JP2003243738A - Stacked piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stacked piezoelectric element in which contact condition between an external electrode and an exposed end face of an internal electrode layer exhibits excellent electric conductivity and durability. <P>SOLUTION: The stacked piezoelectric element comprises a piezoelectric stack 10 in which piezoelectric layers 15 are each interposed between the internal electrode layers 11, 12 so as to form alternately stacked layers. The internal electrode layers 11, 12 each has the exposed end faces at side faces 101, 102, respectively, of the piezoelectric stack 10. The side faces 101, 102 are provided with the external electrodes 13, 14, respectively, and also with recesses 103, 104, respectively. The external electrodes 13, 14 are provided with contact portions 135, 145, respectively. The exposed end faces of the internal electrode layers 11, 12 and the contact portions 135, 145 of the external electrodes 13, 14 are electrically conducted in the recesses 103, 104, respectively. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated piezoelectric element that can be used as an electromechanical conversion element for use in an automobile or industrial actuator.

[0002]

2. Description of the Related Art Hitherto, there has been known a laminated piezoelectric element which can be used as an electromechanical conversion element used for an automobile or industrial actuator. The laminated piezoelectric element is composed of a piezoelectric stack in which piezoelectric layers that expand and contract according to an applied voltage and internal electrode layers for supplying an applied voltage are alternately laminated. Each internal electrode layer is an exposed end surface exposed on the side surface of the piezoelectric stack. Has
An external electrode electrically connected to the exposed end surface is provided on the side surface. A voltage is applied from this external electrode to the piezoelectric layer via the internal electrode layer.

The piezoelectric layer needs to be sandwiched between internal electrode layers having different polarities. Therefore, it is necessary to provide two external electrodes and to connect the external electrodes to the internal electrode layers every other layer. Therefore, in the laminated piezoelectric element 9 shown in FIG. 16, a piezoelectric stack 90 in which piezoelectric layers 95 and internal electrode layers 96 are alternately laminated is prepared, and one side surface 91 of the piezoelectric stack 90 is prepared.
The exposed end faces 960 of the internal electrode layers 96 exposed to the outside are covered with an insulator 92 every other layer.

Internal electrode layer 9 not covered with insulator 92
A side electrode 93 having a corrugated cross-section is coated on the exposed end surface 960 of No. 6 with a conductive adhesive, and an external electrode 95 is further coated on the side electrode 93 with a conductive adhesive or a solder 94 (Japanese Patent Laid-Open No. Hei 4-
255275, JP-A-2-251185, etc.). The other side surface of the piezoelectric stack 90 has the same configuration. Thereby, the internal electrode layers 96 can be alternately energized to different polarities through the external electrodes 95, and the piezoelectric layers 95 can be sandwiched between the internal electrode layers 96 having different polarities.

A voltage is applied to the internal electrode layer 96 through the external electrode 95 and the side surface electrode 93, and a voltage is applied to the piezoelectric layer 95 of the piezoelectric stack 90 through the internal electrode layer 96 to expand and contract the piezoelectric layer 95. The entire piezoelectric stack 90 can be expanded and contracted. The expansion and contraction of the piezoelectric stack 90 can be used as a drive source to form an electromechanical conversion element.

[0006]

In the piezoelectric element 9 described above, the contact portion between the side surface electrode 93 and the exposed end surface 960 of the internal electrode layer 96 is a non-displacement portion that does not expand or contract.
Therefore, when the piezoelectric stack 90 expands or contracts, strain may occur in the non-displacement portion, and stress may concentrate in the non-displacement portion. When the expansion and contraction of the piezoelectric stack 90 is large, the piezoelectric layer 9
5 or the internal electrode layer 96 is thin and their strength is weak, or the piezoelectric stack 90 has a short expansion / contraction cycle,
There are problems that the external electrode 95 and the side surface electrode 93 fall off, the external electrode 95 and the side surface electrode 93 are separated from the piezoelectric stack 90, and cracks and breaks occur in the piezoelectric stack 90.

