Abstract:
The invention comprises a component bridge to reduce the amount of noise entering a passenger compartment of a vehicle through openings in a firewall through which conduits extend. In particular, the component bridge extends from a dashmat to a vehicle component casing to envelop the space around a conduit passing from the engine compartment through the firewall to the component casing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional application Ser. No. 60/481,285, filed Aug. 25, 2003, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to an acoustic barrier for use with a vehicle dashmat. In one of its aspects, the invention relates to an improved acoustic seal for reducing transmission of noise through an opening in the vehicle firewall and the dashmat and from the engine compartment of a vehicle into the passenger compartment. In another of its aspects, the invention relates to a dashmat having an improved acoustic seal for an opening in the dashmat.  
       DESCRIPTION OF THE RELATED ART  
       [0003]     Motor vehicles have a steel firewall between the engine compartment and the passenger compartment. It has been a common practice in the automotive industry to employ an acoustic barrier system between the firewall and the passenger compartment of the vehicle to reduce noise from the engine compartment into the passenger compartment. The acoustic barrier system generally comprises a noise reducing dashmat along the passenger compartment side of the steel wall. The dashmat generally comprises a relatively dense, resilient barrier layer which reflects sound back toward its source, and a foam or fiber sound-absorbing material intermediate the firewall and the barrier layer.  
         [0004]     Various components can be installed in the passenger compartment over the dashmat. Openings through the firewall and dashmat are provided for conduits used to convey fluids and/or electrical power to and from the components. Foam seals and/or flexible boots extend around the openings between the conduits and the firewall to reduce the amount of noise entering the passenger compartment and to prevent water or other materials from entering the passenger compartment. However, the primary purpose of the seal or boot is to provide moisture and debris sealing, with acoustic barrier properties being of secondary importance.  
         [0005]     U.S. Pat. No. 5,975,609 to Campbell discloses a dashmat having an integral boot forming an acoustical barrier around a steering column.  
         [0006]     U.S. Pat. No. 6,070,928 to Campbell discloses an acoustical barrier comprising a pair of interlocking doors attached to a dashmat which must be secured around the component, thereby requiring additional installation steps.  
         [0007]     An acoustic barrier designed to block the transmission of sound through a firewall opening into the passenger compartment is disclosed in U.S. Pat. No. 5,557,078 to Holwerda. Holwerda &#39;078 discloses a dashmat having a pass-through opening circumscribed by an inwardly-extending, flexible, flap-type seal which engages the periphery of a pass-through component.  
       SUMMARY OF THE INVENTION  
       [0008]     In a motor vehicle comprising a firewall extending between an engine compartment and a passenger compartment, having at least one opening therethrough for passage of a vehicle component. A sound attenuating dashmat is mounted to the passenger compartment side of the firewall and has an opening in registry with the at least one opening in the firewall. A vehicle component passes through the openings in the firewall and the dashmat. A component bridge according to the invention surrounds the openings in the firewall and the dashmat and extends upwardly from an upper surface of the dashmat toward the passenger compartment in cooperative register with at least a portion of a perimeter of the vehicle component and with the dashmat. The component bridge has sound absorbing and sound barrier components to attenuate sound that passes through the openings in the firewall and the dashmat and above the upper surface of the dashmat.  
         [0009]     The component bridge is removably attached to the dashmat for selectively installing the component bridge in register with the vehicle component to interrupt the transmission of sound from the engine compartment into the passenger compartment of the motor vehicle, and selectively removing the component bridge from the dashmat when no component is present necessitating the installation of the component bridge. The component bridge is removably attached to the dashmat with a tether. The removable attachment can consist of a tab, a snap, a rivet, a stud, or a strap.  
         [0010]     The component bridge further comprises an upwardly extending side wall and a planar top wall of a sound barrier material. The sound barrier material can comprise a plastic, polypropylene, or a thermoplastic olefin. The component bridge can further comprise a sound absorbing material mounted with the side wall and the planar top wall. The sound absorbing material can comprise a low density, porous material, such as an expanded flexible polyurethane, a flexible fibrous material, a non-woven glass fiber mat, or a shoddy cotton.  
         [0011]     The sound absorbing material can be bonded to the barrier layer along an inner surface of one of the side wall and the top wall. The component bridge can be in register with at least a perimeter of the vehicle component and with the dashmat.  
