Abstract:
A method of forming an airbag assembly for a vehicle including the steps of providing a sheet of hinge material, where the hinge material includes a sheet of scrim material encapsulated within a polymer. Next, a panel is provided that is formed of a substrate material. An under face of the panel may have a tear seam to allow an airbag to exit the panel body when the airbag is deployed, and the tear seam may define an airbag door. Next, a first portion of the sheet of hinge material is secured to the panel within the airbag door defined by the tear seam. Securing the hinge material to the panel may occur by vibration welding a portion of the hinge material to the panel. A second portion of the sheet of hinge material is secured to the airbag housing and an airbag housing is secured to the panel. The hinge material may be secured to the airbag housing such that a third portion of the sheet of hinge material forms a loop.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to vehicle trim components, and in particular relates to a method of manufacturing an airbag assembly and trim component. 
     The interior of a vehicle typically includes a multitude of components for covering various frameworks, instruments, and electrical devices mounted within the interior compartment of a vehicle. Examples of trim components include instrument panels, door panels, center consoles, overhead consoles, and other various interior panels for covering the sides, ceilings, and vertical pillars of the frame members of the vehicle. 
     The instrument panel is generally positioned underneath the windshield and attached to the frame of the vehicle behind the engine compartment. The instrument panel encloses various vehicle components, such as electrical and ventilation systems, audio systems, vehicle instrument gauges and displays, airbag assemblies, and auxiliary compartments. 
     In the past, trim components, such as instrument panels, were made of metal or plastic and commonly had rigid exterior upper and rear surfaces facing the interior of the vehicle. The upper and rear surfaces of the instrument panel are within reach and direct sight of the occupants of the vehicle. Recently, consumers have been demanding a more aesthetically pleasing exposed surface. It is also preferred that the tactile properties of the surfaces are also more pleasing, such as having soft or elastic properties compared to a relatively rigid surface. Thus, the outer surface areas of the trim components have been covered in a suitably soft material over the rigid structurally accommodating framework of the trim component. 
     In certain instances, the occupants of a vehicle may come into physical contact with portions of the trim components. During a vehicle impact condition, sudden large impact forces may be delivered to the occupant of the vehicle, such as in a rearward, frontal, or side impact. These forces may cause the head and limbs of the occupant to be forced against trim components and structures of the vehicle, thereby causing injury. 
     Various countermeasures have been taken to help reduce the degree of injury caused by impact conditions. For example, passive restraint systems having airbags and/or air curtains have been implemented into vehicles. Generally, such airbag assemblies are stored and packaged in deflated condition in storage areas within the passenger compartment of the motor vehicle. The airbag assemblies include sensors located at various points in the vehicle. Upon impact, the sensors are triggered thereby sending a signal to a gas generator or igniter. The gas generator operates to inflate the airbag when it receives a signal from the sensors. The airbags are located at various areas within the interior of the vehicle in which contact with the occupant is likely. For example, airbags are positioned in front of the driver and passenger locations, such as in the steering wheel and passenger side of the trim component or instrument panel. Air curtains may additionally or alternatively be included in such airbag assemblies, and may be positioned along the sides of the occupants, such as mounted at the edges of the headliner and propelled downwardly when inflated. Side air curtains have also been incorporated into the side portions of the seat backs. 
     When incorporating an airbag assembly into a trim component such as an instrument panel, the trim component includes an opening through which the airbag deploys when activated. It is generally desirable to include a mountable door or cover on the trim component to conceal the opening in the trim component. It is becoming increasingly common to provide a seamless or hidden airbag cover portion in the instrument panel that will reliably and safely tear upon deployment of the airbag, such that the passenger is protected. To this end, a tear seam has generally been provided in the airbag cover portion of an instrument panel to insure that the airbag will safely deploy. 
