JPH0463567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crystal resonator that performs thickness-shear vibration.

[Conventional technology and its problems to be solved] Conventionally, a disk-shaped AT cut crystal resonator has been used as a crystal resonator that performs thickness-shear vibration. This AT-cut crystal resonator has been widely used because of its excellent frequency-temperature characteristics, but it has the drawback of being difficult to miniaturize.

A rectangular AT-cut crystal resonator has also been proposed. However, even in this case, if the crystal resonator is made smaller and the ratio of the width and thickness of the crystal piece, that is, the side ratio, is reduced, the main vibration level decreases and the number and level of unnecessary vibrations increase, causing the main vibration characteristics to deteriorate. It was unsuitable for practical use.

Furthermore, a rectangular AT-cut crystal resonator in which the side surface of the crystal piece is inclined by about 5 degrees has been proposed. This was an attempt to prevent the main vibration characteristics from deteriorating by reducing the coupling with the contour system vibration, but even in this crystal resonator, as it becomes smaller, the main vibration level decreases. The drawback of storage was not resolved.

As described above, it has been difficult to miniaturize any of the conventional crystal resonators without degrading the main vibration characteristics.

[Object of the Invention] An object of the present invention is to provide a thickness-shear crystal resonator that can be extremely miniaturized without reducing the main vibration level.

Another object of the present invention is to provide a thickness shear crystal resonator that can keep unnecessary vibration groups of the contour system away from the main vibration region and stably oscillate in the main vibration.

[Means for achieving the object] The thickness-shear crystal resonator according to the present invention has the following features:
Rotate the Y-axis in the Z-axis direction and the Z-axis in the same direction by approximately 35 degrees around the X-axis of the crystal.
Set the Y′-axis and Z′-axis, then rotate the X-axis and Z′-axis by angle φ respectively around the Y′-axis to set the X″-axis and Z″-axis. The angle φ is set to 3 degrees to 30 degrees, and the longitudinal side surface of the crystal piece is in the Z″ axis direction with respect to the X″ axis-Y′ axis plane. It is located at a predetermined angle.

[Function] By configuring the rod-shaped thickness-slip crystal resonator as described above, even if the crystal resonator is made smaller than before, the coupling with the vibration of the contour system can be made loose, and the resonance level of the main vibration can be reduced. is high, so stable oscillation can be performed.

[Example] Examples of the present invention will be described below.

The X, Y, and Z axes shown in FIG. 1 are the electrical, mechanical, and optical axes of the crystal, respectively. Then, the Y'-axis is set by rotating the Y-axis by an angle θ in the Z-axis direction about the X-axis, and the Z'-axis is set by rotating the Z-axis by an angle θ in the same direction. This angle θ is
The cutting angle is approximately 35 degrees, which is the same as the cutting angle of a normal AT cut crystal plate.

Next, the X-axis is set by rotating the X-axis by an angle φ in the Z'-axis direction around the Y'-axis, and the Z''-axis is set by rotating the Z'-axis by an angle φ in the same direction. . In the present invention, the angle φ is set in the range of 3 degrees to 30 degrees.

The crystal piece 1 shown in FIGS. 1 to 4 has a substantially rectangular shape, and its longitudinal direction coincides with the X'' axis direction.
Principal surfaces 1a and 1b of the crystal piece 1 are formed parallel to the X''axis-Z'' plane. The longitudinal side surfaces 1c and 1d are inclined toward the Z'' direction by an angle ζ with respect to the X''axis-Y' axis plane. In the present invention, the angle ζ is set in the range of 1 degree to 6 degrees. Note that the optimum angle ζ is determined based on the angle φ from the relationship shown in FIG. End surfaces 1e and 1f of crystal piece 1
is parallel to the Y′-Z″ plane.

In the example described below, the length l is about 6 mm and the width w is about 1 mm, which is formed by processing a crystal piece 1.
mm, thickness t is approximately 0.4mm, side ratio (width w/thickness t) is
An example of a 2.5 crystal piece is shown.

In addition, in the first example and the second example shown below, the angle φ≒15 degrees and the angle ζ≒5 degrees were set.

