Side impact beam for a motor vehicle

Abstract

Side impact beam for a motor vehicle, comprising a beam (1) which is essentially made of a profile (2) which is predominantly hat-shaped in cross section and which is arranged at least in sections in and / or on a vehicle door structure, with a central web (3), on the upper and lower edges (4, 5) of which a leg (6, 7) is arranged at an angle thereto, wherein at least one flange (8, 9) is arranged at an angle on each of the legs (6, 7) and a bead (10) which extends at least in sections over the longitudinal course of the central web (3) is formed with a base (19) and two opposite flanks (12, 13), and the beam (1) is at least partially closed with a closing plate (14), characterized in that at least one of the legs (6, 7) is formed in cross section in the yz plane in sections with a step (11, 11.1), and the step (11, 11.1) is formed at least at its lateral ends (20, 20.1, 20.2, 20.3) runs out in the x-direction and is designed over its entire extension in the x-direction in the manner of a cylindrical surface or cambered and that as a result of the arrangement of the striking plate (14) the legs (6, 7) are supported on the step (11, 11.1) and the step (11, 11.1) on the striking plate (14).

Description

[0001] The invention relates to a side impact beam for a motor vehicle, comprising a beam which is essentially made of a profile which is predominantly hat-shaped in cross section and which is arranged at least in sections in and / or on a vehicle door structure, with a central web, on the upper and lower edges of which a leg is arranged at an angle thereto, wherein at least one flange is arranged at an angle on each of the legs and a bead which extends at least in sections over the longitudinal course of the central web is formed with a base and two opposite flanks and the beam is at least partially closed with a striker plate.

[0002] Environmental concerns, such as reducing emissions, are driving automobile manufacturers to make their vehicles increasingly lighter. At the same time, however, they are obligated to comply with ever-increasing legal safety requirements. This poses a major challenge, especially for safety-relevant components and assemblies.

[0003] Side impact beams, also known as door impact beams, are generally arranged in and / or on a motor vehicle door structure to protect vehicle occupants from injury in the event of a lateral collision. This is achieved by keeping any intrusions into the passenger compartment as minimal as possible so that the passenger cell and thus the survival space are preserved as best as possible. A prerequisite for this is that such beams have a high degree of energy absorption capacity, which is why materials with a high yield strength are preferably used to improve energy absorption capacity while simultaneously optimizing weight. Generally speaking, side impact beams have so far been manufactured from steel tubes, extruded profiles made of light metal such as aluminum, or from sheet metal or sheet metal shell solutions with a predominantly continuous cross-section.In the event of a lateral collision, the forces acting on the side impact beam are initially absorbed by it and largely transferred into the vehicle body via its connection points so that the passenger cell is preserved as well as possible.

[0004] The specific requirements for a side impact beam vary from vehicle to vehicle and result from the potential loads during a lateral collision in the respective installation space. In order to meet these requirements, there are various legally required tests in which a possible lateral collision during an accident is simulated as realistically as possible. Such approval requirements can be found, for example, in the American approval standard "FMVSS (Federal Motor Vehicle Safety Standard) 214 - Side Impact Protection". In this test, the door structure is subjected to quasi-static and dynamic tests using a pole, among other things. While in the quasi-static test a pole is pushed into the vehicle door, in the dynamic test the entire vehicle is pulled against a pole on a sled.Since the side impact beam typically extends from the front end of the door to the rear end of the door, the beam's maximum load is applied in the center, as the side impact beam's resistance is lowest at this point due to the leverage (worst-case loading). To meet the required approval conditions, the side impact beam must withstand a certain force level up to a defined intrusion depth. In other words, the side impact beam must exceed a defined force level for a given penetration path to minimize intrusions.

