FR2870160A1 - Acoustic protection system for motor vehicle, has fiber-like material layer presenting progressive density variation so that layer has high and low average density zones for presenting mass and spring behaviors - Google Patents

Abstract

The system has a fiber-like material layer (1) presenting a progressive density variation according to its thickness. The density variation is such that the layer has a high average density zone (3) for presenting a mass behavior and a low average density zone (2) for presenting a spring behavior. The layer has charges dispersed within fibers in the form of mineral or metallic powder. Independent claims are also included for the following: (A) a method of producing a fiber-like material layer of an acoustic protection system (B) a motor vehicle liner such as carpet, fire wall or engine compartment sound damper, trunk liner or headlining, including an acoustic protection system.

Description

2870160 1

  The invention relates to an acoustic protection system, especially for a motor vehicle, a method for producing the layer of fibrous material of such a system and a motor vehicle lining comprising such a system.

  More particularly, the protection system ensures both acoustic insulation, according to the mass-spring principle, and acoustic absorption, this because of its porosity.

  It is known to produce mass-spring systems for providing sound insulation against external noise pollution. These systems include a spring-thin, elastic, elastic layer and a high density waterproof layer forming the mass of the system.

  Such systems are commonly used in motor vehicles, for example covering the floor or the deck of the vehicle, to protect the occupants against noise from the underbody or engine compartment.

  It is also known to give the high-density layer a certain porosity making it possible to provide it with acoustic absorption properties with respect to the noise that has penetrated into the passenger compartment.

  Whether the high density layer is watertight or slightly porous, the known systems provide for the separate production of the two layers which are subsequently associated with each other so as to form the mass-spring system, which corresponds to a complex manufacturing process.

  In addition, the sudden variations in acoustic impedance existing during the passage from one layer to another do not make it possible to confer on these systems optimized acoustic performances.

  The object of the invention is to overcome these disadvantages by proposing a sound protection system that is simple to implement and that has good insulating and absorbing properties.

  For this purpose, and according to a first aspect, the invention proposes an insulating and absorbent acoustic protection system, of the porous mass-spring type, said system comprising a layer of fibrous material, said layer having a progressive density variation according to its thickness. said density variation being arranged so that the layer comprises both an area of average density sufficient to essentially exhibit mass behavior and a region of lower average density having essentially a spring behavior.

  Such a system, because of the progressive density variation of the layer, has the advantage of having a progressive acoustic impedance, favorable in terms of acoustic protection. In particular, the variation of the density of the fibrous layer is arranged so that said layer has a spring mass behavior favorable to the insulation, the layer also having a porosity that promotes absorption.

  Schematically, we can consider that the area of greater average density corresponds to the upper half of the layer, while the area of lower average density corresponds to the lower half of said layer.

  Note, however, that this is only a schematization, the gradual change in density does not allow to define in the layer a physical boundary between the zones.

  The spring zone, of lower average density, is more particularly intended to be arranged against the body panels of the vehicle, and the mass zone, of higher average density, facing the passenger compartment of the vehicle.

  By the notion of progressive density variation according to the thickness, it is understood that the local density of the layer, measured in the immediate vicinity of a given point, can be approximated by a monotonic function, increasing or decreasing, of the position of said point. along an axis perpendicular to the layer.

  The proposed embodiment makes it possible to provide the expected insulation and absorption functions, the absorption being related to the porosity of the layer, with a single layer of fibrous material, which simplifies the manufacture thereof, and this with performance increased acoustic protection.

  In a first embodiment, the progressive densification is obtained by the fact that the fiber density varies progressively from one face to the other of said layer.

  The layer of fibrous material may comprise a filler dispersed within the fibers, in particular in the form of mineral, metal or thermoplastic powder (PE, filled EPDM, etc.), or in the form of flexible foam flakes.

  The presence of such a load can allow to use a lower proportion of fibers.

  In a second embodiment, the progressive densification can be achieved by gradually varying the charge density across the layer.

  The fillers, in particular thermoplastic fillers, may be secured to the fibers and / or to each other by melting said fillers.

  The layer of fibrous material may comprise at least a first and a second species of fibers, said fibers differing from each other in particular by their dimensions (length, diameter) and / or by their chemical composition and / or by their geometric shape (textured , ...) and / or by their structure (fibers with fusible sheath, ...) and / or by their specific density.

  In particular, the presence of fusible fibers may allow bonding of the layer of fibrous material after melting of said fibers, in order to allow good cohesion of the layer.

  In a third embodiment, the progressive densification can be achieved by the fact that the fiber density of the first fiber species gradually varies from one side to the other of said layer in inverse function to that of the second species. fiber.

  For all embodiments, the constituents of the fibrous material layer, in particular the fibers and / or fillers, may be derived from recycling.

  Moreover, the various embodiments can be associated with each other. By way of example, the presence of progressively distributed charges can be used to reinforce the gradual densification obtained by progressive variation of the fiber density.

  According to a second aspect, the invention proposes various methods for producing the layer of fibrous material of an acoustic protection system as defined above.

