Abstract:
A framework such as a vehicle body is disclosed and includes at least two components of materials with different heat expansion coefficients fastened to one another on an elongated overlap zone. The overlap zone on a first component is subdivided by weak points oriented in its transverse direction into portions following one another in longitudinal direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 102014011263.2, filed Jul. 28, 2014, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure pertains to a framework of multiple components, e.g., a motor vehicle body, and more particularly to a framework having different material components which reduces thermal stresses that otherwise occur with changing temperatures between components consisting of different materials when these are connected to one another in a fixed manner at multiple points that are distant from one another. 
     BACKGROUND 
     DE 10 2011 107 035 A1 discloses a method for joining components with different heat expansion coefficients, in which the components are preheated to a temperature which is in the middle of a temperature interval in which the finished framework is to keep its shape so that the framework although being under stress at both limits of the temperature interval, but these stresses do not become so severe that they deform the framework. For a motor vehicle body this implies that since in practice the ambient temperature forms the lower limit of the temperature interval, the body during the use of the motor vehicle is constantly subjected to stress and when it is damaged during an accident yield to these stresses through abrupt deformation under certain conditions. In addition, this method requires a major expenditure of time, energy and material since the required tools for heating the components to be connected have to be made available and operated, and the time spent for joining the body is extended at least by the time needed for tempering the components. 
     SUMMARY 
     In accordance with the present disclosure, a framework of components with different heat expansion coefficients is created, which does not tend to a stress-induced deformation even with major temperature fluctuations. In particular, a framework, such as a motor vehicle body, is provided with at least two components in the form of a frame member fastened to one another on an elongated overlap zone of materials with different heat expansion coefficients on at least a first of the two components. The overlap zone is subdivided by weak points oriented in a transverse direction into sections following one another in longitudinal direction. In that the first component locally deforms at the weak points, the occurrence of stresses which globally deform the framework can be prevented. A time-consuming temperature controlling step is not necessary Creating the weak points can be integrated with little effort in the production of the first component, in particular by cutting to size, punching out, deep drawing or the like. 
     A fixed connection to the second component should be formed in multiple of these sections. Preferably, each of these sections should have a fixed connection for when a section remains unconnected to the second component, it and the weak points limiting it could be replaced by a single possibly wider weak point and the structure of the first component simplified in this way. The fixed connection can be of any type which immovably fixes the components locally to one another such as for example a welded, riveted, clinching or gluing connection. 
     In that the weak points become narrower with rising temperature and wider with decreasing temperature, they can adapt the heat expansion behavior of the first component in the overlap zone to that of the second component, so that deformation similar to the known bi-metallic effect does not occur. When the component with the higher heat expansion coefficient is selected as first component, the heat expansion of the entire framework will substantially orient itself towards the lower expansion coefficient of the second component. 
     According to a simple and practical configuration, the weak points are formed as slots oriented in transverse direction of the overlap zone. At least the first component should be a cutting of flat material in particular sheet metal. The overlap zone can then extend along an edge of the flat material cutting. This facilitates the first component yielding to the stress acting in the overlap zone without being irreversibly deformed by this. Obviously, the second component can also be a flat material cutting and the overlap zone can also run at the edge of this cutting. 
     Reversible or elastic yielding of the first component upon thermal stress can be facilitated in particular in that the slots are open towards the edge of the flat material cutting of the first component. Widening at an end of the slots that is distant from an edge contributes to spatially distributing the thermal stresses that occur in the first component and counteract the risk of the formation of stress cracks in the first component, in particular at the end of the slots that are distant from the edge. A further contribution to avoiding excessive stresses at the ends of the slots that are distant from the edge that could possibly be material damaging can be that their distance from the edge is greater than the distance of the fixed connections from the edge. 
