JP2000324860A - Oscillating actuator and method for driving the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the frequency of a drive voltage impressed upon a vibrator from matching with the resonance frequency of the vibrator, at sweeping of the frequency toward the resonance frequency starting from a high value. SOLUTION: An ultrasonic actuator 1 is provided with a vibrator 2 and a drive device 3. The drive device 3 is provided with an oscillating means 8, a power amplifier means 10, a relative operating speed detecting means 11, and a frequency control means 12 which inhibits the setting of the frequency of a drive voltage at a lower value based on the variation of the relative operating speed detected from the vibrator 2 generating relative operations at lowering of the frequency of the drive voltage toward the resonance frequency of the vibrator 2. The actuator 1 surely prevents the frequency of the drive voltage impressed upon the vibrator 2 from matching with the resonance frequency of the vibrator 2 at lowering of the frequency toward the resonance frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vibration actuator and a driving method thereof. More specifically, the present invention relates to a vibrator that generates a relative motion between a relative motion member by vibration generated by applying a driving voltage, and a vibration actuator including a driving device that generates a driving voltage. And a method of driving a vibration actuator.

[0002]

2. Description of the Related Art As this type of vibration actuator, an ultrasonic actuator utilizing an ultrasonic vibration region is known. The ultrasonic actuator changes the frequency of a drive signal (AC voltage) input to the vibrator (hereinafter, referred to as “drive frequency”) to change the speed of the relative motion between the ultrasonic actuator and the relative motion member. (Hereinafter, it is called "relative movement speed" in this specification.). In particular, the relative movement speed can be maximized by matching the driving frequency to the resonance frequency of the vibrator.

By the way, in order to obtain a certain relative movement speed and driving force even when a driving signal having a driving frequency other than the resonance frequency is inputted, the voltage of the driving signal applied to the vibrator is set to be relatively high. There must be. In order to apply this ultrasonic actuator to, for example, a drive source of a positioning mechanism of an XY stage, inevitably, the relative frequency of motion is changed from a low speed to a high speed by changing the drive frequency in a wide range. It is necessary to control in a range.

Therefore, when the drive frequency is changed over a wide range while the voltage of the drive signal applied to the vibrator is set to be relatively high, if the drive frequency matches the resonance frequency of the vibrator, An extremely large amount of energy is input to the child. For this reason, the vibrator deteriorates, and in the worst case, is broken.

In order to prevent excessive energy from being input to the vibrator due to the drive frequency being equal to the resonance frequency when the drive frequency is swept from a high value to the resonance frequency, Various proposals have been made.

For example, Japanese Patent Publication No. 7-8154 discloses a phase difference between an output signal from a vibration detecting electrode for detecting a signal from a piezoelectric body of a vibrator and a drive frequency applied to the vibrator. An invention has been proposed in which when the detected phase difference becomes a value indicating that it is near the resonance frequency, sweeping to a lower frequency is prohibited.

In Japanese Patent Publication No. 7-10189,
When the vibrator is driven at a drive frequency (high frequency band) distant from the resonance frequency, the drive frequency is swept, and the fact that the resonator approaches the resonance frequency is determined based on the detected value of the phase difference between the two-phase drive signals. An invention has been proposed that prohibits sweeping to a lower frequency when detected.

[0008]

By the way, the vibration state of the vibrator changes due to the individual difference of the vibrator, load fluctuation, temperature change and the like. Therefore, when such environmental changes occur, in the inventions proposed in Japanese Patent Publication Nos. 7-8154 and 7-10189, the phase difference is used as a characteristic value, and this characteristic value itself is used. , It is extremely difficult to reliably detect that the drive frequency has approached the resonance frequency. Therefore, it was not possible to reliably prevent excessive energy from being input to the vibrator due to the drive frequency being equal to the resonance frequency.

In particular, the invention proposed in Japanese Patent Publication No. 7-8154 discloses that when the waveform of the driving signal is not a sine wave, the output signal from the vibration detecting electrode and the driving frequency applied to the vibrator are reduced. It is difficult to detect the phase difference itself, and also from this point, it is extremely difficult to reliably detect that the drive frequency has approached the resonance frequency.

As described above, even when these conventional techniques are used, when the drive frequency is swept from a high value to the resonance frequency, it is ensured that the drive frequency does not match the resonance frequency of the vibrator. It was difficult.

The present invention has been made in view of the above-mentioned problems of the prior art. For example, when the driving frequency of a vibration actuator such as an ultrasonic actuator is swept from a high value to a resonance frequency, the driving frequency is reduced. An object of the present invention is to reliably prevent excessive energy from being input to a vibrator due to a frequency matching a resonance frequency.

