Abstract:
A technique for providing localized stiffening of a vehicle trim panel, especially for high curvature areas. The vehicle trim panel includes an outer panel having an outer show surface and an inner surface. A plurality of discrete reinforcement elements are bonded to the inner surface of the outer panel at locations where localized stiffening is desired. The discrete elements can come in a variety of different shapes and sizes, where the combination of elements and the number of elements is selected for a particular trim panel stiffness.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to providing discrete stiffeners to reinforce a panel and, more particularly, to securing thermoplastic injection molded discrete stiffeners to a back surface of a show surface panel of an automotive trim panel. 
         [0003]    2. Discussion of the Related Art 
         [0004]    Trim panels on a vehicle, such as fascias, rockers, door moldings, etc., typically have an outward facing show surface, sometimes referred to as a class-A surface, that gives the panel an aesthetically pleasing appearance. Providing such show surfaces often requires relatively expensive materials and manufacturing processes. Thus, trim panels are typically made very thin to conserve cost. However, such trim panels often times have a two-dimensional or three-dimensional curvature and are required to be stiff enough to resist various loads without excessive deformation. In response to this, it is known in the art to make a trim panel as a two-piece structure including an outer show surface panel and an internal support structure often including a series of stiffening ribs forming a frame that provides structural integrity. The support structure may include a series of welding pads integrated into the support structure at locations where the ribs intersect. The welding pads have the general shape of the show surface panel and are used to ultrasonically weld the support structure to an inside surface of the show surface panel. The stiffness of the trim panel is set mainly by the height, thickness and spacing of the ribs. 
         [0005]    In order to reduce cost and weight, it is desirable to limit the number of ribs in the support structure, which also reduces its stiffening capability. Thus, the ribs are generally selectively positioned and provided with different heights depending on where the structural integrity of the particular trim panel is desired. However, the height of the ribs is limited by the packaging volume of the trim panel. Further, although the show surface panel does possess some inherent stiffness, most of the stiffness is provided by the rib structure. Therefore, in order to further reduce the cost of the trim panel, it is desirable to make the show surface panel as thin as possible consistent with the ability of the support structure to provide the desired rigidity. However, because the support structure is welded to the show surface panel, there are limits as to how thin the show surface panel can be because the welding operation could cause imperfections on the show surface of the show surface panel if it is too thin. Further, for some types of trim panels, the panel is required to have a high degree of curvature to be formed at a desirable location. For these types of panels, traditional stiffeners, such as rib stiffeners, have not been adequate to provide local stiffening at high curvature areas. 
       SUMMARY OF THE INVENTION 
       [0006]    The present disclosure describes a technique for providing localized stiffening of a vehicle trim panel, especially for high curvature areas. The vehicle trim panel includes an outer panel having an outer show surface and an inner surface. A plurality of discrete reinforcement elements are bonded to the inner surface of the outer panel at locations where localized stiffening is desired. The discrete elements can come in a variety of different shapes and sizes, where the combination of elements and the number of elements is selected for a particular trim panel stiffness. 
         [0007]    Additional features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an isometric view of a known vehicle trim panel including a show surface panel and a support frame; 
           [0009]      FIG. 2  is an isometric view of a trim panel for a vehicle including a show surface panel and a plurality of discrete reinforcement elements; 
           [0010]      FIG. 3  is an isometric illustration of a hedgehog-type discrete reinforcement element; 
           [0011]      FIG. 4  is an isometric illustration of a tetrahedron-type discrete reinforcement element; 
           [0012]      FIG. 5  is an isometric illustration of a reinforcement assembly including a number of jack-type discrete reinforcement elements bonded to a backing tape; 
           [0013]      FIG. 6  is an illustration of the reinforcement assembly shown in  FIG. 5  positioned on a vehicle trim panel; 
           [0014]      FIG. 7  is an illustration of a method for depositing discrete reinforcement elements on a vehicle trim panel; 
           [0015]      FIG. 8  is an illustration of a method for fusion welding discrete reinforcement elements to a vehicle trim panel using a pressure pad; 
           [0016]      FIG. 9  is an illustration of a jack-type discrete reinforcement element including particles of a heatable material; and 
           [0017]      FIG. 10  is an illustration of a fused mass of the discrete reinforcement elements shown in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0018]    The following discussion of the embodiments of the invention directed to a technique for providing discrete reinforcement of a structure is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, the discussion below describes reinforcing trim panels for a vehicle. However, as well be appreciated by those skilled in the art, the reinforcement technique of the invention may be applicable for other structures. 
