JPH1118451A - Driver for oscillatory actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize unevenness of velocity by generating oscillations which oscillate in parallel with the direction of the driving force by applying a frequency signal set so that the relative motion reaches a specified velocity to an electromechanical converting element for the drive, and oscillation which oscillates in the direction crossing this, thereby controlling the frequency signal. SOLUTION: The frequency from an amplifier 5 for drive is supplied to a piezoelectric element for longitudinal oscillation of an oscillatory actuator 10, and the frequency signal from an amplifier 6 for drive is supplied to the piezoelectric element for torsional oscillation of the oscillatory actuator 10. In the case of switching the rotational direction of the oscillatory actuator 10, the phase of the output signal from a phase shifting circuit 4 is inverted. Then, a longitudinal oscillation detection signal processing circuit 7 processes the output voltage from the piezoelectric element for the detection of longitudinal oscillations, and extracts a rotation unevenness signal. Moreover, the control of the torsional oscillation detection signal processing circuit 8 corrects the divergence between the set rotational velocity and the average value of actual rotational velocity. As a result, the rotational unevenness can be kept to a minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator, and more particularly to a driving device for a rotary vibration actuator.

[0002]

2. Description of the Related Art Various types of construction principles have been proposed for a rotary vibration actuator (an ultrasonic vibration actuator or an ultrasonic motor which uses an ultrasonic vibration region). Vibration (Longitu
digital) and n-th torsional vibration (Torsiona)
A vibration actuator combining l) has been proposed as an LT vibration actuator. Vibration actuators of this configuration are characterized by low speed / high torque compared to other vibration actuators. However, similar to other rotary vibration actuators, the disadvantage is that rotational unevenness that repeatedly increases and decreases in speed at low speeds is likely to occur. have. As a countermeasure, it is common practice to attach a rotation detector such as an encoder to a rotating shaft, detect a rotation state, and apply feedback to stabilize the rotation state.

[0003]

However, when a rotation detector such as an encoder is mounted on a rotary shaft to detect a rotation state, it is necessary to secure a place for mounting the rotation detector, and the vibration actuator becomes large. Occurs. In addition, there is a problem that the cost increases due to the addition of the rotation detector.

An object of the present invention is to provide a driving apparatus for a vibration actuator which does not require an external speed detector, minimizes speed unevenness, and can reduce the size and cost of the vibration actuator. It is in.

[0005]

The present invention will be described with reference to FIGS. 2 and 7 showing the first embodiment. In order to achieve the above object, the invention according to claim 1 includes an elastic body 11
a, 11b, driving electromechanical transducers 12, 13 joined to the elastic bodies 11a, 11b and generating a plurality of vibrations in the elastic bodies 11a, 11b, and the elastic bodies 11a, 11b.
And a vibrator 18 for detecting a vibration state of the elastic bodies 11a and 11b, and a driving force by a plurality of vibrations. A vibration actuator 1 including a relative motion member 21 for performing relative motion between the vibrator 18 and a driving force.
0 is applied to the driving device of the vibration actuator that drives the vibration element 0, and a frequency signal set so that the relative movement becomes a predetermined speed is applied to the driving electromechanical transducers 12 and 13 to apply a driving force to the elastic bodies 11a and 11b. Generates a first vibration that vibrates in a direction substantially parallel to the direction of vibration and a second vibration that vibrates in a direction that intersects the first vibration direction, and performs relative motion based on the output of the electromechanical transducer 26 for detection. Control devices 1 to 9 for controlling the frequency signal so as to prevent the speed unevenness. According to a second aspect of the present invention, in the driving device for a vibration actuator according to the first aspect, the speed of the relative motion is controlled by changing the frequency of a frequency signal applied to the driving electromechanical transducers 12 and 13. The control devices 1 to 9 have frequency control circuits 2, 3, and 9 for changing the frequency of the frequency signal based on the output of the detection electromechanical transducer 26. According to a third aspect of the present invention, in the driving device for a vibration actuator according to the first or second aspect, the output of the electromechanical transducer for detection 26 is a frequency having a frequency signal applied to the electromechanical transducers 12 and 13 for driving. The control devices 1 to 9 detect the fluctuation of the envelope appearing between adjacent periods of the frequency signal of the output of the electromechanical transducer 26 for detection, based on the detected signal. Thus, the frequency signal applied to the driving electromechanical transducers 12 and 13 is controlled so as to prevent the speed unevenness of the relative motion. According to a fourth aspect of the present invention, there is provided a pair of columnar elastic bodies 11a and 11b having a driving surface intersecting with the longitudinal direction, and an axial line disposed between the elastic bodies 11a and 11b and extending along the longitudinal direction of the elastic bodies 11a and 11b. An electromechanical transducer 12 for torsional vibration that generates torsional vibration vibrating around, and an electric machine for longitudinal vibration that is joined to the elastic bodies 11a and 11b and generates longitudinal vibration that vibrates in the elastic bodies 11a and 11b in the longitudinal direction. The conversion element 13, an electromechanical conversion element 26 for detecting a longitudinal vibration that detects a vibration state of the longitudinal vibration, and a relative element that is rotationally driven by a driving force by being pressed against a driving surface of the vibrator 18 so as to be rotatable around an axis. A frequency set in such a manner as to be applied to a driving device of a vibration actuator that drives the vibration actuator 10 having the moving member 21 and the rotational speed of the relative moving member 21 is set to a predetermined speed. Is applied to the electro-mechanical transducer 13 for longitudinal vibration and the electro-mechanical transducer 12 for torsional vibration, and based on the output of the electro-mechanical transducer 26 for longitudinal vibration detection, the rotation unevenness of the relative motion member 21 is prevented. And control devices 1 to 9 for controlling frequency signals. According to a fifth aspect of the present invention, in the driving device for a vibration actuator according to the fourth aspect, the rotational speed is changed by changing the frequency of a frequency signal applied to the electromechanical transducer 13 for longitudinal vibration and the electromechanical transducer 12 for torsional vibration. The control devices 1 to 9 have frequency control circuits 2, 3, and 9 that change the frequency of the frequency signal based on the output of the electromechanical transducer 26 for detecting longitudinal vibration. The invention of claim 6 is
6. The driving device for a vibration actuator according to claim 4, wherein an output of the electromechanical transducer for detecting longitudinal vibration is applied to an electromechanical transducer for longitudinal vibration and an electromechanical transducer for torsional vibration. The control devices 1 to 9 detect the fluctuation of the envelope appearing between adjacent periods of the frequency signal of the output of the longitudinal vibration detecting electromechanical transducer element 26 as a frequency signal having a frequency corresponding to the frequency of Based on the detected signal, the frequency signal applied to the driving electromechanical transducers 12 and 13 is controlled so as to prevent the rotation unevenness of the relative motion.

