AU2006100111B4 - A multilayered acoustic sheild for a motor vehicle - Google Patents

Description

P001 Section 29 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Application Number: Lodged: Invention Title: A multilayered acoustic shield for a motor vehicle The following statement is a full description of this invention, including the best method of performing it known to us: A MULTILAYERED ACOUSTIC SHIELD FOR A MOTOR VEHICLE FIELD OF THE INVENTION The present invention relates to an acoustic shield for a motor vehicle.

More particularly, the present invention relates to a multilayered acoustic shield for mounting to a panel or transmission tunnel of a motor vehicle. As the acoustic shield is particularly suited for mounting to the transmission tunnel of a motor vehicle, it will therefore be convenient to describe the invention in relation to that example application. It should however be understood that the invention is equally mountable to a panel of a motor vehicle for example, a firewall in the engine bay of a motor vehicle.

BACKGROUND OF THE INVENTION The passenger compartment of a motor vehicle is typically subjected to varying degrees of external sound. External sounds usually originate from the vehicle's engine, transmission, tyres and also other nearby vehicles. Increasingly motorists are expecting the passenger compartment of a motor vehicle to be quieter. In addition, regulatory bodies are increasingly demanding a reduction in the emission of sound by motor vehicles into the surrounding environment.

In the past motor vehicle manufactures have attempted to reduce the impact of external sounds on the passenger compartment by placing sound insulating material around the perimeter of the passenger compartment. In this regard, virtually all modern day motor vehicles now have some form of acoustic insulating material lining the floorpan of the passenger compartment underneath the carpet.

Attempts have also been made in the past to further reduce the impact of external sounds on the passenger compartment by additionally locating acoustic insulating material underneath the floorpan of the passenger compartment on the underside of the transmission tunnel. However, as significant heat is generated underneath the floorpan by the engine, transmission and catalytic converter of the exhaust system, the acoustic insulating material has had to be entirely constructed from metallic material. A problem with this type of arrangement is that the metallic material has to be slightly spaced from the underside of the transmission tunnel to ensure that vibrations are not directly imparted to the floorpan and subsequently to the passenger compartment. Unfortunately, due to space constraints between the underside of the transmission tunnel and the transmission, providing an adequate spacing for this type of arrangement requires using material of a minimal thickness, to the detriment of the arrangement's sound absorption ability.

Accordingly, it would be desirable to provide an acoustic shield which overcomes or ameliorates at least one of the above mentioned problems with the prior art.

Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art in Australia or any other country on or before the priority date of the claims herein.

SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention there is provided a multilayered acoustic shield for mounting to an underside of a transmission tunnel in a motor vehicle floorpan, the shield including: an outer perforated metallic layer; an inner layer of fibrous acoustic material; and a metallic foil located between the inner and outer layers, wherein the shield is fastenable to the vehicle floorpan such that at least a portion of the shield conforms with a curvature of the underside of the transmission tunnel with the inner layer being compressed against the transmission tunnel, to thereby reduce the transmission of noise into a passenger compartment of the vehicle.

The present invention provides an appropriate blend between sound absorption and sound insulation. In this regard the fibrous acoustic material provides a degree of sound absorption by reducing the reflection of sound, whilst the outer metallic layer in conjunction with the metallic foil provides a degree of sound insulation by reducing the transmission of sound. As a result the present invention is able to provide a reduction in the transmission of sound into the passenger compartment of the vehicle whilst at the same time minimising the reflection of sound into the surrounding environment.

Preferably, the outer metallic layer is fastened to the floorpan adjacent to opposing sides of the transmission tunnel.

In a preferred embodiment, the curvature of the shield within the transmission tunnel compresses the inner layer against the transmission tunnel.

In accordance with another aspect of the present invention there is provided a multilayered acoustic shield for mounting to a panel of a motor vehicle, the shield including: an outer perforated metallic layer; an inner layer of fibrous acoustic material; and a metallic foil located between the inner and outer layers, wherein the shield is fastenable to the vehicle panel such that at least a portion of the shield conforms with a curvature of the panel with the inner layer being compressed against the panel, to thereby reduce the transmission of noise into a passenger compartment of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS Further benefits and advantages of the present invention will become apparent from the following description of a preferred embodiment of the invention. The preferred embodiment should not be considered as limiting any of the statements in the previous section. The preferred embodiment will be described with reference to the following figures in which: Figure 1 is a cross-sectional view of a transmission tunnel in a motor vehicle floorpan with the multilayered acoustic shield attached thereto, in accordance with an embodiment of the invention; Figure 2 is a cross-sectional view of a multilayered acoustic shield illustrating the components of the shield according to an embodiment of the invention.

DECSCRIPTION OF PREFERRED EMBODIMENT With reference to Figure 1 of the accompanying drawings there is shown a multilayered acoustic shield 1 mounted to the underside of a transmission tunnel 3 in a motor vehicle floorpan. The shield includes an outer metallic layer 7, an inner layer of fibrous acoustic material 9 and a metallic foil 11 located between the inner and outer layers. Figure 2 of the accompanying drawings illustrates the acoustic shield 1 prior to being suitably shaped and mounted to the transmission tunnel 3.

