JP3673138B2

JP3673138B2 - Torque sensor

Info

Publication number: JP3673138B2
Application number: JP2000063591A
Authority: JP
Inventors: 哲也村上; 真史久世
Original assignee: Koyo Seiko Co Ltd
Current assignee: Koyo Seiko Co Ltd
Priority date: 2000-03-08
Filing date: 2000-03-08
Publication date: 2005-07-20
Anticipated expiration: 2020-03-08
Also published as: JP2001255218A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば操舵トルクに応じた操舵補助力を付与するパワーステアリング装置において、その操舵トルクを検出するのに適したトルクセンサに関する。
【０００２】
【従来の技術】
例えば車両のパワーステアリング装置においては、ステアリングホイールの回転をステアリングシャフトを介して車輪に伝達する際、そのステアリングシャフトにより伝達されるトルクをトルクセンサにより検出し、その検出トルクの大きさに応じて操舵補助力を付与している。
【０００３】
例えば特開平８−２４０４９１号公報、特開平９−６１２６３号公報、特開平９−６１２６４号公報により開示されたトルクセンサにおいては、磁性金属材製の第１回転軸にトーションバーを介して連結された第２回転軸に、導電性を有する非磁性金属製材製の円筒部材が同行回転するように連結され、その円筒部材を囲む磁束発生用コイルが設けられ、その円筒部材に窓が形成され、その円筒部材に囲まれる第１回転軸の外周に溝が形成されている。トルク伝達による両回転軸の相対回転により、その窓と溝との重なり状態が変化するものとされている。その円筒部材により第１回転軸に至る磁束が遮られることから、伝達トルクに応じた両回転軸の相対回転による窓と溝との重なり状態の変化によって、その第１回転軸を通過する磁束が変化する。また、そのコイルの磁束発生に基づき生じる交番磁界内で円筒部材に生じる渦電流によっても第１回転軸に至る磁束が遮られる。すなわち、伝達トルクに応じた両回転軸の相対回転に応じて第１回転軸の通過磁束が変化する。その磁束変化による電磁誘導によりコイル出力が変化するものとされ、そのコイル出力の変化に基づき伝達トルクが検出される。
【０００４】
【発明が解決しようとする課題】
上記従来のトルクセンサにおいては、第１回転軸の外周と円筒部材の内周との間には隙間が形成されている。しかし、その隙間は磁束が通過することから微小なものとされている。そのため、第１回転軸の軸心と第２回転軸の軸心とが外力の作用等により相対的に傾いた場合、第１回転軸の外周と円筒部材の内周とが金属接触することがある。その金属接触により両回転軸の相対回転が阻害されることから、トルク検出精度が低下するという問題がある。
【０００５】
本発明は、上記問題を解決することのできるトルクセンサを提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明のトルクセンサは、第１シャフトと、その第１シャフトに同軸心かつ弾性的に相対回転可能に連結される第２シャフトと、その第２シャフトに同軸心かつ同行回転するように連結される筒状部材と、その筒状部材の外周を囲むように配置されると共に、交番磁界を生じるように磁束を発生させるコイルとを備え、その筒状部材は、その第１シャフトの外周を隙間を介して囲むように配置される絶縁性の合成樹脂製外筒部と、この外筒部内に埋設される導電性を有する非磁性金属材製の内筒部とを有し、その第１シャフトの外周により、前記コイルの発生磁束の通過位置に配置される磁性金属材製の磁束通過部が構成され、その内筒部は、その磁束通過部を囲むと共に前記コイルの発生磁束の通過位置に配置される磁束規制部を有し、その磁束通過部に両シャフトの相対回転軸方向に沿う溝が形成され、その磁束規制部に開口が形成され、両シャフトの径方向において、その相対回転軸方向に沿う溝の縁に連なる磁束通過部外周と前記開口との重なり面積が、両シャフトの相対回転に応じて変化するように、その溝と開口とは両シャフトの径方向において部分的に重なるように配置され、その重なり面積の変化に応じた前記磁束通過部の通過磁束の変化に基づき、両シャフトにより伝達されるトルクが検出される。
その第１シャフトにおける磁束通過部を構成する磁性金属材としては、トルクセンサを構成する上で必要な磁気特性に優れた例えば軟質磁性金属材料を用いることができる。その外筒部を構成する絶縁性の合成樹脂材としては、磁束通過部との接触時の摩擦が小さく耐磨耗性に優れた材料を用いるのが好ましい。その内筒部を構成する導電性を有する非磁性金属材としては、アルミニウム等の導電性に優れると共に透磁率の小さい常磁性体の金属材料を用いることができる。
上記構成においては、トルク伝達時における両シャフトの相対回転により、第１シャフトの磁束通過部に形成された溝と、第２シャフトと同行回転する内筒部の磁束規制部に形成された開口との重なり状態が変化する。これにより、両シャフトの径方向において、その溝の縁に連なる磁束通過部外周と前記開口との重なり面積が両シャフトの相対回転に応じて変化する。その磁束通過部は磁性材製であり、その内筒部は非磁性材製であるので、その重なり面積の変化によって磁束通過部の通過磁束が変化する。また、そのコイルの磁束発生に基づき生じる交番磁界内で導電性の内筒部に生じる渦電流によっても、その磁束通過部に至る磁束が遮られる。これにより、その磁束通過部の通過磁束を、その重なり面積の変化に応じて変化させることができる。その面積変化は伝達トルクに対応する両シャフトの相対回転に対応することから、その磁束変化に基づき両シャフトにより伝達されるトルクを検出できる。なお、その内筒部が埋設されている外筒部は絶縁性であるため、渦電流が発生することはなく、トルク検出に影響を及ぼすことはない。
上記構成によれば、第１シャフトの外周を隙間を介して囲む外筒部は合成樹脂製であるので、第１シャフトの軸心と第２シャフトの軸心とが外力の作用等により相対的に傾いても、第１シャフトの外周が接触するのは合成樹脂である。よって、その接触部において両シャフトの相対回転を阻止する摩擦力を、金属同士が接触するのに比べて低減でき、トルク検出精度の低下を防止できる。
【０００７】
前記コイルを保持する磁性材製のコイルホルダーを備え、そのコイルホルダーは、そのコイルを囲む筒状の外周部分と、その外周部分の一端側から内方に向かう部分と、その外周部分の他端側から内方に向かう部分とを有し、両シャフトの相対回転軸方向において、前記開口の寸法は前記コイルの寸法を超えると共に前記コイルホルダーの寸法未満とされ、前記開口は前記コイルホルダーの両端間に配置され、前記コイルは前記開口の両端間に配置されているのが好ましい。
これにより、第１シャフト、第２シャフト、筒状部材、およびコイルの軸方向における相対位置が、製造公差や組み立て公差により変動しても、両シャフトの相対回転軸方向において開口をコイルの発生磁束の通過位置に配置できる。よって、その磁束通過部の通過磁束の公差による変動をなくし、検出精度の低下を防止できる。
【０００８】
その開口は、両シャフトの回転軸方向に平行な縁と回転周方向に平行な縁とを有する４辺形に沿う形状を有し、その開口は、両シャフトの相対回転軸方向において前記溝の両端間に配置され、両シャフトが相対回転していない検出原点位置にある時、その溝における両シャフトの相対回転軸に沿う縁は、その開口における両シャフトの相対回転軸に沿う中心と、径方向において重なるように配置されているのが好ましい。
これにより、両シャフトが一方向に相対回転した時と、他方向に相対回転した時の何れの場合にも、その相対回転量に応じたトルクを検出できる。
【０００９】
