JP2004093184A

JP2004093184A - Torque sensor for electric power steering

Info

Publication number: JP2004093184A
Application number: JP2002251136A
Authority: JP
Inventors: Mamoru Ichikawa; 市川　守; Kohei Yamanaka; 山中　公平; Koichiro Aso; 麻生　宏一郎; Fumiyuki Yamaoka; 山岡　史之; Tetsuya Okamura; 岡村　哲也
Original assignee: Hitachi Unisia Automotive Ltd; Unisia JKC Steering Systems Co Ltd
Current assignee: Hitachi Unisia Automotive Ltd; Unisia JKC Steering Systems Co Ltd
Priority date: 2002-08-29
Filing date: 2002-08-29
Publication date: 2004-03-25

Abstract

<P>PROBLEM TO BE SOLVED: To easily correct a difference in a characteristic of a magnetic field of both detecting coils without being restricted by a layout and without enlarging a structure by an increase in the coil winding number. <P>SOLUTION: The difference in the characteristic of the magnetic field of a pair of upper-lower both detecting coils 8 and 9 is corrected by making the area of both overlapping part different by mutually making an angle of shaft directional both overlapping parts different with both respective window parts 61 and 71 of a pair of upper-lower both surrounding members 6 and 7 to respective non-cutout parts 52 of a surrounding object member 5 at a neutral point of a torque sensor TS. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、電動パワーステアリング用トルクセンサに関し、特に、トルク検出精度の向上技術に関する。
【０００２】
【従来の技術】
従来の電動パワーステアリング用トルクセンサに適用されるトルクセンサとしては、例えば、特開平９−１８９６２５号公報に記載されているようなものが開示されている。
即ち、この従来例のトルクセンサは、同軸に配設された第１および第２の回転軸をトーションバーを介して連結すると共に、導電性でかつ非磁性の材料からなる円筒部材（被包囲部材）を、前記第１の回転軸の外周面を包囲するように、前記第２の回転軸と回転方向に一体とし、前記第１の回転軸の少なくとも前記円筒部材に包囲された被包囲部（被包囲部材）を磁性材料で形成し、前記被包囲部には軸方向に延びる溝（切欠部）を形成し、前記溝の周方向幅は前記被包囲部の前記溝でない部分（非切欠部）の周方向幅よりも広く形成し、前記円筒部材には前記第１の回転軸との相対回転位置に応じて前記溝との重なり具合が変化するように窓（切欠部）を上下２列形成し、前記円筒部材の前記２列の窓が形成された部分の各窓をそれぞれ包囲するように上下一対のコイル（検出コイル）を配置し、前記両コイルのインピーダンス変化に基づいて前記第１および第２の回転軸に発生するトルクを検出するように構成されたものであった。
【０００３】
なお、このトルクセンサにおける上下一対のコイルは、一方をトルク検出用として用い、他方は温度補償用として用いられるものであるため、互いに同一仕様のものが用いられており、また、上下一対のコイル（検出コイル）に対応して円筒部材（包囲部材）に設けられる２列の窓（切欠部）の開口形状および寸法・面積も全て同一に形成されている。
【０００４】
【発明が解決しようとする課題】
しかしながら、両検出コイルを両回転軸の外形が異なる段違い部に配置した場合にあっては、両検出コイルに同一仕様のものを用いていても両検出コイルにおける磁界のもれ量に差が生じる関係で、両検出コイルの磁界の特性にずれが発生し、トルク検出精度を低下させるため、両検出コイルのレイアウト位置が両回転軸の軸径が同一の個所に限定され、段違い部分には配置できないため、レイアウトに大きな制約を受けるという問題があった。
また、両検出コイルにおけるコイル温度特性のばらつきによっても、両検出コイルの磁界の特性にずれが生じるが、このずれをコイル巻き数の増加により修正しようとすると、構造の大型化を招くと共に、温度によるセンサ出力特性変化代（図９の転舵トルクに対するコイルインダクタンス可変特性図におけるコイルインダクタンスの上下方向の変化）が変わってしまうため、調整が極めて困難であるという問題がある。なお、制御回路内に温度特性のばらつきを補正する補正回路を設けることが考えられるが、回路構成が複雑化すると共に、特に高価なサーミスタにより温度特性を補正する必要があるためにコスト高になるという問題がある。
【０００５】
本発明は、上述の従来の問題点に着目してなされたもので、両回転軸の外形が異なる段違い部に両検出コイルを配置することで両検出コイルの磁界の特性が異なってしまったり、両検出コイルにおけるコイル温度特性のばらつきにより互いに磁界の特性にずれが生じるような場合においても、レイアウトの制約を受けることなく、かつ、コイル巻き数の増加等による構造の大型化を招くことなしに、両検出コイルの磁界の特性のずれを容易に修正することができる電動パワーステアリング用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】
上述の目的を達成するために、本発明請求項１記載の電動パワーステアリング用トルクセンサは、第１回転軸と第２回転軸との間に介装された弾性体と、前記第１回転軸と第２回転軸のいずれか一方側に固定されていて円周方向所定間隔のもとに切欠部と非切欠部が複数形成された磁性材料よりなる被包囲部材と、該被包囲部材における切欠部と非切欠部が形成された面とそれぞれ対向する状態でその基部が前記第１回転軸と第２回転軸のもう一方側に固定されていて前記被包囲部材における切欠部に対応する切欠部が円周方向所定間隔のもとに複数形成された磁路遮断部を構成する導電性かつ非磁性材料よりなる上下一対の包囲部材と、前記上下一対の包囲部材をそれぞれ介して被包囲部材における切欠部と非切欠部が形成された面とそれぞれ対向する状態で設けられていて前記被包囲部材の切欠部および非切欠部と両包囲部材の切欠部との重なり具合の変化をインピーダンス変化に基づいて検出することにより前記第１回転軸と第２回転軸との間に発生するトルクを検出する互いに同一仕様の上下一対の検出コイルと、該両各検出コイルをそれぞれ包囲状態で収容する磁性材料からなるヨーク部材と、前記被包囲部材、両包囲部材、両検出コイルおよびヨーク部材を収容すると共に前記上下一対の両検出コイルをそれぞれ収容したヨーク部材が固定されるハウジングと、を備えた電動パワーステアリング用トルクセンサにおいて、
前記上下一対の両包囲部材における両切欠部の開口面積を異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正するように構成されていることを特徴とする手段とした。
【０００７】
請求項２記載の電動パワーステアリング用トルクセンサは、請求項１記載の電動パワーステアリング用トルクセンサにおいて、前記被包囲部材が、前記第１回転軸に固定される環状基部と該環状基部から複数の棒状部材が放射状に延設された前記非切欠部を構成する磁路形成部とからなっていて各磁路形成部相互間に前記切欠部が形成され、前記包囲部材が、前記第２回転軸に固定される基部と該基部から外向フランジ状に延設されていて前記被包囲部材の第２回転軸側の面に対向する第１磁路遮断部と該第１磁路遮断部の外周縁部から軸方向に延設された接続部と該接続部から内向きに延設されていて前記被包囲部材の第１回転軸側の面と対向する第２磁路遮断部とからなり、前記上下一対の検出コイルは前記被包囲部材および前記上下一対の包囲部材を挟んで軸方向に対向する状態で設けられ、前記第２回転軸の最大外径部が前記被包囲部材、包囲部材および検出コイルを収容するヨーク部材の内径よりも小径に形成され、前記第１磁路遮断部には前記複数の切欠部が窓状に形成され、前記第２磁路遮断部が、その中心部に前記第２回転軸および前記被包囲部材における環状基部を貫通可能な挿通穴が形成されていると共に前記被包囲部材の各磁路形成部に対向する部分には前記挿通穴と連通し前記磁路形成部を貫通可能な状態で前記各切欠部が放射状に形成され、前記上下一対の両包囲部材のうち前記第１磁路遮断部側に形成される切欠部の内径側を軸心方向に延長して両切欠部の開口面積を異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正するように構成されていることを特徴とする手段とした。
【０００８】
請求項３記載の電動パワーステアリング用トルクセンサは、第１回転軸と第２回転軸との間に介装された弾性体と、前記第１回転軸と第２回転軸のいずれか一方側に固定されていて円周方向所定間隔のもとに切欠部と非切欠部が複数形成された磁性材料よりなる被包囲部材と、該被包囲部材における切欠部と非切欠部が形成された面とそれぞれ対向する状態でその基部が前記第１回転軸と第２回転軸のもう一方側に固定されていて前記被包囲部材における切欠部に対応する切欠部が円周方向所定間隔のもとに複数形成された磁路遮断部を構成する導電性かつ非磁性材料よりなる上下一対の包囲部材と、前記上下一対の包囲部材をそれぞれ介して被包囲部材における切欠部と非切欠部が形成された面とそれぞれ対向する状態で設けられていて前記被包囲部材の切欠部および非切欠部と両包囲部材の切欠部との重なり具合の変化をインピーダンス変化に基づいて検出することにより前記第１回転軸と第２回転軸との間に発生するトルクを検出する互いに同一仕様の上下一対の検出コイルと、該両各検出コイルをそれぞれ包囲状態で収容する磁性材料からなるヨーク部材と、前記被包囲部材、両包囲部材、両検出コイルおよびヨーク部材を収容すると共に前記上下一対の両検出コイルをそれぞれ収容したヨーク部材が固定されるハウジングと、を備えた電動パワーステアリング用トルクセンサにおいて、
前記トルクセンサの中立点における前記被包囲部材の各非切欠部に対する前記上下一対の両包囲部材の両各切欠部との軸方向の両重なり部の面積を互いに異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正するように構成されていることを特徴とする手段とした。
【０００９】
