JPH07154005A - Multilayer electrostictive actuator - Google Patents

Abstract

PURPOSE:To suppress deformation by adding a same material as an inner electrode to an electrostrictive ceramic forming the protective layer for a multilayer electrostricive actuator thereby bringing the shrinkage rates of the electrostrictive layer and the protective layer close to each other at the time of firing. CONSTITUTION:Electrostrictive layers 11 and inner electrode layers 12 are laminated alternately to form an electrostrictively active ceramic part. Electrostrictively inactive ceramic parts 17A, 17B of 0.5mm thick are formed on the outside of outermost inner electrodes and electrostrictively inactive ceramic layers 18A, 18B of 2.5mm thick, containing 2 wt.% of silver and palladium alloy with respect to ceramic, are formed thereon. It is then fired and an insulating layer 14 is formed such that the plurality of inner electrodes 12 constitute opposing electrodes for each electrostrictively active ceramic layer. The inner electrodes are connected electrically with outer electrodes 13A, 13B.

Description

Detailed Description of the Invention

[0001]

The present invention utilizes the electrostrictive vertical effect,
The present invention relates to a laminated electrostrictive actuator that converts electrical input energy into mechanical energy such as displacement or force. More specifically, it reduces the difference in shrinkage between firing and electrostriction that constitutes the laminated electrostrictive actuator during firing. The present invention relates to the structure of the laminated electrostrictive actuator.

[0002]

2. Description of the Related Art Generally, a laminated electrostrictive actuator of this type has an end portion of an electrostrictive portion formed of an electrostrictive layer and an internal electrode layer which face each other so that the internal electrode layer sandwiching the electrostrictive layer forms a counter electrode. In the section, glass insulation treatment is performed so that the internal electrodes face each other in each electrostrictive layer.

Such a laminated electrostrictive actuator is
Due to its excellent characteristics of large electrolysis-induced strain and high-speed response, it is being used as a drive source for printer heads, positioners, valves, relays and the like.

The structure of a conventional laminated electrostrictive actuator of this type is shown in FIG. As shown in FIG. 2, the conventional laminated electrostrictive actuator includes an electrostrictively active ceramic layer (electrostrictive layer) 21 sandwiched between corresponding internal electrode layers 22 and innermost upper and lower two inner electrodes. It is composed of electrostrictively inactive ceramic layers (protective layers) 27A and 27B which are in contact with the layer 22.

Generally, when the actuator is fixed to a target equipment, the displacement end surfaces 29A, 2A of the actuator are used.
It was common to directly bond 9B to the equipment, but due to an increase in bonding man-hours, the accuracy of bonding cannot be guaranteed, etc., protective layers 37A and 37A above and below the actuator as shown in FIG.
B mounting screw tap 43 or positioning groove 4
A method of directly processing No. 4 has been implemented.

However, in order to process the protective layers 37A and 37B, it is necessary to increase the thickness of the protective layers. However, increasing the thickness of the protective layer causes the following problems. That is, in the electrostrictive layer 31 during firing of the ceramic, the firing of the electrostrictive layer 31 is promoted by the catalytic action of a noble metal such as silver or palladium contained in the internal electrode layers 32 sandwiching the electrostrictive layer, and the shrinkage due to firing is increased. On the other hand, since the internal electrode layer is not included, the difference in the amount of firing shrinkage between the upper and lower protective layers (piezoelectrically inactive ceramic layers) 37A and 37B with less catalytic action is large, and the protective layer is electrostrictively active. It becomes more prominent as the ratio to the ceramic part increases. If there is a difference in shrinkage amount between the electrostrictive layer and the protective layer of the actuator during firing, warpage of the product or defective shape occurs, and in extreme cases, the part of the electrostrictively active ceramics and the protective layer are The problem of destruction at the interface arises.

[0007]

SUMMARY OF THE INVENTION The technical problem of the present invention is to solve the above-mentioned drawback, that is, the difference in shrinkage between the electrostrictive layer and the protective layer, which occurs during firing, and to improve the thickness of the protective layer. It is an object of the present invention to provide a laminated electrostrictive actuator which does not have a shape defect and has a good yield and which can be easily fixed to equipment.

[0008]

An electrostrictive layer made of electrostrictive ceramics is laminated and sandwiched by internal electrodes, and a protective layer made of electrostrictive ceramic is in contact with two internal electrode layers above and below the outermost layer. In the laminated electrostrictive actuator having the above-mentioned structure, the same electrode material as that of the internal electrode layer is contained in the ceramic protective layer.

That is, by including the same material as the internal electrodes in the electrostrictive ceramics forming the protective layer of the laminated electrostrictive actuator, the firing shrinkage rates of the electrostrictive layer and the protective layer are made close to each other during firing, and The laminated electrostrictive actuator is capable of improving the yield because it has a small amount of warpage and does not cause damage at the interface between the electrostrictively active ceramics portion and the protective layer.

