Pump operated by piezoelectric transducers

Abstract

A pump (1), intended for pumping fluid between an inlet and an outlet, comprising: a first annular piezoelectric transducer (11), extending around a central axis (Δ), and comprising a first electrode (12); a first resonator (10), connected to the first piezoelectric transducer, and extending around the central axis, the first resonator thinning towards the central axis and deforming under the effect of a polarization of the first piezoelectric transducer; a control unit (30), configured to polarize the first electrode according to a polarization voltage; the first resonator delimits a cavity (2), extending around the central axis, and configured to receive the fluid; the pump comprises at least one channel (4), opening from the cavity; under the effect of the polarization of the first piezoelectric transducer, a deformation of the resonator occurs, locally and transiently reducing the thickness of the cavity

Description

Title of the invention: Pump operated by piezoelectric transducers. Technical field

[0001] The technical field of the invention is a pump configured to be operated by a piezoelectric transducer. EARLIER ART

[0002] Most pumps use moving parts, which can lead to problems with reliability, wear, and limited compactness. In the healthcare field, peristaltic pumps are commonly used. However, repeated compression of a tube, which causes the liquid to move, can lead to premature wear of the tube.

[0003] Patent application WO2013 / 41700 describes a non-peristaltic, piezoelectrically actuated, implantable pump. A sleeve, positioned at the center of a resonator, undergoes bending under the effect of a rotational deformation of the resonator, generated by piezoelectric transducers activated at an ultrasonic frequency. The bending of the sleeve generates a pumping effect, which causes the fluid to be expelled. Reducing the cross-sectional area of ​​the resonator, in the vicinity of or along the sleeve, amplifies the vibrations propagating to the sleeve. Such a pump is efficient. However, it has been observed that the sleeve undergoes repeated bending, which can lead to wear. Furthermore, the pump is intended to be coupled to a fluid circuit. Flow control depends on the vibration amplitude of the sleeve, which must be controlled according to the mechanical load of the fluid circuit, which is not easy.

[0004] We are looking for a pump that is as compact as possible, and preferably as flat as possible.

[0005] In particular, we seek to ensure that the pumping principle, the frequency and amplitude of the ultrasonic pumping vibration are less dependent on the mechanical coupling of the pump with the fluidic circuit.

[0006] Another objective is to design a pump, enabling pumping to be carried out, according to a controlled flow rate, with optimized energy expenditure, and which can be particularly compact. Description of the invention

[0007] A first object of the invention is a pump, intended to pump a fluid between an inlet and an outlet, comprising: - a first annular piezoelectric transducer, extending around a central axis, and comprising a first electrode; - a first resonator, connected to the first piezoelectric transducer, and extending around the central axis, the first resonator being formed of a deformable solid material thinning towards the central axis, the first resonator being configured to deform under the effect of a polarization of the first piezoelectric transducer; - a control unit, configured to bias the first electrode according to a bias voltage, modulated according to a modulation frequency greater than 20 KHz;

[0008] The pump being characterized in that: - the first resonator delimits a cavity, extending around the central axis, and configured to receive the fluid, the cavity extending, along the central axis, according to a thickness; - the pump includes a first sleeve, connected to the first resonator, opening into the center of the cavity, forming the pump's intake; - the pump includes at least one channel, opening from the cavity, the channel extending, along the first resonator, around an axis perpendicular to the central axis, the channel forming the pump's discharge; - so that under the effect of the polarization of the first piezoelectric transducer, a deformation of the resonator occurs, locally and transiently reducing the thickness of the cavity, the deformation propagating around the central axis, and causing a propulsion of a fluid, admitted into the cavity, around the central axis, the propulsion inducing a suction effect at the center of the cavity, opposite the admission.

[0009] According to one possibility, the first transducer comprises at least two distinct angular portions configured to deform differently, under the effect of the polarization applied to the first electrode, so as to generate a deformation of the first resonator propagating around the central axis.

[0010] According to one possibility, the first electrode is segmented into n angular sectors, n being greater than 2, the control unit being configured to bias two angular sectors of the first electrode respectively by two voltages phase-shifted by a phase shift less than or equal to or time-shifted by a shift less than or equal to .

[0011] According to one possibility, the first piezoelectric material comprises at least two different portions, in which the electric dipole moment is oriented in opposite directions.

[0012] According to one possibility, the first resonator (10) is arranged facing a support (6), forming a bottom of the cavity, the cavity extending between the first resonator and the bottom.

[0013] According to one possibility, the first sleeve is coaxial with the central axis.

[0014] According to one possibility, the pump comprises - a second annular piezoelectric transducer, extending around the central axis, and comprising a second electrode, connected to the control unit; - a second resonator, connected to the second piezoelectric transducer, and extending around the central axis, the second resonator being formed of a deformable solid, the second resonator thinning towards the central axis, the second resonator being configured to deform under the effect of a polarization of the second piezoelectric transducer; - the second resonator extends in front of the first deformable solid material; - the cavity extends between the first resonator and the second resonator.

[0015] According to one possibility, the second transducer comprises at least two distinct angular portions configured to deform successively, under the effect of the polarization applied to each second electrode, so as to generate a deformation of the second resonator, the deformation propagating around the central axis.

