JP2004029002A - Position sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position sensor for compensating variation of the temperature coefficient in impedance of a detecting coil in relation to a displacement by using a simple circuit. <P>SOLUTION: In the position sensor, AC current Iac and DC current Idc are simultaneously applied from a constant current circuit 3 to the detecting coil 2, and then one or more values among a ratio of the DC current Idc to the AC current Iac, a ratio of an AC component to a DC component in an impedance of a detection section A, a temperature coefficient of the ratio of the DC current Idc to the AC current Iac, and a temperature coefficient of the ratio of the AC component to the DC component in the impedance of the detection section A are set therein, so that the width of variation of the temperature coefficient of peak voltage values output from the the detection section A over a whole variable period is smaller than that of the temperature coefficient of the AC component in the impedance of the detecting coil 2 at a frequency of the AC current Iac. <P>COPYRIGHT: (C)2004,JPO

Description

と表すことができる。（数１）式においては諸量は複素数であるが、電圧Ｖｓのピーク電圧Ｖ１のみを考えると、
【００７７】
【数２】

となり、（数２）式における諸量は実数として扱うことができ、その波形は図５に示すように、ピーク電圧Ｖ１を有する、直流電圧Ｖｄｃと交流電圧Ｖａｃとの和になっている。
【００７８】
図６は、銅ニッケル合金線（ＧＣＮ１５線）で巻回した検出コイル２のインピーダンスの実測値を元に作成したサンプルデータであり、検出コイル２の直流抵抗Ｚｄｃと交流インピーダンスＺａｃとを、図２の回転角θを横軸としたグラフにプロットしたものである。ここでは、インピーダンスＺが回転角θに対して完全に直線的に変化するように設定したが、実測値にかなり近い値となっている。さらに、周囲温度：−４０℃、＋２５℃、＋８５℃、＋１３０℃での各データを示している。
【００７９】
そして、周囲温度＋２５℃において、直流抵抗Ｚｄｃは１８８Ω、温度係数は５１１ｐｐｍ／Ｋであり、交流インピーダンスＺａｃは、
【００８０】
【数３】

と表され、Ｚ０＝６３６Ω、Ｚ’＝−３．４８Ω／ｄｅｇ、β０＝４７８ｐｐｍ／Ｋ、β’＝−２．４９ｐｐｍ／Ｋ／ｄｅｇであり、θは回転角、Ｔは周囲の摂氏温度を表す。
【００８１】
ここで、交流インピーダンスＺａｃの温度係数はθ＝０°では４７８ｐｐｍ／Ｋ、θ＝９０°では２５４ｐｐｍ／Ｋであるので、その変動幅Δ（ｄＺａｃ／ｄＴ）は２２４ｐｐｍ／Ｋに達している。
【００８２】
次に、定電流回路３が出力する直流電流Ｉｄｃ＝１．５ｍＡ、交流電流Ｉａｃ＝０．３ｍＡとし、簡単のため直流電流Ｉｄｃ、交流電流Ｉａｃ及び周波数ｆの温度変化率をゼロとして（数２）式より、検出コイル２両端の直流電圧Ｖｄｃ，交流電圧Ｖａｃ、及び検出コイル２両端のピーク電圧Ｖ１をプロットした結果が図７の各プロットであり、それらの温度係数が図８である。
【００８３】
図８から分かるように、回転角θ＝０°〜９０°に亘って、ピーク電圧Ｖ１の温度係数は略４５０〜５００ｐｐｍ／Ｋであり、その変動幅Δ（ｄＶ１／ｄＴ）は略５０ｐｐｍ／Ｋであり、非常に狭い変動幅に収まっている。従って、ピーク電圧Ｖ１に４７０ｐｐｍ／Ｋ程度の温度補償を施せば、補償後の電圧はほとんど誤差なく常温値に戻すことができる。
【００８４】
次に、定電流回路３が出力する交流電流Ｉａｃ＝０．３ｍＡのまま、直流電流Ｉｄｃを変化させた場合のピーク電圧Ｖ１の温度係数を図８と同様に計算した結果が図９である。直流電流Ｉｄｃ＝０であれば、その温度係数の変位依存性は検出コイル２のインピーダンスＺの変位依存性と同一となる。しかし、直流電流Ｉｄｃを増やすに従って、直流電圧Ｖｄｃの温度係数に近付いて行く。また、コア１の検出コイル２に対する貫入量が少ないほど（本実施形態の場合は回転角θが大きい領域ほど）、ピーク電圧Ｖ１に占める直流電圧Ｖｄｃの割合が大きいので（図６参照）、直流電圧Ｖｄｃの影響を受けやすい。
【００８５】
そして、直流電流Ｉｄｃを少しでも混ぜると、直流電流Ｉｄｃ＝０の場合よりも、ピーク電圧Ｖ１の温度係数の変動幅Δ（ｄＶ１／ｄＴ）はかなり改善され、直流電流Ｉｄｃを増やすほど、ピーク電圧Ｖ１の温度係数の変動幅Δ（ｄＶ１／ｄＴ）は小さいものになるが、その改善具合もあるレベルで飽和する。したがって、直流電流Ｉｄｃを増やすことは消費電流の増加につながることもあり、許容される消費電流と、ピーク電圧Ｖ１の温度係数の変動幅Δ（ｄＶ１／ｄＴ）の値とから直流電流Ｉｄｃの適正値を選べばよいということになる。このとき、発振回路３ａが発生する直流電圧Ｖｄｃ’と交流電圧Ｖａｃ’とを各々設定することで、定電流Ｉｄの直流電流Ｉｄｃと交流電流Ｉａｃとの割合を設定することができる。
【００８６】
また、発振回路３ａが発生する交流電圧Ｖａｃ’の周波数ｆが高いほど、直流電圧Ｖｄｃに対する交流電圧Ｖａｃの比率が増大するので、周波数ｆを適正に選択することによってもＶｄｃとＶａｃとの比率を適正に設定することができ、上記と同様の議論が成り立つ。
【００８７】
上記の説明では、直流電流Ｉｄｃ，交流電流Ｉａｃ、周波数ｆの各温度変化率をゼロとしたが、これらに温度係数がある場合には、図８において、直流電圧Ｖｄｃや交流電圧Ｖａｃの各温度係数が上下にシフトし、その分ピーク電圧Ｖ１の温度特性も変化するということになる。
【００８８】
図８や図９からもわかるように、（ｄＶ１／ｄＴ）はコア１の貫入量が少ない場合には、（ｄＶｄｃ／ｄＴ）の影響を大きく受け、コア１の挿入量が多い場合には、（ｄＶａｃ／ｄＴ）の影響を大きく受ける。それはピーク電圧Ｖ１に占める直流電圧Ｖｄｃと交流電圧Ｖａｃの構成比から当然そうなる。
【００８９】
また、コア１の貫入量によらず、（ｄＶ１／ｄＴ）の値は、（ｄＶｄｃ／ｄＴ）の値と（ｄＶａｃ／ｄＴ）の値との間にある。
【００９０】
さらに、コア１の貫入量が多い（本実施形態では回転角θ＝０°近辺）場合の（ｄＶｄｃ／ｄＴ）の値と、（ｄＶａｃ／ｄＴ）の値とをできるだけ近づけるよう設定すると、（ｄＶ１／ｄＴ）は、コア１の貫入量が多い場合（交流電圧Ｖａｃの温度係数の影響を受けやすいが、直流電圧Ｖｄｃと交流電圧Ｖａｃが近い）にも、コア１の貫入量が少ない場合（もともと直流電圧Ｖｄｃの温度係数の影響を受けやすい）にも、（ｄＶｄｃ／ｄＴ）に近い値となり、ピーク電圧Ｖ１の温度係数の変動幅Δ（ｄＶ１／ｄＴ）を小さくしやすい。
【００９１】
さらに、（ｄＶｄｃ／ｄＴ）の値が、コア１の貫入量最小の場合の（ｄＶａｃ／ｄＴ）値に近い場合と、コア１の貫入量最大の場合の（ｄＶａｃ／ｄＴ）値に近い場合とでは、後者の方がピーク電圧Ｖ１の温度係数の変動幅Δ（ｄＶ１／ｄＴ）を小さくし得るということがいえる。
【００９２】
具体的には、後述するような方法で、直流抵抗Ｚｄｃ、交流インピーダンスＺａｃ、直流電流Ｉｄｃ、交流電流Ｉａｃ、及び周波数ｆの各温度係数を適正値に設定して、（ｄＶｄｃ／ｄＴ）や（ｄＶａｃ／ｄＴ）を制御すればよい。
【００９３】
まず、直流抵抗Ｚｄｃの温度係数は、検出コイル２の巻線材料の選択で決まる。巻線材料としては、通常の銅線では温度係数が非常に大きいため、ニクロム線やマンガニン線、銅ニッケル合金線（ＧＣＮ線）を用いるのが実用的であり、銅ニッケル合金線の場合、銅とニッケルの合金比率によって、体積抵抗率とその温度係数を選択することができる。
【００９４】
次に、直流電流Ｉｄｃ、交流電流Ｉａｃ、及び周波数ｆに適当な温度係数を与える方法について述べる。
【００９５】
定電流回路３は、図１０に示すように、Ｖｄｃ’±Ｖａｃ’の電圧を出力する発振回路３ａと電圧−電流変換回路３ｂとから構成され、電圧−電流変換回路３ｂは、制御電源Ｖｃｃに一端を接続した抵抗Ｒ１と、抵抗Ｒ１の他端にエミッタを接続し、発振回路３ａにベースを接続し、検出コイル２にコレクタを接続したＰＮＰ型トランジスタＱ１とから構成される。信号処理回路４はピーク電圧Ｖ１をとりだす具体的な回路としてピークホールド型の整流回路を用いており、その回路は、制御電源Ｖｃｃに一端を接続した定電流源Ｉ１と、定電流源Ｉ１の他端にコレクタを接続し、ベース−コレクタ間を接続し、検出コイル２にエミッタを接続したＮＰＮ型トランジスタＱ２と、制御電源Ｖｃｃにコレクタを接続し、トランジスタＱ２のベースにベースを接続したＮＰＮ型トランジスタＱ３と、トランジスタＱ３のエミッタとグランドとの間に接続したコンデンサＣ１，定電流源Ｉ２の並列回路とから構成され、コンデンサＣ１の両端電圧は、検出コイル２両端電圧Ｖｓを整流してピークホールドした電圧、すなわちピーク電圧Ｖ１となり、変位信号Ｖｏｕｔとして出力される。
【００９６】
そして、Ｖｄｃ’±Ｖａｃ’の電圧を出力する発振回路３ａは、図１１に示すように、コンパレータＣＰ１と、コンパレータＣＰ１の非反転入力端子と出力端子との間に接続した抵抗Ｒ３と、コンパレータＣＰ１の反転入力端子とグランド間に接続して電圧Ｖｃｃ／２を出力する直流電源Ｅ１と、コンパレータＣＰ１の出力端子に一端を接続した抵抗Ｒ４と、反転入力端子に抵抗Ｒ４の他端を接続し、非反転入力端子に直流電源Ｅ１を接続したオペアンプＯＰ１と、オペアンプＯＰ１の反転入力端子と出力端子との間に接続したコンデンサＣ２と、オペアンプＯＰ１の出力端子とコンパレータＣＰ１の非反転入力端子との間に接続した抵抗Ｒ２と、オペアンプＯＰ１の出力端子と制御電源Ｖｃｃとの間に接続した抵抗Ｒ５，Ｒ６の直列回路とから構成される。
【００９７】
この回路において、オペアンプＯＰ１の出力ＶｏｓｃはＶｃｃ／２をオフセット中心とする三角波となり、出力Ｖｏｓｃを抵抗Ｒ５，Ｒ６で分圧することによって直流電圧Ｖｄｃ’，交流電圧Ｖａｃ’が決定される。このような三角波発振回路は、正弦波発振回路に比べて、温度変化に対して安定な回路を簡単な構成で実現できる。方形波発振回路でも安定な回路を安価に構成できるが、検出コイル２に方形波電流を与えても方形波電流のｄｉ／ｄｔに起因する制御しがたい信号電圧が発生するだけとなるので、使えない。その点、三角波であれば、正弦波と同様にコアの回転角θを反映した出力電圧を得ることができるのである。
【００９８】
図１１において、交流電圧Ｖａｃ’の発振周波数ｆは、（Ｒ３／（Ｃ２×Ｒ４×Ｒ２））に比例し、振幅は（Ｒ２／Ｒ３）に比例する。従って、抵抗Ｒ２〜Ｒ６、及びコンデンサＣ２の値及び温度係数を適正に選択することによって直流電圧Ｖｄｃ’や交流電圧Ｖａｃ’の値及び温度係数を制御することができる。特に、定電流回路３全体がモノリシックＩＣとなる場合でも、コンデンサＣ２は外付けされることが多いため、コンデンサＣ２で温度係数を調整する方法は有効である。
【００９９】
さらに、定電流回路３全体がモノリシックＩＣ化される場合、抵抗Ｒ１〜Ｒ５の一部または全部の抵抗値をデジタルトリミングによって設定して、直流電流Ｉｄｃ、交流電流Ｉａｃ、及び周波数ｆに適当な温度係数を与えることもできる。この場合、コア１や検出コイル２、及びその変位区間等が変わってもＩＣを代えることなく使えるので汎用性が高いものとなる。
【０１００】
ここで、デジタルトリミングとは、調整する抵抗に予め並列に、抵抗とスイッチ素子との並列回路を接続しておき、デジタルデータによってスイッチ素子をオン・オフすることによって抵抗調整を行うものである。具体的にデジタルトリミングを行う場合は、電気的特性をモニターしながらデジタルデータの最適コードを決定し、決定した最適コードをＩＣのＲＯＭに書き込んだり、ＩＣ内に設けられているデータ記憶のためのヒューズを焼き切ることで、ＩＣに最適コードを与え、ＩＣ内の抵抗はこの最適コードに対応する値に設定される。
【０１０１】
なお、三角波発生回路は図１１に示す回路構成でなくてもよく、他の回路構成であってもよい。
【０１０２】
また、図１０の電圧−電流変換回路３ｂにおいては、トランジスタＱ１のベース−エミッタ間電圧Ｖｂｅの温度特性によって、発振回路３ａが発生する直流電圧Ｖｄｃ’の温度係数がゼロであっても、検出コイル２に供給される直流電流Ｉｄｃは正の温度係数を有することになる。ここで、直流電流Ｉｄｃの温度係数を正の温度係数にしたくない場合は、図１０に示す電圧−電流変換回路３ｂのトランジスタＱ１のエミッタを反転入力端子に接続し、トランジスタＱ１のベースを出力端子に接続したオペアンプＯＰ２を付加した図１２に示す電圧−電流変換回路３ｂ’を用いて、オペアンプＯＰ２の非反転入力端子に発振回路３ａの出力を接続すればよい。
【０１０３】
図１３は、図１０の定電流回路３とは異なる定電流回路３’の回路構成であり、定電流回路３’は、交流電流供給回路Ｓａｃと直流電流供給回路Ｓｄｃとから構成されている。交流電流供給回路Ｓａｃは、ＮＰＮ型トランジスタＱ４とＰＮＰ型トランジスタＱ６との直列回路と、トランジスタＱ４，Ｑ６の接続中点に接続した交流電源ＡＣと、制御電源Ｖｃｃ−Ｖｅｅ間に接続したＰＮＰ型トランジスタＱ８、ＮＰＮ型トランジスタＱ５、抵抗Ｒ７，Ｒ８、ＰＮＰ型トランジスタＱ７、ＮＰＮ型トランジスタＱ１０の直列回路と、ＰＮＰ型トランジスタＱ９、ＮＰＮ型トランジスタＱ１１の直列回路とからなり、トランジスタＱ４，Ｑ５、トランジスタＱ６，Ｑ７、トランジスタＱ８，Ｑ９、トランジスタＱ１０，Ｑ１１の各ゲートは互いに接続され、トランジスタＱ８，Ｑ１０の各ベース−コレクタ間は短絡されている。
【０１０４】
直流電流供給回路Ｓｄｃは、トランジスタＱ９，Ｑ１１の接続中点にコレクタを接続し、制御電源Ｖｃｃにエミッタを接続したＰＮＰ型トランジスタＱ１２，Ｑ１３と、トランジスタＱ１３のコレクタとグランド間に接続した抵抗Ｒ９とからなり、トランジスタＱ１２，Ｑ１３の各ゲートは互いに接続され、トランジスタＱ１３のベース−コレクタ間は短絡されている。
【０１０５】
検出コイル２は、トランジスタＱ９，Ｑ１２の接続中点に一端を接続しており、交流電流Ｉａｃを供給する交流電流供給回路Ｓａｃと直流電流Ｉｄｃを供給する直流電流供給回路Ｓｄｃとが独立に存在しているので、交流電流Ｉａｃと直流電流Ｉｄｃとの比率や温度係数の制御をシンプルに行うことができ、さらには、デジタルトリミングによる設定も可能である。
【０１０６】
また、信号処理回路４が検出部Ａの出力電圧のピーク値Ｖ１の温度係数とは逆極性の温度係数を有する増幅器を備え、この増幅器の出力に基づいて変位信号Ｖｏｕｔを出力すれば、増幅器の出力は温度補償済の変位だけに依存する信号であり、この出力を処理することで温度補償済みの変位信号を得ることができる。
【０１０７】
次に、定電流回路３を調整するのみではなく、直流抵抗Ｚｄｃや交流インピーダンスＺａｃの値及び温度係数を制御することも可能である。図１の説明で述べてきた検出部Ａの代わりに、図１４のように検出コイル２と直列に直流抵抗Ｚｄｃ’、交流インピーダンスＺａｃ’を有する回路素子５を設けた検出部Ａを用いる。このとき、回路素子５の直流抵抗Ｚｄｃ’、交流インピーダンスＺａｃ’はコア１の回転角θには無関係であり、直流抵抗Ｚｄｃ’、交流インピーダンスＺａｃ’の値や温度係数を適当に選択すれば検出部Ａの両端電圧のピーク値や温度係数を制御することができる。
【０１０８】
例えば、回路素子５が純抵抗である場合には、交流インピーダンスＺ’ａｃ＝Ｒ（抵抗値）となる。また、回路素子５がインダクタンスであれば直流抵抗Ｚ’ｄｃと交流インピーダンスＺ’ａｃの両方を備えていることになる。さらに、回路素子５としてダイオードを設けると、検出コイル２の両端電圧Ｖｓの直流成分Ｖｄｃだけに影響を与えることができる。
【０１０９】
上記の説明のように、検出コイル２に交流電流Ｉａｃのみならず直流電流Ｉｄｃを与えることによって、変位区間（回転角）θにおける信号電圧の温度係数の変動幅Δ（ｄＶ１／ｄＴ）を相当程度小さくできるが、やはりΔ（ｄＺａｃ／ｄＴ）そのものが小さい方が、さらにΔ（ｄＶ１／ｄＴ）を小さくし得ることは明白である。従来の技術で述べたＵＳ特許はこの目的に合致する技術であるが、前記のように問題点をかかえていた。
【０１１０】
また、Δ（ｄＺａｃ／ｄＴ）を小さくするためには、コア１は透磁率や抵抗率の温度係数の小さな磁性体であることが望ましい。透磁率の温度係数は、たとえば−４０〜＋１３０℃程度の温度範囲ではどの磁性体でもあまり大きくないので、特に抵抗率の温度係数の小さい材料が適している。たとえば、ニクロム（ニッケル、クロム、鉄合金）や鉄クロム（鉄、クロム、アルミ合金）がそれにあたる。これらの金属材料は、電熱線用途に多く使用されるものであり、線材として非常に安価に入手できる。従って、線材の曲げ加工によってコア１を形成すると、温度特性に優れたコア１が安価に製造でき、このことは実施形態２で詳細に説明する。
【０１１１】
次に、本発明の趣旨とは異なるが、直流電流Ｉｄｃ、交流電流Ｉａｃ、直流抵抗Ｚｄｃ、交流抵抗Ｚａｃ、及びそれらの各温度係数の設定が適正でないとΔ（ｄＶ１／ｄＴ）がΔ（ｄＺａｃ／ｄＴ）よりも大きくなり得るということを、例を挙げて説明する。例えば、検出コイル２として、直流抵抗Ｚｄｃ＝１００Ω（温度係数５０ｐｐｍ／Ｋ）、交流インピーダンスＺａｃは（数３）式において、Ｚ０＝８００Ω、Ｚ’＝−８Ω／ｄｅｇ、β０＝３４６ｐｐｍ／Ｋ、β’＝−２．３５ｐｐｍ／Ｋ／ｄｅｇであるものがあり、それに対して直流電流Ｉｄｃ＝０．２ｍＡ、交流電流Ｉａｃ＝１．０ｍＡ（ともに温度係数０）を与えた場合の図８に相当するプロットが図１５である。Δ（ｄＶ１／ｄＴ）がΔ（ｄＺａｃ／ｄＴ）よりも大きくなっていることが分かる。以上のように、単に直流電流Ｉｄｃを与えさえすればΔ（ｄＶ１／ｄＴ）が減少するわけではないということを強調しておく。
【０１１２】
なお、本実施形態では回転型のポジションセンサで説明したが、図３４の従来例に示すような変位方向が直線であるポジションセンサを用いても同様の効果が得られる。
【０１１３】
（実施形態２）
本実施形態では、Δ（ｄＺａｃ／ｄＴ）が最小となる理想の状態として、検出コイル２のインピーダンスＺの温度変化が、コア１と検出コイル２との相対変位によって変わらないようにするための温度補償の方法について説明する。本実施形態のポジションセンサの構成は実施形態１と同様であり、同様の構成には同一の符号を付して説明は省略する。
【０１１４】
まず、温度補償の第１の方法として、コア１が検出コイル２に貫入していない場合のインピーダンスＺの温度変化率をコア１が検出コイル２に貫入した場合の温度変化率に合わせる方法について説明する。
【０１１５】
検出コイル２のインピーダンスＺは図１６に示すように抵抗成分Ｒｓとインダクタンス成分Ｌｓとの直列回路と等価である。
【０１１６】
インダクタンス成分Ｌｓには表皮効果による成分があり、表皮厚さが十分薄く、周波数一定の場合の表皮効果は体積抵抗率ρの１／２乗に比例するので、温度係数も体積抵抗率ρの１／２乗の影響を受ける。図１７は、表皮効果による銅線の抵抗値変動を示すグラフで、周波数と銅線の抵抗値との関係を示す。線径が０．３２ｍｍ，０．１６ｍｍ，０．１０ｍｍ，０．０７ｍｍの時に曲線Ｙ７，Ｙ８，Ｙ９，Ｙ１０が各々対応しており、表皮効果の影響で、コイルの線径と周波数とにより抵抗の変化の具合が変わる。
【０１１７】
また、抵抗成分Ｒｓの温度係数は、巻線材の体積抵抗率ρの温度係数に大きく依存し、抵抗成分Ｒｓは近接効果の影響も受ける。
【０１１８】
図１８は、近接効果による銅線の抵抗値変動を示すグラフで、周波数と銅線の抵抗値との関係を示す。線径及び巻数が０．１６ｍｍ　４０Ｔ，０．０７ｍｍ　６０Ｔの時に曲線Ｙ１１，Ｙ１２が各々対応している。近接効果は、コイルの巻線の巻きピッチが狭い場合に、電流が巻線内を一様に流れなくなる現象であり、巻線ピッチが狭いほど影響が強いが、線径によっても影響は異なる。近接効果による成分は、体積抵抗率ρの−１乗の依存性があるので、その温度係数も体積抵抗率ρの−１乗の影響を受ける。
【０１１９】
すなわち、線径が太いか、あるいは周波数が高い場合、表皮効果、近接効果により、コア１が貫入していない時のインピーダンスＺの温度係数が小さくなる。
【０１２０】
したがって、巻線材の体積抵抗率ρ、線径、巻数、巻きピッチ及び周波数を適切に設定することにより、コア１が貫入していない変位状態での直流抵抗成分、表皮効果成分、近接効果成分のバランスを制御して、検出コイル２のインピーダンスＺの温度係数を小さくすることができるので、変位量によって温度係数が変わるという従来の問題点を解消することができる。
【０１２１】
銅は体積抵抗率ρの温度係数が非常に大きいため、巻線材としては銅よりも体積抵抗率ρの温度係数が小さいものを選択することが望ましい。具体的には、ニクロム、マンガニン、銅−ニッケル合金のうちいずれかで検出コイル２の巻線を形成すればよい。特に銅−ニッケル合金は、その成分比を変えることで体積抵抗率ρの値を制御できるので好適である。
【０１２２】
次に、コア１が検出コイル２に貫入している場合のインピーダンスＺの温度変化率をコア１が検出コイル２に貫入していない場合の温度変化率に合わせる温度補償の第２の方法について説明する。
【０１２３】
コア１が検出コイル２に貫入することによる検出コイル２のインピーダンスＺの増加は、そのコア１の体積抵抗率ρ、透磁率μに起因する。したがって、その温度係数もコア１の体積抵抗率ρ、透磁率μの温度係数に関係するのであるから、コア１が検出コイル２に貫入している場合の温度係数を、コア１が検出コイル２に貫入していない場合の温度係数に合わせるように適した体積抵抗率ρ、透磁率μを有するコア１を選択する、またはコア１の表面が適した体積抵抗率ρ、透磁率μとなるような表面処理を施せばよい。
【０１２４】
ここで、一般にポジションセンサを使用する雰囲気温度はせいぜい１２０〜１３０℃であり、その雰囲気温度よりもコア１のキュリー温度は十分に高い。透磁率μは、キュリー温度付近で急激に小さくなる特性を有しており、逆にポジションセンサを使用する温度領域では透磁率μはほとんど変化しない。
【０１２５】
したがって、検出コイル２のインピーダンスＺの増加に起因するもう１つの要素である体積抵抗率ρの変化が小さな材料で少なくともその表面が形成されたコア１を用いることによって、インピーダンスＺの温度係数を小さくして、検出コイル２のインピーダンスＺの温度による変動を小さくすることができる。
【０１２６】
例えば、実施形態１の検出コイル２のインピーダンス変化によって位置検出を行うポジションセンサでは、このインピーダンスの内訳の大部分はインダクタンスであり、検出コイル２に定電流が流れて発生する磁界は検出コイル２の軸方向となる。すると、この軸方向の磁界を消そうとする環状の電流（いわゆる渦電流）がコア１の内部に流れる。この環状電流は検出コイル２のインダクタンスを低下させる作用があり、大きさは印加される磁界の大きさや周波数（定電流、固定周波数であれば変動しない）以外に、コア１の体積抵抗率が関係する。すなわちコア１の体積抵抗率が大きいほど環状電流は小さくなり、インダクタンスを低下させる作用は小さくなる。それゆえ、コア１の体積抵抗率に温度特性があればインダクタンスにも温度特性ができ、インダクタンスの温度特性はインピーダンスの温度特性に大きく影響する。
【０１２７】
実際に検出コイル２をインピーダンス要素として用いる場合には検出コイル２に供給する電流は数十ＫＨｚ〜数百ＫＨｚで駆動することが多いので、その周波数では検出コイル２が発生する磁界はコア１の内部には届かず、表面付近に集まることになる。
【０１２８】
そこで、体積抵抗率ρの小さな材料であるニッケル−クロム合金、ニッケル−クロム−鉄合金、鉄−クロム−アルミ合金、銅−ニッケル合金、マンガニンのうちいずれかでコア１の少なくとも表面を形成すればよい。これらの材料は電熱用材料と呼ばれており、抵抗の温度係数が小さく、また、鉄やニッケルは磁性材料なので合金としても磁性を有するものがあり、したがって検出コイル２のインピーダンス変化が大きく取れる。
【０１２９】
しかしながら、表面だけでなく、バルク状に形成した体積抵抗率の小さいコア１であれば、より優れた温度特性を有することができる。この場合、ニッケル−クロム合金、ニッケル−クロム−鉄合金、鉄−クロム−アルミ合金、銅−ニッケル合金、マンガニン等の電熱用材料を用いることになるが、これらは、平板から打ち抜きでコア１の形状を得るには材料ロスが多くなって高価になる。そこで、これらの材料は電熱線として市場に出回っていることから、ニッケル−クロム合金、ニッケル−クロム−鉄合金、鉄−クロム−アルミ合金、銅−ニッケル合金、マンガニン等からなる電熱線を必要な長さに切断した後、必要な曲げ加工（または伸ばし加工）を施して用いると経済的であり、無用な産業廃棄物の発生を防ぐことができる。
【０１３０】
また、本実施形態の温度補償の第１の方法と第２の方法との両者を組み合わせることにより、効果的に温度補償を行うことができる。
【０１３１】
（実施形態３）
実施形態１のポジションセンサは直流電流Ｉｄｃと交流電流Ｉａｃとを検出コイル２に供給し、結果として検出コイル２の両端に発生する直流電圧Ｖｄｃと交流電圧Ｖａｃとの比で、変位信号Ｖｏｕｔの温度係数が検出コイル２とコア１との相対変位によって変動する幅（温度係数の変位依存性）の最小化を図っていた。そして図１９に示すように、信号処理回路４を、例えばピークホールド回路４ａ、温度補償回路４ｃ、非線形性補償回路４ｅ、増幅回路４ｄで構成して、ピークホールド回路４ａが検出コイル２の両端電圧Ｖｓのピーク値Ｖ１を抽出し、温度補償回路４ｃはピーク値Ｖ１に、ピーク値Ｖ１の温度係数とは逆極性の温度係数で温度補償し、非線形性補償回路４ｅは検出コイル２とコア１との相対変位に対する直線性を補償して、増幅回路４ｄは信号増幅を行って変位信号Ｖｏｕｔを出力するものである。
【０１３２】
対して本実施形態のポジションセンサは図２０に示すように、信号処理回路４を、ピークホールド回路４ａ、レベルシフト回路４ｂ、温度補償回路４ｃ、増幅回路４ｄで構成して、ピークホールド回路４ａが検出コイル２の両端電圧Ｖｓのピーク値Ｖ１を抽出し、レベルシフト回路４ｂはピーク値Ｖ１にレベルシフト値Ｖｓｈを加算した信号Ｖ２を出力し、温度補償回路４ｃは信号Ｖ２に、信号Ｖ２の温度係数とは逆極性の温度係数で温度補償した信号Ｖ３を出力し、増幅回路４ｄは信号Ｖ３の増幅を行って変位信号Ｖｏｕｔを出力するものである。
【０１３３】
このレベルシフト回路４ｂがピーク値Ｖ１にレベルシフト値Ｖｓｈを加算することによって、検出コイル２へ供給する直流電流Ｉｄｃは０あるいは小さな値であってもよく、消費電流に制約がある場合には有利になる（図３では直流電流Ｉｄｃ＝０としている）。対して実施形態１ではピーク値Ｖ１の変位依存性を最小にするために、Ｉｄｃ／Ｉａｃの値を大きく設定しなければならず、消費電流の増大や、感度の劣化を引き起こす恐れがあった。ここで本実施形態では［数２］で表されるピーク値Ｖ１に対して、信号Ｖ２は、
【０１３４】
【数４】

