Land vehicles: bodies and tops – Bodies – Door or window with specified vehicle feature
Reexamination Certificate
1998-10-06
2001-02-13
Dayoan, D. Glenn (Department: 3612)
Land vehicles: bodies and tops
Bodies
Door or window with specified vehicle feature
C296S084100, C296S090000, C181S284000, C181S289000
Reexamination Certificate
active
06186578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a fixed glazing for improved acoustic protection for vehicles, specifically for automobiles, which is in contact with a peripheral seal. According to the invention, the glazing lacks one or more modes of radiation which are coupled with one or more acoustic cavity modes of the vehicular interior when the glass is excited by an acoustic field.
2. Discussion of the Background
Among the comfort qualities in modem transportation, such as in trains and automobiles, silence is crucial. Indeed, the other sources of discomfort—mechanical, of thermal origin, visibility problems, etc, —have been more or less taken care of. However, improving acoustic comfort presents new problems. It has been partly possible to deal with noises stemming from aerodynamics at their source, that is, noise created by air turbulence. This means that for economizing on energy, the shapes have been modified. Air penetration has been improved, and the turbulence which is itself a source of noise has been diminished.
Among the walls of a vehicle that separate the source of exterior aerodynamic noise from the interior space where the passenger sits, the glass is much more difficult to deal with. One cannot use the pasty or fibrous noise absorbing materials in glass like the ones used in opaque walls, and for reasons of weight, the glass thickness cannot be excessively increased. European patent EP-B1-0387 148 proposes glass which provides good insulation against noise of aerodynamic origin without increasing weight and/or thickness too much. This patent proposes a laminated glazing, the insert of which possesses good sound deadening properties.
Other noises such as motor noises, rolling noises or suspension noises must also be dealt with. These noises have already been dealt with at their origin or, in part, during their propagation, either through the air ( by absorbent sheeting in particular) or through solids (elastomer connecting elements, for example). In contrast, the design of glass so as to absorb noise which has its origin in the vehicle itself, that is, noise transmitted by way of the air or by the intermediary of solids, is more difficult to realize and is yet to be mastered.
The glazing constitutes an important surface of the interior of the vehicle and, consequently, an important surface of propagation. It turns out that using adapted connecting pieces is insufficient for avoiding the propagation of noise due to vibration of the glass, and that at certain speeds of rotation of the motor, a humming occurs that is perceptible by the passenger and thus becomes a source of discomfort. In fact, the rotation of the motor creates vibrations which are transmitted to the glass panes through the air or through solids.
The main parameters influencing the vibro-acoustic behavior of glass panes in this respect reside in the shape of the glass, the structure of the glass, the glass/interior interface, the exciting source and the mode of propagation. Thus, for a given vehicle, the ways of improving the behavior of the panels which the glass panes constitute include the structure of the glass as well as in the glass/vehicle interface.
Numerous efforts have been undertaken in modifying the structure of the glass in order to improve the sound muffling effect in the vehicle interior. In general, one can modify the construction of laminated glass panes, the insert of which possesses properties conferring protection against aerodynamic sound and/or noises of aerial origin and/or noise of solid origin, as well as the creation of multiple, panes of glass. In contrast, the use of such glass in the assembly of a vehicle considerably increases the cost of the vehicle.
SUMMARY OF THE INVENTION
The invention has for an object providing a fixed glass pane in contact with a peripheral seal for a vehicle, and specifically for an automobile, which provides good noise protection, in particular for noise propagated through air or solids, and without considerably increasing the cost of the vehicle.
This and other objects are accomplished in accordance with the invention by a fixed pane of glass in contact with a peripheral seal for a vehicle, and specifically for an automobile, such glass being constructed so as to eliminate at least one mode of acoustic propagation to the cavity defined by the vehicle interior space when such a pane of glass is excited by an acoustic field. By an acoustic field is understood the entirety of sounds created by aerial propagation and transmission of vibrations by intermediary of solids. The structure of the glass is not limited to a monolithic glazing. All types of laminated glazing and multiple glass panes are within the scope of the invention. Likewise, the shape of the glass is not a limitation on the invention. All shapes possible for a fixed glazing destined for a vehicle are within the scope of the invention.
The fixed glazing according to the invention permits diminishing the effect of humming perceptible by the passenger at certain motor rotation speeds, by eliminating the forms of propagation which are linked to the shape of the acoustic cavity formed by the vehicle interior space. In fact, at certain motor vibration frequencies, that is, at certain motor rotation speeds, the glass and the cavity of the interior of the vehicle are each modes of propagation, the coupling of which amplifies the humming noises originating in the operation of the motor. Thus, in eliminating these modes of propagation, one eliminates the amplified effect of humming and increases the acoustic comfort of the passenger.
A modal analysis of the interior of the vehicle permits one to determine the frequency in which the humming caused by the coupling of a mode of propagation of a vehicle glass with a mode of propagation by the cavity of the interior space occurs. For this, one varies the engine speed of the vehicle and surveys the curve of the cavity modes of the volume of the interior. The coupling frequency appears as a significant peak with an accuracy on the order of ±5%. In the fixed glass of the invention, it is possible to eliminate this mode of propagation.
According to an embodiment of the invention, the fixed glass is modified to eliminate the first odd mode of propagation. “Odd mode” means that the glass pane defines an odd number of zones of propagation, and “even mode” means that the glass pane defines an even number of zones of transmission. Thus the first odd mode means the case where the glass pane has one zone of propagation. In this way, when the aforementioned glass of the invention is excited by an acoustic field, it possess at least two zones of transmission.
The fixed glass of the invention permits diminishing the radiation of the glass thanks to elimination of the first odd mode of propagation. In fact, the first odd mode is the most propagating mode owing to its single zone of radiation. Thus, in eliminating this form of propagation, one diminishes transmission by the glass overall by the presence of at least two zones of radiation.
According to a preferred embodiment of the invention, the fixed glass is deprived of all of the odd modes of propagation when it is excited by an acoustic field. In this manner, when this glass is excited by an acoustic field, it possesses an even number of zones of transmission, that is to say, zones of radiation in phase opposition.
The fixed glass of the invention permits diminishing the overall propagation of the aforementioned glass to zones of radiation in phase opposition. In fact, the phase difference of the zones permits obtaining a compensation effect of these zones by each other. In image fashion, when one zone pulls in one direction, the other zone will push in the opposite direction. Thus the vibratory effect of the sum of these zones tends toward a null effect and the active radiation is strongly diminished. By diminishing the propagation, one diminishes the transmission of noises and consequently improves the acoustical comfort in the interior of the vehicle.
According t
Garnier Gilles
Rehfeld Marc
Blankenship Greg
Dayoan D. Glenn
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Saint-Gobain Vitrage
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