Device for Cleaning a Support Member Covered with a Liquid

Abstract

Device for cleaning a support member covered with a liquid Electroacoustic device (10) comprising:—a support member (50),—at least two wave transducers (15a-h) which are acoustically coupled to the support member and each configured to generate an ultrasonic surface wave (Wa-h) which propagates in the support member, the propagation directions (P) of the ultrasonic surface waves generated by the transducers being different;—a control unit (40), the device comprising an analysis unit (35) which is configured to estimate the orientation of the external force (OFe) which is applied to a liquid when the liquid is in contact with the support member and/or the device being configured to receive the estimate of the orientation of the external force, the control unit being configured to control at least one of the transducers, from the estimate of the orientation of the external force, so that the acoustic force which is applied to the liquid and produced by the interaction between the ultrasonic surface wave(s) and the liquid is orientated in a predetermined direction.

Claims

1.-15. (caneled)

16. An electroacoustic device comprising: a support, w ave transducers acoustically coupled to the support and configured to generate ultrasonic surface waves that propagate through the support in different respective directions; an analysis unit configured to estimate a direction of an external force applied to a liquid disposed on the support; and a control unit configured to control the transducers, based on the estimated direction of the external force, such that a direction of an acoustic force applied to the liquid by one or more of the ultrasonic surface waves is oriented at an angle with respect to the estimated direction of the external force.

17. The device of claim 16, wherein the control unit is configured to control the transducers so as to minimize the angle between the direction of the acoustic force and the estimated direction of the external force, in order to maximize displacement of the liquid on the support.

18. The device of claim 16, further comprising a measurement unit connected to the analysis unit and configured to measure a speed of the support with respect to a given frame of reference, a position and/or orientation of the support with respect to a given frame of reference, or a combination thereof.

19. The device of claim 16, comprising a communication module configured to receive meteorological information from a remote data server. Pcm 20. The device of claim 18, wherein the analysis unit is configured to estimate the direction of the external force using a numerical estimation model that is based on measurements taken by the measurement unit, meteorological information, or a combination thereof.

21. The device of claim 16, comprising a communication module configured to receive an estimate of the direction of the external force from a remote device.

22. The device of claim 16, wherein the device comprises at least three wave transducers.

23. The device of claim 16, wherein a fundamental frequency of the ultrasonic surface waves generated by at least one of the transducers is between 0.1 MHz and 1000 MHz.

24. The device of claim 16, the support is transparent or translucent.

25. The device of claim 16, wherein the support comprises a material chosen from piezoelectric materials, polymers, glasses, metals, or ceramics.

26. The device of claim 16, wherein the support comprises: a motor vehicle surface; a visor of a head set; a window of a building; a sensor; a lens of an optical device; or a protective element of an optical device.

27. The device of claim 16, wherein: the transducer comprises interdigitated electrodes that directly contact the support; and the support comprises a piezoelectric material.

28. The device of claim 16, wherein: the transducer comprises interdigitated electrodes disposed on the support; and the device comprises a piezoelectric layer disposed between the interdigitated electrodes and the support.

29. The device of claim 16, wherein the control unit is configured to control the transducers, such that the direction of the acoustic force is parallel to the estimated direction of the external force.

30. The device of claim 16, wherein the acoustic force is generated by an interaction of all of the ultrasonic surface waves.

31. A motor vehicle comprising the device of claim 16.

32. The motor vehicle of claim 31, wherein the motor vehicle comprises a car, a bus, a motorcycle, or a truck.

33. A motor vehicle comprising a vehicle speed sensor and an electroacoustic device comprising: a support; wave transducers acoustically coupled to the support and configured to generate ultrasonic surface waves that propagate through the support in different respective directions; an analysis unit configured to estimate an external force applied to a liquid disposed on the support, based on a speed of the vehicle detected by the vehicle speed sensor; and a control unit configured to control the transducers, based on the estimated external force, such that an acoustic force applied to the liquid by one or more of the ultrasonic surface waves is oriented in a corresponding predetermined direction.

34. The motor vehicle of claim 33, wherein the control unit is configured to control the transducers, such that a direction of the acoustic force is parallel to a direction of the external force.

35. The motor vehicle of claim 33, wherein the support is a windshield of the vehicle.

Description

[0095] The invention will possibly be better understood on reading the following detailed description of non-limiting examples of implementation thereof, and on examining the appended drawing, in which:

[0096] FIG. 1 shows, in a perspective view, a motor vehicle comprising one example of a device according to the invention,

[0097] FIG. 2 is a close-up of FIG. 1 showing a portion of the device according to the invention,

[0098] FIG. 3 is a schematic representation of the device from example 1,

[0099] FIG. 4 illustrates one example of a method for choosing which transducers to activate,

[0100] FIG. 5 shows one embodiment of a transducer front an exemplary device, and

[0101] FIG. 6 shows another embodiment of a transducer from an exemplary device.

[0102] The constituent elements of the drawing are not shown to scale for the sake of clarity.

[0103] FIG. 1 shows a motor vehicle 5 containing one example of a device 10 according to the invention.

[0104] The device comprises a plurality of ultrasonic surface wave transducers 15a-h and a support 20, defined by a porthole mounted in a window 25 made in a protective casing 30 for a lidar, on which the transducers are arranged. The device further comprises an analysis unit 35 and a control unit 40 for the transducers, both housed in the vehicle.

[0105] The porthole is transparent to visible light and is, for example, made of glass or polycarbonate.

