JPH0685451B2 - Multilayer piezoelectric bimorph element and method of using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piezoelectric bimorph element that causes a mechanical displacement by applying a voltage and a method of using the same.

The piezoelectric bimorph element has advantages such as a simple structure, energy saving, and low cost as compared with the electromagnetic displacement element, and has an advantage that a large mechanical displacement can be obtained at a low voltage as compared with the piezoelectric longitudinal effect strain element. have. Further, there is a feature that the displacement amount can be adjusted with high accuracy by the voltage applied to the piezoelectric bimorph element. Therefore, in recent years, this element has been replaced by an electromagnetic displacement element such as a relay, switch, printer,
It is being used as a drive element for precision X-Y tables and the like.

In a conventional piezoelectric bimorph element, for example, as shown in FIG. 1, two piezoelectric upper and lower piezoelectric plates 1 each having an electrode layer 3 formed on the front and back sides are sandwiched via an elastic thin plate (hereinafter referred to as a system material) 2 such as metal. A bonded structure is common. This element utilizes a flexure phenomenon that is fixed at one end, and by making the thickness of the piezoelectric material thin, a large displacement can be obtained although the force is weak. However, since the mechanical strength decreases, it is necessary to bond and reinforce the shim material.

However, the piezoelectric bimorph element having the conventional structure has a drawback that the manufacturing process of the piezoelectric thin plate, the electrode formation, the adhesion to the shim material, and the like are complicated, and the thin plate is used, so that the yield is low. Further, since the adhesive is used for adhesion to the shim material, it is impossible to avoid the influence of the adhesive such as displacement and stress absorption of the adhesive layer and deterioration of the adhesive layer during long-term use.

In view of the above point, the present invention is directed to a piezoelectric bimorph element having a structure in which a plurality of piezoelectric green sheets and piezoelectric raw sheets printed with electrode patterns are laminated, pressure-bonded and sintered, and opposing electrodes are formed above and below the piezoelectric layer as a boundary. A piezoelectric layer having an internal electrode layer that is connected to external electrodes divided above and below the boundary piezoelectric layer at the surface exposed end to form a four-terminal electrode. The main purpose is to propose an element of this kind in which the drawbacks of (1) are solved.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a perspective view of a bimorph element showing an example of the present invention. Reference numeral 11 denotes a piezoelectric layer, which has a thickness of 200 μm. Then, on the upper and lower surfaces of the piezoelectric layer 11 at the center, opposed internal electrodes 12a and 12b having a thickness of 60 μm and a four-layer structure are formed.
A piezoelectric laminated body 12 having is formed. The internal electrodes of each layer are printed on one surface of the piezoelectric green sheet, and the electrode surface is not exposed on the outermost side due to the lamination of four green sheets.
The electrode surface is exposed on the innermost side in contact with. Furthermore, each internal electrode
As shown in FIG. 2, the electrodes 12a and 12b alternately expose the electrodes of each layer to the left and right to enable polarization by applying a voltage. For example, in the internal electrode 12a, the first and third electrodes are not exposed on the left side end face but are exposed on the right side end face from the top, and the second and fourth electrodes are not exposed on the right side end face but are exposed on the left side end face.

The internal electrode exposed on the left side of the upper piezoelectric laminate 12
External electrode 13a is formed by connecting to 12a, similarly external electrode 13b is formed by connecting to the internal electrode 12a exposed on the right side of the piezoelectric laminate 12 on the upper side, and further on the lower piezoelectric laminate 12. The external electrode 13d is formed by connecting to the internal electrode 12b exposed on the left side, and similarly, the external electrode 13c is formed by connecting to the internal electrode 12b exposed on the right side of the lower piezoelectric laminate 12. These chemical compositions consist of those represented by Pb (Ni _1/3 Nb _2/3 ) _0.5 Ti _0.35 Zr _0.15 O ₃ .

At the time of production, the sintering conditions are 1120 ° C. and 2 hours of holding in air. The dimensions of the sintered body are 12 mm in width, 40 mm in length, and thickness.
0.9mm The laminated body 12 can be manufactured by utilizing the commonly used thick film forming or thick film laminating technique from mud. Thereafter, external electrodes 13 are provided so that an end face having a width of 12 mm and a thickness of about 0.9 mm is divided into upper and lower parts, thereby forming a laminated piezoelectric bimorph element 10 having a four-terminal structure.

