JP4810021B2

JP4810021B2 - Position detection device

Info

Publication number: JP4810021B2
Application number: JP2001263941A
Authority: JP
Inventors: 忠敏後藤; 明男山本
Original assignee: Amiteq Co Ltd
Current assignee: Amiteq Co Ltd
Priority date: 2001-08-31
Filing date: 2001-08-31
Publication date: 2011-11-09
Anticipated expiration: 2021-08-31
Also published as: JP2003075106A

Description

【０００１】
【発明の属する技術分野】
この発明は、交流信号で励磁される検出コイルのインピーダンス変化を利用して位置検出を行う位置検出装置に関し、特に、温度特性の補償性能に優れていて、比較的長い直線位置検出可能範囲に対して検出コイルの配置・サイズをかなり小さくできる、コンパクトな構成の直線位置検出装置に関する。
【０００２】
【従来の技術】
従来より知られた誘導型直線位置検出装置としては差動トランスがある。差動トランスは、１つの１次巻線を１相で励磁し、差動接続された２つの２次巻線の各配置位置において検出対象位置に連動する鉄心コアの直線位置に応じて差動的に変化するリラクタンスを生ぜしめ、その結果として得られる１相の誘導出力交流信号の電圧振幅レベルが鉄心コアの直線位置を示すようにしたものである。この差動トランスにおいては、誘導電圧が差動的に変化するように設けられた２つの２次巻線が設けられた範囲において、該誘導電圧値が対直線位置に関して直線性を示す範囲でしか、直線位置を検出することができないものであり、検出可能範囲の長さは、通常、配置されたコイルの全長よりも短い。従って、長尺の長さ検出には全く適していない。すなわち、検出可能範囲を拡張するには巻線長とコア長を長くするしかなく、自ずと限度があると共に、装置の大型化をもたらす。また、誘導出力信号の電圧振幅レベルは、鉄心コアの直線位置のみならず、温度変化等の周辺環境の影響を受けやすいので、精度に難点がある。特に、可動鉄心コアの鉄損更にはコイル巻心コアの鉄損など検出装置に存在する鉄等の金属の磁気的特性の温度特性が考慮されておらず、これらの鉄損が未補償であることによる検出精度低下を来していた。
【０００３】
これに対して、検出対象直線位置に相関する電気的位相角を持つ交流信号を出力するようにした位相シフトタイプの誘導型直線位置検出装置も知られている。例えば、特開昭４９−１０７７５８号、特開昭５３−１０６０６５号、特開昭５５−１３８９１号、実公平１−２５２８６号などに示されたものがある。この種の従来知られた位相タイプの誘導型直線位置検出装置においては、検出対象位置に連動する可動鉄心コアの直線変位方向に関して互いにずらして配置された例えば２つの１次巻線を互いに電気的位相のずれた２相の交流信号（例えばsin ωｔとcos ωｔ）でそれぞれ励磁し、各１次巻線による２次側誘導信号を合成して１つの２次出力信号を生成するようにしている。励磁用の交流信号に対するこの２次出力信号における電気的位相ずれが、検出対象位置に連動する鉄心コアの直線位置を示している。また、実公平１−２５２８６号に示されたものにおいては、複数の鉄心コアを所定ピッチで断続的に繰り返し設け、１次及び２次巻線が設けられた範囲よりも広い範囲にわたる直線位置検出を可能にしている。しかし、これらのタイプのものも、所定の検出範囲の１サイクルの長さに対応して、複数のコイルを分散配置しなければならないため、コイルの配置長さつまりサイズは、検出範囲の１サイクルの長さと同等としなければならず、コンパクトな構成とすることはできない。また、この場合も、可動鉄心コアの鉄損更にはコイル巻心コアの鉄損など検出装置に存在する鉄等の金属の磁気的特性の温度特性が考慮されておらず、これらの鉄損が未補償であることによる検出精度低下を来していた。
【０００４】
【発明が解決しようとする課題】
本発明は上述の点に鑑みてなされたもので、温度特性の補償性能に優れた、精度のよい位置検出装置を提供しようとするものであり、また、小型かつシンプルな構造を持つと共に、広い範囲にわたって直線位置検出が可能な、温度特性の補償性能に優れた、精度のよい直線位置検出装置を提供しようとするものである。
【０００５】
【課題を解決するための手段】
本発明に係る位置検出装置は、交流信号で励磁される第１及び第２の検出コイルと、検出対象たる直線位置に応じて前記各検出コイルに対して異なるインピーダンス変化をもたらすように配置された磁気応答部材と、前記第１の検出コイルに対して差動接続された第１の補助コイルと、前記第２の検出コイルに対して差動接続された第２の補助コイルとを含み、前第１の検出コイルのインピーダンスと前記第１の補助コイルのインピーダンスの差動値に対応する第１の検出信号を出力し、前記第２の検出コイルのインピーダンスと前記第２の補助コイルのインピーダンスの差動値に対応する第２の検出信号を出力する検出部であって、前記磁気応答部材は、第１及び第２の検出コイルに対向する面積又はギャップが検出対象たる位置に応じて変化するものであり、所定の検出範囲の１サイクルの長さに対応して該面積又はギャップが暫時変化する形状からなり、前記第１及び第２の検出コイルの配置のずれは、前記１サイクルの長さよりも短いものと、前記第１の検出信号と第２の検出信号のレベルの比を演算することで、前記検出対象たる位置に応じた位置検出信号を生成する演算手段とを備えることを特徴とする。
