JPH04274377A - Laminated piezoelectric actuator - Google Patents

Abstract

PURPOSE:To improve a rupture in the case of repetitive drive and to obtain a laminated piezoelectric actuator having high reliability by lowering a height of a single unit as compared with that of prior art, and relatively reducing a stress to be operated at a boundary between a piezoelectric active unit and a piezoelectric nonactive unit. CONSTITUTION:A laminated piezoelectric actuator 9 in which sheetlike piezoelectric ceramics 1 and inner electrodes 2 are alternately laminated and the electrodes 2 are exposed in zigzag state at two sides of four sides perpendicular to a laminating direction at each one layer. A plurality of the actuators 9 are further laminated, and flexibly conductive substance (conductive adhesive) 8 for structurally and electrically connecting the actuators 9 is incorporated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator, and more particularly to a highly reliable laminated piezoelectric actuator that has improved the phenomenon of breakage caused by repeated driving.

0002

2. Description of the Related Art FIG. 5 is a sectional view showing the structure of a conventional laminated piezoelectric actuator to which the present invention is applied. In the figure, 1 is a piezoelectric ceramic, 2 is an internal electrode, and 3 is an external electrode. The internal electrodes 2 are alternately electrically connected to two external electrodes 3 on a layer-by-layer basis, and are further connected to lead wires 6 via solder 7. When a voltage is applied between the lead wires 6, charges of opposite signs are induced in the adjacent internal electrodes 2, and an electric field is applied to the piezoelectric ceramic 1 between the internal electrodes 2, causing displacement in the stacking direction. This is the structure of this multilayer piezoelectric actuator. It's blooming.

Conventionally, the piezoelectric ceramic 1 is made of a lead-based perovskite structure composite oxide such as zirconate titanate (PZT), and the internal electrode 2 is made of platinum or a mixture of silver and palladium. Moreover, the external electrode 3 is made of silver,
Alternatively, a paste-like substance produced by dispersing and mixing metal powder such as silver-palladium mixed powder in a vehicle with glass powder is applied to the desired position using a screen printing method, and then baked at 600 to 800°C to form a metal powder. It is made of sintered body.

0004

[Problems to be Solved by the Invention] In this conventional laminated piezoelectric actuator, the piezoelectric ceramic (piezoelectric active portion 4 in FIG. 5) in the region sandwiched between the internal electrodes 2 connected to different external electrodes 3 has a Although an electric field is applied, no electric field is applied to the area not sandwiched between the internal electrodes 2 connected to mutually different external electrodes 3 (piezoelectric inactive area 5 in FIG. , since the piezoelectric inactive portion 5 does not cause displacement, when a voltage is applied to this conventional laminated piezoelectric actuator, it causes a drum-shaped deformation as shown in FIG. A large stress acts near the boundary of the active region 5. This stress increases significantly as the height of the laminated piezoelectric actuator in the stacking direction increases. Therefore, a pulse wave is applied to this conventional laminated piezoelectric actuator, and the stress is repeatedly applied. When driven, a problem arises in that cracks occur near the boundary between the piezoelectric active part 4 and the piezoelectric inactive part 5, and the laminated piezoelectric actuator breaks.

An object of the present invention is to provide a highly reliable laminated piezoelectric device that can reduce the stress that acts near the boundary between the piezoelectric active part and the piezoelectric inactive part, and as a result, improves the rupture phenomenon during repeated driving by pulse waves. Our goal is to provide actuators.

[0006]

[Means for Solving the Problems] The laminated piezoelectric actuator of the present invention alternately laminates sheet-like piezoelectric ceramics and internal electrodes, and the internal electrodes are arranged on two of the four sides perpendicular to the lamination direction for each layer. A piezoelectric actuator unit in which two sets of internal electrodes are exposed alternately and connected by external electrodes formed on two side surfaces is connected to the piezoelectric ceramic of the piezoelectric actuator unit and the internal electrode. A piezoelectric actuator unit laminate comprising a plurality of piezoelectric actuator units laminated in the stacking direction, and a flexible conductive material for structurally and electrically connecting the individual units of the piezoelectric actuator laminate. Ru.

[0007] The operation will be explained below. When voltage is applied to the laminated piezoelectric actuator of the present invention, as shown in FIG. 2, the laminated piezoelectric actuator unit 9 of the present invention has a relatively lower height than the conventional laminated piezoelectric actuator
It has a structure in which multiple are connected. Due to its low height,
As shown in FIG. 2, the degree of the drum-shaped deformation of the conventional example shown in FIG. 6 is small, and therefore the stress acting near the boundary between the piezoelectric active part 4 and the piezoelectric inactive part 5 is also small. As a result, even if the laminated piezoelectric actuator of the present invention is repeatedly driven with pulse waves, it will not break, and its reliability will be dramatically improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a schematic vertical cross-sectional view of a laminated piezoelectric actuator according to an embodiment of the present invention. Zirconate titanate (PZT)
), a small amount of organic binder was added to the piezoelectric ceramic powder, which was dispersed in an organic solvent to form a slurry, and a piezoelectric ceramic sheet having a thickness of about 130 μm was produced by tape casting. Furthermore, a paste containing silver and palladium powder mixed at a ratio of 7:3 was deposited on the piezoelectric ceramic sheet by screen printing to a thickness of about 10 μm. Laminate 19 of the following sheets, and finally place a piezoelectric sheet on which the above paste is not printed, and the weight will be 200 kg/c.
The laminated piezoelectric actuator unit 9 was produced by heat-pressing and integrating under the conditions of m2, cutting into each laminated piezoelectric actuator unit, and firing at approximately 1100° C. for 2 hours. As a result, the piezoelectric ceramic sheet becomes piezoelectric ceramic 1.
Next, the silver-palladium powder paste becomes the internal electrode 2. The prototype laminated piezoelectric actuator unit 9 had a length of 5 mm, a width of 5 mm, and a height of 2 mm.

