JPH07202286A - Layered piezoelectric ceramics element - Google Patents

Abstract

PURPOSE:To prevent a ceramic sheet from breaking by connecting an end edge of an inside electrode fixed to a part of a ceramic sheet by an outside electrode and by coating a side of a layered body with insulating resin excepting the outside electrode. CONSTITUTION:A plurality of ceramic sheets 1 are laminated to superpose their large square parts 1a mutually and to bring an upper surface whereto an inside electrode 3 is fixed into contact with a lower surface of the adjacent ceramic sheet 1 whereto the inside electrode 3 is not fixed shifting two adjacent ceramic sheets 1 by 90 deg. around an axis extending in a lamination direction. A ceramic sheet lamination body 2 is formed in this way. A side surface of the ceramic sheet lamination body 2 is covered with insulation resin 6 excepting a first outside electrode 4a and a second outside electrode 4b. Thereby, functional troubles can be prevented without breaking the ceramic sheet l during operation.

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 element formed by laminating ceramic sheets having an electrostrictive effect or a piezoelectric effect.

[0002]

2. Description of the Related Art In a laminated piezoelectric ceramic element formed by laminating ceramic sheets having an electrostrictive effect or a piezoelectric effect, a film-shaped internal electrode is provided between adjacent ceramic sheets, and a ceramic sheet laminated body is provided. Is provided with a pair of external electrodes, and the internal electrodes are connected to different external electrodes for every other layer. Conventionally known are three types of laminated piezoelectric ceramic elements shown in FIGS. 3 to 5, in which the connection modes of the internal electrodes and the external electrodes are different from each other.

In the piezoelectric actuator shown in FIG. 3, a plurality of ceramic sheets 11 having an electrostrictive effect or a piezoelectric effect are stacked one on top of the other so as to completely overlap each other.
The ceramic sheet laminated body 12 is formed. Between the adjacent ceramic sheets 11, a film-shaped internal electrode 13a that covers the entire surface of the ceramic sheet 11 except for the right end portion.
And film-shaped internal electrodes 13b that cover the entire surface of the ceramic sheet 11 except for the left end portion are arranged in alternate layers. The internal electrodes 13a of the adjacent ceramic sheets 11,
The right end portion and the left end portion facing each other without interposing 13b are fused and integrated during firing. External electrodes 14 are fixed to the right side surface and the left side surface of the ceramic sheet laminate 12, respectively. The film-shaped internal electrode 13b that covers the entire surface of the ceramic sheet except for the vicinity of the left end is the external electrode 1 fixed to the right side surface of the ceramic sheet laminate 12.
The film-shaped internal electrode 13a connected to No. 4 and covering the entire surface of the ceramic sheet except the vicinity of the right end is connected to the external electrode 14 fixed to the left side surface of the ceramic sheet laminate. In the piezoelectric actuator shown in FIG. 3, when the external electrode 14 is connected to a DC power source, a DC voltage is applied to each ceramic sheet 11 via the internal electrodes 13a and 13b connected to the external electrode 14, and due to the electrostrictive effect. Each ceramic sheet 11, and thus the ceramic sheet laminate 12, extends in the stacking direction, that is, in the vertical direction.

In the piezoelectric actuator shown in FIG. 4, a plurality of ceramic sheets 21 having an electrostrictive effect or a piezoelectric effect are stacked one on top of the other so as to completely overlap each other.
The ceramic sheet laminate 22 is formed. Between the adjacent ceramic sheets 21, the ceramic sheet 21
Is provided with a film-shaped internal electrode 23 that covers the entire surface of the. The right end of the internal electrode 13 exposed on the right side surface of the ceramic sheet laminate 22 is covered with a vitreous insulator 25 formed by an electrophoretic method every other layer. Internal electrode 1 exposed on the left side surface of the ceramic sheet laminate 22
The left end of 3 is a vitreous insulator 25 formed by electrophoresis in alternate layers and in a staggered manner with respect to the right end of the internal electrode 23 covered with the vitreous insulator 25.
Is covered by. Ceramic sheet laminate 22
External electrodes 24 are fixed to the right side surface and the left side surface, respectively. The right end of the internal electrode 23 exposed on the right side surface of the ceramic sheet laminate 22 is connected to the external electrode 24 fixed to the right side surface of the ceramic sheet laminate 22, and is exposed on the left side surface of the ceramic sheet laminate 22. The left end of 23 is connected to the external electrode 24 fixed to the left side surface of the ceramic sheet laminate 22. Also in the piezoelectric actuator shown in FIG. 4, when the external electrode 24 is connected to the DC power source, the internal electrode 2 connected to the external electrode 24 is connected.
A DC voltage is applied to each of the ceramic sheets 21 via 3, and the respective ceramic sheets 21, and thus the ceramic sheet laminate 22, extend in the laminating direction, that is, the vertical direction due to the electrostrictive effect.

