EP0781445B1 - Layered sound absorber for absorbing acoustic sound waves - Google Patents

Description

The invention relates to a sound absorber for absorption of acoustic sound waves according to the generic term of claim 1.

So that the environment is not too strong due to acoustic sound waves is affected, it is already known sound waves as soon as possible at the point of origin at the spread in the area. It is also quieter for education Known spaces, the penetration of sound from outside into such To ward off rooms as much as possible. Serve for this purpose Sound absorbers, mostly sound absorbing materials - called "insulation materials" - have. The material consumption for this is however relatively large, which is not only the case with the Manufacturing costs, but also when disposing of such insulation affects.

DE 92 15 132 U1 is an airborne sound-absorbing molded part known for use in the engine compartment of motor vehicles, which consists of a film layer and a porous insulation layer. The molded part consists of an open-pore PU foam that is sealed on all sides by a PU film.

In addition, sound absorbers are known (DE-U-92 15 132, DE-C-3 039 651, 4 011 705, 4 317 828 and 4 334 984), the sound absorbing Molded parts made of closed-cell PP foam, PE fleece bonded with binder, polymeric materials or the like; there are also uncovered ones Helmholtz resonators are used.

A sound absorber for absorbing sound from a relative large frequency spectrum is known for example also from US Pat. No. 3,439,774. Two layers are used spaced by a honeycomb spacer is kept and it is ensured that the layers micropores exhibit. The micropores are based on a special selection rule dimension: The porosity of the outer, a relatively high layer facing the sound Permeability, i.e. Permeability to sound waves, and the other, facing away from the sound, a comparative one have lower sound permeability. Such Layers are made of stainless steel, for example, a pore size between 50 and 500 microns.

Another problem, namely the damping of structure-borne noise, i.e. the damping of sound-producing body parts, for example according to US Pat. Nos. 3,087,571 and 3,087,573 and FR-PS-2 671 899 by applying damping masses, including also of damping spaced apart by spacers Masses on the vibrating and therefore generating sound waves Body loosened.

The invention has for its object a sound absorber to improve the genus mentioned in that the greatest possible sound absorption with as little material expenditure as possible he follows.

The invention is characterized in claim 1 and in subclaims preferred trainings are claimed. Also the the following description relates to preferred forms of training.

According to the invention there is the sound absorbing component from a sequence of layers of different densities and Stiffness, which may be laterally interrupted or can be separated by bars and spacers. This Layers consist of foils, fleeces, foams, others membrane-like materials or fabrics or even from one Gas, which can expediently also be air. Essential for the acoustic effectiveness of this component, it is that the successive materials very clearly - almost abruptly - in their density and in their rigidity differentiate. This leads to the transition points Reflections of the sound waves moving back and forth in the absorber, which, with suitable dimensions, leads to good sound absorption leads in certain preselectable frequency ranges.

It is also advantageous to use this layer system Limit webs or pressings and spacers laterally. This allows the individual materials to be fixed and there is a possibility of different in different places Material sequences and therefore different sound absorptions in the corresponding frequency ranges (absorption spectra) to realize.

One of the layers can expediently be used as a carrier layer, i.e. designed as a carrier body, in particular with a high mass be.

The carrier body can then be used as a shell or trough-like carrier shell be formed while the spacers - or Interlayers - what other thin layers in the distance hold from the carrier shell, designed and arranged in this way are that between the layers and the carrier shell Result in resonance chambers.

In contrast to the most commonly used sound absorbers, where the gaps between layers are due to insulation are filled in, they remain here according to the invention Spaces largely free of materials. The sound absorbing Effect is mainly achieved by that the gas modules between the layers by the incident Sound waves are caused to vibrate. The particular one gas modules consisting of air have an area-related Stiffness with the mass coatings of the layers and the coupled ambient air forms a mass-spring system, which in the Range of resonance frequencies to minima of acoustic impedance and therefore leads to sound absorption.

Thus, the absorber can be connected in series idealize masses and feathers. Per mass-spring pair there is a minimum of acoustic impedance on the absorber surface, which in turn leads to a resonance in the absorption curve of the component in question. By These can be varied by material thicknesses and densities Resonance frequencies vary and therefore any absorption curve realize.

The carrier layer is preferably selected from a material which is characterized by the following properties:

It is advisable to deep-draw the carrier layer, To manufacture injection presses or the like without cutting; also press forming, in particular fibrous structures is suitable for this. It is recommended that the resonance chambers surfaces of the carrier layer facing away from the contours adjust which of the visible side of the sound absorber, for example the passenger compartment of a motor vehicle, facing are. For example, the carrier layer can be the dashboard of the motor vehicle to create in the engine compartment Sound waves from entering the passenger compartment prevent.

