JP2003347614A - Stacked piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stacked piezoelectric actuator having high reliability by using an external electrode of an integrated structure without forming a glass insulator on its surface, having no variation in insulation resistance, and without connecting a lead wire. <P>SOLUTION: The stacked piezoelectric actuator can be obtained, that a plurality of piezoelectric ceramic layers and internal electrode layers are alternately stacked therein, which has a structure in which a comb-shaped external electrode having a plurality of bar-shaped metallic teeth is bonded on an internal electrode portion at a distance two times the distance of the internal electrodes so that the internal electrodes are opposite internal electrodes every other layer on at least one surface of four peripheral surfaces from which the internal electrodes are exposed. Also, in this actuator, where the distance between the internal electrodes exposed from the surface is T1 and the length of a tooth of the comb-shaped external electrode is T2, T1<T2 is given. <P>COPYRIGHT: (C)2004,JPO

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 which generates displacement or force by applying a voltage, and more particularly to a structure for connecting an internal electrode and an external electrode.

[0002]

2. Description of the Related Art A laminated piezoelectric actuator has a structure in which piezoelectric ceramic layers and internal electrode layers are alternately laminated, and the internal electrode layers are connected one by one to a counter electrode. Micron displacement is obtained. Its main applications are industrial equipment such as micro-positioning devices for semiconductor manufacturing, mass flow controller actuators that adjust the flow rate of special gases, and multi-layer piezoelectric actuators in mechanisms that expand displacement.
It covers a wide range of consumer devices such as wire dot printers and inchworm ultrasonic motors.

[0003] Therefore, a multilayer piezoelectric actuator is required to have good usability and reliability in long-term use. In general, the connection structure between the internal electrode and the external electrode of the laminated piezoelectric actuator that is popular in the market is such that the internal electrodes exposed on the surface are glass-insulated every other layer, and on the internal electrode exposed surface including the glass insulating portion, It has a structure in which external electrodes are baked. The appearance is shown in FIG.

[0004] The insulation resistance value of the multilayer piezoelectric actuator itself varies due to variations in the dimensions of the glass insulating portion and the presence of defects inside the glass, and the multilayer piezoelectric actuator having a small insulation resistance gradually becomes insulated during long-term use. There is a problem that the resistance is deteriorated, severely short-circuited, and there is a thing that cannot obtain reliability in long-term use.

A laminated piezoelectric actuator having no glass insulating portion is disclosed in Japanese Patent Laid-Open Publication No. 58-19 / 1983.
No. 6072. According to the publication, a small-area metal plate connected to each of the internal electrodes exposed on the surface is formed,
In this structure, the metal plates are connected to each other by lead wires. However, there is a problem in that electrical connection on individual small metal plates is difficult, and disconnection is likely to occur, and when disconnected, the function as an actuator is reduced or stopped.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has no variation in insulation resistance value without forming a glass insulator on the surface, and connects lead wires. It is another object of the present invention to provide a highly reliable multilayer piezoelectric actuator without using an external electrode having a single structure.

[0007]

According to the present invention, in a laminated piezoelectric actuator in which a plurality of piezoelectric ceramic layers and internal electrode layers are alternately laminated, at least one of the four outer peripheral surfaces on which the internal electrodes are exposed, A laminated structure characterized in that a comb-shaped external electrode having a plurality of rod-shaped metal teeth at an interval of twice the internal electrode interval is joined to an exposed portion of the internal electrode so that every other internal electrode becomes an opposing internal electrode. A piezoelectric actuator is obtained, wherein T1 <T2, where T1 is the distance between the internal electrodes exposed on the surface and T2 is the length of the teeth of the comb-like external electrodes. Can be

According to the structure of the present invention, since the external electrodes in the form of a comb can be collectively connected to the internal electrodes by metal, the connection between the internal electrodes and the external electrodes is easy, and a highly reliable laminated piezoelectric actuator can be obtained.

In the relationship between the interval T1 between the internal electrodes and the length T2 of the teeth of the comb-like external electrode, if T1> T2, the distance between the internal electrode and the opposing external electrode is larger than the distance between the opposing internal electrodes. The discharge voltage is reduced, and the voltage between the internal electrode and the opposing external electrode is easily discharged. As a result, the discharge voltage is reduced, which leads to a reduction in reliability. The length T2 of the electrode teeth is T1> T
There is a need for 2.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Example) First, Pb (Ni-Nb) Zr
Using a TiO ₃ -based piezoelectric ceramic and an Ag / Pd-based internal electrode material, a laminated sintered body having a length of 10 mm in the laminating direction and a cross section in the laminating direction of 5 × 5 mm was prototyped by a green sheet laminating method. The interval between the internal electrodes is 300 microns, and the number of layers is 30 layers.

Next, using a copper plate having a thickness of 100 μm, a comb-shaped external electrode having 15 teeth having a width of 100 μm and a length of 350 μm at a pitch of 600 μm was formed by an etching method. FIG. 2 shows a partially enlarged view of the manufactured comb-shaped external electrode.

Thereafter, 5 × 10 m of the laminated sintered body
The tips of the teeth of the comb-shaped external electrode were fitted to the ends of the internal electrodes exposed on the two opposing surfaces of m dimension, and were fixed with a conductive adhesive. Finally, an insulating paint was applied to the four outer peripheral surfaces to obtain a laminated piezoelectric actuator. FIG. 1 shows a model of a cross-sectional view including an external electrode of the prototyped laminated piezoelectric actuator.

In order to evaluate the reliability of the laminated piezoelectric actuator according to this embodiment, a frequency of 200 Hz and a voltage of 0-
A life test in which a pulse voltage of 200 volts was continuously applied was performed. The quantity is 100 pieces. The test results are shown in Table 1 in terms of the defective rate. For comparison, test results of a laminated piezoelectric actuator using a conventional glass insulating layer are also shown.

[0015]

[Table 1]

It is apparent from Table 1 that the multilayer piezoelectric actuator of the present invention has a smaller initial failure rate in the pulse voltage application test than the comparative example, so that the variation in the insulation resistance is small, Later failure rate,
It can be seen that it is smaller than the conventional structure and high reliability can be obtained.

[0017]

According to the present invention, the use of an external electrode having an integral structure without forming a glass insulator on the surface, having no variation in insulation resistance, connecting a lead wire, and achieving a high level of efficiency. It is possible to provide a reliable laminated piezoelectric actuator.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view including an external electrode of a multilayer piezoelectric actuator of the present invention.

FIG. 2 is a partially enlarged view of a comb-shaped external electrode of the present invention.

FIG. 3 is an external view of a conventional laminated piezoelectric actuator.

[Explanation of symbols]

1 piezoelectric ceramic layer 2 Lead wire 3,3 'internal electrode layer 4,4 'mold insulating resin 11 Piezoelectric ceramic layer 12 Internal electrode layer 13, 13 'Glass insulating layer 14 External electrode 15, 15 'Lead wires connected to external electrodes

Claims (2)

[Claims] 1. A laminated piezoelectric actuator in which a plurality of piezoelectric ceramic layers and internal electrode layers are alternately laminated,
Of at least one of the four outer peripheral surfaces where the internal electrodes are exposed, so that the internal electrodes become opposed internal electrodes every other layer,
A laminated piezoelectric actuator having a structure in which a comb-shaped external electrode having a plurality of rod-shaped metal teeth at intervals of twice the interval between internal electrodes is joined to an exposed portion of the internal electrode. 2. The multilayer piezoelectric actuator according to claim 1, wherein the interval between the internal electrodes exposed on the surface is T1,
T1 <T2, where T2 is the length of the teeth of the comb-shaped external electrode.