【０００６】
検出コイルのインピーダンスにおいて、可動鉄心コアの鉄損更にはコイル巻心コアの鉄損など検出装置に存在する鉄等の金属の磁気的特性の温度特性に基づく誤差は、係数としての成分を持つ。そこで、検出対象たる位置ｘに応じた第１の検出コイルの出力レベルをＡ（ｘ）、第２の検出コイルの出力レベルをＢ（ｘ）とし、可動鉄心コアの鉄損更にはコイル巻心コアの鉄損など検出装置に存在する鉄等の金属の磁気的特性の温度特性に基づく誤差係数をγとすると、実際の第１の検出コイルの出力レベルはγＡ（ｘ）、第２の検出コイルの出力レベルはγＢ（ｘ）と表すことができる。各検出コイルのインピーダンスに応じた検出信号レベルの比は、「γＡ（ｘ）／γＢ（ｘ）」又は「γＢ（ｘ）／γＡ（ｘ）」であり、比をとることによって誤差係数ｅが相殺され、「Ａ（ｘ）／Ｂ（ｘ）」又は「Ｂ（ｘ）／Ａ（ｘ）」という位置検出信号が生成される。Ａ（ｘ）≠Ｂ（ｘ）であるから、「Ａ（ｘ）／Ｂ（ｘ）」又は「Ｂ（ｘ）／Ａ（ｘ）」は、検出対象たる直線位置ｘに応じた値を示す。検出対象範囲の全長に対して、第１の検出コイルと第２の検出コイルの配置は、特定の配置に制限されないので、第１の検出コイルと第２の検出コイルを比較的近付けて配置しても差し支えない。よって、検出対象範囲の長さに比べて第１及び第２の検出コイルからなるコイルアセンブリをコンパクトに配置することができ、小型かつシンプルな構造でありながら長い範囲にわたる直線位置検出が可能である。
【０００７】
【発明の実施の形態】
以下、添付図面を参照してこの発明の実施の形態を詳細に説明しよう。
図１は本発明の一実施例に係る直線位置検出装置の軸方向断面図である。検出ヘッド１０は、第１の検出コイルＡと第２の検出コイルＢを含み、必須ではないが好ましい実施例として補助コイルＣ及びＤを更に含む。検出ヘッド１０において各コイルの円筒空間内を貫通してロッド１１が設けられる。ロッド１１に対して検出ヘッド１０が相対的に直線変位する。例えば、図示しない座席シートのスライド量を検出する目的で使用されるような場合、ロッド１１が所定配置で固定され、検出ヘッド１０が座席シートのスライドに伴って所定の範囲で直線変位する。
【０００８】
ロッド１１においては、検出対象たる直線位置に応じて各検出コイルＡ，Ｂに対して異なるインピーダンス変化をもたらすように配置された磁気応答部材１２が設けられている。磁気応答部材１２は、鉄のような磁性体又は銅のような反磁性体からなり、例えば径方向断面積が長さ方向つまり軸方向に沿って漸次に変化する細長の円錐のような形状（軸方向断面が図示のような三角形のもの）からなる。ロッド１１の外周はプラスチックのような磁気非応答性（非磁性及び非反磁性）のパイプ１１ａで構成され、該パイプ１１ａ内に細長の円錐形状の磁気応答部材１２が挿入され適宜手段を介して固定されている。
【０００９】
磁気応答部材１２が鉄のような磁性体からなるものとすると、径方向断面積が最大の箇所が検出コイルＡ，Ｂに対応している場合、該検出コイルＡ，Ｂのインピーダンスが最大となり、径方向断面積が最小の箇所が検出コイルＡ，Ｂに対応している場合、該検出コイルＡ，Ｂのインピーダンスが最小となる。図示のように、検出コイルＡとＢの配置は、軸方向つまり直線変位方向に関して幾分ずらされているので、各検出コイルＡ，Ｂと磁気応答部材１２との対応関係は検出対象直線位置ｘに応じて幾分異なるインピーダンス変化をもたらすようになっている。図２は、検出対象直線位置ｘに応じた各検出コイルＡ，Ｂのインピーダンス変化の一例を示したものである。本実施例では各検出コイルＡ，Ｂの物理的及び電気的特性（巻数その他）は等しいものとするが、本発明の実施にあたってはそれに限定されるものではなく、磁気応答部材１２の構成に応じて適宜設計変更してもよい。
【００１０】
補助コイルＣ，Ｄは、検出コイルＡ，Ｂの温度ドリフト特性（純抵抗分の温度ドリフト特性）を補償するものであり、検出対象直線位置ｘつまり磁気応答部材１２の変位には応答しないように、磁性体又は反磁性体からなるシールド材１３によって磁気的にシールドされている。これによって、図２に示すように、補助コイルＣ，Ｄのインピーダンスは、検出対象直線位置ｘつまり磁気応答部材１２の変位に応じて変化せず、一定に保たれる。本実施例では各補助コイルＣ，Ｄの物理的及び電気的特性（巻数その他）は各検出コイルＡ，Ｂのそれと同等とするが、本発明の実施にあたってはそれに限らない。
【００１１】
図３（ａ）は、検出コイルＡ，Ｂと補助コイルＣ，Ｄの結線例を示す図である。検出コイルＡに対して補助コイルＣが逆相直列接続（差動接続）され、検出コイルＢに対して補助コイルＤが逆相直列接続（差動接続）され、適宜の交流源１４が印加される。温度ドリフトによるコイルのインピーダンス変化は、検出コイルＡ，Ｂと補助コイルＣ，Ｄとでは同じように顕れるので、この差動接続によって、温度ドリフトによって検出コイルＡ，Ｂに生じる不所望のインピーダンス変化（純抵抗分のインピーダンス変化）が打ち消される若しくは減少される。
【００１２】
検出対象直線位置ｘに応じて検出コイルＡから得られる出力電圧をＶａ（ｘ）で表わし、検出コイルＢから得られる出力電圧をＶｂ（ｘ）で表わす。図３（ｂ）は、検出コイルＡ，Ｂの出力電圧Ｖａ（ｘ），Ｖｂ（ｘ）を処理する回路の構成例を示す。検出コイルＡ，Ｂの出力電圧Ｖａ（ｘ），Ｖｂ（ｘ）は整流回路１５で直流電圧に変換され、更にアナログ／デジタル変換器１６でデジタル値に変換される。検出コイルＡ，Ｂの出力電圧Ｖａ（ｘ），Ｖｂ（ｘ）に対応するデジタル値ａ（ｘ），ｂ（ｘ）の比が演算手段１７で演算される。
