Metamaterial acoustic insulation device

Abstract

A metamaterial sound insulation device is described which has improved efficiency in suppressing sound propagation through it compared to conventional sound insulation devices of comparable size and weight. The device is particularly suitable for sound insulation in the field of motor vehicles.

Description

Technical Field

[0001] This invention relates to a sound insulation device, specifically a device that suppresses the propagation of sound through it. This device is particularly suitable for sound insulation in the automotive industry. Background Technology

[0002] In a variety of static or mobile applications, acoustic insulation is required to ensure and / or enhance people’s comfort; for example, it is desirable to isolate adjacent units in a building, adjacent rooms in an office, or sections of a production workshop; and it is often necessary to isolate the cockpit or passenger compartment of cars and trucks and other vehicles from different noise sources, such as engine compartment, tire noise, or aerodynamic (airborne) noise.

[0003] Because the requirements for sound insulation in the automotive industry are more stringent and demanding than in other industries, the following description will specifically refer to the former, but the present invention is universally applicable in any situation requiring noise insulation.

[0004] Achieving good sound insulation in the automotive field is challenging due to the limited space and mass available for sound insulation components.

[0005] Insulation components for motor vehicle applications are typically fabricated using the following: connectors (depending on a wide range of architectural variations), layers of different materials, such as aggregates of fibers (which can be natural, such as cotton, polymer fibers, or inorganic, such as glass fibers), foams, dense polymer layers, and polymer films (which may be multilayered); one or more of these layers may be loaded with fillers (such as mineral powders) to alter the properties of the base material.

[0006] These components may include at least one of the layers having elastic properties (i.e., the ability to return to their initial shape and size after compression or expansion), and at least a rigid, substantially incompressible layer. These components operate according to the spring-mass principle, wherein the elastic layer (often also referred to as a “damping layer,” which, when present, is typically foam) acts as a spring, and the rigid layer acts as a mass (and is therefore referred to in the art as a “mass layer”).

[0007] One problem with these components is that when improved insulation properties are required, the only possible strategy is to indiscriminately increase the thickness and weight of the mass layer, resulting in an increase in the component's relative weight. This approach is used, for example, in patent application US2004 / 0150128A1, where a rigid layer is prepared by first thermoforming a foil or flat block of thermoplastic material, and then adding an additional amount of the same thermoplastic material to selected areas (preferably, cavities) of the formed foil or block, thereby forming areas of increased thickness within this rigid layer. This document does not provide guidance on the geometry of these added thermoplastic materials, i.e., their thickness (absolute thickness or thickness relative to the initial foil or block), their area (compared to the area of ​​the rigid layer), or their distribution over that area. Furthermore, this document does not provide data on the acoustic properties of a fully insulated component obtained using the described process.

[0008] The automotive industry is working to reduce vehicle weight as much as possible to minimize its power consumption and, consequently, its environmental impact. This trend toward weight reduction is even more pronounced in electric vehicles, where lower weight provides opportunities for increased autonomy, thanks to the ability to move lower masses using the same battery pack or to accommodate larger battery packs due to weight gains.

[0009] To reduce the overall weight of noise attenuation components, several documents suggest creating voids in at least one of its layers, which can be through-holes, recesses, indentations, or similar forms. Components according to this approach are described, for example, in patents US 5,013,597, US 7,182,172B2, and patent application WO 2018 / 091301 A1.

[0010] Patent application US 2012 / 0155688 A1 discloses various acoustic absorbers and transducers with different constructions. One of these acoustic absorbers and transducers (refer to the document) Figure 5 (As described) a discontinuous rigid layer is applied directly to the spring layer; the pattern of this rigid layer can be set as a grid (as described in this document). Figure 5 ) or set as a series of parallel and adjacent elongated rhombuses ( Figure 5 B).

[0011] One known problem with noise attenuation components is that they typically have good insulation properties in the high-frequency range, but poor insulation properties in the range of about 200 Hz to 1000 Hz, which is very relevant to noise sources in motor vehicle applications.

[0012] Currently, a component that achieves a good trade-off between weight reduction and good insulation across the frequency spectrum in a mass-spring-mass mechanism relevant to acoustic comfort frequencies is not yet available regarding the resonant frequency band.

