Bumper crossmember for a motor vehicle with an opening for passing a tow hook through it

Abstract

The invention relates to a bumper crossmember 1, 1.1, 1.2 for a motor vehicle having an opening 6, 6.1, 6.2 pointing in the x-direction for guiding a towing hook 9 through it, wherein the towing hook 9 can be attached at a distance from the opening 6, 6.1, 6.2, so that when a vehicle is towed, a towing hook 9 guided through the opening 6, 6.1, 6.2 and attached at a distance from the opening 6, 6.1, 6.2 contacts the edge 15, 15.1, 15.2 of the bumper crossmember-side opening 6, 6.1, 6.2 due to a lateral load occurring during towing. A special feature is that at least one groove 7, 7.1, 8, 18, 19, 20 is provided at the edge 15, 15.1, 15.2 of the opening 6, 6.1, 6.2 pointing in the y-direction, and at least one unembossed area is provided at the edge 15, 15.1, 15.2 of the opening 6, 6.1, 6.2 pointing in the y-direction, and at least one unembossed area is provided at the edge 15, 15.1, 15.2 of the opening 6, 6.1, 6.2 pointing in the z-direction.

Description

[0001] The invention relates to a bumper crossmember for a motor vehicle with the features of the preamble of claim 1.

[0002] Bumper crossmembers are part of the crash management system in a motor vehicle. They are located at the front and rear of the vehicle and extend – relative to the vehicle – essentially in the y-direction from one side of the vehicle to the other. A bumper crossmember is typically connected to the longitudinal members of the vehicle chassis via two crash boxes at its ends.

[0003] Bumper crossmembers can be designed as extruded profiles. Single- or multi-shell, usually double-shell, bumper crossmembers formed or assembled from appropriately shaped sheets are also known in the art.

[0004] A motor vehicle also has a provision at the front and rear for mounting a tow hook if needed. This tow hook serves as an attachment point for towing the vehicle in the event of a breakdown or for towing another vehicle. Such a tow hook is not usually permanently mounted. Instead, a corresponding bracket is provided, which is typically covered by a cover on many vehicles. When the tow hook is needed, the cover is removed and the tow hook is attached to the bracket.

[0005] A tow hook comprises a shaft with a towing eye at one distal end, which can typically be connected indirectly to a vehicle being towed or towing the vehicle. At its other distal end, the shaft has a mounting section that corresponds to the vehicle-side bracket. The bracket is usually a threaded sleeve and the mounting section a threaded section. Other connection types, such as bayonet fittings, are also possible.

[0006] Various designs are known for the attachment points of such a tow hook.

[0007] DE 10 2021 107 065 A1 discloses a bumper crossmember with a towing sleeve, which is attached directly to the two shell walls of a bumper crossmember spaced apart from each other in the x-direction of the motor vehicle. The towing sleeve is enclosed by the bumper crossmember and partially projects out of the bumper crossmember in the towing direction.

[0008] EP 3 724 012 A1 discloses a different concept: Here, the tow hook is anchored to a bracket in a sleeve on the vehicle chassis, spaced apart from the outwardly facing shell. It therefore protrudes through the bumper crossmember, or at least through the front wall of the bumper crossmember. The front wall of the bumper crossmember provides an opening in the x-direction for the tow hook to pass through. This means that the tow hook is attached at a distance from the opening.

[0009] Due to the spacing of the tow hook bracket – for example, on the flange plate of the longitudinal member or the crash box – from the corresponding bumper crossmember wall with the opening, some pivoting of the tow hook from the bracket within the bumper crossmember opening is unavoidable. This is due to the material elasticity of the bracket connection, the bracket itself, and the tow hook itself. Therefore, contact between the tow hook and the edge of the bumper crossmember opening cannot be ruled out, meaning that the tow hook will also bear against the edge of the bumper crossmember opening in the event of lateral loads.

[0010] Depending on the load, this support can lead to a tear in the bumper cross member, especially if the tow hook does not have a circular, but rather a cross-shaped cross-sectional contour in its shaft area.

[0011] To address this problem, it is known in the prior art to provide reinforcing plates or reinforcing sleeves in this area, as disclosed, for example, in JP 2015189289 A.

[0012] A disadvantage of such additional reinforcement elements is not only the resulting increase in the overall weight of the structure, but also the prevention of uniform deformation of the bumper crossmember in this area during a crash. If the tow hook is attached to the flange plate and routed through the crash box, additional reinforcement elements are avoided, as this area is specifically designed to be deformed or folded in a crash.