前記コイルとして、両シャフトの相対回転軸方向に沿って並列する同一仕様の第１コイルと第２コイルとを備え、前記開口として、両シャフトの相対回転軸方向における間隔をおいて配置される第１開口と第２開口とを備え、その第１コイルは第１開口を通過する磁束を発生する位置に配置され、その第２コイルは第２開口を通過する磁束を発生する位置に配置され、その第１開口と前記溝の縁に連なる磁束通過部外周とは、両シャフトが一方向に相対回転する時は互いとの前記重なり面積が増加し、両シャフトが他方向に相対回転する時は互いとの前記重なり面積が減少するように相対配置され、その第２開口と前記溝の縁に連なる磁束通過部外周とは、両シャフトが一方向に相対回転する時は互いとの前記重なり面積が減少し、両シャフトが他方向に相対回転する時は互いとの前記重なり面積が増加するように相対配置され、両シャフトの相対回転時において、その第１開口と磁束通過部外周との前記重なり面積の変化の絶対値と、その第２開口と磁束通過部外周との前記重なり面積の変化の絶対値とは互いに等しくされ、その重なり面積の変化に応じた前記磁束通過部の通過磁束の変化と、その重なり面積の変化に応じた前記磁束通過部の通過磁束の変化との差に基づき、両シャフトにより伝達されるトルクが検出されるのが好ましい。
この構成によれば、トルク伝達時に両シャフトが一方向に相対回転すると、その相対回転量に応じて第１開口と溝の縁に連なる磁束通過部外周との重なり面積が増加し、第２開口と溝の縁に連なる磁束通過部外周との重なり面積が減少する。トルク伝達時に両シャフトが他方向に相対回転すると、その相対回転量に応じて第１開口と磁束通過部外周との上記重なり面積が減少し、第２開口と磁束通過部外周との上記重なり面積が増加する。各重なり面積の変化に応じて磁束通過部を通過する磁束が変化する。また、両シャフトの相対回転時において、その第１開口と磁束通過部外周との上記重なり面積の変化の絶対値と、その第２開口と磁束通過部外周との上記重なり面積の変化の絶対値とは互いに等しくされている。よって、第１開口と磁束通過部外周との上記重なり面積の変化に応じた磁束通過部の通過磁束の変化と、第２開口と磁束通過部外周との上記重なり面積の変化に応じた磁束通過部の通過磁束の変化との差に基づき、両シャフトにより伝達されるトルクを検出し、トルク検出感度を増大できる。しかも、温度が変動した場合、第１開口と重なる磁束通過部を通過する磁束と、第２開口と重なる磁束通過部を通過する磁束とは同じだけ変化するので、両磁束変化の差に基づきトルクを検出することで温度変動による検出トルクの変動を相殺できる。
【００１０】
前記第１開口は、前記筒状部材の周方向における等間隔をおいて並列するように複数形成され、前記第２開口は、前記筒状部材の周方向における等間隔をおいて並列するように複数形成され、前記溝は、前記第１シャフトの周方向における等間隔をおいて並列するように複数設けられ、各溝の周方向寸法は、各溝相互間における磁束通過部の周方向寸法よりも大きくされると共に、各開口の周方向寸法よりも大きくされ、各溝相互間における磁束通過部の周方向寸法は、各開口の周方向寸法よりも大きくされ、各第１開口の周方向間に各第２開口が配置され、トルク検出範囲に対応する両シャフトの相対回転範囲において、各第１開口は前記溝における両シャフトの相対回転軸に沿う一方の縁に重なり、各第２開口は前記溝における両シャフトの相対回転軸に沿う他方の縁に重なるように配置されているのが好ましい。
これにより第１、第２開口と溝の数を多くしてトルク検出感度を向上できる。
【００１１】
【発明の実施の形態】
図１〜図５に示すトルクセンサ１は、車両のパワーステアリング装置における操舵トルクを検出する。そのトルクセンサ１は、ハウジング２と、第１シャフト３と、第２シャフト４とを備えている。その第１シャフト３は、軸受５を介してハウジング２により支持され、ブッシュ６を介して第２シャフト４の一端に形成された凹部４ａの内周により支持される。その第２シャフト４は、軸受７を介してハウジング２により支持される。その検出トルクに応じて操舵補助力が付与される。
【００１２】
その第１シャフト３に形成された軸方向孔３ａと、その第２シャフト４の凹部４ａとにトーションバー８が挿入されている。そのトーションバー８の一端はピン９により第１シャフト３に同行回転するように連結され、他端はセレーション１０を介して第２シャフト４に同行回転するように連結されている。これにより、その第２シャフト４は、第１シャフト３と同軸心に配置されると共に、第１シャフト３に弾性的に相対回転可能に連結されている。その第１シャフト３の一端側はステアリングホイール（図示省略）に接続され、その第２シャフト４の他端側は例えばラックピニオン式ステアリングギア等のステアリングギアに接続される。これにより、操舵のためのステアリングホイールの回転が第１、第２シャフト３、４を介して車輪に伝達され、操舵角が変化する。
【００１３】
その第２シャフト４は、円筒形の筒状部材１２に同軸心かつ同行回転するように連結されている。本実施形態では、その筒状部材１２は第２シャフト４の一端側外周に圧入されているが、ネジ等の適当な固着手段により一体化されてもよい。図２、図３の（１）、（２）に示すように、その筒状部材１２は絶縁性の合成樹脂製円筒形外筒部１２ａと導電性を有する非磁性金属材製の円筒形内筒部１２ｂとから構成されている。その合成樹脂としては、例えば、第１シャフト３と接触した時の摺動性が良く、アルミニウム等から形成される内筒部１２ｂとインジェクションモールドできるＰＡ６（ナイロン）、ＰＯＭ（ポリアセタール）等が挙げられる。その外筒部１２ａは、ハウジング２内において第１シャフト３の外周を隙間εを介して囲むように配置される。その内筒部１２ｂは外筒部１２ａ内に埋設される。
【００１４】
そのハウジング２の内周に、磁性材製の第１コイルホルダー３１と磁性材製の第２コイルホルダー３２とが挿入されている。図２に示すように、各コイルホルダー３１、３２は、円筒状の外周部分３１ａ、３２ａと、その外周部分３１ａ、３２ａの一端側から内方に向かう円環状の周壁部分３１ｂ、３２ｂと、その外周部分３１ａ、３２ａの他端側から内方に向かう円環状の蓋部分３１ｃ、３２ｃとから構成される。各コイルホルダー３１、３２は、ハウジング２の内周に形成される段差２ａと、ハウジング２の内周に嵌め合わされる止め輪５３とにより、板バネ５４を介して挟み込まれ、これによりハウジング２に固定される。
【００１５】
その第１コイルホルダー３１により保持される第１コイル３３と、その第２コイルホルダー３２により保持される第２コイル３４とが、両シャフト３、４の相対回転軸方向に沿って並列する。両コイル３３、３４は同一仕様であり、導線３３ａ、３４ａを絶縁材製のボビン３３ｂ、３４ｂに第１シャフト３の軸心まわりに巻き付けることで構成され、各コイルホルダー３１、３２の内周に挿入されている。各コイルホルダー３１、３２及びコイル３３、３４は、上記筒状部材１２の外周を隙間を介して囲むように配置される。各コイル３３、３４は、後述のようにトルク検出回路を構成し、交番磁界を生じるように磁束を発生させる。
【００１６】
その第１シャフト３は磁性金属材製とされ、これにより第１シャフト３の外周によりコイル３３、３４の発生磁束の通過位置に配置され、その外周が円筒面に沿う磁性金属材製の磁束通過部が構成されている。本実施形態では、その第１シャフト３は単一部材から形成されているが、磁束通過部を構成する部材と、磁束通過部以外の部分を構成する部材とを一体化することで第１シャフトを形成してもよい。
【００１７】
図３の（１）、（２）、図４に示すように、その磁束通過部に両シャフト３、４の相対回転軸方向に沿う複数の溝４０が形成されている。それら溝４０は互いに第１シャフト３の周方向における等間隔をおいて並列する。各溝４０の寸法は互いに等しくされている。各溝４０の周方向寸法Ｓ１は、各溝４０の相互間における磁束通過部の周方向寸法Ｓ２よりも大きくされている。
【００１８】
上記内筒部１２ｂは、その第１シャフト３の磁束通過部を囲むと共に各コイル３３、３４の発生磁束の通過位置に配置される磁束規制部を有する。その磁束規制部に複数の第１開口４３と複数の第２開口４４とが形成されている。その第１開口４３と第２開口４４とは、両シャフト３、４の相対回転軸方向における間隔をおいて配置されている。それら第１開口４３は、互いに筒状部材１２の周方向における等間隔をおいて並列する。それら第２開口４４は、互いに筒状部材１２の周方向における等間隔をおいて並列する。各開口４３、４４の形状、寸法は互いに等しくされ、本実施形態では両シャフト３、４の回転軸方向に平行な縁と回転周方向に平行な縁とを有する４辺形に沿う形状を有する。上記第１コイル３３は各第１開口４３を通過する磁束を発生する位置に配置され、上記第２コイル３４は各第２開口４４を通過する磁束を発生する位置に配置される。
【００１９】
