JPH05129875A - Torsional crystal vibrator - Google Patents

Abstract

PURPOSE:To provide the small sized torsional crystal vibrator oscillating a low frequency by providing a region having a mass pole moment of inertia different from that of a vibration part to an arm tip of the torsional crystal vibrator excited in the torsional vibration mode with an electric field component in the y-axis direction. CONSTITUTION:A width of a tip 3 of a vibration arm 2 is selected wider than the width of a vibration arm 2 in the torsional crystal vibrator excited in the torsional vibration mode with an electric field component in the y-axis direction so as to make the mass pole moment of inertia of the tip 3 different from the vibration arm 2. Then a ratio mu of the mass moment of inertia of the tip 3 to the mass moment of inertia of the vibration part is preferably selected between 0.428-3.31. Since the torsional crystal vibrator is excited by the electric field component in the y-axis direction in this way, the equivalent series resistance is decreased and since the load mass effect by the pole moment of inertia is provided to the tip of the vibrator, the crystal vibrator 1 oscillating a comparatively lower frequency of 200-600kHz is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shape of a twisted quartz oscillator and an excitation electrode. In particular, the present invention relates to a low-frequency twisted crystal oscillator most suitable as a reference signal source for wristwatches, pagers, IC cards, mobile radios, etc., which are strongly required to be compact, highly accurate, shock resistant and inexpensive.

[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 new crystal resonator of 0 kHz to 600 kHz, which is ultra-compact and has a small R ₁ and can be easily chemically etched.

[0004]

The present invention solves the conventional problems by the following methods. That is, in the crystal oscillator that excites the torsional vibration mode by the electric field component in the y-axis direction, the tip of the vibrating arm is made larger than the width of the vibrating arm, and the vibrating arm and the tip have different mass polar moments of inertia. This solves the problem.

[0005]

As described above, according to the present invention, the oscillator is excited by the twisted crystal oscillator, and the oscillator is excited by the electric field component in the y-axis direction.
₁ becomes smaller, and the load mass effect due to the polar moment of inertia is applied to the tip of the oscillator,
A crystal oscillator having a relatively low frequency of 600 kHz can be obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the shape and excitation electrode configuration of a tuning fork-shaped twisted crystal oscillator according to the present invention. The tuning fork-shaped twisted crystal unit 1 is composed of a tuning fork arm 2 and a tuning fork base 4, and weights 3 are provided at both ends of the tuning fork arm 2. Further, excitation electrodes 5 and 6 are arranged on the tuning fork arm 2 so as to have different polarities, and are arranged on both tuning fork arms 2 via a tuning fork base 4. Although not shown in FIG. 1, the counter electrodes are arranged so as to have different polarities also on the facing surfaces of the tuning fork arm 2 in the z-axis (optical axis) direction.

This oscillator has an electric field in the y'axis (the crystal axis after the coordinate rotation of the y axis, which is the mechanical axis), and is formed at a cut angle having an electric field component in the y axis direction. The vibrator has a tuning fork arm length y ₀ and width x ₀ . By forming such a tuning-fork-shaped twisted crystal unit, 200 kHz
A twisted quartz resonator having a low frequency of up to 600 kHz and a small equivalent series resistance R ₁ can be obtained.

FIG. 2 shows a model shape of the tuning fork-shaped twisted crystal oscillator of the present invention. With this model shape, the weight effect at the tip can be calculated by comparing with the vibrating portion. Tuning fork arm 2
The idea as a cantilever, the length y ₀ of the vibrating portion, the mass polar moment of inertia per unit length I (x), when a mass polar moment of inertia Im of the tip, now, the mass ratio mu = Im /
If defined as Iy ₀ , cotn ′ = μn ′ (∵n ′ = n
The relationship of π / 2) is obtained from FIG. Also, the resonance frequency f
Is given by f = k (n / y ₀ ) ... (1) k is a constant. Therefore, since the resonance frequency is proportional to n according to the equation (1), the frequency can be lowered by reducing n.

Next, the value of n will be described. FIG. 3 shows the relationship between the mass ratio μ and n of the tuning fork-shaped twisted quartz crystal resonator of the present invention. When μ = 0, n = 1 and there is no load mass. Further, when μ is increased, n is gradually decreased, and when μ = 0.428, n = 0.82,
= 3.31 and n = 0.33. Therefore, if μ = 0.428 and f = 600 kHz is designed, at μ = 3.31, a low frequency of f = 240 kHz can be realized. In the present invention, when impact resistance and the like are taken into consideration, μ is limited to around 3.31 at maximum. at the same time,
In order to achieve further miniaturization, it is preferable to select μ from around μ = 0.428.

In the present invention, the tuning fork shape has been described, but it is needless to say that a twisted quartz oscillator having both ends free type has the same effect.

[0011]

As described above, the tuning fork-shaped twisted crystal oscillator of the present invention has the following remarkable effects. (1) 200 kHz to 600 kHz by providing the tip of the tuning fork arm with a load mass effect due to the polar moment of inertia
A low frequency of Hz can be realized in a small size. (2) Since it can be easily formed by a chemical etching method, it can be made compact and thin. 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 is 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. (5) By disposing the excitation electrodes on the front and back surfaces of the tuning fork arm, it is possible to obtain a tuning fork-shaped twisted quartz resonator having a small equivalent series resistance R ₁ and a high Q value.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape and an excitation electrode configuration of a tuning fork-shaped twisted crystal oscillator of the present invention.

FIG. 2 is a diagram showing a model shape of a tuning fork-shaped twisted crystal oscillator of the present invention.

FIG. 3 is a relationship diagram between a mass ratio μ and a constant n of the tuning fork-shaped twisted quartz crystal resonator of the present invention.

[Explanation of symbols]

1 Tuning-fork-shaped torsional crystal oscillator 2 Tuning-fork arm 3 Weight 4 Tuning-fork base 5,6 Excitation electrode x ₀ Tuning-fork arm width y ₀ Tuning-fork arm length I (x) Mass moment of inertia per unit length Im Tuning-fork tip Mass moment of inertia of the part x ', y'coordinates electrical and mechanical axes after rotation z optical axis μ mass ratio

Claims (2)

[Claims] 1. A quartz resonator which excites a torsional vibration mode by an electric field component in the y-axis direction, wherein the tip of the vibrating arm is larger than the width of the vibrating arm, and the mass polar moment of inertia is different between the vibrating arm and the tip. A twisted crystal unit characterized by being shaped. 2. The twisted quartz crystal according to claim 1, wherein the ratio μ of the mass polar moment of inertia of the tip part and the mass polar moment of inertia of the vibrating part is between 0.428 and 3.31. Oscillator.