JP2004279065A

JP2004279065A - Rotation angle detecting apparatus

Info

Publication number: JP2004279065A
Application number: JP2003067172A
Authority: JP
Inventors: Tsutomu Yoshida; 力美田
Original assignee: Calsonic Kansei Corp
Current assignee: Marelli Corp
Priority date: 2003-03-12
Filing date: 2003-03-12
Publication date: 2004-10-07

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle detecting apparatus capable of highly accurately detecting the rotation angle of a rotator while reducing the cost by reducing the number of components in comparison with the conventional apparatus. <P>SOLUTION: The rotation angle detection apparatus is set so that a first gearwheel part 1b and a second gearwheel part 1c both having a different number of teeth from that of a driving gear 1 are formed in the driving gear 1 at locations displaced in axial directions, a first pinion 2 and a second pinion 3 are provided with an identical shape, and the first pinion 2 engages with the first gearwheel part 1b, and the second pinion 2 engages with the second gearwheel part 1c. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、回転体の回転角を検出する回転角検出装置に係り、特に、ステアリングの操舵角を検出するのに好適な回転角検出装置の技術分野に属する。
【０００２】
【従来の技術】
この種の回転角検出装置としては、ステアリングシャフトに固定された駆動歯車と噛み合う２つの小歯車にそれぞれ磁石を設け、この磁石にＡＭＲ（異方性磁気抵抗）センサを付設した構成の測定装置が知られている（例えば、特許文献１参照。）。
【０００３】
２つの小歯車の歯数は１つだけ異なるように設定され、ステアリングシャフトが回転したとき、３つの歯車の回転角が異なるように設定されている。２つのＡＭＲセンサは、磁束密度を検出してそれに応じた電圧を出力するため、２つのＡＭＲセンサが出力する電圧値の変化に基づいて、ステアリングの絶対角（ニュートラル位置からの回転角）を検出することができる。
【０００４】
【特許文献１】
特表２００１−５０５６６７号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、上記従来技術にあっては、次のような問題を有している。
（イ）駆動歯車１つと小歯車２つの計３つの歯車を用いているため、部品費および組立費が高価である。
（ロ）２つの小歯車は歯数が異なるように設定されているが、一目しただけでは歯数の違いを確認できないため、組立作業時において誤組み付けが発生するおそれがある。
【０００６】
本発明は、上記問題に着目してなされたもので、その目的とするところは、従来品と比較して、部品点数の削減によるコスト削減を図りつつ、回転体の回転角を高精度で検出できる回転角検出装置を提供することにある。
【０００７】
【課題を解決するための手段】
上述の目的を達成するため、本発明請求項１に記載の回転角検出装置では、回転体に応じて回転する駆動歯車と、この駆動歯車を収納するハウジングと、このハウジング内に設け、駆動歯車とそれぞれ噛み合う第１小歯車および第２小歯車と、前記第１小歯車に設けた第１磁極と、前記第２小歯車に設けた第２磁極と、
【０００８】
前記第１磁極に面して配置した第１磁気センサと、前記第２磁極に面して配置した第２磁気センサと、これら第１磁気センサと第２磁気センサの検出信号に基づいて回転体の回転角を検出する演算回路を有する回路基板と、を備えた回転角検出装置において、前記駆動歯車に、軸方向に位置をずらして歯数の異なる第１歯車部と第２歯車部とを形成し、前記第１小歯車と第２小歯車を同一形状とし、前記第１小歯車と第２小歯車を、第１小歯車と第１歯車部が噛み合い、第２小歯車と第２歯車部が噛み合うように設定したことを特徴とする。
