JP2004245766A

JP2004245766A - Device for detecting rotation angle

Info

Publication number: JP2004245766A
Application number: JP2003037886A
Authority: JP
Inventors: Kiyotaka Sasanouchi; 清孝笹之内; Koji Oike; 幸司御池
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-02-17
Filing date: 2003-02-17
Publication date: 2004-09-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting rotation angle which accurately detects a rotation angle with high resolution, without being influenced by temperature changes etc. <P>SOLUTION: The device for detecting rotation angle is composed of at least two magnetoresistive elements 12, 13, 14, 15, a magnetism-generating section for applying a magnetic field to each magnetoresistive element 12-15, a signal processing section 21 for detecting the rotation angle by output signals from the magnetoresistive elements 12-15, and a signal controlling section 26 for controlling the output signals of the magnetoresistive elements 12-15, and the at least two magnetoresistive elements 12-15 are arranged so that their phase difference is 90 degrees. The accuracy of detection of the rotation angle is increased, by controlling the output signal levels of the magnetoresistance elements 12-15, arranged so as to be different in phase, and moreover, by comparing them. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は磁気抵抗素子を用いて被検出物の回転角を検出する回転角検出装置に関するものである。
【０００２】
【従来の技術】
従来の回転角検出装置としては、図６に示すものがある。図６に示すように回転角検出装置は、２個の磁石１と主ヨーク２とで構成されるロータと、一組の補助ヨーク３と磁気検出素子４とで構成されるステータとを具備し、被検出物の回転物の回転軸にロータが固定されている。主ヨーク２は２個の磁石１の間をリング状に閉じて磁気回路を構成し、一組の補助ヨーク３は両者間に空隙５を設けるように配置し、その空隙５の中央部に磁気検出素子４が組み込まれている。このステータはロータ内部に配置されロータとの間に設けられるエアギャップＧが周方向で徐々に変化するように配置されている。具体的にはステータの空隙方向をロータの中心線Ａ−Ａに合わせ、さらにステータの中心Ｏｓをロータの中心Ｏｒから所定量だけずらして配置している。
【０００３】
なお、この出願の発明に関連する先行技術文献情報としては、例えば特許文献１が知られている。
【０００４】
【特許文献１】
特開２００１−２８９６９号公報
【０００５】
【発明が解決しようとする課題】
従来の回転角検出装置では温度変化などにより、磁気検出素子の抵抗値や検出レベルなどが大きく変化し、検出される回転角に誤差が生じ易くなる。
【０００６】
本発明は温度変化などの影響を受けず高分解能で回転角を正確に検出する回転角検出装置を提供することを目的とするものである。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、本発明は以下の構成を有する。
【０００８】
本発明の請求項１に記載の発明は、少なくとも２つの磁気抵抗素子と、この磁気抵抗素子に磁界を与える磁気発生部と、前記磁気抵抗素子からの出力信号より回転角を検出する信号処理部と、前記磁気抵抗素子の出力信号を制御する信号制御部とからなり、前記少なくとも２つの磁気抵抗素子からの出力信号の位相が１／４周期異なるように２つの磁気抵抗素子を配置した回転角検出装置であり、異なる位相になるように配置する磁気抵抗素子の出力信号レベルを制御し、さらにこれらの出力信号を比較することにより回転角の検出精度が向上する。
【０００９】