         [0012]     In a second embodiment, a sound attenuating dashmat is adapted to be mounted to a passenger compartment side of a vehicle firewall, the dashmat having an opening adapted for registry with an opening in the firewall, the vehicle having a vehicle component passing through the opening in the firewall. The dashmat comprises a component bridge surrounding the opening in the dashmat and adapted to extend upwardly from an upper surface of the dashmat toward the passenger compartment in cooperative register with at least a portion of a perimeter of the vehicle component and with the dashmat. The component bridge has sound absorbing and sound barrier components to attenuate sound that passes through the openings in the firewall and the dashmat and above the upper surface of the dashmat when the dashmat is attached to the passenger compartment side of the vehicle firewall. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is an exploded view from the passenger compartment of a motor vehicle of a portion of a firewall overlain by a dashmat, a steering assembly adapted to extend therethrough, and a first embodiment of a component bridge according to the invention.  
         [0014]      FIG. 2  is a perspective view of the steering assembly illustrated in  FIG. 1  extending through the firewall with the component bridge installed according to the invention.  
         [0015]      FIG. 3  is a close-up perspective view of a portion of the firewall overlain by the dashmat illustrated in  FIG. 1  with the uninstalled component bridge attached to the dashmat by a connecting strap.  
         [0016]      FIG. 4  is a cross-sectional view of a portion of the steering assembly and the component bridge illustrated in  FIG. 2  taken along line  4 - 4 .  
         [0017]      FIG. 5A  is a cross-sectional view of an electrical control module mounted to a firewall and a second embodiment of the component bridge according to the invention prior to installation of the component bridge onto a dashmat.  
         [0018]      FIG. 5B  is a cross-sectional view similar to  FIG. 5A  of the electrical control module with the component bridge installed onto a dashmat.  
         [0019]      FIG. 6  is a perspective view of the component bridge illustrated in  FIGS. 5A and 5B . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     Referring now to the drawings and to  FIGS. 1 and 2  in particular, a conventional firewall  10  is illustrated separating an engine compartment  11  from a passenger compartment  22  of a motor vehicle. The view in  FIG. 1  is from the passenger compartment  22 . It should be noted that the invention is illustrated in the context of a motor vehicle, such as an automobile, for exemplary purposes only, and that the invention is not limited by the examples described herein. In particular, the invention is not limited to use with a two-layer dashmat described herein, but can be used with any dashmat that has both barrier and absorption properties, including single layer firm-flexible foam. An example of a firm flexible foam suitable for a dashmat is described in International Publication No. WO 2004/062966 A2, published Jul. 29, 2004, and entitled “Molded Lightweight Foam Acoustical Barrier And Method Of Making Same,” which is incorporated by reference as though set forth fully herein. In fact, the acoustic seal can be used to attenuate sound through any opening in a substrate, regardless of the nature of the substrate.  
         [0021]     An acoustic barrier, referred to hereinafter as a dashmat  12 , is located along the passenger compartment side  22  of the wall  10  and comprises a barrier layer  13  and a sound absorbing layer  14 . The barrier layer  13  is typically made of a relatively dense, resilient or flexible synthetic resin, such as a barium sulfate filled polypropylene, a thermoplastic elastomer, elastomer-modified polyurethanes, thermosets such as polyurethanes, or other filled thermoplastic materials, and has an upper surface  13   a  facing the passenger compartment  22 , as illustrated in  FIG. 3 . The sound absorbing layer  14  is typically a foam plastic material, such as expanded flexible polyurethane, or a flexible fibrous material, such as a nonwoven glass fiber mat, shoddy cotton, or other relatively low density, porous sound-absorbing material that is commonly employed to absorb sound and/or act as a decoupling layer in an acoustic barrier assembly. The sound absorbing layer  14  is typically bonded to the barrier layer  13  so that it is interposed between the barrier layer  13  and the firewall  10  when the dashmat  12  is installed in the motor vehicle. One or more openings  19  are provided through the firewall  10 . Openings  15  extending through the barrier layer  13  and the sound absorbing layer  14  are in registry with the openings  19  in the firewall  10  to enable communication between a first component in the passenger compartment  22  and a second component in the engine compartment  11 .  
         [0022]     An automotive component, such as an exemplary steering assembly  16 , is illustrated in  FIGS. 1-4  extending through the firewall  10  and the dashmat  12  in a generally well-known manner. Although an exemplary steering assembly  16  is illustrated in  FIGS. 1-4 , other automotive components, such as an electrical control module  40  illustrated in  FIGS. 5A-6 , are frequently mounted along the passenger side of the firewall  10 , and the inventive concepts described herein are applicable to such other automotive components in addition to the exemplary steering assembly  16  and electrical control module  40 .  
