JPS59218025A - Tuning fork type crystal oscillator - Google Patents

Abstract

PURPOSE:To obtain an oscillator of a sufficiently small size, capable of displaying yearly difference and with high accuracy by utilizing the elastic coupling of the bending fundamental oscillation and the twist fundamental oscillation. CONSTITUTION:A tuning fork type crystal oscillator 41, a lead 42 in common use with the support of the oscillator to apply an AC electric field to an exciting electrode and a plug 43 are sealed in a case 44. The elastic coupling between the bending fundamental oscillation and the twist fundamental oscillation of the tuning fork type crystal osillator is utilized and the value of the ratio w/l of the width (w) of the tuning fork arm to the length (l) is taken as nearly >=0.25. The cutout azimuth of the oscillator is taken so that the Z plane has a larger angle in the negative direction by -15 deg. around the electric axis of crystal in taking the positive direction of rotation at the counter-clockwise rotation around the electric axis of crystal. Or, the value of the ratio w/l of the width (w) of the tuning fork arm to the length (l) is taken as nearly 0.36and the cutout azimuth is taken between -15 deg. and -17 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the dimensions and cutting orientation of a tuning fork type crystal resonator that utilizes elastic coupling of the fundamental vibration of bending vibration and the fundamental vibration of torsional vibration.

BACKGROUND OF THE INVENTION In recent years, a tuning fork type crystal resonator that utilizes elastic coupling between bending vibration and torsional imaging to improve the frequency-temperature characteristics of bending vibration (hereinafter referred to as f-T characteristics) has been attracting attention. This oscillator has much superior f-T characteristics compared to the tuning fork type crystal oscillators currently used as oscillators for wristwatches, so current watches are guaranteed to have a monthly difference of 10 to 15 seconds. In contrast, it is thought that a wristwatch using this oscillator can satisfy the yearly difference of 10 seconds.

Tuning fork crystal oscillators that utilize an elastic coupling between bending vibration and torsional motion conventionally utilize an elastic coupling between the secondary vibration of bending (hereinafter referred to as F2) and the fundamental vibration of torsion (hereinafter referred to as T1). The method has been thought out and it is a hole.

This method has the feature that R1 of the vibrator can be reduced by using F2tl. However, when using the elastic coupling between the fundamental vibration of bending (hereinafter referred to as Fl) and T1, the size of the oscillator becomes smaller when obtaining the same frequency compared to when using the elastic coupling between F2 and T1. , the volume is also reduced, which is advantageous for miniaturizing the vibrator.

The state of vibrational displacement of Fl is shown in FIG. 1, and the state of vibrational displacement of F2 is shown in FIG. 2 by broken lines.

The reason why the vibrator becomes smaller when Fl is used will be explained below. As shown in Fig. 6, when the thickness It of the vibrator, the length of the tuning fork arm, and the vibration sound are respectively 2 and W, the frequency of bending vibration fy (hereinafter referred to as f'') and the frequency of torsional vibration f
T (hereinafter referred to as fT) can be expressed by the following equation.

f F = OF −w/422−− (1) fT=
OT −t /(Aw) --- (2) Here, QF
and QT are constants. In tuning fork type crystal resonators having the same shape, the frequency of F2 has a value about six times the frequency of Fl. Therefore, when trying to achieve the same frequency as the secondary vibration of bending in the fundamental vibration, it is sufficient to increase W and shorten β compared to a tuning fork type crystal resonator that generates secondary vibration of bending. If W is made thicker, it becomes difficult to fit it into a limited container, so it is usually made shorter by nl.

Therefore, if the same frequency as that of F2 is to be achieved in Fl, the length 2 of the tuning fork arm is usually about 40 mm for bending secondary imaging.
It will be around %.

Furthermore, when using elastic coupling between bending vibration and torsional vibration, f
It is necessary to bring T closer to fF. The conditions that fy and fT should satisfy when they have highly accurate frequency-temperature characteristics capable of displaying yearly differences can be approximately expressed by the following equation.

(fF fT)/fF=0.02~0.05-...
(3) Therefore, compared to the case where the elastic connection between F2 and T1 is used, when the elastic connection between Fl and T1 is used, in order to realize the equation (3), since 2 is smaller, the thickness t must be made smaller.

By reducing L and t and using the elastic coupling between Fl and T1, compared to using the elastic coupling between F2 and T1,
The volume of the oscillator becomes much smaller.

Furthermore, when a tuning fork type crystal resonator is manufactured using photolithography, the thinness of the resonator makes it possible to shorten the time required for etching the crystal.

