JP6159985B2 - Piezoelectric element, piezoelectric actuator, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a piezoelectric element in which a piezoelectric layer and an internal electrode layer are laminated, a piezoelectric actuator, and a manufacturing method thereof.

  2. Description of the Related Art Conventionally, a piezoelectric actuator in which rectangular parallelepiped piezoelectric elements are stacked to form a main body is known. 6A to 6C are a perspective view of a conventional piezoelectric actuator body 600, a perspective view of a piezoelectric element 610, and a cross-sectional view of the piezoelectric element 610, respectively. The piezoelectric actuator main body 600 is formed by stacking laminated piezoelectric elements 610 that are integrally fired, and each external electrode 615 is connected by a lead wire 620. The piezoelectric element 610 is formed by laminating a piezoelectric layer and an internal electrode. When a voltage is applied, the piezoelectric layer between the electrodes is deformed as an active region, but other inactive regions are not deformed. For this reason, stress is likely to be generated near the boundary between these regions, and stress is particularly concentrated at the corner C of the internal electrode 612 and breakage is likely to occur.

  On the other hand, a piezoelectric actuator has been developed in which a stress absorbing layer made of powder containing lead titanate as a main component is provided in a piezoelectric element so that the piezoelectric layer is discontinuous to relieve stress (for example, a patent) Reference 1) has a shape in which stress is easily generated at the corners of the internal electrode. On the other hand, a piezoelectric element has also been developed in which internal electrodes are provided on the entire laminated surface and stress concentration is prevented by eliminating inactive regions on the side surfaces (for example, Patent Document 2).

JP 2006-286774 A JP 05-003351 A

  However, in the piezoelectric element described in Patent Document 2, since the internal electrode is uniformly exposed on the side surface, it is necessary to form an insulator on the exposed portion of the internal electrode that should not be connected to the external electrode. I need.

  On the other hand, it is also conceivable to prevent the local stress from being concentrated between the active region and the inactive region by making the piezoelectric element into a disc shape. In this case, stress concentration can be prevented because there are no corners in the internal electrode. However, it is difficult to arrange each piezoelectric element so that external electrodes between the plurality of piezoelectric elements can be connected by lead wires and to stack them in multiple stages. In order to avoid this, it is conceivable to form the piezoelectric elements in an annular shape and to facilitate alignment through the shafts in the holes. However, it is troublesome to provide external electrodes on each piezoelectric element and connect them.

  The laminated element requires external electrodes that connect the internal electrodes every other layer. In order to form the external electrode, the piezoelectric element must be fixed by aligning the positions therefor. For example, when external electrodes are printed by screen printing, the piezoelectric elements are fixed so that the θ direction (rotational position around the central axis) of the piezoelectric elements is aligned and the printed portion hits the screen mask. Also, when the piezoelectric elements are stacked and the external electrodes of a plurality of piezoelectric elements are connected, it is necessary to align the positions of the external electrodes. Although it was easy to align the positions of the external electrodes of a conventional dice-shaped piezoelectric element, in the case of an annular type, it takes time to align.

  The present invention has been made in view of such circumstances, and provides a piezoelectric element, a piezoelectric actuator, and a method of manufacturing the same, in which stress is not easily concentrated locally and work for manufacturing a piezoelectric actuator can be facilitated. The purpose is to do.

  (1) In order to achieve the above object, a method for manufacturing a piezoelectric element according to the present invention is a method for manufacturing a piezoelectric element in which a piezoelectric layer and an internal electrode layer are stacked, on a central axis penetrating in the stacking direction. And a step of manufacturing a sintered body of a rectangular cylinder having a hole of the above and a step of cylindrically processing the sintered body, leaving a side surface having a small distance from the central axis as an unprocessed surface. Yes.

  In this way, by manufacturing an annular piezoelectric element having an unprocessed surface, the annular piezoelectric elements are stacked, and a piezoelectric actuator that does not concentrate stress locally and hardly breaks down can be manufactured.

  In addition, the rotational position around the central axis of the piezoelectric element can be aligned using the unprocessed surface. As a result, the printing positions of the external electrodes of the piezoelectric elements can be aligned, and the external electrode positions when the piezoelectric elements are stacked can be aligned. And the production work of a piezoelectric actuator can be made easy.

  (2) Further, the method for manufacturing a piezoelectric element of the present invention is characterized in that it further includes a step of aligning the printed portion of the external electrode using the unprocessed surface. As a result, the alignment of the printing location is facilitated, and the working efficiency can be improved.

