JP2004264154A - Steering angle sensing device of steering apparatus for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of a sensor simply and to eliminate the necessity of shortening a gap to the sensor due to a high detecting sensitivity. <P>SOLUTION: In the steering angle sensing device of a steering apparatus for an automobile, a magnetic sensor 2 has two magnet impedance elements 21, 22 disposed in a positional relationship that the magnetic properties of a magnetic element 1 arranged on a steering shaft 10 respond to a changing period. A signal processing circuit 23 has a magnetic impedance magnetic detector 20 having one signal processing circuit for processing a signal by alternately switching outputs from the two magnet impedance elements by a switching means. An arithmetic circuit 3 senses an angular displacement based on the ratio of the outputs of the two magnet impedance elements sensed by the two magnet impedance elements 21, 22 and alternately output from the signal processing circuit. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【数３】

【００２１】
ここで２つのマグネト・インピーダンス素子２１、２２の位相角が、φ＝π／２（９０度）となる位置に設定されると、上記数３は、数４に書き換えることができる。
【数４】

【００２２】
次に２つの検出信号の比Ｈｂ／Ｈａを演算すると、数５となる。
【数５】

【００２３】
すなわち数５に示されるごとく、分母および分子に｜Ｂ｜があるので、検出信号の比の演算を行うとＨｂ／Ｈａは、 ｓｉｎθ／ ｃｏｓθになり、回転体磁石の磁場の強さ｜Ｂ｜の項が消去されることが分かる。これは前記検出信号の比の演算結果には、磁場の強さは関係しないことを表しており、すなわち磁場変動には影響されないことを意味している。そして ｓｉｎθ／ ｃｏｓθ＝ ｔａｎθであるから上掲の数１のようにａｒｃｔａｎ（Ｈｂ／Ｈａ）の演算を行うことにより角変位θを線形関係で計測できることが分かる。
【００２４】
上記関係を図示すると図２の（ロ）のようになる。
すなわち角変位θの変化幅がπラジアン（ここでは±π／２）の期間に対して出力である縦軸ａｒｃｔａｎ（Ｈｂ／Ｈａ）の値が−π／２から＋π／２へ直線的に変化する。また、この角変位θの変化が±π／２を超える領域では角度がπ（１８０度）増減するごとにデータが鋸歯状で不連続になり前記の正負の値を繰り返す。
【００２５】
上記数４で見たようにＨｂ／Ｈａの演算結果から磁場強さの項｜Ｂ｜の影響がなくなるということは、前記したごとく回転体磁石１と検出素子であるマグネト・インピーダンス素子とのギャップが機械的な偏心やガタによりマグネト・インピーダンス素子が受ける磁場の強さが変動しても角度計測信号に誤差が混入しないということである。また、温度による前記磁石の磁場強さが変化しても同じ理由で誤差は混入しない。さらに前記Ｈａ、Ｈｂは、マグネト・インピーダンス素子の検出信号であるから、このマグネト・インピーダンス素子の温度による感度変化があっても両者の温度計数を互いに同じにしておけば上記と同様に誤差の混入はなく、高精度の角変位の計測ができる。
【００２６】
なおここでは前記マグネト・インピーダンス素子２１、２２の位相φがπの値をとることとして説明したが、この計測法ではφ≠π以外でも成り立ち（ただしφ＝０を除く）上記の磁場強さの変動やマグネト・インピーダンス素子の感度変化の影響を受けないという特徴は維持される。ただし角変位θとＨｂ／Ｈａとの関係が線形関係にならないということのみが上記と異なる。
【００２７】
次に前記磁電変換素子としてのマグネト・インピーダンス磁気検出器２０は、２つのマグネト・インピーダンス素子２１、２２の駆動とその信号処理を交互に切換えて時系列で行うための１つの電子回路２３から構成される。これは低消費電力でかつ低コストの角変位センサを実現するためである。
【００２８】
このマグネト・インピーダンス磁気検出器２の出力は、前記角度算出装置３に接続される。この角度算出装置３は、前記マグネト・インピーダンス磁気検出器２の２つのマグネト・インピーダンス素子２１、２２の２つの信号Ｈａ、Ｈｂから、Ｈｂ／Ｈａやａｒｃｔａｎ（Ｈｂ／Ｈａ）の演算を行い、角変位および変化方向（回転方向）を算出し出力する。
【００２９】
前記検知コイルと前記１組の電子回路とが、同一の基板上に形成されているものである。
【００３０】
上記構成より成る本第１実施形態の操舵角検知装置は、図１に示されるごとく周囲に磁極を持つ回転体磁石１の回転に伴う磁極Ｓ−Ｎの移動による正弦波の時々刻々の振幅信号から、２つの磁場信号の比にもとづいて角度計測を行うので、高分解能かつ高精度な操舵角検知を可能にするという効果を奏する。
【００３１】
また本第１実施形態の操舵角検知装置は、前記磁電変換素子としてのマグネト・インピーダンス磁気検出器２は、２つのマグネト・インピーダンス素子２１、２２の駆動とその信号処理を交互に切換えて時系列で行うための１つの電子回路２３から構成されるので、低消費電力でかつ低コストの角変位センサを実現するという効果を奏する。
【００３２】
すなわち本第１実施形態においては、一方のマグネト・インピーダンス素子がパルス通電され動作している時には他方のマグネト・インピーダンス素子はパルス通電されていないため動作していないことから、互いに他方のマグネト・インピーダンス素子のパルス通電に伴う動作による電磁的影響を受けることはないため、高精度の回転数検知を可能にするとともに、前記２つのマグネト・インピーダンス素子の同時通電および信号処理回路における同時信号処理をすることはないため、信号処理における干渉も無く、消費電力の低減を可能にするものである。
【００３３】
さらに本第１実施形態の操舵角検知装置は、２つのマグネト・インピーダンス素子からの２つの磁場信号の比にもとづいて角度計測を行うので、２つのマグネト・インピーダンス素子の温度による感度変化があっても、両者を同一の基板上に形成するとともに、同一のパッケージ内に配置して、温度計数その他の物理的特性を互いに同じにしたので、温度誤差の混入はなく、高精度の操舵角変位の計測を実現するという効果を奏する。
【００３４】
また本第１実施形態の操舵角検知装置は、回転体磁石１の回転に伴う磁極Ｓ−Ｎの移動による正弦波の時々刻々の振幅信号から、同一の基板上に形成された前記検知コイルと前記１個の電子回路によって角度計測を行うので、安価でありながら磁場強さの変化および磁電変換素子の感度変化に対して安定かつ高分解能な操舵角検知を可能にするという効果を奏する。
【００３５】
さらに本第１実施形態の操舵角検知装置は、角度情報を抽出して連続的に角変位を求めるものであり、従来の磁極ピッチに基づいてパルスを発生する方式と異なり安価でありながら高分解能かつ高安定度な角変位センサを実現するという効果を奏する。
【００３６】
（第２実施形態）
本第２実施形態の操舵角検知装置は、上述の第１実施形態において操舵軸１０の外周に配設していた回転磁石１を、図３に示されるように自動車の操舵装置の構成要素であるラックに配置された直線状に着磁されたリニア磁石体１１の磁性体に変更した点が相違点である。
【００３７】
ハンドルの操作による操舵軸の回転に伴い前記ラック上のリニア磁石体１１が直線上において図３中矢符によって示されるように直線変位すると、上述の第１実施形態と同様の位相関係で配置されたアモルファスワイヤより成る２つのマグネト・インピーダンス素子２１、２２によって検知される磁場変化も正弦波となるので、上述の第１実施形態と同様に２つの磁場信号の比に基づいて操舵角を検知するものである。
【００３８】
本第２実施形態の操舵角検知装置は、リニア磁石体１１の直線変位に応じて、２つのマグネト・インピーダンス素子２１、２２によって検知される２つの磁場信号の比に基づいて操舵角を検知することにより、操舵角計測を行うことで磁場強さの変化、磁電変換素子の感度変化に対して安定かつ高分解能な計測を可能にするという効果を奏する。
【００３９】
また本第２実施形態の操舵角検知装置は、マグネト・インピーダンス素子としてアモルファスワイヤを用いることで高温度領域でも感度よく計測でき、また低消費電力でかつ小型、安価な角変位、直線変位センサを提供できるようにするものである。
【００４０】
（第３実施形態）
本第３実施形態の操舵角検知装置は、図１に示される前記第１実施形態の基本的構成と同様の基本的構成より成るもので、以下図４を用いて詳細に説明する。
【００４１】
回転体磁石１は、前記図１に示される第１実施形態と同様の構成であるため図４における図示を省略した。図４においてマグネト・インピーダンス磁気検出器２は、２つのマグネト・インピーダンス素子２１、２２と１つの共通の信号処理回路２３からなる。２つのマグネト・インピーダンス素子２１、２２は、前記回転体磁石の磁場を検出するために互いの位相φがπ／２（９０度）となるべく位置に配設されている。
【００４２】
２つのマグネト・インピーダンス素子２１、２２は、アモルファスワイヤ２１０、２２０に検出コイル２１１、２２１が巻回されてなるもので、このアモルファスワイヤ２１０、２２０にパルス電流を通電すると周囲の磁場の軸方向成分に対応する電圧が検出コイル２１１、２２１に瞬間的に誘起される。この検出コイル２１１、２２１に誘起された電圧を信号処理することで磁場信号を得ることができる。
【００４３】
信号処理回路２３は、前記２つのマグネト・インピーダンス素子２１、２２の信号を処理するためのもので、パルスジェネレータ２３１とサンプルホールド回路２３２からなる。
【００４４】
前記パルスジェネレータ２３１は、繰返し周波数が２ＭＨｚでパルス幅が数十ｎｓ（ナノ秒）でかつ所定の位相差で同期する２つのパルス列を発生し、端子Ｐ１、Ｐ２の組とＰ３、Ｐ４の組からそれぞれ５μｓ（マイクロ秒）の周期で切換えて交互に出力する。また、出力端子Ｐ５はこのパルス列を５μｓごとに交互に切換えるときの同期信号が出力されるが、これは後段の角度算出装置３に出力される。