In the section of the means for solving the above-mentioned problems, correspondence is made with the drawings of the embodiment for easy understanding, but the present invention is not limited to the embodiment.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

The structure and operation principle of a rotary vibration actuator whose speed is controlled in an embodiment of the present invention will be described with reference to FIGS. This type of rotary vibration actuator is also called a rod vibration actuator, and one used in the ultrasonic band is also called a rod ultrasonic motor.

FIG. 1A is a sectional view for explaining the structure of the rotary vibration actuator 10. FIG. 1B is a cross-sectional view taken along line II-B in FIG. FIG.
FIG. 3A is a schematic sectional view taken along the line IIIA-i of FIG. 1 and viewed from above. FIG. 2B shows the elastic body 11.
a, 11b, torsional vibration piezoelectric elements 12a, 12b, longitudinal vibration piezoelectric elements 13a, 13b, torsional vibration detecting piezoelectric elements 27a, 27b, longitudinal vibration detecting piezoelectric elements 26a, 2b
6b and electrode plates 15-1a, 15-2a, 15-3a,
15-4a, 15-1b, 15-2b, 15-3b, 1
It is a side view which shows arrangement | positioning of 5-4b. FIG.
1a, 11b, torsional vibration piezoelectric elements 12a, 12b,
Longitudinal vibration piezoelectric elements 13a, 13b, torsional vibration detecting piezoelectric elements 27a, 27b, longitudinal vibration detecting piezoelectric element 26a,
26b and electrode plates 15-1a, 15-2a, 15-3
a, 15-4a, 15-1b, 15-2b, 15-3
It is an exploded view showing arrangement of b, 15-4b. In the drawings and the following description, the torsional vibration piezoelectric element 12
a and 12b are torsional vibration piezoelectric elements 12, longitudinal vibration piezoelectric elements 13a and 13b are longitudinal vibration piezoelectric elements 13, torsional vibration detecting piezoelectric elements 27a and 27b, torsional vibration detecting piezoelectric elements 27, and longitudinal vibration detecting piezoelectric elements. 26a and 26b are piezoelectric elements 26 for detecting longitudinal vibration, and electrode plates 15-1a and 15-2.
a, 15-3a, 15-4a, 15-1b, 15-2
b, 15-3b, and 15-4b may be collectively referred to as the electrode plate 15. A piezoelectric element converts electric energy into mechanical displacement and is also called an electromechanical conversion element.

In FIG. 2A, reference numerals in parentheses are those in FIG.
3 shows a member cut along the line IIIA-ii. Further, in FIG. 3, the stator 18 (also referred to as a vibrator) is configured symmetrically with respect to the axial direction, and the piezoelectric elements 27a, 12a, 13a, and 26a are arranged from top to bottom, and are symmetric with these. , The piezoelectric elements 27b, 12b, 13b,
26b are arranged, and furthermore, the electrodes 15-4a, 15-1
a, 15-2a and 15-3a are arranged, and the electrodes 15-4b, 15-1b, 15-2b and 15-3 are symmetrically arranged.
b is arranged. However, the piezoelectric elements 12b, 13b, 2
6b and the electrodes 15-1b, 15-2b, 15-3b are hidden and not shown.

The stator 18 is a member that generates a driving force by an electromechanical transducer that excites a primary longitudinal vibration and a secondary torsional vibration by a driving frequency signal. Stator 18
Are elastic bodies 11a, 11b and elastic bodies 11a, 11b.
b, the torsional vibration piezoelectric element 12 and the longitudinal vibration piezoelectric element 13, the electrode plate 15 sandwiched between the elastic bodies 11 a, 11 b, and the torsion vibration piezoelectric element 13 between the elastic bodies 11 a, 11 b. It comprises a piezoelectric element 12, a piezoelectric element 13 for longitudinal vibration, and a fastening member 17 for fixing the electrode plate 15.

The elastic members 11a and 11b have two layers of torsional vibration piezoelectric elements 12, longitudinal vibration piezoelectric elements 13, torsional vibration detecting piezoelectric elements 27, and longitudinal vibrations on a flat portion formed along the longitudinal direction. The detection piezoelectric element 26 and the electrode plate 15 are held in a sandwiched state. 1 (A) and 2
As shown in (B), the elastic bodies 11a and 11b are semi-cylindrical members obtained by vertically dividing a thick cylinder into two, and a driving surface 11c is formed on the upper surface thereof. .

