JP2012174947A - Laminated piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost laminated piezoelectric actuator producing a uniform stress to a displacement direction upon a metal case having an encapsulated laminated piezoelectric ceramic element, and hardly inclined to the displacement direction, and further, capable of accurately positioning with a small adjustment man-hour at manufacturing.SOLUTION: With the provision of a fitting portion 10, a laminated piezoelectric ceramic element 6 is positioned and fixed to a metal case 2 and a dummy layer 7 so that the center axis of the laminated piezoelectric ceramic element 6 in the lamination direction coincides with the center axis of the metal case 2 in the expansion/contraction direction.

Description

  The present invention relates to a multilayer piezoelectric device in which a multilayer piezoelectric ceramic element is enclosed in a metal case, which is used for a piezoelectric actuator that generates a displacement or a force by applying a voltage, or a piezoelectric sensor that detects a stress from the outside to generate a voltage. It relates to an actuator.

  2. Description of the Related Art Conventionally, piezoelectric ceramics that are deformed by applying a voltage or generate a voltage by an external stress have been put to practical use in piezoelectric actuators, pressure sensors, and the like. Among them, piezoelectric actuators are used in various fields as precision fine positioning mechanisms such as printer heads and magnetic heads, and as drive sources for pumps and manipulators. Furthermore, in fields that require high reliability, such as semiconductor manufacturing equipment, optical communication equipment, and medical equipment, multilayer piezoelectric ceramic elements are sealed in a stretchable metal case to improve humidity resistance and protect from external stress. Thus, multilayer piezoelectric actuators that have long life and high performance have been used.

  A conventional multilayer piezoelectric actuator will be described with reference to the drawings. FIG. 6 is a perspective view of a conventional multilayer piezoelectric ceramic element. The laminated piezoelectric ceramic element of FIG. 6 shows a structure called a full-surface electrode type in which internal electrodes are arranged on the entire surface of the piezoelectric ceramic layer. The laminated piezoelectric ceramic element 6 comprises a laminated body in which a plurality of piezoelectric ceramic layers 21 and internal electrodes 23 are alternately laminated, and a dummy layer 7 which is an inactive body of piezoelectric ceramic is further laminated on the upper and lower sides. An insulating layer 22 is formed on the side surface of the body so that every other internal electrode 23 becomes a counter electrode, and an external electrode 24 is formed so as to be electrically connected to the internal electrode 23 exposed on the side surface. When a voltage is applied to the two external electrodes 24 of the multilayer piezoelectric ceramic element 6, the piezoelectric ceramic layer 21 is displaced in the displacement direction 25 a and the displacement direction 25 b according to the electric field applied between the internal electrodes 23. It increases in proportion to the intensity.

  FIG. 7 is a perspective view of a conventional multilayer piezoelectric actuator. FIG. 8 is a longitudinal sectional view of a conventional multilayer piezoelectric actuator. The multilayer piezoelectric actuator 1 shown in FIGS. 7 and 8 is manufactured as follows. Lead wires 8 are attached to two external electrodes of the multilayer piezoelectric ceramic element 6, and terminals 9 are connected to the lead wires 8. Next, the laminated piezoelectric ceramic element 6 is put into the expansion / contraction tube 4 of the metal case 2 having the bellows structure, and the center axis of the lamination type piezoelectric ceramic element 6 in the stacking direction is set to the upper lid 3 and the expansion / contraction tube using an alignment jig. 4. The upper and lower dummy layers 7, the upper lid 3, and the lower lid 5 of the laminated piezoelectric ceramic element 6 are bonded to each other so as to coincide with the central axis in the expansion / contraction direction of the metal case 2 constituted by the lower lid 5. Thereafter, the upper lid 3, the telescopic tube 4 and the lower lid 5 are welded and sealed to complete the metal case 2.

