JP3148940B2 - Acceleration sensor - Google Patents
Acceleration sensorInfo
- Publication number
- JP3148940B2 JP3148940B2 JP3771392A JP3771392A JP3148940B2 JP 3148940 B2 JP3148940 B2 JP 3148940B2 JP 3771392 A JP3771392 A JP 3771392A JP 3771392 A JP3771392 A JP 3771392A JP 3148940 B2 JP3148940 B2 JP 3148940B2
- Authority
- JP
- Japan
- Prior art keywords
- piezoelectric element
- acceleration sensor
- electrode
- output
- self
- 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.)
- Expired - Fee Related
Links
Landscapes
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
- Air Bags (AREA)
Description
【０００１】[0001]
【利用される産業分野】本発明は、自動車の衝突時の安
全確保のために用いられるエアバックシステムや悪路に
おける乗り心地の改善などに用いられるサスペンション
制御装置に適する加速度センサに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor suitable for an airbag system used for ensuring safety in the event of an automobile collision and a suspension control device used for improving riding comfort on a rough road.
【０００２】[0002]
【従来の技術】従来から加速度の検出には種々の方式の
ものが実用化されている。その中でも圧電セラミックス
を用いた加速度センサは構造が簡単で、高温での使用が
可能であることから、各種機械の振動検出および自動車
のエンジンのノッキング検出などに広く使用されてい
る。2. Description of the Related Art Conventionally, various types of acceleration detection have been put to practical use. Among them, an acceleration sensor using piezoelectric ceramics has a simple structure and can be used at a high temperature, and thus is widely used for detecting vibration of various machines and detecting knocking of an automobile engine.
【０００３】図２は、従来の圧電方式の加速度センサの
圧電素子を示す斜視図である。図２において、圧電素子
２０は、略円柱形を呈し、一端面に形成された出力電極
２１と、他端面に形成されたアース電極２３とを有す
る。圧電素子２０は、略円柱の軸方向に振動すると、圧
電素子には、力Ｆ＝ｋ１×α（ｋ１は比例定数、αは加
速度）が作用し、出力電極２１−アース電極２３間に
は、電圧Ｖ＝ｋ２×Ｆ（ｋ２は比例定数）が発生する。
即ち、圧電素子の出力電極に発生する電圧は加速度に比
例する。FIG. 2 is a perspective view showing a piezoelectric element of a conventional piezoelectric acceleration sensor. 2, the piezoelectric element 20 has a substantially cylindrical shape, and has an output electrode 21 formed on one end face and an earth electrode 23 formed on the other end face. When the piezoelectric element 20 vibrates in the axial direction of a substantially column, a force F = k1 × α (k1 is a proportional constant, α is an acceleration) acts on the piezoelectric element, and between the output electrode 21 and the ground electrode 23, A voltage V = k2 × F (k2 is a proportional constant) is generated.
That is, the voltage generated at the output electrode of the piezoelectric element is proportional to the acceleration.
【０００４】ところで、前述した圧電素子２０を用いた
加速度センサをエアバック等の安全装置に搭載した場
合、加速度センサの故障や信号処理回路の断線等の有無
を診断する必要がある。従来の主な診断手段を２通り以
下に示す。When an acceleration sensor using the above-described piezoelectric element 20 is mounted on a safety device such as an airbag, it is necessary to diagnose the failure of the acceleration sensor and the disconnection of the signal processing circuit. Two main conventional diagnostic means are shown below.
【０００５】圧電素子２０に機械的振動を印加し、加
速度センサの出力信号を得て、その出力信号が該機械的
振動量相当の信号を出力しているか否かを診断回路（図
示せず）等により判断する。[0005] A mechanical vibration is applied to the piezoelectric element 20, an output signal of the acceleration sensor is obtained, and a diagnostic circuit (not shown) determines whether or not the output signal outputs a signal corresponding to the mechanical vibration amount. Judge by such as.
