DEVICE FOR CLEANING A SUPPORT MEMBER COVERED WITH A LIQUID - Patent application

Abstract

A device for cleaning a support member covered with an electroacoustic device (10), the electroacoustic device (10) comprising a support member (50), at least two wave transducers acoustically coupled to the support member, each wave transducer generating an ultrasonic surface wave (W) propagating through the support member. a-h ) and the propagation directions (P) of the ultrasonic surface waves generated by the transducers are different, and the device comprises a control unit (40) that controls the orientation (OF) of an external force applied to the liquid when the liquid is in contact with the support member. e and / or the device is configured to receive the estimate of the orientation of the external force, and the control unit is configured to control at least one of the transducers based on the estimate of the orientation of the external force, so that an acoustic force applied to the liquid, generated by the interaction between one or more of the ultrasonic surface waves and the liquid, is oriented in a predetermined sense.

Description

[Technical field]

[0001] The present invention relates to a method for displacing a liquid, in particular a drop, a puddle or a film of liquid, on a support, in particular one that is in motion, by means of an ultrasonic surface wave. [Background technology]

[0002] In a variety of fields there is a need to overcome the effects associated with the accumulation of liquids on surfaces.

[0003] It is a known practice to spin the drops of a liquid to remove them from a surface, however such techniques are not suitable for surfaces larger than a few square centimetres in area.

[0004] The implementation of an electric field to control the hydrophobicity of a surface is also known, for example from Korean Patent Publication No. 2018-0086173 (A1). This technique, known by the acronym EWOD (standing for electrowetting on device), consists in electrically polarizing the surface by applying a potential difference between two electrodes to make the surface hydrophilic, thereby detaching the droplet from the surface. By controlling the location of the polarization, the droplet can be displaced. However, this technique can only be implemented on certain materials and in particular requires a precise positioning of the electrodes over the surface where it is desired to control the wettability.

[0005] It is also a well-known practice to apply mechanical force to the liquid, for example by using a windshield wiper on the windshield of a motor vehicle. However, the windshield wiper limits the field of view available to the driver. It also spreads the oily particles that have accumulated on the surface of the windshield. In addition, the wiper trim needs to be renewed periodically.

[0006] Furthermore, autonomous vehicles have many sensors to determine the distance from other vehicles on the road and their speed. Such sensors, such as lidar, are also exposed to bad weather and mud splashes and require frequent cleaning. However, windshield wipers are not suitable for cleaning the small area of ​​such sensors.

[0007] Methods are known for removing liquids accumulating on a support, involving the generation of ultrasonic surface waves and their propagation through the support. In particular, WO 2012 / 095643 A1 describes a method for removing raindrops from a windshield through ultrasonic evaporation. The amplitude and frequency of the vibrations are selected so that raindrops falling on the windshield are evaporated as soon as they enter the zone of the vibration movement of the windshield surface. However, the power level required to vibrate the support in order to evaporate liquid drops, puddles or films is high, which limits practical implementation, especially with regard to the development of autonomous devices. It is also known that evaporation also requires higher energy levels than those required to displace drops on the support. Summary of the Invention [Problem to be solved by the invention]

[0008] There remains a need to improve the removal of liquids from substrates coated with said liquids. [Means for solving the problem]

[0009] The present invention aims to meet this need and achieves this by proposing an electroacoustic device, said electroacoustic device comprising: support, at least two wave transducers acoustically coupled to the support, where each wave transducer detects an ultrasonic surface wave (W a-h ), and the propagation directions of the ultrasonic surface waves generated by the transducers are different from each other. Control Unit Equipped with the device comprises an analysis unit configured to estimate an orientation of an external force being applied to the liquid when the liquid is in contact with the support, and / or the device is configured to receive the estimation of the orientation of the external force, The control unit is configured to control at least one of the transducers based on the estimate of the orientation of the external force such that an acoustic force applied to the liquid generated by interaction between one or more of the ultrasonic surface waves and the liquid is oriented in a predetermined sense.

