JP4249313B2

JP4249313B2 - Multilayer piezoelectric actuator

Info

Publication number: JP4249313B2
Application number: JP05808899A
Authority: JP
Inventors: 秀明 ▲高▼坂; 浩文佐藤; 博行内海
Original assignee: NEC Tokin Corp
Current assignee: Tokin Corp
Priority date: 1999-03-05
Filing date: 1999-03-05
Publication date: 2009-04-02
Anticipated expiration: 2019-03-05
Also published as: JP2000262075A

Description

【０００１】
【発明の属する技術分野】
本発明は積層型圧電アクチュエータの構造に関するものである。
【０００２】
【従来の技術】
従来この分野では、図２に示されるように圧電セラミック層１０３と内部電極１０１が交互に積層され、内部電極１０１は１層おきに対向電極を形成するように、外部電極１０５に接続されている。内部電極１０１が複数積層されてなる内部電極群（内部電極層）の内、最も外側（最上位及び最下位、すなわち両端）に位置している外側内部電極で外側内部電極１０２およびその他の内部電極１０１の極性については、外部電極１０５の材料のマイグレーションおよび積層構造が考慮されず、分極処理を施して決定されていた。以下、両端の外側内部電極2枚合わせて外側内部電極層と呼ぶこととする。
【０００３】
【発明が解決しようとする課題】
上記した従来技術では、積層型圧電アクチュエータの極性について、外部電極１０５材料のマイグレーションに対する分極方向が考慮されていなかった。そのため、外部電極１０５のマイグレーションによる溶解元となる陽極と外側内部電極層１０２との極性が異なった場合、内部電極一層あたりに近接する外部電極量が、他の内部電極層に比較して外側内部電極１０２と外部電極１０５の間で生じるマイグレーションが多く、このマイグレーションによるショートまたは絶縁抵抗の低下が生じる。
【０００４】
したがって、本発明の課題は、外部電極のマイグレーションによる外側内部電極層と外部電極間のショートまたは絶縁抵抗低下を解決する積層型圧電アクチュエータを提供することである。
【０００５】
【解決を解決するための手段】
積層型圧電アクチュエータを製造する際、上下の外側内部電極２が同極性となるように、電極積層の形成および絶縁体層４の形成を行い、その後、外部電極５の形成を行う。更に、外側内部電極層２の極性が、外部電極５材料がマイグレーションにより溶解し移動する際の移動元である陽極となるように分極処理を行う。
【０００６】
【作用】
本発明によれば、外部電極５がマイグレーションにより溶解し移動する際の移動元となる極性と、外側内部電極２の極性を同一にすることにより、近接する外部電極５の材料比率が多い、外側内部電極２に対しての、外部電極５のマイグレーションが無くなるため、外側内部電極２と外部電極５間のショートまたは絶縁抵抗低下を解決できる。
【０００７】
【発明の実施の形態】
以下、本発明の積層型圧電アクチュエータの一実施の形態について、図面を参照して説明する。図１は本発明の積層型圧電アクチュエータの構造を示した図であり、本実施の形態では銀を使用した。積層型圧電アクチュエータは内部電極１の層数が全部でｌ０１層となるよう製造し、内部電極１が１層おきに対向電極となるよう絶縁体層４を形成し、更に、外部電極５を銀により形成している。その後、上下の外側内部電極２が陽極となる様に分極処理を行った。
【０００８】
上記工法により製造された積層型圧電アクチュエータを、４０℃、９０％の環境下で、ＤＣｌ５０Ｖの電圧を印加し、上下各２層（計４層）の内部電極１と外部電極５の間のショートまたは絶縁抵抗劣化の発生状況について調査を行った。
【０００９】
また、比較の為、内部電極１の全層数を１００層とし、上下の内部電極層が異極となるように製造した積層型圧電アクチュエータについても同様の調査を行った。５００時間までの、上下各２層での内部電極１と外部電極２間でのショートまたは絶縁抵抗低下発生数を以下の表１に示す。
【００１０】
【表１】

