JPH09148638A - Multilayered piezoelectric actuator and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To electrically connect multilayered piezoelectric actuator elements and improve productivity, by forming two cylindrical air gaps inside the elements, forming insulator bodies wherein inner electrode exposed parts in the air gaps are arranged zigzag on the wall surfaces, and filling the air gaps with conducting elastic material. SOLUTION: A plurality of piezoelectric sheets on which conducting paste of silver palladium is printed are laminated and sintered, and a lamination body 3 of piezoelectric ceramic 1 and inner electrodes 2 is formed. In the lamination body 3, all inner electrodes are exposed on a pair of facing surfaces. On a pair of the other facing surfaces, the inner electrodes 2 are exposed on every other layers, so that the same electrodes are not exposed. Air gaps 5 are formed by ultrasonic working, and the electrodes 2 are exposed on the inner walls. One row out of two adjacent rows of air gaps of the lamination body 3 is covered with coating material 7, and insulator bodies 6a, 6b are formed. The two air gaps are filled with elastic silver paste, and the elements are electrically connected. Production is possible by a little assembling manhour.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator and a method of manufacturing the same, and more particularly to a laminated piezoelectric actuator having two cylindrical voids in which an insulator is formed and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional laminated piezoelectric actuator will be described with reference to FIG.

FIG. 8 is a perspective view showing the structure of an example of a conventional laminated piezoelectric actuator. Referring to the figure, this laminated piezoelectric actuator has a laminated structure in which piezoelectric ceramics 1 exhibiting a piezoelectric effect and internal electrodes 2 are alternately laminated, and lead wires 13 are soldered above and below this laminated body 3. A protective layer 16 to be the portion 15 is provided.

The internal electrodes 2 are exposed on the four side faces of the laminate 3, but the two facing ones of the four side faces.
On one side (in the figure, the front side and the back side),
An insulator 6c such as glass is formed on the exposed portion of the internal electrode 2 and the piezoelectric ceramic 1 in the vicinity of the exposed portion, and the external electrode 4 is further provided thereon in a strip shape in the stacking direction (vertical direction in the drawing). ing.

In this case, the insulators 6c are formed so as to cover the exposed portions of the internal electrodes 2 every other layer, and are also staggered on the above-mentioned two side surfaces. The lead wire 13 is attached to the external electrode 4 by soldering,
When a voltage is applied to both ends of the lead wire 13, each piezoelectric ceramic 1 sandwiched by the internal electrodes 2 is displaced, and the laminated body 3 is displaced in the laminating direction.

In the laminated piezoelectric actuator having the above-mentioned structure, a lead lead-out portion (external electrode 4) for applying a voltage is required, but since the internal electrode 2 has a structure exposed on the side surface, Insulator 6 for every other internal electrode 2
Since it is necessary to provide c, it is difficult to manufacture various shapes (for example, a perfect circle) depending on the use.

Further, since the lead wire 13 is soldered from the side surface of the element to the voltage application portion, it takes a lot of time and labor for the production, and the space for soldering (protective layer 16) is reliable. It is difficult to reduce the size of the element in the stacking direction because it is necessary to provide the element.

As one of means for solving the above problems,
As shown in FIG. 9, a structure of a laminated piezoelectric actuator in which two void portions 5 are provided inside the element is conceivable (Japanese Patent Application Laid-Open No. Hei 3 (1999)).
(See JP-A-151677).

FIG. 10 shows a manufacturing process diagram of the laminated piezoelectric actuator described in the above publication.

Referring to the figure, in order to manufacture this laminated piezoelectric actuator, first, PbO, TiO ₂ , ZrO is prepared.
₂ , Sr ₂ O _3, etc. are mixed, and the mixed powder is pressure-molded on a disc with a die having pins forming two voids 5 (hole diameter 1 to 2 mmφ), and then temporarily held at 800 ° C. Bake.

The piezoceramic element thus obtained is ground to a predetermined size, and then Ag-Pd paste is applied by printing.

Referring to FIG. 11 at the time of printing, the internal electrode 2 is applied to one void 5 of the piezoelectric ceramic element 14 so as to extend to the edge of the hole, and the other void 5 is concentric with this. The internal electrode 2 is applied with a slightly larger blank 17 provided.

The internal electrodes 2 are also printed on the back surface of the same piezoelectric ceramic element 14.

At this time, on the back surface side of the void 5 in which the internal electrode 2 extends to the edge of the hole on the front surface side, the internal electrode 2 is coated by providing a slightly larger blank portion 15 concentric with the void 5 and vice versa. The back side of the void 5, which is insulated by providing a blank portion 15 on the side, extends to the edge of the hole to print the internal electrode 2.

