BUMPER FOR A MOTOR VEHICLE

Description

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

[0002] Bumpers are installed at the front and rear of motor vehicles to absorb the impact energy from collisions, thus minimizing damage to the vehicle's structural integrity. Bumpers also help to minimize injuries to people. A bumper has a crossmember that incorporates deformation elements in the form of crash boxes, positioned transversely to the longitudinal members of the vehicle frame. The crossmember serves to transfer the energy resulting from an impact into the crash boxes, where the impact energy is converted into deformation work. The bumper's design is such that the crash boxes are positioned as centrally as possible on the vehicle's longitudinal members, and the impact energy is transferred via the crossmembers into the crash boxes, and thus also into the trailing arms, with the lowest possible bending moment.

[0003] Bumpers must comply with legal regulations as well as pedestrian protection requirements. Good crash performance and a space- and weight-optimized design are prerequisites that must be in line with the high demands placed on the safety structure of a motor vehicle. Strict safety requirements must be met, which are verified through crash tests such as the pole test or the RCAR bumper test.

[0004] According to EP 1 928 704 B1, a bumper with a crossmember and two crash boxes is considered state of the art. The crossmember has a hat-shaped profile in cross-section with a web and two legs. Each crash box has an upper and a lower connecting section on the crossmember side. These overlap the upper and lower legs, respectively, and are joined to them.

[0005] US Patent 2006 / 125254 A1 discloses a bumper for a motor vehicle with a crossmember and crash boxes according to the preamble of claim 1, wherein the crossmember has an upper leg and a lower leg connected by a web. A crash box has a coupling section on the crossmember side, which overlaps and is joined to the upper and lower legs. The coupling section has an open recess at its end face. At least one wall section bounding the recess is welded to the upper leg or the lower leg.

[0006] A similar proposal is also found in US 2022 / 0001818 A1.

[0007] In the area where a crash box connects to the crossbeam, a relatively flexible zone is advantageous. Otherwise, cracking and even failure can occur. Current solutions do not offer the best conditions in this regard.

[0008] Starting from the prior art, the invention is based on the objective of providing a functionally improved bumper for a motor vehicle, exhibiting advantageous load and deformation behavior and, in particular, improved with regard to the connection between the cross member and the crash box. The solution to this objective is a bumper according to claim 1. Advantageous embodiments and further developments of the bumper according to the invention are the subject of the dependent claims.

[0009] Designs and modifications of features of the motor vehicle bumper, which individually or in combination make the bumper functionally and technologically advantageous, also result from the description and the accompanying drawings.

[0010] Directional specifications refer to the installation position of the bumper in a motor vehicle and a vehicle coordinate system. A vehicle coordinate system is a three-dimensional Cartesian coordinate system used to define the axes within a motor vehicle and of its components. The x- and y-axes lie in a horizontal plane (the vehicle plane). The x-axis corresponds to the vehicle's longitudinal axis, the y-axis to the vehicle's transverse axis, and the z-axis to the vehicle's vertical axis.

[0011] A motor vehicle bumper consists of a crossmember and crash boxes. The crossmember has an upper leg and a lower leg, which are connected by a web. A crash box has at least one coupling section on its crossmember side, i.e., at its end facing the crossmember. This coupling section overlaps the upper or lower leg and is bonded to it by a material connection.

[0012] The coupling section has a recess open at its front face. At least one wall section bordering the recess is welded to the upper or lower leg.

[0013] This design enables a manufacturing-efficient joining process and a connection between the crash box and crossbeam that is advantageous in terms of load and deformation behavior. In the connection area between a crash box and a crossbeam, both the crash box and the crossbeam deform upon impact. The crossbeam is stretched in front of the crash box without cracking occurring.

[0014] Preferably, the coupling section is configured in a forked shape and has two prongs that laterally define the recess. The prongs extend to the right and left of the recess along the vehicle's longitudinal axis (x-axis). The prongs are welded to the leg of the crossmember and stabilize and support it in the event of a crash.

[0015] The bumper according to the invention provides that the cross member has an outwardly directed upper front web adjoining the upper leg and / or an outwardly directed lower front web adjoining the lower leg, wherein the coupling section is joined to the upper front web or the lower front web.

[0016] In particular, the crossbeam has an upper front web and a lower front web. Furthermore, a crash box has an upper coupling section and a lower coupling section. The upper coupling section overlaps the upper leg of the crossbeam. The lower coupling section overlaps the lower leg of the crossbeam. At their ends, the coupling sections, or the prongs of a coupling section, support the legs and, optionally, the upper front web or the lower front web.

