Abstract
Automotive noise attenuating trim part comprising at least a porous layer whereby the porous layer comprises at least one closed container partly filled with loose particles, whereby the closed container comprises a contact surface formed by a film for contacting a vibrating surface of the vehicle and whereby the surface of the film opposite the contact surface is in contact with at least part of the loose particles, such that the film can transfer vibrational energy from the vibrating surface to the loose particles inside the container.
Claims
1. An automotive noise attenuating trim part comprising at least a porous layer characterised in that the porous layer comprises at least one closed container partly filled with loose particles, whereby the closed container comprises a contact surface formed by a film for contacting a vibrating surface of the vehicle, and whereby the surface of the film opposite the contact surface is in contact with at least part of the loose particles, such that the film can transfer vibrational energy from the vibrating surface to the loose particles inside the container.
2. The automotive noise attenuating trim part according to claim 1, whereby the container comprises a vessel part for maintaining a defined void volume, and a closure part, connected together to form a closed container.
3. The automotive noise attenuating trim part according to claim 2, whereby the closure part comprises the film for contacting the vibrating surface and for contact with at least part of the loose particles.
4. The automotive noise attenuating trim part according to claim 1, whereby the total volume of the loose particles in the container is less than 90%.
5. The automotive noise attenuating trim part according to claim 1, whereby the loose particles have a median particle size between 20 μm and 1250 μm.
6. The automotive noise attenuating trim part according to claim 1, whereby the loose particles are made of at least one of the materials selected from the group consisting of inert minerals, such as calcium carbonate or silicon dioxide, metals, such as steel, ceramic materials, elastomeric materials, such as styrene-butadiene rubber, nitrile rubber, rubber from ethylene propylene diene monomer (EPDM) and butyl rubber or natural rubber and polymeric materials such as polystyrene, or combinations of such materials.
7. The automotive noise attenuating trim part according to claim 1, whereby the total weight of the particles in one container is less than 100 grams.
8. The automotive noise attenuating trim part according to claim 1, wherein the film has a thickness between 10 μm and 1 mm.
9. A noise attenuating trim part according to claim 2, wherein the vessel presents an edge with a protruding flange having a width of at least 1 mm.
10. The automotive noise attenuating trim part according to claim 1, whereby the porous layer comprises up to 30 containers.
11. The automotive noise attenuating trim part according to claim 1, wherein the porous layer is one of an open cell foam layer or a fibrous felt layer.
12. The automotive noise attenuating trim part according to claim 11, whereby the fibrous felt layer comprises fibers and/or filaments, and is further comprising a thermoset or thermoplastic binder.
13. The automotive noise attenuating trim part according to claim 1, further comprising one or more additional layers on the surface of the porous layer opposite the surface for contacting the vibrating surface of the vehicle.
14. The automotive noise attenuating trim part according to claim 13, whereby the at least one or more additional layers is at least one of a foam layer, or felt layer, a film layer, a foil layer, a thermoplastic elastomeric layer with a high filler content, a decorative layer, such as a nonwoven or carpet layer, or any combinations of such layers.
15. A method of producing the automotive noise attenuating trim part according to claim 1, comprising: shaping a vessel part with a with a defined internal volume preferably using at least thermal moulding, blow moulding, vacuum moulding, injection moulding or compression moulding or by additive manufacturing or 3D printing; filling the defined internal volume with loose particles; laminating the closure at least partly comprising the film for the contacting surface to the rim of the vessel to obtain a closed container filled with loose particles; producing a porous layer with recesses fitting the shape of the containers; and inserting the containers in the recesses of the porous layer.
16. A method of using the noise attenuating trim part according to claim 1 as an inner dash, an outer dash, a battery lid silencer, a battery enclosure insulator and/or as a carpet system such as a tufted carpet, a needle-punch carpet, a carpet with flocked surface, or a Dilour carpet, trunk trim part or trim part for the engine bay area, wherein the porous layer is the layer in contact with a vibrating body panel when the part is installed in the vehicle.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0146] FIG. 1 shows a schematic cross section of a trim part according to the invention.
[0147] FIG. 2 shows a schematic cross section of a trim part according to the invention before the containers are embedded into the porous layer.
[0148] FIG. 3 shows a schematic cross section of a part according to the invention, when the part is installed on the vehicle on a predominantly horizontal panel.
[0149] FIG. 4 shows a schematic cross section of a part according to the invention, when the part is installed on the vehicle on a predominantly vertical panel.
[0150] FIG. 5 shows schematic cross sections of containers partly filled with loose particles, according to the invention.
[0151] FIG. 6 shows an example of a 3d-molded part according to the invention.
[0152] FIG. 7 shows a schematic top view of a vehicle floor.
[0153] FIG. 8 shows vehicle body vibration levels.
