Mounting architecture of an inertial electrodynamic transducer in an interior compartment of an automobile

Abstract

The invention relates to an architecture (1) for mounting an inertial electrodynamic transducer (2) in an interior compartment of a motor vehicle, said architecture comprising a box (3) having an opening (4), a rigid plate (5) fixed by its periphery to the periphery of said opening by means of a decoupling means (6), at least one transducer (2) integral with a rigid plate (12) fixedly mounted on said plate, said plate being provided with an orifice (16) allowing passage of said box in an axial direction, said plate resting in close contact by a peripheral strip (17a) on a reciprocal peripheral strip (17b) extending around said orifice on said external face, it further comprises a means for fixing said plate to said plate. Figure 1

Description

Title of the invention: Mounting architecture for an inertial electrodynamic transducer in an interior compartment of a motor vehicle

[0001] The invention relates to a mounting architecture for an inertial electrodynamic transducer in an interior compartment of a motor vehicle.

[0002] It is known to implement a mounting architecture for an inertial electrodynamic transducer in an interior compartment of a motor vehicle, said architecture comprising: • a rigid box made of acoustically airtight material defining an acoustic volume, said box having an opening, • a rigid plate fixed at its periphery to the periphery of said opening by means of a decoupling means allowing its movement relative to said box so as to allow it to vibrate, said plate having an inner face facing said acoustic volume and an opposite outer face, • at least one inertial electrodynamic transducer intended to enable said plate to vibrate, said transducer comprising a coil, provided with an axis of symmetry, one axial end of which is attached to a rigid plate, said plate being fixedly mounted on said plate, said transducer further comprising a magnet housed in a casing, said casing being mounted by means of a suspension on said coil, so that said plate vibrates when said transducer is powered.

[0003] For the record, transduction is the operation that transforms one physical quantity into another, by means of a transducer which transforms the energy received in a given form, for example electrical energy, into usable energy in a different form.

[0004] In the context of the invention, it is a question of transforming an electrical signal into an acoustic signal by using as a radiating surface the rigid plate on which the transducer is fixed, for example in order to deliver a sound audible to an occupant of the seat (music, message, ...) or a sound signal in opposite phase with the sound signal corresponding to the noise in the passenger compartment when the vehicle is in motion.

[0005] It is recalled here that a transducer differs from a loudspeaker in the following way: • A loudspeaker comprises a magnet fixedly mounted on a support and a flexible diaphragm attached to a coil, said diaphragm vibrating when said loudspeaker is powered, • a transducer includes a coil fixedly mounted on a rigid plate and a magnet mounted by means of a suspension on said coil, so that said plate vibrates when said transducer is powered.

[0006] Ultimately, a loudspeaker is an autonomous system generating sound independently of the environment in which it is mounted, whereas a transducer uses the support on which it is fixed, in this case a rigid plate, to generate the expected sound.

[0007] In addition, the use of a transducer is advantageous because of its smaller size and lighter weight compared to a loudspeaker.

[0008] According to the known embodiment, the transducer plate is mounted overlapping the inner face of the plate.

[0009] However, in the case where the vehicle has a reduced space along an axial direction, it may be impossible to accommodate the aforementioned architecture.

[0010] The invention aims to provide an architecture with reduced axial dimensions in order to allow its housing in a reduced space along the axial direction, while preserving the quality of sound emission.

[0011] To this end, the invention proposes a mounting architecture for an inertial electrodynamic transducer in an interior compartment of a motor vehicle, said architecture comprising: • a rigid box made of acoustically airtight material defining an acoustic volume, said box having an opening, • a rigid plate fixed at its periphery to the periphery of said opening by means of a decoupling means allowing its movement relative to said box so as to allow it to vibrate, said plate having an inner face facing said acoustic volume and an opposite outer face, • at least one inertial electrodynamic transducer intended to enable said plate to vibrate, said transducer comprising a coil, provided with an axis of symmetry, one axial end of which is integral with a rigid plate, said plate being fixedly mounted on said plate, said transducer further comprising a magnet housed in a casing, said casing being mounted by means of a suspension device on said coil, so that said plate vibrates when said transducer is powered,

[0012] said architecture further having the following characteristics: • said plate is provided with an opening allowing the passage of said housing along an axial direction, • said plate rests in close contact via a peripheral strip on a reciprocal peripheral strip extending around said orifice on said external face, so as to achieve a seal between said strips, • it further includes a means of fixing said plate to said plate.

[0013] In this description, the term "axial" is taken in reference to the axis of symmetry of the coil.

[0014] With the proposed arrangement, the plate is offset outwards, which makes it possible to reduce the axial dimension of the box by the thickness of the plate added to that of the plate.

[0015] This results in the possibility of reducing the thickness of the plate to the overall axial dimension of the architecture.

[0016] As a result, the architecture exhibits better compactness along the axial direction, which allows it to be housed in a space of reduced dimension along said direction.

[0017] In practice, it is possible to reduce the axial dimension of the architecture by 10 to 30% depending on the case.

[0018] In addition, the applicant unexpectedly observed that the plate with the plate exhibits a modal behavior analogous (evaluated by acoustic radiation, as will be seen later) to that of a prior art plate without an orifice, where said plate is mounted covering the inner face of said plate.

[0019] Such an arrangement is applicable to all types of transducers, regardless of their size and the frequency bands concerned.