5 to 8 show a first example of a crystal blank according to the present invention. This crystal piece 11 is formed by polishing so that one main surface 1a of the crystal piece 1 forms a part of the side surface of a cylinder parallel to the Z' axis. As a result, the main surface 11a has a uniform thickness along the Z′-axis direction, and has a uniform thickness along the X″-axis direction.
It has a cylindrical shape that is thick in the center and thinner towards both ends. Note that the other main surface 11b, side surfaces 11c and 11d, and end surface 11e,
11f, each surface of the crystal piece 1 appears as is without being processed. As shown in FIGS. 6 and 8, since the cylindrical surface machining is performed in the Z'-axis direction, there is a change in thickness at the end surfaces 11e and 11f.

9 to 11 show a second example of a crystal piece according to the present invention. This crystal piece 21 is cut from a normal AT-cut crystal plate 22, which is cut from crystal at a cutting angle of about 35 degrees. That is, A.T.
One surface of the cut crystal plate 22 is machined into a cylindrical surface along the Z'-axis direction, and then cut obliquely at angles φ and ζ. The crystal blank 21 cut in this way has its longitudinal direction aligned with the X'' axis, which is obtained by rotating the X axis by an angle φ in the Z' axis direction, and one main surface 21a is processed by the above-mentioned cylindrical surface processing. Therefore, the thickness is uniform along the Z' axis, and the thickness becomes thinner from the center to both ends along the X axis.Also, the longitudinal side surface 21c of the crystal piece 21 ，
21d is inclined at an angle ζ in the Z″ axis direction with respect to the X″ axis-Y′ axis plane. And end surfaces 21e, 21
f is parallel to the Y'-axis-Z'-axis plane.

In addition, in the crystal blank 11 of the first embodiment and the crystal blank 21 of the second embodiment, both principal surfaces may be processed to have a cylindrical surface. This allows the thickness of both ends to be further reduced. In this case, it is necessary to increase the radius of curvature when machining the cylindrical surface.

A third example of the crystal piece according to the present invention is shown in FIGS. 12 to 15. For this crystal piece 31, a crystal piece having a side ratio w/t larger than that of the crystal piece 1 was used, and the angle was set to φ≒10 degrees and angle ζ≒5.1 degrees.
The crystal piece is formed by bevel-processing both ends of the crystal piece into inclined surfaces along the Z' axis. As a result, the crystal piece 31 has a uniform thickness along the Z' axis, and the thickness of both ends becomes thinner toward the edge along the X axis. The longitudinal direction of the crystal blank 31 coincides with the X'' axis direction, and both ends of the main surfaces 31a and 31b are beveled.Longitudinal side surfaces 31c and 31d
is the angle ζ in the Z″-axis direction with respect to the X″-Y′-axis plane
Only sloping. The end surfaces 31e and 31f are formed parallel to the Y'-axis-Z'' axis plane.

Note that the bevel processing may be performed only on one main surface. Further, the end face may be formed parallel to the Y'-axis-Z'-axis plane.

A fourth embodiment of the present invention is shown in FIGS. 16-19. In manufacturing this crystal piece 41, Y
Centering on the axis, make an angle φ from the X axis in the opposite direction to the Z' axis.
The X″ axis is set by rotating the Z axis by an angle φ in the same direction, and the Z″ axis is set by rotating the Z axis in the same direction by an angle φ. In this embodiment, the angle φ is set to about 5 degrees and the angle ζ is set to a little over 5 degrees. Bicylindrical processing is applied to both main surfaces 41a and 41b of the crystal blank 41 along the Z'' axis.Thus, the crystal blank 41 has a uniform thickness along the Z'' axis. , is formed thinner from the center to both ends along the X″ axis.Longitudinal side surface 41
c and 41d are inclined at an angle ζ in the Z'' axis direction with respect to the X''axis-Y' axis plane. End faces 41e, 41f
is formed parallel to the Y'-axis-Z'' axis plane.

Quartz belongs to the trigonal system, so when setting the X″ and Z′ axes, you can rotate the X and Z′ axes to either side within a range of 3 to 30 degrees around the Y axis. A similar effect can be achieved.

The crystal piece according to the present invention is formed as described above. Next, this driving method will be explained with reference to FIGS. 20 and 21.

Driving electrodes 12 and 13 are formed in the center of both principal surfaces 11a and 11b of the crystal blank 11 by vapor deposition, respectively. It has been extended to the department. When an electric field is applied to the drive electrode,
The crystal piece 11 oscillates. This driving method is the same for all the crystal pieces in the first to fourth embodiments.

