JPH0376281A - Piezoelectric element and polarization thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for polarizing a piezoelectric element and a piezoelectric element manufactured by the method.

More specifically, the present invention relates to a method for polarizing piezoelectric elements used in ultrasonic distance sensor piezoelectric actuators, piezoelectric motors, and the like.

[Conventional technology]

The phenomenon in which strain occurs when an electric field is applied to a certain type of crystal is called the inverse piezoelectric effect, and piezoelectric elements that take advantage of this phenomenon are widely used. Since such a piezoelectric element can directly obtain strain by applying an electric field, it is characterized by a simple structure and precise control.

However, the strain caused by the inverse piezoelectric effect is small, and in order to obtain a large displacement of such a piezoelectric element, it is common to use a structure in which a large number of thin plate-shaped piezoelectric materials are laminated.

The piezoelectric material elements to be laminated include crystal, Rochelle salt, barium titanate, lead zirconate titanate porcelain, and P.
Ceramics such as CM piezoelectric ceramics and certain ferroelectric polymers are used.

By applying a high electric field to a polycrystalline sintered body (ceramics) or thin film that is isotropic and has no piezoelectric properties of a ferroelectric substance, and aligning the direction of their spontaneous polarization to some extent (polarization), it becomes a piezoelectric substance. (polling).

[Problem to be solved by the invention]

Conventionally, the method used to polarize such piezoelectric elements is, for example, in the case of torsional vibration elements, in the case of disk-shaped piezoelectric elements, ceramics are sintered into a donut shape and this ceramic is polarized. For example, divide it into quarters to form a fan shape, form an electrode on the end face of each fan shape, polarize the fan shape, remove the electrode after polarization, re-glue the four fan shapes, and create a doughnut-shaped piezoelectric element again. is formed.

In this way, a torsional vibration element is made, and similarly, in a piezoelectric element for shear vibration, ceramics are sintered into a thin plate shape formed into a rectangular shape, and electrodes are formed on both end faces in the polarization direction. After polarization, the electrodes are removed, the electrode surface for polarization formation is removed, and an electrode surface is formed in a direction perpendicular to the electrode surface to form a shear vibration element.

However, when using this method, there is a problem that the strength of the piezoelectric element is weak because the piezoelectric element itself is bonded and bonded, and it also requires complicated processes such as cutting and bonding. Therefore, the cost is high. Furthermore, the cost of the sliding piezoelectric element is similarly high.

[Purpose of the invention]

The present invention solves the problems associated with the conventional techniques as described above, reduces the cost required for polarization of piezoelectric elements,
It is an object of the present invention to provide a method for manufacturing a piezoelectric element with high strength and improved quality.

[Means to solve the problem]

In the present invention, the piezoelectric element material is formed into a thin plate, a plurality of electrodes are formed on the upper and lower surfaces of the thin plate, each independent in the polarization direction, and a high voltage is applied between the pairs of electrodes on the upper and lower surfaces that are biased in the polarization direction. The above object is achieved by a method of polarizing a piezoelectric element, which is characterized in that the entire thin plate is polarized by repeating the above polarization operation between a plurality of electrode pairs.

When the present invention is applied to a method for polarizing a torsion piezoelectric element, the piezoelectric element material is formed into a circular thin plate, and a plurality of sector-shaped electrodes are formed around the center of the circular thin plate on both upper and lower surfaces of the circular thin plate. do.

Furthermore, when applying the piezoelectric element polarization method of the present invention to a sliding piezoelectric element polarization method, the piezoelectric element material is formed into a rectangular thin plate, and a plurality of band-shaped electrodes are formed on the upper and lower surfaces of the quadrilateral thin plate. It is characterized by the formation of

[For production]

In the present invention, the upper and lower surfaces of a piezoelectric element formed in a thin plate shape are shifted significantly when viewed in the thickness direction, thereby biasing the piezoelectric element and polarizing the piezoelectric element by applying a high voltage to the field of the picture electrode.

Strictly speaking, this means that the polarization direction is not perpendicular to the thickness direction (i.e., parallel to the plane of the thin plate), but is slightly inclined to the plane of the thin plate, but it is important to carefully select the electrode pair. Note that, for example, by setting the polarization inclination angle to 15 degrees or less, the heat direction deformation component becomes extremely small, and the influence of this inclination can be almost ignored.

In addition, by increasing the number of longitudinally vibrating piezoelectric elements and increasing the required value of longitudinal vibration, the effect of such inclination can be almost ignored.

According to the present invention, a piezoelectric element formed in a thin plate shape can be polarized as it is, and processes such as cutting and re-adhesion are not necessary, and production costs can be significantly reduced.

Furthermore, since processes such as cutting and re-bonding are not required, the strength of the piezoelectric element is greatly increased, and the quality of the finished piezoelectric element can be made uniform.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to the drawings, which illustrate embodiments of the invention.

First, a method for polarizing a piezoelectric element for torsional vibration according to the present invention will be explained using examples.

In this example, the ceramic 1 is sintered into a donut shape as shown in FIG. The thickness of the ceramic 1 in this case is made as thin as possible. As shown in Fig. 1, the top and bottom surfaces of the ceramic 1 formed into a thin donut shape (the top surface is visible in Fig. 1) are arranged in a fan shape centered on the center P of this donut-shaped disk. Divide into sections.