[0020] Due to the space saved, the transducer can be installed in a multitude of locations in the vehicle: in a floor under a seat, a window pillar, a headrest, a luggage compartment, a roof, etc.

[0021] Other features and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which:

[0022] [Fig. 1] is a general schematic view of an architecture according to the invention,

[0023] [Fig.2a] and

[0024] [Fig.2b] are schematic detail views of an architecture according to the prior art ([Fig.2a]) and according to the invention ([Fig.2b]),

[0025] [Fig.3] represents measurement curves, carried out in a reference vehicle, of the sound pressure level (in dB) as a function of frequency (in Hz) for a reference architecture according to the prior art (solid line curve) and for an architecture according to the invention (dotted line curve).

[0026] With reference to the figures, an architecture 1 for mounting an inertial electrodynamic transducer 2 in an interior compartment of a motor vehicle is described, said architecture comprising: • a rigid box 3 made of acoustically airtight material defining an acoustic volume, said box having an opening 4, • a rigid plate 5 fixed at its periphery to the periphery of said opening by means of a decoupling means 6 allowing its movement relative to said box so as to allow it to vibrate, said plate having an inner face 7 facing said acoustic volume and an opposite outer face 8, • at least one inertial electrodynamic transducer 2 intended to enable said plate to vibrate, said transducer comprising a coil 10, provided with an axis of symmetry 11, one axial end of which is integral with a rigid plate 12, said plate being fixedly mounted on said plate, said transducer further comprising a magnet 13 housed in a casing 14, said casing being mounted by means of a suspension means 15 on said coil, so that said plate vibrates when said transducer is powered,

[0027] said architecture further having the following characteristics: • said plate is provided with an opening 16 allowing the passage of said housing along an axial direction, • said plate rests in close contact via a peripheral band 17a on a reciprocal peripheral band 17b extending around said orifice on said external face, so as to achieve a seal between said bands, • it further includes a means of fixing said plate onto said plate, not shown.

[0028] Not shown, it may be provided that box 3 is provided with perforations allowing communication with the outside.

[0029] According to one embodiment, the plate 5 has a Young's modulus between 108 and 109Pa, the wafer 12 having a Young's modulus greater than or equal to that of said plate.

[0030] According to one embodiment, the plate 5 is based on rigid polyurethane foam reinforced with overmolded glass fiber.

[0031] Not shown, the plate 5 may be provided with a rigid alveolar reinforcement structure embedded in the foam, said structure being in particular in the form of a honeycomb, being for example made of cardboard.

[0032] According to one embodiment, the plate 12 is made of injection-molded plastic material.

[0033] Not shown, in the case where the plate 12 is based on molded plastic material, the fastening means may include molded elements in one piece, said elements being shaped to snap into reciprocal elements provided on the plate 5.

[0034] According to various embodiments not shown, the fastening means may include screws, glue, welding, etc...

[0035] According to various embodiments, the decoupling means 6 is in the form of a rubber or elastically compressible foam seal.

[0036] According to one embodiment, the suspension means 15 is based on spring metal.

[0037] The curves shown in [Fig.3] are now described.

[0038] It is observed that the acoustic radiation of the plate 5, measured between 20 and 16,000 Hz, is similar for an embodiment according to the invention (curve B in dotted line) and an analogous embodiment according to the prior art (curve A in solid line), this resulting, surprisingly, from an analogous modal behavior for a plate 5 without an orifice and a plate 5 having an orifice 16 filled by a rigid plate 12.

Claims

Demands

1. An architecture (1) for mounting an inertial electrodynamic transducer (2) in an interior compartment of a motor vehicle, said architecture comprising: • a rigid box (3) made of acoustically sealed material defining an acoustic volume, said box having an opening (4), • a rigid plate (5) fixed by its periphery to the periphery of said opening by means of a decoupling means (6) allowing its movement relative to said box so as to enable it to vibrate, said plate having an inner face (7) facing said acoustic volume and an opposite outer face (8), • at least one inertial electrodynamic transducer (2) intended to enable said plate to vibrate, said transducer comprising a coil (10), provided with an axis of symmetry (11), the axial end of which is integral with a rigid plate (12),said plate being fixedly mounted on said plate, said transducer further comprising a magnet (13) housed in a casing (14), said casing being mounted by means of a suspension means (15) on said coil, so that said plate vibrates when said transducer is powered, said architecture being characterized in that: • said plate is provided with an orifice (16) allowing passage of said casing in an axial direction, • said plate rests in close contact by a peripheral strip (17a) on a reciprocal peripheral strip (17b) extending around said orifice on said external face, so as to achieve a seal between said strips, • it further comprises a means for fixing said plate to said plate.

2. Architecture (1) according to claim 1, characterized in that the plate (5) has a Young's modulus between 10⁸ and 10⁹Pa, the plate (12) having a Young's modulus greater than or equal to that of said plate.

3. Architecture (1) according to any one of the preceding claims, characterized in that the plate (5) is based on rigid polyurethane foam reinforced with overmolded glass fiber.

4. Architecture (1) according to any one of the preceding claims, characterized in that the plate (12) is based on injection-molded plastic material.

5. Architecture (1) according to any one of the preceding claims, characterized in that the decoupling means (6) is in the form of a rubber or elastically compressible foam seal.

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