JPH10190078A - Multilayer piezo-electric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayer piezo-electric transducer which is free from an undisplacement part inside a piezo-electric and wherein an electrode does not separate from a piezo-electric substrate by interposing a piezo-electric electrostrictive material between electrode pieces arranged alternately. SOLUTION: A piezo-electric transducer 1 is formed so that a piezo-electric substrate 11 formed of piezo-electric ceramics and an electrode 12 are stacked alternately in multi-layer. The piezo-electric substrate 11 is formed to a thin board or a thin film and a number of electrodes 12 are stacked on a surface of the piezo-electric substrate 11. Thereby, when the multilayer piezo-electric transducer 1 is driven as an actuator, an undisplacement part does not exist inside the transducer 1 and breakage of the transducer 1 due to stress concentration does not occur. Furthermore, the electrode 12 and the piezo-electric thin substrate 11 do not peel in long-term application and long-term repetition application. Furthermore, separation of the electrode 12 and the piezo-electric substrate 11 due to heat shock does not occur also to stress concentration at high/low temperature or during cooling after baking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an element utilizing an electrostrictive effect, and more particularly to a laminated piezoelectric element in which a piezoelectric plate such as a piezoelectric ceramic and electrodes are laminated.

[0002]

2. Description of the Related Art A multilayer piezoelectric actuator has been known as a drive source for electromechanical components. One of the elements using the electrostriction longitudinal effect used as this piezoelectric actuator, after forming a metal electrode surface on the surface of a piezoelectric plate that becomes an electrostrictive material such as a green sheet of a piezoelectric ceramic or a piezoelectric ceramic plate, a large number of layers are laminated, Some are integrated by 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 plate, for example, as shown in FIG. 3, one end of an electrode plate 32 is formed slightly shorter than the piezoelectric plate 31 on the tomographic plane of the piezoelectric element 3. There is something. That is, the electrode plate formed on the thin plate surface of the flat piezoelectric body is not formed on only one side of the thin plate surface, and conversely, the other side is stacked on the side surface of the element when the other side is laminated. The surface on which the electrode plate is formed is provided to be smaller than the surface of the thin plate so that is exposed. The electrode plates 32 are alternately stacked so as to be exposed every other layer, and are connected in parallel by external electrodes 34a and 34b provided on the entire side surface of the element every other layer using the electrode plate exposed on the side surface of the element. .

FIG. 4 shows the improvement in the distortion characteristics of the device.
As shown in FIG. 2, there is known a piezoelectric element 4 in which electrodes are formed on the entire surface of a piezoelectric plate, and piezoelectric plates 41 and electrode plates 42 are sequentially stacked so as to be alternately stacked. In this case, since the edges of the electrode plate are exposed on both sides of the element in both layers, the insulating material 43 is applied alternately on both sides of the edge of the electrode plate 42, and the external electrodes 44a are formed thereon. , 4
4b (Japanese Patent Publication No. 63-1).
No. 7354).

[0005]

In these conventional laminated piezoelectric elements, as shown in FIG. 3, electrode plates are alternately exposed on both sides of the element, that is, the piezoelectric plates are alternately exposed. In the case where the edge of the electrode surface is formed slightly shorter on one side of the element than on the surface, there is an advantage that the configuration of the external electrode 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 element was destroyed due to the concentration of stress.

Therefore, if the internal electrode plate is formed on the entire surface of the piezoelectric plate and electrically connected alternately outside the laminated device as shown in FIG. The existence of the non-displacement portion is also eliminated. 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, an element in which an electrode plate is formed on the entire surface of such a piezoelectric plate has the following problems. Normally, in order to manufacture a piezoelectric element, roughly, a slip mainly composed of ceramic powder is formed by a film forming machine, and a solvent in the slip is dried to form a thin green sheet. An electrode plate is created by screen printing the electrode surface. Then, a large number of sheets are laminated and pressure-bonded and molded to obtain an element. At this time, on the electrode surface printed on the green sheet, a paste-like ink such as silver, palladium, or self-gold is used as an electrode material, and a single electrode plate is formed. 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 electrode material in advance.

