Use of a laminated glazing to dampen solid-transmitted vibrations in a vehicle

The present invention relates to the use of a glazing for a vehicle and particularly for a motor vehicle, having improved sound insulation performance especially with respect to the original structure-borne noise.

acoustic protective glazing is used for windows in the building, but also increasingly in the automobile. While acoustic protection glazing for buildings can be relatively thick, are used in automotive construction of laminated glazing, the thickness generally does not exceed about 6 mm. Should therefore be used as an interlayer between two glass sheets of the glazing, a viscoelastic polymer that, even in relatively thin layers, produces a very effective noise canceling effect. In addition, the polymer must also complete long-term, that is to say, throughout the lifetime of the car, all the conditions that are imposed on polymers used in automotive glazing. Are part of these conditions, particularly low turbidity, high transparency and good resistance to ultraviolet light. In addition, these polymers should ensure a quality and durable assembly with the adjacent layers and maintain their good noise damping properties even at high and low temperatures. Finally, noise layers must not harm the safety glass glazing properties. Viscoelastic acrylic polymers have proved particularly suitable as antinoise layers.

of known from the document <patcit id="pcit0001" dnum="EP0532478A2"><text>EP 0532478 A2</text></patcit> a laminated glazing acoustic protection also suitable as automotive glazing and consisting of an intermediate layer of viscoelastic acrylic polymer. In the case of this known laminated glazing, the intermediate layer separating the two glass sheets is formed of a polymerizable monomer composition consisting of 5 to 50% by weight of an aliphatic polyurethane and 15 to 85% by weight of a photopolymerizable mixture of different acrylic and usual polymerization additives monomers. The monomer mixture is admitted into the space between the two glass sheets and the polymerization is initiated by ultraviolet radiation. This laminated glazing known acoustic protection is not suitable for mass production because its manufacturing process by polymerizing the monomer mixture introduced between the glass sheets is relatively expensive in itself.

In the case of industrial manufacturing process of laminated glazings assembling the two glass sheets with a prefabricated polymer film is generally carried out under heat and pressure. A process of this type for the manufacture of laminated glazing having good noise-damping properties is known from the document<patcit id="pcit0002" dnum="EP0457190A1"><text>EP 0457190 A1</text></patcit>. In the case of this known method uses a prefabricated film of polymer having a damping coefficient of the high noise and consisting of at least two layers one of which is made of a first polyvinyl acetal determined and a plasticizer and the other of another polyvinyl acetal determined and a plasticizer.

Moreover, among all the qualities contributing to comfort in modern means of transport such as trains and automobiles, silence becomes decisive. Indeed, other sources of annoyance of mechanical, thermal or visibility were gradually mastered. But the improved acoustic comfort presents new difficulties, the noise of aerodynamic origin, that is to say created by the friction of the air on the moving vehicle, could, at least in part, be them -Same treated at source, that is to say, to save energy, the forms have changed, penetration was improved in the air and dropped the turmoil that are themselves a source of noise. Among the walls of a vehicle that separate the source of external aerodynamic noise from the interior space where the passenger is located, the windows are obviously more difficult to treat. We can use pasty or fibrous absorbent reserved for opaque walls and for practical or weight reasons, thicknesses can not be increased inconsidérablement. European Patent<patcit id="pcit0003" dnum="EP0387148B1"><text>EP-B1-0 387 148</text></patcit> offers windows that achieve good insulation against noise of aerodynamic origin without their weight and / or thicknesses are increased too. The patent proposes a laminated glazing whose interlayer has a flexural damping ν = Df / f_c greater than 0.15, as measured by exciting by a shock, a laminated bar of 9 cm length and 3 cm in width made of a laminated glass in which the resin is between two thick glass each 4 mm, and by measuring f_c, The first mode resonance frequency, and .DELTA.f, peak width at an amplitude A / √2, where A is the maximum amplitude at frequency f_c such that its acoustic attenuation index does not differ for any of the frequencies above 800 Hz by more than 5 dB from a reference index increasing by 9 dB per octave up to 2000 Hz and 3 dB per octave at higher frequencies. In addition, the standard deviation differences of its acoustic attenuation index relative to the benchmark index remains below 4 dB. The thicknesses of the two lenses can be identical and equal to 2.2 mm. This patent proposes a general solution to the problem of sound insulation of the aerodynamic noise of a vehicle.

