Bumper crossmember

Abstract

This description covers a bumper crossmember for a vehicle. - with a support 2 extending in its longitudinal axis in the transverse direction of the vehicle (y-direction) and open in the direction of travel (x-direction) with a chamber 8 enclosed by an upper leg 5, a lower leg 6 and a web 7 connecting the two legs 5, 6 in the vertical direction of the vehicle (z-direction), with a strike plate 3 spanning the carrier opening in the vehicle's vertical direction (z-direction) and connected to the legs 5, 6 of the carrier 2 and with an insert 9 arranged in the chamber 8 of the carrier 2, having an upper leg 10, a lower leg 11 and a back 12 connecting the legs 10, 11 at their rear end, the open side of which points in the direction of travel (x-direction) and the legs 10, 11 of which are connected to the closing plate 3, wherein the back 12 of the insert 9 is convexly shaped at least in its middle section, with respect to its longitudinal extent (y-direction).

Description

[0001] The invention relates to a bumper cross member for a vehicle - with a beam extending along its longitudinal axis in the transverse direction of the vehicle (y-direction) and open in the direction of travel (x-direction) with a chamber enclosed by an upper leg, a lower leg and a web connecting the two legs in the vertical direction of the vehicle (z-direction), - with a locking plate spanning the beam opening in the vehicle vertical direction (z-direction) and connected to the legs of the beam and - with an insert arranged in the chamber of the carrier, having an upper leg, a lower leg and a spine connecting the legs at their rear end, the open side of which faces in the direction of travel (x-direction) and the legs of which are connected to the striking plate.

[0002] Bumper cross members are located at the front and / or rear of motor vehicles. Bumper cross members comprise a support profile that is typically hat-shaped in cross-section and attached to the vehicle. The profile is formed by an upper leg, a lower leg, and a web connecting the two legs at their longitudinal end facing the vehicle chassis. The support is open in the direction of travel and therefore has a chamber that is typically roughly U-shaped in cross-section and open in the direction of travel. The web connecting the legs faces the vehicle chassis. The support is attached to the vehicle side with the interposition of crash boxes. The two legs enclosing the support chamber have flanges at their ends that are beveled in the vertical direction (y-direction) pointing away from the chamber. A locking plate is attached to these flanges to close the chamber at the front.The strike plate connected to the flanges of the legs also serves to stiffen the beam, as it provides a box profile along the length of the strike plate. This design prevents one or the other leg of the beam from shifting relative to the other in the event of an impact. In some designs, the strike plate extends over the entire or virtually entire length of the beam.

[0003] The deformation behavior and strength of such a bumper cross member are largely determined by the depth of the beam's profiling. The depth of a bumper cross member, and thus its extension in the vehicle's longitudinal direction (x-direction), is generally limited. This must be taken into account when dimensioning the beam's profiling depth in conjunction with the design of the bumper cross member. In some cases, however, this is not sufficient to provide the bumper cross member with the desired strength. To remedy this situation, WO 2016 / 163054 A1 proposes incorporating a stiffening element into the beam's chamber.The stiffening element known from this prior art is an open or closed stiffening element with a roughly trapezoidal cross-section, which is welded to the base of its shorter trapezoidal side with the web of the beam connecting the legs. In a design in which the stiffening element is open, it has legs that are folded outwards in a vertical direction and are integrated into the joint between the folded flanges of the beam's legs and the strike plate. The stiffening element is located centrally with respect to the beam and extends only over a short section relative to its longitudinal extent.

[0004] Even if the installation of such a stiffening element can improve the crash performance of the bumper cross member in the so-called pole test, disadvantages must still be accepted. These include, firstly, the necessary welding of the stiffening element to the web of the support profile, which is not without problems, especially if the stiffening element is closed and thus designed as a hollow chamber profile, due to the lack of or extremely difficult accessibility of the joint.

