JP4847180B2 - Piezoelectric actuator driving method and piezoelectric actuator unit - Google Patents

Description

  The present invention relates to a novel driving method of a piezoelectric actuator and a piezoelectric actuator unit for carrying out the driving method.

  A piezoelectric actuator using the electrostrictive characteristics of a piezoelectric ceramic is used as a drive source for an inkjet printer head or the like. As a piezoelectric actuator, a plate-like actuator including a transverse vibration mode piezoelectric ceramic layer that expands and contracts in a plane direction orthogonal to the thickness direction when a voltage is applied in the thickness direction is known.

  Further, as a plate-like piezoelectric actuator incorporated in the head of the ink jet printer, the piezoelectric ceramic layer in the transverse vibration mode and one side of the piezoelectric ceramic layer are laminated, and the piezoelectric ceramic layer is disposed within the surface of the head. A plurality of individual electrodes partitioned into a plurality of active regions corresponding to a plurality of nozzles, a common electrode laminated on the opposite side of the piezoelectric ceramic layer and having a size including the plurality of active regions, and a piezoelectric ceramic It is known that the piezoelectric ceramic layer is laminated on any surface side of the layer and includes a diaphragm for regulating expansion and contraction in the surface direction.

  The piezoelectric actuator having the above structure is used in a state where the piezoelectric ceramic layer is polarized in the thickness direction, and from the individual electrode corresponding to an arbitrary active region of the piezoelectric ceramic layer and the common electrode, When a voltage in the same direction (referred to as “forward direction”) is applied, the active region contracts in the surface direction. However, as described above, since the diaphragm is fixed on one side of the piezoelectric ceramic layer and expansion and contraction in the surface direction is restricted, the piezoelectric deformation region corresponding to the active region of the piezoelectric actuator is Bends and deforms so that the surface on which the diaphragm is laminated projects in the thickness direction.

  On the other hand, when a voltage in the direction opposite to the polarization direction is applied to an arbitrary active region of the piezoelectric ceramic layer from the corresponding individual electrode and the common electrode, the active region extends in the plane direction. On the contrary, the piezoelectric deformation region corresponding to the active region bends and deforms so that the surface opposite to the surface on which the diaphragms are stacked protrudes in the thickness direction. Further, when the application of voltage is stopped, the expansion and contraction in the surface direction of the active region of the piezoelectric ceramic layer is released, so that the piezoelectric deformation region of the piezoelectric actuator corresponding to the active region has been released from the bending deformation, The original flat state is restored.

  For example, in an inkjet printer head, a drive voltage waveform in which a forward voltage is applied and stopped in the active region of the piezoelectric ceramic layer, a drive voltage waveform in which a forward voltage and a reverse voltage are applied alternately, etc. The active region is expanded and contracted in the surface direction, the piezoelectric deformation region of the piezoelectric actuator is vibrated in the thickness direction, and the ink is vibrated. It is ejected as a drop. The ink droplets ejected from the nozzles fly to the paper surface arranged facing the nozzles, reach the paper surface, and form dots on the paper surface.

  However, in the conventional piezoelectric actuator, the displacement amount of the bending deformation in the thickness direction of the piezoelectric deformation region greatly decreases with time by repeating the operation of driving (vibrating) the piezoelectric deformation region by applying a voltage. Accordingly, in the case of an ink jet printer, the volume of ink droplets ejected from the nozzles and the flying speed are lowered, and there is a problem that the image quality of an image formed on the paper surface is lowered.

  A possible cause of the problem is that electric charges are accumulated in the active region of the piezoelectric ceramic layer corresponding to the piezoelectric deformation region when the driving of the piezoelectric deformation region is repeated. That is, the voltage having the above-described driving voltage waveform applied to the active region is usually a high-speed pulse signal having a pulse width on the order of several tens of μsec. In normal driving, by applying a forward voltage, The electric charge charged in the active region is discharged by stopping the voltage application or applying the reverse voltage, but the next forward direction is performed while the discharge is not completed. Therefore, the electric charge is gradually accumulated in the active region by repeating the driving.

