JP2010220297A - Piezoelectric driving device, piezoelectric driving method, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric driving device, a piezoelectric driving method, and an electronic apparatus adapted to greatly improve efficiency of a piezoelectric actuator on startup. <P>SOLUTION: The piezoelectric driving device includes a piezoelectric actuator and a drive control means. The drive control means executes initial drive control, which is performed at the initial stage of the start of the piezoelectric actuator, and stationary drive control S5, which is performed after the initial drive control. In the initial drive control, it executes non-application control S2, in which a drive signal is not applied to the piezoelectric element, after execution of initial drive signal application control S1, in which an initial drive signal is applied to the piezoelectric element. The timing of switching from the initial drive signal application control to the non-application control is set by the operation start of a driven body by application of the initial drive signal, and the timing of switching from the initial drive control to the stationary drive control is set by the stop time of operation of the driven body after operation start of the driven body by application of the initial drive signal and/or by the time of completion of discharge of the piezoelectric element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric driving device, a piezoelectric driving method, and an electronic apparatus.

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 (ultrasonic motor) has a feature that the efficiency at the time of start-up is poor due to an increase in the amount of power input at the time of start-up.
Therefore, an apparatus for improving the efficiency at the time of startup has been proposed (see, for example, Patent Documents 1 and 2).

  Patent Document 1 discloses a purpose of suppressing a rapid electric current from flowing and a large amount of electric power being consumed by starting charging of a piezoelectric element suddenly when a vibration motor is started (when a voltage is applied). Thus, a method of gradually increasing the pulse width of the drive alternating signal applied to the piezoelectric element (claims 1, 2, 5 and Example 1), and a method of gradually increasing the pulse voltage of the input pulse at startup (claim) 1, 2, 6, Example 2), and a method of increasing the driving frequency at the time of startup (Claim 3, Example 3) is disclosed.

  Patent Document 2 discloses a method of applying a low voltage and then a high voltage at the initial stage of the vibration body in order to start oscillation growth in a stable state and effectively shorten the start-up time in the oscillation circuit. ing. As the definition of the application time of the low voltage, a method of determining the time by a timer until the amplitude is stabilized by detection is described.

Japanese Patent Laid-Open No. 11-215861 JP 2008-99257 A

  However, since the above-mentioned Patent Document 1 gradually increases the pulse width of the driving alternating signal, the input of the driving alternating signal is continued, and the best piezoelectric driving method considering the operation of the driven body I can't say that.

  In Patent Document 2, a first voltage signal having a low voltage is applied at the start of driving, and then a second voltage signal having a high voltage is applied, and the input of the voltage signal is continued from the start of driving. After all, it cannot be said to be the best piezoelectric driving method considering the operation of the driven body.

  Thus, the conventional technique has a problem that the efficiency improvement at the time of starting the piezoelectric actuator is not sufficient.

  An object of the present invention is to provide a piezoelectric driving device, a piezoelectric driving method, and an electronic apparatus that can greatly improve the efficiency at the time of starting a piezoelectric actuator.

  The piezoelectric drive device of the present invention includes a piezoelectric element that includes a piezoelectric element and vibrates when a drive signal is applied to the piezoelectric element, and transmits the vibration of the vibrating body to the driven body. To the piezoelectric actuator Drive control means for controlling the application of the drive signal, the drive control means is configured to be capable of executing initial drive control performed at the initial stage of activation of the piezoelectric actuator and steady drive control performed after the initial drive control, In the initial drive control, an initial drive signal application control that applies an initial drive signal to the piezoelectric element, and a non-application control that does not apply a drive signal to the piezoelectric element after executing the initial drive signal application control, The timing for switching from the initial drive signal application control to the non-application control is set until the operation of the driven body by the application of the initial drive signal is started. The timing of switching from the initial drive control to the steady drive control is after the start of the operation of the driven body due to the application of the initial drive signal and the operation of the driven body driven by the application of the initial drive signal It is set at the time of stopping and / or until the completion of discharge of the piezoelectric element charged by application of the initial drive signal.

As a result of intensive studies by the present inventors, when the driven body is driven by the piezoelectric actuator, there is a period in which the driven body is not driven until the vibration of the vibrating body is stabilized at the initial start-up. It was found to be almost constant regardless of the application time and the amount of current.
In addition, since the piezoelectric element was discharged in the initial stage of activation (immediately after the activation signal was first applied), it was found that when a drive signal is applied, a large current flows and power consumption increases.
The inventor of the present invention has arrived at the present invention based on the knowledge that there is a period in which the driven body hardly operates while a large current flows rapidly and power consumption increases at the initial stage of startup.

In the present invention, since the initial drive signal application control for applying the initial drive signal to the piezoelectric element is executed in the initial drive control, the piezoelectric element can be charged by applying the initial drive signal, and the vibrating body Can be vibrated.
At this time, the timing for switching from the initial drive signal application control to the non-application control is set until the operation of the driven body by the application of the initial drive signal is started. In the initial drive control, the initial drive signal After executing the application control, the non-application control without applying the drive signal to the piezoelectric element is executed. For this reason, it is possible to greatly reduce the power consumption in a period in which the amount of current is large at the initial start of the piezoelectric actuator. After switching to non-application control, the application of the drive signal to the piezoelectric actuator ends, but the vibrating body does not stop immediately, but the damped vibration continues and gradually vibrates suitable for driving the driven body. Therefore, driving of the driven body is started.
In the present invention, after the start of driving of the driven body by application of the initial driving signal and when the operation of the driven body driven by application of the initial driving signal is stopped and / or the initial driving signal In order to switch from the initial drive control to the steady drive control by the completion of the discharge of the piezoelectric element charged by the application of, the driven body is in a state of moving while utilizing the damped vibration of the vibrating body, that is, the vibrating body A drive signal can be applied to the piezoelectric actuator by steady drive control in a state where the locus of vibration is in a form suitable for driving the driven body. For this reason, the driven body can be accelerated immediately after application of the drive signal. As a result, the application time for rising is shortened, and power consumption can be suppressed.
When the operation of the driven body is stopped and / or when the discharge of the piezoelectric element is completed, 1) until the operation of the driven body is stopped, 2) until the discharge of the piezoelectric element is completed, and 3) the driven It refers to three patterns until the body stops operating and until the discharge of the piezoelectric element is completed.

As described above, according to the present invention, there is a time lag until the vibrating body can actually drive the driven body while starting the vibration of the vibrating body by the initial drive control. Considering the fact that a large current can easily flow while the driven body cannot be driven, and the power consumption increases, such a period is a non-application period in which no drive signal is applied, thereby reducing power consumption and power consumption. Can be reduced.
Since the vibration body is damped while the drive signal is not applied in the non-application period, if the steady drive control is started within a certain period, that is, the drive is stopped before the drive of the driven body is stopped. When the control is started, a drive signal in the steady drive control can be applied in the drive state of the driven body, the rising time of the driven body can be shortened, and the power consumption can be reduced.
That is, if the timing for switching to the steady drive control is set before the driven body stops driving, particularly before the vibrating body stops, a signal for steady driving can be applied while the vibrating body is vibrating. The time required for the driven body to rise after the start of steady drive control can be shortened. For this reason, although the drive signal non-application period is provided, the driven body can be started up in the same time as when the non-application period is not provided, and the drive signal application time can be shortened. , Power consumption can be reduced.
Further, if the timing for switching to the steady drive control is set by the time when the discharge of the piezoelectric element charged by the application of the initial drive signal is completed, when applying the drive signal to the piezoelectric actuator by the steady drive control, It is possible to suppress an abrupt current flowing at the time of start-up and to reduce power.

