EP0056549B1 - Elektromechanische Wandleranordnung - Google Patents

Elektromechanische Wandleranordnung Download PDF

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Publication number
EP0056549B1
EP0056549B1 EP19810402050 EP81402050A EP0056549B1 EP 0056549 B1 EP0056549 B1 EP 0056549B1 EP 19810402050 EP19810402050 EP 19810402050 EP 81402050 A EP81402050 A EP 81402050A EP 0056549 B1 EP0056549 B1 EP 0056549B1
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EP
European Patent Office
Prior art keywords
piezoelectric
faces
structure according
polymer
film
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.)
Expired
Application number
EP19810402050
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English (en)
French (fr)
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EP0056549A3 (en
EP0056549A2 (de
Inventor
François Micheron
Jean-Claude Dubois
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.)
Thales SA
Original Assignee
Thomson CSF SA
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Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0056549A2 publication Critical patent/EP0056549A2/de
Publication of EP0056549A3 publication Critical patent/EP0056549A3/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/005—Piezoelectric transducers; Electrostrictive transducers using a piezoelectric polymer

Definitions

  • the invention relates to transducer devices using polymer films capable of exhibiting piezoelectricity phenomena by application of a polarization field.
  • the invention is particularly applicable to structures composed of piezoelectric polymer films associated with other polymer films, in particular to a structure comprising at least one layer of polar polymer associated with another layer of polymer, such as with equal thickness. , the mechanical response to an electrical control voltage is increased compared to that which a homogeneous film of the same polar polymer would produce.
  • Certain films of polar polymers such as polyvinyl chloride (PVC), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVF 2 ) and certain polymers such as PVF 2 - PTFE (polyvinylidene fluoride - polyethylene tetrafluoride) ), are known to have piezoelectric properties, and find their applications in electroacoustic transducers and sensors for example.
  • PVC polyvinyl chloride
  • PVF polyvinyl fluoride
  • PVF 2 - PTFE polyvinylidene fluoride - polyethylene tetrafluoride
  • the piezoelectric properties of these films are described by a tensorial relationship between the P components; of the polarization and the components X jk of the mechanical stresses.
  • a tensor called the tensor of the piezoelectric coefficients D ijk .
  • a piezoelectric polymer has piezoelectric coefficients that are higher as the value of the remanent polarization is high, and as its mechanical flexibility, in a direction considered, is higher .
  • K is equal to the ratio of the mechanical energy transformed by the piezoelectric effect, to the stored electrical energy.
  • the advantage of the invention compared to the devices existing in the prior art lies in the maximum energy coupling. electric, low voltage, to get the maximum mechanical energy.
  • a monolithic device has a certain stiffness which, during an electrical excitation, counteracts the mechanical deformations and therefore limits, by this fact, the piezoelectric effects perceived externally.
  • the results can be improved by increasing the value of the electrical energy given to the device.
  • this effect can be achieved by reducing the thickness of the piezoelectric film, but in this case, the mechanical resistance of the device is no longer satisfactory.
  • a device according to the invention makes it possible to maintain good mechanical strength, since the total thickness of the materials is unchanged, to significantly increase the piezoelectric effects by reducing the influence of the stiffness inherent in the piezoelectric layers used and to deliver more electrical energy to the active layers of the device.
  • the present patent application relates to a structure comprising at least one piezoelectric film in which the relative elongation per applied volt, as well as the mechanical energy supplied by applied volt, are greater than those of the homogeneous polar polymer of the same thickness.
  • the subject of the invention is an electromechanical transducer structure composed of a passive lift element surrounded by two active polymer films made of piezoelectric material having internal faces which adhere to the load-bearing faces of said lift element and external faces coated with 'electrodes; an equipotential electrical connection being established between said load-bearing faces, characterized in that said load-bearing faces are the faces of a film of polymer material ensuring, by own electrical conductivity, said equipotential electrical connection; said polymer material offering a mechanical rigidity lower than that of said piezoelectric material.
  • a device according to the prior art is shown in the left part of the figure, that according to the invention was shown in the right part.
  • a device as it exists in the prior art, consists of a monolithic film of piezoelectric material, for example a polymer, as shown in FIG. 1a.
