Acoustic absorption device for noise-generating equipment of a motor vehicle

Abstract

Acoustic absorption device (100) for noise-generating equipment, such as a compressor or an electric motor, of a motor vehicle, said device comprising at least: - a first layer (10) configured to face and / or be in contact with an external surface of said equipment, said first layer being a nonwoven felt; - a second layer (20) covering the first layer, said second layer being a plastic cellular material; and - an interlayer (30) ensuring the bond between the first layer (10) and the second layer (20).

Description

Description TITLE: ACOUSTIC ABSORPTION DEVICE FOR NOISE-GENERATING EQUIPMENT IN A MOTOR VEHICLE Technical field of the invention

[0001] The present invention relates to a sound absorption device for noise-generating equipment, such as a compressor, an electric motor or any other noise-source auxiliary component, of a motor vehicle. Technological background

[0002] Motor vehicles contain many pieces of equipment, some of which can be a source of vibrations and / or noise, which can be a nuisance for the occupants of the vehicle, or even be noise pollution around the vehicle, i.e. outside of it.

[0003] To reduce these nuisances, it is known to place the equipment that is the source of them, for example a compressor or an electric motor, within a device designed to dampen vibrations and / or noise.

[0004] The evolution of the automotive sector necessitates the search for solutions that are both efficient and economical. Furthermore, it is also important that these solutions have the smallest possible impact on the environment.

[0005] Documents US-A1-2021 / 362461 or US-B2-7410030 present examples of sound-absorbing devices.

[0006] One objective of the present invention is to provide a solution that meets at least some of these criteria. Summary of the invention

[0007] Therefore, a sound absorption device is proposed for noise-generating equipment, such as a compressor or electric motor, in a motor vehicle; this device includes at least: - a first layer configured to face and / or be in contact with an external surface of said equipment, said first layer being a non-woven felt; - a second layer covering the first layer, said second layer being a plastic alveolar material; and an intercalary layer ensuring the bond between the first layer and the second layer.

[0008] Thus, thanks to the invention, the acoustic absorption device is made lighter while maintaining acoustic performance similar to that of the prior art. Indeed, the cellular materials and felts are porous materials that contribute to reducing the mass of the device. This mass loss is counterbalanced by the interlayer which, coupled with the two other layers—felt and plastic cellular material—allows for acoustic performance similar to that of pre-existing devices. Furthermore, the cellular material and felt exhibit acoustic properties that promote sound absorption in the high frequencies.

[0009] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - the interlayer is made of an elastomeric material; - the interlayer is fixed on one side to the first layer by a first adhesive and on the other side to the second layer by a second adhesive; - the interlayer is a skin made of a hot melt material which is chemically compatible with the first and second layers; - the interlayer comprises a skin which is made of a hot melt material, chemically compatible with the first layer, and a sub-layer which is made of a thermoplastic elastomer material, chemically compatible with the second layer, or of an elastomer material. - the first layer, the second layer and the intermediate layer of hot melt material are fixed together by at least one welding point; - the intercalated layer has a surface mass between 0.03 kg / m 2 and 2 kg / m 2 ; - the interlayer extends partly over a surface of the first layer and / or partly over a surface of the second layer; - the non-woven felt is made with polyethylene terephthalate (PET) fibers; - the first layer has open cells; - the second layer of alveolar material comprises closed cells; - the plastic cellular material is a polyolefin, for example a polypropylene (PP), a polyamide (PA) or a polyethylene terephthalate (PET); - the second layer forms a shell intended to receive the noise-generating equipment, the shell comprising at least two parts; - the hull is a single piece.

[0010] The invention also relates to a motor vehicle comprising at least one sound-absorbing device as described above. Brief description of the figures

[0011] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0012] Figure 1 shows a schematic cross-sectional view of one embodiment of a sound-absorbing device according to the invention, particularly when the interlayer is made of a hot-melt material,

[0013] Figure 2 shows a schematic cross-sectional view of another embodiment of a sound-absorbing device according to the invention, in particular where the interlayer comprises an elastomer or thermoplastic elastomer underlayer and a heat-fusible skin,

[0014] Figure 3 shows a schematic cross-sectional view of another embodiment of the device according to the invention, in particular when the layers are fixed together by at least one adhesive,

[0015] Figure 4 shows a schematic view of another embodiment of the device according to the invention, in particular when the second layer forms a shell,

[0016] Figure 5 shows a graph comparing the gain in decibels as a function of frequency of a reference acoustic absorption device with the acoustic absorption device according to the invention,