【０００６】圧電素子に予め駆動用電極（図示せず）
を設け、この駆動用電極にパルス信号を入力し（他励発
振）、加速度センサを他励発振させて加速度センサの出
力信号を得て、その出力信号が該パルス信号値相当の信
号を出力しているか否かを診断回路（図示せず）等によ
り判断する。A driving electrode (not shown) is previously provided on the piezoelectric element.
A pulse signal is input to the driving electrode (separate excitation oscillation), the acceleration sensor is separately excited to obtain an output signal of the acceleration sensor, and the output signal is a signal corresponding to the pulse signal value. Is determined by a diagnostic circuit (not shown) or the like.
【０００７】[0007]
【発明が解決しようとする課題】しかし、前述した診断
手段においては、機械的振動を印加するための駆動系
（発振器、増幅器、振動台）が必要となり、即ち、比較
的複雑な構成となり、実装スペースの大型化やコスト増
加を招くという問題点がある。他方、診断手段におい
ては、圧電素子の共振周波数近傍以外では、圧電素子は
ほとんど他励発振されず、加速度センサの出力信号値は
小さくなるため診断回路による診断時にノイズ等の影響
を受けやすく誤動作の恐れがあるという問題点がある。
さらに、共振周波数での他励発振については、圧電素子
の共振周波数の個々のばらつきや特性変化（温度等によ
る環境変化）により、該パルス信号の駆動周波数を加速
度センサ個々に調整しなければならない等の問題点があ
る。However, the above-mentioned diagnostic means requires a drive system (oscillator, amplifier, shaking table) for applying mechanical vibration, that is, a relatively complicated structure, There is a problem that the space is increased and the cost is increased. On the other hand, in the diagnosing means, except for the vicinity of the resonance frequency of the piezoelectric element, the piezoelectric element hardly oscillates separately, and the output signal value of the acceleration sensor becomes small. There is a problem that there is fear.
Further, with respect to the separately excited oscillation at the resonance frequency, the drive frequency of the pulse signal must be adjusted for each acceleration sensor due to individual variations and characteristic changes (environmental changes due to temperature, etc.) of the resonance frequency of the piezoelectric element. There is a problem.
【０００８】本発明の課題は、比較的簡素な構成で加速
度センサの検出可能状態か否かを判断できる自己診断を
行える加速度センサを提供することである。An object of the present invention is to provide an acceleration sensor capable of performing a self-diagnosis with a relatively simple configuration capable of determining whether or not the acceleration sensor can be detected.
【０００９】[0009]
【課題を解決するための手段】本発明によれば、圧電素
子と、該圧電素子の一端面に備えられた出力電極とを有
し、前記圧電素子は、その軸方向に印加される加速度に
基づいて、前記出力電極に、加速度信号を出力する加速
度センサにおいて、前記圧電素子の前記一端面に備えら
れた入力電極と、該入力電極へ、前記圧電素子を自励さ
せるための自励信号を出力する自励発振器とを有するこ
とを特徴とする加速度センサが得られる。According to the present invention, there is provided a piezoelectric element and an output electrode provided on one end surface of the piezoelectric element, wherein the piezoelectric element responds to an acceleration applied in an axial direction thereof. Based on the output electrode, in an acceleration sensor that outputs an acceleration signal, an input electrode provided on the one end surface of the piezoelectric element, and a self-excited signal for self-exciting the piezoelectric element to the input electrode. An acceleration sensor characterized by having a self-excited oscillator for outputting is obtained.
【００１０】即ち、本発明は、上記目的を達成するため
に、出力電極とアース電極を有する圧電素子からなる加
速度センサ、もしくは前記出力電極からの出力信号を電
荷増幅等を行う信号処理回路を設けた加速度センサにお
いて、前記圧電素子と同一の圧電素子上に入力電極を形
成し、かつ、入力電極とアース電極間の圧電特性を利用
した自励発振器を設ける。That is, in order to achieve the above object, the present invention provides an acceleration sensor comprising a piezoelectric element having an output electrode and a ground electrode, or a signal processing circuit for amplifying an output signal from the output electrode, such as charge amplification. In the acceleration sensor, an input electrode is formed on the same piezoelectric element as the piezoelectric element, and a self-excited oscillator utilizing piezoelectric characteristics between the input electrode and the ground electrode is provided.
