Abstract:
An anti-intrusion beam for incorporation into a vehicle door assembly is manufactured from an outer skin formed from laminated layers of composite materials having fiber reinforcement oriented in a directional pattern in each respective layer. The anisotropic beam includes body members having an interior core formed of high density foam plastic. The transversely corrugated beam includes attachment areas that have the same corrugated configuration which are fastened to mounting lugs of an inner door panel arranged in a corresponding corrugation. Variations in the thickness and formation of the layers of the outer skin can be used to control the failure of the beam during impact to provide a progressive predicable failure pattern for the beam. A frame catcher can be inserted into the body portions of the anti-intrusion beam to permit the transfer of impact forces to the frame of the vehicle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims domestic priority on U.S. Provisional Patent Application Serial No. 60/371,098, filed Apr. 9, 2002, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     This invention relates to the reduction of weight in automotive vehicles, and, more particularly, to a door assembly utilizing magnesium to reduce weight and increase fuel economy. 
     2. Background of the Invention 
     During the last decade, manufacturers of automobiles have undertaken steps to reduce weight of the vehicles in order to improve fuel economy and to reduce vehicle emissions. Such efforts have included the design of automotive vehicle components utilizing light metal alloys, leading to a variety of applications in chassis and power train components. More recently, advances in high-pressure die-casting technologies have enabled these technologies to be applied to larger structural components. Noteworthy examples of such larger components are instrument panel reinforcements, seat frames and door closure panels. While weight reductions of 40% can be realized through the use of magnesium, product engineers are faced with new challenges to incorporate adequate stiffness and crash critical applications with a material system possessing lower modulus and ductility compared to conventional formed sheet metal construction of such components. 
     Increasing the numbers of materials to be utilized in the construction of large structural components for automotive vehicles requires alternative joining strategies for the disparate materials in the assembly of such structural components. Consideration must be given to galvanic corrosion, as well as to differences in thermal expansion rates. Other related issues include the integration of the new materials and assembly techniques into the existing framework of an automotive manufacturing and assembly plant. 
     In U.S. Pat. No. 5,536,060, issued to Moinuddin Rashid, et al. on Jul. 16, 1996, an automotive door assembly is disclosed in which a reinforcement panel is attached to the interior side of the outer panel of the door assembly. This reinforcement panel is described as having superplastic forming qualities such as aluminum and stainless steel, but acknowledges that magnesium can be employed optionally, to provide the complex shape required in the specific reinforcement panel designed for the disclosed application. 
     In U.S. Pat. No. 4,662,115, issued to Takegi Ohya, et al. on May 5, 1987, an automotive vehicle door assembly is disclosed incorporating the employment of an inner panel formed of steel and an outer panel formed of synthetic resin. The hinge and door closure and locking devices are mounted on the steel inner panel. 
     U.S. Pat. No. 5,924,760, was issued to Paul Krajewski, et al. for a one piece corrugated anti-intrusion barrier for an automotive vehicle door. This anti-intrusion barrier is preferably formed in a corrugated configuration from a piece of sheet metal stamped into the preferred form. These barrier panels are preferably formed from aluminum alloys, though other materials including magnesium, steel, and titanium can be alternatively utilized. 
     U.S. Pat. No. 5,944,373, issued to Dinesh Seksaria on Aug. 31, 1999, is directed to a lightweight tailgate assembly for a pick-up truck in which a plastic reinforcing member is positioned between two metal panels to form the completed tailgate assembly. The inner and outer tailgate panels may be formed of aluminum or magnesium to minimize weight considerations. 
     In U.S. Pat. No. 6,068,327, issued to Michael Junginger on May 30, 2000, an upwardly folding rear cargo door for an automotive vehicle is disclosed. Junginger indicates that magnesium would be material preferred over aluminum, steel and plastic because of the reduction in weight of the assembly without the loss of strength. Junginger, however, does not disclose how a composite door structure incorporating magnesium with other structural materials can be effectively combined to create a vehicle door assembly. 
