Architecture for mounting an inertial electrodynamic transducer on a motor vehicle floor

Abstract

The invention relates to an architecture (1) for mounting an inertial electrodynamic transducer on a motor vehicle floor, comprising a box (2), a plate (5), at least one electrodynamic transducer (7) comprising a coil (8) fixed under said plate, a floor wall (11) of said vehicle made of sheet metal having an upper face (12) receiving said box, a 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) 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 wall a cavity (17), said first wall being provided with at least one first orifice (18), so as to extend said acoustic volume by said cavity to benefit from an enlarged acoustic volume.

Description

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

[0002] It is known to create 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 by its periphery to the periphery of said opening by means of a decoupling means allowing its movement relative to said box so as to enable 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 means on said coil, so that said plate vibrates when said transducer is powered, a floor panel of said vehicle made of sheet metal, said panel having an upper face receiving said box, a longitudinal reinforcing cross member made of stamped sheet metal having a cross-section in the general shape of an inverted U,The arms of the U define a first vertical cross-section facing said box and a second vertical cross-section, said cross-section being welded along its edges to said upper face so as to define a cavity with said floor wall.

[0003] As a reminder, transduction is the operation that transforms one physical quantity into another, using a transducer that transforms the energy received in a given form, for example electrical energy, into usable energy in a different form.

[0004] Within the framework 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 worth recalling here that a transducer differs from a loudspeaker in the following way: a loudspeaker includes 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 means on said coil, so that said plate vibrates when said transducer is powered.

[0006] Ultimately, a loudspeaker is a self-contained system that generates 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] Furthermore, the use of a transducer is advantageous because it is smaller and lighter than a loudspeaker.

[0008] According to the known implementation, 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 by its periphery to the periphery of said opening by means of a decoupling means allowing its movement relative to said box so as to enable 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 means on said coil, so that said plate vibrates when said transducer is powered, a floor panel of said vehicle made of sheet metal, said panel having an upper face receiving said box, a longitudinal reinforcing cross member made of stamped sheet metal having a cross-section in the general shape of an inverted U,the branches of the U defining a first vertical cross-wall facing said box and a second vertical cross-wall, said cross-wall being welded along its edges to said upper face so as to define a cavity with said floor wall, 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.

[0011] In this description, the terms of positioning in space (up, under, superior, vertical, ...) are taken in reference to the vehicle, said vehicle extending longitudinally according to its length, transversely according to its width and vertically according to its height.

[0012] With the proposed arrangement, the extension of the acoustic volume allows, as we will see later, a significant increase in the level of acoustic pressure in low frequencies.

[0013] Other features and advantages of the invention will become apparent in the following description, made with reference to the accompanying figures, in which: [ Fig.1 ] is a general schematic view of an architecture according to a realization, [ Fig.2 ] is a schematic view of an inertial electrodynamic transducer arranged in the architecture shown in figure 1 , [ 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).

[0014] With reference to the figures, we describe an architecture 1 for mounting an inertial electrodynamic transducer on a motor vehicle floor, said architecture comprising: a rigid perforated box 2 - in particular by a plurality of openings 3 according to the embodiment shown - 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 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 wall 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 wall 14 facing said box and a second vertical cross member wall 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 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.

[0015] According to the embodiment shown, the architecture 1 further includes 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.

[0016] According to the embodiment shown, the box 2 is housed between the cross member 13 and an additional cross member 21 of similar cross section 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.

[0017] 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.

[0018] According to the embodiment shown, the box 2 is separated from a first wall 14 by a space 23, said space being either empty, 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.

[0019] According to the embodiment shown, the acoustic decoupling layer 19 is coated with a coating layer 24 extending further over the plate 5.

[0020] According to one realization, plate 5 has a Young's modulus between 10⁸ and 10⁹ Pa.

[0021] According to one embodiment, the decoupling means 6 is in the form of a rubber or elastically compressible foam seal.

[0022] We now comment on the curves shown in figure 3 We can see that extending the acoustic volume allows us to increase the sound pressure level in low and mid frequencies - in a range of approximately 70 to 500 Hz - by about 4 dB.

Claims

1. 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 panel having an upper face (12) receiving said box,• a long, reinforced 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 wall (14) facing said box and a second vertical cross member wall (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 thatit further comprises a porous acoustic decoupling layer (19) 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 one 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 thatthe 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 allowing to optimize the acoustic performance of said architecture.

6. Architecture (1) according to any one of the preceding claims, when it relates 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 thatplate (5) has a Young's modulus between 10 8 and 10 9 Pa.

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.

Images