【００１３】
検出コイルＡ，Ｂの磁気回路には、主に、磁気応答部材１２と検出ヘッド１０の鉄心コア１０ａなどが存在し、これらの磁気応答性金属の磁気的特性が温度ドリフト特性（鉄損若しくは銅損）を有し、温度変化に応じて不所望のインピーダンス変化をもたらす。これらの鉄損若しくは銅損によるインピーダンス変化は、検出コイルＡ，Ｂの出力電圧Ｖａ（ｘ），Ｖｂ（ｘ）において、係数成分γとして現われる。すなわち、検出コイルＡ，Ｂの出力電圧Ｖａ（ｘ），Ｖｂ（ｘ）に対応するデジタル値ａ（ｘ），ｂ（ｘ）は、鉄損若しくは銅損によるインピーダンス変化の係数成分γを考慮すると下記のように表わせる。なお、Ａ（ｘ）とＢ（ｘ）は、鉄損若しくは銅損によるインピーダンス変化を除去した、検出対象位置ｘに対応するインピーダンスに応じた値である。
ａ（ｘ）＝γＡ（ｘ）
ｂ（ｘ）＝γＢ（ｘ）
【００１４】
従って、演算手段１７で両検出値ａ（ｘ），ｂ（ｘ）の比を演算することにより、
ａ（ｘ）／ｂ（ｘ）＝γＡ（ｘ）／γＢ（ｘ）＝Ａ（ｘ）／Ｂ（ｘ）
となり、鉄損若しくは銅損によるインピーダンス変化成分γを除去することができる。比の演算における分子・分母は次のように上記とは反対であってもよい。
ｂ（ｘ）／ａ（ｘ）＝γＢ（ｘ）／γＡ（ｘ）＝Ｂ（ｘ）／Ａ（ｘ）
比の演算結果「Ａ（ｘ）／Ｂ（ｘ）」（又はＢ（ｘ）／Ａ（ｘ））は、検出対象位置ｘに相関するため、これをそのまま位置検出データとして使用してよい。すなわち、検出対象直線位置ｘに応じて各検出コイルＡ，Ｂに対して異なるインピーダンス変化をもたらすように磁気応答部材１２が配置されるが故に、Ａ（ｘ）≠Ｂ（ｘ）であり、比の演算結果は、位置ｘを示すデータとして使用できる。
このようにして、検出コイルＡ，Ｂの磁気回路に存在する磁気応答性金属の温度ドリフト特性（鉄損若しくは銅損）を補償することができ、検出精度を向上させることができる。
【００１５】
検出ヘッド１０の構成及び磁気応答部材１２の構成は、上記実施例に限定されることなく、種々に変形してよい。図４はその一例を示し、（ａ）に概略側面図にて示すように、検出ヘッド１０における各コイルＡ，Ｂ，Ｃ，Ｄの一端が、所定間隔のギャップをあけてロッド１１の側面に対向している。図４の（ｂ）に概略平面図にて示すように、ロッド１１の側面には、検出ヘッド１０の各コイルの一端に対向する面積が長さ方向つまり軸方向に沿って漸次に変化する細長の三角形のような形状からなる磁気応答部材１２が配置されている。ロッド１１は、少なくとも磁気応答部材１２を配置した面がフラットであることが好ましいが、それに限らず円柱形状等であってもよい。図４の場合、各検出コイルＡ，Ｂの一端に対向する、ロッド１１の表面の磁気応答部材１２の面積が検出対象位置ｘに応じて変化し、検出対象位置ｘに応じたインピーダンス変化が各検出コイルＡ，Ｂに生じる。
【００１６】
図５は、別の例を示し、検出ヘッド１０における各コイルＡ，Ｂ，Ｃ，Ｄの一端が、ギャップをあけてロッド１１の側面に対向しており、このギャップの距離が検出対象位置ｘに応じて変化する。例えば、ロッド１１の表面において、検出ヘッド１０の各検出コイルＡ，Ｂの一端に対向して配置される磁気応答部材１２の高さが、検出対象位置ｘに応じて変化するように構成されている。これにより、各検出コイルＡ，Ｂの一端とそれに対向するロッド１１の表面の磁気応答部材１２との間のギャップ距離が検出対象位置ｘに応じて変化し、検出対象位置ｘに応じたインピーダンス変化が各検出コイルＡ，Ｂに生じる。
【００１７】
検出コイルＡ，Ｂの磁気回路に存在する磁気応答性金属の温度ドリフト特性（鉄損若しくは銅損）を補償するという観点のみに立てば、上記の各実施例において、補助コイルＣ，Ｄを省略してもよい。
また、上記実施例では、検出対象たる直線位置ｘに応じて前記各検出コイルＡ，Ｂに対して異なるインピーダンス変化をもたらすように配置された磁気応答部材１２は、１個のみであるが、これに限らず、各検出コイルＡ，Ｂ毎に個別に磁気応答部材１２を設けてもよい。例えば、２本のロッド１１の夫々に磁気応答部材１２を設け、各ロッドに対応して夫々検出コイルＡ，Ｂ及び必要に応じて補助コイルＣ，Ｄを設ければよい。
また、上記実施例では、デジタル値ａ（ｘ），ｂ（ｘ）に関して比の演算を行うようにしているが、これに限らず、アナログ値に関する比の演算をアナログ演算手段で行うようにしてもよい。また、演算手段１７は、単体の演算回路に限らず、ＣＰＵ等マイクロコンピュータの演算機能を利用したものであってもよい。
更に、本発明は、直線位置検出装置に限らず、回転位置検出装置にも適用可能である。
【００１８】
【発明の効果】
以上の通り、本発明によれば、検出コイルの磁気回路に存在する磁気応答性金属の温度ドリフト特性（鉄損若しくは銅損）を補償することができ、検出精度を向上させた位置検出装置を提供することができる。また、検出コイルの配置・構成が小型かつシンプルでありながら、広い（長い）範囲にわたって直線位置検出が可能であり、温度特性の補償性能に優れた精度のよい直線位置検出装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施例に係る直線位置検出装置の軸方向断面図。
【図２】同実施例における各コイルのインピーダンス変化の一例を示すグラフ。
【図３】同実施例における各コイルの結線例を示す図、及びコイル出力を処理する回路例を示すブロック図。
【図４】本発明に係る直線位置検出装置の別の実施例を示す概略側面図及び平面図。
【図５】本発明に係る直線位置検出装置の更に別の実施例を示す概略側面図。
【符号の説明】
