LOW-FREQUENCY PNEUMATIC SPEAKER FOR MOTOR VEHICLES

Abstract

LOW-FREQUENCY PNEUMATIC SPEAKER FOR MOTOR VEHICLES The present invention relates to a loudspeaker (2) for a motor vehicle (1), comprising a rigid enclosure (3) provided with a movable diaphragm (10) forming at least a portion of a lateral face (3.1) of said rigid enclosure, notable in that the rigid enclosure delimits an enclosure (3.2) at an internal pressure, said rigid enclosure being surrounded externally by an environment (5) at an external pressure, the internal pressure within the enclosure being configured to vary between values ​​lower than and higher than the external pressure, so as to cause the movable diaphragm to move and generate sound by said movement. (Figure to be published with the abbreviation: Figure 1)

Description

Title of the invention: LOW-FREQUENCY PNEUMATIC SPEAKER FOR MOTOR VEHICLES technical field

[0001] The present invention relates to the field of loudspeakers, more particularly to the field of loudspeakers for motor vehicles. Previous technique

[0002] In the field of automotive audio systems, three main types of loudspeakers are commonly used: electrodynamic transducers, electrostatic transducers and piezo transducers.

[0003] Electrodynamic transducers are the most common. They operate with a magnet and a moving coil driving a diaphragm that moves under the influence of the Laplace force to produce sound. However, these loudspeakers have several drawbacks. They have a relatively low efficiency, generally between 5 and 10%, and their excursion capacity is limited by the size of the magnet and the coil. In addition, their weight increases with the size of these components, and the use of rare materials such as neodymium to improve performance can increase costs and complexity.

[0004] For low frequencies (below 200 Hz), which require a large volume of air displaced, the large size of the diaphragm, coil and magnet can pose space problems, particularly in the passenger compartment of vehicles where space is generally limited.

[0005] Electrostatic transducers, on the other hand, use very high supply voltages, often several hundred or even thousands of volts, which makes them difficult to handle and limits their power.

[0006] Piezo transducers, which operate with piezoelectric materials, are mainly used for high frequencies. Their ability to move large quantities of air being limited, they are not suitable for low frequencies.

[0007] The published patent document KR 2008 0105826 A discloses a pneumatic loudspeaker comprising a reciprocating pneumatic cylinder connected to a diaphragm, the latter being able to vibrate to generate sound according to the movements of the cylinder, the pressure of which is controlled by a signal conversion device.

[0008] However, the loudspeaker disclosed in document KR 2008 0105826 A does not resolve the problems mentioned above. In particular, the arrangement of the reciprocating pneumatic cylinder in the loudspeaker is especially bulky. Description of the invention

[0009] The present invention aims to overcome at least one of the drawbacks of the aforementioned prior art. More particularly, the invention aims to provide a simple and efficient solution for diffusing sound, especially low frequencies, in a motor vehicle passenger compartment, while occupying a small space.

[0010] To this end, the invention relates to a loudspeaker for a motor vehicle, comprising a rigid box provided with a movable diaphragm forming at least part of a lateral face of said rigid box, notable in that the rigid box delimits an enclosure at an internal pressure, said rigid box being surrounded externally by an environment at an external pressure, the internal pressure within the enclosure being configured to vary between values ​​lower and higher than the external pressure, so as to cause the movable diaphragm to move and generate sound by said movement.

[0011] Advantageously, the loudspeaker is devoid of a coil and magnet, the sound being generated exclusively by the movements of the moving diaphragm.

[0012] Preferably, the movement of the moving membrane comprises a linear, dynamic, and repetitive displacement of said moving membrane relative to the rigid housing. More preferably, the moving membrane is configured to oscillate in a controlled manner.

[0013] According to one embodiment, said loudspeaker comprising a pneumatic circuit provided with a pressurized gas flow circulating from upstream to downstream in said pneumatic circuit, from a pressurized gas source to the enclosure.

[0014] Advantageously, the moving membrane is fluidly connected to the pressurized gas within the enclosure, the movement of said moving membrane being exclusively ensured by means of the variation of the internal pressure of said pressurized gas in the enclosure.

[0015] According to one embodiment, the pneumatic circuit further includes an expansion compartment for the pressurized gas flow, said pressurized gas flow circulating from upstream to downstream from the pressurized gas source to the expansion compartment, passing through the enclosure.

