JPS59202720A - Tuning fork type crystal resonator - Google Patents

Abstract

PURPOSE:To make a vibrator small-sized, to ealize a mass-production, and also to execute easily an adjustment of a frequency of a main vibration and an f-T characteristic, by increasing or decreasing a weight of the tip of a tuning fork arm, in a tuning fork type crystal resonator which utilizes an elastic coupling of a basic vibration of a bend vibration and a basic vibration of a twist vibration. CONSTITUTION:A frequency of a main vibration is adjusted by increasing a weight in a width direction center part I of the tip of a tuning fork arm or a width direction end part II, and increasing or decreasing the weight in a position III between I and II. When a vibrator whose both primary and secondary frequency temperature coefficients alpha, beta have a negative value is made to have an F-T characteristic in which alpha and beta both have a value of zero as shown in 51, it is realized by reducing a difference deltaf of a frequency fF and fT, therefore, a weight of II is jumped off. When an adjustment of fF is executed by the weight III after adjusting the f-T characteristic by increasing or decreasing the weight of I or II, it is possible to obtain a lot of tuning fork type crystal resonator which has an excellent f-T characteristic, and whose frequency fF of a main vibration has a target value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for adjusting both the frequency of the main vibration and the frequency temperature characteristic in a tuning fork type crystal resonator that utilizes elastic coupling of the fundamental vibration of bending vibration and the fundamental vibration of torsional vibration. It is related to the position of the weight that increases or decreases.

In recent years, tuning fork type crystal resonators have been proposed that utilize elastic coupling of bending vibrations and torsional vibrations to improve the frequency-temperature characteristics of bending vibrations (hereinafter referred to as fT characteristics).

This tuning fork type crystal oscillator is attracting attention because it can be used as a high-precision wristwatch crystal oscillator that can display annual differences at a relatively low frequency.

By the way, when making use of the elastic coupling of two vibrations to improve the f'-T characteristics of bending vibration, it is necessary to set the frequency difference between the two vibrations (hereinafter referred to as δf) to an appropriate value. This is because the strength of the coupling between the two vibrations mainly depends on δf. As shown in Figure 1, the thickness of the tuning fork crystal resonator is t, and the length of the tuning fork arm is! , when the width of the tuning fork arm is W, the frequency of bending vibration (hereinafter referred to as fF) is W/no・2, and the frequency of torsional vibration (hereinafter referred to as fT) is approximately t/(1w).
) is proportional to Therefore, in order to set δf to an appropriate value, the thickness t of the vibrator should be set to an appropriate value. However, since the amount of change in fT due to the thickness t is very large, it is almost impossible to set δf to an appropriate value based only on the thickness t. Therefore, by increasing and decreasing the weights on the tuning fork crystal resonator, δ
Attempts have been made to adjust f.

There are two types of frequency adjustment by increasing or decreasing the weight: one in which the frequency of the main vibration is set as a target value, and the other in which the f-T% characteristic of the main vibration is adjusted by adjusting δf. Here, the main vibration is the vibration that oscillates when a vibrator is assembled in an oscillation circuit, out of the two vibrations of bending vibration and torsional vibration.
That is, it refers to vibration with a low equivalent resistance R1. From now on, for convenience, we will proceed with the discussion assuming that the bending vibration is the main vibration.

Tuning fork-type crystal oscillators that utilize this elastic coupling of bending vibration and torsional vibration have conventionally been considered, mainly utilizing elastic coupling of secondary vibration of bending and fundamental vibration of torsion. When a tuning fork crystal resonator of the same shape is excited by the secondary vibration of bending and when it is excited by the fundamental vibration of bending, the frequency of the former has a value about six times that of the latter. Therefore, a tuning fork crystal oscillator that utilizes the elastic coupling of the secondary vibration of bending and the fundamental vibration of torsion has a higher
When the frequency of the bending vibration, which is the main vibration, is the same, the length of the tuning fork arm is! You have to hold on to it for a long time. Moreover,! As a result of increasing the length, the thickness t of the vibrator must be increased in order to cause elastic coupling between bending vibration and torsional vibration. In this way, when using an elastic coupling method for the secondary vibration of bending and torsional vibration, the size of the vibrator increases, and it takes a long time to fabricate the vibrator by etching using photolithography. However, it had some drawbacks that made it unsuitable for my production.

