Mounting architecture of an inertial electrodynamic transducer

Abstract

The invention relates to an architecture (1) for mounting an inertial electrodynamic transducer (5) in an interior compartment of a motor vehicle, said architecture comprising a cavity (2) provided with an opening (3) and a generally planar rigid plate (4) for transmitting sound vibrations, said plate being fixed by its periphery to the periphery of said opening by means of a decoupling device allowing movement of said plate relative to said cavity, said transducer being fixed on the reverse side of said plate on the side of said cavity, said decoupling device comprising a rigid frame (6) for supporting said plate, a first decoupling means (7) in the form of an elastic joint extending around said plate, said plate being fixed inside said frame by means of said first means, a second decoupling means (8) extending around said frame,said frame being fixed around said opening by means of said second means. Figure 1,

Description

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

[0001] The invention relates to an architecture for mounting an inertial electrodynamic transducer in an interior compartment of a motor vehicle and a sound propagation assembly intended to be integrated into such an architecture.

[0002] It is known to produce an architecture for mounting an inertial electrodynamic transducer in an interior compartment of a motor vehicle, said architecture comprising: • a cavity provided with an opening, • a generally planar rigid plate for transmitting sound vibrations, said plate being fixed by its periphery to the periphery of said opening by means of a decoupling device allowing movement of said plate relative to said cavity, • said transducer fixed on the reverse side of said plate on the side of said cavity.

[0003] The inertial electrodynamic transducer is intended to emit a sound signal, for example from a radio or a disc player, or of the “anti-noise” type so as to emit a sound in phase opposition with the noise generated inside the passenger compartment.

[0004] Fixing the plate at the periphery of the opening by means of the decoupling device allows said plate to vibrate when the inertial electrodynamic transducer is activated in order to allow the transmission of sound.

[0005] It is specified here that the use of an inertial electrodynamic transducer instead of a loudspeaker is dictated by the desire to save space and weight, a loudspeaker having a volume sometimes incompatible with the space available, and also a significant weight contributing to an increase in the weight of the vehicle in which it is installed.

[0006] For the record, a loudspeaker comprises a magnet fixedly mounted on a support and a flexible membrane secured to a coil, said membrane vibrating when said loudspeaker is powered.

[0007] An inertial electrodynamic transducer, for its part, comprises a coil fixedly mounted on a rigid plate and a magnet fixed on a support, said support being mounted by means of a suspension means integrally with said coil, so that said plate begins to vibrate when said transducer is powered; an electrical signal is thus transformed into an acoustic signal by using the plate on which the transducer is fixed as the radiation surface.

[0008] Ultimately, a loudspeaker is a self-contained system generating sound independently of the environment in which it is mounted whereas an inertial electrodynamic transducer uses the plate on which it is fixed to generate the expected sound.

[0009] The decoupling device must allow both the movement of the plate, its guidance and its static maintenance, and also limit the transmission of vibrations to the environment.

[0010] However, the static holding function of the plate prevents the implementation of a decoupling device that is sufficiently flexible to limit the transmission of vibrations to the environment.

[0011] The aim of the invention is to propose an arrangement making it possible to overcome this drawback.

[0012] To this end, and according to a first aspect, the invention proposes an architecture for mounting an inertial electrodynamic transducer in an interior compartment of a motor vehicle, said architecture comprising: • a cavity provided with an opening, • a generally planar rigid plate for transmitting sound vibrations, said plate being fixed by its periphery to the periphery of said opening by means of a decoupling device allowing movement of said plate relative to said cavity, • said transducer fixed on the reverse side of said plate on the side of said cavity,

[0013] said decoupling device comprising: • a rigid frame supporting said plate, • a first decoupling means in the form of an elastic seal extending around said plate, said plate being fixed inside said frame by means of said first means, • a second decoupling means extending around said frame, said frame being fixed around said opening by means of said second means.

[0014] It has been observed that such an arrangement, implementing two decoupling means, allows the decoupling device to ensure both the movement of the plate, its guidance and its static maintenance, but also to limit the transmission of vibrations to the environment.

[0015] According to a second aspect, the invention proposes a sound propagation assembly intended to be integrated into such an architecture.

