Bumper arrangement for a motor vehicle

Abstract

Bumper assembly (1) for a motor vehicle comprising a cross member (2) and crash boxes (3) arranged in the area of ​​the ends of the cross member (2) for coupling the bumper assembly (1) to the motor vehicle, wherein the cross member (2) is formed as a multi-chamber hollow profile made of a light metal alloy, wherein the cross member (2) has a front (4) facing in the direction of travel and a rear (14) facing away from the direction of travel, wherein the front (4) has a height (H4) in the motor vehicle vertical direction (Z) which is greater than the height (H14) of the rear (14) and the multi-chamber hollow profile has at least two chambers, characterized in that a main chamber (21) has a larger cross-sectional area compared to at least one front chamber (12, 17) and the front chamber (12, 17) forms a part of the front (4) with at least one wall (19, 20).

Description

[0001] The present invention relates to a bumper arrangement for a motor vehicle according to the features in the preamble of patent claim 1.

[0002] Bumper assemblies that are mounted on the front or rear of a motor vehicle are known from the prior art. These bumper assemblies comprise a cross member that essentially extends across at least part of the width of the vehicle body. The cross member should be designed to be as rigid as possible so that various impact scenarios, such as impact with a pole, a bumper-to-bumper crash, or even an impact with an obstacle, particularly overlapping collisions (also known as offset crashes), are covered, and uncontrolled entry into the vehicle is prevented.

[0003] To dissipate the kinetic energy generated during such a crash, such a known cross member is coupled to the vehicle body, and in particular to the side members, via crash boxes. The crash boxes are designed to be deformed by the impact, thus converting the kinetic energy into forming energy through cold forming. The crash boxes are usually coupled to the front side members of the vehicle body to transfer the remaining crash energy into them. The load path thus runs from the cross member via the crash box into the side members of the vehicle.

[0004] Good crash performance goes hand in hand with high rigidity of the cross member and high energy absorption capacity of the crash box and cross member, which is achieved through large component dimensions. However, these large component dimensions result in high deadweight and require a large amount of space.

[0005] The known bumper arrangements therefore face a conflict of objectives: the lowest possible dead weight while simultaneously achieving good crash performance and requiring little installation space.

[0006] EP 2 024 201 B1 discloses a bumper assembly comprising a cross member that, thanks to various stiffening beads and, as a steel component, is highly rigid while simultaneously being compact thanks to the use of hot-forming and press-hardening technology. To ensure sufficient overlap even in the event of a bumper-to-bumper crash with another motor vehicle, the cross member further comprises an asymmetrical central section to sufficiently vertically overlap the center line of the cross member of an impacting motor vehicle. However, this poses the problem that, in the event of an impact, the cross member is subjected to rotation about its longitudinal axis.

[0007] Furthermore, cross members made of extruded light metal profiles are known from the prior art. For example, US 2015 / 0084355 A1, which is generic for claim 1, discloses a bumper assembly with a cross member made of an extruded light metal profile. In this case, the overlap in the event of a bumper-to-bumper crash as well as the rigidity of the cross member are achieved by a corresponding overall height of the cross member relative to the vertical direction of the vehicle.

[0008] Furthermore, DE 10 2010 060 157 A1 discloses a crash box designed as a hollow profile with several longitudinal ribs running parallel to its longitudinal axis. Another crash box is known from US 2009 / 0 102 210 A1.

[0009] The object of the present invention is to provide, based on the prior art, a bumper arrangement which has a small installation space requirement while at the same time having high crash performance and low dead weight.

[0010] The above-mentioned object is achieved according to the invention with a bumper arrangement for a motor vehicle according to the features in patent claim 1.

[0011] Advantageous embodiments of the present invention are the subject of the dependent patent claims.

[0012] The bumper assembly for a motor vehicle has a cross member and crash boxes arranged in the region of the ends of the cross member for coupling the bumper assembly to the motor vehicle, wherein the cross member is made of a light metal alloy from an extruded multi-chamber hollow profile. According to the invention, the bumper assembly is characterized in that the cross member has a front side directed in the direction of travel and a rear side facing away from the direction of travel, wherein the front side has a height in the vertical direction of the motor vehicle which is greater than the height of the rear side and the multi-chamber hollow profile has at least two chambers, wherein a main chamber has a larger cross-sectional area than the at least one front chamber and the front chamber forms the front side with at least one of its walls.Preferably, two front chambers are arranged, wherein both front chambers form the front side with at least one of their walls.