【００１１】
上記表１の結果より、本発明の積層型圧電アクチュエータでは、上下外側内部電極二層と、それと隣接した内部電極１及び外部電極５と間でのショートまたは絶縁抵抗低下は確認されず、従来工法との差が確認できた。
【００１２】
以上の効果は、外部電極材料が銀に限らず、いかなろ電極材料でも、マイグレーションにより、外部電極５材料が陽極で溶解し移動する場合、外側内部電極２が陽極になるように製造することにより、上記同様の効果が得られる。
【００１３】
また、図２に示すように、最上位の外側内部電極とその下の内部電極の２層を連続して同極にし、他方最下位の外側内部電極とその上の内部電極の２層を連続して同極にした場合でも上記同様の効果が得られる。
【００１４】
また、図３に示すように、内部電極が１層おきに対向電極となるように、内部電極の一部を形成せずに、圧電セラミックの一部を絶縁体層としても上記同様の効果が得られる。
【００１５】
【発明の効果】
本発明によれば、外部電極のマイグレーションによる外側内部電極と、それと隣接した異極の内部電極及び外部電極との間のショートまたは絶縁抵抗低下の発生を低減できる利点をもった積層型圧電アクチュエータの提供が可能となった。
【図面の簡単な説明】
【図１】本発明の積層型圧電アクチュエータの断面構造を示した図である。
【図２】上下外側内部電極とそれの隣接内部電極とを同極とした場合の積層型圧電アクチェエータの断面構造を示した図である。
【図３】外部電極と接続される部分に内部電極を形成しない構造の積層型圧電アクチュエータの断面構造を示した図である
【図４】従来の積層圧電アクチュエータの断面構造を示した図である。
【符号の説明】
１内部電極（外側内部電極を含む）
２外側内部電極
３圧電セラミック層
４絶縁体層
５外部電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the structure of a multilayer piezoelectric actuator.
[0002]
[Prior art]
Conventionally, in this field, as shown in FIG. 2, piezoelectric ceramic layers 103 and internal electrodes 101 are alternately stacked, and the internal electrodes 101 are connected to the external electrodes 105 so as to form counter electrodes every other layer. . Of the internal electrode group (internal electrode layer) formed by laminating a plurality of internal electrodes 101, the external internal electrode 102 and other internal electrodes are the external internal electrodes located on the outermost side (uppermost and lowermost, ie, both ends). The polarity of 101 was determined by performing polarization treatment without considering the material migration and the laminated structure of the external electrode 105. Hereinafter, the two outer internal electrodes at both ends are collectively referred to as an outer internal electrode layer.
[0003]
[Problems to be solved by the invention]
In the prior art described above, the polarization direction with respect to the migration of the external electrode 105 material is not taken into consideration for the polarity of the multilayer piezoelectric actuator. Therefore, when the polarity of the anode that is the melting source due to the migration of the external electrode 105 and the outer internal electrode layer 102 are different, the amount of external electrodes adjacent to one internal electrode layer is larger than that of the other internal electrode layers. There are many migrations that occur between the electrode 102 and the external electrode 105, and this migration causes a short circuit or a decrease in insulation resistance.
[0004]
Accordingly, an object of the present invention is to provide a multilayer piezoelectric actuator that solves a short circuit between an outer internal electrode layer and an external electrode due to migration of an external electrode or a decrease in insulation resistance.
[0005]
[Means for solving the problem]
When manufacturing the laminated piezoelectric actuator, the electrode stack and the insulator layer 4 are formed so that the upper and lower outer internal electrodes 2 have the same polarity, and then the external electrode 5 is formed. Furthermore, the polarization treatment is performed so that the polarity of the outer internal electrode layer 2 becomes an anode which is a movement source when the material of the external electrode 5 is dissolved and moved by migration.
[0006]
[Action]
According to the present invention, by making the polarity of the movement source when the outer electrode 5 is dissolved and moved by migration and the polarity of the outer inner electrode 2 the same, the material ratio of the adjacent outer electrode 5 is large. Since migration of the external electrode 5 with respect to the internal electrode 2 is eliminated, a short circuit between the external internal electrode 2 and the external electrode 5 or a decrease in insulation resistance can be solved.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a multilayer piezoelectric actuator of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the structure of a multilayer piezoelectric actuator according to the present invention. In this embodiment, silver is used. The laminated piezoelectric actuator is manufactured so that the total number of layers of the internal electrode 1 is 101, and the insulating layer 4 is formed so that the internal electrode 1 becomes a counter electrode every other layer, and the external electrode 5 is made of silver. It is formed by. Thereafter, polarization treatment was performed so that the upper and lower outer internal electrodes 2 became anodes.
[0008]
The multilayer piezoelectric actuator manufactured by the above method is subjected to a DCL 50 V voltage in an environment of 40 ° C. and 90%, and a short circuit between the internal electrode 1 and the external electrode 5 in two layers (up to four layers in total). Or we investigated the occurrence of insulation resistance degradation.
[0009]
For comparison, the same investigation was performed on a laminated piezoelectric actuator manufactured so that the total number of layers of the internal electrode 1 was 100 and the upper and lower internal electrode layers had different polarities. Table 1 below shows the number of shorts or insulation resistance reductions occurring between the internal electrode 1 and the external electrode 2 in two upper and lower layers up to 500 hours.
[0010]
[Table 1]

