Bumper assembly for a motor vehicle

Abstract

A bumper assembly 1 for a motor vehicle is described, comprising a bumper crossmember 2 and two energy absorption components 3, 3.1 arranged at a distance from each other in the longitudinal direction of the bumper crossmember 2, having horizontal walls 17, 23 and vertical walls 7, 8, 7.1, 8.1, each of which is connected to the rear of the bumper crossmember 2 by at least one connection section extending in the direction of the longitudinal direction of the bumper crossmember 2, wherein the bumper crossmember 2 has at least one recess 11 following its longitudinal direction and extending into its end sections 20, 20.1, which has a greater depth in a middle section 19 than in the end sections 20, 20.1. A special feature is that the energy absorption components 3, 3.1 are connected by at least one connection section to the base 14 of the recess 11 forming the rear of the bumper cross member 2, that a depth transition section 21, 21.1 is provided between the middle section 19 and the end sections 20, 20.1 by a flexural design of the base 14 of the recess 11, which is located between the vertical walls 7, 8, 7.1, 8.1 of an energy absorption component 3, 3.1 and with its concave flexural section 22 is closer to the inner vertical wall 7, 8 pointing towards the center of the bumper cross member 2, and that the at least one connection section of the energy absorption components 3, 3.1 engages in the concave flexural section 22 and is supported thereon.

Description

[0001] The invention relates to a bumper assembly for a motor vehicle, comprising a bumper crossmember and two energy absorption components arranged at a distance from each other in the longitudinal direction of the bumper crossmember, the energy absorption components having horizontal and vertical walls, each of which is connected to the rear of the bumper crossmember by at least one connection section extending in the longitudinal direction of the bumper crossmember at its end face facing the bumper crossmember, wherein the bumper crossmember has at least one recess following its longitudinal direction and extending into its end sections, which has a greater depth in a central section than in the end sections, wherein the energy absorption components are connected to the bottom of the recess forming the rear of the bumper crossmember by at least one connection section.that between the middle section and the end sections, a depth transition section is provided by a flexure-like formation of the bottom of the depression, which is located between the vertical walls of an energy absorption component and with its concave flexure section closer to the inner vertical wall pointing towards the center of the bumper cross member, and that at least one connection section of the energy absorption components engages in the concave flexure section and is supported thereon,

[0002] To protect the vehicle's safety cell and external components such as the engine, radiator, and the like, motor vehicles are equipped with a bumper assembly, at least in the front section. This bumper assembly comprises a crossmember that extends across the width of the vehicle. This crossmember is connected to the vehicle's chassis via two energy-absorbing components, known as crash boxes, spaced apart along the longitudinal axis of the crossmember, if a single load path is required. In configurations with more than one load path, more than two energy-absorbing components are arranged between the crossmember and the vehicle's chassis. These components absorb energy in the event of a collision through plastic deformation.

[0003] Various requirements are placed on such bumper assemblies. One of these requirements is a pendulum impact test that simulates pedestrian collisions. This pendulum impact test is described in the US publication 49 CFR Part 581 – “Bumper Standard” and in the NHTSA publication from June 2022, “Vehicle bumper performance in part 581 versus pedestrian leg protection.” The bumper crossmembers of conventional bumper assemblies are typically manufactured with a constant material thickness along their length and can have a constant or varying cross-section along their length. As a rule, due to a change in depth extending in the x-direction, the cross-sectional area in the middle section of such a bumper crossmember is larger than in the end sections.A typical example of such a bumper crossmember, with a cross-sectional area that decreases towards the end sections, is a profiled crossmember with a longitudinal groove serving as a stiffening rib. Besides the requirement that such a bumper assembly meets the applicable testing requirements, it is also desirable that this assembly have the lowest possible weight. For conventional bumper assemblies of this type to pass the aforementioned pendulum impact test, the bumper crossmember must either have a correspondingly large material thickness and / or a relatively large cross-sectional area. Both of these measures negatively impact the weight of the bumper assembly due to the increased material usage.

