JPS6157823A - Piezoelectric sensor - Google Patents
Piezoelectric sensorInfo
- Publication number
- JPS6157823A JPS6157823A JP18111884A JP18111884A JPS6157823A JP S6157823 A JPS6157823 A JP S6157823A JP 18111884 A JP18111884 A JP 18111884A JP 18111884 A JP18111884 A JP 18111884A JP S6157823 A JPS6157823 A JP S6157823A
- Authority
- JP
- Japan
- Prior art keywords
- oscillation
- external force
- piezoelectric
- piezoelectric sensor
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000013078 crystal Substances 0.000 claims abstract description 13
- 230000010355 oscillation Effects 0.000 abstract description 18
- 239000000758 substrate Substances 0.000 abstract 2
- 238000010586 diagram Methods 0.000 description 9
- 230000035945 sensitivity Effects 0.000 description 8
- 239000000919 ceramic Substances 0.000 description 3
- 230000008602 contraction Effects 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000009347 mechanical transmission Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
- G01L1/162—Measuring force or stress, in general using properties of piezoelectric devices using piezoelectric resonators
Abstract
Description
【発明の詳細な説明】
（発明の技術分野）
本発明は、外部圧力を振動周波数の変化量として検出す
る圧電センサに係り、特に圧力感度が良好で、温度変化
による振動周波数の変化量を補償し、外部圧力にのみ感
応する圧電センサに係るものである。Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to a piezoelectric sensor that detects external pressure as a change in vibration frequency, and has particularly good pressure sensitivity and can compensate for changes in vibration frequency due to temperature changes. However, it relates to a piezoelectric sensor that is sensitive only to external pressure.
（発明の技術背景）
従来より、圧力を加えると電荷が発生する圧電現象を利
用したものとして、例えば水晶振動子がよく知られてお
り、通信機器を主とした電子機器に発振子やフィルタ素
子として有用されてきた。(Technical Background of the Invention) Crystal resonators, for example, have been well known as devices that utilize the piezoelectric phenomenon in which electric charges are generated when pressure is applied. It has been useful as a.
そして、一方では、各種測定器のデジタル表示化が進行
する中にあって、この圧電現象を利用した圧電センサが
俄に注目を浴びている。例えば被測定体の重量を、圧電
板に発生した電荷により計測する試みは旧来よりなされ
ていたものである。しかし、この試みは、被測定体によ
り発生する電荷量が極めて乏しく、その電荷が瞬時にし
て消失してしまうので、現実にはこの方式の圧電センサ
は普及するに至っていない。このため、例えば圧電板を
発振子として使用し、外力によりその共振周波数が変化
することに着目した圧電センサの開発研究がなされてい
る。第２図は、この圧電センサを使用した圧力センサシ
ステムを示す簡単なブロック図で、１は被測定体、２は
圧カセンザの発振子として使用される圧電板、３は発振
回路、４は演算回路、５はデジタル表示器である。従っ
て、この圧力センサシステムによれば、図示しない機械
伝達系により、被測定体１の重量Ｐが圧電板２に外力に
よるひずみを発生させて共振条件を変動させ、発振回路
３の予め設定された出力周波数ｆＯがｆＯからｆ］に変
化することを利用し、振動周波数差ｆｉ −ｆＯを演算
回路４にて検出し重量値に換算して、表示器５に被測定
体の重量をデジタル値として表示するものである。On the other hand, as the digital display of various measuring instruments progresses, piezoelectric sensors that utilize this piezoelectric phenomenon are suddenly attracting attention. For example, attempts have been made in the past to measure the weight of an object to be measured using electric charges generated on a piezoelectric plate. However, in this attempt, the amount of charge generated by the object to be measured is extremely small, and the charge disappears instantly, so in reality, piezoelectric sensors of this type have not become widespread. For this reason, research and development are being conducted on the development of piezoelectric sensors that use, for example, a piezoelectric plate as an oscillator and focus on the fact that its resonance frequency changes with external force. Figure 2 is a simple block diagram showing a pressure sensor system using this piezoelectric sensor, where 1 is the object to be measured, 2 is the piezoelectric plate used as the oscillator of the piezoelectric sensor, 3 is the oscillation circuit, and 4 is the calculation The circuit 5 is a digital display. Therefore, according to this pressure sensor system, the weight P of the object to be measured 1 generates a strain on the piezoelectric plate 2 due to an external force by a mechanical transmission system (not shown), thereby changing the resonance condition, and changing the preset value of the oscillation circuit 3. Utilizing the fact that the output frequency fO changes from fO to f], the arithmetic circuit 4 detects the vibration frequency difference fi -fO, converts it into a weight value, and displays the weight of the object to be measured as a digital value on the display 5. It is to be displayed.