     In order to avoid leakage of the framework the slots should be completely covered by the second component. In order to prevent that dirt or moisture can accumulate in the slots these can be filled out with a permanently elastic sealing compound. When the first component has the lower thermal expansion coefficient, the filling out of the slots with the sealing compound should take place at low temperature. In this way it can be ensured that the sealing compound is subjected to pressure, but not tensile loading which could result in a tearing-open of the connection of the sealing compound to the flanks of the first component limiting the slots. 
     According to a possible application, the two components together form a hollow profile, in the case of a motor vehicle body, in particular a body side or cross member or a sill. According to a preferred application, one of the two components is a roof panel of a vehicle body and the other one is a side beam, which extends laterally of the roof panel, in particular above a door aperture of the body. With a typical application, the first component consists of aluminum while the second component can consist of steel. 
     During the drying of an applied paint layer, a framework such as for example a motor vehicle body is mostly exposed to high temperatures so that in particular during the drying of the paint layer major thermal stresses can occur. Such painted frameworks form a preferred area of application of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
         FIG. 1  is a perspective view of an extract of the frame structure of a motor vehicle body; 
         FIG. 2  is an enlarged detail from the frame structure of  FIG. 1  in perspective view; 
         FIG. 3  shows the detail of  FIG. 2  in top view; 
         FIG. 4  is a top view analogous to  FIG. 3  according to a modified configuration; 
         FIG. 5  shown an upper part of a motor vehicle body; 
         FIG. 6  is a section along the plane VI-VI from  FIG. 5 ; and 
         FIG. 7  shows an overlap zone between two components according to a further configuration of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
     As a first application example of the present disclosure,  FIG. 1  shows an extract from a frame structure forming a lower part of a motor vehicle body. The frame structure includes a side member  1 , which substantially extends over the entire length of the vehicle body and of which merely a rear part is shown here, which extends from a heel plate  2  in the direction of the vehicle rear. The frame structure is mirror-symmetrical with respect to a symmetry plane marked in  FIG. 1  by a dash-dotted line  3 . The halves of the heel plate  2  extending on the other side of the symmetry plane and of cross members  4 ,  5  originating from the side member  1  are not shown in the figure. 
     The side member  1  is assembled from multiple panels, which in overlap zones extending in vehicle longitudinal direction are connected to one another. Elongated flanges formed at the edges of the panels are welded, glued or in another manner fastened to one another. Two such panels which are connected to one another in overlap zones  6 ,  7  and which complement one another at least at a front end of the shown portion of the side member it to form a closed hollow profile are marked with  8  and  9  respectively. 
     A further elongated panel  10 , which in front of the heel plate  2  has an inverted hat-shaped cross section and runs below a floor panel (not shown) of the passenger cell, merges with the panels  8 ,  9  at the height of a rear wheel housing recess  11  and is connected to the panel  9  in an overlap zone  12 . The cross members  4 ,  5  are each also assembled from two elongated panels which are connected to one another on overlap zones  13 . 
     The panels which are connected to one another along the overlap zones  6 ,  7 ,  12  or  13  may have different materials, e.g., one of the panels may be steel and the other panel may be aluminum. 
     In the overlap zones, two flanges each of the two panels touch one another, as is exemplarily shown in an enlarged manner for the panels  8 ,  9  in  FIG. 2 . In order to prevent the panels which are connected to one another from distorted at high temperature, in particular when after the painting of the body the same is dried at high temperature, the flange  15  with one of the two panels, in this case the aluminum panel  9  is divided into tongue-like portions  17  by a multitude of slots  16  which are open towards the edge of the panel. Each individual portion  17  is fastened to the opposite flange  14  of the steel panel  8  by connections  18  in the form of welded spots or glued spots, rivets or the like. The heat expansion of the aluminum which is higher compared to steel results in that the slots  16  at high temperature become slightly narrower. Accordingly, stresses between the panels  8 ,  9 , which could otherwise lead to bending or tearing-open of the connections  18  are avoided. Expansions  19  at the ends of the slots  16  that are distant from the edge facilitate the required deformation of the panel  9  and prevent that the stresses in the panel  9 , in particular at the ends of the slots  16 , are concentrated over a narrow space in such a manner that buckling or tearing of the panel  9  can occur there. 
