Bumper support

Abstract

Bumper support as side impact protection for a motor vehicle body, which is manufactured by forming from a strip-shaped metal sheet, consisting of a first profile (1) with a three-dimensional structure and a second component (2) which spatially closes the first profile (1), wherein the two components have overlapping surfaces (6, 7) which serve for welding, characterized in that the welding is carried out by capacitor pulse welding, wherein the length of the weld seams (9), which extend continuously or with small interruptions along the longitudinal axis of the profile (1), add up to a total length (L2) which corresponds to at least half the length of the profile (L1).

Description

[0001] The invention relates to a bumper support for a motor vehicle body, consisting of a first profile with a three-dimensional structure and a second component that spatially closes the first profile. State of the art

[0002] Bumper supports of the type in question are used in a motor vehicle body. The essential feature of the bumper support according to the invention is simply that, with respect to the direction of an expected impact, which is essentially transverse to the longitudinal extent of the bumper support, it offers effective protection of the interior of the motor vehicle body and enables connection to the associated structural component of the motor vehicle body.

[0003] In line with the principles of lightweight construction in modern vehicle manufacturing, the bumper support not only absorbs energy during a crash but also contributes to structural rigidity during driving. To achieve this, the bumper support is rigidly connected to the longitudinal members of the vehicle structure, resisting bending and torsional forces. The support's geometry is determined by stiffness requirements and the need for high energy absorption capacity at the lowest possible weight and acceptable manufacturing costs. The energy absorption requirements are defined by insurance, legal, and manufacturer-specific regulations.

[0004] It is already known to use a hollow profile part made of steel or aluminum as a bumper support for a motor vehicle body, wherein, starting from a tube, the hollow profile part is designed as a one-piece steel profile exhibiting high strength, toughness, and deformation resistance, the end regions of which are flap-like for attachment to the structural component, in particular in the motor vehicle door (DE 41 33 144 A1). The tube can have a round or an oval, i.e., elliptical, cross-section. If necessary, two tubes can also be arranged side by side with respect to the direction of an expected impact.

[0005] A bumper support for a motor vehicle body with two tubular profiles arranged side by side with respect to the direction of an expected impact has already been further developed in terms of manufacturing technology in such a way that both tubular profiles consist in one piece of a strip steel formed into the desired cross-sectional shape by a roll forming process, wherein the strip steel forming the tubular profiles is fixed at the joints by a longitudinal seam weld (US 6 591 577 B2).

[0006] US Patent 7,926,865 B2 discloses a bumper support comprising a ribbon-shaped support plate and a hat-shaped support element. The two components of the bumper support are connected by upper and lower connecting flanges and attached to the crash boxes. The method of connection is not specified.

[0007] It is also known to manufacture the profiles not as closed tubes, but to form them from sheet steel in the shape of a hat, whereby structures with a double hat shape are also possible. The profiles are closed with a cap to create greater stability and rigidity.

[0008] From US 2003 / 0 218 341 A1, a front bumper is known which is made of strip metal and has two components that are spot-welded together at the impact surfaces.

[0009] From the publication by S. Achatz, G. Reverchon: Classics with new energy. In: Blech In Form, 2006, 4, pp. 70-73. - ISSN 1616-3362, capacitor discharge welding is known, which is also suitable for the automotive industry.

[0010] Capacitor discharge welding for joining workpieces is known from DE10 2005 007 464 A1. Individual weld protrusions are used to control the high-voltage discharge.

[0011] From DE 10 2009 004 884 A1 a deformation element is known which is spot-welded to a crossbeam.

[0012] The side-impact protection bumper support, made of strip steel and the basis of the invention, has flat sections at its ends for connection to the profile component. From these flat sections, one or two parallel hat profiles develop. These profiles are symmetrically designed and have a finishing surface extending along the longitudinal axis of the profile. The free longitudinal edges of the metal sheet and the cover are arranged to overlap and are joined by means of a longitudinal seam weld. In the prior art, the longitudinal seam weld is performed as a laser weld, a MAG weld, and, in particular, as a spot weld.

[0013] The teaching is based on the problem of designing and further developing the known bumper support for a motor vehicle body, which is manufactured from a strip-shaped metal sheet using a forming process, in such a way that the most uniform, continuous force absorption is ensured and the manufacturing process is optimized.

[0014] The solution according to the invention uses a capacitor pulse welding process to close the profile, which has so far only been used for smaller components.

[0015] Previously, the capacitor pulse welding process had limited applicability because the longer the weld seam, the larger the capacitor had to be. For a weld seam length of 500 mm to 1000 mm, a capacitor with a current of one million amperes was required.

[0016] The process is also advantageous because no discoloration of the weld is visible on the surface.