[0013] The bumper assembly is suitable for installation on both the front and rear of the vehicle. The direction of travel at the front is forward. When mounted on the rear, the direction of travel is reverse.

[0014] According to the invention, by designing the cross member as a multi-chamber hollow profile made of a light metal alloy, in particular an aluminum alloy, it is possible to achieve a particularly low dead weight while maintaining high rigidity. To this end, different wall thicknesses are implemented, particularly in the cross section. The requirements of various crash scenarios are well met by the greater height of the front of the cross member compared to the height of the rear of the cross member, relative to the vertical direction of the vehicle. The height of the rear is preferably 40% to 90% of the height of the front.The rear of the cross member often houses peripheral vehicle components, such as a radiator, hoses, connecting hoses, cables, or other components. The lower height here reduces the installation space. At the same time, even in the event of deformation of the cross member, particularly due to twisting around its longitudinal axis when vertically offset cross members collide, the lower height of the rear of the cross member prevents damage to adjacent components. Likewise, penetration and associated damage to components in the engine compartment of the vehicle are prevented or reduced.

[0015] The increased crash performance with simultaneous lower dead weight is further achieved by the cross member being designed as a multi-chamber hollow profile with at least one, preferably two front chambers directed in the direction of travel and a main chamber arranged downstream of these in relation to the direction of travel. The above information refers in each case to the cross section of the cross member. The impacting obstacle therefore first strikes the front chamber or chambers. In the case of two front chambers, these can be arranged directly adjacent to one another in relation to the vertical direction of the vehicle. The front chambers can, however, also be arranged at a distance from one another, in which case the front chambers are connected to one another via a web. The front walls or wall surfaces of the front chambers directed in the direction of travel then simultaneously form at least part of the front side of the cross member.The remaining part is formed by the web. With only one front chamber, the remainder of the front side forms the web. With directly adjacent front chambers, these form the entire front side of the cross member.

[0016] The cross-sectional area of ​​the main chamber is larger than the cross-sectional area of ​​the front chamber. If there are two front chambers, the cross-sectional area of ​​the main chamber is larger than the respective cross-sectional area of ​​one front chamber. The cross-sectional areas of the front chambers can be different or equal to each other. However, the cross-sectional area of ​​the main chamber is particularly preferably larger than the cross-sectional area of ​​both front chambers combined.

[0017] The web can be set back in cross-section relative to the longitudinal direction of the vehicle, so that the front side of the cross member is not flat. Preferably, the web is arranged such that the front walls of the front chambers, together with the web, form the front side, and the front side is essentially flat in cross-section and is oriented, in particular, in the vertical direction of the vehicle.

[0018] In order to achieve the greater height of the front of the cross member compared to the rear, in each case related to the vertical direction of the vehicle, the front chambers are arranged so as to protrude above and below the main chamber, in particular with a step or step offset. This means that the top side of the upper front chamber and the bottom side of the lower front chamber are at a distance from one another which corresponds to the height of the front side and is greater than the height of the rear side. Folded or rounded areas are excluded from this. The height of the rear side is also the height of the main chamber, provided the main chamber has a rectangular cross-section. The main chamber therefore transitions into the upper front chamber with a step offset at the top and into the lower front chamber at the bottom.

[0019] For this purpose, the main chamber is formed in cross-section in particular by the rear side, an upper chord located above and a lower chord located below, the corresponding parts on the front chambers as well as the web optionally arranged on the front. The rear side of the main chamber, which is also the rear side of the cross member, and the web are arranged so as to run vertically in the motor vehicle. The upper chord and the lower chord are therefore oriented in the longitudinal direction of the motor vehicle, preferably at an angle of between -20° and +20° to the longitudinal direction of the motor vehicle. The parts of the front chambers which also form the main chambers are arranged so as to run vertically in the motor vehicle and in the longitudinal direction of the motor vehicle. The front chambers are furthermore preferably essentially rectangular in cross-section.The main chamber preferably also has a rectangular, in particular square, cross-section, wherein the rectangular cross-section is at least partially interrupted due to the part of the main chamber which is formed in cross-section by the front chambers.

[0020] A particularly good force distribution or load path is achieved by the fact that the upper chord and the lower chord of the main chamber each merge into a middle height region of the rear of the front chambers, viewed in cross-section. The middle height region is also referred to below as the middle region. In particular, the upper chord and the lower chord are arranged essentially orthogonally to the respective rear of the front chambers, and thus abutting them. In this case, a high-intensity impact would lead to additional energy dissipation, with the upper chord causing the rear of the upper front chamber to deform and the lower chord causing the rear of the lower front chamber to be indented. This also converts kinetic energy into forming work and improves crash performance. At the same time, the deformation increases the flexural rigidity of the cross member itself, in that a longitudinal bead is formed at least locally in the rear wall of the front chamber.

