JPH06204783A - Piezoelectric vibrator for overtone oscillation - Google Patents

Abstract

(57) [Summary] [Object] To provide a highly reliable piezoelectric vibrator capable of more stable high frequency without deteriorating the CI value of the third overtone. A main part electrode 21a, which is a piezoelectric vibrator that vibrates overtones in a desired order and constitutes a main vibration energy confinement part that confines the main vibrations of the overtone vibrations in the desired order on one surface of the piezoelectric substrate 1. An electrode absent portion 31 forming the vibration energy propagating portion and a peripheral electrode 41a forming the vibration energy absorbing portion are formed,
In the piezoelectric resonator for overtone oscillation in which an electrode is formed on almost the entire other surface of the piezoelectric substrate, the center of gravity O of the piezoelectric substrate and the center of gravity Q of the main portion electrode are decentered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator for overtone oscillation which enables oscillation at a desired overtone frequency without the need for an overtone tuning circuit.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. FIG. 3 is a plan view of a conventional piezoelectric substrate, and FIG.
FIG. The piezoelectric substrate 1 is made of an AT-cut crystal plate that vibrates in thickness shear vibrations. By providing a main electrode 2 at the center of the front surface of the piezoelectric substrate 1 and an electrode 5 at the center of the back surface of the piezoelectric substrate 1, a main vibration energy confining portion is formed. Is provided around the cutoff frequency f of the main vibration energy confining portion.
A vibration energy propagating portion (electrode absent portion) 3 having a cutoff frequency Fc higher than c is provided, and a vibration energy absorbing portion (peripheral electrode) 4 having a cutoff frequency lower than the cutoff frequency Fc is provided outside thereof. The cut-off frequency Fc is set to be lower than the sub-vibration frequency of the desired overtone vibration and higher than the main vibration frequency f0 of the overtone vibration, and the vibration energy absorption unit is lower than the desired overtone order. The energy of the next vibration mode (including the fundamental vibration mode) is absorbed, and the auxiliary vibration higher than the main vibration is leaked to the outside.

[0003]

In such an electrode shape, when the frequency is increased by third-order overtone oscillation, the diameter of the main electrode is reduced as the frequency becomes higher, and the electrode absent portion is used. The general design method is to increase the size of the peripheral electrodes. For example, diameter 5.0
When a main electrode with a diameter of 1.5 mm is formed on a piezoelectric substrate of mm, and the size of the electrode absent portion is 0.4 mm, and the third overtone oscillation is performed, 50 MHz to 55 MHz
Up to frequencies can be handled with these electrode shapes. However, it is necessary to further reduce the diameter of the main part electrode in order to increase the frequency. However, if the diameter of the main part electrode is reduced, the CI value of the third overtone also deteriorates, and it is very difficult to increase the frequency. It was. Moreover, in the circuit configuration which does not have a tuning circuit and which is adjusted by the feedback resistance value R1 or C1 and C2 to cause the third overtone oscillation
In some cases, the fundamental wave was oscillated without obtaining stable third-order overtone oscillation.

An object of the present invention is to provide a C of the third order overtone.
Provided is a highly reliable piezoelectric vibrator capable of achieving more stable high frequency without deteriorating the I value.

[0005]

Therefore, the present invention is a piezoelectric vibrator that vibrates overtones in a desired order, and mainly confines the main vibration of the overtone vibrations in the desired order on one surface of a piezoelectric substrate. A main electrode that constitutes the vibration energy confining portion, an electrode absent portion that constitutes the vibration energy propagating portion, and a peripheral electrode that constitutes the vibration energy absorbing portion are formed, and substantially the entire one surface of the other side of the piezoelectric substrate. In the piezoelectric resonator for overtone oscillation in which the electrode is formed on, the center of gravity of the piezoelectric substrate and the center of gravity of the main part electrode are decentered.

[0006]