[0016] According to one possibility, the second electrode is segmented into n angular sectors (22i, 222), n being greater than or equal to 2, the control unit being configured to bias two angular sectors of the second electrode respectively by two voltages phase-shifted by a phase shift of 2^ or time-shifted by a shift of 2a. n

[0017] According to one possibility, the second piezoelectric material comprises at least two different portions, in which the electric dipole moment is oriented in opposite directions

[0018] According to one possibility: - the first electrode is segmented into symmetrical angular sectors, with respect to a first axis of symmetry, and activated in opposite phase; - the second electrode is segmented into symmetrical angular sectors, with respect to a second axis of symmetry, and activated in opposite phase; - the first axis of symmetry is orthogonal to the second axis of symmetry.

[0019] The pump may include a second sleeve, connected to the second resonator, and opening at the center of the cavity.

[0020] The second sleeve can be coaxial with the central axis of the cavity.

[0021] The modulation frequency can be greater than 100 kHz.

[0022] According to one possibility: - the first electrode is segmented into n angular sectors, n being greater than or equal to 2, - the control unit is configured to address a bias signal successively to each angular sector; - the pump includes a control unit, connected to at least one angular sector of the first electrode, the control unit being configured to detect a control signal between two successive polarization signals.

[0023] Preferably, the thickness of the cavity is less than 1 mm.

[0024] According to one possibility, the control unit is configured to bias the first electrode according to a frequency bias signal, by performing a frequency sweep according to a finite number of successive discrete frequencies.

[0025] According to one possibility, the internal surface of the cavity comprises at least one hydrophobic portion. A second object of the invention is a peristaltic pump, intended for pumping a liquid along a capillary, the pumping resulting from a compression of the capillary exerted successively, in a pumping direction, the pump comprising: - a first annular piezoelectric transducer, extending around a central axis, and configured to be polarized by a first electrode; - a first deformable solid material, connected to the first piezoelectric transducer, and extending around the central axis, the first deformable solid material thinning towards the central axis, the first deformable solid material forming a first resonator configured to deform under the effect of a polarization of the piezoelectric transducer; - a control unit, configured to bias the first electrode according to a bias voltage, modulated according to a modulation frequency greater than 20 KHz;

[0026] The pump being characterized in that: - the capillary is positioned against the resonator, around the central axis; - so that under the effect of the polarization of the first electrode, a deformation of the first resonator occurs, the deformation propagating around the central axis, and causing the compression of the liquid-filled capillary around the central axis, the propulsion inducing a suction effect at the center of the cavity, opposite the intake.

[0027] The capillary can extend around the sleeve, forming several turns, so that each turn is successively deformed along the sleeve.

[0028] The first resonator may include a surface, in particular a flat one, forming a support. The capillary may be positioned against the support, so that the tube undergoes a progressive deformation resulting from the deformation of the first resonator. The capillary may form a loop around the central axis, such that under the effect of the deformation of the resonator, the loop is deformed by a deformation rotating around the central axis.

[0029] The pump may comprise two resonators, arranged one against the other; the capillary may be arranged in a space between the two resonators, around the central axis, such that the tube undergoes a progressive deformation resulting from the deformation of the first and second resonators. The capillary may form a coil around the central axis, such that under the effect of the deformation of the first and second resonators, the coil is deformed by a deformation rotating around the central axis.

[0030] The invention will be better understood upon reading the description of the exemplary embodiments presented later in this description, in connection with the figures listed below. FIGURES

[0031] Figures IA to 1E describe a first embodiment of the invention.

[0032] Figures 2A and 2B describe a second embodiment of the invention.

[0033] Fig. 3 illustrates a frequency sweep.

[0034] Fig. 4A represents a segmentation of an electrode into angular sectors.

[0035] Fig. 4B shows a time sequence of electrode control described in relation to Fig. 4A.

[0036] Figures 5A and 5B show an embodiment of a peristaltic pump.

[0037] Figures 6A, 6B and 6C show another embodiment of a peristaltic pump.

[0038] Figure 7 illustrates a variant of the pump described in connection with Figures 6A to 6C. DESCRIPTION OF SPECIFIC EMBODIMENTS

[0039] Figures IA to 1E describe a first embodiment of a pump according to the invention. This is a pump comprising: - a first annular piezoelectric transducer 11, extending around a central axis A comprising a first layer of a piezoelectric material 13 between at least a first electrode 12 and a first counter electrode 14 on the other hand. - a first deformable solid material 10, extending around the central axis A, which, under the action of the first piezoelectric transducer 11, forms a first resonator. The first resonator 10 is symmetrical with respect to the central axis A. - a second annular piezoelectric transducer 21, around the central axis A, comprising a first layer of a piezoelectric material 23 between at least a second electrode 22 and a second counter electrode 24 on the other hand. - a second deformable solid material 20, extending around the central axis A, which, under the action of the second piezoelectric transducer 21, forms a second resonator. The second resonator is symmetrical with respect to the central axis A.

[0040] The first resonator 10 and the second resonator 20 are annular, around the central axis A. They taper towards this axis. Thus, their thickness, defined parallel to the central axis A, decreases as a function of the distance from the central axis A. This tapering increases the amplitude of the vibrations propagating in each resonator.

