JP2006140954A - Piezoelectric device, drive circuit for piezoelectric device, and actuator and speaker employing the piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device surely generating a high energy traveling wave and being driven by a simple drive circuit, and also to provide an actuator and a speaker employing the piezoelectric device. <P>SOLUTION: The piezoelectric device 300 is formed of: an antiferroelectric piezoelectric member 301; a ferroelectric piezoelectric member 302 in face-connected to the piezoelectric member 1 via an electrode 4; a plurality of electrodes connected to an surface of the piezoelectric member 301; and electrodes on the surface of the piezoelectric member 302 and connected to positions respectively opposed to a plurality of the electrodes. A plurality of unit piezoelectric devices formed by demarcating the piezoelectric device 300 by the electrodes are connected in series by wires interconnecting them. The electrode 4 is connected to points at a reference level and when a voltage vibrated at a high frequency is applied to the electrodes 3, parts demarcated as the unit piezoelectric devices 100 are greatly distorted in the antiferroelectric piezoelectric member 301, parts demarcated as the unit piezoelectric devices 100 in the ferroelectric piezoelectric member 301 are greatly distorted depending on the distortion, and a voltage is outputted from electrodes 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric device, an actuator using the piezoelectric device, and a speaker. More particularly, the present invention relates to a piezoelectric device that utilizes distortion of a piezoelectric element by applying a voltage, an actuator using the piezoelectric device, and a speaker.

  Conventionally, piezoelectric devices have been used in many electronic devices such as oscillators, actuators, speakers, and sensors. A crystal resonator or a ceramic resonator is one that uses a piezoelectric device as an oscillator, and is often used as an oscillation circuit for an operation clock of an integrated circuit combined with an active element (see, for example, Patent Document 1).

  In addition, the piezoelectric device utilizes the characteristic that it is distorted when a voltage is applied, and it is elastic to a buzzer or a small speaker that directly converts vibration into sound, for example, as a vibration source. Non-resonant actuators that cause large distortion at low voltage by laminating actuators and piezoelectric devices utilizing the feature that large vibrations can be generated when the body is resonantly vibrated (see, for example, Patent Document 3) A plurality of ring or disk-shaped piezoelectric devices are arranged in the rotational direction to generate a plurality of standing waves with different phases, and a traveling wave is created by providing a time lag between the generated standing waves. Conventionally, an actuator (for example, see Patent Document 4) is known.

  On the other hand, a piezoelectric member capable of generating reversible giant electrostriction using the property of symmetry of the nanoorder of point defects has been studied (for example, see Non-Patent Document 1).

  This piezoelectric member has domains with different electric polarization directions. When an electric field is applied, the giant electrostriction that is several tens of times larger than the normal piezoelectric effect occurs, and when the electric field is removed, the giant electrostriction disappears. It has the characteristics.

  The giant electrostriction is strong when an electric field is applied to a piezoelectric member having domains with different electric polarization directions, so that the polarization direction of the domains changes along the voltage direction (hereinafter referred to as “domain conversion”). This is strain that occurs when the major axis direction of the ferroelectric phase is exchanged with the minor axis direction due to the symmetry of the nano-order of point defects when the major axis direction of the dielectric phase becomes low symmetry. That is, the magnitude of the giant electrostriction obtained by this domain conversion is proportional to the difference between the major axis and the minor axis of the ferroelectric phase.

  In the member used for the piezoelectric member 2 having the above-described characteristics, the occupancy of other point defects around a certain point defect (nanometer range) matches the symmetry of the crystal at equilibrium. It can be obtained by utilizing the property that the point defect symmetry in is high, the point defect symmetry in the ferroelectric phase is low, and the polarization due to the point defect in the ferroelectric phase coincides with the spontaneous polarization.

Specifically, first, the paraelectric phase member is cooled to a ferroelectric phase state. At this time, the member immediately after cooling maintains the crystal symmetry of the paraelectric phase, but the point defect symmetry in the member diffuses over time, and gradually changes to the crystal symmetry of the ferroelectric phase. Thus, when the symmetrical diffusion of point defects occurs, the member is in a state where domains (regions) having different electric polarization directions exist.
Japanese Patent Laid-Open No. 08-130437 JP-A-10-277484 JP 2004-048984 A Japanese Patent Laid-Open No. 11-215861 Xiaobing Ren, “Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching”, Nature Materials, Nature Publishing Group, February 1, 2004, Volume 3, p. 91-94 and [online], January 11, 2004, Internet <URL: www.nature.com/naturematerials>

  However, an actuator using a conventional piezoelectric device needs to apply an alternating drive voltage, and there is a problem that a drive circuit for supplying the drive voltage becomes complicated.

  In addition, in order to form a traveling wave using a plurality of piezoelectric devices, it is necessary to control a driving voltage to be applied to each of a plurality of electrode patterns of the piezoelectric device, which further complicates the driving circuit. There is a problem.

  Furthermore, there is a problem that it is difficult to generate a large traveling wave in a rod-shaped vibrating body having a piezoelectric device attached to one end and a vibration absorbing material attached to the other end.