[0005] This means that the crash-proof design of a side impact beam differs considerably from the design of a bumper cross member, as the load application is fundamentally different, even though both beams are components subject to bending and crash loads. While a bumper cross member is subjected to a more planar load with associated energy absorption via the side crash boxes mounted behind it, the centrally acting force of a side impact beam is crucial for the respective crash-proof design. This means that different performance goals are pursued with the two beams. While a defined penetration path must not be exceeded for a given energy with a bumper cross member, care must be taken with a side impact beam to ensure that a defined force level is not undercut for a specific penetration path.Consequently, in contrast to a bumper cross member, a side impact beam must be able to ensure high energy absorption or force transmission even after the beam has begun to buckle.

[0006] In the event of a lateral collision, particularly in the case of a worst-case load, the plastic deformations of a side impact beam predominantly occur in the central structural area of ​​the beam, which is why numerous approaches are being pursued in the state of the art to ensure that this profile section is stabilized in accordance with the requirements of the standardized tests.

[0007] EP 2 394 834 A2 discloses a door impact beam made of sheet metal with a predominantly hat-shaped profile in cross-section. In the central structural area of ​​the beam, an embossed portion in the form of an inserted longitudinal bead is formed, giving the profile a W-shaped cross-sectional contour in this section. For further optimization, flanges are formed on the legs adjacent to the central web, angled to the central web.

[0008] DE 199 54 647 C2 also discloses a door impact beam whose cross-section is essentially W-shaped, in that a central bead extending almost across the entire beam is incorporated into a hat-shaped profile. The central structural area of ​​the beam is additionally stiffened by several tension elements connecting the two outer legs. This makes the production of the beam more complex and expensive, and also leads to a significant increase in weight.

[0009] DE 10 2012 215 598 A1 shows a side impact beam for a side door of a motor vehicle body. It is designed as a three-dimensional structure, particularly W-shaped with flanges attached to it, and is additionally spatially closed with a locking plate.

[0010] Likewise, from DE 693 09 699 T3 or DE 196 54 376 B4 a door impact beam is known which essentially consists of a hat-shaped profile viewed in cross section, in which a channel in the form of a longitudinal bead is formed in the central region.

[0011] A fundamental disadvantage of the known solutions is that, for door impact beams with predominantly continuous profile cross-sections, at least in the central region, the intrusion force drops relatively rapidly once the respective "buckling force" is exceeded. This means that after buckling of such a door impact beam, the geometric stiffness and thus also the resistance force opposed to a penetrating object, such as a barrier, a pole, or a motor vehicle, etc., decreases abruptly. It should therefore be noted at this point that once a buckling load is exceeded, the energy absorption capacity is greatly reduced, and larger intrusions can occur.While known state-of-the-art measures, such as the additional insertion of reinforcement sleeves, generate greater resistance to intrusions, they sometimes cannot prevent the sudden drop in force after a critical intrusion depth. Furthermore, these measures lead to an increase in weight and rising process costs. While strike plates attached to the rear of the support profile to create a profile that is at least partially closed, they alone increase the buckling load of a component, they also cannot prevent the steep drop in resistance force after buckling. The function of a strike plate in conventional door impact beams is primarily to prevent the legs from gaping open unhindered during a force intrusion. Gaping open would, in turn, lead to a premature collapse of the door impact beam, posing an increased risk to the vehicle occupants.By attaching a striker plate to the rear of an open door impact beam profile, gaping can be counteracted by holding the legs together and thus maintaining geometric rigidity. However, even the mere use of a striker plate cannot completely prevent the legs from collapsing, which continually reduces the resistance to further deformation. This is explained by the fact that the buckling resistance of a door impact beam depends, among other things, on the height of the legs of the beam profile. As the height of a straight leg increases, its lever arm automatically increases, which promotes buckling of the leg in an impact and thus a sudden reduction in the resistance force.

[0012] Based on this discussed prior art, it is therefore the object of the present invention to improve the deformation behavior of the door impact beam in a lateral collision and to optimize the force-displacement behavior.

[0013] This object is achieved by a generic side impact beam as mentioned above with the features of claim 1.

[0014] Advantageous embodiments are specified in the dependent claims.

