JPS644371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides various characteristics of a tuning fork crystal resonator, namely:
Regarding a tuning fork type crystal resonator with improved Q value, CI value, vibration leakage, and frequency aging.

Conventionally, a tuning fork type crystal resonator has often been used as a frequency standard for electronic wristwatches. This is mainly due to its small size and low frequency, such as electronic watches.
This is because it is ideal for equipment that is required to be small and consume low energy.

In recent years, as electronic wristwatches have become thinner, the tuning fork crystal oscillators used in them have also become smaller year by year. However, miniaturization of tuning fork crystal resonators is fraught with problems such as deterioration of Q value, CI value, vibration leakage, and frequency aging. In short, just by downsizing, the above characteristics deteriorate, and to some extent,
It is difficult to obtain the same characteristics as larger ones. For example, currently, wristwatches have a diameter of 2 mm.
Tuning fork crystal resonators housed in cylindrical cases with a total length of 6 mm and a total length of 6 mm are often used;
When a tuning fork crystal resonator is miniaturized to fit into a cylindrical case with a length of 1.5 mm and a total length of 5 mm, the Q value decreases by 40%, the IC value increases by 2 to 3 times, and the characteristics deteriorate despite the miniaturization. is remarkable. A decrease in the Q value results in deterioration of frequency aging, which has a large negative effect on time accuracy. Further, the deterioration of the CI value causes an increase in energy consumption, resulting in a disadvantage that the battery life is shortened. There is a method to improve the CI value by carefully examining the electrode shape in detail and modifying the electrode shape so that the excitation electric field can be used effectively, but this method does not require the equivalent of a crystal oscillator. The series capacitance of the circuit constant increases. This is due to the following reasons. The Q value of the resonator is Q, the CI value is R ₁ , and the series capacitance is
C ₁ and the series resonance angular frequency is ω ₀ , then Q=1/ω ₀ C ₁ R ₁ . Q hardly changes even if the electrode is modified. ω ₀ is constant. Therefore, if R ₁ decreases,
C ₁ increases. As C ₁ increases, the oscillation frequency tends to become unstable because it becomes more susceptible to the influence of external circuits, especially stray capacitance. Therefore, the method of modifying the electrode cannot be a fundamental solution.
It is desirable that the decrease in the CI value be accompanied by an increase in the Q value.

Therefore, the present invention eliminates these drawbacks and aims to improve the Q value, lower the CI value, reduce vibration leakage, and improve frequency aging.

Now, let's consider the cause of the deterioration of the above characteristics when a tuning fork type crystal resonator is downsized.

Simply put, the cause is an imbalance between the two tuning fork arms. Currently, there are two methods of processing tuning fork crystal resonators. One is a machining method typified by a band saw. The other method is a chemical processing method called the Lingraphie manufacturing method. When a resonator is processed using a chemical processing method, the finished product has an error of about 1 μm, that is, a variation in the design value of the resonator dimensions. The mechanical processing method is somewhat larger than the chemical processing method. Let's consider below what kind of negative effects this dimensional variation has.

FIG. 1 shows an ideal tuning fork type crystal resonator with no dimensional variations during processing. 1 and 2 are tuning fork arms with equal tuning fork arm width w and tuning fork arm length l, 3 is the vibration direction of the tuning fork arm at a certain time, 4 is the vibration direction of the tuning fork arm after half a cycle, 5 is the center line of the tuning fork base, 6 is a mount part. In addition, the X-axis, Y'-axis, and Z'-axis represent the directions when the resonator is cut out from the crystal raw stone, and are the electrical axis, the mechanical axis rotated around the electric axis, and the optical axis rotated around the electric axis, respectively. be. Now, the tuning fork arm bends and vibrates in the X-axis direction as shown at 3 and 4. 2
If the width and length of the two tuning fork arms are equal, the displacements in the X direction of the portion indicated by the straight line 5 completely cancel each other out and become zero. Therefore, the displacement in the mount portion 6 is extremely small. However, in reality, there are always variations in the dimensions of the tuning fork arm due to processing.

FIG. 2 shows a tuning fork type crystal resonator with dimensional variations due to processing. The width and length of the left tuning fork arm are w and l, and the width and length of the right tuning fork arm are w+△
Let w, l+△l. Here, △w≠0, △l≠0. Therefore, the vibrational displacements of the left and right tuning fork arms in the X direction do not cancel each other out at the portion corresponding to 5 in FIG. 1, and the portion where the displacement in the X direction becomes zero is as shown by curve 7. As a result, the displacement of the mount portion 8 is
This value is two to three orders of magnitude larger than the displacement of the mount portion 6 shown in FIG. In this way, when a portion with large vibration displacement is mounted, the Q value decreases and vibration leakage occurs. The Q value is expressed as Q=E/ΔE. E is the total energy of the vibration system, △E
is the energy lost in one cycle. If the displacement of the mount portion is large, the loss of vibration energy at the mount portion will be large, resulting in a decrease in the Q value. Vibration leakage occurs through the following mechanism.

