JPH05121998A - Torsional crystal vibrator - Google Patents

Abstract

PURPOSE:To suppress the spurious radiation by selecting side ratios Rzy, Ryx to be prescribed ranges from a crystal plate almost being a Z plate and forming the vibrator by the etching method. CONSTITUTION:The coordinate system consists of an origin O, an electric axis (x), a mechanical axis (y), an optical axis (z) to form the O-xyz system. A tuning fork torsional vibrator 1 whose thickness is Z0, whose width is y0, whose length is x0 is made of a crystal plate almost being a Z plate. The plate being almost the Z plate offers ease of chemical etching. Side ratios Rzy(z0/y0), Ryx(y0/ x0) of the crystal vibrator are respectively selected to be 0.910/1.20 and 0.196 or over and 0.129 or below and the crystal vibrator is formed by the etching method. Thus, the small sized crystal vibrator suppressing spurious vibration is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cut angle, a side ratio Rzy (thickness z ₀ / width y ₀ ) and a side ratio Ryx (width y ₀ / length x ₀ ) of a twisted quartz crystal unit. In particular, downsizing, high precision,
Wristwatches, pagers, with strong demands for shock resistance and cost reduction,
The present invention relates to a twisted crystal oscillator having an optimum cut and side ratio as a reference signal source for IC cards, mobile radios, and the like.

[0002]

2. Description of the Related Art As a crystal unit having a frequency of 200 kHz to 600 kHz, a bending crystal unit having a tuning fork shape and a vertical crystal unit have been used.

[0003]

However, since the tuning fork type bent crystal resonator used in the related art uses the harmonic mode, the electrode formation is complicated and the vibration energy loss due to the support of the lead wire is large. As a result, there remain problems such as an increase in equivalent series resistance R ₁ . on the other hand,
The frequency of the vertical crystal oscillator is inversely proportional to the length of the vibrating arm, so if you try to realize an oscillator of 600 kHz or less,
There was a problem that the size naturally increased and it could not be downsized. Therefore, the frequency is 20
There has been a demand for a quartz resonator which has a temperature coefficient of 0 kHz to 600 kHz, is ultra-compact, has a zero temperature coefficient, suppresses spurious vibrations, and can be easily chemically etched.

[0004]

The present invention solves the conventional problems by the following methods. That is, in a crystal oscillator that vibrates in a torsional vibration mode, the oscillator is formed so that the length x ₀ is approximately the same as the x-axis (electrical axis) direction from the crystal plate of Z plate, and the thickness z of the oscillator is set. Ratio Rzy of ₀ and width y ₀
(Z ₀ / y ₀₎ of 0.910 to 1.18, the ratio Ryx width y ₀ and length x ₀ (y ₀ / x ₀₎ of 0.196 or more, 0.
The problem is solved by setting it to 129 or less.

[0005]

As described above, the present invention is a twisted quartz crystal oscillator, and moreover, the side ratio Rzy is 0.910 from that of a substantially Z quartz crystal plate.
1.18, the side ratio Ryx is set to 0.196 or more and 0.129 or less, and is formed by an etching method to obtain a small twisted quartz crystal resonator having a zero temperature coefficient and suppressing spurious vibrations.

[0006]

EXAMPLES Next, the present invention will be specifically described based on Examples. FIG. 1 shows a tuning fork-shaped twisted crystal oscillator 1 of the present invention and its coordinate system. The coordinate system is the origin o, the electrical axis x, the mechanical axis y,
It is composed of the optical axis z and constitutes o-xyz. The tuning fork-shaped twisted quartz crystal resonator 1 having a thickness z ₀ , a width y ₀ and a length x ₀ is formed from a crystal plate of approximately Z plate. About Z here
The plate refers to a crystal plate having an angle of 0 ° to 10 ° around the x axis (φ degrees) or the z axis (θ degrees) based on the plate perpendicular to the Z axis. This roughly Z plate is selected because it is extremely easy to chemically etch.

Next, the side ratio Rzy (z ₀ / y ₀ ) at which the primary temperature coefficient α of the Z plate becomes approximately zero will be described. Figure 2
Is the relationship between the cut angle φ and the first-order temperature coefficient α when the side ratio Rzy of the tuning fork-shaped twisted quartz crystal resonator of the present invention is used as a parameter. φ = 0 indicates the Z plate, but the side ratio Rzy = 1.1
When 0, α = 0. Although α changes with a slight change in φ, it can be set to α = 0 by changing Rzy.

