JPS6039878A - Laminating type piezoelectric body - Google Patents

Abstract

PURPOSE:To prevent the generation of a crack by forming an air gap between a section, through which an end-surface electrode is conducted to a side-surface electrode, and an adjacent piezoelectric body opposite to the section. CONSTITUTION:There is no protrusive section 2', which must be conducted to side- surface electrodes 4, on the upper end surface of each piezoelectric simple body 1 in a laminated and formed piezoelectric body A. Air gaps R are formed among conducting sections 2' existing on the lower end surfaces of each piezoelectric simple body 1 and the upper end surfaces of the lower piezoelectric simple bodies 1 adjacent to the conducting section 2', and each piezoelectric simple body is not bonded with the adjacent piezoelectric simple bodies at sections except end-surface electrodes 2. Lead wires 3 are given sufficiently dips by netting, etc., and each side-surface electrode 4 is connected. Consequently, even when voltage is applied to the laminating type piezoelectric body A at high frequency, stress by the expansion and contraction of the piezoelectric simple bodies 1 is not applied to the outer circumferential sections (particularly, sections in the vicinity of the side-surface electrodes 4) of the piezoelectric simple bodies 1. Accordingly, the generation of cracks and breakings by shearing force of the piezoelectric simple bodies can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laminated ceramic piezoelectric body used as various actuators.

Conventional Ceramic piezoelectric materials have good responsiveness, so research is underway to apply them to various actuators.

However, since it has good responsiveness, if pressure is applied to take advantage of this property, stress may be concentrated in a specific position if non-uniform force is applied, and an ill force may be generated in the ceramic piezoelectric body. Conventionally, as shown in FIG. 1, this type of piezoelectric body is generally provided with an end face electrode 2 having a diameter equal to the diameter of the piezoelectric body 1 on one end surface of the ceramic piezoelectric body 1, and a groove on the side surface thereof. 1] A surface electrode 4 is provided, and this side electrode 4 is electrically connected to this end surface electrode 2 via a conductive portion 2' extended to one end surface electrode 2 11S, and the other end surface of this piezoelectric unit 1 and the end surface 1j Also on the surface, electrodes having the same shape as the end surface electrode 2 and the side surface electrode 4 are placed at an angle of 1800 m with respect to the central axis of the piezoelectric unit 1.
The piezoelectric units constructed in this way are stacked at positions with different phases, and the side electrodes 4 are connected every other side with lead wires 3, as shown in FIG. 3. As shown, a multilayer piezoelectric material A was constructed by laminating a large number of layers.

However, when the laminated piezoelectric body A configured as described above is driven with a specific load or a high frequency higher than a specific frequency,
For example, there was a problem in that cracks occurred at positions as shown in FIG. 4, and the function as a piezoelectric body was impaired.

Purpose of the Invention The present invention has been made to solve the problems of the conventional laminated piezoelectric material as described above, and its purpose is to provide an actuator using such a laminated piezoelectric material. It is an object of the present invention to provide a laminated piezoelectric body in which a single ceramic piezoelectric body does not crack even when driven under any conditions.

Structure of the Invention In order to achieve all of the above objects, the structure of the present invention includes an end surface electrode provided on the end surface of a piezoelectric element and having a diameter smaller than the outer diameter of the piezoelectric element, and an end surface electrode provided on a side surface of the piezoelectric element and electrically connected to the end surface electrode. In a laminated piezoelectric body in which piezoelectric units having both electrodes, such as the ll1111m electrode, are laminated and integrated, there is a gap between a portion where the end electrode is electrically connected to the side electrode and an adjacent piezoelectric body opposite thereto. It is assumed that .

Embodiments An embodiment of the present invention will be described with reference to the drawings. Figure 3 shows a laminated piezoelectric unit A of the present invention constructed by laminating a large number of piezoelectric units.
shows the overall structure of. Structure 1 of this laminated piezoelectric body A
Examples of piezoelectric elements of the order of 1j are illustrated in FIGS. 5 to 9.

