JP4848853B2 - Piezoelectric actuator driving method, piezoelectric actuator driving apparatus, electronic device - Google Patents

Description

The present invention is a method for driving a piezoelectric actuator, the piezoelectric actuator drive device, relates to an electronic device.

  The piezoelectric element is excellent in conversion efficiency from electrical energy to mechanical energy and responsiveness. For this reason, in recent years, various piezoelectric actuators utilizing the piezoelectric effect of piezoelectric elements have been developed. This piezoelectric actuator is applied to the fields of various electronic devices such as a piezoelectric buzzer, an ink jet head of a printer, an ultrasonic motor, an electronic timepiece, and a portable device.

Incidentally, since the resonance frequency of the piezoelectric actuator varies due to the influence of ambient temperature, load, and the like, the frequency of the drive signal that can drive the piezoelectric actuator also varies according to the ambient temperature, load, and the like.
Therefore, in order to efficiently drive the piezoelectric actuator, two types of drive control are mainly performed next.
The first control method is a method of controlling the phase difference of the drive signal and detection signal of the piezoelectric actuator so as to approach a preset target phase difference. This control method has an advantage that the drive efficiency can be greatly increased by controlling the drive in the vicinity of the target phase difference. However, this control method needs to know in advance the correlation between the phase difference in the piezoelectric element to be controlled and the driving state, and cannot be applied to a piezoelectric element in which such a correlation is not recognized. There was a problem.

  Therefore, the second control method for sweeping (changing) the frequency of the drive signal in a wide range and driving the motor reliably is also widely used (see, for example, Patent Documents 1 and 2).

In Patent Document 1, a triangular or sawtooth sweep voltage is output to a voltage controlled oscillator, and the oscillation frequency of the voltage controlled oscillator is constantly changed in the range from f _L to f _H, so that the frequency at which the piezoelectric vibrator can be driven is always set. Thus, the piezoelectric vibrator (piezoelectric actuator) can be reliably driven.

  Further, as shown in FIG. 18, Patent Document 2 compares a detection voltage that changes according to the vibration state of the piezoelectric element with a predetermined comparison voltage (threshold value). If it is less than the comparison voltage, the time during which the piezoelectric element is not driven is shortened by increasing the sweep speed, and there is an advantage that the driving efficiency can be improved as compared with Patent Document 1.

Japanese Patent Publication No. 5-16272 JP 2006-20445 A

By the way, as in Patent Documents 1 and 2, when the oscillation frequency is swept, the frequency region in which the piezoelectric vibrator can actually be driven is a part of the frequency f _L to f _H , and This drive frequency region changes depending on the ambient temperature, load variation, and the like. For this reason, since the drive signal output from the voltage controlled oscillator continues even in the frequency region where the piezoelectric vibrator is not driven, unnecessary current consumption occurs.
In addition, since the frequency region in which the piezoelectric vibrator can be driven fluctuates due to changes in ambient temperature, load, etc., the period (time) in which the piezoelectric vibrator is actually driven while the oscillation frequency is swept from f _L to f _H Fluctuate, and a section in which the piezoelectric vibrator is not driven occurs. For this reason, particularly noticeable in Patent Document 1, when the driven body is rotated or moved by the piezoelectric vibrator, the driving amount per unit time of the driven body, that is, the driving speed varies, and the driving efficiency is increased. It cannot be improved.

An object of the present invention is to provide a piezoelectric actuator driving method and a piezoelectric actuator driving apparatus that can reliably drive the piezoelectric actuator, reduce power consumption, and reduce variations in driving speed of a driven body driven by the piezoelectric actuator. An object of the present invention is to provide an electronic device including the piezoelectric actuator.

  The piezoelectric actuator driving method of the present invention is a piezoelectric actuator driving method including a vibrating body that vibrates when a driving signal having a predetermined frequency is applied to the piezoelectric element, and the frequency of the driving signal supplied to the piezoelectric element. Is swept in a predetermined direction from a preset initial frequency, and a detection signal indicating a vibration state of the vibrating body is detected. After the detection signal first exceeds a predetermined threshold, the detection signal exceeds the threshold. Within the range, the frequency of the drive signal supplied to the piezoelectric element is swept.

Here, the detection signal includes the vibration amplitude voltage, current consumption, level correlated with the frequency of the drive signal and the drive state of the drive target driven by the piezoelectric actuator (for example, the rotational speed if the drive target is a rotor). Any signal that can be detected by a piezoelectric actuator such as a phase difference may be used. Further, the predetermined threshold value may be set so that the value of the detection signal (for example, the amplitude of the detection voltage) is equal to or greater than the threshold value when the piezoelectric element is driven.
The detection signal first exceeds a predetermined threshold when the frequency of the drive signal first supplied to the piezoelectric element is a frequency outside the drive range of the piezoelectric element. This means that the element is driven and its detection signal is equal to or greater than the threshold value. If the frequency of the drive signal first supplied to the piezoelectric element is a frequency within the driving range of the piezoelectric element, the piezoelectric is driven at that frequency. It means that the element is driven and the detection signal becomes equal to or greater than a threshold value.
Furthermore, the range where the detection signal is greater than or equal to the threshold is the upper limit of the frequency at which the detection signal changes from greater than or equal to the threshold to less than the threshold when the frequency is swept in the up direction (the direction in which the frequency increases). When sweeping in the direction (frequency lowering direction), the lower limit is the frequency at which the detection signal changes from the threshold value to less than the threshold value, and it means the range between these upper and lower limits. The range in which the detection signal is equal to or greater than the threshold may be the entire range between the upper limit and the lower limit, or may be a part of the range included in the range. In short, in the present invention, the frequency of the drive signal is swept. At this time, it is sufficient to control so as not to exceed the range.

In the present invention, since the frequency of the drive signal is changed (sweep) within a range where the detection signal is equal to or higher than a predetermined threshold, the threshold is set based on the detection signal when the piezoelectric element is driven. This ensures that the piezoelectric element can be driven.
Further, since the drive signal is constantly swept within the above range, even if the drive frequency of the piezoelectric element varies due to ambient temperature, disturbance, load fluctuation, etc., it is possible to cope with the variation without adjustment. For this reason, it is not necessary to provide the drive device with a detection circuit for detecting ambient temperature, disturbance, load variation, etc., and an adjustment circuit for adjusting the frequency of the drive signal based on the detection data, and the configuration of the drive device is simple. Can be
Furthermore, since the sweep range of the frequency of the drive signal is controlled based on the detection signal indicating the vibration state of the vibrating body, once the detection signal becomes equal to or higher than the threshold after the start of driving, the detection signal exceeds the threshold. Since the sweep control is performed within the range, that is, the range where the piezoelectric element is in the driving state, the piezoelectric element can be continuously driven. As a result, useless drive signal output time during which the drive target cannot be driven can be eliminated, wasteful current consumption can be reduced, and efficiency can be improved. In addition, since the time of the non-driving state can be eliminated, even if there is a change in the load or the like, variation in the driving time in a predetermined time (for example, 1 minute) can be reduced, and the driving target driven by the vibrating body (driven) Body) driving speed deviation (variation) can be reduced, and high-speed driving can also be realized.
In addition, since the driving of the piezoelectric element can be continued at all times, the wear of the driven object and the piezoelectric actuator can be reduced and the life of the piezoelectric actuator can be extended as compared with the case where the piezoelectric element repeats stop → drive → stop. .

  In the piezoelectric actuator driving method of the present invention, after the detection signal first exceeds a predetermined threshold value, the drive signal supplied to the piezoelectric element is changed each time the detection signal changes from the threshold value to less than the threshold value. It is preferable to reverse the frequency sweep direction.

  According to such a configuration, when the frequency is swept in the up direction (the direction in which the frequency increases), the frequency at which the detection signal changes from the threshold value to the threshold value is set as the upper limit frequency, and the frequency is set in the down direction (frequency is When the frequency is swept in the lower direction), the frequency at which the detection signal changes from the threshold value to less than the threshold value is set as the lower limit frequency, and the sweep is performed over the entire range between these upper limit frequency and lower limit frequency. The frequency of the drive signal can be swept within the range. For this reason, the piezoelectric element can be reliably driven even when the ambient temperature or the like fluctuates.

  In the piezoelectric actuator driving method of the present invention, after the detection signal first becomes equal to or higher than the predetermined threshold value, the predetermined frequency is determined based on the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value. It is preferable to set a range and sweep the frequency of the drive signal supplied to the piezoelectric element within the frequency range.

  Here, setting a predetermined frequency range based on the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value means, for example, that the detection is performed by sweeping the frequency in either the down direction or the up direction. The frequency when the signal changes from the threshold value to the threshold value is set as the reference frequency, the reference frequency is set as the lower limit or upper limit frequency, and the frequency shifted from the reference frequency by a predetermined frequency, for example, 4 kHz, is set as the upper and lower frequencies or the lower limit. Not only when a frequency range is set as a frequency, but also a frequency that is shifted by a predetermined frequency from the frequency when the detection signal changes from a threshold value to a threshold value is set as a reference frequency, and this reference frequency is a lower limit or upper limit frequency. The frequency shifted from the reference frequency by a predetermined frequency is the upper and lower frequencies or I.e., an those set the frequency range as a limited frequency.

