JP2000188883A - Piezoelectric actuator, method for driving the same, portable apparatus, and timepiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which can efficiently amplifies the vibration of a piezoelectric element and the thickness of which can be reduced. SOLUTION: A piezoelectric actuator A is provided with a plate-like diaphragm 10 and a stator 20. The diaphragm 10 is constituted by sticking together a piezoelectric element 11 and a shim section 12 which is composed of a thin plate of phosphor bronze, etc., and functions as an elastic plate to each other. When the element 11 extends and contacts, the diaphragm 10 vibrates. The stator 20 is constituted of a rectangular thin plate and is provided with a circular-arcuate mobile end 21, a narrow constricted part 22, and a fixed section 23. Since a drive signal having the characteristic frequency of the stator 20 is impressed upon the piezoelectric element 21, the stator 20 efficiently amplifies the displacement of the diaphragm 10 and transmits the amplified displacement to the mobile end 21 of the stator 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator utilizing bending vibration of a stator, a driving method thereof, a portable device and a timepiece using the piezoelectric actuator.

[0002]

2. Description of the Related Art Various types of piezoelectric actuators utilizing the piezoelectric effect of a piezoelectric element have been developed in recent years because the piezoelectric element has excellent conversion efficiency from electric energy to mechanical energy and excellent responsiveness. This piezoelectric actuator is applied to fields such as a shutter mechanism of a camera, an ink jet head of a printer, and an ultrasonic motor. FIG. 25 is a plan view schematically showing an ultrasonic motor using a conventional piezoelectric actuator. This type of ultrasonic motor is of the so-called "stick type" type, in which the tip of a vibrating piece connected to a piezoelectric element is brought into contact with the rotor surface with a slight inclination. The principle of rotation is that when the piezoelectric element expands and contracts due to the AC voltage from the oscillating unit and the vibrating piece reciprocates in the length direction, a component force is generated in the circumferential direction of the rotor and the rotor rotates. Also, there is known a technology in which two ultrasonic vibrators (piezoelectric elements) are provided, each ultrasonic vibrator is vibrated at its own electric resonance frequency, and the vibrating element is displaced by this vibration (particularly, Japanese Patent Application Laid-Open No. H11-157572). Japanese Unexamined Patent Publication No. Hei 10-225151).

[0003]

However, the displacement of the piezoelectric element is very small, depending on the applied voltage, and is usually about several μm. The same applies to the case where the piezoelectric element is vibrated at the above-mentioned resonance frequency. For this reason, it is desirable to amplify the displacement by some amplification mechanism and transmit it to the rotor. On the other hand, when the amplification mechanism is used, there is a problem in that energy is consumed to move itself, and efficiency is reduced. Also, small portable devices such as wristwatches and cameras are driven by batteries, so it is necessary to reduce power consumption and drive voltage. Therefore, when a piezoelectric actuator is incorporated in such a portable device, it is particularly important that the energy efficiency is high and the driving voltage is low.

In a calendar display mechanism for displaying the day, day of the week or the like in a wristwatch or the like, the rotational driving force of an electromagnetic step motor is intermittently transmitted to a date wheel and the like via a wheel train for moving hands. It is common to drive and drive a car. On the other hand, since a wristwatch is carried around a wrist with a belt, there has been a long-standing demand for a thin wristwatch for convenient carrying. For this purpose, it is necessary to reduce the thickness of the calendar display mechanism. However, since the step motor is configured by incorporating components such as a coil and a rotor in an out-of-plane direction, there is a limit in reducing the thickness thereof. For this reason, the conventional calendar display mechanism using the step motor has a problem that it is not structurally suitable for thinning.

In particular, a clock having a calendar display mechanism,
In order to share the mechanical system of hand movement (so-called movement) with a timepiece without such a display mechanism, it is necessary to configure a calendar display mechanism on the dial side. It is difficult to reduce the thickness to such an extent that it can be configured. Therefore, in the conventional timepiece, it is necessary to separately design and manufacture the mechanical system of the hand movement depending on the presence or absence of the display mechanism, which has been a problem in improving the productivity.

The present invention has been made in view of the above circumstances, and provides a piezoelectric actuator that efficiently amplifies the vibration of a piezoelectric element and is suitable for thinning, and a portable device and a timepiece using the same. Aim.

[0007]

In order to solve the above-mentioned problems, a piezoelectric actuator according to the present invention includes a plate portion at least one end of which is displaced as a movable end by vibration, and a force applied to the plate portion. A vibration plate provided with a piezoelectric element is provided, and driving means for applying a driving signal having a frequency substantially equal to the natural vibration frequency of the plate portion to the piezoelectric element is provided. In the present invention, since the diaphragm is arranged so as to apply a force for displacing the plate portion, when the diaphragm vibrates, at least one movable end of the plate portion is displaced by the vibration. Here, a drive signal having a frequency substantially equal to the natural vibration frequency in the primary vibration mode or higher-order vibration mode of the plate portion is applied to the piezoelectric element provided on the vibration plate. Therefore, the plate portion vibrates at the natural vibration frequency. When a structure vibrates at a natural vibration frequency, its mechanical impedance is minimized and a large displacement occurs. Therefore, according to the piezoelectric actuator of the present invention, a large displacement can be obtained at a low driving voltage with high energy efficiency.

Further, in the piezoelectric actuator according to the present invention, at least one end portion is displaced in the in-plane direction as a movable end by vibration, and a force for displacing the plate portion in the in-plane direction is applied to the plate portion. A vibration plate provided with a piezoelectric element and a driving unit for applying a driving signal having a frequency substantially equal to the natural vibration frequency of the plate portion to the piezoelectric element. In this case, it is desirable that the diaphragm be disposed on the side surface of the plate portion.

In the present invention, since the diaphragm is arranged so as to apply a force for displacing the plate portion in the in-plane direction to the plate portion, when the diaphragm vibrates, the vibration causes at least one of the plate portions. The movable end is displaced in the in-plane direction. The piezoelectric actuator of the present invention is a new type of piezoelectric actuator that extracts vibration of a plate portion as in-plane vibration, and can be configured with a small number of components. further,
When the diaphragm is arranged on the side surface of the plate portion, the piezoelectric actuator can be reduced in thickness, and the force in the feed direction can be greatly converted because the force does not escape in the out-of-plane direction. For this reason, the conversion efficiency from input energy to output energy can be further improved.

In the present invention, the piezoelectric element may be arranged so that the vibration plate bends and vibrates in an out-of-plane direction.
For example, when the plate portion is formed in a substantially rectangular shape, the narrower the width, the lower the internal loss and the lower the natural vibration frequency. On the other hand, when the diaphragm is flexed and vibrated in the out-of-plane direction, it is easy to set the vibration frequency to a low frequency. Therefore, the piezoelectric actuator according to the present invention is suitable for setting the vibration frequency to a relatively low frequency and reducing the width of the plate portion, thereby reducing internal loss in the plate portion and improving energy efficiency. ing.