【００１１】[0011]
【作用】一般に、圧電素子の一対の電極間（例えば、図
１における出力電極１１−アース電極１３間）は、その
共振周波数の近傍において近似的に、図３に示すよう
に、並列等価容量Ｃ0 、等価質量Ｌ、等価コンプライア
ンスＣ、等価抵抗Ｒの諸特性（諸定数）で表わされる。
本発明においては、圧電素子に入力電極を形成し、入力
電極−アース電極間の圧電諸特性を利用した自励発振器
を設けることにより、所定の状態に入力電極−アース電
極間を自励発振させ圧電素子を自励発振させ、出力電極
から前記自励発振量相当の出力電圧を発生させる。つま
り、自励発振によりその相当量の出力信号が得られるた
め、素子の破損、電極の剥がれ、断線等といった圧電素
子の故障や信号処理回路の断線の有無を診断できる。In general, between a pair of electrodes of a piezoelectric element (for example, between the output electrode 11 and the ground electrode 13 in FIG. 1), as shown in FIG. 0 , equivalent mass L, equivalent compliance C, and equivalent resistance R (various constants).
In the present invention, the input electrode is formed on the piezoelectric element, and a self-excited oscillator utilizing various piezoelectric characteristics between the input electrode and the ground electrode is provided, whereby the self-excited oscillation between the input electrode and the ground electrode is performed in a predetermined state. The piezoelectric element self-oscillates, and an output voltage corresponding to the self-oscillation amount is generated from the output electrode. That is, since a considerable amount of output signal is obtained by self-excited oscillation, it is possible to diagnose the failure of the piezoelectric element such as the damage of the element, the peeling of the electrode and the disconnection, and the presence or absence of the disconnection of the signal processing circuit.
【００１２】[0012]
【実施例】以下、図面を参照して本発明の一実施例によ
る加速度センサを説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An acceleration sensor according to an embodiment of the present invention will be described below with reference to the drawings.
【００１３】図１は、本実施例による加速度センサを示
す図、即ち、圧電素子の斜視図および信号処理回路図で
ある。図１において、本実施例による加速度センサは、
略円柱形を呈する圧電素子１０と、圧電素子１０に接続
された信号処理回路３０とを有する。圧電素子１０は、
その上面に円形に形成された出力電極１１と、出力電極
１１と同じ面に環状形に形成された入力電極１２と、下
面に形成されたアース電極１３とを有する。FIG. 1 is a diagram showing an acceleration sensor according to this embodiment, that is, a perspective view of a piezoelectric element and a signal processing circuit diagram. In FIG. 1, the acceleration sensor according to the present embodiment
The piezoelectric element 10 has a substantially cylindrical shape, and a signal processing circuit 30 connected to the piezoelectric element 10. The piezoelectric element 10
It has an output electrode 11 formed in a circular shape on its upper surface, an input electrode 12 formed in an annular shape on the same surface as the output electrode 11, and an earth electrode 13 formed on its lower surface.
【００１４】信号処理回路３０は、圧電素子１０の出力
電極１１に接続された電荷増幅器３１と、電荷増幅器３
１に接続され、出力端子３５を備える出力調整部３２
と、圧電素子の入力電極１２に接続され、入力端子３４
を備える自励発振器３３とを有する。尚、入力電極１２
は、自励発振器３３内のトランジスタ４０のベースに接
続されている。また、自励発振器３３内の抵抗等の定数
は、入力電極１２−アース電極１３間の圧電諸特性（諸
定数）を考慮し自励発振可能なように設定されている。The signal processing circuit 30 includes a charge amplifier 31 connected to the output electrode 11 of the piezoelectric element 10 and a charge amplifier 3
1 and an output adjusting unit 32 having an output terminal 35
And the input terminal 34 connected to the input electrode 12 of the piezoelectric element.
