JPH05110156A - Lamination piezoelectric effect element - Google Patents

Abstract

PURPOSE:To provide a lamination piezoelectric effect element which eliminates a need for providing an insulation layer for preventing an unneeded contact between an external electrode and an internal electrode and prevents rupture of the element since no shear stress is generated between an active layer and an inactive layer. CONSTITUTION:A plurality of band-shaped ceramic sheets which indicate a piezoelectric effect where a conductive internal electrode is formed on one surface are piled up while they are shifted one another, an external electrode 8 is provided an electrode edge part which is exposed by forming a cylindrical lamination body by exposing one part of the internal electrode on each ceramic sheet at a band-shaped edge part to an outside and then laminating it helically, and further holding it from upper and lower surfaces of a lamination body 7 with a protection body which is made of an insulator through a spring 12 which passes through an empty hole at a central part of the lamination body and then coating an entire surface with a resin 11, thus enabling an insulation layer to be eliminated, preventing migration failure within drive without causing any crazing to be generated, and preventing release of a layer due to shear stress at an interface between the active layer and the inactive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric effect element, and more particularly to a laminated piezoelectric effect element having a spiral laminated structure.

[0002]

2. Description of the Related Art A conventional laminated piezoelectric effect element has a structure as shown in FIG. 5, in which a plurality of internal electrodes 3 are sandwiched with a piezoelectric ceramic layer 23 sandwiched between them. is doing. The external electrodes 8 are provided on two of the four side surfaces where the internal electrodes are exposed.
Insulating layers 24 are alternately provided in layers around the inner electrodes 3 on the two side surfaces. As a result, the inner electrodes are electrically connected to the same outer electrode every other layer. A lead wire 9 is electrically connected to the external electrode 8 by a solder 10. Further, the two side surfaces provided with the external electrode 8 and the other two side surfaces are covered with the resin 11. The piezoelectric ceramic layer 23 is made of a lead-based perovskite structure composite oxide such as lead zirconate titanate, and the electric insulating layer 24 is 500 to 700 ° C.
It consists of a glass body formed by adhering glass powder having a softening point to a desired position by electrophoresis and then firing it at 600 to 800 ° C. In addition, the external electrode 8 is formed by dispersing and mixing metal powder such as silver or silver-palladium mixed powder with glass powder in an organic solvent and applying it to a desired position by a screen printing method.
It consists of a sintered body of metal powder fired at 0 to 800 ° C. Resin 11 is a powder of epoxy resin that is electrostatically coated.
It was cured at a temperature of 0 to 200 ° C.

[0003]

In the laminated piezoelectric effect element having the conventional structure as shown in FIG. 5, the insulating layer 24 is formed by depositing glass powder by an electrophoretic method and then firing the glass. .. This is considered to be one of the most efficient methods at present, but the skill of the operator is required in this step, and the glass of the insulating layer has a different coefficient of thermal expansion from the piezoelectric ceramic layer. The glass may be cracked or cracked in the step of heating the element such as the step of curing the exterior resin, which may cause migration failure during element driving.

Further, in the element having the conventional structure, since the protective layer and the piezoelectric ceramic layer are integrated, shear stress is generated at the boundary of both layers due to expansion and contraction of the piezoelectric ceramic, and this stress is generated at the boundary of both layers. This may cause peeling (element cracking).

The object of the present invention is to prevent migration defects during device driving due to cracks and cracks in the glass of the insulating layer, which is a drawback of the conventional structure, and to occur at the boundary between the protective layer and the piezoelectric ceramic layer. Another object of the present invention is to provide a laminated piezoelectric effect element capable of preventing layer delamination (element cracking) at the boundary between both layers due to shear stress.

[0006]

The laminated piezoelectric effect element according to the present invention comprises two ceramic green sheets having a piezoelectric effect and having conductive internal electrodes formed on one side thereof by vertically shifting them in a longitudinal direction. Stack. At this time, the electrodes formed on the lower green sheet are exposed at either end of the strip green sheet. A strip-shaped sheet is spirally wound and laminated so that this end portion comes to the uppermost surface, and an external electrode portion is provided at the uppermost end portion and a lead wire is soldered thereto.
Further, the laminated body after sintering is only sandwiched between the protective bodies, and the protective body is not sintered into the laminated body.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1 is a perspective exploded view of an embodiment of the present invention, FIG. 2 is a perspective view of an end portion of a green sheet of the embodiment of the present invention, and FIG. 3 is a perspective view of a sintered laminate of the embodiment of the present invention. is there.