         [0019]      FIG. 1  is an isometric view of a known vehicle trim panel  10  including a show surface panel  12  and a rib support structure  14  of the type discussed above. The structure  14  is mounted to a backside surface  16  of the show surface panel  12  opposite to the show face of the panel  12 . The structure  14  includes a series of crossing ribs  18  having a height, width and spacing determined by the desired structural integrity of the panel  10 . A number of welding patches  20  are integrated into the structure  14  at intersection points  22  between the crossing ribs  18  to provide a surface to secure the structure  14  to the surface  16 . The panel  10  has a number of drawbacks as discussed above, including limits to the height of the structure  14  by the packaging volume of the panel  10  and the thickness of the show face panel  12  to allow welding thereto. 
         [0020]    As will be discussed in detail below, the present invention proposes employing discrete thermoplastic reinforcement elements that have been injection molded as stiffening elements adhered to a back surface of a vehicle trim panel to provide localized stiffening, especially at locations where the trim panel has a high degree of curvature. Different types and combinations of the discrete elements can be bonded to a particular trim panel, where the discrete elements have a desired shape, size, material, spacing, etc. Although the reinforcement elements discussed herein are described as thermoplastic reinforcement elements that allows them to be easily secured to thermoplastic trim panels by fusion bonding, the present invention contemplates any suitable material for the discrete reinforcement elements which may depend on the particular material of the trim panel. 
         [0021]      FIG. 2  is an isometric view of a vehicle trim panel  30  including a show surface panel  32  similar to the show surface panel  12  discussed above. Instead of using the rib support structure  14  to reinforce the show surface panel  32 , the present invention employs a number of discrete reinforcement elements  34 , here jack-type reinforcement elements, adhered to an inside surface  36  of the show surface panel  32  opposite to the show surface of the panel  32  to provide structural integrity for the panel  30 . As mentioned above, the number, size, spacing, location, material, etc. of the reinforcement elements  34  would depend on a particular trim panel and desired level of rigidity. Further, the present invention proposes any suitable technique for securing the discrete elements to the show surface panel  32 , where a couple of suitable techniques will be discussed in detail below. 
         [0022]    The present invention proposes any suitable shape for the discrete thermoplastic reinforcement elements that can be readily injection molded in mass quantities. Examples of other, non-limiting, discrete reinforcement elements are shown in  FIGS. 3 and 4 . Particularly,  FIG. 3  shows a hedgehog-type reinforcement element  40  and  FIG. 4  shows a tetrahedron dragon&#39;s tooth-type reinforcement element  50 . The hedge-hog and tetrahedron-type reinforcement elements  40  and  50  may require a two-step injection molding process. The tetrahedron-type reinforcement elements  50  may require injection molding an open tetrahedron and then folding over molded arms of the tetrahedron to fusion bond or weld them together to form the final tetrahedron shape, where both steps can be accomplished in a single mold employing side-acting elements. The elements  34 ,  40  and  50  are symmetric elements and as such the orientation in which they are placed on the particular trim panel is not specific in that any orientation that they happen to be deposited on the trim panel will be just as effective as any other orientation. It is noted that a particular application for using the discrete reinforcement elements includes mixing and matching any suitable type of the elements for that application. 
         [0023]      FIG. 5  is an isometric view of a reinforcement assembly  60  for a trim panel that includes a flexible support tape or skin  62  possibly provided in a roll. A number of discrete reinforcement elements  64  are adhered to a surface of the tape  62 , where here the jack-type reinforcement elements are shown. The reinforcement elements  64  can be secured to the backing tape  62  by any suitable technique, such as gluing, adhesion, fusion welding, etc. The number, size, spacing, materials, etc., of the elements  64  is application specific for a particular trim panel to provide the desired flexibility and stiffness. Further, it is noted that although the jack-type reinforcement elements are shown in this embodiment, other reinforcement elements can also be employed and different types and sizes of reinforcement elements can be mixed and matched depending on the particular size. The pattern, number, orientation, etc. of the many discrete reinforcement elements  64  adhered to the tape  62  is designed to be sufficient to provide the flexibility and stiffness for a particular trim panel. The tape  62  includes perforations  66  that allow sections of the tape  62  to be removed to easily provide different lengths of tape sections for a particular application. 
