Abstract:
The invention relates to a bumper arrangement with a crossmember and two crashboxes which are in each case connectable on one side to the crossmember on an outer region thereof and are arrangeable on the other side on a vehicle-side longitudinal member. It is distinguished in that the crossmember has a hollow chamber profile with a hollow chamber which is round at least in sections in cross section, which hollow chamber profile is arranged in a crossmember longitudinal axis running perpendicularly to the vehicle center longitudinal axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of German Patent Application No. DE 10 2015 112 935.3, filed Aug. 6, 2015, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The invention relates to a bumper arrangement according to the preamble of claim  1 . 
       BACKGROUND 
       [0003]    Bumper arrangements of this type are installed in motor vehicles both on the front side and on the rear side in order to absorb or to dissipate the energy from impacts in such a manner that the support structure of the motor vehicle is as far as possible not damaged. A bumper arrangement of this type generally consists of a component, for example a crashbox, converting impact energy into work of deformation, and a crossmember which serves to introduce or to dissipate the energy resulting from a collision into the crashbox. 
         [0004]    Bumper arrangements of this type are known for example from DE 10 2009 053 861 A1 and EP 2 318 237 B1. Although, in the case of these bumper arrangements, good dissipation or introduction of energy into the crashboxes and good deformation of the crashboxes in the event of a collision already take place, there continues to be a need for improvement in respect of the energy introduction properties and also in respect of the deformation properties of the bumper arrangement and with regard to the degradation of energy by the bumper crossmember itself. 
       SUMMARY 
       [0005]    It is therefore the object of the invention to develop a bumper arrangement according to the preamble of claim  1  in such a manner that there is improved energy dissipation and reduced load peaks in the crashbox and vehicle body and also improved or more targeted deformation of the bumper arrangement in a crash scenario. 
         [0006]    This object is achieved by a bumper arrangement having all of the features of claim  1 . Advantageous refinements of the invention are claimed in the dependent claims. 
         [0007]    The bumper arrangement according to the invention has a crossmember and two crashboxes, wherein the crashboxes are each connectable on one side to the crossmember on an outer region thereof and are arrangeable on the other side on a vehicle-side longitudinal member. The bumper arrangement according to the invention is now distinguished in that the crossmember has a hollow chamber profile with a hollow chamber which is round at least in sections in cross section, which hollow chamber profile is arranged in a crossmember axis running perpendicularly to the vehicle center longitudinal axis. The refinement according to the invention of the bumper arrangement now makes it possible that, by means of the hollow chamber profile provided with a hollow chamber which is round at least in sections in cross section, even crash load situations of greater severity have the required deformation properties or energy dissipation properties in order to allow the support structure or body not to be damaged in the event of a crash load. In particular, it is possible by means of this refinement of the crossmember to degrade impact energy in the crossmember at the initial stage of a crash situation and thus to reduce load peaks on crashbox and vehicle body. It is advantageous here for the hollow chamber of the hollow chamber profile to have at least in sections on the front side, i.e. on the side facing toward the crashboxes, a cross section which is substantially in the shape of a segment of a circle. Also on the rear side, i.e. on the side facing toward the crashboxes, the hollow chamber of the hollow chamber profile can have a cross section substantially in the shape of a segment of a circle at least in sections. To this extent, hollow chambers which are formed to be circular in cross section at least in sections and with flattened circular cross sections of this type, i.e. only with a front-side and rear-side cross section of the shape of a segment of a circle, are therefore intended to be included according to the invention. 
         [0008]    So that energy dissipation or deformation that is uniform as possible can occur on both sides of the bumper arrangement, it has proven successful, in a first refinement of the invention, for the hollow chamber profile to extend substantially over the entire crossmember longitudinal extent and/or to be formed mirror-symmetrically with respect to a plane which runs through the center longitudinal axis of the vehicle and is perpendicular to the carriageway. By this means, it is provided that the bumper arrangement is formed identically both on the left and on the right side of a vehicle, and therefore the same energy dissipation and/or deformation properties arise on both sides of the motor vehicle. 
