Arrangement of a bumper crossmember and a crash box for a vehicle

Abstract

The invention discloses an arrangement (1) of a bumper crossmember (2) and at least one crash box (3), (4) for a vehicle, the crash box (3), (4) having - at least one horizontal wall (12) - a baseplate-side connection portion (5), (6) for connecting the crash box (3), (4) to a chassis of a motor vehicle, for example to a longitudinal member, and - a bumper-crossmember-side connection portion (7), (8) to which the bumper crossmember (2) is connected, wherein part of the bumper-crossmember-side connection portion (7), (8) is a flange (16) projecting from the end of the horizontal wall (12), to which flange (16) the bumper crossmember (2) is connected. The invention is characterised in particular in that the flange (16), in its profile (18) following the longitudinal extent of the bumper crossmember (2), has a connection region (19) at which the bumper crossmember (2) is connected to the crash box (3), (4), and has a support region (20) which, in a starting position of the bumper crossmember (2), is spaced apart from the rear side (17) of the bumper crossmember (2), wherein the support region (20) is designed such that when the bumper crossmember (2) is deformed in the x-direction of the vehicle, in particular in the central region (21) thereof, the bumper crossmember (2) is additionally supported on the crash box (3), (4) on the support region (20) of the flange (16).

Description

[0001] Arrangement of a bumper crossmember and a crash box for a vehicle

[0002] The invention relates to an arrangement of a bumper crossmember and a crash box for a vehicle with the features of the preamble of claim 1.

[0003] To minimize the consequences of accidents and ensure occupant safety, passive safety systems are used in vehicles. A key component is the bumper crossmember, which extends essentially transversely to the vehicle's longitudinal axis (in the y-direction) and is located at the front and rear of the vehicle. A bumper crossmember is also called a bumper. The bumper crossmember ensures that frontal and rear impact loads are distributed evenly into the chassis, particularly into the vehicle's longitudinal members. For this purpose, the bumper crossmember is connected to the chassis, usually to the longitudinal members, via at least one crash box. The aim is to absorb the crash energy in the event of a collision and thus preserve the vehicle's structural integrity as much as possible.

[0004] A crash box is formed by a hollow body, essentially prismatic in shape, which may have pre-formed folds, usually perpendicular to the crash box's direction of extension. The crash box has a baseplate-side connection section for attaching it to the vehicle's chassis, such as the longitudinal member. It also has a bumper-side connection section to which the bumper crossmember is attached. The bumper crossmember is usually welded to the crash box.

[0005] The prismatic shape of the crash box is usually rectangular or hexagonal; rounded shapes are also possible. One or more walls along the longitudinal axis of the crash box are essentially horizontal, while other walls are vertical. In a rectangular crash box, two opposite walls are typically horizontal, while the other two opposite walls are essentially vertical.

[0006] To connect a bumper crossmember to a crash box at its end on the bumper crossmember side, it is known to provide a flange projecting from the end of the horizontal wall. Such a design is known, for example, from CN 1 12874459 A or DE 19 958996 A1. In these disclosures, the projecting flanges are angled away from the end of the horizontal wall on the bumper crossmember side.

[0007] In other designs, such as JP 2000 127 873 A, the crash box is to be closed at its end facing the bumper crossmember with a separate attachment, thus providing a basis for connecting the bumper crossmember. However, the additional provision of a separate component for closing the crash box is considered disadvantageous due to higher manufacturing costs.

[0008] JP 2006 327 463 A discloses an arrangement of a bumper crossmember and a crash box, in which the crash box has a flange connected to the bumper crossmember and projecting from the horizontal wall of the crash box. A deformation notch is provided in the transition area between the flange and the crash box wall, which influences the deformation of the crash box. During deformation, the rear wall of the bumper crossmember conforms to the groove provided by the notch.

[0009] WO 2012 / 101 923 A1 discloses a crash box with an additional bracket attached to its horizontal wall. The bumper crossmember is mounted to the leg of this bracket facing the bumper. An additional bracket is also attached to a vertical wall of the crash box, providing extra support in the middle of the bumper crossmember in the event of deformation. With the increasing prevalence of electromobility in the automotive sector, the structure and, consequently, the crash behavior in the front engine compartment are changing. In this context, the so-called pole test becomes important. In this test, a vehicle impacts a single pole at high speed. The bumper crossmember is then subjected to a central load but is typically only supported at its edges relative to the rest of the chassis.The aim of the pole test is to ensure that a certain intrusion path into the engine compartment is not exceeded and that the pole does not tear in order to guarantee continuous power transmission.