[0005] Another bumper cross member with an insert is known from WO 2019 / 072653 A1. This insert has a U-shaped profile and is connected to the striker plate by means of a weld seam along its entire length, with the end faces of its legs facing forward in the direction of travel. The back of this insert is straight along the insert's length and is positioned within the beam chamber at a distance from the beam. This insert stiffens the bumper cross member. An additional stiffening element is inserted in the center section of this insert.

[0006] The aim of inserts such as those described above is to stiffen the bumper cross member, thus making it less susceptible to deformation. While on the one hand such a bumper cross member is intended to be stiffened by such an insert, it must also meet the usual test requirements, for example the MPDB test (Mobile Progressive Deformable Barrier) or the Pole test. Absorption of the impact force should occur not only via the crash boxes provided for this purpose, but also through deformation of the bumper cross member. Therefore, a bumper cross member must not be designed to be too stiff in those sections that are intended to deform, for example in an MPDB test. A problem with conventional bumper cross members is that after a certain amount of deformation, the side facing the vehicle chassis breaks open and can then no longer absorb energy.To counteract this, the supports and inserts are designed with appropriate wall thicknesses to prevent premature breakage. This is achieved at the expense of increased weight for the bumper cross member. Based on this discussed prior art, the invention is therefore based on the object of improving a bumper cross member in which an insert is arranged in the chamber of the support, in such a way that it has an improved crash performance, in particular can absorb even higher deformation rates without cracks or breakage.

[0007] This object is achieved according to the invention by a bumper cross member of the generic type mentioned at the outset, in which the back of the insert is convexly shaped at least in its middle section, relative to its longitudinal extent (y-direction).

[0008] The directions used in this document are those typically used in motor vehicles. Thus, the x-direction is the longitudinal direction of the vehicle, the y-direction is the transverse direction (width direction), and the z-direction is the vertical axis.

[0009] In this bumper cross member, the back of the insert is bulged toward the vehicle chassis, at least in its central section. This provides a material specification so that, in the event of an MPDB load case, greater deformation can be absorbed without cracking or breakage. The convex shape of the back of the insert, pointing away from the strike plate, is thus already preformed in the direction of the deformation to the dimensions of the convex shape corresponding to the deformation, thus already providing a deformation system for absorbing forces in an MPDB load case. The tensile forces acting on the back when force absorption is required are correspondingly lower.

[0010] This central section of the insert preferably extends over at least 25% of the distance between the two crash boxes installed on the bumper cross member for connecting it to the side members of a vehicle. This central section preferably occupies at least 35% to 40% of the longitudinal extent of the insert.

[0011] In a preferred embodiment, the improved crash performance described above is supported by providing a transition section shaped relative to the back between a central section with its convex shape and the respective end sections of the insert. This transition section is concave in one embodiment, but can also have a convex shape. These transition sections in the back of the insert create a material reservoir, allowing the insert to be stretched in these insert sections under the aforementioned load case without overloading due to the tensile forces acting on the back.

[0012] The insert is typically located centrally in its chamber with respect to the longitudinal extent of the beam. However, a different positioning is also possible, for example, if a different crash behavior is desired in relation to the width of the vehicle (longitudinal extent of the bumper cross member).

[0013] To further improve crash performance, i.e., to prevent bending of the bumper cross member in the x-direction, for example, in an MPDB load case, the insert can be connected to the striker plate only in individual sections that are spaced apart from one another along the insert's length. The striker plate with the attached insert is located on the side of the obstacle and thus on the inside of any deformation of the bumper cross member. This measure means that the sections between the connecting sections, where the insert is connected to the striker plate, act as prepared bending or buckling points. The reason for this is the lack of the weld seams typically required to connect the insert to the striker plate.This deformation behavior on the side of the bumper cross member facing the obstacle can be further enhanced if the insert does not contact the striker plate between its connection points, where it is connected to the striker plate, meaning that the leg ends facing the striker plate are spaced from the striker plate in these sections. Relative to the longitudinal extent of the insert, the sum of the extensions of the connection sections in this direction, with which the insert is connected to the striker plate, is less than the sum of the sections not connected to the striker plate, which, according to a preferred embodiment, are also spaced from the striker plate.