         [0009]    According to a further refinement of the invention, it can be provided that the hollow chamber profile is formed asymmetrically with respect to a plane running through the crossmember longitudinal axis and parallel to the carriageway. This refinement of the invention serves to be able to compensate in particular for a height offset of the crossmember of the bumper arrangement with respect to the longitudinal members on which the crashboxes can be arranged on the vehicle. By this means, it is made possible for the above-described load situations even in the case of bumper arrangements of this type to nevertheless ensure, according to the invention, improved energy dissipation or deformation of the bumper arrangement. 
         [0010]    With respect to the energy dissipation into the crashboxes, it has proven particularly advantageous here for the hollow chamber profile to have a circular cross section at least between the outer regions of the crossmember, on which outer regions the crashboxes are arranged. By means of this circular cross section of the hollow chamber profile, it is possible to provide the bumper arrangement with a particularly stable crossmember, with the aid of which energy is dissipated into the crashboxes in a particularly advantageous manner. 
         [0011]    However, it has been shown that the buckling resistance can advantageously be increased if the hollow chamber profile has a cross section which is flattened in relation to a circular cross section at least between the outer regions of the crossmember, on which outer regions the crashboxes are arranged. It is particularly advantageous here if the hollow chamber profile continues to have a circular cross section at its ends since such cross sections can be closed in a particularly simple manner in terms of process engineering with corresponding end side elements. 
         [0012]    With respect to improved stability of the bumper arrangement or of the crossmember, it has also proven successful for the hollow chamber profile to be designed as a multi-chamber profile. The hollow chamber profile can be subdivided here into a plurality of chambers by the fact that a plurality of chambers are arranged in the hollow chamber profile at least in the vertical direction. 
         [0013]    In the same way, the refinement of the invention also aims at providing at least one inner web in the hollow chamber profile. Inner webs of this type likewise increase the stability of the crossmember or of the hollow chamber profile, and therefore the energy dissipation and deformation properties of the bumper arrangement according to the invention are once again also improved as a result. The at least one inner web can also serve here as a partition between the previously described plurality of chambers of a hollow chamber profile designed as a multi-chamber profile. 
         [0014]    In order once again to improve the stability of the bumper arrangement and therefore the energy dissipation and deformation properties of the entire bumper arrangement, it is provided that the crossmember is provided in its outer regions with deformation inserts or reinforcing inserts. In addition to these advantages, the effect also achieved by this refinement of the invention is a further integration of functions since, by this means, connections to further elements, such as, for example, a crashbox, a towing attachment, sealing elements and more of the like, can advantageously take place in these regions. 
         [0015]    A further improvement in the stability of the bumper arrangement and therefore in the energy dissipation and deformation properties of the entire bumper arrangement is achieved in that the crossmember is provided in its central region lying between the outer regions with at least one reinforcing attachment, reinforcing insert or with an embossing. 
         [0016]    According to another concept of the invention, the crossmember and/or the hollow chamber profile are formed in the outer regions of the crossmember with a wall thickness which is reduced in relation to the central region, said wall thickness preferably being reduced by 0.2 mm to 2 mm, and, particularly preferably, said wall thickness reduction extending at least 5 mm to 45 mm from the ends of the crossmember or of the hollow chamber profile into the interior of the hollow chamber. This measure also leads to the energy dissipation and deformation properties of the entire bumper arrangement according to the invention being improved once again. Wall thicknesses of 2.5 mm to 6 mm are advantageous in the central region of the crossmember or of the hollow chamber profile. However, even outer wall thicknesses are predictable which then, however, are associated with an increased weight and therefore with a more unfavorable environmental footprint of a vehicle provided therewith. 
         [0017]    According to a further concept of the invention, a towing attachment can also be provided which, preferably in the form of an extruded profile, is adapted to the contour of the crossmember or of the hollow chamber profile, and which is arranged on the hollow chamber profile or the crossmember of the bumper arrangement according to the invention. By this means, it is possible to use the bumper arrangement according to the invention for towing motor vehicles and the like without having to touch the support structure of the motor vehicle. 
         [0018]    The hollow chamber profile is preferably closed at its ends, wherein this measure likewise contributes to increased stability of the bumper arrangement according to the invention or to improved energy dissipation or deformation of the bumper arrangement. 
