JPS62271513A - Vibrator - Google Patents

Abstract

PURPOSE:To form a timing extraction filter not causing spurious response near the pass band by forming the thickness at both ends of a piezoelectric ceramic plate having an electrode at upper and lower faces smaller than that of the middle part. CONSTITUTION:The electrode and constant elastic metallic plates 14, 15 and 24, 25 for temperature compensation are soldered to upper/lower faces of piezoelectric ceramic plates 11, 21. The plates 14, 24 at the upper face of the plates 11, 21 are connected together and supports 4, 5, 6 of a mechanical filter are provided. Then steps 12, 13 and 22, 23 are formed respectively to both ends of the plates 11, 12. Then the characteristic before adjustment shown by solid lines is improved as shown by broken lines after adjustment and while the resonance frequency of the longitudinal vibration mode changes largely from fL to fL', the change in the resonance frequency of the bending vibration mode is only from fB to fB'. Thus, no spurious response is caused in the vicinity of pass band and the filter has a characteristic as a timing extracting filter.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Summary] A vertical vibrator used in a mechanical filter, in which electrode plates are provided on the top and bottom surfaces of a piezoelectric ceramic, has not only the length dimension but also the thickness. By reducing the size, the change in the resonant frequency f of the bending mode is reduced relative to the change of the resonant frequency f of the longitudinal vibration mode.

[Industrial application field]

The present invention relates to improvements in longitudinal vibration mode vibrators.

Generally, in designing a longitudinal vibration mode mechanical filter, the length l of each vibrator is determined in advance so that the resonant frequency of each vibrator is lower than a predetermined frequency, taking manufacturing variations into account.

By shortening the length of the vibrator, the resonant frequency of the vibrator is raised to match a desired value.

[Conventional technology]

A conventional mechanical filter had a configuration shown in FIG. That is, it is composed of longitudinal vibrators 10 and 20, each of which is composed of rectangular piezoelectric ceramic plates 101 and 201 polarized in the thickness direction. Constant elastic metal plates 102, 103, 202, 203 are connected to the upper and lower surfaces thereof with an adhesive such as solder. a constant elastic metal plate 102 formed on the top surface;
202 are connected by a connector 30, and the mechanical filter is provided with support parts 40, 41, and 42.

[Problem that the invention seeks to solve]

FIG. 8 is a characteristic diagram of the conventional mechanical filter shown in FIG. In the figure, the vertical axis shows the attenuation amount D, and the horizontal axis shows the frequency f, where fL shows the resonance frequency of the longitudinal vibration mode, and f shows the resonance frequency of the bending vibration mode.

FIG. 8 (8) is a characteristic diagram when the constant elasticity metal plates are properly bonded to the upper and lower surfaces of the piezoelectric ceramic plates 101, 201 and the symmetry is good. In this case, the oscillator 10°20 is the seventh
Longitudinal vibrations that expand and contract in the length direction as shown by α, β, γ, and δ in Figure (C) are performed. However, if the symmetry of the adhesion is broken, vibration ε due to the bending mode is excited in the vibrators 10 and 20 as shown in Figure 7 (C), and the frequency response in this case is as shown in Figure 8 (B). Become. In other words, when the symmetry is broken, unnecessary vibrations occur.

However, in conventional frequency adjustment work, a oscillator with broken symmetry (having a frequency response as shown in Figure 8 (B))
When adjusting , the frequency response after adjustment is shown in Figure 8 (
The result will be as shown in C).

That is, a bending mode response (fll) occurs between the resonance and anti-resonance frequencies of the longitudinal vibrator.

When a mechanical filter is constructed using such a vibrator, the frequency characteristics are as shown in Figure 8 (D), and there is a problem that a spurious response SP occurs near the passband, making it impossible to use it as a timing extraction filter. There was a point. This is due to the following reason.

That is, conventionally only the length p was adjusted, but the resonance frequency f of the longitudinal vibration mode is inversely proportional to the length l of the longitudinal vibrator and can be expressed as fLoc-(1).

On the other hand, the resonant frequency fll of the bending mode is inversely proportional to 12 and can be expressed as fi''(2>).

In other words, the change in f with respect to the change in length p is greater than fL, so as the length l is shortened, f increases and approaches fL.
), fB is larger than fL.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vibrator that solves the above problems and reduces changes in the resonance frequency of the bending mode.

As shown in FIG. 1, the means for this purpose is to adjust the thickness dimension d2 of both end surfaces of the piezoelectric ceramic plate 11 of the vertical vibrator 1, which is made of a piezoelectric ceramic plate 11 provided with electrode plates 14 and 15 on the upper and lower surfaces. A portion is formed that is smaller than the length dimension d1 of the central portion.

[For production]

The bending vibration mode is inversely proportional to 12 as shown in equation (2), but is also proportional to the thickness dimension d of the vibrator. That is, equation (2) can be rewritten as f[1oc-(3).

Therefore, there are stepped portions 12 and 11 at both ends of the piezoelectric ceramic plate.
is provided, the thickness dimension d2 at both ends becomes the dimension d at the center,
Therefore, the change in fIl can be made smaller than when d is kept constant.

Therefore, it has become possible to provide a timing extraction filter having predetermined frequency characteristics.

〔Example〕

The invention will now be explained by way of example with reference to the accompanying drawings.

FIG. 2 is a perspective view showing a first application example of the present invention, and FIG. 3 is a sectional view taken along line m-m' in FIG.

On the upper and lower surfaces of the piezoelectric ceramic plates u and 21 are constant elastic metal plates 14, 15 and 24, which serve as electrode plates and temperature compensation.
, 25, are bonded with solder.

The constant elastic metal plates I4 and 24 on the upper surface of the piezoelectric ceramic plates 11 and 21 are connected to each other by a connector 3, and support portions 4 and 5 for the mechanical filter are provided.

These constant elastic metal plates 14, 24, connector 3, and support portions 4, 5.6 are integrally formed.

Furthermore, at both ends of the piezoelectric ceramic plates 11 and 21,
Stepped portions 12, 13 and 22, 23 are formed, respectively.

Therefore, as shown in the characteristic diagram of FIG. 6, if the characteristic before adjustment is represented by a solid line, the characteristic after adjustment is represented by a broken line.

That is, the resonance frequency of the longitudinal vibration mode is 11' from fL.
On the other hand, the resonant frequency of the bending vibration mode changes only slightly from fB to rO'.

Therefore, as in the conventional case (Fig. 8 (C))
) No spurious response sp occurs and it has characteristics as a timing extraction filter. 4 and 5 are cross-sectional views showing second and third application examples of the present invention, respectively, and only the first longitudinal vibrator 1 is shown for convenience.

The difference from the first application example is that in the second application example, both ends of the piezoelectric ceramic plate 11 have sloped surfaces 121 and 12.
2, and in the third application example, 1 by laser irradiation
123 to 128 are formed.

In either case, thinner portions are formed at both ends of the piezoelectric ceramic plate.

Both have the characteristics shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, a piezoelectric ceramic plate having electrode plates provided on its upper and lower surfaces has portions with reduced thickness at both ends. Therefore, the resonance frequency fL of the longitudinal vibration mode
It has become possible to reduce the change in the resonant frequency fIl of the bending mode with respect to the change in , and to realize a timing extraction filter that does not generate spurious responses near the passband.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Figs. 2 to 5 are diagrams showing application examples of the present invention, Fig. 6 is a characteristic diagram according to the present invention, Fig. 7 is a configuration diagram of the prior art, and Fig. 8 is an explanatory diagram of problems in the prior art. ■...First longitudinal oscillator, 2...Second longitudinal oscillator, 1
1, 21... piezoelectric ceramic plate, 12, 13,
22, 23... stepped portion, 14, 15, 24,
25... Electrode plate.

Claims (1)

[Claims] On the upper and lower surfaces of the piezoelectric ceramic plate (11) are electrode plates (1
4) A vibrator characterized in that (15) is provided, and further comprising portions formed at both ends of each piezoelectric ceramic plate having a thickness smaller than that of the central portion.