【００４５】
前記パルスジェネレータ２３１の出力端子Ｐ１およびＰ３は、２つのマグネト・インピーダンス素子２１、２２のアモルファスワイヤに接続されているので、５μｓごとに交互に２ＭＨｚのパルス列の電流が印加される。パルスが印加されるとマグネト・インピーダンス素子２１、２２の検知コイルとしての各検出コイル２１１、２２１には周囲の磁場に対応する電圧が瞬間的に誘起される。
【００４６】
アナログスイッチＳ１、Ｓ２の制御端子に前記パルスジェネレータ２３１の出力端子Ｐ２、Ｐ４のパルスが印加されるが、前記のごとく端子Ｐ１のパルスとＰ２のパルスおよびＰ３のパルスとＰ４のパルスはそれぞれ同期しているので、Ｐ２あるいはＰ４のパルスがそれぞれのタイミングで印加されるとごく短期間このアナログスイッチが” 閉” になり前記マグネト・インピーダンス素子２１、２２の検出コイル２１１、２２１に瞬間的に誘起した磁場に対応する電圧が、サンプルホールド回路２３２を構成するコンデンサＣにホールドされる。
【００４７】
前述のごとくマグネト・インピーダンス素子に印加されるパルス列は２ＭＨｚであるので磁場の計測は２ＭＨｚの繰り返し頻度で間欠的に実行されるが、アナログスイッチＳ１ 、Ｓ２とコンデンサＣおよび増幅器Ａが、前記サンプルホールド回路２３２を形成しているのでこの出力端子Ｐ６の信号はほぼ連続的な波形である。
【００４８】
しかしながら前述のようにパルスジェネレータ２３１は、５μｓの周期でパルス列をＰ１、Ｐ２の組とＰ３、Ｐ４の組と交互に出力するので、このマグネト・インピーダンス磁気検出器２の出力端子Ｐ６の信号は前記マグネト・インピーダンス素子２１、２２が検出した磁気信号を時系列的に交互に出力する。
【００４９】
図５の（イ）は、図１に示される回転体磁石１が回転したときのマグネト・インピーダンス素子２１、２２が検出する磁場信号を表す。したがって横軸は時間でありかつ角度である。図５の（ロ）はこのときのマグネト・インピーダンス磁気検出器２の出力端子Ｐ６の信号波形を表す。図５の（ロ）においてａ、ｂの記号は前記したごとくマグネト・インピーダンス素子２１、２２の出力が５μｓの周期で交互に切換えられていることを表している。図５の（ロ）はわかりやすくするためにａ、ｂの切換えの時間幅を機械的な角度変化する早さに対して誇張して幅広く描いているが、実際の角度変化に対して十分短かい時間であるため実用上角度情報が途絶えるようなことはない。
【００５０】
図４に示される角度算出装置３は、主としてＡ／Ｄコンバータ３１とコンピュータ３２からなり信号処理回路２の出力にもとづいて回転角度（操舵角）および回転方向を演算し出力するものである。
【００５１】
前記信号処理回路２の出力端子Ｐ６の磁場信号は、Ａ／Ｄコンバータ３１に接続されており、時系列的に交互に切換えられたａ、ｂの各磁場信号は順次デジタル変換される。このときＡ／Ｄ変換された信号をａのデータとｂのデータとに弁別するため同期信号として前記パルスジェネレータ２３１の端子Ｐ５の切換え信号をマイクロコンピュータ３２に入力している。
【００５２】
すなわちパルスジェネレータ２３１の端子Ｐ５から出力される前記５μｓの切換え信号がロジックレベルの” １” になっている期間はａの磁場信号そして” ０” の期間はｂの磁場信号としてコンピュータ３２はａ、ｂのデータを整列する。
【００５３】
コンピュータ３２は、角度算出の基となるａｒｃｔａｎ（Ｈｂ／Ｈａ）の演算を行う角度演算器３２１と回転の方向を判別する回転方向判別器３２２と不連続に算出される角度データを連続化処理する加減算器３２３からなるが、これらの処理はすべてソフトウエアにしたがって行う。
【００５４】
まず角度演算器３２１は、前記数１にもとづきａｒｃｔａｎ（Ｈｂ／ Ｈａ）の演算を行い基本的な角変位信号を算出する。
この角度演算器３２１の情報は、回転方向判別器３２２と加減算器３２３に出力される。回転方向判別器３２２は微分演算機能からなるもので前記角度演算器３２１の出力を微分演算して、その結果が正であれば角度θが正回転、負であれば逆回転していると判断する。この回転方向信号は出力端子Ｐ３１を通して外部へ出力するとともに加減算器３２３へも出力する。
【００５５】
加減算器３２３は、前記回転角θが±π／２以上の領域において角度データが不連続になることを防ぐため、データの連続化処理を行うものであり、前記角度演算器３２１の出力が±π／２を超えたときの角度データ値にθ＝±π／２のときのデータの２倍の値を加算あるいは減算することでθの変化に対してデータを連続化する。すなわち回転の方向が正転の場合は加算を行い、逆転の場合は減算を行う。この正転、逆転の情報は前記回転方向判別器３２２の出力から得る。このように加減算器３２３によってデータの連続化処理をすることで必要に応じて任意の角度計測範囲を実現することができる。図６はこの連続化処理の結果の例であり、θの値が±π／２を超えたとき前記角度演算器３２１のデータが点線のごとく鋸歯状になるが、加減算器３２３の出力は実線のように連続化される。この実線で表されるデータが本角変位センサの出力端子Ｐ３２の信号である。
【００５６】
本第３実施形態の操舵角検知装置は、磁石体１の回転による回転磁場を２つのマグネト・インピーダンス素子２１、２２で検出し１つの信号処理回路２３で信号処理し、その２つの磁気信号の比から角度演算するので、前記数５に示したごとく回転体磁石の磁場の強さ｜Ｂ｜の項が消去されるため、操舵系に加わる加速度、振動などによる回転する磁性体と磁電変換素子とのギャップの変動あるいは温度変化による磁場変動、磁電磁変換素子の感度変化の影響を受けない安定で高精度の操舵角検出を可能にするとともに、その他上述の第１実施形態と同様の作用効果を奏する。
【００５７】
（第４実施形態）
第４実施形態の操舵角検知装置は、前記マグネト・インピーダンス磁気検出器２として２つのマグネト− インピーダンス素子２１、２２と時系列で切換えて信号処理する１つの信号処理回路をＩＣ化して超小型素子として構成し回転磁場内に容易に配設できるようにまとめたものである。
【００５８】
すなわち図７に示されるようにマグネト・インピーダンス磁気検出器２００は、マグネト− インピーダンス素子として長さ２ｍｍ、直径３０μｍのアモルファスワイヤ２０１、２０３を用い、その周囲に検出コイル２０２、２０４を巻回したものである。
【００５９】
またこの２つのマグネト・インピーダンス素子は、検出した磁気信号の互いの位相がπ／２となる位置に配設するとともにＩＣ化した信号処理回路２０５とともに同一の基板ＢＰ上に形成して一つのパッケージ２０６内に収納したものであるので、２つのセンサの特性を揃えることが出来るため、精度の高い測定を可能にするものである。
【００６０】
また前記信号処理回路２０５は、上述の実施形態と同様に切換えで２つのマグネト・インピーダンス素子の信号を交互に処理するものであるので、これにより装置全体を低消費電力とともに小型化でき、さらに前記回転磁場内に容易に取り付けることができ、また機械的な振動にも十分対応できるようにした。
【００６１】
さらに前記マグネト・インピーダンス素子の材料としてアモルファスワイヤを用いたことで、通常の磁電変換素子では厳しい１２０℃以上の温度領域でも計測可能になり、温度環境の厳しい自動車のステアリング角センサとして小型、低価格に実現できるようになった。
【００６２】
（第５実施形態）
第５実施形態の操舵角検知装置は、図１に示される回転体磁石１の材料としてフェライトを用いるものであり、図８は既設のステアリングシャフト１０に多極着磁したフェライト材のリング磁石１０２を装着したものである。
【００６３】
本第５実施形態の操舵角検知装置においては、磁場の強さが弱くても磁電変換素子として後述する高感度のマグネト− インピーダンス素子を用いることで十分な磁場検出が可能であり、堅牢かつ生産コストが安い操舵角センサを実現できるという効果を奏する。
【００６４】
【実施例】
以下上述の実施形態の自動車用操舵角検知装置において、用いることが出来る磁気検出器の実施例につき、図面を用いて説明する。
【００６５】
（実施例）
本実施例の磁気検出器は、図９に示されるように自動車分野における適用を考慮して、小型化して高感度化したもので、以下図９ないし図１１を用いて説明する。
【００６６】
前記磁気検出器２を構成する２つのマグネト・インピーダンス素子２１、２２の基板１００の大きさは、幅０．５ｍｍ、高さ０．５ｍｍとし、長手方向の長さを３ｍｍとし、感磁体２１０、２２０は、ＣｏＦｅＳｉＢ系合金を使った直径３０μｍまたは２０μｍであって長さ３ｍｍ以下のアモルファスワイヤである。 電磁コイル２１１、２２１は、 前記基板１００の長手方向に形成した溝１００Ｇの溝面１１１に形成されたコイルの片側２１１Ａ、２２１Ａと、溝１００Ｇに対向する溝上面１１２（樹脂ＳＲの上面ＳＲＵ）に形成された残り片側のコイル２１１Ｂ、２２１Ｂの２層構造により形成したものである。
【００６７】
前記溝面１１１および溝上面１１２に形成されるコイルの片側２１１Ａ、２２１Ａおよび残り片側のコイル２１１Ｂ、２２１Ｂは、図９および図１０に示されるように電極配線基板１００の長手方向に形成された溝１００Ｇの溝上面１１２よりある程度広い範囲にコイルを構成する導電性の磁性金属薄膜を蒸着により形成し、形成された金属薄膜が螺旋状に残るように間隙部を構成する導電性金属薄膜部を選択エッチング手法により除去することにより、コイルの全体の長手方向の長さを１．５ｍｍまたは２ｍｍの長さに亘り形成される。なお図１０において、図９のＡ−Ａ′断面にかかわらず、理解の便のために溝１００Ｇの全面の４面にロの字状にコイルが形成されている状態を示した。
【００６８】
電磁コイル２１１、２２１の円相当内径（高さと幅で形成される溝断面積と同一面積となる円の直径）は、２００μｍまたは１００μｍ以下であるのが望ましいので、６６μｍに一例として設定した。 電磁コイル２１１、２２１の１ターン当たりの（単位長さ当たり）の捲線間隔は１００μｍ／巻以下であるのが望ましいので、一例として５０μｍ／巻に設定されている。
【００６９】
素子基板１００の長さとして３ｍｍを採用して前記２つのマグネト・インピーダンス素子２１、２２のアモルファスワイヤ２１０、２２０および電磁コイル２１１、２２１が、図１０に示されるように一つの電極配線基板１００上に一体に形成され、前記磁気検出器２１、２２の両端に配設した電極を介して接続された前記信号処理回路２３としての電子回路も一つの電極配線基板１００上に形成され、かかる電子回路２３からのセンサ出力を横軸が外部磁場と縦軸が出力電圧を示す図１１に示す。
【００７０】
本実施例の磁気検出器は、自動車分野における適用を考慮して、小型化、薄型化、小容積化（幅０．５ｍｍ、高さ０．５ｍｍとし、長手方向の長さを３ｍｍ）を実現しながら、図１１から明らかなように４０ガウス（Ｇ）で０．２Ｖのフルスケールまでリニアな出力が得られ、リニアな測定および高感度な測定を実現するものである。
【００７１】
また本実施例の磁気検出器は、前記２つのマグネト・インピーダンス素子２１、２２のアモルファスワイヤ２１０、２２０および電磁コイル２１１、２２１が、同一全体基板上に一体に形成され、前記磁気検出器２１、２２の両端に配設した電極を介して接続された前記電子回路２３も同一全体基板上に形成され、同一のパッケージ内に配設されるので、２つのセンサの特性を揃えることが出来るため、精度の高い測定を可能にするとともに、センサを小さくし、高感度化を可能にし、処理回路および信号処理もシンプルにし、全体として小型化して、重量および消費電力を低減するという効果を奏する。
