JPH02180082A - Laminated piezoelectric element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a laminated piezoelectric element used as an actuator.

[Conventional technology]

With the rapid development of mechatronic equipment, the actuators used in this field are attracting attention. Currently, the majority of actuators are driven by electromagnetic force, which not only consumes a large amount of power but also generates heat and electromagnetic noise.Therefore, there is a desire to develop actuators that can replace this. On the other hand, an actuator that utilizes the piezoelectric effect of a solid material not only can overcome the disadvantages of a wooden and electromagnetic actuator, but also has the advantage of being small and lightweight, and strong against vibrations and shocks. As this piezoelectric actuator, there is a laminated piezoelectric element driven by a piezoelectric longitudinal effect, in which a large number of piezoelectric plates are stacked in layers. This multilayer piezoelectric element has excellent features such as fast response speed and large generated force, and is expected to be applied in various fields. FIG. 4 shows a conventional general configuration of such a laminated piezoelectric element. In FIG. 4, 1 is a piezoelectric material layer made of piezoelectric ceramics, 2A and 2B are internal electrode layers, and 3A and 3B are external electrode layers. In such a laminated piezoelectric element, when a voltage is applied between the internal electrode layers 2A and 2B of each piezoelectric material layer 1 via the external electrode layers 3A and 3B, each piezoelectric material layer 1 expands and contracts due to the piezoelectric longitudinal effect. As a result of the sum total, the laminated piezoelectric element is displaced in the vertical direction.

[Question B that the invention attempts to solve]

By the way, the laminated piezoelectric element with such a configuration directly utilizes the piezoelectric longitudinal effect, but the amount of displacement of the piezoelectric material with respect to the applied voltage has hysteresis due to wood quality.
This hysteresis becomes a problem when using a laminated piezoelectric element as a servo element. This invention has been made in view of the above points, and an object thereof is to provide a laminated piezoelectric element with reduced hysteresis.

[Means to solve the problem]

In order to achieve the above object, the present invention has piezoelectric material layers and internal electrode layers stacked alternately, and a voltage is applied between the internal electrode layers via an external electrode layer to cause the piezoelectric material layers to expand and contract. The laminated piezoelectric element is constructed by overlapping a piezoelectric longitudinal effect displacement element section that utilizes a piezoelectric longitudinal effect and a piezoelectric transverse effect displacement element section that utilizes a piezoelectric transverse effect. Here, as the piezoelectric material, it is preferable to use a material with good voltage-strain characteristics, temperature-strain characteristics, creep characteristics, responsiveness, etc., such as lead zirconate titanate-based piezoelectric ceramics. As the internal electrodes, silver electrodes, conductive adhesives, etc. are used. The piezoelectric material layers are laminated by laminating sintered piezoelectric ceramic plates 1 or molded piezoelectric ceramic plates 1. Molded piezoelectric ceramic green sheets may be laminated.

[For use]

By combining a piezoelectric longitudinal effect displacement element section that utilizes a piezoelectric longitudinal effect and a piezoelectric transverse effect displacement element section that utilizes a piezoelectric transverse effect in the same laminate, hysteresis in the elongation direction of the piezoelectric longitudinal effect is reduced in the contraction direction of the piezoelectric transverse effect. This is offset by the hysteresis of , reducing the hysteresis as a whole.

