JPH02164081A - Laminated piezoelectric element - Google Patents

Abstract

PURPOSE:To acquire high moisture resistance characteristics by providing an armor of a heat shrinkable tube to a laminated piezoelectric element whose surface and interior are impregnated with highly insulating oil. CONSTITUTION:A sheet whereto an inner conductor paste of silver palladium is printed on a green sheet of a piezoelectric is laminated in a structure of an inner electrode 6 and a piezoelectric ceramics member 7 which are laminated alternately. Thereafter, this laminate is sintered for debinder to form a laminated piezoelectric element 1. The formed element 1 is immersed into silicon oil and the oil is fully impregnated into the inside of the element. Since electric insulating oil is impregnated to the inside of the element 1, deterioration of moisture resistance is prevented between the inner electrodes 6 of the element 1. Furthermore, sides of the element 1 is coated with a heat shrinkable tube and the tube is made to shrink thermally due to heating; therefore, the tube adheres closely to a surface of the element 1, and a coating of extremely good airtightness can be formed, thereby remarkably improving moisture resistance characteristics of the piezoelectric element 1.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a laminated piezoelectric element.

[Conventional technology 1] Conventional laminated piezoelectric elements have internal electrode conductors arranged at intervals of about 100 u exposed in tens to hundreds of layers on the sides of the element, so it is difficult to apply voltage when driving the piezoelectric element. Then, the electrical insulation resistance (IR) value between the exposed internal electrode conductors is significantly reduced by the moisture in the atmosphere, which may eventually lead to a short circuit.

For this reason, in the past, as a method to prevent moisture from entering, a simple resin exterior was applied by applying powdered resin to the laminated piezoelectric element using a powder coating method such as an electrostatic coating method or a fluidized dipping method. Ta.

[Problem to be solved by the invention]

In the conventional resin packaging method described above, since the resin that adheres to the element surface is a powdered resin, the resin exterior has an extremely large number of pores, has poor adhesion to the element surface, and has a resin thickness of 0. Since it is thin (less than .2 mm), it has the disadvantage that the characteristics of the device change significantly (referred to as moisture resistance characteristics) in a humid atmosphere, making it unsuitable for practical use.

E Means for Solving Problem] The laminated piezoelectric element of the present invention includes a laminated sintered body in which sheet-like piezoelectric ceramic members and internal electrode conductors are alternately laminated, and a pair of the laminated sintered bodies facing each other An internal electrode conductor is exposed on the side surface of the inner electrode conductor, one end of the internal electrode conductor exposed on the other pair of opposing side surfaces is insulated every other layer on the side surface, and an end of the internal electrode conductor that is not insulated is In the laminated piezoelectric elements each connected to an external electrode provided on each side, the surface and inside of the laminated piezoelectric element are impregnated with electrical insulating oil, and all of the side surfaces of the laminated piezoelectric element are After being covered with a heat-shrinkable tube made of an organic polymer material, the heat-shrinkable tube is heat-shrinked.

[Function] In this way, since the electrical insulating oil is impregnated into the inside of the element, deterioration of the moisture resistance between the internal electrodes of the element is prevented.
Furthermore, since the sides of the element are covered with a heat-shrinkable tube and this tube is heat-shrinked by heating, the tube adheres to the surface of the element, forming an extremely airtight exterior covering. Since a tube is used, 0.
A coating with a thickness of 3 mm or more is obtained, and the moisture resistance properties of the piezoelectric element are significantly improved.

〔Example〕

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

FIG. 1 is a perspective view of a first embodiment of the laminated piezoelectric element of the present invention;
Figure 2 is a cross-sectional view taken along line A-A in Figure 1, and Figure 3 is B in Figure 1.
-B sectional view.

As shown in FIGS. 1 to 3, the laminated piezoelectric element 1 of this embodiment includes a laminated sintered body in which piezoelectric ceramic members 7 and internal electrodes 6 are stacked alternately. The internal electrodes 6 are exposed on one pair of side surfaces to form an internal electrode exposed surface 5, and the other pair of opposing side surfaces are provided with insulating parts 9 that alternately insulate the exposed ends of the internal electrodes 6, External electrodes 8 are provided to connect the remaining non-insulated ends to each of these side surfaces to form an external electrode forming surface 4. An element covering resin 2 made of a heat-shrinkable tube made of an organic polymer material is provided to cover all of the electrode exposed surface 5 and the pair of external electrode forming surfaces 4.

Next, a method for forming the laminated piezoelectric element 1 of this example will be described.

As shown in FIGS. 2 and 3, a sheet with silver baladium internal conductor paste printed on a piezoelectric ceramic green sheet is placed so that the internal electrodes 6 and piezoelectric ceramic members 7 are alternately laminated. The laminated body is then sintered to remove the binder to form the laminated piezoelectric element 1.