【００７２】
本実施例の磁気検出器は、自動車分野における適用を考慮して上述のように小型化、薄型化、小容積（幅０．５ｍｍ、高さ０．５ｍｍ、長手方向の長さ３ｍｍ）を実現しながら、図１１から明らかなように４０ガウス（Ｇ）で０．２Ｖのフルスケールまでリニアな出力が得られ、リニアな測定および高感度な測定を実現するものである。
【００７３】
また本実施例の磁気検出器は、マグネト・インピーダンス素子としてアモルファスワイヤを採用したので、アモルファスワイヤの本来の性質上、１２０℃の温度環境でも安定な動作が可能なため、自動車における１２０℃の温度環境でも安定な動作が可能であり、自動車用操舵装置の操舵角の検出に適するという効果を奏するものである。
【００７４】
さらに本実施例の磁気検出器は、マグネト・インピーダンス素子をより高感度な磁気センサとするために、検知コイルとしての電磁コイル２１１、２２１の円相当内径の半径を２００μｍまたは１００μｍ以下にするのが望ましい、本実施例においては一例として６６μｍに設定し、極めて小さくしてアモルファスワイヤと検出コイルとの電磁結合を大きくすることに対して有効であるとともに、センサの薄型化および小容量化にとっても有効である。
【００７５】
また本実施例の磁気検出器は、前記２つのマグネト・インピーダンス素子および信号処理回路を１つの基板にマウント（装荷）することにより、小型かつ取り扱いを容易にすることができ、さらにマグネト・インピーダンス素子が高感度のため回転体とのギャップを１ｍｍ以上に大きくしても安定な磁気計測ができるので自動車に取り付ける際に精密な組付け作業を必要としないので生産コストを抑制するという非常に大きな効果を奏する。
【００７６】
さらに本実施例においては、２ つのマグネト・インピーダンス素子を所定の精度で管理された自動機で製作するとともに、２つのマグネト・インピーダンス素子をそれぞれ駆動するＩＣ回路からなるパルスジェネレータの２つのドライバー回路の駆動特性およびそれぞれに対応するサンプルホールド回路の２つのアナログスイッチのスイッチ特性を同一とするため、それぞれ近接した場所に回路を形成するようにマスク設計を行い、２つのマグネト・インピーダンス素子の特性を互いに等しくしたので、２ つのマグネト・インピーダンス素子の特性を互いに等しくすることが出来るものである。
【００７７】
本実施例においては、基板１００の大きさは、幅０．５ｍｍ、高さ０．５ｍｍとし、長手方向の長さを３ｍｍとし、アモルファスワイヤの長さは３ｍｍ以下であることから、上述した図１１から明らかなように４０ガウスで０．２Ｖのフルスケールまでリニヤーな出力が得られるため、従来ヒステリシス特性や非直線特性を無くするためにアモルファスワイヤにもう一つのコイルを設けてこれにフィードバック電流を流したり、バイアス電流を流したりするフィードバック技術の必要性を解消するものである。これにより常時直流電流を流すことが不要となり低消費電力化が可能となった。またバイアスコイルを省略できマグネト・インピーダンス素子をシンプル化するものである。
【００７８】
上述の実施形態は、説明のために例示したもので、本発明としてはそれらに限定されるものでは無く、特許請求の範囲、発明の詳細な説明および図面の記載から当業者が認識することができる本発明の技術的思想に反しない限り、変更および付加が可能である。
【図面の簡単な説明】
【図１】本発明の第１実施形態の操舵角検知装置を示すブロック図である。
【図２】本第１実施形態の操舵角検知装置における出力波形を示す線図である。
【図３】本発明の第２実施形態の操舵角検知装置のセンサ部を示す斜視図である。
【図４】本発明の第３実施形態の操舵角検知装置を示す詳細ブロック図である。
【図５】本第３実施形態の操舵角検知装置における出力波形を示す線図である。
【図６】本第３実施形態の操舵角検知装置における連続化処理の結果を示す線図である。
【図７】本発明の第４実施形態の操舵角検知装置のセンサ部を示す斜視図である。
【図８】本発明の第５実施形態の操舵角検知装置のセンサ部を示す斜視図である。
【図９】本発明の実施例における磁気検出器を示す平面図である。
【図１０】本実施例における磁気検出器を示す図９中Ａ−Ａ′線に沿う横断面図である。
【図１１】本実施例における磁気検出器の外部磁場と出力電圧の関係を示す線図である。
【符号の説明】
１ 磁性体
１０ 操舵軸
２ 磁気センサ
２０ マグネト・インピーダンス磁気検出器
２１、２２ マグネト・インピーダンス素子
２３ 信号処理回路
３ 演算回路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic sensor for detecting a change in a periodic magnetic field associated with the movement of a moving member that moves with the rotation of a steering shaft of an automobile steering device in which a magnetic material whose magnetic properties change periodically is provided. A vehicle steering system comprising: a signal processing circuit that processes a detected change in a periodic magnetic field; and a calculation circuit that calculates a rotation angle of a steering shaft of a vehicle steering device based on an output signal output from the signal processing circuit. The present invention relates to a device for detecting a steering angle of a device.
[0002]
[Prior art]
The conventional steering angle detection device has a multi-pole magnetized part on the outer ring part of the rotating cam attached to the steering shaft that is linked to the rotation of the steering wheel, and a unipolar magnetized part with a unipolar magnetic field formed on the inner ring part. A magnetoresistive element for detecting a change in a multipolar magnetic field in opposition to the multipolar magnetized portion of the arranged magnetized ring, and detecting a change in a unipolar magnetic field in opposition to the monopolar magnetized portion. It comprises a Hall element, and converts a change in the magnetic field detected by the magnetoresistive element and the Hall element into a pulse signal to detect the rotation angle of the steering wheel (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-249574 (Pages 4 to 7, FIGS. 1 to 13)
[0004]
[Problems to be solved by the invention]
The conventional steering angle detection device includes a magnetoresistive element that detects a change in a multipolar magnetic field facing the multipolar magnetized portion of the magnetizing ring, and a magnetic resistance element that faces the single pole magnetized portion. Since the change in the magnetic field detected by the Hall element that detects the change in the magnetic field of the pole is converted into a pulse signal to detect the rotation angle of the steering wheel, the sensor becomes complicated and large, and in order to increase the angle detection accuracy If the number of poles is finely reduced, the magnetic force is reduced, so that there is a problem that the gap between the sensor and the sensor must be reduced.
[0005]
On the other hand, further improvement in angle detection accuracy (resolution) is required with the improvement of automobile control devices. In a conventional steering angle detection device, it is necessary to magnetize magnetic poles finely and densely. But it had physical and cost limitations.
[0006]