The applicant is conducting experiments under various conditions.
First, let's look at two of the examples in Figure 22,
This will be explained with reference to FIG. 23. In these experiments, the crystal piece 11 shown in the first embodiment was
Similarly, a crystal piece having a length l≈6 mm and a thickness t≈0.4 mm was formed by performing cylindrical processing on one main surface.

As the first experiment, angle φ≒15 degrees, angle ζ≒5
The resonant frequency of the above-mentioned crystal blank formed under the following conditions was measured. The relationship between the width w of this crystal blank and the resonance frequency is shown in FIG. In this graph, indicates the main vibration, and the size of the circle indicates the height of the resonance level. Other circles indicate secondary vibrations, and vibrations with low resonance levels are indicated by dots.
Looking at this result, the width w is around 1mm and 1.35mm
It can be seen that the resonance level of the main vibration is very high in the vicinity, and there are few sub-vibrations in the vicinity of the main vibration, showing the best vibration characteristics. However, even in other ranges, those with a width w smaller than 1.55 mm generally exhibit good vibration characteristics.

In the second experiment, the angle φ≒30 degrees and the angle ζ
The resonance frequency of the above-mentioned crystal piece formed under the condition of ≒4.5 degrees was measured. The relationship between the width w of this crystal blank and the resonant frequency is shown in FIG. 23, and the symbols in the graph are the same as those shown in FIG. 22. According to this, when the width w is in the range of about 0.95 mm to 1.35 mm, the resonance level of the main vibration is high, and there are few sub-vibrations close to the main vibration, and the vibration characteristics are excellent. This is especially noticeable at 1.25 mm or less.

The present applicant conducted experiments under various conditions in addition to the first and second experiments described above. Next, the second
The experiments shown in Figures 4 to 30 will be explained. In these graphs, the vertical axis shows the magnitude of the resonance level, and the horizontal axis shows the frequency.

Figure 24 shows a conventional crystal oscillator, that is, the angle φ
These are the measurement results of the resonance level when the width w is approximately 1.00 mm for a case where the angle is 0 degrees. According to this, it can be seen that although the resonance level of the main vibration A is sufficiently high, the resonance level of the sub-vibration B having a frequency close to the main vibration is large and unsuitable for practical use.

In Figures 25 to 29, the angle φ is 5 degrees, 10 degrees, 15 degrees,
For 30 degree and 45 degree crystal oscillators, the width w is approx.
The results of each measurement when the diameter is 1.00 mm are shown. It can be seen that in all of these, the resonance level of the main vibration A is sufficiently large, and there are almost no sub-vibrations at frequencies close to this main vibration, making them suitable for practical use.
In the case of φ≒30 degrees as shown in FIG. 28, a slightly larger secondary vibration B is seen, but since this is also far from the main vibration A, it is considered that there is no problem in practical use.

In Figure 30, the angle φ is 60 degrees and the width is approximately
Measurement results for a 1.00mm crystal resonator are shown. Although the resonance level of the main vibration A is high, the resonance level of the adjacent sub-vibration B is also large, so
Not suitable for practical use.

Next, the graph shown in FIG. 31 will be explained.
In this graph, the length l is approximately 5.90 mm and the width w is approximately 1.00 mm.
In mm, the angle φ is 0 degrees, 5 degrees, 10 degrees, 15 degrees, 30 degrees,
It shows the results of measuring crystal impedance (hereinafter referred to as "CI value") for each 45-degree crystal resonator. Note that since there were variations in the measured values, the vicinity of the center is indicated by a circle, and the range of variation is indicated by a solid line. In addition, as a comparative example, we will use a crystal resonator that has been put into practical use in the past, namely:
A crystal resonator with a width w of around 1.67 mm and an angle φ of 0 degrees.
CI values and the range of their dispersion are shown by △ and dashed lines. Note that the CI value decreases as the main vibration level increases, and the smaller this value is, the more suitable it is for practical use.

As is clear from this graph, in the conventional crystal resonator where the angle φ is 0 degrees, the width w is 1.67
The CI value was sufficiently low for the size of around mm to be suitable for practical use, but when the width w is as small as about 1.00 mm,
Since the CI value was too high for use, it was not possible to miniaturize the crystal unit. On the other hand, when the angle φ is 5 degrees, 10 degrees, 15 degrees, and 30 degrees, the width w is
Even if it is around 1.00mm, the CI value is small and suitable for practical use. However, if the angle φ is 45 degrees, CI
It was found that the value was high and it was not suitable for practical use.

