Pneumatic pulsing loudspeaker for a motor vehicle

Abstract

The present invention relates to a loudspeaker (2) for a motor vehicle (1), characterized in that the loudspeaker comprises: - a pneumatic circuit (4) which is provided with a pressurized gas flow (F) circulating from upstream to downstream in the pneumatic circuit; and - a flexible membrane (10) which is fluidically connected to the pressurized gas flow and is configured to deform according to pressure variations of the pressurized gas within the flexible membrane, so that deformations of the flexible membrane generate sound.

Description

[0001] DESCRIPTION

[0002] TITLE: PNEUMATIC PULSATING SPEAKER FOR MOTOR VEHICLES

[0003] technical field

[0004] The present invention claims priority from French application 2409203 filed on August 29, 2024, the content of which (text, drawings, and claims) is incorporated herein by reference. The present invention relates to the field of loudspeakers, more particularly to the field of loudspeakers for motor vehicles.

[0005] Previous technique

[0006] In the field of automotive audio systems, three main types of speakers are commonly used: electrodynamic transducers, electrostatic transducers, and piezo transducers.

[0007] Electrodynamic transducers are the most common type. They operate using a magnet and a voice coil that drive a diaphragm, which is moved by the Laplace force to produce sound. However, these speakers have several drawbacks. They have relatively low efficiency, generally between 5 and 10%, and their excursion capacity is limited by the size of the magnet and voice coil. Furthermore, their weight increases with the size of these components, and the use of rare materials like neodymium to improve performance can increase both cost and complexity.

[0008] For low frequencies (below 200 Hz), which require a large volume of air to be moved, 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.

[0009] 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.

[0010] Piezo transducers, which operate using piezoelectric materials, are primarily used for high frequencies. Their limited ability to move large volumes of air makes them unsuitable for low frequencies.

[0011] The published patent document FR 2 807 277 A1 discloses a miniaturized pneumatic loudspeaker, powered by a flow of pressurized gas flowing through a sonic throat and modulated by an axial displacement of a moving assembly in an annular air gap of a magnetic circuit formed by an axial stack of permanent magnet and soft iron disks inside a soft iron yoke.

[0012] However, the loudspeaker disclosed in document FR 2 807 277 A1 does not solve the problems announced above, in particular because the axial stacking of permanent magnet and soft iron discs is bulky and unsuitable for diffusing low sound frequencies.

[0013] Description of the invention

[0014] The present invention aims to overcome at least one of the drawbacks of the aforementioned prior art. More specifically, the invention aims to provide a simple and efficient solution for diffusing sound, particularly low frequencies, in a motor vehicle's passenger compartment, while occupying a small space.

[0015] To this end, the invention relates to a loudspeaker for a motor vehicle, remarkable in that said loudspeaker comprises:

[0016] - a pneumatic circuit equipped with a pressurized gas flow circulating from upstream to downstream in said pneumatic circuit; and

[0017] - a flexible membrane fluidly connected to the pressurized gas flow, configured to deform according to pressure variations of the pressurized gas within said flexible membrane, so that deformations of said flexible membrane generate sound.

[0018] According to one embodiment, said loudspeaker is devoid of a coil and magnet, the sound being generated exclusively by the deformations of the flexible diaphragm.

[0019] In one embodiment, the pneumatic circuit further comprises a flow modulator configured to modulate the flow rate of the pressurized gas stream according to the sound to be generated. In another embodiment, the pneumatic circuit further comprises an exhaust for the pressurized gas stream, the flexible diaphragm being arranged upstream of said exhaust.

[0020] According to one embodiment, the flexible membrane includes a tubular channel connecting the flow modulator to the exhaust.

[0021] According to one embodiment, the pressurized gas flow is configured to pass successively through the flow modulator, the flexible membrane and the exhaust.

[0022] According to one embodiment, the flexible membrane comprises a balloon disposed downstream of the flow modulator, said flexible membrane being isolated from the exhaust and forming a closed termination point for the pressurized gas flow.

[0023] According to one embodiment, the flow modulator includes a controlled displacement valve, or a butterfly valve, or a rotary disc valve, or a circular passage valve.

[0024] Preferably, an external electrical signal is used to adjust the position and / or rotational speed of the valve. This signal can originate from an automatic sound management control system.

[0025] According to one embodiment, the flexible membrane is obtained from an elastic material, preferably butyl, rubber or latex.

[0026] 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.

[0027] The measures of the invention are advantageous in that the elimination of the coil and magnet, compared with prior art loudspeakers, allows for a considerable reduction in size, making the loudspeaker of the invention substantially more compact, and therefore easier to integrate into the passenger compartment of the motor vehicle.