Further, when the diaphragm is caused to flex and vibrate in an out-of-plane direction, the piezoelectric element may be divided at nodes of the flexural vibration.
When the diaphragm is driven by high-order vibration, a plurality of inflection points are generated on the diaphragm, and a portion that extends and a portion that contracts are generated in one piezoelectric element. Since the directions of polarization of the expanding portion and the contracting portion are opposite to each other, the charges are internally canceled, and the electric energy efficiency is reduced. On the other hand, when the piezoelectric element is divided at the node of the flexural vibration as in the present invention, the extending part and the contracting part in each piezoelectric element do not exist simultaneously,
Electric energy efficiency can be improved, and large displacement can be obtained with a low driving voltage. in this case,
A plurality of piezoelectric elements divided by nodes of vibration are respectively arranged on the upper and lower surfaces of the vibration plate, and the polarization directions of vertically adjacent piezoelectric elements are matched via the vibration plate, and the piezoelectric elements adjacent in the longitudinal direction are arranged. It is preferable to make the polarization direction of the reverse polarity.

A single piezoelectric element is provided on each of the upper and lower surfaces of the vibration plate, and a plurality of divided electrodes are disposed on each piezoelectric element. The driving means has a phase difference of 180 degrees between the electrodes adjacent in the longitudinal direction. A shifted drive signal may be supplied.

In the present invention, the piezoelectric element may be arranged so that the diaphragm expands and contracts in an in-plane direction.
In this case, it is not necessary to convert out-of-plane stress between the diaphragm and the plate portion into in-plane stress, so that the plate portion does not torsion, etc. Is not in principle. Therefore, mechanical energy efficiency can be improved, and a large displacement can be obtained with a low driving voltage. Further, since the motion of the diaphragm is in the in-plane direction, the diaphragm is more suitable for thinning as compared with the one that flexes and vibrates in the vertical direction.

Further, when the diaphragm is caused to expand and contract in the in-plane direction, the electric field applied to the piezoelectric element may be set in the longitudinal direction of the diaphragm. In this case, since the longitudinal effect of the piezoelectric element can be used, a large force or displacement can be obtained with the same drive signal, and the electrical energy efficiency can be improved.

In the present invention, the diaphragm may include a piezoelectric element formed in a disk shape. In general, the piezoelectric coefficient indicating the amount of displacement with respect to an applied electric field is maximum when the shape of the piezoelectric element is a disk. Therefore, according to the present invention, a large displacement can be obtained with the same drive signal, and the electrical energy efficiency can be further improved.

In the present invention, the driving means may supply the driving signal having a frequency substantially equal to a natural vibration frequency of the plate portion and a natural vibration frequency of the diaphragm to the piezoelectric element. According to this invention, the diaphragm and the plate portion vibrate at the natural vibration frequency, respectively. Therefore, when viewed as a whole piezoelectric actuator, mechanical energy efficiency can be improved.

In the present invention, the plate portion may be provided with a support portion for supporting the movable end so as to be displaceable, and the support portion may be provided by a constricted portion narrower than the width of the plate portion. It is preferable to configure. Since the constricted portion acts as an elastic body, it is possible to support the plate portion without significantly damping the vibration.

In the present invention, the support portion may be provided at an end of the plate portion opposite to the movable end, or may be provided near a node generated when the plate portion vibrates. . Since the node of the vibration acts as a fixed point, it is a portion of the plate portion where the magnitude of the stress is the smallest. Therefore, if the support is provided in the vicinity of the node, the mechanical energy consumed there can be further reduced. When the support portion is formed by the constricted portion, it is preferable to provide the constricted portion on a side surface of the plate portion corresponding to a node generated when the plate portion bends and vibrates. In particular, when the plate portion is vibrated in an even-numbered order, it is preferable that the plate portion is supported by the central node of the plate portion. In this case, since the plate portion can be supported while maintaining the balance, the mechanical strength can be increased.

In the present invention, it is preferable that the vibration plate is arranged so as to vibrate the vicinity of an antinode generated when the plate portion vibrates. Generally, in a vibrating body, the maximum transmission efficiency can be obtained by exciting the antinode. Therefore, according to the present invention, the vibration of the diaphragm can be transmitted to the plate portion with high efficiency, a large amplitude can be extracted from the movable end, and the driving voltage can be reduced. In this case, even if the vibration position is not the antinode itself, the vibration can be transmitted with high efficiency within a certain range according to the vibration transmission characteristic of the plate portion. Therefore, the vibration position may be near the antinode.

In the present invention, the plate portion and the diaphragm may be formed in substantially the same plane. In this case, the thickness of the piezoelectric actuator can be reduced. Specifically, it is preferable that the plate portion and the vibrating plate are formed of a single plate-shaped member, and the thin plate-shaped piezoelectric element is formed on the vibrating plate. In this case, the main part of the piezoelectric actuator can be composed of two parts, so that the configuration can be extremely simplified.

Preferably, the piezoelectric actuator according to the present invention includes a disk-shaped rotor that contacts the movable end and rotates when the movable end vibrates in the in-plane direction. In this case, reciprocating vibration of the movable end can be converted into rotational stress by the rotor.

A portable device according to the present invention includes the piezoelectric actuator and a battery for supplying power to the piezoelectric actuator. In this case, since the piezoelectric actuator has extremely high energy efficiency, it can be used continuously for a long time. The battery may be a large-capacity capacitor, a lithium-ion secondary battery, or a secondary battery having a storage capacity such as Ni-Cd, in addition to a primary battery such as a dry battery or a mercury battery. Further, the secondary battery may be charged with power by any power generation mechanism.

A timepiece according to the present invention includes the piezoelectric actuator and a ring-shaped calendar display wheel which is rotated by a rotational force of the rotor. As the calendar display car, there are day cars in addition to day cars. Since the piezoelectric actuator has a structure suitable for thinning, the entire timepiece can be thinned.

Further, in the driving method of a piezoelectric actuator according to the present invention, there is provided a plate part whose at least one end is displaced in the in-plane direction as a movable end by vibration, and a force which displaces this plate part in the in-plane direction by the plate. A piezoelectric actuator provided with a vibrating plate provided with a piezoelectric element, wherein the driving signal has a frequency substantially equal to the natural vibration frequency of the plate portion. Is supplied to the piezoelectric element. According to the present invention, it is possible to positively use the resonance of the plate portion,
A large displacement can be taken out by minimizing the mechanical impedance of the plate portion. As a result, a large displacement can be obtained at a low driving voltage with high energy efficiency. Further, it is preferable that a frequency of the drive signal matches a natural vibration frequency of the diaphragm. In this case, since not only the plate portion but also the diaphragm vibrates at the natural vibration frequency, a large displacement can be obtained at a lower driving voltage with higher energy efficiency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A timepiece using a piezoelectric actuator according to the present invention will be described below with reference to the drawings.

[1. Principle of Piezoelectric Actuator] First, the principle of the piezoelectric actuator used in the present embodiment will be described. FIG. 1 is a plan view of the piezoelectric actuator. The piezoelectric actuator A is schematically constituted by a plate-shaped diaphragm 10 and a stator 20, as shown in the drawing.
The vibration plate 10 is formed by bonding a piezoelectric element 11 and a shim 12 made of a thin plate such as phosphor bronze and functioning as an elastic plate. When an AC voltage is supplied to the piezoelectric element 11, the piezoelectric element 11 expands and contracts, whereby the diaphragm 10 vibrates. The stator 20 is formed of a thin plate having a substantially rectangular shape, and includes an arc-shaped movable end 21, a constricted portion 22 having a reduced width, and a fixed portion 23.

