JPH0864881A - Layered piezoelectric actuator - Google Patents

Abstract

PURPOSE: To eliminate the damage to an external electrode by driving and to reduce the danger of earth leakage by forming an inner electrode except parts to be covered at both sides of each piezoelectric ceramic board, and forming the external electrode electrically connected to the inner electrode of each layer at both sides of the layer parallel to the displacing direction of the board. CONSTITUTION: An inner electrode 13 is so formed that the length of the electrode 13 in a displacing direction is longer by the length of a part 12 to be covered than the length of a piezoelectric ceramic board 11 in its displacing direction not to be exposed with a fixed end face 10c and a driving end face 10d. The electrode 13 is extended to be formed at inner electrode part 13a and an inner electrode part 13b alternately exposed with two opposed sides 10e, 10f parallel to the displacing direction of a laminated piezoelectric actuator 10 at each one layer with the part 12 to be covered. Thus, even if a voltage is applied when an object to be driven or a fixed object is metal, danger of earth leakage is low, and the driving end face can be pressed in direct contact with the object to be driven. Further, the fixed end face can be adhered directly with the fixed object.

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 more particularly to a laminated piezoelectric actuator used for precise positioning, or a laminated piezoelectric actuator used for an ink jet printer head or the like.

[0002]

2. Description of the Related Art Conventionally, when a stress is applied, an electric field proportional to the stress is generated, and when an electric field is applied, a strain proportional to the electric field is generated, or a mechanical stress is generated. Utilizing its characteristics, it is used in various applications such as vibrators, filters and actuators. Among them, the laminated piezoelectric actuator that utilizes mechanical strain in proportion to the applied electric field has a precise displacement amount, and the displacement amount can be freely adjusted depending on the number of stacked piezoelectric bodies or the length in the displacement direction. It has many excellent characteristics such as choice, low power consumption, low heat generation and low noise generation. Therefore, the laminated piezoelectric actuator has been widely used in the fields of precision positioning, inkjet printer heads, etc. by utilizing these characteristics.

There are mainly two types of laminated piezoelectric actuators which utilize the piezoelectric vertical effect and those which utilize the piezoelectric lateral effect. FIG. 7 is a schematic perspective view showing a laminated piezoelectric actuator 50 utilizing the piezoelectric vertical effect, and is indicated by an arrow A in the figure.
The direction is the displacement direction. From the fixed end surface 50a to the drive end surface 5
From 0b, about 150 to 350 piezoelectric ceramic substrates 51 having a thickness of 100 to 300 μm are usually stacked. On the laminated surface of the piezoelectric ceramic substrate 51 that has been subjected to the polarization treatment, an internal electrode 53 made of a metal plating layer or the like is formed except for the non-adhered portion 52, and the piezoelectric ceramic substrate 51 on which the internal electrode 53 is formed. Are laminated such that the polarization directions of the layers are opposed to each other. The ends of the internal electrodes 53 are alternately exposed on two opposing side surfaces 50c and 50d parallel to the displacement direction, and the external electrodes 54 are formed on the exposed stacked side surfaces of the internal electrodes 53, respectively. And the internal electrode 53 are electrically connected. The external electrode 54 is electrically led to the outside by a lead terminal (not shown).

In the laminated piezoelectric actuator 50 utilizing the piezoelectric vertical effect configured as described above, the external electrode 54 is usually formed on the surface parallel to the displacement direction, so that the driving end surface which is the laminated side surface perpendicular to the displacement direction. No external electrode is formed on 50b. Therefore, friction between the external electrode 54 and the object to be driven due to driving does not occur, and the external electrode 54 is less likely to be damaged. Further, since the external electrode 54 is not formed on the fixed end surface 50a, it is easy to mount and fix. Also, the piezoelectric ceramic substrate 5
Since the displacement output is increased by increasing the number of laminated layers of 1, there are advantages such as excellent load bearing characteristics.

However, in the laminated piezoelectric actuator 50 utilizing the piezoelectric longitudinal effect, it is needless to say that a high voltage close to the dielectric breakdown voltage of the piezoelectric ceramic substrate 51 is applied to operate in order to obtain the maximum displacement output. Since a large number of piezoelectric ceramic substrates 51 must be stacked in order to obtain a desired displacement amount, there is a problem that the manufacturing process becomes complicated.