【Example】

FIG. 1 is a schematic sectional view showing an embodiment of the invention. The illustrated laminated piezoelectric element shown in FIG. 1 is constructed by integrally laminating two parts, a piezoelectric longitudinal effect displacement element part 10 and a piezoelectric transverse effect displacement element part 20, which utilize the piezoelectric longitudinal effect. The piezoelectric longitudinal effect displacement element section 10 is a section for obtaining the original amount of displacement as an actuator, and the piezoelectric transverse effect displacement element section 20 is a section provided for reducing hysteresis. The structure of the piezoelectric longitudinal effect displacement element section 10 is the same as the conventional one in terms of wood quality, and 1 is a piezoelectric material layer made of piezoelectric ceramics;
2 and 2B are internal electrode layers, and 3A and 3B are external electrode layers connected to the internal electrode layers 2A and 2B, respectively. A voltage is applied between the internal electrode layers 2A and 2B via the external electrode layers 3A and 3B. The piezoelectric transverse effect displacement element section 20 also has the same structure as the piezoelectric longitudinal effect displacement element section 10, but the external electrode layer 3C
is formed only on one side, and the laminate is laid down horizontally with the external electrode layer 3C facing upward, and this is laminated and integrated on the second part of the piezoelectric longitudinal effect displacement element section 10. That is, in the piezoelectric transverse effect element section 20, 1 is a piezoelectric material layer made of piezoelectric ceramics, 2C and 2D are internal electrode layers, and 3C is an external electrode layer connected to the internal electrode layer 2C. Note that the internal electrode layer 2D is connected to the external electrode layer 3A via the internal electrode layer 2A, and the internal electrode layer 2C, 2B
A voltage is applied between them via external electrode layers 3C and 3A. Such a laminated piezoelectric element is formed as follows. First, raw material powder for lead zirconate titanate piezoelectric ceramics is well dispersed in a solution containing a binder such as polyvinyl alcohol, and then this is dried by a spray drying method to obtain powder for pressing with a particle size of approximately 100 μm. . Therefore,
Using this pressing powder, press molding is performed, and the − side is 25 mm.
, a square piezoelectric ceramic molded body with a thickness of 1 mm is obtained. This molded body is fired at a temperature of 1200° C. for 2 hours, and then polished to obtain a piezoelectric ceramic plate 1 having a thickness of 0.5 mm. Therefore, silver electrode paste was applied to both the front and back surfaces of the piezoelectric ceramic plate 1 with a thickness of 0.5 mm to form internal electrode layers 2A and 2B.
form. Internal electrode layers 2A and 2B each have a portion exposed on the side surface of piezoelectric ceramic plate 1. The exposed portions are arranged in opposite directions on the front and back sides of the piezoelectric ceramic plate 1. Piezoelectric ceramic plate 1 on which internal electrode layers 2A and 2B are formed
Laminate each layer with the front and back sides reversed. Pressure of this laminate is 1kg/cII! , the piezoelectric ceramic plates 1 are bonded together by thermocompression bonding at a temperature of 600° C. for 10 minutes. Furthermore,
A conductive adhesive is applied to the internal electrode layers 2A and 2B exposed on the side surfaces of the laminate and dried to form external electrode layers 3A and 3B, thereby obtaining the piezoelectric longitudinal effect displacement element section 10. Similarly, internal electrode layers 2C and 2D are formed and laminated on a square piezoelectric ceramic plate 1 with a side of 25 mm and a thickness of 0.5 mm, and an external electrode layer 3C is further formed on one side of this laminate. A piezoelectric transverse effect displacement element section 20 is obtained. The piezoelectric transverse effect displacement element part 20 is stacked on top of the piezoelectric longitudinal effect displacement element part 10 laminated in this way with the external electrode layer 3C facing upward, so that the lamination directions of the piezoelectric ceramic plates 1 are orthogonal to each other. The illustrated laminated piezoelectric element is constructed. Between the external electrode layers 2A and 2B and 3A of this laminated piezoelectric element
, 3C, the piezoelectric longitudinal effect displacement element part 1
0 and the amount of displacement of the piezoelectric lateral effect displacement element section 20 are as shown in FIG. That is, the displacement amount of the piezoelectric longitudinal effect displacement element section 10 is on the positive side due to the piezoelectric longitudinal effect, and the displacement amount of the piezoelectric transverse effect displacement element section 20 is on the one side due to the piezoelectric transverse effect. Compared to the piezoelectric longitudinal effect, the absolute value of the displacement amount of the piezoelectric transverse effect is about 3 per layer, and the magnitude of the hysteresis is almost the same. The displacement amount and hysteresis of the laminated piezoelectric element in which these two kinds of displacement amounts occur simultaneously are as shown in FIG. 3, with an example of the + side of FIG. 2 being superimposed. As is clear from FIG. 3, in the laminated piezoelectric element of the illustrated embodiment, the hysteresis of the piezoelectric longitudinal effect displacement element part 10 and the piezoelectric transverse effect displacement element part layer 20 are offset, resulting in low hysteresis.

【Effect of the invention】

According to this invention, by configuring a laminated piezoelectric element by overlapping a piezoelectric longitudinal effect displacement element section that utilizes a piezoelectric longitudinal effect and a piezoelectric lateral effect displacement element section that utilizes a piezoelectric transverse effect, the above two effects can be achieved. The hysteresis of the displacement element portions can be canceled out, and the hysteresis of the laminated piezoelectric element as a whole can be kept small.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, FIG. 2 is a diagram separately showing the relationship between the applied voltage and the displacement amount of the two displacement element parts in the multilayer piezoelectric element of FIG. 1, and FIG. Figure 3 is the first
FIG. 4 is a diagram showing the relationship between applied voltage and displacement amount of the laminated piezoelectric element shown in the figure, and FIG. 4 is a schematic cross-sectional view of a conventional example. ■... Piezoelectric material layer, 2A, 2B, 2C... Internal electrode layer, 3A, 3B, 3C... External electrode layer, 10... Piezoelectric longitudinal effect displacement element part, 20... Piezoelectric transverse effect Displacement element part.

Claims (1)

[Claims] 1) In a laminated piezoelectric element in which piezoelectric material layers and internal electrode layers are alternately laminated, and the piezoelectric material layers expand and contract by applying a voltage between the internal electrode layers via an external electrode layer, the piezoelectric longitudinal effect 1. A laminated piezoelectric element characterized in that it is constructed by overlapping a piezoelectric longitudinal effect displacement element section using a piezoelectric longitudinal effect and a piezoelectric lateral effect displacement element section using a piezoelectric transverse effect.