The bimorph element 10 thus configured is arranged between the counter electrodes 13a and 13b and between the counter electrodes 13c and 13d. By applying a voltage to each, the piezoelectric body between the opposing electrodes is polarized, and the opposing electrodes 13a and 13d side of the element is fixed. Then, a first driving voltage in the same direction as the polarization is applied between the counter electrodes 13a and 13b,
By applying a second drive voltage in the direction opposite to the polarization and causing no polarization reversal between d, the counter electrode 13 at the free end of the element 10
The b and 13c sides are displaced upward in the drawing, and by reversing the voltage, they are displaced downward in the drawing. Then, if the voltage is switched in an alternating manner, it will continuously vibrate up and down in synchronization with the frequency.

It should be noted that the piezoelectric material used in the present invention is advantageous because a material having a large piezoelectric strain constant can obtain a large displacement at a low voltage. Actually, a lead titanate-lead zirconate so-called PZ is used.
A T-based piezoelectric material is desirable.

As the internal electrode material, a silver-palladium-based material having a composition that can withstand the sintering temperature of the PZT-based piezoelectric material can be used.

Table 1 shows various electromechanical characteristics of the device. As a comparative example, electrodes formed on the upper and lower surfaces of a thin plate of the same piezoelectric material with a thickness of 0.17 mm, and two electrodes were attached to a shim material with a thickness of 0.05 mm.
The characteristics of a bimorph element with a length of 12 mm and a length of 40 mm are also shown. The measurement method was carried out by fixing one end in the 40 mm length direction and using an electric micrometer projector on the free end side. In the device according to the present invention, the measurement conditions are the same as those described above, in which a positive voltage of 40 V is applied between the opposing electrodes and a negative voltage of 10 V is applied between the opposing electrodes.

As can be seen from Table 1, the element according to the present invention has a slightly small displacement amount, but the generated stress is three times or more that of the comparative example. Further, in the comparative example, it is understood that the plastic deformation of the piezoelectric thin plate itself and the influence of the adhesive and the shim material cause a large shift and creep, which is a problem in practical use. That is, the element according to the present invention is excellent in small shift and creep because it is composed of a piezoelectric body and its internal electrode and does not use an adhesive and the element thickness is as thick as 0.9 mm. In addition, by using the thick film stacking technology, the manufacturing process of the device can be shortened to about 2/3, which can be expected to greatly increase the manufacturing yield.

The effects of the structure of the present invention are apparent for piezoelectric materials and internal electrode materials having chemical compositions other than the piezoelectric materials and internal electrode materials shown in the examples, and the piezoelectric materials and internal electrode materials shown in the examples are clear. It is not limited to.

As described above, according to the present invention, a laminated piezoelectric bimorph having a structure in which electrodes are printed on a piezoelectric raw sheet and plural piezoelectric laminates are laminated by pressure bonding and sintered on the upper and lower surfaces of the central piezoelectric raw sheet. In the element, the electrodes of each layer of the internal electrodes of the piezoelectric laminate are alternately exposed to the left and right, and the external electrode is provided at the left end of the upper piezoelectric laminate and the external electrode is provided at the right end of the upper piezoelectric laminate. Since the external electrode is formed on the left end of the piezoelectric laminate and the external electrode is formed on the right end of the lower piezoelectric laminate, and the four internal electrodes are connected to the exposed internal electrodes, respectively. Since there is no metal shim in the middle,
Laminate that contributes to the increase of generated force during driving, has larger generated stress, smaller shift and creep, is more reliable than conventional piezoelectric bimorph elements, shortens the manufacturing process, and improves the manufacturing yield. Type piezoelectric bimorph element can be provided.

Further, according to the present invention, on the upper and lower surfaces of the piezoelectric raw sheet in the center, in a laminated piezoelectric bimorph element having a structure in which electrodes are printed on the piezoelectric raw sheet and a plurality of laminated piezoelectric laminates are pressure-bonded and sintered, The electrodes of each layer of the internal electrodes of the piezoelectric laminate are alternately exposed to the left and right, and the first external electrode is located at the left end of the upper piezoelectric laminate and the second external electrode is located at the right end of the upper piezoelectric laminate. A third external electrode is formed at the left end of the side piezoelectric laminate and a fourth external electrode is formed at the right end of the lower piezoelectric laminate so as to be electrically connected to the internal electrode, and the polarization of the internal electrode is distributed between the first and second external electrodes. Since a driving voltage in the opposite direction of the polarization of the inner electrode is applied between the third and fourth outer electrodes, a metal shim or the like is not present in the middle unlike the conventional case.
This has the effect of contributing to the generated force during driving and obtaining the maximum generated force by applying different voltages to the upper and lower electrodes.

