Acoustic foam decoupler

Abstract

A noise attenuating trim part for a vehicle, with acoustic mass-spring characteristics comprising a mass layer comprising at least an impervious barrier layer, and a decoupling layer consisting of open cell foam and wherein the decoupling layer has a first surface adjacent to the mass layer and a second surface facing away from the mass layer, and wherein the decoupling layer and mass layer are laminated together and wherein the decoupling layer has at least one region with a plurality of indentations wherein each indentation comprises a round base area wherein the round base areas are situated in plane with the second surface and wherein the total surface area of the round base areas is between 10 and 40% of the total surface area of the second surface of the decoupling layer.

Claims

1. A noise attenuating trim part for a vehicle, with acoustic mass-spring characteristics, comprising: a mass layer having an impervious barrier layer; a decoupling layer comprising open cell foam, the decoupling layer having a first surface laminated to the mass layer and a second surface facing away from the mass layer and adapted for interconnection to a vehicle body, wherein the second surface includes at least one region with a plurality of indentations, and wherein each indentation is defined by a geometric shape bounded by a generally round base area that corresponds with the second surface, such that the entirety of the round base areas are configured to contact the vehicle body and the geometric shapes define cavities between the decoupling layer and the vehicle body; wherein the total surface area of the generally round base areas is between 10 and 40% of the total surface area of the second surface of the decoupling layer; and wherein a shortest distance (D) between two indentations is more than 4 mm.

2. The noise attenuating trim part according to claim 1, wherein the radius (r) of the generally round base areas is between 4 to 20 mm.

3. The noise attenuating trim part according to claim 1, wherein the total surface area of the base areas is between 15 and 35% of the total surface area of the second surface of the decoupling layer.

4. The noise attenuating trim part according to claim 1, wherein the height (h) of the indentations is between 40 and 74% of the total thickness (T) of the decoupling layer being the shortest distance from the base area of the indentation to the first surface of the decoupling layer.

5. The noise attenuating trim part according to claim 1, wherein the height (h) of the indentations is between 4 to 20 mm.

6. The noise attenuating trim part according to claim 1, wherein the decoupling layer includes a convex portion that defines the at least one region with a plurality of indentations, and wherein the region has at least 15 indentations and wherein the total surface area of the generally round base areas within the at least one region is between 25 and 50% of the surface area of the at least one region.

7. The noise attenuating trim part according to claim 1, wherein the decoupling layer is made of polyurethane foam.

8. The noise attenuating trim part according to claim 1, wherein at least one of the generally round base areas has an elliptic shape.

9. The noise attenuating trim part according to claim 1, wherein at least one of the indentations has the geometrical shape of a hemi spheroid.

10. The noise attenuating trim part according to claim 9, wherein the hemispheroid shape with a profile adjacent to the second surface is cylindrical, perpendicular to the second surface, and bounded by the round base areas.

11. The noise attenuating trim part according to claim 1, wherein the foam has a density between 25 to 100 kg/m.sup.3.

12. The noise attenuating trim part according to claim 1, wherein the impervious barrier layer is made of a thermoset plastic material selected from the group consisting of ethylene vinyl acetate (EVA) copolymer, polyester, polyethylene terephthalate, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, thermoplastic elastomer, thermoplastic rubber and polyvinyl chloride (PVC), or any combination thereof.

13. The noise attenuating trim part according to claim 1, wherein the mass layer has an area weight between 500 to 6500 g/m.sup.2.

14. The noise attenuating trim part according to claim 13, wherein the mass layer consists of the impervious barrier layer with an area weight between 800 to 6000 g/m.sup.2.

15. The noise attenuating trim part according to claim 14, further comprising an additional layer adjacent to the mass layer, wherein the additional layer is made of porous felt with an area weight of 200 to 600 g/m.sup.2 or open cell foam.

16. The noise attenuating trim part according to claim 13, wherein the mass layer consists of the impervious barrier layer and a porous fibrous layer; wherein the porous fibrous layer has a dynamic compression Young's modulus E of at least 96*AW* t.sub.p (Pa), with AW area weight (g/m.sup.2) and t.sub.p thickness (mm) of the porous fibrous layer; wherein the impervious barrier layer has an area weight of less than 200 g/m.sup.2; and wherein the impervious barrier layer is situated between the fibrous layer and the decoupling layer and all layers are laminated together.

17. The noise attenuating trim part according to claim 16, wherein the mass layer has an area weight between 500 to 2600 g/m.sup.2.

