EP1097484A1 - Piezoelektrische elektrobewegliche bauelemente - Google Patents

Piezoelektrische elektrobewegliche bauelemente

Info

Publication number
EP1097484A1
EP1097484A1 EP98937730A EP98937730A EP1097484A1 EP 1097484 A1 EP1097484 A1 EP 1097484A1 EP 98937730 A EP98937730 A EP 98937730A EP 98937730 A EP98937730 A EP 98937730A EP 1097484 A1 EP1097484 A1 EP 1097484A1
Authority
EP
European Patent Office
Prior art keywords
bender
piezoelectric
film
layers
elements
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98937730A
Other languages
English (en)
French (fr)
Other versions
EP1097484A4 (de
Inventor
Frank E. Sager
William C. Robertson
Christopher J. Matice
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oceaneering International Inc
Original Assignee
Oceaneering International Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oceaneering International Inc filed Critical Oceaneering International Inc
Publication of EP1097484A1 publication Critical patent/EP1097484A1/de
Publication of EP1097484A4 publication Critical patent/EP1097484A4/de
Withdrawn legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04BPOSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B43/00Machines, pumps, or pumping installations having flexible working members
    • F04B43/02Machines, pumps, or pumping installations having flexible working members having plate-like flexible members, e.g. diaphragms
    • F04B43/04Pumps having electric drive
    • F04B43/043Micropumps
    • F04B43/046Micropumps with piezoelectric drive
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04BPOSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B43/00Machines, pumps, or pumping installations having flexible working members
    • F04B43/12Machines, pumps, or pumping installations having flexible working members having peristaltic action
    • F04B43/14Machines, pumps, or pumping installations having flexible working members having peristaltic action having plate-like flexible members
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00Piezoelectric or electrostrictive devices
    • H10N30/01Manufacture or treatment
    • H10N30/08Shaping or machining of piezoelectric or electrostrictive bodies
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00Piezoelectric or electrostrictive devices
    • H10N30/20Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H10N30/204Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00Piezoelectric or electrostrictive devices
    • H10N30/80Constructional details
    • H10N30/802Circuitry or processes for operating piezoelectric or electrostrictive devices not otherwise provided for, e.g. drive circuits

Definitions

  • the present invention is directed to electro-motional devices, especially piezoelectric pumps. More specifically, the present invention is directed to the method of fabrication of piezoelectric bender-elements; specifically, using multi- layers of piezoelectric material by bonding the layers in a press and heating the layers to form a bender element with a mechanical bias or curve.
  • a piezoelectric unit cell of the present invention is fabricated using two mechanically biased bender-elements, each mechanically and electrically biased in opposite direction. Any number of piezoelectric unit cells of the present invention may be employed in making an electromotional device.
  • a drive circuit of the present invention provides the electrical source to sequentially in an alternating mode activate the unit cells.
  • Piezoelectric materials have been used extensively as sensors and acoustical/electric coupling devices. Materials that have been used in these devices are made from films of polymer such as polyvinylidene fluoride (PVDF) which are drawn or stretched while subjecting the polymer film to an electric field. The piezoelectric film will then respond to applied electrical fields by either lengthening or shortening depending upon the direction of the applied field. The deflection which can be obtained using piezoelectric polymer films are substantially greater than those obtained using piezoelectric ceramic crystals.
  • PVDF polyvinylidene fluoride
  • Papers disclosing making sensors using bimorph elements and specific techniques in making the elements are: "Application of PVF 2 Bimorph Cantilever Elements to Display Devices", M. Toda and S. Osaka, Proceeding of the S.I.D., Vol 19/2, Second Quarter 1978, pp 35-41; "Electro-motional Device Using PVF 2 Multilayer Bimorph", M. Toda and S. Osaka, Transactions of the IECE of Japan, Vol E61 No 7, July 1978, pp 507-512; "Theory of Air Flow Generation By a Resonant Type PVF 2 Bimorph Cantilever Vibrator", M.
  • U.S. 4,162, 511 discloses a pickup cartridge for use in a velocity correction system which includes a polymer bimorph element mechanically interposed between a cartridge housing and a pickup arm carrying a groove-riding stylus.
  • U.S. 4,164,756 discloses a signal pickup stylus which cooperates with an information storing spiral groove on a video disc record which is caused to selectively skip groove convolutions of the disc record to produce special effects.
  • U.S. 4,176 378 discloses a pickup arm pivotally coupled to a housing support at one end thereof and which is coupled to the housing near its other end by means of bimorph elements attached together at right angles.
  • U.S. 4,351,192 discloses a piezoelectric, acoustic vibration detecting element which is positioned in a fluid flow to be measured so as to be moved according to the intensity of the fluid flow away from a source of acoustic vibration.
