JP2003086853A - Laminated piezoelectric element, its manufacturing method, and injection equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element in which disconnection does not occur between external electrodes and internal electrodes even when the element is continuously driven for a long period under a high-electric field and high-pressure condition and which is excellent in durability. SOLUTION: This laminated piezoelectric element is provided with a columnar laminate 1a constituted by alternately laminating a plurality of piezoelectric layers 1 and a plurality of internal electrodes 2 upon another, and a pair of external electrodes 4 which are respectively provided on both side faces of the laminate 1a and to which the internal electrodes 2 are connected alternately at every other layer. Projecting conductive terminals 5 protruded from the side faces of the laminate 1a are provided at the end sections of the internal electrodes 2 at every other layer, and are bonded to the external electrodes 4 composed of plate-shaped conductive members 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element, a method of manufacturing the laminated piezoelectric element, and an injection device, for example, a laminated device used for a precision positioning device such as a fuel injection device for an automobile or an optical device, a drive element for preventing vibration, and the like. TECHNICAL FIELD The present invention relates to a piezoelectric element, a manufacturing method thereof, and an injection device.

[0002]

2. Description of the Related Art Hitherto, as a laminated piezoelectric element, a laminated piezoelectric actuator in which piezoelectric bodies and internal electrodes are alternately laminated has been known. Multi-layer piezoelectric actuators are classified into two types: co-firing type and stack type in which piezoelectric ceramics and internal electrode plates are alternately laminated. Considering low voltage and manufacturing cost, co-firing The advantage of the laminated piezoelectric actuator of the type is being demonstrated because it is advantageous for thinning.

FIG. 10 shows a conventional laminated piezoelectric actuator. In this actuator, a piezoelectric body 51 is used.
And internal electrodes 52 are alternately laminated to form a columnar laminated body 53, and an inactive layer 55 is formed on both end faces in the laminating direction.
Are stacked. The inner electrode 52 is formed such that one end of the inner electrode 52 is alternately covered with the insulator 61, and the strip-shaped outer electrodes 70 are electrically connected to the inner electrode 52 on every other layer. A lead wire 76 is further fixed on the strip-shaped external electrode 70 by solder 77.

By the way, in recent years, in order to secure a large amount of displacement under a large pressure with a small piezoelectric actuator, a higher electric field is applied and continuous driving is performed for a long period of time.

[0005]

However, in the above-described piezoelectric actuator, when continuously driven under a high electric field and a high pressure for a long period of time, the internal electrodes 52 formed between the piezoelectric bodies 51 and the positive and negative electrodes are formed. There is a problem that peeling occurs between the external electrode 70 and a voltage is not supplied to a part of the piezoelectric body 51, and the displacement characteristic changes during driving.

[0006] For example, in Japanese Patent Laid-Open No. 4-237172, the end portions of the internal electrodes exposed on the side surfaces of the columnar laminated body are covered with an insulating layer made of glass every other layer.
A laminated type in which the internal electrode and the piezoelectric bodies above and below the electrode are firmly bonded, and an insulating layer that insulates the end of the internal electrode is housed in the recess of the external electrode to ensure insulation between the external electrode and the internal electrode. Although a piezoelectric actuator is disclosed, in such a piezoelectric actuator, when the piezoelectric actuator is continuously driven under a high electric field and a high pressure for a long period of time, a crack is generated in an insulating layer made of glass, and the internal electrode and the outside are broken through the crack. There is a problem that a short circuit occurs between the electrodes and a voltage is not supplied to a part of the piezoelectric body, and the displacement characteristic changes during driving.

That is, since the columnar laminated body expands and contracts in the laminating direction of the piezoelectric body and the internal electrode, the insulating layer made of high Young's modulus glass provided on the piezoelectric body at the end of the internal electrode and in the vicinity thereof, There is a problem in that it cannot withstand the expansion and contraction operation due to continuous driving for a long period of time and is broken, and a short circuit easily occurs between the internal electrode and the external electrode via this broken portion.

Further, Japanese Unexamined Patent Publication No. 7-283451 and Japanese Unexamined Patent Publication No. 8-51240 disclose that conductive protrusions are formed by plating on the end portions of every other internal electrode. Since the bonding strength between the conductive convex portion and the laminated body is weak, the conductive convex portion and the end portion of the internal electrode are separated during driving, the voltage is not supplied to a part of the piezoelectric body, and the displacement characteristic is deteriorated. There was a problem of doing.

The present invention provides a laminated piezoelectric element excellent in durability without disconnection between the external electrode and the internal electrode even when continuously driven for a long time under a high electric field and a high pressure, a method for producing the same, and a jet method. The purpose is to provide a device.

[0010]

A laminated piezoelectric element of the present invention is provided with a columnar laminated body formed by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes, and provided on a side surface of the columnar laminated body. A laminated piezoelectric element comprising a pair of external electrodes in which the internal electrodes are alternately connected to each other, and protrusions protruding from the side surface of the columnar laminated body at every other end of the internal electrodes. A conductive terminal, and the protruding conductive terminal,
It is characterized by being joined to an external electrode made of a plate-shaped conductive member.

In the laminated piezoelectric element of the present invention, protruding conductive terminals projecting from the side surface of the columnar laminated body are provided at every other end of the internal electrode, and the protruding conductive terminals and the plate-shaped conductive member are connected to each other. When the actuator is driven in the stacking direction, the protruding conductive terminals are deformed to absorb the stress generated by the expansion and contraction of the actuator, so that it is operated continuously for a long time under a high electric field and pressure. However, disconnection between the external electrode and the internal electrode can be suppressed, and the durability can be significantly improved.

Further, the present invention is characterized in that the root portion of the protruding conductive terminal is embedded in the silicon-containing layer formed on the side surface of the columnar laminated body.

In such a laminated piezoelectric element, since the root of the protruding conductive terminal is embedded in the silicon-containing layer formed on the piezoelectric body surface on the side surface of the columnar laminated body, the silicon-containing layer is It is firmly bonded to the piezoelectric surface on the side surface of the columnar laminated body, and the root portion of the protruding conductive terminal is embedded in this silicon-containing layer, so that the protruding conductive terminal is firmly attached to the end of the internal electrode. A laminated piezoelectric element that can be held while being bonded to, and has excellent durability without disconnection between external electrodes and internal electrodes even when continuously driven under a high electric field and high pressure for a long time. Can be provided.

Furthermore, in the present invention, the thickness of the silicon-containing layer is preferably 2 to 100 μm. This allows
The protruding conductive terminal can be more firmly joined and held to the end portion of the internal electrode, and disconnection between the external electrode and the internal electrode can be further suppressed. This is because the thickness of the silicon-containing layer is 2 μm.
By the above, the bonding strength between the protruding conductive terminal, the internal electrode, and the columnar laminate can be sufficiently strengthened, and the problem arises that the protruding conductive terminal is separated from the internal electrode during driving. Can be prevented, and the thickness of 100 μm or less can prevent the characteristics of the piezoelectric body from being deteriorated by the silicon-containing layer.