     Vehicle designers prefer to have a continuous surface on the front face of the trim component, whenever possible, so they would prefer to avoid having a part line or seam in the trim component. Thus, for trim components such as instrument panels, recently there has been an effort to achieve a “seamless” design wherein there is no indication on the front face of the instrument panel that the airbag is behind the instrument panel. To achieve this design, hidden tear seams or tear strips provided in the instrument panel are only provided on the under face, and not on the front face of the instrument panel. 
     The trim component should perform the utilitarian function of breaking apart along its tear seam to allow the airbag to exit through the airbag cover portion of the trim component when deployed. Preferably, the airbag cover portion of the trim component should not break apart, especially during cold deployment. 
     Thus, it is desirable to provide an improved method of manufacturing a trim component and airbag assembly in a “seamless” design that will deploy without undesirable failures, such as during cold deployment. It is also desirable to provide an improved method of manufacturing a trim component and airbag assembly that is cost effective and simplifies the manufacturing process. 
     In a known method of manufacturing an airbag assembly, a scrim material is used as a hinge to attach an airbag cover to the vehicle. A first end portion of the scrim material is coated in a plastic material. A second end portion of the scrim material is also coated in the plastic material. The first end portion of the scrim material is attached to the vehicle by a fastener disposed through the scrim and plastic material. Next, the second end portion of the scrim material is vibration welded to the instrument panel. An intermediate portion of the scrim material is disposed between the first and second portions. The intermediate portion is not coated in plastic material. The uncoated intermediate portion of the hinge material acts as a flexible hinge between the vehicle and the airbag cover. Although this method has worked successfully, the manufacture of this hinge is expensive and time intensive, because of the numerous steps required to coat only the first and second end portions of the scrim to produce the hinge. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention relates to a method of forming an airbag assembly for a vehicle. The method includes providing a sheet of hinge material, where the hinge material includes a sheet of scrim material encapsulated within a polymer. Next, a panel is provided that is formed of a substrate material. The panel has a front face and an under face. The under face has a tear seam to allow an airbag to exit the panel body when the airbag is deployed. The tear seam defines an airbag door. Next, a first portion of the sheet of hinge material is secured to the panel within the airbag door defined by the tear seam. Securing the hinge material to the panel may occur by welding a portion of the hinge material to the panel. The hinge material may be subjected to vibratory motion during the welding process. An airbag housing having an airbag disposed therein is then provided. Finally, a second portion of the sheet of hinge material is secured to the airbag housing, a chute, or other portion of the vehicle, and the airbag housing is also secured to the panel. The hinge material may be secured to the airbag housing such that an intermediate portion of the sheet of hinge material is disposed between the first portion and the second portion such that the intermediate portion is not attached to the panel, the airbag collar, or the airbag housing. The intermediate portion acts as a flexible hinge to allow the airbag door to be retained yet allowed to move free of the airbag when the airbag is deployed. 
     Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of an instrument panel and airbag assembly manufactured in accordance with the method of the present invention. 
         FIG. 2  is a cross-sectional view of a portion of the instrument panel of  FIG. 1  and a welding apparatus illustrating a preferred method of manufacturing the instrument panel of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a portion of the instrument panel and a portion of the airbag assembly of  FIG. 1 , illustrating another step of the preferred method of manufacturing the instrument panel and airbag assembly of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of the instrument panel and airbag assembly of  FIG. 1  taken along lines  4 — 4  in  FIG. 1   
         FIG. 5  is a schematic representation of a manufacturing assembly for producing a polymer encapsulated scrim mat for use in the airbag assembly of  FIG. 1 . 
         FIG. 6  is a schematic representation of a manufacturing assembly for producing a portion of the airbag assembly of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, there is illustrated in  FIG. 1 , an instrument panel, indicated generally at  10 . It should be understood that while the method of manufacturing a trim component in accordance with the present invention will be described and shown in  FIGS. 1 through 9  with respect to the instrument panel  10 , the method may be practiced to form any type of trim component or portions of trim components for a vehicle. Other suitable examples of trim components which can be formed from the present invention include door panels, center consoles, overhead consoles, and other various interior panels for covering the sides, ceilings, and/or vertical pillars of the frame members of the vehicle. 
