JP4265493B2 - Drive device for piezoelectric actuator, electronic device - Google Patents

Description

The present invention drives the pressure electrostatic actuator relates to an electronic equipment.

  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, a method is known in which the frequency of the drive signal is swept (changed) in a wide range including the frequency range of the drive signal that fluctuates, and the motor is driven reliably (see, for example, Patent Document 1).

That is, in Patent Document 1, a triangular wave or a sawtooth wave 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 to drive the piezoelectric vibrator. Therefore, it is possible to reliably drive the piezoelectric vibrator (piezoelectric actuator).

Japanese Patent Publication No. 5-16272

By the way, as in Patent Document 1, 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 The drive frequency region changes depending on the ambient temperature and load fluctuations. 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 Also fluctuate. For this reason, 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 cannot be improved.

An object of the present invention can reliably drive the piezoelectric actuator, and power consumption can be reduced, the drive of the pressure electrostatic actuator that can reduce variations of the drive speed of the driven body driven by the piezoelectric actuator, the piezoelectric actuator the invention is to provide an electronic equipment having.

The piezoelectric actuator driving apparatus according to the present invention includes a vibrating body that vibrates when a driving signal having a predetermined frequency is applied to the piezoelectric element, and a contact portion that is provided on the vibrating body and is in contact with a drive target. A piezoelectric actuator driving device for supplying a driving signal to the piezoelectric element in the piezoelectric actuator, wherein the frequency of the driving signal supplied to the piezoelectric element is swept within a predetermined range, and a detection signal indicating a vibration state of the vibrating body is generated. Frequency control means for detecting and controlling the sweep speed of the frequency of the drive signal based on the detection signal, and the frequency control means outputs an amplitude detection reference voltage for detecting the amplitude of the detection signal. Compare the constant voltage circuit, the amplitude detection reference voltage output from the constant voltage circuit with the amplitude of the detection signal, and output a comparison result signal. An amplitude detection circuit, a voltage adjustment circuit that adjusts the change speed of the output voltage based on the comparison result signal, and a variable frequency oscillator that can vary the frequency of the output signal according to the voltage output from the voltage adjustment circuit 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 conversion for setting a voltage value of an output voltage based on a counter value of the up / down counter And a control circuit for controlling a counter value of the up / down counter based on the clock signal, the control circuit controlling an increase / decrease pattern of the up / down counter and used based on the comparison result signal characterized in that switching the clock signal for controlling the count rate of the up-down counter It is intended to.

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, since 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, when the drive target is in the non-drive state, the sweep speed of the frequency of the drive signal is increased and the drive state Sometimes it can be slow. 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 (Variation) can be reduced, and high-speed driving can also be realized.
Further, in the present invention, by comparing the amplitude detection reference voltage output from the constant voltage circuit and the amplitude (voltage) of the detection signal, it is possible to detect whether the driving target is in a driving state or a non-driving 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 rate of the voltage output from the voltage adjustment circuit. Since the frequency sweep speed can be set, the frequency of the drive signal and the frequency sweep speed can be adjusted easily and with high accuracy.
Furthermore, if the counter value of the up / down counter is controlled by the control circuit, the frequency of the drive signal can be controlled, so that various increase / decrease patterns can be easily controlled. For example, in the case of performing a down pattern in which the frequency of the drive signal is decreased from the set maximum value to the minimum value, and when the minimum value is reached, the value is returned to the maximum value again and repeatedly decreased to the minimum value. The initial value of the down counter is set to the maximum value, a signal is input to the down input of the counter, the counter value is decreased, and when the counter reaches the minimum value, the counter only needs to be reset to the initial value, and 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, the frequency of the signal input to the counter can be easily realized by simply switching the frequency of the clock signal output from the clock circuit in the control circuit. .

