JP2726751B2 - Multilayer piezoelectric element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an element utilizing the electrostriction effect,
More specifically, the present invention relates to a laminated piezoelectric element formed by laminating a piezoelectric thin plate such as a piezoelectric ceramic and an electrode plate, and a method of manufacturing the same.

[Prior art]

2. Description of the Related Art Conventionally, a laminated piezoelectric actuator has been known as a drive source of an electromechanical component. One type of element that uses the electrostriction longitudinal effect, which is used as this piezoelectric actuator, is to form a metal sheet on the surface of a piezoelectric plate that becomes an electrostrictive material such as a green sheet of a piezoelectric ceramic or a piezoelectric ceramics plate, and then stack a large number of them. , Sintering or bonding. In order to drive, as an actuator, a laminated piezoelectric element in which such a piezoelectric plate and an electrode plate are sequentially laminated, it is necessary to electrically connect every other electrode plate between the piezoelectric bodies. As a configuration of an element for connecting each electrode layer, for example, as shown in FIG. 4, on the tomographic plane of the piezoelectric element 4, one end of an electrode plate 42 is formed slightly shorter than the piezoelectric plate 41. is there. That is, the electrode plate formed on the thin plate surface of the rectangular flat plate or the circular flat plate is not formed on only one side of the thin plate surface, and conversely, the other side is stacked on the side of the element. The surface area of the electrode plate is smaller than that of the thin plate so that the edge of the electrode plate is exposed.
Then, the electrode plates 42 are alternately laminated so that the edges thereof are exposed every other layer, and are connected in parallel by external electrodes 44a and 44b every other layer using the electrode plates exposed on the element side surfaces. In addition, from the viewpoint of the improvement in the distortion characteristics of the element, as shown in FIG. 5, the piezoelectric element 5 forms an electrode plate on the entire surface of the piezoelectric plate and the piezoelectric plates 51 and 52 are sequentially stacked so as to be alternately stacked. Laminated ones are known. In this case, since the edge of the electrode plate is exposed on both sides of the element in each layer, this electrode plate is exposed.
The element structure is such that insulating material 53 is applied alternately on both sides with the edges of 52 placed alternately and external electrodes 54a and 54b are formed thereon (Japanese Patent Publication No. 63-17354).

[Problems to be solved by the invention]

In these conventional laminated piezoelectric elements, as shown in FIG. 4, electrode plates were alternately exposed on both side surfaces of the element alternately, that is, the electrode plate was placed on one side of the element from the surface of the piezoelectric plate. In the one whose edge is formed slightly shorter on the side,
There is an advantage that the configuration of the external electrodes is extremely simple, and the electrode plates can be easily and alternately connected alternately. However, when such a piezoelectric element is driven as an actuator, there is a non-displacement part that does not expand and contract piezoelectrically inside the element near both external electrodes, and this non-displacement part suppresses the occurrence of distortion. At the same time, the device was destroyed due to the generation of stress. Therefore, if the electrode plate is formed on the entire surface of the piezoelectric plate and electrically connected alternately outside the stacked device as shown in FIG. 5, the non-displacement inside the device is as described above. There are no parts. Therefore, since concentration of stress can be prevented without suppressing generation of distortion, an element having high electromechanical conversion efficiency such as displacement can be configured. On the other hand, such an element in which an electrode plate is formed on the entire surface of a piezoelectric plate has the following problems. Normally, to manufacture a piezoelectric element, a slip containing ceramic powder as a main component is generally formed by a film forming machine, and then the solvent in the slip is dried to form a green sheet. An electrode plate is created by screen printing. Then, an element is obtained by sintering a product formed by laminating and pressing a large number of sheets. At this time, a paste-like ink such as silver, palladium, or platinum is used as an electrode material on the electrode surface printed on the green sheet to form a single electrode plate. In some cases, the adhesion strength between the electrode material and the ceramic has been improved by, for example, mixing a material which is familiar with the ceramic into the material in advance. However, if a large amount of such impurities are mixed in the electrode material, the internal resistance of the electrode plate is increased. On the other hand, if the purity of the electrode material is increased, the electrode plate is provided on the entire surface of the piezoelectric plate. The strength is low, and there has been a problem that the electrode plate and the piezoelectric plate are peeled off by repeated application or application of a high voltage for a long time or a long time. Therefore, the present invention has been made in view of the above problems,
The purpose is that there is no non-displacement part inside the piezoelectric body, so that the element does not break down due to stress concentration, and the electrode plate is applied for a long time, long-term repetition, or high voltage application. An object of the present invention is to provide an improved laminated piezoelectric element which does not cause separation from a piezoelectric plate and a method for producing the same.

