JPS5824968B2 - Onsagata Atsudenshindoushi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuning fork-shaped piezoelectric vibrator that is miniaturized while ensuring high stability of oscillation frequency.

In the conventional tuning fork type piezoelectric vibrator, as shown in Fig. 1,
It is known that the supporting member is integrally formed from a flat metal plate, but this is originally the supporting method shown in FIG. Since it is a wire, it was difficult to obtain the relative positional accuracy of the support point 4 with respect to the piezoelectric body 1.
It was created to solve this problem.

In addition to these, there is also a third
There are some types as shown in Fig. 4 and Fig. 4, but in order to prevent the leakage of vibration to the outside, the support line is an integer of λ/4 (λ: wavelength) from the support point on the piezoelectric body, which is the antinode of vibration. The vibration node is supported at the support point on the base with double the length.

In order to meet the recent growing demand for miniaturization of isotuning fork-shaped piezoelectric vibrators for wristwatches, the present inventor has decided to increase the distance between the support point on the piezoelectric body and the base from λ/4 as in the conventional case. While pursuing an optimal support structure while maintaining a smaller size, we found that with the support structure shown in FIG. It has been confirmed that even if the distance between the two is made sufficiently smaller than λ/4, it is possible to capture and support the nodes of vibration on the base T.

However, when we conducted an experiment to examine the fluctuation of the oscillation frequency when the position of the support point 5 on the base was changed, which is an indicator of the degree of influence of the support state on vibration leakage, we found that the rate of change was as follows. According to this support structure, it is much smaller than the conventional one, and moreover, at a certain frequency and the width of the support line, the shortest distance between the support point 4 on the piezoelectric body and the curved part of the support line is It became clear that it was related.

Therefore, the present inventor further pursued this point and came to accomplish the present invention.

That is, in the present invention, the support wire supporting the bases of both principal surfaces of the tuning fork-shaped piezoelectric vibrator extends along the longitudinal direction of the piezoelectric body in the opposite direction to the base of the vibrator, and then curves. It has a structure in which the direction is reversed, and the main cross-sectional dimension W (it) of the support wire is reversed, and the support wire is installed at the base, and the shortest distance between the support point on the piezoelectric body and the curved part of the support wire. f with K as a constant between L(m) and the fundamental resonant frequency f(kHz)
The main component thereof is a tuning fork-shaped piezoelectric vibrator characterized by the following relationship: =Kw/L2 (provided that ≧40 (kHz-mm)).

What is a "tuning fork piezoelectric vibrator"?The principal surface (the widest surface) is formed in a U-shape, and the legs are arranged with electrodes that excite bending vibration.It is made of crystal, lithium tantalate, or lithium niobate. , a vibrator made of a piezoelectric material such as piezoelectric ceramic, and the part that connects the legs is called the "base".

Furthermore, the "longitudinal direction of the piezoelectric body" is the direction of the maximum dimension of the piezoelectric body.

Hereinafter, the present invention will be specifically explained based on examples.

FIG. 6 shows a tuning fork-shaped piezoelectric vibrator which is an embodiment of the present invention.

The transducer frequency is 32kHz, K is 80, and L is 0.
7 mm, and the main cross-sectional dimension W of the support wire is 0.2 m1tt.

The distance H=λ/4 between the vibration antinode 6 and the base 7 is 1.6 m, while the distance d between the piezoelectric body 1 and the base 7 is 0.6 m.
It is m.

The support line is supported at its joints on the base, and is formed integrally with the external leader line.

Here, as a result of moving the position of the support point 5 on the base and measuring the change in the oscillation frequency accompanying the change, the characteristic curve shown in Figure T a was obtained.

Similarly, b is a tuning fork-shaped piezoelectric whose vibration node is supported at a support point on the base with a length that is an integral multiple of λ/4 from the conventional support point on the piezoelectric body as shown in Figures 1, 2, 3, and 4. This is the case with a vibrator.

The frequency on the vertical axis is expressed as a rate of variation with respect to the reference value.

Further, the horizontal axis simply indicates the movement of the position of the support point on the base.

As mentioned earlier, this characteristic curve is generally an indicator of the degree of vibration leakage or the influence of the support condition on it, and the slope of this curve is small and the range of zero slope is wide. This is a condition that enables desirable support without vibration leakage.

As is clear at first glance, there is an incomparable difference in the characteristics of both a and b.

In a, A and B correspond to the antinode of vibration, but apart from this part, in the support structure of the tuning fork type piezoelectric vibrator of the present invention, the position of the support point on the base is shifted from the vibration node (0 in the same figure). However, there is almost no change in the oscillation frequency.

This means that there is no vibration leakage, and that the oscillation frequency of the vibrator can maintain its stability reliably.

FIG. 8 shows the experimental results of determining this characteristic curve for various values of K.

At this time, the basic resonance frequency f was set to 32.768 kHz, and a desired value of K was obtained by combining W and L.

For example, in the same figure, a is -80, b is -60, and C is =4.
0 and d = 20.

Furthermore, almost similar results were obtained when the frequency was 16.384 kHz.

According to the same figure, if it is ≧40, a tilted tower part can be obtained near the node, but if it is further limited to ≧60, almost flat characteristics can be obtained except for a very narrow area near the belly. I understand.

In fact, as a result of performing a clamp test (a test of variation in resonance frequency before and after applying a load of approximately 100 g to the container containing the vibrator) on the manufactured vibrator, the yield rate was 95% for lofts with K≧40. , 1 for K≧60
The yield rate was 0.00%.

As described above, according to the present invention, since the distance between the piezoelectric body and the base can be reduced, it is possible to downsize the piezoelectric body, and even if the position of the support point is slightly shifted, there is no leakage of vibration, so the stable Oscillation is obtained.

Furthermore, since the support wire and the external leader wire can be formed all at once, it is useful for improving reliability and workability.

[Brief explanation of drawings]

1, 2, 3, and 4 are explanatory diagrams of a conventional tuning fork-shaped piezoelectric vibrator, FIG. 5 and 6 are explanatory diagrams of an embodiment according to the present invention, and FIG. 7 and FIG. FIG. 8 is a characteristic curve diagram illustrating the state of frequency fluctuation caused by movement of the support point of the tuning fork-shaped piezoelectric vibrator according to the present invention in comparison with that of a conventional one. 1...Piezoelectric body, 2...Support wire, 5...
...Support point on the base, 7...Base.

Claims (1)

[Claims] 1. The support wire that supported the bases of both main surfaces of the tuning fork-shaped piezoelectric vibrator extends along the longitudinal direction of the piezoelectric body in the opposite direction to the -tan vibrator base, and then curves and reverses its direction. death,
It has a structure that reaches the base and is planted there, and the main cross-sectional dimension W of the support wire - the shortest distance L (mm) between the support point on the piezoelectric body and the curved part of the support wire, and the fundamental resonance frequency f (
kHz), where K is a constant, f = Kw7L2, where ≧40 (kHz-7n7IL).