JP3806358B2 - Inductive position transducer - Google Patents

Description

となる。ここで、Ｓλ１はλ１周期信号、Ｓλ２はλ２クロストーク信号、Ｓ（ｎ）はｎ番目の受信コイルの検出信号、αはクロストーク信号の混合率である。
【００２３】
１からｎまでの受信コイルの検出信号を加算すると、その和Ｓは
【数５】

となる。例えばＮ＝４、ｍ＝０とすると、和Ｓは、
【数６】

となる。α項目内については、
【数７】

となり、全てキャンセルされる。結局、和Ｓとしての検出信号は
【数８】

となって、λ２を含まないλ１のみの信号となる。
【００２４】
【発明の実施の形態】
以下、図面に基づき本発明の実施形態について説明する。
【００２５】
＜第１実施形態＞
図３には、本実施形態における２波長型誘導型位置トランスデューサのグリッド側受信コイル３０の第１相（０度位相）の構成が示されている。なお、グリッド側の送信コイルの構成、及びスケール側の受信コイル及び送信コイルの構成は従来と同様であるためその説明は省略する。
【００２６】
図３に示されるように、本実施形態の第１層の受信コイル３０−０は、従来のように１個の受信コイルで検出するのではなく、複数個（図では３個）の受信コイル（受信コイルアレイ）で構成される。３個の受信コイルはそれぞれ波長λ２に対して０度、１２０度、２４０度に相当する距離だけ離間させて測定方向に配置されている。これら３個の受信コイル３０−０−０、３０−０−１２０、３０−０−２４０からの検出信号は加算器５０に出力される。ちなみに、符号「３０−Ｘ−Ｙ」の２番目の数字Ｘはλ１に対する位相を示しており、３番目の数字Ｙはλ１の各相におけるλ２に対する位相を表している。加算器５０では、これら３つの検出信号の和を演算して検出信号として出力する。第２相コイル３０−１２０、第３相コイル３０−２４０についても第１相コイル３０−０と同様であり、それぞれ３個の受信コイルからなる受信コイルアレイであり、３個の受信コイルは互いにλ２に対して０度、１２０度、２４０度の位置に配置され、各受信コイルからの検出信号は加算器５０で加算される。
【００２７】
図４には、第１相の受信コイル３０−０を構成する受信コイル３０−０−０、３０−０−１２０、３０−０−２４０の配置位置が示されている。受信コイル３０−０には、上述したように波長λ１検出信号の他、λ２クロストーク信号が混入している。３個の受信コイル３０−０−０、３０−０−１２０、３０−０−２４０は、λ２クロストーク信号に対してそれぞれ０度、１２０度、２４０度の位置に配置されており、それぞれ０度、１２０度、２４０度の位相信号を検出する。
【００２８】
一般式Ｐ＝｛（ｎ−１）／Ｎ＋ｍ｝・λ２において、Ｎ＝３、ｍ＝０であり、受信コイル３０−０−０はＰ（１）＝０に配置され、受信コイル３０−０−１２０はＰ（２）＝λ２／３に配置され、受信コイル３０−０−２４０はＰ（３）＝２λ２／３に配置されていることに相当する。これら３個の受信コイルからの検出信号の和を加算器５０で算出することで、λ２クロストーク成分はキャンセルされ、λ１の検出信号のみが加算器５０から出力される。第２相受信コイル３０−１２０及び第３相受信コイル３０−２４０も同様であり、加算器５０で加算することでλ２クロストーク成分が除去される。
【００２９】
図５には、受信コイル３０を３相分グリッドに配置した場合の構成が示されている。なお、波長λ１＝９．０ｍｍ、波長λ２＝６．０ｍｍと想定している。図５（ａ）は、３相のうちの第１相（０度位相）を検出する受信コイル３０−０の構成である。送信コイル２０は従来と同様にスケール側の受信コイル１２に対向配置され、受信コイル３０−０はスケール側の送信コイル１０に対向配置される。受信コイル３０−０は、３個の受信コイル３０−０−０、３０−０−１２０、３０−０−２４０から構成され、各受信コイルは互いにλ２／３＝２．０ｍｍだけ測定方向に離間して配置される。
【００３０】
図５（ｂ）は、３相のうちの第２相（１２０度位相）を検出する受信コイル３−１２０の構成である。受信コイル３−１２０も３個の受信コイル３０−１２０−０、３０−１２０−１２０、３０−１２０−２４０から構成され、３個の受信コイルは互いにλ２／３＝２．０ｍｍだけ離間して配置される。また、この受信コイル３０−１２０は、第１相の受信コイル３０−０に対してλ１／３＝３．０ｍｍだけ測定方向にシフトして配置される。
【００３１】
図５（ｃ）は、３相のうちの第３相（２４０度位相）を検出する受信コイル３０−２４０の構成が示されている。受信コイル３０−２４０も３個の受信コイル３０−２４０−０、３０−２４０−１２０、３０−２４０−２４０から構成され、各受信コイルはλ２／３＝２．０ｍｍだけ測定方向に離間して配置される。また、受信コイル３０−２４０は、第１相の受信コイル３０−０に対し、２λ１／３＝６．０ｍｍだけシフトして配置される。
【００３２】
図５（ｄ）には、第１相、第２相及び第３相の受信コイルをグリッド上に配置した構成が示されている。各相の受信コイルは互いに干渉なく配置される。
【００３３】
このような受信コイル構造により、λ２クロストーク成分が除去されたλ１の３相の信号が検出されることとなり、３相信号を合成してλ１検出信号が得られる。また、送信コイル２２を駆動することで受信コイル３２からλ２検出信号が得られるから、これらの検出信号を用いて絶対位置が検出される。
【００３４】
＜第２実施形態＞