  In general, many metal cases have a bellows structure, and can have stretchability, springiness, and airtightness. Elasticity and springiness exist in the displacement direction of the multilayer piezoelectric ceramic element, and the stress applied to the metal case needs to be uniform in order to prevent the metal case from being inclined. Furthermore, in order to equalize the stress, when encapsulating the multilayer piezoelectric ceramic element in the metal case, it is necessary to match the central axes of the metal case expansion and contraction direction and the lamination direction of the multilayer piezoelectric ceramic element. is there.

  Regarding the high reliability and high performance characteristic of the multilayer piezoelectric actuator enclosed in a metal case, the positional relationship between the multilayer piezoelectric ceramic element in the metal case and the metal case is particularly important in terms of high performance in the direction of operation. It is an element.

  The positional relationship between the metal case and the multilayer piezoelectric ceramic element is disclosed in, for example, Patent Document 1 and Patent Document 2. In Patent Document 1, a metal cap having a spherical recess that matches a spherical protrusion of an inert body (corresponding to the above-described dummy layer) is formed so that an average load is applied to the inert body. It has become. Further, in Patent Document 2, a configuration in which a convex spherical alignment spherical surface portion that easily aligns the piezoelectric element in the storage case and a concave spherical alignment spherical surface receiving portion that fits into the alignment spherical surface portion is provided. It has become.

Japanese Patent Application Laid-Open No. 11-026829 JP 2008-041983 A

  However, according to the conventional technique, when a laminated piezoelectric ceramic element is sealed in a metal case, there is no mechanism for aligning the center axis of the expansion / contraction direction of the metal case and the laminated direction of the laminated piezoelectric ceramic element. There is a drawback that the stress applied to the metal case is biased due to the deviation, and the displacement direction is inclined. In order to solve this problem, it is necessary to position the laminated piezoelectric ceramic element and the metal case with high accuracy using an expensive dedicated jig, and there is a problem that a great amount of adjustment man-hour is required.

  Further, in the conventional technique described in Patent Document 1, a spherical protrusion is accurately processed on an inert body, and a metal cap having a spherical recess that matches the spherical protrusion is processed. Therefore, there is a problem that high-precision processing is required, and man-hours and costs are high.

  Furthermore, in the conventional technique described in Patent Document 2, alignment is possible even when the piezoelectric element is tilted. However, since the metal case itself is not displaced, in addition to the metal case, the stacked piezoelectric element is used. There existed a subject that the drive member and the transmission member which take out the displacement and drive force of a ceramic element were needed.

  Therefore, the present invention provides a highly accurate positioning with a uniform stress in the displacement direction applied to the metal case encapsulating the multilayer piezoelectric ceramic element, is less prone to tilt in the displacement direction, and requires less adjustment man-hours during fabrication, and is low in cost. It is an object of the present invention to provide a multilayer piezoelectric actuator that can be manufactured by the following method.

  In order to solve the above-described problems, the present invention performs processing for aligning the central axis in the expansion / contraction direction of the lid surface of the metal case with the central axis in the stacking direction on the end surface of the dummy layer that is an inert body of the multilayer piezoelectric ceramic element. By applying, the eccentricity of the laminated piezoelectric ceramic element is suppressed without using a new member, and the inclination of the displacement direction of the metal case is suppressed.

  That is, according to the present invention, a multi-layered multi-layered body in which a plurality of piezoelectric ceramic layers and internal electrodes are alternately stacked and a dummy layer which is an inactive piezoelectric ceramic layer is stacked on both ends in the stacking direction. A laminated piezoelectric ceramic element having a pair of external electrodes formed by electrically connecting the internal electrode layers adjacent to each other through the piezoelectric ceramic layer so as to be equipotential. A laminated piezoelectric actuator enclosed in a case, wherein the metal case and the dummy layer are positioned so that a central axis in a stretching direction of the metal case coincides with a central axis in a lamination direction of the laminated piezoelectric ceramic element. A laminated piezoelectric actuator characterized in that a fitting portion for fixing is provided and fixed.

