Amplified deformation type piezoelectric actuator

Abstract

The present invention relates to an amplified deformation electromechanical actuator comprising, on the one hand, at least one drive element (21) connected to an alternating voltage source in such a way as to generate a deformation of said drive element (21), and, on the other hand, a plate (22) configured to amplify the amplitude of the vibrations that the drive element (21) must transmit to a support (40) to be actuated, characterized in that a first side of the plate (22) is rigidly fixed to the drive element (21) and a second side of the plate (22) opposite the first side is fixed to the support (40) to be actuated via an actuation pad (23).

Description

[Technical field]

[0001] The present invention relates to amplified deformation electromechanical actuators, and in particular to amplified deformation piezoelectric actuators. [Background technology]

[0002] The use of amplified deformation piezoelectric actuators is already known in various contexts, namely in sonar, ultrasonic cleaners, ultrasonic machining / welding techniques, systems called HIFU (acronym for the English "High Intensity Focused Ultrasounds"), and in many other fields of application requiring large amplitudes of surface displacement to be exploited.

[0003] Another use case for piezoelectric actuators is that of devices with tactile feedback through ultrasonic lubrication. However, when the medium is dissipative, such as a plastic material support or other viscoelastic medium, large displacements of the surface are difficult to obtain using simple piezoelectric actuators of conventional design.

[0004] In fact, known piezoelectric actuators make it possible to realize a significant ultrasonic lubrication-based tactile feedback only on rigid surfaces (i.e. surfaces made of purely elastic materials) and therefore non-dissipative surfaces, in particular metallic or glass surfaces that are not in contact with any viscoelastic elements of the adhesive or equivalent type that create energy dissipation. In particular, in the field of screens, known actuators are thin-layered and can only be used for touch screens that have an air space between the surface glass and the display (e.g. OLED or LCD), and the actuators must be applied directly on the glass to create standing waves there that are not dissipated by the viscoelastic parts of the screen.

[0005] If the medium to be actuated is more dissipative, such as plastic, wood or other types of viscoelastic materials, it is necessary to use piezoelectric actuators with amplified deformation compared to that which would be obtained with a simple thin-film piezoelectric actuator, in order to make the haptic effect easily perceptible to the user.

[0006] However, known amplified deformation piezoelectric actuators suffer from several drawbacks that limit their use for certain applications other than screens.

[0007] Therefore, in an industrial context, the use of amplified deformation type piezoelectric actuators poses a certain number of problems.

[0008] First, a mechanical reference is often required. In practice, it is often desired to maximize the deformation of one of the faces of the piezoelectric actuator, which implies embedding its opposite face in the support. However, obtaining this embedding is not so easy. The support must be significantly stiffer and more rigid than the element to be activated. For example, to activate a display with a 2 mm thick protective glass, the actuator must be anchored in a metal support at least 1 cm thick. If a large number of actuators are required, this implies the ability to add a large metal structure just to perform this function of mechanical reference.

[0009] Secondly, the external dimensions of known amplified deformation actuators are large and are not always compatible with the products they are intended to be integrated in. By way of example, piezoelectric actuators are known commercially under the trademark Thorlabs that are capable of creating deformations of approximately 10-30 μm and function within a frequency range of 40 kHz to 120 kHz, but they have dimensions of approximately 10 mm to 30 mm, which are approximately ten times larger than are acceptable for application in certain fields of application, for example integration into screens or other structures of small thickness.

[0010] A variation of these resonant piezoelectric actuators exists with magnetostrictive actuators such as those described in WO 91 / 01814 A1, but their overall dimensions remain comparable since the amplification effect is similarly based on compression-expansion resonances with wavelengths in the centimeter range in the range of 20 kHz to 120 kHz.

[0011] Third, the cost of known amplified deformation piezoelectric actuators severely limits their volume and application.