[0012]

Means for Solving the Problems The above-mentioned conventional technology is as follows.
In any case, the fact that the drive frequency has approached the resonance frequency
For example, based on the magnitude of the characteristic value itself such as a phase difference,
That is what we are trying to detect. However, according to the knowledge of the present inventor, when individual differences in oscillators, load fluctuations, and temperature changes occur, the correlation between the magnitude of this characteristic value and the approach of the driving frequency to the resonance frequency changes. However, it is not possible to reliably detect that the drive frequency has approached the resonance frequency.

According to the present invention, the vibration state of the vibrator is relatively grasped by using the change rate of the characteristic value detected from the vibrator or the relative motion member when the relative motion is generated, whereby It is based on a new finding that the drive frequency can be reliably prevented from being equal to the resonance frequency of the vibrator even when there are individual differences in the vibrator, load fluctuations, and temperature changes.

According to the first aspect of the present invention, there is provided a vibrator for generating a relative motion between a relative motion member by a vibration generated by applying a driving voltage, and a driving device for generating a driving voltage. However, when the frequency of the drive voltage is reduced toward the resonance frequency, the rate of change of the characteristic value detected from the vibrator or the relative motion member during the occurrence of the relative motion reaches a predetermined value. And a frequency control unit for prohibiting the setting of the frequency of the drive voltage to a frequency lower than the frequency when the vibration actuator is operated.

According to a second aspect of the present invention, in the vibration actuator according to the first aspect, when the characteristic value has an inflection point at a frequency higher than the resonance frequency and reaches a predetermined value. The frequency is a frequency at or near the inflection point.

According to a third aspect of the present invention, in the vibration actuator according to the first or second aspect, the characteristic value includes a relative movement speed, a distortion generated in the vibrator, or
The phase difference is a phase difference between the vibration generated in the vibrator and the drive voltage.

According to a fourth aspect of the present invention, there is provided the first to third aspects.
In the vibration actuator according to any one of the above, the driving device can change the frequency of the driving voltage applied to the vibrator, and the power amplifying device amplifies the output signal from the oscillating device And a characteristic value detecting means for detecting a characteristic value, wherein the frequency control means adjusts the frequency of the drive voltage to a frequency lower than the frequency corresponding to the predetermined value in accordance with a signal from the characteristic value detecting means. The setting is prohibited.

According to a fifth aspect of the present invention, in the vibration actuator according to the fourth aspect, the frequency control means uses the average value of the signal from the characteristic value detection means for a predetermined period of time to calculate the characteristic value. It is characterized by detecting a change.

The invention of claim 6 is the invention of claims 1 to 5
In the vibration actuator described in any one of the above, the vibrator has a rectangular flat plate-shaped outer shape, and vibrates in a direction substantially parallel to the direction of the relative motion, And a second vibration that vibrates in an intersecting direction.

Further, according to the invention of claim 7, when the frequency of the drive voltage applied to the vibrator that generates relative motion with the relative motion member by generating vibration is reduced toward the resonance frequency. In addition, the rate of change of the drive voltage to a frequency lower than the frequency when the rate of change of the characteristic value detected from the vibrator or the relative motion member when the relative motion is generated reaches a predetermined value is determined. A driving method of a vibration actuator characterized in that setting is prohibited.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, an embodiment of a vibration actuator according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the embodiments, an example in which the vibration actuator is an ultrasonic actuator using an ultrasonic vibration region will be described.

FIG. 1 is a block diagram showing the configuration of an ultrasonic actuator 1 according to this embodiment. As shown in FIG. 1, the ultrasonic actuator 1 includes a vibrator 2 and a driving device 3. Hereinafter, these components will be sequentially described.

[Vibrator 2] FIG. 2 is a perspective view showing the vibrator 2 used in the present embodiment together with the relative motion member 4. FIG. 3 is an explanatory diagram showing the vibrator 2 together with an example of a generated vibration waveform. As shown in FIGS. 2 and 3, the vibrator 2 of the present embodiment includes an elastic body 5 and a piezoelectric body 6 mounted on one plane of the elastic body 5.

The elastic body 5 is preferably made of a metal material having a large resonance sharpness, such as steel, stainless steel, phosphor bronze, or Elinvar material, and is formed in a rectangular flat plate shape. The dimensions of each part of the elastic body 5 are set such that the natural frequencies of the generated primary longitudinal vibration L1 and the generated quaternary bending vibration B4 substantially coincide with each other.

On one plane of the elastic body 5, a piezoelectric body 6, which will be described later, is adhered, for example. On the other plane of the elastic body 5, two grooves are provided in the width direction of the elastic body 5 at a predetermined distance from each other in the relative movement direction (the direction of the double arrow in FIG. 2). A rectangular rod-shaped sliding member having a rectangular cross-sectional shape and mainly composed of a polymer material or the like is fitted and mounted in these grooves, and is mounted in a protruding manner. As the polymer material, PTFE, polyimide resin, PEN, PP
S, PEEK and the like are exemplified.