[0041] Each resonator extends from a flat portion to an end formed by a cylindrical sleeve 3b 32 described below. The flat portion allows for mechanical coupling with a piezoelectric transducer.

[0042] The outer radius R of each resonator, defined around the central axis A, can extend up to 50 mm, or more. The planar portion of each resonator extends beyond a first radius Rb, which is smaller than the previously defined outer radius R. Below the first radius RB, each resonator has a portion that tapers towards the central axis A. The first radius Ri is, for example, equal to 50% of the outer radius R of the resonator.

[0043] The first resonator 10 is assembled opposite the second resonator 20. A cylindrical cavity 2 extends between the first resonator 10 and the second resonator 20. The thickness of the cavity, parallel to the central axis, is preferably less than 2 mm and is, for example, on the order of 1 mm. In the example shown, the first and second resonators are symmetrical about a median plane PM perpendicular to the central axis A. The minimum thickness depends on the pumping force required to overcome static forces opposing the fluid's movement, for example, forces related to friction or surface tension. The minimum thickness may also depend on the pump's operating conditions, for example, on the movements to which the pump is subjected, such as when the pump is implanted in a living body or when the pump is integrated into a mobile system, such as a vehicle or a robot, subjected to jerky movements.

[0044] Surface conditions allowing the reduction of static forces are subsequently described.

[0045] The first resonator extends to a first cylindrical sleeve 3b, coaxial with the central axis A, and opening into the cavity 2. The diameter of the sleeve 3i is between approximately 0.2 mm and 2 mm, and preferably close to 1 mm. The first sleeve 3i can be formed by an extension of the first resonator. The first sleeve 3i is open, so as to form a first inlet h of the pump. The radius of the first sleeve forms an internal radius of the first resonator 10.

[0046] The pump may include a second cylindrical sleeve 32, coaxial with the central axis A, opening into the cavity 2. The diameter of the sleeve 32 may be identical to the diameter of the first sleeve 3i. The second sleeve 32 may be formed by an extension of the second deformable resonator. The second sleeve 32 may be open, so as to form a second inlet l' of the pump.

[0047] Each sleeve and the cavity are dimensioned so that the liquid flow within them is subject to capillary forces greater than gravity. Thus, in the absence of activation of each resonator, the liquid is held stationary in each sleeve and in cavity 2 by the action of capillary forces. This makes it possible to form a pump without moving parts, limiting the risk of leakage.

[0048] The cavity 2 is delimited, in a radial direction, perpendicular to the central axis A, by a rib 5, the latter connecting the first resonator 10 to the second resonator 20.

[0049] Preferably, the inner wall of the cavity is coated with a hydrophobic material. The presence of the hydrophobic material can facilitate the minimization of frictional forces and surface tension forces at the interface between the fluid and the material on or within which the ultrasonic waves propagate, thereby facilitating the fractionation of this fluid. Combined with ultrasonic vibrations, a hydrophobic coating allows the liquid to be fractionated into microdroplets, or liquid fractions, which increases the fluid's mobility. This minimizes the pumping force. Around the central axis, by a centrifugal effect, as described below. The inner wall of each sleeve can be coated with a hydrophilic material. The height of each sleeve, along the central axis, is approximately 2 or 3 mm. This allows for the formation of a particularly flat pump.

[0050] More generally, the internal surface of the cavity is advantageously hydrophobic either as a result of a functionalization of the parts of each resonator delimiting the cavity, or by an appropriate structuring of the latter, for example a grooving type texturing or a formation of microchannels.

[0051] In general, the pump design aims to optimize the surfaces along which energy is transferred to the fluid: the design aims to distribute the fluid along the internal surfaces of the cavity, which are preferably made hydrophobic. The geometric configuration used, in which the fluid is moved within a cavity with a high surface area to volume ratio, favors the movement of the fluid along the surface of the resonator. To this end, the diameter of the cavity is greater than its thickness, and preferably at least 5 or 10 times greater than its thickness. This essentially surface-based configuration minimizes the energy required by the fluid. This avoids transferring excess energy to a large volume of fluid, which could lead to cavitation.

[0052] Note that this is a counterintuitive configuration, since the usual practice is to push a thick volume. When the fluid spreads out in a thin film, a creeping effect of the fluid is obtained on the inner wall of the cavity.

[0053] The radius of the cavity, perpendicular to axis A, is greater than the radius of the sleeve or each sleeve. The radius of the cavity is preferably at least two to ten times greater than the diameter of the sleeve or each sleeve.

[0054] A channel 4, extending between the first resonator 10 and the second resonator 20, opens into the cavity 2. The channel 4 extends in the radial direction, perpendicular to the central axis A. The channel 4 forms an outlet lo of the pump 1.

[0055] Each deformable solid material, forming the first and second resonator can be of the type metal (titanium, stainless steel, aluminum or aluminum alloy, brass, or other copper-based alloy, or nickel-based alloy), inorganic material (glass), organic material (PEEK), alumina without limitation of choice of other materials outside this non-exhaustive list.

