Automotive energy absorption components

Abstract

To provide an energy absorption member for an automobile capable of exerting superb energy absorption efficiency.SOLUTION: An energy absorption member 20 for an automobile includes coupling parts 41, each of which is coupled to a sub-frame 16 when seen in a predetermined direction; first arm parts 43, each of which extends forward via a first inflection point 42 set ahead of the coupling part 41; second arm parts 45, each of which extends forward via a second inflection point 44 from the distal end of the first arm part 43; third arm parts 47, each of which extends forward via a third inflection point 46 from the distal end of the second arm part 45; and fourth arm parts 49, each of which extends forward via a fourth inflection point 48 from the distal end of the third arm part 47.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to an energy absorbing member for automobiles. [Background technology]

[0002] As an energy absorbing member for automobiles, a structure is known that comprises a rear portion extending from the front end of a subframe toward the front of the vehicle body, as disclosed in Patent Document 1, and a front portion extending from the rear portion toward the front of the vehicle body. The rear portion is formed from a press-formed member, and the front portion is formed from a hollow pipe-formed member.

[0003] This energy-absorbing component allows for the effective absorption of impact energy during a collision with a simple configuration, and also enables the lightweight and inexpensive manufacture of a suspension frame of a predetermined shape. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2002-200988 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in recent years, there has been a demand for the practical application of technologies that can ensure high energy absorption performance while maintaining a lightweight energy absorption structure. In other words, there is a need for automotive energy absorption materials with high energy absorption efficiency, which is the amount of energy absorbed per unit weight. Therefore, the present invention aims to provide an energy absorbing member for automobiles that can exhibit excellent energy absorption efficiency. [Means for solving the problem]

[0006] To solve the above problems, the present invention adopts the following configuration. (1) One aspect of the present invention is an automotive energy absorbing member attached to the subframe of an automobile so as to extend forward, and when viewed from a predetermined direction, having a connecting portion connected to the subframe and a first bending point provided forward of the connecting portion The vehicle body is designed to slope outwards in the width direction as it moves towards the front. An extending first arm portion, and from the tip of the first arm portion, via a second bending point Front of the vehicle A second arm portion extending toward and from the tip of the second arm portion via a third bending point The vehicle body is designed to slope outwards in the width direction as it moves towards the front. An extending third arm portion, and from the tip of the third arm portion, via a fourth bending point Front of the vehicle It comprises a fourth arm section extending toward and The first bending point is formed to be less prone to bending than the third bending point, the second bending point is formed to be less prone to bending than the fourth bending point, and the section modulus at a position 20 mm away from the second bending point in the second arm portion is greater than the section modulus at a position 20 mm away from the third bending point in the second arm portion. This is an energy-absorbing component for automobiles characterized by the following features. (2) The automotive energy absorbing member described in (1) above is preferably made of a metal material. (3) As described in (1) or (2) above In the automotive energy absorbing member, it is preferable that the Vickers hardness at a position 20 mm away from the second bending point in the second arm portion is greater than the Vickers hardness at a position 20 mm away from the third bending point in the second arm portion. (4) As described in any of (1) to (3) above In the automotive energy absorbing member, it is preferable that the section modulus at the base end bending point, which is the bending point closest to the subframe, is 1.2 times or more than that of the first arm portion. (5) Any of the above (1) to (4) In the automotive energy absorbing member, it is preferable that the Vickers hardness at the base end bending point, which is the bending point closest to the subframe, is 1.2 times or more than that of the first arm portion. (6) Any of the above (1) to (5) In the automotive energy absorbing member, it is preferable that at least one of the following conditions is met: (A1) the bending angle of the first bending point is greater than 90 degrees and less than 175 degrees; (A2) the bending angle of the second bending point is greater than 90 degrees and less than 175 degrees; (A3) the bending angle of the third bending point is greater than 90 degrees and less than 175 degrees; and (A4) the bending angle of the fourth bending point is greater than 90 degrees and less than 175 degrees. (7) Any of the above (1) to (6)In the energy absorbing member for automobiles, when the length of the third arm portion is L3 and the length of the third arm portion in the vehicle width direction is W3, the length L4 of the fourth arm portion is (L3 - W3) or greater and (L3 2 +W3 2 ) 1 / 2 The following is preferable: (8) Any of the above (1) to (7) In the automotive energy absorbing member, it is preferable that the length α in the vehicle length direction between the third bending point and the tip of the fourth arm portion is greater than 20 mm and less than 500 mm. (9) Any of the above (1) to (7) In the automotive energy absorbing member, (B1) the thickness at the first bending point is 10% or more greater than the thickness at the connecting portion or the thickness at the first arm portion, and (B2) the thickness at the second bending point is the same as the thickness at the second arm portion. Goodbye (B3) The thickness at the third bending point is more than 10% greater than the thickness at the third arm portion. Goodbye (B4) The thickness at the fourth bending point is greater than the thickness at the fourth arm portion. Goodbye It is preferable that at least one of the following conditions is met: it is 10% or more larger than the specified value. [Effects of the Invention]