The sliding member is a driving force take-out portion 5.
Functions as a and 5b. Therefore, the elastic body 5 is pressed by a pressing member (not shown), and comes into pressure contact with the relative motion member 4 via the driving force extracting portions 5a and 5b formed by these sliding members.

As shown in FIG. 3, the driving force take-out portions 5a and 5b generate four fourth-order bending vibrations B4 generated in the elastic body 5.
Loop position l located outside of the One belly position l ₁ to l _4
1, is provided at a position that matches the l _4. The driving force output portions 5a, 5b need not be provided in a position that exactly matches the loop position l _1, l ₄ bending vibration B4, it may be provided in the vicinity of the antinode position.

In this embodiment, the piezoelectric body 6 is composed of a thin plate-like piezoelectric element made of PZT (lead zirconate titanate). The input regions 6a and 6c to which the A-phase drive signal is input and the B-phase drive signal whose phase is shifted by (π / 2) from the A-phase drive signal are input to the piezoelectric body 6. Regions 6b and 6d are formed. Each input area 6a-6d
Is a bending vibration B generated in the elastic body 5 as shown in FIG.
It is formed continuously in four regions partitioned by five nodal position n ₁ ~n ₅ 4. That is, each input region 6a~6d to be deformed by the input of the driving signal are both, it does not cross the nodal position n ₁ ~n ₅ is fixed point. Therefore, variations in the input area 6a~6d is not to be inhibited by the nodal positions n ₁ ~n _5. Thereby, each of the input areas 6a to 6d
Can be converted into mechanical energy with maximum efficiency.

At the nodal positions n ₂ and n ₄ of the bending vibration B4, detection areas 6p and 6p 'are provided. Detection area 6
The distortion caused by the longitudinal vibration L1 generated in the vibrator 2 is detected by p and 6p ′, and electric energy corresponding to the magnitude of the distortion is output as a pickup voltage. Thus, the amplitude of the longitudinal vibration L1 generated by the vibrator 2 is obtained.

Each of the input areas 6a to 6d and each of the detection areas 6p,
6p 'means that silver electrodes 7a to 7d, 7
p and 7p 'are adhered. Thereby, each input area 6a
To 6d, a drive signal is input independently, or each detection region 6
A pickup voltage, which is a detection signal, can be output independently of p and 6p '. Although not shown, each silver electrode 7
Lead wires for transferring electric energy are soldered and connected to a to 7d, 7p, and 7p '.

In this embodiment, as shown in FIG. 3, the vibrator 2 is formed so as to be point-symmetric with respect to the center of the plane. As a result, the elliptical motions generated in the driving force extracting portions 5a and 5b can be made to have substantially the same shape, and the driving difference due to the reversal of the relative motion direction is almost eliminated.

An A-phase drive signal having a frequency substantially equal to the natural frequency of each of the longitudinal vibration L1 and the bending vibration B4 is input to the input areas 6a and 6c of the piezoelectric body 6 from the driving device 3 described later. Also, A is displayed in the input areas 6b and 6d.
As the phase drive signal, a B-phase drive signal having a phase difference of (π / 2) is input. Then, as shown in FIG. 3, the elastic body 5 has a primary longitudinal vibration L1, which is the first vibration vibrating in the relative movement direction (the direction of the double arrow in FIG. 2), and is orthogonal to the relative movement direction. 4 which is the second vibration oscillating in the direction
The next bending vibration B4 occurs simultaneously.

These vibrations are combined, and counterclockwise and half-period elliptical movements are generated in the driving force output portions 5a and 5b of the vibrator 2. Due to the generated elliptical motion, the relative motion member 4 that comes into pressure contact is linearly driven in one of the left and right directions. Further, in order to reverse the direction of the relative movement, the B-phase drive signal may be set to have a phase difference of (−π / 2) with respect to the A-phase drive signal.

In the present embodiment, the vibrator 2 is configured as described above. Further, as shown in FIG. 2, the relative motion member 4 as a moving element is disposed in pressure contact with the driving force extracting portions 5a and 5b of the vibrator 2.

In the present embodiment, the relative movement member 4 is formed in a strip shape from stainless steel. The relative motion member 4 is
The same direction as the vibration direction of the longitudinal vibration L1 (the left-right direction in FIG. 3) due to the elliptical motion generated in the driving force extraction units 5a and 5b.
Is driven. The relative motion member 4 may be made of a copper alloy, an aluminum alloy, a polymer material, or the like.

The relative motion member 4 includes two transport rollers that contact one of the planes of the relative motion member 4 and a relative motion member 4.
Are guided and conveyed by four conveying rollers (both not shown) contacting both end surfaces in the width direction of. Thereby, the relative movement member 4 can reciprocate in both directions of the relative movement direction. In the present embodiment, the relative motion member 4 is configured as described above.