[0056] Each layer of piezoelectric material can be formed from a PZT (lead zirconate titanate) type material, in particular Ferroperm references PZ26, PZ27, PZ46 and PZ29. Preferably, the coefficients d33 and d31, which account for the coefficient of the observed deformation for an applied electric field (also perceived as a charge density collected for an applied stress), are respectively: - of at least 200 pC / N and preferably beyond 570 pC / N for the coefficient d33 quantifying the response of the piezoelectric material in a direction parallel to the direction of the applied electric field. - less than -50 pC / N and preferably on the order of -240 pC / N. for d31, which quantifies the response of the piezoelectric material in a direction perpendicular to the direction of the applied electric field.

[0057] The pump includes a control unit 30, connected to the first electrode 12 and the second electrode 22, and allowing a bias voltage to be applied to them Frequency modulated. The modulation frequency depends on the size and material of each resonator. When the diameter of each resonator is 50 mm, the modulation frequency can be approximately 25 kHz. When the diameter of each resonator is 25 mm, the modulation frequency can be approximately 50 kHz. When the diameter of each resonator is 13 mm, the modulation frequency can be approximately 100 kHz. In all cases, the modulation frequency is ultrasonic, so as to avoid generating an audible sound.

[0058] The counter electrodes 14, 24 can be left at a floating potential or connected to a fixed potential, for example a ground.

[0059] According to one possibility, the first and / or second electrode may be annular. In this case, the first and second transducers are segmented into angular sectors so as to present opposite electric dipole moments between two adjacent angular sectors. Each angular sector can extend over a pocket angular value of 22°, where M denotes the number of different angular sectors of the transducer.

[0060] According to one possibility, the first and second transducers are annular and the first and / or second electrode is segmented into angular sectors of where N denotes the number of angular sectors. According to one possibility, each angular sector can extend by a value of a few degrees less than , so as to promote isolation between two adjacent sectors of the electrode. The control unit 30 is configured to apply a phase shift or delay of the bias voltage between two adjacent sectors 12b 122 of 2s, where N corresponds to N to the number of sectors of the first electrode. The same applies to the second electrode, which can be segmented into adjacent sectors 22b 222

[0061] When the bias voltage is sinusoidal, 22 corresponds to a phase shift. When the bias voltage is pulsed, the phase shift corresponds to a time delay relative to a characteristic time, which is the main resonance period T of the actuator. When the bias voltage is pulsed, it is common, but not required, for each pulse to be square-shaped, with a duration less than or equal to one-quarter of the resonance period T of the resonator.

[0062] Figures IB and IC show a first possible arrangement of the pump. In this example: - The first piezoelectric transducer comprises a first portion 13i and a second portion 132, forming two angular semi-sectors, and exhibiting respectively permanent electric dipole moments oriented in opposite directions: M = 2. The dipole moments The electrical components are denoted -P and +P. The first piezoelectric transducer 13 is biased by a first annular, unsegmented electrode 11 according to the voltage Vcos(wt). The first piezoelectric transducer is segmented along an X axis parallel to the median plane PM. - The second piezoelectric transducer 23 comprises a first portion 231 and a second portion 232, forming two angular semi-sectors, and exhibiting respectively permanent electric dipole moments -P and +P oriented in opposite directions: M = 2. The second piezoelectric transducer 23 is polarized by a second annular, unsegmented electrode 22, according to the voltage Vsin(wt). The second piezoelectric transducer is segmented along a Y-axis parallel to the median plane PM, perpendicular to the X-axis.

[0063] The angle y between the X and Y axes, segmenting the transducers 13, 23, combined with the phase shift of the bias voltages of the first and second electrodes, causes a rotation of the cavity compression by quadrants of angle 7, at the bias frequency. Thus, under the effect of the respective biases of the first and second electrodes, combined with the spatial segmentation of the electric moments of the first and second piezoelectric transducers, the resonators 10 and 20 deform periodically, each deformation resulting in a rotating compression of the cavity 2 with a maximum of the deformation located inside the radius RL

[0064] The deformation of cavity 2 rotates around the central axis A due to the polarization voltages being out of phase with each other. The compression of the cavity, propagating in a circular fashion, causes centrifugal force on the liquid. This results in a depression forming in the central part of cavity 2, opposite the sleeves. This facilitates the admission of a fluid, liquid or gas, into the cavity through one of the sleeves. The opposite sleeve can allow the admission of a complementary fluid. In this case, the pump mixes the fluid with the complementary fluid. Alternatively, one of the sleeves allows the admission of a liquid while the opposite sleeve can admit a gas, which then mixes with the pumped liquid. This could, for example, be oxygen, to meet the oxygenation requirements of a liquid.

[0065] Centrifugation tends to press the pumped liquid against the contour 5 of the cavity. The liquid can be evacuated through the channel 4. Preferably, the surface of the channel is treated hydrophilically, which facilitates the admission of the liquid into the channel, and then its evacuation.

[0066] Another transducer configuration is shown in Figures 1D and 1E. In these figures, the first and second transducers are annular. Each The transducer exhibits a uniform electric dipole moment around the ring. Rotating deformation of the cavity is achieved by segmenting the first electrode 12 and the second electrode 22 into two sectors 12b 122 and two sectors 22b 222, respectively. The first and second electrodes are segmented along the X and Y axes, respectively. The opposing sectors of the first and second electrodes are polarized by voltages out of phase by j. As in the previous case, this induces rotating deformation of the cavity at an ultrasonic frequency, resulting in centrifugation of the liquid and a pumping effect through the formation of a depression at the center of the cavity.