     U.S. Pat. No. 4,919,473, issued to Johann Laimighofer on Apr. 24, 1990, is directed to a structural beam for incorporation into an automotive vehicle door as an anti-intrusion device. Like the other references noted above, Laimighofer acknowledges that the structural beam may be formed from magnesium, but does not address the issues of how the disparate materials may be properly joined and deployed into a composite vehicle door assembly. 
     It would, therefore, be desirable to provide a composite automotive vehicle door assembly formed from disparate materials to provide a lightweight door assembly without sacrificing strength and intrusion resistance. 
     SUMMARY OF INVENTION 
     It is an object of this invention to overcome the aforementioned disadvantages of the known prior art by providing a composite vehicle door assembly utilizing disparate structural materials to form the components thereof. 
     It is another object of this invention to reduce the weight of a vehicle door assembly, when compared to conventional vehicular door assemblies, by using lightweight structural materials. 
     It is an advantage of this invention that fuel economy for automotive vehicles is increased while vehicle emissions are reduced. 
     It is a feature of this invention that improved joining strategies are provided to permit the effective mounting and connection of disparate structural component materials. 
     It is still another object of this invention to provide a composite vehicle door assembly that utilizes an outer door panel formed of aluminum, an inner door panel formed of magnesium, a mounted intrusion beam formed of composite materials, and an internal hardware module formed of thermoplastic. 
     It is another feature of this invention that the inner door panel can be manufactured from magnesium using high-pressure die-casting techniques. 
     It is still another feature of this invention that the assembly of the vehicle door components and the mounting of hardware and other components to the magnesium inner door panel is accomplished through the use of two-part inserts. 
     It is another advantage of this invention that the two-piece thermoplastic fastener inserts provides a dielectric barrier between the fastener and the magnesium inner door panel to prevent corrosion at the interface therebetween. 
     It is still another advantage of this invention that the fastener holes in the magnesium inner door panel can be formed by machining, piercing, or by casting in place followed by a clean-out during trimming. 
     It is yet another feature of this invention that the assembly of the aluminum outer door panel and the magnesium inner door panel can be accomplished through a hemming process. 
     It is yet another advantage of this invention that an increased flange hem thickness on the magnesium inner door panel casting provides an acceptable radius of curvature for the aluminum outer door panel to permit the utilization of a hemming process for assembly of the inner and outer door panel components. 
     It is yet another object of this invention to provide an affordable corrosion protection solution for use in a mixed material vehicular door assembly system that offers a satisfactory performance in the aggressive environment of a vehicle door closure. 
     It is a further feature of this invention that the magnesium inner door casting can be formed with a seal channel that encapsulates the seal mounted on the body of the vehicle. 
     It is a further advantage of this invention that the capture of the door seal within a formed seal channel improves noise reduction and performance of the seal. 
     It is a further feature of this invention to incorporate the hinges for the vehicle door assembly on the magnesium inner door panel. 
     It is a further object of this invention to provide a composite reinforcement beam to provide an anti-intrusion device for the vehicular door assembly. 
     It is still a further feature of this invention that the reinforcement member can be formed from an outer layer of a polymer composite material reinforced with glass or carbon fibers with an interior core of polyurethane. 
     It is yet another feature of this invention that the shaped interface between the composite reinforcing beam and the corresponding mounting lugs formed in the inner door panel increase improves the load transfer from the reinforcing beam to the inner door panel during impacts. 
     It is still a further advantage of this invention that the composite reinforcement beam has a reduced weight compared to conventional steel reinforcement beams. 
     It is yet a further feature of this invention that the vehicle door assembly incorporates a modular concept to decrease complexity of assembly. 
     It is still a further object of this invention to provide a door hardware module on which substantially all of the hardware required for the vehicle door can be mounted. 
     It is still another feature of this invention that the door hardware can be pre-assembled on a module component for installation on the inner door panel as a unit. 
     It is yet a further advantage of this invention that the assembly of a vehicle door is made less complex by reducing the number of assembly operations and by using a modular configuration. 
