Abstract:
A method of producing a composite component uses a deep-drawing mold with indentations or raised portions. Slots are provided in the deep-drawing mold at each corner of these indentations or raised portions. Air is sucked off through the slots during deep-drawing.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The application claims priority to European Application No. 04 028 715.3, which was filed on Dec. 3, 2004.  
         [0002]     The invention relates to a method of producing a composite component, in particular a large-surface vehicle body attachment part, as well as to a deep-drawing mold for deep-drawing a foil to be provided with a foamed or injection-molded backing.  
         [0003]     Vehicle body attachment parts are those parts that define a portion of an outer skin in a completely mounted state of the vehicle, and which are secured to a vehicle body. Such vehicle body attachment parts include vehicle roofs, doors, door exterior linings, flaps such as hatchbacks or engine hoods, fenders, bumpers, wind deflectors etc., for example. These vehicle body attachment parts can be produced in a simple manner by using a foil, in particular a plastic or aluminum foil, which is provided with a foamed or injection-molded backing to form a composite component.  
         [0004]     Having produced the composite component, the foil constitutes a visible outer skin of the vehicle. Large-area composite components, which have a thickness that is by far smaller than their visible outer surface, are provided with beads for technical or aesthetic reasons. For aesthetic appeal, these beads should have a relatively shaped edge or square-edged cross-sectional shape. Even a step-like shoulder is considered as a bead in this context.  
         [0005]     For the formation of this bead, a deep-drawing mold has an indentation or raised portion formed by two surfaces meeting along a line of intersection. A bottom of the bead is formed by the line of intersection. Holes of a suction channel open out into the line of intersection so that the foil receives the correspondingly desired edge during deep-drawing. Due to a vacuum which is applied during deep-drawing, any air between the foil and deep-drawing mold will be sucked off, and the foil is drawn into a corner of the indentation, as seen in cross-section. A deep-drawing mold is a part of the deep-drawing tool and is for deep-drawing foils. The deep-drawing mold is not part of the final product, i.e. the composite component.  
         [0006]     It is the object of the invention to provide a method and a deep-drawing mold which provides for a better surface quality of the outer skin of the composite component.  
       SUMMARY OF THE INVENTION  
       [0007]     The method of producing a composite component according to the invention includes the following steps. A deep-drawing mold having an elongated, angular indentation or raised portion is used to form an elongated, square-edged bead in foil that defines an outer skin of a finished composite component. The indentation or raised portion is formed by two surfaces meeting along a line of intersection. The foil is placed in a deep-drawing tool provided with the deep-drawing mold. The foil is sucked in through a slot provided in the deep-drawing mold, and runs along the line of intersection. The slot constitutes an extension of a suction channel. The foil is deep-drawn. The suction process may commence before deep-drawing, however, at least during the deep-drawing process a suction effect occurs.  
         [0008]     The suction takes place via a very long, narrow slot rather than through small suction holes spaced away from each other. Other than the suction holes, the slot will not become apparent in the plastically deformed, deep-drawn foil, so that the composite component has a higher aesthetic quality.  
         [0009]     Moreover, as determined during testing, the bottom of the bead, or more generally the corners or edges of the bead, are formed so as to be definitely more sharp-edged than with the spaced suction holes. Beads are in particular starting points of raised portions such as build-ups or other convex contours that directly adjoin the bead. It should be understood that the finished composite component does not necessarily have to have a bead in the region of the line of intersection, but could instead have an edge protruding outwards. A bead can be produced by deep-drawing, but if the foil is turned, the bead will be a protrusion that can be provided with a foamed or injection-molded backing.  
         [0010]     With a preferred embodiment, however, the foil is provided with a foamed or injection-molded backing on a side that faces the deep-drawing mold provided with the slot.  
         [0011]     The composite component preferably is a large-area vehicle body attachment part.  
         [0012]     The foil used for deep-drawing is, for instance, a multilayered coextrusion foil with an outer layer that has an outstanding resistance to scratching. It is preferred that the foil is dyed throughout, so that the composite component will not be lacquered.  
         [0013]     According to the preferred embodiment, the foil has a thickness of at least 1 mm, preferably more than 1.2 mm.  
         [0014]     In order to be able to build up the vacuum in the region of the slot as quickly as possible, a plurality of suction channels or suction holes are provided that open out into the slot.  