[0004] From US 2022 / 0048455 A1, a bumper assembly is known whose bumper crossmember is profiled in the manner described above. This bumper crossmember has a central section extending between the two energy-absorbing components, in which it has a constant depth (extent in the longitudinal direction of the vehicle). Between the central section and the end sections, there is a transition section. In this transition section, the legs extending from the central section to the respective end section are shortened in an S-shape by a flexure incorporated into the legs. This is achieved by a rib-like indentation, extending in the direction of the longitudinal extent of the bumper crossmember, which is incorporated into the outer surface of the legs of each end section.This is achieved by creating a predefined folding pattern in the end sections of the bumper crossmember through this indentation. Upon impact, the end sections of the bumper crossmember are deformed first in the x-direction, and only then is energy absorbed by the energy-absorbing components attached to the bumper crossmember.

[0005] The energy absorption components are connected to the end sections. The flexural transition section, which reduces the depth of the bumper crossmember over a short distance starting from the central section, is located adjacent to the wall of the energy absorption components facing the center of the bumper crossmember. The flexure provides a predetermined buckling point where, in the event of an impact with an obstacle in the central section of the bumper crossmember, the bumper crossmember is compressed. This works in conjunction with the recess in the legs of the end sections, where, in such a case, the bumper crossmember is compressed laterally (in the x-direction). With this known bumper assembly, it is necessary that the legs are connected to the energy absorption components at their ends facing the energy absorption components.This restricts the design freedom in the cross-sectional geometry of the bumper crossmembers of such a bumper assembly. Furthermore, a plate is required to connect the end face of the energy-absorbing components facing the bumper crossmember to the legs of the bumper crossmember. In addition, it is not always desirable for the bumper crossmember to be folded in a defined manner for energy absorption in the event of an impact before energy absorption takes place in the energy-absorbing components.

[0006] Furthermore, US 2017 / 0021868 A1 discloses the generic bumper crossmember as the next best in the art.

[0007] Based on this discussed state of the art, the invention therefore aims to further develop a bumper assembly of the type mentioned at the outset in such a way that not only are the design freedoms in the design of the cross-sectional geometry of the bumper cross member less restricted, but also that the effective usable length of the energy absorption components for energy absorption is maximized.

[0008] This problem is solved according to the invention by a bumper assembly of the generic type mentioned above, in which at least one connection section is provided by a connecting flange angled outwards in a vertical direction relative to a horizontal wall.

[0009] The directional terms used in this description – the x-direction, the y-direction, and the z-direction – are the coordinate directions of a vehicle, where the x-direction represents the longitudinal extent, the y-direction the lateral extent, and the z-direction the vertical extent (vertical axis) of the vehicle. This coordinate system is applied in the same way to the description of the energy absorption component according to the invention.

[0010] In this bumper assembly, the energy absorption components are connected to the side of the floor of the recess located along the longitudinal extension of the bumper crossmember that faces the vehicle chassis via at least one connection section. Typically, each energy absorption component is connected to the floor at its end face facing the bumper crossmember by two connection sections arranged at a vertical distance from each other. These connection sections are typically the end faces of the horizontal walls of the energy absorption components, which themselves have a square or rectangular cross-sectional geometry. In a preferred embodiment, the connection sections of the energy absorption components are provided by connection flanges angled outwards in the vertical direction. This has the advantage, among others, of providing a larger contact area.A support surface for the energy absorption components is provided on the bumper crossmember. This allows the two parts to be joined by welding, thus requiring heat input, without impairing the material properties relevant for energy absorption in the horizontal walls through heat input and any associated structural changes. The sections of the bumper crossmember adjoining the recess can be designed as desired with regard to the connection of the energy absorption components.

[0011] To prevent any weakening of the section of the bumper crossmember located between the energy-absorbing components, which could lead to buckling, the depth transition section, provided in the bumper assembly according to the invention by a flexural design of the recess bottom, is situated between the vertical walls of each energy-absorbing component. Thus, the central section of the bumper crossmember extends into the energy-absorbing components with a constant depth (extent in the x-direction) or with a continuous decrease in depth towards the end sections. The S-shaped flexural section of the recess bottom is positioned closer to the vertical wall facing the center of the bumper crossmember.This means that the depth transition section is offset from the center of the bumper crossmember with respect to the extent of the end face of the energy absorption components. The connection section of an energy absorption component engages with the concave flexure section at its concave apex and is supported within it. Therefore, the horizontal walls of the energy absorption components in this section of their connection section have a greater extent in the x-direction than in the adjacent sections. This increases the effective length of the energy absorption components (extent in the x-direction) compared to a design where the energy absorption components are connected to a section of the bumper crossmember with a constant depth. Consequently, more energy can be absorbed by the energy absorption components in the event of an impact.Such a bumper assembly meets the requirements of the aforementioned pendulum impact test without requiring the bumper crossmember to be manufactured with a larger cross-sectional geometry or greater material thickness. Rather, the depth transition section and the resulting change in the depth of the recess running longitudinally along the bumper crossmember over a short distance in the y-direction result in weight savings compared to a bumper crossmember where the depth continuously tapers towards the ends of the end sections. In the bumper assembly according to the invention, the end sections can be designed with a constant depth and thus with minimal weight over their entire length.