The formed element is immersed in silicone oil, and the oil is sufficiently impregnated to the inside of the element. A laminated piezoelectric element l sufficiently impregnated with silicone oil is wrapped in a heat-shrinkable tube made of cross-linked polyolefin, and heated to a temperature of 120°C for approximately 30 minutes.
Heat for 0 minutes. As a result, the heat-shrinkable tube was heat-shrinked, and the laminated piezoelectric element 1 was firmly covered by this tube, thereby forming the laminated piezoelectric element 1 as shown in FIGS. 1 to 3. The thickness of the element coating resin at this time is 0.4 mm.
Met.

The laminated piezoelectric element 1 thus formed was heated to a temperature of 40°C.
When the piezoelectric element 1 was placed in a humidifying tank with a relative humidity of 95% or more and a voltage of 100V or more was applied to measure changes in the electrical insulation resistance value, it was confirmed that it maintained sufficiently stable characteristics for about 500 hours or more. It was done. On the other hand, when a conventional piezoelectric element without the exterior according to the present invention was evaluated in a similar manner, a decrease in electrical insulation resistance was observed in about several tens of hours. Next, a second embodiment of the present invention will be described. In this example, a laminated piezoelectric element 1 formed in the same manner as in the first example described above is placed in a vacuum container, and the inside of the piezoelectric element is thoroughly impregnated with highly electrically insulating silicone oil by a vacuum impregnation method. let The laminated piezoelectric element 1 thus obtained is a heat-shrinkable two-layer structure in which the inner layer is made of highly adhesive and heat-melting polyimide, and the outer layer is made of crosslinked polyolefin with excellent heat and chemical resistance. It was placed in a tube and heat-treated at a temperature of 120'C or higher for about 30 minutes. In this way, a laminated piezoelectric element 1 as shown in FIGS. 1 to 3 was formed. In particular, according to this embodiment, the silicone oil is sufficiently filled not only on the element surface but also inside the element, and the element covering resin 2 formed by heat shrinkage has a heat-meltable inner layer with excellent adhesive properties. Since the polyimide material used here has excellent adhesion to the piezoelectric element, a laminated piezoelectric element with extremely excellent airtightness could be formed. The thickness of the element coating resin 2 at this time is:
It was 0.7mm. As a result, when the moisture resistance was evaluated in the same manner as in the first example, it was confirmed that the electrical insulation resistance value remained stable for about 1000 hours or more. This can be achieved by using a two-layered heat shrink tube as in this example.
It is thought that the polyolefin in the outer layer contracted due to heating, and the heat and shrinkage force caused the polyimide in the inner layer to melt and adhere to the piezoelectric element, completely preventing moisture from entering. For double-layer heat shrink tubes, the inner layer is a heat-melting polymer with excellent adhesive strength, while the outer layer is made of polyimide, polyamide, other gel-like polyeboxy, polyolefin, or polyurethane, and the outer layer is chemical-resistant and heat-resistant. It is made of materials such as polyolefin, polyimide, polyamide, and polyvinylidene fluoride, which are excellent heat-shrinkable polymers, and these heat-shrinkable tubes were used to fabricate laminated piezoelectric elements in the first implementation. As a result of coating and exterior packaging in the same manner as in the example, a laminated piezoelectric element 1 with extremely excellent moisture resistance and high airtightness was formed.

In this example, silicone oil was used as the electrical insulating oil to be impregnated into the element, but other examples such as chlorophenylnaphthalenes, chlorobiphenyls, trichlorobenzene, tris(nonafluorobutyl)amine, and mineral oil were also used. Similar to this example, good moisture resistance was obtained.

〔Effect of the invention〕

As explained above, the present invention has a laminated piezoelectric element whose surface and interior are impregnated with highly insulating oil, and which is covered with a heat-shrinkable tube, so that the piezoelectric element can be operated in a relative humidity of 95%. This has the effect of making it possible to obtain a laminated piezoelectric element that maintains high moisture resistance properties that can be put to practical use.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a first embodiment of the laminated piezoelectric element of the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, and FIG. 3 is a cross-sectional view taken along line B-B in FIG. be. DESCRIPTION OF SYMBOLS 1...Laminated piezoelectric element, 2...Element coating resin, 3a, 3b...Element drive end surface, 4
...External electrode forming surface, 5...Internal electrode exposed surface 6...Internal electrode, 7...Piezoelectric ceramic member, 8...
External electrode, 9...Insulating part.

Claims (1)

[Claims] 1. It includes a laminated sintered body in which sheet-like piezoelectric ceramic members and internal electrode conductors are alternately laminated, the internal electrode conductor is exposed on a pair of opposing side surfaces of the laminated sintered body, and the internal electrode conductor is exposed on the other pair of opposing side surfaces. One end of the internal electrode conductor exposed to the side surface is insulated on every other layer, and the uninsulated end of the internal electrode conductor is connected to an external electrode provided on each side surface. In the element, the surface and interior of the laminated piezoelectric element are impregnated with electrical insulating oil, and all of the side surfaces of the laminated piezoelectric element are
1. A laminated piezoelectric element characterized in that it is covered with a heat-shrinkable tube made of an organic polymer material, and then the heat-shrinkable tube is heat-shrinked.