JPH0228922B2 - ATSUDENSHINDOSHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric vibrator that utilizes thickness shear vibration.

An object of the present invention is to provide a piezoelectric vibrator that suppresses spurious vibrations and is advantageous in manufacturing.

That is, the gist of this invention is that a piezoelectric diaphragm has electrodes on two main surfaces, has a polarization axis parallel to the electrode surfaces, and has a length L, a width W, and a thickness T. Then, the piezoelectric vibrator has the following relationships: 1.0T≦W≦1.5T 1.5W≦L≦4.0W.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a piezoelectric diaphragm made of piezoelectric ceramic or the like, and 2 and 3 are electrode films provided on two main surfaces of the piezoelectric diaphragm 1.

In the present invention, the reason for setting 1.0T≦W≦1.5T is as follows.

The piezoelectric diaphragm 1 is held by bringing the electrode films 2 and 3 into contact with an external connection terminal plate (not shown), but if T>W, the piezoelectric diaphragm cannot be processed. Since this would be difficult and the holding state would become unstable, T≦W was set. Also, if W > 1.5T, piezoelectric diaphragm 1
W≦1.5T because there will be a negative effect on the effective use of
And so.

In the present invention, the reason for setting 1.5W≦L≦4.0W is as follows.

In the piezoelectric vibrator shown in FIG. 1, there are two vibration modes: thickness shear vibration and longitudinal vibration in the length L direction. Since the present invention uses thickness shear vibration, longitudinal vibration must be suppressed as much as possible.

In Figure 2, for multiple samples, L/W
When changing from 1.0 to 2.16, the excitation strength in thickness shear vibration and longitudinal vibration is 20 log
Ra/R ₁ (Ra is anti-resonant resistance, R ₁ is resonant resistance) was measured and its tendency was shown as a curve. Curve A shows thickness shear vibration, and curve B shows longitudinal vibration.

Moreover, in FIG. 3, when L/W is changed from 1.0 to 2.16, the trends of changes in the resonant frequency and anti-resonant frequency in thickness shear vibration and longitudinal vibration, respectively, are shown by curves. Curve C shows the tendency of longitudinal vibration, and curve D shows the tendency of thickness shear vibration. In the figure, ○ is the resonant frequency, and × is the anti-resonant frequency.

As is clear from both figures, as L increases, the resonant frequency and anti-resonant frequency of the thickness shear vibration to be used hardly change. In this case, the strength of the excitation is advantageously increased. On the other hand, the resonant frequency and anti-resonance of longitudinal vibration, which are unnecessary vibrations, decrease rapidly, and the excitation strength also decreases rapidly, until around L/W = 2.16, the excitation strength of thickness shear vibration decreases. This is about 1/8th of the total, and it is on the verge of extinction. When manufacturing normal filters and resonators, the strength and frequency of the spurious response is weaker than that of the main response.
The further away the better. Practically speaking, it is sufficient if L/W=1.5 or more. Although L>4.0W is acceptable, from the point of view of effective use of the piezoelectric diaphragm, it is preferable that L≦4.0W.

As is clear from the above embodiments, according to the present invention, an optimal structure can be obtained particularly for mass-producing resonators around 1 to 2 MHz.

[Brief explanation of drawings]

Fig. 1 is a perspective view of an example of a resonator used in the present invention, Fig. 2 is a graph showing changes in excitation intensity when the resonator dimensions are changed, and Fig. 3 is a graph showing changes in excitation intensity when the resonator dimensions are changed. 12 is a graph showing changes in resonance frequency and anti-resonance frequency when 1 is a piezoelectric diaphragm, 2 and 3 are electrode films.

Claims (1)

[Claims] 1 A piezoelectric diaphragm has electrodes on two main surfaces, has a polarization axis parallel to the electrode surfaces, and where the length of the piezoelectric diaphragm is L, the width is W, and the thickness is T. , 1.0T≦W≦1.5T 1.5W≦L≦4.0W A piezoelectric vibrator using a non-energy confined thickness shear vibration mode.