JPH09148640A - Laminated piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated piezoelectric actuator which is uniform in displacement through all the displacement surface of its piezoelectric ceramics at driving. SOLUTION: A laminated piezoelectric actuator is equipped with first-side inner electrodes 22 and second-side inner electrodes 23 which confronts each other interposing a piezoelectric ceramic 20 between them respectively, the first-side inner electrodes 22 are connected to a first-side outer electrode 3 and provided with cutouts 22a so as not to come into contact with a second-side outer electrode 4, and the second-side inner electrodes 23 are connected to the second-side outer electrode 4 and provided with cutouts 23a so as not to come into contact with the first-side outer electrode 3. At this point, when all the cutouts 22a and 23a of the inner electrode 22 and 23 are projected onto the same plane in a direction in which a laminate 2 is laminated, the cutouts 22a and 23a are so arranged as to be uniformly distributed along the periphery of the piezoelectric ceramic 20, and the first-side electrode 3 and the second-side electrode 4 are formed corresponding to the cutouts 22a and 23a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator that converts electric input energy into mechanical energy such as displacement or force by utilizing a piezoelectric effect, and more specifically, a laminated piezoelectric actuator having high driving life performance. Belongs to the structure of the actuator.

[0002]

2. Description of the Related Art Conventional laminated piezoelectric actuators include
It includes a laminated body formed by alternately laminating piezoelectric ceramics and electrode layers, and first side and second side external electrodes formed on the outer peripheral surface of the laminated body, wherein the electrode layers sandwich the piezoelectric ceramics. A first side internal electrode and a second side internal electrode facing each other, the first side internal electrode being connected to the first side external electrode and being cut to avoid contact with the second side external electrode. The second side internal electrode has a cutout portion, and
Some have a notch portion that is connected to the side external electrode and that avoids contact with the first side external electrode.
A conventional laminated piezoelectric actuator of this type is generally formed in a cylindrical shape or a cylindrical shape.

This type of laminated piezoelectric actuator has a large electric field-induced strain and a high-speed response. Therefore, this type of laminated piezoelectric actuator has come to be used as a drive source for printer heads, positioners, valves, relays, and the like.

FIG. 4 shows an example of a conventional laminated piezoelectric actuator. (A) is a plan view, (b) is a front view, and (c).
Is a side view. The conventional multilayer piezoelectric actuator will be described more specifically with reference to FIG.

As shown in FIG. 4, the conventional laminated piezoelectric actuator has a structure in which the first side and second side inner electrodes 22,
The structure 23 is exposed on the outer peripheral surface of the laminated body 2. The exposed first and second side internal electrodes 22, 23
Are electrically connected to a pair of first-side and second-side external electrodes 3 and 4 formed on the outer peripheral surface of the laminated body 2, respectively, and at the same time, the first-side internal electrode 22 is connected to the second-side external electrode. In order to prevent the second-side internal electrode 23 from coming into contact with the first-side external electrode 3, respectively, in other words, the first-side and second-side electrodes
In order to prevent a part of the side internal electrodes 22, 23 from being exposed on the outer peripheral surface of the laminated body 2, the first side internal electrode 2 and the second side internal electrode 2
Notches 22a and 23a are formed in the reference numerals 2 and 23, respectively.

Then, the first and second side external electrodes 3, 4
By connecting the lead wires 5 and 6 for external connection respectively to, a laminated piezoelectric actuator is formed.

[0007]

In this conventional laminated piezoelectric actuator, the portion of the piezoelectric ceramic adjacent to the cutout portion of the internal electrode does not displace when a voltage is applied to the laminated piezoelectric actuator, and In the prior art, the cutout portions of the internal electrodes are arranged in a line along the stacking direction of the stacked body. Therefore, the conventional laminated piezoelectric actuator has a problem in that it is impossible to obtain a uniform displacement amount on the entire surface of the piezoelectric ceramic layer. Further, stress is generated at the boundary with the inactive portion of the piezoelectric ceramic, and there is a risk of serious damage at this boundary.

Therefore, a technical object of the present invention is to provide a laminated piezoelectric actuator capable of obtaining a uniform displacement on the entire displacement surface of the piezoelectric ceramic during driving.

[0009]

According to the present invention, a laminated body formed by alternately laminating piezoelectric ceramics and electrode layers, and a first side and a second side outside formed on an outer peripheral surface of the laminated body are provided. An electrode, wherein the electrode layer includes a first-side internal electrode and a second-side internal electrode facing each other with the piezoelectric ceramic interposed therebetween,
The first-side internal electrode has a notch portion that is connected to the first-side external electrode and that avoids contact with the second-side external electrode, and the second-side internal electrode is the second-side internal electrode. In the laminated piezoelectric actuator, which is connected to a side external electrode and has a cutout portion for avoiding contact with the first side external electrode, a cutout portion of the first side and second side internal electrodes is provided. When all are projected on the same plane along the stacking direction of the laminated body, these cutouts are arranged so as to be evenly distributed in the outer peripheral portion of the piezoelectric ceramic. Corresponding to the first side and the second
A laminated piezoelectric actuator having a side external electrode is obtained.

