Patent Application
20050126848
The present invention relates generally to a sound insulating system.
Automotive makers have endeavored to reduce the overall noise and vibration in vehicles. Limiting noise and vibration as well as harshness (NVH) has become an important consideration in vehicle designs. Previously, engine noise typically dominated the overall vehicle noise. More recently, other noise sources, such as from tires, wind and exhaust have become as important to reduce as engine noise. Exterior pass-by noise has been regulated by governmental restrictions. Yet, interior vehicle noise constriction has been a direct result of consumer demands to reduce the noise in the vehicle.
It is desirable to minimize the overall interior and exterior vehicle noise. Accordingly, significant efforts have been directed to reduction of interior vehicle noise. One of these efforts has been to use a barrier concept or a dashmat. These dashmats are used to reduce noise from the engine to the interior of the vehicle. Typically such dashmats are placed on or adjacent a substrate, such as a firewall to reduce the amount of noise passing from the engine through the firewall to the vehicle interior.
Prior dashmats are typically made of a decoupler, usually made of foam (slab or cast foam) and a barrier made of thermoplastic polyolefin (TPO) or ethylene vinyl acetate sheet (EVA). These dashmats are all intended to reduce overall engine compartment noise. Such barrier type dashmats have typically been relatively heavy to produce the desired noise reduction results.
More recently, lightweight dashmats have been used. The lightweight concept utilizes absorptive material, such as shoddy cotton. Rather than blocking the engine noise, the goal of this type of dashmat is to absorb and dissipate the engine noise as it travels from the engine compartment to the vehicle interior. One such lightweight dashmat system is shown in U.S. Pat. No. 6,145,617 to Alts and assigned to Rieter Automotive AG. Another type of lightweight dashmat system is shown in U.S. Pat. No. 6,296,075 to Gish et al and assigned to Lear Corporation. These lightweight dashmat systems also decrease the overall weight of the vehicle.
Yet another type of dashmat system is shown in Japanese Application numbers 2000-209070 and 2000-209059 and European Paten Application publication No. EP 1,428,656 A1. These applications show soundproofing materials which include absorptive materials and a barrier material.
The primary function of these types of dashmats is to reduce noise levels in the vehicle's interior. Traditionally, it was believed that blocking the noise in accordance with the mass law provides the best noise transmission loss and noise reduction. Transmission loss and noise reductions are typical measurement parameters used to quantify the noise reduction.
Blocking the noise is only effective if the barrier covers all holes and pass throughs. If not, leaks can occur and NVH performance is degraded. Since dashmats are used in various areas of the vehicle having openings or pass throughs, such as in the areas of air conditioners or steering columns, the blocking technique is not wholly effective. Typically, in certain dashmats using the blocking technique, the insulation foam (i.e., the decoupler) has been less effective and does not possess good absorptive acoustic properties. Thus, the noise is not dissipated enough as it travels through the dashmat.
It would be desirable to provide lightweight dashmats that treat both engine compartment noise coming through the firewall and noise that comes into the passenger compartment from other sources during vehicle operation. In addition, it would be desirable to have a dashmat system that is tunable or adjustable for any particular vehicle application.
According to one embodiment of the present invention, there is provided a sound insulating system. The sound insulating system comprises a first absorbing layer. A barrier layer is adjacent the first absorbing layer. The system further comprises a second absorbing layer adjacent the barrier layer. The surface weight of said barrier layer is greater than about 0.1 kg/m2.
According to a second embodiment of the present invention, there is provided a vibration damping system. The vibration damping system comprises a vibration damping layer. A sound barrier layer is adjacent the vibration damping layer. A sound absorbing layer is adjacent the sound barrier layer.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
The system 10 shown provides a multi-layer dashmat that is preferably used to reduce noise transmission to the interior of the vehicle through the front-of-dash panel. In addition to the noise blocking feature, the system 10 reduces noise levels within the vehicle interior through sound absorption. Additionally, the system 10 preferably can be used in the engine compartment to reduce noise exiting the engine compartment to the exterior of the vehicle. The system 10 also preferably enhances the sound quality perception for interior and/or exterior environments. The system 10 can also be incorporated into other automotive components such as, but not limited to, liners for wheel wells, fenders, engine compartments, door panels, roofs, floor body treatments, trunks and packaging shelves. Furthermore, the system 10 can be incorporated into non-automotive applications.
In the
The barrier layer 14 preferably comprises a relatively thin substantially impermeable layer. In the embodiment of
It will be appreciated that alternative materials can be used to form either of the absorbing layers 12, 16 and the barrier layer 14. Some examples are set forth below.
