JP2003219667A - Driving method of piezoelectric actuator, drive control circuit of piezoelectric actuator, clock and portable electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power required for driving a piezoelectric actuator. <P>SOLUTION: A drive control circuit 82 controls a drive circuit 80 such that a positive voltage is applied to a piezoelectric actuator A1 only during a drive interval R<SB>2</SB>where kinetic energy must be transmitted to a rotor 100 in a period where the protrusion 36 of the piezoelectric actuator A1 is touching the rotor 100. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator driving method, a piezoelectric actuator drive control circuit, a timepiece, and a portable electronic device.

[0002]

2. Description of the Related Art Since a piezoelectric element is excellent in conversion efficiency from electric energy to mechanical energy and responsiveness, various piezoelectric actuators utilizing the piezoelectric effect of the piezoelectric element have been developed in recent years. This piezoelectric actuator is applied to the field of portable electronic devices such as wristwatches and mobile phones.

[0003]

By the way, the portable electronic equipment as described above uses a battery as a power source. In addition, a portable electronic device that is required to be particularly small and lightweight can only be provided with a battery having a small capacity. Therefore, when the piezoelectric actuator is provided in the portable electronic device, the electric energy stored in the battery is consumed by the piezoelectric actuator, so that the continuous operation time of the portable electronic device is shortened.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric actuator driving method, a piezoelectric actuator drive control circuit, a timepiece, and a portable electronic device which can reduce power consumption. .

[0005]

In order to achieve the above object, the present invention is to vibrate a piezoelectric actuator having a contact portion that comes into contact with the circumference of a rotatable disk together with the contact portion by applying a voltage. Then, when the first step of rotating the disc and the velocity component of the vibration have a component that coincides with the rotation direction of the disc, the velocity component in the tangential direction of the circumferential portion of the velocity component of the vibration. 2) estimating whether or not is lower than the peripheral speed of the circumferential portion
There is provided a method for driving a piezoelectric actuator, comprising: a step; and a third step of interrupting application of a voltage of a polarity that brings the contact portion into contact with the circumferential portion when the estimation result is affirmative.

In order to achieve the above object, the present invention is directed to vibrate a piezoelectric actuator having a contact portion that comes into contact with a circumferential portion of a rotatable disc together with the contact portion to rotate the disc. When the first voltage applying means for applying a voltage to the piezoelectric actuator and the velocity component of the vibration have a component that coincides with the rotation direction of the circumferential portion, the circumference of the velocity component of the vibration is The tangential velocity component of the part, it is estimated whether or not the peripheral speed of the circumferential portion is lower than the circumferential speed, if the estimation result is affirmative, the voltage of the polarity to contact the contact portion to the circumferential portion. And a voltage interruption means for interrupting the application of the piezoelectric actuator.

In general, of the velocity components of the contact portion, while the tangential velocity component of the circumferential portion exceeds the circumferential velocity of the circumferential portion, the contact portion is decelerated by friction with the circumferential portion of the disk. Therefore, this speed component is also decelerated. Here, the contact portion applies the rotational force to the disc only during the period when the velocity component exceeds the circumferential velocity of the circumferential portion. In the past,
Even if the velocity component is lower than the circumferential velocity of the circumferential portion, the voltage of the polarity that makes the contact portion contact the circumferential portion is applied. On the other hand, according to the piezoelectric actuator drive method and the piezoelectric actuator drive control circuit of the present invention, the application of the drive voltage is stopped when the tangential velocity component of the contact portion is lower than the tangential velocity of the circumferential portion. Therefore, useless power consumption is prevented. Here, in the above-described piezoelectric actuator driving method and piezoelectric actuator drive control circuit, when the tangential velocity component of the contact portion is lower than the tangential velocity of the circumferential portion, the polarity of separating the contact portion from the circumferential portion is set. A configuration in which a voltage is applied to the piezoelectric actuator is desirable. More specifically, as described above, when the tangential velocity component of the contact portion is lower than the tangential velocity of the circumferential portion, if the contact portion is in contact with the circumferential portion of the disc, the rotation of the disc is suppressed. Will be done. Therefore, by promptly separating the contact portion from the circumferential portion of the disk, it is possible to prevent the rotation of the disk from being suppressed.