The vibration mode of the diaphragm 10 is shown in FIG.
2A, there is a bending mode in which the diaphragm 10 bends and vibrates so as to undulate in a vertical direction, and as shown in FIG. 2B, a longitudinal vibration mode in which the diaphragm 10 expands and contracts in a longitudinal direction. The vibration mode is determined by the configuration of the piezoelectric element 11, and in either mode, the end 13 of the diaphragm 10 pushes the side surface of the stator 20 in the direction of the arrow shown in FIG. Assuming that the stator 30 is a rigid body, the stator 20 is displaced around the constricted portion 22 as shown in FIG. In this case, when the diaphragm 10 is displaced,
The displacement of the end 13 is amplified by the principle of leverage around the constricted portion 22 and transmitted to the movable end 21. But,
Since the stator 20 has a so-called cantilever structure, a large stress is applied to the constricted portion 22 serving as a support portion, and the stress escapes from the constricted portion 22 to increase energy loss. For this reason, there is a problem that conversion efficiency from electric energy to mechanical energy is reduced.

By the way, when the excitation frequency is gradually increased under the condition of a constant force with respect to the mechanical structure, the amplitude of the structure takes a maximum value at a certain frequency and then takes a minimum value. Repeat the response. That is, there are a plurality of frequencies at which the amplitude has a maximum, and the frequencies corresponding to the respective maximums are collectively referred to as a natural vibration frequency. The mode of vibration corresponding to the lowest natural frequency is referred to as a primary vibration mode, and the mode of vibration corresponding to the next lowest natural frequency is referred to as a secondary mode. It is known that when a structure vibrates at the natural vibration frequency of these vibration modes, its mechanical impedance is minimized, and a large displacement can be easily obtained with a small driving force.

The piezoelectric actuator A used in the present embodiment is constructed by paying attention to this point, and has a frequency substantially equal to the natural vibration frequency of the primary vibration mode or the higher vibration mode of the movable portion 21. Excites the movable part 21. FIG. 3B schematically illustrates the displacement of the movable portion 21 in the primary vibration mode, and FIG. 3C schematically illustrates the displacement of the movable portion 21 in the secondary vibration mode. It is a thing. As shown in FIGS. 3B and 3C,
The movable portion 21 vibrates while bending in the plane.

Here, assuming that the movable portion is vibrated in the n-th vibration mode, the frequency of the drive signal V is set to be substantially equal to the natural vibration frequency of the n-th mode. According to the piezoelectric actuator A, the movable portion 2
Since the mechanical impedance of 1 is minimized, a large displacement can be easily obtained with a small driving force. Although it depends on the damping coefficient of the movable part 21, the movable part 21 is generally regarded as a rigid body,
As compared with the case where the vibration is applied without considering the natural vibration frequency, a displacement several to several thousand times can be obtained. In the following embodiments, an example will be described in which a piezoelectric actuator A that actively utilizes the natural vibration of the stator 20 is applied to a calendar display mechanism of a timepiece.

[2. First Embodiment] [2-1. Overall Configuration] FIG. 4 is a transparent plan view showing a main configuration of a calendar display mechanism in a timepiece according to a first embodiment of the present invention. In the piezoelectric actuator A of this example, the vibration plate 10 bends and vibrates in a bending mode. In this case, the piezoelectric actuator A amplifies the vibration in the out-of-plane direction as the vibration in the in-plane direction, and outputs it as the displacement of the movable end 21. The movable end 21 is in contact with the rotor 30.
Here, the stator 20 and the rotor 30 are arranged so that an appropriate stress is applied in a stationary state. When the movable end 21 vibrates in the direction of arrow X, the rotor 30
Rotate in the direction of. The rotation of the rotor 30 is transmitted to the date wheel 50 via the intermediate wheel 40, and the date wheel 50 rotates in the direction of arrow Z.

FIG. 5 is a sectional view of a timepiece according to the first embodiment of the present invention. In the figure, the above-described calendar mechanism is incorporated in the shaded portion, and the thickness thereof is 0.5 mm.
Extremely thin with a degree. A disc-shaped dial 60 is provided above the calendar display mechanism (hatched portion). A window 61 for displaying a date is provided on a part of the outer peripheral portion of the dial 60 so that the date of the date dial 50 can be seen through the window 61. In addition, a movement for driving the hands 70 is provided below the dial 60.

In the above-described configuration, the piezoelectric actuator A has a configuration in which the diaphragm 10, the stator 20, and the rotor 30 are arranged in the same plane, instead of stacking coils and rotors in an out-of-plane direction unlike a conventional step motor. Therefore, it is structurally suitable for thinning. For this reason, the calendar display mechanism can be made thinner,
As a result, the thickness of the entire watch can be reduced. Further, the movement can be shared between a timepiece having a calendar display mechanism and a timepiece having no such display mechanism, and productivity can be improved.

[2-2. Configuration Examples of Piezoelectric Actuator] Next, configuration examples of various piezoelectric actuators will be described together with drive circuits. [2-2-1. First Embodiment] FIG. 6 shows a configuration example of a piezoelectric actuator A1 according to a first embodiment. In this piezoelectric actuator A1, a unimorph type piezoelectric element 11 of about 0.2 mm is bonded to the upper surface side of a metallic diaphragm 10 having a thickness of about 0.05 mm.
Are in contact with the stator 20. The material of the piezoelectric element 11 is quartz, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zirconate titanate, lead zinc niobate ((Pb (Z
n1 / 3-Nb2 / 3) O3 1-x-Pb Ti O3 x) x differs depending on the composition. x = 0.09), lead scandium niobate ((Pb
{(Sc1 / 2Nb1 / 2) 1-x Tix)} O3) x varies depending on the composition. X
= About 0.09).

The drive circuit 100 uses an electrode (not shown) provided on the upper surface of the piezoelectric element 11 and the diaphragm 10 as both poles, and applies a drive signal V between them. The drive circuit 100 that generates the drive signal V includes a separately-excited type and a self-excited type. First, FIG. 7A shows a block diagram of a separately excited drive circuit. In the separately-excited type, the oscillation signal output from the oscillation circuit 101 is
In step 2, the drive signal V is converted to a desired oscillation frequency to generate a drive signal V. In this case, the configuration can be simplified by using the oscillation circuit 101 also as a crystal oscillation circuit in a clock circuit for driving the hands, and using a frequency dividing circuit for the frequency conversion circuit 102. Next, FIG. 7B shows a block diagram of a self-excited drive circuit. The self-excited type shown in FIG.
The driving signal V is applied to the piezoelectric element 11 by positively feeding back only a signal of a predetermined frequency.

Here, the frequency of the drive signal V is set to be the natural vibration frequency in the primary vibration mode or the higher vibration mode of the stator 20. As described above, when a structure vibrates at the natural vibration frequency,
It has the lowest mechanical impedance. Therefore,
By driving the stator 20 at the natural vibration frequency, the stator 20 can be largely displaced. In other words, the amplitude of the diaphragm 10 can be efficiently amplified and transmitted to the movable end 21. As a result, the power consumption of the drive circuit 100 can be reduced and the drive voltage can be reduced.
1 can be used.

The vibration plate 10 in which the piezoelectric element 11 is bonded to the shim portion 12 has a natural vibration frequency fp independent of the natural vibration frequency fs of the stator 20. If the width of the stator 20 is Ws and the length is Ls, the natural vibration frequency fs is Ws
/ Ls, and if the length of the diaphragm 10 is Lp, the natural vibration frequency fp is proportional to 1 / Lp.