As indicated in the previously described embodiments, the first and second absorbing layers 12, 16 can comprise several different materials. It is preferred that the materials exhibit enhanced sound absorption and transmission loss properties. Further, it is preferred that the materials have vibration damping performance properties. Thus, the absorbing layers 12, 16 dissipate the noise and minimize panel vibration. Preferred are materials that have a damping performance, tan delta, of between about 0.01 and about 1.5. Still more preferred are materials that have a tan delta between about 0.3 and about 1.5. This damping performance helps eliminate noise due to vibration of the substrate.
Preferred materials that meet these criteria include natural or synthetic fibrous materials, such as, for example, wool, cotton, polyester, polyolefins and glass. Other preferred materials include natural or synthetic foams, both slab and molded, such as, for example, latex, polystyrene, polyurethane, polyolefin or polyester. Viscoelastic foams are most preferred. These foams could also be recycled foam, fiber composite, foam impregnated fiber mats or microcellular elastic foam. The materials may also include organic and/or inorganic fillers.
The thickness of the absorbing layers 12, 16 can vary depending on the particular application. By way of a non-limiting example, the thickness of the absorbing layers 12, 16 can be non-uniform. While it is preferred that the thickness be between about 0 mm and about 100 mm, it will be appreciated that the thickness can vary, even outside these ranges depending on the particular application. It is most preferred that the thickness of the absorbing layer 12, 16 be between about 0 mm and about 50 mm.
Further, in each example shown above, a single material is used to make each absorbing layer 12, 16. It is to be understood that the absorbing layers 12, 16 may also comprise combinations of materials adjacent one another. That is, each absorbing layer 12, 16 may comprise more than one sublayer of either a similar or dissimilar material. Furthermore, blends of material may be used as the absorbing layer 12, 16. Additionally, it will be appreciated that the first absorbing layer 12 and second absorbing layer 16 may comprise the same material or may be made of different materials.
By utilizing either an absorbing layer 12, 16 made of a single material or by using a multi-sublayer assembly as the absorbing layer 12, 16 having varying thickness, the system 10 can be tuned or adjusted to meet the specific noise reduction and absorption requirements for any particular location in the vehicle. This flexibility to adjust the system 10 allows for it to be used in various applications. This type of system also allows suppression of noise created by the engine, drive train or other vehicle components as well as suppression of vibration or damping of various vehicle components.
The barrier layer 14, as stated above, is preferably substantially impermeable and reduces the noise passing therethrough. Optionally, the barrier layer 14 can provide enhanced stiffness and shape retention. The barrier layer thus utilizes the blocking technique to reduce noise transmission therethrough. As with the absorbing layers 12, 16, the barrier layer 14 can have varying thickness. It is preferred that the thickness of the barrier layer be between 0.1 and 50 mm. Again, it is to be understood that the thickness can be varied, even outside the preferred range, in order to tune or adjust the system 10 to meet the specific noise reduction requirements for a particular location within the vehicle.
The barrier layer 14 has a surface weight of about 0.1 kg/m2 or greater. It is preferred that the barrier layer 14 have a surface weight greater than 0.4 kg m2. Generally, the greater surface weight of the barrier layer results in better noise reduction capabilities of the sound insulating system. The surface weight of the barrier layer 14 is calculated by multiplying the density of the barrier layer by the thickness of the barrier layer.
It is preferred that the sound insulating system has a bending stiffness from about 0.18 N/mm to about 45 N/mm. The bending stiffness is measured by using a sample that is 2 inches×4.5 inches simply supported with a span of 3 inches in accordance with ASTM test procedure D-5934-02. The bending stiffness aids in installation of the system, particularly into a vehicle.
Examples of flexural stiffness of various samples are set forth below:
The shoddy material used in each example comprises recycled polyester fibers. The shoddy material is available from Janesville Products of Ohio. Further, the thickness of each absorbing layer 12, 16 are shown. The density of the shoddy is also given. In the first sample, the shoddy density is 85 g/m3. In each of the other samples the shoddy density 110 g/m3.
While a single barrier layer 14 is shown, it is to be understood that multiple barrier layers 14 of varying thickness may be used. Thus, each barrier layer 14 may comprise more than one sublayer of either a similar or dissimilar material. Each layer may be of the same or different material. Additionally, blends of different materials may be used. Additionally, the barrier layer may have varying thickness.