The elastic members 11a and 11b have four large-diameter portions 14A, 14B, 14C and 14D and three small-diameter portions 1A.
4a, 14b, and 14c. Elastic body 11a,
When the shape of 11b is set in this way, the elastic bodies 11a, 11b
b can perform a desired vibration when the resonance frequency of the primary longitudinal vibration and the resonance frequency of the secondary torsional vibration substantially match. Through holes are formed in the large diameter portions 14A and 14D, respectively, in a direction intersecting the longitudinal direction. In addition,
The elastic members 11a and 11b are made of a metal material having a large resonance sharpness, such as steel, stainless steel, phosphor bronze, and elinvar.

The torsional vibration piezoelectric element 12 is a piezoelectric body using a piezoelectric constant d15 that generates shear deformation according to the direction of the voltage when a frequency voltage is applied, thereby generating torsional vibration. As shown in FIG. 2A, the torsional vibration piezoelectric element group according to the embodiment of the present invention is composed of two torsional vibration piezoelectric elements 12a and two torsional vibration piezoelectric elements 12b. . Piezoelectric element for torsional vibration 1
Since the piezoelectric element 2a and the torsional vibration piezoelectric element 12b are arranged such that the respective shear deformations are in opposite directions when a voltage in the same direction is applied, as shown in FIG. The torsional displacement in a certain direction occurs in the child 18. Also, the torsional vibration piezoelectric element 12a,
As shown in FIG. 2B, 12b includes a node near the drive surface 11c of the generated secondary torsional vibration, and includes a small-diameter portion 14b.
c.

The longitudinal vibration piezoelectric element 13 is a piezoelectric material that uses a piezoelectric constant d31 that undergoes expansion and contraction according to the direction of the voltage when a frequency voltage is applied, thereby generating longitudinal vibration. The longitudinal vibration piezoelectric element group according to the present embodiment is shown in FIG.
As shown in the figure, the piezoelectric vibrator includes two longitudinal vibration piezoelectric elements 13a and two longitudinal vibration piezoelectric elements 13b. The piezoelectric elements 13a and 13b for longitudinal vibration are arranged so as to be vertically deformed in the same direction when a voltage in the same direction is applied. Also, the longitudinal vibration piezoelectric elements 13a, 13b
As shown in FIG. 2 (B), includes nodes of the first-order longitudinal vibration generated, and are arranged so as to straddle the nodes. When the longitudinal vibration piezoelectric elements 13a and 13b are arranged in this manner, the primary longitudinal vibration mode is easily excited when the same frequency voltage is applied to the longitudinal vibration piezoelectric element group.

The torsional vibration detecting piezoelectric element 27 is a piezoelectric body for detecting the torsional vibration of the torsional vibration piezoelectric element 12. As shown in FIG. 2B, the torsional vibration detecting piezoelectric elements 27a and 27b are
It is arranged closer to the drive surface 11c side than a and 12b.

The longitudinal vibration detecting piezoelectric element 26 is a piezoelectric body for detecting the longitudinal vibration of the longitudinal vibration piezoelectric element 13, and as shown in FIG. 2B, the longitudinal vibration detecting piezoelectric element 26a,
26b is arranged closer to the end face 11d side than the longitudinal vibration piezoelectric elements 13a and 13b.

The electrode plate 15 is made of a piezoelectric element 12 for torsional vibration.
And an electrode for applying a voltage to the longitudinal vibration piezoelectric element 13 to detect a voltage from the torsional vibration detecting piezoelectric element 27 and the longitudinal vibration detecting piezoelectric element 26. The electrode plate 15 is shown in FIG.
As shown in (B), the longitudinal vibration piezoelectric element 13 adhered to the plane portions of the semi-cylindrical elastic bodies 11a and 11b, respectively.
a, 13b, torsional vibration piezoelectric elements 12a, 12b, longitudinal vibration detecting piezoelectric elements 26a, 26b, and torsional vibration detecting piezoelectric elements 27a, 26b. I have.

As shown in FIG. 3, the electrode plate 15 is composed of the piezoelectric elements 12a, 12b for torsional vibration and the piezoelectric element 1 for longitudinal vibration.
Electrode plates 15-1a and 15-1b and an electrode plate 15 for simultaneously applying a drive frequency signal to each of the electrodes 3a and 13b.
-2a, 15-2b, and electrode plates 15-3a, 15-3b and 15-4a, 15- for detecting voltages from the piezoelectric element 26 for detecting longitudinal vibration and the piezoelectric element 27 for detecting torsional vibration, respectively. 4b. Electrode plates 15-1a, 15-1b, 15-2a, 15-2b, 1
As shown in FIG. 3, 5-3a, 15-3b, 15-4a, and 15-4b partially protrude from the outer peripheral surfaces of the elastic bodies 11a and 11b.

The fastening member 17 is a piezoelectric element 1 for torsional vibration.
2, the longitudinal vibration piezoelectric element 13, the torsional vibration detecting piezoelectric element 27, the longitudinal vibration piezoelectric element 13, the longitudinal vibration detecting piezoelectric element 26, and the electrode plate 15 are connected to the elastic bodies 11a, 11b.
It is a member for fixing between. The fastening member 17 includes a bolt 17a inserted into the through hole 17c and a nut 17b, and a part of the bolt 17a and the nut 17a.
b protrudes from the outer peripheral surfaces of the elastic bodies 11a and 11b.