However the sounds themselves as engine noise, road noise or suspension shall at the same time be treated. These sounds have been treated in their origin or in part during their spread, or air (especially absorbing coating) or in solid (elastomer connecting parts, for example). At the windows, the European patent<patcit id="pcit0004" dnum="EP0100701B1"><text>EP-B1-0 100 701</text></patcit> offers windows that achieve good protection against road noise, that is to say, good insulation of noises during their airborne spread.

A glazing according to this patent comprises at least one laminated glass pane and the resin of the laminated pane is such that a bar 9 cm long and 3 cm wide formed of a laminated glass comprising two glass sheets 4 mm thickness joined by a 2 mm layer of this resin, has a critical frequency which differs by at most 35% of that of a glass bar having the same length, the same width and 4 mm thick. The glazing according to this patent have an excellent sound reduction index vis-à-vis road traffic.

The European patent application <patcit id="pcit0005" dnum="EP0763420A"><text>EP 0763420</text></patcit> also provides glazing that achieve good insulation against the noises of aerodynamic origin by combining a polyvinyl butyral film with a resin layer having a high acoustic efficiency against the aerodynamic noise origin such as a polyvinyl acetate resin.

By cons, the treatment of glazing against the original structure-borne noise, that is to say against noise transmitted via solid, is more difficult. Indeed, it appears that the use of connecting parts is insufficient to prevent the transmission of noise by vibration of the glass. It was found, for this purpose, at certain engine speeds, a hum in the passenger appeared and thus causing a source of annoyance. Indeed, the engine rotation causes the creation of vibrations that are transmitted, for example, to the body and thus by chain effect, to glazing. We know that the energy acquired by an object subjected to a shock causes a vibration phenomenon and immediately after the shock, the object become free vibrates in its own way. Each mode has a frequency of vibration. The amplitude of the vibration depends on the initial excitation, that is to say, the spectral component of the shock (amplitude of the shock at the frequency studied) and the impact zone of the shock, the modal deformation being more or less important depending on whether the shock occurs at a stomach or a vibration node.

For a natural mode to be excited, you must:<ol><li>(1) the deformation caused at the impact point is not located on a vibration mode node,</li><li>(2) the shock energy spectrum have a component at the resonant frequency of the mode.</li></ol>

This latter condition is practically always satisfied because a very brief shock has a virtually uniform energy spectrum.

The first condition is met and, for a bar free at its ends, for example, just type in one of the ends to excite all modes.

In the application in this case, the structure-borne excitation is peripheral and the inventors have demonstrated that, at certain frequencies of vibration of the engine, that is to say at certain engine speeds, glazing and the vehicle cabin each had a mode of vibration, the coupling amplified the buzz, from the radiation of noise from the motor in this case, by the glass. Of course, the engine rotational speed causing these phenomena is specific to each vehicle type and can not be generalized in this way to a unique value.

The applicant has established that by using a resin of the original conditions, different from those proposed in the patents mentioned above, to bring together the sheets of laminated glass, it offers damping qualities audible sounds of structure-borne origin particularly satisfactory, although higher than those obtained previously.

The invention is intended in use, to vibration damping of structure-borne origin, of a laminated glazing comprising at least one glass sheet and an intermediate film according to the features of claim 1.

The technique of the invention provides an acoustic protective glazing consisting of laminated glazing whose interlayer film provides a vibration damping forwarded particularly by the body from the engine, such as radiation damping vibration modes glazing is so weakened that there is no coupling with the interior of the vibration modes and this irrespective of the engine rotational speed.

According to the invention, the interlayer film giving the damping properties is associated with at least one film having commonplace sound performance. Thus, it is possible to substitute part of the thickness of an expensive acoustic film by a "banal" movie cheap and without degradation of the acoustic properties but with, for example, a significant improvement in mechanical properties and also whole range of additional properties that can provide such a film, for example: colors, UV or light scattering.

According to the invention, the intermediate film is a film of thermoplastic acrylic polymer of 0.05 to 1.0 mm thick and the film is joined to a glass sheet with the interposition of a film of from 0.01 to polyester 0.1 mm thick and a thermoplastic adhesive layer of 0.3 to 0.8 mm thick. According to the invention, a thin film of polyester, especially of polyethylene terephthalate is interposed between the film of acrylic polymer and the thermoplastic adhesive layer.

