Side impact beam for a motor vehicle

Abstract

Side impact beam for a motor vehicle, comprising a beam (1) essentially made of a hat-shaped profile (2) in cross-section, which is arranged at least partially open in and / or on a vehicle door structure towards the vehicle interior, with a central web (3) at whose upper and lower edges (4, 5) a leg (6, 7) is arranged at an angle thereto and wherein at least one flange (8, 9) is arranged at an angle to each of the legs (6, 7) and wherein a groove (10) extending at least partially over the longitudinal course of the central web (3) is formed with a bottom (19) and two opposing flanks (12, 13) characterized in that the groove (10) is tapered on both sides in a tapered partial area (11) in the z-direction and is arranged centrally in the x-direction.

Description

The invention relates to a side impact beam for a motor vehicle, comprising a beam which is produced substantially from a profile which is hat-shaped in cross section and is arranged at least in sections in and / or on a vehicle door structure, open in the direction of the vehicle interior, having a central web, on the upper and lower edge of which in each case one limb is arranged at an angle thereto, and wherein in each case at least one flange is arranged at an angle on the limbs, and wherein 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.The environmental idea in the form of emission values to be reduced causes the automobile manufacturers to make their vehicles increasingly light. At the same time, however, there is a requirement to take account of the constantly increasing legal safety requirements. This represents a great challenge, especially in the case of safety-relevant components or assemblies.Side impact beams, which are also referred to as door impact beams, are generally arranged in and / or on a door structure of a motor vehicle in order to protect the vehicle occupants from injuries in the event of a lateral collision. This is done by keeping any intrusions into the passenger compartment as small as possible, so that the passenger compartment is maintained as well as possible. A prerequisite for this is that such carriers have a high level of energy absorption capacity, for which reason materials with a high yield strength are preferably used for this purpose. This against the background above all is that this can prevent a sudden failure of the side impact beam, which is associated with buckling and, associated therewith, with a sharp drop in the force counteracting an impact. In principle, side impact beams have hitherto been produced from pipes, extruded profiles made of light metal, such as aluminum, for example, or from sheet metal or sheet metal shell solutions with a predominantly continuous cross-sectional profile. In the case of a lateral collision, the forces acting on the side impact beam are initially absorbed by the latter and introduced as far as possible via the attachment points thereof into the vehicle body, so that the passenger compartment is maintained as well as possible.The specific requirements for a side impact beam differ from vehicle to vehicle and result from the possible loads during a lateral collision in the respective installation space. In order to meet these requirements, there are various tests to be observed legally, in which a possible lateral collision during an accident is simulated as realistically as possible. Such approval requirements are found, for example, in the American approval specification "FMVSS (Federal Motor Vehicle Safety Standard) 214-side impact protection". In this case, the door structure is subjected to quasistatic and dynamic tests, inter alia, with the aid of a pile. While a pile is pressed into the vehicle door in the quasi-static test, the entire vehicle is pulled against a pile on a carriage in the dynamic test. Since the side impact beam generally extends from a front door end to a rear door end, the highest load on the beam takes place centrally, since a resistance of the side impact beam at this point is the lowest due to the acting lever conditions (worst-case load). In order to meet the required approval conditions, the side impact beam must maintain a certain force level up to a defined intrusion depth. In other words, the side impact beam must exceed a defined force level at a predetermined penetration path in order to prevent premature buckling of the side impact beam.A crash-appropriate design of a side impact beam thus also differs considerably from the design of a bumper cross member, since the introduction of load differs fundamentally, although both beams represent components which are subjected to bending loads and are subject to crash loads. Whereas in the case of a bumper cross member, a more extensive load with accompanying energy absorption takes place via the lateral crash boxes attached behind it, in the case of a side impact member, the centrally acting force is decisive for the respective crash-appropriate design. Different performance objectives are thus tracked with both carriers. While a defined penetration path for a bumper cross member must not be exceeded at a predetermined energy, it must be ensured for a side impact member that a defined force level is exceeded 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 beginning of the buckling of the beam.In the case of a lateral collision, in particular in the case of a worst-case