[0016] Other features and advantages of the invention will appear in the following description, given with reference to the attached figures, in which:

[0017] [Fig.l] is a schematic sectional view of an architecture according to one embodiment, said architecture being arranged under a vehicle seat,

[0018] [Fig.2] is a schematic sectional view of an electrodynamic transducer inertial fixed to a plate according to one embodiment.

[0019] With reference to the figures, an architecture 1 is described for mounting an inertial electrodynamic transducer 5 in an interior compartment of a motor vehicle, said architecture comprising: • a cavity 2 provided with an opening 3, • a generally planar rigid plate 4 for transmitting sound vibrations, said plate being fixed by its periphery to the periphery of said opening by means of a decoupling device allowing movement of said plate relative to said cavity, • said transducer fixed on the reverse side of said plate on the side of said cavity,

[0020] said decoupling device comprising: • a rigid frame 6 for supporting said plate, • a first decoupling means 7 in the form of an elastic seal extending around said plate, said plate being fixed inside said frame by means of said first means, • a second decoupling means 8 extending around said frame, said frame being fixed around said opening by means of said second AVERAGE.

[0021] According to the embodiment shown, the internal face of the cavity 2 is lined with an acoustic absorption layer 9 made of porous material with open porosity, so as to dampen the “rear wave” and to provide an insulation function associated with the plate 4 (“double wall” principle).

[0022] According to the embodiment shown, the porous material of the absorption layer 9 is elastically compressible, the frame 6 resting by at least part of its periphery on the edge 10 of said absorption layer, so that the second decoupling means 8 is formed at least in part by said absorption layer.

[0023] According to the embodiment shown, the edge 10 of the absorption layer 9 is provided with a recess 11 allowing the frame 6 to be crimped and held horizontally.

[0024] According to one embodiment, the porous material is based on elastically compressible foam flakes connected to each other by “two-component” fibers provided with a core that is fusible at high temperature and a sheath that is fusible at lower temperature, the connection of the flakes to each other having been ensured by fusion of said sheath.

[0025] The advantage of such a material is in particular that it has a high load-bearing capacity (static compressibility at large deformations) and a low Young's modulus at small deformations.

[0026] “Bi-component” fibers comprise, for example, a core made of polyethylene terephthalate (PET) and a sheath made of polyethylene terephthalate modified to lower its melting point.

[0027] According to an embodiment not shown, the opening 3 extends only partially over the cavity 2, so that the frame 6 rests only by part of its periphery on the edge 10 of the absorption layer 9, an openwork wall being arranged in said cavity - the openwork nature of said wall allowing communication between the parts of said cavity separated by said wall - so as to receive on its edge the other part of the periphery of said frame, so that the second decoupling means 8 is formed partly by said absorption layer and partly by said openwork wall.

[0028] According to one embodiment, the perforated wall is - as can be the absorption layer 9 - based on elastically compressible foam flakes connected to each other by "two-component" fibers provided with a core that is fusible at high temperature and a sheath that is fusible at lower temperature, the connection of the flakes to each other having been ensured by fusion of said sheath.

[0029] By way of example, the perforated wall may be provided with at least one circular orifice with a diameter of between 30 and 50 mm.

[0030] According to one embodiment, the first decoupling means 7 is made of elastomer material.

[0031] According to the embodiment shown, the first decoupling means 7 has a generally U-shaped section, allowing significant movement of the plate 4 during vibration.

[0032] According to one embodiment, the first decoupling means 7 has a hardness of between 25 and 90 shore A (measured according to the ISO 868 standard in force on the date of filing of the application).

[0033] According to one embodiment, the first decoupling means 7 has a residual compression deformation of less than 40% (measured according to the ISO 815 standard in force on the date of filing of the application, at 23°C over a period of 24 hours).

[0034] According to one embodiment, the first decoupling means 7 has an elongation at break greater than 200%.

[0035] According to one embodiment, the second decoupling means 8 has a Young's modulus of between 20 and 200 KPa.

[0036] According to various embodiments, the frame 6 is based on: • rigid polyurethane, • or molded thermoplastic material, • or aluminum, • or chipboard, • or a structure having a honeycomb core - for example in the form of honeycomb, in particular made of cardboard - said core being reinforced by two reinforcing fibrous layers - for example based on glass fibers - arranged on each of its faces, said layers being impregnated with polyurethane foam.

