JPH05146171A - Ultrasonic oscillator - Google Patents

Abstract

PURPOSE:To provide an ultrasonic oscillator which is compact and outputs large oscillation. CONSTITUTION:A laminate for bending vibration is made by laminating first piles 111, in each of which the inner electrodes 108 of two sheets of piezoelectric elements 101 are divided and these divided faces are put opposite on top of each other, and second piles 112, in each of which the inner electrodes 108 of two sheets of piezoelectric elements 103 are divided and these divided faces are put opposite on top of each other in the direction orthogonal to the direction of the division of the first pile 111, alternately in large numbers, and a laminate for elastic vibration is accumulated on the laminate for bending vibration so as to make an ultrasonic oscillator. Large vibration is outputted by the composition of the vibration of the laminate for bending vibration and the laminate for elastic vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vibrator using an electromechanical conversion element such as a piezoelectric element as a vibration source.

[0002]

2. Description of the Related Art Recently, an ultrasonic motor using an ultrasonic vibrator has been developed as a new motor replacing an electromagnetic motor. This ultrasonic motor has the following advantages over conventional electromagnetic motors.

(1) Thin, lightweight and compact. (2) Low speed and high torque can be obtained without gears. (3) The parts configuration is simple and highly reliable. (4) There is no exchange of magnetic effects. (5) There is no backlash and positioning is easy.

There are two types of ultrasonic motors, a rotary type and a linear type, and FIGS. 15 to 18 show conventional examples of the linear type ultrasonic motor. In the conventional example of FIG. 15, when the Langevin type piezoelectric vibrator 1 on the left side is vibrated and the tip of the horn 2 is applied to the propagation rod 3 made of an elastic body, a bending traveling wave is generated in the propagation rod 3. This bending traveling wave propagates rightward in the propagating rod 3 as indicated by an arrow D. Then, this traveling wave excites the Langevin type piezoelectric vibrator 5 through a similar horn 4 attached to the right end of the propagating rod 3.
At this time, L and R in the figure are appropriately selected and impedance matching is performed to absorb all the energy of the traveling wave. In this way, the traveling wave constantly travels from left to right.

When the slider 6 is held in pressure contact with the surface of the propagating rod 3 in which such a bending traveling wave is generated by a certain pressing force, the slider 6 moves leftward in the figure as indicated by an arrow H. Move on.

FIG. 16 is a perspective view schematically showing the relationship between the bending traveling wave of the propagation rod 3 and the slider 6. In the figure, 3A is an elastic body corresponding to the propagation rod 3, and 6A is a slider 6.
Is a moving body equivalent to. As shown in the figure, the elastic body 3A
The mass point P of is drawing an elliptical locus. Therefore, when the moving body 6A is brought into pressure contact with the elastic body 3A that draws a counterclockwise elliptical locus in the figure at a predetermined pressure, the moving body 6A is in the direction opposite to the traveling direction D of the traveling wave, that is, in the left side of the figure. Driven in the direction. If the traveling direction of the traveling wave is reversed, the moving body 6
A drives to the right in the figure.

FIG. 17 shows another conventional example, in which a vibrating piece 8 is attached to the tip of the Lambaj type vibrator 7. The tip of the vibrating body 8 is in contact with the slider 6B with a constant pressing force in a state of being inclined by a predetermined angle θ with respect to the normal line of the surface of the slider 6B. When an AC voltage having the same frequency as the natural frequency of the Langevin type vibrator is applied from the AC power supply 9 to the Langevin type vibrator 7,
The Langevin type vibrator 7 performs longitudinal vibration. At this time, since the tip of the vibrating piece 8 is in contact with the slider 6B at a predetermined angle θ, lateral vibration is also performed. By combining these vibrations, the tip of the vibrating piece 8 draws an elliptical locus. Thus, the slider 6B moves to the left as shown by the arrow in the figure.