[0010] The present invention enhances the displacement of the liquid on the support by combining the effect of the external force with the effect of the acoustic force.

[0011] By "external force" is meant any force other than the acoustic force. The weight of the liquid or the aerodynamic forces caused by a fluid flowing over the liquid are examples of external forces.

[0012] Those skilled in the art can easily determine the orientation of the acoustic force exerted on a liquid placed on a support, caused by a surface wave generated by a transducer. In the case of a plane surface wave, the acoustic force is directed along a wave vector associated with the plane wave. In the case of a focused surface wave, the liquid is displaced towards the focal point of the transducer. The effect at the origin of the displacement of the liquid may be nonlinear. Therefore, the acoustic force may be substantially proportional to the intensity of the emitted acoustic wave and the strength of the current powering the transducer.

[0013] The control unit in particular a storage module, e.g., a flash memory, in which the set of orientations of the acoustic forces and the associated characteristics of the currents for controlling the transducers are recorded, e.g., in the form of a table; and a synthesis module configured to compare the estimated orientation of the external force with the set of orientations of the acoustic force recorded in the module and to supply an associated electrical control current to the transducer.

[0014] Preferably, the control unit is configured to control the one or more transducers to minimize an angle between an orientation of the acoustic force applied to the support and an estimated orientation of the external force applied to the support to facilitate the displacement of the liquid on the support, thus accelerating the removal of the liquid from the surface of the support.

[0015] The control unit may be configured to select a transducer that generates an ultrasonic surface wave that is oriented in a direction close to the external force applied to the support. By "close to" is meant that the angle between the direction of the external force and the direction of propagation of the wave is smaller than 90°, or even smaller than 45°. The control unit may be configured to control each of the transducers thus selected such that the acoustic energy of the wave generated by the corresponding transducer is proportional to the angle between the external force applied to the support and the direction of propagation of the wave.

[0016] Preferably, the control unit is configured to control the one or more transducers such that an orientation of the acoustic force applied to the support is substantially parallel to an orientation of the external force applied to the support.

[0017] The control unit may include a plurality of switches, each configured to electrically open or close a power supply circuit for a corresponding transducer.

[0018] The control unit may comprise an electrical amplification device configured to amplify a current being supplied to one of the transducers. In particular, the control unit may be configured such that at least two of the transducers generate surface ultrasonic waves of different amplitudes.

[0019] To ensure optimal displacement of the liquid on the surface of the support, the fundamental frequency of the ultrasonic surface waves generated by at least one of the transducers, or even each of the transducers, is preferably between 0.1 MHz and 1000 MHz, preferably between 10 MHz and 100 MHz, for example equal to 40 MHz.

[0020] The amplitude of the surface ultrasonic waves generated by at least one of the transducers, or even each of the transducers, may be between 1 picometer and 500 nanometers. It may depend, inter alia, on the fundamental frequency of the wave. It corresponds to a displacement in the normal direction of the surface of the support along which the ultrasonic surface wave propagates, and may be measured using laser interferometry.

[0021] The ultrasonic surface wave may be a Rayleigh wave or a Lamb wave. In particular, if the substrate has a thickness greater than the wavelength of the ultrasonic surface wave, it may be a Rayleigh wave. Rayleigh waves are preferred because the energy of the wave is concentrated on the surface of the substrate along which it propagates and can therefore be efficiently transferred to the liquid.

[0022] The analysis unit is configured to estimate the orientation of the external force applied to the liquid when the liquid is disposed on the support.

[0023] Preferably, the device comprises a measurement unit connected to the analysis unit and configured to measure at least one physical quantity, in particular configured to receive said physical quantity at a frequency higher than 1 Hz, or even higher than 10 Hz, for example equal to 50 Hz.

[0024] The physical quantity may characterize the support. For example, the physical quantity may be selected from the speed of the support relative to a frame of reference, and the position and / or the orientation of the support in the frame of reference. For example, the physical quantity is the speed of a motor vehicle equipped with the electro-acoustic device.