[Means for Solving the Problems]

In order to solve the above problems, in the present invention, in a laminated piezoelectric element in which piezoelectric plates and electrode plates are alternately laminated, the electrode plates cover half surfaces on the piezoelectric plates and are adjacent to each other in the laminating direction. Are arranged on opposite sides of the piezoelectric plate. And in the manufacturing method of the laminated piezoelectric element,
Forming an electrode plate on a half surface on the piezoelectric plate, and arranging the electrode plates on the piezoelectric plates adjacent to each other in the laminating direction on the opposite sides of the piezoelectric plate and sequentially laminating them. I have.

[Action]

The electrode plate formed on the piezoelectric plate has a predetermined electrode pattern, and does not cover the entire surface of the thin plate, and has an electrode present portion and an electrode non-existent portion. Since the surface of the piezoelectric plate is exposed in the portion where no electrode is present, the exposed portion is pressed against the lower surface of another piezoelectric plate laminated on the upper surface of the piezoelectric plate,
The upper and lower piezoelectric plates are integrally connected. Further, the electrode plates adjacent to each other in the thickness direction to be laminated have a planar pattern complementary to each other. That is, on the surface of the piezoelectric plate, an electrode plate of the same pattern closest to the existing portion of the electrode plate generates an electric field correspondingly. In the absence part of the electrode, the existence part between the other piezoelectric plates complements the absence part,
An electric field is created between the existing parts in correspondence with each other. Therefore, the piezoelectric body has the same electric field in any part, and has a laminated structure of a piezoelectric plate and an electrode plate having no non-displacement portion inside the piezoelectric body.