第１実施形態では、１つの相を構成する受信コイルアレイ内の各受信コイルを互いにλ２／３だけ離間して配置する場合を示したが、各受信コイルをλ２／Ｎ＋ｍλ２（Ｎは２以上の整数、ｍは０以上の整数）だけ離間して配置することも可能である。第１実施形態は、上述したようにＮ＝３、ｍ＝０の場合に相当するが、本実施形態ではＮ＝３、ｍ＝１の場合について説明する。
【００３５】
この場合、１つの相を構成する受信コイルアレイは、互いにλ２／３＋λ２だけ離間して配置される。例えば第１相受信コイル３０−０の場合、図６に示されるように受信コイル３０−０−１２０は受信コイル３０−０−０に対してλ２／３＋λ２だけ離間した位置に配置され、受信コイル３０−０−２４０は受信コイル３０−０−０に対して２λ２／３＋λ２だけ離間した位置に配置される。一般式Ｐ＝｛（ｎ−１）／Ｎ＋ｍ｝・λ２において、受信コイル３０−０−０はＰ（１）＝０に配置され、受信コイル３０−０−１２０はＰ（２）＝λ２／３＋λ２に配置され、受信コイル３０−０−２４０はＰ（３）＝２λ２／３＋λ２に配置されることに相当する。各受信コイルからの検出信号に含まれるλ２クロストーク成分はそれぞれ０度、１２０度、２４０度であり、これらの和を演算することでλ２クロストーク成分はキャンセルされる。具体的には、λ２＝６．０ｍｍの場合、各受信コイルは２．０ｍｍ＋６．０ｍｍ＝８．０ｍｍだけ離間して配置されることとなる。
【００３６】
図７には、受信コイルの具体的な配置が示されている。図７（ａ）は第１相（０度位相）を検出する受信コイル３０−０の構成である。受信コイル３０−０は、互いに８．０ｍｍだけ測定方向に離間した３個の受信コイル３０−０−０、３０−０−１２０、３０−０−２４０から構成される。
【００３７】
図７（ｂ）は第２相（１２０度位相）を検出する受信コイル３０−１２０の構成である。第２相の受信コイル３０−１２０も、互いに８．０ｍｍだけ測定方向に離間して配置された３個の受信コイル３０−１２０−０、３０−１２０−１２０、３０−１２０−２４０から構成される。第２相の受信コイル３０−１２０は、第１相の受信コイル３０−０に対してλ１／３＝３．０ｍｍだけ測定方向にシフトして配置される。
【００３８】
図７（ｃ）は、第３相（２４０度位相）を検出する受信コイルの３０−２４０の構成である。第３相受信コイル３０−２４０も、互いに８．０ｍｍだけ測定方向に離間した３個の受信コイル３０−２４０−０、３０−２４０−１２０、３０−２４０−２４０から構成される。第３相受信コイル３０−２４０は、第１相の受信コイル３０−０に対し、２λ１／３＝６．０ｍｍだけ測定方向にシフトして配置される。
【００３９】
図７（ｄ）は、これら第１相、第２相及び第３相の受信コイルをグリッド上に配置した構成である。
【００４０】
＜第３実施形態＞
第１及び第２実施形態では、ある１つの相を構成する受信コイルアレイ内の各受信コイルは等間隔に配置されているが、λ２クロストーク成分をキャンセルするためには必ずしも等間隔である必要はない。例えば、第１相受信コイル３０−０において、受信コイルアレイの各受信コイルを（ｎ−１）λ２／Ｎに従い等間隔に配置するのではなく、受信コイルアレイのある受信コイルは（ｎ−１）λ２／Ｎで配置し、他の受信コイルは（ｎ−１）λ２／Ｎ＋λ２で配置することもできる。例えば、Ｎ＝３とした場合、ある受信コイル（ｎ＝２に対応するコイル）はλ２／３の間隔で配置され、同一受信コイルアレイ内の他の受信コイル（ｎ＝３に対応するコイル）は２λ２／３＋λ２の間隔で配置される等である。
【００４１】
図８には、このように１つの相を構成する受信コイルアレイ内の各受信コイルを非等間隔で配置する場合が例示されている。図８（ａ）は第１相（０度位相）を検出する受信コイル３０−０の構成である。受信コイル３０−０を構成する第１番目の受信コイル（ｎ＝１）は任意の位置に配置される。次に、受信コイル３０−０を構成する第２番目の受信コイル（ｎ＝２）は、第１番目の受信コイルに対し、λ２／３＋λ２＝８．０ｍｍだけ離間して配置される。受信コイル３０−０を構成する第３番目の受信コイル（ｎ＝３）は、第１番目の受信コイルに対し２λ２／３＝４．０ｍｍだけ離間して配置される。したがって、第３番目の受信コイルは、第１番目の受信コイルと第２番目の受信コイルの間に配置されることになる。
【００４２】
図８（ｂ）は、第２相（１２０度位相）を検出する受信コイル３０−１２０の構成である。第２相受信コイル３０−１２０においても、受信コイルアレイの各受信コイルを非等間隔で配置する。すなわち、第１番目の受信コイルは、第１相の受信コイル３０−０の第１番目の受信コイルに対してλ１／３＝３．０ｍｍだけ測定方向にシフトして配置される。受信コイル３０−１２０を構成する第２番目の受信コイルは、第２相の受信コイル３０−１２０を構成する第１番目の受信コイルに対して８．０ｍｍだけ離間して配置される。第３番目の受信コイルは、第１番目の受信コイルに対し、４．０ｍｍだけ離間して配置される。
【００４３】
図８（ｃ）は、第３相（２４０度位相）を検出する受信コイル３０−２４０の構成である。第１番目の受信コイルは、第１相の受信コイル３０−０の第１番目の受信コイルに対して２λ１／３＝６．０ｍｍだけ測定方向にシフトして配置される。また、第２番目の受信コイルは、第１番目の受信コイルに対して８．０ｍｍだけ離間して配置される。第３番目の受信コイルは、第１番目の受信コイルに対して４．０ｍｍだけ離間して配置される。
【００４４】
図８（ｄ）は、第１相、第２相及び第３相の受信コイルをグリッド上に配置した構成である。この場合、第１相、第２相及び第３相の受信コイルは互いに混在することとなる。
【００４５】
第１相、第２相及び第３相の受信コイルをグリッド上に配置する場合、１つの相を構成する受信コイルアレイの間隔によっては各相の受信コイルアレイが互いに位置的に干渉する場合もあり得る。各相を構成する受信コイルの間隔を適宜調整することで互いに干渉なく配置することが必要である。