請求項２に記載の発明は、信号制御部が電源電圧を切り換える電源回路と、回転角の検出誤差に応じて電源回路を制御する制御部とから構成される請求項１に記載の回転角検出装置であり、異なる位相になるように配置する磁気抵抗素子の出力信号レベルを制御し、さらに比較することにより回転角の検出精度が向上する。
【００１０】
請求項３に記載の発明は、信号制御部が電源回路と磁気抵抗素子間およびＧＮＤと磁気抵抗素子間に抵抗素子とこの抵抗素子と並列にスイッチを挿入したスイッチ部と、回転角の検出誤差に応じて前記スイッチを制御する制御部とから構成される請求項１に記載の回転角検出装置であり、異なる位相になるように配置する磁気抵抗素子の出力信号レベルを制御し、さらに比較することにより回転角の検出精度が向上する。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態について図を用いて説明する。
【００１２】
（実施の形態１）
図１は本発明の回転角検出装置の回路ブロック図である。
【００１３】
本発明の回転角検出装置の回路構成について図１を用いて説明する。図１に示す本発明の回転角検出装置は２組のブリッジ回路１１，１６からの出力信号の位相が１／４周期異なる４つの磁気抵抗素子１２，１３，１４，１５と、２組の２つのＯＰアンプ１８，１９からなる増幅部１７，２０と、回転角を検出する信号処理部２１から構成される。
【００１４】
そして、２組のブリッジ回路１１，１６は４つの磁気抵抗素子１２，１３，１４，１５からなり、電源２７から磁気抵抗素子１２、磁気抵抗素子１２および磁気抵抗素子１３、磁気抵抗素子１３を介してＧＮＤに接続される。同様に電源２７から磁気抵抗素子１４、磁気抵抗素子１４および磁気抵抗素子１５、磁気抵抗素子１５を介してＧＮＤにそれぞれ接続される。
【００１５】
ブリッジ回路１１，１６の磁気抵抗素子１２と磁気抵抗素子１３の接続点および磁気抵抗素子１４と磁気抵抗素子１５の接続点から増幅部１７，２０のＯＰアンプ１８の反転入力端子および非反転入力端子に接続される。そして増幅部１７，２０のＯＰアンプ１８の出力端子から次段のＯＰアンプ１９、信号処理部２１の入力端子２３，２５に接続される。さらに増幅部１７，２０のＯＰアンプ１９から信号処理部２１の入力端子２２，２４に接続される構成となっている。
【００１６】
以下、本発明の回転角検出装置の動作について図２（ａ），（ｂ）、図３（ａ）〜（ｃ）を用いて説明する。図２（ａ），（ｂ）は回転角検出装置の構成を示す側面図および正面図、図３は本発明の回転角検出装置内の信号処理部に入力される信号波形図である。
【００１７】
図２（ａ），（ｂ）に示すように磁気抵抗素子１２，１３，１４，１５からなるブリッジ回路１１とブリッジ回路１６は位相が１／４周期異なるように配置されている。またブリッジ回路１１とブリッジ回路１６に近接して磁気発生部２８ａ，２８ｂが回転する稼働部に配置され、磁気発生部２８ａ，２８ｂが回転することにより磁気抵抗素子１２，１３，１４，１５の抵抗値が変化し、磁気抵抗素子１２と磁気抵抗素子１３の接続点と磁気抵抗素子１４と磁気抵抗素子１５の接続点から微小出力信号として出力され、増幅部１７，２０により増幅される。この増幅部１７，２０からの出力信号波形を図３（ａ）に示す。
【００１８】
次に、磁気抵抗素子１２，１３，１４，１５からなるブリッジ回路１１について説明する。対向する磁気抵抗素子１２と磁気抵抗素子１５は同じ感磁方向を有し、また磁気抵抗素子１３と磁気抵抗素子１４も同じ感磁方向を有している。さらにブリッジ回路１１とブリッジ回路１６は１／４周期異なるように配置される。
【００１９】
例えば、磁気発生部２８ａが回転してブリッジ回路１１の磁気抵抗素子１２，１３，１４，１５に同じ磁界が作用すると、磁気抵抗素子１２，１３，１４，１５は同じ抵抗値Ｒ１となり磁気抵抗素子１２と磁気抵抗素子１３の接続点および磁気抵抗素子１４と磁気抵抗素子１５の接続点の電位は電源電圧の１／２となる。さらに磁気発生部２８ａが回転して２つの磁気抵抗素子１２と磁気抵抗素子１５の抵抗値がΔＲだけ大きく、もう２つの磁気抵抗素子１３と磁気抵抗素子１４の抵抗値がΔＲだけ小さくなると、磁気抵抗素子１２と磁気抵抗素子１３の接続点の電位（（Ｒ１−ΔＲ）×Ｖｃｃ）／２Ｒ１と磁気抵抗素子１４と磁気抵抗素子１５の接続点の電位（（Ｒ１＋ΔＲ）×Ｖｃｃ）／２Ｒ１となり、電位差は（ΔＲ１×Ｖｃｃ）／Ｒ１となり、この２つの信号が増幅部１７に入力され電位差の（ΔＲ１×Ｖｃｃ）／Ｒ１に増幅部１７の利得倍された信号として図３に示す電圧２９ａが得られる。そしてさらに磁気発生部２８ａが回転して２つの磁気抵抗素子１２と磁気抵抗素子１５の抵抗値がΔＲだけ小さくなり、もう２つの磁気抵抗素子１３と磁気抵抗素子１４の抵抗値がΔＲだけ大きくなると、磁気抵抗素子１２と磁気抵抗素子１３の接続点の電位（（Ｒ１−ΔＲ）×Ｖｃｃ）／２Ｒ１と磁気抵抗素子１４と磁気抵抗素子１５の接続点の電位（（Ｒ１＋ΔＲ）×Ｖｃｃ）／２Ｒ１が増幅部１７に入力され、増幅部１７により増幅され図３に示す電圧２９ｂが得られる。そして磁気発生部２８ａが連続回転の動作を繰り返すと、図３に示す信号波形２９が得られることになる。
【００２０】
一方、位相が１／４周期異なる磁気抵抗素子１２，１３，１４，１５からなるブリッジ回路１６についてはブリッジ回路１１と位相が９０度異なる信号を磁気抵抗素子１２と磁気抵抗素子１３および磁気抵抗素子１４と磁気抵抗素子１５の接続点から出力され、これらの信号が増幅部２０に入力され、同様に図３に示す信号波形３０が得られる。