Further, in the present invention, it is desirable that a raised portion of the silicon-containing layer is formed around the protruding conductive terminal. The raised portion of the silicon-containing layer assists the protruding conductive terminal, so that the bonding strength between the protruding conductive terminal, the internal electrode, and the columnar laminate can be further strengthened. Even when it is continuously driven by, the durability can be significantly improved without disconnection of the external electrode and the internal electrode.

Further, in the present invention, each of the protruding conductive terminals and the external electrode has a length equal to 50 of the tip length of the protruding conductive terminal.
It is desirable that the joints be made at a percentage of at least%. this is,
The protrusion-shaped conductive terminals are joined to the external electrodes made of a plate-shaped conductive member by 50% of the tip length of each protrusion-shaped conductive terminal.
Since it is performed in the above part, it is possible to sufficiently reduce the resistance of the joint portion between the protruding conductive terminal and the external electrode, and even when driving a large current at a high speed, the protruding conductive terminal and the external electrode Local heat generation does not occur at the joint, and durability can be greatly improved.

Further, in the present invention, it is desirable that the thickness of the plate-shaped conductive member is 50 μm or less. When the thickness of the plate-shaped conductive member is larger than 50 μm, the plate-shaped conductive member cannot follow the expansion and contraction of the actuator, and the space between the plate-shaped conductive member and the protruding conductive terminal or between the protruding conductive terminal and the internal electrode. This is because the wire breakage easily occurs between the two. Therefore,
By setting the thickness of the plate-shaped conductive member to 50 μm or less,
Even when the actuator is continuously driven, the expansion and contraction of the actuator can be sufficiently followed, and the problem of disconnection between the external electrode and the internal electrode can be prevented.

Further, in the present invention, it is desirable that a slit or a groove is formed in the plate-shaped conductive member between the protruding conductive terminals. Since the slit or groove is formed in the external electrode made of the plate-shaped conductive member, the external electrode can be easily deformed and followed in response to the expansion and contraction of the columnar laminated body, and the external electrode and the protruding conductive terminal An unreasonable load does not act on the connection part and the connection part between the protruding conductive terminal and the internal electrode, which allows the external electrode and the internal electrode to separate even when continuously driven under a high electric field and a high pressure for a long period of time. Durability can be improved without breaking.

Further, in the present invention, it is desirable that a conductive resin is filled between the plate-shaped conductive member and the side surface of the columnar laminated body. Due to the repeated stress generated by the expansion and contraction of the columnar laminated body, even if the plate-shaped conductive member is broken from the slit or the concave groove, the broken external electrode pieces are connected to each other by the conductive resin, so that the internal electrodes are An electric field can be applied.

Further, in the present invention, it is desirable that a conductive auxiliary member is provided on the outer surface of the plate-shaped conductive member. By providing a conductive auxiliary member on the outer side of the plate-shaped conductive member, it is possible to prevent local external heat from being generated and disconnection even when a large current is applied to the actuator and driven at high speed. It can be greatly improved.

Further, in the present invention, the conductive auxiliary member is
It is desirable to be composed of at least one of a conductive adhesive, a conductive coil, a conductive corrugated sheet, and a conductive fiber aggregate.
When the conductive auxiliary member is made of a conductive adhesive, the conductive auxiliary member can sufficiently follow the expansion and contraction of the actuator by using a flexible conductive adhesive as the conductive auxiliary member, and It is possible to suppress disconnection of the conductive auxiliary member.

It is preferable that the conductive adhesive is made of a polyimide resin in which the conductive agent is dispersed. In this case, by using a polyimide resin having high heat resistance as a matrix component of the conductive adhesive, the conductive adhesive does not deteriorate even when it is driven at high temperature, and has high durability. It is possible to provide a laminated piezoelectric element having such a structure.

Further, it is desirable that the conductive auxiliary member is a conductive coil, a conductive corrugated plate or a conductive fiber aggregate, and the conductive auxiliary member is joined to the plate-shaped conductive member. In this case, the conductive auxiliary member can follow expansion and contraction of the actuator, the conductive auxiliary member is disconnected during driving, or stress is generated between the conductive auxiliary member and the plate-shaped conductive member. The problem that the conductive auxiliary member is peeled off can be prevented, and the durability can be greatly improved.

Further, in the present invention, it is desirable that the protruding conductive terminals and the plate-shaped conductive member contain silver as a main component. This is because the main component of the protruding conductive terminal and the plate-shaped conductive member is silver, so that the bonding strength between the protruding conductive terminal and the internal electrode and between the protruding conductive terminal and the plate-shaped conductive member is increased. Can be strengthened, and even when the actuator is driven under a high electric field, the external electrode and the internal electrode are not disconnected, and the durability can be greatly improved. Also, by using silver having a low Young's modulus as the main component of the protruding conductive terminal and the plate-shaped conductive member, it is possible to sufficiently absorb the stress generated when the actuator is driven, and it is possible to suppress disconnection between the external electrode and the internal electrode. .

Further, in the method for manufacturing a laminated piezoelectric element of the present invention, a columnar laminated body is produced in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and the end portions of the internal electrodes are exposed on the side surfaces. And a step of applying a conductive paste containing a solid component consisting of 50 to 80% by volume of a conductive metal powder and 20 to 50% by volume of a glass powder containing silicon as a main component on the side surface of the columnar laminate. And a step of heating the conductive paste applied to the side surface of the columnar laminated body to form a protruding conductive terminal projecting from the side surface of the columnar laminated body at the end portion of the internal electrode; And a step of connecting an external electrode made of a plate-shaped conductive member to the tip of the sex terminal.

According to such a method, the conductive material containing a solid component consisting of 50 to 80% by volume of the conductive metal powder and 20 to 50% by volume of the glass powder containing silicon as the main component is provided on the side surface of the columnar laminate. Glass is melted by applying a conductive paste and heating, and the conductive metal particles present in the melted glass are aggregated at the end of the internal electrode and protruded from the side surface of the columnar laminate to form a conductive protrusion. And a silicon-containing layer (glass layer) containing the diffused piezoelectric component and silicon is formed on the surface of the piezoelectric body on the side surface of the columnar laminated body, and the silicon-containing layer forms a protruding conductive terminal. The root portion of is embedded, and the protruding conductive terminal can be firmly bonded to the end portion of the internal electrode.

Here, it is preferable that the height variation of the protruding conductive terminals formed by heating the conductive paste is 0.3 times or less of the average height of the protruding conductive terminals. This is because when the height variation of the protruding conductive terminals is set to 0.3 times or less of the average height of the protruding conductive terminals, the protruding conductive terminals and the external electrodes made of a plate-shaped conductive member are The connection can be made surely and firmly, and it is possible to prevent the problem that the protruding conductive terminal and the external electrode are disconnected during driving. In the present invention, the height variation of the protruding conductive terminals means the difference between the maximum height and the minimum height of each protruding conductive terminal.