[0012] Since the bumper crossmember is typically curved along its longitudinal extent, the effect described above is greater the closer the depth transition section, and thus its concave flexure section, is to the inner vertical wall of an energy absorption component. It should be taken into account that both the convex and concave apex of the flexure-like depth transition section are located between the vertical walls of an energy absorption component. Preferably, the distance of the concave flexure section from the track of the plane of the inner vertical wall is designed to be less than 30%, and in particular less than 25%, of the distance to the outer vertical wall.The concave flexure section can be positioned particularly close to the inner vertical wall of an energy absorption component if this is flared in its end section on the bumper crossbeam side in the direction of the center of the bumper crossbeam relative to the track of the plane of this vertical wall.

[0013] In such a bumper assembly, the depth of the bumper crossmember can be defined by the depth of the recess running along its longitudinal axis, and thus by the bottom of that recess. The sections molded onto the recess and extending in the z-direction can have any desired height. Similarly, the bumper crossmember flanges or legs, which are typically angled in the x-direction towards the vehicle chassis, can have a constant or varying flange height along the length of the crossmember. The stiffness of the bumper crossmember can be adjusted via this flange height, as well as via the depth of the recess running along its longitudinal axis.

[0014] For the purposes mentioned, it is sufficient if the bumper crossmember has a single recess extending along its longitudinal axis. The base connecting the leg of the recess is preferably straight in the z-direction and thus provides a flat connection surface in the vertical direction. The bumper crossmember can also be designed with several recesses, for example, two arranged at a vertical distance from each other, extending along its longitudinal axis.While in one design of the bumper crossmember the vertical extent of the base of the recess following the longitudinal extent has a height to allow the energy absorption components to be connected to it with two vertically spaced connection sections, in a design of the bumper crossmember with two vertically spaced recesses, one recess can each be provided for the connection of a connection section of an energy absorption component. It is understood that each recess then has a depth transition section, as described above using an embodiment of the bumper crossmember with a single recess.In a bumper crossmember with two longitudinally extending recesses, the depth transition sections are typically aligned with each other in the vertical direction, but can also be offset from each other in the y-direction if desired.

[0015] The invention is described below with reference to an exemplary embodiment and the accompanying figures. These show: Fig. 1: A top view of a bumper assembly according to the invention for a motor vehicle, Fig. 2: a perspective rear view of the in Fig. 1 right-hand end section of the bumper assembly shown, viewed from below, Fig. 3: A sectional view of the bumper assembly of the preceding figures along the line shown in Fig. 5 section line marked BB, Fig. 4: A front view of the bumper assembly of the Fig. 1, Fig. 5: a sectional view along the section line AA of the Fig. 4 and Fig. 6: An enlarged view of the right end section of the bumper assembly of the Fig. 5.

[0016] A bumper assembly 1 for a motor vehicle comprises a bumper crossmember 2 and two energy absorption components 3, 3.1, so-called crash boxes, which are attached to the rear of the bumper crossmember 2 at a distance from each other in the longitudinal direction. The energy absorption components 3, 3.1 each have a so-called baseplate 4, 4.1 at their end pointing away from the bumper crossmember 2, by means of which the bumper assembly 1 is connected to the chassis of a vehicle.

[0017] The bumper crossmember 2 of the embodiment shown in the figures is curved over its length extending in the y-direction, so that its front side is convex.

