Fully enclosed engine or unit cover with air cushion membrane for motor vehicles

Abstract

The invention relates to a fully enclosed engine hood or unit hood (1) of a motor vehicle with an air cushion membrane, having: (a) a sound-insulating carrier layer (2) made of a readily bendable compound having a Shore hardness in the range of 60 to 95, a thickness in the range of 1.2 to 4 mm, a density of 1.2 to 3.0 g / cm 3 resulting in a unit area weight of 1.44 to 12 kg / m 2 , (b) a PUR foam (3) having a density in the range of 45 to 105 g / l, a storage modulus in the range of 20 to 250 kN / m 2 and a loss factor of 0.3 to 0.8, and (c) an air cushion membrane (4) made of at least two layers of polyethylene terephthalate, polyamide 6 or 6.6 between the carrier layer (2) and the PUR foam (3) partially or over the entire surface. The acoustic properties of the component can thus be decisively influenced, adjusted.

Description

TECHNICAL FIELD

[0001] The subject of the present invention is a fully enclosed engine cover or unit cover of a motor vehicle with air cushion film, whereby the acoustic properties of the construction can be decisively influenced, adjusted. BACKGROUND

[0002] Air cushion film applications are known in the prior art, which mainly relate to the packaging sector. These air cushion films are used here as insulating packaging; in particular for the storage, transport and dispatch of temperature-sensitive, heat-sensitive and cold-sensitive and impact-sensitive products; see for example DE 20 2019 101 109 U1.

[0003] For this purpose, US 2019 / 0375193 A1 discloses an insulating packaging material, which is typically produced by using a thermoplastic, for example a polyethylene (PE) air cushion film laminated onto a metallized polyester (PET) film. This material has insulating properties due to the heat-reflecting properties of the metallized polyester and the air encapsulation of the bubble film.

[0004] In addition to two-layer and three-layer PE air cushion films, polypropylene (PP) air cushion films are also known (EP 1 477 299 B1, DE 60 2004 007 185 T2).

[0005] Recyclable air cushion films have also been found, biodegradable plastics involve blends of polylactic acid (PLA), polyhydroxyalkanoates (PHA), in particular polyhydroxybutyrate (PHB), thermoplastic starch or mixtures of these and / or other biodegradable fillers (DE 20 2009 014 881 U1); furthermore biodegradable aliphatic-aromatic copolyesters or blends of at least one biodegradable aliphatic-aromatic copolyester with polylactic acid or thermoplastic starch (DE 20 2010 008 483 U1).

[0006] In addition, self-adhesive (EP 1 621 330 B1) and provided with a textile fabric (DE 20 2008 014 014 U1) air cushion films are known.

[0007] In particular, in the literature of the automotive industry, it is found in the bottom trim foam insulation to introduce and foam hollow chamber or cushion film packs (air cushions) in the soundproofing structure (DE 35 31 886 C2).

[0008] It is also mentioned to fill the cushions with a gas lighter than air, for example helium (DE 79 29 637 U1).

[0009] However, the introduction and foaming of hollow chambers or cushion film packs (air cushions) has not proven to be effective in practice.

[0010] Naturally, air gaps or air bubbles can also be present in other sound-insulating structures, for example in the front wall, wheelhouse and underbody cladding. DE 10 2004 022 895 A1 discloses a cladding component composed of thermoplastic for shielding an engine and / or exhaust system, which has at least partially a hollow body. For a wheelhouse, this is described in US 2018 / 0050731 A1 and US 10 131 383 B2. DE 100 22 902 A1 discloses air gaps in the roofliner cladding of a motor vehicle by variable wall spacing.

[0011] In DE 10 2004 037 767 B4, US 2008 / 0020199 A1, an inflatable air cushion is described, which consists of a sound-attenuating sleeve of an elastic material between a sound-emitting component and the interior space of the vehicle passenger compartment.