Here, the frequency control means detects a driving state in which the vibration target vibrates and the driving target is driven or a non-driving state in which the driving target is not driven based on the detection signal, and the driving target is When in the drive state, it is preferable to set the sweep speed of the frequency of the drive signal to be lower than the speed when the drive target is in the non-drive state.
Further, the frequency control means compares the amplitude of the detection signal with an amplitude detection reference voltage, and determines that the drive target is in a non-drive state when the amplitude is less than the amplitude detection reference voltage. When the sweep speed of the frequency of the drive signal is set to the first set speed and the amplitude is equal to or larger than the reference voltage for amplitude detection, it is determined that the drive target is driven and the frequency of the drive signal is It is preferable to set the sweep speed to a second set speed that is lower than the first set speed.
At this time, the first set speed is preferably 10 to 200 times the second set speed.
According to these inventions, the same operational effects as those of the piezoelectric actuator driving method according to the second to fourth aspects can be obtained.

  In the piezoelectric actuator driving apparatus according to the present invention, the frequency control means includes a frequency increase / decrease control means for increasing or decreasing the frequency of the drive signal, and a frequency for controlling a sweep speed for increasing or decreasing the frequency of the drive signal. An increase / decrease speed control means, wherein the frequency increase / decrease control means performs control to increase or decrease the frequency of the drive signal within a preset frequency range, and the frequency increase / decrease speed control means is based on the detection signal. It is preferable to control the sweep speed of the frequency of the drive signal.

  In the invention of this configuration, the frequency increase / decrease control means sets the frequency increase / decrease pattern of the drive signal, and the frequency increase / decrease speed control means sets the frequency sweep speed of the drive signal. For this reason, since the increase / decrease pattern and the sweep speed can be set independently, control is facilitated and various patterns and speed changes can be set in combination, and optimal control for various piezoelectric actuators can be easily realized.

An electronic apparatus according to the present invention includes a vibrating body that vibrates when a drive signal having a predetermined frequency is applied to the piezoelectric element, a piezoelectric actuator that is provided on the vibrating body and has a contact portion that is in contact with a driving target, 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. .

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 mechanism driven by a piezoelectric actuator is illustrated.

[1. overall structure]
FIG. 1 is a plan view showing a date display mechanism 90 of the electronic timepiece 1 according to the present embodiment. In FIG. 1, the main part of the date display mechanism 90 is a piezoelectric actuator 91, a rotor 92 as a driving target (driven body) that is rotationally driven by the piezoelectric actuator 91, and transmission while reducing the rotation of the rotor 92. And a date wheel 93 that is rotated by a driving force transmitted through the speed reduction wheel train. The speed reduction wheel train includes a date turning intermediate wheel 94 and a date turning wheel 95. The piezoelectric actuator 91, the rotor 92, the date driving intermediate wheel 94, and the date driving wheel 95 are supported by the bottom plate 9A.

  A disk-shaped dial (not shown) is provided above the date display mechanism 90, and a window for displaying the date is provided on a part of the outer periphery of the dial. You can see the date of the date wheel 93. Further, below the bottom plate 9A (on the back side), a moving wheel train (not shown) connected to a stepping motor to drive a pointer, a secondary battery 9B as a power source, and the like are provided. The secondary battery 9B supplies power to each circuit of the stepping motor, the piezoelectric actuator 91, and the application device (not shown). The secondary battery 9B is connected to a generator that generates power using solar (solar) power generation or rotation of a rotating weight, and the power generated by the generator is charged to the secondary battery 9B. May be. The power source is not limited to the secondary battery 9B charged by the generator, but may be a general primary battery (for example, a lithium ion battery).