  An object of the present invention is to provide a piezoelectric device that can reliably generate a large traveling wave and that can have a simple driving circuit, an actuator using the piezoelectric device, and a speaker.

  In order to achieve the above object, the piezoelectric device according to claim 1 is composed of electro-mechanical energy conversion means having a hysteresis characteristic in which an amount of strain corresponding to an applied voltage has a hysteresis characteristic, and a first section having a first electrode; A plurality of unit piezoelectric devices connected in series, each comprising a second section having a second electrode and a third electrode connected to the first section and the second section, each comprising a mechanical-electrical energy conversion element A piezoelectric device that, when a voltage is applied between the first electrode and the third electrode of the first device of the unit piezoelectric devices, the first device of the first device And a voltage output means for distorting the section, distorting the second section of the first device according to the distortion, and outputting a voltage from between the second electrode and the third electrode. Features.

  According to the present invention, a rectangular signal-like voltage is successively applied to the first electrode of each unit piezoelectric device, and the periodic distortion generated by the electric field applied by this voltage application is propagated to the connected unit piezoelectric device. Thus, a large traveling wave can be generated reliably, and since it is not necessary to apply a voltage to each unit piezoelectric device, the drive circuit can be simplified.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram schematically showing the configuration of a piezoelectric device 300 according to an embodiment of the present invention.

  In the piezoelectric device 300 according to the present embodiment, a plurality of unit piezoelectric devices 100 having a configuration equivalent to the configuration of the unit piezoelectric device 200 of FIG. 2 to be described later and unit piezoelectric devices having the same configuration are used. Therefore, among the configurations of the unit piezoelectric device 100, components equivalent to the unit piezoelectric device 200 of FIG. 2 are denoted by the same reference numerals, and unit piezoelectric devices having the same configuration as the unit piezoelectric device 100 are denoted by the same symbols. Alphabet is attached and duplicate explanation is omitted.

  In FIG. 1, a piezoelectric device 300 is connected to a surface of the piezoelectric member 301 via an electrode 4 and an antiferroelectric piezoelectric member 301 (first section) that functions as one electro-mechanical energy conversion element. A ferroelectric piezoelectric member 302 (second section) that acts as one mechanical-electrical energy conversion element, and a plurality of electrodes 3, 3 a, 3 b, 3 c, 3 d, 3 e connected to the outer surface of the piezoelectric member 301, The electrodes 5, 5 a, 5 b, 5 c, 5 d, 5 e, which are connected to the outer surface of the piezoelectric member 302 and face each of the plurality of electrodes 3, 3 a, 3 b, 3 c, 3 d, 3 e, A plurality of unit piezoelectric devices 100, 100a, 100b, 100c, 100d, and 100e formed by partitioning with these electrodes are wirings 32, 33, 34, 35, and 3 that connect them. By connecting to the series.

  In addition, the movable body 37 is pressed against the piezoelectric device 300 on the side of the ferroelectric piezoelectric members 2, 2 a, 2 b, 2 c, 2 d, 2 e by a pressing means (not shown). Here, in this embodiment, the moving body 37 is a material having an insulating property, and even if different voltages are generated between the electrodes 5, 5a, 5b, 5c, 5d, and 5e, the electrodes are not short-circuited.

  The electrode 4 is connected to the reference potential, the electrode 3 is connected to the drive circuit 12, and the output voltage of the drive circuit 12 is applied between the electrode 3 and the electrode 4. This voltage is a DC voltage having a value larger than the saturation voltage of an antiferroelectric piezoelectric member described later or an AC voltage having an amplitude larger than the saturation voltage. The electrodes 5, 5a, 5b, 5c, and 5d apply a voltage to other unit piezoelectric devices connected via wiring.

  By configuring the piezoelectric device 300 as shown in FIG. 1, a simple configuration with only two power supply terminals connected to the outside can be achieved.

  FIG. 2 is a configuration diagram schematically showing a configuration of a unit piezoelectric device constituting the piezoelectric device 300 in FIG. The unit piezoelectric devices 100, 100a, 100b, 100c, 100d, and 100e in FIG. 1 have the same configuration as the unit piezoelectric device 200 in FIG.

  In FIG. 2, a unit piezoelectric device 200 is composed of an antiferroelectric piezoelectric member acting as an electromechanical energy conversion element, and includes a piezoelectric member 1 (first section) having an electrode 3 (first electrode), A piezoelectric member 2 (second section) comprising a ferroelectric piezoelectric member acting as a mechanical-electrical energy conversion element, having an electrode 5 (second electrode), and electrodes connected to the piezoelectric member 1 and the piezoelectric member 2 4 (third electrode).

  As described above with reference to FIG. 1, the drive voltage is applied between the electrode 3 and the electrode 4, and the voltage output from the piezoelectric member 2 of the unit piezoelectric device 100 is output between the electrode 4 and the electrode 5. The voltage between the electrode 4 and the electrode 5 is applied between the electrode 3 and the electrode 4 of another unit piezoelectric device.

