JPH0275211A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To obtain a demodulation characteristic as designed by forming a frequency adjustment load member so as to surround the vibration electrode and not to reach the side ridge of the vibration electrode. CONSTITUTION:A frequency adjustment load member 16 made of a synthetic resin or a rubber is coated to a ring area D shown in hatched lines. That is, the frequency adjustment load member 16 is formed so as to surround the vibration electrode 12 and so as not to reach the outer circumferential ridge of the vibration electrode 12 with a distance from the outer circumferential ridge of the vibration electrode 12. Since no load member 16 exists just above the vibration electrode 12, a bulk wave excited between the vibration electrodes 12 and 13 is not propagated in the load member 16 and a reflected bulk wave from the load member 16 is exerted to the base 11 between the vibration electrodes 12 and 13. Thus, the demodulation characteristic as designed is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an energy confinement type piezoelectric resonant device used as, for example, a discriminator, and in particular, a piezoelectric resonator device in which a frequency adjustment load member is coated on a piezoelectric substrate. It relates to something with a structure.

[Prior Art] FIGS. 3 and 4 are a plan view and a partially enlarged sectional view for explaining a conventional piezoelectric resonator device.

A vibrating electrode 2 is formed in the central region of one principal surface of the polarized piezoelectric substrate 1, and a vibrating electrode 3 is formed on the other principal surface so as to face each other with the vibrating electrode 2 and the piezoelectric substrate 1 interposed therebetween.

Although the vibrating electrode 2 and the vibrating electrode 3 are formed to have the same diameter,
It should be pointed out that in FIG. 3, the vibrating electrode 3 on the back side is shown with a larger diameter than the vibrating electrode 2 for convenience of illustration.

Extracting electrodes 4 and 5 are connected to the vibrating electrodes 2.3, respectively, in order to achieve electrical connection with the outside.

By applying a voltage from this extraction electrode 4.5, the piezoelectric substrate portion sandwiched between the vibrating electrodes 2 and 3 vibrates, and the energy of the vibration is confined in the substrate portion sandwiched between the vibrating electrodes 2.3. It is composed of

In order to adjust the resonant frequency of this type of piezoelectric resonator, a structure is adopted in which a frequency adjustment resin material 6 is applied to the hatched region A in FIG. 3 as shown in FIG. 4. has been done. That is, by coating the resin material 6 on the vibration region, vibrations are damped and the resonance frequency is thereby adjusted.

[Technical problem to be solved by the invention] However,
When the frequency adjustment resin material 6 as described above is applied, there is a problem that discontinuity occurs in the admittance characteristics and phase characteristics, as shown in the portions x and Y surrounded by broken lines in FIG. This discontinuity in characteristics is thought to be caused by the following reasons.

That is, when a voltage is applied from the vibrating electrodes 2 and 3 to excite them, the excited bulk waves propagate in the thick direction as shown by arrow B in FIG. 4, are reflected at the electrodes 2 or 3, and become stationary. Waves are formed.

However, in the direction of propagation of this bulk wave, there is a resin material 6 whose density is extremely different from that of the piezoelectric substrate. Therefore, this bulk wave also propagates into the resin material 6, and arrow C
As shown, the wave is reflected on the outer surface of the resin material 6, and the reflected wave propagates into the piezoelectric substrate 1 again. Therefore, in the vibration region, the reflected waves reflected from the resin material 6 side are added to the standing waves. As a result, it is thought that discontinuity occurs at a certain frequency position in the amitance and phase characteristics of the resonant device as described above.

Therefore, in conventional piezoelectric resonators, discontinuities occur in the admittance characteristics and phase characteristics at a certain frequency position, so when used as a discriminator, for example, discontinuities occur in the demodulation characteristics. A problem had arisen.

Therefore, an object of the present invention is to provide an energy confinement type piezoelectric resonator having a structure that can eliminate discontinuities in admittance characteristics and phase characteristics caused by applying a frequency adjustment load member.

[Means for Solving Technical Problems] The present invention is an energy confinement type piezoelectric resonator device that utilizes a thickness longitudinal vibration mode, and includes a piezoelectric substrate and piezoelectric substrates on both main surfaces of the piezoelectric substrate. vibrating electrodes formed so as to face each other through the vibrating electrode, and a frequency adjustment load member coated so as to surround at least one vibrating electrode but not reaching the edge of the vibrating electrode. It is characterized by having

[Effect]

A frequency adjustment load member that performs frequency adjustment by damping vibrations is applied so as to surround the vibrating electrode and not to reach the edges of the vibrating electrode. Therefore, since there is no load member directly above the vibrating electrodes, the bulk wave excited between the vibrating electrodes does not propagate into the load member. Therefore, reflected waves of bulk waves from the load member side are not applied to the substrate portion between the vibrating electrodes, so that designed resonance characteristics can be achieved.

[Explanation of Examples]

FIGS. 1 and 2 are a plan view and a partially cutaway sectional view illustrating an embodiment of the present invention.

