JPH04190682A - Piezoelectric transducer for oscillatory wave motor - Google Patents

Abstract

PURPOSE:To obtain a high motor torque by forming electrodes of silver paste prepared by mixing two kinds of silver powder having particle size distributions of prescribed grain diameters with glass frit. CONSTITUTION:Electrodes 7a, 7b, 9a, and 9b are formed on a piezoelectric ceramic board by using silver paste prepared by mixing silver powder having a particle size distribution of grain diameters of 0.01-0.1mum and another kind of silver powder having a particle size distribution of grain diameters of 0.5-5mum. Since the silver powder having the particle size distribution of grain diameters of 0.01-0.1mum between each particle of the silver powder having the particle size distribution of the grain diameter of 0.55mum comes into contact with the ceramic board 5, no uneven contact occurs between the board 5 and electrodes. Especially, when the electrodes are formed of silver paste prepared by mixing silver powder having an average grain diameter of 5mum with the silver powder having an average grain diameter of 3mum at a weight ratio of 3:7, the mechanical strength and solderability of the electrodes are improved. Namely, a sufficiently strong electric field is impressed upon the piezo-electric ceramic board 5 and sufficient and accurate polarization alternately takes place in different directions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric vibrator for a vibration wave motor, and particularly relates to an improvement in electrodes formed on the piezoelectric vibrator as a vibration generation source in a vibration wave motor.

[Conventional technology]

Vibration wave motors obtain high torque even at low speeds by generating rotational elliptical vibrations generated in an elastic body as rotational motion or -dimensional motion via a moving body when a frequency signal as a driving voltage is applied to a piezoelectric ceramic plate. It has the advantage of being

This vibration wave motor is formed by forming, for example, two polarization group regions, which are alternately polarized in different thickness directions, on a piezoelectric ceramic plate and are shifted by λ/4 (the symbol λ is the wavelength of a frequency voltage described later) in a plane. A common electrode corresponding to each polarization group region is formed on one side of the piezoelectric ceramic plate, and an independent electrode corresponding to each polarization portion is formed in each polarization group region on the opposite surface, and each independent electrode is formed with an elastic material. The movable body is attached to the elastic body so as to be in contact with the elastic body, and the movable body is pressed against the elastic body.

Note that the polarization process is performed using the common electrode or independent electrode formed on the piezoelectric ceramic plate for polarization.

Then, the elastic body side is set to a common potential, and between the elastic body and the common electrode of each polarization group region, a frequency voltage V (V = VO sin ωt) is applied to one polarization group from an AC power supply, and λ/4 is applied to the other polarization group. Out of phase frequency voltage V
By applying '(V' = VOs in (ωt±π/2)), the piezoelectric vibrating body vibrates and progressive vibration waves are generated on the upper surface of the elastic body. moves.

[Problem to be solved by the invention]

However, in such a vibration wave motor, it is necessary to apply accurate and sufficient polarization to the piezoelectric ceramic plate in order to obtain good motor torque, but polarization is achieved by applying treatments in different directions to the piezoelectric ceramic plate at narrow intervals. Therefore, it cannot be said that sufficient polarization treatment has been achieved, and there is still room for improvement.

Therefore, as a result of various experimental studies to obtain a good polarization state, the present inventor discovered that the silver paste material used as a polarization electrode, which had not received much attention in the past, greatly influences polarization, and developed the present invention. Completed.

The present invention was made under these circumstances, and is intended to provide a piezoelectric vibrator that can easily and accurately polarize in different directions alternately at narrow intervals, and that can provide high motor torque. be.

[Means to solve the problem]

In order to solve these problems, the present invention has electrodes formed by baking silver paste mixed with silver powder on both opposing main surfaces of a piezoelectric ceramic plate, one side of which is attached to an elastic body, and the electrodes are bonded to an elastic body. the first of mutually different phases through
and a piezoelectric vibrating body of a vibration wave motor that vibrates upon application of a second frequency signal to generate a progressive vibration wave in an elastic body, the electrodes of which have a particle size distribution of 0.01 to 0.1 μm. Silver powder and particle size 0. It is made of a silver paste in which a glass frit is mixed with silver powder having a particle size distribution of 5 to 5 μm.

Further, the present invention provides the above electrode with a particle size of 0.01 to 0.1.
2 to 5 parts by weight of silver powder with a particle size distribution of μm, particle size 0.
It is preferable to use a silver paste containing 8 to 5 parts by weight of silver powder having a particle size distribution of 5 to 5 μm.

