JP2004301510A

JP2004301510A - Tuning fork type angular velocity sensor

Info

Publication number: JP2004301510A
Application number: JP2003091276A
Authority: JP
Inventors: Yoshiro Tomikawa; 義朗富川; Takahiro Otsuka; 隆宏大塚
Original assignee: Nihon Dempa Kogyo Co Ltd
Current assignee: Nihon Dempa Kogyo Co Ltd
Priority date: 2003-03-28
Filing date: 2003-03-28
Publication date: 2004-10-28
Anticipated expiration: 2023-03-28
Also published as: JP4163031B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-axial detection type angular velocity sensor for detecting angular velocities Ωx and Ωz each having their centers of rotation on an X-axis and a Z-axis of a tuning fork type oscillator, an angular velocity having its center of rotation on A Y-axis, and a combinational angular velocity. <P>SOLUTION: The tuning fork type angular velocity sensor uses the tuning fork type oscillator having the X-axis of crystallographic axes (XYZ) as a width, the Y-axis as a length, and the Z-axis as a thickness and comprising both a tuning fork base part and and a pair of tuning fork arms. In the tuning fork type angular velocity sensor, when the angular velocity Ωx having a center of rotation on the X-axis is added to the tuning fork type oscillator, the pair of tuning fork arms are twisted in opposite directions to each other with the center of rotation on the Y-axis to deflect the tuning fork base part. A charge generated by the deflection of the tuning fork base part is detected by a detecting electrode. In addition, the function of detecting the angular velocities Ωx and Ωz each having their centers of rotation on the X-axis and the Z-axis is added to this. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は車やカメラの位置制御システム等に使用される音叉型角速度センサを産業上の技術分野とし、特に音叉型振動子における結晶軸（ＸＹＺ）のＸ軸を中心とした角速度を検出する音叉型角速度センサに関する。
【０００２】
【従来の技術】
（発明の背景）音叉型振動子を用いた角速度センサは、周波数温度特性を含めて振動周波数が安定なことから、各種電子機器への利用が期待されている。近年では、音叉型振動子のＹ軸（長さ方向）のみならず、Ｚ軸（厚み方向）を中心とする角速度をも検出し、高機能化とする試みがなされている（非特許文献１）。
【０００３】
（従来技術の一例）第１１図は一従来例を説明する図で、同図（ａ）は音叉型角速度センサの外形図、同図（ｂ）は電極配置を示す上面図である。
音叉型角速度センサは、音叉基部１と一対の音叉腕２（ａｂ）とを有する音叉型振動子からなる。音叉型振動子は主面がＺ軸に直交したＺカット板からなり、結晶軸（ＸＹＺ）のＸ軸を幅、Ｙ軸を長さ、Ｚ軸を厚み方向とする。音叉型振動子の音叉腕には駆動電極３及び一対の検出電極４（ａｂ）が形成される。
【０００４】
駆動電極３は例えば各音叉腕２（ａｂ）の両主面、一方の音叉腕２ａの両側面及び他方の音叉腕２ｂの内側面に形成される。一方の音叉腕２ａは両主面の駆動電極３を基準電位（電位を有するグランドＧ）とし、両側面には±の交番電位（Ｄ）が印加される。他方の音叉腕２ｂは内側面を基準電位Ｇとして、両主面に±の交番電圧が印加される。
【０００５】
但し、一方の音叉腕２ａの両主面と、他方の音叉腕２ｂの内側面の交番電位は同電位とする。一対の検出電極４（ａｂ）は他方の音叉腕２ｂの外側面に厚み方向に沿って形成される。
【０００６】
このようなものでは、図示しない発振回路に接続して駆動電極３に印加される交番電圧よって矢印で示す電界が発生する「第１１図（ｂ）」。そして、Ｘ軸方向の電界ベクトル成分によって互いに反対方向の水平方向に変位する音叉振動を生ずる。
【０００７】
一方、音叉振動中に、Ｙ軸を中心とした回転力（角速度）Ωｙが加わると、コリオリの力が作用して、一対の音叉腕２（ａｂ）は互いに反対方向となる厚み方向である板面方向（垂直方向）に振動する。これにより、Ｘ軸方向に発生する正負の電荷（Ｓ＋、Ｓ−）を検出電極４（ａｂ）によって検出する。そして、例えば電流増幅器及び差動増幅器を用いて電圧値として読み取る。したがって、Ｙ軸を回転中心とした角速度Ωｙを検出できる（特許文献１）。
【０００８】
