WO2020230176A1

WO2020230176A1 - Soundproofing cover for an engine

Info

Publication number: WO2020230176A1
Application number: PCT/IT2020/050113
Authority: WO
Inventors: Giovanni RONZONI
Original assignee: Isp S.R.L.
Priority date: 2019-05-13
Filing date: 2020-05-12
Publication date: 2020-11-19

Abstract

The present invention relates to a soundproofing cover for engine comprising a rigid or semi-rigid cover whose inner surface is coated by one or more superimposed layers of polyester fiber whose last surface opposite to the side of the cover is at least partially covered by a layer of carbon fiber; wherein the one or more superimposed layers of polyester fiber has a thickness comprised between 30 and 80 mm and a density comprised between 30 and 70 Kg/m³. The present invention also relates to the use of one or more superimposed layers of polyester fiber or one layer of carbon fiber for soundproofing cover for engine.

Description

SOUNDPROOFING COVER FOR AN ENGINE

Description

Technical field

[0001] The present invention relates to efficient soundproofing covers for engines, in particular, for vehicle engines, for example car engines. Furthermore, it also relates to the process for the manufacture of said covers and to the particular material used for the same and the use thereof.

Prior Art

[0002] Due to the continuous world population growth, industrial development, as well as the development of emerging market economies in crowded territories, an increase of both air pollution level and noise pollution in cities recently occurred, specifically in big metropolises.

[0003] In order to face the noise pollution increase, several measures were involved, such as, for example, the installation of sound-absorbing panels along streets and motorways, rather than the recent introduction of electric cars that, unlike traditional combustion engine, emits very lower noise levels.

[0004] Indeed, one of the successful strategies is to develop engines, particularly engines for vehicles, such as motor-vehicles, motorcycles, three-wheeler vans, etc., with low noise emission.

[0005] Vehicle engines, today on the market, have a cover, in which said cover, through one layer of expanded polyurethane (PUR), allows to attenuate the noise emitted by the engine.

[0006] However, the results today available for this technology are not optimal and, therefore, it is still looking for more efficient systems for the abatement, or for the soundproofing, of engines, in particular for the soundproofing of combustion engines, therefore, for example, for car engines, motorcycles and other vehicles.

[0007] The patent publication EP2860294A1 discloses a car soundproofing cover comprising a fibrous-shaped article that includes two or more types of fibers, the fibrous formed article including 50 to 80 mass% of organic fibers, 10 to 40 mass% of flame retardant-containing fibers (see par. [0014]). The coating material 2 is provided on the outer surface of the automotive soundproofing cover and may be a nonwoven fabric or a woven fabric formed by organic fibers or inorganic fibers (see par. [0098]). An inner surface 3 of the soundproofing cover 1 is positioned opposite to the engine and may be covered with a scale clay mineral using a binder (see par. [0102]).

[0008] The patent publication GB2265569A discloses an heat and sound insulating cowling for engines of motor-vehicles which comprises a plurality of layers wherein the absorption layer 2 consists of 94% vol. of mineral fibers and 6% vol of phenolic resin (see pag. 4), a support layer 3 consisting of glass fibers, mineral filler and binder (see pag. 4), a top layer 4 of carbon fibers having a thickness of 1 to 2 mm and a weight per unit area of 100 to 150 g/m² (see pag. 5) a top layer 5 having a layer thickness of about 1 mm and a weight per unit area of 100 to 150 g/m², which consists of a nonwoven polyester or polyacrylonitrile fibers (see pag. 5).

The patent publication US20100081354A1 discloses a multi-layered article comprising a layer of regenerated PET.

Summary of the invention

[0009] Therefore, the problem addressed by the present invention is to provide a device adapted to reduce engine-generated noise, particularly vehicle engines, and, more particularly combustion engines of cars.

[0010] In the case of combustion engines, it is necessary to consider an additional problem related to high-operating temperature resistance.

[0011] Such problem is solved by the soundproofing device of the present invention, as outlined by the attached claims, whose definitions are integral part of the present description.