図２に示すように、両シャフト３、４の相対回転軸方向において、各開口４３、４４の寸法は各コイル３３、３４の寸法を超えると共に各コイルホルダー３１、３２の寸法未満とされ、第１開口４３は第１コイルホルダー３１の両端間に配置され、第２開口４４は第２コイルホルダー３２の両端間に配置され、第１コイル３３は第１開口４３の両端間に配置され、第２コイル３４は第２開口４４の両端間に配置される。これにより、第１シャフト３、第２シャフト４、第１コイル３３、第２コイル３４、および筒状部材１２の軸方向における相対位置が、製造公差や組み立て公差により変動しても、両シャフト３、４の相対回転軸方向において各開口４３、４４をコイル３３、３４の発生磁束の通過位置に配置できる。よって、その磁束通過部の通過磁束の公差による変動をなくし、検出精度の低下を防止できる。
【００２０】
両シャフト３、４の径方向において、上記溝４０の縁に連なる磁束通過部外周、すなわち第１シャフト３における溝４０の間の部分における外周、と上記開口４３、４４との重なり面積が両シャフト３、４の相対回転に応じて変化するように、その溝４０と開口４３、４４とは両シャフト３、４の径方向において部分的に重なるように配置されている。
【００２１】
すなわち図４に示すように、各溝４０相互間における磁束通過部の周方向寸法Ｓ２は、各開口４３、４４の周方向寸法Ｐ１よりも大きくされ、各第１開口４３の周方向間に各第２開口４４が配置されている。その第１、第２開口４３、４４は、両シャフト３、４の相対回転軸方向において溝４０の両端間に配置される。各第１開口４３は、トルク検出範囲に対応する両シャフト３、４の相対回転範囲では、両シャフト３、４の径方向において、溝４０における両シャフト３、４の相対回転軸に沿う一方の縁４０ａと重なる。その第２開口４４は、トルク検出範囲に対応する両シャフト３、４の相対回転範囲では、両シャフト３、４の径方向において、溝４０における両シャフト３、４の相対回転軸に沿う他方の縁４０ｂと重なる。これにより、各第１開口４３と各溝４０の縁４０ａに連なる磁束通過部外周とは、両シャフト３、４が一方向に相対回転する時は互いとの上記重なり面積が増加し、両シャフト３、４が他方向に相対回転する時は互いとの上記重なり面積が減少するように相対配置されている。また、各第２開口４４と各溝４０の縁４０ｂに連なる磁束通過部外周とは、両シャフト３、４が一方向に相対回転する時は互いとの上記重なり面積が減少し、両シャフト３、４が他方向に相対回転する時は互いとの上記重なり面積が増加するように相対配置されている。すなわち、その第１開口４３が重なる溝４０の縁４０ａと、第２開口４４が重なる溝４０の縁４０ｂとは、両シャフト３、４の回転周方向において、その溝４０の中心からみて互いに逆の側に位置するものとされている。
【００２２】
両シャフト３、４が相対回転していない検出原点位置にある時、すなわち舵角が零の時、第１開口４３と磁束通過部外周との上記重なり面積と、第２開口４４と磁束通過部外周との上記重なり面積とは互いに等しくされている。すなわち図４に示すように、両シャフト３、４が検出原点位置にある時、各溝４０における両シャフト３、４の相対回転軸に沿う一方の縁４０ａは、各第１開口４３における両シャフト３、４の相対回転軸に沿う中心と径方向において重なるように配置されている。また、各溝４０における両シャフト３、４の相対回転軸に沿う他方の縁４０ｂは、各第２開口４４における両シャフト３、４の相対回転軸に沿う中心と径方向において重なるように配置されている。これにより、両シャフト３、４の相対回転時において、その第１開口４３と磁束通過部外周との上記重なり面積の変化の絶対値と、その第２開口４４と磁束通過部外周との上記重なり面積の変化の絶対値とは互いに等しくされている。
【００２３】
図２において二点鎖線βで示すように、第１コイル３３の発生磁束が第１コイルホルダー３１、筒状部材１２の第１開口４３、第１シャフト３の磁束通過部を通過することで、その第１コイルホルダー３１および第１シャフト３の磁束通過部を構成要素として含む第１磁気回路が構成され、また、第２コイル３４の発生磁束が第２コイルホルダー３２、筒状部材１２の第２開口４４、第１シャフト３の磁束通過部を通過することで、その第２コイルホルダー３２および第１シャフト３の磁束通過部を構成要素として含む第２磁気回路が構成される。
【００２４】
上記構成においては、トルク伝達時における両シャフト３、４の相対回転により、第１シャフト３の磁束通過部に形成された溝４０と、第２シャフト４と同行回転する内筒部１２ｂの磁束規制部に形成された開口４３、４４との重なり状態が変化する。これにより、両シャフト３、４の径方向において、その溝４０の縁４０ａ、４０ｂに連なる磁束通過部外周と上記開口４３、４４との重なり面積が両シャフト３、４の相対回転に応じて変化する。その磁束通過部は磁性材製であり、その内筒部１２ｂは非磁性材製であるので、その重なり面積の変化によって磁束通過部の通過磁束が変化する。また、コイル３３、３４の磁束発生に基づき生じる交番磁界内で導電性の内筒部１２ｂに生じる渦電流によっても、その磁束通過部に至る磁束が遮られる。これにより、その磁束通過部の通過磁束を、その重なり面積の変化に応じて変化させることができる。その面積変化は伝達トルクに対応する両シャフト３、４の相対回転に対応する。その磁束変化に基づく電磁誘導によりコイル３３、３４出力が変化するものとされ、そのコイル出力の変化に基づき伝達トルクが検出される。なお、その内筒部１２ｂが埋設されている外筒部１２ａは絶縁性であるため、渦電流が発生することはなく、トルク検出に影響を及ぼすことはない。
【００２５】
また、上記構成においては、トルク伝達時に両シャフト３、４が一方向に相対回転すると、その相対回転量に応じて第１開口４３と溝４０の一方の縁４０ａに連なる磁束通過部外周との重なり面積が増加し、第２開口４４と溝４０の他方の縁４０ｂに連なる磁束通過部外周との重なり面積が減少する。トルク伝達時に両シャフト３、４が他方向に相対回転すると、その相対回転量に応じて第１開口４３と磁束通過部外周との上記重なり面積が減少し、第２開口４４と磁束通過部外周との上記重なり面積が増加する。各重なり面積の変化に応じて磁束通過部を通過する磁束が変化する。また、両シャフト３、４の相対回転時において、その第１開口４３と磁束通過部外周との上記重なり面積の変化の絶対値と、その第２開口４４と磁束通過部外周との上記重なり面積の変化の絶対値とは互いに等しくされている。よって、第１開口４３と磁束通過部外周との上記重なり面積の変化に応じた磁束通過部の通過磁束の変化と、第２開口４４と磁束通過部外周との上記重なり面積の変化に応じた磁束通過部の通過磁束の変化との差に基づき、両シャフト３、４により伝達されるトルクを検出し、トルク検出感度を増大できる。また、両シャフト３、４が一方向に相対回転した時と、他方向に相対回転した時の何れの場合にも、その相対回転量に応じたトルクを検出できる。しかも、温度が変動した場合、第１開口４３と重なる磁束通過部を通過する磁束と、第２開口４４と重なる磁束通過部を通過する磁束とは同じだけ変化するので、両磁束変化の差に基づきトルクを検出することで温度変動による検出トルクの変動を相殺できる。
【００２６】
本実施形態では、各コイル３３、３４は、ハウジング２の外面側に取り付けられるプリント基板３５に配線を介して接続される。そのプリント基板３５に、図５に示すトルク検出回路が形成されている。その回路において、第１コイル３３は抵抗４５を介して発振器４６に接続され、第２コイル３４は抵抗４７を介して発振器４６に接続され、各コイル３３、３４は差動増幅回路４８に接続される。これにより、両シャフト３、４間でのトルク伝達によりトーションバー８が捩れることで両シャフト３、４が弾性的に相対回転し、その伝達トルクに応じて各開口４３、４４と磁束通過部外周との重なり面積が変化し、その重なり面積の変化により磁束通過部の通過磁束が変化することで、第１、第２コイル３３、３４の出力が変化する。その第１開口４３と重なる磁束通過部の通過磁束の変化と、第２開口４４と重なる磁束通過部の通過磁束の変化との差に対応する差動増幅回路４８の出力に基づき、両シャフト３、４により伝達されるトルクが検出される。その差動増幅回路４８から出力される伝達トルクに対応した信号に応じて駆動されるモータ等の図外アクチュエータにより操舵補助力が付与される。その操舵補助力の付与機構は公知の構成を採用できる。
【００２７】