FIG. 8 shows the natural vibration frequencies fs, fp and Ws / Ls
6 is a graph showing a relationship between the values and 1 / Lp. Since the driving signal V having the natural vibration frequency fs of the stator 20 is applied to the piezoelectric element 11, the vibration plate 10
Vibrates at fs. Here, if the natural vibration frequency fs and the natural vibration frequency fp are far apart, the mechanical impedance of the diaphragm 10 becomes large and a large displacement cannot be obtained, resulting in poor efficiency. For this reason, the natural vibration frequencies fs, fp and the width Ws and length Ls of the stator 20 and the vibration plate 1 are substantially matched.
The length Lp of 0 is set. In this case, the natural vibration frequency
It is desirable that fs and fp be set within a range of ± 5%.
Here, the stator 20 is set in the secondary vibration mode (FIG. 2C).
When driving in a higher-order vibration mode such as a third-order vibration mode,..., An n-th vibration mode, the diaphragm 10 may be vibrated in accordance with the order. Alternatively, if the natural vibration frequencies fs, fp are represented by functions using the order of the vibration mode as a variable, the frequency f of the drive signal V is set so as to be given by the following equation, and the stator 20 is driven by the n-th vibration. The diaphragm 10 may be driven in an m-th order vibration mode while being driven in the mode. f = fs (n) =
fp (m) where n and m are natural numbers, for example, stator 2
Natural vibration frequency fs (2) corresponding to secondary vibration mode of 0
If the natural vibration frequency fp (3) corresponding to the third vibration mode of the diaphragm 10 matches, the stator 20 is set to 2
What is necessary is just to vibrate the diaphragm 10 in the third vibration mode while vibrating in the next vibration mode.

By the way, the natural vibration frequency of the stator 20
Although fs is proportional to the width Ws, the Q value decreases and the internal loss of the stator 20 increases as the width Ws increases. For this reason, it is desirable that the width Ws of the stator 20 be narrow. When the width Ws of the stator 20 is reduced, the natural frequency fs is reduced accordingly. That is, the lower the natural vibration frequency fs, the higher the mechanical energy efficiency.

Further, the driving circuit 100 supplies the piezoelectric element 11
There is a stray capacitance in the actual wiring up to
There is also a parasitic capacitance inside the "00". Therefore, when the frequency of the drive signal V is high, a leakage current flows through these capacitors, and the electrical energy efficiency is reduced. In other words, the lower the natural vibration frequency fp, the higher the electrical energy efficiency.

In order to improve the mechanical energy efficiency and the electrical energy efficiency, the natural vibration frequency of the stator 20 is reduced by reducing the width Ws of the stator 20.
It is desirable to set fs to be low and to set the natural vibration frequency fp of the diaphragm 10 so as to substantially coincide with the fs, thereby lowering the frequency of the drive signal V. Here, diaphragm 10
The bending mode is a mode in which the diaphragm 10 bends and vibrates in the up-down direction as shown in FIG. 2A, and thus has a lower frequency than the longitudinal mode shown in FIG. 2B. Suitable for driving. Therefore, in this example, the piezoelectric element 11 capable of vibrating in the bending mode and the stator 20 having a small width Ws are combined. This combination can improve mechanical and electrical energy efficiency.

[2-2-2. Second Embodiment] Next, FIG. 9 shows a configuration example of a piezoelectric actuator A2 according to a second embodiment. The piezoelectric actuator A2 of this example includes a piezoelectric element 11
Except for the configuration described above, the configuration is the same as that of the piezoelectric actuator according to the first embodiment. The piezoelectric element 11 of this example has a bimorph structure. Specifically, as shown in the figure, a sandwich structure is formed in which a piezoelectric element 11a is bonded to the upper surface of the shim portion 12 and a piezoelectric element 11b is bonded to the lower surface. In such a sandwich structure, the shim 12
As a result, the strength of the diaphragm 10 can be increased, so that the diaphragm 10 is resistant to a drop impact and the durability can be increased.

In this case, the diaphragm 10 includes the piezoelectric elements 11a,
11b acts as a common electrode, and there is a drive circuit 10b
From 0, the ground potential GND is supplied. The drive signal V is supplied to the piezoelectric elements 11a and 11b. In general, when the direction of the electric field applied to the piezoelectric element and the direction of displacement (strain direction) match, the longitudinal effect is used, and when the direction of the electric field is perpendicular to the direction of displacement, the lateral effect is used. In this example, the lateral effect is used. are doing. Here, the polarization directions of the piezoelectric element 11a and the piezoelectric element 11b are set such that the polarization directions coincide with each other as shown by arrows in the figure. Therefore, when the drive signal V is applied, when one of the piezoelectric elements expands in the longitudinal direction, the other piezoelectric element contracts in the longitudinal direction. Therefore, when an AC voltage is applied, the diaphragm 10 bends. The connection shown in the figure is called a parallel connection. In the parallel connection, a large displacement can be obtained by low-voltage driving as compared with the first mode. Therefore, it is suitable for application to portable equipment driven by a battery such as a watch.

[2-2-3. Third Embodiment] In an actual piezoelectric actuator, the width Ws and the length Ls of the stator 20 are expressed as follows.
It is necessary to determine in consideration of the driving force for rotating the rotor 30 and the mechanical strength. Further, the structure of the diaphragm 10 is subject to restrictions such as the arrangement of other components. For this reason,
As described in the first embodiment, the stator 20 may be vibrated in the n-th mode and the diaphragm 10 may be vibrated in the m-th mode. Here, if m is a natural number of 2 or more, two or more inflection points occur on the diaphragm 10.

The vibration plate 10 of the piezoelectric actuator A2 described in the second embodiment has a structure in which a single piezoelectric element 11a and a single piezoelectric element 11b are bonded to the upper surface and the lower surface of the shim 12, respectively. Therefore, when driven by high-order vibration that generates a plurality of inflection points, there is a portion that extends and a portion that contracts in one piezoelectric element. The direction of polarization is opposite in polarity between the extending part and the contracting part. For this reason, the electric charges are canceled inside the piezoelectric element, so that a large displacement cannot be obtained, and the electric energy efficiency is reduced. Thus, in the piezoelectric actuator A3 according to the third embodiment, the electric energy efficiency is improved by dividing the piezoelectric element at the nodes of vibration in accordance with the order of the vibration mode.

FIG. 10 shows a configuration example of a piezoelectric actuator A3 according to the third embodiment. In this example, the diaphragm 1
0 is driven in the secondary vibration mode. The piezoelectric actuator A3 has the second configuration except for the configuration of the piezoelectric element 11.
The configuration is the same as that of the piezoelectric actuator A2 according to the embodiment. As shown in the drawing, the piezoelectric element 11 of this example has a piezoelectric element 11a1 on the upper left side of the shim portion 12, a piezoelectric element 11a2 on the upper right side, a piezoelectric element 11b1 on the lower left side, and a piezoelectric element 11b2 on the lower right side. It is configured together. The direction of polarization when no voltage is applied to each piezoelectric element is indicated by an arrow in the figure. In this case, the piezoelectric element 11
The polarization directions of the piezoelectric elements 11a1 and 11b1 are set to be the same, and the polarization directions of the piezoelectric elements 11a2 and 11b2 are set to be the same. The polarity is set to be opposite.