In particular, consider the case where the piezoelectric element 9 is used for the injector of the automobile engine. The vicinity of the automobile engine is a harsh environment that is subject to many vibrations and shocks in a high temperature atmosphere. In such a place, the piezoelectric element 9 having the above-described conventional structure is provided.
Is installed, the external electrodes 95 and the side electrodes 93 are likely to fall off the piezoelectric stack 90, or are displaced,
Contact failure and conduction failure are likely to occur between the internal electrode layer 96 and the exposed end surface 960.

The present invention has been made in view of the above conventional problems, and a laminated piezoelectric element in which a contact state between an external electrode and an exposed end surface of an internal electrode layer is excellent in electrical conductivity and durability. Is to provide.

[0009]

According to a first aspect of the present invention, there is provided a piezoelectric stack in which piezoelectric layers that expand and contract in response to an applied voltage are sandwiched by first and second internal electrode layers for supplying an applied voltage and are alternately laminated. The first internal electrode layer has an exposed end surface exposed on the first side surface of the piezoelectric stack, and the second internal electrode layer has an exposed end surface exposed on the second side surface of the piezoelectric stack. A first external electrode is provided on one side surface, a second external electrode is provided on the second side surface, and the first and second external electrodes are used to adjoin the first and second adjacent electrodes via a piezoelectric layer. The internal electrode layers are configured to be energized with different polarities, the first and second side surfaces have a concave portion, the first and second external electrodes have a contact portion, and the first electrode is provided in the concave portion. And the exposed end surface of the second internal electrode layer and the contact portion of the first and second external electrodes In stacked piezoelectric device which is characterized in that the gas-continuity (claim 1).

Next, the function and effect of the present invention will be described.
In the laminated piezoelectric element according to the first aspect of the present invention, the exposed end surface of the internal electrode layer and the contact portion of the first external electrode are electrically connected to each other in the concave portion provided on the first side surface. That is, the contact portion is in contact with the exposed end surface while being fitted in the recess.

Therefore, when the piezoelectric stack expands or contracts,
Since the contact portion can always be held in the concave portion, it is possible to reliably ensure the electrical continuity between the two regardless of the state of the piezoelectric stack. The same applies when vibration or shock is applied to the laminated piezoelectric element from the outside. Further, since the contact portion in the recess has a certain degree of freedom and can move in the recess, the stress generated at the contact portion between the external electrode and the exposed end surface can be relaxed. Further, since the contact portion of the external electrode and the exposed end surface of the internal electrode layer are not rigidly connected, the stress can be absorbed by moving the contact portion in the recess.

The contact portion of the external electrode is electrically connected to the exposed end surface of the internal electrode layer in the recess. As long as the movement or displacement of the contact portion is within the range of the concave portion, electrical conduction between the two can be secured, so compared to securing electrical conduction by mere contact or joining, the external electrode portion according to the first aspect of the invention. The electrical continuity between the and internal electrode layers is excellent in flexibility, durability, and reliability. The above description also applies to the second internal electrode layer and the second external electrode.

A second aspect of the present invention comprises a piezoelectric stack in which piezoelectric layers that expand and contract according to an applied voltage are sandwiched by first and second internal electrode layers for supplying an applied voltage and are alternately laminated. The electrode layer has an exposed end surface exposed on the first side surface of the piezoelectric stack, and the second internal electrode layer has an exposed end surface exposed on the second side surface of the piezoelectric stack. A first external electrode on the second side surface and a second external electrode on the second side surface.
An external electrode is provided, and the first and second external electrodes are used so that adjacent first and second internal electrode layers are energized with different polarities via the piezoelectric layer. The second side surface has a concave portion, the first and second external electrodes have a contact portion, and each concave portion provided on the first or second side surface has a plurality of first or second internal electrodes. The external electrode is formed obliquely with respect to a surface that extends over the exposed end surface of the layer and is orthogonal to the stacking direction of the piezoelectric stack, and the external electrode includes the contact portion and a connecting portion that connects the contact portion to another contact portion. The contact portion has a shape corresponding to the recess, and the exposed end surfaces of the first and second internal electrode layers and the contact portion of the first and second external electrodes are electrically connected to each other in the recess. According to another aspect of the present invention, there is provided a laminated piezoelectric element (claim 7).