[0007] According to the present invention, the energy absorbing member can be deformed at at least four bending points during a frontal collision, thereby achieving excellent energy absorption efficiency. [Brief explanation of the drawing]

[0008] [Figure 1] This is a bottom view of an automobile equipped with an energy-absorbing member according to one embodiment of the present invention, viewed from below. [Figure 2] This is a bottom view illustrating the energy absorbing member according to the same embodiment. [Figure 3] This is a cross-sectional view obtained along line II in Figure 2. [Figure 4] This is a bottom view illustrating the state in which the energy absorbing member according to the same embodiment has been deformed by a frontal collision. [Figure 5] It is a bottom view showing the state in which an automobile equipped with an energy absorption member according to the same embodiment is deformed due to a frontal collision. [Figure 6] It is a bottom view for explaining an energy absorption member of a comparative example. [Figure 7] It is a bottom view for explaining the state in which the energy absorption member of the comparative example is deformed due to a frontal collision.

Mode for Carrying Out the Invention

[0009] Hereinafter, an energy absorption member for an automobile according to an embodiment of the present invention will be described based on the drawings. In the drawings, arrow FR indicates the front of the automobile, arrow UP indicates the upper side of the automobile, and arrow LH indicates the left side of the automobile. Also, the front direction of the automobile will be described as the vehicle body front (or simply the front), the rear direction of the automobile as the vehicle body rear (or simply the rear), the longitudinal direction of the automobile as the vehicle body longitudinal direction, and the width direction of the automobile as the vehicle width direction.

[0010] (Automobile 10) FIG. 1 is a bottom view of an automobile 10 equipped with an energy absorption member 20 according to the present embodiment as viewed from below. As shown in FIG. 1, the automobile 10 includes, for example, a pair of front side frames 12, a subframe 16, and a pair of energy absorption members 20 for automobiles at the front part of the vehicle body. The pair of front side frames 12 are arranged outside the engine room 13 in the vehicle width direction and extend in the vehicle body longitudinal direction. A front bumper beam 15 is spanned at the front end portions of the pair of front side frames 12 so as to extend in the vehicle width direction via a crash box. The pair of front side frames 12 absorb part of the impact energy, for example, by the front end portion being crushed rearward of the vehicle body due to a frontal collision.

[0011] A subframe 16 is provided below the pair of front side frames 12 and the drive source 24 (for example, an engine / transmission unit). In this subframe 16, a pair of automotive energy absorbing members 20 are attached to the front end 16a. A pair of suspension arms 17, each supporting a front wheel 18, are connected to the side end 16b of the subframe 16 in the vehicle width direction. The pair of energy absorbing members 20 are formed to be generally symmetrical. Therefore, the same reference numerals are used to denote each component of the pair of energy absorbing members 20 below, and the energy absorbing member 20 on the left will be described as the energy absorbing member 20 according to this embodiment (sometimes abbreviated as energy absorbing member 20), while the description of the energy absorbing member 20 on the right will be omitted.

[0012] (Energy absorbing member 20) The energy absorbing member 20 is attached to the automobile 10 so as to extend toward the front of the vehicle body. Specifically, the energy absorbing member 20 is attached to the automobile 10 by connecting its rear end (connecting portion 41, described later) to the subframe 16 and connecting its front end (fourth arm portion 49, described later) to the front lower bumper beam 22 which extends in the width direction of the vehicle. Furthermore, the energy absorbing member 20 may be attached to the automobile 10 in such a manner that its tip is connected to the tip of the front side frame 12 via a bracket (not shown). Alternatively, the tip of the energy absorbing member 20 may be attached to other components such as the radiator or beam components other than the bumper.