A small gap IC is provided between a large number of these divided sections, and an electrode 1a is formed in each section by vapor deposition. Similarly, a large number of electrodes 1b are formed on the lower surface.

Next, as shown in FIG. 3, the vertical positions of the electrodes 1a and lb on the top and bottom surfaces of the donut plate-shaped piezoelectric element are shifted. That is, in FIG. 3, the upper electrode (2) and the lower electrode (2) are shifted by 3 pitches.

In this way, a high voltage is applied between the upper and lower electrodes 1as1b in the shifted state.

As a result, as shown in FIG. 3, the inside of the piezoelectric element is polarized between the upper and lower electrodes (2), albeit in a direction slightly inclined with respect to the surface of the thin plate.

This polarization operation is then performed between the electrodes (■■) and between the electrodes (■■). Note that during this polarization operation, polarization between a plurality of electrodes may be performed simultaneously if the polarization operation with other electrodes is not hindered.

As described above, in the present invention, when polarizing the piezoelectric element, the piezoelectric element is not cut but is polarized as it is.

Electrodes for applying a voltage for driving the piezoelectric element are formed on the upper and lower surfaces of the piezoelectric element which has been polarized in this manner. For this purpose, the small electrodes formed in a fan shape as described above are passed through each other. As this method, one continuous electrode may be bonded onto the electrodes on the upper and lower surfaces. Alternatively, a thin film electrode may be formed by omitting the fan-shaped small electrodes that are independent from each other and depositing metal over the entire upper and lower surfaces of the thin plate.

By doing as described above, a piezoelectric element for torsional vibration according to the present invention can be obtained.

Next, an example in which the method of the present invention is applied to polarization of a piezoelectric element for sliding vibration will be described with reference to FIGS. 4, 5, and 6.

In this case, the piezoelectric element 11 is formed in the same manner as described above, but instead of being circular, the piezoelectric element 11 is formed in a rectangular thin plate shape.

This thin plate-like piezoelectric element 11 has a large number of electrodes 11a in a band shape,
A large number of strip-shaped electrodes 11a, 11a, 11a, 11a, 11a, 11a, 11a, 11a, 11a, 11a, 11a, 11a, 11a, llb are made independent, that is, there is no conduction between adjacent electrodes.
b are formed on the upper and lower surfaces as shown in FIG. Next, the electrodes on the upper and lower surfaces are polarized in the same manner as described above, with their pitches shifted, and as a result, the electrodes are polarized in a direction slightly inclined with respect to the surface when viewed as a whole.

Formation of electrodes for applying a driving voltage to the piezoelectric element thus formed is performed in the same manner as in the piezoelectric element for torsional vibration described above.

[1] Effects of the Invention According to the present invention, the upper and lower surfaces of a piezoelectric element formed in a thin plate shape are significantly shifted when viewed in the thickness direction, thereby being biased and polarized by applying a high voltage to both electrode fields.

Therefore, according to the present invention, a piezoelectric element formed in a thin plate shape can be polarized as it is, and processes such as cutting and re-adhesion are not necessary, and production costs can be significantly reduced. Further, since processes such as cutting and re-adhesion are not required, the strength of the piezoelectric element is greatly increased, and the quality of the finished piezoelectric element can be made uniform.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining the polarization method of the piezoelectric element for torsional vibration according to the present invention, in which FIG. 1 is a plan view, FIG. 2 is also a plan view, and FIG. 3 is a schematic diagram. FIGS. 4 to 6 are diagrams showing a polarization method of the piezoelectric element for sliding vibration according to the present invention, FIGS. 4 and 5 are plan views, and FIG. 6 is a schematic diagram. FIG. 1.11...Piezoelectric element, la, lb, lla, 11b-...electrode. Engraving of the drawing (no changes to the content) Figure 1

Claims (5)

[Claims] 1. A piezoelectric element material is formed into a thin plate, a plurality of electrodes are formed independently in the polarization direction on the upper and lower surfaces of the thin plate, and a high voltage is applied between the pairs of electrodes with upper and lower tone planes biased in the polarization direction to polarize. A method for polarizing a piezoelectric element, characterized in that the above polarization operation is repeated between a plurality of electrode pairs to polarize the entire thin plate. 2. 2. The method for polarizing a piezoelectric element according to claim 1, wherein the piezoelectric element material is formed into a circular thin plate, and a plurality of sector-shaped electrodes are formed around the center of the circular thin plate on both upper and lower surfaces of the circular thin plate. polarization method. 3. A method for polarizing a piezoelectric element according to claim 1, characterized in that the piezoelectric element material is formed into a rectangular thin plate, and a plurality of band-shaped electrodes are formed on the upper and lower tone surfaces of the rectangular thin plate. Method. 4. A piezoelectric element characterized in that a large number of electrodes formed on a thin plate polarized by the method according to any one of claims 1 to 3 are removed, and electrodes are formed on the entire upper and lower surfaces of the thin plate by vapor deposition. 5. 4. A piezoelectric element characterized in that electrode plates are respectively bonded to the upper and lower surfaces of the thin plate so as to establish conduction between a large number of independent electrodes formed on the thin plate polarized by the method according to any one of claims 1 to 3.