The second invention has the following effects in addition to the effects of the first invention. That is,
The recessed portion provided on the first side surface extends over the exposed end faces of the plurality of first internal electrode layers. Furthermore, the recesses are inclined with respect to the plane orthogonal to the stacking direction of the piezoelectric stack (see Example 1, FIG. 3 and FIG. 4). Therefore, when the piezoelectric layer is thin and the pitch between the exposed end faces is narrow, it becomes easy to form the recesses. Similarly, when the internal electrode layer is thin and the exposed end face is thin, the formation of the recess is facilitated.

Further, since the contact portion has a shape corresponding to the concave portion, the contact area between the contact portion and the exposed end face can be further increased by fitting the entire contact portion in the concave portion.
As a result, the conductivity with the exposed end surface can be ensured more reliably. Furthermore, since the concave portion extends over the plurality of exposed end surfaces, one concave portion has a plurality of exposed end surfaces, and therefore one contact portion electrically connects the plurality of exposed end surfaces at the one concave portion. As a result, the width of the recess can be made easy to process, and the recess having a width suitable for the external electrode can be processed. The above description also applies to the second internal electrode layer and the second external electrode.

As described above, according to the present invention, it is possible to obtain a laminated piezoelectric element in which the contact state between the external electrode and the exposed end surface of the internal electrode layer is excellent in electrical conductivity and durability.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the piezoelectric element according to claim 1, the first and second internal electrode layers are provided as partial electrodes with respect to the piezoelectric layer, and the end face of the first internal electrode layer is formed on the second side surface. Configure so that it is not exposed. The same applies to the second internal electrode layer. The same applies to the first and second internal electrode layers of the piezoelectric element according to claim 7.

Further, the above contact portion is covered with a conductive film,
It is preferable to enhance conductivity with the exposed end surface of the internal electrode layer. Further, in connecting the contact portion and the exposed end surface, it is preferable that a conductive adhesive is used to bond the two to secure superior conductivity between the two. In addition, after the contact part is pressed against the recess so that a compressive force is generated between them, the piezoelectric stack and the external electrode are housed in a case or the like, and a force is applied in the radial direction to contact the contact part and the exposed end surface. It is possible to ensure close contact between the two and ensure highly reliable conductivity.

Further, it is preferable that the contact portion and the concave portion are shaped so that they can be fitted to each other. This makes it possible to more effectively prevent the contact portion from falling off when vibration or shock is applied from the outside.

Further, in the second invention, in particular, the external electrode includes the contact portion and a connecting portion for connecting the contact portion. The contact portion and the connecting portion are formed by bending a conductive wire. It can be configured (see Example 1, FIG. 1). It is also possible to give springiness by bending the wire rod. In the case of having a spring property, the expansion and contraction of the piezoelectric stack, external vibration, and shock can be absorbed by the entire external electrode having a spring property, making it difficult for the external electrode to drop off from the piezoelectric stack and making contact with the contact part. It is possible to secure contact with the exposed end surface and maintain electrical conductivity with excellent durability between them.

Further, it is preferable that each of the recesses provided on the first or second side surface extends over the exposed end surface of the plurality of first or second internal electrode layers (claim 2). By this,
When the piezoelectric layer is thin and the pitch between the exposed end faces is narrow, it is easy to form the recess. Similarly, when the internal electrode layer is thin and the exposed end face is thin, the formation of the recess is facilitated. In addition, since a plurality of exposed end faces are located inside the recess, the piezoelectric layer is thin, and the recess can be formed even if the internal electrodes have variations in pitch due to deformation by stacking and firing in multiple layers. it can.

Further, it is preferable that the contact portion is made of a flexible conductive wire, and the external electrode is formed by implanting the conductive wire on a plate-shaped body (claim 3). Further, the external electrode may have a contact portion formed by filling a flexible main body with a flexible conductive wire and projecting the conductive wire from a window provided on a side surface of the cylindrical main body. Preferred (Claim 4).

In this case, since the contact portion is made of a flexible conductive material, the contact portion is deformed and absorbs the stress even if the laminated piezoelectric element expands or contracts or external shock or vibration is applied. ， Can be relaxed. Therefore, the contact portion is unlikely to fall off, and the conductivity can be maintained.

As the flexible conductive wire, a metal such as stainless steel or copper, a material obtained by plating a metal with gold or silver, or a resin, a conductive resin mixed with a conductive material, or a conductive material on the surface is used. A resin coated with a functional metal can be used. When a metal wire is used, the effect of the present claim can be more reliably exhibited by using a material having a small diameter and easily bendable.