上記構成によれば、第１シャフト３の外周を隙間εを介して囲む外筒部１２ａは合成樹脂製であるので、第１シャフト３の軸心と第２シャフト４の軸心とが外力の作用等により相対的に傾いても、第１シャフト３の外周が接触するのは合成樹脂である。よって、その接触部において両シャフト３、４の相対回転を阻止する摩擦力を、金属同士が接触するのに比べて低減でき、トルク検出精度の低下を防止できる。
【００２８】
本発明は上記実施形態に限定されない。例えば、第１シャフト３の一端側をステアリングギアに接続し、第２シャフト４の他端側をステアリングホイールに接続するようにしてもよい。また、本発明のトルクセンサをステアリング装置以外においてトルクを検出するために用いてもよい。
【００２９】
【発明の効果】
本発明によれば、検出精度、検出感度に優れたトルクセンサを提供できる。
【図面の簡単な説明】
【図１】本発明の実施形態のトルクセンサの断面図
【図２】本発明の実施形態のトルクセンサの要部の断面図
【図３】本発明の実施形態の（１）はトルクセンサの要部の横断面図、（２）は筒状部材の部分破断斜視図
【図４】本発明の実施形態のトルクセンサの筒状部材の部分展開図
【図５】本発明の実施形態のトルク検出回路を示す図
【符号の説明】
１トルクセンサ
３第１シャフト
４第２シャフト
１２筒状部材
１２ａ外筒部
１２ｂ内筒部
３１、３２コイルホルダー
３３第１コイル
３４第２コイル
４０溝
４３第１開口
４４第２開口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torque sensor suitable for detecting the steering torque in, for example, a power steering apparatus that applies a steering assist force according to the steering torque.
[0002]
[Prior art]
For example, in a power steering device for a vehicle, when the rotation of a steering wheel is transmitted to a wheel via a steering shaft, torque transmitted by the steering shaft is detected by a torque sensor, and steering is performed according to the magnitude of the detected torque. Auxiliary power is given.
[0003]
For example, in the torque sensor disclosed in JP-A-8-240491, JP-A-9-61263, and JP-A-9-61264, it is connected to a first rotating shaft made of a magnetic metal material via a torsion bar. In addition, a cylindrical member made of a nonmagnetic metal material having conductivity is connected to the second rotating shaft so as to rotate along with it, a magnetic flux generating coil surrounding the cylindrical member is provided, and a window is formed in the cylindrical member. A groove is formed on the outer periphery of the first rotation shaft surrounded by the cylindrical member. It is assumed that the overlapping state of the window and the groove changes due to the relative rotation of both rotating shafts by torque transmission. Since the magnetic flux reaching the first rotating shaft is blocked by the cylindrical member, the magnetic flux passing through the first rotating shaft is changed by the change in the overlapping state of the window and the groove due to the relative rotation of both rotating shafts according to the transmission torque. Change. Further, the magnetic flux reaching the first rotating shaft is also blocked by the eddy current generated in the cylindrical member in the alternating magnetic field generated based on the magnetic flux generation of the coil. That is, the passing magnetic flux of the first rotating shaft changes according to the relative rotation of both rotating shafts according to the transmission torque. The coil output is changed by electromagnetic induction due to the magnetic flux change, and the transmission torque is detected based on the change of the coil output.
[0004]
[Problems to be solved by the invention]
In the conventional torque sensor, a gap is formed between the outer periphery of the first rotating shaft and the inner periphery of the cylindrical member. However, the gap is very small because the magnetic flux passes through it. Therefore, when the axial center of the first rotating shaft and the axial center of the second rotating shaft are relatively inclined due to the action of an external force, the outer periphery of the first rotating shaft and the inner periphery of the cylindrical member may be in metal contact. is there. Since the relative rotation of both rotating shafts is hindered by the metal contact, there is a problem that the torque detection accuracy is lowered.
[0005]
An object of this invention is to provide the torque sensor which can solve the said problem.