In the above-mentioned piezoelectric actuator driving method, in the second step, when a predetermined time has elapsed from the start of voltage application to the piezoelectric actuator, among the velocity components of the vibration,
It is desirable to estimate that the tangential velocity component of the circumferential portion is lower than the circumferential velocity of the circumferential portion. Further, in the second step, a velocity characteristic showing a time series variation of a velocity component in a tangential direction of the circumferential portion among velocity components of the vibration when the piezoelectric actuator rotates the disk, Whether the tangential velocity component of the circumferential portion of the velocity components of the vibration is lower than the circumferential velocity of the circumferential portion in accordance with the previously measured correspondence with the circumferential velocity of the circumferential portion. It is also desirable that

In the above-mentioned method for driving a piezoelectric actuator, after the application of the voltage of the polarity for contacting the contact portion with the circumferential portion is interrupted in the third step,
A fourth step of estimating whether or not the circumferential velocity of the circumferential portion is higher than the tangential velocity component of the circumferential portion among the velocity components of the vibration, and if the estimation result is affirmative, A fifth step of restarting the application of a voltage of a polarity that brings the contact portion into contact with the circumferential portion is desirable. More specifically, in the fourth step, the third
In step, after the application of the voltage of the polarity for contacting the contact portion with the circumferential portion is interrupted, when a predetermined time has elapsed, the circumferential velocity of the circumferential portion is the velocity component of the vibration. , It is estimated that the velocity component exceeds the tangential velocity component of the circumferential portion. Furthermore, in the fourth step, a velocity characteristic indicating a time series variation of a velocity component in a tangential direction of the circumferential portion, of the velocity components of the vibration when the piezoelectric actuator rotates the disk, Whether the circumferential velocity of the circumferential portion exceeds the tangential velocity component of the circumferential portion among the velocity components of the vibration according to a previously measured correspondence with the circumferential velocity of the circumferential portion. It may be estimated.

On the other hand, in the above-mentioned piezoelectric actuator drive control circuit, after the voltage interruption means interrupts the application of the voltage of the polarity for bringing the contact portion into contact with the circumferential portion,
The circumferential velocity of the circumferential portion, of the velocity component of the vibration, is estimated whether it is higher than the tangential velocity component of the circumferential portion, if the estimation result is affirmative, in the piezoelectric actuator On the other hand, it is desirable to further include a second voltage applying unit that restarts the voltage application of the polarity that brings the contact portion into contact with the circumferential portion. Specifically, when the second voltage applying unit has interrupted the application of the voltage of the polarity for contacting the contact portion with the circumferential portion by the voltage interrupting unit, a predetermined time has elapsed. It is estimated that the peripheral velocity of the circumferential portion is higher than the tangential velocity component of the circumferential portion among the velocity components of the vibration.

Generally, when the contact portion of the piezoelectric actuator starts contacting the disk, of the velocity components of the contact portion,
The tangential velocity component of the circumferential part is smaller than the circumferential velocity, and then the contact part is accelerated by the frictional force with the disk,
This velocity component almost reaches the circumferential velocity of the disk. In the past, the drive voltage was applied to the piezoelectric actuator when the contact section began to contact the disk, but this contact section applies rotational force to the disk while this speed component is smaller than the peripheral speed. No electric power is supplied, and useless electric power is supplied to the piezoelectric actuator.

On the other hand, according to the piezoelectric actuator driving method and the piezoelectric actuator drive control circuit of the present invention, the peripheral velocity of the disk is a velocity component in the tangential direction of the circumferential portion of the velocity components of the vibration. Is exceeded, and if the result of this estimation is affirmative, the voltage application to the piezoelectric actuator is restarted.
Therefore, since the electric power is supplied to the piezoelectric actuator only during the period when the contact portion can apply the rotational force to the disk,
It is possible to prevent unnecessary power supply to the piezoelectric actuator.

In the piezoelectric actuator drive control circuit, among the speed components of the vibration when the piezoelectric actuator rotates the disk,
The voltage interrupting means further includes: a speed characteristic that shows a change in the tangential direction speed component of the circumferential portion in time series; and a storage unit that stores the circumferential speed of the circumferential portion. From the circumferential velocity, it is estimated whether, of the velocity components of the vibration, the tangential velocity component of the circumferential portion is lower than the circumferential velocity of the circumferential portion, and the second voltage applying means It is also preferable that the circumferential speed of the circumferential portion is higher than the tangential speed component of the circumferential portion of the velocity components of the vibration. According to this configuration, since the piezoelectric actuator drive control circuit does not need to include a speed detection device that detects the speed of each of the contact portion and the disk,
The configuration of the piezoelectric actuator drive control circuit can be simplified, and the size of the piezoelectric actuator drive control circuit can be suppressed to be compact.

Further, in the above-mentioned piezoelectric actuator drive control circuit, the storage means stores the circumferential portion of the velocity component of the vibration when the normally operating piezoelectric actuator rotates the disk by the vibration. The velocity component in the tangential direction and the voltage value of the potential induced according to the displacement of the bending vibration on the surface of the plate-shaped piezoelectric element included in the normally operating piezoelectric actuator are stored in association with each other, and the piezoelectric element to be driven is stored. The voltage acquisition means for acquiring the voltage value of the potential induced on the surface of the piezoelectric element included in the actuator, and the piezoelectric element to be driven according to the difference between the acquired voltage value and the stored voltage value. A configuration including a frequency control unit that adjusts the frequency of the drive voltage applied to the actuator is also desirable.

