Abstract:
An automotive vehicle body includes a generally tubular, hydroformed cowl with integral mounting flanges which are welded to an engine compartment structural member and a cowlside member. The cowl may be hydroformed from several different preforms having both symmetrical and asymmetrical geometric characteristics.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a generally tubular, hydroformed cowl structure which is incorporated in an automotive body. The cowl extends laterally across the body either at the base of a windshield or at the base of the vehicle&#39;s rear window.  
         [0003]     2. Disclosure Information  
         [0004]     Automotive cowl structures are typically formed in two pieces, as shown in  FIG. 6 . According to this prior art construction, the inner cowl,  100 , is stamped and then welded into place between the cowl sides of the vehicle. Then, the cowl top outer panel,  102 , is added to the cowl inner, usually by spot welding. This process necessitates a multi-step operation with attendant complexity and high cost, because separate welding machines must be employed to both weld the cowl top inner  100  to the body as a whole, and then to weld the cowl top outer  102  to the assembled body structure. The present inventive hydroformed cowl eliminates the need to weld and seal a separate top, while allowing reduced complexity in terms of parts needed to join the cowl with the cowl sides and the balance of the front end structure of a vehicle, while providing increased torsional rigidity and body integrity.  
       SUMMARY OF THE INVENTION  
       [0005]     An automotive vehicle body includes a generally tubular, hydroformed cowl having at least one end with a plurality of integral mounting flanges. A cowlside member and a tubular, longitudinally extending engine compartment structural member are welded directly to the cowl flanges. Advantageously, the integral mounting flanges of the cowl are formed in a hydroforming die along with the balance of the cowl. The cowl&#39;s mounting flanges are vertically separated so as to allow the flanges to be welded to the top and bottom surfaces of a longitudinally extending engine compartment structure member.  
         [0006]     According to another aspect of the present invention, the inventive cowl further has an integral double thickness flange which is employed for attaching the A-pillar of the body to the cowl. A long, double thickness flange extends laterally across the body and supports the vehicle&#39;s windshield. Optionally, an integral double-thickness flange extending laterally across the vehicle body at a lower portion of the cowl may be attached to a dash panel of the body.  
         [0007]     According to yet another aspect of the present invention, a cowl may be hydroformed from a preform tube having two frustro-conical end sections either joined by a cylindrical midsection, or joined at the smallest diameter of each of the frustro-conical sections. Alternatively, the cowl may be hydroformed from a preform which includes a single frustro-conical preform tube. In any event, the preforms may be advantageously formed from metallic or non-metallic materials, including materials having different gauge thicknesses.  
         [0008]     As formed, a hydroformed cowl structure for an automotive vehicle according to the present invention includes a hydroformed tubular member having a mid-section and a plurality of end sections which are generally larger than the mid-section. A plurality of lateral mounting flanges is also formed, preferably by the hydroforming die, integrally from each of the end sections so that the flanges are adapted to join the cowl structure to a plurality of structural members of an engine compartment. A cowl according to the present invention, as noted above, preferably includes A-pillar, windshield, and dash panel mounting flanges.  
         [0009]     According to another aspect of the present invention, a method for assembling a body of an automotive vehicle includes the steps of hydroforming a cowl having integral, vertically separated mounting flanges, from a cylindrical preform having a non-constant diameter, and hydroforming at least one engine compartment structural member. Finally, the method includes welding the integral mounting flanges of the cowl directly to the structural member and to an A-pillar of the vehicle. Additional steps include welding of a dash panel to the cowl and mounting a windshield to the assembled A-pillar and cowl.  
         [0010]     It is an advantage of the present cowl that a vehicle body may be produced with increased structural integrity, but at a lower cost due to the elimination of welding machines and stations and other ancillary operations such as sealing and installation of a cowl top.  
         [0011]     It is a further advantage of the present invention that the body made with the current cowl is expected to exhibit increased resistance to unwanted noise vibration and harshness, particularly the phenomenon know as “cowl shake”.  
         [0012]     Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a vehicle body having a hydroformed cowl according to the present invention.  
