Abstract:
An automotive interior component including an airbag chute having at least one weld bar, and a pre-stressed instrument panel having a substrate layer for bonding to the weld bar. The pre-stressing provides tensile stress at weld bar bonding areas to reduce any deformation visible on an exposed surface of the instrument panel.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority to Provisional Application Ser. No. 60/873,274, filed Dec. 7, 2006, incorporated by reference in its entirety. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    a. Field of Invention 
         [0003]    The invention relates generally to automotive instrument panels, an apparatus for and method of manufacture thereof, and, more particularly, to an apparatus for and method of manufacturing automotive instrument panels and other automotive components which eliminates distortion in the area of vibration welded Passenger Side Inflatable Restraint (PSIR) chutes and other vibration welded components. 
         [0004]    b. Description of Related Art 
         [0005]    Automobiles are commonly equipped with airbags for reducing driver and passenger injuries in the case of an accident. Automobile airbags are generally located in areas where a driver or passenger would potentially contact an automobile interior in the event of an accident. Airbags can reduce injuries by providing a substantially non-solid surface for the driver or passenger to contact, as opposed to the generally solid surfaces of the automotive interior. Although the functionality of the airbag is greatly valued, the visual appeal of the instrument panel, and invisibility of the airbag system are also of value to automobile manufacturers and consumers alike. 
         [0006]    In order to install an airbag, the airbag is generally folded into a module that is installed into or behind an automotive interior component. The module housing a passenger-side airbag is generally installed on the underside of an instrument panel, within a PSIR chute protruding behind the instrument panel. The instrument panel will generally have a pre-weakened area, allowing an airbag to release therethrough. A PSIR chute will be bonded to the instrument panel, and will generally include doors that line up with the pre-weakened area of the instrument panel. 
         [0007]    A known method for attaching a PSIR chute to an instrument panel includes vibration welding the PSIR chute to the instrument panel. Vibration welding joins components by “rubbing” them together, creating heat through the friction, melting the connection points, and applying/holding pressure until the components cool together, thereby welding the components at the contact points. During the cooling process, there is known to be shrinkage/deformation of materials. Namely, during the known vibration welding of an instrument panel and PSIR chute, there is a visible deflection of the instrument panel at the connection points between the components caused by uneven shrinkage during the cooling process. 
         [0008]    It would therefore be of benefit to provide an apparatus and method of manufacturing automotive instrument panels and other structures including air bags and other vibration welded components to include a flat (or predetermined contoured) appearance in the area of the vibration welds. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention overcomes the drawbacks and deficiencies of known methods and apparatus for attaching a PSIR chute to an instrument panel by providing an automotive interior component including an airbag chute having one or more weld bars and a pre-stressed instrument panel having a substrate layer for bonding to the weld bar. For the instrument panel, tensile stress at weld bar bonding areas reduces any deformation visible on an exposed surface of the pre-stressed instrument panel, by matching the “B” surface stretch under the tensile stress of local bending to the expected shrink of the melted layer. 
         [0010]    For the automotive interior component described above, the weld bars of the airbag chute may be vibration welded to the “B” side of the plastic instrument panel. The interior component may further include a cover layer bonded to the substrate layer. The cover layer may be made of polyvinyl chloride or ThermoPlastic Olefin, and in an exemplary embodiment, may have a thickness of 0.4-1.0 mm. The interior component may further include a cover layer and an intermediate foam layer bonded to the substrate layer. The foam layer may be made of polypropylene, and in an exemplary embodiment, may have a thickness of 0.5-3.0 mm. The substrate layer may include thermoplastic polymers, and in an exemplary embodiment, may have a thickness of 2.0-4.0 mm. 
         [0011]    The invention also provides an apparatus for pre-stressing an automotive instrument panel for eliminating distortion in an area of vibration welded airbag chutes. The apparatus may include a weld fixture including a plurality of convex pre-stressors disposable against an instrument panel for creating compression in an area of contact with an instrument panel and creating tension in a surface opposite the contact area upon application of vacuum to draw the instrument panel toward the weld fixture. The weld fixture may be disposable against a cover layer of the instrument panel and creates tension in a substrate layer of the instrument panel, with the substrate layer being disposed adjacent an opposite face of the cover layer with or without an intermediate foam layer being disposed between the cover and substrate layers. 
         [0012]    The invention yet further provides a method of manufacturing an automotive instrument panel for eliminating distortion in an area of vibration welded air bags. The method may include providing a weld fixture including a plurality of pre-stressor protrusions, and placing the pre-stressor protrusions against an instrument panel. The method may also include generating a force to press the weld fixture against the instrument panel to create compression in an area of contact of the weld fixture with the instrument panel and tension in a surface opposite the contact area, and vibration welding an air bag chute to the instrument panel such that a weld bar of the air bag chute is welded to the surface placed in tension. 