[Driving Apparatus 3] As shown in FIG. 1, the driving apparatus 3 of this embodiment comprises an oscillating means 8 and a 1/4 frequency divider 9
, Power amplifying means 10a and 10b, and characteristic value detecting means 1
1, a frequency control means 12 and a speed control means 13. Hereinafter, these elements will be described.

In this embodiment, the oscillating means 8 is constituted by an oscillating circuit. The oscillating means 8 has a driving frequency f of 4 corresponding to each of the longitudinal vibration L1 and the bending vibration B4 of the vibrator 2.
A drive signal (rectangular wave) having double frequency 4f is output. The oscillating unit 8 can freely change the drive frequency of the output drive signal by receiving a control signal from a frequency control unit 12 described later.

In the present embodiment, the drive signal output from the oscillating means 8 is input to the １ ／ frequency divider 9. The driving signal input by the ４ frequency divider 9 is a B-phase driving signal (π / 2) having a phase difference of (π / 2) between the A-phase driving signal (sine wave) and the A-phase driving signal. Sine wave).

In this embodiment, an amplification circuit is used as the power amplification means 10. The power amplifying unit 10 amplifies the A-phase drive signal and the B-phase drive signal generated by the 1/4 frequency divider 9, respectively. That is, the power amplification means 10
A-phase drive signal is input to a and is amplified to a voltage necessary for driving the vibrator 2. Further, a B-phase drive signal is input to the power amplifying unit 10b, and is amplified to a voltage required for driving the vibrator 2.

The output of the power amplifying means 10a is input to the input areas 6a and 6c of the vibrator 2 as an A-phase drive signal. The output of the power amplifying unit 10b is input to the input areas 6b and 6d of the vibrator 2 as a B-phase drive signal. Thus, as described above, the driving force output portions 5a and 5b of the vibrator 2 generate counterclockwise elliptical motions that are shifted by a half cycle, and generate relative motion with the relative motion member 4. I do.

In this embodiment, an encoder attached to the relative motion member 4 is used as the characteristic value detecting means 11.
The characteristic value detecting means 11 detects the relative movement speed of the vibrator 2 when the relative movement is occurring.

FIG. 4 is a graph showing an example of the relationship between the magnitude of various characteristic values detected from the vibrator or the relative motion member when the relative motion is generated and the drive frequency f. In the graph shown in the figure, the solid line indicates the input area 6 of the vibrator 2.
a to 6d indicate the current value i of the drive signal, the broken line indicates the relative movement speed v, and the dashed line indicates the oscillator 2
Are the pickup voltages detected in the detection areas 6p and 6p ′, and indicate the distortion caused by the longitudinal vibration L1 generated in the vibrator 2.

In the graph shown in FIG.
Is the resonance frequency f _B of the bending vibration B4 generated in the vibrator 2.
To lower. Then, relative movement velocity v indicated by a broken line, the arrival of from having an inflection point at a higher frequency f ₂ higher than the resonance frequency f _B a vicinity of the resonance frequency f _B, the inflection point, the drive frequency f it is possible to detect that approaches the resonant frequency f _B.

Therefore, in this embodiment, the characteristic value is
The change rate of the relative movement speed, that is, the change rate of the movement speed of the relative movement member 4 was used. The relative motion speed detected in the present embodiment is a characteristic value that directly indicates the driving state, in which fluctuation factors such as individual differences of the vibrator 2 itself and various operating environments are finally combined. Therefore, the change rate of the relative motion speed used as the characteristic value in the present embodiment can also directly and accurately detect the driving state of the vibrator 2 without being affected by the above-mentioned fluctuation factors. in this way,
In the present embodiment, the characteristic value detection unit 11 outputs a signal that is substantially proportional to the relative movement speed.

In this embodiment, a frequency control circuit is used as the frequency control means 12. The frequency control means 12 includes:
A signal output from the characteristic value detecting means 11 and an oscillating means 8
And a control signal output from a speed control unit 13 described later.
The frequency control unit 12 monitors changes in the drive frequency of the signal input from the characteristic value detection unit 11 and the drive frequency of the drive signal input from the oscillation unit 8.

FIG. 5 shows that the driving frequency f input to the vibrator 2 is set to a value f ₁ higher than the resonance frequency f _B of the bending vibration B4.
When sweeping toward the resonance frequency f _B of the bending vibration B4 from a graph showing an example of a change rate of the relative movement velocity v. In this graph, the solid line indicates the relative movement speed v, and the dashed line indicates the rate of change v 'of the relative movement speed.

[0048] As shown in the graph of FIG. 5, when sweeping toward the resonance frequency f _B of the driving frequency f of the driving signal from the high frequency f ₁ from the resonance frequency f _B, first change rate v 'is a positive value As shown, the speed change rate v ′ decreases as the resonance frequency f _B approaches. Then, at the frequency f ₂ immediately before reaching the resonance frequency f _B, the change rate v 'is zero.
When the frequency is further decreased, the rate of change v 'shows a negative value. When the rate of change v ′ becomes zero, the frequency control means 12 of the present embodiment determines the drive frequency f of the drive signal.
There detects that approaches the resonant frequency f _B.