Generally, the velocity component in the tangential direction of the contact portion depends on the displacement of the bending vibration, and the displacement of the bending vibration depends on the frequency of the drive voltage applied to the piezoelectric actuator. Therefore, according to this configuration, when the voltage value of the piezoelectric actuator to be driven deviates from the voltage value of the piezoelectric actuator that operates normally, that is, the tangential velocity component of the contact portion of the piezoelectric actuator to be driven is When there is a deviation from the normal value, the frequency of the drive voltage is adjusted so as to cancel the deviation, so that the piezoelectric actuator to be driven operates normally (specifically, in the tangential direction of the contact portion). It is driven so that the velocity component becomes a normal value.

In the piezoelectric actuator drive control circuit described above, the voltage applied to the piezoelectric actuator may be a pulse voltage. Further, the piezoelectric actuator drive control circuit described above is preferably provided in a timepiece provided with a timepiece, such as a hand for indicating the time and a calendar display mechanism for displaying the date, and a portable device driven by the piezoelectric actuator. It is also desirable to be provided in a portable electronic device with a portable electronic device element.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments,
A case where a piezoelectric actuator attached to a calendar display mechanism of a wristwatch is driven will be exemplified.

FIG. 1 is a plan view showing the main structure of a calendar display mechanism of a wrist watch according to an embodiment of the present invention. The piezoelectric actuator A1 is generally composed of a diaphragm 10 and a rotor 100 that vibrate in an in-plane direction (direction parallel to the paper surface of the drawing). The rotor 100 is rotatably supported by the main plate 103 and is arranged at a position where it abuts on the vibration plate 10. When the outer peripheral surface of the rotor 100 is struck by vibration generated in the vibration plate 10, the rotor 100 moves in a direction indicated by an arrow in the figure. It is designed to be rotated.

The calendar display mechanism is connected to the piezoelectric actuator A1 and is driven by its driving force. The main part of the calendar display mechanism is roughly composed of a reduction gear train that reduces the rotation of the rotor 100 and a ring-shaped date wheel 50. The reduction gear train includes a date driving intermediate wheel 40 and a date driving wheel 60. Here, when the diaphragm 10 vibrates in the in-plane direction as described above, the rotor 100 in contact with the diaphragm 10 is rotated in the clockwise direction. The rotation of the rotor 100 is transmitted to the date driving wheel 60 via the date driving intermediate wheel 40, and the date driving wheel 60 is driven by the date driving wheel 50.
Rotate clockwise.

FIG. 2 is a top view showing the structure of the piezoelectric actuator A1. As shown in the figure, the piezoelectric actuator A1 includes a long plate-shaped vibrating plate 10 formed long in the left-right direction of the figure, and the vibrating plate 10 as a base plate 103 (see FIG. 1).
And a support member 11 for supporting the. A protrusion 36 made of stainless steel or the like is provided on the end portion 35 in the longitudinal direction of the diaphragm 10 so as to protrude toward the rotor 100. The protrusion 36 contacts the outer peripheral surface of the rotor 100. There is. By providing such protrusions 36, the weight balance of the diaphragm 10 is unbalanced, and the protrusions 36 move along an elliptical orbit as described later.

One end portion 37 of the support member 11 is attached to the rotor 100, which is slightly closer to the rotor 100 side than the longitudinal center thereof. The other end 38 of the support member 11 has a screw 39
Is supported by the main plate 103 (see FIG. 1). Under this structure, the support member 11 supports the diaphragm 10 in a state of being urged toward the rotor 100 by its elastic force,
As a result, the protrusion 36 of the diaphragm 10 is brought into contact with the side surface of the rotor 100. When the protruding portion 36 brought into contact with the rotor 100 is displaced in this manner, the rotor 100 and the protruding portion 3 are also caused by friction between the rotor 100 and the protruding portion 36.
6, and is driven to rotate in the direction indicated by the arrow in FIG.

As shown in FIG. 3, the vibrating plate 10 has the same shape as the piezoelectric elements 30 and 31 between the two rectangular piezoelectric elements 30 and 31, and the piezoelectric elements 30 and 31 have the same shape.
Reinforcing plate 32 made of stainless steel or the like having a smaller wall thickness than 31
Has a laminated structure. As the reinforcing plate 32, one having a smaller wall thickness than the piezoelectric elements 30 and 31 is used so that the vibration of the piezoelectric elements 30 and 31 is not disturbed as much as possible. Piezoelectric elements 30, 3 arranged vertically
An electrode 33 is formed on each of the surfaces 1. The drive circuit 80 controls the electrodes 33 under the control of the drive control circuit 82.
Electric power is supplied to the drive circuit piezoelectric elements 30 and 31 via the. The details of the drive control circuit 82 will be described later.