         [0019]    According to a particularly advantageous refinement of the invention, end side elements are provided for the end-side closing of the hollow chamber profile. Said end side elements here are essentially designed in such a manner that they securely close the hollow chamber profile at its ends; such a closing can be undertaken here by means of welding or screwing. However, it can also be provided that the end side elements can be screwed onto the hollow chamber profile with an external thread, in particular if the hollow chamber profile still has a circular cross section in its region. Said external thread can correspond here to an already present internal thread of the hollow chamber profile. However, it is also possible for said external thread to cut the inner wall of the hollow chamber of the hollow chamber profile or of the crossmember as it is being screwed on and, in the process, to cut a corresponding internal thread into the hollow chamber profile. 
         [0020]    Furthermore, it is also provided here that the hollow chamber profile is closed fluid-tightly, in particular with an internal pressure which is increased in relation to the ambient pressure. Such a fluid-tight closure can take place, for example, in that, firstly, the end side elements are welded all the way around in the end region of the hollow chamber profile. However, it is furthermore also possible for such a fluid-tight closure to be possible by the use of end side elements with plug-in elements. Sealing rings advantageously enclosure said plug-in elements, and therefore fluid-tight closure is made possible as a result. These possibilities are appropriate in a simple manner if the ends of the hollow chamber profile have a circular cross section. However, closure is also possible with different cross sections, wherein, however, an increased technical outlay may have to be made in order to ensure the fluid tightness. In particular, the previously mentioned plug-in elements can also serve as reinforcing elements since the crashboxes, possible towing attachments and more of the like can also be arranged in these regions of the crossmember. 
         [0021]    It should also be noted here that fluid can be understood according to the invention as being both a gas and a liquid. In order, however, to reach an internal pressure which is increased in relation to the ambient pressure, when a liquid fluid is used the hollow chamber profile must not be completely filled with the liquid since liquids are as a rule incompressible. To this extent, even when liquids are used as the fluid, a residual region of the hollow chamber profile also always has to be filled with a gaseous medium in order to obtain the internal pressure which is increased in relation to the ambient pressure. 
         [0022]    According to a further concept of the invention, the crossmember is produced from an aluminum or a magnesium alloy or from a fiber-filled thermoplastic, in particular by extrusion or pultrusion. Materials of this type satisfy the specifications necessary for the deformation and energy dissipation properties of the entire bumper arrangement. 
         [0023]    According to the invention, it can be provided here that the hollow chamber profile is designed as part of the crossmember. In this case, the hollow chamber is produced at the same time during the production of the crossmember, for example when aluminum is extruded. 
         [0024]    Furthermore, a front wall and a rear wall can already be arranged on the crossmember, wherein said walls may also be formed integrally with the crossmember. The crashboxes can then be arranged on the rear wall, while corresponding bumper elements can be arranged on the front wall. 
         [0025]    However, it can also be provided that a protective element made from an elastomer or a thermoplastic polymer is arranged in the hollow chamber, wherein the protective element has a cavity for receiving a fluid. In particular, a hollow chamber profile of this type can also contain at least one injected, injection molded or extruded plastics liner. 
         [0026]    The bumper arrangement according to the invention can be designed here in such a manner that the internal pressure in the hollow chamber is increased by at least 1.5 bar, preferably at least 5 bar, in relation to the external pressure. However, it is provided in particular, in order to obtain the desired deformation and energy dissipation properties of the bumper arrangement according to the invention, to keep the internal pressure in the hollow chamber profile above the ambient pressure by 10 bar to 40 bar. The energy introduction or dissipation properties and the deformation properties in the bumper arrangement according to the invention are also improved in the event of a crash by this means without the support structure of the motor vehicle provided with at least one bumper arrangement according to the invention being damaged. Furthermore, a hollow chamber of the hollow chamber profile or of the crossmember can also be used as a container for liquid or gaseous operating media of a motor vehicle. 
         [0027]    Furthermore, the crossmember can have a substantially flat rear wall facing the crashboxes and a front wall facing away from the crashboxes. Crossmembers of this type can be produced integrally from aluminum or an aluminum alloy in a simple manner by extrusion. 