  (3) A method for manufacturing a piezoelectric actuator according to the present invention is a method for manufacturing a piezoelectric actuator in which piezoelectric elements are stacked in a stacking direction, and a plurality of piezoelectric elements obtained by the method according to claim 1 or 2. And a step of stacking in the stacking direction and a step of aligning the external electrodes of the stacked piezoelectric elements using the unprocessed surface. Thereby, the connection of an external electrode becomes easy and the working efficiency of piezoelectric actuator manufacture can be improved.

  (4) A piezoelectric element according to the present invention is a piezoelectric element in which a piezoelectric layer and an internal electrode layer are laminated and has an outer surface parallel to the central axis, and includes a hole on the central axis penetrating in the stacking direction. And a machined surface that is an outer surface having the largest distance from the central axis, and a non-machined surface that is an outer surface having a distance from the central axis smaller than the processed surface.

  Thereby, those rotational positions can be easily matched by matching the unprocessed surfaces between the piezoelectric elements. As a result, the working efficiency of manufacturing a piezoelectric actuator using a piezoelectric element can be improved. Moreover, it becomes easy to fit according to a dimension because a process surface becomes an outermost surface, and alignment becomes easy. By leaving the unprocessed surface, it is difficult to cause cracks in the piezoelectric element, and an effect of improving durability can be obtained.

  (5) The piezoelectric actuator according to the present invention is a piezoelectric actuator in which piezoelectric elements are stacked in a stacking direction, and the unprocessed surface is aligned on a common surface, and the piezoelectric element according to claim 4 is the stacked layer It is connected in the direction. When manufacturing such a piezoelectric actuator, the rotation position can be easily adjusted when the piezoelectric elements are stacked, and therefore, the manufacture becomes easy.

  According to the present invention, it is possible to manufacture a piezoelectric actuator in which stress is not concentrated locally and breakage hardly occurs. In addition, the rotational position around the central axis of the piezoelectric element can be aligned using the unprocessed surface. As a result, the manufacturing operation of the piezoelectric actuator can be facilitated.

(A), (b) It is the plane sectional view and perspective sectional view which show the piezoelectric element which concerns on 1st Embodiment. It is sectional drawing which shows the piezoelectric actuator of this invention. It is a perspective view which shows a piezoelectric actuator main body. (A), (b) It is the plane sectional view and perspective sectional view which show the piezoelectric element which concerns on 2nd Embodiment. (A), (b) It is the plane sectional view and perspective sectional view which show the piezoelectric element of a comparative example. (A)-(c) is the perspective view of the conventional piezoelectric actuator main body, the perspective view of a piezoelectric element, and sectional drawing of a piezoelectric element, respectively.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

[First Embodiment]
(Configuration of piezoelectric element)
1A and 1B are a plan view and a perspective sectional view showing the piezoelectric element 110, respectively. 1B is a cross-sectional view taken along the plane 1b shown in FIG. 1A, and FIG. 1A is a cross-sectional view taken along the plane 1a shown in FIG. The same applies to FIGS. 4A, 4B, 5A, and 5B).

  The piezoelectric element 110 includes an element body 111 and external electrodes 115 and 116. The element body 111 is formed by laminating a piezoelectric layer 112 and an internal electrode layer 113. The element body 111 has a hole 119 on the central axis C1 penetrating in the stacking direction, and is formed in an annular shape. Therefore, the element main body 111 does not concentrate stress locally and hardly breaks down.

  Further, the movement of the piezoelectric element 110 can be constrained by the hole 119, and the piezoelectric element 110 can be fixed in the direction perpendicular to the central axis C1, and the alignment can be performed accurately and easily. In the present embodiment, the term “annular” refers to a shape in which the entire outer surface is not formed in a circular cross section but only a part of the outer surface is formed in a circular arc shape. . The piezoelectric element 110 is used by being stacked in the expansion / contraction direction (stacking direction) for a piezoelectric actuator.

  The element body 111 has an outer surface parallel to the central axis C1. That is, the element body 111 has a machining surface 117 having a circular arc in cross section by a cylindrical machining and a flat unmachined surface 118. The processing surface 117 is an outer surface having the longest distance from the central axis C1. When the processing surface 117 is the outermost surface, the processing surface 117 is easily accommodated according to the dimensions, and alignment is facilitated.