[0012] Particularly, an object of the invention is a soundproofing cover for engine consisting of one or more layers of material that, due to its inherent characteristics and the way in which it is used and combined, allows to reduce the engine generated noise emissions.

[0013] Another object is the process for the manufacture of said soundproofing covers and, finally, the use of said specific material for the manufacture of soundproofing covers for engines.

[0014] Further characteristics and advantages of the cover of the invention will be evident from the description of the embodiment of the invention, provided as an indication of the invention.

Brief description of the drawings [0015] FIG. 1 -a shows the inner layer of a cover for engine, which is free of inner coating, or of the heat protection, made of metal material.

[0016] FIG.1 -b shows the upper part, or the outer layer, of a cover for engine, made of plastic material.

[0017] FIG. 2 shows an engine cover, whose inside is coated by a layer of expanded polyurethane (abbreviated PUR) (cover NP).

[0018] FIG. 3 shows a cover for engine, whose inside is coated by a layer of polyester fibers having a thickness of 20 mm and a part of which is covered by a layer of carbon fiber arranged on the zone subjected to the greater heat of the engine (cover 1 ).

[0019] FIG. 4 shows a cover for engine, whose inside is coated by a layer of polyester fibers having a thickness of 20 mm, which is totally covered by a layer of carbon fiber (cover 2).

[0020] FIG. 5-a shows the comparison of the noise emissions which are emitted by an engine covered with a traditional cover, coated by a layer of expanded polyurethane (cover NP), and the same cover coated by a layer of polyester fiber having a thickness of 20 mm, then partially covered by one layer of carbon fiber (cover 1 ), and another cover, then totally covered by one layer of carbon fiber (cover 2).

[0021] FIG. 6-a and FIG. 6-b show the comparison of the noise emissions emitted by an engine covered with a traditional cover, coated by one layer of expanded polyurethane (PUR) (cover NP), and the same cover coated by a layer of polyester fiber having a thickness of 40 mm and a density of 40 Kg/m³, then partially covered by a layer of carbon fiber (cover 1 ), and another cover, then totally covered by a layer of carbon fiber (cover 2).

[0022] In FIG. 6-b, the noise emission of the soundproofing covers for engine, at maximum rpm or full acceleration, is measured. Particularly, the test is performed with uphill car and at the maximum rpm and then at the maximum presumable noise and temperature.

Detailed description of the invention

[0023] An object of the present invention is a soundproofing cover for engine comprising a rigid or semi-rigid cover whose inner surface is covered by one or more superimposed layers of polyester fiber whose last surface opposite to the side of the cover is at least partially covered by a layer of carbon fiber; wherein the one or more superimposed layers of polyester fiber has a thickness comprised between 30 and 80 mm and a density comprised between 30 and 70 Kg/m³.

[0024] Particularly, with reference to fig. 1 a and 1 b, it can be observed the cover for engine wholly indicated with the reference number 1 , object of the present invention.

[0025] With refe re nce also to fig. 2, it can be observed an embodiment of the cover for engine 1’ (also“cover IMP”), the interior of which is coated by one layer 2’ of expanded polyurethane (abbreviated PUR), delimited in dashed lines for clarity. Said layer 2' is suitably shaped, so as to protect the various parts of the engine (the latter not shown in the figures), and in particular to encapsulate the injection system. At the bottom there is also a metal sheet 3' arranged on the hot area, for dissipative purposes.

[0026] With reference now to fig. 3, it is observed a further embodiment of the cover 1” for engine (also“cover 1”), the interior of which in such case is coated by a layer 2” of polyester fiber, always suitable shaped to coat particularly, but not exclusively, the injection system (also in such case not shown in the figures), having in the embodiment at issue a thickness of 20 mm, and a layer 3”, covered by a layer of carbon fiber (or, also Preox), positioned on the zone subjected to the greater heat of the engine.

[0027] At last, with reference now to fig. 4, a further embodiment of cover 1’” (also“cover 2”) for engine, which has a layer oriented towards the inside made of polyester and an outer layer made of carbon fiber (or Preox), the interior of which in this case has an inner layer of polyester and an outer layer of carbon fiber or, as said above, also Preox.