[0014] Thanks to the special design of the insert in this bumper cross member, it easily meets the crash performance requirements. The crash performance of the bumper cross member is significantly influenced by the design of the insert. Due to the special design of the insert, both the beam and the insert can be manufactured with relatively thinner walls. The same applies to the striker plate. The overall weight of the bumper cross member is correspondingly lower, despite the improved crash performance.

[0015] According to a preferred embodiment, the insert is arranged within the chamber of the support in such a way that it does not contact the support, while also maintaining a sufficient distance between the insert and the support. Should the bumper cross member be coated, for example, during dip painting, there are no gaps that are not wetted.

[0016] To achieve the crash performance described above, or in addition to this, the insert can have differently designed insert sections along its longitudinal extent in terms of its height, width, the final contour of the legs, and / or the material thickness. In this way, the crash performance of the bumper cross member as well as its strength can be influenced simply by the appropriate design and selection of the insert to be installed in a support. This means that one and the same supports and one and the same striker plates can be used for vehicles with different crash performance designs, whereby the bumper cross members formed from them with the respective insert differ only in their respective insert and / or in the design of the connecting sections of the insert to the striker plate.

[0017] Typically, the insert sections are designed to be mirror-symmetrical to the center of the insert. This can also be done differently if uneven crash behavior is required across the width of the vehicle and thus the longitudinal extent of the bumper cross member.

[0018] The transitions from a first insert section to the adjacent insert section can be provided equally in both legs of the insert and also aligned with each other in the z-direction. However, it is also possible for such transitions to be designed differently in the upper leg than in the lower leg. This affects both the positioning of the transition and the degree of change.

[0019] In a preferred embodiment of such a bumper cross member, the insert is divided into several insert sections along its longitudinal extent. Such an insert can, for example, have a central section as the first insert section and an end section adjoining it with an intermediate transition section. In a preferred embodiment, the transition section between the two end sections and the central section is tapered with respect to the cross-sectional area of ​​the insert, whereby such a taper can relate to both the height and / or the width of the insert.

[0020] Such a bumper cross member is typically connected to the striker plate by the legs of its two end sections and by the first section of the middle section. According to one embodiment, the sections of the insert located between these connecting sections are not connected to the striker plate and have a corresponding, typically concave, notch at the ends of their legs to prevent them from contacting the striker plate. According to another embodiment, the middle section is connected to the striker plate at its edge sections and additionally in the middle of this central section. The number and length of the respective connections, typically created by fusion joining, between the insert and the striker plate influence crash performance.Therefore, the type of connection of the insert to the striker plate can also be used to design the crash performance of the bumper cross member.

[0021] The support of such a bumper cross member is typically a hat profile. This can be made from a single steel plate. In such a case, it is advisable to also manufacture the striker plate and insert from sheet steel plates, as these components of the bumper cross member can then be easily fused together by welding.

[0022] The crash performance of the stressed bumper cross member can be optimized in a variety of ways by designing its insert or adapting it to the respective requirements, for example, so that during a pole test the deformed bumper cross member adheres to the outer surface of the pole without cracks or breakage.

[0023] With regard to the bumper cross member according to the invention, it should also be emphasized that, due to the connection of the insert to the striker plate, this connection remains intact even if the bumper cross member breaks on its side facing the vehicle chassis due to excessive force, for example, during a pole test. Fracture on the side of the bumper cross member facing away from the vehicle chassis is prevented by the connection of the insert.