[0021] A further essential aspect of the invention is that the cross member has a longitudinal profile oriented in the transverse direction of the vehicle. Thus, the longitudinal axis of the cross member is arranged oriented in the transverse direction of the vehicle. For this purpose, the cross member preferably furthermore has a curvature along its longitudinal profile, with the curvature being directed in the longitudinal direction of the vehicle. Thus, the cross member is slightly curved toward the front in the longitudinal direction of the vehicle.

[0022] Alternatively or additionally, the cross member has a central section with respect to its longitudinal direction which is bent or deformed asymmetrically in the vertical direction of the vehicle. In particular, the asymmetric central section is shaped upwards in the vertical direction of the vehicle. The central section can also be arranged offset parallel to the longitudinal axis of the cross member with respect to the vertical direction of the vehicle. This then results in a respective transition section. In the bumper-to-bumper crash scenario, this achieves good coverage for an impacting bumper, particularly in passenger cars, particularly in the mid-range or small or subcompact cars. Their vehicle bodies and in particular the longitudinal members are often arranged lower with respect to the vertical direction of the vehicle than the centerline of luxury vehicles, SUVs or even commercial vehicles.The asymmetrically upwardly shaped central section, in turn, ensures a high level of overlap with the aforementioned vehicles. The design, particularly as a multi-chamber hollow profile, nevertheless allows for sufficient flexural rigidity of the cross member.

[0023] For this purpose, the cross member is further preferably designed such that it has different wall thicknesses in cross-section, wherein the upper front chamber preferably has a greater wall thickness than the lower front chamber. If a reversed arrangement of the bumper arrangement according to the invention were to take place on an SUV, for example, the central section would preferably be oriented downwards. In this case, the lower front chamber would have a greater wall thickness than the upper front chamber. Furthermore, the wall thickness of the main chamber is particularly preferably greater than or equal to the wall thickness of the lower front chamber. In particular, the wall thickness of the main chamber is less than or equal to, and particularly preferably less than, the wall thickness of the upper front chamber.This makes it possible to achieve optimal crash performance with low material usage and thus a possible low dead weight of the cross member, without reducing the crash performance of the bumper arrangement, since a high flexural rigidity of the cross members is realized.

[0024] Furthermore, each front chamber particularly preferably has a height that corresponds to 20% to 60%, preferably 25% to 50%, in particular 30% to 40%, and essentially 1 / 3 of the height of the main chamber. The height again refers to the vertical direction of the motor vehicle. The front chambers can each have the same height. However, within the scope of the invention, it is also possible for the front chambers to have different heights. The upper front chamber preferably has a greater height than the lower front chamber, in particular with an upwardly arranged central section of the cross member.

[0025] Furthermore, it is particularly preferred that the rear side of the cross member transitions into the upper and lower chords in a rounded manner. This makes it possible to minimize the associated damage if the cross member penetrates the engine compartment or passenger compartment. In the event of slight torsion and / or rotation of the cross member about its longitudinal axis, the rounded transition area from the rear side to the upper chord or from the rear side to the lower chord mitigates damage that could be caused, for example, by a 90° edge on a connecting hose or similar.

[0026] Furthermore, the cross member is particularly preferably made of an aluminum alloy, in particular a 6000 or 7000 series aluminum alloy. The cross member particularly preferably has a yield strength Rp 0.2 between 200 MPa and 500 MPa, particularly preferably between 300 MPa and 450 MPa. The yield strength of the cross member material is particularly preferably further increased by artificial aging and / or cold aging.

[0027] The bumper assembly according to the invention further comprises a crash box. Within the scope of the invention, the crash box described below can also be considered independently, with its respective features and associated properties, without the previously described cross member.

[0028] The crash box according to the invention itself is designed as a hollow profile, wherein the hollow profile has a rectangular configuration in cross-section. The hollow profile can be made in one piece and from the same material, but also in two or more parts. The central longitudinal axis of the crash box runs in the longitudinal direction of the vehicle when mounted on the vehicle. A crash box upper side and a crash box lower side each have two curvatures, wherein the curvatures are oriented outwards with respect to an interior of the hollow profile of the crash box. The curves of the curvatures are oriented vertically of the vehicle. Thus, the curvatures of the crash box upper side are oriented upwards in the vertical direction of the vehicle, and the curvatures of the lower side are oriented downwards in the vertical direction of the vehicle. The curvature itself is formed over a longer course, in the manner of an outwardly oriented bead.This curve itself is oriented in the longitudinal direction of the vehicle. This curve pattern increases the rigidity of the crash box and its energy absorption capacity in the longitudinal direction of the vehicle. Even in the event of rotational movement resulting from bumper-to-bumper crash configurations offset vertically in the vehicle, the connection between the cross member and the crash box is ensured. Overall, more crash energy is dissipated per deformation distance traveled by the crash box's longitudinal path.

