JPH09285149A - Vibration actuator and its drive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily switch the drive characteristics of a vibration actuator by changing a pressuring force between an oscillator and a relative motion member by a pressuring mechanism in response to the frequency of a drive voltage input to an electric-mechanical conversion element. SOLUTION: An oscillator comprising piezoelectric elements 2a, 2b, 2p and 2p' as four electric-mechanical conversion elements is mounted in parallel on one of the planes of a rectangular flat-shaped elastic body 1. Also, a pressuring mechanism 24 for pushing the elastic body 1 to the surface of a rail 22 as a relative motion member with a predetermined pressuring force is mounted between the elastic body 1 and a frame 23 having a box-shaped cross section. The pressuring force between the rail 22 and the oscillator by the pressuring mechanism 24 is changed by adjusting an adjusting disk 50 by the change in a compressive coil spring 49 relative to a pressuring plate 48 in response to the frequency of a drive voltage input to the oscillator. By doing this, the drive characteristics of the vibration actuator 20 can be easily switched.

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 its driving method.

[0002]

2. Description of the Related Art At least two electromechanical transducers are joined to an elastic body and a plurality of vibrations are generated harmoniously in the elastic body by applying an AC voltage as a drive signal to each of the electromechanical transducers. A vibration actuator that generates an elliptical motion on the surface of an elastic body is known.

[0003] As such a vibration actuator,
"Piezoelectric linear motor for moving optical pickup" (Yoshiro Tomikawa et al .: Proceedings of the 5th Electromagnetic Force-related Dynamic Symposium, pp. 393-398) details its configuration and load characteristics It is explained.

FIG. 8 shows such a vibration actuator 1
8A is a top view, FIG. 8B is a front view, FIG. 8C is a right side view, and FIG.
Is a bottom view. In FIG. 8D, the friction material 5a,
5b is shown in a partially broken state.

The vibrating actuator 1 has a rectangular flat plate shape, and the driving force extracting portions 2a, 2b
And an elastic body 2 (which is made of an elastic material such as a metal material such as stainless steel or an aluminum alloy or a plastic material) in which the above are formed, and an elastic body by a pressurizing mechanism (not shown) via the driving force extracting portions 2a and 2b 1 and a relative motion member 3 that is in pressure contact with the first member 1. Driving force take-out section 2a, 2
As will be described later, b is formed at two positions of the antinode of the fourth-order bending vibration generated in the elastic body 2.

On the other plane of the elastic body 2, piezoelectric bodies 4a, 4b, 4p, 4 which are rectangular thin plate-like electromechanical transducers are provided.
p 'is attached. The piezoelectric bodies 4a and 4b are driving piezoelectric bodies. Alternating current voltages whose phases are electrically different by 90 degrees are applied to the piezoelectric bodies 4a and 4b. The piezoelectric bodies 4p, 4
p ′ is a piezoelectric body which is a mechanical-electrical conversion element for detecting a vibration state generated in the elastic body 2. Lead wires (not shown) are soldered to these piezoelectric bodies 4a, 4b, 4p, 4p ', and each lead wire is also connected to a control circuit (not shown).

By applying an AC voltage, which is a drive signal, from a drive voltage generator (not shown) to each of the piezoelectric bodies 4a and 4b, first-order longitudinal vibration and fourth-order bending vibration are harmonically generated in the elastic body 2. . The generated longitudinal vibration and bending vibration are combined to generate an elliptical displacement in the longitudinal direction of the elastic body on the end faces of the driving force extraction units 2a and 2b, and the driving force extraction unit 2
A relative motion is generated with respect to the relative motion member 3 which comes into pressure contact with the elastic body 2 via the a and 2b. This relative movement is taken out and used as thrust.

In such a vibration actuator 1, 1
The natural frequencies of the next longitudinal vibration and the fourth bending vibration are designed to be very close to each other or the same value. Therefore, by applying an AC voltage having a frequency close to two natural frequencies to each of the piezoelectric bodies 4a and 4b, it is possible to harmonically generate the first longitudinal vibration and the fourth bending vibration.