  • U.S. 4,417,169 discloses a photoelectric circuit arrangement for driving a piezoelectric bimorph element to bend and thereby to open or close a window blind according to the quantity of transmitted light through the blind.
  • U.S. 4,342,936 discloses a piezoelectric flexure mode device (called a "unimorph") comprising a layer of piezoelectric active material bonded to a layer of piezoelectric inactive material.
  • U.S. 4,405,402 discloses a thick piezoelectric/pyroelectric element made from polarized plastics such as polyvinylidene fluoride.
  • U.S. 4,670,074 discloses a composite co-laminated piezoelectric transducer with at least one layer of polymeric substance capable of acquiring piezoelectric properties when co-laminated in the presence of an electric field.
  • U.S. 4,708,600 discloses a piezoelectric fluid pumping apparatus which includes a pumping apparatus incorporating a piezoelectric energizer.
  • U.S. 4,939,405 discloses a pump comprised of a piezoelectric vibrator mounted in a casing.
  • U.S. 5,113,566 discloses a method of producing a multilayer piezoelectric element.
  • the present invention is directed to electro-motional devices, especially piezoelectric pumps. More specifically, the present invention is directed to the method of fabrication of piezoelectric bender-elements; specifically, using multilayers of piezoelectric material by bonding the layers in a press and heating the layers to form a bender element with a mechanical bias or curve.
  • a piezoelectric unit cell of the present invention is fabricated using two mechanically biased bender-elements, each mechanically and electrically biased in opposite direction. Any number of piezoelectric unit cells of the present invention may be employed in making an electromotional device.
  • a drive circuit of the present invention provides the electrical source to sequentially in an alternating mode activate the unit cells.
  • Fig. 1 is a schematic series of views (a; b; c; and d) illustrating the fabrication of a bender-element using two strips of polyvinylidene fluoride having a thin layer of silver electrode coating on each side (the film being cut with tabs and the coating being the shaded layers applied to top and bottom) , the polarity of the top film of polyvinylidene fluoride being in opposite direction than that of the bottom film of polyvinylidene fluoride; specifically, Fig. 1 (a) is one strip of film having only the top of the tabs coated and one tab folded; Fig. 1 (b) is a second strip of film having the top of one tab and the bottom of the other tab coated and one tab folded; Fig. 1 (c) shows placing the two films together; and Fig. 1 (d) showing the two film connected;
  • Fig. 2 is a schematic series of views illustrating the folding of the two strips of piezoelectric multimorph film before bonding or laminating the strips; specifically, Fig. 2 (a) shows that two films are connected as fully shown in Fig. 1; Fig. 2 (b) shows the geometry of the strips and the polarity-machine orientation; and Fig. 2 (c) illustrates the folding of the films to form a bender-element of the present invention;
  • Fig. 3 is a cross-sectional and end view of a press with jaws having a size and shape to bond a bender-element with a desired radius of curvature
  • Fig. 4 is a schematic illustrating the sine curve of an alternating electric field changing the polarity placed on a unit cell and the corresponding deflection changes of the unit cell; specifically, Fig. 4 (a) illustrates the deflection of the unit cell at one extreme of polarity; Fig. 4 (b) illustrates the unit cell with no deflection due to polarity; and Fig. 4 (c) illustrates the deflection of the unit cell at the other extreme of polarity;
  • Fig. 5 are schematic views illustrating the piezoelectric unit cell of the present invention; specifically one view, Fig. 5 (a) , with an electrical polarity which provides a field across the bender-elements of the unit cell and the unit cell is in the expanded state; the second view, Fig. 5 (b) in which the polarity of the electric field on the unit cell is reversed and the unit cell is in the contracted state;
  • Fig. 6 are schematic views of a stack or plurality of unit cells on a backing plate; specifically one view, Fig. 6 (a), with an initial electrical polarity which contracts the unit cells and the other view, Fig. 6 (b) , with an opposite electrical polarity providing a field across the bender- elements which expands the unit cells;
  • Fig. 7 is a schematic view which illustrates a simple piezoelectric electro-motional device with a plurality of unit cells acting as the drive block for a single chamber pump, the pump in cross-section without the outside housing;
  • Fig. 8 is a schematic view which illustrates a piezoelectric pump with parallel multi unit cells activating push-pull pistons of a piezoelectric pump with double parallel chambers;
  • Fig. 9 is a schematic diagram illustrating the electrical circuit to operate the piezoelectric pump
  • Fig. 10 is a schematic diagram of a unique circuit for powering the unit cells of the present invention.
  • Fig. 11 is a schematic view which illustrates a piezoelectric pump with parallel multi unit cells activating push-pull pistons of a piezoelectric pump with double parallel chambers and inlet and outlet pulse dampers
  • Fig. 12 is a schematic view of a piezoelectric pump with push-pull pistons in double parallel cylinders and inlet and outlet pulse dampers;
  • Fig. 13 is a schematic view of a peristalic pump with three multi cells activating the fluid flow through a flexible tubing; Fig 13(a) and 13(b) shows the cyclic activation of the three piezoelectric unit cells to maintain positive flow; and
  • Fig. 14 is a schematic view of a piezoelectrically driven centrifugal pump.
