Headrest for seat of motor vehicle

Abstract

The invention relates to a headrest for a seat of a motor vehicle, comprising a support block (1) provided with a filling pad (2) made of an elastically compressible foam, said support block being supported by a rigid mounting frame (3) for mounting the headrest at the top of the backrest of the seat, the invention relates to a headrest equipped with a sound wave generator for generating sound waves in the surroundings of the headrest, said sound wave generator comprising at least one plate (6) on which an electrodynamic transducer (7) is arranged, said plate being attached to a support block (1) and arranged to be excited by said transducer to generate sound waves, the support block (1) comprising a rear wall (14) covered by a sound insulation layer (16), the sealing performance of the sound insulation layer to airflow is sufficient to prevent sound waves from penetrating through the sound insulation layer.

Description

Technical Field

[0001] The invention relates to a headrest for a seat of a motor vehicle and to an assembly for generating sound waves in a passenger compartment of a motor vehicle comprising such a headrest. Background Art

[0002] As is known, headrests are equipped with sound wave generators that allow sound signals to be emitted near the head of the occupant of the seat in which the headrest is mounted. These sound waves are then generated as close as possible to the user's ears in order to limit sound losses.

[0003] In addition to the audible signal, the generator can also emit an acoustic signal of the “anti-noise” type, ie an acoustic signal that is in phase opposite to the noise in the passenger compartment, so as to enable active control of the noise in said passenger compartment.

[0004] To achieve this, at least one speaker can be integrated into the space of the headrest. However, the size of the speaker makes it difficult to fit into a small component such as a headrest, and the weight of the speaker also makes the headrest equipped with the speaker significantly heavier.

[0005] Furthermore, the speakers fitted to the headrests emit mid-range and / or high frequencies but, due to their size, are unable to emit frequencies below 150 Hz, whereas these low frequencies, in particular those of 100 Hz or even 60 Hz, are essential for the quality of the sound signal, especially that of the "anti-noise" type.

[0006] Known acoustic wave generators comprise a rigid plate excited to vibrate by an electric transducer to generate the waves. In this way, the transducer allows the conversion of an electrical control signal into an acoustic signal by using the plate to which the transducer is attached as a radiating surface.

[0007] Although this solution allows reducing the space required to integrate the sound wave generator into the headrest due to its compactness, it also presents the significant problem of the transmission of vibrations to the headrest, which in turn may cause discomfort in the environment surrounding the headrest, in particular for a passenger sitting in a seat equipped with such a headrest. Summary of the Invention

[0008] The object of the present invention is to provide a headrest that overcomes these drawbacks, in particular the transmission of vibrations to the rear of the headrest, which may generate an acoustic signal that is disturbing to a passenger seated behind the seat on which the headrest is mounted.

[0009] To this end, according to a first aspect, the invention proposes a headrest for a seat of a motor vehicle, the headrest comprising a support block provided with a padding made of elastically compressible foam, the support block being supported by a rigid frame for mounting the headrest at the top of the backrest of the seat, the headrest being equipped with a sound wave generator for generating sound waves in the surroundings of the headrest, the sound wave generator comprising at least one plate on which an electric transducer is arranged, the plate being attached to the support block and being arranged to be excited into vibration by the transducer in order to generate sound waves, the support block comprising a rear wall covered with a sound insulation layer whose sealing properties to the air flow are sufficient to prevent sound waves from passing through it.

[0010] According to a second aspect, the invention proposes an assembly for generating sound waves in a passenger compartment of a motor vehicle, said assembly comprising such a headrest and a control system for controlling at least one transducer to excite vibrations of a panel, the transducer being arranged on the panel. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, in which:

[0012] [ Figure 1 ] is a schematic front perspective view of a headrest according to an embodiment of the present invention;

[0013] [ Figure 2 ]yes[ Figure 1 ] is a schematic rear exploded perspective view of the headrest shown;

[0014] [ Figure 3 ]and[ Figure 4 ] are respectively according to the corresponding embodiments of the present invention Figure 1 Schematic horizontal cross-section of the head restraint shown. DETAILED DESCRIPTION

[0015] In conjunction with these figures, a headrest for a seat of a motor vehicle and an assembly for generating sound waves in a passenger compartment of a motor vehicle including such a headrest will be described below.

[0016] In this manual, the terms spatial positioning (side, transverse, top, rear, etc.) refer to the positioning of the headrest in the vehicle when in use.

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

[0018] The rigid frame 3 may comprise at least one rod 4 , in particular made of metal material and fitting into a duct 5 formed in the support block 1 .

[0019] In particular, the support block 1 may comprise a shell for absorbing energy in the event of an impact on the head of an occupant, in particular made of molded plastic material and surrounded by the padding 2 , in which shell the duct 5 is formed.

[0020] In the embodiment shown, the rigid frame 3 has an inverted U-shaped geometry, branching out to form two rods 4 , each of which is fitted in a corresponding guide 5 formed in the support block 1 .

