JP4631124B2 - Piezoelectric actuators, watches and equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric actuator, a timepiece, and a device, and more particularly to a technique for improving driving efficiency of a piezoelectric actuator.
[0002]
[Prior art]
Since piezoelectric elements are excellent in conversion efficiency from electrical energy to mechanical energy and responsiveness, various piezoelectric actuators utilizing the piezoelectric effect of piezoelectric elements have been developed in recent years. This piezoelectric actuator is applied to fields such as a piezoelectric buzzer, an inkjet head of a printer, or an ultrasonic motor.
By the way, the displacement of the piezoelectric element is small although it depends on the applied voltage, and is usually on the order of submicrons. Therefore, in order to efficiently transmit the vibration of the piezoelectric element to the outside, some contrivance is applied to the piezoelectric actuator. It is necessary to apply. For example, in a device using a conventional piezoelectric actuator, the displacement is amplified by some amplification mechanism and transmitted to the rotor.
[0003]
[Problems to be solved by the invention]
However, when the amplification mechanism is used, there is a problem that energy is consumed to move itself and efficiency is lowered, and there is a problem that the size of the apparatus is increased.
[0004]
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a piezoelectric actuator, a timepiece, and a device that improve driving efficiency without causing an increase in size.
[0005]
In order to solve the above-described problems, the invention described in claim 1 is a diaphragm in which a support, a plate-like piezoelectric element having a longitudinal direction, and a reinforcing portion are stacked, is oscillatably supported, there is the balance of the longitudinal direction of the longitudinal vibration plate that have a balance portion protruding from the diaphragm at a position shifted from the center in the width direction at one end side of the vibrating plate side and Oite at one end of the opposite side, provided at a position shifted to the side opposite to the side with the balance portion in the width direction from the center in the width direction are brought into contact with the driven object, facing the driven surface by There is a curved surface, the contact point between the driven moves the a position near Ru driver offset from the center in the width direction, the drive portion by vibrating the vibrating plate along the elliptical orbit, A predetermined drive is applied to the drive target that is in contact with the drive unit. A piezoelectric actuator that drives in a direction, and includes a driving unit that supplies electric power to the piezoelectric element to vibrate the diaphragm, and the driving unit has a major axis direction of the elliptical orbit substantially equal to the predetermined driving direction. The driving frequency for vibrating the diaphragm so as to match and driving the piezoelectric element is a resonance frequency of longitudinal vibration in which the diaphragm expands and contracts in the longitudinal direction due to vibration of the piezoelectric element, and the diaphragm It is a frequency between the resonance frequency of the bending vibration that oscillates in the width direction orthogonal to the longitudinal direction.
[0010]
The invention of claim 2 is the piezoelectric actuator according to claim 1, the driving frequency is characterized by varying with the resonance frequency of the bending vibration and the resonance frequency of the longitudinal vibration.
[0013]
The invention according to claim 3 is a timepiece comprising the piezoelectric actuator according to claim 1 or 2 and a ring-shaped calendar display wheel that is rotationally driven by the piezoelectric actuator. Yes.
[0014]
A fourth aspect of the present invention is an apparatus, comprising the piezoelectric actuator according to the first or second aspect and a power source for supplying electric power to the piezoelectric actuator.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[1] Configuration of Embodiment [1.1] Overall Configuration The first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view showing a main configuration of a calendar display mechanism incorporating a piezoelectric actuator in the wristwatch according to the first embodiment.
The piezoelectric actuator A1 is generally composed of a diaphragm 10 and a rotor 30 that expand and contract in an in-plane direction (a direction parallel to the drawing sheet).
The rotor 30 is rotatably supported by the base plate (supporting body) 70 and is disposed at a position where it abuts on the protrusion 17 of the diaphragm 10. As a result, the protrusion 17 moves along an elliptical orbit as will be described later due to vibration generated in the diaphragm 10, and the protrusion 30 abuts on the outer peripheral surface of the rotor 30, whereby the rotor 30 is indicated by an arrow in the figure. It is designed to be rotated in the direction to be
[0016]
The calendar display mechanism is connected to the piezoelectric actuator A1 and is driven by the driving force of the piezoelectric actuator A1. The main part of the calendar display mechanism is roughly composed of a reduction wheel train composed of a date turning intermediate wheel 40 and a date turning wheel 60 that decelerate the rotation of the rotor 30, and a ring-shaped date wheel 50.