[0016] According to one embodiment, the pneumatic circuit further includes at least one flow modulator configured to modulate the flow rate of the pressurized gas stream according to the sound to be generated.

[0017] According to one embodiment, the at least one flow modulator comprises a first flow modulator arranged between the pressurized gas source and the enclosure, and a second flow modulator arranged between said enclosure and the expansion compartment.

[0018] According to one embodiment, the at least one flow modulator comprises a controlled displacement valve, or a butterfly valve, or a rotary disc valve, or a circular passage valve.

[0019] Preferably, an external electrical signal is used to adjust the position and / or rotational speed of the valve. This signal may originate from an automatic sound management control system.

[0020] According to one embodiment, the movable membrane is connected in a suspended manner to the rigid box by means of a suspension.

[0021] Preferably, the suspension is obtained from an elastic material, preferably butyl, rubber or latex.

[0022] The invention also relates to a motor vehicle comprising at least one loudspeaker, notable in that said at least one loudspeaker is according to the invention.

[0023] The invention also relates to a method of generating sound by means of a loudspeaker, remarkable in that said loudspeaker is according to the invention, and in that said method comprises the variation of the internal pressure within the box between values ​​lower and higher than the external pressure, so as to cause the moving membrane to move and generate sound.

[0024] According to one embodiment, the variation of the internal pressure includes a simultaneous control of the first flow modulator and the second flow modulator.

[0025] The measures of the invention are advantageous in that the suppression of the coil and the magnet, compared with the loudspeakers of the prior art, allows a considerable gain in size, making the loudspeaker of the invention substantially more compact, and consequently easier to integrate into the passenger compartment of the motor vehicle.

[0026] Dynamic control of the gas flow pressure upstream of the moving membrane also promotes larger and more linear displacements of said membrane, which improves the level and quality of sound, particularly for low frequencies, below 200 Hz.

[0027] Furthermore, the absence of a coil eliminates heat loss, making the system more efficient. In addition, the invention reduces the use of rare materials, making the loudspeaker more economical and environmentally friendly. Brief description of the drawings

[0028] [Fig. 1] schematically illustrates a loudspeaker according to the invention, comprising a rigid enclosure provided with a movable diaphragm configured to move into movement following pressure variations within said rigid box to generate sound. Detailed description

[0029] Fig. 1 is an illustration of the loudspeaker 2 according to the invention, adapted to be placed in the passenger compartment of a motor vehicle 1.

[0030] The loudspeaker 2 includes a rigid housing 3 provided with a movable diaphragm 10 arranged at the level of a lateral face 3.1 of said housing 3. In this configuration, the movable diaphragm 10 forms at least a part of said lateral face 3.1.

[0031] Preferably, the movable membrane 10 has a circular shape (viewed from the front) and is substantially flat in its initial rest position (as illustrated). The movable membrane 10 is suspended from the rigid housing 3 by means of a suspension 11. This suspension extends circumferentially around the membrane 10, continuously over 360°. The suspension 11 may consist of at least one return spring or a flexible and elastically deformable material, ensuring a direct connection between the movable membrane 10 and the housing 3 and allowing linear displacement movements of said movable membrane 10.

[0032] The box 3 delimits an enclosure 3.2 comprising a pressurized gas having an internal pressure "Pi", while said box 3 is surrounded externally by an environment 5 at an external pressure "Pe", which may correspond, for example, to atmospheric pressure.

[0033] Advantageously, the internal pressure Pi within the enclosure 3.2 is configured to vary (successively) between values ​​lower and higher than the external pressure Pe, so as to set the movable membrane 10 in motion and generate sound.

[0034] Thus, when Pi > Pe, the membrane 10 moves outwards (towards the environment 5), and when Pi < Pe, the membrane 10 moves inwards towards the interior of the enclosure 3.2. The succession of entry and exit movements of the moving membrane 10 (illustrated by the dashed arrow) generates sound. Indeed, the movement of the moving membrane 10 can be manifested by a rapid series of linear displacements successively inwards and outwards, creating vibrations. These vibrations are transmitted to the surrounding air in contact with the membrane 10, thus generating sound.

[0035] The loudspeaker 2 preferably comprises a pneumatic circuit 4 provided with a pneumatic source 6 which may correspond, for example, to a pressurized gas reservoir and an appropriate pump, capable of transmitting a pressurized gas flow F to circulate upstream to downstream in the pneumatic circuit 4.