The moving element 21 is a member that makes a relative movement on the driving surface 11c. The moving element 21 is composed of a moving element base material 21a made of a thick annular stainless steel, an aluminum alloy, a copper alloy, or the like, and a sliding material 21b mainly made of a polymer material or the like that comes into contact with the driving surface 11c. Have been. The moving child base material 2 is provided on the inner periphery of the moving child base material 21a.
A bearing 22 for positioning 1a with respect to a fixed shaft 20 to be described later is fitted. An output take-out gear 23 meshing with a tooth surface of an object rotated and driven by the rotary vibration actuator 10 is provided on an outer peripheral portion of the mover base material 21a.
Is provided.

The fixed shaft 20 is a shaft for supporting the stator 18 and the moving member 21. The fixed shaft 20 is
a, 11b, penetrates through the hollow portions formed in the longitudinal direction of the elastic bodies 11a, 11b, rotatably supports the movable element 21 via the bearing 22, and also supports the movable element 21 in the radial direction. We are positioning. A groove 20a as shown in FIG. 1B and a fastening member are provided on the fixed shaft 20 to prevent the fixed shaft 20 from rotating around an external mounting member (not shown) by a set screw (not shown). 17 is formed therein. The surface of the groove 20a is provided so as to have an angle of about 30 to 60 degrees with respect to the through direction of the through hole 20d.

The pin 16 is a member for fixing the elastic members 11a and 11b and the fixed shaft 20, and for preventing the fixed shaft 20 from rotating due to the reaction force of the driving force generated by the stator 18. , Small diameter part 1 corresponding to torsional vibration nodes
4c, the elastic bodies 11a, 11b and the fixed shaft 20 are penetrated.

The collar 19 is a member for preventing the fixed shaft 20 from moving in the hollow portion of the stator 18 in a direction intersecting the longitudinal direction of the fixed shaft 20. Color 1
Reference numeral 9 is arranged in the hollow portion of the stator 18 corresponding to the large diameter portions 14A and 14D.

The pressing member 24 moves the moving member 21 to the driving surface 11.
a member for making pressure contact with a, for example, a disc spring,
It consists of a coil spring, a leaf spring and the like. The amount of pressure applied by the pressure member 24 can be changed by adjusting the amount of screwing of the nut 25 screwed into the screw portion 20c.

Next, the operation of the rotary vibration actuator 10 will be described. As shown in FIG. 2A, a voltage of the same polarity is applied to the torsional vibration piezoelectric element 12a on the near side and the torsional vibration piezoelectric element 12b on the back side via the electrodes 15-1a and 15-1b. Then, the torsional vibration piezoelectric elements 12a and 12b undergo shear deformation in the direction indicated by the solid arrow in FIG. 2B, and the drive surface 11c is twisted in the arrow direction in FIG. When voltages of opposite polarities are applied to the torsional vibration piezoelectric elements 12a and 12b, the torsional vibration piezoelectric elements 12a and 12b undergo shear deformation in the direction opposite to that of FIG. It is twisted in the direction opposite to the arrow direction of (A). On the other hand, the longitudinal vibration piezoelectric elements 13a, 13b
When the same sine wave voltage is applied to the piezoelectric elements 13a and 13b via the electrodes 15-2a and 15-2b,
Respectively, expands and contracts in the same direction according to the polarity of the voltage, and the drive surface 11c vibrates longitudinally. Note that the dotted arrows of the torsional vibration piezoelectric elements 12a and 12b in FIG. 2B indicate the polarization direction.

When two driving frequency signals having a (（) λ (wavelength) phase difference are input to the piezoelectric element 13 for longitudinal vibration and the piezoelectric element 12 for torsional vibration, longitudinal vibration and torsional vibration are obtained. The phases of the respective vibrations are shifted by 90 °, and an elliptical motion obtained by combining these vibrations is generated on the driving surface 11c of the stator 18.

FIG. 4 is an explanatory diagram showing that the torsional vibration (T) and the longitudinal vibration (L) generated in the stator 18 of this embodiment are combined to generate an elliptical motion on the drive surface 11c. . At time t = 0, the displacement of the torsional motion (T) is the largest on the left, and the displacement of the longitudinal vibration (L) is zero. In this state, the moving member 21 is in contact with the driving surface 11c of the stator 18 by the pressing member 24.

When the driving frequency is f, the angular frequency is ω
(= 2πf), t = 0 to (4/4) · (π /
Up to ω), the torsional movement (T) is displaced from the left maximum to the right maximum, and the longitudinal vibration (L) is displaced from zero to the upper maximum and back to zero again. Therefore, the driving surface 11c of the stator 18 rotates rightward while pressing the moving member 21, so that the moving member 21 is driven rightward. The drive of the moving element 21 is transmitted to the rotary cylinder 4 via the gear 23, and the lens holding cylinder 3 moves straight in the direction A shown in FIG.

T = (4/4) · (π / ω) to (8/4)
· Until (π / ω) (note that t = (8/4) · (π / ω)
= 0), the torsional vibration (T) is displaced from the maximum on the right to the maximum on the left, and the longitudinal vibration (L) is displaced from zero to the lower maximum and back to zero again. Therefore,
Since the drive surface 11c of the stator 18 rotates leftward while moving away from the movable member 21, the movable member 21 is not driven.
At this time, the moving member 21 is pressurized by the pressing member 24, but since the natural frequency of the pressing member 24 is lower than the ultrasonic vibration range, the moving member 21 is compressed by the stator 18. I can't follow.