【０００９】
請求項２に記載の発明では、請求項１に記載の回転角検出装置において、前記第１小歯車と第２小歯車の一面側に環状の第１軸部を形成するとともに、第１小歯車と第２小歯車の他面側に環状の第２軸部を形成し、前記第１軸部と第２軸部の長さを、第１小歯車と第２小歯車を互いに軸方向逆向きにしてハウジングに組み付けたとき、第１小歯車が第１歯車部と噛み合い、第２小歯車が第２歯車部と噛み合うように設定したことを特徴とする。
【００１０】
請求項３に記載の発明では、請求項２に記載の回転角検出装置において、前記第１軸部と第２軸部を異径に形成し、前記ハウジングに、第１軸部と嵌合可能な第１軸受け部と、第２軸部と嵌合可能な第２軸受け部を設け、前記第１小歯車の第１軸部を第１軸受け部と嵌合させるとともに、第２小歯車の第２軸部を第２軸受け部と嵌合させ、前記第１小歯車の第２軸部と第２小歯車の第１軸部に回路基板を当接させて第１小歯車と第２小歯車を回動自在に固定し、前記第１磁気センサと第２磁気センサを、第１小歯車の第２軸部と第２小歯車の第１軸部に囲まれるように回路基板上に実装したことを特徴とする。
【００１１】
請求項４に記載の発明では、請求項１ないし請求項３のいずれか１項に記載の回転角検出装置において、前記駆動歯車を車両のステアイングシャフトと一体に設け、前記駆動歯車の第１歯車部の歯数をｍ１、第２歯車部の歯数をｍ２とし、前記第１小歯車および第２小歯車の歯数をｍ３、１回転当たりの波形数をｎ１としたとき、ｍ１，ｍ２，ｍ３，ｎ１が、
０＜｜４×ｎ１×ｍ１／ｍ３−４×ｎ１×ｍ２／ｍ３｜＜０．５
を満足することを特徴とする。
【００１２】
【発明の効果】
請求項１に記載の発明では、駆動歯車の回転により、駆動歯車の第１歯車部と噛み合う第１小歯車と、駆動歯車の第２歯車部と噛み合う第２小歯車が回転する。このとき、第１小歯車と第２小歯車は同一形状であるが、第１小歯車と噛み合う第１歯車部と、第２小歯車と噛み合う第２歯車部は、異なる歯数に設定されているため、第１小歯車と第２小歯車は異なる回転速度で回転する。よって、第１磁気センサと第２磁気センサから出力される検出信号は同一とならないため、２つの検出信号に基づいて、回転体の回転角を検出可能である。
【００１３】
すなわち、本発明では、駆動歯車に異なる歯数の第１歯車部と第２歯車部を形成することにより、第１小歯車と第２小歯車を同一形状とした場合でも、回転体の回転角を検出できる。したがって、歯数の異なる２種類の小歯車を用いて回転角を検出する従来技術と比較して、小歯車が１つで済むため、部品点数の削減による製造コストの低減を図りつつ、回転体の回転角を高精度で検出できる。
【００１４】
請求項２に記載の発明では、第１小歯車と第２小歯車を互いに軸方向逆向きにしてハウジングに組み付けたとき、第１小歯車と第１歯車部、および第２小歯車と第２歯車部がそれぞれ噛み合うように第１軸部と第２軸部の長さを設定したため、第１小歯車と第２小歯車のハウジングに対する軸方向位置を同じとしたまま、歯車部分の軸方向位置をずらすことができる。
【００１５】
例えば、第１軸部と第２軸部とを同一長さに設定し、ハウジング側で第１小歯車と第２小歯車の軸方向位置をずらす構成とした場合、ずらした分だけ軸方向寸法が大きくなってしまう。これに対し、本発明では、ハウジングに組み付けられた第１小歯車と第２小歯車は、歯車部分の位置は軸方向にずれた状態であるが、ハウジングに対する軸方向位置は同一とすることが可能であるため、軸方向寸法をより小さくしてハウジングの薄型化を図ることができる。
【００１６】
請求項３に記載の発明では、第１小歯車の第１軸部を第１軸受け部と嵌合させ、第２小歯車の第２軸部を第２軸受け部と嵌合させることで、第１小歯車と第２小歯車とが互いに軸方向逆向きでハウジングに組み付けられる。さらに、第１軸部と第２軸部は異径に形成され、これに応じて第１軸受け部と第２軸受け部の形状も異なるため、第１小歯車と第２小歯車の組み付け方向を間違うことがない。
【００１７】
また、第１小歯車の第２軸部と第２小歯車の第１軸部には、第１磁気センサと第２磁気センサを実装した回路基板が当接しているため、軸方向寸法をより小さくできる。
【００１８】
請求項４に記載の発明では、下記の式を満足するように、ｍ１，ｍ２，ｍ３，ｎ１を設定した。
０＜｜４×ｎ１×ｍ１／ｍ３−４×ｎ１×ｍ２／ｍ３｜＜０．５．．．式▲１▼
【００１９】
通常、ステアリングホイールは、片側２回転、すなわち、一方の回転端から他方の回転端まで４回転するように設定されている。よって、駆動歯車がステアリングシャフト一体に設けられている場合、第１磁気センサから出力される波形数は、４×ｎ１×ｍ１／ｍ３個となる。一方、第２磁気センサから出力される波形数は、４×ｎ１×ｍ２／ｍ３個となる。
【００２０】