また、第１２図に示したように、一対の音叉腕２（ａｂ）の先端にいずれも外側に向かう突出部を設けて質量を付加する。そして、Ｚ軸を中心とする回転力例えば左回りの回転力（角速度）Ωｚを加えると、一方（左側）の音叉腕２ａにはＹ軸の伸張方向に、他方（右側）の音叉腕２ｂには縮小方向にコリオリの力Ｆｃが発生する。
【０００９】
したがって、一対の音叉腕２（ａｂ）が例えば外方向に変位する場合は左側の音叉腕１ａは実線で示す定常時の振幅よりも点線で示すように揺れ幅を小さくし、右側の音叉腕１ｂは定常時よりも振幅を小さくする。このことから、定常時の振幅によって生ずる電荷との差を検出すれば、Ｚ軸を回転中心とした角速度Ωｚを検出できる（非特許文献２）。
【００１０】
【発明が解決しようとする課題】
（従来技術の問題点）しかしながら、上記構成の角速度センサでは音叉型振動子のＹ軸及びＺ軸を回転中心とした角速度Ωｙ、Ωｚを検出できることが示されるものの、一対の音叉腕２（ａｂ）からなるニ脚音叉でＸ軸を回転中心とした角速度Ωｘの検出については未解明であった。
【００１１】
また、Ｚ軸を回転中心とした角速度Ωｚの検出についてはシュミレーションによって確認されているのみで、具体的な検出電極４の配置については明らかにされていなかった。また、角速度Ωｙ、Ωｚを個々の音叉型振動子で検出することは述べられていても、単一の音叉型振動子によって複数軸を回転中心とした角速度の検出についても未解明であった。
【００１２】
（発明の目的）本発明は音叉型振動子のＸ軸を回転中心とした角速度Ωｘを検出できる角速度センサを提供することを第１目的とし、Ｚ軸を回転中心とした角速度の電極配置を明示した角速度センサを提供することを第２目的とし、複数軸を回転中心とした角速度を単一の音叉型振動子で検出できる角速度センサを提供することを第３目的とする。
【００１３】
【特許文献１】特許第３３３５１２２号
【非特許文献１】第３０回ＥＭシンポジウム、平成１３年５月１７日〜１８日、千葉大学自然科学研究化大会議室、ｐ３５〜４０、水晶３脚音叉３軸ジャイロの有限要素法シミュレーション
【非特許文献２】ＵＳＥ９９第２０回超音波シンポジウム１９９９年１１月東京ＰＣ−２０単一共振モードを利用した音さ型振動ジャイロの構成
【００１４】
【課題を解決するための手段】
本件に係る請求項１の発明では、音叉型振動子にＸ軸を回転中心とする角速度Ωｘを加えたとき、Ｙ軸を回転中心として一対の音叉腕が互いに逆方向に捩れて音叉基部が撓み、前記音叉基部の撓みによって生ずる電荷を検出電極によって検出する。したがって、検出電極による電荷量からＸ軸を回転中心とする角速度Ωｘを検出できる。
【００１５】
同請求項２の発明では、前記検出電極は前記音叉腕が延出する音叉基部の根本部側面に設けるので、角速度Ωｘによって生ずる電荷を検出できる。
【００１６】
同請求項３の発明では、前記Ｙ軸を回転中心とする角速度Ωｙによって生ずる電荷を前記音叉腕の側面に設けた検出電極によって検出するので、Ｘ軸及びＹ軸を回転中心とした角速度Ωｘ、Ωｙのいずれも検出でき、２軸検出型の音叉型角速度センサが得られる。
【００１７】
同請求項４の発明では、音叉基部と先端に質量の付加された一対の音叉腕とからなる音叉型振動子を用いてなり、前記音叉型振動子に前記Ｚ軸を回転中心とする角速度Ωｚを加えたとき、前記一対の音叉腕の変位量が変化することによって生ずる電荷を前記音叉基部の側面に設けた検出電極によって検出する。
【００１８】
これにより、Ｚ軸を回転中心とした角速度Ωｚによって一対の音叉腕の変化量が変化して、音叉腕の不平衡な振動によって音叉基部が歪むことから、これによる電荷を検出して角速度Ωｚを検出できる。
【００１９】
同請求項５の発明では、請求項４の前記Ｘ軸を回転中心とする角速度Ωｘによって生ずる電荷を前記音叉基部の側面に設けた検出電極によって検出する。したがって、Ｘ軸及びＺ軸を回転中心とした角速度Ωｘ及びΩｚの何れをも検出できて、２軸検出型の音叉型角速度センサを得られる。
【００２０】
同請求項６の発明では、請求項４の前記Ｙ軸を回転中心とする角速度Ωｙによって生ずる電荷を前記音叉腕の側面に設けた検出電極によって検出する。したがって、Ｘ軸及びＹ軸を回転中心とした角速度Ωｘ及びΩｙの何れをも検出できて、２軸検出型の音叉型角速度センサを得られる。
【００２１】
同請求項７の発明では、請求項４の前記Ｘ軸を回転中心とする角速度Ωｘによって生ずる電荷を前記音叉基部の側面に設けた検出電極によって検出するとともに、前記Ｙ軸を回転中心とする角速度Ωｙによって生ずる電荷を前記音叉腕の側面に設けた検出電極によって検出する。したがって、Ｘ軸、Ｙ軸及びＺ軸を回転中心とした角速度Ωｘ、Ωｙ及びΩｚの何れをも検出できて、３軸検出型の音叉型角速度センサを得られる。
【００２２】
【第１実施例、請求項１及び２】
第１図乃至第３図は本発明の第１実施例を説明する図で、第１図は角速度センサの図の外観図、第２図及び第３図は作用を説明する上面図である。なお、前従来例と同一部分には同番号を付与してその説明は簡略又は省略する。
【００２３】
角速度センサは前述したように音叉基部１と音叉腕２（ａｂ）を有する、結晶軸（ＸＹＺ）のＸ軸を幅、Ｙ軸を長さ及びＺ軸を厚みとした音叉型振動子からなる。各音叉腕２（ａｂ）の４面には駆動電極３が形成され、音叉腕２（ａｂ）が延出する音叉基部１の根元部側面に一対の検出電極５（ａｂ）を有する。
【００２４】
ここでの駆動電極３は各音叉腕２（ａｂ）の両主面及び両側面に形成され、一方の音叉腕の両主面と他方の音叉腕の両側面を、一方の音叉腕２ａの両主面と他方の音叉腕２ｂの両側面を同電位として、両者間で互いに逆電位とした交番電位が印加される。そして、前述した音叉振動を生ずる。
【００２５】
ここで、一対の音叉腕２（ａｂ）が音叉振動中にＸ軸を回転中心とした角速度Ωｘが加わったとすると、一対（左右）の音叉腕２（ａｂ）には次に示すコリオリの力が発生する。例えばＸ軸を回転中心とした左回りの角速度＋Ωｘが加わったとすると、次の動作になる。
【００２６】
すなわち、第２図（ａ）に示したように、一対の音叉腕２（ａｂ）が矢印ＰＰで示す外方向に変位（振動）するときには、一方の音叉腕２ａの外側面には裏面から正面方向に、内側面には正面から裏面方向へコリオリの力Ｆｃが作用する。これにより、一方の音叉腕２ａではＹ軸を回転中心とした左回りの捩れＲが、他方の音叉腕２ｂではこれとは逆に右回りの捩れＳが生ずる。その結果、同図（ｂ）に示したように、一対の音叉腕２（ａｂ）は捩れＲＳ方向にいわば回転する。
【００２７】