If the timing for switching to the steady drive control is set until the time when the operation of the driven body is stopped and the discharge of the piezoelectric element charged by the application of the initial drive signal is completed, the above-described operation is performed. Realizes both reduction of the time until the driven body starts to move by applying a drive signal while the driven body is moving, and reduction of power by preventing sudden current flow at the time of startup can do.
For these reasons, according to the piezoelectric driving device of the present invention, the efficiency at the time of starting the piezoelectric actuator can be improved.

In the present invention, it is preferable that the timing of switching to the steady drive control is set to a timing at which the operation speed of the driven body by application of the initial drive signal is equal to or higher than a predetermined value.
As a result, acceleration due to the application of the drive signal is started from a state where the operation speed of the driven body due to the application of the initial drive signal is approximately equal to or higher than the predetermined value, and thus the steady state until the movement amount of the driven body reaches the predetermined distance. The drive control time is shortened and power consumption can be suppressed.
In addition, the specific setting of the switching timing of the present invention may be set based on the experimental result obtained by previously measuring the operating speed of the driven body when the initial driving signal is applied.
Here, the driving signal during the steady driving control is an alternating signal having a frequency suitable for driving, and this signal may be a fixed frequency or may be always controlled to an optimum frequency by control such as phase difference control. The frequency suitable for driving is a frequency at which the vibration mode to be driven is excited. For example, in the case of controlling the driving of a piezoelectric actuator driven using longitudinal resonance and bending resonance, the resonance frequency of longitudinal vibration is The frequency is between the resonance frequencies of the bending vibrations.

In the present invention, it is preferable that the application control period of the initial drive signal is set so that a current flowing through the piezoelectric element with the application of the initial drive signal becomes a predetermined value or less.
As a result, the value of the current that flows when the initial drive signal is applied can be suppressed to a predetermined value or less, so that power consumption can be limited and power consumption can be reduced. Further, since a large current can be prevented from flowing, the load on the power source can be reduced.
In addition, the specific setting of the switching timing of the present invention may be set based on an experimental result obtained by measuring a change in current value when an initial drive signal is applied in advance.
Here, the drive signal during the initial drive control is an alternating signal having a frequency suitable for driving, and this signal may be a fixed frequency or a frequency optimized by control such as phase difference control in the previous steady drive control. It may be controlled.

In the present invention, it is preferable that the initial drive signal is composed of an alternating signal having a duty ratio of 50%.
In general, a piezoelectric actuator is driven by turning a driver on and off using a voltage controlled oscillator (VCO), and the voltage controlled oscillator circuit is configured to handle a signal with a duty ratio of 50%. There are many. When the duty ratio of the initial drive signal and the corresponding duty ratio of the voltage control transmission circuit are different, it is necessary to convert the duty ratio, but in order to change the duty ratio, the signal of the voltage control oscillation circuit is converted to the conversion circuit. Need to be input and output. In this case, a clock faster than the frequency of the drive signal is required for the circuit for converting the duty ratio, and an extra configuration increases. Even if a circuit that changes the duty ratio is configured with an analog circuit inside the voltage controlled oscillation circuit, the circuit scale of the analog circuit becomes large, and an extra configuration increases.
On the other hand, if the initial drive signal is an alternating signal with a duty ratio of 50%, the initial drive signal can be generated without adding an extra configuration to the circuit.

In the present invention, the pulse for controlling the output of the initial drive signal may be a single pulse input or a plurality of pulses (for example, two to three pulses).
Thereby, even when it is necessary to set the length of the initial drive period for performing the initial drive signal application control to be shorter (for example, 0.2 msec, etc.) based on, for example, current consumption, the number of pulses is increased. Can be dealt with.

In the present invention, it is preferable that the timing of switching to the steady drive control is determined based on a detection signal obtained from a detection electrode provided on the vibrating body.
If a detection electrode is provided on the electrode on the surface of the vibrating body, a detection signal is output according to the expansion and contraction of the piezoelectric element. Since the detection signal is generated even while the vibration is attenuated, it can be determined that the vibration is extremely small when the voltage of the detection signal falls below a predetermined value. There is a variation in the operation of the vibrating body, and there is a high possibility that it will vary at the start of the operation of the driven body, but it is possible to start the driven body stably by determining the timing of switching to steady drive control by detection. And power consumption can be reduced.

  The piezoelectric driving method of the present invention includes a vibrating body that has a piezoelectric element and vibrates when a driving signal is applied to the piezoelectric element, and drives a piezoelectric actuator that transmits the vibration of the vibrating body to a driven body. In this initial drive control, an initial drive signal application for applying an initial drive signal to the piezoelectric element is performed, and an initial drive control performed at the initial start of the piezoelectric actuator and a steady drive control performed after the initial drive control are executed. Control and non-application control in which no drive signal is applied to the piezoelectric element after executing the initial drive signal application control, and the timing of switching from the initial drive signal application control to the non-application control is applied to the initial drive signal. The timing for switching from the initial drive control to the steady drive control is set until the operation of the driven body is started by the initial drive signal. Of the piezoelectric element charged after the start of operation of the driven body by application and when the operation of the driven body driven by application of the initial drive signal is stopped and / or by application of the initial drive signal It is set by the time of completion of discharge.

  An electronic apparatus according to the present invention includes a piezoelectric actuator including a vibrating body having a piezoelectric element, and any one of the piezoelectric driving devices according to the present invention.

  In these piezoelectric driving methods and electronic devices, the same operational effects as those of the piezoelectric driving device described above can be obtained.

  According to the present invention, the efficiency at the time of starting the piezoelectric actuator can be greatly improved.

It is a figure which shows schematic structure of the electronic timepiece which concerns on embodiment of this invention. It is a top view which shows the detailed structure of the date display mechanism in the said electronic timepiece. It is a block diagram which shows the structure of a drive control apparatus. It is a figure which shows the speed change of the to-be-driven body according to the application time of a drive signal. It is a figure which shows the electric power change according to the application time of a drive signal. It is a flowchart which shows the flow of control of a drive control method. It is a figure which shows time until the operating distance of a to-be-driven body reaches a predetermined value. It is a figure which shows the application time of the drive signal in the steady drive control until the operating distance of a to-be-driven body reaches a predetermined value. It is a figure which shows the change of the operating speed of a to-be-driven body. It is explanatory drawing at the time of applying a drive signal at the time of the maximum operation speed. It is an enlarged view which shows the waveform of a drive signal. It is explanatory drawing at the time of switching to the steady drive control before discharge completion. It is explanatory drawing in the case of using the initial pulse by a modification. It is an enlarged view which shows the waveform of the drive signal in a modification.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. overall structure〕
FIG. 1 is a diagram showing a schematic configuration of an electronic timepiece 1 as an electronic apparatus in the present embodiment. FIG. 2 is a plan view showing a detailed configuration of the date display mechanism 10 in the electronic timepiece 1.
As shown in FIG. 1, the electronic timepiece 1 is a wristwatch including a pointer 2 that displays time and a stepping motor 3 that drives the pointer 2. The driving of the stepping motor 3 is controlled by the oscillation circuit 4, the frequency dividing circuit 5, and the drive circuit 6. The oscillation circuit 4 has a reference oscillation source made of a crystal oscillator and outputs a reference pulse. The frequency dividing circuit 5 receives the reference pulse output from the oscillation circuit 4 and generates a reference signal (for example, a 1 Hz signal) based on the reference pulse. The drive circuit 6 generates a motor drive pulse for driving the stepping motor 3 based on the reference signal output from the frequency divider circuit 5.
The date display mechanism 10 of the electronic timepiece 1 includes a piezoelectric actuator A and a drive control device 100 that drives and controls the piezoelectric actuator A. The drive control device 100 is actuated with a switch 8 that detects and opens and closes the time (for example, 24:00) of the electronic timepiece 1 as a trigger, and drives the date display mechanism 10. In the present embodiment, the switch 8 outputs a detection signal to the drive control device 100 when detecting 24:00. The drive control device 100 starts drive control of the piezoelectric actuator A by this detection signal. The drive of the piezoelectric actuator A is started by the start of this drive control.