In addition, the magnetic field that can be detected becomes extremely small, resulting in insufficient sensitivity of magnetic sensors such as Hall elements, and the distance between the magnetized ring and the Hall elements needs to be further shortened (gap is reduced). Therefore, there is a problem of a defect due to contact between the rotating magnetizing ring and the Hall element of the fixed portion, a decrease in durability, and an increase in cost due to difficulty in assembling.
[0007]
Therefore, the present inventor has proposed a magnetic field detecting device for detecting a change in a periodic magnetic field accompanying the movement of a moving member that moves with the rotation of a steering shaft of an automobile steering device provided with a magnetic body whose magnetic properties change periodically. A vehicle comprising: a sensor; a signal processing circuit for processing a detected change in a periodic magnetic field; and a calculation circuit for calculating a rotation angle of a steering shaft of a vehicle steering device based on an output signal output from the signal processing circuit. In the steering angle detection device for a steering device, the magnetic sensor constituting the magneto-impedance magnetism detector has a phase relationship corresponding to a cycle in which the magnetic property of the magnetic material disposed on the moving member changes. The two magneto-impedance elements are arranged so that the one signal processing circuit switches the output from the two magneto-impedance elements. The signal processing is performed by alternately switching the stages, and the arithmetic circuit detects an angle based on a ratio of outputs of the two magneto-impedance elements detected by the two magneto-impedance elements and alternately output from the signal processing circuit. Focusing on the technical idea of the present invention to detect displacement, and as a result of further research and development, the aim was to make the sensor simple and small, and to eliminate the need to reduce the gap with the sensor because of its high detection sensitivity. Achieved invention reached.
[0008]
[Means for Solving the Problems]
The steering angle detection device for a vehicle steering device according to the present invention (the first invention according to claim 1) includes:
A magnetic sensor that detects a change in a periodic magnetic field accompanying movement of a moving member that moves with rotation of a steering shaft of an automobile steering device in which a magnetic material whose magnetic properties change periodically is provided; A steering angle of a vehicle steering system including a signal processing circuit for processing a change in a periodic magnetic field and a calculation circuit for calculating a rotation angle of a steering shaft of the vehicle steering system based on an output signal output from the signal processing circuit In the detection device,
The magnetic sensor is configured by two magneto-impedance elements arranged so as to have a phase relationship according to a cycle in which the magnetic properties of the magnetic body arranged on the moving member change,
The signal processing circuit includes a magneto impedance magnetic detector including one signal processing circuit that performs signal processing by alternately switching the output from the two magneto impedance elements by switching means,
The arithmetic circuit detects angular displacement based on a ratio of outputs of the two magneto-impedance elements detected by the two magneto-impedance elements and output alternately from the signal processing circuit.
Things.
[0009]
According to a second aspect of the present invention, there is provided a steering angle detecting device for a steering device for an automobile.
In the first invention,
The two magneto-impedance elements are arranged so as to have a phase difference of 90 degrees with respect to the pitch of N-S of the magnetic poles of the magnetic body,
The arithmetic circuit calculates a steering angle θ from the output Ha of one magneto-impedance element and the output Hb of the other magneto-impedance element according to the relationship of Equation 1.
The arithmetic circuit calculates a rotation direction of a steering shaft of a vehicle steering device based on a change rate of an output signal from the two magneto-impedance elements.
Things.
[0010]
According to a third aspect of the present invention, there is provided a steering angle detecting device for a vehicle steering device.
In the second invention,
The two magneto-impedance elements comprise an amorphous wire and a sensing coil wound around the amorphous wire;
The one signal processing circuit alternately switches the two magneto-impedance elements to supply a pulse, and alternately holds two magnetic signals obtained in synchronization with the pulse generator for a predetermined time. A set of electronic circuits consisting of sample and hold circuits that output in series
Things.