１０検出ヘッド
１１ロッド
１２磁気応答部材
Ａ，Ｂ検出コイル
Ｃ，Ｄ補助コイル
１７演算手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a position detection device that performs position detection using a change in impedance of a detection coil that is excited by an AC signal, and in particular, has excellent temperature characteristic compensation performance and has a relatively long linear position detection range. The present invention relates to a linear position detection device having a compact configuration that can significantly reduce the arrangement and size of detection coils.
[0002]
[Prior art]
As a conventionally known inductive linear position detecting device, there is a differential transformer. The differential transformer excites one primary winding in one phase, and differentially varies according to the linear position of the iron core that is linked to the detection target position at each of the two secondary windings that are differentially connected. The reluctance which changes continuously is produced, and the voltage amplitude level of the one-phase induction output AC signal obtained as a result indicates the linear position of the iron core. In this differential transformer, in the range in which two secondary windings are provided so that the induced voltage changes in a differential manner, the induced voltage value is only in a range showing linearity with respect to the straight line position. The linear position cannot be detected, and the length of the detectable range is usually shorter than the total length of the arranged coils. Therefore, it is not suitable for long length detection at all. That is, in order to extend the detectable range, the winding length and the core length must be increased, which naturally has limitations and increases the size of the apparatus. Further, the voltage amplitude level of the induction output signal is susceptible to the influence of not only the linear position of the iron core but also the surrounding environment such as a temperature change, and thus there is a problem in accuracy. In particular, the temperature characteristics of the magnetic characteristics of metals such as iron existing in the detection device such as the iron loss of the movable core and the core loss of the coil core are not considered, and these iron losses are uncompensated. The detection accuracy has been reduced due to this.
[0003]
