JPH03218111A - Piezoelectric vibrator for overtone oscillation - Google Patents

Abstract

PURPOSE:To stably extract a desired frequency component without using together a resonance circuit or the like by attenuating or making leak the overtone vibration of a fundamental wave and low-order harmonic waves whose frequency is lower than the major vibration and undesired sub vibration whose frequency is high to extract the major vibration effectively. CONSTITUTION:A main vibration energy confinement part 2 is provided on the middle of a piezoelectric substrate 1 with electrodes 2a, 2b, a vibration energy propagation part 3 having an interruption frequency Fc higher than the interruption frequency fc is provided around the part 2, and a vibration energy absorbing part 4 having a cutoff frequency lower than the frequency Fc is provided on the outside of the part 3. The frequency Fc is set lower than the sub vibration frequency of the desired overtone vibration and higher than the major vibration frequency fo of the overtone vibration, the vibration energy absorbing part 4 absorbs the energy of the vibration mode of lower-order than the desired overtone order to make the sub vibration higher than the main vibration leak to the outside. Thus, all the undesired vibration energy is made to leak to the absorbing part 4 and the third overtone without undesired vibration is confined as the major vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a piezoelectric vibrator for overtone oscillation that enables oscillation at a desired overtone frequency without requiring an overtone resonant circuit.

<Conventional technology> Conventionally, when trying to use overtone vibration in a piezoelectric vibrator using an AT-shaped crystal plate, it is generally necessary to set a desired overtone frequency to an oscillation circuit using this piezoelectric vibrator. By inserting an LC tuning circuit that matches the overtone frequency ei. He was taking out a number.

However, inserting a tuned circuit in this way complicates the circuit configuration, and sub-oscillations relative to the extracted Ohartone vibration are not sufficiently suppressed, making the frequency of the oscillation circuit unstable and lacking reliability. It had drawbacks.

On the other hand, Japanese Patent Laid-Open No. 61-236208 discloses an idea for realizing overtone vibration with a single piezoelectric vibrator. For example, as shown in FIG. 13, circular electrodes 2 and 2' are provided on both sides of the central part of the piezoelectric substrate 1.
The cutoff frequency f of the vibration energy propagation section 3.3' around it
2, the main vibration frequency fI of the center electrode 2.2' is set low, and a cutoff frequency difference of f2-f is provided between them, so that the center electrode becomes the main vibration energy confinement part, and the vibration energy around it is transmitted If! Further on the outer periphery of j3.3', there is a vibration energy absorbing part 4.4' with a cutoff frequency f3 (however, f: +
<fz).

<Problems to be Solved by the Invention> According to this conventional example, the wave number 12 of the vibration wave propagation parts 3, 3 becomes high, and therefore the desired wave number 12 including the fundamental wave vibration mote is increased. It is easy to leak the energy of vibration motes of lower orders. However, it is possible to attenuate unnecessary sub-vibration frequencies that occur near the main vibration frequency of the desired overtone vibration, but as with the case of using the above-mentioned tuning circuit, there may be problems with the instability of the desired frequency. there were.

Therefore, the first objective of the present invention is to easily set the cutoff frequency f2 of the vibration energy transmission section lower than the unnecessary vibration frequency with respect to the main vibration frequency in a desired overtone order, thereby eliminating all unnecessary vibration energy. By providing an improved piezoelectric vibrator for overtone oscillation, which can easily confine third-order overtones as main vibrations without causing unnecessary vibrations, for example. be.

(Means for Solving the Problems) Fig. 1: This is a sectional view schematically showing the configuration of the present invention.The configuration of the piezoelectric vibrator for overtone oscillation of the present invention will be explained with this.Piezoelectric base 1 Electrodes 2a, 2b are placed in the center of
A main vibration energy confinement section 2 is provided by providing a main vibration energy confinement section 2, a vibration energy propagation section 3 having a cutoff frequency Fc higher than the cutoff frequency fc of the main vibration energy confinement section is provided around the main vibration energy confinement section 2; A vibration energy absorption section 4 having a cut-off frequency lower than Fc is provided,
The cutoff frequency Fc is set lower than the sub-vibration frequency of the desired O-Herton vibration and higher than the main vibration frequency fo of the O-Her-Tone vibration, and the vibration mechanical contradiction absorbing section 4 is set to be lower than the desired overtone order. It is configured to absorb the energy of low-order vibration motes (including fundamental wave vibration modes) and to leak secondary vibrations higher than the main vibrations to the outside.

The present invention can be carried out in various ways, but the feature of the present invention is that vibration energy is transferred by a region in which an electrode is provided on only one side of a piezoelectric substrate and an electrode-free area is formed on the other side. This means that the department is composed of: Second
The invention described in item 3 is an embodiment in which the electrode-absent portion is formed in a C shape only on one side of the piezoelectric substrate, and the invention described in item 3 is an embodiment in which the electrode-absent portion is formed in a C shape on both sides of the piezoelectric substrate. be.

<Operation> In the present invention, for example, the third Oher-1 vibration (
If you want to use the vibration frequency fo) as the main vibration, the fundamental wave vibration (frequency fo/3) and the third order
The energy of unnecessary sub-vibrations (frequency f, f2, etc.) of tone vibration can be suppressed to a practically acceptable level.

This will be explained using empirical rules.

As shown in FIG. 2, a central electrode 2a is provided at the center of the piezoelectric substrate 1 and constitutes a main vibration energy trapping section, and a peripheral electrode 2a is provided at the periphery of the piezoelectric substrate 1 and constitutes a vibration energy absorbing section. Changes in the CI value (crystal impedance, vibration resistance) of the piezoelectric vibrator when the width dimension G of the vibration energy transmission part formed between the external electrode 4a, that is, the electrode absent part 3, is changed. is shown in Figure 3.

According to this, for example, the width dimension G of the electrode absent portion is G. When it is relatively large, the fundamental wave F. , 3rd O'Hartton F3
．． The 5th overtone F has a low CR value, and is naturally the fundamental wave F. The frequency component is the strongest, followed by the frequency component of the third-order Ochertone vibration F3, and the frequency component of the fifth-order overtone vibration F. Therefore, the overtone of a desired order, for example, only the third-order overtone component, becomes weaker. ,
It is difficult to extract it without using a resonant circuit. However, if the width of the non-electrode portion is relatively small, for example 62, the fundamental wave F. The frequency component of the overtone vibration F3, F, is significantly reduced, whereas the frequency component of the overtone vibration F3, F, is not reduced, and the frequency component of the fifth-order Ohartone vibration F5 is weaker than the frequency component of the third-order overtone vibration F3. Therefore, the frequency component of the third overtone vibration F3 can be extracted without using a resonant circuit, and for example, if the width of the electrode-absent part is further reduced to 63,
Fundamental wave F. While the frequency components of , as well as the frequency components of the third-order Ocher tone vibration F3 are both greatly attenuated,
, the fifth-order overtone vibration F, do not undergo any decay, and therefore, the frequency component of the fifth-order overtone vibration F5 can be extracted without using a resonant circuit.

Next is Figure 4! Vibration energy transfer by computer simulation {Main vibration (for example, useful frequency vibration f of third overtone vibration) when changing the plate puncture amount R, which has an important relationship with the cutoff frequency Fc of the killing section 3
Fig. 3 shows a characteristic diagram of the extinction ratio of sub-vibrations (for example, unnecessary frequency vibrations f+, fz of third-order overtone vibration) with respect to o). Here, plate hanoku iR means, as shown in Fig. 2, when the thickness of the piezoelectric substrate is t, and the thickness of the electrode on one side of the substrate constituting the vibration energy transmission goose section 3 is S, S R is C. It is given from this. This is also the natural frequency of the piezoelectric substrate. ′ and the natural frequency f of the first part with the electrode attached.

The natural frequency f of the difference (f.'-fo). It corresponds to the ratio f0 to '. Further, FIG. 5 shows an example of an admit frequency characteristic diagram of a piezoelectric vibrator.

Note that the experimental diagram shown in Figure 4 is
This is done by uniformly changing the thickness S of the electrode attached to the entire surface of one side of the piezoelectric substrate, and therefore, the cutoff frequency fc of the main vibration energy confinement section 2 changes according to the change in the plate thickness.
, and also affects the cutoff frequency of the vibration energy absorbing section 4.

According to the experimental data, the plate hassock amount R is 0.005
It is recognized that as the value becomes smaller, the attenuation ratio of the admittance of the sub-vibration component to the atmittance of the main vibration component, that is, the spurious level (dB) increases rapidly. Therefore, by appropriately selecting the thickness of the electrode layer on one side of the piezoelectric substrate constituting the vibration energy transmission goose portion, unnecessary sub-vibration components can be suppressed.

<Embodiment> Figures 6(al) and 6(bl) show a plan view and a bottom view of an embodiment of the present invention.

Circular piezoelectric base {The surface of the diagonal 11 has an electric +】1
Two electrode-free areas 13 having a width G are provided around the electrodes, and two electrodes 14 are provided around the outer periphery thereof. Moreover, an electrode 15 is provided on the entire back surface of the piezoelectric substrate 11. In such a structure, the electrode 12 and the corresponding part of the electrode 15 constitute the main vibration energy confinement part, the electrode absent part 13 and the corresponding part of the electrode 15 constitute the vibration energy propagation part, and the electrode 14 and the corresponding part of the electrode 15 constitute the vibration energy propagation part. A portion of the electrode 15 corresponding thereto constitutes a vibration energy absorption section. A lead electrode 16 is formed from the center electrode 12 to one end edge A of the piezoelectric substrate 11, and extends to the opposite end 8MB of the piezoelectric substrate 11 through the outer peripheral electrode 1 and the back electrode 15. The circular piezoelectric base 11 is supported by both end edges A and B. In the frequency adjustment step, the thickness of the electrode 15 can be finely adjusted by applying metal to the center portion 16 of the back electrode 15.

The thickness of the electrode 15 on the back surface does not have to be uniform over the entire surface, and can be changed depending on each component. Similarly, the thickness of the surface electrodes 12, 14 can be set individually. The cutoff frequency of each part is piezoelectric substrate 1
The cutoff frequency depends on the material and thickness of the electrode 1 and the material and thickness of the electrodes provided on both sides, and the cutoff frequency can be controlled by changing the thickness of the electrode on one side.

FIG. 7 shows the specific resistance (G-00) for the fundamental wave vibration and the third overtone vibration when the diameter of the central electrode 12 is 21 and the width G of the electrode absent area 13 is changed in the above embodiment. 1) is shown. When the dimension G becomes 0.7 or less, the resistivity to the fundamental wave vibration exceeds that of the third overtone, and when the dimension G becomes 0.4 or less, the resistivity to the fundamental wave vibration becomes very thick. In comparison, the resistivity for the third overtone is kept at a small value.

FIG. 8 shows attenuation of unnecessary secondary vibrations (spurious) with respect to the main vibration of the tertiary overtone when the plate width R of the back electrode 15 is set to 0.01 and the dimension G is changed in the same embodiment as above. Indicates a measurement of a quantity.

FIG. 9 shows measured values of the amount of attenuation of unnecessary sub-vibration (spurious) with respect to the main vibration of the tertiary ohno tone when the thickness S of the back electrode 15 is changed in the same example.

Furthermore, FIG. 10 shows the frequency characteristics of the third overtone in the same example. (The a+ figure is for the plate thickness R=0.003 of the back electrode 15, and the fbl figure is for R=
0.01.

FIG. 11 shows another embodiment of the present invention. The difference from the embodiment shown in FIG. 6 is that the lead electrode 16 formed integrally with the center electrode 12 is enlarged into a semicircle with a center angle of 180°, and the outer electrode 14 is accordingly formed into a semicircle with a center angle of 180°. There are some things that have been reduced. A back electrode 15 is provided on the entire back surface. In this embodiment, the entire outer circumference where the lead electrode 16 and the outer circumferential electrode 14 are provided constitutes a vibration energy absorbing section.

FIG. 12 shows an embodiment of the present invention.

+al figure is top view, (bl is bottom view, (ci figure or A-B
FIG. As shown in the figure, the structure of this embodiment is point symmetrical with respect to the midpoint of the piezoelectric substrate 11. To explain this, on one side 11a of the piezoelectric substrate 11, a first center electrode 21 constituting the main vibration energy confinement section is formed integrally with the first center electrode, and the periphery of the center electrode 21 is a first peripheral electrode 22 formed in a part of the first peripheral electrode 22;
A central part electrode 21 and a second peripheral part electrode 24 formed through the first electrode absent part 23 are provided, and a main vibration energy confinement part is provided on the other side 1 lb of the piezoelectric substrate 11. a third peripheral electrode 26 formed integrally with the second central electrode 25 and corresponding to the second peripheral electrode 24; , second central electrode 25 and second electrode absent area 2
A fourth peripheral electrode 28 formed through the 7 is provided, and a region where the first and fourth peripheral electrodes 22 and 28 face each other, and a region where the second and third peripheral electrodes 2
The region where the electrodes 426 face each other constitutes a vibration energy absorbing portion, and the region where the first and second electrode absent portions 23 and 27 are provided constitutes a vibration energy propagation portion.

<Effects of the Invention> According to the present invention, not only fundamental waves and low-order overtone vibrations having a lower frequency than the main vibration, but also unnecessary sub-vibrations having a higher frequency than the main vibration are attenuated or leaked.
Since only the main vibration can be effectively extracted, only the desired frequency component can be stably extracted without using a resonant circuit or the like.

In addition, since the electrodes are provided over a relatively large area on the entire back surface or half of the back surface, the metal deposition work in the frequency fine adjustment process does not require high positional accuracy as in the past.
Adjustment work has become easier.

[Brief explanation of drawings]

Fig. 1 is a sectional view schematically showing the structure of the present invention, Fig. 2 is a sectional view with dimensions of each part to explain the function of the present invention, and Figs. 3 and 4 are sectional views showing the function of the present invention. FIG. 5 is a diagram showing an example of frequency characteristics of admittance of overtone vibration, and FIG. 6 is a diagram showing an example of the present invention.
The figure is a plan view, and the figure (b) is a bottom view. 7, 8, 9 and 10 are characteristic diagrams of the embodiment shown in FIG. 6, and FIG. 11 is a diagram showing another embodiment of the present invention.
Figure l is a plan view, and figure fbl is a sectional view taken along line A-B. FIG. 12 is a diagram showing still another embodiment of the present invention (al figure is a plan view, fbl figure is a bottom view, (C) figure is A
-B sectional view. FIG. 13 is a sectional view showing a conventional example. 1.11... Piezoelectric substrate 2... Main vibration energy confinement section 3... Vibration energy propagation section 4... Vibration energy absorption section 12... Center electrode 13... Electrode absent section 14... Peripheral electrode 1 5 ・Back electrode

Claims (3)

[Claims] (1) A piezoelectric vibrator that vibrates overtone at a desired order, in which a main vibration energy confinement section is provided in the center of the piezoelectric substrate to confine the main vibration of the overtone vibration of the desired order, and around the main vibration A vibration energy propagation part having a cut-off frequency Fc higher than the cut-off frequency fc of the energy confinement part is provided, and a vibration energy absorption part having a cut-off frequency lower than the cut-off frequency Fc is provided outside the vibration energy propagation part, and the cut-off frequency Fc is It is set lower than the secondary vibration frequency of the desired overtone vibration and higher than the main vibration frequency fo of this overtone vibration, and the vibration energy absorbing section is set to a frequency lower than the desired overtone order including the fundamental wave vibration mode. A piezoelectric vibrator for overtone oscillation, characterized in that the piezoelectric vibrator is configured to absorb the energy of the next vibration mode and to leak the secondary vibration higher than the main vibration to the outside. (2) On one side of the piezoelectric substrate, a central electrode that constitutes the main vibration energy trapping section, an electrode absent section that constitutes the vibration energy propagation section, and a peripheral electrode that constitutes the vibration energy absorption section are formed. , a piezoelectric vibrator for overtone oscillation, wherein an electrode is formed on the entire other surface of the piezoelectric substrate. (3) A first center electrode constituting the main vibration energy confinement section is formed integrally with the first center electrode on one side of the piezoelectric substrate, and a part of the periphery of the center electrode is formed integrally with the first center electrode. A first peripheral electrode is formed, and a second peripheral electrode is formed via the first center electrode and the first electrode absent area, and On one side, a second central electrode constituting the main vibration energy confinement section, and a second central electrode formed integrally with the second central electrode and corresponding to the second peripheral electrode. 3 peripheral electrode, and the second peripheral electrode.
a central electrode and a fourth peripheral electrode formed through the second electrode-absent part, and the opposing regions of the first and fourth peripheral electrodes and the second peripheral electrode are provided. and the opposing regions of the third peripheral electrode constitute the vibration energy absorbing section, and the first and second peripheral electrodes constitute the vibration energy absorbing section.
An electrode vibrator for overtone oscillation, wherein a region corresponding to the electrode absent part constitutes the vibration energy propagation part.