Here, as the piezoelectric elements 30 and 31, lead zirconate titanate (PZT (trademark)), crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, zinc niobium are used. Lead acid ((Pb (Zn1 / 3-Nb2 / 3) 03 1-x-Pb Ti03 x) x depends on the composition. X = 0.09), lead scandium niobate ((Pb
((Sc1 / 2Nb1 / 2) 1-x Tix)) 03) x depends on the composition. x
= About 0.09) etc. can be used.

The vibrating plate 10 having such a structure vibrates when the driving circuit 80 applies an AC voltage to the piezoelectric elements 30 and 31 through the electrodes 33, and the piezoelectric elements 30 and 31 expand and contract to vibrate. Has become. At that time, as shown in FIG. 4, the diaphragm 10 is adapted to vibrate by longitudinal vibration that expands and contracts in the longitudinal direction.
It will vibrate in the direction indicated by the middle arrow. When an alternating voltage is applied to the piezoelectric elements 30 and 31 in this way to excite longitudinal vibration, bending vibration in the width direction is induced in the vibrating plate 10 due to the imbalance of the weight balance of the vibrating plate 10, as shown in FIG. Will be done. Specifically, when the vibration plate 10 vibrates longitudinally, a rotational moment about its fulcrum (the center of gravity when no load is applied) acts, and the bending vibration as shown in the drawing is induced in the vibration plate 10. ing. When such vertical vibrations and bending vibrations occur and are combined, the contact portion of the protrusion 36 of the diaphragm 10 with the outer peripheral surface of the rotor 100 moves along an elliptical orbit as shown in FIG. Will be done.

Meanwhile, when the rotor 100 is rotationally driven by the piezoelectric actuator A1, the inertial force of the rotor 100 is larger than the inertial force of the piezoelectric actuator A1. Therefore, as shown in FIG. In, the tangential velocity (peripheral velocity) Vr of the rotor 100 is considered to be constant. On the contrary,
Of the speed components of the protrusions 36 after the rotor 100 is rotationally driven, the tangential speed Va, which is the speed component in the tangential direction of the circumference of the rotor 100, should be considered from the speed fluctuations in the following four periods. You can That is, the acceleration period R1
A driving period R2, a deceleration period R3, and a leaving period R4.

Acceleration period R1, drive period R2, deceleration period R
Each of the periods 3 is a period in which the protrusion 36 is in contact with the rotor 100 due to the extension of the piezoelectric actuator A1. To further explain, during the acceleration period R1, the protrusion 36
Is a period during which the frictional force drags the rotor 100 to the rotational movement of the rotor 100 to accelerate the tangential velocity Va of the protrusion 36. And this acceleration period R
1, the tangential velocity Va of the protrusion 36 is
It is accelerated to a velocity that is substantially equal to the tangential velocity Vr of 0.
During the driving period R2, the tangential velocity Va of the protrusion 36 is equal to the rotor 1
00 is higher than the tangential velocity Vr of 00, and during this period, the kinetic energy of the protrusion 36 is in the rotor 10
0, and the rotor 100 is rotationally driven (that is, a rotational force is applied to the rotor 100). Then, the deceleration period R3 is a period in which the tangential velocity Va of the protrusion 36 is decelerated by the frictional force with the rotor 100 and falls below the tangential velocity Vr of the rotor 100. The withdrawal period R4 is
This is a period during which the protrusion 36 is separated from the rotor 100. More specifically, during the detachment period R4, the piezoelectric actuator A1 contracts in the longitudinal direction, so that the protrusion 36 detaches from the rotor 100. Further, the tangential velocity Va of the protrusion 36 has a negative value. The tangential velocity Va having a negative value means that the rotor 100 moves in a direction opposite to the rotation direction of the rotor 100. Each of these periods R1 to R4
The time length of is obtained from the speed measurement result of the protrusion 36 by a speed measuring device such as a laser Doppler vibrometer.

More specifically, as shown in FIG. 8, by using two laser Doppler vibrometers 300-X and 300-Y, the time lengths of the respective periods R1 to R4 can be obtained. Laser Doppler Vibrometer 300-X
Irradiates the projection 36 of the piezo-electric actuator A1 that is being driven with vibration from the X-axis direction with the laser beam Rx, and determines the movement speed of the projection 36 in the X-axis direction at regular intervals from the Doppler shift amount of the return light. And output sequentially.

On the other hand, laser Doppler vibrometer 300-Y
Are two laser beams Ry1 and Ry from the X-axis direction toward the protrusion 36 of the piezoelectric actuator A1 that is being driven by vibration.
Irradiate y2. Here, the laser beam Ry2 is obtained by splitting the laser beam Ry1 with a beam splitter or the like, and has the same phase as the laser beam Ry1. The laser Doppler vibrometer 300-Y detects the movement speed of the protrusion 36 in the Y-axis direction at regular time intervals from the time variation of interference fringes (fringes) obtained by interfering the respective return lights, and at each time interval. To Y-axis speed signal. Thus, X from the laser Doppler vibrometer 300-X
The tangential velocity Va of the protrusion 36 is obtained from the axial velocity signal and the Y-axis velocity signal from each of 300-Y, and the velocity characteristic as shown in FIG. 7 is thereby obtained. Then, this velocity characteristic and the tangential velocity V of the rotor 100 measured separately
From r, the acceleration period R1, the driving period R2, and the deceleration period R3
And the respective lengths of the withdrawal period R4 are specified.