[0012] Although there are other types of amplified deformation actuators, such as those based on electroactive polymers as described in US 2013 / 328447 A1, these are limited to low frequency vibrations and in any case do not make it possible to generate ultrasonic vibrations capable of creating tactile feedback by ultrasonic lubrication. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] International Publication No. 91 / 01814A1 [Patent Document 2] US Patent Application Publication No. 2013 / 328447A1 Summary of the Invention [Problem to be solved by the invention]

[0014] The main object of the present invention is to propose a new type of amplified deformation electromechanical actuator, in particular a piezoelectric actuator, capable of alleviating the above-mentioned drawbacks of known actuators.

[0015] In particular, the invention has the specific objective of proposing an actuator capable of functioning without requiring inlaying of one of its faces.

[0016] Another object of the invention is to propose an actuator of very small size, i.e. with a thickness of 2-5 mm, compatible with application in many new fields of application involving displacement amplitudes on the support surface that are even larger than those known, i.e. displacements of 1-3 micrometers within the ultrasonic frequency range of approximately 20 kHz to 200 kHz.

[0017] Another object of the invention is to propose an actuator which is easy to manufacture and use and which has a significantly reduced cost compared to the costs of known actuators, again allowing its use to be generalized in new fields of application. [Means for solving the problem]

[0018] The invention consists in principle in coupling a driving element, such as a low-cost "common" monolithic piezoelectric ceramic, to a plate vibrating in bending mode. In the description we are limited to piezoelectric actuators, but this does not limit the scope of the invention insofar as other types of driving elements (magnetic, electrostatic) can be used.

[0019] The actuator according to the present invention is therefore composed of three elements: - Miniaturized drive elements, e.g. piezoelectric ceramics of square, circular or rectangular shape. - A rigid plate made of bronze, steel, zinc, etc. that is vibrated by a miniaturized driving element, inducing an amplifying effect on the motion of the driving element. and an actuating pad arranged on the rigid plate and embossed relative to said plate, the actuating pad being adapted to be applied against the surface of the support to be actuated. The actuation pads are placed on the plate, whether they are completely part of the plate or are retrofitted and secured onto the plate, particularly by gluing.

[0020] The actuation pad is of small size relative to the plate and is centered relative to the plate.

[0021] The three elements are firmly attached to one another using a strong adhesive, such as a two-part epoxy type adhesive, capable of maintaining adhesion between the elements even during ultrasonic frequency movements involving strong mechanical stresses.

[0022] The invention therefore relates to an amplified deformation electromechanical actuator comprising, on the one hand, at least one drive element connected to an alternating voltage source in such a way as to generate a deformation of said drive element, and, on the other hand, a plate configured to amplify the amplitude of the vibrations that said drive element must transmit to a support to be actuated, characterized in that a first side of the plate is rigidly fixed to the drive element and that a second side of the plate, opposite the first side, is fixed via an actuation pad to the support to be actuated.

[0023] According to one embodiment of the invention, the actuating element is preferably a piezoelectric actuator, but it may also be other types of actuators, such as a magnetic actuator or an electrostatic actuator.

[0024] According to one embodiment, the plate is configured to generate maximum bending deformation at a dominant resonant frequency between 20 kHz and 200 kHz.

[0025] In order for the actuator to be compatible with ultrasonic lubricated haptic processes, the plate is configured such that at the resonant frequency the amplitude of vibration generated by the plate is an amplification factor of 4 to 50 greater than the amplitude of vibration generated by the drive element alone.

[0026] According to one embodiment, the plate has the shape of a disk with a diameter of 9 mm to 12 mm, for example 11 mm, and a thickness of 0.2 mm to 1 mm, for example 0.5 mm, for a no-load operating frequency of about 60 kHz.

[0027] According to an advantageous embodiment, the plate has the shape of a parallelepiped plate with a length L between 9 mm and 11 mm, for example 10 mm, a width B between 4 mm and 6 mm, for example 5 mm, and a thickness h between 1 mm and 2 mm, for example 1.5 mm, for a no-load operating frequency of approximately 70 kHz.

