JPH03138987A - Electrostrictive effect element - Google Patents

Abstract

PURPOSE:To extend the mechanical life of an element by widening the width of one or more grooves formed in a laminating direction at predetermined intervals in parallel on an inner electrode wider than the side face of the element toward the interior of the element. CONSTITUTION:The width of grooves 5 formed in parallel with inner electrodes 2a, 2b parallel to the laminating direction of an element 1 in the laminating direction is widened at the interior of the element as compared with the side face of the element. Part of a periphery which does not cause the deformation of an element in a section perpendicular to the laminating direction of the element is removed to alleviate a stress concentration to prolong the life until a mechanical damage occurs due to application of repetition pulses of a voltage. However, a crack tends to occur from the end of the groove toward the interior of the element. Thus, the width of the groove in the laminating direction is widened in the inside of the element as compared with the side face of the element to prevent cracks from the end of the groove, thereby further extending the mechanical life of the element.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of an electrostrictive element.

[Conventional technology]

An electrostrictive effect element is a transducer that converts electrical energy into mechanical energy by utilizing the electrostrictive effect of a solid state. Specifically, electrodes such as metal films are formed on opposing surfaces of a solid that has a large electrostrictive effect, and the strain in the solid that occurs when a potential difference is applied between the electrodes is utilized. Since the strain that occurs in the direction parallel to the electric field (longitudinal effect strain) is generally larger than the strain that occurs in the perpendicular direction (transverse effect strain), the energy conversion efficiency is higher when the former is used. In an electrostrictive element that utilizes this longitudinal effect with high energy conversion efficiency, the strain generated increases as the electric field strength increases, so in order to obtain a large amount of displacement, the applied voltage must be increased so that the electrostrictive strength does not decrease. is necessary. However, increasing the voltage requires a large and expensive power supply, which also increases the risk of handling.

In order to improve the above drawbacks, a multilayer chip capacitor type structure has been proposed. A vertical cross-sectional view of this structure is shown in Figure 4 (
a), and a projected view of the internal electrodes is shown in FIG. 4(b).

In FIG. 4(a), an internal electrode 2a is provided inside the electrostrictive material 1.
, 2b are formed at regular intervals, and every other one is connected to external electrodes 3a, 3b.

The spacing between the internal electrodes 2a and 2b can be set to about several tens of micrometers using ordinary multilayer film capacitor technology. If this structure is adopted, the distance between the electrodes becomes narrower, and an electrostrictive element utilizing the longitudinal effect that can be driven at a low voltage can be realized.

By the way, as is clear from the projection view of FIG. 4(b) viewed from the stacking direction, in this structure, the overlapping area of the internal electrodes (the central rectangular part) is small compared to the cross-sectional area of the element. The overlapping part of the electrodes deforms in response to the electric field, but the other parts do not. Therefore, when a high voltage is applied to generate a large strain, a large stress is generated at the boundary between the deformed part and the undeformed part. There is a drawback that concentration occurs and the device is mechanically destroyed.9 In order to improve this drawback of the conventional device, an electrostrictive effect device having a multilayer chip capacitor type structure has the disadvantage that each internal portion on the side surface parallel to the stacking direction is There is a structure in which grooves are formed parallel to the electrodes (Japanese Patent Application Laid-open No. 58-196077). FIG. 5 shows a longitudinal sectional view of an element having this structure. That is, in a cross section perpendicular to the stacking direction of the element, by removing a part of the peripheral part that does not participate in the deformation of the element, the stress concentration is reduced by M,
It is possible to extend the lifespan until mechanical breakdown occurs when voltage is repeatedly applied with pulses, and also to increase the displacement of the element.

[Problem to be solved by the invention]

In the electrostrictive effect element of the conventional structure described above, as shown in a part of the vertical cross-sectional view of the electrostrictive effect element of the conventional structure in FIG. It has a certain size throughout. However, in grooves with such a shape, cracks tend to form from the tips of the grooves toward the inside of the element due to the tensile stress that acts around the grooves when voltage is applied, as shown in Figure 6(b). This is one of the characteristics of electrostrictive effect elements that have grooves, as this leads to defects in which the element is mechanically destroyed.
Long mechanical life against repeated voltage pulse application
There is a drawback that this feature cannot be fully utilized.

An object of the present invention is to eliminate the occurrence of cracks from the tips of the grooves when grooves are formed at one or more locations parallel to the internal electrodes at predetermined intervals on the side surface parallel to the stacking direction of the element, and to eliminate repeated voltage pulses. It is an object of the present invention to provide an electrostrictive effect element having a structure that prevents mechanical destruction of the element during application and extends the mechanical life of the element.

