Abstract:
A car body part for a motor vehicle comprises an outer skin which consists of an at least partially deformable material, an inner layer which consists of foamed plastics, and a mounting part which is placed in a recess of the outer skin and is anchored there by means of an interlocking fit. There is further proposed a method of producing such car body part.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to a car body part for a motor vehicle, in particular a roof module, as well as to a method of producing such car body part.  
         BACKGROUND OF THE INVENTION  
         [0002]    In case it is desired to fasten mount-on parts to a car body part of a vehicle, for instance a roof railing to a roof module or a second car body part, then it is required to provide either additional fastening elements and usually holes in the car body part or particular provisions for connecting the two car body parts. This has disadvantages both in terms of costs and expenses. It is also true that tolerances have to be kept small so that undesirably large gap dimensions will not occur.  
           [0003]    It is the object of the invention to provide a car body part which allows mount-on parts to be installed thereon at low expenses and which provides visually appealing gap dimensions.  
         BRIEF SUMMARY OF THE INVENTION  
         [0004]    According to the invention, car body part for a motor vehicle comprises an outer skin which consists of an at least partially deformable material, an inner layer which consists of foamed plastics, and a mounting part which is placed in a recess of the outer skin and is anchored there by means of an interlocking fit. The invention is based on the basic idea of clamping the mounting part in the recess of the outer skin; to this end, an elastic pretension of the car body part is made use of. The holding force is increased through the fact that there is made provision of a form-fitting anchoring of the mounting part in the recess, for instance by means of anchoring protrusions provided on the mounting part which are forced into the outer skin of the car body part. Moreover, by positioning the mounting part in the recess, low tolerances will be produced.  
           [0005]    In order to clamp the outer skin against the mounting part, it is particularly suitable to use the inner layer which is made of a foamed plastics and, if applicable, is provided with reinforcement fibers, for instance glass fibers. This arrangement has the particular advantage that the foaming pressure, which will be generated during foaming of the inner layer, can be used to strongly press the outer skin against the mounting part and deform the outer skin in the process such that the mounting part is received with an interlocking fit.  
           [0006]    It is particularly suitable to use a rail as the mounting part; such rail can be, for instance, an extruded aluminum profile that has a plurality of anchoring protrusions on its outer surface. The anchoring protrusions serve for a positive anchoring of the mounting part in the outer skin. It is also possible to insert a mounting part in the form of e.g. a threaded piece, which may serve as a base part of a roof antenna, for instance.  
           [0007]    It is also particularly suitable to use a second car body part, the car body part having a bent-off edge portion which is accommodated in the recess of the first car body part. This allows to obtain assemblies which on the one hand are preferably formed from deep-drawn plastics parts and on the other hand have dimensions which could not be obtained if formed in one piece.  
           [0008]    Preferably it is provided for that the recess in the outer skin has a rectangular cross-section and the mounting part is fully received in the recess. This makes it possible to fasten a mount-on part to the mounting part, if required, for instance a roof railing, while the mounting part—due to it being arranged so as to be let in—not impairing the visual appearance in case the mount-on part is not provided. In such case it is possible to attach a covering which is flush with the outer surface of the outer skin.  
           [0009]    It may also be provided to design the mounting part so as to terminate flush with the outer surface of the outer skin and to match the upper side of the mounting part with the curvature of the outer skin, so that the outer contour is not interrupted in visual terms.  
           [0010]    With respect to the necessary deformability of the outer skin it is of advantage if it is made of plastics. In spite of the deformability of the outer skin, the strength of the car body part will be sufficient in any case, because the inner layer provides for the required strength.  
           [0011]    In case plastics is used for the outer skin, then the recess in the outer skin can also be realized with an undercut, behind which the mounting part will latch in place automatically. After having applied the inner layer, the grip of the mounting part in the outer skin is further improved. Such an undercut does not incur big problems in terms of removing the outer skin from the mold, because the yielding nature of the plastics material is sufficiently high.  
           [0012]    The car body part according to the invention can be a roof module, in particular. In this case the mounting part allows to simply attach the various mount-on parts which can be provided on a roof module.  
           [0013]    According to the invention, there is also provided a method of producing a car body part, in particular a roof module. In this method, there is first provided an outer skin which has a recess. Then a mounting part is placed in the recess. As a next step, the outer skin including the mounting part is placed in a foaming mold, and a foamed inner layer is applied on the rear side of the outer skin, with a foaming pressure generated in this process strongly pressing the outer skin against the mounting part, so that the latter is firmly anchored in the recess. This method makes use of the foaming pressure, which anyway exists during producing foamed car body parts including a foamed component, for fastening the mounting part to the outer skin. Hence, additional process steps are not required which results in reduced process costs.  