In the piezoelectric actuator shown in FIG. 5, a plurality of ceramic sheets 31 having an electrostrictive effect or a piezoelectric effect are completely overlapped with each other and are laminated one above the other.
The ceramic sheet laminated body 32 is formed. Between the adjacent ceramic sheets 31, the ceramic sheet 31
Is provided with a film-shaped internal electrode 33 that covers the entire surface of the. In the middle portion near the right end of the internal electrode 33, every other cutout portion 33a extending in the front-rear direction is provided every other layer.
In the middle portion near the left end of the internal electrode 33, all the cutout portions 33b extending in the front-rear direction are provided in alternate layers and in a staggered manner with respect to the cutout portions 33a. External electrodes 34 are fixed to the right side surface and the left side surface of the ceramic sheet laminate 32, respectively. Also in the piezoelectric actuator shown in FIG. 5, when the external electrode 34 is connected to the DC power source,
A DC voltage is applied to each ceramic sheet 31 via the internal electrode 33 connected to the external electrode 34, and each ceramic sheet 31, and thus the ceramic sheet laminate 32, extends in the stacking direction, that is, the vertical direction due to the electrostrictive effect. .

[0006]

In the piezoelectric actuator shown in FIG. 3, focusing on only the ceramic sheet 11,
The ceramic sheet laminated body 12 fused by firing has a structure in which a plurality of slit-shaped notches for receiving the internal electrodes 13a and 13b are formed in a laminated shape. In the piezoelectric actuator shown in FIG. 3, both surfaces are internal electrodes 13a and 1a.
A DC voltage is applied to the central portion of the ceramic sheet 11 in contact with 3b in the left-right direction to extend in the stacking direction.
The right and left end portions of the ceramic sheet 11, which face the adjacent ceramic sheets 11 without interposing 3a and 13b and are fused with the adjacent ceramic sheets 11 during firing, extend in the stacking direction without being applied with a DC voltage. Absent. As a result, there is a problem that excessive stress is generated due to stress concentration in a portion of the fused ceramic sheet 11 in the vicinity of the end portion of the slit-shaped notch and the portion may be damaged. The piezoelectric actuator shown in FIG. 4 requires a large amount of cost to form the glassy insulator 25 by electrophoresis.
There was a problem that it would increase the cost of the product. The piezoelectric actuator shown in FIG. 5 has a problem that a potential difference is generated between the end faces of the internal electrodes 33 facing each other with the notches 33a and 33b sandwiched therebetween, so that discharge occurs between the two and the function of the piezoelectric actuator is hindered. It was The present invention has been made in view of the above problems, and an object of the present invention is to provide a multilayer piezoelectric ceramics element that does not have a possibility of damaging a ceramic sheet during operation, can be manufactured at low cost, and does not cause functional failure. And

[0007]

In order to solve the above problems, according to the present invention, there is provided a ceramic sheet having a plurality of electrostrictive effects or piezoelectric effects in which a film-shaped internal electrode is fixed on the entire surface of one surface. , A surface of one of the two adjacent ceramic sheets, to which one internal electrode is fixed, and a surface of the other two, to which the internal electrode is not fixed, abut, and the two adjacent ceramic sheets partially overlap each other. In the portion of the ceramic sheet that is provided with a laminated body that is laminated in a state where it does not overlap with the adjacent ceramic sheets, the first group of every other layer is overlapped at intervals in the laminating direction, and the other of every other layer is laminated. The second group does not overlap with the first group in the stacking direction but overlaps with each other in the stacking direction with a space therebetween, and the gap between the portions of the ceramic sheets belonging to the first group is filled with the insulating resin. , The gap between the portions of the ceramic sheets belonging to the second group is filled with an insulating resin, and the edges of the internal electrodes fixed to the portions of the ceramic sheets belonging to the first group are connected to each other by the first external electrodes, Second
The edges of the internal electrodes fixed to the portion of the ceramic sheet belonging to the group are connected to each other by a second external electrode,
There is provided a laminated piezoelectric ceramics element characterized in that the side surface of the laminated body is covered with an insulating resin except for the first external electrode and the second external electrode.