[0017]
[1.2] Configuration of Piezoelectric Actuator Next, the piezoelectric actuator A1 according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the piezoelectric actuator A <b> 1 includes a long plate-like diaphragm 10 that is long in the left-right direction in the figure, and a support member 20 that supports the diaphragm 10 on a ground plane 70 (see FIG. 1). I have.
[0018]
Here, a protruding portion (driving portion) 17 protrudes from one end portion 15 in the longitudinal direction of the diaphragm 10 toward the rotor 30, and the protruding portion 17 contacts the outer peripheral surface of the rotor 30. Touching. The protrusion 17 may be a conductor or a non-conductor. However, if the protrusion 17 is formed of a non-conductor, the piezoelectric element does not short-circuit even when it is in contact with the rotor 30 generally formed of metal. Can be.
Further, the protrusion 17 has a curved surface shape that protrudes toward the rotor 30 in plan view. By forming the protrusion 17 that contacts the rotor 30 in a curved shape in this way, even if the positional relationship between the rotor 30 and the diaphragm 10 varies due to dimensional variation or the like, the outer peripheral surface of the rotor 30 that is a curved surface and the curved shape are reduced. The contact state with the protrusion 17 does not change much. Therefore, a stable contact state between the rotor 30 and the protrusion 17 can be maintained.
[0019]
In addition, a balance portion 18 is provided at the other end portion 16 in the longitudinal direction of the diaphragm 10. As shown in FIG. 4, when the diaphragm 10 performs longitudinal vibration that expands and contracts in the longitudinal direction, a rotational moment centered on the center of gravity of the diaphragm 10 is generated by the protrusion 17 and the balance portion 18. Due to this rotational moment, the diaphragm 10 is excited by bending vibration that swings in the width direction orthogonal to the longitudinal direction of the diaphragm 10 as shown in FIG.
As described above, by providing the balance portion 18, longitudinal vibration and bending vibration are generated in the diaphragm 10. As a result, the protrusion 17 moves along an elliptical orbit as shown in FIG.
Note that the resonance frequency of the flexural vibration generated in the diaphragm 10 varies depending not only on the balance portion 18 but also on the aspect ratio of the diaphragm 10.
[0020]
Further, one end 21 of the support member 20 is attached to the rotor side slightly from the longitudinal center of the diaphragm 10. The other end 22 of the support member 20 is supported on the ground plane 70 (see FIG. 1) by screws 23.
Under this configuration, the support member 20 supports the diaphragm 10 in a state in which the diaphragm 10 is urged toward the rotor 30 by its elastic force, so that the protrusion 17 of the diaphragm 10 contacts the outer peripheral surface of the rotor 30. It has been made.
[0021]
Next, the configuration of the diaphragm 10 will be described with reference to FIG. As shown in FIG. 3, the diaphragm 10 is between the two rectangular piezoelectric elements 11, 12 and has substantially the same shape as the piezoelectric elements 11, 12 and is thicker than the piezoelectric elements 11, 12. It has a laminated structure in which reinforcing plates (reinforcing portions) 13 such as thin stainless steel are arranged.
By disposing the reinforcing plate 13 between the piezoelectric elements 11 and 12 in this way, it is possible to reduce damage to the diaphragm 10 due to overamplitude of the diaphragm 10 or external force. The reinforcing plate 13 is thinner than the piezoelectric elements 11 and 12 so as not to disturb the vibration of the piezoelectric elements 11 and 12 as much as possible.
Electrodes 14 are disposed on the surfaces of the piezoelectric elements 11 and 12 disposed above and below, respectively. A voltage is supplied to the piezoelectric elements 11 and 12 through the electrode 14.
The diaphragm 10 having such a configuration expands and contracts when an AC voltage is applied to the piezoelectric elements 11 and 12 through the electrodes 14 from the driving means S1 that supplies power to vibrate the diaphragm 10. The diaphragm 10 vibrates longitudinally by this expansion and contraction as shown in FIG.
[0022]
Here, as the piezoelectric elements 11 and 12, lead zirconate titanate (PZT (trademark)), crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zinc niobate ( (Pb (Zn1 / 3-Nb2 / 3) 03 1-x-Pb Ti 03 x) x varies depending on the composition. About x = 0.09), lead scandium niobate ((Pb ((Sc1 / 2-Nb1 / 2) 1-x Tix) 03) x varies depending on the composition, x = 0.09) and the like.
