JPH0661776A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To make the size of the resonator small even when a resonance frequency in the unit of a kHz band is obtained by forming a piezoelectric plate to be a ring plate. CONSTITUTION:A piezoelectric resonator 10 includes a piezoelectric plate 12 and the piezoelectric plate 12 is formed in a ring plate by using, e.g. a piezoelectric ceramic. The piezoelectric plate 12 is subject to polarization processing in the broadwise direction. Furthermore, Electrodes 14, 16 are formed to both sides of the piezoelectric plate 12 and the piezoelectric resonator element is vibrated by applying a signal between the electrodes 14, 16. Thus, the stiffness is decreased more than the piezoelectric resonator 10 employing the piezoelectric plate 12 of the same outer diameter and the resonance frequency of the piezoelectric vibrator 10 is decreased. When the outer diameter of the piezoelectric plate 12 is the same, the resonance frequency of the piezoelectric resonator 10 gets lower as the inner diameter increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator, and more particularly to a piezoelectric resonator which is applied to a ceramic filter or the like and uses a lateral effect vibration mode as a resonance mode.

[0002]

2. Description of the Related Art As a conventional piezoelectric resonator, for example, there is one in which electrodes are formed on both main surfaces of a square plate-shaped piezoelectric plate or a rectangular plate-shaped piezoelectric plate. By polarizing the piezoelectric plates in the thickness direction and applying a signal to the electrodes on both main surfaces, the piezoelectric resonator vibrates. Such a vibration mode is applied to a ceramic filter or the like, and its resonance frequency is determined by the material constant, shape, and vibration mode of the element. For example, in a filter in the kHz band, the spreading vibration mode is used in the case of a piezoelectric resonator using a square plate-shaped piezoelectric plate. Further, in the case of a piezoelectric resonator using a rectangular plate-shaped piezoelectric plate, the extension vibration mode is used.

[0003]

However, in such a conventional piezoelectric resonator, PZT is used as the material of the piezoelectric plate.
When (lead zirconate titanate) is used, for example, 4
In order to obtain a resonance frequency of 55 kHz, the dimension of one side is at least about 5 mm. Moreover, when the outer dimensions of the piezoelectric plate are determined, the resonance frequency of the piezoelectric resonator is uniquely determined. Therefore, when trying to obtain the desired resonance frequency,
Since the external dimensions of the piezoelectric plate were determined, miniaturization could not be expected.

Therefore, the main object of the present invention is k
An object of the present invention is to provide a piezoelectric resonator that can be downsized even when obtaining a resonance frequency in the Hz band.

[0005]

According to the present invention, there is provided a piezoelectric resonator including a piezoelectric plate and an electrode formed on the piezoelectric plate, wherein a lateral effect vibration mode is used as a resonance mode. A piezoelectric resonator characterized by being formed into a ring plate shape.

[0006]

By making the piezoelectric plate a ring plate, the stiffness is reduced and the resonance frequency of the piezoelectric resonator is lowered as compared with a piezoelectric resonator using a piezoelectric plate having the same maximum external dimensions. If the outer diameters of the piezoelectric plates are the same,
The larger the inner diameter dimension, the lower the resonance frequency of the piezoelectric resonator.

[0007]

According to the present invention, the resonance frequency of the piezoelectric resonator can be adjusted by appropriately selecting the outer diameter and the inner diameter of the piezoelectric plate. Therefore, kHz
A piezoelectric resonator used in a low frequency region such as a band can be downsized.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0009]

1A is a plan view showing an embodiment of the present invention, and FIG. 1B is a sectional view thereof. The piezoelectric resonator 10 includes a piezoelectric plate 12. The piezoelectric plate 12 is formed in a ring plate shape using, for example, piezoelectric ceramic.
The piezoelectric plate 12 is polarized in its thickness direction. Further, electrodes 14 and 16 are formed on both surfaces of the piezoelectric plate 12, respectively. These electrodes 1
By applying a signal between 4 and 16, the piezoelectric resonator 10 vibrates.

