Mounting architecture of an inertial electrodynamic transducer

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 rigid housing (3) housed in a cavity (10) delimited by a wall (11) separated from said housing so as to define an extension space (12), and a separation means (13) interposed between said housing and said wall, the wall of said housing being provided with a plurality of orifices (14) and said housing being provided with an internal layer (15) extending opposite said orifices.

Description

Title of the invention: Mounting architecture for an inertial electrodynamic transducer

[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 enclosure made of acoustically sealed material defining an acoustic volume, said enclosure having an external face, an internal face and 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 housing so as to allow it to vibrate, • at least one inertial electrodynamic transducer intended to enable said plate to vibrate, said transducer being fixed under said plate so as to be turned towards said acoustic volume.

[0003] It is recalled here that an inertial electrodynamic transducer comprises a coil intended to be fixed to the plate and a magnet fixed to a support, said support being mounted by means of a suspension means attached to said coil, so that said plate vibrates when said transducer is powered.

[0004] 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, for example acoustic.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] In addition, a transducer has the advantages of being smaller and lighter than a loudspeaker.

[0009] However, an architecture such as the one described above does not allow for good transmission of low frequencies within the passenger compartment.

[0010] The invention aims to overcome this drawback, while ensuring good sound absorption and good acoustic damping of the casing, and also preventing the transmission of vibrations from the casing to its environment.

[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 enclosure made of acoustically sealed material defining an acoustic volume, said enclosure having an external face, an internal face and 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 housing so as to allow it to vibrate, • at least one inertial electrodynamic transducer intended to enable said plate to vibrate, said transducer being fixed under said plate so as to be oriented towards said acoustic volume,

[0012] said architecture further having the following characteristics: • said casing is housed in a cavity provided in said vehicle, said cavity being delimited by a wall set apart from said casing so as to define an extension space for said acoustic volume allowing the acoustic transmission spectrum to be broadened towards lower frequencies, • it further comprises at least one means of spacing interposed between said housing and said wall, said means being made of acoustically absorbing material, in order to achieve acoustic absorption in said extension space, and being elastically compressible, so as to avoid any contact between said housing and said wall and transmission of vibrations from said housing to its environment, • the wall of said enclosure is provided with a plurality of openings, so as to achieve communication between said acoustic volume and said extension space, • said casing is provided with an internal layer of acoustically absorbing material, in order to achieve acoustic absorption in said acoustic volume, and elastically compressible, so as to achieve acoustic damping of said casing inserted between said internal layer and said spacing means, said internal layer extending in relation to said orifices, so as to maximize acoustic absorption.

[0013] With the proposed arrangement, as will be seen later, an accentuated transmission of low frequencies is achieved within the passenger compartment, while ensuring good acoustic absorption and good acoustic damping of the housing, and also avoiding transmission of vibrations from the housing to its environment.

[0014] Other features and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which: • Fig. 1 is a schematic view of an architecture according to one embodiment, • [Fig.2] is a schematic view of a transducer used in the architecture shown in [Fig.1], • Fig. 3 represents measurement curves, taken in a reference vehicle, of the sound pressure level (in dB) as a function of frequency (in Hz) for a housing located in a cavity not defining an extension space (dotted curve) and for the same housing located in a cavity defining an extension space (solid curve).

[0015] 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 enclosure 3 made of acoustically airtight material - for example molded plastic or chipboard - defining an acoustic volume 4, said enclosure having an external face 5, an internal face 6 and an opening 7, • a rigid plate 8 fixed at its periphery to the periphery of said opening by means of a decoupling means 9 allowing its movement relative to said housing so as to allow it to vibrate, • at least one inertial electrodynamic transducer 2 intended to enable said plate to vibrate, said transducer being fixed under said plate so as to be oriented towards said acoustic volume,

[0016] said architecture further having the following characteristics: • said housing is located in a cavity 10 provided in said vehicle, said cavity being delimited by a wall 11 separated from said housing so as to define an extension space 12 of said acoustic volume allowing to broaden the acoustic transmission spectrum towards low frequencies, • it further comprises at least one spacing means 13 interposed between said housing and said wall, said means being made of acoustically absorbing material, in order to achieve acoustic absorption in said extension space, and being elastically compressible, so as to avoid any contact between said housing and said wall and a transmission of vibrations from said housing to its environment, • the wall of said casing is provided with a plurality of openings 14, so as to achieve communication between said acoustic volume and said extension space, • said casing is provided with an internal layer 15 of acoustically absorbing material, in order to achieve acoustic absorption in said acoustic volume, and elastically compressible, so as to achieve acoustic damping of said casing inserted between said internal layer and said spacing means - and thus avoid acoustic radiation from said casing -, said internal layer extending in relation to said orifices, so as to maximize acoustic absorption.

