Bumper crossmember for a vehicle

Abstract

Bumper crossmember for a vehicle with a carrier (2, 2.1) that is convexly curved in the transverse direction away from the vehicle side with respect to its cross-sectional geometry by an upper leg (8), a lower leg (9) and a web (10) connecting the two legs (8, 9), the carrier opening of which points away from the web (10), wherein a flange (11, 12) angled towards the outside of the carrier relative to the plane of the respective leg (8, 9) is formed on the legs (8, 9) at the ends pointing away from the web (10), wherein a recessed flange web (15, 16) extending over a section of the respective leg (8, 9) is formed on the flanges (11, 12) at least in certain areas, and wherein the carrier (2, 2.1) has a crash box connection section in each end section. (13, 14) has, characterized in that the carrier (2, 2.1) at least in a zone between the crash box connection sections (13, 14) a deformation zone (17, 18) has a concave structure in the direction of the support cavity (19) in the web (10) connecting the legs (8, 9) and that the flange web (15, 16) has a greater flange height in the area of ​​the extension of the concave structure in the longitudinal direction of the support by means of a convexly shaped flange web projection (20) than the adjacent flange web sections.

Description

[0001] A bumper cross member for a vehicle is described, comprising a support which, with regard to its cross-sectional geometry, is hat-shaped and profiled by an upper leg, a lower leg and a web connecting the two legs to one another, and which is convexly curved in the transverse direction pointing away from the vehicle side, the support opening of which points away from the web, wherein a flange is formed on the legs at the ends pointing away from the web, which flange is angled towards the outside of the support relative to the plane of the respective leg, wherein a recessed flange web extending over a section of the respective leg is formed at least in some regions onto the flanges, and wherein the support has a crash box connection section in each end section.

[0002] The directional terms x-direction, y-direction, and z-direction used in this discussion correspond to the directional terms commonly used for vehicles. The x-direction corresponds to the longitudinal direction of the vehicle. The y-direction is the transverse direction of the vehicle, and the z-direction is the direction along the height of the vehicle.

[0003] In the event of a head-on collision, a bumper cross member serves to protect the components behind the vehicle as well as the passenger compartment. The bumper cross member extends transversely (y-direction) to the direction of travel (x-direction) of the vehicle and is positioned in front of the components to be protected. The longitudinal extent of the bumper cross member follows the y-direction. At its lateral end areas, the bumper cross member is connected to a longitudinal member component of the vehicle, typically a crash box. When absorbing forces acting on a vehicle from the front, the bumper cross member is subjected to bending stresses in particular. To counteract this, bumper cross members have stiffening structures to prevent bending or buckling and the associated tearing as much as possible.

[0004] Such bumper cross members comprise a single- or double-shell support, with a first shell profile having a U-shaped profile and the opening in the profile pointing in the direction of travel. If a box profile is to be provided, a locking plate serves to close this support opening. The U-shaped profile represents the stiffening structure. Additional beads introduced into the locking plate and / or the U-shaped support profile in the longitudinal extension of the bumper cross member serve to stiffen the bumper cross member. Such a support has a convex curve pointing away from the vehicle. The apex of the curvature is located in the longitudinal extension of the vehicle (x-direction) in front of the connection to the crash boxes. The connection of the crash boxes is therefore spaced apart from the apex of the support in the x-direction.

[0005] Bumper cross members have been further developed in various aspects. For example, DE 10 2013 100 720 B4 discloses a one-piece bumper cross member for a vehicle that does not require a locking plate. This reduces the dead weight and manufacturing costs.

[0006] EP 1 730 002 B1 discloses a bumper cross member with a double-shell beam. The rear beam section, located closer to the vehicle, has a hat-shaped profile. The beam opening facing away from the vehicle is closed by a closing plate. In this bumper cross member, the middle section, located between the crash boxes, is designed with a smaller depth to leave space for a radiator at this point and thus the bumper cross member contributes as little as possible to the overall length of the vehicle. Angled flanges pointing away from each other are formed on the legs of the U-shaped beam profile section. These give the beam profile section its hat-shaped cross-sectional geometry. The closing plate is connected to these angled flanges. In the area of ​​the radiator recess, the hat-shaped beam section has a greater height (z-direction) and a smaller depth (x-direction).In addition, flange webs that are recessed are formed onto the flanges.