  Further, according to the present invention, the cross-sectional shape parallel to the stacking direction of the fitting portion is such that one is a hemispherical convex portion and the other is a conical concave portion. Is obtained.

  In addition, according to the present invention, there is obtained the above multilayer piezoelectric actuator characterized in that the shape of the fitting portion surface parallel to the lamination direction of the fitting portion is a cross shape.

  Further, according to the present invention, the shape of the cross section of the fitting portion parallel to the stacking direction is a conical recess, and the spherical structure is disposed so as to contact the inside of the recess. The multilayer piezoelectric actuator is obtained.

  Further, according to the present invention, it is only necessary to position and bond at least one of the dummy layer and the upper cover of the metal case or at least one of the dummy layer and the lower cover of the metal case.

  Further, according to the present invention, the metal case can be applied to a structure in which the expansion tube of the metal case and the lower lid of the metal case are connected.

  According to the present invention, the metal case is applied by providing a fitting portion that is processed to have a concave and convex shape so that the center axes of the dummy layer end face of the multilayer piezoelectric ceramic element and the lid surface inside the metal case are aligned. It is possible to provide a multilayer piezoelectric actuator in which the stress in the displacement direction is uniform and the inclination in the displacement direction hardly occurs.

  In addition, it is possible to provide a multilayer piezoelectric actuator that requires a small number of adjustment man-hours during production, can be positioned with high accuracy without using a dedicated jig, and can be produced at low cost.

It is a longitudinal cross-sectional view of the lamination type piezoelectric actuator which comprised the shape of the cross section parallel to the lamination direction of the fitting part which concerns on Embodiment 1 of this invention with the conical unevenness | corrugation. It is a longitudinal cross-sectional view of the lamination type piezoelectric actuator which comprised the shape of the cross section parallel to the lamination direction of the fitting part which concerns on Embodiment 2 of this invention with the cylindrical unevenness | corrugation. It is a longitudinal cross-sectional view of the lamination type piezoelectric actuator which comprised the shape of the cross section parallel to the lamination direction of the fitting part which concerns on Embodiment 3 of this invention on the other side by hemispherical and the other was conical unevenness. It is the lamination type piezoelectric actuator which comprised the shape of the fitting part surface parallel to the lamination direction of the fitting part which concerns on Embodiment 4 of this invention with the cross shape. 4A is a perspective view of a laminated piezoelectric ceramic element in which the shape of the fitting portion surface is configured in a cross shape, and FIG. 4B is a metal case upper lid in which the shape of the fitting portion surface is configured in a cross shape. FIG. 4C is a perspective view of the upper lid of the metal case in which the shape of the fitting portion surface is a cross shape. It is a longitudinal cross-sectional view of the lamination type piezoelectric actuator which comprised the shape of the cross section parallel to the lamination direction of the fitting part which concerns on Embodiment 5 of this invention, and put the resin-made spheres in the inside by a conical recessed part. It is a perspective view of the conventional laminated piezoelectric ceramic element. It is a perspective view of the conventional multilayer piezoelectric actuator. It is a longitudinal cross-sectional view of a conventional multilayer piezoelectric actuator.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The basic structure of a multilayer piezoelectric actuator in which a multilayer piezoelectric ceramic element is enclosed in a metal case is the same as the conventional example described in the background art. The fitting portions are not limited to a pair, and a plurality of fitting portions may be provided according to the characteristics and design specifications required for the product.