また、第３図（ａｂ）に示したように、音叉腕が矢印ＱＱで示す内方向に変位（振動）したときには、外側面には正面から裏面方向に、内側面には裏面から正面方向へのコリオリの力が作用する「第３図（ａ）」。したがって、一方の音叉腕２ａではＹ軸を回転中心とした左回りの捩れＳが、他方の音叉腕２ｂではこれとは逆に右りの捩れＲが生じる「同図（ｂ）」。その結果、同図（ｂ）に示したように、一対の音叉腕２（ａｂ）は捩れＳＲ方向にいわば回転する。
【００２８】
これらのことから、音叉振動中にＸ軸を回転中心として左回りの角速度＋Ωｘが加わると、一対の音叉腕２（ａｂ）はそれぞれＹ軸を回転中心として互いに逆方向に捩れる。そして、一対の音叉腕２（ａｂ）の逆向きの捩れは、音叉基部１の２等分線を回転中心として互いに反対方向の撓みを発生させる。したがって、音叉基部１のＸ軸方向となる両側面には圧電効果によって逆符号の電荷Ｓ＋、Ｓ−が発生する。
【００２９】
そして、この電荷は両側面に設けた検出電極５（ａｂ）によって検出され、図示しない電流増幅器及び差動増幅器を用いて電圧値として表示される。したがって、Ｘ軸を回転中心とした左回りの角速度＋Ωｘを検出できる。また、同様にしてＸ軸を回転中心とした右回りの角速度−Ωｘをも検出できる。
【００３０】
なお、第１実施例においては一対の音叉腕２（ａｂ）は何れも同一幅としたが、例えば第４図に示したように、各音叉腕２（ａｂ）の先端に外方向への突出部を設けて質量を付加すれば、音叉基部１の撓み量が大きくなってＸ軸を回転中心とした角速度Ωｘの検出感度を高められる。
【００３１】
【第２実施例、請求項３】
第５図は本発明の第２実施例を説明する角速度センサの図で、同図（ａ）は正面図、同図（ｂ）は右側面図である。なお、これ以降の実施例では前実施例と同一部分の説明は省略又は簡略する。
【００３２】
第１実施例ではＸ軸を回転中心とした角速度Ωｘを検出したが、第２実施例ではＹ軸を回転中心とした角速度Ωｙをも検出する。すなわち、第２実施例では従来例で述べた駆動電極３及び検出電極４（ａｂ）を有する音叉型角速度センサに第１実施例の検出電極５（ａｂ）を設けてなる。
【００３３】
このような構成であれば、音叉型振動子のＹ軸を回転中心とする角速度Ωｙによって生ずる電荷は他方の音叉腕２ｂの外側面に設けた検出電極４（ａｂ）によって検出する。また、Ｘ軸を回転中心とする角速度Ωｘによって生ずる電荷は、前述したように一対の音叉腕２（ａｂ）の延出する音叉基部１の例えば根本部の側面に設けた検出電極５（ａｂ）によって検出する。したがって、Ｙ軸及びＸ軸を回転中心とした角速度Ωｙ、Ωｘのいずれをも検出でき、２軸検出型の音叉型角速度センサが得られる。
【００３４】
【第３実施例、請求項３】
第６図は本発明の第３実施例を説明する音叉型角速度センサの図で、同図（ａ）は正面図、同図（ｂ）は作用を説明する一部拡大正面図である。第３実施例では従来例で説明したＺ軸を回転中心とした角速度Ωｚによる検出電極６（ａｂ）の好ましい位置を明確にする。なお、駆動電極３は第１実施例と同様に各音叉腕２（ａｂ）の４面に形成される。
【００３５】
従来例（第１２図）で説明したように、Ｚ軸を回転中心とした角速度Ωｚ例えば左回りの角速度＋Ωｚが加わり、一対の音叉腕２（ａｂ）が外方向に変位しているとすると、左側の音叉腕２ａは振幅が大きく、右側の音叉腕２ｂは振幅が小さくなる。
【００３６】
したがって、この場合には、音叉振動が不平衡となって重心は左側に移動し、音叉基部１は左側に傾斜する（撓む）。このため、音叉基部１における両側面の点線枠で示す中央領域での応力が最も高く、電荷の発生量が多くなる。これにより、第３実施例例では検出電極６（ａｂ）を音叉基部１の両側面の中央領域に形成する。これにより、Ｚ軸を回転中心とした角速度Ωｚの検出を容易にする。
【００３７】
【第４実施例、請求項５】
第７図は本発明の第４実施例を説明する音叉型角速度センサの正面図である。第４実施例ではＺ軸を回転中心とした角速度Ωｚを検出する第３実施例の音叉型角速度センサに、Ｘ軸を回転中心とした角速度Ωｘによる電荷を検出する検出電極５（ａｂ）を設けた構成とする。すなわち、音叉腕２（ａｂ）の延出する音叉基部１の根本部に角速度Ωｘによる電荷検出の検出電極５（ａｂ）を形成する。
【００３８】
このような構成であれば、音叉型振動子のＺ軸を回転中心とする角速度Ωｚによって生ずる電荷は音叉基部１における両側面の中央領域に設けた検出電極６（ａｂ）によって検出する。また、Ｘ軸を回転中心とする角速度Ωｘによって生ずる電荷は前述の音叉基部１の根本部に設けた検出電極５（ａｂ）によって検出する。したがって、Ｚ軸及びＸ軸を回転中心とした角速度Ωｚ、Ωｘのいずれをも検出でき、２軸検出型の音叉型角速度センサが得られる。
【００３９】
【第５実施例、請求項６】
第８図は本発明の第５実施例を説明する音叉型角速度センサ図で、同図（ａ）は正面図、同図（ｂ）は他方の音叉腕の外側面図である。
【００４０】
第５実施例ではＺ軸を回転中心とした角速度Ωｚを検出する第３実施例の音叉型角速度センサに、Ｙ軸及びＸ軸を回転中心とした角速度Ωｙ及びΩｘによる電荷を検出する検出電極４（ａｂ）及び５（ａｂ）を設けた構成とする。すなわち、他方の腕部２ｂの外側面にＹ軸を回転中心とした角速度Ωｙの検出電極４（ａｂ）を、音叉腕２（ａｂ）の延出する音叉基部１の根本部両側面に角速度Ωｘの検出電極５（ａｂ）を、音叉基部１の両側面の中央領域に角速度Ωｚの検出電極６（ａｂ）形成する。
【００４１】
このような構成であれば、音叉型振動子のＺ軸を回転中心とする角速度Ωｚによって生ずる電荷は音叉基部１における両側面の中央領域に設けた検出電極６（ａｂ）によって検出する。また、Ｘ軸を回転中心とする角速度Ωｘによって生ずる電荷は前述の音叉基部１の根本部に設けた検出電極５（ａｂ）によって検出する。
【００４２】
そして、Ｙ軸を回転中心とする角速度Ωｙによって生ずる電荷は他方の音叉腕２ｂ１の外側面に設けた検出電極４（ａｂ）によって検出する。したがって、Ｚ軸、Ｘ軸及びＹ軸を回転中心とした角速度Ωｚ、Ωｘ及びΩｙのいずれをも検出でき、３軸検出型の音叉型角速度センサが得られる。
【００４３】
【他の事項】
上記各実施例では音叉基部１は便宜的に矩形状として説明したが、例えば第９図に示したようにしてもよい。すなわち、音叉基部１の根本部と下端部に外側に向かう突出部を設ける。そして、突出部の両側面にＸ軸を回転中心とした角速度Ωｘの検出電極５（ａｂ）を設け、両突出部間の幅狭部両側面にＺ軸を回転中心とした角速度Ωｚの検出電極６（ａｂ）を設ける。