On the other hand, a phase shift type inductive linear position detection device that outputs an alternating current signal having an electrical phase angle correlated with a detection target linear position is also known. For example, there are those disclosed in JP-A-49-107758, JP-A-53-106065, JP-A-55-13891, JP-A-1-25286, and the like. In this type of conventionally known phase type induction type linear position detecting device, for example, two primary windings arranged so as to be shifted from each other with respect to the linear displacement direction of the movable core core linked to the detection target position are electrically connected to each other. Excitation is performed with two-phase AC signals (for example, sin ωt and cos ωt) that are out of phase, and the secondary induction signals from the primary windings are combined to generate one secondary output signal. . The electrical phase shift in the secondary output signal with respect to the excitation AC signal indicates the linear position of the iron core that is linked to the detection target position. Moreover, in what is shown in Japanese Utility Model Publication No. 1-25286, a plurality of iron cores are intermittently repeatedly provided at a predetermined pitch, and linear position detection over a wider range than the range in which primary and secondary windings are provided. Is possible. However, in these types as well, since a plurality of coils must be dispersedly arranged corresponding to the length of one cycle of a predetermined detection range, the arrangement length of the coils, that is, the size is one cycle of the detection range. The length must be equal to the length of and cannot be made compact. Also in this case, the temperature characteristics of the magnetic characteristics of the metal such as iron existing in the detection device such as the core loss of the movable core and the core loss of the coil core are not considered. The detection accuracy was lowered due to the uncompensation.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described points, and is intended to provide an accurate position detection device excellent in temperature characteristic compensation performance, and has a small and simple structure and a wide range. It is an object of the present invention to provide a highly accurate linear position detecting apparatus capable of detecting a linear position over a range and excellent in temperature characteristic compensation performance.