  As shown in FIG. 2, the main part of the date display mechanism 10 decelerates the rotation of the piezoelectric actuator A, the rotor 20 as a driving target (driven body) driven to rotate by the piezoelectric actuator A, and the rotation of the rotor 20. The speed reduction wheel train is transmitted while the date wheel 50 is rotated by the driving force transmitted through the speed reduction wheel train. The reduction gear train includes a date turning intermediate wheel 30 and a date turning wheel 40. The piezoelectric actuator A, the rotor 20, the date driving intermediate wheel 30, and the date driving wheel 40 are supported by the bottom plate 11. The piezoelectric actuator A has a flat strip-shaped vibrating body 12, and the vibrating body 12 is disposed so that the tip end thereof is in contact with the outer peripheral surface of the rotor 20. As shown in FIG. 1, a disk-shaped dial 7 is provided above the date display mechanism 10, and a window 7 </ b> A for displaying the date is provided on a part of the outer peripheral portion of the dial 7. It is provided so that the date of the date indicator 50 can be seen from the window portion 7A. In addition, a movement or the like that is connected to the stepping motor 3 and drives the pointer 2 is provided below the bottom plate 11 (on the back side).

The intermediate date wheel 30 is composed of a large diameter portion 31 and a small diameter portion 32. The small-diameter portion 32 is a cylindrical shape having a slightly smaller diameter than the large-diameter portion 31, and a substantially square notch 33 is formed on the outer peripheral surface thereof. The small diameter portion 32 is fixed to the large diameter portion 31 so as to be concentric. The large-diameter portion 31 meshes with the gear 21 at the top of the rotor 20. Therefore, the date driving intermediate wheel 30 including the large diameter portion 31 and the small diameter portion 32 rotates in conjunction with the rotation of the rotor 20.
A leaf spring 34 is provided on the bottom plate 11 on the side of the intermediate date wheel 30, and a base end portion of the leaf spring 34 is fixed to the bottom plate 11, and a distal end portion 34 </ b> A is bent into a substantially V shape. Is formed. The distal end portion 34A of the leaf spring 34 is provided so as to be able to enter and leave the notch 33 of the intermediate date wheel 30. A contact 35 is disposed at a position close to the leaf spring 34. The contact 35 is rotated when the intermediate date wheel 30 rotates and the front end 34 A of the leaf spring 34 enters the notch 33. The leaf spring 34 is brought into contact. A predetermined voltage is applied to the leaf spring 34, and when the contact is made with the contact 35, the voltage is also applied to the contact 35. Therefore, by detecting the voltage of the contactor 35, the date feeding state can be detected, and the amount of rotation of the date dial 50 for one day can be detected.
The amount of rotation of the date wheel 50 is not limited to that using the leaf spring 34 or the contact 35, but the rotation amount of the rotor 20 or the date turning intermediate wheel 30 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 40 has a five-tooth gear and meshes with an internal gear 51 of the date dial 50. A shaft 41 is provided at the center of the date driving wheel 40, and the shaft 41 is loosely inserted into a through hole 42 formed in the bottom plate 11. The through hole 42 is formed long along the circumferential direction of the date dial 50. The date driving wheel 40 and the shaft 41 are urged in the upper right direction in FIG. 2 by a plate spring 43 fixed to the bottom plate 11. The urging action of the leaf spring 43 prevents the date dial 50 from swinging.

The vibrating body 12 of the piezoelectric actuator A is a rectangular plate surrounded by two long sides and two short sides (for example, a long side and a short side in which the ratio of the long side length to the short side length is approximately 7 to 2). It is. For example, the long side × the short side is a dimension between 7 mm × 2 mm and 3.3 mm × 1 mm. The vibrating body 12 has a reinforcing plate made of stainless steel or the like sandwiched between two rectangular and plate-like piezoelectric elements that are substantially the same shape as these piezoelectric elements and are thinner than the piezoelectric elements. It has a laminated structure. Piezoelectric elements include lead zirconate titanate (PZT ™), quartz, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zinc niobate, lead scandium niobate, etc. Various things can be used.
The vibrating body 12 has a contact portion 13 at a substantially end portion in the width direction of one short side. The contact portion 13 is obtained by a method such as cutting and molding a reinforcing plate, and a tip portion having a gently curved surface is projected from the piezoelectric element. The vibrating body 12 is configured such that the abutting portion 13 is disposed on one end side in the width direction and a weight imbalance is generated in the width direction. The vibrating body 12 maintains a posture in which the tip of the contact portion 13 is in contact with the outer peripheral surface of the rotor 20. In order to cause the vibrating body 12 to maintain such a posture, the support member 14 and the biasing member 15 are provided in the piezoelectric actuator A. Note that a balance projection 13A having the same size as the contact portion 13 is also formed on the other short side that is not the short side on which the contact portion 13 is formed. The balance protrusion 13 </ b> A is provided at a point-symmetrical position with respect to the center point of the planar shape of the vibrating body 12.

  The support member 14 of the piezoelectric actuator A is integrally formed with the reinforcing plate by a method such as cutting and forming the reinforcing plate. The support member 14 is an L-shaped member, and a vertical portion that protrudes perpendicularly from the approximate center of one long side of the vibrating body 12 and the rotor 20 side parallel to the long side from the tip of the vertical portion. And a horizontal portion extending toward the surface. A pin protruding from the bottom plate 11 passes through the end of the horizontal portion opposite to the vertical portion, and the support member 14 and the vibrating body 12 fixed thereto can be rotated with this pin as a rotation axis. . One end of the urging member 15 is engaged with the approximate center of the horizontal portion of the support member 14. The urging member 15 has a pin protruding from the bottom plate 11 passing through a substantially central portion thereof, and is rotatable about the pin as a rotation axis. Further, the end of the biasing member 15 on the side opposite to the support member 14 is engaged with the bottom plate 11, and the contact portion 13 of the vibrating body 12 is changed to the outer peripheral surface of the rotor 20 by changing the position of this end. The pressure to be pressed against can be adjusted.