     It is still another feature of this invention that the inner door panel can be formed with integrated reinforcements cast into the panel to increase resistance to impacts without adding reinforcement attachments to the door structure. 
     It is a further object of this invention to provide a lightweight vehicle door assembly that is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
     These and other objects, features and advantages are accomplished according to the instant invention by providing an anti-intrusion beam for incorporation into a vehicle door assembly. The outer skin is formed from laminated layers of composite materials having fiber reinforcement oriented in a directional pattern in each respective layer. The anisotropic beam includes body members having an interior core formed of high density foam plastic. The transversely corrugated beam includes attachment areas that have the same corrugated configuration which are fastened to mounting lugs of an inner door panel arranged in a corresponding corrugation. Variations in the thickness and formation of the layers of the outer skin can be used to control the failure of the beam during impact to provide a progressive predicable failure pattern for the beam. A frame catcher can be inserted into the body portions of the anti-intrusion beam to permit the transfer of impact forces to the frame of the vehicle. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is an elevational view of an assembled automotive vehicle door assembly incorporating the principles of the instant invention; 
     FIG. 2 is an elevational view of the magnesium inner door panel taken from the interior view with respect to the vehicle on which the door assembly is to be mounted; 
     FIG. 3 is an elevational view of the magnesium inner door panel taken from the exterior view with respect to the vehicle on which the door assembly is to be mounted; 
     FIG. 4 is an enlarged partial elevational view of the forward portion of the magnesium inner door panel depicting the area for mounting the reinforcement beam for the door assembly; 
     FIG. 5 is an enlarged partial elevational view of the rearward portion of the magnesium inner door panel depicting the area for mounting the reinforcement beam for the door assembly; 
     FIG. 6 is a partial perspective view of the composite reinforcement beam to be mounted between the inner and outer door panels; 
     FIG. 7 is an end view of the composite reinforcement beam depicted in FIG. 6; 
     FIG. 8 is a partial perspective view of the forward end of the inner door panel depicting the hinge mounting areas integrally formed therein; 
     FIG. 8A is a schematic elevational view of a two-piece fastener system having an insert member and a fastener engaged with the insert member; 
     FIG. 9 is a schematic elevational view of the inner plastic hardware module panel viewed from the interior side with respect to the vehicle onto which the door assembly is to be mounted, which is the side of the module panel positioned next to the inner door panel seen in FIGS. 2 and 3; 
     FIG. 10 is a schematic elevational view of the inner plastic hardware module viewed from the exterior side, also known as the trim side, with respect to the vehicle onto which the door assembly is to be mounted; 
     FIG. 11 is an enlarged expanded view of the layering forming the composite reinforcement beam, the respective layers of the outer skin reflecting representative arrangements of the fiber reinforcement in the respective layers thereof; and 
     FIG. 12 is an enlarged perspective detail view of a frame catcher that is an optional insert for the composite reinforcement beam. 
    
    
     DETAILED DESCRIPTION 
     Referring to drawings, an automotive vehicle door assembly  10  incorporating the principles of the instant invention can best be seen. The outer panel  12  is preferably formed of aluminum or an aluminum alloy to provide lightweight characteristics desirable to reduce the overall weight of the door assembly  10  without sacrificing strength and integrity for the door assembly structure. Other suitable materials for the construction of the outer panel  12  would be steel, polypropylene, or composite materials, which can provide similar weight reduction characteristics as aluminum alloys. The outer panel  12  is conventionally provided with openings  13  for the door handles and latching hardware (not shown). 
     The inner door panel  15  is preferably formed from magnesium cast through high-pressure die-casting techniques to provide lightweight, yet strong and durable, characteristics for the completed door assembly  10 . The inner panel  15  has a formed configuration to mate with the outer door panel  12  and with a hardware mounting module  20 , as will be described below, such that the inner door panel  15  will be sandwiched between the outer door panel  12  and the module  20 . The inner door panel  15  has a formed shape that will provide strength and rigidity for the assembled door  10  and includes reinforcement ribs  16  appropriately positioned around the formed perimeter of the inner panel  15  and a mounting face  17  for the attachment of the modular hardware attachment panel  20 . The inner door panel  15  is sufficiently strong as to permit the hinges  11  pivotally connecting the door assembly  10  to the vehicle to be formed as an integral part of the inner door panel structure  15 . 