  If the frequency range is set in this way, the frequency sweep range can be limited to only a portion where the drive efficiency is high, and efficient drive control of the piezoelectric element can be performed.

  In the piezoelectric actuator driving method of the present invention, after the detection signal first exceeds a predetermined threshold value, the frequency of the driving signal is swept in the down direction in which the frequency decreases or in the up direction in which the frequency increases. In this case, the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value is set as the lower limit or upper limit frequency, and when the sweep signal is swept in the direction opposite to the sweep direction from the lower limit or upper limit frequency, It is preferable that the frequency separated from the lower limit or upper limit frequency by a predetermined frequency is the upper limit or lower limit frequency, and the frequency of the drive signal supplied to the piezoelectric element is swept within the range between the lower limit frequency and the upper limit frequency.

In other words, when the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value when swept in the down direction is set as the lower limit frequency, only a predetermined frequency (for example, 4 kHz) from the lower limit frequency. A large frequency may be set as the upper limit frequency and swept between these lower limit and upper limit frequencies.
Similarly, when the frequency of the drive signal when the detection signal changes from the threshold value to the threshold value when swept in the up direction is set as the upper limit frequency, a predetermined frequency (for example, 6 kHz) from the upper limit frequency. It is only necessary to set a lower frequency as the lower limit frequency and sweep between these upper limit and lower limit frequencies.

If the frequency sweep range is set in this way, the frequency sweep range can be limited to only a portion where the drive efficiency is high, the piezoelectric element can be efficiently driven and controlled, and the lower end of the sweep range or Since the upper end can be set to a frequency at which the detection signal has changed from the threshold value to less than the threshold value, the piezoelectric element can be reliably driven even when the range in which the piezoelectric element is driven changes due to changes in ambient temperature or the like. .
For example, as a piezoelectric element, longitudinal vibration that vibrates in the longitudinal direction and flexural vibration that vibrates in the width direction of the piezoelectric element in a plate shape by adjusting the position and weight balance of the drive electrode of the piezoelectric element configured in a plate shape. When using a piezoelectric element that causes the tip of the protrusion provided at the end of the piezoelectric element to move in an elliptical orbit, the resonance frequency of the longitudinal vibration that is the lower limit of the range in which the detection signal is equal to or greater than the threshold is on the bending resonance frequency side The range of several kHz is a preferable sweep range in terms of driving force and rotational speed. In the present invention, since the piezoelectric element can be easily driven in this sweep range, the driving efficiency can be improved as compared with the case where the frequency is swept over the entire range where the detection signal is equal to or greater than the threshold value.

  In the piezoelectric actuator driving method of the present invention, after the detection signal first exceeds a predetermined threshold value, the frequency of the driving signal is swept in the down direction in which the frequency decreases or in the up direction in which the frequency increases. In this case, a frequency that is a predetermined frequency away from the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value on the side opposite to the sweep direction is set as the lower limit or upper limit frequency. When the frequency is swept in the direction opposite to the sweep direction, a frequency that is a predetermined frequency away from the lower limit or upper limit frequency is defined as an upper limit or lower limit frequency, and within a range between the lower limit frequency and the upper limit frequency. It is preferable to sweep the frequency of the drive signal supplied to the piezoelectric element.

  According to such a configuration, since the frequency sweep range can be set in a portion away from the lower limit and the upper limit of the range where the detection signal is equal to or greater than the threshold, depending on the piezoelectric element, it is possible to sweep within the range where the driving efficiency is the highest. The driving efficiency can be further improved.

  In the driving method of the piezoelectric actuator of the present invention, it is preferable that the range in which the frequency of the driving signal is swept is narrowed as the driving of the piezoelectric element is continued.

  According to such a configuration, since the sweep range can be gradually narrowed to a portion where the driving efficiency is high, the driving efficiency can be further improved.

  In the piezoelectric actuator driving method of the present invention, when the detection signal is less than the threshold value, the sweep speed of the frequency of the drive signal is set to the first set speed, and when the detection signal is equal to or more than the threshold value. Preferably, the sweep speed of the frequency of the drive signal is set to a second set speed that is lower than the first set speed.

  In the present invention, since the sweep speed of the frequency of the drive signal is controlled based on the detection signal indicating the vibration state of the vibration body, the drive signal is obtained when the vibration amount of the vibration body is small and the drive target is in the non-drive state. The sweep speed of this frequency can be increased, and the amount of vibration of the vibrating body can be increased to decrease the speed when the drive target is in the drive state. Accordingly, it is possible to shorten a useless drive signal output time during which the drive target cannot be driven, reduce useless current consumption, and improve efficiency. In addition, since the time of the non-driving state can be shortened, variation in driving time in a predetermined time (for example, 1 minute) can be reduced even if there is a change in load or the like, and a driving target (driven body) driven by a vibrating body Drive speed deviation (variation) can be reduced, and high-speed driving can also be realized.

  The piezoelectric actuator drive device of the present invention is a piezoelectric actuator drive device that supplies a drive signal to the piezoelectric element in a piezoelectric actuator having a vibrating body that vibrates when a drive signal having a predetermined frequency is applied to the piezoelectric element. And a frequency control means for sweeping the frequency of the drive signal supplied to the piezoelectric element, wherein the frequency control means detects a detection signal indicating a vibration state of the vibrating body, and the detection signal first exceeds a predetermined threshold value. After that, the frequency of the drive signal supplied to the piezoelectric element is swept within a range equal to or greater than the threshold value.

In the present invention, since the frequency of the drive signal is changed (swept) within a predetermined range, any piezoelectric element that is driven within this frequency range can be reliably driven.
In addition, since the drive signal is constantly swept within a predetermined frequency range, even if the drive frequency of the piezoelectric element varies due to ambient temperature, disturbance, load fluctuation, etc., it is possible to cope with the variation without adjustment. For this reason, it is not necessary to provide the drive device with a detection circuit for detecting ambient temperature, disturbance, load variation, etc., and an adjustment circuit for adjusting the frequency of the drive signal based on the detection data, and the configuration of the drive device is simple. Can be
Further, when the sweep speed of the frequency of the drive signal is controlled based on the detection signal representing the vibration state of the vibrating body, the sweep speed of the frequency of the drive signal is when the drive target driven by the piezoelectric actuator is in the non-drive state. Can be made high speed and low speed when driven. Accordingly, it is possible to shorten a useless drive signal output time during which the drive target cannot be driven, reduce useless current consumption, and improve efficiency. In addition, since the time of the non-driving state can be shortened, variation in driving time in a predetermined time (for example, 1 minute) can be reduced even if the load or the like fluctuates, and the driving speed bias of the driving target driven by the vibrating body can be reduced. (Variation) can be reduced, and high-speed driving can also be realized.
In addition, since the driving of the piezoelectric element can be continued at all times, the wear of the driven object and the piezoelectric actuator can be reduced and the life of the piezoelectric actuator can be extended as compared with the case where the piezoelectric element repeats stop → drive → stop. .

  In the piezoelectric actuator driving apparatus according to the present invention, the frequency control means outputs a reference voltage for amplitude detection serving as a threshold for detecting the amplitude of the detection signal, and is output by the constant voltage circuit. An amplitude detection circuit that compares the amplitude detection reference voltage with the amplitude of the detection signal and outputs a comparison result signal; a voltage adjustment circuit that switches a change direction of the output voltage based on the comparison result signal; and a voltage adjustment circuit And a variable frequency oscillator capable of changing the frequency of the output signal according to the voltage output from.

  In the invention of this configuration, by comparing the reference voltage for amplitude detection output from the constant voltage circuit and the amplitude (voltage) of the detection signal, it can be detected whether the drive target is in the drive state or the non-drive state, It can be output as a comparison result signal. Based on the comparison result signal, the frequency of the drive signal can be set by controlling the voltage value output from the voltage adjustment circuit, and the drive signal can be controlled by controlling the change direction of the voltage output from the voltage adjustment circuit. Since the frequency sweep direction can be set, the frequency sweep range of the drive signal can be easily set within a range where the comparison result signal is equal to or greater than a predetermined threshold.

  In the piezoelectric actuator driving apparatus of the present invention, the voltage adjustment circuit includes a clock circuit capable of outputting a plurality of clock signals having different frequencies, an up / down counter, and an output voltage based on a counter value of the up / down counter. A digital / analog converter for setting a voltage value; and a sweep control circuit for controlling a counter value of the up / down counter based on the clock signal, wherein the sweep control circuit inputs a clock signal to the up / down counter. A first clock selector that switches the frequency of the clock signal in two stages of high and low, a second clock selector that switches the input destination of the clock signal to either the counter-up input or the counter-down input of the up / down counter, and the amplitude detection Based on comparison result signal from circuit It is preferable to provide an adjustment circuit for controlling the respective selectors.