In order to manufacture such a piezoelectric resonator 10, Pb (Zr _0.52 Ti _0.48 ) O ₃ +0.5 wt% Nb
A material represented by ₂ O ₅ was prepared. After calcination of this material, 5 wt% vinyl acetate binder was added to produce granulated powder, and this granulated powder was applied at a pressure of 1.0 ton / cm ² to an outer diameter of 5 mm, an inner diameter of 1 mm and a thickness of 1 mm Was pressed into a ring shape. The obtained molded body was fired at 1250 ° C. in an electric furnace to obtain a sintered body. This sintered body was lapped to a thickness of 0.5 mm. Then, a silver electrode was vapor-deposited on the lapping-processed sintered body, and the sintered body was polished to a predetermined size by an outer peripheral polishing machine and an inner peripheral polishing machine. After that, 6
2.0 to 3.0 kV in silicone oil at 0 ° C
An electric field of / mm was applied to perform polarization treatment in the thickness direction of the sintered body to obtain a piezoelectric resonator. The silver electrode was formed such that both main surfaces of the sintered body were equipotential surfaces.

By applying an excitation signal between the electrodes 14 and 16 of the piezoelectric resonator 10 thus obtained, the spreading vibration mode could be excited as shown by the arrow in FIG.

In order to excite vibration modes other than the spreading vibration mode, a piezoelectric resonator 10 as shown in FIG. 3 can be manufactured. In this piezoelectric resonator 10, the electrode 14 on one surface of the piezoelectric plate 12 has four electrodes 14a, 14
It is divided into b, 14c and 14d. Similarly, the piezoelectric plate 1
The other electrode 16 of 2 also has four electrodes 16a, 16b, 1
It is divided into 6c and 16d. In these electrodes 14 and 16, the electrodes 14a and 16a and the electrode 14
b and 16b, electrodes 14c and 16c, and electrodes 14d and 1
6d are formed so as to face each other. Then, as shown in FIG. 3, the electrodes 14a, 14c, 16b, 16d are connected to one end of the excitation circuit, and the electrodes 14b, 14d, 16a,
16c is connected to the other end of the excitation circuit. Therefore,
When an excitation signal is applied from the excitation circuit to each electrode, the directions of the electric fields applied to the piezoelectric plate 12 are alternately reversed in the portions where the divided electrodes are formed. Therefore, FIG.
As indicated by the arrow, the piezoelectric resonator 10 has an expanding portion and a contracting portion. Therefore, the piezoelectric resonator 1
The vibration mode of 0 is a vibration mode other than the uniform spreading vibration.

With respect to the piezoelectric resonator thus obtained, the relationship between its size, resonance frequency, and electromechanical coupling coefficient was measured and shown in Table 1.

[0014]

[Table 1]

As can be seen from Table 1, the resonance frequency and the electromechanical coupling coefficient of the piezoelectric resonator can be changed by forming the piezoelectric plate in the shape of a ring plate and appropriately selecting the outer diameter and the inner diameter thereof. For example, in order to obtain a resonance frequency of 455 kHz using the piezoelectric resonator of the present invention, the outer diameter of the piezoelectric plate should be 3.0 mm and the inner diameter of the piezoelectric plate should be 2.2 mm. 5.0 for resonator
Although the external dimensions of mm were required, it was possible to reduce the size. As described above, according to the present invention, the piezoelectric resonator used in a low frequency region such as the kHz band can be downsized.

[Brief description of drawings]

FIG. 1A is a plan view showing an embodiment of the present invention, and FIG. 1B is a sectional view thereof.

FIG. 2 is an illustrative view showing a vibration state of the piezoelectric resonator shown in FIG.

FIG. 3 is an illustrative view showing another embodiment of the present invention.

[Explanation of symbols]

 10 Piezoelectric Resonator 12 Piezoelectric Plate 14 Electrode 16 Electrode

Claims (3)

[Claims] 1. A piezoelectric resonator including a piezoelectric plate and an electrode formed on the piezoelectric plate, wherein a lateral effect vibration mode is used as a resonance mode, wherein the piezoelectric plate is formed in a ring plate shape. A piezoelectric resonator characterized in that 2. The piezoelectric resonator according to claim 1, wherein the piezoelectric plate has an outer diameter of 5 mm or less. 3. The piezoelectric resonator according to claim 1, wherein the resonance mode of the piezoelectric plate includes a mode other than a spreading vibration in which the piezoelectric plate uniformly expands and contracts.