As shown in the longitudinal sectional view of FIG. 9, the piezoelectric ceramic element 14 thus printed is alternately laminated with the front surface and the back surface reversed, and sintered at 1150 ° C. under pressure to laminate. Get 3.

Then, the conductive elastic body is placed at a pressure of several atmospheres,
The laminated piezoelectric actuator is completed by press-fitting into the void 5 of the laminated body 3 and filling it without any gap.

In this laminated piezoelectric actuator, two voids 5 are provided inside the laminated piezoelectric actuator element.
By filling the inside with a conductive elastic body, it is electrically connected in parallel, so that it is not necessary to provide a voltage application portion from the side surface of the element by soldering 15 the lead wire 13 to the side surface of the laminated piezoelectric actuator. Also, it is not necessary to provide the insulator 6c on the side surface.

Therefore, the insulator 6 is provided on each of the left and right sides alternately.
Since it is not necessary to provide c, it is possible to manufacture various shapes such as a perfect circle depending on the use of the laminated piezoelectric actuator.

Since it is not necessary to provide the voltage applying section from the side surface, productivity can be improved.

[0020]

A first problem is that it is difficult to improve productivity in manufacturing a laminated piezoelectric actuator in the conventional technique. The reason is that, in the laminated piezoelectric actuator described in the above publication, in order to form one laminated body 3, one piezoelectric ceramic element 14 is prepared and polished to a predetermined size, and then the front and back surfaces are complicated. This is because the internal electrodes 2 of the pattern are applied, and the piezoelectric ceramic elements 14 are laminated one by one with the voids 5 aligned with each other and integrally fired under pressure.

The second problem is that in the prior art, it is quite difficult to manufacture the laminated piezoelectric actuator so that the internal electrode 2 and the external electrode 4 can be reliably connected to each other.

The reason is that, in the laminated piezoelectric actuator described in the above publication, the void 5 is provided inside the element, and the void 5
Since a voltage application part is formed from the part, a small void 5 (1 to 2 mmφ) is provided together at the time of pressure molding so that a shape suitable for use can be created, and then 800 ° C. to prevent warpage.
It is supposed to be calcined in.

The temperature of this calcination is 800 ° C., which is 11 during the main firing.
Although the temperature is set lower than 15 ° C, the shrinkage of the ceramic material starts at about 600 ° C.

Regarding the shrinkage of this ceramic system, even if the same powder is used, there is a great possibility that the shrinkage state will change due to the mixed state of various oxides or the variation of the dimensions, and the shrinkage state is constant. It is not possible to prevent variations from occurring.

Therefore, even if the void 5 is not filled up due to the difference in shrinkage at the time of calcination, there is a possibility that the size and shape of the void may vary, and further the internal electrode 2 is applied thereafter. This is because there is a possibility that the positions of the overlapping voids 5 may be displaced when they are stacked.

The third problem is that it is difficult to reduce the size and the voltage in the length direction.

The reason for this is that, in the laminated piezoelectric actuator described in the above publication, an oxide such as PbO is mixed and the mixed powder is pressed into a disk shape by a die having pins that form the voids 5 at two places. After molding, the piezoelectric ceramic element 14 is prepared by calcining at 800 ° C. and polished to a predetermined size. However, for polishing, it is necessary to set the distance between layers to a certain size or more. Is.

The present invention has been made in order to solve the above-mentioned conventional problems, and the purpose thereof is to improve the productivity, to make the size more efficient, and to easily form various shapes according to the use. It is to provide a laminated piezoelectric actuator that can be manufactured.

[0029]

A laminated piezoelectric actuator of the present invention is an element in which a plurality of thin plate piezoelectric ceramic films and internal electrode films are alternately laminated, and two cylindrical voids are provided inside the element. Insulators are provided (5 in FIG. 1) and the inner electrode exposed portions in each void are staggered on the wall surface of the cylindrical void (6 in FIG. 3), and in the void. The laminated piezoelectric actuator element is electrically connected by filling a conductive elastic member (4 in FIG. 1).

Furthermore, the distance between the cylindrical voids inside the element (A in FIG. 1) is 0.5 mm or more, the size of the cylindrical voids (B in FIG. 1), and the diameter is 1.5 mm. The above is also characterized in that the outer dimension (C in FIG. 1) passing through the centers of the two cylindrical void portions is 5 mm or more.