     The instrument panel  10  is preferably installed on a vehicle frame (not shown) generally in the area underneath a windshield  11  and between the engine compartment and the interior of the vehicle. The instrument panel  10  can include any suitable frame structure (not shown) for supporting the instrument panel  10  on the vehicle frame. The portion of the instrument panel  10  illustrated in  FIG. 1  preferably defines the upper portion and a section of the rear portion of the instrument panel facing the interior of the vehicle. Since the upper and rear portion of the instrument are within reach and direct sight of the occupants of the vehicle, it is desirable for this portion of the instrument panel to be aesthetically pleasing in color and texture as well as having a desirable tactile feel, such as a soft or slightly elastic feel. 
     The instrument panel  10  generally includes a substrate  12 . An aesthetically pleasing outer layer (not shown) may be provided that generally covers the upper portion and a section of the rear portion of the substrate  12  such that the outer layer is visible to passengers of the vehicle. The substrate  12  of the instrument panel  10  can be molded in accordance with the present invention with materials molded at various areas to form various features such as outer layers, seals, pads, gap hiding strips, membranes, living hinges, trays, storage compartment liners, and membrane speakers. 
     The substrate  12  is preferably made of a relatively rigid material so as to provide support for any additional features and to retain the shape of the instrument panel  10 , and more preferably is made of a polymer or plastic material. Although additional members or framework may be attached to the substrate  12  for supporting the instrument panel  10  onto the frame of the vehicle, preferably the substrate  12  is rigid enough to structurally support itself. Examples of suitable materials for the substrate  12  include thermoplastic elastomer, thermoplastic elastomer olefin, thermoplastic elastomer polyolefin, Santoprene®, styrene maleic anhydride, Dylark®, polycarbonate, polypropylene, acrylonitrile butadiene styrene (ABS), polycarbonate acrylonitrile butadiene styrene, styrene maleic anhydride (SMA), polyphenylene oxide (PPO), nylon, polyester, acrylic, polysulfone, thermoplastic polyether, thermoplastic urethane, polypropylene, polyurethane, copolyester, thermoplastic styrenic elastomer, nylon, and any combination thereof. The substrate  12  can also have any suitable textured surface and color. 
     Various covers and panels may be attached to the substrate  12  to cover exposed positions thereof. For example, an aesthetically pleasing trim panel, such as a faux wood or carbon fiber panel (not shown) may be used to cover a portion of the substrate  12 . Other components, such as vent covers, display devices, electronic controls, audio/video entertainment units, and the like may be attached to the substrate  12  and covering at least a portion of the substrate  12 . Alternatively, all of the exposed portions of the instrument panel  10  may be covered and not seen from within the interior of the vehicle. 
     The substrate  12  can be formed of a single part or can be formed from attaching separate relatively rigid sections, thereby forming the substrate  12  as shown in  FIG. 1 . It should also be understood that portions of the substrate  12  can be partially or totally covered in separate trim panels. Also, portions of the substrate  12  may be covered by housings of various vehicle components mounted thereon or within the apertures formed in the substrate  12 . 
     Shown schematically in phantom outline in  FIG. 1  is an airbag module  18  located behind the substrate  12 . As shown in  FIGS. 1 and 4 , a tear seam  20  is formed in an under face  22  of the substrate  12 . Preferably, the tear seam  20  defines an airbag door  24 . It will be appreciated that the tear seam  20  can be any weakened area of the substrate  12 , such that an airbag  27 , as shown schematically in  FIG. 4 , can exit the instrument panel  10  when the airbag  27  is deployed, for example, during a vehicle collision. The airbag door  24  is attached to the vehicle by a hinge  26 . The hinge  26  allows the airbag  27  to force the airbag door  24  free from the instrument panel  10 , while retaining the airbag door  24  such that the airbag door  24  does not freely enter the interior cabin of the vehicle. 