[0009]

By the way, in the conventional vibration actuator 1, in order to have different drive characteristics, such as a coarse movement type (high speed type) and a fine movement type (high load type), desired characteristics are required. Therefore, it is necessary to appropriately change the shapes, dimensions, etc. of the elastic body, the relative motion member, etc., and to newly manufacture them.

That is, in the conventional vibration actuator 1, since the drive characteristics are determined by the specifications of the vibration actuator, it is extremely difficult to change the drive characteristics using a single elastic body. Therefore, in order to obtain the vibration actuators having different driving characteristics, it is necessary to design and manufacture the vibration actuators individually.
Therefore, there is a problem in that the number of manufactured products increases and the manufacturing cost increases.

Further, when it is desired to change the drive characteristics after incorporating the vibration actuator into the equipment, it is necessary to remove the existing vibration actuator and mount a vibration actuator having a new desired drive characteristic. There was a problem that it took time.

Incidentally, it is not impossible to obtain desired drive characteristics by incorporating several types of vibration actuators having different drive characteristics into the device and switching these appropriately. However, this is not easy because a large installation space is required due to an increase in the number of vibration actuators to be installed, and a vibration actuator switching mechanism needs to be newly provided.

[0013]

According to the present invention, a resonance frequency fB of bending vibration generated in an elastic body and a resonance frequency fL of longitudinal vibration are shifted from each other to manufacture a vibration actuator, and a resonance frequency fB of bending vibration is generated. Resonance frequency f of longitudinal vibration
By changing the drive frequency between L and L, the ratio between the amplitude of bending vibration and the amplitude of longitudinal vibration is changed to change the form of the elliptical displacement generated in the driving force extracting portion of the elastic body. The drive characteristics of the vibration actuator are easily switched.

According to a first aspect of the present invention, a vibrator having an elastic body and an electromechanical conversion element that is mounted on the elastic body and applies bending voltage and longitudinal vibration to the elastic body in a harmonious manner. And a relative motion member that comes into contact with the vibrator, and a pressurizing mechanism that pressurizes the relative motion member and the vibrator, and further pressurizes according to the frequency of the drive voltage input to the electromechanical conversion element. A vibration actuator comprising: a relative movement member of a mechanism and a pressing force control unit that changes a pressing force between the vibrator.

According to a second aspect of the present invention, in the vibration actuator according to the first aspect, the frequency is set to a predetermined value between the resonance frequency of the bending vibration and the resonance frequency of the longitudinal vibration. When the frequency of the drive voltage is closer to the resonance frequency of the longitudinal vibration than the predetermined frequency, the pressure control section applies a predetermined predetermined pressure to the applied force between the relative motion member and the vibrator. It is characterized in that the pressure is changed to be smaller than the pressure, and when the frequency of the drive voltage is a value closer to the resonance frequency of the bending vibration than the predetermined frequency, the pressure is changed to be larger than the predetermined pressure.

According to a third aspect of the present invention, a drive voltage is applied to the electromechanical conversion element mounted on the elastic body to generate flexural vibration and longitudinal vibration in the elastic body in a harmonic manner, and the pressure contact is made with the vibrator. A method for driving a vibration actuator that generates relative motion with a relative motion member, characterized in that the frequency of the driving voltage is a value between the resonance frequency of flexural vibration and the resonance frequency of longitudinal vibration. .

According to a fourth aspect of the present invention, in the method of driving a vibration actuator according to the third aspect, the frequency is set to a predetermined value between the resonance frequency of bending vibration and the resonance frequency of longitudinal vibration. If the frequency of the drive voltage is closer to the resonance frequency of the longitudinal vibration than the predetermined frequency, the pressure between the elastic body and the relative motion member is smaller than the predetermined pressure. However, when the frequency of the drive voltage is a value closer to the resonance frequency of the flexural vibration than the predetermined frequency, the pressure force between the elastic body and the relative motion member is larger than the predetermined pressure force. It is characterized by doing.

According to a fifth aspect of the present invention, in the method for driving the vibration actuator according to the fourth aspect, the pressure applied between the elastic body and the relative motion member is changed by a predetermined force applied and the drive voltage. It is characterized in that it is performed based on the relationship with the frequency.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Note that the description of each embodiment is as follows.
An example of an ultrasonic actuator using an ultrasonic vibration region as the vibration actuator will be described.