The accumulated charge acts as a reverse bias with respect to the polarization direction of the piezoelectric ceramic layer. As the charge is accumulated, the amount of polarization in the active region decreases. As a result, the piezoelectric actuator corresponding to the active region The displacement amount of the bending deformation in the thickness direction in the piezoelectric deformation region greatly decreases with time. Moreover, as described in Patent Document 1, for example, the tendency becomes more prominent as the pulse width of the drive voltage waveform is shortened in order to improve the printing speed of the ink jet printer.
JP 2004-136666 A

  An object of the present invention is to prevent the displacement amount of the bending deformation in the thickness direction of the piezoelectric deformation region of the piezoelectric actuator from greatly decreasing over time, and maintain a sufficient displacement amount over a long period of time. Another object of the present invention is to provide a piezoelectric actuator driving method that can be used, and a piezoelectric actuator unit for carrying out the driving method.

The present invention includes a plate-like piezoelectric ceramic layer, wherein are laminated on one side of the piezoelectric ceramic layer, the piezoelectric ceramic layer, in its plane, and a plurality of individual electrodes defining a plurality of active regions, the is laminated on the opposite side of the piezoelectric ceramic layer, a piezoelectric actuator and a common electrode having a size including a plurality of active regions, the piezoelectric deformation region corresponding to the active region, between the two electrodes by applying a voltage, a driving method for driving individually, the plurality of individual electrodes, as well as connected so that the ground at the same potential of any of the individual electrodes to the selected択的, other and connected such that the individual electrodes to the common electrode at the same potential, the common electrode by applying a voltage, the piezoelectric deformation region corresponding to the individual electrodes connected to the ground, the individual electrodes and the front The potential difference between the common electrode, a driving method of a piezoelectric actuator for causing selectively driven.

Further, the present invention includes a plate-like piezoelectric ceramic layer, wherein are laminated on one side of the piezoelectric ceramic layer, the piezoelectric ceramic layer, in its plane, and a plurality of individual electrodes defining a plurality of active regions the is laminated on the opposite side of the piezoelectric ceramic layer, a piezoelectric actuator and a common electrode having a size including a plurality of active regions, the piezoelectric actuator, the plurality of individual electrodes, optionally with connecting the individual electrodes so as to ground the same potential to the selected択的, connect the other individual electrodes so that the common electrode at the same potential, by applying a voltage to the common electrode , the piezoelectric deformation region corresponding to the individual electrodes connected to the ground, by the potential difference between the individual electrode and the common electrode, further comprising a driving circuit for selectively driving the A piezoelectric actuator unit according to symptoms.

In a conventional piezoelectric actuator, a voltage having a predetermined drive voltage waveform is selectively applied to an arbitrary active region on the piezoelectric ceramic layer, and a piezoelectric deformation region of the piezoelectric actuator corresponding to the active region is obtained. In order to selectively bend and deform, the common electrode is connected to have the same potential as the ground, and the voltage is individually applied to a plurality of individual electrodes. However, in order to meet the recent demand for higher image quality of inkjet printers, the number of nozzles provided on one head is increased and the formation interval of the individual electrodes is miniaturized. Since the area tends to be reduced, the charge in the active region cannot be quickly discharged in a short time.

On the other hand, according to the present invention, contrary to the conventional case, the individual electrodes corresponding to the piezoelectric deformation region to be driven are selectively connected to have the same potential as the ground and include a plurality of active regions. By applying a voltage having a predetermined drive voltage waveform to a large common electrode having a size, the piezoelectric deformation region is selectively driven by a potential difference between the two electrodes. The charge applied to the active region by the application is stopped until the next forward voltage is applied, or more quickly in the state where the reverse voltage is applied. It is possible to prevent the charge from being accumulated in the active region.

  Therefore, according to the present invention, the displacement amount of the bending deformation in the thickness direction of the piezoelectric deformation region of the piezoelectric actuator is prevented from greatly decreasing with time, and a sufficient displacement amount can be obtained over a long period of time. Can be maintained. In the present invention, the individual electrodes that are not connected to the ground are connected to the common electrode, so that it is possible to reliably prevent malfunction of the piezoelectric deformation region corresponding to the individual electrodes.

  According to the present invention, the displacement amount of the bending deformation in the thickness direction of the piezoelectric deformation region of the piezoelectric actuator is prevented from greatly decreasing with time, and the sufficient displacement amount is maintained over a long period of time. It is possible to provide a piezoelectric actuator driving method that can be used, and a piezoelectric actuator unit for carrying out the driving method.