The present invention improves the conventional drawbacks and makes the vibrator smaller by utilizing the elastic coupling of the fundamental vibration of bending and the fundamental vibration of torsion.Moreover, when manufactured by photolithography,
It can be manufactured in a short time, and the main vibration frequency and f-T characteristics can be easily adjusted by increasing or decreasing the weight.

The object of the present invention is to provide a tuning fork type crystal resonator that utilizes elastic coupling of fundamental vibrations of bending and fundamental vibrations of torsion.

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

FIG. 2 shows the increasing and decreasing positions 21 and 21' of the weights in a tuning fork type crystal resonator that utilizes the elastic coupling of the fundamental vibration of bending and the fundamental vibration of torsion.

The position on the tuning fork arm for increasing or decreasing the weight is from the tip to I, where k is the length of the tuning fork arm. ="= A15. Figure 3 shows the amount of change in fT and fy when a weight is attached to this position by vapor deposition. In Figure 3, the horizontal axis is H and I in Figure 2.
, Hl, represents the position in the width direction of the tip of the tuning fork arm indicating the work 1. The vertical axis represents the rate of change δf/f between fy and fT. 31 represents fy and 32 represents the amount of change in fT. This result was obtained from calculation using the finite element method.

As is clear from Fig. 3, the amount of change in fp is almost constant and does not depend on the position of the tuning fork arm in the width direction, but fTFi
There is almost no change at the center in the width direction of the tuning fork arm, and there is a large change at both ends in the width direction. Further, as is clear from 31 and 32 in FIG. 3, there is a position between the center and both ends of the tuning fork arm in the width direction where the frequency changes of fF and fT are almost equal due to the attachment of the weights.

By the way, the f-T characteristic can be expressed by the following equation.

(fTlfTo)/fTo = a (TsTo
)+β, (Vt 'o)2+γ(Tl-To)++ Here, % fT+ is the frequency at any temperature TIK,
fTo represents the frequency at the reference temperature To, and α, β, and γ represent the primary, secondary, and tertiary frequency temperature coefficients, respectively. Figure 4 is a graph showing the relationship between δf (CfF-fT) of the main vibrations α and β of a tuning fork type crystal resonator that utilizes the elastic coupling of bending vibration and torsional vibration in a certain cutting direction of the crystal. be. 401 represents α and 402 represents β, respectively. Frequency difference δ between bending vibration and torsional vibration
When f is δfo, α and β become zero, and excellent f-T characteristics with almost no change in frequency due to temperature can be obtained. As is clear from FIG. 4, δf is δf.

If δf is large, both α and β have negative values, and δf becomes δfo
If it is very small, both α and β have positive values.

FIG. 5 is a graph showing the f-T characteristics of the main vibration depending on the magnitude of δf. When 51id δf is δfo,
52 means that δf is smaller than δfo, 53 means that δf is less than δfo
It shows the f-T characteristic when it is large.

By the way, when mass producing a tuning fork type crystal resonator that utilizes the elastic coupling of bending vibration and torsional vibration, the main problem is the variation in the thickness of the resonator pδf. As a result, the f-T of a large number of mass-produced tuning fork crystal resonators
The characteristics are non-constant, with α and β having positive or negative values, as shown at 51, 52, and 53 in FIG. Therefore, in order to make the f-T characteristics of all the vibrators such that α and β are both zero, it is necessary to increase or decrease the weights.

FIG. 6 is a plan view showing an example of the position of the weight of the tuning fork type crystal resonator of the present invention, which utilizes elastic coupling of the fundamental vibration of bending and the fundamental vibration of torsion. In FIG. 6, only the weight is shown, and the excitation electrode is omitted. In FIG. 6, I, II, and III represent the positions of the weights of the present invention. As mentioned above, in a vibrator that utilizes the elastic coupling of two vibrations, there are two types of adjustment: temperature characteristic adjustment that adjusts the f-T characteristic of the main vibration, and frequency adjustment that adjusts the frequency of the main vibration to a target value. It is necessary to increase or decrease the amount.

First, consider adjusting the weight increase/decrease and f-T characteristics. As is clear from FIG. 3, when the weight is increased or decreased at the position (■), the amount of change in fT is small and the amount of change in fF is large. On the other hand, if you increase or decrease the weight at the H position,
The amount of change in fT is greater than the amount of change in fy. I, II,
1 [Consider adjustment by having a weight attached to the position of I in advance and blowing the weight away with a laser. The initial f-T characteristic is as shown at 53 in Figure 5, and the oscillator where both α and β have negative values is α and β as shown in 51.
K, which has the value of both zero and makes f-T characteristic, is fl'(
! : Since it is sufficient to reduce the difference δf between fT, it is sufficient to skip the weight of H. On the other hand, the initial f-T characteristic is 5 in Figure 5.
As shown in Figure 2, 5 oscillators with both α and β having positive values are
In order to obtain the f-T characteristic in which both α and β have a value of zero as shown in 1, it is sufficient to increase δf, so it is sufficient to skip the weight in ■. In this way, by skipping either one of the weights ■ and ■, we can obtain an excellent f where both a and β become zero.
-A vibrator with T characteristics can be obtained. This completes the temperature adjustment.

Next, consider frequency adjustment in which the main vibration fy is set as the target value. The f-T characteristic, which has been adjusted by flying ■ or ■ geometry, must not be destroyed when adjusting fF. The value of (fF-fT)/fF when good f-T characteristics where α and β are both zero is usually 2 to 5.
This is a very small value of %. Therefore, if the amount of change in fF and fT due to increase or decrease in weight is approximately equal, then CfF
-fT)/fF maintains a substantially constant value, and the f-1 characteristic hardly changes. As shown in the 3rd v1, 3
At positions 3 and 34, the amount of change in fv and fT is equal. Therefore, the position between I and H in Figure 6! When the weight is increased or decreased at the position of
The vj nature hardly changes. Therefore, ■The reason for this is that after adjusting the f-T characteristics due to the increase or decrease of the weight in ■, if you adjust the front IJ [7yoshi fF, it will have excellent f-T characteristics,
Moreover, it becomes possible to obtain a large number of tuning fork type crystal resonators having a desired value for the frequency fy of the main vibration. - FIG. 7 shows a plan view of a fork-shaped crystal resonator showing another embodiment of the present invention. Similar to FIG. 6, the excitation electrodes are omitted and only the weights are shown. 71 and 7 on the tip of the tuning fork arm
2 weights are evenly attached. The weight is uniformly attached to the tip of the tuning fork arm, but the f-
, T characteristics and the main vibration frequency fy to a target value may be performed by using a laser to blow weights corresponding to the positions i, n, and m shown in FIG.

Setting the laser beam at the position of the weight to be thrown can be done automatically and easily. Therefore, as shown in FIG. 6, the weight of the present invention has I, n,
It does not have to be attached separately from III.

FIG. 8 is a plan view of a tuning fork type crystal resonator showing another embodiment of the present invention. 81, 82, and 83 are respectively 1.81, 82.83 shown in FIG. II, corresponds to the weight in the position of I[[, and f-
This is a weight for rough adjustment when adjusting the T characteristic or setting the target frequency of the main vibration. 81', 82'
, 83' correspond to the weights at positions I, II, and III shown in Fig. 6, respectively, and are weights for fine adjustment when adjusting the f-T characteristic or setting the frequency of the main vibration to a target value. . The weight of 81.82.83 is 81',
It is formed thicker than the weights 82' and 83'. It is not possible to precisely set the f-T characteristics and the frequency of the main vibration to the desired characteristics using only coarse adjustment weights. In particular, when making a high-precision vibrator for a wristwatch, two types of adjustments must be made strictly, so a weight for fine adjustment is essential.

