JPH078909A - Drive device of ultrasonic vibrator - Google Patents

Abstract

PURPOSE:To always set drive frequency in the vicinity of mechanical resonance frequency by measuring the sonic wave propagation time of an ultrasonic vibrator and determining the frequency of a drive signal on the basis of the measured result. CONSTITUTION:A sonic wave propagation time is measured by a counter 17. The frequency of the drive signal of an electromechanical energy conversion element is determined on the basis of the measured sonic wave propagation time. Vibration is applied to a vibrator 5 by an oscillator 1 oscillating alternating voltage having the determined frequency. In this case, even when the resonance frequency of the electromechanical conversion element is changed, drive frequency always follows the resonance frequency. By this constitution, even when the mechanical resonance frequency of the vibrator 5 is changed by temp. and mechanical load conditions, etc., the drive frequency can be always set in the vicinity of the mechanical resonance frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an ultrasonic vibrator, more specifically, an elastic body and an electro-mechanical energy conversion element provided on the elastic body. The present invention relates to a drive device for an ultrasonic vibrator that generates ultrasonic vibration when a drive signal is applied.

[0002]

2. Description of the Related Art Ultrasonic actuators and ultrasonic motors that use an electro-mechanical energy conversion element such as a piezoelectric element as a drive source are already known, and two piezoelectric elements fixed to an elastic body are used as drive sources and the elastic body is used. An ultrasonic oscillator (an ultrasonic oscillator is simply referred to as an oscillator in this specification) that generates longitudinal vibration and bending vibration in the body, and combines these vibrations to generate ultrasonic elliptical vibration. The applicant has previously proposed an ultrasonic linear motor having a driven member that is pressed by a part of the substrate and that moves relative to the oscillator (Japanese Patent Application No.
-321096).

As shown in FIG. 14, this is an elastic body 100.
The two laminated piezoelectric elements 101 and 102 are attached to the holding member 10
It is fixed by 3, 104 and 105, and the elastic body 100
Sliding members 106 and 107 are fixed to both ends of the lower surface of the device by adhesion to form a vibrator.

As shown in FIG. 15, this vibrator has a linear guide 108, a guide rail 109, a holding frame 110,
While holding the screw 111, the pressing force adjusting screw 112, the spring 113, and the vibrator holding member 114 so as to be linearly movable in the left-right direction, the vibrator sliding member 1 is held on the sliding plate 115.
06 and 107 are pressed so as to make frictional contact with each other to form a linear motor.

When the alternating voltage is applied to the laminated piezoelectric elements 101 and 102 by appropriately adjusting the dimensions of this vibrator, the structure shown in FIG.
The longitudinal resonance vibration shown in FIG. 6 and the bending resonance vibration shown in FIG. 17 occur at the same time. When the phase difference between the voltages applied to the two laminated piezoelectric elements 101 and 102 is appropriately adjusted, the longitudinal vibration and the bending vibration are combined to generate an elliptical vibration at the antinode position of the bending vibration. Sliding members 106, 10 fixed to the elliptical vibrating section
7. A driving force is generated between the sliding plate 115.

The driving method of this linear motor is as follows. That is, an alternating voltage of about 10 Vp-p that matches the resonance frequencies of the longitudinal vibration and the bending vibration of the vibrator is applied to the laminated piezoelectric element, and at this time, the phase difference between the alternating voltages applied to the two laminated piezoelectric elements is The other piezoelectric element to +90
By setting the angle to -90 degrees, the moving direction of the linear motor is reversed.

[0007]

However, in the above linear motor, the laminated piezoelectric element of the vibrator has a voltage of 10 Vp-p.
When an alternating voltage of a certain degree is applied, heat generation due to internal friction of the elastic body is large, reaching about 50 to 60 ° C. When the temperature of the elastic body changes, the resonance frequency of the vibrator changes as shown in the graph of FIG. 18, which changes the drive frequency that maximizes the speed of the actuator as shown in the graph of FIG. However, there is a problem that uneven speed occurs.