load, the plastic deformations in a side impact beam take place predominantly in the central structural region of the beam, for which reason numerous approaches are followed in the prior art so that this profile section is designed to be stabilized in accordance with the requirements of the standardized tests.EP 2 394 834 A2 discloses a door impact beam made of sheet metal with a hat-shaped profile of predominant cross section. In this case, in the central structural region of the carrier, an embossing is formed in the form of an introduced longitudinal bead, as a result of which the profile in this section receives a w-shaped cross-sectional contour. In addition, for further optimization, flanges set down at an angle to the legs adjoining the central web are formed.In addition, DE 199 54 647 C2 discloses a door impact beam, the cross section of which is of substantially W-shaped design by incorporating a central bead extending virtually over the entire beam into a hat-shaped profile. The central structural region of the carrier is additionally reinforced by a plurality of tension elements connecting the two outer legs. This makes the production of the carrier more complicated, more expensive and additionally leads to a marked increase in weight.Likewise, DE 693 09 699 T3 or DE 196 54 376 B4 discloses a door impact beam which essentially comprises a profile which is hat-shaped when viewed in cross section and in which a channel in the form of a longitudinally running bead is formed in the central region.DE 195 32 808 C1 discloses a door impact beam having a plurality of beads introduced, which are intended to contribute to stiffening of the beams.EP 1 604 851 A1 and US 2014 / 0 001 788 A1 each disclose a side impact beam of w-shaped profile with a bead extending over its longitudinal course, in which the cross section is formed to be the largest in the central region of the beam and is reduced at least in sections towards its lateral ends. This takes place above all in order to delay, at least in time, an early buckling with the associated total failure of the carrier.A disadvantage of the known solutions is in principle that, in many disclosed door impact beams from the prior art, in the central regions thereof, especially in the bending region, in the event of a collision, cracking occurs at a relatively early point in time as a result of the associated high plastic expansions and the high stress states. In particular, higher-strength alloys or materials are particularly susceptible to failure or crack formation. This then often spreads over wide regions of the component and ultimately leads to total failure of the carrier by the latter tearing. Attempts have therefore been made in the past to achieve a continuous optimization of the support by means of improved rigidity, which is in contrast to the occurring high expansions and multiaxial stress states and the associated high risk of sudden crack formation.Proceeding from this discussed prior art, it is therefore an object of the present invention to improve the deformation behavior of the door impact beam in the event of a lateral collision, and at least to reduce the plastic expansions and the probability of crack formation.This object is achieved by a generic side impact beam mentioned at the beginning, in which the bead is formed in the central region in a partial region so as to taper on both sides in the z direction and is arranged centrally in the x direction.Advantageous embodiments are specified in the dependent claims.If, within the scope of these embodiments, reference is made to "front", "rear", "top", "bottom", "outer", "inner", "lateral", these are descriptions of the directions of the coordinate system stored in the figures, wherein "front" and "rear" are directions in the x-axis, "top" and "bottom" are directions in the z-axis and "outer", "inner" are directions in the y-axis.The side impact beam accordingly consists of a profile whose cross-sectional shape can be referred to as w-shaped. It is essential to the invention that the bead extending in the longitudinal direction (x-direction) of the side impact beam is formed non-uniform in cross section in the central web, in that it narrows on both sides in a central region of the side impact beam, in which the load of the component is greatest in the event of a collision. The tapering is effected in each case in a smooth and / or jump-like manner and has the result that the distance between the two flanks of the middle bead is formed to be significantly smaller in this tapered partial region than in the remaining course of the bead without tapering. This creates a predetermined buckling point, as a result of which, in the event of lateral application of force to the carrier, the latter begins to buckle at this point early. This is in contradiction to the previous understanding of the mode of action of a side impact beam, according to which it was considered to prevent a kink in the component for as long as possible, in order thereby to avoid any crack formation up to the total failure of the component. Surprisingly, however, it has been shown that a predetermined buckling point is extremely helpful if the buckling behavior of the side impact beam in the event of a collision can be controlled in a defined manner, i.e. if it can be initiated in a targeted manner with a defined origin. In the course of the buckling, the opposite