と表され、（Ｉｄｃ＊Ｚｄｃ＋Ｖｓｈ）が直流電圧Ｖｄｃとなる。
【０１３５】
そして、レベルシフト値Ｖｓｈの大きさ（絶対値）または温度係数を適正に設定することは、実施形態１のように直流電流Ｉｄｃと交流電流Ｉａｃとの比や温度係数を適正に設定することと同じことになる。さらに、レベルシフト値Ｖｓｈ以外に、直流電流Ｉｄｃ、交流電流Ｉａｃ、直流抵抗Ｚｄｃ、交流インピーダンスＺａｃの各値及び温度係数のうちいずれか１つ以上を適正に設定した場合も、信号Ｖ２の直流電圧Ｖｄｃと交流電圧Ｖａｃとの比及び温度係数を適正に設定することになるので、信号Ｖ２の温度係数の変動幅を最小にすることができる。
【０１３６】
本実施形態のポジションセンサの形状は実施形態１と同様であるが、本実施形態では図２１に示すように可動ブロック１３が回転し、回転角θが０°から９０°になるにしたがって、検出コイル２に貫入しているコア１の部分が多くなる構成としている。図２２はこの回転角θに対する検出コイル２の交流インピーダンスＺａｃの温度係数を示しており、交流インピーダンスＺａｃは変位依存性を持っており、回転角θが大きいほどコア１の検出コイル２に対する貫入量が多くなって、増大している（回転角θ＝０〜１００°で約４７０ｐｐｍ／℃の差がある）。交流インピーダンスＺａｃの測定周波数は７０ＫＨｚ、直流抵抗Ｚｄｃは５８Ω（２５℃）で、直流抵抗Ｚｄｃの温度係数は３９００ｐｐｍ／℃である。
【０１３７】
ここで図１９の構成で抽出したピーク値Ｖ１の温度係数を図２３に示す。交流電流Ｉａｃ＝１ｍＡとして、Ｉｄｃ／Ｉａｃを変化させることでピーク値Ｖ１の温度係数の変位依存性を制御することができ、Ｉｄｃ／Ｉａｃ＝１．０程度の場合に、ピーク値Ｖ１の温度係数の変位依存性を最小にすることができる。なお、簡単のために直流電流Ｉｄｃ、交流電流Ｉａｃ、周波数には温度変化がないと仮定している（以下同様）。
【０１３８】
対して図２４は、図２０の本実施形態の構成でレベルシフト値Ｖｓｈを０ｍＶから２００ｍＶまで変化させた場合の信号Ｖ２の温度係数を示しており、直流電流Ｉｄｃを０、レベルシフト値Ｖｓｈの温度係数ｈを３０００ｐｐｍ／℃としている。この場合、レベルシフト値Ｖｓｈを変化させることで信号Ｖ２の温度係数の変位依存性を制御することができ、Ｖｓｈ＝１００ｍＶ程度の場合に、信号Ｖ２の温度係数の変位依存性を最小にすることができて、上記図１９の構成と同様の効果を得ることができる。
【０１３９】
さらに図２５は、図２０の本実施形態の構成でレベルシフト値Ｖｓｈの温度係数ｈを０ｐｐｍ／℃からから５０００ｐｐｍ／℃まで変化させた場合の信号Ｖ２の温度係数を示しており、直流電流Ｉｄｃを０、レベルシフト値Ｖｓｈを１００ｍＶとしている。この場合、温度係数ｈを変化させることで信号Ｖ２の温度係数の変位依存性を制御することができ、ｈ＝２０００ｐｐｍ／℃程度の場合に、信号Ｖ２の温度係数の変位依存性を最小にすることができて、上記図１９の構成と同様の効果を得ることができる。
【０１４０】
このようにして得られた信号Ｖ２に、温度補償回路４ｃで変位に依らない温度補償（例えば図２３の場合、約−１２００ｐｐｍ／℃、図２４の場合、約−１４５０ｐｐｍ／℃、図２５の場合、約−１３００ｐｐｍ／℃）を行って得られる信号Ｖ３は周囲温度に依らず、常温でのその変位での信号Ｖ２にほぼ等しい値となる。そして増幅回路４ｄで信号Ｖ３に所定の増幅を行うことで変位信号Ｖｏｕｔを出力している。（特に増幅の必要がなければ信号Ｖ３を変位信号Ｖｏｕｔとして出力する。）なお、温度補償回路４ｃは、必ずしも温度に対して１次の補償を行うものに限るものではなく、温度について２次あるいはその他の非線形の方程式で表現される補償を行う回路でもよい。同様に、増幅回路４ｄも信号Ｖ３について非線形の方程式で表現される増幅度を有する回路でもよい。
【０１４１】
また、図２６に示すようにレベルシフト回路４ｂを検出コイル２とピークホールド回路４ａとの間に接続しても、信号Ｖ２は［数４］で表されるため、同様の効果を得ることができる。
【０１４２】
そして本実施形態のレベルシフト値Ｖｓｈやレベルシフト値Ｖｓｈの温度係数ｈ、さらには温度補償の温度係数、増幅のための回路定数、係数等をＥＥＰＲＯＭ等に記憶できるようにして、個別の製品毎にその値や係数、定数を最適値に設定できるようにすれば、検出コイル２や信号処理回路４の温度特性の個体差に左右されないため、温度変化による特性変動を最小限にすることができる。
【０１４３】
次に、ポジションセンサの製造工程で個別に行うレベルシフト値Ｖｓｈやレベルシフト値Ｖｓｈの温度係数ｈのキャリブレーションについて、以下説明する。まず、図２４のようにレベルシフト値Ｖｓｈを制御して温度特性の変位依存性を最小化する場合には、温度サイクルによって各変位（各回転角）でのピーク値Ｖ１、信号Ｖ２の温度特性を測定して最適なレベルシフト値Ｖｓｈを求め、そのレベルシフト値Ｖｓｈに基づいて増幅回路４ｄの係数（回路定数）を決める。そして、増幅回路４ｄの係数設定後、はじめて変位信号Ｖｏｕｔが得られるため、変位信号Ｖｏｕｔの温度特性を確認するためには、温度サイクルを再度行う必要がある。
【０１４４】
一方、図２５のようにレベルシフト値Ｖｓｈの温度係数ｈを制御して温度特性の変位依存性を最小化する場合は、まず常温状態（温度補償回路４ｃのゲインは１になる）で増幅回路４ｄの係数を決めることができる。その後、温度サイクルによって各変位（各回転角）でのピーク値Ｖ１、信号Ｖ２の温度特性を測定して最適な温度係数ｈや温度補償回路４ｃの温度係数を決めることができ、この温度サイクルで変位信号Ｖｏｕｔも同時に確認することができるので、２回目の温度サイクルを行う必要はない。このようにレベルシフト値Ｖｓｈを制御するよりもレベルシフト値Ｖｓｈの温度係数ｈを制御するほうがキャリブレーションは簡単に実施できる。
【０１４５】
なお実施形態１のように検出コイル２にバイアス電流を供給して制御する場合は、図２３のようにＩｄｃ／Ｉａｃを制御するよりも、直流電流Ｉｄｃ、交流電流Ｉａｃ、または周波数の温度係数を制御するほうがキャリブレーションは簡単に実施できる。
【０１４６】
また上記説明では、検出コイル２の両端電圧のピーク値Ｖ１を元の信号として信号処理を行っているが、検出コイル２の両端電圧のボトム電圧を元の信号として信号処理を行ってもよく、この場合は［数２］、［数４］の代わりに、
【０１４７】
【数５】