[0011]
The steering angle detecting device of the steering device for a vehicle according to the present invention (the fourth invention according to claim 4) includes:
In the third invention,
The two magneto-impedance elements and the set of electronic circuits are formed on the same substrate.
Things.
[0012]
Function and Effect of the Invention
The steering angle detecting device for a vehicle steering system according to the first aspect of the present invention, wherein the magnetic property of the magnetic body disposed on the moving member that configures the magnetic sensor that configures the magneto-impedance magnetic detector. The two magneto-impedance elements arranged so as to have a phase relationship corresponding to the changing cycle detects a change in the periodic magnetic field, and the one signal processing circuit constituting the signal processing circuit is The output from the two magneto-impedance elements is alternately switched by switching means to perform signal processing, and the arithmetic circuit is detected by the two magneto-impedance elements and output alternately from the signal processing circuit. Detects angular displacement based on the ratio of the outputs of two magneto-impedance elements. Since the other magneto-impedance element is not operating when the other impedance element is operating, it is not electromagnetically affected by the operation of the other magneto-impedance element. In addition, since the sensor is simple and small, and the detection sensitivity is high, it is not necessary to reduce the gap between the sensor and the sensor.
[0013]
The steering angle detecting device for a vehicle steering system according to a second invention having the above-mentioned structure is arranged so as to have a phase difference of 90 degrees with respect to the pitch of NS of the magnetic poles of the magnetic body in the first invention. The two magneto-impedance elements are used to detect a change in the periodic magnetic field of the magnetic material, and the signal processing circuit outputs an output Ha of one magneto-impedance element and an output Hb of the other magneto-impedance element. The steering angle θ is calculated according to the relationship of Equation 1, and the arithmetic circuit calculates the rotational direction of the steering shaft of the vehicle steering device based on the change rate of the output signal from the two magneto impedance elements. Therefore, high-resolution and high-precision steering angle detection without temperature errors can be detected, and the rotation direction of the steering shaft can be detected. Achieve the.
[0014]
In the steering angle detecting device for a vehicle steering system according to a third aspect of the present invention, in the second aspect, the two magneto-impedance elements detect an ambient magnetic field when a pulse current is applied to an amorphous wire. A voltage is induced by the detection coil wound around the wire, and the electronic circuit as the one signal processing circuit is used for the pulse application of the pulse generator that alternately switches the two magneto-impedance elements and applies the pulse. Since the two magnetic signals obtained by the sample-and-hold circuit in synchronization are alternately held for a predetermined time and output in a time series, when one of the magneto-impedance elements is energized by a pulse and is operating, the other of the magneto-impedance elements is operated. Since the impedance elements are not energized due to pulsed current, the other The sensor is not affected by the electromagnetic current caused by the pulsed power supply and operation of the impedance element, which enables high-precision rotation speed detection and reduces power consumption by eliminating simultaneous signal processing in the electronic circuit. This has the effect of making the signal processing circuit compact and simple.
[0015]
The steering angle detecting device for a vehicle steering system according to a fourth aspect of the present invention is the steering angle detecting device according to the third aspect, wherein the two magneto-impedance elements and the set of electronic circuits are formed on a same substrate. Since the characteristics of the two sensors can be matched, high-precision measurement is possible, and at the same time, the size of the sensors is reduced, the sensitivity is increased, the processing circuit is simplified, and the overall size is reduced. In addition to reducing power consumption, it is possible to eliminate the necessity of assembling the conventional steering angle sensor with high precision.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
(1st Embodiment)
As shown in FIG. 1 and FIG. 2, the steering angle detecting device for a vehicle steering system according to the first embodiment has a periodic magnetic property on the outer periphery of a part of the steering shaft 10 of the vehicle steering system in the axial direction. A magnetic body 1 is disposed on the outer periphery, and a magnetic sensor 2 that detects a change in a periodic magnetic field accompanying rotation of a steering shaft, a signal processing circuit 23 that performs signal processing on the detected change in the periodic magnetic field, and In the steering angle detecting device for a vehicle steering system provided with a calculation circuit 3 for calculating the rotation angle of the steering shaft of the vehicle steering system based on the output signal output from the signal processing circuit 23, the magnetic sensor 2 is used for controlling the steering angle. The two magnetic impedance elements 21 and 22 are arranged so that the magnetic property of the magnetic body 1 disposed on the shaft 10 has a phase relationship corresponding to a changing cycle. 23 comprises a magneto impedance magnetic detector 20 comprising one signal processing circuit for alternately switching the output from the two magneto impedance elements by switching means and processing the signal, and the arithmetic circuit 3 comprises The angular displacement is detected based on the ratio of the outputs of the two magneto-impedance elements which are detected by the two magneto-impedance elements 21 and 22 and output alternately from the signal processing circuit.
[0018]
The basic configuration of the first embodiment is, as shown in FIG. 1, to have a rotating body magnet 1 as the magnetic body and a predetermined phase angle φ for detecting a magnetic signal that changes sinusoidally with the rotation. Magneto-impedance magnetism detection comprising two magneto-impedance elements 21 and 22 as disposed magneto-electric conversion elements and one signal processing circuit 23 for alternately switching between the two magneto-impedance elements and outputting a magnetic signal. And an angle calculator 3 for calculating an angular displacement based on a ratio of two magnetic signals of the two magneto-impedance elements 21 and 22.
[0019]
Next, the principle of the angular displacement sensor in the steering angle detecting device of the automotive steering device according to the first embodiment will be described.
[0020]
Now, suppose that the magneto-impedance element 21 which is a magnetoelectric conversion element is closest to the N pole of the rotating magnet 1 in FIG. 1, and that the magneto-impedance element b is separated by a phase φ. The signals Ha and Hb detected by the two magneto-impedance elements a and b when the angular displacement (angle) θ (radian) is rotated in the direction of the arrow in FIG. Become like Here, assuming that the maximum value of the magnetic field received by the two magneto-impedance elements a and b is | B |, Ha and Hb are represented by Equations 2 and 3.
(Equation 2)

[Equation 3]

[0021]
Here, when the phase angle of the two magneto-impedance elements 21 and 22 is set at a position where φ = π / 2 (90 degrees), Equation 3 can be rewritten as Equation 4.
(Equation 4)

[0022]
Next, when the ratio Hb / Ha of the two detection signals is calculated, Equation 5 is obtained.
(Equation 5)

[0023]
That is, as shown in Equation 5, since the denominator and the numerator have | B |, when the ratio of the detection signals is calculated, Hb / Ha becomes sin θ / cos θ, and the magnetic field strength | B | Is eliminated. This means that the strength of the magnetic field is not related to the calculation result of the ratio of the detection signals, that is, it is not affected by the magnetic field fluctuation. Then, since sin θ / cos θ = tan θ, it can be seen that the angular displacement θ can be measured in a linear relationship by performing the operation of arctan (Hb / Ha) as shown in Equation 1 above.
[0024]
The above relationship is illustrated in FIG.
That is, the value of the vertical axis arctan (Hb / Ha), which is the output, changes linearly from -π / 2 to + π / 2 during a period in which the change width of the angular displacement θ is π radians (± π / 2 in this case). I do. In a region where the change of the angular displacement θ exceeds ± π / 2, the data becomes saw-toothed and discontinuous every time the angle increases or decreases by π (180 degrees), and the above-described positive and negative values are repeated.
[0025]
The fact that the term | B | of the magnetic field strength disappears from the calculation result of Hb / Ha as seen from the above equation 4 means that the gap between the rotating magnet 1 and the magneto-impedance element, which is the detection element, as described above. However, even if the strength of the magnetic field applied to the magneto-impedance element fluctuates due to mechanical eccentricity or backlash, no error is mixed in the angle measurement signal. Even if the magnetic field strength of the magnet changes due to temperature, no error is mixed for the same reason. Further, since Ha and Hb are detection signals of the magneto-impedance element, even if there is a change in sensitivity due to the temperature of the magneto-impedance element, if the two temperature counts are the same, errors are mixed in the same manner as described above. No, it can measure the angular displacement with high accuracy.