However, if a large amount of the above 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 surface is provided on the entire surface of the piezoelectric plate. Therefore, there is a problem that the adhesion strength is low, and peeling occurs between the electrode plate and the piezoelectric plate due to long-time or long-term repeated application or high-voltage application.

Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to have no non-displacement portion inside the piezoelectric body, so that the element does not break down due to concentration of power, and , Long-time application or long-term repeated application,
Another object of the present invention is to provide an improved laminated piezoelectric element that does not cause separation between an electrode and a piezoelectric plate due to application of a high voltage.

[0010]

According to the present invention, there is provided a laminated piezoelectric element in which a piezoelectric plate and an electrode are alternately laminated in the thickness direction thereof. Characterized in that the electrode pieces are arranged alternately. In the above structure, a piezoelectric electrostrictive material may be interposed between the electrode pieces. In the above structure, it is preferable that the intervals between the electrode pieces constituting the electrodes existing in the laminating direction of the piezoelectric plates are substantially equal every other row of the electrode pieces.

[Effect] The electrodes provided on the surface of the piezoelectric plate include a first electrode piece having a pattern divided in a plane and a second electrode piece formed in a pattern complementary to the first electrode piece. Since the electrodes are formed with the electrode pieces, there is almost no electrode-free part with respect to the upper and lower piezoelectric plates to be laminated. When a voltage is applied during element driving, a uniform electric field is applied between the electrodes. Occurs. Further, a coupling layer made of a piezoelectric electrostrictive material that is filled and interposed between the first electrode layer and the second electrode layer enters the gap between the electrode pieces, and integrates the laminated upper and lower piezoelectric thin plates. Strongly bonded.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a multilayer piezoelectric element of the present invention and an example of a method for manufacturing the same will be described with reference to FIGS. The piezoelectric element 1 is formed such that piezoelectric plates 11 made of piezoelectric ceramics and electrodes 12 are alternately stacked in multiple layers. Although exaggeratedly shown in the drawings, the piezoelectric plate 11 has a rectangular shape formed of a thin plate or a thin film, or a circular shape (not shown), and an electrode 12 is provided on the surface of the piezoelectric plate 11. Many are laminated.

First, a piezoelectric plate (piezoelectric ceramic) 11
Is a method for forming a multilayer capacitor by using a slip obtained by mixing a solvent, a dispersant, a binder, and a plasticizer with a ceramic powder mainly composed of Pb (Mg _1/3 Nb _2/3 ) O _3. It is formed into a thin film by a machine. Then, the solvent in the thin film is evaporated and dried to obtain a green sheet. The obtained green sheet molded into a predetermined shape is used as the piezoelectric plate 11. Next, an electrode 12 is provided on the surface of the piezoelectric plate 11. The electrode 12 is formed by printing with a screen printing machine using a base-like ink obtained by mixing a glass frit with silver, palladium, self-gold or the like as an electrode material.

In the present invention, when forming the electrode 12, as shown in FIG. 2B, first, the first electrode piece 121,
…, Are created. A plurality of first electrode pieces 121 are provided in a band shape in parallel with one side on the surface of the piezoelectric plate 11, and each band-shaped electrode piece is formed in a pattern having a gap therebetween.
After the first electrode pieces 121,... Are formed, a paste-like piezoelectric material or a piezoelectric electrostrictive material made of an electrostrictive material that becomes the same or near-quality piezoelectric ceramic as the piezoelectric plate 11 is applied to the entire surface of the piezoelectric plate 11. Then, the bonding layer 123 is formed by applying the solution from above the first electrode piece 121. The bonding layer 123 is initially a soft paste made of a mixture of an electrostrictive material or a piezoelectric material powder and a glass frit that are heat-treated at the firing temperature of the piezoelectric electrostrictive material. Is a filler which exhibits some fluidity.

