Collision Damper for Motor Vehicles

This application claims the priority of German application Serial No. 195 26 707.9, filed Jul. 24, 1995, which is incorporated herein by reference.

The invention relates to a collision damping arrangement for absorbing energy in a possible head-on and/or rear end collision of a motor vehicle. More particularly, the present invention, relates to such a collision damping arrangement which is of the type comprising a bumper-side cross member, a plurality of longitudinal members arranged on the cross member and connected or connectable to the passenger compartment of a motor vehicle, and at least one collision damper arranged on each longitudinal member.

In order to protect the occupants of a motor vehicle during a head-on or rear end collision, it is known to embody the longitudinal members, which are arranged on the bumper-side cross members and which, in turn, are connected with the passenger compartment, in such a manner that they absorb the energy released by the impact by way of deformation. Such a deformation can be accomplished, on the one hand, in that the longitudinal members are curved, with the bending moment generated during the collision resulting in a deformation of the longitudinal member and the deformation points being determined by the selection of the cross sections. On the other hand, a deformation of the longitudinal members can also be brought about by beading of the longitudinal members in the longitudinal direction.

Collision dampers of the above-mentioned type, in which essentially only the longitudinal members themselves form the respective collision damper, are relatively expensive to produce. Since the collision dampers must also absorb an impact in the low speed range (e. g., at 10 km/h), the longitudinal members must be replaced after collisions with corresponding frequency, a process which is extremely time-consuming and expensive.

Furthermore, collision dampers have become known which are respectively comprised of a relatively short hollow section (so-called crashboxes) and which are used in-between the corresponding bumper-side cross members and the associated longitudinal members. Usually, these hollow sections are also made from sheet metal pieces. In these collision dampers or, the hollow space of the profile extends in the longitudinal direction of the longitudinal member, with a matching of the collision behavior of the vehicle implemented primarily by way of the shape of the hollow section and the wall thickness of the sheet metal pieces. It is very expensive to produce the appropriate hollow sections because the sheet metal pieces must be punched out and they must then be connected with one another by means of spot welding. Furthermore, such collision dampers do not allow a precise, speed-dependent matching of the collision behavior of the respective motor vehicle.

From DE 42 04 826 A1, it is known to use gusset elements for the cost-advantageous connection of hollow profiles; the gusset elements are also embodied as hollow sections and are produced by means of extrusion. on the one hand, such gusset elements can be produced in a cost-advantageous manner and, on the other, they possess a high degree of rigidity.

It is the object of the invention to provide a collision damping arrangement with a collision damper of the type mentioned at the outset which can be produced in a straightforward manner and at reasonable cost and which allows a precise matching of a predeterminable collision behavior of the vehicle in a simple manner.

The above object is achieved according to the present invention by a collision damping arrangement for absorbing energy in a possible head-on and/or rear end collision of a motor vehicle, comprising a bumper-side cross member; a plurality of longitudinal members arranged on the cross member and connected or connectable to a corresponding passenger compartment of a motor vehicle; and at least one collision damper for absorbing energy arranged on each longitudinal member, with the collision damper comprising an extruded section whose constant cross-sectional profile extends transversely to the longitudinal axis of the associated longitudinal member for the motor vehicle. Further particularly advantageous embodiments and features of the invention are disclosed.

The invention is essentially based on the concept that the collision damper is comprised of an extruded section, preferably made of aluminum or an aluminum alloy, whose cross-sectional profile extends transversely to the longitudinal axis of the longitudinal member (transversely molded extruded section).

The collision dampers according to the invention can be produced in a straightforward and cost-advantageous manner by cutting a corresponding extruded section into lengths. By orienting the profile transversely to the longitudinal direction of the longitudinal member, the collision damper can be very precisely adapted to the desired collision behavior of the vehicle, even in the low speed range, by a corresponding number of hollow chambers disposed next to one another and by the shaping of the profile and by the wall thickness of the section walls and of possible stiffening ribs.

Further details and advantages of the invention ensue from the embodiments described below which are explained by use of the figures wherein:

FIG. 1 is a perspective view of a first embodiment of two collision dampers (crashboxes) according to the invention arranged in-between the cross member and two longitudinal members of a motor vehicle;

FIGS. 2 to 5, each show a side view of the arrangement illustrated in FIG. 1 in different collision situations;

FIG. 6 is a perspective view of a second embodiment of a collision damper according to the invention, with the cross section dimensions both changing in the longitudinal direction of the longitudinal member;

FIG. 7 is a perspective view of a third embodiment of a collision damper according to the invention mounted into a longitudinal member on the end of the longitudinal member facing the passenger compartment; and,

FIG. 8 shows an embodiment according to FIG. 7 having an X-shaped profile.

