Patent Application
20240359649
The disclosure relates to a bumper crossmember for a vehicle with a crossmember which is convexly curved pointing away from the vehicle side and extends in the vehicle transverse direction, with a crash box attachment portion in each end of the crossmember. The crossmember comprises a hat-shaped cross-sectional geometry profile with an upper limb/arm, a lower limb/arm, and a connecting piece/web connecting the two limbs, the opening of which points away from the connecting piece. A flange is formed on each limb at the ends opposite the connecting piece. The flange is angled towards the outside of the crossmember relative to the plane of its respective limb. A rebounding flange connecting piece is formed at least in some regions on the flanges extending over a portion of the respective limb.
The directions used within the context of this disclosure, i.e. the x direction, y direction, and z direction correspond to the directions as they are usually used in vehicles. The x-direction corresponds to the longitudinal extent of the vehicle. The y-direction is the vehicle transverse direction, and the z-direction is the height direction of the vehicle.
In a motor vehicle, a bumper crossmember serves to protect the units behind it and the passenger compartment in the event of a head-on collision. The bumper crossmember extends transversely (y-direction) to the direction of travel (x-direction) of the vehicle and is arranged in front of the units to be protected. The longitudinal extent of the bumper crossmember follows the y-direction. At its lateral end regions, the crossmember of the bumper crossmember is connected to a longitudinal member component of the vehicle, typically to a crash box. When absorbing forces acting frontally on a motor vehicle, the bumper crossmember is subjected in particular to bending stress. To counteract this, bumper crossmembers have stiffening structures in order to prevent bending or buckling and the associated tearing as far as possible.
Such bumper crossmembers include a single- or double-shell crossmember, with a first shell profile having a U-shaped profile and the opening of the U-shaped profile facing in the direction of travel. If a box profile is to be provided, a striking plate is used to close this crossmember opening. The U-shaped profile represents the stiffening structure. Additional beads, which are incorporated into the striking plate and/or in the U-shaped member profile along the longitudinal extent of the bumper crossmember, serve to stiffen the bumper crossmember. Such a crossmember is convexly curved in a direction away from the vehicle. The apex of the curvature is located in the longitudinal extension of the vehicle (x direction) in front of the attachment to the crash boxes. The connection of the crash boxes is therefore located at a distance from the vertex of the crossmember in the x direction.
Bumper crossmembers have been further developed in different aspects. DE 10 2013 100 720 B4, for example, discloses a bumper crossmember for a vehicle which is in one piece and does not require a striking plate. This reduces the weight and manufacturing costs.
EP 1 730 002 B1 discloses a bumper crossmember with a double-shell crossmember. The rear support part, which is located closer to the vehicle, has a hat-shaped profile. The crossmember opening facing away from the vehicle is closed by a striking plate. In this bumper crossmember, the middle portion located between the crash boxes is provided with a smaller depth so that there is space for a radiator at this point, and thus the bumper crossmember contributes as little as possible to the overall length of the vehicle. Angled flanges directed away from one another are formed on the limbs of the U-shaped member profile part. These give the crossmember profile its hat-shaped cross-sectional geometry. The striking plate is connected to these angled flanges. In the region of the radiator recess, the hat-shaped member part has a greater height (z-direction) and a smaller depth (x-direction). In addition, rebounding flange connecting pieces are formed onto the flanges.
Furthermore, another bumper system is known from DE 10 2013 015 420 A1, which is formed with a convex hat-shaped profile with depressed flanges.
Such bumper crossmembers must meet different tests with their crash boxes connected to the crossmember part. One of these tests is the crash repair test (AZT test) developed at the Allianz Center for Technology. This test is used internationally as a test for assessing the ease of repair of vehicles after minor accidents. In this test, the vehicle drives at 15 km/h in a frontal crash into a hard barrier with a 40 percent vehicle front overlap and an inclination of the barrier of 10°. In order to meet the AZT test, the impact energy must be dissipated by the bumper crossmember without damaging units or chassis components behind it, such as longitudinal members or the like. Then, in the event of an accident under these conditions, only the bumper crossmember needs to be replaced.
In order to meet the requirements of the AZT test, the crash boxes used for energy absorption can have an appropriate length, because the longer a crash box is, the more energy can be absorbed. In other designs, insert parts are located within the crash box so that more energy can be absorbed in the event of an impact. The cross-sectional area of a crash box cannot be increased arbitrarily because it should not exceed the height of a bumper crossmember.
Bumper crossmembers also have to pass other tests, such as a so-called high-speed bumper test or a rear impact test to check the integrity of the fuel system. The latter test is described in Laboratory Test Procedure for FMVS 301R—Fuel System Integrity—Rear Impact of the US Department of Transportation National Highway Traffic Safety Administration (TP-301R-02 dated Jan. 17, 2007). In this test, a barrier with an overlap of approximately 70% acts on the rear of the vehicle and thus on the center of the bumper crossmember.
Proceeding from this background, one aspect of the disclosure is therefore to develop a bumper crossmember for a vehicle in such a way that neither overly long crash boxes nor crash boxes with specific absorption inserts have to be used, for example in order to meet the AZT test or the Fuel System Integrity—Rear Impact test. In addition, it should be inexpensive to produce.