18. The noise attenuating trim part according to claim 13, wherein the mass layer consists of the impervious barrier layer and a porous fibrous layer, with the impervious barrier layer being situated between the porous fibrous layer and the decoupling layer and all layers are laminated together, and wherein the porous fibrous layer has a dynamic compression Young's modulus (Pa) of at least 118* t.sub.p*(AW.sub.b*AW.sub.p+(AW.sub.p*AW.sub.p/4))/(AW.sub.b+AW.sub.p); wherein AW.sub.b being area weight (g/m.sup.2) of the barrier layer, AW.sub.p being area weight (g/m.sup.2) of the porous fibrous layer, t.sub.p being thickness (mm) of the porous fibrous layer; and wherein the impervious barrier layer has an area weight of at least 500 g/m.sup.2.

19. The noise attenuating trim part according to claim 18, wherein the impervious barrier layer has an area weight between 500 to 4000 g/m.sup.2; and wherein the porous fibrous layer has an area weight between 400 to 2500 g/m.sup.2.

20. The noise attenuating trim part according to claim 16, wherein the thickness t.sub.p of the porous fibrous layer is between 2 and 15 mm.

21. The noise attenuating trim part according to claim 1, further comprising at least one of a decorative layer or a carpet layer, and wherein the mass layer is situated in between the decoupling layer and the decorative layer or carpet layer.

22. The noise attenuating trim part according to claim 1, wherein the plurality of indentations comprise at least one of indentations of a first size and indentations of a second size, and indentations of a first shape and indentations of a second shape.

23. The noise attenuating trim part according to claim 1, wherein the plurality of indentations are not equally spaced from each other.

24. The noise attenuating trim part according to claim 1, wherein the plurality of indentations are randomly spaced.

25. The noise attenuating trim part according to claim 1, wherein the compression stiffness of the foam is comprised between 4 kPa and 20 kPa, being the compression stiffness corresponding to the CLD40 value measured according to ISO 3386-1.

26. The noise attenuating trim part according to claim 1, wherein the second surface is selectively deformable and adapted to engage a vehicle body having an irregular surface.

27. A method of using the noise attenuating trim part according to claim 1, as a floor covering or inner dash, wherein the second surface of the decoupling layer with a plurality of indentations is facing the vehicle floor and or firewall.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a schematic example of indentation positions on a 3D trim part according to the invention.

(2) FIG. 2 shows a schematic cross section of a 3D part according to the invention.

(3) FIGS. 3A, 3B and 3C shows schematic examples of one hemispheroids (10, 11, 12) with a radius (r) and height (h) and round base area (13) according to the invention.

(4) FIGS. 4A, 4B and 4C shows schematic examples of cross sections of a noise attenuating trim part (14) according to the invention.

(5) FIG. 5 shows a schematic example of a decoupling layer according to the invention with the second surface of the decoupling layer comprising indentations with round base areas.

(6) FIG. 6 shows a schematic example of a decoupling layer according to the invention with the second surface of the decoupling layer comprising a region with indentations wherein the region is the convex hull of the round base areas of the indentations.

(7) FIG. 7 shows measured insertion loss of flat samples according to the state of the art and according to the invention.

(8) FIG. 8 shows measured insertion loss of an inner dash according to the state of the art and according to the invention.

(9) FIGS. 9A, 9B, 9C and 9D shows schematic examples of cross sections of a noise attenuating trim part according to the invention with different mass layers.

(10) FIG. 1 shows a schematic figure of an inner dash (1) with the position of indentations and the round base areas (2). The indentions and base areas have different sizes and are spread over the surface.

(11) FIG. 2 shows a schematic cross section of a 3D trim part (3) according to the invention. The indentations (8) with round base areas directed to the vehicle body (9) and with a decoupler foam layer (5) and a mass layer (4). The first surface (6) of the decoupling layer is directed to the mass layer and the second surface (7) is directed to the vehicle body.

(12) FIG. 3A shows a schematic example of a hemispherical shaped indentation (10) according to the invention with a radius (r) and a circular base area (13). Due to the hemispherical shape and circular base area the radius (r) and height (h) have the same length or at least approximately the same length. The hemispherical shaped indentation is creating a cavity with air and the circular base area located at the second surface of the decoupler is an area where the foam is not in contact with the metal layer, e.g. vehicle body. The circular base area may also have an oval shape or being approximately circular.

(13) The total area of the circular base areas of the hemispherical shaped indentations is also referred to as the “area not in contact” with the vehicle body.

(14) FIG. 3B shows a schematic example of a symmetrical hemispheroidal shaped indentation (11) according to the invention with a radius (r) and a circular base area (13). Due to the hemispheroidal shape and circular base area or round base area the radius (r) and height (h) does not have the same length.