The method of manufacturing the laminated piezoelectric element of the present invention is as follows.
A step of producing a columnar laminated body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and the end portions of the internal electrodes are exposed on the side surface; and the side surface of the columnar laminated body and the plate-shaped conductive member. Glass containing silicon as a main component in an amount of 50 to 80% by volume of conductive metal powder so as to cover the exposed end portions of the inner electrodes and the piezoelectric body surface in the vicinity thereof between the outer electrodes. A step of interposing a conductive paste containing a solid component consisting of 20 to 50% by volume of powder, and heating the conductive paste to protrude from the side surface of the columnar stacked body at every other end portion of the internal electrode. And a step of joining the external electrode to the tip end portion of the protruding conductive terminal.

According to such a method, between the side surface of the columnar laminated body and the external electrode made of the plate-like conductive member, the exposed end portions of the internal electrodes and the piezoelectric surface in the vicinity thereof are exposed. 50 to 80% by volume of conductive metal powder and 20 to 50% by volume of glass powder containing silicon as a main component so as to cover
By interposing a conductive paste containing a solid component consisting of and heating, the glass is melted, and the conductive metal particles present in the melted glass are aggregated at the end of the internal electrode to form a columnar laminate. The protruding conductive terminal is formed so as to project from the side surface, and the tip end of the protruding conductive terminal can be bonded to the external electrode. At the same time, a silicon-containing layer is formed on the surface of the piezoelectric body on the side surface of the columnar laminated body, and the root portion of the protruding conductive terminal is embedded by this silicon-containing layer, so that the protruding conductive terminal is firmly attached to the internal electrode end. Can be joined.

The jetting device of the present invention comprises a container having a jetting hole, the laminated piezoelectric element housed in the casing, and a valve for ejecting a liquid from the jetting hole by driving the laminated piezoelectric element. And is equipped with.

In such an ejecting apparatus, as described above, the laminated piezoelectric element can suppress the disconnection between the external electrode and the internal electrode and can greatly improve the durability, so that the durability of the ejecting apparatus is also improved. it can.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a laminated piezoelectric element comprising a laminated piezoelectric actuator according to the present invention. (A) is a perspective view, (b) is AA 'in (a). FIG. 3 is a vertical cross-sectional view taken along the line, (c) is a perspective view showing a part of (a) in an enlarged manner, and (d) is an enlarged view in the vicinity of a joint portion between an internal electrode and an external electrode.

As shown in FIG. 1, the laminated piezoelectric actuator includes a plurality of piezoelectric bodies 1 and a plurality of internal electrodes 2 which are alternately laminated on the side surface of a rectangular columnar laminated body 1a. Every other edge is covered with an insulator 3,
At the end of the internal electrode 2 which is not covered with the insulator 3, a protruding conductive terminal 5 which is deformable in the expansion and contraction direction of the laminated piezoelectric element is provided, and the protruding conductive terminal 5 is connected to the plate conductive member 4a. The external electrodes 4 are joined to each other, and the lead wire 6 is connected and fixed to each external electrode 4.

The piezoelectric body 1 is made of, for example, lead zirconate titanate Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT) or a piezoelectric ceramic material containing barium titanate BaTiO ₃ as a main component. . It is desirable that this piezoelectric ceramic has a high piezoelectric strain constant d ₃₃ showing its piezoelectric characteristics.

The thickness of the piezoelectric body 1, that is, the internal electrode 2
The distance between them is preferably 50 to 250 μm. This is because the laminated piezoelectric actuator has a method of increasing the number of laminated layers in order to apply a voltage to obtain a larger displacement amount, but when the number of laminated layers is increased, the piezoelectric body 1 is too thick. The actuator cannot be made smaller and the height cannot be reduced,
On the other hand, if the piezoelectric body 1 is too thin, dielectric breakdown is likely to occur.

Internal electrodes 2 are arranged between the piezoelectric bodies 1. The internal electrodes 2 are made of a metallic material such as silver-palladium, and a predetermined voltage is applied to each piezoelectric body 1. This serves to cause the piezoelectric body 1 to be displaced by the inverse piezoelectric effect.

Further, every other layer has a depth of 50 to 500 μm on the side surface of the columnar laminated body 1a on which the protruding conductive terminals 5 are formed.
m, a groove having a width of 30 to 200 μm in the stacking direction is formed, and the insulator 3 is formed by filling the groove with glass, epoxy resin, polyimide resin, polyamideimide resin, silicone rubber, or the like. This insulator 3 is used for strengthening the joint with the columnar laminated body 1a.
It is preferable to use a material having a low elastic modulus that follows the displacement of a, specifically, silicone rubber or the like.

The protruding conductive terminals 5 and the insulators 3 are alternately formed on the internal electrodes 2 exposed on the side surfaces of the columnar laminate 1a on which the external electrodes 4 are formed.

That is, the end portions of the internal electrodes 2 are alternately insulated by the insulator 3 filled in the groove, and the other non-insulated end portions of the internal electrodes 2 are protruded conductive terminals 5. It is joined to the external electrode 4 composed of the plate-shaped conductive member 4a via.

External electrodes 4 each made of a plate-shaped conductive member 4a are connected and fixed to opposite side surfaces of the columnar laminated body 1a through projecting conductive terminals 5, and are laminated on the external electrodes 4. The internal electrodes 2 are electrically connected to every other layer. The external electrode 4 composed of the plate-shaped conductive member 4a has a function of commonly supplying a voltage necessary for displacing the piezoelectric body 1 to each connected internal electrode 2 by the inverse piezoelectric effect.

Further, a lead wire 6 is connected and fixed to the external electrode 4 by soldering. The lead wire 6 serves to connect the external electrode 4 to an external voltage supply section.

In the present invention, as described above, the external electrode 4 made of the plate-shaped conductive member 4a is provided with the protruding conductive terminal 5.
It is connected to the internal electrode 2 via. Therefore, even when the actuator is continuously driven under a high electric field and a high pressure for a long period of time, the protruding conductive terminal 5 absorbs the stress generated by the expansion and contraction of the actuator, and the disconnection between the external electrode 4 and the internal electrode 2 is suppressed. Therefore, it is possible to provide an actuator having excellent durability.

The width B in the same direction as the stacking direction of the protruding conductive terminals 5 protruding from the silicon-containing layer described later is as shown in FIG.
As shown in (c), the resistance of the connection portion between the external electrode 4 and the internal electrode 2 is reduced, and the stress generated when the actuator is driven is sufficiently absorbed, and the thickness of the piezoelectric body 1 is 1 μm or more and 1 It is desirable that it is / 2 or less. Particularly, the width B is preferably 5 to 25 μm.

Further, the protruding height h of the protruding conductive terminal 5 protruding from the silicon-containing layer is 1/20 or more of the thickness of the piezoelectric body 1 from the viewpoint of sufficiently absorbing the stress generated by the expansion and contraction of the actuator. Is desirable. Particularly, the protrusion height h is preferably 15 to 50 μm.

Further, the thickness t of the plate-shaped conductive member 4a follows the expansion and contraction of the actuator, and disconnection between the external electrode 4 and the protruding conductive terminal 5 or between the protruding conductive terminal 5 and the internal electrode 2. It is preferable that the thickness is 50 μm or less from the viewpoint of not causing.