[0015] Whenever in this context the terms “above”, “below”, “inside” or “side” are used, these are descriptions of the directions of the Fig. 2 stored coordinate system, where “side” are directions in the x-axis, “top” and “bottom” are directions in the z-axis and “inside” are directions in the y-axis.

[0016] The side impact beam consists of a profile that is closed at least in sections, which consists of a substantially predominantly hat-shaped profile that is at least partially W-shaped and is assembled with a striker plate. Essential to the invention is that at least one of the legs is partially formed with a step in the yz plane in cross-section, and the step tapers off in the x-direction at least at its lateral ends.

[0017] This measure makes it possible to maintain the penetration resistance during deformation higher than with conventional door impact beams, i.e. at a high level over a longer period of time.

[0018] On the one hand, the introduced step enlarges the profile cross-section at this point. On the other hand, however, it also weakens the profile, which is stiffened by the legs, so that if a lateral force is applied to the beam, it begins to buckle at this point earlier than with a cross member with straight legs. This contradicts the previous understanding of the optimal mode of action of a side impact beam, according to which the aim was to prevent buckling in the component for as long as possible. However, unlike conventional door impact beams, this measure makes it possible to increase the section modulus during plasticization without additional components. Surprisingly, it has been shown that an additional step in the leg of the profile is extremely helpful in being able to precisely control the buckling behavior of the side impact beam in the event of a collision.

[0019] This is achieved by influencing the deformation behavior of the door impact beam by means of a step incorporated into the leg of the door impact beam. The cross-section of the door impact beam only provides a higher section modulus during deformation than conventional door impact beams. This means that with the door impact beam according to the invention, the force does not increase as much at the beginning of intrusion compared to conventional side impact beams. Consequently, the buckling load is lower than for a beam without the step. As the deformation progresses, however, the step incorporated allows the profile cross-section to be maintained for longer than conventional solutions without the step. As a result, the door impact beam according to the invention offers greater overall resistance to deformation during a crash.

[0020] Therefore, a door impact beam according to the invention with an optimally designed step behaves more consistently during the intrusion of a test specimen. In other words, the force level does not drop abruptly due to the increased section modulus during a collision.

[0021] In addition, the integrated step is designed in the form of a cylindrical surface or is cambered. At the same time, it is imperative that the beam is at least partially closed with an attached locking plate. In the event of an impact, this curvature of the step, which points toward the collision object, significantly increases the beam's buckling resistance compared to conventional solutions. Ultimately, this makes it possible to withstand a greater resistance force in the event of an impact.

[0022] Furthermore, the step according to the invention in the leg of the door impact beam simultaneously allows for additional advantages. To ensure that a door impact beam can be optimally manufactured to meet the requirements, a softer material with good formability is generally required for the recess extending in the central web. For the leg, however, a material with a particularly high yield point is desirable. While it is possible to use well-known tailored welded blanks, this is associated with increased costs and an inhomogeneous transition that may represent a weak point.

[0023] The additional step introduced according to the invention results in one exemplary embodiment in the respective leg in that a higher yield point is achieved by stretching the material in the area of ​​the legs by means of work hardening. In principle, the depth of the step to be achieved depends on the material and its forming properties. The tests have shown that it is advisable to go to the limits of formability with the step in order to achieve maximum work hardening. However, it is essential that the edges or flanges, i.e. the areas in which the material is cut off, remain "soft", i.e. are not stretched excessively further during production and thus work hardened. If this area is stretched too much, there is a risk of a crack migrating from the edge into the material and thus leading to failure of the entire component.The high yield strength of the material after targeted hardening, preferably at a distance of more than 10 mm, and especially more than 15 mm, from the cut edge, can therefore ensure an increase in the force required to deform the beam. Thus, the step makes it possible to maintain the geometric stiffness of the impact beam more stable throughout the penetration process while simultaneously locally modifying the material properties to enable optimal buckling with a more uniform force distribution in the event of a crash. This effect can be further enhanced by using a material with a bake-hardening effect.