[0023]
[1.3] Configuration for Obtaining High Driving Efficiency In the present embodiment, the rotor 30 can be driven with high efficiency by moving the protrusion 17 along the elliptical orbit as described above. The inventor of the present application analyzed the relationship between the direction of the ellipse and the driving efficiency in order to further improve the driving efficiency, and obtained a result as shown in FIG.
Here, the angle φ in FIG. 8 will be described with reference to FIG. As shown in FIG. 7, the angle φ is determined by the tangent line S on the outer peripheral surface of the rotor 30 at the contact point P where the protruding portion 17 of the diaphragm 10 and the outer peripheral surface of the rotor 30 are in contact, and the protruding portion 17 of the diaphragm 10. It is an angle formed by the long axis direction line T of the moving elliptical orbit. As shown in FIG. 8, when the angle φ formed by the tangent S on the outer peripheral surface of the rotor 30 and the long axis direction line T of the elliptical orbit where the protrusion 17 moves is 0, that is, when both coincide, High driving efficiency can be obtained.
Therefore, the diaphragm 10 and the rotor 30 are set so that the angle φ formed by the tangent line S on the outer peripheral surface of the rotor 30 and the long axis direction line T of the elliptical orbit where the protrusion 17 moves is 0 degree. Is most preferred. However, in the case where the angle φ is within the range of about ± 5 degrees, the same effect as that obtained at the maximum driving efficiency is obtained, so that the angle φ is within this range. In this case, it is considered that sufficient driving efficiency can be obtained.
[0024]
In consideration of the relationship between the ellipse direction and the driving efficiency as described above, the piezoelectric actuator so that the tangent S on the outer peripheral surface of the rotor 30 and the major axis T of the elliptical orbit along which the protrusion 17 moves substantially coincide. In order to improve drive efficiency, it is preferable to configure A1.
Therefore, the inventor of the present application considered what requirements determine the orientation of the ellipse in the piezoelectric actuator A1. As a result, it has been found that the relationship between the tangent line S and the long axis direction line T described above is greatly influenced by the positional relationship between the diaphragm 10 and the rotor 30 and the setting of the driving frequency of the piezoelectric elements 11 and 12. .
Specifically, when the drive frequency of the piezoelectric elements 11 and 12 and the configuration of the diaphragm 10 to be used are the same conditions, the positional relationship between the rotor 30 and the diaphragm 10 is the elliptical orbit of the protrusion 17 described above. It was found that it greatly affects the orientation of
[0025]
On the other hand, when conditions such as the positional relationship between the rotor 30 and the diaphragm 10 and the configuration of the diaphragm 10 are the same, it has been found that the driving frequency of the piezoelectric elements 11 and 12 is greatly affected. This will be described with reference to the simulation result shown in FIG.
Here, in FIG. 9, the vibration shape at the lowest drive frequency is indicated by the shape K1, the vibration shape at the second lowest drive frequency is indicated by the shape K2, and is the third lowest drive frequency. The vibration shape at the time is the shape K3, the vibration shape at the fourth lowest drive frequency is indicated by the shape K4, and the vibration shape at the highest drive frequency is indicated by the shape K5.
As shown in FIG. 9, it can be seen that the size of the vibration shape and the major axis direction of the ellipse that is the vibration shape differ depending on the drive frequency of the piezoelectric elements 11 and 12. Therefore, by changing the driving frequency of the piezoelectric elements 11 and 12, the size and the major axis direction of the elliptical trajectory along which the protrusion 17 of the diaphragm 10 moves can be changed. In other words, by changing the driving frequency of the piezoelectric elements 11 and 12, the tangent S on the outer peripheral surface of the rotor 30 at the contact P described above and the long axis direction line T of the elliptical orbit where the protrusion 17 of the diaphragm 10 moves. Can be matched.
From the above, it has been found that the high driving efficiency of the piezoelectric actuator A1 can be obtained by adjusting the positional relationship between the diaphragm 10 and the rotor 30 and the setting of the driving frequency of the piezoelectric elements 11 and 12.
[0026]
By the way, depending on the product, the drive frequency of the piezoelectric elements 11 and 12 may be set to be constant in advance because of restrictions on the design of the product. In such a case, the optimum driving efficiency of the piezoelectric actuator A1 may be set by adjusting the positional relationship between the diaphragm 10 and the rotor 30 described above. Specifically, the diaphragm 10 and the rotor 30 are arranged such that the long axis direction line T of the elliptical orbit along which the protrusion 17 of the diaphragm 10 moves coincides with the tangent S on the outer peripheral surface of the rotor 30 at the contact P described above. If it is arranged, high driving efficiency can be obtained.