[0013] Figure 2 is a bottom view illustrating the energy absorbing member 20 in more detail, and Figure 3 is a cross-sectional view obtained along line II in Figure 2. As shown in Figures 2 and 3, the energy absorbing member 20 is a long member having a continuous hollow rectangular cross-section. Specifically, the energy absorbing member 20 has an inner vertical wall 31, an outer vertical wall 32, a top portion 33, a bottom portion 34, a first curved corner portion 35, a second curved corner portion 36, a third curved corner portion 37, and a fourth curved corner portion 38. The inner vertical wall 31 and the outer vertical wall 32 are spaced apart in the vehicle width direction. The top portion 33 and the bottom portion 34 are spaced apart in the vertical direction. The first curved corner 35 is the part where the inner vertical wall 31 and the top portion 33 intersect. The second curved corner 36 is the part where the inner vertical wall 31 and the bottom portion 34 intersect. The third curved corner 37 is the part where the outer vertical wall 32 and the bottom portion 34 intersect. The fourth curved corner 38 is the part where the outer vertical wall 32 and the top portion 33 intersect. In this embodiment, the energy absorbing member 20 has a rectangular closed cross-sectional shape, but the energy absorbing member 20 may have a circular, elliptical, or polygonal closed cross-sectional shape. Furthermore, another component may be packed inside the energy absorbing member 20.

[0014] The energy absorbing member 20 can be obtained, for example, by hydroforming a metal tube or by press-forming a metal plate. Examples of materials for the energy absorbing member 20 include metal materials such as steel, aluminum, or aluminum alloy. From the viewpoint of weight reduction, the energy absorbing member 20 preferably has a tensile strength of 590 MPa or more, and more preferably 980 MPa or more.

[0015] As shown in Figure 2, the energy absorbing member 20 according to this embodiment includes a connecting portion 41, a first arm portion 43, a second arm portion 45, a third arm portion 47, and a fourth arm portion 49. More specifically, in the energy absorbing member 20, the connecting portion 41, the first bending point 42, the first arm portion 43, the second bending point 44, the second arm portion 45, the third bending point 46, the third arm portion 47, the fourth bending point 48, and the fourth arm portion 49 are formed in this order in a continuous manner toward the front of the vehicle body. Furthermore, the connecting portion 41, the first arm portion 43, the second arm portion 45, the third arm portion 47, and the fourth arm portion 49 may be integrated by processing a single member, or they may be connected by welding or other means to two or more separate members. The following describes each component.

[0016] (Connection part 41) The base end of the connecting portion 41 is fixed to the front end portion 16a of the subframe 16 by welding. As a means of fixing, fastening members such as bolts and nuts may be used instead of welding. The connecting portion 41 is attached so as to extend from the front end 16a of the subframe 16 toward the front of the vehicle body. In a plan view, for example, the base end of the connecting portion 41 is formed to be wider in the vehicle width direction than the tip end. A first arm portion 43 is continuously formed in front of the connecting portion 41 via a first bending point 42.

[0017] (First arm section 43) The first arm portion 43 extends from the first bending point 42 toward the front of the vehicle body, inclined toward the outside in the width direction of the vehicle. The first arm portion 43 has a cross-section that is approximately the same as the cross-section at the first bending point 42. A second arm portion 45 is continuously formed at the tip of the first arm portion 43 via a second bending point 44.

[0018] (Second arm section 45) The second arm portion 45 extends forward from the second bending point 44 towards the front of the vehicle body. The second arm portion 45 has a cross-section that is approximately the same as the cross-section at the second bending point 44. A third arm portion 47 is continuously formed at the tip of the second arm portion 45 via a third bending point 46.

[0019] (Third arm section 47) The third arm portion 47 extends from the third bending point 46 toward the front of the vehicle body, inclined outward in the width direction of the vehicle. The third arm portion 47 has a cross-section that is approximately the same as the cross-section at the third bending point 46. A fourth arm portion 49 is continuously formed at the tip of the third arm portion 47 via a fourth bending point 48.

[0020] (Fourth arm section 49) The fourth arm section 49 extends forward from the fourth bending point 48 towards the front of the vehicle body. The fourth arm portion 49 has a cross-section that is approximately the same as the cross-section at the fourth bending point 48. The front lower bumper beam 22 is attached to the tip 49a of the fourth arm portion 49 (i.e., the tip of the energy absorbing member 20) so as to extend in the vehicle width direction.