【００４６】
以上、本発明の実施形態について説明したが、本発明はこれに限定されるものではなく種々の変更が可能である。
【００４７】
例えば、上述した実施形態においては、λ１及びλ２の２波長型位置トランスデューサについて説明したが、３波長型位置トランスデューサにおいても同様に受信コイル３０を配置することが可能である。すなわち、図９に示されるように、スケール側に波長λ１の送信コイル１０、波長λ２の受信コイル１２及び波長λ３の受信コイル１４を備え、λ１、λ２、λ３で絶対位置を検出する場合、波長λ１の送信コイル１０に対向配置されたグリッド側の受信コイル３０には、λ１検出信号の他、λ２クロストーク信号及びλ３クロストーク信号が混入することとなる。なお、３波長型ではλ１、λ２、λ３により
【数９】
λｆｉｎｅ＝λ１
λｍｅｄ＝λ２λ１／（λ２−λ１）＝ｎλｆｉｎｅ
λｃｏａ＝λ３λ２／（λ３−λ２）＝ｍλｍｅｄ
を定義してλｃｏａ、λｍｅｄ、λｆｉｎｅで絶対位置を検出できるが、λ１検出信号にλ２クロストーク成分及びλ３クロストーク成分が混入するとλｆｉｎｅの精度が低下する。
【００４８】
そこで、このような場合、λ２クロストーク成分をキャンセルできる受信コイルアレイをさらにλ３クロストーク成分がキャンセルされるように複数個離間して配置すればよい。具体的には、第１相の受信コイル３０−０に着目すると、λ２／Ｎの間隔でＮ個の受信コイルを配置し、これらの検出信号を加算することでλ２クロストーク成分をキャンセルする。その検出信号は、λ１検出信号とλ３クロストーク成分が混入した信号となる。そして、λ３クロストーク信号をキャンセルする受信コイルアレイを、さらにλ３／Ｍの間隔で測定方向に離間配置する。離間配置されたＭ個の受信コイルアレイの検出信号を加算することでλ３クロストーク成分をキャンセルできる。
【００４９】
図１０には、λ２クロストーク成分及びλ３クロストーク成分を除去する受信コイルの１つの相の概念構成が示されている。３個の受信コイルからなる受信コイルアレイは互いにλ２／３だけ離間して配置され、３個の受信コイルアレイは互いにλ３／３だけ離間して配置される。各受信コイルアレイ内の受信コイルの検出信号は加算器５０ａ、５０ｂ、５０ｃでそれぞれ加算され、λ２クロストーク成分が除去された信号として加算器５０ｄに供給される。加算器５０ｄでは、これらの検出信号をさらに加算し、λ３クロストーク成分が除去されたλ１周期の検出信号を出力する。
【００５０】
もちろん、２波長型あるいは３波長型の位置トランスデューサに限定されるものではなく、それ以上の波長を有する位置トランスデューサにも同様に適用できる。
【００５１】
また、本実施形態では、２波長型位置トランスデューサにおいて、Ｎ＝３として各相の受信コイルを３個の受信コイルで構成しているが、Ｎ＝２として各相の受信コイルを互いに１８０度の位相差をなす２個の受信コイルで構成してもよく、あるいはＮ＝４として各相の受信コイルを互いに９０度の位相差をなす４個の受信コイルで構成することもできる。
【００５２】
さらに、本実施形態では、２波長型位置トランスデューサにおいて、λ１検出信号に混入するλ２クロストーク成分を除去しているが、同様にしてλ２検出信号に混入するλ１クロストーク成分を除去することも可能である。図１１の構成で説明したように、送信コイル２０を駆動した後に、送信コイル２２を駆動して受信コイル３２で周期λ２の信号を検出するが、この際に送信コイル１０に誘導電流が生じるため、この送信コイル１０からの漏洩磁界によりλ２検出信号にはλ１クロストーク成分が混入することになる。この場合、受信コイル３２の１つの相を複数の受信コイルで構成し、各受信コイルをＰ＝｛（ｎ−１）／Ｎ＋ｍ｝・λ１に従って離間配置し、各受信コイルからの検出信号を加算することでλ１クロストーク成分を除去できる。
【００５３】
【発明の効果】
以上説明したように、本発明によれば漏洩磁界によるクロストーク信号をキャンセルし、高精度の位置検出が可能となる。
【図面の簡単な説明】
【図１】 本発明の受信コイル配置説明図である。
【図２】 本発明の検出信号説明図である。
【図３】 実施形態に係る第１相の受信コイル説明図である。
【図４】 実施形態に係る第１相受信コイルの配置説明図である。
【図５】 実施形態に係る３相受信コイル配置説明図である。
【図６】 他の実施形態に係る第１相受信コイルの配置説明図である。
【図７】 他の実施形態に係る３相受信コイル配置説明図である。
【図８】 さらに他の実施形態に係る３相受信コイルの配置説明図である。
【図９】 ３波長型位置トランスデューサのクロストーク説明図である。
【図１０】 ３波長型位置トランスデューサの受信コイル配置説明図である。
【図１１】 従来の２波長型位置トランスデューサの配置説明図である。
【図１２】 従来の２波長型位置トランスデューサの３相受信コイル配置説明図である。
【図１３】 従来の２波長型位置トランスデューサのクロストーク説明図である。
【符号の説明】
１０ 送信コイル（波長λ１）、１２ 送信コイル（波長λ２）、２０ 送信コイル（グリッド側）、３０ 受信コイル（グリッド側）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inductive position transducer, and more particularly to removal of a crosstalk component contained in a detection signal.