[0025] The frame of reference may be an absolute frame of reference. By "absolute frame of reference" is meant a geodesic frame of reference in which the location of an object on the Earth can be unambiguously determined. The absolute frame of reference may be selected from among the Reseau Geodesique Francais 1993 (RGF93), the World Geodetic System (WGS84), the International Terrestrial Rotational Service (ITRS), and the European Terrestrial Reference System (ETRS).

[0026] The measurement unit may be connected to the analysis unit by an electric cable. As a variant, the connection between the measurement unit and the analysis unit may be made by a link via electromagnetic waves.

[0027] The electroacoustic device may comprise the measurement unit. According to another variant, the measurement unit may be remote from the device.

[0028] For example, the support is a surface of a motor vehicle and the measurement unit is located in a transmission and configured to convert a motor / engine shaft speed into vehicle speed, or is located in a wheel of the vehicle and configured to measure the rotational speed of the wheel and convert it into the speed of the vehicle.

[0029] The measurement unit may be a GPS transceiver configured to measure the position and / or orientation of the support.

[0030] The physical quantity may characterize the liquid, for example it may be the area of ​​the liquid covering the substrate or the thickness of the liquid.

[0031] It may also characterize the environment of the support. For example, if the support is movable in a reference frame, the physical quantity may be the velocity of a fluid, e.g. air, flowing around the support. A measuring unit capable of measuring the velocity of the fluid is for example a Pitot probe or a MEMS sensor that may be mounted on the support.

[0032] Preferably, as described above, the device comprises a plurality of measuring units.

[0033] Furthermore, in order to improve the estimation of the orientation of the external force, the device may comprise a communication module configured to communicate with a remote data server and to receive from the data server meteorological information, such as the average speed and / or average direction of the wind relative to the position and / or relative to the orientation of the support, which communication module may in particular comprise remote communication means, in particular cellular telecommunication means, for communicating with the data server.

[0034] Preferably, the analysis unit is configured to estimate the orientation of the external force using a numerical estimation model taking as input data the physical quantity, the orientation of the support relative to the horizontal, and optionally the weather information provided by the communication module.

[0035] As a variant or in addition, the communications module may be configured to communicate with at least one other remote device comprising an analysis unit configured to estimate the orientation of the external force applied to the liquid, the communications module being further configured to receive the estimation of the orientation of the external force from the analysis unit of the other device.

[0036] The device and the other device may be more than 1 m apart, or even more than 5 m apart, and / or less than 1 km, or even less than 100 m apart.

[0037] For example, the device may be mounted on one motor vehicle and the other device may be mounted on another motor vehicle, and the vehicles may follow a common route, and the device mounted on the upstream vehicle on the route may transmit the estimate of the external force to the device mounted on the downstream vehicle.

[0038] The skilled person will of course know how to develop such an estimation model. For example, in one variant where the support is carried by or is the surface of a vehicle, the skilled person may determine the trajectories of the airflow in various regions of the envelope of a vehicle moving at a defined speed, based on aerodynamic performance tests in a wind tunnel. The skilled person may also determine the local speed of the airflow in each of said regions, and thus calculate an estimate of the force exerted on the liquid in each of said regions.

[0039] For example, the analysis unit may estimate the orientation of the external force applied to a liquid, such as a raindrop, on an external surface of a support, such as a windshield or a protective member for a vehicle sensor, from measurements of the vehicle's speed, the vehicle's orientation transmitted by a GPS transceiver, and the average speed and average direction of wind obtained from the data server.

[0040] The displacement of the liquid caused by the ultrasonic surface waves may result, inter alia, from an acoustic streaming effect and / or from a radiation pressure effect caused by the one or more ultrasonic surface waves.

[0041] The liquid may take the form of at least one drop or a number of drops, each of which may have different sizes. The liquid may take the form of at least one film, which may be continuous or discontinuous. By "film" is meant a thin film formed on the support. The liquid may take the form of a pool.

[0042] The liquid may be aqueous. In particular, it may be rainwater or dewwater. Rainwater and / or dewwater may in particular contain oily particles. Dewwater forms a mist on the surface of the support. It results from water held in the air in the form of vapour, which condenses on the support under suitable pressure and temperature conditions.