         [0023]     The steering assembly  16  comprises a well-known steering column  17  and a steering wheel  18 . As illustrated in  FIGS. 1 and 2 , the steering column  17  extends through openings  15 ,  19  in the firewall  12  to link with a steering mechanism in the engine compartment (not shown). In order to prevent moisture and debris from entering from the engine compartment  11  to the passenger compartment  22 , and to provide some reduction in noise transmitted from the engine compartment  11  to the passenger compartment  22 , a seal, illustrated in  FIGS. 1 and 4  as a steering column boot  20  around the steering column  17 , is provided for sealing the openings  15 ,  19  between the steering column  17  and the firewall  10 . The boot  20  is typically a thin, flexible rubber material that seals to the steering column  17  by way of an inserted bearing (not shown) of metal or rigid plastic. Noise from the engine compartment  11  can pass through the thin, flexible boot  20 , which is a relatively weak acoustic barrier, between the steering column  17  and the dashmat  12 , into the passenger compartment  22 .  
         [0024]     An acoustic seal, comprising a component bridge  24  according to the invention, comprises a regularly or irregularly shaped, thin-shelled body adapted for cooperative register with the steering column  17  and the dashmat  12 . Preferably, the component bridge  24  comprises a rigid or semi-rigid outer shell, typically referred to as a barrier layer  34 , comprising a polymeric material, such as polypropylene or a thermoplastic olefin, which can be readily formed into a pre-selected shape using conventional plastic forming methods, such as vacuum forming or injection molding. As illustrated in  FIGS. 1-4 , the component bridge  24  is illustrated as having a generally truncated cone shape having at a first, smaller radius end an aperture  30  adapted for insertion of the steering column  17 , and terminating at a second, larger radius end in a perimetric lip  28 . However, the component bridge  24  can have any shape suitable for the acoustic sealing function described herein, based upon, for example, the shape of the component to be sealed, the configuration of the adjoining barrier layer surface  13   a , space requirements, and the like.  
         [0025]     A sound absorbing layer  32 , comprising a suitable sound absorbing material, such as expanded flexible polyurethane, or a flexible fibrous material, such as a non-woven glass fiber mat, shoddy cotton, or other relatively low density, porous sound-absorbing material that is commonly employed to absorb sound and/or act as a decoupling layer, can be selectively bonded to the barrier layer  34  to form an annular body along the inner perimeter thereof, as illustrated in  FIGS. 3 and 4 . It is preferable that the aperture  30  closely circumscribe the steering column  17  to minimize unimpeded sound paths through the aperture  30  along the steering column  17 .  
         [0026]     In one embodiment, illustrated in  FIG. 1 , the component bridge  24  is provided with a flexible connecting tether  26  attached at a first end along or proximate to the lip  28 . The connecting tether  26  is illustrated as a flexible strap  38  transitioning at its second, free end to an enlarged, somewhat flexible attachment tab  35 . The attachment tab  35  can be inserted into a slot  39 , illustrated in  FIG. 3 , or other opening in the barrier layer  13  during fabrication of the dashmat  12  to retain the attachment tab  35  in the slot  39 . The flexibility of the attachment tab  35  and its engagement in the slot  39  enables the attachment tab  35  to be removed from the slot  39  by pulling on the connecting tether  26 . Alternatively, the tether can have a removable connector, such as a snap, a stud, a breakable rivet, or the like, for attaching the tether to the dashmat  12  until the component bridge  24  is to be installed. The connector is readily separable for removal of the component bridge  24  from the dashmat  12  in preparation for installation of the component bridge  24  with the steering column  17  or other component. Alternatively, the tether  26  can be cut to separate the component bridge  24  from the dashmat  12 .  
         [0027]     As illustrated in  FIGS. 3 and 4 , the tether  26  is used to temporarily attach the component bridge  24  to the dashmat  12 . The component bridge  24  can be installed to the dashmat  12  around the steering column  17  by first separating the tether  26  from the dashmat  12 . Alternatively, as illustrated in  FIG. 4 , the tether  26  can continue to connect the component bridge  24  to the dashmat  12  if the tether  26  does not impede the installation of the component bridge  24  around the steering column  17 .  
         [0028]     As illustrated in  FIG. 4 , the component bridge  24  extends from the steering column  17  to the dashmat  12 , thereby interrupting sound transmitted through the openings  15 ,  19 , and preventing its entry into the passenger compartment  22 . The sound will be reflected back toward the interior of the component bridge  24  by the barrier layer  34 , and also absorbed by the sound absorbing layer  32 , as illustrated by the sound vectors  36  of  FIG. 4 .  