In addition to the temperature, the mechanical frequency applied to the vibrator causes the resonance frequency to change and the optimum drive frequency cannot be determined.

The object of the present invention is to eliminate the above-mentioned drawbacks of the drive device of the vibrator, and even if the mechanical resonance frequency of the vibrator changes due to temperature, mechanical load conditions, etc., the drive frequency is always mechanical. Another object of the present invention is to provide a drive device for an ultrasonic transducer near the resonance frequency.

[0010]

The present invention comprises an elastic body and an electro-mechanical energy conversion element provided on the elastic body, and a drive signal is applied to the electro-mechanical energy conversion element. In an ultrasonic transducer driving device for generating ultrasonic vibration, a measuring means for measuring the sound wave propagation time of the ultrasonic transducer and a frequency determining means for determining the frequency of the drive signal by the output of the measuring means. It is characterized by having.

[0011]

[Operation] Sound wave propagation time in the vibrator is measured. The frequency of the drive signal for the electro-mechanical energy conversion element is determined based on the sound wave propagation time, and an oscillator that oscillates an alternating voltage having the determined frequency is applied to the vibrator. Even if the resonance frequency of the electro-mechanical energy conversion element changes, the drive frequency always follows.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.
An example will be described. As shown in FIG. 1, one output of the oscillator 1 is supplied to the piezoelectric element 7 via a phase shifter 2 and a power amplifier 4 that have a phase difference of ± 90 degrees with respect to the other output. The other output of the oscillator 1 is supplied to the piezoelectric element 6 via the power amplifier 3. The ultrasonic actuator including the piezoelectric elements 6 and 7 and the vibrator 5 having the piezoelectric element 6 and 7 has the same configuration as that described in the related art and is publicly known, and therefore redundant description will be omitted.

A piezoelectric element 8 is bonded to one side surface of the vibrator 5, and a high frequency pulse output from the pulser 10 is supplied to the piezoelectric element 8. A trigger signal TRG is supplied to the pulsar 10 from a trigger signal forming means (not shown). The trigger signal TRG is also supplied to the S terminal of the flip-flop 15 described later.

The pulser 10 is constructed as shown in the circuit diagram of FIG. That is, the diode D1 is connected between the input terminals IN, one of the input terminals IN is connected to the gate terminal of the thyristor S1, and the other of the input terminals IN is grounded.

The anode side of the thyristor S1 is connected to the power supply Vcc via the resistor R1. Further, one end of the capacitor C1 is connected to the anode side of the thyristor S1. An inductance L1 and a resistor R2 are connected in parallel between the other end of the capacitor C1 and the ground, and are connected to the output terminal Out.

Returning to FIG. 1, the piezoelectric element 9 is also bonded to the other side surface of the vibrator 5, and the output voltage of the piezoelectric element 9 is passed through the inductance 11 connected between the ground and the piezoelectric element 9. Is supplied to the + side terminal of the comparator 12. The negative terminal of the comparator 12 has a DC constant voltage source 1
3 is connected. The DC constant voltage source 13 is for setting a threshold value VTH for forming a Low / High logic signal in the comparator 12. The output of the comparator 12 is supplied to one input terminal of the OR gate 14, and the reset signal RST is supplied to the other input terminal of the OR gate 14.

The inductance 11 and the piezoelectric element 9 constitute a bandpass filter as shown in FIG. That is, the mechanical vibration is generated by the constant voltage source 35 and the piezoelectric element 9.
Is equivalently expressed as a transformer 36 that converts this mechanical vibration into an electric signal, a resistor 37 that is an internal loss, and a capacitor 38 that is derived from the structure of the piezoelectric element. Therefore, if the inductance 11 is connected in parallel to the capacitor 38 of the piezoelectric element 9, a bandpass filter that passes only this parallel resonance frequency is obtained.