【０１４８】
【数６】

となる。この場合も、レベルシフト値Ｖｓｈ、レベルシフト値Ｖｓｈの温度係数ｈを適正に設定することで（少なくともいずれか一方を負の値にする）上記と同様の効果を得ることができる。さらには、検出コイル２の両端電圧のピーク−ピーク電圧や実効値を元の信号として、その元の信号にレベルシフトを施しても上記と同様の効果を得ることができる。
【０１４９】
このように本実施形態では検出コイル２の直流抵抗Ｚｄｃの温度係数を利用する必要はなく、検出コイル２の両端電圧から交流電圧Ｖａｃのみを取り出して、レベルシフト回路４ｂで直流電圧（レベルシフト値Ｖｓｈ）を与えればよく、回路設計の自由度が向上している。
【０１５０】
（実施形態４）
本実施形態のポジションセンサの構成は図２７に示すように、実施形態３のピークホールド回路４ａの次段にＡＤ変換回路４ｆを接続し、ＡＤ変換回路４ｆの次段にはレベルシフト部４１、温度補償部４２、増幅部４３を構成するデジタル演算ブロック４ｇを接続している。そして、検出コイル２の両端電圧のピーク値Ｖ１をＡＤ変換回路４ｆでデジタル信号ＤＶ１に変換し、以降、デジタル演算ブロック４ｇではデジタル信号演算としてレベルシフト部４１で所定のデジタル量を加算してレベルシフトを行ったデジタル信号ＤＶ２を出力し、温度補償部４２では温度補償を実行する演算をデジタル信号ＤＶ２に対して行い、増幅部４３では温度補償部４２が出力するデジタル信号を増幅して、デジタル信号の変位信号Ｖｏｕｔを出力する。
【０１５１】
このように信号をデジタル化すると、１回の温度サイクルでピーク値Ｖ１の温度特性のみを測定すれば、レベルシフトのデジタル量やその温度係数、温度補償の温度係数や、増幅の係数等は計算によって求めることができ、且つ出力される変位信号Ｖｏｕｔの温度特性も計算で確認できる（実際の出力と計算で求めた出力との誤差は量子化誤差以下となる）という長所がある。また、デジタル演算結果をＤＡ変換してアナログ信号出力とすることもできる。
【０１５２】
（実施形態５）
本実施形態では、出力の直線性の改善について説明する。本実施形態のポジションセンサの構成は実施形態１乃至４いずれかと同様であり、同様の構成には同一の符号を付して説明は省略する。
【０１５３】
まず、直線性改善の第１の方法としては、コア１の材料に適正なものを選択し、且つ交流電流Ｉａｃの周波数ｆも適正に設定することである。発明者は実施形態１で例をあげた検出コイル２において、コア材質を変えて交流インピーダンスＺａｃの直線性に関する実験を行なった。図２８は用いた金属材料：電磁軟鉄，パーマロイ，電磁ステンレス，ＳＵＳ４３０，鉄クロムと、それらの推定特性値：抵抗率である。図２８の中で「電磁ステンレス」と記されたものは、Ｃｒ１１％の他、Ｓｉ、Ｍｎ、Ｐ、Ｎｉ、Ｔｉなどを添加した金属で電磁弁やリレーのヨーク等に使用されるものである。また、各金属はいずれも各々の磁気特性を引き出すために、各金属固有の条件で熱処理が施されており、形状は同一である。
【０１５４】
図２９（ａ）〜（ｅ）に交流電流Ｉａｃの周波数ｆを１０ＫＨｚ、３０ＫＨｚ、５０ＫＨｚ、７０ＫＨｚ、９０ＫＨｚに対する、各金属の交流インピーダンスＺａｃの直線性の実験結果を示す。電磁軟鉄や純鉄に比べ、磁性ステンレス（電磁ステンレス）は良好な直線性を有することが分かる。特に、ＳＵＳ４３０（１８Ｃｒ系フェライト系ステンレス）は、角度スパンに対しても周波数に対しても良好な直線性を有する上、耐食性も備え、且つ安価であるのでポジションセンサのコア材料として好適であるといえる。これらの直線性は抵抗率、透磁率のバランスと周波数特性で決定されるものと考えられる。鉄クロムも５０ｋＨｚ以上では良好な直線性を有するので、耐食性についての対策さえ施せば、前述の抵抗率温度変化率の利点と合わせて良好なコア材料となり得ることがわかる。
【０１５５】
第２の改善方法としては、従来技術の問題点として挙げた端部効果を低減するための対策を施すことである。図３０（ａ）、（ｂ）は、コア１の形状を工夫することでコア先端部１ａまたは１ｂの、交流インピーダンスＺａｃに対する寄与率を高める方法である。図３０（ａ）においては、先端部１ａに略直角の段差を設けて太くしたもので、図３０（ｂ）においては、先端部１ｂを楔状に太くしたものであり、両方共、先端部１ａまたは１ｂが他の部分より太くなっているため、巻線間の鎖交磁束量を多くすることができ、よりインダクタンスの増加に寄与することができる。また、このとき、エッチングや金属射出成形でコア１を形成する場合には、特にコストアップ要因にはならない。
【０１５６】
図３０（ｃ）は、コア１の先端部１ｃをコア本体より透磁率の高い材料で構成することにより、コア先端部１ｃでの鎖交磁束量を多くすることができ、よりインダクタンスの増加に寄与することができるものである。図３０（ａ）、（ｂ）が先端部以外の部分を細くしなければならず、若干の感度低下を伴なうのに対し、図３０（ｃ）の実施例では感度低下が起こらない。また、太さが均一であるので力学的に安定（少しくらい当たっても、変形しにくい）である。
【０１５７】
図３０（ｄ）は、高透磁率の材料でコア先端部１ｄに表面処理（めっき等）を施した例である。図３０（ｃ）が製造上、手間がかかり、位置決めも難しいことを改善することができる。また、めっきだけでなく、たとえば高透磁率の箔体を貼り付ける等の構成でもよい。
【０１５８】
図３１に示すポジションセンサは、中空のボビン１５に巻回された検出コイル２と、検出コイル２の巻軸方向Ｘに変位してボビン１５の中空部分に貫入するコア１とを備え、定電流回路と信号処理回路とは（図示なし）、実施形態１乃至４いずれかと同様に設けられている。この例は、コア１は従来のままの形状であり、巻線が検出コイル２の端部で太く（すなわち、巻層数が多く）巻かれている例である。したがって、コア１の先端部のみの貫入に対しても、多くの巻線の磁束が鎖交するため、よりインダクタンスが増加するものである。
【０１５９】
さらに、コア１と検出コイル２のボビン内壁との引っ掛かりをなくするために、図３２（ａ）〜（ｅ）の例では、コア１の先端部に面取り、Ｒ付けなどのエッジ除去構造を取り入れることにより、引っ掛かりをなくしている。図３２（ｂ）〜（ｅ）は図３０（ａ）〜（ｅ）に示したコア１の先端に面取り、Ｒづけを施したものである。
【０１６０】
また、コア１及び検出コイル２の断面図を示す図４においては、コア１が貫入する湾曲ボビン１０の内面に銅などの非磁性金属を蒸着したコーティング１１を施して、コア１の引っ掛かりをなくしている。コーティング１１に金属等、導電性を有する物質を用いる場合には、物質が断面内で閉ループを形成しないようにする必要がある。なお、金属蒸着等の代りに、貫通穴側面の一部を板金部品で形成してもよいし、フッ素コーティングなど摺動性と耐摩耗性を有する物質であれば同じ効果を発揮することができる。このようにすることで、コア１として箔体や線状体（特にアモルファスなど）を用い、湾曲ボビン１０の貫通穴の側面に沿わせて変位させることもできるので、薄型化や小径化が図れるとともに直線性の向上にも効果がある。
【０１６１】
さらに、スプリングコイルを用いて検出コイル２の巻線を形成し、スプリングコイルを湾曲ボビン１０に挿入すれば、角度方向に均一なピッチの巻線が容易に形成できる。
【０１６２】
次に、図２においては、検出コイル２の巻線テンションで変形し、曲率が減少した湾曲ボビンを元の形に戻すための曲率矯正用部材１２を備えており、曲率矯正用部材１２は検出コイル２と略同様の曲率に形成された溝を形成しており、その溝に検出コイル２を入れ込むことによって、検出コイル２の内側半径部分と底面側とが曲率矯正用部材１２に当接して、湾曲ボビン１０の曲率の減少を矯正している。図２ではハウジング１４が曲率矯正用部材１２を備えているが、ハウジング１４そのものに同様の溝を形成してもよい。
【０１６３】
このような曲率矯正用部材１２を用いる構造には、別の意味でもメリットがある。このような構造をとらない検出コイル２では、図３３に示すように保持固定のための保持・固定用部材１６を検出コイル２の両端部の鍔付近外側に設ける必要がある。この保持・固定用部材１６があると、コア１のストローク（機械的変位量）が制限されてしまう。しかし、保持固定の構造が鍔の外側にない図２の場合は、コア１のストロークを長くとることができ、あるいは、ストロークを長くとる代りに、湾曲ボビン１０の巻線部の角度を広くとることができ、これらも、直線性の改善に繋がるものである。
【０１６４】
（実施形態６）
図３４〜３７に示す本実施形態のポジションセンサは、自動車用（例えばアクセルペダルポジションの検出等）に使用することを考慮し、フェールセーフシステムの思想に基づいて、図２，図３に示すポジションセンサの検出部を２重にしたものであり、図３４，図３５では、同一の曲率で湾曲した２つの検出コイル２ａ，２ｂと、可動ブロック１３の回転軸を中心に回転することで２つの検出コイル２ａ，２ｂに各々貫入する同一の曲率で湾曲した２つのコア１ａ，１ｂとを備え、２つの検出コイル２ａ，２ｂは、コア１ａ，１ｂの回転軸方向に重ねて配置されている。特開２０００−１８６９０３号公報に記載の同一平面上に２つの検出コイルを配置する構成に比べて、検出コイル２ａ，２ｂの巻き線部の見込角度も、可動ブロック１３の機械的回転角度も増える。したがって、検出コイル２ａ，２ｂの各インピーダンスＺの直線性が良好な回転角度θの範囲が広がる。また、検出コイル２ａ，２ｂの仕様が同一であるので、２つの検出コイル２ａ，２ｂの特性を略同一にすることができ、巻線加工、コスト面で有利である。
【０１６５】
さらに、図３６，図３７に示すポジションセンサは、小さい曲率で湾曲した検出コイル２ａと、大きい曲率で湾曲した検出コイル２ｂと、可動ブロック１３の回転軸を中心に回転することで２つの検出コイル２ａ，２ｂに各々貫入する小さい曲率で湾曲したコア１ａと、大きい曲率で湾曲したコア１ｂとを備え、検出コイル２ａ，２ｂは、コア１ａ，１ｂの回転軸に対して同一回転角度θ上、且つ同一平面上に配置されている。したがって、図３４，図３５に示すポジションセンサと同様に、検出コイル２ａ，２ｂの巻き線部の見込角度も、可動ブロック１３の機械的回転角度も増えて、検出コイル２ａ，２ｂの各インピーダンスＺの直線性が良好な回転角度θの範囲が広がり、さらに薄型化も可能となる。
【０１６６】
ここで、本実施形態の検出コイル２ａ，２ｂを湾曲ボビン１０ａ，１０ｂに巻回した後、組み立て前に、検出コイル２ａ，２ｂと湾曲ボビン１０ａ，１０ｂとを一体的に樹脂１７でモールドすれば、組み立て時、振動・衝撃時の断線防止になり、２つのコイル２ａ，２ｂ間の位置関係がずれることがないので、組み立て時の位置ずれによる２系統間の出力変動が発生しない。さらに、一体的に成形して２つの検出部で１つの部品になるので、可動ブロック１３との位置決めが容易になり、組み立て時間も短時間となる。
【０１６７】
また、湾曲ボビン１０ａ，１０ｂの変形を矯正した状態で樹脂モールドすることにより、ハウジング１４側に湾曲ボビン１０ａ，１０ｂの変形を矯正する特別な部材を設ける必要がなくなる。
【０１６８】
さらに、２つのコア１ａ，１ｂも一体的に樹脂モールドすれば、互いの位置がずれないので、組み立て時の位置ずれによる２系統間の特性変動が発生しない。
【０１６９】
（実施形態７）
本実施形態のポジションセンサの構成は実施形態１乃至６のうちいずれかと同様であり、同様の構成には同一の符号を付して説明は省略する。本実施形態では、信号処理回路４が出力する変位信号Ｖｏｕｔの構成について説明する。
【０１７０】
ポジションセンサの信号を受けて処理するシステムであるＥＣＵがデジタル回路である場合、変位信号Ｖｏｕｔがアナログ信号であると余計なＡ／Ｄ変換やＤ／Ａ変換を繰り返すことにより誤差が生じ、且つ応答遅れを伴うが、変位信号Ｖｏｕｔがデジタル信号であればアナログ信号のような前記問題はなく、さらに信号伝達の際の外部ノイズの影響を受けにくい。そこで、信号処理回路４が出力する変位信号Ｖｏｕｔをデジタル信号で構成した例を示す。ここで信号処理回路４は、検出部Ａの出力電圧のピーク値Ｖ１をデジタル信号に変換するＡ／Ｄ変換回路（実施形態４以外では図示なし）と、前記デジタル信号をデジタルトリミングする補正回路とを備える信号補正回路とを具備している。
【０１７１】
図３８は、信号処理回路４が出力する変位信号Ｖｏｕｔの第１の例を示し、変位信号Ｖｏｕｔは、基準パルスＶｒのパルス幅３個分の幅Ｔ１を有する出力開始信号と、出力開始信号が出力してから位置情報に応じた時間Ｔ２を経て出力されるパルス信号とから構成される。ＥＣＵ側では出力開始信号のパルス幅Ｔ１と、パルス信号が表れるまでの時間Ｔ２とをタイマで測定することによって、コア１と検出コイル２との相対位置を判断することができる。
【０１７２】
図３９は、信号処理回路４が出力する変位信号Ｖｏｕｔの第２の例を示し、変位信号Ｖｏｕｔは、基準パルスＶｒのパルス幅３個分の幅を有する出力開始信号と、出力開始信号に続いて出力される位置情報に応じた数のパルス信号とから構成される。
【０１７３】
ＥＣＵ側では出力開始信号に続くパルス信号の数をカウンタで計数することによって、コア１と検出コイル２との相対位置を判断することができる。
【０１７４】
図４０は、信号処理回路４が出力する変位信号Ｖｏｕｔの第３の例を示し、変位信号Ｖｏｕｔは、位置情報に応じたデューティ比のパルス信号とから構成され、そのデューティ比のオン，オフ時間は基準パルスＶｒのパルス数によって各々決められる。
【０１７５】
ＥＣＵ側では周期とパルス幅とをタイマで計測することによって、コア１と検出コイル２との相対位置を判断することができる。
【０１７６】
なお、必要ビット数のデジタル出力を確保するとポジションセンサ−ＥＣＵ間の配線数が増えてしまうが、図３８〜図４０に示す例によれば信号線は１本で済む。また、変位信号Ｖｏｕｔは、位置情報に応じたパルス幅のパルス信号とから構成されてもよい。さらに、信号線の数が問題にならなければ、変位信号Ｖｏｕｔを位置検出に必要な分解能を満たすビット数のデジタル信号で構成してもよい。
【０１７７】
（実施形態８）
本実施形態のポジションセンサの検出コイルの断面構造、回路構成を、図４１，図４２に各々示す。なお、信号処理回路４ａ，４ｂの構成は実施形態１，３，４のうちいずれかと同様である。
【０１７８】
本実施形態のポジションセンサは、車載用に使用することを考慮して、フェールセーフシステムの思想に基づいてセンサの検出部を２重にしたものである。
【０１７９】
ポジションセンサは、中空のボビン１５ａ，１５ｂに各々巻回されて巻軸方向に対向して配置された検出コイル２ａ，２ｂと、検出コイル２ａ，２ｂの巻軸方向Ｘに変位してボビン１５ａ，１５ｂの中空部分に貫入するコア１と、定電流Ｉｄａ，Ｉｄｂを検出コイル２ａ，２ｂに各々出力する定電流回路３と、定電流回路３が出力する定電流Ｉｄａ及び検出コイル２ａのインピーダンスＺａにより決まる検出コイル２ａの両端電圧のピーク値をコア１と検出コイル２ａとの位置情報を示す変位信号に変換する信号処理回路４ａと、定電流回路３が出力する定電流Ｉｄｂ及び検出コイル２ｂのインピーダンスＺｂにより決まる検出コイル２ｂの両端電圧のピーク値をコア１と検出コイル２ｂとの位置情報を示す変位信号に変換する信号処理回路４ｂとを備える。
【０１８０】
本実施形態においては、２つの検出コイル２ａ，２ｂは構造部材（図示なし）に取り付けられた同一のコア１を共用すること、同一の定電流回路３が所定の周波数及び振幅の定電流Ｉｄａ，Ｉｄｂを２つの検出コイル２ａ，２ｂに各々出力することによって、検出部の２重化に伴うコストアップを低減することができる。
【０１８１】
また、定電流回路３、信号処理回路４ａ，４ｂの能動回路部をモノリシックＩＣで構成すれば、ＩＣ部は最もコストの高い部品であるので、検出部の２重化に伴うコストアップをさらに低減することができる。
【０１８２】
以下、実施形態１乃至８のポジションセンサの具体的な使い方について説明する。まず、車載のアクセルペダル検出用ポジションセンサとして用いる場合は、検出角度が３０°程度と狭いので、同一平面内に同一曲率の湾曲ボビンを配置することができ、検出コイルのインピーダンスを相補的とすることができる。また、車室内に配置されるため、動作上限温度はそれほど高くない。さらに、検出角度に対して、十分大きなストロークがあるため、コアの材質や形状にあまり工夫を施さなくても、ストローク中央部分の直線性のよい部分をも用いることができる。
【０１８３】
次に、スロットルポジションセンサとして用いる場合は、検出角度が９０°以上と大きく、且つ機械的ストロークも大きくする必要があるため、図３４，３５に示す湾曲ボビンの２段重ねか、あるいは図３６，３７に示すように、同一平面内の同一角度範囲に異なる曲率を有する湾曲ボビンを並べる構造が適している。また、検出角度に対する機械的ストロークの余裕が限られているため、コアとしてはＳＵＳ４３０等のコイルインピーダンスの直線性が得られやすい材料を選択することが望ましい。スロットルポジションセンサはエンジンルーム内に配置されるため、高い動作上限温度が要求され、コアとして直線性が得られやすい材料を選択した上で、適度なバイアス電流をコイルに与え、角度変位による温度特性（温度係数）を最小限にすることが望ましい。
【０１８４】
また、発電設備等のプラント用に用いるポジションセンサは、高温にさらされるため、コア材料としては鉄クロムを用いた上、適度なバイアス電流をコイルに与え、角度変位による温度特性（温度係数）を最小限にする工夫が望ましい。
【０１８５】
さらに、原動機付き自転車に用いる角度検出用のポジションセンサはコスト面から検出部を１系統のみとしている場合があるが、一般に自動車に用いられる角度検出用のポジションセンサは、システムとしての信頼性を確保するために検出部の２重化を図ってもよい。
【０１８６】
【発明の効果】
請求項１の発明は、所定の振幅の直流電流に所定の周波数及び振幅の交流電流を重畳した定電流を出力する定電流回路と、前記定電流を供給される少なくとも検出コイルからなる検出部と、前記検出コイルに対して前記検出コイルの巻軸方向に相対変位する磁性材料からなるコアと、前記定電流によって発生する前記検出部の出力電圧のピーク値に基づいて前記コアと前記検出コイルとの位置情報を示す変位信号を出力する信号処理回路とを備え、前記コアの前記検出コイルに対する全変位区間における前記検出部の出力電圧のピーク値の温度係数の変動幅が、前記コアの前記検出コイルに対する全変位区間における前記所定の周波数での前記検出部のインピーダンスの交流成分の温度係数の変動幅より小さくなるように、前記定電流の直流電流と交流電流との割合と、前記検出部のインピーダンスの交流成分と直流成分との割合と、前記定電流の直流電流と交流電流との割合の温度特性と、前記検出部のインピーダンスの交流成分と直流成分との割合の温度特性とのうちいずれか１つ以上を設定するので、検出コイルは検出対象に応じて自由に選択でき、検出コイルのインピーダンスの温度係数の変位依存性を回路上の定数を設定することで容易に低減でき、したがって、変位に対する検出コイルのインピーダンスの温度係数の変化を簡単な回路で補償できるという効果がある。
【０１８７】
請求項２の発明は、請求項１において、前記コアは、前記検出コイルの巻線内に貫入自在であるので、検出コイルのインピーダンスの変化を大きくできるという効果がある。
【０１８８】
請求項３の発明は、請求項２において、前記検出部の出力電圧の直流成分の温度係数は、前記検出コイルの巻線内に対するコアの貫入量が最小の場合の前記検出部の出力電圧の交流成分の温度係数より、前記コアの貫入量が最大の場合の前記検出部の出力電圧の交流成分の温度係数に近いので、検出部の出力電圧のピーク値の温度係数の変動幅を小さくすることができるという効果がある。
【０１８９】
請求項４の発明は、請求項１または２において、前記定電流回路は、所定の振幅の直流電圧に所定の周波数及び振幅の交流電圧を重畳した電圧を発生する発振回路と、前記発振回路の出力電圧を電流に変換する電圧−電流変換回路とから構成され、前記直流電圧と交流電圧とを各々設定することで、前記定電流の直流電流と交流電流との割合を設定するので、簡単な回路構成と、回路上の定数の設定とによって、定電流の直流電流と交流電流との割合を設定することができるという効果がある。
【０１９０】
請求項５の発明は、請求項１または２において、前記定電流回路は、所定の振幅の直流電圧に所定の周波数及び振幅の交流電圧を重畳した電圧を発生する発振回路と、前記発振回路の出力電圧を電流に変換する電圧−電流変換回路とから構成され、前記発振回路が備える直流電圧の値を決定する抵抗の抵抗値の温度係数を設定することで、前記定電流の直流電流と交流電流との割合の温度特性を設定するので、簡単な回路構成と、回路上の定数の設定とによって、定電流の直流電流と交流電流との割合の温度特性を設定することができるという効果がある。
【０１９１】
請求項６の発明は、請求項１または２において、前記定電流回路は、所定の振幅の直流電圧に所定の周波数及び振幅の交流電圧を重畳した電圧を発生する発振回路と、前記発振回路の出力電圧を電流に変換する電圧−電流変換回路とから構成され、前記交流電圧の周波数の温度特性を設定することで、前記検出部のインピーダンスの交流成分と直流成分との割合の温度特性を設定するので、定電流回路がＩＣで構成されて容易に回路上の定数設定を行うことができない場合でも、交流電圧の発振周波数を決定するための抵抗やコンデンサが外付けになっておれば、これらの抵抗やコンデンサの温度係数を選択することによって、検出部のインピーダンスの交流成分の温度特性を設定することができるという効果がある。
【０１９２】
請求項７の発明は、請求項１または２において、前記定電流回路は、所定の振幅の直流電流を出力する直流定電流回路と、所定の周波数及び振幅の交流電流を出力する交流定電流回路とからなり、前記直流電流の振幅の温度特性と前記交流電流の周波数の温度特性と前記交流電流の振幅の温度特性とのうち少なくとも１つを設定することで、前記定電流の直流電流と交流電流との割合と、前記検出部のインピーダンスの交流成分と直流成分との割合と、前記定電流の直流電流と交流電流との割合の温度特性と、前記検出部のインピーダンスの交流成分と直流成分との割合の温度特性とのうちいずれか１つ以上を設定するので、簡単な回路構成と、回路上の定数の設定とによって、請求項１と同様の効果を奏する。
【０１９３】
請求項８の発明は、請求項１または２において、前記検出部は、前記検出コイルと、前記検出コイルに直列接続し、前記コアの変位によってインピーダンスが変化しない回路素子とを備え、前記信号処理回路は、前記定電流によって発生する前記検出コイルと回路素子との直列回路の両端電圧のピーク値に基づいて前記コアと前記検出コイルとの位置情報を示す変位信号を出力し、前記回路素子のインピーダンスの交流成分及び直流成分と、前記回路素子のインピーダンスの交流成分及び直流成分の温度係数とのうち少なくとも１つを設定することで、前記検出部のインピーダンスの交流成分と直流成分との割合と、前記検出部のインピーダンスの交流成分と直流成分との割合の温度特性とのうち少なくとも１つを設定するので、定電流回路がＩＣで構成されて容易に回路上の定数設定を行うことができない場合でも、変位に対する検出部のインピーダンスの温度係数の変化を簡単な回路で補償できるという効果がある。
【０１９４】
請求項９の発明は、請求項８において、前記回路素子は抵抗であるので、低コストで検出部のインピーダンスを制御できるという効果がある。
【０１９５】
請求項１０の発明は、請求項８において、前記回路素子はインダクタであるので、低コストで検出部の直流抵抗と交流インピーダンスとを制御できるという効果がある。
【０１９６】
請求項１１の発明は、請求項１または２において、前記定電流回路は、前記直流電流の振幅、前記交流電流の周波数及び振幅を設定する抵抗と、前記抵抗の値を設定するデジタルトリミング手段とを備える集積回路からなり、前記デジタルトリミング手段によって前記抵抗の値を設定することで、前記定電流の直流電流と交流電流との割合と、前記検出部のインピーダンスの交流成分と直流成分との割合と、前記定電流の直流電流と交流電流との割合の温度特性と、前記検出部のインピーダンスの交流成分と直流成分との割合の温度特性とのうちいずれか１つ以上を設定するので、容易に請求項１または２の効果を奏することができる。
【０１９７】
請求項１２の発明は、請求項１または２において、前記信号処理回路は、整流回路と、前記整流回路の出力をピークホールドする回路とからなるので、信号処理回路を簡単な回路で構成することができるという効果がある。
【０１９８】
請求項１３の発明は、請求項１または２において、前記信号処理回路は、前記検出部の出力電圧のピーク値の温度係数とは逆極性の温度係数を有する増幅器を備え、前記増幅器の出力に基づいて前記コアと前記検出コイルとの位置情報を示す変位信号を出力するので、増幅器の出力は温度補償済の変位だけに依存する信号であり、この出力を処理することで温度補償済みの変位信号を得ることができるという効果がある。
【０１９９】
請求項１４の発明は、請求項４において、前記発振回路が発生する交流電圧は三角波であるので、正弦波電圧よりも簡単に得ることができるという効果がある。
【０２００】
請求項１５の発明は、請求項７において、前記交流定電流回路が出力する交流電流は三角波であるので、正弦波電流よりも簡単に得ることができるという効果がある。
【０２０１】
請求項１６の発明は、請求項１または２において、前記検出コイルの巻線のターン数、巻線の巻ピッチ、及び前記検出コイルに入力される定電流の周波数は、前記検出コイルのインピーダンスの温度係数と、前記コアが前記検出コイルに対して相対変位することに起因する前記検出コイルのインピーダンスの温度係数とが等しくなる各値であるので、コアが貫入していない場合の検出コイルのインピーダンスを制御して、インピーダンスの温度変化が、コアと検出コイルとの相対変位によって変わらないようにすることができるという効果がある。
【０２０２】
請求項１７の発明は、請求項１または２において、前記コアは、前記検出コイルのインピーダンスの温度係数と、前記コアが前記検出コイルに相対変位することに起因する前記検出コイルのインピーダンスの温度係数とが等しくなる材料で形成されるので、コアが貫入している場合の検出コイルのインピーダンスを制御して、インピーダンスの温度変化が、コアと検出コイルとの相対変位によって変わらないようにすることができるという効果がある。
【０２０３】
請求項１８の発明は、請求項１または２において、前記コアに施された表面処理は、前記検出コイルのインピーダンスの温度係数と、前記コアが前記検出コイルに相対変位することに起因する前記検出コイルのインピーダンスの温度係数とが等しくなる表面処理であるので、コアが貫入している場合の検出コイルのインピーダンスを制御して、インピーダンスの温度変化が、コアと検出コイルとの相対変位によって変わらないようにすることができるという効果がある。
【０２０４】
請求項１９の発明は、請求項１または２において、前記コアは、少なくとも表面を体積抵抗率の温度係数が小さな材料で形成されるので、コアが貫入している場合の検出コイルのインピーダンスの温度変動を小さくすることができるという効果がある。
【０２０５】
請求項２０の発明は、請求項１９において、前記コアは、少なくとも表面をニッケル−クロム合金、ニッケル−クロム−鉄合金、鉄−クロム−アルミ合金、銅−ニッケル合金、マンガニンのうちいずれかで形成されるので、請求項１９を容易に実現できるという効果がある。
【０２０６】
請求項２１の発明は、請求項１９において、前記コアは、所望の長さに切断した電熱線を、曲げ加工して形成したので、コアが貫入している場合の検出コイルのインピーダンスの温度変動をより小さくすることができ、且つ材料のロスを少なくすることができるという効果がある。
【０２０７】
請求項２２の発明は、請求項２１において、前記電熱線は、ニッケル−クロム合金、ニッケル−クロム−鉄合金、鉄−クロム−アルミ合金、銅−ニッケル合金、マンガニンのうちいずれかで形成されるので、請求項２１を容易に実現できるという効果がある。
【０２０８】
請求項２３の発明は、請求項１または２において、前記検出コイルの巻線は、ニクロム、マンガニン、銅−ニッケル合金のうちいずれかで形成されるので、コアが貫入していない場合の検出コイルのインピーダンスの温度変動を小さくすることができるという効果がある。
【０２０９】
請求項２４の発明は、少なくとも所定の周波数及び振幅の交流の定電流を出力する定電流回路と、前記定電流を供給される少なくとも検出コイルからなる検出部と、検出コイルに対して検出コイルの巻軸方向に相対変位する磁性材料からなるコアと、前記定電流によって発生する検出部の出力電圧からの抽出値に基づいてコアと検出コイルとの位置情報を示す変位信号を出力する信号処理回路とを備え、前記信号処理回路は、検出部の出力電圧から前記抽出値を得る抽出回路と、前記抽出値に対して所定の大きさのレベルシフトを行うレベルシフト回路と、温度補償をレベルシフト回路の出力に対して行う温度補償回路とを具備し、レベルシフト回路出力の温度係数が検出コイルとコアとの相対変位によって変動する幅が、前記抽出値の温度係数が検出コイルとコアとの相対変位によって変動する幅より小さくなるように、前記レベルシフトの大きさと温度係数とのうち少なくとも何れか一方を設定するので、検出コイルに供給される電流は温特調整に依らず一定にでき、温特調整のために消費電流が変わってしまうという不都合はなく消費電流を低減でき、且つ巻線材料の直流抵抗の温度係数に依存しないで調整を行うことができて、変位に対する検出コイルのインピーダンスの温度係数の変化を簡単な回路で補償できるという効果がある。
【０２１０】
請求項２５の発明は、少なくとも所定の周波数及び振幅の交流の定電流を出力する定電流回路と、前記定電流を供給される少なくとも検出コイルからなる検出部と、検出コイルに対して検出コイルの巻軸方向に相対変位する磁性材料からなるコアと、前記定電流によって発生する検出部の出力電圧からの抽出値に基づいてコアと検出コイルとの位置情報を示す変位信号を出力する信号処理回路とを備え、前記信号処理回路は、検出部の出力電圧から前記抽出値を得る抽出回路と、前記抽出値をデジタル信号に変換するＡ／Ｄ変換回路と、Ａ／Ｄ変換回路が出力するデジタル信号に対して所定のデジタル量のレベルシフトを行うレベルシフト回路と、温度補償を実行する演算をレベルシフト回路の出力に対して行う温度補償回路とを具備し、レベルシフト回路出力の温度係数が検出コイルとコアとの相対変位によって変動する幅が、前記抽出値の温度係数が検出コイルとコアとの相対変位によって変動する幅より小さくなるように、前記レベルシフトの所定のデジタル量の大きさと温度係数とのうち少なくとも何れか一方を設定するので、請求項２４と同様の効果を奏するとともに、キャリブレーション（較正）を簡単、正確に行うことができるという効果がある。
【０２１１】
請求項２６の発明は、請求項２４または２５において、前記抽出値は、前記検出部の出力電圧のピーク値であるので、ピーク値に基づいて温度補償を行うことができるという効果がある。
【０２１２】
請求項２７の発明は、請求項２４または２５において、前記抽出値は、前記検出部の出力電圧のボトム値であるので、ボトム値に基づいて温度補償を行うことができるという効果がある。
【０２１３】
請求項２８の発明は、請求項２４または２５において、前記抽出値は、前記検出部の出力電圧の振幅に比例した値であるので、出力電圧の振幅に比例した値に基づいて温度補償を行うことができるという効果がある。
【０２１４】
請求項２９の発明は、請求項２４において、前記レベルシフトの大きさと温度係数とのうち少なくとも何れか一方を調整する手段を備えるので、製造時のばらつきに起因する温度特性の個体差を調整して、より高精度な温特を実現することができるという効果がある。
【０２１５】
請求項３０の発明は、請求項２５において、前記レベルシフトの所定のデジタル量の大きさと温度係数とのうち少なくとも何れか一方を調整する手段を備えるので、請求項２９と同様の効果を奏する。
【０２１６】
請求項３１の発明は、請求項２４または２５において、前記コアは、前記検出コイルの巻線内に貫入自在であるので、検出コイルのインピーダンスの変化を大きくできるという効果がある。
【０２１７】
請求項３２の発明は、請求項１、２、２４または２５において、前記コアの端部から所定の長さの部分を、他の部分より磁束が通りやすくしたので、端部効果が軽減され、出力の直線性が確保できる区間が広がるという効果がある。
【０２１８】
請求項３３の発明は、請求項３２において、前記コアの端部から所定の長さの部分は、他の部分より太いので、金属射出成形でコアを成形する場合に有利であり、あるいは２部材の組み合わせでも容易に形成できるという効果がある。
【０２１９】
請求項３４の発明は、請求項３２において、前記コアの端部から所定の長さの部分は、他の部分より透磁率が高い材料で形成されるので、コアの太さを一定にすることができ力学的に安定となり、また、２部材の組み合わせでも容易に形成できるという効果がある。
【０２２０】
請求項３５の発明は、請求項３２において、前記コアの端部から所定の長さの部分は、他の部分より透磁率が高い材料で表面処理されたので、コアの太さを一定にすることができ力学的に安定となり、湾曲したコアでも容易に形成できるという効果がある。
【０２２１】
請求項３６の発明は、請求項３５において、前記コアは端部から所定の長さの部分の表面にパーマロイめっきを施した電磁ステンレスからなるので、コアの端部と他の部分との透磁率のバランスがよく、また耐食性にも優れているという効果がある。
【０２２２】
請求項３７の発明は、請求項１、２、２４または２５において、前記コアの端部は、面取り処理を行ってエッジを除去したので、ボビンの内部でコアが引っ掛かることなく、引っ掛かりによる直線性の悪化を防止することができるという効果がある。
【０２２３】
請求項３８の発明は、請求項１、２、２４または２５において、前記検出コイルは所定の曲率で湾曲した形状を有しており、前記検出コイルを固定し、前記検出コイルの曲率変化を矯正する手段を有するハウジングを備えるので、検出コイルの曲率変化を矯正、防止することができるという効果がある。
【０２２４】
請求項３９の発明は、請求項３８において、前記ハウジングは前記検出コイルの内側半径部分の少なくとも一部に当接することによって、前記検出コイルの曲率変化を矯正するので、請求項３８と同様の効果を奏することができる。
【０２２５】
請求項４０の発明は、請求項１、２、２４または２５において、前記検出コイルを巻回したボビンを備え、組み立て前に前記コイルとボビンとを樹脂モールドしたので、組立て時の断線防止、振動・衝撃に対する断線防止を図ることができるという効果がある。さらに、湾曲ボビンの場合、変形を矯正した状態で樹脂モールドすることで、ハウジング側に検出コイルの曲率変化を矯正する手段がなくても、請求項３８と同様の効果を奏する。
【０２２６】
請求項４１の発明は、請求項１、２、２４または２５において、２つの前記検出コイルを各々巻回した２つのボビンを備え、組み立て前に２つの前記コイルと２つの前記ボビンとを一体に樹脂モールドしたので、請求項４０の効果に加えて、２つの検出コイルの位置関係がずれることがなく、組立て時の位置ずれによる２系統の検出部間の出力変動が生じないという効果がある。
【０２２７】
請求項４２の発明は、請求項２または３１において、２つの前記検出コイルを備え、前記検出コイルに貫入する２つの前記コアを一体に樹脂モールドしたので、請求項４１と同様の効果を奏する。
【０２２８】
請求項４３の発明は、請求項２または３１において、同一の曲率で湾曲した２つの前記検出コイルと、回転軸を中心に回転することで前記２つの検出コイルに各々貫入し、同一の曲率で湾曲した２つの前記コアとを備え、２つの前記検出コイルは、前記コアの回転軸方向に重ねて配置されるので、検出コイルの巻線部の見込み角度、可動ブロックの機械的回転角度を大きくとることができ、したがって検出コイルのインピーダンスの直線性が良好な回転角度の範囲が広がるという効果がある。さらに、２つの検出コイルの仕様を同じにできるので、２つの検出コイルの特性を同一にでき、巻線加工、コスト面で有利になる。
【０２２９】
請求項４４の発明は、請求項２または３１において、互いに異なる曲率で湾曲した２つの前記検出コイルと、回転軸を中心に回転することで前記２つの検出コイルに各々貫入し、互いに異なる曲率で湾曲した２つの前記コアとを備え、２つの前記検出コイルは、前記コアの回転軸に対して同一回転角度上、且つ同一平面上に配置されるので、検出コイルの巻線部の見込み角度、可動ブロックの機械的回転角度を大きくとることができ、したがって検出コイルのインピーダンスの直線性が良好な回転角度の範囲が広がるという効果がある。さらに、薄型化が可能となる。
【０２３０】
請求項４５の発明は、請求項１、２、２４または２５において、前記信号処理回路は、前記検出部の出力電圧のピーク値をデジタル信号に変換するＡ／Ｄ変換回路と、前記デジタル信号をデジタルトリミングする補正回路とを備える信号補正回路を具備し、前記信号処理回路が出力する前記変位信号は、位置検出に必要な分解能を満たすビット数のデジタル信号であるので、ポジションセンサの出力を入力されて処理するシステム（ＥＣＵ）がデジタル回路である場合、ポジションセンサの出力がアナログ信号であると余計なＡＤ変換、ＤＡ変換を繰り返すことによって誤差が生じ、且つ応答遅れを伴うが、ポジションセンサの出力はデジタル出力であるのでこのような問題は発生しない。また、アナログ出力に比べて信号伝達の際に外部ノイズの影響を受けにくい。さらに、必要な分解能を満たすビット数のデジタル信号であるので、ＥＣＵ側はリアルタイムに読出しを行うことができ、且つ処理を迅速に行うことができるという効果がある。
【０２３１】
請求項４６の発明は、請求項１、２、２４または２５において、前記信号処理回路は、前記検出部の出力電圧のピーク値をデジタル信号に変換するＡ／Ｄ変換回路と、前記デジタル信号をデジタルトリミングする補正回路とを備える信号補正回路を具備し、前記信号処理回路が出力する前記変位信号は、出力開始信号と、前記出力開始信号が出力してから前記位置情報に応じた時間を経て出力されるパルス信号とから構成されるので、ポジションセンサの出力を入力されて処理するシステム（ＥＣＵ）がデジタル回路である場合、ポジションセンサの出力がアナログ信号であると余計なＡＤ変換、ＤＡ変換を繰り返すことによって誤差が生じ、且つ応答遅れを伴うが、ポジションセンサの出力はデジタル出力であるのでこのような問題は発生しない。また、アナログ出力に比べて信号伝達の際に外部ノイズの影響を受けにくい。さらに、信号線が１本でよいという効果がある。
【０２３２】
請求項４７の発明は、請求項１、２、２４または２５において、前記信号処理回路は、前記検出部の出力電圧のピーク値をデジタル信号に変換するＡ／Ｄ変換回路と、前記デジタル信号をデジタルトリミングする補正回路とを備える信号補正回路を具備し、前記信号処理回路が出力する前記変位信号は、出力開始信号と、前記出力開始信号に続いて出力される前記位置情報に応じたデューティ比のパルス信号とから構成されるので、請求項４６と同様の効果を得ることができる。
【０２３３】
請求項４８の発明は、請求項１、２、２４または２５において、前記信号処理回路は、前記検出部の出力電圧のピーク値をデジタル信号に変換するＡ／Ｄ変換回路と、前記デジタル信号をデジタルトリミングする補正回路とを備える信号補正回路を具備し、前記信号処理回路が出力する前記変位信号は、出力開始信号と、前記出力開始信号に続いて出力される前記位置情報に応じたパルス幅のパルス信号とから構成されるので、請求項４６と同様の効果を得ることができる。
【０２３４】
請求項４９の発明は、請求項１、２、２４または２５において、前記信号処理回路は、前記検出部の出力電圧のピーク値をデジタル信号に変換するＡ／Ｄ変換回路と、前記デジタル信号をデジタルトリミングする補正回路とを備える信号補正回路を具備し、前記信号処理回路が出力する前記変位信号は、出力開始信号と、前記出力開始信号に続いて出力される前記位置情報に応じた数のパルス信号とから構成されるので、請求項４６と同様の効果を得ることができる。
【０２３５】
請求項５０の発明は、請求項１、２、２４または２５において、前記検出コイルを２つ具備し、前記２つの検出コイルは構造部材に取り付けられた同一の前記コアを共用するので、検出部の２重化に伴うコストアップを低減できるという効果がある。
【０２３６】
請求項５１の発明は、請求項１、２、２４または２５において、前記検出コイルを２つ具備し、同一の前記定電流回路が所定の周波数及び振幅の定電流を前記２つの検出コイルに出力するので、検出部の２重化に伴うコストアップを低減できるという効果がある。
【０２３７】
請求項５２の発明は、請求項５０または５１において、前記各回路の能動回路はモノリシックＩＣで構成したので、検出部の２重化に伴うコストアップを低減できるという効果がある。特にＩＣ部は最もコストが高い部品であるので、共用化のメリットが大きい。
【図面の簡単な説明】
【図１】本発明の実施形態１の回路構成を示す図である。
【図２】同上の上面を示す図である。
【図３】同上の側面断面を示す図である。
【図４】同上の検出コイルの断面図を示す図である。
【図５】同上の検出コイルの両端電圧波形を示す図である。
【図６】同上の回転角度と検出コイルのインピーダンスとの関係を示す図である。
【図７】同上の回転角度と検出コイルの両端電圧との関係を示す図である。
【図８】同上の回転角度と検出コイルの両端電圧の温度係数との関係を示す図である。
【図９】同上の回転角度と検出コイルの両端のピーク電圧の温度係数との関係を示す図である。
【図１０】同上の定電流回路と信号処理回路との具体的な回路構成を示す図である。
【図１１】同上の発振回路の具体的な回路構成を示す図である。
【図１２】同上の電圧−電流変換回路の別の回路構成を示す図である。
【図１３】同上の定電流回路の別の回路構成を示す図である。
【図１４】同上の別の回路構成を示す図である。
【図１５】回転角度と検出コイルの両端電圧の温度係数との関係を示す参考図である。
【図１６】本発明の実施形態２の検出コイルの等価回路を示す図である。
【図１７】同上の表皮効果による銅線の抵抗値変動を示す図である。
【図１８】同上の近接効果による銅線の抵抗値変動を示す図である。
【図１９】本発明の実施形態１の信号処理回路の構成を示す図である。
【図２０】本発明の実施形態３の回路構成を示す図である。
【図２１】同上の上面を示す図である。
【図２２】同上の回転角度と検出コイルの交流インピーダンスの温度係数との関係を示す図である。
【図２３】図１９の回転角度と検出コイルの両端電圧の温度係数との関係を示す図である。
【図２４】図２０のレベルシフト値の大きさを可変としたときの回転角度とピークホールド回路の出力信号の温度係数との関係を示す図である。
【図２５】図２０のレベルシフト値の温度係数を可変としたときの回転角度とピークホールド回路の出力信号の温度係数との関係を示す図である。
【図２６】同上の別の回路構成を示す図である。
【図２７】本発明の実施形態４の回路構成を示す図である。
【図２８】本発明の実施形態５のコアに用いる磁性体の特性を示す図である。
【図２９】（ａ）〜（ｅ）同上の角度スパンと検出コイルの交流インピーダンスの直進性との関係を周波数毎に示す図である。