The intermediate date wheel 94 is composed of a large diameter portion 941 and a small diameter portion 942. The small diameter portion 942 is a cylindrical shape having a slightly smaller diameter than the large diameter portion 941, and a substantially square notch portion 943 is formed on the outer peripheral surface thereof. The small diameter portion 942 is fixed to the large diameter portion 941 so as to be concentric. The large diameter portion 941 is engaged with a gear 921 at the top of the rotor 92. Therefore, the date driving intermediate wheel 94 composed of the large diameter portion 941 and the small diameter portion 942 rotates in conjunction with the rotation of the rotor 92.
A leaf spring 944 is provided on the bottom plate 9A on the side of the date driving intermediate wheel 94. A base end portion of the leaf spring 944 is fixed to the bottom plate 9A, and a distal end portion is bent into a substantially V shape. Has been. The front end of the leaf spring 944 is provided so as to be able to enter and leave the notch 943 of the intermediate date wheel 94. A contact 945 is disposed in the vicinity of the leaf spring 944, and the contact 945 is rotated when the intermediate date wheel 94 rotates and the tip of the leaf spring 944 enters the notch 943. It comes in contact with the leaf spring 944. A predetermined voltage is applied to the leaf spring 944, and when the contact is made with the contact 945, the voltage is also applied to the contact 945. Therefore, by detecting the voltage of the contact 945, the date feeding state can be detected, and the amount of rotation of the date wheel 93 for one day can be detected.
The amount of rotation of the date wheel 93 is not limited to that using the leaf spring 944 or the contact 945, and the rotation amount of the rotor 92 or the date turning intermediate wheel 94 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 wheel 93 has a ring shape, and an internal gear 931 is formed on the inner peripheral surface thereof. The date indicator driving wheel 95 has a five-tooth gear and meshes with an internal gear 931 of the date dial 93. A shaft 951 is provided at the center of the date driving wheel 95, and the shaft 951 is loosely inserted into a through hole 9C formed in the bottom plate 9A. The through hole 9 </ b> C is formed long along the circumferential direction of the date dial 93. The date indicator driving wheel 95 and the shaft 951 are urged in the upper right direction in FIG. 1 by a leaf spring 952 fixed to the bottom plate 9A. The bias of the leaf spring 952 prevents the date wheel 93 from swinging.

FIG. 2 shows an enlarged view of the piezoelectric actuator 91 and the rotor 92. As shown in FIG. 2, the piezoelectric actuator 91 includes a substantially rectangular plate-shaped reinforcing plate 911 and piezoelectric elements 912 bonded to both surfaces of the reinforcing plate 911.
Arm portions 913 projecting on both sides are formed at substantially the center in the longitudinal direction of the reinforcing plate 911, and one of these arm portions 913 is fixed to the bottom plate 9A with screws or the like. The other arm portion 913 is not fixed to the bottom plate 9A, is in a free state, and serves as a weight that balances vibration when the piezoelectric actuator 91 vibrates.
At both diagonal ends of the reinforcing plate 911, substantially semicircular convex portions 914 that protrude along the longitudinal direction of the reinforcing plate 911 are formed. One of the convex portions 914 is in contact with the side surface of the rotor 92.

  The piezoelectric element 912 is formed in a substantially rectangular plate shape, and is bonded to substantially rectangular portions on both surfaces of the reinforcing plate 911. Electrodes are formed on both surfaces of the piezoelectric element 912 by plating layers. A substantially rectangular detection electrode 912 </ b> B is formed on the surface of the piezoelectric element 912 by insulating the plating layer with a groove. The detection electrode 912B is formed on the rotor 92 side with respect to the longitudinal center of the piezoelectric element 912 and on the convex portion 914 side with respect to the lateral center of the piezoelectric element 912. A portion other than the detection electrode 912B is a drive electrode 912A. Here, the area of the detection electrode 912B is set to 1/30 to 1/7 of the area of the drive electrode 912A, and more preferably set to 1/15 to 1/10. .

  When a voltage having a predetermined frequency is applied to the drive electrode 912A of the piezoelectric actuator 91 as described above, the piezoelectric element 912 excites vibration in the longitudinal primary vibration mode that expands and contracts along the longitudinal direction. At this time, since the convex portions 914 are provided at both diagonal ends of the piezoelectric actuator 91, the weight of the piezoelectric actuator 91 is unbalanced with respect to the center line in the longitudinal direction as a whole. Due to this imbalance, the piezoelectric actuator 91 excites vibrations in a bending secondary vibration mode that bends in a direction substantially orthogonal to the longitudinal direction. Therefore, the piezoelectric actuator 91 excites vibrations that combine these longitudinal primary vibration mode and bending secondary vibration mode, and the convex portion 914 vibrates in a substantially elliptical orbit. At this time, the piezoelectric actuator 91 is fixed only by the arm portion 913 on one side, and the convex portion 914 is provided at the upper end portion of the diagonal line and receives a reaction force from the rotor 92. And the vibration node in the bending secondary vibration mode are at positions shifted from the center of the piezoelectric element 912. That is, the detection electrode 912B is formed in the piezoelectric actuator 91 at a position including a vibration node in the longitudinal primary vibration mode and a vibration node in the bending secondary vibration mode. Accordingly, in the present embodiment, the vibrating body is configured by the reinforcing plate 911 and the piezoelectric element 912, and the contact portion is configured by the convex portion 914.