[0028] The soundproofing cover for engine of the present invention can be applied to any kind of engine, for example combustion engine, electric engine, naval engines, etc.; preferably, the soundproofing cover is for combustion engine.

[0029] The soundproofing cover for engine can also be defined as thermo acoustic cover for engine.

[0030] The combustion engine can be used on vehicles, for example on motor- vehicles, cars, motorcycles, three-wheeler vans, trucks, etc., on crafts, aircrafts, etc..

[0031] According to a preferred embodiment the soundproofing cover for engine is applied on motor-vehicle engines, and even more preferably, on car engine. [0032] According to a preferred embodiment, the soundproofing cover for engine is applied on combustion engines of motor-vehicles, and even more preferably, on car engine.

[0033] Indeed, it was surprisingly found that, only by using one or more superimposed layers of polyester fiber having a total thickness comprised between 30 and 80 mm and having a density comprised between 30 and 70 Kg/m³, a marked engine soundproofing is obtained, which is better than that obtained by a traditional cover for engine having a layer of expanded polyurethane.

[0034] Indeed, if polyester fibers having densities lower than 30 Kg/m³ are used, the effect of the invention, or the best engine soundproofing, at least compared to the traditional cover of expanded polyurethane, is not obtained.

[0035] On the other hand, polyester fibers having a density higher than 70 Kg/m³ are not suitable for this kind of applications.

[0036] As parameter, density or the specific weight of the layer or layers of polyester fibers of the invention is the more critical, while the thickness has the lower effect on performances in terms of engine soundproofing. However, the combination, i.e. the space delimited by these two parameters, is that within the soundproofing effect of the cover of the invention occurs.

[0037] According to a preferred embodiment, the soundproofing cover has one or more superimposed layers of polyester fiber having a density comprised between 30 and 50 Kg/m³, even more preferably having a density of 40 Kg/m³.

[0038] The soundproofing cover has one or more superimposed layers of polyester fiber having a total thickness comprised between 30 and 80 mm. The thickness to which reference is made, also hereinafter, is always referred to the total thickness of the layer or superimposed layers of polyester fiber. In fact, the thickness of the layer or layers of polyester fibers can be made with only one layer of polyester fibers or two or more layers of polyester. Preferably, the thickness of the layers of polyester fibers of the invention is made by two layers of polyester fibers.

[0039] According to an even more preferred embodiment, the thickness of the layers of polyester fiber of the invention is made with one layer having a thickness of 20 mm in addition to a second layer having a thickness comprised between 10 and 60 mm, more preferably the second layer of polyester fiber having a thickness comprised between 20 and 50 mm. According to an even more preferred embodiment, the one or more superimposed layers of polyester fiber having a (total) thickness comprised between 30 and 80 mm, are manufactured by a layer of polyester fiber having a thickness of 20 mm, which is superimposed by a layer of polyester fiber having a thickness of 20 mm or 50 mm.

[0040] Therefore, according to a preferred embodiment, the soundproofing cover has one or more superimposed layers of polyester fiber having a thickness comprised between 40 and 70 mm.

[0041] According to a preferred embodiment, the polyester fiber has a thickness comprised between 40 and 70 mm and a density comprised between 30 and 50 Kg/m³.

[0042] According to an even more preferred embodiment, the soundproofing cover has one or more superimposed layers of polyester fiber having a thickness comprised between 40 and 70 mm, which is manufactured by a layer of polyester fiber having a thickness of 20 mm, superimposed by a layer of polyester fiber having a thickness comprised between 20 and 50 mm.

[0043] According to a preferred embodiment, the soundproofing cover has one or more superimposed layers of polyester fiber having a thickness of 40 mm and a density of 40 Kg/m³, or has a thickness of 60 mm and a density of 30 Kg/m³.

[0044] According to a preferred embodiment, the soundproofing cover has two superimposed layers of polyester fiber each having a thickness of 20 mm, thus making a total thickness of 40 mm and a density of 40 Kg/m³.

[0045] According to a preferred alternative embodiment, the soundproofing cover has a layer of polyester fiber having a thickness of 60 mm and a density of 30 Kg/m³.