[0067] In the configuration described in relation to [Fig. 1A], one of the sleeves can be closed. The sleeve closure can be removable, allowing access through the sleeve for cleaning or for functionalizing the resonator surfaces delimiting the cavity. Functionalization can consist of applying a hydrophobic coating to the internal surfaces of the cavity and a hydrophilic coating to the inlet sleeve or outlet channel.

[0068] Figures 2A to 2B describe another embodiment in which a single resonator 10 is used. The resonator 10 is as described in relation to [Fig. 1A].

[0069] Each first electrode is obtained by segmenting a first annular electrode 12, forming angular sectors 12b, 122, 123, 124 extending along an angular displacement of y. In the example shown in Figures 2A and 2B, each angular sector extends along j steradians. Two diametrically opposed sectors 121123 are biased by a voltage Vsin(wt) phase-shifted by y with respect to the two other diametrically opposed sectors 122124.

[0070] The transducer 13 is divided into two half-rings whose electric moments are opposite, so that the sectors 12b 122 polarize the half-ring with electric dipole moment -P, the other two sectors 123, 124 polarize the half-ring with opposite electric dipole moment.

[0071] The cavity 2 extends between the resonator 10 and a support 6, forming a base. A rib 5 allows the connection between the resonator 10 and the support 6. When the plug is made of duralumin aluminum alloy, for a frequency of 100 kHz, the thickness of the base can be 0.5 mm, and its diameter 7 mm.

[0072] Under the effect of a deformation of the resonator 10, rotating around the central axis, taking into account the described polarizations and the structure of the piezoelectric transducer, the cavity 2 is deformed by a rotating deformation wave around the central axis, during which the resonator presses against the bottom 6. This results in centrifugation of the liquid, causing a depression at the center of the cavity 2, facing the sleeve 3, as well as an evacuation of the liquid pumped by the channel 4, extending between the resonator and the bottom 6, perpendicular to the central axis.

[0073] The configurations described in connection with figures IA and 2A may include several discharge channels 4, which allows distribution of the pumped liquid in different orientations around the central axis.

[0074] Regardless of the configuration, the sleeve, or sleeves, are preferably positioned at a vibration node of each resonator, thus allowing for a connection with minimal damping losses to the fluidic circuit connected to the sleeves. The height of the sleeve can be adjusted accordingly. Preferably, the sleeve and the resonator to which it is connected should be formed from a single piece, with the sleeve extending the resonator: thus, sleeve 3i described in relation to [Fig. 1A] is part of resonator 10 and forms one end of it. Sleeve 32 is part of resonator 20 and forms one end of it. In the example given in [Fig. 2A], sleeve 3 extends resonator 10.

[0075] Regardless of the configurations described in Figures IA and 2A, the cavity 2 extends over a larger diameter than the sleeve, so as to allow a centrifugal effect, resulting in a sufficient vacuum opposite the sleeve to draw the liquid present in the sleeve out. Suction is favored when the inner surface of the sleeve is hydrophilic. Centrifugation is favored when the inner surface of the cavity is hydrophobic.

[0076] Regardless of the configuration, piezoelectric transducers have a small thickness, typically between 0.05 mm and 5 mm, preferably 0.5 mm for a radius R of 25 mm and 0.2 mm for a radius R less than 10 mm, which maximizes the electric field, which can be on the order of 300 V / mm. This makes it possible to increase the mechanical stress, which is directly proportional to the electric field.

[0077] Regardless of the configurations, the peak / peak bias voltage can vary, for example, from a few volts to several hundred volts, the voltage acting on the amplitude of the out-of-plane deformation component of the resonator which itself acts on the volume of centrifuged fluid and therefore on the pumping pressure.

[0078] The configurations described in connection with Figures IA and 2A can be particularly compact: the external diameter of each piezoelectric transducer is preferably less than 10 mm, and the internal diameter can be 5 mm. Shorter external diameters, for example 7 mm, are possible. The dimensions can be determined analytically, particularly for simple geometries, or by numerical simulation.

[0079] The configurations described in relation to Figures IA and 2A result in a predominance of surface effects over volume effects: At centrifugation speed At zero, the gravitational forces are weaker than the surface effects, and the liquid conforms to these surface effects. Energizing the fluid by applying ultrasonic waves reduces its wettability, causing it to organize itself into smaller, spherical microdroplets. This results in weaker overall cohesion. The spatial distribution of surface forces is thus modified. When the liquid is set in motion by the rotating ultrasonic wave due to its viscosity, adhesion to the surface decreases. Beyond a certain angular velocity, the inertial effects induced by the ultrasonic wave generate a pumping effect by creating a central low pressure and a peripheral high pressure. Thus, in static conditions, the liquid tends to adhere to the inner wall of the cavity. The rotating ultrasonic wave, through shearing, creates an overall fluid motion, which is the source of the pumping effect.The pumping effect is achieved when the energy supplied is below a threshold that would cause the liquid to vaporize. This is advantageous because vaporization can generate aggressive mechanical effects on the walls.

