Mounting architecture of an inertial electrodynamic transducer on a vehicle floor

Abstract

The invention relates to an architecture (1) for mounting an inertial electrodynamic transducer on the floor of a motor vehicle, comprising a box (2), a plate (5), at least one electrodynamic transducer (7) comprising a coil (8) fixed under said plate, a metal sheet floor panel (11) of said vehicle having an upper face (12) receiving said box, a cross member (13) of stamped sheet metal having a cross-section in the general shape of an inverted U, the arms of the U defining a first wall (14) facing said box and a second wall (15), said cross member being welded along its edges (16) to said upper face so as to define with said floor panel a cavity (17), said first wall being provided with at least one first opening (18), so as to extend said acoustic volume by said cavity to benefit from an enlarged acoustic volume. Figure 1

Description

Title of the invention: Mounting architecture for an inertial electrodynamic transducer on a motor vehicle floor

[0001] The invention relates to a mounting architecture for an inertial electrodynamic transducer on a motor vehicle floor.

[0002] It is known to implement a mounting architecture for an inertial electrodynamic transducer on a motor vehicle floor, said architecture comprising: • a rigid, perforated box defining an acoustic volume, said box having an opening leading upwards, • 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 housing so as to allow it to vibrate, • at least one electrodynamic transducer comprising a coil fixed under 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, • a metal sheet metal floor panel of said vehicle, said panel having an upper surface receiving said box • a long, reinforced cross member made of stamped sheet metal having a cross-section in the general shape of an inverted U, the arms of the U defining a first vertical cross member wall facing said box and a second vertical cross member wall, said cross member being welded along its edges to said upper face so as to define a cavity with said floor wall.

[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, an insufficient level of sound pressure is sometimes observed in low frequencies (below 200 Hz).

[0009] The invention aims to overcome this drawback.

[0010] To this end, the invention proposes a mounting architecture for an inertial electrodynamic transducer on the floor of a motor vehicle, said architecture comprising: • a rigid, perforated box defining an acoustic volume, said box having an opening leading upwards, • 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 housing so as to allow it to vibrate, • at least one electrodynamic transducer comprising a coil fixed under 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, • a metal sheet metal floor panel of said vehicle, said panel having an upper surface receiving said box • a long, reinforced cross member made of stamped sheet metal with a cross-section in the general shape of an inverted U, the arms of the U defining a first vertical cross member facing said box and a second vertical cross member, said cross member being welded according its edges on said upper face so as to define a cavity with said floor wall,

[0011] said first wall being provided with at least one first opening, so as to extend said acoustic volume by said cavity to benefit from an enlarged acoustic volume.

[0012] In this description, the terms of positioning in space (top, under, superior, vertical, ...) are taken with reference to the vehicle, said vehicle extending longitudinally along its length, transversely along its width and vertically along its height.

[0013] With the proposed arrangement, the extension of the acoustic volume makes it possible, as will be seen later, to significantly increase the level of acoustic pressure in low frequencies.

[0014] Other features and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which:

[0015] [Fig-1] is a general schematic view of an architecture according to one embodiment,

[0016] [Fig.2] is a schematic view of an inertial electrodynamic transducer arranged in the architecture represented in [Fig.1],

[0017] [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 (dotted curve) and for an architecture according to an embodiment of the invention (solid line curve).

[0018] With reference to the figures, an architecture 1 for mounting an inertial electrodynamic transducer on a motor vehicle floor is described, said architecture comprising: • a rigid, perforated box 2 – notably by a plurality of openings 3 according to the embodiment shown – defining an acoustic volume, said box having an opening 4 leading upwards, • 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 housing so as to allow it to vibrate, • at least one electrodynamic transducer 7 comprising a coil 8 fixed under said plate, said transducer further comprising a magnet 9 housed in a casing 25, said casing being mounted by means of a suspension means 10 on said coil, so that said plate vibrates when said transducer is powered, • a floor panel 11 of said vehicle made of sheet metal, said panel having an upper face 12 receiving said box, • a longline reinforcement cross member 13 made of stamped sheet metal having a cross-section in the general shape of an inverted U, the arms of the U defining a first wall 14 of vertical cross member facing said box and a second wall 15 of vertical cross member, said cross member being welded along its edges 16 on said upper face so as to define with said floor wall a cavity 17,

[0019] said first wall being provided with at least one first opening 18, so as to extend said acoustic volume by said cavity to benefit from an enlarged acoustic volume.