         [0028]    According to a further advantageous refinement of the invention, the crossmember or the hollow chamber profile, in its outer regions, has a flat surface, preferably in the form of a flange, as part of the rear wall. A crashbox can be connected to a flange-shaped surface of this type in a simple manner. 
         [0029]    So that closure means, such as, for example, the previously mentioned end side elements, can be easily fastened to the crossmember or to the hollow chamber profile, connection elements for the fastening of closure means are attached to the crossmember or to the hollow chamber profile at its ends by welding. 
         [0030]    Further aims, advantages, features and use possibilities of the present invention emerge from the description below of exemplary embodiments with reference to the drawings. All of the features described and/or illustrated pictorially form the subject matter of the present invention by themselves or in any expedient combination, also irrespective of the summary thereof in the claims or the dependency reference thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  shows an exemplary embodiment of a bumper arrangement according to the invention in a perspective view, 
           [0032]      FIG. 2  shows a detailed illustration of  FIG. 1 , 
           [0033]      FIGS. 3 a  and 3 b    show a possible embodiment of end side elements for closing the ends of a hollow chamber profile, in various views, 
           [0034]      FIGS. 4 and 5  show an exemplary embodiment of a further bumper arrangement according to the invention, 
           [0035]      FIGS. 6 to 15  show various embodiments of a bumper arrangement according to the invention in the region of a crashbox, in a cross-sectional illustration, 
           [0036]      FIG. 16  shows an embodiment of a towing attachment for connection to a bumper arrangement according to the invention, in a perspective illustration, 
           [0037]      FIG. 17  shows a cross-sectional illustration of a possible embodiment of a bumper arrangement according to the invention, 
           [0038]      FIGS. 18 to 20  show various embodiments of a crossmember of a bumper arrangement according to the invention, in a cross-sectional illustration, 
           [0039]      FIGS. 21 to 24  show a further possible embodiment of a bumper arrangement according to the invention, in various illustrations. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]      FIG. 1  illustrates a first exemplary embodiment of a bumper arrangement  1  according to the invention. The latter substantially consists of a crossmember  2  which is produced here as a hollow chamber profile  5  integrally and uniformly in terms of material from an aluminum alloy or a magnesium alloy by extrusion and is in each case connected in its outer regions  4  to a corresponding crashbox  3  via a rear wall  20  which is provided with a flat, flange-shaped surface  27  for this purpose in said outer regions  4 . At their other end, the crashboxes  3  here have flanges  18  with which the bumper arrangement  1  can be fastened to corresponding longitudinal members (not illustrated here) or flange plates of the longitudinal members of a motor vehicle. 
         [0041]    The bumper arrangement  1  is arranged here in a motor vehicle in such a manner that a crossmember longitudinal axis  7  is perpendicular to a center longitudinal axis  6  of the vehicle. 
         [0042]    The crossmember  2  which is designed as the hollow chamber profile  5  has end side elements  16  at its ends  8  and  9 , with which a hollow chamber  33  (indicated in  FIG. 2 ) of the hollow chamber profile  5  or of the crossmember  2  can be sealed fluid-tightly in relation to the surroundings. 
         [0043]    On that side of the crossmember  2  which lies opposite the rear wall  20 , said crossmember has a front wall  19  which is flat, as viewed in the vertical direction, and on which pedestrian protective elements (not illustrated here) or the like can be arranged. 
         [0044]    So that the internal pressure in the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2  can be varied, the end side elements  16  have removal devices  17 , with the aid of which fluid can be removed from the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2 . On the other hand, it is also possible to transfer fluid in the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2  via said removal devices  17 . 
         [0045]    Here and below, fluid is intended to be understood as meaning both gaseous and liquid media. So that, however, a positive pressure can be produced within the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2 , when a liquid fluid is used it should be noted that the entire hollow chamber should not be filled with the liquid since, because of the incompressibility of liquids, the positive pressure could then not be achieved in relation to the ambient pressure. 