[0026]
Although the description has been given here assuming that the phase φ of the magneto-impedance elements 21 and 22 takes a value of π, this measurement method is valid even if φ ≠ π (except for φ = 0). The feature of being unaffected by fluctuations and changes in the sensitivity of the magneto-impedance element is maintained. However, the only difference from the above is that the relationship between the angular displacement θ and Hb / Ha does not become a linear relationship.
[0027]
Next, the magneto-impedance magnetic detector 20 as the magneto-electric conversion element is constituted by one electronic circuit 23 for alternately switching the driving of the two magneto-impedance elements 21 and 22 and the signal processing to perform the time series. Is done. This is for realizing an angular displacement sensor with low power consumption and low cost.
[0028]
The output of the magneto-impedance magnetic detector 2 is connected to the angle calculator 3. The angle calculating device 3 calculates Hb / Ha and arctan (Hb / Ha) from two signals Ha and Hb of the two magneto-impedance elements 21 and 22 of the magneto-impedance magnetic detector 2 to calculate the angle. Calculate and output the displacement and change direction (rotation direction).
[0029]
The detection coil and the set of electronic circuits are formed on the same substrate.
[0030]
As shown in FIG. 1, the steering angle detecting device according to the first embodiment having the above-described configuration provides a momentary amplitude signal of a sine wave due to the movement of the magnetic pole SN along with the rotation of the rotating magnet 1 having the magnetic poles around it. Therefore, since the angle measurement is performed based on the ratio of the two magnetic field signals, an effect of enabling high-resolution and high-accuracy steering angle detection is achieved.
[0031]
Further, in the steering angle detecting device according to the first embodiment, the magneto-impedance magnetism detector 2 as the magneto-electric conversion element performs time series by alternately switching between driving of the two magneto-impedance elements 21 and 22 and signal processing thereof. Since it is composed of one electronic circuit 23 for performing the operation, an effect of realizing a low power consumption and low cost angular displacement sensor can be achieved.
[0032]
That is, in the first embodiment, when one of the magneto-impedance elements is operating with the pulse current, the other magneto-impedance element is not operating because the pulse is not energized. Since there is no electromagnetic influence due to the operation accompanying the pulse energization of the element, high-precision rotation speed detection is enabled, and simultaneous energization of the two magneto-impedance elements and simultaneous signal processing in the signal processing circuit are performed. Therefore, the power consumption can be reduced without interference in signal processing.
[0033]
Further, since the steering angle detecting device of the first embodiment measures the angle based on the ratio of two magnetic field signals from the two magneto impedance elements, there is a sensitivity change due to the temperature of the two magneto impedance elements. Also, since both were formed on the same substrate and arranged in the same package and the temperature counting and other physical characteristics were the same as each other, there was no mixing of temperature error, and the steering angle displacement was highly accurate. This has the effect of realizing measurement.
[0034]
Further, the steering angle detecting device according to the first embodiment uses the detection coil formed on the same substrate based on a sine wave momentary amplitude signal due to the movement of the magnetic pole SN accompanying the rotation of the rotating magnet 1. Since the angle measurement is performed by the single electronic circuit, an effect of enabling a stable and high-resolution steering angle detection with respect to a change in the magnetic field strength and a change in the sensitivity of the magneto-electric conversion element while being inexpensive is achieved.
[0035]
Further, the steering angle detecting device of the first embodiment extracts angle information and continuously calculates angular displacement. Unlike the conventional method of generating a pulse based on the magnetic pole pitch, the steering angle detecting device is inexpensive and has a high resolution. In addition, there is an effect that an angular displacement sensor having high stability is realized.
[0036]
(2nd Embodiment)
The steering angle detecting device according to the second embodiment uses the rotating magnet 1 disposed on the outer periphery of the steering shaft 10 in the above-described first embodiment as a component of a steering device of an automobile as shown in FIG. The difference is that the magnetic body is changed to a linear magnet body 11 linearly magnetized and arranged in a certain rack.
[0037]
When the linear magnet body 11 on the rack is linearly displaced in a straight line as indicated by an arrow in FIG. 3 along with the rotation of the steering shaft by the operation of the steering wheel, the linear magnet bodies 11 are arranged in the same phase relationship as in the first embodiment. Since the magnetic field change detected by the two magneto-impedance elements 21 and 22 made of an amorphous wire also becomes a sine wave, the steering angle is detected based on the ratio of the two magnetic field signals as in the first embodiment. It is.
[0038]
The steering angle detecting device according to the second embodiment detects a steering angle based on a ratio of two magnetic field signals detected by two magneto impedance elements 21 and 22 according to a linear displacement of the linear magnet body 11. Thus, there is an effect that the measurement of the steering angle enables stable and high-resolution measurement with respect to the change in the magnetic field strength and the change in the sensitivity of the magnetoelectric conversion element.
[0039]
Further, the steering angle detecting device of the second embodiment can measure with high sensitivity even in a high temperature region by using an amorphous wire as a magneto-impedance element, and has a small and inexpensive angular displacement and linear displacement sensor with low power consumption. To make it available.
[0040]
(Third embodiment)
The steering angle detecting device according to the third embodiment has the same basic configuration as that of the first embodiment shown in FIG. 1, and will be described in detail below with reference to FIG.
[0041]
Since the rotating magnet 1 has the same configuration as that of the first embodiment shown in FIG. 1, it is not shown in FIG. 4, the magneto-impedance magnetic detector 2 includes two magneto-impedance elements 21 and 22 and one common signal processing circuit 23. The two magneto-impedance elements 21 and 22 are arranged at positions where the mutual phase φ becomes π / 2 (90 degrees) in order to detect the magnetic field of the rotating magnet.
[0042]
The two magneto-impedance elements 21 and 22 are formed by winding detection coils 211 and 221 around amorphous wires 210 and 220. When a pulse current is applied to the amorphous wires 210 and 220, axial components of the surrounding magnetic field are applied. Are instantaneously induced in the detection coils 211 and 221. A magnetic field signal can be obtained by performing signal processing on the voltage induced in the detection coils 211 and 221.
[0043]
The signal processing circuit 23 is for processing signals of the two magneto-impedance elements 21 and 22 and includes a pulse generator 231 and a sample and hold circuit 232.
[0044]
The pulse generator 231 generates two pulse trains having a repetition frequency of 2 MHz, a pulse width of several tens of ns (nanoseconds), and synchronizing with a predetermined phase difference, and outputs a pair of terminals P1 and P2 and a pair of terminals P3 and P4. The signals are switched and output alternately at a period of 5 μs (microsecond). The output terminal P5 outputs a synchronizing signal for alternately switching the pulse train every 5 μs, which is output to the angle calculating device 3 at the subsequent stage.
[0045]
The output terminals P1 and P3 of the pulse generator 231 are connected to the amorphous wires of the two magneto-impedance elements 21 and 22, so that a pulse train of 2 MHz is applied alternately every 5 μs. When a pulse is applied, a voltage corresponding to a surrounding magnetic field is instantaneously induced in each of the detection coils 211 and 221 as detection coils of the magneto-impedance elements 21 and 22.
[0046]
The pulses at the output terminals P2 and P4 of the pulse generator 231 are applied to the control terminals of the analog switches S1 and S2. As described above, the pulses at the terminals P1 and P2 and the pulses at P3 and P4 are synchronized, respectively. Therefore, when the pulse of P2 or P4 is applied at each timing, this analog switch is turned "closed" for a very short time and instantaneously induced the detection coils 211 and 221 of the magneto-impedance elements 21 and 22. The voltage corresponding to the magnetic field is held by the capacitor C that forms the sample and hold circuit 232.
[0047]
As described above, since the pulse train applied to the magneto-impedance element is 2 MHz, the measurement of the magnetic field is performed intermittently at a repetition frequency of 2 MHz. However, the analog switches S1 and S2, the capacitor C and the amplifier A are Since the circuit 232 is formed, the signal at the output terminal P6 has a substantially continuous waveform.
[0048]
However, as described above, the pulse generator 231 alternately outputs a pulse train with a set of P1 and P2 and a set of P3 and P4 with a period of 5 μs. Therefore, the signal of the output terminal P6 of the magneto-impedance magnetic detector 2 is The magnetic signals detected by the magneto-impedance elements 21 and 22 are alternately output in time series.
[0049]
FIG. 5A illustrates a magnetic field signal detected by the magneto-impedance elements 21 and 22 when the rotating magnet 1 illustrated in FIG. 1 rotates. Thus, the horizontal axis is time and angle. FIG. 5B shows the signal waveform at the output terminal P6 of the magneto-impedance magnetic detector 2 at this time. In FIG. 5B, the symbols a and b indicate that the outputs of the magneto-impedance elements 21 and 22 are alternately switched at a period of 5 μs as described above. In FIG. 5B, for the sake of simplicity, the time width of switching a and b is exaggerated with respect to the speed at which the mechanical angle changes, but is sufficiently short with respect to the actual angle change. Because it is a padding time, there is no practical interruption of angle information.
[0050]
The angle calculation device 3 shown in FIG. 4 mainly includes an A / D converter 31 and a computer 32, and calculates and outputs a rotation angle (steering angle) and a rotation direction based on an output of the signal processing circuit 2.
[0051]
The magnetic field signal at the output terminal P6 of the signal processing circuit 2 is connected to the A / D converter 31, and the magnetic field signals a and b alternately switched in time series are sequentially converted to digital signals. At this time, a switching signal of the terminal P5 of the pulse generator 231 is input to the microcomputer 32 as a synchronization signal in order to discriminate the A / D converted signal into data a and data b.
[0052]
That is, while the 5 μs switching signal output from the terminal P5 of the pulse generator 231 is at the logic level “1”, the computer 32 generates a magnetic field signal of “a” and a magnetic field signal of “b” during the period of “0”. Align the data of b.
[0053]
The computer 32 continually processes the angle data that is calculated discontinuously and the angle calculator 321 that calculates arctan (Hb / Ha), which is the basis of the angle calculation, and the rotation direction determiner 322 that determines the direction of rotation. It comprises an adder / subtractor 323, and all of these processes are performed according to software.
[0054]
First, the angle calculator 321 performs a calculation of arctan (Hb / Ha) based on Equation 1 to calculate a basic angular displacement signal.
The information of the angle calculator 321 is output to the rotation direction discriminator 322 and the adder / subtractor 323. The rotation direction discriminator 322 has a differential operation function. The output of the angle operation unit 321 is differentiated, and if the result is positive, it is determined that the angle θ is rotating forward, and if the result is negative, it is determined that the angle θ is rotating reversely. I do. This rotation direction signal is output to the outside through the output terminal P31 and also to the adder / subtractor 323.
[0055]
The adder / subtractor 323 performs a data continuation process in order to prevent the angle data from becoming discontinuous in a region where the rotation angle θ is ± π / 2 or more. By adding or subtracting twice the value of the data when θ = ± π / 2 to or from the angle data value when the value exceeds π / 2, the data is made continuous with respect to the change in θ. That is, when the rotation direction is forward rotation, addition is performed, and when the rotation direction is reverse rotation, subtraction is performed. The information of the normal rotation and the reverse rotation is obtained from the output of the rotation direction discriminator 322. By performing the data continuation processing by the adder / subtractor 323 in this manner, an arbitrary angle measurement range can be realized as necessary. FIG. 6 shows an example of the result of this continuation process. When the value of θ exceeds ± π / 2, the data of the angle calculator 321 becomes saw-toothed like a dotted line, but the output of the adder / subtractor 323 is a solid line. It is continuous as follows. The data represented by the solid line is the signal of the output terminal P32 of the angular displacement sensor.
[0056]
The steering angle detecting device according to the third embodiment detects the rotating magnetic field due to the rotation of the magnet body 1 with the two magneto-impedance elements 21 and 22, performs signal processing with one signal processing circuit 23, and processes the two magnetic signals. Since the angle is calculated from the ratio, the term of the magnetic field strength | B | of the rotating magnet is eliminated as shown in Equation 5, so that the rotating magnetic body and the magnetoelectric conversion element due to acceleration, vibration, etc. applied to the steering system And enables stable and accurate steering angle detection without being affected by magnetic field fluctuations due to gap fluctuations or temperature changes, and changes in the sensitivity of the magneto-electromagnetic transducer. Other effects similar to those of the above-described first embodiment are provided. To play.
[0057]
(Fourth embodiment)
The steering angle detecting apparatus according to the fourth embodiment is a microminiature element which is formed by integrating one signal processing circuit for performing signal processing by switching in time series with two magneto-impedance elements 21 and 22 as the magneto-impedance magnetic detector 2. And are arranged so that they can be easily arranged in a rotating magnetic field.
[0058]
That is, as shown in FIG. 7, the magneto-impedance magnetic detector 200 uses amorphous wires 201 and 203 having a length of 2 mm and a diameter of 30 μm as magneto-impedance elements, and detection coils 202 and 204 are wound therearound. It is.
[0059]
The two magneto-impedance elements are arranged at positions where the phases of the detected magnetic signals are π / 2, and are formed on the same substrate BP together with the signal processing circuit 205 formed as an IC. Since the sensor is housed in the sensor 206, the characteristics of the two sensors can be made uniform, thereby enabling highly accurate measurement.
[0060]
Since the signal processing circuit 205 processes signals of the two magneto-impedance elements alternately by switching in the same manner as in the above-described embodiment, the overall device can be reduced in size with low power consumption. It can be easily installed in a rotating magnetic field, and can sufficiently cope with mechanical vibration.
[0061]
Further, by using an amorphous wire as the material of the magneto-impedance element, it is possible to measure even in a severe temperature range of 120 ° C. or more with a normal magneto-electric conversion element, and it is small and inexpensive as a steering angle sensor for an automobile having a severe temperature environment. It can now be realized.
[0062]
(Fifth embodiment)
The steering angle detecting device according to the fifth embodiment uses ferrite as a material of the rotating magnet 1 shown in FIG. 1, and FIG. 8 shows a ring magnet 102 made of a ferrite material multipolarly magnetized on an existing steering shaft 10. Is attached.
[0063]
In the steering angle detecting device of the fifth embodiment, even if the strength of the magnetic field is weak, a sufficient magnetic field can be detected by using a high-sensitivity magneto-impedance element, which will be described later, as the magnetoelectric conversion element. There is an effect that a steering angle sensor with low cost can be realized.
[0064]
【Example】
Hereinafter, an example of a magnetic detector that can be used in the vehicle steering angle detecting device of the above embodiment will be described with reference to the drawings.
[0065]
(Example)
As shown in FIG. 9, the magnetic detector of the present embodiment is miniaturized and has high sensitivity in consideration of application in the field of automobiles, and will be described below with reference to FIGS.
[0066]
The size of the substrate 100 of the two magneto-impedance elements 21 and 22 constituting the magnetic detector 2 is 0.5 mm in width and 0.5 mm in height, and 3 mm in the longitudinal direction. Reference numeral 220 denotes an amorphous wire having a diameter of 30 μm or 20 μm and a length of 3 mm or less using a CoFeSiB-based alloy. The electromagnetic coils 211 and 221 are provided on one side 211A and 221A of the coil formed on the groove surface 111 of the groove 100G formed in the longitudinal direction of the substrate 100 and on the groove upper surface 112 (the upper surface SRU of the resin SR) facing the groove 100G. It is formed by a two-layer structure of the formed one-sided coils 211B and 221B.
[0067]
The coils 211A and 221A on one side and the coils 211B and 221B on the other side formed on the groove surface 111 and the groove upper surface 112 have grooves formed in the longitudinal direction of the electrode wiring board 100 as shown in FIGS. A conductive magnetic metal thin film forming a coil is formed by vapor deposition in a range wider than the 100G groove upper surface 112 to some extent, and a conductive metal thin film portion forming a gap is selected so that the formed metal thin film remains spirally. By removing by an etching technique, the entire length of the coil in the longitudinal direction is formed over a length of 1.5 mm or 2 mm. Note that FIG. 10 shows a state in which coils are formed in a rectangular shape on four surfaces on the entire surface of the groove 100G for convenience of understanding, irrespective of the AA ′ cross section in FIG.
