rectangular tube portion 10 in Figure 2(a) is an example of the invention in which the width W1 of the first flat portion 11-1 and the width W2 of the second flat portion 11-2 are 24 mm, and the radius of curvature R3 of the curved portion 13 is 20.0 mm, and the width-to-thickness ratio of the first flat portion 11-1 and the second flat portion 11-2 and the radius-to-thickness ratio of the curved portion 13 satisfy the relationship of formula (1) described above. The rectangular tube section 20 in Figure 2(b) is a comparative example in which the width W1 of the first flat section 21-1 and the width W2 of the second flat section 21-2 are 42 mm, and the radius of curvature R3 of the curved section 23 is 11.0 mm, and the width-to-thickness ratio of the flat section 21 (first flat section 21-1 and second flat section 21-2) and the radius-to-thickness ratio of the curved section 23 do not satisfy the relationship in formula (1) described above.

[0041] Figure 3 shows (a) the deformation state of the rectangular tube section 10 at a punch stroke of 42 mm in a collision simulation, and (b) the deformation state of the rectangular tube section 20 at a punch stroke of 19 mm in a collision simulation.

[0042] In the example of the invention, the rectangular tube portion 10 undergoes deformation in the out-of-plane direction, convex (outward in the thickness direction of the rectangular tube portion 10) in the first flat portion 11-1 and the second flat portion 11-2, and deformation in the out-of-plane direction, concave (inward in the thickness direction of the rectangular tube portion 10) in the curved portion 13, both occurring at the same position in the axial crushing direction (indicated by the arrow in Figure 3(a)), resulting in a bellows-like deformation.

[0043] In contrast, in the comparative example, the rectangular tube portion 20, although the first flat portion 21-1 and the second flat portion 21-2 deformed out of plane into a convex or concave shape and buckled, the curved portion 23 bent significantly toward the second flat portion 21-2 and did not deform out of plane, so a bellows-like deformation was not obtained.

[0044] Figure 4 shows the load-stroke curves obtained by collision simulation of the rectangular tube section 10 of the inventive example and the rectangular tube section 20 of the comparative example. During the deformation process of the rectangular tube sections 10 and 20 due to the movement of the punch, the impact load increases and decreases as deformation resistance increases and buckling occurs repeatedly. When the deformation of the rectangular tube sections 10 and 20 bottoms out, the impact load increases monotonically, and the deformation ends.

[0045] In the rectangular tube section 10, after the collision load reaches its maximum value (the peak at the beginning of the collision), buckling is repeated at short intervals while maintaining a high collision load. In contrast, in the rectangular tube section 20, the load decreases significantly after the collision load reaches its maximum value, and the interval between increases and decreases in the collision load is long. These results indicate that in the rectangular tube section 10, the average collision load after the collision load reaches its maximum value is high, and because the pitch of repeated buckling is short, high absorbed energy can be obtained.

[0046] The difference in deformation state during the axial crushing process between the rectangular tube section 10 and the rectangular tube section 20 can be explained by the balance of the ease of deformation between the flat section 11 and the curved section 13 or between the flat section 21 and the curved section 23.

[0047] In the example of the invention, the rectangular tube portion 10 has a width-to-thickness ratio of the first flat portion 11-1 to the second flat portion 11-2 (W1 / t1 + W2 / t2) / 2 = (24mm / 1.6mm + 24mm / 1.6mm) / 2 = 15.0, and the radius-to-thickness ratio of the curved portion 13 is R3 / t3 = 20.0mm / 1.6mm = 12.5. Therefore, the shape factor (width-to-thickness ratio / radius-to-thickness ratio) representing the balance of the ease of deformation between the flat portion 11 and the curved portion 13 in the rectangular tube portion 10 is 15.0 / 12.5 = 1.2.

[0048] On the other hand, in the comparative example, the rectangular tube section 20 has a width-to-thickness ratio of the first flat section 21-1 to the second flat section 21-2 (W1 / t1+W2 / t2) / 2=(42mm / 1.6mm+24mm / 1.6mm) / 2=26.3, and a radius-to-thickness ratio of the curved section 23 (R3 / t3=11.0mm / 1.6mm=6.9). Therefore, the shape factor (width-to-thickness ratio / radius-to-thickness ratio) representing the balance of the ease of deformation between the flat section 21 and the curved section 23 in the rectangular tube section 20 is 26.3 / 6.9=3.8, which is larger than that of the rectangular tube section 10 in the example invention.