[0008]

In the present invention, since the ceramic sheet laminate has no notch where stress concentration occurs when the ceramic sheet extends in the laminating direction, the ceramic sheet is damaged by excessive stress during operation of the ceramic element. There is no fear of doing it. Further, in the present invention, since it is not necessary to form the glassy insulator by the electrophoresis method, the ceramic element can be manufactured at low cost. Further, in the present invention, since the internal electrode is not provided with the notch that causes a potential difference, there is no possibility of causing a functional failure due to discharge during operation.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A piezoelectric actuator according to an embodiment of the present invention will be described with reference to FIGS. Large square part 1a
And the film-shaped internal electrode 3 is fixed on the entire upper surface of the ceramic sheet 1 having an electrostrictive effect or a piezoelectric effect, which is composed of a small square portion 1b added to one corner of the large square portion 1a. The plurality of ceramic sheets 1 is a large square portion 1
a is overlapped with each other, the upper surface to which the internal electrode 3 is fixed is brought into contact with the lower surface of the adjacent ceramic sheet 1 to which the internal electrode 3 is not fixed, and two adjacent ceramic sheets 1 extend in the stacking direction. The ceramic sheet laminated body 2 is formed by laminating the ceramic sheet laminated bodies in a state of being deviated from each other by 90 ° around the axis.

In the small square portion 1b, the first groups A for every one layer are superposed at intervals in the laminating direction, and the second groups B for every other layer are laminated with the first group A. Instead of overlapping in the direction, they are overlapped in the stacking direction at intervals. As shown in FIG. 2, the gaps between the small square portions 1b belonging to the first group A and the small square portions 1b belonging to the second group B.
The gap is filled with the insulating resin 6.
The inner electrodes 3 fixed to the small square portion 1b belonging to the first group A are connected to each other by the first external electrode 4a, and the internal electrodes fixed to the small square portion 1b belonging to the second group B are connected. The edges of 3 are connected to each other by a second external electrode 4b. As shown in FIG. 2, the side surface of the ceramic sheet laminate 2 is covered with an insulating resin 6 except for the first external electrode 4a and the second external electrode 4b.

This piezoelectric actuator is manufactured by the following procedure. Silver paste, silver-palladium are formed on the entire upper surface of the ceramic sheet 1 having an electrostrictive effect or a piezoelectric effect, which is composed of a large square portion 1a and a small square portion 1b added to one corner of the large square portion 1a. The internal electrode 3 is fixedly formed by applying a paste, a platinum paste or the like. A plurality of ceramic sheets 1 to which internal electrodes 3 are fixed
The large square portions 1a are overlapped with each other, the upper surface to which the internal electrode 3 is fixed is brought into contact with the lower surface to which the internal electrode 3 of the adjacent ceramic sheet 1 is not fixed, and the adjacent 2
The ceramic sheets 1 are laminated by shifting them by 90 ° around an axis extending in the laminating direction. At this time, the small square portion 1b
The first group A for every one layer and the second group B for every other layer in the stacking direction with a space therebetween.
Without overlapping with the group A in the stacking direction, the stack A and the group A are overlapped with each other in the stacking direction. The laminated ceramic sheets 1 are fired to form a ceramic sheet laminate 2.

The side surface of the ceramic sheet laminate 2 is
It is covered with an insulating resin 6 such as epoxy resin, silicon resin, rubber or the like. At this time, the gap between the small square portions 1b is also filled with the insulating resin 6. The insulating resin 6 covering the side surface of the small square portion 1b is ground and removed to expose the edge of the internal electrode 3. The exposed edge of the internal electrode 3 fixed to the small square portion 1b belonging to the first group A and the surface of the insulating resin filling the gap between the small square portions 1b belonging to the first group A are plated. Or a low temperature curing conductor paste or the like is applied to connect the exposed edges of the internal electrodes 3 fixed to the small square portion 1b belonging to the first group A to the first external electrode 4a.
To form. Similarly, a second outer electrode 4b connecting the exposed edge of the inner electrode 3 fixed to the small square portion 1b belonging to the second group B is formed.