[0017] Thanks to corresponding advancements in plant engineering, it is now also possible to economically represent larger connection cross-sections.

[0018] Advantageously, the bumper support is formed from two components that have surfaces which are welded together.

[0019] In an advantageous embodiment, one of the components forms a lid on the other component.

[0020] However, it is also advantageous to provide both components with a three-dimensional structure.

[0021] One embodiment has a double-hat structure for advantageous stiffness.

[0022] To create an optimized connection, weld grooves are provided on at least one component.

[0023] It is considered advantageous that the lengths of the welds add up to a total length (L2) that is at least half the length of the profile (L1). Description of the invention

[0024] Advantageous embodiments of the invention are explained in more detail in the following figures and in the description. It shows Fig. 1 A view of an exemplary bumper support. Fig. 2 sections through two embodiments Fig. 3 an advantageous design of the bumper support Fig. 4 another embodiment.

[0025] In Fig. Figure 1 shows an exemplary bumper support. A first profile 1 extends along the entire length L1 of the bumper support. On the right side of the drawing, it can be seen that the profile is flattened towards an end piece 3 to simplify installation. This design is not relevant to the invention.

[0026] The profile forms a U-shaped groove 5 extending from the first end piece 3 to the second end piece. The profile 1 is covered by a second component 2 as a cover, which in this embodiment has recesses 4. Both components are joined at their edges by welds that extend continuously or with minor interruptions along the longitudinal axis of the profile and the cover, together forming a weld seam of length L2, which is more than 2 / 3 of the length L1.

[0027] Fig. Figure 2 shows cross-sections through two examples, where profile 1 exhibits a simple or a double hat-shaped profile. The second component 2 is designed as a flat lid.

[0028] The profile 1 forms a first welding surface 6, which is opposite a second welding surface 7 formed by the cover.

[0029] The solution according to the invention uses a capacitor pulse welding process to close the profile, a process that has previously only been used for smaller components. The process is a variant of resistance welding for electrically conductive materials based on the Joule heating of an electric current flowing through the joint.

[0030] This heats the components to melt. After the current flows, a weld is formed once the molten metal solidifies again.

[0031] In resistance pressure welding, the formation of a close bond is supported by compression during and after the current flow.

[0032] Capacitor discharge welding (CD welding) differs from conventional resistance welding.

[0033] Energy is transferred to the workpiece via charged capacitors. Advantages of this process include very high welding currents, a steep current rise, a short welding time, and consequently, a smaller heat-affected zone in the component due to the energy concentration. This also enables the reliable welding of high-strength steels. One of the greatest advantages of this welding method is that, due to the rapid current rise and the associated rapid heat transfer into the weld geometry, the process temperature at the weld point is reached before the surrounding material heats up.

[0034] In order to optimally utilize the capacitor pulse welding process, the bumper supports are provided with a welding groove 8, which increases the contact between the two surfaces 6 and 7 and ensures the position of the weld, since the welding groove 8 determines the location of the current flow.

[0035] The weld grooves 8a, 8b are constructed as in Fig. 3 shown either on the side of the cover 2 attached to surface 7 or on the profile side on the first weld surface 6.

[0036] Fig. Figure 4 shows an embodiment in which both components to be welded are formed as three-dimensional components in order to create a bumper carrier with optimized properties.

[0037] The bumper supports can be manufactured much faster and more cost-effectively using the proposed capacitor pulse welding process.

Claims

[1] Bumper support as side impact protection for a motor vehicle body, which is manufactured by forming from a strip-shaped metal sheet, consisting of a first profile (1) with a three-dimensional structure and a second component (2) which spatially closes the first profile (1), wherein the two components have overlapping surfaces (6, 7) which serve for welding, characterized by , that the welding is carried out by capacitor pulse welding, wherein the length of the weld seams (9) extending continuously or with slight interruptions along the longitudinal axis of the profile (1) add up to a total length (L2) which is at least half the length of the profile (L1). [2] Bumper support according to claim 1 characterized by , that the second component (2) is designed as an almost flat lid. [3] Bumper support according to claim 1 characterized by, that the second component (2) also has a three-dimensional structure. [4] Bumper support according to claim 1 characterized by , that at least one of the components (1, 2) has a double-hat structure. [5] Bumper support according to claim 1 characterized by , that the components (1, 2) are made of steel as stamped and pressed parts. [6] Bumper support according to claim 1 characterized by , that the overlapping surfaces (6, 7) have weld grooves (8a, 8b). [7] Method for manufacturing bumper supports for a motor vehicle body, comprising a first profile (1) with a three-dimensional structure and a second component (2) that spatially closes the first profile (1), wherein the two components have overlapping surfaces (6, 7) which serve for welding, characterized by , that the surfaces (6, 7) are welded using capacitor pulse welding.

Images