JPH0220080A - Laminated type displacement element - Google Patents

Abstract

PURPOSE:To prevent the occurrence of shearing stress at the interface between a protecting plate and a thin plate and the occurrence of cracks and other undesirable phenomena caused by the shearing stress by forming the protecting plate with an electromechanical transducer material, and polarizing the plate in the same direction of the thin plate. CONSTITUTION:A thin plate 1 is formed in a square shape with a piezoelectric material so that, e.g., one side is 10mm and a thickness is 100mum. For example, 100 sheets of the thin plates 1 are laminated through inner electrodes 2. Then, outer electrodes 3 and 4 are provided as pairs at both side surface parts of the laminated body of the thin plates 1 so that the end parts of the inner electrodes 2 are connected at every other layer with insulating materials 6 as ground materials. Then, protecting plates 5 are formed with the same piezoelectric material as that of the thin plates 1 at a thickness of, e.g., (n) times that of the thin plate. The protecting plate 5 is fixed to both upper and lower end surface of the laminated body which is formed by the lamination of the thin plates 1 through the inner electrodes 2. When the element is polarized, electrodes 5a are provided on the upper and lower end surfaces of the protecting plates 5. A polarizing voltage having the value (np) with respect to a polarizing voltage (p) required for the polarization of the thin plate 1 is applied to the electrodes 5a. After the polarization, the voltage is removed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an actuator for an industrial robot.

This relates to electromechanical transducers used in ultrasonic motors, etc., and in particular to improvements to laminated displacement elements in which the amount of displacement is increased by laminating multiple thin plates made of electromechanical transducer material via electrodes. It is.

[Conventional technology]

Conventionally, laminated piezoelectric elements used as displacement elements used in X-Y stage positioning mechanisms and brakes, etc., are made by attaching electrodes to a thin plate of piezoelectric ceramic material processed into a predetermined shape, and then polarizing it. , a method of joining using an organic adhesive directly or via a thin metal has been adopted. However, when stacking layers using adhesive as described above, depending on the usage conditions, the adhesive layer may absorb displacement due to vibration of the piezoelectric element, or the adhesive may deteriorate due to high temperature environment or long-term use. There are drawbacks.

For this reason, recently, multilayer piezoelectric elements having a multilayer chip capacitor structure have been put into practical use. That is, 1. For example, as described in Japanese Patent Publication No. 59-32040, a paste-like piezoelectric ceramic material made by adding a binder to raw material powder and kneading is formed into a thin plate of a predetermined thickness, and one side of this thin plate or A conductive material such as palladium is coated on both sides to form internal electrodes. A predetermined number of the above thin plates are laminated and pressed together, further processed into a predetermined shape, and then fired to form a ceramic, and external electrodes are formed on both sides of the laminate. The laminated piezoelectric element with the above structure has excellent adhesion between the thin plate made of piezoelectric ceramic material and the internal electrode, and has stable thermal properties, so it can be used satisfactorily even in high-temperature environments, and can be used for long periods of time. It has the advantage of extremely little deterioration over time.

FIG. 3 is an explanatory diagram schematically showing an example of the above-mentioned conventional device. In the figure, 1 is a thin plate, 1 is made of, for example, lead zirconate titanate or other piezoelectric material, and 2 is made of, for example, 10flX.
Form into a layer of 10 x 0.2 tm. Reference numeral 2 denotes an internal electrode, which is brought into contact with the thin plate 1 through a conductive metal film and is formed so as to protrude from one side of the thin plate 1. The thin plates 1 and internal electrodes 2 are alternately stacked, and the protruding ends 2a of the internal electrodes 2 are connected to the terminals of the external electrodes 3.4 every other layer. Protective plates 5 are brought into contact with the outer sides of the internal electrodes 2 at both ends to ensure insulation between the laminated piezoelectric element and the outside, and to make it usable as a connecting part with other members. . The number of laminated thin plates 1 is, for example, 50, and the thickness of the laminated piezoelectric element is approximately IQni. With the above configuration, when positive and negative voltages are applied to the terminals of the external electrodes 3.4, an electric field is generated between the internal electrodes 2.2, and the thin plate 1 is stretched in the thickness direction due to the longitudinal effect of the piezoelectric material, causing strain. . On the other hand, due to the generation of the electric field, the piezoelectric material shrinks in the direction along the surface of the thin plate 1 due to the lateral effect, and lateral strain also occurs at the same time. Therefore, the stacked piezoelectric element as a whole looks like the one shown by the chain line in Figure 3! It is curved.