Next, as shown in FIG. 2A, on the film of the bonding layer 123 made of the piezoelectric electrostrictive material, second electrode pieces 122,. And print. At this time, the second electrode piece 122 is formed complementarily on the gap 124 between the plurality of strip-shaped patterns of the first electrode piece 121. That is, the piezoelectric electrostrictive material-filled coupling layer 123
And the electrode pattern of the first electrode piece 121 and the electrode pattern of the second electrode piece
Are alternately and complementarily arranged from the upper and lower surfaces in the thickness direction. Then, when the layers are pressure-bonded, the piezoelectric electrostrictive material-filled bonding layer 123 moves fluidly, and the electrode pieces 121 are moved.
And 122, the configuration is such that the electrode pieces are disposed almost all over the surface of the piezoelectric plate 11.

On the surface of the piezoelectric plate 11, a first electrode piece 121,
After the electrodes 12 are formed by providing the second electrode pieces 122, a predetermined number of the piezoelectric plates 11 are laminated in a predetermined number according to the intended use, and are pressed by a hot press. Thereafter, the laminate is cut into a predetermined size and sintered. In sintering, main sintering is performed after pre-baking for removing binders.

Subsequently, external electrodes 14a and 14b are provided on the outer surface of the obtained laminate. To this end, an insulating band 13 for insulating the external electrode 14a (14b) to be formed and the electrode 12 is provided at an edge of the electrode 12 exposed on both side surfaces of the laminate, Electrode pieces 121 and 122
Are connected, and the external electrodes 14a (14
A conductive band 15 for connecting b) to the electrode 12 is provided. The insulating bands 13 and the conductive bands 15 are provided alternately every other layer and alternately on both side surfaces. Subsequently, external electrodes 14a and 14b are formed in the laminating direction on both sides of the insulating band 13 and the conductive band 15, respectively. Insulation strip 1
3, the insulating material or the conductive material for the conductive band 15 or the external electrodes 14a and 14b can be applied by screen printing or the like, similarly to the electrode 12.

In addition, voltages of different polarities are applied to the external electrodes 14a and 14b so that the polarities of the elements 12,... I just need. The piezoelectric element 1 of the present invention manufactured in this manner is provided with the electrodes 12 provided on the piezoelectric plate 11 and is laminated in large numbers. The electrodes 12 have the first electrode piece 121 and the And two electrode pieces 122. And the pattern of each electrode piece is complementary, and the first electrode piece 121 and the second electrode piece 122
They are arranged via a piezoelectric electrostrictive material filling coupling layer 123 filling the gap.

Next, the piezoelectric element 1 configured as described above
The electrode 12 provided on the surface of the piezoelectric plate 11 is formed by an aggregate of the first electrode piece 121 and the second electrode piece 122, and when driving the element, a voltage is applied. In this case, a uniform electric field is generated between the electrodes 12 and 12 as in the case of the integrated electrodes. That is, as shown in FIGS. 2A and 2B, after forming the first electrode piece 121 to form the electrode 12, the piezoelectric electrode material is applied from the upper surface of the first electrode piece 121 to the entire surface of the piezoelectric plate 11. Since the filling connection layer 123 is formed, and then the second electrode piece 122 is formed and the piezoelectric plate is laminated and pressed, the paste connection layer 123 is formed by the gap 1 between the electrode patterns of the first electrode piece 121.
24 and the gap 125 of the electrode pattern of the second electrode piece. In addition, the printed electrode pieces 121 and 122
Is slightly rolled, so that no electrodes are absent on the upper and lower piezoelectric plates to be laminated, and the electrodes are uniform as described above.

Further, the piezoelectric electrostrictive material filling and binding layer 123 is
The electrode pattern of the first electrode piece 121 and the second electrode piece 12
Even if there is a slight overlap with the second electrode pattern, the upper and lower piezoelectric plates 11, 11 are integrally and firmly joined in the fired piezoelectric element 1 without being completely separated.