flanks of the bead bulge in this region in the z-direction in such a way that they move towards one another. This has the result that after a certain penetration path the two opposing flanks of the bead are themselves supported in the tapered partial region. A further expansion of the kink and the associated local loading of the material used is thereby prevented or at least greatly delayed. Rather, the progressive deformation of the side impact beam is shifted to other areas.Overall, it was possible to establish with this concept that the plastic expansions and thus also the probability of fracture could be significantly reduced compared to conventional side impact beams in the event of a crash.The tapered partial region is arranged centrally in the x direction, since most force is introduced into the side impact beam at this point within the scope of the approval regulations. However, it is also conceivable that a plurality of defined and mutually spaced-apart tapered regions are formed over the longitudinal course of the central bead.In addition, the tapered partial region is designed structurally in such a way that at least one defined predetermined buckling point is formed there, which initiates a desired deformation of the side impact beam when a corresponding force is applied. In other words, this means specifically that the resisting moment is lower in the region of the predetermined bending point than in the regions adjoining the tapered partial region.Furthermore, the jump in rigidity can be set in a targeted manner by the size of the transition region.Thus, the tapering of the tapered partial region takes place in a step-like or smooth manner and then extends parallel to the adjoining flanks of the middle bead without any introduced tapering. The taper in the x direction preferably extends over at least 20 mm. This jump-like or flowing tapering is a suitable means for forming a corresponding predetermined bending point. In the case of a configuration shorter than 20 mm, it has additionally been shown that a sufficiently required support can no longer be ensured, but rather the plastic expansions increase greatly and result in rapid crack formation.Furthermore, the hat-shaped profile of the side impact beam is extremely variable in design terms. Thus, without additional add-on parts in the x direction, at least one connection region can be formed at its left and right ends. When viewed in cross section, these ends can be configured as a flat and / or profiled section, in particular W-shaped.In addition, the deformation behavior of the side impact beam according to the invention during a force input can be easily adapted by further structural measures using simple means. Depending on the available installation space, the depth of the middle bead can vary as viewed over its longitudinal course. Preferably, however, this is formed with a constant depth at least in the central region. However, it is also conceivable that the introduced bead is not formed in partial regions, but instead merges there, in the x-y direction, in each case in a flowing manner into the central web.The functional side impact beam can likewise be produced from any desired number of different materials or material combinations. For example, the carrier can be manufactured from a press-hardenable steel, a cold-formable steel, a light metal, a light metal alloy or an organosheet made from carbon and / or glass fiber or any desired material combinations thereof.It is furthermore advantageous that the side impact beam can preferably be produced cold or warm in one piece from a metal sheet by standardized and process-safe deep-drawing methods, for which reason the associated process costs are extremely low. The production process of the side impact beam can therefore be realized in an extremely economical manner.Further advantages and embodiments of the invention will become apparent from the following description of an exemplary embodiment with reference to the appended figures. The following are shown: FIG. 1a is an isometric view of a preferred embodiment of a side impact beam of the present invention, FIG. 1 b : an enlarged detail view of the tapered partial region of the section C of the preferred embodiment of the side impact beam in FIG. 1 a, FIG. 2 is a cross-section along the line A-A in FIG. 1 a, FIG. 3 is a cross-section along the line B--B in FIG. 1a, FIGS. 4 a- c : a schematic view of a side impact beam of FIG. 1 a during a lateral force application process, FIG. 5 : a force-path diagram of a preferred embodiment of the present invention in FIGS. 1 and 4.Referring to Figs. 1a to 3, these show a preferred embodiment of a side impact beam 1 for a vehicle of the present invention. This is fastened in order to absorb any force effect in and / or on a door structure of a motor vehicle.The side impact beam 1 is preferably made from a sheet of high-strength steel. However, other materials or combinations of materials are also conceivable, such as, for example, generally press-hardenable steel, cold-formable steel, alloys thereof, light metals or light metal alloys, such as, for example, aluminum, organosheets made of carbon and / or glass fiber or any desired combinations of materials.The side impact beam 1 according to the invention substantially comprises a beam manufactured from a profile 2 having a hat-shaped cross section, the profile 2 of which is illustrated