【００２１】
増幅部１７，２０からの出力信号２９，３０は信号処理部２１の入力端子２２，２４に入力され、結果として回転角が検出される。回転角を検出する方法として、例えば一方の出力信号２９を正弦波ａ・ｓｉｎθとすると、もう一方の出力信号３０を余弦波ａ・ｃｏｓθとすることができる。そしてｔａｎθ＝（ａ・ｓｉｎθ）／（ａ・ｃｏｓθ）となり、Ａ＝ｔａｎθとすると、θ＝ｔａｎ^−１Ａとなり、振幅レベルに関係なく回転角θを求めることができる。さらに正弦波を振幅の中心である回転角θ＝０とすると、余弦波が最大となり係数ａの振幅レベルが求まる。また（（ａ・ｓｉｎθ）^２＋（ａ・ｃｏｓθ）^２）^１／２により求めることもできる。
【００２２】
しかし、温度変化などの影響により磁気抵抗素子１２，１３，１４，１５の抵抗値が変化するため、磁気発生部２８ａ，２８ｂの回転によりブリッジ回路１１，１６の磁気抵抗素子１２と磁気抵抗素子１３および磁気抵抗素子１４と磁気抵抗素子１５の接続点に発生する信号レベルも変化する。
【００２３】
例えば、周囲温度が低下すると、磁気抵抗素子１２，１３，１４，１５の抵抗値が変化し、増幅部１７，２０から信号処理部２１の入力端子２２，２４に入力される信号は図３（ｂ）に示すように所定の回転角検出の許容誤差範囲の最大閾値レベルｅ（Ｖ）、ｆ（Ｖ）を超え、さらに増幅部１７，２０の出力電圧の上限および下限にクリップする信号波形３１，３２となる。そこで信号処理部２１の内部の制御部２６が常に回転角の検出誤差を監視し、この回転角の検出誤差が大きくなると瞬時に増幅部１７，２０の利得より数ｄＢ低い利得のＯＰアンプ１８から入力される入力端子２３，２５に切り換え、図３（ａ）に示す信号波形２９，３０となるように制御することができ、回転角の検出精度が向上する。
【００２４】
また、周囲温度が高くなると、増幅部１７，２０からの出力信号は図３（ｃ）に示すように所定の回転角検出の許容誤差範囲の最小閾値レベルｇ（Ｖ）、ｈ（Ｖ）に達しない信号波形３３，３４となる。そこで信号処理部２１の内部の制御部２６が常に回転角の検出誤差を監視し、この回転角の検出誤差が大きくなると瞬時に入力端子２３，２５に入力される信号から数ｄＢ高い利得のＯＰアンプ１９より入力端子２２，２４に入力される信号に切り換え、図３（ａ）に示す信号波形２８，２９となるように制御することができ、回転角の検出精度が向上する。
【００２５】
（実施の形態２）
図４は本発明の回転角検出装置の回路ブロック図である。本発明の実施の形態１と異なる構成および動作について図を用いて説明する。
【００２６】
図４に示すように電源電圧値を切り換える電源回路３５と、４つの磁気抵抗素子１２，１３，１４，１５からなるブリッジ回路１１，１６と、１つのＯＰアンプからなる増幅部１８ａ，１８ｂ、入力信号より回転角を検出する信号処理部２１から構成される。
【００２７】
信号処理部２１は２つの入力端子２２，２４を有し、さらにこの入力端子２２，２４に入力される信号から常に回転角の検出誤差を監視して、この回転角の検出誤差が大きくなると瞬時に電源回路３５の電源電圧を所定の電圧に切り換えて信号レベルを所定範囲になるように制御する制御部２６を有している。この場合は回転角の検出誤差を抑制するため電源回路３５の電源電圧の切り換えと同時に信号処理部２１に入力される信号レベルの許容範囲の変更またはシフトを信号処理部２１の内部で行われる。
【００２８】
例えば、ブリッジ回路１１，１６に電源回路３５からＶｘ（Ｖ）の電圧が供給されている場合、ブリッジ回路１１，１６に隣接して磁気発生部２８ａ，２８ｂが配置され、この磁気発生部２８ａ，２８ｂの回転により磁界方向が変化し、４つの磁気抵抗素子１２，１３，１４，１５の抵抗値が変化し、ブリッジ回路１１，１６からそれぞれ位相が１／４周期異なる信号が出力される。この信号はＶｘ／２（Ｖ）を中心に微弱な信号であり、この信号を増幅部１８ａ，１８ｂにより所定の信号レベルに増幅する。そしてこの増幅された信号は信号処理部２１の入力端子２２，２４に入力され回転角の検出が行われる。
【００２９】
しかし、温度変化などの影響により磁気抵抗素子１２，１３，１４，１５の抵抗値が変化するため、磁気発生部２８ａ，２８ｂの回転によりブリッジ回路１１，１６の磁気抵抗素子１２と磁気抵抗素子１３および磁気抵抗素子１４と磁気抵抗素子１５の接続点に発生する信号レベルも変化する。
【００３０】
例えば、周囲温度が低下すると、増幅部１８ａ，１８ｂから信号処理部２１の入力端子２２，２４に入力される信号は図３（ｂ）に示すように所定の回転角検出の許容誤差範囲の最大閾値レベルｅ（Ｖ）、ｆ（Ｖ）を超え、さらに増幅部１８ａ，１８ｂの出力電圧の上限および下限にクリップする信号波形３１，３２となる。そこで信号処理部２１の内部の制御部２６が常に回転角の検出誤差を監視し、この回転角の検出誤差が大きくなると瞬時に信号処理部２１の制御部２６から電源回路３５をＶｙ（Ｖ）となるように切り換え、図３（ａ）に示す信号波形２９，３０となるように制御することができ、回転角の検出精度が向上する。
【００３１】