The protruding conductive terminal 5 is made of a conductive metal such as silver, nickel, copper, gold, or aluminum, and an alloy thereof, and sufficiently absorbs the stress generated by the expansion and contraction of the actuator. Therefore, silver having a low Young's modulus or an alloy containing silver as a main component is preferable.

Further, the plate-like conductive member 4a is made of a metal having conductivity such as silver, nickel, copper, gold, aluminum and alloys thereof, and of these, the protruding conductive terminal 5 is provided.
From the point that the joint strength with is strong and the Young's modulus is low,
Silver or an alloy containing silver as a main component is preferable.

The protrusion-shaped conductive terminal 5 and the external electromotive force 4 made of the plate-shaped conductive member 4a are bonded to each other by applying a load 70
By heat treatment at 0 to 950 ° C., the main component, silver, diffuses between the protruding conductive terminals 5 and the plate-shaped conductive member 4a, and this is achieved by so-called silver diffusion bonding. Also,
The joint portion between the internal electrode 2 and the protruding conductive terminal 5 is embedded in the silicon-containing layer 10, and silver-palladium forming the internal electrode 2 and silver forming the protruding conductive terminal 5 interdiffuse. The internal electrodes 2 and the protruding conductive terminals 5 are continuously joined.

That is, according to the present invention, the root portion 5a of the protruding conductive terminal 5 has the piezoelectric body 1 on the side surface of the columnar laminated body 1a.
It is embedded in the silicon-containing layer 10 formed on the surface, and the tip end portion of the protruding conductive terminal 5 is connected to the external electrode 4 composed of the plate-shaped conductive member 4a.

Here, the root portion 5a of the protruding conductive terminal 5
Means the portion of the protruding conductive terminal 5 in the vicinity of the connecting portion between the internal electrode 2 and the protruding conductive terminal 5, and silver forming the protruding conductive terminal 5 and silver-palladium forming the internal electrode 2 Are mutually diffused and the internal electrode 2 and the protruding conductive terminal 5 are continuously connected, so that the portion where the thickness starts to become larger than the thickness of the internal electrode 2 is connected to the internal electrode 2 and the protruding conductive terminal 5. And the tip side thereof becomes the root portion 5a of the protruding conductive terminal 5.

The minimum thickness d of the silicon-containing layer 10 strengthens the bonding strength between the protruding conductive terminal 5 and the internal electrode 2 and the columnar laminate 1a, and the silicon-containing layer 10 allows the piezoelectric body 1 to have a strong bonding strength. From the viewpoint of preventing the characteristics from deteriorating, the thickness is preferably 2 to 100 μm, particularly 5 to 5 μm.
15 μm is desirable. Silicon-containing layer 1 having such a thickness
In order to form 0, 50 to 80% by volume of a conductive metal powder such as silver and the balance silicon as a main component, and a softening point of 60
A binder is added to a solid component consisting of 20 to 50% by volume of glass powder at 0 to 950 ° C. to prepare a conductive paste, and the conductive paste is applied to the side surface of the columnar laminate 1a to obtain a softening point of glass. Above temperature, ie 700-950 ° C
This can be achieved by baking in.

Here, the thickness d of the silicon-containing layer 10 is 2 μm.
If it is smaller than m, the bonding strength between the protruding conductive terminal 5, the internal electrode 2 and the columnar laminated body 1a is weak, and the protruding conductive terminal 5 peels off during driving, resulting in a part of the internal electrode 2. However, if the thickness d of the silicon-containing layer 10 is larger than 100 μm, the piezoelectric body 1 is not cracked in the step of forming the groove for filling the insulator 3. This is because it tends to occur or the piezoelectric characteristics of the piezoelectric body 1 deteriorate.

The distribution of silicon in the silicon-containing layer 10 is largest in the vicinity of the surface and decreases toward the inner side, that is, as the depth becomes deeper, and conversely, Pb forming the piezoelectric body 1 has a deeper depth. It decreases as it becomes shallower. Although silicon exists as a small amount of impurities or additives even inside the piezoelectric body 1, the columnar laminated body 1 starts when the amount of silicon existing in a uniform distribution state inside the piezoelectric body 1 starts to increase.
The distance to the surface a is defined as the thickness d of the silicon-containing layer 10.

In addition, in the present invention, in order to further firmly and firmly bond the protruding conductive terminals 5 to the internal electrodes 2 and the columnar laminate 1a, as shown in FIG. As the layer 10 assists the protruding conductive terminal 5,
A raised portion 10 a of the silicon-containing layer 10 is formed around the root portion 5 a of the protruding conductive terminal 5. That is, the root portion 5 a of the protruding conductive terminal 5 is embedded in the raised portion 10 a of the silicon-containing layer 10. Raised portion 1 of silicon-containing layer 10
The height of 0a from the portion having the minimum thickness d of the silicon-containing layer 10 is preferably 1 to 5 μm. The cross-sectional shape of the protruding conductive terminal 5 is preferably a brush or mushroom shape.

The protruding height h of the protruding conductive terminal 5 from the silicon-containing layer 10, that is, the distance from the portion having the minimum thickness d of the silicon-containing layer 10 to the plate-shaped conductive member 4a is:
The thickness is preferably 1/20 or more of the thickness of the piezoelectric body 1 in order to sufficiently absorb the stress generated by the expansion and contraction of the actuator. Particularly, the protrusion height h is 15 to 50 μm.
Is desirable.

Further, in the present invention, as shown in FIG.
Each of the protruding conductive terminals 5 and the plate-shaped conductive member 4a are joined to each other at 50% or more of the tip length L of the protruding conductive terminals 5. As a result, the resistance of the joint between the protruding conductive terminal 5 and the plate-shaped conductive member 4a is sufficiently lowered, and even when the actuator is driven at a high speed by passing a large current, the protruding conductive terminal 5 and the plate-shaped conductive member 4a are driven. It is possible to prevent local heat generation from occurring at the joint portion of the conductive member 4a. Particularly, 80% or more is preferable. In this way, in order to bond each protruding conductive terminal 5 and the plate-shaped conductive member 4a to 50% or more of the tip length L of the protruding conductive terminal 5, the protruding conductive terminals 5 are manufactured. When the average height h of the protruding conductive terminals 5 is 0.
3 times or less, and 70 with a uniform load applied
The heat treatment may be performed at 0 to 950 ° C.

Further, the lead wire 6 is connected and fixed to the external electrode 4 by soldering. The lead wire 6 serves to connect the external electrode 4 to an external voltage supply section.

A method of manufacturing the laminated piezoelectric element of the present invention will be described. First, the columnar laminated body 1a is manufactured. A columnar laminated body 1a formed by alternately laminating a plurality of piezoelectric bodies 1 and a plurality of internal electrodes 2 is a calcined powder of piezoelectric ceramics such as PZT and a binder made of an organic polymer such as an acrylic or butyral type. , DBP (diotyl phthalate), DOP
A slurry is prepared by mixing with a plasticizer such as (dibutyl phthalate), and the slurry is prepared by a known tape molding method such as a doctor blade method or a calendar roll method to prepare a ceramic green sheet to be the piezoelectric body 1.

