JP3311490B2 - Ultrasonic motor drive - Google Patents

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 motor, and more particularly, to an ultrasonic vibrator for exciting longitudinal vibration and bending vibration by applying a driving signal to an electro-mechanical energy conversion element. The present invention relates to an ultrasonic motor driving device provided.

[0002]

2. Description of the Related Art In recent years, an ultrasonic motor has attracted attention as a new motor replacing an electromagnetic motor. This ultrasonic motor has the following advantages over a conventional electromagnetic motor.

(1) A low speed and high thrust can be obtained without a gear.

(2) The holding force is large.

(3) The stroke is long and the resolution is high.

(4) Quietness is achieved.

(5) No magnetic noise is generated, and there is no influence of noise.

Here, the present applicant has previously filed Japanese Patent Application No. 5-390.
The ultrasonic linear motor proposed in No. 11 will be described with reference to the drawings.

First, the configuration of the ultrasonic transducer will be described.

FIG. 9 is an external perspective view showing an example of the conventional ultrasonic vibrator.

In the figure, reference numeral 100 denotes an ultrasonic transducer,
On the upper part of the basic elastic body 101, a laminated piezoelectric element 103 is disposed at a portion corresponding to substantially the antinode of the secondary resonance bending vibration. The multilayer piezoelectric element 103 is fixed above the basic elastic body 101 by a holding elastic body 102. Further, although not shown, the basic elastic body 10
On the upper surface of the base 1, two taps for screws are formed, and the holding elastic body 102 is made of a basic elastic body 1 with screws.
01 is fixed. Thereby, the multilayer piezoelectric element 1
03 is held in contact with the elastic body 102 for holding.

At the center of the front face of the basic elastic body 101, a holding projection 104 is provided. Also, the sliding is performed at a position where the bending vibration amplitude of the surface of the basic elastic body 101 opposite to the surface on which the laminated piezoelectric element 103 is arranged (the surface on the side in contact with the driven body) is maximized. The member 105 is joined using, for example, an epoxy-based adhesive.

Next, the operation of the ultrasonic transducer 100 will be described.

By appropriately setting the dimensions of the ultrasonic transducer 100, the primary resonance longitudinal vibration and the secondary resonance bending vibration can be excited at almost the same frequency. In FIG. 9, electrical terminals taken out of the left multilayer piezoelectric element 103 are denoted by A and GND (referred to as A phase), and electrical terminals taken out of the right multilayer piezoelectric element 103 are denoted by B and GND (B
Phase). Therefore, when an alternating voltage having a predetermined amplitude at a frequency Fr is applied to the A phase and an alternating voltage having the same frequency, the same amplitude and the same phase is applied to the B phase, the primary resonance longitudinal vibration can be excited. Next, when an alternating voltage having the same frequency and the same amplitude is applied to the A phase and an alternating voltage having the same frequency and the same amplitude and the opposite phase is applied to the B phase, the secondary resonance bending vibration can be excited.

By applying an alternating voltage of the same amplitude at the frequency Fr to the A phase and the B phase and setting the phase difference to 90 degrees or -90 degrees, the primary longitudinal vibration and the secondary bending vibration can be excited simultaneously. At the position of the sliding member 105, clockwise or counterclockwise ultrasonic elliptical vibration can be excited. At this time, when a driven body made of a zirconia ceramic material is pressed against the position of the sliding member 105, the driven body is driven rightward or leftward.

[0016]

However, in the ultrasonic linear motor described in Japanese Patent Application No. 5-39011, when the ultrasonic vibrator is driven for a long time and the temperature of the vibrator rises, the motor is not driven. Thrust and speed may be reduced. That is, when the temperature rises, the effective Young's modulus of the adhesive layer between the laminated piezoelectric element and the holding elastic body decreases, and the vibration of the laminated piezoelectric element is less likely to be transmitted to the basic elastic body. As a result, a high-order vibration mode is generated, which causes a problem that the thrust and the speed of the motor are reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is intended to suppress the high-order vibration mode and to reduce the thrust and speed of the ultrasonic motor in spite of the temperature rise of the vibrator. It is intended to provide a device.