[0002]
[Prior art]
Conventionally, a position transducer (or magnetic encoder) using an induced current is known. The position transducer includes a read head and a scale that are opposed to each other. A transmission coil and a reception coil are provided on the read head side, and a reception coil and a transmission coil are also provided on the scale side. A magnetic field is generated from the transmitting coil on the read head side, and an induced current is generated in the receiving coil on the scale side by this magnetic field. The transmission coil and the reception coil on the scale side are connected, and a magnetic field is generated from the transmission coil by the induced current generated. The receiving coil on the reading head side detects the magnetic field generated from the transmitting coil on the scale side and outputs it as a detection signal. Since the phase of the detection signal varies depending on the positional relationship between the read head and the scale, the position from the reference point on the scale of the read head, that is, the absolute position can be detected based on the phase of the detection signal.
[0003]
Usually, on the scale side, transmission coils having different pitches (wavelengths) λ1 and λ2 are arranged side by side in the width direction of the scale, and the absolute position is detected based on the phase difference between λ1 and λ2. In other words, since the phase of the detection signal is the same for each λ1 with only the λ1 coil, the absolute position exceeding λ1 cannot be uniquely determined. Therefore, based on the phase difference between λ1 and λ2, the absolute position is detected by detecting the number of periods of λ1. If λ1 is λfine, one period of the phase difference between λ1 and λ2 is defined as λmed, and the number of λfines included in λmed is n, the following equation holds.
[0004]
[Expression 1]
λmed = n · λfine (1)
n is a value determined by the wavelength difference between λ1 and λ2, and as the wavelength difference is smaller, n increases and the length (measurement range) at which the absolute position can be detected increases. By determining which of the ranges obtained by dividing the phase difference between λ1 and λ2 into 360 degrees divided by n, the number of periods of λ1 can be determined, and (period of λ1) × (number of periods of λ1) The absolute position is calculated by + (the phase of λ1).
[0005]
Note that λmed is specifically:
[Expression 2]
λmed = λ2λ1 / (λ2-λ1) (2)
Can be defined.
[0006]
FIG. 11 shows the configuration of such a two-wavelength inductive position transducer. FIG. 11A shows the configuration on the scale side, and FIG. 11B shows the configuration on the grid side. In an actual apparatus, the scale and the grid are arranged to face each other, but these are shown side by side on a plane.
[0007]
On the scale side, a transmission coil 10 having a pitch (wavelength) λ1 and a reception coil 12 having a wavelength λ2 are provided. The reception coil 12 is arranged on both sides of the transmission coil 10 (with respect to the width direction of the scale) so as to sandwich the transmission coil 10. The transmission coil 10 and the reception coil 12 are connected to each other to form a loop. On the other hand, the transmission coil 20 is provided on the grid side so as to face the reception coil 12, and the reception coil 30 is provided so as to face the transmission coil 10. On the grid side, as indicated by a broken line in the figure, a transmission coil 22 disposed to face the transmission coil 10 and a reception coil 32 disposed to face the reception coil 12 are also provided. The transmission coil 20 and the reception coil 30 are for detecting λ1, and the transmission coil 22 and the reception coil 32 are for detecting λ2.
[0008]
When a drive current is supplied to the transmission coil 20 of the grid, a magnetic field is generated from the transmission coil 20 toward the reception coil 12, and an induced current is generated in the reception coil 12. The induced current is supplied to the transmission coil 10. The transmission coil 10 generates a magnetic field by the induced current, detects this magnetic field by the reception coil 30 disposed opposite to the transmission coil 10, and outputs it as a detection signal. The period of the detection signal is basically the wavelength λ1 of the transmission coil 10.
[0009]
When a drive current is supplied to the transmission coil 22 of the grid, a magnetic field is generated from the transmission coil 22 toward the transmission coil 10, and an induced current is generated in the transmission coil 10. The induced current is supplied to the receiving coil 12. The receiving coil 12 generates a magnetic field by this induced current, detects this magnetic field by the receiving coil 32 arranged opposite to the receiving coil 12, and outputs it as a detection signal. That is, in this case, the transmission coil 10 functions as a reception coil, and the reception coil 12 functions as a transmission coil. The period of the detection signal is basically the wavelength λ2 of the receiving coil 12. The absolute value is detected from the λ1 detection signal and the λ2 detection signal according to the equations (1) and (2).
[0010]
In order to detect the phase of the wavelength λ1, a plurality of grid-side receiving coils 30 are actually arranged. For example, when detecting in three phases, three receiving coils are formed that are shifted from each other in the measurement direction by λ1 / 3.
[0011]
FIG. 12 shows the configuration on the scale and grid side in the case of detection with three phases. For convenience of explanation, only the transmission coil 20 and the reception coil 30 for λ1 are shown as coils on the grid side. FIG. 12A shows the configuration on the scale side, which is the same as FIG. On the other hand, FIG. 12B shows a configuration on the grid side, and the receiving coil 30 detects the first coil (0 degree phase) and the second coil (120 degree phase). The receiving coil 30-120 and the receiving coil 30-240 that detects the third phase (240-degree phase) are included. When λ1 = 9.0 mm, the second phase coil 30-120 is arranged by shifting the first phase coil 30-0 by 3.0 mm in the measurement direction, and the third phase coil 30-240 is the first phase coil 30. It is arranged by shifting −0 by 6.0 mm in the measurement direction. The phase of λ1 is calculated by combining these three-phase detection signals.
