【発明の詳細な説明】[Detailed description of the invention]
本発明は、厚みすべり水晶振動子に関し、特に
輪郭対厚み寸法の比が小さい振動片を持つ水晶振
動子に関する。
水晶振動子はその小型寸法化に伴つて輪郭寸法
と厚み寸法の比が小さくなると、主振動の厚み振
動に対して輪郭振動の副振動が大きな影響を及ぼ
すようになる。更に、水晶振動片の輪郭を支持す
ることによつて主振動の厚み振動の抵抗損失を増
大させる結果となり易い。従つて、輪郭対厚み寸
法の比が小さい小形寸法の振動子の設計にあたつ
ては第一に主振動の近くに大きな副振動のない輪
郭外形寸法を設計する必要がある。更に、輪郭を
支持することによつて振動損失の増大する割合が
少ない輪郭外形にする必要がある。
従来、水晶振動子の設計にあたつては、輪郭影
響の少ない比率の振動片を用いるようにしてき
た。そして、輪郭対厚み寸法比が大きくとれない
周波数領域では振動片の外形寸法もそれ相当の大
きさを持つたものを使用し、特に小型寸法のもの
を使用することもなかつた。
しかるに腕時計用水晶振動子など振動子の小型
化要求により、従来比較的寸法の大きかつた周波
数領域（例えば1MHz〜7MHz）でも振動子の小型
化が要望されるようになり、主振動に対する副振
動の影響及び振動子の抵抗損失の増大が問題にな
つてきた。
本発明は、輪郭対厚み寸法の比が小さい水晶振
動片を使用する振動子において、輪郭の影響によ
る副振動、振動損失の少ない構造の振動子を提供
するにある。
第１図は本発明に係る水晶振動片の平面図と側
面図を示す。図示の如く、また斜視図を第２図に
示す如く、本発明に係る水晶振動片は片面から見
て四角形で側面から見て両表面が円錐台状に形成
され、くさび形状の四隅を持つ輪郭構造にされ
る。こうした構造は、目的とする周波数から決定
される厚みｔを持ち要求される外形寸法から決定
される四辺の長さａを持つ正方形板の両面からテ
ーパ削り、研磨して製作される。なお実施例では
正方形板が開示されているが、こうした正方形板
に限らず矩形板でもいい。
くさび形状にされる四隅のうち、一方の対角隅
は振動片の支持部として使用され、振動損失が少
なくなる支持にされる。また、両表面の円錐台面
に夫々蒸着、等の手段で電極が形成され、該電極
からはリード線又は電極と同じ手段で形成された
薄膜がリード線として引出される。
こうした構造の水晶振動子において、寸法、形
状によつては使用する主振動の共振周波数に一致
あるいは極めて近くに振動が生じ、それが主振動
と結合するという好ましくない特性を呈する。即
ち、輪郭寸法、円錐台面の直径ｂ、くさび形状の
曲率、厚さ寸法の比によつては多数の複雑な共振
周波数を生じる。また、水晶振動片の共振周波数
はその各寸法を変えることによつて規則的に周波
数変化があることが知られている。第３図は輪郭
寸法に対する共振周波数特性を示し、特性Ａが主
振動に相当する。また、第４図ａには輪郭形状比
が適切にあり、主振動周波数0の近傍に副振動1
のない共振特性を示し、ｂには主振動0近傍に生
じた副振動2，3に影響されることを示す。
本発明においては、第１図、第２図に示す形状
の水晶振動片において、輪郭寸法ａ、厚みｔに対
する円錐台面ｂ寸法を適切に規定することによつ
て主振動の近傍周波数帯から不要振動（副振動）
を無くした構造としている。すなわち、所要の輪
郭ａ、厚みｔ寸法を定めた矩形板から研磨加工す
るにおいて、輪郭端部での振動変位（抵抗損失）
が少なくかつ不要振動が主振動近傍に生じないｂ
寸法まで研磨加工する。円錐台平面の直径ｂの変
更は矩形外形寸法を僅かづつ変化させた場合と同
様に、共振周波数が規則的に変化することは理論
的にも説明されるし、実験上でも確認された。
本発明による水晶振動子の振動片形状を規定す
る具体的な数値は次のとおりである。すなわち、
ａ／ｔ範囲に対してａ／ｂを表に示す如き範囲内
に研磨加工する。ここで、規定される輪郭寸法ａ
とは水晶振動片のＸ軸方向についてとつたもので
あり、実施例の場合には正方形板であるためその
方向については問題はないが、矩形板の場合に
は、その一辺をＸ軸方向にとり、他の一片をＺ軸
方向にとつた時、Ｘ軸方向の輪郭寸法だけを規定
するだけでよくＺ軸方向についての輪郭寸法につ
いては、特に規定する必要はない。これにより、
副振動に影響されない主振動でかつ抵抗損失の少
ない振動片を実現できる。
The present invention relates to a thickness-shear quartz crystal resonator, and particularly to a quartz crystal resonator having a vibrating element having a small profile-to-thickness ratio. As the crystal resonator becomes smaller in size, the ratio of the contour dimension to the thickness dimension becomes smaller, and the auxiliary vibration of the contour vibration comes to have a large influence on the thickness vibration of the main vibration. Furthermore, supporting the contour of the crystal vibrating piece tends to increase the resistance loss of the thickness vibration of the main vibration. Therefore, when designing a small-sized vibrator with a small profile-to-thickness ratio, it is first necessary to design a profile without large secondary vibrations near the main vibration. Furthermore, it is necessary to provide a contoured shape in which the rate of increase in vibration loss due to supporting the contour is small. Conventionally, when designing a crystal resonator, it has been attempted to use a vibrating element with a ratio that has less influence on the contour. In a frequency range where the profile-to-thickness ratio cannot be large, a vibrating element with a correspondingly large outer dimension is used, and a particularly small one is not used. However, due to the demand for smaller oscillators such as crystal oscillators for wristwatches, there is now a demand for smaller oscillators even in the frequency range (for example, 1MHz to 7MHz), where the size was relatively large in the past. The effects of this and an increase in the resistance loss of the vibrator have become problems. An object of the present invention is to provide a vibrator that uses a crystal vibrating piece with a small profile-to-thickness ratio and has a structure that causes less secondary vibration and vibration loss due to the influence of the profile. FIG. 1 shows a plan view and a side view of a crystal vibrating piece according to the present invention. As shown in the drawings, and as shown