         [0013]    For the method described above, the instrument panel may also include a substrate layer, a foam layer attached to the substrate layer, and a cover layer attached to the foam layer. For the method described above, placing the pre-stressor protrusions includes placing the pre-stressor protrusions against the cover layer of the instrument panel, and vibration welding further includes vibration welding an air bag chute to the substrate layer. 
         [0014]    Additional features, advantages, and embodiments of the invention may be set forth or become apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide explanation without limiting the scope of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the detail description serve to explain the principles of the invention. In the drawings: 
           [0016]      FIG. 1  is a view illustrative of a related art instrument panel and PSIR chute, prior to vibration welding of the PSIR chute to the instrument panel; 
           [0017]      FIG. 2A  is a view illustrative of the related art instrument panel construction of  FIG. 1 , illustrating various distortions in the instrument panel visible surface due to vibration welding of the PSIR chute; 
           [0018]      FIG. 2B  is an enlarged view of the related art instrument panel construction of  FIG. 1 , illustrating distortion in the area of the center score weakening line; 
           [0019]      FIG. 3  is a view illustrative of a modified weld fixture surface for pre-stressing of the instrument panel according to the present invention; 
           [0020]      FIG. 4  is a view illustrating pre-stressing of the instrument panel according to the present invention; 
           [0021]      FIG. 5  is a view illustrating vibration welded attachment of a PSIR chute; 
           [0022]      FIG. 6A  is a view illustrative of a pre-stress layered instrument panel according to the present invention, illustrating a PSIR chute vibration welded thereon; and 
           [0023]      FIG. 6B  is an enlarged view of the pre-stressed layered instrument panel of  FIG. 6A  for absorbing any distortions from vibration welding of the PSIR chute. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    Referring now to the drawings wherein like reference numerals designate corresponding parts throughout the several views,  FIGS. 1-2B  are views illustrative of a related art instrument panel construction,  FIGS. 3-5  are views illustrative of an instrument panel construction for eliminating distortion in the area of vibration welded PSIR chutes according to the present invention, and  FIGS. 6A and 6B  are views illustrative of a pre-stressed layered instrument panel according to the present invention. 
         [0025]    Referring to  FIG. 1 , in “hard hidden” constructions, a PSIR Chute  10  is often vibration welded to the underside of prior art instrument panel  12 . As briefly discussed above, the technique of vibration welding generally involves the physical movement PSIR Chute  10  having weld bars  14  relative to prior art instrument panel  12 , with weld bars  14  being moved horizontally relative to instrument panel  12  under pressure. This physical movement creates heat which melts contact area  16  of prior art instrument panel  12 , and thus allows weld bars  14  to be welded to prior art instrument panel  12  upon cooling of areas  16  when the relative movement is stopped. 
         [0026]    Referring to  FIGS. 2A and 2B , upon cooling, the thermal shrinkage in contact areas  16  causes compression in areas  16  and tension in the opposite visible areas  18  of the prior art instrument panel. Further, the thermal shrinkage in contact areas  16  also causes bending in area  20  of center score line  22 . 
         [0027]    Referring to  FIG. 3 , the present invention generally provides an instrument panel construction technique using a modified weld fixture  32  (illustrated as a lower weld fixture in  FIG. 3 ) including a plurality of spaced convex pre-stressors  34 . In the embodiment illustrated, each pre-stressor  34  may be a smooth convex curved shape, however protrusions of various configurations may be used to transfer the desired force to the instrument panel. Referring to  FIGS. 3-5 , each pre-stressor  34  may be disposed adjacent visible surface  36  of instrument panel  38  and is further disposed opposite weld bars  14 . Referring to  FIG. 3 , each pre-stressor  34  may include a predetermined height to bend instrument panel  38  such that the tension induced stretch on the back surface  40  matches the expected. weld shrink to thus eliminate distortion in the area of weld bars  14 . Where the technique is used on a pre-stressed layered instrument panel (as discussed below), pre-stressors  34  may be disposed adjacent to a cover layer and tension may be on substrate layer  30  (refer to  FIG. 6B ). Modified weld fixture  32  may further include a plurality of holes (not shown) for creating compression in areas  42  and tension in areas  44  of instrument panel  38  upon the application of a vacuum to draw instrument panel  38  toward fixture  32 . A vacuum seal (not shown) may be provided around instrument panel  38  for creating a vacuum as discussed above. Although a vacuum force is described herein, those skilled in the art would appreciate the application of similar forces to the modified weld fixture  32  and instrument panel  38 . Namely, instead of using vacuum to draw instrument panel  38  toward weld fixture  32 , weld fixture  32  (and another upper weld fixture (not shown) for holding the air bag chute) may be simply pressed against instrument panel  38  (and air bag chute  46 ) to thus create the aforementioned compressed/tensioned areas. 