[0021] (Inflection point) The first bending point 42 and the third bending point 46 are locations where, when the energy absorbing member 20 is viewed from above, the outer edge in the vehicle width direction is bent at bending angles θ1 and θ3 of less than 175 degrees. In other words, at the first bending point 42 and the third bending point 46, the energy absorbing member 20 is bent so as to protrude inward in the vehicle width direction. On the other hand, the second bending point 44 and the fourth bending point 48 are locations where, when the energy absorbing member 20 is viewed from above, the inner edge in the vehicle width direction is bent at bending angles θ2 and θ4 of less than 175 degrees. In other words, the energy absorbing member 20 is bent at the second bending point 44 and the fourth bending point 48 so as to protrude outward in the vehicle width direction.

[0022] The bending angles θ1 to θ4 are defined as follows. The bending angle θ1 at the first bending point 42 is the outer angle in the vehicle width direction formed by a virtual line obtained by approximating the outer edge of the connecting portion 41 in the vehicle width direction with a straight line, and a virtual line obtained by approximating the outer edge of the first arm portion 43 in the vehicle width direction with a straight line. The bending angle θ2 at the second bending point 44 is the inner angle in the vehicle width direction formed by a virtual line obtained by approximating the inner edge of the first arm portion 43 in the vehicle width direction with a straight line, and a virtual line obtained by approximating the inner edge of the second arm portion 45 in the vehicle width direction with a straight line. The bending angle θ3 at the third bending point 46 is the outer angle in the vehicle width direction formed by a virtual line obtained by approximating the outer edge of the second arm portion 45 in the vehicle width direction with a straight line, and a virtual line obtained by approximating the outer edge of the third arm portion 47 in the vehicle width direction with a straight line. The bending angle θ4 at the fourth bending point 48 is the inner angle in the vehicle width direction formed by a virtual line obtained by approximating the inner edge of the third arm portion 47 in the vehicle width direction with a straight line, and a virtual line obtained by approximating the inner edge of the fourth arm portion 49 in the vehicle width direction with a straight line.

[0023] Furthermore, the connecting portion 41 may have one or more additional bending points located closer to the proximal end than the first bending point 42, i.e., closer to the subframe 16. However, if the bending angle is 175 degrees or more, it will not be considered a bending point. In this specification, the inflection point of the energy absorbing member 20 that is closest to the subframe 16 may be referred to as the "base end inflection point."

[0024] As described above, the energy absorbing member 20 according to this embodiment has four bending points 42, 44, 46, and 48, which are arranged from the rear of the vehicle body toward the front of the vehicle body and have sequentially different bending directions. Furthermore, the energy absorbing member 20 is bent so as to protrude inward in the vehicle width direction at the first bending point 42 and the third bending point 46, and so as to protrude outward in the vehicle width direction at the second bending point 44 and the fourth bending point 48. In other words, the energy absorbing member 20 is bent in opposite directions in the vehicle width direction at the first bending point 42 and the third bending point 46, and at the second bending point 44 and the fourth bending point 48. Therefore, when an impact load is applied to the tip 49a of the fourth arm portion 49 from the front of the vehicle body during a frontal collision, the energy absorbing member 20 bends further inward in the vehicle width direction at the first bending point 42 and the third bending point 46, and bends further outward in the vehicle width direction at the second bending point 44 and the fourth bending point 48.

[0025] (Effects and Benefits) Next, we will explain the impact energy absorption performance of the energy absorbing member 20. First, an example of how the energy absorbing member 20 according to this embodiment absorbs impact energy from a frontal collision will be explained based on Figures 4 and 5.

[0026] Figure 4 is a bottom view illustrating the deformation of the energy absorbing member 20 due to a frontal collision. Figure 5 is a bottom view showing the state in which the automobile 10 equipped with the energy absorbing member 20 has been deformed due to a frontal collision.

[0027] As shown in Figure 4, the energy absorbing member 20 absorbs the impact energy E1 from the frontal collision by deformation at the first bending point 42, the second bending point 44, the third bending point 46, and the fourth bending point 48. More specifically, the energy absorbing member 20 bends inward in the vehicle width direction at the first bending point 42 and the third bending point 46, and bends outward in the vehicle width direction at the second bending point 44 and the fourth bending point 48. As a result of these deformations, the energy absorbing member 20 is bent in a roughly Z-shape at the rear, with the connecting portion 41, the first arm portion 43, and the second arm portion 45 being bent in a roughly Z-shape at the front.