請求項４記載の電動パワーステアリング用トルクセンサは、請求項３記載の電動パワーステアリング用トルクセンサにおいて、前記被包囲部材が、前記第１回転軸に固定される環状基部と該環状基部から複数の棒状部材が放射状に延設された前記非切欠部を構成する磁路形成部とからなっていて各磁路形成部相互間に前記切欠部が形成され、前記包囲部材が、前記第２回転軸に固定される基部と該基部から外向フランジ状に延設されていて前記被包囲部材の第２回転軸側の面に対向する第１磁路遮断部と該第１磁路遮断部の外周縁部から軸方向に延設された接続部と該接続部から内向きに延設されていて前記被包囲部材の第１回転軸側の面と対向する第２磁路遮断部とからなり、前記上下一対の検出コイルは前記被包囲部材および前記上下一対の包囲部材を挟んで軸方向に対向する状態で設けられ、前記第２回転軸の最大外径部が前記被包囲部材、包囲部材および検出コイルを収容するヨーク部材の内径よりも小径に形成され、前記第１磁路遮断部には前記複数の切欠部が窓状に形成され、前記第２磁路遮断部が、その中心部に前記第２回転軸および前記被包囲部材における環状基部を貫通可能な挿通穴が形成されていると共に前記被包囲部材の各磁路形成部に対向する部分には前記挿通穴と連通し前記磁路形成部を貫通可能な状態で前記各切欠部が放射状に形成され、前記トルクセンサの中立点における前記被包囲部材の各非切欠部に対する前記上下一対の両包囲部材の両各切欠部との軸方向の両重なり部の角度を互いに異ならせて両重なり部の面積を異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正するように構成されていることを特徴とする手段とした。
【００１０】
【作用および効果】
この発明請求項１記載の電動パワーステアリング用トルクセンサでは、上述のように、前記上下一対の両包囲部材における両切欠部の開口面積を異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正することができるようになる。
従って、例えば、第１回転軸と第２回転軸との外径が異なる段違い部に両検出コイルを配置することで両検出コイルの磁界の特性が異なってしまうような場合においても、両検出コイルの磁界の特性のずれを容易に修正できるため、両検出コイルのレイアウトの自由度を拡大させることができるようになる。
また、両検出コイルにおけるコイル温度特性のばらつきも、コイル巻き数の増加等による構造の大型化を行うことなしに、調整することができるようになる。
【００１１】
請求項２記載の電動パワーステアリング用トルクセンサは、請求項１記載の電動パワーステアリング用トルクセンサにおいて、上述のように、前記第２回転軸の最大外径部が前記被包囲部材、包囲部材および検出コイルを収容するヨーク部材の内径よりも小径に形成されることで、第１回転軸と第２回転軸とを弾性部材を介して接続した後からでも、第２回転軸側に固定される包囲部材はもちろん、第１回転軸側に固定される被包囲部材およびハウジング側に固定される両検出コイルをも全て第２回転軸側から装着することができ、これにより、組み付け作業性を向上させることができるようになる。
さらに、包囲部材が第２回転軸側に固定されるため、包囲部材を固定した後に第２回転軸側の検出コイルを挿入することができ、よって、包囲部材を容易に第２回転軸に固定することができるようになる。
【００１２】
また、前記包囲部材における第１磁路遮断部には複数の切欠部が窓状に形成され、第２磁路遮断部が、その中心部に第２回転軸および被包囲部材における環状基部を貫通可能な挿通穴が形成されていると共に被包囲部材の各磁路形成部に対向する部分には挿通穴と連通し前記磁路形成部を貫通可能な状態で各切欠部が放射状に形成されている構成とすることで、被包囲部材が包囲部材の第２磁路遮断部を軸方向に貫通可能であるため、第１回転軸に被包囲部材を装着固定した後に、第１磁路遮断部と第２磁路遮断部とが接続部を介して一体に形成された構造の包囲部材を第２回転軸側から挿入し、被包囲部材の軸方向両面から挟む状態で第１磁路遮断部と第２磁路遮断部を組み付け配置することができるようになる。
従って、組み付け作業性をさらに高めることができるようになる。
【００１３】
また、前記上下一対の両包囲部材のうち前記第１磁路遮断部側に形成される窓状切欠部の内径側を軸心方向に延長して両切欠部の開口面積を異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正するように構成されているため、包囲部材の大きさを径方向に拡大することなしに、両検出コイルの磁界の特性のずれを修正することができるようになる。
【００１４】
請求項３記載の電動パワーステアリング用トルクセンサは、上述のように、前記トルクセンサの中立点における前記被包囲部材の各非切欠部に対する前記上下一対の両包囲部材の両各切欠部との軸方向の両重なり部の面積を互いに異ならせることにより、前記上下一対の両検出コイルの磁界の特性のずれを修正することができるようになる。
従って、前記請求項１の発明と同様の作用・効果が得られる他、径方向および軸方向のいずれにもトルクセンサを拡大させることなしに、両検出コイルの磁界の特性のずれを修正することができるようになるという追加の効果が得られる。
【００１５】
請求項４記載の電動パワーステアリング用トルクセンサは、請求項３記載の電動パワーステアリング用トルクセンサにおいて、上述のように構成したことで、前記請求項２の発明と同様の作用・効果が得られる他、前記第１磁路遮断部側に形成される窓状切欠部の内径側を軸心方向に延長して面積を拡大させるだけでは補えない分の磁界の特性のずれをも修正することができるようになる。
【００１６】
【発明の実施の形態】
以下に、本発明の実施の形態を図面に基づいて説明する。
まず、本発明の実施の形態の構成を図面に基づいて説明する。
図１は、発明の実施の形態の電動パワーステアリング用トルクセンサＴＳが適用された電動パワーステアリングを示す縦断面図、図２は同要部拡大断面図であり、両図において、１はハウジング、２は入力軸（第２回転軸）、３は出力軸（第１回転軸）、４はトーションバー（弾性体）、５は被包囲部材、６はトルク検出側包囲部材（第１磁路遮断部）、７は温度補償側包囲部材（第２磁路遮断部）、８はトルク検出用コイル（検出コイル）、９は温度補償用コイル（検出コイル）、１０はスペーサ、１１はベース部材、１２は皿ばね、１３は出力軸側ウォームホイール、１４はモータ軸側ウォームシャフトを示す。
【００１７】
さらに詳述すると、前記ハウジング１は、前記トルクセンサＴＳ部分が主に収容される上部ハウジング１１０と、前記減速ギヤＧ部分が主に収容される中央ハウジング１２０と、ラックＲ＆ピニオンＰ部分が主に収容される下部ハウジング１３０とに分割形成されていて、それぞれ軸方向に組み付けることにより１つのハウジング１が構成されるようになっている。
【００１８】
即ち、中央ハウジング１２０の上部に備えた大径部１２０ａ内に上部ハウジング１１０の下端開口縁部１１０ａを挿入すると共に、フランジ部１１０ｂを中央ハウジング１２０の開口部上端面に当接係止させた状態とし、この状態で、ボルト等により上部ハウジング１１０と中央ハウジング１２０とが締結固定される。
【００１９】
前記入力軸２および出力軸３は、前記各ハウジング１１０、１２０、１３０内に軸受けベアリング１ａ、１ｂ、１ｃを介してそれぞれ回転自在に支持された状態で、同軸に配置されている。
【００２０】
前記トーションバー４は、前記入力軸２の軸心穴２ａ内に回転可能に挿入され、その一端が軸心穴２ａの奥側で入力軸２に対しピン２ｂで固定される一方、もう一端側は出力軸３の軸心穴３ａにスプライン結合されている。
【００２１】
そして、前記入力軸２には、図外のステアリングホイールが連結されていて、このステアリングホイールの操舵力が、入力軸２、トーションバー４、および、出力軸３を経由し、出力軸３の下端に設けられたラックＲ＆ピニオンＰによりラックＲの直線運動に変換され、図外の左右の前輪に伝達されるようになっている。
【００２２】
前記被包囲部材５は、前記トルク検出用コイル８および温度補償用コイル９で発生する磁界の磁路を構成するものであり、このためステンレス等の磁性材料で焼結加工により形成され、上部ハウジング１１０内において出力軸３の上端部（入力軸２側端部）に本体部３１とは環状段部３２を形成して設けられた小径部３３の外周に圧入結合されている。（図２参照）
【００２３】
この被包囲部材５は、図３にその底面図を示すように、その中心部に前記小径部３３に圧入結合するための結合穴５０を有する環状基部の外周側には非切欠部（磁路形成部）５２を残し、円周方向所定間隔のもとに軸方向に貫通する切欠部５１が複数（この発明の実施の形態では８個）形成されている。
【００２４】
図１、２に戻り、前記トルク検出用コイル８は、インピーダンス変化に基づいて入力軸２と出力軸３との間に作用するトルクを検出するためのもので、被包囲部材５の入力軸２側の面と軸方向に対面する状態で、その下面以外を包囲するヨーク部材８０を介して上部ハウジング１１０側に固定されていて、被包囲部材５およびヨーク部材８０を磁路とする磁界を発生させる。
【００２５】
前記ヨーク部材８０は、図２に示すように、前記被包囲部材５と対向する下面以外を包囲する断面門型の本体部を構成する上面包囲部８０ａ、内周包囲部８０ｂ、外周包囲部８０ｃ、および、該外周包囲部８０ｃの下端開口端縁部から外向きに突出された固定フランジ部８０ｄとで構成されている。
【００２６】
前記温度補償用コイル９は、前記トルク検出用コイル８でトルクを検出する際に温度変化に基づく検出値の変動を修正するためのもので、被包囲部材５の出力軸３側の面と軸方向に対面する状態で、その上面以外を包囲するヨーク部材９０を介して上部ハウジング１１０側に固定されていて、被包囲部材５およびヨーク部材９０を磁路とする磁界を発生させる。
【００２７】
前記ヨーク部材９０は、図２に示すように、前記被包囲部材５と対向する上面以外を包囲する断面門型の本体部を構成する下面包囲部９０ａ、内周包囲部９０ｂ、外周包囲部９０ｃ、および、該外周包囲部９０ｃの上端開口端縁部から外向きに突出された固定フランジ部９０ｄとで構成されている。
【００２８】
前記スペーサ１０は、トルク検出用コイル８側のヨーク部材８０と温度補償用コイル９側のヨーク部材９０との軸方向間隔を決定するために介装されるもので、非導電性部材である合成樹脂材料（ＰＰＳ）で円筒状に形成され、その内側上部にはヨーク部材８０における固定フランジ部８０ｄを軸方向において位置決め係止する環状段部１０ａが形成され、内側下部にはヨーク部材９０における固定フランジ部９０ｄを位置決め係止する環状段部１０ｂが形成されている。即ち、両環状段部１０ａ、１０ｂ相互間の軸方向長さでトルク検出用コイル８と温度補償用コイル９との軸方向位置関係が決定されるようになっている。
【００２９】
前記ベース部材１１は、その下端フランジ部１１ａを中央ハウジング１２０における大径部１２０ａの内側に形成された係止段部１２０ｄ上に係止させた状態で組み込まれるもので、その上端小径円筒部１１ｂの内側にヨーク部材９０における本体部を収容する環状凹部１１ｃが形成されている。そして、前記小径円筒部１１ｂが前記スペーサ１０の下端開口部から挿入され、その上端面にヨーク部材９０の固定フランジ部９０ｄを当接係止させた状態で組み付けられる。即ち、このベース部材１１の軸方向長さにより、中央ハウジング１２０（ハウジング１）とトルク検出用コイル８および温度補償用コイル９との軸方向位置関係が決定されることになる。
【００３０】
前記固定フランジ部８０ｄと上部ハウジング１１０の内部の軸方向中間部に形成された環状段部１１０ｄとの間に前記皿ばね１２を介装させた状態で中央ハウジング１２０に対する上部ハウジング１１０の組み付けおよびボルト等による締結固定が行われることにより、皿ばね１２の付勢力により両ヨーク部材８０、９０（トルク検出用コイル８、温度補償用コイル９）の位置ずれを防止し、軸方向位置関係を維持させた状態でハウジング１への組み付けが行われる。
【００３１】
前記トルク検出側包囲部材６は、その内周側円筒部６０を入力軸２の下端部寄りの位置に形成された最大外径部２ｃの外周にかしめることにより、入力軸２に対する組み付け固定がなされている。
前記トルク検出側包囲部材６は、以上のようにその内周側円筒部６０を入力軸２に固定することにより、前記被包囲部材５とトルク検出用コイル８との間に所定のクリアランスをもって介装されている。そして、このトルク検出側包囲部材６には、図４（平面図）および図５（底面図）にその詳細を示すように、前記被包囲部材５における切欠部５１および非切欠部５２の数に対応し軸方向に貫通する窓部（切欠部）６１が円周方向所定間隔のもとに複数（この発明の実施の形態では８個）形成されている。なお、各窓部６１の周方向幅が被包囲部材５の非切欠部５２と同一幅に形成されている。
【００３２】
