JPH03257880A - Electrostrictive effect element - Google Patents

Abstract

PURPOSE:To improve humidity resistance greatly and to acquire a compact electrorestrictive effect element by providing an insulating section having elasticity to an approximately central part of a metallic case. CONSTITUTION:An electrorestrictive effect element 1 is temporarily fixed with a thermosetting conductive adhesive 5 to be planted in an inside bottom of a metallic case 2. Thermosetting insulating adhesive is applied to upper and lower surfaces of an elastic insulator 4 such as rubber of a thickness of 2 to 3mm to seal the insulator 4 and a member 3. A combination of the metallic case 2, the member 3 and the insulator 4 is put in a drying furnace to cure thermosetting conductive adhesive 5 and thermosetting insulating adhesive 6. Then, an end part of a flange part 2a and an end part of the member 3 are welded by arc welding to complete hermetic seal. In the process, since an edge face electrode provided to an edge face of the battery jar effect element 1 and the metallic case 2 are connected by conductive adhesive, the metal case 2 can be used as an external electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostrictive effect element, and particularly to an electrostrictive effect element housed in a small metal case.

[Conventional technology]

Recently, piezoelectric actuators have become extremely promising as optical or magnetic disk heads, various optical devices, precision positioning devices for precision machine tools, and other mechanical drive elements.

However, since the mechanical displacement caused by the piezoelectric effect is essentially extremely small, the electrostrictive effect element that serves as the drive source of the actuator is made by stacking piezoelectric ceramic members and internal electrode conductors in multiple layers to enhance the vertical piezoelectric effect. A structure with a similar structure is usually used. In other words, this electrostrictive effect element is made by mixing an organic binder with a multi-component solid solution ceramic powder having a perovskite crystal structure to form a green sheet, and then applying a silver electrode conductor layer on the paste and then forming several tens of layers (for example, 64 layers). ) and sintered. The ends of the silver electrode conductor layers are fully exposed on the side surfaces of the laminate, and in order to form comb-shaped internal electrodes, the ends of the silver electrode conductor layers are insulated every other layer on one side, and the other is insulated. On the side surface, the ends of the silver electrode conductor layer on which the insulating layer was not formed are insulated. Here, a glass insulating film is formed. The silver electrode conductor layers are alternately connected every other layer to form two comb-shaped internal electrodes, and when a DC voltage of about 100 V is applied from the outside, a static displacement of about 8 μm is easily generated.

However, in this electrostrictive effect element made of a laminate, since silver is used as the metal forming the internal electrodes, migration occurs in a humid atmosphere and significantly contaminates the side surfaces of the piezoelectric ceramic and the members. That is, since the ends of the silver thread electrode conductor layer are all exposed on the side surfaces of the laminate, migration is likely to occur, and the contaminated side surfaces of the piezoelectric ceramic member rapidly deteriorate its insulation properties. Therefore, when a moisture resistance test is performed, discharges occur many times on the sides or corners, which greatly impairs yield and reliability.

Therefore, conventional electrostrictive elements have an airtight structure using metallic cylindrical bellows, as shown in FIG. 3, for the purpose of improving moisture resistance. In other words, the lead wire 9 of the electrostrictive element
and a lead terminal 8 made of glass attached to the metal member 10 are connected by soldering, and the metal member (lower part)
The electrostrictive effect element 1 is fixed to the inner bottom surface of the bellows 10 and the metal member (upper part) 11 with adhesive, and both ends of the bellows 7 are arc welded to the upper and lower metal members 10 and 11 over the entire circumference to form an airtight structure. ing.

[Problems to be Solved by the Invention] The conventional electrostrictive effect element described above has an airtight structure and a
Glass terminals are used to take out the metallic cylindrical bellows and the electrodes in order to take out minute displacements of μm, but the outside dimensions are larger than those of the electrostrictive effect element placed inside the bellows, making it smaller and lighter. The disadvantage is that it is difficult to

An object of the present invention is to provide an electrostrictive effect element housed in a metal case that has significantly improved moisture resistance and is much smaller in size.

[Means to solve the problem]

The electrostrictive effect element of the present invention is an electrostrictive effect element in which a laminate in which piezoelectric ceramic members and internal electrode conductor layers are alternately laminated is enclosed in a metal case, and the metal case has a stretchable insulating part approximately in the center thereof. It is characterized by containing.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.