(Embodiment 1)
As a first embodiment, a case where the fitting portion is configured by conical unevenness will be described. FIG. 1 is a longitudinal sectional view of a multilayer piezoelectric actuator in which the shape of a cross section parallel to the stacking direction of the fitting portion according to Embodiment 1 of the present invention is configured by conical irregularities. The present embodiment is a multilayer piezoelectric actuator 1 in which the fitting portion 10 is configured by conical unevenness, and the fitting portion 10 has a conical projection as an upper lid convex portion 11 at the center of the upper lid 3 of the metal case 2. This portion is configured with a conical recess as a dummy layer recess 12 at the center of the end face of the dummy layer 7 of the multilayer piezoelectric ceramic element 6. The shape of the conical unevenness of the upper lid convex portion 11 and the dummy layer concave portion 12 may be reversed between the concave and convex. Moreover, although the fitting part 10 was arrange | positioned between the upper cover 3 of the metal case 2, and the dummy layer 7, you may arrange | position between the lower cover 5 of the metal case 2, and the dummy layer 7, or both. The positions of the upper lid convex portion 11 and the dummy layer concave portion 12 constituting the fitting portion 10 are aligned so that the respective central axes of the expansion / contraction direction of the metal case 2 and the stacking direction of the multilayer piezoelectric ceramic element 6 coincide with each other. To fix.

  The conical concave portion which is the dummy layer concave portion 12 on the end face of the multilayer piezoelectric ceramic element 6 is processed by grinding using a drill in accordance with the size of the conical convex portion of the upper lid convex portion 11. This processing may be processing using a grinding device using ultrasonic vibration or another grinding means such as a laser, and may be before or after sintering the ceramic. However, the conical concave portion which is the dummy layer concave portion 12 is processed to be slightly larger so that it can be fitted to the conical convex portion of the upper lid convex portion 11.

  As a result of manufacturing the multilayer piezoelectric actuator 1 by enclosing the multilayer piezoelectric ceramic element 6 in the metal case 2 using the fitting portion 10 described above, the inclination of the upper lid 3 and the lower lid 5 of the metal case 2 can be achieved only by assembling work. It is on the order of 10 μm, and it can greatly improve the tilt that has occurred in the past several tens of μm, and can eliminate the need for high-precision and expensive dedicated jigs and the occurrence of a large amount of adjustment man-hours. It was.

(Embodiment 2)
As a second embodiment, a case will be described in which the fitting portion is configured by cylindrical irregularities. FIG. 2 is a longitudinal sectional view of a multilayer piezoelectric actuator in which the shape of a cross section parallel to the stacking direction of the fitting portion according to the second embodiment of the present invention is configured by cylindrical irregularities. The present embodiment is a multilayer piezoelectric actuator 1 in which the fitting portion 10 is configured by cylindrical irregularities, and the fitting portion 10 has a cylindrical convex as an upper lid convex portion 11 at the center of the upper lid 3 of the metal case 2. This portion is configured to have a cylindrical recess as a dummy layer recess 12 at the center of the end face of the dummy layer 7 of the multilayer piezoelectric ceramic element 6. The shape of the cylindrical irregularities of the upper lid convex portion 11 and the dummy layer concave portion 12 may be reversed in the concave and convex shapes. Moreover, although the fitting part 10 was arrange | positioned between the upper cover 3 of the metal case 2, and the dummy layer 7, you may arrange | position between the lower cover 5 of the metal case 2, and the dummy layer 7, or both. Positions of the upper lid convex portion 11 and the dummy layer concave portion 12 constituting the fitting portion 10 are positioned so that the central axis in the expansion / contraction direction of the metal case 2 coincides with the central axis in the stacking direction of the multilayer piezoelectric ceramic element 6. Combine and fix.

  The processing method and effects of the cylindrical recesses arranged in the dummy layer 7 on the end face of the multilayer piezoelectric ceramic element are the same as those in the first embodiment.