[0017] As visualized in [Fig.2], the transducer 2 comprises a coil 16 fixedly mounted on the plate 8 and a magnet 17 fixed on a support 20 mounted by means of a suspension means 18 on said coil, so that said plate vibrates when said transducer is powered.

[0018] According to one embodiment, the inner layer 15 and / or a spacing means 13 is based on elastically compressible foam - in particular polyurethane - or on fibers linked together by a bonding agent, for example in the form of two-component fibers having a high-temperature fusible core and a moderate-temperature fusible sheath, the bond between the fibers being ensured by melting of said sheath.

[0019] According to the embodiment shown, a spacing means 13 is integral with the housing 3, said means being in the form of an external layer 19 extending over the entire external face 5 of said case - or only over a part, in an alternative not shown.

[0020] In particular, according to the embodiment shown: • the casing 3 is overmolded with elastically compressible foam covering all its external face 5 and internal face 6 - or only part of it, in a variant not shown - said foam forming the internal layer 15 and external layer 19, • said foam covers the 14 openings.

[0021] According to an embodiment not shown, a spacing means 13 is detached from the housing 3, said means being: • in the form of a block of cavity filling material 10 in which a receiving housing is provided for the interlocking of said housing, • or in the form of a plurality of studs interposed between wall 11 and said housing.

[0022] According to an embodiment not shown, the two types of spacing means 13 - studs and block - can be combined, and spacing means 13 can also be used in combination, attached or separated from the housing 3.

[0023] According to an embodiment applicable to all embodiments, the plate 8 has a Young's modulus between 108 and 109Pa.

[0024] According to an embodiment applicable to all embodiments, the decoupling means 9 is in the form of a rubber or elastically compressible foam seal.

[0025] The curves shown in [Fig.3] are now described.

[0026] A very significant gain in the sound pressure level - of at least 5dB - is observed in the low frequencies - approximately between 25 and 250 Hz - when moving from a housing located in a cavity not defining an extension space (dotted curve) to the same housing located in a cavity defining an extension space (solid line curve).

Claims

Demands

1. Architecture (1) for mounting an inertial electrodynamic transducer (2) in an interior compartment of a motor vehicle, said architecture comprising: • a rigid enclosure (3) made of acoustically sealed material defining an acoustic volume (4), said enclosure having an external face (5), an internal face (6) and an opening (7), • a rigid plate (8) fixed at its periphery to the periphery of said opening by means of a decoupling means (9) allowing its movement relative to said housing so as to allow it to vibrate, • at least one inertial electrodynamic transducer (2) intended to enable said plate to vibrate, said transducer being fixed under said plate so as to be oriented towards said acoustic volume, said architecture being characterized in that: • said housing is located in a cavity (10) provided in said vehicle, said cavity being delimited by a wall (11) separated from said housing so as to define an extension space (12) of said acoustic volume allowing to broaden the acoustic transmission spectrum towards low frequencies, • it further comprises at least one spacing means (13) interposed between said housing and said wall, said means being made of acoustically absorbing material, in order to achieve acoustic absorption in said extension space, and being elastically compressible, so as to avoid any contact between said housing and said wall and transmission of vibrations from said housing to its environment, • the wall of said casing is provided with a plurality of openings (14), so as to achieve communication between said acoustic volume and said extension space, • said housing is provided with an internal layer (15) of acoustically absorbing material, in order to achieve a acoustic absorption in said acoustic volume, and elastically compressible, so as to achieve acoustic damping of said casing inserted between said inner layer and said spacing means, said inner layer extending in relation to said orifices, so as to maximize acoustic absorption.

2. Architecture (1) according to claim 1, characterized in that the inner layer (15) and / or a spacing means (13) is based on elastically compressible foam or fibers bonded together by a bonding agent.

3. Architecture (1) according to any one of claims 1 or 2, characterized in that a spacing means (13) is integral with the housing (3), said means being in the form of an outer layer (19) extending over all or part of the outer face (5) of said housing.

4. Architecture (1) according to the preceding claim, characterized in that: • the housing (3) is overmolded with elastically compressible foam covering all or part of its external (5) and internal (6) faces, said foam forming the internal (15) and external (19) layers, • said foam covers the orifices (14).

5. Architecture (1) according to any one of claims 1 or 2, characterized in that a spacing means (13) is detached from the housing (3), said means being: • in the form of a block of cavity filling material (10) in which a receiving housing is provided for fitting into said housing, • or in the form of a plurality of studs interposed between the wall (11) and said housing.

6. Architecture (1) according to any one of the preceding claims, characterized in that the plate (8) has a Young's modulus between 108 and 109Pa.

7. Architecture (1) according to any one of the preceding claims, characterized in that the decoupling means (9) is in the form of a rubber or elastically compressible foam seal.