[0024] The invention is described below using exemplary embodiments with reference to the accompanying figures. They show: Fig. 1: a three-dimensional representation of a bumper cross member according to the invention, in which the front locking plate is shown transparent to allow identification of the insert located therein. Fig. 2: the insert of the bumper cross member of the Fig. 1 in a perspective view, Fig. 3: a longitudinal section in the xy plane through the bumper cross member of the Fig. 1, Fig. 4: another bumper cross member according to the invention, which differs from that of the Fig. 3 by using a different insert, Fig. 5: the bumper cross member of the Fig. 4, Fig. 6: the bumper cross member deformed by the obstacle of the Fig. 5 and Fig. 7: a representation corresponding to that of the Fig. 6, but with a cross member according to the state of the art.

[0025] A bumper cross member 1 for a motor vehicle comprises a support 2. The support 2 is a U-shaped profile made from a sheet steel blank. In an embodiment not shown in the figures, the support 2 is designed as a hat profile. The support 2 extends over the entire longitudinal extent of the bumper cross member 1. The open side of the support 2 points forward in the direction of travel (x-direction). At the front, the support 2 is closed by a locking plate 3 in a manner known per se. Two crash boxes 4, 4.1 are connected at a distance from one another to the rear of the support 2 facing the vehicle chassis. The bumper cross member 1 is fastened to the chassis side by means of these crash boxes.

[0026] The profiling of the support 2 is provided by an upper web 5, a lower web 6, and a web 7 connecting the two webs 5, 6 along their longitudinal side facing the chassis. The two legs 5, 6 and the web 7 enclose a chamber 8. This chamber is closed at the front by the strike plate 3. The support 2 with the strike plate 3 thus forms a hollow chamber profile.

[0027] An insert 9 is arranged within chamber 8. The insert 9 is also U-shaped. Its open side, like that of the support 2, faces in the direction of travel (x-direction). The insert is connected by welded joints to the side of the strike plate 3 facing chamber 8 by sections of the end faces of its legs 10, 11.

[0028] The design of insert 9 is explained below using the perspective view of the Fig. 2. The two legs 10, 11 are connected to one another at their rear, longitudinal end by a spine 12. In contrast to previously known inserts of this type, the spine 12 is not straight, but in the illustrated embodiment is characterized by straight sections at the ends, an adjoining concave section, and a central section that is convexly shaped in the direction of the web 7 of the support 2. The legs 10, 11 also do not run uniformly over the longitudinal extent of the insert 9. Their width changes over the longitudinal extent of the insert 9. The spine 12 is not only non-uniform in terms of its longitudinal extension over its longitudinal extent, but also differently designed with regard to its height (extension in the z-direction). In a central section, the height of the insert 9 is less than in the sections adjacent to it on either side.

[0029] The structural division of insert 9 is shown in the longitudinal section of the Fig. 3. The insert 9 comprises a central section 13. This section is the section in which the back 12 is convex in the direction of the vehicle chassis and is thus bulged. The central section 13 merges into a transition section 14, 14.1, which in turn is followed by an end section 15. The back 12 of the illustrated embodiment is straight in the region of its end sections 15, 15.1 and runs parallel or approximately parallel to the web 7 of the support 2 in these sections. In the transition sections 14, 14.1 the insert 9 is tapered, whereby its cross-sectional area is significantly reduced, namely to approximately 50% in the illustrated embodiment. The waist is achieved by a concave shape of the back 12 in the transition sections 14, 14.1 and a likewise concave shape of the leg ends pointing to the strike plate 3 (in Fig. 3 (visible through the lower leg 11). The leg ends of the insert 9 pointing towards the striking plate 3 are also contoured in the central section 13 in such a way that they do not rest against the inside of the striking plate 3 over their entire extent. In the exemplary embodiment shown, the leg ends rest against the inside of the striking plate 3 in three sections of the central section 13. In these sections, also referred to as connecting sections 16, the leg ends of the legs 10, 11 are connected to the inside of the striking plate 3 by means of a weld seam. The connecting sections 16 are arranged at a distance from one another in the direction of the longitudinal extent of the insert 9. The leg ends of the insert 9 between the connecting sections 16, however, do not contact the inside of the insert 3.These sections are also concavely shaped, whereby the leg ends are spaced from the inside of the striking plate 3.