Further, according to the present invention, in the above-mentioned laminated piezoelectric actuator, there is obtained a laminated piezoelectric actuator in which the laminated body has a cylindrical shape or a cylindrical shape.

Furthermore, according to the present invention, in the above-mentioned laminated piezoelectric actuator, when the number of laminated layers of the first-side and second-side internal electrodes is N, 180 with respect to the axis of the laminated body. A laminated piezoelectric actuator is obtained in which the first-side internal electrode and the second-side internal electrode are laminated so that the notches are shifted by ° / N.

[0012]

[Function] By allocating a piezoelectrically inactive portion (a portion that does not displace when a voltage is applied) to almost the entire displacement surface,
The displacement variation of the displacement surface is reduced, and the partial stress concentration inside the laminated piezoelectric actuator is eliminated, which improves the driving reliability of the laminated piezoelectric actuator.

[0013]

1 shows a laminated piezoelectric actuator according to an embodiment of the present invention, (a) is a plan view,
2 (b) is a front view, FIG. 2 (c) is a side view, FIG. 2 is a main part of the laminated piezoelectric actuator shown in FIG. 1, (a) is a plan view, and (b) is a front view.

Referring to FIGS. 1 and 2, the laminated piezoelectric actuator 1 of this embodiment has a laminated body 2 and first and second side external electrodes 3 and 4.

The laminated body 2 is formed by alternately laminating piezoelectric ceramics 20 and electrode layers 21. In this electrode layer 21,
There is a first side internal electrode 22 and a second side internal electrode 23.
These internal electrodes 22 and 23 face each other with the piezoelectric ceramic 20 sandwiched therebetween, and form counter electrodes. In the case of the present embodiment, the piezoelectric ceramic 20 is formed in a substantially ring shape, and the first and second side internal electrodes 22, 23 are formed by the piezoelectric ceramic 2.
It is formed in substantially the same shape as 0. Therefore, these piezoelectric ceramics 20 and the first and second side internal electrodes 22, 23
The laminated body 2 formed by laminating and is substantially cylindrical.

The first-side internal electrode 22 is connected to the first-side external electrode 3 on the outer peripheral surface of the laminated body 2. Also,
The first-side internal electrode 22 has a notch 22a at the outer peripheral edge thereof.
have. The cutout portion 22 a is provided to avoid contact with the second-side external electrode 4 on the outer peripheral surface of the laminated body 2.

The second-side internal electrode 23 is connected to the second-side external electrode 4 on the outer peripheral surface of the laminated body 2. Also,
The second-side internal electrode 23 has a notch 23a at its outer peripheral edge.
have. The notch 23 a is provided to avoid contact with the first-side external electrode 3 on the outer peripheral surface of the laminated body 2.

The above-mentioned first-side and second-side internal electrodes 22, 2
The cutouts 22a and 23a formed in FIG. 3 are clear from FIG. 1A when all of the cutouts 22a and 23a are projected on the same plane along the stacking direction of the stacked body 2. As described above, the notches 22a and 23a are arranged so as to be evenly distributed on the outer peripheral portion of the piezoelectric ceramic 20. As described above, in order to evenly distribute the cutouts 22a and 23a, the cutouts 22 are formed in the stacking direction of the stack 2.
It is sufficient to shift a and 23a little by little. This way of shifting is
When the number of laminated layers of the first-side and second-side internal electrodes 22 and 23 is N, it may be shifted by 180 ° / N. In the case of this embodiment, since the first-side and second-side internal electrodes 22 and 23 are laminated by four layers, the notches 22a and 23a are formed into 18 layers.
It is shifted by 0 ° / 4, that is, by 45 °.

The first-side and second-side external electrodes 3, 4 are formed on the outer peripheral surface of the laminate 2. As described above, the first-side external electrode 3 is connected to the first-side internal electrode 22 on the outer peripheral surface of the laminated body 2. At the same time, the first side external electrode 3 is
In order to avoid contact with the second-side internal electrode 23, the laminated body 2
23a on the outer peripheral surface of the second side internal electrode 23
It is formed in a spiral shape so as to pass through. Second
The side external electrode 4 is similar to the first side external electrode 3 in the laminated body 2
Is connected to the second side internal electrode 23 at the outer peripheral surface of the first side internal electrode 22, and at the same time, in order to avoid contact with the first side internal electrode 22, the notch of the first side internal electrode 22 is formed on the outer peripheral surface of the laminated body 2. It is formed in a spiral shape so as to pass through the portion 22a. The lower ends of the first and second side external electrodes 3, 4 are
On the outer peripheral surface of the laminated body 2, the external connection terminals 5 and 5, respectively.
6 is connected.

In the present embodiment, the laminated body 2 is formed in a cylindrical shape, but the laminated body is not particularly limited in shape, and may be a prismatic cylinder, a cylinder, a prism, or the like. It doesn't matter.

The laminated piezoelectric actuator 1 of this embodiment
Was manufactured as follows.