FIG. 1 is a front view showing a carrying device incorporating the ultrasonic actuator 20 of the first embodiment in a partially broken state. 2 is a sectional view taken along the line II-II in FIG. FIG. 3 is a front view of the elastic body 1 that constitutes the ultrasonic actuator 20 of the first embodiment. Furthermore, FIG. 4 is an explanatory view showing the periphery of the pressurizing mechanism 24 in FIG. 2 in an enlarged manner, and FIGS. 4A and 4B are enlarged sectional views showing a state at the time of pressurizing. FIG. 7C is a plan view showing a meshing state between the adjusting plate 50 and the pressurizing motor gear 60.

1 to 3, an ultrasonic actuator 20 according to the first embodiment includes a rectangular flat plate-shaped elastic body 1 and four electromechanical conversion elements mounted in parallel on one plane of the elastic body 1. And a piezoelectric element 2a, 2b, 2p, 2p '.

The drive device in the present embodiment is provided with the ultrasonic actuator 20 and a flexible printed circuit board (hereinafter referred to as "flexible printed circuit board") which is mounted so as to cover one flat surface of the elastic body 1.
It is simply abbreviated as “FPC”. ) 21 and a rail 22 which is a relative movement member movably arranged with respect to the elastic body 1.
And a box-shaped frame 23 having a box-shaped cross-section for supporting the ultrasonic actuator 20, the pressurizing mechanism 24, etc., and the elastic body 1 disposed between the frame 23 and the elastic body 1 on the surface of the rail 22 with a predetermined pressing force. The main part is constituted by the pressing mechanism 24 which is pressed by.

In this embodiment, the elastic body 1 is the frame 2
The rail 22 that is fixed to the pressure roller 3 together with the pressurizing mechanism 24 makes contact with the elastic body 1 to form a moving body (relative movement member) that linearly moves.

The elastic body 1 is formed in a rectangular flat plate shape with a metal material such as stainless steel or aluminum alloy, or an elastic material such as ceramic material or plastic material. On the other plane of the elastic body 1 (the surface on which the piezoelectric element is not mounted),
The driving force take-out portions 1a and 1b are integrally formed in a protruding shape. The driving force output portions 1a and 1b are provided symmetrically on both sides of the center line (II line in FIG. 3) of the elastic body 1 (the antinode position of the bending vibration generated). , Its end surface contacts the upper surface of the rail 22. In addition, screw attachment portions 26A and 26B for a pressure mechanism having a screw hole 25 are integrally formed at the centers of both long side surfaces of the elastic body 1.

In FIG. 3, of the four piezoelectric elements, the inner two piezoelectric elements 2a and 2b cause the elastic body 1 to generate a first-order longitudinal vibration (L1 mode) and a fourth-order bending vibration (B4 mode). A driving piezoelectric element for converting electric energy into mechanical energy (mechanical displacement). These piezoelectric elements 2a and 2b are arranged in parallel on both sides of the center line (II line) of the elastic body 1 with a substantially equal distance therebetween.

On the other hand, the piezoelectric elements 2p and 2p 'arranged outside the elastic body 1 are vibration monitoring piezoelectric elements for monitoring the state of vibration generated in the elastic body 1, and are mechanical energy (mechanical energy). Displacement) electrical energy (electrical signal)
Convert to These piezoelectric elements 2p and 2p 'are arranged outside the piezoelectric elements 2a and 2b, and are elastic bodies 1 with respect to each other.
It is mounted at a position equidistant from the center (line I-I).

Two electrodes are formed on each of the front and back surfaces of the elastic body 1 by baking. The two electrodes on the front surface side are respectively connected to the piezoelectric elements 2a and 2b via drive terminal portions 28a and 29a provided at one ends of the conductive foils 28 and 29 formed on the FPC 21, respectively.

A first AC voltage is applied to the driving terminal portion 28a, while a second AC voltage whose electrical phase is 90 ° different from that of the first AC voltage is applied to the driving terminal portion 29a. It In this embodiment, the polarization directions of the piezoelectric elements 2a and 2b in the thickness direction are set in the same direction, but they may be set in opposite directions. Two electrodes and drive terminal 2
8a and 29a are joined by appropriate means such as adhesion, welding and pressure bonding.