Therefore, when the drive signal V is applied so that the piezoelectric element 11a1 contracts in the longitudinal direction due to the lateral effect, the piezoelectric elements 11a2 and 11b1 extend in the longitudinal direction and the piezoelectric element 11b
2 shrinks in the longitudinal direction (as shown). Conversely, when the drive signal V is applied so that the piezoelectric element 11a1 extends in the longitudinal direction due to the lateral effect, the piezoelectric elements 11a2 and 11b1 contract in the longitudinal direction, and the piezoelectric element 11b2 extends in the longitudinal direction. By repeating this bending motion, diaphragm 10 vibrates in a bending mode.

FIG. 11A shows a configuration example of the diaphragm 10 driven in the m-th order vibration mode. As shown in this figure, when driving in the m-th order vibration mode, (m
Is a natural number of 2 or more), the diaphragm 10 is divided into m parts in the longitudinal direction, and piezoelectric elements having the same polarization direction are attached to the top and bottom of each area (for example, 11am and 11bm), and the piezoelectric elements adjacent in the longitudinal direction May be configured so that the polarization directions thereof are opposite to each other (for example, 11b1 and 11b2).

As described above, according to the piezoelectric actuator A3 according to the third embodiment, in accordance with the vibration order of the diaphragm 10,
Since the piezoelectric elements are divided and arranged at the node of vibration, each piezoelectric element expands or contracts uniformly, so that the polarization direction is reversed in one piezoelectric element and the charge is canceled. Disappears. As a result, the electrical energy efficiency can be improved, and the driving voltage can be reduced. Further, as shown in FIG. 11B, the piezoelectric elements 11a having the same polarization direction on the upper and lower surfaces of the shim plate 12.
And the piezoelectric elements 11a and 11b are provided with m electrodes A1 to Am and B1 to Bm so that the phases of the drive signals V and V ′ applied to the electrodes adjacent in the longitudinal direction are shifted by 180 degrees. You may. In this case, FIG.
The same effect as (a) can be obtained.

[2-2-4. Fourth Aspect] In the first to third aspects described above, the diaphragm 10 is flexibly vibrated in the bending mode. These cases are suitable for setting the vibration frequency low. When the driving frequency is low, a leakage current flowing through a parasitic capacitance in the driving circuit 100 or a stray capacitance due to wiring layout is reduced, so that electrical efficiency can be increased. However, in the bending mode, the displacement in the out-of-plane direction is converted into the displacement in the in-plane direction at the end portion 13 of the diaphragm 10, but in the process, the stator 20 is twisted. Originally, the stator 20 amplifies the displacement of the diaphragm 10 by bending and vibrating in the in-plane direction. Therefore, when the torsion occurs, the mechanical energy efficiency is reduced. On the other hand, the parasitic capacitance of the driver circuit 100 can be reduced by using a transistor with a high transition frequency or devising a circuit configuration. Also,
The stray capacitance of the wiring can be reduced by using an insulator having a low dielectric constant or by shortening the wiring. Therefore, in the fourth embodiment, the diaphragm 10 is vibrated in the longitudinal vibration mode on the premise that the parasitic capacitance and the stray capacitance are reduced, thereby improving mechanical energy efficiency. .

FIG. 12 shows a configuration example of a piezoelectric actuator A4 according to the fourth embodiment. This piezoelectric actuator A4
Has the same configuration as the piezoelectric actuator A2 shown in FIG. 9 except that the piezoelectric element 11b 'is used instead of the piezoelectric element 11b. Here, the polarization direction of the piezoelectric element 11b 'is set to be opposite to the polarization direction of the piezoelectric element 11a provided on the upper surface side of the shim portion 12. In this case, the piezoelectric element 1
When the drive signal V is applied to 1a and 11b ', both piezoelectric elements expand and contract simultaneously due to the lateral effect. Therefore, the diaphragm 10 expands and contracts in the longitudinal direction as indicated by arrows in the figure.

Since the vibrating plate 10 vibrates in the in-plane direction, the end portion 13 does not change the direction of displacement, but only transmits the in-plane vibration. For this reason, the torsion does not occur in the stator 20 and mechanical energy can be transmitted with high efficiency.

[2-2-5. Fifth Mode] In the fourth mode described above, the polarization directions of the piezoelectric elements 11a and 11b 'are set to be opposite to each other, and the piezoelectric elements 11a and 11b' are driven by the lateral effect, so that the piezoelectric elements 11a and 11b 'are driven in the bending mode. The diaphragm 10 was vibrated. By the way, when an electric field is applied to the piezoelectric element to cause polarization, a displacement (strain) proportional to the electric field occurs, but a displacement (vertical effect) in the same direction as the direction of the electric field and a displacement (direction) perpendicular to the direction of the electric field ( Side effect)
Are known to be different. The amount of displacement with respect to the electric field strength (m / V) is called a piezoelectric coefficient and is represented by "dxy". Here, the subscript x indicates the direction of the electric field, and 1 when the electric field direction is the X-axis direction, 2 when the electric field direction is the Y-axis direction, and Z
If it is in the axial direction, it is represented by 3. The suffix y represents the direction of displacement in the same rule as the direction of the electric field. Generally, the piezoelectric coefficient d33 corresponding to the vertical effect is larger than the piezoelectric coefficient d31 corresponding to the horizontal effect. Therefore, it is more advantageous to use the longitudinal effect to convert electric energy into mechanical energy. Therefore, in the fifth mode, the energy efficiency is improved by driving the vibration plate 10 in the longitudinal vibration mode by utilizing the longitudinal effect of the piezoelectric element.

FIG. 13 shows a configuration example of a piezoelectric actuator A5 according to the fifth embodiment. The piezoelectric actuator A5 shown in this figure is composed of a piezoelectric element 11c having a rectangular parallelepiped shape, a diaphragm 10 having a shim 12, and a stator 20. Electrodes are respectively formed on the left and right side surfaces (hatched portions) of the piezoelectric element 11c, and a drive signal V is applied between both electrodes. Here, the polarization direction of the piezoelectric element 11c is a direction from the left side to the right side as shown in the figure. Therefore, when the drive signal V is applied to the piezoelectric element 11c, the piezoelectric element 11c repeatedly expands and contracts in the longitudinal direction. In this case, since expansion and contraction occur due to the longitudinal effect of the piezoelectric element 11c, the stator 20 can be vibrated with high energy efficiency.

Note that, instead of the piezoelectric element 11c, FIG.
May be used. In this piezoelectric element 11d, the distance D between the electrodes is reduced. The electric field intensity increases as the distance D between the electrodes becomes shorter even when the same voltage is applied. Therefore, the piezoelectric element 11
As for d, a larger displacement can be extracted as compared with the piezoelectric element 11c. In other words, the amount of displacement required for the diaphragm 10 can be extracted with the low-voltage drive signal V. Therefore, the piezoelectric actuator A5 using the piezoelectric element 11d is suitable for application to a portable device driven by a battery such as a timepiece.

[2-2-6. Sixth Embodiment] In the first to fifth embodiments described above, each of the piezoelectric elements has a rectangular parallelepiped shape. On the other hand, the sixth mode is characterized in that a disc-shaped piezoelectric element is used. FIG. 15 shows a configuration example of a piezoelectric actuator A6 according to the sixth embodiment. The piezoelectric actuator A6 includes a diaphragm 10 in which a piezoelectric element 11e is attached to the upper surface of a disk-shaped shim 12 and a piezoelectric element 11f is attached to the lower surface thereof, and a stator 20. The shim 12 acts as a common electrode for the piezoelectric elements 11e and 11f, and the driving circuit 100
ND is powered. The drive signal V is supplied to the piezoelectric elements 11e and 11f. Here, the polarization directions of the piezoelectric element 11e and the piezoelectric element 11f are set such that the polarization directions are opposite as indicated by arrows in the figure. When the drive signal V is applied, the piezoelectric element 11e and the piezoelectric element 11f radially expand and contract at the same time. As a result, the diaphragm 10 vibrates in the radial direction.