[0007] Furthermore, another bumper system is known from DE 10 2013 015 420 A1, which is formed from a convex hat-shaped profile with offset flanges.

[0008] Such bumper cross members, with their crash boxes connected to the support section, must pass various tests. One of these tests is the Crash Repair Test (AZT test), developed at the Allianz Center for Technology. This test is used internationally to determine the repairability of vehicles after minor accidents. In this test, the vehicle travels at 15 km / h (9.3 mph) in a frontal collision against a hard barrier with 40 percent vehicle front overlap and a barrier angle of 10°. To meet the AZT test, the impact energy must be dissipated by the bumper cross member without damaging the assemblies or chassis components behind it, such as side members or the like. In the event of an accident under these conditions, only the bumper cross member needs to be replaced.

[0009] To meet the requirements of the AZT test, the crash boxes used for energy absorption can be of a suitable length, as the longer a crash box is, the more energy it can absorb. Other designs incorporate inserts within the crash box to absorb more energy in the event of an impact. The cross-sectional area of ​​a crash box cannot be increased indefinitely, as it should not exceed the height of a bumper cross member.

[0010] Bumper cross members must also pass other tests, such as a high-speed bumper test or a rear impact to test the integrity of the fuel system. The latter test is described in the Laboratory Test Procedure for FMVS 301R - Fuel System Integrity - Rear Impact of the U.S. Department of Transportation National Highway Traffic Safety Administration (TP-301 R - 02 dated January 17, 2007). In this test, a barrier with an approximately 70% overlap acts on the rear of the vehicle, thus affecting the center of the bumper cross member.

[0011] Based on this discussed prior art, the invention is therefore based on the object of developing a bumper cross member for a vehicle according to the preamble of claim 1 in such a way that neither extra-long crash boxes nor crash boxes with specific absorption inserts are required to meet, for example, the AZT test or the Fuel System Integrity - Real Impact test. Furthermore, it should be cost-effective to manufacture.

[0012] This object is achieved according to the invention on the one hand by a bumper cross member of the type mentioned at the outset, in which the member has a deformation zone at least in one zone between the crash box connection sections by a concave structure present in the direction of the member cavity in the web connecting the legs and in which the flange web has a greater flange height than the adjacent flange web sections in the region of the extension of the concave structure in the longitudinal direction of the member due to a convexly shaped flange web projection.

[0013] This object is further achieved according to the invention by a bumper cross member of the type mentioned at the outset, in which the support has a greater depth adjacent to the crash box connection sections in the direction of the center of the support than in the crash box connection sections and in that the transition from the crash box connection sections to those with a greater depth is provided with the interposition of a deformation zone provided by a concave web section.

[0014] In contrast to the prior art discussed above, this bumper cross member has at least one deformation zone. The axis of deformation in the y-direction runs in the vertical direction of the beam (z-direction), at least largely. The deformation zone is located on the side of the beam facing the vehicle and is provided by a concave structure or concave web section incorporated into the web connecting the two legs. In this bumper cross member, a defined deformation of the beam, limited to the deformation zone and limited to the deformation zone, is integrated into the crash management system in such a way that impact energy is absorbed in the deformation zone through corresponding deformation, without any risk of the beam tearing open under normal test conditions, such as the AZT test conditions.The same applies to a high-speed bumper test and the rear-end impact test described above. For this reason, at least one deformation zone is defined by a concave, rounded structure, with the apex of this structure pointing towards the beam cavity. This ensures that, during such an AZT test, the concave, rounded structure of the web provides a certain material reservoir to compensate for any elongation of the web during such an impact in the area of ​​the deformation zone, so that the beam does not tear open under such stress. According to the first proposed solution, the flange webs, in their extension following the longitudinal extent of the concave structure, have a greater flange height than the adjacent flange web sections due to a convex and thus also rounded projection.This strengthens the beam's front side in the x-direction, opposite the concave structures that define the deformation zones, allowing the flange webs in this section to withstand higher tensile loads without cracking. This clever measure reduces elastic stiffness and concentrates deformation on the deformation zones.