     As shown in  FIG. 1 , the tear seam  20  may have a substantially rectangular shape. However, it will be appreciated that the tear seam  20  can be of any desired shape, such as U-shaped, or H-shaped to permit the deployment of the airbag  27 . The tear seam  20  can be formed by any desired method. Preferably, the tear seam  20  is formed by laser scoring, as will be described below. As will be described below, the hinge  26  may be vibration welded to the substrate  12  of the instrument panel  10  by the method of this invention. Preferably, the hinge  26  is welded to the substrate  12  within the airbag door  24  defined by the tear seam  20 . 
     The hinge  26  is preferably made of a material having a tensile strength that will allow the hinge  26  to restrain the airbag door  24  during a deployment and is strong enough to withstand a vibration welding operation to attach the hinge  26  to the instrument panel  10 . In a preferred embodiment, the hinge  26  is made of a thermoplastic elastomer, such as Santoprene® with a nylon or polyester scrim and has a durometer of less than about 85 Shore A. In a more preferred embodiment, the hinge  26  has a durometer of about 65 Shore A. The hinge  26  comprises a layer of scrim  28  that is preferably completely encapsulated within a polymer  30 , such that preferably neither of the major surfaces of the scrim  28  are exposed. Examples of suitable materials for the scrim  28  include lightweight polymers or plastics, such as polyethylene terephthalate (PET), nylon, polyester or blends thereof. The scrim material  28  may be woven, non-woven, or film backing or barrier. Examples of suitable materials for the polymer  30  of the hinge  26  include thermoplastic elastomer, thermoplastic elastomer olefin, thermoplastic elastomer polyolefin, Santoprene®, styrene maleic anhydride, Dylar®, polycarbonate, polypropylene, acrylonitrile butadiene styrene (ABS), polycarbonate acrylonitrile butadiene styrene, styrene maleic anhydride (SMA), polyphenylene oxide (PPO), nylon, polyester, acrylic, polysulfone, thermoplastic polyether, thermoplastic urethane, polypropylene, polyurethane, copolyester, thermoplastic styrenic elastomer, nylon, and any combination thereof. It will be appreciated that the scrim  28  and the polymer  30  of the hinge  26  may be formed of any materials that are capable when formed into the hinge  26  of performing during welding and flexing operations as described herein. It will be appreciated that the material of the substrate  12  and the polymer  30  may be the same materials or different materials with melt temperature and melt flow indexes that are compatible to facilitate plastic welding with one another, as will be described herein. 
     The instrument panel  10  is preferably manufactured by the method of the present invention, as schematically illustrated in  FIGS. 2 through 4 . As shown in  FIG. 2 , the hinge  26  has been molded so that the hinge  26  comprises a layer of scrim  28  encapsulated within a polymer  30 . The layer of scrim  28  is preferably disposed is within the polymer  30 , such that neither of the major surfaces of the scrim  28  are substantially exposed. It will be appreciated that the scrim  28  may not be encapsulated within the polymer  30  at or along the edges of the hinge  26 . The manufacture of the hinge  26  will be described in more detail below. The substrate  12  and hinge  26  are positioned within a vibration welding machine  32  to be vibration welded to one another. The substrate  12  is placed on an anvil  34  of the vibration welding machine  32  to support the instrument panel  10  during the welding operation. The substrate  12  is positioned against the anvil  34  such that the under face  22  of the substrate  12  faces away from the anvil  34 . A first portion  35  of the hinge  26  is positioned against the under face  22  of the substrate  12  of the instrument panel  10  opposite the anvil  34 . A horn  36  of the vibration welding machine  32  is preferably positioned adjacent the hinge  26  opposite the portion of the hinge  26  that is adjacent the substrate  12 . Thus, the horn  36  and the anvil  34  surround the portion of the substrate  12  and the first portion  35  of the hinge  26  to be vibration welded to one another. The horn  36  engages the polymer  30  of the hinge  26  and moves the hinge  26 . Meanwhile, the substrate  12  is held in position by the anvil  34 . The relative motion between the hinge  26  and the substrate  12  as the hinge  26  and substrate  12  are held in pressing engagement with one another creates enough heat to melt the polymer  30  to the substrate  12 . Thus, when molten polymer  30  and/or the substrate  12  are cooled, the hinge  26  is vibration welded to the substrate  12 . It will be appreciated that although the welding of the hinge  26  to the substrate  12  has been described above as vibration welding, other welding techniques such as orbital, frictional, ultrasonic, hot plate, or heat stake welding may be used to attached the hinge  26  to the substrate  12 . It will further be appreciated that at least one of the substrate  12  and the hinge  26  may be provided with weld beads (not shown) to facilitate the welding of the hinge  26  to the substrate  12 , as is conventional in the welding art. 