In this embodiment, the drive control circuit 82
Is a control unit such as a CPU (Central Processing Unit) and a RAM (Random Access Memory) or a ROM (Read O
nly Memory) and the like. This storage unit stores the time length of each of the periods R1 to R4 and the time length T required for the protrusion 36 to make one round of the elliptical orbit (hereinafter, simply referred to as “cycle T”). Note that the time lengths and periods T of the periods R1 to R4 stored in the storage unit are measured for a large number of piezoelectric actuators A1 even if they are measurement values obtained by measurement for the piezoelectric actuator A1 that operates normally. It may be an average value of the measured values obtained by performing the above, or may be a theoretically determined design value.

Under this structure, the drive control circuit 82 controls the drive circuit 80 to adjust the voltage applied to the piezoelectric actuator A1 in each of the periods R1 to R4, so that the electric power for driving the piezoelectric actuator A1 is controlled. Are being reduced. More specifically, as shown in FIG. 9, the drive control circuit 82 controls the drive circuit 80 to rotate the rotor 100 at a constant tangential velocity Vr, so that the time corresponding to the period T of the piezoelectric actuator A1 elapses. Drive normally until. Specifically, the drive control circuit 8
0 controls the drive circuit 80 so that the voltage v applied to the piezoelectric actuator A1 becomes a step pulse of one cycle. The piezoelectric actuator A1 is adapted to extend in the longitudinal direction when a positive voltage is applied, and the protrusion 36
Is contacted with the rotor 100, and when a negative voltage is applied, the piezoelectric actuator A1 contracts in the longitudinal direction, and the protrusion 36 separates from the rotor 100. As a result, the protrusion 36 of the piezoelectric actuator A1 moves only once along the elliptical orbit, and the rotor 100 is rotationally driven.

Next, the drive control circuit 82 continues until the time corresponding to the acceleration period R1 elapses from the time T (time t
1), do not apply voltage to the piezoelectric actuator A1. From time T to t1, since the protrusion 36 of the piezoelectric actuator A1 is in contact with the rotor 100, it is accelerated by being dragged by the rotational movement of the rotor 100, and the tangential velocity Va of the protrusion 36 is also the rotor 1.
The tangential velocity Vr of 00 is substantially equal to Vr.

Next, the drive control circuit 82 continues from the time t1 until the time corresponding to the drive period R2 elapses (time t
2), the drive circuit 80 is controlled to control the piezoelectric actuator A1.
A positive voltage is applied to. That is, since the piezoelectric actuator A1 is oscillated by the drive circuit 80, the kinetic energy of the protrusion 36 increases, and the tangential velocity Va becomes higher than the tangential velocity Vr of the rotor 100. Therefore,
Due to the protrusion 36, the rotor 10 of the piezoelectric actuator A1
Kinetic energy is transmitted to 0, and the rotary motion of the rotor 100 is maintained.

The drive control circuit 82 does not apply a voltage to the piezoelectric actuator A1 until the time corresponding to the deceleration period R3 has elapsed from the time t2 (time t3). At times t2 to t3, the protrusion 36 is decelerated by friction caused by contact with the rotor 100, and the protrusion 36
Of the rotor 100 is lower than the tangential velocity Vr of the rotor 100.

Then, the drive control circuit 82 continues from the time t3 until the time corresponding to the leaving period R4 elapses (time t
4), the drive circuit 80 is controlled to control the piezoelectric actuator A.
A negative voltage is applied to 1. As a result, the piezoelectric actuator A1 contracts in the longitudinal direction, so that the protrusion 36 is formed on the rotor 10.
Leave from 0. As described above, by applying the negative voltage during the disengagement period R4, the protrusion 36 decelerated by friction is applied.
Is quickly disengaged from the rotor 100, so that the protrusion 36 is prevented from restraining the rotational movement of the rotor 100.