  FIG. 1 is a cross-sectional view showing an example in which an example of a piezoelectric actuator unit 1 according to the present invention is incorporated as a drive source in a head of an ink jet printer. Referring to FIG. 1, the head of this example is formed by arranging a plurality of pressure chambers 2 filled with ink in the surface direction on the upper surface in the drawing and corresponding to each pressure chamber 2 on the lower surface. A plurality of nozzles 3 for ejecting ink droplets are formed, and each pressure chamber 2 and nozzle 3 are individually connected by a communication passage 4 filled with ink. 5 and a piezoelectric actuator 6 constituting the piezoelectric actuator unit 1 laminated on the upper surface of the substrate 5 where the pressure chamber 2 is formed.

  The piezoelectric actuator 6 is formed individually for each pressure chamber 2 on the upper surface of the piezoelectric ceramic layer 7 in the figure of the piezoelectric ceramic layer 7 formed in a thin plate shape having a size covering the plurality of pressure chambers 2. A so-called unimorph type structure comprising a common electrode 9 and a diaphragm 10 that are stacked in order on the lower surface of the individual electrode 8 and the piezoelectric ceramic layer 7, and have a size that covers the plurality of pressure chambers 2. Have.

  The unimorph-type piezoelectric actuator 6 is disposed so as to surround a plurality of piezoelectric deformation regions 11 corresponding to the individual pressure chambers 2, the piezoelectric deformation regions 11, and is fixed to the substrate 5. It is partitioned into a restrained area 12 where deformation is prevented. The individual electrodes 8 and the common electrode 9 are individually connected to a drive circuit 13 that constitutes the piezoelectric actuator unit 1, and the drive circuit 13 is connected to a control unit 14 of the ink jet printer. .

  Among the above portions, the substrate 5 is formed, for example, by laminating and integrating a plurality of plate materials in which the pressure chambers 2, the communication passages 4, and the through holes to be the nozzles 3 are formed in order. can do. Each plate material is formed in a flat plate shape having a constant thickness by metal, ceramic, resin, etc., and has a predetermined planar shape that becomes each of the above parts by etching using a photolithographic method, for example. What the through-hole which has is formed in the predetermined position can be used. When the plate material is formed of a metal, examples of the metal include Fe-Cr alloys, Fe-Ni alloys, WC-TiC alloys, and the like. In particular, considering the corrosion resistance to ink and workability, Fe -Cr-based alloy is preferable.

  The piezoelectric ceramic layer 7 is, for example, lead zirconate titanate (PZT), PLZT, or the like obtained by adding one or more oxides of lanthanum, barium, niobium, zinc, nickel, manganese, etc. to the PZT. The PZT piezoelectric ceramic can be formed into a thin plate shape. The piezoelectric ceramic layer 7 is mainly composed of lead magnesium niobate (PMN), lead nickel niobate (PNN), lead zinc niobate, lead manganese niobate, lead antimony stannate, lead titanate, barium titanate, and the like. It can also be formed of a piezoelectric ceramic. Furthermore, it can also be formed of a so-called non-lead material such as a bismuth layered compound, a tungsten bronze structure, a perovskite type compound such as alkali niobate or barium titanate.

  The diaphragm 10 can be formed in a plate shape having a predetermined thickness by using, for example, a metal such as molybdenum, tungsten, tantalum, titanium, platinum, iron, or nickel, an alloy of the metal, stainless steel, or the like. Alternatively, the piezoelectric ceramic layer 7 can be formed of the same piezoelectric ceramic. Alternatively, the diaphragm 10 may be formed of a metal having excellent conductivity such as gold, silver, platinum, copper, or aluminum, and the common electrode 9 may be omitted.

  The individual electrode 8 and the common electrode 9 can be formed by a foil, a plating film, a vacuum deposition film, or the like made of a metal having excellent conductivity, such as gold, silver, platinum, copper, and aluminum. The conductive paste containing fine particles of each metal can be applied and dried, and then fired as necessary.

  In order to form the pattern of the individual electrode 8, for example, in the case of a plating film or a vacuum deposition film, only the area where the individual electrode 8 is formed on the surface of the piezoelectric ceramic layer 7 is selectively exposed, and the other area. Are coated with a plating mask, and a film is selectively formed on the exposed region, or after the film is formed on the entire surface of the piezoelectric ceramic layer 7, the individual electrodes of the film are formed. For example, a method may be used in which only the region corresponding to 8 is covered with an etching mask and the film in the exposed region is selectively etched and removed while the other regions are exposed. In the case of a coating film made of a conductive paste, the conductive paste may be patterned directly on the surface of the piezoelectric ceramic layer 7 by a printing method such as a screen printing method.