The operation of the piezoelectric actuator according to this embodiment having the above structure will be described below. External electrodes 4a, 4
b is connected to the DC power supply 100, the external electrodes 4a, 4b
A direct current voltage is applied to each ceramic sheet 1 via the internal electrodes 3 connected to each other, the large square portion 1a of each ceramic sheet 1 extends in the laminating direction due to the electrostrictive effect, and the ceramic sheet laminated body 2 extends in the laminating direction. Extend to. In this piezoelectric actuator, the ceramic sheet laminated body 2
Since there is no notch where stress concentration occurs when the ceramic sheet 1 extends in the stacking direction, there is no possibility that the ceramic sheet 1 will be damaged by excessive stress when the piezoelectric actuator operates. The insulating resin that fills the gap between the small square portions 1b easily elastically deforms as the large square portion 1a of the ceramic sheet 1 extends in the stacking direction.
There is no risk of damaging the insulating resin filling the gap between b. In this piezoelectric actuator, it is not necessary to form a glassy insulator by an electrophoretic method. Therefore, the present piezoelectric actuator can be manufactured at low cost. In the present piezoelectric actuator, since the internal electrode 3 is not provided with a notch that causes a potential difference, there is no possibility of causing a functional failure due to discharge during operation. Although the present invention is embodied as a piezoelectric actuator in the above-described embodiments, the present invention can be embodied as another laminated piezoelectric ceramic element such as a piezoelectric transformer.

[0014]

[Effect] As described above, in the present invention, the laminated body of the ceramic sheets does not have the notch where stress concentration occurs when the ceramic sheets extend in the laminating direction. There is no risk of damaging the ceramic sheet. Further, in the present invention, since it is not necessary to form the glassy insulator by the electrophoresis method, the ceramic element can be manufactured at low cost. Further, in the present invention, since the internal electrode is not provided with the notch that causes a potential difference, there is no possibility of causing a functional failure due to discharge during operation.

[Brief description of drawings]

FIG. 1 shows a piezoelectric actuator according to an embodiment of the present invention,
It is a perspective view which shows the structure except the insulating resin part.

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 including an insulating resin portion.

FIG. 3 is a perspective view showing a structure of a conventional piezoelectric actuator.

FIG. 4 is a perspective view showing the structure of a conventional piezoelectric actuator.

FIG. 5 is a perspective view showing the structure of a conventional piezoelectric actuator.

[Explanation of symbols]

 1, 11, 21, 31 Ceramic sheet 1a Large square portion 1b Small square portion 2, 12, 22, 32 Ceramic sheet laminated body 3, 23, 33 Internal electrode 6 Insulating resin 13a, 13b Internal electrode 33a, 33b Notch 4a, 4b external electrode 14, 24, 34 external electrode 25 glassy insulator

Claims (1)

[Claims] 1. A ceramic sheet having a plurality of electrostrictive effects or piezoelectric effects, wherein a film-shaped internal electrode is fixed on the entire surface of one surface, and one internal electrode of two adjacent ceramic sheets is fixed. And a surface to which the other internal electrode is not fixed, and two adjacent ceramic sheets are laminated in a partially overlapped state. In the portion of the ceramic sheet that does not overlap with each other, the first group of every other layer overlaps at a distance from each other in the stacking direction, and the other second group of every other layer overlaps with the first group in the stacking direction. Without overlapping, the gaps between the portions of the ceramic sheets belonging to the first group are overlapped with each other in the stacking direction, and the gaps between the portions of the ceramic sheets belonging to the first group are filled with an insulating resin. The space is filled with insulating resin,
The edges of the internal electrodes fixed to the portion of the ceramic sheet belonging to the first group are connected to each other by the first external electrodes, and the edges of the internal electrodes fixed to the portion of the ceramic sheet belonging to the second group are A multi-layer piezoelectric ceramic element, which is connected to each other by a second external electrode and whose side surfaces are covered with an insulating resin except for the first external electrode and the second external electrode.