The outer metallic layer 7 is made of aluminium with a thickness between 0.4 mm and 1.0 mm. The metallic layer's 7 primary function is to protect the underlying layers, particularly the acoustic material 9, from road debris and water.

In addition the metallic layer 7 functions to protect the underlying layers from heat generated by nearby components of the vehicle, such as the catalytic converter.

In this regard the outer metallic layer 7 is able to maintain the acoustic material 9 to a temperature below approximately 180 0

C.

The metallic layer 7 has a series of perforations in selected areas with the perforations being between approximately 2.5 mm and 5.0 mm in diameter. The perforations enable sounds to more readily penetrate the metallic layer 7 and subsequently be absorbed by the acoustic material 9. The perforations in the metallic layer 7 preferably cover no more than approximately 20 to 30 percent of the surface area of the metallic layer 7 such that the strength of the layer 7 is maintained. In order to provide additional strength the metallic layer 7 can be embossed.

The metallic foil 11 is also made of aluminium and can range between 0.01 mm and 0.04 mm in thickness. In conjunction with the metallic layer 7 the metallic foil 11 adds an additional layer of protection to the underlying acoustic material 9. The metallic foil 11 may have a series of micro-perforations to enable sounds to more readily penetrate the foil 11 and subsequently be absorbed by the acoustic material 9.

The acoustic material 9 is made of polyester fibres with a fibre diameter of approximately 2 denier to 8 denier, depending upon the wavelengths and frequencies of the sounds which are required to be absorbed. The acoustic material 9 also includes a percentage of polyester co-extrusion melt fibre ranging from 5 to 10 percent to ensure that the surface of the acoustic material 9 adjacent to the transmission tunnel 3 is relatively smooth. The acoustic material 9 typically has a minimum of 800 grams per square metre and has a thickness of 6 mm.

In order to tune the shield 1 to absorb or reflect specific wavelengths and frequencies of sound, specific diameters of polyester fibres in the acoustic material 9, perforations in the metallic layer 7 and micro-perforations in the foil 11 are selected. In addition the thickness of each layer can also be suitably selected.

In the embodiment of the invention shown in Figure 1 the acoustic shield 1 is fastened to the vehicle floorpan at a series of spaced locations across the width of shield 1 by three fasteners 13. However, as three fasteners are not always needed across the width of the shield, the acoustic shield 1 can instead be fastened with only two fasteners 13 at opposing sides of the transmission tunnel 3. In addition to fastening the shield 1 to the transmission tunnel 3 the fasteners 13 assist to compress the acoustic material 9. The fasteners 13 may be of any suitable form, for example rivets, studs, nuts, self-tapping screws or the like. The acoustic shield 1 extends longitudinally along the transmission tunnel 3, directly above the transmission of the motor vehicle, and may have additional fasteners 13 at spaced locations along the length of the acoustic shield 1.

Whilst the metallic layer 7 does have a degree of flexibility it also has a level of rigidity. This advantageously enables the shield 1 to maintain conformance with the curvature of the underside of the transmission tunnel 3 and compress the acoustic material 9 against the transmission tunnel 3. Further, the compression of the acoustic material 9 ensures that the shield 1 is of minimal thickness and that no gap remains between the acoustic material 9 and the transmission tunnel 3.

As the present invention may be embodied in several forms without departing from the essential characteristics of the invention, it should be understood that the above-described embodiment should not be considered to limit the present invention but rather should be construed broadly. Various modifications and equivalent arrangements are intended to be included within the spirit of the invention and the scope of the appended claims.

Claims (4)

1. A multilayered acoustic shield for mounting to an underside of a transmission tunnel in a motor vehicle floorpan, the shield including: an outer perforated metallic layer; an inner layer of fibrous acoustic material; and a metallic foil located between the inner and outer layers, wherein the shield is fastenable to the vehicle floorpan such that at least a portion of the shield conforms with a curvature of the underside of the transmission tunnel with the inner layer being compressed against the transmission tunnel, to thereby reduce the transmission of noise into a passenger compartment of the vehicle.

2. A multilayered acoustic shield as claimed in claim 1 wherein in use the outer metallic layer is fastened to the floorpan adjacent to opposing sides of the transmission tunnel.

3. A multilayered acoustic shield as claimed in claim 2 wherein the curvature of the shield within the transmission tunnel compresses the inner layer against the transmission tunnel.

4. A multilayered acoustic shield for mounting to a panel of a motor vehicle, the shield including: an outer perforated metallic layer; an inner layer of fibrous acoustic material; and a metallic foil located between the inner and outer layers, wherein the shield is fastenable to the vehicle panel such that at least a portion of the shield conforms with a curvature of the panel with the inner layer being compressed against the panel, to thereby reduce the transmission of noise into a passenger compartment of the vehicle. A multilayered acoustic shield substantially as hereinbefore described with reference to the accompanying drawings. DATED this 14th day of February 2006 MARK BORRONI WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA UIP1107AU00