And a self-excited oscillator 33 having The input electrode 12
Is connected to the base of the transistor 40 in the self-excited oscillator 33. The constants such as the resistance in the self-excited oscillator 33 are set so that self-oscillation can be performed in consideration of various piezoelectric characteristics (various constants) between the input electrode 12 and the ground electrode 13.
【００１５】次に、本実施例による加速度センサの動作
について説明する。いま、出力電極１１とアース電極１
３の方向（圧電素子１０の円環方向）に加速度が加わる
と、圧電素子１０内部では圧縮力もしくは引張力が作用
し、出力電極１１には電圧（電荷）が発生し、電荷増幅
器３１によりインピーダンス変換を行い、出力調整部３
２により出力調整し所定の出力を得る。つまり、前述し
たように加速度に比例した出力が得られる。Next, the operation of the acceleration sensor according to this embodiment will be described. Now, the output electrode 11 and the ground electrode 1
When acceleration is applied in the direction of 3 (circular direction of the piezoelectric element 10), a compressive force or a tensile force acts inside the piezoelectric element 10, and a voltage (charge) is generated on the output electrode 11. Performs the conversion, and the output adjustment unit 3
2, the output is adjusted to obtain a predetermined output. That is, an output proportional to the acceleration is obtained as described above.
【００１６】さらに、本加速度センサの診断動作につい
て説明する。いま、加速度センサに加速度が印加されて
いない時、例えば自動車の運転開始前などに、自励発振
器３３の入力端子３４にある一定電圧を印加し、入力電
極１２−アース電極１３間と自励発振器３３によって圧
電素子１０が自励発振することにより、出力電極１１に
は、その相当量の出力信号（電圧）が出力端子３５より
出力される。ここで、圧電素子１０の故障（素子の破
損、電極の剥離、断線等）が生じた場合、出力信号（電
圧）が変化し、また、信号処理回路３０の故障（結線の
断線、機能劣下等）が生じた場合でも出力端子３５から
の出力値が変化する。つまり、圧電素子１０および信号
処理回路３０の故障や異常があれば、加速度センサの出
力電圧は異常な値を示すためその異常を検知することが
出来自己診断が可能である。Further, a diagnostic operation of the present acceleration sensor will be described. Now, when no acceleration is applied to the acceleration sensor, for example, before the start of driving of the automobile, a constant voltage is applied to the input terminal 34 of the self-excited oscillator 33, and the self-excited oscillator is connected between the input electrode 12 and the ground electrode 13. The self-oscillation of the piezoelectric element 10 by 33 causes the output terminal 11 to output a considerable amount of output signal (voltage) to the output electrode 11. Here, when a failure of the piezoelectric element 10 (breakage of the element, peeling of the electrode, disconnection, etc.) occurs, the output signal (voltage) changes, and failure of the signal processing circuit 30 (disconnection of the connection, functional deterioration). ) Occurs, the output value from the output terminal 35 changes. That is, if there is a failure or abnormality in the piezoelectric element 10 and the signal processing circuit 30, the output voltage of the acceleration sensor indicates an abnormal value, so that the abnormality can be detected and self-diagnosis is possible.
【００１７】[0017]
【発明の効果】本発明による加速度センサは、圧電素子
の出力電極の備えられた一端面に備えられた入力電極
と、該入力電極へ、前記圧電素子を自励させるための自
励信号を出力する自励発振器とを有するため、機械的振
動を印加するための駆動系が不要となり、省スペースか
つ低コストで加速度センサの自己診断を行える。According to the acceleration sensor of the present invention, an input electrode provided on one end face provided with an output electrode of a piezoelectric element and a self-excitation signal for self-exciting the piezoelectric element are output to the input electrode. Since a self-excited oscillator is provided, a drive system for applying mechanical vibration is not required, and the self-diagnosis of the acceleration sensor can be performed at a small space and at low cost.