In the disk-shaped piezoelectric element, the electromechanical coupling coefficient Kp (representing the conversion between mechanical energy and electric energy) of the disk is represented by the longitudinal effect electromechanical coupling coefficient k33 (d33).
Derived from). Therefore, according to the sixth aspect, the efficiency of converting electrical energy to mechanical energy can be further improved.

[3. Second Embodiment] Next, a timepiece according to a second embodiment of the present invention will be described. The timepiece according to the second embodiment has substantially the same configuration as that of the first embodiment, except for the configuration of the piezoelectric actuator. In the piezoelectric actuator A of the first embodiment, a fixed portion 23 is provided at the end of the stator 20 opposite to the movable end 21 via a constricted portion 22, and the piezoelectric actuator A is fixed at the fixed portion 23. . Since the width of the constricted portion 22 is narrow, the constricted portion 22 can move relatively freely, and can support the stator 20 without significantly damping the vibration.

However, since the width of the constricted portion 22 is determined by a balance between mechanical strength and energy loss, a certain amount of energy loss occurs in the constricted portion 23. In particular, in a wristwatch in which a large acceleration is likely to be applied during use, such as a sports type, it is necessary to increase the width of the constricted portion 22 to some extent to increase the mechanical strength. Therefore, depending on the use of the wristwatch, the energy loss in the constricted portion 22 may not be negligible. By the way, as shown in FIGS. 2B and 2C, the stator 20 of the present embodiment vibrates at the natural vibration frequency fs, and the order of the vibration mode is predetermined. Since the bending state of the stator 20 is determined according to the order of the vibration mode, the position of the node of the vibration is also determined according to the order of the vibration mode. Here, the node of the vibration of the stator 20 acts as a fixed point.

The piezoelectric actuator B according to the second embodiment
Is made in view of this point, and by supporting the stator 20 at nodes of vibration, reduces energy loss and increases mechanical strength. In addition,
As the piezoelectric actuator B, there are various modes described below.

[3-1. First Embodiment] FIG. 16 is a plan view showing a configuration example of a piezoelectric actuator B1 according to a first embodiment. The piezoelectric actuator B1 shown in FIG.
It is assumed that it is driven in the primary vibration mode.

In the figure, the piezoelectric actuator B1
Includes a diaphragm 10 and a stator 20. As the diaphragm 10, any one of the first to sixth modes described in the first embodiment can be applied. The stator 20 is formed of a thin plate having a substantially rectangular shape, and has an arc-shaped movable end 21 and a narrowed narrow portion 2.
2 'and a fixed portion 23' are provided, and both ends in the longitudinal direction are free ends.

Here, the constricted portion 22 'is provided on the side surface opposite to the diaphragm 10 at the position of the node 24 generated when the stator 20 vibrates in the primary vibration mode, and the stator 20 is constricted. It is fixed to the fixing part 23 'via the part 22'. The driving signal V is supplied to the diaphragm 10. The AC frequency of the drive signal V is set to be equal to the natural vibration frequency fs of the stator 20. In addition,
The natural vibration frequency fp of the diaphragm 10 is selected so as to substantially match the natural vibration frequency fs. For this reason, mechanical energy efficiency can be improved.

In the above configuration, when the diaphragm 10 vibrates, the stator 20 vibrates primary while bending in the plane. Since the longitudinal direction of the stator 20 is a free end, the nodes 24 and 25 of vibration are 0.224L when the length of the stator is Lp.
It occurs at the position of p, 0.776Lp. The nodes 24 and 25 function as fixed points even when the stator 20 bends and vibrates. In this example, since the constricted portion 22 ′ is provided on the side surface of the stator 20 corresponding to the node 24, a large stress is not applied to the constricted portion 22 ′, and the constricted portion 22 ′ does not deform much. Therefore, compared with the case where the constricted portion 22 is provided at the end of the stator 20 as in the first embodiment, the loss of mechanical energy can be reduced in the constricted portion 22 ′. Further, since the stress applied thereto is small, even if the width of the constricted portion 22 'is slightly increased in order to obtain mechanical strength, the loss of mechanical energy does not increase so much. Therefore, it is preferable to apply the piezoelectric actuator B1 to a wristwatch of a type in which a large acceleration is expected by increasing the mechanical strength by slightly increasing the width of the constricted portion 22 '.

When driving the stator 20 in the secondary vibration mode, the piezoelectric actuator B1 may be configured as shown in FIG. In this case, the stator 2
0 has three nodes 26, 27, 28,
2 ′ may be provided on the side surface of the stator 20 corresponding to any of the nodes 26, 27, 28. In this example, the central section 2
7, a constricted portion 22 'is provided. When the constricted portion 22 'is provided at the center of the stator 20, the stator 20 can be supported while maintaining a balance in the longitudinal direction, so that the mechanical strength is increased and the structure is resistant to impact.

[3-2. Second Embodiment] FIG. 18 is a plan view showing a configuration example of a piezoelectric actuator B2 according to a second embodiment, and FIG. 19 is a sectional view thereof. It is assumed that the piezoelectric actuator B1 shown in the drawing is driven in a secondary vibration mode. Piezoelectric actuator B of this example
2 is not provided with the constricted portion 22 'and the fixed portion 23, and instead of these, the fixed portion 23' is directly provided on the node 24 of the vibration. The fixing portion 23 'may be fixed to the base with a pin as shown in FIG. 19, or may be one fixing the stator 20 to the base by spot welding. According to the above configuration, since the fixing portion 23 'is directly provided at the node of the vibration, mechanical energy loss in the supporting portion can be further reduced as compared with the first mode. Further, since there is no need to provide the constricted portion 22 'and the fixed portion 23, the space can be effectively used.

When the stator 20 is driven in the secondary vibration mode, the piezoelectric actuator B2 may be configured as shown in FIG. In this example, as in the first embodiment, the stator 20 can be supported while maintaining the balance in the longitudinal direction by providing the fixing portion 23 'at the central node 27, so that the mechanical strength is increased. The structure is strong against impact.

[4. Third Embodiment] Next, a timepiece according to a third embodiment of the present invention will be described. The timepiece according to the third embodiment has substantially the same configuration as that of the first or second embodiment except for the configuration of the piezoelectric actuator. In the piezoelectric actuators A and B of the first and second embodiments, no special consideration is given to the position where the diaphragm 10 vibrates the stator 20. However, the vibrator has
There is a portion called a node that does not displace at all during vibration, and a portion called an antinode that is the most displaced portion during vibration. The most efficient way to vibrate the vibrating body is to support the node and apply vibration to the belly. The piezoelectric actuator C according to the third embodiment is configured by paying attention to this point. By vibrating antinodes of the vibration of the stator 20 with the vibration plate 10, the vibration of the vibration plate 10 can be efficiently reduced. 20. As the piezoelectric actuator C, there are various modes described below.

[4-1. First Embodiment] FIG. 21 is a plan view showing a configuration example of a piezoelectric actuator C1 according to a first embodiment. The piezoelectric actuator C1 shown in FIG.
It corresponds to the piezoelectric actuator A of the first embodiment,
It shall be driven by primary vibration.