           [0014]    The outer skin can be deep-drawn, in particular, in order to obtain the recess for receiving the mounting part. It is in this way that the required recess can be produced in a very cost-effective manner, for instance in one single step together with the formation of the outer skin.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 shows in schematic, broken sectional view an outer skin for a car body part according to a first embodiment of the invention;  
         [0016]    [0016]FIG. 2 shows in a schematic, broken sectional view the outer skin of FIG. 1 which is inserted in a foaming tool and provided with a mounting part;  
         [0017]    [0017]FIG. 3 shows in a schematic, broken sectional view the finished car body part according to the first embodiment;  
         [0018]    [0018]FIG. 4 shows a in schematic, broken sectional view an outer skin for a car body part according to a second embodiment of the invention; and  
         [0019]    [0019]FIG. 5 shows a in schematic, broken sectional view the finished car body part according to the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    In FIG. 1 there can be seen an outer skin  10  according to a first embodiment, which later on will represent the outer skin of a roof module for a motor vehicle. The outer skin  10  is made of plastics and has been deep-drawn, so that there is formed a recess  12  with a bottom  14  and two side walls  16 .  
         [0021]    In FIG. 2 there is to be seen the outer skin of FIG. 1, it being placed in a foaming tool which consists of a lower part  18  and an upper part  20 . Placed in the recess  12  is a mounting part  22  which in this arrangement is a rail made of aluminum and having a rectangular cross-section. The mounting part  22  has one side lying against the bottom  14  of the recess  12  across a large surface area. On the opposite side, the mounting part  22  is provided with a slot, so that a mount-on part, to be anchored later on, can be inserted into the mounting part  22 . For fixing the mounting part  22 , the lower part  18  of the foaming mold is provided with a web  24  which projects into the interior of the mounting part through the slotted side thereof. On its side surfaces  26  opposite the side walls  16  of the recess, the mounting part is provided with a plurality of anchoring protrusions  28  which are realized here as several individual bumps. As can be taken from FIG. 2, the mounting part  22  rests against the side walls  16  of the recess  12  only by its anchoring protrusions  28 .  
         [0022]    Applied onto the side of the outer skin  10  which later will face the vehicle interior is a foamable plastics material  30  which will be cured.  
         [0023]    After having applied the foamable plastics material  30 , the foaming mold will be closed, and due to the increase in volume of the foamable plastics material  30  the interior pressure in the foaming mold will increase. In the process, the foaming pressure strongly presses the bottom  14  and the side walls  16  of the recess against the mounting part  22  which, however, will not give way due to its strength and it being supported by the web  24 . On the other hand, the foaming pressure will provide for that the side walls  16  of the recess  12  lay on the side surfaces  26  of the mounting part  22 , i.e. will be deformed such that they receive the anchoring protrusions  28  and the gap between the side surfaces  26  of the mounting part and the outer skin disappears. This can be seen in FIG. 3 in which the roof module is shown in its finished state. The foamable plastics material is cured and forms an inner layer  30 ′ which ensures due to its strength that the outer skin  10  has a tight fit with the mounting part  22  in the region of the recess  12 , in particular at its side surfaces  26  having the anchoring protrusions  28 . In this way the mounting part  22  is anchored on the car body part with an interlocking fit, so that it is possible to attach mount-on parts. In case mount-on parts are not used, a covering can be attached which is flush with the outer side of the outer skin, so that a visually attractive appearance will be produced.  
         [0024]    [0024]FIGS. 4 and 5 show a second embodiment of the invention. For elements known from the first embodiment, the same reference numerals are used, and reference is made in this regard to the above explanations.  
         [0025]    The main difference between the first and the second embodiment is that in the second embodiment, the mounting part is no element used for mounting other parts but a car body element which is directly mounted to the first car body part. This allows to obtain large assemblies made from plastics which cannot be produced integrally, e.g. since they cannot be deep-drawn due to their geometry or since they are to feature different colors in some portions.  
         [0026]    As is shown in FIG. 4, the outer skin  10  is provided with a recess  12  having a rectangular cross-section, the depth of the recess being greater than the width. The mounting part  22  is provided with an edge portion  32  which is curved in the shape of a question mark, the edge portion  32  being arranged in the interior of the recess.  
         [0027]    When the foamable plastics material is cured, a foaming pressure is applied to those portions of the outer skin  10  which form the recess. The foaming pressure is indicated in FIG. 4 by means of the arrows, and results in a deformation of the side walls  16  of the recess so that they contact the edge portion  32 . Thus, the edge portion is held in the recess in a form-locking manner.