[For production]

In the present invention equipped with such means, the electrode has a particle size of 0.0
Silver powder with particle size distribution of 1 to 0.1 μm and particle size of 0.5 to
Since the piezoelectric ceramic plate is made of silver paste mixed with silver powder with a particle size distribution of 5 μm, the particle size is 0.5~
The particle size is between 0.01 and 0 between silver powder with particle size distribution of 5 μm.
．． Silver powder with a particle size distribution of 1 μm intervenes and contacts the piezoelectric ceramic plate, resulting in less uneven contact between the piezoelectric ceramic plate and the electrode.

In particular, in a configuration in which the electrode is formed from a silver paste containing silver powders with average particle diameters of 0.05 μm and 3 μm mixed at a weight ratio of 3, the mechanical strength and soldering properties of the electrode are good.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 are a top view, a back view, and a cross-sectional view (cross section along mm in FIG. 1) showing an embodiment of a piezoelectric vibrating body according to the present invention.

The piezoelectric vibrating body 1 includes a ring plate-shaped piezoelectric ceramic plate 5 having a first polarization group region 3a and a second polarization group region 3b shifted by λ/4 from the first polarization group region 3a, and a piezoelectric ceramic plate 5 formed on one side of the piezoelectric ceramic plate 5. first and second electrodes 7a, 7b
(FIG. 1), and third and fourth electrodes 9a and 9b (FIG. 2) formed in arc shapes on opposing surfaces of the piezoelectric ceramic plate 5.

The first and second electrodes 7a and 7b are arranged at a pitch of λ/2 (λ
are formed at a narrow interval from each other at a frequency of a driving voltage (to be described later).

The third and fourth electrodes 9a, 9b are piezoelectric so as to face the first and second electrodes 7a, 7b in the first and second polarization group regions 3a, 3b on three sides of the piezoelectric ceramic plate 5. It is formed on a ceramic plate 5,
The distance between each tip of the third electrode 9a19b is wider on one side than on the other.

These first to fourth electrodes 7a, 7b, 9a, 9b are as follows:
It is formed by applying so-called silver paste mixed with silver powder, glass frit, synthetic resin, and solvent to the piezoelectric ceramic plate 5 and baking it.

In particular, silver powder has an average particle size of 0.05 μm and an average particle size of 3 μm.
Silver powder with an average particle size of 0.05 μm and silver powder with an average particle size of 3 μm are preferably mixed at a weight ratio of 3 nia.

The first and second polarization group regions 3a, 3b in the piezoelectric ceramic plate 5 are connected to the first to fourth electrodes 7a, 7b,
9a and 9b are used as polarization electrodes, and as shown in FIG. 6, which will be described later, they are polarized in the thickness direction with alternating directions at a pitch of λ/2.

Next, a method for manufacturing a piezoelectric vibrator according to the present invention will be briefly explained using FIG. 4.

First, a ring-shaped piezoelectric ceramic plate 5 is formed by mixing, molding, firing, and shaping ceramic powder.
and Bl, the above-mentioned silver paste is printed on one side and the opposite side of this piezoelectric ceramic plate 5 to form the first to fourth electrodes 7.
a, 7b, 9a, and 9b (FIG. 4C), and then baked in a baking furnace at a peak temperature of 600°C to 700°C to form the first to fourth electrodes 7a17.
b, 9a, 9b (FIG. 4D), polarization treatment is performed using these first to fourth electrodes 7a, 7b, 9a, 9b as polarization electrodes (FIG. 4E), and the piezoelectric vibrating body 1 is formed.

The polarization treatment is carried out in high temperature oil by using the third and fourth electrodes 9a and 9b as common electrodes as shown in FIG.
A high voltage of V/mm is applied from the power supply 11 to polarize in the thickness direction, and then the first and second electrodes 7a are shifted by one position,
A negative high voltage is applied to 7b to polarize it in the opposite thickness direction.

By polarizing in this way, as shown in Figure 6,
First and second polarization group regions 3a.

3b is alternately polarized in different thickness directions.

In FIG. 6, the symbol 0 indicates polarization from the front surface to the back surface of the paper, and the symbol - indicates polarization in the opposite direction.