Next, for example, a binder, a plasticizer, etc. are added to and mixed with silver-palladium powder to prepare a conductive paste, which is printed on the upper surface of each green sheet to a thickness of 1 to 40 μm by screen printing or the like. To do.

Then, a green sheet having a conductive paste printed on the upper surface thereof is laminated, the binder is debindered at a predetermined temperature, and then baked at 900 to 1200 ° C.

Then, as shown in FIG. 3A, for example, a grain size of 0.1 to 1 is provided on the opposite side surfaces of the columnar laminated body 1a.
50 μm to 80% by volume of silver powder of 0 μm, and the balance of grain size is 0.
1 to 10 μm and a softening point containing silicon as a main component is 600 to
A silver glass conductive paste 21 prepared by adding a binder to a mixture of 20 to 50% by volume of glass powder at 950 ° C. is applied, and the temperature is 700 to 700 at a temperature equal to or higher than the softening point of glass.
By baking at 950 ° C., the silver in the silver glass conductive paste 21 gathers at the end portions of the internal electrodes 2, and FIG.
As shown in (b), the brush-shaped or mushroom-shaped protruding conductive terminals 5 and the silicon-containing layer 10 can be formed.

That is, by dispersing the glass component in the paste, the glass is softened during baking, and in this state silver, which is difficult to diffuse in the piezoelectric body 1, diffuses and gathers at the end of the internal electrode 2. The protruding conductive terminal 5 as shown in FIG. 1B can be formed.

This protruding conductive terminal 5 is a columnar laminate 1a.
It is formed on a part of the side surface of the
The length thereof is substantially the same as the width of the external electrode 4 made of the plate-shaped conductive member 4a. The length of the protruding conductive terminal 5 may be shorter than the width of the external electrode 4, as shown in FIG.

The silver powder in the silver glass conductive paste 21 is set to 50 to 80% by volume and the balance of the glass powder is set to 20 to 50% by volume when the silver powder is less than 50% by volume. Since the silver component forming the terminal 5 is small,
When the protruding height h of the protruding conductive terminal 5 formed is small and the silver powder is more than 80% by volume, the glass component which is the solid content remaining in the silver glass conductive paste 21 is relatively small. Since the silver component becomes less, the glass component that melts when the silver glass conductive paste 21 is baked is inevitably reduced, and it becomes difficult for the silver component to collect at the end portion of the internal electrode 2, and the protruding height of the protruding conductive terminal 5 increases. This is because h becomes low.

In particular, the ridge 10 of the silicon-containing layer 10
To effectively form a, the silver glass conductive paste 21
60 to 70% by volume of silver powder and 30 to 4 of glass powder
It is preferably 0% by volume.

The height variation (maximum value-minimum value) of the protruding conductive terminals 5 after the heat treatment ensures the connection between the protruding conductive terminals 5 and the plate-shaped conductive member 4a. It is desirable that the height h of the sex terminal 5 is 0.3 times or less, and particularly 0.1 times or less. In addition,
In order to make the variation of the height h of the protruding conductive terminals 5 0.3 times or less of the average value of the height h of the protruding conductive terminals 5, the protruding conductive terminals 5 are formed. It suffices to reduce variations in the coating thickness of the silver glass conductive paste 21 that is previously coated on the side surfaces of the columnar stacked body 1a.

After forming the protruding conductive terminals 5 as described above, one layer is placed on the side surface of the columnar laminated body 1a on which the protruding conductive terminals 5 are formed by a dicing device or the like as shown in FIG. 3 (c). To form a groove.

Thereafter, as shown in FIG. 3 (d), the plate-shaped conductive member 4a made of silver is brought into contact with the protruding conductive terminals 5 and pressed to apply a load and heat-treated at 700 to 950.degree. The main component, silver, diffuses between the protruding conductive terminal 5 and the plate-shaped conductive member 4a, and is joined by so-called silver diffusion bonding.

The load applied at this time is pressure,
2-500 kPa is desirable. This has a pressure of 2 kPa
In the following cases, the protruding conductive terminal 5 is used because the pressure is low.
And the plate-shaped conductive member 4a are not sufficiently diffusion-bonded to each other, and the strength of the bonded portion is reduced. On the other hand, when the pressure is 500 kPa or more, the pressure is too high, so that the protruding conductive terminal 5 is This is because there is a risk of deformation.

Then, the groove 3 is filled with the insulator 3 and the lead wire 6 is connected to complete the laminated piezoelectric element of the present invention.

Alternatively, the protruding conductive terminals 5 may be formed by forming grooves on the side surfaces of the columnar laminate 1a and then applying the silver glass conductive paste 21 and baking the grooves.

Next, another method for manufacturing the laminated piezoelectric element of the present invention will be described. After forming the columnar laminated body 1a in the same manner as described above, grooves are formed on the side surface of the columnar laminated body 1a in every other layer.

After that, the internal electrodes 2 and the internal electrodes 2 exposed on the columnar laminate 1a other than the grooves of the columnar laminate 1a are exposed.
The same silver glass conductive paste 21 as described above is applied and dried on the surface of the piezoelectric body 1 in the vicinity of, and a load is applied to the silver glass conductive paste 21 so as to press the plate-shaped conductive member 4a. By the heat treatment at 950 ° C., the glass in the silver glass conductive paste 21 is melted, and the silver component present in the melted glass is collected at the end of the internal electrode 2 and protrudes from the side surface of the columnar laminated body 1 a. The protruding conductive terminal 5 is formed, and the tip end portion of the protruding conductive terminal 5 can be connected to the plate-shaped conductive member 4a.

The internal electrodes 2 and the internal electrodes 2 exposed in the columnar laminated body 1a other than the grooves of the columnar laminated body 1a are previously exposed.
The silver glass conductive paste 21 was applied and dried on the portion of the plate-shaped conductive member 4a corresponding to the surface of the piezoelectric body 1 in the vicinity of, and a load was applied so as to press the plate-shaped conductive member 4a against the columnar laminated body 1a. You may heat-process in a state. Further, a silver glass conductive paste is applied and dried on the entire surface of the plate-shaped conductive member 4a,
Even when the plate-shaped conductive member 4a is pressed against the surface where the internal electrode 2 of the columnar laminated body 1a is exposed with the conductive paste application surface side, and the heat treatment is performed, the protruding conductive terminal 5 is formed, and the tip portion thereof is formed. It can be connected to the plate-shaped conductive member 4a. In this case, the process can be further shortened.

Then, the groove 3 is filled with the insulator 3 and the lead wire 6 is connected to complete the laminated piezoelectric element of the present invention.

Then, a DC voltage of 0.1 to 3 kV / mm is applied to the pair of external electrodes 4 via the lead wires 6 to polarize the columnar laminated body 1a, whereby a laminated piezoelectric actuator as a product is obtained. When completed, the lead wire 6 is connected to an external voltage supply unit, and a voltage is applied to the internal electrode 2 via the lead wire 6 and the external electrode 4, each piezoelectric body 1 is largely displaced by the inverse piezoelectric effect, With this, for example, it functions as a fuel injection valve for an automobile that injects fuel to the engine.