FIG. 18 shows still another conventional example, in which piezoelectric elements 11 and 12 are provided on both sides of a rectangular conductive vibrator 10.
Are glued together. Lead terminals A and B for voltage application are drawn out from the piezoelectric elements 11 and 12, respectively.
From 0, the ground terminal E is drawn out. The shape of the vibrator 10 is such that the resonance frequency of longitudinal vibration of the vibrator 10 and the resonance frequency of flexural vibration match. Thus, when an AC voltage having the above resonance frequency is applied to the lead terminals A and B with a constant phase difference, the mass point of the end surface S of the vibrator 10 makes an elliptic motion. Then, when the slider 6C is pressed against the cross section S with a constant force, the slider 6C moves in the direction of an arrow HH in the drawing. This moving direction is determined by the phase difference between the voltages applied to the terminals A and B.

[0009]

The basic principle of the ultrasonic motor shown in FIGS. 15 to 18 is to transfer the energy of the elliptical locus motion at the mass point of the ultrasonic oscillator to the moving body (slider) by friction. However, in the conventional example of FIG. 15, since traveling waves have to be generated in the entire propagation rod 3, there is a problem that efficiency is poor and the entire device becomes large. Further, in the conventional example shown in FIG. 17, the traveling direction of the slider 6B is limited to one direction, and there is a problem that the entire apparatus becomes large in size as in the conventional example. Further, in the conventional example shown in FIG. 18, since a vibration output is obtained by the piezoelectric elements 11 and 12 adhered to both sides of the vibrator 10, it is difficult to secure a large force for moving the slider 6C. Therefore, in order to obtain a larger vibration output, the piezoelectric element 1 bonded to the side surface of the vibrator 10 described above.
When the number of sheets 1 and 12 is increased, there is a drawback that the apparatus becomes larger by that amount. Further, in the conventional example of FIG. 18, the longitudinal vibration and the flexural vibration of the vibrator 10 are combined to generate an elliptical vibration, but a large output cannot be obtained unless both vibrations are in a resonance state. Therefore, it is necessary to match the resonance frequency of longitudinal vibration with the resonance frequency of flexural vibration.
For this reason, the shape of the vibrator 10 must be determined by trial and error, which requires a large amount of labor and is not easy to manufacture.

Therefore, an object of the present invention is to be compact, to have a high energy conversion efficiency, to be able to take out a large vibration output, and to be able to reversibly move the driven body when used as a linear motor, and to design it. An object of the present invention is to provide an ultrasonic transducer which has few restrictions and is easy to manufacture.

[0011]

The ultrasonic vibrator of the present invention has two internal electrodes on one side of the internal electrodes provided on both sides.
A first stacked body in which two divided piezoelectric elements are stacked with the divided surfaces of the internal electrodes facing each other, and a direction in which one of the internal electrodes formed on both surfaces is orthogonal to the divided direction. A first laminated body in which a plurality of piezoelectric elements divided into two are alternately laminated a plurality of times with a second laminated body in which the divided surfaces of the internal electrodes face each other, and internal electrodes are provided on both surfaces. A second laminated body in which a plurality of piezoelectric elements are laminated, and the first laminated body and the second laminated body are joined in series in the laminating direction,
An outer electrode for electrically connecting the inner electrode of the piezoelectric element is provided on the outer surface.

[0012]

In the above structure, the direction of polarization of each piezoelectric element is reversed by applying a voltage to the piezoelectric element of the first laminated body and subjecting the divided internal electrodes to polarization. In addition, a voltage is applied to the piezoelectric element of the second laminated body to similarly perform polarization processing. Then, a voltage is applied to the first stacked body of the first stacked body to generate a first eigenmode of bending having a predetermined frequency f, and the second natural frequency is generated by this frequency f.
The laminate is vibrated. At this time, by appropriately setting the phase difference, it is possible to generate the first ultrasonic elliptical vibration on the driven body side.

On the other hand, a voltage is applied to the second stack of the first stack to generate a second eigenmode (frequency f) of bending that is orthogonal to the first eigenmode of bending, and this frequency is generated. The second laminate is vibrated by f. At this time, ultrasonic elliptical vibration can be generated on the driven body side by appropriately setting the phase difference. The vibrating surface of the first ultrasonic elliptical vibration and the vibrating surface of the second ultrasonic elliptical vibration are orthogonal to each other. Therefore, by changing the magnitude of each ultrasonic elliptical vibration, the combined vibrating surface is obtained. Can be arbitrarily rotated around the axis of the ultrasonic transducer. Therefore, when the driven body is brought into pressure contact with the end portion of the ultrasonic transducer, the driven body can be moved in the direction of the ultrasonic elliptical vibration surface by the force of the ultrasonic elliptical vibration.