【Example】

Embodiments of a method for manufacturing a multilayer piezoelectric element of the present invention and a multilayer piezoelectric element obtained thereby will be described with reference to FIGS. 1 and 2. FIG. The piezoelectric element 1 of the present invention is formed such that piezoelectric plates 11 and electrode plates 12 are alternately stacked in multiple layers. Although exaggeratedly shown in the drawings, the piezoelectric plate 11 is a square-shaped piezoelectric member formed of a thin plate or a thin film, or a circular piezoelectric member (not shown), and an electrode plate 12 is provided on the surface of the piezoelectric plate 11. That is, many sheets are laminated. First, the piezoelectric plate (ceramic layer) 11 is made of Pb (Mg _1/3 Nb
_2/3 ) A slip formed by mixing a solvent, a dispersant, a binder, and a plasticizer with ceramic powder containing O ₃ as a main component is formed into a thin film by a film forming machine used for manufacturing a multilayer capacitor. Then, the solvent in the thin film is evaporated and dried to obtain a green sheet. The obtained green sheet was molded into a predetermined shape (square shape in this embodiment),
Used as 11. Next, the electrode plate 12 is placed on the surface of the piezoelectric plate 11.
Is provided. The electrode plate 12 is formed by printing with a screen printing machine using a paste ink such as silver, palladium, or platinum as an electrode material. In the present invention, when forming the electrode plate 12, the piezoelectric plate
An electrode plate 12 having a predetermined pattern is provided on the surface of 11. Then, on the surface of another piezoelectric plate 11, an electrode plate 12 having a pattern complementary to the electrode plate 12 provided earlier is provided. That is, the two-dimensional pattern of the electrodes is configured so that the existing portion and the non-existent portion of the electrode correspond to each other front and back. In the present embodiment, as shown in FIG.
Are formed on exactly half of the surface of the piezoelectric plate 11. This is because, when the piezoelectric plates 11 are stacked, the electrode plates 12 may be formed only for one type of pattern by alternately reversing the stacking direction of the piezoelectric plates. Next, after the electrode plate 12 is formed on the surface of the piezoelectric plate 11, a large number of the piezoelectric plates 11 are laminated by a predetermined number according to the application.
At this time, the electrode plates 12 are stacked alternately on the opposite side for each of the piezoelectric plates 11 to be stacked. That is, in each half region of the laminate, the electrode plate 12 is sandwiched between two piezoelectric plates 11.
a and 12a are provided. Then, in the side surface fault of the laminated body of the piezoelectric plates 11, two opposite sides (the front surface in FIG. 1 (b)) are alternately distributed left and right for each layer of the piezoelectric plate 11 so that the electrode plates 12a and 12b are separated. The edge is exposed. As described above, after the electrode plates 12 are provided and the piezoelectric plates 11 are stacked in a large number in a predetermined direction, they are pressure-bonded by a hot press. Thereafter, the laminate is cut into desired dimensions and sintered. In sintering, main sintering is performed after pre-firing for removing binders. Subsequently, external electrodes 14a, 14b were provided on the outer surface of the obtained laminate.
Is provided. The external electrodes 14a and 14b are provided on the above-described two side surfaces where the edges of all the electrode plates 12 of the piezoelectric plates 11 are exposed on the side surface of the laminate. Then, the electrode plates 12a and 12b of the two-layer piezoelectric plate 11 vertically adjacent to each other are paired, and
Connection is made every other pair, and external electrodes are provided so as to alternately connect every two pairs on two sides. Electrode plate 12
The structures of the external electrodes 14a and 14b that enable such a connection include, first, two layers of piezoelectric plates 11 and 1 that are vertically adjacent to each other.
One electrode plate 12a, 12b is paired, and insulation bands 13a,..., (13b,. As shown in FIG. 1 (a), the insulating bands 13a (13b) are arranged alternately on both sides of each pair of the electrode plates 12a and 12b. Subsequently, external electrodes 14a and 14b are formed in the laminating direction on both side surfaces from above the insulating band 13. The application of the insulating material of the insulating band 13 and the conductive material of the external electrodes 14a and 14b can be easily performed by screen printing or the like as in the case of the electrode plate 12. In the polarization processing of the element, voltages having different polarities may be applied to the external electrodes 14a and 14b so that the polarities of the pair of electrode plates 12a and 12a are alternately changed for each pair in the stacking direction. The piezoelectric element 1 of the present invention thus manufactured is
The electrode plates 12 are adjacent to each other in the thickness direction.
The patterns provided on the half surface of the piezoelectric plate 12b complement each other. Next, the operation of the piezoelectric element 1 configured as described above will be described. The electrode plate 12 formed on the piezoelectric plate 11
It has a pattern existing on a half surface of the surface of the piezoelectric plate 11.
Then, since the surface of the piezoelectric plate 11 is exposed to the other half of the surface where the electrodes are not present, the exposed portion is pressed against the lower surface of another piezoelectric plate 11 laminated on the upper surface of the piezoelectric plate 11, The upper and lower piezoelectric plates 11, 11 are integrally connected. That is, the fired piezoelectric element 1 is formed by coupling the upper and lower piezoelectric plates 11, 11 without being separated from each other by the electrode plate 12. In the electrode plates 12a and 12b adjacent in the thickness direction, their planar electrode patterns are formed complementarily to each other. The electrode plate 12a generates an electric field corresponding to the upper and lower electrode plates 12a, 12a which are arranged in the same direction with one layer therebetween, ie, two piezoelectric plates 11 interposed therebetween. Then, in a portion of the electrode plate 12a where no electrode is present, the electrode plates 12b and 12b of the vertically adjacent piezoelectric plates 11 and 11 complement each other to form the electrode plates 12b and 12b.
Since an electric field is generated between the electrodes 12b, the electric field is the same at any part of each piezoelectric plate 11, and there is no non-displacement portion inside the piezoelectric body. The above is an embodiment by the green sheet method of the present invention. Next, an embodiment by the pressure bonding method will be described with reference to FIG. First, the sintered piezoelectric or electrostrictive material block is polished to form the piezoelectric plate 11. Then, on a half surface of the surface of the piezoelectric plate 11, a paste-like electrode material made of silver, palladium, platinum or the like to which glass frit has been added is printed by screen printing or the like, thereby forming the electrode plate 12. Next, a paste containing the piezoelectric electrostrictive material powder and the glass frit that have been heat-treated at the firing temperature of the piezoelectric material is applied to the remaining half surface of the piezoelectric plate 11 to form the piezoelectric electrostrictive material layer 15. Then, a plurality of piezoelectric plates 11 having an electrode plate 12 and a piezoelectric electrostrictive material layer 15 on the surface.
In the same manner as in the above-described embodiment, a predetermined number of the electrode plates 12 are stacked alternately so as to be alternately arranged on the opposite side, and pressure-bonded by hot pressing to obtain a stacked body. In the embodiment of the present invention, the electrode plate has a half surface of the piezoelectric plate as an electrode, but any two-layer or multi-layer electrode plate whose planar pattern is complementary to each other. Well, also in the method of manufacturing the element in the embodiment,
Although the so-called green sheet method is used, another bonding method may be used from the characteristics of the present invention. Further, the above-mentioned piezoelectric plate may use an electrostrictive material having a history or a piezoelectric material having no history.