The carrier layer can therefore also be a component that is necessary anyway, for example, a partition made of sheet metal, without the sound absorber needs an additional carrier shell, itself if the sound absorber prefers an integrated unit forms, which are prefabricated and integrated at the place of their application Unit is installed.

The layers should have a layer thickness in the range of 10 µm - 5 mm. Use is particularly recommended a polyurethane elastomer (PU), polypropylene (PP) and / or of polyester (PET) for the layers. It is advisable also, the layers of carbon, PAN- (polyacrylonitrile) or natural fibers and / or made of fiber-reinforced thermoplastic produce or from mixtures of these fibers. You can especially with the natural fiber materials flax, coconut, sisal, Jute, hemp or cellulose are used, which are either thermoplastic bound, more or less pressed or with natural binders, e.g. Lignin or starch, bound could be.

The spacers should be spaced between each other the carrier layer and the further layers can be arranged, that the resonance chambers each of the carrier shell on one End and one of the layers at the other end or between the Layers themselves are completed. For special cases it is advisable to use the layers with the resonance chambers To provide openings; the carrier layer can also have openings exhibit.

Very simple spacers are formed by web or plate-shaped Columns formed between the layers pull out and arranged substantially at right angles to these are; the spacers can also be different Angles to these aggregates of the sound absorber run, if for spatial reasons, for example Accommodation of other components, such as electrical components, or is appropriate for resonance purposes.

The spacers are made of PU (polyurethane elastomer), PET (polyester), PP- (polypropylene), carbon, PAN- (polyacrylonitrile) or natural fibers and / or made of fiber-reinforced thermoplastic or from mixtures of these fibers, similar to the material composition of layers. Just like the thin layers can the spacers are made of fleece, foam or foil.

According to a preferred embodiment of the invention Spacers made of a foam made of polyurethane elastomer (PU) or from a PET (polyester) fleece; in this case wear the spacers themselves for sound absorption in the form of a Combination of the "layer absorber" and "insulation absorbers". This combination allows certain frequency spectra "Tailor" the sound absorption to a certain extent.

According to another preferred embodiment of the invention the spacers made of deep-drawn material, in particular made of the same material as either the layers or the carrier layer consists. Is the deep-drawn material even as a chamber resonator or by introducing openings effective as a Helmholtz resonator, a combination results of the layer absorber with these types of absorbers. Especially In the Helmholtz resonator, the chamber is also protected against pollution (see Fig. 3). Are through the deep drawing process created chambers from the material, which, as is known, by varying the chamber dimensions also as a resonance absorber are effective, a combination of chambers is created and layer absorbers. So it is recommended the deep-drawn Spacers to unite with the layers and this assembly in the carrier shell in order to integrate the To form unit of the sound absorber. It is advisable, attach the edge of the layers to the edge of the carrier shell, in particular to stick.

Figur 1

eine Abfolge verschiedener Schichten im schematischen Schnittbild;

Figur 2

eine Abfolge verschiedener Schichten und Zwischenschichten bzw. Abstandhalter;

Figur 3

ein System aus Membran- und Luftschichten, die seitlich durch Stege abgegrenzt sind;

Figur 4

ein System aus Membran- und Luftschichten sowie Abstandhalter, die durch Stege abgegrenzt sind;

Figur 5

eine Schichtenfolge aus durch Thermoformen oder Warmpressen geformten Membranen als dünnen Schichten;

Figur 6

eine Schichtenfolge aus durch Thermoformen oder Warmpressen geformten Membrane mit entsprechenden Zwischenschichten bzw. Abstandhaltern;

Figur 7

System einer Übereinanderschichtung von Absorberkammern;

Figur 8

Schichtensystem mit seitlich abgepreßten oder an die Trägerschale angeschweißten Schichten;

Figur 9/9a

schematische Querschnitte durch Schallabsorber mit plattenförmigen Abstandhaltern;

Figur 10

einen entsprechenden schematischen Querschnitt durch den Schallabsorber mit Schaumstoff als Abstandhaltern;

Figur 11

eine schematische Ansicht einer alternativen Ausbildung der Erfindung, bei der die Absorberkammern aus tiefgezogenem Material durch eine dünne Schicht bzw. Membran überzogen sind.