[0068]
The inner diameter of a circle equivalent to the circle of the electromagnetic coils 211 and 221 (diameter of a circle having the same area as the cross-sectional area formed by the height and width) is desirably 200 μm or 100 μm or less. The winding interval per turn (per unit length) of the electromagnetic coils 211 and 221 is desirably 100 μm / turn or less, and is set to 50 μm / turn as an example.
[0069]
By adopting 3 mm as the length of the element substrate 100, the amorphous wires 210 and 220 and the electromagnetic coils 211 and 221 of the two magneto-impedance elements 21 and 22 are placed on one electrode wiring substrate 100 as shown in FIG. An electronic circuit as the signal processing circuit 23, which is formed integrally with the magnetic detectors 21 and 22 and connected via electrodes provided at both ends of the magnetic detectors 21 and 22, is also formed on one electrode wiring board 100. FIG. 11 shows the sensor output from 23 in which the horizontal axis represents the external magnetic field and the vertical axis represents the output voltage.
[0070]
The magnetic detector of the present embodiment realizes miniaturization, thinning, and volume reduction (width 0.5 mm, height 0.5 mm, and length in the longitudinal direction 3 mm) in consideration of application in the automotive field. On the other hand, as is clear from FIG. 11, a linear output up to a full scale of 0.2 V at 40 Gauss (G) is obtained, realizing a linear measurement and a highly sensitive measurement.
[0071]
Further, in the magnetic detector of this embodiment, the amorphous wires 210 and 220 and the electromagnetic coils 211 and 221 of the two magneto-impedance elements 21 and 22 are integrally formed on the same whole substrate. Since the electronic circuit 23 connected via the electrodes provided at both ends of 22 is also formed on the same overall substrate and is provided in the same package, the characteristics of the two sensors can be made uniform. In addition to enabling high-accuracy measurement, the size of the sensor can be reduced, the sensitivity can be increased, the processing circuit and signal processing can be simplified, the overall size can be reduced, and the weight and power consumption can be reduced.
[0072]
The magnetic detector of the present embodiment realizes miniaturization, thinning, and small volume (width 0.5 mm, height 0.5 mm, length in the longitudinal direction 3 mm) as described above in consideration of application in the automobile field. On the other hand, as is clear from FIG. 11, a linear output up to a full scale of 0.2 V at 40 Gauss (G) is obtained, realizing a linear measurement and a highly sensitive measurement.
[0073]
Further, since the magnetic detector of this embodiment employs an amorphous wire as the magneto-impedance element, it can operate stably even in a temperature environment of 120 ° C. due to the inherent properties of the amorphous wire. It is possible to operate stably even in an environment, and it is effective in detecting a steering angle of a vehicle steering system.
[0074]
Furthermore, in the magnetic detector of this embodiment, in order to make the magneto-impedance element a magnetic sensor with higher sensitivity, the radius of the inner diameter of the electromagnetic coils 211 and 221 as the detection coil should be 200 μm or 100 μm or less. Desirably, in this embodiment, it is set to 66 μm as an example, which is effective for increasing the electromagnetic coupling between the amorphous wire and the detection coil by making it extremely small, and also effective for making the sensor thinner and smaller in capacity. It is.
[0075]
Further, the magnetic detector of this embodiment can be compact and easy to handle by mounting (loading) the two magneto-impedance elements and the signal processing circuit on one substrate. However, because of its high sensitivity, stable magnetic measurement can be performed even when the gap with the rotating body is increased to 1 mm or more, so there is no need for precise assembly work when mounting the product on a car, so a very large effect of suppressing production costs. To play.
[0076]
Further, in the present embodiment, two magneto impedance elements are manufactured by an automatic machine controlled with a predetermined accuracy, and two driver circuits of a pulse generator including an IC circuit for driving the two magneto impedance elements, respectively. In order to make the drive characteristics and the switch characteristics of the two analog switches of the corresponding sample-and-hold circuits the same, a mask is designed so that the circuits are formed in close proximity to each other, and the characteristics of the two magneto-impedance elements are compared with each other. Because they are equal, the characteristics of the two magneto-impedance elements can be made equal to each other.
[0077]
In the present embodiment, the size of the substrate 100 is 0.5 mm in width and 0.5 mm in height, the length in the longitudinal direction is 3 mm, and the length of the amorphous wire is 3 mm or less. As is clear from FIG. 11, since a linear output is obtained up to a full scale of 0.2 V at 40 Gauss, another coil is provided on the amorphous wire to eliminate the hysteresis characteristic and the non-linear characteristic, and a feedback current is supplied to the amorphous wire. This eliminates the need for a feedback technique for flowing a bias current or a bias current. As a result, it is not necessary to always supply a direct current, and power consumption can be reduced. Further, the bias coil can be omitted to simplify the magneto-impedance element.
[0078]
The above-described embodiment has been described by way of example, and the present invention is not limited to the embodiment. It will be recognized by those skilled in the art from the claims, the detailed description of the invention, and the drawings. Modifications and additions are possible without violating the technical idea of the present invention.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a steering angle detection device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an output waveform in the steering angle detecting device of the first embodiment.
FIG. 3 is a perspective view showing a sensor unit of a steering angle detecting device according to a second embodiment of the present invention.
FIG. 4 is a detailed block diagram illustrating a steering angle detection device according to a third embodiment of the present invention.
FIG. 5 is a diagram showing an output waveform in the steering angle detection device according to the third embodiment.
FIG. 6 is a diagram showing a result of a continuation process in the steering angle detection device according to the third embodiment.
FIG. 7 is a perspective view showing a sensor unit of a steering angle detecting device according to a fourth embodiment of the present invention.
FIG. 8 is a perspective view showing a sensor unit of a steering angle detecting device according to a fifth embodiment of the present invention.
FIG. 9 is a plan view showing a magnetic detector according to the embodiment of the present invention.
FIG. 10 is a cross-sectional view of the magnetic detector according to the present embodiment, taken along line AA 'in FIG.
FIG. 11 is a diagram showing a relationship between an external magnetic field and an output voltage of the magnetic detector in the present embodiment.
[Explanation of symbols]
1 Magnetic material
10 Steering axis
2 Magnetic sensor
20 magneto impedance magnetic detector
21,22 magneto impedance element
23 signal processing circuit
3 Operation circuit

Claims (4)

A magnetic sensor that detects a change in a periodic magnetic field accompanying movement of a moving member that moves with rotation of a steering shaft of an automobile steering device in which a magnetic material whose magnetic properties change periodically is provided; A steering angle of a vehicle steering system including a signal processing circuit for processing a change in a periodic magnetic field and a calculation circuit for calculating a rotation angle of a steering shaft of the vehicle steering system based on an output signal output from the signal processing circuit In the detection device,
The magnetic sensor is configured by two magneto-impedance elements arranged so as to have a phase relationship according to a cycle in which the magnetic properties of the magnetic body arranged on the moving member change,
The signal processing circuit includes a magneto impedance magnetic detector including one signal processing circuit that performs signal processing by alternately switching the output from the two magneto impedance elements by switching means,
An automobile wherein the arithmetic circuit detects angular displacement based on a ratio of outputs of the two magneto-impedance elements detected by the two magneto-impedance elements and output alternately from the signal processing circuit. Angle detection device for a steering device. In claim 1,
The two magneto-impedance elements are arranged so as to have a phase difference of 90 degrees with respect to the pitch of N-S of the magnetic poles of the magnetic body,
The arithmetic circuit calculates a steering angle θ from the output Ha of one magneto-impedance element and the output Hb of the other magneto-impedance element according to the following equation 1.

A steering angle detecting device for a vehicle steering system, wherein the arithmetic circuit calculates a rotation direction of a steering shaft of the vehicle steering system based on a change rate of an output signal from the two magneto-impedance elements. In claim 2,
The two magneto-impedance elements comprise an amorphous wire and a sensing coil wound around the amorphous wire;
The one signal processing circuit alternately switches the two magneto-impedance elements to supply a pulse, and alternately holds two magnetic signals obtained in synchronization with the pulse generator for a predetermined time. A steering angle detecting device for a steering device for a vehicle, wherein the steering angle detecting device is a set of electronic circuits including a sample and hold circuit that outputs the signals in a series. In claim 3,
A steering angle detecting device for an automobile steering system, wherein the two magneto-impedance elements and the one set of electronic circuits are formed on the same substrate.

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