[0018]

Driving device for an ultrasonic motor that by the present invention in order to achieve the above object In order to achieve the above, applying an alternating drive signal to at least two stacked electric over mechanical energy conversion element An ultrasonic transducer that excites longitudinal vibration and bending vibration, and detects vibration of the ultrasonic transducer
Vibration detection means , based on the output of the vibration detection means ,
Higher mode circumferential in an operating temperature range of the ultrasonic vibrator
DC voltage at a level where no wave number component is generated
A DC power supply applied to the electro-mechanical energy conversion element .

[0019] by that drive of the ultrasonic motor of the present invention, the feed output of the vibration detecting means to the DC power supply
Further comprising feedback means for backing up
You.

[0020] by that drive of the ultrasonic motor of the present invention, the feed output of the vibration detecting means to the DC power supply
A feedback means for backing up the feed
The back means outputs the higher-order mode from the output of the vibration detecting means.
Equipped with a filter that extracts only the
You.

[0021]

Drive device by that the ultrasonic motor to the work for the present invention, by applying an alternating drive signal to at least two stacked electric over mechanical energy conversion element, bending vibration and the longitudinal vibration to the ultrasonic vibrator Is excited. Vibration detection means
Detects the vibration and outputs a DC voltage of a level at which no higher-order mode frequency component occurs in the operating temperature range of the ultrasonic vibrator based on the output of the vibration.
A DC power supply is applied to the energy conversion element .

[0022] by that drive of the ultrasonic motor in the present invention, the feedback means, out of said vibration detecting means
The force is fed back to the DC power supply.

[0023] In the driving device of the ultrasonic motor that by the present invention, the feedback means, the filter
From the output of the vibration detecting means.
Extract only the minutes.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a driving apparatus for an ultrasonic motor according to a first embodiment of the present invention. Hereinafter, the driving device of the ultrasonic motor will be described along the flow of signals.

In the figure, reference numeral 1 denotes an oscillator, which is adapted to transmit a drive signal (alternating voltage) having a predetermined drive frequency. The output signal from the oscillator 1 is first input to the amplifier 3, amplified at a predetermined amplification degree, and then applied to the A-phase input terminal A of the ultrasonic transducer 10. The output signal from the oscillator 1 is also input to the phase shifter 2, where the phase is shifted to +90 degrees or -90 degrees. The output signal from the phase shifter 2 is amplified by the amplifier 4 at a predetermined amplification degree, and then the ultrasonic transducer 1
0 is applied to the B-phase input terminal B. A DC power supply 5 is connected in parallel to the output terminals of the amplifiers 3 and 4, that is, the A-phase and B-phase input terminals of the ultrasonic transducer 10, as shown in the drawing.

The DC power supply 5 generates and outputs a predetermined DC voltage.
The DC voltage is applied to the laminated piezoelectric element 13 (described later in detail).

FIG. 2 is an external perspective view showing the ultrasonic vibrator 10 according to the first embodiment.

For example, a basic elastic body 11 made of brass material
Has a rectangular shape in which a protrusion 11a is formed on the center upper surface,
In this embodiment, the size is 30 m width except for the protrusion 11a.
m, depth 4mm, height 7.5mm. Hereinafter, the dimensions related to the ultrasonic vibrator indicate preferable dimensions, and it goes without saying that an ultrasonic vibrator having a shape other than the indicated dimensions can also be used. The protrusion 1
The dimensions of 1a are 4 mm in width, 4 mm in depth, and 2.5 mm in height. A pin made of stainless steel having a diameter of φ2 mm is provided at the center of the front surface of the basic elastic body 11 and at a position 6 mm from the bottom surface. 14 is press-fitted.