Further, when the contact portion moves or slides in the recess, abrasion is less likely to occur because the contact portion is a wire rod.
In addition, when the external electrode is attached to the piezoelectric stack, the contact portion can be freely moved because the contact portion is a conductive wire material and is flexible, and the contact portion can be easily housed in the concave portion and between the both. The conductivity can be ensured. Therefore, the external electrodes can be easily attached.

Further, it is preferable that the external electrode and the contact portion are integrally formed, and both of them are made of a conductive elastic body whose surface is coated with a conductive film (claim 5). In this case, since the external electrode and the contact portion are both made of an elastic body, they are highly flexible.
Stress is unlikely to occur when the piezoelectric stack expands and contracts, and shock and vibration can be absorbed from the outside. Therefore, it is possible to secure the durability of the electrical continuity between the external electrode and the exposed end surface of the internal electrode layer.

In particular, when a conductive resin mixed with a conductive substance or a resin whose surface is coated with a conductive metal is used as the conductive elastic body, the electric resistance thereof is much lower than that of the metal. Although not provided, the height of these resistance values can be covered by providing a conductive film on the surface.

As the conductive elastic body, metals such as stainless steel and copper and various alloys can be used.
Further, as the conductive film on the surface, a plating film made of gold, silver, copper or the like can be used.

Further, it is preferable that the external electrode and the contact portion are integrally formed, and that both are formed by bending a conductive wire (claim 6). The shape of the external electrodes and contact parts can be configured with a high degree of freedom, and the fitted external electrodes and contact parts that are less likely to fall off are created according to the shape of the side surface of the piezoelectric stack and the shape of the recess. be able to.

Further, in claim 8 of the second invention, it is preferable that the connecting portion is formed in a direction parallel to the piezoelectric stack laminating direction (see FIGS. 4 and 5). In addition, claim 9
It is preferable that the connecting portion is formed in a direction orthogonal to the stacking direction of the piezoelectric stack (see FIG. 8). By this,
The contact area with the external electrode can be increased and the joint strength is also improved.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) The laminated piezoelectric element 1 according to this embodiment is shown in FIG.
As shown in FIG. 9, the piezoelectric layer 15 that expands and contracts according to the applied voltage is formed on the first and second internal electrode layers 1 for supplying the applied voltage.
Piezoelectric stack 10 sandwiched by 1 and 12 and alternately laminated
The first internal electrode layer 11 has an exposed end surface (not shown) exposed on the first side surface 101 of the piezoelectric stack 10, and the second internal electrode layer 12 has the exposed end surface (not shown). 2 has an exposed end surface (not shown) exposed on the side surface 102.

Further, the first external electrode 13 is provided on the first side surface 101, the second external electrode 14 is provided on the second side surface 102, and the first and second external electrodes 13, 14 are used. , The first and second internal electrode layers 11 and 12 adjacent to each other via the piezoelectric layer 15 are energized with different polarities.

The first and second side surfaces 101,
102 has concave portions 103 and 104, and the first and second external electrodes 13 and 14 have contact portions 1 as shown in FIG.
35, 145, the exposed end surfaces (not shown) of the first and second internal electrode layers 11, 12 in the recesses 103, 104, and the first and second external electrodes 13, 14
The contact portions 135 and 145 of the above are electrically connected.

The details will be described below. As shown in FIGS. 1 and 2, the laminated piezoelectric element 1 according to the present example includes a piezoelectric layer 15 that expands and contracts according to an applied voltage by using first and second internal electrode layers 11 and 12 for supplying an applied voltage. The piezoelectric stack 10 is sandwiched and alternately laminated. The first and second internal electrode layers 11, 1 are formed on both upper and lower ends of the piezoelectric stack 10 in the stacking direction.
Dummy layers 191, 192 composed of piezoelectric layers not sandwiched by two
Have. Then, on the first and second side surfaces 101, 102 of the piezoelectric stack 10, the first and second external electrodes 13,
14 is provided.