  FIG. 3 is a diagram schematically showing the relationship of the amount of strain (amount of strain) with respect to the electric field strength of the piezoelectric and electrostrictive material, which is schematically represented with reference to the characteristics of the material of Non-Patent Document 1 above. The amount of distortion is represented by 0. The solid lines 201a and 201b indicate the characteristics of the piezoelectric material that generates reversible giant electrostriction using the property of the target of the nano-order of the point defects, and the dotted line 202 indicates the ferroelectric piezoelectric material such as PZT. The characteristics are shown.

  In FIG. 3, it can be seen that the piezoelectric members exhibiting the characteristics of the solid lines 201a and 201b cause a very large strain. However, when the electric field strength exceeds a certain level, the strain increases rapidly. The characteristic is similar to that of an antiferroelectric piezoelectric material, such as the return to the state of FIG.

  In the following description, an antiferroelectric piezoelectric member will be described as an example of an electro-mechanical energy conversion element having such characteristics, but the electro-mechanical energy conversion element having characteristics as indicated by solid lines 201a and 201b in FIG. If so, it is not limited to an antiferroelectric piezoelectric member. Similarly, a ferroelectric piezoelectric member such as PZT will be described as an example of a mechanical-electrical energy conversion element. However, the mechanical-electrical energy conversion element is not limited to this as long as the mechanical-electrical energy conversion element has characteristics as indicated by a dotted line 202. .

  The antiferroelectric piezoelectric member 1 exhibiting hysteresis characteristics as indicated by the solid lines 201a and 201b in FIG. 3 has a predetermined electric field strength, for example, 20 [kV / mm] (the material of Non-Patent Document 1 is 170 [ V / mm]), a distortion characteristic that abruptly increases the distortion when a voltage (saturation voltage) that is larger than that is applied, and when the electric field strength becomes 0, there may be some distortion actually remaining. However, the distortion also becomes substantially 0 (approximately the same amount of distortion every time when the electric field strength is 0) (in other words, the same amount of distortion becomes almost every time when the electric field intensity is 0). The antiferroelectric piezoelectric member 1 has a large hysteresis characteristic. Further, as indicated by a dotted line 202 in FIG. 3, the polarized ferroelectric piezoelectric member 2 such as PZT has a distortion characteristic proportional to the electric field strength and generates a charge proportional to the strain. Have the nature of

  FIG. 4 is a circuit diagram of an oscillation means using the unit piezoelectric device in FIG.

  A unit piezoelectric device 100 ′ a having the same configuration as that of the unit piezoelectric device 100 of FIG. 1 is used except that there is no electrode corresponding to the electrode 3. Accordingly, for the unit piezoelectric device 100 ′ a, “′” is given to those having the same structure as the constituent elements of the unit piezoelectric device 100, and redundant description is omitted.

  In FIG. 4, the unit piezoelectric device 100 and the unit piezoelectric device 100 ′ a in which the piezoelectric member 1 ′ is connected to the electrode 3 are arranged in line symmetry with respect to the electrode 3.

  The electrode 3 is connected to a reference potential by a resistor 11 and is connected to a power source 400 that outputs a DC voltage, and applies a power source voltage Vcc to the unit piezoelectric devices 100 and 100'a.

  The electrodes 4 and 4 'are connected to a reference potential by a resistor 10 and output the output voltage Vout from the unit piezoelectric devices 100 and 100'a to the outside.

  The electrodes 5 and 5 'are both connected to a reference potential.

  FIG. 5 is a diagram showing the voltage waveform of the power supply voltage Vcc applied from the power supply 400 to the oscillating means of FIG. 4 and the output voltage Vout output from the piezoelectric device 300 accompanying this voltage application.

  In FIG. 5, while the power supply voltage Vcc from the power supply 400 is not applied to the electrode 3 (t0 ≦ t <t1), the electrode 3 is connected to the reference potential by the resistor 11 and the electrodes 4 and 4 ′ are connected to the reference potential by the resistor 10, respectively. Therefore, no distortion occurs in the piezoelectric members 1, 2, 1 ′, 2 ′.

  Next, when a DC power supply voltage Vcc is applied from the power supply 400 to the electrode 3 at time t1, an electric field is applied to the piezoelectric members 1 and 1 'that are in contact with the electrode 3, and according to the characteristics indicated by the dotted line 202 in FIG. Distorted. Here, when the power supply voltage Vcc is equal to or higher than the saturation voltage Vs of the piezoelectric members 2 and 2 ′, a large distortion is generated in the piezoelectric members 2 and 2 ′ as shown in FIG. Electrodes 4 and 4 'output.

  Since the voltage Vout output from the electrodes 4 and 4 ′ and the power supply voltage Vcc applied from the electrode 3 are configured to have the same polarity, in addition to the piezoelectric members 1 and 1 ′, the distortion increases. When the magnitude of the applied electric field is reduced and the output voltage of the electrodes 4 and 4 'approaches the power supply voltage Vcc, the applied electric field approaches 0 and the distortion of the piezoelectric member 1 and the piezoelectric member 6 suddenly becomes 0. The distortion of the piezoelectric members 2 and 2 'is also zero. Then, the voltage output from the electrodes 4 and 4 ′ is also close to 0, and the state returns to the moment when the power supply voltage Vcc from the power supply 400 is applied to the electrode 3 at time t 2.