         [0046]      FIG. 2  now shows a detailed illustration of the bumper arrangement  1  according to the invention from  FIG. 1  in the region of the end  8  of the crossmember  2  designed as a hollow chamber profile  5 . In this illustration, the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2  is not yet closed with the end side element  16 . However, connecting elements  25  with which the corresponding end side element  16  can be arranged fluid-tightly on the hollow chamber profile  5  of the crossmember  2  by means of screws  24  can be seen in this illustration. Furthermore, this illustration also does not show the crashbox  3  which is connected to the crossmember  2  via the rear wall  20  thereof. 
         [0047]      FIGS. 3 a  and 3 b    now show a detailed illustration of an end side element  16  in a perspective view from the front and from the rear. A plate  26  on which and to which a plug-in element  23  is arranged and fastened by means of screws  22  can clearly be seen here. Furthermore, the position of the connection elements  25  in the fitted position is indicated here. The screws  24  serve to fasten the entire end side element  16  to the connection elements  25  of the crossmember  2  according to  FIG. 2 . In this exemplary embodiment, the plug-in element  23  is of circular design and is therefore suitable for closing the opening in the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2  in the end region  8  according to  FIG. 2 . So that a fluid-tight closure can be ensured, said plug-in element  23  is provided with an encircling sealing ring  21 . 
         [0048]    Furthermore, the removal device  17 , which can be designed as a valve, can also be clearly seen in these illustrations. With the aid of said removal device  17 , it is possible to remove fluid from the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2 . However, it is also possible to supply fluid to the hollow chamber  33  of the hollow chamber profile  5  or of the crossmember  2  via said removal device. 
         [0049]      FIGS. 4 and 5  show the bumper arrangement according to the invention according to  FIG. 1  in a different illustration. The connection elements  25  of the crossmember  2  are not illustrated here. However, the flanges  18  of the crashboxes  3  and how the latter can be arranged with screws (not illustrated here) via openings  28  and with a positioning element  29  on a corresponding longitudinal member of the vehicle can clearly be seen in this illustration. 
         [0050]      FIGS. 6 to 15  now show various bumper arrangements according to the invention in cross-sectional illustrations in the region of a crashbox  3 . 
         [0051]    The exemplary embodiment of  FIG. 6  has a crossmember  2  which is designed as a hollow chamber profile  5  and has a hollow chamber  33  with a circular cross section. On the front side, the crossmember  2  here has a front wall  19 , while a rear wall  20  is provided on the rear side. A crashbox  3  is arranged on the rear wall  20  via the flange-shaped, flat surface  27 , said crashbox being provided in turn on the other side with a flange  18  with which the entire bumper arrangement according to the invention can be arranged on a longitudinal member of a motor vehicle. The wall thicknesses of the different regions of the crossmember  2  likewise differ. While the rear wall has a wall thickness of 2.5 mm to 4 mm, the front wall  19  has a wall thickness of 3 mm to 4 mm. The wall thickness of the crossmember  2  normally has a thickness of 3 mm to 6 mm. However, it can be provided that a wall thickness reduction of the crossmember has been introduced at the ends  8  and  9  of the hollow chamber profile  5  by machining when corresponding closure elements with a corresponding external thread cut a corresponding internal thread into the crossmember  2  or into the hollow chamber profile  5  in the circular opening at the ends  8  and  9 . 
         [0052]    The exemplary embodiment of  FIG. 7  substantially corresponds to that of  FIG. 6 , wherein, however, additional supports  30  are arranged between the rear wall  20  of the crossmember  2  and the crossmember  2  in order to reinforce the entire bumper arrangement. The wall thicknesses can be designed here corresponding to the wall thicknesses of the exemplary embodiment according to  FIG. 6 . As a result, the force flux from the crossmember  2  to the crashboxes  3  is optimized. 
         [0053]    The exemplary embodiments of  FIGS. 8 and 9  also substantially correspond to that of  FIG. 6 . However, in the exemplary embodiment of  FIG. 8 , an inner web  10  is provided in this case in order to reinforce the entire bumper arrangement. If said connecting web  10  passes through the entire hollow chamber profile  5 , the hollow chamber profile  5  is designed as a two-chamber profile with two hollow chambers  33 ′ and  33 ″. In the case of such a hollow chamber profile  5  with two hollow chambers  33 ′ and  33 ″, it would be possible to fill the different hollow chambers  33 ′ and  33 ″ with different pressures. This may be expedient for specific applications in order to optimize certain energy dissipation properties. 