  According to the invention of this configuration, if the count value of the up / down counter is controlled by the sweep control circuit, the frequency of the drive signal can be controlled, so that various increase / decrease patterns can be easily controlled. For example, when the frequency of the driving signal is reciprocated within a set range, when the counter value reaches the minimum value in the preset range, the counter value is changed in the up direction by controlling the second clock selector. When the maximum value is reached, it is only necessary to control the second clock selector again to change the counter value in the down direction, which can be controlled with a simple configuration. Further, since the frequency sweep speed of the drive signal is proportional to the change speed of the counter value, it can be easily realized only by switching the frequency of the signal input to the counter by the first clock selector of the sweep control circuit.

The electronic apparatus according to the present invention includes a piezoelectric actuator having a vibrating body that vibrates when a drive signal having a predetermined frequency is applied to the piezoelectric element, and a drive device for the piezoelectric actuator.
The invention with this configuration includes a piezoelectric actuator that consumes less power, has a small variation in driving speed, and can realize stable driving. Therefore, it is possible to provide a particularly small and portable electronic device such as a wristwatch. .

According to the present invention, there is provided a control program for a drive device for a piezoelectric actuator, wherein a drive signal for supplying a drive signal to the piezoelectric element in a piezoelectric actuator having a vibrating body that vibrates when a drive signal having a predetermined frequency is applied to the piezoelectric element A control program for the apparatus, wherein a computer incorporated in the driving device sweeps the frequency of the driving signal supplied to the piezoelectric element, and detects a detection signal indicating a vibration state of the vibrating body, and this detection signal After the frequency first exceeds a predetermined threshold value, it functions as a frequency control means for sweeping the frequency of the drive signal supplied to the piezoelectric element within a range equal to or higher than the threshold value.
The storage medium of the present invention is a computer-readable storage medium storing the program.

  According to the present invention as described above, by causing a computer incorporated in a drive device to function as the frequency control means, the power consumption of the piezoelectric actuator can be reduced and the drive speed variation is small and high, as described above. Efficient drive can be realized. If each means is configured by a computer, the condition can be easily changed by simply changing the program, so that appropriate control according to the drive target can be easily performed.

  ADVANTAGE OF THE INVENTION According to this invention, a piezoelectric actuator can be driven reliably, power consumption can be reduced, and the variation in the drive speed of the to-be-driven body driven with a piezoelectric actuator can be reduced.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, as an embodiment of an electronic apparatus, an electronic timepiece having a date display device driven by a piezoelectric actuator is illustrated.

[1. overall structure]
FIG. 1 is an external view of an electronic timepiece 1 according to the present embodiment. The electronic timepiece 1 is a watch (watch) provided with a date display device 10 for displaying a date from a window 3A provided on the dial 3 in addition to the movement 2, dial 3, hour hand 4, minute hand 5, second hand 6. is there.

[2. Configuration of date display device]
FIG. 2 is a plan view showing the date display device 10 supported by the bottom plate 1A. The date display device 10 includes a piezoelectric actuator 20, a rotor 30 as a driven body that is rotationally driven by the piezoelectric actuator 20, a speed reduction wheel train 40 that transmits the rotation of the rotor 30 while reducing the speed, and a speed reduction wheel train 40. And a date wheel 50 that rotates by the driving force transmitted through the vehicle.
The rotor 30 is rotationally driven by the piezoelectric actuator 20 at the turn of the day or at the time of date correction. The reduction wheel train 40 includes a gear 41 that is arranged coaxially with the rotor 30 and rotates integrally with the rotor 30, a date turning intermediate wheel 42 that meshes with the gear 41, and a date turning wheel 43.

  Below the bottom plate 1A (behind) is a stepping motor (not shown) that operates with a pulse signal oscillated by a crystal resonator, and a hand movement that is connected to the stepping motor to drive the hour hand 4, the minute hand 5, and the second hand 6. A train wheel (not shown), a battery 1B, and the like are provided. The battery 1B supplies power to each circuit such as a stepping motor, the piezoelectric actuator 20, and a drive circuit (not shown) that applies an AC voltage to the piezoelectric actuator 20.

  The intermediate date driving wheel 42 includes a large diameter portion 421 and a small diameter portion 422. The small-diameter portion 422 has a cylindrical shape that is slightly smaller in diameter than the large-diameter portion 421, and a substantially square-shaped notch 423 is formed on the outer peripheral surface thereof. The small diameter part 422 is fixed to the large diameter part 421 so as to be concentric. Since the gear 41 on the upper portion of the rotor 30 is engaged with the large diameter portion 421, the intermediate date driving wheel 42 rotates in conjunction with the rotation of the rotor 30.

  A leaf spring 424 is provided on the bottom plate 1A on the side of the date driving intermediate wheel 42. A base end portion of the leaf spring 424 is fixed to the bottom plate 1A, and a distal end portion is bent into a substantially V shape. Has been. The tip of the leaf spring 424 is provided so as to be able to enter and leave the notch 423 of the intermediate date wheel 42. A contact 425 is disposed at a position close to the leaf spring 424, and this contact 425 is arranged when the intermediate date wheel 42 rotates and the tip of the leaf spring 424 enters the notch 423. It comes into contact with the spring 424. A predetermined voltage is applied to the leaf spring 424, and when the leaf spring 424 contacts the contact 425, the voltage is also applied to the contact 425. Therefore, by detecting the voltage of the contact 425, the date feeding state can be detected, and the amount of rotation of the date dial 50 for one day can be detected.

  The rotation amount of the date wheel 50 is not limited to that using the leaf spring 424 or the contact 425, but the rotation amount of the rotor 30 or the date turning intermediate wheel 42 is detected and a predetermined pulse signal is output. Specifically, various rotary encoders such as known photo reflectors, photo interrupters, and MR sensors can be used.

  The date dial 50 has a ring shape, and an internal gear 51 is formed on the inner peripheral surface thereof. The date indicator driving wheel 43 has a five-tooth gear and meshes with the internal gear 51 of the date dial 50. A shaft 431 is provided at the center of the date driving wheel 43, and the shaft 431 is loosely inserted into a through hole 1C formed in the bottom plate 1A. The through-hole 1 </ b> C is formed long along the circumferential direction of the date dial 50. The date driving wheel 43 and the shaft 431 are urged in the upper right direction in FIG. 2 by a plate spring 432 fixed to the bottom plate 1A. The urging action of the leaf spring 432 prevents the date dial 50 from swinging.

[3. Configuration of piezoelectric actuator]
Next, the piezoelectric actuator 20 will be described with reference to FIG. 3 which is a partially enlarged view of FIG.
The piezoelectric actuator 20 includes a piezoelectric vibrator 20A having a laminated structure including two piezoelectric elements 21 each having a rectangular plate shape and a conductive reinforcing plate 60 interposed between the piezoelectric elements 21, and a drive circuit mounted thereon. And a circuit board (not shown), which is slidably attached and fixed to a bottom plate 1A (FIG. 2) to be attached by a slider 70.
Hereinafter, the configuration of the piezoelectric vibrating body 20A constituting the piezoelectric actuator 20 will be described in detail.

[Configuration of piezoelectric element]
The piezoelectric element 21 includes lead zirconate titanate (PZT (registered trademark)), crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zinc niobate, lead scandium niobate, etc. It is made of any material selected from.
The surface of these piezoelectric elements 21 is provided with electrodes by plating, sputtering, vapor deposition or the like with nickel or gold, etc., and this electrode is divided by grooves by etching or the like, so that five drive electrodes 261 to 265 are provided. It has been. Specifically, the electrode is divided into three equal parts by two grooves extending along the longitudinal direction of the piezoelectric element 21, and the electrodes on both ends in the width direction of the piezoelectric element 21 are further formed by grooves extending along the width direction of the piezoelectric element 21. By being divided into two equal parts, five drive electrodes 261 to 265 are provided.
The back side piezoelectric element 21 facing the slider 70 is also provided with drive electrodes 261 to 265 similarly to the front side piezoelectric element 21. For example, the drive electrode 261 is disposed on the back side of the drive electrode 261. ing.

  These drive electrodes 261 to 265 and the reinforcing plate 60 are connected to the drive circuit through lead wires and a circuit board (not shown), and a voltage is applied to the piezoelectric element 21 between each of the drive electrodes 261 to 265 and the reinforcing plate 60. Is done. These drive electrodes 261 to 265 are provided point-symmetrically with respect to the plane center of the piezoelectric element 21.