As shown in FIG. 2, the piezoelectric layer 15 is a barrel type, and the piezoelectric stack 10 has two planar first side surfaces 10.
1, having a second side surface 102. First and second side surfaces 10
The side surfaces 109 other than 1, 102 are curved. As shown in FIG. 3, there is an exposed end surface 110 of the first internal electrode layer 11 on the first side surface 101. There is a groove-shaped recess 103 that obliquely intersects the exposed end surface 110. The recess 103 is formed so as to penetrate from the end portion 105 of the side surface 101 to the end portion 106.

The drawings according to this example are illustrated with the piezoelectric layer 15 and the internal electrode layers 11 and 12 being thick and the number of laminated layers being small for the sake of clarity. The piezoelectric element used as the drive source of the injector of the automobile engine is the piezoelectric layer 1
When the thickness of 5 is 80 μm, the number of stacked piezoelectric stacks 10 is about 500 layers.

The first and second external electrodes 13 and 14 of this example will be described. As shown in FIGS. 4 and 5, in the second external electrode 14, the contact portion 145 has a shape that can be fitted into the groove-shaped recess 104, and both ends of the contact portion 145 are connected to each other by the connecting portions 146 and 147. It is connected to the contact portion 145. Then, when the contact portion 145 slides along the concave portion 104 in parallel with the side surface 104 of the piezoelectric element, the connecting portions 146 and 147 play a role of preventing disengagement.

Further, the take-out portion 141 is extended further upward from the contact portion 145 fitted in the concave portion 104 at the top in the stacking direction of the piezoelectric stack 10. This take-out part 1
An external power source (not shown) is connected to 41. In addition, the conductive wire material forming the second external electrode 14 is a silver-plated stainless wire.

When fixing the external electrode 14 to the side surface 102, a conductive adhesive is applied to the recess 104 in advance, and the external electrode 14 is pressed and bonded in this state. Other,
Baking is performed by using a ceramic conductive bonding film. Alternatively, a ceramic conductive material is thinly baked in the recess 104, and the surface and the external electrode 14 are joined by soldering. The structure and the fixing method of the external electrodes are the same for both the first and second electrodes. The above description also applies to the first external electrode 13.

The operation and effect of this example will be described. In the multilayer piezoelectric element 1 of this example, in the recess 103 provided in the first side surface 101, the exposed end surface of the first internal electrode layer 11 and the contact portion 135 of the first external electrode 13 are electrically connected. To do. Further, the contact portion 135 has a shape corresponding to the concave portion 103, and the contact portion 135 is in contact with the exposed end surface while being fitted in the concave portion 103.

Therefore, when the piezoelectric stack 10 expands and contracts, the contact portion 135 can always be held in the recess 103, so that the electrical continuity between the two can be reliably ensured regardless of the state of the piezoelectric stack 10. The same applies when vibration or impact is applied to the laminated piezoelectric element 1 from the outside. Furthermore, since the contact portion 135 can move within the recess 103, the stress generated at the contact portion between the first external electrode 13 and the exposed end surface can be relieved. Further, since the contact portion 135 of the first external electrode 13 and the exposed end surface of the first internal electrode layer 11 are not rigidly connected,
The stress can be absorbed by the movement of the contact part 135 in the area 03.

Further, since the contact portion 135 has a shape corresponding to the concave portion 103, the contact area between them is large, and high conductivity can be secured between them.

Further, the contact portion 135 of the first external electrode 13
Is electrically connected to the exposed end surface of the first internal electrode layer 11 at the recess 103. The movement or displacement of the contact portion 135 causes the recess 1
As long as it falls within the range of 03, electrical conduction between the two can be secured, so compared with securing electrical conduction by mere contact or joining, the first outer electrode 13 and the first inner electrode layer 11
The continuity between and is excellent in durability.

The recess 10 provided on the first side surface 101
3 is provided so as to straddle the exposed end surfaces of the plurality of first internal electrode layers 11 and obliquely with respect to the surface orthogonal to the stacking direction of the piezoelectric stack 10. Therefore, the piezoelectric layer 15 is thin,
When the pitch between the exposed end faces is narrow, the recess 103 can be easily formed. Similarly, when the first internal electrode layer 11 is thin and the exposed end face is thin, the recess 103 can be easily formed.