したがって、式▲１▼を満足するようにｍ１，ｍ２，ｍ３，ｎ１を設定することにより、ステアリングホイールを４回転させたとき、第１磁気センサと第２磁気センサの出力電圧が描く波形のずれが、０．５波形未満となる。すなわち、ステアリングホイールの回転操作可能範囲のどの角度においても、２つの波形の位置関係が同一とならないため、ステアリングホイールの絶対角を高精度に検出できる。
【００２１】
【発明の実施の形態】
以下に、本発明の回転角検出装置を実現する実施の形態を、第１実施例と第２実施例とに基づいて説明する。
【００２２】
（第１実施例）
まず、構成を説明する。
図１は、第１実施例の回転角検出装置の構造を示す正面図であり、図において、１は駆動歯車、２は第１小歯車、３は第２小歯車、６は第１磁気センサ、７は第２磁気センサである。
【００２３】
駆動歯車１は、その中心部に形成された開口部１ａに図外のステアリングシャフトが嵌挿され、ステアリングシャフトと一体に回転する。この駆動歯車１は、軸方向に位置をずらして歯数５０に設定された第１歯車部１ｂと、歯数４８に設定された第２歯車部１ｃとが形成されている。
【００２４】
第１小歯車２は、歯数２０に設定され、駆動歯車１の第１歯車部１ｂと噛み合っている。また、第２小歯車３は、第１小歯車２と同一形状のものであり、駆動歯車１の第２歯車部１ｃと噛み合っている。これら第１小歯車２と第２小歯車３は、駆動歯車１を挟んで対称位置に配置されている。
【００２５】
次に、第１小歯車２と第２小歯車３の構造を説明する。なお、第１小歯車２と第２小歯車３とは同一形状であるため、第１小歯車２の構造についてのみ説明する。
【００２６】
図２に示すように、第１小歯車２は、歯車部２ａと、この歯車部２ａの両面に突出する第１軸部２ｂと第２軸部２ｃとから構成されている。歯車部２ａの中心には、Ｎ極とＳ極が１８０度ずつで入れ替わるように１組の第１磁極４（第２小歯車３では第２磁極５）が歯車部２ａの両面に露出した状態で固定されている。
【００２７】
第１軸部２ｂと第２軸部２ｃは、どちらも環状に形成されている。第２軸部２ｃの方が第１軸部２ｂよりも大径であるが、軸方向長さは、第１軸部２ｂの方が第２軸部２ｃよりも長く設定されている。すなわち、歯車部２ａの軸方向位置は、第１小歯車２の軸方向中心位置から第２軸部２ｃ側へオフセットして設定されている。
【００２８】
図３は回転角検出装置の構造を示す縦断面図である。
図において、１０は回転角検出装置のハウジングであり、ケースアッパ８とケースロア９とから構成されている。
【００２９】
駆動歯車１の駆動歯車軸１ｄは、回転角検出装置のハウジングを構成するケースアッパ８とケースロア９により回動自在に挟装されている。
【００３０】
第１小歯車２は、第１軸部２ｂがケースアッパ８に設けられた第１軸受け部８ａと回動自在に嵌合し、第２軸部２ｃが回路基板１１上に当接した状態で、ケースアッパ８と回路基板１１に挟装されている。
【００３１】
一方、第２小歯車３は、第２軸部３ｃがケースアッパ８に設けられた第２軸受け部８ｂと回動自在に嵌合し、第１軸部３ｂが回路基板１１上に当接した状態で、ケースアッパ８と回路基板１１とに挟装されている。
【００３２】
すなわち、第１小歯車２と第２小歯車３は、互いに逆向きの状態でハウジング１０に組み付けられており、第１小歯車２の歯車部２ａが駆動歯車１の第１歯車部１ｂと噛み合い、第２小歯車３の歯車部３ａが駆動歯車１の第２歯車部１ｂと噛み合っている。
【００３３】
第１磁気センサ６は、第１小歯車２の第１磁極４に面し、周囲を第２軸部２ｃに囲まれた状態で、回路基板１１上に実装されている。また、第２磁気センサ７は、第２小歯車３の第２磁極５に面し、周囲を第１軸部３ｂに囲まれた状態で、回路基板１１上に実装されている。これら第１磁気センサ６および第２磁気センサ７としては、例えば、ＭＲ（ＭａｇｎｅｔｏＲｅｓｉｓｔａｎｃｅ）センサやホールＩＣが用いられる。
【００３４】
第１磁気センサ６および第２磁気センサ７は、第１小歯車２と第２小歯車３の回転に伴って変化する磁束密度に応じて出力電圧を変化させる。この出力電圧は、回路基板１１上の増幅回路を介して回路基板１１上の演算回路に入力される。演算回路では、２つの出力電圧を比較してステアリングの絶対角を算出する。算出されたステアリングの絶対角は、図外のステアリングハーネスを介して車両の制御装置に入力され、４輪操舵制御等の車両制御に利用される。
【００３５】
第１磁気センサ６と第２磁気センサ７の出力電圧を比較してステアリングの絶対角を求める場合、ステアリングを一方の回転端から他方の回転端まで回転させたとき、２つの出力電圧値が描く波形の位置関係がいずれの角度でも同一とならないよう、２つの波形のずれを０．５未満に設定する必要がある。
【００３６】
２つの波形のずれが０．５未満となるためには、駆動歯車１の第１歯車部１ｂの歯数をｍ１、第２歯車部１ｂの歯数をｍ２、第１小歯車２および第２小歯車３の歯数をｍ３、１回転当たりの波形数をｎ１としたとき、
０＜｜４×ｎ１×ｍ１／ｍ３−４×ｎ１×ｍ２／ｍ３｜＜０．５
上記の式を満足するｍ１，ｍ２，ｍ３，ｎ１を設定しなければならない。
【００３７】
第１実施例では、ｍ１＝４８，ｍ２＝５０，ｍ３＝２０，ｎ１＝１であるから、ステアリングシャフトが４回転したとき、第１磁気センサ６出力される波形数と、第２磁気センサ７から出力される波形数は、
