Motor vehicle seat headrest

Abstract

The invention relates to a headrest comprising a support block (1) provided with a padding cushion (2) made of elastically compressible foam, supported by a rigid mounting frame (3) for said headrest at the top of the seat backrest, said headrest being equipped with an acoustic wave generator comprising at least one plate (6) on which an electrodynamic transducer (7) is associated, said plate being fixed to the support block (1) and arranged to be excited into vibration by said transducer in order to generate the acoustic waves, said headrest comprising a vibration decoupling means (9, 10) which is disposed between said plate and said support block and / or between said support block and the rigid frame (3), said decoupling means comprising an elastomeric material having a Young's modulus E of less than 20 kPa. Figure 3

Description

Title of the invention: Motor vehicle seat headrest

[0001] The invention relates to a motor vehicle seat headrest, as well as an acoustic wave generation assembly in a motor vehicle passenger compartment comprising such a headrest.

[0002] It is known to equip a headrest with an acoustic wave generator that emits a sound signal near the head of an occupant of the seat on which the headrest is mounted. The waves are then generated as close as possible to the user's ears in order to limit acoustic loss.

[0003] In addition to an audible signal, the generator can emit an "anti-noise" type sound signal, i.e. in opposition to the noises inside the passenger compartment, in order to allow active control of passenger compartment noise.

[0004] To achieve this, at least one speaker can be integrated into the headrest volume. However, the size of a speaker makes it difficult to fit into a small component such as a headrest, and its weight significantly increases the weight of the headrest in which it is installed.

[0005] In addition, the speakers fitted to the headrests emit at medium frequency and / or high frequency but, for reasons of size, cannot emit at frequencies below 150 Hz, whereas these low frequencies, in particular frequencies of 100 Hz or even 60 Hz, are necessary for the quality of a sound signal in particular of the "anti-noise" type.

[0006] Acoustic wave generators are known, comprising a rigid plate which is excited into vibration by an electrodynamic transducer in order to generate said waves. Thus, the transducer makes it possible to transform an electrical control signal into an acoustic signal by using the plate on which it is fixed as the radiating surface.

[0007] Due to its compactness, this solution makes it possible to limit the problem of the bulk of the acoustic wave generator to be integrated into a headrest, but generates an important problem of transmission of vibrations to said headrest, which can be a source of discomfort in the environment of said headrest, in particular for the passenger sitting on the seat which is equipped with it.

[0008] The invention aims to provide a headrest that overcomes these drawbacks, in particular the transmission of vibrations between the headrest and the seat on which it is mounted.

[0009] To this end, according to a first aspect, the invention proposes a headrest for a motor vehicle seat, said headrest comprising a support block provided with a cushion of elastically compressible foam padding, said block being carried by a rigid mounting frame for said headrest at the top of the seat back, said headrest being equipped with an acoustic wave generator in the environment of said headrest, the generator comprising at least one plate on which an electrodynamic transducer is associated, said plate being fixed to the support block and arranged to be excited into vibration by said transducer in order to generate the acoustic waves, said headrest comprising a vibration decoupling means which is disposed between said plate and said support block and / or between said support block and the rigid frame, said decoupling means comprising an elastomeric material having a Young's modulus E of less than 20 kPa.

[0010] According to a second aspect, the invention proposes an acoustic wave generation assembly in a motor vehicle cabin, said assembly comprising such a headrest and a control system for at least one transducer to excite into vibration the plate on which it is associated.

[0011] Other features and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which:

[0012] [Fig.1] is a schematic perspective representation seen from the front of a headrest according to an embodiment of the invention;

[0013] [Fig.2] is a schematic exploded perspective view schematic representation from the front of the headrest of [Fig.1];

[0014] [Fig.3] is a schematic horizontal cross-sectional representation of the headrest of [Fig.1].

[0015] In relation to these figures, a motor vehicle seat headrest is described below, as well as an acoustic wave generation assembly in a motor vehicle passenger compartment which includes such a headrest.

[0016] In this description, the terms of positioning in space (lateral, transverse, high, rear, ...) are taken with reference to the headrest arranged in the vehicle in a situation of use.

[0017] The headrest comprises a support block 1 provided with a padding cushion 2 made of elastically compressible foam, said block being carried by a rigid frame 3 for mounting said headrest to the top of the backrest of a motor vehicle seat (not shown).

[0018] The mounting frame 3 may include at least one rod 4, in particular made of metallic material, which is fitted into a conduit 5 formed in the support block 1.

[0019] In particular, the support block 1 may include a housing, in particular made of molded plastic material, for absorbing energy in the event of a head impact on an occupant, which is surrounded by the padding cushion 2, the conduit 5 being formed in said housing.

[0020] In the embodiment shown, the mounting bracket 3 has an inverted U-shaped geometry, the arms of which form two rods 4 which are each fitted into respectively a conduit 5 formed in the support block 1.

[0021] The cushion 2 may be in the form of a molded skin foam block, the skin of which is disposed on the outside, said foam having a hardness greater than 25 shore A, and in particular of the order of 30 shore A.

[0022] The foam of the support block 1 may also have a density between 0.20 and 0.30, and in particular of the order of 0.25.

[0023] The headrest is equipped with an acoustic wave generator in the environment of said headrest, the generator comprising at least one plate 6 on which is associated an electrodynamic transducer 7.

[0024] The plate 6 is fixed to the support block 1 in such a way as to be excited into vibration by the transducer 7, in order to generate acoustic waves. The acoustic wave generation assembly in the passenger compartment includes a control system for the transducer 7 to excite into vibration the plate 6 to which it is attached.