即ち、トルク検出側包囲部材６の窓部６１および非切欠部６２と前記被包囲部材５の切欠部５１および非切欠部５２との重なり具合の変化をインピーダンス変化に基づいて検出することにより入力軸２と出力軸３との間に発生するトルクを検出するためのものであり、このため、トルク検出側包囲部材６はアルミニウム等の導電性かつ非磁性材料で形成されている。
【００３３】
前記温度補償用包囲部材７は、前記被包囲部材５と温度補償用コイル９との間に介装されるもので、図１に示すように、その内周側は出力軸３側には固定されないフリーの状態で温度補償用包囲部材７の外周に形成される外筒部（接続部）７３とトルク検出側包囲部材６の外筒部（接続部）６３とが互いに軸方向に延長され一体に連結することにより、トルク検出側包囲部材６と一体に回動するように構成されている。
なお、温度補償用包囲部材７内周側から温度補償用コイル９の下部に至るまでの出力軸３の外周には、温度補償用包囲部材７と同一材料の円筒部材７５が圧入されており、温度補償用コイル９から出力軸３への磁束の逃げを防止して磁界を安定させるようになっている。
【００３４】
そして、図４、５に示すように、トルク検出側包囲部材６の窓部６１と温度補償側包囲部材７の窓部７１とが軸方向において互いに重ならないように所定角度（１７°、２度）ずらした状態に配置されると共に、図８（図６のＶＩＩＩ−ＶＩＩＩ線における縦断面図）に示すように、トルク検出側包囲部材６の各窓部６１と温度補償側包囲部材７の各窓部７１との間における各非切欠部６２、７２の重なり部の幅ａが被包囲部材５の各非切欠部５２の周方向幅ｂよりは狭い幅に形成されることにより、被包囲部材５における各非切欠部５２の両側部が両各窓部６１、７１側にそれぞれ突出すると共に、入力軸２側に回転力が加わっていないトルク値０の状態（中立点）で、図６（平面図）、図７（底面図）および図８に示すように、両突出部ｃ、ｄの突出比率を互いに異ならせた状態で配置されている。ちなみに、両窓部６１、７１の周方向幅は回転角で１２．５°、非切欠部５２は１１°に設定されている。
【００３５】
また、温度補償側包囲部材７は、図２、５、７に示すように、各窓部７１の軸心側がそれぞれ軸心穴（挿通穴）７４と連通する切り欠き状に形成されることにより、前記被包囲部材５における環状基部および被切欠部（磁路形成部）５２が温度補償側包囲部材７を軸方向に通過可能となっている。
そして、前記入力軸２におけるの最大外径部２ｃが、前記トルク検出用包囲部材６における内周側円筒部６０の内径はもちろん、前記被包囲部材５における結合穴５０の内径、トルク検出用コイル８および温度補償用コイル９を収容するヨーク部材８０、９０の内径よりも小径に形成されていて、これら全てのセンサ部材が入力軸２側から組み付けられるようになっている。
【００３６】
一方、トルク検出側包囲部材６の窓部６１は四方を完全に囲まれた窓状に形成されているのに対し、温度補償側包囲部材７の窓部７１は上述のように軸心側がそれぞれ軸心穴（挿通穴）７４と連通する切り欠き状に形成されている関係で、窓状に比べて磁束の逃げが大きくなり、これにより、トルク検出用コイル８と温度補償用コイル９の磁界の特性にずれが生じることになる。そこで、この発明の実施の形態では、図４、５に示すように、トルク検出側包囲部材６の窓部６１の内径側を軸心方向に延長して同窓部６１の開口面積を拡大することにより、両コイル８、９の磁界の特性のずれを修正するように構成されている。
なお、この窓部６１の開口面積の拡大による磁界の特性のずれの修正は、予め現物を製作し、磁路がどのように形成されるかをシュミレーションし、その結果を基に窓部６１の延長寸法を決定する。
【００３７】
そこで、主にトルクセンサＴＳ部分の各部材の組み付け手順、および、トルク検出用コイル８と温度補償用コイル９の磁界の特性のずれのもう１つの修正方法について説明する。
（イ）ベアリング１ｂが圧入固定された出力軸３を中央ハウジング１２０の下方から挿通させ、ベアリング１ｂを小径部１２０ｂ内面に圧入することにより、中央ハウジング１２０に対し出力軸３の中間部を回転自在に軸支した状態に組付ける。なお、出力軸３にはその軸心穴３ａに対しトーションバー４の下端をスプライン結合すると共に、トーションバー４の上端部を入力軸２の軸心穴２ａ内に挿入した状態で、トーションバー４および入力軸２を直径方向に貫通するピン装着穴２ｇを穿設し、この装着穴２ｇにピン２ｃを圧入装着することによりトーションバー４の上端部側を入力軸２に固定する。なお、ピン装着穴２ｇの穿設加工時に発生する切削油や切粉の除去処理をした後、次の工程に進む。
【００３８】
（ロ）ベース部材１１の下端フランジ部１１ａを中央ハウジング１２０における大径部１２０ａ内に形成された環状段部１２０ｄ上に係止させた状態で組み付ける。
（ハ）ベース部材１１の環状凹部１１ｃ内にヨーク部材９０の本体部を収容し、かつ、固定フランジ部９０ｄをベース部材１１の上端小径円筒部１１ｂの上端面に当接係止させた状態でヨーク部材９０（温度補償用コイル９）を組み付ける。
（ニ）出力軸３の上端小径部３３に被包囲部材５の結合穴５０を圧入して組み付ける。その際、温度補償用コイル９と被包囲部材５相互間のクリアランスをセンサなどで計測しながら被包囲部材５の軸方向位置決めが行われる。
【００３９】
（ホ）外筒部７３、６３を介して温度検出側包囲部材７が一体化されたトルク検出側包囲部材６は、その内周側円筒部６０を入力軸２の最大外形部２ｃの外周にかしめることにより、入力軸２に対し組み付け固定する。この固定に際しては、温度検出側包囲部材７は、前述のように、前記被包囲部材５における環状基部および被切欠部（磁路形成部）５２が温度補償側包囲部材７を軸方向に通過可能となっているため、この温度検出側包囲部材７を被包囲部材５と温度補償用コイル９との間に所定のクリアランスが形成されるように軸方向配置させると共に、入力軸２側に回転力が加わっていないトルク値０の状態（中立点）で、トルク検出用コイル８と温度補償用コイル９の磁界の特性のずれの修正が行われる。
即ち、被包囲部材５における各非切欠部５２の周方向両側部が両各窓部６１、７１側にそれぞれ突出する部分の比率を変えることにより、トルク検出用コイル８および温度補償用コイル９で検出されるインピーダンスの差が０になるように包囲部材６の回転角度を調整した状態とし、この状態でポンチ等のかしめ具で前記内周側円筒部６０を入力軸２に対しかしめ状態とすることにより、入力軸２に対しトルク検出側包囲部材６および温度補償側包囲部材７を軸方向および周方向において位置決め調整した状態で組み付け固定する。
【００４０】
（ヘ）スペーサ１０における下向きの環状段部１０ｂを温度補償用コイル９側のヨーク部材９０における固定フランジ部９０ｄの上面に当接係止させた状態で、スペーサ１０を組み付ける。
（ト）固定フランジ部８０ｄをスペーサ１０における上向きの環状段部１０ａに当接係止させた状態でヨーク部材８０（トルク検出用コイル８）を組み付ける。これにより、予め設定された両環状段部１０ａ、１０ｂの相互間隔により、トルク検出側包囲部材６を被包囲部材５とトルク検出用コイル８との間に所定のクリアランスのもとに配置させた状態とすることができる。
【００４１】
（チ）ヨーク部材８０における固定フランジ部８０ｄ上に皿ばね１２を載置した状態で、中央ハウジング１２０に対し上部ハウジング１１０の組み付を行う。即ち、入力軸２を上部ハウジング１１０の軸心穴内に圧入固定されたベアリング１ａ内に圧入することにより、上部ハウジング１１０に対し入力軸２を回転自在に軸支状態とし、中央ハウジング１２０の上部に備えた大径部１２０ａ内に上部ハウジング１１０の下端開口縁部１１０ａを挿入すると共に、フランジ部１１０ｂを中央ハウジング１２０の開口部上端面に当接係止させた状態とし、この状態で、ボルト等により上部ハウジング１１０と中央ハウジング１２０とを軸方向に締結固定することにより、固定フランジ部８０ｄと環状段部１１０ｄとの間で皿ばね１２が押圧圧縮され、その強い反発力により、ヨーク部材８０、スペーサ１０、ヨーク部材９０、および、ベース部材１１が、皿ばね１２と環状段部１２０ｄとの間に軸方向に挟持された状態で固定される。
【００４２】
次に、この発明の実施の形態のトルクセンサＴＳのトルク検出方法について説明する。
この発明の実施の形態のトルクセンサＴＳは、トルク０の状態では、上述のように、トルク検出用コイル８と温度補償用コイル９の磁界の特性のずれの修正が行われているため、トルク検出用コイル８および温度補償用コイル９で検出されるインピーダンス値の差は略０（トルク値０）となっている。
【００４３】
そこで、まず、入力軸２にステアリング回転が入力されると、トーションバー４が捻じれることで、包囲部材６と被包囲部材５に相対角度差が生じ、これにより、トルク検出用コイル８と温度補償用コイル９が形成する磁路回路が変化し、トルク検出用コイル８と温度補償用コイル９のインダクタンスが変化する。
【００４４】
即ち、図９のコイルインダクタンス可変特性図に示すように、右転舵方向では、被包囲部材５に対し、トルク検出用包囲部材６および温度補償用包囲部材７が時計方向に相対回動し、これにより、温度補償用包囲部材７の窓部７１に対する被包囲部材５の非切欠部５２の重なり面積が減少してコイル検出用包囲部材６の窓部６１に対する重なり面積が増加する方向に変化するため、トルク検出用コイル８側のコイルインダクタンスが増加して温度補償用コイル９のコイルインダクタンスが減少する方向に変化し、また、左転舵方向では、以上とは逆に、トルク検出用コイル８側のコイルインダクタンスが減少して温度補償用コイル９コイルインダクタンスが増加する方向に変化する。このように、コイルインダクタンスの差が０を中心として互いにプラスとマイナスの逆方向に変化することになる。
【００４５】
そこで、トルク検出用コイル８で検出されコイルインダクタンス値と、温度補償用コイル９で検出されたコイルインダクタンス値と差分値を検出することにより、常に温度補償された状態のトルク値を検出することができると共に、トルク検出用コイル８と温度補償用コイル９でそれぞれ検出される両コイルインダクタンスの差分値として大きな値が得られるため、トルク検出精度を高めることができる。
【００４６】
以上説明してきたようにこの発明の実施の形態の電動パワーステアリング用トルクセンサにあっては、以下に列挙する効果が得られる。
即ち、前記入力軸２における最大外径部２ｃを、トルク検出側包囲部材６における内周側円筒部６０の内径はもちろん、出力軸３側に固定される被包囲部材５における結合穴５０の内径、トルク検出用コイル８および温度補償用コイル９を収容するヨーク部材８０、９０の内径よりも小径に形成したことにより、入力軸２と出力軸３とをトーションバー４を介して接続した後からでも、入力軸２側に固定される両包囲部材６、７はもちろん、出力軸３側に固定される被包囲部材５の他、ハウジング１側に固定されるトルク検出用コイル８および温度補償用コイル９をも全て入力軸２側から装着することができるようになる、従って、組み付け作業性を向上させることができるようになるという効果が得られる。
また、両包囲部材６、７が入力軸２側に固定されるため、両包囲部材６、７を固定した後に入力軸２側のトルク検出用コイル８を挿入することができるため、両包囲部材６、７を容易に入力軸２に固定することができるようになる。
【００４７】
また、前記温度補償側包囲部材７にはその中心部に入力軸２および被包囲部材５における環状基部を貫通可能な軸心穴７４が形成されていると共に被包囲部材５の各非切欠部５２と対向する部分には軸心穴７４と連通し非切欠部５２を貫通可能な状態で各窓部７１が放射状に形成された構成としたことで、被包囲部材５が温度補償側包囲部材７を軸方向に貫通可能であり、このため、出力軸３に被包囲部材５を装着固定した後に、トルク検出側包囲部材６と温度補償側包囲部材７とが外筒部６３、７３介して一体に形成された構造の包囲部材を入力軸２側から挿入し、被包囲部材５の軸方向両面から挟む状態でトルク検出側包囲部材６と温度補償側包囲部材７を組み付け配置することができるようになり、従って、組み付け作業性をさらに向上させることができるようになる。
【００４８】
また、前記両ヨーク部材８０、９０相互間にトルク検出用コイル８と温度補償用コイル９の軸方向間隔を決定する環状のスペーサ１０を介装するようにしたことで、トルク検出用コイル８と温度補償用コイル９相互間の位置関係を維持した状態での組み付けが可能となり、これにより、両ヨーク部材８０、９０（両コイル８、９）相互間のクリアランス管理を容易に行うことができるようになる。