Referring to FIG. 1, a vibrating electrode 12 is disposed in the central region of one main surface of the piezoelectric substrate 11, and a vibrating electrode 13 is disposed in the central region of the other principal surface such that the vibrating electrode 12 and the piezoelectric substrate 11 face each other.
is formed. The vibrating electrodes 12, 1.3 are formed to have the same diameter as shown in FIG. 2, but as in the case of FIG. 3, the vibrating electrode 13 on the other main surface side is shown in FIG. It should be noted that, for convenience, the vibrating electrode 13 is shown with a large diameter.

Extracting electrodes 14 and 15 are connected to each of the vibrating electrodes 12 and 13 in order to achieve electrical connection with the outside. It is being pulled out.

The feature of this embodiment is that, as shown in FIG. 2, a frequency adjustment load member 16 made of synthetic resin, rubber, etc. is applied to the ring-shaped area indicated by hatching in FIG. There is a particular thing. That is, the frequency adjustment load member 16 is formed at a certain distance from the outer peripheral edge of the vibrating electrode 12 so as to surround the vibrating electrode 12 and not to reach the outer peripheral edge of the vibrating electrode 12. .

In this embodiment, since the vibrating electrodes 12, 1.3 are circular and the load member 16 is circular, the dimensions a, b, and c shown in FIG. There is a relationship c-b>0. However, the vibrating electrodes 12, 13 and the load member 1
The planar shape of 6 is not limited to that shown in the drawings. That is, the vibrating electrodes 12, 13 may be rectangular,
Further, the load member 16 can also be formed into any shape such as a rectangular ring shape. Furthermore, the load member 16 only needs to have a shape that surrounds the vibrating electrode, and does not necessarily have to be a closed ring, but may have a partially open shape.

In this embodiment, since the load member 16 is formed so as not to reach the vibrating electrode 12, the bulk wave excited between the vibrating electrodes 12 and 13 hardly propagates into the load member 16. Therefore, since the reflected wave from the load member 16 side is not applied to the vibration region, no discontinuity occurs in the admittance characteristic or phase characteristic.

The amount of frequency adjustment in the above embodiment can be adjusted in the direction of lowering the resonant frequency by changing the coating thickness of the load member 16, as shown in FIG. 6, as in the conventional example. be. Note that the frequency reduction amount ratio in FIG. 6 is a numerical value expressed by the following formula.

Frequency reduction amount ratio - (frequency reduction amount/resonant frequency before adjustment) x 100 (%) Curves P, Q and R in FIG. 6 show the characteristics of the embodiment when the shape of the load member is changed. As shown by the characteristics of these curves PH, it can be seen that the resonance frequency can be adjusted by changing the thickness of the frequency adjustment load member 16 in this embodiment as well.

In addition, in the characteristics shown by curves P, Q, and R, P-
>Q→R, the inner diameter b (second
The graph shows the characteristics when the load member 16 is changed to become smaller or the outer diameter C becomes larger (see figure).As is clear from these characteristic examples, in this example, the load member 16 It can be seen that by changing the application shape, it is possible to perform more fine frequency adjustment than in the conventional example.

In the embodiment described above, the vibrating electrode 1 formed on one main surface
Although the frequency adjustment load member 16 is applied only to the second side, the load member may be similarly applied to the vibrating electrode 13 formed on the other main surface side.

Further, in the illustrated embodiment, one vibrating electrode is formed on the amphibatic surface, but a plurality of divided electrodes are formed on one main surface, and the electrodes are formed on the other main surface. The present invention can also be applied to an energy confinement type three-terminal type resonator device formed so as to face a common electrode on the front and back sides.

Moreover, as the piezoelectric substrate 11, it is possible to use one made of other piezoelectric materials in addition to one made of piezoelectric ceramic.

[Effects of the Invention] In the present invention, since the frequency adjustment load member is formed so as to surround the vibrating electrode and not reach the edge of the vibrating electrode, the admittance characteristics and phase characteristics of the resonant device are It becomes possible to adjust the resonant frequency without causing discontinuity.

Therefore, for example, when used as a discriminator,
It becomes possible to realize demodulation characteristics as designed.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a partially cutaway enlarged sectional view of the embodiment of FIG. 1, and FIG. 3 is a plan view of a conventional example.
Fig. 4 is a partially cutaway enlarged sectional view of the conventional example, Fig. 5 is a diagram for explaining the problems of the conventional example and shows the admittance characteristics and phase characteristics, and Fig. 6 is the resonance of the conventional example and the embodiment. It is a figure which shows the relationship of frequency reduction amount ratio - thickness of the load member for frequency adjustment. In the figure, 11 is a piezoelectric substrate, 12.13 is a vibrating electrode,
Reference numeral 16 indicates a frequency adjustment load member. He + a Figure 3

Claims (1)

[Claims] An energy confinement type piezoelectric resonator using thickness longitudinal vibration, comprising: a piezoelectric substrate; and formed on both main surfaces of the piezoelectric substrate so as to face each other with the piezoelectric substrate interposed therebetween. Piezoelectric resonance characterized by comprising a plurality of vibrating electrodes and a frequency adjustment load member applied so as to surround at least one of the vibrating electrodes and not to reach the edges of the vibrating electrodes. Device.