JPH0564465A - Ultrasonic transducer - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic transducer which simply excites a longitudinal vibration as a drive source and which can easily switch the output of a mover, and the like. CONSTITUTION:The ultrasonic transducer comprises means 1 for producing a longitudinal vibration and means 2 for producing a bending vibration in the direction crossing with the longitudinal vibrating direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer used as a driving source for various actuators.

[0002]

2. Description of the Related Art In recent years, ultrasonic actuators and ultrasonic motors have been used in various industrial fields and are being actively developed.

Structurally, these are roughly classified into a vibration direction conversion type and a composite oscillator type traveling wave type.

On the other hand, the vibration direction conversion type ultrasonic actuator utilizes only vertical vibration, and a vertically vibrating contactor is brought into contact with the surface of a movable body while inclining to the moving direction of the movable body. By doing so, the movable body is formed to be rotated and linearly driven.

On the other hand, the composite vibrator type ultrasonic motor uses a combination of torsional vibration and longitudinal vibration and longitudinal vibration and longitudinal vibration, and is formed so as to rotate and linearly drive the rotor. There is.

[0006]

However, in the above-mentioned vibration direction conversion type ultrasonic actuator, the vertically vibrating contactor must be tilted and brought into contact with a movable body such as a slider, and the mutual position of the contactor must be increased. It is difficult to adjust the relationship to an appropriate one, and the structure must be complicated, and in order to change the operation direction of the force applied to the movable body, the contactor and the movable body must be changed. However, there is a problem in that the contact direction must be changed and a plurality of ultrasonic actuators must be arranged with different contact directions.

Further, in the composite vibrator type ultrasonic motor, both the torsion vibrator and the vertical vibrator have to be electrically driven, and there is a problem that the power consumption is large.

The present invention has been made in view of these points, and as a drive source, it is sufficient to excite longitudinal vibrations, but the operation direction of an output applied to the outside of a movable body or the like, for example. It is an object of the present invention to provide an ultrasonic transducer that can be easily switched, has a wide application range when used as an actuator, has high efficiency, and has a simple structure.

[0009]

In order to achieve the above object, an ultrasonic transducer according to the present invention as defined in claim 1 is provided with a longitudinal excitation means for outputting a longitudinal vibration, and an ultrasonic transducer receiving the longitudinal vibration. And a vibration direction control means for outputting a flexural vibration that vibrates in a direction intersecting with the vibration direction.

In the ultrasonic transducer of the present invention as defined in claim 2, the longitudinal direction excitation means in claim 1 is formed by a longitudinal oscillator which is electrically driven, and the vibration direction control means is output from the longitudinal oscillator. A piezoelectric element that is excited by longitudinal vibration, and an electrode that is attached to the piezoelectric element so as to face the longitudinal vibration direction, and one electrode is divided into a plurality of electrodes; It is characterized in that the plurality of divided electrodes are formed by switching means for short-circuiting the undivided electrodes with a phase difference.

[0011]

According to the first aspect of the present invention, when longitudinal vibration is output from the longitudinal excitation means, the vibration direction control means that receives the vibration vibrates in a direction intersecting with the longitudinal vibration. The flexural vibration is output, and the flexural vibration and the vertical vibration are combined and the vibration direction control means vibrates in a Lissajous manner.

According to the second aspect of the present invention, when a drive voltage having a predetermined vibration frequency is applied to the vertical vibrator,
Vertical vibration is excited by the vertical vibrator. When this vertical vibration is transmitted to the piezoelectric element of the vibration direction control means, the piezoelectric element tends to distort in the vertical direction. At this time, regarding the piezoelectric element divided into a plurality of electrodes, the amount of vertical strain differs between the short-circuited electrode portion and the non-short-circuited electrode portion. Bend in the crossing direction. By switching the short-circuited state of the electrodes by the switching operation of the switching means, the bending direction of the piezoelectric element is reversed, and by repeating this switching operation, flexural vibration is generated. As a result, the vertical vibration and the flexural vibration are combined, and the vibration direction control means vibrates in a Lissajous manner.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.

1 to 4 show an embodiment of the present invention.

The ultrasonic transducer of the present embodiment comprises a vertical excitation means 1 for outputting a vertical vibration and a vibration direction for outputting a flexural vibration that receives the vertical vibration and vibrates in a direction intersecting the vibration direction. And the control means 2.