[Problem to be solved by the invention]

The deformation indicated by the chain line in FIG. 3 can only be realized if displacement in the longitudinal and lateral directions is not suppressed at all. However, in an actual laminated piezoelectric element, the above-mentioned displacement is suppressed because the protection plate 5 is bonded to the outside of the internal electrode 2 at both ends as described above. Namely.

In the thin plate 1a adjacent to the protective plate 5, the application of an electric field generates a force due to the transverse effect of the piezoelectric material, and the thin plate 1
Although the piezoelectric material tries to shrink in the direction along the plane a, since no electric field is applied to the protection plate 5, no elongation or shrinkage strain occurs due to the longitudinal effect and transverse effect of the piezoelectric material. Therefore, the shrinkage displacement due to the lateral effect occurring in the thin plate 1a adjacent to the protective plate 5 is suppressed, and a shear center force is generated at the interface between the conduit thin plate 1a and the protective plate 5, and the laminated piezoelectric element This may cause cracks or other undesirable phenomena to occur during voltage application during the decentralization process or during actual driving.
There is a problem that reliability is reduced.

In order to solve the above problems, it has been proposed that the thickness of the thin plate 1a adjacent to the protective plate 5 is made larger than the thickness of the other thin plates 1 (see Japanese Patent Publication No. 10596/1983).
. However, combining the 7R tentatives with different thicknesses as in the above-mentioned one has problems in that it requires separate manufacturing processes and the management of the two parts is extremely complicated.

Furthermore, even in the above configuration, since no electrode is provided on the outside of the protective plate 5, when the thin plates 1 and 1a are polarized, the protective plate 5 is not displaced at all even though the thin plate 1a is displaced. The same inconvenience as described above occurs. Moreover, since the displacement during polarization (■) is larger than the amount of displacement during driving, there is a greater tendency for the above-mentioned cracks and other undesirable phenomena to occur.
There is a problem that this results in deterioration of the characteristics of the multilayer piezoelectric element.

The present invention solves the problems existing in the above-mentioned conventional techniques, prevents the occurrence of shear core force at the interface between the protective plate and the thin plate, and prevents the occurrence of cracks and other undesirable phenomena caused by this, and improves properties. The present invention aims to provide a laminated displacement element.

[Means to solve the problem]

In order to achieve the above object, there are two aspects of the present invention.

Thin plates made of an electromechanical transducer material and internal electrodes made of a conductive material are alternately laminated to have substantially the same contour and contact area, and 2 thin plates made of an electromechanical transducer material and internal electrodes made of a conductive material are formed to have substantially the same contour and contact area on the outside of the internal electrodes at both ends. In the laminated displacement element configured to include a protective plate made of a formed electromechanical conversion material and to apply an electric field to the thin plate via the internal electrode, the protective plate is formed of the electromechanical conversion material and the thin plate is Polarize in the same direction. A technical method was adopted.

[Effect]

The above configuration can be expected to have an effect of preventing the generation of shear stress at the interface between the 3i plate and the adjacent thin plate.