また、スペーサ１０を設けたことで、入力軸２側のトルク検出用コイル８をハウジング１側に固定する必要がなくなるため、入力軸２側の上部ハウジング１１０を装着する前に、全てのセンサ部材を組み付けることができるようになる。
【００４９】
また、前記両ヨーク部材８０、９０を、スペーサ１０が相互間に介装された両固定フランジ部８０ｄ、９０ｄの部分において皿ばね１２およびベース部材１１を介して軸方向に押圧された状態でハウジング１に対して固定するようにしたことで、皿ばね１２を介装するだけで、両ヨーク部材８０、９０における磁界の磁路を構成する本体部の内部応力を変化させることなしにハウジング１への組み付け固定を容易に行うことができるようになると共に、皿ばね１２の付勢力により両ヨーク部材８０、９０（トルク検出用コイル８、温度補償用コイル９）の位置ずれを防止することができるようになる。
【００５０】
また、前記スペーサ１０が相互間に介装された両固定フランジ部８０ｄ、９０ｄの部分において軸方向に介装されたベース部材１１を介して軸方向に押圧した状態で両ヨーク部材８０、９０をハウジング１に対して固定するようにしたことで、ハウジング１自体を設計変更することなしに、ベース部材１１を変更するだけで、ハウジング１、両包囲部材７、８および被包囲部材５に対する両ヨーク部材８０、９０（トルク検出用コイル８、温度補償用コイル９）の軸方向取り付け位置を容易に変更することができるようになる。
【００５１】
また、上下一対のトルク検出側包囲部材６の窓部６１と温度補償側包囲部材７の窓部７１の開口面積を異ならせることにより、前記上下一対のトルク検出用コイル８と温度補償用コイル９の磁界の特性のずれを修正することができるため、この発明の実施の形態におけるように、入力軸２と出力軸３との外径が異なる段違い部にトルク検出用コイル８および温度補償用コイル９を配置することで両コイルの磁界の特性が異なってしまうような場合においても、両コイルの磁界の特性のずれを容易に修正することができ、従って、両コイル８、９のレイアウトの自由度を拡大させることができるようになる。
また、トルク検出用コイル８と温度補償用コイル９におけるコイル温度特性のばらつきも、コイル巻き数の増加等による構造の大型化を行うことなしに、調整することができるようになる。
【００５２】
また、トルク検出側包囲部材６における窓部６１の内径側を軸心方向に延長して同窓部６１の開口面積を拡大することにより、両コイル８、９の磁界の特性のずれを修正するようしたことで、トルク検出側包囲部材６の大きさを径方向に拡大することなしに、両検出コイルの磁界の特性のずれを修正することができるようになる。
【００５３】
さらに、被包囲部材５における各被切欠部５２の周方向両側部が両各窓部６１、７１側に突出する突出部ｃ、ｄの比率を調整することにより、両コイル８、９の磁界のずれを修正するようにしたことで、径方向および軸方向のいずれにもトルクセンサを拡大させることなしに、両コイル８、９の磁界の特性のずれを修正することができるようになる。これにより、前記トルク検出側包囲部材６の窓部６１と温度補償側包囲部材７の窓部７１の開口面積を異ならせることでは補えない分の磁界の特性のずれをも修正することができるようになる。
【００５４】
以上発明の実施の形態を図面により説明したが、具体的な構成はこれらの発明の実施の形態に限られるものではなく、本発明の要旨を逸脱しない範囲における設計変更等があっても本発明に含まれる。
例えば、発明の実施の形態では、入力軸２側に包囲部材を設け、出力軸３側に被包囲部材を設けたが、逆であってもよい。
【００５５】
また、発明の実施の形態では、トルク検出側包囲部材６の窓部６１と温度補償側包囲部材７の窓部７１の開口面積を異ならせると共に、被包囲部材５における各被切欠部５２の周方向両側部が両各窓部６１、７１側に突出する突出部ｃ、ｄの比率を調整するようにしたが、いずれか一方の方法のみでも十分に効果を得ることができる。
また、発明の実施の形態では、コイルと包囲部材と被包囲部材を軸方向に対向させる構造のものを例にとったが、従来例におけるように径方向に対向させる構造のものにも適用することができる。
【図面の簡単な説明】
【図１】発明の実施の形態の電動パワーステアリング用トルクセンサを示す縦断面図である。
【図２】発明の実施の形態の電動パワーステアリング用トルクセンサを示す要部拡大断面図である。
【図３】発明の実施の形態の電動パワーステアリング用トルクセンサにおける被包囲部材を示す底面図である。
【図４】発明の実施の形態の電動パワーステアリング用トルクセンサにおける両包囲部材を示す平面図である。
【図５】発明の実施の形態の電動パワーステアリング用トルクセンサにおける両包囲部材を示す底面図である。
【図６】発明の実施の形態の電動パワーステアリング用トルクセンサにおける両包囲部材と被包囲部材との位置関係を示す平面図である。
【図７】発明の実施の形態の電動パワーステアリング用トルクセンサにおける両包囲部材と被包囲部材との位置関係を示す底面図である。
【図８】図６のＶＩＩＩ−ＶＩＩＩ線における拡大縦断面図である。
【図９】発明の実施の形態の電動パワーステアリング用トルクセンサにおける操舵トルクに対するコイルインダクタンスの可変特性図である。
【符号の説明】
ＴＳ　電動パワーステアリング用トルクセンサ
１　ハウジング
２　入力軸（第２回転軸）
２ｃ　最大外径部
３　出力軸（第１回転軸）
４　トーションバー（弾性体）
５　被包囲部材
５１　切欠部
５２　非切欠部
６　トルク検出側包囲部材（第１磁路遮断部）
６１　窓部（切欠部）
６２　非切欠部
６３　外筒部（接合部）
７　温度補償側包囲部材（第２磁路遮断部）
７１　窓部（切欠部）
７２　非切欠部
７３　外筒部（接合部）
７４　軸心穴（挿通穴）
８　トルク検出用コイル（検出コイル）
８０　ヨーク部材
９　温度補償用コイル（検出コイル）
９０　ヨーク部材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a torque sensor for electric power steering, and more particularly to a technique for improving torque detection accuracy.
[0002]
[Prior art]
As a torque sensor applied to a conventional torque sensor for electric power steering, for example, a torque sensor described in Japanese Patent Application Laid-Open No. 9-189625 is disclosed.
That is, in the conventional torque sensor, the first and second rotating shafts arranged coaxially are connected via a torsion bar, and a cylindrical member (enclosed member) made of a conductive and non-magnetic material is used. ) Is integrated with the second rotating shaft in the rotating direction so as to surround the outer peripheral surface of the first rotating shaft, and the enclosed portion () surrounded by at least the cylindrical member of the first rotating shaft. The surrounding member is formed of a magnetic material, and a groove (notch portion) extending in the axial direction is formed in the surrounding portion, and the circumferential width of the groove is a non-groove portion of the surrounding portion (non-cut portion). ) Is formed wider than the circumferential width of the cylindrical member, and the cylindrical member is provided with two rows of upper and lower windows (notches) so that the degree of overlap with the groove changes according to the relative rotation position with respect to the first rotation shaft. And each of the windows in the portion of the cylindrical member where the two rows of windows are formed are wrapped. A pair of upper and lower coil (detection coil) arranged to, were those configured to detect the torque generated in the first and second axis of rotation on the basis of the impedance change of the two coils.
[0003]
In this torque sensor, one pair of upper and lower coils is used for detecting torque, and the other is used for temperature compensation. The two rows of windows (notches) provided in the cylindrical member (surrounding member) corresponding to the (detection coil) have the same opening shape, dimensions, and area.
[0004]
[Problems to be solved by the invention]
However, when the two detection coils are arranged on a stepped portion having different outer shapes of both rotating shafts, a difference occurs in the amount of leakage of the magnetic field between the two detection coils even if both detection coils have the same specification. Due to the relationship, the magnetic field characteristics of both detection coils deviate and the torque detection accuracy is reduced, so the layout position of both detection coils is limited to the same diameter of both rotating shafts, and located at the step Because of this, there is a problem that the layout is greatly restricted.