Further, since the recess 103 extends over a plurality of exposed end faces, there are a plurality of exposed end faces in one recess 103, so that one contact portion is electrically connected to the plurality of exposed end faces in one recess. . The above description is based on the second internal electrode layer 12, the second external electrode 14, and the second side surface 10.
The same applies to 2 and the like.

As described above, according to the present example, it is possible to obtain the laminated piezoelectric element in which the contact state between the external electrode and the exposed end surface of the internal electrode layer is excellent in electrical conductivity and durability.

In the laminated piezoelectric element 1 according to the present example, the external electrode 14 is composed of an upper electrode 148 and a lower electrode 1 made of two bent conductive wires as shown in FIG.
It is also possible to use it by constructing it from 49 and connecting both as an external electrode 14 as shown in FIG. in this case,
The schematic shape of the external electrode 14 is similar to that shown in FIG. 1 and the like of this example. By using this external electrode 14, it is possible to effectively absorb the expansion caused by the expansion of the laminated piezoelectric element during operation with a small stress.

In the laminated piezoelectric element 1 according to this example, the external electrode 15 extends in the direction orthogonal to the laminating direction of the piezoelectric stack 10 with respect to the contact portion 145, as shown in FIGS. The connecting portion 156 can be provided and configured. As a result, the external electrodes 15 provided on both side surfaces 101 and 102 can have the same bent shape.

(Example 2) Multilayer piezoelectric element 1 of this example
Includes an external electrode 21 having a contact portion 212 formed by implanting a flexible conductive wire. Note that the following description of Examples 2 to 4 is common to the first and second external electrodes.

As shown in FIGS. 10 and 11, the piezoelectric layer 15
Of the piezoelectric stack 10 sandwiched between the first and second internal electrode layers 11 and 12, and are alternately laminated. Recesses 103 and 104 are provided on the first and second side surfaces 101 and 102 of the piezoelectric stack 10, respectively. The recesses 103 and 10
Reference numeral 4 is provided parallel to the exposed end faces of the first and second internal electrode layers 11 and 12, and only one exposed end face exists in each of the recesses 103 and 104. In addition, the external electrode 21 of the present example is a so-called brush-like and is composed of a metal plate 211 and a contact portion 212 configured by bristling a metal wire, which is a flexible conductive wire, on the metal plate 211.

Then, the fixing of the external electrode 21 to the piezoelectric stack 10 in this example is performed by the recesses 103 and 104.
The conductive adhesive is applied to the contact part 212 of the external electrode 21.
Is closely attached to the recesses 103 and 104, and is lightly slid vertically in the drawing. As a result, the hair-like contact portion 212 is formed into the concave portion 1
The external electrodes 21 are fixed by inserting them into 03 and 104 while ensuring electrical conductivity between them. Other details are the same as in the first embodiment.

In this example, since the contact portion 212 is made of a flexible conductive wire, the contact portion 212 absorbs the stress even when the laminated piezoelectric element 1 is expanded or contracted or external shock or vibration is applied. Can be relaxed. Therefore, the contact part 2
It is difficult for the outer electrode 21 to drop off, and the conductivity between the outer electrode 21 and the inner electrode layers 11 and 12 can be maintained. Other functions and effects are the same as those of the first embodiment.

(Example 3) Multilayer piezoelectric element 1 of this example
Has an external electrode 22 in which a flexible conductive wire is filled in the tubular main body 221, and the contact portion 222 is formed by projecting from a window 223 provided on the side surface of the tubular main body 221.

As shown in FIG. 12, the external electrode 22 of this example is
The cylindrical main body 221 is filled with a large number of conductive wires made of thin metal wires, and the side surfaces 101, 1 of the piezoelectric stack 10 are
The window part 223 provided at a position facing 02 makes the metal wire extend outward to serve as a contact part. Further, the fixing of the external electrode 21 to the piezoelectric stack 10 in this example is
It can be realized in the same manner as the second embodiment described above. Other details are the same as in the first embodiment.

In this example, since the contact portion 212 is made of a flexible conductive wire, the contact portion 212 absorbs the stress even if the laminated piezoelectric element 1 is expanded or contracted or external shock or vibration is applied. Can be relaxed. Therefore, the contact part 2
It is difficult for the outer electrode 21 to drop off, and the conductivity between the outer electrode 21 and the inner electrode layers 11 and 12 can be maintained. Other functions and effects are the same as those of the first embodiment.