[Configuration of reinforcing plate]
The reinforcing plate 60 is made of stainless steel or other conductive material, and includes a rectangular main body on which the piezoelectric element 21 is disposed, a pair of support portions 62 that protrude on both sides in the width direction of the main body, and a support portion 62. A fixed portion 63 provided at the end and fixed to the slider 70 is integrally provided.
The main body vibrates by applying a voltage to each piezoelectric element 21, and constitutes a substantially rectangular plate-shaped vibrating portion together with each piezoelectric element 21. The vibration unit excites a longitudinal primary vibration and a bending secondary vibration by applying a voltage to each piezoelectric element 21.
Protrusions 611 and 612 projecting along the longitudinal direction are formed at substantially the center of the short sides on both sides of the main body, and one protrusion 611 is in contact with the side surface of the rotor 30. The piezoelectric actuator 20 is disposed substantially perpendicular to the side surface of the rotor 30, and the direction of the protrusion 611 is along the radial direction of the rotor 30. Further, the plane of the vibration part is disposed so as to be orthogonal to the axis of the rotor 30. Even if the protrusion 611 is brought into contact with the rotor 30, the other protrusion 612 contributes to excitation, so that the amplitude can be increased and the startability is good.
The support part 62 is provided on both sides of the vibration part, and supports the vibration part so as to vibrate.

Each fixing portion 63 in the piezoelectric vibrating body 20 </ b> A is fixed to the slider 70 with a screw 712. There is a gap between the piezoelectric vibrating body 20A other than the fixed portion 63 and the slider 70, and the piezoelectric vibrating body 20A is configured not to contact the slider 70 during vibration.
The slider 70 is slidably attached to the bottom plate 1A through a long hole.

  As shown in FIGS. 2 and 3, the piezoelectric vibrator 20A and the slider 70 integrally assembled in this way are urged in the longitudinal direction of the piezoelectric vibrator 20A by two compression coil springs 11 provided on the bottom plate 1A. ing. The spring 11 is locked between the spring mounting portion 12 formed on the bottom plate 1A and the protrusion 633 formed on the fixing portion 63 of the piezoelectric vibrating body 20A. Due to the pressure applied by the spring 11, an appropriate frictional force is generated between the protrusion 611 of the piezoelectric vibrating body 20 </ b> A and the rotor 30, and the transmission efficiency of vibration to the rotor 30 of the piezoelectric actuator 20 is good.

[4. Operation of piezoelectric actuator]
Next, the operation of the piezoelectric actuator 20 will be described. Through the drive circuit (not shown), the voltage application to the drive electrodes 261 to 265 in each piezoelectric element 21 is switched axisymmetrically with respect to the center line connecting the protrusions 611 and 612 of the vibration unit 20B. Is changed.
That is, when a voltage is applied only to the drive electrodes 261, 263, and 265, the vibration unit 20B vibrates in a mixed mode of longitudinal vibration and bending vibration, and as a Lissajous figure based on the phase difference between these longitudinal vibration and bending vibration, The protrusion 611 draws an elliptical vibration locus. The rotor 30 is intermittently driven in a direction tangential to the vibration locus, and the protrusion 611 continues to move elliptically at a predetermined drive frequency, whereby the rotor 30 rotates at a predetermined speed in the positive direction R1 (FIG. 3). At this time, the piezoelectric actuator 20 is in a forward rotation mode in which the date is changed by counting time, and the date wheel 50 (FIG. 2) is sent in the forward direction R1 through the speed reduction wheel train 40 by the forward rotation of the rotor 30.

  On the other hand, when a voltage is applied only to the drive electrodes 262, 264 and 265, the vibration behavior of the vibration part 20B is different from the case where a voltage is applied to the drive electrodes 261, 263 and 265 with respect to the longitudinal direction of the vibration part 20B. It becomes line symmetrical and the rotor 30 rotates in the reverse direction R2. At this time, the piezoelectric actuator 20 is in a reverse rotation mode in which the date is changed at the time of date correction, and the date wheel 50 (FIG. 2) is sent in the reverse direction via the speed reduction wheel train 40 by the reverse rotation of the rotor 30.

[5. Piezoelectric Actuator Driving Device and Driving Method]
Next, the configuration of the driving device 80 of the piezoelectric actuator 20 will be described with reference to FIG.
In FIG. 4, the driving device 80 is output from a driving circuit 81 that outputs a driving signal to the piezoelectric element 21 of the piezoelectric actuator 20, a constant voltage circuit 82 that outputs a reference voltage for amplitude detection, and a constant voltage circuit 82. The amplitude detection circuit 83 that compares the amplitude detection reference voltage and the amplitude (voltage) of the detection signal output from the piezoelectric actuator 20 and outputs a comparison result signal, and the comparison result signal from the amplitude detection circuit 83 A voltage adjustment circuit 84 that adjusts the output voltage, and a variable frequency oscillator (VCO) 85 that adjusts the frequency of the signal output to the drive circuit 81 corresponding to the voltage output from the voltage adjustment circuit 84 are provided. . The drive circuit 81 outputs a drive signal corresponding to the frequency of the signal input from the variable frequency oscillator 85 to the piezoelectric element 21.

Here, in the present embodiment, a drive control unit that includes the drive circuit 81, the variable frequency oscillator 85, and the voltage adjustment circuit 84 and controls the frequency of the drive signal supplied to the piezoelectric actuator 20 is configured. The drive control unit, the constant voltage circuit 82, and the amplitude detection circuit 83 are included to constitute a frequency control means.
The amplitude detection circuit 83 outputs an H-level comparison result signal when the amplitude of the detection signal is greater than or equal to the amplitude detection reference voltage, and when the amplitude of the detection signal is less than the amplitude detection reference voltage. An L level comparison result signal is set to be output.
The detection signal output from the piezoelectric element 21 is a signal output from the electrodes 261 to 264 to which no driving voltage is input in the piezoelectric element 21.

The voltage adjustment circuit 84 is configured to increase or decrease the output voltage within a predetermined range, and to switch the adjustment speed (change speed) based on the comparison result signal from the amplitude detection circuit 83. An example of the configuration of the voltage adjustment circuit 84 is shown in FIG.
The voltage adjustment circuit 84 is a clock as a reference signal oscillator that can output a clock signal (reference signal) of at least two frequencies of a high clock (for example, 1 MHz) and a low clock (a frequency lower than the high clock, for example, 1 kHz). A circuit 841, a sweep control circuit 842 for performing sweep control based on a clock signal output from the clock circuit 841, an up / down counter (UD counter) 843 to which a signal from the sweep control circuit 842 is input, and the UD A digital / analog converter (D / A converter) 844 that converts the digital signal output from the counter 843 into an analog signal.

  As shown in FIG. 6, the sweep control circuit 842 adjusts the sweep speed and the sweep direction based on the amplitude detection result, and the first sweep speed is selected based on the control signal from the adjustment circuit 90. A clock selector 91 and a second clock selector 92 that selects a sweep direction based on a control signal from the adjustment circuit 90 are provided.

The first clock selector 91 includes AND circuits 911 and 912 to which a low clock signal and a high clock signal from the clock circuit 841 are input, respectively, and an OR circuit 913 to which outputs of the AND circuits 911 and 912 are input. And a NOT circuit 914 that inverts the sweep speed selection signal from the adjustment circuit 90 and inputs the inverted signal to the AND circuit 912.
Therefore, when the sweep speed selection signal is an H level signal, a low clock signal is output as it is from the AND circuit 911, but since an L level signal is input from the NOT circuit 914 to the AND circuit 912, Is also maintained at the L level. Therefore, the low clock signal output from the AND circuit 911 is output from the OR circuit 913 as it is.
On the other hand, when the sweep speed selection signal is the L level signal, the output from the AND circuit 911 is maintained at the L level. However, since the H level signal is input from the NOT circuit 914 to the AND circuit 912, the AND circuit From 912, a high clock signal is output as it is. Therefore, the high clock signal output from the AND circuit 912 is output from the OR circuit 913 as it is.
Therefore, the sweep control circuit 842 is configured to switch the counting speed (counter value changing speed) of the UD counter 843 in accordance with the amplitude detection result signal input from the amplitude detection circuit 83. For example, if the detection result signal is H level, the sweep control circuit 842 uses the low clock signal (for example, 1 kHz) among the clock signals output from the clock circuit 841 to set the counter value of the UD counter 843. If the detection result signal is L level, the counter value is changed using a high clock signal (for example, 1 MHz). Thereby, the changing speed of the counter value of the UD counter 843 is switched.

  The second clock selector 92 inverts the sweep direction selection signal from the AND circuits 921 and 922 to which the signal output from the first clock selector 91 is input and the adjustment circuit 90 and inputs the inverted signal to the AND circuit 922. A circuit 923. The signal output from the AND circuit 921 is input to the counter UP input of the UD counter 843, and the signal output from the AND circuit 922 is input to the counter DOWN input of the UD counter 843.

Therefore, when the sweep direction selection signal is an H level signal, the signal from the first clock selector 91 is output as it is from the AND circuit 921, but the output from the AND circuit 922 is maintained at the L level. For this reason, the UD counter 843 is gradually counted up by the input of the clock signal selected by the clock selector 91.
On the other hand, when the sweep direction selection signal is an L level signal, the signal from the first clock selector 91 is output as it is from the AND circuit 922, but the output from the AND circuit 921 is maintained at the L level. Therefore, the UD counter 843 is gradually counted down by the input of the clock signal selected by the clock selector 91.