     The slots  16  are shown empty in  FIGS. 2 and 3 . In practice, however, they may be practically filled out with a permanently elastic sealing compound when there is the possibility of contact with corrosion-promoting substances such as precipitation water or dirt swirled up from the road. The sealing compound prevents these substances from accumulating in the slots  16  and imparts the flange  15  on its top side facing away from the flange  14 , preferably with a flat surface that is difficult for substances to adhere to. 
       FIG. 4  shows a top view of flanges  14 ,  15  of the two panels  8 ,  9  which are connected to one another analogously to  FIG. 3 . The connection in this case is formed by an adhesive bead  20  that is continuously applied onto the non-slotted flange  14  of the panel  8 . During the pressing-together and gluing together of the flanges  14 ,  15 , the adhesive enters a small distance into the slots  16  of the panel  9  but is resilient enough even in the cured state so as not to obstruct a narrowing of the slots  16  at high temperature. Here, too, the slots  16  can be filled out with the sealing compound mentioned above provided they have not already been filled out by the adhesive. 
       FIG. 5  shows a perspective view of a top part of a motor vehicle body. A roof panel  21  in this case is flanked by side beams  22  on both sides, which connect A pillar  25  and C-pillar  26  of the body to one another above door apertures  23 ,  24 .  FIG. 6  shows in section along the plane marked VI-VI in  FIG. 5 , a partial section through one of the side beams  22  and the adjacent roof panel  21 . The side beam  22  is joined together from an outer panel  27 , an inner panel  28 , which are connected to one another via flanges  30 ,  31  which are elongated in vehicle longitudinal direction projecting into a roof aperture  29  that is limited on both sides by the side beams  22  and via flanges on the upper edge of the door aperture  24  which is not shown in  FIG. 6 . A reinforcing panel  32  extends through the hollow space limited by the outer and inner panel  27 ,  28  and engages between the flanges of outer and inner panel  27 ,  28  which are each connected to one another. 
     On its lateral edge, the roof panel  21  is bent C-like with an approximately upright flank  33 , which is located opposite a rising flank of the outer panel  27 , and an approximately horizontally oriented flange  34  following the flank  33 . The flanges  30 ,  31  and  34  form an overlap zone in which the flange  34  of the roof panel  21  supports itself on the flanges  30 ,  31  of the side beam  22  and is fastened to the same by an adhesive bead  20  running in vehicle longitudinal direction analogously to the representation of  FIG. 4 . Here, too, the flange  34  of the roof panel  24  consisting of aluminum is subdivided in longitudinal direction by numerous slots  16  which, by getting narrower at high temperature, prevent the occurrence of deforming stresses between the roof panel  23  and the steel panels  27 ,  28 ,  32  of the side beam  22 . 
     In a perspective view,  FIG. 7  shows an extract of two flanges  14 ,  15  which are connected to one another, analogous to those of the  FIGS. 3 and 4 . While, however, in  FIGS. 3 and 4  slots  16  weaken the flange  15  of the panel  9 , beads  35  are stamped into the panel  9  in  FIG. 7  for this purpose. When the portions  17  located between them expand more greatly at high temperature than the opposite panel  8 , these beads can also absorb stresses by becoming narrower. As a further example of a possible fixed connection  18  between the panels  8  and  9 , clinch connections in the portions  17  are indicated in  FIG. 7 . 
     It is to be understood that the above detailed description and the drawings represent certain exemplary configurations of the present disclosure but that they are only intended for illustration and should not be interpreted as being restrictive of the scope of the present disclosure. Various modifications of the described configurations are possible without leaving the scope of the following claims and their range of equivalents. In particular, the mentioned panels may include metals other than steel and/or aluminum, pairings of metal with composite materials such as for example “Organoplate” or pairings of composite materials among them are possible. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.