[0028] Advantageous Alternative Embodiments (Figure 8A) According to the method, the plate is rectangular with a length L significantly greater than its width B, and carries a number of driving elements on one of its faces, and a number of driving elements on the opposite face of the plate. Length L and a width b less than the width B of the plate.

[0029] Alternative Embodiments (Fig. 10A, Fig. 10B) According to the formula, a plate of length L is closed at its two ends into the shape of a flat ring or a 3D ring. Ring This plate, in the shape of a ring, has spaced drive elements located on one of its faces, and a drive element extending around its circumference on the other face of the ring. Width B It includes an activation pad having a smaller width b.

[0030] One embodiment (Figure 3) According to the method, the amplification factor of the movement of the driving element is a function of the ratio between the width b of the actuation pad and the length L of the plate, thus manipulating this ratio makes it possible to control the desired amplification factor. According to a preferred embodiment, the ratio b / L of the width of the actuation pad to the length of the plate is between 0.1 and 0.45. However, according to other embodiments (FIGS. 8A-8C, 10A, 10B), it is the ratio between the width b of the pad and the width B of the plate that makes it possible to control the amplification factor.

[0031] According to one embodiment, the driving element of the actuator is a piezoelectric ceramic slab of square, rectangular or circular shape with maximum dimensions (length, width, diameter) of 6 mm to 8 mm, in particular 7 mm, for an operating frequency of 64 kHz.

[0032] According to one practical embodiment, the actuator is configured in such a way that the deformation amplitude in the direction perpendicular to the support at the main resonant frequency is between 10 micrometers and 30 micrometers for an actuator not coupled to a support, and the amplitude of the deformation transmitted to the surface by the actuator in the coupled mode is between 1 and 2.5 micrometers.

[0033] Preferably, the drive element and the plate of the actuator are joined together using a strong adhesive, in particular an epoxy adhesive, with low energy dissipation.

[0034] The present invention is also directed to a device including a viscoelastic surface to be actuated with a haptic effect, in particular an ultrasonically lubricated haptic effect, and including a plurality of actuators as described above.

[0035] According to one advantageous variant, the device comprises a fixing lamella fixed orthogonally to the support, and one or more actuators fixed to said fixing lamella via their actuation pads.

[0036] In an advantageous embodiment, said support to be activated comprises a surface with poor ultrasonic vibration transmission capacity, such as a multi-layer plate or plastic containing a viscoelastic core, and therefore may be a device such as an OLED or LCD screen to be activated by a haptic effect, in particular by ultrasonic lubrication.

[0037] Detailed Description The invention will now be described in further detail with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0038] [Figure 1] 1 shows a schematic representation of three known examples of amplified deformation type piezoelectric actuators. [Diagram 2] 1 shows a schematic representation of a first embodiment of an actuator according to the invention in the form of an exploded perspective view, an assembled perspective view and a sectional perspective view. [Diagram 3]5A-5D show multiple schematic diagrams of a second embodiment of an actuator according to the invention; [Figure 4] 1 shows a cross-sectional view of an example of the assembly of an actuator according to the invention on a support to be actuated; [Diagram 5] 1 represents a schematic distribution of a number of actuators according to the invention on a surface to be actuated. [Figure 6] 4 depicts a graph illustrating the effect of amplifying the amplitude of motion of an actuator according to the present invention. [Figure 7] 4 represents a curve showing the maximum deformation amplitude of the support of the actuator as a function of the ratio between the width of the actuation pad of the piezoelectric actuator and the length of the amplifier plate. [Figure 8A-8C] 8A and 8B show perspective views of a variant of an actuator according to the invention, respectively in top view (FIG. 8A) and bottom view (FIG. 8B) alone and in top view with its modal distortion (FIG. 8C). [Figure 9] 3D digital simulation (COMSOL) with finished elements showing the modal strains 41 obtained by calculation of the eigenvalues ​​of the assembly constituted by the vibrating surface and the actuator according to FIG. 8 for two different geometries of the surface to be actuated. [Figure 10A.10B] 2 shows two actuator variants using an amplifier plate in the shape of a ring. [Figure 11A.11B] 8A-8C respectively depict a perspective view and a cross-sectional view of a device incorporating an actuator according to FIGS. 8A-8C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Reference is made to FIG. 1 which relates to three types of known devices making it possible to amplify the deformation of a piezoelectric actuator.