[0046] The one or more superimposed layers of polyester fiber consist of polyester fibers or contain only fibers consisting of polyester, thus excluding other materials, such as, for example, polyurethanes or polyesters-polyurethane. Therefore, the one or more superimposed layers of polyester fibers consist of polyesters 100% (weight/weight).

[0047] The polyesters constituting fibers of the layer or layers of polyester fiber of the invention are compounds obtained by condensation reaction of dicarboxylic acids with bi-alcohols, or diols, thus obtaining alkyl, aryl or alkyl-aryl chains, separated by ester bonds. The polyester fibers of the invention, therefore, contain only ester functional groups, and end-chain hydroxyl or carboxyl functions. Carbamate, urea and urea-carbamate groups are thus excluded. Therefore, the polyesters of the invention differs from polyurethane-polyesters due to the absence of carbamate-function.

[0048] According to a preferred embodiment of the invention, the one or more superimposed layers of polyester fiber consist of polyethylenterephtalate fiber.

[0049] The polyethylenterephtalate (PET) is a polyester used to obtain plastic bottles e containers for food and beverage packaging.

[0050] The polyethylenterephtalate is a thermoplastic polymer of polycondensation of linear type, which is obtained starting from 1 ,4- benzendicarboxylic acid known as terephthalic acid and 1 ,2-ethanediol known as ethylene glycol.

[0051] PET is classified as a semi-crystalline polymer and, when heated above 72 °C, corresponding to the glass transition temperature, passes from a glass-like rigid state to an elastic and rubbery form in which the polymer chain can be elongated and aligned in only one direction to form fibers of in two directions to form films.

[0052] If the polymer is subjected to stretching and remains at a temperature above 72 °C, it crystallizes and starts to become opaque, more rigid and less flexible. This form known as crystalline PET or cPET, which is capable of resisting to the highest temperatures.

[0053] According to a preferred embodiment of the invention, the one or more superimposed layers of polyester fiber consist of polyethylenterephtalate fibers for high temperatures.

[0054] According to a preferred embodiment of the invention, the one or more superimposed layers of polyester fiber consist of polyethylenterephtalate fibers, which are thermo-linked and without gluing agents. Thermo-linked means that fibers are bound from each other by only heat treatment, or without the addition of any binding agent, such as glue or adhesives.

[0055] According to an even more preferred embodiment of the invention, the one or more superimposed layers of polyester fiber consist of polyethylenterephtalate fibers for high temperatures, which are thermo-linked and without gluing agents. [0056] According to a preferred embodiment of the invention, the one or more superimposed layers of polyester fiber consist of fibers of polyethylenterephtalate having a melting temperature of 246 °C and/or crystallization temperature of 194 °C.

[0057] The soundproofing cover of the invention has a layer of carbon fiber. Said layer of carbon fiber, can consist only of oxidized polyacrylonitrile (abbreviated PANOX^® or PREOX) or mixtures of oxidized polyacrylonitrile and carbon fiber. Optionally said layer of carbon fiber, in addition to the oxidized polyacrylonitrile or the mixture of oxidized polyacrylonitrile and carbon fiber, can comprise other components. Said layer of carbon fiber can be prepared by partial or total oxidation of polyacrylonitrile (abbreviated PAN; chemical formula C₃H₃N and structural formula (-CH₂-CH(CN)-)n), and, depending on the oxidation degree, therefore it can consist only of oxidized polyacrylonitrile or mixtures of carbon fiber and oxidized polyacrylonitrile. Therefore, when carbon fiber is cited hereinafter, the term carbon fiber means, therefore, the oxidized polyacrylonitrile or its mixtures with carbon fiber. Therefore, the term layer of carbon fiber consisting of carbon fiber 100% (weight/weight), should be intended as one layer consisting of 100% (weight/weight) of oxidized polyacrylonitrile or all the possible mixtures of oxidized polyacrylonitrile and carbon fiber.

[0058] Since polyacrylonitrile contains nitrogen (chemical formula C₃H₃N), the layer of carbon fibers, by definition cannot be only a layer of carbon fibers but, it is instead a layer of oxidized polyacrylonitrile or a layer of mixtures of oxidized polyacrylonitrile and carbon fibers or a layer of mixtures of oxidized polyacrylonitrile and other components, such as glass, glass wool or amorphous silica and their combinations.