[0010] Due to the smaller number of components in the engine compartment of an electric vehicle compared to a conventionally powered vehicle, the intrusion path that a bumper crossmember must withstand is greater than that of conventional bumper crossmembers. The required larger intrusion paths result in greater deformation of the bumper crossmember in the x-direction of the vehicle, potentially extending beyond the baseplate-side connection of the crash box to the chassis, or the longitudinal members.

[0011] With such severe deformation of the bumper crossmember, cracking is frequently observed in the area where the bumper crossmember connects to the crash boxes. Against this background, the present invention aims to provide an improved arrangement of a bumper crossmember with a crash box, in which cracking of the bumper crossmember in the area of ​​the crash box is reduced.

[0012] This problem is solved by an arrangement of a bumper crossmember and a crash box as described above, having the features of claim 1.

[0013] A special feature of the proposed arrangement, or rather the proposed crash box, is that the flange, which extends from a horizontal wall (usually outwards, away from the interior of the crash box) and follows the longitudinal extent of the bumper crossmember, has two distinct functional areas. The flange's course refers to the portion of the flange that defines the contact surface or edge to which the bumper crossmember is attached or which faces it. The flange's course describes how it geometrically extends along its length. Thus, the flange's course is essentially horizontal; the flange's end face typically points essentially vertically, roughly parallel to the transverse extent of the bumper crossmember.

[0014] The flange has a connection area as its first functional area in a section leading to the bumper crossmember. The bumper crossmember is connected to the crash box at this connection area, for example by means of a welding process.

[0015] Furthermore, the flange, in its extension towards the bumper crossmember, features a support area as a second functional area. This means that the side of the flange facing the bumper crossmember is divided into two functional areas along the longitudinal direction of the bumper crossmember. Looking at the front of the crash box, these functional areas are arranged side by side.

[0016] The bumper crossmember is not connected to this support area; it is spaced from the rear of the bumper crossmember. This support area is typically non-functional under normal conditions. In a crash, when the bumper crossmember is deformed towards the vehicle chassis, it presses against the flange's support area and is further braced against the crash box by this support area. This increases the surface area over which the force from the bumper crossmember is transferred to the crash box, thus increasing the surface pressure at the interface between the bumper crossmember and the crash box in a crash.In particular, by setting the support area back relative to the flange connection area, the fact is taken into account that the bumper crossmember can initially deform slightly in the x-direction of the vehicle (towards the chassis) before the support area supports the bumper crossmember. Cracking, which is typically observed in highly deformed areas resulting in high stress concentrations, is avoided by the setback support area of ​​the flange, which is positioned further back from the rear wall in its normal position: the stress concentrations are distributed over a larger area and thus dissipated into more material.

[0017] Typically, two crash boxes are provided to support a bumper crossmember, positioned at its ends. A flange-side support area, as described above, is particularly important on the side of the flange facing the center of the bumper crossmember. Deformation in the center of the bumper crossmember results in a particularly high load at the crash box-side connection, potentially leading to cracking. This is because, due to the connection to a second crash box, the bumper crossmember is also subjected to tensile stress during such deformation, further increasing the risk of cracking. Therefore, it becomes clear that a flange-side support area extending towards the free ends of the bumper crossmember is not strictly necessary.

[0018] In particular, the support area and the connection area are designed to merge seamlessly. This means that the support area and the connection area essentially provide a continuous surface for the bumper crossmember, either a contact area or a contact edge. The support area and the connection area are therefore not separated by a recess. By directly connecting the support area to the connection area, any edge bearing or indentation into the bumper crossmember due to deformation during the placement of the bumper crossmember is avoided.

[0019] In particular, it can be provided, especially preferably in an embodiment where the support area transitions directly into the connection area, that a substantially straight contact area of ​​the support area and the course of the connection area are arranged at an angle to each other, so that the contact area essentially follows the expected longitudinal extent of the deformed bumper crossmember. A change in direction from the connection area to the contact area of ​​> 0 to 50 degrees, particularly in the range of 20 to 30 degrees, is generally considered sufficient and practically feasible; the latter has been determined by the inventors in the present case to be the optimum.Due to the angled positioning of the mounting area relative to the connection area, the support area is set back from the bumper crossmember: Along its course, starting from its transition area bordering the connection area towards its other, usually free end along the mounting area, the distance between the support area and the undeformed bumper crossmember increases.