Therefore, recently, a laminated piezoelectric actuator utilizing the piezoelectric lateral effect capable of obtaining a large displacement amount even if the number of laminated layers is small has begun to be used. The laminated piezoelectric actuator utilizing the piezoelectric lateral effect can increase the displacement amount by increasing the length in the displacement direction even with a small number of piezoelectric ceramic substrates.
FIG. 8 shows a schematic perspective view of a laminated piezoelectric actuator 60 utilizing the piezoelectric lateral effect. The arrow B direction in the drawing is the displacement direction, and about 20 to 30 piezoelectric ceramic substrates 61 having a normal thickness of 20 to 100 μm are stacked. On the laminated surface of the piezoelectric ceramic substrate 61 that has been subjected to the polarization treatment, an internal electrode 63 formed of a metal plating layer or the like is formed except for the non-adhered portion 62, and the end portion of the internal electrode 63 is perpendicular to the displacement direction. The external electrodes 64 are formed on the exposed side surfaces 60c and 60d of the internal electrodes 63, which are alternately exposed to the two opposite side surfaces 60c and 60d.
And 3 are electrically connected. Separate external electrodes 65 are formed on the lower surface of the lowermost piezoelectric ceramic substrate 61 and the upper surface of the uppermost piezoelectric ceramic substrate 61, respectively.
4 and the external electrodes 64 are electrically led to the outside by lead terminals (not shown). The side surfaces 60c and 60d on which the external electrode 64 is formed serve as a fixed end surface and a driving end surface, respectively.

A laminated piezoelectric actuator 60 utilizing the piezoelectric lateral effect constructed as described above is a piezoelectric ceramic substrate 61.
Since it is possible to obtain a large amount of displacement by increasing the length in the displacement direction and obtain a desired amount of displacement with a small number of laminated sheets, it is used in inkjet printer heads and the like.

[0008]

However, in the laminated piezoelectric actuator 60 utilizing the above-mentioned piezoelectric lateral effect, the external electrode 64 has the drive end face 60d and the fixed end face 6.
Since it is formed on the driving end surface 60d, there is a problem that the external electrode 64 is easily damaged by friction with the object to be driven or the like on the driving end surface 60d, and there is a problem that mounting and fixing is difficult on the fixed end surface 60c. Further, the internal electrode 63 is connected to the external electrode 64 by being exposed on the drive end face 60d side and the fixed end face 60c side, and moreover, since the external electrode 64 is formed on the fixed end face 60c and the drive end face 60d, the drive target or the fixed object is fixed. When the target object is a metal, there is a risk of leakage current when a voltage is applied, and the drive end surface 60d cannot be directly pressed against the drive target object, or the fixed end surface 6
There is a problem that 0c cannot be directly adhered to the object to be fixed.

The present invention has been made in view of the above problems, and provides a laminated piezoelectric actuator which is easy to mount and fix, does not damage external electrodes due to driving, and can reduce the risk of leakage. It is an object.

[0010]

In order to achieve the above object, a laminated piezoelectric actuator according to the present invention is a laminated piezoelectric actuator that utilizes the piezoelectric lateral effect so as not to be exposed on a surface perpendicular to the displacement direction. Internal electrodes are formed on both surfaces of the piezoelectric ceramic substrate, leaving non-adhered portions, and external electrodes, which are electrically connected to the internal electrodes layer by layer, are formed on the laminated side surfaces parallel to the displacement direction of the piezoelectric ceramic substrate. It is characterized by being.

[0011]

According to the laminated piezoelectric actuator having the above-mentioned structure, the internal electrodes are formed on both pieces of each piezoelectric ceramic substrate leaving the non-adhered portion so as not to be exposed on the surface perpendicular to the displacement direction.
In addition, since external electrodes that are electrically connected to the internal electrodes for each layer are formed on both side surfaces of the stack, which are parallel to the displacement direction of the piezoelectric ceramic substrate, when the driving target or the fixing target is metal. Even if a voltage is applied, the risk of leakage is low, and the drive end face can be directly pressed against the drive target. Further, the fixed end surface can be directly adhered to the object to be fixed.

Moreover, since the external electrode is not formed on the driving end surface, damage due to friction of the external electrode with the object to be driven is reduced, and the external electrode is not formed on the fixed end surface, so that mounting and fixing can be performed. It will be easier.

[0013]

EXAMPLES AND COMPARATIVE EXAMPLES Examples and comparative examples of the laminated piezoelectric actuator according to the present invention will be described below with reference to the drawings.