         [0054]    In the exemplary embodiment of  FIG. 9 , in addition to the inner web  10 , a further inner web  11  is arranged in the hollow chamber profile  5 . Said inner web  11  also serves primarily to reinforce the entire bumper arrangement. If, however, this inner web  11  also passes completely through the hollow chamber profile  5 , the hollow chamber profile  5  becomes a four-chamber profile with four hollow chambers  33 ′,  33 ″,  33 ′″ and  33 ″″. It would also be possible in turn here to fill the different hollow chambers  33 ′,  33 ″,  33 ′″ and  33 ″″ with different pressures. 
         [0055]    In the exemplary embodiment according to  FIG. 10 , the crossmember  2  is now formed as a rectangle with an upper wall  31  and a lower wall  32  that connect the front wall  19  to the rear wall  20  of the crossmember  2 . A cross-sectionally circular hollow chamber profile  5  with a hollow chamber  33  is arranged within the crossmember  2 . A further hollow chamber  35  is now also formed between the hollow chamber profile  5  and the upper wall  31 . A further hollow chamber  34  is now also formed between the hollow chamber profile  5  and the lower wall  32 . 
         [0056]    In the exemplary embodiment according to  FIG. 11 , the crossmember  2  is of U-shaped design with a front wall  19 , a lower wall  32  and a rear wall  20 , wherein a hollow chamber profile  5  with a circular cross section is furthermore arranged in the crossmember  2 . A further hollow chamber  34  is now also formed between the hollow chamber profile  5  and the lower wall  32 . 
         [0057]      FIGS. 12 and 13  show crossmembers  2  which are designed as a hollow chamber profile  5  with a hollow chamber  33  and have different front walls  19  and rear walls  20 . Whereas, in the exemplary embodiment according to  FIG. 13 , the front wall  19  and the rear wall  20  extend approximately in the same way over the crossmember  2  designed as a hollow chamber profile  5 , the rear wall  20  of the crossmember  2  is shortened in relation to the front wall  19 , according to the exemplary embodiment of  FIG. 12 . 
         [0058]    A crossmember  2  provided with a shortened rear wall  20  is also used in the exemplary embodiment according to  FIG. 14 . However, in this exemplary embodiment, the rear wall  20  of the crossmember  2  is connected again to the front wall  19  via a lower wall  32 . The entire crossmember  2  therefore forms a two-chamber profile with two hollow chambers  33  and  34 , wherein the hollow chamber  33  is formed by the hollow chamber profile  5 , and a hollow chamber  34  is formed by the lower wall  32  and the hollow chamber profile  5 . In the exemplary embodiment according to  FIG. 14 , the crossmember  2  is also arranged in a height-offset manner in relation to the longitudinal member, to which the entire bumper arrangement is secured by means of the flange  18  of the crashbox  3 , wherein the crashbox  3  and the lower wall  32  are each oriented at an angle of less than 90° with respect to the flange  18 . A corresponding exemplary embodiment according to  FIG. 14 , but without a height offset, is illustrated in  FIG. 15 . Two hollow chambers  33  and  34  are correspondingly also realized here by the configuration there. 
         [0059]      FIG. 16  now shows a possible design for a towing attachment  15  which can be arranged on a bumper arrangement according to the invention, for example in the outer region  4  of the crossmember  2 . The towing attachment  15  has a thread receiver  36  for a threaded lug (not illustrated here). The towing attachment  15  can be connected here firstly to the crossmember  2  or to the hollow chamber profile  5  and secondly also to the rear wall  20  and the front wall  19  by connecting technology, for example by screwing or welding to the bumper arrangement according to the invention. The towing attachment is extruded here in such a manner that it is adapted to the shape of the crossmember  2  in the region of the fastening thereof. 