４×ｎ１×ｍ１／ｍ２＝４×１×４８／２０＝９．６
４×ｎ１×ｍ１／ｍ３＝４×１×５０／２０＝１０
となり、第２磁気センサ７の出力波形が第１磁気センサ６の出力波形よりも０．４だけ進む（図４参照）ため、２つの出力電圧値が描く波形の位置関係がいずれの角度でも同一とならず、ステアリングの絶対角を検出できる。
【００３８】
次に、作用を説明する。
［ハウジングへの小歯車組み付け作用］
第１実施例の回転角検出装置では、ケースロア９に駆動歯車１と回路基板１１を組み付け、ケースアッパ８に第１小歯車２と第２小歯車３を組み付けた後、ケースアッパ８とケースロア９を重ね合わせる構造となっている。
【００３９】
ケースアッパ８に第１小歯車２と第２小歯車３を組み付ける場合、ケースアッパ８の第１軸受け部８ａに、第１小歯車２の第１軸部２ｂを嵌合させ、ケースアッパ８の第２軸受け部８ｂに、第２小歯車３の第２軸部３ｃを嵌合させる。
【００４０】
このとき、第１軸部２ｂ（３ｂ）と第２軸部２ｃ（３ｃ）は異径に形成され、第１軸受け部８ａと第２軸受け部８ｂもこれに合わせた形状となっているため、第１小歯車２と第２小歯車３は常に適正な方向（逆向き）で組み付けられる。
【００４１】
次に、効果を説明する。
第１実施例の回転角検出装置にあっては、次に列挙する効果を得ることができる。
【００４２】
（１）駆動歯車１に歯数４８の第１歯車部１ｂと歯数５０の第２歯車部１ｃを形成することにより、第１小歯車２と第２小歯車３を同一形状とした場合でも、ステアリングの操舵角を検出できるため、歯数の異なる２種類の小歯車を用いて回転角を検出する従来技術と比較して、小歯車が１つで済み、部品点数の削減による製造コストの低減を図ることができる。
【００４３】
（２）第１小歯車２と第２小歯車３を互いに軸方向逆向きにしてハウジング１０に組み付けたとき、第１小歯車２と第１歯車部１ｂ、および第２小歯車３と第２歯車部１ｃがそれぞれ噛み合うように第１軸部２ｂ（３ｂ）と第２軸部２ｃ（３ｃ）の長さを設定したため、組み付け時のハウジング１０に対する軸方向寸法を小さくできる。さらに、第１小歯車２の第２軸部２ｃと第２小歯車３の第１軸部３ａを回路基板１１を当接させ、ケースアッパ８と回路基板１１で第１小歯車２と第２小歯車３を固定する構成としたため、回路基板１１上に実装した第１磁気センサ６と第２磁気センサ７を第１磁極４と第２磁極５に近接配置することができるとともに、ハウジング１０の薄型化を図ることができる。
【００４４】
（３）第１軸部２ｂ（３ｂ）と第２軸部２ｃ（３ｃ）は異径に形成され、第１軸受け部８ａと第２軸受け部８ｂもこれに合わせた形状となっているため、ケースアッパ８に第１小歯車２と第２小歯車３を組み付ける場合、作業者は意識することなく第１小歯車２と第２小歯車３を適正な方向に組み付けることができ、誤組付けを防止できる。
【００４５】
（４）ステアリングホイールを一方の回転端から他方の回転端まで回転させたとき、第２磁気センサ７の出力電圧が描く波形を、第１磁気センサ６の出力電圧が描く波形よりも０．４波形進むように、駆動歯車１の第１歯車部１ｂおよび第２歯車部１ｃの歯数、第１小歯車２と第２小歯車３の歯数と磁極数を設定したため、ステアリングホイールの回転操作可能範囲のどの角度においても、２つの波形の位置関係が同一となることがなく、ステアリングホイールの絶対角を高精度に検出できる。
【００４６】
（その他の実施例）
以上、本発明の回転角検出装置を実現する実施の形態を、第１実施例に基づいて説明したが、本発明の具体的な構成は第１実施例に限定されるものではなく、発明の要旨を逸脱しない範囲の設計変更等があっても本発明に含まれる。
【図面の簡単な説明】
【図１】第１実施例の回転角検出装置の構造を示す正面図である。
【図２】第１小歯車と第２小歯車の構造を示す正面図である。
【図３】回転角検出装置の構造を示す縦断面図である。
【図４】第１磁気センサと第２磁気センサの出力波形を示す図である。
【符号の説明】
１駆動歯車
１ａ開口部
１ｂ第１歯車部
１ｃ第２歯車部
１ｄ駆動歯車軸
２第１小歯車
２ａ歯車部
２ｂ第１軸部
２ｃ第２軸部
３第２小歯車
３ａ歯車部
３ｂ第１軸部
３ｃ第２軸部
４第１磁極
５第２磁極
６第１磁気センサ
７第２磁気センサ
８ケースアッパ
８ａ第１軸受け部
８ｂ第２軸受け部
９ケースロア
１０ハウジング
１１回路基板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotation angle detection device for detecting a rotation angle of a rotating body, and particularly to a technical field of a rotation angle detection device suitable for detecting a steering angle of a steering wheel.