In addition, variations in the coil temperature characteristics of the two detection coils also cause a deviation in the magnetic field characteristics of the two detection coils. However, if this deviation is corrected by increasing the number of coil turns, the structure becomes large, and the temperature increases. The change in the sensor output characteristic (the change in the coil inductance in the vertical direction of the coil inductance variable characteristic with respect to the turning torque in FIG. 9) due to the change in the sensor output characteristic causes a problem that the adjustment is extremely difficult. It is conceivable to provide a correction circuit for correcting variations in temperature characteristics in the control circuit. However, the circuit configuration becomes complicated, and the cost increases because it is necessary to correct the temperature characteristics using an especially expensive thermistor. There is a problem.
[0005]
The present invention has been made by paying attention to the above-mentioned conventional problems, and by arranging both detection coils in a step portion having different outer shapes of both rotating shafts, the characteristics of the magnetic field of both detection coils may be different, Even when the characteristics of the magnetic field deviate from each other due to variations in the coil temperature characteristics of the two detection coils, the layout is not restricted and the structure is not enlarged due to an increase in the number of coil turns. It is another object of the present invention to provide an electric power steering torque sensor that can easily correct the deviation of the magnetic field characteristics of the two detection coils.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a torque sensor for electric power steering according to claim 1 of the present invention includes an elastic body interposed between a first rotation shaft and a second rotation shaft; And a surrounding member made of a magnetic material having a plurality of cutouts and non-cutouts formed at predetermined intervals in a circumferential direction, the cutout being formed on the surrounding member. Notch corresponding to a notch in the enclosed member, the base of which is fixed to the other side of the first rotation shaft and the second rotation shaft in a state in which the base opposes the surface on which the notch and the non-notch are formed, respectively. A pair of upper and lower surrounding members made of a conductive and non-magnetic material constituting a plurality of magnetic path blocking portions formed at predetermined intervals in the circumferential direction, and a pair of upper and lower surrounding members in the surrounding member via the pair of upper and lower surrounding members, respectively. Surface with notch and non-notch formed and it The first rotating shaft and the first rotating shaft are detected by detecting a change in the degree of overlap between the notch portion and the non-notch portion of the surrounding member and the notch portions of both the surrounding members based on a change in impedance. A pair of upper and lower detection coils of the same specification for detecting a torque generated between the two rotation shafts, a yoke member made of a magnetic material for accommodating each of the two detection coils in an enclosing state, A housing for accommodating the surrounding member, the two detection coils and the yoke member, and a yoke member accommodating the pair of upper and lower detection coils respectively, and a housing to which the yoke member is fixed.
The difference in the magnetic field characteristics of the pair of upper and lower detection coils is corrected by making the opening areas of the notches of the pair of upper and lower surrounding members different from each other. .
[0007]
The torque sensor for electric power steering according to claim 2 is the torque sensor for electric power steering according to claim 1, wherein the enclosed member is formed by a plurality of annular bases fixed to the first rotation shaft. A rod-shaped member extending radially extending from the magnetic path forming part constituting the non-notched part, wherein the notch part is formed between the magnetic path forming parts, and the surrounding member comprises the second rotating shaft. A first magnetic path interrupting portion extending from the base in an outward flange shape and facing the surface of the enclosed member on the second rotation axis side, and an outer peripheral edge of the first magnetic path interrupting portion A connecting portion extending in the axial direction from the portion, and a second magnetic path interrupting portion extending inward from the connecting portion and facing the surface of the enclosed member on the first rotation shaft side, A pair of upper and lower detection coils are provided for the surrounding member and the upper and lower The second rotating shaft is provided with a maximum outer diameter portion having a diameter smaller than the inner diameter of the yoke member that houses the surrounding member, the surrounding member, and the detection coil. The plurality of cutouts are formed in a window shape in the first magnetic path interrupting section, and the second magnetic path interrupting section penetrates the center of the second magnetic axis and the annular base of the enclosed member. A possible insertion hole is formed and a portion of the surrounding member facing each magnetic path forming portion is communicated with the insertion hole so that each of the cutout portions is formed in a radial manner so as to be able to penetrate the magnetic path forming portion. By extending the inner diameter side of the notch formed on the first magnetic path interrupting part side of the pair of upper and lower surrounding members in the axial direction to make the opening areas of both notches different, Correct the deviation of the magnetic field characteristics of the pair of upper and lower detection coils. It is configured as a means for said.
[0008]
The torque sensor for electric power steering according to claim 3, wherein the torque sensor is provided on an elastic body interposed between the first rotating shaft and the second rotating shaft and on one of the first rotating shaft and the second rotating shaft. An enclosed member made of a magnetic material having a plurality of notches and non-notches formed at predetermined intervals in a circumferential direction, and a surface in which the notches and non-notches are formed in the enclosed member; The base portions are fixed to the other side of the first rotation shaft and the second rotation shaft in a state where they face each other, and a plurality of notches corresponding to the notches in the enclosed member are formed at predetermined circumferential intervals. A pair of upper and lower surrounding members made of a conductive and non-magnetic material constituting the formed magnetic path blocking unit, and a surface on which a notched portion and a non-notched portion are formed in the enclosed member via the pair of upper and lower surrounding members, respectively. Is provided in a state facing each other Torque generated between the first rotation shaft and the second rotation shaft by detecting a change in the degree of overlap between the notch portion and the non-notch portion of the surrounding member and the notch portions of both the surrounding members based on the impedance change. A pair of upper and lower detection coils of the same specification, and a yoke member made of a magnetic material for accommodating each of the two detection coils in an enclosing state, And a housing to which a yoke member accommodating each of the pair of upper and lower detection coils is fixed, and a housing to which the yoke member is fixed.
The upper and lower pair of upper and lower enclosing members at the neutral point of the torque sensor differ from each other in the area of both axially overlapping portions of the upper and lower enclosing members with respect to the respective non-notched portions of the enclosing member. The means is characterized in that it is configured to correct the deviation of the characteristics of the magnetic field of both detection coils.
[0009]
The torque sensor for electric power steering according to claim 4 is the torque sensor for electric power steering according to claim 3, wherein the surrounding member includes a plurality of annular bases fixed to the first rotation shaft. A rod-shaped member extending radially extending from the magnetic path forming part constituting the non-notched part, wherein the notch part is formed between the magnetic path forming parts, and the surrounding member comprises the second rotating shaft. A first magnetic path interrupting portion extending from the base in an outward flange shape and facing the surface of the enclosed member on the second rotation axis side, and an outer peripheral edge of the first magnetic path interrupting portion A connecting portion extending in the axial direction from the portion, and a second magnetic path interrupting portion extending inward from the connecting portion and facing the surface of the enclosed member on the first rotation shaft side, A pair of upper and lower detection coils are provided for the surrounding member and the upper and lower The second rotating shaft is provided with a maximum outer diameter portion having a diameter smaller than the inner diameter of the yoke member that houses the surrounding member, the surrounding member, and the detection coil. The plurality of cutouts are formed in a window shape in the first magnetic path interrupting section, and the second magnetic path interrupting section penetrates the center of the second magnetic axis and the annular base of the enclosed member. A possible insertion hole is formed and a portion of the surrounding member facing each magnetic path forming portion is communicated with the insertion hole so that each of the cutout portions is formed in a radial manner so as to be able to penetrate the magnetic path forming portion. The two overlapping portions are formed such that the angles of the axial overlapping portions of the upper and lower surrounding members with respect to the non-notched portions of the enclosed member at the neutral point of the torque sensor are different from each other. By changing the area of the front It was a means, characterized in that is configured to modify the deviation of the magnetic field characteristics of the pair of upper and lower both detection coils.
[0010]
[Action and effect]
In the torque sensor for an electric power steering according to the first aspect of the present invention, as described above, the opening areas of the notches of the pair of upper and lower surrounding members are made different from each other, so that the magnetic field of the pair of upper and lower detecting coils is reduced. The deviation of the characteristic can be corrected.
Therefore, for example, even in a case where the two detection coils are arranged in a stepped portion where the outer diameters of the first rotation shaft and the second rotation shaft are different from each other, the characteristics of the magnetic fields of the two detection coils are different from each other. Since the deviation of the characteristics of the magnetic field can be easily corrected, the degree of freedom of the layout of the two detection coils can be increased.
In addition, variations in the coil temperature characteristics of the two detection coils can be adjusted without increasing the size of the structure due to an increase in the number of coil turns.
[0011]
The torque sensor for electric power steering according to claim 2 is the torque sensor for electric power steering according to claim 1, wherein, as described above, the maximum outer diameter portion of the second rotating shaft is the enclosed member, the enclosed member, By being formed to have a diameter smaller than the inner diameter of the yoke member that houses the detection coil, the yoke member is fixed to the second rotation shaft even after the first rotation shaft and the second rotation shaft are connected via the elastic member. Not only the surrounding member but also the surrounding member fixed to the first rotating shaft side and the two detection coils fixed to the housing side can all be mounted from the second rotating shaft side, thereby improving the assembling workability. Will be able to do that.
Furthermore, since the surrounding member is fixed to the second rotating shaft side, the detection coil on the second rotating shaft side can be inserted after the surrounding member is fixed, so that the surrounding member is easily fixed to the second rotating shaft. Will be able to
[0012]
A plurality of cutouts are formed in the first magnetic path interrupting portion of the surrounding member in a window shape, and the second magnetic path interrupting portion penetrates the center of the second magnetic axis and the annular base of the enclosed member. A possible insertion hole is formed, and a notch is formed radially in a portion of the enclosed member facing each magnetic path forming portion so as to communicate with the insertion hole and penetrate the magnetic path forming portion. Since the surrounding member can penetrate the second magnetic path blocking portion of the surrounding member in the axial direction, the first magnetic path blocking portion is attached and fixed to the first rotating shaft. The first magnetic path interrupting section is inserted in a state in which the surrounding member having a structure in which the surrounding section and the second magnetic path interrupting section are integrally formed via the connecting section is inserted from the second rotation shaft side and sandwiched from both axial sides of the enclosed member. And the second magnetic path interrupting portion can be assembled and arranged.
Therefore, the assembling workability can be further improved.
[0013]
In addition, by extending the inner diameter side of the window-shaped notch portion formed on the first magnetic path blocking portion side of the pair of upper and lower surrounding members in the axial direction to make the opening areas of both notches different, Since it is configured to correct the deviation in the magnetic field characteristics of the pair of upper and lower detection coils, the deviation in the magnetic field characteristics of the two detection coils can be corrected without increasing the size of the surrounding member in the radial direction. Will be able to
[0014]
The torque sensor for electric power steering according to claim 3, wherein, as described above, the axis of each of the upper and lower pair of the surrounding members with respect to each of the non-cut portions of the surrounding member at the neutral point of the torque sensor. By making the areas of the overlapping portions in the directions different from each other, it is possible to correct the deviation of the magnetic field characteristics of the pair of upper and lower detection coils.