  • the fabrication of the bender-element and the piezoelectric unit cell are unique and provide the basis of the piezoelectric devices of the present invention.
  • piezoelectric elements have principally been used as sensors and the deflection movement of the element has been the major consideration. Thus, mechanical integrity was a minor part of the element.
  • the fabrication of any multiple layer piezoelectric bender element heretofore has employed an epoxy resin or some other adhesive to bind the layers.
  • the piezoelectric bender-elements and more specifically the piezoelectric unit cells of the present invention are used as driving blocks or force sources which may be used in many applications such as a piezoelectric pump.
  • the present invention uses mechanically biased piezoelectric bender-elements (meaning that the bender-elements are curved in their fabrication) . Two of these mechanically biased piezoelectric bender-elements are then fabricated into a unit cell wherein the two bender-elements are both mechanically and electrically biased in opposite directions.
  • This basic structure of the unit cell as compared to a single piezoelectric element has at least four times the deflection for a given drive voltage.
  • the force can be multiplied while retaining the maximum deflection possible for a given drive voltage.
  • the bender-elements of the present invention are fabricated using multilayered films of a piezoelectric material such as a film of polyvinylidene fluoride.
  • a piezoelectric film has the property that when the film is subjected to an electric field the film either lengthens or shortens depending upon the direction or polarity of the applied electrical field.
  • a film of poly-vinylidene fluoride is made piezoelectric by drawing or stretching the film while subjecting the film to an electric field.
  • a two layer or bimorph bender-element is fabricated with the layers arranged so that one layer lengthens while the other layer contracts.
  • a multilayer or multimorph bender-element is fabricated.
  • the electrode coating may be a highly conductive metal, such as silver or a metal such as platinum, gold, copper or any combination of conductive material.
  • Piezoelectric polyvinylidene fluoride films are the preferred materials used in the fabrication of the multimorph bender-elements. Such films are available from Amp Incorporated in film thicknesses which range from 9 microns to 600 microns and are available with a silver coating.
  • the fabrication method of the present invention involves the steps of bonding by heating while under pressure the layers of piezoelectric material and then annealing to form the bender-elements of the present invention.
  • the layers of piezoelectric material are placed in a curved press so that the bender-elements are fabricated with a mechanial bias or a natural curve.
  • a preferred embodiment of the present invention involves the folding of the electrode coated piezoelectric polymer films and is unique to the present invention.
  • the cutting of the film and the presence or non-presence of the electrode coating on certain portions of the cut film is shown in Fig. 1.
  • a first strip 2 of polyvinylidene fluoride is shown in Fig. 1(a) and a second strip 4 of polyvinylidene fluoride is shown in Fig. 1(b) .
  • Each strip 2 and 4 have a thin layer of silver electrode coating 6 (cross hatching) applied to each side of the strips 2 and 4 in preparation to fabricate a multimorph bender-element of the present invention.
  • the first strip 2 has two tabs 8 and 10 extending from the strip 2; however, only the top of tabs 8 and 10 are coated with the silver coating 6 and neither of the bottom surfaces of tabs 8 and 10 have any silver electrode coating 6.
  • the tab 10 when fabricating the bender-element of the present invention is folded or bent downward as shown in the bottom figure of Fig. 1(a) .
  • the strip 4 on the other hand has two tabs 12 and 14 which are positioned opposite that of the tabs 8 and 10 of strip 2 as shown in Fig. 1(a).
  • the top surface of tab 12 and the bottom surface of tab 14 have a thin layer of the silver electrode coating; whereas, neither the bottom surface of tab 12 or the top surface of tab 14 have any silver electrode coating as shown in the upper figure of Fig.
  • the tab 14 when fabricating the bender-element of the present invention is folded or bent upward as shown in the lower figure of Fig. 1(b) .
  • the two strips 2 and 4 are then placed one on top of the other as shown in Fig. 1(c) .
  • the tabs 8 and 12 extend from the end of the two strips and the electric wires or connections from an electrical circuit are connected to each of these tabs 8 and 12.
  • the tabs 10 and 14 on the other hand are folded to provide electrical contact with the reverse side of the respective strip as shown in Fig. 1(d). Sheets of piezoelectric film are available with an electrode coating already applied to both surfaces of the film.
  • the electrode coating be removed at the edges of strips 2 and 4 as well as removing the coating from the tabs as indicated when cutting the strips from already coated polyvinylidene fluoride or PVF 2 strips. Removing the conductive silver electrode material from the edges prevents high voltage arcing.