At both ends of the protrusion 11a on the upper surface of the basic elastic body 11, there are provided laminated piezoelectric elements 13 in which several tens to several hundreds of electrode-treated piezoelectric elements are laminated. In the present embodiment, the multilayer piezoelectric element 13 is a multilayer piezoelectric element NLA-
2 × 3 × 9 is adopted and its dimensions are 2mm × 3.1mm ×
9 mm. The end face of each piezoelectric element other than both ends of the laminated piezoelectric element 13 is coated with an epoxy resin or the like. In this embodiment, the coating thickness is about 20 μm
It has become. Also, in the figure, the right side of the laminated piezoelectric element 13
, An electric terminal is taken out, and constitutes an input terminal A and a ground terminal GND (referred to as an A phase). On the other hand, electric terminals are also taken out from the left-side laminated piezoelectric element 13 and constitute an input terminal B and a ground terminal GND (referred to as phase B).

The lower surface of the basic elastic body 11, that is, the surface opposite to the surface on which the laminated piezoelectric element 13 is disposed (the surface on the side in contact with the driven body) has two rectangular shapes ( A driver 15 having dimensions (width: 3 mm, depth: 4 mm, thickness: 1 mm) is provided. The two drivers 15 are respectively arranged at two positions where the vibration amplitude of the resonance bending vibration of the ultrasonic vibrator shows a maximum value, and the position is 9 mm from both ends of the lower surface in the present ultrasonic vibrator. Position. The driver 15 is made of, for example, a grindstone material in which alumina abrasive grains are dispersed in a resin, and is joined using an epoxy-based adhesive or the like.

Next, a method of assembling the ultrasonic vibrator 10 will be described with reference to FIG.

First, the piezoelectric element 13 is placed on the upper surface of the basic elastic body 11 with one end surfaces of the laminated piezoelectric element 13 being in contact with both side surfaces of the projection 11a of the basic elastic body 11, respectively. The holding elastic members 12 (width 4 mm, depth 4 mm, height 2.5 mm) are mounted on the upper surface of the basic elastic body 11 while the holding elastic members 12 (width 4 mm, depth 4 mm, height 2.5 mm) are in contact with the other end surfaces of the respective laminated piezoelectric elements 13. Although not shown, a tap portion for a screw is formed on the upper surface of the basic elastic body 11 where the elastic body for holding 12 is mounted, and as shown in FIG. The body 12 is made up of two basic elastic bodies 11 by two screws 12a.
Fixed to Thereby, the multilayer piezoelectric element 13 is held and fixed in a state where a compressive force is applied between the protrusion 11 a of the basic elastic body 11 and the holding elastic body 12.

Further, the one end face of the laminated piezoelectric element 13 and the opposing face of the projection 11a of the basic elastic body 11 and the other end face of the laminated piezoelectric element 13 and the opposing face of the holding elastic body 12 are epoxy-based. It is fixed with an adhesive such as. In addition, the lower surface of the multilayer piezoelectric element 13 and the opposing surface of the basic elastic body 11 are also bonded using an epoxy resin or the like. Further, the lower surface of the holding elastic body 12 and the opposing surface of the basic elastic body 11 are also joined by an epoxy-based adhesive or the like.

Next, the operation of the ultrasonic vibrator 10 in this embodiment will be described.

When the ultrasonic vibrator 10 has the shape of the dimensions described above, the primary resonance longitudinal vibration in the maximum length direction and the secondary resonance bending vibration in the plane having the maximum area have substantially the same frequency Fr ( 53kHz-56kHz). Based on this, first, in the oscillator 1, the frequency Fr
(53 kHz to 56 kHz), and one of the output signals is output from the amplifier 3 to, for example, an amplitude of 10 Vp.
The signal is amplified to a -p (peak-to-peak) signal. On the other hand, the output signal is amplified by the amplifier 4 via the phase shifter 2 to a signal having an amplitude of, for example, 10 Vp-p.

Thus, the input terminals A and B (see FIG. 1) of the ultrasonic vibrator 10 have the frequency Fr (53 kHz to 56 k).
Hz), an alternating voltage having an amplitude of 10 Vp-p and a phase difference of ± 90 degrees is applied. When the alternating voltage is applied, clockwise or counterclockwise ultrasonic elliptical vibration can be excited in the ultrasonic transducer 10 at the position of the driver 15. At this time, when the driven body is pressed against the driver 15, the driven body moves right and left.