In such a piezoelectric vibrating body of the present invention, the first to fourth electrodes 7a, 7b, 9a, 9b for polarization have an average particle diameter of 0.05μ.
As shown in FIG. 7, the piezoelectric ceramic plate 5
The first to fourth electrodes 7a, 7b, 9a, 9 on the surface of
Since the electrode contact density of b is increased and contact unevenness is reduced, a sufficient electric field is applied to the piezoelectric ceramic plate 5, and sufficient and accurate polarization is applied in alternating different directions.

Therefore, the torque of the vibration wave motor using the piezoelectric vibrator of the present invention is improved.

Moreover, if it is formed from a silver paste made by mixing silver powders with average particle diameters of 0.05 μm and 3 μm at a weight ratio of approximately 3 nia,
The mechanical strength of the first to fourth electrodes 7a, 7b, 9a, and 9b is also good, and the solder adheres well when soldering a flexible lead pattern or the like. On the other hand, the average particle size is 0.
If the amount of silver powder with an average particle size of 3 μm is increased, the mechanical strength tends to decrease, and if the amount of silver powder with an average particle size of 3 μm is increased, the solderability tends to decrease.

According to the inventor's experiments, the outer diameter is 60 mm and the inner diameter is 45 mm.
, a piezoelectric ceramic plate 5 having a thickness of 0.5 mm and mainly composed of lead zirconate titanate is printed with silver powder, silver paste with various glass frit amounts and glass frit softening points, and then baked. The change (increase) in relative permittivity was analyzed.

Specifically, as shown in the following table, the analysis was conducted using an experimental design method using a known three-level orthogonal array table L9 using three factors (levels): silver powder, glass frit amount, and glass frit softening point.

Glass frit contains 5-20 wt% of 5iC)*, pbo
45-90 wt%, B, 03 5-20 wt%,
The composition range was 0 to 5 wt% for M2O and 0 to 10 wt% for NO. However, here, the symbol M is an alkali metal, and the symbol N is an alkaline earth metal.

Further, as for the silver powder, a mixture of powders having the minimum and maximum particle sizes in the particle size range at a ratio of 3 nia (weight ratio) was used.

[Table] According to this analysis, 1 for each of the nine types of silver paste.
Regarding the piezoelectric vibrator 1 in which electrodes were formed using 0 samples, the change (increase rate) in the relative dielectric constant before and after polarization was as shown in FIG.

The lower end of each vertical line in each silver-based 1 to 9 in Figure 8 is 10.
The highest rate of change is at the top, and the black dot in the vertical line is the average of 10.

According to this Figure 8, compared to silver pastes 1 to 3 with average particle diameters of 0.3 and 3 μm and silver pastes 7 to 9 with average particle diameters of 0.5 and 5 μm, the average particle diameter is 0°05. It can be seen that the change (increase rate) in the dielectric constant of silver pastes 4 to 6, which is 3 μm, is large.

Figure 9 shows the increase in dielectric constant from the viewpoint of changing the weight ratio of silver powder with a particle size distribution of 0.01 to 0.1 μm and silver powder with a particle size distribution of 0.5 to 5 μm. It shows the results of an investigation, and the above-mentioned findings can be seen.

FIG. 10 is a half-sectional view showing an example of a vibration wave motor using the piezoelectric vibrator of the present invention described above.

A radial bearing 15 is fixed to a through hole in the center of the metal base 13, and an annular recess 17 is formed to surround the bearing 15.

A disk-shaped conductive elastic body 19 made of a metallic conductive material such as phosphor bronze is mounted on the base 13 and is fixed to the base 13 with screws (not shown) so as not to interfere with its vibration.

This elastic body 19 has an annular convex portion 21 that projects integrally on one end surface side (upper side in the figure), and this convex portion 21 is divided into many parts in the circumferential direction by cuts in the radial direction.
The piezoelectric vibrating body 1 described above is attached to the lower surface of the elastic body 19 at a position overlapping with the convex portion 21, and a flexible printed circuit board 23 is attached to the third and fourth electrodes 9a, 9b of this piezoelectric vibrating body 1. is pasted.

The base 13 is covered with a cup-shaped metal case 25, and the center part of the case 25 protrudes in a convex shape, and a bearing 27 is placed inside the protrusion, and the bearing 27 and the case 25 form an outer ring. A thrust type bearing 29 that supports the is fixed.