The drive electrode 912A, the detection electrode 912B, and the reinforcing plate 911 are each connected to a drive device (applying device) (not shown) by a lead wire or the like. A specific configuration of the driving device will be described later.
A leaf spring 922 is attached to the rotor 92, and the rotor 92 is biased toward the piezoelectric actuator 91 side. As a result, an appropriate frictional force is generated between the convex portion 914 and the side surface of the rotor 92, and the transmission efficiency of the driving force of the piezoelectric actuator 91 is improved.

In such a timepiece 1, when a drive signal of a predetermined frequency is applied by the drive device controlling the drive signal to the piezoelectric actuator 91, the piezoelectric actuator 91 is in the longitudinal primary vibration mode and the bending secondary vibration mode. Exciting vibration combined with. The convex portion 914 vibrates in a substantially elliptical orbit combining these vibration modes, and rotates the rotor 92 by pressing the rotor 92 with a part of the vibration orbit.
The rotational movement of the rotor 92 is transmitted to the date indicator driving intermediate wheel 94, and when the teeth of the date indicator driving wheel 95 are engaged with the notch 943, the date indicator driving wheel 95 is rotated by the date indicator driving intermediate wheel 94, and the date indicator 93 is rotated. Let By this rotation, the date displayed by the date wheel 93 is changed.

[2. Piezoelectric Actuator Driving Device and Driving Method]
Next, the configuration of the driving device 50 for the piezoelectric actuator 91 will be described with reference to FIG.
In FIG. 3, the drive device 50 is output from a drive circuit 55 that outputs a drive signal to the piezoelectric element 912 of the piezoelectric actuator 91, a constant voltage circuit 52 that outputs a reference voltage for amplitude detection, and a constant voltage circuit 52. The amplitude detection circuit 57 that compares the amplitude detection reference voltage and the amplitude (voltage) of the detection signal output from the piezoelectric actuator 91 and outputs a comparison result signal, and the comparison result signal from the amplitude detection circuit 57 A voltage adjustment circuit 54 that adjusts the output voltage, and a variable frequency oscillator (VCO) 56 that adjusts the frequency of the signal output to the drive circuit 55 corresponding to the voltage output from the voltage adjustment circuit 54 are provided. . The drive circuit 55 outputs a drive signal corresponding to the frequency of the signal input from the variable frequency oscillator 56 to the piezoelectric element 912.

Here, in the present embodiment, a drive control unit that includes the drive circuit 55, the variable frequency oscillator 56, and the voltage adjustment circuit 54 and controls the frequency of the drive signal supplied to the piezoelectric actuator 91 is configured. The drive control unit, the constant voltage circuit 52, and the amplitude detection circuit 57 are included to constitute a frequency control means.
The amplitude detection circuit 57 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.
In addition, as a detection signal output from the piezoelectric element 912, a signal output from the detection electrode 912B of the piezoelectric element 912 is used.

The voltage adjustment circuit 54 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 57. An example of the configuration of the voltage adjustment circuit 54 is shown in FIG.
The voltage adjustment circuit 54 includes a voltage adjustment unit 541 that adjusts a voltage output to the variable frequency oscillator 56, a clock circuit 542 as a reference signal oscillator that can output clock signals (reference signals) having a plurality of frequencies, and the clock circuit. And a control circuit 543 that outputs a signal to the voltage adjustment unit 541 corresponding to the clock signal output at 542.

The voltage adjustment unit 541 includes an up / down counter (UD counter) 544 and a digital / analog converter (D / A converter) 545 that converts a digital signal output from the UD counter 544 into an analog signal. .
The control circuit 543 performs control so that the counter value of the UD counter 544 is increased or decreased within a preset range. This increase / decrease pattern may be set in advance, or may be selected from a plurality of patterns registered in advance according to the driving state of the piezoelectric element 912 and the like. As the increase / decrease pattern, the counter value is sequentially decreased from the maximum value to the minimum value of the UD counter 544, and when the minimum value is reached, the count value is returned to the maximum value again. From the minimum value to the maximum value of the UD counter 544 The counter value is sequentially increased, and when it reaches the maximum value, it returns to the minimum value again. The counter value is decreased from the maximum value to the minimum value of the UD counter 544, and when it reaches the minimum value, the counter value is increased to the maximum value. When the maximum value is reached, a reciprocating pattern for reducing the counter value to the minimum value is appropriately set.