[0027]
In addition, depending on the product, the installation position of the piezoelectric actuator A1 may be limited due to product design restrictions such as a lack of installation space.
In such a case, the optimum driving efficiency of the piezoelectric actuator A1 may be set by adjusting the setting of the driving frequency of the piezoelectric elements 11 and 12 described above. Specifically, by changing the drive frequency of the piezoelectric elements 11 and 12, the long axis direction line T of the elliptical orbit where the projection 17 of the diaphragm 10 moves is tangent to the outer peripheral surface of the rotor 30 at the contact point P described above. By making it coincide with S, it becomes possible to obtain high driving efficiency.
[0028]
[2] Operation of Embodiment Next, the operation of the piezoelectric actuator A1 according to the first embodiment will be described with reference to FIG. 1 and FIG. First, when a voltage is applied from the driving unit S <b> 1 to the diaphragm, the diaphragm 10 vibrates longitudinally due to the expansion and contraction of the piezoelectric elements 11 and 12, and the diaphragm 10 vibrates in a state where the protrusion 17 contacts the rotor 30. Due to this vibration, the protrusion 17 moves along the elliptical orbit, and the rotor 30 is rotated in the direction of the arrow in the drawing along with this displacement.
When the rotor 30 is rotated, the date indicator driving wheel 60 is rotated via the date indicator driving intermediate wheel 40 (see FIG. 1), and the displayed day and day are switched.
[0029]
Here, if the drive frequency of the piezoelectric elements 11 and 12 is set to a frequency between the resonance frequency of the longitudinal vibration of the diaphragm 10 and the resonance frequency of the bending vibration, that is, the piezoelectric element 11 at a drive frequency within such a range. , 12 can easily induce both longitudinal vibration and flexural vibration, and vibrations can be generated in the diaphragm 10 such that the elliptical trajectory along which the protrusion 17 of the diaphragm 10 moves becomes larger. As a result, more efficient rotational driving of the rotor 30 can be obtained.
[0030]
[3] Effects of First Embodiment As described above, according to the present embodiment, on the outer circumference circle of the rotor 30 at the contact point P where the projection 17 of the diaphragm 10 and the outer circumference circle of the rotor 30 contact each other. By setting the positional relationship between the diaphragm 10 and the rotor 30 and the drive frequency of the piezoelectric elements 11 and 12 so that the tangent line S and the major axis T of the elliptical orbit along which the projection 17 of the diaphragm 10 moves are coincident with each other. It becomes possible to obtain high driving efficiency of the piezoelectric actuator A1.
[0031]
[4] Modification [4.1] First Modification In the above-described embodiment, the positional relationship between the diaphragm 10 and the rotor 30, the piezoelectric element 11, and the like so that the piezoelectric actuator A1 can obtain high driving efficiency. Although the drive frequency of 12 is set, even if the piezoelectric actuator A1 is set with high drive efficiency at the time of manufacturing the product, the vibration characteristics of the diaphragm 10 depend on temperature, humidity, etc. The orientation of the ellipse and the like change due to changes in temperature, humidity, and the like at the time of use. Therefore, even if the tangent line S on the outer circumference of the rotor 30 and the long axis direction line T of the elliptical trajectory are made to coincide with each other so that high driving efficiency can be obtained under a certain setting environment, the rotor is changed due to changes in temperature, humidity, and the like. The tangent line S on the outer circumference of the circle 30 and the long axis direction line T of the elliptical orbit are shifted, and the drive efficiency varies.
[0032]
Therefore, in order to suppress the fluctuation range of the driving efficiency of the piezoelectric actuator A1 as much as possible, when the piezoelectric actuator A1 is driven, the driving frequency of the piezoelectric elements 11 and 12 within a predetermined range determined by the driving means S1. You may make it fluctuate by. In this case, for example, in the case of the diaphragm 10 shown in FIG. 10, the range of the driving frequency to be varied is within a frequency range between the resonance frequency of the longitudinal vibration and the resonance frequency of the bending vibration. It is preferable to set so as to fit.
When the drive frequency of the piezoelectric elements 11 and 12 is varied within a predetermined range, the drive frequency may be continuously varied, or may be intermittently varied at a constant frequency. In short, it is only necessary to change the driving frequency to reduce the fluctuation range of the driving efficiency to reduce the driving efficiency that may occur when the temperature, humidity, or the like changes.