     The reinforcement of the inner door panel  15 , through the formation of the reinforcing ribs  16  at appropriate locations on the inner door panel  15 , permits selective stiffness and flexibility to be designed into the vehicle door  10 . One particular advantage to the location of reinforcing ribs  16  at the top of the door  10  is a greater performance in vehicle rollover situations where the greater torsional stiffness at the top of the door  10  will resist separation of the door  10  from the body frame. Furthermore, an upper belt line reinforcement  49  can be selectively added to the inner door panel  15  when desired to increase stiffness of the door  10  for mounting the outer panel  12  and the hardware mounting module  20 . 
     Holes  17   a  through the magnesium inner door panel  15  can be formed through machining, piercing, or simply cast in place. To avoid galvanic corrosion at the interface between fasteners and the magnesium inner door panel, the fasteners are preferably not of the self-tapping variety, as is conventional in automotive vehicle doors. Preferably, a two-piece fastener system  30 , such as a VARIOboss™ fastener schematically depicted in FIG. 8A, in which a polydactyl insert  31  is first pressed into the opening  17   a  in the magnesium inner door casting so that the fastener  33  can engage the insert  31 , is used to mount components to the inner door panel  15 , or the module  20  as described below, to dielectrically insulate the fasteners  33  from the magnesium inner door panel  15 . 
     Such a fastener system  30  compensates for any variation in the opening  17   a  and in the material due to tolerances in the material thickness. Two and four way locators are molded into the hardware module panel  20  to align the module  20  with the inner door panel  15  before making the final door handle connections and inserting the steel screw fasteners therefore. The thermoplastic inserts  31  and locators isolate the respective screws and provide a dielectric barrier to prevent corrosion at the interface. 
     As is reflected in the drawings, a modular architecture is designed into the door assembly  10 . As with most automotive applications, closure design is driven primarily by stiffness requirements. The flexibility of the die-casting process for the magnesium inner door panel  15  provides an opportunity to integrate reinforcements and rely on section design to offset any reduction in intrinsic stiffness. Where needed, additional stiffness and strength may be realized by changes in section properties in localized regions of the casting, such as through the utilization of the reinforcing ribs  16 . 
     Such design capabilities, avoids any incompatibility issues between the magnesium inner door panel  15  and internal reinforcement panels. Furthermore, use of the die-casting techniques for the inner door panel  15  enables features such as fastener and access holes  17   a , sealing channels  40  and styling options, like deep draws, to be included in the raw casting at minor tooling expense, as compared to secondary machining and assembly operations that would be required with conventional sheet metal design to add such features to the component part. 
     Referring now to FIGS. 9 and 10, the hardware mounting module  20  can best be seen. The module panel  20  is designed to carry the majority of the conventional door hardware components, thus reducing the number of assembly steps required for the manufacture of the completed door assembly  10 . The module panel  20  is preferably formed via compression molding from long fiber reinforced thermoplastic. The fiber reinforcement, which can represent up to 40% of the mass of the panel  20 , serves to increase tensile modulus and strength. Distribution of the fibers along the length of the living hinge  22  also increases service performance enabling access to the internal space of the assembly  10 , by bending up the lower portion of the panel  20 , on multiple occasions without significant deterioration of the module panel  20 . 
     The module panel  20  is also formed with belt line reinforcement in the form of ribs  24  along the belt line to meet design stiffness requirements and resist any service loads associated with the weather strip and window glass regulators. Water sealing of the internal door cavity can be accomplished by utilizing an expandable foam that is applied to a sealing channel (not shown) on the module panel  20 . The foam sealant eliminates requirements for an additional water shield that would otherwise be applied during a conventional vehicle door assembly process. 