[0080] The resonant frequency of the resonators can vary. To account for a possible drift in the resonant frequency, the control unit can be configured to apply a frequency sweep. Figure 3 shows the magnitude of the Fourier transform of one of the excitation signals when it consists of a succession of a finite number of sinusoidal periods with amplitude normalized to 1 and at frequencies increasing in frequency increments. In this example, a frequency sweep was performed between 195 kHz and 202 kHz in 3% frequency increments. The frequency sweep allows traversing the optimal frequency, taking into account the variability affecting pumps, and in particular manufacturing processes: bonding, fastening systems.The pumped fluid can also influence the resonance frequency, as it causes a variation in the mechanical impedance of the system, due to its viscosity, its movement within the pump, or its temperature.

[0081] For example, the resonant frequency of the resonators may be 200 kHz under nominal operating conditions. However, the resonant frequency may vary, within a predetermined spectral range, depending on the operating conditions, which include the nature and composition of the fluid, its homogeneity, its possible multiphase composition, the temperature, the amount of fluid inside the cavity, or the viscosity of the fluid. The spectral range may vary between a minimum resonant frequency, for example 195 kHz, and a maximum resonant frequency, for example 203 kHz. The control unit is configured to apply an excitation signal by performing a spectral sweep within the predetermined spectral range. The excitation signal is thus formed a succession of an integer number of sinusoidal periods between the minimum frequency of 195 kHz and the maximum frequency of 203 kHz, according to a predetermined frequency increment. When several phase-shifted excitation signals are successively applied to different angular sectors of an electrode, the excitation signals are at the same frequency, which allows the pumped fluid to rotate.

[0082] Frequency sweeping makes it possible to address the resonant frequency, regardless of the operating conditions, provided they are within predetermined limits. The pump excitation frequency is not continuously centered on the optimal resonant frequency, but reaches the optimal frequency during each sweep.

[0083] The frequency sweep is renewed periodically. The time interval separating two consecutive frequency sweeps can be adjusted, so as to allow continuous pumping (zero time interval) or cyclic pumping, during which an excitation duty cycle is taken into account, corresponding to the duration of the frequency sweep over the duration of the time interval between two consecutive frequency sweeps.

[0084] According to one possibility, when an electrical transducer is coupled to several segmented electrodes, the electrical excitation potential of each electrode, referred to here as polarization, varies in the form of pulses, which are successively addressed to the electrodes in a predetermined direction of rotation. If T is the period required to address all the sectors, each sector is polarized with a delay of y relative to the preceding electrode, and the duration of this polarization is at most equal to y. It may be shorter.

[0085] To excite the pump while remaining locked to the optimal excitation frequency of the device, useful information can be extracted from a sector between two polarizations to perform an analysis of the pump's operation. For this purpose, the pump includes a control unit 31, connected to each electrode, and programmed to analyze control signals generated by a sector between two successive polarizations. The control signal generated by the sector can be considered as a representation of the pump's operation. This allows information to be obtained about the vibration of the resonator, which can vary depending on the pump's operation or the filling level.

[0086] The control signal generated by the mains can be connected to a low-impedance input LZ or a high-impedance input HZ of the control unit. A connection to a low-impedance input LZ has the disadvantage of drawing charge from the piezoelectric transducer, which reduces the efficiency of actuation using another electrode. Using such a low-impedance connection This allows for tracking the resonant frequency using a series equivalent electrical model (EEM) based on collected loads. A connection to a high-impedance Hz input preserves actuation efficiency, but at the cost of increased analysis complexity. Using such a high-impedance connection also enables tracking the resonant frequency using a parallel EEM based on a measured voltage. The user can choose to perform low-impedance and / or high-impedance signal analysis.

[0087] Figure 4A shows an electrode 12 arranged in angular sectors 12i, 12i, 124, 124 of angle j. Figure 4B schematically represents a connection of each angular sector during a measurement period T. The measurement period is segmented into four time sequences (abscissa axis), during which each sector is: - either polarized with an actuation signal V; - either connected to a low impedance LZ input of the control unit; - either connected to a high impedance HZ input of the control unit; - or unused.

[0088] On [Fig.4B], the successive connections, during the period T, of each sector 12b 122, 123 and 124 have been represented from top to bottom.

[0089] Using a control signal allows observation of the pump's operation. This makes it possible, for example, to monitor a resonant frequency. Indeed, sampling the voltage (high-impedance measurement) or the electrical charge (low-impedance measurement) that appears in a sector reflects the electrical impedance of the sector. Regardless of the measurement, the resonant frequency depends on the temperature and the fluid load conditions. The control signal makes it possible to estimate an electrical impedance at the angular sector. This impedance varies according to the temperature and the fluid load conditions. The control signal thus makes it possible to control the resonant frequency by maintaining the voltage (measured in high-impedance mode) or the measured electrical charge (measured in low-impedance mode, oscilloscope) at a certain setpoint value.Furthermore, performing a frequency sweep allows for the reconstruction of a real-time actuator transfer function at each sweep, with precise identification of the optimal electro-mechanical coupling frequency corresponding to the minimum sector impedance.

