JPH07221358A - Layered piezoelectric ceramic actuator - Google Patents

Abstract

PURPOSE:To eliminate cracks in a layered piezoelectric ceramic actuator at the time of polarizing or driving the actuator so as to eliminate electrical shorts by separating both end sections of belt-like electrode sections from each other toward the inside of a layered body from its facing side faces and separately extending linear electrode sections inward from its facing side faces except their one end sections. CONSTITUTION:A layered body 10 has a prism-like shape and is formed by alternately piling up internal electrodes 11 and 12 and piezoelectric ceramic sheets 13. The electrodes 11 have belt-like electrode sections 111 and linear electrode sections 112 and both ends of the electrode sections 111 are separated from each other toward the inside of the layered body 10 from the facing side faces 101 and 102 of the body 10. The linear electrode sections 112 connect the sections 111 to each other and are extended along one side face 101 of the body 10 a little inside of the side face 101. The sections 112 are connected to an external electrode 20 through lead-out sections 112a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric ceramic actuator that converts electric input energy into mechanical energy such as displacement or force.

[0002]

2. Description of the Related Art A multilayer piezoelectric ceramic actuator is a device utilizing electric field induced strain of piezoelectric ceramics and generally has a structure similar to a multilayer ceramic capacitor in which electrodes and ceramics are multilayered. The structure of a conventional laminated piezoelectric ceramic actuator is shown in FIG. As is apparent from FIG. 4, the inner electrode 50 and the outer electrode 5
The internal electrode 50 exposed on the same side surface so that the lead-out portion of the internal electrode 50 does not become piezoelectrically inactive due to the connection of No. 1.
Glass insulating portions 52 are provided on every other layer, and external electrodes 51 are formed thereon. The laminated piezoelectric ceramic actuator having such a structure obtains displacement and generated force in the piezoelectric longitudinal direction in the laminating direction. Also, if you want to obtain a large displacement,
The piezoelectric ceramics 53 and the internal electrode 50 may be laminated to increase the length in the lamination direction. However, if the lamination number is increased, defects such as delamination and cracks may occur during debinding and sintering. The limit of the length dimension was about 20 mm.

In the case of a laminated piezoelectric ceramic actuator in which the piezoelectric ceramics and the internal electrodes are displaced by the piezoelectric longitudinal effect in the direction orthogonal to the laminating direction, the length dimension can be increased and a large displacement can be obtained. A structure has been proposed. An example thereof is shown in FIG. This laminated piezoelectric ceramic actuator is a prismatic laminated body 6 formed by alternately laminating piezoelectric ceramic sheet layers and electrode layers.
In the laminated piezoelectric ceramic actuator having 0, the electrode layer has a first electrode layer and a second electrode layer, and these electrode layers extend in a direction orthogonal to the longitudinal direction of the laminate 60. It is composed of a plurality of strip electrodes 61, 62. The strip electrode 61 of the first electrode layer is connected to the first external electrode 63 on the side surface of the stacked body 60, and the strip electrode 62 of the second electrode layer is the adjacent strip electrode of the first electrode layer. 6
The first external electrode 63 is connected to the second external electrode 64 at a side surface that is located approximately in the middle of the first external electrode 63 and that faces the side surface of the stacked body 60 provided with the first external electrode 63.

In addition to the structure shown in FIG. 5, there is a laminated piezoelectric ceramic actuator shown in FIG. This laminated piezoelectric ceramic actuator also has a laminated body 10 having a piezoelectric ceramic sheet layer and an electrode layer.
The second electrode layer has a plurality of strip-shaped electrode portions 111,
121 and the internal electrodes 11 and 12 including the line electrode portions 112 and 122. Strip electrode parts 111, 12
1 extends in a direction orthogonal to the longitudinal direction of the laminate 10,
One end thereof is exposed on one side surface of the laminated body 10, and the other end is spaced inward from the other side surface of the laminated body 10. The line electrode portions 112 and 122 extend along one side surface of the stacked body 10 and connect the strip-shaped electrode portions 111 and 121 to each other at one end thereof. In addition, one end of each of the line electrode portions 112 and 122 has first and second external electrodes 2 respectively provided on opposite side surfaces of the laminated body 10.
It is connected to 0 and 21.

However, in the laminated piezoelectric ceramic actuator having the structure shown in FIG. 5 and FIG. 6, the other end of the strip electrode (portion), that is, the strip electrode (portion) which is separated from the side surface of the laminated body. In the vicinity of the end, a portion where the piezoelectric ceramic sheet becomes piezoelectrically inactive occurs, and as a result, stress concentrates on the piezoelectrically inactive portion when polarization or high voltage is applied during use, and cracks or the like occur. There is a defect that a defect occurs and, in the worst case, the multilayer piezoelectric ceramic actuator is destroyed.