Explaining further, one longitudinal excitation means 1
Is formed with a bolted Langevin type vertical vibrator (Nippon Special Ceramics Co., Ltd .: No. D2328PC), and is formed in a cylindrical shape with a diameter of about 30 mm. A longitudinal piezoelectric element 3 that vibrates in the axial direction is provided. Two electrodes 4a, 4b are mounted on the longitudinal piezoelectric element 3 so as to face each other in the axial direction, and a drive voltage for excitation having a predetermined vibration frequency is applied by a power source 5 between them. It has become.

The other vibration direction control means 2 is in close contact with one axial end surface of the longitudinal excitation means 1, that is, the radiating end surface, and the piezoelectric element 6 which is mounted in close contact with the other end surface of the piezoelectric element 6. Is formed by the vibrator 7. One electrode 8a is mounted on the surface of the piezoelectric element 6 facing the longitudinal excitation means 1, and the axial direction intermediate portion of the piezoelectric element 6 has a vertical piezoelectric element 3 as shown in FIG. Electrodes 8b and 8c divided into two are mounted in a plane intersecting (in the present embodiment, orthogonal to) the vertical vibration direction. A switching means 9 is provided outside the piezoelectric element 6 to electrically short-circuit the divided two electrodes 8b and 8c with respect to the electrode 8a mounted on the one end face side of the piezoelectric element 6. There is. That is, in the switching means 9, the movable contact 10 swinging around the contact 9a as the base end is used as the contact 9 connected to the electrodes 8b and 8c.
It is formed so as to switch the connection state with b and 9c. In FIG. 1, the switching means 9 is shown as a symbol, but in practice, the connection is electronically switched using a switching transistor or the like. The vibrator 7 has a substantially U-shaped tip and has two substantially rectangular contact end surfaces 7a, 7a.

Next, the operation of this embodiment thus formed will be described.

First, a drive voltage having a vibration frequency substantially equal to the natural frequency f of the piezoelectric element 6 of the vibration direction control means 2 is applied to the vertical piezoelectric element 3 of the vertical excitation means 1 from the power source 5 and both electrodes 4a, 4b. Apply through. As a result, the longitudinal piezoelectric element 3 longitudinally vibrates at a vibration frequency substantially equal to the natural frequency f. The vertical vibration of the vertical piezoelectric element 3 is transmitted through the vertical excitation means 1 and the piezoelectric element 6 of the vibration direction control means 2.
And transmitted to the vibrator 7 in order. As a result, the piezoelectric element 6 is vibrated with its own natural frequency and tends to be distorted in the vertical direction. In this state, the switching means 9
The movable contact 10 is operated to short-circuit one of the electrodes 8b and 8c with the electrode 8a. Now electrode 8b is electrode 8
3 and 4, assuming that the electrode 8a and the electrode 8b short-circuited are mounted, the Young's modulus of the portion where the electrode 8a and the electrode 8b short-circuited is not mounted. It becomes smaller than the Young's modulus of the part. As a result, the piezoelectric element 6 is distorted so that the vertical length on the electrode 8b side becomes shorter than the vertical length on the electrode 8c side, and the piezoelectric element 6 crosses the vertical vibration of the vertical piezoelectric element 3, that is, 3 and in the direction of the arrow in FIG. As a result, the contact end surface 7a of the vibrator 7, which is in close contact with the piezoelectric element 6, tends to move in the arrow direction in FIGS. When the switching means 9 opens the one electrode 8b and switches the connection state so as to short-circuit the other electrode 8c and the electrode 8a, the piezoelectric element 6 bends in the opposite direction. In this way, the piezoelectric element 6 of the vibration direction control means 2 causes flexural vibration,
This flexural vibration and the longitudinal piezoelectric element 3 of the longitudinal excitation means 1
Is combined with the longitudinal vibration of the vibration direction control means 2, and the output end of the vibration direction control means 2, that is, each contact end face 7 of the vibrator 7 in this embodiment.
a and 7a draw a Lissajous and vibrate. In particular, each contact 9b by the movable contact 10 in the switching means 9,
9c switching timing, that is, each electrode 8b, 8c
When the longitudinal piezoelectric element 3 is going to extend in the longitudinal direction, one of the electrodes is turned on and the other electrode is turned off, and conversely, the longitudinal piezoelectric element 3 tries to contract in the longitudinal direction. If one of the electrodes is turned off and the other electrode is turned on when the
a and 7a oscillate while drawing an ellipse. In this embodiment, when the electrode 8b is turned ON when the longitudinal piezoelectric element 3 is about to extend in the longitudinal direction, the contact end surfaces 7a of the vibrator 7 are
7a vibrates by drawing a clockwise ellipse in FIGS. 3 and 4, and applies a force that moves rightward in FIG. 3 to a movable body (not shown) contacting the contact end surface 7a of the contactor 7. Give. On the contrary, when the electrode 8c is turned on when the longitudinal piezoelectric element 3 is trying to extend in the longitudinal direction, the contact end surfaces 7a, 7a of the vibrator 7 draw a counterclockwise ellipse in FIGS. 3 and 4. A force that moves to the left in the figure is applied to the movable body that vibrates and contacts the contact end surface 7 a of the vibrator 7.