[0043] The device may comprise a detection unit configured to detect the presence of the liquid on the support. For example, the detection unit may be configured to process a stream of images acquired by a camera and detect when the camera is obscured by liquid. The detection unit may be configured to process an information stream from a LiDAR to detect a reduction in LiDAR range caused by the liquid.

[0044] Furthermore, the detection unit may be configured to measure and analyze surface waves emitted by at least one of the transducers in order to detect the presence of the liquid in contact with the support. For example, the detection unit may be configured to measure waves transmitted between two of the transducers arranged opposite each other on the support. According to another example, the device may be configured such that one of the transducers generates an ultrasonic wave in the form of a pulse, for example a square wave or a Dirac pulse, and measures whether a response wave is generated through an interaction between the liquid and the pulse when the liquid is in contact with the support.

[0045] Finally, the surface wave transducer itself can be used to detect the presence of liquid on the support by measuring the transmission of a signal between two transducers positioned opposite each other, or by sending out a pulse and measuring the echo produced by the reflection of the wave by the liquid.

[0046] The support may consist of any material capable of propagating ultrasonic surface waves. Preferably, it consists of a material in which the absorption length for the ultrasonic surface waves is at least 10 times greater than the area of ​​the support, or even at least 100 times greater.

[0047] The surface of the support along which the longitudinal surface waves propagate can be planar. It can also be curved, provided that the radius of curvature of the surface is greater than the wavelength of the ultrasonic surface waves.

[0048] The surface may be a rough surface. It may have a roughness Ra less than the wavelength.

[0049] The support may in particular take the form of a flat plate or a plate with at least one curvature in one direction. The thickness of the plate may be less than 10 cm, or less than 1 cm, or even less than 1 mm. The length of the plate may be greater than 1 cm, or greater than 10 m, or even greater than 1 m.

[0050] By "thickness of the support" is meant the smallest dimension of the support measured in a direction perpendicular to the surface through which the ultrasonic waves propagate.

[0051] The support may be arranged flat to the horizontal. As a variant, it may be inclined to the horizontal by an angle α of more than 10°, or more than 20°, or even more than 45°, or even more than 70°. It may be arranged vertically.

[0052] The support may be optically transparent, in particular to light in the visible range, so that the method is then particularly suitable for applications in which an increase in the visual comfort of a user observing the surroundings through the support is desired.

[0053] The support may consist of a material chosen from among piezoelectric materials, polymers, in particular thermoplastics, in particular polycarbonates, glasses, metals and ceramics.

[0054] Preferably, the support is made of a material other than a piezoelectric material.

[0055] Preferably, the support comprises: a surface of a motor vehicle, for example a surface of a motor vehicle selected from among a windshield or a rear-view mirror glass of a vehicle, or Helmet visor, Windows of buildings, The surfaces of optical devices, for example the surfaces of camera lenses, eyeglass lenses, and sensors, in particular probes, for example Pitot probes or Lidar, Protection elements for such sensors The compound is selected from the group formed by:

[0056] The support may be a structural element of an aircraft, such as a wing, a fuselage, or a tail.

[0057] The device comprises at least two transducers, in order to more precisely define the orientation of the acoustic force, the device preferably comprises at least three, or even at least four, better still at least eight, wave transducers, preferably regularly distributed around an axis perpendicular to one face of the support.

[0058] Preferably, the device comprises at least two pairs, or even at least three pairs, better still at least four pairs of transducers, the transducers of one and the same pair being arranged to generate ultrasonic surface waves propagating in the same direction, but in different orientations, preferably the transducers of one and the same pair being arranged opposite each other in the direction of propagation of the waves they may generate.

[0059] The device may have an even number of transducers.

[0060] The transducers may be attached, preferably glued, to the support, in particular they may be arranged at the ends of the support.

[0061] The transducer may at least partially cover the support, particularly the surface of the support on which the liquid rests.