In order to solve this drawback, the multilayer piezoelectric ceramic actuator shown in FIG. 7 was invented. This laminated piezoelectric ceramic actuator has an internal electrode 1
Both ends of the strip-shaped electrode portions 111 and 121 of 1, 12 are exposed at the side surfaces of the laminated body 10, respectively, and the line electrode portion 112,
122 passes through the central portion of the laminated body 10 and connects a large number of strip-shaped electrode portions 111, 121 to each other. The line electrode portion 112 of the first internal electrode 11 is connected at one end thereof to the first external electrode 20 provided on one side surface of the stacked body 10, and similarly, the strip electrode of the second internal electrode 12 is formed. The part 121 is connected at one end thereof to the second external electrode 21 provided on the other side surface of the stacked body 10.

However, although the multilayer piezoelectric ceramic actuator shown in FIG. 7 can prevent the occurrence of cracks and the like, since both ends of the strip-shaped electrode portion are exposed at the side surfaces of the multilayer body, the surface leak is caused. A problem has arisen when an electrical short circuit due to is likely to occur.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a laminated piezoelectric ceramic actuator in which cracks and the like do not occur during polarization and driving, and electrical short circuits do not occur. To do.

[0009]

According to the present invention, a prismatic laminated body formed by alternately laminating piezoelectric ceramic sheets and internal electrodes, and an external member provided on each of opposite side surfaces of the laminated body. And a plurality of strip electrode portions and line electrode portions, the plurality of strip electrode portions each extending in a direction orthogonal to the longitudinal direction of the laminate, the line electrode. In a laminated piezoelectric ceramic actuator in which a plurality of strip-shaped electrode portions are connected to each other and one end thereof is connected to the external electrode, both end portions of the strip-shaped electrode portion face each other of the laminated body. Separated from the side surface to the inside, further, the wire electrode portion,
A laminated piezoelectric ceramic actuator is obtained, which is spaced apart from the opposite side surfaces of the laminated body and extends inward except the one end.

[0010]

In the laminated piezoelectric ceramic actuator of the present invention, since both ends of the strip-shaped electrode portion of the electrode are spaced inwardly from opposite side surfaces of the laminated body, the laminated body is separated from the end portion of the strip-shaped electrode portion. The portion of the piezoelectric ceramic sheet reaching the side surface becomes a piezoelectrically inactive portion, and
Since there are more piezoelectrically inactive portions than the type of laminated piezoelectric ceramic actuator shown in (4), stress does not concentrate on a specific portion when polarized or when a high voltage is applied during use, as in the past. As a result, cracks and the like hardly occur.

In the laminated piezoelectric ceramic actuator of the present invention, both end portions of the strip-shaped electrode portion of the electrode are spaced inwardly from opposite side surfaces of the laminated body, and the wire electrode portion is also laminated except for one end portion thereof. Since it extends inwardly from the opposite side surfaces of the body, an electrical short circuit due to surface leakage does not occur.

[0012]

EXAMPLE A first example of the laminated piezoelectric ceramic actuator of the present invention will be described with reference to FIG.

The laminated piezoelectric ceramic actuator 1 of this embodiment comprises a laminated body 10 and first and second external electrodes 20, 21 provided on opposite side surfaces 101, 102 of the laminated body 10 in the longitudinal direction. It consists of and.

The laminated body 10 has a prismatic shape, and the internal electrode 1
1, 12 and the piezoelectric ceramic sheet 13 are alternately laminated. The inner electrode includes a first inner electrode 11 and a second inner electrode.
Inner electrode 12 of The first internal electrode 11 has a plurality of first strip electrode portions 111 and a first line electrode portion 112. The first strip-shaped electrode portion 111 includes the laminated body 10
Extending in a direction orthogonal to the longitudinal direction of the laminated body 10 and arranged on the plurality of piezoelectric ceramic sheets 13 at predetermined intervals in the longitudinal direction of the laminated body 10. Further, both ends of each strip-shaped electrode portion 111 have side surfaces 10 facing each other in the longitudinal direction of the laminated body 10.
It is distant from the inside of the laminated body 10 from 1, 102. The first line electrode portion 112 connects the plurality of first strip-shaped electrode portions 111 to each other, and one end portion of the first line electrode portion 112 is formed as a lead portion 112a bent in an L shape. In addition, the first wire electrode portion 112 extends along the one side surface 101 of the laminated body 10 at a position slightly closer to the inside of the laminated body 10 from the one side surface 101 of the laminated body 10, and through the lead-out portion 112a. It is connected to the first external electrode 20.