[0015] A special feature of this bumper cross member is that it achieves the properties described above solely due to its special shape, and therefore no tailor rolled blanks need to be used to manufacture the member. This is possible, but not required to implement the invention. The advantage of this bumper cross member compared to the use of tailer rolled blanks is that the member has a uniform material thickness in its legs and web. A deformation zone between the two crash box connection sections is thus provided solely by the concave structure incorporated into the web of the member and the flange web projection. With a tailer rolled blank, the member would be weakened overall by a lower material thickness in order to form such a deformation zone.

[0016] Since the beam in this bumper cross member is also integrated into the crash management system for energy absorption, utilizing its convex curvature pointing away from the vehicle, the crash boxes only need to be relatively short. The energy to be absorbed by the bumper cross member in the event of an impact, for example, according to the AZT test, is thus distributed between the crash boxes and the beam. This also applies to impact tests in which the barrier is designed with a larger overlap than in the AZT test and acts on the center of the bumper cross member.The above applies equally to the second proposed solution, which involves providing a deformation zone in the immediate vicinity of a crash box connection section by means of a concave web section, since in this exemplary embodiment, the bumper cross member has a shallower depth in its crash box connection sections than in the adjacent section located between the crash box connection sections. As a result, due to the shallower depth of the beam, the stress on the tension side is not so high that a flange web projection would also be necessary at this point. As a rule, it is sufficient to have a flange web opposite the concave web section in the x-direction and thus on the tension side of the beam in the event of deformation according to the AZT test.

[0017] An improvement in the crash performance of the bumper cross member can be achieved by integrating the concave structure or concave web section present in the web of the beam into the web sections adjacent to the beam's longitudinal extension with a likewise curved transition section. According to one embodiment, the radius of curvature of such a transition section corresponds to the radius of the concave structure or concave web section.

[0018] The same applies to the design of the convex flange web projection, which also merges into the flange web sections adjacent to the beam's longitudinal extension with a curved transition section.

[0019] The crash performance of such a bumper cross member, with regard to the energy it can absorb, can also be influenced by the number of deformation zones described above. Each deformation zone absorbs a defined amount of energy in the event of an impact. Therefore, a bumper cross member with more than one deformation zone, as described above, can also absorb more energy without requiring any modifications to the crash box.

[0020] According to one exemplary embodiment, such a bumper cross member has several, for example two, deformation zones between its crash box connection sections, each provided by a concave structure introduced into the web in the direction of the support cavity and by flange projections at a corresponding position on the tension side of the support. When two such deformation zones are provided between the crash box connection sections, the distance between the deformation zones is greater than the distance between them from the crash box connection sections. With respect to the center of the support in its longitudinal extent, the distance from the apex of such a concave structure to the crash box connection section is thus greater than the distance from the center of the support.In one embodiment, it is provided that the distance of the apex of the concave structure from the adjacent crash box connection section is approximately 55 - 60% of the total distance of the center of the carrier from the crash box connection section.

[0021] A further development proposes a third deformation zone located centrally between these two deformation zones. A larger number of deformation zones is also possible on the web connecting the legs. However, the number of deformation zones should not be so large that the desired rigidity is lost, and ultimately, individual deformation zones are no longer present as spatially limited zones.

[0022] Since the second proposed solution does not require the tension side of the beam to be designed to absorb greater tensile forces, the flange webs can taper towards the connection section, for example, when they just reach the crash box connection section. With this design, the end sections of the beam do not have flange webs, which reduces the beam's weight accordingly.

[0023] The height of the beam's legs (extension in the x-direction) can be the same for both legs. It is also possible to make one leg, preferably the upper leg, longer than the other. The longer upper leg in this design then protrudes beyond the lower leg. This projection, which is present in the event of an impact, is deformed with less energy, so this projection also contributes to the absorption of impact energy.

[0024] The beam is typically formed from high-strength steel. It is quite possible to equip individual sections of the beam with varying degrees of ductility.

[0025] In a further development, the support cavity, which is open away from the vehicle, is closed at least in one section at the front by a locking plate. As a general rule, when designing the bumper cross member with a locking plate, this is provided over the entire length of the support.