  • the first step in fabricating the bender-elements of the preferred embodiment of the present invention is to fold at least two strips 2 and 4 of the film as illustrated in Fig. 1.
  • the first strip 2 is folded into layers (2 shown and can extend to any number desired) to produce a multi-layered bender-element.
  • the polarity-machine orientation of the strip 2 of piezoelectric film is opposite that of the strip 4 of piezoelectric film when a voltage is applied to the films or the polarity directions of the film are opposite.
  • What opposite polarity-machine orientation means is that when an applied voltage is applied to the films, the field voltage is in a direction which is the same as the polymer orientation and the one film will expand while the field voltage is opposite the polymer orientation and the other film will contract.
  • the arrow 16 shows the polarity-machine orientation or polarity of the strip 2.
  • the second strip 4 is folded into the same length and same number of layers as strip 2 but the polarity of the film, as shown by the arrow 18, is in the other direction.
  • the polarity-machine orientation of the second strip 4 is 180° from the first strip 2 and therefore one film will expand while the other will contract.
  • polarity will be discussed in two ways in the understanding of the present invention: (1) the applied voltage polarity which is a function of the electrical circuit connected to the strips and (2) the inherent polarity or polymer orientation of the strips 2 and 4 which is the function of the machine direction of the respective strip (indicated by an x or . in a circle and a machine direction away from the tabs) .
  • the voltage polarity is reversed on the tabs 8 and 12 it reverses the polarity-machine orientation of the films such that the film that expanded will contract and the film that contracted will expand.
  • tabs 8, 10, 12 and 14 provide the continuity of applied polarity to the multimorph or folded structure shown in Fig. 2 through a single set of leads attached to tab 8 and tab 12.
  • the tabs provide opposite polarities to the electrode film surfaces of the two strips 2 and 4.
  • tab 10 provides the same polarity to the bottom surface of strip 4 when that strip is folded back over the tab 10 as shown in Fig. 2.
  • tab 12 is negative and the same negative polarity is on the top surface of strip 4 and the bottom surface of strip 2 and that polarity continues however many number of layers the strips are folded.
  • the tab 14 is redundant as to requiring this tab to provide the same polarity from the bottom surface of strip 4 to the top surface of strip 2; however, the two tabs 10 and 14 provide a greater surface area for the flow of electrons to provide the same polarity to these two surfaces. A restricted path for the flow of electrons may cause a hot spot or short.
  • the uniqueness of the tabs and the folding is that only two leads are required. A multi-layer bender-element may be made without all the specifics of the preferred embodiment.
  • the piezoelectric material need not be solely strips of polyvinyl- idene fluoride film coated with silver as the electrode coating.
  • the orientation of the layers of electrode coated piezoelectric material need to be the same as a single folded film.
  • the respective layers will have the same orientation as a single folded film.
  • the respective layers of material can not be simply randomly stacked.
  • the discontinuous piezoelectric film or material may have small opening extending though the layers of piezoelectric material for electron flow.
  • the folded strips 2 and 4 of film are positioned into a press 20 having an upper jaw 22 and lower jaw 24, preferably each jaw made of machined pieces of polycarbonate.
  • a preferred set of jaws 22 and 24 have a slight radius of curvature or curved portion 26 to fabricate the bender-elements with a mechanical curvature or bias.
  • the two folded strips 2 and 4, as shown in Fig. 2(c), are positioned between upper jaw 22 and lower jaw 24.
  • the jaws 22 and 24 of the press 20 are closed and as much pressure as required is applied to the two separate folded films.
  • the pressure may range from 100 pounds per square inch (psi) to 10,000 psi.
  • the press 20 and the compressed films are then subjected to a heating cycle to bond the films, such as placing the compressed films into a low temperature oven.
  • the temperature of the oven may range from 35° C. (95° F. ) to 65° C.(149° F. ) .
  • the compressed films in press 20 are left in the oven for a shorter time, approximately a half hour, while at the lowest temperatures the press 20 will be kept in the oven for as long as 12 hours.
  • the press 20 is then removed from the oven and without removing the compression on the films, is air cooled to room temperature.
  • the bonded and annealed films are removed from the vice as a multi-layered bender-element 30 having a desired mechanical bias or curved shape.
  • the continuity of the multimorph bender-element is tested.
  • a simple test is to apply an electrical field and if the multi- layered or multimorph bender-element expands or contracts then the bender-element has the desired electrical continuity.
  • the natural state of the bonded bender-element 30 is that of Fig. 4(b), i.e. having a curvature or mechanical bias such as shown.
  • the bender-element as shown in Fig. 4(a) is in the expanded state and when the polarity is reversed, the bender-element as shown in Fig. 4(c) is in the contracted state.
  • the multi-layered bender-element 30 from an electrical viewpoint acts as a capacitor and resistor in the electrical circuit.
  • a piezoelectric unit cell 40 The configuration of a piezoelectric unit cell 40 is illustrated in Fig. 5.