In the same figure, the piezoelectric actuator C1
Includes a diaphragm 10 and a stator 20. As the diaphragm 10, any one of the first to sixth aspects described in the first embodiment can be applied. The stator 20 is formed of a thin plate having a substantially rectangular shape. A movable end 21 is provided at one end in the longitudinal direction, and the other end is fixed at a fixed portion 23 via a constricted portion 22.

Here, the diaphragm 10 is arranged so as to be located at a portion of an antinode generated when the stator 20 primary-vibrates, and a drive signal V applied to the diaphragm 10 is provided.
Is set to be equal to the natural vibration frequency fs of the stator 20. Therefore, diaphragm 1
0 excites primary vibration in the stator 20 and excites the antinode of the vibration. Therefore, the stator 20 can be excited most efficiently. As a result, the amplitude of the vibration of the diaphragm 10 is amplified by the stator 20, and the movable end 21 can be largely displaced.

As described above, when vibrating the vibrating body,
It is most efficient to vibrate the antinode of the vibration, but from the viewpoint of transmission efficiency, a slight shift from the antinode does not cause much problem. FIG. 22 is a graph showing transmission efficiency when a disk-shaped vibrator is vibrated in the radial direction. In this graph, the transmission efficiency at the center of the disk (that is, a = 0) is normalized as 100. In the case of a disk-shaped vibrator, it is most efficient to vibrate the center corresponding to the antinode, so that the transmission efficiency becomes maximum at a = 0, but 0 <a <
In the range of 0.1, the transmission efficiency is within 98% of the maximum value. Therefore, if you vibrate within this range,
It can be said that almost maximum efficiency can be obtained. Since the vibrating body in the present embodiment is the rectangular stator 20, the same thing as the knowledge obtained from FIG. 22 does not always apply to the stator 20. However, whether it is a disk or an elongated stator 20, it is still a vibrating body. Therefore, the position of the vibration of the stator 20 does not need to be the antinode of the vibration itself.
Vibration can be transmitted efficiently. Note that the actual vibration position may be obtained in a range near the antinode which is allowed by an experiment.

[4-2. Second Embodiment] FIG. 23 is a plan view showing a configuration example of a piezoelectric actuator C2 according to a second embodiment. The piezoelectric actuator C2 shown in FIG.
It corresponds to the piezoelectric actuator B of the second embodiment,
It is assumed that it is driven in the secondary vibration mode.

In the figure, the piezoelectric actuator C2
Includes a diaphragm 10 and a stator 20. As the diaphragm 10, any one of the first to sixth aspects described in the first embodiment can be applied. The stator 20 is formed of a thin plate having a substantially rectangular shape, and a fixing portion 23 ′ is provided at a central node 27. Here, the diaphragm 10 is arranged so as to be located at an antinode generated when the stator 20 vibrates in the secondary vibration mode, and the AC frequency of the drive signal V applied to the diaphragm 10 Is the natural vibration frequency of the stator 20
fs (2) is set. Therefore, diaphragm 10 excites secondary vibration in stator 20 and excites the antinode of the vibration. Therefore, the stator 20 can be excited most efficiently. As a result, the amplitude of the vibration of the diaphragm 10 is amplified by the stator 20, and the movable end 21 can be largely displaced. Note that, as in the first embodiment, the position at which the diaphragm 10 vibrates the stator 20 does not need to be the antinode of the vibration itself, and if a certain range near the antinode is vibrated, the vibration can be transmitted efficiently. Can be.

[5. Modifications] (1) In each of the above-described embodiments, the order of the vibration mode is mainly described as the first order and the second order. However, the present invention is not limited to this. Of course, the vibration may be the same.

(2) In each of the embodiments described above, the shim portion 12 and the stator 20 are formed of a single plate-like member, and the thin May be configured.
In this case, the main part of the piezoelectric actuator can be composed of two parts, so that the configuration can be extremely simplified.

(3) In the above embodiments, the date wheel 50 of the calendar display mechanism is rotated, but the day wheel may be rotated by the piezoelectric actuators A, B, and C. In addition to the watch's calendar display mechanism,
It can be used as a driving device for a device that displays time, month, year, age, sun position, water depth, atmospheric pressure, temperature, humidity, azimuth, speed, and the like. Further, it is needless to say that the present invention can be used as various driving devices other than the display device. For example, the present invention can be applied to a mechanism driving device incorporated in a picture book or a card. In particular, since the piezoelectric actuators A, B, and C have extremely high energy efficiency, they are preferably applied to portable devices driven by batteries. In this case, the use time can be lengthened. The batteries include primary batteries such as dry batteries and mercury batteries, as well as large-capacity capacitors, lithium-ion batteries, Ni-C
It may be a secondary battery capable of storing electricity such as d. Further, the secondary battery may be charged with electric power by some power generation mechanism.

(4) In each of the above-described embodiments, an example has been described in which the in-plane bending vibration is excited in the stator 20 in accordance with the natural vibration frequency. However, the present invention is not limited to this. It may be one that excites the stator 20 with torsional vibration or vibration that expands and contracts in the longitudinal direction. In these cases, the vibration plate 10 is driven at the natural vibration frequency of the stator 20 determined according to the type of vibration such as torsional vibration or stretching vibration. Further, torsional vibration may be excited in diaphragm 10. By the way, when torsional vibration is excited in the stator 20, the diaphragm 10 may be connected to the upper surface of the stator 20 as shown in FIG. In this case, the diaphragm 10 is
Vibrating the upper surface of the stator 20, it is possible to excite a large twist in the stator 20. That is, the diaphragm 1
0 is not necessarily connected to the side surface of the stator 20. In short, it may be arranged so as to apply a force that can excite the stator 20 to a predetermined vibration mode (bending, twisting, expansion and contraction, etc.).

[0078]

As described above, according to the present invention, the plate portion can be vibrated at a frequency substantially equal to the natural vibration frequency, so that the mechanical impedance of the plate portion can be minimized. In addition, a large displacement can be extracted from the movable end with a low driving voltage under high energy efficiency. Further, the piezoelectric actuator of the present invention
It is suitable for thinning and can be configured easily.

[Brief description of the drawings]

FIG. 1 is a plan view of a piezoelectric actuator according to the present invention.

2A is a diagram showing a state in which a diaphragm bends and vibrates in a bending mode in a piezoelectric actuator according to the present invention; FIG. is there.

3 (a) is a plan view showing vibration when the stator is considered as a rigid body, FIG. 3 (b) is a plan view showing primary vibration of the stator, and FIG. 3 (c) shows secondary vibration of the stator. It is a top view.

FIG. 4 is a timepiece according to the first embodiment of the present invention.
FIG. 3 is a transparent plan view showing a main configuration of a calendar display mechanism.

FIG. 5 is a sectional view of the timepiece according to the embodiment.

FIG. 6 is a perspective view showing a configuration example of a piezoelectric actuator A1 according to a first mode of the embodiment.

FIG. 7A is a block diagram in the case where the drive circuit of the embodiment is separately excited, and FIG. 7B is a circuit diagram in a case where the drive circuit is separately excited.

FIG. 8 is a graph showing a relationship between the natural vibration frequencies fs, fp of the stator and the diaphragm according to the embodiment, and Ws / Ls and 1 / Lp.