For example, when φ = -10 °, Rzy = 0.9.
On the other hand, if φ = 10 °, Rzy = 1.18. FIG. 3 shows the side ratio R of the tuning fork-shaped twisted crystal unit of the present invention.
It is the relationship between the cut angle θ and the primary temperature coefficient α when zy is used as a parameter. θ = 0 ° indicates a Z plate, but Rzy
When = 1.10, α = 0. α for changes in θ
Also changes, but α = 0 can be obtained by changing Rzy similarly to φ. For example, θ = −10 °
Then Rzy = 1.13, while θ = 10 ° Rzy
= 1.16 is sufficient. As described above, when a tuning fork-shaped twisted quartz oscillator is formed from a crystal plate of approximately Z plate, the oscillator with α = 0 can be obtained by sufficiently grasping the relationship with the side ratio Rzy of the oscillator. You can

FIG. 4 shows an example of frequency-temperature characteristics of a tuning fork-shaped twisted quartz crystal vibrator formed from a Z-plate crystal plate of the present invention. Α = 0 at room temperature and the secondary temperature coefficient β at that time
Was about −3.2 × 10 ⁻⁸ / ° C ^2, which was similar to the frequency-temperature characteristic of the bent crystal unit. FIG. 5 shows the relationship between the side ratio Ryx (y ₀ / x ₀ ) and the frequency constant (f · x ₀ ) when the thickness Z ₀ of the tuning-fork-shaped twisted quartz crystal resonator of the present invention is used as a parameter. In the bending mode, the side ratio Ryx (y ₀ /
When x ₀ ) (x ₀ : constant) increases, the frequency constant (f ·
x ₀ ) becomes large and increases proportionally at first, but the edge ratio R
When yx (y ₀ / x ₀ ) increases, the influence of the inertial term and the shearing force increases, and the tendency is saturated. On the other hand, in the case of the torsion mode, since it is approximately inversely proportional to the width y ₀ and proportional to the thickness z ₀ , the result shown in FIG. 5 is obtained. Since the present invention is mainly formed by the chemical etching method, the thickness z ₀ is 50 μm to 200 μm.
μm is selected. For example, when z ₀ = 50 μm, the side ratio Ryx is 0.162, and the torsional mode and the bending mode are strongly coupled, and when z ₀ = 200 μm, the ratio becomes 0.164.
Therefore, normally, if the frequencies between both vibrations are separated by 20% or more, they do not affect each other. Therefore, when z ₀ = 50 μm, the side ratio Ryx is 0.129 or less, or
When it is 0.195 or more, on the other hand, when z ₀ = 200 μm, 0.13 or less, and when 0.196 or more, the coupling between both vibrations can be removed. Therefore, z ₀ = 50 μm-2
Between 00 μm, Ryx is 0.196 or more, 0.12
It can be seen that 9 or less is sufficient. In this calculation, φ = 0 and θ = 0 were obtained, but the cut angle dependence is almost the same for almost Z plates.

[0010]

As described above, the tuning fork-shaped twisted crystal oscillator of the present invention has the following remarkable effects. (1) A tuning fork-shaped twisted quartz crystal resonator having a small equivalent series resistance R ₁ is obtained by optimally selecting the side ratio of the thickness z _{0 of the} tuning fork arm, the width y ₀ and the length x ₀ , and there is no coupling with spurious vibration. Is obtained. (2) Since it can be easily formed by an etching method, it can be made smaller and thinner. At the same time, a large number of vibrators can be batch-processed on one wafer at a time, so that the cost can be reduced. (3) Since the zero temperature coefficient can be obtained at room temperature, the twisted quartz crystal resonator has high accuracy. (4) Since it is processed into a tuning fork shape, the loss of vibration energy due to the support of lead wires and the like is reduced, and a twisted quartz crystal resonator having excellent impact resistance can be obtained.

[Brief description of drawings]

FIG. 1 shows a tuning fork-shaped twisted crystal oscillator of the present invention and its coordinate system.

FIG. 2 is a side ratio Rzy of a tuning fork-shaped twisted quartz crystal resonator of the present invention.
Cut angle φ and primary temperature coefficient α
Relationship with.

FIG. 3 is a side ratio Rzy of a tuning fork-shaped twisted quartz oscillator according to the present invention.
Cut angle θ and the first-order temperature coefficient α
Relationship with.

FIG. 4 shows an example of frequency-temperature characteristics of a tuning fork-shaped twisted quartz crystal resonator formed from a Z-plate crystal plate of the present invention.

[5] side ratio Ryx and frequency constant when the thickness z ₀ of the tuning fork shaped torsional quartz oscillator and the parameters of the present invention (f ·
x ₀ ).

[Explanation of symbols]

1 Tuning-fork-shaped twisted crystal unit x ₀ , y ₀ , z ₀ Length, width, thickness φ, θ Cut angle

Claims (1)

[Claims] 1. A tuning-fork-shaped crystal oscillator that vibrates in a torsional vibration mode, wherein the oscillator is formed so that a length x ₀ of a crystal plate of a Z plate substantially coincides with an x-axis (electrical axis) direction. The ratio Rzy (z ₀ / y ₀ ) of the thickness z ₀ and the width y ₀ of the vibrator is 0.910 to 1.20, and the ratio Ryx of the width y ₀ and the length x ₀ .
A twisted quartz crystal resonator having (y ₀ / x ₀ ) of 0.196 or more and 0.129 or less.