[0024] Overall, with this concept, it was found that the resistance of the cross member to deformation could be kept constant or at a high level for as long as possible and especially during deformation, although the maximum force was reduced by the introduced step.

[0025] Preferably, the inserted step is positioned centrally in the x-direction, since this is where the greatest force is applied to the side impact beam according to the approval regulations. However, it is also conceivable that several defined and spaced-apart steps are formed in at least one leg.

[0026] In addition, the step is preferably designed in such a way that it is optionally symmetrical to each other in both legs over its entire extension in the x-direction. However, it is also conceivable to arrange the steps offset from each other or to form multiple steps in any arrangement on the respective legs.

[0027] Preferably, the introduced step extends in the x-direction over at least 1 / 8 of the total length of the beam, and in particular over at least 1 / 3 of the total length. This introduced step is a suitable means of maintaining the resistance force at a relatively constant level for a long time in the event of a collision and counteracting an abrupt drop in force. With a shorter design, it has also been shown that the required sufficient support can no longer be guaranteed.

[0028] Furthermore, the hat-shaped profile of the side impact beam is extremely variable in terms of design. For example, at least one connection area can be formed at each of its left and right ends in the x-direction without additional attachments. These ends can be designed as flat and / or profiled sections, particularly W-shaped, when viewed in cross-section.

[0029] Likewise, the functional side impact beam can be manufactured from any number of different materials or material combinations. For example, the beam can be made from press-hardenable steel, cold-formable steel, their alloys, a light metal, a light metal alloy such as aluminum, or a fiber composite material, such as carbon and / or glass fibers embedded in a plastic matrix, or any combination of these materials.

[0030] Another advantage is that the side impact beam can be produced using standardized and reliable deep-drawing processes, either cold or hot, particularly press-hardened, which keeps the associated process costs extremely low. The manufacturing process for the side impact beam can therefore be implemented extremely economically.

[0031] Further advantages and embodiments of the invention will become apparent from the following description of an embodiment with reference to the accompanying figures. They show: Fig. 1: an isometric view of a preferred embodiment of a side impact beam of the present invention, Fig. 2: a cross section along the line AA in Fig. 1, Fig. 3: a force-displacement diagram of a preferred embodiment and associated reference models, Fig. 4: Schematic functional diagram of the inventive embodiment of Fig. 1 compared to a conventional door impact beam.

[0032] With reference to Fig. 1 and Fig. 2, these show a preferred embodiment of a side impact beam 1 for a vehicle according to the present invention. This beam is mounted in and / or on a door structure of a motor vehicle (not shown) to absorb any force. The side impact beam 1 and a striker plate 14 attached thereto are preferably made of a sheet of high-strength steel.

[0033] Essentially, the side impact beam 1 according to the invention comprises a beam made of a profile 2 which is predominantly hat-shaped in cross section, the profile 2 of which is in particular Fig. 2 along section line AA. In the assembled state, it is arranged at least partially closed in and / or on a vehicle door structure. In addition, the side impact beam 1 has a central web 3, on the upper and lower edges 4, 5 of which a leg 6, 7 is arranged at an angle thereto. At least one flange 8, 9 is also arranged at an angle on each of the legs 6, 7, thereby stiffening the side impact beam 1. Furthermore, a bead 10 extending partially over the longitudinal course of the central web 3 is formed, having a base 19 and two opposing flanks 12, 13, which basically ensures further stiffening of the component. Depending on the available installation space, this bead 10 can also extend over the entire side impact beam 1 or be interrupted only in individual partial areas.The depth of the bead 10 can be chosen arbitrarily and can be constant or varying over its longitudinal course.