[0013] Against the background of the problems outlined, the invention aims to propose a bumper crossmember that not only has a lower probability of tearing in the area of ​​the opening for a tow hook compared to previously known designs, but also has a reduced weight and is simpler to manufacture. Furthermore, the invention aims to provide an arrangement for a crash management system of a motor vehicle.

[0014] The problem relating to the bumper crossmember is solved by a bumper crossmember of the aforementioned type with the features of claim 1. The problem relating to the arrangement is solved by an arrangement with the features of claim 12.

[0015] Advantageous designs result from the dependent requirements and the description.

[0016] When x, y, or z directions are mentioned below in relation to the bumper crossmember, these directions refer to the standard coordinate system of a motor vehicle when the bumper crossmember is mounted. This means that the bumper crossmember extends primarily in the y-direction (transverse direction) and has a smaller extension in the z-direction (vertical direction). The direction from which a force is potentially introduced in an accident is the x-direction. A tow hook, when mounted, also points in this direction, as does the opening in the bumper crossmember, allowing the tow hook to pass through it.

[0017] Furthermore, y- and z-regions are defined on the bumper crossmember around the opening: A y-region of the bumper crossmember is an area that adjoins the opening in the y-direction, thus, with a mounted bumper crossmember, to the left or right of the opening. A z-region is an area that adjoins the opening of the bumper crossmember in the z-direction, thus, with a mounted bumper crossmember, above or below the opening.

[0018] The core of the invention is that one or more beads are provided only partially at the edge of the opening for the tow hook on the bumper crossmember side. This means: There is an area in which at least one bead is provided, and an area adjacent to this at the edge of the opening that is unembossed and therefore has no bead.

[0019] According to the invention, the area equipped with at least one bead is at least a y-area; the areas that do not have a bead are the two opposing z-areas. This means that when the bumper crossmember is mounted on a motor vehicle, at least one bead is arranged in the right and / or left area around the opening, while an unembossed area is provided above and below the opening.

[0020] An "unembossed area" does not mean that the bumper crossmember in the opening area should not be deformed at all. It merely means that no additional local embossing is provided at the edge of the opening. The aim of the inventive design is to provide areas of varying stiffness along the edge of the opening. Those areas that have an additional rib are stiffened geometrically and also by inherent work hardening compared to those areas that do not have a rib. This means that while at least one y-region (right / left) around the opening should be stiffened with at least one rib, the z-region (above / below) should be softer in comparison. This design allows the z-region to yield slightly in the y-direction when the tow hook is supported against the edge of the bumper crossmember opening, thus supporting the stiffened areas.The intention is to create a tensile deformation of the z-areas in order to relieve the at least one loaded, stiffened y-area and thus distribute the forces introduced into the stiffened area evenly and in a distributed manner into the material of the bumper cross member.

[0021] For optimal force transmission into the y-region, which has at least one bead, the bead terminates in the opening. This means that the bead is closed only on one side; it is open at the edge, so that the opening intersects the bead in cross-section. As a result, when the tow hook contacts the edge of the opening, the force is transmitted into the deformed area of ​​the bead, which is particularly stiffened by the geometric stiffening and work hardening. The longitudinal extent of the at least one bead is essentially radial to the opening. This orientation directs the force introduced into the bead far into the material surrounding the opening, thus already resulting in a more uniform force transmission.

[0022] Additional reinforcing plates or other reinforcing elements are not necessarily required at the edge of the opening.

[0023] In many cases, the bumper crossmember is curved in the y-direction, and the opening is positioned eccentrically on the bumper crossmember with respect to the y-direction. This means that, in the area of ​​the opening, the material surrounding the opening is angled relative to the exact y-direction, such that the material surrounding the opening forms an angle of essentially other than 90° with the x-direction in which a tow hook, when mounted, points. It is then preferably provided that the at least one groove, in the area of ​​its opening, is designed such that it forms an angle of 90° ± 6° with the x-axis, preferably an angle of 90° ± 4°. The groove thus orients the material forming the edge of the opening differently than the material surrounding the groove and the opening.This ensures that the edge of the opening is essentially perpendicular to the tow hook, so that when the tow hook contacts the edge, the force is applied perpendicularly to the edge, preventing the material from slipping off the tow hook. Furthermore, this design directs the force applied to the edge of the opening as a compressive force towards the face of the opening, resulting in improved force transmission into the material surrounding the opening.