The piezoelectric element 12 for torsional vibration and the piezoelectric element 13 for longitudinal vibration of the rotary vibration actuator 10 described above.
Is applied with a constant frequency and a voltage value, the moving element 21 of the rotary vibration actuator 10 rotates at a constant rotation speed. FIG. 5A is a diagram showing the output characteristics of the vertical vibration detecting piezoelectric element 26 with respect to the rotation speed of the moving element 21 of the rotary vibration actuator 10 described above, and FIG. FIG. 4 is a diagram illustrating output characteristics of a torsional vibration detecting piezoelectric element 27. As can be seen from both figures, the output voltage of the vibration detecting piezoelectric element is output in correlation with the rotation speed of the moving element 21 of the rotary vibration actuator 10.

However, the movement of the moving element
Is a rotating type vibration actuator 10 which rotates, but when its rotation speed is viewed microscopically, rotation unevenness occurs, and it appears particularly when rotating at a low speed. FIG.
(A) is a figure which shows the voltage waveform of the plus side of the piezoelectric element 26 for longitudinal vibration detection per rotation of the moving element 21. FIG. FIG.
In (a), the vertical waveform indicates that this voltage waveform is an AC voltage having a constant frequency. FIG. 6 (b)
Indicates the envelope of FIG. As can be seen from FIG. 6, various experiments have revealed that the peak value fluctuates per rotation of the mover 21, and this fluctuation corresponds to the rotation unevenness. Note that no signal corresponding to the rotation unevenness appeared on the torsional vibration detecting piezoelectric element 27.

FIG. 7 is a block diagram showing a configuration of a driving device for driving the rotary vibration actuator 10. As shown in FIG. This driving device includes a speed control voltage setting unit 1, an amplifier 2, a voltage controlled oscillator (also referred to as a VCO) 3, a phase shift circuit 4, and driving amplifiers 5 and 6. The speed control voltage setting unit 1 sets a voltage corresponding to a desired rotation speed of the moving member 21 of the rotary vibration actuator 10. The voltage controlled oscillator 3 generates a signal having a frequency according to the input voltage. The phase shift circuit 4 generates a signal having a phase different from the input signal by (π / 2). The drive amplifiers 5 and 6 amplify signals input to the drive level of the rotary vibration actuator 10. The driving frequency signal from the driving amplifier 5 is applied to an electrode 15 for driving the longitudinal vibration piezoelectric element 13 of the rotary vibration actuator 10.
-2a, 15-2b, and the driving frequency signal from the driving amplifier 5 is used to drive the electrodes 15-1a, 15- for driving the torsional vibration piezoelectric element 12 of the rotary vibration actuator 10.
1b. When switching the rotation direction of the rotary vibration actuator 10, the phase of the output signal from the phase shift circuit 4 may be inverted.

The driving device includes a longitudinal vibration detection signal processing circuit 7, a torsional vibration detection signal processing circuit 8, and a comparator 9. The vertical vibration detection signal processing circuit 7 is provided with the electrode 15-3a or the electrode 15- of the piezoelectric element 26 for vertical vibration detection.
3b is connected to either or both. Then, the output voltage from the vertical vibration detecting piezoelectric element 26 is processed to extract a rotation unevenness signal. The torsional vibration detection signal processing circuit 8
It is connected to one or both of the electrodes 15-4a and the electrodes 15-4b of the torsional vibration detecting piezoelectric element 27.
Then, the output voltage from the torsional vibration detecting piezoelectric element 27 is processed to extract a rotation speed control signal. The torsional vibration detection signal processing circuit 8 calculates a difference between the output voltage of the speed control voltage setting unit 1 and the output voltage of the torsional vibration detecting piezoelectric element 27, and performs the speed control by feeding back the difference. The piezoelectric element 27 for torsional vibration detection here
Is detected as an averaged value even if the peak value fluctuates. That is, the control of the torsional vibration detection signal processing circuit 8 is not a signal of rotation unevenness, but a correction of a deviation between the set rotation speed and the average value of the actual rotation speed.

Here, the rotation unevenness means that the rotation speed changes in a relatively short time such that the rotation speed increases or decreases in one rotation, for example. Refers to the case where the rotation speed is fixedly deviated to one or the other or changes over a relatively long time. For example, a change within a few milliseconds is referred to as rotation unevenness, and a change in rotation speed detected in units of several hundred milliseconds is not referred to as rotation unevenness, but is referred to as a deviation of the average value of the rotation speed. In addition, it is possible to measure the average value of the output voltage of the torsional vibration detecting piezoelectric element 27 having a frequency corresponding to the frequency of the drive frequency signal as to whether or not it is a relatively short time corresponding to the rotation unevenness. It may be defined by whether or not it is time. For example, about 5
In the case of the output voltage of the torsional vibration detecting piezoelectric element 27 having a frequency corresponding to the frequency of the driving frequency signal of 0 KHz, it is generally difficult to measure the average value of the output voltage if the time is about 2 ms or less. It may be called a time interval indicating unevenness.

The comparator 9 compares the signal from the speed control voltage setting unit 1, the signal from the longitudinal vibration detection signal processing circuit 7, and the signal from the torsional vibration detection signal processing circuit 8. The comparator 9 includes an operational amplifier (hereinafter, referred to as an operational amplifier) and peripheral elements.