Preferred materials for the barrier layer 14 include polymer film or sheet, closed cell foam, metal film, and skinned foam. As set forth above, the barrier layer 14 can comprise olefins, PET, PVC or any other suitable material. When the barrier layer comprises a skinned foam, the skin can be the skin of a material used to form the absorbing layer 12, 16. Further, the barrier layer 14 may include recycled polymer products. The barrier layer 14 may also include natural or synthetic fibers to add strength. The barrier layer 14 can also comprise a honeycomb structure or a mesh having substantially impermeable material, such as skins, films or sheets added to one or both sides of the honeycomb or mesh.
The barrier layer 14 is preferably shape formable and retainable in order to conform the shape of the system 10 to the substrate for any application. In order to combine the absorbing layers 12, 16 with the barrier layer 14, any suitable fabrication technique may be used. Some such examples include connecting the various layers by heat laminating, or by applying adhesives between the various layers. Such adhesives may be heat activated. The various layers may also be adhered during the process of shape forming by heating the layers and then applying pressure in the forming tool, or by applying adhesive to the layers and then applying pressure in the forming tool.
The barrier layer 14 can also be a stand alone sheet layer, or it could be applied directly to the absorbing layer by spray application of a material, such as, for example, polyurethane. The barrier layer may also be formed as a skin on the absorbing layer such as polyurethane or latex foam during the foaming process.
The system could also be constructed in a cast foam tool by inserting the barrier layer material, such as a polymer film into the center section of a mold and then injecting material to make the foam, such as polyurethane foam into both sides of the tool. The system 10 can also be formed by creating each of the absorbing layers 12, 16 and barrier layers 14 jointly and/or independently and then securing them by conventional methods, for example, using mechanical fasteners, heat fusing, sonic fusing, and/or adhesives.
Further, as set fotth above, the absorbing layers need not necessarily have a uniform thickness over the entire part. For example, the absorbing layers may be compacted in certain areas during the forming process. Additionally, it may be necessary to have different thicknesses of absorbing layers to fit in different areas of the vehicle. That is, there may be different clearances in the vehicle that require thinner absorbing layers in those areas. This by designing a variable thickness, the need to cut holes in the system is reduced. This allows maximum coverage area by the system, resulting in an increase in the overall noise reduction of the system.
As shown above each embodiment comprises a first absorbing layer 12 adjacent a barrier layer 14. A second absorbing layer 16 is adjacent the barrier layer 14 on the opposite side of the first absorbing layer. This system allows for sound absorption to take place on either side of the barrier layer, as well as noise transmission suppression into the vehicle. Further, the use of the barrier layer in connection with the absorbing layers also aids in noise suppression in either direction through the system.
The system 10 can also be made by first producing the first absorbing layer 12 and barrier layer 14. The second absorbing layer 16 can then be added.
Four examples using various absorber layers and barrier layers were made and tested as set forth below. The test results from these four samples are shown in
The absorber-barrier-absorber dash insulator or system 10 was made using viscoelastic foams as the absorbing layers 12, 16 and polyethylene sheet as the barrier layer 14.
Three-layer samples with dimensions 0.69 m×0.69 m×27 mm thick were made using 2 layers of Dow Developmental viscoelastic polyurethane foam #76-16-10-HW with a thickness of 13 mm, and a 0.36 mm thick polyethylene sheet as the middle barrier layer. The areal density of the sample was calculated by measuring the mass of the sample and dividing by the area of the sample. The areal density is shown in
NR=(average SPL1)−(average SPL2) Equation 1.
The normal incidence sound absorption coefficient of the sample was measured by cutting a 29 mm diameter disk from the 3-layer sample and inserting into a Bruel and Kjaer (Denmark) two-microphone Impedance Tube. The Impedance Tube test method is described in ASTM E-1050. The absorption coefficient results are shown in
The absorption coefficient of the viscoelastic foam was also measured using the Impedance Tube method. In addition, the damping loss factor of the foam was measured using compression testing and the hysteresis loop method. The viscoelastic foam showed a damping factor of 1.6.
The absorber-barrier-absorber dash insulator or system 10 was made with viscoelastic foam as the first absorbing layer 12 against the sheet metal, 0.36 mm polyethylene sheet as the barrier layer 14 and a polymer fiber mat as the second absorber layer 16.
Three-layer samples with dimensions 0.69 m×0.69 m×32 mm thick were made using 1 layer of Dow Developmental viscoelastic foam #76-16-10-HW with a thickness of 13 mm, one layer of Owens Corning VERSAMAT (Sample 506R4800) fiber material with a thickness of 18 mm, and a 0.4 mm thick polyethylene sheet as the barrier layer 14. The areal density of the sample was calculated by measuring the mass of the sample and dividing by the area of the sample. The areal density is shown in
The normal incidence sound absorption of this sample was measured using Impedance Tube method of Example A.