Example 1 FIG. 1A is a schematic perspective view showing a laminated piezoelectric actuator 10 according to Example 1, and FIG. 1B is a schematic exploded perspective view showing an internal electrode pattern. is there. The direction of arrow B in the figure is the direction of displacement, and the piezoelectric ceramic substrate 11 having a thickness of 20 to 100 μm is typically 2
0 sheets are stacked. The internal electrode 13 is formed so as not to be exposed on the fixed end face 10c and the driving end face 10d.
The length in the displacement direction of is less than the length of the piezoelectric ceramic substrate 11 in the displacement direction by the length of the non-adhered portion 12. Further, in the internal electrode 13, the internal electrode portions 13a and the internal electrode portions 13b, which are alternately exposed on the two opposing side surfaces 10e and 10f parallel to the displacement direction of the multilayer piezoelectric actuator 10, are formed on the non-adhered portion 12 one by one. The internal electrode portions 13a and 13b are formed to extend, and the exposed laminated side surfaces 10e and 1e of the internal electrode portions 13a and 13b
An external electrode 14 is formed on 0f, and the external electrode 14 and the internal electrode 13 are electrically connected to each of the side surfaces 10e and 10f layer by layer. Also, the top piezoelectric ceramic substrate 1
Another external electrode 15 is formed on the upper surface of 1 and the lower surface of the lowermost piezoelectric ceramic substrate 11, and the side surface 10 e and the side surface 10
Each of them is electrically connected to the external electrode 14 on f. Each of these external electrodes 14 is electrically led to the outside by a lead terminal (not shown).

The laminated piezoelectric actuator 10 having the above structure
The manufacturing method of will be described below. First, the composition of the material of the piezoelectric ceramic substrate is finally Pb {(Mg _1/3 Nb _2/3 ).
_0.325 (Ni _1/3 Nb _2/3 ) _0.05 Zr _0.25 Ti _0.375 }
As represented by O ₃ , lead oxide, magnesium oxide, niobium oxide, nickel zirconium oxide, and titanium oxide are mixed in appropriate amounts, and calcined and synthesized at about 900 ° C. for about 2 hours, and then pulverized to form a piezoelectric material. To generate. Polyvinyl butyral was added as a binder to the piezoelectric material thus produced, and the thickness was about 3 by the doctor blade method.
A 0 μm green sheet was molded.

Next, a conductive paste for forming the internal electrodes 13 was produced by adding a vehicle, which is an organic solvent, to a mixture of Ag 70 wt% and Pd 30 wt% and thoroughly mixing them. Further, this conductive paste was printed on the green sheet as a 13-layer internal electrode and laminated. Here, 20 layers of green sheets are laminated, and a temperature of 120 ° C. and a pressure of 5 at the time of lamination.
Thermocompression bonding was performed under the condition of 0 kg / cm ² . The molded body thus formed was heated to a temperature of about 600 ° C. to remove the binder contained in the molded body. Next, it was transferred to a sintering furnace, gradually heated to a temperature of about 1100 ° C., and fired for about 2 hours.

Next, as shown in FIG.
The external electrode 14 of Au / Ni / Cr as shown in (a) was formed by vapor deposition to complete the laminated piezoelectric actuator 10.

When the internal electrode portion 13a electrically connected to the external electrode 14 and the internal electrode portion 13b overlap each other, the overlapped portion is displaced, but the peripheral portion is not displaced. Cracks are likely to occur. In order to avoid this, the internal electrode portion 13a and the internal electrode portion 13b are formed on the non-adhered portion 12 so as not to overlap each other.

Comparative Example 1 As Comparative Example 1, a conventional laminated piezoelectric actuator 60 shown in FIG. 8 was manufactured. In Comparative Example 1, a piezoelectric ceramic substrate 61 was prepared in the same manner as the piezoelectric ceramic substrate 11 of Example 1, and the external electrode 64 had the driving end face 60d.
And the fixed end face 60c. The number of layers, the layering conditions and the firing conditions were the same as in Example 1.

Next, the results of evaluation of damage to the external electrodes 14 and 64 when a pulse voltage is applied to the laminated piezoelectric actuators according to Example 1 and Comparative Example 1 to drive them will be described. As shown in FIG. 2, the fixed end 10c of the laminated piezoelectric actuator 10 according to the first embodiment is fixed to the metal base 70 with an adhesive (not shown), and the metal piece 71 is pressed against the drive end 10d. A pulse voltage of 30 V _PP at 20 kHz was applied for 72 hours. After that, as a result of observation using SEM, no damage or the like was found on the external electrode 14.

On the other hand, as shown in FIG. 3, the fixed end 60c of the laminated piezoelectric actuator 60 according to the comparative example 1 is connected to the metal base 7.
0 with an adhesive (not shown) through the insulating ceramics 72, and the metal piece 71 with the insulating ceramics 72 adhered is pressed against the drive end 60d at 20 kHz.
Pulse of 30 V _PP was applied for 72 hours. Then S
As a result of observation using EM, a portion where the external electrode 64 was peeled off was recognized at the edge portion of the driving end 60d.

As described above, the laminated piezoelectric actuator 10 according to the first embodiment is different from the laminated piezoelectric actuator 60 according to the first comparative example in comparison with the driving end face 10d.
Since the external electrode 14 is not formed on the above, the external electrode 14 is less likely to be damaged by driving. In addition, the fixed end surface 10
c and the driving end surface 10d, the internal electrode 13 and the internal electrode 14
Since it is not exposed, even if it is brought into direct contact with the drive target 71 and the fixed target 70, no electrical leakage or the like occurs.