FIG. 5 shows the piezoelectric unit of the first embodiment. The piezoelectric unit 1 is made of a plate-shaped ceramic plate 9 with a diameter of 15 mm and a thickness of about 0.5 mm. A laminated piezoelectric body A shown in FIG. The outer dimensions of the laminated piezoelectric body A thus formed are a cylindrical body with a diameter of about 15mm and a height of about 40mm. As shown in FIG. 5, end face electrodes 2 having a diameter smaller than the outer diameter of the piezoelectric element 1 are formed with a thickness of 5 to 15 microns on both the front and back end surfaces of the piezoelectric element 10 using a silver wave strike, and similarly on a part of the outer side surface. A side electrode 4 having a thickness of 5 to 15 microns is formed using silver paste. This side electrode 4 is electrically connected to the end electrode 2 through an overhang 2' of the end electrode 2 formed on one end surface. Note that the other end face does not have the above-mentioned overhang 5 portion 2'. When a large number of piezoelectric elements 1 thus formed are laminated, each piezoelectric element 1 is integrally joined by the adhesive action of the silver paste, forming a laminated piezoelectric element A as shown in FIG. 3. This piezoelectric unit 1
As shown in FIG.
The piezoelectric elements 1 are stacked so that the positions of the side electrodes 4 are aligned with the axis of the piezoelectric unit 1 by 180 degrees with respect to the axis of the piezoelectric unit 1. The lead wires 3 are connected to every other side electrode 4 by silver paste with slack. The connection between the side electrodes 4 using the lead wires 3 is actually made by removing a part of the vertical lines of the stainless A mesh 34 of about 100 meshes and connecting the horizontal lines 34' of the mesh 34, as shown in FIG. Side electrode 4
This is done by connecting them with silver paste.

In addition, 35 in the same figure is a silver paste 1 and a half (E etc. attached to silk 34) 91 in order to reduce the contact resistance between the vertical line and the horizontal line of the net, and from the point 35 on the side of the lead wire 3t. It is taken out.

As shown in FIG. 6, the piezoelectric body A laminated in this manner does not have a projecting portion 2' on the upper end surface of each piezoelectric body 1 to be electrically connected to the side electrode 4.
A gap R is formed between the conductive portion 2' existing on the lower end surface of the conductive portion 2' and the upper end surface of the lower piezoelectric unit 1 adjacent thereto.

Laminated piezoelectric body A tJ of the above configuration, 500-700
When a voltage of V is applied, a displacement of 60 to 90 microns occurs in the axial direction, so this displacement pF is used to fabricate an actuator. The laminated piezoelectric unit A of this embodiment has the above-mentioned gap R between each piezoelectric unit 1 and the adjacent piezoelectric unit A)
The pieces 'f51 other than the end face '7t\pole 2' are not bonded to the adjacent piezoelectric unit. Also, IJ-do 1a, +3 is available via network etc.
With sufficient slack, each τ1; mountain + 'Wt pole 4
are connected. Therefore, the percentage of laminated piezoelectric material A is 100%.
Even if a voltage is applied at a high frequency of ~1000 Hz, the stress due to expansion and contraction of the piezoelectric unit 1 is not applied to the outer periphery of the piezoelectric unit 1 (especially near the side electrode 4), so cracks occur in the piezoelectric unit 1 due to shear force. No more cracks or cracks. According to experiments by the present inventors, when applying a load of 9/cd to 250 and applying O ~ 500V at 100Hz, approximately 10
It was confirmed that it continued to operate without any abnormality even after 00 hours had passed.

Note that the piezoelectric unit 1 used in this example is PbTi0. ,
.

Pb (CoVsNb%) O3, P in PbZrOs
b (Znl/3Nb relaxation)03.

A solid solution of pb (Nb2f') os, etc. from Ni, or a doge of Nb20a, WOs, etc. are used, but any material can be used as long as it has piezoelectricity, and preferably the piezoelectric constant dos The thicker the better. Further, the side electrode 4 does not necessarily need to be arranged at a position facing the axis of the laminated piezoelectric body A, and can of course be arranged at a position suitable for taking out the electrode.

In order to compare the effects of this example with those of the prior art, a comparative example was constructed and an experiment was conducted. The structure of this comparative example is such that the piezoelectric unit 1 is as shown in FIG. Then, as shown in FIG. 2, the mutual orientation of the side electrodes 4 is set so that the position of every other side electrode 4 is aligned, and the layers are laminated to form a fyt layer type piezoelectric material similar to the above embodiment. It is something that

For this comparative example, 250 Kg-/c in its axial direction
As a result of applying a load of a and driving the piezoelectric unit 1 at LOOHz''c, a crack was generated in the center of the mutually bonded side electrodes 4 in parallel to the piezoelectric unit 1, and the piezoelectric unit 1 was driven as shown in FIG. Cracks and fissures were observed near the dotted lines, and traces of partial leakage were observed.