（従来技術の問題点）
」二記圧カセンサシステムに使用される圧力センサ用の
圧電板２としては、電気−機械結合係数が大きく、微圧
に感応して良好な圧力感度が得られるものとして、通常
多結晶体の圧電セラミックス：１ が使用されてい
る。しかし、この圧電セラミックスは、温度に対して共
振周波数が著しく変化し、周囲温度の変化により測定値
が一定でなくなる問題がある。一方、温度−周波数特性
（以下、単に温度特性と称する。）が圧電セラミックス
に比Ｌ１より優れた三次曲線を呈するＡＴカットの水晶
板を圧力センサ用として使用する場合にはその電気−機
械結合係数が小さく圧力感度が低下してしまう欠点があ
る。例えば温度による共振周波数の変化を防止するもの
としては、特開昭５４−２０７８０号に開示されている
ように、同一特性の水晶板を２つ使用し一方を圧カセン
ザ用に他方をダミー用としてそれぞれ発振させ、その出
力周波数差を検出して温度特性による測定誤差を防１１
−するようにしたものがある。しかし、この圧電センサ
では、水晶板を２枚要することζこ加え、同公報中に記
載されている通り２つの水晶板を全く同一の温度特性と
することは困難である。更に、長方形状の水晶片の長手
方向の両端を保持しているため、測定すべき外力が長手
方向中央部振動部に到達しにくく圧力感度の」１昇が望
めない欠点がある。(Problems with the Prior Art) The piezoelectric plate 2 for the pressure sensor used in the two-note pressure sensor system has a large electro-mechanical coupling coefficient and can respond to minute pressures to provide good pressure sensitivity. , polycrystalline piezoelectric ceramics: 1 are usually used. However, this piezoelectric ceramic has a problem in that the resonant frequency changes significantly with temperature, and the measured value becomes unstable due to changes in ambient temperature. On the other hand, when an AT-cut crystal plate whose temperature-frequency characteristics (hereinafter simply referred to as temperature characteristics) exhibits a cubic curve superior to the ratio L1 of piezoelectric ceramics is used for a pressure sensor, its electro-mechanical coupling coefficient The disadvantage is that the pressure sensitivity is reduced due to the small amount of pressure. For example, to prevent the resonance frequency from changing due to temperature, as disclosed in Japanese Patent Laid-Open No. 54-20780, two crystal plates with the same characteristics are used, one for the pressure sensor and the other for the dummy. oscillate each and detect the output frequency difference to prevent measurement errors due to temperature characteristics11
- There is something that was designed to do so. However, in addition to the fact that this piezoelectric sensor requires two crystal plates, it is difficult to make the two crystal plates have exactly the same temperature characteristics as described in the publication. Furthermore, since both longitudinal ends of the rectangular crystal piece are held, it is difficult for the external force to be measured to reach the vibrating part at the central part in the longitudinal direction, making it impossible to expect an increase in pressure sensitivity.
（発明の目的）
本発明は圧力感度が良好で、圧電板の温度特性による振
動周波数の変化分をキャンセルして外力のみに感応した
変化分を検出できる圧電センサを提供することを目的と
する。(Objective of the Invention) An object of the present invention is to provide a piezoelectric sensor that has good pressure sensitivity and can cancel changes in vibration frequency due to temperature characteristics of a piezoelectric plate and detect changes in response only to external force.
（発明の解決手段）
外力に対し振動周波数が互いに反対方向に変化する第１
と第２との振動部を、厚み系の振動が励起される同一圧
電板に形成し、前記第１と第２との振動周波数差を検出
するようにした点にある。(Solution Means of the Invention) The first vibration frequency changes in opposite directions in response to an external force.