The above is an embodiment by the green sheet method of the present invention. Next, an embodiment by the pressure bonding method of the present invention will be described with reference to FIGS. First, the piezoelectric plate 11 is formed by polishing a block of the fired piezoelectric or electrostrictive material. A first electrode piece 121 is formed by printing a paste-like electrode material to which glass frit is added on the surface of the piezoelectric plate 11 by means such as screen printing. Next, the piezoelectric electrostrictive material-filled coupling layer 123 is formed of an electrostrictive material heat-treated at the firing temperature of the glass frit and the electrostrictive material or the piezoelectric material, or a paste of a piezoelectric material powder. Further, the second electrode piece 122 is made of the electrode material and the first electrode piece 12
1 is created in a pattern to capture it. Then, the piezoelectric plate 1
1 are laminated and pressure-bonded by a hot press to form a laminate. Subsequently, the insulating band 13, the conductive band 15, and the external electrodes 14a and 14b are formed in the same manner as in the above-described green sheet method.

In the embodiment of the present invention, the patterns of the electrode pieces 121 and 122 provided as the electrodes 12 are shown in the form of two strips in the drawing, however, a plurality of desired numbers can be provided. In addition, various types of pattern shapes can be implemented. Further, in the method of manufacturing the piezoelectric plate 11 in the embodiment, a so-called green sheet method and a pressure bonding method are used.
Other bonding methods may be used. For the piezoelectric plate 11, an electrostrictive material having hysteresis or a piezoelectric material having no hysteresis may be used.

[0023]

Since the present invention is configured as described above, the following effects can be obtained. When the multilayer piezoelectric element of the present invention is driven as an actuator, there is no non-displacement portion that does not expand and contract piezoelectrically, and a uniform electrostrictive effect is obtained, and the element is caused by stress concentration. There is no destruction. Further, there is no occurrence of peeling between the electrode and the piezoelectric thin plate due to long-term application, long-term repetitive application, or high-voltage application due to the problem of electrode adhesion strength. This structure also disperses stress concentration at high / low temperatures or during cooling after firing due to the difference in the thermal expansion coefficient between the electrode and the piezoelectric plate, and there is no separation between the electrode and the piezoelectric plate due to heat shock.

[Brief description of the drawings]

FIG. 1A is a side view showing an embodiment of the multilayer piezoelectric element of the present invention, and FIG. 1B is a cross-sectional view showing an embodiment of the multilayer piezoelectric element of the present invention.

2A is a cross-sectional view showing one embodiment of the configuration of the electrode shown in FIG. 1, and FIG. 2B is an exploded perspective view showing one embodiment of the configuration of the electrode.

FIG. 3 is a sectional view showing an example of a conventional laminated piezoelectric element.

FIG. 4 is a cross-sectional view of another example of a conventional laminated piezoelectric element viewed from another direction.

[Explanation of symbols]

11: piezoelectric plate, 12: electrode, 121: first electrode piece, 1
22: second electrode piece, 123: one piezoelectric electrostrictive material-filled coupling layer, 124, 125: gap, 13: insulating band, 14a, 1
4b: external electrode, 15: conductive band.

Claims (3)

[Claims] 1. A laminated piezoelectric element in which piezoelectric plates and electrodes are alternately laminated in a thickness direction thereof, wherein the electrodes have a structure in which a plurality of electrode pieces are alternately arranged. Characteristic multilayer piezoelectric element. 2. The laminated piezoelectric element according to claim 1, wherein a piezoelectric electrostrictive material is interposed between said electrode pieces. 3. The method according to claim 1, wherein the intervals between the electrode rows constituting the electrodes existing in the laminating direction of the piezoelectric plates are substantially equal every other row of the electrode rows. Or the multilayer piezoelectric element according to 2.