  In the above configuration, the vibrating body 12 of the piezoelectric actuator A is excited by the longitudinal vibration, which is the first vibration mode (main vibration mode), when a drive signal having a predetermined frequency is applied from the drive control device 100 to the piezoelectric element. In addition, since the weight imbalance is generated by the contact portion 13 and the balance projection portion 13A, the bending vibration which is the second vibration mode (sub vibration mode) is excited by the longitudinal vibration, and these are excited. Are mixed, and the contact portion 13 moves in an elliptical orbit in a plane including the plate surface. The outer surface of the rotor 20 is hit by the contact portion 13 of the vibrating body 12, and is rotated clockwise as indicated by an arrow in FIG. The rotation of the rotor 20 is transmitted to the date indicator driving wheel 40 via the date indicator driving intermediate wheel 30, and the date indicator driving wheel 40 rotates the date indicator 50 in the clockwise direction. The transmission of force from the vibrating body 12 to the rotor 20, the rotor 20 to the speed reduction wheel train (the date turning intermediate wheel 30 and the date turning wheel 40), and the speed reduction wheel train to the date wheel 50 are both transmitted to the bottom plate of the vibration body 12. Transmission of force in a direction parallel to the eleventh surface. For this reason, the date display mechanism 10 can be thinned by arranging the vibrating body 12 and the rotor 20 in the same plane, instead of stacking coils and rotors in the thickness direction as in the step motor. Since the date display mechanism 10 can be made thin, the entire electronic timepiece 1 can be made thin.

[2. Configuration of Piezoelectric Actuator Drive Control Device]
Next, the drive control apparatus 100 of this embodiment is demonstrated based on the block diagram of FIG.
As shown in FIG. 3, the drive control device 100 that drives and controls the piezoelectric actuator A detects the phase difference between the drive signal output to the piezoelectric element 17 and the detection signal detected by the piezoelectric element 17, and corresponds to the phase difference. A phase difference-voltage conversion circuit 101 that outputs a phase difference voltage signal of a voltage value to be output, a constant voltage circuit 102 that outputs a reference voltage for comparing the phase difference and a reference voltage for detecting an amplitude signal, and The comparison circuit 103 that compares the phase comparison reference voltage output from the constant voltage circuit 102 with the phase difference voltage output from the phase difference-voltage conversion circuit 101 and outputs a comparison result signal; A voltage adjustment circuit 104 that controls the output voltage, a drive circuit (driver) 105 that outputs a drive signal to the piezoelectric element 17, and a voltage output by the voltage adjustment circuit 104. In response, the voltage control oscillator (VCO) 106 that adjusts the frequency output to the drive circuit 105 and the amplitude detection reference voltage output from the constant voltage circuit 102 and the amplitude signal of the piezoelectric element 17 are compared. And an amplitude detection circuit 107 for detection.

The voltage adjustment circuit 104 controls the voltage level applied to the voltage controlled oscillator 106 based on the signal output from the comparison circuit 103 and the predetermined time based on the signal output from the amplitude detection circuit 107. And a control speed adjustment function for adjusting the voltage control amount.
The drive circuit 105 outputs a drive signal having a frequency controlled by the voltage adjustment circuit 104 and the voltage controlled oscillator 106 to the piezoelectric element 17. With these configurations, the drive control device 100 always detects (scans) the phase difference between the drive signal and the detection signal, compares it with the reference phase difference, and controls the optimum drive frequency so that the detected phase difference approaches the reference phase difference. Do. This optimum drive frequency exists between the resonance frequency of longitudinal vibration and the resonance frequency of bending vibration.
Further, the drive circuit 105 has an output control function for switching output of a drive signal to the piezoelectric element 17 at a predetermined timing after a predetermined time from the start of driving of the piezoelectric actuator A. For example, the predetermined timing can be detected by measuring the time after the detection signal is input from the switch 8 using a timer circuit or the like. Thus, the application / non-application of the drive signal to the piezoelectric element 17 is controlled by this output control function. The output control function generates a control pulse at a predetermined timing according to the setting, and switches the output to the voltage controlled oscillator 106 on and off based on the generated control pulse. For example, the output from the voltage controlled oscillator 106 and the generated control pulse are input to an AND gate, and the output signal is output to the piezoelectric element 17 so that the drive signal is applied or not at the timing of the generated control pulse. Application is controlled. The application / non-application control may be performed inside the voltage adjustment circuit 104 and the voltage controlled oscillator 106.

[3. Piezoelectric actuator drive control method]
In this embodiment, when the 24-hour detection means (switch) 8 detects that the time of the electronic timepiece 1 has reached 24:00, the detection signal turns on / off the power supply battery of the drive control device 100. Turn on (not shown). For this reason, when the drive control device 100 operates as described above, the piezoelectric actuator A is operated, and the date feeding operation of the date dial 50 is performed.
Here, the operation at the time of activation of the piezoelectric actuator A will be described. At the start of application of the drive signal, only longitudinal vibration is generated in the piezoelectric actuator A and only linear motion is generated, but bending vibration is gradually generated. Then, elliptical vibration occurs due to the synergistic action of longitudinal vibration and bending vibration, and the ellipse gradually increases. When the elliptical motion of a certain size is reached, the contact portion 13 can drive the rotor 20. Immediately after the start of application of the drive signal, the rotor 20 is less likely to be driven by the friction between the contact portion 13 and the rotor 20 even if the contact portion 13 moves somewhat. Therefore, immediately after the start of application of the drive signal, there is a period in which the rotor 20 does not operate even if the vibrating body 12 vibrates.

  FIG. 4 shows changes in the speed of the rotor 20 according to the application time of the drive signal. In FIG. 4, the horizontal axis represents time [msec] from the start of activation of the piezoelectric actuator A (start of application of drive signal to the piezoelectric actuator A), and the vertical axis represents the speed [mm / sec] of the rotor 20. As the application time of the drive signal, seven conditions at 0.06 to 4 msec are shown. As shown in the figure, the time until the rotor 20 starts to move under any of the conditions is substantially constant after about 0.5 msec from the start of activation (at the start of application of the drive signal). That is, whether the drive signal is continuously applied for 0.5 msec or more, or only when the drive signal is applied for less than 0.5 msec, the rotor 20 starts to move when about 0.5 msec elapses after starting. This phenomenon hardly changes even when the voltage applied as the drive signal is changed.

  As described above, the vibrating body 12 operates (vibrates) in two or more mixed modes when a drive signal is applied, and vibrates so that the contact portion 13 with the rotor 20 draws an elliptical locus. If the state of vibration at the initial stage of startup is viewed in detail, the inclination gradually changes in the width direction from the vibration in the longitudinal direction (longitudinal direction) of the vibrating body 12, and is stabilized at a predetermined angle. This predetermined angle is determined by the interval between the longitudinal resonance frequency and the bending resonance frequency of the vibrating body 12 and the driving frequency. This interval is mainly determined by the vertical and horizontal dimensions of the vibrating body 12.

In the vibrating body 12 using resonance vibration, after applying a drive signal, the amplitude gradually increases and becomes a constant amplitude. The vibration body 12 gradually increases in amplitude due to longitudinal vibration after the drive signal is applied. When the longitudinal vibration is excited, the bending vibration gradually increases following the excitation. However, since there is a delay, the inclination gradually changes from the longitudinal direction to the bending vibration direction, and becomes stable after a certain time.
Since the time to stabilization is small in amplitude and the inclination at the time of contact is not suitable for driving, a phenomenon occurs in which the rotor 20 does not move even when the vibrating body 12 vibrates. Therefore, it can be said that the period until the rotor 20 starts moving is a wasteful time after the drive signal is input. After this period, the operation of the rotor 20 is accelerated. Immediately after the rotor 20 starts to move, the speed of the contact portion 13 of the vibrating body 12 is high, and the speed difference with the rotor 20 is large. The transmission rate is low and the acceleration is slow.