In the laminated piezoelectric element configured as described above, since the external electrode 4 made of the plate-shaped conductive member 4a is connected to the internal electrode 2 via the protruding conductive terminal 5, the actuator is operated in a high electric field. Even when driven continuously,
Since the protruding conductive terminals 5 are deformed and the protruding conductive terminals 5 can sufficiently absorb the stress generated during driving, the external electrodes 4
It is possible to prevent a problem that a spark occurs between the internal electrode 2 and the internal electrode 2, and it is possible to provide a highly reliable actuator.

FIG. 4 shows a laminated piezoelectric actuator in which a groove is formed in a plate-shaped conductive member. In this laminated piezoelectric actuator, a plate-shaped conductive member 4a is provided between the protruding conductive terminals 5. A groove 11 is formed substantially parallel to the end of the internal electrode 2. The recessed grooves 11 are formed between the protruding conductive terminals 5, respectively, and the depth thereof is 1/2 or more in the thickness direction of the plate-shaped conductive member 4a.
The concave groove 11 does not have to be formed over the entire width of the external electrode 4, but may be formed in a part in the width direction.

A conductive resin 4b is filled between the side surface of the columnar laminated body 1a and the plate-shaped conductive member 4a, and the plate-shaped conductive member 4 is formed.
The exposed surface of a is also covered with the conductive resin 4b.

In the laminated piezoelectric actuator constructed as described above, since the groove 11 is formed in the external electrode 4, the external electrode 4 is easily deformed and follows the expansion and contraction of the columnar laminated body 1a. The external electrode 4 and the protruding conductive terminal 5
An unreasonable load does not act on the connection part between the external electrode 4 and the connection between the protruding conductive terminal 5 and the internal electrode 2, so that the external electrode 4 can be continuously driven even under a high electric field and a high pressure for a long period of time. Therefore, the internal electrode 2 is not disconnected and the durability can be improved.

Further, even if the external electrode 4 made of the plate-shaped conductive member 4a should break from the concave groove 11 due to the repeated stress generated by the expansion and contraction of the columnar laminated body 1a, the broken external electrode 4 pieces are made of conductive resin. Since they are connected by 4b, an electric field can be applied to the internal electrode 2.

FIG. 5 shows a laminated piezoelectric actuator in which a slit is formed in a plate-shaped conductive member. In this laminated piezoelectric actuator, the plate-shaped conductive member 4a has a slit 13 with a predetermined length from one end face. Are formed.
The length of the slit 13 is 2 times the width of the plate-shaped conductive member 4a.
The length is / 3 or more. A conductive resin 4b is filled between the side surface of the columnar laminated body 1a and the plate-shaped conductive member 4a, and the exposed surface of the plate-shaped conductive member 4a is also covered with the conductive resin 4b.

Even with such a laminated piezoelectric actuator, the same effects as those of the laminated piezoelectric actuator shown in FIG. 4 can be obtained. At the time of fabrication, the slit 13 is formed over the entire width of the external electrode 4 made of the plate-shaped conductive member 4a, that is, the external electrode 4 made of the plate-shaped conductive member 4a is divided in advance between the protruding conductive terminals 5. You may keep it.

The groove 11 and the slit 13 formed in the external electrode 4 may be formed after the plate-shaped conductive member 4a is bonded to the protruding conductive terminal 5 of the columnar laminated body 1a, or may be formed in the plate-shaped. The conductive member 4a may be formed before being joined to the protruding conductive terminal 5, but in view of workability in the process of joining the plate conductive member 4a to the protruding conductive terminal 5, the plate conductive member 4 is considered.
It is desirable to form it after joining a to the protruding conductive terminal 5.

Further, in the present invention, as shown in FIG.
The conductive auxiliary member 7 may be formed outside the external electrode 4 made of the plate-shaped conductive member 4a. In this case, by providing the conductive auxiliary member 7 on the outer surface of the plate-shaped conductive member 4a, a large current can be supplied to the actuator, and a large current can flow through the conductive auxiliary member 7 even when the actuator is driven at high speed. For this reason, the current flowing through the external electrode 4 can be reduced, so that the external electrode 4 can be prevented from causing local heat generation and disconnection, and the durability can be significantly improved.

The conductive auxiliary member 7 is preferably formed of a flexible conductive adhesive 7a in order to follow the expansion and contraction of the actuator and prevent disconnection of the conductive auxiliary member 7 during driving. In addition, the conductive adhesive 7
From the viewpoint of preventing cracks from occurring in a, a mesh of metal or the like or a mesh-shaped metal plate may be embedded in the conductive adhesive 7a.

Further, since the conductive adhesive 7a does not deteriorate even when it is driven at a high temperature, it is preferable that the conductive agent is dispersed in a polyimide resin having high heat resistance.

Further, according to the present invention, as shown in FIGS.
As shown in (c), the conductive coil 7b, the conductive corrugated plate 7c, or the conductive fiber aggregate (wool-like) 7
The conductive auxiliary member 7 may be formed by d. In this case, the conductive auxiliary member 7 can follow the expansion and contraction of the actuator, the conductive auxiliary member 7 is disconnected during driving, or stress is applied between the conductive auxiliary member 7 and the external electrode 4. The problem that the conductive auxiliary member 7 is peeled off can be prevented, and the durability can be greatly improved. The conductive auxiliary member 7 and the external electrode 4 are preferably connected by a brazing material or a conductive adhesive.

The conductive auxiliary member 7 is preferably a conductive corrugated plate 7c made of silver because it has a low resistance value and Young's modulus, is highly stretchable, and can reduce the cross-sectional area of the actuator.

The laminated piezoelectric element of the present invention is not limited to these, and various modifications can be made without departing from the scope of the present invention.

In the above example, the external electrodes 4 are formed on the opposite side surfaces of the columnar laminated body 1a. However, in the present invention, for example, a pair of external electrodes may be formed on adjacent side surfaces. .

FIG. 8 shows the injection device of the present invention.
In the figure, reference numeral 31 indicates a storage container. An injection hole 33 is provided at one end of the storage container 31, and a needle valve 35 that can open and close the injection hole 33 is stored in the storage container 31.

A fuel passage 37 is provided so as to be able to communicate with the injection hole 33. The fuel passage 37 is connected to an external fuel supply source so that fuel is always supplied to the fuel passage 37 at a constant high pressure. Therefore, when the needle valve 35 opens the injection hole 33, the fuel supplied to the fuel passage 37 is ejected at a constant high pressure into a fuel chamber (not shown) of the internal combustion engine.

The upper end of the needle valve 35 has a large diameter, and serves as a piston 41 slidable with a cylinder 39 formed in the container 31. The piezoelectric actuator 43 described above is stored in the storage container 31.

In such an injection device, when the piezoelectric actuator 43 is extended by being applied with a voltage, the piston 41 is expanded.
Is pressed, the needle valve 35 closes the injection hole 33, and the supply of fuel is stopped. Further, when the voltage application is stopped, the piezoelectric actuator 43 contracts, and the disc spring 45
Pushes back the piston 41, and the injection hole 33 moves into the fuel passage 37.
Fuel injection is performed in communication with the.