[0002]
[Prior art]
As this kind of rotation angle detecting device, there is a measuring device having a configuration in which a magnet is provided on each of two small gears meshing with a driving gear fixed to a steering shaft, and an AMR (anisotropic magnetoresistance) sensor is attached to the magnet. It is known (for example, refer to Patent Document 1).
[0003]
The number of teeth of the two small gears is set to be different by one, and the rotation angles of the three gears are set to be different when the steering shaft rotates. Since the two AMR sensors detect a magnetic flux density and output a voltage corresponding to the detected magnetic flux density, an absolute steering angle (a rotation angle from a neutral position) is detected based on a change in a voltage value output by the two AMR sensors. can do.
[0004]
[Patent Document 1]
JP 2001-505667 A
[Problems to be solved by the invention]
However, the above prior art has the following problems.
(A) Since a total of three gears, one driving gear and two small gears, are used, the cost of parts and assembly is high.
(B) Although the two small gears are set to have different numbers of teeth, the difference in the number of teeth cannot be confirmed at a glance, so that there is a possibility that erroneous assembly may occur during the assembly operation.
[0006]
The present invention has been made with a focus on the above problem, and its object is to detect the rotation angle of a rotating body with high accuracy while reducing costs by reducing the number of parts compared to conventional products. It is an object of the present invention to provide a rotation angle detecting device which can be used.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the rotation angle detecting device according to the first aspect of the present invention, a drive gear that rotates according to a rotating body, a housing that houses the drive gear, and a drive gear that is provided in the housing, A first small gear and a second small gear meshing with the first small gear, a first magnetic pole provided on the first small gear, a second magnetic pole provided on the second small gear,
[0008]
A first magnetic sensor arranged to face the first magnetic pole, a second magnetic sensor arranged to face the second magnetic pole, and a rotator based on detection signals of the first magnetic sensor and the second magnetic sensor. And a circuit board having an arithmetic circuit for detecting the rotation angle of the first and second gear units, wherein the drive gear is provided with a first gear unit and a second gear unit having different numbers of teeth by shifting the positions in the axial direction. The first small gear and the second small gear are formed in the same shape, the first small gear and the second small gear are meshed with the first small gear and the first gear portion, and the second small gear and the second gear are formed. The parts are set so as to mesh with each other.
[0009]
According to a second aspect of the present invention, in the rotation angle detecting device according to the first aspect, an annular first shaft portion is formed on one surface side of the first small gear and the second small gear, and the first small gear is formed. An annular second shaft portion is formed on the other surface side of the second pinion and the second pinion, and the lengths of the first shaft portion and the second shaft portion are set such that the first pinion and the second pinion are axially opposite to each other. The first small gear meshes with the first gear and the second small gear meshes with the second gear when assembled to the housing.
[0010]
According to a third aspect of the present invention, in the rotation angle detecting device according to the second aspect, the first shaft portion and the second shaft portion are formed to have different diameters, and the first shaft portion can be fitted to the housing. A first bearing portion and a second bearing portion that can be fitted to the second shaft portion. The first shaft portion of the first pinion is fitted to the first bearing portion, and the second bearing portion of the second pinion is The first pinion and the second pinion are fitted by fitting the two-axis section with the second bearing section, and bringing the circuit board into contact with the second axis section of the first pinion and the first axis section of the second pinion. Is rotatably fixed, and the first magnetic sensor and the second magnetic sensor are mounted on a circuit board so as to be surrounded by the second shaft portion of the first small gear and the first shaft portion of the second small gear. It is characterized by the following.
[0011]
According to a fourth aspect of the present invention, in the rotation angle detecting device according to any one of the first to third aspects, the drive gear is provided integrally with a steering shaft of a vehicle, and the first drive gear is provided. When the number of teeth of the gear portion is m1, the number of teeth of the second gear portion is m2, the number of teeth of the first and second small gears is m3, and the number of waveforms per rotation is n1, m1 and m2 , M3, n1
0 <| 4 × n1 × m1 / m3-4 × n1 × m2 / m3 | <0.5
Is satisfied.
[0012]
【The invention's effect】
According to the first aspect of the present invention, the rotation of the drive gear rotates the first small gear meshing with the first gear portion of the drive gear and the second small gear meshing with the second gear portion of the drive gear. At this time, the first pinion and the second pinion have the same shape, but the first gear portion that meshes with the first pinion and the second gear portion that meshes with the second pinion have different numbers of teeth. Therefore, the first small gear and the second small gear rotate at different rotational speeds. Therefore, since the detection signals output from the first magnetic sensor and the second magnetic sensor are not the same, the rotation angle of the rotating body can be detected based on the two detection signals.
[0013]
That is, in the present invention, by forming the first gear portion and the second gear portion having different numbers of teeth on the drive gear, even when the first small gear and the second small gear have the same shape, the rotation angle of the rotating body is increased. Can be detected. Therefore, as compared with the related art in which the rotation angle is detected using two types of small gears having different numbers of teeth, only one small gear is required, so that the manufacturing cost can be reduced by reducing the number of parts and the rotating body can be reduced. Can be detected with high accuracy.