  By repeating this, the voltage Vout output from the electrodes 4 and 4 ′ becomes an alternating waveform oscillating at a predetermined frequency. That is, it is possible to realize an oscillating means that outputs the AC voltage having a predetermined frequency by simply arranging the unit piezoelectric members 100 and 100'a as shown in FIG. 4 and applying the DC power supply voltage Vcc from the power supply 400 to the electrode 3. .

  Further, when the resistance value of the resistor 10 is changed, the frequency of the output voltage Vout can be changed. As an element that can actively change the resistance value, there is an FET, a combination of an analog switch and a resistor, etc. If one of these resistance variable elements is used as the resistor 10, the oscillation frequency can be switched by an external signal. Become.

  In the present embodiment, the unit piezoelectric devices 100 and 100′a are arranged symmetrically with respect to the electrode 3 so that the oscillation of the unit piezoelectric device can be made symmetric, and the vibration near the electrode 3 can be reduced. By suppressing the vicinity of the electrode 3 to a support (not shown), vibration attenuation can be prevented. Furthermore, if the electrode 3 serves as the support, the configuration can be simplified.

  Further, in the present embodiment, the antiferroelectric piezoelectric members 1 and 1 ′ are configured to be inside the ferroelectric piezoelectric members 2 and 2 ′. However, the antiferroelectric piezoelectric members 1 and 1 ′ are outside the ferroelectric piezoelectric members 2 and 2 ′. You may comprise. Accordingly, since the ferroelectric piezoelectric members 2 and 2 'can be distorted from both sides, a larger distortion can be generated. As shown here, the unit piezoelectric device can constitute various logic devices, D / A conversion means, etc., although not described, in addition to the above-described oscillation means. If such a unit piezoelectric device as a functional element is used in place of the unit piezoelectric device 100 of FIG. 1, it has various interfaces (described in the fourth modification of FIG. 13 to be described later). A piezoelectric device can be constructed.

  FIG. 6 is a diagram showing voltage waveforms appearing on the input terminal side electrodes 3, 3a, 3b, 3c, 3d, 3e and the output terminal side electrode 5e of the unit piezoelectric device constituting the piezoelectric device 300 of FIG.

  In FIG. 6, first, when a drive voltage exceeding the saturation voltage Vs (FIG. 5) shown in the output waveform 600 is applied between the electrode 3 and the electrode 4 from the drive circuit 12, a large distortion occurs in the piezoelectric member 1. The piezoelectric member 2 is distorted. Due to this distortion, a voltage is output from the piezoelectric member 2, and this output voltage is output to the electrode 3 a via the electrode 5.

  In the electrode 3a, the voltage of the output waveform 601 delayed from the output waveform 600 of the voltage applied to the electrode 3 is applied, so that the piezoelectric member 1a is first largely distorted and then the piezoelectric member 2a is distorted.

  Similarly, voltages of output waveforms 602, 603, 604, and 605 that are sequentially delayed are applied to the electrodes 3b, 3c, 3d, and 3e. In this way, the voltage waveform propagates to the electrodes 3, 3a, 3b, 3c, 3d, 3e, 5e with a time delay.

  FIG. 7 is a diagram showing bending vibration generated in the piezoelectric device 300 of FIG.

  In FIG. 7, each graph represents the position of the bending wave viewed from the input side of the unit piezoelectric devices 100, 100a, 100b, 100c, 100d, and 100e at times T1 to T12.

  First, when a driving voltage equal to or higher than the saturation voltage of the unit piezoelectric device 100 is applied to the electrode 3, the unit piezoelectric device 100 is distorted as indicated by the bending wave 700 at time T1. By applying a voltage output according to this distortion to the unit piezoelectric device 100a, not only the unit piezoelectric device 100 but also the unit piezoelectric device 100a is distorted as indicated by the bending wave 701 at time T2. Thereafter, distortion occurs in the unit piezoelectric devices 100b, 100c, 100d, and 100e in order until time T5 as shown by bending waves 702, 703, 704, and 705, and at time T6, as shown by bending wave 706, All unit piezoelectric devices 100, 100 a, 100 b, 100 c, 100 d, and 100 e are bent with great distortion on the piezoelectric device 300.

  During this time, the bending wave front moves from the position of the unit piezoelectric device 100 toward the center of the piezoelectric device 300 while the bending amplitude increases.

  Next, when the application of the driving voltage to the electrode 3 is stopped, the distortion of the unit piezoelectric device 100 is released at time T7, and the distortion of the unit piezoelectric device 100a is released at time T8. Thereafter, the distortion of the unit piezoelectric devices 100b, 100c, 100d, and 100e is released in order until time T12. During this time, the bending wave front moves from the center of the piezoelectric device 300 toward the unit piezoelectric device 100e while the bending amplitude decreases.