[0011]
From the results of Table 1 above, in the multilayer piezoelectric actuator of the present invention, no short circuit or reduction in insulation resistance between the upper and lower inner electrode two layers and the inner electrode 1 and the outer electrode 5 adjacent to the upper and lower outer electrode is confirmed. The difference was confirmed.
[0012]
The above effect is achieved by manufacturing the outer electrode 5 so that the outer electrode 2 becomes the anode when the outer electrode 5 is melted and moved by the migration due to migration even if the outer electrode material is not limited to silver. The same effect as described above can be obtained.
[0013]
In addition, as shown in FIG. 2, the uppermost outer internal electrode and the lower internal electrode have the same polarity, and the lowermost outer internal electrode and the upper internal electrode have the same layer. Even in the case of the same polarity, the same effect as described above can be obtained.
[0014]
In addition, as shown in FIG. 3, the same effect as described above can be obtained by forming a part of the piezoelectric ceramic as an insulator layer without forming a part of the internal electrode so that the internal electrode becomes a counter electrode every other layer. can get.
[0015]
【The invention's effect】
According to the present invention, there is provided a multilayer piezoelectric actuator having an advantage that it is possible to reduce the occurrence of a short circuit or a decrease in insulation resistance between an outer internal electrode due to migration of an external electrode and an adjacent internal electrode and external electrode of a different polarity. Offering became possible.
[Brief description of the drawings]
FIG. 1 is a view showing a cross-sectional structure of a multilayer piezoelectric actuator of the present invention.
FIG. 2 is a view showing a cross-sectional structure of a stacked piezoelectric actuator in which upper and lower outer internal electrodes and adjacent internal electrodes have the same polarity.
FIG. 3 is a diagram showing a cross-sectional structure of a multilayer piezoelectric actuator having a structure in which an internal electrode is not formed in a portion connected to an external electrode. FIG. 4 is a diagram showing a cross-sectional structure of a conventional multilayer piezoelectric actuator. .
[Explanation of symbols]
1 Internal electrode (including outer internal electrode)
2 outer internal electrode 3 piezoelectric ceramic layer 4 insulator layer 5 external electrode

Claims

A laminated body in which two or more piezoelectric ceramic layers and three or more internal electrode layers are laminated, an insulating layer formed on the side surface of the laminated body so that every other internal electrode serves as a counter electrode, and on the insulating layer In the multilayer piezoelectric actuator formed with external electrodes, each layer of the outermost internal electrodes positioned at the uppermost and lowermost positions of the internal electrode layers and the internal electrodes adjacent to the outer internal electrodes are continuously connected. Then , the laminated piezoelectric actuator is characterized in that the external electrode is an anode that becomes a movement source when the external electrode is dissolved and moved by migration.

2. The multilayer piezoelectric actuator according to claim 1 , wherein a part of the piezoelectric ceramic layer is formed as an insulator layer without forming a part of the internal electrode so that the internal electrode becomes a counter electrode every other layer. A laminated piezoelectric actuator characterized by the above.