[0034] In particular with reference to Fig. 1, the legs 6, 7 in the side impact beam 1 according to the invention are formed, in particular centrally in the x-direction and in cross-section in the yz plane in sections, with a step 11, 11.1, and the steps taper off at their lateral ends 20, 20.1, 20.2, 20.3 in the x-direction. In the preferred exemplary embodiment shown, the lateral ends 20, 20.1, 20.2, 20.3 taper off continuously, in particular tangentially continuously. At the same time, the step 11, 11.1 is preferably formed in both legs 6, 7 and is preferably designed entirely over its respective longitudinal extent in the manner of a cylindrical jacket surface, which points with the axis of the cylinder in the y-direction and thus in the direction of an impact object. This makes it possible for the step 11, 11.1, the weakening of the profile does not represent a disadvantage in the event of a collision, but rather the resistance force can be maintained at a relatively constant level for longer due to the enlarged profile cross-section. In other words, a developed step 11, 11.1 leads to, as in . Fig. 3 and Fig. 4 shows that, although the profile tends to buckle more quickly than known solutions, the slower reduction in the profile cross-section during deformation counteracts a sudden drop in force and enables more uniform energy absorption in the event of a collision. In the present embodiment, the steps 11, 11.1 preferably extend over approximately one-third of the total length of the side impact beam 1 and are arranged in its central region.

[0035] The step or steps 11, 11.1 incorporated into the side impact beam can, however, in another exemplary embodiment (not shown), also be arranged in just one leg 6, 7. The step or steps 11, 11.1 can extend over just one partial area or over several partial areas. The arrangement can be arbitrary and can be adapted to the installation situation of the side impact beam 1. This generally means that, for example, steps 11, 11.1 can be designed and arranged next to one another at a distance from one another, can be designed and arranged symmetrically and / or asymmetrically, or can be offset from one another. This applies both to the arrangement of the steps 11, 11.1 in one leg 6, 7, but also to the arrangement of the step or steps 11, 11.1 in both legs 6, 7.

[0036] Preferably, in the side impact beam 1, all edges subjected to forming are provided with a rounded outer radius so that the risk of crack formation at these points during the manufacturing process can be excluded.

[0037] The hat-shaped profile 2 comprises a first and a second end 15, 16, which, viewed in cross-section, are designed on the one hand as a flat section and on the other hand as a W-shaped profiled section. Preferably, at least one connection region 17, 18 is provided at the first and second ends 15, 16, via which the side impact beam 1 is fastened to the door structure (not shown). In the present exemplary embodiment, this is achieved via two holes through which a connection to the door structure is made by means of screws. However, it is also conceivable for the side impact beam 1 to be fastened to and / or in the door structure with the first and second ends 15 and 16 using conventional connection technologies, such as thermal joining, gluing, clinching, riveting, etc.

[0038] In a further embodiment (not shown), it is also conceivable for the first and / or second ends 15 and 16 to be flat or profiled as viewed in cross-section. If both ends 15 and 16 are flat as viewed in cross-section, the largely hat-shaped profile is further stiffened in its connection areas by a circumferential flange.

[0039] Referring to Fig. Figure 3 shows a force-displacement diagram with the characteristic curves of a preferred embodiment of the present invention with a step 11, 11.1 incorporated in both legs 6, 7, as well as a reference system without corresponding steps at the same or higher weight. The curves demonstrate the functionality, which was created using a standard 3-point bending test. At the same time, a force-displacement window is disclosed, which sets out the requirements of legal safety regulations and must not be undercut.