[0012] In DE 10 2005 003 994 B4, a method for manufacturing an acoustic absorber and different applications are generally set out. It is further mentioned that the hollow chamber elements are constructed with different dimensions in terms of height and in terms of diameter or width, and that the hollow chamber elements are manufactured with different stresses or relaxations of their outer shell. SUMMARY

[0013] The object of the present application is therefore, in contrast to the prior art described above, to provide a sound-insulating structure, in particular an engine cover and a crew cover, by using an air cushion film which withstands the process parameters required when manufacturing the sound-insulating structure and ensures a reliable bonding and positioning with the adjoining layers, so that the decoupling of the excitation of the carrier layer by the components to be encapsulated is then achieved by positioning the air cushion film between the carrier layer and the PUR foam when used in an engine cover or crew cover.

[0014] In a first embodiment, the subject of the present application is a fully enclosed crew cover 1, which has:

[0015] (a) a sound-insulating carrier layer 2, which is made of an easily bendable compound having a Shore (A) hardness in the range of 60 to 95, a thickness of 1.2 to 4 mm, which is determined by requirements, a density of 1.2 to 3.0 g / cm 3 , a unit area weight of 1.44 to 12 kg / m 2 ,

[0016] (b) a polyurethane (PUR) foam 3, which has a density in the range of 45 to 105 g / l, an energy storage modulus in the range of 20 to 250 kN / m 2 and a loss factor of 0.3 to 0.8, and (b) a polyurethane (PUR) foam 3, which has a density in the range of 45 to 105 g / l, an energy storage modulus in the range of 20 to 250 kN / m 2 and a loss factor of 0.3 to 0.8, and

[0017] (c) at least two layers of air cushion film 4, which are made of polyethylene terephthalate (PET), polyamide (PA) 6 or 6.6 between the carrier layer 2 and the PUR foam 3, partially or over the entire area.

[0018] From the prior art, in particular from the prior art of the motor vehicle industry, it is not known to apply air cushions in the field of the encapsulation of engines or aggregates.

[0019] Furthermore, on the one hand, air cushion film materials are not discussed at all, or on the other hand, only PE is mentioned. For example, there is also no statement about the adhesion of the PUR foam on the air cushion film, since the PUR foam does not adhere to PE.

[0020] Furthermore, there is no statement about the positioning / fixing of the sound-insulating component in the multilayer composite and the manufacturing technology associated therewith. It is precisely here that, due to the process parameters (temperature, pressure...) required in the hot deformation process and the backfoaming process, the film material is the focus according to the invention.

[0021] The manufacturing of the carrier layer 2 can take place in different ways and methods. Particularly preferably, the carrier layer 2 is injection molded in the sense of the invention, since thereby a contour-compliant, unit-area-weight-optimized design of the structure is given and at the same time a reproducibility can be ensured. Thus, the sound-insulating carrier layer 2 can have a thickness in the range of 1.2 to 4 mm and a density of 1.2 to 3.0 g / cm 3 , which results in a unit-area weight of 1.44 to 12 kg / m 2 . These parameters can be varied as required within the above-mentioned density, thickness or unit-area weight.

[0022] The PUR foam 3 can also be connected to the air cushion film 4 in any manner. Particularly preferred in the sense of the invention is the backfoaming of the PUR foam 3. For this, the precursor consisting of the carrier layer 2 and the air cushion film 4 is placed into a correspondingly contoured mold and backfoamed with the raw material of the foam in a manner known per se.

[0023] Particularly preferably, the PUR foam 3 has a density in the range of 55 to 85 g / l and / or an energy storage modulus in the range of 40 to 100 kN / m 2 and / or a loss factor of 0.33 to 0.50; thus, the softness of the spring and its viscoelasticity (of the PUR foam 3) is ensured.

[0024] Air cushion films 4 are commercially available in various specifications. In particular, two-layer and three-layer air cushion films 4 are distinguished. They are usually made of a smooth cover film and a second layer in which regularly spaced air cushions, usually circular, are machined by means of blisters and vacuum rollers, said air cushions being known for damping impacts. Three-layer embodiments have a second smooth cover film and are therefore more loadable. According to Wikipedia (keyword: air cushion film; accessed March 2020), the blister diameter of small-bubble films is approximately 10 mm, and the blister diameter of large-bubble films is approximately 25 mm. Particularly preferred according to the application are air cushion films having a blister diameter in the range from 2 to 20 mm and a blister height (bister height) in the range from 1 to 15 mm.