As described above, the drive control circuit 8 of this embodiment
2 controls the drive circuit 80 so that the positive voltage is applied to the piezoelectric actuator A1 only during the drive period R2 during which the kinetic energy should be transmitted to the rotor 100, while the protrusion 36 is in contact with the rotor 100. To do. On the other hand, when the piezoelectric actuator A1 is normally driven, as shown in FIG.
As shown in, the positive voltage is applied to the piezoelectric actuator A1 during the period in which the protrusion 36 is in contact with the rotor 100. Therefore, according to the present embodiment, the electric power required for driving is reduced as compared with the case where the piezoelectric actuator A1 is always driven normally. For example, the period during which the protrusion 36 is in contact with the rotor 100 is Ta, the time length of the acceleration period R1 is T1, the time length of the driving period R2 is T2, the time length of the deceleration period R3 is T3, and T1 = T2 = T3. = Ta / 2
Then, if the applied power is constant (= P), (power for driving only during the driving period R2) / (power required for normal driving) = (T2 × P) / (Ta × P) = 1/2 Therefore, according to the driving of this embodiment, the electric power for driving the piezoelectric actuator A1 can be suppressed to half the electric power required for the normal driving. Although the drive control circuit 82 includes a CPU and a storage device and performs digital processing in the present embodiment, the drive control circuit 82 is not limited to this. The drive control circuit 82 includes a plurality of electric circuits. May be.

<Modification> The above-mentioned embodiment shows one aspect of the present invention, and can be arbitrarily modified within the scope of the present invention. Therefore, various modifications will be described below.

(Modification 1) In the above-described embodiment,
Although the case where the present invention is applied to the driving of the piezoelectric actuator A1 incorporated in the calendar mechanism of the wristwatch is illustrated, the present invention is applicable to the driving of the actuator incorporated in any portable electronic device and the fixing device. . For example, in addition to a wristwatch, there are driving a thin actuator used for oscillating a vibrator included in a mobile phone and driving a thin actuator for moving a character in a picture book or a greeting card.

(Modification 2) In the above-described embodiment,
The case where the pulse voltage is applied to the piezoelectric actuator A1 has been illustrated, but the present invention is not limited to this. That is, FIG.
As shown in FIG. 7, the present embodiment may be modified so that the voltage waveform becomes a sine wave in the driving period R2 and the leaving period R4, or the present embodiment may be modified so that a plurality of pulse voltages are applied. You may. Further, as shown in FIG. 11, a minute voltage pulse having density depending on the applied voltage value may be applied. That is, the drive circuit 80
Applies fine pulses densely when increasing the applied voltage value. With such a configuration, the drive section R
Since the applied voltage value is finely adjusted in 2 and the separation section R4, the timing at which the applied voltage should be applied can be adjusted more accurately. Also, with this configuration,
The drive control circuit 82 can adjust the magnitude of the applied voltage value.
Therefore, in the drive section R2, a larger applied voltage is applied to the piezoelectric actuator A in accordance with the timing at which the drive control circuit 82 should transfer kinetic energy to the rotor 100.
The drive circuit 80 can be controlled so that the piezoelectric actuator A1 is applied to the rotor 10.
The driving force for driving 0 can be increased.

(Modification 3) In the above-described embodiment, the projection 36 of the piezoelectric actuator A1 is assumed to move along an elliptical orbit previously measured. However, when the piezoelectric actuator A1 is attached to the calendar mechanism, depending on how the piezoelectric actuator A1 is attached, the protrusion 36
May not follow the elliptical orbit, which may hinder the driving of the rotor 100. Therefore, when the piezoelectric actuator A1 is driven, the protrusion 36
In the case where A moves out of the elliptical orbit, the drive control circuit 82 preferably controls the drive circuit 80 so that the trajectory of the protrusion 36 is corrected. More specifically, as shown in FIG. 12, in addition to the electrode 33, minute electrodes 33a and 33b are provided on the upper surface of the piezoelectric actuator A1. The minute electrode 33a is provided at one end of the piezoelectric actuator A1, while the minute electrode 33b is provided.
Is provided at the other end, and the minute electrodes 33a, 33
Each of b is provided so as to be point-symmetric with respect to the center point of the piezoelectric actuator A1 in the longitudinal direction. Each of the minute electrodes 33a and 33b is connected to the drive control circuit 82, and the drive control circuit 82 controls the minute electrodes 33a and 33b.
Each voltage value of b is detected, and the frequency of the voltage applied to the piezoelectric actuator A1 is adjusted according to the detection result.

More specifically, the minute electrodes 33a, 33
The voltage value of the potential induced in b is the piezoelectric actuator A
1 according to the displacement of the bending vibration. The displacement of the flexural vibration depends on the frequency of the voltage applied to the piezoelectric actuator A1. Therefore, at the time of measuring the elliptical orbit with respect to the protrusion 36 of the piezoelectric actuator A1 that operates normally, the voltage value response characteristics of each of the micro electrodes 33a and 33b are measured, and the measured voltage value response characteristics are driven. It is stored in the control circuit 82. Under this configuration, when the drive control circuit 82 controls the drive circuit 80 to drive the piezoelectric actuator A1, the minute electrodes 33
The drive circuit 80 is controlled so as to adjust the frequency of the voltage applied to the piezoelectric actuator A1 when the voltage values detected from a and 33b are compared with the above-mentioned voltage value response characteristics and the difference between them is large. . Then, the drive circuit 80 adjusts the frequency of the voltage applied to the piezoelectric actuator A1 under the control of the drive control circuit 82. As a result, the displacement of the flexural vibration of the piezoelectric actuator A1 is adjusted, and the protrusion 3
2 is adjusted to move along an elliptical orbit. That is, even if the tangential velocity Va of the protrusion 36 deviates from the normal value, the frequency of the applied voltage is adjusted so as to cancel the displacement, so that the tangential velocity Va of the protrusion 36 is driven to the normal value. To be done.