In addition, at the initial stage of driving when the driving signal input to the piezoelectric element 17 is started, the driving signal is input while the piezoelectric element 17 is discharged, so that the amount of current flowing through the piezoelectric element 17 increases and the power consumption also increases. Increase.
FIG. 5 shows the change in power according to the application time of the drive signal. In FIG. 5, the horizontal axis represents the time [msec] from the start of activation of the piezoelectric actuator A (at the start of application of the drive signal to the piezoelectric actuator A), and the vertical axis represents the power consumption [mW] due to the application of the drive signal. is there. As the application time of the drive signal, seven conditions at 0.06 to 4 msec are shown as in the case of FIG. As shown in the figure, under any of the conditions, the power is high immediately after the drive signal is applied, a power peak occurs around 0.2 msec, the fluctuation continues for a while, and becomes stable after about 1 msec.

Based on the above, the drive control apparatus 100 of the present embodiment executes initial drive control performed at the initial startup of the piezoelectric actuator A and steady drive control performed after the initial drive control. In the initial drive control, an initial drive signal application control that applies an initial drive signal to the piezoelectric element 17 is executed, and then a non-application control that does not apply a drive signal to the piezoelectric element 17 is executed.
The timing for switching from the initial drive signal application control to the non-application control is set until the operation of the rotor 20 by the application of the initial drive signal is started, that is, a shorter time than the operation of the rotor 20 is started. The timing for switching from the initial drive control to the steady drive control is set after the start of the operation of the rotor 20 and until the operation of the rotor 20 is stopped and the discharge of the piezoelectric element 17 charged by the application of the initial drive signal is completed. ing. The charging of the piezoelectric element 17 means that the piezoelectric element 17 is charged, and the discharging of the piezoelectric element 17 means that the charge of the piezoelectric element 17 is discharged.

  FIG. 6 shows a control flow of the drive control method according to the present embodiment. When the piezoelectric actuator A is activated, the drive control device 100 first performs initial drive signal application control, and an initial drive signal is applied from the drive circuit 105 to the piezoelectric element 17 (step S1). The initial drive signal is applied to the piezoelectric element 17 by the voltage adjustment circuit 104 and the voltage controlled oscillator 106 controlling the drive circuit 105.

  After the application of the initial drive signal is started in step S1, it is determined whether or not it is a switching timing to non-application control (step S2). This determination is made based on whether or not a predetermined period set in advance from the time of activation. The passage of this predetermined period can be detected by the timer circuit or the like as described above. When the predetermined period has not elapsed, it is determined that it is not the switching timing, and when the predetermined period has elapsed, it is determined that it is the switching timing.

  When the determination in step S <b> 2 is “No”, that is, it is determined that it is not the switching timing to the non-application control, the application of the initial drive signal is continued by the initial drive signal application control. If the determination in step S2 is “Yes”, that is, it is determined that it is the switching timing to non-application control, non-application control is started and application of the initial drive signal is stopped (step S3).

After the non-application control is started, it is determined whether or not it is a switching timing to the steady drive control (step S4). This determination is also made based on whether or not a predetermined period set in advance from the time of activation. The elapse of this predetermined period can also be detected by the timer circuit or the like as described above. When the predetermined period has not elapsed, it is determined that it is not the switching timing, and when the predetermined period has elapsed, it is determined that it is the switching timing. If the determination in step S4 is “No”, that is, it is determined that it is not the timing for switching to steady drive control, non-application control (non-application state) is continued. When the determination in step S4 is “Yes”, that is, it is determined that it is the switching timing to the steady drive control, the steady drive control is started and the application of the steady drive signal is started (step S5).
After the start of steady drive control, a normal drive control state is established. That is, as shown in FIG. 3, the frequency of the drive signal is controlled based on the phase difference between the drive signal and the detection signal. Thereafter, the application of the steady drive signal is stopped based on the voltage detection of the contact 35, the drive of the piezoelectric actuator A is stopped, and the date feeding is finished.

[Initial drive signal application period]
In this embodiment, the application period (switching timing to non-application control) of the initial drive signal determined in step S2 is specifically set as follows.
That is, in the case of the piezoelectric actuator A having the characteristics shown in FIG. 4, the application period of the initial drive signal, that is, the switching timing to the non-application control from the viewpoint of electric power and the predetermined time described above, the operation start of the rotor 20 It is set within 0.5msec until the hour. Even if the application time of the initial drive signal is within 0.5 msec, the rotor 20 operates after 0.5 msec on the same principle as when the steady drive signal is applied. This is because vibration is excited, the inclination changes in the bending direction, and the bulge is increased to be suitable for driving.
In the present embodiment, as shown in FIG. 5, in consideration of the point where the power peaks at about 0.2 msec, it is set to switch to non-application control within 0.2 msec from the start of application of the initial drive signal. Yes. Therefore, when a predetermined period (for example, 0.2 msec) elapses from the time of activation, “Yes” is determined in step S2. The elapse of this predetermined period can also be detected by the timer circuit or the like as described above.

[Initial drive control period]
In the present embodiment, the initial drive control period (switching timing to the steady drive control) determined in step S4 is from the start of operation of the rotor 20 to the stop of the operation accompanying the end of the application of the initial drive signal and the application of the initial drive signal. Is set within the period until the discharge of the piezoelectric element 17 charged is completed.
For example, in the example shown in FIG. 4, when the drive signal application time is 0.2 msec, the operation start of the rotor 20 is about 0.5 msec from the start of the initial drive control. The stop is about 2.75 msec. Therefore, the switching timing to the steady drive control may be set in advance within this range (0.5 to 2.75 msec).

Note that the switching timing to the steady drive control can also be set by detecting the vibration state of the vibrating body 12. The vibration state of the vibrating body 12 can be determined by detecting the detection signal of the piezoelectric element 17 by the amplitude detection circuit 107. That is, when the vibration of the vibrating body 12 becomes small, the detection signal also becomes small. Therefore, based on this detection signal, the vibration state of the vibrating body 12 is determined, and when the voltage of the detection signal becomes a predetermined value or less, it is steady. It can also be controlled to switch to drive control.
If the vibration state is detected and the switching timing is adjusted in this manner, even if there is a variation in the operation of the vibrating body 12 and there is a possibility that the operation of the rotor 20 may start and stop, stable and steady drive control is performed. The power can be reduced, and the rotor 20 can also be reliably started.

Here, the setting of the switching timing to the steady drive control will be described in detail with reference to the drawings.
FIG. 7 shows the time until the operating distance of the rotor 20 reaches a predetermined distance (drive end time). In FIG. 7, the horizontal axis is the steady drive signal application start time [msec] from the time of initial drive signal application of the piezoelectric actuator A, and the vertical axis is the drive end time [msec] until the moving distance of the rotor 20 reaches 0.45 mm. ]. As the application time of the initial drive signal, three conditions of 0.06 msec, 0.1 msec, and 0.2 msec are shown.