  The piezoelectric ceramic layer 7 and the diaphragm 10 made of piezoelectric ceramic can be formed by firing and then firing the green sheet containing the compound that becomes the piezoelectric ceramic described above into a predetermined planar shape. In particular, when the piezoelectric ceramic layer 7 and the diaphragm 10 are both formed of piezoelectric ceramic, a layer of conductive paste that becomes the common electrode 9 by firing between the green sheets that form the respective layers. A laminated body in which the piezoelectric ceramic layer 7, the common electrode 9, and the diaphragm 10 are laminated can be obtained by producing a laminated body sandwiching the layers and firing the laminated body at one time.

  The piezoelectric actuator 6 is formed by patterning the individual electrodes 8 on the surface of the piezoelectric ceramic layer 7 of the laminate by the method described above. Then, the piezoelectric actuator 6 is fixed on the surface of the substrate 5 on the side where the pressure chamber 2 is formed by adhering using an adhesive or the like, thereby forming the head of the ink jet printer. As the adhesive, in consideration of heat resistance required for the head, resistance to ink, etc., thermosetting such as epoxy resin type, phenol resin type, polyphenylene ether resin type having a thermosetting temperature of 100 to 250 ° C. A resin-based adhesive is preferable.

  In order to set the thin plate-like piezoelectric ceramic layer 7 to the transverse vibration mode, the polarization direction of the piezoelectric ceramic is oriented in the thickness direction of the piezoelectric ceramic layer 7, for example, the direction from the individual electrode 8 to the common electrode 9. For this purpose, for example, a polarization method such as a high temperature polarization method, a room temperature polarization method, an AC electric field superposition method, or an electric field cooling method is employed.

  FIG. 2 is a circuit diagram showing a portion corresponding to one piezoelectric deformation region 11 of the piezoelectric actuator 6 in the drive circuit 13 constituting the piezoelectric actuator unit 1 of FIG. Referring to FIG. 2, the drive circuit 13 includes a single power source 16 and a first circuit connected to the ground 17 from one output terminal of the power source 16 as a portion common to all the piezoelectric deformation regions 11. 18 and one second circuit 19 connected to the common electrode 9 from the other output terminal of the power supply 16.

  The drive circuit 13 branches from the middle of the first circuit 18 and branches from the middle of the third circuit 21 connected to the individual electrode 8 via the switching element 20 and the second circuit 19. The fourth circuit 22 connected to the switching element 20 is provided for each piezoelectric deformation region 11 by the number of piezoelectric deformation regions 11. The switching element 20 determines whether the individual electrode 8 corresponding to each piezoelectric deformation region 11 is connected to the first circuit 18 via the third circuit 21 or to the second circuit 19 via the fourth circuit 22. The switching is performed individually for each piezoelectric deformation region 11 based on a control signal input from the control unit 14 of the inkjet printer to the drive circuit 13.

That is, in the piezoelectric deformation region 11 corresponding to the nozzle 3 that ejects ink droplets, the switching element 20 is switched in a direction in which the individual electrode 8 is connected to the first circuit 18 via the third circuit 21. Therefore, the individual electrode 8 is connected so as to have the same potential as the ground 17 through the third circuit 21 and the first circuit 18. Further, in the piezoelectric deformation region 11 corresponding to the nozzle 3 that does not eject ink droplets, the switching element 20 is switched to a direction in which the individual electrode 8 is connected to the second circuit 19 via the fourth circuit 22. Therefore, the individual electrode 8 is connected so as to have the same potential as the common electrode 9 via the fourth circuit 22 and the second circuit 19.

In this state, when the voltage having the driving voltage waveform described above is applied from the power supply 16, the voltage is common in the piezoelectric deformation region 11 connected so that the individual electrode 8 has the same potential as the ground 17. By being applied to the electrode 9, a potential difference is generated between the electrodes 8 and 9. When the voltage application direction based on the potential difference is a forward direction, that is, a voltage in the same direction as the polarization direction of the piezoelectric ceramic layer 7, the active region 15 contracts in the plane direction of the layer. However, since the lower surface of the piezoelectric ceramic layer 7 is fixed to the vibration plate 10 via the common electrode 9, when the active region 15 contracts, the piezoelectric deformation region 11 is laminated with the vibration plate 10 accordingly. The surface is bent and deformed so as to protrude in the direction of the pressure chamber 2.

