JP2531304Y2 - SC-cut crystal unit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SC-cut crystal resonator, and more particularly to suppression of a sub-vibration mode.

[0002]

2. Description of the Related Art In general, a quartz resonator has a unique vibration characteristic according to a cutting angle with respect to a crystal axis. AT-cut quartz resonators most commonly used at frequencies from several MHZ to several tens of MHZ exhibit a cubic curve-like temperature characteristic having an inflection point near 25 ° C.

[0003] As a reference oscillator which requires a high stability frequency in measuring equipment, wireless equipment, etc., for example, an oven-type oscillator is used. In this thermostatic oven, the crystal oscillator is housed in a thermostat heated to a constant temperature of about 80 ° C., thereby removing a change in frequency due to the temperature characteristics of the crystal oscillator and stabilizing the crystal oscillator.

An SC-cut crystal resonator is known as a crystal resonator suitable for such an oscillator. The SC-cut quartz resonator has better thermal shock characteristics than the AT-cut quartz resonator, exhibits a zero temperature coefficient at a relatively high temperature of about 80 ° C., and can obtain a high Q value. Such characteristics are extremely desirable characteristics for a highly stable crystal oscillator which is used by being housed in a constant temperature bath at a constant temperature of about 80 ° C., for example.

Therefore, for example, the 34th FCS (FREQ. CONTROLS) held in May 1980
187 to 193 of the proceedings of YMPOSIUM), the fundamental mode SC cut resonator (FUNDAMEN)
TAL MODE SC-CUT RESONATOR
Various reports have been made as disclosed as S).

By the way, such an SC-cut quartz-crystal vibrator has a high-frequency side near the C-mode resonance (C in FIG. 4) which is the main vibration as shown in FIG. A sub-vibration occurs in the illustrated B) and the A mode (the illustrated A). Here, since the value of the crystal impedance (hereinafter abbreviated as CI) of the A mode vibration is larger than that of the C mode, it does not pose a particular problem. In contrast, the CI of the B mode is equal to or smaller than that of the C mode.

For this reason, when an oscillator is actually manufactured, there is a problem in that the oscillator oscillates in a sub-mode B mode. Therefore, when an SC-cut crystal resonator is used, it is necessary to suppress the B-mode vibration and make its CI larger than that of the C-mode in order to reliably excite the C-mode main vibration.

For this purpose, for example, a convex process for processing only one main surface of the crystal blank into a convex lens shape has been devised. The value of the sub-vibration in the B mode is about twice the value, and there is a problem that the sub-vibration cannot be suppressed reliably.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and can suppress the resonance of the B mode as well as the A mode, thereby reliably exciting the resonance of the C mode. It is an object of the present invention to provide an SC-cut crystal unit that can perform the above-described operations.

[0010]

According to the present invention, an SC cut is obtained by cutting a plane orthogonal to the Y axis of a crystal by about 34 ° about the X axis and then about 22 ° about the Z axis. In the double-rotating quartz resonator described above, an end portion of the plate surface rotated by 30 to 50 degrees from the Z-axis direction of the plate surface of the crystal blank is held.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the front view of a crystal unit with a cover shown in FIG. In the figure, reference numeral 1 denotes an SC-cut crystal blank. The crystal blank 1 is obtained by cutting a crystal of a crystal twice from a plane rotated by about 35 ° from the optical axis (Z axis), for example, 35 ° 56 ′, and about 22 ° from the electric axis (X axis), for example, 22 ° 56 ′. It is a rotating crystal blank.

After the crystal blank 1 is formed into a round plate or a strip having a thickness corresponding to a desired resonance frequency, a base electrode is formed at the center of both side plate surfaces by vapor deposition or the like.
The end of the plate surface in the axial direction rotated by 30 ° to 50 °, for example, 40 ° with respect to the ZZ ′ axis of the plate surface of the crystal blank 1 is held by the holding member 2. The holding member 2 is formed, for example, by fixing an end of a strip-shaped metal plate having a holding groove formed along the longitudinal direction to a tip of a pair of terminals 4 implanted in the base 3.

Then, after a frequency adjusting electrode is vapor-deposited on the base electrode of the crystal blank 1 held by the holding member 2 to accurately adjust to a desired resonance frequency, a cover (not shown) is put on the airtight sealing. In the above embodiment, a round plate-shaped crystal piece is described. However, it is needless to say that the same can be applied to a case using a strip-shaped crystal piece as shown in FIG.

That is, the graph shown in FIG. 3 shows the change in CI with respect to the rotation angle of the support position of the crystal blank from the ZZ 'axis. According to this graph, the CI of the C mode (illustrated C) has a constant value of about 80Ω regardless of the supporting position, whereas that of the B mode (illustrated B) is 200Ω to 33Ω.
It changes between 0Ω. Here, in order to surely excite the resonance of the C mode, it is desirable that the CI of the B mode is as large as possible.

Therefore, as is apparent from the graph shown in FIG. 3, the quartz piece is shifted from the ZZ ′ axis by 30 ° to 5 °.
By holding the axial end rotated by 0 °, B
The CI of the mode is larger than approximately 280Ω, which is about four times or more that of the C mode. If the CI of the B mode is set to be four times or more that of the C mode, the resonance of the B mode is suppressed and the resonance of the C mode is surely excited even in consideration of the electrical variation of the elements. Can be.
Therefore, in the present invention, Z of the plate surface of the SC-cut crystal blank is
The end of the plate surface rotated by 30 ° to 50 ° from the axial direction is held.

With such a configuration, the main vibration C
The CI of the B mode can be made four times or more larger than the CI of the mode, so that it is possible to obtain an SC-cut crystal resonator that can be reliably excited by the main vibration of the C mode. In addition, since the essential characteristics of the SC-cut quartz resonator are not lost even if the holding position of the quartz piece is limited in this way, a quartz resonator particularly suitable for a highly stable oscillator using a thermostat can be obtained. .

[0017]

[Effect of the Invention] As described in detail above, according to the present invention, A
It is possible to provide an SC-cut crystal resonator that can suppress the resonance in the mode and the B mode and can surely excite the resonance in the C mode that is the main vibration.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a front view of another embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a holding position of a crystal blank and CI.

FIG. 4 is a graph showing resonance characteristics of an SC-cut quartz resonator.

[Explanation of symbols]

 1 crystal blank 2 holding member 3 base 4 terminal

Claims (1)

(57) [Scope of request for utility model registration] 1. An SC-cut double-rotational crystal oscillator obtained by rotating a plane orthogonal to the Y-axis of a quartz crystal by about 34 ° about an X-axis and further cutting it by about 22 ° about a Z-axis. 3. The SC-cut crystal unit according to claim 1, wherein an end of the plate surface rotated by 30 to 50 degrees from the Z-axis direction of the plate surface of the crystal blank is held.