Returning to FIG. 1, the output terminal of the OR gate 14 is connected to the R terminal of the flip-flop 15. In the OR gate 14, the output of the comparator 12 and the reset signal RST are ORed, and the result is connected to the R terminal of the flip-flop 15.

At the other input terminal of the AND gate 16,
A clock signal CL is supplied from a clock signal forming means (not shown).
K is supplied. The AND gate 16 takes a logical product between the output of the flip-flop 15 and the clock signal CLK and supplies the result to the counter 17.

The counter 17 counts the output pulse of the AND gate 16. This count value is supplied to the ROM 18 as an address. Further, this count value is reset by the reset signal RST.

The data read from the ROM 18 is latched by a latch signal LT generated by means (not shown).
It is supplied to the oscillator 1 after being latched at. The reset signal RST, the trigger signal TRG, the latch signal LT,
The timings of the clock signal CLK and the like occur in the order shown in the timing chart of FIG.

Next, the operation will be described. First, the flip-flop 15 and the counter 17 are reset when the reset signal RST is supplied from the control means (not shown).

Next, the trigger signal TRG shown in FIG. 2 (FIG. 3A) is supplied to the pulser 10 and the flip-flop 15. When the trigger signal TRG is supplied to the pulser 10, the pulser 10 is triggered. Trigger signal TRG
Is supplied to the flip-flop 15, the output Q of the flip-flop 15 becomes high level, so that the clock signal CLK passes through the AND gate 16. Then, the counter 17 starts counting the clock signal CLK.

When the trigger signal TRG is supplied to the input terminal IN of the pulser 10 shown in FIG. 4, a high frequency pulse as shown in FIG. 3 (B) is output from the output terminal OUT and is shown in FIG. It is supplied to the piezoelectric element 8.

The high frequency pulse is converted into a sound wave by the piezoelectric element 8, propagates through the vibrator 5 in this state, and is converted into an electric signal again by the piezoelectric element 9 on the other side.

Inductor 11 connected to piezoelectric element 9
As described above, a bandpass filter is configured with the piezoelectric element 9, and the drive frequency voltage of the oscillator 5 by the oscillator 1 and the sound wave propagation time measurement frequency signal (hereinafter, (Referred to as a sound wave measurement signal), and the sound wave measurement signal is extracted.

The waveform of the signal passed through the bandpass filter is as shown in FIG. 3C, which is converted into the logic signal shown in FIG. 3D by the threshold value VTH by the comparator 12 and the constant voltage source 13. It When the output of the comparator 12 shown in FIG. 1 becomes high level, the flip-flop 15 is reset and the counter 17 outputs the clock signal CL.
Stop counting K. From the above, the sound wave propagation time of the vibrator 5 including the delay of the circuit system is measured.

An instruction value for causing the oscillator 1 to oscillate a signal having an oscillation frequency equal to the resonance frequency of the vibrator 5 calculated from the measurement time is recorded in the ROM 18 at an address equal to the measurement value of the counter 17. Then, this data having the measured value of the counter 17 as an address is transferred to the latch 19
To the latch signal L after a sufficient time has elapsed.
It is latched by T and the oscillation frequency of the oscillator 1 is determined.

By periodically executing the above operation, the oscillation frequency of the oscillator 1 is constantly updated, and the ultrasonic actuator is always driven at the resonance frequency of the vibrator 5.

Next, experimental results show that the resonance frequency of the vibrator 5 can be determined by the sound wave propagation time. 2 in FIG.
FIG. 7 is a graph showing how the vibration propagation time changes depending on the temperature of the vibrator 5 with 0 ° C. as a reference. FIG. 7 shows the electric admittance when the electric terminals of the driving piezoelectric elements 6 and 7 are connected in parallel. 3 is a graph in which the temperature change of the obtained resonance frequency is measured. Then, FIG. 8 is a graph in which the horizontal axis represents the resonance frequency and the vertical axis represents the sound wave propagation time, and the fluctuations at that time are plotted from the above two measurement results. As is clear from this graph, there is a correlation between the resonance frequency and the sound wave propagation time, and the resonance frequency can be obtained from the sound wave propagation time. 6 to 8 and the graphs of FIGS. 18 and 19 of the above-described conventional example are measured values separately, and the data do not match.