The second vibrating section is formed on the same piezoelectric plate that excites thickness-related vibrations, and the difference in vibration frequency between the first and second vibrating sections is detected.
（発明の実施例） 以下、図により本発明の一実施例を説明する。(Example of the invention) Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.
第１図は本発明の圧電センサの図で、この圧電センサは
、圧電板を厚みすべり振動が励起され、その温度特性が
第３図の符号（ａ）にて示す三次曲線となるＡＴカット
形の水晶片６とし、座標軸Ｘ。FIG. 1 is a diagram of a piezoelectric sensor of the present invention. This piezoelectric sensor is an AT-cut type in which thickness-shear vibration is excited in a piezoelectric plate, and its temperature characteristic becomes a cubic curve as shown by the symbol (a) in FIG. The crystal piece 6 is the coordinate axis X.
Ｙ’、Ｚ’のｘ−ｚ’而を主面とするＺ′力方向両端部
両主面にそれぞれ対をなす電極７（７ａ、７ｂ）と８（
８ａ 、８ｂ）を形成し、それぞれ第１の振動部、第２
の振動部としたものである。そして、この水晶片６は、
その振動周波数が大略決定される厚み即ちＹ′方向を一
定として略正方形状に加工され、電極７．８はそれぞれ
厚みすべり振動の主振動が励起されるＸ軸方向に長く形
成されている。Pairs of electrodes 7 (7a, 7b) and 8 (
8a and 8b), respectively.
This is the vibrating part of the And this crystal piece 6 is
The electrodes 7 and 8 are formed into a substantially square shape with a constant thickness, that is, the Y' direction, where the vibration frequency is roughly determined, and the electrodes 7 and 8 are each formed long in the X-axis direction, where the main vibration of the thickness shear vibration is excited.
従って、第１と第２との振動部は同一の水晶片６に形成
されているので、その温度特性は前述した符号（ａ）で
示す同一の三次曲線となり、又その振動周波数は、Ｙ′
軸方向の厚みが一定なので、同一の振動周波数ｆＯにて
振動する。Therefore, since the first and second vibrating parts are formed on the same crystal blank 6, their temperature characteristics become the same cubic curve indicated by the above-mentioned symbol (a), and their vibration frequency is Y'
Since the thickness in the axial direction is constant, they vibrate at the same vibration frequency fO.
以下、このｔｌり成の圧電センサの作用及び効果につい
て説明する。The operation and effects of this tl-based piezoelectric sensor will be explained below.
今、例えば、この圧電センサにおいて第１図の矢印で示
す外力Ｑが、水晶片６の第１の振動部の両側即ちｙ’−
ｚ面に加わったとすると、第１の振動部には外力Ｑと同
方向の縮み力ｑ１が作用し、第２の振動部には外力Ｑと
反対方向の伸張力ｑ２が作用する。従って、第１の振動
部には縮み力ｑ１によりひずみを発生し、その振動周波
数がｆＯから例えばｆＯより高いｆ＋１に変化し、第２
の振動部には伸張力ｑ２によりその振動周波数がｆＯか
ら第１の振動部とは反対にｆＯより低いｆ−１に変化す
る。従って、外力Ｑが加わらないときの第１と第２との
振動部の振動周波数差は零なので、外力Ｑが加わったと
きの第１と第２との振動周波数差ｆ＋１−ｆ−１を検出
することにより、外力Ｑの値を測定できる。加えて、そ
の振動周波数ｆ＋１−ｆ−１は基準の振動周波数差ｆＯ
との差△ｆ ＝ ｆ ＋ １． （又はｆ−１）−ｆｏ
を検出するよりも略２倍の振動周波数差２△ｆを検出で
きるので、その圧力感度は良好なものとなる。更に、外
力Ｑが加わったときの第１と第２との振動部の温度特性
は第３図の曲線（ｂ） 、 （Ｃ）で示すように、外力
Ｑが加わらないときの符号（ａ）で示した三次曲線を中
心として、それぞれ上下に平行な三次曲線となる。従っ
て、温度変化があったとしても、外力Ｑは、第１と第２
との振動周波数差ｆ＋１−ｆ−１として検出されるので
、外力Ｑの値は温度変化に左右されず一定の値を得るこ
とができる。第４図は、この圧電センサを使用した圧力
センサシステムの一例を示すブロック図で、１０は被測
定体、１］はこの圧電センサを適用した圧力センサ、１
２は第１の振動部と接続した発振回路、］３は第２の振
動部と接続した第２の発振回路、］４はミキサ、１５は
演算回路、１６はデジタル表示器である。従って、この
圧力センサシステムによれば、ミキサ１４により被測定
体の重量値を第１と第２との発振回路の出力周波数差と
して同一時に検出できるので、温度変化による振動周波
数差は常時一定で、演算回路１５により振動周波数差を
重量値に換算して表示器１６にてデジタル値として表示
できる。従って、この圧力センサシステムに使用される
圧電センサは、例えば刻時その外力が変化する加速度計
等の測定器には最適なものとなる。Now, for example, in this piezoelectric sensor, the external force Q shown by the arrow in FIG.
When applied to the z-plane, a contraction force q1 in the same direction as the external force Q acts on the first vibrating part, and a stretching force q2 in the opposite direction to the external force Q acts on the second vibrating part. Therefore, strain is generated in the first vibrating part due to the contraction force q1, and the vibration frequency changes from fO to f+1, which is higher than fO, and the second vibrating part
Due to the stretching force q2, the vibration frequency of the vibrating part changes from fO to f-1, which is lower than fO, contrary to the first vibrating part. Therefore, since the vibration frequency difference between the first and second vibrating parts when no external force Q is applied is zero, the vibration frequency difference f+1-f-1 between the first and second vibrating parts when external force Q is applied is detected. By doing so, the value of external force Q can be measured. In addition, the vibration frequency f+1-f-1 is the reference vibration frequency difference fO
Difference △f = f + 1. (or f-1)-fo
Since it is possible to detect a vibration frequency difference 2Δf which is approximately twice as large as when detecting the vibration frequency difference 2Δf, the pressure sensitivity is good. Furthermore, the temperature characteristics of the first and second vibrating parts when external force Q is applied are as shown by curves (b) and (C) in Fig. 3, and when external force Q is not applied, the temperature characteristics are sign (a). Centering on the cubic curve shown in , the cubic curves are vertically parallel to each other. Therefore, even if there is a temperature change, the external force Q
Since it is detected as the vibration frequency difference f+1-f-1 between the external force Q and the external force Q, a constant value can be obtained without being affected by temperature changes. FIG. 4 is a block diagram showing an example of a pressure sensor system using this piezoelectric sensor, in which 10 is an object to be measured, 1] is a pressure sensor to which this piezoelectric sensor is applied, 1
Reference numeral 2 is an oscillation circuit connected to the first vibrating section, ]3 is a second oscillation circuit connected to the second vibrating section, ]4 is a mixer, 15 is an arithmetic circuit, and 16 is a digital display. Therefore, according to this pressure sensor system, the weight value of the object to be measured can be detected at the same time by the mixer 14 as the output frequency difference between the first and second oscillation circuits, so the vibration frequency difference due to temperature change is always constant. The arithmetic circuit 15 converts the vibration frequency difference into a weight value, which can be displayed as a digital value on the display 16. Therefore, the piezoelectric sensor used in this pressure sensor system is ideal for measuring instruments such as accelerometers in which the external force of time changes, for example.
（発明の他の実施例）
第５図は本発明の他の実施例図で、この実施例による圧
電センサは、水晶片６の第１と第２との振動部の間に両
主面を貫通するスリット９を形成し、このスリット９に
より第１と第２との振動部を機械的に分離し、互いの振
動に影響を及ぼさずその圧力感度を高めようとしたもの
である。尚、この実施例にては、スリット９を第１と第
２との振動部の１箇所に形成したが、例えば第５図（ｂ
）に示すように複数個のスリット９を形成してもよく、
要は第１と第２との振動部との機械的振動が互いに干渉
しないように、かつ第１と第２との振動部とが外力によ
りひずみを発生し易いように形成されてあればよい。(Other Embodiments of the Invention) FIG. 5 is a diagram showing another embodiment of the present invention, in which a piezoelectric sensor according to this embodiment has both main surfaces between the first and second vibrating parts of the crystal piece 6. A penetrating slit 9 is formed, and the slit 9 mechanically separates the first and second vibrating parts, thereby increasing their pressure sensitivity without affecting each other's vibrations. In this embodiment, the slit 9 is formed at one location of the first and second vibrating parts, but for example, as shown in FIG.