[0040] It is recalled again that there are mainly two types of piezoelectric actuators: - Unamplified actuators, where the resulting displacement is directly equivalent to the deformation of the piezoelectric material under the application of a voltage. - Amplified actuators, in which a mechanical device amplifies the motion of the piezoelectric material, typically by a factor of 2 to 20.

[0041] Today, multilayer ceramics are conventionally used as driving elements in amplified piezoelectric actuators. The incorporation of this type of material requires specific attention, such as the need to ensure mechanical prestress or to avoid torsional stresses. Provided that they are designed and used correctly, piezoelectric actuators are extremely reliable and robust.

[0042] Fig. 1a corresponds to a known example of an amplified piezoelectric actuator 1a, composed of an assembly of layers of elementary piezoelectric ceramics 2 stacked one on top of the other. The amplification effect is obtained by multiplying the deformation of the elementary ceramics 2 by the number of unit ceramics present in the device. Thus, although it can be seen that this can be effective in terms of the amplitude of the generated vertical movement, which is diagrammatically indicated by the double-headed arrow, the stacking implies that the dimensions of the actuator become excessively large, excluding the device from certain fields of application that require actuators of small dimensions. Moreover, the device requires very rigid fixed attachment points 3, which are themselves also rather bulky.

[0043] Figure 1b corresponds to a so-called bending-tension type piezoelectric actuator 1b, which adopts the principle of stacking unit ceramics 2 of Figure 1a, but tilts and confines the stack in a mechanical structure 4 which converts the deformation of the ceramics 2 into an orthogonal deformation indicated diagrammatically by a vertical double arrow. Ultimately, this known variant does not solve the problems inherent in the variant of Figure 1a.

[0044] Figure 1c corresponds to a so-called two-mode actuator, comprising two piezoelectric ceramics 2, 2' working in opposition to each other. This structure has the advantage of offering a large travel distance, but it also requires a fixed and rigid reference point 3 and, finally, is not suitable for actuating a surface, such as the surface of a screen.

[0045] In FIG. 2, an amplified actuator 20 according to a first embodiment of the present invention is shown in the form of an exploded perspective view (a), an assembled perspective view (b) and a cross-sectional perspective view (c).

[0046] This first embodiment consists of a piezoelectric driving element 21 in the upper part, an amplifier plate 22, here of circular shape, integrated with the driving element 21 for vibrating the plate in bending mode, and an actuation pad or actuation pin 23 integrated with the plate 22. This actuation pad is intended to transmit the motion of the combined assembly made up of the driving element 21 and the plate 22 relative to the surface to be actuated (not shown in this figure). The actuation pad 23 is located on the face of the plate 22 opposite to the face carrying the driving element 21.

[0047] The driving element 21 is preferably, but not necessarily, a basic piezoelectric actuator in the form of a ceramic slab. This slab is represented with a rectangular shape, but it can be circular or of other shapes. As is known, the ceramic slab 21 has two metal electrodes (not shown) for the application of a supply voltage making it possible to obtain the piezoelectric effect, i.e. a deformation of the ceramic thickness depending on the applied voltage.

[0048] According to the invention, the ceramic slab 21 is glued as rigidly as possible onto the amplifier plate 22, for example by means of an epoxy glue layer (not shown), in order to avoid as much as possible energy dissipation at the interface between the ceramic slab 21 and the plate 22. If the glue used is electrically insulating, the excitation voltage must be applied directly onto the electrodes of the piezoelectric slab. On the other hand, if the glue used is conductive and the plate 22 is made of metal, for example brass, steel or zinc, it is possible to apply the excitation voltage between the upper electrodes of the piezoelectric slab 21 and the plate 22.