[0037] According to various embodiments, the plate 4 is based on: • rigid polyurethane, • or molded thermoplastic material, • or aluminum, • or chipboard, • or a structure having a honeycomb core - for example in the form of honeycomb, in particular made of cardboard - said core being reinforced by two reinforcing fibrous layers - for example based on glass fibers - arranged on each of its faces, said layers being impregnated with polyurethane foam.

[0038] According to one embodiment, the plate 4 has a Young's modulus of between 108 and 1010 Pa.

[0039] According to one embodiment, the plate 4 has a loss factor of between 1 and 8%, so as to minimize its secondary radiation lobes.

[0040] According to one embodiment, the plate 4 has a thickness of between 5 and 30 mm.

[0041] According to the embodiment shown, the cavity 2 is formed by a stamping made in a 12 sheet of the vehicle floor.

[0042] According to an embodiment not shown, the cavity 2 is made with sealed walls provided with vents, so as to form a “bass reflex” system making it possible to preserve the performance of the sound reproduction at low frequencies.

[0043] According to the embodiment shown, the plate 4 is located under a seat 13, so as to be protected from pressure from the passengers' feet.

[0044] A sound propagation assembly intended to be integrated into such an architecture 1 is now described, said assembly comprising: • a rigid plate 4, • an inertial electrodynamic transducer 5 fixed on the back of said plate, • a rigid frame 6 for supporting said plate, • a first decoupling means 7 in the form of an elastic seal extending around said plate, said plate being fixed inside said frame by means of said first means.

[0045] With reference to [Fig.2], an inertial electrodynamic transducer 5 is finally described, according to one embodiment, intended to be mounted in an architecture 1 as previously described, said transducer comprising a coil 14 and a magnet 15 fixed on a support 16, said support being fixed integrally to said coil by by means of a suspension means 17, said means being for example in the form of elastic blades shaped like bellows.

Claims

Claims

1. Architecture (1) for mounting an inertial electrodynamic transducer (5) in an interior compartment of a motor vehicle, said architecture comprising: • a cavity (2) provided with an opening (3), • a generally planar rigid plate (4) for transmitting sound vibrations, said plate being fixed by its periphery to the periphery of said opening by means of a decoupling device allowing movement of said plate relative to said cavity, • said transducer fixed on the reverse side of said plate on the side of said cavity, said decoupling device comprising: • a rigid frame (6) for supporting said plate, • a first decoupling means (7) in the form of a seal elastic extending around said plate, said plate being fixed inside said frame by means of said first means, • a second decoupling means (8) extending around said frame, said frame being fixed around said opening by means of said second means, said architecture being characterized in that: • the internal face of the cavity (2) is lined with an acoustic absorption layer (9) made of porous material with open porosity, • the porous material of the absorption layer (9) is elastically compressible, the frame (6) resting by at least part of its periphery on the edge (10) of said absorption layer, so that the second decoupling means (8) is formed at least in part by said absorption layer.

2. Architecture (1) according to claim 1, characterized in that the opening (3) extends only partially over the cavity (2), so that the frame (6) rests only by part of its periphery on the edge (10) of the absorption layer (9), an openwork wall being arranged in said cavity so as to receive on its edge the other part of the periphery of said frame, so that the second decoupling means (8) is formed partly by said absorption layer and partly by said openwork wall.

3. Architecture (1) according to any one of the preceding claims, characterized in that the first decoupling means (7) is made of elastomeric material.

4. Architecture (1) according to the preceding claim, characterized in that the first decoupling means (7) has a generally U-shaped section.

5. Architecture (1) according to any one of the preceding claims, characterized in that the first decoupling means (7) has a hardness of between 25 and 90 shore A.

6. Architecture (1) according to any one of the preceding claims, characterized in that the second decoupling means (8) has a Young's modulus of between 20 and 200 KPa.

7. Sound propagation assembly intended to be integrated into an architecture (1) according to any one of the preceding claims, said assembly comprising: • a rigid plate (4), • an inertial electrodynamic transducer (5) fixed to the back of said plate, • a rigid frame (6) for supporting said plate, • a first decoupling means (7) in the form of an elastic joint extending around said plate, said plate being fixed inside said frame by means of said first means.

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