(15) FIG. 3C shows a schematic example of an unsymmetrical hemispheroidal shaped indentation (12) according to the invention with a radius (r) and a circular base area (13). Due to the hemispheroidal shape and circular base area or round base area the radius (r) and height (h) does not have the same length.

(16) All the indentation shapes in FIGS. 3A, 3B and 3C have favourably shapes for demoulding properties and for improving the local stiffness of the decoupler layer compared to other cavities, for example square and or rectangular cavities.

(17) FIGS. 4A, 4B and 4C shows examples of cross sections of noise attenuating trim parts for a vehicle (14) according to the invention with examples of hemispheroid e.g. hemispherical shaped indentations (10, 15, 16) in the decoupler layer (5) with a mass layer (4) and the vehicle body (9), e.g. a steel or aluminium layer. The thickness (T) is the total thickness of the decoupling layer being the thickness of the foam layer in areas without hemispheroidal shaped indentations and in areas with hemispheroidal shaped indentation T being the total height of the hemispheroidal shaped indentations and the foam layer thickness above the top (t) of the hemispheroidal shaped indentation. The round base area of the indentations is situated at the second surface (7) of the decoupling layer.

(18) The indentations may be designed for better demoulding properties and or to improve the flow of the foam components during the foaming process. The hemispheroidal showed shown in FIGS. 4A, 4B and 4C have all both good demoulding properties and enhance the flow of the foam components during the foaming process. The indentations, also depending on the position, mostly do not have any walls parallel to the demoulding direction except just next to the second surface of the decoupling layer.

(19) The shape of the hemispherical shaped indentation may vary depending on designed restrictions and space available.

(20) FIG. 4A shows an example of a cross section of a trim part (14) according to the invention with an example of a non-symmetric hemispheroidal shaped indentation (15).

(21) FIG. 4B shows an example of a cross section of a trim part (14) according to the invention with an example of a hemispheroidal shaped indentation with rounded edges (16).

(22) FIG. 4C shows an example of a cross section of a trim part (14) according to the invention with an example of a substantially symmetric hemispherical shaped indentation (10). The distance (D) between two indentations should not be too small in order to simplify the demoulding of the trim part as well as ensure that local stiffness of the decoupling layer.

(23) FIG. 5 shows a schematic example of a decoupling layer (17) with the second surface (7) of the decoupling layer (5) with the round base areas (13) of the indentations.

(24) FIG. 6 shows a schematic example of a decoupling layer (17) with the second surface (7) of the decoupling layer (5) with the round base areas (13) of the indentations arranged in a group, the group of indentations being in a region (19) defined by the convex hull (18) around the group of indentations and their round base areas.

(25) FIG. 7 shows measured insertion loss of four flat samples according to the state of the art and according to the invention. The insertion loss was measured with the, at Autoneum commercially available, device “Isokell”.

(26) The samples were measured on a steel panel representing the vehicle body.

(27) All samples were made with decoupler layer made of the same type of polyurethane foam with density of about 50 kg/m.sup.3 and a thickness of about 15 mm. The same type of mass layers, heavy layer with area weight 3 kg/m.sup.2, is used for all samples.

(28) Samples B, C and D where made with hemispherical shaped indentations with a circular base with 8 mm radius. Since the shape of the indentations was hemispherical the heights were also 8 mm.

(29) Sample A is the reference sample according to the state of the art with a foam decoupler layer without any indentations.

(30) Sample B has a total area of the circular base areas of the hemispherical shaped indentations that is approximately 6% of the total area of the second surface of the decoupling layer. As a result approximately 6% of the foam decoupler layer is not in contact with the steel panel.

(31) Sample C has a total area of the circular base areas of the hemispherical shaped indentations that is approximately 40% of the total area of the second surface of the decoupling layer, according to the invention. As a result approximately 40% of the foam decoupler layer is not in contact with the steel panel.

(32) Sample D has a total area of the circular base areas of the hemispherical shaped indentations that is approximately 60% of the total area of the second surface of the decoupling layer. As a result approximately 60% of the foam decoupler layer is not in contact with the steel panel.

(33) As can be seen from FIG. 7 the resonance frequency for sample C and D is reduced from about 400 Hz to about 315 Hz indicating that the decoupler is overall softer than the reference sample and the sample B with only 6% of the second surface not in contact with the steel panel.

(34) The sample C with 40% of the second surface not in contact with the steel panel is surprisingly performing the same or is even improving the IL in the important frequency range 1000 Hz to 4000 Hz, compared to the sample D that has a higher area not in contact with the steel panel.