[0049] According to a first embodiment represented in figure 2, the plate 22 has the shape of a circular disk. Depending on the desired resonance frequency, in particular for example 60 kHz at no load, i.e. before coupling with the surface to be activated, and also depending on other parameters, in particular the density of the material used for the plate, the thickness of the plate can for example be 0.2 mm to 1 mm, for example 0.5 mm, and its diameter can be 9 mm to 12 mm, for example 11 mm, in order to obtain a resonance frequency within the intended ultrasonic range, i.e. 20 kHz to 200 kHz.

[0050] According to an advantageous embodiment, the piezoelectric ceramic 21 presents a surface having the shape of a rectangle inscribed in the surface of the plate 22, with sides of approximately 7 mm and a thickness of approximately 0.5 mm, for an intended operating frequency of approximately 64 kHz.

[0051] The actuation pad 23 is constituted either by a retrofitted, for example metallic or glass, rigid element integrated with the plate 22 (FIG. 2a) or by a material extension of the plate 22 (FIG. 2c). This second solution makes it possible to avoid additional energy dissipation, since there is no adhesive interface between the plate 22 and the actuation pad 23.

[0052] When the actuator 20 is fixed to a surface to be actuated (not shown in FIG. 2), the deformations of the ceramic slab 21 are transferred to the plate 22, which amplifies these deformations and transmits them via the actuation pads 23 to the surface to be actuated.

[0053] In figure 3a a second practical embodiment of an actuator 20 according to the invention is represented. In this configuration a right-angled parallelepiped structure is used for the drive element 21 and the plate 22, which exhibits a bending behaviour like a beam of rectangular cross section.

[0054] The actuation pad 23 has a smaller dimension compared to the plate and is centered relative to the plate.

[0055] In the embodiment shown, the plate 22 has a width B, a length L and a thickness h.

[0056] The transverse displacement of a beam with rectangular cross section in bending, denoted as y(x, t), is described by the wave equation:

[0057] [Formula 1]

number

[0058] [Formula 3]

number

number

[0059] [Formula 4]

number

[0060] [Formula 6]

number

[0061] It is therefore contemplated that multiple geometries (length, width, thickness) of the beam-shaped plate 22 may be suitable to obtain a given vibration frequency.

[0062] 3b and 3c respectively represent a side view and a perspective view of one particular embodiment of a parallelepiped actuator 20 of width B and length L in a bent state corresponding to a particular moment of the actuator during actuation. In the represented example, the width and length of the ceramic slab 21 are equal to those of the plate 22, but this is not obligatory. The actuation pad 23 has a length B equal to the width of the plate and a width b smaller than the length L of the plate.

[0063] Figure 4 shows A support to be actuated in the form of a plate 4 shows a schematic representation of the assembly of an amplified actuator 20 according to the invention on one surface of a plate 40. The actuator 20 is attached to the free surface 24 of the actuation pad 23 by a force of 0.1 V. support 40. The lower surface 42 of the Actuator The plate 22 is between the actuation pad 23 and the ceramic slab 21. In order to limit losses due to energy dissipation, support The fixing means used to fix the activation pad 23 to the lower surface 42 of the piezoelectric slab 40 should be as rigid as possible, for example by using an epoxy adhesive. The terminals of the piezoelectric slab 21 are then energized with an excitation signal at ultrasonic frequencies via electrodes (not shown).

[0064] The amplitude of motion of the uncoupled amplified actuator 20 can then be approximately 10-30 micrometers, a factor of 4-50 greater than the amplitude of known piezoelectric actuators.

[0065] In addition, it should be started support The amplitude of the motion induced by the actuator 20 via the actuation pad 23 at the surface of 40 is similarly amplified by a factor of 4 to 50 compared to that which would be transmitted by an unamplified actuator consistent with the state of the art.