[0026] The invention is described below using an exemplary embodiment with reference to the accompanying figures. They show: Fig. 1: A plan view of a bumper cross member according to the invention, Fig. 2: a sectional view through the bumper cross member of the Fig. 1, Fig. 3: the bumper cross member of the previous figures in an arrangement for carrying out the AZT test, Fig. 4: the bumper cross member of the Fig. 3 after AZT testing and Fig. 5.: a perspective view of another bumper cross member according to the invention.

[0027] A bumper cross member 1 for a vehicle, which is intended to be attached to the front or rear of a vehicle, comprises a hat-shaped profiled support 2, wherein the opening side of the support 2 points away from the vehicle (in the illustration of the Fig. 1 upwards), two crash boxes 3, 4 and a striker plate 5 closing the support opening. In the illustrated embodiment, the support 2, the crash boxes 3, 4 and the striker plate 5 are steel components made of a high-strength steel that is common for such components. The support 2 itself is convexly curved in the direction of its profile opening and thus points away from the vehicle. In the illustrated embodiment, the curvature is continuous. The crash boxes 3, 4 are connected to the rear side of the support 2 facing the vehicle and each carry a connecting plate 6, 7 at their other end for connecting the bumper cross member 1 to the chassis of a vehicle. The hat-shaped profile of the support 2 is evident from the sectional view of the Fig. 2. The support 2 comprises two legs 8, 9 which are connected to one another by a web 10. In the illustrated embodiment, the legs 8, 9 are inclined towards one another, with the smallest distance between the legs 8, 9 being in the region of the web 10. A flange 11, 12 is formed on each of the ends of the legs 8, 9 opposite the web 10. The flanges 11, 12 are folded away from one another with respect to the legs 8, 9. The alignment of the flanges 11, 12 runs in the z-direction. The striking plate 5, which in the illustrated embodiment also extends over the entire longitudinal extent of the support 2, is connected to the flanges 11, 12. The two outer end sections of the beam 2 are the crash box connection sections.The crash boxes 3, 4 have, on their end faces facing the beam 2, a shape complementary to the cross-sectional shape of the beam 2 in this section, in their walls facing in the y-direction. Thus, the crash boxes overlap the web-side end section of the beam 2 with their upper and lower walls. The crash boxes 3, 4 are welded to the beam 2.

[0028] In the support section between the two crash box connection sections 13, 14, a flange web 15, 16 is formed on each of the flanges 11, 12, which flange webs therefore extend over the legs 8, 9 in some areas.

[0029] The bumper cross member 1 is designed such that it has two deformation zones 17, 18 in the middle section located between the crash box connection sections 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 web 10 of the support 2 in the direction of the support cavity 19 enclosed by the legs 8, 9 and the web 10. This concave structure reduces the depth of the support 2 (extension in the x-direction) compared to a profile of the web 10 without a concave structure. The concave structure of the deformation zone 17 transitions into the adjacent support sections via a transition section with a radius similar to that of the concave structure.This embossing extends over the entire height of the web 10 and is visible in the plan view of the bumper cross member 1 of the . Fig. 1. The extension of the deformation zone 17, including the adjacent transition sections in the longitudinal direction of the beam 2, corresponds to approximately 15% of the longitudinal extension of the beam 2 between the two crash box connection sections 13, 14. The flange webs 15, 16, with their concave structure, carry a convex flange web projection 20 in the area of ​​the deformation zone 17. Thus, the height of the flange web 15 is greater in the area of ​​the flange web projection 20 than in the adjacent flange web sections.

[0030] In addition to the two deformation zones 17, 18, the bumper cross member 1 has two further deformation zones 21, 22. The deformation zones 21, 22 each border a crash box connection section 13 and 14, respectively. The deformation zone 21 is described below. The same explanations apply equally to the deformation zone 22. The deformation zone 21 is provided by a concave web section. The concave web section is a transition section from the crash box connection section 13 to the adjacent section of the support 2, which has an increasingly greater depth. Therefore, the section of the web 10 within the crash box connection section 13 is in a different spatial position than in the adjacent support section.