  Further, the control circuit 543 is configured to switch the counting speed (counter value changing speed) of the UD counter 544 in accordance with the comparison result signal input from the amplitude detection circuit 57. For example, if the comparison result signal is at the H level, the control circuit 543 changes the counter value of the UD counter 544 using a slow clock signal (for example, 100 kHz) among the clock signals output from the clock circuit 542. If the comparison result signal is at the L level, the counter value is changed using a high-speed clock signal (for example, 1 MHz). Thereby, the changing speed of the counter value of the UD counter 544 is switched.

As the UD counter 544, a counter of about 10 bits or 12 bits can be used. By inputting a pulse signal from the control circuit 543 to the down input or the up input of the UD counter 544, the signal is counted and the counter value is changed. Is. Note that the number of bits of the UD counter 544 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.
The D / A converter 545 has a frequency control voltage value corresponding to the counter value of the UD counter 544 set therein. When the D / A converter 545 receives the counter value output from the UD counter 544, the D / A converter 545 outputs a frequency control voltage corresponding to the frequency control voltage value corresponding to the counter value to the variable frequency oscillator 56.
The variable frequency oscillator 56 outputs a frequency signal corresponding to the voltage output from the D / A converter 545 to the drive circuit 55, and the drive circuit 55 outputs a drive signal having a frequency corresponding to the frequency of the input signal to the piezoelectric element. Output to 912. Therefore, the frequency of the drive signal is set by the counter value of the UD counter 544, 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 544, that is, the frequency of the clock signal used by the control circuit 543. Will be set.

  Therefore, the voltage adjustment circuit 54 sweeps (increases / decreases) the frequency of the drive signal supplied to the piezoelectric element 912 via the variable frequency oscillator 56 and the drive circuit 55 and outputs from the amplitude detection circuit 57. 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 the present embodiment, among the frequency control means, the frequency adjustment control means for controlling the increase / decrease in the frequency of the drive signal, and the frequency for controlling the increase / decrease ratio (sweep speed) of the frequency of the drive signal, mainly by the voltage adjustment circuit 54. An increase / decrease ratio control means is configured.

Next, a driving method of the piezoelectric actuator using the driving device 50 will be described based on the flowcharts of FIGS.
As shown in FIG. 5, when the drive device 50 is turned on or instructed to start driving, the drive device 50 starts a frequency sweep of the drive signal output to the piezoelectric element 912 (Step 1, “S” hereinafter). 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 54. For example, the sweep direction is DOWN (direction in which the frequency of the drive signal is lowered), the sweep speed is high (A × 10 kHz / sec), and the drive signal frequency at the start of driving is MAX. Therefore, the frequency of the drive signal is sequentially decreased from MAX in the frequency range according to the sweep speed.

Specifically, the frequency control of the drive signal is performed as follows. That is, the control circuit 543 sets the counter value of the UD counter 544 to a value corresponding to the drive signal frequency MAX, and then inputs a pulse signal to the down input of the UD counter 544 based on the clock signal from the clock circuit 542. Then, the counter value of the UD counter 544 is decreased.
Since the voltage corresponding to the count value of the UD counter 544 is output from the D / A converter 545, if the counter value of the UD counter 544 decreases, the voltage output from the D / A converter 545 also decreases sequentially. .
Then, a signal having a frequency corresponding to the voltage value is output from the variable frequency oscillator 56, and a drive signal corresponding to the frequency is output from the drive circuit 55, and the piezoelectric element 912 is driven (excited) (S2).

When the piezoelectric element 912 is driven, the amplitude detection circuit 57 and the voltage adjustment circuit 54 execute a sweep speed switching process based on the detection signal output from the detection electrode 912B of the piezoelectric element 912 (S3).
In the sweep speed switching process (S3), as shown in FIG. 6, the amplitude detection circuit 57 monitors the detection signal output from the piezoelectric element 912 (S31), and sets the amplitude (voltage) of the detection signal to a constant voltage circuit. The amplitude detection reference voltage output from 52 is compared (S32).