Next, ten of these laminated piezoelectric actuator units 9 were stacked with the exposed side surfaces of the internal electrodes 2 aligned, conductive epoxy adhesive was applied on the side surfaces, and the layers were heated at 150° C. for 1 hour. It was cured under the following conditions and integrated with the lead wire 6 to produce a laminated piezoelectric actuator with an element length of 20 mm.

FIG. 2 is a schematic cross-sectional view showing deformation when a voltage is applied to the laminated piezoelectric actuator of this embodiment. As described above, since it is divided into a plurality of laminated piezoelectric actuator units 9, the height of each unit is lower than that of the laminated piezoelectric actuator having the conventional structure shown in FIG. As a result, the drum-shaped deformation caused by the piezoelectric active part 4 and the piezoelectric inactive part 5 being adjacent to each other is smaller than the deformation of the laminated piezoelectric actuator having the conventional structure shown in FIG. The stress acting on the boundary with the piezoelectric inactive portion 5 is also small.

The laminated piezoelectric actuator of the present invention described above (
The size is approximately 5 mm in length, approximately 5 mm in width, and 20 mm in height).
0 prototypes were manufactured, and a repeated life test was conducted by applying a 150 V 30 Hz sine wave together with 50 laminated piezoelectric actuators of conventional structure (size: approximately 5 mm in length, approximately 5 mm in width, and 20 mm in height). The results are shown in FIG. It can be seen that the reliability against repeated driving has been greatly improved.

FIG. 3 is a longitudinal sectional view of a laminated piezoelectric actuator according to another embodiment of the present invention. A laminated piezoelectric actuator unit 9 was prototyped using the same construction method and structure as in the first embodiment. Next, a paste prepared by dispersing and mixing silver powder and glass powder in a vehicle is applied to the two side surfaces of the laminated piezoelectric actuator unit 9 where the internal electrodes 2 are exposed by screen printing, and heated to approximately 600°C. It was fired for 1 hour, and the internal electrode 2 was electrically connected.

Next, this laminated piezoelectric actuator unit 9 is aligned with the side surfaces coated with the external electrodes 3 described above, and then placed at 10.
They were laminated individually, and a conductive epoxy adhesive was applied near the connection portion and cured at 150° C. for 1 hour. This epoxy adhesive provides electrical connection between the external electrodes 3 and structural connection between the laminated piezoelectric actuator units 9. Finally, lead wires 6 were soldered onto appropriate external electrodes 3 to complete the process.

[0014] A laminated piezoelectric actuator according to a second embodiment of the present invention (size: approximately 5 mm in length, approximately 5 mm in width, and 20 m in height)
50 samples of m) were produced, and 150V30 was prepared in the same manner as in Example 1.
A repeated life test was conducted in which a sine wave of Hz was applied. The results are shown in FIG. It can be seen that similar to Example 1, remarkable effects were obtained.

Although a conductive epoxy adhesive was used in this embodiment, it is not limited to any conductive material that is flexible and can electrically connect the laminated piezoelectric actuator unit 9. do not have.

[0016]

Effects of the Invention As explained above, the present invention has a structure in which a laminated piezoelectric actuator is divided into a plurality of laminated piezoelectric actuator units and these are connected with a conductive material. It is relatively low, and as a result, the stress acting near the boundary between the piezoelectric active part and the piezoelectric inactive part is also small. Therefore, the present invention has the effect of providing a highly reliable laminated piezoelectric actuator in which the phenomenon of breakage during repeated driving by pulse waves is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional view of an embodiment of the present invention.

FIG. 2 is a schematic vertical cross-sectional view showing deformation when a voltage is applied to the embodiment of FIG. 1 of the present invention.

FIG. 3 is a schematic cross-sectional view of another embodiment of the present invention.

FIG. 4 is a diagram showing the repeated life test results of Example 1, Example 2 of the present invention, and a conventional example.

FIG. 5 is a schematic vertical cross-sectional view of an example of a conventional laminated piezoelectric actuator.

FIG. 6 is a schematic vertical cross-sectional view showing deformation when a voltage is applied to an example of a conventional laminated piezoelectric actuator.

[Explanation of symbols]

1 Piezoelectric ceramic 2 Internal electrode 3 External electrode 4 Piezoelectric active part 5 Piezoelectric inactive part 6 Lead wire 7 Solder 8 Conductive adhesive

Claims (2)

[Claims] 1. Sheet-shaped piezoelectric ceramics and internal electrodes are alternately laminated, and the internal electrodes are alternately exposed on two sides of four sides perpendicular to the lamination direction for each layer, forming two sets of internal electrodes. , a piezoelectric actuator unit in which a plurality of piezoelectric actuator units in which the two sets of internal electrodes are connected by external electrodes formed on the two side surfaces are stacked in a stacking direction of the piezoelectric ceramic and the internal electrode of the piezoelectric actuator unit. A laminated piezoelectric actuator comprising a laminated body and a flexible conductive material that structurally and electrically connects the individual units of the piezoelectric actuator unit laminated body. 2. The laminated piezoelectric actuator according to claim 1, wherein the conductive substance is a conductive adhesive.