(35) Sample C has additionally better stiffness properties, such as tread strength, compared to sample D.

(36) Sample C shows much better performance compared to sample B over most of the frequency range.

(37) FIG. 8 shows measured insertion loss of two 3D samples, inner dash insulators, according to the state of the art and according to the invention. The insertion loss was measured according to the current ISO 140-3.

(38) The samples were measured on a steel dash, cut out from the vehicles body in white.

(39) The two samples were made with decoupler layer made of the same type of polyurethane foam with density of about 50 kg/m.sup.3 and a thickness of about 15 mm and the same type of mass layer of 2 kg/m.sup.2 heavy layer.

(40) Sample F is according to the invention comprising Indentations with two different dimensions in different areas of the decoupling layer depending on the thickness and space available in order to optimise the area not in contact. The indentations used for sample F are hemispheres with circular base areas with the radius and height of 8 mm and the second size with the radius and height of 12 mm.

(41) Sample F has a total area of circular base areas of the hemispherical shaped indentations that is approximately 15% of the total area of the second surface of the decoupling layer, according to the invention. As a result approximately 15% of the foam decoupler layer is not in contact with the steel body. Indentation with two different dimensions has be used in different areas of the decoupling layer depending on the thickness and space available in order to optimise the area not in contact.

(42) The indentations used for sample F are hemispheres with circular base areas with the radius and height of 8 mm and the second size with the radius and height of 12 mm.

(43) The samples were measured on a steel dash, cut out from the vehicles body in white.

(44) FIGS. 9A, 9B, 9C and 9D shows examples of cross sections of noise attenuating trim parts for a vehicle according to the invention with different mass layers, a decoupling layer (5) placed on a vehicle body (9), and the decoupler layer having hemispherical shaped indentations (10).

(45) FIG. 9A shows a trim part (20) wherein the mass layer is a single impervious barrier layer e.g heavy layer (21) laminated to the decoupling layer (5). Preferably the area weight of the single mass layer is 800 to 6000 g/m.sup.2, preferable 1500 to 4000 g/m.sup.2.

(46) FIG. 9B shows a trim part (22) wherein the mass layer is the same single impervious heavy layer (21) as shown in FIG. 9A, laminated to the decoupling layer (5) and wherein the trim part has an additional porous absorption layer (23) adjacent to the heavy layer. The additional porous absorption layer may be a lofty felt, 200-600 g/m.sup.2, or soft open cell foam. Due to its loftiness and or low density this additional layer is not part of the mass layer since there is no, or very limited, weight contribution to the mass in the mass spring system and it does not participate actively to the insulating function of the trim part.

(47) FIG. 9C shows a trim part (24) with a decoupling layer according to the invention and with a mass layer consisting of a thin impervious barrier layer in the form of a thin film or foil (26) and a porous fibrous layer (25) with a dynamic compression Young's modulus E>96*AW*t.sub.p in Pascal (Pa). AW is the area weight in g/m.sup.2 of the porous fibrous layer and is between 400 to 2500 g/m.sup.2, preferably 700 to 1500 g/m.sup.2, and the thickness (t.sub.p) of the fibrous layer is between 2 and 15 mm, preferably between 3 and 10 mm. The thin film or foil and has an area weight of less than 200 g/m.sup.2 and a thickness of at least 40 micrometers (μm), preferably 60 to 100 (μm), preferably 60 to 80 (μm).

(48) FIG. 9D shows a trim part (27) with a decoupling layer according to the invention and with a mass layer consisting of a impervious barrier layer in the form of a heavy layer (28) and a porous fibrous layer (29) with a dynamic compression Young's modulus
E>118*t.sub.p*(AW.sub.b*AW.sub.p+(AW.sub.p*AW.sub.p/4))/(AW.sub.b+AW.sub.p) in Pascal(Pa)

(49) AW.sub.b is the area weight in g/m.sup.2 of the impervious barrier layer and is between 500 to 4000 g/m.sup.2, preferably 1500 to 3000 g/m.sup.2.

(50) The impervious barrier layer has an area weight of at least 500 g/m.sup.2, preferably between 500 to 4000 g/m.sup.2, preferably 1500 to 3000 g/m.sup.2.

(51) AW.sub.p is the area weight in g/m.sup.2 of the porous fibrous layer and is between 400 to 2500 g/m.sup.2, preferably 800 to 1600 g/m.sup.2, and the thickness (t.sub.p) of the fibrous layer is between 2 and 15 mm, preferably between 3 and 10 mm.