また、周囲温度が高くなると、増幅部１８ａ，１８ｂからの出力信号は図３（ｃ）に示すように所定の回転角検出の許容誤差範囲の最小閾値レベルｇ（Ｖ）、ｈ（Ｖ）に達しない信号波形３３，３４となる。そこで信号処理部２１の内部の制御部２６が常に回転角の検出誤差を監視し、この回転角の検出誤差が大きくなると瞬時に信号処理部２１の制御部２６から電源回路３５をＶｘ（Ｖ）となるように切り換え、図３（ａ）に示す信号波形２９，３０となるように制御することができ、回転角の検出精度が向上する。
【００３２】
（実施の形態３）
図５は本発明の回転角検出装置の回路ブロック図である。本発明の実施の形態１と異なる構成および動作について図を用いて説明する。
【００３３】
図５に示すように電源２７とブリッジ回路１１，１６の間およびＧＮＤとブリッジ回路１１，１６との間に挿入された抵抗素子３６ａ，３６ｂ，３６ｃ，３６ｄと、この抵抗素子３６ａ，３６ｂ，３６ｃ，３６ｄと並列に挿入されたスイッチとしてのトランジスタ３７ａ，３７ｂ，３７ｃ，３７ｄと、ブリッジ回路１１，１６と、１つのＯＰアンプからなる増幅部１８ａ，１８ｂ、入力信号より回転角を検出する信号処理部２１から構成される。ここでトランジスタ３７ａ，３７ｂ，３７ｃ，３７ｄのコレクタおよびエミッタが抵抗素子３６ａ，３６ｂ，３６ｃ，３６ｄの両端と接続されている。
【００３４】
信号処理部２１は２つの入力端子２２，２４を有し、さらにこの入力端子２２，２４に入力される信号から常に回転角の検出誤差を監視して、この回転角の検出誤差が大きくなると制御部２６からの信号によりトランジスタ３７ａ，３７ｂ，３７ｃ，３７ｄをＯＮ／ＯＦＦしてブリッジ回路１１，１６の両端の印加電圧を切り換えて信号レベルを所定範囲になるように制御する制御部２６を有している。
【００３５】
例えば、周囲温度が低下すると、増幅部１８ａ，１８ｂから信号処理部２１の入力端子２２，２４に入力される信号は図３（ｂ）に示すように所定の回転角検出の許容誤差範囲の最大閾値レベルｅ（Ｖ）、ｆ（Ｖ）を超え、さらに増幅部の出力電圧の上限および下限にクリップする信号波形３１，３２となる。そこで信号処理部２１の内部の制御部２６が常に回転角の検出誤差を監視し、この回転角の検出誤差が大きくなると瞬時に信号処理部２１の制御部２６からトランジスタ３７ａ，３７ｂ，３７ｃ，３７ｄのベースにＯＦＦ信号を入力し、抵抗素子３６ａ，３６ｂ，３６ｃ，３６ｄに電圧が生じるため、ブリッジ回路の両端に印加される電圧を低くし、結果として図３（ａ）に示す信号波形２９，３０となるように制御することができ、回転角の検出精度が向上する。
【００３６】
また、周囲温度が高くなると、増幅部１８ａ，１８ｂからの出力信号は図３（ｃ）に示すように所定の回転角検出の許容誤差範囲の最小閾値レベルｇ（Ｖ）、ｈ（Ｖ）に達しない信号波形３３，３４となる。そこで信号処理部２１の内部の制御部２６が常に回転角の検出誤差を監視し、この回転角の検出誤差が大きくなると瞬時に信号処理部２１の制御部２６からトランジスタ３７ａ，３７ｂ，３７ｃ，３７ｄのベースにＯＮ信号を入力し、抵抗素子３６ａ，３６ｂ，３６ｃ，３６ｄに電圧がほとんど生じなくなりブリッジ回路の両端に印加される電圧が高くなり、結果として図３（ａ）に示す信号波形２９，３０となるように制御することができ、回転角の検出精度が向上する。
【００３７】
【発明の効果】
以上のように本発明は、少なくとも２つの磁気抵抗素子と、この磁気抵抗素子に磁界を与える磁気発生部と、前記磁気抵抗素子からの出力信号より回転角を検出する信号処理部と、前記磁気抵抗素子の出力信号を制御する制御部からなり、前記少なくとも２つの磁気抵抗素子の位相が１／４周期異なるように２つの磁気抵抗素子を配置した回転角検出装置であり、異なる位相になるように配置する磁気抵抗素子の出力信号レベルを制御し、さらにこれらの出力信号を比較することにより回転角の検出精度が向上する。
【図面の簡単な説明】
【図１】本発明の回転角検出装置の回路ブロック図
【図２】（ａ）本発明の回転角検出装置の構成を示す側面図
（ｂ）本発明の回転角検出装置の構成を示す正面図
【図３】（ａ）〜（ｃ）本発明の回転角検出装置内の信号処理部に入力される信号波形図
【図４】本発明の回転角検出装置の回路ブロック図
【図５】本発明の回転角検出装置の回路ブロック図
【図６】従来の回転角検出装置の構成図
【符号の説明】
１１ブリッジ回路
１２磁気抵抗素子
１３磁気抵抗素子
１４磁気抵抗素子
１５磁気抵抗素子
１６ブリッジ回路
１７増幅部
１８ＯＰアンプ
１８ａＯＰアンプ
１８ｂＯＰアンプ
１９ＯＰアンプ
２０増幅部
２１信号処理部
２２入力端子
２３入力端子
２４入力端子
２５入力端子
２６制御部
２７電源
２８ａ磁気発生部
２８ｂ磁気発生部
２９ＯＰアンプからの出力信号
２９ａ電圧
２９ｂ電圧
３０ＯＰアンプからの出力信号
３０ａ電圧
３０ｂ電圧
３１ＯＰアンプからの出力信号
３２ＯＰアンプからの出力信号
３３ＯＰアンプからの出力信号
３４ＯＰアンプからの出力信号
３５電源回路
３６ａ抵抗素子
３６ｂ抵抗素子
３６ｃ抵抗素子
３６ｄ抵抗素子
３７ａトランジスタ
３７ｂトランジスタ
３７ｃトランジスタ
３７ｄトランジスタ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotation angle detection device that detects a rotation angle of an object using a magnetoresistive element.