[0014]

Embodiment 1 FIGS. 1 to 9 show Embodiment 1 of the present invention. As shown in FIG. 1, the ultrasonic transducer 100 has a laminated body 106 in which a lower first laminated body 106a and an upper second laminated body 106b are joined in series. A driven body (not shown) is brought into contact with the upper end portion of the second laminated body 106b, and the protrusion base 103 having the protrusion 104 at the center of the upper surface is provided at the upper end portion of the second laminated body 106b. Is provided. On the other hand, the fixed base 102 made of an insulating element is provided at the lower end of the first stacked body 106a.

The first and second laminated bodies 106a, 106
Each of b is formed by stacking a plurality of piezoelectric elements 101. FIG. 3 is an exploded perspective view of the first stacked body 106a from above, and FIG. 14 is an exploded perspective view from below. The piezoelectric element 101 is made of a rectangular PZT-PMN-based material, and a preliminary sintered powder of this material is mixed with a binder to form a slurry, and the slurry is 100 μm on a film by a doctor blade method. It is cast with the thickness of to make a green sheet. Then, after the green sheet is dried, it is peeled off from the film and the piezoelectric material film 107 is removed.
And After that, Ag-Pb is formed on both surfaces of the piezoelectric material film 107.
The internal electrode 108 is formed by using a paste or the like to form the piezoelectric element 101.

In the lowermost piezoelectric element 101 in FIGS. 3 and 4, the internal electrode 108 on the upper surface is divided into two parts in the left-right direction, and the piezoelectric element 101 of the second step is laminated on the divided surface of this internal electrode 108. To be done. Second-stage piezoelectric element 101
As shown in FIG. 4, the internal electrode 108 on the lower surface is divided into two parts in the left-right direction, and the divided surface of the internal electrode 108 and the divided surface of the piezoelectric element 101 at the lowermost stage are laminated so as to face each other. As a result, the first stacked body 11 is formed.
As shown in FIG. 3, the third-stage piezoelectric element 101 stacked on the second-stage piezoelectric element 101 has an internal electrode 10 on the upper surface.
8 is divided into two in the front-rear direction, and the fourth-stage piezoelectric element 101, in which the internal electrode 108 on the lower surface is divided in the same direction, is laminated, whereby a second stacked body 112 is formed.
Therefore, the first stacked body 111 and the second stacked body 112 are such that the dividing directions of the internal electrodes are orthogonal to each other, and the first stacked body 111 and the second stacked body 112 are alternated a plurality of times (for example, , Several tens of times) to form the first laminated body 106a.
Is configured.

5 and 6 are exploded perspective views of the second stack 106b from above and below. The piezoelectric element 101 of the second laminated body 106b is the same as the first laminated body 106a.
The piezoelectric element 101 is formed by the same method as the above-mentioned piezoelectric element 101, but the internal electrodes 108 on both surfaces are formed on almost the entire surface without being divided. Then, the second laminated body 106b is configured by laminating a plurality of (several dozen) piezoelectric elements 101. These laminated bodies 106 a and 106 b are laminated in series to form a laminated body 106.
6 is hot pressed and then sintered at about 1200 ° C.

After the sintering, the upper and lower end faces of the laminated body 106 are polished, and the fixing base 102 made of ceramics, metal or the like is fixed to the lower end face by adhesion, and the protrusion base 103 made of ceramics, metal or the like is fixed on the upper end face by adhesion. To do. In this case, the fixed base 102 and the protrusion base 103 may be integrally fired simultaneously with the firing of the laminated body 106.

After the laminated body 106 is formed as described above, the external electrode 105 is formed on the outer surface of the laminated body 106. The external electrode 105 can be formed by applying a conductive paste such as silver paste. Figure 1
In addition, in FIG. 2, reference numeral 105a denotes a ground external electrode, which is formed over the entire length of the laminated body 106.
Reference numeral 105b denotes an external electrode for bending vibration, which is the first laminated body 1
It is formed over the entire length of 06a. 105 c is an external electrode for stretching vibration, which is formed over the entire length of the second stacked body 106 b. Then, these external electrodes 10
The lead wire 107 is connected to 5a, 105b, and 105c. The outer surface of the ultrasonic transducer 100 is covered with an insulating protective film (not shown) to perform a dielectric breakdown prevention process.