[0018] The two energy absorption components 3 and 3.1 are mirror images of each other with respect to the central longitudinal plane (xz-plane), but are otherwise identical. Therefore, the following statements regarding one energy absorption component 3 or 3.1 apply equally to the other energy absorption component 3.1 and 3.1. Fig. Figure 2 shows the energy absorption component 3 without the attached baseplate 4. The energy absorption component 3 has a two-shell construction and comprises a first shell 5, also referred to as the inner shell, and a second shell 6, also referred to as the outer shell. The two shells 5 and 6 have a U-shaped profile. The open sides of the two shells 5 and 6 face each other. In this way, a hollow chamber profile is formed by the two interlocking shells 5 and 6. The legs 7 and 7.1 of shell 6 are slightly further apart than the legs 8 and 8.1 of shell 5, which is the lower shell in the illustrated embodiment. The distance between legs 7 and 7.1 is designed so that they contact the outer surfaces of legs 8 and 8.1 of the other shell 6. In this way, the bowl 5 is inserted into the bowl 6 with sections of its legs 8, 8.1.Both shells 5, 6 are joined together by welding along the vertical joint of the legs 7, 7.1.

[0019] The lower shell 6 is slightly longer than the upper shell 5 with its end face facing the bumper crossmember 2. Both shells 5, 6 are supported and connected to the rear of the bumper crossmember 2, as explained below.

[0020] The bumper crossmember 2 is, as can be seen from the sectional view of the Fig. 3, profiled in the vertical direction. This is basically C-shaped and comprises a front wall 9 and two legs 10, 10.1, which are beveled on their upper and lower sides in the x-direction towards the rear of the bumper crossmember 2. A recess 11, following the longitudinal extent of the bumper crossmember 2, is formed in the front wall 9. This recess has a U-shaped profile in cross-section and therefore has an upper leg 12, a lower leg 13, and a base 14 connecting the two legs 12, 13. The base 14 is straight in the vertical direction (z-direction). The side of the base 14 facing the energy absorption components 3, 3.1 forms, as can be seen from the top view of the Fig. 1. The rear end of the bumper crossmember is recognizable. 2. In Fig. Figure 3 clearly shows the support of the upper shell 5 with its front end face 15 facing the bumper crossmember 2 on the bumper crossmember 2, as well as the fact that the lower shell 6 with its legs 8, 8.1 is set back slightly and is not supported on the bottom 14 of the recess 11. The lower shell 6 is supported by a projection 16 of its horizontal wall 17 on the rear of the upper part of the front wall 9, adjacent to the recess 11. The projection 16 has a connecting flange 18 projecting vertically outwards, which is supported with its side facing the bumper crossmember 2 on the rear of the front wall 9 and welded to it. Thus, the longitudinal extent of this connection section of the energy absorption component 3, provided by the connecting flange 18, follows the longitudinal extent of the bumper crossmember 2. As can be seen from a summary of the Fig. 2 and Fig. As can be seen in Figure 3, the legs 7, 7.1 of the upper shell 5, and thus also the upper horizontal wall 23 of the energy absorption component 3 connecting the two legs 7, 7.1, are supported on the rear side of the base 14 and connected to it. This connection area, formed by the extension of the lower horizontal wall 23, also extends in the direction of the longitudinal extension of the bumper cross member 2.

[0021] Fig. Figure 4 shows a front view of the bumper crossmember 2. The front wall 9 is higher in the central area of ​​the bumper crossmember 2 than in the outer sections. In this central area, the recess 11 is offset relative to the overall height, slightly downwards in a vertical direction.