[0062] At least one of the transducers, or even each of the transducers, may generate the ultrasonic surface wave directly. Alternatively, at least one of the transducers, or even each of the transducers, may generate an ultrasonic guided wave that propagates at the interface between the support and the transducer and is then converted into the ultrasonic surface wave along a portion of the support located at a distance from the transducer.

[0063] At least one of the transducers, or even each transducer, may be in direct contact with the support or with an intermediate layer disposed on the support, for example an intermediate layer formed by an adhesive.

[0064] Preferably, at least one of the transducers, preferably each transducer, comprises a first electrode and a second electrode forming a first comb and a second comb, respectively, where the first comb and the second comb are comb-shaped and are arranged on the support and / or in direct contact with the support and / or in contact with an intermediate substrate in contact with the support, in particular an intermediate substrate arranged on the support, where the substrate consists of a piezoelectric material.

[0065] The piezoelectric material may be selected from the group formed by lithium niobate, aluminum nitride, lead zirconate titanate, zinc oxide, and mixtures thereof. The piezoelectric material may be opaque to light in the visible range.

[0066] In one variant, the support is made of the piezoelectric material and at least one of the transducers comprises the support, and the first and second combs are preferably arranged in contact with the support.

[0067] In another variation, the support is made of a material other than a piezoelectric material and the electrodes are disposed on the intermediate substrate.

[0068] The first and second electrodes may be deposited on the support and / or on the substrate using photolithography.

[0069] The first and second electrodes may be sandwiched between the support and the substrate, the substrate preferably having a thickness at least one or even at least two times greater than the fundamental wavelength of the ultrasonically guided wave. Alternatively, the substrate may be sandwiched between the support and the first and second electrodes, the substrate preferably having a thickness less than the fundamental wavelength of the ultrasonically guided wave.

[0070] The first and second combs may preferably include a base with an array of fingers extending therefrom, the fingers preferably being parallel to one another. The fingers may have a width between one-eighth and one-half the wavelength of the ultrasonic surface wave, preferably equal to one-quarter of the wavelength. The width of the fingers partly determines the fundamental frequency of the ultrasonic surface wave.

[0071] Furthermore, the spacing between two consecutive adjacent fingers of a row of the first comb or the second comb, respectively, may be between one-eighth of the wavelength of the ultrasonic surface wave and one-half of said wavelength, and is preferably equal to one-quarter of said wavelength.

[0072] The row of fingers of the first comb and / or the row of fingers of the second comb may each comprise 3 or more fingers, or even 11 or more fingers, or even 40 or more fingers. Increasing the number of fingers increases the quality factor of the transducer.

[0073] The substrate may be a thin layer deposited, for example by chemical vapor deposition or by sputtering, onto the support. In one variant, the substrate may be self-supporting, i.e. sufficiently rigid that it does not bend under its own weight. The self-supporting substrate may be attached, for example glued, to the support.

[0074] The portion of the liquid furthest from the transducer may be located at a distance corresponding to several times the attenuation length of the surface wave in the support.

[0075] Furthermore, the device may comprise a generator, e.g. a battery, to power each transducer. The generator may be connected to the control unit, which may provide power to the analysis unit.

[0076] The generator may deliver between 10 milliwatts and 50 watts of power to at least one of the transducers, or even to each of the transducers.

[0077] Finally, the invention also relates to a motor vehicle chosen from among a car, a bus, a motorcycle and a truck, said vehicle being equipped with a device according to the invention.

[0078] Preferably, the vehicle comprises a chassis and the device is fixed to the chassis.

[0079] The invention also relates to a method comprising providing a device, in particular a device according to the invention, comprising a surface covered by a liquid and at least two wave transducers, each configured to generate ultrasonic surface waves acoustically coupled to a support and propagating through the support, the ultrasonic surface waves generated by each transducer having a different propagation direction, The method includes estimating an orientation of an external force applied to the liquid and, based on the estimation, supplying power to at least one of the transducers to propagate one or more ultrasonic surface waves through the support such that an acoustic force applied to the liquid generated by interaction between the one or more ultrasonic surface waves and the liquid is oriented in a predetermined sense.