[0014]
According to the second aspect of the present invention, when the first small gear and the second small gear are assembled to the housing in the axial direction opposite to each other, the first small gear and the first gear portion, and the second small gear and the second small gear are arranged. Since the lengths of the first shaft portion and the second shaft portion are set so that the gear portions mesh with each other, the axial position of the gear portion is maintained while the axial position of the first small gear and the second small gear with respect to the housing is the same. Can be shifted.
[0015]
For example, when the first shaft portion and the second shaft portion are set to the same length, and the axial positions of the first pinion and the second pinion are shifted on the housing side, the axial dimension is shifted by the shifted amount. Becomes large. On the other hand, in the present invention, the first pinion and the second pinion assembled to the housing are in a state where the position of the gear portion is shifted in the axial direction, but the axial position with respect to the housing is the same. Since it is possible, the dimension in the axial direction can be made smaller and the housing can be made thinner.
[0016]
According to the third aspect of the present invention, the first shaft portion of the first pinion is fitted to the first bearing portion, and the second shaft portion of the second pinion is fitted to the second bearing portion. The 1st pinion and the 2nd pinion are assembled to the housing in opposite axial directions. Further, the first shaft portion and the second shaft portion are formed to have different diameters, and accordingly, the shapes of the first bearing portion and the second bearing portion are different, so that the assembling direction of the first pinion and the second pinion is changed. There is no mistake.
[0017]
Further, since the circuit board on which the first magnetic sensor and the second magnetic sensor are mounted is in contact with the second shaft portion of the first small gear and the first shaft portion of the second small gear, the axial dimension is reduced. Can be smaller.
[0018]
In the invention according to claim 4, m1, m2, m3, and n1 are set so as to satisfy the following expression.
0 <| 4 × n1 × m1 / m3-4 × n1 × m2 / m3 | <0.5. . . Formula ▲ 1 ▼
[0019]
Normally, the steering wheel is set to make two rotations on one side, that is, four rotations from one rotation end to the other. Therefore, when the drive gear is provided integrally with the steering shaft, the number of waveforms output from the first magnetic sensor is 4 × n1 × m1 / m3. On the other hand, the number of waveforms output from the second magnetic sensor is 4 × n1 × m2 / m3.
[0020]
Therefore, by setting m1, m2, m3, and n1 so as to satisfy the expression (1), when the steering wheel is rotated four times, the deviation of the waveform drawn by the output voltages of the first magnetic sensor and the second magnetic sensor. Is less than 0.5 waveform. That is, the positional relationship between the two waveforms is not the same at any angle in the range where the rotation of the steering wheel is possible, so that the absolute angle of the steering wheel can be detected with high accuracy.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment for realizing the rotation angle detecting device of the present invention will be described based on a first embodiment and a second embodiment.
[0022]
(First embodiment)
First, the configuration will be described.
FIG. 1 is a front view showing the structure of a rotation angle detecting device according to a first embodiment, in which 1 is a driving gear, 2 is a first small gear, 3 is a second small gear, and 6 is a first magnetic sensor. , 7 are second magnetic sensors.
[0023]
The drive gear 1 has a steering shaft (not shown) inserted into an opening 1a formed at the center thereof, and rotates together with the steering shaft. The drive gear 1 is formed with a first gear portion 1b having a number of teeth of 50 and a second gear portion 1c having a number of teeth of 48 with the position shifted in the axial direction.
[0024]
The first small gear 2 is set to have 20 teeth and meshes with the first gear portion 1 b of the drive gear 1. The second small gear 3 has the same shape as the first small gear 2, and meshes with the second gear portion 1 c of the drive gear 1. The first small gear 2 and the second small gear 3 are arranged symmetrically with respect to the drive gear 1.
[0025]
Next, the structure of the first small gear 2 and the second small gear 3 will be described. Since the first small gear 2 and the second small gear 3 have the same shape, only the structure of the first small gear 2 will be described.
[0026]
As shown in FIG. 2, the first small gear 2 includes a gear portion 2a, and a first shaft portion 2b and a second shaft portion 2c protruding from both surfaces of the gear portion 2a. At the center of the gear portion 2a, a pair of first magnetic poles 4 (second magnetic poles 5 in the case of the second small gear 3) are exposed on both surfaces of the gear portion 2a such that the N pole and the S pole are switched at 180 degrees. It is fixed at.
[0027]
Both the first shaft portion 2b and the second shaft portion 2c are formed in an annular shape. Although the second shaft portion 2c has a larger diameter than the first shaft portion 2b, the axial length is set to be longer in the first shaft portion 2b than in the second shaft portion 2c. That is, the axial position of the gear portion 2a is set to be offset from the axial center position of the first small gear 2 toward the second shaft portion 2c.
[0028]
FIG. 3 is a longitudinal sectional view showing the structure of the rotation angle detecting device.
In the figure, reference numeral 10 denotes a housing of the rotation angle detecting device, which comprises a case upper 8 and a case lower 9.
[0029]
A drive gear shaft 1d of the drive gear 1 is rotatably sandwiched between a case upper 8 and a case lower 9 which constitute a housing of the rotation angle detecting device.
[0030]
The first pinion 2 has a first shaft portion 2b rotatably fitted to a first bearing portion 8a provided on the case upper 8, and a second shaft portion 2c abutting on the circuit board 11. , Between the case upper 8 and the circuit board 11.