【００４４】
このようにすると、音叉基部１のＹ軸方向に沿った中央に括れができる。この括れは、音叉腕２（ａｂ）による音叉振動の下端部以下への漏れを防止して駆動効率を高める。また、この構造であると、音叉基部１の括れより上方部分（根本部）は角速度Ωｘに、括れ部は同Ωｚに応じて撓みやすく、角速度Ωｘ、Ωｚの検出効果が高まると考えられる。勿論、Ωｘ、Ωｚのいずれか一方の検出の場合は、他方の電極は不要である。
【００４５】
また、Ｚ軸を回転中心とした角速度Ωｚを検出する場合（第２実施例、第５図）の音叉型振動子は一対の音叉腕２（ａｂ）の先端には互いに外側に向かう突出部を設けて対称構造としたが、例えば第１０図に示したようにしてもよい。すなわち、一方の音叉腕２ａは先端の突出部を内側にし、他方の音叉腕２ｂは外側にして非対称構造とする。
【００４６】
このようなものではＺ軸を回転中心とした角速度Ωｚが加わると、音叉腕２（ａｂ）が外方向（矢印Ｐ）に変位している場合は、各音叉腕はコリオリの力によって定常振幅よりも大きくなる（実線から点線）。したがって、音叉基部１の両側面の中央領域に検出電極６（ａｂ）を設けて電荷を検出し、定常振幅時の電荷量との差を検出すれば角速度Ωｚを検出できる。
【００４７】
また、Ｙ軸を回転中心とした各速度Ωｙを検出する場合の検出電極４（ａｂ）は他方の音叉腕２ｂの外側面に設けたが、駆動電極３との兼ね合いから各アーム２（ａｂ）に設けてよい。そして、一方の音叉腕２ａは駆動電極３のみとして、他方の音叉腕２ｂの内側面及び外側面に検出電極４（ａｂ）を設けてもよい。
【００４８】
そして、検出電極４（ａｂ）は正負の電荷を検出する一対としたが、電位を有するグランドを基準として検出してもよい。また、駆動電極３についてもグランドを基準とした電界を印加して音叉振動してもよく、これらは任意に選択できる。
【００４９】
また、音叉型振動子は単板から形成したが、特許文献１で示すようなＸ軸の±極性を逆向きとした二枚の水晶片を所謂直接接合によって貼りあわせて形成した場合でも同様に適用でき、この場合でも基本的な動作原理は同一である。
【００５０】
【発明の効果】
本発明は、以上に説明したように音叉型振動子のＸ軸を回転中心とした角速度Ωｘを検出できる角速度センサを第１に提供でき、Ｚ軸を回転中心とした角速度の電極配置を明示した角速度センサを第２に提供でき、複数軸を回転中心とした角速度を単一の音叉型振動子で検出できる角速度センサを提供できる。
【図面の簡単な説明】
【図１】本発明の第１実施例を説明する角速度センサの図の外観図である。
【図２】本発明の第１実施例の作用を説明する角速度センサの上面図である。
【図３】本発明の第１実施例の作用を説明する角速度センサの上面図である。
【図４】本発明の第１実施例の他の例を説明する音叉型角速度センサの正面図である。
【図５】本発明の第２実施例を説明する角速度センサの図で、同図（ａ）は正面図、同図（ｂ）は右側面図である。
【図６】本発明の第３実施例を説明する音叉型角速度センサの図で、同図（ａ）は正面図、同図（ｂ）は作用を説明する一部拡大正面図である。
【図７】本発明の第４実施例を説明する音叉型角速度センサの正面図である。
【図８】本発明の第５実施例を説明する音叉型角速度センサ図で、同図（ａ）は正面図、同図（ｂ）は他方の第２音叉腕の外側面図である。
【図９】本発明の他の実施例を説明する音叉型角速度センサの正面図である。
【図１０】本発明の第２実施例の他の例を説明する音叉型角速度センサの正面図である。
【図１１】従来例を説明する図で、同図（ａ）は音叉型角速度センサの外形図、同図（ｂ）は電極配置を示す上面図である。
【図１２】従来例を説明する音叉型角速度センサの正面図である。
【符号の説明】
１音叉基部、２音叉腕、３駆動電極、４、５、６検出電極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tuning fork type angular velocity sensor used for a position control system of a car or a camera and the like in an industrial technical field, and particularly to a tuning fork for detecting an angular velocity around a X axis of a crystal axis (XYZ) in a tuning fork type vibrator. The angular velocity sensor.
[0002]
[Prior art]
(Background of the Invention) An angular velocity sensor using a tuning-fork type vibrator is expected to be used for various electronic devices because its vibration frequency is stable including frequency-temperature characteristics. In recent years, attempts have been made to improve the functionality by detecting not only the Y axis (length direction) of the tuning fork vibrator but also the angular velocity centered on the Z axis (thickness direction) (Non-Patent Document 1). ).
[0003]
(Example of Prior Art) FIGS. 11 (a) and 11 (b) are views for explaining a conventional example. FIG. 11 (a) is an external view of a tuning fork type angular velocity sensor, and FIG. 11 (b) is a top view showing an electrode arrangement.