         [0060]      FIG. 17  now illustrates an exemplary embodiment of a crossmember  2  of a bumper arrangement according to the invention. This crossmember is also designed here as a hollow chamber profile  5  with a hollow chamber  33 . However, the front wall  19  there is designed as a bent-over front flange. In addition, the cross section of the hollow chamber profile  5  in this exemplary embodiment is not circular, but is somewhat flattened. 
         [0061]      FIGS. 18 to 20  now show different longitudinal sections of crossmembers  2 , which have a hollow chamber  33  and are in the form of a hollow chamber profile  5 , in an illustration without a curvature. The ends  8 ,  9  of said crossmembers  2  which are in the form of a hollow chamber profile  5  are formed with a thinner wall than the rest of the hollow chamber profile  5 . The ends  8  and  9  of the hollow chamber profile  5  can extend here over a length of 5 mm up to 45 mm. Said thinner-walled design is achieved in that the respective crossmember  2  has been machined from the inside. This machining realizes a neater surface for rubber contact when sealing with a plug-in element  23 , as is shown for example in  FIGS. 3 a  and 3 b   . In such a refinement, a sealing ring  21  which is arranged on the plug-in element  23  can fluid-tightly seal the hollow chamber  33  of the crossmember  2  in the form of a hollow chamber profile  5 . In the end regions  8  and  9 , the crossmember  2  therefore has a wall thickness which is reduced by 5% to 15% in relation to the remaining wall thickness. 
         [0062]    A corresponding illustration with plugged-in plug-in element  23  is shown in  FIG. 19 . The sealing ring  21  which lies against both the plug-in element  23  and against the inner wall of the crossmember  2  in the form of a hollow chamber profile  5  and therefore seals the hollow chamber  33  fluid-tightly can also be seen particularly readily here. 
         [0063]      FIG. 20  now shows an exemplary embodiment in which the ends  8 ,  9  are provided with a ribbed insert which additionally acts as a deformation element. In the case of a necessary closure, in particular fluid tight closure, a radial groove with a sealing ring  21  can furthermore be provided. 
         [0064]    Finally,  FIGS. 21 to 24  show a further exemplary embodiment of a bumper arrangement according to the invention in various illustrations. In contrast to the exemplary embodiment according to  FIG. 1 , this exemplary embodiment has a crossmember  2  which does not have the same cross section over its entire longitudinal extent. While the crossmember  2  continues to have a circular cross section in its outer regions  4 , according to  FIG. 22 , it is flattened in its central region  13 , as illustrated in  FIG. 23 . This has the result that the hollow chamber  33  has a smaller width b in the outer region  4  of the crossmember  2  than the width B in the central region  13  of the crossmember  2 . Said larger width B in the central region  13  is caused by the fact that the flattening of the crossmember  2  and therefore of the hollow chamber  33  of the hollow chamber profile  5  is carried out mechanically. In addition, in contrast to the exemplary embodiment of  FIG. 1 , the bumper arrangement is not closed at the ends. The crossmember  2  is extruded integrally and from the same material in the form of a hollow chamber profile  5  with the hollow chamber  33  being formed. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  Bumper arrangement 
           2  Crossmember 
           3  Crashbox 
           4  Outer region 
           5  Hollow chamber profile 
           6  Central longitudinal axis of the vehicle 
           7  Crossmember longitudinal axis 
           8  End 
           9  End 
           10  Inner web 
           11  Inner web 
           12  Reinforcing inserts 
           13  Central region 
           14  Reinforcing attachment 
           15  Towing attachment 
           16  End side element 
           17  Removal device 
           18  Flange 
           19  Front wall 
           20  Rear wall 
           21  Sealing ring 
           22  Screw 
           23  Plug-in element 
           24  Screw 
           25  Connection element 
           26  Plate 
           27  Surface 
           28  Opening 
           29  Positioning element 
           30  Additional support 
           31  Upper wall 
           32  Lower wall 
           33  Hollow chamber 
           33 ′ Hollow chamber 
           33 ″ Hollow chamber 
           33 ′″ Hollow chamber 
           33 ″″ Hollow chamber 
           34  Hollow chamber 
           35  Hollow chamber 
           36  Thread receiver 
         b Width 
         B Width