  • at least two multi-layered bender-elements 30 are placed end-to-end, specifically bender-element 32 and 34, with the ends held together with a compliant hinge 36 and the mechanical bias or curvature of each bender-element is in the opposite direction.
  • the unit cell 40 in which the bender-elements 32 and 34 are in the contracted state is shown in Fig. 5b.
  • a unit cell 40 of the present invention has a greater deflection potential than if only one polarity can be placed on bender-elements 30 of a unit cell 40.
  • Fig. 5(a) illustrates the unit cells 40 with an opposite field polarity across bender-element 32 and bender-element 34.
  • the advantage of having two biased or curved bender-elements is that when subjected to an electrical field the unit cell 40 has much greater deflection than a single bender-element.
  • the unit cell 40 will expand as shown in Fig. 5(a). It can be seen that when the voltage polarity on the unit cell 40 is reversed from that shown in Fig. 5(a), the unit cell 40 in Fig. 5(b) becomes almost flat, thus obtaining the greatest deflection between the two peaks of the sine wave 42.
  • the upper bender-element 32 and the lower bender-element 34 of unit cell 40 are held together with a compliant hinge 36 such as a piece of tape.
  • the hinge 36 may be on the inside of the two bender-elements 32 and 34 as shown in Fig. 5 or may be on the outside of the two bender-elements 32 and 34, such as a piece of tape stuck to the upper surface of the top bender- element 32 and to the lower surface of the bottom bender- element 34 or a hinge of comparable design may be used.
  • the opposite polarity of the strips 2 and 4 of piezoelectric films in the upper bender-element 32 will cause one film to expand while the other film will contract, for example, the uppermost strip of film therein may expand while the lower strip of film in the same bender-element 32 will contract.
  • the opposite polarity of the strips of film in the lower bender-element 34 will cause the lowermost strip of film therein to expand while the upper strip of film in the same bender-element 34 will contract.
  • a single polarity field increases the deflection within a single bender-element 30, rather than requiring two fields in the opposite direction across films to obtain the greatest deflection.
  • only a single field is required for the unit cell 40, since the two bender-elements 32 and 34 are electrically in parallel, to obtain the desired maximum deflection of the unit cell 40.
  • a piezoelectric unit cell 40 is symmetrical having the same number of folds in each of the bender-elements 30 of the top bender-element 32 and the bottom bender-element 34.
  • an asymmetrical unit cell 40 may also be fabricated.
  • the unit cell 40 has an application for any linear motion use.
  • a unit cell 40 the linear electro-motional application of a unit cell 40 is illustrated.
  • a plurality of unit cells 40 may be stacked one on the other to obtain a greater displacement per unit force when the plurality of cells 40 are subjected to an electrical field and deflection of each unit cell 40 occurs.
  • the unit cells 40 are shown stacked on a backing plate 44. This structure of a plurality of unit cells 40 and a backing plate 44 is basic to many alternatives for the remaining structure to which the unit cells 40 are put to use.
  • the backing plate 44 may represent a fixed structure from which the deflection occurs.
  • the stack of unit cells 40 may have a movable member extending across the top of the stack and the backing plate 44 represents such a member, for example a membrane or a piston actuator which will receive the force of the deflection and move with the upper surface of the top unit cell as the field is applied and removed or the polarity of the field is reversed.
  • the deflection will cause a force on the backing plate 44 to move downward and represents the movable structure or the structure against which the force is applied. It is apparent that there are many variations which are readily possible to benefit from the deflection of the stack of unit cells 40 and therefore the force of the plurality of unit cells 40.
  • the pump 50 in its simplest form has a housing (not shown) with a drive block chamber 52 containing side-by-side unit cells 40 and preferably a plurality or stack of unit cells 40. At the top of chamber 52 is a diaphragm 54. The unit cells 40 may be in direct contact with the diaphragm 54 or as shown are in contact with a piston 56. An accumulator chamber 58 is at the top portion of the housing of pump 50. A fluid inlet 60 has an inlet check valve 61 for fluid entering the accumulator chamber 58. At the outlet of accumulator chamber 58 is a fluid outlet 62 having an outlet check valve 63.
  • the unit cells 40 are in their expanded state causing an upward force to be applied to the piston 56 and diaphragm 54 forcing the fluid out of the accumulator chamber 58.
  • the unit cells 40 contract from the position shown and remove the force on the diaphragm 54 permitting fluid to flow into the chamber 58.
  • the piezoelectric pumps of the present invention can have a variety of configurations.
  • a multichambered pump with chambers in series or multichambered pump with chambers in parallel or combinations thereof A multichambered pump 70 is shown in Fig. 8 which operates in the same manner as the single chamber pump except that while fluid enters one chamber the fluid in the other chamber in being forced out.