     Preferably, the hardware mounting module will have mounted thereon the normal door hardware items so that the completed module  20  can be fastened to the inner door panel  15  as a module. For example, the speaker hole  21  can be molded into the module  20  for the mounting of the stereo speaker (not shown) final assembly. A depression  23  for the door handle can be formed into the module  20 , along with the mounting of the motor for regulating the door glass. Furthermore, a sealing channel can also be molded into the module in the same manner as for the inner door  15  as will be described in greater detail below. The module  20  is attached to the mounting face  17  formed in the inner door panel  15  with the two piece fasteners  30  engaging the openings  17   a  in the mounting face  17 . 
     Referring now to FIG. 17, the incorporation of an anti-intrusion, reinforcement beam  25  into the modular door assembly  10  can best be seen. The reinforcement beam  25  is preferably formed as a composite having an outer skin layer  26  of a polymer reinforced with glass and carbon fibers and an interior core  27  of polyurethane. To achieve weight reduction objectives, the reinforcement beam can also be formed of aluminum or an aluminum allow; however, the composite material offers a 25% reduction in weight, compared to a conventional high strength steel reinforcement beam. The reinforcement beam  25  is formed in a corrugated configuration with opposing side attachment flanges  28  that have appropriate openings formed therein for the passage of fasteners connecting the reinforcement beam  25  to the inner door panel  15 . Between the attachment flanges  28  and a central attachment web  28   a , the reinforcement beam  25  is formed with the stiffening body members  29  that provide the anti-intrusion resistance. 
     The composite reinforcement beam  25  is formed in a layered configuration, as is depicted in FIG.  11 . The outer skin  26  is formed of many layers of a glass or carbon fiber reinforced polymer to provide an anisotropic reinforcing beam. Preferably, the fibers are oriented in different directions in succeeding layers to optimize the stiffness and the strength of the final composite outer skin  26 . For the body members  29 , the interior core  27  is sandwiched between opposing outer skins  26  which are formed of multiple layers with the fibers oriented in differing directions. Furthermore, the fibers on any particular layer could be glass or carbon fibers. 
     By designing the layers of the outer skin  26  in a selective manner, the reinforcing beam  25  can be made to fail in a predetermined and predictive manner upon impact. For example, the design of the composite beam can, through thickness of the layers and the respective fiber orientation thereof, tailor certain areas to fail early or late, thus providing a predictability to progressive failure for the reinforcing beam. The tear out performance of the fasteners attaching the reinforcing beam  25  to the mounting lugs  18  can be controlled to allow the beam  25  to conform inwardly and resist crash impact. 
     In addition, the composite beam  25  could be further reinforced through the utilization of 3D stitching of fibers, such as Kevlar fibers, through the multiple layers forming the outer skin  26 . The cost of stitching the outer skin  26  with such fibers is substantial; therefore, selected areas might be stitched to tailor the design of the beam  25  for appropriate failure mode during crash impact. 
     As is reflected in FIG. 12, the composite beam  25  can be formed with an optional frame catcher  40  to further integrate the reinforcing beam  25  into the vehicle frame (not shown). The frame catcher  40  is formed with a base member  41  including a pair of prongs  42  that are inserted into the body members  29  at the end of the reinforcing beam  25  at the attachment area thereof. The frame catcher  40  is also formed with a hook member  44  that is operable to engage with a latch member (not shown) formed in the vehicle frame when the door is closed. Accordingly, an interlock mechanism (not shown) would be required to effect an engagement between the hook member  44  and the latch member in the vehicle frame in response to the door being moved to the closed position against the vehicle frame. The frame catcher  40  is preferably used at the rearward end of the reinforcing beam  25  to engage the “B Pillar” to interlock the reinforcing beam  25  with the frame of the vehicle. 