[0028] In this way, by providing the energy absorbing member 20 with an even number of bending points (first bending point 42 to fourth bending point 48) that are sequentially different in bending direction toward the front of the vehicle body, the entire energy absorbing member 20 can be bent appropriately, and high energy absorption performance can be stably ensured. Therefore, as shown in Figure 5, the amount of movement of the subframe 16, drive source 24, etc. toward the rear of the vehicle body can be suitably suppressed, and components on the engine compartment 13 side can be prevented from entering the passenger compartment side.

[0029] Furthermore, the energy absorbing member 20 can be made into a simple configuration with only four inflection points: a first inflection point 42, a second inflection point 44, a third inflection point 46, and a fourth inflection point 48. Therefore, the energy absorbing member 20 can exhibit excellent energy absorption efficiency.

[0030] (Preferred embodiment) In order to achieve even better energy absorption efficiency in the energy absorbing member 20, it is preferable to deform the front energy absorbing portion 54 before the rear energy absorbing portion 52. As shown in Figure 2, the rear energy absorption section 52 is the portion from the connecting section 41 to the middle 45a of the second arm section 45, and the front energy absorption section 54 is the portion from the middle 45a of the second arm section 45 to the fourth arm section 49.

[0031] Thus, when the front energy absorption section 54 deforms first, the portion of the front energy absorption section 54 near the third bending point 46 deforms in the initial stages of the stroke to interfere with the front lower bumper beam 22, as shown in Figure 5. Then, in the later stages of the stroke, the deformation of the rear energy absorption section 52 progresses with the area near the third bending point 46 as the fulcrum. Therefore, by bending the entire energy absorbing member 20 in a suitable sequence, even better energy absorption efficiency can be achieved.

[0032] In order to deform the front energy absorption section 54 before the rear energy absorption section 52, it is preferable that the first bending point 42 in the rear energy absorption section 52 is formed to be less prone to bending than the third bending point 46 in the front energy absorption section 54, and that the second bending point 44 in the rear energy absorption section 52 is formed to be less prone to bending than the fourth bending point 48 in the front energy absorption section 54. Here, the "difficulty of bending" at the bending point can be adjusted by making the cross-sectional shape and material strength different between the rear energy absorption section 52 and the front energy absorption section 54. Methods for varying the cross-sectional shape and material strength from part to part include using steel pipes with different thicknesses or tailored blanks, attaching reinforcing members such as patches, and performing heat treatments such as partial hardening.

[0033] (section modulus) As one measure to deform the front energy absorption section 54 before the rear energy absorption section 52, the section modulus of the portion constituting the rear energy absorption section 52 may be adjusted to be larger than the section modulus of the portion constituting the front energy absorption section 54. Specifically, in the second arm portion 45 of the rear energy absorption section 52, if the section modulus near the second bending point 44 is greater than the section modulus near the third bending point 46, the front energy absorption section 54 is more likely to deform before the rear energy absorption section 52, thereby ensuring a higher energy absorption performance more stably. The section modulus near the second bending point 44 is, more precisely, the section modulus of the cross section perpendicular to the axial direction of the second arm portion 45 at a position 20 mm away from the second bending point 44. The section modulus near the third bending point 46 is, more precisely, the section modulus of the cross section perpendicular to the axial direction of the second arm portion 45 at a position 20 mm away from the third bending point 46. Furthermore, it is more preferable to adjust the section modulus of the portion constituting the rear energy absorption section 52 to be at least 1.2 times larger than the section modulus of the portion constituting the front energy absorption section 54.

[0034] (Vickers hardness) Another measure to deform the front energy absorption section 54 before the rear energy absorption section 52 is to adjust the Vickers hardness of the portion constituting the rear energy absorption section 52 to be greater than that of the portion constituting the front energy absorption section 54. Specifically, if the Vickers hardness near the second bending point 44 of the second arm portion 45 of the rear energy absorption portion 52 is greater than the Vickers hardness near the third bending point 46, the front energy absorption portion 54 is more likely to deform before the rear energy absorption portion 52, thereby ensuring a higher energy absorption performance more stably. The Vickers hardness near the second bending point 44 is, more precisely, the Vickers hardness of the second arm portion 45 at a measurement position 20 mm away from the second bending point 44. The Vickers hardness near the third bending point 46 is, more precisely, the Vickers hardness of the second arm portion 45 at a measurement position 20 mm away from the third bending point 46. Vickers hardness is measured by cutting out a sample including the measurement location and performing the test according to the method described in JIS Z 2244:2009. The sample should be cut from a flat surface as much as possible, avoiding processed areas such as bends and hole edges. Five measurements are taken at 1 / 4 of the sample thickness, under a load of 50 gf, at intervals of at least three times the indentation width. The average value of these measurements is taken as the Vickers hardness.