[0013] The objective of this invention is to provide a sound insulation device, particularly for use in the automotive industry, that overcomes the problems of the prior art. Summary of the Invention

[0014] This objective is achieved by the present invention, which relates to a metamaterial sound insulation device, comprising:

[0015] - A first layer composed of a first material, which does not necessarily have a uniform thickness, has a static Young's modulus between 1 kPa and 1 MPa;

[0016] - A second layer made of a second material having a first surface and a second surface, the first surface being adhered to the surface of the first layer, the second surface being away from the first surface, the second material having a static Young's modulus between 10 MPa and 2500 MPa and a weight per unit area between 0.5 kg / m2 and 20 kg / m2;

[0017] - One or more independent protrusions in the form of a mesh, wherein the one or more independent protrusions are adhered to or integrally formed with at least one of the first or second surfaces of the second layer, wherein the one or more independent protrusions are made of a material having a static Young's modulus between 10 MPa and 2500 MPa and 0.5 kg / m³. 2 and 20kg / m 2 The unit area weight between, wherein the area occupied by each of the independent protrusions is no more than 2% of the area of ​​the first or second surface of the second layer, and the total area occupied by the one or more protrusions is between 10% and 60% of the area of ​​the first or second surface of the second layer. Attached Figure Description

[0018] The present invention will be described below with reference to the accompanying drawings, in which:

[0019] - Figure 1 A first possible embodiment of the sound insulation device of the present invention is shown in a cross-sectional view (upper part of the figure) and a top view (lower part of the figure), the sound insulation device comprising a plurality of independent protrusions arranged in a two-dimensional periodic array on a second surface of a second layer;

[0020] - Figure 2 The top and sectional views illustrate possible alternative shapes for the independent protrusion, which may exist in... Figure 1 In the device;

[0021] - Figure 3Another possible sound insulation device of the present invention is shown in a side view (upper part of the figure) and a top view (lower part of the figure), which includes a plurality of independent protrusions randomly arranged on the second surface of the second layer.

[0022] - Figure 4 With similar Figure 1 The sectional and top views show another possible sound insulation device of the invention, which includes a plurality of independent protrusions arranged in a two-dimensional periodic array on the first surface of the second layer, wherein the protrusions have different shapes.

[0023] - Figure 5 With similar Figure 1 The sectional and top views show another possible sound insulation device of the invention, which includes a plurality of independent protrusions arranged in a two-dimensional periodic array on the second surface of the second layer;

[0024] - Figures 6 to 8 With similar Figure 1 The sectional and top views show other different possible sound insulation devices of the invention, which include a plurality of individual protrusions arranged in a two-dimensional periodic array on a second surface of a second layer, wherein the first layer has recesses or through holes having the same arrangement as the protrusions.

[0025] - Figure 9 and Figure 10 With similar Figure 1 The sectional and top views show two possible sound insulation devices of the present invention, each comprising a protrusion in the form of a regular mesh and a protrusion in the form of an irregular mesh, respectively;

[0026] - Figure 11 With similar Figure 1 The sectional and top views show a possible sound insulation device of the present invention, which includes a plurality of independent protrusions arranged in a two-dimensional periodic array on a second surface of a second layer, wherein the first and second layers are non-planar and have non-constant thicknesses.

[0027] - Figure 12 The geometry of a specific device of the present invention is shown, which has been tested in an example;

[0028] - Figure 13 A graph is shown that compares the sound insulation properties of the device of the present invention with those of prior art devices. Detailed Implementation

[0029] The sound insulation device of the present invention is an improvement on the prior art spring-mass system. The inventors have observed that it is possible to improve the acoustic insulation properties of conventional systems by adding localized independent protruding elements or single protruding elements (in the form of a mesh) to the mass layer; this can be achieved without increasing the overall mass of the noise attenuation system.

[0030] Materials that acquire modified properties (compared to their inherent properties) through shaping are called "metamaterials" in materials science and engineering; this definition is used in this specification and claims to refer to components consisting of the second layer and protrusions described above.

[0031] The first and second layers will be referred to as the “damping layer” and the “mass layer”, respectively, in the following description.

[0032] "Protrusions integral with the surface of the mass layer" means that the one or more protrusions and layers are formed as separate parts, such as those obtained by die casting or injection molding.