  • the pump 70 is illustrated as having two chambers and a "push- pull" arrangement of the piezoelectric unit cells which operate on both sides of the drive piston 72.
  • the lower unit cells 40L are driven by the same electronic signal as the top unit cells 40T; however, the polarity of the lower unit cells is opposite that of the upper unit cells.
  • the advantage is that the entire capacitance of the system, including both upper and lower unit cells is incorporated into the electronic drive circuit. This results in a highly accurate timing system.
  • Another advantage is that as the field polarity is reversed, the contracting unit cells are putting work into the system as well as the expanding unit cells .
  • a variety of electric circuits may be used to provide the field to the unit cells 40 (T and L) .
  • a direct drive circuit would provide an on-off field to the unit cells.
  • An alternative to using a direct drive circuit is to employ a parallel resonate drive circuit. The parallel resonate circuit, when driven by a sine wave, allows the phase angle between the drive voltage and current to approach 90 degrees. Power is defined as the product of the voltage and the current.
  • the power required to maintain the oscillation is at a minimum.
  • Application of a parallel resonate circuit reduces the power required to operate the system, and therefore increases system efficiency. This is accomplished using a circuit configuration that takes advantage of the capacitive nature of the unit cells 40 (T and L) .
  • the capacitance of the unit cells is used in conjunction with an inductance to produce a tuned LC parallel resonate circuit where the L refers to a measure of inductance and C refers to a measure of capacitance.
  • the inductance is supplied to the circuit in the form of a step-up transformer.
  • the step- up transformer being required to boost the supply voltage to a range appropriate for driving piezoelectric unit cells.
  • resonant circuits are avoided when building control circuits for piezoelectric films because of the narrow frequency response of the resulting circuit and because most applications of piezoelectric films are as sensors, which generally need to operate over a wide range of frequencies.
  • a resonant circuit is not a problem for mechanical power applications, such as a pump, because the operating frequency of the drive circuit is fixed to optimize the desired mechanical output of the bender-elements. Once the drive frequency is established, the LC circuit can be designed precisely to the mechanical frequency required.
  • a piezoelectric pump 80 with an electrical circuit diagram is illustrated in Fig. 9.
  • the electrical diagram shown utilizes the inherent inductance of a transformer 81 as part of the tuned resonant tank 82.
  • This electrical diagram allows the resonant frequency of the tuned resonant tank 82 to be adjusted using a low voltage capacitor in the drive module 83 across the primary of the transformer 81 rather than having to add inductors or high voltage capacitors across the piezoelectric pump 80.
  • the present invention is more fully set forth and illustrated by the following examples:
  • EXAMPLE I A 1.1 mil thick sheet of polyvinylidene fluoride (Amp Incorporated) coated with silver ink is labeled and cut into two strips. The edges of the strips are masked off with 3M soft stick tape and the border of silver ink is removed with methyl-ethyl ketone (MEK) . The two strips are carefully folded
  • Fig. 2 (eight folds) as shown in Fig. 2, with the polarity-machine orientations of the strips in opposite directions.
  • the two strips are placed into a vice with polycarbonate jaws.
  • the vice is closed applying as much pressure as possible.
  • the vice is placed in an oven and heated at 122°F (50°C) for ten hours to bond the silver ink layers. Without removing the pressure, the vice is removed from the oven and allowed to air cool to room temperature .
  • the bonded and annealed bender-element is removed from the vice.
  • the bender-element is tested for continuity of the multimorph by applying a field on the bender-element and observing the deflection.
  • This example illustrates the method of fabricating the bender-elements of the present invention.
  • This example illustrates the method of fabricating the biased bender-elements of the present invention.
  • a pair of bender-elements fabricated by the method of Example II are placed in juxtaposition to one another such that an applied field will cause the deflection to be in opposite directions.
  • the ends of each biased bender-element is fixed to the corresponding ends with Scotch tape.
  • An applied field causes the deflection of the pair of bender-elements as shown in Fig . 5 .
  • This example illustrates the piezoelectric unit cell of the present invention.
  • the piezoelectric unit cells of the present invention have a wide potential of uses.
  • the configuration of a pump 80 and the circuit diagram as illustrated in Fig. 9 is suited as a liquid cooling ventilation garment (LCVG) pump.
  • LCVG liquid cooling ventilation garment
  • piezoelectric pumps can act as electro-mechanical actuators.
  • the piezoelectric pump may provide solutions to control problems in robotics, bioengineering, advanced remote control and telepresence technologies.
  • the piezoelectric electro-mechanical device of the present invention besides being used in a pump may be used as an actuator, such as any linear short stroke actuator, which may fill the demand for output devices that are more energy efficient, rugged, economical and easier to control than conventional actuators.
  • the present invention also includes a unique circuit for the piezoelectric (piezo) film drive circuit shown in Fig. 10.