[0006]
[Means for Solving the Problems]
A torque sensor according to the present invention is connected to a first shaft, a second shaft that is coaxially and elastically connected to the first shaft, and a second shaft that is coaxially and rotationally connected to the second shaft. And a coil that generates a magnetic flux so as to generate an alternating magnetic field, and the cylindrical member has a gap around the outer periphery of the first shaft. An insulating synthetic resin outer cylinder portion disposed so as to surround the inner cylinder portion, and a conductive nonmagnetic metal inner cylinder portion embedded in the outer cylinder portion, and a first shaft thereof A magnetic metal material magnetic flux passage portion disposed at a position where the magnetic flux generated by the coil passes is constituted by the outer periphery of the coil, and the inner cylinder portion surrounds the magnetic flux passage portion and is located at the position where the magnetic flux generated by the coil passes. A magnetic flux restricting portion to be disposed; A groove along the relative rotational axis direction of both shafts is formed in the magnetic flux passing part, an opening is formed in the magnetic flux restricting part, and the magnetic flux passing part connected to the edge of the groove along the relative rotational axis direction in the radial direction of both shafts The groove and the opening are arranged so as to partially overlap in the radial direction of both shafts so that the overlapping area of the outer periphery and the opening changes according to the relative rotation of both shafts. The torque transmitted by both shafts is detected based on the change in the passing magnetic flux of the corresponding magnetic flux passing portion.
As the magnetic metal material constituting the magnetic flux passage portion in the first shaft, it is possible to use, for example, a soft magnetic metal material having excellent magnetic characteristics necessary for constituting the torque sensor. As the insulating synthetic resin material that constitutes the outer cylinder portion, it is preferable to use a material that has low friction at the time of contact with the magnetic flux passage portion and excellent wear resistance. As the nonmagnetic metal material having conductivity which constitutes the inner cylinder portion, a paramagnetic metal material having excellent conductivity and low permeability such as aluminum can be used.
In the above configuration, due to the relative rotation of both shafts during torque transmission, a groove formed in the magnetic flux passage portion of the first shaft, and an opening formed in the magnetic flux regulating portion of the inner cylinder portion that rotates along with the second shaft, The overlapping state of changes. Thereby, in the radial direction of both shafts, the overlapping area of the outer periphery of the magnetic flux passage part connected to the edge of the groove and the opening changes according to the relative rotation of both shafts. Since the magnetic flux passage part is made of a magnetic material and the inner cylinder part is made of a non-magnetic material, the passing magnetic flux of the magnetic flux passage part changes due to the change of the overlapping area. Further, the magnetic flux reaching the magnetic flux passage portion is also blocked by the eddy current generated in the conductive inner cylinder portion in the alternating magnetic field generated based on the magnetic flux generation of the coil. Thereby, the passage magnetic flux of the magnetic flux passage part can be changed according to the change of the overlapping area. Since the change in area corresponds to the relative rotation of both shafts corresponding to the transmission torque, the torque transmitted by both shafts can be detected based on the change in magnetic flux. In addition, since the outer cylinder part in which the inner cylinder part is embed | buried is insulating, an eddy current does not generate | occur | produce and it does not affect torque detection.
According to the above configuration, the outer cylinder portion that surrounds the outer periphery of the first shaft with a gap is made of synthetic resin, so that the axial center of the first shaft and the axial center of the second shaft are relatively relative to each other by the action of external force or the like. Even if it is inclined, the outer periphery of the first shaft is in contact with the synthetic resin. Therefore, the frictional force that prevents the relative rotation of the two shafts at the contact portion can be reduced as compared with the case where the metals are in contact with each other, and the decrease in torque detection accuracy can be prevented.
[0007]
A coil holder made of a magnetic material for holding the coil is provided, the coil holder including a cylindrical outer peripheral portion surrounding the coil, a portion inward from one end side of the outer peripheral portion, and the other end of the outer peripheral portion In the relative rotational axis direction of both shafts, the size of the opening exceeds the size of the coil and is less than the size of the coil holder, and the opening is at both ends of the coil holder. Preferably, the coil is disposed between both ends of the opening.
Thereby, even if the relative positions in the axial direction of the first shaft, the second shaft, the cylindrical member, and the coil fluctuate due to manufacturing tolerances and assembly tolerances, the magnetic flux generated by the coils in the relative rotational axis direction of both shafts is changed. Can be placed at the passing position. Therefore, the fluctuation | variation by the tolerance of the passage magnetic flux of the magnetic flux passage part is eliminated, and the fall of detection accuracy can be prevented.
[0008]
The opening has a shape along a quadrilateral having an edge parallel to the rotation axis direction of both shafts and an edge parallel to the rotation circumferential direction, and the opening is formed in the relative rotation axis direction of both shafts. When the shaft is located at both ends and is at the detection origin position where both shafts are not rotating relative to each other, the edge along the relative rotation axis of both shafts in the groove is the center along the relative rotation axis of both shafts in the opening and the diameter It is preferable that they are arranged so as to overlap in the direction.
As a result, it is possible to detect a torque corresponding to the amount of relative rotation in both cases where both shafts are relatively rotated in one direction and when they are relatively rotated in the other direction.
[0009]
The coil includes a first coil and a second coil of the same specification arranged in parallel along the relative rotational axis direction of both shafts, and the opening is disposed at an interval in the relative rotational axis direction of both shafts. 1 opening and 2nd opening, the 1st coil is arranged in the position which generates the magnetic flux which passes the 1st opening, the 2nd coil is arranged in the position which generates the magnetic flux which passes the 2nd opening, The first opening and the outer periphery of the magnetic flux passing part connected to the edge of the groove increase the overlapping area with each other when both shafts rotate in one direction, and when both shafts rotate in the other direction. The second opening and the outer periphery of the magnetic flux passing portion connected to the edge of the groove are relatively arranged so that the overlapping area with each other decreases, and when the two shafts rotate in one direction, the overlapping area with each other. Both shuffling Are relatively arranged so that the overlapping area with each other increases when they rotate relative to each other direction, and the absolute change of the overlapping area between the first opening and the outer periphery of the magnetic flux passage portion is relatively determined when both shafts rotate relative to each other. And the absolute value of the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage portion are equal to each other, the change in the passage magnetic flux of the magnetic flux passage portion according to the change in the overlap area, and the overlap area It is preferable that the torque transmitted by both shafts is detected based on the difference from the change in the passing magnetic flux of the magnetic flux passing portion in accordance with the change in.
According to this configuration, when both shafts relatively rotate in one direction at the time of torque transmission, the overlapping area between the first opening and the outer periphery of the magnetic flux passage portion connected to the edge of the groove increases according to the relative rotation amount, and the second opening And the overlapping area between the outer periphery of the magnetic flux passage part connected to the edge of the groove is reduced. When both shafts rotate relative to each other during torque transmission, the overlapping area between the first opening and the outer periphery of the magnetic flux passage decreases according to the amount of relative rotation, and the overlapping area between the second opening and the outer periphery of the magnetic flux passage Will increase. The magnetic flux passing through the magnetic flux passing portion changes according to the change in each overlapping area. Also, during relative rotation of both shafts, the absolute value of the change in the overlap area between the first opening and the outer periphery of the magnetic flux passage part and the absolute value of the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage part Are equal to each other. Therefore, the change of the passing magnetic flux of the magnetic flux passing portion according to the change of the overlapping area between the first opening and the outer periphery of the magnetic flux passing portion, and the passage of the magnetic flux according to the change of the overlapping area of the second opening and the outer periphery of the magnetic flux passing portion. Torque transmitted by both shafts can be detected based on the difference from the change in the passing magnetic flux of the part, and the torque detection sensitivity can be increased. In addition, when the temperature fluctuates, the magnetic flux passing through the magnetic flux passing portion overlapping the first opening and the magnetic flux passing through the magnetic flux passing portion overlapping the second opening change by the same amount, so torque based on the difference between the two magnetic flux changes. By detecting this, fluctuations in detected torque due to temperature fluctuations can be offset.