Therefore, in this embodiment, a drive voltage having a vibration frequency substantially equal to the natural frequency f of the piezoelectric element 6 of the vibration direction control means 2 is applied to the vertical piezoelectric element 3 of the vertical excitation means 1. The contact end surfaces 7a, 7a of the vibrator 7 vibrate in an elliptical manner, and the switching means 9 controls the timing of short-circuiting between the electrodes 8b, 8c and the electrode 8a. The direction of the force applied to the movable body brought into contact with 7a can be variably controlled.

Next, the fact that the ultrasonic transducer of this embodiment acts as an actuator will be described with experimental data.

FIG. 5 shows measured values of the admittance characteristics of the longitudinal piezoelectric element 3 when one of the two divided electrodes 8b and 8c of the piezoelectric element 6 of the vibration direction control means 2 is short-circuited. The measured values of the admittance characteristics of the longitudinal piezoelectric element 3 when both electrodes 8b and 8c are opened are shown in FIG.
The admittance characteristic between the electrodes 8b and 8c of the piezoelectric element 6 is as shown in FIG.

As shown in FIGS. 5 and 6, the resonance frequencies of the two modes are close to each other, and by bending one of the electrodes 8b and 8c with the electrode 8a, flexural vibration is generated while driving longitudinal vibration. You can see how you are excited.

Further, the operation of the ultrasonic transducer of this embodiment as an actuator will be described with reference to experimental data obtained when the ultrasonic transducer is operated as a motor.

FIG. 8 shows a motor formed by the ultrasonic transducer of this embodiment so as to rotate the cylindrical rotor 11. The rotor 11 is formed by providing a large diameter portion 11a at the center of the small diameter portion 11b, and the small diameter portion 11b is pivotally supported by the bearing member 12. In the ultrasonic transducer of the present embodiment, the contact end surface 7a of the vibrator 7 of the vibration direction control means 2 is pressed against the outer peripheral surface of the large diameter portion 11a of the rotor 11. In this case, the axial direction of the ultrasonic transducer of the present embodiment is orthogonal to the axial direction of the rotor 11 so that the ultrasonic transducer is brought into contact with the outer peripheral surface of the large diameter portion 11a in the normal direction.

In FIG. 8, when a drive voltage having a vibration frequency substantially equal to the natural frequency f of the piezoelectric element 6 of the vibration direction control means 2 is applied to the vertical piezoelectric element 3 of the vertical vibration means 1, the rotor 11 is driven. It rotated. In addition, the piezoelectric element 6
The rotation direction of the rotor 11 could be easily changed by adjusting the timing of short-circuiting the divided electrodes 8b and 8c with the electrode 8a. When the vibration distribution in the longitudinal direction and the bending direction of the ultrasonic transducer of this example at this vibration frequency is examined, the longitudinal primary mode is as shown in FIG. 9A, and the bending secondary mode is As shown in FIG. 9B, it can be seen that vibrations of both modes are excited. In FIG. 9, the amplitude and the phase represent the magnitude under the same drive voltage.

The ultrasonic transducer of the present embodiment has a wide range of use. For example, as shown in FIG. 10, four ultrasonic transducers are arranged on the outer peripheral surface of the rotor 11 at equal positions in the circumferential direction, and The rotation torque applied to 11 may be increased. Further, the slider can be easily reciprocated by pressing the contact end surface 7a of the vibrator 7 of the vibration direction control means 2 of the ultrasonic transducer of this embodiment against the slider which can reciprocate in the linear direction.