[0020] The transition area of ​​the support section, facing the connection area, provides the bending edge for the bumper crossmember during deformation. It is therefore preferred that the transition area from the connection area to the essentially straight contact area of ​​the support section is rounded. This allows the bumper crossmember to roll on the transition area during deformation. The bending radius is determined by this rounding and is typically relatively large, approximately 5 to 10 mm. The rounded section of the transition area is elongated and can be longer than the contact area. This prevents the bumper crossmember from tearing in the transition area between the connection and support sections.

[0021] Typically, the bumper crossmember is positioned at least slightly away from the front face of the support-side, vertical wall of the crash box. Specifically, the bumper crossmember is not connected to this wall. This provides a clearance between the bumper crossmember and this vertical wall when the bumper crossmember is undeformed. In the event of deformation, the bumper crossmember is first bent at the flange until the expected longitudinal extension direction within the crash box area of ​​the bumper crossmember is achieved, and only then does the bumper crossmember come into contact with the vertical wall of the crash box. Crash forces are then transferred into the crash box via the vertical wall, thus further absorbing the impact energy.

[0022] In another embodiment, it is provided that the force transmission into this support area-side vertical wall is influenced by the fact that, if the crash box is composed of two half-shells arranged one above the other in the vertical direction, the support area-side vertical wall is only supported by one of the two shells, typically the upper shell, on the rear of the bumper cross member and, according to one embodiment, is also welded to it.

[0023] The force transmission into the vertical walls of the crash box can also be influenced by notches incorporated into their end face facing the crash box.

[0024] To allow for deformation within the flange, it can be designed so that the flange is flared from the horizontal wall at a specific radius. This radius is the bending radius at which the flange is bent away from the wall. The rounded transition from the longitudinal extension of the crash box to the transverse section of the crash box provides a buffer that prevents the bumper crossmember from rolling directly onto the frontal, and therefore very rigid, support of the crash box wall in the event of an impact. The radius is typically chosen to be relatively large in order to positively influence the bending behavior of the bumper crossmember. The material thickness of the bumper crossmember also plays a role here. The radius in the flange preferably corresponds at least to the material thickness of the bumper crossmember. Embodiments in which the radius is at least 3 mm are preferred.Due to the generously flared flange, it initially deforms upon impact; it absorbs crash energy and gradually conforms to the bumper crossmember. This creates a material cushion that adapts to the specific crash scenario, providing additional support, particularly where bending gaps occur on the bumper crossmember side. The crash box is typically designed with two shells: one shell forms a horizontal wall and two projecting legs that constitute part of the vertical walls; the other shell forms the corresponding counterpart. The backs of the shells thus usually form the horizontal walls.

[0025] The connection section of the crash box on the bumper crossmember side can be designed to consist of a flange on a first horizontal wall of the crash box and a flangeless end face on a second horizontal wall opposite the wall with the flange. The flange is thus only present on one side of the crash box, while on the other side, the bumper crossmember is connected to the end face, and therefore to the edge of the crash box, usually welded. It has been found that providing a flange on only one side already results in significant improvements in crash performance. Manufacturing costs can therefore be reduced.

[0026] In this configuration, it can be specifically designed that, when mounted on a vehicle, the crash box has a longitudinal extension inclined relative to the horizontal, starting from its base plate-side connection. This is necessary, for example, to bridge a vertical offset between the base plate-side and bumper crossmember-side connections. The bumper crossmember is then connected to the flange on the wall of the crash box facing in the direction of the inclination and to the end face of the wall facing away from the inclination. The crash box, which has a flange on the horizontal wall, is thus oriented so that, for example, if it is inclined downwards, the flange also points downwards. The crash box can therefore also be used for the second load path.The inclination provides greater flexibility in terms of installation space; although the force transmission into the crash box from the bumper crossmember is then no longer concentric but slightly eccentric in the direction of the inclination, the flared flange prevents the bumper crossmember from tearing open in this area. The crash behavior of the crash box relative to the bumper crossmember can thus be precisely adjusted. The invention is explained in more detail with reference to the accompanying figures. These show:

[0027] Fig. 1: An arrangement according to the invention of a bumper crossmember with two crash boxes connected to it in a view from below of the arrangement,

[0028] Fig. 2: a detail of the left side shown in Figure 1

[0029] Crashbox

[0030] Fig. 3: a side section view of the bumper crossmember shown in Figure 1 and

[0031] Fig. 4: a three-dimensional oblique-from-below view of a

[0032] Crashbox of an arrangement according to the invention.