[0017] Figure 6 represents a very schematic cross-sectional view of an assembly comprising a sound-absorbing device according to the invention and a noise-generating device. Detailed description of the invention

[0018] With reference to Figures 1 to 4, the sound-absorbing device 100, 100', 200 according to the invention, for a noise-generating component 2 of a motor vehicle, comprises at least a first layer 10 configured to face and / or be in contact with an external surface 4 of the noise-generating component 2, and a second layer 20 covering the first layer 10. The first layer 10 is a non-woven felt, and the second layer 20 is a plastic cellular material, commonly referred to as "foam." The device 100, 100', 200 also includes an interlayer layer 30 providing the bond between the first layer 10 and the second layer 20. It is understood that the interlayer layer 30 is located between the first layer 10 and the second layer 20.

[0019] Felt and plastic honeycomb material are porous materials, generally containing air. This type of structure helps to reduce the weight of the device. Preferably, the felt is chosen to provide acoustic absorption in the high frequencies.

[0020] Preferably, the plastic cellular material comprises closed cells. It is understood that the proportion of closed cells can be predominant in the plastic cellular material. This allows the airtightness of the second layer 20 to be maintained, thus enabling this layer to exhibit mass-law sound insulation behavior.

[0021] The cellular material is in the form of a foam. Therefore, the cellular material does not have a honeycomb structure or anything similar.

[0022] Advantageously, the non-woven felt of the first layer 10 is made with thermoplastic fibers, for example, polyethylene terephthalate (PET). This material has the advantage of being recyclable. Thus, at the end of the vehicle's life, and consequently at the end of the use of device 100, 100', 200 for this vehicle, the first layer 10 of device 100, 100', 200 can be recycled. This reduces the environmental impact of device 100, 100', 200. Furthermore, this also has the advantage of allowing the recycling of offcuts from the first layer 10 generated during the manufacturing of device 100, 100', 200.

[0023] The first layer 10 can have a thickness D10 between 3 mm and 30 mm, and preferably substantially between 7 mm and 20 mm, and more preferably substantially between 7 and 13 mm.

[0024] The first layer 10 can have a density approximately between 5 kg / m³3 and 100 kg / m 3 , preferably approximately between 20 kg / m 3 and 70 kg / m 3 , and even more preferably substantially between 35 kg / m 3 and 50 kg / m 3 .

[0025] The thickness and density of the first layer 10 allow us to define a surface mass that represents an important factor in the mass law for sound insulation. Indeed, the higher the surface mass, the better the sound insulation, that is to say, the higher the absorption.

[0026] The first layer 10 can have an air resistance resistance approximately between 5000 Nsm -4 and 200,000 Nsm -4 (or Rayl / m).

[0027] Advantageously, the plastic forming the honeycomb material of the second layer 20 is made of a thermoplastic material, for example a polyolefin such as polypropylene (PP), polyamide (PA) or polyethylene terephthalate (PET). As with the first layer 10, these materials have the advantage of being recyclable.

[0028] The second layer 20 can have a thickness D20 substantially between 1 mm and 10 mm, preferably between 2 mm and 8 mm, and even more preferably substantially between 2 mm and 5 mm.

[0029] The second layer 20 can have a density approximately between 50 kg / m³ 3 and 300 kg / m 3 , preferably approximately between 100 kg / m 3 and 200 kg / m 3 , and even more preferably substantially between 125 kg / m 3 and 175 kg / m 3 .

[0030] As with the first layer 10, the thickness and density of the second layer 20 define a surface mass. The higher the surface mass, the better the sound insulation, i.e., the higher the absorption.

[0031] The intercalated layer 30, which is located between the first layer 10 and the second layer 20, can extend continuously between the first layer 10 and the second layer 20. It is understood that the intercalated layer 30 covers substantially the entire surface of the first layer 10 and substantially the entire surface of the second layer 20.

[0032] Alternatively, the intermediate layer 30 is discontinuous and only partially covers the surface of the first layer 10 and / or the second layer 20. In this way, the acoustic performance can be improved at specific points on the device 100, 100', 200 without affecting its overall mass. Indeed, the equipment 2 intended to be received by the device 100, 100', 200 is a three-dimensional object, and noise is therefore emitted in these three dimensions. Consequently, the noise can be more or less intense depending on the spatial direction. The intermediate layer 30 can therefore be positioned discontinuously between the first and second layers 10, 20 so as to attenuate noise in specific directions. In other words, we improve acoustic absorption in the directions where the noise is highest by a local mass gain without making the device heavier 100, 100', 200 in the places where the noise is lowest.