[0025] The air cushion film 4 can fill the entire structural space between the carrier layer 2 and the PUR foam 3, around the circumference. According to the application, however, the air cushion film 4 is cut accordingly before introduction, so that the air cushion film 4 is positioned identically and / or requirement-determined in terms of geometry / profile on the face.

[0026] In the same way, it is also possible according to the application for the air cushion film 4 to be positioned identically and / or requirement-determined in terms of geometry / profile of the individual air cushions on the face. Here, in particular the diameter and / or height of the blisters varies on the face of the air cushion film.

[0027] Another variant possibility of the application-oriented variants of the air cushion film 4 lies in the different filling of the blisters. For example, it is preferred according to the application for the individual air cushions of the air cushion film 4 to be filled with air, nitrogen or a (rare) gas.

[0028] In addition, alternatively or cumulatively, it is also possible according to the application for some of the air cushions of the air cushion film 4 to be filled, in part or completely, requirement-determined with:

[0029] fibres, in particular plastic fibres, plant fibres, animal fibres and / or inorganic fibres;

[0030] foam wadding, in particular polyurethane foam wadding, polyester foam wadding and / or polyolefin foam wadding;

[0031] springs;

[0032] hollow bodies, in particular polyolefins, ceramics, glass, EPS, EPP and / or PEPP;

[0033] wood chips;

[0034] wood powder

[0035] as a single material and / or as a mixture of two or more of the said materials.

[0036] It is particularly preferred that the individual films of the air cushion film 4 have a film thickness in the range from 20 to 500 μιη.

[0037] In another embodiment of the application, the air cushion film 4 comprises on its upper and / or lower side a film nonwoven made of PA plus PET fibers, PET plus PET fibers and / or PE plus PET fibers; thereby, the connection of the further layer is more effectively and more stably solved.

[0038] The air cushion film 4 can be adhered to the carrier layer 2, but also welded to the carrier layer, for example. This means, however, that in the case of adhesion, the air cushion film 4 is equipped either self-adherently (expensive) on the one hand, or must be adhered by means of an additional adhesive by means of a further work step (expensive, cycle time) on the other hand. In all known possibilities of fastening (adhesion, welding, etc.), additional process steps are required which significantly increase the manufacturing costs of the cover. In correspondence therewith, the air cushion film 4 according to the application preferably has perforations 5 for fastening on the carrier layer 2. Thus, the PUR foam 3 fixes the air cushion film 4 punctiformly on the carrier layer 2 without further work steps or equipment as such.

[0039] The core of the application is therefore to provide an acoustically and thermally acting, fully enclosing engine cover or unit cover 1, in which a unit area weight on the carrier layer level, as required, with different designs if necessary, is implemented (einhergehen) in combination with a hydrolysis-resistant, viscoelastic PUR foam and a sound-insulating cover element, in which a multilayered air cushion film made of PA 6 or PA 6.6 is positioned in a demand-oriented manner locally or over the entire area between the carrier layer 2 and the PUR foam 3 in terms of the geometry / profile of the individual air cushions (bubbles), identically and / or differently over the area.

[0040] The advantage of the application lies especially in the combination of the carrier layer 2 with the foam system 3 in such a form that the carrier layer 2 can have a demand-oriented unit area weight, the foam system has a high acoustic effect, especially also hydrolysis-resistant,

[0041] The perforations for cables and the like in the fully enclosing cover 1 do not constitute an acoustically leaking point, just as the (form-locking) edge / overlap design of the cover element / cover shell, and

[0042] It is precisely by positioning the multilayered air cushion film 4 made of PA 6 or PA 6.6 between the carrier layer 2 and the PUR foam 3 that decoupling of the excitation of the carrier layer 2 by the components to be encapsulated is achieved. DETAILED DESCRIPTION

[0043] Embodiment:

[0044] The unit area weight of 5 kg / m2consistently over the entire surface is produced with the aid of injection molding from a self-compounded PP-based compound made essentially from TPE / PP and mineral fillers 2 and a carrier layer 2 with a Shore (A) hardness of 78.