DETAILED DESCRIPTION
[0154] FIG. 1 shows a schematic cross section of an example of a trim part (11) according to the invention. The part comprises a porous layer (7), a mass layer (8) and a carpet layer (9). The porous layer has a section of its outer surface (10) that is for contacting the vibrating vehicle surface, when the part is installed in the vehicle. The part further comprises closed containers (1) partially filled with loose particles (3). The internal volume of the containers that is not occupied by the loose particles (2) is filled by air. In this example, the walls of the container comprise a contact surface (4) consisting of a film and the remaining part of the walls of the container (5) is shaped like a vessel and it is much thicker and stiffer than the film. The contact surface (4) and the vessel (5) are connected along their edges in such a way that the contact surface (4) acts as a closure for the vessel (5) and together they form the closed container (11). The containers are integrated into the porous layer (7) in such a way that the closure (4) consisting of a film remains flush with the section (10) of the porous layer that is for contacting the vibrating vehicle surface, when the part is installed in the vehicle. The loose particles (3) are in contact with the closure (4) consisting of a film and, under the load due to the weight of the particles, the film (4), being thin and flexible, deforms and ‘bulges’ outwards. As a consequence of this deformation, when the part is laid on a vehicle vibrating surface, the contact surface (4) will adapt to the shape of the vibrating surface itself.
[0155] The deformation of the film will depend on the mechanical and physical properties of the film as well as on its dimensions. The lower the Young's modulus of the film and or its thickness, the higher will be the deformation. For example, for a film having a Young's modulus of 250 MPa and a thickness of 27 μm and dimensions 50 mm×50 mm, the deformation of the film will be such that the maximum ‘outward bulging’ of the film will be about 2 mm. This would already compensate for most of the unevenness observed in vehicle body panels.
[0156] FIG. 2 shows the same schematic cross section of a noise attenuating part according to the invention, before the containers (1) are embedded into the porous layer (7). The porous layer (7) preferably presents recesses (16) having a shape that matches the shape of the containers (1). The containers (1) may be embedded into the porous layer (7) by inserting them into the recesses (16). This operation is preferably carried out in an automated way by means of suitable mechanical tools known in the art, but it may be carried out also manually. Preferably, some glue (18) is distributed over at least a part of the surface of the containers (1) in such a way to favour their adhesion to the surface of the porous layer and avoid that they fall off during the handling operations necessary to install the part on the vehicle. However, gluing the containers to the porous layer is not strictly necessary to obtain this effect, which may be obtained also in other ways, e.g. by shaping the containers in a suitable way and/or by fixing the containers to the porous layer by means of some mechanical fixation element.
[0157] FIG. 3 shows the same schematic cross section of a noise attenuating trim part (11) according to the invention, when it is installed on the vehicle body (14). When the part is installed on the vehicle body (14), the contact surface (4) consisting of a film adapts to the shape of the vehicle body (14) itself, guaranteeing close contact with it. Being the film very thin and flexible, this happens also in areas where the vehicle body (14) is not flat, as it is shown in FIG. 3 for the right-most container. The contact surface (4) consisting of a film is in close contact with the vehicle body (14) on one side and with the loose particles (3) on the other side and can then transmit the vehicle body vibrations to the loose particles in a very efficient way.
[0158] FIG. 4 shows a schematic cross section of a noise attenuating trim part according to the invention similar to the one shown in FIG. 3, but for application on a vertical body panel. As shown in FIG. 4, in such an application, the loose particles (3) will tend to fill-up the lower part of the container volume, but they will still remain at least partially in contact with the contact surface (4) consisting of a film and, due to their granular nature, their overall weight will have a component normal to the film. In the region where the loose particles are in contact with the contact surface (4) consisting of a film, the film will adapt to the vehicle body (14), it will remain in close contact with it and it will then transmit the vehicle body vibrations to the loose particles (3).
[0159] In the examples shown in FIGS. 1 to 4, the section of the outer surface of the trim part that is the vehicle body when the part is installed on the car consists only of the portion belonging to the porous layer and of the portions belonging to the containers. However, in a trim part according to the invention the section of its outer surface that is for contacting the vehicle body when the part is installed on the car may comprise also other portions, neither belonging to the porous layer nor belonging to the containers.
[0160] FIG. 5a shows an embodiment of a container (1) according to the invention that is similar to the one shown in FIGS. 1 to 4, where the container is shaped like a parallelepiped and the vessel (5) presents, along its edge, a small flange (6).
[0161] The small flange (6) may help preventing that the container (1) sinks into the porous layer (7) during the integration process. However, a proper and accurate integration of the container into the trim part is possible also without this flange.
[0162] FIGS. 5b and 5c show other embodiments of the container (1) according to the invention that differ from the one shown in FIG. 5a for the shape of the container. FIG. 5b shows a schematic cross section of a hemispherical container, while FIG. 5c shows a schematic cross section of a container having the shape of an inverted truncated cone.
[0163] In particular, the embodiment shown in FIG. 5c is an example of a ‘self-clamping’ shape, i.e. a shape such that, once the container is inserted into the porous layer (7), it cannot fall out simply by gravity. Other shapes having the same property (e.g. inverted truncated pyramid, barrel-like shape) are possible and will appear obvious to the man skilled in the art. All these shapes can advantageously simplify the embedding of the containers (1) into the porous layer (7). However, it is possible to avoid that the containers (1) fall out of the porous layer (7) also by other means, e.g. by gluing the containers (1) to the porous layer (7) at least on a part of their surface or by providing the container with some mechanical fixation element.