11 and 12 show another embodiment of the ultrasonic transducer of the present invention. In this embodiment, the piezoelectric element 6 of the vibration direction control means 2 is provided with four divided electrodes 8b, 8c, 8d and 8e, and
A switching means 9 is provided which is capable of independently controlling the short-circuit state between the electrodes 8b, 8c, 8d, 8e and the electrode 8a.

In this embodiment, the electrodes 8b, 8c,
The contact end face 7a of the vibrator 7 of the vibration direction control means 2 can be vibrated in the three-dimensional space by variously controlling the short-circuit state between the electrodes 8a and 8d and the electrode 8a by using the switching means 9. Therefore, if this embodiment is used as an actuator, it is possible to apply a moving force in a free direction to a driven object within a two-dimensional plane. For example, a combination of a four-divided operation and a two-divided operation provides a self-propelled actuator capable of linear movement / rotation.

The number of divisions of the electrodes arranged on the piezoelectric element 6 of the vibration direction control means 2 is 2 or 4 in each of the above embodiments.
It is not limited to individual pieces.

The present invention is not limited to the above-mentioned embodiments, but can be modified as required.

[0032]

As described above, since the ultrasonic transducer of the present invention is constructed and operates, a longitudinal direction vibration is excited by applying a driving voltage having a predetermined vibration frequency to the longitudinal vibration means as a driving source. Moreover, it is possible to easily change the Lissajous figure drawn by the vibration of the vibration direction control means, so that the operation direction of the output given to the outside such as the movable body can be easily switched. When it is used as an actuator, it has a wide application range, high efficiency, and a simple structure.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an ultrasonic transducer of the present invention.

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

FIG. 3 is a perspective view for explaining a flexural vibration state of a vibration direction control means portion of the embodiment of FIG.

FIG. 4 is a side view for explaining the flexural vibration state of the vibration direction control means portion of the embodiment of FIG.

5 is a characteristic diagram showing the admittance characteristic of a vertical piezoelectric element when one of two electrodes of the piezoelectric element of the vibration direction control means of the embodiment shown in FIG. 1 is short-circuited.

6 is a characteristic diagram showing the admittance characteristic of the longitudinal piezoelectric element when both of the two electrodes of the piezoelectric element of the vibration direction control means of the embodiment of FIG. 1 are opened.

7 is a characteristic diagram showing an admittance characteristic between two electrodes of the piezoelectric element of the vibration direction control means of the embodiment of FIG.

FIG. 8 is a perspective view showing a motor configured to rotate a rotor according to the embodiment of FIG.

9 (a) and 9 (b) are longitudinal vibration distributions of the vibration direction control means when the longitudinal direction excitation means is excited at the resonance frequency of the piezoelectric element of the vibration direction control means of the embodiment of FIG. And diagram showing vibration distribution in the deflection direction

FIG. 10 shows the ultrasonic transducer of the embodiment of FIG.
Sectional view showing a motor that uses a single rotor to rotate the rotor

FIG. 11 is a perspective view showing another embodiment of the ultrasonic transducer of the present invention.

FIG. 12 is a sectional view taken along line XII-XII in FIG.

[Explanation of symbols]

 1 Vertical Excitation Means 2 Vibration Direction Control Means 3 Vertical Piezoelectric Elements 6 Piezoelectric Elements 8a, 8b, 8c, 8d, 8e Electrodes 9 Switching Means 11 Rotors

Claims (2)

[Claims] 1. An ultrasonic transducer comprising: a longitudinal excitation means for outputting a longitudinal vibration; and a vibration direction control means for receiving the longitudinal vibration and outputting a flexural vibration vibrating in a direction intersecting with the vibration. 2. The vertical excitation means is formed by an electrically driven vertical vibrator, and the vibration direction control means is a piezoelectric element excited by the vertical vibration output from the vertical vibrator. And an electrode which is mounted on the piezoelectric element so as to face each other in the longitudinal vibration direction, in which one electrode is divided into a plurality of electrodes, and the plurality of divided electrodes are not divided. The ultrasonic transducer according to claim 1, wherein the ultrasonic transducer is formed by an electrode and a switching unit that short-circuits with a phase difference.