JPH03190291A - Lamination-type displacement element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electromechanical transducer used in actuators of industrial robots, ultrasonic motors, etc. This invention relates to an improvement of a laminated displacement element in which the amount of displacement is increased by laminating a plurality of displacement elements via internal electrodes.

[Conventional technology]

Conventionally, laminated displacement elements used for displacement elements used in X-Y stage positioning mechanisms, brakes, etc. are made by attaching electrodes to a thin plate of piezoelectric ceramic material processed into a predetermined shape, and then polarizing it. , a method of joining using an organic adhesive either directly or via a thin metal is used. However, when stacking layers using adhesive as described above, depending on the usage conditions, the adhesive layer may absorb displacement due to vibration of the piezoelectric element, or the adhesive may deteriorate due to high temperature environment or long-term use. There are drawbacks.

For this reason, recently, multilayer piezoelectric elements having a multilayer chip capacitor structure have been put into practical use. That is, for example, as described in Japanese Patent Publication No. 59-32040, a paste-like piezoelectric ceramic material made by adding a binder to raw material powder and kneading is formed into a thin plate of a predetermined thickness, and one side of this thin plate or Internal electrodes are formed by coating both sides with a conductive material such as silver-palladium. A predetermined number of the above-mentioned thin plates are laminated and pressed together, further processed into a predetermined shape, and then fired to form a ceramic, and external electrodes are formed on both sides of the laminate. The laminated piezoelectric element with the above structure has excellent adhesion between the thin plate made of piezoelectric ceramic material and the internal electrode, and has stable thermal properties, so it can be used satisfactorily even in high-temperature environments, and can be used for long periods of time. It has the advantage of extremely little deterioration over time.

FIG. 1 shows an example of the configuration of the above-mentioned laminated displacement element, in which an internal electrode 2 is sandwiched and laminated between thin plates l and 1 made of piezoelectric ceramic material, and the side surfaces of the formed laminated body are made of an insulating material. A coating 3 is provided. After that, for example, along the internal electrode 2a and the internal electrode 2 by an automatic cutting machine or the like,
A plurality of grooves 5 are provided every other layer so that a is exposed.

Next, a pair of external electrodes 4 are baked and connected to the internal electrodes.

[Problem to be solved by the invention]

The insulation coating 3 is usually made of lead oxide, aluminum oxide,
The external electrode 4 is made of glass compounded with silica, etc.
is made of a composite material of glass frit made of a conductive material such as silver or palladium, and lead oxide, bismuth oxide, etc. to increase the adhesion strength with the coating 3.

During baking of the external electrode 4 described above, the insulating coating 3 and the glass frit in the constituent components of the external electrode 4 react, but at that time, the conductive material diffuses into the insulating coating 3 and becomes a factor in the insulation coating. However, in some cases, the device may be short-circuited, reducing the reliability of the device.

An object of the present invention is to provide a highly reliable element in which the conductive material in the external electrode does not diffuse into the insulation coating.

[Means to solve the problem]

In order to achieve the above object, the present invention employs a technical measure in which the external electrode is made of only a conductive material and does not contain any glass frit.

[For production]

In the configuration described in ``2'', there is no glass frit that intervenes in the reaction between the insulation coating and the external electrode, so it is possible to prevent diffusion into the insulation coating of the external electrode, making it possible to create a highly reliable laminated displacement element. You can get it.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

(Example 1) Pb(Zr,Ti)O, powder as an organic binder)) VB, BPBG as a plasticizer, and trichlene as an organic solvent were added and mixed, and this mixed material was thickened by a doctor blade method. Form into a sheet with a diameter of 200 mm. Next, a silver-palladium paste constituting the internal electrodes is screen printed over the entire surface of this sheet material.

For example, 50 thin films 1 thus formed were laminated and pressure-bonded, and then cut into a predetermined size and shape to form a laminate.

Next, this laminate was fired at 1050 to 1200°C for 1 to 5 hours to obtain a 10 mm square laminate.

A coating 3 made of glass is screen printed on the side surface of the obtained laminate and baked at 500 to 900°C for 1 hour. After baking, grooves 6 were created using an automatic cutting machine, and a paste consisting of silver, binder, and solvent was screen printed.
External electrodes 4a and 4b were created by baking at 500 to 750°C. After polarization, a 300 VIOHz sine wave was applied at 50°C.
A driving test was performed by applying 0' times. Although 300 samples were tested, there were no defects such as dielectric breakdown. Incidentally, when the same test was conducted on samples made using conventional glass frit-containing external electrodes, 5 out of 300 had cracks in the coating and dielectric breakdown between the internal and external electrodes.

(Example 2) FIG. 2 shows another example according to the present invention. After obtaining a sintered laminate in the same manner as in Example 1, coatings 3a and 3b made of glass were obtained by a method such as electrophoresis.

After that, the external electrode 4a is made of only a conductive material in the same manner as in Example 1.

4b was created. After polarization, a driving test similar to that in Example 1 was conducted, and there were no defects such as dielectric breakdown among the 300 test samples.

In the above embodiment, the case where the electromechanical conversion material is a piezoelectric material is described, but since the Curie temperature is lower than room temperature, there is no need for polarization, the amount of displacement is large, and there is little hysteresis. A similar effect can be expected for electrostrictive materials having . Examples of such electrostrictive materials include (Pbo, srs Lao,
oaa) (Zro, 86 Tio, 55)o,
Q7.03゜(Pbo, ab Sro, +5) (Zro, 61
Tio, sa Zno, 0116 Nio,.

376 Nbo, to)O1+ (Pbo, as Sro, +6) (Zro, 6
0 Tio, , o Zno, as Nio, oa
Nbo, to) Oa, etc. can be used.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above,
The present invention provides a highly reliable laminated displacement element that suppresses reactions between external electrodes and coatings and does not cause defects such as dielectric breakdown.

[Brief explanation of drawings]

FIG. 1 is a configuration example of a laminated displacement element according to the present invention, and FIG. 2 is a configuration diagram showing another embodiment according to the present invention. 1. Piezoelectric ceramic plate, 2a, internal electrode, 3a.

Claims (2)

[Claims] (1) A laminate is formed by alternately stacking a plurality of thin plates made of an electromechanical transducer material and internal electrodes made of a conductive material, which are formed to have approximately the same planar outline and contact area, and A laminated displacement element comprising a pair of external electrodes to be connected to the internal electrodes every other layer, wherein the external electrodes are made of only a conductive material. (2) A laminated displacement element characterized in that the external electrode according to claim (1) is any one of silver, silver-palladium alloy, palladium, gold, gold-platinum alloy, copper, aluminum, and nickel. .