JPS63299384A - Layer-built type piezoelectric actuator - Google Patents

Abstract

PURPOSE:To unnecessitate any adhesive and to improve the reliability of a product, by holding a plurality of piezoelectric unit substrates in the layered state by means of elastic plates, conductive members and clamping members, and electrically connecting outer electrodes of the piezoelectric unit substrates in parallel. CONSTITUTION:A piezoelectric unit substrate 13 is built in the manner wherein, external electrodes 16 are provided on the opposite side faces of the piezoelectric plate 14, while internal electrodes 15 connected to the electrodes 16, respectively, are provided on the principal faces of the plate 14 such that they are opposed diagonally to each other. A plurality of such substrates 13 are laid one upon another such that they are polarized in the same direction P and that the electrodes 15 of the adjacent substrates are aligned with each other. Conductive eelastic plates 17 are applied against the side faces of the assembly corresponding to the electrodes 16. Four conductive members 18, two by two, are arranged on the outside of the elastic members 17 such that each pair is opposed to each other. The members are clamped together by means of clamping members 19. In this manner, the piezoelectric actuator can be assembled without using any adhesive and the reliability of the product can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stacked piezoelectric actuator in which a plurality of piezoelectric unit substrates are stacked.

[Conventional technology]

FIG. 3 is a longitudinal cross-sectional view showing an example of a conventional laminated piezoelectric actuator.

This piezoelectric actuator 2 has internal electrodes 5 formed diagonally opposite each other on two main surfaces of a piezoelectric plate 4 made of, for example, Pb (Zr, Ti)Os, as shown in FIG. A plurality of piezoelectric unit substrates 3 consisting of a plurality of piezoelectric unit substrates 3 whose polarization direction P
For example, the internal electrodes 5 on each side are bonded and laminated with a conductive adhesive (not shown) so that the internal electrodes 5 are in the same direction and the adjacent internal electrodes 5 are aligned, and the internal electrodes 5 on each side are connected in parallel. External electrodes 6 are formed on both opposing sides.

[Problem that the invention seeks to solve]

For the purpose of operating the piezoelectric actuator 2 as an actuator, when a DC voltage is applied between both external electrodes 6, each piezoelectric plate 4 is displaced in the thickness direction, but at this time, a load is applied to the piezoelectric actuator 2. When you are there,
Since the adhesive layer existing between each piezoelectric unit substrate 3 acts as a cushion and absorbs the displacement of the piezoelectric plate 4, each piezoelectric plate 4
There is a problem in that the effectiveness of the displacement amount (which is basically proportional to the applied voltage) deteriorates, and the repeatability of the displacement amount of the piezoelectric actuator 2 as a whole also deteriorates.

In addition, if the adhesive is applied poorly, the electrical connection between the internal electrodes 5 and the external electrodes 6 may be inhibited, resulting in piezoelectric unit substrates 3 that are not connected to the external electrodes 6, or conversely, the open ends of the internal electrodes 5 may be In some cases, the side of the piezoelectric unit substrate 3 may be connected to the external electrode 6, and in either case, there is a problem in that the piezoelectric unit substrate 3 does not function as an actuator.

Moreover, since each piezoelectric plate 4 is polarized in advance in its thickness direction, in order to not damage this polarization, the process for attaching the external electrode 6 must be performed at a temperature below the Curie temperature of the piezoelectric plate 4. Therefore, a conductive adhesive is normally used for the external electrode 6 as it is suitable for this purpose, but since it cures at a low temperature (approximately 150"C), it may deteriorate over time or be used as an actuator. There is also the problem that cracks may occur in the external electrode 6 due to the displacement stress of the actuator itself when used for a long time.

Therefore, an object of the present invention is to provide a laminated piezoelectric actuator that solves these problems.

Means for Solving Problem C] The laminated piezoelectric actuator of the present invention has external electrodes formed on two opposing sides of a piezoelectric plate, and internal electrodes connected to the respective external electrodes formed on the two main surfaces thereof. A plurality of piezoelectric unit substrates made up of It is characterized by applying electrically conductive elastic plates connected in parallel, disposing electrically conductive members on the outside of each elastic plate so as to face each other, and tightening the opposing electrically conductive members with an insulating tightening member. do.

[Effect]

In this piezoelectric actuator, the plurality of piezoelectric unit substrates are mechanically held in a stacked state by the functions of the elastic plate, the conductive member, and the tightening member, and
Since the predetermined external electrodes of each piezoelectric unit substrate are electrically connected in parallel, there is no need to use adhesives or external electrodes as in the past, and the problems associated therewith are eliminated.

〔Example〕

FIG. 1 shows a laminated piezoelectric actuator according to an embodiment of the present invention, (A> is a plan view thereof, and (B
) is its front view.