In the present embodiment, the adjustment circuit 90 includes a D latch 901 and a T flip-flop 902 as shown in FIG.
An actual drive ON / OFF signal is input to the data input of the D latch 901, and a detection result signal from the amplitude detection circuit 83 is input to the clock input. For this reason, even if the driving of the piezoelectric element 21 is instructed at the time when the date is changed and the actual driving is turned ON (H level), the D latches until the detection result signal first becomes H level. In other words, the adjustment circuit 90 outputs an L level signal as the sweep speed selection signal, and the clock selector 91 selects the high clock signal. On the other hand, when the detection result signal first changes from the L level to the H level, the output of the D latch 901 becomes the H level signal, and thereafter, as long as the actual drive signal that is the data input is ON (H level), the output of the D latch 901. Is maintained at the H level, and the clock selector 91 always selects the low clock signal.
Note that, as described with a two-dot chain line in FIG. 7, the adjustment circuit 90 eliminates the D latch 901, directly uses the detection result signal as the sweep speed selection signal, and selects the sweep speed according to the detection result. May be.

  A detection result signal from the amplitude detection circuit 83 is input to the input of the T flip-flop 902, and an ON / OFF signal for actual driving is input to the reset input. For this reason, every time the detection result signal changes from detection (H level) to non-detection (L level) in a state where the actual drive is an ON signal, the signal output from the T flip-flop 902 is H level and L Switch to level and select sweep direction.

  The UD counter 843 can use a counter of about 10 bits or 12 bits. By inputting a pulse signal from the sweep control circuit 842 to the down input or the up input of the UD counter 843, the signal is counted and the counter value is counted. Is to change. Note that the number of bits of the UD counter 843 may be selected according to the frequency width to be swept. That is, when the resolution (frequency change amount when the counter value changes by 1) is about 0.01 to 0.25 kHz and the sweep frequency width is about 50 to 100 kHz, a counter of about 10 to 12 bits is set. Although it is necessary to use the counter, if the sweep frequency width is smaller, a counter having a smaller number of bits, for example, a counter having 8 to 9 bits can be used.

In the D / A converter 844, a frequency control voltage value corresponding to the counter value of the UD counter 843 is set. When the D / A converter 844 receives the counter value output from the UD counter 843, the D / A converter 844 outputs a frequency control voltage corresponding to the frequency control voltage value corresponding to the counter value to the variable frequency oscillator 85.
The variable frequency oscillator 85 outputs a frequency signal corresponding to the voltage output from the D / A converter 844 to the drive circuit 81, and the drive circuit 81 outputs a drive signal having a frequency corresponding to the frequency of the input signal to the piezoelectric element. To 21. Therefore, the frequency of the drive signal is set by the counter value of the UD counter 843, and the sweep speed of the frequency of the drive signal is changed by the change speed of the counter value of the UD counter 843, that is, the frequency of the clock signal used by the sweep control circuit 842. Will be set.

  Therefore, the voltage adjustment circuit 84 outputs a frequency sweep (increase / decrease) control function for sweeping (increase / decrease) the frequency of the drive signal supplied to the piezoelectric element 21 via the variable frequency oscillator 85 and the drive circuit 81, and an output from the amplitude detection circuit 83. And a frequency sweep speed control function for controlling the sweep speed of the frequency of the drive signal based on the comparison result signal. Therefore, in this embodiment, among the frequency control means, a frequency increase / decrease control means for controlling increase / decrease in the frequency of the drive signal, and a frequency for controlling the increase / decrease rate (sweep speed) of the drive signal frequency, mainly by the voltage adjustment circuit 84. An increase / decrease ratio control means is configured.

Next, a method of driving the piezoelectric actuator using the driving device 80 will be described based on the flowchart of FIG.
As shown in FIG. 8, when the drive device 80 is turned on or instructed to start driving, the drive device 80 starts a frequency sweep of the drive signal output to the piezoelectric element 21 (step S, step “S”). Abbreviated).
In the present embodiment, the frequency sweep direction, speed, and drive signal frequency at the start of driving are preset in the voltage adjustment circuit 84. For example, the sweep direction is DOWN (direction in which the frequency of the drive signal is lowered), the sweep speed is high (high clock: A × 1 MHz / sec), and the drive signal frequency at the start of driving is the initial frequency fmax. Accordingly, the frequency of the drive signal is sequentially decreased from fmax in the frequency range according to the sweep speed.

Specifically, the frequency control of the drive signal is performed as follows. That is, the sweep control circuit 842 sets the counter value of the UD counter 843 to a value corresponding to the drive signal frequency fmax, and then applies a pulse signal to the down input of the UD counter 843 based on the clock signal from the clock circuit 841. The counter value of the UD counter 843 is input to decrease.
Since the voltage corresponding to the count value of the UD counter 843 is output from the D / A converter 844, if the counter value of the UD counter 843 decreases, the voltage output from the D / A converter 844 also decreases sequentially. .
Then, a signal having a frequency corresponding to the voltage value is output from the variable frequency oscillator 85, and a drive signal corresponding to the frequency is output from the drive circuit 81, and the piezoelectric element 21 is driven (excited) (S2).

When the piezoelectric element 21 is driven, the amplitude detection circuit 83 and the voltage adjustment circuit 84 execute a sweep speed switching process based on the detection signal output from the detection electrode of the piezoelectric element 21 (S3).
In the sweep speed switching process (S3), as shown in FIG. 9, the amplitude detection circuit 83 monitors the detection signal output from the piezoelectric element 21 (S31), and sets the amplitude (voltage) of the detection signal to a constant voltage circuit. It is compared with the amplitude detection reference voltage output from 82 (S32).

In S32, the amplitude detection circuit 83 outputs an H level comparison result signal if the detection signal amplitude is greater than or equal to the reference voltage (S33). On the other hand, if the detection signal amplitude is less than the reference voltage, the amplitude detection circuit 83 outputs an L level comparison result signal (S34).
When the voltage adjustment circuit 84 receives the H level comparison result signal, the voltage adjustment circuit 84 sets the sweep speed to a low speed (S35). That is, when the sweep speed is set to a low speed, the state is maintained, and when the sweep speed is set to a high speed, the speed is switched to a low speed. Once the low speed is set, the low speed is maintained by the D latch 901 in the adjustment circuit 90 of the sweep control circuit 842 even if the comparison result signal becomes L level (S36).
In this embodiment, as shown in FIG. 9, the low speed sweep is AkHz / sec, and the high speed sweep is A × 1 MHz / sec, 1000 times the low speed. A is, for example, “1” and may be set as appropriate.
Thus, in the sweep speed switching process S3 of the present embodiment, the sweep speed is switched between two types of high speed and low speed.

When the sweep speed switching process S3 ends, a sweep direction switching process S4 is executed as shown in FIG.
In the sweep direction switching process S4, as shown in FIG. 10, it is detected whether or not the amplitude detection result signal output from the amplitude detection circuit 83 has changed from H level to L level (S41). When the amplitude detection result signal changes from H level to L level, the sweep direction is reversed and switched (S42). That is, if the sweep direction is the DOWN direction, the direction is switched to the UP direction, and if the sweep direction is the UP direction, the direction is switched to the DOWN direction.
On the other hand, if “No” is determined in S41, the sweep direction is not switched and the direction is maintained as it is.

  When the sweep direction switching process S4 ends, as shown in FIG. 8, it is determined whether or not power-off or drive stop has been instructed (S5). If “No” is determined in S5, the processes in S2 to S4 are repeated. On the other hand, if “Yes” is determined in S5, the drive control is terminated.

FIG. 11 shows the relationship between the rotational speed (rps) of the driven body and the frequency of the drive signal when such control is performed. In FIG. 11, Z (Ω) indicates the relationship between the driving frequency and impedance in the vibrating body 20A. Here, the frequency at which the impedance (Z) becomes the smallest is the resonance point of the longitudinal primary vibration. Further, as the drive frequency increases from the resonance point of the longitudinal primary vibration, the impedance gradually increases, then decreases slightly and then increases again to the maximum value. The portion where the impedance is slightly lowered is the resonance point of the bending secondary vibration.
When the vibrating body 20A is driven between the longitudinal resonance frequency of the longitudinal vibration and the bending resonance frequency of the bending vibration, the amplitude of both the longitudinal vibration and the bending vibration is ensured, and the piezoelectric actuator 20 is driven with high efficiency. For this reason, this embodiment is also configured to perform sweep drive control between the resonance frequencies so as to improve.