  According to a first embodiment method, the layer of fibrous material is produced according to the following steps: E Form an initial layer of fibers, É Perform a gradual densification of said layer in its thickness, so as to produce the layer of fibrous material.

  The densification step may be performed by successive needling of the fiber layer, from one of its faces, on variable fractions of its thickness, so as to achieve a gradual intermingling of the fibers between them.

  In particular, said variable fractions of the thickness of the fiber layer may vary gradually, increasing or decreasing.

  The fraction of maximum thickness subjected to needling may more particularly correspond to 100% of the total thickness of the fiber layer.

  The successive needling can be carried out according to the following steps: E Move the initial layer of fibers substantially parallel to its plane with respect to a set of notched needles arranged on at least one board parallel to said plane, É Animate the needles of a reciprocating movement substantially perpendicular to said plane so that the notches of the needles intermingle the fibers, said needles being arranged in strips extending substantially perpendicularly to the direction of movement of the layer, each of said bands comprising needles identical to each other whose positioning of the notches is arranged so as to entangle the fibers on a determined fraction of the thickness of the fiber layer, said strips being arranged between them so that said determined fraction varies from one band to another.

  In particular, said determined fraction can vary gradually, increasing or decreasing, depending on the direction of travel of the fiber layer.

  In the case, for example, of a decreasing variation, the layer of fibers is first needled by a first band of needles over all or fraction of its thickness. The second band of needles then needling on a smaller fraction. And more generally, the nth band of needles operates a needling on a fraction of less thickness than the (n-1) th band of needles.

  It will be noted that the fraction of thickness needled by the nth band of needles has already been needled by all the preceding needle strips, from the first to the (n-1) th, which gives it a degree of densification, each new needling in a given fraction resulting in densification, and thereby reduce its thickness.

  Ultimately, the layer of fibrous material has at the end of realization a variable density in a progressive manner, from one side to the other of the layer.

  It will further be noted that the needling operations have the effect of reducing the thickness of the fiber layer. This results in the need for having needles arranged to take account of this gradual decrease in thickness during the production of the layer of fibrous material.

  Moreover, despite the discontinuity existing between the needles of two successive bands, a gradual change in the density of the layer of fibrous material is obtained because of the heterogeneous nature of said material. It is not possible indeed, insofar as a sufficient number of fractions is envisaged, to distinguish different sub-layers of defined density, no boundary between layers being perceptible on the finished product.

  For example, a layer of fibrous material 20 mm thick, obtained from an initial layer of fibers 100 mm thick, may have a progressive density variation from 5 needle strips different.

  In one exemplary embodiment, the density of the layer of fibrous material varies progressively from 20 to 160 kg / m 2 from one of its faces to the other.

  In a particular embodiment, the needle strips are formed of needles all aligned with each other, the band then being reduced to a line.

  In addition, a filler may be added within the layer of fibrous material.

  The filler can be homogeneously mixed with the fibers used to make the initial layer, said filler then being homogeneously distributed in the layer of fibrous material once obtained.

  According to a second method of realization, the progressive densification can be obtained by a gradual distribution of the charge density in the layer of fibrous material, this for example according to the following steps: Sprinkle one face of the initial layer of fibers with the Charge, vibrate the layer of fibers to achieve a progressive distribution of the load in its thickness.

  When the charge has magnetic properties, the vibration step can be performed in a magnetic field arranged to promote the penetration of the charge into the initial layer of fibers.

  As an alternative, it is possible to use the electrostatic character of the charge in the presence of an electric field to achieve this result.

  A step of intermingling the fibers with each other can then be provided, for example by needling.

  It may be provided a step of heating the charged layer, in combination optionally with the step of entangling the fibers, accompanied optionally by its compression, this to improve the cohesion of the layer and to ensure its thickness.

  According to a third embodiment, when the layer comprises two species of fibers, differing in particular in their diameter, the gradual densification of the fibers may be carried out by needling carried out according to the following steps: E Move an initial layer of fibers, comprising a mixture of a first and a second kind of fibers, substantially parallel to its plane, with respect to a set of notched needles arranged on at least one board parallel to said plane, 2870160 8 É Animating the needles of a reciprocating movement substantially perpendicular to said plane so that the notches of the needles intermingle the fibers, said needles being arranged so as to perform a transfer and a gradual intermingling of the fibers of a species towards a face of the fiber layer.

  Such a selective transfer of the fibers of a species is related to their geometrical characteristics, in particular their diameter which allows their selection by the needles arranged for this purpose.

  Such an embodiment method can be combined with a charge incorporation as described above.

  According to a third aspect, the invention provides an automotive lining comprising an acoustic protection system as described above.

  Such packing may for example be in the form of a carpet associated with an acoustic protection system according to the invention, so as to form a floor mat, a soundproofing apron or trunk lining. Other types of packings may be pavilion gaskets or sound-absorbing engine compartment parts. The carpet, because of its porous nature, contributes to improving the absorption of the noise already provided by the porosity of the layer.