[0080] Preferably, the device is mounted on a motor vehicle and the estimation of the external forces includes a measurement of the speed of the vehicle.

[0081] Finally, the invention relates to a motor vehicle equipped with a vehicle speed sensor and, in particular, an electroacoustic device according to the invention, which support, at least two wave transducers acoustically coupled to the support, each wave transducer being configured to generate an ultrasonic surface wave that propagates through the support, the ultrasonic surface waves generated by the transducers each having a different propagation direction; and a control unit configured to control at least one of the transducers using a velocity of the vehicle such that an acoustic force applied to the liquid, generated by an interaction between one or more of the ultrasonic surface waves and the liquid, is oriented in a predetermined sense when the liquid is disposed on the support. The above-mentioned motor vehicle is provided with:

[0082] The invention will be better understood on reading the following detailed description of non-limiting examples of its implementation and on examining the accompanying drawings, in which: [Brief description of the drawings]

[0083] [Figure 1] FIG. 1 shows in a perspective view a motor vehicle equipped with one example of a device according to the invention. [Diagram 2] FIG. 2 is a close-up of FIG. 1 showing a portion of the device according to the invention. [Diagram 3] FIG. 3 is a schematic representation of the device from Example 1. [Figure 4] FIG. 4 illustrates one example of a method for selecting which transducers to activate. [Diagram 5] FIG. 5 shows one embodiment of a transducer from an exemplary device. [Figure 6] FIG. 6 shows another embodiment of a transducer from an exemplary device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] Components in the figures are not drawn to scale for clarity.

[0085] FIG. 1 shows a motor vehicle 5 including one example of a device 10 according to the invention.

[0086] The device comprises a number of ultrasonic surface wave transducers 15a-h and a support 20 defined by a round window mounted in a window 25 made in a protective lidar case 30, on which the transducers are arranged. The device further comprises an analysis unit 35 and a control unit 40 for the transducers, both housed within the vehicle.

[0087] The porthole is transparent to visible light and is made, for example, of glass or polycarbonate.

[0088] A lidar is housed within the protective case and emits a laser beam L through the porthole to detect obstacles 45, pedestrians, and other vehicles in the vehicle's environment. In the example shown, the porthole is planar, but in one variation it could be curved.

[0089] The transducers are arranged around the periphery of the outer face 50 of the round window and are exposed to wind and rain. They are furthermore regularly arranged around an axis X that passes through the centre C of the round window and is perpendicular to said face. Thus, for example, 15 a and 15 e The transducers, which are symmetrically arranged about the center, referred to as , form pairs, and each transducer of one pair emits an ultrasonic surface wave, e.g., Wa, in an opposite sense to the wave, e.g., We, emitted by the transducer of the other pair.

[0090] In the example shown in FIG. 1, each transducer emits an ultrasonic surface wave W directed substantially toward the center C.a~e Thus, whatever the estimated orientation of the external force applied to the support, at least one of the transducers of the device can be controlled to generate a surface wave capable of generating an acoustic force whose component applied to the support is oriented substantially parallel to the applied external force.

[0091] Of course, other configurations of the transducers can be envisaged. Likewise, the number of transducers is not limiting and can be reduced or increased.

[0092] The analysis unit is housed in the vehicle, for example under the front bonnet or in the passenger compartment. It is connected by an electrical cable 53 to a vehicle speed measurement unit 55 arranged in a wheel 60 of the vehicle and is configured to measure the rotational speed of the wheel and convert it to the speed of the vehicle. The analysis unit is also connected to a GPS transceiver 65, which measures the position and orientation of the vehicle and may also estimate the speed of the vehicle.

[0093] Thus, according to a given acquisition frequency, for example higher than 1 Hz, or even higher than 10 Hz, for example equal to 50 Hz, the analysis unit is able to receive the speed, the orientation and the position of the vehicle.

[0094] Additionally, the analysis unit is connected to a cellular communication module 70 for querying a remote weather data server and receiving therefrom wind direction and speed for the location of the vehicle.