[0024] Preferably, the groove is positioned along its longitudinal axis at a substantially 90° angle to the exact x-direction over at least 10%, preferably at least 25%, and more preferably at least 50% of the diameter of the opening.

[0025] If it is intended that at least one groove is provided in only one of the two y-areas, it is preferred if the y-area that points towards the center of the bumper crossmember has at least one groove.

[0026] Alternatively, it is provided that at least one groove leading into the opening is provided on both sides of the opening in the y-direction, pointing in the y-direction. This means that at least one groove leading into the opening is provided in each of the two y-regions. These grooves can be of the same or different dimensions. Preferably, however, their arrangement—even if they are of different dimensions—is mirror-symmetrical with respect to the y-direction.

[0027] Furthermore, it is preferably provided that, if at least one groove is provided on each side of the opening, these grooves are of different sizes. The width of one groove is preferably less than 80%, preferably less than 75%, of the width of the opposite groove. Typically, the narrower groove is arranged on the side of the opening that is closer to a distal end of the bumper crossmember, and the wider groove on the side that faces the center of the bumper crossmember.

[0028] In a further preferred embodiment, if at least one bead is provided on each side of the opening, the orientation of the opposite bead is inverse, meaning that the one or more beads on one side of the opening are oriented in one x-direction and the one or more beads on the other side in the opposite x-direction. This facilitates the simple manufacture of the bumper crossmember.

[0029] If the bumper crossmember is curved in the y-direction, one embodiment provides that the embossed direction of the bead, which is arranged on the side towards the center of the bumper crossmember relative to the y-direction, points against the direction of curvature. Typically, the bumper crossmember is curved such that the convex side faces outwards. In this case, the direction of curvature points towards the vehicle. If at least one bead is provided in each of the two y-regions of the bumper crossmember, the bead that is arranged on the side towards the center of the bumper crossmember relative to the y-direction preferably points against the direction of curvature.The preferred design allows for easy production of the beads, even if the bumper cross member is curved: The bumper cross member, including the opening and the beads, can be formed in one forming step, with the press tool being able to form in the x-direction.

[0030] Preferably, the edge region of the opening, which has at least one bead, comprises at least 25%, preferably at least 40%, and more preferably at least 75% of the diameter of the opening on the bumper crossmember side. If several beads are arranged in a y-region, the aforementioned region refers to the total area of ​​the beads in that y-region. Preferably, the bead or beads together have a width of no more than 95%, more preferably no more than 85%, and more preferably no more than 75% of the diameter of the opening. The width of the bead is, in any case, substantially in the z-direction. It has been observed that significant effects can be achieved even with a relatively small partial embossing.

[0031] Preferably, the bead(s) should have a length of at least 20%, preferably at least 50%, more preferably at least 75%, and more preferably at least 110% of the diameter of the opening on the bumper crossmember side. It is also preferred that the bead(s) have a length of no more than 300% of the diameter of the opening. More preferably, the bead(s) should have a length of no more than 200%, and more preferably not more than 150%, of the diameter of the opening. The length of the bead is in any case substantially in the y-direction, although it is conceivable that the bead be set at an angle of less than 75° to the y-direction.

[0032] Preferably, the groove tapers to a point on its side facing away from the opening, particularly in an ogival shape. This improves the transition to the non-grooved material, as material closer to the opening is available that is not additionally embossed and is therefore softer, thus better supporting the forces introduced into the edge of the opening. At the same time, this prevents this soft material from being subjected to point loads from the tow hook.

[0033] Preferably, the height of the indentation in the bead is at least the material thickness of the material surrounding the opening in the bead area, preferably twice the material thickness. This achieves sufficient geometric stiffening with accompanying work hardening. It can also be provided that the height of the bead decreases continuously or tapering to a point, approximately ogival, along the bead extending away from the opening.

[0034] Preferably, at least two adjacent beads are provided in at least one y-region at the edge of the opening, oriented in a star shape with respect to the opening on the bumper crossmember side. This means that their longitudinal extent is essentially radial to the opening on the bumper crossmember side. An unembossed area is then provided between these two beads. This softer area provides additional support to the respective y-region. Alternatively, three beads arranged in a star shape may be provided in one y-region.