  A bending wave that travels in this way is configured, and the mobile body 37 moves due to the elliptical motion of the mass point where the wave front moves in the direction opposite to the traveling direction of the traveling bending wave generated at the contact portion between the moving body 37 and the piezoelectric device 300. Therefore, a large traveling wave can be reliably generated on the piezoelectric device 300.

  FIG. 9 is a diagram showing a modification of the bending vibration of FIG.

  In FIG. 9, each graph represents the position of the bending wave viewed from the input side of the unit piezoelectric devices 100, 100a, 100b, 100c, 100d, and 100e at times T1 'to T9'.

  In the embodiment of FIG. 7, the application of the drive voltage between the electrode 3 and the electrode 4 is stopped after all the unit piezoelectric devices are distorted, but in this embodiment, as shown in FIGS. When the unit piezoelectric device 100b is distorted (t = T3 ′), the application of the driving voltage is first stopped. After that, when the unit piezoelectric device 100e is distorted (t = T6 ′), the application of the driving voltage is started again. Further, after that, when the unit piezoelectric device 100b is distorted (t = T9 ′), the application of the drive voltage is stopped again.

  First, since a driving voltage is applied between the electrode 3 and the electrode 4 from time T1 ′ to T3 ′, the unit piezoelectric devices 100, 100a, 100b,... A bending wave 900 appears that moves the position of the wave front in the direction of the unit piezoelectric device 100e while increasing the amplitude.

  Next, since the application of the drive voltage is stopped from time T4 ′ to T6 ′, the unit piezoelectric devices 100, 100a, 100b,. The position of the wave front is continuously moved in the direction of the unit piezoelectric device 100e while decreasing.

  Thereafter, since the driving voltage is applied to the electrode 3 again at time T <b> 7 ′, the unit piezoelectric device 100 is distorted, the second bending wave 901 is formed, and the two bending waves 900 and 901 appear on the piezoelectric device 300. Since the drive voltage is applied to the electrode 3 from time T7 ′ to T9 ′, the unit piezoelectric devices 100, 100a, 100b,... Are distorted in order, and the second bending wave 901 increases its amplitude. However, the position of the wave front is moved in the direction of the unit piezoelectric device 100e. On the other hand, since the distortion of the unit piezoelectric devices 100c, 100d, and 100e is released in order, the first bending wave 900 continues to move to the position of the unit piezoelectric device 100e and decreases its amplitude.

  8 and 9, since a plurality of bending waves, which are traveling waves, can be generated on the piezoelectric device 300, the contact between the bending wave and the moving body 37 can always be maintained, so that the driving is stably performed. be able to.

  In the present embodiment, the movable body 37 is moved. However, if the movable body 37 is fixed, the piezoelectric device 300 can be self-propelled.

  FIG. 10 is a block diagram schematically showing the configuration of the first modification of the piezoelectric device 300 of FIG.

  The piezoelectric device 300a in this modification uses a unit piezoelectric device 100 having a configuration equivalent to the configuration of the unit piezoelectric device 200 in FIG. 2 and a plurality of unit piezoelectric devices having the same configuration. Therefore, among the configurations of the unit piezoelectric device 100, components equivalent to the unit piezoelectric device 200 of FIG. 2 are denoted by the same reference numerals, and unit piezoelectric devices having the same configuration as the unit piezoelectric device 100 are denoted by the same symbols. Alphabet is attached and duplicate explanation is omitted.

  In FIG. 10, a piezoelectric device 300a is formed of an antiferroelectric piezoelectric member and a ferroelectric piezoelectric member that are alternately arranged via electrodes, and among these electrodes, electrodes 4, 4f, 4g, 4h , 4i, 4j are connected to a reference voltage.

  In addition, the piezoelectric device 300a moves the moving body 37 pressed against the elastic member 39 by a pressing means (not shown). The insulating member 38 insulates between the elastic member 39 and the electrodes of the piezoelectric device 300a.

  By configuring the piezoelectric device 300a as shown in FIG. 10, the wirings 32, 33, 34, 35, and 36 required to connect the unit piezoelectric devices in series in the piezoelectric device 300 of FIG. Can do.

  FIG. 11 is a block diagram schematically showing the configuration of the second modification of the piezoelectric device 300 of FIG.

  The piezoelectric device 300b according to this modification includes the piezoelectric device 300 of FIG. 1 and the piezoelectric device 300 'having the same configuration as that of the piezoelectric device 300 of FIG. The piezoelectric devices 300 and 300 ′ are pressed against each other by a pressing unit (not shown) via insulating members 38 a and 38 a ′, and are configured to drive each other as a moving body.

  Further, the electrodes 3 and 3 ′ of the piezoelectric devices 300 and 300 ′ are configured so that the connection with the drive circuit 12 can be switched by the switch 40.

  Accordingly, in the piezoelectric device 300 of FIG. 5, the direction of the bending wave that travels is one direction as shown in FIGS. The piezoelectric device 300b switches the relative movement direction of the piezoelectric devices 300 and 300 ′ only by switching the electrode 3 (electrode 3 ′) to which the drive voltage is applied by the switch 40 to the electrode 3 ′ (electrode 3). Can do.