FIG. 8 is a principle circuit diagram of the vertical vibration detection signal processing circuit 7 of FIG. 7, and FIG. 9 shows waveforms at various parts in FIG. The operation of the principle circuit diagram will be described below with reference to FIGS. FIG. 9A shows an output voltage from the longitudinal vibration detecting piezoelectric element 26 supplied between the terminals T1 and T2. The change in the envelope of the output voltage corresponds to the rotation unevenness. In FIG. 8, diodes D1 and D1 are located at point P1.
2. A negative double rectified pulsating voltage shown in FIG. 9B is obtained by the capacitors C1 and C2. This signal is supplied to an operational amplifier A1, resistors R1, R2, R3, and a capacitor C.
When the signal is supplied to an inverting amplifier having a pseudo-integral function constituted by the signal P3, the output P2 of the signal is output as shown in FIG.
The average value of the signal of FIG. 9B (R2 / R1 of the signal of FIG.
(Average value). further,
The signal of FIG. 9B and the signal of FIG.
2. When supplied to an adder composed of resistors R4, R5, R6, and R7, the signal of FIG.
The signal shown in FIG. 9D obtained by taking the sum of the signals in FIG. 9C and inverting the sum is obtained. In this way, in the frequency signal of the output voltage of the longitudinal vibration detecting piezoelectric element 26 shown in FIG. 9A, the change of the envelope corresponding to the rotation unevenness, in other words, the change of the peak value between the adjacent cycles is reduced. Is extracted.

The minus signal in the X1 part of FIG.
9A shows a portion where the amplitude is small, and indicates that the rotation speed is lower than the rotation speed indicated by the average value of the envelope in FIG. 9A. Conversely, the plus signal in the X2 portion indicates a portion where the amplitude is large in FIG. 9A, and indicates that the speed is higher than the rotation speed indicated by the average value of the envelope in FIG. 9A. ing. FIG.
The rotation speed indicated by the average value of the envelope in (a) corresponds to the set rotation speed. If an error occurs between the rotation speed indicated by the average value of the envelope and the set rotation speed, the error is detected and corrected by the torsional vibration detection signal processing circuit 8 as described above. In the torsional vibration detection signal processing circuit 8, the average value of the envelope, that is, the average value of the rotation speed is measured as the average value of the output voltage of the piezoelectric element 27 for detecting the torsional vibration.

When the rotation unevenness signal as shown in FIG. 9D obtained by the circuit of FIG. 8 is input to the comparator 9 of FIG. 7, for example, the signal of the X1 part of FIG. A voltage lower than the set voltage is supplied. When the signal of the X2 portion is input, a voltage higher than the set voltage is supplied to the voltage controlled oscillator 3.

FIG. 10A is a diagram showing characteristics of the voltage controlled oscillator 3 used in the present embodiment. FIG.
As shown in (a), the voltage controlled oscillator 3 is an oscillator whose oscillation frequency increases in proportion to the input voltage. When the signal shown in FIG. 9D is input to the voltage controlled oscillator 3 having such a characteristic, the input voltage decreases in the portion corresponding to the X1 portion, and the output frequency decreases. In a portion corresponding to the portion X2, the input voltage increases and the output frequency increases.
If FIG. 10A having the opposite characteristic to FIG.
When using the voltage controlled oscillator 3 having the characteristic shown in FIG. 9B, a signal obtained by inverting the signal shown in FIG.

FIG. 11 shows the present rotary vibration actuator 1.
FIG. 9 is a diagram showing a frequency f of a driving voltage to the torsional vibration piezoelectric element 12 and the longitudinal vibration piezoelectric element 13 at 0, and an amplitude a of an elliptical motion on the driving surface 11c. f0 is the resonance frequency, and the speed control is performed in the range of the waveform Y1 falling to the right. When the amplitude of the elliptical motion of the driving surface 11c increases,
The distance over which the movable element 21 is carried by one elliptical movement increases, and the rotational speed of the movable element 21 increases. That is, by lowering the frequency f, it approaches the resonance frequency f0 to increase the amplitude of the elliptical vibration to increase the rotation speed, and conversely, by increasing the frequency f, it separates from the resonance frequency f0 to decrease the amplitude of the elliptical vibration and reduce the rotation speed. I have.

Therefore, in the portion X1 where the speed is decreasing, the frequency decreases as described above and approaches the resonance frequency, so that the speed of the rotary vibration actuator 10 increases and the rotation unevenness is corrected. Conversely, the speed is increasing X
In the two portions, the frequency increases and departs from the resonance frequency, the speed of the rotary vibration actuator 10 decreases, and rotation unevenness is corrected.

In the above-described embodiment, the speed control voltage setting section 1 uses the torsional vibration detection signal processing circuit 8 (FIG. 7).
A description has been given of the case where the difference between the output voltage of the torsion vibration detection piezoelectric element 27 and the output voltage of the torsion vibration detection piezoelectric element 27 is obtained and the difference is fed back to perform the speed control. It is not necessary to limit to 27 output voltages. For example, as shown in FIG. 12, the longitudinal vibration detection signal speed control processing circuit 101 calculates the difference between the output voltage of the longitudinal vibration detection piezoelectric element 26 and the output voltage of the speed control voltage setting unit 1. The speed control can be similarly performed.