     During the welding process described above, the horn  36  engages the hinge  26  and a plurality of teeth  37  attached to the horn  36  contact the hinge  26 . The major surfaces of the scrim  28  of the hinge  26  are substantially covered by the polymer  30 , such that the teeth  37  of the horn  36  do not undesirably damage the scrim  28  when the hinge  26  is subjected to vibration welding. Preferably, the teeth  37  grip the polymer  30  during the vibration welding of the hinge  26 , so that the teeth  37  have minimal direct contact with the scrim  28 . Thus, the hinge  26  is capable of withstanding the force applied to the hinge  26  by the teeth  37  as vibratory movement is induced in the hinge  26  by the horn  36  during the plastic welding process. In a preferred embodiment, the hinge  26  is formed such that the thickness of the hinge  26  is about 1.5 millimeters, such that the scrim  28  is embedded substantially within the center of the thickness of the hinge  26 , although such is not required. 
     As is also shown in  FIG. 2 , the tear seam  20  has been formed, preferably by laser scoring, in the under face  22  of the instrument panel  10 . It will be appreciated that the tear seam  20  may be formed at any step of the manufacture of the instrument panel  10  as described herein. The tear seam  20  defines the airbag door  24 , and, preferably, the portion of the substrate  12  to be vibration welded the substrate  12  is within the tear seam  20 , such that the first portion  35  of the hinge  26  is secured to the airbag door  24 . 
     In  FIG. 3 , the instrument panel  10  and hinge  26  have been removed from the vibration welding machine  32 . An airbag collar  38  may be secured to the substrate  12  by any suitable method, such as vibration welding. Preferably, the airbag collar  38  surrounds the airbag door  24 , although such is not required. It will be appreciated that the airbag collar  38  may extend around only a portion or around multiple portions of the airbag door  24 . The airbag collar  38  may include weld beads  40  to facilitate securing the airbag collar  38  to the substrate  12 , although such is not required 
     Next, the airbag module  18  may be then secured to the collar  38  by any suitable method, such as by bolts  42 , as shown in  FIG. 4 . A second portion  43  of the hinge  26  may also be secured to the collar  38  by the bolts  42 , or by any other suitable attachment means. The bolts  42  or other attachment means may be inserted through the hinge  26 , or, if desired, the hinge  26  may include an aperture (not shown) formed therethrough to facilitate the attachment of the hinge  26  to the collar  38  or other portion of the vehicle. It will be appreciated that the second portion  43  of the hinge  26  may be attached to the vehicle and/or the collar  38  by any known fastening means, such that the airbag door  24  is attached to the vehicle by the hinge  26 . Thus, the hinge  26  allows the airbag  27  to force the airbag door  24  free from the instrument panel  10 , yet retains the airbag door  24  such that the airbag door  24  does not freely enter the interior cabin of the vehicle. 