The ultrasonic transducer 10 manufactured as described above
0 is polarized in oil, air, or the like. That is, the flexural vibration external electrodes 105b located on opposite sides of the laminated body 106 apply voltage to the ground external electrodes 105a so that the polarities thereof are opposite to each other, while the stretching vibration external electrode 105c is applied to the ground external electrode 105a. Polarization processing is performed by applying a voltage of positive or negative polarity to the electrode 105a.

In the above structure, the bending vibration external electrode 1 is used.
The alternating voltage of the phase is applied between 05b and the ground external electrode 105a, and the frequency f is made to correspond to the natural frequency of the ultrasonic transducer 100. FIG. 7 shows this bending primary vibration as shown in FIG.
Indicates a bending secondary vibration, and the frequency f of the alternating voltage is made to coincide with these natural frequencies. As a result, the protrusions 104 of the protrusion base 103 vibrate alternately in the X direction in FIG.
On the other hand, an alternating voltage of frequency f is applied between the stretching vibration external electrode 105c and the ground external electrode 105a. As a result, stretching vibration as shown in FIG. 9 occurs in a non-resonant state. As a result, the protrusion 104 alternately vibrates in the Z direction in FIG.

Furthermore, by appropriately adjusting the phases of the voltages applied to the flexural vibration external electrode 105b and the ground external electrode 105a, the ultrasonic waves can be rotated clockwise or counterclockwise in the XZ plane on the protrusion 104. Elliptical vibration can be generated, and when the plate-shaped driven body is pressed against the projection 104 in this state, the driven body can be moved in the positive or negative direction in the X direction.

By applying an alternating voltage of the same phase between the stretching vibration external electrode 105c and the ground external electrode 105a and matching the frequency f thereof with the natural frequency of the bending primary vibration shown in FIG. Oscillates alternately in almost the Y direction of FIG. On the other hand, when an alternating voltage of frequency f is applied to the stretching vibration external electrode 105c and the grounding external electrode 105a, stretching vibration as shown in FIG. 9 occurs in a non-resonant state. Due to this vibration, the protrusion 104 alternately vibrates in the Z direction of FIG. By appropriately adjusting the phase of the voltage applied to the flexural vibration external electrode 105b and the ground external electrode 105a, a clockwise or counterclockwise ultrasonic elliptical vibration is generated in the YZ plane on the protrusion 104. In this state, a flat plate-shaped driven body (not shown) is provided with the protrusion 10
By making pressure contact with 4, the driven body can be moved in the positive or negative direction in the Y direction.

Further, the bending vibration external electrode 105b, the stretching vibration external electrode 105c, and the ground external electrode 10 are provided.
By applying a voltage of the same frequency f to 5a to excite the above-mentioned two kinds of vibrations and change the magnitude of each vibration, ultrasonic elliptical vibrations including the Z axis of FIG. Can be generated. At this time, if a driven body (not shown) is brought into pressure contact with the protrusion 104, the driven body can move in any direction on the XY plane.

FIGS. 10, 11, and 13 show examples of the protrusion base 103. As shown in FIG. 11, the protrusions 104 may be provided on the side surfaces so that the side surfaces serve as driving surfaces. As shown in FIG. The protrusion 104 may be provided so that any surface can be used as a driving surface. Further, although the flexural vibration is used in the resonance state in the present embodiment, it may be used in the non-resonance state, and the piezoelectric element 101 may have a columnar shape other than the prismatic shape.
Furthermore, the piezoelectric element may be bonded by adhesion.

[0026]

Second Embodiment FIGS. 13 and 14 show a second embodiment of the present invention, in which the same elements as those in the above-mentioned embodiment are designated by the same reference numerals. In the second embodiment, a laminated body 106c for bending vibration excitation bent in an antiphase is laminated on the lower first laminated body 106a for performing bending vibration excitation.
A second laminated body 106b that performs stretching vibration excitation is laminated on c.