First, as shown in FIG. 2, the composition formula Pb (N
i _1/3 Nb _2/3 ) _0.5 Ti _0.35 Zr _0.15 O ₃ Piezoelectric ceramic sheets 2a, 2b made of perovskite-structured composite oxides were coated with silver-palladium internal electrodes 3 made of 70% silver and 30% palladium on one side. Shift the two sheets and stack them. In particular, of the upper and lower two sheets, there is an electrode non-forming portion 4 at the end of the upper sheet 2a, and an internal electrode exposed portion 5 at which the internal electrodes are exposed at the end of the lower sheet 2b. Figure 3
1 shows a laminated body 6 in which the green sheet of FIG. 1 is spirally wound. The sintered laminated body 7 of FIG. 1 is obtained by pressing the laminated body 6 of FIG. 3 at a pressure of 80 kg / cm ² and then sintering it. An external electrode 8 is formed on the end portion of the sintered laminated body 7 by baking a silver paste, and a lead wire 9 is soldered thereto by a solder 10. The sintered laminated body 7 is further covered with a resin 11 having a thickness of about 200 μm. By using this spiral laminate structure, electrodes having different polarities are alternately laminated, and the external electrode 8 may be locally provided at the end of the laminate. For this reason,
The step of forming the insulating layer 24 in the conventional device of FIG. 5 can be omitted. The sintered laminated body 7 shown in FIG.
Sandwiched by four. The metal spring 12 is isolated from the laminated body internal electrode 3 by a protective tube 15 made of aluminum oxide.
This is to prevent the metal spring from short-circuiting the internal electrodes having different polarities. Further, the protective tube 15 is a protective body 14.
It also fits into the circular hole portion 16 and has a function of suppressing the lateral movement of the protectors 13 and 14. Within the circular hole 16 is a beam 18 for hooking the hooked end 17 of the spring. Further, the protective body 13 on the external electrode 8 has a cutting portion 19 so that the external electrode 8 is not pressed.

FIG. 4 is an exploded perspective view of another embodiment of the present invention. In this embodiment, when the sintered laminated body 7 is sandwiched by the protective body 13, not the spring but the bolt 20 and the nut 21.
Is used. The material of the bolt shall be stainless steel, etc., which has appropriate elasticity, and may interfere with the operation of the element.
Make sure that the bolts and elements do not break.

[0010]

As described above, according to the present invention, the step of forming an insulating layer can be omitted by spirally stacking the piezoelectric ceramic layers on which the internal electrodes are formed, and a protective body can be formed on the stacked body. By not sintering, it is possible to eliminate the shear stress at the layer boundary surface and prevent the element from breaking.
Has the effect.

[Brief description of drawings]

FIG. 1 is a perspective exploded view of a laminated piezoelectric effect element according to an embodiment of the present invention.

FIG. 2 is a perspective view of an end portion of a green sheet used in one embodiment of the present invention.

FIG. 3 is a perspective view of a sintered laminate used in one example of the present invention.

FIG. 4 is a perspective exploded view of a laminated piezoelectric effect element according to another embodiment of the present invention.

FIG. 5 is a perspective view and a vertical sectional view of a conventional laminated piezoelectric effect element.

[Explanation of symbols]

 1 Belt-shaped ceramic green sheet 2 Piezoelectric ceramic sheet 2a Upper sheet 2b Lower sheet 3 Internal electrode 4 Electrode non-forming part 5 Internal electrode exposed part 6 Laminated body (spiral laminated body before sintering) 7 Helical laminated body after sintering ( Sintered laminate) 8 External electrode 9 Lead wire 10 Solder 11 Exterior resin 12 Metal spring 13 Upper protector 14 Lower protector 15 Insulator 16 Circular hole 17 Hook end 18 Beam 19 Cutting part 20 Bolt 21 Nut 22 Protective layer 23 Piezoelectric ceramic layer 24 Insulating layer

Claims (2)

[Claims] 1. A plurality of strip-shaped ceramic sheets each having a piezoelectric effect and having a conductive internal electrode formed on one side thereof are shifted and overlapped, and a part of the internal electrodes on each ceramic sheet is exposed to the outside at a strip-shaped end portion. Items are spirally laminated to form a cylindrical laminated body, external electrodes are provided at the exposed electrode ends, and the upper and lower surfaces of the laminated body are connected via springs that pass through holes in the center of the laminated body. Sandwiched by a protective body made of an insulator,
A laminated piezoelectric effect element having an entire surface coated with a resin. 2. A plurality of strip-shaped ceramic sheets each having a piezoelectric effect and having a conductive internal electrode formed on one surface thereof are staggered and overlapped to expose a part of the internal electrodes on each ceramic sheet to the outside at the strip-shaped end portions. Cylindrical laminates are formed by stacking things in a spiral shape, external electrodes are provided on the exposed electrode ends, and from the top and bottom surfaces of the laminate through bolts that pass through holes in the center of the laminate. A laminated piezoelectric effect element characterized in that it is sandwiched by a protective body made of an insulating material and the entire surface is covered with a resin.