  FIG. 12 is a block diagram schematically showing the configuration of the third modification of the piezoelectric device 300 of FIG.

  The piezoelectric device 300c in this modification is obtained by changing only the wiring of the piezoelectric device 300 in FIG. Accordingly, components having the same structure as the components of the piezoelectric device 300 are denoted by the same reference numerals, and redundant description is omitted.

  In the piezoelectric device 300c in the present modification, the moving directions of the six unit piezoelectric devices 100, 100a, 100b, 100c, 100d, and 100e when the driving current is applied to the electrodes are opposite to each other. Wiring is connected so as to be divided into two groups. Specifically, the unit piezoelectric devices 100, 100a, and 100b are a first group, the unit piezoelectric devices 100c, 100d, and 100e are a second group, and the electrodes 5 and 3a, the electrodes 5a and 3b, and the electrodes 5e The electrode 3d, the electrode 5d, and the electrode 3c are connected by wiring members 32, 33, 35, and 34, respectively.

  Further, the electrode 3 and the electrode 3e are connected to the power source 12 by the switch 40 so that the connection can be switched.

  Accordingly, the piezoelectric device 300c of FIG. 12 can change the traveling direction of the bending wave at the time of application between the first group and the second group, and the electrode 3 (electrode) to which the drive voltage is applied by the switch 40 The moving direction of the moving body 37 can be easily switched simply by switching 3e) to the electrode 3e (electrode 3).

  FIG. 13 is a block diagram schematically showing a configuration of a fourth modification of the piezoelectric device 300 of FIG.

  In the piezoelectric device 300d in this modification, a unit piezoelectric device 500 having a configuration equivalent to the configuration of the unit piezoelectric device 200 in FIG. 2 and a plurality of unit piezoelectric devices having the same configuration as this are used. Therefore, among the configurations of the unit piezoelectric device 500, components equivalent to those of the unit piezoelectric device 200 of FIG. 2 are denoted by the same reference numerals, and are identical to unit piezoelectric devices having the same configuration as the unit piezoelectric device of FIG. The duplicated explanation is omitted.

  The piezoelectric device 300d uses the unit piezoelectric device 500 as an oscillation circuit, and applies an output voltage to a section including the other unit piezoelectric devices 100a, 100b, 100c, 100d, and 100e, thereby causing distortion in these unit piezoelectric devices. Actuator.

  Specifically, one sheet of anti-ferroelectric piezoelectric member 301, one sheet of ferroelectric piezoelectric member 302 connected to the surface of piezoelectric member 1 via electrodes 4 and 42, and the outer surface of piezoelectric member 301 A plurality of electrodes 3, 3 a, 3 b, 3 c, 3 d, and 3 e connected to the electrode 3, and a position on the outer surface of the piezoelectric member 302 that faces each of the plurality of electrodes 3, 3 a, 3 b, 3 c, 3 d, and 3 e A plurality of unit piezoelectric devices 500, 100a, 100b, 100c, 100d, and 100e formed by partitioning with these electrodes 5 and 5a, 5b, 5c, 5d, and 5e. The wirings 32, 33, 34, 35, and 36 to be connected are connected in series.

  The electrode 4 is disposed so as to be located only at the boundary between the piezoelectric members 1 and 2 and is connected to the feedback circuit together with the electrode 5. The feedback circuit in this embodiment is a circuit configured by connecting the electrode 4 and the electrode 5 via the resistor 10 to the connection portion connected to the reference potential by the resistor 11, and is output from the electrode 5. Any circuit may be used as long as the voltage to be fed back to the electrode 4 is not limited to this circuit. The electrode 42 is disposed at the boundary between the antiferroelectric piezoelectric members 1a, 1b, 1c, 1d, and 1e and the ferroelectric piezoelectric members 2a, 2b, 2c, 2d, and 2e, and is connected to a reference potential. The electrode 3 is connected to a DC power source 400 (not shown).

  The operation of the unit piezoelectric device 500 as an oscillation circuit constituted by the wiring will be described.

  When a driving voltage is applied between the electrode 3 and the electrode 4 from a DC power supply 400 (not shown), first, the antiferroelectric piezoelectric member 1 is largely distorted, and thereby the ferroelectric piezoelectric member 2 is greatly distorted. . Then, a positive voltage corresponding to the strain is generated at the electrode 5, and the voltage divided by the resistors 10 and 11 is input to the electrode 4. Then, the distortion of the piezoelectric member 1 is released, and accordingly, the distortion of the piezoelectric member 2 is released. By repeating the above operation, oscillation continues while a DC voltage is input to the electrode 3.

  Since an AC voltage is output from the electrode 5 of the unit piezoelectric device 500 serving as the oscillation circuit, when this AC voltage is input to the electrode 3a connected to the electrode 5 via the wiring 32, the electrode of the unit piezoelectric device 100a. A bending wave is generated in 5a, and subsequently bending waves are also generated in order in the electrodes 5b, 5c, 5d, and 5e of the unit piezoelectric devices 100b, 100c, 100d, and 100e.