[0012]
[Problems to be solved by the invention]
However, in order to obtain the λ1 detection signal, the grid-side transmission coil 20 is driven to generate an induced current in the reception coil 12. Therefore, in addition to the magnetic field from the transmission coil 10, a magnetic field (leakage magnetic field) is also generated from the reception coil 12. And the leakage magnetic field is detected by the receiving coil 30. When a leakage magnetic field is detected by the reception coil 30, the signal from the reception coil 30 includes not only the original λ1 detection signal but also the λ2 detection signal that is the wavelength of the reception coil 12 (crosstalk of the λ2 detection signal).
[0013]
FIG. 13 schematically shows the generation of such a λ2 crosstalk signal. Originally, only the magnetic field from the transmission coil 10 may be detected by the reception coil 30, but the leakage magnetic field from the reception coil 12 having the wavelength λ2 acts on the reception coil 30 as indicated by the arrow in the figure. . The presence of such a λ2 crosstalk signal becomes an error of the λ1 detection signal, which causes a decrease in position detection accuracy. In particular, the λ1 detection signal defines λfine, and the influence of errors on position accuracy is large.
[0014]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an inductive position transducer capable of detecting a position with high accuracy by removing the λ2 crosstalk signal.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a reading head having a magnetic field generating means and a magnetic field detecting means, a receiving coil disposed opposite to the reading head and generating an induced current by a magnetic field from the magnetic field generating means, A detection signal obtained by detecting a magnetic field from the transmission coil of the scale by the magnetic field detection means, and a magnetic coupling coil comprising a transmission coil for generating a magnetic field by an induced current. An inductive position transducer for detecting the position of the read head relative to the scale based on the phase of the magnetic coupling coil, wherein the transmission coil of the magnetic coupling coil is formed with a pitch λ1, and the reception coil of the magnetic coupling coil is Formed at a pitch λ2 different from λ1, the magnetic field detecting means is determined based on the pitch λ2. It is spaced in the measuring direction at intervals, characterized in that to cancel the leakage magnetic field components from the receiving coil by calculating the sum of the detection signals from the spaced arranged magnetic field detector.
[0016]
Here, the magnetic field detecting means includes
[Equation 3]
P = {(n−1) / N + m} · λ2
However, n = 1 to N
N is an integer greater than or equal to 2
m is an integer greater than or equal to 0
It is preferable that they are spaced apart at a position determined by
[0017]
Further, it is preferable that a plurality of sets are shifted in the measurement direction by λ1 / L (L is an integer of 2 or more), with the magnetic field detection means arranged at a distance as one set.
[0018]
In the transducer according to the aspect of the invention, the receiving coil of the magnetic coupling coil may be formed with a pitch λ3 different from the λ1 and λ2, and the magnetic field detecting unit may be measured at intervals determined based on the pitch λ2 and the pitch λ3. It is preferable to cancel the leakage magnetic field component from the receiving coil having the pitch λ2 and the pitch λ3 by calculating the sum of the detection signals from the magnetic field detecting means arranged at a distance.
[0019]
In the present invention, a plurality of magnetic field detecting means are arranged so as to cancel the λ2 crosstalk component, and only the λ1 detection signal is extracted by calculating the sum thereof.
[0020]
FIG. 1 shows the λ1 signal detected by the magnetic field detection means of the read head (grid) and the λ2 crosstalk signal mixed in the λ1 signal. When a plurality of, for example, four magnetic field detection means are arranged at positions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees with respect to λ2, the signals from these magnetic field detection means include the λ1 signal, respectively. A signal of 0 degrees, 90 degrees, 180 degrees, and 270 degrees of λ2 is mixed. Therefore, by adding these, as shown in FIG. 2, the λ2 crosstalk signal is canceled, and only the signal having the period λ1 can be extracted. The signal having the period λ1 is different in phase and amplitude from the original λ1 detection signal, but may be processed as an offset.
[0021]
In order to cancel the λ2 crosstalk component by a plurality of magnetic field detecting means, generally, P = {(n−1) / N + m} · λ2 (where n = 1 to N, N is an integer of 2 or more, m Is an integer greater than or equal to 0). Assuming that N = 4 and m = 0, the magnetic field detecting means is positioned at P (1) = 0, P (2) = λ2 / 4, P (3) = 2λ2 / 4, P (3) = 3λ2 / 4. Respectively. If m = 1, the positions are P (1) = λ2, P (2) = λ2 / 4 + λ2, P (3) = 2λ2 / 4, and P (4) = 3λ2 / 4.
[0022]
It will be apparent from the following formula that the λ2 crosstalk component is removed by the present invention. That is, each periodic signal and detection signal S (n) at position x are
[Expression 4]

It becomes. Here, Sλ1 is a λ1 periodic signal, Sλ2 is a λ2 crosstalk signal, S (n) is a detection signal of the nth receiving coil, and α is a mixing ratio of the crosstalk signal.
[0023]
When the detection signals of the receiving coils from 1 to n are added, the sum S is
[Equation 5]

It becomes. For example, if N = 4 and m = 0, the sum S is
[Formula 6]

It becomes. For the α item,
[Expression 7]

And all are canceled. After all, the detection signal as sum S is
[Equation 8]

Thus, only a signal λ1 that does not include λ2 is obtained.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
<First Embodiment>
FIG. 3 shows the configuration of the first phase (0-degree phase) of the grid-side receiving coil 30 of the two-wavelength inductive position transducer according to this embodiment. Note that the configuration of the grid-side transmission coil and the configuration of the scale-side reception coil and transmission coil are the same as those in the prior art, and the description thereof is omitted.