Further, according to the present invention, on the upper and lower surfaces of the central piezoelectric raw sheet, in a laminated piezoelectric bimorph element having a structure in which electrodes are printed on the piezoelectric raw sheet and a plurality of laminated piezoelectric laminates are pressure-bonded and sintered, The electrodes of each layer of the internal electrodes of the piezoelectric laminate are alternately exposed to the left and right, and the first external electrode is located at the left end of the upper piezoelectric laminate and the second external electrode is located at the right end of the upper piezoelectric laminate. A third external electrode is formed at the left end of the side piezoelectric laminate and a fourth external electrode is formed at the right end of the lower piezoelectric laminate so as to be electrically connected to the internal electrode, and the polarization of the internal electrode is distributed between the first and second external electrodes. A first drive voltage in the direction opposite to the polarization direction of the inner electrode between the third and fourth outer electrodes, and
Also, since the second drive voltage is switched to alternating current, there is no metal shim or the like in the middle unlike the conventional case, which contributes to the generated force during driving and is synchronized with the frequency to the upper and lower electrodes. By applying different voltages, it is possible to obtain the maximum generating force that continuously vibrates up and down.

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional piezoelectric bimorph element, FIG. 2 is a perspective view of a laminated piezoelectric bimorph element having a structure of the present invention, and FIG. 3 is a side view in which the left half is also omitted. 11 ... Piezoelectric layer, 12 ... Internal electrode, 12a, 12b ... Piezoelectric layer having opposing internal electrodes, 13a, 13b, 13c, 13d ... External electrode.

Claims (3)

[Claims] 1. A laminated piezoelectric bimorph element having a structure in which electrodes are printed on a piezoelectric green sheet on the central upper and lower surfaces of a piezoelectric green sheet, and a plurality of laminated piezoelectric laminates are pressure bonded and sintered. The electrodes of each layer of the internal electrode of the body laminate are alternately exposed to the left and right, and the external electrode is provided at the left end of the upper piezoelectric laminate.
An external electrode is formed on the right end of the upper piezoelectric laminate, an external electrode is formed on the left end of the lower piezoelectric laminate, and an external electrode is formed on the right end of the lower piezoelectric laminate, and each is electrically connected to the exposed internal electrode.
A laminated piezoelectric bimorph element having a terminal electrode. 2. A laminated piezoelectric bimorph element having a structure in which an electrode is printed on a piezoelectric green sheet and a plurality of laminated piezoelectric laminated layers are pressure-bonded and sintered on the upper and lower surfaces of the central piezoelectric green sheet. The electrodes of each layer of the internal electrodes of the body laminate are alternately exposed to the left and right, and the first external electrode is provided at the left end of the upper piezoelectric laminate, the second external electrode is provided at the right end of the upper piezoelectric laminate, and the lower piezoelectric body is formed. A third external electrode is formed at the left end of the body laminate and a fourth external electrode is formed at the right end of the lower piezoelectric laminate so as to be electrically connected to the internal electrode, and the first electrode and the second external electrode are connected in the same polarization direction. A method of using a laminated piezoelectric bimorph element, characterized in that a drive voltage is applied and a drive voltage in the polarization reverse direction of the internal electrode is applied between the third and fourth external electrodes. 3. A multilayer piezoelectric bimorph element having a structure in which electrodes are printed on a piezoelectric green sheet and a plurality of piezoelectric multilayers are laminated on the upper and lower surfaces of a central piezoelectric green sheet by pressure bonding and sintering. The electrodes of each layer of the internal electrodes of the body laminate are alternately exposed to the left and right, and the first external electrode is provided at the left end of the upper piezoelectric laminate, the second external electrode is provided at the right end of the upper piezoelectric laminate, and the lower piezoelectric body is formed. A third external electrode is formed at the left end of the body laminate and a fourth external electrode is formed at the right end of the lower piezoelectric laminate so as to be electrically connected to the internal electrode, and the first electrode and the second external electrode are connected in the same polarization direction. First
And a second drive voltage in the polarization reverse direction of the inner electrode is applied between the third and fourth outer electrodes, and the first and second
A method of using a laminated piezoelectric bimorph element, characterized in that the driving voltage of the above is switched in an alternating manner.