JPH037076A - Laminated piezoelectric actuator - Google Patents

Abstract

PURPOSE:To improve strength against mechanical impact by baking metallic paste containing glass frit of borosilicate zinc/lead series glass uniformly onto the opposite end faces and the edge sections of a laminated ceramic. CONSTITUTION:Metallic paste containing glass frit of borosilicate zinc/lead series glass having thermal expansion coefficient approximately equal to that of a piezoelectric ceramic constituting a piezoelectric actuator is baked onto a pair of ceramic faces 11a, 11b crossing perpendicularly with the laminating direction of inner electrodes 12a, 12b and onto the edge sections 10a, 10b located closely to the ceramic faces 11a, 11b thus obtaining a metallized structure. When the metallic paste is baked and metallization is carried out, glass frit in the paste is dispersed into the porous piezoelectric ceramic thus filling the porous layer with glass and metallic layer. Consequently, strength against mechanical impact is improved for the ceramic faces 11a, 11b and the edge sections 10a, 10b at the opposite ends of the actuator.

Description

Detailed Description of the Invention A. Object of the Invention [Field of Industrial Application] This invention relates to a laminated piezoelectric actuator that converts displacement or force into mechanical energy in proportion to energy, and particularly relates to a laminated piezoelectric actuator that converts energy into mechanical energy in the form of displacement or force. The present invention relates to a sintered laminated piezoelectric actuator.

[Conventional technology]

Conventionally, electromagnetic actuators such as voice coil motors and pulse motors have been used as actuators for precision positioning devices and precision X-Y tables, but in recent years,
Due to the demand for higher positioning accuracy, faster response speed, lower power consumption, etc., multilayer piezoelectric actuators, which have superior characteristics compared to the electromagnetic actuators, are being used.

Due to advances in manufacturing technology, laminated piezoelectric actuators have been developed by increasing the cross-sectional area of the piezoelectric ceramic plate perpendicular to the direction of displacement,
By creating a structure in which the cross-sectional areas of the internal electrodes, which are laminated between the piezoelectric ceramic plates, match, stress concentration can be eliminated and the amount of strain generated can be increased.

Figure 2 shows a conventional laminated piezoelectric actuator I.
Internal electrodes 12a and 12b facing each other with the piezoelectric ceramic sintered body 3 in between are provided, and the piezoelectric ceramic sintered body 3
and internal electrodes are stacked to form internal electrodes 12a, 12.
a pair of ceramic surfaces 11a perpendicular to the stacking direction of b;
llb, a glass insulating part 13 for electrically insulating the opposing electrode end faces, external electrodes 14 (one external electrode is not shown) connected to the internal electrodes 12a and 12b, respectively, and the like. Furthermore, in order to ensure electrical insulation of the laminated piezoelectric actuator, the ceramic surface 11a is provided.

The four peripheral sides except 11b are usually covered with an organic resin layer (not shown). On the other hand, since the amount of displacement of a laminated piezoelectric actuator is minute in microns, high precision is required for the dimensions in the displacement direction, and it is common to re-dimension the ceramic surfaces 11a and 11b by machining during the manufacturing process. It is true.

[Problem to be solved by the invention]

However, when incorporating a laminated piezoelectric actuator into a positioning device or an X-Y table, it is common to use a pair of ceramic surfaces orthogonal to the internal electrode lamination direction and fix it by adhesive or the like. The ceramic surface has low strength against mechanical impact, and stress tends to concentrate particularly on the edges of the ceramic surface, making the edges of the ceramic surface easy to crack.

An object of the present invention is to provide a multilayer piezoelectric actuator that has sufficient strength against mechanical impact and does not cause cracks in the ceramic surface or cracks at the edges of the ceramic surface.

1. Structure of the Invention [Means for Solving the Problems] The present invention provides a laminated piezoelectric actuator having a plurality of internal electrode layers facing each other, a pair of ceramic surfaces perpendicular to the direction in which the internal electrodes are laminated, and a ceramic surface formed on the ceramic surfaces. A laminated type characterized by having a metallized structure by baking a metal paste containing a glass frit of zinc borosilicate/lead glass whose coefficient of thermal expansion is approximately the same as that of the piezoelectric ceramics constituting the piezoelectric actuator on adjacent edges. It is a piezoelectric actuator.

That is, the present invention provides a multilayer piezoelectric actuator in which a plurality of internal electrode layers facing each other are laminated on a piezoelectric ceramic sintered body, in which ceramic surfaces at both ends perpendicular to the internal electrode lamination direction and edges of the ceramic surfaces are , a laminated structure characterized by having a metallized structure with a metal paste containing 1 to 20 parts by weight of a zinc/lead borosilicate glass frit having a coefficient of thermal expansion approximately equal to that of the piezoelectric ceramic sintered body. type piezoelectric actuator.

[Effect]

In the multilayer piezoelectric actuator according to the present invention, the surfaces of the ceramic surfaces on both end faces perpendicular to the stacking direction of the internal electrodes and the adjacent edges have characteristics that the coefficient of thermal expansion is almost equal to that of the piezoelectric ceramic forming the multilayer piezoelectric actuator. , metallization is performed using a metal paste containing a glass frit of zinc borosilicate/lead glass whose main components are boric acid, silicic acid, zinc oxide, and lead oxide. Therefore, when metallizing is performed by baking the metal paste, the glass frit in the paste diffuses into the piezoelectric ceramic, which is porous in nature, and fills the porous layer with glass and metal layers. ceramic surface,
And the strength against mechanical impact of the edge following the ceramic surface is improved.