Further, the present invention is also characterized in that the insulators (6a, 6b in FIG. 3) formed in the cylindrical void portion inside the element are deposited by the electrophoresis method (FIG. 5).

[0032]

Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the structure of the laminated piezoelectric actuator according to the first embodiment of the present invention, and FIG. 2 is a process drawing for explaining the manufacturing method thereof.

A method of manufacturing this laminated piezoelectric actuator is shown in FIGS. 3 and 4.

FIG. 3 shows the step of FIG. 4 in the AA 'cross section.

Referring to FIG. 3, the laminated piezoelectric actuator of this embodiment differs from the conventional laminated piezoelectric actuator shown in FIG. 9 in that insulators 6a and 6b are provided in two voids 5 inside the element. It is that you are.

In this case, the above-mentioned insulators 6a, 6b are formed so as to cover the exposed portions of the internal electrodes 2 every other layer, and in addition, the above-mentioned two voids 5 are staggered.

Therefore, the external electrode 4 in the space 5 on the right side is
All the even-numbered internal electrodes 4 from the top are connected so as to have the same potential, and the external electrodes 4 in the voids 5 on the left side are connected so that the odd-numbered internal electrodes 2 have the same potential.

Here, a pair of lead wires 13 are attached, for example, by soldering, and when a voltage is applied to both ends of the lead wires 13, the respective piezoelectric ceramics 1 sandwiched by the internal electrodes 2 are displaced, and the laminated body 3 is laminated. It is displaced in the direction.

Further, referring to FIG. 2, the manufacturing method of the present embodiment is different from the conventional manufacturing method shown in FIG. 10 in that after firing, the voids 5 inside the element are subjected to a mechanical method such as ultrasonic machining. The point that the piezoelectric ceramics 1 are formed, the point that the piezoceramic 1 is formed into a sheet shape, laminated and then fired to form several tens of laminated bodies at one time, and finally separated into individual parts, and that there are two voids 5
This is the point that the insulators 6a and 6b are provided so that the exposed portions of the internal electrodes in the portions are staggered from each other.

Embodiments of the present invention will be described below in order with reference to FIGS. 2, 3 and 4.

The laminated piezoelectric actuator of the present invention is shown in FIG.
As shown in FIGS. 4 (a) and 4 (a), first, a plurality of piezoelectric ceramic sheets printed with a silver-palladium conductor paste were laminated and press-debinding was performed to laminate the piezoelectric ceramic 1 and the internal electrode 2. The laminated body 3 is obtained.

In the laminated body 3, all the internal electrodes 2 are exposed on one pair of side faces facing each other, and the internal electrodes 2 are exposed on every other pair of side faces, which are the same in each case. The internal electrode 2 is not exposed.

Every other layer, the temporary surfaces 8a and 8b are formed on the exposed surface of the internal electrode 2 with silver paste or conductive resin.
To form

The void 5 is formed by ultrasonic processing or the like.

The inner electrode 2 is exposed on the inner wall of the void 5 as shown in FIG. 3 (a).

Next, the two adjacent layers of the laminated body 3 of FIG.
One of the rows of voids 5 is covered with a covering material 7 such as an adhesive tape or a masking agent, and an insulator 6a is formed by electrophoresis.

As shown in FIG. 5, the insulator 6a disperses powder particles made of an inorganic substance such as glass or ceramic in the container 11 or an insulator such as a polymer such as polyamide, polyimide, fluorine resin, or epoxy. A voltage is applied between the reference electrode 9 and the temporary electrodes 8a and 8b on one side of the laminated body 3 by immersing in the suspension 10 thus prepared.

The other temporary electrode 8b is connected to the reference electrode 9. When the power source 12 is connected between the temporary electrode 8a and the reference electrode 9 and a voltage is applied in this way, the particles of the insulating material in the suspension 10 are moved by the electric field, and the particles in FIG. As in b), only the internal electrode 2 of the laminated body 3 which is connected to the temporary electrode 8a is attached to form the insulator 6a.

The insulator forming method according to this method is generally called an electrophoresis method.

The laminated body 3 having the insulator 6a attached thereto is suspended in the suspension 1
It is taken out from 0 and the covering material 7 is peeled off.

Next, as shown in FIGS. 3 (c) and 4 (c), the covering material 7b is applied to the row of voids in which the insulator 6a is formed.
Then, a voltage is applied between the temporary electrode 4b and the reference electrode 9 opposite to the above, the insulator 6b is formed, the covering material 7 is peeled off, and the insulator 6a and 6b are laminated by heating. Stick to.