In the first embodiment, as shown in FIG. 9, the sound wave propagation time between both ends of the oscillator 5 is
It is measured by the piezoelectric elements 8 and 9 adhered to both side surfaces of the transducer 5, but as a modified example, the propagation time of a sound wave traveling back and forth in the transducer 5 is adhered to one side surface of the transducer 5 as shown in FIG. It is also possible to measure the piezoelectric element 33 as a transmitting / receiving element.

According to this first embodiment, the reset signal R
Since the time from the time ST is applied until the reset signal RST is applied again and the flip-flop 15 is reset and the counter 17 stops counting the clock signal CLK is used, fluctuations in the resonance frequency of the oscillator 5 are prevented. It can be tracked automatically, which allows the ultrasonic actuator to be driven optimally and stably.

FIGS. 11A and 11B show a second embodiment of the present invention. FIG. 11A shows a vibrator 41 having stacked piezoelectric elements 42 and 43 for driving, and a drive circuit of the vibrator 41 is shown in FIG. 11B.

As shown in FIG. 11B, the output of the oscillator 44 for generating the alternating voltage is the phase shifter 45 and the power amplifier 4.
6 respectively. The phase shifter 2 outputs the output whose phase is shifted ± 90 degrees with respect to the output of the oscillator 1 to the power amplifier 47.
I have to.

The outputs of the power amplifiers 46 and 47 pass through the inductances 48 and 49 and the DC blocking capacitors 50 and 52, respectively, and are supplied to the respective one ends of the piezoelectric elements 42 and 43. The other end side of each of the piezoelectric elements 42 and 43 is D
It is grounded through capacitors 51 and 53 for C cutoff.

On the other hand, in order to apply an offset voltage of about +30 V to the piezoelectric element, the DC voltage source 56 is AC-insulated by the inductances 54 and 55 so that the piezoelectric elements 42 and 43 are insulated.
Is supplied to the piezoelectric element 43 in this case.
A high-speed changeover switch 57 is provided on the side for switching between supplying the DC voltage source 56 to the piezoelectric element 43 as usual or short-circuiting the piezoelectric element 43.

The signal taken out between the inductor 48 and the capacitor 50 is converted into a signal component in a desired band by the filter 58, and this is supplied to the waveform shaper 59. In the waveform shaper 59, the signal component in the desired band is converted into a logical signal, and the signal is supplied to the stop terminal of the time counter 60 for measuring time. The signal from the start terminal of the time counter 60 is supplied to the control terminal of the switch 57 together with the signal output from the CPU 61 as a signal for switching the high speed changeover switch 57. The measurement time counted by the time counter 60 is input to the CPU 61, and the output of the CPU 61 is supplied to the frequency setting terminal of the oscillator 44. The drive circuit of the second embodiment having such a configuration operates as follows. Normally, the high-speed changeover switch 57 connected to the DC voltage source 56 is switched to the side where the piezoelectric element 43 is short-circuited for a very short time under the control of the CPU 61. That is, the connection state of the switch 57 is controlled so as to form a loop of the positive electrode of the DC voltage source 56 → the inductor 55 → the switch 57 → the negative electrode of the DC voltage source 56. Then, the piezoelectric element 43 is rapidly deformed to generate a sound wave. At the same time, the time measurement of the time counter 60 is started.