【図３０】（ａ）〜（ｄ）同上のコアの端部を示す図である。
【図３１】同上の直線ストローク構成のポジションセンサの側面断面を示す図である。
【図３２】（ａ）〜（ｅ）同上のエッジを除去したコアの端部を示す図である。
【図３３】同上の両端部に保持・固定用部材を設けた検出コイルを示す図である。
【図３４】本発明の実施形態６の検出部を２つ備える第１のポジションセンサの上面を示す図である。
【図３５】同上の第１のポジションセンサの側面断面の一部を示す図である。
【図３６】同上の検出部を２つ備える第２のポジションセンサの上面を示す図である。
【図３７】同上の第２のポジションセンサの側面断面の一部を示す図である。
【図３８】（ａ），（ｂ）本発明の実施形態７の変位信号を示す第１の図である。
【図３９】（ａ），（ｂ）同上の変位信号を示す第２の図である。
【図４０】（ａ），（ｂ）同上の変位信号を示す第３の図である。
【図４１】本発明の実施形態８の断面構造を示す図である。
【図４２】同上の回路構成を示す図である。
【図４３】従来の第１のポジションセンサの側面断面を示す図である。
【図４４】同上の変位と検出コイルの交流インピーダンスとの関係を示す図である。
【図４５】同上の回路構成を示す図である。
【図４６】従来の第２のポジションセンサの側面断面を示す図である。
【図４７】従来の第３のポジションセンサの側面断面を示す図である。
【図４８】従来の第４のポジションセンサの構成を示す図である。
【図４９】同上の変位と検出コイルの交流インピーダンスの温度係数との関係を示す図である。
【図５０】同上の変位と検出コイルの交流インピーダンスとの関係を実際に近い状態で示した図である。
【符号の説明】
２　検出コイル
３　定電流回路
３ａ　発振回路
３ｂ　電圧−電流変換回路
４　信号処理回路
Ａ　検出部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position sensor for detecting a displacement of a moving body.
[0002]
[Prior art]
Conventionally, there has been proposed a position sensor that inserts a core 1 into a detection coil 2 and detects a change in impedance of the detection coil 2 to output a displacement signal. FIG. 43 is a schematic diagram of the detection unit, FIG. 44 is a schematic diagram showing the relationship between the core displacement X and the AC impedance Zac of the detection coil 2, and FIG. 45 is a schematic diagram of the entire circuit. Department. In FIG. 44, the larger the displacement X, the larger the amount of penetration of the core 1 into the detection coil 2 and the higher the AC impedance Zac, but the larger the displacement X, the smaller the amount of penetration of the core 1 into the detection coil 2. As a configuration, the AC impedance Zac may decrease as the displacement X increases. In this case, an alternating current is applied to the detection coil 2, the amplitude and phase of the voltage generated at both ends of the detection coil 2 are detected, and appropriate signal processing is performed. An AC current is applied because a voltage amplitude proportional to the AC impedance Zac of the detection coil 2 is obtained.
[0003]
The position sensor shown in FIG. 46 essentially cancels out the temperature change of the impedance Z (inductance component) caused by the magnetic material 21 of the core 1 and the temperature change of the impedance Z (eddy current component) caused by the non-magnetic material 22. This is one in which the detection coil 2 is built. (For example, refer to Patent Document 1.)
Further, there are many position sensors using a permanent magnet and a magnetic sensitive element. In this method, the most important point is the configuration of a magnetic circuit that applies a linear magnetic field to the magnetic sensitive element. For example, as shown in FIG. 47, a taper is formed in a permanent magnet 101 provided on an inner upper surface of a yoke 100 having a U-shaped cross section, and a magnetic-sensitive element 102 is arranged between the permanent magnet 101 and the inner and lower surfaces of the yoke 100. Thus, a linear magnetic field change of the magnetic flux 103 is realized with respect to the displacement of the magnetic sensitive element 102 in the Z direction. (See, for example, Patent Document 2.) The greatest advantage is that the magnetic sensing element 102 and the sensor circuit (power supply to the magnetic sensing element 102 and a signal processing circuit) are formed as a monolithic IC and housed in one package. That is, it is possible to reduce the size and the number of parts.
[0004]
Further, as another conventional example, there is a high frequency magnetic type, and the configuration is shown in FIG. A rotating shaft 201 that rotates in conjunction with the object to be detected, and an arc-shaped movable metal that is connected to the rotating shaft 201 by a connecting piece 202c and moves on a circumference around the rotating shaft 201 in conjunction with the rotation of the rotating shaft 201. The body 202 and the arms 202a and 202b of the movable metal body 202 which are fixedly arranged on the circumference and move into and out of the respective center through-holes so that the occupation amount with respect to the magnetic path can be freely changed. A sensor that drives and excites the two sensor coils 203a and 203b curved in an arc shape to generate a high-frequency modulated magnetic field, and detects a magnetic change generated when the arms 202a and 202b enter and exit the sensor coils 203a and 203b. It comprises a circuit 204 and resistors 205a and 205b for detecting coil currents flowing through the sensor coils 203a and 203b. . In this conventional example, the arms 202a and 202b of the moving metal body 202 are made to penetrate the two sensor coils 203a and 203b in a complementary manner, and the change in the impedance of the sensor coils 203a and 203b is detected by the sensor circuit 204. Since detection is performed, there is an advantage that precise positioning is not required.
[0005]
[Patent Document 1]
U.S. Pat. No. 5,0032,258 (page 3, right column, line 16 to page 4, left column, line 12, FIG. 1)
[Patent Document 2]
Japanese Patent Publication No. 6-82041 (page 2, left column, line 20 to right column, line 14, FIG. 1)
[Patent Document 3]
JP 2000-186903 A (page 3, right column, line 28 to page 4, left column, line 17, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, when the core 1 is a magnetic material in FIG. 43, the rate of temperature change (temperature coefficient) of the impedance Z of the detection coil 2 when the core 1 is inserted is not uniform with respect to the displacement X of the core 1, and FIG. It is known that as the insertion amount of the core 1 increases, the temperature change rate Δ (dZac / dt) also increases. Therefore, there is a problem that the circuit configuration becomes complicated to obtain the displacement signal by temperature-compensating the output voltage of the detection coil 2 in a circuit manner.
[0007]
To solve the above problems, there are techniques such as US Pat. No. 5,003,258, US Pat. No. 4,864,232, US Pat. No. 5,898,300. In order to solve the problem of dependence on the displacement X, the dependence of the temperature coefficient of the impedance Z on the displacement is reduced by devising the structure of the detection coil 2 and its surroundings. However, there are problems that the number of components is increased, positioning between components is difficult, design constraints on the detection coil are large, versatility is poor, and cost is increased due to the above-mentioned reasons.
[0008]
Next, FIG. 50 illustrates a relationship between the displacement X of the detection coil 2 and the AC impedance Zac of the detection coil 2 in FIG. In FIG. 50, the linearity of the AC impedance Zac with respect to the displacement X is good at the center of the stroke, but the linearity is poor at both ends. In particular, the linearity is particularly poor when the penetration of the core 1 into the detection coil 2 is small. This is thought to be because the tip of the core 1 has a lower rate of contribution to the increase in the impedance Z of the detection coil 2 than the other portions. This may be referred to as an edge effect. Normally, the sensor is configured such that a desired displacement section is a section having good linearity at the center, but there is also a problem that it is difficult to obtain a desired linearity when there are dimensional restrictions.
[0009]
Next, conventional structural problems will be described. As one of the geometrical means for improving the linearity of the position sensor, the cross-sectional area of the bobbin winding portion is made as small as possible, and the ratio of the cross-sectional area of the core 1 to the cross-sectional area of the bobbin 15 (see FIG. 43) is made as small as possible. There is a way to make it bigger. That is, it is better that the clearance between the inner wall (the side surface of the through hole) of the winding portion of the bobbin 15 and the core 1 is small. As long as the bobbin 15 is formed of a non-metallic body such as plastic, contact between the core 1 and the inner wall of the bobbin 15 does not greatly affect the electrical characteristics (coil impedance and the like). The relative displacement between the core 1 and the detection coil 2 does not smoothly proceed, which may cause problems such as deformation of the core 1 and occurrence of mechanical hysteresis.
[0010]
In particular, in the case of a rotary type position sensor, since it is difficult to position the curved core and the curved detection coil, the core and the inner wall of the bobbin come into contact with each other, and the above-described problem often occurs. Further, in the case of such a rotary type position sensor, there is a problem related to the coil winding. First, since the bobbin is curved, uniform winding is difficult, and the winding takes a long time. Further, when winding on a curved bobbin, the curvature of the bobbin after winding becomes locally smaller than the curvature before winding due to the tension at the time of winding, and this curvature change causes the core as described above. And the inner wall of the bobbin winding portion, and in extreme cases, the movable body can be displaced only halfway.
[0011]
Further, in the magnetic position sensor shown in FIG. 47, in order to obtain the linearity of the magnetic field 103 with respect to the displacement, accurate dimensioning of the permanent magnet 101 by grinding or the like, and the In addition to the need for precise positioning, the magnetic sensitive element 102 uses an InSb thin film or the like and requires a special semiconductor process, so it is expensive, and its sensitivity characteristic greatly changes due to ambient temperature. And the circuit becomes complicated. In addition, when the magnetic sensing element 102 and the sensor circuit are used as a monolithic IC for a vehicle, the detection unit of the sensor must be doubled based on the concept of a fail-safe system, and two monolithic ICs are essential. Is required.
[0012]
Further, in the high-frequency magnetic position sensor as shown in FIG. 48, when the sensor coils 203a and 203b are driven by the constant voltage Vo and the coil impedance is Z, the coil current (Vo / Z) is measured. That is, even if the coil impedance Z is in the denominator and the coil impedance Z changes linearly with the angle change, the coil current that is the sensor output does not change linearly but changes hyperbolically with the angle. become.
[0013]
In the angle state where the arms 202a and 202b of the movable metal member 202 do not penetrate the sensor coils 203a and 203b, the coil impedance of the sensor coils 203a and 203b is only the impedance of the coil winding and its temperature characteristic (temperature The factor of the coefficient is also only the coil winding. However, in the angular state where the arms 202a and 202b penetrate the sensor coils 203a and 203b, the coil impedance of the sensor coils 203a and 203b is the impedance of the coil winding and the coil impedance due to the penetration of the arms 202a and 202b. There is an increase (increase in inductance, eddy current loss, hysteresis loss, etc.). Therefore, the temperature coefficient is a sum of different temperature coefficients for each factor of the increase in impedance, so that it is inevitably different from the temperature coefficient in the angular state where the arms 202a and 202b do not penetrate the sensor coils 203a and 203b. . That is, the temperature coefficient changes depending on the angle. Therefore, even if the temperature is corrected by digital trimming in the correction circuit 210 of the sensor circuit 204, there is a problem that an accurate output cannot be output to the ECU unless the troublesome correction of changing the amplification factor depending on the angle is performed.
[0014]
Further, since the sensor coils 203a and 203b are arc-shaped, it is difficult to form a uniform winding, and it is impossible to form a close-aligned winding at least outside the arc.
[0015]
As described above, in each of the above conventional examples, it is a common problem to improve the temperature characteristics with a simple structure.
[0016]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a position sensor that can compensate for a change in the temperature coefficient of the impedance of a detection coil with respect to a displacement with a simple circuit.
[0017]
[Means for Solving the Problems]
The invention according to claim 1 is a constant current circuit that outputs a constant current obtained by superimposing an alternating current having a predetermined frequency and amplitude on a direct current having a predetermined amplitude, and a detecting unit including at least a detection coil supplied with the constant current. A core made of a magnetic material that is displaced relative to the detection coil in a winding axis direction of the detection coil, and the core and the detection coil based on a peak value of an output voltage of the detection unit generated by the constant current. A signal processing circuit that outputs a displacement signal indicating the position information of the core, wherein the fluctuation range of the temperature coefficient of the peak value of the output voltage of the detection unit in the entire displacement section of the core with respect to the detection coil is the detection range of the core. The DC current of the constant current is set so as to be smaller than the variation width of the temperature coefficient of the AC component of the impedance of the detection unit at the predetermined frequency in the entire displacement section with respect to the coil. The ratio between the current and the AC current, the ratio between the AC component and the DC component of the impedance of the detection unit, the temperature characteristic of the ratio between the DC current and the AC current of the constant current, and the AC component of the impedance of the detection unit. And one or more of the temperature characteristics of the ratio of the DC component to the DC component.
[0018]
According to a second aspect of the present invention, in the first aspect, the core is capable of penetrating into the winding of the detection coil.
[0019]
According to a third aspect of the present invention, in the second aspect, the temperature coefficient of the direct current component of the output voltage of the detection unit is a temperature coefficient of the output voltage of the detection unit when the amount of penetration of the core into the winding of the detection coil is minimum. The temperature coefficient of the AC component is closer to the temperature coefficient of the AC component of the output voltage of the detection unit when the amount of penetration of the core is the maximum.
[0020]
According to a fourth aspect of the present invention, in the first or second aspect, the constant current circuit is configured to generate a voltage in which an AC voltage having a predetermined frequency and amplitude is superimposed on a DC voltage having a predetermined amplitude; A voltage-current conversion circuit that converts an output voltage into a current, and by setting the DC voltage and the AC voltage, respectively, setting a ratio between the DC current and the AC current of the constant current. I do.
[0021]
According to a fifth aspect of the present invention, in the first or second aspect, the constant current circuit is configured to generate a voltage obtained by superimposing an AC voltage having a predetermined frequency and amplitude on a DC voltage having a predetermined amplitude; A voltage-current conversion circuit that converts an output voltage to a current, and by setting a temperature coefficient of a resistance value of a resistor that determines a value of a DC voltage included in the oscillation circuit, the DC current and the AC of the constant current are set. It is characterized in that the temperature characteristic of the ratio to the current is set.
[0022]
According to a sixth aspect of the present invention, in the first or second aspect, the constant current circuit is configured to generate a voltage in which a DC voltage having a predetermined amplitude and an AC voltage having a predetermined frequency and amplitude are superimposed on each other; A voltage-current conversion circuit for converting an output voltage into a current, and setting a temperature characteristic of a frequency of the AC voltage, thereby setting a temperature characteristic of a ratio between an AC component and a DC component of the impedance of the detection unit. It is characterized by doing.
[0023]
According to a seventh aspect of the present invention, in the first or second aspect, the constant current circuit outputs a DC constant current circuit having a predetermined amplitude, and an AC constant current circuit outputs an AC current having a predetermined frequency and amplitude. By setting at least one of the temperature characteristic of the amplitude of the DC current, the temperature characteristic of the frequency of the AC current, and the temperature characteristic of the amplitude of the AC current, the DC current and the AC of the constant current are set. The ratio of the current to the current, the ratio of the AC component and the DC component of the impedance of the detection unit, the temperature characteristic of the ratio of the DC current to the AC current of the constant current, and the AC component and the DC component of the impedance of the detection unit. 3. The position sensor according to claim 1, wherein at least one of the temperature characteristics of the ratio and (b) is set. 4.
[0024]
According to an eighth aspect of the present invention, in the first or second aspect, the detection unit includes the detection coil, and a circuit element connected in series to the detection coil, the impedance of which is not changed by the displacement of the core. The circuit outputs a displacement signal indicating positional information of the core and the detection coil based on a peak value of a voltage between both ends of a series circuit of the detection coil and a circuit element generated by the constant current, and outputs a displacement signal of the circuit element. By setting at least one of the AC component and the DC component of the impedance and the temperature coefficient of the AC component and the DC component of the impedance of the circuit element, the ratio of the AC component and the DC component of the impedance of the detection unit is determined. Setting at least one of a temperature characteristic of a ratio between an AC component and a DC component of the impedance of the detection unit.
[0025]
In a ninth aspect of the present invention, in the ninth aspect, the circuit element is a resistor.
[0026]