In this way, by using the elastic coupling between Fl and T1, the resonator can be made smaller, and when making the resonator using photolithography, it can be manufactured in a short time, which has the great advantage of being low cost. .

Conventionally, in a tuning fork type crystal resonator that utilizes elastic coupling of bending vibration and torsional vibration, the cutting direction of the crystal resonator that provides the erosion r (fT%) that can display the annual difference is such that the two sides are aligned with the electrical axis of the crystal. It has been thought that it cannot be obtained between 0 degrees and 115 degrees when counterclockwise rotation is considered positive for the rotation of the (X axis).Here, the second plane is the optical axis ( A plane perpendicular to Z (@it).

However, when making use of the elastic coupling between Fl and T1 and realizing a sufficiently small oscillator as a wristwatch oscillator, it has been found that good f-T characteristics cannot be obtained with the cut angle considered by the US. It was.

Purpose of the Invention The present invention provides Fl and T characteristics that are sufficiently small and have f-T characteristics that can be used as a high-precision watch vibrator that can display yearly differences.
The object of the present invention is to provide a tuning fork type crystal resonator that utilizes the elastic coupling described above.

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

FIG. 4 is a plan view showing a tuning fork type crystal resonator sealed in a container. 41 is a tuning fork type crystal resonator, 4
Reference numeral 2 represents a lead that also serves as a support for a vibrator for applying an alternating electric field to the excitation electrode, 43 represents a plug, and 44 represents a container. Due to restrictions on the thickness and size of wristwatches, the diameter of containers for crystal units for watches is currently 1.5 to 2.0 mm.
The size is M, long, or 6m long. The size of the tuning fork crystal resonator is naturally limited by the size of the tuning fork crystal resonator. Due to limitations on the diameter of the container, the arm width W of one tuning fork arm of the tuning fork type crystal resonator shown in FIG. 3 must be approximately 0.5 or less. W to 0.5
This is because if the value is 8 or more, the space between the inner wall of the container and the vibrator becomes narrow, so that the tuning fork type crystal vibrator may collide with the container and break during a fall impact.

In addition, by using the elastic coupling of two imaging systems, we can
In order to improve the T characteristics, 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. The frequency fT of torsional vibration is proportional to the thickness of the vibrator,
When the thickness t of the vibrator is 1 μm', fTil-i is approximately 2
~"s K Hz also changes. On the other hand, the frequency 1'y of bending vibration hardly depends, so the variation in fF is small. From this, more than 100 oscillators can be made from one piece of crystal Ueno. When manufacturing, if there is a large variation in the thickness of the quartz crystal, the variation in δf between the oscillators will be large, resulting in completely different f-T% characteristics between the oscillators. Sea urchin／・The variation in the inner thickness is 1μ
Must be within m. Satisfying this condition is
With current polishing techniques, it becomes difficult to polish when the absolute value of the thickness of the crystal wafer is too thin, that is, less than 50 μm.

From the above discussion, when using a tuning fork type crystal oscillator that utilizes the elastic coupling of Fl and 71 as a oscillator for all wristwatches, the arm width of one tuning fork arm should be 0.5 mm or less, and the thickness of the oscillator should be It is desirable that the thickness is 50 μm (0.05 μm) or more.

By the way, the wristwatch c1 ultimately requires an IHz signal. The current wristwatch is 52768H which is 2 to the 15th power.
The IH2 signal is created by frequency-dividing the vibration of the 2nd crystal oscillator. Therefore, when using a tuning fork type crystal sensor that utilizes the elastic coupling between Fl and T1 as a wristwatch vibrator, the frequency fF of the bending vibration, which is the main vibration of this vibrator, is 5276.
The value must be an integral multiple or a fraction of 8 Hz.

Here, the main vibration refers to a vibration that oscillates when assembled in an oscillation circuit, that is, a vibration with a low equivalent resistance R1.

As mentioned above, in order to obtain a tuning fork type crystal resonator that utilizes elastic coupling between bending vibration and torsional vibration and has good f-T characteristics, it is necessary to satisfy equation (3). As is clear from equation (3), in order to obtain good f-T characteristics, fy and fT need to have fairly close values, which also determines the optimum value of the difference δf between fF and fT. fy is proportional to w/ji, 2,
Since fT is almost proportional to t/βW, let f and P be 3276
When set to a certain value that is an integer or a fraction of an integer of 8Hz, the relationship between °C, W, and t is almost uniquely determined. That is, once L is determined, the first W to make fye the desired value is determined,
In order to improve the f-T characteristic, t is also determined by itself so that fT has a value close to the value of fF.

FIG. 5 is a perspective view showing the orientation of the tuning fork type crystal sensor. 51 is a tuning fork type crystal Shinko 1 child, X, 7. Z-axis (1 represents the electrical axis, 1 mechanical axis, and optical axis of the crystal, respectively.
The tuning fork crystal resonator shown in the figure is formed in two planes, that is, in a plane perpendicular to the two axes, which is rotated counterclockwise by an angle θ around the X axis, and in the longitudinal direction of the lifter. The y' axis and the thickness direction of the vibrator are oriented toward the 2' axis. The cut angle θ is
The case where the axis rotates counterclockwise at rotation 9 is considered to be the king.

FIG. 6 shows that when fF of a tuning fork crystal resonator that utilizes the elastic coupling between Fl and T1 has a value that is an integer multiple of 52768 Hz, A, w, which are almost uniquely determined to satisfy equation (3), are shown.
It is a graph showing the relationship between the width dimension W of the tuning fork arm and the thickness t of the vibrator. The curves of 61°62.65 and 64.65 have fIl of 32768Hz and 65.5, respectively.
KH2,13,1,1KHz.

It shows the relationship between t and W when 'klz is set to 196.6 KHz and 262.1 KHz. The graph in FIG. 6 is for the case where the cut angle θ shown in FIG. 5 is 115 degrees. If θ is in the range between 110 degrees and 120 degrees,
Most of the relationships shown in Figure 6 apply as is.

In FIG. 6, the broken line 66 is a straight line indicating t=50 μm;
The dashed line 67 indicates w == [1,5 brain! ! Fully expressed. In order to put the tuning fork type crystal resonator into the container shown in FIG. The combination must be located in the area further to the left. As is clear from FIG. 6, the curve 61 is not in this region, and when fy is 32768 Hz, a tuning fork type water J4 vibrator that utilizes the elastic coupling between Fl and T1 is placed in the container shown in FIG. It is impossible. When fF is 65.5 KHz, it is possible to put it into the container shown in FIG. 4 under only a few conditions among the combinations of W and t.

In other words, when a tuning fork crystal resonator that utilizes the elastic coupling between Fl and T1 is used as a wristwatch camera, fIP is 1 s.
It is necessary to turn off at 5KHz or higher.

FIG. 7 shows t and w/Il for the combination of W and mono in the area above the straight line 66 and to the left of the straight line 67 in FIG.
This is a graph showing the relationship between . 71°72.73.
74 has an flf of 65.5KHz.

131, lKH2, 196, 6KH2, 262, 1KH
The relationship between t and W/μ in the case of 2 is shown. As fye becomes higher and -C goes, the direct value of w/54 becomes larger.

As is clear from FIG. 7, when a tuning fork type crystal oscillator that utilizes the elastic coupling between Fl and T1 is used as a wristwatch oscillator, the value of the ratio W/β of the width W and length L of the tuning fork arm is approximately 0.2
Must be 5 or more.

Incidentally, the f-'r characteristic can be expressed by the following equation.

(f(T)−f(To)/f(To)=α(T
-To) 10β(T-To)2+γ(T-To)3...
...(4) Here, f(T) is the frequency % at any temperature T
f (To) represents the frequency at the reference temperature 'ro, and α, β, and γ are called primary, secondary, and tertiary frequency temperature coefficients, respectively. Reference temperature T. Usually, a value near normal temperature, such as 20 degrees Celsius, is selected.

Traditionally, tuning fork crystal oscillators used in wristwatches utilize only bending vibration, and when α is zero, β is not zero and has a negative value. Therefore, the f-'l'% property shows an upwardly convex quadratic curve.

However, in the case of a tuning fork crystal resonator that utilizes elastic coupling between bending vibration and torsional vibration, as fT approaches fF, α
and β both change from negative values to positive values. ff-fF
That is, when δf is set to a certain value, α is always zero. However, in order to make β zero at the same time, the cut angle θ shown in Fig. 5 must be set to an appropriate value.
and β at the same time, f-T special 91. is far superior, and can be used as a high-precision wristwatch crystal unit with a hand difference of about 10 seconds. Conventionally, it has been said that the value where α and β become zero at the same time is when θ is between 0 degrees and 115 degrees. However, in a tuning fork type crystal resonator that utilizes the elastic coupling between Fl and T1, that is, when the value of w/X is as large as 0.25 or more, it is clear that the appropriate θ is not within the above range. Ta. Incidentally, the value of w/n of a tuning fork type crystal resonator that utilizes the elastic coupling between F2 and T1 that has been conventionally considered is in the range of about 0.1 to 0.15.