  Since the oscillation frequency can be changed depending on the values of the resistors 10 and 11, the size of the unit piezoelectric device 500, etc., if these conditions are designed in advance so as to oscillate at an optimum frequency, the voltage input to the electrode 3 The amount of movement of the moving body 37 can be controlled by turning on and off. Further, if the ON-OFF cycle and duty of the driving power output to the electrode 3 are made variable, the moving member 37 can be moved at an arbitrary moving speed.

  As described above, by using the unit piezoelectric device 500 as the oscillation means, a piezoelectric device in which the oscillator and the actuator are combined into one can be configured, and the actuator can be controlled with a simple control circuit.

  FIG. 14 is a block diagram schematically showing a configuration of a fifth modification of the piezoelectric device 300 of FIG. 1, in which (a) shows its planar arrangement, and (b) shows an AA plane.

  The piezoelectric device 300e in this modification is obtained by changing only the shape of the piezoelectric device 300 in FIG. Accordingly, components having the same structure as the components of the piezoelectric device 300 are denoted by the same reference numerals, and redundant description is omitted.

  Specifically, the piezoelectric members 301 and 302 are disks, and the electrodes 3 and 5 have a disk shape whose diameter is smaller than that of the piezoelectric members 301 and 302, and the other electrodes 3a, 3b, 3c, 3d, 3e, 5a, 5b, Reference numerals 5c, 5d, and 5e are ring shapes. Each electrode is arranged concentrically with the piezoelectric members 301 and 302, and the electrode width is narrower as the electrode is more distant from the electrodes 3 and 5.

  By configuring the piezoelectric device 300e as shown in FIG. 14, the piezoelectric device 300e can be a speaker in which a bending wave advances from the center to the outside when a driving voltage is applied to the electrode 3.

  In this embodiment, the traveling direction of the bending wave is outward from the center of the piezoelectric device 300e. However, the wirings 32, 33, 34, 35, and 36 are changed, and If the driving voltage is applied from the electrode 3e, the traveling direction can be reversed.

  Since the antiferroelectric piezoelectric member 301 is a member equivalent to the piezoelectric member 1 that is largely distorted at the predetermined voltage described above with reference to FIG. 2, the piezoelectric device 300e can reliably generate a loud sound.

  Further, when the voltage applied to the electrode 3 is equal to or higher than the saturation voltage Vs, a large bending wave which is a traveling wave can be formed by a large strain being propagated to each unit piezoelectric device one after another, and the piezoelectric device 300e is configured. It is possible to generate a low frequency vibration in which the entire disk to be bent is greatly bent. On the other hand, when a relatively small voltage compared to the saturation voltage Vs is applied to the antiferroelectric piezoelectric member 301 as a drive voltage, high-frequency vibrations that are deflected only by the central unit piezoelectric device to which the drive voltage is applied can be generated. As described above, since the size of the region to vibrate can be changed depending on the magnitude of the driving voltage, it is possible to generate a sound having a wide frequency range.

  In the above embodiment, for ease of explanation, a voltage in which a piezoelectric member made of an antiferroelectric material having hysteresis characteristics shown in FIG. 2 and a piezoelectric member made of a ferroelectric material are adjacent to each other is shown. The conversion element has been described as an example. As described above, if one member is an electro-mechanical energy conversion element and the other member is a mechanical-electric energy conversion element, the piezoelectric element is not necessarily used. It is not necessary to consist of members.

  The point-defect electrostrictive material described in Non-Patent Document 1 has the same hysteresis characteristic (strain amount characteristic with respect to electric field strength) as a conventional antiferroelectric piezoelectric material. Compared with an antiferroelectric piezoelectric material, it is possible to generate an equivalent strain at an electric field strength of several tens to hundreds of minutes. Therefore, a piezoelectric member that generates a large strain at a low voltage can be used, and application to various uses has been studied.

  Since these voltage conversion elements have a large distortion generated in the piezoelectric member constituting the voltage conversion element, it is necessary to take measures against peeling and fracture of the electrodes due to the distortion. The present invention generates a large strain in an anti-ferroelectric piezoelectric member that is an electro-mechanical energy conversion means, and converts it into a voltage by using a ferroelectric piezoelectric member that is a mechanical-electric energy conversion element adjacent to the anti-ferroelectric piezoelectric member. There is a possibility that a large stress is applied to the adjacent interface. An example of a method for reducing the stress at the interface is given below.

  As a first method, there is a method in which the electrode at the interface is divided into a plurality of regions and the plurality of regions are arranged at an appropriate distance from each other. By arranging the plurality of regions in parallel with the interface, the component in the direction parallel to the interface of the electric lines of force increases. When distortion in the direction of increasing thickness occurs due to the electric field in the thickness direction, the contraction by the Poisson's ratio works in the direction perpendicular to the thickness direction, but here the electric field lines are parallel to the interface perpendicular to the thickness direction. By providing a directional component, a strain extending in a direction perpendicular to the thickness direction is added, and the strain in a direction parallel to the interface can be reduced. Since this method changes the distortion transmission rate, it can also be used to adjust the gain of the voltage conversion element.