The sound wave generated by the one piezoelectric element 43 propagates through the vibrator 41, reaches the other piezoelectric element 42, and is converted into an electric signal. This electric signal is supplied to the filter 58 after being prevented from being transmitted to the power amplifier 46 by the inductance 48. The filter 58 separates the drive signal from the power amplifier 46. Filter 58
After passing through, the waveform is shaped by the waveform shaper 59 and converted into a logic signal. This logic signal causes the time counter 6
When the time counting operation of 0 is stopped, the measured time value is the CPU
61 is supplied. The CPU 61 performs a predetermined calculation from the time value to determine the driving frequency of the ultrasonic actuator, and changes the frequency of the oscillator 44. As in the first embodiment, the resonance frequency of the oscillator 41 can be determined by the sound wave propagation time.

According to the second embodiment, the resonance frequency fluctuation of the vibrator can be automatically tracked as in the first embodiment, and the driving frequency of the ultrasonic actuator can be matched with the resonance frequency of the vibrator. Needless to say, the feature of this second embodiment is that the piezoelectric elements 42 and 43 for exciting the vibrator are used.
Is also used as a transmitting / receiving element for measuring the sound wave propagation time. Therefore, it is possible to reduce the number of electric wires connecting the driving device and the vibrator without making a special change to the vibrator 5.

12 and 13 show a third embodiment of the present invention when the present invention is applied to an ultrasonic motor on a ring. The toroidal ultrasonic motor is known as the best known ultrasonic motor at present. The structure thereof will be described with reference to FIG. 12. This ultrasonic motor applies a two-phase alternating voltage having a phase difference of 90 degrees to a piezoelectric element 82 bonded to an annular stator 81, thereby holding it (not shown). The rotor 83 is pressed by the pressing mechanism in the direction of the arrow and is held rotatably.

As shown in FIG. 13, the ultrasonic motor of this type is not used between the two-phase piezoelectric elements 84 and 85 attached to the back surface of the stator 81 in order to generate a traveling wave. There are parts 86, 87. In the present invention,
Utilizing this, a wave-transmitting element 88 for measuring sound wave propagation time is attached to one of them and a wave-receiving element 89 is attached to the other, respectively. In addition, a drive device for operating the wave transmitting element 88, the wave receiving element 89 and the driving piezoelectric elements 84 and 85,
Since the specific time measuring means is the same as that of the first embodiment, detailed description will be omitted.

According to the third embodiment, since the unused portion of the piezoelectric element adhered to the stator can be used as the means for measuring the sound wave propagation time, the effect of the first embodiment can be obtained. The stator 81 has few changes and can be easily realized.

[0043]

As described above, according to the present invention, the driving frequency can always be automatically tracked to the mechanical resonance frequency.
With this, it is possible to provide a drive device capable of optimally and stably driving the ultrasonic actuator.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a drive device for an ultrasonic transducer showing a first embodiment of the present invention.

FIG. 2 is a timing chart of each signal for controlling the operation of the driving device shown in FIG.

FIG. 3 is a waveform chart showing the relationship between the input / output signals of the ultrasonic transducer and the measurement time of the signals in the driving device of the first embodiment.

FIG. 4 is a circuit diagram of a pulser in the driving device of FIG.

FIG. 5 is a piezoelectric element 9 in the driving device of the first embodiment.
FIG. 3 is an equivalent circuit diagram of a bandpass filter composed of and an inductance 11.

FIG. 6 is a graph showing the relationship between acoustic wave propagation time and oscillator temperature.

FIG. 7 is a graph showing the relationship between resonance frequency and oscillator temperature.

FIG. 8 is a graph showing the relationship between sound wave propagation time and resonance frequency.

FIG. 9 is a schematic view of an ultrasonic transducer showing an example of a means for measuring a sound wave transit time.

FIG. 10 is a schematic view of an ultrasonic transducer showing another example of the means for measuring the sound wave transit time.

FIG. 11 is a block configuration diagram of an ultrasonic transducer and a driving apparatus therefor showing a second embodiment of the present invention.

FIG. 12 is a perspective view of an annular ultrasonic motor showing a third embodiment of the present invention.

13 is a rear view of the stator in the ultrasonic motor of FIG.

FIG. 14 is a conventional perspective view showing an example of an ultrasonic transducer used in a linear ultrasonic actuator.