[0031] The flange webs 15, 16 terminate in their respective first section in the crash box connection sections 13, 14. However, their height already decreases in the section of the beam 2 to which the deformation zones 21, 22 also belong. The majority of the crash box sections 13, 14 no longer support a flange web.

[0032] Fig. 3 shows the bumper cross member 1 with the deformation zones 17, 18, 21, 22 marked therein in a grid, together with a barrier B corresponding to the AZT test, before the impact of the vehicle (not shown in detail) with its bumper cross member 1.

[0033] Fig. Figure 4 shows the bumper cross member and its energy absorption behavior after the impact according to the specifications of the AZT test. Since barrier B is positioned on the left side of the vehicle, the left crash box 3 of the bumper cross member 1 was compressed. In addition to the compression of crash box 3 for energy absorption, impact energy was also absorbed in deformation zones 17, 18, and 21, although less so in deformation zone 22. During the impact, the beam 2 bent with its locking plate 5 around deformation zone 22 toward the vehicle due to the compression of crash box 3. The crash box 4 on the right side of the vehicle, however, is largely unaffected by the impact on the left side.As the beam 2 buckles due to the compression of the crash box 3, the deformation zone 21 immediately adjacent to the crash box 3 experiences a certain stretching, while the deformation zones 17, 18 are deformed in the y-direction, namely also stretched (elongated), due to the one-sided bending of the beam 2 during the AZT test. In this respect, the deformation zones 17, 18, with their concave structures, represent a material specification that allows a certain stretching during such an impact without tearing. The flange web projections 20, which increase the height of the flange webs 15, 16, prevent buckling at the front, since the beam 2 is compressed overall in the x-direction by the barrier B, and thus this part of the beam 2 is also subjected to tensile stress.

[0034] 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 a defined wrinkling and thus a defined energy absorption occurs.

[0035] Fig. Figure 5 shows a support 2.1 of another bumper cross member (shown without crash boxes connected to it). In this bumper cross member 1.1, the forward-facing support opening is not closed with a locking plate. The remaining structure and functionality of this support 2.1 correspond to those of the Fig. 1 to 4 described support 2 of the bumper cross member 1.

[0036] The same advantages as those described above using the example of the bumper cross member when subjected to the AZT test also apply equally to other tests in which the web connecting the legs of the member is subjected to tensile stress due to deformation, as is the case, for example, in the Fuel System Integrity - Real Impact - Test. In this test, the barrier acts on the center of the bumper cross member. Due to the at least one, but preferably several, deformation points between the two crash box connection sections, the cross member initially bends due to its convex curvature pointing away from the vehicle; this means that the initial deformation work is performed by the member itself and thus absorbs the corresponding energy before the crash boxes are included in the deformation process.For this reason, the crash boxes can also be designed to be shorter than previously known systems.

[0037] The invention has been described using exemplary embodiments. Without departing from the scope of the applicable claims, numerous possibilities for implementing it will become apparent to a person skilled in the art without the need for further explanation within the scope of these statements. List of reference symbols 1, 1.1 Bumper cross member 2, 2.1 Carrier 3 Crashbox 4 Crashbox 5 Strike plate 6 Connection plate 7 Connection plate 8 legs 9 legs 10 jetty 11 Flange 12 Flange 13 Crashbox connection section 14 Crashbox connection section 15 flange web 16 flange web 17 Deformation zone 18 Deformation zone 19 Beam cavity 20 flange web projection 21 Deformation zone 22 Deformation zone B Barrier