), a plurality of slits 9 may be formed,
In short, it is sufficient that the mechanical vibrations of the first and second vibrating parts do not interfere with each other, and that the first and second vibrating parts are formed so that they are likely to be strained by external force. .
尚、上述したいずれの実施例においても、水晶片の形状
を略正方形として説明したが、その形状は円形状、長方
形状あるいはそれらの変形でもよく、本発明の趣旨を逸
脱しない範囲で任意に変更できるものである。In each of the embodiments described above, the shape of the crystal piece is described as being approximately square, but the shape may be circular, rectangular, or a modification thereof, and may be arbitrarily changed without departing from the spirit of the present invention. It is possible.
（発明の効果）
以」二により、本発明は圧力感度が良好で、圧電板の温
度特性による振動周波数の変化分をキャンセルして外力
のみに感応した振動周波数の変化分を検出できる圧電セ
ンサを提供できる。(Effects of the Invention) Based on the above, the present invention provides a piezoelectric sensor that has good pressure sensitivity and can cancel the change in vibration frequency due to the temperature characteristics of the piezoelectric plate and detect the change in vibration frequency that is sensitive only to external force. Can be provided.
第１図は本発明の圧電センサの図である。第２図は圧力
センサシステムの一例を示すブロック図、第３図は本発
明の圧電センサの温度特性を示す図、第４図は本発明の
圧電センサを使用した圧力センすのブロック図、第５図
は本発明の圧電センサの他の実施例図である。FIG. 1 is a diagram of a piezoelectric sensor of the present invention. FIG. 2 is a block diagram showing an example of a pressure sensor system, FIG. 3 is a diagram showing temperature characteristics of the piezoelectric sensor of the present invention, FIG. 4 is a block diagram of a pressure sensor using the piezoelectric sensor of the present invention, and FIG. FIG. 5 is a diagram showing another embodiment of the piezoelectric sensor of the present invention.
Claims (3)
に対し振動周波数が互いに反対方向に変化する第１と第
２との振動部を形成し、前記第１と第２との振動周波数
差を検出するようにしたことを特徴とする圧電センサ。(1) First and second vibrating parts whose vibration frequencies change in opposite directions in response to an external force are formed on the same piezoelectric plate where thickness-based vibrations are excited, and the first and second vibrating parts are A piezoelectric sensor characterized by detecting a vibration frequency difference.
電板は前記第１と第２との振動部との間に両主面を貫通
するスリットが形成されてあることを特徴とする圧電セ
ンサ。(2) In the first claim, the piezoelectric plate is characterized in that a slit passing through both main surfaces is formed between the first and second vibrating parts. Piezoelectric sensor.
電板は厚みすべり振動が励起される水晶片としたことを
特徴とする圧電センサ。(3) A piezoelectric sensor according to claim 1, wherein the piezoelectric plate is a crystal piece that excites thickness shear vibration.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18111884A JPS6157823A (en) | 1984-08-30 | 1984-08-30 | Piezoelectric sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18111884A JPS6157823A (en) | 1984-08-30 | 1984-08-30 | Piezoelectric sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS6157823A true JPS6157823A (en) | 1986-03-24 |
Family
ID=16095162
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18111884A Pending JPS6157823A (en) | 1984-08-30 | 1984-08-30 | Piezoelectric sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6157823A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011164042A (en) * | 2010-02-15 | 2011-08-25 | Panasonic Corp | Physical quantity sensor |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5720635B2 (en) * | 1974-09-26 | 1982-04-30 |
-
1984
- 1984-08-30 JP JP18111884A patent/JPS6157823A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5720635B2 (en) * | 1974-09-26 | 1982-04-30 |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011164042A (en) * | 2010-02-15 | 2011-08-25 | Panasonic Corp | Physical quantity sensor |
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