[0096]

Example 1 First, a columnar laminate was prepared. Piezoelectric material has a thickness of 150 μm
Of PZT, the internal electrode was formed of a silver-palladium alloy having a thickness of 3 μm, and the number of laminated layers of the piezoelectric body and the internal electrode was 300 layers.

Next, 60% by volume of silver powder having an average particle size of 5 μm and 40% by volume of borosilicate glass powder having a balance of silicon having a mean particle size of 5 μm as a main component and containing aluminum and having a softening point of 750 ° C. A binder is added to the mixture and sufficiently mixed to prepare a silver glass conductive paste, and the silver glass conductive paste is applied to the side surface of the columnar laminate as shown in FIG. As shown in FIG. 3B, a protruding conductive terminal is formed on the end of the internal electrode exposed on the side surface of the columnar laminated body, and a silicon-containing material for burying the root of the protruding conductive terminal is included. Layers were formed.

Thereafter, as shown in FIG. 3C, a depth of 15 is provided at every other end of the internal electrode including the protruding conductive terminal.
After forming a groove having a width of 0 μm and a width of 50 μm, a plate-shaped conductive member made of silver and having a thickness of 25 μm was formed as shown in FIG.
The protrusion-shaped conductive terminal was pressed at 30 kPa and joined at 900 ° C.

Thereafter, the groove was filled with silicone rubber as an insulator, and the lead wire was connected to the plate-shaped conductive member.

After that, a direct current electric field of 3 kV / mm was applied to the external electrodes of the positive electrode and the negative electrode through the lead wires for 15 minutes to perform polarization treatment, and a laminated piezoelectric actuator as shown in FIG. 1 was produced.

Silver and palladium were dispersed in the protruding conductive terminals. In addition, the surface of the columnar laminated body on which the protruding conductive terminals are formed contains silicon and lead and has a thickness of 1
A silicon-containing layer (glass layer) having a thickness of 0 μm was formed, and a raised portion of the silicon-containing layer was formed at the root of the protruding conductive terminal. In this case, the width B of the protruding conductive terminals in the same direction as the stacking direction is 10 μm, and the height h is 2 on average.
The height variation was 0 μm and the height variation was 2 μm. The thickness d of the silicon-containing layer was calculated as the thickness from the portion where Si element is substantially absent in the X-ray diffraction measurement.

Further, each protruding conductive terminal and the external electrode made of a plate-shaped conductive member were joined at 85% or more of the tip length of the protruding conductive terminal. This bonding ratio was calculated by the length ratio of the part that was bonded and the part that was not bonded after the external electrode was peeled off from the protruding conductive terminal.

The obtained laminated piezoelectric actuator has 15
As a result of applying a DC voltage of 0 V, a displacement amount of 40 μm was obtained in the stacking direction. Further, as a result of performing a drive test by applying an AC voltage of 0 to +150 V at a frequency of 120 Hz to this actuator at a frequency of 120 Hz, a displacement amount of 40 μm was obtained when the actuator was driven up to 1 × 10 ⁹ cycles. I couldn't see it. Sample No. of Table 1 It is described in 1. Example 2 Next, a laminated piezoelectric element having the same configuration as in Example 1 except that the width B and height h of the protruding conductive terminal and the thickness t of the plate-shaped conductive member were changed as shown in Table 1. Actuators (Samples No. 2 to No. 7) were produced. Sample N
o. In No. 8, a glass paste in which silver is dispersed is applied and heat-treated to form an external electrode.

An AC voltage of 150 V was applied to the obtained laminated piezoelectric actuator at room temperature at a frequency of 120 Hz, and a drive test was conducted. The amount of displacement initially obtained was 40 μm in all the samples (No. 1 to 8). The results obtained are shown in Table 1.

[0105]

[Table 1]

Sample No. 1 in all samples other than the sample in which the external electrode was formed of silver glass of 8
When driven up to × 10 ⁸ cycles, a displacement of 40 μm was obtained, and no abnormality of the external electrode was observed. Sample No. in which the external electrode was formed of silver glass. In the case of No. 8, the external electrode made of silver glass could not follow the expansion and contraction of the actuator, peeling occurred between the external electrode and the internal electrode, and the external electrode was sparked in a short time. On the other hand, Sample No. 1 having an external electrode composed of a protruding conductive terminal and a plate-shaped conductive member was formed. In the cases of Nos. 1 to 7, no abnormality such as breakage was observed in the external electrodes because the protruding conductive terminals could follow the expansion and contraction of the actuator even after driving up to 1 × 10 ⁸ cycles.

When the driving was further continued, the width of the protruding conductive terminals was 75 μm or less, the height h was 7.5 μm or more,
Sample N in which the thickness t of the plate-shaped conductive member is 50 μm or less
o. Since Nos. 1, 2, 3, and 6 have sufficiently low resistance at the joint between the external electrode and the internal electrode and can sufficiently absorb the stress generated by the expansion and contraction of the actuator, 1 × at high speed.
Even when continuously driven for 10 ⁹ cycles, the displacement was hardly reduced, and no abnormality was found in the external electrodes. Example 3 Next, a laminated piezoelectric actuator having the same configuration as in Example 1 was prepared except that the conductive auxiliary member shown in Table 2 was provided outside the plate-shaped conductive member. Sample No. 1 shows the sample of Example 1.

An AC voltage of 150 V was applied to the obtained laminated piezoelectric actuator at room temperature at a frequency of 120 Hz, and a drive test was conducted. The amount of displacement initially obtained was 40 μm in all the samples (No. 1, 9 to 12). Further, when a drive test was conducted up to 1 × 10 ⁹ cycles under the same conditions, all samples (No. 1, 9 to
No abnormality was found in 12).

Next, in order to perform driving under more severe conditions, an AC voltage of 200 V was applied at a frequency of 240 Hz at room temperature, and a drive test was conducted. The results are shown in Table 2.

[0110]

[Table 2]

From Table 2, sample No. In No. 1, the external electrode locally generates heat in response to a large current that is applied when the actuator is driven at high speed, disconnection occurs at a part inside the external electrode, and the displacement amount is reduced.

On the other hand, Sample No. 1 having a conductive auxiliary member formed on the outside of the external electrode. Nos. 9 to 11 cause local heat generation in the external electrode or disconnection of the external electrode even when a large current is applied to the actuator and continuously driven at high speed, because the resistance of the external electrode is sufficiently low. Since it was not present, no abnormality was observed even after driving up to 1 × 10 ⁹ cycles. Example 4 Next, except that the mixing ratio of the silver powder and the glass powder in the silver glass paste used for forming the protruding conductive terminal, the softening point of the glass, and the coating amount of the silver glass paste were changed, Piezoelectric actuators were manufactured in the same manner as in Example 1 except that the thickness d of the silicon-containing layer, the height h of the protruding conductive terminal, and the height of the raised portion from the silicon-containing layer were changed.
Described in. The protruding conductive terminals and the plate-shaped conductive member were joined together at 85% or more of the tip length of the protruding conductive terminals.