[0033] Figure 1 shows an arrangement 1 according to the invention comprising a bumper crossmember 2 and a crash box 3, 4 for a vehicle, here a passenger car. The bumper crossmember 2 is cut away in such a way that a flange pointing towards the crash boxes 3, 4, which would obscure the connection of the crash boxes 3, 4 to the bumper crossmember 2 in this view, is hidden. The crash boxes 3, 4 are equipped with a base-plate-side connection section 5, 6 for connection to a longitudinal member (not shown) of a vehicle chassis (not shown), for example via a screw connection. At their other end, the crash boxes 3, 4 have a bumper crossmember-side connection section 7, 8 to which the bumper crossmember 2 is connected.

[0034] With reference to Figures 2 and 3, the connection of the bumper crossmember 2 to the crash box 3 on the left in Figure 1 is explained in more detail. The explanations also apply analogously to the crash box 4 on the right in Figure 1. The crash box 3 on the left in Figure 1 is first explained in more detail with reference to Figure 4. In the three-dimensional view of the crash box 3 in Figure 4, the flat baseplate 9 can be seen, by means of which the crash box 3 can be connected to a longitudinal member. The crash box 3 has a two-shell construction; a first shell 10 and a second shell 11 are connected to each other at their respective free ends with their opposing legs to form an essentially prismatic body. The shells 10, 11 provide horizontal walls 12, 13 with their backs and, together with their respective opposing legs, vertical walls 14, 15 of the crash box 3.In addition, creases in the form of pre-folds are incorporated perpendicular to the longitudinal extent of the crashbox 3 in order to provoke a bellows-like folding of the crashbox 3 in the event of a crash.

[0035] As can be seen particularly in the combination of Figures 2 to 4, a horizontal wall 12 has at its end, for the formation of part of the bumper cross member connection section 7, a flared flange 16 to which the bumper cross member 2 is connected with its rear side 17 to the crash box 3, here welded.

[0036] According to the invention, the flange 16 is specially designed with regard to the bumper cross member 2: In its course 18, which follows the longitudinal extent of the bumper cross member 2, it has a connection area 19 and a support area 20. At the connection area 19, the bumper cross member 2 is connected to the crash box 3, or to the flange 16, usually by welding.

[0037] In contrast, the flange 16 in its further course 18 in its support area 20 in the initial position of the bumper cross member 2 as shown in the figures, as it is mounted in a vehicle, is spaced away from the rear side 17 of the bumper cross member 2.

[0038] If the bumper crossmember 2 is subjected to a load in its central region 21 during a crash and deformed in the direction of the baseplate-side connection section 5, 6 of the arrangement 1 according to the invention, the bumper crossmember 2 is additionally supported by the support area 20 of the flange 16, thus preventing the bumper crossmember 2 from tearing open in this area. To achieve this particularly effectively, the support area 20 is divided into a transition area 22 and a contact area 23 in the present embodiment. In the transition area 22, the flange 16 is rounded along its course 18, transitioning into the contact area 23, which is essentially straight in the direction 18 of the flange 16 and is perpendicular to the connection area 19. Due to the generous curvature in the course 18 of the flange 16 in the transition area 22 towards the contact area 23, the bumper cross member 2 can roll off the flange 16 in the event of deformation.

[0039] To allow the bumper crossmember 2 to roll on the flange 16, a clearance 24 is left at least in sections between the vertical wall 14 of the crash box 3 and the rear side 17 of the bumper crossmember 2.

[0040] The flange 16 itself is – as can be seen in Figure 3 – rounded and flared with a generous radius (the radius of the flange 16 is designated by reference numeral 25 in Figure 3). This means that in a crash, the flange 16 itself is deformed, and the radius 25 prevents stress concentrations in the material during deformation, thus counteracting material tearing.

[0041] As can be seen in Figure 3, the crash box 3 is inclined downwards in its longitudinal extension from its baseplate-side connection section 5 to its bumper crossmember-side connection section 7. This creates a vertical offset from the baseplate-side connection 5 to the bumper crossmember-side connection 7. A notable feature is that, according to experiments, it was deemed sufficient to have a flange 16 for connecting the bumper crossmember 2 only on the horizontal wall 12 facing the incline. On the side facing away from the incline (horizontal wall 13), however, a flange is not strictly necessary to achieve significantly improved crash performance and a reduction in the tendency of the bumper crossmember 2 to crack. Here, the bumper crossmember 2 can be directly connected to the end face 26, usually by welding.In the embodiment described in the figures, the lower shells 10 of the crash boxes 3, 4 support the flange 16 that provides the support area 20. In the illustrated embodiment, the crash boxes 3, 4 are arranged inclined upwards towards the respective baseplate 9 between the bumper crossmember 2 and the respective baseplate 9. It is understood that the same advantages also arise in embodiments in which the crash boxes are arranged horizontally or inclined in the other direction, and also when, unlike the illustrated embodiment, the crash boxes are installed rotated 180° about their longitudinal axis, so that the upper shell supports the flange that provides the support area 20.