[0035] Furthermore, in order to stably ensure the energy absorption performance of the energy absorbing member 20, it is important to strengthen the bending point on the base end to suppress breakage. In other words, for example, in the case of an energy absorbing member 20 having four bending points as in this embodiment, the section modulus and material strength at the first bending point 42 are important. Specifically, at the base end bending point, it is preferable that the section modulus is 1.2 times or more than that of the first arm portion 43. The section modulus of the base end inflection point is the section modulus of the cross section perpendicular to the axial direction of the energy absorbing member 20, including the base end inflection point. The section modulus of the first arm portion 43 is the section modulus of a cross section perpendicular to the axial direction of the energy absorbing member 20, which includes a position 20 mm away from the second bending point 44 in the first arm portion 43.

[0036] Furthermore, it is preferable that the Vickers hardness at the base end bending point is 1.2 times or more than that of the first arm portion 43. Vickers hardness at the proximal bend refers to the Vickers hardness at the proximal bend. The Vickers hardness of the first arm portion 43 is the Vickers hardness at a position 20 mm away from the second bending point 44 of the first arm portion 43.

[0037] (Angle of bending) The smaller the bending angle θ1 at the first bending point 42, the bending angle θ2 at the second bending point 44, the bending angle θ3 at the third bending point 46, and the bending angle θ4 at the fourth bending point 48, the longer the linear length of the energy absorbing member 20 in the axial direction of the material, and therefore the greater the weight of the energy absorbing member 20. In other words, a larger bending angle is better for achieving excellent energy absorption efficiency. Also, (A1) The bending angle θ1 at the first bending point 42 is greater than 90 degrees and less than 175 degrees. (A2) The bending angle θ2 at the second bending point 44 is greater than 90 degrees and less than 175 degrees. (A3) The bending angle θ3 at the third bending point 46 is greater than 90 degrees and less than 175 degrees, and (A4) The bending angle θ4 at the fourth bending point 48 is greater than 90 degrees and less than 175 degrees. It is preferable that at least one of the following conditions be met, and more preferably that all of them be met. Also, (A5) The bending angle θ1 at the first bending point 42 is greater than 120 degrees and less than 175 degrees. (A6) The bending angle θ2 at the second bending point 44 is greater than 120 degrees and less than 175 degrees. (A7) The bending angle θ3 at the third bending point 46 is greater than 120 degrees and less than 175 degrees, and (A8) The bending angle θ4 at the fourth bending point 48 is greater than 120 degrees and less than 175 degrees. It is more preferable that at least one of the conditions is met, and even more preferable that all of them are met.

[0038] (length) The length L4 of the fourth arm section 49 is (L3-W3) or greater, (L3 2 +W3 2 ) 1 / 2 The following is preferable. Here, L3 is the length of the third arm portion 47, and W3 is the length of the third arm portion 47 in the vehicle width direction (= L3 × sinθ3).

[0039] If the length L4 of the fourth arm portion 49 is longer than (L3-w3), deformation behavior such that the third bending point 46 translates toward the center in the vehicle width direction can be prevented, thereby further increasing the energy absorption efficiency of the energy absorption member 20. Also, when the length L4 of the fourth arm portion 49 is shorter than (L3 2 + W3 2 ) 1 / 2 , since the reaction force of the impact load can be exerted at the third bending point 46, the energy absorption efficiency of the energy absorption member 20 can be further enhanced.

[0040] Furthermore, the length α in the vehicle length direction between the third bending point 46 and the tip 49a of the fourth arm portion 49 is preferably more than 20 mm and less than 500 mm. When the length α is too short, the energy absorption amount at the initial stage of the stroke cannot be obtained sufficiently. Therefore, the length α in the vehicle length direction is preferably more than 20 mm. On the other hand, when the length α is too long, the sufficient energy absorption amount cannot be obtained until the maximum stroke is reached. Therefore, the length α is preferably less than 500 mm. In addition, the total length in the vehicle width direction of the first arm portion 43 to the fourth arm portion 49 is preferably as small as possible.