[0106] A lidar is housed in the protective casing and emits a laser beam L through the porthole in order to detect obstacles 45, pedestrians and other vehicles located in the vehicle's environment. In the example illustrated, the porthole is planar, but as one variant, it may be curved.

[0107] The transducers are arranged on the periphery of the outer face 50 of the porthole, exposed to the wind and the rain. They are moreover arranged in a regular manner around the axis X which passes through the center C of the porthole and which is perpendicular to the face. Thus, the transducers, for example referenced 15.sub.a and 15.sub.e, arranged symmetrically with respect to the center, form pairs, each transducer of a pair emitting an ultrasonic surface wave, for example Wa, in an opposite sense to the sense of the wave, for example We, emitted by the transducer of the other pair.

[0108] In the example illustrated in FIG. 1, each transducer is configured to propagate an ultrasonic surface wave W.sub.a-e oriented substantially toward the center C. Thus, whatever the estimated orientation of the external force projected onto the support, at least one of the transducers of the device can be controlled so as to generate a surface wave capable of producing an acoustic force whose component projected onto the support is oriented. substantially parallel to the projected external force.

[0109] Of course, other arrangements of the transducers may be envisaged. Likewise, the number of transducers is not limiting, and may be decreased or increased.

[0110] The analysis unit is housed in the vehicle, for example under the front hood or in the passenger compartment. It is connected by means of electrical cables 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 into 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 which may also estimate the speed of the vehicle.

[0111] Thus, according to a predetermined frequency of acquisition, for example higher than 1 Hz, or even higher than 10 Hz, for example equal to 50 Hz, the analysis unit can receive the speed, the orientation and the position of the vehicle.

[0112] Furthermore, the analysis unit is connected to a cellular communication module 70 in order to interrogate a remote meteorological data server and to receive from the server the direction and the speed of the wind, with respect to the position of the vehicle.

[0113] The analysis unit estimates the orientation of the external force by means of a numerical estimation model that takes, as input data, the speed, the position and the orientation of the vehicle and the meteorological information. The estimation model also takes into account the position of the porthole with respect to the horizontal in order to estimate the component related to the weight of the liquid.

[0114] Thus, when a liquid 88 is detected on the face of the porthole, for example in rainy weather, the analysis unit can estimate the orientation OF.sub.e of the external force and transmit it to the control unit 40. The control unit is electrically connected to the analysis unit and to a multichannel current generator 75. Each channel 80a-h of the current generator is electrically connected to a corresponding transducer 15a-h in order to provide the transducer with power. The control unit further comprises a plurality of switches 85a-h, each electrically arranged between the current generator and the transducer.

[0115] The control unit further comprises a synthesis module 90. The synthesis module chooses, from among the set of transducers of the device, those transducers which generate an ultrasonic surface wave that has an angle a of less than 90° with respect to the orientation of the external force OF.sub.ep projected onto the support. For example, in FIG. 3, the transducers 15d, 15.sub.e and 15f are chosen because they have angles α.sub.d-f of less than 90°. The control unit then places the switches of the electrical power supply circuits for the chosen transducers in the open position and the other switches in the closed position. It then controls the current generator so that the strength of the current transmitted to each of the chosen transducers is proportional to the angle α. Thus, the acoustic force generated by the interaction between the acoustic waves of the chosen transducers and the liquid, projected onto the support OF.sub.ap, is substantially parallel and oriented in the same sense as the external force projected onto the support. The liquid is then subjected to a force of higher strength than the external force alone, which facilitates the debonding and displacement thereof with respect to the support

[0116] FIG. 5 illustrates one exemplary arrangement of one of the transducers on the support from the example shown in FIG. 1.

[0117] The transducer comprises a substrate 100 on which are arranged first 105 and second 110 electrodes. The substrate is, for example, made of lithium niohate cut at 128°.

[0118] The electrodes are deposited using photolithography. They consist of a tie layer for attachment to the intermediate substrate formed of titanium and with a thickness equal to 20 nm and of a conductive layer of gold with a thickness of 100 nm.

[0119] The first and second electrodes form first 115 and second 120 combs. Each comb has a base 125, 130 and a row of fingers 135, 140 extending parallel to one another from the base. The first and second combs are interdigitated.

[0120] The spacing between the fingers determines the resonant frequency of the transducer, which a person skilled in the art readily knows how to determine.

[0121] The powering of the first and second electrodes in alternation induces a mechanical response in the piezoelectric material arranged between two consecutive fingers of the first and second combs, which results in the generation of an ultrasonic surface wave W which propagates through the support in a sense of propagation P, perpendicular to the fingers of the first and second combs.

[0122] FIG. 6 illustrates another arrangement of the transducers on the support.

[0123] The transducer comprises a self-supporting substrate 100 and the first 105 and second 110 electrodes are deposited on the face of the substrate 50 bonded to the support 100. When an electric 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 end 150 of the substrate along its direction of propagation, it is transformed into an ultrasonic surface wave W which propagates through the portion 160 of the support separate from the substrate, substantially in the same direction of propagation as the guided wave. The transformation of the guided wave into a surface wave is brought about by the absence of an interface between two solids in the portion of the support.

[0124] The arrangement of the transducer illustrated in FIG. 6 has the advantage of protecting the first and second electrodes. For example, the liquid 88 cannot flow over the electrodes and oxidize them. Furthermore, optionally, the device illustrated in FIG. 4 may comprise a protective member 155 which defines, together with the support, a housing for the transducer. This prevents objects striking the device from damaging the transducer.

[0125] Obviously, the invention is not limited to the embodiments and examples presented by way of illustration.