  The unprocessed surface 118 is an outer surface whose distance from the central axis C1 is smaller than the processed surface 117. By aligning the unprocessed surfaces 118 between the piezoelectric elements 110, their rotational positions can be easily aligned. As a result, the working efficiency of manufacturing the piezoelectric actuator 100 using the piezoelectric element 110 can be improved. Further, leaving the unprocessed surface 118 in the element body 111 makes it difficult for the piezoelectric element 110 to crack and improves the durability.

  The external electrodes 115 and 116 are provided at predetermined positions on the processing surface 117 of the element body 111. In the example shown in FIGS. 1 and 2, external electrodes 115 and 116 are provided at positions that intersect a plane 1b (parallel to the unprocessed surface 118) passing through the central axis C1. Although an external electrode may be provided on the unprocessed surface 118, it is preferable to provide the external surface on the processed surface 117 in order to ensure connection with the external electrode.

  The element body 111 includes piezoelectric layers 112 and internal electrodes 113 that are alternately stacked via the piezoelectric layers 112.

(Piezoelectric element manufacturing method)
A method for manufacturing the piezoelectric element 110 configured as described above will be described. First, a rectangular-type stacked piezoelectric element having a hole on the central axis penetrating in the stacking direction is designed, and a sintered body in which a piezoelectric layer and internal electrodes are stacked and integrally fired is manufactured. Although it is preferable to produce a rectangular cylinder whose cross section perpendicular to the stacking direction is rectangular, a square cylinder may be produced as described later. The shape of the internal electrode 113 is determined according to the final shape of the piezoelectric element. The piezoelectric layer 112 and the internal electrode 113 are laminated, and a layer without the internal electrode 113 is provided at the end portions on both main surfaces.

  Next, the outer shape of the piezoelectric element 110 is processed. For example, the thickness is surface ground and the inner hole is milled. Then, the side surface having a small distance from the central axis C1 is left as the unprocessed surface 118, and the sintered body is cylindrically processed. In this manner, the annular piezoelectric element 110 having the unprocessed surface 118 can be easily manufactured. As a result, the alignment of the printing location is facilitated, and the working efficiency can be improved.

  Then, external electrodes 115 and 116 are formed at predetermined locations on the outer surface of the element body 111. The printing positions of the external electrodes 115 and 116 are aligned using the unprocessed surface 118, the electrode paste is applied by screen printing, and baked to form the external electrodes 115 and 116. By using the unprocessed surface 118, the piezoelectric element 110 can be easily manufactured. Further, even when the piezoelectric elements 110 are stacked, a piezoelectric actuator that does not concentrate stress locally and hardly breaks down can be manufactured.

(Configuration of piezoelectric actuator)
FIG. 2 is a cross-sectional view showing one embodiment of the piezoelectric actuator 100. FIG. 3 is a perspective view showing the piezoelectric actuator main body 105. As shown in FIG. 2, the piezoelectric actuator 100 includes a piezoelectric actuator main body 105, a shaft 121, spacers 122 and 123, protrusions 124, lead wires 131 and 132, solder 135 and 136, a fixing portion 150, and a housing 180.

  The piezoelectric actuator main body 105 is formed in a cylindrical shape by stacking a plurality of piezoelectric elements 110 formed in the same annular shape on substantially the same central axis C1 in the expansion / contraction direction. By stacking a plurality of piezoelectric elements 110, the piezoelectric actuator 100 can be configured to obtain a large displacement.

  The unprocessed surface 118 of the element body 111 is aligned on a common surface, and the external electrodes provided on the processed surface are connected by lead wires 131 and 132 and solders 135 and 136. Due to the presence of the unprocessed surface 118 in the element body 111, the rotation position can be easily adjusted when the piezoelectric elements 110 are stacked, and the manufacture of the piezoelectric actuator 100 is facilitated.

  The fixing unit 150 fixes one end of the piezoelectric actuator main body 105. The fixing unit 150 is coupled to the shaft 121 and fixes the position of the shaft 121. The shaft 121 is inserted into the central hole 119 of the plurality of stacked piezoelectric elements 110 and fixes the axis of the actuator body 105. The spacers 122 and 123 are provided at both ends of the piezoelectric actuator main body 105. The shaft 121 is slightly shorter than the piezoelectric actuator body 105 and is designed so as not to hinder expansion and contraction of the piezoelectric actuator body 105.

  The protrusion 124 is a hemispherical member that transmits the displacement to the outside. The housing 180 is made of metal, for example, and covers the piezoelectric actuator main body 105 and the like. The lead wires 131 and 132 are connected to the outside by connecting the external electrodes 115 and 116 of the piezoelectric elements 110 with solders 135 and 136, respectively.