When the frequency control means 12 detects the frequency f _{2 at} which the rate of change v ′ becomes zero, the frequency f
A signal for prohibiting the setting of the driving frequency f to a frequency lower than ₂ is output to the oscillating means 8. As a result, the driving frequency of the driving signal output from the oscillating means 8 becomes the frequency f ₂
Same or is controlled to a value larger than the frequency f ₂ and.

The speed control circuit 13 compares the value of a speed setting input from the outside (not shown) with the value of speed information input from the characteristic value detection circuit 11. Then, a control signal for instructing how to change the drive frequency of the drive signal output from the oscillation unit 8 is output to the frequency control unit 12.

The driving device 3 of the present embodiment is configured as described above. Next, the operation of the ultrasonic actuator 1 of the present embodiment will be described. As shown in FIG. 5, the ultrasonic actuator 1 of the present embodiment shown in FIGS. 1 to 3 receives a drive signal having a drive frequency f ₁ , so that the speed v _{Assume that} a relative motion of ₁ is generated.

In this state, in order to increase the relative movement speed, the drive frequency f of the drive signal output from the oscillation means 8 is increased.
When swept toward the resonance frequency f _B of the high frequency f _1, along with this, the relative movement speed increases.

When the driving frequency f reaches the frequency f ₂ (speed: v ₂ ), the rate of change v ′ becomes zero. When the speed change rate v 'becomes zero, the oscillating means 8 from the frequency control unit 12, a signal for inhibiting the setting of the driving frequency f to a frequency lower than the frequency f ₂ is outputted. Thus, the driving frequency f of the driving signal output from the oscillating means 8 is changed to a value greater than or held to a frequency f ₂ or frequency f _2,.

As described above, according to the present embodiment, the drive frequency f of the drive signal is set to the frequency f ₁ higher than the resonance frequency f _B.
It is swept toward the resonance frequency f _B from, the driving frequency f
Is not smaller than the frequency f ₂ (= resonance frequency f _B + Δf).

In particular, in the present embodiment, the driving state is directly determined by using, as characteristic values, the rate of change of the relative motion speed that appears as a result of a combination of fluctuation factors such as individual differences in the vibrator 2 itself and various operating environments. Therefore, the drive frequency f of the drive signal is not affected by the above-mentioned fluctuation factors, and
_The approach to _B can be reliably detected.

Therefore, when the drive frequency f is swept from the high value f ₁ to the resonance frequency f _B , excessive energy is input to the vibrator 2 because the drive frequency f matches the resonance frequency f _B. Can be reliably prevented.

According to the present embodiment, the driving frequency f
The range that can be set to be a frequency f ₂ or close to the resonance frequency f _B. That is, in the above-described conventional technique, since it is necessary to allow for a change in the environment, it is possible to set the drive frequency to a frequency lower than the frequency f ₂ ′ (f ₂ ′> f ₂ ) in FIG. 5, for example. Did not. On the other hand, in the present embodiment, the range in which the drive frequency f can be set can be expanded on the low frequency side by the difference (f ₂ ′ −f ₂ ) between the frequency f ₂ ′ and the frequency f ₂ . Therefore, according to the present embodiment, it is possible to increase the maximum relative movement speed by (v ₂ −v ₂ ′) as compared with the related art.

(Second Embodiment) Next, a second embodiment will be described. In the following description of each embodiment, portions different from those of the above-described first embodiment will be described, and common portions will be denoted by the same reference numerals in the drawings, and redundant description will be omitted.

FIG. 6 is a block diagram showing the configuration of the ultrasonic actuator 1-1 of the present embodiment. The difference between the ultrasonic actuator 1-1 of the present embodiment and the ultrasonic actuator 1 of the first embodiment is that
Is that the change of the characteristic value is obtained by using the average value of the relative movement speed output from the average value circuit 14.

If the signal output from the characteristic value detecting means 11 is not stable or is erroneously detected, for example, due to the influence of noise, this output is output to the characteristic value change detecting circuit 12.
, There is a possibility that the characteristic value change detection circuit 12 malfunctions. Therefore, in the present embodiment, an average circuit 14 is provided between the characteristic value detecting means 11 and the characteristic value change detecting circuit 12.

The average value circuit 14 detects the rate of change of the characteristic value by calculating the average value of the signal from the characteristic value detection circuit 12 in a predetermined time by receiving the clock signal c. . Then, the calculated average value is input to the frequency control means 12.

The other configuration is the same as that of the first embodiment. According to the present embodiment, even when the output value from the characteristic value detecting means 11 is unstable or erroneously detected, the same effect as that of the first embodiment can be obtained without malfunction.