[0066] At this time, support The amplified deformation of 40 has an amplitude of approximately 1 to 2.5 micrometers at the ultrasonic resonant frequency, and at this time, even if support Even if 40 is made of a viscoelastic material such as plastic material, wood or the like, support The axial length of the pad 42 is clearly felt by the user's finger 41 positioned on the upper surface of the pad.

[0067] Support to be activated 40. When it is necessary to generate or activate a haptic effect that is discriminative in multiple respects, support If the vibration loss is excessively large, Support 40 On one side of the A-8C ), it is then possible to provide a matrix network of actuators 20, or 50, such as that shown diagrammatically in FIG.

[0068] Figure 6 shows the start support 2 shows the results of a simulation of the displacement amplitude of an amplified piezoelectric actuator 20 according to the present invention coupled to 40 and functioning at an ultrasonic frequency of 71.3 kHz.

[0069] In the left part of Fig. 6, the actuator used is a simple unamplified piezoelectric slab 21. The amplitude of the bending deformation between the center and the edge, which corresponds to the antinode of the deformation, is approximately 2·10 -8 meters, or 0.02 micrometers.

[0070] In the right part of FIG. 6, the actuator used is an amplified actuator 20 according to the invention. The amplitude of the bending deformation between the center and the edge, which corresponds to the antinode of the deformation, is approximately 10 -6meters, which is equal to 1 micrometer. The invention thus makes it possible, in the case of this figure, to amplify by a factor of 50 an amplitude that is barely or not perceptible by a human finger (0.02 micrometers) to a much more perceptible displacement amplitude on the surface of the plate of 1 micrometer.

[0071] Tests have shown that the amplified actuator 20 of the present invention provides support It has been shown that the displacement amplitude of the amplifier plate 22 at 40 depends strongly on the ratio between the dimensions of the amplifier plate 22 and the dimensions of its actuation pad 23 for a given operating frequency and a given surface type. The results of the tests are reproduced in the curve of FIG. 7, where the abscissa indicates the displacement amplitude of the amplifier plate 22 at 40. Figure 3 The amplitude of deformation of the actuator according to the invention as a function of the ratio, noted b / L, between the width b of the actuator's actuation pad and the length L of the plate 22 is plotted on the ordinate.

[0072] As can be seen, this deformation amplitude remains above 1 micrometer as long as the aforementioned ratio b / L remains within a range of values ​​between about 0.1 and 0.45. Thus, for one substrate and one frequency in the coupled mode, the maximum amplitude even approaches 2.5 micrometers when the aforementioned dimension ratio is approximately 0.3.

[0073] The principles of the present invention may also be used in embodiments other than those of FIGS.

[0074] Thus, as shown in Figs. 8A and 8B, A very advantageous embodiment consists in adding a number of drive elements 21 on one face of a plate 22 which continues to be rectangular in shape but whose length L is much greater than its width B. On one face of this plate a series of drive elements 21, in particular made of ceramic, are fixed which are spaced apart by areas free of drive elements, which makes it possible to save on the surface of the required drive elements, a rather costly component, without compromising the results obtained. The surface opposite to the surface carrying the drive element 21 On the face of the plate 22, as before, an actuation pad 23 is arranged or provided. However, in this embodiment, the actuation pad is (rather than over width B of the plate as in Figure 3)Running on the length L of the rectangular plate 22 Width b The actuation pads or actuation rails 23 are again either retrofitted and rigidly fixed onto the plate 22 or are directly formed by projections of the plate 22. In this embodiment, it is the ratio between the width b of the actuation pad 23 and the width B of the plate 22 that makes it possible to control the amplification factor.

[0075] FIG. 8c presents the cross-sectional shape of the modal strain 41 that can maximize the vertical displacement of the actuation pad for an uncoupled actuator 50.

[0076] Figures 9a and 9b represent the modal analysis realised on two coupled systems of actuators 50 with two different structures 40 to be actuated (one in the form of a rectangular plate in Figure 9a and the other in the form of a semicircular plate in Figure 9b), and it can be seen that the cross-sectional shape of the modal strain 41 of Figure 8c can be found again in each of the two configurations of Figures 9a and 9b. In other words, the resonant modes of the free actuator 50 are preserved for the coupled system, independent of the geometry of the plate to be actuated.