In S32, the amplitude detection circuit 57 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 57 outputs an L level comparison result signal (S34).
When the voltage adjustment circuit 54 receives the H level comparison result signal, the voltage adjustment circuit 54 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.
On the other hand, when the voltage adjustment circuit 54 receives the L level comparison result signal, the voltage adjustment circuit 54 increases the sweep speed (S36). That is, when the sweep speed is set to a high speed, the state is maintained, and when the sweep speed is set to a low speed, the speed is switched to a high speed.
In the present embodiment, as shown in FIG. 6, the low speed sweep is AkHz / sec, and the high speed sweep is A × 10 kHz / sec which is 10 times the low speed. A is, for example, “10” 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 drive signal frequency initialization process S4 is performed as shown in FIG.
In the drive signal frequency initialization process S4, as shown in FIG. 7, the control circuit 543 of the voltage adjustment circuit 54 confirms the setting of the sweep direction (S41). If the sweep direction is the DOWN direction, the control circuit 543 determines whether or not the drive frequency is the minimum value (MIN) within a predetermined frequency range (S42). Specifically, since the frequency of the drive signal corresponds to the counter value of the UD counter 544, the control circuit 543 confirms the counter value of the UD counter 544 to determine whether or not the drive frequency is the minimum value. to decide.
If the sweep direction is DOWN and the drive frequency is the minimum value, the control circuit 543 changes the drive frequency to the maximum value (S43). Specifically, the control circuit 543 changes the counter value of the UD counter 544 to a counter value corresponding to the maximum value of the driving frequency.
If the drive frequency is not the minimum value in S42, the drive signal frequency initialization process S4 is terminated without performing the frequency initialization process.

In this embodiment, the sweep direction is set to the DOWN direction. However, if the sweep direction is set to the UP direction, “No” is obtained in S41, and the control circuit 543 has a drive frequency of a predetermined frequency. It is determined whether or not the maximum value (MAX) within the range (S44). Specifically, the control circuit 543 checks the counter value of the UD counter 544 and determines whether or not the drive frequency is the maximum value.
If the sweep direction is UP and the drive frequency is the maximum value, the control circuit 543 changes the drive frequency to the minimum value (S45). Specifically, the control circuit 543 changes the counter value of the UD counter 544 to a counter value corresponding to the minimum value of the driving frequency.
If the drive frequency is not the maximum value in S44, the drive signal frequency initialization process S4 is terminated without performing the frequency initialization process.

  When the drive signal frequency initialization process S4 ends, as shown in FIG. 5, 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. 8 shows the relationship between the rotational speed (rps) of the driven body and the frequency of the drive signal when such control is performed.
The frequency of the drive signal is swept in the DOWN direction from fmax to fmin. Here, the frequency range in which the piezoelectric element 912 is excited (driven) varies depending on the ambient temperature, the load of the driven body, and the like. When the piezoelectric element 912 is excited (driven), the amplitude (detection voltage) of the detection signal increases. Therefore, it can be determined whether or not the vibration of the piezoelectric actuator 91 reaches the vibration that can drive the rotor 92 to be driven, based on whether or not the detected voltage is equal to or higher than the comparison voltage (reference voltage for amplitude detection).
Therefore, as described above, when the detected voltage is lower than the comparison voltage (amplitude detection reference voltage), that is, when it is determined that the rotor 92 is not driven, the sweep speed is set to a high speed, and the detected voltage is When it is less than the comparison voltage (amplitude detection reference voltage), that is, when it is determined that the rotor 92 is driven, the sweep speed is set to a low speed.

  In the example of FIG. 8, the rotor 92 does not rotate at the time when the detected voltage changes from less than the comparison voltage to more than the comparison voltage and in the vicinity thereof. However, even in such a case, since the frequency of the drive signal has reached the vicinity of the frequency range in which the rotor 92 is driven, if the drive signal is input as it is, the rotor 92 starts driving in a short time. That is, the comparison voltage may be set to a value that allows the rotor 92 to be driven reliably. However, as shown in FIG. 8, the frequency of the drive signal is in the vicinity of the frequency range that the rotor 92 is driven, and the drive is performed soon. It may be set to a value that starts. In this way, a low speed sweep can be controlled without fail in the frequency range where the rotor 92 is driven.