The piezoelectric actuator 12 of this embodiment is, for example, Pb
External electrodes 16 are formed on two opposing sides of a piezoelectric plate 14 of the (Zr , Ti )03 system, and internal electrodes 15 connected to each external electrode 16 are diagonally opposed to each other on its two main surfaces. A plurality of piezoelectric unit substrates 13 formed of .

Then, a conductive elastic plate 17 made of, for example, a conductive rubber sheet, which electrically connects the external electrodes 16 on each side in parallel, is applied to the two sides on the external electrode 16 side, and the outer side of each elastic plate 17 is Four conductive members 18 made of metal rods or the like, which serve as pillars and voltage applying electrodes, are arranged two by two to face each other, and the oppositely facing conductive members 1
An insulating tightening member 1 made of, for example, a rubber band is connected between the
It is constructed by closing with 9.

Incidentally, an example of the manufacturing process of each piezoelectric unit substrate 13 as described above will be explained with reference to FIG. (A, )), and then cut it into slices as shown by broken lines to obtain a plurality of piezoelectric plates 14 with external electrodes 16 formed on two opposing sides (Fig. (B)).

Next, internal electrodes 15 connected to each external electrode 16 are formed diagonally opposite each other on the two main surfaces of each piezoelectric plate 14 by, for example, vapor deposition, sputtering, printing, plating, etc. (FIG. 1(C)) ). Then, a DC high voltage is applied between the opposing internal electrodes 15 to polarize each piezoelectric plate 14 (
Same figure (D)). P indicates an example of the polarization direction. As a result, a plurality of piezoelectric unit substrates 13 as described above are obtained.

In the piezoelectric actuator 12, the elastic plate 17,
Since the plurality of piezoelectric unit substrates 13 are mechanically held in a stacked state by the action of the conductive member 18 and the tightening member 19, conventional adhesives for laminating the piezoelectric unit substrates 13 are not required. There is no need to use Therefore, the conventional problems associated with the use of adhesives are eliminated.

In addition, each piezoelectric unit substrate 13 is
Since the external electrodes 16 are electrically connected in parallel, there is no need to use the conventional external electrodes 6 made of conductive adhesive for parallel connection of the piezoelectric unit substrates 13. Therefore, the conventional problems associated with this are also solved.

C. Effects of the invention] As described above, according to the piezoelectric actuator of this invention,
Since no adhesive is required for laminating the piezoelectric unit substrates, the cushioning effect of the adhesive is eliminated, improving the effectiveness of the displacement of each piezoelectric plate, and making it possible to repeatedly reproduce the displacement of the entire piezoelectric actuator. Sexuality also improves. Furthermore, since electrical connection failures caused by adhesive are eliminated, generation of piezoelectric unit substrates that do not function as actuators is also prevented.

Furthermore, since there is no need for conventional external electrodes for parallel connection of each piezoelectric unit substrate, problems such as deterioration over time and generation of cracks are eliminated, and the reliability of the product is improved.

Moreover, in conventional piezoelectric actuators, multiple piezoelectric unit substrates are integrated using adhesive, which naturally limits the number of layers that can be stacked.However, with this piezoelectric actuator structure, the number of layers that can be stacked is Since there is no restriction on the amount of displacement, an actuator with a large amount of displacement can be realized.

[Brief explanation of the drawing]

FIG. 1 shows a laminated piezoelectric actuator according to an embodiment of the present invention, (A) is a plan view thereof, and (B)
) is its front view. FIG. 2 is a diagram showing an example of the manufacturing process of the piezoelectric unit substrate shown in FIG. 1. Figure 3 shows
FIG. 2 is a vertical cross-sectional view showing an example of a conventional laminated piezoelectric actuator. FIG. 4 is a perspective view showing an example of the piezoelectric unit substrate shown in FIG. 3. 12...Laminated piezoelectric actuator according to Example, 1
3. Piezoelectric unit substrate, 14... Piezoelectric plate, 15...
Internal electrode, 16... External electrode, 17... Elastic plate, 1
8... Conductive member, 19... Tightening member, P... Polarization direction.

Claims (1)

[Claims] (1) External electrodes are formed on two opposing sides of the piezoelectric plate,
A plurality of piezoelectric unit substrates each having an internal electrode connected to each external electrode formed on the two main surfaces thereof are stacked so that their polarization directions are in the same direction and adjacent internal electrodes are aligned. Conductive elastic plates connecting the external electrodes on each side in parallel are placed on the two sides of the external electrodes, conductive members are placed on the outside of each elastic plate so as to face each other, and the opposite conductive members are placed on the outside of each elastic plate. A laminated piezoelectric actuator characterized in that members are tightened with an insulating tightening member.