Next, a method of setting a preferred value of the DC voltage generated by the DC power supply 5 in this embodiment will be described. The preferred values are set based on experiments performed by the present applicant, and the means for setting are described below.

FIG. 3 is an (a) front view of the ultrasonic vibrator when setting a suitable value of the DC voltage generated by the DC power supply in the ultrasonic motor driving device of the first embodiment. (B) is a rear view, and (c) is a side view.

As shown in FIG.
A vibration detecting piezoelectric element 20 (a type of electro-mechanical energy conversion element) having a vertical and horizontal dimension of 3 mm × 5 mm and a thickness of 0.2 mm is adhered to the lower part of the front and back of the device. At this time, two vibration detecting piezoelectric elements 20 are adhered on the front side of the ultrasonic vibrator 10 so that the polarization directions are the same, F1 was provided. On the other hand, on the back side of the ultrasonic vibrator 10, two vibration detecting piezoelectric elements 20 are adhered as shown in the drawing so that the polarization directions are different from each other, and a lead wire is arranged in series to provide an electric terminal F2. Was. The output signals from the terminals F1 and F2 are input to a detection device (not shown) and monitored by the detection device.

When the ultrasonic transducer 10 is vibrated as described above after the vibration detecting piezoelectric element 20 is arranged as described above, an electric output proportional to the primary longitudinal vibration is obtained from the terminal F1. And an electric output proportional to the secondary bending vibration is obtained from the terminal F2. Then, based on the detection result, the following suitable values are set.

FIG. 4 shows the output signals from the terminals F1 and F2 in the initial state (when the temperature of the ultrasonic vibrator is the same as the room temperature and the temperature is 25 ° C. in the experiment by the present applicant). FIG.

As shown in FIG. 4, the ultrasonic vibrator 1
The bending vibration and the longitudinal vibration of 0 are both substantially sinusoidal vibrations. At this time, the starting thrust of the ultrasonic linear motor was 400 gf, and the no-load speed was 300 mm / sec.

FIG. 5 is a diagram showing the output signals from the terminals F1 and F2 after the continuous operation of the ultrasonic vibrator in the experiment.

According to the experiment, when the ultrasonic vibrator 10 is continuously vibrated, the temperature of the ultrasonic vibrator 10
The temperature rose to 0 ° C. At this time, the signals from the terminals F1 and F2 are as shown in FIG. As is clear from this figure, in the vibration waveform of the ultrasonic vibrator, in both the bending vibration and the longitudinal vibration, a vibration in a higher mode is observed in addition to the driving fundamental frequency. At this time, the starting thrust and the no-load speed of the ultrasonic linear motor were reduced to about 1/10 of the initial state.

In this state, that is, after the ultrasonic vibrator 10 is continuously vibrated, a DC voltage is applied to the laminated piezoelectric element 13 in a direction in which the laminated piezoelectric element 13 tends to extend. When the voltage is gradually increased, the higher-order vibration mode decreases, and the DC voltage becomes
When the voltage reached 50 V, the vibration completely returned to the initial state shown in FIG. At this time, the characteristics of the ultrasonic motor also returned to the initial state.

In the driving apparatus for the ultrasonic motor according to the first embodiment, the DC voltage output from the DC power supply 5 was set to 50 V based on the above experimental results. Further, in the ultrasonic motor driving device set as described above, when the temperature of the ultrasonic vibrator is in the range of room temperature to 60 ° C., the starting thrust of the ultrasonic motor is 400 gf, and the no-load speed is 300 mm / sec. It has also been confirmed that this was done.

In the first embodiment, the direct current voltage value is determined by the above-described method, and the direct current voltage from the DC power source is applied to the laminated piezoelectric element, whereby the ultrasonic vibrator is continuously operated. Even if the temperature of the ultrasonic vibrator rises, stable operation can be continued without deteriorating the motor characteristics.