         [0029]     The lip  28  is adapted to communicate intimately with the upper surface  13   a  of the barrier layer  13  in order to enhance the sound blocking capabilities of the component bridge  24 . The lip  28  can also provide a means of securing the component bridge  24  against the barrier layer  13  with conventional fasteners, such as threaded or unthreaded studs, snaps, and the like (not shown), or an adhesive applied therealong. The lip  28  can be adapted with a suitable contour for cooperative register with the contour of the dashmat  12 . The shape of the component bridge  24  can also be adapted to minimize the space in the passenger compartment  22  occupied by the component bridge  24 .  
         [0030]     FIGS.  5 A-B and  6  show a second embodiment of the component bridge  48  for use with an electrical control module  40 . As illustrated in  FIG. 5A , the electrical control module  40  is attached to the firewall  10  and extends through the openings  15 ,  19  beyond the dashmat  12  in conventional fashion. A connector  42  is adapted for electrical communication with the module  40 . The dashmat  12  terminates in a raised perimeter wall  44  circumscribing the openings  15 ,  19  and orthogonal to the dashmat  12 . The perimeter wall  44  is provided with a perimeter locking rib  46  extending outwardly along the perimeter of the perimeter wall  44  and spaced somewhat away from the dashmat  12 .  
         [0031]     The component bridge  48  is illustrated in  FIG. 6  as a generally rectilinear thin-shelled body comprising a perimeter wall  52  and a top wall  53 , and adapted for operable communication with the perimeter wall  44 . Preferably, the component bridge  48  comprises a rigid or semi-rigid plastic barrier layer  64  similar to that described previously herein, and can comprise one or more sound absorbing layers or components  62  ( FIGS. 5A and 5B ) similar to that described previously herein and adapted to the configuration of the electrical control module  40 . The perimeter wall  52  is adapted for fixed, cooperative register with the perimeter locking rib  46  to secure the component bridge  48  to the perimeter wall  44 . A perimeter locking slot  54  is illustrated extending through and along a portion of the perimeter wall  52 , and adapted for locking communication with the perimeter locking rib  46 . Other suitable connecting devices such as snaps, threaded fasteners, friction or interference fit assemblies, and the like can also be utilized to secure the component bridge  48  to the perimeter wall  44 . The top wall  53  is provided with apertures  50  to receive the module  40  and/or the connectors  42  therethrough.  FIG. 6  illustrates the component bridge  48  with a connecting strap  56  for attaching the component bridge  48  to the dashmat  12 , as previously described herein.  
         [0032]     During vehicle assembly, the dashmat  12  will be typically installed against the firewall  10 , followed at some later time by installation of the steering assembly  16  and/or the electrical control module  40 . The steering assembly  16  will be installed by inserting the steering column  17  through the openings  15 ,  19  with the boot  20  properly positioned to seal the space between the steering column  17  and the openings  15 ,  19 . Similarly, the electrical control module  40  will be installed to the firewall  10  so that the module  40  extends through the openings  15 ,  19  for attachment of the connectors  42 . At some later time, the component bridge  24 ,  48  can be installed around the steering column  17  and/or the electrical control module  40  and secured to the dashmat  12  and/or the firewall  10  using conventional fasteners, as described above.  
         [0033]     The component bridge described herein provides effective blocking and absorption of sound traveling from the engine compartment of a motor vehicle through openings in the firewall associated with vehicle components mounted in the passenger compartment. It is readily fabricated using well-known fabrication processes, and easily installed around the perimeter of the component after installation of the component in the passenger compartment. It can be adapted to closely follow the contour of the component in order to minimize the space occupied by the component bridge. The use of a rigid outer shell with a sound absorbing foam provides effective sound blocking while taking up little additional space. The use of a connecting strap or a removable connecting tab retains the component bridge attached to the dashmat until the component bridge is installed, thereby reducing the number of lost or unavailable parts, and the necessity of maintaining a separate supply of component bridges.  
         [0034]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. For example, the invention is not limited to use of the acoustic seal with a two layer dashmat but can be used with any dashmat that has both barrier and absorption properties, including single layer firm-flexible foam. In fact, the acoustic seal can be used to attenuate sound through any opening in a substrate, regardless of the nature of the substrate. Reasonable variation and modification are possible within the scope of the foregoing description and drawings without departing from the spirit of the invention.