[0031]
On the other hand, in the second small gear 3, the second shaft portion 3 c is rotatably fitted to the second bearing portion 8 b provided on the case upper 8, and the first shaft portion 3 b abuts on the circuit board 11. In this state, it is sandwiched between the case upper 8 and the circuit board 11.
[0032]
That is, the first small gear 2 and the second small gear 3 are assembled to the housing 10 in a state opposite to each other, and the gear 2a of the first small gear 2 meshes with the first gear 1b of the drive gear 1. The gear portion 3a of the second small gear 3 meshes with the second gear portion 1b of the drive gear 1.
[0033]
The first magnetic sensor 6 is mounted on the circuit board 11 so as to face the first magnetic pole 4 of the first small gear 2 and to be surrounded by the second shaft portion 2c. The second magnetic sensor 7 is mounted on the circuit board 11 so as to face the second magnetic pole 5 of the second small gear 3 and to be surrounded by the first shaft portion 3b. As the first magnetic sensor 6 and the second magnetic sensor 7, for example, an MR (Magneto Resistance) sensor or a Hall IC is used.
[0034]
The first magnetic sensor 6 and the second magnetic sensor 7 change the output voltage according to the magnetic flux density that changes with the rotation of the first small gear 2 and the second small gear 3. This output voltage is input to an arithmetic circuit on the circuit board 11 via an amplifier circuit on the circuit board 11. The arithmetic circuit compares the two output voltages to calculate the absolute steering angle. The calculated absolute angle of the steering is input to a control device of the vehicle via a steering harness (not shown), and is used for vehicle control such as four-wheel steering control.
[0035]
When the absolute angle of the steering is obtained by comparing the output voltages of the first magnetic sensor 6 and the second magnetic sensor 7, when the steering is rotated from one rotation end to the other rotation end, two output voltage values are drawn. It is necessary to set the deviation between the two waveforms to be less than 0.5 so that the positional relationship between the waveforms is not the same at any angle.
[0036]
In order for the difference between the two waveforms to be less than 0.5, the number of teeth of the first gear portion 1b of the driving gear 1 is m1, the number of teeth of the second gear portion 1b is m2, the first small gear 2 and the second When the number of teeth of the small gear 3 is m3 and the number of waveforms per rotation is n1,
0 <| 4 × n1 × m1 / m3-4 × n1 × m2 / m3 | <0.5
M1, m2, m3, and n1 that satisfy the above equation must be set.
[0037]
In the first embodiment, since m1 = 48, m2 = 50, m3 = 20, and n1 = 1, when the steering shaft rotates four times, the number of waveforms output from the first magnetic sensor 6 and the second magnetic sensor 7 The number of waveforms output from
4 × n1 × m1 / m2 = 4 × 1 × 48/20 = 9.6
4 × n1 × m1 / m3 = 4 × 1 × 50/20 = 10
And the output waveform of the second magnetic sensor 7 is advanced by 0.4 from the output waveform of the first magnetic sensor 6 (see FIG. 4), so that the positional relationship of the waveforms drawn by the two output voltage values is the same at any angle. And the absolute steering angle can be detected.
[0038]
Next, the operation will be described.
[Assembly of small gear to housing]
In the rotation angle detection device of the first embodiment, the drive gear 1 and the circuit board 11 are assembled to the case lower 9, the first small gear 2 and the second small gear 3 are assembled to the case upper 8, and then the case upper 8 and the case lower 9 are assembled. Are superimposed.
[0039]
When assembling the first small gear 2 and the second small gear 3 to the case upper 8, the first shaft portion 2 b of the first small gear 2 is fitted to the first bearing portion 8 a of the case upper 8, and The second shaft portion 3c of the second small gear 3 is fitted to the second bearing portion 8b.
[0040]
At this time, the first shaft portion 2b (3b) and the second shaft portion 2c (3c) are formed to have different diameters, and the first bearing portion 8a and the second bearing portion 8b are also formed in a shape corresponding thereto. The first small gear 2 and the second small gear 3 are always assembled in an appropriate direction (opposite direction).
[0041]
Next, effects will be described.
In the rotation angle detecting device according to the first embodiment, the following effects can be obtained.
[0042]
(1) By forming the first gear portion 1b having 48 teeth and the second gear portion 1c having 50 teeth on the drive gear 1, even when the first small gear 2 and the second small gear 3 have the same shape. Since the steering angle of the steering wheel can be detected, only one small gear is required as compared with the prior art in which the rotation angle is detected using two types of small gears having different numbers of teeth. Reduction can be achieved.
[0043]
(2) When the first pinion 2 and the second pinion 3 are assembled in the housing 10 with their axial directions opposite to each other, the first pinion 2 and the first gear portion 1b, and the second pinion 3 and the second pinion 3 Since the lengths of the first shaft portion 2b (3b) and the second shaft portion 2c (3c) are set so that the gear portions 1c mesh with each other, the axial dimension with respect to the housing 10 at the time of assembly can be reduced. Further, the circuit board 11 is brought into contact with the second shaft portion 2c of the first small gear 2 and the first shaft portion 3a of the second small gear 3, and the first small gear 2 and the second Since the small gear 3 is fixed, the first magnetic sensor 6 and the second magnetic sensor 7 mounted on the circuit board 11 can be arranged close to the first magnetic pole 4 and the second magnetic pole 5, and the housing 10 The thickness can be reduced.