[0042] The invention has been described using an exemplary embodiment. 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.

[0043] Reference symbol list

[0044] 1. Arrangement

[0045] 2 bumper crossmembers

[0046] 3, 4 Crashbox

[0047] 5, 6 baseplate-side connection section

[0048] 7, 8 bumper crossmember-side connection section

[0049] 9 Baseplate, 11 Shell, 13 Horizontal wall, 15 Vertical wall

[0050] 16 flange

[0051] 17 Rear bumper crossmember

[0052] 18. Flange orientation

[0053] 19 Connection area

[0054] 20 Support area

[0055] 21 Center area bumper crossmember

[0056] 22 Transition area

[0057] 23 Investment area

[0058] 24 Free space

[0059] 25 Rounding Flange

[0060] 26 Front side horizontal wall

Claims

Patent claims 1. Arrangement (1) of a bumper crossmember (2) and at least one crashbox (3, 4) for a vehicle, comprising the crashbox (3, 4) - at least one horizontal wall (12), a baseplate-side connection section (5, 6) for connecting the crash box (3, 4) to a chassis of a motor vehicle, such as a longitudinal member, and a bumper crossmember-side connection section (7, 8) to which the bumper crossmember (2) is connected, wherein part of the bumper crossmember-side connection section (7, 8) is a flange (16) projecting at its end from the horizontal wall (12) to which the bumper crossmember (2) is connected, characterized in that the flange (16) in its course (18) following the longitudinal extent of the bumper crossmember (2) has a connection area (19) to which the bumper crossmember (2) is connected to the crash box (3, 4), and a support area (20) which, in a starting position of the bumper crossmember (2), is spaced from the rear (17) of the bumper crossmember (2), wherein the support area (20) is designed in such a way,that in the course of a deformation of the bumper cross member (2) in the x-direction of the vehicle, in particular in its central area (21), the bumper cross member (2) is additionally supported on the support area (20) of the flange (16) on the crash box (3, 4).

2. Arrangement of a bumper cross member according to claim 1, characterized in that the support area (20) and the connection area (19) merge into one another and the essential course of the support area (20) and the course of the connection area (19) are arranged at an angle to each other, so that the support area (20) essentially follows the expected longitudinal extent of the deformed bumper cross member in its course.

3. Arrangement of a bumper cross member according to one of claims 1 to 2, characterized in that the support area (20) has a transition area (22) whose course is rounded starting from the connection area (19).

4. Arrangement of a bumper cross member according to claim 3, characterized in that the support area (20) has a contact area (23) which has a substantially straight course and whose course connects to the transition area (22).

5. Arrangement of a bumper cross member according to one of claims 1 to 4, characterized in that the bumper cross member (2) is spaced apart from the support area-side vertical wall (14) of the crash box (3, 4) at least in a part pointing towards the flange (16), forming a free space (24).

6. Arrangement of a bumper cross member according to one of claims 1 to 5, characterized in that the flange (16) is projected from the horizontal wall (12) with a rounding (25) having a radius >3mm.

7. Arrangement of a bumper cross member according to one of claims 1 to 6, characterized in that the crash box (3, 4) is designed as a two-part shell.

8. Arrangement of a bumper crossmember according to one of claims 1 to 7, characterized in that the bumper crossmember-side connection section (7, 8) of the crashbox (3, 4) is formed from - the flange (16) on a first horizontal wall (12) of the crashbox (3, 4) and - a flangeless end face (26) of a second horizontal wall (13) opposite the wall (12) having the flange (16).

9. Arrangement of a bumper crossmember according to claim 8, characterized in that the crashbox (3, 4), when mounted on a vehicle, has a longitudinal extension inclined relative to the horizontal from its baseplate-side connection section (5, 6) in order to bridge an offset between the baseplate-side (5, 6) and bumper crossmember-side (7, 8) connection in the vertical direction, and wherein the bumper crossmember (2) is attached to the horizontal wall (12) of the crashbox (3, 4) pointing in the direction of inclination at the flange (16) and to the horizontal wall pointing away from the direction of inclination. wall (13) is connected to its front side (26).

10. Arrangement of a bumper cross member according to claim 9, characterized in that the crash box (3, 4) is inclined downwards when mounted on a vehicle.

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