In the first embodiment, the external electrodes 14 are formed on the opposite side surfaces 10e, 10f which are perpendicular to the displacement direction, but the present invention is not limited to this, and another embodiment will be described. The laminated piezoelectric actuator 20 is shown in FIG.
As shown in (a), two external electrodes 24 may be formed on one side surface 20e or 20f parallel to the displacement direction. The internal electrode pattern in that case is formed as shown in FIG. 4B, and the internal electrode portion 23a and the internal electrode portion 23b are formed.
That is, the internal electrode 23 is formed leaving the non-adhered portion 22 so as not to be overlapped at the time of stacking.

Further, in the above embodiment, the internal electrode 1
The printing patterns of the adhered portions 3 and 23 are alternately changed and laminated, but the present invention is not limited to this, and the laminated piezoelectric actuator 30 according to another embodiment has a structure shown in FIG.
As shown in FIG. 5, the internal electrodes 33 composed of adhered portions having the same print pattern may be laminated. In this case, the internal electrodes 33 exposed on the opposite side surfaces 30e and 30f parallel to the displacement direction B are insulated by the insulating member 35 every other layer, and the end portions of the internal electrodes 33 which are not insulated by the insulating member 35 are one layer. Every other time, it is connected to the external electrode 34.

In the case of forming two external electrodes 44 on one side surface 40e or one side surface 40f parallel to the displacement direction B as in the laminated piezoelectric actuator 40 according to another embodiment shown in FIG. 6, Insulating members 45a formed every other layer, and the insulating member 45a is further displaced from the formation site,
And the insulating member 45b formed every other layer has one side surface 4
0e or one side surface 40f, the end portion of the internal electrode 43 which is not insulated is connected to the external electrode 44 every other layer.

[0026]

As described in detail above, in the laminated piezoelectric actuator according to the present invention, the internal electrodes are left on both pieces of each piezoelectric ceramic substrate so as not to be exposed on the surface perpendicular to the displacement direction. Is formed, and external electrodes electrically connected to the internal electrodes for each layer are formed on both side surfaces of the stack parallel to the displacement direction of the piezoelectric ceramic substrate. In the case of metal, even if a voltage is applied, the risk of leakage is low, and the drive end face can be directly pressed against the drive target. Further, the fixed end surface can be directly adhered to the object to be fixed.

Moreover, since no external electrode is formed on the driving end surface, damage due to friction of the external electrode with the object to be driven can be reduced. Further, since no external electrode is formed on the fixed end face, mounting and fixing can be facilitated.

Therefore, it can be widely used as a laminated piezoelectric actuator used for precision positioning, a laminated piezoelectric actuator used for an ink jet printer head or the like.

[Brief description of drawings]

FIG. 1A is a schematic perspective view showing a first embodiment of a laminated piezoelectric actuator according to the present invention, and FIG. 1B is a schematic exploded perspective view showing internal electrode patterns.

FIG. 2 is a side view schematically showing an apparatus for checking the driving state of the laminated piezoelectric actuator according to the example.

FIG. 3 is a side view schematically showing an apparatus for checking a driving state of a laminated piezoelectric actuator according to a comparative example.

4A is a schematic perspective view showing a laminated piezoelectric actuator according to a second embodiment, and FIG. 4B is a schematic exploded perspective view showing internal electrode patterns.

5A is a schematic perspective view showing a laminated piezoelectric actuator according to a third embodiment, and FIG. 5B is a schematic exploded perspective view showing internal electrode patterns.

FIG. 6 is a schematic perspective view showing a laminated piezoelectric actuator according to a fourth embodiment.

FIG. 7 is a schematic perspective view showing a conventional laminated piezoelectric actuator utilizing the piezoelectric vertical effect.

FIG. 8 is a schematic perspective view showing a conventional laminated piezoelectric actuator utilizing a piezoelectric lateral effect.

[Description of Reference Signs] 10, 20, 30, 40 Multilayer Piezoelectric Actuator 11 Piezoelectric Ceramic Substrate 13, 23, 33, 43 Internal Electrode 14, 24, 34, 44 External Electrode

Claims (1)

[Claims] 1. In a laminated piezoelectric actuator utilizing a piezoelectric lateral effect, internal electrodes are formed on both surfaces of each piezoelectric ceramic substrate so as not to be exposed on a surface perpendicular to a displacement direction, and internal electrodes are formed. A laminated piezoelectric actuator, wherein external electrodes electrically connected to the internal electrodes layer by layer are formed on a laminated side surface parallel to the displacement direction of the porcelain substrate.