[0077] Another embodiment of an actuator 60 according to the present invention is shown in FIG. A, Figure 10B In this embodiment, a flat ring-shaped plate 22 (FIG. 10A) or a 3D ring-shaped plate 22 (FIG. 10B) is used. In the case of these figures, the driving element 21 may be located on one of the faces of the plate 22, while the actuation pad 23 is located on the opposite face of the plate 22, Throughout its circumference It extends along the plate. Also in this embodiment, it is the ratio between the width b of the actuation pad and the width B of the plate 22 that makes it possible to control the amplification factor. The 3D ring shaped actuator 60 can be used, inter alia, to actuate balls, cylinders, levers, etc.

[0078] Here, for example, a part of a screen on which it is desired to generate a haptic feedback effect by ultrasonic lubrication is formed. support Reference is now made to FIG. 11 which illustrates an advantageous use of the actuator 50 of FIG.

[0079] In this embodiment, FIG. A-8C The actuator 50 is rotated 90 degrees and is to be vibrated. Support 40 The actuator 50 may be mounted on a fixing slat 43 (FIG. 11B) which is connected to the surface by a rigid fixing means 42. This allows the surface of the actuator 50 to be fixed to the surface that is no longer to be actuated. support 40, but in a plane perpendicular to this surface, allowing for miniaturization.

[0080] It should be pointed out that instead of the only actuator 50 represented in FIG. 11, it seems likewise possible to fix several elementary actuators 20 according to FIG. 2 or FIG. 3 and / or several actuators 50 according to FIG. 8 on the fixing slat 43.

[0081] Figure 11 A, Figure 11B In this configuration, the support The bending waves in 40 are generated by the creation of a bending moment which is maximized by the presence of actuators 50, which, as mentioned in connection with Figure 9, create large amplitude vibrations independent of the shape of the surface to be vibrated. Optimization of this vibration can be obtained by manipulating different dimensions of actuators 50.

[0082] Advantages of the invention The present invention meets the stated objectives and makes it possible to obtain large tactile feedback amplitudes, including on viscoelastic surfaces that exhibit strong attenuation of ultrasound, such as plastic materials, wood, or touch screens with optical bonding between the surface glass and the display.

[0083] The present invention makes it possible to create ultrasonic displacements larger than those of known piezoelectric actuators, which are sufficient to obtain an ultrasonic lubrication effect, i.e., modification of finger friction, on surfaces excited by standing waves, even if these surfaces are of the type that dissipate vibrational energy.

[0084] The present invention also allows for the elimination of large scale mechanical standards, thereby allowing for much greater miniaturization of the amplified actuator.

[0085] Thus, the present invention allows the use of amplified deformation actuators directly on surfaces whose friction is programmed by ultrasonic lubrication.

[0086] The novel structure is extremely simple and economical to manufacture, making it possible to equip large surfaces or surfaces that could not previously benefit from significant haptic feedback effects, such as the back of a screen, with actuators according to the invention. [Explanation of symbols]

[0087] 2 Basic Piezoelectric Ceramics 4 Mechanical structure 20 Actuator 21 Driving Elements 22 Plate 23 Launch Pad 24 sides 40 Support 41 fingers 43 Thin plate for fixing 50 Actuator 60 Actuator

Claims

1. An amplified deformation electromechanical actuator (20; 50; 60) comprising, on the one hand, at least one driving element (21) connected to an alternating voltage source in such a way as to generate a deformation of said driving element (21), and on the other hand, a plate (22) having a free end adapted to amplify the amplitude of ultrasonic vibrations that said driving element (21) must transmit to a support (40) to be actuated, 1. An amplified deformation electromechanical actuator, characterized in that a first surface of a plate (22) is rigidly fixed to a drive element (21) and a second surface of the plate (22) opposite the first surface is fixed only via an actuation pad (23) to a support (40) to be actuated.