Therefore, the same operation and effect as those of the first aspect of the invention can be obtained, and the deviation of the magnetic field characteristics between the two detection coils can be corrected without expanding the torque sensor in both the radial direction and the axial direction. This has the additional effect of enabling
[0015]
The torque sensor for electric power steering according to claim 4 is the same as the torque sensor for electric power steering according to claim 3, and the same operation and effect as the invention of claim 2 can be obtained by configuring as described above. In addition, it is also possible to correct a deviation in magnetic field characteristics that cannot be compensated for by simply extending the inner diameter side of the window-shaped notch formed on the first magnetic path interrupting portion side in the axial direction to increase the area. become able to.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
First, a configuration of an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an electric power steering to which a torque sensor TS for an electric power steering according to an embodiment of the present invention is applied, and FIG. 2 is an enlarged sectional view of a main part of the electric power steering. 2 is an input shaft (second rotating shaft), 3 is an output shaft (first rotating shaft), 4 is a torsion bar (elastic body), 5 is a surrounding member, 6 is a torque detecting side surrounding member (first magnetic path cutoff). , 7 is a temperature compensation side surrounding member (second magnetic path interrupting portion), 8 is a torque detection coil (detection coil), 9 is a temperature compensation coil (detection coil), 10 is a spacer, 11 is a base member, Reference numeral 12 denotes a disc spring, 13 denotes an output shaft side worm wheel, and 14 denotes a motor shaft side worm shaft.
[0017]
More specifically, the housing 1 mainly includes an upper housing 110 in which the torque sensor TS is mainly housed, a central housing 120 in which the reduction gear G is mainly housed, and a rack R & pinion P. The housing 1 is divided into a lower housing 130 to be housed, and is assembled in the axial direction to form one housing 1.
[0018]
That is, a state in which the lower end opening edge portion 110a of the upper housing 110 is inserted into the large diameter portion 120a provided on the upper portion of the central housing 120, and the flange portion 110b abuts and locks on the upper end surface of the opening portion of the central housing 120. In this state, the upper housing 110 and the central housing 120 are fastened and fixed by bolts or the like.
[0019]
The input shaft 2 and the output shaft 3 are coaxially arranged in the respective housings 110, 120, 130 while being rotatably supported via bearings 1a, 1b, 1c, respectively.
[0020]
The torsion bar 4 is rotatably inserted into the shaft hole 2 a of the input shaft 2, and one end thereof is fixed to the input shaft 2 by a pin 2 b at the back of the shaft hole 2 a, while the other end is Is spline-coupled to a shaft hole 3a of the output shaft 3.
[0021]
A steering wheel (not shown) is connected to the input shaft 2, and the steering force of the steering wheel passes through the input shaft 2, the torsion bar 4, and the output shaft 3, and the lower end of the output shaft 3. Is converted into a linear motion of the rack R by a rack R & pinion P provided to the left and right front wheels (not shown).
[0022]
The surrounding member 5 constitutes a magnetic path of a magnetic field generated by the torque detecting coil 8 and the temperature compensating coil 9, and is formed by sintering a magnetic material such as stainless steel. Inside 110, the main body 31 is formed at the upper end of the output shaft 3 (the end on the side of the input shaft 2) by press fitting to the outer periphery of a small diameter portion 33 provided by forming an annular step portion 32. (See Fig. 2)
[0023]
As shown in a bottom view of FIG. 3, the surrounding member 5 has a non-cut-out portion (magnetic path) on the outer peripheral side of an annular base having a coupling hole 50 at the center thereof for press-fitting the small diameter portion 33. A plurality of cutouts 51 (eight in the embodiment of the present invention) penetrating in the axial direction are formed at predetermined intervals in the circumferential direction except for the formation part) 52.
[0024]
Returning to FIGS. 1 and 2, the torque detecting coil 8 is for detecting a torque acting between the input shaft 2 and the output shaft 3 based on a change in impedance. A magnetic field that is fixed to the upper housing 110 side via a yoke member 80 surrounding the lower surface thereof in a state facing the side surface in the axial direction to generate a magnetic field using the enclosed member 5 and the yoke member 80 as a magnetic path. Let it.
[0025]
As shown in FIG. 2, the yoke member 80 includes an upper surface surrounding portion 80a, an inner circumferential surrounding portion 80b, and an outer circumferential surrounding portion 80c which form a main body having a cross-sectional gate shape surrounding the lower surface facing the surrounded member 5. And a fixed flange portion 80d protruding outward from the lower end opening edge of the outer peripheral surrounding portion 80c.
[0026]
The temperature compensating coil 9 is for correcting a fluctuation of a detection value based on a temperature change when the torque is detected by the torque detecting coil 8. In a state facing in the direction, it is fixed to the upper housing 110 side via a yoke member 90 surrounding other than its upper surface, and generates a magnetic field having the enclosed member 5 and the yoke member 90 as magnetic paths.
[0027]
As shown in FIG. 2, the yoke member 90 includes a lower surface surrounding portion 90a, an inner circumferential surrounding portion 90b, and an outer circumferential surrounding portion 90c which form a main body having a cross-sectional gate shape surrounding a portion other than the upper surface facing the surrounded member 5. And a fixed flange portion 90d protruding outward from the upper end opening edge of the outer peripheral surrounding portion 90c.
[0028]
The spacer 10 is interposed in order to determine an axial distance between the yoke member 80 on the torque detecting coil 8 side and the yoke member 90 on the temperature compensating coil 9 side, and is a non-conductive member. An annular step portion 10a is formed in a cylindrical shape of a resin material (PPS), and has an inner upper portion formed with an annular step portion 10a for positioning and locking the fixing flange portion 80d of the yoke member 80 in the axial direction. An annular step portion 10b for positioning and locking the flange portion 90d is formed. That is, the axial positional relationship between the torque detecting coil 8 and the temperature compensating coil 9 is determined by the axial length between the two annular steps 10a and 10b.
[0029]
The base member 11 is incorporated with its lower end flange portion 11a locked on a locking step 120d formed inside the large diameter portion 120a of the central housing 120, and has its upper end small diameter cylindrical portion 11b. An annular concave portion 11c for accommodating the main body of the yoke member 90 is formed on the inner side. Then, the small-diameter cylindrical portion 11b is inserted from the lower end opening of the spacer 10, and is assembled in a state where the fixed flange portion 90d of the yoke member 90 is abutted on the upper end surface thereof. That is, the axial positional relationship between the center housing 120 (housing 1), the torque detecting coil 8 and the temperature compensating coil 9 is determined by the axial length of the base member 11.
[0030]
Assembling the upper housing 110 to the central housing 120 and bolts with the disc spring 12 interposed between the fixed flange portion 80d and an annular step portion 110d formed at an axially intermediate portion inside the upper housing 110. As a result, the displacement of the two yoke members 80 and 90 (torque detecting coil 8 and temperature compensating coil 9) is prevented by the urging force of the disc spring 12, and the axial positional relationship is maintained. In this state, assembly to the housing 1 is performed.
[0031]
The torque detection side surrounding member 6 is fixed to the input shaft 2 by caulking the inner cylindrical portion 60 to the outer periphery of the maximum outer diameter portion 2c formed at a position near the lower end of the input shaft 2. Has been done.
By fixing the inner cylindrical portion 60 to the input shaft 2 as described above, the torque detecting side surrounding member 6 is provided with a predetermined clearance between the surrounded member 5 and the torque detecting coil 8. Is equipped. As shown in detail in FIGS. 4 (plan view) and FIG. 5 (bottom view), the number of the cut-out portions 51 and the non-cut-out portions 52 in the enclosed member 5 is set in the torque detecting side surrounding member 6. A plurality (eight in the embodiment of the present invention) of corresponding windows (notches) 61 penetrating in the axial direction are formed at predetermined intervals in the circumferential direction. The circumferential width of each window 61 is formed to be the same as the width of the non-cutout portion 52 of the surrounding member 5.
[0032]
That is, a change in the degree of overlap between the window 61 and the non-notched portion 62 of the torque detecting side surrounding member 6 and the notched portion 51 and the non-notched portion 52 of the enclosing member 5 is detected based on the impedance change. This is for detecting a torque generated between the output shaft 2 and the output shaft 3, and for this purpose, the torque detecting side surrounding member 6 is formed of a conductive and non-magnetic material such as aluminum.
[0033]
The surrounding member 7 for temperature compensation is interposed between the surrounding member 5 and the coil 9 for temperature compensation, and the inner peripheral side thereof is fixed to the output shaft 3 side as shown in FIG. In a free state, the outer cylindrical portion (connecting portion) 73 formed on the outer periphery of the temperature compensating surrounding member 7 and the outer cylindrical portion (connecting portion) 63 of the torque detecting side surrounding member 6 are axially extended and integrated with each other. To rotate integrally with the torque detecting side surrounding member 6.
A cylindrical member 75 of the same material as the temperature compensating surrounding member 7 is press-fitted on the outer periphery of the output shaft 3 from the inner peripheral side of the temperature compensating surrounding member 7 to the lower portion of the temperature compensating coil 9. The magnetic flux is prevented from escaping from the temperature compensation coil 9 to the output shaft 3 to stabilize the magnetic field.
[0034]
As shown in FIGS. 4 and 5, the window 61 of the torque detecting side surrounding member 6 and the window 71 of the temperature compensating side surrounding member 7 do not overlap with each other in the axial direction by a predetermined angle (17 °, 2 °). 8) (FIG. 8 (longitudinal sectional view taken along the line VIII-VIII in FIG. 6)), each window 61 of the torque detecting side surrounding member 6 and each of the temperature compensating side surrounding member 7 as shown in FIG. The width a of the overlapping portion of each of the non-cut portions 62 and 72 between the window portion 71 and the window portion 71 is formed to be smaller than the circumferential width b of each of the non-cut portions 52 of the surrounding member 5, so that the surrounding member In a state (neutral point) at a torque value of 0 (neutral point) in which both the side portions of each of the non-cutout portions 52 in FIG. Plan view), FIG. 7 (bottom view) and FIG. It is arranged in a state having different projecting ratio of d to each other. Incidentally, the circumferential width of both windows 61 and 71 is set to 12.5 ° in rotation angle, and the non-notched portion 52 is set to 11 °.
[0035]
The temperature compensation side surrounding member 7 is formed in a notch shape in which the axial side of each window 71 communicates with the axial hole (insertion hole) 74 as shown in FIGS. The annular base and the notched portion (magnetic path forming portion) 52 of the surrounding member 5 can pass through the temperature compensation side surrounding member 7 in the axial direction.
The maximum outer diameter portion 2c of the input shaft 2 is determined not only by the inner diameter of the inner cylindrical portion 60 of the torque detection surrounding member 6 but also by the inner diameter of the coupling hole 50 of the enclosed member 5 and the torque detecting coil. The diameter of the yoke members 80 and 90 for accommodating the coil 8 and the temperature compensation coil 9 is smaller than the inner diameter of the yoke members 80 and 90, and all of these sensor members are assembled from the input shaft 2 side.
[0036]
On the other hand, the window 61 of the torque detecting side surrounding member 6 is formed in a window shape completely surrounded on all sides, whereas the window 71 of the temperature compensating side surrounding member 7 has the axial center side as described above. Due to the cutout shape communicating with the shaft hole (insertion hole) 74, the escape of the magnetic flux is larger than that of the window shape, so that the magnetic field of the torque detection coil 8 and the temperature compensation coil 9 is increased. Will be shifted. Therefore, in the embodiment of the present invention, as shown in FIGS. 4 and 5, the inner diameter side of the window 61 of the torque detecting side surrounding member 6 is extended in the axial direction to increase the opening area of the window 61. Thereby, the deviation of the characteristics of the magnetic field between the coils 8 and 9 is corrected.