The absorber-barrier-absorber dash insulator or system 10 was made using skinned, open cell polyurethane foam Grade ES-50 from E-A-R Specialty Composites (Indianapolis, Ind.) as the absorbing layers 12, 16 and a polypropylene honeycomb sheet from Plascore (Zeeland, Mich.) as the barrier layer 14.
Three-layer samples with dimensions 0.69 m×0.69 m×30 mm thick were made using two layers 12, 16 of E-A-R foam, each 12.5 mm thick, with a 7.5 mm thick polypropylene honeycomb material, Plascore PCTR250WO.250, in the middle as the barrier layer 14. The surface skin on the E-A-R foam sheets, in contact with the honeycomb, for the barrier layer 14 for this construction. This example utilizes a structural air gap that includes a barrier to give a very lightweight, yet strong and formable barrier layer for the system 10. The areal density is shown in
The normal incidence sound absorption of this sample was measured using the Impedance Tube method of Example A, and the results are shown in
The absorber-barrier-absorber dash insulator or system 10 was made using a low density latex as the first absorbing layer 12 and a higher density latex foam as the barrier layer 14 that is deposited on a woven substrate which comprises the second absorbing layer 16.
Three layer samples with measurements 0.61 m×0.61 m×22 mm thick were provided by Dow-Reichhold (North Carolina). The thickness of the fiber layer was 11 mm, the thickness of the middle latex foam was 3 mm and the thickness of the outer latex foam was 8 mm. The samples were cut and glued together to make a 0.69 m×0.69 m×22 mm plaque for measuring noise reduction. The areal density is shown in
Reiter ULTRALIGHT dash Insulator. A Reiter ULTRALIGHT dash insulator for the 2003 DCX RS Minivan was cut into sections and glued together (areal density was adjusted for the glue mass) to make a 0.69 m×0.69 m×22 mm sample for measuring noise reduction. The sample was attached to a 0.8 mm steel plate and tested for noise reduction as described in Example A. The sound absorption coefficient results are shown in
Lear SONOTEC dash insulator. A Lear SONOTEC dash insulator for a 2003 Ford U-222 vehicle was cut into sections and glued together (areal density was adjusted for the glue mass) to make a 0.69 m×0.69 m×25 mm sample for measuring noise reduction. The sample was attached to a 0.8 mm steel plate and tested for noise reduction as described in Example A. The sound absorption coefficient results are shown in
Additional tests were performed on systems 10 having varying configurations.
In
B refers to the barrier layer 14. In the various samples, the B layer comprises different materials. In the B layers where the thickness is shown to be 0.05 mm, 0.19 mm and 0.25 mm, the B layers comprise PVA. The B layer where the thickness is shown to be 0.5 mm, 0.78 mm and 1.0 mm comprise HIPS. The B layer where the thickness is shown to be 2.25 mm comprises TPO. As shown in the legend on
It is appreciated that an increase in the surface weight of the barrier layer 14 yields higher transmission loss and noise reduction. This results in lower noise levels in the interior of the vehicle.
The use of viscoelastic foam as the absorbing layer 12, 16 increases the damping of vibration on the steel sheet metal to which the system 10 is applied. This reduces the noise radiation into the interior of the vehicle. The viscoelastic foam also reduces the vibration motion of the barrier layer 14 through damping. That is, the absorbing layer dampens vibrations to the barrier layer to reduce vibration of said barrier layer. In this manner, the absorbing layer also acts as a vibration damping layer. This may result in an increase in transmission loss of the system 10. Further viscoelastic foams have good sound absorption properties due to the foam's cell structure and viscoelasticity. When using a viscoelastic foam as an absorbing or A layer, it is preferred that the foam have a Young Modulus of less than 7.0e+5 Pa and damping greater than 0.3. It will be appreciated that the viscoelastic foam layer is adapted to be placed against a substrate, such as the component of the vehicle.
The system 10 as set forth above can absorb and block noise in either direction. This is advantageous in that the system 10 can be used and adjusted to meet many noise reduction requirements in a vehicle. It will also be appreciated that, while particularly well suited for automotive applications, the system 10 can also be used in other applications. Such other applications include construction, industrial, appliance, aerospace, truck/bus/rail, entertainment, marine and military applications.
It will be appreciated that the invention has been described in an illustrative manner. The terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modification and variations are apparent in light of the above teachings. It is, therefore, to be understood that the invention set forth in the claims may be practiced other than as specifically described.
This application claims the benefit of U.S. Provisional Application No. 60/516,539, filed Oct. 31, 2003. The disclosure of the above application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60516539 | Oct 2003 | US |