A shaft 31 is rotatably supported by a bearing 15 fixed to the base 13 and a bearing 29 fixed to the case 25 side, and one end protrudes from the bearing 15 side.

A disc-shaped rotating body 33 as a moving body is fixed to the shaft 31 between the bearings 15 and 290, and the shaft 3
A disc spring 37 presses the peripheral edge of the rotating body 33 against the convex portion 21 of the elastic body 19 by means of a flange 35 attached to the elastic body 19 .

The vibration wave motor configured in this way has two types of alternating frequency voltages of, for example, 40 KHz that differ in phase by 90 degrees from each other (V=VOs in(c) t) and (v'=VOs
in (ωt±π/2)] of the first and third electrodes 7a
, 9a and between the second and fourth electrodes 7b and 9b, a progressive vibration wave that travels in the circumferential direction is generated in the convex portion 21 of the elastic body 19, and the convex portion 21 is pressed against the convex portion 21. The rotated body 33 rotates in the circumferential direction, and the shaft 31 rotates.

Note that the configuration of the vibration wave motor described above is an example, and can be implemented in a conventionally known vibration wave motor.

〔Effect of the invention〕

As explained above, in the present invention, since the polarization electrodes are formed on the piezoelectric ceramic plate using a silver paste containing a mixture of silver powder with an average particle size of 0.05 μm and 3 μm, uneven contact between the piezoelectric ceramic plate and the electrodes is prevented. It is easy to accurately and sufficiently apply polarization in different directions alternately at narrow intervals.

Therefore, when the piezoelectric vibrator of the present invention is used in a vibration wave motor, high motor torque can be obtained.

Furthermore, the structure in which the electrodes are formed from a silver paste containing silver powders with average particle diameters of 0.05 μm and 3 μm mixed in a weight ratio of 3 nia has the advantage that mechanical strength and soldering properties are also good.

[Brief explanation of drawings]

1 to 3 are a top view, a back view, and a cross-sectional view (cross section between mm and m in FIG. 1) showing an embodiment of the piezoelectric vibrating body according to the present invention, and -FIG. 4 A to E are Figure 1 is a process diagram showing the manufacturing method of the piezoelectric vibrating body, Figure 5 is a diagram showing the method of polarization treatment, Figure 6 is a diagram showing the method of manufacturing the piezoelectric vibrating body,
The figure shows the polarization state of the piezoelectric vibrator, Figure 7 is a schematic enlarged view of the main parts of the piezoelectric ceramic plate and electrode in the piezoelectric vibrator of the present invention, and Figures 8 and 9 show the polarization state of the piezoelectric vibrator and the piezoelectric vibrator. FIG. 10, which is a diagram showing changes in relative permittivity, is a half-sectional view showing an example of a vibration wave motor using a piezoelectric vibrator. 1......9 piezoelectric vibration bodies 3a, 3b...First and second polarization group regions 5... ......Piezoelectric ceramic plates 7a, 7b... Electrodes (first and second electrodes) 9a, 9b... Electrodes (third and fourth electrodes) Electrode) 11・・・・・・・・・・・・・・・Power supply 1
3・・・・・・・・・・・・・・・・・・Base 25...
・・・・・・・・・・・・・・・・Case 31・・・・
・・・・・・・・・・・・・・・Shaft 33・・・・・・
・・・・・・・・・・・・Rotating body (moving body) patent applicant Fukori Co., Ltd.

Claims (2)

[Claims] (1) Electrodes formed by baking silver paste mixed with silver powder are formed on both opposing main surfaces of a piezoelectric ceramic plate, one side is attached to an elastic body, and first and second In a piezoelectric vibrating body of a vibration wave motor that vibrates upon application of a second frequency signal to generate a progressive vibration wave in the elastic body, the electrode comprises silver powder having a particle size distribution of 0.01 to 0.1 μm. A piezoelectric vibrating body for a vibration wave motor, characterized in that it is formed of a silver paste in which a glass frit is mixed with silver powder having a particle size distribution of 0.5 to 5 μm. (2) The electrode contains 2 to 5 parts by weight of silver powder with a particle size distribution of 0.01 to 0.1 μm, and 8 to 5 parts by weight of silver powder with a particle size distribution of 0.5 to 5 μm. 2. The piezoelectric vibrating body of a vibration wave motor according to claim 1, wherein the piezoelectric vibrating body is formed of silver paste mixed in a weight ratio.