(Method for manufacturing piezoelectric actuator)
A method for manufacturing the piezoelectric actuator 100 configured as described above will be described. A plurality of piezoelectric elements 110 manufactured as described above are used. The piezoelectric element 110 is manufactured by cylindrically processing a sintered body so that a side surface having a small distance from the central axis C1 remains as an unprocessed surface 118.

  The unprocessed surface 118 is used to align the external electrodes 115 and 116 of the stacked piezoelectric elements 110. That is, the positions of the external electrodes when the piezoelectric elements 110 are stacked are aligned. Thereby, the connection of the external electrodes 115 and 116 becomes easy and work efficiency can be improved.

  Next, the shaft 121 is passed through the hole so that the position on the surface perpendicular to the central axis of the piezoelectric element 110 does not shift, and spacers 122 and 123 are disposed at both ends of the piezoelectric actuator body 105. Further, the piezoelectric actuator 100 can be manufactured by fixing one of the fixing portions and bonding the protrusion 124 to the other and covering the casing 180.

[Second Embodiment]
In the above embodiment, the piezoelectric element 110 has the two processed surfaces 117 and the two unprocessed surfaces 118 and has orientation in the shape, but the shape of the piezoelectric element has four processed surfaces and four The shape may have two unprocessed surfaces.

  4A and 4B are a plan sectional view and a perspective sectional view showing the piezoelectric element 210, respectively. As shown in FIGS. 4A and 4B, the cross section of the piezoelectric element 210 is formed in a shape in which a square corner having a hole 219 on the central axis C2 is an arc. Thus, since it is a shape without a bias | inclination, a square cylinder can be produced uniformly and work efficiency can be raised.

  In the piezoelectric element 210, piezoelectric layers 211 and internal electrodes 212 are alternately stacked, and have round processed surfaces 217 at four corners. All of the four processed surfaces 217 exist at the same distance from the central axis C2. Further, an unprocessed surface 218 closer to the central axis C2 than the processed surface 217 is formed at an intermediate position between the adjacent processed surfaces 217. Such a shape can be obtained by cylindrically processing a square cylindrical piezoelectric element.

  In addition, it is preferable that the taking-out portion 214 of the internal electrode 212 is provided so as to be exposed to any two adjacent processing surfaces 217. As a result, the connection can be established even if the rotational position of the piezoelectric element 210 around the central axis differs from the original position by 90 °.

  In addition, it is conceivable to provide electrodes on both end faces of the annular piezoelectric element in the stacking direction to establish electrical connection between the piezoelectric elements. However, since pressure in the stacking direction is applied to the piezoelectric actuator body, It becomes necessary to control the thickness of the electrode. In the present invention, such control is unnecessary.

[Examples and Comparative Examples]
As the piezoelectric element 110 according to the first embodiment, the piezoelectric element of Example 1 was manufactured. Similarly, the piezoelectric element of Example 2 was fabricated as the piezoelectric element 210 according to the second embodiment. On the other hand, as Comparative Example 1, a piezoelectric element 510 shown in FIG. A plurality of piezoelectric elements were stacked to produce a piezoelectric actuator.

  5A and 5B are a plan sectional view and a perspective sectional view showing a piezoelectric element 510 of a comparative example. The piezoelectric element 510 has a hole 519 on the central axis and is formed in an annular shape. The entire outer surface 511 is a processed surface and has a circular cross section. An internal electrode 512 is provided inside, and is connected to the external electrodes 515 and 516 at the extraction portion 514.

Example 1
First, a fired body of an integrally fired rectangular cylindrical piezoelectric element having an outer diameter of 5 mm × 7 mm, an inner diameter of 2 mm, and a thickness of 3 mm was produced. 50 layers each having a thickness of 50 μm were laminated, and layers having no internal electrode were provided on the top and bottom each by 0.25 mm. This was processed to a thickness of 2.5 mm by surface grinding. The outer diameter was processed into a cylinder and stopped when the outer diameter was processed to 6 mm, and a 5 mm wide oval element was produced.

  The externally processed surface was designed in advance so that the extraction portion of the internal electrode was exposed, and alignment was performed using a portion having a width of 5 mm, and the external electrode was formed by screen printing. A plurality of piezoelectric elements fabricated in this manner were prepared, and the external electrodes were baked and then stacked through the shaft. Then, the positions of the 5 mm width portions were aligned, temporarily fixed by a jig, and the external electrodes were connected by lead wires.