[0029] Furthermore, the crash box is particularly preferably designed in a fork-shaped manner towards the front and, in the fork opening, accommodates the cross member at least partially in the longitudinal direction of the vehicle. For this purpose, the upper chord of the cross member is at least partially, in particular completely, overlapped by the upper side of the crash box, and the lower chord is partially, in particular completely, overlapped by the lower side of the crash box. Furthermore, the cross member is particularly preferably not only positively coupled to the crash box in this area. The coupling is particularly additionally carried out by a riveting process or, more preferably, by a screw connection. This simultaneously enables simple and easy assembly and disassembly of the cross member and, in particular, pre-assembly of the entire bumper arrangement so that it can be completely mounted on the vehicle.Furthermore, a spacer sleeve is particularly preferably arranged in the interior of the cross member, particularly in the main chamber, so that a screw connection is formed from the top of the crash box through the cross member to the bottom of the crash box. Alternatively, the crash box can be welded to the top and bottom of the cross member, particularly to the top and / or bottom chords.

[0030] The particularly good crash performance of the bumper arrangement is further achieved by the fact that the crash box is designed in such a way that the upper side of the crash box rests against a rear wall of the upper front chamber of the cross member, in particular with the front ends of the curvatures, and the lower side of the crash box rests against a rear wall of the lower front chamber, in particular with the front ends of the curvatures. A crash initiated at the front of the cross member is thus passed on via the front chamber directly to the crash box or the curvatures of the crash box. If there is only one front chamber, the web on the cross member on the side opposite the front chamber in the vertical direction of the vehicle is extended with a flange. The front end of the curvature of the crash box then rests directly against the flange.

[0031] Furthermore, the crash box particularly preferably has a flange that protrudes laterally in the transverse direction of the vehicle, which flange rests against the rear wall of the cross member and is particularly coupled to the rear wall of the cross member. The coupling can again be achieved by a riveting process and particularly preferably by a screw connection. Together with the coupling of the top and bottom of the crash box to the cross member, this creates a three-sided coupling, which in particular prevents twisting or torsion of the cross member in the event of a crash.

[0032] Furthermore, the crash box, in particular, is also formed in one piece and made of a uniform material, in particular from a light metal alloy, preferably an aluminum alloy. This makes it possible to manufacture the crash box using an extrusion process. A back plate or flange plate can be coupled to the crash box, with which the crash box or the entire bumper assembly is then coupled to the vehicle body, particularly in the area of ​​the front ends of the longitudinal members of the vehicle body.

[0033] In the case of the production of a one-piece crash box made of the same material, it is possible to produce it as an extruded profile and then to process it using cutting and forming technology so that the top and bottom of the crash box as well as the laterally protruding flange are formed.

[0034] In particular, in this case, the crash box also has different wall thicknesses in cross-section. Preferably, strips oriented in the longitudinal direction of the vehicle are formed with greater wall thickness than the other regions of the crash box. The strips are most preferably formed such that they extend from the flange plate of the crash box, at least partially in the region of the curvatures, over the entire longitudinal extent of the crash box, so that the region with greater wall thickness and thus greater rigidity extends from the flange plate of the crash box to the rear wall of the front chamber of the cross member, particularly in the region of the curvature.

[0035] This in turn makes it possible for the crash or impact initiated via the front chambers to have an optimal load path through the crash box up to the flange plate due to the strip with a higher wall thickness and, at the same time, a targeted deformation remains possible even in bumper-to-bumper crash constellations that are offset in the vertical direction of the vehicle.

[0036] Further advantages, features, properties, and aspects of the present invention are the subject of the following description. Preferred embodiments are illustrated in the schematic figures. These serve to facilitate understanding of the invention. They show: Fig. 1 the bumper arrangement according to the invention in perspective view, Fig. 2 the bumper arrangement according to the invention in a plan view, Fig. 3 the bumper arrangement according to the invention in a view from behind, Fig. 4 the cross member in a view from behind, Fig. 5 the bumper arrangement in a side view, Fig. 6 the crash box according to the invention in perspective view, Fig. 7 the cross member according to the invention in a cross-sectional view, Fig. 8a to c show the load path through a bumper arrangement according to the invention and a bumper arrangement known from the prior art, Fig. 9a to e Cross-sectional views of different variants of the cross member and Fig. 10a to f show a bumper arrangement according to the invention before and after a crash with force level progression in contrast to a bumper arrangement known from the prior art.