[0033] The metamaterial sound insulation device of the present invention is characterized in that the mass layer has continuous protrusions or multiple independent protrusions in the form of a mesh on at least one of its surfaces.

[0034] In the case of a single protrusion in the form of a mesh, the single protrusion may have a regular arrangement, thereby defining, for example, a square, rectangular, triangular or hexagonal pattern; or the arrangement may be irregular, wherein the intersections (or nodes) of the mesh lines are randomly distributed on the surface of the mass layer.

[0035] Similarly, multiple independent protrusions can be arranged on the surface of the mass layer according to regular and periodic patterns (thus defining the array) or randomly.

[0036] Each of the individual protrusions may occupy up to 2% of the surface area of ​​the mass layer; the total area occupied by a single protrusion or multiple individual protrusions in the form of a mesh on the surface of the mass layer is between 10% and 60% of the surface area.

[0037] The damping layer is made of a material having a static Young's modulus in the range of 1 kPa to 1 MPa, and a static modulus of 1 kg / m². 3 Up to 500kg / m 3 Preferably at 50 kg / m 3 and 100kg / m 3 The density is within the range between [specific values]. This material can be, for example, loose felt; preferably, it is foam (especially polyurethane (PU) foam), which is prepared in a mold of suitable shape by reacting diisocyanate or polyisocyanate monomers with diol or polyol monomers in the presence of a catalyst or by activation by ultraviolet light.

[0038] The mass layer is made of a material having a static Young's modulus between 50 MPa and 2500 MPa, preferably between 50 MPa and 300 MPa, and a mass of 0.5 kg / m³. 3 Up to 20kg / m 3 Between, preferably between 2 kg / m 3 and 7kg / m 3 The weight per unit area is within the range between these values. The material used to prepare this layer may be selected from felt (natural or synthetic fibers), or preferably, a dense polymer; preferred polymers for preparing this layer are dense PU (i.e., non-foamed form), PVC, polyester (PET), polyolefins (especially polyethylene (PE) and polypropylene (PP)), and polyamide (PA, often also called nylon).

[0039] One or more protrusions are made of a material having a static Young's modulus between 10 MPa and 2500 MPa, and a static modulus of 500 kg / m³. 3 and 8000kg / m 3 The density between [specific values]. The material used to prepare the protrusions is conveniently selected from the same material used to prepare the mass layer.

[0040] The mass layer and one or more protrusions can be prepared separately and, for example, adhered together by adhesive. However, in a preferred embodiment of the invention, the mass layer and protrusions are manufactured as unique pieces by injection molding and are therefore made of the same material.

[0041] Various possible embodiments of the metamaterial sound insulation device of the present invention are as follows: Figures 1 to 12 The figures are shown in the accompanying drawings. In the drawings, the protrusions are shown as independent elements in contact with the mass layer, but it should be understood that these figures also represent devices with corresponding structures in which the protrusions and the mass layer are fabricated as single pieces; furthermore, the elements and features indicated by the same reference numerals in the figures are the same in all embodiments.

[0042] Figure 1 The device 10 of the present invention is shown in a top view (lower portion of the figure) and a cross-sectional view along line A-A' of the top view (upper portion of the figure). The device 10 is made of a damping layer 11, a mass layer 12, and protrusions on a second surface 13 of the mass layer 12, which are cumulatively indicated as 14a. In this embodiment, the mass layer and the spring layer are flat and have a constant thickness. The protrusions 14a are independent elements (separated from each other) and are arranged on the surface 13 according to a regular periodic pattern (in this case, a rectangular grid); however, the basic unit of the two-dimensional (2D) regular pattern can also be square, rhomboid, hexagonal, or triangular.

[0043] Figure 2 The different shapes of the protrusions 14b to 14f are shown, which can be used to replace... Figure 1 The protrusion 14a in the device. In the drawings, the upper row shows a top view of the protrusion, and the lower row shows a cross-section of the corresponding element along the dashed line shown in the top view. Very simply, protrusion 14b is a solid cylinder; protrusion 14c is a hollow cylinder in which the cavity extends across the entire thickness of the protrusion; protrusion 14d is a cylinder with a recess; protrusion 14e is a solid body of constant thickness but irregular shape; and protrusion 14f is a solid body of constant thickness and regular but complex shape.