According to a tenth aspect, in the eighth aspect, the circuit element is an inductor.
[0027]
According to an eleventh aspect of the present invention, in the first or second aspect, the constant current circuit includes a resistor for setting an amplitude of the DC current, a frequency and an amplitude of the AC current, and a digital trimming unit for setting a value of the resistor. By setting the value of the resistor by the digital trimming means, the ratio between the DC current and the AC current of the constant current, and the ratio between the AC component and the DC component of the impedance of the detection unit. One or more of a temperature characteristic of a ratio of a DC current and an AC current of the constant current and a temperature characteristic of a ratio of an AC component and a DC component of the impedance of the detection unit. And
[0028]
A twelfth aspect of the present invention is characterized in that, in the first or second aspect, the signal processing circuit includes a rectifier circuit and a circuit for peak-holding an output of the rectifier circuit.
[0029]
According to a thirteenth aspect of the present invention, in the first or second aspect, the signal processing circuit includes an amplifier having a temperature coefficient having a polarity opposite to a temperature coefficient of a peak value of an output voltage of the detection unit. And outputting a displacement signal indicating position information between the core and the detection coil based on the displacement signal.
[0030]
According to a fourteenth aspect, in the fourth aspect, the AC voltage generated by the oscillation circuit is a triangular wave.
[0031]
According to a fifteenth aspect, in the seventh aspect, the alternating current output from the alternating current constant circuit is a triangular wave.
[0032]
According to a sixteenth aspect, in the first or second aspect, the number of turns of the winding of the detection coil, the winding pitch of the winding, and the frequency of the constant current input to the detection coil are the impedance of the detection coil. The temperature coefficient and the temperature coefficient of the impedance of the detection coil caused by the relative displacement of the core with respect to the detection coil are equal to each other.
[0033]
According to a seventeenth aspect of the present invention, in the first or second aspect, the core has a temperature coefficient of impedance of the detection coil and a temperature coefficient of impedance of the detection coil due to relative displacement of the core with respect to the detection coil. Are formed of a material that is equal to
[0034]
According to an eighteenth aspect of the present invention, in the first or the second aspect, the surface treatment performed on the core includes the temperature coefficient of impedance of the detection coil and the detection due to the relative displacement of the core relative to the detection coil. The surface treatment is such that the temperature coefficient of the impedance of the coil is equal.
[0035]
According to a nineteenth aspect, in the first or second aspect, at least a surface of the core is formed of a material having a small temperature coefficient of volume resistivity.
[0036]
According to a twentieth aspect, in the nineteenth aspect, the core has at least a surface formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and a manganin. It is characterized by being performed.
[0037]
According to a twenty-first aspect, in the nineteenth aspect, the core is formed by bending a heating wire cut to a desired length.
[0038]
In a preferred embodiment of the present invention, the heating wire is formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and a manganin. It is characterized by the following.
[0039]
A twenty-third aspect of the present invention is characterized in that, in the first or second aspect, the winding of the detection coil is formed of one of nichrome, manganin, and a copper-nickel alloy.
[0040]
The invention of claim 24 is a constant current circuit that outputs an alternating constant current having at least a predetermined frequency and amplitude, a detecting unit that is supplied with at least the detecting coil that is supplied with the constant current, A signal processing circuit that outputs a displacement signal indicating positional information between the core and the detection coil based on an extracted value from an output voltage of the detection unit generated by the constant current, the core being made of a magnetic material that is relatively displaced in the direction of the winding axis; An extraction circuit for obtaining the extracted value from an output voltage of a detection unit, a level shift circuit for performing a level shift of a predetermined magnitude with respect to the extracted value, and a level shift for temperature compensation. A temperature compensation circuit for the output of the circuit, wherein the temperature coefficient of the output of the level shift circuit fluctuates due to the relative displacement between the detection coil and the core; As the number is less than the width that varies by the relative displacement between the detection coil and the core, and sets the at least one of the magnitude and temperature coefficient of the level shift.
[0041]
According to a twenty-fifth aspect of the present invention, there is provided a constant current circuit that outputs an alternating constant current having at least a predetermined frequency and an amplitude, a detecting unit including at least a detecting coil supplied with the constant current, A signal processing circuit that outputs a displacement signal indicating positional information between the core and the detection coil based on an extracted value from an output voltage of the detection unit generated by the constant current, the core being made of a magnetic material that is relatively displaced in the direction of the winding axis; The signal processing circuit comprises: an extraction circuit that obtains the extracted value from an output voltage of a detection unit; an A / D conversion circuit that converts the extracted value into a digital signal; and a digital signal that is output by the A / D conversion circuit. A level shift circuit for performing a level shift of a predetermined digital amount on the signal; and a temperature compensation circuit for performing an operation for performing temperature compensation on an output of the level shift circuit. The level shift of the level shift circuit is changed so that the temperature coefficient of the output of the shift circuit varies depending on the relative displacement between the detection coil and the core. At least one of the magnitude of the predetermined digital quantity and the temperature coefficient is set.
[0042]
The invention of claim 26 is characterized in that, in claim 24 or 25, the extracted value is a peak value of the output voltage of the detection unit.
[0043]
The invention of claim 27 is characterized in that, in claim 24 or 25, the extracted value is a bottom value of the output voltage of the detection section.
[0044]
The invention of claim 28 is characterized in that, in claim 24 or 25, the extracted value is a value proportional to the amplitude of the output voltage of the detection unit.
[0045]
The invention of claim 29 is characterized in that, in claim 24, there is provided means for adjusting at least one of the magnitude of the level shift and the temperature coefficient.
[0046]
The invention of claim 30 is characterized in that in claim 25, there is provided means for adjusting at least one of a magnitude of a predetermined digital amount of the level shift and a temperature coefficient.
[0047]
The invention of claim 31 is characterized in that, in claim 24 or 25, the core is capable of penetrating into the winding of the detection coil.
[0048]
The invention according to Claim 32 is characterized in that, in Claim 1, 2, 24 or 25, the magnetic flux is more easily passed through a portion having a predetermined length from the end of the core than other portions.
[0049]
A thirty-third aspect of the present invention is characterized in that, in the thirty-second aspect, a portion having a predetermined length from an end of the core is thicker than other portions.
[0050]
According to a thirty-fourth aspect, in the thirty-second aspect, a portion having a predetermined length from an end of the core is formed of a material having a higher magnetic permeability than other portions.
[0051]
The invention according to claim 35 is characterized in that, in claim 32, a portion having a predetermined length from the end of the core is surface-treated with a material having a higher magnetic permeability than other portions.
[0052]
According to a thirty-sixth aspect, in the thirty-fifth aspect, the core is made of an electromagnetic stainless steel having a surface of a predetermined length from an end portion subjected to permalloy plating.
[0053]
The invention of claim 37 is characterized in that, in claim 1, 2, 24 or 25, the edge of the core is chamfered to remove the edge.
[0054]
According to a thirty-eighth aspect of the present invention, in any one of the first, second, twenty-fourth, and twenty-fifth aspects, the detection coil has a shape curved at a predetermined curvature, fixes the detection coil, and corrects a change in curvature of the detection coil. And a housing having means for performing the following.
[0055]
The invention according to claim 39 is characterized in that, in claim 38, the housing corrects a change in curvature of the detection coil by abutting at least a part of an inner radial portion of the detection coil.
[0056]
The invention according to claim 40 is characterized in that in claim 1, 2, 24 or 25, a bobbin around which the detection coil is wound is provided, and the coil and the bobbin are resin-molded before assembly.
[0057]
The invention according to claim 41 is based on claim 1, 2, 24, or 25, further comprising two bobbins each wound with two detection coils, and integrally integrating the two coils and the two bobbins before assembling. It is characterized by resin molding.
[0058]
The invention of claim 42 is characterized in that, in claim 2 or 31, the two detection coils are provided, and the two cores penetrating into the detection coils are integrally resin-molded.
[0059]
The invention of claim 43 is the invention according to claim 2 or 31, wherein the two detection coils curved at the same curvature and the two detection coils rotate through a rotation axis to respectively penetrate the two detection coils and have the same curvature. The device includes two curved cores, and the two detection coils are arranged so as to overlap with each other in a rotation axis direction of the cores.
[0060]
The invention according to claim 44 is the invention according to claim 2 or 31, wherein the two detection coils curved with different curvatures and the two detection coils are respectively rotated by rotating about a rotation axis, and have different curvatures. And two detection coils, wherein the two detection coils are arranged at the same rotation angle and on the same plane with respect to the rotation axis of the core.
[0061]
According to a forty-fifth aspect, in the first, second, twenty-fourth, or twenty-fifth aspect, the signal processing circuit includes an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; A signal correction circuit including a correction circuit for performing digital trimming, wherein the displacement signal output by the signal processing circuit is a digital signal having a number of bits that satisfies a resolution required for position detection.
[0062]
According to a forty-sixth aspect, in the first, second, twenty-fourth, or twenty-fifth aspect, the signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; A signal correction circuit comprising a digital trimming correction circuit, the displacement signal output by the signal processing circuit is an output start signal, and after a time corresponding to the position information after the output start signal is output, And an output pulse signal.
[0063]
According to a forty-seventh aspect, in the first, second, twenty-fourth, or twenty-fifth aspect, the signal processing circuit includes an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; A signal correction circuit including a digital trimming correction circuit, wherein the displacement signal output from the signal processing circuit is an output start signal, and a duty ratio according to the position information output following the output start signal. And a pulse signal of
[0064]
In the invention of claim 48, in accordance with claim 1, 2, 24 or 25, the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection section into a digital signal, A signal correction circuit including a digital trimming correction circuit, wherein the displacement signal output by the signal processing circuit is an output start signal and a pulse width corresponding to the position information output following the output start signal. And a pulse signal of
[0065]
In the invention of claim 49, in accordance with claim 1, 2, 24 or 25, the signal processing circuit comprises: an A / D conversion circuit for converting a peak value of an output voltage of the detection section into a digital signal; A signal correction circuit including a correction circuit for digital trimming, wherein the displacement signal output by the signal processing circuit is an output start signal and a number corresponding to the position information output following the output start signal. And a pulse signal.
[0066]
The invention of claim 50 is characterized in that in claim 1, 2, 24 or 25, two detection coils are provided, and the two detection coils share the same core attached to a structural member. I do.
[0067]
According to a fifty-first aspect of the present invention, in the first, second, twenty-fourth, or twenty-fifth aspect, two detection coils are provided, and the same constant current circuit outputs a constant current having a predetermined frequency and amplitude to the two detection coils. It is characterized by doing.
[0068]
The invention of claim 52 is characterized in that in claim 50 or 51, the active circuit of each circuit is constituted by a monolithic IC.
[0069]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0070]
(Embodiment 1)
FIG. 1 shows a circuit configuration of the position sensor of this embodiment, FIG. 2 is a top view, FIG. 3 is a cross-sectional view taken along line AA ′ of FIG. 2, and FIG. 4 is a cross-sectional view of the detection coil 2. The position sensor has a U-shaped cross section. The coating 11 is applied to the inside of the U-shape, and the detection coil 2 wound on a curved bobbin 10 curved at a constant curvature, and the center of the curved detection coil 2 is rotated. A movable block 13 having a projection 13a formed on the outside of a cylindrical body serving as an axis; a core 1 made of a magnetic material having a fixed curvature and having one end connected to the projection 13a and penetrating into a hollow portion of the detection coil 2; A member 12 for correcting a curvature change of the detection coil 2, a housing 14 for arranging and fixing each component on a fixing surface, a predetermined frequency f and a predetermined amplitude Iac to a DC current Idc having a predetermined amplitude. A constant current circuit 3 that outputs a constant current Id on which the alternating current is superimposed to the detection coil 2, and a detection coil 2 that is determined by the constant current Id that the constant current circuit 3 outputs and the impedance Z of the detection coil 2. A signal processing circuit 4 that outputs a displacement signal Vout indicating positional information between the core 1 and the detection coil 2 in accordance with the peak value V1 of the voltage Vs (detection signal), and the detection coil 2 supplies a constant current Id Thus, a detection unit A that outputs a detection signal is configured. In the present embodiment, the cross-sectional shape of the curved bobbin 10 is a U-shape that is easily formed by injection molding or the like, but may be another shape.
[0071]
Then, as the movable block 13 rotates and the rotation angle θ changes from 0 ° to 90 °, the portion of the core 1 penetrating the detection coil 2 decreases.
[0072]
Further, the constant current circuit 3 includes an oscillation circuit 3a that generates a constant voltage Vd ′ obtained by superimposing an AC voltage having a predetermined frequency f and an amplitude Vac ′ on a DC voltage Vdc ′ having a predetermined amplitude, and a constant voltage output by the oscillation circuit 3a. A voltage-current conversion circuit 3b for converting the voltage Vd 'into a constant current Id.
[0073]
First, the temperature characteristics of the detection signal of the detection unit A will be described based on a specific example. Normally, in the position sensor, the output linearity error of the detection signal in a certain predetermined displacement section is defined at room temperature, and a certain margin is given to define the value in the entire operating temperature range. For example, "position detection angle range θ = 0 to 90 °, linearity error of detection signal is ± 1% FS or less at room temperature, and ± 2% FS at -40 to + 130 ° C.”. In this case, the deterioration of the linearity error due to the temperature fluctuation factor must be suppressed to about ± 1% FS. Assuming that the room temperature is 30 ° C., the high temperature side has a temperature range of 100 ° C. Therefore, assuming that the detection signal changes linearly with temperature, the fluctuation range of the temperature change rate (temperature coefficient) is ± 100 ppm / K must be kept below K.
[0074]
Also, at an arbitrary displacement within a desired displacement section, if the fluctuation range Δ (dV1 / dT) of the temperature coefficient of the peak value V1 of the voltage Vs across the detection coil 2 is ± 100 ppm / K or less, the constant temperature coefficient By adding the simple temperature compensation circuit described above, the voltage after the temperature compensation can be set to the normal temperature value ± 100 ppm / K at the displacement. This is the aim of the present invention.
[0075]
Next, the operation of the present embodiment will be described. As shown in FIG. 1, the AC current Iac is supplied from the constant current circuit 3 to the detection coil 2 and the DC current Idc is supplied at the same time. Assuming that the DC resistance of the detection coil 2 is Zdc, the AC impedance at the oscillation frequency f of the AC current Iac is Zac, and the voltage across the detection coil 2 is Vs, the voltage Vs can be considered as the sum of the DC voltage Vdc and the AC voltage Vac. ,
[0076]
(Equation 1)