2. 2. An electromechanical actuator according to claim 1, characterized in that the actuation pad (23) has a smaller dimension compared to the plate (22) and is centred in relation to the plate (22).

3. 3. The actuator according to claim 1 or 2, characterized in that the driving element (21) is a piezoelectric actuator, a magnetic actuator or an electrostatic actuator.

4. An actuator according to any one of claims 1 to 3, characterized in that the plate (22) is configured to generate a maximum bending deformation at a main resonant frequency between 20 kHz and 200 kHz.

5. 5. The actuator according to claim 1, wherein the shape, dimensions and material of the plate (22) are selected in such a way that the amplitude of vibrations generated by the plate (22) at its resonant frequency is an amplification factor between 4 and 50 greater than the amplitude of vibrations generated by the drive element (21) alone.

6. An actuator (20) according to any one of claims 1 to 5, characterized in that the plate (22) has the shape of a disk with a diameter of 9 mm to 12 mm and a thickness of 0.2 mm to 1 mm for a no-load operating frequency of about 60 kHz.

7. 7. The actuator (20) according to claim 6, characterized in that said plate (22) has the shape of a disk with a diameter of 11 mm and a thickness of 0.5 mm.

8. An actuator (20) according to any one of claims 1 to 5, characterized in that the plate (22) has a parallelepiped shape of length L, width B and thickness h.

9. 9. The actuator (20) according to claim 8, characterized in that for an unloaded operating frequency of approximately 70 kHz, the plate (22) has a length L of 9 mm to 11 mm, a width B of 4 mm to 6 mm and a thickness h of 1 mm to 2 mm.

10. 9. The actuator (20) according to claim 8, characterized in that said plate (22) has a length L of 10 mm, a width B of 5 mm and a thickness h of 1.5 mm.

11. 9. The actuator (20) according to claim 8, characterized in that the amplification factor of the movement of each of the driving elements (21) is a function of the ratio b / L between the width b of the actuation pad (23) and the length L of the plate (22).

12. An actuator according to claim 11, characterized in that the ratio b / L of the width b of the actuation pad to the length L of the plate (22) is between 0.1 and 0.

45.

13. An actuator (50) according to any one of claims 1 to 5 and 8, characterized in that the length L of the plate (22) is significantly greater than its width B, and that the plate (22) comprises on one of its faces a plurality of drive elements (21) and on its opposite face an actuation pad (23) of the same length L as the plate and of a width b smaller than the width B of the plate (22).

14. 6. An actuator (60) according to any one of claims 1 to 5, characterized in that the plate (22) is closed at both ends in the shape of a flat or 3D ring and comprises spaced drive elements (21) located on one of the faces of the plate (22) and actuation pads (23) located on the opposite face of the plate, extending over the length L of the plate and having a width b smaller than the length B of the plate (22).

15. 15. An actuator (50; 60) according to claim 13 or 14, characterized in that the amplification factor of the movement of each of the drive elements (21) is a function of the ratio b / B between the width b of the actuation pad (23) and the width B of the plate (22).

16. The actuator (20; 50; 60) according to any one of claims 1 to 15, characterized in that the driving element (21) is a piezoelectric ceramic slab of square, rectangular or circular shape with maximum dimensions (length, width, diameter) of 6 mm to 8 mm, in particular 7 mm, for an operating frequency of 64 kHz.

17. An actuator (20; 50; 60) according to any one of claims 1 to 16, characterized in that it is configured in such a way that the deformation amplitude in a direction perpendicular to the support (40) at the main resonant frequency is between 10 micrometers and 30 micrometers for an actuator not coupled to a support, and that the amplitude of the deformation transmitted by the actuator to the support (40) in the coupled mode is between 1 and 2.5 micrometers.

18. 18. An actuator (20; 50; 60) according to any one of the preceding claims, characterized in that the driving element (21) and the plate (22) are joined together by means of a strong adhesive with low energy dissipation, in particular an epoxy adhesive.

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