FIG. 9 is a perspective view showing a configuration example of a piezoelectric actuator A2 according to a second mode of the embodiment.

FIG. 10 is a perspective view showing a configuration example of a piezoelectric actuator A3 according to a third mode of the embodiment.

FIG. 11 is a perspective view showing a configuration example of a diaphragm driven by m-order vibration in the piezoelectric actuator A3 according to the same embodiment of the embodiment.

FIG. 12 is a perspective view showing a configuration example of a piezoelectric actuator A4 according to a fourth mode of the embodiment.

FIG. 13 is a perspective view showing a configuration example of a piezoelectric actuator A5 according to a fifth mode of the embodiment.

FIG. 14 is a perspective view showing a configuration example of a laminated piezoelectric element according to the same embodiment.

FIG. 15 is a perspective view showing a configuration example of a piezoelectric actuator A6 according to a sixth mode of the embodiment.

FIG. 16 is a plan view illustrating an example of a piezoelectric actuator B1 according to a first embodiment in the second embodiment of the present invention.

FIG. 17 is a plan view showing another example of the piezoelectric actuator B1 according to the first mode of the embodiment.

FIG. 18 is a plan view showing an example of a piezoelectric actuator B2 according to a second mode of the embodiment.

FIG. 19 is a sectional view of a piezoelectric actuator B2 according to a second mode of the embodiment.

FIG. 20 is a plan view showing another example of the piezoelectric actuator B2 according to the second mode of the embodiment.

FIG. 21 is a plan view illustrating a configuration example of a piezoelectric actuator C1 according to a first embodiment in the third embodiment of the present invention.

FIG. 22 is a graph showing the transmission efficiency when a disk-shaped vibrator is vibrated in the radial direction.

FIG. 23 is a plan view showing a configuration example of a piezoelectric actuator C2 according to a second mode of the embodiment.

FIG. 24 is a perspective view illustrating a configuration example of a piezoelectric actuator according to a modification.

FIG. 25 is a plan view schematically showing an ultrasonic motor using a conventional piezoelectric actuator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Vibration plate 11 ... Piezoelectric element 12 ... Shim part 20 ... Stator (plate part) 21 ... Movable end 22, 22 '... Constricted part 50 ... Date dial (calendar display car) A, A1, A2, A3, A4, A5 , A6, B1, B2, C1, C2 ... piezoelectric actuator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsukasa Funasaka 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor Taiji Hashimoto 3-3-5 Yamato, Suwa-shi, Nagano Seiko-Epson F term (reference) 5H680 AA04 AA19 BB02 BB15 BC01 BC02 BC04 CC10 DD01 DD15 DD23 DD24 DD28 DD44 DD53 DD82 DD85 DD92 DD97 EE10 EE12 EE24 FF08 FF25 FF26 FF30 FF32 GG02 GG23

Claims (23)

[Claims] 1. A plate part at least one end of which is displaced as a movable end by vibration, a vibration plate arranged to apply a force to the plate part and provided with a piezoelectric element, and a plate part provided on the piezoelectric element. A driving means for applying a driving signal having a frequency substantially equal to the natural vibration frequency of the piezoelectric actuator. 2. A piezoelectric element, wherein at least one end of the plate is displaced in the in-plane direction as a movable end by vibration, and a force is applied to the plate for displacing the plate in the in-plane direction. And a driving means for applying a driving signal having a frequency substantially equal to the natural vibration frequency of the plate portion to the piezoelectric element. 3. The piezoelectric actuator according to claim 2, wherein the diaphragm is connected to a side surface of the plate. 4. The piezoelectric actuator according to claim 2, wherein the vibrating plate has the piezoelectric element arranged so as to bend and vibrate in an out-of-plane direction. 5. The piezoelectric actuator according to claim 4, wherein the piezoelectric element is divided at nodes of flexural vibration. 6. When driving the diaphragm in a higher-order vibration mode, a plurality of piezoelectric elements divided by nodes of vibration are arranged on upper and lower surfaces of the diaphragm, respectively, and the piezoelectric elements are vertically arranged via the diaphragm. While matching the polarization directions of adjacent piezoelectric elements,
The piezoelectric actuator according to claim 5, wherein the polarization directions of the piezoelectric elements adjacent to each other in the longitudinal direction have opposite polarities. 7. When driving the diaphragm in a higher-order vibration mode, a single piezoelectric element is provided on each of the upper and lower surfaces of the diaphragm, and a plurality of divided electrodes are arranged on each piezoelectric element. The piezoelectric actuator according to claim 4, wherein the driving means supplies a driving signal having a phase shifted by 180 degrees to the electrodes adjacent in the longitudinal direction. 8. The piezoelectric actuator according to claim 3, wherein the vibrating plate has the piezoelectric elements arranged so as to expand and contract in an in-plane direction. 9. The piezoelectric actuator according to claim 8, wherein an electric field applied to the piezoelectric element extends in a longitudinal direction of the vibration plate to cause the vibration plate to expand and contract in an in-plane direction. 10. The piezoelectric actuator according to claim 2, further comprising the diaphragm in which the piezoelectric element is formed in a disk shape. 11. The piezoelectric device according to claim 11, wherein the driving unit supplies the piezoelectric element with a driving signal having a frequency substantially equal to a natural vibration frequency of the plate portion and a natural vibration frequency of the vibration plate. 3. The piezoelectric actuator according to 2. 12. The piezoelectric actuator according to claim 2, wherein a support portion for displaceably supporting the movable end is provided on the plate portion. 13. The device according to claim 1, wherein the support portion is formed by a narrow portion narrower than a width of the plate portion.
2. The piezoelectric actuator according to 1. 14. The piezoelectric actuator according to claim 11, wherein the support portion is provided at an end of the plate portion opposite to the movable end. 15. The piezoelectric actuator according to claim 11, wherein the support portion is provided near a node generated when the plate portion vibrates. 16. The support portion is provided on a side surface of the plate portion corresponding to a node generated when the plate portion bends and vibrates,
The piezoelectric actuator according to claim 11, wherein the piezoelectric actuator is configured by a constricted portion narrower than the width of the plate portion. 17. The piezoelectric actuator according to claim 2, wherein the vibration plate is arranged so as to vibrate the vicinity of an antinode generated when the plate portion vibrates. 18. The piezoelectric actuator according to claim 2, wherein said plate portion and said diaphragm are formed in substantially the same plane. 19. The piezoelectric actuator according to claim 1, further comprising a disk-shaped rotor that contacts the movable end and rotates when the movable end vibrates in an in-plane direction. 20. A portable device comprising: the piezoelectric actuator according to claim 19; and a battery for supplying electric power to the piezoelectric actuator. 21. A timepiece comprising: the piezoelectric actuator according to claim 19; and a ring-shaped calendar display wheel that is rotated by a rotational force of the rotor. 22. A plate portion, at least one end of which is displaced in the in-plane direction as a movable end by vibration, and a force for displacing the plate portion in the in-plane direction is arranged on the plate portion,
A method for driving a piezoelectric actuator comprising: a vibration plate provided with a piezoelectric element, the method comprising: generating a drive signal having a frequency substantially equal to a natural vibration frequency of the plate portion; and supplying the drive signal to the piezoelectric element. Characteristic driving method of a piezoelectric actuator. 23. The apparatus according to claim 2, wherein a frequency of the drive signal is equal to a natural vibration frequency of the diaphragm.
3. The method for driving a piezoelectric actuator according to item 2.