[0017] In a practically advantageous embodiment, the upper and lower coupling sections can each be configured in a forked shape with a recess and two prongs laterally delimiting the recess. The prongs run in a straight line and extend over the upper leg and the lower leg, respectively, to the upper and lower front webs of the cross member.

[0018] Another embodiment provides that the upper coupling section has a recess open at its end face. The lower coupling section has a molded recess with lateral slopes and a bottom area in which a hole is provided. The hole has a completely closed rim. The hole in the lower coupling section is not open at its end face. The lower coupling section is joined to the lower leg of the crossbeam by means of a spot weld.

[0019] The crossbeam is designed as a closed hollow profile for at least the majority of its length. In particular, the crossbeam has a central section to which a connection section for a crash box is attached on both sides. At least in the central section and the connection sections for the crash boxes, the crossbeam is designed as a hollow profile and has a closed interior.

[0020] The crossbeam can be an extruded profile with at least one hollow chamber extending in its longitudinal direction.

[0021] A practically advantageous embodiment provides that the crossbeam has a shell body configured in a U-shaped or hat-shaped cross-section and a closing plate arranged on the front side of the shell body.

[0022] Due to its shell construction, the cross-sectional profile of the hollow crossbeam is designed to withstand the loads along its length and advantageously has a greater depth in the central section than in the connection and / or end sections. The crossbeam height, i.e., the width of the web and / or front webs, can also vary and be adapted to compatibility and / or crash test requirements.

[0023] The shell body and the striker plate are made of steel. Particularly with regard to crash performance, the shell body can be made of ultra-high-strength steel (UHSS) or be a press-hardened steel component made of manganese-boron steel. The striker plate is preferably made of medium-strength or high-strength steel. The shell body has a tensile strength greater than 1,250 MPa. The striker plate has a tensile strength between 400 MPa and 1,200 MPa. For a hot-formed and press-hardened shell body, the tensile strength is greater than 1,450 MPa.

[0024] An embodiment of the bumper according to the invention, particularly improving its deformation behavior, provides that the upper front rib and / or the lower front rib in the area in front of a crash box has a groove oriented in the vehicle's vertical axis (z-axis). The groove in the cross member in at least one front rib can be efficiently integrated into the manufacturing process and gives the cross member deformability without making the inside of a crash box softer.

[0025] According to the invention, the groove is provided in a region of the cross member in front of a crash box. In particular, the groove is arranged in front of the recess in a coupling section.

[0026] A groove in one or both of the front struts effectively improves the deformability of the bumper system. In particular, the bumper's deformation behavior in a crash is improved for the "center pole" load case. The crossmember is stretched in the connection area in front of a crash box. The crash boxes tilt inwards. This counteracts crack formation and propagation, especially in or originating from the joint between a highly deformed crossmember and a crash box.

[0027] Preferably, the bead is formed in the direction of the crash box. Furthermore, it is advantageous for the bead to be offset laterally along the vehicle's transverse axis (y-axis) with respect to a central longitudinal axis of a crash box. In particular, the bead is offset inwards towards the inner prong of the coupling section.

[0028] Preferably, the groove extends over the entire height of a front web. The height of the front web is measured along the vehicle's vertical axis (z-axis). The groove extends over the height of the front web and preferably reaches into the transition between the front web and the upper or lower leg.

[0029] The groove has a width measured in the vehicle's transverse axis (y-axis) that is less than 30 mm, in particular less than 20 mm.

[0030] The front strike plate extends lengthwise along the cross member. The strike plate covers the groove. It can extend straight across the groove. Alternatively, the strike plate may have a recess in the groove area that engages with the groove in a front web.

[0031] The strike plate can have one or more grooves. These grooves can extend longitudinally or transversely across the strike plate.

[0032] It is also possible to provide a locally end-strengthened or soft zone instead of or in addition to ribs in the strike plate or in the cross member, particularly in the legs of the cross member or one or each front web, with the aim of adjusting the deformation and load behavior of the bumper and, in particular, adapting it to compatibility and / or crash test requirements.

[0033] The invention is described in more detail below with reference to the drawings. These show: Figure 1 shows a bumper according to the invention in a top view; Figure 2 shows a section of the bumper with a perspective view of a crash box and the connection section of the cross member; Figure 3 shows the section corresponding to the representation of the Figure 2in a top view; Figure 4 technically schematically shows a vertical cross-section through a crash box in the area of ​​a recess in the upper coupling section of the crash box and Figure 5 also technically schematically shows a vertical cross-section through the crash box in the area of ​​a groove in the upper front web.

[0034] The Figure 1 Figure 1 shows a bumper 1 according to the invention. A bumper 1 is used in the front or rear area of ​​the body of a motor vehicle.