Modification FIG. 13 is a modification of the principle circuit diagram of the vertical vibration detection signal processing circuit 7 of FIG. FIG. 14 shows waveforms at various points in FIG. Hereinafter, the operation of the circuit diagram of this modified example will be described with reference to FIGS. FIG. 14A shows the state shown in FIG.
The output voltage from the vertical vibration detecting piezoelectric element 26 supplied between the terminals T5 and T6 is the same as that shown in FIG.
FIG. 14B is a diagram showing a state where half-wave rectification is performed by the diode D11. The high-frequency component of the half-wave rectified signal is cut by the capacitor C11.
As shown in (c), a signal corresponding to the envelope can be extracted (P
11 points). The DC component of the signal of FIG. 14C is cut by the capacitor C12, and the signal of FIG.
An AC signal shown in (d) is obtained. This signal is
8A, a signal representing the variation of the envelope on the plus side, that is, a signal representing the variation of the peak value in the adjacent cycle, and is a signal corresponding to the extracted rotation unevenness, as in FIG. The capacitor C11 has such a value that the frequency component (for example, about 50 KHz) of the drive voltage applied to the torsional vibration piezoelectric element 12 and the longitudinal vibration piezoelectric element 13 is bypassed and the pulsation of the envelope is not bypassed. C12 has a larger value than capacitor C11. However, depending on the input impedance of the circuit receiving the output of this circuit, the condition that the capacitor C12 has a larger value than the capacitor C11 may not be necessary.

The circuit shown in FIG. 13 is generally the same as a circuit that detects (demodulates) an amplitude-modulated signal in an AM radio or the like. Therefore, the longitudinal vibration detection signal processing circuit 7 shown in FIG. 7 does not need to be limited to the circuit shown in FIG. 8 or the circuit shown in FIG. 13, and can detect (demodulate) an amplitude-modulated signal to extract a fluctuation in amplitude. Any circuit capable of replacing the circuit of FIG. 8 can be used.

As described above, the vertical vibration detecting piezoelectric element 2 conventionally used only for detecting a static speed error is used.
6, it was found that rotation unevenness, which is a dynamic speed error, appeared. Therefore, in the present embodiment and the modified example, the rotation unevenness signal of the moving element 21 of the rotary vibration actuator 10 appearing in the vertical vibration detection piezoelectric element 26 is extracted by the vertical vibration detection signal processing circuit 7, and the signal is extracted. Feedback is fed back to the preceding stage of the voltage controlled oscillator 3 to correct the rotation unevenness. Therefore, it is not necessary to newly attach an encoder or the like to the rotating shaft in order to detect the rotation unevenness, and the rotary vibration actuator can be reduced in size and cost. The position where the detected rotation unevenness signal is fed back need not be limited to the above embodiment. If the voltage controlled oscillator 3 has a control terminal for receiving such a signal, the signal may be directly input to the voltage controlled oscillator 3.

In the above embodiment, the torsional vibration,
Although the rotary type vibration actuator based on longitudinal vibration has been described, the contents of the present invention can be applied to a vibration actuator based on bending vibration and longitudinal vibration.

[0048]

The present invention has the following effects. According to the first aspect of the invention, control is performed to prevent the speed unevenness of the relative motion member based on a signal corresponding to the speed unevenness appearing in the output of the detection electromechanical transducer. Therefore, an external speed detector is not required, and speed unevenness is minimized, and the size and cost of the vibration actuator can be reduced. According to a fourth aspect of the present invention, control is performed to prevent the rotation unevenness of the relative motion member based on a signal corresponding to the rotation unevenness of the relative motion member appearing in the output of the electromechanical transducer for detecting longitudinal vibration of the rotary vibration actuator. ing.
Therefore, the vibration actuator does not require an external rotation speed detector, thereby minimizing rotation unevenness, and enabling the vibration actuator to be reduced in size and cost. The invention according to claims 2 and 5 can be applied to the case where the speed or the rotation speed of the relative motion member is controlled by controlling the frequency near the resonance frequency of the vibration actuator. According to the third and sixth aspects of the present invention, the fluctuation of the envelope appearing between adjacent periods of the frequency signal output from the electromechanical transducer for detection is detected to prevent the speed unevenness or the rotation unevenness of the relative motion member. In addition, it is possible to reliably prevent speed or rotation unevenness appearing in a short time.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a structure of a vibration actuator used in an embodiment of the present invention. (B)
FIG. 2 is a schematic sectional view taken along line IIB of FIG.

FIG. 2 (A) is a cross-sectional view taken along line IIIA-i of FIG. 2 and IIIA.
It is the schematic sectional drawing cut | disconnected by the -ii line. (B) is a side view showing an arrangement of an elastic body, a torsional vibration piezoelectric element, a longitudinal vibration piezoelectric element, a torsional vibration detecting piezoelectric element, a longitudinal vibration detecting piezoelectric element, and an electrode plate.

FIG. 3 is an elastic body, a piezoelectric element for torsional vibration, a piezoelectric element for longitudinal vibration, a piezoelectric element for detecting torsional vibration, a piezoelectric element for longitudinal vibration,
FIG. 3 is an exploded view showing an arrangement of a piezoelectric element for detecting longitudinal vibration and an electrode plate.

FIG. 4 is an explanatory diagram showing that elliptical motion is generated on a drive surface by combining torsional vibration (T) and longitudinal vibration (L) generated in a stator.

5A is a diagram showing output characteristics of a rotary vibration actuator with respect to rotation speed of a longitudinal vibration detecting piezoelectric element, and FIG. 5B is a diagram showing output characteristics of a torsional vibration detecting piezoelectric device with respect to rotation speed. It is.

6A is a diagram illustrating a positive-side voltage waveform of the longitudinal vibration detecting piezoelectric element per rotation of the rotary vibration actuator, and FIG. 6B is a diagram illustrating an envelope of FIG. is there.

FIG. 7 is a block diagram of a driving device that drives the rotary vibration actuator.

FIG. 8 is a principle circuit diagram of a longitudinal vibration detection signal processing circuit.