[0044] Figure 3 Another possible device 30 of the invention is shown in a top view (lower portion of the figure) and a side view (upper portion of the figure). Device 30 has the same structure as device 10, the only difference being that protrusions 31 are randomly arranged on surface 13. The protrusions 31 in the figure are shown in the top view as having a circular cross-section, but these protrusions can obviously have any shape, for example, Figure 2 One of those shown.

[0045] The protrusions on the mass layer of the device of the present invention do not need to be uniform. Figure 4 With similar Figure 1 Those sectional and top views show an example of this type of device of the invention: the device 40 of this embodiment has the same general geometry as the device 10, but the protrusions indicated by the cumulative number 41 have different shapes and heights.

[0046] Figure 5 Another possible embodiment of the device of the invention is shown in a top view (lower portion of the figure) and a cross-sectional view along line A-A' of the top view (upper portion of the figure). The device 50 is made of a damping layer 51 having a recess in its surface in contact with the mass layer 12; protrusions 52 are adhered to or integral with a first surface 53 of the mass layer and precisely fitted into the recesses in the damping layer. The dashed rectangle in the top view represents the projection of the protrusions 52 onto the second (upper) surface of the mass layer 12.

[0047] Figure 6 , Figure 7 and Figure 8 Other possible embodiments of the device of the present invention are schematically illustrated, wherein the damping layer has holes. In these three figures, the dashed rectangles in the top view represent projections onto the mass layer of the holes in the damping layer.

[0048] Device 60 ( Figure 6 The mass layer and protrusions are similar in construction to device 10; the damping layer 61 instead has holes 62 that traverse its entire thickness.

[0049] Device 70 ( Figure 7 Similar to device 10, except that the damping layer 71 has a recess 72 in the surface of the contact mass layer.

[0050] Device 80 ( Figure 8 Similar to device 70, but in this case, the damping layer 81 has a cavity 82 in the surface opposite to the surface of the contact mass layer.

[0051] As mentioned above Figures 6 to 8 In other embodiments illustrated, the protrusions on the mass layer (generally indicated as element 14) are shown as solid cylinders, and the holes (62, 72, or 82) in the damping layer have rectangular cross-sections; however, it will be apparent that both elements can have any shape, for example, the protrusions can have… Figure 2 Any of the shapes represented, and in the top view, the holes in the damping layer can have any shape, such as square, hexagonal, circular, elliptical, etc. Furthermore, devices 50, 60, 70, and 80 have... Figures 5 to 8 The arrangement is represented by an ordered, periodic arrangement of protrusions within / above the mass layer and holes in the damping layer; however, in these embodiments, the arrangement of these elements in the top view can be random, as in device 30. Finally, in the top view drawing ( Figure 6 , Figure 7 and Figure 8 In the lower part of the mass layer, the protrusions are shown as being concentric with the holes in the damping layer, but this is not a necessary condition for the present invention; and in the top view of a possible device of the present invention, the center of the drawing (rectangle, circle, etc.) representing the protrusions may not coincide with the center of the drawing representing the holes.

[0052] Figure 9 Another possible device 90 of the invention is shown; device 90 is shown in the figures as a top view (lower portion of the figure) and a cross-sectional view along line A-A' of the top view (upper portion of the figure). In this embodiment, the damping layer 11 and the mass layer 12 are similar to those of device 10, but in this case, a single protrusion 91 (in the form of an ordered mesh) rather than multiple protrusions 14a (or 14b to 14f) exists on the second surface of layer 12; in the case shown in the figures, the mesh 91 defines a rectangular grid, but it can be, for example, square, triangular, or hexagonal.

[0053] Figure 10 Another possible device 100 of the present invention is shown. This is similar to device 90, except that in this embodiment, the protrusions 101 are in the form of an irregular grid.

[0054] at last, Figure 11Another possible embodiment of the device of the present invention is schematically illustrated. The device 110 is irregular in thickness and shape: the thicknesses of the damping layer 111 and the mass layer 112 are not constant, and the cross-section of the device is not flat; in the drawings, the protrusions 114 are shown as uniform and arranged according to a regular pattern, but in this case, these protrusions may be non-uniform and irregularly arranged (e.g., Figure 3 Furthermore, in the example shown in this figure, protrusions 114 are depicted on the second surface 13 of the mass layer, but these protrusions may also exist on the first surface of the mass layer, such as... Figure 5 As shown; and the protrusions on any surface of the mass layer can also be combined with holes in the damping layer, as in devices 60, 70 and 80.