in particular in FIG. 2 along the section line A-A and FIG. 3 along the section line B-B. In the mounted state, it is arranged at least in sections open in and / or on a vehicle door structure in the direction of the vehicle interior. In addition, the side impact beam 1 has a central web 3 on the upper and lower edges 4, 5 of which a respective 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, as a result of which the side impact beam 1 is braced. Furthermore, a bead 10 is formed, which extends in some regions over the longitudinal course of the central web 3 and has a base 19 and two opposite flanks 12, 13, which in principle ensures a further stiffening of the component. It is important that the bead 10 of the side impact beam 1 is formed at least in the middle over at least 1 / 3 of the length of the side impact beam 1. Depending on the installation space available, however, this can also extend over the entire side impact beam 1 or be embodied interrupted only in individual partial regions. The depth of the bead 10 can be selected as desired and, viewed over its longitudinal course, can be made constant or varying. In the central portion C of the side impact beam, a constant depth of the bead 10 is preferred.In particular with reference to FIG. 1 b, it is essential to the invention that the bead 10 in the side impact beam 1 according to the invention is formed so as to taper on both sides in the tapered partial region 11 in the section C, in particular centrally, in the z direction. Both sides are understood to mean that the tapering is realized by being formed opposite the middle bead 10 both on the lower and on the upper flank 12, 13. As a result, the stiffening in this region is reduced and a predetermined bending point 14, 14.1 is formed in the event of a collision. The tapering of the tapered partial region 11 is clearly recognizable, provided that FIGS. 2 and 3 are compared with one another, in which the distance of the flanks 12 and 13 in FIG. 2 is formed to be substantially smaller than in FIG. 3. This means that the tapering from left and right initially increases continuously in the x-z plane direction toward the center and then extends parallel to the flanks 12, 13 of the middle bead 10 in which no tapering has been carried out, preferably in a straight line and over at least 20 mm in the x direction.In another exemplary embodiment (not shown), the tapering can also be effected in a jump-like manner and is fundamentally dependent on the selected deformability of the selected material. An embodiment is likewise conceivable in which a plurality of tapers on both sides are arranged spaced apart from one another in the x direction.In addition, in the side impact beam 1, all edges subjected to a forming process are preferably provided with a rounded outer radius, so that the risk of crack formation at these points during the production process can be ruled out.The hat-shaped profile 2 comprises a first and a second end 15, 16, which, viewed in cross section, is formed on the one hand as a flat and on the other hand as a W-shaped profiled section. Preferably, at least one connection region 17, 18 is provided at each of the first and second ends 15, 16, via which connection region the side impact beam 1 is fastened to the door structure. In the present exemplary embodiment, this is realized via two holes introduced, via which a connection to the door structure takes place by means of a screw connection. However, it is also conceivable for the side impact beam to be fastened to and / or in the door structure by means of conventional connection technologies, such as thermal joining, adhesive bonding, clinching, riveting, etc.In a further exemplary embodiment (not shown), it is also conceivable for the first and second ends 15 and 16, viewed in cross section, to be of flat or arbitrarily profiled design. If both ends 15 and 16 are flat, viewed in cross section, the profile, which is substantially hat-shaped, is further reinforced by a circumferential flange in its connection regions.Referring to FIGS. 4 a- c, there is shown a schematic view of a side impact beam of FIG. 1 during a lateral force application process. It can be clearly seen how the side impact beam 1 deforms in the region of the force introduced by a pile (not shown). Initialized by the predetermined bending point 14, 14.1, the flanks 12, 13 of the middle bead 10 move towards one another in the tapered partial region 11 and are supported on one another. This means that the buckling of the side impact beam 1 proceeds in a defined manner and thereby has its origin in the tapered partial area 11 on both flanks 12 and 13 of the middle bead 10. Due to the fact that they are supported against one another, a further progression of the kink in the region of the predetermined kink location 14, 14.1 is counteracted despite increasing intrusion and a local load associated therewith at this location is minimized. Instead, the deformations are transferred in a skillful manner to surrounding regions of the side impact beam 1. This makes it possible that, despite targeted buckling of the side impact beam 1, the plastic expansions and existing stresses in the area of the intrusion of the pile (not shown) or in the event of a collision with another vehicle or object can be reduced, whereby it is possible to exclude or at least to reduce the probability of fracture at a required force