Figure 8g8 is a graph showing the relationship between α and β of a tuning fork type crystal resonator that utilizes the elastic coupling between Fl and T1, using the cut angle θ as a haramometer. This graph shows f! + is 1
96.6 KHz and the value of w/1 is approximately r1.56. 81, 82, 83°84 are respectively θ
α for -10 degrees, -12 degrees, -15 degrees, -16 degrees
and β.

FIG. 9 is a graph showing the relationship between the value of β and θ when α is zero, based on the results of FIG. As is clear from FIG. 9, when θ is 116 degrees, α and β become zero at the same time.

In order to satisfy the accuracy of about 10 seconds for manual difference, the f-
In the T characteristic, the absolute value of β when α is zero is approximately I
A value of 10"" or less is required. As is clear from Figure 9, in the case of a tuning fork crystal resonator that uses elastic coupling between Fl and T1 with a w/n value of approximately 0.56, θ is between 115 degrees and 117 degrees. This is desirable.

θ at which both α and β become zero depends on the value of W/μ.

Compared to the conventional tuning fork type crystal resonator which utilizes the elastic coupling between bending vibration and torsional vibration, especially the tuning fork type crystal resonator which utilizes the elastic coupling between F'2 and T1, the tuning fork which utilizes the elastic coupling between Fl and T1. Does the type crystal oscillator have a large v/L value? , Therefore, the appropriate cut angle θ is a value that is further away from the z-plane.

Effects of the Invention As explained in detail above, the tuning fork type crystal resonator of the present invention utilizes the elastic coupling between Fl and T1, and is therefore different from the conventional tuning fork type crystal resonator that utilizes the elastic coupling between F2 and T1. It can be made much smaller, and both α and β can be made zero, making it excellent as a small and highly accurate wristwatch vibrator.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a tuning fork crystal resonator showing the displacement of the fundamental vibration of bending. FIG. 2 is a plan view of a tuning fork crystal resonator showing the state of displacement during secondary imaging of bending. FIG. 3 is a trunk view showing the external shape of a tuning fork type crystal resonator. FIG. 4 is a partial cross-sectional view showing a state in which a tuning fork type crystal vibrator is inserted into a container. FIG. 5 is a perspective view showing the cutting direction of a tuning fork type crystal resonator. Figure 6 shows the tuning fork type crystal oscillator fl that utilizes the elastic coupling of Fl and T1! When the value is an integer multiple of +2768Hz, n is almost uniquely determined to satisfy equation (3).
, w, and t, is a graph showing the relationship between the width dimension W of the tuning fork arm and the thickness t of the vibrator. Figure 7 shows the direct i! of Figure 6!
166 and to the left of the direct spinning 67. FIG. FIG. 8 is a graph showing the relationship between α and β of a tuning fork crystal resonator that utilizes the elastic coupling between Fl and T1 in terms of all parameters of the cut angle θ. FIG. 9 is a graph showing the relationship between β and θ when α is zero. 51... Tuning fork type crystal oscillator L... Length of tuning fork arm W... Width of tuning fork arm θ... Cutting direction or more Applicant Daini Seikosha Co., Ltd. Agent Patent Attorney Tsutomu Mogami Figure 1 Figure 2 Figure 3 ftf54 Figure 5 +y (μm) /, :PS Figure 7 ψm) θ2 θ25 0M o, J! ;041) 0.4
5 asvgind (X10'/'C) 00 degrees)

Claims (2)

[Claims] (1) A tuning fork type crystal oscillator that utilizes the simple combination of the fundamental vibration of bending and the fundamental vibration of torsion, and the ratio W/μ of the width W and length λ of the tuning fork arm is 75. In a tuning fork type crystal resonator with a f of approximately 0.25 or more, the cutting direction of the resonator is: When rotating counterclockwise around the electric axis of the crystal, When rotating in the positive direction of rotation, the direction of cutting the resonator is A tuning fork type crystal resonator characterized in that two faces around the oscillator are at an angle larger in the negative direction than 115 degrees. (2) The ratio W and l of the width W and length L of the line arm is about 0.
36, and the cutting direction is within a range between 115 degrees and 117 degrees g! A 1st
Tuning fork type crystal resonator as described in section.