The tuning fork type angular velocity sensor includes a tuning fork type vibrator having a tuning fork base 1 and a pair of tuning fork arms 2 (ab). The tuning-fork type vibrator is made of a Z-cut plate having a main surface orthogonal to the Z-axis. The X-axis of the crystal axis (XYZ) is a width, the Y-axis is a length, and the Z-axis is a thickness direction. A drive electrode 3 and a pair of detection electrodes 4 (ab) are formed on the tuning fork arm of the tuning fork vibrator.
[0004]
The drive electrodes 3 are formed, for example, on both main surfaces of each tuning fork arm 2 (ab), on both side surfaces of one tuning fork arm 2a, and on the inner surface of the other tuning fork arm 2b. In the tuning fork arm 2a, the drive electrodes 3 on both main surfaces are set to a reference potential (ground G having a potential), and alternating alternating potentials (D) of ± are applied to both side surfaces. The other tuning fork arm 2b has an inner surface as a reference potential G, and an alternating voltage of ± is applied to both main surfaces.
[0005]
However, the alternating potentials on both main surfaces of one tuning fork arm 2a and the inner surface of the other tuning fork arm 2b are the same. The pair of detection electrodes 4 (ab) are formed on the outer surface of the other tuning fork arm 2b along the thickness direction.
[0006]
In such a case, an electric field indicated by an arrow is generated by an alternating voltage applied to the drive electrode 3 by being connected to an oscillation circuit (not shown) (FIG. 11B). Then, a tuning fork vibration displaced in the horizontal direction opposite to each other is generated by the electric field vector component in the X-axis direction.
[0007]
On the other hand, when a rotational force (angular velocity) Ωy about the Y axis is applied during the tuning fork vibration, Coriolis force acts, and the pair of tuning fork arms 2 (ab) are in a thickness direction in which directions are opposite to each other. Vibrates in the plane direction (vertical direction). Thus, positive and negative charges (S +, S−) generated in the X-axis direction are detected by the detection electrode 4 (ab). Then, it is read as a voltage value using, for example, a current amplifier and a differential amplifier. Therefore, it is possible to detect the angular velocity Ωy about the Y axis as the rotation center (Patent Document 1).
[0008]
In addition, as shown in FIG. 12, a pair of tuning fork arms 2 (ab) are provided with protruding portions that are directed outward at both ends to add mass. When a rotational force about the Z-axis, for example, a counterclockwise rotational force (angular velocity) Ωz is applied, one (left) tuning fork arm 2a is applied in the Y-axis extension direction, and the other (right) tuning fork arm 2b is applied to the other (right) tuning fork arm 2b. Generates a Coriolis force Fc in the contraction direction.
[0009]
Therefore, when the pair of tuning fork arms 2 (ab) are displaced outward, for example, the left tuning fork arm 1a has a smaller swing width as shown by a dotted line than the steady-state amplitude shown by a solid line, and the right tuning fork arm 1b. Make the amplitude smaller than in the steady state. From this, if the difference from the charge generated by the amplitude at the steady state is detected, the angular velocity Ωz around the Z axis as the rotation center can be detected (Non-Patent Document 2).
[0010]
[Problems to be solved by the invention]
(Problems of the prior art) However, although it is shown that the angular velocity sensor having the above configuration can detect the angular velocities Ωy and Ωz around the Y axis and the Z axis of the tuning fork vibrator, a pair of tuning fork arms 2 (ab) The detection of the angular velocity Ωx with the X-axis as the center of rotation in a two-leg tuning fork composed of
[0011]
Further, the detection of the angular velocity Ωz about the Z axis as the rotation center has only been confirmed by simulation, but the specific arrangement of the detection electrodes 4 has not been clarified. Although it is described that the angular velocities Ωy and Ωz are detected by individual tuning fork vibrators, the detection of angular velocities around a plurality of axes by a single tuning fork vibrator has not been elucidated.
[0012]
(Purpose of the Invention) The first object of the present invention is to provide an angular velocity sensor capable of detecting an angular velocity Ωx about the X axis of a tuning fork type vibrator, and to specify an electrode arrangement of an angular velocity about the Z axis as a rotational center. It is a second object to provide an angular velocity sensor that has been described, and to provide an angular velocity sensor that can detect an angular velocity about a plurality of axes as a rotation center with a single tuning fork vibrator.
[0013]
[Patent Document 1] Patent No. 3335122 [Non-Patent Document 1] The 30th EM Symposium, May 17-18, 2001, Chiba University Conference on Natural Science and Technology, p35-40, quartz crystal three-leg tuning fork Finite element method simulation of three-axis gyro [Non-patent document 2] USE99 20th ultrasonic symposium November 1999 Tokyo Configuration of pitch type vibration gyro using PC-20 single resonance mode
[Means for Solving the Problems]
According to the first aspect of the present invention, when an angular velocity Ωx having the X axis as the center of rotation is applied to the tuning fork vibrator, the pair of tuning fork arms are twisted in opposite directions about the Y axis and the tuning fork base is bent. An electric charge generated by the bending of the tuning fork base is detected by a detection electrode. Therefore, the angular velocity Ωx about the X-axis as the rotation center can be detected from the amount of charge by the detection electrode.
[0015]
According to the second aspect of the present invention, since the detection electrode is provided on the side of the root of the tuning fork base where the tuning fork arm extends, it is possible to detect the charge generated by the angular velocity Ωx.
[0016]
According to the third aspect of the present invention, the charge generated by the angular velocity Ωy about the Y axis as the rotation center is detected by the detection electrode provided on the side surface of the tuning fork arm, so that the angular velocity Ωx about the X axis and the Y axis as the rotation center, Ωy can be detected, and a two-axis detection type tuning fork angular velocity sensor can be obtained.
[0017]
According to the invention of claim 4, a tuning fork vibrator comprising a tuning fork base and a pair of tuning fork arms having a mass added to the tip is used, and the tuning fork vibrator has an angular velocity Ωz about the Z axis as a rotation center. Is applied, a charge generated by a change in the displacement amount of the pair of tuning fork arms is detected by a detection electrode provided on a side surface of the tuning fork base.
[0018]
Thereby, the change amount of the pair of tuning fork arms is changed by the angular velocity Ωz about the Z axis as the rotation center, and the tuning fork base is distorted due to unbalanced vibration of the tuning fork arm. Can be detected.