[0059] The layer of carbon fiber, therefore, can optionally comprise other components, such as, for example, glass, glass wool or amorphous silica.

[0060] According to a preferred embodiment of the invention, the layer of carbon fiber comprises at least 90% (weight/weight) of oxidized polyacrylonitrile and the remaining 10% can be carbon fiber or other components, then excluding any amount of carbon fiber.

[0061] According to a more preferred embodiment of the invention, the layer of carbon fiber comprises at least 90% (peso/peso) of oxidized polyacrylonitrile and the remaining 10% consists of other components, excluding the carbon fiber. Said other components can be, for example, glass, glass wool, amorphous silica, and resins or binders being excluded. [0062] According to a preferred embodiment of the invention, the layer of carbon fiber comprises at least 90% (weight/weight) of oxidized polyacrylonitrile and the remaining 10% consists of glass, glass wool or amorphous silica, and mixtures thereof.

[0063] According to a preferred embodiment, the layer of carbon fiber consists of oxidized polyacrylonitrile.

According to an more preferred embodiment of the invention, the layer of carbon fiber consists of 100% (weight/weight) of oxidized polyacrylonitrile, and then not comprising resins. When in combination with the layer/layers of polyester fiber of the invention, it provides the best performances both in terms of soundproofing and heat resistance. In such a case, the layer of carbon fibers is a layer of oxidized polyacrylonitrile. Thus, the cover of the invention includes a layer of oxidized polyacrylonitrile. Such effects also apply to the layer of carbon fibers comprising at least 90% (weight/weight) of oxidized polyacrylonitrile. Preferably, the layer of carbon fibers provides indeed heat resistance to the soundproofing cover. Preferably, the layer of carbon fibers can be a nonwoven fabric or a woven fabric.

[0064] The soundproofing cover of the invention has one layer of carbon fiber partially or totally covering the surface of the layer or the last layer of the polyester fiber surface opposite to the rigid or semi-rigid cover.

[0065] According to a preferred embodiment, the layer of carbon fiber covers only partially the layer of polyester fiber.

[0066] According to an even more preferred embodiment, the soundproofing cover has the layer of carbon fiber positioned on the hot zone of the engine.

[0067] According to an alternative embodiment, the layer of carbon fiber totally covers the layer of polyester fiber. Or, in the soundproofing cover for engines the inner surface can be coated by one or more superimposed layers of polyester fiber whose last surface opposite to the side of the cover is totally covered by a layer of carbon fiber.

[0068] Preferably, the layer of carbon fiber has a thickness comprised between 4 and 10 mm.

[0069] Preferably, the layer of carbon fiber has a density comprised between 80 and 300 Kg/m³.

[0070] The layer of carbon fiber has a thickness comprised between 4 and 10 mm and a density comprised between 80 and 300 Kg/m³. [0071] According to a preferred embodiment, the layer of carbon fiber has a thickness comprised between 4 and 10 mm and a density comprised between 80 and 120 Kg/m³.

[0072] According to a preferred embodiment, the layer of carbon fiber has carbon fibers having a diameter comprised between 12 and 15 microns.

[0073] According to a more preferred embodiment, the layer of carbon fiber has a thickness comprised between 4 and 10 mm, a density comprised between 80 and 120 Kg/m³ and carbon fibers having a diameter comprised between 12 and 15 microns.

[0074] According to an even more preferred embodiment, the layer of carbon fiber has a thickness comprised between 4 and 10 mm, a density comprised between 80 and 120 Kg/m³, carbon fibers having a diameter comprised between 12 and 15 microns, and it consists of carbon fiber 100% (weight/weight). Such layer, in fact, in combination with the layer/layers of polyester fiber of the invention generally provides the best performances both in terms of acoustic soundproofing and heat resistance.

