JP2812994B2 - Stacked displacement element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stacked displacement element in which a large number of thin plate-shaped displacement elements made of a piezoelectric body, an electrostrictive body, or the like are stacked, and in particular, improves the displacement efficiency of the displacement element. In addition, the thin plate-like displacement element is prevented from cracking due to stress concentration or the like generated near the external electrode.

[Background Art] A stacked displacement element has a configuration in which a plurality of thin plate-shaped displacement elements are stacked via internal electrodes, and the range in which the thin plate-shaped displacement element is displaced is a portion where the internal electrodes on both surfaces overlap. For this reason, there is a device having a so-called full-surface electrode structure so that the displacement element can be effectively displaced over as wide a range as possible. It is formed almost in the same plane as the internal electrode thin plate-shaped displacement element forming the laminated body, covers the outer edge of every other internal electrode with a coated insulator, and externally covers the outside in the thickness direction of the laminated body. Electrodes are attached. (JP-A-58-196068).

In the laminated displacement element, the thickness of the thin plate-shaped displacement element is 10
Because it is very thin, 0 to 200 μm, it is not easy to form it on the insulator along every other edge of the internal electrode. For this reason, the applicant has filed an application for a laminated displacement element having the following configuration as a device which can be easily manufactured (Japanese Patent Application Laid-Open No. 62-200778). In this case, the projection for forming the external electrode is formed on the thin plate-like displacement element, and the internal electrode is also formed in substantially the same shape as the thin plate-like displacement element, and the internal electrodes are arranged at every other layer in the stacking order. , And the remaining internal electrodes are not led out. External electrodes are attached to the outer ends of the protruding portions to connect to the other internal electrodes.

[Problems to be Solved by the Invention] Conventionally, in order to easily form an external electrode of a stacked displacement element, there is a thin plate-shaped displacement element in which a projection is formed and an external electrode is formed at an outer end of the projection. . In this case, the internal electrodes at the protruding portions are formed short so as not to protrude to the outer end every other layer, and have a structure similar to a so-called alternating electrode structure in which an external electrode is provided at the end and connected to the internal electrode every other layer. I have. Since most of the multilayer displacement element has a full-surface electrode structure except for the protrusions, the displacement efficiency and the reliability are greatly improved as compared with the conventional multilayer capacitor structure (alternate electrode structure). However, the protruding portion has an alternating electrode structure, and a large strain is generated at the boundary between the displaced portion and the non-displaced portion to concentrate the stress.

Therefore, the present invention facilitates the manufacture of the external electrode, and furthermore, provides a cut so as not to apply a large stress between the displaced portion and the non-displaced portion near the external electrode so that the thin plate-shaped displacement element is not broken. The purpose is to:

"Means for Solving the Problems" The present invention provides a stacked type in which a large number of thin plate-like displacement elements are stacked via internal electrodes having substantially the same shape as the thin plate-shaped displacement elements, and a pair of external electrodes are provided which are connected to alternately different internal electrodes. It is a displacement element. The laminate consisting of the thin plate displacement element and the internal electrode is
A notch is provided to divide the two corners into smaller widths. The internal electrode portions located at the two narrow portions are
The inner electrodes 2 were alternately connected to the outer electrodes 3 by alternately leading the outer ends to the outer ends, and attaching the outer electrodes to the outer ends of the two narrow sections.

Note that the two cuts 4 are provided on one side surface of the stacked body and the cuts are opened in parallel, thereby simplifying the cut operation. Further, in the narrow section 5, the area of the internal electrode 2 is gradually reduced from the inside to the outside, and a stress relaxation portion is provided between the non-displacement portion not sandwiched between the internal electrodes and the inside displacement portion. If this is the case, cracks in the thin plate-shaped displacement element can be further prevented.

[Operation] The stacked displacement element of the above means is provided with a cut at a position where the internal electrode is close to the external electrode, and thus is divided.
The displacement of the displacement element is not transmitted to the narrow section from the cut side. Therefore, in the narrow section, a large distortion is hardly generated between the non-displacement section at the outer end which is not sandwiched between the internal electrodes and the inner section, so that stress is hardly generated. In the boundary region, the thin displacement element does not crack.

"Embodiment" A first embodiment of the present invention will be described with reference to FIGS.

In the laminated displacement element, a large number of thin plate-shaped displacement elements 1 are laminated via internal electrodes 2 having substantially the same planar shape, and external electrodes 3 are provided at two adjacent corners of the laminated body. The two external electrodes are respectively connected to every other internal electrode, and a large displacement can be obtained by applying a voltage to the pair of external electrodes 3. The internal electrode 2 is formed by screen-printing silver-palladium, platinum paste or the like on the plane of the thin plate-shaped displacement element 1, and the external electrode 3 is also formed by screen-printing silver, silver-palladium, platinum paste, or the like. You.

Since two corners of the laminated body provided with the external electrode 3 are divided into small widths, cuts 4 are formed in each corner in a direction perpendicular to the surface of the thin plate-shaped displacement element. Although the depth of the cut 4 is substantially the same as the width of the small section 5, the section 5 may be made longer to make the section 5 less susceptible to displacement. The innermost part of the notch 4 is formed in an arcuate cross section so that stress concentration can be prevented.

If two notches 4 are provided on one side surface of the laminate and opened in the same direction, manufacturing becomes easy. However, in the present invention, the two cuts are not limited to being provided at any two corners of the laminate.