[0005]
[Means for Solving the Problems]
The position detection device according to the present invention is arranged so as to bring different impedance changes to the first and second detection coils excited by an AC signal and the detection coils according to the linear position to be detected. Including a magnetic response member, a first auxiliary coil differentially connected to the first detection coil, and a second auxiliary coil differentially connected to the second detection coil. A first detection signal corresponding to the differential value of the impedance of the first detection coil and the impedance of the first auxiliary coil is output, and the impedance of the second detection coil and the impedance of the second auxiliary coil are output. a detecting unit for outputting a second detection signal corresponding to the differential value, the magnetic response members, the area or gap opposite the first and second detection coils according to the detection target serving position The area or gap has a shape that changes temporarily corresponding to the length of one cycle of a predetermined detection range, and the displacement of the arrangement of the first and second detection coils is the one cycle. And a calculation means for generating a position detection signal corresponding to the position to be detected by calculating a ratio of the levels of the first detection signal and the second detection signal. It is characterized by.
[0006]
In the impedance of the detection coil, an error based on the temperature characteristic of the magnetic characteristic of a metal such as iron existing in the detection device, such as the iron loss of the movable core and the core loss of the coil core, has a component as a coefficient. Therefore, the output level of the first detection coil corresponding to the position x to be detected is A (x), the output level of the second detection coil is B (x), the iron loss of the movable core, and the coil core. When the error coefficient based on the temperature characteristic of the magnetic characteristic of the metal such as iron existing in the detection device such as iron loss of the core is γ, the actual output level of the first detection coil is γA (x), and the second detection The output level of the coil can be expressed as γB (x). The ratio of the detection signal level corresponding to the impedance of each detection coil is “γA (x) / γB (x)” or “γB (x) / γA (x)”, and the error coefficient e is obtained by taking the ratio. The position detection signal is canceled and “A (x) / B (x)” or “B (x) / A (x)” is generated. Since A (x) ≠ B (x), “A (x) / B (x)” or “B (x) / A (x)” indicates a value corresponding to the straight line position x to be detected. . Since the arrangement of the first detection coil and the second detection coil is not limited to a specific arrangement with respect to the entire length of the detection target range, the first detection coil and the second detection coil are arranged relatively close to each other. There is no problem. Therefore, the coil assembly composed of the first and second detection coils can be compactly arranged as compared with the length of the detection target range, and linear position detection over a long range is possible with a small and simple structure. .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view in the axial direction of a linear position detecting apparatus according to an embodiment of the present invention. The detection head 10 includes a first detection coil A and a second detection coil B. Although not essential, the detection head 10 further includes auxiliary coils C and D as a preferred embodiment. In the detection head 10, a rod 11 is provided through the cylindrical space of each coil. The detection head 10 is linearly displaced relative to the rod 11. For example, when used for the purpose of detecting the sliding amount of a seat, not shown, the rod 11 is fixed in a predetermined arrangement, and the detection head 10 is linearly displaced within a predetermined range as the seat is slid.
[0008]
The rod 11 is provided with a magnetic response member 12 arranged so as to cause different impedance changes with respect to the detection coils A and B in accordance with the linear position to be detected. The magnetic response member 12 is made of a magnetic material such as iron or a diamagnetic material such as copper, and has, for example, an elongated cone shape whose radial cross-sectional area gradually changes along the length direction, that is, the axial direction ( The axial cross section is of a triangular shape as shown in the figure. The outer periphery of the rod 11 is composed of a non-magnetic (non-magnetic and non-diamagnetic) pipe 11a such as plastic, and an elongated conical magnetic response member 12 is inserted into the pipe 11a through appropriate means. It is fixed.
[0009]
If the magnetic response member 12 is made of a magnetic material such as iron, the impedance of the detection coils A and B is maximized when the portion having the largest radial cross-sectional area corresponds to the detection coils A and B. When the portion having the smallest radial cross-sectional area corresponds to the detection coils A and B, the impedance of the detection coils A and B is minimum. As shown in the figure, since the arrangement of the detection coils A and B is somewhat shifted with respect to the axial direction, that is, the linear displacement direction, the correspondence relationship between the detection coils A and B and the magnetic response member 12 is the detection target linear position x. Depending on the situation, the impedance changes somewhat differently. FIG. 2 shows an example of impedance changes of the detection coils A and B according to the detection target linear position x. In the present embodiment, the physical and electrical characteristics (number of turns and the like) of the detection coils A and B are assumed to be equal. However, the present invention is not limited to this, and depends on the configuration of the magnetic response member 12. The design may be changed as appropriate.