[0028] Dynamic control of the gas flow pressure upstream of the flexible diaphragm and the use of elastic materials also allow for greater diaphragm deformation, improving sound level and quality, particularly at low frequencies below 200 Hz. Furthermore, the absence of a voice coil eliminates heat loss, making the system more efficient. In addition, the invention reduces the need for rare materials, making the loudspeaker more economical and environmentally friendly.

[0029] Brief description of the drawings

[0030] [Fig 1] schematically illustrates a loudspeaker according to the invention, comprising a pressurized gas flow passing through a flexible membrane configured to deform according to pressure variations of said pressurized gas to generate sound;

[0031] [Fig 2] schematically illustrates the loudspeaker according to a second mode of the invention, in which the flexible diaphragm forms a closed termination point for the pressurized gas flow.

[0032] Detailed description

[0033] Figure 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.

[0034] The loudspeaker 2 preferably includes a pneumatic circuit 4 provided with a pneumatic source 6 which can correspond, for example, to a pressurized gas reservoir and a suitable pump capable of transmitting a pressurized gas flow F to circulate upstream to downstream in the pneumatic circuit 4.

[0035] The pressurized gas flow F preferably corresponds to air with a pressure greater than atmospheric pressure. The flow F preferentially passes through a flow modulator 8, also referred to as a chopper 8, 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.

[0036] 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.

[0037] Advantageously, the loudspeaker 2 is equipped with a flexible diaphragm 10 connected to the pressurized gas flow F. This diaphragm 10 is designed to deform in response to variations in gas pressure (caused by the flow modulator 8), such that these deformations produce sound. The deformations of the flexible diaphragm 10 can manifest as a rapid series of inflations and deflations, creating vibrations. These vibrations are transmitted to the surrounding air in contact with the diaphragm 10, thus generating sound.

[0038] The flexible membrane 10 can be made of different materials depending on the level of pressure available at the source 6. Preferably, the flexible membrane is obtained from an elastic material, more preferably butyl, rubber or latex.

[0039] It should be noted that, in Figure 1, the flexible membrane 10 is shown in a deformed state by the passage of the flux F. The dotted lines illustrate an example of the maximum deformation 10' of said membrane 10.

[0040] In the configuration illustrated in Figure 1, the flexible membrane 10, in its initial state prior to the passage of the flow F, the flexible membrane 10 preferably comprises a tubular channel connecting the flow modulator 8 to an exhaust 12 for the flow F.

[0041] The flexible diaphragm 10 can thus have a diameter that is preferably constant at rest (measurable along a direction transverse to the flow F), ranging from 10 to 100 mm. This diaphragm 10 can extend longitudinally (along the flow F) for a few centimeters, preferably at least 2 cm and at most 50 cm. More preferably, the flexible diaphragm 10 has a longitudinal length of 10 cm or less, making the loudspeaker considerably compact and allowing for easy integration into the passenger compartment of the motor vehicle 1.

[0042] Preferably, approximately ten centimeters of the flexible membrane 10 may be required to achieve the desired high pressure levels, these levels being linked to the gas pressure F in the circuit 4 and the flow rate of the pneumatic source 6

[0043] For example, the flexible membrane 10 could correspond to a piece of butyl inner tube with a diameter between 25 and 50 mm and a length of 9 cm, or to a latex tube with a length of 5 cm and a diameter of approximately 19 mm (±10%). Several tests were carried out with flexible membranes 10 less than 10 cm long, a pressurized gas flow pressure between 5 and 20 PSI, and a mass flow rate at the outlet of the flow modulator 8 of 25 g / s, which made it possible to generate a sound of 95 dB at 1 meter.

[0044] Advantageously, the elasticity of the flexible membrane 10 allows, in addition to generating sound, to ensure attenuation of up to 50 dB of any possible parasitic noise that may be caused by the continuous circulation of the pressurized gas flow F (air jet) through the pneumatic circuit 4.

[0045] The exhaust 12 may include a duct extending from a few centimeters to a few meters. It may also be fitted with a suitable silencer. The exhaust 12 may open to the surrounding air, in which case the pneumatic circuit 4 is open, or it may alternatively redirect the flow F back to the pneumatic source 6 to form a closed loop circuit.

[0046] Advantageously, the pneumatic source 6 and the flow modulator 8 can be located remotely, thus facilitating their integration into the passenger compartment of the motor vehicle 1.