[0002]
[Prior art]
FIG. 6 shows a conventional rotation angle detecting device. As shown in FIG. 6, the rotation angle detection device includes a rotor composed of two magnets 1 and a main yoke 2, and a stator composed of a set of an auxiliary yoke 3 and a magnetic detection element 4. The rotor is fixed to the rotating shaft of the rotating object to be detected. The main yoke 2 closes the two magnets 1 in a ring shape to form a magnetic circuit, and a pair of auxiliary yokes 3 are arranged so as to provide a gap 5 between them. The detection element 4 is incorporated. The stator is arranged such that an air gap G provided inside the rotor and provided between the stator and the rotor gradually changes in the circumferential direction. Specifically, the direction of the air gap of the stator is aligned with the center line AA of the rotor, and the center Os of the stator is further shifted from the center Or of the rotor by a predetermined amount.
[0003]
As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
[0004]
[Patent Document 1]
JP-A-2001-28969
[Problems to be solved by the invention]
In the conventional rotation angle detection device, the resistance value, the detection level, and the like of the magnetic detection element greatly change due to a temperature change or the like, and an error easily occurs in the detected rotation angle.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a rotation angle detection device that accurately detects a rotation angle with high resolution without being affected by a temperature change or the like.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configurations.
[0008]
The invention according to claim 1 of the present invention provides at least two magnetoresistive elements, a magnetism generating unit for applying a magnetic field to the magnetoresistive elements, and a signal processing unit for detecting a rotation angle from an output signal from the magnetoresistive elements. And a signal control unit for controlling an output signal of the magnetoresistive element, wherein the two magnetoresistive elements are arranged such that the phases of the output signals from the at least two magnetoresistive elements differ by １／ period. The detection device controls the output signal levels of the magnetoresistive elements arranged so as to have different phases, and further compares these output signals to improve the detection accuracy of the rotation angle.
[0009]
According to a second aspect of the present invention, the rotation angle detection device according to the first aspect includes a power supply circuit that switches a power supply voltage by the signal control unit and a control unit that controls the power supply circuit according to a rotation angle detection error. The device controls the output signal levels of the magnetoresistive elements arranged so as to have different phases, and further improves the detection accuracy of the rotation angle by comparing the output signal levels.
[0010]
According to a third aspect of the present invention, the signal control unit includes a resistance element between the power supply circuit and the magnetoresistive element and between the GND and the magnetoresistive element, and a switch unit in which a switch is inserted in parallel with the resistance element. 2. The rotation angle detection device according to claim 1, further comprising: a control unit configured to control the switch in accordance with a control signal, wherein the output signal levels of the magnetoresistive elements arranged to have different phases are controlled and further compared. This improves the detection accuracy of the rotation angle.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
(Embodiment 1)
FIG. 1 is a circuit block diagram of the rotation angle detecting device of the present invention.
[0013]
The circuit configuration of the rotation angle detecting device of the present invention will be described with reference to FIG. The rotation angle detecting device of the present invention shown in FIG. 1 has four magnetoresistive elements 12, 13, 14, 15 in which the phases of the output signals from the two sets of bridge circuits 11, 16 are different by 周期 period, and two sets of two magnetoresistive elements. Amplifying sections 17 and 20 each including two OP amplifiers 18 and 19, and a signal processing section 21 for detecting a rotation angle.
[0014]
The two sets of bridge circuits 11 and 16 are composed of four magnetoresistive elements 12, 13, 14 and 15, and are connected to the power supply 27 via the magnetoresistive element 12, the magnetoresistive element 12, the magnetoresistive element 13, and the magnetoresistive element 13. Connected to GND. Similarly, the power supply 27 is connected to GND via the magnetoresistive element 14, the magnetoresistive element 14, the magnetoresistive element 15, and the magnetoresistive element 15, respectively.
[0015]
Inverting input terminals and non-inverting input terminals of the OP amplifiers 18 of the amplifying units 17 and 20 from a connection point between the magnetoresistive elements 12 and 13 of the bridge circuits 11 and 16 and a connection point between the magnetoresistive elements 14 and 15. Connected to. The output terminals of the OP amplifiers 18 of the amplification units 17 and 20 are connected to the OP amplifier 19 of the next stage and the input terminals 23 and 25 of the signal processing unit 21. Further, the amplifiers 17 and 20 are connected from the OP amplifier 19 to the input terminals 22 and 24 of the signal processing unit 21.
[0016]
Hereinafter, the operation of the rotation angle detecting device of the present invention will be described with reference to FIGS. 2 (a) and 2 (b) and FIGS. 3 (a) to 3 (c). 2A and 2B are a side view and a front view showing a configuration of the rotation angle detection device, and FIG. 3 is a signal waveform diagram input to a signal processing unit in the rotation angle detection device of the present invention.