[0090] Figures 5A to 7 illustrate different embodiments of a pump operating in a peristaltic mode.

[0091] Figure 5A shows a pump comprising: - a first annular piezoelectric transducer 11, extending around a central axis A as described in connection with [Fig.1A]. - a deformable solid material 10, extending around the central axis A, which, under the action of the first piezoelectric transducer 11, forms a resonator. The resonator 10 forms a disk around the central axis A and thins towards it. Thus, its thickness, defined parallel to the central axis A, decreases as a function of the distance from the central axis. The resonator 10 comprises a flat portion surrounding a thinned portion, the latter being centered around a sleeve 3. - a second annular piezoelectric transducer 21, also connected to the resonator 10, and extending around a central axis A symmetrical to the first piezoelectric transducer.

[0092] The radius R of the resonator, defined around the central axis, can extend up to 50 mm. In the example shown, the resonator has an outer portion of constant thickness beyond a first radius Rb, which is smaller than the previously defined radius R. Below the first Rh, the resonator has a portion that thins out towards the central axis A. The first radius Ri is, for example, equal to 50% of the radius R of the resonator.

[0093] The pump comprises a cylindrical sleeve 3, coaxial with the central axis, formed by an extension of the first resonator. The diameter of the sleeve 3 can be on the order of 1 mm. The sleeve and the resonator form a single piece, as described in connection with Figures IA and 2A. The base of the sleeve is a vibration node while it vibrates by a rocking or bending motion, and its end is chosen to define a vibration antinode of the resonator 10.

[0094] Under the effect of cyclic activation of the first piezoelectric transducer 11 and the second piezoelectric transducer 21, the sleeve can undergo deformation forming a bending wave propagating along the axis of the sleeve, at a resonance frequency corresponding to the activation frequency of the first and second electrodes. The amplitude of the bending is preferably greater than 1 pm.

[0095] The pump includes a capillary 8, fixedly wound around the sleeve 3, and preferably tightened around the latter on a portion near its end, where the amplitude of the tilting motion is high. The capillary preferably has several turns, pressed against the outer surface of the sleeve.

[0096] Figure 5B is a cross-sectional view of the sleeve 3, showing several turns of the capillary 8, preferably touching, pressed against the sleeve. Under the effect of the bending of the sleeve, and its propagation along the central axis A, each turn of the capillary is progressively deformed, which causes the liquid to advance in the capillary. This results in peristaltic-type pumping without a part. mobile in rotation. Bending creates a periodic rotating mechanical stress applied to the turns, one part of the turns being periodically compressed while the diametrically opposite part being periodically stretched.

[0097] This type of pump can be very compact, with a diameter of less than 10 mm and a maximum resonator thickness of 0.5 mm. The resonator can be made of metal or plastic. The capillary can be made of silicone. A single turn around the sleeve is sufficient, but operation is more efficient with multiple turns.

[0098] Figures 6A and 6B show another peristaltic pump configuration. The pump includes a resonator 10 as described in relation to [Fig. 5A]. The resonator is connected to a ring-shaped piezoelectric transducer 11, as previously described. The resonator extends between a base 10b and a flat support face 10a. The capillary 8 is arranged on a flat portion of the flat support face. The reduction in the resonator's thickness is achieved by bringing the base closer to the flat support face.

[0099] Figure 6A shows a segmentation of the first electrode 12 into 4 sectors angular, of angle y. As in previous embodiments, the transducer is configured to generate a deformation of the resonator which rotates around the central axis, according to an ultrasonic frequency.

[0100] The pump includes a capillary 8, held against the flat face of the resonator by means of a clamping ring 9, at a vibration antinode. The antinode is such that the out-of-plane deformation is positive at every instant on a semicircle passing through the maximum of the vibration antinode and negative on the other semicircle. In [Fig. 0C], the absolute value of the amplitude of the out-of-plane vibration (ordinate axis) with respect to plane 10a is shown as a function of a coordinate along a radial axis (abscissa axis). A first vibration node extends over a region in which the transducer is held against the resonator. A second vibration node is located at the center of the resonator at the base of the sleeve. The height of the sleeve defines the radial position of the vibration antinode, between the first and second vibration nodes.

[0101] The capillary 8 forms at least one turn around the central axis. Under the effect of the rotating deformation of the resonator, the capillary 8 undergoes rotating compression, which enables pumping by peristaltic effect. Depending on the direction of rotation of the deformation, the pumping can be carried out in two opposite directions.

[0102] Figure 7 represents an embodiment based on a principle similar to that governing the pump described in connection with Figures 6A to 6C. A capillary 8 is arranged between a first resonator 10, as described in connection with Figures 6A and 6C, and a second resonator 20. The second resonator 20 is symmetrical to the first resonator with respect to a median plane PM perpendicular to the central axis A.

[0103] The first resonator 10 is coupled to a first piezoelectric transducer IL. The second resonator 20 is coupled to a second piezoelectric transducer 21. Each piezoelectric transducer is arranged to generate compression of the capillary 8, rotating about the central axis A. This results in peristaltic pumping. The direction of pumping depends on the direction of rotation of the deformation.