FIG. 7 shows a second embodiment of the present invention, in which the piezoelectric unit 1 of this embodiment is one of the piezoelectric units 1 (see FIG. 1) having end face electrodes 2 and side electrodes 4 similar to those of the above-mentioned comparative example. Another layer of silver paste with the same diameter as the end electrode 2 is screen printed on the end surface of the electrode 2, and this is laminated using the adhesive action of the silver paste in the same manner as in the first embodiment. A laminated piezoelectric body having end face electrodes 20 is constructed. As shown in the figure, the laminated piezoelectric body thus obtained also has a gap R between adjacent piezoelectric bodies 1, so that uneven stress does not act on the piezoelectric bodies 1. Therefore, this example is also the first example.
It has the same effect as the example. Note that in the second embodiment, the pattern of the end face electrode 2 is not particularly limited. In other words, when piezoelectric elements 1 having a pattern of end electrodes 2 as in the third embodiment (FIG. 8) described later are laminated in the same manner as in the comparative example, the surface permanence is improved compared to the comparative example. Since this has been confirmed, it is preferable to use such an end face electrode pattern in this example as well.

FIG. 8 shows a piezoelectric unit 1 according to a third embodiment of the present invention, and this structural feature is such that the side electrodes 4 are thicker than those of the fourth embodiment and can be applied over a wide range on the side surface of the piezoelectric unit 1. The width of the conductive portion 2' with the end face electrode 2 is also made wide in accordance with the width of the strip 7'L formed by sliding. It has been confirmed that such a structure improves durability.

FIG. 9 shows a piezoelectric unit 1 according to a fourth embodiment of the present invention, and the feature of this embodiment is that by cutting out a part of the end face electrode 2 where the two electrodes are close to each other, leakage between the two electrodes can be prevented. It is designed to have the effect of reducing the risk of

Effects of the Invention As explained above, in the present invention, a gap is formed between the conductive portion of the end face electrode and the side electrode of the laminated piezoelectric unit and the adjacent piezoelectric unit facing this, so that frost 1 is generated by high frequency. Even when pressure is applied, the stress due to the expansion and contraction of the piezoelectric unit does not concentrate on the outer periphery of the piezoelectric unit, and cracks do not occur near the single pole of the side type, which has been thought to be the most prone to cracking since Tsuchiya. Therefore, even if a high-frequency voltage is applied for a long period of time, the multilayer piezoelectric material can operate without abnormality and is highly reliable.

[Brief explanation of the drawing]

Figure 1 shows a conventional piezoelectric unit, aj is its bottom view, Φ
) is a side view of the same, (C) is a top view of the same, FIG. 2 is a front view showing the laminated state of the piezoelectric units shown in FIG. 1, and FIG. FIG. 4 is a front view of the laminated piezoelectric body, FIG. 4 is a bottom view showing a state in which a crack has occurred in the piezoelectric unit shown in FIG. 1, and FIG. (a) is a bottom view, (b) is a side view, (c) is a top view, FIG. 6 is a front view showing the laminated state of the piezoelectric unit of FIG. 5, and FIG. FIG. 8 is a front view showing the laminated state of the piezoelectric unit in the second embodiment, and FIG. 8 shows the piezoelectric unit in the third c, jz embodiment of the present invention,
(a) is a bottom view, (b) is a side view, (C) is a top view, and FIG. 9 shows a piezoelectric unit in the fourth embodiment of the present invention; (a) is a bottom view, ( b) Ipsilateral supra, (C)
is a top view of the same. 1...Piezoelectric unit, 2...End surface electrode, 2'...Conducting part, 3...Lead wire, 4...Side electrode, ■ζ...
Gap, A...Laminated piezoelectric material Fig. 1 (a') (b) (c) Fig. 2 Fig. 3, Fig. 5 1 (a) (b) (c) Fig. 6

Claims (1)

[Claims] ・1. Piezoelectric units are laminated, each having two electrodes: an end electrode that is provided on the end face of the piezoelectric unit and has a smaller diameter than the outer diameter of the piezoelectric unit, and a side electrode that is provided on the side surface of the piezoelectric unit and is electrically connected to the end electrode. What is claimed is: 1. A multilayer piezoelectric body, characterized in that, in the integrated multilayer piezoelectric body, a gap is formed between a portion where the end face electrode is electrically connected to the side electrode and an adjacent piezoelectric unit facing thereto. 2. The laminated piezoelectric material according to claim 1, wherein the piezoelectric material is not bonded to an adjacent piezoelectric material except for the end surface electrodes. 3. The laminated piezoelectric body according to claim 1, wherein the conductive portion between the end face electrode and the side electrode is formed only on the end face electrode on one end face side of the piezoelectric unit. 4. An end face electrode was further laminated on the end face electrode on one end face side of the piezoelectric unit except for the conductive portion with the side electrode. /I? A laminated piezoelectric material according to claim 1.