(Embodiment 3)
As a third embodiment, a case where the fitting portion is configured by hemispherical and conical irregularities will be described. FIG. 3 is a longitudinal sectional view of a multilayer piezoelectric actuator in which the shape of the cross section parallel to the stacking direction of the fitting portion according to the third embodiment of the present invention is configured by unevenness with one hemisphere and the other conical. . The present embodiment is a stacked piezoelectric actuator 1 in which the fitting portion 10 is formed of a hemispherical shape and a conical asperity, and the fitting portion 10 is a hemisphere as an upper lid convex portion 11 at the center of the upper lid 3 of the metal case 2. The convex portion is formed with a conical concave portion as a dummy layer concave portion 12 at the center of the end face of the dummy layer 7 of the multilayer piezoelectric ceramic element 6. As for the shape of the hemispherical and conical irregularities of the upper lid convex portion 11 and the dummy layer concave portion 12, the concave and convex shapes may be reversed. Moreover, although the fitting part 10 was arrange | positioned between the upper cover 3 of the metal case 2, and the dummy layer 7, you may arrange | position between the lower cover 5 of the metal case 2, and the dummy layer 7, or both. Positions of the upper lid convex portion 11 and the dummy layer concave portion 12 constituting the fitting portion 10 are positioned so that the central axis in the expansion / contraction direction of the metal case 2 coincides with the central axis in the stacking direction of the multilayer piezoelectric ceramic element 6. Combine and fix.

  As a result of manufacturing the multilayer piezoelectric actuator 1 by enclosing the multilayer piezoelectric ceramic element 6 in the metal case 2 using the fitting portion 10, the upper lid 3 and the lower lid 5 of the metal case 2 in the first and second embodiments. Better results were obtained than the slope improvement effect. When the concave portion according to the third embodiment is conical and the convex portion is hemispherical, the inclination of the upper lid 3 and the lower lid 5 is 10 μm or less.

(Embodiment 4)
As a fourth embodiment, a case where the fitting portion is configured by cross-shaped processing will be described. FIG. 4 shows a stacked piezoelectric actuator in which the shape of the fitting portion surface parallel to the stacking direction of the fitting portions according to the fourth embodiment of the present invention is configured in a cross shape. 4A is a perspective view of a laminated piezoelectric ceramic element in which the shape of the fitting portion surface is configured in a cross shape, and FIG. 4B is a metal case upper lid in which the shape of the fitting portion surface is configured in a cross shape. FIG. 4C is a perspective view of the upper lid of the metal case in which the shape of the fitting portion surface is a cross shape. The present embodiment is a multilayer piezoelectric actuator 1 in which the fitting portion 10 is configured to be concave and convex by cross-shaped processing when viewed from the inside of the upper lid as shown in the figure inside the upper lid 3 of the metal case 2. The metal case 2 has a cross-shaped convex portion as the upper lid convex portion 11 at the center of the upper lid 3 and a dummy layer concave portion 12 at the center of the end face of the dummy layer 7 of the laminated piezoelectric ceramic element 6 as shown in the figure. The upper part of 7 is provided with the recessed part by cross-shaped process. The concave and convex shapes of the upper lid convex portion 11 and the dummy layer concave portion 12 formed by cross-shaped processing may be reversed. Moreover, although the fitting part 10 was arrange | positioned between the upper cover 3 of the metal case 2, and the dummy layer 7, you may arrange | position between the lower cover 5 of the metal case 2, and the dummy layer 7, or both. Positions of the upper lid convex portion 11 and the dummy layer concave portion 12 constituting the fitting portion 10 are positioned so that the central axis in the expansion / contraction direction of the metal case 2 coincides with the central axis in the stacking direction of the multilayer piezoelectric ceramic element 6. Combine and fix.

  The cross-shaped concave portion of the end face of the dummy layer 7 of the multilayer piezoelectric ceramic element 6 is processed by grinding using a drill in accordance with the size of the cross-shaped convex portion formed on the upper lid 3 of the metal case 2. This processing may be processing using a grinding device using ultrasonic vibration, another grinding means such as laser or dicing, or before or after sintering the ceramics. However, the concave portion is processed slightly larger than the convex portion.

  As a result of manufacturing the multilayer piezoelectric actuator 1 by encapsulating the multilayer piezoelectric ceramic element 6 in the metal case 2 using the fitting portion 10 described above, the inclination of the upper lid 3 and the lower lid 5 is on the order of 10 μm only by normal assembling work. Thus, the same effect as in the first and second embodiments was obtained.