     The second portion  43  of the hinge  26  may be secured to the collar  38  such that the hinge  26  includes a loop portion  44  disposed between the first portion  35  of the hinge  26  secured to the airbag door  24  and the second portion of the hinge  26  secured to the collar  38 . The loop portion  44  provides slack to allow the airbag door  24  to extend further away from the airbag module  18 , such that the airbag door  24  is clear of the airbag  27  as the airbag  27  deploys. Thus, the loop portion  44  of the hinge  26  allows the airbag door  24  to move free of the path of the airbag  27  during deployment. The loop portion  44  of the hinge  26  must be flexible, even in extreme temperatures as low as about −40° Fahrenheit, such that the airbag door  24  does not interfere with the airbag  27  as the airbag  27  deploys. The loop portion  44  of the hinge  26  is formed of the same material as the first portion  35  of the hinge  26 . Thus, the hinge  26  must be formed of a material that is able to withstand a welding operation and remain flexible during airbag deployment, as described herein. 
     The airbag module  18  preferably includes the airbag  27  and an airbag inflator  46 . Any conventional airbag inflator  46  may be used for deployment of the airbag  27 . The airbag inflator  46  and the airbag  27  are shown schematically for illustration purposes since they are known in the art and their construction forms no part of the invention. As will be understood by one of ordinary skill in the art, the shape of the airbag module  18 , airbag inflator  46 , and airbag  27  may vary from that shown. 
     An embodiment of the manufacture of the scrim material  28  will now be described. As shown in  FIG. 5 , a roll of scrim  60  is unrolled onto a conveyor assembly  62 . An adhesive promoter and/or accelerant may be sprayed onto at least one side of the scrim  60  from a sprayer  64 , although such is not required. The scrim  60  enters an alignment roller assembly  66 . Next, a polymer  68  is applied to the scrim  60  from a reservoir  70 . The scrim  60  and polymer  68  enter a hot roller assembly  72  in which the polymer is molded to the scrim  60  to form a scrim mat  74 . In a preferred embodiment, the polymer  68  is molded such that scrim  60  is encapsulated within the polymer  68 . In a more preferred embodiment, the polymer  68  is molded such that the scrim  60  is completely encapsulated within the polymer  68 , such that neither of the major surfaces of the scrim are exposed. Finally, the scrim mat  74  exits the conveyor assembly  62  and is rolled into a scrim mat roll  76 . 
     Although the scrim mat  74  has been described as being manufactured using a molding process, it will be appreciated that the scrim mat  74  may be manufactured by any suitable process, for example, an extrusion process, such as double extruding, or any molding process, such as insert molding. 
     The scrim mat roll  76  may be sized to be larger than required to produce the hinge  26 . The scrim mat roll  76  is sized such that the scrim mat roll  76  is suitable for shipment. Preferably, the scrim mat roll  76  is then cut into the desired size necessary to form hinges, such as the hinge  26 , as will be described below. 
     As shown in  FIG. 6 , a scrim mat roll  76  is unrolled onto a conveyor assembly  78 . The scrim mat roll  76  is placed in a cutter  80  and the scrim mat roll  76  is cut to form a plurality of hinges  82 . Each of the hinges  82  are suitable for use in accordance with the invention as described herein for the hinge  26 . Thus, each of the hinges  82  are formed of a scrim  60  encapsulated in polymer  68 . The major surfaces of the hinges  82  are primarily covered by the polymer  68 , such that the hinges  82  have characteristics suitable to facilitate plastic welding of a portion of each of the hinges  82  to an instrument panel, as described herein. Additionally, the polymer  68  has characteristics suitable for operation as the hinge  26  as described above. The polymer  68  and scrim  60  allows the airbag door  24  to be retained, yet are preferably flexible even in temperatures as low as about −40° Fahrenheit, such that the airbag  27  deploys successfully. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.