[0037] In the figures, the same reference symbols are used for identical or similar components, even if a repeated description is omitted for reasons of simplification.

[0038] Fig. Figure 1 shows the bumper assembly 1 according to the invention in a perspective view. The bumper assembly 1 comprises a cross member 2 and crash boxes 3 arranged in a respective end region of the cross member 2. The cross member 2 itself has a flat front side 4 and is designed as a multi-chamber hollow profile. The multi-chamber hollow profile is illustrated and described in more detail in Fig. 7. Mounting holes 5 are formed in the front for arranging a towing eye (not shown in detail) through the cross member 2. Flange plates 6 are attached to the crash boxes 3, via which they can be coupled to the vehicle body (not shown in detail) or to the longitudinal member of the vehicle body.

[0039] The cross member 2 is initially manufactured as an extruded component and then further processed by forming and / or cutting. For this purpose, as shown in particular in accordance with Fig. 2, in the vehicle longitudinal direction X, a curvature is formed. The curvature takes place in the vehicle longitudinal direction. The longitudinal direction 8 runs in an arc shape in the vehicle transverse direction Y so that the arc of curvature is formed pointing in the vehicle longitudinal direction X. Thus, the cross member 2 has an arc shape along its central longitudinal axis 7. It is also clearly visible that a respective crash box upper side 9 overlaps an upper flange 10 of the cross member 2 and in doing so rests on a rear wall 11 of the upper front chamber 12, shown in Fig. 7, comes into contact. Furthermore, the cross member 2 is coupled to the crash boxes 3 via a respective screw connection 13 between the crash box top 9 and the upper chord 10. Furthermore, the screw connections 13 are designed such that the rear side 14 of the cross member 2 is also screw-coupled to laterally projecting flanges 15 of the crash box 3.

[0040] Instead of screw connections, it is also possible to weld the crash boxes and the cross member. For this purpose, the crash box top 9 and crash box bottom 26 can preferably be coupled to the upper chord 10 and the lower chord 22 by welded connections. In particular, alternatively or additionally, the front walls 28 of the bulges 27 can be coupled to the rear walls 11, 24 of the front chambers 12, 17 of the cross member 2.

[0041] Fig. 3 shows a rear view of the bumper arrangement 1 according to the invention and Fig. 4 a rear view of only the cross member 2. It is clearly visible that a central section 16 of the cross member 2 is offset upwards relative to the vehicle vertical direction Z and parallel to the central longitudinal axis 7. Due to this upwardly offset central section 16, the greatest possible overlap relative to the vehicle vertical direction Z is achieved in the event of a bumper-to-bumper crash.

[0042] How Fig. 7 shows, in particular the upper front chamber 12 has a greater wall thickness W12 than a lower front chamber 17 with a smaller wall thickness W17. A web 18 connecting the upper and lower front chambers 12, 17 is arranged between them. The front wall 19 of the upper front chamber 12 as well as the front wall 20 of the lower front chamber 17 and the web 18 together form the front side 4 of the cross member 2, which is flat in cross section. The web 18 itself has a wall thickness W18 that is less than or equal to the wall thickness W12 of the upper front chamber 12 and greater than or equal to the wall thickness W17 of the lower front chamber 17.

[0043] The main chamber 21 itself forms the third chamber of the multi-chamber hollow profile, with all chambers having a substantially rectangular cross-section. The main chamber 21 itself is formed by the upper chord 10, a lower chord 22, and the rear side 14. The rear side 14 merges into the upper chord 10 and the lower chord 22, respectively, with a curve 23. The upper chord 10 and the lower chord 22, as well as the rear side 14, preferably each have a wall thickness W10, W22, W14 that is less than or equal to the wall thickness W12 of the upper front chamber 12 and greater than or equal to the wall thickness W17 of the lower front chamber 17.

[0044] It is also clearly visible that the height H14 of the rear side 14 is smaller than the height H4 of the front side 4 of the cross member 2. This provides the largest possible impact surface at the front side 4 for impact with a bumper, pole, or other obstacle. The front chambers 12, 17 ensure correspondingly high rigidity. The height H14 of the rear side 14, on the other hand, requires less installation space and minimizes the risk of damage if the cross member 2 penetrates the engine compartment.