[0022] A special feature of bumper assembly 1 is that, as shown in Fig. As can be seen in Figure 5, the bottom 14 of the recess 11 of the bumper crossmember 2 does not have a uniform depth (extension in the x-direction) along its longitudinal extent. The recess 11 has a greater depth in a central section 19 than in the adjacent end sections 20, 20.1. Between the central section 19 and the end sections 20, 20.1, there is a depth transition section 21, 21.1. The enlarged view of the connection of the energy absorption component 3 to the bumper crossmember 2 in the Fig.Figure 6 illustrates the design of the depth transition section 21 as a transition between the middle section 19 and the end section 20. The depth transition section 21 is characterized by an S-shaped flexure of the base 14, whereby the depth of the recess 11 of the bumper cross member 2 decreases over a short distance in the y-direction from the middle section 19 to the end section 20. This depth transition section 21 is located within the support of the energy absorption component 3 on the bumper cross member 2 and is therefore enclosed in the y-direction by the vertical walls formed by the legs 7, 8 and 7.1, 8.1. The depth transition section 21 is located off-center between the vertical walls 7, 8, 7.1, 8.1 of the energy absorption component 3, specifically offset from the vertical wall 7, 8 which points towards the center of the bumper crossmember 2. The depth transition section 21 is located entirely on the inside of the vertical wall formed by the legs 7, 8.The depth transition section 21 has a concave flexure section 22 due to its S-shaped flexure. The lower horizontal wall 23 of the energy absorption component 3 is adapted to the rear contour of the depth transition section 21 with respect to the design of its end face facing the bumper crossmember 2 and engages in the concave flexure section 22. This extends the effective length of this horizontal wall 23. This engagement and the support of the horizontal wall 23 extends in the x-direction to the apex of the concave flexure section 22. In the illustrated embodiment, the vertical wall 7, 8 of the energy absorption component 3, which points towards the center of the bumper crossmember 2, is flared towards the center of the bumper crossmember 2 in the area of ​​its end section facing the bumper crossmember 2, relative to the track 24 of this vertical wall 7, 8.This counteracts buckling of the bumper crossmember 2 at the inner vertical wall 7, 8 of the energy absorption component 3 in the event of an impact. This is a further measure to prevent a predetermined buckling point from being created on the inside of the bumper crossmember 2 with respect to the energy absorption components 3, 3.1, despite the reduction in depth over a short distance.

[0023] In the illustrated embodiment, the bumper cross member 2 and the two shells 5, 6 are components press-formed from a single sheet of steel, which may be fully or partially hardened.

[0024] By increasing the effective length of the horizontal walls of the energy absorption components 3, 3.1, namely by supporting the lower horizontal wall 23 on the bottom 14 of the recess 11 in the concave flexure section 22 and by supporting the lower horizontal wall 17 with its extension 18 on the rear of the front wall 9, the effective length for energy absorption of the energy absorption components 3, 3.1 is optimized with the effect that this bumper assembly 1 meets the requirements of a pendulum impact test, as specified in the introductory description, without the bumper cross member having to have an excessively large cross-sectional geometry or material thickness.

[0025] As can be seen from the figures, the energy absorption components 3, 3.1 are structured by vertical corrugations incorporated into the vertical walls 7, 8, 7.1, 8.1 and the horizontal walls 17, 23, or by corrugations following the longitudinal extent of the bumper cross member 2. These serve to induce folds for energy absorption in the event of an impact.

[0026] In the embodiment shown in the figures, the longitudinal extent of the crash boxes 3, 3.1 is inclined upwards from the bumper crossmember 2. Depending on the application and possible configurations, it is understood that the same advantages are also achieved if the crash boxes have a horizontal extent or are inclined in the other direction. The same inventive advantages also arise if the crash boxes are rotated 180° about their longitudinal axis and installed between the bumper crossmember 2 and the respective baseplate 4, 4.1, so that shell 6 is then the upper shell and shell 5 the lower shell of the crash boxes.

[0027] The invention has been described with reference to exemplary embodiments. Without departing from the scope of protection described by the applicable claims, numerous further embodiments of the inventive concept would be apparent to a person skilled in the art, without these needing to be explained in more detail within the scope of these explanations. Reference symbol list 1 Bumper assembly 2 bumper crossmembers 3.1 Energy absorption component 4, 4.1 Baseplate 5 upper bowl 6 bottom bowl 7, 7.1 thigh 8, 8.1 thigh 9 Front wall 10, 10.1 thigh 11 In-depth study 12 Upper thigh 13 Lower thigh 14 Floor 15 Front 16th continuation 17 Horizontal wall 18 Connecting flange 19 Middle Section 20, 20.1 End section 21, 21.1 Depth transition section 22 Concave flexure segment 23 Horizontal wall 24 lanes of a vertical wall