On the piezoelectric elements 2p and 2p ', the vibration monitor terminal portion 33 of the conductive foils 33 and 34 formed on the FPC 21 is provided.
a and 33b are respectively connected. Piezoelectric elements 2p, 2
Two electrodes are formed on each side of p'by baking. The two electrodes on the front surface side are connected to the piezoelectric elements 2p, 2 via the vibration monitor terminal portions 33a, 33b provided at one end of the conductive foils 33, 34 formed on the FPC 21.
It is joined to p ′ by an appropriate means such as adhesion, welding and pressure bonding.

The vibrating state of the elastic body 1 depends on the piezoelectric elements 2p and 2p.
It is converted into an electric signal by p ′ and is output via the two electrodes on the front surface side. This electric signal contains a combination of two different vibration modes, that is, the vibration state of the fourth bending vibration (B4 mode) and the vibration state of the first longitudinal vibration (L1 mode). Then, a signal having a magnitude substantially corresponding to the vibration amplitude generated in the elastic body 1 is obtained.

The FPC 21 is composed of two upper and lower films, and a conductive foil 28 electrically isolated from each other between them.
29, 33, 34, 36 are arranged. These conductive foils 28, 29, 33, 34 and 36 form a part of the drive circuit. Unlike the present embodiment, the FPC 21 may be one in which a conductive portion is formed on one film by plating, screen printing, or the like, and the conductive portion has a function of a conductive foil.

The terminal portions 28a, 29a, 33a, 34a of the conductive foils 28, 29, 33, 34 are exposed on the back surface side of the FPC 21, and as described above, the electrodes 4a, 4a of the piezoelectric elements are formed.
It is joined to 5a, 6a and 7a. Further, the conductive foil 36 is provided with a ground terminal portion 36 a, which is exposed on the back surface side of the FPC 21.

As shown in FIG. 3, a strip-shaped connecting portion 37A and a tongue-shaped fixing portion 37B are integrally formed at the centers of both side surfaces of the FPC 21 on the long side. Connection part 37
In A, the conductive foils 28, 29, 33, 34, and 36 are concentrated and formed in parallel, and the tips are connected to the terminals A, B, P, P ′,
It is connected to a motor drive circuit (described later with reference to FIG. 5) via the G terminal.

A screw mounting hole is formed in the base portion of the connecting portion 37A of the FPC 21 corresponding to the screw hole of the screw mounting portion 26A for the pressure mechanism. One of a pair of mounting screws 38, which is a connecting member that connects the elastic body 1 and the frame 23, is inserted into the screw mounting hole. On the rear surface side of the base of the connecting portion 37A, the terminal portion 36a of the conductive foil 36 for ground described above is exposed in the vicinity of the screw mounting hole.

The tongue-shaped fixing portion 37B is provided with a screw mounting hole (not shown) formed corresponding to a screw hole (not shown) of the pressure mechanism mounting portion 26B, and the elastic body 1 and the frame 23 are provided. The other of the pair of mounting screws 38 that connects and is inserted.

In FIGS. 1 and 2, the rail 22 is arranged so as to penetrate the frame 23. Frame 23
Is formed in a box shape, and the elastic body 1 is fixed and supported inside by a pair of mounting screws 38, 38. Also,
Below the inside of the frame 23, guides 44, which come into contact with both side surfaces of the rail 22 via bearings 43, are provided by mounting screws 55, and the rail 22 is sandwiched between the elastic body 1 and the guides 44 from above and below. It In this way, the smooth movement of the rail 22 is enabled and the movement of the elastic body 1 in the width direction is restricted.

The pressure mechanism 24 includes a pair of mounting screws 38,
A pressing plate 48 provided to be movable up and down on 38, a pair of compression coil springs 49, 49 mounted on the mounting screws 38, 38 to press the pressing plate 48 against the elastic body 1, and the mounting screws 38, 38. Each compression coil spring 4 is screwed to the top
A pair of adjusting disks 50, 50 for adjusting the spring force of 9, 49
And a pair of washers 5 fitted into the lower ends of the mounting screws 38, 38 and located between the elastic body 1 and the pressing plate 48.
1, 51 and the like.