  • a separation line 14 which limits two layers (10 and 11) in the film.
  • a device which will be described more precisely in the following description, comprises a lifting film 1 of flexible non-piezoelectric material, sandwiched between two films of piezoelectric materials 3 and 3 ', as indicated in FIG. 1b. Films 3 and 3 'are mechanically integral with film 1.
  • the piezoelectric layers work in bending, as shown in FIG. 1c by a device of the prior art and in FIG. 1d by a device according to the invention, it is seen that the overall thickness differences of the films, as well as the stiffness differences at the level of the separation of the different layers, make it possible to obtain a greater driving torque in the device according to the invention assuming that the excitation voltage is exclusively applied to layers 3 and 3 '.
  • FIG. 2 represents an embodiment of a device according to the invention.
  • layers 3 and 3 ′ of piezoelectric polymer for example polyvinylene fluoride PVF 2 .
  • Each of these layers is covered with an electrode 4 and 4 ', connected respectively by connections 5 and 5', to an electric generator delivering a voltage V.
  • the electric energy delivered by this electric generator is only supplied to the layers active 3 and 3 '.
  • the transformed mechanical energy is greater than in a piezoelectric polymer device of the same thickness, since the capacity of the piezoelectric layers is higher, due to the reduction in thickness.
  • a symmetrical structure is adopted which provides the assembly with a stable shape during the effects of thermal expansion.
  • layer 6 is made of a conductive polymer.
  • Such conductive polymers are generally prepared from an elastomer, in which particles of carbon, or of metals: copper, silver copper, etc. are included.
  • the remanent polarizations of the piezoelectric layers 3 and 3 ′ are oriented in the same direction to obtain the most intense traction and compression effects; taking into account that the electric control fields have the same direction. However, by reversing one of the polarizations one can obtain an operation in bending.
  • FIG. 3 is a variant of FIG. 2.
  • the conductive polymer therefore acts as an electrode for the piezoelectric layers 3 and 3 '.
  • the remanent polarizations of the layers 3 and 3 ′ must be in the opposite direction, for traction-compression effects.
  • FIG. 4 represents the evolution of the characteristics of a device according to the invention. For flexion operation, it suffices to change the direction of a polarization.
  • the gain in relative elongation of a composite film compared to a homogeneous film is represented by the ordinate G of the curve of FIG. 4.
  • the magnitude on the abscissa ⁇ represents the ratio of the sum of the thicknesses of the piezoelectric films 3 and 3 ', to the total thickness of the stratified structure.
  • the coefficient ⁇ 7 represents the flexibility ratio of the active piezoelectric material composing the layers 3 to 3 ′, to the flexibility of elastic material, composing the layer 1 or 6.
  • Figure 4 shows the variation of the gain as a function of the thickness ratio ⁇ , according to certain values of the coefficient ⁇ .
  • ⁇ 1
  • the gain G is minimal whatever the value of the quantity tP
  • An example of a device according to the invention can be produced in the following manner, without limiting.
  • the piezoelectric layers are polyvinylidene fluoride PYF 2 deposited on the intermediate polymer by dipping.
  • PVF 2 is dissolved in dymethyl formamide DMF in an amount of 100 to 200 g / 1.
  • the intermediate polymer film is coated by passage through a tank of PVF 2 + DMF solution.
  • the solvent is evaporated at the temperature of 70 to 80 ° C by jets of hot air, or radiation of electrical resistances.
  • the low temperature favors the appearance of the non-oriented y phase.
  • the film can then be stretched, by a factor of 2 to 3 at 90 - 100 ° C: the phase there is therefore transformed into oriented ⁇ phase; if the composite film is not stretched, its mechanical and piezoelectric properties will be isotropic in its plane.
  • the composite film is then metallized on its two faces, using for example the deposition of aluminum under vacuum. It is then polarized between these latter electrodes, by applying an electric field of 0.5 to 1 MV / cm in the PVF 2 layers, at 80 ° C. for a few minutes: the polarization configuration essentially depends on the results that the 'we wish to obtain.
  • the voltage generator of Figures 2 and 3 is then replaced by a bias voltage generator.
  • the thicknesses of the achievable piezoelectric layers are greater than or equal to 1 ⁇ m. In the case described, using a conductive intermediate polymer, the same polymers can be used, loaded with carbon or metal particles.
  • the flexible material has been specially described as a polymer having a low stiffness. It is also possible, without departing from the scope of the invention, to use other extensible materials.
  • the invention relates to all the applications of piezoelectric films and transducers, in particular electroacoustic ones such as loudspeakers, headphones, various transmitters.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Claims (7)