[3. Effects of the embodiment]
Therefore, according to the present embodiment, the following operational effects can be achieved.
(1) Since the drive device 50 for the piezoelectric actuator of the present embodiment sweeps the drive signal for driving the piezoelectric element 912 within a predetermined frequency range, the piezoelectric element 912 that is driven within this frequency range is sure. Can be driven. For this reason, if it is an ultrasonic motor using the piezoelectric element 912, a to-be-driven body can be rotated reliably.

(2) Since the drive signal is constantly swept within a predetermined frequency range, even if the drive frequency of the piezoelectric element 912 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 50 with a detection circuit for detecting ambient temperature, disturbance, load fluctuation, or the like, or an adjustment circuit for adjusting the frequency of the drive signal based on the detected data, and the configuration of the drive device 50 Can also be simplified.

(3) Further, the detection state of the rotor 92 is detected by comparing the amplitude (voltage) of the detection signal from the piezoelectric element 912 with the reference voltage for amplitude detection, and the detected amplitude is greater than the reference voltage, that is, the rotor 92 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 92 is not driven, the sweep speed is set to a high speed.
For this reason, for example, in one sweep processing time for sweeping the frequency from fmax to fmin, the time during which the rotor 92 is driven can be lengthened, and the time during the non-driven state can be shortened.
Therefore, since a useless drive signal output time during which the rotor 92 cannot be driven can be shortened, useless current consumption can be reduced and efficiency can be increased. Further, since the time of the non-driving state can be shortened, even if there is a change in the load or the like, the variation of the driving time in a predetermined time such as 1 minute can be reduced, and the rotational speed of the rotor 92 rotated by the piezoelectric element 912 is reduced. Can be reduced, and high-speed driving is also possible.

(4) In the present embodiment, the amplitude detection circuit 57 compares the amplitude of the detection signal with the reference voltage, and the voltage adjustment circuit 54 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 50 can be simplified, and control processing can be easily performed.

(5) The voltage adjustment circuit 54 includes a clock circuit 542, a control circuit 543, a UD counter 544, and a D / A converter 545, and the frequency speed change is controlled by the frequency of the clock signal output from the clock circuit 542. As a result, the speed change range can be widened, and the sweep speed can be easily adjusted in multiple stages.
In addition, since the voltage adjustment unit 541 includes the UD counter 544, an external component is unnecessary, and the sweep speed can be easily changed, so that an IC is advantageous.

(6) The electronic timepiece includes a vibrating body having a piezoelectric element 912, a piezoelectric actuator 91 having a convex portion 914 provided on the vibrating body and abutting against a driving target, the driving device 50 having the above-described configuration, and a piezoelectric actuator. Therefore, it is possible to provide an electronic timepiece that consumes less power and can achieve stable drive control in a short time.

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 above embodiment, the amplitude of the detection signal output from the piezoelectric element 912 is compared with the amplitude detection reference voltage to control the driving of the piezoelectric element 912. However, in the present invention, for example, a driver for driving the piezoelectric actuator Further, the switching process of the sweep speed 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.

  Further, when a plurality of detection signals are detected, the amplitude of one predetermined detection signal may be detected to control the frequency of the drive signal. The amplitude may be detected and stored, and 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.

The sweep pattern of the frequency of the drive signal is swept from the predetermined maximum frequency fmax to the minimum frequency fmin as in the above embodiment, and when the minimum frequency fmin is reached, the sweep returns to the maximum frequency fmax and again sweeps toward the minimum frequency fmin. The up pattern that always sweeps from the minimum frequency fmin to the maximum frequency fmax, or the round trip that increases the frequency to the maximum value when the minimum value is reached, and decreases the frequency to the minimum value when the maximum value is reached. A pattern may be adopted.
Further, these sweep patterns may be selected based on the driving state of the piezoelectric element 912.
Furthermore, in the embodiment, the sweep speed in the initial setting is set to a high speed, but may be set to a low speed. However, in the normal case, the object to be driven is not driven at the initially set frequency, so even if it is set to a low speed, it can be immediately switched to a high speed. Therefore, it can be controlled more efficiently when the initial setting is set to a high speed.