The polarization process in the above configuration is performed as follows. That is, the two adjacent external electrodes 105b of the first laminated body 106a and the two external electrodes 105d of the laminated body 106c facing the opposite side of the external electrodes 105b.
Applies a voltage to the external electrode for ground 105a so that the polarity is the same. Further, the remaining external electrodes 105b of the first laminated body 106a and the remaining external electrodes 105d of the laminated body 106c apply a polarity voltage opposite to the above-mentioned pole.
The external electrode 105c of the second laminated body 106b applies a positive or negative polarity voltage to the ground external electrode 105a.

Then, the external electrodes 105 at the opposite positions
Alternating voltages of the same phase are applied to b and 105c and the external electrode for ground 105a, and the frequency f thereof is made to coincide with the natural vibration of bending such as bending secondary vibration or bending third order vibration (not shown). Due to this vibration, the protrusion 104 alternately vibrates in the substantially X direction in FIG. Further, an alternating voltage of frequency f is applied between the external electrode 105c of the second stacked body 106b and the external electrode for ground 105a to generate the stretching vibration as shown in FIG. 9 without resonance. Due to this vibration, the protrusion 104 alternately vibrates in the Z direction of FIG. Next, by appropriately adjusting the phases of the voltages applied to the remaining remaining external electrodes 105b and 105c and the external electrode for ground 105a, the protrusion 104 is rotated in the clockwise or counterclockwise direction in the XY plane. Sonic elliptical vibration can be generated. In this state, when a flat plate-shaped driving body (not shown) is brought into pressure contact with the protrusion 104, the driven body can move in the positive or negative direction in the X direction.

Since the method of generating the ultrasonic elliptical vibration in the YZ plane is the same, the explanation is omitted. Therefore, in the second embodiment, by changing the magnitudes of the two kinds of ultrasonic vibrations, the driven body is moved in the XY direction as in the first embodiment.
It can be moved in any direction of the plane.

[0030]

As described above, the ultrasonic transducer of the present invention can drive a driven body linearly or two-dimensionally, and can drive the driving voltage at a low voltage of 10V or less. .. Further, the ultrasonic transducer of the present invention is
It can be used as a scanner of an M (scanning tunneling microscope) probe and is compact and can be driven with high efficiency.

[0031]

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment of the present invention.

FIG. 3 is an exploded perspective view of the first stack from above.

FIG. 4 is an exploded perspective view of the first stack from below.

FIG. 5 is an exploded perspective view of the second stack from above.

FIG. 6 is an exploded perspective view of the second stack from below.

FIG. 7 is a side view showing the vibration characteristics of the ultrasonic transducer.

FIG. 8 is a side view showing the vibration characteristics of the ultrasonic transducer.

FIG. 9 is a side view showing the vibration characteristics of the ultrasonic transducer.

FIG. 10 is a perspective view of a protrusion base.

FIG. 11 is a perspective view of a modified example of the protrusion base.

FIG. 12 is a perspective view of a modified example of the protrusion base.

FIG. 13 is a perspective view of the second embodiment.

FIG. 14 is a plan view of the second embodiment.

FIG. 15 is a side view of a conventional example.

FIG. 16 is a perspective view showing an operation of a conventional example.

FIG. 17 is a side view of another conventional example.

FIG. 18 is a perspective view of still another conventional example.

[Explanation of symbols]

 100 ultrasonic transducer 101 piezoelectric element 105a ground external electrode 105b external electrode 105c external electrode

Claims (3)

[Claims] 1. A first layered body in which two piezoelectric elements, of which internal electrodes on one side are divided into two among the internal electrodes formed on both sides, are overlapped with the divided surfaces of the internal electrodes facing each other, and both sides. A second stacked body in which two piezoelectric elements in which one side of the internal electrodes is divided in a direction orthogonal to the dividing direction are overlapped with the divided surfaces of the internal electrodes facing each other. A first laminate in which a plurality of layers are alternately laminated, and a second laminate in which a plurality of piezoelectric elements having internal electrodes on both surfaces are laminated.
And a first laminated body and a second laminated body which are joined in series in the laminating direction, and external electrodes for electrically connecting the internal electrodes of the piezoelectric element are provided on the outer surface. Ultrasonic transducer characterized by. 2. The ultrasonic transducer according to claim 1, further comprising a protrusion stand having a protrusion on the driven body side. 3. The ultrasonic transducer according to claim 1, further comprising a fixed base provided on the opposite side of the driven body.