BACKGROUND

The present disclosure relates to a bumper cross member, designed as a hollow chamber profile, for a motor vehicle having an upper component and a lower component joined to the upper component, wherein the upper component and the lower component are each embodied as a half shell having legs spaced apart from one another and a web connecting the legs, wherein an insert plate is joined to the legs of the half shells.

The term bumper cross member used in the context of this disclosure includes such a bumper cross member, regardless of whether it is for passenger vehicles or utility vehicles, in particular trucks, wherein the latter can also be used as underrun protection.

A bumper cross member is known from DE 10 2015 101 435 B3. This previously known bumper cross member comprises an upper P-shaped profiled component and a lower P-shaped profiled component joined to it. Since the two components are rotated 180 degrees in relation to one another and arranged with their protruding legs facing each other, this arrangement provides a hollow chamber profile for forming the bumper cross member having three hollow chambers lying one above the other in the vertical direction. The crash performance of such a bumper cross member having more than two hollow chambers is improved over the design of a bumper cross member having only two hollow chambers or only one hollow chamber. However, the production of such a previously known multi-chamber hollow profile bumper cross member is expensive due to the multiple process steps to be carried out, which also include roll forming to produce the individual components, in particular if they are manufactured from sheet steel.

A two-shell bumper cross member which is composed of an upper shell and a lower shell is known from EP 1 182 095 A1. The profile formed by the two shells is open in the direction of the chassis of the vehicle and therefore has a C-shaped cross section.

A cross member is known from the prior art from DE 10 2009 005 606 B9, which comprises a hat-shaped shell profile arranged on the vehicle chassis side, which is closed by a strike plate facing in the direction of travel. The strike plate is welded to these profile parts on the flanges which are bent over in the vertical direction from the profiled shell profile. A similar concept is known from DE 10 2010 050 013 A1, wherein the strike plate can also be profiled in this previously known bumper cross member

Furthermore, a bumper is known from DE 20 2008 017 596 U1 which consists of two essentially symmetrical half shells which are placed against one another in such a way that they delimit a cavity. These two half shells are arranged one above the other so that one half shell forms a lower half shell and a further half shell forms an upper half shell. These two half shells each have a web connecting the legs that are spaced apart from one another. Crash boxes are formed onto the chassis side of this known bumper cross member.

A generic bumper is also known from DE 195 11 868 A1, which has a cross member. This bumper cross member is also constructed from a lower and an upper half shell, the legs of which are spaced apart from one another and are connected to one another by a web. In addition, an insert plate is provided between these two half shells, which is joined to the legs.

These bumper cross members meet the conventional requirements for crash performance. More recently, the IIHS (Insurance Institute for Highway Safety, USA) implemented a so-called “small overlap test” in vehicle testing. In this test, bumper cross members are also exposed to significant side impact forces. The bumper cross members described above sometimes fail these tests. Even if bumper cross members of this type are easy to manufacture, it would be desirable if the crash properties (crash performance) could be improved in relation to the so-called “small overlap test” of the IIHS.

SUMMARY

This aspect is achieved according to the present disclosure by an above-mentioned generic bumper cross member, in which the insert plate is arranged between the joints of the legs of the half shells facing toward one another and bridges the joint spacing between the legs of the two half shells.

This bumper cross member is designed as a hollow chamber profile. The hollow chamber profile is formed by an upper half shell, a lower half shell, and an insert plate inserted between the half shells. The hollow chamber profile is therefore formed having two chambers. This does not rule out that each chamber formed by the half shell can be further subdivided. Both the upper and also the lower half shell have two legs which are spaced apart from one another in the travel direction of the vehicle (x-direction) and which are connected at one end by a web. The half shells are arranged in relation to one another in such a way that the joints formed by the free ends of the legs face toward one another. An insert plate is interposed between the joints of the legs of the half shells facing toward one another. This bridges the joint spacing between the legs of the two half shells. The joints of the one half shell are thus spaced apart or separated from those of the other half shell by the insert plate. The legs of the half shells are welded to the insert plate, typically on the outside. The joint connection of the three components mentioned, which are involved in the construction of the bumper cross member, can be joined in adaptation to the requirements placed on the bumper cross member as a continuous weld seam over the longitudinal extension of the bumper cross member, as a stitched seam having different lengths of the individual welds, or by spot welds.