[0045] Furthermore, clearly visible in Fig. 7 is that the upper chord 10 and the lower chord 22 each merge into the rear wall of the upper front chamber 12 and the rear wall 24 of the lower front chamber 17, in particular at a right angle. Preferably, the upper chord 10 and the lower chord 22 each merge into the rear wall 11 in a central region 25 thereof, so that an ideal load path is achieved, with simultaneous possibility of deformation of the multi-chamber hollow profile. The height H12 of the upper front chamber 12 and the height H17 of the lower front chamber 17 can be the same or different from each other. In the event that the central section according to Fig. 3 is oriented upwards and offset parallel to the vertical direction of the motor vehicle, the height H12 of the upper front chamber 12 is preferably greater than or equal to the height H17 of the lower front chamber 17. Preferably, the height H12, H17 of the respective front chamber 12, 17 corresponds to 20% to 60% of the height H21 of the main chamber 21.

[0046] Furthermore, the crash box 3 according to the invention is clearly visible in the perspective view of Fig. 6. Clearly visible here is the flange plate 6, which is fixed to the rear side 14 of the crash box 3 and that the crash box 3 itself is designed as a hollow component. Its cross-sectional profile according to Fig. 6, the crash box 3 itself is designed as a two-part component, but the crash box 3 can also be designed as a one-piece and uniform material component, in particular as a single extruded component.

[0047] In particular, curvatures 27 are formed on the crash box upper side 9 and on the crash box lower side 26, wherein the curvatures 27 of the crash box upper side 9 are oriented upwards relative to the motor vehicle vertical direction Z, and the curvatures 27 on the crash box lower side 26 are oriented downwards relative to the motor vehicle vertical direction Z. The respective curvatures 27 extend over the respective length of the crash box 3, so that a front edge or a front end of each curvature 27, shown as an example only at the top right, comes into positive contact with the respective rear wall 24 of the front chamber 17 of the cross member 2.

[0048] Furthermore, the crash box 3 particularly preferably has wall thicknesses W27 that differ from one another in cross-section, wherein strips 29 are formed in particular in the end regions of the curvatures 27, wherein the wall thickness W29 of the strips 29 is greater than the remaining wall thickness W27, for example of the curvature 27 and / or on the crash box top side or crash box bottom side 26. These strips 29 then also extend over the entire length of the crash box 3, so that these strips 29 with increased wall thickness W29 and simultaneously higher rigidity extend from the flange plate 6 to the rear wall 24 of the front chamber 17. The strips 29 then each lie at right angles on the upper chord 10 or lower chord 22 of the main chamber 21 of the cross member 2 in a form-fitting manner. This is clearly illustrated in Fig. 5.

[0049] It is also clearly visible that the crash box upper side 9 and the crash box lower side 26 are fork-shaped in such a way that a receiving area for the positive and in particular fork-shaped reception of the cross member 2 and here significantly the main chamber 21 is created, so that the upper chord 10 and the lower chord 22 of the main chamber 21 are overlapped and the crash box 3 is designed to rest on the rear side 14 of the cross member 2.

[0050] In Fig. Figure 8 shows bumper-to-bumper crash scenarios with an offset in the vehicle vertical direction Z.

[0051] Fig. 8a shows a load path 30. Upon impact with an obstacle 31, the crash energy is introduced via the front side 4 and in this case passes through the upper front chamber 12 via the upper flange 10 and the crash box top 9, the crash box 3 and is guided into a downstream longitudinal member 32. In contrast, Fig. 8c shows a modified design variant, wherein a gap 38 is formed between the front wall 28 of the crash box top 9 and the rear wall 11 of the upper front chamber 12. Upon impact with an obstacle 31, the upper chord 10 is thus deformed first, before the front wall 28 impacts the rear wall 11 of the upper front chamber 12. Only when the gap 38 has been reduced to zero, the rear wall 11 of the upper front chamber 12 is also noticeably deformed as a result of the additional impact of the crash box top 9. In contrast, according to Fig. 8b shows a load path 30 according to the prior art, wherein when encountering an obstacle 31 of a cross member 33 known from the prior art, the load path 30 is also guided over an upper chord 10 shown there, but then abruptly breaks off at a rear wall 35 in order to be guided again into a longitudinal member 32 or the crash box 37 upstream of it.