The second internal electrode 12 also has a plurality of second strip-shaped electrode portions 121 and a second line electrode portion 122. The second strip-shaped electrode portions 121 extend in a direction orthogonal to the longitudinal direction of the laminated body 10 and are arranged on the plurality of piezoelectric ceramic sheets 13 at predetermined intervals in the longitudinal direction of the laminated body 10. Further, both ends of each strip-shaped electrode portion 121 are separated from the side surfaces 101, 102 of the laminate 10 that face each other in the longitudinal direction toward the inside of the laminate 10. Each of the second strip-shaped electrode portions 121 has an adjacent first strip-shaped electrode portion 11
It is arranged to be located in the middle of 1. The second line electrode portion 122 connects the plurality of second strip-shaped electrode portions 121 to each other, and one end portion of the lead portion 122 is bent in an L shape.
It consists of a. In addition, the second wire electrode portion 122 extends along the other side surface 102 of the stacked body at a position slightly closer to the inside of the stacked body 10 from the other side surface 102 of the stacked body 10,
It is connected to the second external electrode 21 through the lead portion 122a.

[0016] In this embodiment, the chemical composition formula Pb (Ni · Nb) as a piezoelectric ceramic _{0. 5} Ti _0.35 Zr _0.15
Using a lead zirconate titanate porcelain represented by O ₃ , a laminated piezoelectric ceramic actuator having a cross-sectional dimension of 5 mm × 5 mm and a length of 70 mm was prototyped. The thickness of the piezoelectric ceramic sheet 13 is 50 μm, and the number of laminated layers is 100.
In each layer, the strip-shaped electrode portions 111 and 121 have dimensions of a width of 100 μm, a length of 3 mm, and an interval of 0.6 mm, and the number of repetitions of the strip-shaped electrode portions 111 and 121 in the longitudinal direction is 80. The portions 112 and 122 have a width of 250 μm and a length of 6
Drawer part 112a, 1 which is 6 mm and is bent in an L shape.
22 a has a length of 250 μm and is provided on the side surface 10 of the laminate 10.
It is exposed at 1,102. The external electrodes 20 and 21 are formed in the side surfaces 101 and 102 of the laminated body 10 in the areas where the lead-out portions 112a and 122a are exposed.

The laminated piezoelectric ceramic actuator produced as described above was subjected to polarization and humidity resistance load test by applying a high voltage of DC350V. As a comparative example, a laminated piezoelectric ceramic actuator having the structure shown in FIG. 6 and having the same material and dimensions as in this example was tested. The test conditions were a test environment of 40 ° C.-90% RH and an applied voltage of DC350V. The test results are shown in Table 1 for each of 50 samples.

[0018]

[Table 1]

As can be seen from Table 1, the laminated piezoelectric ceramic actuator according to the present embodiment has a defective rate in polarization reduced to about 1/6 as compared with the conventional product of the comparative example, and the defective in the moisture resistance load test. It can be seen that the rate has improved significantly.

Next, a second embodiment of the laminated piezoelectric ceramic actuator of the present invention will be described with reference to FIG.

The present embodiment has substantially the same structure as the first embodiment. In the case of the first embodiment, the line electrode portions 112 and 122 of the internal electrodes 11 and 12 are the strip electrode portions 111 and 1 respectively.
In the present embodiment, the line electrode portions 112 and 122 of the internal electrode portions 11 and 12 are connected to the strip electrode portions 111 and 121, respectively.
Specifically, between the one end and the other end of the strip-shaped electrode 121, the strip-shaped electrode portions 111, 121 are located at the central portions of the strip-shaped electrode portions 111, 121.
1 is connected to each other. Since the other parts are the same as those in the first embodiment, the description thereof will be omitted.

In this embodiment, as in the first embodiment, the chemical composition formula of the piezoelectric ceramic is Pb (Ni.N).
b) Using a lead zirconate titanate porcelain represented by _0.5 Ti _0.35 Zr _0.15 O ₃ , a prototype of a laminated piezoelectric ceramic actuator having a cross sectional dimension of 5 mm × 5 mm and a length of 70 mm was manufactured. The thickness of the piezoelectric ceramic sheet 13 is 50
μm, the number of laminated layers is 100, and the strip-shaped electrode portion 11 is provided for each layer.
The dimensions of 1,121 are 200 μm wide and 4.5 m long
m, the interval is 0.6 mm, and the strip-shaped electrode portion 11 in the longitudinal direction
The number of repetitions of 1,121 is 80, and the line electrode portion 112,
122 has a width of 300 μm and a length of 66 mm, and the L-shaped bent lead-out portions 112a and 122a have a length of 2.
It is 5 mm.

The laminated piezoelectric ceramic actuator produced as described above was subjected to polarization and humidity resistance test under application of a high voltage of DC300V. As a comparative example, a laminated piezoelectric ceramic actuator having the structure shown in FIG. 7 and having the same material and dimensions as in this example was tested at the same time. The test conditions are: test environment 40 ° C-90% RH, applied voltage DC300V
And The test results for 50 samples each are shown in Table 2.
Shown in.