【effect】

The present invention is configured as described above, and has the following effects. When the multilayer piezoelectric element of the present invention is driven as an actuator, there is no non-displacement portion so as not to expand and contract piezoelectrically inside the element, a uniform electrostrictive effect is obtained, and the element is caused by stress concentration. There is no destruction. In addition, since there is a portion where adjacent piezoelectric plates are integrally joined, the problem of adhesion strength of the electrode plate causes a long-time application, a long-term repeated application, or a high voltage application between the electrode plate and the piezoelectric plate. No peeling occurs. This structure also disperses the stress concentration at the time of high / low temperature or cooling after sintering due to the difference in the coefficient of thermal expansion between the electrode plate and the piezoelectric plate, and the electrode plate and the piezoelectric plate are not separated by heat shock.

[Brief description of the drawings]

1 and 2 are views showing an embodiment of the present invention. FIGS. 1 (a) and 1 (b) are side views of a laminated piezoelectric element, FIG. 2 is a perspective view showing a configuration of an electrode plate, FIG. 3 is a perspective view showing a configuration of an electrode plate in another manufacturing method, and FIGS. 4 and 5 are side views of a conventional laminated piezoelectric element. 11: Piezoelectric plate, 12 (12a, 12b): Electrode plate, 13 (13a, 13
b) ... insulation band, 14a, 14b ... external electrode, 15 ... piezoelectric electrostrictive material layer.

Claims (2)

(57) [Claims] 1. A laminated piezoelectric element comprising a piezoelectric plate and an electrode plate alternately laminated, wherein the electrode plate covers a half surface on the piezoelectric plate and is mutually connected on the piezoelectric plates adjacent to each other in the laminating direction. A laminated piezoelectric element, which is arranged on the opposite side. 2. A step of forming an electrode plate on a half surface on a piezoelectric plate, and a step of arranging electrode plates on a piezoelectric plate adjacent to each other in a laminating direction on the piezoelectric plate and sequentially stacking them on opposite sides. A method for manufacturing a laminated piezoelectric element, comprising: