JPS59218022A - Long side piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To reduce the effect of harmonics by setting the length of an electrode adhered to a side face part in the long side direction supported perpendicularly of a piezoelectric vibrating plate to 78.0-79.5% of the vibrating plate so as to increase (series resonance resistance to ternary harmonics/series resonance resistance to fundamental wave. CONSTITUTION:The vibrating plate 11 is fixed to a frame-formed support part 13 via a connecting part 12 led vertically from both side faces (X planes). Electrodes 14a, 14b for exciting lengthwise vibration are adhered nearly symmetrically around the connecting part 12 and lead electrodes 15a, 15b are adhered from a leg part 13a of the support part 13 to a base 13b. L-d subtracting a width (d) from the total length L of the vibrating plate 11 is taken as the length of the vibrating plate as a part participating to the vibration and similarly (l-d) subtracting the width (d) from the total length (l) of the electrodes 14a, 14b is used as the length of the electrodes, then it is considered that the optimum electrode length for vibrating the fundamental wave is within nearly 66.7-80% or 83% of the length of the vibrating plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a long-side piezoelectric vibrator, and particularly to its excitation electrode structure.

[Prior art]

When trying to utilize the fundamental vibration of a long-side piezoelectric vibrator, in addition to the fundamental vibration, there are spurious harmonics such as the 3rd and 5th harmonics, which have frequencies approximately 3 to 5 times the fundamental vibration. There are vibrations, and these must be suppressed as much as possible in order to stabilize the fundamental wave vibration, but in order to suppress the third-order vibration, which has a particularly strong influence, the series resonant resistance (CI, ) to the fundamental wave must be suppressed. The ratio between the value and the value of the series resonant resistance (CI3) for the third harmonic: c3/cII
It is necessary to make it as large as possible.

[Object and structure of the invention]

The present invention has been made in view of these circumstances, and its purpose is to provide a long-side piezoelectric vibrator for fundamental wave excitation in which C1, /CI is increased.

In order to achieve such an object, the present invention sets the length of the electrode attached to the vertically supported side surface of the piezoelectric diaphragm to be 78.0 to 79.5 times the length of the diaphragm. This is the setting. Hereinafter, the present invention will be explained in detail using Examples.

〔Example〕

FIG. 1 is a perspective view showing an embodiment of the present invention.

In this example, a diaphragm is formed from ZQK straight crystal plates (two plates) into a quadrilateral shape with the long side direction parallel to the Y axis and the short side direction parallel to the X axis. In the example used, the diaphragm 11 has a frame that surrounds the periphery integrally formed by photolithography on both sides (X plane) of the diaphragm 11 via connecting parts 12 drawn out perpendicularly from the sides. shaped support part 1
3. On the side surface, electrodes 14g and 14L+ for long-side vibration excitation are attached symmetrically around the connecting portion 12 pulled out from the center thereof, and further extend from the leg portion 138 of the support portion 13 to the base portion 13b. The extraction electrodes 15a and 15b are in contact with each other. Note that similar extraction electrodes are also provided on the back surface. Here, regarding the portion of the width d of the connecting portion 120, since it is a dead portion with respect to the vibration of the diaphragm 11, the width d is subtracted from the entire length of the diaphragm 11 as a portion that is substantially involved in vibration. deducted[,
-d is the length of the diaphragm, and t-d, which is obtained by subtracting the width d from the total length of the electrodes 14a and 14b, is called the length of the electrode.

Generally, the larger the area of the excitation electrode, the larger the parallel capacitance C6 in the electrical equivalent constant of the piezoelectric plate, and the CI
However, when used for fundamental wave excitation as in the present invention, it is necessary to use an electrode structure that suppresses the excitation of harmonics, especially third harmonics, as described above. There is.

Here, if we consider purely theoretically, the fundamental wave, 3rd order, 5th order
The state of distortion of the diaphragm during the next vibration is shown in Figure 2 (a) (
(fundamental wave), the same figure (b) (3rd order) and the same figure (C) (5th order), in order to minimize the 3rd order vibration, B It is considered that an electrode length of #0.667A and an electrode length of C=0.8OA are desirable in order to minimize the fifth-order vibration.

However, in reality, for a vibrator as shown in Figure 3,
When we observe the state of distortion in the diaphragm 11 using a line topography, we find that it does not show the ideal vibration mode as shown in FIG. 2, but instead shows a vibration mode as shown in FIG. 4. was confirmed (however, the sign (■e) is not clear)
. The vibrator used here is the vibrator shown in Figure 1 on the diaphragm 1.
The diaphragm 1 has a frame-shaped support part 13 that surrounds the entire circumference of the diaphragm 1, while a tuning fork-shaped support part 16 is provided.
It is considered that there is almost no difference in the vibration mode of No. 1 itself. The results of this observation indicate that an electrode length of 0.83A is good. In addition, in FIG. 3, the extraction electrode 15. is attached to the back side of the support portion 16 from the leg portion 16a to the base portion 16b.

From the above results, it is considered that the optimum electrode length for fundamental wave excitation is within the range of approximately 66.7% of the length of the diaphragm to 80 to 83 inches.

Next, regarding the vibrator shown in FIG. 1, the total length of the diaphragm 11 is 2.8 mm, the width W is 0.08 mm, and the thickness t is approximately 0.2 mm.
When the dependence of CI3/C1 on ('')/(t, -d) was investigated while changing the total length t of the electrodes 15a+15b in mm, the experimental results shown in FIG. 5 were obtained.

In this case, the frequency of the fundamental wave is IMHz, and the above cr3/C
Since the value of 1 only needs to be approximately 100 or more, it can be seen that the length of the excitation electrode may be set to 78.0 to 79.5% of the length of the diaphragm. The value of CI3/C1 tends to be 100 or more even in the region where the electrode length ratio exceeds 83 cm, but in the range of 78 to 79.5 cm, the value of CI3/C1,
While I3/C1 showed a very steep rise and had a high peak value, its rising tendency was gentle, and the experimental results also varied widely. On the other hand, 78.
In the range of 0 to 79.5%, there is little variation, and by setting it within this range, excellent fundamental wave excitation can be obtained reliably.

Note that if the frequency changes, the absolute value of CI3/CI changes, but the (1-d)/(L-d) dependence shows the same tendency as shown in Figure 5, and is 78.0 to 79.
．． Good results are obtained with 5%.

In addition to the crystal oscillator shown in Fig. 1, the oscillator shown in Fig. 3 can also be used with counter electrodes for long-side vibration excitation on both sides in the direction of its narrow sides, and supported vertically on the sides. Similar effects can be obtained by applying the present invention to general long-side piezoelectric vibrators.

〔Effect of the invention〕

As explained above, according to the present invention, by setting the length of the excitation electrode to 78.0 to 79.5% of the length of the diaphragm,
By increasing CI s / CI H and reducing the influence of harmonics, it is possible to obtain a long-side piezoelectric vibrator for good fundamental wave excitation.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a vibrator showing one embodiment of the present invention, and FIG.
Figures (-), (b), and (C) are fundamental waves, 3rd order, 5
Figure 3 is a perspective view showing the vibrator used for observation in the imaging mode using X-ray topography; Figure 4 is a diagram showing the observation results; Figure 5 shows the following theoretical vibration modes. is the first
It is a graph which shows (z-d)/(shi-d) dependence of CI3/CII about the oscillator of a figure. 11... Meeting diaphragm, 12... Connection part, 13.16
----Support part, 14a, 14b - Excitation electrode. Patent applicant Kinseki Co., Ltd. Agent Masa Yamakawa, Itsuki (and one other person) 41 Figure 3 Figure 5 (f-d)/(L-d) ('/.)

Claims (1)

[Claims] In a long-side piezoelectric vibrator in which electrodes for long-side vibration excitation are attached to both sides in the long side direction of a piezoelectric diaphragm and the t-hills are supported perpendicularly on the sides, the length of the electrodes is determined by the length of the diaphragm. A long side piezoelectric vibrator whose zero characteristic is 78.0 to 79.5% of the length.