[0041] (Thickness) It is preferable to satisfy at least one of the following B1, B2, B3, and B4, and more preferably to satisfy all of them. (B1) The thickness at the first bending point 42 is 10% or more greater than the thickness at the connecting portion 41 or the thickness at the first arm portion 43. (B2) The thickness at the second bending point 44 is 10% or more greater than the thickness at the second arm portion 45. Goodbye (B3) The thickness at the third bending point 46 is 10% or more greater than the thickness at the third arm portion 47. Goodbye (B4) The thickness at the fourth bending point 48 is 10% or more greater than the thickness at the fourth arm portion 49. Goodbye

[0042] As described above, the energy absorption member 20 according to the present embodiment and its preferred embodiments have been described. However, within the scope not departing from the gist of the present invention, it is possible to appropriately replace the components in the above embodiments with well-known components. For example, in the energy absorbing member 20 according to this embodiment, the pair of energy absorbing members 20 have been described as being formed in a generally symmetrical manner, but the left energy absorbing member 20 and the right energy absorbing member 20 are not limited to being symmetrical. Furthermore, in the energy absorbing member 20 according to this embodiment, there are four bending points (i.e., multi-point locations) from the first bending point 42 to the fourth bending point 48, but the number of bending points is not limited to four. As another example, the energy absorbing member 20 may have a large number of bending points at four or more locations, and an even number of multi-point locations. In this case as well, by bending the energy absorbing member at a large number of bending points, a Z-shaped bend can be made by bending two consecutive bending points, and the energy absorption efficiency of the energy absorbing member 20 can be further increased.

[0043] (Examples) Next, embodiments of the present invention will be described. The conditions in the embodiments are merely examples of conditions adopted to confirm the feasibility and effectiveness of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention. The collision analysis was performed using CAE simulation with LS-DYNA®.

[0044] (Comparative example) In the comparative example, a CAE simulation was performed using an energy-absorbing member 100 obtained by forming a steel plate with a thickness of 2.0 mm into a hollow rectangular cross-section. As shown in Figure 6, the comparative example energy absorbing member 100 has a shape that bends inward in the vehicle width direction at bending point 104 and bends outward in the vehicle width direction at bending point 106. In other words, bending points are formed at only two locations. Figure 7 shows the deformation that occurs when the front end portion 102 of the energy absorbing member 100 absorbs impact energy E2 due to a frontal collision.

[0045] (Examples of Inventions 1 and 2) In Invention Examples 1 and 2, CAE simulations were performed using energy-absorbing members having a shape similar to the energy-absorbing member 20 described in the above embodiment. In each invention example, the plate thickness and weight were changed.

[0046] CAE simulations were performed with the subframes, to which the energy-absorbing members of the above comparative examples and inventive examples 1 and 2 were attached, and the attachment points to the automobile body were fully constrained. Specifically, an impactor (rigid wall) was collided from the front of the energy-absorbing member at 56 km / h, and the amount of energy absorbed during a 500 mm stroke of the impactor was calculated. Table 1 shows the characteristics and evaluation results of the energy absorbing members of the comparative example and inventive examples 1 and 2.

[0047] [Table 1]

[0048] (Example of Invention 1) The energy absorbing member of Invention Example 1 has a rear energy absorbing section 52 and a front energy absorbing section 54, which are made from a steel plate with a thickness of 2.0 mm and processed into a hollow rectangular cross-section. The energy absorbing member of Invention Example 1 has four bending points (from the first bending point 42 to the fourth bending point 48), resulting in a longer wire length and a weight of 5.11 kg compared to the comparative example. However, its energy absorption capacity was 13.4 kJ. Converting this to an energy absorption efficiency of 2.62 kJ / kg, it was confirmed that it exhibits superior energy absorption efficiency compared to the comparative example.

[0049] (Example of Invention 2) The energy absorbing member of Invention Example 2 has a rear energy absorbing section 52 made from a 2.2 mm thick steel plate with a hollow rectangular cross-section, and a front energy absorbing section 54 made from a 1.8 mm thick steel plate with a hollow rectangular cross-section. The energy absorbing member of Invention Example 2 has four bending points (from the first bending point 42 to the fourth bending point 48). Furthermore, the rear energy absorbing section 52 has a plate thickness of 2.2 mm, and the front energy absorbing section 54 has a plate thickness of 1.8 mm. Therefore, when the energy absorbing member absorbs impact energy, the third bending point 46 located at the front of the vehicle body can be bent inward in the vehicle width direction, followed by the first bending point 42 located at the rear of the vehicle body, which can then be bent inward in the vehicle width direction. Furthermore, the fourth bending point 48 located at the front of the vehicle body can be bent outward in the vehicle width direction, followed by the second bending point 44 located at the rear of the vehicle body, which can then be bent outward in the vehicle width direction. As a result, the energy absorbing member of Invention Example 2 had a weight of 5.09 kg, which is almost the same as that of Invention Example 1, but absorbed 14.5 kJ. Converting this to an energy absorption efficiency of 2.85 kJ / kg, it was confirmed that it exhibits even better energy absorption efficiency than Invention Example 1.