(Embodiment 5)
As a fifth embodiment, a case where the fitting portion is formed of a resin sphere inside a conical recess will be described. FIG. 5 is a longitudinal sectional view of a laminated piezoelectric actuator in which the shape of a cross section parallel to the laminating direction of the fitting portion according to the fifth embodiment of the present invention is formed by placing resin spheres inside with conical recesses on both sides. FIG. The present embodiment is a multilayer piezoelectric actuator 1 having a configuration in which a spherical structure is arranged so that the fitting portion 10 is in contact with the inside of the conical recess, and the fitting portion 10 is formed on the upper lid 3 of the metal case 2. A conical concave portion as the upper lid convex portion 11 at the center, a conical concave portion as the dummy layer concave portion 12 at the center of the end face of the dummy layer 7 of the multilayer piezoelectric ceramic element 6, and a resin so as to contact the inside of the fitting portion 10 It is configured by inserting a sex sphere 13. Moreover, although the fitting part 10 was arrange | positioned between the upper cover 3 of the metal case 2, and the dummy layer 7, you may arrange | position between the lower cover 5 of the metal case 2, and the dummy layer 7, or both. Positions of the upper lid convex portion 11 and the dummy layer concave portion 12 constituting the fitting portion 10 are positioned so that the central axis in the expansion / contraction direction of the metal case 2 coincides with the central axis in the stacking direction of the multilayer piezoelectric ceramic element 6. Combine and fix.

  As a result of manufacturing the multilayer piezoelectric actuator 1 by enclosing the multilayer piezoelectric ceramic element 6 in the metal case 2 using the fitting portion 10, the same effects as those of the first, second, and fourth embodiments were obtained.

  As described above, according to the present invention, the stress in the displacement direction applied to the metal case is obtained by processing the fitting portion so that the center axes of the dummy layer end surface of the multilayer piezoelectric ceramic element and the lid surface inside the metal case are aligned. It is possible to provide a laminated piezoelectric actuator that is uniform and hardly tilts in the displacement direction.

DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric actuator 2 Metal case 3 Upper lid 4 Telescopic tube 5 Lower lid 6 Laminated piezoelectric ceramic element 7 Dummy layer 8 Lead wire 9 Terminal 10 Fitting part 11 Upper lid convex part 12 Dummy layer concave part 13 Resin sphere 21 Piezoelectric ceramic layer 22 Insulating layer 23 Internal electrode 24 External electrodes 25a, 25b Displacement direction

Claims (4)

  A plurality of piezoelectric ceramic layers and internal electrodes are alternately stacked, and a dummy layer which is an inactive piezoelectric ceramic layer is stacked at both ends in the stacking direction to form a multi-layered laminated body, and the piezoelectric ceramic layer A laminated piezoelectric actuator in which a laminated piezoelectric ceramic element having a pair of external electrodes formed by electrically connecting so that the internal electrode layers adjacent to each other at an equal potential via a gap are formed in a metal case A fitting portion for positioning is provided on the metal case and the dummy layer so that the central axis in the expansion / contraction direction of the metal case and the central axis in the stacking direction of the multilayer piezoelectric ceramic element coincide with each other. A laminated piezoelectric actuator characterized by being fixed by   2. The multilayer piezoelectric actuator according to claim 1, wherein a shape of a cross-section parallel to the stacking direction of the fitting portion is one hemispherical convex portion and the other is a conical concave portion.   The multilayer piezoelectric actuator according to claim 1, wherein the shape of the fitting portion surface parallel to the lamination direction of the fitting portion is a cross shape.   The shape of a cross section parallel to the stacking direction of the fitting portion is a conical concave portion, and a spherical structure is disposed so as to be in contact with the inside of the concave portion. Multilayer piezoelectric actuator.

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