(Embodiment 4) In the laminated piezoelectric element 1 of this embodiment, the external electrode 23 and the contact portion 232 are integrally formed, and both are made of a conductive elastic body whose surface is coated with a conductive film. As shown in FIG. 13, the external electrode 23 protrudes from the plate-shaped main body 231 and the surface of the main body 231 and the recess 10
3 and 104, and a contact portion 232 having a shape that can be fitted. The entire external electrode 23 is made of an elastic material such as conductive rubber or conductive resin, and the entire surface is covered with a conductive film made of gold or silver. Other details are the same as in the first embodiment.

Alternatively, the conductive rubber may be used to form the following external electrode 24. As shown in FIG. 14, in the external electrode 24, a small plate-shaped main body 241 is made of a conductive elastic body, and a linear contact portion 242 made of the same conductive elastic body is formed in the main body 241 as a recess 103. , 10
It is constructed by joining only the number of 4.

The linear contact portions 242 are formed in the recesses 103 and 10 respectively.
4, so that the external electrode 24 is fitted into the piezoelectric stack 1
Fixed at 0. Further, the lengths of the linear bodies of the conductive elastic body forming the contact portion 242 are different from each other, and the linear bodies fitted in the recesses 103 and 104 located at the top are short, and the recesses 103 and 104 located at the bottom are short. The linear body that fits in is the longest. Other details are the same as in the first embodiment.

In this example, the external electrodes 23 and 24 are connected to the contact portion 23.
Since it is made of a conductive elastic body together with 2,242, it is highly flexible. Stress is unlikely to occur when the piezoelectric stack 10 expands and contracts, and shock and vibration can be absorbed from the outside.
Therefore, it is possible to secure the durability of the electrical continuity between the external electrodes 23 and 24 and the exposed end surfaces of the internal electrode layers 11 and 12. Other functions and effects are the same as those of the first embodiment.

(Embodiment 5) This embodiment shows a piezoelectric stack having square piezoelectric layers in FIG. In the piezoelectric stack 30 of this example, the first and second internal electrode layers (not shown) are exposed only to the first and second side surfaces 301 and 302, and are not exposed to the other side surfaces. Also, the first and second side surfaces 30
The recesses 303 and 304 provided in the recesses 1 and 302 are provided in parallel with the exposed end face 120 of the internal electrode layer, and only one exposed end face 120 is exposed in one recess 302.

Other details are the same as in the first embodiment.
Also in the laminated piezoelectric element including the piezoelectric stack 30 having this shape, the same effect as that of the first embodiment can be obtained by attaching the external electrodes having the shapes according to the first to fourth embodiments.

The specific shape of the external electrode according to the present invention is not limited to the first to fourth embodiments.

[Brief description of drawings]

FIG. 1 is a perspective view of a laminated piezoelectric element according to a first embodiment.

FIG. 2 is a perspective view of the piezoelectric stack according to the first embodiment.

FIG. 3 is an explanatory diagram of a piezoelectric stack and a concave portion provided on a side surface in the first embodiment.

FIG. 4 is an explanatory diagram of a laminated piezoelectric element including an external electrode having a connecting portion that is provided obliquely with respect to a contact portion in the first embodiment.

FIG. 5 is an explanatory view of a main part of the external electrode of FIG. 4 in the first embodiment.

FIG. 6 is a development explanatory diagram of an external electrode including two parts according to the first embodiment.

FIG. 7 is an explanatory diagram of an external electrode including two parts according to the first embodiment.

FIG. 8 is an explanatory diagram of a laminated piezoelectric element including an external electrode having a connecting portion that is provided obliquely with respect to the contact portion in the first embodiment.

FIG. 9 is an explanatory diagram of the external electrode according to FIG. 8 in the first embodiment.

FIG. 10 is an explanatory diagram of a laminated piezoelectric element including an external electrode having a contact portion formed by implanting conductive wire in Example 2;

FIG. 11 is a development view of a laminated piezoelectric element including an external electrode having a contact portion configured by implanting conductive wire in Example 2;

FIG. 12 is an explanatory diagram of a laminated piezoelectric element including an outer electrode having a contact portion made of a flexible conductive wire filled in a tubular body in Example 3.