In this example, a mixed solution of ethanol and an electrolyte in which glass powder is dispersed in insulator particles to be the insulators 6a and 6b is used as a suspension 10 and a voltage of 20 V is applied for 5 minutes and then 650 ° C. is set to 20. The insulators 6a and 6b having a thickness of about 50 μm were fixed by heating with a profile maintained for a minute.

As a result of the above operation, the exposed internal electrodes 2 in the two voids provided inside the element of the laminated body 3 as shown in FIG.
It will be covered with a and 6b.

Next, an elastic silver paste or a conductive resin is injected into the voids at two positions of the laminate 3 at a pressure of several atmospheres, and the mixture is filled without leaving a gap and fired, and then cut into a predetermined shape. A laminated piezoelectric actuator as shown in is obtained.
The external electrode 4 in the void 5 can also be formed by electroless plating or the like. Example 1 Below, a DC voltage of 200 V is applied to the laminated piezoelectric actuator of the present embodiment manufactured as described above and the conventional laminated piezoelectric actuator shown in FIG. 9 to measure the maximum displacement amount. The results will be described.

The theoretical value of the displacement amount per unit electric field is 100
The percentage is shown in FIG.

The sample has a piezoelectric ceramic 1 thickness of 5
00 μm, the number of layers of the internal electrode 2 is 20, and the size of the void φ
1.5 mm, cross-sectional shape perpendicular to the displacement direction has an outer diameter of 5 m
m, the length in the displacement direction is 15 mm.

The piezoelectric ceramic 1 is made of Pb (Ni1 / 3N).
b2 / 3) _0.50 Zr _0.15 Ti _0.35 O ₃ based perovskite structure composite compound, and the internal electrode 2 is a silver / palladium mixed electrode containing 70% silver and 30% palladium.

The external electrode 4 was formed by using silver as a conductor.

It can be seen from FIG. 6 that the present invention exhibits a displacement amount closer to the theoretical value as compared with the conventional example.

The displacement of the laminated piezoelectric actuator produced by the conventional method was smaller because the size of the void 5 and the void 5 were different due to the variation in the contracted state during calcination (800 ° C.) of the piezoelectric ceramic element 14. It is considered that there is a variation in the position and the connection between the internal electrode 2 and the external electrode 4 is deteriorated. [Embodiment 2] Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

The method of manufacturing the laminated piezoelectric actuator is the same as that of the first embodiment.

However, the thickness of the sample piezoelectric ceramic 1 is set to 105 μm.

In this embodiment, the intervals A between adjacent voids are 0.3 mm, 0.4 mm, 0.45 mm and 0.50 m.
m, 0.6 mm, 0.8 mm.

A reliability test was conducted on each laminated piezoelectric actuator.

The reliability test was repeated durability test at 150 V and 1 kHz.

Referring to Table 1, in the example, when the space between the adjacent voids 5 was less than 0.5 mm, the dielectric breakdown occurred in 10 ¹⁰ cycles or less, whereas when it was 0.5 mm or more, the dielectric breakdown occurred.
It was able to operate for more than 0 ¹² cycles.

This is because when the distance between the two voids 5 is too short, the two voids 5 can be opened at one time, but microcracks are generated due to impact due to vibration when opening.
It is considered that this is because the conductor expands when it is movable or when the conductor for the external electrode 4 is press-fitted, resulting in a short circuit.

[0068]

[Table 1] Although the laminate 3 has a circular cross-sectional shape in this example, similar results were obtained with other shapes (for example, quadrangle and triangle). [Third Embodiment] FIG. 1 is a perspective view showing the structure of a laminated piezoelectric actuator according to a third embodiment of the present invention. The method of manufacturing the laminated piezoelectric actuator is the same as that of the second embodiment.

In this embodiment, the size B of the void 5 inside the laminated body 3 is 0.5 mm, 1 mm, 1.5 mm, 2.0 m.
m and 5 mm.

The displacement amount of each laminated piezoelectric actuator was measured in the same manner as in the first embodiment.

With reference to FIG. 7, in the example, the amount of displacement was close to the theoretical value when the size of the void 5 was 1.5 mm or more.

The displacement amount was less than 1.5 mm because the gaps 5 were too small.
This is considered to be because when applied by the electrophoresis method, the layers are not selectively attached to each layer, and even the adjacent internal electrodes 2 are covered with each other so that electrical conduction cannot be properly established.

In this embodiment, the laminated body 3 has a circular cross-sectional shape as an example, but other shapes (for example,
Similar results were obtained with squares and triangles). [Fourth Embodiment] Next, a fourth embodiment of the present invention will be described.