(Third Embodiment) FIG. 7 is a block diagram showing the configuration of an ultrasonic actuator 1-2 according to this embodiment. The ultrasonic actuator 1-2 of the present embodiment is the first
The difference from the ultrasonic actuator 1 of the embodiment is that a distortion caused by the longitudinal vibration L1 generated in the vibrator 2 is used as the characteristic value.

In this embodiment, the characteristic value detecting means 11-1
The detection areas 6p and 6p 'formed on the piezoelectric body 6 mounted on the vibrator 2 were used as the detection areas. The characteristic value detecting means 11
The detection area 6p of the vibrator 2 when the relative motion is generated,
The pickup voltage output from 6p ', that is, distortion caused by the longitudinal vibration L1 generated in the vibrator 2 is detected.
In the graph shown in FIG. 4 described above, lowers toward the driving frequency f to the resonance frequency f _B.

Here, the vibrator 2 is designed such that the resonance frequency f _L of the longitudinal vibration L1 is higher than the resonance frequency f _B of the bending vibration B4. Further, indicated by a dashed line, the detection region 6p of the vibrator 2, the pickup voltage a detected by 6p 'is an inflection point to a higher frequency f ₄ than the resonance frequency f _B a vicinity of the resonance frequency f _B Have. Frequency f ₄ to give this inflection point is the resonant frequency f _L of the longitudinal vibration L1.

Therefore, the frequency f giving this inflection point
The access to _4, the drive frequency f, it is possible to detect that it has approached each of the resonance frequency f _L of the resonance frequency f _B and the longitudinal vibration L1 of the bending vibration B4.

Therefore, in this embodiment, the characteristic value is
The change rate of the pickup voltage output from the detection areas 6p and 6p 'of the vibrator 2, that is, the change rate of the distortion caused by the longitudinal vibration L1 generated in the vibrator 2 was used. The pickup voltage a detected in the present embodiment is a characteristic value that directly indicates a driving state, in which fluctuation factors such as individual differences of the vibrator 2 itself and various operating environments are finally combined. Therefore, the change rate a ′ of the pickup voltage a used as the characteristic value in the present embodiment can also directly and accurately detect the driving state of the vibrator 2 without being affected by the above-mentioned respective fluctuation factors. it can.

As described above, in this embodiment, the characteristic value detecting means 11-1 outputs the pickup voltage a substantially proportional to the distortion caused by the longitudinal vibration L1 generated in the vibrator 2. Other configurations are the same as in the first embodiment.

FIG. 8 shows that the driving frequency f input to the vibrator 2 is set to a value f ₃ higher than the resonance frequency f _B of the bending vibration B4.
When sweeping toward the resonance frequency f _B of the bending vibration B4 from a graph showing an example of a detection region 6p, 6p 'change rate a of the pickup voltage a outputted from'. In this graph, the solid line indicates the pickup voltage a, and the two-dot chain line indicates the rate of change a 'of the pickup voltage a.

[0070] As shown in the graph of FIG. 8, when sweeping toward the resonance frequency f _B of the driving frequency f of the driving signal from the resonant frequency f higher frequency f ₃ from _B, the change rate of the first pick-up voltage a a 'is Shows a positive value, but the resonance frequency f _B
, The rate of change a ′ of the pickup voltage a decreases. When the frequency f ₄ (resonance frequency f _L ) is reached, the change rate a ′ of the pickup voltage a becomes zero. When the frequency is further reduced, the change rate a 'of the pickup voltage a shows a negative value.

Therefore, the frequency control means 12 of the present embodiment
In, have set up the frequency f ₅ indicating that the change rate a 'is a positive value in advance a value greater than the frequency f _4,
By the driving frequency f it is detected that it has reached the frequency f _5, the driving frequency f of the drive signal, the resonant frequency f of the resonance frequency f _B and the longitudinal vibration L1 of the bending vibration B4
It detects that each approached _L.

The frequency control means 12 determines the frequency f
At the time point when ₅ is detected, a signal for prohibiting the setting of the driving frequency f to a frequency lower than the frequency f ₅ is output to the oscillating means 8. Thereby, the drive frequency of the drive signal output from the oscillating means 8 is a frequency f ₅ or more.

The driving device 3-2 of this embodiment is configured as described above. Next, the operation of the ultrasonic actuator 1-2 of the present embodiment will be described. Ultrasonic actuator 1-2 of the present embodiment shown in FIG. 7, as shown in FIG. 8, by inputting a drive signal having a drive frequency f _3, with the relative moving member 4, the pickup voltage a ₃
It is assumed that distortion due to the longitudinal vibration L1 is generated.