  Other features and advantages of the invention will appear in the description which follows, made with reference to the attached figures in which: Figure 1 is a schematic perspective view of a layer of fibrous material of a system according to invention; FIG. 2 is a schematic perspective view of a device for implementing a method for producing the layer represented in FIG. 1.

  Referring to Figure 1, there is now described a layer of fibrous material 1 included in a system according to the invention, its progressive density being schematized by the progression in the density of the dots.

  The layer has a zone 2 essentially forming the spring of a mass-spring system and a zone 3 essentially forming its mass.

  Referring to Figure 2, there is schematically described a device for implementing a method of producing the fibrous material layer io of the acoustic protection system.

  An initial layer 4 of fibers is moved, in the direction represented by the horizontal arrow, under a reciprocating needle board 5 represented by the vertical double arrow, perpendicular to the direction of travel of the layer 4.

  Needles 6 are arranged in strips 7 extending substantially perpendicularly to the direction of displacement of the layer 4, each of said bands comprising needles 6 identical to each other, the positioning of the notches is arranged so as to entangle the fibers on a determined fraction the thickness of the layer 4 of fibers.

  The strips 7 are arranged together so that said determined fraction varies in a decreasing manner from one strip 7 to the other, in the direction of travel 25 of the layer 4.

  In this way, a layer 1 of integrable fibrous material is obtained in a system according to the invention, the thickness A of the layer 1 of fibrous material being less than that B of the initial layer 4, which progressively decreases with increasing thickness. needling.

Claims (15)

  An insulating and absorbent acoustic protection system, of porous mass-bearing type, said system comprising a layer of fibrous material (1), characterized in that said layer has a progressive density variation according to its thickness, said density variation being arranged to the layer comprises both an area (3) of medium density sufficient to have substantially mass behavior and a region (2) of lower average density having essentially a spring behavior.   2. System according to claim 1, characterized in that the fiber density varies progressively from one side to the other of the layer (1).   3. System according to claim 1 or 2, characterized in that the layer (1) comprises a filler dispersed within the fibers.   4. System according to claim 3, characterized in that the charge density varies progressively from one side to the other of the layer (1).   5. System according to any one of claims 1 to 4, characterized in that the layer (1) of fibrous material comprises at least a first and a second species of fibers, said fibers differing from each other in particular by their dimensions and / or by their chemical composition and / or by their geometrical shape and / or by their structure and / or by their specific density.   6. System according to claim 5, characterized in that the fiber density of the first fiber species varies progressively from one side to the other of the layer (1) in inverse function to that of the second species of fibers.   7. A method of producing the layer of fibrous material (1) of a system according to any one of claims 1 to 6, comprising the following steps: É forming an initial layer (4) of fibers, 2870160 11 É Realize a progressive densification of said layer in its thickness so as to obtain the layer of fibrous material (1).   8. Method according to claim 7, characterized in that the densification step is carried out by successive needling of the layer (4) of fibers, from one of its faces, on variable fractions of its thickness, so to achieve a gradual intermingling of fibers between them.   9. A method according to claim 8, characterized in that said variable fractions of the thickness of the layer (4) of fibers vary progressively, increasing or decreasing.   10. Process according to claim 8 or 9, characterized in that the fraction of maximum thickness subjected to needling corresponds to 100% of the total thickness of the layer (4) of fibers.   11. Method according to any one of claims 8 to 10, characterized in that the successive needling are performed according to the following steps: E Move the initial layer (4) of fibers substantially parallel to its plane relative to a set of needles (6) with notches arranged on at least one board (5) parallel to said plane, é animating the needles (6) of a reciprocating movement substantially perpendicular to said plane so that the notches of said needles intermingle the fibers, said needles being arranged in strips (7) extending substantially perpendicularly to the direction of movement of the layer (4), each of said bands comprising needles (6) identical to each other whose positioning of the notches is arranged so as to entangle the fibers on a determined fraction the thickness of the layer (4) of fibers, said strips being arranged between them so that said determined fraction varies from one band e (7) to another.   2870160 12 12. The method of claim 11, characterized in that said determined fraction varies gradually, increasing or decreasing, in the direction of travel of the layer (4) of fibers.   s 13. The method of claim 7, when dependent on claim 4, characterized in that the densification step is performed by a gradual distribution of the charge density in the layer (4) of fibrous material.   14. A method according to claim 7, when it depends on claim 6, characterized in that the densification step is carried out by needling the layer (4) of fibers made in the following steps: E Move a layer ( 4) initial fibers, comprising a mixture of a first and a second species of fibers, substantially parallel to its plane, with respect to a set of needles (6) with notches arranged on at least one board (5) parallel to said plane, E animating said needles of a reciprocating movement substantially perpendicular to said plane so that the notches of said needles intermingle the fibers, said needles being arranged so as to effect a progressive transfer and intermingling of the fibers of a species towards a face of the layer (4) of fibers.   15. Car upholstery, in particular floor mats, soundproofing of apron or engine compartment, trunk or roof trim, said lining comprising an acoustic protection system according to any one of claims 1 to 6.