  In addition, when the voltage application direction is opposite to the polarization direction, the active region 15 conversely extends in the plane direction of the layer, so that the piezoelectric deformation region 11 has a surface on which the diaphragm 10 is laminated. The opposite surface is bent and deformed so as to protrude in a direction opposite to the direction of the pressure chamber 2. Furthermore, in the state where the application of voltage is stopped, the expansion and contraction in the surface direction of the active region 15 is released, so that the piezoelectric deformation region 11 returns to the original flat plate state where the bending deformation is released. .

  Therefore, a voltage having a drive voltage waveform that repeats application and stop of forward voltage and a drive voltage waveform that alternately applies forward and reverse voltages is applied to the common electrode 9 from the power source 16. When the piezoelectric deformation region 11 of the piezoelectric actuator 6 is vibrated in the thickness direction of the piezoelectric actuator 6, the volume of the corresponding pressure chamber 2 is increased or decreased by the vibration, and the ink in the pressure chamber 2 vibrates. Then, the vibration is transmitted to the nozzle 3 through the ink in the communication path 4, and the meniscus of the ink formed in the nozzle 3 vibrates, and a part of the ink forming the meniscus is caused by this vibration. The ink droplets are separated and discharged from the nozzle 3.

On the other hand, in the piezoelectric deformation region 11 in which the individual electrode 8 is connected so as to have the same potential as the common electrode 9, even if a voltage is applied from the power source 16 to the common electrode 9, a potential difference is present between the electrodes 8 and 9. Therefore, the piezoelectric deformation region 11 of the piezoelectric actuator 6 remains stationary, and no ink droplet is ejected from the nozzle 3. Therefore, as in the prior art, an arbitrary piezoelectric deformation region 11 of the piezoelectric actuator 6 is driven, and ink droplets are ejected from the nozzle corresponding to the piezoelectric deformation region 11, so that the sheet is disposed on the paper surface facing the nozzle. Any image can be formed.

  In addition, since the voltage for driving the piezoelectric deformation region 11 is applied to the active region 15 through the large common electrode 9 having a size including the plurality of active regions 15, by applying a forward voltage, The charge applied to the active region 15 is stopped more quickly until the next forward voltage is applied, or more quickly when the reverse voltage is applied. It can be discharged, and the accumulation of electric charges in the active region 15 can be suppressed.

  Therefore, it is possible to prevent the displacement amount of the bending deformation in the thickness direction of the piezoelectric deformation region 11 of the piezoelectric actuator 6 from greatly decreasing over time, and to maintain a sufficient displacement amount over a long period of time. It becomes possible. Further, the individual electrode 8 not connected to the ground 17 is connected to the common electrode 9 via the switching element 20, and when a voltage is applied to the common electrode 9, a potential difference occurs between the individual electrode 8 and the individual electrode 8. Therefore, it is possible to reliably prevent the piezoelectric deformation region 11 corresponding to the individual electrode 8 from malfunctioning.

<Preparation of head>
PZT powder (purity 99.9% or more) as a piezoelectric ceramic material is milled using zirconia balls having a diameter of 2 mm, adjusted to an average particle size of 0.3 to 0.5 μm, and dried. Thereafter, a raw material powder was obtained through a mesh pass, and the raw material powder was molded to produce two green sheets serving as the basis of the piezoelectric ceramic layer 7 and the diaphragm 10.

  Next, referring to FIG. 1, a conductive paste that is the basis of the common electrode 9 is printed on the surface of one green sheet so as to have a thickness of 4 μm, and another green sheet is formed thereon. Were laminated, pressed and fired to obtain a laminated body of the piezoelectric ceramic layer 7, the common electrode 9, and the diaphragm 10. And after printing Au paste in the shape corresponding to the planar shape of the individual electrode 8 by the screen-printing method on the surface of the piezoelectric ceramic layer 7 among the said laminated body, the whole is 800-900 in air | atmosphere. The piezoelectric actuator 6 was obtained by baking at 0 ° C. to form the individual electrodes 8.

  Next, the piezoelectric actuator 6 was laminated on the substrate 5 with an epoxy adhesive layer in an aligned state so that the individual electrode 8 was disposed at a position corresponding to the pressure chamber 2. Thereafter, a heat treatment at 150 ° C. for 4 hours was performed to cure the epoxy adhesive, thereby producing a head for an ink jet printer. As the substrate 5, a through-hole having a shape obtained by slicing the pressure chamber 2, the nozzle 3, the communication passage 4, and the like in the thickness direction of the substrate 5 is formed by etching on a thin plate made of SUS316 steel obtained by a rolling method. A plurality of types of thin plates were sequentially laminated via an epoxy adhesive layer, and the epoxy adhesive was cured and adhered.