FIG. 3 shows the vibrator shown in FIG. 2 having varying dimensions mounted on a plug body.
9 is a vibrator, 10 is a lead for mounting the vibrator and establishing electrical continuity with the electrode, 11 is a plug body, 12 is an arrow indicating vibration of the mount part, 13
is an arrow indicating the vibration of the plug body. As shown in this figure, when the vibration displacement of the mount portion is large, the vibrator 9 becomes a vibration source, causing the plug body 11 to vibrate as shown by an arrow 13. According to vibration theory, adding another mass to a vibrating part, that is, a part whose equivalent mass is not infinite, lowers the frequency of the vibrating system. That is, when another mass is added to the plug body 13, the resonant frequency of the vibrator 9 is lowered.
If the mass added to the plug body 13 moves somewhat unsteadily, the resonant frequency of the vibrator 9 will also fluctuate accordingly. This is the mechanism by which vibration leakage occurs. As described above, it can be seen that variations in dimensions between the two tuning fork arms have a very adverse effect on the characteristics.

Now, let's consider the dimensional variation of the vibrator from another perspective. Let the resonance frequencies of the left and right tuning fork arms in Figure 2 be _L and _R , respectively. Approximately, the tuning fork arm can be considered as a cantilever beam with the broken line part in Figure 2 completely fixed, and _L and _R are _L = Kw/l ² _R = Kw + △w/(l + △l), where K is a constant. ) ² Kw/l ² {1+(△w/w−2△l/l)}. Therefore, if the difference between _L and _R is △, then △= _R − _L = Kw/l ² (△w/w−2△l/l)
becomes. That is, the resonance frequencies of the left and right tuning fork arms differ by the amount expressed by the equation. In the equation, if the processing method is the same, △w and △l have the same size regardless of the size of the vibrator. Therefore, the larger the vibrator size, the smaller △w/w, △l/l, and the smaller △. That is, the degree of influence of dimensional variations is reduced. The opposite is true when the transducer size is reduced. When a vibrator is made smaller, the influence of dimensional variations becomes larger. This is why the characteristics deteriorate when the vibrator is made smaller.

In the formula, if △w=0, △l=0, then △=0, and the imbalance between the left and right tuning fork arms as shown in FIG. 1 disappears. The formula may be rephrased as _R = _L. That is, if the resonance frequency of the left tuning fork arm and the resonance frequency of the right tuning fork arm are made equal,
The imbalance of the tuning fork arm will disappear. This is the origin of the idea of the present invention. Before describing specific examples of the present invention, let us give one conventional example.

Figure 4 shows a 32KHz tuning fork crystal oscillator with a +5°X cut, which is currently most commonly used in electronic wristwatches. Reference numerals 14 and 15 are electrodes to which electric fields of opposite polarity are applied. 16 and 17 are leads for supporting the vibrator and establishing conduction with the electrodes, 18 is solder for bonding the vibrator to the lead, 19 is a plug body, and 2
0, 21 shows the cross section of the tuning fork arm at position A-A'.
Now, when a positive electric field is applied to the lead 16 and a negative electric field is applied to the lead 17, an electric field is generated in the cross section at the position A-A' as shown in the left diagram. This electric field causes bending vibration.

Specific examples of the present invention are given below. Since the mounting electrode is a two-terminal element, there are naturally two mounting electrodes as shown in this figure. There are not four because they are tied on the front and back.

FIG. 5 is a specific example of the present invention. Figure 5a
1 shows the front and back sides of a tuning fork type crystal resonator according to the present invention. 22 and 23 are left and right tuning fork arms, respectively;
24, 25, 26 are excitation electrodes, 27 is excitation electrode 2
4 and 26 are divided slits, 28 is a mount partial electrode, and 29 is a frequency adjustment electrode. The difference between the conventional electrode shape shown in FIG. 4 and the electrode shape shown in FIG. 5a according to the present invention is that one of the mount partial electrodes is divided into two. The reason for dividing in this way will be described below. In addition, in Figure 5 a,
The electrodes marked with 〓, 〓, 〓 are electrically connected to each other.