The outer ends of the two internal electrodes 2 located at the two narrow sections 5 formed by the cuts 4 are alternately formed in the overlapping order, and the rest is led out to the outer ends to form the narrow inner sections 5. It is connected to an external electrode 3 formed at the outer end. The step of forming the internal electrodes 2 of the narrow section 5 to be short is performed before laminating the thin plate-shaped displacement elements 1 on the laminate. The notch 4 is formed after the thin plate-shaped displacement elements 1 are stacked.

A stacked displacement element provided with the notch 4 as in the above embodiment and a stacked displacement element of the comparative example not provided with the notch 4 are formed, and a polarization process is performed by applying a voltage of 400 V to each for 10 minutes. The durability life by driving was measured. As a result, no abnormality occurred in the driving of the element of this example even when the number of driving was 10 ¹² , but the driving of the element of the comparative example was stopped when the number of driving was near 10 ⁷ . This stop is considered to be due to the occurrence of a crack in a portion near the external electrode 3 in the thin plate-shaped displacement element.

In the above embodiment, the case where the thin plate-shaped displacement element is not provided with the projection of the conventional example for the external electrode is described, but the present invention is also applied to the case where the thin plate-shaped displacement element is provided with the projection for the external electrode. In that case, a cut may be provided along the width of the protrusion. Also, the cut 4 of the laminate may be coated or buried with epoxy resin to make its surface hard to break. In this case, since the epoxy resin is soft, the displacement of the displacement element is eased. It is not transmitted through the part. Further, by coating the outer periphery of the stacked displacement element, corrosion can be prevented and durability can be improved.

Next, a second embodiment will be described with reference to FIGS.

In this embodiment, a strain relief portion 7 is formed between the outer end portion and the inner portion of the narrow section 5 at the corner of the laminate. That is, in order to provide an external electrode at the outer end of the narrow section 5 and connect it to every other internal electrode, the internal electrodes 2 of the narrow section are formed slightly short so as not to reach the outer end every other layer. For this reason, the thin plate-like displacement element 1 at the outer end of the narrow section 5 is not sandwiched between the internal electrodes 2 and serves as a non-displacement part. For this reason, the occurrence of distortion at the boundary between the non-displaced portion and the displaced portion of the thin plate-like displacement element 1 and the cracking of the thin plate-like displacement element due to stress concentration are prevented by the cut and the strain relief portion of the present embodiment.

As shown in FIG. 3, the strain relief portion 7 is formed in a sawtooth shape so that the internal electrode 2 in the narrow section 5 has a gradually decreasing area from the inside to the outside. The displacement of the shape displacement element 1 was gradually reduced outward.
As described above, when the internal electrode 2 is reduced in area toward the outside,
As a result, the area between the internal electrodes of the thin plate-like displacement element is reduced, and the displacement becomes difficult. Therefore, the displacement gradually becomes smaller toward the outside, the displacement between the non-displaced portion and the displaced portion does not change suddenly, distortion is less likely to occur, and stress concentration is less likely to occur. Other configurations are the same as in the first embodiment.

Further, as shown in FIG. 4, the strain relaxation portion 7 may be arranged by connecting a band-shaped electrode so that the width of the internal electrode 2 gradually decreases toward the outside, or as shown in FIG. Alternatively, the continuous circular electrodes may be arranged in several rows in the divided small width portion 5 so that the diameter of the continuous circular electrodes is reduced outward.

[Effects of the Invention] Since the stacked displacement element of the present invention has a cut near the external electrode formed at the corner of the laminate, the portion where the external electrode is formed is the displacement of the displaced portion of the displacement element. Is not affected. For this reason, the non-displacement part of the thin plate-like displacement element near the external electrode is hardly subjected to displacement, and the displacement difference does not increase at a position near the external electrode. Therefore, the stress due to the strain at that portion is small, and cracking of the thin plate displacement element can be prevented.

In addition, since the area of the internal electrode near the external electrode is gradually reduced outward, the displacement of the displacement element can be gradually reduced outward, and the displacement difference between the non-displaced portion and the displaced portion near the external electrode is sharply reduced. In this case, the stress concentration can be prevented, and the thin plate-shaped displacement element is less likely to be broken.

[Brief description of the drawings]

FIG. 1 is a perspective view of a laminated displacement element of the present invention, FIG. 2 is a plan view of a thin plate-shaped displacement element, FIG. 3 is a perspective view showing the internal electrode shape of the second embodiment, and FIGS. The figure is a modified example of the different second embodiment. 1; thin plate-shaped displacement element, 2; internal electrode 3; external electrode, 4; cut 5; narrow section, 7; strain relief section

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-200778 (JP, A) JP-A-1-157581 (JP, A) JP-A-2-237083 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) H01L 41/09

Claims (3)

(57) [Claims] 1. A laminated body is formed by laminating a plurality of thin plate-shaped displacement elements via substantially the same planar internal electrodes as the laminated body, and the laminated body is formed by cutting two corners into small widths. The inner electrode portions located at the two divided small width portions are formed such that the outer ends opposite to each other are alternately shortened in the overlapping order, and the outer electrodes are respectively attached to the outer sides of the divided small width portions, so that the other inner electrode portions are formed. A stacked displacement element characterized by being connected to a. 2. The stacked displacement element according to claim 1, wherein the two cuts are provided on one side surface of the stacked body. 3. The stacked displacement element according to claim 1, wherein the internal electrode in the narrow section has a gradually decreasing area from the inside toward the external electrode.