FIG. 9 is a diagram showing waveforms at various parts in FIG.

FIG. 10 is a diagram illustrating characteristics of a voltage controlled oscillator.

FIG. 11 is a diagram illustrating frequency characteristics of a rotary vibration actuator.

FIG. 12 is a block diagram illustrating a modified example of a driving device that drives a rotary vibration actuator.

FIG. 13 is a diagram showing a modification of the principle circuit diagram of the longitudinal vibration detection signal processing circuit.

FIG. 14 is a diagram showing waveforms at various parts in FIG.

[Explanation of symbols]

Reference Signs List 1 speed control voltage setting unit 2 amplifier 3 voltage controlled oscillator 4 phase shift circuit 5, 6 drive amplifier 7 longitudinal vibration detection signal processing circuit 8 torsional vibration detection signal processing circuit 9 arithmetic unit 10 vibration actuator 11a, 11b elastic body 11c driving surface 12, 12a, 12b Piezoelectric element for torsional vibration (electromechanical transducer for driving) 13, 13a, 13b Piezoelectric element for longitudinal vibration (electromechanical transducer for driving) 14A, 14B, 14C, 14D Large diameter portion 14a, 14b, 14c, 14d Small diameter portion 15 Electrode plate 17 Fastening member 17a Bolt 17b Nut 18 Stator (vibrator) 20 Fixed shaft 21 Moving member (relative moving member) 23 Gear 24 Pressing member 26, 26a, 26b Piezoelectric element for detecting longitudinal vibration (Electro-mechanical transducer for detection) 27, 27a, 27b Piezoelectric element for torsional vibration detection 101 Longitudinal vibration Signal speed control processing circuit R1~R7 out, R11 resistor C1 to C3, C11, C12 capacitor D1, D2, D11 diode T1~T8 terminal

Claims (6)

[Claims] An elastic body, a driving electromechanical transducer that is joined to the elastic body and generates a plurality of vibrations in the elastic body, and a detection device that is joined to the elastic body and detects a vibration state of the elastic body. A vibrator having an electromechanical transducer for use and obtaining a driving force by the plurality of vibrations, and a relative motion member which is in pressure contact with the vibrator and performs relative motion between the vibrator and the driving force. A driving device for a vibration actuator that drives a vibration actuator, comprising: applying a frequency signal set such that the relative movement is at a predetermined speed to the driving electromechanical transducer, and driving the elastic body by the driving device. Vibrating in a direction substantially parallel to the direction of force
And a second vibration that vibrates in a direction intersecting with the first vibration direction, and the frequency is controlled so as to prevent speed unevenness of the relative motion based on an output of the electromechanical transducer for detection. A driving device for a vibration actuator, comprising a control device for controlling a signal. 2. The driving device for a vibration actuator according to claim 1, wherein a speed of the relative movement is controlled by changing a frequency of the frequency signal applied to the driving electromechanical transducer. Comprises a frequency control circuit for changing the frequency of the frequency signal based on the output of the electromechanical transducer for detection. 3. The driving device for a vibration actuator according to claim 1, wherein an output of the electromechanical transducer for detection corresponds to a frequency of the frequency signal applied to the electromechanical transducer for driving. A frequency signal having a frequency, wherein the control device detects a fluctuation of an envelope appearing between adjacent periods of the frequency signal of the output of the detection electromechanical transducer, and based on the detected signal, the relative motion. A driving device for the vibration actuator, wherein the frequency signal applied to the driving electromechanical transducer is controlled so as to prevent the speed unevenness. 4. A pair of columnar elastic bodies having a driving surface intersecting with the longitudinal direction, and a torsion disposed between the elastic bodies and generating torsional vibrations of the elastic bodies oscillating around an axis along the longitudinal direction. An electromechanical transducer for vibration, an electromechanical transducer for longitudinal vibration joined to the elastic body to generate longitudinal vibration in the elastic body in the longitudinal direction, and longitudinal vibration for detecting a vibration state of the longitudinal vibration A vibration actuator for driving a vibration actuator comprising: a detection electromechanical conversion element; and a relative motion member rotatably driven around the axis by being brought into pressure contact with a driving surface of the vibrator and rotationally driven by the driving force. In the driving device, a frequency signal set such that a rotation speed of the relative motion member is a predetermined speed is transmitted to the electromechanical transducer for longitudinal vibration and the electromechanical transducer for torsional vibration. And a control device for controlling the frequency signal so as to prevent rotation unevenness of the relative motion member based on the output of the electromechanical transducer for detecting longitudinal vibration. apparatus. 5. The driving device for a vibration actuator according to claim 4, wherein the rotation speed changes a frequency of the frequency signal applied to the electromechanical transducer for longitudinal vibration and the electromechanical transducer for torsional vibration. Wherein the control device has a frequency control circuit that changes the frequency of the frequency signal based on the output of the electromechanical transducer for detecting longitudinal vibration. 6. The driving device for a vibration actuator according to claim 4, wherein an output of the electromechanical transducer for detecting longitudinal vibration has a frequency corresponding to a frequency of the frequency signal applied to the electromechanical transducer for driving. A frequency signal having a corresponding frequency, wherein the control device detects a fluctuation of an envelope appearing between adjacent periods of the frequency signal of the output of the electromechanical transducer for longitudinal vibration detection, based on the detected signal. A driving device for a vibration actuator, wherein the frequency signal applied to the electro-mechanical transducer for longitudinal vibration and the electro-mechanical transducer for torsional vibration is controlled so as to prevent uneven rotation of the relative motion.