[0033]
Even when the driving conditions of the piezoelectric elements 11 and 12 are changed within a predetermined range as in this modification, the environmental conditions such as temperature and humidity change and the vibration characteristics of the diaphragm 10 are changed. It is possible to reduce the fluctuation range of the efficiency and to prevent the driving efficiency from greatly decreasing.
[0034]
[4.2] Second Modification Also, depending on the product, the positional relationship between the diaphragm 10 and the rotor 30 and the setting of the drive frequencies of the piezoelectric elements 11 and 12 may be restricted depending on the design. .
Therefore, the inventor of the present application has provided a notch 19 that cuts in the plane direction of the protrusion 17 of the diaphragm 10 as shown in FIG. I tried an experiment.
As a result of this experiment, it was found that by providing the notch 19 in the protrusion 17, the protrusion 17 is locally bent by the reaction force from the rotor 30 against the longitudinal vibration of the diaphragm 10. It has also been found that the protrusion 17 moves along an elliptical orbit by locally bending the protrusion 17.
Therefore, also in this modification, as in the above-described embodiment, the tangent S on the outer peripheral surface of the rotor 30 at the contact point at which the protrusion 17 of the diaphragm 10 and the outer peripheral surface of the rotor 30 are in contact with each other, If the long axis direction line T of the elliptical orbit along which the protrusion 17 moves is set to coincide, it is possible to obtain high driving efficiency of the piezoelectric actuator A1.
[0035]
In the above-described embodiment, by adjusting the drive frequency of the piezoelectric elements 11 and 12 and the positional relationship between the rotor 30 and the diaphragm 10, the tangent S on the outer peripheral surface of the rotor 30 and the elliptical orbit where the protrusion 17 moves are arranged. Although the major axis direction line T is substantially matched, the method for matching both is not limited to this, and other methods may be used. For example, as shown in FIG. 11, a notch 19 that cuts in the planar direction is provided in the protrusion 17 of the diaphragm 10, and the protrusion 17 is locally bent by a reaction force from the rotor 30 with respect to the longitudinal vibration of the diaphragm 10. Even in the configuration in which the protrusion 17 is moved along the elliptical orbit, the long axis direction line T and the tangent line S of the elliptical orbit may be substantially matched.
[0036]
Hereinafter, in the piezoelectric actuator A1 shown in FIG. 11 with reference to FIGS. 12 and 13, a method of matching the tangent S on the outer peripheral surface of the rotor 30 with the long axis direction line T of the elliptical orbit where the protrusion 17 moves. Will be described.
As shown in FIG. 12, the size of the notch 19 is determined by the depth h of the protrusion 17 in the planar direction and the width t of the notch. Then, the magnitude of the bending vibration excited in the cut portion 19 by the reaction force from the rotor 30 is determined by the cut depth h and the cut width t.
[0037]
Further, the angle ψ shown in FIG. 11 is an angle between a line R passing through the center of the rotor 30 parallel to the longitudinal direction of the diaphragm 10 and a long axis direction line T of the elliptical orbit where the protrusion 17 moves. It is.
Here, FIG. 13 is a graph showing the relationship between the angle ψ and the depth of cut h when the width t of cut is constant. As shown in FIG. 13, the angle ψ increases as the depth of cut h increases. Therefore, by adjusting the depth h of the cut and the width t of the cut, the inclination of the long axis direction line T of the elliptical orbit along which the protrusion 17 moves can be changed.
[0038]
From the above, by changing the notch depth h and the notch width t of the notch 19, the size of the elliptical orbit along which the protrusion 17 moves and the inclination of the major axis T of the ellipse orbit can be changed. Can be changed.
Therefore, by changing the notch depth h and the notch width t, the tangent line S on the outer peripheral surface of the rotor 30 shown in FIG. The angle φ indicated by the difference can be set to be 0 degree.
[0039]
As described above, in this modification, it is possible to change the frequency of the bending vibration generated in the cut portion 19 only by adjusting the cut depth h and the cut width t of the cut portion 19. Since it is possible to obtain a high drive efficiency of the piezoelectric actuator A1, the piezoelectric actuator A1 that can easily adjust the drive efficiency even when it is difficult to adjust the drive efficiency due to design reasons. Can be provided.