[0017]
As shown in FIGS. 2A and 2B, the bridge circuit 11 and the bridge circuit 16 including the magnetoresistive elements 12, 13, 14, and 15 are arranged so that the phases are different from each other by １／ period. In addition, the magnetic generators 28a and 28b are disposed in an operating section in which the magnetic generators 28a and 28b rotate close to the bridge circuit 11 and the bridge circuit 16, and the resistance of the magnetoresistive elements 12, 13, 14, and 15 is increased by the rotation of the magnetic generators 28a and 28b. The value changes and is output as a minute output signal from a connection point between the magnetoresistive element 12 and the magnetoresistive element 13 and a connection point between the magnetoresistive element 14 and the magnetoresistive element 15, and is amplified by the amplifiers 17 and 20. FIG. 3A shows the output signal waveforms from the amplifiers 17 and 20.
[0018]
Next, the bridge circuit 11 including the magnetoresistive elements 12, 13, 14, and 15 will be described. The opposing magnetoresistive elements 12 and 15 have the same magnetic sensing direction, and the magnetoresistive elements 13 and 14 also have the same magnetic sensing direction. Further, the bridge circuit 11 and the bridge circuit 16 are arranged so as to differ by 1/4 cycle.
[0019]
For example, when the magnetism generating section 28a rotates and the same magnetic field acts on the magnetoresistive elements 12, 13, 14, 15 of the bridge circuit 11, the magnetoresistive elements 12, 13, 14, 15 have the same resistance value R1 and the magnetoresistive element. The potential at the connection point between the magnetoresistive element 12 and the magnetoresistive element 13 and the potential at the junction point between the magnetoresistive element 14 and the magnetoresistive element 15 are の of the power supply voltage. Further, when the magnetism generating part 28a rotates and the resistance values of the two magnetoresistive elements 12 and 15 increase by ΔR and the resistance values of the other two magnetoresistive elements 13 and 14 decrease by ΔR, The potential ((R1−ΔR) × Vcc) / 2R1 at the connection point between the resistance element 12 and the magnetoresistance element 13 and the potential ((R1 + ΔR) × Vcc) / 2R1 at the connection point between the magnetoresistance element 14 and the magnetoresistance element 15 are obtained. The potential difference is (ΔR1 × Vcc) / R1, and these two signals are input to the amplifier 17 and the voltage 29a shown in FIG. 3 is obtained as a signal obtained by multiplying the potential difference by (ΔR1 × Vcc) / R1 by the gain of the amplifier 17. Can be When the magnetism generating part 28a further rotates, the resistance values of the two magnetoresistive elements 12 and 15 decrease by ΔR, and the resistance values of the other two magnetoresistive elements 13 and 14 increase by ΔR. , The potential at the connection point between the magneto-resistive elements 12 and 13 ((R1−ΔR) × Vcc) / 2R1 and the potential at the connection point between the magneto-resistive elements 14 and 15 ((R1 + ΔR) × Vcc) / 2R1 Is input to the amplifier 17 and is amplified by the amplifier 17 to obtain a voltage 29b shown in FIG. Then, when the magnetism generating section 28a repeats the operation of the continuous rotation, the signal waveform 29 shown in FIG. 3 is obtained.
[0020]
On the other hand, for the bridge circuit 16 composed of the magnetoresistive elements 12, 13, 14, and 15 whose phases are different from each other by 1/4 period, a signal whose phase is different from the bridge circuit 11 by 90 degrees is applied to the magnetoresistive elements 12, 13, and The signals are output from the connection point of the magnetic resistance element 14 and the magnetoresistive element 15, and these signals are input to the amplifying unit 20, and the signal waveform 30 shown in FIG. 3 is similarly obtained.
[0021]
Output signals 29 and 30 from the amplifying units 17 and 20 are input to input terminals 22 and 24 of the signal processing unit 21, and as a result, a rotation angle is detected. As a method of detecting the rotation angle, for example, if one output signal 29 is a sine wave a · sin θ, the other output signal 30 can be a cosine wave a · cos θ. Then, tan θ = (a · sin θ) / (a · cos θ), and if A = tan θ, θ = tan ⁻¹ A, and the rotation angle θ can be obtained regardless of the amplitude level. Further, when the sine wave is the rotation angle θ = 0, which is the center of the amplitude, the cosine wave becomes maximum and the amplitude level of the coefficient a is obtained. It can also be determined by ((a · sin θ) ² + (a · cos θ) ² ) ^1/2 .
[0022]
However, since the resistance values of the magnetoresistive elements 12, 13, 14, and 15 change due to the influence of temperature change and the like, the rotation of the magnetism generating units 28a and 28b causes the magnetoresistive elements 12 and 16 of the bridge circuits 11 and 16 to rotate. In addition, the signal level generated at the connection point between the magnetoresistive elements 14 and 15 also changes.
[0023]
For example, when the ambient temperature decreases, the resistance values of the magnetoresistive elements 12, 13, 14, 15 change, and the signals input from the amplifying units 17, 20 to the input terminals 22, 24 of the signal processing unit 21 are as shown in FIG. As shown in b), the signal waveform 31 exceeds the maximum threshold levels e (V) and f (V) within the predetermined error range of the rotation angle detection and further clips to the upper and lower limits of the output voltages of the amplifiers 17 and 20. , 32. Therefore, the control unit 26 inside the signal processing unit 21 always monitors the detection error of the rotation angle, and when the detection error of the rotation angle becomes large, the control unit 26 instantaneously outputs the gain from the OP amplifier 18 having a gain several dB lower than the gain of the amplification units 17 and 20. Switching to the input terminals 23 and 25 to be input can be performed so that the signal waveforms 29 and 30 shown in FIG. 3A can be controlled, and the detection accuracy of the rotation angle is improved.