[0019]
According to the fifth aspect of the present invention, the electric charge generated by the angular velocity Ωx about the X axis of the fourth aspect is detected by the detection electrode provided on the side surface of the tuning fork base. Therefore, it is possible to detect both the angular velocities Ωx and Ωz about the X-axis and the Z-axis as the center of rotation, and to obtain a two-axis detection type tuning fork type angular velocity sensor.
[0020]
According to the invention of claim 6, the electric charge generated by the angular velocity Ωy about the Y axis of rotation of claim 4 is detected by the detection electrode provided on the side surface of the tuning fork arm. Therefore, it is possible to detect both the angular velocities Ωx and Ωy about the X-axis and the Y-axis as the center of rotation, and to obtain a two-axis detection type tuning fork type angular velocity sensor.
[0021]
According to the seventh aspect of the present invention, the electric charge generated by the angular velocity Ωx about the X axis as the rotation center of the fourth aspect is detected by the detection electrode provided on the side surface of the tuning fork base, and the angular velocity about the Y axis as the rotation center. The charge generated by Ωy is detected by a detection electrode provided on the side surface of the tuning fork arm. Therefore, any of the angular velocities Ωx, Ωy, and Ωz around the X, Y, and Z axes can be detected, and a three-axis detection type tuning fork-type angular velocity sensor can be obtained.
[0022]
First Embodiment, Claims 1 and 2
FIGS. 1 to 3 are views for explaining a first embodiment of the present invention. FIG. 1 is an external view of an angular velocity sensor, and FIGS. 2 and 3 are top views for explaining the operation. The same parts as those in the prior art are denoted by the same reference numerals, and description thereof will be simplified or omitted.
[0023]
The angular velocity sensor is composed of a tuning fork vibrator having the tuning fork base 1 and the tuning fork arm 2 (ab) as described above and having the X axis of the crystal axis (XYZ) as the width, the Y axis as the length, and the Z axis as the thickness. Driving electrodes 3 are formed on four surfaces of each tuning fork arm 2 (ab), and a pair of detection electrodes 5 (ab) are provided on the side surface of the root of the tuning fork base 1 from which the tuning fork arm 2 (ab) extends.
[0024]
The drive electrodes 3 here are formed on both main surfaces and both side surfaces of each tuning fork arm 2 (ab), and connect both main surfaces of one tuning fork arm and both side surfaces of the other tuning fork arm to both ends of one tuning fork arm 2 a. An alternating potential, which is the same potential on both sides of the main surface and the other tuning fork arm 2b, is applied between the two surfaces. Then, the above-described tuning fork vibration occurs.
[0025]
Assuming that a pair of (left and right) tuning fork arms 2 (ab) are subjected to an angular velocity Ωx about the X axis during tuning fork vibration, a pair of (left and right) tuning fork arms 2 (ab) have the following Coriolis force. appear. For example, if a counterclockwise angular velocity + Ωx with the X axis as the rotation center is applied, the following operation is performed.
[0026]
That is, as shown in FIG. 2 (a), when the pair of tuning fork arms 2 (ab) is displaced (vibrated) in the outward direction indicated by the arrow PP, the outer surface of one tuning fork arm 2a is positioned from the back to the front. Direction, Coriolis force Fc acts on the inner surface from the front to the back. As a result, a counterclockwise twist R about the Y axis is generated in one tuning fork arm 2a, and a counterclockwise twist S is generated in the other tuning fork arm 2b. As a result, as shown in FIG. 2B, the pair of tuning fork arms 2 (ab) rotate in the torsional RS direction, so to speak.
[0027]
Further, as shown in FIG. 3 (ab), when the tuning fork arm is displaced (vibrated) in the inward direction indicated by the arrow QQ, the outer surface is directed from the front to the back, and the inner surface is directed from the back to the front. FIG. 3 (a) in which the Coriolis force acts. Accordingly, one tuning fork arm 2a has a counterclockwise twist S about the Y axis as the rotation center, and the other tuning fork arm 2b has a right-hand twist R, which is opposite thereto (FIG. 2B). As a result, as shown in FIG. 2B, the pair of tuning fork arms 2 (ab) rotate in a torsion SR direction.
[0028]
From these facts, when a counterclockwise angular velocity + Ωx about the X axis as the rotation center is applied during the tuning fork vibration, the pair of tuning fork arms 2 (ab) are twisted in opposite directions about the Y axis as the rotation center. The twisting of the pair of tuning fork arms 2 (ab) in opposite directions causes bending in opposite directions about the bisector of the tuning fork base 1 as the center of rotation. Therefore, charges S + and S− of opposite signs are generated on both sides of the tuning fork base 1 in the X-axis direction due to the piezoelectric effect.
[0029]
Then, this charge is detected by the detection electrodes 5 (ab) provided on both side surfaces, and is displayed as a voltage value using a current amplifier and a differential amplifier (not shown). Therefore, the counterclockwise angular velocity + Ωx about the X axis as the rotation center can be detected. Similarly, the clockwise angular velocity −Ωx about the X axis as the rotation center can be detected.
[0030]
In the first embodiment, each of the pair of tuning fork arms 2 (ab) has the same width. However, for example, as shown in FIG. If the mass is added by providing the portion, the amount of deflection of the tuning fork base 1 increases, and the detection sensitivity of the angular velocity Ωx about the X axis as the rotation center can be increased.
[0031]
Second Embodiment, Claim 3
FIG. 5 is a diagram of an angular velocity sensor for explaining a second embodiment of the present invention. FIG. 5 (a) is a front view, and FIG. 5 (b) is a right side view. In the following embodiments, the description of the same parts as those in the previous embodiment will be omitted or simplified.
[0032]
In the first embodiment, the angular velocity Ωx about the X axis as the rotation center is detected, but in the second embodiment, the angular velocity Ωy about the Y axis as the rotation center is also detected. That is, in the second embodiment, the detection electrode 5 (ab) of the first embodiment is provided to the tuning fork type angular velocity sensor having the drive electrode 3 and the detection electrode 4 (ab) described in the conventional example.