This may be provided by a bumper crossmember of the type mentioned at the outset, wherein the crossmember has at least one deformation zone between the crash box attachment portions due to a concave structure present in the direction of the crossmember cavity in the connecting piece connecting the limbs, and wherein the flange connecting piece, in the region of the extension of the concave structure in the longitudinal direction of the crossmember, has a greater flange height than the adjacent sections or portions of the flange connecting piece due to a convexly shaped protrusion of the flange connecting piece.
This may also be provided by a bumper crossmember of the type mentioned at the outset, wherein the crossmember adjacent to the crash box attachment portions has a greater depth towards the center of the crossmember than in the crash box attachment portions, and the transition from the crash box attachment portions to those with a greater depth is provided with the interposition of a deformation zone provided by a concave connecting piece portion.
In contrast to the prior art discussed above, this bumper crossmember has at least one deformation zone. The axis of a deformation in the y-direction runs in the vertical direction of the member (z-direction), at least mainly. The deformation zone is located on the side of the crossmember facing the vehicle and is provided by a concave structure or concave connecting piece portion introduced into the connecting piece/web connecting the two limbs/arms. In this bumper crossmember, a defined local deformation of the crossmember, limited to the deformation zone, is integrated into the crash management in such a way that impact energy is absorbed in the deformation zone by corresponding deformation, without the risk of the crossmember tearing open under normal test conditions, for example according to the AZT test conditions. The same also applies to a high-speed bumper test and the rear impact test described above. For this reason, the at least one deformation zone is defined by a concave, rounded structure, with the apex of this structure pointing towards the crossmember cavity. This ensures that during such an AZT test, a certain material reservoir is provided by the concave, rounded structure of the connecting piece in order to compensate for elongation of the connecting piece in the event of such an impact in the area of the deformation zone, so that the crossmember does not tear open under such stress. According to the first proposed solution, the flange connecting pieces, in their extension following the longitudinal extent of the concave structure, have a greater flange height than the adjacent flange connecting piece portions due to a convex and thus also rounded protrusion. As a result, the front of the crossmember in the x direction opposite the concave structures defining the deformation zones is reinforced in such a way that the flange connecting pieces in this portion can be exposed to a higher tensile load without tearing. This measure cleverly reduces the elastic stiffness and concentrates deformation on the deformation zones.
A special feature of this bumper crossmember is that it obtains its properties described above solely due to its particular shape, and therefore no tailor rolled blanks need to be used to produce the crossmember. Although this is possible, it is not necessary. The advantage of this bumper crossmember compared to using tailor rolled blanks is that the crossmember has a uniform material thickness in its limbs and connecting piece. A deformation zone between the two crash box attachment portions is thus provided solely by the concave structure introduced into the connecting piece of the crossmember and the flange connecting piece protrusion. In the case of a tailer rolled blank, the crossmember would be weakened overall by a lower material thickness to form such a deformation zone.
Since in this bumper crossmember, the crossmember is also integrated into the crash management for energy absorption using its convex curvature, which is directed away from vehicle, the crash boxes only need to be relatively short. The energy to be absorbed by the bumper crossmember in the event of an impact, for example according to the AZT test, is thus distributed between the crash boxes and the crossmember. This also applies to impact tests in which the barrier is provided with a larger coverage than in the AZT test and acts on the center of the bumper crossmember. The above applies equally to the second proposed solution of providing a deformation zone in the immediate vicinity of a crash box attachment portion via a concave connecting piece portion, since in this embodiment, the bumper crossmember has a smaller depth in its crash box attachment portions than in the adjacent portion located between the crash box attachment portions. As a result, due to the smaller depth of the crossmember, the stress on the tension side is not so high to require a flange connecting piece protrusion also be provided at this point. In general, it is sufficient if a flange connecting piece is present opposite the concave connecting piece portion in the x direction and thus on the tension side of the crossmember in the event of deformation according to the AZT test.
An increase in crash performance of the bumper crossmember can be achieved by integrating the concave structure or the concave connecting piece portion present in the connecting piece, or web, of the crossmember with a transition portion, which is also curved, in the connecting piece portions adjacent in the longitudinal extent of the crossmember. According to an example embodiment, the radius of curvature of such a transition portion corresponds to the radius of the concave structure or concave connecting piece portion.
The same applies to the design of the convex flange connecting piece protrusion, which also merges into the flange connecting piece portions adjacent in the longitudinal member extent with a curved transition portion.
The crash performance of such a bumper crossmember can also be influenced in terms of absorbable energy by the number of deformation zones described above. In the event of an impact, a defined energy is absorbed in each deformation zone. Therefore, a bumper crossmember with more than one deformation zone, as described above, can also absorb more energy without having to make changes to the crash box.