     Attachment of the reinforcement beam  25  is accomplished by the use of two-piece fasteners, such as push nut fasteners, that secure the beam  25  at multiple locations at the two opposing ends of the beam  25 , as is best seen in FIGS. 4 and 5, to dielectrically insulate the fasteners and the reinforcement beam  25  from the magnesium inner door panel  15 . The inner door panel  15  is formed with mounting lugs  18  shaped to correspond to the reinforcement beam  25  to mate therewith. The mounting lugs are formed with openings to receive the fasteners attaching the reinforcement beam  25  to the inner door panel  15 . 
     Conventional reinforcement beam mounting is via a flat mounting panel formed at the opposing ends of the reinforcement beam  25 . The shaped interface between the reinforcement beam  25  and the mounting lugs  18  on the inner door panel  15  improves the load transfer between the reinforcement beam  25  and the remaining door structure during impact situations. The extension of the corrugated shape of the reinforcement beam  25  into the attachment area at the opposing ends of the reinforcement beam  25  improves the interface between the beam  25  and the inner door  15 . 
     Because of the potential for material degradation when using polymer composite materials, the use of the composite material is best utilized when the door assembly  10  utilizes a low temperature paint process during the paint bake cycle, or when the reinforcement beam  25  can be installed into the door assembly  10  after the paint process is completed. 
     The use of magnesium, even for components manufactured using high-pressure die-casting techniques, subjects the components to corrosion, which is well documented and known. Surface treatments for the magnesium components, such as chromating and anodizing, have been presented as potential methods of abating the corrosion problem. Other solutions include a titanium zirconium conversion coating in conjunction with an epoxy powder coat, which will provide a dielectric insulation to the magnesium component. This latter solution is particularly effective in conjunction with the utilization of adhesives to bond the magnesium inner panel  15  to the aluminum outer panel  12 . 
     Attachment of the inner panel  15  to the outer panel  12  is preferably accomplished through a hemming process which forms a hem  14  to wrap the aluminum flange extending around the perimeter of the outer door panel  12  around the peripheral edge  19  of the inner door panel  15  to encapsulate the peripheral edge  19 . Adhesives are applied between the outer and inner door panels  12 ,  15  at the hem  14  around the peripheral edge  19  to meet static and dynamic performance requirements and promote load transfer through the assembled door  10 . 
     Aluminum was selected as the preferred material for the outer panel  12  because of the opportunity for weight reduction and concerns over differences in thermal expansion. A representative CTE value for steel is 11.7×10 −6  m/m/K, compared to 26.0×10 −6  m/m/K for magnesium and 23.4×10 −6  m/m/K for aluminum. Accordingly, adoption of aluminum as the material for the outer door panel  12  minimizes any thermal stresses that would be encountered during the E-coat and paint bake cycle. Execution of the hemming process to mount the inner door panel  15  to the outer door panel  12  would normally be technically challenging for an aluminum material selection due to the reduction in formability of aluminum compared to steel. The increased flange thickness at the peripheral edge  19  of the magnesium casting for the inner door panel  15 , e.g. greater than 2 mm in thickness, provides a more generous radius of curvature, which eliminates any requirement to protect the hem  14  from splitting or cracking. 
     An important key to the development of a mixed material vehicle door assembly  10  is the provision of an affordable corrosion protection solution that offers satisfactory performance in the aggressive corrosive environment of an automotive vehicle door  10 . Dielectrically insulating the magnesium inner door panel  15  from the adjoining metals of the fasteners and the outer door panel  12  provides an acceptable solution. Integration of conventional reinforcement ribs and formed shapes into the die-cast inner door panel  15  and the use of a thermoplastic module carrier  20  minimize direct contact of the magnesium with other dissimilar materials. Additional material isolation for the magnesium inner door panel  15  can be provided by pre-treating the magnesium panel  15  with a titanium zirconium conversion coating in addition to an epoxy powder coat. Another benefit of such insulation of the magnesium inner door panel  15  is the elimination of dissolution into the electro-coat tank in the vehicle assembly plant, thus opening up the possibility of processing the magnesium die-cast inner door panel  15  through existing automotive assembly lines. 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention.