JPS58119216A - Piezoelectric tuning fork for high frequency - Google Patents

Abstract

PURPOSE:To excite the primary harmonic strongly, by coupling an electrode lead provided at the side of a tuning fork oscillator base and an electrode of piezoelectric transducer with a narrow straight line connecting electrode formed by being made excentric at the outside from the center line of oscillator legs. CONSTITUTION:One outer side surface of the tuning fork oscillating legs 12, 12 and one side surface of a base 13 leading to it are formed with a piezoelectric film 14, a square electrode 15 is formed on the film 14 and the electrode 15 and the film 14 form a piezoelectric transducer 16. The electrode 15 of the transducer 16 is formed between a bottom 18 and a tip of the legs 12, 12 by taking the bottom 18 of a tuning fork groove 17 formed between the legs 12, 12 of the oscillator 11 as a reference. The electrode lead 19 is provided on the film 14 of the base 13 of the oscillator 11. The electrode lead 19 and the electrode 15 of the transducer 16 are mutually coupled with the narrow straight line connecting electrode 20 formed by being made excentric to the outside than the center line of the legs 12, 12. Thus, the fundamental wave is suppressed and the primary harmonic is excited.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency piezoelectric tuning fork that utilizes harmonics in higher-order modes.

Generally, in order to increase the resonant frequency of a tuning fork vibrator, it is sufficient to shorten the length of the vibrating leg of the tuning fork vibrator and increase the width of the vibrating leg.

Conventionally, in order to obtain a piezoelectric tuning fork in a high frequency range exceeding, for example, 1QQKHz, the length of the vibrating leg of the tuning fork vibrator is shortened and the width of the vibrating leg is widened.As long as the fundamental wave of the tuning fork vibrator is used, However, due to the large series resonance resistance, the resonance characteristics were poor and it could not be put to practical use.

Therefore, it is conceivable to use a device that uses another vibration mode, such as a vibrating unit vibrator, but this has drawbacks such as an increase in size. Therefore, it is conceivable to excite the tuning fork vibrator in a higher order mode, particularly in the first harmonic.

Japanese Unexamined Patent Publication No. 55-8172 discloses that a piezoelectric material such as crystal is shaped into a tuning fork, and that high-order modes, especially the first
A tuning fork crystal resonator using harmonics has been disclosed. FIG. 1 of the publication shows the distribution of generated charges in the fundamental wave and the first harmonic. However, such a so-called tuning fork crystal resonator has a drawback of having a complicated structure.

Therefore, there has been a desire for a practical piezoelectric tuning fork structure that is considered to be suitable for use in the high frequency range of 100 KHz or higher, considering various factors such as external dimensions, cost, and performance.

The present invention has been made in view of the above-mentioned circumstances regarding the conventional piezoelectric tuning fork for high frequency, and is realized by using the fundamental wave as in the conventional piezoelectric tuning fork by utilizing the higher order mode, especially the first harmonic. The purpose of the present invention is to provide a piezoelectric tuning fork for high frequencies that can be put to practical use in high frequency regions where it is impossible to perform high frequency applications.

For this reason, 1 the present invention provides a piezoelectric tuning fork in which a piezoelectric transducer is provided on the vibrating legs of a tuning fork vibrator, and an electrode lead-out portion is provided on the side surface of the base of the tuning fork vibrator that connects both vibrating legs of the tuning fork vibrator. , the electrode extension part and the electrode of the piezoelectric transducer are connected by a narrow linear connection electrode formed eccentrically outward from the center line of the vibrating leg part.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 11 denotes a tuning fork vibrator, and its constituent material may be arbitrary, such as a constant elastic metal such as Elinvar, glass, or resin. Reference numeral 12 and 12 are vibrating legs of the tuning fork vibrator 11, and 13 is a tuning fork vibrator base (hereinafter abbreviated as the base) to which these vibrating legs 12 and 12 are connected.

On one outer surface of the vibrating leg portion 12.12 and one side surface of the base portion 13 connected thereto, Z z O, AI N are provided.

A piezoelectric film 14 made of a well-known piezoelectric material such as ZnS CdS LiNb0 LiTaO3°3+ γ-Bi203 group compound, lead zirconate titanate piezoelectric ceramics, etc. is formed.

A rectangular electrode 15 made of gold (Au), aluminum (Al), etc. is formed on the piezoelectric film 14,
The electrode 15 and the piezoelectric film 14 form a piezoelectric transducer 16.

The electrode 15 of the piezoelectric transducer 16 is connected to the tuning fork groove 1 formed between the vibrating legs 12.12 of the tuning fork vibrator 11.
7 is formed at a position between the bottom 18 and the tip of the vibrating leg 12.12.

On the other hand, an electrode extension portion 19 is provided on the piezoelectric film 14 of the base portion 13 of the tuning fork vibrator 11.

The electrode extension part 19 and the electrode 15 of the piezoelectric transducer 16 are connected to each other by a narrow linear connecting electrode 20 formed eccentrically outward from the center line of the vibrating leg part 12.12. There is.

It is preferable that the width of the linear connection electrode 20 is as narrow as possible, for example, 50 μm or less, and short.

As described above, the tuning fork vibrator 11 provided with the piezoelectric transducer 16 and its extraction electrode portion 19 has two external connection terminals 22. The base 13 of the tuning fork vibrator 11 is fixed to one of the terminals 23 and a support 24 protruding from the stem 21, and the other external connection terminal 23 and the electrode extension part 19 are wire-bonded with a wire 25. .

If you do the above, the tuning fork vibrator 1 will be
While the fundamental wave of 1 is suppressed, the first harmonic is strongly excited, the Q of the first harmonic is high, and the characteristics as a resonator are greatly improved.

Incidentally, as shown in FIGS. 2(a), (b), (C), and (d), four types of piezoelectric tuning forks 30a, 30b, 30C, and 30d have different forming positions and widths of the linear connection electrodes 20. was created, and the parallel resonant resistance Ra, series resonant resistance kO, and the ratio Ra/Ro of these parallel resonant resistances Ra and series resonant resistance RO of the fundamental wave and first harmonic were determined, as shown in Table 1 below. It became like this.

However, in Table 1 above, the piezoelectric tuning fork 30a.

30b, 30C and 30d piezoelectric transducer 1
2 (a), (b), (C
) As shown in Oyohi (d), the same dimensions and length I
From the tip of the vibrating leg 13 of O=2.47m X□=0.2
5 m, and the width WO is 4 m.

Further, the electrode pull-out section 19 is located at a distance of
(D1m surrounding area is formed, and its width WO is WO=0.4
It is ms.

The width of each linear connection electrode 20 of the piezoelectric tuning forks 30a, 30b, 30C and 30d is 50 μm.

100μmy50μfi and 100μm, the linear connection electrodes 20 of the piezoelectric tuning forks 30a and 30b are formed on the center line of the vibrating leg 12, and the linear connection electrodes 20 of the piezoelectric tuning forks 3', O, C and 30d are offset from the center line. It is formed with care.

As can be seen from Table 1 above, R at the first harmonic
The piezoelectric tuning fork 30C having a large a/Ro and a small Ra/Ro in the fundamental wave is formed by eccentrically forming a linear connection electrode 20 with a width of 50 μm.

As mentioned above, Ra/R at the first harmonic.

When becomes larger, the piezoelectric tuning fork 30C at the first harmonic
Q becomes large for the following reason.

That is, in general, the Q of a piezoelectric tuning fork is determined by the series resonance frequency F.
O1 Parallel resonant frequency Fa, series resonant resistance kO, and parallel resonant resistance Ra.
o) Or you can increase Ra/Ro, but F o
/2(Fa-Fo) is determined by determining the dimensions of the piezoelectric tuning fork, so it can be seen that in order to increase Q, it is sufficient to increase Ra/Ro.

From the above, if the linear connecting electrode 20 having a width of, for example, 50 μm or less is formed eccentrically from the center line of the vibrating leg portion 12.12, a stable high-frequency piezoelectric tuning fork with a high Q can be obtained.

As is clear from the above detailed explanation, the present invention provides a piezoelectric tuning fork in which the electrode lead-out portion provided on the side surface of the base of the tuning fork vibrator and the electrode of the piezoelectric transducer are placed outside the center line of the vibrating leg. Since the connection is made using a narrow linear connecting electrode formed eccentrically from the center, the fundamental wave is suppressed while the first harmonic is strongly excited, which makes it practical when using the fundamental wave. It is possible to obtain a piezoelectric tuning fork for high frequencies that can be put to practical use even in a high frequency range where it would otherwise be impossible, and has greatly improved characteristics as a resonator.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of a tuning fork for high frequency according to the present invention, FIG. 2(a), FIG. 2(b), FIG. 2(C), and FIG. and a side view of a piezoelectric tuning fork having various linear connection electrodes used to measure parallel resonance resistance. 11... tuning fork vibrator, 12... vibrating leg, 13...
・Base, 14... Piezoelectric film, 15... Electrode, 16...
・Piezoelectric transducer, 19... electrode extraction part, 2
0...Linear connection electrode. Patent applicant Murata Manufacturing Co., Ltd. Agent
Patent attorneys Aohaku Ao and 2 others Figure 1

Claims (1)

[Claims] (1) In a piezoelectric tuning fork in which a piezoelectric transducer is provided on a vibrating leg of a tuning fork vibrator, an electrode drawer is provided on a side surface of a tuning fork vibrator base that connects both vibrating legs of the tuning fork vibrator; and an electrode of the piezoelectric transducer are connected to each other by a narrow linear connecting electrode formed eccentrically outward from the center line of the vibrating leg.