[0040]
[4.3] Third Modification In the above-described embodiment, the rotor 30 is illustrated as an example of the drive target of the piezoelectric actuator A1, but the drive target is not necessarily limited to a disk shape such as a rotor. Further, it may be a driving object such as a plate-like body or a rod-like body. In this case, the piezoelectric actuator A1 vibrates the vibration plate 10 and moves the projecting portion 17 as a driving portion along the elliptical orbit to thereby select a driving object such as a plate-like body or a rod-like body that contacts the projecting portion 17. Driving is performed in a predetermined driving direction, for example, a longitudinal direction of a plate-like body or a rod-like body.
[0041]
[4.4] Fourth Modification In the above-described embodiment, the piezoelectric actuator is mounted not only on the calendar display mechanism of the watch as described above but also on a device other than the power-driven watch. It is also possible to use it.
[0042]
【The invention's effect】
As described above, according to the present invention, drive efficiency can be improved without increasing the size.
[Brief description of the drawings]
FIG. 1 is a plan view showing a main configuration of a calendar display mechanism incorporating a piezoelectric actuator in a timepiece according to each embodiment of the present invention.
FIG. 2 is a plan view showing an overall configuration of a piezoelectric actuator.
FIG. 3 is a side sectional view showing a diaphragm that is a component of a piezoelectric actuator.
FIG. 4 is a diagram illustrating a state in which a diaphragm vibrates longitudinally.
FIG. 5 is a diagram for explaining how bending vibration occurs when a diaphragm vibrates.
FIG. 6 is a diagram for explaining the activation of the protrusion during bending vibration.
FIG. 7 is a diagram illustrating a positional relationship between a diaphragm and a rotor.
FIG. 8 is a graph showing the relationship between the angle φ and the drive efficiency of the piezoelectric actuator.
FIG. 9 is a diagram illustrating a vibration shape represented by a longitudinal displacement and a lateral displacement of a protrusion of the diaphragm.
FIG. 10 is a graph showing an example of the relationship between vibration frequency and impedance of a diaphragm.
FIG. 11 is a plan view showing an overall configuration of a piezoelectric actuator in a second modification.
FIG. 12 is a plan view showing a configuration of a protrusion in a second modification.
FIG. 13 is a graph showing a relationship between an angle ψ and a notch depth h in the second modified example.
[Explanation of symbols]
A1: Piezoelectric actuator,
10 ... diaphragm,
17... Projection part (drive part),
18 …… Balance section,
11, 12 ... Piezoelectric element,
13 …… Reinforcing plate (reinforcing part),
30 …… Rotor (drive target),
50 …… Date wheel (calendar display car),
70: Ground plate (support).

Claims (4)

A support;
A vibration plate in which a plate-like piezoelectric element having a longitudinal direction and a reinforcing portion are laminated, and is supported so as to be able to vibrate with respect to the support, and at a position shifted from the center in the width direction on one end side in the longitudinal direction. a vibration plate that have a balance portion projecting from the diaphragm,
The longitudinal direction of the Oite at one end with a certain balanced portion the side opposite to the diaphragm, provided at a position shifted to the side opposite to the side with the balance portion in the width direction from the center in the width direction, driven and allowed to contact a surface facing to the driven object is curved, and a position near Ru driver the contacts are offset from the center of the width direction of the driven,
A piezoelectric actuator that drives the drive object in contact with the drive unit in a predetermined drive direction by vibrating the diaphragm and moving the drive unit along an elliptical orbit,
Driving means for supplying electric power to the piezoelectric element to vibrate the diaphragm;
The driving means vibrates the diaphragm so that the major axis direction of the elliptical orbit is substantially coincident with the predetermined driving direction,
The driving frequency for driving the piezoelectric element is a resonance frequency of longitudinal vibration in which the diaphragm expands and contracts in the longitudinal direction due to vibration of the piezoelectric element, and the diaphragm swings in a width direction orthogonal to the longitudinal direction. A piezoelectric actuator having a frequency between a resonance frequency of bending vibration. The piezoelectric actuator according to claim 1,
The piezoelectric actuator, wherein the drive frequency is varied between a resonance frequency of the longitudinal vibration and a resonance frequency of the bending vibration. The piezoelectric actuator according to claim 1 or 2,
A timepiece comprising a ring-shaped calendar display wheel driven to rotate by the piezoelectric actuator. The piezoelectric actuator according to claim 1 or 2,
And a power supply for supplying power to the piezoelectric actuator.

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