In the present invention, the internal electrode layer material is
Generally, silver (Ag), palladium (Pd), platinum (Pt)
Noble metal alloy material can be appropriately selected according to the firing temperature of the electrostrictive ceramic used.

[0011]

By including the same material as the internal electrodes in the ceramic forming the protective layer of the laminated electrostrictive actuator, the electrostrictive layer made of electrostrictive ceramic and the electrostrictively inactive ceramic portion (protective layer ), The shrinkage rate during firing is made closer to suppress shape defects such as warpage caused by strain due to the difference in shrinkage rate, and the electrostrictively active ceramic part and the protective layer It is possible to prevent destruction from the interface.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the structure of a laminated electrostrictive actuator according to an embodiment of the present invention. In this figure, the electrostrictive layer 11 is sandwiched between the internal electrode layers 12 and laminated to form an electrostrictively active ceramic portion.

Further, 0.5 mm electrostrictionally inactive ceramic parts (protective layers) 17A, 17B are formed on the outer sides of the upper and lower outer two inner electrode layers of the inner electrode. At the top and bottom of the ceramic part, 2.
5mm thick internal electrode material silver (Ag) and palladium (P
d) Ceramic layers containing alloy in an amount of 2 wt% with respect to the weight of the ceramic are sequentially laminated to form electrostrictively inactive ceramic portions (protective layers) 18A and 18B. After firing, an insulating layer 14 is formed so that a plurality of internal electrodes 12 extending in parallel to each other constitute an opposing electrode for each electrostrictively active ceramics layer (electrostrictive layer). It is electrically connected to the electrodes 13A and 13B. The actuator has a cross section of 10 × 10 mm and a length of 18 mm, and the thickness of the electrostrictively active ceramic portion is 12 mm. The interval between the internal electrode layers is 115 μm, and the number of internal electrode layers is 104.

In order to examine the warpage of the prototyped laminated electrostrictive actuator and the breakdown yield during firing, 10 × after firing.
The amount of waviness on the end faces 19A and 19B of 10 mm, and the crack occurrence rate at the interface between the electrostrictively active ceramic part and the protective layer were examined with a surface roughness meter and an optical microscope.
For comparison, a laminated electrostrictive actuator manufactured by a conventional manufacturing method was simultaneously fired and investigated. Firing temperature is 1150 ° C
Is. The survey results are shown in Table 1.

[0016]

[Table 1]

Here, the waviness on the diagonal line of the end face of 10 × 10 mm is the maximum waviness amount when the diagonal line of the end face is examined by a surface roughness meter. The yield is the yield of 100 pieces of products inspected for cracking (breakage) during firing. As shown in Table 1, in the laminated electrostrictive actuator according to the present invention, the undulation of the end face is 1/100 as compared with the conventional example.
It is reduced to 10 and the firing yield is improved.

[0018]

As described above, according to the present invention, it is possible to provide a laminated electrostrictive actuator which does not have a shape defect such as undulation of a product and has a good firing yield. In particular, it is suitable for a laminated electrostrictive actuator that can be easily fixed to equipment.

[Brief description of drawings]

1A and 1B are explanatory views showing a structure of a laminated electrostrictive actuator according to an embodiment of the present invention, in which FIG. 1A is a plan view and FIG.
Is a side view.

2A and 2B are explanatory views showing a structure of a conventional laminated electrostrictive actuator, in which FIG. 2A is a plan view and FIG. 2B is a side view.

FIG. 3 is a laminated electrostrictive actuator in which mounting screw holes and alignment grooves are formed in upper and lower inert ceramic layers of the laminated electrostrictive actuator. It is explanatory drawing which shows a structure, (a)
Is a plan view, (b) is a side view, and (c) is a plan view (bottom).

[Explanation of symbols]

11, 21, 31 Electrostrictive layer (electrostrictive active ceramic layer) 12, 22, 32 Internal electrode layers 13A, 13B, 23, 33 External electrodes 14, 24, 34 Insulating layers 15, 25, 35 Exterior part 16 , 26, 36 terminals 17A, 17B, 27A, 27B, 37A, 37B
Protective layer (electrostrictive inactive ceramic part) 18A, 18B (containing the same material as the internal electrodes)
Ceramic part 19A, 19B, 29A, 29B, 39A, 39B
End face 43 Screw tap 44 Positioning groove

Claims (1)

[Claims] 1. A laminated electrostrictive device having an electrostrictive layer made of electrostrictive ceramics sandwiched between internal electrode layers and a protective layer made of electrostrictive ceramics in contact with the outermost layer of the internal electrode layers. In the actuator, the laminated electrostrictive actuator, wherein the protective layer contains the same electrode material as that of the internal electrode layer.