Claims

[1] Bumper assembly for a motor vehicle, comprising a bumper cross member (2) and two energy absorption components (3, 3.1) arranged at a distance from each other in the longitudinal direction of the bumper cross member (2), the energy absorption components having horizontal walls (17, 23) and vertical walls (7, 8, 7.1, 8.1), each of which is connected to the rear of the bumper cross member (2) by at least one connection section extending in the direction of the longitudinal direction of the bumper cross member (2) at their end face facing the bumper cross member (2), wherein the bumper cross member (2) has at least one recess (11) following its longitudinal direction and extending into its end sections (20, 20.1), the recess having a greater depth in a central section (19) than in the end sections (20, 20.1), wherein the energy absorption components (3, 3.1) are connected with at least one connection section to the bottom (14) of the recess (11) forming the rear of the bumper cross member (2), that a depth transition section (21, 21.1) is provided between the middle section (19) and the end sections (20, 20.1) by a flexure-like formation of the bottom (14) of the recess (11), which is located between the vertical walls (7, 8, 7.1, 8.1) of an energy absorption component (3, 3.1) and with its concave flexure section (22) is closer to the inner vertical wall (7, 8) pointing towards the center of the bumper cross member (2), and that the at least one connection section of the energy absorption components (3, 3.1) engages in and is supported by the concave flexure section (22), . characterized by , that at least one connection section is provided by a connecting flange (18) angled outwards in a vertical direction relative to a horizontal wall (17). [2] Bumper assembly according to claim 1, characterized by , that each energy absorption component (3, 3.1) has two connection sections arranged at a vertical distance from each other, the second connection section of which is either also connected to the bottom (14) of the recess (11) forming the rear of the bumper cross member (2) or to the rear of a section of the front wall (9) of the bumper cross member (2) that is spaced apart from this in the x-direction and extends in the z-direction. [3] Bumper assembly according to one of claims 1 to 2, characterized by , that the apex of the concave flexure section (22) from the track (24) of the inner vertical wall (7, 8) is less than 30%, in particular less than 25% of the distance to the outer vertical wall (7.1, 8.1) of an energy absorption component (3). [4] Bumper assembly according to any one of claims 1 to 3, characterized by, that in the middle section (19) of the bumper cross member (2) the bottom (14) of the recess (11) forms the rear end of the bumper cross member (2). [5] Bumper assembly according to any one of claims 1 to 4, characterized by , that the depth of at least one recess (11) in the end sections (20, 20.1) of the bumper cross member (2) adjacent to the depth transition section (21, 21.1) is constant, or at least largely constant. [6] Bumper assembly according to any one of claims 1 to 5, characterized by , that the depth of at least one depression (11) in the middle section (19) decreases continuously towards the depth transition sections (21, 21.1). [7] Bumper assembly according to claim 6, characterized by , that in the middle section (19) a central section with a constant depth of depression (11) is provided. [8] Bumper assembly according to any one of claims 1 to 7, characterized by , that at least one recess (11) of the bumper cross member (2) is U-shaped by two legs (12, 13) spaced apart from each other in the vertical direction and a base (14) connecting the legs (12, 13) which is not curved in the vertical direction. [9] Bumper assembly according to claim 8, characterized by that the bumper cross member (2) has a single recess (11). [10] Bumper assembly according to any one of claims 1 to 9, characterized by , that the vertical wall (7, 8) of the energy absorption components (3, 3.1) pointing towards the center of the bumper cross member (2) is flared in its end section on the bumper cross member side in the direction towards the center of the bumper cross member (2) relative to its track (24). [11] Bumper assembly according to any one of claims 1 to 10, characterized by, that the energy absorption components (3, 3.1) are composed of two shells (5, 6) arranged one above the other in a vertical direction, together forming a hollow chamber profile. [12] Bumper assembly according to claim 11, characterized by , that the two shells (5, 6) are U-shaped and a first shell (6) forms an outer shell, in the open side of which the legs (8, 8.1) of the second shell (5) engage as an inner shell with a section of their height. [13] Bumper assembly according to claim 11 or 12, characterized by, that the upper shell (5) with its end face (15) facing the bumper cross member (2) is supported as a connection section to the rear of the bottom (14) of the recess (11) and the lower shell (6) with its vertical wall portions (8, 8.1) is set back from the rear of the bumper cross member (2) and is supported on the bumper cross member (2) with a projection (16) of its horizontal wall (17) adjacent to the recess (11) of the bumper cross member (2). [14] Bumper assembly according to any one of claims 11 to 13, characterized by , that the energy absorption components (3, 3.1) are structured by vertical beads and / or by horizontal beads running in the longitudinal direction of the longitudinal extent of the bumper cross member (2).

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