in a perspective view in FIG. 2, the crystal vibrating piece according to the present invention has a rectangular shape when viewed from one side, a truncated cone shape on both surfaces when viewed from the side, and a contour with four wedge-shaped corners. made into a structure. Such a structure is manufactured by tapering and polishing both sides of a square plate having a thickness t determined from the desired frequency and a length a on each side determined from the required external dimensions. Although a square plate is disclosed in the embodiment, the present invention is not limited to such a square plate, and may be a rectangular plate. Among the four wedge-shaped corners, one diagonal corner is used as a support for the vibrating element, and is supported to reduce vibration loss. Further, electrodes are formed on each of the truncated conical surfaces of both surfaces by vapor deposition or the like, and a lead wire or a thin film formed by the same method as the electrode is drawn out from the electrode as a lead wire. In a crystal resonator having such a structure, depending on its size and shape, vibration occurs at a resonance frequency that coincides with or is very close to the resonance frequency of the main vibration used, and exhibits an undesirable characteristic of being coupled with the main vibration. That is, a large number of complex resonance frequencies are generated depending on the profile dimensions, the diameter b of the truncated conical surface, the curvature of the wedge shape, and the ratio of the thickness dimensions. Further, it is known that the resonant frequency of a crystal vibrating piece changes regularly by changing its dimensions. FIG. 3 shows resonance frequency characteristics with respect to contour dimensions, and characteristic A corresponds to the main vibration. In addition, in Fig. 4a, the contour shape ratio is appropriate, and the secondary vibration 1 is near the main vibration frequency 0 .
It shows resonance characteristics with no vibration, and b shows that it is affected by secondary vibrations 2 and 3 that occur near 0 of the main vibration. In the present invention, in the crystal vibrating piece having the shape shown in FIGS. 1 and 2, by appropriately specifying the contour dimension a and the truncated conical surface b dimension with respect to the thickness t, it is possible to eliminate unnecessary vibrations from the frequency band near the main vibration. (secondary vibration)
It has a structure that eliminates. In other words, when polishing a rectangular plate with the required profile a and thickness t, the vibration displacement (resistance loss) at the edge of the profile
is small and unnecessary vibrations do not occur near the main vibration b
Polish to size. It has been theoretically explained and experimentally confirmed that changing the diameter b of the truncated conical plane causes the resonance frequency to change regularly in the same way as changing the rectangular outer dimensions little by little. Specific numerical values defining the shape of the vibrating element of the crystal resonator according to the present invention are as follows. That is,
Polishing is performed so that a/b is within the range shown in the table for the a/t range. Here, the defined contour dimension a
is taken in the X-axis direction of the crystal vibrating piece, and in the case of the example, since it is a square plate, there is no problem with that direction, but in the case of a rectangular plate, one side of it is taken in the X-axis direction. , when the other piece is taken in the Z-axis direction, it is only necessary to specify the contour size in the X-axis direction, and there is no need to particularly specify the contour size in the Z-axis direction. This results in
It is possible to realize a vibrating element whose main vibration is unaffected by secondary vibrations and which has low resistance loss.