level with a specific penetration path.For this purpose, the side impact beam 1 according to the invention can be produced simply and cost-effectively by standardized deep-drawing methods. Referring to FIG. 5, there is shown a force-path diagram with the characteristic curves of a preferred exemplary embodiment of the present invention with introduced mutual tapering in the tapering region 11 and of a reference system without corresponding tapering. The curves show the mode of operation which was produced on the basis of a conventional 3-point bending test.It can be seen from the diagram that the profile of the force-displacement curves does not differ significantly from a conventional side impact beam without a centrally introduced taper and a model according to the teaching according to the invention. The force peak in the conventional side impact beam initially has a slightly greater magnitude than in the side impact beam 1 according to the invention. Viewed over the entire path, however, it is found that, despite this somewhat lower force peak, the force level can be kept at a somewhat longer level overall than is the case with the conventional side impact beam, which is to be led back to the mutual support of the buckling flanks. As a result, with a predetermined penetration path, an approximately equally large integral results in the solution according to the invention compared to the prior art. However, the local plastic expansions in the bending area of the intrusion can be reduced by up to 50% in the invention compared to conventional side impact beams without introduced tapering. Accordingly, despite the predetermined buckling point 14, 14.1, the side impact beam 1 according to the invention is able, in contrast to previous solutions, to significantly reduce the plastic expansions and thus the risk of cracking in the region of the application of force during the impact during an accident, with approximately the same energy absorption. This can be explained on the one hand by the mutual support of the flanks 12 and 13 in the tapered region 11 and on the other hand by the skillful force distribution in the side impact beam up to the introduction of force into the correspondingly bound door or vehicle structure, which is degraded by corresponding deformation work.The above description is only preferred embodiments. The applicable claims are not limited to these embodiments alone.List of reference characters1 Side impact beam 2 Hat-shaped profile 3 Central web 4 Upper edge 5 Lower edge 6 Leg 7 Leg 8 Flange 9 Flange 10 Bead 11 Tapered partial region 12 Flank 13 Flank 14, 14.1 Predetermined bending point 15 First end 16 Second end 17 Connecting region 18 Connecting region 19 Floor

Claims

Side impact beam for a motor vehicle, comprising a beam (1) which is produced substantially from a profile (2) which is hat-shaped in cross section and is arranged at least in sections in and / or on a vehicle door structure so as to be open in the direction of the vehicle interior, having a central web (3) on the upper and lower edge (4, 5) of which in each case one limb (6, 7) is arranged at an angle thereto, and wherein in each case at least one flange (8, 9) is arranged at an angle offset, and wherein a bead (10) which extends at least in sections over the longitudinal course of the central web (3) and has a base (19) and two opposite flanks (12, 13) is formed, characterized in that the bead (10) is formed in a tapered subregion (11) so as to taper on both sides in the z direction and is arranged centrally in the x direction.Side impact beam according to Claim 1, characterized in that the tapered subregion (11) forms at least one predetermined buckling point (14, 14.1).Side impact beam according to one of Claims 1 to 2, characterized in that the tapering of the tapered partial region (11) takes place in a sudden or smooth manner and then extends parallel to the flanks (12, 13) of the central bead (10) without any introduced tapering.Side impact beam according to one of Claims 1 to 3, characterized in that the tapering of the tapered partial region (11) extends at least over 20 mm in the x direction.Side impact beam according to one of Claims 1 to 4, characterized in that the hat-shaped profile (2) has at least one connection region (17, 18) in each case at its first and second ends (15, 16).Side impact beam according to claim 5, characterised in that the first and second ends (15, 16), as viewed in cross-section, are designed as a flat and / or W-shaped profiled section.Side impact beam according to one of Claims 1 to 6, characterized in that a plurality of tapers spaced apart from one another in the x direction are arranged over the longitudinal course of the central bead (10).Side impact beam according to one of the preceding claims, characterized in that the side impact beam (1) is produced from a press-hardenable steel, a cold-formable steel, a steel alloy, a light metal, a light metal alloy or an organoplate made of carbon and / or glass fibre.Side impact beam according to one of Claims 1 to 8, characterized in that the depth of the central bead (10) varies over its longitudinal course.Side impact beam according to one of Claims 1 to 9, characterized in that the central bead (10), as viewed over its longitudinal course, is formed at a constant depth at least in the tapered partial region (11).

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