[0035] Typically, the bumper crossmember is made of a steel or aluminum alloy of various grades. Preferably, it is a single-shell design. In this case, the bumper crossmember consists solely of a sheet metal plate, which is usually profiled, for example, in a shell-like profile. The tow hook is then spaced apart from the bumper crossmember, usually mounted on a flange plate on the longitudinal member side or on the bottom side of the crash box. Such a bumper crossmember is particularly lightweight, and the advantages of this lightweight design are not lost due to the inventive design of the opening for a tow hook. At the same time, such a single-shell bumper crossmember is particularly prone to cracking, which must be avoided to ensure the complete functionality of the bumper crossmember.

[0036] A crash management system according to the invention comprises a bumper crossmember, which is preferably single-shell, and which bumper crossmember can be connected to each longitudinal member of the chassis of a motor vehicle by means of two crash boxes. A flange plate is provided for connecting the crash boxes to the longitudinal member, which is located on the longitudinal member side and / or on the crash box side. The crash boxes are connected to the longitudinal members at the flange plates, usually by means of a bolted connection.

[0037] A bracket for a tow hook, preferably designed as a screw sleeve, is provided on a flange plate. The bracket is located inside the crash box. A tow hook can be mounted in this bracket. For installation, the tow hook is inserted through an opening in the bumper crossmember that is aligned with the bracket. The tow hook thus protrudes from the bumper crossmember.

[0038] The opening in the bumper crossmember, which is aligned with the bracket and through which the tow hook is then passed, is designed according to the above descriptions, so that the edge of the opening is stiffened in the y-direction.

[0039] Even if a lateral load in the y-direction acts on the towing hook and the towing hook contacts the edge of the opening in the bumper cross member, the partial stiffening of the edge of the opening effectively prevents the bumper cross member from tearing in the area of ​​the opening.

[0040] The invention is explained in more detail with reference to the accompanying figures. They show: Fig. 1: An arrangement of a crash management system according to the invention with a bumper crossmember according to the invention in a perspective view, Fig. 2a: a sectional top view of the bumper crossmember according to the invention, Fig. 2b: the arrangement shown in Fig. 2a, with a mounted tow hook, Fig. 3: A close-up of a front view of the bumper crossmember with an opening for the tow hook, Fig. 4: a side view, corresponding to Fig. 3, Fig. 5: a sectional top view, corresponding to Fig. 3, Fig. 6: a detailed view of the front view of a second bumper crossmember according to the invention, wherein a towing hook is passed through the opening provided, Fig. 7: one to Fig. 6 corresponding, sectioned top view, and Fig. 8: a front view of a third bumper crossmember according to the invention.

[0041] Fig. Figure 1 shows a bumper crossmember 1 in a perspective view. The direction axes x, y and z referenced in the description are also shown.

[0042] The bumper crossmember 1, made of a steel material, is part of a crash management system 2, comprising the bumper crossmember 1 and two crash boxes 3, 4, which are connected on one side to the bumper crossmember 1 and on the other side each to a flange plate 5a, 5b. These flange plates 5a, 5b are attached to a longitudinal member of a vehicle chassis (not shown) for fastening the crash management system 2, here by means of a bolted connection. The bumper crossmember 1 extends essentially across the width of the vehicle in the y-direction and is designed as a profiled sheet metal in the z-direction. It is therefore designed as a single-shell structure in this embodiment. Furthermore, the bumper crossmember 1 is curved in the y-direction; its curvature direction points essentially in the x-direction towards the sides of the crash boxes 3, 4.

[0043] The bumper crossmember 1 has an opening 6 in the area of ​​a crash box 3. A tow hook 9 can be inserted through this opening 6. Two ribs 7, 8 are provided at the edge of the opening in the y-direction, each of which opens into the opening 6. In the z-direction, however, the edge of the opening 6 is free of additional ribs and indentations.

[0044] The Fig. 2a and Fig. 2b shows this in Fig. Figure 1 shows a sectional top view of the crash management system 2. The crash management system 2 is cut through the center point of opening 6.

[0045] Additionally, in Fig. 2b A towing hook 9 is passed through the opening 6 and attached to a bracket 10 connected to the flange plate 5a. The bracket 10 has a mounting section 11, here a threaded sleeve. Complementarily, the towing hook 9 has a complementary fastening section 13, here a threaded bolt, at one distal end of its shaft 12. At the other distal end of the shaft 12, the towing hook 9 has a towing eye 14.

[0046] The in the Fig. 1, Fig. 2a and Fig. The grooves 7 and 8 shown in 2b are also referred to in the Fig. Sections 3 to 5 are explained in more detail. The mounting section 11 is spaced in the x-direction from the bumper crossmember 1, or rather from the part of the bumper crossmember 1 that has the opening 6 for the tow hook 9. This means that, under a lateral load on the tow hook 9 in the y-direction, the outer surface of the tow hook 9 may bear against the edge 15 of the opening 6. Such bearing can potentially lead to a tear in the material of the edge 15 of the opening 6.