[0040] It can be seen from the diagram that the course of the force-displacement curves of a conventional side impact beam without a step in the respective leg and a model according to the teaching of the invention differ significantly. The force peak in the conventional side impact beam is initially much greater than in the side impact beam 1 according to the invention. This can be explained by the fact that the introduced steps 11, 11.1 initially weaken the side impact beam 1 according to the invention, as a result of which it begins to buckle earlier than the reference models. At the same time, once the force peak is reached, the force level in the side impact beam according to the invention can be maintained at a high or relatively slowly and evenly decreasing level for much longer. This can be explained by the fact that the steps 11, 11.1 Ideally, on the one hand, the section modulus is kept higher during deformation than with conventional door impact beams. As can be seen from . Fig.4, the step 11, 11.1 remains largely intact during a collision and thus forms the basis for the optimized section modulus. On the other hand, in the ideal collision case, when a force F is applied, a type of support of the leg 6, 7 takes place on the step 11, 11.1 or the step 11, 11.1 on the striking plate 14. In other words, an earlier buckling compared to conventional side impact members is compensated for by the introduced step 11, 11.1, in that forces and stresses can be distributed over more material and thus in the component in an optimized manner. For this reason, the leg 6, 7 buckles more slowly, i.e. only with increasing force introduction, and can therefore counteract this with a higher resistance force. As a result, it is possible to meet the legal safety requirements despite a defined earlier buckling of the side impact member 1 according to the invention.Furthermore, it is not necessary to increase the weight, for example, by increasing the wall thickness, or to undertake complex post-processing steps to meet the requirements. Thus, the side impact beam 1 according to the invention makes it possible to design it lighter and thus more effective than conventional solutions, while taking safety requirements into account. For this purpose, the side impact beam 1 according to the invention can be manufactured simply and cost-effectively using standardized deep-drawing processes.

[0041] The foregoing description represents only preferred embodiments. The applicable claims are not limited to these embodiments alone. Rather, all equivalent changes and modifications derived or made by one skilled in the art within this technical field are intended to be included within the scope of the present invention within the scope of the applicable claims. List of reference symbols 1 side impact beam 2 Hat-shaped profile 3 Middle Bridge 4 Top edge 5 Lower edge 6 legs 7 legs 8 Flange 9 Flange 10 bead 11, 11.1 Level 12 flank 13 flank 14 Strike plate 15 First End 16 Second Ending 17 Connection area 18 Connection area 19 Floor 20, 20.1, 20.2, 20.3 Side end

Claims

[1] A side impact beam for a motor vehicle, comprising a beam (1) made essentially of a profile (2) with a predominantly hat-shaped cross-section, which is arranged at least in sections in and / or on a vehicle door structure, with a central web (3), on the upper and lower edges (4, 5) of which a leg (6, 7) is arranged at an angle thereto, wherein at least one flange (8, 9) is arranged at an angle on each of the legs (6, 7), and a bead (10) extending at least in sections over the longitudinal course of the central web (3) is formed with a base (19) and two opposite flanks (12, 13), and the beam (1) is at least partially closed with a striker plate (14). characterized bythat at least one of the legs (6, 7) is formed in cross-section in the yz plane in sections with a step (11, 11.1), and the step (11, 11.1) runs out in the x-direction at least at its lateral ends (20, 20.1, 20.2, 20.3) and is formed over its entire extent in the x-direction in the manner of a cylindrical jacket surface or cambered, and that as a result of the arrangement of the striking plate (14), the legs (6, 7) are supported on the step (11, 11.1) and the step (11, 11.1) is supported on the striking plate (14). [2] Side impact beam according to claim 1, characterized by that the step (11, 11.1) is arranged centrally in the x-direction. [3] Side impact beam according to one of claims 1 or 2, characterized by that the step (11, 11.1) introduced into the legs (6, 7) is arranged symmetrically to one another. [4] Side impact beam according to one of claims 1 to 3, characterized bythat the step (11, 11.1) extends in the x-direction over at least 1 / 8 of the total length of the support (1). [5] Side impact beam according to one of claims 1, 2 or 4, characterized by that the steps (11, 11.1) in the legs (6, 7) are arranged offset from one another. [6] Side impact beam according to one of claims 1 to 5, characterized by that the hat-shaped profile (2) has at least one connection region (17, 18) at its first and second ends (15, 16). [7] Side impact beam according to claim 6, characterized by that the first and / or the second end (15, 16) is formed as a flat and / or W-shaped profiled section when viewed in cross section. [8] Side impact beam according to one of the preceding claims, characterized bythat the side impact beam (1) is made of a press-hardenable steel, a cold-formable steel, a steel alloy, a light metal, a light metal alloy or a fiber composite material made of carbon and / or glass fibers embedded in a plastic matrix. [9] Motor vehicle with a side impact beam (1) according to one of the preceding claims.

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