In FIG. 1, a cross member of a motor vehicle bumper, which cross member is embodied as a hollow section, is identified by 1. Longitudinal members 4 and 5 are arranged or mounted on the cross member 1 via collision dampers 2, 3 according to the invention which are comprised of an aluminum alloy. The longitudinal members 4,5 extend up to the passenger compartment which is not shown for the sake of clarity.

The collision dampers 2, 3 are extruded hollow sections, whose constant cross-sectional profiles extend transversely to the longitudinal axis 6 of the respective longitudinal member 4, 5. The hollow section of each damper 2,3 essentially comprised of two chambers 7, 8 or 9, 10, which are preferably square or rectangular as shown and are arranged next to one another in the direction of the longitudinal axis 6, and which are respectively stiffened by stiffening ribs 11-14, which as illustrated preferably extend in the diagonal direction of the respective chamber.

The functioning of the collision dampers 2,3 according to the invention is illustrated in FIGS. 2 to 5. Of these, FIG. 2 reflects the normal case (collision damper without load). In the example shown in FIG. 3, an impact of the corresponding vehicle occurred against a rigid wall at a speed of 5 km/h. The wall thicknesses of chambers 9 and 10 as well as of the stiffening ribs 13, 14 and of the cross member 1 are designed such that, in this case, only the first chamber 9, i.e., the chamber facing the cross member 1, of the hollow section collapses. If the impact speed, however, amounts to 10 km/h, the second chamber 10 of the hollow section also collapses as shown in FIG. 4. Finally, if the impact speed of the vehicle amounts to approx. 15 km/h, the cross member 1 is also compressed as shown in FIG. 5. Only at speeds exceeding 15 km/h is the longitudinal member 4 or 5 deformed as well.

For designing the collision dampers with a view to a predeterminable collision behavior, the outside dimensions of the collision damper can also be changed in addition to the selection of the material, the number of chambers of the profile, the thickness of the chamber walls and, optionally, the design of the stiffening ribs. A corresponding embodiment is illustrated in FIG. 6. Here, the cross member and the longitudinal members are again identified by reference numerals 1, 4 and 5, respectively. As the distance from the cross member 1 increases, the two collision dampers 15 and 16 have an increasing outside dimensions in the two directions which are perpendicular to the longitudinal axis 6.

FIG. 7 illustrates an embodiment wherein the collision damper identified by 17 is arranged in-between a longitudinal member 19 connected to the cross member 18 and the passenger compartment 20. As shown the end of the collision damper 17 extends into the hollow interior of the longitudinal member 19. The collision damper 17 is comprised of an extruded profiled section which, due to various re-enforcing ribs, has several chambers arranged next to one another in the longitudinal direction of the longitudinal member 19. In a practical embodiment, the collision behavior of this collision damper 17 was selected such that all chambers of the hollow section had collapsed at an impact speed of approx. 50 km/h, and a deformation of the longitudinal member 19 occurred only at speeds higher than that.

It is understood that the invention is not limited to the embodiments specifically illustrated and described above. Thus, instead of the simple hollow sections, for example, profiled sections having an X-shaped or double X-shaped cross section (FIG. 8) or profiled sections having an asymmetrical design can also be used.

In order to accomplish a precise matching of the collision behavior, it turned out to be of advantage if the collision damper had a modular construction made up of individual, prefabricated extruded sections with optionally different properties, and if the collision damper was specifically tailored to the vehicle which is to be equipped. Furthermore, the collision damper can also be part of a modular longitudinal member which can be put together from a plurality of individual extruded sections, e.g. a plurality of section 2,3, or a plurality of sections with different shapes, such as the collision dampers 2 and 15.

Finally, it is certainly not imperative to change the outer dimensions of the collision dampers in both the x-direction and the y-direction for the matching of the collision behavior, as is shown in FIG. 6, but the dimensions can also be changed in one direction only. Here, the change does not have to extend linearly but can also follow a nonlinear function. All of these variants can be implemented in a straightforward manner by the production of an extruded section and by appropriate trimming.

The invention now being fully described, it will be apparent to one of ordinary skill in the art that any changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.