[0052] Fig. 9a to e each reveal cross-sectional views through different design variants of the cross member 2. Fig. 9a shows the previously described design variant with upper and lower front chamber 12, 17 as well as the main chamber 21 and the web 18 connecting them. According to Fig. 9b, the web 18 is offset from the front side and connects the upper and lower front chambers 12, 17.

[0053] In the design variant according to Fig. 9c, the lower front chamber 17 has been omitted, with a projecting flange 34 being formed here, which then forms the front side 4 of the cross member 2. The flange 34 and the upper front chamber 12 are in turn connected by the web 18.

[0054] According to Fig. Figure 9d shows a design variant in which the upper and lower front chambers 12, 17 directly adjoin one another and are therefore immediately adjacent. These thus form the front side 4 without the web 18. The main chamber 21 is then also bounded by the upper chord 10, the lower chord 22, and the rear side 14, as well as parts of the respective rear sides of the front chambers 12, 17.

[0055] The Fig. 9e shows a modification of the representation from Fig. 9a. In contrast to the design variant according to Fig. 9a, the cross member 2 is designed in cross-section such that the front side 4 has a curved profile. The arc of the curvature points in the vehicle's longitudinal direction X. Therefore, in the upper front chamber 12, the upper wall is shorter in the vehicle's longitudinal direction X than the lower wall, relative to the vehicle's vertical direction Z. In the lower front chamber 17, the upper wall is longer than the lower wall, relative to the vehicle's vertical direction Z, in each case in the vehicle's longitudinal direction X.

[0056] Fig. 10a to f show a comparison of a bumper arrangement 1 according to the invention according to Fig. 10a to c in contrast to a bumper arrangement 1 known from the prior art, shown in Fig. 10d to f, each shown in simplified form without a crash box. For this purpose, the bumper assembly 1 according to the invention is located according to Fig. 10a in its initial state. According to Fig. 10b, a force F is applied to the front side 4 of the cross member 2. As a result, the upper chord 10 and the lower chord 22 bulge outwards with respect to the vertical direction Z of the vehicle and thus reduce the force F via the associated deformation path in the longitudinal direction X of the vehicle. This corresponds to the force path diagram 1 according to Fig. 10c. This deformation occurs particularly in the case of a low-intensity impact. At the same time, the upper chord 10 and lower chord 22 of the main chamber 21 press into the rear sides 11, 24 of the two front chambers 12, 17, thereby deforming both the rear sides 11, 24 and, in turn, the respective upper and lower sides of each front chamber 12, 17. This results in a conversion of force F into deformation energy. In particular, this dissipates the crash energy that must be dissipated in the case of a high-intensity impact. This corresponds to the force level 2 in the force path diagram according to Fig. 10c. In Fig. Figure 10c then shows the acting force F and the associated deformation path in the longitudinal direction X of the vehicle.

[0057] In contrast, the variant known from the state of the art according to Fig. 10d to f only show a two-chamber hollow profile cross member 36 known from the prior art. It can be clearly seen here according to Fig. 10e and f, that only one force level ① of an impact force F is realized in the vehicle longitudinal direction X. Overall, the force level ① is thus according to Fig. 10f less than that in Fig. 10c, thus ensuring less movement work for cross members 2 known from the prior art. Reference symbol: 1 bumper arrangement 2 cross members 3 Crashbox 4 Front 5 mounting hole 6 Flange plate 7 Central longitudinal axis to 2 8 Longitudinal direction to 2 9 Crashbox top 10 Upper chord 11 Back wall to 12 12 upper front chamber 13 Screw connection 14 Back of 2 15 flange to 3 16 middle section to 2 17 lower front chamber 18 jetty 19 front wall to 12 20 front wall to 17 21 Main Chamber 22 lower chord 23 Rounding 24 back wall to 17 25 middle range to 11 or 24 26 Crashbox bottom 27 Curvature 28 front wall to 27 29 stripes 30 Load path 31 Obstacle 32 longitudinal members 33 cross members 34 flange 35 Rear wall 36 two-chamber hollow profile cross members 37 Crashbox 38 gap F Force H4 height to 4 H12 height to 12 H14 Height to 14 H17 Height to 17 H21 Height to 21 W10 wall thickness to 10 W12 wall thickness to 12 W14 wall thickness to 14 W17 wall thickness to 17 W18 wall thickness to 18 W22 wall thickness to 22 W26 wall thickness to 26 W27 wall thickness to 27 W29 wall thickness to 29 X Longitudinal direction of the vehicle Y vehicle transverse direction Z Motor vehicle vertical direction