[0047] In an alternative (not shown) configuration, the pneumatic circuit 4 may include several flexible membranes 10 arranged in parallel. In this configuration, each membrane 10 functions as a loudspeaker. Thus, a pressurized reservoir (a pneumatic source 6) could power different loudspeakers in the passenger compartment. This can offer a significant advantage in terms of space requirements within the motor vehicle 1.

[0048] Figure 2 schematically illustrates the loudspeaker 102 according to a second embodiment of the invention, in which the flexible membrane 110 forms a closed termination point for the pressurized gas flow F.

[0049] Preferably, the flexible membrane 110 includes, in this configuration, a balloon disposed downstream of the flow modulator 8 while being isolated from the exhaust 12 so as to form a closed termination point for the pressurized gas flow F at the level of said balloon 12.

[0050] It is understood that the gas flow F continues to circulate from upstream to downstream in the pneumatic circuit 104 between the pneumatic source 6 and the exhaust 12. It should be noted that the flexible diaphragm 10 is shown in Figure 2 in an initial state of deformation caused by the flow F. The dashed lines illustrate an example of the maximum deformation 110' of the flexible diaphragm 110 caused by a high pressure of the gas flow F in the pneumatic circuit 104.

[0051] Advantageously, the present invention eliminates the need for a coil and magnet in the loudspeaker, generating sound exclusively through the deformation of the flexible diaphragm. This offers several significant advantages, including a substantial reduction in size and decreased heat loss, since the absence of a coil eliminates associated heat dissipation. Furthermore, the overall mass of the loudspeaker is reduced.

[0052] The rear chamber 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 allows this volume to be reduced to a few tenths of a liter. Furthermore, since the energy is contained within the pressurized gas, it is no longer necessary to use rare materials like those used for the magnet and voice coil.

[0053] Furthermore, the dynamic control of the gas flow pressure F upstream of the flexible diaphragm 10, 110 and the choice of elastic material also allow for greater diaphragm movement. This significantly improves the sound quality and volume, particularly at low frequencies below 200 Hz. Indeed, greater movement results in a higher volume, even with a smaller, more compact flexible diaphragm.

Claims

DEMANDS [Claim 1.] Loudspeaker (2; 102) for a motor vehicle (1), characterized in that said loudspeaker (2; 102) comprises: - a pneumatic circuit (4; 104) provided with a pressurized gas flow (F) circulating from upstream to downstream in said pneumatic circuit (4; 104); and - a flexible membrane (10; 110) fluidly connected to the pressurized gas flow (F), configured to deform according to pressure variations of the pressurized gas within said flexible membrane (10; 110), so that deformations of said flexible membrane (10; 110) generate sound, said loudspeaker (2; 102) being without coil and magnet, the sound being exclusively generated by the deformations of the flexible membrane (10; 110). [Claim 2.] Loudspeaker (2; 102) according to claim 1, wherein the pneumatic circuit (4; 104) further comprises a flow modulator (8) configured to modulate the flow rate of the pressurized gas stream (F) according to the sound to be generated. [Claim 3.] Loudspeaker (2; 102) according to any one of claims 1 and 2, wherein the pneumatic circuit (4; 104) further comprises an exhaust (12) for the pressurized gas flow (F), the flexible diaphragm (10; 102) being arranged upstream of said exhaust (12). [Claim 4.] Loudspeaker (2) according to claims 2 and 3, wherein the flexible diaphragm (10) comprises a tubular-shaped channel connecting the flow modulator (8) to the exhaust (12). [Claim 5.] Loudspeaker (2) according to claim 4, wherein the pressurized gas flow (F) is configured to pass successively through the flow modulator (8), the flexible diaphragm (10) and the exhaust (12). [Claim 6.] Loudspeaker (102) according to claims 2 and 3, wherein the flexible diaphragm (110) comprises a balloon disposed downstream of the flow modulator (8), said flexible diaphragm (110) being isolated from the exhaust (12) and forming a closed termination point for the pressurized gas flow (F). [Claim 7.] A loudspeaker (2; 102) according to claim 2 and any one of claims 3 to 6, wherein the flow modulator (8) comprises a controlled displacement valve, or a butterfly valve, or a rotary disc valve, or a circular passage valve. [Claim 8.] A loudspeaker (2; 102) according to any one of claims 1 to 7, wherein the flexible diaphragm (10; 110) is made of an elastic material, preferably butyl, rubber, or latex. [Claim 9.] Motor vehicle (1) comprising at least one loudspeaker (2; 102), characterized in that said at least one loudspeaker (2; 102) is according to any one of claims 1 to 8.

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