The glass used for the glass frit of the metallized layer formed on both end faces of the laminated piezoelectric actuator used in the present invention is a glass with a thermal expansion coefficient almost the same as that of the piezoelectric ceramic sintered body, and has a boric acid content of 15 to 15. 25 parts by weight,
40 to 60 parts by weight of zinc oxide.

It consists of 2 to 10 parts by weight of lead oxide, 0.1 to 5 parts by weight of bismuth oxide, and residual silicic acid, and has a thermal expansion coefficient that is approximately equal to the thermal expansion coefficient of the piezoelectric ceramic sintered body due to the combination of the above-mentioned composition parameters. A silver paste with a ratio of glass frit to hexagonal silver of 1 to 20 parts by weight is used, but if the amount of glass frit contained in the silver is less than 1 part by weight, the glass cannot be baked into piezoelectric ceramics. It does not act as a glue for the structure, and if it exceeds 20 parts by weight, the properties of the glass become stronger and cracks are more likely to occur.

〔Example〕

Examples of the present invention will be described in more detail below.

On the laminated piezoelectric actuator according to the present invention shown in FIG. 1, Pb ((Nio, xs −Nbo 3
This is a laminated piezoelectric actuator made by the thick film lamination method using 03 series piezoelectric ceramics as a starting material, and has a cross section of 5 mm x 5 mm and a length of 18 mm. The material of the internal electrodes 12a and 12b is a silver-palladium alloy.
The distance between the electrodes 2b is 115 μm, and the number of stacked internal electrodes is 150. The external electrode 14 is formed by baking silver paste containing glass frit.

Next, ceramic surfaces 11a and 11a on both end surfaces of this multilayer piezoelectric actuator perpendicular to the internal electrode stacking direction
b, and an edge 10a close to the ceramic surface.

10b was coated with a silver paste containing a glass frit containing 4 parts by weight of zinc borosilicate and lead glass. After drying, it was heated at 550'C for 30 minutes.
It was heat treated, baked and metallized.

The glass frit used in the present invention has 50 parts by weight of zinc oxide, 5 parts by weight of lead oxide, 1 part by weight of bismuth oxide, and 15 parts by weight of boric acid, which has almost the same coefficient of thermal expansion as the piezoelectric ceramic sintered body. Using a glass frit containing silicic acid in the remaining weight part, a metallized layer was formed in the area shown by hatching in FIG. The thickness of the metallized layer is 1 to 2 μm, 10
It was carried out for three types, 15 μm and 50 to 60 μm. After that, in order to investigate the mechanical impact strength of the laminated piezoelectric actuator according to the embodiment of the present invention, metallized edges 10a and 10b were coated with a thickness of 0.5 mm and a width of 2 mm.
01IIIi, using a steel plate with a length of 50 mm, an impact test was conducted on the edge of the steel plate repeatedly so that the thick portion of the steel plate collided with the steel plate. The number of repeated impacts was 10 times per test, and the test was performed at 10 locations by changing the impact position.

For comparison, a similar test was conducted on a stacked piezoelectric actuator with a conventional structure. The test results are shown in Table 1.

The following is a margin in Table 1. [Presence or absence of cracks] The cracks shown in Table 1 were measured as cracks with a length of 0.5 mm or more and a depth of 50 mm or more.

As is clear from Table 1, cracks were observed in 9 out of 10 places in the conventional laminated piezoelectric actuator of the comparative example, but in the laminated piezoelectric actuator according to the present invention, when the metallization thickness was 10 μm or more, In the example of the present invention, cracking was observed at only one location, and it was observed that the strength against mechanical impact was improved by the example of the present invention. Although silver was used as the metal in the examples of the present invention, metals other than silver may also be used.
Gold, platinum, or alloys of silver and these metals may be used, and when baking the full-length paste to metalize piezoelectric ceramics is performed in a non-oxidizing gas atmosphere, as a metal, It goes without saying that the same effect as the present invention can be obtained even if nickel or copper is used.

C6 Effects of the Invention [Effects of the Invention] As explained above, the laminated piezoelectric actuator unit of the present invention has zinc borosilicate/lead glass uniformly applied to both end faces and the edges of the end faces of the laminated ceramics. This is a laminated piezoelectric actuator with a structure in which a metal paste containing glass frit is baked.It has improved strength against mechanical shock, making it possible to provide a higher quality laminated piezoelectric actuator and expanding its application fields.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a laminated piezoelectric actuator according to the present invention. FIG. 2 is a perspective view of a conventional multilayer piezoelectric actuator. 1... Laminated piezoelectric actuator of the present invention, 2...
Conventional laminated piezoelectric actuator, 3... piezoelectric ceramic sintered body, 10a, 10b... edge, lla
, llb... Ceramic surface, 12a, 12b.
...Internal electrode, 13...Glass insulation part, 14...External electrode, 21...Metallized part.

Claims (1)

[Claims] 1. In a multilayer piezoelectric actuator configured by laminating a plurality of internal electrode layers facing each other on a piezoelectric ceramic sintered body, the ceramic surfaces at both ends perpendicular to the internal electrode lamination direction and the edges of the ceramic surfaces are formed by piezoelectric ceramic sintering. A laminated piezoelectric actuator characterized in that it has a structure metallized with a metal paste containing 1 to 20 parts by weight of a zinc/lead borosilicate glass frit having a coefficient of thermal expansion substantially equal to that of the compact.