The main part electrode forming the main vibration energy confining part for confining the main vibration of the overtone vibration of the desired order, the electrode absent part forming the vibration energy propagating part, and the vibration energy on one surface of the piezoelectric substrate. By forming the peripheral electrode that constitutes the absorbing part and forming the electrode on almost the entire other surface of the piezoelectric substrate, for example, when it is desired to use the third-order overtone vibration as the main vibration, the fundamental vibration and the third-order vibration are generated. Secondary vibration that does not require tone vibration (f
The energy (1, f2, etc.) can be kept low enough to be practically acceptable. Then, by decentering the center of gravity of the piezoelectric substrate and the center of gravity of the main part electrode, from the energy displacement distribution of the fundamental wave and the third-order overtone, the loss of the fundamental wave vibration at one end of the piezoelectric substrate is determined by the third-order overtone. Since it is larger than the loss of, the fundamental vibration is suppressed and the third overtone vibration is facilitated. From the above, it is possible to obtain a more stable overtone oscillation in which a more stable high frequency can be obtained without suppressing the fundamental wave and reducing the diameter of the excitation electrode used for the high frequency.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.
Will be described with reference to. 1 is a plan view of a piezoelectric substrate showing an embodiment of the present invention, and FIG. 2 is a bottom view of FIG.
The same parts as those in the conventional example are designated by the same reference numerals. The piezoelectric substrate 1 is composed of an AT-cut quartz plate that oscillates in a circular thickness-shear vibration, and on the surface of the piezoelectric substrate 1, a point Q at a position having a width P from the center of gravity O of the piezoelectric substrate in the holding direction, which is the X-axis direction. A main electrode 21a having a center of gravity is provided, an electrode absent portion 31 having a width G is provided around the main electrode 21a, and an electrode 41a is provided on the outer periphery thereof. On the back surface of the piezoelectric substrate 1, an electrode 51a is provided on almost the entire surface of the piezoelectric substrate 1. That is, the back surface electrode 51a is the front surface main electrode 21.
a, the electrode absent portion 31, and the peripheral electrode 41a are formed on the entire surface. In such a structure, the main electrode 2
1a and a part of the electrode 51a corresponding thereto constitute a main vibration energy confinement portion, the electrode absent part 31 and a part of the electrode 51a corresponding thereto constitute a vibration energy propagating portion, and the electrode 41a and a part of the electrode 51a corresponding thereto. Constitutes the vibration energy absorbing portion. The lead electrode 21b is formed from the central electrode 21a to one end A of the piezoelectric substrate 1, and the outer peripheral electrode 41a and the back surface electrode 51a are formed with lead electrodes 41b and 51b to the end B on the opposite side of the piezoelectric substrate 1. Then, these electrodes are formed by vacuum vapor deposition. With these configurations, when the piezoelectric substrate is used as the main vibration, for example, the third overtone vibration,
Suppresses fundamental wave vibration and facilitates third-order overtone vibration. Furthermore, by further eccentricizing the main electrode 21a to both ends in the holding direction (end A in this embodiment) and attaching a support (not shown), a further fundamental wave suppression effect can be expected. Further, in the present invention, the main electrode 21a is formed with the point Q at the position of the width P in the holding direction as the center of gravity, but the center of gravity Q may be set at the position of the width P in the direction orthogonal to the holding direction. That is, if the center of gravity Q of the main electrode is set in any direction such as up, down, left, right, or the like by shifting the width from the center of gravity O of the piezoelectric substrate by the dimension of P, the fundamental wave vibration is suppressed and the third-order overtone vibration is generated. It has the effect of facilitating. Further, since the CI ratio between the fundamental wave and the third-order overtone changes depending on the dimension widths G and P, it is necessary to set in advance to obtain a desired CI ratio.

FIG. 5 shows a piezoelectric substrate having a diameter of 5.0 mm and a diameter of 1.5 mm.
mm main electrode is formed, G dimension is 0.4 mm, and the frequency is 54.5 MHz with the third overtone.
Piezoelectric vibrator, P dimension from 0mm to 0.75mm
6 is a graph showing CI values of a fundamental wave and a third-order overtone when changed to (a conventional electrode structure is shown when the P dimension is 0 mm) based on experimental results. FIG. 6 is a graph showing the CI ratio between the fundamental wave and the third overtone based on the experimental result of FIG. As shown in these graphs, the P dimension of the conventional electrode structure is 0
Increasing the P dimension to be larger than that of mm has a remarkable effect on suppressing the fundamental wave, and the CI ratio (C
I1 / CI3) is a large result.

[0009]

With the piezoelectric resonator for overtone oscillation of the present invention, the CI value of the third-order overtone is not deteriorated by reducing the diameter of the excitation electrode for increasing the frequency, and a more stable high frequency is achieved. You can now do. Also, in the case of a circuit configuration in which there is no tuning circuit in the third-order overtone oscillating circuit and the feedback resistance value R1 or C1, C2 is adjusted to set the constant to a value that facilitates the third-order overtone oscillation. In the above, if the CI ratio (CI1 / CI3) of the crystal unit is relatively small, the fundamental wave does not oscillate even if the circuit easily vibrates the fundamental wave, and more stable fundamental wave suppression can be performed. Further, by holding the main electrode at the end portion of the piezoelectric substrate in the eccentric direction, a further fundamental wave suppressing effect can be obtained.
With the above effects, it is possible to provide a piezoelectric resonator for overtone oscillation that is highly reliable in terms of higher frequencies and suppression of the fundamental wave.

[Brief description of drawings]

FIG. 1 is a plan view of a piezoelectric substrate showing an embodiment of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a plan view of a conventional piezoelectric substrate.

FIG. 4 is a bottom view of FIG.

FIG. 5 is a graph showing CI values of a fundamental wave and a third-order overtone when P dimension is changed, based on experimental results.

FIG. 6 is a graph showing CI ratios of a fundamental wave and a third-order overtone when the P dimension is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate 2, 21a ... Main central electrode 3, 31a ... Electrode absent part 4, 41a ... Peripheral electrode 5, 51a ... Back surface electrode 21b, 41b, 51b ... Lead electrode

Claims (2)

[Claims] 1. A piezoelectric vibrator which overtones in a desired order and which constitutes a main vibration energy confining part for confining a main vibration of the overtone vibration of the desired order on one surface of a piezoelectric substrate. An overtone oscillation in which an electrode absent portion forming the vibration energy propagating portion and a peripheral electrode forming the vibration energy absorbing portion are formed, and an electrode is formed on almost the entire other surface of the piezoelectric substrate. A piezoelectric vibrator for overtone oscillation, wherein the center of gravity of the piezoelectric substrate and the center of gravity of the main portion electrode are decentered. 2. The piezoelectric vibrator for overtone oscillation according to claim 1, wherein the piezoelectric vibrator is held by at least an end portion of the piezoelectric substrate in an eccentric direction of the main portion electrode.