[0104] Each resonator can extend to a diameter of 50 mm and a thickness of 3.8 mm, with a resonant frequency of 26.6 kHz. The smaller the diameter, the higher the resonant frequency. For a diameter of 25 mm, the resonant frequency is approximately 50 kHz. For a diameter of 13 mm, the resonant frequency is approximately 100 kHz. The excitation voltage, which defines the inertial compression level of the capillary, can range from a few volts to several hundred volts peak-to-peak.

Claims

1. Demands Pump (1), intended to pump a fluid between an inlet and an outlet, comprising: - a first annular piezoelectric transducer (11), extending around a central axis (A), and comprising a first electrode (12); - a first resonator (10), connected to the first piezoelectric transducer, and extending around the central axis, the first resonator being formed of a deformable solid material thinning towards the central axis, the first resonator being configured to deform under the effect of a polarization of the first piezoelectric transducer; - a control unit (30), configured to bias the first electrode according to a bias voltage, modulated according to a modulation frequency greater than 20 KHz; the pump being characterized in that: - the first resonator delimits a cavity (2), extending around the central axis, and configured to receive the fluid, the cavity extending, along the central axis, according to a thickness; - the pump includes a first sleeve (3i), connected to the first resonator, opening into the center of the cavity, forming the pump's inlet; - the pump includes at least one channel (4), opening from the cavity, the channel extending, along the first resonator, around an axis perpendicular to the central axis, the channel forming the pump outlet; - so that under the effect of the polarization of the first piezoelectric transducer, a deformation of the resonator occurs, locally and transiently reducing the thickness of the cavity, the deformation propagating around the central axis, and resulting in the propulsion of a fluid, admitted into the cavity, around the axis central, the propulsion inducing a suction effect in the center of the cavity, opposite the intake.

2. Pump according to claim 1, wherein the first transducer comprises at least two distinct angular portions configured to deform differently, under the effect of the polarization applied to the first electrode, so as to generate a deformation of the first resonator propagating around the central axis.

3. A pump according to claim 2, wherein the first electrode is segmented into n angular sectors (12i, 122), n being greater than 2, the control unit being configured to bias two angular sectors of the first electrode respectively by two voltages phase-shifted by a phase shift less than or equal to or time-shifted by a time shift less than or equal to

4. Pump according to any one of claims 2 or 3, wherein the first piezoelectric material comprises at least two different portions (13i, 132), in which the electric dipole moment is oriented in opposite directions.

5. Pump according to any one of the preceding claims, wherein the first resonator (10) is disposed facing a support (6), forming a bottom of the cavity, the cavity extending between the first resonator and the bottom.

6. Pump according to any one of the preceding claims, wherein the first sleeve is coaxial with the central axis.

7. Pump according to any one of the preceding claims, comprising - a second ring-shaped piezoelectric transducer (21), extending around the central axis, and comprising a second electrode (22), connected to the control unit; - a second resonator, connected to the second piezoelectric transducer, and extending around the central axis, the second resonator being formed of a deformable solid, the second resonator thinning towards the central axis, the second resonator being configured to deform under the effect of a polarization of the second piezoelectric transducer; - the second resonator extends opposite the first deformable solid material; - the cavity extends between the first resonator and the second resonator.

8. Pump according to any one of the preceding claims, wherein the second transducer comprises at least two distinct angular portions configured to deform successively, under the effect of the polarization applied to each second electrode, so as to generate a deformation of the second resonator, the deformation propagating around the central axis.

9. Pump according to claim 8, wherein the second electrode is segmented into n angular sectors (22b 222), n being greater than or equal to 2, the control unit being configured to bias two angular sectors of the second electrode respectively by two voltages out of phase of .

10. A pump according to any one of claims 8 to 9, wherein the second piezoelectric material comprises at least two different portions (23b 232), in which the electric dipole moment is oriented in opposite directions

11. Pump according to claim 10, wherein: - the first electrode is segmented into symmetrical angular sectors, with respect to a first axis of symmetry, and activated in opposite phase; - the second electrode is segmented into symmetrical angular sectors, with respect to a second axis of symmetry, and activated in opposite phase; - the first axis of symmetry is orthogonal to the second axis of symmetry.

12. Pump according to any one of claims 8 to 11, comprising a second sleeve (32), connected to the second resonator, and opening into the center of the cavity.

13. Pump according to any one of claims 8 to 12, wherein the second sleeve is coaxial with the central axis of the cavity.

14. Pump according to any one of the preceding claims, wherein the modulation frequency is greater than 100 kHz.

15. Pump according to any one of the preceding claims, wherein: - the first electrode is segmented into n angular sectors, n being greater than or equal to 2, - the control unit is configured to address a bias signal successively to each angular sector; - the pump comprises a control unit, connected to at least one angular sector of the first electrode, the control unit being configured to detect a control signal between two successive bias signals.

16. Pump according to any one of the preceding claims, wherein the thickness of the cavity is less than 1 mm.

17. Pump according to any one of the preceding claims, wherein the control unit is configured to bias the first electrode according to a frequency bias signal, by performing a frequency sweep over a finite number of successive discrete frequencies.

18. Pump according to any one of the preceding claims, wherein the internal surface of the cavity comprises at least one hydrophobic part.

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