[0024]

[Table 2]

As is clear from Table 2, the multilayer piezoelectric ceramic actuator according to the present embodiment has a defective rate at the time of polarization reduced to about 1/2 as compared with the conventional product of the comparative example, and the defective in the moisture resistance load test. It can be seen that the rate has improved significantly.

Next, a third embodiment of the laminated piezoelectric ceramic actuator of the present invention will be described with reference to FIG.

This embodiment has substantially the same structure as the second embodiment. In the case of this embodiment, of the strip-shaped electrode portions 111 and 121,
In order that the strip-shaped electrode portions 111 and 121 arranged closest to the outer electrodes 20 and 21 also serve as the lead-out portions 112a and 122a of the line electrode portions 112 and 122, these strip-shaped electrode portions 111 and 121 are Connection parts 111a and 121a connected to the external electrodes 20 and 21 are provided in series. Since the other parts are the same as those in the second embodiment, the description thereof will be omitted.

Also in this embodiment, as in the second embodiment, the chemical composition formula of the piezoelectric ceramic is Pb (Ni.N).
b) Using a lead zirconate titanate porcelain represented by _0.5 Ti _0.35 Zr _0.15 O ₃ , a prototype of a laminated piezoelectric ceramic actuator having a cross sectional dimension of 5 mm × 5 mm and a length of 70 mm was manufactured. The thickness of the piezoelectric ceramic sheet 13 is 50
μm, the number of laminated layers is 100, and the strip-shaped electrode portion 11 is provided for each layer.
The dimensions of 1,121 are 200 μm wide and 4.5 mm long.
(The one that also serves as the drawer part has a length of 5 mm) and the interval is 0.
6 mm, the number of repetitions of the strip-shaped electrode portion 111.121 in the longitudinal direction is 80, and the width of the line electrode portions 112 and 122 is 30.
The length is 0 μm and the length is 64 mm.

The laminated piezoelectric ceramic actuator was tested in the same manner as in the case of the second embodiment, and the same test result as that of the second embodiment was obtained.

[0030]

As described above, according to the present invention, it is possible to provide a highly reliable multilayer piezoelectric ceramic actuator which is hardly broken during polarization or driving and which is free from electrical short circuit. .

[Brief description of drawings]

FIG. 1 is a schematic diagram of a laminated piezoelectric ceramic actuator according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a laminated piezoelectric ceramic actuator according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a laminated piezoelectric ceramic actuator according to a third embodiment of the present invention.

FIG. 4 is a perspective view of a conventional laminated piezoelectric ceramic actuator of a type that is displaced in a stacking direction.

FIG. 5 is a schematic configuration diagram of a first example of a conventional laminated piezoelectric ceramic actuator of a type that causes displacement in a direction orthogonal to the stacking direction.

FIG. 6 is a schematic configuration diagram of a second example of a conventional laminated piezoelectric ceramic actuator of a type that causes displacement in a direction orthogonal to the laminated direction.

FIG. 7 is a schematic configuration diagram of a third example of a conventional laminated piezoelectric ceramic actuator of a type that causes displacement in a direction perpendicular to the stacking direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer piezoelectric ceramic actuator 10 Multilayer body 11 1st internal electrode 12 2nd internal electrode 13 Piezoelectric ceramic sheet 20 1st external electrode 21 2nd external electrode 111 1st strip | belt-shaped electrode part 112 1st line electrode Part 121 Second strip electrode part 122 Second line electrode part

Claims (3)

[Claims] 1. A prismatic laminated body formed by alternately laminating piezoelectric ceramic sheets and internal electrodes, and external electrodes provided on opposite side surfaces of the laminated body, wherein the internal electrodes are It has a plurality of strip-shaped electrode portions and a line electrode portion, the plurality of strip-shaped electrode portions, each extending in a direction orthogonal to the longitudinal direction of the laminate, the line electrode portion, the plurality of strip-shaped electrode portions In the laminated piezoelectric ceramic actuator, wherein one end of each of the strip-shaped electrode parts is connected to the external electrode, and both ends of the strip-shaped electrode part are spaced inwardly from opposite side surfaces of the laminate, respectively. Further, the wire electrode portion extends inwardly apart from the opposite side surfaces of the laminated body except for the one end, and the laminated piezoelectric ceramic actuator. 2. The multilayer piezoelectric ceramic actuator according to claim 1, wherein the line electrode portion connects the strip electrode portions to each other at one end of the strip electrode portion. 3. The multilayer piezoelectric ceramic actuator according to claim 1, wherein the line electrode portion connects the strip electrode portions to each other between one end and the other end of the strip electrode portion. .