In this state, when the drive frequency f of the drive signal output from the oscillating means 8 is swept from the high frequency f ₃ to the resonance frequency f _B in order to increase the pickup voltage a ₃ , the frequency is accordingly increased. , The pickup voltage a increases.

When the drive frequency f reaches the frequency f ₅ (pickup voltage: a ₅ ), the frequency control means 12
To oscillating means 8, the signal for inhibiting the setting of the driving frequency f to a frequency lower than the frequency f ₅ is output. Thus, the driving frequency f of the driving signal output from the oscillating means 8 is either held in the frequency f _5, it is changed to a value greater than the frequency f _5.

As described above, according to the present embodiment, the driving frequency f of the driving signal is set to the frequency f ₃ higher than the resonance frequency f _B.
It is swept toward the resonance frequency f _B from, the driving frequency f
Is not smaller than the frequency f ₅ (= resonance frequency f _B + Δf). Therefore, according to the ultrasonic actuator 1-2 of the present embodiment, the same effect as the ultrasonic actuator 1 of the first embodiment can be obtained.

(Fourth Embodiment) Next, a fourth embodiment will be described. This embodiment is an improvement on the third embodiment.

FIG. 9 is a block diagram showing the configuration of the ultrasonic actuator 1-3 according to the present embodiment. The ultrasonic actuator 1-3 according to the present embodiment is different from the ultrasonic actuator 1-2 according to the third embodiment in that the frequency control unit 12 determines the average value of the relative motion speed output from the average value circuit 14 by That is, the change of the characteristic value is obtained.

If the signal output from the characteristic value detecting means 11 is not so stable or erroneously detected due to, for example, noise, this output is output to the characteristic value change detecting circuit 1.
If it is input directly to 2, the characteristic value change detection circuit 12 may malfunction. Therefore, in the present embodiment, an average value circuit 14 is provided between the characteristic value detecting means 11 and the characteristic value change detecting circuit 12, as in the second embodiment.

The average value circuit 14 receives the clock signal c and calculates the average value of the signal from the characteristic value detection circuit 12 at a predetermined time, thereby detecting a change in the characteristic value. Then, the calculated average value is input to the frequency control means 12.

The other structure is the same as that of the third embodiment. According to the present embodiment, even when the output value from the characteristic value detecting means 11 is unstable or involves erroneous detection, the same effect as in the third embodiment can be obtained without malfunction.

(Modification) In the description of each embodiment, the case where the vibration actuator is an ultrasonic actuator utilizing an ultrasonic vibration region is taken as an example. However, the present invention is not limited to the ultrasonic actuator, and is similarly applied to a vibration actuator using a vibration region other than the ultrasonic wave.

In the description of each embodiment, the characteristic value is
The case where the inflection point is at a frequency higher than the resonance frequency is taken as an example. However, the present invention is not limited to the magnitude of the frequency of the inflection point, and can be used equally as long as the characteristic value is detected from the vibrator or the relative motion member when the relative motion is occurring. .

In the description of each embodiment, the characteristic value is
The case where the change rate of the detected relative motion speed or the change rate of the strain caused by the detected longitudinal vibration is taken as an example.
However, the present invention is not limited to the rate of change of the relative motion speed or the rate of change of the strain caused by the longitudinal vibration, and the characteristic value detected from the vibrator or the relative motion member when the relative motion is generated. Apply equally. Examples of such characteristic values include the rate of change of the relative motion speed and the rate of change of the phase difference between the vibration generated in the vibrator and the drive voltage, in addition to the rate of change of the strain caused by the detected longitudinal vibration. can do.

In the description of the first embodiment, the case where the frequency at which the characteristic value becomes zero is obtained and the setting of the drive frequency to a frequency lower than this frequency is prohibited is taken as an example. However, the present invention is not limited to this mode. For example, as shown in the third embodiment, the frequency when the characteristic value reaches a predetermined value other than zero is obtained, and the setting of the driving frequency to a frequency lower than this frequency is prohibited. Is also good. This makes it possible to more reliably prevent the drive frequency from being equal to the resonance frequency.

Further, in the description of the first and second embodiments, the relative movement speed is detected by mounting the encoder on the relative movement member. However, the present invention is not limited to this form, and the vibration is applied to the vibrator. An encoder may be provided to detect the relative movement speed.

In the description of the first embodiment and the second embodiment, the encoder is used for detecting the relative movement speed. However, the present invention is not limited to this embodiment. The same applies to members that can be made.

Further, in the description of each embodiment, the case where the driving device has the oscillating means, the power amplifying means, and the characteristic value detecting means is taken as an example. However, the present invention is not limited to this mode, and any drive device that can generate a drive voltage that generates vibration by applying a voltage to a vibrator and generates relative motion between the device and a relative motion member. , Apply equally.