[0024]
When the ambient temperature increases, the output signals from the amplifying units 17 and 20 change to the minimum threshold levels g (V) and h (V) within a predetermined allowable range of rotation angle detection as shown in FIG. The signal waveforms 33 and 34 do not reach. Therefore, the control unit 26 in the signal processing unit 21 constantly monitors the detection error of the rotation angle, and when the detection error of the rotation angle increases, the OP having a gain several dB higher than the signal input to the input terminals 23 and 25 instantaneously. Switching to signals input from the amplifier 19 to the input terminals 22 and 24 can be performed so that the signal waveforms 28 and 29 shown in FIG. 3A are controlled, and the rotation angle detection accuracy is improved.
[0025]
(Embodiment 2)
FIG. 4 is a circuit block diagram of the rotation angle detecting device of the present invention. The configuration and operation different from the first embodiment of the present invention will be described with reference to the drawings.
[0026]
As shown in FIG. 4, a power supply circuit 35 for switching a power supply voltage value, bridge circuits 11 and 16 including four magnetoresistive elements 12, 13, 14, and 15, amplifying sections 18a and 18b including one OP amplifier, and inputs. The signal processing unit 21 detects a rotation angle from a signal.
[0027]
The signal processing unit 21 has two input terminals 22 and 24, and further monitors a rotation angle detection error from a signal input to the input terminals 22 and 24. When the rotation angle detection error becomes large, an instantaneous The control unit 26 controls the power supply voltage of the power supply circuit 35 to a predetermined voltage to control the signal level to be within a predetermined range. In this case, in order to suppress the detection error of the rotation angle, the allowable range of the signal level input to the signal processing unit 21 is changed or shifted at the same time as the switching of the power supply voltage of the power supply circuit 35 inside the signal processing unit 21.
[0028]
For example, when a voltage of Vx (V) is supplied to the bridge circuits 11 and 16 from the power supply circuit 35, the magnetic generators 28a and 28b are arranged adjacent to the bridge circuits 11 and 16, and the magnetic generators 28a and 28b are The direction of the magnetic field changes due to the rotation of 28b, the resistance values of the four magnetoresistive elements 12, 13, 14, and 15 change, and the bridge circuits 11 and 16 output signals whose phases are different by １／ period. This signal is a weak signal centered on Vx / 2 (V), and this signal is amplified to a predetermined signal level by the amplifiers 18a and 18b. The amplified signal is input to the input terminals 22 and 24 of the signal processing unit 21 and the rotation angle is detected.
[0029]
However, since the resistance values of the magnetoresistive elements 12, 13, 14, and 15 change due to the influence of temperature change and the like, the rotation of the magnetism generating units 28a and 28b causes the magnetoresistive elements 12 and 16 of the bridge circuits 11 and 16 to rotate. In addition, the signal level generated at the connection point between the magnetoresistive elements 14 and 15 also changes.
[0030]
For example, when the ambient temperature decreases, the signals input from the amplifying sections 18a and 18b to the input terminals 22 and 24 of the signal processing section 21 have the maximum allowable error range for the predetermined rotation angle detection as shown in FIG. The signal waveforms 31 and 32 exceed the threshold levels e (V) and f (V) and further clip to the upper and lower limits of the output voltages of the amplifiers 18a and 18b. Therefore, the control unit 26 in the signal processing unit 21 constantly monitors the detection error of the rotation angle, and when the detection error of the rotation angle becomes large, the control unit 26 of the signal processing unit 21 instantaneously changes the power supply circuit 35 to Vy (V). And control can be performed so that the signal waveforms 29 and 30 shown in FIG. 3A are obtained, and the detection accuracy of the rotation angle is improved.
[0031]
When the ambient temperature increases, the output signals from the amplifying units 18a and 18b fall to the minimum threshold levels g (V) and h (V) within the predetermined error range for detecting the rotation angle as shown in FIG. The signal waveforms 33 and 34 do not reach. Therefore, the control unit 26 inside the signal processing unit 21 always monitors the detection error of the rotation angle, and when the detection error of the rotation angle becomes large, the control unit 26 of the signal processing unit 21 instantaneously changes the power supply circuit 35 to Vx (V). And control can be performed so that the signal waveforms 29 and 30 shown in FIG. 3A are obtained, and the detection accuracy of the rotation angle is improved.
[0032]
(Embodiment 3)
FIG. 5 is a circuit block diagram of the rotation angle detecting device of the present invention. The configuration and operation different from the first embodiment of the present invention will be described with reference to the drawings.
[0033]
As shown in FIG. 5, resistance elements 36a, 36b, 36c, 36d inserted between the power supply 27 and the bridge circuits 11, 16 and between GND and the bridge circuits 11, 16, and the resistance elements 36a, 36b, 36c , 36d, transistors 37a, 37b, 37c, and 37d as switches, bridge circuits 11 and 16, amplifying sections 18a and 18b each including one OP amplifier, and signal processing for detecting a rotation angle from an input signal. It comprises a unit 21. Here, the collectors and emitters of the transistors 37a, 37b, 37c, 37d are connected to both ends of the resistance elements 36a, 36b, 36c, 36d.