[0049] This indicates that in the comparative example's rectangular tube portion 20, the curved portion 23 is less prone to deformation in the out-of-plane direction compared to the flat portion 21. Therefore, in the comparative example, it is considered that the curved portion 23 deformed by bending toward the second flat portion 21-2 without deforming in the out-of-plane direction.

[0050] In contrast, the width-to-thickness ratio / radius-to-thickness ratio of the rectangular tube portion 10 in the inventive example shows that the rigidity of the curved surface portion 13 is lower compared to the rectangular tube portion 20 of the comparative example, indicating a good balance between the ease of deformation of the first flat portion 11-1 and the second flat portion 11-2 and the curved surface portion 13. As a result, in the inventive example, it is considered that the first flat portion 11-1, the second flat portion 11-2 and the curved surface portion 13 all buckled together and deformed into a bellows shape.

[0051] Next, collision simulations were performed by changing the shapes of the rectangular tube sections 10 and 20 in various ways, and the relationship between the width-to-thickness ratio / radius-to-thickness ratio of the rectangular tube sections 10 and 20, absorbed energy, and weight efficiency was examined.

[0052] Table 1 shows the various combinations of width W1 and thickness t1 of the first flat section, width W2 and thickness t2 of the second flat section, and radius of curvature R3 and thickness t3 of the curved section that were modified in the collision simulation. The rectangular tube sections No. 1 to No. 11 in Table 1 are made of steel plate with a tensile strength of 590 MPa, as described in Figure 2 above, and have a total length of 200 mm in the direction of axial crushing. [Table 1]

[0053] Furthermore, Table 1 shows the cross-sectional area of ​​the rectangular tube section, as well as the absorbed energy and absorbed energy efficiency obtained from collision simulations. The cross-sectional area of ​​the rectangular tube section is calculated by multiplying the plate thickness of the first flat section, the second flat section, and the curved section by the cross-sectional line length of the rectangular tube section. Furthermore, the absorbed energy was defined as the integrated value of the collision load up to a stroke of 130 mm in the load-stroke curve obtained by collision simulation. In addition, the absorbed energy efficiency was defined as the absorbed energy divided by the cross-sectional area. Note that since the total length of the rectangular tube sections No. 1 to No. 11 is the same, the absorbed energy efficiency is equivalent to the absorbed energy divided by the weight of the rectangular tube section, i.e., the weight efficiency of the absorbed energy.

[0054] In Table 1, No. 1 is the rectangular tube portion 20 according to the comparative example in Figure 2(b) described above, and No. 2 is the rectangular tube portion 10 according to the inventive example in Figure 2(a) described above. Models No. 3 through No. 11 are based on the rectangular tube section 10 of No. 2, with the dimensions of each part modified. No. 3 and No. 4 are rectangular tube sections 10 according to the inventive example, with a cross-sectional area that is relatively similar to that of No. 2, and with changes to the width W1 of the first flat section 11-1, the width W2 of the second flat section 11-2, and the radius of curvature R3 of the curved section 13. Nos. 5 to 7 are examples of the rectangular tube portion 10 according to the invention, in which the plate thickness t1 or width W1 of the first flat portion 11-1 and the plate thickness t2 or width W2 of the second flat portion 11-2 are changed. No. 8 is a rectangular tube section 10 according to the invention example, in which the width W1 of the first flat section 11-1 and the width W2 of the second flat section 11-2 are both 80 mm, and the ratio of the radius of curvature R3 of the curved section 13 to the plate thickness t3 is 14.0. No. 9 is a rectangular tube portion 20 relating to a comparative example, in which the width of the first flat portion 21-1 and the width of the second flat portion 21-2 are the same as in No. 8, but the radius-to-thickness ratio of the curved portion 23 is set to 12.5, and the ratio of the width-to-thickness ratio to the radius-to-thickness ratio is outside the scope of the present invention. No. 10 is a rectangular tube portion 10 according to an example of the invention, in which the width-to-thickness ratio of the first flat portion 11-1 and the second flat portion 11-2 is reduced, and the radius-to-thickness ratio of the curved portion 13 is increased. No. 11 is a comparative example of the rectangular tube section 20, in which the width W1 of the first flat section 21-1 and the width W2 (=15 mm) of the second flat section 21-2, as well as the width-to-thickness ratio / radius-to-curvature-to-thickness ratio (=0.17), are all outside the scope of the present invention.