It can be expressed as. In the equation (1), the various quantities are complex numbers, but considering only the peak voltage V1 of the voltage Vs,
[0077]
(Equation 2)

The quantities in the equation (2) can be treated as real numbers, and the waveform thereof is the sum of the DC voltage Vdc and the AC voltage Vac having the peak voltage V1, as shown in FIG.
[0078]
FIG. 6 shows sample data created based on the measured values of the impedance of the detection coil 2 wound with a copper-nickel alloy wire (GCN15 wire). The DC resistance Zdc and the AC impedance Zac of the detection coil 2 are shown in FIG. Are plotted on a graph having the rotation angle θ as the horizontal axis. Here, the impedance Z is set so as to change completely linearly with respect to the rotation angle θ, but the value is quite close to the actually measured value. Further, data at ambient temperatures of −40 ° C., + 25 ° C., + 85 ° C., and + 130 ° C. are shown.
[0079]
At an ambient temperature of + 25 ° C., the DC resistance Zdc is 188Ω, the temperature coefficient is 511 ppm / K, and the AC impedance Zac is
[0080]
[Equation 3]

Z0 = 636Ω, Z ′ = − 3.48Ω / deg, β0 = 478 ppm / K, β ′ = − 2.49 ppm / K / deg, θ is the rotation angle, and T is the ambient temperature in degrees Celsius. Represent.
[0081]
Here, since the temperature coefficient of the AC impedance Zac is 478 ppm / K at θ = 0 ° and 254 ppm / K at θ = 90 °, the fluctuation width Δ (dZac / dT) reaches 224 ppm / K.
[0082]
Next, the DC current Idc output from the constant current circuit 3 is set to 1.5 mA, the AC current Iac is set to 0.3 mA, and the temperature change rates of the DC current Idc, the AC current Iac, and the frequency f are set to zero for simplicity (Equation 2). 7), the DC voltage Vdc and the AC voltage Vac across the detection coil 2 and the peak voltage V1 across the detection coil 2 are plotted in FIG. 7 and their temperature coefficients are shown in FIG.
[0083]
As can be seen from FIG. 8, the temperature coefficient of the peak voltage V1 is approximately 450 to 500 ppm / K over the rotation angle θ = 0 ° to 90 °, and the variation Δ (dV1 / dT) is approximately 50 ppm / K. And falls within a very narrow range of fluctuation. Therefore, if temperature compensation of about 470 ppm / K is performed on the peak voltage V1, the compensated voltage can be returned to the normal temperature value with almost no error.
[0084]
Next, FIG. 9 shows the result of calculating the temperature coefficient of the peak voltage V1 when the DC current Idc is changed while the AC current Iac output from the constant current circuit 3 is 0.3 mA in the same manner as in FIG. If the DC current Idc = 0, the displacement dependence of the temperature coefficient is the same as the displacement dependence of the impedance Z of the detection coil 2. However, as the DC current Idc increases, it approaches the temperature coefficient of the DC voltage Vdc. Further, the smaller the amount of penetration of the core 1 into the detection coil 2 (in the case of the present embodiment, the larger the rotation angle θ), the larger the ratio of the DC voltage Vdc to the peak voltage V1 (see FIG. 6). It is easily affected by the voltage Vdc.
[0085]
When the DC current Idc is mixed even a little, the fluctuation width Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1 is considerably improved as compared with the case where the DC current Idc = 0, and the peak voltage increases as the DC current Idc increases. Although the fluctuation width Δ (dV1 / dT) of the temperature coefficient of V1 is small, the improvement is saturated at a certain level. Therefore, increasing the DC current Idc may lead to an increase in the current consumption, and the appropriate DC current Idc is determined based on the allowable current consumption and the value of the fluctuation range Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1. You just have to choose a value. At this time, by setting the DC voltage Vdc 'and the AC voltage Vac' generated by the oscillation circuit 3a, the ratio between the DC current Idc of the constant current Id and the AC current Iac can be set.
[0086]
Further, the higher the frequency f of the AC voltage Vac 'generated by the oscillation circuit 3a, the higher the ratio of the AC voltage Vac to the DC voltage Vdc. Therefore, by appropriately selecting the frequency f, the ratio between Vdc and Vac can be reduced. It can be set appropriately, and the same argument holds.
[0087]
In the above description, each temperature change rate of the DC current Idc, the AC current Iac, and the frequency f is set to zero. However, when these have a temperature coefficient, in FIG. 8, each temperature of the DC voltage Vdc and the AC voltage Vac The coefficient shifts up and down, and the temperature characteristic of the peak voltage V1 changes accordingly.
[0088]
As can be seen from FIGS. 8 and 9, (dV1 / dT) is greatly affected by (dVdc / dT) when the amount of penetration of the core 1 is small, and when the amount of insertion of the core 1 is large, (DVac / dT). This naturally follows from the composition ratio of the DC voltage Vdc and the AC voltage Vac in the peak voltage V1.
[0089]
Further, regardless of the amount of penetration of the core 1, the value of (dV1 / dT) is between the value of (dVdc / dT) and the value of (dVac / dT).
[0090]
Further, if the value of (dVdc / dT) and the value of (dVac / dT) when the amount of penetration of the core 1 is large (in the present embodiment, the rotation angle θ is around 0 °) are set as close as possible, (dV1 / DT) is large when the amount of penetration of the core 1 is large (it is easily affected by the temperature coefficient of the AC voltage Vac, but the DC voltage Vdc is close to the AC voltage Vac), and when the amount of penetration of the core 1 is small (original). (Which is easily affected by the temperature coefficient of the DC voltage Vdc), the value is close to (dVdc / dT), and the fluctuation width Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1 is easily reduced.
[0091]
Furthermore, the case where the value of (dVdc / dT) is close to the value (dVac / dT) when the penetration amount of the core 1 is minimum, and the case where it is close to the value (dVac / dT) when the penetration amount of the core 1 is maximum. Then, it can be said that the latter can reduce the fluctuation width Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1.
[0092]
More specifically, the DC resistance Zdc, the AC impedance Zac, the DC current Idc, the AC current Iac, and the temperature coefficient of the frequency f are set to appropriate values by a method to be described later, and (dVdc / dT) or ( dVac / dT) may be controlled.
[0093]
First, the temperature coefficient of the DC resistance Zdc is determined by the selection of the winding material of the detection coil 2. As a coil material, since a normal copper wire has a very large temperature coefficient, it is practical to use a nichrome wire, a manganin wire, or a copper-nickel alloy wire (GCN wire). The volume resistivity and its temperature coefficient can be selected according to the alloy ratio of nickel and nickel.
[0094]
Next, a method for giving appropriate temperature coefficients to the DC current Idc, the AC current Iac, and the frequency f will be described.
[0095]
As shown in FIG. 10, the constant current circuit 3 includes an oscillation circuit 3a that outputs a voltage of Vdc '± Vac' and a voltage-current conversion circuit 3b. The voltage-current conversion circuit 3b is connected to the control power supply Vcc. The PNP transistor Q1 has one end connected to a resistor R1, an emitter connected to the other end of the resistor R1, a base connected to the oscillation circuit 3a, and a collector connected to the detection coil 2. The signal processing circuit 4 uses a peak hold type rectifier circuit as a specific circuit for extracting the peak voltage V1. The circuit includes a constant current source I1 having one end connected to the control power supply Vcc, and a constant current source I1. An NPN transistor Q2 having a collector connected to the end, a base-collector connection, and an emitter connected to the detection coil 2, and an NPN transistor having a collector connected to the control power supply Vcc and a base connected to the base of the transistor Q2. Q3 and a parallel circuit of a capacitor C1 and a constant current source I2 connected between the emitter of the transistor Q3 and the ground, and the voltage across the capacitor C1 is peak-held by rectifying the voltage Vs across the detection coil 2. It becomes a voltage, that is, a peak voltage V1, and is output as a displacement signal Vout.
[0096]
As shown in FIG. 11, the oscillation circuit 3a that outputs the voltage of Vdc ′ ± Vac ′ includes a comparator CP1, a resistor R3 connected between a non-inverting input terminal and an output terminal of the comparator CP1, and a comparator CP1. A DC power source E1 connected between the inverting input terminal and the ground to output the voltage Vcc / 2, a resistor R4 having one end connected to the output terminal of the comparator CP1, and the other end of the resistor R4 connected to the inverting input terminal; An operational amplifier OP1 having a DC power supply E1 connected to a non-inverting input terminal, a capacitor C2 connected between an inverting input terminal and an output terminal of the operational amplifier OP1, and a capacitor C2 connected between an output terminal of the operational amplifier OP1 and a non-inverting input terminal of a comparator CP1. And a series circuit of resistors R5 and R6 connected between the output terminal of the operational amplifier OP1 and the control power supply Vcc. Be composed.
[0097]
In this circuit, the output Vosc of the operational amplifier OP1 becomes a triangular wave with the offset centered at Vcc / 2, and the DC voltage Vdc 'and the AC voltage Vac' are determined by dividing the output Vosc by the resistors R5 and R6. Such a triangular wave oscillating circuit can realize a circuit that is more stable against temperature changes with a simpler configuration than a sine wave oscillating circuit. Although a stable circuit can be formed at low cost even with a square wave oscillation circuit, even if a square wave current is applied to the detection coil 2, a signal voltage that is difficult to control due to the di / dt of the square wave current is generated. Not available. On the other hand, in the case of a triangular wave, an output voltage reflecting the rotation angle θ of the core can be obtained as in the case of the sine wave.
[0098]
In FIG. 11, the oscillation frequency f of the AC voltage Vac ′ is proportional to (R3 / (C2 × R4 × R2)), and the amplitude is proportional to (R2 / R3). Therefore, by appropriately selecting the values and the temperature coefficients of the resistors R2 to R6 and the capacitor C2, the values and the temperature coefficients of the DC voltage Vdc 'and the AC voltage Vac' can be controlled. In particular, even when the entire constant current circuit 3 is a monolithic IC, since the capacitor C2 is often provided externally, a method of adjusting the temperature coefficient with the capacitor C2 is effective.
[0099]
Further, when the entire constant current circuit 3 is formed into a monolithic IC, the resistance values of some or all of the resistors R1 to R5 are set by digital trimming, and the temperature suitable for the DC current Idc, the AC current Iac, and the frequency f is adjusted. Coefficients can also be provided. In this case, even if the core 1, the detection coil 2 and the displacement section thereof are changed, the IC can be used without changing the IC, so that the versatility is high.
[0100]
Here, digital trimming refers to connecting a parallel circuit of a resistor and a switch element in parallel with a resistor to be adjusted in advance, and performing resistance adjustment by turning on and off the switch element using digital data. Specifically, when digital trimming is performed, the optimum code of the digital data is determined while monitoring the electrical characteristics, and the determined optimum code is written to the ROM of the IC, or the data stored in the IC is stored. By blowing out the fuse, an optimum code is given to the IC, and the resistance in the IC is set to a value corresponding to the optimum code.
[0101]
Note that the triangular wave generation circuit does not have to have the circuit configuration shown in FIG. 11 and may have another circuit configuration.
[0102]
Further, in the voltage-current conversion circuit 3b of FIG. 10, even if the temperature coefficient of the DC voltage Vdc 'generated by the oscillation circuit 3a is zero due to the temperature characteristic of the base-emitter voltage Vbe of the transistor Q1, the detection coil 2 will have a positive temperature coefficient. If the temperature coefficient of the DC current Idc is not desired to be a positive temperature coefficient, the emitter of the transistor Q1 of the voltage-current conversion circuit 3b shown in FIG. 10 is connected to the inverting input terminal, and the base of the transistor Q1 is connected to the output terminal. The output of the oscillation circuit 3a may be connected to the non-inverting input terminal of the operational amplifier OP2 by using the voltage-current conversion circuit 3b 'shown in FIG.
[0103]
FIG. 13 shows a circuit configuration of a constant current circuit 3 ′ different from the constant current circuit 3 of FIG. 10. The constant current circuit 3 ′ includes an AC current supply circuit Sac and a DC current supply circuit Sdc. The AC current supply circuit Sac includes a series circuit of an NPN transistor Q4 and a PNP transistor Q6, an AC power supply AC connected to a connection midpoint between the transistors Q4 and Q6, and a PNP transistor connected between the control power supplies Vcc and Vee. It comprises a series circuit of Q8, NPN transistor Q5, resistors R7, R8, PNP transistor Q7, NPN transistor Q10 and a series circuit of PNP transistor Q9, NPN transistor Q11. Transistors Q4, Q5, transistor Q6 The gates of Q7, transistors Q8 and Q9, and transistors Q10 and Q11 are connected to each other, and the bases and collectors of transistors Q8 and Q10 are short-circuited.
[0104]
The DC current supply circuit Sdc includes PNP transistors Q12 and Q13 having a collector connected to the midpoint between the transistors Q9 and Q11 and an emitter connected to the control power supply Vcc, and a resistor R9 connected between the collector of the transistor Q13 and ground. The gates of the transistors Q12 and Q13 are connected to each other, and the base and collector of the transistor Q13 are short-circuited.
[0105]
The detection coil 2 has one end connected to a connection midpoint between the transistors Q9 and Q12, and an AC current supply circuit Sac for supplying an AC current Iac and a DC current supply circuit Sdc for supplying a DC current Idc exist independently. Therefore, control of the ratio between the AC current Iac and the DC current Idc and the temperature coefficient can be simply performed, and furthermore, setting by digital trimming is also possible.
[0106]
In addition, if the signal processing circuit 4 includes an amplifier having a temperature coefficient having a polarity opposite to that of the temperature coefficient of the peak value V1 of the output voltage of the detection unit A, and outputs the displacement signal Vout based on the output of this amplifier, The output is a signal dependent only on the temperature-compensated displacement, and by processing this output, a temperature-compensated displacement signal can be obtained.
[0107]
Next, it is possible to control not only the constant current circuit 3 but also the values of the DC resistance Zdc and the AC impedance Zac and the temperature coefficient. Instead of the detection unit A described in the description of FIG. 1, a detection unit A provided with a circuit element 5 having a DC resistance Zdc ′ and an AC impedance Zac ′ in series with the detection coil 2 as shown in FIG. 14 is used. At this time, the DC resistance Zdc ′ and the AC impedance Zac ′ of the circuit element 5 are independent of the rotation angle θ of the core 1 and can be detected by appropriately selecting the values of the DC resistance Zdc ′ and the AC impedance Zac ′ and the temperature coefficient. The peak value and the temperature coefficient of the voltage across the section A can be controlled.
[0108]
For example, when the circuit element 5 is a pure resistor, the AC impedance Z'ac = R (resistance value). If the circuit element 5 is an inductance, it has both the DC resistance Z'dc and the AC impedance Z'ac. Further, when a diode is provided as the circuit element 5, it is possible to affect only the DC component Vdc of the voltage Vs across the detection coil 2.
[0109]
As described above, by providing the detection coil 2 with not only the AC current Iac but also the DC current Idc, the fluctuation width Δ (dV1 / dT) of the temperature coefficient of the signal voltage in the displacement section (rotation angle) θ is considerably large. Although it can be reduced, it is clear that the smaller Δ (dZac / dT) itself can further reduce Δ (dV1 / dT). The US patent mentioned in the prior art is a technique that meets this purpose, but has problems as described above.
[0110]
In order to reduce Δ (dZac / dT), it is desirable that the core 1 is a magnetic material having a small temperature coefficient of magnetic permeability and resistivity. Since the temperature coefficient of magnetic permeability is not so large in any magnetic material in a temperature range of, for example, about -40 to + 130 ° C., a material having a small temperature coefficient of resistivity is particularly suitable. For example, nichrome (nickel, chromium, iron alloy) and iron chrome (iron, chromium, aluminum alloy) correspond to this. These metal materials are often used for heating wires, and can be obtained at very low cost as wires. Therefore, when the core 1 is formed by bending a wire, the core 1 having excellent temperature characteristics can be manufactured at low cost, and this will be described in detail in Embodiment 2.
[0111]
Next, although different from the gist of the present invention, if the DC current Idc, the AC current Iac, the DC resistance Zdc, the AC resistance Zac, and their respective temperature coefficients are not properly set, Δ (dV1 / dT) becomes Δ (dZac / DT) will be described by way of example. For example, as the detection coil 2, the DC resistance Zdc = 100Ω (temperature coefficient 50 ppm / K), and the AC impedance Zac is expressed by the following equation (3): Z0 = 800Ω, Z ′ = − 8Ω / deg, β0 = 346 ppm / K, β '= −2.35 ppm / K / deg, corresponding to FIG. 8 in the case where DC current Idc = 0.2 mA and AC current Iac = 1.0 mA (both have a temperature coefficient of 0). The plot is shown in FIG. It can be seen that Δ (dV1 / dT) is larger than Δ (dZac / dT). As described above, it should be emphasized that Δ (dV1 / dT) does not decrease merely by providing the direct current Idc.
[0112]
In this embodiment, the description has been given of the rotary type position sensor. However, the same effect can be obtained by using a position sensor having a straight displacement direction as shown in the conventional example of FIG.
[0113]
(Embodiment 2)
In the present embodiment, as an ideal state in which Δ (dZac / dT) is minimized, a temperature for preventing the temperature change of the impedance Z of the detection coil 2 from being changed by the relative displacement between the core 1 and the detection coil 2 is set. The method of compensation will be described. The configuration of the position sensor of this embodiment is the same as that of the first embodiment, and the same components are denoted by the same reference numerals and description thereof is omitted.
[0114]
First, as a first method of temperature compensation, a method of adjusting the temperature change rate of the impedance Z when the core 1 does not penetrate the detection coil 2 to the temperature change rate when the core 1 penetrates the detection coil 2 will be described. I do.
[0115]
The impedance Z of the detection coil 2 is equivalent to a series circuit of a resistance component Rs and an inductance component Ls as shown in FIG.
[0116]
The inductance component Ls has a component due to the skin effect. The skin effect when the skin thickness is sufficiently small and the frequency is constant is proportional to the 1/2 power of the volume resistivity ρ. / 2 squared. FIG. 17 is a graph showing the change in the resistance value of the copper wire due to the skin effect, and shows the relationship between the frequency and the resistance value of the copper wire. Curves Y7, Y8, Y9, and Y10 correspond to the wire diameters of 0.32 mm, 0.16 mm, 0.10 mm, and 0.07 mm, respectively. The resistance depends on the wire diameter and frequency of the coil due to the skin effect. Changes.
[0117]
Further, the temperature coefficient of the resistance component Rs greatly depends on the temperature coefficient of the volume resistivity ρ of the winding material, and the resistance component Rs is also affected by the proximity effect.
[0118]
FIG. 18 is a graph showing a change in the resistance value of the copper wire due to the proximity effect, and shows the relationship between the frequency and the resistance value of the copper wire. When the wire diameter and the number of turns are 0.16 mm 40T and 0.07 mm 60T, the curves Y11 and Y12 respectively correspond. The proximity effect is a phenomenon in which a current does not flow uniformly in a winding when the winding pitch of the coil winding is narrow. The effect is stronger as the winding pitch is smaller, but the effect differs depending on the wire diameter. The component due to the proximity effect has a dependency of the volume resistivity ρ to the −1 power, so that its temperature coefficient is also affected by the volume resistivity ρ to the −1 power.
[0119]
That is, when the wire diameter is large or the frequency is high, the temperature coefficient of the impedance Z when the core 1 does not penetrate becomes small due to the skin effect and the proximity effect.
[0120]
Therefore, by appropriately setting the volume resistivity ρ, the wire diameter, the number of turns, the winding pitch, and the frequency of the winding material, the DC resistance component, the skin effect component, and the proximity effect component in a displacement state where the core 1 does not penetrate. Since the temperature coefficient of the impedance Z of the detection coil 2 can be reduced by controlling the balance, the conventional problem that the temperature coefficient changes depending on the displacement amount can be solved.
[0121]
Since copper has a very large temperature coefficient of volume resistivity ρ, it is desirable to select a winding material having a smaller volume coefficient of temperature coefficient ρ than copper. Specifically, the winding of the detection coil 2 may be formed of any one of nichrome, manganin, and a copper-nickel alloy. In particular, a copper-nickel alloy is preferable because the value of the volume resistivity ρ can be controlled by changing the component ratio.
[0122]
Next, a second method of temperature compensation for adjusting the temperature change rate of the impedance Z when the core 1 penetrates the detection coil 2 to the temperature change rate when the core 1 does not penetrate the detection coil 2 will be described. I do.
[0123]
The increase in the impedance Z of the detection coil 2 due to the penetration of the core 1 into the detection coil 2 results from the volume resistivity ρ and the magnetic permeability μ of the core 1. Therefore, the temperature coefficient is also related to the temperature coefficient of the volume resistivity ρ and the magnetic permeability μ of the core 1, and the temperature coefficient when the core 1 penetrates the detection coil 2 is determined by the core 1. The core 1 having a volume resistivity ρ and a magnetic permeability μ suitable for adjusting to the temperature coefficient in the case where the core 1 does not penetrate into the core 1 is selected, or the surface of the core 1 has a suitable volume resistivity ρ and the magnetic permeability μ. What is necessary is just to perform a surface treatment.
[0124]
Here, generally, the ambient temperature at which the position sensor is used is at most 120 to 130 ° C., and the Curie temperature of the core 1 is sufficiently higher than the ambient temperature. The magnetic permeability μ has a characteristic of rapidly decreasing near the Curie temperature, and conversely, the magnetic permeability μ hardly changes in a temperature region where the position sensor is used.
[0125]
Therefore, the temperature coefficient of the impedance Z is reduced by using the core 1 having at least the surface formed of a material having a small change in the volume resistivity ρ, which is another factor caused by the increase in the impedance Z of the detection coil 2. As a result, the fluctuation of the impedance Z of the detection coil 2 due to the temperature can be reduced.
[0126]
For example, in the position sensor that performs position detection by changing the impedance of the detection coil 2 according to the first embodiment, most of the breakdown of the impedance is inductance, and the magnetic field generated when a constant current flows through the detection coil 2 is Axial direction. Then, an annular current (so-called eddy current) that tries to eliminate the axial magnetic field flows inside the core 1. This annular current has the effect of lowering the inductance of the detection coil 2. The magnitude is related to the volume resistivity of the core 1 in addition to the magnitude and frequency of the applied magnetic field (it does not fluctuate at a constant current or a fixed frequency). I do. That is, as the volume resistivity of the core 1 increases, the annular current decreases, and the effect of reducing the inductance decreases. Therefore, if the volume resistivity of the core 1 has a temperature characteristic, the inductance also has a temperature characteristic, and the temperature characteristic of the inductance greatly affects the temperature characteristic of the impedance.
[0127]
When the detection coil 2 is actually used as an impedance element, the current supplied to the detection coil 2 is often driven at several tens KHz to several hundred KHz. It does not reach the inside and gathers near the surface.
[0128]
Therefore, if at least the surface of the core 1 is formed of any of nickel-chromium alloy, nickel-chromium-iron alloy, iron-chromium-aluminum alloy, copper-nickel alloy, and manganin, which are materials having a small volume resistivity ρ, Good. These materials are called electric heating materials, and have a small temperature coefficient of resistance. Further, since iron and nickel are magnetic materials, some of them have magnetism even as alloys, so that a large change in impedance of the detection coil 2 can be obtained.
[0129]
However, not only the surface but also the core 1 formed in a bulk and having a small volume resistivity can have more excellent temperature characteristics. In this case, materials for electric heating, such as nickel-chromium alloy, nickel-chromium-iron alloy, iron-chromium-aluminum alloy, copper-nickel alloy, and manganin, are used. In order to obtain the shape, material loss increases and the cost increases. Therefore, since these materials are on the market as heating wires, heating wires made of nickel-chromium alloy, nickel-chromium-iron alloy, iron-chromium-aluminum alloy, copper-nickel alloy, manganin, etc. are required. It is economical to use necessary bending (or stretching) after cutting to length, and it is possible to prevent generation of unnecessary industrial waste.
[0130]
Further, by combining both the first method and the second method of temperature compensation of the present embodiment, temperature compensation can be performed effectively.
[0131]
(Embodiment 3)
The position sensor according to the first embodiment supplies the DC current Idc and the AC current Iac to the detection coil 2, and as a result, determines the temperature of the displacement signal Vout by the ratio of the DC voltage Vdc and the AC voltage Vac generated at both ends of the detection coil 2. The width in which the coefficient fluctuates due to the relative displacement between the detection coil 2 and the core 1 (displacement dependence of the temperature coefficient) is minimized. 19, the signal processing circuit 4 includes, for example, a peak hold circuit 4a, a temperature compensation circuit 4c, a non-linearity compensation circuit 4e, and an amplification circuit 4d. The temperature compensating circuit 4c extracts the peak value V1 of Vs, and the temperature compensating circuit 4c performs temperature compensation on the peak value V1 with a temperature coefficient having a polarity opposite to the temperature coefficient of the peak value V1, and the non-linearity compensating circuit 4e has The amplifier circuit 4d amplifies the signal and outputs the displacement signal Vout by compensating for the linearity with respect to the relative displacement.
[0132]
On the other hand, in the position sensor of this embodiment, as shown in FIG. 20, the signal processing circuit 4 includes a peak hold circuit 4a, a level shift circuit 4b, a temperature compensation circuit 4c, and an amplifier circuit 4d. The peak value V1 of the voltage Vs across the detection coil 2 is extracted, the level shift circuit 4b outputs a signal V2 obtained by adding the level shift value Vsh to the peak value V1, and the temperature compensation circuit 4c outputs the signal V2 and the temperature of the signal V2. A signal V3 temperature-compensated with a temperature coefficient having a polarity opposite to the coefficient is output, and the amplifier circuit 4d amplifies the signal V3 and outputs a displacement signal Vout.
[0133]
The level shift circuit 4b adds the level shift value Vsh to the peak value V1, so that the DC current Idc supplied to the detection coil 2 may be 0 or a small value, which is advantageous when the current consumption is restricted. (In FIG. 3, the DC current Idc = 0). On the other hand, in the first embodiment, in order to minimize the displacement dependence of the peak value V1, the value of Idc / Iac has to be set large, which may cause an increase in current consumption and deterioration in sensitivity. Here, in the present embodiment, for the peak value V1 represented by [Equation 2], the signal V2 is
[0134]
(Equation 4)

And (Idc * Zdc + Vsh) becomes the DC voltage Vdc.
[0135]
To properly set the magnitude (absolute value) or temperature coefficient of the level shift value Vsh is to appropriately set the ratio between the DC current Idc and the AC current Iac and the temperature coefficient as in the first embodiment. It will be the same. Further, when any one or more of the DC current Idc, the AC current Iac, the DC resistance Zdc, the AC impedance Zac, and the temperature coefficient other than the level shift value Vsh are properly set, the DC voltage of the signal V2 is not changed. Since the ratio between Vdc and AC voltage Vac and the temperature coefficient are appropriately set, the fluctuation range of the temperature coefficient of signal V2 can be minimized.
[0136]
The shape of the position sensor of the present embodiment is the same as that of the first embodiment, but in this embodiment, as the movable block 13 rotates as shown in FIG. The configuration is such that the portion of the core 1 penetrating into the coil 2 is increased. FIG. 22 shows the temperature coefficient of the AC impedance Zac of the detection coil 2 with respect to the rotation angle θ. The AC impedance Zac has a displacement dependency. As the rotation angle θ increases, the amount of penetration of the core 1 into the detection coil 2 increases. Increases (there is a difference of about 470 ppm / ° C. when the rotation angle θ = 0 to 100 °). The measurement frequency of the AC impedance Zac is 70 KHz, the DC resistance Zdc is 58Ω (25 ° C.), and the temperature coefficient of the DC resistance Zdc is 3900 ppm / ° C.
[0137]
Here, FIG. 23 shows the temperature coefficient of the peak value V1 extracted by the configuration of FIG. By changing Idc / Iac with the AC current Iac = 1 mA, the displacement dependence of the temperature coefficient of the peak value V1 can be controlled. When Idc / Iac = about 1.0, the temperature coefficient of the peak value V1 can be controlled. Can be minimized. For simplicity, it is assumed that there is no temperature change in the DC current Idc, the AC current Iac, and the frequency (the same applies hereinafter).
[0138]
On the other hand, FIG. 24 shows the temperature coefficient of the signal V2 when the level shift value Vsh is changed from 0 mV to 200 mV in the configuration of the present embodiment in FIG. 20, where the DC current Idc is 0 and the level shift value Vsh is The temperature coefficient h is 3000 ppm / ° C. In this case, the displacement dependence of the temperature coefficient of the signal V2 can be controlled by changing the level shift value Vsh. When Vsh = about 100 mV, the displacement dependence of the temperature coefficient of the signal V2 is minimized. Thus, the same effect as the configuration of FIG. 19 can be obtained.
[0139]
Further, FIG. 25 shows the temperature coefficient of the signal V2 when the temperature coefficient h of the level shift value Vsh is changed from 0 ppm / ° C. to 5000 ppm / ° C. in the configuration of the present embodiment of FIG. Is set to 0, and the level shift value Vsh is set to 100 mV. In this case, the displacement dependence of the temperature coefficient of the signal V2 can be controlled by changing the temperature coefficient h. When h = about 2000 ppm / ° C., the displacement dependence of the temperature coefficient of the signal V2 is minimized. Therefore, the same effect as the configuration of FIG. 19 can be obtained.
[0140]
The signal V2 thus obtained is subjected to temperature compensation independent of displacement by the temperature compensation circuit 4c (for example, about -1200 ppm / ° C. in FIG. 23, about −1450 ppm / ° C. in FIG. 24, and FIG. 25) , About -1300 ppm / ° C.), the signal V3 has a value substantially equal to the signal V2 of the displacement at room temperature regardless of the ambient temperature. Then, the displacement signal Vout is output by performing predetermined amplification on the signal V3 by the amplifier circuit 4d. (If there is no particular need for amplification, the signal V3 is output as the displacement signal Vout.) Note that the temperature compensation circuit 4c is not necessarily limited to one that performs first-order compensation on temperature. A circuit that performs compensation represented by another nonlinear equation may be used. Similarly, the amplifier circuit 4d may be a circuit having an amplification degree expressed by a nonlinear equation for the signal V3.
[0141]
Further, even if the level shift circuit 4b is connected between the detection coil 2 and the peak hold circuit 4a as shown in FIG. 26, the same effect can be obtained because the signal V2 is represented by [Equation 4]. it can.
[0142]
Then, the level shift value Vsh of this embodiment, the temperature coefficient h of the level shift value Vsh, the temperature coefficient of temperature compensation, the circuit constant for amplification, the coefficient, and the like can be stored in an EEPROM or the like. If the values, coefficients, and constants can be set to the optimum values, the variation in the characteristics due to the temperature change can be minimized because the temperature characteristics of the detection coil 2 and the signal processing circuit 4 are not affected by individual differences. .
[0143]
Next, the calibration of the level shift value Vsh and the temperature coefficient h of the level shift value Vsh performed individually in the manufacturing process of the position sensor will be described below. First, when the level shift value Vsh is controlled to minimize the displacement dependency of the temperature characteristics as shown in FIG. 24, the temperature characteristics of the peak value V1 and the signal V2 at each displacement (each rotation angle) are determined by the temperature cycle. Is measured to determine the optimum level shift value Vsh, and the coefficient (circuit constant) of the amplifier circuit 4d is determined based on the level shift value Vsh. Then, since the displacement signal Vout is obtained for the first time after setting the coefficient of the amplifier circuit 4d, it is necessary to perform the temperature cycle again to confirm the temperature characteristics of the displacement signal Vout.
[0144]
On the other hand, when the temperature coefficient h of the level shift value Vsh is controlled to minimize the displacement dependence of the temperature characteristic as shown in FIG. 25, first, the amplifier circuit is operated in a normal temperature state (the gain of the temperature compensation circuit 4c becomes 1). A 4d coefficient can be determined. Thereafter, the temperature characteristics of the peak value V1 and the signal V2 at each displacement (each rotation angle) are measured by a temperature cycle to determine the optimum temperature coefficient h and the temperature coefficient of the temperature compensation circuit 4c. Since the displacement signal Vout can be checked at the same time, there is no need to perform the second temperature cycle. Thus, the calibration can be performed more easily by controlling the temperature coefficient h of the level shift value Vsh than by controlling the level shift value Vsh.
[0145]
Note that when controlling by supplying a bias current to the detection coil 2 as in the first embodiment, the DC current Idc, the AC current Iac, or the temperature coefficient of the frequency is more controlled than controlling Idc / Iac as shown in FIG. Calibration can be performed more easily by controlling.
[0146]
In the above description, the signal processing is performed using the peak value V1 of the voltage across the detection coil 2 as the original signal. However, the signal processing may be performed using the bottom voltage of the voltage across the detection coil 2 as the original signal. In this case, instead of [Equation 2] and [Equation 4],
[0147]
(Equation 5)

[0148]
(Equation 6)

It becomes. Also in this case, the same effect as described above can be obtained by appropriately setting the level shift value Vsh and the temperature coefficient h of the level shift value Vsh (at least one of them is a negative value). Furthermore, the same effect as described above can be obtained even when the peak-to-peak voltage or the effective value of the voltage across the detection coil 2 is used as an original signal and the original signal is level-shifted.
[0149]
As described above, in the present embodiment, it is not necessary to use the temperature coefficient of the DC resistance Zdc of the detection coil 2, and only the AC voltage Vac is extracted from the voltage between both ends of the detection coil 2, and the DC voltage (level shift value) is output by the level shift circuit 4b. Vsh), and the degree of freedom in circuit design is improved.
[0150]
(Embodiment 4)
As shown in FIG. 27, the configuration of the position sensor of the present embodiment is such that the AD conversion circuit 4f is connected to the next stage of the peak hold circuit 4a of the third embodiment, and the level shift unit 41 is connected to the next stage of the AD conversion circuit 4f. The digital operation block 4g constituting the temperature compensator 42 and the amplifier 43 is connected. Then, the peak value V1 of the voltage between both ends of the detection coil 2 is converted into a digital signal DV1 by the AD conversion circuit 4f. The shifted digital signal DV2 is output, the temperature compensating section 42 performs an operation for executing temperature compensation on the digital signal DV2, and the amplifying section 43 amplifies the digital signal output from the temperature compensating section 42 to obtain a digital signal. A displacement signal Vout of the signal is output.
[0151]
When the signal is digitized in this way, if only the temperature characteristic of the peak value V1 is measured in one temperature cycle, the digital amount of the level shift, its temperature coefficient, the temperature coefficient of the temperature compensation, the amplification coefficient, and the like are calculated. And the temperature characteristic of the output displacement signal Vout can be confirmed by calculation (the error between the actual output and the calculated output is less than or equal to the quantization error). Further, the digital operation result can be converted into an analog signal by DA conversion.
[0152]
(Embodiment 5)
In the present embodiment, an improvement in output linearity will be described. The configuration of the position sensor of this embodiment is the same as that of any one of the first to fourth embodiments, and the same components are denoted by the same reference numerals and description thereof is omitted.
[0153]
First, as a first method of improving the linearity, an appropriate material is selected for the core 1 and the frequency f of the alternating current Iac is also set appropriately. The inventor conducted an experiment on the linearity of the AC impedance Zac by changing the core material in the detection coil 2 exemplified in the first embodiment. FIG. 28 shows the metal materials used: electromagnetic soft iron, permalloy, electromagnetic stainless steel, SUS430, iron chromium, and their estimated characteristic values: resistivity. In FIG. 28, “Electromagnetic stainless steel” is a metal to which Si, Mn, P, Ni, Ti, or the like is added in addition to Cr 11% and is used for a yoke of an electromagnetic valve or a relay. . In addition, each metal is subjected to heat treatment under conditions unique to each metal in order to bring out its magnetic properties, and the shapes are the same.
[0154]
FIGS. 29A to 29E show experimental results of the linearity of the AC impedance Zac of each metal when the frequency f of the AC current Iac is 10 KHz, 30 KHz, 50 KHz, 70 KHz, and 90 KHz. It can be seen that magnetic stainless steel (magnetic stainless steel) has better linearity than electromagnetic soft iron and pure iron. In particular, SUS430 (18Cr ferritic stainless steel) has good linearity with respect to the angle span and the frequency, has corrosion resistance, and is inexpensive, so that it is suitable as the core material of the position sensor. I can say. It is considered that these linearities are determined by the balance between the resistivity and the magnetic permeability and the frequency characteristics. Since iron chromium also has a good linearity at 50 kHz or more, it can be seen that if measures are taken for corrosion resistance, a good core material can be obtained in addition to the above-mentioned advantage of the rate of change in resistivity.
[0155]
A second improvement method is to take measures to reduce the end effect, which is a problem of the related art. FIGS. 30A and 30B show a method in which the shape of the core 1 is devised to increase the contribution ratio of the core tip 1a or 1b to the AC impedance Zac. In FIG. 30 (a), the end portion 1a is provided with a substantially right-angled step to increase the thickness. In FIG. 30 (b), the end portion 1b is increased in a wedge shape. Alternatively, since 1b is thicker than other portions, the amount of interlinkage magnetic flux between the windings can be increased, which can further contribute to an increase in inductance. At this time, when the core 1 is formed by etching or metal injection molding, it does not particularly cause a cost increase.
[0156]
FIG. 30 (c) shows that the tip 1c of the core 1 is made of a material having higher magnetic permeability than the core body, so that the amount of interlinkage magnetic flux at the core tip 1c can be increased, and the inductance can be further increased. Can contribute. In FIGS. 30A and 30B, portions other than the tip portion must be thinned, and the sensitivity is slightly reduced. On the other hand, in the embodiment of FIG. 30C, the sensitivity is not reduced. Also, since the thickness is uniform, it is mechanically stable (even if it hits a little, it is hardly deformed).
[0157]
FIG. 30D shows an example in which a surface treatment (eg, plating) is performed on the core tip 1d with a material having high magnetic permeability. In FIG. 30C, it is possible to improve the troublesome manufacturing process and the difficulty in positioning. Further, in addition to plating, for example, a configuration in which a foil having a high magnetic permeability is attached may be used.
[0158]
The position sensor shown in FIG. 31 includes a detection coil 2 wound around a hollow bobbin 15 and a core 1 that is displaced in the winding axis direction X of the detection coil 2 and penetrates into the hollow portion of the bobbin 15. The circuit and the signal processing circuit (not shown) are provided as in any of the first to fourth embodiments. In this example, the core 1 has the same shape as before, and the winding is wound thick (that is, the number of winding layers is large) at the end of the detection coil 2. Therefore, even when only the tip of the core 1 penetrates, the magnetic flux of many windings is linked, so that the inductance is further increased.
[0159]
Further, in order to prevent the core 1 from being caught by the inner wall of the bobbin of the detection coil 2, in the examples of FIGS. 32A to 32E, an edge removing structure such as chamfering and rounding is adopted at the tip of the core 1. By doing so, the catch is eliminated. FIGS. 32B to 32E are obtained by chamfering the tip of the core 1 shown in FIGS.
[0160]
In FIG. 4 showing a cross-sectional view of the core 1 and the detection coil 2, a coating 11 in which a nonmagnetic metal such as copper is deposited is applied to the inner surface of the curved bobbin 10 through which the core 1 penetrates, so that the core 1 is not caught. ing. When a conductive material such as a metal is used for the coating 11, it is necessary to prevent the material from forming a closed loop in the cross section. Instead of metal deposition or the like, a part of the side surface of the through-hole may be formed of a sheet metal part, or the same effect can be exerted if the material has slidability and wear resistance such as fluorine coating. . In this manner, the foil 1 or the linear body (especially amorphous) can be used as the core 1 and can be displaced along the side surface of the through hole of the curved bobbin 10, so that the thickness and the diameter can be reduced. This is also effective in improving linearity.
[0161]
Furthermore, if the winding of the detection coil 2 is formed using a spring coil and the spring coil is inserted into the curved bobbin 10, a winding having a uniform pitch in the angular direction can be easily formed.
[0162]
Next, in FIG. 2, a curvature correcting member 12 for returning the curved bobbin deformed by the winding tension of the detection coil 2 and having a reduced curvature to the original shape is provided. A groove formed with substantially the same curvature as the coil 2 is formed, and by inserting the detection coil 2 into the groove, the inner radial portion and the bottom surface of the detection coil 2 come into contact with the curvature correcting member 12. Thus, a decrease in the curvature of the curved bobbin 10 is corrected. Although the housing 14 includes the curvature correcting member 12 in FIG. 2, a similar groove may be formed in the housing 14 itself.
[0163]
Such a structure using the curvature correcting member 12 has advantages in another sense. In the detection coil 2 which does not have such a structure, it is necessary to provide holding / fixing members 16 for holding and fixing outside the vicinity of the flanges at both ends of the detection coil 2 as shown in FIG. The presence of the holding / fixing member 16 limits the stroke (mechanical displacement) of the core 1. However, in the case of FIG. 2 where the holding and fixing structure is not on the outside of the flange, the stroke of the core 1 can be made longer, or the angle of the winding portion of the curved bobbin 10 is made wider instead of making the stroke longer. These also lead to an improvement in linearity.
[0164]
(Embodiment 6)
The position sensor of the present embodiment shown in FIGS. 34 to 37 is used in a vehicle (for example, detection of an accelerator pedal position), and based on the concept of a fail-safe system, the position sensor shown in FIGS. In FIG. 34 and FIG. 35, two detection coils 2a and 2b curved at the same curvature and two rotations about the rotation axis of the movable block 13 are shown in FIGS. There are provided two cores 1a and 1b curved at the same curvature that penetrate into the detection coils 2a and 2b, respectively, and the two detection coils 2a and 2b are arranged so as to overlap with each other in the rotation axis direction of the cores 1a and 1b. Compared to the configuration in which two detection coils are arranged on the same plane described in Japanese Patent Application Laid-Open No. 2000-186903, the expected angle of the winding portions of the detection coils 2a and 2b and the mechanical rotation angle of the movable block 13 also increase. . Therefore, the range of the rotation angle θ in which the linearity of each impedance Z of the detection coils 2a and 2b is good is widened. Since the specifications of the detection coils 2a and 2b are the same, the characteristics of the two detection coils 2a and 2b can be made substantially the same, which is advantageous in terms of winding processing and cost.
[0165]
Further, the position sensors shown in FIGS. 36 and 37 are a detection coil 2a curved with a small curvature, a detection coil 2b curved with a large curvature, and two detection coils by rotating about the rotation axis of the movable block 13. 2a and 2b are provided with a core 1a curved with a small curvature and a core 1b curved with a large curvature, and the detection coils 2a and 2b are at the same rotation angle θ with respect to the rotation axis of the cores 1a and 1b. In addition, they are arranged on the same plane. Therefore, similarly to the position sensors shown in FIGS. 34 and 35, the expected angles of the winding portions of the detection coils 2a and 2b and the mechanical rotation angle of the movable block 13 increase, and the impedance Z of each of the detection coils 2a and 2b increases. The range of the rotation angle θ where the linearity is good is widened, and the thickness can be further reduced.
[0166]
Here, after the detection coils 2a and 2b of the present embodiment are wound around the curved bobbins 10a and 10b, the detection coils 2a and 2b and the curved bobbins 10a and 10b are integrally molded with the resin 17 before assembly. Also, disconnection during vibration and impact during assembly is prevented, and the positional relationship between the two coils 2a and 2b does not shift, so that output fluctuation between the two systems due to a position shift during assembly does not occur. Furthermore, since the two detection parts are integrally formed into one part, the positioning with the movable block 13 is facilitated, and the assembling time is short.
[0167]
Further, by performing resin molding in a state where the deformation of the curved bobbins 10a and 10b is corrected, it is not necessary to provide a special member for correcting the deformation of the curved bobbins 10a and 10b on the housing 14 side.
[0168]
Furthermore, if the two cores 1a and 1b are also integrally resin-molded, their positions do not deviate from each other, so that there is no characteristic variation between the two systems due to positional deviation during assembly.
[0169]
(Embodiment 7)
The configuration of the position sensor of this embodiment is the same as any one of the first to sixth embodiments, and the same components are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, a configuration of the displacement signal Vout output from the signal processing circuit 4 will be described.
[0170]
When the ECU, which is a system that receives and processes the signal of the position sensor, is a digital circuit, if the displacement signal Vout is an analog signal, an error occurs due to repeated A / D conversion and D / A conversion, and a response occurs. Although there is a delay, if the displacement signal Vout is a digital signal, there is no such problem as an analog signal, and the signal is hardly affected by external noise during signal transmission. Therefore, an example in which the displacement signal Vout output from the signal processing circuit 4 is configured by a digital signal will be described. Here, the signal processing circuit 4 includes an A / D conversion circuit (not shown in the embodiments other than the fourth embodiment) for converting the peak value V1 of the output voltage of the detection unit A into a digital signal, and a correction circuit for digitally trimming the digital signal. And a signal correction circuit comprising:
[0171]
FIG. 38 illustrates a first example of the displacement signal Vout output from the signal processing circuit 4. The displacement signal Vout includes an output start signal having a width T1 corresponding to three pulse widths of the reference pulse Vr, and an output start signal. And a pulse signal output after a time T2 according to the position information after the output. The ECU can determine the relative position between the core 1 and the detection coil 2 by measuring the pulse width T1 of the output start signal and the time T2 until the pulse signal appears with a timer.
[0172]
FIG. 39 shows a second example of the displacement signal Vout output from the signal processing circuit 4. The displacement signal Vout is composed of an output start signal having a width corresponding to three pulse widths of the reference pulse Vr, and an output start signal following the output start signal. And the number of pulse signals corresponding to the position information output.
[0173]
The ECU can determine the relative position between the core 1 and the detection coil 2 by counting the number of pulse signals following the output start signal with a counter.
[0174]
FIG. 40 shows a third example of the displacement signal Vout output from the signal processing circuit 4. The displacement signal Vout is composed of a pulse signal having a duty ratio according to the position information, and the on / off time of the duty ratio. Is determined by the number of pulses of the reference pulse Vr.
[0175]
The ECU can determine the relative position between the core 1 and the detection coil 2 by measuring the period and the pulse width with a timer.
[0176]
Although securing the digital output of the required number of bits increases the number of wires between the position sensor and the ECU, according to the examples shown in FIGS. 38 to 40, only one signal line is required. Further, the displacement signal Vout may be composed of a pulse signal having a pulse width corresponding to the position information. Further, if the number of signal lines does not matter, the displacement signal Vout may be constituted by a digital signal having the number of bits satisfying the resolution required for position detection.
[0177]
(Embodiment 8)
FIGS. 41 and 42 show a cross-sectional structure and a circuit configuration of the detection coil of the position sensor of the present embodiment, respectively. The configuration of the signal processing circuits 4a and 4b is the same as any one of the first, third, and fourth embodiments.
[0178]
The position sensor according to the present embodiment has a double detection unit based on the concept of a fail-safe system in consideration of use in a vehicle.
[0179]
The position sensor is wound around hollow bobbins 15a and 15b, respectively, and is provided with detection coils 2a and 2b which are arranged to face each other in the winding axis direction. 15b, a constant current circuit 3 for outputting constant currents Ida and Idb to the detection coils 2a and 2b, and a constant current Ida output from the constant current circuit 3 and impedance Za of the detection coil 2a. A signal processing circuit 4a for converting a peak value of the determined voltage between both ends of the detection coil 2a into a displacement signal indicating positional information between the core 1 and the detection coil 2a; a constant current Idb output by the constant current circuit 3 and an impedance of the detection coil 2b A signal processing circuit that converts a peak value of a voltage between both ends of the detection coil 2b determined by Zb into a displacement signal indicating positional information between the core 1 and the detection coil 2b. And a b.
[0180]
In the present embodiment, the two detection coils 2a and 2b share the same core 1 attached to a structural member (not shown), and the same constant current circuit 3 uses the constant current Ida, By outputting Idb to each of the two detection coils 2a and 2b, it is possible to reduce the cost increase due to the duplicated detection unit.
[0181]
Further, if the active circuit sections of the constant current circuit 3 and the signal processing circuits 4a and 4b are constituted by monolithic ICs, the IC section is the most expensive part, so that the cost increase due to the duplicated detection section is further reduced. can do.
[0182]
Hereinafter, a specific use of the position sensors according to the first to eighth embodiments will be described. First, when used as a vehicle-mounted accelerator pedal detection position sensor, the detection angle is as narrow as about 30 °, so that curved bobbins having the same curvature can be arranged in the same plane, and the impedance of the detection coil is made complementary. be able to. In addition, since it is arranged in the vehicle cabin, the operation upper limit temperature is not so high. Furthermore, since there is a stroke that is sufficiently large with respect to the detection angle, a portion with good linearity at the center of the stroke can be used even if the material and shape of the core are not devised so much.
[0183]
Next, when used as a throttle position sensor, the detection angle must be as large as 90 ° or more, and the mechanical stroke needs to be large. Therefore, the curved bobbin shown in FIGS. As shown in 37, a structure in which curved bobbins having different curvatures are arranged in the same angle range in the same plane is suitable. In addition, since the margin of the mechanical stroke with respect to the detection angle is limited, it is desirable to select a material such as SUS430 that can easily obtain the linearity of the coil impedance, such as SUS430. Since the throttle position sensor is located in the engine room, a high operating upper limit temperature is required. After selecting a material that is easy to obtain linearity as the core, an appropriate bias current is applied to the coil, and the temperature characteristics due to angular displacement It is desirable to minimize (temperature coefficient).
[0184]
In addition, since position sensors used for plants such as power generation facilities are exposed to high temperatures, iron chromium is used as the core material, an appropriate bias current is applied to the coil, and the temperature characteristics (temperature coefficient) due to angular displacement are obtained. It is desirable to minimize it.
[0185]
Furthermore, the position sensor for angle detection used for a motor-driven bicycle may have only one detection unit in terms of cost, but the position sensor for angle detection generally used for automobiles secures reliability as a system. For this purpose, the detection unit may be duplicated.
[0186]
【The invention's effect】
The invention according to claim 1 is a constant current circuit that outputs a constant current obtained by superimposing an alternating current having a predetermined frequency and amplitude on a direct current having a predetermined amplitude, and a detecting unit including at least a detection coil supplied with the constant current. A core made of a magnetic material that is displaced relative to the detection coil in a winding axis direction of the detection coil, and the core and the detection coil based on a peak value of an output voltage of the detection unit generated by the constant current. A signal processing circuit that outputs a displacement signal indicating the position information of the core, wherein the fluctuation range of the temperature coefficient of the peak value of the output voltage of the detection unit in the entire displacement section of the core with respect to the detection coil is the detection range of the core. The DC current of the constant current is set so as to be smaller than the variation width of the temperature coefficient of the AC component of the impedance of the detection unit at the predetermined frequency in the entire displacement section with respect to the coil. The ratio between the current and the AC current, the ratio between the AC component and the DC component of the impedance of the detection unit, the temperature characteristic of the ratio between the DC current and the AC current of the constant current, and the AC component of the impedance of the detection unit. And at least one of the temperature characteristics of the ratio of the DC component, the detection coil can be freely selected according to the detection target, and the displacement dependency of the temperature coefficient of the impedance of the detection coil on the circuit can be determined. By setting the constant, it can be easily reduced, and therefore, there is an effect that a change in the temperature coefficient of the impedance of the detection coil with respect to the displacement can be compensated for by a simple circuit.
[0187]
According to the invention of claim 2, in claim 1, since the core can penetrate freely into the winding of the detection coil, there is an effect that a change in impedance of the detection coil can be increased.
[0188]
According to a third aspect of the present invention, in the second aspect, the temperature coefficient of the direct current component of the output voltage of the detection unit is a temperature coefficient of the output voltage of the detection unit when the amount of penetration of the core into the winding of the detection coil is minimum. Since the temperature coefficient of the AC component is closer to the temperature coefficient of the AC component of the output voltage of the detection unit when the amount of penetration of the core is the maximum, the fluctuation width of the temperature coefficient of the peak value of the output voltage of the detection unit is reduced. There is an effect that can be.
[0189]
According to a fourth aspect of the present invention, in the first or second aspect, the constant current circuit is configured to generate a voltage in which an AC voltage having a predetermined frequency and amplitude is superimposed on a DC voltage having a predetermined amplitude; A voltage-current conversion circuit for converting an output voltage into a current, and by setting the DC voltage and the AC voltage respectively, the ratio between the DC current and the AC current of the constant current is set. There is an effect that the ratio between the constant current DC current and the alternating current can be set by the circuit configuration and the setting of the constants on the circuit.
[0190]
According to a fifth aspect of the present invention, in the first or second aspect, the constant current circuit is configured to generate a voltage obtained by superimposing an AC voltage having a predetermined frequency and amplitude on a DC voltage having a predetermined amplitude; A voltage-current conversion circuit that converts an output voltage to a current, and by setting a temperature coefficient of a resistance value of a resistor that determines a value of a DC voltage included in the oscillation circuit, the DC current and the AC of the constant current are set. Since the temperature characteristic of the ratio with the current is set, the effect that the temperature characteristic of the ratio of the constant current DC current and the AC current can be set by a simple circuit configuration and the setting of the constants on the circuit is achieved. is there.
[0191]
According to a sixth aspect of the present invention, in the first or second aspect, the constant current circuit is configured to generate a voltage in which a DC voltage having a predetermined amplitude and an AC voltage having a predetermined frequency and amplitude are superimposed on each other; A voltage-current conversion circuit for converting an output voltage into a current, and setting a temperature characteristic of a frequency of the AC voltage, thereby setting a temperature characteristic of a ratio between an AC component and a DC component of the impedance of the detection unit. Therefore, even if the constant current circuit is composed of an IC and it is not possible to easily set the constants on the circuit, if a resistor or capacitor for determining the oscillation frequency of the AC voltage is external, By selecting the temperature coefficient of the resistor or the capacitor, there is an effect that the temperature characteristic of the AC component of the impedance of the detection unit can be set.
[0192]
According to a seventh aspect of the present invention, in the first or second aspect, the constant current circuit outputs a DC constant current circuit having a predetermined amplitude, and an AC constant current circuit outputs an AC current having a predetermined frequency and amplitude. By setting at least one of the temperature characteristic of the amplitude of the DC current, the temperature characteristic of the frequency of the AC current, and the temperature characteristic of the amplitude of the AC current, the DC current and the AC of the constant current are set. The ratio of the current to the current, the ratio of the AC component and the DC component of the impedance of the detection unit, the temperature characteristic of the ratio of the DC current to the AC current of the constant current, and the AC component and the DC component of the impedance of the detection unit. Since at least one of the temperature characteristics of the ratio is set, the same effects as those of the first aspect can be obtained by a simple circuit configuration and setting of constants on the circuit.
[0193]
According to an eighth aspect of the present invention, in the first or second aspect, the detection unit includes the detection coil, and a circuit element connected in series to the detection coil, the impedance of which is not changed by the displacement of the core. The circuit outputs a displacement signal indicating positional information of the core and the detection coil based on a peak value of a voltage between both ends of a series circuit of the detection coil and a circuit element generated by the constant current, and outputs a displacement signal of the circuit element. By setting at least one of the AC component and the DC component of the impedance and the temperature coefficient of the AC component and the DC component of the impedance of the circuit element, the ratio of the AC component and the DC component of the impedance of the detection unit is determined. , At least one of the temperature characteristics of the ratio of the AC component and the DC component of the impedance of the detection unit is set. Even if it is not possible to easily perform the constant setting of the circuit consists of the IC, there is the effect that a change in the temperature coefficient of the impedance of the detector can be compensated by a simple circuit with respect to the displacement.
[0194]
According to a ninth aspect of the present invention, in the eighth aspect, since the circuit element is a resistor, the impedance of the detection unit can be controlled at low cost.
[0195]
According to a tenth aspect, in the eighth aspect, since the circuit element is an inductor, there is an effect that the DC resistance and the AC impedance of the detection unit can be controlled at low cost.
[0196]
According to an eleventh aspect of the present invention, in the first or second aspect, the constant current circuit includes a resistor for setting an amplitude of the DC current, a frequency and an amplitude of the AC current, and a digital trimming unit for setting a value of the resistor. By setting the value of the resistor by the digital trimming means, the ratio between the DC current and the AC current of the constant current, and the ratio between the AC component and the DC component of the impedance of the detection unit. And one or more of the temperature characteristics of the ratio of the DC current and the AC current of the constant current and the temperature characteristics of the ratio of the AC component and the DC component of the impedance of the detection unit are set. The effect of claim 1 or 2 can be obtained.
[0197]
According to a twelfth aspect of the present invention, in the first or second aspect, the signal processing circuit includes a rectifier circuit and a circuit for peak-holding the output of the rectifier circuit. There is an effect that can be.
[0198]
According to a thirteenth aspect of the present invention, in the first or second aspect, the signal processing circuit includes an amplifier having a temperature coefficient having a polarity opposite to a temperature coefficient of a peak value of an output voltage of the detection unit. The output of the amplifier is a signal that depends only on the temperature-compensated displacement, and the output of the amplifier is a signal that depends on only the temperature-compensated displacement. There is an effect that a signal can be obtained.
[0199]
According to a fourteenth aspect of the present invention, in the fourth aspect, since the AC voltage generated by the oscillation circuit is a triangular wave, the AC voltage can be obtained more easily than a sine wave voltage.
[0200]
According to a fifteenth aspect of the present invention, since the alternating current output by the alternating current constant circuit is a triangular wave in the seventh aspect, there is an effect that it can be obtained more easily than a sine wave current.
[0201]
According to a sixteenth aspect, in the first or second aspect, the number of turns of the winding of the detection coil, the winding pitch of the winding, and the frequency of the constant current input to the detection coil are the impedance of the detection coil. Since the temperature coefficient and the temperature coefficient of the impedance of the detection coil caused by the relative displacement of the core with respect to the detection coil are equal values, the impedance of the detection coil when the core does not penetrate is detected. Is controlled so that the temperature change of the impedance is not changed by the relative displacement between the core and the detection coil.
[0202]
According to a seventeenth aspect of the present invention, in the first or second aspect, the core has a temperature coefficient of impedance of the detection coil and a temperature coefficient of impedance of the detection coil due to relative displacement of the core with respect to the detection coil. Is formed of a material that is equal to the above, so that the impedance of the detection coil when the core is penetrated is controlled so that the temperature change of the impedance is not changed by the relative displacement between the core and the detection coil. There is an effect that can be.
[0203]
According to an eighteenth aspect of the present invention, in the first or the second aspect, the surface treatment performed on the core includes the temperature coefficient of impedance of the detection coil and the detection due to the relative displacement of the core relative to the detection coil. Since the surface treatment makes the temperature coefficient of the impedance of the coil equal, the impedance of the detection coil when the core is penetrated is controlled, and the temperature change of the impedance does not change due to the relative displacement between the core and the detection coil. This has the effect of being able to do so.
[0204]
According to a nineteenth aspect, in the first or second aspect, at least the surface of the core is formed of a material having a small temperature coefficient of volume resistivity, so that the temperature of the impedance of the detection coil when the core penetrates is formed. There is an effect that the fluctuation can be reduced.
[0205]
According to a twentieth aspect, in the nineteenth aspect, the core has at least a surface formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and a manganin. Therefore, there is an effect that claim 19 can be easily realized.
[0206]
According to a twenty-first aspect, in the nineteenth aspect, the core is formed by bending a heating wire cut to a desired length, so that the temperature variation of the impedance of the detection coil when the core penetrates is formed. Is further reduced, and the loss of material can be reduced.
[0207]
In a preferred embodiment of the present invention, the heating wire is formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and a manganin. Therefore, there is an effect that Claim 21 can be easily realized.
[0208]
According to a twenty-third aspect of the present invention, in the first or second aspect, since the winding of the detection coil is formed of any one of nichrome, manganin, and a copper-nickel alloy, the detection coil in a case where the core does not penetrate is provided. There is an effect that the temperature fluctuation of the impedance of the semiconductor device can be reduced.
[0209]
The invention of claim 24 is a constant current circuit that outputs an alternating constant current having at least a predetermined frequency and amplitude, a detecting unit that is supplied with at least the detecting coil that is supplied with the constant current, A signal processing circuit that outputs a displacement signal indicating positional information between the core and the detection coil based on an extracted value from an output voltage of the detection unit generated by the constant current, the core being made of a magnetic material that is relatively displaced in the direction of the winding axis; An extraction circuit for obtaining the extracted value from an output voltage of a detection unit, a level shift circuit for performing a level shift of a predetermined magnitude with respect to the extracted value, and a level shift for temperature compensation. A temperature compensation circuit for the output of the circuit, wherein the temperature coefficient of the output of the level shift circuit fluctuates due to the relative displacement between the detection coil and the core; Since at least one of the magnitude of the level shift and the temperature coefficient is set so that the number becomes smaller than the width fluctuated by the relative displacement between the detection coil and the core, the current supplied to the detection coil is a temperature characteristic. The current consumption can be reduced without any inconvenience that the current consumption changes due to temperature adjustment, and the adjustment can be performed without depending on the temperature coefficient of the DC resistance of the winding material. Therefore, there is an effect that a change in the temperature coefficient of the impedance of the detection coil with respect to the displacement can be compensated for by a simple circuit.
[0210]
According to a twenty-fifth aspect of the present invention, there is provided a constant current circuit that outputs an alternating constant current having at least a predetermined frequency and an amplitude, a detecting unit including at least a detecting coil supplied with the constant current, A signal processing circuit that outputs a displacement signal indicating positional information between the core and the detection coil based on an extracted value from an output voltage of the detection unit generated by the constant current, the core being made of a magnetic material that is relatively displaced in the direction of the winding axis; The signal processing circuit comprises: an extraction circuit that obtains the extracted value from an output voltage of a detection unit; an A / D conversion circuit that converts the extracted value into a digital signal; and a digital signal that is output by the A / D conversion circuit. A level shift circuit for performing a level shift of a predetermined digital amount on the signal; and a temperature compensation circuit for performing an operation for performing temperature compensation on an output of the level shift circuit. The level shift of the level shift circuit is controlled such that the temperature coefficient of the output of the shift circuit varies with the relative displacement between the detection coil and the core, and the temperature coefficient of the extracted value varies with the variation of the relative coefficient between the detection coil and the core. Since at least one of the magnitude of the predetermined digital quantity and the temperature coefficient is set, the same effect as that of the twenty-fourth aspect can be obtained, and the calibration (calibration) can be performed simply and accurately. .
[0211]
According to a twenty-sixth aspect of the present invention, in the twenty-fourth aspect or the twenty-fifth aspect, the extracted value is a peak value of the output voltage of the detection unit, and thus has an effect that temperature compensation can be performed based on the peak value.
[0212]
According to a twenty-seventh aspect, in the twenty-fourth or twenty-fifth aspect, since the extracted value is a bottom value of the output voltage of the detection unit, there is an effect that temperature compensation can be performed based on the bottom value.
[0213]
According to a twenty-eighth aspect of the present invention, in the twenty-fourth or twenty-fifth aspect, the extracted value is a value proportional to the amplitude of the output voltage of the detection unit, so that the temperature compensation is performed based on the value proportional to the amplitude of the output voltage. There is an effect that can be.
[0214]
According to a twenty-ninth aspect, in the twenty-fourth aspect, a means for adjusting at least one of the magnitude of the level shift and the temperature coefficient is provided. Therefore, there is an effect that more accurate temperature characteristics can be realized.
[0215]
According to a thirty-fifth aspect, in the twenty-fifth aspect, a means for adjusting at least one of the magnitude of the predetermined digital amount of the level shift and the temperature coefficient is provided, so that the same effect as the twenty-ninth aspect is obtained.
[0216]
According to a thirty-first aspect of the present invention, in the twenty-fourth aspect or the twenty-fifth aspect, since the core is capable of penetrating into the winding of the detection coil, there is an effect that a change in impedance of the detection coil can be increased.
[0219]
According to the invention of claim 32, in claim 1, 2, 24 or 25, since a magnetic flux is more easily passed through a portion having a predetermined length from an end of the core than other portions, an end effect is reduced, There is an effect that a section where output linearity can be ensured is widened.
[0218]
According to a thirty-third aspect of the present invention, in the thirty-second aspect, since a portion having a predetermined length from an end of the core is thicker than other portions, it is advantageous when molding the core by metal injection molding, or two members. There is an effect that it can be easily formed even with the combination of.
[0219]
According to a thirty-fourth aspect of the present invention, in the thirty-second aspect, the portion having a predetermined length from the end of the core is formed of a material having a higher magnetic permeability than other portions, so that the core has a constant thickness. This has the effect of being mechanically stable and of being easily formed by a combination of two members.
[0220]
According to a thirty-fifth aspect of the present invention, in the thirty-second aspect, a portion having a predetermined length from the end of the core is surface-treated with a material having a higher magnetic permeability than the other portions, so that the core has a constant thickness. This has the effect of being mechanically stable and of being easily formed even with a curved core.
[0221]
In the invention according to claim 36, in claim 35, since the core is made of electromagnetic stainless steel whose surface at a predetermined length from the end is permalloy-plated, the magnetic permeability between the end of the core and other parts is made. Has a good balance and is also excellent in corrosion resistance.
[0222]
In the invention according to claim 37, in claim 1, 2, 24 or 25, the edge of the core is subjected to chamfering processing to remove the edge, so that the core is not caught inside the bobbin, and the linearity due to the hook is eliminated. There is an effect that deterioration of the image can be prevented.
[0223]
According to a thirty-eighth aspect of the present invention, in any one of the first, second, twenty-fourth, and twenty-fifth aspects, the detection coil has a shape curved at a predetermined curvature, fixes the detection coil, and corrects a change in curvature of the detection coil. Since the housing having the means for performing the detection is provided, it is possible to correct and prevent a change in the curvature of the detection coil.
[0224]
According to a thirty-ninth aspect, in the thirty-eighth aspect, the housing corrects a change in curvature of the detection coil by abutting at least a part of an inner radial portion of the detection coil. Can be played.
[0225]
According to a fortieth aspect of the present invention, in any one of the first, second, twenty-fourth, and twenty-fifth aspects, a bobbin around which the detection coil is wound is provided, and the coil and the bobbin are resin-molded before assembling. -There is an effect that disconnection due to an impact can be prevented. Furthermore, in the case of a curved bobbin, by performing resin molding in a state where the deformation is corrected, the same effect as that of the thirty-eighth aspect can be obtained even if there is no means for correcting the change in curvature of the detection coil on the housing side.
[0226]
The invention according to claim 41 is characterized in that, in claim 1, 2, 24 or 25, two bobbins each of which is wound with the two detection coils are provided, and the two coils and the two bobbins are integrated before assembly. Since the resin molding is used, in addition to the effect of claim 40, there is an effect that the positional relationship between the two detection coils does not deviate, and the output does not fluctuate between the two detection units due to a positional deviation during assembly.
[0227]
The invention of claim 42 has the same effect as that of claim 41 because the two detection coils are provided and the two cores penetrating into the detection coils are integrally resin-molded.
[0228]
The invention according to claim 43 is the invention according to claim 2 or 31, wherein the two detection coils curved with the same curvature and the two detection coils rotate through a rotation axis to respectively penetrate into the two detection coils and have the same curvature. It is provided with two curved cores, and the two detection coils are arranged so as to overlap with each other in the rotation axis direction of the core. Therefore, the expected angle of the winding part of the detection coil and the mechanical rotation angle of the movable block are increased. Therefore, there is an effect that the range of the rotation angle in which the linearity of the impedance of the detection coil is favorable is widened. Further, since the specifications of the two detection coils can be made the same, the characteristics of the two detection coils can be made the same, which is advantageous in terms of winding processing and cost.
[0229]
The invention according to claim 44 is the invention according to claim 2 or 31, wherein the two detection coils curved with different curvatures and the two detection coils are respectively rotated by rotating about a rotation axis, and have different curvatures. With the two cores that are curved, the two detection coils are arranged on the same rotation angle and the same plane with respect to the rotation axis of the core, so that the expected angle of the winding part of the detection coil, It is possible to increase the mechanical rotation angle of the movable block, so that there is an effect that the range of the rotation angle in which the linearity of the impedance of the detection coil is favorable is widened. Further, the thickness can be reduced.
[0230]
According to a forty-fifth aspect, in the first, second, twenty-fourth, or twenty-fifth aspect, the signal processing circuit includes an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; The displacement signal output from the signal processing circuit is a digital signal having the number of bits that satisfies the resolution required for position detection. If the system (ECU) that performs the processing is a digital circuit, if the output of the position sensor is an analog signal, an error occurs due to repeated AD conversion and DA conversion, and a response delay occurs. Since the output is a digital output, such a problem does not occur. In addition, the signal transmission is less susceptible to external noise than the analog output. Furthermore, since the digital signal has the number of bits that satisfies the required resolution, the ECU side can read out in real time and can perform the processing quickly.
[0231]
According to a forty-sixth aspect, in the first, second, twenty-fourth, or twenty-fifth aspect, the signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; A signal correction circuit comprising a digital trimming correction circuit, the displacement signal output by the signal processing circuit is an output start signal, and after a time corresponding to the position information after the output start signal is output, When the system (ECU) that receives and processes the output of the position sensor is a digital circuit, the output of the position sensor is an analog signal. Is repeated and the response is delayed, but such a problem occurs because the output of the position sensor is a digital output. No. In addition, compared to analog output, signal transmission is less susceptible to external noise. Further, there is an effect that only one signal line is required.
[0232]
According to a forty-seventh aspect, in the first, second, twenty-fourth, or twenty-fifth aspect, the signal processing circuit includes an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; A signal correction circuit including a digital trimming correction circuit, wherein the displacement signal output from the signal processing circuit is an output start signal, and a duty ratio according to the position information output following the output start signal. Therefore, the same effect as that of claim 46 can be obtained.
[0233]
In the invention of claim 48, in accordance with claim 1, 2, 24 or 25, the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection section into a digital signal, A signal correction circuit including a digital trimming correction circuit, wherein the displacement signal output by the signal processing circuit is an output start signal and a pulse width corresponding to the position information output following the output start signal. Therefore, the same effect as that of claim 46 can be obtained.
[0234]
In the invention of claim 49, in accordance with claim 1, 2, 24 or 25, the signal processing circuit comprises: an A / D conversion circuit for converting a peak value of an output voltage of the detection section into a digital signal; A signal correction circuit including a correction circuit for digital trimming, wherein the displacement signal output by the signal processing circuit is an output start signal and a number corresponding to the position information output following the output start signal. Since it is composed of a pulse signal, the same effect as that of claim 46 can be obtained.
[0235]
According to a fifty-second aspect of the present invention, in the first, second, twenty-fourth, or twenty-fifth aspect, two detection coils are provided, and the two detection coils share the same core attached to a structural member. There is an effect that the cost increase accompanying the duplication of can be reduced.
[0236]
According to a fifty-first aspect of the present invention, in the first, second, twenty-fourth, or twenty-fifth aspect, two detection coils are provided, and the same constant current circuit outputs a constant current having a predetermined frequency and amplitude to the two detection coils. Therefore, there is an effect that the cost increase due to the duplexing of the detection unit can be reduced.
[0237]
According to the invention of claim 52, in claim 50 or 51, since the active circuit of each circuit is constituted by a monolithic IC, there is an effect that it is possible to reduce the cost increase due to the duplicated detection unit. In particular, since the IC section is the most expensive component, there is a great merit of sharing.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a circuit configuration according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an upper surface of the above.
FIG. 3 is a diagram showing a side cross section of the above.
FIG. 4 is a diagram showing a cross-sectional view of the detection coil according to the first embodiment;
FIG. 5 is a diagram showing a voltage waveform between both ends of the detection coil according to the first embodiment;
FIG. 6 is a diagram showing a relationship between the rotation angle and the impedance of the detection coil in the above.
FIG. 7 is a diagram showing a relationship between a rotation angle and a voltage between both ends of a detection coil.
FIG. 8 is a diagram showing the relationship between the rotation angle and the temperature coefficient of the voltage between both ends of the detection coil.
FIG. 9 is a diagram showing the relationship between the rotation angle and the temperature coefficient of the peak voltage at both ends of the detection coil.
FIG. 10 is a diagram showing a specific circuit configuration of a constant current circuit and a signal processing circuit according to the embodiment.
FIG. 11 is a diagram showing a specific circuit configuration of the above oscillator circuit.
FIG. 12 is a diagram showing another circuit configuration of the voltage-current conversion circuit of the above.
FIG. 13 is a diagram showing another circuit configuration of the constant current circuit of the above.
FIG. 14 is a diagram showing another circuit configuration of the above.
FIG. 15 is a reference diagram illustrating a relationship between a rotation angle and a temperature coefficient of a voltage between both ends of a detection coil.
FIG. 16 is a diagram showing an equivalent circuit of a detection coil according to the second embodiment of the present invention.
FIG. 17 is a diagram showing a change in the resistance value of the copper wire due to the skin effect of the Embodiment.
FIG. 18 is a diagram showing a change in the resistance value of the copper wire due to the proximity effect of the Embodiment.
FIG. 19 is a diagram illustrating a configuration of a signal processing circuit according to the first embodiment of the present invention.
FIG. 20 is a diagram illustrating a circuit configuration according to a third embodiment of the present invention.
FIG. 21 is a diagram showing an upper surface of the above.
FIG. 22 is a diagram showing the relationship between the rotation angle and the temperature coefficient of the AC impedance of the detection coil.
23 is a diagram showing a relationship between the rotation angle in FIG. 19 and a temperature coefficient of a voltage between both ends of the detection coil.
24 is a diagram illustrating a relationship between a rotation angle and a temperature coefficient of an output signal of the peak hold circuit when the magnitude of the level shift value in FIG. 20 is variable.
25 is a diagram illustrating a relationship between a rotation angle and a temperature coefficient of an output signal of a peak hold circuit when a temperature coefficient of a level shift value in FIG. 20 is variable.
FIG. 26 is a diagram showing another circuit configuration of the above.
FIG. 27 is a diagram illustrating a circuit configuration according to a fourth embodiment of the present invention.
FIG. 28 is a diagram illustrating characteristics of a magnetic material used for a core according to the fifth embodiment of the present invention.
29 (a) to 29 (e) are diagrams showing, for each frequency, the relationship between the same angular span and the straightness of the AC impedance of the detection coil.
FIGS. 30 (a) to (d) are views showing an end of the core of the above.
FIG. 31 is a diagram showing a side cross section of the position sensor having the straight stroke configuration according to the third embodiment.
32 (a) to (e) are views showing the ends of the core from which the edges of the core have been removed.
FIG. 33 is a diagram showing a detection coil provided with holding / fixing members at both ends of the detection coil.
FIG. 34 is a diagram illustrating an upper surface of a first position sensor including two detection units according to the sixth embodiment of the present invention.
FIG. 35 is a diagram showing a part of a side cross section of the first position sensor of the above.
FIG. 36 is a diagram illustrating an upper surface of a second position sensor including two detection units according to the above.
FIG. 37 is a diagram showing a part of a side cross section of the second position sensor of the above.
FIGS. 38A and 38B are first diagrams illustrating displacement signals according to the seventh embodiment of the present invention.
39 (a) and (b) are second views showing displacement signals of the above.
FIGS. 40A and 40B are third diagrams showing displacement signals of the above.
FIG. 41 is a diagram showing a cross-sectional structure according to an eighth embodiment of the present invention.
FIG. 42 is a diagram showing a circuit configuration of the above.
FIG. 43 is a diagram showing a side cross section of a conventional first position sensor.
FIG. 44 is a diagram showing a relationship between the displacement and the AC impedance of the detection coil.
FIG. 45 is a diagram showing a circuit configuration of the above.
FIG. 46 is a diagram showing a side cross section of a conventional second position sensor.
FIG. 47 is a diagram showing a side cross section of a conventional third position sensor.
FIG. 48 is a diagram showing a configuration of a conventional fourth position sensor.
FIG. 49 is a diagram showing a relationship between the displacement and the temperature coefficient of the AC impedance of the detection coil.
FIG. 50 is a diagram showing the relationship between the displacement and the AC impedance of the detection coil in a state close to actuality.
[Explanation of symbols]
2 Detection coil
3 Constant current circuit
3a Oscillation circuit
3b Voltage-current conversion circuit
4 Signal processing circuit
A Detector