[0044]
(3) Since the first shaft portion 2b (3b) and the second shaft portion 2c (3c) are formed to have different diameters, and the first bearing portion 8a and the second bearing portion 8b also have shapes corresponding to these. When assembling the first small gear 2 and the second small gear 3 to the case upper 8, the operator can assemble the first small gear 2 and the second small gear 3 in an appropriate direction without being conscious of the operation, and Can be prevented.
[0045]
(4) When the steering wheel is rotated from one rotation end to the other rotation end, the waveform drawn by the output voltage of the second magnetic sensor 7 is 0.4 times smaller than the waveform drawn by the output voltage of the first magnetic sensor 6. Since the number of teeth of the first gear portion 1b and the second gear portion 1c of the drive gear 1, the number of teeth of the first small gear 2 and the second small gear 3 and the number of magnetic poles are set so as to advance the waveform, the rotation operation of the steering wheel is performed. At any angle in the possible range, the positional relationship between the two waveforms does not become the same, and the absolute angle of the steering wheel can be detected with high accuracy.
[0046]
(Other Examples)
As described above, the embodiment for realizing the rotation angle detecting device of the present invention has been described based on the first embodiment. However, the specific configuration of the present invention is not limited to the first embodiment, and Even a design change within a range not departing from the gist is included in the present invention.
[Brief description of the drawings]
FIG. 1 is a front view showing the structure of a rotation angle detection device according to a first embodiment.
FIG. 2 is a front view showing a structure of a first small gear and a second small gear.
FIG. 3 is a longitudinal sectional view showing a structure of a rotation angle detecting device.
FIG. 4 is a diagram showing output waveforms of a first magnetic sensor and a second magnetic sensor.
[Explanation of symbols]
1 Drive Gear 1a Opening 1b First Gear 1c Second Gear 1d Drive Gear Shaft 2 First Small Gear 2a Gear 2b First Shaft 2c Second Shaft 3 Second Small Gear 3a Gear 3b First Shaft Part 3c Second shaft part 4 First magnetic pole 5 Second magnetic pole 6 First magnetic sensor 7 Second magnetic sensor 8 Case upper 8a First bearing 8b Second bearing 9 Case lower 10 Housing 11 Circuit board

Claims

A drive gear that rotates according to the rotating body,
A housing for accommodating the driving gear;
A first small gear and a second small gear provided in the housing and respectively meshing with the drive gear;
A first magnetic pole provided on the first small gear;
A second magnetic pole provided on the second small gear;
A first magnetic sensor arranged facing the first magnetic pole;
A second magnetic sensor disposed facing the second magnetic pole;
A circuit board having an arithmetic circuit for detecting a rotation angle of the rotating body based on detection signals of the first magnetic sensor and the second magnetic sensor;
In the rotation angle detection device provided with
A first gear portion and a second gear portion having different numbers of teeth are formed on the drive gear by shifting the positions in the axial direction,
The first pinion and the second pinion have the same shape,
A rotation angle detecting device, wherein the first small gear and the second small gear are set such that the first small gear and the first gear unit mesh with each other, and the second small gear and the second gear unit mesh with each other.

The rotation angle detection device according to claim 1,
An annular first shaft portion is formed on one surface side of the first and second small gears, and an annular second shaft portion is formed on the other surface side of the first and second small gears;
When the first pinion and the second pinion are assembled to the housing with the first pinion and the second pinion being axially opposite to each other, the first pinion meshes with the first pinion, A rotation angle detecting device, wherein the second small gear is set to mesh with the second gear portion.

The rotation angle detection device according to claim 2,
The first shaft portion and the second shaft portion are formed to have different diameters,
A first bearing portion that can be fitted to the first shaft portion and a second bearing portion that can be fitted to the second shaft portion,
A first shaft portion of the first pinion is fitted with the first bearing portion, and a second shaft portion of the second pinion is fitted with the second bearing portion;
A circuit board is brought into contact with a second shaft portion of the first pinion and a first shaft portion of the second pinion to fix the first pinion and the second pinion rotatably;
The rotation angle detection, wherein the first magnetic sensor and the second magnetic sensor are mounted on a circuit board so as to be surrounded by a second shaft portion of the first small gear and a first shaft portion of the second small gear. apparatus.

The rotation angle detection device according to any one of claims 1 to 3,
The drive gear is provided integrally with a steering shaft of a vehicle,
The number of teeth of the first gear portion of the drive gear is m1, the number of teeth of the second gear portion is m2,
When the number of teeth of the first and second small gears is m3, and the number of waveforms per rotation is n1, m1, m2, m3, and n1 are:
0 <| 4 × n1 × m1 / m3-4 × n1 × m2 / m3 | <0.5
A rotation angle detector that satisfies the following.