ACOUSTIC PROTECTION SYSTEM FOR A MOTOR VEHICLE

The invention relates to an An acoustic protection system for a motor vehicle has two walls extending opposite each other; an elastically compressible acoustic decoupling layer arranged in compression at least along its periphery between the walls, the layer having two opposing faces pressed respectively against each of the walls, the faces being connected to each other by an edge, the layer being enclosed in a bag made from plastic film closed so as to form a sealed barrier on the edge, at least one air passage hole being provided in the bag opposite at least one of the faces, the hole being arranged at a distance from the edge so as to provide, around the hole, a seal created by the bag bearing on the corresponding wall.

FIELD OF THE DISCLOSURE

The invention relates to an acoustic protection system for a motor vehicle.

BACKGROUND

It is known to produce an acoustic protection system for a motor vehicle, said system comprising:two walls extending opposite each other,an elastically compressible acoustic decoupling layer arranged in compression at least along its periphery between said walls, said layer having two opposing faces pressed respectively against each of said walls, said faces being connected to each other by an edge.

The presence of such a compressed decoupling layer makes it possible to obtain a damping effect resulting in an improvement of the treatment of the “solidborne” noise.

In addition, the fact of using a decoupling layer instead of discrete elements—such as compressible studs—not only makes it possible to produce a damping but also to improve the acoustic transparency of the whole (acoustic insulation).

Such an arrangement may particularly be implemented outside of the passenger compartment.

It then makes it possible to prevent a portion of the outside noise from being propagated inside the passenger compartment, which makes it possible to reduce the weight of the acoustic protection means usually implemented within said passenger compartment, regardless of whether they are based on insulation and/or absorption principles.

It also makes it possible to avoid, or at least reduce, the use of damping materials, for example based on bitumen (treatment sometimes known as IFF), which are usually deposited on the walls of the floor panel type.

The result of all of these options is a simplification and a weight reduction of the vehicle.

However, in some cases it is necessary, for example when the decoupling layer is close to the ground, to guarantee the non-penetration of liquids—particularly water—within said layer, and this particularly through its edge that is not protected by the walls, this in order to preserve the decoupling properties of said layer.

In addition, such a protection must be achieved while making it possible for the decoupling layer to be able to compress during its mounting within the system.

SUMMARY OF THE DISCLOSURE

The aim of the invention is to propose a system making it possible to meet these requirements.

To this end, the invention proposes an acoustic protection system for a motor vehicle, said system comprising:two walls extending opposite each other,an elastically compressible acoustic decoupling layer arranged in compression at least along its periphery between said walls, said layer having two opposing faces pressed respectively against each of said walls, said faces being connected to each other by an edge,

knowing that:said layer is enclosed in a bag made from plastic film closed so as to form a sealed barrier on said edge,at least one air passage hole is provided in said bag opposite at least one of said faces, said hole being arranged at a distance from said edge so as to provide around said hole a seal created by said bag bearing on said corresponding wall.

With the arrangement proposed, the decoupling layer is protected from liquids by the bag.

Furthermore, the presence of at least one hole in the bag makes it possible to evacuate a portion of the air present in the bag during the compression of the decoupling layer during its mounting within the system.

In addition, the positioning of the hole such as provided makes it possible to create a sealing around its periphery, and thus to prevent liquids from penetrating from the outside towards said hole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures, an acoustic protection system1for a motor vehicle is described, said system comprising:two walls2,3extending opposite each other,an elastically compressible acoustic decoupling layer4arranged in compression at least along its periphery between said walls, said layer having two opposing faces5,6pressed respectively against each of said walls, said faces being connected to each other by an edge7,

knowing that:said layer is enclosed in a bag8made from plastic film closed so as to form a sealed barrier on said edge,at least one—plurality according to the embodiment shown—air passage hole9is provided in said bag opposite at least one 5, 6 of said faces—only one 5 according to the embodiment shown—, said hole being arranged at a distance10from said edge so as to provide around said hole a seal11—particularly with regard to liquids coming from the outside such as water—created by said bag bearing on said corresponding wall—in this case the wall2according to the embodiment shown.

According to the embodiment shown, the decoupling layer4is compressed according to its entire surface, which makes it possible to optimise the damping effect. According to one embodiment, the hole9is arranged at a distance10of at least 20 mm from the edge7.

According to miscellaneous embodiments, the decoupling layer4is based on foam—either cut, or moulded, particularly in the case of a complex geometry—or fibrous material.

According to one embodiment, the density of the decoupling layer4is between 25 and 80 kg/m3.

According to one embodiment, the decoupling layer4is compressed by 5 to 50% in relation to its thickness in the non-compressed state, and in particular by 25 to 35%.

According to one embodiment, the compressed decoupling layer4has a thickness12between 5 and 50 mm.

According to one embodiment, the decoupling layer4has a relative compression stress-strain characteristic less than 5 kPa, and particularly less than 3 kPa, the measurement being made for an indentation of 25% of the initial thickness of the test specimen during the fourth compressive cycle, said characteristic being measured according to ISO 3386-1 standard in force on the priority date of the present application.

According to one embodiment, the decoupling layer4has a Young's modulus less than 50 kPa, particularly less than 20 kPa.

According to one embodiment, the decoupling layer4has a structural loss factor greater than 0.18, so as to have accentuated damping characteristics, at a temperature of 20° C. and at a frequency of 20 Hz.

According to the embodiment shown, the walls2,3are substantially parallel.

According to the embodiment shown, one wall3is formed by a battery pack face13—in particular for an electric vehicle—and the other wall2is formed by a floor panel of said vehicle.

According to one embodiment not shown, the walls2,3are part of a hollow metal body, said body particularly being a wing inner panel.