[0055] In Table 1, for Nos. 2 to 8 and No. 10 (inventive examples), where the width-to-thickness ratio / radius-to-thickness ratio is between 0.23 and 3.6 within the range of the present invention, the absorbed energy is large, ranging from 10.0 kJ to 17.8 kJ, and the absorbed energy efficiency is high, at 0.025 or higher. In contrast, for No. 1 (0.017 < 0.23) and No. 11 (3.8 > 3.6), where the width-to-thickness ratio / radius-to-thickness ratio was outside the range of the present invention, the absorbed energy was 8.3 kJ and 6.2 kJ, and the absorbed energy efficiency was 0.022 and 0.021, both of which were lower than those for No. 2 to No. 8 and No. 10. Furthermore, No. 9 (4.0), whose width-to-thickness ratio / radius-to-thickness ratio was outside the range of the present invention, had a sufficient absorbed energy of 14.0 kJ, but its absorbed energy efficiency was low at 0.020 compared to the inventive example.

[0056] Figure 5 shows a graph plotting the relationship between the width-to-thickness ratio / radius-to-thickness ratio and the absorbed energy efficiency for No. 1 to No. 11 shown in Table 1. As the width-to-thickness ratio / radius-to-curvature thickness ratio increased, the absorbed energy efficiency increased, reaching a maximum value at approximately 1.2, and then decreased as the width-to-thickness ratio / radius-to-curvature thickness ratio increased further. Furthermore, when the width-to-thickness ratio / radius-to-curvature thickness ratio was between 0.23 and 3.6, the absorbed energy efficiency was 0.025 or higher, indicating that collision energy could be absorbed efficiently and that the weight efficiency was high.

[0057] In summary, the present invention demonstrates that collision energy can be sufficiently absorbed by making the widths of both the first flat portion 11-1 and the second flat portion 11-2 in the rectangular tube portion 10 20 mm or more. Furthermore, it has been demonstrated that when the width W1 and thickness t1 of the first flat portion 11-1, the width W2 and thickness r2 of the second flat portion 11-2, and the radius of curvature R3 and thickness t3 of the curved portion 13 satisfy the relationship in equation (1) described above, the weight efficiency of absorbed energy is high, and collision energy can be absorbed efficiently. [Explanation of Symbols]

[0058] 1. Collision energy absorption component 10. Rectangular tube section (invention) 11 Plane part 11-1 1st plane section 11-2 2nd plane part 13 Curved part 20. Rectangular tube section (comparative example) 21. Planar section 21-1 First Plane Section 21-2 Second Plane Section 23 Curved Face

Claims

[Claim 1] An automotive collision energy absorbing component comprising a rectangular tubular portion extending in the longitudinal direction at the front or rear of the vehicle body, wherein when a collision load is applied from the front or rear of the vehicle, the rectangular tubular portion axially collapses to absorb the collision energy, The rectangular tube portion is formed into a cylindrical shape with a substantially rectangular cross-sectional shape perpendicular to the direction of axial crushing, by comprising two first planar portions parallel to each other, two second planar portions perpendicular to the first planar portions and parallel to each other, and four curved portions connecting the first planar portions and the second planar portions. An automotive collision energy absorbing component characterized in that the width W1 of the first flat portion and the width W2 of the second flat portion are both 20 mm or more, and the plate thickness t1 and width W2 of the first flat portion, the plate thickness t2 and width W2 of the second flat portion, and the plate thickness t3 and radius of curvature R3 of the curved portion satisfy the following relationship. 0.23×(R3 / t3)≦((W1 / t1)+(W2 / t2)) / 2≦3.60×(R3 / t3)

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