  For example, when the initial drive signal application time is 0.2 msec and the steady drive signal is applied from 1.5 msec, the drive end time is about 4.8 msec. When driving by applying only the steady drive signal from the start of startup without performing the initial drive control, the drive end time is about 4.4 msec. Therefore, the drive end time is delayed by about 0.3 msec compared to the steady drive signal alone. Will be. However, similarly, even when the application time of the initial drive signal is 0.2 msec, it can be seen that when the application of the steady drive signal is performed within 1 msec, the activation end time hardly changes. Accordingly, it can be understood that the steady drive signal should be applied at an early stage after the rotor 20 starts operating in order to quickly achieve the operating distance of the rotor 20 to a predetermined value. That is, by setting the switching timing to the steady drive control immediately after the operation of the rotor 20 is started, the time until the rotor 20 rotates by a predetermined angle can be shortened to the same extent as when the drive signal is continuously input.

  FIG. 8 shows the application time [msec] of the steady drive signal until the operating distance of the rotor 20 reaches a predetermined position. FIG. 9 shows changes in the operating speed of the rotor 20 due to the application of the initial drive signal when the steady drive signal is applied. 8 and 9, the horizontal axis represents the steady drive signal application start time [msec] from the time of application of the initial drive signal of the piezoelectric actuator A. In FIG. 8, the vertical axis represents the application time [msec] of the steady drive signal until the moving distance of the rotor 20 reaches 0.45 mm. Further, in FIG. 9, the vertical axis represents the speed [mm / s] at the start of steady drive signal application of the rotor 20. As the application time of the initial drive signal, three conditions of 0.06 msec, 0.1 msec, and 0.2 msec are shown as in the case of FIG.

For example, when the initial drive signal is applied at 0.2 msec and the steady drive signal is applied from 1.4 msec near the maximum speed of the rotor 20 (see FIG. 9), the application time is about 3.55 msec. . When driving by applying only the steady drive signal from the start of startup without using the initial drive signal, the application time is about 4.4 msec. Therefore, compared with the case of only the steady drive signal, the applied time is about 0.85 msec. Has been shortened. Since the power consumption is substantially proportional to the application time, the power can be reduced when the application time is short. The effect of this power reduction increases as the usage distance is shorter.
On the other hand, when the steady drive signal is applied from about 0.5 msec, the difference in application time from the case of only the steady drive signal is reduced, and the power reduction effect is reduced accordingly. As a result, in order to suppress the electric power, it is understood that the application of the steady drive signal should be started near the maximum value of the operating speed of the rotor 20 due to the application of the initial drive signal.
That is, even when the application of the steady drive signal is being attenuated while the initial drive signal is being attenuated, the bending has already been excited, so that the inclination and bulge become suitable as in the case of input of the initial drive signal. The time of about 5 msec is not necessary, and it is considered that vibration starts immediately after application of the steady drive signal. Therefore, if the locus of the vibrating body 12 is suitable for driving, the rotor 20 is also accelerated immediately after application of the steady drive signal. It is considered that the acceleration at this time is accelerated from the speed that has been reached by the application of the initial drive signal up to the application point of the steady drive signal. For this reason, if a steady drive signal is applied in the vicinity where the operating speed of the rotor 20 is maximum, the application time to the predetermined operating speed or operating position can be shortened most efficiently, and the power can be suppressed.

  Further, the application timing of the steady drive signal is until the discharge of the piezoelectric element 17 is completed. When the piezoelectric element 17 is completely discharged, a sudden current is applied when the steady drive signal is applied, as in the case of charging at the start-up. This is because it will flow. By applying the steady drive signal before the completion of the discharge, it is possible to prevent the same power consumption as at the start of startup when applying the steady drive signal, and to increase the efficiency at startup. .

FIG. 10 shows an example of speed change, power change, and vibration of the vibrating body 12 when a steady driving signal is applied when the operating speed of the driven body (rotor 20) by applying the initial driving signal is maximum. Is shown. FIG. 11 is an enlarged view showing the waveform of the drive signal.
10 and 11, the application timing of the drive signal is controlled by a control pulse. The initial pulse in the control pulse is a pulse generated by the drive circuit 105 to output the initial drive signal applied to the piezoelectric element 17 by the initial drive control, and is output while the initial pulse is being output (during the ON state). ), An initial drive signal is output. Further, the steady drive pulse, which is another control pulse, is a pulse generated by the drive circuit 105 to output a steady drive signal applied to the piezoelectric element 17 by steady drive control, and the steady drive pulse is output. During this period, a steady drive signal is output.
In the figure, point a is the switching timing from the initial drive signal application control to non-application control, point b is the start of operation of the rotor 20, and point c is the switching timing to steady drive control, that is, the operation of the rotor 20. It is the maximum point of speed. The point c is a timing for switching from the initial drive control (non-application control) to the steady drive control. This timing is before the charge of the piezoelectric element 17 is completely discharged, and naturally the vibration of the vibrating body 12 is stopped. Before.
For example, in the example shown in FIG. 10, from the start of the initial drive signal application control (application of the initial drive signal) to the point a (when application of the initial drive signal is stopped), 0.1 msec, from the start of the initial drive signal application control to b The time from the start of the initial drive signal application control to the point c (at the start of steady drive control) is 1.5 msec until the point (at the start of the operation of the driven body).

In this example, the initial drive signal is applied by one initial pulse in the initial drive signal application control, and a drive signal similar to the steady drive signal is applied for a predetermined time as the initial drive signal. By applying a drive signal similar to the steady drive signal, there is no need to separately provide a circuit for generating the initial drive signal. For example, in the steady drive control, a drive signal having a frequency of 500 kHz to 400 kHz is continuously applied as the steady drive signal, and the same drive signal is applied as the initial drive signal in the initial drive control accordingly.
The steady drive signal is set to a frequency that is optimal for driving the piezoelectric actuator A. As described above, the frequency that is optimal for driving is set based on the phase difference between the driving signal and the detection signal. Thereby, after starting the rotor 20, it can transfer to efficient normal drive immediately. The waveforms of the initial drive signal and the steady drive signal are not particularly limited, and can be configured with various waveforms such as a sine wave, a rectangular wave, a triangular wave, and a sawtooth wave.

As shown in “Change in speed of driven body”, when a steady drive signal is applied from the maximum point of operation speed by applying an initial drive signal, the speed change immediately after application (immediately after the elapse of point c) is as shown in FIG. You can see that it is bigger than Further, as shown in “Power change”, it can be seen that the power can be significantly reduced by setting most of the initial start-up periods of the high power shown in FIG. 5 as the initial drive signal non-application period. Although it is desirable to apply the steady drive signal at the maximum operating speed of the driven body as described above, as shown in FIGS. 8 and 9, the operating speed of the driven body is not less than a predetermined value (for example, Needless to say, even if the operation speed is 90% or more of the maximum speed (depending on the characteristics of the driving body), the same effect as that at the maximum can be obtained. Further, as shown in “Vibration of vibrating body”, it can be seen that the vibration of the vibrating body 12 continues even after the application of the initial drive signal is completed.
The change in the discharge from the piezoelectric element 17 charged by the application of the initial drive signal is similar to the change waveform of “vibration of the vibrating body” in FIG. 10, and in particular from the application of the initial drive signal to the point c. More similar to the changing waveform.