The correction of the deviation of the magnetic field characteristics due to the enlargement of the opening area of the window 61 is performed by manufacturing an actual product in advance, simulating how a magnetic path is formed, and based on the result. Determine the extension dimensions.
[0037]
Therefore, a procedure for assembling each member of the torque sensor TS part and another method of correcting the deviation of the magnetic field characteristics of the torque detecting coil 8 and the temperature compensating coil 9 will be mainly described.
(A) The output shaft 3 having the bearing 1b press-fitted therein is inserted from below the central housing 120, and the bearing 1b is press-fitted into the inner surface of the small-diameter portion 120b so that the intermediate portion of the output shaft 3 can rotate with respect to the central housing 120. Assemble in a state supported by. The lower end of the torsion bar 4 is spline-coupled to the shaft hole 3a of the output shaft 3, and the upper end of the torsion bar 4 is inserted into the shaft hole 2a of the input shaft 2 while the torsion bar 4 is being inserted. In addition, a pin mounting hole 2g which penetrates the input shaft 2 in the diameter direction is formed, and a pin 2c is press-fitted into the mounting hole 2g to fix the upper end side of the torsion bar 4 to the input shaft 2. After the cutting oil and chips generated during the drilling of the pin mounting hole 2g are removed, the process proceeds to the next step.
[0038]
(B) The lower end flange portion 11a of the base member 11 is engaged with an annular step portion 120d formed in the large-diameter portion 120a of the central housing 120 in a state of being locked.
(C) A state in which the main body of the yoke member 90 is accommodated in the annular concave portion 11c of the base member 11, and the fixed flange portion 90d is abutted on the upper end surface of the small-diameter cylindrical portion 11b of the upper end of the base member 11. The yoke member 90 (the coil 9 for temperature compensation) is assembled.
(D) The coupling hole 50 of the surrounding member 5 is press-fitted into the small diameter portion 33 at the upper end of the output shaft 3 and assembled. At this time, the surrounding member 5 is positioned in the axial direction while measuring the clearance between the temperature compensation coil 9 and the surrounding member 5 with a sensor or the like.
[0039]
(E) The torque detecting side surrounding member 6 in which the temperature detecting side surrounding member 7 is integrated via the outer cylindrical portions 73 and 63 has the inner peripheral side cylindrical portion 60 on the outer periphery of the largest outer portion 2 c of the input shaft 2. By caulking, it is assembled and fixed to the input shaft 2. In this fixing, as described above, the temperature detecting side surrounding member 7 allows the annular base portion and the cutout portion (magnetic path forming portion) 52 of the surrounding member 5 to pass through the temperature compensating side surrounding member 7 in the axial direction. Therefore, the temperature detecting side surrounding member 7 is axially arranged so that a predetermined clearance is formed between the surrounding member 5 and the temperature compensating coil 9, and the rotational force is applied to the input shaft 2 side. In the state where the torque value is 0 (neutral point) where no torque is applied, the deviation of the magnetic field characteristics between the torque detecting coil 8 and the temperature compensating coil 9 is corrected.
That is, by changing the ratio of the portions of the surrounding member 5 at which both sides in the circumferential direction of each of the non-cut portions 52 protrude toward the window portions 61 and 71, the torque detecting coil 8 and the temperature compensating coil 9 are used. The rotation angle of the surrounding member 6 is adjusted so that the difference in the detected impedance becomes 0. In this state, the inner peripheral side cylindrical portion 60 is swaged with respect to the input shaft 2 by a swaging tool such as a punch. By doing so, the torque detection side surrounding member 6 and the temperature compensation side surrounding member 7 are assembled and fixed to the input shaft 2 in a state where the positioning is adjusted in the axial direction and the circumferential direction.
[0040]
(F) The spacer 10 is assembled in a state where the downward annular step portion 10b of the spacer 10 is abutted and locked on the upper surface of the fixed flange portion 90d of the yoke member 90 on the temperature compensating coil 9 side.
(G) The yoke member 80 (torque detection coil 8) is assembled in a state where the fixed flange portion 80d is abutted and locked on the upward annular step portion 10a of the spacer 10. Thus, the torque detecting side surrounding member 6 is disposed between the surrounding member 5 and the torque detecting coil 8 with a predetermined clearance due to the preset interval between the two annular steps 10a and 10b. State.
[0041]
(H) The upper housing 110 is assembled to the central housing 120 with the disc spring 12 placed on the fixed flange portion 80d of the yoke member 80. That is, the input shaft 2 is press-fitted into the bearing 1 a which is press-fitted and fixed in the shaft hole of the upper housing 110, thereby rotatably supporting the input shaft 2 with respect to the upper housing 110. The lower end opening edge portion 110a of the upper housing 110 is inserted into the large diameter portion 120a provided, and the flange portion 110b is brought into abutment engagement with the upper end surface of the opening portion of the central housing 120. By fastening the upper housing 110 and the central housing 120 in the axial direction, the disc spring 12 is pressed and compressed between the fixed flange portion 80d and the annular step portion 110d, and the yoke member 80, The spacer 10, the yoke member 90, and the base member 11 are disposed between the disc spring 12 and the annular step portion 120d in the axial direction. Fixed in lifting state.
[0042]
Next, a method of detecting the torque of the torque sensor TS according to the embodiment of the present invention will be described.
In the torque sensor TS according to the embodiment of the present invention, when the torque is 0, the deviation of the magnetic field characteristics between the torque detecting coil 8 and the temperature compensating coil 9 is corrected as described above. The difference between the impedance values detected by the detection coil 8 and the temperature compensation coil 9 is substantially 0 (torque value 0).
[0043]
Therefore, first, when steering rotation is input to the input shaft 2, the torsion bar 4 is twisted to cause a relative angle difference between the surrounding member 6 and the surrounding member 5. The magnetic circuit formed by the compensating coil 9 changes, and the inductance of the torque detecting coil 8 and the temperature compensating coil 9 changes.
[0044]
That is, as shown in the coil inductance variable characteristic diagram of FIG. 9, in the right-turning direction, the torque detecting surrounding member 6 and the temperature compensating surrounding member 7 rotate clockwise relative to the surrounding member 5, Thereby, the overlapping area of the non-cut portion 52 of the surrounding member 5 with respect to the window 71 of the temperature compensating surrounding member 7 decreases, and the overlapping area of the coil detecting surrounding member 6 with respect to the window 61 increases. Therefore, the coil inductance on the side of the torque detecting coil 8 increases and changes in the direction in which the coil inductance of the temperature compensating coil 9 decreases. The coil inductance on the side decreases and the temperature compensation coil 9 changes in a direction to increase the coil inductance. As described above, the difference between the coil inductances changes in opposite directions of plus and minus with respect to 0.
[0045]
Therefore, by detecting a difference value between the coil inductance value detected by the torque detecting coil 8 and the coil inductance value detected by the temperature compensating coil 9, it is possible to always detect the torque value in a temperature compensated state. In addition to this, a large value is obtained as the difference value between the two coil inductances detected by the torque detection coil 8 and the temperature compensation coil 9, respectively, so that the torque detection accuracy can be improved.
[0046]
As described above, in the torque sensor for electric power steering according to the embodiment of the present invention, the following effects can be obtained.
That is, the maximum outer diameter portion 2c of the input shaft 2 is determined not only by the inner diameter of the inner cylindrical portion 60 of the torque detecting side surrounding member 6 but also by the inner diameter of the coupling hole 50 of the enclosed member 5 fixed to the output shaft 3 side. The input shaft 2 and the output shaft 3 are connected via the torsion bar 4 by forming the yoke members 80 and 90 having smaller diameters than the inner diameters of the yoke members 80 and 90 for accommodating the torque detection coil 8 and the temperature compensation coil 9. However, in addition to the surrounding members 6 and 7 fixed to the input shaft 2 side, the enclosed member 5 fixed to the output shaft 3 side, the torque detecting coil 8 fixed to the housing 1 side, and the temperature compensating member The effect that the entire coil 9 can be mounted from the input shaft 2 side, and therefore, the assembling workability can be improved can be obtained.
In addition, since the two surrounding members 6 and 7 are fixed to the input shaft 2 side, the torque detecting coil 8 on the input shaft 2 side can be inserted after the two surrounding members 6 and 7 are fixed. 6, 7 can be easily fixed to the input shaft 2.
[0047]
The temperature compensating side surrounding member 7 is formed at its center with a shaft hole 74 which can penetrate the input shaft 2 and the annular base of the surrounding member 5, and each of the non-cutout portions 52 of the surrounding member 5. The window member 71 is formed radially in a portion facing the shaft hole 74 so as to communicate with the shaft hole 74 and penetrate the non-cutout portion 52, so that the surrounding member 5 can be surrounded by the temperature compensation side surrounding member 7. Therefore, after the surrounding member 5 is mounted and fixed to the output shaft 3, the torque detecting side surrounding member 6 and the temperature compensation side surrounding member 7 are integrated through the outer cylindrical portions 63 and 73. Is inserted from the input shaft 2 side, and the torque detection side surrounding member 6 and the temperature compensation side surrounding member 7 can be assembled and arranged in a state of being sandwiched from both sides of the surrounding member 5 in the axial direction. Therefore, the assembly workability is further improved. It is possible to.
[0048]
In addition, an annular spacer 10 for determining the axial interval between the torque detecting coil 8 and the temperature compensating coil 9 is interposed between the two yoke members 80 and 90, so that the torque detecting coil 8 and the temperature compensating coil 9 are interposed. The assembly can be performed while maintaining the positional relationship between the temperature compensating coils 9, whereby the clearance between the two yoke members 80 and 90 (both the coils 8 and 9) can be easily managed. become.
Also, since the spacer 10 is provided, it is not necessary to fix the torque detecting coil 8 on the input shaft 2 side to the housing 1 side. Therefore, before mounting the upper housing 110 on the input shaft 2 side, all the sensor members are required. Can be assembled.
[0049]
Further, the two yoke members 80, 90 are axially pressed via the disc spring 12 and the base member 11 at the portions of the two fixed flange portions 80d, 90d where the spacer 10 is interposed therebetween. The housing 1 is fixed to the housing 1 only by interposing the disc spring 12 without changing the internal stress of the main body constituting the magnetic path of the magnetic field in the two yoke members 80 and 90. Can be easily fixed, and the displacement of the two yoke members 80 and 90 (torque detecting coil 8 and temperature compensating coil 9) can be prevented by the urging force of the disc spring 12. Become like
[0050]
Further, the two yoke members 80 and 90 are pressed in a state where the spacer 10 is pressed in the axial direction through the base member 11 provided in the axial direction at the portions of the two fixed flange portions 80d and 90d provided therebetween. Since the housing 1 is fixed to the housing 1, the yoke for the housing 1, both the surrounding members 7, 8 and the enclosed member 5 can be obtained by changing the base member 11 without changing the design of the housing 1 itself. The axial mounting positions of the members 80 and 90 (torque detecting coil 8 and temperature compensating coil 9) can be easily changed.