This bumper cross member has a significantly improved crash performance, especially with respect to the “small overlap test”. The insert plate arranged between the joints of the legs and the joint connection between this and the legs of the half shells effectively counteracts buckling of the bumper cross member transversely to its longitudinal extension. This is due not only to the fact that the provision of the insert plate requires more energy for deformation of the bumper cross member and thus more energy is absorbed in the event of a crash, but in particular also because a force acting in the horizontal direction on the bumper cross member is not only absorbed via the insert plate, because it is joined to the spaced-apart legs of the two half shells, but also via the half shells themselves and transferred to the rear connection of the bumper cross member to the vehicle. The spatial position of the legs is fixed by joining the insert plate to the legs. Conversely, the legs joined to the insert plate counteract both tensile and compressive stresses acting in the horizontal plane on the insert plate. In a “small overlap test”, the end section of the bumper cross member that is on the outside in the x-direction is subjected to tensile stress outside of its connection to a longitudinal member of the vehicle, while compressive stress acts on the inside of the bumper cross member. When subjected to pressure, the insert plate attempts to undulate, but this is effectively prevented by the legs of the two half shells that stand on it and are joined to the insert plate. The same applies to the tension side, on which tearing of the insert plate is also effectively counteracted by the legs of the half shells connected to it.

The concept described above enables the bumper cross member to be produced from the three components without great effort. This means that they can be manufactured with basically the same production steps as is the case with previously known bumper cross members composed of multiple components. Above all, it is easily possible to produce these from sheet steel parts. The insert plate is preferably a steel plate stamped into shape.

The concept of arranging an insert plate between the joints of the legs of the half shells facing toward one another, bridging the joint spacing of the legs of the two half shells, and joining it with the legs of the half shells, also enables the crash performance of the bumper cross member to be adapted to the respective requirements solely by modifying the insert plate. This can be done via the geometry of the insert plate, therefore its geometry in the x-y plane and/or also with regard to its thickness and/or with regard to the material used and/or the material quality used. The crash performance may be influenced, for example, by varying the material thickness of the insert plate. Influencing the geometry in the x-y plane of the bumper cross member includes the possibility that the insert plate protrudes on the front and/or rear over the outside of the legs of the half shells facing in the x direction. This excess enlarges the area of the insert plate effective against buckling, and therefore significantly increases the force required to buckle such a bumper cross member, for example in the context of a “small overlap test”.

In the case of the bumper cross member according to the present disclosure, when the same half shells are used, the crash performance can be influenced solely by using differently designed insert plates on the structure of the bumper cross member, so that in different bumper cross member series these can be produced with identical parts with respect to the half shells and can be differentiated simply by switching in a differently designed insert plate between the joints of the half shells.

The width of the protruding excess of the insert plate can be the same on the front and rear. The width of the excess protruding at the front can also be smaller than the width of the rear excess facing toward the chassis of the vehicle—for example due to limitations in the available installation space. The same also applies in the opposite case that the front excess is larger than the rear. The excess of the insert plate can also be bent at the front and/or rear, typically in the plane of one of the two legs of the half shells.

A further improvement in the crash performance of such a bumper cross member, which has an excess due to its insert plate at the rear and thus facing towards the chassis of the vehicle, can be achieved if the rear excess is notched in this connection region to connect the bumper cross member to a longitudinal member component, typically a crash box. What is achieved hereby is that the end face of the excess formed by the notch and facing towards the center of the bumper cross member is supported on the side of the longitudinal member component facing outward in the y-direction. This lateral support of the bumper cross member on the longitudinal member component results in further improved lateral impact protection. This effect can be increased by the fact that the width of the projection facing toward the chassis increases in the direction of the notch. The support on the side wall of the longitudinal member component is then correspondingly longer and more effective.

Interestingly, it has been shown that despite the weakening of the bumper cross member by such a notch, this is more than compensated for by the above-described lateral support of the front face of the notch facing towards the center.

The interposing of an insert plate between the joints of the legs of two half shells facing toward one another and the resulting significantly improved crash performance takes place without any significant increase in the weight of the bumper cross member. This is also because the joining or assembly flanges fundamentally required in the prior art are basically not required on the half shells. In addition, due to the above-described force distribution in the event of a crash via the components involved in the construction of the bumper cross member, a material with a lower material thickness can sometimes also be used by providing such an insert plate. In this respect, such a bumper cross member can be designed to be weight-optimized.

A further weight reduction can be achieved if the insert plate has recesses. These are openings introduced into the insert plate which are used for reducing weight. The recesses will be arranged in such a way that the desired force-transmitting properties of the insert plate are retained. These recesses can have any shape, for example circular, rectangular, star-shaped, or the like. The remaining structure of the insert plate is decisive, for example in the manner of a framework by which the spaced-apart legs of the half shells are connected to one another.

The directions mentioned in the context of this disclosure—x-direction, y-direction, or z-direction—are the directions commonly used in the industry for motor vehicles. The x-direction corresponds to the longitudinal extension of the vehicle, the y-direction to the transverse extension of the vehicle, and the z-direction to the direction of the height of the vehicle.