(Example 2)
First, a fired body of an integrally fired square cylindrical piezoelectric element having an outer shape of 5 mm × 5 mm, an inner diameter of 2 mm, and a thickness of 3 mm was produced. 50 layers each having a thickness of 50 μm were laminated, and layers having no internal electrode were provided on the top and bottom each by 0.25 mm. This was processed to a thickness of 2.5 mm by surface grinding. The outer diameter was cylindrically processed and stopped when it was processed to 6 mm, and an element with 5 mm square and rounded corners to φ6 was produced.

  The externally processed surface was designed in advance so that the extraction portion of the internal electrode was exposed, and alignment was performed using a portion having a width of 5 mm, and the external electrode was formed by screen printing. A plurality of piezoelectric elements fabricated in this manner were prepared, and the external electrodes were baked and then stacked through the shaft. Then, the positions of the 5 mm width portions were aligned, temporarily fixed by a jig, and the external electrodes were connected by lead wires.

(Comparative Example 1)
First, a fired body of an integrally fired square cylinder piezoelectric element having an outer diameter of 7 mm × 7 mm, an inner diameter of 2 mm, and a thickness of 3 mm was produced. 50 layers each having a thickness of 50 μm were laminated, and layers having no internal electrode were provided on the top and bottom each by 0.25 mm. This was processed to a thickness of 2.5 mm by surface grinding. Also, the outer diameter was processed into a cylinder and stopped when the outer diameter was processed to 6 mm, to produce a φ6 annular element.

  The externally processed surface was designed in advance so that the lead-out portion of the internal electrode was exposed, the electrode exposed on the outer peripheral surface was visually confirmed and aligned, and the external electrode was formed by screen printing. After the external electrode was baked, the shaft was stacked through the hole. Then, the external electrodes were visually aligned, temporarily fixed with a jig, and the external electrodes were connected to each other by lead wires.

  In the printing of the external electrodes, by producing a jig, the processing in the example was about 100 times that of the comparative example. Further, in the comparative example, when the piezoelectric elements were stacked, it was not possible to completely align them, for example, what was once aligned during visual alignment would be rotated and shifted when aligning other positions. In the comparative example, it took 30 times as much time as in the example for the approximate positioning.

DESCRIPTION OF SYMBOLS 100 Piezoelectric actuator 105 Piezoelectric actuator main body 110 Piezoelectric element 111 Element main body 112 Piezoelectric layer 113 Internal electrode layer (internal electrode)
115, 116 External electrode 117 Processed surface 118 Unprocessed surface 119 Hole 121 Shaft 122, 123 Spacer 124 Protrusion 131, 132 Lead wire 135, 136 Solder 150 Fixing part 180 Housing 210 Piezoelectric element 211 Piezoelectric layer 212 Internal electrode 214 Extraction part 217 Processed surface 218 Unprocessed surface 219 Hole

Claims (5)

A method of manufacturing a piezoelectric element in which a piezoelectric layer and an internal electrode layer are laminated,
A step of producing a sintered body of a rectangular cylindrical body in which a piezoelectric layer having a hole on the central axis penetrating in the laminating direction and an internal electrode layer are laminated and integrally fired ;
And a step of cylindrically processing the sintered body, leaving a side surface with a small distance from the central axis as an unprocessed surface.   The method for manufacturing a piezoelectric element according to claim 1, further comprising a step of aligning a printed portion of the external electrode using the unprocessed surface. A method of manufacturing a piezoelectric actuator in which piezoelectric elements are stacked in a stacking direction,
Passing a shaft through a plurality of piezoelectric elements obtained by the method according to claim 1 or 2, and stacking them in the stacking direction;
And a step of aligning external electrodes of the stacked piezoelectric elements using the unprocessed surface. A piezoelectric element in which a piezoelectric layer and an internal electrode layer are stacked and has an outer surface parallel to the central axis,
A hole on the central axis penetrating in the stacking direction;
A machining surface which is an outer surface having the largest distance from the central axis;
A non-machined surface that is an outer surface whose distance from the central axis is smaller than the machined surface ;
The piezoelectric element characterized that you have external electrode is arranged on the processing surface. A piezoelectric actuator in which piezoelectric elements are stacked in the stacking direction,
The piezoelectric actuator according to claim 4, wherein the raw surfaces are aligned on a common surface, and the piezoelectric elements according to claim 4 are connected in the stacking direction.

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