  The drive device 50 is not limited to the one using the voltage adjustment circuit 54 having the UD counter 544, but may be one having a voltage adjustment circuit using a plurality of loop filters having different time constants. What is necessary is that the frequency of the drive signal output from 55 to the piezoelectric element 912 can be swept and the sweep speed can be changed in a plurality of stages.

  The amplitude detection circuit 57 does not ask a specific configuration as long as it detects an amplitude. For example, the amplitude detection circuit 57 may detect a certain number of amplitudes within a certain time, or simply detect 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 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.

  Further, 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. Further, 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. Further, the driving mechanism of the meter pointer of a measuring instrument, the driving mechanism of a movable toy, the driving mechanism of a meter pointer of an instrument panel of an automobile, a piezoelectric buzzer, an inkjet head of a printer, an ultrasonic motor, etc. Means may be used.

  In the above embodiment, the piezoelectric actuator is used for driving the date display mechanism 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.

It is a top view which shows the structure of the principal part of the date display mechanism in the electronic timepiece which concerns on embodiment of this invention. It is a top view which shows the piezoelectric actuator used with the said electronic timepiece. It is a block diagram which shows the internal structure of the drive device of a piezoelectric actuator. It is a block diagram which shows the internal structure of a voltage adjustment circuit. It is a flowchart explaining the method to drive a piezoelectric actuator in this embodiment. It is a flowchart explaining the sweep speed switching processing method in the flowchart of FIG. 6 is a flowchart for explaining a drive signal frequency initialization processing method in the flowchart of FIG. 5. It is a graph which shows the relationship between the frequency of the drive signal in this embodiment, and the rotation speed of a to-be-driven body.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electronic timepiece, 50 ... Drive apparatus, 52 ... Constant voltage circuit, 54 ... Voltage adjustment circuit, 55 ... Drive circuit, 56 ... Variable frequency oscillator, 57 ... Amplitude detection circuit, 90 ... Date display mechanism, 91 ... Piezoelectric actuator, 92 ... Rotor, 93 ... Date wheel, 541 ... Voltage regulator, 542 ... Clock circuit, 543 ... Control circuit, 544 ... UD counter, 545 ... D / A converter, 911 ... Reinforcing plate, 912 ... Piezoelectric element, 912A ... Drive electrode, 912B ... detection electrode, 914 ... projection.

Claims (3)

A drive signal to the piezoelectric element in a piezoelectric actuator including a vibrating body that vibrates when a driving signal having a predetermined frequency is applied to the piezoelectric element, and a contact portion that is provided on the vibrating body and is in contact with a driving target. A piezoelectric actuator drive device for supplying
Frequency control for sweeping the frequency of the drive signal supplied to the piezoelectric element within a predetermined range, detecting a detection signal indicating the vibration state of the vibrating body, and controlling the sweep speed of the frequency of the drive signal based on the detection signal With means,
The frequency control means includes
A constant voltage circuit for outputting a reference voltage for amplitude detection for detecting the amplitude of the detection signal;
An amplitude detection circuit for comparing a reference voltage for amplitude detection output by the constant voltage circuit and the amplitude of the detection signal and outputting a comparison result signal;
A voltage adjustment circuit that adjusts the rate of change of the output voltage based on the comparison result signal;
A variable frequency oscillator that can vary the frequency of the output signal according to the voltage output from the voltage adjustment circuit;
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 control circuit for controlling the counter value of the up / down counter based on the clock signal,
The control circuit controls an increase / decrease pattern of the up / down counter and controls a count speed of the up / down counter by switching a clock signal to be used based on the comparison result signal. . In the drive device of the piezoelectric actuator according to claim 1,
The frequency control means includes a frequency increase / decrease control means for controlling to increase or decrease the frequency of the drive signal, and a frequency increase / decrease speed control means for controlling a sweep speed for increasing or decreasing the frequency of the drive signal,
The frequency increase / decrease control means performs control to increase or decrease the frequency of the drive signal in a preset frequency range,
The frequency increase / decrease speed control means controls the sweep speed of the frequency of the drive signal based on the detection signal.   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 contact portion that is provided on the vibrating body and that is in contact with a driving target. An electronic apparatus comprising the piezoelectric actuator driving device described above.

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