[0010]
A plurality of the first openings are formed so as to be arranged in parallel at equal intervals in the circumferential direction of the cylindrical member, and the second openings are arranged in parallel at equal intervals in the circumferential direction of the cylindrical member. A plurality of the grooves are provided so as to be arranged in parallel at equal intervals in the circumferential direction of the first shaft, and the circumferential dimension of each groove is greater than the circumferential dimension of the magnetic flux passage portion between the grooves. And the circumferential dimension of the magnetic flux passage portion between the grooves is larger than the circumferential dimension of each opening, and between the circumferential directions of the first openings. In the relative rotation range of both shafts corresponding to the torque detection range, each first opening overlaps one edge along the relative rotation axis of both shafts in the groove, and each second opening is Both shuffs in the groove Preferably arranged along the relative rotational axis so as to overlap the other edge.
Thereby, the torque detection sensitivity can be improved by increasing the number of first and second openings and grooves.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The torque sensor 1 shown in FIGS. 1-5 detects the steering torque in the power steering apparatus of a vehicle. The torque sensor 1 includes a housing 2, a first shaft 3, and a second shaft 4. The first shaft 3 is supported by the housing 2 via a bearing 5 and is supported by an inner periphery of a recess 4 a formed at one end of the second shaft 4 via a bush 6. The second shaft 4 is supported by the housing 2 via a bearing 7. A steering assist force is applied according to the detected torque.
[0012]
A torsion bar 8 is inserted into the axial hole 3 a formed in the first shaft 3 and the recess 4 a of the second shaft 4. One end of the torsion bar 8 is connected to the first shaft 3 by a pin 9 so as to rotate together, and the other end is connected to the second shaft 4 via a serration 10 so as to rotate together. Thus, the second shaft 4 is arranged coaxially with the first shaft 3 and is elastically coupled to the first shaft 3 so as to be relatively rotatable. One end side of the first shaft 3 is connected to a steering wheel (not shown), and the other end side of the second shaft 4 is connected to a steering gear such as a rack and pinion type steering gear. Thereby, the rotation of the steering wheel for steering is transmitted to the wheels via the first and second shafts 3 and 4, and the steering angle changes.
[0013]
The second shaft 4 is connected to a cylindrical tubular member 12 so as to be coaxial and rotate together. In the present embodiment, the cylindrical member 12 is press-fitted into the outer periphery of the second shaft 4 on one end side, but may be integrated by an appropriate fixing means such as a screw. As shown in FIGS. 2 and 3, (1) and (2), the cylindrical member 12 is made of an insulating synthetic resin cylindrical outer cylinder portion 12a and a conductive non-magnetic metal cylindrical inner portion. It is comprised from the cylinder part 12b. Examples of the synthetic resin include PA6 (nylon), POM (polyacetal), and the like, which have good slidability when in contact with the first shaft 3 and can be injection-molded with the inner cylindrical portion 12b formed of aluminum or the like. . The outer cylinder portion 12 a is arranged in the housing 2 so as to surround the outer periphery of the first shaft 3 with a gap ε. The inner cylinder part 12b is embedded in the outer cylinder part 12a.
[0014]
A first coil holder 31 made of a magnetic material and a second coil holder 32 made of a magnetic material are inserted into the inner periphery of the housing 2. As shown in FIG. 2, each coil holder 31, 32 includes cylindrical outer peripheral portions 31a, 32a, and annular peripheral wall portions 31b, 32b extending inwardly from one end side of the outer peripheral portions 31a, 32a, It is comprised from the cyclic | annular cover parts 31c and 32c which go to an inner side from the other end side of the outer peripheral parts 31a and 32a. Each of the coil holders 31 and 32 is sandwiched between the step 2 a formed on the inner periphery of the housing 2 and the retaining ring 53 fitted on the inner periphery of the housing 2 via the leaf spring 54. Fixed.
[0015]
The first coil 33 held by the first coil holder 31 and the second coil 34 held by the second coil holder 32 are arranged in parallel along the relative rotational axis direction of the shafts 3 and 4. Both coils 33 and 34 have the same specifications, and are configured by winding the conductive wires 33a and 34a around bobbins 33b and 34b made of an insulating material around the axis of the first shaft 3, and around the inner circumferences of the coil holders 31 and 32 , respectively. Has been inserted. The coil holders 31 and 32 and the coils 33 and 34 are arranged so as to surround the outer periphery of the cylindrical member 12 with a gap. Each coil 33, 34 constitutes a torque detection circuit as described later, and generates a magnetic flux so as to generate an alternating magnetic field.
[0016]
The first shaft 3 is made of a magnetic metal material, so that the outer periphery of the first shaft 3 is disposed at the position where the magnetic flux generated by the coils 33 and 34 passes, and the outer periphery of the first shaft 3 passes through the magnetic metal material along the cylindrical surface. The part is composed. In the present embodiment, the first shaft 3 is formed from a single member, but the first shaft 3 is integrated by integrating the member constituting the magnetic flux passage part and the member constituting the part other than the magnetic flux passage part. May be formed.
[0017]
As shown in (1), (2), and FIG. 4 of FIG. 3, a plurality of grooves 40 are formed in the magnetic flux passage portion along the relative rotational axis direction of both shafts 3 and 4. The grooves 40 are arranged in parallel with each other at equal intervals in the circumferential direction of the first shaft 3. The dimensions of the grooves 40 are equal to each other. The circumferential dimension S1 of each groove 40 is larger than the circumferential dimension S2 of the magnetic flux passage portion between the grooves 40.
[0018]
The inner cylinder portion 12b has a magnetic flux restricting portion that is disposed at a position where the magnetic flux generated by the coils 33 and 34 passes while surrounding the magnetic flux passing portion of the first shaft 3. A plurality of first openings 43 and a plurality of second openings 44 are formed in the magnetic flux restricting portion. The first opening 43 and the second opening 44 are arranged at an interval in the relative rotational axis direction of the shafts 3 and 4. The first openings 43 are arranged in parallel at equal intervals in the circumferential direction of the cylindrical member 12. These second openings 44 are arranged in parallel at equal intervals in the circumferential direction of the cylindrical member 12. The shapes and dimensions of the openings 43 and 44 are equal to each other. In this embodiment, the openings 43 and 44 have a shape along a quadrilateral having an edge parallel to the rotation axis direction and an edge parallel to the rotation circumferential direction of the shafts 3 and 4. . The first coil 33 is disposed at a position where a magnetic flux passing through each first opening 43 is generated, and the second coil 34 is disposed at a position where a magnetic flux passing through each second opening 44 is generated.
[0019]
As shown in FIG. 2, in the relative rotational axis direction of the shafts 3 and 4, the dimensions of the openings 43 and 44 exceed the dimensions of the coils 33 and 34 and are smaller than the dimensions of the coil holders 31 and 32. The first opening 43 is disposed between both ends of the first coil holder 31, the second opening 44 is disposed between both ends of the second coil holder 32, the first coil 33 is disposed between both ends of the first opening 43, The two coils 34 are disposed between both ends of the second opening 44. Thereby, even if the relative position in the axial direction of the first shaft 3, the second shaft 4, the first coil 33, the second coil 34, and the cylindrical member 12 fluctuates due to manufacturing tolerances or assembly tolerances, both shafts 3 4, the openings 43 and 44 can be arranged at positions where the magnetic flux generated by the coils 33 and 34 passes. Therefore, the fluctuation | variation by the tolerance of the passage magnetic flux of the magnetic flux passage part is eliminated, and the fall of detection accuracy can be prevented.