[0045] After the injection-molded carrier layer 2 is placed in the foaming mold, a commercially available air cushion film 4 based on PA 6 (total thickness 3 mm, bubble cylinder diameter 10 mm, with position-determined perforations 5 for positioning on the carrier layer 2) is placed thereon and then foamed from the back with a commercially available soft PUR foam 3 (density 80 g / l, storage modulus 90 kN / m 2 and a loss factor of 0.4).

[0046] As shown in Figure 1 , after the application of the cover around the motor vehicle power unit, the cover is measured on a test stand; air noise in dB(A).

[0047] The power unit cover 1 is shown in Figure 1 ; wherein the air cushion film 4 is positioned between the PUR cold foam 3 and the injection-molded carrier layer 2. The double-layered air cushion film 4 is explained in more detail in Figure 2 .

[0048] The difference in the acoustic effect of the cover without air cushion film 4 and with air cushion film can be clearly seen in Figure 3 . In particular in the here critical medium frequency range between the band pass (filter) BP 300 and 800 Hz [about 6 dB reduction in sound level].

Claims

1. Motor vehicle's fully enclosed engine hood or engine compartment hood (1) having: (a) a soundproof carrier layer (2) made of an easily bendable compound having a Shore hardness in the range of 60 to 95, a thickness in the range of 1.2 to 4 mm, a density of 1.2 to 3.0 g / cm 3 resulting in a unit area weight of 1.44 to 12 kg / m 2 2, (b) a PUR foam (3) having a density in the range of 45 to 105 g / l, a storage modulus in the range of 20 to 250 kN / m 2 and a loss factor of 0.3 to 0.8, and (c) at least two layers of air cushion film (4) made of polyethylene terephthalate, polyamide 6 or 6.6 partially or completely across the surface between the carrier layer (2) and the PUR foam (3).

2. An engine or unit cowling (1) according to claim 1, characterised in that The carrier layer (2) is injection molded.

3. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that The thickness and density of the carrier layer vary as required.

4. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that The PUR foam (3) is back foamed.

5. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that The PUR foam (3) has a density in the range of 55 to 85 g / l and / or a storage modulus in the range of 40 to 100 kN / m 2 and / or a loss factor of 0.33 to 0.

50.

6. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that The air cushion film (4) is double-layered.

7. The hood or cowling (1) according to claim 1 or 2, characterized in that The air cushion film (4) is triple-layered.

8. The hood or cowling (1) according to claim 1 or 2, characterized in that The air cushion film (4) is identical and / or positioned as required in terms of geometry / profile across the surface.

9. The hood or cowling (1) according to claim 1 or 2, characterized in that The air cushion film (4) is identical and / or positioned as required in terms of geometry / profile of individual air cushions across the surface.

10. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that The individual air cushions of the air cushion film (4) are filled with air, nitrogen or noble gases.

11. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that Some air cushions of the air cushion film (4) are filled partially or completely as required with: fibers; foam wadding; springs; hollow bodies; wood chips; wood powder as a single material and / or a mixture of two or more of the above-mentioned materials.

12. The engine or engine compartment hood (1) according to claim 11, characterized in that The fibers are plastic fibers, plant fibers, animal fibers and / or inorganic fibers.

13. The engine or engine compartment hood (1) according to claim 11, characterized in that The foam wadding is polyurethane foam wadding, polyester foam wadding and / or polyolefin foam wadding.

14. The engine or engine compartment hood (1) according to claim 11, characterized in that The hollow bodies are made of polyolefins, ceramics, glass, EPS, EPP and / or PEPP.

15. The engine or engine compartment hood (1) according to claim 1 or 2, characterized in that The air cushion film (4) comprises on its upper and / or lower side a film nonwoven made of PA plus PET fibers, PET plus PET fibers and / or PE plus PET fibers.

16. The hood or cowling (1) according to claim 1 or 2, characterized in that The air cushion film (4) has perforations (5) for fixing the air cushion film (4) to the carrier layer (2).

17. A bonnet or cowl (1) according to claim 1 or 2, characterised in that, The individual bubbles of the air cushion film (4) have identical or different geometry / profile in terms of their size across the surface.

18. The hood or cowling (1) according to claim 1 or 2, characterized in that The single film of the air cushion film (4) has a film thickness in the range of 20 to 500 µm.

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