[0010]
The auxiliary coils C and D compensate the temperature drift characteristics (temperature drift characteristics corresponding to the pure resistance) of the detection coils A and B, and do not respond to the detection target linear position x, that is, the displacement of the magnetic response member 12. , And is shielded magnetically by a shield material 13 made of a magnetic material or a diamagnetic material. Thereby, as shown in FIG. 2, the impedances of the auxiliary coils C and D do not change according to the detection target linear position x, that is, the displacement of the magnetic response member 12, and are kept constant. In this embodiment, the physical and electrical characteristics (number of turns and the like) of the auxiliary coils C and D are the same as those of the detection coils A and B. However, the present invention is not limited to this.
[0011]
FIG. 3A is a diagram illustrating a connection example of the detection coils A and B and the auxiliary coils C and D. The auxiliary coil C is connected in reverse phase in series (differential connection) to the detection coil A, the auxiliary coil D is connected in reverse phase series (differential connection) to the detection coil B, and an appropriate AC source 14 is applied. The Since the change in the impedance of the coil due to temperature drift appears in the same way in the detection coils A and B and the auxiliary coils C and D, this differential connection causes an undesired change in impedance generated in the detection coils A and B due to temperature drift ( (Impedance change of pure resistance) is canceled or reduced.
[0012]
The output voltage obtained from the detection coil A according to the detection target linear position x is represented by Va (x), and the output voltage obtained from the detection coil B is represented by Vb (x). FIG. 3B shows a configuration example of a circuit that processes the output voltages Va (x) and Vb (x) of the detection coils A and B. The output voltages Va (x) and Vb (x) of the detection coils A and B are converted into DC voltages by the rectifier circuit 15 and further converted into digital values by the analog / digital converter 16. The calculation means 17 calculates the ratio of the digital values a (x) and b (x) corresponding to the output voltages Va (x) and Vb (x) of the detection coils A and B.
[0013]
The magnetic circuits of the detection coils A and B mainly include a magnetic response member 12 and an iron core 10a of the detection head 10, and the magnetic characteristics of these magnetic response metals are temperature drift characteristics (iron loss or copper And an undesired impedance change in response to a temperature change. These impedance changes due to iron loss or copper loss appear as coefficient components γ in the output voltages Va (x) and Vb (x) of the detection coils A and B. That is, the digital values a (x) and b (x) corresponding to the output voltages Va (x) and Vb (x) of the detection coils A and B take into account the coefficient component γ of the impedance change due to iron loss or copper loss. It can be expressed as follows. A (x) and B (x) are values corresponding to the impedance corresponding to the detection target position x from which the impedance change due to iron loss or copper loss is removed.
a (x) = γA (x)
b (x) = γB (x)
[0014]
Therefore, by calculating the ratio of both detected values a (x) and b (x) by the calculating means 17,
a (x) / b (x) = γA (x) / γB (x) = A (x) / B (x)
Thus, the impedance change component γ due to iron loss or copper loss can be removed. The numerator and denominator in the ratio calculation may be opposite to the above as follows.
b (x) / a (x) = γB (x) / γA (x) = B (x) / A (x)
Since the ratio calculation result “A (x) / B (x)” (or B (x) / A (x)) is correlated with the detection target position x, it may be used as it is as position detection data. That is, since the magnetic response member 12 is arranged so as to cause different impedance changes for the detection coils A and B depending on the detection target linear position x, A (x) ≠ B (x), and the ratio Can be used as data indicating the position x.
In this way, the temperature drift characteristic (iron loss or copper loss) of the magnetically responsive metal existing in the magnetic circuit of the detection coils A and B can be compensated, and the detection accuracy can be improved.