[0020] According to the embodiment shown, the architecture 1 further comprises a porous acoustic decoupling layer 19 placed on the upper face, said layer having a slice extending against the second wall 15, said second wall being provided with at least one second orifice 20, so as to extend the acoustic volume enlarged by the volume of said layer.

[0021] According to the embodiment shown, the box 2 is housed between the cross member 13 and an additional cross member 21 of a cross section similar to that of said cross member so as to define an additional cavity 22, said additional cross member being provided with at least one first orifice 18, so as to extend the acoustic volume by the cavity 17 and said additional cavity.

[0022] According to the embodiment shown, the cavity 17 and the additional cavity 22 both open through respective second orifices 20 onto the porous acoustic decoupling layer 19, so as to extend the acoustic volume enlarged by the volume of said layer.

[0023] According to the embodiment shown, the box 2 is separated from a first wall 14 by a space 23, said space being either vacant, according to the embodiment shown, or filled with a porous material - for example in soft foam or fibrous material -, according to an embodiment not shown, so as to achieve acoustic absorption allowing to optimize the acoustic performance of the architecture 1.

[0024] According to the embodiment shown, the acoustic decoupling layer 19 is coated with a coating layer 24 extending further over the plate 5.

[0025] According to one embodiment, plate 5 has a Young's modulus between 108 and 109Pa.

[0026] According to one embodiment, the decoupling means 6 is in the form of a rubber or elastically compressible foam seal.

[0027] We now comment on the curves shown in [Fig.3]. We see that the extension of the acoustic volume makes it possible to increase the level of acoustic pressure in low and mid frequencies - in a range of approximately 70 to 500 Hz - by the order of 4 dB.

Claims

Demands

1. An architecture (1) for mounting an inertial electrodynamic transducer on the floor of a motor vehicle, said architecture comprising: • a rigid, perforated box (2) defining an acoustic volume, said box having an opening (4) opening upwards, • 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, • at least one electrodynamic transducer (7) comprising a coil (8) fixed under said plate, said transducer further comprising a magnet (9) housed in a casing (25), said casing being mounted by means of a suspension means (10) on said coil, so that said plate vibrates when said transducer is powered, • a floor panel (11) of said vehicle made of sheet metal,said wall having an upper face (12) receiving said box, • a long, straight reinforcing cross member (13) made of stamped sheet metal having a cross-section in the general shape of an inverted U, the arms of the U defining a first vertical cross member (14) facing said box and a second vertical cross member (15), said cross member being welded along its edges (16) to said upper face so as to define with said floor wall a cavity (17), said architecture being characterized in that said first wall is provided with at least one first opening (18), so as to extend said acoustic volume by said cavity to benefit from an enlarged acoustic volume.

2. Architecture (1) according to claim 1, characterized in that it further comprises an acoustic decoupling layer (19) porous layer placed on the upper face (12), said layer having a slice extending against the second wall (15), said second wall being provided with at least one second orifice (20), so as to extend the acoustic volume enlarged by the volume of said layer.

3. Architecture (1) according to any one of the preceding claims, characterized in that the box (2) is housed between the cross member (13) and an additional cross member (21) of a cross section similar to that of said cross member so as to define an additional cavity (22), said additional cross member being provided with at least a first orifice (18), so as to extend the acoustic volume by the cavity (17) and said additional cavity.

4. Architecture (1) according to claims 2 and 3, characterized in that the cavity (17) and the additional cavity (22) both open through respective second orifices (20) onto the porous acoustic decoupling layer (19), so as to extend the acoustic volume enlarged by the volume of said layer.

5. Architecture (1) according to any one of the preceding claims, characterized in that the box (2) is separated from a first wall (14) by a space (23), said space being either vacant or filled with a porous material, so as to achieve acoustic absorption enabling the optimization of the acoustic performance of said architecture.

6. Architecture (1) according to any one of the preceding claims, when related to claim 2, characterized in that the acoustic decoupling layer (19) is coated with a coating layer (24) further extending over the plate (5).

7. Architecture (1) according to any one of the preceding claims, characterized in that the plate (5) has a Young's modulus between 108 and 109Pa.

8. 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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