[0036] The pressurized gas flow F preferably corresponds to air having a pressure greater than atmospheric pressure. The flow F preferably passes through at least one flow modulator 8.1, 8.2, also referred to as: chopper 8.1, configured to modulate the flow rate of said flow F according to an electrical signal corresponding to the sound to be generated by the loudspeaker 2. This signal may originate from an external automatic control system separate from the loudspeaker 2.

[0037] It is understood that the modulation of the flow rate of the gas flow F includes the variation of the pressure of said flow F, which makes it possible to act directly on the internal pressure Pi within the enclosure 3.2.

[0038] The at least one flow modulator 8.1, 8.2 may comprise a controlled displacement valve, or a butterfly valve, or a rotary disc valve, or a circular bore valve. More preferably, the at least one flow modulator 8.1, 8.2 corresponds to a solenoid valve or a butterfly valve.

[0039] Advantageously, the movable membrane 10 is exclusively connected in a fluidic way to the pressurized gas flow F, said membrane 10 is designed to move in response to variations in gas pressure (managed by the flow modulator 8.1, 8.2), so that these movements produce sound.

[0040] The moving membrane 10 can be made of different materials depending on the pressure level available at the source 6. Preferably, the moving membrane is made of a lightweight and rigid material that allows it to push outside air from the environment 5. The moving membrane 10 can be made of materials similar to those used for the membranes of traditional electrodynamic loudspeakers. More preferably, the moving membrane 10 is made of at least one of the following: coated cardboard, resin-coated fiber (including carbon fiber, e.g., epoxy).

[0041] The pneumatic circuit 4 preferably comprises an inlet duct 4.1 connecting the pressurized gas source 6 to the enclosure 3.2, and preferably further comprises an exhaust duct 4.2 connecting said enclosure 3.2 to an expansion chamber 12. The latter may correspond to an exhaust 12 allowing the airflow F to be discharged to the external environment 5; in this case, the pneumatic circuit 4 is open. Alternatively, the expansion chamber 12 may correspond to a low-pressure reservoir 12 where the gas flow F is preferably maintained at a pressure lower than that of the external environment 5. In this alternative configuration, the circuit 4 is closed.

[0042] At the expansion compartment 12, the pressure of the pressurized gas exiting the circuit 4 can be less than or equal to the external pressure Pe. This allows the enclosure 3.2 to be forced to "drain" and ensures the return (by a "recoil" movement) of the movable diaphragm 10 to its initial position. While the gas pressure at the level of the pneumatic source 6 is greater than the internal pressure Pi within the enclosure 3.2.

[0043] Preferably, at least one flow modulator 8.1, 8.2 comprises a first flow modulator 8.1 arranged at the right of the inlet duct 4.1 between the pressurized gas source 6 and the enclosure 3.2, and a second flow modulator 8.2 arranged at the right of the exhaust duct 4.2 between said enclosure 3.2 and the expansion compartment 12.

[0044] In this regard, a sound generation method according to the present invention includes varying the internal pressure Pi within the box 3 by means of simultaneous, preferably synchronized, control of the first flow modulator 8.1 and the second flow modulator 8.2.

[0045] For example, control of the internal pressure Pi in the housing 3 can be ensured by means of a synchronized oscillation of the butterfly housings 8.1, 8.2. Thus, it is possible to control as a function of time the pressure in the enclosure 3.2 and therefore the movement of the movable diaphragm 10.

[0046] Advantageously, the pneumatic source 6 and the flow modulators 8.1, 8.2 can be remote, thus further facilitating their integration into the passenger compartment of the motor vehicle 1.

[0047] When the pressure at the expansion chamber 12 is equal to the external pressure Pe (e.g., atmospheric pressure), then the pressurized gas escapes freely. In this configuration, a pre-charge of the chamber 3 (i.e., an initial internal pressure greater than the external pressure Pe) can be used to oscillate the movable diaphragm 10 around an average position. In this configuration, the suspension 11 can act as a return mechanism to force the movable diaphragm 10 back towards the chamber 3.2.

[0048] It is understood that the sections S and S' of the intake duct 4.1 and exhaust duct 4.2 can be defined by those skilled in the art according to the requirements and desired performance. The same applies to the gas pressure at the expansion chamber 12 and to the speed of the modulators 8.1, 8.2.