[0095] The analysis unit estimates the orientation of the external force using a numerical estimation model whose input data are the speed, the position and the orientation of the vehicle and meteorological information, which also takes into account the position of the porthole relative to the horizontal in order to estimate a component related to the weight of liquid.

[0096] Thus, for example, when liquid 88 is detected on the surface of the round window during rainy weather, the analysis unit determines the orientation of the external force OF e and transmits it to the control unit 40.

[0097] The control unit is electrically connected to the analysis unit and to a multi-channel current generator 75. Each channel 80a-h of the current generator is electrically connected to a corresponding transducer 15a-h for providing power to the transducer. The control unit further comprises a plurality of switches 85a-h, each electrically disposed between the current generator and the transducer.

[0098] The control unit further comprises a synthesis module 90, which determines the orientation OF of the external force applied to the support from among the set of transducers of the device. ep For example, in FIG. 3, the transducers 15d and 15 e , and 15f is an angle α less than 90° d~f The control unit then places the switches of the power supply circuits for the selected transducers in an open position and the other switches in a closed position. It then controls the current generators such that the strength of the current transmitted to each of the selected transducers is proportional to the angle α. Thus, the acoustic force OF generated by the interaction between the acoustic wave of the selected transducer and the liquid and applied to the support is ap is substantially parallel to and oriented in the same direction as the external force applied to the substrate, and the liquid is subjected to a force of higher magnitude than the external force alone, which promotes its detachment and displacement relative to the substrate.

[0099] FIG. 5 shows one example arrangement of the transducers on the support from the example shown in FIG.

[0100] The transducer comprises a substrate 100 on which a first electrode 105 and a second electrode 110 are disposed. The substrate is, for example, made of lithium niobate cut at 128°.

[0101] The electrodes are deposited using photolithography: they consist of a bonding layer for attachment to the intermediate substrate, made of titanium and having a thickness equal to 20 nm, and a conducting layer of gold, having a thickness of 100 nm.

[0102] The first and second electrodes form a first comb 115 and a second comb 120. Each comb has a base 125, 130 and a row of fingers 135, 140 extending parallel to each other from the base. The first and second combs are interdigitated.

[0103] The spacing between the fingers determines the resonant frequency of the transducer, which one skilled in the art would readily know how to determine.

[0104] The alternating current power supply of the first and second electrodes induces a mechanical reaction in a piezoelectric material arranged between two consecutive fingers of the first and second combs, resulting in the generation of an ultrasonic surface wave W which propagates through the support in a direction of propagation P perpendicular to the fingers of the first and second combs.

[0105] FIG. 6 shows an alternative arrangement of the transducers on the support.

[0106] The transducer comprises a self-supporting support substrate 100, with a first electrode 105 and a second electrode 110 deposited on the face of a substrate 50 bonded to the support 100. When a current passes through the first and second electrodes, the transducer generates an ultrasonic guided wave G, which propagates between the support and the substrate. When the guided wave reaches the edge 150 of the substrate along its propagation direction, it is transformed into an ultrasonic surface wave W, which propagates through a portion 160 of the support away from the substrate in substantially the same propagation direction as the guided wave. The transformation of the guided wave into a surface wave is caused by the absence of an interface between two solid bodies within the portion of the support.

[0107] The transducer arrangement shown in Fig. 6 has the advantage of protecting the first and second electrodes. For example, liquid 88 cannot flow over the electrodes and oxidize them. Furthermore, optionally, the device shown in Fig. 4 may comprise a protective member 155 that defines, together with the support, a housing for the transducer. This prevents objects hitting the device from damaging the transducer.

[0108] Needless to say, the invention is not limited to the embodiments and examples presented by way of example.