[0026]
As shown in FIG. 3, the first-layer receiving coil 30-0 of this embodiment is not detected by one receiving coil as in the prior art, but a plurality (three in the figure) of receiving coils. (Receiver coil array). The three receiving coils are arranged in the measurement direction at a distance corresponding to 0 degrees, 120 degrees, and 240 degrees with respect to the wavelength λ2. Detection signals from these three reception coils 30-0-0, 30-0-120, and 30-0-240 are output to the adder 50. Incidentally, the second number X of the code “30-XY” indicates the phase with respect to λ1, and the third number Y indicates the phase with respect to λ2 in each phase of λ1. The adder 50 calculates the sum of these three detection signals and outputs it as a detection signal. The second-phase coil 30-120 and the third-phase coil 30-240 are the same as the first-phase coil 30-0, and each is a receiving coil array composed of three receiving coils. The three receiving coils are mutually connected. Arranged at 0 °, 120 °, and 240 ° with respect to λ 2, the detection signal from each receiving coil is added by the adder 50.
[0027]
FIG. 4 shows the arrangement positions of the receiving coils 30-0-0, 30-0-120, and 30-0-240 constituting the first phase receiving coil 30-0. As described above, the receiving coil 30-0 is mixed with the λ2 crosstalk signal in addition to the wavelength λ1 detection signal. The three receiving coils 30-0-0, 30-0-120, and 30-0-240 are arranged at 0 degree, 120 degrees, and 240 degrees, respectively, with respect to the λ2 crosstalk signal. Phase signals of degrees, 120 degrees, and 240 degrees are detected.
[0028]
In the general formula P = {(n−1) / N + m} · λ2, N = 3 and m = 0, the receiving coil 30-0-0 is arranged at P (1) = 0, and the receiving coil 30-0 This corresponds to -120 being arranged at P (2) = λ2 / 3 and the receiving coil 30-0-240 being arranged at P (3) = 2λ2 / 3. By calculating the sum of the detection signals from these three receiving coils by the adder 50, the λ2 crosstalk component is canceled and only the detection signal of λ1 is output from the adder 50. The same applies to the second-phase receiving coil 30-120 and the third-phase receiving coil 30-240, and addition by the adder 50 removes the λ2 crosstalk component.
[0029]
FIG. 5 shows a configuration when the receiving coil 30 is arranged on a three-phase grid. It is assumed that the wavelength λ1 = 9.0 mm and the wavelength λ2 = 6.0 mm. FIG. 5A shows the configuration of the receiving coil 30-0 that detects the first phase (0-degree phase) of the three phases. The transmission coil 20 is disposed opposite to the scale-side reception coil 12 and the reception coil 30-0 is disposed opposite to the scale-side transmission coil 10 as in the conventional case. The receiving coil 30-0 is composed of three receiving coils 30-0-0, 30-0-120, 30-0-240, and each receiving coil is separated from each other in the measurement direction by λ2 / 3 = 2.0 mm. Arranged.
[0030]
FIG. 5B shows a configuration of the receiving coil 3-120 that detects the second phase (120-degree phase) of the three phases. The reception coil 3-120 is also composed of three reception coils 30-120-0, 30-120-120, 30-120-240, and the three reception coils are separated from each other by λ2 / 3 = 2.0 mm. Be placed. Further, the receiving coil 30-120 is arranged to be shifted in the measurement direction by λ1 / 3 = 3.0 mm with respect to the first-phase receiving coil 30-0.
[0031]
FIG. 5C shows the configuration of the receiving coil 30-240 that detects the third phase (240-degree phase) of the three phases. The receiving coil 30-240 is also composed of three receiving coils 30-240-0, 30-240-120, 30-240-240, and each receiving coil is separated in the measurement direction by λ2 / 3 = 2.0 mm. Be placed. The receiving coil 30-240 is arranged with a shift of 2λ1 / 3 = 6.0 mm with respect to the first-phase receiving coil 30-0.
[0032]
FIG. 5D shows a configuration in which first-phase, second-phase, and third-phase receiving coils are arranged on a grid. The receiving coils for each phase are arranged without interference.
[0033]
With such a receiving coil structure, a λ1 three-phase signal from which the λ2 crosstalk component is removed is detected, and a λ1 detection signal is obtained by synthesizing the three-phase signals. Further, since the λ2 detection signal is obtained from the reception coil 32 by driving the transmission coil 22, the absolute position is detected using these detection signals.
[0034]
Second Embodiment
In the first embodiment, the case where the receiving coils in the receiving coil array constituting one phase are arranged apart from each other by λ2 / 3 is shown. However, each receiving coil is λ2 / N + mλ2 (N is 2 or more). It is also possible to arrange them separated by an integer (m is an integer of 0 or more). The first embodiment corresponds to the case where N = 3 and m = 0 as described above, but in this embodiment, the case where N = 3 and m = 1 will be described.
[0035]
In this case, the receiving coil arrays constituting one phase are arranged apart from each other by λ2 / 3 + λ2. For example, in the case of the first phase receiving coil 30-0, as shown in FIG. 6, the receiving coil 30-0-120 is disposed at a position spaced apart from the receiving coil 30-0-0 by λ2 / 3 + λ2. 30-0-240 is arranged at a position 2λ2 / 3 + λ2 away from the receiving coil 30-0-0. In the general formula P = {(n−1) / N + m} · λ2, the receiving coil 30-0-0 is arranged at P (1) = 0, and the receiving coil 30-0-120 is P (2) = λ2 / The receiving coil 30-0-240 is arranged at 3 + λ2, which corresponds to the arrangement at P (3) = 2λ2 / 3 + λ2. The λ2 crosstalk components included in the detection signal from each receiving coil are 0 degree, 120 degrees, and 240 degrees, respectively, and the λ2 crosstalk component is canceled by calculating the sum of these. Specifically, in the case of λ2 = 6.0 mm, the receiving coils are spaced apart by 2.0 mm + 6.0 mm = 8.0 mm.