According to one example embodiment, such a bumper crossmember has multiple, for example two, deformation zones between its crash box attachment portions, each deformation zone provided by a concave structure introduced into the connecting piece in the direction of the crossmember cavity with flange protrusions at a corresponding position on the tension side of the crossmember. When two such deformation zones are provided between the crash box attachment portions, the distance between the deformation zones is greater than the distance between them and the crash box attachment portions. With respect to the center of the crossmember in its longitudinal extent, the distance of the apex of such a concave structure to the crash box attachment portion is greater than the distance from the center of the crossmember. In one example embodiment it is provided that the distance of the apex of the concave structure from the adjacent crash box attachment portion is approximately 55-60% of the total distance of the center of the crossmember from the crash box attachment portion.
In a further development, a third deformation zone is centrally provided between these two deformation zones. A larger number of deformation zones on the connecting piece connecting the limbs is also possible. However, the number of deformation zones should not be so large that the desired stiffness is lost and ultimately there are no longer any individual deformation zones as spatially limited zones.
Since the tension side of the crossmember does not have to be designed to absorb a larger tensile force in the second proposed solution, the flange connecting pieces can taper off towards the crash box attachment portion, for example when they just reach the crash box attachment portion. With such a design, the end portions of the crossmember have no flange connecting pieces, whereby the weight of the crossmember is reduced accordingly.
The height of the limbs (extension in the x direction) of the crossmember can be the same for both limbs. It is also possible to make the height of one limb, preferably the upper limb, longer than that of the other limb. The upper limb, which is longer in this configuration, then protrudes in relation to the lower limb. In the event of an impact, this protrusion is already deformed with less energy, so that this protrusion also contributes to the absorption of impact energy.
The crossmember is typically formed from a high strength steel. It is entirely possible to provide the crossmember with different ductility in individual portions.
In a further development, it is provided that the crossmember cavity, which opens away from the vehicle, is closed at the front in at least one section by a striking plate. In general, when designing the bumper crossmember with a striking plate, the striking plate is provided over the entire length of the crossmember.
The following description is provided using an example embodiments with reference to the attached figures, wherein:
A bumper crossmember 1 for a vehicle, which is intended for attachment to the front or rear of a vehicle, comprises a hat-shaped profiled crossmember 2, wherein the opening side of the crossmember 2 faces away from the vehicle (upward in the illustration in
In the crossmember portion between the two crash box attachment portions 13, 14, a rebounding flange connecting piece 15, 16 is formed on the flanges 11, 12 and therefore extends in some regions over the limbs 8, 9.
The bumper crossmember 1 is designed in such a way that it has two deformation zones 17, 18 in the central portion located between the crash box attachment portions 13, 14. The deformation zone 17 is described in more detail below. These explanations apply equally to the deformation zone 18, which is designed in the same way. The deformation zone 17 is defined by a concave structure introduced into the connecting piece 10 of the crossmember 2 in the direction of the crossmember cavity 19 enclosed by the limbs 8, 9 and the connecting piece 10. This concave structure reduces the depth of the crossmember 2 (extent in the x direction) compared to a course of the connecting piece 10 without a concave structure. The concave structure of the deformation zone 17 merges into the adjacent crossmember portions via a respective transition portion with a radius similar to that of the concave structure. This embossing extends over the entire height of the connecting piece 10 and can be clearly seen in the top view of the bumper crossmember 1 in
In addition to the two deformation zones 17, 18, the bumper crossmember 1 has two further deformation zones 21, 22. The deformation zones 21, 22 are respectively adjacent to a crash box attachment portion 13 and 14. The deformation zone 21 is described below. The same applies equally to the deformation zone 22. The deformation zone 21 is provided by a concave connecting piece portion. The concave connecting piece portion is a transition portion from the crash box attachment portion 13 to the adjacent portion of the crossmember 2, which has a progressively increasing depth. Therefore, the portion of the connecting piece 10 within the crash box attachment portion 13 is in a different spatial position than in the adjacent crossmember portion.
The flange connecting pieces 15, 16 end in the crash box attachment portions 13, 14 in their respective first portion. However, their height already decreases in the portion of the crossmember 2 to which the deformation zones 21, 22 also belong. The majority of the crash box portions 13, 14 no longer have a flange connecting piece.
The deformation zones 17, 18 can also absorb impact energy acting in the y direction. In this case, the concave structures represent predetermined buckling zones in which the concave structures cause a defined folding and thus a defined energy absorption.
The same advantages as described above using the example of the bumper crossmember when subjected to the AZT test also apply to other tests in which the connecting piece connecting the limbs of the crossmember is exposed to tensile stress due to deformation, such as for example in the case of the Fuel System Integrity—Rear Impact test. In this test, the barrier acts on the center of the bumper crossmember. Due to the at least one, but preferably multiple, deformation points between the two crash box attachment portions, the crossmember initially bends through due to its convex curvature pointing away from the vehicle; this means that the first deformation work is carried out by the crossmember itself and energy is therefore absorbed before the crash boxes are involved in the deformation process. From this aspect, too, the crash boxes can be designed to be correspondingly shorter than previously known systems.
The invention has been described on the basis of example embodiments. Without departing the scope of the claims, numerous further embodiments and options for implementing the invention result for a person skilled in the art, without these having to shown or explained in greater detail within the context of this disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 126 164.3 | Oct 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/077257 | 9/30/2022 | WO |