First, a titanate / zirconate / lead based piezoelectric ceramic was used as a starting material, and an outer diameter of 1
A piezoelectric ceramic green sheet having a diameter of 3.6 mm and an inner diameter of 10 mm was prepared.

A silver-palladium alloy is used as a material for the internal electrodes 22 and 23, and the internal electrodes 22 and 23 are laminated on the piezoelectric ceramic 20 at intervals of 115 μm as shown in FIG. The cutout portions 22a and 23a of the internal electrodes 22 and 23 are laminated so as to face each other. The internal electrodes 22 and 23 are laminated such that the notched portions 22a and 23a are shifted from each other by 45 ° about the center points of the internal electrodes 22 and 23 on the same pole side. Here, the total number of laminated internal electrodes is eight, but since there are four layers on the same pole side, as described above, 180 ° /
4, that is, they are shifted by 45 °.

Next, the height 13.
External electrodes 3 and 4 are formed on the outer peripheral surface of the laminated body 2 having a thickness of 5 mm. At this time, on the outer peripheral surface of the laminated body 2, the external electrode 3 is formed in a spiral shape so as to pass through the notch 23a and the external electrode 4 passes through the notch 22a. Finally, lead wires 5 and 6 for external connection were connected to the lower ends of the external electrodes 3 and 4, respectively.

In order to investigate the variation in the amount of displacement on the displacement surface of the cylindrical laminated piezoelectric actuator 1 of the present embodiment produced as described above, the piezoelectric actuator 1 is provided with D
Applying a voltage of C100V, the part shown in FIG. 3 (A to H)
Was measured. For comparison, the variation of the displacement amount of the conventional cylindrical laminated actuator 1 shown in FIG. 5 was also investigated (sites A ′ to H ′). Table 1 shows the results.

The results are the average of 10 samples each.

[0027]

[Table 1]

As is clear from Table 1, in the conventional laminated piezoelectric actuator, the amount of displacement varies greatly on the displacement surface. On the other hand, in the laminated piezoelectric actuator of the present embodiment, the variation in the amount of displacement is small, and it can be seen that the displacement characteristics are far superior to those of the conventional laminated piezoelectric actuator.

Table 2 shows DC0 to 100 VP-P x 48
The defect occurrence rates of the laminated piezoelectric actuator of the present embodiment and the conventional laminated piezoelectric actuator at Hr × 30 Hz are described. The test quantity is 20 each.

[0030]

[Table 2]

As is clear from Table 2, the conventional laminated piezoelectric actuator has a defect rate of 15%, whereas the laminated piezoelectric actuator of the present embodiment has a low defect occurrence rate of 5%. There is.

[0032]

As described in detail above, the laminated piezoelectric actuator of the present invention can provide a highly reliable laminated piezoelectric actuator with less variation in displacement on the product displacement surface. It can be expanded.

[Brief description of the drawings]

FIG. 1 shows a laminated piezoelectric actuator according to an embodiment of the present invention, (a) is a plan view, (b) is a front view, and (c) is a side view.

2A and 2B show a main part of the laminated piezoelectric actuator shown in FIG. 1, where FIG. 2A is a plan view and FIG. 2B is a front view.

3 is a perspective view showing displacement measurement points of the laminated piezoelectric actuator shown in FIG.

FIG. 4 shows an example of a conventional laminated piezoelectric actuator, (a) is a plan view, (b) is a front view, and (c) is a side view.

5 is a perspective view showing displacement measurement points of the laminated piezoelectric actuator shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer piezoelectric actuator 2 Multilayer body 3 First side external electrode 4 Second side external electrode 20 Piezoelectric ceramic 21 Electrode layer 22 First side internal electrode 22a Cutout 23 Second side internal electrode 23a Cutout

Claims (3)

[Claims] 1. A laminated body formed by alternately laminating piezoelectric ceramics and electrode layers, and a first formed on an outer peripheral surface of the laminated body.
Side and second side external electrodes, the electrode layer includes a first side internal electrode and a second side internal electrode that face each other with the piezoelectric ceramic interposed therebetween.
A side inner electrode, and the first side inner electrode is the first inner electrode.
A second external electrode connected to the second external electrode and having a notch for avoiding contact with the second external electrode, the second internal electrode being connected to the second external electrode and the first external electrode.
In the laminated piezoelectric actuator having a cutout portion for avoiding contact with the side external electrode, all the cutout portions of the first side and second side internal electrodes are arranged along the stacking direction of the laminate. Are projected on the same plane, the notches are arranged so as to be evenly distributed on the outer peripheral portion of the piezoelectric ceramic, and the first side and the second side are arranged so as to correspond to the notches. A laminated piezoelectric actuator, wherein a side external electrode is formed. 2. The laminated piezoelectric actuator according to claim 1, wherein the laminated body has a cylindrical shape or a cylindrical shape. 3. The laminated piezoelectric actuator according to claim 2, wherein when the number of laminated layers of the first-side and second-side internal electrodes is N, 18
A laminated piezoelectric actuator, wherein the first side internal electrode and the second side internal electrode are laminated so that the cutout portion is shifted by 0 ° / N.