[0021] The filling pad 2 may be in the form of a molded skin foam block, with the skin being on the outside, the foam having a hardness greater than 25 Shore A, in particular approximately 30 Shore A.

[0022] The foam density of the support block 1 can also be between 0.20 and 0.30, in particular approximately 0.25.

[0023] The headrest is equipped with a sound wave generator for generating sound waves in the surroundings of said headrest, said sound wave generator comprising at least one plate 6 on which an electric transducer 7 is arranged.

[0024] A plate 6 is attached to the support block 1 and is arranged to be excited into vibration by a transducer 7 to generate sound waves. The assembly for generating sound waves in the passenger compartment comprises a control system for controlling the transducer 7 to excite into vibration the plate 6 on which the transducer is arranged.

[0025] In the embodiment shown, the headrest comprises two generators arranged transversely on either side of the support block 1 , each generator comprising a transducer 7 placed on a respective plate 6 to excite said plate to vibrate in order to generate sound waves on either side of the seat occupant's head.

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

[0027] The filling pad 2 is provided with two cavities 8 arranged transversely on either side of the support block 1 , in each cavity a plate 6 is attached to said filling pad by the periphery of the plate.

[0028] In particular, each cavity 8 has an orifice 10 opening into a front wall 11 of the support block 1 , against which the head of the occupant will be positioned, and in which the plate 6 is mounted.

[0029] The Young's modulus E of each plate 6 is greater than 10 MPa, in particular between 100 MPa and 1 GPa, so as to provide sufficient rigidity to generate acoustic waves without deformation when excited to vibrate by their transducers 7 .

[0030] In order to prevent the transmission of vibrations generated by the plate 6 , the headrest comprises a vibration decoupling device arranged between said plate and said support block.

[0031] In particular, the vibration decoupling device comprises two seals 9 made of elastomeric material, each seal being interposed between a respective plate 6 and a filling pad 2 around the periphery of said plate.

[0032] In a variant not shown, the headrest may also comprise a vibration decoupling device arranged between the support block 1 and the rigid frame 3, in particular in the form of sleeves made of elastomeric material, each sleeve being interposed between a rod 4 and a mounting conduit 5 of said rod in said support block, in order to avoid the propagation of vibrations at the point of mounting of said support block on said frame, and thereby to avoid the propagation of said vibrations from said frame to the backrest of the seat.

[0033] The decoupling device 9 comprises an elastomeric material with a Young's modulus E of less than 20 kPa, in order to provide sufficient flexibility to decouple the vibration plate 6 from the support block 1 and to be able to decouple the support block from the frame 3. In particular, the high flexibility of this material allows particularly effective vibration decoupling at low frequencies, in particular below 150 Hz, or even between 100 Hz and 60 Hz.

[0034] Furthermore, the flexibility of the elastomeric material is suitable for allowing the decoupling device 9 to withstand the mechanical stresses required of the headrest when the head of the seat occupant strikes the headrest.

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

[0036] Furthermore, the ETA loss factor of the elastomeric material of the decoupling device 9 is greater than 0.2, in order to optimize the decoupling function of the decoupling device.

[0037] Advantageously, the foam filling the pad 2 is sufficiently flexible to facilitate vibration decoupling between the support block 1 and the plate 6, while being sufficiently rigid to ensure that the plates are retained within their respective cavities 8. In particular, the Young's modulus E of the foam filling the pad 2 is greater than 20 kPa, thereby allowing vibration decoupling of medium and high frequencies.

[0038] In order to prevent vibrations from being transmitted from the support block 1 to the head of the seat occupant, the support block comprises a support layer 12 arranged on at least a portion of the front wall 11 (to which the occupant's head will be opposed), the Young's modulus of the support layer being less than 40 kPa.

[0039] In this way, the support layer 12 makes the support block 1 more flexible in the area facing the occupant's head to provide local acoustic decoupling, while maintaining higher stiffness in other areas of the padding 2 to maintain the stresses associated with holding the plate 6 in place and absorbing impacts.

[0040] The support layer 12 also has a strength of less than 5,000 Nm -4 .s of air flow resistance in order to allow the sound waves generated by the vibration of the panel 6 to pass through the support layer, thereby allowing the sound waves to reach the ears of the occupant with fidelity. Therefore, the support layer 12 forms a solid insulating barrier with both sound insulation and damping properties.

[0041] In one embodiment, the support layer 12 is made of a membrane-free, highly open-cell foam, in particular a foam having open cells with a diameter greater than 1 mm, more particularly between 2 mm and 3 mm. For example, this foam may be of the same type as the foam commonly used for wind protection of microphones (so-called "pop-up" foams).