[0030] In addition to the connection points 13 of the central section 6, the insert 9 is also connected to the striking plate 3 by welding via the leg ends of the end sections 15, 15.1.

[0031] The central section 13 is, as can be seen Fig. 2, additionally structured by the fact that the middle area of ​​the central section 13 has a lower back height than in the adjacent sections.

[0032] Fig. Figure 4 shows a longitudinal section of a bumper cross member 1.1 which, with the exception of the contouring of the leg ends of its insert 9.1, corresponds to the bumper cross member 1 of the preceding figures. In this respect, the statements regarding the bumper cross member 1 apply equally to the bumper cross member 1.1. The insert 9.1 has only two connection points 16.1 in its central section 13.1. The third connection point 16 located between the two outer connection points 16 of the insert 9 is not provided in the insert 9.1. In this exemplary embodiment, the entire intermediate piece between the two connection points 16.1 is not in contact with the inside of the striker plate 3 and is concave over this length.

[0033] The above-mentioned bumper cross members 1, 1.1 are significantly improved in terms of their crash performance compared to conventional bumpers in which inserts are inserted into the member but which do not have the structure of the inserts 9 or 9.1.

[0034] Fig. 5 shows the bumper cross member 1 in a representation corresponding to that of Fig. 3 in front of an obstacle H. The bumper cross member 1 moves in the x-direction towards the obstacle H. The special design of the insert 9 causes the bumper cross member 1 to wrap around the obstacle H, but without cracking or even breaking. The reason for this is the special design of the insert 9, which provides a curvature or deformation facility on the tensile side (the side facing the vehicle chassis) due to the convex design of its central section 13 and the material specification present in the transition sections 14, 14.1 as a result of the convex shape. For this reason, the back 12 of the insert 10 can absorb or withstand significantly higher tensile forces than conventional bumper cross members.

[0035] Fig. 6 shows the bumper cross member 1 after a deformation of about 260 mm, which was crack-free due to deformation of the bumper cross member 1, as in Fig. 6. The concave recesses on the strike plate side serve as predefined bending or kinking points.

[0036] Fig. For comparison, Figure 7 shows a bumper cross member 17 with a conventional insert 18, which has the same cross-sectional geometry over its entire longitudinal extent. It is clearly evident in this illustration that for the same amount of deformation as the bumper cross member 1 of the Fig. 6 has been easily picked up, the bumper cross member 17 is broken.

[0037] Through the described measures, the crash performance efficiency of the bumper cross member according to the invention is significantly increased, specifically by approximately 30% to 40% in the illustrated embodiment. Compared to the bumper cross member 17 according to the prior art, the bumper cross member 1 has a weight that is 2.5 kg, generally about 20 to 30% lower. The energy absorbed during the illustrated deformation is approximately 2.6 kJ / kg. In the bumper cross member 17, as shown in Fig. As shown in Figure 7, only 2.0 kJ / kg can be absorbed. The lower mass and higher energy absorption result in significantly increased efficiency.

[0038] The invention has been described using exemplary embodiments. Without departing from the scope of the applicable claims, numerous further 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 carriers 3 strike plate 4, 4.1 Crashbox 5 legs 6 legs 7 jetty 8 chamber 9, 9.1 Insert 10 legs 11 legs 12 backs 13, 13.1 Central section 14, 14.1 Transitional section 15, 15.1 Final section 16, 16.1 Connection section 17 bumper cross members (state of the art) 18 inserts (state of the art) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2016 / 163054 A1

[0003] WO 2019 / 072653 A1

[0005]