[0033]
With such a configuration, the charge generated by the angular velocity Ωy about the Y-axis of the tuning fork vibrator as the rotation center is detected by the detection electrode 4 (ab) provided on the outer surface of the other tuning fork arm 2b. Further, as described above, the electric charge generated by the angular velocity Ωx about the X axis as the rotation center is, as described above, the detection electrode 5 (ab) provided on, for example, the side surface of the root of the extending tuning fork base 1 of the pair of tuning fork arms 2 (ab). To detect. Therefore, both the angular velocities Ωy and Ωx about the Y axis and the X axis as the rotation center can be detected, and a two-axis detection type tuning fork type angular velocity sensor can be obtained.
[0034]
Third Embodiment, Claim 3
FIG. 6 is a view of a tuning fork type angular velocity sensor for explaining a third embodiment of the present invention. FIG. 6 (a) is a front view, and FIG. 6 (b) is a partially enlarged front view for explaining the operation. In the third embodiment, the preferred position of the detection electrode 6 (ab) based on the angular velocity Ωz about the Z axis as the rotation center described in the conventional example is clarified. The drive electrodes 3 are formed on the four surfaces of each tuning fork arm 2 (ab) as in the first embodiment.
[0035]
As described in the conventional example (FIG. 12), assuming that an angular velocity Ωz about the Z axis as a rotation center, for example, a counterclockwise angular velocity + Ωz is applied, and the pair of tuning fork arms 2 (ab) are displaced outward. The left tuning fork arm 2a has a large amplitude, and the right tuning fork arm 2b has a small amplitude.
[0036]
Therefore, in this case, the tuning fork vibration becomes unbalanced, the center of gravity moves to the left, and the tuning fork base 1 tilts (bends) to the left. For this reason, the stress in the central region indicated by the dotted frame on both sides of the tuning fork base 1 is the highest, and the amount of generated charges is large. Thus, in the third embodiment, the detection electrodes 6 (ab) are formed in the central regions on both side surfaces of the tuning fork base 1. This facilitates detection of the angular velocity Ωz with the Z axis as the center of rotation.
[0037]
[Fourth embodiment, Claim 5]
FIG. 7 is a front view of a tuning-fork type angular velocity sensor for explaining a fourth embodiment of the present invention. In the fourth embodiment, the tuning fork type angular velocity sensor of the third embodiment for detecting the angular velocity Ωz about the Z axis as the rotation center is provided with the detection electrode 5 (ab) for detecting the electric charge based on the angular velocity Ωx about the X axis as the rotation center. Configuration. That is, the detection electrode 5 (ab) for detecting electric charge by the angular velocity Ωx is formed at the root of the tuning fork base 1 extending from the tuning fork arm 2 (ab).
[0038]
With such a configuration, the charge generated by the angular velocity Ωz about the Z axis of the tuning fork vibrator as the rotation center is detected by the detection electrodes 6 (ab) provided in the central regions on both sides of the tuning fork base 1. The electric charge generated by the angular velocity Ωx about the X axis as the rotation center is detected by the detection electrode 5 (ab) provided at the root of the tuning fork base 1. Therefore, it is possible to detect both the angular velocities Ωz and Ωx about the Z-axis and the X-axis as the center of rotation, and to obtain a two-axis detection type tuning fork type angular velocity sensor.
[0039]
[Fifth embodiment, Claim 6]
FIG. 8 is a diagram of a tuning fork type angular velocity sensor for explaining a fifth embodiment of the present invention. FIG. 8 (a) is a front view, and FIG. 8 (b) is an outer side view of the other tuning fork arm.
[0040]
In the fifth embodiment, the tuning electrode 4 for detecting the electric charges based on the angular velocities Ωy and Ωx about the Y axis and the X axis as the tuning fork type angular velocity sensor according to the third embodiment for detecting the angular velocity Ωz about the Z axis as the rotation center. (Ab) and 5 (ab). That is, the detection electrode 4 (ab) having an angular velocity Ωy about the Y axis as the rotation center is provided on the outer surface of the other arm 2b, and the angular velocity Ωx is provided on both sides of the root of the tuning fork base 1 extending from the tuning fork arm 2 (ab). Are formed in the central regions on both side surfaces of the tuning fork base 1 with the angular velocity Ωz.
[0041]
With such a configuration, the charge generated by the angular velocity Ωz about the Z axis of the tuning fork vibrator as the rotation center is detected by the detection electrodes 6 (ab) provided in the central regions on both sides of the tuning fork base 1. The electric charge generated by the angular velocity Ωx about the X axis as the rotation center is detected by the detection electrode 5 (ab) provided at the root of the tuning fork base 1.
[0042]
The electric charge generated by the angular velocity Ωy about the Y axis as the rotation center is detected by the detection electrode 4 (ab) provided on the outer surface of the other tuning fork arm 2b1. Therefore, it is possible to detect any of the angular velocities Ωz, Ωx, and Ωy about the Z axis, the X axis, and the Y axis as a rotation center, and to obtain a tuning fork angular velocity sensor of a three-axis detection type.
[0043]
[Other matters]
In each of the above embodiments, the tuning fork base 1 has been described as having a rectangular shape for convenience, but may be configured as shown in FIG. 9, for example. That is, outwardly projecting portions are provided at the root portion and the lower end portion of the tuning fork base 1. A detection electrode 5 (ab) having an angular velocity Ωx about the X-axis as the rotation center is provided on both side surfaces of the protrusion, and a detection electrode 5 having an angular velocity Ωz about the Z-axis as the rotation center on both sides of the narrow portion between the protrusions. 6 (ab) is provided.
[0044]
By doing so, the tuning fork base 1 can be constricted at the center along the Y-axis direction. This constriction prevents leakage of the tuning fork vibration by the tuning fork arm 2 (ab) below the lower end, thereby increasing the driving efficiency. Further, with this structure, it is considered that a portion (root portion) above the constriction of the tuning fork base 1 is easily bent in accordance with the angular velocity Ωx, and the constricted portion is easily bent in accordance with the same Ωz, and the detection effect of the angular velocities Ωx and Ωz is considered to be enhanced. Of course, in the case of detecting either Ωx or Ωz, the other electrode is unnecessary.