FIG. 13 is an explanatory diagram of a laminated piezoelectric element including an external electrode having a contact portion integrally formed of a conductive elastic body according to the fourth embodiment.

FIG. 14 is an explanatory diagram of a laminated piezoelectric element including an external electrode having a linear body contact portion integrally formed of a conductive elastic body according to the fourth embodiment.

FIG. 15 is an explanatory diagram of a piezoelectric stack having a square piezoelectric layer according to a fifth embodiment.

FIG. 16 is a cross-sectional explanatory view of a conventional laminated piezoelectric element.

[Explanation of symbols]

1. ． ． Multilayer piezoelectric element, 10. ． ． Piezoelectric stack, 101, 102. ． ． First and second sides, 103, 104. ． ． First and second recesses, 11,12. ． ． First and second internal electrode layers, 110, 120. ． ． The first and second exposed end faces, 13, 14. ． ． First and second external electrodes, 15. ． ． Piezoelectric layer,

Claims (9)

[Claims] 1. A piezoelectric stack in which piezoelectric layers that expand and contract according to an applied voltage are alternately laminated with first and second internal electrode layers for supplying an applied voltage sandwiched between the first internal electrode layers. The second internal electrode layer has an exposed end surface exposed on the first side surface of the piezoelectric stack, the second internal electrode layer has an exposed end surface exposed on the second side surface of the piezoelectric stack, and a first external surface on the first side surface. An electrode, a second external electrode is provided on the second side surface, and by using the first and second external electrodes, the adjacent first and second internal electrode layers have different polarities via a piezoelectric layer. The first and second side surfaces have a concave portion, the first and second external electrodes have a contact portion, and the first and second internal electrode layers are provided in the concave portion. The exposed end surface of the and the contact portions of the first and second external electrodes are electrically connected. A laminated piezoelectric element characterized by the following. 2. The method according to claim 1, wherein the first or second
2. The laminated piezoelectric element according to claim 1, wherein each of the recesses provided on the side surface extends over the exposed end surface of the plurality of first or second internal electrode layers. 3. The laminate according to claim 1, wherein the contact portion is made of a flexible conductive wire, and the external electrode is formed by implanting the conductive wire in a plate-shaped body. Type piezoelectric element. 4. The external electrode according to claim 1 or 2, wherein the tubular body is filled with a flexible conductive wire, and the conductive wire is projected from a window provided on a side surface of the tubular body. A laminated piezoelectric element having a contact portion constituted by the above. 5. The laminated piezoelectric body according to claim 1, wherein the external electrode and the contact portion are integrally formed, and both of them are made of a conductive elastic body whose surface is coated with a conductive film. element. 6. The laminated piezoelectric element according to claim 1, wherein the external electrode and the contact portion are integrally formed, and both are formed by bending a conductive wire. 7. A piezoelectric stack in which piezoelectric layers that expand and contract according to an applied voltage are alternately laminated with first and second internal electrode layers for supplying an applied voltage sandwiched therebetween, wherein the first internal electrode layers are The second internal electrode layer has an exposed end surface exposed on the first side surface of the piezoelectric stack, the second internal electrode layer has an exposed end surface exposed on the second side surface of the piezoelectric stack, and a first external surface on the first side surface. An electrode, a second external electrode is provided on the second side surface, and by using the first and second external electrodes, the adjacent first and second internal electrode layers have different polarities via a piezoelectric layer. Each of the first and second side surfaces has a concave portion, the first and second external electrodes have a contact portion, and each concave portion is provided on the first or second side surface. Extends over the exposed end faces of the plurality of first or second internal electrode layers and is laminated with the piezoelectric stack. The external electrode is formed obliquely with respect to a surface orthogonal to the direction, and the external electrode includes the contact portion and a connecting portion that connects the contact portion to another contact portion, and the contact portion has a shape corresponding to the recess. In the recess, the exposed end surfaces of the first and second internal electrode layers and the contact portions of the first and second external electrodes are electrically connected to each other. 8. The laminated piezoelectric element according to claim 7, wherein the connecting portion is formed in a direction parallel to the piezoelectric stack laminating direction. 9. The laminated piezoelectric element according to claim 7, wherein the connecting portion is formed in a direction orthogonal to a piezoelectric stack laminating direction.