[0055] The invention will also be illustrated by the following examples.

[0056] Example 1

[0057] A sound insulation device according to the present invention has been prepared, the sound insulation device having Figure 12 The geometry shown is consistent with the dimensions and physical characteristics described below. The device has a lateral dimension of 1000mm × 1200mm; in Figure 12 Only a representative part of the device is shown in the image.

[0058] Device 120 is made of a damping layer 121, which is made of polyurethane foam with a thickness of 10 mm and a static Young's modulus of 80 kPa. The damping layer has a square shape and a series of recesses 122 arranged in a square periodic array (in the top view of the device). The recesses have a lateral dimension of 15 mm × 15 mm and a thickness of 8 mm, i.e., the thickness not extending through the damping layer; the distance between the centers of two adjacent recesses is 30 mm.

[0059] The mass layer 12 is made of a thermoplastic polymer with mineral fillers, has a thickness of 0.6 mm, and a density of 2000 kg / m³. 3 The static Young's modulus is 300 MPa. A protrusion 14 is present on the surface 13 of the mass layer (away from the damping layer), and the protrusion 14 is made of the same material as the mass layer; the mass layer and the protrusion are prepared together as a single part by injection molding. The protrusion 14 has a prism shape, with a square base of 7 mm on its lateral side and a height of 10 mm; and is arranged according to a square array, concentric with the trace of the recess 122, as shown in the figure.

[0060] Example 2 (Comparison Device)

[0061] Prepare a prior art sound insulation device that has the same lateral dimensions as the device in Example 1.

[0062] The device includes a damping layer made of the same polyurethane foam as in Example 1, with a constant thickness of 10 mm (no depressions). The mass layer of this comparative device is made of the same polymer as in Example 1, but with a constant thickness of 1 mm and no protrusions. Therefore, the resulting device has an overall weight per unit area that is almost equivalent to the device of the present invention prepared as described in Example 1.

[0063] Example 3

[0064] The acoustic insulation properties of the devices prepared as described in Examples 1 and 2 were measured.

[0065] The test was performed according to standard ISO 15186-1; according to this standard, measurements were performed by placing the test sample in a chamber divided into a reverberation chamber (containing the sound source) and a receiving chamber (containing the sound detector). The two chambers were arranged vertically, with the receiving chamber above the reverberation chamber; the two chambers were separated by a support frame having orifices of substantially the same size as the test sample. The edges of the sample were laid on the frame and sealed to the frame with putty to prevent any sound leakage between the two chambers.

[0066] The difference between the excitation sound pressure level in the reverberation chamber and the level in the receiving chamber (measured in dB) is the transmission loss R, which is calculated using the following formula:

[0067] R = L 激发 -L 接收 10. log(S / A)

[0068] in:

[0069] L represents the measurement level;

[0070] S is the area test window (the hole in the support frame); and

[0071] A represents the equivalent absorption area of ​​the receiving chamber.

[0072] Measurements were performed at different frequency values: 200Hz, 250Hz, 315Hz, 400Hz, 500Hz, 630Hz, 800Hz, 1000Hz, 1250Hz, 1600Hz, and 2000Hz. The measured values ​​were recorded at... Figure 13 In the diagram, the transmission loss TL is a function of frequency; the value measured on the sample of the present invention is represented by a solid line, while the value measured on the sample of the prior art is represented by a dashed line (even if the spectrum of the above frequency is sampled only with a given value, the result is represented as a broken line).

[0073] according to Figure 13The two curves clearly show that the device of the present invention has acoustic insulation properties comparable to those of prior art devices in a portion of the spectrum, and the properties are improved in the frequency range between 630 Hz and 1000 Hz.