[0050] (Example of Invention 3) The energy absorbing member of Invention Example 3 has a higher strength class and a thinner plate thickness compared to Invention Example 2. By configuring it in this way, it was possible to reduce the weight while ensuring an energy absorption amount equal to or greater than that of the comparative example, thereby further improving the energy absorption efficiency. [Explanation of Symbols]

[0051] 10…Automobiles 16…Subframe 20…Energy absorbing material (energy absorbing material for automobiles) 41...Connection part 42...1st bending point 43...First arm section 44…Second bending point 45...Second arm section 45a...Partway through the second arm section 46...Third bending point 47...Third arm section 48…4th bending point 49...Fourth arm section 52…Rear energy absorption section 54…Front energy absorption section L1…Length of the third arm L2…Length of the fourth arm θ1…Angle of bending at the first bending point θ2…Angle of inflection at the third inflection point θ3…Angle of inflection at the second inflection point θ4…Angle of inflection at the fourth inflection point

Claims

1. An automotive energy absorbing member that is attached to the subframe of a vehicle so as to extend forward, When viewed from a predetermined direction, A connecting portion connected to the aforementioned subframe, A first arm portion extends so as to the front of the vehicle body, inclined outward in the width direction of the vehicle, via a first bending point located forward of the aforementioned connecting portion, A second arm portion extends from the tip of the first arm portion toward the front of the vehicle body via a second bending point, A third arm extends from the tip of the second arm portion, inclined outward in the vehicle width direction as it moves forward towards the vehicle body via a third bending point, A fourth arm extends from the tip of the third arm towards the front of the vehicle body via a fourth bending point, Equipped with, The first bending point is formed to be less prone to bending than the third bending point, and the second bending point is formed to be less prone to bending than the fourth bending point. An energy absorbing member for automobiles, characterized in that the section modulus at a position 20 mm away from the second bending point in the second arm portion is greater than the section modulus at a position 20 mm away from the third bending point in the second arm portion.

2. Formed from metal materials The energy absorbing member for automobiles according to feature 1.

3. The Vickers hardness at a position 20 mm away from the second bending point in the second arm portion is greater than the Vickers hardness at a position 20 mm away from the third bending point in the second arm portion. The energy absorbing member for automobiles according to feature 1.

4. At the base end bending point, which is the bending point closest to the subframe, the section modulus is 1.2 times or more that of the first arm portion. The energy absorbing member for automobiles according to claim 1 or 2.

5. At the base end bending point, which is the bending point closest to the subframe, the Vickers hardness is 1.2 times or more than that of the first arm portion. The energy absorbing member for automobiles according to claim 1 or 2.

6. (A1) The angle of inflection at the first inflection point is greater than 90 degrees and less than 175 degrees; (A2) The angle of inflection at the second inflection point is greater than 90 degrees and less than 175 degrees; (A3) The angle of inflection at the third inflection point is greater than 90 degrees and less than 175 degrees; and (A4) The angle of inflection at the fourth inflection point is greater than 90 degrees and less than 175 degrees. The energy absorbing member for automobiles according to claim 1 or 2.

7. Let the length of the third arm portion be L ３ and the vehicle width direction length of the third arm portion be W ３ When this is the case, the length L ４ of the fourth arm portion is (L ３ −W ３ ) or more and (L ３ ２ +W ３ ２ ) １／２ or less The energy absorbing member for automobiles according to claim 1 or 2.

8. The length α in the vehicle-length direction between the third bending point and the tip of the fourth arm is greater than 20 mm and less than 500 mm. The energy absorbing member for automobiles according to claim 1 or 2.

9. (B1) The thickness at the first bending point is 10% or more greater than the thickness at the connecting portion or the thickness at the first arm portion. (B2) The thickness at the second bending point is 10% or more greater than the thickness at the second arm portion. (B3) The thickness at the third bending point is 10% or more greater than the thickness at the third arm portion, (B4) The thickness at the fourth bending point is 10% or more greater than the thickness at the fourth arm portion. satisfying at least one of the following conditions The energy absorbing member for automobiles according to claim 1 or 2.

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