〔Example〕

FIG. 1 is a front view of essential parts showing an embodiment of the present invention, and the same parts are designated by the same reference numerals as in FIG. 3. In FIG. 1, the thin plate 1 is made of the same piezoelectric material as described above.
Formed into a square shape with a thickness of 0 mm and a thickness of 1008 m,
For example, a total area of 100 sheets is provided via the internal electrodes 2. Next, a pair of external electrodes 3.4 are provided on both side surfaces of the laminated body of the thin plates 1, with an insulating material 6 as a base, so as to connect the end edges of the internal electrodes 2 every other layer. Next, the protection plate 5 is formed of the same piezoelectric material as the thin plate 1 and has a H of 1, for example, n times, and is fixed via the internal electrodes 2 to both upper and lower end surfaces of the laminate formed by laminating the thin plates 1. Note that the protective plate 5 is configured to be polarized in advance in the same direction as the thin plate 1 by means described later.

FIG. 2 is a front view of essential parts showing the polarized state of the element shown in FIG. 1, and the same parts are designated by the same reference numerals as in FIG. 1. In FIG. 2, reference numeral 5a denotes an electrode, which is provided on the upper and lower end surfaces of the protection plate 5. However, the electrode 5a is not electrically connected to the external electrodes 3 and 4.

With the above configuration, a polarization voltage is applied between the external electrodes 3 and 4, but in this case, the protection plate 5 is formed to be n times thicker than the thin plate 1.

A polarization voltage having a value of np is applied to the electrode 5a with respect to the polarization voltage p necessary for polarization of each thin plate 1. Due to such polarization, a polarization voltage is applied to the protection plate 5 by the electrode 5a as well as to the thin plate 1, so that the protection plate 5 can be polarized in the same direction as the thin plate 1. Therefore, no shear stress or strain is generated between the protective plate 5 and the adjacent thin plate 1a. Next, after the above polarization is completed, the electrodes 5a provided on the upper and lower end surfaces of the protection plate 5 are removed to obtain the element shown in FIG.

In the element formed as described above, the protection plate 5 does not suppress the polarization direction of the adjacent 7gJ temporary 1a and other thin plates 1 and the displacement in the direction perpendicular to the polarization direction during polarization. Interface with thin plate 1a and other thin plate 1
Since the generation of shear stress at the mutual interface can be completely prevented, this example shows an example in which the protective plate is formed to be n times the thickness of the thin plate. It may be formed by forming a thin plate and removing part of the polarization electrodes and external electrodes on the upper and lower end surfaces after processing for 1 minute. Furthermore, the type of internal electrodes is not limited to the full-surface electrode shown in this embodiment, but also two so-called alternating electrodes, which have the same effect. Furthermore, although a case has been shown in which the planar outline shapes of the protection plate, thin plate, and internal electrode are square, any other geometric shape such as circular, rectangular, etc. can be arbitrarily selected.

〔Effect of the invention〕

Since the present invention has the structure and operation as described in section 9 above, it is possible to completely prevent the generation of shear stress at the interface between the protective plate and the thin plate and at the interface between the thin plates when a voltage is applied during the polarization process. This eliminates the occurrence of undesirable cracks and other undesirable phenomena caused by the above-mentioned shear stress.

obtain. Therefore, there is an effect that the characteristics and reliability of the laminated displacement element can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a front view of the main part showing an embodiment of the present invention, FIG. 2 is a front view of the main part showing the state of the element shown in FIG. 1 during polarization processing,
FIG. 3 is an explanatory diagram schematically showing an example of a conventional device. 1: Thin plate, 2: Internal electrode, 5: Protective plate 55a: Electrode. Patent distributor Hitachi Metals, Ltd.

Claims (3)

[Claims] (1) Thin plates made of an electromechanical transducer material and internal electrodes made of a conductive material are alternately laminated to have approximately the same contour and contact area, and a layer having approximately the same contour and contact area as these is formed on the outside of the internal electrodes at both ends. In a laminated displacement element configured to provide a protective plate made of an electromechanical conversion material formed in a contact area and apply an electric field to the thin plate via the internal electrode, the protection plate is formed of the electromechanical conversion material, A laminated displacement element characterized by being polarized in the same direction as the thin plate. (2) The laminated displacement element according to claim (1), wherein the protective plate is formed to have approximately the same thickness as the thin plate. (3) Claim (1) in which the electromechanical conversion material is a piezoelectric material
) or the laminated displacement element described in (2).