In this way, by combining the measurement results shown in Figures 24 to 30 and the measurement results shown in Figure 31, and taking into account experimental errors and variations, the angle φ of the crystal resonator can be determined.
is in the range of about 3 to 30 degrees, the width w is about 1.00
It can be concluded that it can be made as small as mm.

FIG. 2 shows the experimentally determined combination of angle φ and angle ζ that is optimal for practical use in terms of the resonance level of the main vibration and the number and level of sub-vibration, and plotted on a graph. From this graph, it can be seen that when the angle φ is within the range of 3 degrees to 30 degrees as described above, the angle ζ is within the range of 1 degree to 6 degrees. Note that the range of the angle ζ is approximately 5 degrees, which is almost the same as in the conventional product.

As described above, crystal resonators with an angle φ in the range of 3 to 30 degrees have a high resonance level of the main vibration, few sub-vibrations close to the main vibration, and a low CI value.
It has become clear that the performance is sufficient for practical use.

Note that, similarly to the conventional AT-cut crystal plate, the angle θ in the present invention is in the range of 34 degrees to 36 degrees, and the angle ζ is in the range of 1 to 6 degrees.

As described above, according to the present invention, a crystal resonator with a small side ratio and excellent main vibration characteristics can be obtained. Therefore, even if the width of the crystal resonator is reduced, the main vibration characteristics do not deteriorate, so it is possible to make the crystal resonator smaller than before.

[Effects] As described above, according to the present invention, a thickness-shear crystal resonator can be extremely downsized. Also,
Since most unnecessary vibrations can be removed from the main vibration region, the main vibration characteristics can be stabilized. Therefore, even if manufacturing tolerances are increased,
A thickness-shear crystal resonator capable of stable oscillation can be provided.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the crystal piece of the present invention, Fig. 2 is a graph showing the relationship between angle φ and angle ζ, Fig. 3 is a front view of the crystal piece, and Fig. 4 is a crystal piece. A side view of a crystal piece, FIG. 5 is a front view of the first embodiment of a crystal piece obtained by processing a crystal piece, and FIG. 6 is a side view thereof.
FIG. 7 is a bottom view thereof, FIG. 8 is a view taken along the line in FIG. 5, and FIG. 9 is a front view of the second embodiment of the crystal piece.
Figure 10 is its side view, Figure 11 is Figure 9-
12 is a front view of the third embodiment of the crystal piece, FIG. 13 is a side view thereof, FIG. 14 is a bottom view thereof, FIG. 15 is a view taken from FIG. FIG. 16 is a front view of the fourth embodiment of the crystal piece;
Figure 17 is its side view, Figure 18 is its bottom view,
Figure 19 is Figure 16 IX - line arrow view, 2
Figure 0 is a front view of a crystal resonator with drive electrodes formed on the crystal piece, Figure 21 is its back view, Figure 22 is a diagram of the relationship between the width of the crystal resonator and the resonant frequency, and Figure 23 is a diagram of other crystal units. Relationship diagram between vibrator width and resonant frequency, 2nd
4 to 30 are relationship diagrams between resonance levels and frequencies of crystal oscillators having different angles φ, and FIG. 31 is a relationship diagram between angle φ and CI value of the crystal oscillators. 1... Crystal piece, 11, 21, 31, 41...
Crystal piece, 11a, 11b, 21a, 21b, 31
a, 31b, 41a, 41b...main surface, 11c,
11d, 21c, 21d, 31c, 31d, 41
c, 41d...Side surface, θ, φ, ζ...Angle, t...
...thickness, w...width.

Claims (1)

[Claims] 1. With the X-axis of the crystal as the center and the Y-axis in the Z-axis direction,
Also, rotate the Z axis in the same direction by about 35 degrees each.
Set the Y′-axis and Z′-axis, then rotate the X-axis and Z′-axis by angle φ respectively around the Y′-axis to set the X″-axis and Z″-axis. The angle φ is set to 3 degrees to 30 degrees, and the longitudinal side surface of the crystal piece is in the Z″ axis direction with respect to the X″ axis-Y′ axis plane. A thickness-shear crystal resonator characterized in that the crystal piece has a uniform thickness along the Z′-axis direction, and has a uniform thickness along the X-axis direction from the center. The thickness shear vibrator according to claim 1, wherein the thickness shear vibrator is formed to become thinner toward both ends.