Motor vehicle seat headrest

Abstract

The invention relates to a motor vehicle seat headrest, said headrest comprising a support block (1) provided with a cushion (2) of elastically compressible foam padding, said block being supported 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 vicinity of said headrest, the 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, the support block (1) comprising a rear wall (14) which is covered with an acoustically insulating layer (16) the airtightness of which is sufficient to prevent the passage of said acoustic waves through it. 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 to the rear of the headrest which could generate a sound signal disturbing passengers sitting behind the seat on which said headrest 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 supported 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, the support block comprising a rear wall which is covered with an acoustically insulating layer whose airtightness is sufficient to prevent the passage of said acoustic waves through it.

[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 viewed from the front of a support- head according to an embodiment of the invention;

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

[0014] [Fig.3] and [Fig.4] are schematic horizontal cross-sectional representations of the headrest of [Fig.1], according respectively to an embodiment of the invention.

[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 embodiments shown, the mounting frame 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] In particular, each cavity 8 has an opening 10 leading into a front wall 11 of the support block 1 opposite which the head of the occupant is intended to come, the plate 6 being mounted in said opening.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] In an alternative not shown, the headrest may also include a vibration decoupling means disposed between the support block 1 and the rigid frame 3, in particular in the form of elastomeric material sleeves interposed each between a rod 4 and its mounting conduit 5 in said support block, in order to prevent the propagation of vibrations at the mounting of said support block on said frame, and thus to prevent the propagation of said vibrations from said frame to the seat back.

[0033] The decoupling means 9 comprises an elastomeric material whose Young's modulus E is less than 20 kPa, in order to exhibit sufficient flexibility to decouple the vibrating plate 6 from the support cushion, and possibly to decouple said support cushion from the armature 3. 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 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 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] To avoid the transmission of vibrations from the support block 1 to the head of the seat occupant, said block includes a support layer 12 which is disposed on at least a part of the front wall 11 opposite which said head is intended to come, said support layer having a Young's modulus of less than 40 kPa.

[0039] Thus, the support layer 12 allows the support block 1 to have greater flexibility in the area facing the occupant's head, in order to provide localized acoustic decoupling while maintaining greater rigidity in the other areas of the cushion 2, in order to maintain the constraints related to the retention of the plates 6 and the absorption of shocks.

[0040] The support layer 12 also has an air resistance of less than 5,000 Nm⁴.s, in order to allow the passage through it of acoustic waves generated by the vibration of the plates 6, and thus allow said waves to reach the occupant's ears with preserved quality. The support layer 12 thus forms a solid insulating barrier, with both acoustic and sound-insulating properties. and shock-absorbing.

[0041] According to one embodiment, the support layer 12 is formed of a very open-cell foam without a membrane, in particular with cells having a diameter greater than 1 mm, and more particularly between 2 and 3 mm. This foam may, for example, be of the same type as the foams generally used for wind protection of microphones (so-called "pop-up" foams).

[0042] In the embodiments shown, the openings 10 of the cavities 8 are separated by a central zone 13 of the front wall 11, and the support layer 12 covers at least each of these openings 10 and said central zone. Advantageously, the support layer 12 extends over the entire front wall 11, which improves the comfort of the seat occupant.

[0043] Furthermore, the support block 1 is fitted with an appearance layer 15 under which the support layer 12 is arranged, which makes it possible to improve the aesthetic appearance of the headrest while protecting said support layer.

[0044] To avoid the propagation of acoustic waves to the rear of the headrest, and thus not to disturb any passengers located at the rear of the passenger compartment, the support block 1 includes a rear wall 14 which is covered with an acoustically insulating layer 16 whose airtightness is sufficient to prevent the passage of said acoustic waves through said insulating layer.

[0045] Advantageously, the acoustically insulating layer 16 has a surface mass between 400 g / m2 and 2 kg / m2 in order to have a good compromise between insulation and weight of said layer.

[0046] According to a first embodiment ([Fig.3]), the acoustically insulating layer 16 has a Young's modulus that is less than 500 MPa, in order to give said insulating layer sufficient flexibility to allow it to also have damping properties, and thus prevent the propagation to the rear of the headrest of the vibrations generated by the plates 6.

[0047] In this case, the insulating layer 16 constitutes a solid insulating barrier, with both acoustically insulating and damping properties.

[0048] Furthermore, in this first embodiment, the support block 1 can be fitted with a textile-based rear appearance layer (not shown), the acoustically insulating layer 16 being disposed under said rear appearance layer, in order to improve the aesthetic appearance of the headrest and to conceal and / or protect said insulating layer.

[0049] According to a second embodiment ([Fig.2]), the support block 1 has a rear shell 17 made of rigid material, in particular thermoplastic, said shell forming the acoustically insulating layer 16.

[0050] In this second embodiment, the insulating layer 16 notably has a Young's modulus exceeding 500 MPa gives the insulating layer excessive rigidity, preventing it from exhibiting damping properties. Therefore, this rigid layer 16 is combined with a vibration-damping layer 18 to form a barrier against vibration propagation to the rear of the headrest.

[0051] In particular, the vibration decoupling layer 18 is arranged under the insulating shell 16, 17, so as to be protected and / or concealed by it while improving the aesthetic appearance of the headrest.

[0052] The vibration decoupling layer 18 is based on an elastomer material whose Young's modulus is less than 40 kPa, in order to have sufficient flexibility to ensure its function of damping vibrations from the plates 6 and propagated to the support block 1.

[0053] The elastomeric material of this layer 18 is preferably foam-based, in particular polyurethane (PU) foam or EPDM (ethylene propylene diene monomer) rubber foam. Furthermore, this elastomeric material has a loss factor ETA greater than 0.25.

Claims

Demands

1. Motor vehicle seat headrest, said headrest comprising a support block (1) provided with a cushion (2) of elastically compressible foam padding, said block being supported 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 vicinity 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, the support block (1) comprising a rear wall (14) which is covered with an acoustically insulating layer (16) the airtightness of which is sufficient to prevent the passage of said acoustic waves through it,said acoustically insulating layer having a surface mass between 400 g / m2 and 2 kg / m2.

2. Headrest according to claim 1, characterized in that the acoustically insulating layer (16) has a Young's modulus E which is less than 500 MPa.

3. Headrest according to any one of claims 1 or 2, characterized in that the support block (1) is fitted with a textile-based appearance layer, the acoustically insulating layer (16) being disposed under said appearance layer.

4. Headrest according to claim 1, characterized in that the acoustically insulating layer (16) has a Young's modulus E which is greater than 500 MPa, said layer being associated with a vibration decoupling layer (18).

5. Headrest according to claim 4, characterized in that the vibration decoupling layer (18) is based on an elastomeric material whose Young's modulus E is less than 40 kPa.

6. Headrest according to any one of claims 4 or 5, characterized in that the vibration decoupling layer (18) is based on an elastomeric material having a loss factor ETA which is greater than 0.

25.

7. Headrest according to any one of claims 4 to 6, characterized in that the support block (1) has a rear shell of appearance (17), said shell forming the acoustically insulating layer (16) under which is disposed the vibration decoupling layer (18).

8. Headrest according to any one of claims 1 to 7, characterized in that the support block (1) is provided with at least one cavity (8) in which the plate (6) is fixed, said cavity having an opening (10) leading into a front wall (11) of said block.

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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