[0042] In the embodiment shown, the openings 10 of the cavity 8 are separated by a central region 13 of the front wall 11, with the support layer 12 covering at least each of these openings 10 and said central region. Advantageously, the support layer 12 extends over the entire front wall 11, thereby enhancing the comfort of the seat occupant.

[0043] Furthermore, the support block 1 is equipped with an appearance layer 15 , beneath which the support layer 12 is arranged, which allows improving the aesthetic appearance of the headrest while protecting said support layer.

[0044] In order to prevent the sound waves from propagating behind the headrest and thus disturbing any passenger at the rear of the passenger compartment, the support block 1 comprises a rear wall 14 covered with a sound insulation layer 16 which is sufficiently impervious to airflow to prevent the sound waves from passing through it.

[0045] Advantageously, the mass per unit area of the sound insulation layer 16 is between 400 g / m² and 2 kg / m², thereby achieving a good balance between the insulating properties and the weight of the sound insulation layer.

[0046] According to the first embodiment ( Figure 3 ), the Young's modulus of the sound insulation layer 16 is less than 500 MPa, in order to give the sound insulation layer sufficient flexibility so that the sound insulation layer also has damping performance, thereby preventing the vibration generated by the plate 6 from propagating to the rear of the headrest.

[0047] In this case, the sound insulation layer 16 acts as a solid insulating barrier that combines sound insulation and damping properties.

[0048] Furthermore, in this first embodiment, the support block 1 may be equipped with a fabric-based rear appearance layer (not shown), said sound insulation layer 16 being arranged beneath said rear appearance layer in order to improve the aesthetic appearance of the headrest and to hide and / or protect said sound insulation layer.

[0049] In the second embodiment ( Figure 2 ), the support block 1 has a rear appearance shell 17 made of a rigid material, in particular a thermoplastic material, which forms the sound insulation layer 16.

[0050] In this second embodiment, the Young's modulus of the sound insulation layer 16 is specifically greater than 500 MPa, which makes the sound insulation layer too rigid to provide damping performance. Therefore, the rigid layer 16 is combined with the vibration decoupling layer 18 to form a barrier that prevents vibrations from propagating to the rear of the headrest.

[0051] In particular, the vibration decoupling layer 18 is arranged below the insulating shells 16 , 17 so as to protect and / or hide the vibration decoupling layer while improving the aesthetic appearance of the headrest.

[0052] The vibration decoupling layer 18 is based on an elastomeric material having a Young's modulus of less than 40 kPa, so as to provide a sufficient flexibility to ensure its function of damping vibrations originating from the plate 6 and propagating to the support block 1 .

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

Claims

1. A headrest for a seat of a motor vehicle, the headrest comprising a support block (1) provided with a filling pad (2) made of elastically compressible foam, the support block being supported by a rigid mounting frame (3) for mounting the headrest at the top of the backrest of the seat, the headrest being equipped with a sound wave generator for generating sound waves in the surroundings of the headrest, the headrest being characterized in that the sound wave generator comprises at least one plate (6) provided with an electric transducer (7), the plate being attached to the support block (1) and being arranged to be excited into vibration by the electric transducer to generate sound waves, the support block (1) comprising a rear wall (14) covered with a sound insulation layer (16), the sound insulation layer being sufficiently airtight to prevent the sound waves from passing through the sound insulation layer.

2. The headrest according to claim 1, characterized in that The Young's modulus E of the sound insulation layer (16) is less than 500 MPa.

3. The headrest according to claim 1 or 2, characterized in that: The support block (1) is equipped with a textile-based appearance layer, the sound insulation layer (16) being arranged below the appearance layer.

4. The headrest according to claim 1, wherein: The Young's modulus E of the sound insulation layer (16) is greater than 500 MPa, and the sound insulation layer is connected to the vibration decoupling layer (18).

5. The headrest according to claim 4, characterized in that The vibration decoupling layer (18) is based on an elastomeric material having a Young's modulus E of less than 40 kPa.

6. The headrest according to claim 4 or 5, characterized in that: The vibration decoupling layer (18) is based on an elastomeric material having an ETA loss factor greater than 0.

25.

7. The headrest according to any one of claims 4 to 6, characterized in that The support block (1) has a rear appearance shell (17), which forms the sound insulation layer (16), and the vibration decoupling layer (18) is arranged below the sound insulation layer.

8. The headrest according to any one of claims 1 to 7, characterized in that The unit area mass of the sound insulation layer (16) is between 400 g / m 2 and 2kg / m 2 between.

9. The headrest according to any one of claims 1 to 8, characterized in that The support block (1) is provided with at least one cavity (8) in which the plate (6) is attached, the cavity having an orifice (10) leading to a front wall (11) of the support block.

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

11. An assembly for generating sound waves in a passenger compartment of a motor vehicle, the assembly comprising: A headrest according to any one of claims 1 to 10, and a control system for controlling at least one electrodynamic transducer (7) to excite the plate (6) to vibration, the electrodynamic transducer being arranged on the plate.

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