[0015]
The configuration of the detection head 10 and the configuration of the magnetic response member 12 are not limited to the above embodiment, and may be variously modified. FIG. 4 shows an example, and as shown in a schematic side view in FIG. 4A, one end of each of the coils A, B, C, D in the detection head 10 is formed on the side surface of the rod 11 with a gap of a predetermined interval. Opposite. As shown in the schematic plan view of FIG. 4B, the side surface of the rod 11 is an elongated shape in which the area facing one end of each coil of the detection head 10 gradually changes along the length direction, that is, the axial direction. The magnetic response member 12 having a triangular shape is disposed. The rod 11 is preferably flat at least on the surface on which the magnetic response member 12 is disposed, but is not limited thereto, and may be a cylindrical shape or the like. In the case of FIG. 4, the area of the magnetic response member 12 on the surface of the rod 11 facing one end of each of the detection coils A and B changes according to the detection target position x, and the impedance change according to the detection target position x varies. It occurs in the detection coils A and B.
[0016]
FIG. 5 shows another example. One end of each of the coils A, B, C, and D in the detection head 10 is opposed to the side surface of the rod 11 with a gap, and the distance of this gap is the detection target position x. It changes according to. For example, on the surface of the rod 11, the height of the magnetic response member 12 arranged to face one end of each of the detection coils A and B of the detection head 10 is configured to change according to the detection target position x. Yes. As a result, the gap distance between one end of each of the detection coils A and B and the magnetic response member 12 on the surface of the rod 11 facing the detection coil changes according to the detection target position x, and the impedance changes according to the detection target position x. Occurs in each of the detection coils A and B.
[0017]
From the standpoint of compensating for the temperature drift characteristic (iron loss or copper loss) of the magnetically responsive metal existing in the magnetic circuit of the detection coils A and B, the auxiliary coils C and D are omitted in the above embodiments. May be.
In the above embodiment, only one magnetic response member 12 is provided so as to cause different impedance changes for the detection coils A and B according to the linear position x to be detected. However, the magnetic response member 12 may be provided individually for each of the detection coils A and B. For example, the magnetic response member 12 may be provided for each of the two rods 11, and the detection coils A and B and auxiliary coils C and D may be provided for the respective rods as necessary.
In the above embodiment, the ratio is calculated for the digital values a (x) and b (x). However, the present invention is not limited to this, and the ratio calculation for the analog value is performed by the analog calculation means. Also good. Further, the calculation means 17 is not limited to a single calculation circuit, and may use a calculation function of a microcomputer such as a CPU.
Furthermore, the present invention can be applied not only to a linear position detection device but also to a rotational position detection device.
[0018]
【The invention's effect】
As described above, according to the present invention, it is possible to compensate for the temperature drift characteristic (iron loss or copper loss) of the magnetically responsive metal existing in the magnetic circuit of the detection coil, and to provide a position detection device with improved detection accuracy. Can be provided. In addition, it is possible to provide a highly accurate linear position detection device that is capable of detecting a linear position over a wide (long) range while having a small and simple arrangement and configuration of detection coils, and has excellent temperature characteristic compensation performance. it can.
[Brief description of the drawings]
FIG. 1 is an axial sectional view of a linear position detection apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing an example of impedance change of each coil in the same embodiment.
FIG. 3 is a diagram showing a connection example of each coil in the embodiment, and a block diagram showing a circuit example for processing the coil output.
FIGS. 4A and 4B are a schematic side view and a plan view showing another embodiment of the linear position detection apparatus according to the present invention. FIGS.
FIG. 5 is a schematic side view showing still another embodiment of the linear position detecting apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Detection head 11 Rod 12 Magnetic response member A, B Detection coil C, D Auxiliary coil 17 Calculation means

Claims

First and second detection coils excited by an AC signal, a magnetic response member arranged to cause a different impedance change for each detection coil according to a linear position to be detected , and the first A first auxiliary coil differentially connected to the detection coil; and a second auxiliary coil differentially connected to the second detection coil, wherein the impedance of the first detection coil and the A first detection signal corresponding to the differential value of the impedance of the first auxiliary coil is output, and a second value corresponding to the differential value of the impedance of the second detection coil and the impedance of the second auxiliary coil is output. a detecting unit for outputting a detection signal, the magnetism-responsive member is one area or a gap facing the first and second detection coil changes in response to the detection target serving position, a predetermined test Range corresponding to the length of one cycle consists shape the area or gap varies interim, the deviation of the arrangement of the first and second detection coils, and shorter than a length of the one cycle,
A position detection apparatus comprising: a calculation means for generating a position detection signal corresponding to the position to be detected by calculating a ratio of the levels of the first detection signal and the second detection signal .