【表】
上記表におけるａ／ｔ、ａ／ｂの範囲は実験的
に求められたもので、その実験結果例を以下に示
す。
主振動の共振周波数＝3.58MHzを得るのに、
厚さｔ＝0.464mmの水晶片の寸法ａを上記表中の
条件
23.55＜ａ／ｔ＜23.88
の範囲になる1.093＜ａ＜11.08からａ＝11.00mmに
加工し、寸法ｂを種々変えた周波数スペクトラム
を第５図Ａ〜第５図Ｅに示す。同図での寸法ｂ
は、
第５図Ａ：ｂ＝11mm
第５図Ｂ：ｂ＝10mm
第５図Ｃ：ｂ＝ 9mm
第５図Ｄ：ｂ＝ 8mm
第５図Ｅ：ｂ＝ 7mm
に加工したもので、これら特性から寸法ｂとし
て、主振動の近傍に副振動が表われない範囲
6.70mm＜ｂ＜7.43mm
即ち、
1.48＜ａ／ｂ＜1.64
を得た。
表中の他の条件ａ／ｔに対するａ／ｂも同様の
実験で求められたものである。また、寸法ａと厚
さｔの比が表中の条件から外れたときに寸法ｂを
種々変えた場合の周波数スペクトラムを第６図Ａ
〜第６図Ｃに示す。同図での寸法比は、
ａ／ｔ＝12.06／1.743
の同じ条件で、寸法ｂを
第６図Ａ：ｂ＝10.5
第６図Ｂ：ｂ＝ 8.5
第６図Ｃ：ｂ＝ 5.5
とするもので、これら図からも明らかなように条
件ａ／ｔが表中の条件から外れるときには寸法ｂ
を変えるも主振動の近傍に副振動が表われる結果
を得た。
以上のとおり、本発明は輪郭対厚み寸法の比が
小さい水晶振動片において、厚みｔと輪郭ａの比
ａ／ｔに対する円錐台直径ｂを適切にすること
で、主振動に対する副振動の影響少なくかつ振動
損失の少ない振動子を実現できる効果がある。[Table] The ranges of a/t and a/b in the above table were determined experimentally, and examples of the experimental results are shown below. To obtain the main vibration resonance frequency = 3.58MHz,
Dimension a of a crystal piece with thickness t = 0.464 mm was processed from 1.093 < a < 11.08 to a = 11.00 mm, which is in the range of 23.55 < a / t < 23.88 under the conditions in the table above, and dimension b was changed variously. The spectra are shown in FIGS. 5A to 5E. Dimension b in the same figure
Figure 5 A: b = 11 mm Figure 5 B: b = 10 mm Figure 5 C: b = 9 mm Figure 5 D: b = 8 mm Figure 5 E: b = 7 mm As dimension b, we obtained the range in which the secondary vibration does not appear near the main vibration: 6.70 mm<b<7.43 mm, that is, 1.48<a/b<1.64. The a/b values for other conditions a/t in the table were also determined through similar experiments. In addition, Figure 6A shows the frequency spectrum when dimension b is variously changed when the ratio of dimension a and thickness t deviates from the conditions in the table.
- Shown in Figure 6C. The dimension ratio in the same figure is the same condition of a/t = 12.06/1.743, and the dimension b is Figure 6 A: b = 10.5 Figure 6 B: b = 8.5 Figure 6 C: b = 5.5 As is clear from these figures, when the conditions a/t deviate from the conditions in the table, the dimension b
Even when changing the oscillation, we obtained results in which sub-oscillations appeared near the main oscillation. As described above, the present invention reduces the influence of secondary vibrations on main vibrations by optimizing the truncated cone diameter b for the ratio a/t of thickness t and contour a in a crystal vibrating piece with a small ratio of profile to thickness. This also has the effect of realizing a vibrator with less vibration loss.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は本発明に係る水晶振動片の形状を示す
図、第２図は第１図の斜視図、第３図は第１図、
第２図に示す振動片における輪郭寸法に対する共
振周波数特性を示す図、第４図は主振動に対する
副振動を示す周波数スペクトラム。第５図及び第
６図は本発明の条件を得るためにした実験結果の
周波数スペクトラムである。
FIG. 1 is a diagram showing the shape of a crystal vibrating piece according to the present invention, FIG. 2 is a perspective view of FIG. 1, FIG.
FIG. 2 is a diagram showing resonance frequency characteristics with respect to contour dimensions in the vibrating element, and FIG. 4 is a frequency spectrum showing sub-vibrations with respect to main vibrations. FIGS. 5 and 6 are frequency spectra of experimental results conducted to obtain the conditions of the present invention.