15 is a side view of a linear type ultrasonic actuator using the vibrator of FIG.

FIG. 16 is a perspective view showing the action of the ultrasonic transducer.

FIG. 17 is a perspective view showing the action of the ultrasonic transducer.

FIG. 18 is a graph showing the relationship between resonance frequency and oscillator temperature.

FIG. 19 is a graph showing the relationship between drive frequency and actuator speed.

[Explanation of symbols]

 5, 41 Vibrator 6, 7, 8, 9, 42, 43 Piezoelectric element 10 Pulser 14 OR gate 15 Flip-flop 16 AND gate 17 Counter 18 ROM 19 Latch 60 Timer counter 61 CPU

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[Procedure amendment]

[Submission date] July 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

As shown in FIG. 15, this vibrator is linearly moved in the left-right direction by a linear guide 108, a guide rail 109 , a holding frame 110, a screw 111, a pressing force adjusting screw 112, a spring 113, and a vibrator holding member 114. While holding as much as possible, the sliding member 115 of the vibrator is attached to the sliding plate 115.
A linear motor is constructed by pressing the members 6 and 107 so as to make frictional contact.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The driving method of this linear motor is as follows. That is, an alternating voltage of about 10 Vp-p that matches the resonance frequencies of the longitudinal vibration and the bending vibration of the vibrator is applied to the laminated piezoelectric element, and at this time, the phase difference between the alternating voltages applied to the two laminated piezoelectric elements is When the other piezoelectric element is set to +90 degrees and -90 degrees, the moving direction of the linear motor is reversed.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

The inductance 11 and the piezoelectric element 9 constitute a bandpass filter as shown in FIG. That is, the mechanical vibration is generated by the constant voltage source 35 and the piezoelectric element 9.
Is equivalently expressed as a transformer 36 that converts this mechanical vibration into an electric signal, a resistor 37 that is an internal loss, and a capacitor 38 that is derived from the structure of the piezoelectric element. Therefore, if the inductance 11 is connected in parallel with the capacitor 38 of the piezoelectric element 9, the resonance frequency of the vibrator 5 and the surrounding frequency are always maintained.
It is a bandpass filter that passes only the wave number .

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

The signal taken out between the inductor 48 and the capacitor 50 is converted into a signal component in a desired band by the filter 58, and this is supplied to the waveform shaper 59. In the waveform shaper 59, the signal component in the desired band is converted into a logical signal, and the signal is supplied to the stop terminal of the time counter 60 for measuring time. The signal from the start terminal of the time counter 60 is supplied to the control terminal of the switch 57 together with the signal output from the CPU 61 as a signal for switching the high speed changeover switch 57. The measurement time counted by the time counter 60 is input to the CPU 61, and the output of the CPU 61 is supplied to the frequency setting terminal of the oscillator 44. The drive circuit of the second embodiment having such a configuration operates as follows. Normally, the high-speed changeover switch 57 connected to the DC voltage source 56 is switched to the side where the piezoelectric element 43 is short-circuited for a very short time under the control of the CPU 61. That is, the piezoelectric element 43 is always offset by the constant voltage source 56.
Is applied to the piezoelectric element 43 for a very short time.
The piezoelectric element 43 is short-circuited by disconnecting it from the pressure source 56. Then, the piezoelectric element 43 is rapidly deformed to generate a sound wave. At the same time, the time measurement of the time counter 60 is started.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 18

[Correction method] Change

[Correction content]

FIG. 18

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Ouchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (1)

[Claims] 1. An ultrasonic wave, comprising an elastic body and an electro-mechanical energy conversion element provided on the elastic body, wherein ultrasonic waves are generated by applying a drive signal to the electro-mechanical energy conversion element. A vibrator driving device includes: a measuring unit that measures a sound wave propagation time of the ultrasonic vibrator; and a frequency determining unit that determines a frequency of the drive signal based on an output of the measuring unit. Drive device for ultrasonic transducer.