[0025] In the embodiment shown, the headrest comprises two generators arranged laterally on either side of the support block 1, each comprising a transducer 7 associated respectively with a plate 6 to excite it into vibration, so as to generate acoustic waves on each side of the head of a seat occupant.

[0026] Furthermore, the control system is arranged to control each of the two transducers 7, jointly or independently.

[0027] The padding cushion 2 is provided with two cavities 8 arranged laterally on either side of the support block 1, and in each of which a plate 6 is fixed by its periphery to said padding cushion.

[0028] The plates 6 each have a Young's modulus E greater than 10 MPa, in particular between 100 MPa and 1 GPa, in order to have sufficient rigidity to generate acoustic waves without deformation when excited into vibration by their transducer 7.

[0029] To avoid the transmission of vibrations generated by the plate 6, the headrest includes a vibration decoupling means which is disposed between said plate and said support block and / or between said support block and the rigid frame 3.

[0030] In particular, the vibration decoupling means comprises two seals 9 made of elastomeric material which are interposed each between respectively a plate 6 and the padding cushion 2, each surrounding the periphery of said plate.

[0031] In the embodiment shown, the headrest also includes a vibration decoupling means disposed between the support block 1 and the rigid frame 3, in order to prevent the propagation of vibrations at the mounting of said support block on said frame, and thus the propagation of said vibrations from said frame to the seat back.

[0032] To do this, this second decoupling means comprises two sleeves 10 made of elastomeric material which each equip a rod 4 respectively, so as to be interposed between said rod and its mounting conduit 5 in the support block 1.

[0033] Each decoupling means 9, 10 comprises an elastomeric material having a Young's modulus E of less than 20 kPa, in order to exhibit sufficient flexibility to decouple the vibrating plate 6 from the support pad (for the joints 9) or to decouple said support pad from the reinforcement 3 (for the sleeves 10). In particular, the high flexibility of the material allows for particularly effective vibration decoupling at low frequencies, notably below 150 Hz, or even 100 Hz and down to 60 Hz.

[0034] In addition, the flexibility of the elastomer material is adapted to allow the decoupling means 9, 10 to withstand the mechanical stresses required for the headrest in the event of an impact on it from the head of the seat occupant.

[0035] The elastomeric material is preferably foam-based, in particular polyurethane (PU) foam or EPDM rubber foam (for "ethylene-propylene-diene monomer").

[0036] Furthermore, the elastomeric material of the decoupling means 9, 10 has a loss factor ETA which is greater than 0.2 in order to optimize its decoupling function.

[0037] Advantageously, the foam of the cushion 2 has a flexibility suitable for contributing to vibration decoupling between the support block 1 and the plates 6, while also having sufficient rigidity to ensure that said plates remain in their respective cavities 8. In particular, the foam of the cushion 2 has a Young's modulus E greater than 20 kPa, enabling vibration decoupling at medium and high frequencies.

[0038] The support block 1 can also be fitted with an appearance layer (not shown), in particular for aesthetic reasons and to conceal and / or protect the acoustic wave generators.

Claims

Demands

1. Motor vehicle seat headrest, said headrest comprising a support block (1) provided with a padding cushion (2) of elastically compressible foam, said block being carried by a rigid mounting frame (3) for said headrest at the top of the seat back, said headrest being equipped with an acoustic wave generator in the environment of said headrest, said headrest being characterized in that the generator comprises at least one plate (6) on which an electrodynamic transducer (7) is associated, said plate being fixed to the support block (1) and arranged to be excited into vibration by said transducer in order to generate the acoustic waves, said headrest comprising a vibration decoupling means (9, 10) which is disposed between said plate and said support block and / or between said support block and the rigid frame (3),said decoupling means comprising an elastomeric material having a Young's modulus E of less than 20 kPa.

2. Headrest according to claim 1, characterized in that the elastomeric material of the decoupling means (9, 10) has a loss factor ETA which is greater than 0.

2.

3. Headrest according to any one of claims 1 or 2, characterized in that it comprises two generators arranged laterally on either side of the support block (1), so as to generate acoustic waves on each side of the head of a seat occupant.

4. Headrest according to any one of claims 1 to 3, characterized in that the mounting frame (3) comprises at least one rod (4) which is fitted into a conduit (5) formed in the support block (1), the vibration decoupling means comprising a sleeve (10) made of elastomeric material which is interposed between the rod (4) and the conduit (5).

5. Headrest according to claim 4, characterized in that the mounting frame (3) comprises two rods (4) each equipped with a sleeve (10) made of elastomeric material.

6. Headrest according to any one of claims 1 to 5, characterized in that the plate (6) is fixed to the padding cushion (2).

7. Headrest according to claim 6, characterized in that the vibration decoupling means comprises a seal (9) made of elastomeric material which is interposed between the plate (6) and the padding cushion (2).

8. Headrest according to claim 7, characterized in that the cushion of padding (2) is provided with at least one cavity (8) in which the plate is fixed by its periphery, the joint (9) surrounding said periphery.

9. Headrest according to any one of claims 1 to 8, characterized in that the plate (6) has a Young's modulus E which is greater than 10 MPa.

10. Acoustic wave generation assembly in a motor vehicle cabin, said assembly comprising a headrest according to any one of claims 1 to 9 and a control system for at least one transducer (7) to excite into vibration the plate (6) on which it is associated.

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