In the embodiments of the present invention shown in FIGS. 6, 7, and 8, the weights can be increased or decreased on only one side of the main surface (the widest surface of the tuning fork type crystal resonator) or on both sides. Either is fine. The effect of the invention remains the same in each case. FIG. 9 and FIG. 1O show cross-sectional views of the tuning fork type crystal resonator of the present invention taken along a straight line connecting 84 and 85 in FIG. 8. FIG. 9 shows an example in which weights are attached only to one side, and FIG. 10 shows an example in which weights are attached to both sides.

91 and 101 are cross sections of tuning fork arms of a tuning fork crystal resonator, 92
and 102 represent the base metal of the weight which increases and decreases.

The base metal is usually formed of two layers of Cγ and Au. 93 and 103 are weights that increase or decrease in the I position shown in Figure 6.94 and 104 are weights that increase or decrease in the H position shown in Figure 6.95 and 105 are weights that increase or decrease in the I position shown in Figure 6.
They each represent weights that increase or decrease in position II.

Furthermore, although the above description has been made assuming the case where the main vibration is bending vibration, the present invention also applies to cases where torsional vibration is used as the main vibration.

Even if the main vibration is torsional vibration, the f-
The T% property can be adjusted, and f-T4? This is because it is possible to set the frequency of the main vibration to a target value without changing the frequency.

As explained in detail above, the tuning fork crystal oscillator of the present invention that utilizes the elastic coupling of the fundamental vibration of bending and the fundamental vibration of torsion is different from the conventional tuning fork crystal oscillator that utilizes the elastic coupling of the fundamental vibration of bending and torsion. It has the advantage that it is smaller than the conventional rotor, and the f-T characteristic and the frequency of the main vibration can be easily adjusted to the desired values by increasing or decreasing the weight. As a result, the tuning fork type crystal resonator of the present invention has the excellent advantage that it can be easily mass-produced as a high-precision resonator.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the outer shape of a tuning fork type crystal resonator. Second
The figure is a plan view of a tuning fork crystal resonator showing the positions of the weights as they increase and decrease. FIG. 3 is a graph showing the amount of frequency change of bending vibration and torsional vibration when the weight is increased to the position shown in FIG. 2. Figure 4 shows the frequency difference δf between bending vibration and torsional vibration and f−T.
Graph showing the relationship between primary and secondary frequency temperature coefficients in characteristics. Figure 5 shows f-T at three types of δf of a tuning fork crystal resonator that utilizes elastic coupling between bending vibration and torsional vibration.
Graph showing characteristics. FIG. 6, uS7, and FIG. 8 are plan views of a tuning fork type crystal resonator showing the positions of increasing and decreasing weights according to the present invention. 9 and 10 are cross-sectional views of the tuning fork arm of the tuning fork type crystal resonator, showing the positions of increasing and decreasing weights according to the present invention. 91.101...Cross section of the tuning fork arm of a tuning fork type crystal resonator 92.102...Base metal 93.103...Central part in the width direction of the tuning fork arm 1 [Increase/decrease weight 94.104...End part in the width direction of the tuning fork arm■ A weight that increases or decreases to 95.105...A weight that increases or decreases to a position between I and H.

Claims (1)

[Scope of Claims] [1] In a tuning fork crystal resonator that utilizes the elastic coupling of the fundamental vibration of bending vibration and the fundamental vibration of torsional vibration, the frequency of the main vibration can be adjusted by increasing or decreasing the weight at the tip of the tuning fork arm. A tuning fork type crystal resonator characterized by adjusting both frequency and temperature characteristics. (2) By increasing or decreasing weights at the widthwise center (referred to as I) or the widthwise end (referred to as ■) of the tip of the tuning fork arm, the frequency-temperature characteristics of the main vibration can be adjusted to a position between ■ and ■. The tuning fork type crystal resonator according to claim 1, wherein the frequency of the p-main vibration is adjusted by increasing or decreasing the weight (referred to as ■).