An AC voltage of 0 to +150 V was applied to the obtained laminated piezoelectric actuator at room temperature at a frequency of 120 Hz, and a drive test was conducted. The obtained results are shown in FIG.

[0114]

[Table 3]

From FIG. 9, the thickness d of the silicon-containing layer is 2-1.
With a sample of 00 μm, even when continuously driven at high speed,
It can be seen that there is no problem such as disconnection or sparking between the internal electrode and the external electrode, and high reliability is provided.

[0116]

According to the laminated piezoelectric element of the present invention, the protruding conductive terminals projecting from the side surface of the columnar laminated body are provided at the end portions of the internal electrodes every other layer, and the protruding conductive terminals and the plate are provided. Since the external electrode made of a conductive member is joined, the stress generated by the expansion and contraction of the laminated piezoelectric element can be sufficiently absorbed, and there are problems such as contact failure between the external electrode and the internal electrode and disconnection of the external electrode. Therefore, it is possible to provide a multilayer piezoelectric element having high reliability.

[Brief description of drawings]

FIG. 1 is a view showing a laminated piezoelectric element of the present invention, (a)
Is a perspective view, (b) is a longitudinal sectional view taken along the line AA 'of (a), (c) is a perspective view showing a part of (a) in an enlarged manner,
(D) is sectional drawing which expands and shows a part of (b).

FIG. 2 is a cross-sectional view taken along the line BB ′ of FIG. 1 (c) for explaining the joining state between the tip end portion of the protruding conductive terminal and the plate-shaped conductive member.

FIG. 3 is a schematic view showing a method of manufacturing a laminated piezoelectric element of the present invention.

4A and 4B show a laminated piezoelectric actuator in which a groove is formed in a plate-shaped conductive member, wherein FIG. 4A is a perspective view and FIG. 4B is a vertical cross-sectional view taken along the line AA of FIG. .

5A and 5B show a laminated piezoelectric actuator in which a slit is formed in a plate-shaped conductive member, FIG. 5A is a perspective view, and FIG.
FIG. 4A is a vertical sectional view taken along line AA of FIG.

6A and 6B show a laminated piezoelectric element in which a conductive auxiliary member is formed, wherein FIG. 6A is a perspective view, and FIG. 6B is AA ′ of FIG.
It is sectional drawing which followed the line.

FIG. 7 (a) is a coil-shaped conductive auxiliary member, FIG. 7 (b) is a corrugated conductive auxiliary member, and FIG. 7 (c) is a laminated type of the present invention when a wool-shaped conductive auxiliary member is used. It is a longitudinal cross-sectional view of a piezoelectric element.

FIG. 8 is an explanatory view showing an injection device of the present invention.

FIG. 9 is a graph showing the results of a drive test of Example 4.

FIG. 10 is a vertical sectional view of a conventional laminated piezoelectric actuator.

[Explanation of symbols]

1 ... Piezoelectric body 1a: Columnar laminated body 2 ... internal electrodes 4 ... External electrode 4a: plate-shaped conductive member 4b ... Conductive resin 5: protruding conductive terminal 5a ... Root 7 ... Conductive auxiliary member 7a ... Conductive adhesive 7b ... Conductive coil 7c ... Conductive corrugated plate 7d ... Conductive fiber assembly 10 ... Silicon-containing layer 10a ... Protuberance 11 ... Concave groove 13 ... Slit 31 ... Storage container 33 ... Injection hole 35 ... Valve 43 ... Piezoelectric actuator

Claims (15)

[Claims] 1. A columnar laminated body formed by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes, and a pair provided on the side surface of the columnar laminated body, wherein the internal electrodes are alternately connected to every other layer. A multilayer piezoelectric element comprising an external electrode of
Protruding conductive terminals protruding from the side surface of the columnar laminated body are provided at every other end of the internal electrode, and the protruding conductive terminals are joined to the external electrodes made of a plate-shaped conductive member. A laminated piezoelectric element characterized by: 2. The laminated piezoelectric element according to claim 1, wherein a root portion of the protruding conductive terminal is embedded in a silicon-containing layer formed on a side surface of the columnar laminated body. 3. The multilayer piezoelectric element according to claim 1, wherein the silicon-containing layer has a thickness of 2 to 100 μm. 4. The laminated piezoelectric element according to claim 1, wherein a raised portion of the silicon-containing layer is formed around the protruding conductive terminal. 5. The projecting conductive terminal and the external electrode are joined together at a portion of 50% or more of the tip length of the projecting conductive terminal. The laminated piezoelectric element according to any one of claims. 6. The laminated piezoelectric element according to claim 1, wherein the thickness of the plate-shaped conductive member is 50 μm or less. 7. The laminated piezoelectric element according to claim 1, wherein a slit or a groove is formed in the plate-shaped conductive member between the protruding conductive terminals. 8. A conductive resin is filled between the plate-shaped conductive member and the side surface of the columnar laminated body.
8. The laminated piezoelectric element according to any one of 1 to 7. 9. The laminated piezoelectric element according to claim 1, wherein a conductive auxiliary member is provided on the outer surface of the plate-shaped conductive member. 10. The laminated piezoelectric material according to claim 9, wherein the conductive auxiliary member is made of at least one of a conductive adhesive, a conductive coil, a conductive corrugated sheet and a conductive fiber aggregate. element. 11. The laminated piezoelectric element according to claim 1, wherein the protrusion-shaped conductive terminal and the plate-shaped conductive member contain silver as a main component. 12. A step of producing a columnar laminate in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and the end portions of the internal electrodes are exposed on the side surfaces, and a step of forming the columnar laminate on the side surfaces. ,
A step of applying a conductive paste containing a solid component consisting of 50 to 80% by volume of a conductive metal powder and 20 to 50% by volume of a glass powder containing silicon as a main component, and a step of applying to the side surface of the columnar laminate. A step of heating a conductive paste to form projecting conductive terminals projecting from the side surface of the columnar laminated body at the ends of the internal electrodes; and a plate-shaped conductive member at the tip of the projecting conductive terminals. And a step of connecting an external electrode. 13. The height variation of the protruding conductive terminals formed by heating the conductive paste is not more than 0.3 times the average height of the protruding conductive terminals. Item 13. A method for manufacturing a laminated piezoelectric element according to item 12. 14. A step of producing a columnar laminated body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and an end portion of the internal electrode is exposed on a side surface, and a side surface of the columnar laminated body. Between the external electrodes made of a plate-shaped conductive member, 50 to 80% by volume of conductive metal powder and silicon are coated so as to cover the exposed end portions of the internal electrodes and the piezoelectric body surface in the vicinity thereof. The step of interposing a conductive paste containing a solid component consisting of 20 to 50% by volume of glass powder as a main component, and heating the conductive paste to form the columnar stacks at every other end at the end of the internal electrode. And a step of forming a protruding conductive terminal projecting from a side surface of the body and bonding the external electrode to a tip end portion of the protruding conductive terminal. 15. An accommodating container having an ejection hole, the laminated piezoelectric element according to claim 1 accommodated in the accommodating container, and the ejection hole by driving the laminated piezoelectric element. An injection device comprising a valve for ejecting liquid from the injection device.