[0047] To counteract this, in this first embodiment, a bead 7, 8 is provided on both sides of the opening 6 in the y-direction. These beads 7, 8 stiffen the edge 15 of the opening 6 in the y-direction. The areas in which the beads 7, 8 are arranged in this first embodiment can also be referred to as y-areas. These are in Fig. Figure 3 is shown in a sketched, structured manner, with the y-regions designated by reference numeral 16 and the z-regions by reference numeral 17. A special feature is that the edge 15 of the opening 6 only partially has at least one groove 7, 8, and furthermore, there are areas along the edge 15 of the opening 6 that do not have a groove. According to the invention, these non-grooved areas are the z-regions and are thus arranged above and below the opening 6.

[0048] Especially in the Fig. 2a, Fig. 2b and Fig. Figure 5 clearly shows that the pre-embossing direction of the opposing beads 7, 8 is inverse: While the bead 7, which is located on the side towards the center of the bumper cross member 1 with respect to the y-direction, is embossed outwards, the pre-embossing direction of the other bead 8 points inwards, towards crash box 3 and thus towards the motor vehicle not shown.

[0049] In the present embodiment, the widths of the ribs 7 and 8, which are symmetrically opposite each other with respect to the y-direction, differ. The rib 7 that is embossed outwards and thus protrudes against the direction of curvature of the bumper crossmember 1 is wider than the rib 8 that is embossed in the direction of curvature.

[0050] Fig. 6 and Fig. Figure 7 shows a further embodiment of a bumper crossmember 1.1. In this embodiment, the edge 15.1 of the opening 6.1 for guiding a tow hook 9 is provided only with a groove 7.1 in a y-region, namely in the y-region that points towards the center of the bumper crossmember 1.1. The tow hook 9 is in the Fig. 6 and Fig. 7 is also at least partially depicted.

[0051] The bumper crossmember 1.1 is curved, analogous to the one in the Fig. 1 and Fig. 2 bumper crossmember 1 shown and thus positioned in the area of ​​opening 6.1 relative to the exact y-direction. For optimal force transmission from the tow hook 9 into the groove 7.1, this embodiment provides that the groove 7.1, in the area of ​​its opening towards the edge 15.1, is aligned with the Fig. The x-axis shown in Figure 7 forms an angle of essentially 90°. This results in the edge 15.1 being perpendicular to the shaft 12 of the tow hook 9. This prevents the edge 15.1 of the opening 6.1 from sliding along the shaft 12 of the tow hook 9 when the tow hook 9 is supported against the edge 15.1 of the opening 6.1.

[0052] Fig. Figure 8 shows a further embodiment with another bumper crossmember 1.2, which is constructed analogously to the one shown in the Fig.Figures 1 to 2 are shown. However, in this embodiment, the opening 6.2 for guiding a tow hook (not shown) is bordered by three beads 18, 19, 20 in the edge region 15.2 of the opening 6.2. The beads 18, 19, 20 terminate in the opening 6.2, respectively, at the edge 15.2.

[0053] At their end pointing away from the opening 6.2, the beads 18, 19, 20 are ogival in shape, thus essentially tapering to a point. Their respective longitudinal extents are arranged essentially in a star shape relative to the opening 6.2. In this embodiment as well, the three beads 18, 19, 20 are provided only in one of the two y-regions, namely the one that points towards the center of the bumper crossmember 1.2 with respect to the y-direction.

[0054] The invention has been explained using three exemplary embodiments. Without departing from the scope of protection described by the applicable claims, numerous further embodiments of the inventive concept would be apparent to the person skilled in the art, without these needing to be explained in more detail within the scope of these explanations. Reference symbol list 1, 1.1, 1.2 Bumper crossmember 2 Crash management system 3, 4 Crashbox 5a, 5b Flange plate 6, 6.1, 6.2 Opening 7, 7.1, 8, 18, 19, 20 groove 9 tow hooks 10 brackets 11 Mounting section 12 shaft 13 Fastening section 14 Towing eye 15, 15.1, 15.2 Margin 16 y-range 17 z-range QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2021 107 065 A1

[0007] EP 3 724 012 A1

[0008] JP 2015189289 A

[0011]

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