[0036]
FIG. 7 shows a specific arrangement of the receiving coils. FIG. 7A shows the configuration of the receiving coil 30-0 that detects the first phase (0 degree phase). The reception coil 30-0 includes three reception coils 30-0-0, 30-0-120, and 30-0-240 that are spaced apart from each other by 8.0 mm in the measurement direction.
[0037]
FIG. 7B shows the configuration of the receiving coil 30-120 that detects the second phase (120-degree phase). The second-phase receiving coil 30-120 is also composed of three receiving coils 30-120-0, 30-120-120, 30-120-240 that are spaced apart from each other in the measurement direction by 8.0 mm. The The second-phase receiving coil 30-120 is arranged shifted in the measurement direction by λ1 / 3 = 3.0 mm with respect to the first-phase receiving coil 30-0.
[0038]
FIG. 7C shows the configuration of the receiving coil 30-240 for detecting the third phase (240 degree phase). The third phase receiving coil 30-240 is also composed of three receiving coils 30-240-0, 30-240-120, 30-240-240 spaced apart from each other by 8.0 mm in the measurement direction. The third phase receiving coil 30-240 is arranged to be shifted in the measurement direction by 2λ1 / 3 = 6.0 mm with respect to the first phase receiving coil 30-0.
[0039]
FIG. 7D shows a configuration in which the first-phase, second-phase, and third-phase receiving coils are arranged on a grid.
[0040]
<Third Embodiment>
In the first and second embodiments, the receiving coils in the receiving coil array constituting a certain phase are arranged at equal intervals. However, in order to cancel the λ2 crosstalk component, the receiving coils need not be equally spaced. There is no. For example, in the first-phase receiving coil 30-0, the receiving coils in the receiving coil array are not arranged at equal intervals according to (n−1) λ2 / N, but the receiving coils with the receiving coil array are (n−1). ) Λ2 / N, and the other receiving coils may be (n−1) λ2 / N + λ2. For example, when N = 3, certain receiving coils (coils corresponding to n = 2) are arranged at intervals of λ2 / 3, and other receiving coils (coils corresponding to n = 3) in the same receiving coil array. Are arranged at intervals of 2λ2 / 3 + λ2.
[0041]
FIG. 8 illustrates the case where the receiving coils in the receiving coil array constituting one phase are arranged at non-equal intervals. FIG. 8A shows the configuration of the receiving coil 30-0 that detects the first phase (0 degree phase). The first receiving coil (n = 1) constituting the receiving coil 30-0 is arranged at an arbitrary position. Next, the second receiving coil (n = 2) constituting the receiving coil 30-0 is arranged away from the first receiving coil by λ2 / 3 + λ2 = 8.0 mm. The third receiving coil (n = 3) constituting the receiving coil 30-0 is arranged 2λ2 / 3 = 4.0 mm apart from the first receiving coil. Accordingly, the third receiving coil is disposed between the first receiving coil and the second receiving coil.
[0042]
FIG. 8B shows the configuration of the receiving coil 30-120 that detects the second phase (120-degree phase). Also in the second phase receiving coil 30-120, the receiving coils of the receiving coil array are arranged at unequal intervals. In other words, the first receiving coil is arranged to be shifted in the measurement direction by λ1 / 3 = 3.0 mm with respect to the first receiving coil of the first-phase receiving coil 30-0. The second receiving coil constituting the receiving coil 30-120 is arranged with a distance of 8.0 mm from the first receiving coil constituting the second phase receiving coil 30-120. The third receiving coil is arranged away from the first receiving coil by 4.0 mm.
[0043]
FIG. 8C shows the configuration of the receiving coil 30-240 that detects the third phase (240-degree phase). The first receiving coil is arranged to be shifted in the measurement direction by 2λ1 / 3 = 6.0 mm with respect to the first receiving coil of the first-phase receiving coil 30-0. Further, the second receiving coil is arranged with a distance of 8.0 mm from the first receiving coil. The third receiving coil is arranged with a distance of 4.0 mm from the first receiving coil.
[0044]
FIG. 8D shows a configuration in which first-phase, second-phase, and third-phase receiving coils are arranged on a grid. In this case, the first-phase, second-phase, and third-phase receiving coils are mixed together.
[0045]
When the first-phase, second-phase and third-phase reception coils are arranged on the grid, the reception coil arrays of the respective phases may interfere with each other depending on the interval between the reception coil arrays constituting one phase. possible. It is necessary to arrange them without interference by appropriately adjusting the interval between the receiving coils constituting each phase.
[0046]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.
[0047]
For example, in the above-described embodiment, the two-wavelength position transducers of λ1 and λ2 have been described. However, the receiving coil 30 can be similarly arranged in the three-wavelength position transducer. That is, as shown in FIG. 9, when a transmitter coil 10 having a wavelength λ1, a receiver coil 12 having a wavelength λ2 and a receiver coil 14 having a wavelength λ3 are provided on the scale side and the absolute position is detected at λ1, λ2, and λ3, In addition to the λ1 detection signal, the λ2 crosstalk signal and the λ3 crosstalk signal are mixed in the reception coil 30 on the grid side that is disposed opposite to the λ1 transmission coil 10. In the case of the 3-wavelength type, λ1, λ2, and λ3
[Equation 9]
λfine = λ1
λmed = λ2λ1 / (λ2-λ1) = nλfine
λcoa = λ3λ2 / (λ3-λ2) = mλmed
The absolute position can be detected by λcoa, λmed, and λfine. However, if the λ2 crosstalk component and the λ3 crosstalk component are mixed in the λ1 detection signal, the accuracy of λfine decreases.