[0164] FIG. 6 shows a schematic cross section of a 3d molded noise attenuating trim part (19) according to the invention. In this figure, for simplicity all containers have the same parallelepiped shape and the same size. Depending on the needs and on production convenience, the containers may have any other kind of shape and they may have different size. The number and position of the containers is preferably corresponding to the areas where the vehicle body vibration is the highest, i.e. the so called “hot-spots”, which can be identified with test or simulation methods well-known in the art. Preferably, the total surface of the walls of the containers that are in contact with the vehicle body (when the part is installed in the vehicle) is much smaller than that the total surface of the section of the trim part outer surface that is in contact with the vehicle body (when the part is installed in the vehicle). This assures that the embedding of the containers does not impact negatively the sound insulation and absorption performance of the trim part.
[0165] FIG. 7 shows a schematic top view of a vehicle floor (20) cut-out from a body in white (BIW). The vehicle floor is made of 0.8 mm thick steel. Tests have been done on the front left area (21) of the floor, here also referred to as the test area (21) and indicated by a dashed rectangle in the figure, where different configurations of trim parts have been placed. The positions of the containers with loose particles (23) and of the damping pads (24) are shown in the same figure, but the configuration with traditional damping pads and the configuration with the part embedding containers partly filled with loose particles according to the invention were tested separately. During the tests the floor was excited using an electro-dynamic shaker at an excitation point (22) situated in the front left corner of the vehicle floor. The signal used for the excitation was recorded in real driving conditions and covered a frequency bandwidth between 50 and 700 Hz.
[0166] Three configurations have been tested wherein configurations 1 and 2 are state of the art and configuration 3 is according to the invention. Configuration 1 is a trim part made of a porous fibrous layer facing and contacting the vehicle floor and a mass layer facing away from the floor. The porous fibrous layer has a thickness of 20 mm, an area weight of 1700 gsm and is made of 20% Bico PET/CoPET and 80% shoddy cotton, wherein the shoddy cotton comprises 40% recycled fibers. The mass layer is an EPDM layer with 2 mm thickness and an area weight of 2.8 kg/m.sup.2.
[0167] Configuration 2 is the same trim part as in configuration 1 but with additional three damping pads (24) laminated on the vehicle floor and wherein the damping pads (24) are situated between the vehicle floor and the porous fibrous layer of the trim part. The damping pads (24) are bitumen based pads with a thickness of 2 mm and area weight of 4 kg/m.sup.2, wherein each pad weighs 50 grams. The area of one damping pad is 128 square centimetres and the three damping pads cover some of the test area (21) as shown in FIG. 6.
[0168] Configuration 3 is the same trim part as in configuration 1 but with 3 containers partly filled with loose particles according to the invention embedded in the porous fibrous layer as shown for example in FIG. 3. The containers are parallelepiped shaped boxes wherein the vessel, i.e. the side walls and the wall facing away from the vehicle floor are made of polypropylene with a thickness of 2.0 mm, while the closure, i.e. and the wall facing and contacting the vehicle floor is a thin foil. The foil is 27 mm thick PA/PE film, has an area weight of 38 gsm and a tensile modulus of 250 MPa. The inner volume of each chamber is 20 cubic centimetres (5×5×0.8 cm) and it is partly filled with 42 grams steel particles with a median particle size of 400 mm and a particle size distribution span of about 2. These values are chosen in order to have a good performance predominantly over the frequency range above 250 Hz. The total weight of one container with steel particles is 50 grams. When the trim part with the integrated containers according to configuration 3 is placed on the test area (21) the part is simply laid on (not glued, not even locally where the containers are positioned) and contacting the vehicle floor. The porous fibrous layer is 20 mm thick and the total height of a container is about 11 mm which means that in the areas where the containers with loose particles are positioned there is about 9 mm of porous fibrous material between the containers and the mass layer.
[0169] FIG. 8 shows measured average vibration velocity levels per unit excitation force in dB [(m/s)/N] for the different configurations. The floor vibration velocity levels were measured for each configuration on the steel side by eight accelerometers attached on the underside of the test area (16) and evenly distributed over its surface.
[0170] Higher vibration level amplitudes mean higher noise inside the vehicle and therefore lower vibration levels are desired.
[0171] FIG. 8 shows average vibration levels measured on the vehicle floor in third-octaves between 100 Hz and 630 Hz. The vibration level at each frequency is an average of the eight measurement points where the accelerometers were mounted on the steel floor (body). Configuration 1 without any damping shows the highest levels except below 200 Hz where configuration 2 shows the highest levels due to the stiffening of the floor caused by the damping pads. Configuration 3 with containers partly filled with loose particles shows the lowest levels at the same weight as configuration 2, in particular above 250 Hz.
[0172] The principles of the configurations may of course be applied on the complete floor and not just the test area (21).