[0051]
Further, by making the opening areas of the window 61 of the pair of upper and lower torque detecting side surrounding members 6 and the window 71 of the temperature compensating side surrounding member 7 different, the pair of upper and lower torque detecting coils 8 and temperature compensating coils 9 are formed. Can be corrected, the torque detecting coil 8 and the temperature compensating coil 8 are provided at a stepped portion where the outer diameters of the input shaft 2 and the output shaft 3 are different from each other as in the embodiment of the present invention. Even in the case where the characteristics of the magnetic fields of the two coils differ due to the arrangement of the coils 9, the deviation of the characteristics of the magnetic fields of the coils can be easily corrected. The degree can be expanded.
In addition, variations in coil temperature characteristics between the torque detecting coil 8 and the temperature compensating coil 9 can be adjusted without increasing the size of the structure due to an increase in the number of coil turns and the like.
[0052]
Further, by extending the inner diameter side of the window 61 in the torque detecting side surrounding member 6 in the axial direction to enlarge the opening area of the window 61, the deviation of the magnetic field characteristics of the coils 8, 9 is corrected. By doing so, it is possible to correct the deviation of the characteristics of the magnetic field of both detection coils without enlarging the size of the torque detection side surrounding member 6 in the radial direction.
[0053]
Further, by adjusting the ratio of the projections c and d, the circumferential both sides of each cutout portion 52 of the surrounding member 5 project toward the window portions 61 and 71, the magnetic field of the coils 8 and 9 is reduced. By correcting the deviation, it is possible to correct the deviation of the characteristics of the magnetic field of the coils 8 and 9 without expanding the torque sensor in both the radial direction and the axial direction. This makes it possible to correct the deviation of the magnetic field characteristics that cannot be compensated for by making the opening areas of the window 61 of the torque detecting side surrounding member 6 and the window 71 of the temperature compensating side surrounding member 7 different from each other. become.
[0054]
Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to the embodiments of the present invention, and the present invention is not limited to a design change or the like without departing from the gist of the present invention. include.
For example, in the embodiment of the present invention, the surrounding member is provided on the input shaft 2 side, and the surrounding member is provided on the output shaft 3 side.
[0055]
In the embodiment of the invention, the opening area of the window 61 of the torque detection-side surrounding member 6 and the opening area of the window 71 of the temperature-compensating-side surrounding member 7 are made different from each other. Although the ratio of the protruding portions c and d whose both side portions in the direction protrude toward the window portions 61 and 71 is adjusted, a sufficient effect can be obtained by only one of the methods.
Further, in the embodiment of the present invention, the structure in which the coil, the surrounding member and the surrounding member are opposed in the axial direction is taken as an example. be able to.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a torque sensor for electric power steering according to an embodiment of the present invention.
FIG. 2 is an enlarged sectional view of a main part showing the torque sensor for electric power steering according to the embodiment of the invention.
FIG. 3 is a bottom view showing an enclosed member in the electric power steering torque sensor according to the embodiment of the present invention;
FIG. 4 is a plan view showing both surrounding members in the torque sensor for electric power steering according to the embodiment of the invention.
FIG. 5 is a bottom view showing both surrounding members in the torque sensor for electric power steering according to the embodiment of the present invention.
FIG. 6 is a plan view showing a positional relationship between both surrounding members and a surrounding member in the torque sensor for electric power steering according to the embodiment of the present invention.
FIG. 7 is a bottom view showing a positional relationship between both surrounding members and a surrounding member in the torque sensor for electric power steering according to the embodiment of the present invention.
8 is an enlarged vertical sectional view taken along line VIII-VIII in FIG.
FIG. 9 is a variable characteristic diagram of a coil inductance with respect to a steering torque in the electric power steering torque sensor according to the embodiment of the present invention.
[Explanation of symbols]
TS Torque sensor for electric power steering
1 Housing
2 Input shaft (second rotating shaft)
2c Maximum outer diameter part
3 Output shaft (1st rotation shaft)
4 Torsion bar (elastic body)
5 Surrounding members
51 Notch
52 Non-notch
6 Torque detection side surrounding member (first magnetic path cutoff part)
61 Window (Notch)
62 non-notch
63 outer cylinder (joint)
7 Temperature compensation side surrounding member (second magnetic path cutoff part)
71 Window (Notch)
72 Notch
73 outer cylinder (joint)
74 Shaft center hole (insertion hole)
8 Torque detection coil (detection coil)
80 Yoke member
9 Temperature compensation coil (detection coil)
90 Yoke member

Claims

An elastic body interposed between the first rotation axis and the second rotation axis;
An enclosing member fixed to one of the first rotation shaft and the second rotation shaft and formed of a magnetic material having a plurality of notches and non-notches formed at predetermined circumferential intervals;
The base of the enclosing member is fixed to the other side of the first rotation shaft and the second rotation shaft in a state facing the cutout portion and the surface on which the non-notch portion is formed, respectively. A pair of upper and lower surrounding members made of a conductive and non-magnetic material constituting a plurality of magnetic path blocking portions formed at predetermined intervals in the circumferential direction,
The cutout portion and the non-cutout portion of the enclosed member are provided so as to face the cutout portion and the non-notched portion of the enclosed member, respectively, via the pair of upper and lower enclosure members. A pair of upper and lower detection coils of the same specification for detecting a torque generated between the first rotation shaft and the second rotation shaft by detecting a change in the degree of overlap with the notch portion based on a change in impedance;
A yoke member made of a magnetic material that accommodates each of the two detection coils in an enclosing state,
A housing to which the yoke members accommodating the enclosing member, both enclosing members, both detection coils and the yoke member, and accommodating the pair of upper and lower detection coils, respectively, are fixed.
In the torque sensor for electric power steering provided with
An electric power steering system wherein the gaps in the magnetic field characteristics of the pair of upper and lower detection coils are corrected by making the opening areas of both notches in the pair of upper and lower surrounding members different from each other. Torque sensor.

The surrounding member includes an annular base fixed to the first rotation shaft, and a magnetic path forming portion constituting the non-notched portion in which a plurality of rod-shaped members are radially extended from the annular base. The notch is formed between the magnetic path forming parts,
A base portion fixed to the second rotating shaft, a first magnetic path blocking portion extending from the base portion in an outward flange shape and facing a surface on the second rotating shaft side of the enclosed member; A connecting portion extending in an axial direction from an outer peripheral edge of the first magnetic path interrupting portion, and a connecting portion extending inward from the connecting portion and facing a surface on the first rotation shaft side of the enclosed member. It consists of two magnetic path interruption parts,
The pair of upper and lower detection coils are provided in a state of being opposed in the axial direction with the surrounding member and the pair of upper and lower surrounding members interposed therebetween,
A maximum outer diameter portion of the second rotating shaft is formed to have a smaller diameter than an inner diameter of the yoke member that houses the surrounding member, the surrounding member, and the detection coil,
The plurality of cutouts are formed in a window shape in the first magnetic path blocking unit,
The second magnetic path blocking portion has a central portion formed with an insertion hole that can penetrate the second rotating shaft and the annular base of the enclosed member, and faces each magnetic path forming portion of the enclosed member. The cutout portions are formed radially in a portion that communicates with the insertion hole and can penetrate the magnetic path forming portion,
By extending the inner diameter side of the notch formed on the first magnetic path blocking portion side in the axial direction in the pair of the upper and lower surrounding members, the opening areas of the notches are different, so that the upper and lower paired 2. The torque sensor for an electric power steering according to claim 1, wherein the torque sensor is configured to correct a difference in characteristics of a magnetic field between the two detection coils.

An elastic body interposed between the first rotation axis and the second rotation axis;
An enclosing member fixed to one of the first rotation shaft and the second rotation shaft and formed of a magnetic material having a plurality of notches and non-notches formed at predetermined circumferential intervals;
The base of the enclosing member is fixed to the other side of the first rotation shaft and the second rotation shaft in a state facing the cutout portion and the surface on which the non-notch portion is formed, respectively. A pair of upper and lower surrounding members made of a conductive and non-magnetic material constituting a plurality of magnetic path blocking portions formed at predetermined intervals in the circumferential direction,
The cutout portion and the non-cutout portion of the enclosed member are provided so as to face the cutout portion and the non-notched portion of the enclosed member, respectively, via the pair of upper and lower enclosure members. A pair of upper and lower detection coils of the same specification for detecting a torque generated between the first rotation shaft and the second rotation shaft by detecting a change in the degree of overlap with the notch portion based on a change in impedance;
A yoke member made of a magnetic material that accommodates each of the two detection coils in an enclosing state,
A housing to which the yoke members accommodating the enclosing member, both enclosing members, both detection coils and the yoke member, and accommodating the pair of upper and lower detection coils, respectively, are fixed.
In the torque sensor for electric power steering provided with
The upper and lower pair of upper and lower enclosing members at the neutral point of the torque sensor differ from each other in the area of both axially overlapping portions of the upper and lower enclosing members with respect to the respective non-notched portions of the enclosing member. A torque sensor for an electric power steering, wherein the torque sensor is configured to correct a difference between characteristics of a magnetic field of both detection coils.

The surrounding member includes an annular base fixed to the first rotation shaft, and a magnetic path forming portion constituting the non-notched portion in which a plurality of rod-shaped members are radially extended from the annular base. The notch is formed between the magnetic path forming parts,
A base portion fixed to the second rotating shaft, a first magnetic path blocking portion extending from the base portion in an outward flange shape and facing a surface on the second rotating shaft side of the enclosed member; A connecting portion extending in an axial direction from an outer peripheral edge of the first magnetic path interrupting portion, and a connecting portion extending inward from the connecting portion and facing a surface on the first rotation shaft side of the enclosed member. It consists of two magnetic path interruption parts,
The pair of upper and lower detection coils are provided in a state of being opposed in the axial direction with the surrounding member and the pair of upper and lower surrounding members interposed therebetween,
A maximum outer diameter portion of the second rotating shaft is formed to have a smaller diameter than an inner diameter of the yoke member that houses the surrounding member, the surrounding member, and the detection coil,
The plurality of cutouts are formed in a window shape in the first magnetic path blocking unit,
The second magnetic path blocking portion has a central portion formed with an insertion hole that can penetrate the second rotating shaft and the annular base of the enclosed member, and faces each magnetic path forming portion of the enclosed member. The cutout portions are formed radially in a portion that communicates with the insertion hole and can penetrate the magnetic path forming portion,
At the neutral point of the torque sensor, the angles of the axially overlapping portions with the respective notched portions of the pair of upper and lower surrounding members with respect to the respective non-notched portions of the enclosed member are made different from each other to reduce the area of the overlapping portions. 4. The torque sensor for an electric power steering according to claim 3, wherein a difference between the characteristics of the magnetic field of the pair of upper and lower detection coils is corrected by making them different.