[0035] The bumper 1 has a cross member 2 that extends along the vehicle's transverse axis (y-axis) and can be fixed transversely to the longitudinal members of the vehicle (not shown). The bumper 1 is supported on the longitudinal members by means of crash boxes 3, each incorporating a flange plate 4 on the longitudinal member side. The connection between the bumper 1 and the vehicle is established via the flange plates 4. In addition to the cross member 2, the crash boxes 3 are intended to absorb the energy resulting from an impact, particularly at low speeds, by converting it into deformation work.

[0036] The crossbeam 2 has a central length section 5, to which a connection section 6 for a crash box 3 and an end section 7 are attached on both sides.

[0037] The crossbeam 2 has a shell body 8 that is open at the front and closed by a closing plate 9 extending over the length of the shell body 8. The shell body 8 has a U-shaped or hat-shaped cross-section and has a web 10, an upper leg 11, and a lower leg 12 (see also Figures 2 to 5 The web 10 is arranged on the side of the bumper 1 facing the motor vehicle and connects the upper leg 11 and the lower leg 12. The upper leg 11 and the lower leg 12 each extend forward from the web 10 in the longitudinal direction of the vehicle.

[0038] The closing plate 9 ensures that the crossbeam 2 is designed as a closed hollow profile 13 over its length L.

[0039] An outwardly directed upper front web 14 adjoins the upper leg 11. An outwardly directed lower front web 15 adjoins the lower leg 12. The upper front web 14 and the lower front web 15 are oriented along the vehicle's vertical axis (z-axis), with the upper front web 14 extending upwards from the upper leg 11 and the lower front web 15 extending downwards from the lower leg 12. The strike plate 9 rests against the upper front web 14 and the lower front web 15 and is bonded to them.

[0040] A crash box 3 is constructed using a shell design, consisting of two shell parts 16, 17. The shell parts 16, 17 are configured to fit each other and preferably overlap at the ends of their side walls 18. Here, the shell parts 16, 17 are joined together by a material bond. Vertical ribs 19 oriented along the vehicle's vertical axis (z-axis) are provided in the side walls 18 of a crash box 3. Furthermore, a crash box 3 has an upper wall 20 and a lower wall 21. Ribs 22 extending in the transverse direction (y-axis) of the vehicle are embossed in the upper wall 20, as well as in the lower wall 21. The ribs 19 in the side walls 18 are formed outwards from the interior of a crash box 3. The ribs 22 in the upper wall 20 and in the lower wall 21 are formed inwards towards the interior of a crash box 3.

[0041] In connection section 6, a crash box 3 is connected to the crossbeam 2. On the crossbeam side, at its end 23 facing the crossbeam 2, a crash box 3 has a coupling section 24, 25 extending from the upper wall 20 and the lower wall 21, respectively. The upper coupling section 24 overlaps the upper leg 11 of the crossbeam 2. The lower coupling section 25 overlaps the lower leg 12 of the crossbeam 2. In the coupling sections 24, 25, the crash box 3 is joined to the crossbeam 2 by welding.

[0042] In the illustrated embodiment, the upper coupling section 24 has a recess 27 open at its end face 26. The coupling section 24 is configured in a fork shape and has two prongs 28, 29 that laterally define the recess 27. The prongs 28, 29 extend in line with the upper wall 20 to the upper front web 14 and support the upper leg 11 and the upper front web 14 in the event of a frontal impact. This ensures good load transfer and a sufficient force level for controlled deformation of the crash box 3 in the event of a frontal impact with an obstacle at a different height, even with minimal vertical overlap. The prongs 28, 29 are welded to the leg 11.

[0043] In an embodiment in which the lower coupling section 25 is also configured in a fork shape with a recess and two prongs laterally limiting the recess, the prongs support the lower leg 12 and the lower front web 15.

[0044] The recess 27 is bounded by a wall section 29 oriented in the vehicle's transverse axis (y-axis) and by two wall sections 31, 32 oriented to the left and right of the recess 27 in the vehicle's longitudinal axis (x-axis). The coupling section 24 is welded to the upper leg 11 at least on one wall section 30, 31, 32, and in particular on all three wall sections 30, 31, 32. Furthermore, the coupling section 24 can be welded to the upper front web 14 at the end face of the tines 28, 29.

[0045] How in particular the Figures 4 and 5As shown, the upper wall 20 of the crash box 3 transitions into the upper coupling section 24 via a sloping transition section 33, which is recessed towards the central longitudinal axis ML of the crash box 3. The lower wall 21 of the crash box 3 also transitions into the lower coupling section 25 via a sloping transition section 34, which is recessed towards the central longitudinal axis ML of the crash box 3. The transition section 33 proceeds as shown in the Figures 2 and 3 recognizable in the two straight prongs 28, 29.