In the first embodiment, the case where the maximum temperature of the ultrasonic vibrator is 60 ° C. has been described.
Depending on the usage environment of the ultrasonic motor, the temperature of the ultrasonic vibrator may reach 70 ° C. to 80 ° C. In such a case, a DC voltage corresponding to the temperature of the ultrasonic vibrator, that is, a DC voltage that attenuates a higher-order vibration mode of the ultrasonic vibrator is selected and applied to the multilayer piezoelectric element 13. do it.

The DC voltage output from the DC power supply may be constantly applied to the ultrasonic vibrator or may be applied only when the ultrasonic motor is driven.

Next, a second embodiment of the present invention will be described.

FIG. 6 is a block diagram showing the configuration of the ultrasonic motor driving device according to the second embodiment. In the figure,
The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted to avoid duplication. Since the ultrasonic vibrator according to the second embodiment uses the same ultrasonic vibrator as that of the first embodiment, illustration and description thereof will be omitted. Hereinafter, the driving device of the ultrasonic motor according to the second embodiment will be described along the flow of signals.

A drive signal of a drive frequency Fr (frequency between 53 kHz and 56 kHz) is transmitted from the oscillator 1 in the same manner as in the first embodiment, and is passed through the phase shifter 2 and the amplifiers 3 and 4 to the ultrasonic vibrator. Input terminals A and B (see FIG. 1), drive frequency Fr (53 kHz to 56 kHz), amplitude 10 Vp-p, phase difference ± 90
Alternate voltage is applied. Also, instead of the DC power supply 5 in the first embodiment, an AC-DC converter type DC power supply 6 described later is connected in parallel to the input terminals A and B of the ultrasonic transducer. In the ultrasonic transducer according to the second embodiment, the above-described vibration detecting piezoelectric element 20 is provided in advance, and the electric terminals F1 and F2 are provided. Then, the feedback signal from the vibration detecting piezoelectric element 20 is added via the terminal F1 or the terminal F2, and then amplified by the amplifier 8 at a predetermined amplification degree. The feedback signal amplified by the amplifier 8 has a cutoff frequency of 60 kHz.
The high-pass filter 7 is input to the high-pass filter 7. Then, only the high-order mode frequency component is extracted from the feedback signal by the high-pass filter 7 and output.

Thereafter, the signal is input to the AC-DC converter type DC power source 6 of the feedback type. A DC voltage output from the AC-DC converter type DC power supply 6 is applied to an input terminal A and an input terminal B of the ultrasonic transducer.

The AC-DC converter type DC power supply 6 functions to gradually increase the DC voltage as an output until the alternating input signal becomes an effective value of zero. That is, the DC voltage is controlled so that a frequency component corresponding to the higher-order vibration mode of the ultrasonic transducer is removed. However, in order to eliminate the oscillation phenomenon, in this embodiment, the AC-
The response time of the DC converter type DC power supply 6 was set to several tens msec to several seconds.

According to the ultrasonic motor driving device described in this embodiment, the temperature of the ultrasonic vibrator is changed from room temperature to 60 ° C.
400 g as the starting thrust of the ultrasonic motor in the range of
f, 300 mm / sec as a no-load speed was obtained.

In the ultrasonic motor driving apparatus according to the second embodiment, in addition to the effects of the first embodiment, the direct current is applied so that the vibration of the ultrasonic vibrator is always detected and the vibration of the higher mode is removed. Since the voltage is applied to prevent the deterioration of the ultrasonic motor characteristics, the minimum necessary DC voltage is applied, and the effect of reducing the load on the multilayer piezoelectric element is achieved.

FIG. 7 shows a modification of the second embodiment.
It is a front view of an ultrasonic vibrator.

As shown in this figure, the modification is an example in which the vibration detecting piezoelectric element is reduced to one in the second embodiment requiring two vibration detecting piezoelectric elements. In the case of this modified example, the obtained feedback signal is a signal obtained by synthesizing the longitudinal vibration and the bending vibration.
An effect similar to that of the embodiment can be obtained.

