JPS60121785A - Structure of piezoelectric bimorph - Google Patents

Abstract

PURPOSE:To miniaturize the whole shape while improving durability by mutually connecting internal electrodes facing to the same end surface side of a piezoelectric body plate in internal electrodes extended up to the end surface of the piezoelectric body plate by an external electrode. CONSTITUTION:With a piezoelectric bimorph 20, a piezoelectric body plate 31 in which first-third internal electrodes 23-25 and fourth-sixth internal electrodes 26-28 are each opposed mutually and formed at regular intervals on the upper side 21 and the lower side 22 and a hollow section 30 is shaped at the central section 29 is mounted. Sections held by each internal electrode 23-28 in the piezoelectric body plate 31 are polarized. The direction of polarization is represented by the arrows P. The pairs of the internal electrodes extended and formed up to the same end surface sides 32, 33 of the piezoelectric body plate 31, the pair of the internal electrodes 24, 26 and 28 and the pair of the internal electrodes 23, 25 and 27, in several electrodes 23-28 extended up to the end surfaces 32, 22 of the piezoelectric body plate 31 are each connected mutually by external electrodes 34, 35.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric bi (luer) structure in which the direction of displacement is reversed depending on the polarity direction when an electric field is applied.

FIG. 1 is a schematic diagram of a conventional piezoelectric bimorph. The piezoelectric bimorph 1 shown in FIG. It has second piezoelectric bimorph parts 2 and 3. First piezoelectric bimorph section 2
is made by pasting piezoelectric sheets 45.6 on both sides of the reinforcing plate 4. The second piezoelectric bimorph section 3 is also formed by pasting piezoelectric sheets 8.9 on both sides of the reinforcing plate 7. Both ends of the reinforcing plates 4 and 7 are bent and fixedly connected to each other at the bent ends. 10 is an object that is displaced by the piezoelectric bimorph 1 having such a structure. When an electric field is applied to the piezoelectric bimorph 1 from an electric field applying means (not shown), the piezoelectric bimorph 1 bends and displaces, for example, in the direction shown by the imaginary line 11 in FIG. 1 or in the opposite direction, depending on the polarity of the electric field. In the case of a bending displacement indicated by a phantom line 11, the object 10 is displaced as indicated by a phantom line 12 due to this bending displacement.

By the way, in the piezoelectric bimorph 1 having such a structure, it is difficult to attach thin piezoelectric sheets 5, 6.8°9 on both sides of the reinforcing plate 4.7 due to manufacturing technology and strength issues. Therefore, the thickness of the piezoelectric sheet had to be increased. Therefore, in the conventional piezoelectric bimorph, the thickness of the piezoelectric sheets attached to both sides of the reinforcing plates 4 and 7 is increased, so that the overall shape becomes large. In addition to this, in the conventional piezoelectric bimorph 1, the first. Second piezoelectric bimorph section 2.3
are integrated through the reinforcing plates 4 and 7, so due to repeated bending displacement of the piezoelectric bimorph, deterioration becomes noticeable at the connecting portions 13 and 14 between the reinforcing plates 4 and 7, resulting in poor durability. It became.

The present invention has been made in view of the above, and an object of the present invention is to make it possible to reduce the overall shape and to improve durability.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 2 is a cross-sectional view of the schematic structure of the piezoelectric bimorph of this embodiment. This piezoelectric bimorph 20 is
It is a parallel type.

This piezoelectric bimorph 20 has first to third internal electrodes 23, 24, . . . on its upper side 21 and its lower side 22, respectively.
25th and 4th! ItJ6 internal electrode 26°27.28
are formed facing each other at predetermined intervals, and a piezoelectric plate 31 having a hollow portion 30 formed in the center portion 29 is provided. Each internal electrode 23, 24, 25.2 of this piezoelectric plate 31
The portion between 6, 27, and 28 is polarized.

This polarization direction is indicated by an arrow P in the figure. Furthermore, among the internal electrodes 23, 24, 2S, 26, 27, 28 extending to the end surfaces 32, 33 of the piezoelectric plate 31,
A set of internal electrodes extending to the same end face side 32 and 33 of the piezoelectric plate 31, that is, a second internal electrode Fi2
4, a set of a fourth internal electrode 26 and a sixth internal electrode 28;
The sets of the first internal electrode 23, the third internal electrode 25, and the fifth internal electrode 27 are interconnected by the first and second external electrodes 34, 35, respectively.

FIGS. 3 and 4 are diagrams for explaining the manufacturing procedure of the piezoelectric bimorph 20 having the above structure. First.

The third step is to manufacture the piezoelectric bimorph 20 of the embodiment.
As shown in the figure, piezoelectric ceramic green sheets 36 to 45 are prepared. Among these piezoelectric ceramic green sheets, the codes are 36, 37, 38, 42, 43.
In the case of No. 44, the internal electrodes 23 to 28 are formed of conductive paste or the like by printing or coating.

Further, through holes 46 and 47 for the hollow portion 30 are formed in the one having the reference numeral 40°41. The piezoelectric ceramic green sheets are laminated in this order, pressed together using an oil press, and fired to form a sintered body, thereby obtaining a piezoelectric plate 31 shown in FIG.

Next, the polarization process is carried out as shown in FIG. That is, the first and second DC power supplies 48 and 49, the third and third DC power supplies are connected in series with each other. Each internal electrode is connected to a fourth DC power source 50.degree. 51 by each lead wire 52 to 57 as shown. In this connected state, a high DC voltage is applied to the portion of the piezoelectric plate sandwiched between each internal electrode. Then, this portion of the piezoelectric plate is polarized in the direction indicated by arrow P in FIG.

