JPH0582086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for eliminating acoustic leakage caused by imbalance in the arm shape of a tuning fork type piezoelectric vibrator, particularly a wide tuning fork type piezoelectric vibrator.

Conventionally, as shown in Fig. 1, tuning fork type crystal oscillators and the like for frequency reference of watches have a side ratio r (r=w/g; w is the width of the oscillator 1, g is the width of the tuning fork arm 2, 2) of 1 front and back. Since the transducer 1 was extremely thin, the balance between the left and right arms 2, 2 only needs to be considered with respect to its width g, so the balance adjustment was carried out as shown in Fig. 2 while observing the degree of acoustic leakage of the transducer 1. This was generally done by polishing the edges 3, 3 on both outer sides of the tips of the arms 2, 2.

However, it has been found that it is impossible to completely eliminate acoustic leakage from the vibrator using such an adjustment method, and this is particularly noticeable in the case of a wide tuning fork type vibrator with a large side ratio r. There is.

The present invention has been made to realize a vibrator having a high Q by sufficiently eliminating acoustic leakage of the above-mentioned tuning fork type piezoelectric vibrator, and in which one of the four outer edges in the longitudinal direction of the arm is It is an object of the present invention to provide a method for removing acoustic leakage from a tuning fork type piezoelectric vibrator in which both the left and right arms are balanced by removing two or more of them by a required amount.

Hereinafter, the present invention will be explained in detail based on its theory.

FIG. 3 is a cross-sectional view showing the types of shape imbalance that occur when the arms 2, 2 of the tuning fork type piezoelectric vibrator 1 are molded.

That is, FIG. 3A shows a case where the width g of the arm 2 is not equal on the left and right sides, and in this case, the balance can be restored by cutting the outer end portion 3 of the arm, as described above.

On the other hand, Figures b and c show cases where a slope is applied to the gap between the arms 2, 2 or to the outside of both arms, and in this case, torsional vibration occurs in the arms of the vibrator.

Furthermore, d and e in the same figure show the case where the gap between the arms 2, 2 or the outside of both arms is trapezoidal, and it will be understood that in this case, bending vibration occurs in the width w direction of the vibrator. .

Therefore, it is thought that the tuning fork type piezoelectric vibrator formed in the actual mass production process contains a mixture of the five types of unbalance mentioned above, and if such unbalance exists, displacement and stress will occur. If this is fixed to the base of the vibrator, which does not have the desired shape, complex stress will occur, and sound, that is, vibration energy will leak from this part, resulting in a decrease in the Q of the vibrator.

In order to solve this problem, the present invention takes the following method.

FIG. 4 is a diagram illustrating a method for preventing acoustic leakage of a tuning fork type piezoelectric vibrator according to the present invention.

That is, if the widths g of the arms 2 and 2 of the tuning fork are simply different, balance can be achieved by cutting off the outer end 3 of the arms as shown in FIG. 2 as described above, but otherwise, as shown in FIGS. If there is an imbalance as shown, the hatched parts in b to e of this figure, respectively.
That is, the four outer edges 4 along the longitudinal direction of the arm 2,
4. Just remove one or more of... by the required amount.

The above-mentioned amount of shaving of the ridge 4 corresponds to the resonance frequency in two states, for example, a state in which the base of the tuning fork type piezoelectric vibrator 1 is clamped and a state in which it is substantially not clamped.
fc and f _f are measured, and (fc - f _f )/fc (ppm) is regarded as the amount of acoustic leakage and controlled so that this becomes the minimum, preferably zero, and fc becomes a desired resonance frequency.

The above-mentioned adjustment process is shown in FIG. 5, for example. That is, as the outer edge of the vibrator is shaved off, the resonant frequency increases, and the elimination of the unbalance as shown in FIG. 3 does not necessarily coincide with the reaching of the desired value of the resonant frequency.

Therefore, the resonant frequency of the vibrator should be designed to be slightly lower than the desired value and adjusted according to the present invention so that it matches the target value and at the same time minimizes acoustic leakage.

The present invention uses the method explained above to correct the unbalance of the arm shape that occurs during the processing of the tuning fork type piezoelectric vibrator and eliminate acoustic leakage, so vibration can be achieved by a relatively simple procedure. It has the effect of improving the child's Q.

Furthermore, the above-mentioned effect is particularly effective when applied to a wide tuning fork type sensor, etc., in which the side r is set large and the pressure change in the surrounding outside air is detected by a change in the equivalent series resistance of the vibrator. The dynamic range of sensor sensitivity can be expanded.

[Brief explanation of the drawing]

Fig. 1 is an external perspective view of a tuning fork type piezoelectric vibrator to which the method according to the present invention is applied, Fig. 2 is an external perspective view of a tuning fork type piezoelectric vibrator to which the conventional acoustic leakage removal method is applied, and Fig. 3a Figures 4a to 4e are cross-sectional views of the tuning fork arm portion, respectively, illustrating the form of imbalance in the tuning fork arm that occurs during the manufacturing process, and Figures 4a to 4e are sectional views of the tuning fork arm portion, respectively, showing embodiments of the acoustic leakage removal method according to the present invention. FIG. 5 is a diagram showing a general change in the characteristics of the vibrator when carrying out the method according to the invention. 1... Tuning fork type piezoelectric vibrator, 2... Arm, 4...
...Outer ridge of tuning fork arm.

Claims (1)

[Claims] 1. While monitoring a value representative of the amount of acoustic leakage, remove at least one or more of the four outer edges along the longitudinal direction of the arm of the tuning fork type piezoelectric vibrator by the required amount so that the value becomes the minimum, preferably zero. A method for eliminating acoustic leakage of a tuning fork type piezoelectric vibrator, characterized in that the torsional vibration of the arm or the bending vibration in the width direction of the arm caused by a processing error of the vibrator is eliminated.