Claims

1. Metamaterial acoustic insulation device (10, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120) comprising: - a first layer (11, 51, 61, 71, 81, 111, 121) of a first material having a static Young's modulus between 1 kPa and 1 MPa and a density ranging between 1 kg / m3 3 and 500 kg / m 3 ; - a second layer (12, 112) of a second material, said second layer (12, 112) having a first surface and a second surface (13), said first surface adhering to the surface of said first layer, said second surface (13) facing away from said first surface, said second material having a static Young's modulus between 10 MPa and 2500 MPa and a weight per unit area between 0.5 kg / m 2 and 20 kg / m 2 ; - a protrusion or a plurality of independent protrusions (14, 14a, 14b, 14c, 14d, 14e, 14f, 31, 41, 52, 91, 101, 114) in the form of a mesh, adhered to or integral with at least one of the first or second surface of the second layer, made of a material having a static Young's modulus between 10 MPa and 2500 MPa, a density between 500 kg / m 3 and 8000 kg / m 3 and an area weight per unit between 0.5 kg / m 2 and 20 kg / m 2 , wherein the footprint of each of the independent protrusions is not higher than 2% of the area of the first or second surface of the second layer and the overall footprint of the protrusion or plurality of independent protrusions is between 10% and 60% of the area of the first or second surface of the second layer.

2. The metamaterial sound insulating device of claim 1, wherein the first material has a density ranging between 50 kg / m 3 and 100 kg / m 3 .

3. The metamaterial sound insulation device of claim 1 or 2, wherein the second material has a static Young's modulus between 50 MPa and 300 MPa and a weight per unit area between 2 kg / m 2 and 7 kg / m 2 .

4. The metamaterial acoustic insulation device according to claim 1, wherein said first material is polyurethane foam.

5. The metamaterial acoustic insulation device according to claim 1, wherein said second material is a felt of natural or synthetic fibers or polymers selected from the group consisting of polyurethane, polyvinyl chloride, polyester, polyolefin and polyamide.

6. The metamaterial acoustic insulation device according to claim 1, wherein said protrusions are adhered to said second layer by gluing.

7. The metamaterial acoustic insulation device according to claim 1, wherein said protrusions are integral with said second layer.

8. The metamaterial acoustic insulation device (10, 40, 50, 60, 70, 80, 110, 120) according to claim 1, wherein a plurality of independent protrusions (14, 14a, 14b, 14c, 14d, 14e, 14f, 41, 52, 114) are arranged on the first or second surface of said second layer according to a regular and periodic pattern.

9. The metamaterial acoustic insulation device (30) according to claim 1, wherein a plurality of independent protrusions (31) are arranged on the first or second surface of said second layer in a random arrangement.

10. The metamaterial acoustic insulation device (90) according to claim 1, comprising a single protrusion (91) in the form of a mesh having a regular arrangement, defining a square, rectangular, triangular or hexagonal pattern.

11. The metamaterial acoustic insulation device (100) according to claim 1, comprising a single protrusion (101) in the form of a mesh having an irregular geometry.

12. The metamaterial acoustic insulation device according to claim 1, wherein said first layer has holes through its entire thickness, or recesses in the surface contacting the first surface of said second layer (12), or cavities in the surface opposite to the surface contacting said second layer (12).

13. The metamaterial acoustic insulation device (50, 60, 70, 80, 120) according to claim 12, wherein said holes (62), recesses (72) or cavities (82, 122) are arranged in said first layer (51, 61, 71, 81, 121) according to a regular and periodic pattern.

14. The metamaterial acoustic insulation device (50) according to claim 13, wherein the surface of said first layer (51) contacting said second layer (12) has recesses in it, said recesses being completely occupied by protrusions (52) present on the first surface of said second layer (12).

15. The metamaterial acoustic insulation device according to claim 12, wherein said holes, recesses or cavities are arranged in said first layer in a random arrangement.

16. The metamaterial sound insulating device (50, 60, 70, 80) of claim 12, wherein in a top view of the device, the protrusions (14, 52) on the second layer (12) are in positions corresponding to positions of the holes (62), recesses (72), or cavities (82, 122) in the first layer (51, 61, 71, 81, 121).

17. The metamaterial sound insulating device (10, 30, 40, 90, 100) of claim 1, wherein the first layer (11) has a uniform thickness.

18. The metamaterial sound insulating device (50, 60, 70, 80, 110, 120) of claim 1, wherein the first layer (51, 61, 71, 81, 111, 121) has a non-uniform thickness.

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