Claims (52)

A constant current circuit that outputs a constant current obtained by superimposing an alternating current having a predetermined frequency and amplitude on a direct current having a predetermined amplitude, a detection unit including at least a detection coil supplied with the constant current, A core made of a magnetic material that is relatively displaced in the direction of the winding axis of the detection coil, and a displacement signal indicating position information between the core and the detection coil based on a peak value of an output voltage of the detection unit generated by the constant current. And a fluctuation range of the temperature coefficient of the peak value of the output voltage of the detection unit in the entire displacement section of the core with respect to the detection coil, the variation range of the temperature coefficient of the peak value of the output voltage of the core with respect to the detection coil. The DC current and the AC current of the constant current are set so as to be smaller than the fluctuation range of the temperature coefficient of the AC component of the impedance of the detection unit at a predetermined frequency. And the ratio of the AC component and the DC component of the impedance of the detection unit, the temperature characteristic of the ratio of the DC current and the AC current of the constant current, and the ratio of the AC component and the DC component of the impedance of the detection unit. A position sensor for setting at least one of the following temperature characteristics. The position sensor according to claim 1, wherein the core is penetrable into a winding of the detection coil. The temperature coefficient of the DC component of the output voltage of the detection unit is obtained by calculating the amount of penetration of the core from the temperature coefficient of the AC component of the output voltage of the detection unit when the amount of penetration of the core into the winding of the detection coil is minimum. 3. The position sensor according to claim 2, wherein the temperature coefficient is close to a temperature coefficient of an AC component of an output voltage of the detection unit when the maximum value is. The constant current circuit includes an oscillation circuit that generates a voltage obtained by superimposing an AC voltage having a predetermined frequency and amplitude on a DC voltage having a predetermined amplitude, and a voltage-current conversion circuit that converts an output voltage of the oscillation circuit into a current. 3. The position sensor according to claim 1, wherein the ratio of the constant current DC current to the AC current is set by setting the DC voltage and the AC voltage. 4. The constant current circuit includes an oscillation circuit that generates a voltage obtained by superimposing an AC voltage having a predetermined frequency and amplitude on a DC voltage having a predetermined amplitude, and a voltage-current conversion circuit that converts an output voltage of the oscillation circuit into a current. By setting a temperature coefficient of a resistance value of a resistor that determines a value of a DC voltage included in the oscillation circuit, a temperature characteristic of a ratio between a DC current of the constant current and an AC current is set. The position sensor according to claim 1 or 2, wherein The constant current circuit includes an oscillation circuit that generates a voltage obtained by superimposing an AC voltage having a predetermined frequency and amplitude on a DC voltage having a predetermined amplitude, and a voltage-current conversion circuit that converts an output voltage of the oscillation circuit into a current. The position according to claim 1 or 2, wherein a temperature characteristic of a ratio between an AC component and a DC component of the impedance of the detection unit is set by setting a temperature characteristic of a frequency of the AC voltage. Sensors. The constant current circuit includes a DC constant current circuit that outputs a DC current having a predetermined amplitude, and an AC constant current circuit that outputs an AC current having a predetermined frequency and amplitude. By setting at least one of the temperature characteristic of the frequency of the AC current and the temperature characteristic of the amplitude of the AC current, the ratio of the DC current of the constant current to the AC current and the AC component of the impedance of the detection unit are set. At least one of a temperature characteristic of a ratio between a direct current and an alternating current of the constant current, and a temperature characteristic of a ratio between an alternating current component and a direct current component of the impedance of the detection unit. 3. The position sensor according to claim 1, wherein The detection unit includes the detection coil, and a circuit element connected in series to the detection coil, the impedance of which does not change due to displacement of the core.The signal processing circuit includes a detection coil and a circuit generated by the constant current. A displacement signal indicating positional information between the core and the detection coil is output based on a peak value of a voltage between both ends of a series circuit with the element, and an AC component and a DC component of an impedance of the circuit element and an impedance of the circuit element are output. By setting at least one of the temperature coefficient of the AC component and the DC component of the ratio, the ratio of the AC component and the DC component of the impedance of the detection unit, and the AC component and the DC component of the impedance of the detection unit 3. The position sensor according to claim 1, wherein at least one of the temperature characteristics of the ratio is set. 9. The position sensor according to claim 8, wherein the circuit element is a resistor. The position sensor according to claim 8, wherein the circuit element is an inductor. The constant current circuit is an integrated circuit including an amplitude of the DC current, a resistor for setting the frequency and amplitude of the AC current, and a digital trimming unit for setting the value of the resistor. By setting the value of the constant current, the ratio of the DC current and the AC current of the constant current, the ratio of the AC component and the DC component of the impedance of the detection unit, and the ratio of the DC current and the AC current of the constant current 3. The position sensor according to claim 1, wherein at least one of a temperature characteristic of the detection unit and a temperature characteristic of a ratio between an AC component and a DC component of the impedance of the detection unit is set. 4. The position sensor according to claim 1, wherein the signal processing circuit includes a rectifier circuit and a circuit that peak-holds an output of the rectifier circuit. The signal processing circuit includes an amplifier having a temperature coefficient of a polarity opposite to a temperature coefficient of a peak value of an output voltage of the detection unit, and indicates position information of the core and the detection coil based on an output of the amplifier. 3. The position sensor according to claim 1, wherein the position sensor outputs a displacement signal. The position sensor according to claim 4, wherein the AC voltage generated by the oscillation circuit is a triangular wave. 8. The position sensor according to claim 7, wherein the alternating current output from the alternating current constant circuit is a triangular wave. The number of turns of the winding of the detection coil, the winding pitch of the winding, and the frequency of the constant current input to the detection coil are determined by the temperature coefficient of the impedance of the detection coil and the core relative to the detection coil. 3. The position sensor according to claim 1, wherein the temperature coefficient of the impedance of the detection coil caused by the displacement is equal to a temperature coefficient. The core is formed of a material in which a temperature coefficient of impedance of the detection coil is equal to a temperature coefficient of impedance of the detection coil due to relative displacement of the core with respect to the detection coil. The position sensor according to claim 1. The surface treatment applied to the core is a surface treatment in which the temperature coefficient of the impedance of the detection coil and the temperature coefficient of the impedance of the detection coil resulting from the relative displacement of the core with respect to the detection coil are equal. The position sensor according to claim 1 or 2, wherein: The position sensor according to claim 1, wherein at least a surface of the core is formed of a material having a small temperature coefficient of volume resistivity. 20. The core according to claim 19, wherein at least a surface of the core is formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and manganin. Position sensor. 20. The position sensor according to claim 19, wherein the core is formed by bending a heating wire cut to a desired length. The position sensor according to claim 21, wherein the heating wire is formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and a manganin. . The position sensor according to claim 1, wherein a winding of the detection coil is formed of one of nichrome, manganin, and a copper-nickel alloy. A constant current circuit that outputs at least an AC constant current having a predetermined frequency and amplitude; a detection unit that includes at least a detection coil to which the constant current is supplied; and a displacement relative to the detection coil in a winding axis direction of the detection coil. A signal processing circuit that outputs a displacement signal indicating position information between the core and the detection coil based on a value extracted from an output voltage of the detection unit generated by the constant current, the core being made of a magnetic material; The circuit includes an extraction circuit that obtains the extracted value from the output voltage of the detection unit, a level shift circuit that performs a level shift of a predetermined magnitude on the extracted value, and performs temperature compensation on an output of the level shift circuit. A temperature compensation circuit, wherein the temperature coefficient of the output of the level shift circuit fluctuates due to the relative displacement between the detection coil and the core, and the temperature coefficient of the extracted value is Position sensor and sets the at least one of the relative displacement to be less than the width that varies by the size and temperature coefficient of the level shift of the. A constant current circuit that outputs at least an AC constant current having a predetermined frequency and amplitude; a detection unit that includes at least a detection coil to which the constant current is supplied; and a displacement relative to the detection coil in a winding axis direction of the detection coil. A signal processing circuit that outputs a displacement signal indicating position information between the core and the detection coil based on a value extracted from an output voltage of the detection unit generated by the constant current, the core being made of a magnetic material; The circuit includes an extraction circuit that obtains the extracted value from the output voltage of the detection unit, an A / D conversion circuit that converts the extracted value into a digital signal, and a predetermined digital signal that is output from the A / D conversion circuit. A level shift circuit for performing a level shift of an amount, and a temperature compensation circuit for performing an operation for performing temperature compensation on an output of the level shift circuit. The predetermined digital amount of the level shift is set so that the width in which the degree coefficient varies due to the relative displacement between the detection coil and the core is smaller than the width in which the temperature coefficient of the extracted value varies due to the relative displacement between the detection coil and the core. A position sensor for setting at least one of a size of the image and a temperature coefficient. 26. The position sensor according to claim 24, wherein the extracted value is a peak value of an output voltage of the detection unit. 26. The position sensor according to claim 24, wherein the extracted value is a bottom value of an output voltage of the detection unit. 26. The position sensor according to claim 24, wherein the extracted value is a value proportional to an amplitude of an output voltage of the detection unit. 25. The position sensor according to claim 24, further comprising: means for adjusting at least one of the level shift magnitude and the temperature coefficient. 26. The position sensor according to claim 25, further comprising means for adjusting at least one of a magnitude of a predetermined digital amount of the level shift and a temperature coefficient. 26. The position sensor according to claim 24, wherein the core is penetrable into the winding of the detection coil. 26. The position sensor according to claim 1, wherein a portion having a predetermined length from an end of the core has a magnetic flux more easily passed than other portions. 33. The position sensor according to claim 32, wherein a portion having a predetermined length from an end of the core is thicker than other portions. 33. The position sensor according to claim 32, wherein a portion having a predetermined length from an end of the core is formed of a material having a higher magnetic permeability than other portions. 33. The position sensor according to claim 32, wherein a portion having a predetermined length from an end of the core is surface-treated with a material having a higher magnetic permeability than other portions. 36. The position sensor according to claim 35, wherein the core is made of an electromagnetic stainless steel whose surface at a predetermined length from the end is permalloy-plated. 26. The position sensor according to claim 1, wherein the edge of the core is chamfered to remove an edge. 3. The detection coil according to claim 1, wherein the detection coil has a shape curved at a predetermined curvature, and includes a housing having a means for fixing the detection coil and correcting a change in curvature of the detection coil. 4. 24. The position sensor according to 24 or 25. 39. The position sensor according to claim 38, wherein the housing abuts at least a part of an inner radial portion of the detection coil to correct a change in curvature of the detection coil. 26. The position sensor according to claim 1, further comprising a bobbin around which the detection coil is wound, wherein the coil and the bobbin are resin-molded before assembly. 26. The apparatus according to claim 1, further comprising two bobbins each of which is wound with the two detection coils, wherein the two coils and the two bobbins are integrally molded with resin before assembly. Position sensor. 32. The position sensor according to claim 2, further comprising two detection coils, wherein the two cores penetrating the detection coils are integrally resin-molded. The two detection coils curved with the same curvature, and the two cores that respectively penetrate the two detection coils by rotating about a rotation axis and are curved with the same curvature; 32. The position sensor according to claim 2, wherein the coils are arranged so as to overlap with each other in a rotation axis direction of the core. The two detection coils curved with different curvatures, and the two cores respectively penetrating into the two detection coils by rotating about a rotation axis and curved with different curvatures; 32. The position sensor according to claim 2, wherein the coils are arranged at the same rotation angle and on the same plane with respect to the rotation axis of the core. The signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; and a correction circuit that digitally trims the digital signal. 26. The position sensor according to claim 1, wherein the displacement signal output by the circuit is a digital signal having a bit number satisfying a resolution required for position detection. The signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; and a correction circuit that digitally trims the digital signal. 2. The displacement signal output by a circuit, comprising: an output start signal; and a pulse signal output after a time corresponding to the position information after the output start signal is output. 25. The position sensor according to 2, 24 or 25. The signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; and a correction circuit that digitally trims the digital signal. 3. The device according to claim 1, wherein the displacement signal output from the circuit includes an output start signal and a pulse signal output following the output start signal and having a duty ratio according to the position information. , 24 or 25. The signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; and a correction circuit that digitally trims the digital signal. 3. The apparatus according to claim 1, wherein the displacement signal output from the circuit includes an output start signal, and a pulse signal having a pulse width corresponding to the position information and output following the output start signal. , 24 or 25. The signal processing circuit includes: an A / D conversion circuit that converts a peak value of an output voltage of the detection unit into a digital signal; and a correction circuit that digitally trims the digital signal. The said displacement signal which a circuit outputs is comprised from the output start signal and the pulse signal of the number according to the said positional information output following the said output start signal, The characterized by the above-mentioned, 24. The position sensor according to 24 or 25. 26. The position sensor according to claim 1, wherein two detection coils are provided, and the two detection coils share the same core attached to a structural member. 26. The position according to claim 1, wherein two detection coils are provided, and the same constant current circuit outputs a constant current having a predetermined frequency and amplitude to the two detection coils. Sensors. 52. The position sensor according to claim 50, wherein an active circuit of each of the circuits is formed of a monolithic IC.

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