[0075] The soundproofing cover of the present invention comprises a rigid or semi-rigid cover. Said cover can be of a substantially-flat form, or having a substantially-flat form, or alternatively it can have concave form, convex form, it can have a three-dimensional structure and then having a cube-shaped form, prismoid-shaped form or parallelepiped-shaped form. Said cover, in whatever form, can have holes, for example for the passage of engine feed tubes, for the exhaust, or for the fastening elements.

[0076] According to a preferred embodiment, the soundproofing cover has a substantially-flat form.

[0077] The soundproofing cover of the present invention comprises a rigid or semi-rigid cover, therefore it can be made of metal, metal alloys, plastic material, rigid or semi-rigid plastic material, honeycomb plastic, glass-plastic such those generally known and used in the automotive industry.

[0078] According to a preferred embodiment, the soundproofing cover is made of plastic material.

[0079] According to an even more preferred embodiment, the soundproofing cover is made of plastic material and has a substantially flat form. [0080] Optionally, the soundproofing cover can further comprise grommet separators and/or fastening elements.

[0081] The cover of the present invention, as well as ensuring a better soundproofing, provides better performances in terms of heat resistance compared to the current soundproofing covers covered with a layer of expanded polyurethane.

[0082] The following table summarizes the aspect related to heat resistance:

[0083] Therefore, the cover according to the invention has a peak temperature

(^qC) at the heat test, which is higher compared to covers having the layer of expanded polyurethane currently on the market.

[0084] A further improvement of the heat resistance is carried out through the layer of carbon fiber, which is preferably positioned in the hottest zone of the engine.

[0085] In the traditional covers, having a cover of expanded polyurethane, a metal sheet is positioned in the hottest zone of the engine (see fig. 2), also to thermally protect the layer of polyurethane. The replacement of the metal sheet with the layer of carbon fiber of the invention, also leads to an improvement of the cover heat resistance as the temperature detected on the polyester layer is lower compared to the use of the metal sheet.

[0086] Another object is a process for the manufacture of the above soundproofing cover comprising the following steps:

[0087] a) coating the inner surface of the rigid or semi-rigid cover with one or more superimposed layers of polyester fiber, [0088] b) covering at least partially the surface of the one or more superimposed layers of polyester fiber, the last surface opposite to the side of the covering, with a layer of carbon fiber,

[0089] c) optionally, inserting grommet separators and/or fixing elements;

[0090] wherein the one or more superimposed layers of polyester fiber has a thickness comprised between 30 and 80 mm and a density comprised between 30 and 70 Kg/m³.

[0091] The step a) of coating the inner surface of the rigid or semi-rigid cover with one or more superimposed layers of polyester fiber, can be carried out by gluing the layer(s) of polyester fiber, of die-cut polyester fiber, or by insertion of fastening elements, such as, by way of example only, screws and bolts or starlook such as, for example, cross round screw. The coating of the rigid or semi-rigid cover can be alternatively made by gluing, for example with vinyl or acrylic aqueous dispersions.

[0092] The step b) of covering, at least partially, the surface of the layer of polyester fiber or, in the case of more superimposed layers of polyester fiber, of the last surface opposite to the side of the cover, with a layer of carbon fiber, can be carried out by gluing or by the application of specific fastening means, according the same modes already described for step a).

[0093] The optional step c), is carried out by simple application of fastening elements and therefore, for example, by making holes on the surface of the cover or on the surface of the layers and by inserting the fastening elements, for example screws fixed on the opposite side by bolts.

[0094] Another object is the polyester fiber having a thickness comprised between 30 and 80 mm and having a density comprised between 30 and 70 Kg/m³. Therefore, said fiber is the intermediate constituent, which allows to make the soundproofing cover of the invention.

[0095] According to a preferred embodiment, the polyester fiber has a thickness comprised between 40 and 70 mm and has a density comprised between 30 and 50 Kg/m³.

[0096] According to an even more preferred embodiment, the polyester fiber has a thickness comprised between 40 and 70 mm and has a density comprised between 30 and 50 Kg/m³ and the polyester fiber is polyethylenterephtalate fiber. [0097] At last, another object is the use of one or more superimposed layers of polyester fiber having a thickness comprised between 30 and 80 mm and having a density comprised between 30 and 70 Kg/m³ for soundproofing cover for engine.