[0046] In the area in front of a crash box 3, the upper front web 14 has a groove 35. The groove 35 is oriented in the vehicle's vertical axis (z-axis) and is located in the area in front of the recess 27. The groove 35 is formed in the direction of the crash box 3. This can be seen particularly in the illustration of the Figure 3It can be seen that the groove 35 is laterally offset relative to the central longitudinal axis ML of a crash box 3 in the vehicle's transverse axis (y-axis). The groove 33 is laterally offset relative to the vehicle's center in the direction of the inner prong 28.

[0047] The groove 35 extends over the height h of the upper front web 14, measured in the vehicle's vertical axis (z-axis), to the transition 36 between the upper front web 14 and the upper leg 11. The groove 35 has a width b, measured in the vehicle's transverse axis (y-axis), which is less than 30 mm, in particular less than 20 mm.

[0048] The strike plate 9 extends along the front of the shell body 8 and covers the groove 35. The strike plate 9 can run straight along the front. This is shown in the illustration of the Figure 5The strike plate 9 can also have one or more grooves, in particular the strike plate 9 can have a groove-shaped indentation 37, which is provided in the area of ​​the groove 35 in the upper front web 14. Reference symbol:

[0049] 1 - Bumper 2 - Crossmember 3 - Crash box 4 - Flange plate 5 - Central longitudinal section 6 - Connection section 7 - End section 8 - Shell body 9 - Strike plate 10 - Web 11 - Upper leg 12 - Lower leg 13 - Hollow profile 14 - Upper front web 15 - Lower front web 16 - Shell part 17 - Shell part 18 - Side wall of 16, 17 19 - Corrugation 20 - Upper wall of 3 21 - Lower wall of 3 22 - Corrugation 23 - End of 3 24 - Coupling section 25 - Coupling section 26 - Front of 24 27 - Recess 28 - Prong 29 - Prong 30 - Wall section of 27 31 - Wall section of 27 32 -Wall section of 27 33 -Transition section 34 -Transition section 35 -Corner 36 -Transition 37 -Shaping b -width h -height L -length ML -central longitudinal axis

Claims

1. Bumper with a cross member (2) and crash boxes (3), for a motor vehicle, wherein the cross member (2) has an upper leg (11) and a lower leg (12) which are connected via a web (10), and a crash box (3) has, on the cross member side, a coupling section (24, 25), which overlaps the upper leg (11) or the lower leg (12) and is joined thereto, wherein the coupling section (24, 25) has a recess (27), open on its end face (26), and at least one wall section (30, 31, 32), delimiting the recess (27), is welded to the upper leg (11) or the lower leg (12) and the cross member (2) has an outwardly directed upper front web (14) adjoining the upper leg (11) and / or an outwardly directed lower front web (15) adjoining the lower leg (12), characterised in that the upper front web (14) and / or the lower front web (15) has a bead (35) in the region in front of a crash box (3).

2. Bumper according to claim 1, characterised in that the coupling section (24, 25) is fork-shaped and has two prongs (28, 29) laterally delimiting the recess (27).

3. Bumper according to claim 2, characterised in that the coupling section (24, 25) is joined to the upper front web (14) or the lower front web (15).

4. Bumper according to any one of claims 1 to 3, characterised in that the cross member (2) is configured as a closed hollow profile (13), at least over the majority of its length (L).

5. Bumper according to any one of claims 1 to 4, characterised in that the cross member (2) has a shell body (8), configured in a U-shaped or hat-shaped cross section and a locking plate (9) arranged on the front side of the shell body (8).

6. Bumper according to any one of claims 1 to 5, characterised in that the bead (35) is oriented in the vehicle vertical axis (z-axis).

7. Bumper according to any one of claims 1 to 6, characterised in that the bead (35) is arranged in front of the recess (27).

8. Bumper according to any one of claims 1 to 7, characterised in that the bead (35) is moulded in the direction of the crash box (3).

9. Bumper according to any one of claims 1 to 8, characterised in that the bead (35) is laterally offset in relation to the central longitudinal axis (ML) of a crash box (3) in the vehicle transverse axis (y-axis).

10. Bumper according to any one of claims 1 to 9, characterised in that a front web (14, 15) has a height (h) measured in the vehicle vertical axis (z-axis) and the bead (35) extends over the height (h).

11. Bumper according to any one of claims 1 to 10, characterised in that the bead (35) has a width (b) measured in the vehicle transverse axis (y-axis) of less than 30 mm, in particular less than 20 mm.

12. Bumper according to any one of claims 5 to 11, characterised in that the locking plate (9) covers the bead (35).