The manufacturing method and structure of the laminated piezoelectric actuator are the same as those in the second and third embodiments.

In this embodiment, the outer dimensions C passing through the centers of the two voids 5 inside the laminate 3 are 4.0 mm and 4.5 m.
m, 5.0 mm, 6.0 mm, and 10 mm.

A reliability test was conducted on each laminated piezoelectric actuator.

The reliability test was conducted in the same manner as in Example 2.

With reference to Table 2, in the examples, when the size of the outer dimension C was less than 5.0 mm, the dielectric breakdown occurred in 10 ¹⁰ cycles or less, while when it was 5.0 mm or more, the dielectric breakdown occurred.
It was able to operate for more than ¹² cycles.

This means that when the external dimension C is small, that is,
It is presumed that this is because when the distance from the outer shape of the element to the void 5 is short, the distance between the void 5 and the side surface becomes considerably short due to the cutting accuracy of ± 50 μm at the time of cutting. It is also considered that, when the laminated body 3 is driven, the stress applied to the element increases as it goes outward from the center of the element, and therefore it is difficult to withstand the endurance stress if it is too thin.

[0080]

[Table 2] In this example, the laminate 3 has a circular cross-sectional shape, but similar results were obtained with other shapes.

[0081]

The first effect is that it is possible to produce laminated piezoelectric actuators of various shapes with high productivity and with a small number of assembling steps depending on the use. The reason is that several tens of laminated bodies 3 can be created at one time.

The second effect is that the internal electrode portion 2 and the external electrode 4 are
It can be realized with a small number of man-hours with high productivity to make sure that the can be connected. The reason is that it is possible to mechanically provide the voids 5 after the laminated and integrally fired, and to easily and selectively form the insulators 6a and 6b in the voids 5 by the current technology. This is because it is possible to ensure reliable insulation every other time.

The third effect is that size reduction and voltage reduction in the length direction can be facilitated with high productivity. The reason is that the piezoelectric ceramic 1 is formed in a sheet shape, and the internal electrodes 2 are laminated after printing and before firing, so that the distance per layer can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a laminated piezoelectric actuator of the present invention.

FIG. 2 is a process drawing showing the manufacturing method according to the embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a laminate according to each manufacturing process of the present invention.

FIG. 4 is a perspective view of a laminate according to each manufacturing process of the present invention.

FIG. 5 is an apparatus for forming an insulator by the electrophoretic method of the present invention.

FIG. 6 is a diagram showing a displacement amount per unit electric field strength of the laminated piezoelectric actuator of Example 2 of the present invention.

FIG. 7 is a diagram showing a displacement amount per unit electric field strength of the laminated piezoelectric actuator of the fourth embodiment.

FIG. 8 is a perspective view of a conventional laminated piezoelectric actuator.

FIG. 9 is a vertical sectional view of a conventional laminated piezoelectric actuator.

FIG. 10 is a process drawing showing the conventional manufacturing method.

FIG. 11 is a trihedral view ((a) plan view, (b) sectional view, (c) rear view) of a laminated ceramic element that constitutes a conventional laminated body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic 2 Internal electrode 3 Laminated body 4 External electrode 5 Voids 6a, 6b, 6c Insulator 7 Coating material 8a, 8b Temporary electrode 9 Reference electrode 10 Suspension 11 Container 12 Power supply 13 Lead wire 14 Piezoceramic element 15 Soldering Part 16 Protective layer 17 Blank part

Claims (5)

[Claims] 1. A device in which a plurality of thin plate piezoelectric ceramic films and internal electrode films are alternately laminated, wherein two cylindrical voids are provided inside the device, and a wall surface between the cylindrical voids is provided. Insulators are formed so that the exposed portions of the internal electrodes in each void are staggered, and the laminated piezoelectric actuator element is electrically connected by filling the voids with a conductive elastic member. A laminated piezoelectric actuator characterized by: 2. The laminated piezoelectric actuator according to claim 1, wherein the distance between the cylindrical voids inside the element is 0.5 mm or more. 3. The laminated piezoelectric actuator according to claim 1, wherein the cylindrical void portion inside the element has a diameter of 1.5 mm or more. 4. The laminated piezoelectric actuator according to claim 1, wherein an outer dimension passing through the centers of two cylindrical voids inside the element is 5 mm or more. 5. The method of manufacturing a laminated piezoelectric actuator according to claim 1, wherein the insulator is deposited by an electrophoretic method.