[0098] According to a preferred embodiment, the use for soundproofing cover for engine, wherein the polyester fiber is polyethylenterephtalate fiber, is preferred.

[0099] Another object relates to the use of a layer of carbon fiber comprising at least 90% (weight/weight) of oxidized polyacrylonitrile or consisting of 100% (weight/weight) of oxidized polyacrylonitrile for soundproofing cover for engine.

[00100] According to a preferred embodiment, the layer of carbon fiber has a thickness comprised between 4 and 10 mm and has a density comprised between 80 and 300 Kg/m³ or between 80 and 120 Kg/m³.

[00101] According to another preferred embodiment, the layer of carbon fiber has any one or more features described in the paragraphs above, with reference to the layer of carbon fiber.

EXPERIMENTAL PART

[00102] The layer of polyester fiber having the characteristics of the invention can be found on the market, from the day of the publication of the present patent application, at ISP Sri, Ciserano (BG), Italy, under the product name PM FELT HM and product code 307-7.

[00103] The layer of carbon fiber having the characteristics of the invention, can be found on the market, for example at ISP Sri, Ciserano (BG), Italy, under the product name PREOX FELT and product code 313, or PREOX FIT and product code 316, or PREOX HTE 317.

Example 1

[00104] A cover for engine of plastic material is illustrated in fig. 1 -b was coated with a layer of polyester fiber having a thickness of 20 mm. Said layer of polyester fiber was then partially coated, superimposing a layer of carbon fiber. The layers was then fixed by specific fastening means thus manufacturing the cover for engine illustrated in fig. 3 (cover 1 ).

[00105] Another cover for engine in plastic material is illustrated in fig. 1 -b is coated with a layer of polyester fiber having a thickness of 20 mm. Said layer of polyester fiber was then totally coated, by entirely superimposing it by one layer of carbon fiber. The layers are then fixed by specific fastening means thus manufacturing the cover for engine illustrated in fig. 4 (cover 2). [00106] Fig. 5-a highlights that there is no difference, in terms of acoustic abatement of a car engine, between coverl (cover 1 ) and cover 2 (cover 2) (fig. 3 and fig. 4), both manufactured with one layer of polyester fiber having a thickness of 20 mm. Therefore, the total or partial cover of the layer of polyester fiber with the layer of carbon fiber has not influence on the reduction of the engine noise emission.

Example 2

[00107] 5 covers for engine was manufactured through the same process of manufacturing of the covers of example 1 and they were subjected to acoustic soundproofing tests on a car engine. Two superimposed layers of polyester fiber having a specified thickness in the specific column were used in the first 4 covers.

[00108] The following table summarizes the results obtained:

[00109] Where

X = efficiency on the quality of the steady state sound noise (Kl - Konfort Insulation),

Y = acoustic efficiency on the sound radiation of the steady state engine (Decibel).

[00110] The higher the X and Y values, the better the engine soundproofing.

[00111] The covers identified in the table numbers 1 , 2, 3 are acceptable for NVH (Noise Vibration Harshness).

[00112] Therefore, the above table shows as the cover of the invention provides better results compared to both the covers with the layer of expanded polyurethane currently on the market and also compared to covers (N. 4 - comparative), wherein layers of polyesters, with density lower than that of the invention, were used. [00113] The sound frequency audible from the human ear ranges from 20 Hz to 20.000 Hz.

[00114] The cover of the present invention proved to be particularly effective in the soundproofing of acoustic frequencies comprised between 4.000 and 10.000 Hz. The cover of the present invention proved to be even more effective in the soundproofing of acoustic frequencies comprised between 4.500 and 5.500 Hz. Example 3

[00115] A cover for engine made of plastic material, as illustrated in fig. 1 -b, was coated with a layer of polyester fiber having a thickness of 40 mm and having a density of 40 Kg/m³. Said layer of polyester fiber was then partially coated, superimposing a layer of carbon fiber. The layers were then fixed by specific fastening means thus manufacturing a cover for engine similar to that illustrated in fig. 3.