[0048]
Therefore, in such a case, a plurality of receiving coil arrays that can cancel the λ2 crosstalk component may be arranged apart from each other so that the λ3 crosstalk component can be canceled. Specifically, focusing on the first-phase receiving coil 30-0, N receiving coils are arranged at an interval of λ2 / N, and these detection signals are added to cancel the λ2 crosstalk component. The detection signal is a signal in which the λ1 detection signal and the λ3 crosstalk component are mixed. A receiving coil array for canceling the λ3 crosstalk signal is further spaced apart in the measurement direction at an interval of λ3 / M. The λ3 crosstalk component can be canceled by adding detection signals of M receiving coil arrays that are spaced apart.
[0049]
FIG. 10 shows a conceptual configuration of one phase of the receiving coil that removes the λ2 crosstalk component and the λ3 crosstalk component. The receiving coil array composed of three receiving coils is spaced apart from each other by λ2 / 3, and the three receiving coil arrays are spaced apart from each other by λ3 / 3. The detection signals of the reception coils in each reception coil array are added by the adders 50a, 50b, and 50c, respectively, and supplied to the adder 50d as a signal from which the λ2 crosstalk component has been removed. The adder 50d further adds these detection signals and outputs a detection signal having a λ1 period from which the λ3 crosstalk component has been removed.
[0050]
Of course, the position transducer is not limited to the two-wavelength type or the three-wavelength type position transducer, and can be similarly applied to a position transducer having a longer wavelength.
[0051]
In this embodiment, in the two-wavelength position transducer, N = 3 and each phase receiving coil is composed of three receiving coils, but N = 2 and each phase receiving coil is 180 degrees from each other. It may be configured by two receiving coils having a phase difference, or each phase receiving coil may be configured by four receiving coils having a phase difference of 90 degrees with N = 4.
[0052]
Furthermore, in this embodiment, the λ2 crosstalk component mixed in the λ1 detection signal is removed from the two-wavelength position transducer, but it is also possible to remove the λ1 crosstalk component mixed in the λ2 detection signal in the same manner. It is. As described in the configuration of FIG. 11, after driving the transmission coil 20, the transmission coil 22 is driven and a signal having a period λ <b> 2 is detected by the reception coil 32, but an induced current is generated in the transmission coil 10 at this time. The leakage magnetic field from the transmission coil 10 causes a λ1 crosstalk component to be mixed into the λ2 detection signal. In this case, one phase of the receiving coil 32 is constituted by a plurality of receiving coils, and each receiving coil is spaced apart according to P = {(n−1) / N + m} · λ1, and detection signals from the respective receiving coils are added. By doing so, the λ1 crosstalk component can be removed.
[0053]
【The invention's effect】
As described above, according to the present invention, it is possible to cancel a crosstalk signal due to a leakage magnetic field and detect a position with high accuracy.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a receiving coil arrangement according to the present invention.
FIG. 2 is an explanatory diagram of a detection signal of the present invention.
FIG. 3 is an explanatory diagram of a first-phase receiving coil according to the embodiment.
FIG. 4 is an explanatory diagram of arrangement of first phase receiving coils according to the embodiment.
FIG. 5 is an explanatory diagram of a three-phase receiving coil arrangement according to the embodiment.
FIG. 6 is a diagram illustrating the arrangement of first phase receiving coils according to another embodiment.
FIG. 7 is an explanatory diagram of a three-phase receiving coil arrangement according to another embodiment.
FIG. 8 is an explanatory view of arrangement of a three-phase receiving coil according to still another embodiment.
FIG. 9 is a crosstalk explanatory diagram of a three-wavelength type position transducer.
FIG. 10 is an explanatory diagram of a receiving coil arrangement of a three-wavelength position transducer.
FIG. 11 is a diagram illustrating the arrangement of a conventional two-wavelength position transducer.
FIG. 12 is an explanatory diagram of a three-phase receiving coil arrangement of a conventional two-wavelength position transducer.
FIG. 13 is a crosstalk explanatory diagram of a conventional two-wavelength type position transducer.
[Explanation of symbols]
10 transmitting coil (wavelength λ1), 12 transmitting coil (wavelength λ2), 20 transmitting coil (grid side), 30 receiving coil (grid side).

Claims (4)

A read head having magnetic field generation means and magnetic field detection means;
A scale which is disposed opposite to the reading head and includes a receiving coil that generates an induced current by a magnetic field from the magnetic field generating means and a magnetic coupling coil that includes a transmitting coil that generates a magnetic field by the induced current along a measurement direction; ,
An inductive position transducer for detecting a position of the read head relative to the scale based on a phase of a detection signal obtained by detecting a magnetic field from the transmission coil of the scale by the magnetic field detection means,
The transmission coil of the magnetic coupling coil is formed with a pitch λ1,
The receiving coil of the magnetic coupling coil is formed with a pitch λ2 different from the λ1,
The magnetic field detection means are spaced apart in the measurement direction at intervals determined based on the pitch λ2,
An inductive position transducer, wherein a leakage magnetic field component from the receiving coil is canceled by calculating a sum of detection signals from the magnetic field detection means arranged at a distance. The transducer of claim 1, wherein
The magnetic field detection means includes
P = {(n−1) / N + m} · λ2
However, n = 1 to N
An inductive position transducer, wherein N is an integer greater than or equal to 2 and m is spaced apart at a position determined by an integer greater than or equal to 0. The transducer according to any one of claims 1 and 2,
An inductive position transducer characterized in that a plurality of sets are shifted from each other in the measurement direction by λ1 / L (L is an integer of 2 or more), with the magnetic field detection means arranged as spaced apart as one set. The transducer according to any one of claims 1 to 3, further comprising:
The receiving coil of the magnetic coupling coil is formed with a pitch λ3 different from the λ1 and λ2.
The magnetic field detection means is spaced apart in the measurement direction at intervals determined based on the pitch λ2 and the pitch λ3,
An inductive position transducer characterized by canceling a leakage magnetic field component from the receiving coil having the pitch λ2 and the pitch λ3 by calculating a sum of detection signals from the magnetic field detecting means arranged at a distance.

Images