Claims

[1] Bumper cross member for a vehicle - with a support (2) extending in its longitudinal axis in the transverse direction of the vehicle (y-direction) and open in the direction of travel (x-direction) with a chamber (8) enclosed by an upper leg (5), a lower leg (6) and a web (7) connecting the two legs (5, 6) in the vertical direction of the vehicle (z-direction), - with a locking plate (3) spanning the support opening in the vehicle vertical direction (z-direction) and connected to the legs (5, 6) of the support (2) and - with an insert (9, 9.1) arranged in the chamber (8) of the carrier (2), having an upper leg (10), a lower leg (11) and a back (12) connecting the legs (10, 11) at their rear end, the open side of which points in the direction of travel (x-direction) and the legs (10, 11) of which are connected to the striking plate (3), characterized bythat the back (12) of the insert (9, 9.1) is convexly shaped at least in its central section, relative to its longitudinal extent (y-direction). [2] Bumper cross member according to claim 1, characterized by that the insert (9, 9.1) is arranged centrally in its chamber (8) with respect to the longitudinal extent of the carrier (2). [3] Bumper cross member according to claim 1 or 2, characterized by that the insert (9, 9.1) is connected to the striking plate (3) with its legs (10, 11) only in individual sections spaced apart from one another in the direction of its longitudinal extension. [4] Bumper cross member according to claim 3, characterized by that the legs (10, 11) of the insert (9, 9.1) only reach up to the striking plate (3) in those sections in which they are connected to the striking plate (3) and are spaced from the striking plate (3) in the sections in between. [5] Bumper cross member according to one of claims 1 to 4, characterized by that the maximum height of the insert (9, 9.1) (extension in z-direction) is less than the height of the chamber (8) of the carrier (2). [6] Bumper cross member according to claim 5, characterized by that the insert (9, 9.1) is arranged within the chamber (8) of the carrier (2) at a distance from its legs (5, 6) and its web (7). [7] Bumper cross member according to claim 5 or 6, characterized by that the insert (9, 9.1) is arranged centrally in relation to the height of the chamber (8) of the carrier (2). [8] Bumper cross member according to one of claims 1 to 7, characterized by that the insert (9, 9.1) has insert sections (13, 14, 14.1, 15, 15.1; 13.1) which are differently designed in relation to its height, its width, the contour of the leg ends and / or its material thickness in the direction of its longitudinal extent. [9] Bumper cross member according to claim 8, characterized by that the insert sections (13, 14, 14.1, 15, 15.1; 13.1) are designed mirror-symmetrically to the center of the insert (9, 9.1) with respect to its longitudinal extent. [10] Bumper cross member according to claim 8 or 9, characterized by that the transitions from the legs (10, 11) of a first insert section to an adjacent second insert section are designed differently. [11] Bumper cross member according to one of claims 8 to 10, characterized by that the insert (9, 9.1) has a central section (13) and an end section (15, 15.1) as insert sections, wherein the end sections (15, 15.1) are separated from the central section (13) by a transition section (14, 14.1) as a further insert section with a concave contouring of the back (12). [12] Bumper cross member according to claim 11, characterized bythat in the transition section (14, 14.1) the leg ends also have a concave contour. [13] Bumper cross member according to claim 11 or 12, characterized by that the legs of the end sections (15, 15.1) and those of the first section of the central section (13, 13.1) are connected to the striking plate (3). [14] Bumper cross member according to claim 13, characterized by that those sections with which the insert (9, 9.1) is connected with its legs to the striking plate (3) are the only connection points (16, 16.1) of the insert (9, 9.1) to the striking plate (3). [15] Bumper cross member according to claim 13, characterized by that the insert (9) is additionally connected to the striking plate (3) with its legs in the middle of its central section (13). [16] Bumper cross member according to one of claims 1 to 15, characterized bythat the carrier (2), the striking plate (3) and the insert (9, 9.1) are parts made of sheet steel plates. [17] Bumper cross member according to one of claims 1 to 16, characterized by that the insert (9) is connected to the striking plate (3) and the striking plate (3) is connected to the legs (5, 6) of the carrier (2) by fusion joints, in particular welding.

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