FIG. 5b shows the electric field in the cross section of the tuning fork arm at position B-B' when a positive electric field is applied to the electrode 24 and a negative electric field is applied to the electrode 25. That is, in this case,
An electric field is applied only to the right tuning fork arm 23.

FIG. 5c shows a case where a negative electric field is applied to the electrode 25 and a positive electric field is applied to the electrode 26. At this time, the electric field is applied only to the left tuning fork arm 22. Therefore, when a positive electric field is applied to the electrodes 24 and 26 and a negative electric field is applied to the electrode 25, electric fields are applied to both tuning fork arms with opposite phases, as shown in FIG. arise.

Now, an object of the present invention is to equalize the resonance frequencies of the left and right tuning fork arms to eliminate imbalance between the tuning fork arms. Therefore, the slit 2 as shown in Fig. 5a is
7 is used to adjust the balance of the tuning fork arm. Next, the balance adjustment method will be described.

This will be explained based on FIGS. 5a to 5c. First, the left tuning fork arm 22 is fixed, an alternating current electric field is applied to the electrodes 24 and 25, the frequency is swept, and the resonance frequency _R of the right tuning fork arm 23 is measured. Next, the right tuning fork arm 23
is fixed, and an alternating current electric field is applied to the electrodes 25 and 26.
Sweep the frequency and find the resonance frequency _L of the left tuning fork arm
Measure.

Then, the frequency adjustment electrode 29 of the tuning fork arm with the lower frequency is removed by a laser beam to equalize the resonance frequencies of both tuning fork arms. If adjustment is done by vapor deposition, for the tuning fork arm with the higher resonance frequency,
Just make adjustments. In this way, △=0,
The imbalance of the tuning fork arm disappears.

In this way, adjust the balance and then mount it. Alternatively, both _L and _R may be adjusted to desired predetermined values before mounting, and then mounted. That is, balance adjustment and frequency adjustment may be performed simultaneously. A perspective view of the vibrator thus adjusted and mounted is shown in FIG. 5e. 30
is a lead, and 31 and 32 are solders, and 32 also serves to make the electrodes 24 and 26 conductive. 3
3 is a hole in the electrode section that was removed by balance adjustment and frequency adjustment.

The resonator according to the present invention has no problems such as a decrease in Q value, an increase in CI value, an increase in vibration leakage, and deterioration in frequency aging due to miniaturization, and has characteristics that are completely equivalent to those of larger resonators. is obtained.

The tuning fork type crystal resonator according to the present invention is most easily mass-produced when processed by photolithography. This is because it is possible to adjust the balance and frequency in the pellet state. In Figure 6, vibrators processed using the photolithography method are lined up on a single pellet. Since it is possible to attach electrodes as shown in FIG. 5a in the pellet state, adjustments can be made on the pellet.

In the first embodiment, in FIG. 5a, the electrode 24
is the first excitation electrode, and the electrode 26 is the second excitation electrode,
These are collectively referred to as the first electrode. Further, the electrode 25 is used as a second electrode. The first and second excitation electrodes of the second electrode are the same as the first electrode, and illustration thereof is omitted (the same applies hereinafter).

Another specific example of the present invention is shown in FIG. Figure 7a
b shows the front and back electrodes, and b shows the mounted vibrator. Reference numerals 39, 40, and 41 are electrodes, which correspond to the electrodes 24, 26, and 25 in FIG. 5a. Figure 7b shows the mounted device after balance adjustment and frequency adjustment.
42 and 43 are solder. The solder 42 serves to connect the two divided electrodes, but the solder 43 adheres only to the electrode 41.

In the second embodiment, the electrode 39 in FIG.
is the first excitation electrode, and the electrode 40 is the second excitation electrode,
These are collectively referred to as the first electrode. Further, the electrode 41 is used as a second electrode.

FIG. 8 shows another specific example of the present invention. Figure 8 shows the present invention applied to a coupled tuning fork type crystal resonator that uses the combination of the first harmonic of bending vibration and the fundamental vibration of torsional vibration to make the frequency-temperature characteristic of bending vibration a cubic curve. This is an example. 44 is a coupled tuning fork type crystal resonator, and 45 is a mount portion. The electrode shapes on the front and back sides of the mount portion are the same as the mount partial electrodes in FIG. 5a. 50, 51, 52 are electrodes. Conventionally, coupled tuning fork type crystal resonators suffer from severe vibration leakage, and λ/4 (λ is the wavelength) support is often used. However, by improving the balance of the tuning fork arms, vibration can be reduced even with the support method shown in Figure 8. It has become possible to prevent leakage. This is the same support method currently used for mainstream 32KHz tuning forks. It is very suitable for mass production.