Claims

[1] Bumper assembly (1) for a motor vehicle, comprising a cross member (2) and crash boxes (3) arranged in the region of the ends of the cross member (2) for coupling the bumper assembly (1) to the motor vehicle, wherein the cross member (2) is formed from a light metal alloy as a multi-chamber hollow profile, wherein the cross member (2) has a front side (4) directed in the direction of travel and a rear side (14) facing away from the direction of travel, wherein the front side (4) has a height (H4) in the vertical direction (Z) of the motor vehicle which is greater than the height (H14) of the rear side (14) and the multi-chamber hollow profile has at least two chambers, characterized by that a main chamber (21) has a larger cross-sectional area than at least one front chamber (12, 17) and the front chamber (12, 17) forms part of the front side (4) with at least one wall (19, 20). [2] Bumper arrangement according to claim 1, characterized bythat two front chambers (12, 17) are formed, wherein the two front chambers (12, 17) each form the front side (4) with at least one wall (19, 20). [3] Bumper arrangement according to claim 2, characterized by that the front chambers (12, 17) are located directly adjacent to one another or that the front chambers (12, 17) are arranged at a distance from one another, the front chambers being connected to one another via a web (18). [4] Bumper arrangement according to claim 2 or 3, characterized by that the two front chambers (12, 17) together with the web (18) form the front side (4), wherein the front side (4) is flat or curved. [5] Bumper arrangement according to one of claims 2 to 4, characterized by that the front chambers (12, 17) project above and below the main chamber (21) with a step in relation to the vertical direction (Z) of the motor vehicle. [6] Bumper arrangement according to one of the preceding claims, characterized by in that the main chamber (21) is formed in cross-section by the rear side (14), an upper chord (10) and a lower chord (22), parts of the front chambers (12, 17) and a web (18) which extends to the front chamber (12, 17), wherein the rear side (14) and the web (18) run oriented in the vertical direction (Z) of the motor vehicle and the upper chord (10) and the lower chord (22) run oriented in the longitudinal direction (X) of the motor vehicle. [7] Bumper arrangement according to the preceding claim, characterized by that in the cross-section the upper chord (10) and the lower chord (22) merge into a central region (25) on the respective rear side (24) of the front chambers (12, 17). [8] Bumper arrangement according to one of the preceding claims, characterized bythat the cross member (2) has a longitudinal profile which runs oriented in the transverse direction (Y) of the motor vehicle and that the cross member (2) has a curvature in the longitudinal direction (X) of the motor vehicle over its longitudinal profile and / or that the cross member (2) is bent asymmetrically in the vertical direction (Z) of the motor vehicle in a central section. [9] Bumper arrangement according to one of claims 2 to 8, characterized by that the cross member (2) has different wall thicknesses in cross section. [10] Bumper arrangement according to one of claims 2 to 9, characterized by that each front chamber (12, 17) has a height (H12, H17) corresponding to 20 to 60% of the height of the main chamber (21). [11] Bumper arrangement according to one of claims 6 to 10, characterized by that the back (14) merges into the upper chord (10) and the lower chord (22) in a rounded manner. [12] Bumper arrangement according to one of claims 1 to 11, characterized bythat the cross member (2) is made of an aluminum alloy. [13] Bumper arrangement according to one of claims 1 to 12, characterized by that the crash box (3) is designed as a hollow profile, wherein a crash box upper side (9) and a crash box lower side (26) each have two curvatures (27), wherein the curvatures (27) extend in the vertical direction (Z) of the motor vehicle and are oriented in the longitudinal direction (Y) of the motor vehicle. [14] Bumper arrangement according to one of claims 1 to 13, characterized by that the upper chord (10) is overlapped by the crash box top side (9) and / or the lower chord (22) is overlapped by the crash box bottom side (26). [15] Bumper arrangement according to the preceding claim, characterized by that the crash box top (9) rests against a rear wall of the upper front chamber (12) and the crash box bottom (26) rests against a rear wall of the lower front chamber (17). [16] Bumper arrangement according to one of claims 1 to 15, characterized by that the crash box (3) has a flange (15) oriented laterally in the transverse direction (Y) of the motor vehicle, wherein the flange (15) rests against the rear wall (11) of the cross member (2). [17] Bumper arrangement according to one of claims 1 to 16, characterized by that the crash box (3) is made in one piece and from a uniform material of a light metal alloy. [18] Bumper arrangement according to one of claims 1 to 17, characterized by that the crash box (3) has strips (2) oriented in the longitudinal direction (X) of the vehicle with a greater wall thickness (W29) than the other areas of the crash box (3).

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