  As a second method, there is a method of filling fine irregularities generated on the contact surface between the piezoelectric member and the electrode with a high dielectric constant or conductive gel. In this case, it is necessary to apply pressure to the voltage conversion element in order to efficiently transmit the strain.

  As a third method, there is a method of using a soft material for the electrode itself.

  By applying such a device, it is possible to put it into practical use without damaging the voltage conversion element.

1 is a block diagram schematically showing a configuration of a piezoelectric device according to an embodiment of the present invention. FIG. 2 is a block diagram schematically showing a configuration of a unit piezoelectric device in FIG. 1. It is a figure which shows typically the distortion characteristic of the piezoelectric member which has a reversible giant electrostriction, and the ferroelectric piezoelectric member using the property of the nanoorder objectivity of the point defect described in the nonpatent literature 1. It is a circuit diagram of the oscillation means using the unit piezoelectric device in FIG. It is a figure which shows the voltage waveform of the output voltage Vout output from the power supply voltage Vcc applied from a power supply to the oscillation means of FIG. 4, and this voltage application from a piezoelectric device. It is a figure which shows the voltage waveform which appears in the electrode by the side of the input terminal of the unit piezoelectric device which comprises the piezoelectric device of FIG. 1, and the electrode by the side of an output terminal. It is a figure which shows the bending vibration generate | occur | produced in the piezoelectric device of FIG. It is a figure which shows the output waveform of the voltage given to the piezoelectric device of the modification of the bending vibration of FIG. It is a figure which shows the modification of the bending vibration of FIG. It is a block diagram which shows roughly the structure of the 1st modification of the piezoelectric device of FIG. It is a block diagram which shows roughly the structure of the 2nd modification of the piezoelectric device of FIG. It is a block diagram which shows roughly the structure of the 3rd modification of the piezoelectric device of FIG. It is a block diagram which shows roughly the structure of the 4th modification of the piezoelectric device of FIG. It is a block diagram which shows roughly the structure of the 5th modification of the piezoelectric device of FIG. 1, (a) shows the planar arrangement | positioning, (b) shows an AA surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antiferroelectric piezoelectric member 2 Ferroelectric piezoelectric member 3, 4, 5 Electrode 12 Drive circuit 32, 33, 34, 35, 36 Wiring member 37 Moving body 38 Insulating member 39 Elastic body 40 Switch 100 Unit piezoelectric device 300 Piezoelectric device

Claims (12)

A strain amount corresponding to the applied voltage is composed of electro-mechanical energy conversion means having hysteresis characteristics, a first section having a first electrode, and a second section composed of a mechanical-electric energy conversion element and having a second electrode. A plurality of unit piezoelectric devices comprising a plurality of unit piezoelectric devices connected in series, and a third electrode connected to the first compartment and the second compartment,
When a voltage is applied between the first electrode and the third electrode of the first device of the unit piezoelectric devices, the first section of the first device is distorted; A piezoelectric device comprising: voltage output means for distorting the second section of the first device according to strain and outputting a voltage from between the second electrode and the third electrode. .   2. The piezoelectric device according to claim 1, wherein the first section is made of an antiferroelectric piezoelectric member.   The piezoelectric device according to claim 1 or 2, wherein the functional elements including the unit piezoelectric device are integrally formed.   The piezoelectric device according to claim 3, wherein the functional element constitutes oscillation means.   The plurality of unit piezoelectric devices are connected to a plurality of the first electrodes connected to the outer surface of the first section, and positions on the outer surface of the second section facing the first electrodes. A plurality of the second electrodes and a third electrode provided between the first section and the second section, and the plurality of unit piezoelectric devices are connected in series by a wiring connecting between the plurality of unit piezoelectric devices. The piezoelectric device according to claim 1 or 2, characterized in that   The plurality of unit piezoelectric devices are formed of the first section and the second section that are alternately arranged via electrodes, and each of the electrodes corresponding to the third electrode among the electrodes is the 3. The piezoelectric device according to claim 1, wherein a voltage is outputted to the outside by a voltage output means.   The amplitude of the DC voltage or AC voltage applied to the first section of the first device is equal to or higher than a saturation voltage at which the distortion of the first section by the electro-mechanical energy conversion means is almost saturated. The piezoelectric device according to any one of claims 1 to 6.   8. The piezoelectric device according to claim 1, further comprising a period setting unit that sets a period for turning on and off a DC voltage applied to the first section of the first device. 9. .   The piezoelectric device according to claim 1, further comprising duty setting means for setting a duty of a DC voltage applied to the first section of the first device.   An actuator using the piezoelectric device according to any one of claims 1 to 6.   A speaker using the piezoelectric device according to any one of claims 1 to 6.   The speaker according to claim 11, wherein the piezoelectric devices are arranged concentrically.

Images