In the present embodiment, as shown in FIG. 4, a screw portion is engraved on the outer peripheral portion of the adjusting disks 50, 50, and the pressurizing motor gear 60 meshes with the screw portion. The pressurizing motor gear 60 is fixed to the output shaft of the pressurizing motor 61 fixed to the outer upper side of the frame 23, and by driving the pressurizing motor 61, the adjusting disc 50, 50 rotates.

The adjusting disc 50 moves up and down along with the mounting screw 38 as it rotates. Therefore, the spring force of the compression coil spring 49 with respect to the pressing plate 48 changes, and the pressing force between the elastic body 1 and the rail 22 is adjusted.

The washer 51 is a connecting portion 37 of the FPC 21.
The base portion of A and the fixed portion 37B are attached to the attachment portion 26 of the elastic body 1.
Press and fix to A and 26B. This allows FPC2
The electrical connection between the ground terminal portion 36a exposed on the back surface side of 1 and the elastic body 1 is ensured. If pressure is applied to the antinode of the bending vibration generated in the elastic body 1, the amplitude of the bending vibration is reduced.
It is desirable that the position where the pressure is applied does not reach the antinode position of the bending vibration.

FIG. 5 is a block diagram showing a drive circuit of the ultrasonic actuator 20 in this embodiment. The oscillator 71 outputs a drive signal of a predetermined frequency according to the control signal output from the actuator control circuit 70.
One of the drive signals oscillated from the oscillator 71 is input to the piezoelectric element 2b as an A-phase voltage via the amplifier 72, and the other is phase-shifted by 90 ° via the phase shifter 73 to be an amplifier 74 as a B-phase voltage. Is input to the piezoelectric element 2a via.

At this time, part of the control signal is input to the pressurizing motor drive circuit 75, and the frequency of the drive signal (drive frequency) is transmitted. On the other hand, the pressurizing motor drive circuit 75 outputs the pressurizing force set value set by the pressurizing force setting board 76 operated and set by the operator. The pressurizing motor drive circuit 75 determines the operation amount of the pressurizing motor 61 on the basis of the current drive frequency and the pressurizing force set value, and on the basis of the table values determined in advance.

In this table value, a pressing force value is preset in a plurality of stages for a driving frequency in a certain frequency range. By setting the pressing force, the driving characteristics of the ultrasonic actuator are The coarse movement type (high speed type) can be gradually changed to the fine movement type (high load type).

As described above, in the present embodiment, the actuator control circuit 70, the pressurizing motor drive circuit 75, and the pressurizing force setting board 76 allow the pressurizing mechanism 24 to move the rail according to the drive frequency input to the piezoelectric elements 2a and 2b. A pressing force control unit that changes the pressing force between 22 and the elastic body 1 (vibrator) is configured.

The transfer device using the ultrasonic actuator in this embodiment is constructed as described above. next,
In the transport apparatus according to the present embodiment, when the operator sets the pressing force setting value using the pressing force setting board 76, the pressurizing motor 61 is activated and stopped at a predetermined position. As a result, the pressing force is applied by the pressurizing mechanism as shown in FIGS.
It is adjusted as shown in (b).

FIG. 6 is a graph showing an example of the relationship between the frequency of the drive signal (drive frequency) and the amplitudes of bending vibration and longitudinal vibration in the ultrasonic actuator of this embodiment. Hereinafter, in the graph shown in FIG. 6, switching between the coarse movement type (high speed type) and the fine movement type (high load type), that is, the switching of the drive characteristics will be described with the drive at the drive frequency f2 as the standard drive state.

In the ultrasonic actuator 20 of this embodiment, the resonance frequency fB of the bending vibration and the resonance frequency fL of the longitudinal vibration are set to be different from each other by appropriately setting the dimensions of the elastic body and the like (resonance frequency fL> Resonance frequency f
B), the frequency f2 between them is used as the drive frequency. In the present embodiment, driving at such a frequency f2 is the standard state.