Next, after the piezoelectric ceramic layer 7 of the manufactured head is polarized by the high temperature polarization method, the drive circuit 13 having the circuit portion shown in FIG. 2 is connected to the individual electrode 8 and the common electrode 9, and the piezoelectric actuator 6 A state in which the switching element 20 of the drive circuit 13 connected to the individual electrode 8 corresponding to the arbitrary piezoelectric deformation region 11 above is switched in a direction to connect the individual electrode 8 so as to be at the same potential as the ground 17. It was.

  Then, a voltage having a driving voltage waveform of ± 1.83 kV / cm and a frequency of 1 kHz is applied to the common electrode 9 at room temperature (5 to 35 ° C.) to vibrate the piezoelectric deformation region 11 over 100 million cycles. The displacement amount at the center position in the surface direction of the piezoelectric deformation region 11 was measured by the laser Doppler method, and the reduction rate (%) of the displacement amount with respect to the initial value before continuous driving was obtained. This was taken as an example.

For comparison, the common electrode 9 of the head is connected so as to have the same potential as the ground, and a voltage having the same drive voltage waveform is applied to the individual electrode 8 so that the piezoelectric deformation region 11 becomes 100 million cycles. The rate of decrease (%) in the amount of displacement when oscillating over was determined as a comparative example. The results of Examples and Comparative Examples are shown in FIG. As can be seen from the figure, according to the present invention, the displacement amount of the bending deformation in the thickness direction of the piezoelectric deformation region 11 is prevented from greatly decreasing with time, and sufficient over a long period of time. It was confirmed that a large amount of displacement could be maintained.

It is sectional drawing which shows the example which incorporated one example of the piezoelectric actuator unit of this invention in the head of the inkjet printer as a drive source. FIG. 2 is a circuit diagram showing a portion corresponding to one piezoelectric deformation region of the piezoelectric actuator out of the drive circuit constituting the piezoelectric actuator unit of FIG. 1. It is a graph which shows transition of the fall rate of the displacement amount of the bending deformation of the thickness direction of the piezoelectric deformation area | region measured by the Example and comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator unit 2 Pressure chamber 3 Nozzle 4 Communication path 5 Substrate 6 Piezoelectric actuator 7 Piezoelectric ceramic layer 8 Individual electrode 9 Common electrode 10 Diaphragm 11 Piezoelectric deformation area 12 Restraint area 13 Drive circuit 14 Control unit 15 Active area 16 Power supply 17 Ground 18 circuit 19 circuit 20 switching element 21 circuit 22 circuit

Claims (2)

A plate-shaped piezoelectric ceramic layer, wherein are laminated on one side of the piezoelectric ceramic layer, the piezoelectric ceramic layer, in its plane, and a plurality of individual electrodes defining a plurality of active regions, the piezoelectric ceramic layer is laminated on the opposite side, of the piezoelectric actuator and a common electrode having a size including a plurality of active regions, the piezoelectric deformation region corresponding to the active region, a voltage is applied between the two electrodes Te, a driving method for driving individually, the plurality of individual electrodes, as well as connected so that the ground at the same potential of any of the individual electrodes to select択的, the other individual electrodes the and connected so that the common electrode at the same potential, the common electrode by applying a voltage, the piezoelectric deformation region corresponding to the individual electrodes connected to the ground, the individual electrodes and the common electrode The potential difference between the driving method of the piezoelectric actuator, characterized in that to selectively driven. A plate-shaped piezoelectric ceramic layer, wherein are laminated on one side of the piezoelectric ceramic layer, the piezoelectric ceramic layer, in its plane, and a plurality of individual electrodes defining a plurality of active regions, the piezoelectric ceramic layer is laminated on the opposite side, a piezoelectric actuator and a common electrode having a size including a plurality of active regions, the piezoelectric actuator, the plurality of individual electrodes, selecting any of the individual electrodes to thereby connected so that the ground at the same potential, by connecting the other individual electrodes so that the common electrode at the same potential, by applying a voltage to the common electrode, and connected to the ground piezoelectric a, characterized in that it comprises the piezoelectric deformation region corresponding to the individual electrodes, the potential difference between the individual electrode and the common electrode, and a driving circuit for selectively driving the Ju mediator unit.

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