As described in the conventional example, the electrostrictive effect element used in this example is made by mixing an organic binder with a multi-component solid solution ceramic powder having a perovskite crystal structure to form a green sheet with a thickness of about 100 μm, and then placing a paste pot on top of the green sheet. After coating and drying the internal electrode conductor layer, a laminate is first prepared in which several tens of layers (for example, 64 layers) are laminated and sintered. Since the ends of the pot internal electrode conductor layer are exposed on the side surfaces of this laminate, the ends are selectively covered with a glass insulating film, and then external electrode conductors are formed on the side surfaces to further cover the pot internal electrode conductor layer. Two comb-shaped electrodes are formed by connecting the electrodes alternately at intervals. Then, end-face electrodes each having two comb-shaped electrodes connected thereto are formed on each end face of this laminate, and only the side faces are coated with resin.

That is, a chip-shaped electrostrictive element having electrodes formed on both end faces is obtained. The electrostrictive effect element manufactured in this way is attached with the member shown in FIG. 1 and sealed.

That is, a thermosetting conductive adhesive 5 is applied so that the electrostrictive element 1 is erected on the inner bottom surface of a metal case 2 made of stainless steel and having a U-shaped cross section and a cylindrical shape having a collar 2a at the opening. Temporarily fix it with.

Next, the inner diameter is almost the same as the metal case 2, the outer diameter is almost the same as the collar 2a of the metal case 2, and the thickness is 1~
A member 3 having a thickness of 2 mm and made of stainless steel is assembled so that the electrostrictive effect element 1 penetrates through the member 3, and the member 3 and the metal case 2 are assembled.
The flange portion 2a is brought into contact with the flange 2a.

Next, use elastic insulation such as rubber, which has an inner diameter that is almost the same as the metal case 2, an outer diameter that is almost the same as the outer diameter of the metal case 2 (excluding the part 2a), and a thickness of 2 to 3 mm. The object 4 is assembled in the same manner as the member 3 described above to bring the lower surface of the insulator 4 into contact with the member 3. At this time, on the insulator 4,
A thermosetting insulating adhesive is applied to the lower surface to fix the insulator 4 and the member 3 together.

Next, another member 3 is assembled as described above to bring the upper surface of the insulator 4 into contact with the member 3.

Next, the metal case 2 coated with a thermosetting conductive adhesive 5 so that the electrostrictive effect element 1 is planted on the inner bottom surface is assembled so that the collar portion 2a is in contact with the member 3.

Next, the combination of the metal case 22 members 3 and insulator 4 as described above is placed in a drying oven at a temperature of 150°C for 1 hour, and is insulated with a thermosetting and conductive adhesive 5. The adhesive 6 is cured.

Next, the end of the collar 2a and the end of the member 3 are welded together by arc welding to complete the sealing. At this time, electrostrictive element 1
Since the end surface electrode provided on the end surface of the metal case 2 is connected with a conductive adhesive, each of the metal cases 2 can be used as an external electrode.

FIG. 2 is a longitudinal sectional view of another embodiment of the invention. The difference from the first embodiment is that the member 3 is eliminated and the metal case 2 is directly bonded to the insulator 4.

This embodiment has the advantage that it can be manufactured at lower cost than the first embodiment since the member 3 can be omitted.

〔Effect of the invention〕

As explained above, the present invention has the effect of providing a small electrostrictive effect element housed in a metal case with significantly improved moisture resistance by housing the electrostrictive effect element in a sealed container made of a metal case and an insulator. be.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an electrostrictive effect element according to an embodiment of the present invention;
FIG. 2 is a longitudinal sectional view of an electrostrictive effect element according to another embodiment of the present invention, and FIG. 3 is a longitudinal sectional view of a conventional electrostrictive effect element housed in a metal case. 1... Electrostrictive effect element, 2... Metal case, 2a...
・Brim part, 3... Member, 4... Insulator, 5... Conductive adhesive, 6... Insulating adhesive, 7... Bellows, 8... Lead terminal, 9...・Lead wire, 1o...
Metal member (lower part), 11... Metal member (upper part).

Claims (1)

[Claims] An electrostrictive effect element in which a laminate in which piezoelectric ceramic members and internal electrode conductor layers are alternately laminated is enclosed in a metal case, characterized in that the metal case includes a stretchable insulating part approximately in the center thereof. distortion effect element.