【００１８】また、圧電素子の共振周波数や、環境ノイ
ズ等の影響にかかわらず、誤動作のない確実な自己診断
が行える。さらに、自己診断に際し、圧電素子の共振周
波数の個々のばらつきや特性変化（温度等による環境変
化）により、該パルス信号の駆動周波数を加速度センサ
個々に調整する必要がない。Further, irrespective of the influence of the resonance frequency of the piezoelectric element, environmental noise, etc., a reliable self-diagnosis without malfunction can be performed. Further, at the time of the self-diagnosis, it is not necessary to adjust the drive frequency of the pulse signal for each acceleration sensor due to individual variations and characteristic changes (environmental changes due to temperature or the like) of the resonance frequency of the piezoelectric element.
【図１】本発明の一実施例による加速度センサに用いる
圧電素子の斜視図および信号処理回路図である。FIG. 1 is a perspective view and a signal processing circuit diagram of a piezoelectric element used in an acceleration sensor according to an embodiment of the present invention.
【図２】従来の加速度センサに用いる圧電素子の斜視図
である。FIG. 2 is a perspective view of a piezoelectric element used for a conventional acceleration sensor.
【図３】図１に示す圧電素子の共振点近傍での電気的等
価回路図である。FIG. 3 is an electrical equivalent circuit diagram near the resonance point of the piezoelectric element shown in FIG.
１０、２０ 圧電素子 １１、２１ 出力電極 １２ 入力電極 １３、２３ アース電極 ３０ 信号処理回路 ３１ 電荷増幅器 ３２ 出力調整部 ３３ 自励発振器 ３４ 入力端子 ３５ 出力端子 ４０ トランジスタ 10, 20 Piezoelectric element 11, 21 Output electrode 12 Input electrode 13, 23 Ground electrode 30 Signal processing circuit 31 Charge amplifier 32 Output adjustment unit 33 Self-excited oscillator 34 Input terminal 35 Output terminal 40 Transistor
Claims (1)
られた出力電極とを有し、前記圧電素子は、その軸方向
に印加される加速度に基づいて、前記出力電極に、加速
度信号を出力する加速度センサにおいて、前記圧電素子
の前記一端面に備えられた入力電極と、該入力電極へ、
前記圧電素子を自励させるための自励信号を出力する自
励発振器とを有することを特徴とする加速度センサ。1. A piezoelectric element comprising: a piezoelectric element; and an output electrode provided on one end surface of the piezoelectric element. The piezoelectric element transmits an acceleration signal to the output electrode based on an acceleration applied in an axial direction of the piezoelectric element. In an acceleration sensor that outputs, the input electrode provided on the one end surface of the piezoelectric element, to the input electrode,
An acceleration sensor, comprising: a self-excited oscillator that outputs a self-excited signal for self-exciting the piezoelectric element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3771392A JP3148940B2 (en) | 1992-02-25 | 1992-02-25 | Acceleration sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3771392A JP3148940B2 (en) | 1992-02-25 | 1992-02-25 | Acceleration sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05232133A JPH05232133A (en) | 1993-09-07 |
| JP3148940B2 true JP3148940B2 (en) | 2001-03-26 |
Family
ID=12505161
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3771392A Expired - Fee Related JP3148940B2 (en) | 1992-02-25 | 1992-02-25 | Acceleration sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3148940B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101991273B1 (en) | 2017-08-09 | 2019-06-20 | 이주찬 | Collecting equipment of mud flat living things |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6531884B1 (en) * | 2001-08-27 | 2003-03-11 | Rosemount Inc. | Diagnostics for piezoelectric sensor |
| CN113366320A (en) | 2019-02-04 | 2021-09-07 | Asml荷兰有限公司 | Electronic system, accelerometer, calibration method, lithographic apparatus and device manufacturing method |
-
1992
- 1992-02-25 JP JP3771392A patent/JP3148940B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101991273B1 (en) | 2017-08-09 | 2019-06-20 | 이주찬 | Collecting equipment of mud flat living things |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05232133A (en) | 1993-09-07 |
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