[0020]
In the radial direction of both shafts 3, 4, the outer periphery of the magnetic flux passage part connected to the edge of the groove 40, that is, the outer periphery in the portion between the grooves 40 in the first shaft 3, and the overlapping area of the openings 43, 44 are The groove 40 and the openings 43 and 44 are arranged so as to partially overlap in the radial direction of the shafts 3 and 4 so as to change according to the relative rotation of the shafts 3 and 4.
[0021]
That is, as shown in FIG. 4, the circumferential dimension S <b> 2 of the magnetic flux passing portion between the grooves 40 is larger than the circumferential dimension P <b> 1 of each opening 43, 44, and between each circumferential direction of each first opening 43. A second opening 44 is disposed. The first and second openings 43 and 44 are disposed between both ends of the groove 40 in the relative rotational axis direction of the shafts 3 and 4. In the relative rotation range of both shafts 3 and 4 corresponding to the torque detection range, each first opening 43 is one of the shafts 3 and 4 along the relative rotation axis of the shafts 3 and 4 in the groove 40 in the radial direction of both shafts 3 and 4. It overlaps with the edge 40a. In the relative rotation range of both shafts 3 and 4 corresponding to the torque detection range, the second opening 44 is the other in the radial direction of both shafts 3 and 4 along the relative rotation axis of both shafts 3 and 4 in the groove 40. It overlaps with the edge 40b. Thereby, when the both shafts 3 and 4 rotate in one direction relative to each other, the overlapping area between the first openings 43 and the outer periphery of the magnetic flux passage portion connected to the edge 40a of each groove 40 increases. When 3 and 4 rotate relative to each other, they are arranged so as to reduce the overlapping area with each other. Moreover, when the shafts 3 and 4 rotate in one direction relative to each other, the overlap area between the second openings 44 and the outer periphery of the magnetic flux passage portion connected to the edge 40b of each groove 40 is reduced. When the fours rotate relative to each other, they are arranged so that the overlapping area with each other increases. That is, the edge 40a of the groove 40 where the first opening 43 overlaps and the edge 40b of the groove 40 where the second opening 44 overlaps are opposite to each other when viewed from the center of the groove 40 in the rotational circumferential direction of the shafts 3 and 4. It is supposed to be located on the side.
[0022]
When the shafts 3 and 4 are at the detection origin position where they are not rotating relative to each other, that is, when the steering angle is zero, the overlapping area of the first opening 43 and the outer periphery of the magnetic flux passage part, the second opening 44 and the magnetic flux passage part The overlapping areas with the outer periphery are equal to each other. That is, as shown in FIG. 4, when both shafts 3, 4 are at the detection origin position, one edge 40 a along the relative rotation axis of both shafts 3, 4 in each groove 40 corresponds to both shafts in each first opening 43. It arrange | positions so that it may overlap in the center and radial direction along 3 and 4 relative rotating shafts. The other edge 40b along the relative rotational axis of the shafts 3 and 4 in each groove 40 is disposed so as to overlap in the radial direction with the center along the relative rotational axis of the shafts 3 and 4 in each second opening 44. ing. Thus, during relative rotation of the shafts 3 and 4, the absolute value of the change in the overlap area between the first opening 43 and the outer periphery of the magnetic flux passage and the overlap between the second opening 44 and the outer periphery of the magnetic flux passage. The absolute value of the change in area is made equal to each other.
[0023]
As indicated by a two-dot chain line β in FIG. 2, the magnetic flux generated by the first coil 33 passes through the first coil holder 31, the first opening 43 of the cylindrical member 12, and the magnetic flux passage portion of the first shaft 3. A first magnetic circuit including the first coil holder 31 and the magnetic flux passing portion of the first shaft 3 as components is configured, and the magnetic flux generated by the second coil 34 is generated by the second coil holder 32 and the cylindrical member 12. The second magnetic circuit including the second coil holder 32 and the magnetic flux passage portion of the first shaft 3 as components is configured by passing through the two openings 44 and the magnetic flux passage portion of the first shaft 3.
[0024]
In the above configuration, the magnetic flux regulation of the groove 40 formed in the magnetic flux passage portion of the first shaft 3 and the inner cylinder portion 12b rotating along with the second shaft 4 due to the relative rotation of the shafts 3 and 4 during torque transmission. The overlapping state with the openings 43 and 44 formed in the part changes. Thereby, in the radial direction of both shafts 3, 4, the overlapping area between the outer periphery of the magnetic flux passage part connected to the edges 40 a, 40 b of the groove 40 and the openings 43, 44 changes according to the relative rotation of both shafts 3, 4. To do. Since the magnetic flux passage part is made of a magnetic material and the inner cylinder part 12b is made of a non-magnetic material, the passing magnetic flux of the magnetic flux passage part changes due to the change in the overlapping area. Further, the magnetic flux reaching the magnetic flux passing portion is also blocked by the eddy current generated in the conductive inner cylindrical portion 12b in the alternating magnetic field generated based on the magnetic flux generation of the coils 33 and 34. Thereby, the passage magnetic flux of the magnetic flux passage part can be changed according to the change of the overlapping area. The area change corresponds to the relative rotation of the shafts 3 and 4 corresponding to the transmission torque. The output of the coils 33 and 34 is changed by electromagnetic induction based on the change in magnetic flux, and the transmission torque is detected based on the change in the coil output. In addition, since the outer cylinder part 12a in which the inner cylinder part 12b is embedded is insulative, eddy current is not generated and torque detection is not affected.
[0025]
Further, in the above configuration, when the shafts 3 and 4 are relatively rotated in one direction at the time of torque transmission, the first opening 43 and the outer periphery of the magnetic flux passage portion connected to one edge 40a of the groove 40 according to the relative rotation amount. The overlapping area increases, and the overlapping area between the second opening 44 and the outer periphery of the magnetic flux passage portion connected to the other edge 40b of the groove 40 decreases. When the shafts 3 and 4 are relatively rotated in the other direction during torque transmission, the overlapping area between the first opening 43 and the outer periphery of the magnetic flux passage is reduced according to the amount of relative rotation, and the second opening 44 and the outer periphery of the magnetic flux passage is reduced. And the above overlapping area increases. The magnetic flux passing through the magnetic flux passing portion changes according to the change in each overlapping area. In addition, when the shafts 3 and 4 are relatively rotated, the absolute value of the change in the overlap area between the first opening 43 and the outer periphery of the magnetic flux passage and the overlap area between the second opening 44 and the outer periphery of the magnetic flux passage. The absolute values of the changes are equal to each other. Therefore, according to the change of the passing magnetic flux of the magnetic flux passing part according to the change of the overlapping area between the first opening 43 and the outer periphery of the magnetic flux passing part, and according to the change of the overlapping area of the second opening 44 and the outer periphery of the magnetic flux passing part. Based on the difference from the change in the passing magnetic flux of the magnetic flux passing portion, the torque transmitted by both shafts 3 and 4 can be detected, and the torque detection sensitivity can be increased. Also, the torque corresponding to the amount of relative rotation can be detected both when the shafts 3 and 4 are relatively rotated in one direction and when they are relatively rotated in the other direction. In addition, when the temperature fluctuates, the magnetic flux passing through the magnetic flux passing portion overlapping the first opening 43 and the magnetic flux passing through the magnetic flux passing portion overlapping the second opening 44 change by the same amount. By detecting the torque based on this, it is possible to cancel the variation in the detected torque due to temperature variation.