[0034]
The signal processing unit 21 has two input terminals 22 and 24, and further monitors the detection error of the rotation angle from the signals input to the input terminals 22 and 24, and controls when the detection error of the rotation angle becomes large. A control unit 26 controls ON / OFF of the transistors 37a, 37b, 37c and 37d by a signal from the unit 26 to switch the applied voltage between both ends of the bridge circuits 11 and 16 so as to control the signal level to be within a predetermined range. ing.
[0035]
For example, when the ambient temperature decreases, the signals input from the amplifying sections 18a and 18b to the input terminals 22 and 24 of the signal processing section 21 have the maximum allowable error range for the predetermined rotation angle detection as shown in FIG. The signal waveforms 31 and 32 exceed the threshold levels e (V) and f (V) and further clip to the upper and lower limits of the output voltage of the amplifier. Therefore, the control unit 26 inside the signal processing unit 21 always monitors the detection error of the rotation angle, and when the detection error of the rotation angle becomes large, the control unit 26 of the signal processing unit 21 instantaneously sends the transistors 37a, 37b, 37c, 37d. Since an OFF signal is input to the bases of the bridge circuits, and a voltage is generated in the resistance elements 36a, 36b, 36c, and 36d, the voltage applied to both ends of the bridge circuit is reduced. As a result, the signal waveform 29 shown in FIG. It can be controlled to be 30 and the detection accuracy of the rotation angle is improved.
[0036]
When the ambient temperature increases, the output signals from the amplifying units 18a and 18b fall to the minimum threshold levels g (V) and h (V) within the predetermined error range for detecting the rotation angle as shown in FIG. The signal waveforms 33 and 34 do not reach. Therefore, the control unit 26 inside the signal processing unit 21 always monitors the detection error of the rotation angle, and when the detection error of the rotation angle becomes large, the control unit 26 of the signal processing unit 21 instantaneously sends the transistors 37a, 37b, 37c, 37d. Signal is input to the base of the bridge circuit, and almost no voltage is generated in the resistance elements 36a, 36b, 36c, and 36d, and the voltage applied to both ends of the bridge circuit is increased. As a result, the signal waveform 29, shown in FIG. It can be controlled to be 30 and the detection accuracy of the rotation angle is improved.
[0037]
【The invention's effect】
As described above, the present invention provides at least two magneto-resistive elements, a magnetism generating unit for applying a magnetic field to the magneto-resistive elements, a signal processing unit for detecting a rotation angle from an output signal from the magneto-resistive elements, A rotation angle detection device comprising a control unit for controlling an output signal of the resistance element, wherein the two magnetic resistance elements are arranged so that the phases of the at least two magnetic resistance elements are different from each other by 1/4 cycle, By controlling the output signal level of the magnetoresistive element arranged in the first position and comparing these output signals, the detection accuracy of the rotation angle is improved.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of a rotation angle detection device according to the present invention; FIG. 2A is a side view illustrating a configuration of the rotation angle detection device according to the invention; FIG. FIGS. 3 (a) to 3 (c) are diagrams of signal waveforms input to a signal processing unit in the rotation angle detection device of the present invention. FIG. 4 is a circuit block diagram of the rotation angle detection device of the present invention. FIG. 6 is a circuit block diagram of a rotation angle detection device of the present invention. FIG. 6 is a configuration diagram of a conventional rotation angle detection device.
DESCRIPTION OF SYMBOLS 11 Bridge circuit 12 Magnetic resistance element 13 Magnetic resistance element 14 Magnetic resistance element 15 Magnetic resistance element 16 Bridge circuit 17 Amplifying unit 18 OP amplifier 18a OP amplifier 18b OP amplifier 19 OP amplifier 20 Amplifying unit 21 Signal processing unit 22 Input terminal 23 Input terminal 24 Input terminal 25 Input terminal 26 Control unit 27 Power supply 28a Magnetic generation unit 28b Magnetic generation unit 29 Output signal 29a from OP amplifier Voltage 29b Voltage 30 Output signal from OP amplifier 30a Voltage 30b Voltage 31 Output signal from OP amplifier 32 OP Output signal from amplifier 33 Output signal from OP amplifier 34 Output signal from OP amplifier 35 Power supply circuit 36a Resistance element 36b Resistance element 36c Resistance element 36d Resistance element 37a Transistor 37b Transistor 37c Transistor 37d Transistor

Claims

At least two magneto-resistive elements, a magnetism generating unit for applying a magnetic field to the magneto-resistive elements, a signal processing unit for detecting a rotation angle from an output signal from the magneto-resistive elements, and controlling an output signal of the magneto-resistive elements A rotation angle detection device, comprising: a signal control unit; and arranging two magnetoresistive elements such that phases of output signals from the at least two magnetoresistive elements are different by １／ cycle.

The rotation angle detection device according to claim 1, wherein the signal control unit includes a power supply circuit that switches a power supply voltage, and a control unit that controls the power supply circuit according to a rotation angle detection error.

A signal control unit for connecting a resistance element between the power supply circuit and the magnetoresistive element and between GND and the magnetoresistive element, a switch unit having a switch inserted in parallel with the resistance element, and control for controlling the switch according to a rotation angle detection error; The rotation angle detection device according to claim 1, further comprising a unit.