Embodiments of the invention will now be described with reference to the drawing, show

Figure 1

a sequence of different layers in the schematic sectional view;

Figure 2

a sequence of different layers and intermediate layers or spacers;

Figure 3

a system of membrane and air layers that are laterally delimited by webs;

Figure 4

a system of membrane and air layers as well as spacers, which are delimited by webs;

Figure 5

a layer sequence of membranes formed by thermoforming or hot pressing as thin layers;

Figure 6

a layer sequence of membranes formed by thermoforming or hot pressing with corresponding intermediate layers or spacers;

Figure 7

System of stacking absorber chambers;

Figure 8

Layer system with layers pressed laterally or welded to the carrier shell;

Figure 9 / 9a

schematic cross sections through sound absorbers with plate-shaped spacers;

Figure 10

a corresponding schematic cross section through the sound absorber with foam as spacers;

Figure 11

is a schematic view of an alternative embodiment of the invention, in which the absorber chambers made of deep-drawn material are covered by a thin layer or membrane.

1 shows a sequence of each as an exemplary embodiment thin layers 2 or membranes (foil, fleece, foam etc.) with the corresponding intermediate layers 3a. This Intermediate layers 3a form simple resonance chambers 4, which can be filled with gas and especially air. Completed this system with a layer of very high mass 1, like they are formed, for example, as a carrier shell of an engine capsule is.

FIG. 2 shows an alternative embodiment of FIG. 1, in which the spacers 3a, i.e. the intermediate layers porous absorber material such as Foam or non-woven material consist. Instead of the air layers, these increase here Materials damping the resulting resonances, leading to a broadening of the absorption curve in the area of the concerned Leads resonance maxima.

Figure 3 shows a system of layers 2 (membranes) and Intermediate layers 3a (air), which is laterally used as supports, in particular support walls or webs formed spacers 3b is delimited. These spacers 3b, which advantageously integrally connected to the carrier layer 1 can be used to fix the individual layers 2. Furthermore, different layer sequences can be made Realize in different places, making different large resonance chambers 4 arise. This is another Ability to vary the absorption spectra.

Figure 4 shows an alternative embodiment of the system according to Figure 3, here the intermediate layers 3a made of nonwoven or foam and similar tasks as in Figure 2 fulfill.

Figure 5 shows a layer sequence made by thermoforming or (Warm) presses etc. shaped layers 2 (membrane), which applied to the corresponding spacers 3b (webs) are. Due to the different degree of deformation realize different layer spacings here. Thereby arise resonance chambers 4 of different sizes, which too Here, depending on the location and location, a great variety ensure for the absorption spectra.

Figure 6 shows analogous to the previous embodiments a system according to Figure 5, wherein the corresponding intermediate layers 3a from appropriate fleeces, foams or Foils exist that dampen the corresponding resonance maxima.

According to FIG. 7, the absorber consists of a superimposition of absorber chambers 4, which are shared by a largely flat cover membrane 5 or cover film are covered. Thin layers 2 are arranged between the absorber chambers 4, with the cover membrane 5 and the support shell 1 certain places can be connected. This additional The top layer improves due to its additional acoustic effectiveness the absorption. Instead, it may be enough only a single layer of absorber chambers 4 on the Build carrier layer 1 and with a cover film as a thinner Cover layer 2.

FIG. 8 shows a layer system made up of layers 2, which pass through lateral pressing or welding onto the carrier layer 1 are fixed. This embodiment is recommended especially with a sequence of foil, fleece, foil, fleece (e.g. PES film, PET fleece ... or PP film, PP fleece ...) or Foil, foam, foil, foam (e.g. PU foil, PU foam, PU foil, PU foam) or different with a sequence of nonwovens Compression. For recycling reasons and due to Environmental protection measures can only be used here Types of material are used.

According to Figure 9, the carrier shell 1 is trough-shaped; it exists e.g. from GMT and is prefabricated using the deep-drawing process. Pull from the inside 1b of the carrier shell 1 plate-shaped spacers 3b substantially perpendicular to Level of the carrier shell 1 to the point at which they to support the spanned as a thin layer 2 effective film. The film is on the edge with the edge la the carrier shell 1 glued. The film is stretched tight. Resonance chambers are formed between the carrier shell 1 and the film 4 formed. The film is e.g. made of polypropylene, while the Spacers 3b made of the same material as the carrier shell 1 exist and with this also in one piece, for example in Injection molding process can be made.

According to Figure 9a is the thin layer 2 to improve the Absorbance at high frequencies with a thin layer of foam or fleece layer 10 and a thin cover film 11 or covered with a thin cover fleece.

According to Figure 10, the carrier shell 1 is e.g. made from GMT and brought into the shell shape shown here in the pressing process. At a distance from each other are on the inside 1b of the carrier shell 1 spacer 3b in the form of foam strips made of polyurethane elastomer and / or polyester fleece introduced. Their breadth is much smaller than their distance so that the Resonance chambers 4 between the carrier shell 1 and the the spacers 3b and the edge la of the carrier shell 1 stretched Form film or thin cover layer 2.