[4. Effects of this embodiment]
In this embodiment, in the initial drive control, after the initial drive signal application control for applying the initial drive signal to the piezoelectric element 17 is executed, the timing for switching from the initial drive signal application control to the non-application control is determined by the application of the initial drive signal. It is set until the operation of the rotor 20 is started. In the initial drive control, after the initial drive signal application control is executed, the non-application control without applying the drive signal to the piezoelectric element 17 is executed. It is possible to greatly reduce power consumption during a period in which there is a large amount of current.
In addition, after switching to non-application control, application of the initial drive signal to the piezoelectric actuator A ends, but the rotor 20 accelerates and the vibration of the vibrating body 12 continues after this switching, so that steady drive control is performed. If the timing for switching to is appropriately set, the time for moving the rotor 20 by a predetermined distance can be set to the same level as when the drive signal is continuously input even in the non-application period. For this reason, by providing a non-application period, it is possible to avoid driving during a period in which the amount of current increases, and by starting steady-state drive control at an appropriate timing, the time required to move the rotor 20 by a predetermined distance can also be obtained. As a result, the power consumption can be greatly reduced as compared with the case where the drive signal is continuously input.

  By setting the timing for switching to the steady drive control from the start of the operation of the rotor 20 to before the stop of the operation, the state in which the rotor 20 is moving while using the damped vibration of the vibrator 12, that is, the vibration of the vibrator 12 Can be applied in a state suitable for driving the rotor 20, and the rotor 20 can be accelerated immediately after the application of the steady drive signal. As a result, the application time for rising is shortened, and power consumption can be suppressed.

When the timing for switching to the steady drive control is set immediately after the start of the operation of the rotor 20, the operating distance of the rotor 20 can be quickly reached to a predetermined value. Thereby, the application time to a predetermined value can be shortened, and power consumption can be reduced.
By setting the timing for switching to the steady drive control until the completion of the discharge of the piezoelectric element 17 charged by the application of the initial drive signal, a rapid current flows at the time of activation when the steady drive signal is applied. Can be suppressed, and power can be reduced.
From these things, according to this embodiment, the efficiency at the time of starting of the piezoelectric actuator A can be improved. In addition, since the circuit for realizing the present embodiment can be configured by a logic circuit that determines application and non-application timings, the circuit size can be reduced as compared with a case where a constant voltage circuit is provided.

Further, when the timing of switching to the steady drive control is set to a timing at which the operating speed of the rotor 20 due to the application of the initial driving signal is equal to or higher than a predetermined value, the operating speed of the rotor 20 due to the application of the initial driving signal is higher than a predetermined value Since the acceleration by the application of the steady drive signal is started, the application time to the predetermined speed of the rotor 20 is shortened, and the power consumption can be suppressed.
Further, when the timing for switching to the steady drive control is determined based on the detection signal obtained from the detection electrode provided on the vibrating body 12, the driven body can be started more stably.

[Modification]
The present invention is not limited to the above embodiment.
For example, the switching timing to the steady drive control is not limited to the measurement using a timer circuit or the like, but is determined based on the operating state of the rotor 20 that is the driven body (for example, the light emitting element with respect to the rotor 20). Determination using an optical position detection means for optically detecting the moving position of the rotor 20 using the light receiving element) or determination based on the discharge state of the piezoelectric element 17 (for example, measuring the current of the piezoelectric element 17 using an ammeter or the like). Determination by current measuring means). The switching timing may be set until the operation of the rotor 20 is stopped or until the discharge of the piezoelectric element 17 charged by applying the initial drive signal is completed.

  Further, the initial drive signal application period may be set until the current flowing through the piezoelectric element 17 is detected by an ammeter or the like and the current value reaches a predetermined value. As a result, it is possible to suppress an abrupt increase in current when the piezoelectric actuator A is activated when the initial drive signal is applied, and to reduce power consumption.

In FIG. 12, the steady drive signal is applied before the vibration of the vibrating body 12 stops and before the discharge of the piezoelectric element 17 is completed, and the current value due to the application of the initial drive signal is non-application control based on the predetermined value α. An example of the speed change of the driven body (rotor 20), the current change, and the vibration of the vibrating body when switching to is shown.
In the figure, point a is when application / non-application of the initial drive signal is switched, and point c is when application of the steady drive signal is started (before discharge of the piezoelectric element 17 is completed). The application period of the initial drive signal is set to a time during which the current due to the application of the initial drive signal does not exceed the predetermined value α.

As in the case of FIG. 10, as shown in “Speed change of driven body”, a steady drive signal is applied during operation of the driven body. It turns out that it is larger than the case of 4. Further, as shown in “Power change”, it can be seen that the power can be significantly reduced because most of the initial start-up time of the high power shown in FIG. 5 is the initial application signal non-application period. Further, as shown in “Vibration of vibrating body”, it can be seen that the vibration of the vibrating body 12 continues even after the application of the initial drive signal is completed.
Furthermore, as shown in “Power change”, since the steady drive signal is applied while the piezoelectric element 17 is charged to some extent, a current that is significantly higher than the current in the steady state does not flow, thereby reducing power. And the burden on the battery can be reduced.
The change in the discharge from the piezoelectric element charged by the application of the initial drive signal is similar to the change waveform of “vibration of the vibrating body” in FIG. 12, and in particular, from the application of the initial drive signal to the point c. More similar to the changing waveform.

In the above embodiment, the initial pulse for controlling the output of the initial drive signal is composed of one pulse. However, the present invention is not limited to this, and the configuration of the initial pulse can drive the rotor 20 by applying the initial drive signal. If it is. For example, the initial pulse can be composed of a plurality of pulses.
FIG. 13 shows an example of the speed change of the driven body, the power change, and the vibration of the vibrating body 12 when the initial pulse is composed of a plurality of pulses. FIG. 14 is an enlarged view showing the waveform of the drive signal in the modification shown in FIG. In the figure, point a is the switching timing from the initial drive signal application control to non-application control, point b is the start of operation of the rotor 20, and point c is the switching timing to steady drive control, that is, the vibration body 12 It is a time before the vibration stops and before the discharge of the piezoelectric element 17 is completed.

In the initial drive signal application control of FIG. 13, the pulse width of each of a plurality of (two in this example) initial pulses is about 0.05 msec, for example. The initial pulse may be generated separately as in the above embodiment, or the initial pulse used in another circuit may be used. Since the piezoelectric actuator A is charged by applying a plurality of initial drive signals up to point a and the normal drive signal is applied at point c before it is fully discharged, the power may be small as shown in “Power change”. The rotor 20 can be driven at a predetermined speed at an early stage.
The change in discharge from the piezoelectric element charged by the application of the initial drive signal is similar to the change waveform of “vibration of the vibrating body” in FIG. 13, and in particular, the change waveform from the application of the initial drive signal to the point c. Is more similar.

  10, 12, and 13, the point c at which the steady drive signal is applied (at the start) is the point at which the operating speed of the rotor 20 (driven body) is maximized by the application of the initial drive signal. However, the present invention is not limited to this, and may be performed while the rotor 20 is operating. That is, in each of the above drawings, it may be from the point b when the operation of the rotor 20 (driven body) is started by the application of the initial drive signal until the operation stops. In this case, since the steady drive signal is applied while the rotor 20 (driven body) is operating, the operation of the rotor 20 is easily promoted and driven to a predetermined position at an early stage.