It was found that laminated glazing of this structure could not only be manufactured easily using the usual methods of assembly and fit well for mass production, but also could allow the exclusion of all adverse influences the film of acrylic polymer by adding a thin film of PET film between the acrylic polymer and the thermoplastic adhesive layer which is made of a polyvinylbutyral film usual for the manufacture of laminated glazing. Indeed, when the acrylic polymer film is in direct contact with the film of polyvinylbutyral, plasticizer particles of the PVB film apparently diffuse into the acrylic polymer and there cause turbidity effects and degradation of properties of silencing. Surprisingly, the PET films, even when they have only a very small thickness less than 50 microns, are a perfect barrier against the diffusion of the plasticizer of the PVB film. In addition, thanks to their surface properties, the PET films unite both the thermoplastic acrylate film to the usual PVB film, so that the laminated glazing for use according to the invention satisfy all requirements even with respect to the long-term durability and safety.

In its simplest embodiment, the laminated glass to be used according to the invention consists of two sheets of glass between which are interposed the following above dandruff order layers PVB-PET-PET-PVB-acrylate. obviously it can also replace the usual PVB film of thermoplastic adhesive films of other materials, particularly such films made of suitable thermoplastic polyurethanes.

According to another embodiment, the laminated glass to be used according to the invention consists only of a glass sheet which, in the mounted state, is turned outwards, while the facing surface of the laminated glazing towards the passenger compartment is formed of a polymer layer having sufficient abrasion resistance. Such glazing glass and plastic offer some advantages with regard to weight and safety properties and are known as such in various forms.

Consist of films of viscoelastic acrylic polymers having a shear modulus G 'between 10^6.5 Pa at 0 ° C and 10^4.5 Pa at 60 ° C, and a loss factor tanδ between 0.8 and 1 in a temperature range of 0 to 60 ° C, prove suitable for the invention. Makes such party products from the 3M company marketed under the name "Scotchdamp-Polymer". These products consist of acrylic polymers which do not contain plasticizer and whose damping properties cover a wide range of temperatures. Product type ISD 112, the damping properties can be found in the temperature range between 0 and 60 ° C, has proved particularly suitable.

According to an advantageous variant of the invention, one of the layers of the laminated glazing, in particular a film of polyethylene terephthalate is provided with a layer reflecting infrared radiation.

According to one embodiment of the invention, the laminated glass comprises two sheets of identical thickness glass. This common thickness may be equal to 2.2 mm. Thus, the technique of the invention allows to obtain an acoustic protection glazing whose total thickness is relatively small.

According to an advantageous embodiment of the invention, the shear modulus G 'of the intermediate film giving damping properties to noise is between 10⁶ and 2.10⁷ N / m².

The glass used according to the invention have the advantage that a good insulation against the original structure-borne noise is achieved and good insulation against noise of aerodynamic origin and also against external noise.

The dynamic characterization of the intermediate film is made on a viscoanalyser of viscoanalyser Metravib kind in certain circumstances measures set out below:<ul><li>sinusoidal stress,</li><li>called double shear test consists of two rectangular parallelepipeds size:<ul><li>* Thickness = 3.31 mm</li><li>* Width = 10.38 mm </li><li>* Height = 6.44 mm</li></ul></li><li>dynamic range: ± 5 mm around the rest position,</li><li>Frequency range: 5 to 700 Hz</li><li>temperature range: - 20 to + 60 ° C.</li></ul>

The viscoanalyser allows you to submit a sample of material to deformation stresses under specific conditions of temperature and frequency, and thus to obtain and process all of the rheological parameters characterizing the material.

The exploitation of raw data measurements of force, displacement and phase shift as a function of frequency at each temperature, allows in particular the calculation of the following variables:<ul><li>elastic component (or shear modulus) G '</li><li>loss tangent of the angle (or loss factor) tanδ</li></ul>

Thus, traces the master curves of G 'and tanδ as a function of the frequency and for various temperatures, using the equivalence law frequency / temperature.

The exploitation of these master curves shows the glass transition zones. This calculates depreciation at the glass transition.