FIG. 8 is a block diagram showing a configuration of a driving apparatus for an ultrasonic motor according to a third embodiment of the present invention. In addition,
In the figure, the same reference numerals are given to the same components as those in the first and second embodiments, and description thereof will be omitted here to avoid duplication. Since the ultrasonic vibrator according to the third embodiment uses the same ultrasonic vibrator as that of the first embodiment, the illustration and description thereof are omitted here.

As shown in FIG. 8, in the third embodiment, the Hall element 25 is used as a current detection circuit to detect the vibration of the ultrasonic transducer. That is, the present embodiment focuses on the fact that the current flowing through the input terminals A and B of the ultrasonic vibrator is proportional to the vibration speed of the ultrasonic vibrator. Is provided. Hereinafter, the driving device of the ultrasonic motor according to the third embodiment will be described along the flow of signals.

First, a drive signal of a drive frequency Fr (frequency between 53 kHz and 56 kHz) is transmitted from the oscillator 1 in the same manner as in the first and second embodiments, and the phase shifter 2 and the amplifiers 3 and 3 are driven.
4, input terminals A and B of the ultrasonic transducer (see FIG. 1)
In addition, drive frequency Fr (53kHz-56kHz), amplitude 10Vp-
p, an alternating voltage having a phase difference of ± 90 degrees is applied. The input terminals A and B of the ultrasonic transducer are
Instead of the DC power supply 5 in the first embodiment, a feedback DC power supply 21 described later is connected in parallel. The feedback DC power supply 21 performs the same function as the AC-DC converter DC power supply 6 in the second embodiment, and a detailed description thereof will be omitted.

The output signal from the Hall element 25 disposed near the input terminals A and B of the ultrasonic vibrator is amplified by amplifiers 23 and 24, and a high-pass filter 7 similar to the second embodiment is used. Feedback type DC power supply 2
1 is input. The operations of the high-pass filter 7 and the feedback DC power supply 21 are the same as those in the second embodiment, and the description thereof is omitted.

According to the third embodiment, the fact that the current flowing through the input terminals A and B of the ultrasonic vibrator is proportional to the vibration speed of the ultrasonic vibrator (however, the braking capacity of the vibrator is not sufficient) ), The same effect as in the second embodiment can be obtained without disposing a vibration detecting piezoelectric element on the ultrasonic vibrator.

On the other hand, in the second and third embodiments, when a power supply having a high output impedance is used as the DC power supplies 6 and 21, the following modified examples can be configured. That is, in the present embodiment, the high-pass filter 7 is omitted, a voltage detection circuit (not shown) of the DC power supply is newly provided, the output voltage waveform of the DC power supply is monitored, and the voltage applied to the ultrasonic vibrator is reduced. To control. This utilizes the fact that the output voltage from the DC power supply is distorted in proportion to the harmonic vibration component input to the power supply. By monitoring this output voltage, the voltage applied to the ultrasonic transducer is controlled. It is possible to do.

As a further modification, the piezoelectric element for detecting vibration is provided on the side surface of the basic elastic body in the second and third embodiments. It may be provided between them.

According to such an embodiment, in the first embodiment, by applying a proper DC voltage to the laminated piezoelectric element with a simple structure, the proper characteristics of the ultrasonic motor can be obtained over a wide temperature range. Can be maintained.

Further, according to the second and third embodiments, since the vibration of the ultrasonic vibrator is constantly monitored and a DC voltage is applied so as to eliminate the higher-order vibration mode, the insulation of the laminated piezoelectric element is prevented. Breakdown can be prevented, and proper characteristics of the ultrasonic motor can be maintained over a wide temperature range.

The above-described driving apparatus of each of the above embodiments employs a linear type ultrasonic motor as an ultrasonic motor to be applied to the driving apparatus. However, the present invention is not limited to this. Then, the present invention can be applied to a rotary ultrasonic motor.

In each of the above embodiments, the value of the DC voltage is the same for the two stacked piezoelectric elements, but it is more effective to use different values to achieve the object described in the embodiment. May have different values.