Further, in the description of each embodiment, an example is described in which a vibrator having a substantially rectangular flat outer shape and generating primary longitudinal vibration and quaternary bending vibration is used. However, the present invention is not limited to this oscillator. For example, the document "VI
BROMOTORS FORPRECISION MI
The various types of transducers disclosed in Table 2.8 on page 37 of "CROROBOTS" and the disc-shaped transducers disclosed in "New Edition Ultrasonic Motor" (by Sadayuki Ueba and Yoshiro Tomikawa, published by Trikeps). The same applies to various vibrators such as an annular vibrator, a rod-shaped vibrator, a plate-shaped vibrator, and a linear vibrator.

Further, in the description of each embodiment, the case where the piezoelectric element is mounted on the vibrator is taken as an example. However, the present invention is not limited to the piezoelectric element, and the mutual conversion element between electric energy and mechanical energy is used. Can be used equally.
In addition to the piezoelectric element, for example, an electrostrictive element can be used.

[0091]

As described in detail above, claims 1 to 5
According to the seventh aspect of the present invention, when the drive frequency of the vibration actuator is swept from a high value to a resonance frequency, the drive frequency is not affected even if there is an individual difference in the vibrator, a load variation, and a temperature change. Is matched with the resonance frequency, it is possible to reliably prevent excessive energy from being input to the vibrator.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ultrasonic actuator according to a first embodiment.

FIG. 2 is a perspective view showing a vibrator used in the first embodiment together with a relative motion member.

FIG. 3 is an explanatory diagram showing a vibrator used in the first embodiment together with an example of a generated vibration waveform.

FIG. 4 is a graph showing an example of a relationship between the magnitude of various characteristic values detected from a vibrator or a relative motion member when a relative motion is generated and a drive frequency f.

FIG. 5 is an example of a change in relative motion speed when a drive frequency input to a vibrator is swept from a value higher than a resonance frequency of bending vibration toward a resonance frequency of bending vibration in the first embodiment. FIG.

FIG. 6 is a block diagram illustrating a configuration of an ultrasonic actuator according to a second embodiment.

FIG. 7 is a block diagram illustrating a configuration of an ultrasonic actuator according to a third embodiment.

FIG. 8 is a longitudinal vibration generated in the vibrator when the drive frequency input to the vibrator is swept from a value higher than the resonance frequency of the bending vibration toward the resonance frequency of the bending vibration in the third embodiment. 5 is a graph showing an example of a change in amplitude of the data.

FIG. 9 is a block diagram illustrating a configuration of an ultrasonic actuator according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic actuator 2 Vibrator 3 Drive device 8 Oscillation means 9 Quarter-cycle 10a, 10b Power amplification means 11 Relative motion speed detection means 12 Frequency control means 13 Speed control circuit

Claims (7)

[Claims] A driving device that generates a driving voltage; a vibrator that generates a relative motion between a relative motion member by vibration generated by applying a driving voltage; and a driving device that generates the driving voltage. When the frequency of the drive voltage is reduced toward the resonance frequency, the rate of change of the characteristic value detected from the vibrator or the relative motion member when the relative motion is occurring becomes a predetermined value. A vibration actuator comprising frequency control means for prohibiting setting of the frequency of the driving voltage to a frequency lower than the frequency at which the driving voltage has been reached. 2. The characteristic value has an inflection point at a frequency higher than the resonance frequency, and a frequency when the predetermined value is reached is a frequency at or near the inflection point. The vibration actuator according to claim 1, wherein: 3. The apparatus according to claim 1, wherein the characteristic value is a speed of the relative motion, a distortion generated in the vibrator, or a phase difference between the vibration and the drive voltage. 2. The vibration actuator according to 2. 4. The driving device includes: an oscillating unit that can change a frequency of the driving voltage applied to the vibrator; a power amplifying unit that amplifies an output signal from the oscillating unit; And a characteristic value detecting means for detecting, wherein the frequency control means sets a frequency of the driving voltage to a frequency lower than a frequency corresponding to the predetermined value in accordance with a signal from the characteristic value detecting means. The vibration actuator according to any one of claims 1 to 3, wherein the vibration actuator is prohibited. 5. The apparatus according to claim 4, wherein the frequency control means detects a change in the characteristic value by using an average value of a signal from the characteristic value detection means during a predetermined period of time. Vibration actuator as described. 6. The first vibrator has a rectangular plate-like outer shape, and vibrates in a direction substantially parallel to a direction of the relative movement.
The vibration actuator according to any one of claims 1 to 5, wherein the vibration actuator generates a second vibration that vibrates in a direction crossing the direction of the relative motion. 7. When lowering the frequency of a drive voltage applied to a vibrator that generates relative motion between a relative motion member by generating vibration toward a resonance frequency,
The rate of change of the characteristic value detected from the vibrator or the relative motion member when the relative motion is being generated is lower than the frequency when the drive voltage reaches a predetermined value. A method of driving a vibration actuator, wherein setting of a frequency is prohibited.