[0049] In an alternative not shown, the pneumatic circuit 4 may comprise several movable diaphragms 10 arranged in parallel. In this configuration, each diaphragm 10 functions as a loudspeaker. Thus, a single gas source 6 could power different loudspeakers in the passenger compartment. This can offer a significant advantage in terms of space requirements in the motor vehicle 1.

[0050] Advantageously, the present invention eliminates the need for a coil and magnet in the loudspeaker, generating sound exclusively through the movements of the moving diaphragm 10. This offers several notable advantages, including a significant reduction in size and a decrease in losses. thermal, since the absence of a voice coil eliminates the associated heat losses. In addition, the overall mass of the speaker is reduced.

[0051] The rear volume, also called the enclosure or rear loading volume, required for the operation of traditional transducers is no longer influenced by the characteristics of the magnet and voice coil. It now depends on the "energy reserve" stored in the pressurized gas. Thus, this volume can be considerably reduced. While traditional loudspeakers require a loading volume of several liters, or even tens of liters for low frequencies, the pneumatic system makes it possible to reduce this volume to a few tenths of a liter. Moreover, since the energy is contained in the pressurized gas, it is no longer necessary to use rare materials as in the magnet and voice coil.

[0052] Furthermore, the dynamic control of the gas flow pressure F upstream of the moving diaphragm 10, particularly at the enclosure 3.2, allows for greater and more linear displacements of the diaphragm. This considerably improves the quality of the sound produced as well as the sound level, especially at low frequencies below 200 Hz. Indeed, greater displacements result in a higher sound level, even with a smaller and more compact moving diaphragm.

Claims

Demands

1. Loudspeaker (2) for motor vehicle (1), comprising a rigid enclosure (3) having a movable diaphragm (10) forming at least a part of a side face (3.1) of said rigid enclosure (3), characterized in that the rigid enclosure (3) delimits an enclosure (3.2) at an internal pressure, said rigid enclosure (3) being surrounded externally by an environment (5) at an external pressure, the internal pressure within the enclosure (3.2) being configured to vary between values ​​lower and higher than the external pressure, so as to cause the movable diaphragm (10) to move and generate sound by said movement.

2. Loudspeaker (2) according to claim 1, comprising a pneumatic circuit (4) provided with a pressurized gas flow (F) circulating upstream to downstream in said pneumatic circuit (4), from a pressurized gas source (6) to the enclosure (3.2).

3. Loudspeaker (2) according to claim 2, wherein the pneumatic circuit (4) further comprises an expansion compartment (12) for the pressurized gas flow (F), said pressurized gas flow (F) flowing upstream to downstream from the pressurized gas source (6) to the expansion compartment (12), passing through the enclosure (3.2).

4. Loudspeaker (2) according to any one of claims 2 and 3, wherein the pneumatic circuit (4) further comprises at least one flow modulator (8.1, 8.2) configured to modulate the flow rate of the pressurized gas stream (F) according to the sound to be generated.

5. Loudspeaker (2) according to claims 2 to 4, wherein at least one flow modulator (8.1, 8.2) comprises a first flow modulator (8.1) arranged between the pressurized gas source (6) and the enclosure (3.2), and a second flow modulator (8.2) arranged between said enclosure (3.2) and the expansion compartment (12).

6. Loudspeaker (2) according to any one of claims 4 and 5, wherein at least one flow modulator (8.1, 8.2) comprises a controlled displacement valve, or a butterfly valve, or a rotary disc valve, or a circular passage valve.

7. Loudspeaker (2) according to any one of claims 1 to 6, wherein the movable diaphragm (10) is connected in a suspended manner to the rigid enclosure (3) by means of a suspension (11).

8. Motor vehicle (1) comprising at least one loudspeaker (2), characterized in that said at least one loudspeaker (2) is according to any one of claims 1 to 7.

9. A method for generating sound by means of a loudspeaker (2), characterized in that said loudspeaker (2) is according to any one of claims 1 to 7, and in that said method comprises varying the internal pressure within the enclosure (3.2) between values ​​lower and higher than the external pressure, so as to cause the moving diaphragm (10) to move and generate sound.

10. Method according to claim 9, wherein the loudspeaker (2) is according to claim 5, and the variation of the internal pressure comprises simultaneous control of the first flow modulator (8.1) and the second flow modulator (8.2).

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