         [0014]      FIG. 2  is a perspective view of a cowl according to the present invention.  
         [0015]      FIG. 3  is a perspective view of a preform for hydroforming a cowl according to the present invention.  
         [0016]      FIG. 4  is a perspective view of a second type of preform for hydroforming a cowl according to the present invention.  
         [0017]      FIG. 5  is a perspective view of a third type of preform for hydroforming a cowl according to the present invention.  
         [0018]      FIG. 6  is a perspective view of prior art stamped cowl and cowl top. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     As shown in  FIG. 1 , vehicle body  10  has cowl  16 , which is attached to cowlside  22  and structural member  24  by means of weldments  20  which directly mount cowl  16  to the cowlside  22  and structural member  24 . This mounting is permitted by lateral mounting flanges  18   a  and  b . Flange  18   a  is an upper flange, whereas flange  18   b  is a lower flange. Together, flanges  18   a  and  18   b  allow direct welding of cowl  16  to cowlside  22  and structural member  24 , without the need for intermediate parts.  
         [0020]     In addition to being welded to cowlside  22  and structural member  24 , cowl  16  is welded at A-pillar mounting flange  26  to A-pillar  28 . Mounting flanges  26  are double thickness flanges which are, as is the case with lateral mounting flanges  18 , formed within the hydroforming die itself. This obviates the need for additional steps or processes to create the lateral and A-pillar mounting flanges.  
         [0021]     Cowl  16  has windshield support flange  34 , which is a double thickness flange, extending laterally across body  10  and supporting windshield  36 . Because windshield support flange  34  is integral with cowl  16 , there are no additional welding or sealing steps required to install windshield support flange  34 , as would be the case with many prior art windshield mounting systems.  
         [0022]     Depending upon the needs of a particular automotive body into which the inventive hydroformed cowl is being installed, cowl  16  may include a dash panel mounting flange,  38 , ( FIG. 2 ) which is a double-thickness flange extending laterally across body  10 , and which may be attached to dash panel  40  by means of welding, bonding, mechanical fastening, or other types of fastening known to those skilled in the art and suggested by this disclosure.  
         [0023]      FIG. 2  illustrates additional features of a cowl according to the present invention. In addition to flanges  18   a  and  b  which are clearly seen in  FIG. 2 , as well as windshield support flange  34  and dash panel flange  38 , it is seen that cowl  16  has a smaller dimensional mid-section  46 , with larger end sections  48  and  50  hydroformed integrally with mid-section  46 . The present inventors have determined that it is advantageous in certain applications to provide a preform for generating hydroformed part  16  as a laser welded blank having, as needed, different gauge thicknesses of metal or other materials joined together in an assembled preform which is placed in a hydroforming die and formed using conventional hydroforming practice.  
         [0024]      FIG. 3  illustrates a first type of composite preform which two frustro-conical sections,  54  are joined by a single cylindrical section  56 . This type of construction could be used where the cowl&#39;s configuration includes a constant cross-sectional mid-section occupying a considerable portion of the cowl&#39;s total length, combined with much larger end sections for housing such items as a climate control system, a brake booster, and a driver control system such as pedals, a steering column, etc.  
         [0025]     In certain cases, it may be desirable for a hydroformed cowl to have a generally varying cross section with the midpoint of the cowl being smaller than the ends, and in this case the preform construction of  FIG. 4  which as before, contains laser welded blanks which may be of different metal thicknesses, may be optimal. For example, the metal gauge may be increased on the ends to accommodate more demanding loads imposed by structural strength considerations or mechanical equipment requirements.  
         [0026]      FIG. 5  illustrates a third type of preform having a continuously varying diameter, which may be employed where the desired cowl structure is largely asymmetrical. This may arise, for example, in a vehicle in which a climate control air handling system is mounted almost entirely within the engine compartment of the vehicle, necessitating a larger cowl structure. The preform of  FIG. 5  could further be useful if the cowl is “dry”, or in other words, not intended to permit an internal flow of rain water, as is the case with the cowl illustrated in  FIGS. 1 and 2 .  
         [0027]     Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations, and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention set forth in the following claims.