In the present embodiment, when the ultrasonic actuator 20 is of the coarse movement type from such a standard state, the drive frequency is driven close to the resonance frequency fL of the longitudinal vibration (drive frequency f2 → f3). . FIG. 6 schematically shows an example of an elliptical displacement in the elastic body driving force output portion when the driving frequencies are f2 and f3. Resonance point fL of longitudinal vibration
At a drive frequency f3 close to, the elliptical displacement becomes a horizontally long flat and the vertical vibration amplitude becomes larger than that at f2, so the drive speed increases and the drive characteristics of the ultrasonic actuator 20 are changed to the coarse movement type (high speed type). ) Can be

At this time, by setting the applied pressure to be smaller than the applied pressure at the standard time, the running resistance at the time of relative movement can be suppressed, so that a higher speed ultrasonic actuator can be obtained. Yes, it is desirable.

On the other hand, when the ultrasonic actuator 20 is of the fine movement type, the driving frequency is the resonance frequency f of bending vibration.
It is driven closer to B (driving frequency f2 → f1). At the drive frequency f1 close to the resonance frequency fB of bending vibration, the elliptical displacement becomes a vertically long flat shape and the vertical vibration amplitude becomes smaller than when it is f2. Therefore, the drive speed becomes small and the fine movement operation at low speed becomes possible. Become.

Further, the bending vibration amplitude becomes larger than that of the standard drive frequency f2. Therefore, even if the pressing force between the elastic body and the relative motion member is increased, the elliptical displacement (elliptical locus) in the driving force output portion can be maintained, and the speed fluctuation due to the unevenness on the surface of the relative motion member can be maintained. It is hard to occur. Therefore, it becomes possible to drive stably at a low speed. That is, by increasing the applied pressure, the frictional force between the elastic body and the relative motion member increases, and the ultrasonic actuator can be driven even when a larger load is applied, and the ultrasonic actuator is of the fine movement type (high load type). be able to.

As described above, by changing the driving frequency and, if necessary, the pressing force between the elastic body and the relative motion member, the driving characteristics of the ultrasonic actuator can be changed to a desired state. It is possible to switch.

FIG. 7 is a graph showing changes in the performance of the ultrasonic actuator (relationship between load load and speed) when driven at drive frequencies f1, f2 and f3. As shown in the graph of FIG. 7, when driving at the driving frequency f1 as compared with driving at the driving frequency f2 which is the standard state, a high load-
It can be seen that the low-speed drive characteristics are obtained and a fine-motion (high load) ultrasonic actuator is obtained.

On the other hand, it can be seen that when the driving frequency f3 is used, a low load-high speed type driving characteristic is obtained and a coarse motion type (high speed type) ultrasonic actuator is obtained. Note that FIG.
, The driving force between the elastic body and the relative motion member when the driving frequency is f1, f2, f3 is P1, P
2, P3. At the driving frequency f1, in order to make the performance of the high load type ultrasonic actuator clearer, it is desirable to apply a pressure P1 larger than the pressure P2. Further, at the drive frequency f3, in order to make the performance of the high-speed ultrasonic actuator clearer, it is desirable to apply a pressure P3 that is smaller than the pressure P2.

(Modification) In the first embodiment, an ultrasonic actuator utilizing the vibration range of ultrasonic waves is taken as an example of the vibration actuator, but the vibration actuator according to the present invention is limited to such a mode. not,
The same can be applied to vibration actuators using other vibration regions.

Further, in the first embodiment, the piezoelectric element is used as the electromechanical conversion element, but the vibration actuator according to the present invention is not limited to such a mode, and electric energy is converted into mechanical displacement. Anything that can be applied is equally applicable. For example, an electrostrictive element other than the piezoelectric element can be exemplified.

In the first embodiment, the so-called L1 which causes the elastic body to generate the first-order stretching vibration and the fourth-order bending vibration.
Although the -B4 type vibration actuator has been taken as an example, the vibration actuator according to the present invention is not limited to such a mode, and is equally applied to other vibration actuators utilizing longitudinal vibration and bending vibration. It is possible.

In the first embodiment, the case where the driving frequencies f1, f2 and f3 of three levels are changed stepwise has been described as an example, but the present invention is not limited to such an aspect. The driving frequency may be continuously changed and the pressing force may be continuously changed corresponding to the change of the driving frequency.