[0041]

As described above, according to the present invention,
Driving method of piezoelectric actuator capable of reducing power consumption,
A piezoelectric actuator drive control circuit, a timepiece, and a portable electronic device are provided.

[0042]

[Brief description of drawings]

FIG. 1 is a plan view showing a main configuration of a calendar display mechanism including a piezoelectric actuator in a wristwatch.

FIG. 2 is a plan view showing the overall configuration of the piezoelectric actuator.

FIG. 3 is a side sectional view showing a driving configuration of the piezoelectric actuator.

FIG. 4 is a diagram showing how the diaphragm vibrates vertically.

FIG. 5 is a diagram for explaining flexural vibration induced by longitudinal vibration of the diaphragm.

FIG. 6 is a diagram showing how the protrusion of the piezoelectric actuator operates.

FIG. 7 is a diagram showing time characteristics of a tangential velocity of a rotor and a tangential velocity of a protrusion of a piezoelectric actuator.

FIG. 8 is a diagram for explaining a method of measuring a time characteristic with respect to a tangential velocity of a protrusion of the piezoelectric actuator.

FIG. 9 is a diagram for explaining a driving method of the piezoelectric actuator according to the embodiment of the present invention.

FIG. 10 is a diagram for explaining a driving method of the piezoelectric actuator according to Modification 2 of the present invention.

FIG. 11 is a diagram for explaining a driving method of the piezoelectric actuator.

FIG. 12 is a diagram showing a drive configuration of a piezoelectric actuator according to Modification 3 of the present invention.

[Explanation of symbols]

A1 ... Piezoelectric actuator, 10 ... Vibration plate, 11 ... Support member, 36 ... Projection part, 30 ... Piezoelectric element, 32 ... Reinforcing plate,
33 ... Electrodes, 33a, 33b ... Micro electrodes, 80 ... Drive circuit, 82 ... Drive control circuit, 100 ... Rotor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Seto             Seiko, 3-3-3 Yamato, Suwa City, Nagano Prefecture             -In Epson Corporation F term (reference) 2F082 AA01 BB02 DD03 DD10 EE02                       EE05 FF01 HH00                 5H680 AA06 BB02 BC02 CC02 FF32                       FF37 FF38

Claims (17)