         [0028]    The manufacturing method of instrument panel  38  according to the present invention will now be described in detail with reference to  FIGS. 3-5 . As shown in  FIG. 3  and briefly discussed above, instrument panel  38  may be disposed relative to modified weld fixture  32 , with visible surface  36  of instrument panel  38 , or the surface of substrate layer  30  adjacent foam layer  28  of pre-stressed layered instrument panel  24  as shown in  FIG. 6B  (see discussion below), being disposed in contact with pre-stressors  34  of weld fixture  32 . The instrument panels may be laterally aligned relative to weld fixture  32  such that each pre-stressor  34  is disposed opposite the weld bars  14 . A vacuum may then be created to draw instrument panel  38  (or  24  of  FIGS. 6A and 6B ) towards weld fixture  32  via the holes (not shown) in weld fixture  32 . In an exemplary embodiment of the present invention, the vacuum may be generated at 13 psi, with the instrument panel being maintained at room temperature. Further, in an exemplary embodiment, weld fixture  32  (and the weld fixture for air bag chute  46 ) may be machined aluminum and include a thin (i.e. ⅓ min) urethane layer to prevent scratching or damage to the grain of instrument panel  38  (or  24  of  FIGS. 6A and 6B ). 
         [0029]    Referring to  FIG. 4 , after vacuum application, instrument panel  38  (or  24  of  FIGS. 6A and 6B ) may include compression in areas  42  and tension in areas  44  to thus create an uneven instrument panel visible surface prior to vibration welding of air hag chute  46 . 
         [0030]    Referring next to  FIG. 5 , with weld fixture  32  held in place relative to instrument panel  38  (or  24  of  FIGS. 6A and 6B ), air bag chute  46  including weld bars  14  (and another upper weld fixture (not shown) for holding the air bag chute) may be vibration welded to instrument panel  38 . Upon cooling of weld areas  44 , the initial stretch due to tension in areas  44  (see  FIG. 4 ) is matched by the thermal shrinkage created by cooling of weld areas  44  to thus create a horizontal (or otherwise predetermined contoured) instrument panel visible surface  36  without distortion. 
         [0031]    Referring now to  FIGS. 6A and 6B , as briefly discussed above, in an alternative embodiment of the instrument panel, PSIR Chute  10  having weld bars  14  may be vibration welded to pre-stressed layered instrument panel  24  at contact areas  16 . As shown in  FIG. 6B , pre-stressed layered instrument panel  24  may include cover layer  26 , which may be about 0.4-1.0 mm of polyvinyl chloride, ThermoPlastic Olefin, a blend of polypropylene, polyethylene and/or rubber, or like thermoplastic polymers. Panel  24  may further include a foam layer  28  including polypropylene foam or like material of about 0.5-3.0 mm thickness, and a substrate layer of  30  of 2.0-4.0 mm thick ThermoPlastic Olefin or like material. Substrate layer  30  may be formed by an injection molding process. Cover layer  26  and foam layer  28  may be vacuum wrapped over the substrate layer  30 . Weld bars  14  may be vibration molded at contact areas  16  to substrate layer  30 . 
         [0032]    Whereas visible distortion in areas  18  and center area  20  appear in the related art (see  FIGS. 2A and 2B ), distortions are not visible through the pre-stressed layered instrument panel  24 , as the pros-stressed combination of substrate layer  30 , foam layer  28 , and cover layer  26  act to absorb any distortion caused by vibration welding. Whereas the embodiment of pre-stressed layered instrument panel  24  has been described as being formed by placement of convex pre-stressors  34  adjacent the surface of substrate layer  30  adjacent foam layer  28 , it is conceivable that pre-stressors  34  may be placed on the exposed surface of cover layer  26 . 
         [0033]    Those skilled in the art would readily appreciate in view of this disclosure that various modifications may be made to the instrument panel construction technique described above, without departing from the scope of the present invention. For example, while instrument panel construction technique has generally been discussed in conjunction with vibration welded assembly of air bags, this technique may be readily used with other vibration welded components for eliminating distortion in the area of the vibration weld. Further, while the use of pre-stressors  34  has been discussed for eliminating distortion in an instrument panel, pre-stressors  34  may be also used as needed to create a predetermined contoured appearance in the area of an instrument panel or other structures for providing a desirable contoured aesthetic appearance. 
         [0034]    Although particular embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those particular embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.