         [0024]    The reinforcement assembly  60  can be secured to a trim panel in any desirable or effective manner. For example,  FIG. 6  shows a processing assembly  70  including a highly curved vehicle trim panel  72  formed to a support or mold  74 . The mold  74  can be an injection mold or otherwise that forms the trim panel  72 , and may be a mold half of the entire mold. An articulating device including one or more articulating pins  76 , such as a set of clamps, robotic end-effector, etc., picks up the assembly  60 , positions it relative to the desired location on the trim panel  72  and bends the assembly  60  to conform it to the curvature of the trim panel  72 , as shown. While in this position, the backing tape  62  is adhered to the trim panel  72 , using, for example, fusion welding provided by a heat source  78 . Alternatively, the backing tape  62  may have induction heatable particles embedded in or bonded to it, which can be heated by a remote RF source, such as the heat source  78 , to enable fusion welding to the trim panel. Once the assembly  60  is secured to the trim panel  72 , the articulating device releases the assembly  60  and may then place another reinforcement assembly. 
         [0025]    Other techniques can also be employed to deposit the discrete reinforcement elements onto the trim panel.  FIG. 7  shows another processing assembly  80  including the trim panel  72  and support mold  74  shown in  FIG. 7 . In this embodiment, the area of the trim panel  72  to be reinforced with the discrete elements is enclosed by a suitable enclosure  82  and desirable areas or locations within the blocked off area of the trim panel  72  are applied with patches  84  of glue provided by, for example, a glue applicator. Once the glue patches  84  are provided at the desirable location, a hopper  90  is positioned over the blocked off area and reinforcement elements  92 , here non-limiting jack-type elements, are sprinkled into the enclosed area where those particular reinforcement elements  92  that land on the glue patches  84  are secured thereto and where the other reinforcement elements  92  fall away and are later collected. This process can be repeated where the glue patches  84  are applied at different times to adhere different types, sizes, etc. of the discrete elements  92  within the particular enclosed area. 
         [0026]    Once the desired number of the reinforcement elements  92  are attached to the reinforcement area by the glue, heat and pressure can be applied to the reinforcement elements  92  to further rigidly secure them to the trim panel  72 .  FIG. 8  shows a processing assembly  100  illustrating this. Particularly, the processing assembly  100  shows the discrete reinforcement elements  92  adhered to the trim panel  72  within the enclosure  82 . A heat source  102  provides heat for fusion welding to weld the discrete elements  92  to the trim panel  72 , where a pressure device  104  including a deformable portion  106  applies pressure to the discrete elements  92 . 
         [0027]    Once the discrete elements  92  are secured to the trim panel  72 , it may be desirable to provide a thin thermoplastic skin (not shown) or other type of layer on an opposite side of the reinforcement elements  92  from the trim panel  72  to improve stiffness. This skin can be very flexible if the panel design is such that the skin is loaded in tension for at least most of the time. For regions of the trim panel  72  that can be reinforced using a small number of the discrete reinforcement elements  92 , the particular reinforcement element  92  can be directly located at the desired position on the trim panel surface and pressed against the trim panel  72  and fusion welded in place. 
         [0028]    In an alternate embodiment, a number of the discrete reinforcement elements are first fused together to form a mass of several of the reinforcement elements prior to the reinforcement elements being secured to the trim panel to provide the stiffening. This embodiment is partially illustrated in  FIG. 9  showing a jack-type discrete reinforcement element  110  formed with particles  112  of a heatable material. In one particular embodiment, the particles  112  of the heatable material are formed at termination ends  114  of the arm of the jack-type reinforcement elements  110 . To form such a discrete element, the injection process can employ two different types of pellets including one type of pellet having the heatable material particles dispersed  112  therein, which is injection molded first, and a second type of pellet having the plastic material without the particles  112  that is injection molded second. Alternately, only the pellets with the heatable material particles  112  can be employed. The particles  112  can be any suitable particle for the purposes described herein, such as induction current heating particles, eddy current heating particles and RF heatable particles. 
         [0029]    Several of the discrete elements  110  can be nested together using a suitable enclosure device (not shown) so that they are in contact with each other. Slight pressure is applied to push the reinforcement elements  110  together and then fusion welding is employed to heat the heatable particles  112  and fuse the elements  110  together.  FIG. 10  is an illustration of a nested mass  120  of the reinforcement elements  110  after they have been fused together, but before the mass  120  is adhered to the trim panel. Once the mass  120  of the discrete elements  110  is formed, it is then placed on the trim panel at the desired location and fusion welding is again used to secure the mass  120  to the trim panel. Pressure can be applied to the nested reinforcement elements  110  to further enhance the fusion welding process. The reinforcement elements  110  provided in the mass  120  can be of different materials, different dimensions, different flake loadings, etc. Additionally, all of the termination ends  114  can be loaded with the heatable particles  112  or only some of the termination ends can be loaded with the heatable particles  112  where the non-loaded termination ends  114  may create fold lines in the nested mass  120  to allow it to be better formed to the trim panel. 
         [0030]    The foregoing discussion disclosed and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.