Further, in the first embodiment, when the pressing force is changed, the pressing force setting panel 76 is installed so that the operator can manually input the pressure. However, the vibration actuator according to the present invention has such a configuration. However, the embodiment is not limited to this. For example, in order to improve the operability when changing the pressing force, the relationship between the drive frequency and the pressing force is input to the calculator as a table value, and the calculator and the control device are combined to change the drive frequency according to the drive frequency. It is also possible to configure so that the applied pressure is changed automatically.

[Brief description of drawings]

FIG. 1 is a front view showing a transport device incorporating the ultrasonic actuator of the first embodiment in a partially broken state.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a front view of an elastic body that constitutes the ultrasonic actuator of the first embodiment.

4A and 4B are explanatory views showing the periphery of the pressurizing mechanism in FIG. 2 in an enlarged manner, and FIGS. 4A and 4B are enlarged cross-sectional views showing a state at the time of pressurization, and FIG. (C) is a plan view showing a meshing state between the adjusting plate and the pressurizing motor gear.

FIG. 5 is a block diagram showing a drive circuit of the ultrasonic actuator according to the first embodiment.

FIG. 6 is a graph showing an example of the relationship between the frequency of a drive signal (drive frequency) and the amplitudes of bending vibration and longitudinal vibration in the ultrasonic actuator of the first embodiment.

FIG. 7 shows drive frequencies f1 and f in the first embodiment.
It is a graph which shows the performance change (load load and speed) of an ultrasonic actuator when it drives with 2 and f3.

8A and 8B are explanatory views showing a configuration of a conventional vibration actuator, in which FIG. 8A is a top view, FIG. 8B is a front view, and FIG.
8C is a right side view and FIG. 8D is a bottom view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 elastic body 2a, 2b piezoelectric element (electromechanical conversion element) 22 rail (relative movement member) 24 pressurizing mechanism 70 actuator control circuit 75 pressurizing motor drive circuit 76 pressurizing force setting panel

Claims (5)

[Claims] 1. A vibrating body having an elastic body, and an electromechanical conversion element which is mounted on the elastic body and harmonically generates bending vibration and longitudinal vibration in the elastic body when a driving voltage is applied to the elastic body, and the vibration. A relative movement member that contacts the child; and a pressure mechanism that presses the relative movement member and the vibrator, and further, the pressure mechanism according to the frequency of the drive voltage input to the electromechanical conversion element. A vibration actuator including: a pressure control unit that changes a pressure between the relative motion member and the vibrator. 2. The vibration actuator according to claim 1, wherein the frequency is set to a predetermined value between a resonance frequency of the bending vibration and a resonance frequency of the longitudinal vibration, and the pressing force control unit. When the frequency is a value closer to the resonance frequency of the longitudinal vibration than the predetermined frequency which is set in advance, the press force is changed to be smaller than the predetermined press force which is set in advance, and the frequency is set in advance. A vibration actuator, wherein when the value is closer to the resonance frequency of the flexural vibration than a predetermined frequency, the vibration pressure is changed to be larger than a predetermined pressure. 3. A relative motion member that applies a drive voltage to an electromechanical conversion element mounted on an elastic body to generate flexural vibration and longitudinal vibration in the elastic body in a harmonic manner and press-contacts with the vibrator. A method of driving a vibration actuator that generates a relative motion between the vibration voltage and the vibration frequency, wherein the frequency of the driving voltage is a value between the resonance frequency of the bending vibration and the resonance frequency of the longitudinal vibration. Driving method of vibration actuator. 4. The method of driving a vibration actuator according to claim 3, wherein the frequency is set to a predetermined value between a resonance frequency of the bending vibration and a resonance frequency of the longitudinal vibration, When the frequency of the voltage is a value closer to the resonance frequency of the longitudinal vibration than the predetermined frequency, the pressure between the elastic body and the relative motion member is smaller than the predetermined pressure. However, when the frequency of the drive voltage is a value closer to the resonance frequency of the flexural vibration than a predetermined frequency, a predetermined pressure applied between the elastic body and the relative motion member is predetermined. A method for driving a vibration actuator, which is characterized by making the pressure larger than the pressure. 5. The vibration actuator driving method according to claim 4, wherein the change of the pressing force is performed based on a predetermined relationship between the pressing force and the frequency of the driving voltage. And a method for driving a vibration actuator.