JPH02125676A - Electrostrictive element - Google Patents

Abstract

PURPOSE:To prevent penetration of moisture from outside air by covering the sides of an inner electrode conductor with an insulating porous material impregnated with an insulating liquid. CONSTITUTION:Four vertical sides of an inner electrode conductor is covered with a pipe 2 of porous Teflon impregnated with silicon oil, which is further covered with a pipe 3 of vinyl chloride. Gaps defined at the opposite ends of the vinyl chloride pipe 3 between the pipe 3 and the Teflon pipe 2 are filled with epoxy resin 4 such that the epoxy resin 4 reaches the electrostrictive element body 1, whereby the silicone oil is enclosed between the inner wall of the vinyl chloride pipe 3 and the electrostrictive element body 1. According to such arrangement, penetration of moisture can be prevented effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostrictive element used in a piezoelectric actuator.

[Conventional technology]

Recently, piezoelectric actuators have been viewed as 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 of an electrostrictive element is essentially small, the electrostrictive element that should be the drive source of the actuator is
As disclosed in 1999, a structure in which an electrostrictive ceramic member or a piezoelectric ceramic member and an internal electrode conductor are laminated in multiple layers to enhance the piezoelectric longitudinal effect is usually used.

In other words, this piezoelectric or 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 with a thickness of about 100μ, and then a pair of silver electrode conductor layers are formed on the green sheet. After being applied in paste form, several tens of layers (for example, 72 layers) are laminated and sintered, and the fired silver electrode conductor layers are alternately connected to external electrodes provided on a pair of opposing sides. Two comb-shaped internal electrodes are formed. 9 from the outside to this external electrode.
When a DC voltage of about 0 V is applied, a static displacement of about 8 μ... is easily generated. Therefore, the problem of mechanical displacement due to electrostrictive effect or piezoelectric effect, which is essentially extremely small, has been solved to some extent by using the "lever device" in combination.

[Problem to be solved by the invention]

However, in the piezoelectric or electrostrictive effect element made of this sintered body, since silver is used as the metal forming the internal electrodes, migration occurs in a humid atmosphere and the side surfaces of the piezoelectric ceramic member are significantly altered. In other words, since the end surface of the silver-based electrode conductor layer is exposed on the side surface of the laminated sintered body,
Migration is likely to occur, and the altered side surfaces of the piezoelectric ceramic member rapidly reduce its insulation properties.

Therefore, when used for a long time in a high humidity environment, conventional electrostrictive elements may discharge at the sides or corners, which seriously impedes reliability.

In order to prevent this, attempts have been made to coat with an insulating resin to prevent moisture from entering, but the moisture resistance has not been sufficiently satisfied.

[Means to solve the problem]

The piezoelectric or electrostrictive effect element of the present invention has an insulating porous body containing an insulating liquid and covering all sides perpendicular to the inner layer 'C'.

(Function) Therefore, no migration occurs on the end face of the silver thread electrode conductor, and moisture resistance is maintained.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a first embodiment of the electrostrictive effect element f of the present invention.

In this embodiment, the four sides of the electrostrictive element main body 1 that are perpendicular to the internal electrode conductor are covered with a silicone oil-impregnated porous Teflon pipe 2, and the top thereof is covered with a vinyl chloride pipe 3. The electrostrictive effect element main body 1 includes a laminated sintered body in which an electrostrictive ceramic member and internal ′ and π polar conductors are stacked alternately, and one of the internal electrode conductors exposed on a pair of opposing sides of the sintered body. A conventional electrician consisting of an insulating layer that insulates the end faces of every other layer on each side, and a pair of external electrodes that electrically connect the other exposed end face of the internal electrode conductor to form two comb-shaped electrodes. The effect element has a cross section of 2 mm x 3 mm and a length of 11 mm. The silicone oil-impregnated porous Teflon vibe 2 that covers this is 2n+m x 3mm, length 8.5Il1
A porous Teflon pipe (for example, Voretex ■) with a wall thickness of 0.3+11111 m and a porosity of 85 t is impregnated with silicone oil. A vinyl chloride vibe 3 covering this silicone oil-impregnated porous Teflon vibe 2
Inner dimension 2.6+++m x 3.6mm, length 9.5mm
, meat p is 0.2 mm. Epoxy resin 4 is filled between both ends of the vinyl chloride pipe 3 and the ends of the porous Teflon vibe 2 impregnated with silicone oil up to the electrostrictive effect element body 1. Silicone oil is sealed between the inner wall and the electrostrictive element body 1.

In this example, the temperature was 40°C, the humidity was 90 to 9596RH, and the applied voltage was 40°C. No defects occurred during the 1000 hour durability test under the condition of 50VDC.

FIG. 2 is a longitudinal sectional view of a second embodiment of the electrostrictive effect element of the present invention.

In the second embodiment, an aluminum film 5 with a thickness of 10 μm is used, and the silicone oil-impregnated porous Teflon vibe 2 covering the electrostrictive element main body 1 has the same length of 8.5 μm.
+ua and hardened with epoxy resin 4 between both edges thereof and each edge of the electrostrictive element main body 1, thereby sealing in silicone oil.

The second example was also conducted under the same conditions as the first example.
We conducted a long durability test, but no problems were found.

FIG. 3 is a longitudinal sectional view of a third embodiment of the electrostrictive effect element of the present invention.

In the third embodiment, a silicone oil-impregnated porous Teflon vibe 2 covering the electrostrictive element body 1 is coated with an aluminum film 5 having a longer thickness of lOμ-, and the electrostrictive element body 1 and An epoxy resin-impregnated part 6 is provided on the outside of both ends of the silicone oil-impregnated porous Teflon vibe 2 between the aluminum film 5 and the edge of the aluminum film 5 on the outer ring and the edge of the electrostrictive element body 1. The space between them is solidified with epoxy resin 4, thereby doubly sealing the silicone oil.

In addition, in the first to third embodiments above, a porous Teflon pipe is used as the insulating porous body, but similar materials such as polypropylene, vinyl chloride, nonwoven fabric, etc. that are not corroded by the insulating liquid to be impregnated may be used. Similar results can be obtained with not only silicone oil but also fluorocarbon oil and mineral oil as the insulating liquid.

(Effects of the Invention) As explained above, the present invention prevents moisture from entering from the outside air by covering the side surfaces of a piezoelectric or electrostrictive element with an insulating porous body containing an insulating liquid. It has the advantage of being able to be used for long periods of time in high-humidity environments, and eliminating the need for a resin exterior.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a first embodiment of an electrostrictive effect element of the present invention, FIG. 2 is a vertical cross-sectional view of a second embodiment of an electrostrictive effect element of the present invention, and FIG. FIG. 3 is a vertical cross-sectional view of a third embodiment of the electrostrictive effect element of FIG. 1... Electrostrictive effect element, 2... Porous Teflon pipe impregnated with silicone oil, 3... Vinyl chloride pipe, 4... Epoxy resin, 5... Aluminum film, 6... Impregnated with epoxy resin Department. Patent applicant NEC Corporation

Claims (1)

[Claims] 1. A laminated sintered body in which sheet-like piezoelectric ceramic members and internal electrode conductors are alternately stacked, and one end face of the internal electrode conductor exposed on a pair of opposing sides of the laminated sintered body, respectively, on each side. In an electrostrictive effect element including an insulating layer that insulates every other layer and a pair of external electrodes that electrically connect the other exposed end surface of an internal electrode conductor to form two comb-shaped electrodes, an insulating liquid is used. An electrostrictive effect element comprising an insulating porous body covering all sides perpendicular to an internal electrode conductor.