Indeed, it is the glass transition that depreciation is the best.

The technique of the invention provides the use of a laminated glazing for a vehicle comprising an intermediate film having a good damping of noise transmitted by the solids. This damping can also meet the insulation requirements for wind noise and exterior noise. Thus, the glazing according to the invention allows to obtain a good general acoustic protection.

Other advantages and features of the invention appear from the following description made with reference to the accompanying drawings:<ul><li>the <figref idrefs="f0001">Fig. 1</figref> shows a first embodiment of the laminated glass to be used according to the invention;</li><li>the <figref idrefs="f0001">Fig. 2</figref> shows a second embodiment of the laminated glass to be used according to the invention, and</li><li>the <figref idrefs="f0002">Fig. 3</figref> represents the degree of damping according to the frequency of a usual laminated glass and the laminated glass shown in <figref idrefs="f0001">Fig. 1</figref>.</li></ul>

The <figref idrefs="f0001">Fig. 1</figref> is a fragmentary sectional view of the structure of a laminated glazing, as used for the windshield and also increasingly for the side windows and rear windows. Of course, i t is also possible to use the same structure for windshields and automobile rear windows, where appropriate with the silicate glass sheets of slightly different thicknesses.

The laminated glazing is constituted by two glass sheets silicate 1, 2, each 1.6 to 3 mm in thickness, two polyvinylbutyral layers 3, 4, each 0.38 mm in thickness, two thin PET films 5, 6, and 7 of a film of acrylic viscoelastic polymer interposed therebetween. Dandruff PET 5, 6 have a thickness of 0.05 mm respectively. 7 The film consists of a polymer film Scotchdamp 0.05 mm thick, type ISD 112 from 3M. The layers are juxtaposed in a usual manner in the manufacture of laminated panes and their assembly is carried out under heat and pressure.

PET film 5 or the PET film 6 may be placed on one face of a layer system that reflects infrared radiation. In addition to its noise damping properties, such laminated glazing reflecting infrared radiation ensures thermal protective effect against increased thermal radiation incident. In addition, the laminated glazing for use according to the invention have, through the integration of PET films, increased anti-burglary effect, so auto very comfortable can be made.

The laminated glazing shown <figref idrefs="f0001">Fig. 2</figref> only comprises a silicate glass sheet 10. The glass sheet silicate 10, for example, 4 mm thick, is rotated, in the mounted state, towards the outside of the automobile. A PVB layer 11 of 0.76 mm thick is joined to the glass sheet silicate 10. The PVB layer 11 is followed by a 12 PET film of 0.05 mm thick, of a polymer film Scotchdamp ISD 13 type 112, 0.05 mm thickness and a PET film 14 of 0.1 mm thick, which is provided on its free surface with an abrasion-resistant layer 15. as in the case of the first described embodiment, the PET film 12 and the PET film 14 may, in this case also be provided with a layer reflecting infrared radiation, for example a layer multiple applied in a vacuum process and consisting of a functional layer of silver.

The diagram shown in <figref idrefs="f0002">Fig. 3</figref> highlights improved noise damping achieved by the invention. In this diagram, the damping of the noise expressed in dB is given as a function of frequency, and this, for a laminated glazing usual structure (curve A) and for a laminated glazing structure described with reference to<figref idrefs="f0001">Fig. 1</figref> (Curve B). The measurements are performed on laminated glazing dishes of 80 x 50 cm. The thickness of the glass sheets to silicate is, in both cases, 2.1 mm. The comparison model having the damping curve shape A has the following structure: glass 2.1 mm - 0.76 mm PVB - 2.1 mm glass, while the model according to the invention has the following structure: glass 2.1 mm - 0.38 mm -0.05 mm PVB PET - 0.05 mm acrylic polymer - 0.05 mm of PET - 0.38 mm PVB - 2, 1 mm glass.

The results show that the degree of damping of the glazing to be used according to the invention is greater than the degree of damping of the comparison glazing in part by far the largest of the frequency spectrum. However, it is in particular in the region between about 200 and 300 Hz and in the region of the coincidence frequency to approximately 3000 Hz, in which the damping curves of the glazing has the biggest recesses in the case of usual laminated glazing, the measured levels of noise damping are much higher, so that, overall, a considerable improvement of noise damping is achieved.