Further, in FIGS. 10, 12, and 13, the point c at which the stationary drive signal is applied (when starting) is the point after the point b at which the rotor 20 (driven body) is driven by the application of the initial drive signal, If the element 17 is not completely discharged, the rotor 20 (driven body) may be stopped by applying an initial driving signal, or the operation of the rotor 20 (driven body) may be stopped by applying an initial driving signal. If it is before, the piezoelectric element 17 may be completely discharged.
In that case, if the piezoelectric element 17 is not completely discharged even when the rotor 20 (driven body) is stopped at the point c, the charging of the piezoelectric element is completed earlier by applying the steady drive signal, and the vibrating body 12 The vibration of is promoted early. Even if the piezoelectric element 17 is completely discharged, if the operation of the rotor 20 (driven body) continues, the operation of the rotor 20 (driven body) accompanying the vibration of the vibrating body 12 by application of a steady drive signal. Is promoted early.

Furthermore, in FIG. 10, FIG. 12, and FIG. 13, the point c at which the steady drive signal is applied (at the start time) is the point b after the point at which the rotor 20 (driven body) is driven by the application of the initial drive signal. However, the present invention is not limited to this.
That is, in FIG. 10, FIG. 12, and FIG. 13, when the point c at which the steady drive signal is applied (when starting) is after the point b at which the rotor 20 (driven body) is driven by the application of the initial drive signal, If 17 is before the completion of the discharge, the vibration of the vibrating body 12 by the application of the initial driving signal may be stopped, or if the vibration of the vibrating body 12 by the application of the initial driving signal is stopped, the piezoelectric element. 17 may be after discharge completion.
In that case, even if the vibration of the vibrating body 12 is stopped at the point c, if the steady drive signal is applied before the piezoelectric element 17 completes discharging, the charging of the piezoelectric element is completed quickly, and the vibration of the vibrating body 12 is reduced. It can be promoted early. Similarly, at the point c, if the steady drive signal is applied before the vibration of the vibrating body 12 stops even after the piezoelectric element 17 is completely discharged, the vibration of the vibrating body 12 can be immediately promoted.

  10 to 14, the initial drive signal application control period (initial pulse period) is set shorter than the non-application control period. However, it is not limited to that. Depending on the situation, the initial drive signal application control period (initial pulse period) may be set equal to or longer than the non-application control period.

  In FIGS. 10 to 14, the period of the initial pulse (including single and multiple shots) needs to start driving the rotor 20 (driven body) until the electric charge charged in the piezoelectric element is discharged. For example, it is about 0.05 msec or more.

For example, the type of the piezoelectric element 17 is not particularly limited to that described in the above embodiment as long as the above-described vibration operation is possible. For example, a piezoelectric element provided with four drive electrodes by a configuration in which the drive electrodes are divided into two in the longitudinal direction and the width direction, and two outer parts of the three equally divided electrodes in the width direction are further elongated. It may be a piezoelectric element having five drive electrodes by a structure divided into two equal parts in the direction. When these are used, the vibration provided in the central portion in the width direction by applying a driving signal to the driving electrode in the diagonal direction (in the latter case, including the central driving electrode among the three divided electrodes). The rotor 20 can be driven in the same manner as in the above embodiment by vibrating the protrusions of the body. In this case, by changing the electrode to which the drive signal is applied to another diagonal electrode, it is possible to change the direction of the elliptical rotation caused by the vibration of the protrusion that is in contact with the rotor 20. That is, the rotation direction of the rotor 20 can be changed.
The piezoelectric actuator of the present invention is not limited to driving the date wheel 50 but may be used for driving the hands 2. Furthermore, the present invention is not limited to being used as a drive mechanism in an electronic timepiece, but can also be used as a drive source for various electronic devices such as a camera lens mechanism. That is, the electronic device having the piezoelectric driving device of the present invention may be, for example, various instruments that drive the display needle with the piezoelectric driving device, or an electronic device that drives the driven body such as a turntable. In particular, the piezoelectric drive device of the present invention is widely used as a drive source that requires anti-magnetism because it has excellent anti-magnetic performance compared to a stepping motor or the like.

  DESCRIPTION OF SYMBOLS 1 ... Electronic timepiece, 8 ... 24 hour detection means, 9 ... Power supply, 10 ... Date display mechanism, 12 ... Vibrating body, 17 ... Piezoelectric element, 20 ... Rotor, 30 ... Date turning intermediate wheel, 40 ... Date turning wheel, 50 DESCRIPTION OF SYMBOLS ... Date wheel, 100 ... Drive control apparatus, 101 ... Phase difference-voltage conversion circuit, 102 ... Constant voltage circuit, 103 ... Comparison circuit, 104 ... Voltage adjustment circuit, 105 ... Drive circuit, 106 ... Voltage control oscillator, 107 ... Amplitude Detection circuit, A: Piezoelectric actuator.

Claims (7)

A piezoelectric actuator having a piezoelectric element and having a vibrating body that vibrates when a driving signal is applied to the piezoelectric element, and transmitting the vibration of the vibrating body to a driven body;
Drive control means for controlling application of a drive signal to the piezoelectric actuator,
The drive control means includes
An initial drive control performed at the initial start of the piezoelectric actuator and a steady drive control performed after the initial drive control are configured to be executable.
In the initial drive control, an initial drive signal application control that applies an initial drive signal to the piezoelectric element, and a non-application control that does not apply a drive signal to the piezoelectric element after executing the initial drive signal application control,
The timing for switching from the initial drive signal application control to the non-application control is set until the operation of the driven body by the application of the initial drive signal is started,
The timing of switching from the initial drive control to the steady drive control is after the start of the operation of the driven body due to the application of the initial drive signal and the operation of the driven body driven by the application of the initial drive signal The piezoelectric driving device is set up at the time of stopping and / or when the discharge of the piezoelectric element charged by the application of the initial driving signal is completed. The piezoelectric drive device according to claim 1,
The timing for switching to the steady drive control is set to a timing at which the operation speed of the driven body by application of the initial drive signal becomes a predetermined value or more. In the piezoelectric drive device according to claim 1 or 2,
The application period of the initial drive signal is set so that the current of the initial drive signal is a predetermined value or less. In the piezoelectric drive device according to any one of claims 1 to 3,
The piezoelectric drive device according to claim 1, wherein the initial drive signal is an alternating signal having a duty ratio of 50%. In the piezoelectric drive device according to any one of claims 1 to 4,
The piezoelectric drive device characterized in that the timing of switching to the steady drive control is determined based on a detection signal obtained from a detection electrode provided on the vibrating body. A piezoelectric driving method for driving a piezoelectric actuator having a piezoelectric element and having a vibrating body that vibrates by application of a driving signal to the piezoelectric element and transmitting the vibration of the vibrating body to a driven body,
The initial drive control performed at the initial startup of the piezoelectric actuator and the steady drive control performed after the initial drive control are executed,
In the initial drive control, an initial drive signal application control that applies an initial drive signal to the piezoelectric element, and a non-application control that does not apply a drive signal to the piezoelectric element after executing the initial drive signal application control,
The timing for switching from the initial drive signal application control to the non-application control is set until the operation of the driven body by the application of the initial drive signal is started,
The timing of switching from the initial drive control to the steady drive control is after the start of the operation of the driven body by the application of the initial drive signal and the operation of the driven body driven by the application of the initial drive signal The piezoelectric driving method is characterized in that the piezoelectric driving method is set at the time of stopping and / or when the discharging of the piezoelectric element charged by the application of the initial driving signal is completed.   An electronic apparatus comprising: a piezoelectric actuator including a vibrating body having a piezoelectric element; and the piezoelectric driving device according to any one of claims 1 to 5.

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