1. Elektromechanische Wandlerstruktur, die zusammengesetzt ist aus einem passiven Stützelement (6), welches von zwei aktiven Polymerfilmen (3, 3') aus piezoelektrischem Material eingerahmt ist, deren Innenflächen an den Trägerflächen des genannten Stützelementes anhaften und deren Außenflächen von Elektroden (4, 4') bedeckt sind; wobei eine elektrische Äquipotentialverbindung zwischen den genannten Trägerflächen hergestellt ist, dadurch gekennzeichnet, daß die genannten Trägerflächen die Flächen eines Films (6) aus einem Polymermaterial sind, welches durch elektrische Eigenleitfähigkeit die elektrische Äquipotentialverbindung gewährleistet; wobei dieses Polymermaterial eine mechanische Steifigkeit bietet, die geringer als die des piezoelektrischen Materials ist.
2. Struktur nach Anspruch 1, dadurch gekennzeichnet, daß die genannten Elektroden (4, 4') durch Metallisierungen gebildet sind, welche ausschließlich auf den genannten Außenflächen liegen.
3. Struktur nach Anspruch 2, dadurch gekennzeichnet, daß die genannten Metallisierungen elektrisch miteinander verbunden sind; wobei der Film (6) eine gemeinsame Gegenelektrode der genannten aktiven Polymerfilme (3,3') bildet.
4. Struktur nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Polymermaterial ein Polymer mit einem Zuschlag aus Kohlenstoff- oder Metallteilchen ist.
5. Struktur nach Anspruch 1, dadurch gekennzeichnet, daß die remanenten Polarisationen der genannten aktiven Polymerfilme dieselbe Richtung und denselben Sinn haben.
6. Struktur nach Anspruch 1, dadurch gekennzeichnet, daß die remanenten Polarisationen der genannten aktiven Polymerfilme dieselbe Richtung und entgegengesetzten Sinn haben.
7. Struktur nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß das genannte piezoelektrische Polymermaterial Polyvinylidenfluorid ist.
EP19810402050 1981-01-16 1981-12-22 Elektromechanische Wandleranordnung Expired EP0056549B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8100780A FR2498406A1 (fr) 1981-01-16 1981-01-16 Structure de transducteur electromecanique
FR8100780 1981-01-16

Publications (3)

Publication Number Publication Date
EP0056549A2 EP0056549A2 (de) 1982-07-28
EP0056549A3 EP0056549A3 (en) 1982-08-04
EP0056549B1 true EP0056549B1 (de) 1985-03-27

Family

ID=9254236

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810402050 Expired EP0056549B1 (de) 1981-01-16 1981-12-22 Elektromechanische Wandleranordnung

Country Status (4)

Country Link
EP (1) EP0056549B1 (de)
JP (1) JPS57138300A (de)
DE (1) DE3169622D1 (de)
FR (1) FR2498406A1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3267853D1 (en) * 1981-02-06 1986-01-23 Emi Ltd Device sensitive to pressure waves
FR2519503B1 (fr) * 1981-12-31 1991-09-06 Thomson Csf Transducteurs piezoelectriques polymeres et procede de fabrication
US5166573A (en) * 1989-09-26 1992-11-24 Atochem North America, Inc. Ultrasonic contact transducer and array

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3816774A (en) * 1972-01-28 1974-06-11 Victor Company Of Japan Curved piezoelectric elements
GB1515287A (en) * 1974-05-30 1978-06-21 Plessey Co Ltd Piezoelectric transducers
GB1593271A (en) * 1976-09-21 1981-07-15 Standard Telephones Cables Ltd Electro-acoustic transducers
DE2803168C3 (de) * 1978-01-25 1982-10-21 Friedemann Dipl.-Ing. Dr. 8069 Jetzendorf Meggl Elektromechanischer Wandler

Also Published As

Publication number Publication date
EP0056549A3 (en) 1982-08-04
FR2498406A1 (fr) 1982-07-23
DE3169622D1 (en) 1985-05-02
JPS57138300A (en) 1982-08-26
EP0056549A2 (de) 1982-07-28

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