According to Figure 11, the carrier shell 1 is a deep-drawn trough-shaped Component e.g. from GMT. On the inside 1b are the Tips 6 of the spacers 3b are attached, which thereby are connected that they are a deep-drawn component form in particular polypropylene.

On the side facing away from the tips 6 of the spacers 3b is the thin layer 2, e.g. a fleece, pulled along. At this embodiment of the invention, the resonance chambers 4 the side facing away from the carrier shell 1 not only by the Layer 2, but also by connecting the spacers 3b Bridges 7 covered. By making openings 4b Helmholtz resonators can be inserted into the connecting webs 7 produce. The openings 4b are covered by the layer 2 and thus the resonance chambers 4 are protected against contamination. Unless the cover layer 2 and the spacers 3b are not made are made of the same material as polypropylene (PP), what favors disposal can be by choosing another Material or by varying the material thickness of the mass coating can be adapted even better to the desired resonance frequency. Using the same material can improve the rosonance frequency adjustment achieved by varying the material thickness will. Inside the spacers 3b there are further chambers 4a formed only by the fleece or a film are covered on one side, and thereby as a layer resonator can work.

The sound absorber according to the invention thus forms a layer resonance absorber, in which the layer sequence is preferably such built up by cascading and possibly side by side and is dimensioned so that a maximum per mass-spring pair arises in the absorption curve.

Claims (13)

1. Layer absorber for absorbing acoustic airborne sound waves having a number of layers (1, 2), of which at least one thin layer (2) has a layer thickness of between 0.01 and 5 mm, which layers are kept spaced apart from one another, characterised in that, on the one hand, the layers (1, 2), and, on the other hand, the intermediate layers (3a) or spacers (3b), which ensure the spacing between said layers, have different densities and/or degrees of rigidity, and in that the intermediate layers (3a) or spacers (3b) are configured and disposed in such a manner that a plurality of resonance chambers (4) are formed in the spaces between the layers (1, 2).
2. Layer absorber in accordance with claim 1, characterised in that one of the layers is formed as a support layer, support body or support section (1) with a high mass and in that at least one spacer (3a, 3b) fo; ms a plurality of gas-filled resonance chambers (4) between at least one thin layer (2) and the support layer (1).
3. Layer absorber in accordance with claim 2, characterised in that the support layer (1) is formed as a dish-shaped or tub-shaped support body.
4. Layer absorber in accordance with one of the preceding claims, characterised in that the layer sequence of the absorber is dimensioned and designed by connecting masses and springs in series in such a manner that a maximum in the absorption curve is produced per mass/spring pair.
5. Layer absorber in accordance with one of the preceding claims, characterised in that resonance chambers (4) or mass/spring pairs are adapted to different resonance frequencies.
6. Layer absorber in accordance with one of the preceding claims, characterised in that at least one spacer is configured as intermediate layer (3a).
7. Layer absorber in accordance with one of the preceding claims, characterised in that the layers (1, 2) and/or the spacers: (3a, 3b) are made of non woven fabric, foam or film.
8. Layer absorber in accordance with one of the preceding claims, characterised in that the thin layers (1, 2) and/or the spacers (3a, 3b) are made of PU (polyurethane elastomer), PET (polyester), PP (polypropylene), PE (polyethylene), ABS (acrylic nitrile/butadiene/styrene terpolymerisat), PAN (polyacrylic nitrile) and/or fibre re-inforced thermoplastics material and/or fibre re-inforced thermosetting plastics material.
9. Layer absorber in accordance with claim 7 or 8, characterised in that the thin layers (1, 2) comprise non woven fabrics formed from fibres of the following materials : PET, PP, carbon, PAN, PI (polyimide) and/or natural fibres.
10. Layer absorber in accordance with one of the claims 7 - 9 , characterised in that thin layers (1, 2) and/or spacers (3a, 3b) are severely compressed.
11. Layer absorber in accordance with one of the preceding claims, characterised in that a spacer (3a, 3b) is configured in one piece with a layer (1, 2).
12. Layer absorber in accordance with claim 11, characterised in that the support body (1) ) with spacer (3b) is configured in one piece and/or edges of the layers (2, 3a) are mounted on the edge (1a) of the support body (1).
13. Layer absorber in accordance with one of the preceding claims, characterised in that a common, in particular diaphragm-like, cover film (5), and/or non woven fabric - spanning the resonance chambers (4) - is disposed over the entire sound absorber on the side facing the incidence of the sound wave.

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