[Claims] 1. A first step of rotating a disk by vibrating a piezoelectric actuator, which includes a contact portion that contacts a circumferential portion of a rotatable disk, together with the contact portion by applying a voltage, and a speed of the vibration. In the case where the component has a component that coincides with the rotation direction of the disk, whether the velocity component in the tangential direction of the circumferential portion of the velocity component of the vibration is lower than the circumferential velocity of the circumferential portion. And a third step of interrupting the application of the voltage of the polarity for contacting the contact portion with the circumferential portion when the result of this estimation is affirmative. Driving method. 2. The driving of the piezoelectric actuator according to claim 1, wherein in the third step, a voltage having a polarity that separates the contact portion from the circumferential portion is applied to the piezoelectric actuator. Method. 3. In the second step, when a predetermined time elapses after the voltage application to the piezoelectric actuator is started, a velocity of the vibration in the tangential direction of the circumferential portion, of the velocity components of the vibration. The method for driving a piezoelectric actuator according to claim 1, wherein the component is estimated to be lower than the peripheral velocity of the circumferential portion. 4. In the second step, a velocity indicating a change in a velocity component in a tangential direction of the circumferential portion in a time series among the velocity components of the vibration when the piezoelectric actuator rotates the disk. According to the characteristic and the previously measured correspondence between the circumferential speed of the circumferential portion, the speed component of the vibration in the tangential direction of the circumferential portion is lower than the circumferential speed of the circumferential portion. 3. The method for driving a piezoelectric actuator according to claim 1, wherein it is estimated whether or not there is. 5. The method according to claim 3, wherein after the application of the voltage of the polarity for contacting the contact portion with the circumferential portion is interrupted in the third step, the circumferential velocity of the circumferential portion is the vibration velocity component among the velocity components of the vibration. A fourth step of estimating whether or not the tangential velocity component of the circumferential portion is exceeded, and if the result of this estimation is affirmative, the application of a voltage of a polarity that brings the contact portion into contact with the circumferential portion is restarted. The method for driving a piezoelectric actuator according to claim 1, further comprising a fifth step of: 6. In the fourth step, when a predetermined time has elapsed after the application of the voltage of the polarity for contacting the contact portion with the circumferential portion in the third step is stopped, the circle The method of driving a piezoelectric actuator according to claim 5, wherein it is estimated that the peripheral velocity of the peripheral portion is higher than the tangential velocity component of the circumferential portion among the velocity components of the vibration. 7. The velocity, in the fourth step, which indicates, in a time series, a variation in a velocity component in a tangential direction of the circumferential portion, of the velocity components of the vibration when the piezoelectric actuator rotates the disk. According to the previously measured correspondence between the characteristics and the circumferential speed of the circumferential portion, the circumferential speed of the circumferential portion is higher than the tangential velocity component of the circumferential portion among the velocity components of the vibration. The method for driving a piezoelectric actuator according to claim 5, wherein it is estimated whether or not it has occurred. 8. A first actuator for applying a voltage to the piezoelectric actuator so as to rotate the disk by vibrating the piezoelectric actuator together with the contact portion, the piezoelectric actuator having a contact portion that contacts a circumferential portion of a rotatable disk. When the voltage applying means and the velocity component of the vibration have a component that coincides with the rotation direction of the circumferential portion, the velocity component in the tangential direction of the circumferential portion among the velocity components of the vibration is the circumferential portion. And a voltage interrupting means for interrupting the application of the voltage of the polarity for bringing the contact portion into contact with the circumferential portion when the result of the estimation is affirmative. A piezoelectric actuator drive control circuit characterized by the above. 9. The piezoelectric actuator drive control circuit according to claim 8, wherein the voltage interrupting means applies a voltage having a polarity that separates the contact portion from the circumferential portion to the piezoelectric actuator. . 10. The voltage interrupting means, when a predetermined time has elapsed after the first voltage applying means starts applying voltage to the piezoelectric actuator,
The piezoelectric actuator according to claim 8 or 9, wherein, of the velocity components of the vibration, a velocity component in a tangential direction of the circumferential portion is estimated to be lower than a circumferential velocity of the circumferential portion. Drive control circuit. 11. The voltage interrupting means interrupts application of a voltage of a polarity for contacting the contact portion with the circumferential portion,
The circumferential velocity of the circumferential portion, of the velocity component of the vibration, is estimated whether it is higher than the tangential velocity component of the circumferential portion, if the estimation result is affirmative, in the piezoelectric actuator On the other hand, second voltage applying means for restarting the voltage application of the polarity for bringing the contact portion into contact with the circumferential portion,
The piezoelectric actuator drive control circuit according to claim 10, further comprising: 12. The second voltage applying means, when a predetermined time has elapsed after the voltage interrupting means interrupts the application of the voltage of the polarity for bringing the contact portion into contact with the circumferential portion. The piezoelectric actuator drive control circuit according to claim 11, wherein it is estimated that the peripheral velocity of the circumferential portion is higher than the tangential velocity component of the circumferential portion in the velocity component of the vibration. . 13. Among the velocity components of the vibration when the piezoelectric actuator rotates the disk,
Further, a velocity characteristic indicating a change in a tangential velocity component of the circumferential portion in time series, and a storage unit that stores the circumferential velocity of the circumferential portion, the voltage interruption unit, the voltage characteristic From the circumferential velocity, it is estimated whether, of the velocity components of the vibration, a tangential velocity component of the circumferential portion is lower than the circumferential velocity of the circumferential portion, and the second voltage application unit 12. The piezoelectric actuator drive control according to claim 11, wherein it is estimated whether the peripheral velocity of the circumferential portion is higher than the tangential velocity component of the circumferential portion among the velocity components of the vibration. circuit. 14. The storage means stores a normal speed component of a tangential direction of the circumferential portion, out of the speed components of the vibration when the normally operating piezoelectric actuator rotates the disk by vibration. The voltage value of the potential induced according to the displacement of the bending vibration is stored in association with the surface of the plate-shaped piezoelectric element included in the piezoelectric actuator that operates in A voltage acquisition unit that acquires a voltage value of a potential to be driven, the acquired voltage value, and the difference between the stored voltage value, the drive voltage to be applied to the piezoelectric actuator to be driven. 14. The piezoelectric actuator drive control circuit according to claim 13, further comprising frequency control means for adjusting the frequency. 15. The piezoelectric actuator drive control circuit according to claim 8, wherein the voltage applied to the piezoelectric actuator is a pulse voltage. 16. A piezoelectric actuator drive control circuit according to claim 8, further comprising: a piezoelectric actuator; and a disk that is rotationally driven by vibration of the piezoelectric actuator to drive a timepiece element. A clock characterized by being driven by. 17. A piezoelectric actuator, comprising: a piezoelectric actuator; and a disk that is rotationally driven by vibration of the piezoelectric actuator and drives a portable electronic device element. The piezoelectric actuator according to any one of claims 8 to 15. A portable electronic device driven by a drive control circuit.