         [0015]     The width of the slot depends on the foil thickness and/or the shape of the bead and, above all, on the radius at the bottom of the bead. The slot should have a maximum width of approximately 0.8 mm. More generally, the maximum slot width should amount to half the radius of curvature at the line of intersection. The maximum slot width should amount to 60%, preferably even to 50% of the foil thickness, as it is defined in a preferred embodiment.  
         [0016]     The foil is trimmed after the deep drawing. The foil is also preferably trimmed before or after the foamed or injection-molded backing has been applied, with the bead being situated in the portion that is not severed, i.e. in a visible part of the finished composite component.  
         [0017]     The slot extends substantially along the entire length of the indentation or raised portion, so that irritating marks on the foil are avoided.  
         [0018]     The invention further relates to a deep-drawing mold for deep-drawing a foil that is provided with a foamed/injection-molded backing. The deep-drawing mold has a contact surface provided for the foil, and comprises an elongated indentation or raised portion formed by two surfaces meeting along a line of intersection. A suction channel is also provided in the deep-drawing mold. The deep-drawing mold according to the invention provides that, along the line of intersection, the contact surface has an elongated slot in fluid communication with the suction channel. The slot has already been described above in detail in connection with the method according to the invention. All the details which have been mentioned above are optionally to be seen as the details of the deep-drawing mold itself.  
         [0019]     According to one embodiment, the indentation or raised portion has a U-shaped cross-sectional shape, with the corners of the “U” each being provided with one slot running in a longitudinal direction. Other embodiments implement a V-shaped groove.  
         [0020]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a perspective top view of a deep-drawing mold of a deep-drawing tool according to the invention, with a superimposed deep-drawn foil that is already adapted to the contour.  
         [0022]      FIG. 2  is an enlarged view of the front, right-hand corner region of the deep-drawing mold according to  FIG. 1 .  
         [0023]      FIG. 3  is a cross-sectional view through the deep-drawing tool along line III-III in  FIG. 2 .  
         [0024]      FIG. 4  is a schematic sectional view through a tool for making a foamed or injection-molded backing, with a finished, foamed or injection-molded composite component according to the invention.  
         [0025]      FIG. 5  shows a vehicle front piece with an engine hood produced according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]      FIG. 1  shows a right half of a deep-drawing mold  10 . The deep-drawing mold serves for deep-drawing a multilayered coextrusion foil  12  that has a thickness of at least 1 mm, and which is dyed throughout. As shown in  FIG. 1 , this foil  12  is already placed on a contact surface (upper side) of the deep-drawing mold  10 , has already been deep-drawn, and therefore reflects the contour of the contact surface.  
         [0027]     The foil  12 , delivered in the form of thin plates, is deep-drawn in a deep-drawing tool and later on will form an outer skin of a large-area body attachment part. In the present case the body attachment part is a vehicle roof module. As can be seen in FIGS.  1  to  3 , the outer skin (i.e. the foil  12 ) has a bulging bar  14  protruding upwards and extending in a longitudinal direction of a vehicle on an outer rim of the future roof module. This bar  14  is raised compared to the remaining, curved inner portion  16  of the roof. The bar  14  extends towards the outer rim as far as to a U-shaped bead  18 , which is in the form of a water drain gutter. The U-shaped bead  18  is followed by a lateral build-up  20 , which in turn is followed by a similar U-shaped bead  22 . A lateral flange rim  26  extends from the bead  22  across an entire rim of the foil  12 . In other words it is circumferentially closed. The flange rim  26  has a shoulder  28 .  
         [0028]     The deep-drawing mold  10  has several indentations and raised portions, which are provided for forming beads in the foil  12 . Provided between the inner portion  16  and the bar  14  is a sharp-edged, V-shaped indentation  32  ( FIG. 3 ) in the deep-drawing mold  10  for forming a bead  34  in the foil  12 . The indentation  32  is generated by two surfaces  36 ,  38  meeting along a line of intersection S, with the surface  36  defining a raised portion. A thin, elongated slot  40  extends along the line of intersection S. Numerous suction holes  42 , which are spaced from each other perpendicular to the drawing plane, act as suction channels and open out into this slot  40 .  