Initially, the frequency of the drive signal is swept in the DOWN direction from fmax to fmin (arrow A in FIG. 11). Here, the frequency range in which the piezoelectric element 21 is excited (driven) varies depending on the ambient temperature, the load of the driven body, and the like. When the piezoelectric element 21 is excited (driven), the amplitude of the detection signal (detection voltage VANP) increases. Therefore, it is determined whether or not the vibration of the piezoelectric actuator 20 reaches the vibration capable of driving the rotor 30 to be driven, based on whether or not the detection voltage VANP is equal to or higher than the comparison voltage (amplitude detection reference voltage) Vref. it can.
Therefore, as described above, when the detection voltage VANP is less than the comparison voltage Vref, that is, when it is determined that the rotor 30 is not driven, the sweep speed is set to a high speed, and the detection voltage VANP is equal to or higher than the comparison voltage Vref. In this case, that is, when it is determined that the rotor 30 is driven, the sweep speed is set to a low speed.

Then, when the frequency of the drive signal changes until the detection voltage VANP drops below the comparison voltage Vref (point B in FIG. 11), that is, when the amplitude detection result signal changes from H to L level, the sweep control circuit 842 The sweep direction is switched, and the frequency of the drive signal is swept in the UP direction (arrow C in FIG. 11).
When the frequency of the drive signal changes until the detection voltage VANP drops to the comparison voltage Vref or lower (point D in FIG. 11), that is, when the amplitude detection result signal changes from H to L level, the sweep control circuit 842 The sweep direction is switched again, and the frequency of the drive signal is swept in the DOWN direction (arrow E in FIG. 11).
Thereafter, by repeating the same operation, the frequency of the drive signal is changed while reciprocating in a range where the detection voltage VANP is equal to or higher than the comparison voltage Vref. The sweep speed is maintained in a low clock state by the D latch 901.

[3. Effects of the embodiment]
Therefore, according to the present embodiment, the following operational effects can be achieved.
(1) Since the drive device 80 for driving the piezoelectric actuator according to this embodiment sweeps the drive signal for driving the piezoelectric element 21 within a range where the amplitude detection signal is equal to or higher than the comparison voltage Vref, the piezoelectric element 21 is always driven. can do. For this reason, if it is an ultrasonic motor using the piezoelectric element 21, the rotor 30 which is a to-be-driven body can be rotated reliably.
Therefore, since there is almost no useless drive signal output time during which the rotor 30 cannot be driven, useless current consumption can be reduced and drive efficiency can be improved. In addition, since there is almost no time for the non-driving state, even if there is a change in the load or the like, variation in driving time in a predetermined time such as 1 minute can be reduced, and the rotational speed of the rotor 30 driven to rotate by the piezoelectric element 21 is reduced. Can be reduced, and high-speed driving is also possible.
For this reason, for example, compared with the conventional control method which repeats the sweep of fmax to fmin, the efficiency improvement of one digit or more can be aimed at. That is, when the relationship between the driving force and the rotor rotational speed when driven by the four methods of Patent Documents 1 and 2, the present embodiment, and the control based on the phase difference is confirmed by experiment, as shown in FIG. The results according to the present embodiment indicated by are lower than the results when controlled by the phase difference indicated by the two-dot chain line 122, but the results according to Patent Document 1 indicated by the dotted line 123 and the patent documents indicated by the one-dot chain line 124. Driving efficiency can be improved as compared with the result of 2. Therefore, when controlling a piezoelectric element in which there is no correlation between the phase difference and the driving state, the most efficient driving can be realized by performing the control according to the present invention.

(2) Also, if the amplitude detection signal is less than the comparison voltage Vref, the sweep direction is switched so that the amplitude detection signal is constantly swept within the range where the comparison voltage Vref is always higher than the comparison voltage Vref. Even if the drive frequency of the piezoelectric element 21 varies due to fluctuation or the like, the variation can be handled without adjustment. For this reason, it is not necessary to provide the drive device 80 with a detection circuit for detecting ambient temperature, disturbance, load fluctuation, and the like, and an adjustment circuit for adjusting the frequency of the drive signal based on the detection data. Can also be simplified.

(3) Furthermore, the amplitude (voltage) of the detection signal from the piezoelectric element 21 is compared with the reference voltage for amplitude detection to detect the driving state of the rotor 30, and the detected amplitude is greater than the reference voltage, that is, the rotor 30 is driven. In this case, the sweep speed is set to a low speed, and when the detected amplitude is less than the reference voltage, that is, the rotor 30 is not driven, the sweep speed is set to a high speed.
For this reason, for example, even during the first sweep processing time for sweeping the frequency from fmax to fmin, the time during which the rotor 30 is not driven can be shortened. Further, after that, the detected amplitude can always be maintained at the reference voltage or higher, that is, the rotor 30 is driven.

(4) In the present embodiment, the amplitude detection circuit 83 compares the amplitude of the detection signal with the reference voltage, and the voltage adjustment circuit 84 sets the frequency sweep speed of the drive signal to high or low 2 based on the comparison result signal. Since switching is performed in stages, the circuit configuration of the driving device 80 can be simplified, and control processing can be easily performed.

(5) The voltage adjustment circuit 84 includes a clock circuit 841, a sweep control circuit 842, a UD counter 843, and a D / A converter 844, and changes the frequency speed with the frequency of the clock signal output from the clock circuit 841. Since it can be controlled, the range of speed change can be widened, and the sweep speed can be easily adjusted in a plurality of stages.
Further, since the voltage adjustment circuit 84 includes the UD counter 843, no external parts are required, and the sweep speed can be easily varied, so that an IC is advantageous.

(6) The electronic timepiece includes a vibrating body having the piezoelectric element 21 and a piezoelectric actuator 20 that is provided on the vibrating body and has a protrusion 611 that is in contact with a driving target, the driving device 80 having the above-described configuration, and the piezoelectric actuator 20. Therefore, it is possible to provide an electronic timepiece that consumes less power and can achieve stable drive control in a short time.

(7) In the case of the control method in which the process of sweeping the frequency of the drive signal from fmax to fmin is repeated, the piezoelectric element 21 repeats stop → drive → stop → drive, but in this embodiment, the piezoelectric element 21 is always turned on. Since the driving can be continued, the wear of the rotor 30 and the protrusions 611 contacting the rotor 30 can be reduced, the efficiency of the piezoelectric actuator 20 can be prevented from being lowered due to the wear, and the life of the piezoelectric actuator 20 can be extended.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Since the second embodiment is different from the first embodiment only in the configuration of the adjustment circuit 90 of the sweep control circuit 842, description of other configurations is omitted.
As shown in FIG. 13, the adjustment circuit 90 </ b> A of the second embodiment includes a D latch 901 and a T flip-flop 902 as well as a clock counter 903 in the same manner as the adjustment circuit 90 of the first embodiment.
The clock counter 903 receives a clock signal from the clock circuit 841, and after the frequency of the drive signal changes from the DOWN direction to the UP direction, the clock corresponding to the amount by which the frequency of the drive signal changes by a preset frequency. When the signal is counted, a signal for switching in the DOWN direction is output to the T flip-flop 902 again. Then, the T flip-flop 902 outputs a sweep direction selection signal for selecting the DOWN direction to the second clock selector 92.
Further, when the T flip-flop 902 sweeps in the DOWN direction and the detection signal changes from the threshold value to less than the threshold value, the T flip-flop 902 sends a second sweep direction selection signal for inverting the sweep direction from the DOWN direction to the UP direction. It is configured to output to the clock selector 92.

  According to the present embodiment, as shown in FIGS. 14 and 15, first, the frequency of the drive signal is swept in the DOWN direction from fmax to fmin (arrow A in FIGS. 14 and 15). At this time, since the sweep speed is set to a high speed, the sweep clock input to the clock counter 903 is set to a high speed (high frequency). When the piezoelectric element 21 is excited (driven) and the amplitude of the detection signal (detection voltage VANP) becomes equal to or higher than the comparison voltage Vref and the amplitude detection result signal changes from L to H level, the sweep speed is switched to low speed, The sweep clock is also switched to a low frequency lower than the high speed frequency.

Further, when the frequency of the drive signal changes until the detection voltage VANP drops to the comparison voltage Vref or lower (point B in FIGS. 14 and 15), that is, when the amplitude detection result signal changes from H to L level, the sweep control circuit. The sweep direction is switched by 842, and the frequency of the drive signal is swept in the UP direction (arrow C in FIGS. 14 and 15).
That is, when the detection result input falls from H to L, the clock counter 903 outputs a single pulse to the T flip-flop 902. The T flip-flop 902 inverts the output at the falling edge of the input single pulse and switches the sweep direction.
Further, the clock counter 903 starts the count processing of the sweep clock input to the clock counter 903 at the falling edge of the detection result input from H to L. When the detection result changes from H to L, the sweep clock is also switched to a high speed, but the sweep direction is switched, so the detection voltage VANP immediately exceeds the reference voltage and the detection result also rises to H, and the sweep clock also Switch to low speed instantly.