[00116] Said cover of the invention was subjected to an acoustic test for soundproofing a car engine and it was directly compared to the soundproofing provided by a traditional cover having a layer of expanded polyurethane.

[00117] Figures 6-a and 6-b provide the evidence of the unequivocal soundproofing effect of the covers of the invention.

[00118] The present invention was described to be illustrative, but non-limiting, according to preferred embodiment thereof, but it is to be intended that variations and/or modifications could be made by the skilled person without departing from the related scope of protection, as defined by the appended claims.

Claims

1 . Soundproofing cover for engine comprising a rigid or semi-rigid cover whose inner surface is coated by one or more superimposed layers of polyester fiber whose last surface opposite to the side of the cover is at least partially covered by a layer of carbon fiber;

wherein the one or more superimposed layers of polyester fiber has a thickness comprised between 30 and 80 mm and a density comprised between 30 and 70 Kg/m³.

2. Soundproofing cover according to claim 1 , wherein the one or more superimposed layers of polyester fiber has a density comprised between 30 and

50 Kg/m³.

3. A soundproofing cover according to any one of claims from 1 to 2, wherein the one or more superimposed layers of polyester fiber has a thickness comprised between 40 and 70 mm.

4. Soundproofing cover according to any one of claims from 1 to 3, wherein the one or more superimposed layers of polyester fiber has a thickness of 40 mm and a density of 40 Kg/m³, or a thickness of 60 mm and a density of 30 Kg/m³.

5. Soundproofing cover according to any one of claims from 1 to 4, wherein the one or more superimposed layers of polyester fiber consist of polyethylenterephthalate fiber.

6. Soundproofing cover according to any one of claims from 1 a 5, wherein the one or more superimposed layers of polyester fiber consist of polyesters 100% (weight/weight).

7. Soundproofing cover according to any one of the claims from 1 to 6, wherein the layer of carbon fiber has a thickness comprised between 4 and 10 mm.

8. A soundproofing cover according to any one of claims from 1 to 7, wherein the layer of carbon fiber has a thickness comprised between 4 and 10 mm and has a density comprised between 80 and 300 Kg/m³ or comprised between 80 and 120 Kg/m³.

9. Soundproofing cover according to any one of claims from 1 to 8, wherein the layer of carbon fiber comprises at least 90% (weight/weight) of oxidized polyacrylonitrile or consists of 100% (weight/weight) of oxidized polyacrylonitrile.

10. Soundproofing cover according to claim 9, wherein the layer of carbon fiber comprises at least 90% (weight/weight) of oxidized polyacrylonitrile and the remaining 10% consists of other components excluding the carbon fiber.

1 1. Soundproofing cover according to any one of claims from 1 to 9, wherein the layer of carbon fiber comprises at least 90% (weight/weight) of oxidized polyacrylonitrile and the remaining 10% consists of glass, glass wool or amorphous silica, and mixtures thereof.

12. Soundproofing cover for engine according to any one of claims from 1 to 1 1 , wherein the inner surface is coated by one or more superimposed layers of polyester fiber whose last surface opposite to the side of the cover is totally covered by a layer of carbon fiber.

13. Process for the manufacture of the soundproofing cover according to any of the claims from 1 to 12 comprising the following steps:

a) coating the inner surface of the rigid or semi-rigid cover with one or more superimposed layers of polyester fiber,

b) covering at least partially the surface of the one or more superimposed layers of polyester fiber, the last surface opposite to the side of the covering, with a layer of carbon fiber,

c) optionally, inserting grommet separators and/or fixing elements;

14. Use of one or more superimposed layers of polyester fiber having a thickness comprised between 30 and 80 mm and having a density comprised between 30 and 70 Kg/m³ for soundproofing cover for engine.

15. Use of one layer of carbon fiber comprising at least 90% (weight/weight) of oxidized polyacrylonitrile or consists of 100% (weight/weight) of oxidized polyacrylonitrile for soundproofing cover for engine.

16. Use according to claim 15, wherein the layer of carbon fiber has a thickness comprised between 4 and 10 mm and has a density comprised between 80 and 300 Kg/m³ or comprised between 80 and 120 Kg/m³.