[0026]
In the present embodiment, the coils 33 and 34 are connected to a printed circuit board 35 attached to the outer surface side of the housing 2 via wiring. A torque detection circuit shown in FIG. 5 is formed on the printed board 35. In the circuit, the first coil 33 is connected to the oscillator 46 through the resistor 45, the second coil 34 is connected to the oscillator 46 through the resistor 47, and the coils 33 and 34 are connected to the differential amplifier circuit 48. The As a result, the torsion bar 8 is twisted by torque transmission between the shafts 3 and 4 so that the shafts 3 and 4 are elastically rotated relative to each other. The overlapping area with the outer periphery changes, and the passing magnetic flux of the magnetic flux passing part changes due to the change in the overlapping area, whereby the outputs of the first and second coils 33 and 34 change. Based on the output of the differential amplifying circuit 48 corresponding to the difference between the change in the passing magnetic flux of the magnetic flux passing portion overlapping the first opening 43 and the change of the passing magnetic flux of the magnetic flux passing portion overlapping the second opening 44, both shafts 3 The torque transmitted by 4 is detected. A steering assist force is applied by an unillustrated actuator such as a motor driven in accordance with a signal corresponding to the transmission torque output from the differential amplifier circuit 48. A known configuration can be adopted as the steering assist force applying mechanism.
[0027]
According to the above configuration, since the outer cylinder portion 12a surrounding the outer periphery of the first shaft 3 with the gap ε is made of synthetic resin, the axial center of the first shaft 3 and the axial center of the second shaft 4 are external forces. Even if it is relatively inclined due to the action or the like, it is the synthetic resin that the outer periphery of the first shaft 3 contacts. Therefore, the frictional force that prevents the relative rotation of the shafts 3 and 4 at the contact portion can be reduced as compared with the case where the metals are in contact with each other, and a decrease in torque detection accuracy can be prevented.
[0028]
The present invention is not limited to the above embodiment. For example, one end side of the first shaft 3 may be connected to the steering gear, and the other end side of the second shaft 4 may be connected to the steering wheel. In addition, the torque sensor of the present invention may be used to detect torque other than the steering device.
[0029]
【The invention's effect】
According to the present invention, a torque sensor excellent in detection accuracy and detection sensitivity can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a torque sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part of the torque sensor according to an embodiment of the present invention. FIG. 4 is a partially exploded perspective view of a tubular member. FIG. 4 is a partially developed perspective view of a tubular member of a torque sensor according to an embodiment of the present invention. Diagram showing detection circuit 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 Torque sensor 3 1st shaft 4 2nd shaft 12 Tubular member 12a Outer cylinder part 12b Inner cylinder parts 31, 32 Coil holder 33 First coil 34 Second coil 40 Groove 43 First opening 44 Second opening

Claims

A first shaft;
A second shaft connected coaxially and elastically to the first shaft so as to be relatively rotatable;
A cylindrical member connected to the second shaft so as to rotate coaxially with the second shaft;
A coil that is arranged so as to surround the outer periphery of the cylindrical member and generates a magnetic flux so as to generate an alternating magnetic field,
The cylindrical member includes an insulating synthetic resin outer cylindrical portion disposed so as to surround the outer periphery of the first shaft via a gap, and a conductive nonmagnetic metal material embedded in the outer cylindrical portion. An inner cylinder part made of,
The outer periphery of the first shaft constitutes a magnetic flux passing portion made of a magnetic metal material arranged at a position where the generated magnetic flux of the coil passes,
The inner cylinder portion has a magnetic flux restricting portion that surrounds the magnetic flux passage portion and is disposed at a passage position of the generated magnetic flux of the coil,
A groove along the relative rotational axis direction of both shafts is formed in the magnetic flux passage part,
An opening is formed in the magnetic flux regulating part,
In the radial direction of both shafts, the groove and the opening are arranged such that the overlapping area between the outer periphery of the magnetic flux passage part connected to the edge of the groove along the direction of the relative rotation axis and the opening changes according to the relative rotation of both shafts. Is arranged so as to partially overlap in the radial direction of both shafts,
Based on the change of the passing magnetic flux of the magnetic flux passing part according to the change of the overlapping area, the torque transmitted by both shafts is detected ,
A coil holder made of a magnetic material for holding the coil is provided, the coil holder including a cylindrical outer peripheral portion surrounding the coil, a portion inward from one end side of the outer peripheral portion, and the other end of the outer peripheral portion Having a portion that faces inward from the side,
In the relative rotation axis direction of both shafts, the size of the opening exceeds the size of the coil and is less than the size of the coil holder, the opening is disposed between both ends of the coil holder, and the coil is disposed at both ends of the opening. Placed between
The opening has a shape along a quadrilateral having an edge parallel to the rotation axis direction of both shafts and an edge parallel to the rotation circumferential direction,
The opening is disposed between both ends of the groove in the relative rotational axis direction of both shafts,
When both shafts are at the detection origin position where they are not rotating relative to each other, the edge along the relative rotation axis of both shafts in the groove is arranged to overlap the center along the relative rotation axis of both shafts in the opening in the radial direction And
The cylindrical member is a torque sensor that is connected to the second shaft at one end side and has a free end at the other end side .

As the coil, comprising a first coil and a second coil of the same specification arranged in parallel along the relative rotational axis direction of both shafts,
As the opening, provided with a first opening and a second opening arranged with an interval in the relative rotational axis direction of both shafts,
The first coil is disposed at a position for generating a magnetic flux passing through the first opening, and the second coil is disposed at a position for generating a magnetic flux passing through the second opening.
The first opening and the outer periphery of the magnetic flux passing part connected to the edge of the groove increase the overlapping area with each other when both shafts rotate in one direction, and when both shafts rotate in the other direction. Arranged relative to each other to reduce the overlapping area with each other,
The outer periphery of the magnetic flux passage portion connected to the edge of the second opening and the groove reduces the overlapping area with each other when both shafts rotate in one direction, and when both shafts rotate in the other direction. Arranged to increase the overlapping area with each other,
The absolute value of the change in the overlap area between the first opening and the outer periphery of the magnetic flux passage and the absolute value of the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage at the time of relative rotation of both shafts are: Equal to each other,
Based on the difference between the change in the passing magnetic flux of the magnetic flux passing portion in response to changes in the overlapping area, the change in the passing magnetic flux of the magnetic flux passing portion corresponding to the change of the overlapping area, the torque transmitted by the shafts The torque sensor according to claim 1, wherein is detected .

A plurality of the first openings are formed so as to be arranged in parallel at equal intervals in the circumferential direction of the cylindrical member,
A plurality of the second openings are formed so as to be arranged in parallel at equal intervals in the circumferential direction of the cylindrical member,
A plurality of the grooves are provided so as to be arranged in parallel at equal intervals in the circumferential direction of the first shaft,
The circumferential dimension of each groove is made larger than the circumferential dimension of the magnetic flux passage between each groove, and larger than the circumferential dimension of each opening,
The circumferential dimension of the magnetic flux passing part between the grooves is larger than the circumferential dimension of each opening, and each second opening is disposed between the circumferential directions of each first opening,
In the relative rotation range of both shafts corresponding to the torque detection range, each first opening overlaps one edge along the relative rotation axis of both shafts in the groove, and each second opening corresponds to the relative rotation axis of both shafts in the groove. The torque sensor according to claim 2 , wherein the torque sensor is disposed so as to overlap the other edge along the line .