When the number of counters of the clock counter 903 reaches a preset setting value while sweeping in the UP direction as in the period of the arrow C in FIGS. 14 and 15, a signal is sent from the clock counter 903 to the T flip-flop 902. (Single pulse) is output, and the sweep direction is reversed to the DOWN direction (arrow D in FIGS. 14 and 15). Note that the number of counters set in the clock counter 903 is set to the number of clocks corresponding to a frequency change of 4 kHz when the frequency is desired to be swept, for example, in the range of 4 kHz width. That is, the sweep width is set by the count number set in the clock counter 903.
In the example shown in FIG. 15, when the rising edge of the sweep clock is counted eight times, the clock counter 903 outputs a single pulse to the T flip-flop 902 and resets the counter at the next rising edge of the clock. It is configured.

Thereafter, by repeating the same operation, the frequency of the drive signal changes while reciprocating within the frequency range defined by the number of counts set in the clock counter 903 within the range where the detection voltage VANP is equal to or higher than the comparison voltage Vref. Is done. Further, since the detection voltage VANP is equal to or higher than the comparison voltage Vref, the sweep speed is maintained at a low clock state except for a moment when the sweep direction is switched from the DOWN direction to the UP direction.
Note that the clock counter 903 and the T flip-flop 902 to which the detection result is input may directly receive the detection result signal, but it is preferable to receive the detection result signal via a chattering prevention circuit because stable control can be performed.
That is, the actual detection voltage signal (amplitude voltage) VANP is output at a frequency equivalent to the drive frequency. The detection voltage VANP shown in FIG. 11 and the like is a plot of the maximum value of the output waveform. When the detection voltage VANP is compared with the comparison voltage Vref, if the number of detection signals exceeding the comparison voltage (threshold) Vref is, for example, 3 pulses or more out of a predetermined number of detection signals (for example, 4 pulses), the comparison voltage or more is exceeded. As a result, the result is output as “H”, and if it exceeds 2 pulses or less, “L” is output and discriminated. At this time, in the actual actuator drive, even in the frequency range where the detected voltage is equal to or higher than the comparison voltage, the amplitude may rarely become the threshold value or less due to individual differences, fluctuations in the load, etc., and the control result is “L”. In other words, there is a possibility that it becomes a state like general chattering (a phenomenon in which the signal repeats ON / OFF). Therefore, by providing a known chattering prevention circuit using a latch circuit or the like, the detection result becomes “L” in the frequency region where the detection voltage should be equal to or higher than the comparison voltage when the actuator is driven, and the high speed It is possible to prevent the sweep process from being performed and to perform stable control.

In such a second embodiment, the same operational effects as the first embodiment can be obtained.
Furthermore, since the frequency range to be swept is narrowed, only the region where the rotational speed and torque are high can be swept, and the drive efficiency can be further improved. In particular, the piezoelectric element 21 of the present embodiment has a driving force in the region of several kHz on the bending resonance frequency side from the resonance frequency of the longitudinal vibration that is the lower limit (point B in FIG. 14) of the range in which the detection voltage VANP is equal to or greater than the threshold value. In the second embodiment, the piezoelectric element 21 can be easily driven in this sweep range, and the driving efficiency can be improved as compared with the first embodiment.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the second embodiment, the detection signal is set to sweep within a predetermined (for example, 4 kHz) range based on the lower limit frequency in the range where the detection signal is equal to or higher than the threshold value. It may be set to sweep within the predetermined range.

Further, as indicated by an arrow A in FIG. 16, a frequency separated by a predetermined frequency from a lower limit or an upper limit frequency of the range where the detection signal is equal to or greater than the threshold is used as a reference, and the frequency is swept within the predetermined range from this frequency. May be set.
Furthermore, when the frequency of the drive signal is swept within a predetermined range, the range may be controlled to be narrowed as driving continues. For example, when one round-trip sweep control of the drive frequency continues for a predetermined number of times, as shown by an arrow B in FIG. 16, the sweep range is narrowed (for example, a sweep of 4 kHz is reduced to a half of a sweep of 2 kHz). May be performed.
In this case, control may be performed so that the sweep range is gradually narrowed in proportion to the number of continuations. For example, the sweep range may be controlled to be gradually narrowed from 4 → 3 → 2 → 1 kHz.

  In the above-described embodiment, the amplitude of the detection signal output from the piezoelectric element 21 is compared with the amplitude detection reference voltage to control the driving of the piezoelectric element 21. However, in the present invention, for example, a resistance is applied to a driver that drives the piezoelectric actuator. And the switching process of the sweep direction of the frequency of the drive signal may be controlled based on the value of the current flowing through the piezoelectric actuator by detecting a change in the value of the current flowing through the piezoelectric actuator as a voltage value.

  If a plurality of detection signals are detected, the amplitude of one predetermined detection signal may be detected to control the frequency sweep direction of the drive signal. The amplitude of the signal may be detected and stored, and the frequency control may be performed based on the amplitude of the detection signal having the larger amplitude change. In this case, since the control can be performed based on the detection signal having a large change in amplitude, the change can be reliably detected and efficient control can be performed.

Further, the switching of the sweep speed is not limited to switching in two stages as in the above embodiment, and may be configured to switch to three stages or four or more stages. When switching the sweep speed, for example, a plurality of reference voltages may be output from the constant voltage circuit 52, and the voltage of the detection signal may be compared with each reference voltage for control.
Furthermore, in the present invention, after the piezoelectric element 21 starts to drive after the first sweep starts, the frequency sweep is always performed in the range in which the piezoelectric element is driven, so that there is almost no period during which the sweep speed is controlled at a high speed. For this reason, in the present invention, switching of the sweep speed is not essential. For example, the first clock selector 91 is eliminated, and the second clock selector 92 is configured so that a low clock signal is always input, and the sweep speed is increased. You may always maintain a low clock.

The sweep pattern of the frequency of the drive signal is not limited to the reciprocating pattern that switches alternately between the down direction and the up direction as in the above-described embodiment, and the up pattern that always sweeps in the up direction within the set frequency range, or the down direction always. A down pattern that sweeps may be used. In any pattern, it is sufficient to sweep at least within a range where the value (amplitude, etc.) of the detection signal is equal to or greater than the threshold value.
Further, these sweep patterns may be selected based on the driving state of the piezoelectric element 21.

  In the above embodiment, the initial setting of the frequency of the drive signal is fixed to the predetermined frequency fmax. However, the frequency range in which the detection signal exceeds the threshold at the previous drive ON is stored, and based on this frequency range You may control to set the said initial setting frequency.

  The drive device 80 is not limited to the one using the voltage adjustment circuit 84 having the UD counter 843, but may be one having a voltage adjustment circuit using a plurality of loop filters having different time constants. It is only necessary that the frequency of the drive signal output from 81 to the piezoelectric element 21 can be swept and the sweep range can be set based on the detection signal.

  The amplitude detection circuit 83 is not particularly limited as long as it detects amplitude, and may be, for example, a circuit that detects the number of fixed amplitudes within a fixed time, or simply detects an amplitude level. It may be one that detects the peak level of amplitude.

Furthermore, in the present invention, each means in the control unit is configured by hardware such as various logic elements, a computer (CPU) (central processing unit), a memory (storage device), etc. The computer may be configured so that each means is realized by incorporating a predetermined program or data (data stored in each storage unit) into the computer.
Here, the program and data may be stored in advance in a memory such as a RAM or a ROM incorporated in an electronic device such as a watch or a portable device. Further, for example, a predetermined control program and data may be installed in a memory in a watch or a portable device via a communication means such as the Internet or a recording medium such as a CD-ROM or a memory card. Then, each means may be realized by operating a CPU or the like with a program stored in the memory. In order to install a predetermined program or the like on a watch or portable device, a memory card or CD-ROM or the like may be directly inserted into the watch or portable device, or an external device for reading these storage media may be installed. You may connect to a watch or mobile device. Furthermore, a program or the like may be supplied and installed by communication by connecting a LAN cable, a telephone line or the like to a watch or a portable device, or may be supplied and installed by wireless.

  If a control program or the like provided by such a recording medium or communication means such as the Internet is incorporated in a watch or a portable device, the functions of the inventions can be realized only by changing the program. A control program to be selected can be selected and incorporated. In this case, since various types of watches and portable devices having different control formats can be manufactured only by changing the program, the parts can be shared, and the manufacturing cost when developing variations can be greatly reduced.

  In the above embodiment, the piezoelectric actuator is used for driving the date display device of the electronic timepiece 1, but the present invention is not limited to this, and may be used for driving the time display hand (pointer) of the electronic timepiece 1. In this way, the electronic timepiece 1 can be made thinner by replacing the stepping motor that drives the hands with a piezoelectric actuator, and the piezoelectric actuator is less susceptible to magnetism than the stepping motor. In addition, it is possible to achieve high magnetization resistance of the electronic timepiece.