         [0029]     As can be seen in  FIG. 1 , slot  40  extends along an entire length of the indentation  32  ( FIG. 3 ). Slot  40  is illustrated with broken lines in  FIG. 1 , because the slot  40  is situated underneath foil  12 . For better illustration, the edges produced by the beads  34 ,  38  are not illustrated as lines in  FIGS. 1 and 2 . In the drawing they coincide with the slots  40 ,  52  and the lines of intersections S. The slots  40 ,  52 , however, are continuous. Discontinuous slots with an appearance similar to a perforation are actually possible, but there is a risk that the longitudinal ends of the slots may become apparent in the foil  12 . In the invention the slots are very narrow, significantly narrower than the suction holes used up to now. Due to this circumstance, the foil  12  will not be drawn into the slots  40 ,  52 . By the suction area, which is enlarged due to the length of the slots  40 ,  52 , however, the suction effect is improved, the suction itself is accelerated and the quality of the product is better.  
         [0030]     Bead  18  is formed by an indentation  44  in the deep-drawing mold  10 . At the corners of the “U”, where surfaces  46 ,  48  and surfaces  48 ,  50  meet each other, there is provided two slots  52 ,  54  that extend along an entire length of the indentation  44 . The indentation  44  is delimited by raised portions (surfaces  46 ,  50 ), with the terms “indentation” and “raised portion” being relative terms that depend on the reference plane. The “corners” of the indentation  44  thus form elongated lines of intersections S, with the slots  52 ,  54  opening out here. Reference numeral S, however, is omitted here for improving the clarity. The slots  52 ,  54  open out into shared suction holes  56 .  
         [0031]     Also, an indentation  58  provided in the deep-drawing mold  10  and associated to bead  22 , is defined by slots  60 ,  62  at the corners, i.e. at the lines of intersections S of meeting surfaces. The respective slots have the reference numerals  60 ,  62  and likewise are connected with the suction holes  56  in terms of flow.  
         [0032]     All slots extend along substantially the entire length of the respective indentation/raised portion in the edge portion of the indentation/raised portion. The slots have a maximum width of 0.8, preferably 0.6 mm and are produced by sawing, milling, etching or laser cutting.  
         [0033]     The production of the body attachment part is described below. At first, the foil  12  is clamped in a region of its outer circumferential rim  66  by a clamping frame  68 ,  70 , and is placed in the deep-drawing tool and heated by an inserted heating element. Subsequently, the heated deep-drawing mold  10  is moved upwards in order to plastically deform the foil  12 , and subject the foil  12  to deep-drawing. During the deep-drawing process a vacuum is applied at the suction channel, i.e. the suction holes  42 ,  56 , so that no air will remain between the foil  12  and the deep-drawing mold  10  in the regions of the corners of the indentations  32 ,  44 ,  58 , and the foil  12  is sucked into the corners.  
         [0034]     This makes a foil  12  with sharp tear-off edges in the beads  18 ,  22 ,  34 , and even undercuts in the deep-drawing direction (see bead  22 ). The slots cannot be seen on the finished foil  12 . The maximum width of the slots preferably amounts to half a radius R at the line of intersection S concerned. For more clarity, there has been illustrated only one radius R in  FIG. 3 , with the understanding that this also applies to the other lines of intersection. Further, the maximum width of each slot amounts to 50 or 60% of the foil thickness d.  
         [0035]     After having deep-drawn the foil  12 , the foil  12  is removed from the deep-drawing tool and placed in a foaming or injection-molding mold (see  FIG. 4 ). The rear of the foil  12 , namely a side which rests at the deep-drawing mold  10 , is oriented towards the top. Liquid polyurethane (PU) material  72  with glass fibers from a long fiber injection (LFI) dispersed therein is applied on the rear side. Then the foaming mold is closed and the plastic foams up. As an alternative, the foil  12  is provided with an injection-molded backing.  
         [0036]     In  FIG. 5  there is illustrated a second embodiment of a composite component produced according to the invention, namely in the form of an engine hood  80 . The engine hood  80  has a step-shaped raised portion starting from a radiator grill, with a lower step forming a bead  82  that extends so as to be elongated and is formed by a corresponding slot in the deep-drawing mold  10 .  
         [0037]     After having made the foamed backing, a rim area of the composite component is trimmed all around. In  FIG. 2  there is shown the future cutting edge, having reference numeral  84 .  
         [0038]     The trimming takes place in the bead  22 , which represents an undercut in the deep-drawing direction (vertical direction). With this, the slots  40 ,  52 ,  54 ,  62  are situated in the visible region of the composite component and not in the region where the trimming is performed.  
         [0039]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.