[0045]
In the case of detecting the angular velocity Ωz about the Z-axis as the rotation center (the second embodiment, FIG. 5), the tuning-fork type vibrator has a pair of tuning-fork arms 2 (ab) having outwardly projecting portions at the tips. Although a symmetrical structure is provided, for example, it may be as shown in FIG. That is, one of the tuning fork arms 2a has an asymmetrical structure with the protruding portion at the tip inside and the other tuning fork arm 2b outside.
[0046]
In such a case, when the tuning fork arm 2 (ab) is displaced in the outward direction (arrow P) when the angular velocity Ωz about the Z axis as the rotation center is applied, each tuning fork arm is deviated from the steady amplitude by Coriolis force. (From the solid line to the dotted line). Therefore, the angular velocity Ωz can be detected by detecting the charge by providing the detection electrode 6 (ab) in the central region on both side surfaces of the tuning fork base 1 and detecting the difference from the charge amount at the time of steady amplitude.
[0047]
The detection electrode 4 (ab) for detecting each speed Ωy about the Y axis as the rotation center is provided on the outer surface of the other tuning fork arm 2 b. May be provided. Then, one tuning fork arm 2a may be provided only with the drive electrode 3, and the detection electrode 4 (ab) may be provided on the inner surface and the outer surface of the other tuning fork arm 2b.
[0048]
Although the detection electrodes 4 (ab) are paired to detect positive and negative charges, they may be detected with reference to a ground having a potential. Also, the driving electrode 3 may be subjected to tuning fork vibration by applying an electric field based on the ground, and these can be arbitrarily selected.
[0049]
Although the tuning fork type vibrator is formed from a single plate, the same applies to a case where two quartz pieces having opposite polarities of the X axis as shown in Patent Document 1 are bonded by so-called direct bonding. Applicable, in which case the basic operating principle is the same.
[0050]
【The invention's effect】
As described above, the present invention can first provide an angular velocity sensor capable of detecting the angular velocity Ωx about the X axis of the tuning fork type vibrator as described above, and clearly shows the electrode arrangement of the angular velocity about the Z axis as the rotational center. Secondly, an angular velocity sensor can be provided, and an angular velocity sensor capable of detecting an angular velocity around a plurality of axes as a rotation center with a single tuning fork vibrator can be provided.
[Brief description of the drawings]
FIG. 1 is an external view of an angular velocity sensor illustrating a first embodiment of the present invention.
FIG. 2 is a top view of the angular velocity sensor for explaining the operation of the first embodiment of the present invention.
FIG. 3 is a top view of the angular velocity sensor for explaining the operation of the first embodiment of the present invention.
FIG. 4 is a front view of a tuning-fork type angular velocity sensor for explaining another example of the first embodiment of the present invention.
5A and 5B are diagrams of an angular velocity sensor for explaining a second embodiment of the present invention, wherein FIG. 5A is a front view and FIG. 5B is a right side view.
6A and 6B are diagrams of a tuning fork type angular velocity sensor for explaining a third embodiment of the present invention, wherein FIG. 6A is a front view, and FIG. 6B is a partially enlarged front view for explaining the operation.
FIG. 7 is a front view of a tuning-fork type angular velocity sensor for explaining a fourth embodiment of the present invention.
8A and 8B are diagrams illustrating a tuning fork type angular velocity sensor for explaining a fifth embodiment of the present invention. FIG. 8A is a front view, and FIG. 8B is an outer side view of the other second tuning fork arm.
FIG. 9 is a front view of a tuning-fork type angular velocity sensor for explaining another embodiment of the present invention.
FIG. 10 is a front view of a tuning-fork type angular velocity sensor illustrating another example of the second embodiment of the present invention.
11A and 11B are diagrams illustrating a conventional example. FIG. 11A is an external view of a tuning-fork type angular velocity sensor, and FIG. 11B is a top view illustrating an electrode arrangement.
FIG. 12 is a front view of a tuning fork type angular velocity sensor for explaining a conventional example.
[Explanation of symbols]
1 tuning fork base, 2 tuning fork arm, 3 drive electrodes, 4, 5, 6 detection electrodes

Claims

In the tuning fork type angular velocity sensor using a tuning fork type vibrator having a tuning fork base and a pair of tuning fork arms with the X axis of the crystal axis (XYZ) being the width, the Y axis being the length and the Z axis being the thickness direction, When an angular velocity Ωx about the X axis as the rotation center is applied to the vibrator, the detection electrode detects a charge generated when the pair of tuning fork arms are twisted in directions opposite to each other about the Y axis as the rotation center and the tuning fork base bends. A tuning fork-type angular velocity sensor characterized by being detected by:

2. The tuning fork type angular velocity sensor according to claim 1, wherein the detection electrode is provided on a side surface of the tuning fork base.

2. A two-axis detection type tuning fork type angular velocity sensor according to claim 1, wherein a charge generated by the angular velocity Ωy about the Y axis as a rotation center is detected by a detection electrode provided on a side surface of the tuning fork arm.

The X-axis of the crystal axis (XYZ) is a width, the Y-axis is a length, and the Z-axis is a thickness direction. When an angular velocity Ωz about the Z axis as a rotation center is applied to a tuning fork vibrator, a charge generated by a change in the amount of displacement of the pair of tuning fork arms is detected to detect the angular velocity Ωz, thereby obtaining a tuning fork angular velocity. 3. The tuning fork type angular velocity sensor according to claim 1, wherein the charge is detected by a detection electrode provided on a side surface of the tuning fork base.

5. The two-axis detection type tuning fork type angular velocity sensor according to claim 4, wherein electric charge generated by the angular velocity Ωx about the X axis as a rotation center is detected by a detection electrode provided on a side surface of the tuning fork base.

5. The two-axis detection type tuning fork angular velocity sensor according to claim 4, wherein electric charges generated by the angular velocity Ωy about the Y axis as a rotation center are detected by a detection electrode provided on a side surface of the tuning fork arm.

5. The tuning fork arm according to claim 4, wherein a charge generated by an angular velocity Ωx about the X axis as a rotation center is detected by a detection electrode provided on a side surface of the tuning fork base, and a charge generated by the angular velocity Ωy about the Y axis as a rotation center. A tuning fork-type angular velocity sensor of a three-axis detection type, which is detected by a detection electrode provided on a side surface of the sensor.