[Appendix] According to the embodiment of the present invention as described in detail above, the following configuration can be obtained. That is,
(1) By applying a drive signal to at least two electro-mechanical energy conversion elements, an ultrasonic transducer that excites longitudinal vibration and bending vibration, and applying a DC voltage to the electro-mechanical energy conversion elements. And a DC power supply, wherein the DC voltage is a DC voltage at a level that does not generate a higher-order mode of a frequency other than the drive frequency in the operating temperature range of the ultrasonic vibrator. A driving device for an ultrasonic motor, comprising:

(2) By applying a drive signal to at least two electro-mechanical energy conversion elements, an ultrasonic vibrator that excites longitudinal vibration and bending vibration, and the vibration of the ultrasonic vibrator is detected. The ultrasonic motor driving device according to (1), further comprising: a vibration detection unit; and a DC power supply that applies a DC voltage to the electro-mechanical energy conversion element based on an output signal from the vibration detection unit. .

(3) The ultrasonic motor driving device according to (2), wherein the vibration detecting means is an electro-mechanical energy conversion element provided in the ultrasonic vibrator.

(4) The ultrasonic motor driving device according to (2), wherein the vibration detecting means is a voltage detecting circuit applied to the ultrasonic vibrator or a current detecting circuit flowing through the ultrasonic vibrator.

(5) The ultrasonic motor driving device according to (3), wherein the electromechanical energy conversion element for detecting the vibration of the ultrasonic transducer is a piezoelectric element.

[0076]

As described above, according to the present invention, high-order vibration modes can be suppressed despite the temperature rise of the vibrator.
It is possible to provide an ultrasonic motor driving device that does not cause a decrease in thrust or speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a driving device of an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2 is an external perspective view showing an ultrasonic vibrator in the ultrasonic motor driving device of the first embodiment.

3A and 3B are a front view and a back view of an ultrasonic vibrator when setting a preferable value of a DC voltage generated by a DC power supply in the ultrasonic motor driving device according to the first embodiment. Figure,
(C) It is one side view.

FIG. 4 is a diagram showing an output signal from a monitor terminal in an initial state when a suitable value of a DC voltage generated by a DC power supply is set in the ultrasonic motor driving device according to the first embodiment. It is.

FIG. 5 is an output from a monitor terminal after continuous operation of the ultrasonic vibrator when setting a suitable value of a DC voltage generated by a DC power supply in the ultrasonic motor driving device according to the first embodiment. FIG. 3 is a diagram showing signals.

FIG. 6 is a block diagram showing a configuration of a driving device of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 7 is a front view of an ultrasonic transducer in a modified example of the ultrasonic motor driving device according to the second embodiment.

FIG. 8 is a block diagram showing a configuration of a driving device for an ultrasonic motor according to a third embodiment of the present invention.

FIG. 9 is an external perspective view showing an example of an ultrasonic vibrator in a conventional ultrasonic motor driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Oscillator 2 ... Phase shifter 3, 4 ... Amplifier 5 ... DC power supply 10 ... Ultrasonic vibrator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (3)

(57) [Claims] 1. An ultrasonic vibrator for exciting longitudinal vibration and bending vibration by applying an alternating drive signal to at least two stacked electro-mechanical energy conversion elements, and a vibration of said ultrasonic vibrator. A vibration detecting means for detecting , based on an output of the vibration detecting means, a DC voltage at a level at which no higher-order mode frequency component is generated in a working temperature range of the ultrasonic vibrator , the laminated electric-mechanical energy
A driving device for an ultrasonic motor, comprising: a DC power source applied to a conversion element . 2. An output of said vibration detecting means is supplied to said DC power supply.
Further comprising feedback means for providing feedback
Ultrasonic motor driving apparatus according to claim 1, characterized in that the. 3. The apparatus according to claim 2, wherein the feedback means detects the vibration.
Extract only the higher-order mode frequency component from the output of the means
3. The ultrasonic motor driving device according to claim 2, further comprising a filter .