[Means to solve the problem]

The electrostrictive effect element of the present invention is an electrostrictive effect element in which materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated, and each internal electrode is connected to the same external electrode every other layer. In an electrostrictive effect element in which one or more grooves are formed parallel to the internal electrode at a predetermined interval on a side surface parallel to the lamination direction of the element, the width of the groove in the lamination direction is wider than the width of the inside of the element than the side surface of the element. It is characterized by being wider.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view of an electrostrictive effect element according to an embodiment of the present invention, and FIG. 2 is a perspective view showing laminated turns showing the structure of FIG.

The effects of the present invention were investigated using a lead zirconate titanate-based material exhibiting an electrostrictive effect. An organic solvent, a binder, and a plasticizer were added to the pre-fired powder of this material, and a green sheet with a thickness of about 130 μm was created using a doctor blade method. After drying this green sheet, a predetermined number of internal electrode paste containing silver-palladium alloy powder as a main component and a pore-forming material paste containing carbon as a main component are screen printed onto it to give it a predetermined shape. They were cut, laminated, thermocompressed, and fired at 1100°C.

Grooves are formed by scattering the pore-forming material during the temperature rise.

As shown in Fig. 2, the hole forming pattern consists of a pattern 8b printed with a hole forming material paste with a thickness of 5 μm and a length of 1 mm from the periphery of the element to the inside, Q, 8 from the periphery of the element.
Two types of sheets 8a were prepared, each having a length of 1 mm printed from the inside of the sheet, and were laminated so that the printed surfaces overlapped each other.

In this embodiment shown in FIG. 1, 1 is an electrostrictive material, 2a,
2b is an internal electrode, 3a and 3b are external electrodes, and 4 is a lead wire. The dimensions of the element are 6 mm x 6 m rn
I Q m m, groove 5 is 0.4 m in the stacking direction of the element
They were formed every m, and had a structure with a width of 5 μm around the element and a width of 10 μm inside the element.

Next, a sinusoidal voltage pulse with a maximum voltage of 150 V and a pulse width of 1 ms was repeatedly and continuously applied to 50 elements of this structure. As a result, while about 10% of the electrostrictive elements with the conventional structure were mechanically destroyed after being driven 4x108 times, the electrostrictive element according to the present invention did not cause any defects even after being driven 8x108 times. .

FIG. 3 is a longitudinal sectional view of an electrostrictive element according to another embodiment of the present invention. In the second example, the hole forming pattern was formed by applying a hole forming material paste to a thickness of 5 μm and extending 0°8 from the periphery of the element.
Print to a length of 1 mm from the point inside the m m, and place the two sides so that the printed sides face each other.
A polyester film having a thickness of 10 μm and processed to form holes with a length of 1 m and 1 m from the periphery to the inside of the element was sandwiched between them and laminated.

In the second embodiment shown in Fig. 3, the dimensions of the element are 6 mm x 6 m.
m, x 10 mm, grooves are formed every 0.4 mm in the stacking direction of the element, 10 μm wide around the element, and 2 grooves inside the element.
The structure should be 0 μm.

Repeated pulses of the same voltage as in the first example were continuously applied to these 50 electrostrictive elements. As a result, the same effects as in the first example were obtained.

〔Effect of the invention〕

As explained above, in the present invention, the width of the groove in the stacking direction is made wider inside the element than on the side of the element, thereby eliminating the occurrence of cracks from the tips of the grooves, thereby improving the stability of the element when voltage pulses are repeatedly applied. This has the effect of providing an electrostrictive element with a structure that prevents mechanical destruction and extends the mechanical life of the element.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an electrostrictive effect element according to an embodiment of the present invention;
2 is a perspective view showing a laminated pattern for constructing the embodiment shown in FIG. 1, FIG. 3 is a longitudinal sectional view of an electrostrictive effect element according to another embodiment of the present invention, and FIG. 4(a) 4 is a vertical cross-sectional view of an example of an electrostrictive effect element having a conventional multilayer chip capacitor structure.
Figure (b) is a projected view of the internal electrodes 2a and 2b of the electrostrictive effect element having the multilayer chip capacitor structure shown in Figure 4 (a).
The figure is a vertical cross-sectional view of an example of an electrostrictive effect element with a conventional structure, and FIGS. 6(a) and 6(b) illustrate a situation in which cracks occur at the tips of grooves due to voltage application in an electrostrictive effect element with a conventional structure. FIG. 1... Electrostrictive material, 2a, 2b... Internal electrode, 3a. 3b...External electrode, 4...Lead wire, 5...Groove,
6... Green sheet, 7a, 7b... Internal electrode pattern, 8a, 8b... Hole formation pattern. Figure 1

Claims (1)

[Claims] An electrostrictive element in which materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated and each internal electrode is connected to the same external electrode every other layer, and a side surface parallel to the lamination direction of the element is , an electrostrictive effect element in which grooves are formed at one or more locations parallel to the internal electrodes at predetermined intervals, characterized in that the width of the grooves in the stacking direction is wider inside the element than on the sides of the element. Electrostrictive effect element.