Furthermore, the present invention is not limited to being applied to the electronic timepiece of the embodiment. That is, the method of driving the piezoelectric actuator of the present invention and the electronic device adopting the driving device are not limited to electronic timepieces such as watches, table clocks, wall clocks, etc., and the present invention can be applied to various electronic devices. It is suitable for portable electronic devices that require miniaturization. Here, examples of various electronic devices include a phone having a clock function, a mobile phone, a non-contact IC card, a personal computer, a personal digital assistant (PDA), a camera, and the like. The present invention can also be applied to electronic devices such as a camera without a clock function, a digital camera, a video camera, and a mobile phone with a camera function. When applied to an electronic apparatus having these camera functions, the driving means of the present invention can be used to drive a lens focusing mechanism, a zoom mechanism, an aperture adjustment mechanism, and the like.
Furthermore, a meter pointer drive mechanism for measuring instruments, a drive mechanism for movable toys, a meter pointer drive mechanism for instrument panels of automobiles, piezoelectric buzzers, inkjet heads for printers, paper feed mechanisms for printers, etc. The driving means of the present invention may be used for a motor or the like.
For example, as shown in FIG. 17, in the printer 100, the piezoelectric actuator 20 of the present invention may be used as a drive source for rotationally driving the paper feeding roller 101.
Further, the configuration of the piezoelectric actuator is not limited to that of the above-described embodiment, and may be, for example, a so-called ultrasonic motor that rotates a rotor by a traveling wave of ultrasonic waves. In short, the present invention is various piezoelectric actuators including piezoelectric elements. Widely available.

1 is an external view of an electronic timepiece according to an embodiment of the present invention. The top view of the date display apparatus in the said embodiment. The elements on larger scale of FIG. The block diagram which shows the internal structure of the drive device of a piezoelectric actuator. The block diagram which shows the internal structure of a voltage adjustment circuit. The block diagram which shows the internal structure of a sweep control circuit. The block diagram which shows the structure of the adjustment circuit in a sweep control circuit. The flowchart explaining the method of driving a piezoelectric actuator. The flowchart explaining the sweep speed switching process in the flowchart of FIG. The flowchart explaining the sweep direction switching process in the flowchart of FIG. The graph which shows the relationship between the frequency of the drive signal in this embodiment, the rotation speed of a to-be-driven body, a detection voltage, and an impedance. The graph which shows the relationship between the driving force of this embodiment and a comparative example, and a rotor rotational speed. The block diagram which shows the structure of the adjustment circuit in 2nd Embodiment of this invention. The graph which shows the relationship between the frequency of the drive signal in 2nd Embodiment, the rotation speed of a to-be-driven body, a detection voltage, and an impedance. The timing chart which shows the operation | movement relationship of the detection result in 2nd Embodiment, a counter clock output, a sweep clock, and a T flip-flop output. The graph which shows the relationship between the frequency of the drive signal in a modification, the rotation speed of a to-be-driven body, a detection voltage, and an impedance. The schematic perspective view which shows the modification of this invention. 6 is a graph for explaining a drive control method of Patent Document 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electronic timepiece, 2 ... Movement, 10 ... Date display apparatus, 20 ... Piezoelectric actuator, 21 ... Piezoelectric element, 30 ... Rotor, 50 ... Date indicator, 80 ... Drive apparatus, 81 ... Drive circuit, 82 ... Constant voltage circuit, DESCRIPTION OF SYMBOLS 83 ... Amplitude detection circuit, 84 ... Voltage adjustment circuit, 85 ... Oscillator, 90 ... Adjustment circuit, 91 ... 1st clock selector, 92 ... 2nd clock selector, 100 ... Printer, 101 ... Roller, 261-265 ... Drive Electrode, 841... Clock circuit, 842... Sweep control circuit, 843... UD counter, 844... D / A converter, 901 ... D latch, 902 ... T flip-flop, 903.

Claims (11)

A method of driving a piezoelectric actuator including a vibrating body that vibrates when a drive signal having a predetermined frequency is applied to the piezoelectric element,
The frequency of the drive signal supplied to the piezoelectric element is swept in a predetermined direction from a preset initial frequency, and a detection signal representing a vibration state of the vibrating body is detected,
A method for driving a piezoelectric actuator, comprising: sweeping a frequency of a drive signal supplied to the piezoelectric element within a range in which the detection signal first becomes equal to or greater than a predetermined threshold. The method for driving a piezoelectric actuator according to claim 1,
After the detection signal first exceeds a predetermined threshold value, the frequency sweep direction of the drive signal supplied to the piezoelectric element is reversed every time the detection signal changes from the threshold value to less than the threshold value. A method for driving a piezoelectric actuator. The method for driving a piezoelectric actuator according to claim 1,
After the detection signal first becomes equal to or greater than the predetermined threshold, a predetermined frequency range is set based on the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value. A method of driving a piezoelectric actuator, wherein the frequency of a drive signal supplied to the piezoelectric element is swept. The method for driving a piezoelectric actuator according to claim 3.
After the detection signal first exceeds a predetermined threshold,
When the drive signal frequency is swept in the down direction where the frequency is reduced or in the up direction where the frequency is increased, the frequency of the drive signal when the detection signal changes from the threshold value to the threshold value is set as the lower limit or upper limit frequency. ,
When swept in the direction opposite to the sweep direction from the lower limit or upper limit frequency, the frequency separated from the lower limit or upper limit frequency by a predetermined frequency is set as the upper limit or lower limit frequency,
A method of driving a piezoelectric actuator, wherein the frequency of a drive signal supplied to the piezoelectric element is swept within a range between the lower limit frequency and the upper limit frequency. The method for driving a piezoelectric actuator according to claim 3.
After the detection signal first exceeds a predetermined threshold,
When the frequency of the drive signal is swept in the down direction in which the frequency is decreased or in the up direction in which the frequency is increased, the frequency of the drive signal when the detection signal changes from the threshold value to less than the threshold value is opposite to the sweep direction. The frequency that is a predetermined frequency away on the side is the lower limit or upper limit frequency,
When swept in the direction opposite to the sweep direction from the lower limit or upper limit frequency, the frequency separated from the lower limit or upper limit frequency by a predetermined frequency is set as the upper limit or lower limit frequency,
A method of driving a piezoelectric actuator, wherein the frequency of a drive signal supplied to the piezoelectric element is swept within a range between the lower limit frequency and the upper limit frequency. In the driving method of the piezoelectric actuator according to any one of claims 3 to 5,
A method for driving a piezoelectric actuator, characterized by narrowing a range in which the frequency of the drive signal is swept as the driving of the piezoelectric element is continued. In the drive method of the piezoelectric actuator in any one of Claims 1-6,
When the detection signal is less than the threshold value, the sweep speed of the frequency of the drive signal is set to the first set speed,
When the detection signal is equal to or greater than the threshold value, the sweep speed of the frequency of the drive signal is set to a second set speed that is lower than the first set speed. A drive device for a piezoelectric actuator that supplies a drive signal to the piezoelectric element in a piezoelectric actuator having a vibrating body that vibrates when a drive signal having a predetermined frequency is applied to the piezoelectric element,
Comprising frequency control means for sweeping the frequency of the drive signal supplied to the piezoelectric element;
The frequency control means detects a detection signal indicating a vibration state of the vibrating body, and supplies the piezoelectric element to the piezoelectric element within a range in which the detection signal first exceeds a predetermined threshold value after the detection signal first exceeds the predetermined threshold value. A drive device for a piezoelectric actuator, wherein the frequency of a drive signal is swept. The drive device for a piezoelectric actuator according to claim 8,
The frequency control means includes
A constant voltage circuit that outputs a reference voltage for amplitude detection serving as a threshold for detecting the amplitude of the detection signal;
An amplitude detection circuit that compares a reference voltage for amplitude detection output by the constant voltage circuit with the amplitude of the detection signal and outputs a comparison result signal;
A voltage adjustment circuit that switches the change direction of the output voltage based on the comparison result signal;
A piezoelectric actuator driving apparatus comprising: a variable frequency oscillator capable of changing a frequency of an output signal according to a voltage output from a voltage adjusting circuit. The drive device for a piezoelectric actuator according to claim 9,
The voltage adjustment circuit includes: a clock circuit capable of outputting a plurality of clock signals having different frequencies; an up / down counter; and a digital / analog converter that sets a voltage value of an output voltage based on a counter value of the up / down counter; A sweep control circuit for controlling a counter value of the up / down counter based on the clock signal,
The sweep control circuit includes a first clock selector that switches a frequency of a clock signal input to the up / down counter in two stages, high and low, and an input destination of the clock signal that is a counter up input or a counter down input of the up / down counter A piezoelectric actuator driving apparatus comprising: a second clock selector that switches to any one of the above, and an adjustment circuit that controls each of the selectors based on a comparison result signal from the amplitude detection circuit.   A piezoelectric actuator having a vibrating body that vibrates when a driving signal having a predetermined frequency is applied to the piezoelectric element, and a driving device for the piezoelectric actuator according to any one of claims 8 to 10. Electronic equipment.

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