  • the key to the circuit system lies in its ability to transfer energy from the charged piezo film, transfer the energy to an inductor and recharge the piezo film with the opposing polarity all at frequencies which provide the desired maximum energy to be applied to the film or more specifically the unit cell(s).
  • the frequency is controlled by the use of a triac and triac driver in the circuit which will be explained in reference to Fig. 10.
  • the piezo film (unit cell or cells) acts as a resistor and capacitor, shown as Rl and Cl in the circuit.
  • a power source illustrated as 450 volts DC, is used to initially charge the film. This is accomplished by the control circuit turning on Ql, or closing the circuit as illustrated, and allowing the piezo film to charge to 450 volts (v) .
  • the charge current, and hence the charge time is controlled by cycling Ql on and off (e.g. 2kHz).
  • the duty cycle is set so as not to exceed the maximum allowable current available from the power source.
  • the inductance of L2 is used to reduce the initial spike in current during each recharge cycle as will be explained in more detail hereinafter.
  • the circuits other components are a triac XI which acts as a gate to a storage inductor, LI and R3; a triac driver Ul operated by an opto-isolator with a pulse signal VI; and a replenish control.
  • the timing pulses required to set the frequency are TTL level signals with a pulse width of 10 ⁇ s or less delivered at twice the desired drive frequency.
  • the narrow pulse width is required so that the triac is allowed to turn off when the current in the inductor reaches zero.
  • the control signal is represented as VI in the schematic and supplies the drive current to the opto-isolator which, in turn, provides the switch on signal for the triac gate.
  • the first pulse occurs after Ql is opened. When the first pulse occurs, the triac XI is turned on and current begins to flow from the piezo film through the triac XI and the main inductor LI.
  • the triac As the current magnitude increases above the minimum hold current for the triac, the triac is latched on and will continue to conduct until the current drops below the minimum hold current (near zero) , at which point triac XI will switch off.
  • the voltage present on the piezo film during this time from the triac being turned on to off has gone from a positive peak (+450v) to a negative peak (near -450v) .
  • the polarity reversal is provided by the inductor.
  • the actual voltage of the negative peak is determined by the amount of energy lost in the inductor and piezo film during the cycle. With the triac XI off, the piezo film will remain in its negatively charged state with only parasitic dielectric losses slowly reducing the voltage present on the piezo film.
  • the piezo film remains in this negatively charged state until a next (second) pulse from VI.
  • the second pulse again turns on triac XI; however, the current flow and voltages will be reversed and the process is reversed.
  • the piezo film is left positively charged (somewhat below +450v) from its previous negatively charged state. Again, the actual positive peak voltage is determined by the amount of energy lost in the inductor and piezo film in the two cycles of the triac XI being on and off.
  • the voltages would continue to decay and the system would come to a halt after a number of cycles.
  • the energy lost during each two pulse cycles must be replenished. This is accomplished by using the control circuit to turn on Ql and using the power source to charge the piezo film to the positive peak (+450v) .
  • the control circuit senses the large positive voltage which occurs at triac XI to turn on Ql .
  • the turn on of Ql replenishs or energizes the circuit to maximum voltage and the turn off of Ql is accomplished before the next (third) pulse from VI.
  • the third pulse initiates the next cycle which is then repeated and repeated.
  • the period of the "hold time” is sufficiently long to allow the piezo film to be charged back to 450v using relatively low charging currents.
  • a slight DC offset will be induced; however, in general it will be a small percentage of the drive voltage and should not effect the operation of the piezo film.
  • This unique circuit has the capability of powering any capacitive device which requires the voltage of the device to alternate polarity (positive to negative) while recovering the charging energy and at controlled frequencies.
  • This use of a triac is different than in applications where it is normally used.
  • the configuration of the pumps illustrated herein above are characterized as diaphram pumps or double action piston pumps
  • the versatility of the piezoelectric unit cells of the present invention are illustrated in piezoelectric peristaltic pumps and centrifugal pumps.
  • the specific pump structure may be modified for specific applications. For example, referring to Fig. 11, double-acting diaphram pump 70 is shown with an inlet pulse dampener 90 and an outlet dampener 91.
  • dampeners are essential to allow the pump 70 to operate between a relatively uniform pressure difference if it is to operate well at resonance.
  • Flow rates and pressures of piezoelelectric pumps are limited only by the size which can be economically made. Small pumps which operate in the 0 - 50 psi and 0 - 5 gpm (gallons per minute) range are normal.
  • a peristaltic pump 95 has three piezoelectic unit cells 96, 96(a) and 96(b).
  • a flexible tubing or bladder 97 carries the fluid being pumped.
  • the tubing 97 is within a larger tubing or chamber having surfaces 98 and 99.
  • a unit cell 96, not electrically activated, and the tubing 97 fit between the surfaces 98 and 99 without compressing the flexible tube 97.