[0033] The interlayer layer 30 can have a thickness D30 substantially between 0.1 mm and 5 mm, preferably substantially between 0.3 mm and 2 mm.

[0034] The intercalated layer 30 can have a surface mass approximately between 0.03 kg / m 2 and 4 kg / m 2 , preferably approximately between 0.03 kg / m 2 and 2 kg / m 2 .

[0035] Referring to Figure 1, the interlayer 30 can be made of a hot-melt material. "Hot-melt" means that it is capable of melting under the effect of heat. This hot-melt material must be conformable to the first and second layers 10, 20; that is, the interlayer 30 can adapt to the shape of the first layer 10 and the second layer 20, between which it is located. The hot-melt material is also chosen to be chemically compatible with both the first layer 10 and the second layer 20. Preferably, the hot-melt material is a thermoplastic, such as PP or PET, or a thermoplastic elastomer (TPE).

[0036] Figure 2 shows that the interlayer 30 can comprise a sublayer 31 and a skin 32. The sublayer 31 can be made of a thermoplastic elastomer material, chemically compatible with the second layer 20. The skin 32 can be made of a hot-melt material, chemically compatible with the first layer 10. The sublayer 31 is configured to face the second layer 20 while the skin 32 is configured to face the first layer 10.

[0037] Alternatively, the underlayer 31 can be made of elastomeric material, for example ethylene-propylene-diene monomer (EPDM).

[0038] The skin 32 can have a significantly higher density than the first layer 10. This allows for a local weight reduction and also facilitates easier adhesion between the first layer 10 and subsequent layers. For example, the skin 32 can be made of a non-woven material. The skin 32 can be made of PP or PET.

[0039] Taken individually, the sublayer 31 and the skin 32 in the intercalary layer 30 can have different surface masses.

[0040] Preferably, the sublayer 31 has a surface mass approximately between 0.3 kg / m 2 and 2 kg / m 2 , and more preferably between 0.5 and 0.8 kg / m 2 .

[0041] Preferably, the underlayer 31 has a thickness between 0.3 mm and 2 mm.

[0042] Skin 32, on the other hand, preferably has a surface mass approximately between 0.03 kg / m 2 and 0.2 kg / m 2 , and preferably approximately between 0.04 and 0.08 kg / m 2 .

[0043] Preferably, skin 32 has a thickness between 0.2 mm and 1 mm, and preferably between 0.4 mm and 0.7 mm.

[0044] In the examples in Figures 1 and 2, to secure the different layers together, the first layer 10, the second layer 20, and the intermediate layer 30 can be joined by at least one localized weld point 40, preferably at least two weld points 40, as shown in Figure 4. The weld points 40 are located to ensure optimal bonding. Spot welding of the layers 10, 20, and 30 can be facilitated when the layers 10, 20, and 30 are chemically similar, in other words, compatible. This is the case, for example, with a thermoplastic felt, a heat-fusible intermediate layer, and a thermoplastic cellular material. Furthermore, spot welding has the advantage of not requiring the addition of any material to achieve the bond, since it consists of fusing the layers at a single point.

[0045] To avoid compressing the first layer 10 during spot welding, the number of weld points 40 must be kept to a minimum. Compressing the first felt layer 10 reduces its sound absorption properties. Therefore, a minimal number of weld points 40 ensures that layers 10, 20, and 30 are securely bonded together while preserving the sound absorption properties of the first layer 10.

[0046] In another embodiment, shown in Figure 3, the interlayer 30 can be made of an elastomeric material. This elastomeric material is also conformable to the first and second layers 10, 20. The elastomeric material can be made of ethylene propylene diene monomer (EPDM) or its derivatives, or a similar material.

[0047] With an elastomeric material, the interlayer 30 can be attached to the first layer 10 by a first adhesive 51 and to the second layer 20 by a second adhesive 52. The first adhesive 51 and / or the second adhesive 52 can be in the form of a layer, a strip, or localized dots. The first adhesive 51 and the second adhesive 52 can be of the same type. In some cases, the elastomeric interlayer 30 can be welded to the other layers.

[0048] When the interlayer 30 is made of or comprises an elastomeric material, such as the sublayer 31 of Figure 2, the elastomeric material is fixed to the adjacent layers by adhesives 51, 52.