FIG. 5 is a front view of the piezoelectric bimorph 720 for explaining the bending displacement of the piezoelectric bimorph 20 of FIG.

In FIG. Code 58.59 is piezoelectric bimorph 2
1st of 0. This is a second driving power source.

This drive power source 58,59 is the first. It is selectively connected to the external electrode 34.35 of the piezoelectric bimorph 20 by a second changeover switch 60.61. As shown in the figure, when the first drive power source 58 is selected by the first changeover switch 60, the piezoelectric bimorph 20 is bent and displaced in the direction of the virtual line 62 (the direction in which the amount of displacement is expanded). Conversely, when the second drive power source 59 is selected by the second changeover switch 61, the piezoelectric bimorph 20 is bent and displaced in the direction of the virtual line 63 (the direction in which the amount of displacement is reduced). Therefore, according to the piezoelectric bimorph 20 of this embodiment, the overall shape can be made thinner, and the risk of mechanical strength deterioration even if bending displacement is repeated is reduced compared to the conventional example.

FIG. 6 is a schematic cross-sectional view of a piezoelectric bimorph 20° according to another embodiment, and parts corresponding to those in FIG. 2 are given the same reference numerals. The piezoelectric bimorph 20' of this embodiment is of a series type. This piezoelectric bimorph 20゛ is the second
Internal electrodes 23, 24, 25, 26,
27.2'8. However, unlike the case of the embodiment shown in FIG. 25 and the fourth internal electrode 26 are connected at the other end surface 32 of the piezoelectric plate 31 by an external electrode 34'. Further, neither the second inner electrode 24 nor the fifth inner electrode 27 appears on the end surfaces 32 and 33. Furthermore, the direction of polarization in the portion of the piezoelectric plate sandwiched between the internal electrodes is also different between the first internal electrode 23 and the second internal electrode 24 and between the fourth internal electrode 26 and the fifth internal electrode 27. In the figure, the direction is indicated by an arrow mark P'', and between the second internal electrode 24 and the third internal electrode 25, and between the fifth internal electrode 27 and the tIrJ6 internal electrode 28, the arrow mark P'' The direction is indicated by P. Therefore, in the piezoelectric bimorph 20' shown in Fig. tJ46, the first... When driven by the second DC power source 58, 59, the piezoelectric bimorph 20 in FIG. 2 is bent and displaced in the opposite direction.

Note that the shape of the piezoelectric bimorphs 20, 20'' in the above embodiments may be formed of piezoelectric ceramic green sheets having a rectangular shape, a circular shape, or other shapes.
The number of stacked piezoelectric ceramic green sheets is not limited to the embodiment. Furthermore, it is of course possible to use a method other than the method shown in FIG. 4 to terminate the polarization process.

As described above, the present invention includes a piezoelectric plate in which a plurality of internal electrodes are formed facing each other at predetermined intervals on the upper side and the lower side thereof, and a hollow part is formed in the center of the piezoelectric plate, The portions of this piezoelectric plate sandwiched between the internal electrodes are polarized, and among the internal electrodes extending to the end face of the piezoelectric plate, the internal electrodes facing the same end face of the piezoelectric plate are polarized. Since they are connected by external electrodes, there is no longer a structure in which piezoelectric sheets are pasted on both sides of a reinforcing plate like in conventional piezoelectric bimorphs.For example, internal electrodes are formed on piezoelectric ceramic green sheets and laminated. It can be constructed thinly and the overall shape can be made small. In addition, unlike conventional piezoelectric bimorphs, even if the piezoelectric bimorph is repeatedly bent and displaced, there is no deteriorated portion due to the repeated bending displacement, so that a product with excellent durability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a piezoelectric bimorph of a conventional example, FIGS. 2 to 6 relate to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a piezoelectric bimorph of this embodiment. Figure 3 is a diagram used to explain the manufacturing procedure for the piezoelectric bimorph shown in Figure 2, Figure 4 is a diagram used to explain how to polarize the piezoelectric bimorph shown in tpJQ, and tI115 is a diagram used to explain how to drive the piezoelectric bimorph shown in Figure 2. FIG. 6 is a schematic cross-sectional view of a piezoelectric bimorph according to another embodiment. 20.20' is the piezoelectric bimorph, 21.22 is the upper and lower sides of the piezoelectric bimorph, 23, 24, 25, 26° 27.
28 is an internal electrode, 29 is a central portion, 3o is a hollow portion, 31 is a piezoelectric plate, 32.33 is an end face of the piezoelectric plate 31, 34, 3
5. 34' and 35' are external electrodes, P and P' are arrow marks in the direction of polarization.Applicant: Zaiyo Seisakusho Co., Ltd. Representative, Patent Attorney Oka1) KazuhideFigure 1Figure 2Figure 3Figure 4

Claims (3)

[Claims] (1) A piezoelectric plate is provided with a plurality of internal electrodes facing each other and formed at predetermined intervals on the upper side and the lower side thereof, and a hollow part is formed in the center of the piezoelectric plate. The portion sandwiched between the electrodes is polarized, and among the internal electrodes extending to the end face of the piezoelectric plate, the internal electrodes facing the same end face side of the piezoelectric plate are connected by external electrodes. The structure of a piezoelectric bimorph. (2) Piezoelectric bimorph structure 1 according to claim 1, wherein the piezoelectric plate is formed by laminating piezoelectric green sheets and then sintering them. (3) In the piezoelectric bimorph structure according to claim 2, the piezoelectric green sheet includes one in which internal electrodes are formed and one in which through holes are formed.