Claims

[1] Bumper cross member for a vehicle with a support (2, 2.1) which is hat-shaped in its cross-sectional geometry and which is convexly curved in the transverse direction, pointing away from the vehicle side, by an upper leg (8), a lower leg (9) and a web (10) connecting the two legs (8, 9), the support opening of which points away from the web (10), wherein a flange (11, 12) is formed onto the legs (8, 9) at the ends pointing away from the web (10), which flange is angled towards the outside of the support relative to the plane of the respective leg (8, 9), wherein a recessed flange web (15, 16) extending over a section of the respective leg (8, 9) is formed at least in some areas onto the flanges (11, 12), and wherein the support (2, 2.1) has a crash box connection section (13, 14), characterized bythat the support (2, 2.1) has a deformation zone (17, 18) at least in one zone between the crash box connection sections (13, 14) by a concave structure present in the direction of the support cavity (19) in the web (10) connecting the legs (8, 9), and that the flange web (15, 16) has a greater flange height than the adjacent flange web sections in the region of the extension of the concave structure in the longitudinal direction of the support due to a convexly shaped flange web projection (20). [2] Bumper cross member according to claim 1, characterized by that the transition of the concave structure into the web sections adjacent in the longitudinal extension of the support (2, 2.1) is designed with a curved transition section. [3] Bumper cross member according to claim 2, characterized by that the radius of the transition sections corresponds to the radius of curvature of the concave structure. [4] Bumper cross member according to one of claims 1 to 3, characterized by that the transition of the convex flange web projection (20) into the flange web sections adjacent in the longitudinal extension of the support (2, 2.1) is designed with curved transition sections. [5] Bumper cross member according to claim 4, characterized by that the radius of the flange web transition sections is smaller than the radius with which the convex flange web projection (20) is designed. [6] Bumper cross member according to one of claims 1 to 5, characterized by that the support (2, 2.1) has, in its section located between the crash box connection sections (13, 14), a plurality of deformation zones (17, 18) of the type described in the preceding claims. [7] Bumper cross member according to claim 6, characterized bythat the support (2, 2.1) has two deformation zones (17, 18) and the distance of the deformation zones (17, 18) between the region of the apex of their concave structure and the crash box connection section (13, 14) arranged at a smaller distance is greater than the distance of the same from the center of the support (2, 2.1) in relation to its longitudinal extent. [8] Bumper cross member according to claim 7, characterized by that the deformation zones (17, 18) in the region of the apex of their concave structure are spaced from the crash box connection section (13, 14) by 55 - 60% of the distance of the crash box connection section (13, 14) to the center of the support (2, 2.1). [9] Bumper cross member for a vehicle, with a cross-sectional geometry comprising an upper leg (8), a lower leg (9) and a web (10) connecting the two legs (8, 9) to one another, wherein a flange (11, 12) is formed on the legs (8, 9) at the ends pointing away from the web (10) and angled towards the outside of the support relative to the plane of the respective leg (8, 9), with a hat-shaped profiled support (2, 2.1), the support opening of which points away from the web (10), wherein a recessed flange web (15, 16) extending over a section of the respective leg (8, 9) is formed at least in regions onto the flanges (11, 12), and the support (2, 2.1) has a crash box connection section (13, 14) in each end section, wherein the Beam (2, 2.1) adjacent to the crash box connection sections (13, 14) in the direction of the center of the beam (2, 2.1) has a greater depth than in the crash box connection sections (13, 14), in particular according to one of claims 1 to 8, . characterized by that the transition from the crash box connection sections (13, 14) to those with a greater depth is provided with the interposition of a deformation zone (21, 22) provided by a concave web section. [10] Bumper cross member according to one of claims 1 to 9 characterized by that the flange webs (15, 16) run out into the crash box connection sections (13, 14). [11] Bumper cross member according to claim 10 characterized by that the flange webs (15, 16) extend a maximum of up to 20% into the crash box connection section (13, 14). [12] Bumper cross member according to one of claims 1 to 11 characterized bythat the two legs (8, 9) of the support (2, 2.1) have an unequal length at least in the section located between the crash box connection sections (13, 14). [13] Bumper cross member according to claim 12 characterized by that the upper leg (8) has a greater leg height than the lower leg (9) and thus protrudes from the lower leg of the support (2, 2.1). [14] Bumper cross member according to one of claims 1 to 13 characterized by that the carrier cavity (19) is closed at least in one section at the front by a locking plate (5). [15] Bumper cross member according to one of claims 1 to 14 characterized by that the support (2, 2.1) is formed from a high-strength steel. [16] Bumper cross member according to one of claims 1 to 15 characterized bythat two crash boxes (3, 4) are connected to the support (2, 2.1) in such a way that they engage with their upper and lower walls on the outside over the legs (8, 9) of the support (2, 2.1) and the side walls of the crash boxes (3, 4) are supported on the front side on the rear of the web (10) of the support (2, 2.1).

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