[0049] With reference to Figure 4, the device 200 comprises a first layer 10, a second layer 20 and an intercalary layer 30 as described above.

[0050] In device 200, the second layer 20 forms a shell 20'. The shell 20' is intended to receive the noise-generating equipment 2 which may be, without limitation, a compressor, an electric motor or any other auxiliary noise-generating component in a motor vehicle.

[0051] The 20' hull can comprise at least two parts 21, 22.

[0052] Advantageously, the 20' shell is monobloc, meaning it is formed from a single piece. The two parts 21 and 22 are then connected to each other. These two parts 21 and 22 can be joined by a hinge 24. It is understood that the hinge 24 is an integral part of the 20' shell. This facilitates the installation or removal of the device around the equipment 2.

[0053] Alternatively, the two parts 21, 22 of the hull can be distinct from each other.

[0054] To keep the 20' hull closed, the 200 device is equipped with at least one locking system to keep the device closed around the noise generator equipment.

[0055] In this configuration, the intermediate layer 30 and the first layer 10 are placed in the shell 20' and fixed to the second layer 20. In the example shown in Figure 5, two weld points 40 allow a piece of the first layer 10 to be fixed to the other layers in part 22 of the shell 20', while another piece of the first layer 10 is fixed to the other layers in a similar way in part 21 of the shell 20'.

[0056] In this example, the first layer 10 is cut to conform to the shape taken by the hull 20', i.e. the second layer 20. Depending on the shape adopted by the hull 20', the first layer 10 can be cut into several separate sections within the same part 21, 22 of the hull 20'.

[0057] It should also be noted that the materials used for device 100, 100', 200 also meet other criteria such as resistance to liquids, corrosion resistance, and low thermal conductivity. These criteria are required to protect equipment 2 inside device 100, 100', 200.

[0058] The manufacturing process of the acoustic absorption device 100, 100', 200 as described above is briefly described below.

[0059] First, the second layer 20, made of plastic honeycomb material, is thermoformed to adopt a predetermined shape. This predetermined shape corresponds approximately to the shape of the noise-generating equipment 2.

[0060] The first 10-layer non-woven felt is cut from a tablecloth according to a predefined pattern.

[0061] The interlayer layer 30 is cut according to a predefined shape.

[0062] The interlayer 30 is installed on / in the second thermoformed layer 20 and then the first layer 10 is installed so that it covers the interlayer 30.

[0063] The first layer 10, the second layer 20, and the intermediate layer are then bonded together. This bonding can be achieved by an adhesive or by at least one weld point as described previously.

[0064] The sound absorption device is then mounted around a noise-generating equipment 2 so that the first layer 10 is facing and / or in contact with an external surface 4 of the noise-generating equipment 2.

[0065] Comparative test:

[0066] We now refer to Figure 5, which shows a comparison of the evolution of the gain Aw in decibels (dB) as a function of frequency, in Hertz (Hz), for an existing acoustic absorption device (symbol triangle and dashed line) and an acoustic absorption device according to the invention (symbol circle and solid line). It should be noted that the x-axis is on a logarithmic scale. Gain Aw in decibels is understood to be the difference between a measurement taken without the acoustic absorption device, i.e., with the noise-generating equipment alone, and a measurement taken with the acoustic absorption device mounted around the noise-generating equipment.

[0067] The existing acoustic absorption device, also called the reference, is a device made of a single layer of a cellular material made of polyurethane (PU) with a thickness between 10 and 20 mm. This reference device therefore has a mass of approximately 514 grams.

[0068] The sound-absorbing device according to the invention is as described above. In particular, the device, denoted E1, comprises a first layer 10 of 10 mm thick PET felt, a second layer 20 of 3 mm thick PP cellular material, and an interlayer 30 of EPDM elastomer. The PET felt layer 10 has a surface mass of approximately 455 g / m². 2 , layer 20 of PP cellular material has a surface mass approximately equal to 450 g / m 2 and the elastomer interlayer 30 has a surface mass approximately equal to 630 g / m² 2This E1 device then has a total mass of approximately 275 grams.

[0069] Thus, it appears that the device according to the invention exhibits acoustic performance similar to the reference device, particularly from approximately 1.6 kHz towards higher frequencies where the average gain is approximately 9 dB. The acoustic performance is therefore similar, and this is achieved with a significantly lower mass for the device according to the invention.