Even with the support method shown in FIG. 7 for a coupled tuning fork type crystal resonator, vibration leakage can be suppressed as long as the balance is adjusted.

In this third embodiment, the electrode 5 in FIG.
0 as the first excitation electrode, electrode 51 as the second excitation electrode, and these together as the first electrode. Also electrode 5
2 is the second electrode.

FIG. 9 is another specific example of the present invention. 46 is a vibrator, and 47, 48, and 49 are leads, respectively. The front and back electrodes of the vibrator 46 are the same as those shown in FIG. 5a. In this specific example, after mounting, balance adjustment, frequency adjustment, and when incorporating into the oscillation circuit, lead 48 and lead 4 are removed outside the resonator case.
This is an example of a mounting method that connects 9. This mounting method can also be applied to coupled tuning fork type crystal resonators.

As mentioned above, by dividing one of the front electrodes and one of the back electrodes of the two electrodes on the mount part of the tuning fork crystal resonator into two parts, the tuning fork arm is excited on one side at a time, and the balance is adjusted. became possible.
By applying this method to a small tuning fork type crystal resonator, it is possible to suppress the deterioration of characteristics and achieve high Q, low CI, and reduced vibration leakage. Furthermore, if the present invention is applied to a coupled tuning fork type crystal resonator, λ/4 support becomes unnecessary, and a support method similar to that for a 32KHz tuning fork can be adopted. This leads to improved mass productivity.

By using the tuning fork type crystal oscillator of the present invention in an electronic wristwatch, it is possible to achieve small size, long life, and high precision.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an unbalanced tuning fork.
FIG. 2 is a diagram showing an unbalanced tuning fork. FIG. 3 is a diagram for explaining why an unbalanced tuning fork causes vibration leakage. FIG. 4 is a diagram showing a conventional example. FIG. 5a is a diagram showing a specific example of the present invention. FIG. 5b is a diagram showing the direction of the electric field when the right tuning fork arm is excited. FIG. 5e is a diagram showing the direction of the electric field when the left tuning fork arm is excited. FIG. 5d is a diagram showing the direction of the electric field when both tuning fork arms are excited. FIG. 5e is an external view of a mounted tuning fork crystal resonator according to the present invention. FIG. 6 is a diagram showing a tuning fork on a pellet processed by photolithography. FIG. 7a is a diagram showing another specific example of the present invention. FIG. 7b is an external view when a is mounted. FIG. 8 is a diagram showing an example in which the present invention is applied to a coupled tuning fork type crystal resonator. FIG. 9 is a diagram showing an example in which the vibrator of the present invention is supported by three leads. 1... Right tuning fork arm, 2... Left tuning fork arm, 3... Vibration direction of the tuning fork arm at a certain time, 4... Vibration direction of the tuning fork arm after half a cycle, 5... Center line of the base, 6... Mount part, 7 ...Line with zero displacement in the X direction, 8...Mount part, 9...Tuning fork, 10...Reed, 11...Plug, 1
2...Arrow indicating that the tuning fork base is vibrating, 1
3...Arrow indicating that the plug body is vibrating, 1
4, 15... Electrode, 17, 16... Lead, 18... Solder, 19... Plug, 20... Left tuning fork arm, 21... Right tuning fork arm, 22... Left tuning fork arm, 23... Right tuning fork arm, 24, 25, 26...electrode, 27...slit,
28...Mount part, 29...Balance adjustment, frequency adjustment area, 30...Lead, 31, 32...Solder,
33... Traces of balance adjustment and frequency adjustment, 39,4
0,41...Electrode, 42,43...Solder, 44...Coupled tuning fork type crystal resonator, 45...Mount part, 46...
Tuning fork, 47, 48, 49...Reed.

Claims (1)

[Scope of Claims] 1. In a tuning fork type crystal resonator having two excitation electrodes, the first electrode is connected to a mount portion disposed at the base of the tuning fork type crystal resonator, and at least a portion of one of the forks is a first excitation electrode located at the center of the
The other fork includes a second excitation electrode, at least a portion of which is disposed on the side surface of the fork, and the second electrode includes a mount portion disposed at the base of the tuning fork type crystal resonator; a second excitation electrode that is at least partially disposed on a side surface of the fork; and a first excitation electrode that is at least partially disposed at the center of the other fork, and the first excitation electrode is provided with a slit in the mount portion to separate and divide the first excitation electrode and the second excitation electrode, and only one prong vibrates due to the separated and divided first excitation electrode and the second electrode. , wherein the second excitation electrode and the second electrode are arranged so that only the other prong vibrates, and the slit portion is electrically connected by connecting a lead terminal. A tuning fork type crystal oscillator.