  • the unit cells 96, 96(a) and 96(b) are operated sequentially in an alternating mode of negative (contracted position) and positive (expanded position) .
  • unit cell 96 is in the negative mode whereas unit cells 96(a) and 96(b) are in the positive mode such as shown in Fig. 13.
  • unit cell 96 is switched positive and unit cell 96(a) is switched negative as shown in Fig. 13(a).
  • unit cell 96(a) is switched positive and unit cell 96(b) is switched negative as shown in Fig. 13 (b) .
  • This cycle is repeated to operate the pump 95. It is noted in this pump configuration that the unit cells 96, 96(a) and 96(b) each provide direct force and not indirect force as through a piston.
  • the piezoelectric cell may be used to power a force actuator where the force actuator is illustrated by a rack and pinion.
  • Centrifugal pump 100 has a centrifugal pump head 102 with an outlet 103. The inlet is opposite the drive mechanism of pump 100.
  • the pump 100 has a drive shaft 104 which is attached to the impeller in the pump head 102. Between the outside surface of pump head 102 and the pinion 105 on the drive shaft 104 is a unidirectional clutch (not shown) .
  • a piezoelectric unit cell 106 is affixed to a surface 108. On top of the unit cell 106 is a rack 110.
  • the expansion of the unit cell 106 moves the rack 110 upwards rotating the pinion 106 counterclockwise and rotates the drive shaft 104.
  • rack 110 moves downward and pinion 105 rotates clockwise but drive shaft 104 does not rotate since the clutch is not engaged.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)
  • Reciprocating Pumps (AREA)
EP98937730A 1998-06-08 1998-06-08 Piezoelektrische elektrobewegliche bauelemente Withdrawn EP1097484A4 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IB1998/001321 WO1999065088A1 (en) 1998-06-08 1998-06-08 Piezoelectric electro-motional devices

Publications (2)

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EP1097484A1 true EP1097484A1 (de) 2001-05-09
EP1097484A4 EP1097484A4 (de) 2004-12-01

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JP (1) JP2002518620A (de)
AU (1) AU8642998A (de)
WO (1) WO1999065088A1 (de)

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CN106762566A (zh) * 2016-12-28 2017-05-31 南京航空航天大学 半柔性阀压电泵及其工作方法

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GB2376724B (en) * 2001-06-20 2004-10-27 1 Ltd Pumps using an electro-active device
EP1992024A2 (de) * 2006-02-16 2008-11-19 nanoswys SA Kraftumsetzer
US7632041B2 (en) 2007-04-25 2009-12-15 Single Buoy Moorings, Inc. Wave power generator systems
CN102661269B (zh) * 2012-06-01 2015-06-10 浙江师范大学 基于多振子串联驱动的柱塞式压电泵
AU2014308618B2 (en) * 2013-08-23 2017-06-22 Apple Inc. Remote control device
DE102016121587B4 (de) * 2016-11-10 2023-06-01 Pi Ceramic Gmbh Piezoelektrischer Antrieb, insbesondere für den Einsatz in feuchter Umgebung
CN109578287B (zh) * 2019-01-25 2020-08-07 卡川尔流体科技(上海)有限公司 一种输送泵
CN114320845B (zh) * 2021-12-08 2024-05-28 吉林大学 一种集驱动传感于一体的压电精密输液泵

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DD140946A1 (de) * 1978-12-21 1980-04-02 Manfred Rauch Anordnung zur feinpositionierung
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DD287813A5 (de) * 1989-09-05 1991-03-07 Technische Universitaet Karl-Marx-Stadt,De Vorrichtung aus piezoelektrischen biegescheiben fuer einen translatorischen antrieb
DE19644161A1 (de) * 1995-11-07 1997-05-15 Daimler Benz Aerospace Ag Piezoelektrischer Aktuator

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US3963380A (en) * 1975-01-06 1976-06-15 Thomas Jr Lyell J Micro pump powered by piezoelectric disk benders
DE2848812A1 (de) * 1978-11-10 1980-05-22 Daimler Benz Ag Stellglied aus piezoelektrischen elementen
DD140946A1 (de) * 1978-12-21 1980-04-02 Manfred Rauch Anordnung zur feinpositionierung
US4731076A (en) * 1986-12-22 1988-03-15 Baylor College Of Medicine Piezoelectric fluid pumping system for use in the human body
DD287813A5 (de) * 1989-09-05 1991-03-07 Technische Universitaet Karl-Marx-Stadt,De Vorrichtung aus piezoelektrischen biegescheiben fuer einen translatorischen antrieb
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CN106762566B (zh) * 2016-12-28 2018-12-07 南京航空航天大学 半柔性阀压电泵及其工作方法

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EP1097484A4 (de) 2004-12-01
AU8642998A (en) 1999-12-30
JP2002518620A (ja) 2002-06-25

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