Claims

1. An electroacoustic device (10), comprising: support (50), at least two wave transducers acoustically coupled to the support, where each wave transducer detects an ultrasonic surface wave (W ａ－ｈ ), and the propagation directions (P) of the ultrasonic surface waves generated by the wave transducers are different from each other; Control unit (40) Equipped with The electroacoustic device is adapted to detect the orientation of an external force (OF) applied to the liquid when the liquid is in contact with the support. ｅ and / or the electroacoustic device is configured to receive the estimate of the orientation of the external force, the control unit is configured to control at least one of the wave transducers based on the estimation of the orientation of the external force, such that an acoustic force applied to the liquid, generated by an interaction between one or more of the ultrasonic surface waves and the liquid, is oriented in a predetermined sense; the control unit is configured to control one or more of the wave transducers to minimize an angle between an orientation of the acoustic force applied to the support (OF ap ) and the estimated orientation of the external force applied to the support (OF ep ) to facilitate displacement of the liquid on the support; the wave transducer is disposed on a periphery of the support; Each wave transducer is configured to propagate the ultrasonic surface wave directed towards a center (C) of the support. The electroacoustic device.

2. Electroacoustic device according to claim 1, characterized in that the electroacoustic device comprises at least one measurement unit (55; 65) connected to the analysis unit and configured to measure at least one physical quantity.

3. 3. An electroacoustic device according to claim 2, comprising a communication module (70) configured to communicate with a remote data server and to receive weather information from the remote data server.

4. 4. An electroacoustic device according to claim 3, wherein the analysis unit is adapted to estimate the orientation of the external force using a numerical estimation model having as input data the physical quantities and, optionally, the meteorological information.

5. The device according to claim 1 further comprising an analysis unit and adapted to communicate with at least one other remote device; receiving the estimate of the orientation of the external force from the analysis unit of the other device; 5. An electroacoustic device according to claim 1, comprising a communication module configured to:

6. Electroacoustic device according to any one of the preceding claims, comprising at least three, or even at least four, wave transducers.

7. 7. An electroacoustic device according to any one of the preceding claims, wherein the fundamental frequency of the ultrasonic surface waves generated by at least one of the wave transducers is between 0.1 MHz and 1000 MHz.

8. 8. An electroacoustic device according to any one of claims 1 to 7, wherein the support is transparent or translucent.

9. 9. An electroacoustic device according to any one of the preceding claims, wherein the support is made of a material selected from the group consisting of piezoelectric materials, polymers, glasses, metals and ceramics.

10. The support is Surface of motor vehicles, Helmet visor, Windows of buildings, A surface of an optical device, and Electroacoustic device according to any one of the preceding claims, selected from the group formed by protective elements for such optical devices.

11. 11. An electroacoustic device according to any one of the preceding claims, wherein the wave transducer is in direct contact with the support or with an intermediate layer arranged on the support.

12. 12. The electroacoustic device according to claim 1, wherein the wave transducer comprises a first electrode 1 and a second electrode forming a first comb (115) and a second comb (120), respectively, the first comb and the second comb being arranged in interdigitated relation with each other and in direct contact with the support and / or in contact with an intermediate substrate (100) in contact with the support, the intermediate substrate being made of a piezoelectric material.

13. A motor vehicle (5) selected from among a car, a bus, a motorcycle and a truck, said motor vehicle comprising an electroacoustic device according to any one of claims 1 to 12.

14. 1. A motor vehicle comprising a vehicle speed sensor and an electroacoustic device, the electroacoustic device comprising: support (50), At least two wave transducers (15) acoustically coupled to the support. ａ－ｈ ), where each wave transducer detects an ultrasonic surface wave (W ａ－ｈ ), the propagation directions (P) of the ultrasonic surface waves generated by the wave transducers are different, and a control unit configured to control at least one of the wave transducers using a speed of the motor vehicle such that an acoustic force generated by an interaction between one or more of the ultrasonic surface waves and the liquid is directed in a predetermined sense when the liquid is disposed on the support. Equipped with the control unit is configured to control one or more of the wave transducers to minimize an angle between an orientation of the acoustic force applied to the support (OF ap ) and an estimated orientation of an external force applied to the support (OF ep ) to facilitate displacement of the liquid on the support; the wave transducer is disposed on a periphery of the support; Each wave transducer is configured to propagate the ultrasonic surface wave directed towards a center (C) of the support.

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