[0070] The invention also relates to an ENS assembly, represented very schematically by Figure 6, comprising an acoustic absorption device 100, 100', 200 as described above and a noise-generating equipment 2, such as a compressor or an electric motor, of a motor vehicle.

[0071] The invention also relates to a motor vehicle comprising at least one sound-absorbing device as described above. The motor vehicle may comprise at least one sound-absorbing system as described previously.

[0072] In light of the foregoing, the invention offers the advantage of reducing the weight of the sound-absorbing device while maintaining acoustic performance similar to that of the prior art. Indeed, the cellular materials and felts are porous materials that contribute to reducing the device's mass. This mass reduction is offset by the interlayer, which, combined with the two other layers—felt and plastic cellular material—enables acoustic performance similar to that of pre-existing devices. Furthermore, the cellular material and felt possess acoustic properties that enhance sound absorption in the high frequencies.

[0073] Another advantage of using honeycomb material and felt is the flexibility it gives the product. This makes it easier to mount on the compressor and compensate for any existing play.

[0074] Another advantage of the invention, particularly when the felt is made of PET and / or the cellular material is made of PET, PP or PA, is to improve the recyclability of the device, and therefore reduce its environmental impact.

Claims

Demands [1] Sound-absorbing device (100, 100', 200) for noise-generating equipment (2) of a motor vehicle, said device comprising at least: a first layer (10) configured to face and / or be in contact with an external surface (4) of said equipment (2), said first layer (10) being a non-woven felt; a second layer (20) covering the first layer, said second layer (20) being a plastic cellular material; and an intercalated layer (30, 31, 32) ensuring the link between the first layer (10) and the second layer (20), characterized in that the intercalated layer (30) is made of an elastomeric material. [2] Device (100, 100', 200) according to claim 1, wherein the interlayer (30) is fixed on the one hand to the first layer (10) by a first adhesive (51) and to the second layer (20) by a second adhesive (52) on the other hand. [3] Sound-absorbing device (100, 100', 200) (100, 100', 200) for noise-generating equipment (2) of a motor vehicle, said device comprising at least: a first layer (10) configured to face and / or be in contact with an external surface (4) of said equipment (2), said first layer (10) being a non-woven felt; a second layer (20) covering the first layer, said second layer (20) being a plastic cellular material; and an intercalated layer (30) ensuring the link between the first layer (10) and the second layer (20), characterized in that said intercalated layer (30) comprises: a skin (32) which is made of a thermofusible material, chemically compatible with the first layer (10), and a sub-layer (31) which is made of a thermoplastic elastomeric material, chemically compatible with the second layer (20), or of an elastomeric material.[4] Device (100', 200) of claim 3, wherein the first layer (10), the second layer (20) and the interlayer layer (30) of hot melt material are fixed together by at least one weld point (40). [5] Device (100, 100', 200) according to any one of claims 1 to 4, wherein said interlayer (30) has a surface mass between 0.03 kg / m 2 and 2 kg / m 2 . [6] Device (100, 100', 200) according to any one of claims 1 to 5, wherein said interlayer (30) extends partly over a surface of the first layer (10) and / or partly over a surface of the second layer (20). [7] Device (100, 100', 200) according to any one of claims 1 to 6, wherein the non-woven felt is made with polyethylene terephthalate (PET) fibers. [8] Device (100, 100', 200) according to any one of claims 1 to 7, wherein the first layer (10) has open cells. [9] Device (100, 100', 200) according to any one of claims 1 to 8, wherein the second layer (20) of alveolar material comprises closed cells. [10] Device (100, 100', 200) according to any one of claims 1 to 9, wherein the plastic cellular material is a polyolefin, for example a polypropylene (PP), a polyamide (PA) or a polyethylene terephthalate (PET). [11] Device (100, 100', 200) according to any one of claims 1 to 10, wherein the second layer forms a shell (20') intended to receive said noise-generating equipment (2), said shell (20') comprising at least two separate parts (21, 22). [12] Device (100, 100', 200) according to any one of claims 1 to 10, wherein the second layer forms a one-piece shell (20') for receiving said noise-generating equipment (2), said shell (20') comprising at least two interconnected parts (21, 22). [13] Assembly (AEA) comprising a device (100, 100', 200) according to any one of claims 1 to 12 and noise-generating equipment (2), such as a compressor or an electric motor, of a motor vehicle. [14] Motor vehicle comprising at least one sound-absorbing device (100, 100', 200) according to any one of claims 1 to 12 or at least one assembly (ENS) according to claim 13.

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