JP4354191B2 - Planetary differential gear reduction device and image forming apparatus - Google Patents

Description

【数４】

【数５】

【００１９】
以上の説明では、遊星歯車４２１における固定歯車４１４に噛み合う固定歯車用噛合部分と出力歯車４１６に噛み合う出力歯車用噛合部分の歯数が同一である構成について説明したが、この歯数が同一でない遊星差動歯車減速装置においても、上述したような角速度変動は生じる。
【００２０】
本発明は、上記問題に鑑みなされたものであり、その目的とするところは、高コストとなる高精度な加工や組み付けなどを行うことなく、遊星歯車の個数に応じた周波数で発生する角速度変動を抑制することが可能な遊星差動歯車減速装置及び画像形成装置を提供することである。
【００２１】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明は、駆動源の回転数を駆動対象が必要とする回転数まで減速し、該駆動源からの回転力を伝達するための遊星差動歯車減速装置において、上記駆動対象に連結される出力軸に固定された出力歯車と、該出力歯車よりも少ない歯数を有し、該出力歯車と同軸上に配置され、かつ、回転不能に固定された固定歯車と、上記駆動源からの回転力により該出力歯車及び該固定歯車の外周を回転駆動される遊星歯車軸に回転自在に支持され、該出力歯車及び該固定歯車の双方に噛み合いながら遊星回転する２つの遊星歯車とを備えており、該２つの遊星歯車を、遊星回転の中心軸について互いに軸対称となる位置に配置し、上記出力歯車及び上記固定歯車のうちの少なくとも一方は、互いに別体の歯車中心に近い内側部と該中心から遠い外側部とからなる二重構造を有し、該内側部の外周面と該外側部の内周面との間には間隔を有し、該間隔に複数の弾性部材が配置され、上記弾性部材により上記内側部と上記外側部との周方向の相対的な移動が規定さ、前記弾性部材は、前記像担持体を回転駆動している間の噛み合いによって生じる接触圧が加わったときに、該弾性部材の変形する変形量が前記外側部の偏心量と前記出力歯車の角速度変動の許容範囲とに基づいて求められる変形量となるような縦弾性係数を有するものを用いたことを特徴とするものである。
また、請求項２の発明は、請求項１の遊星差動歯車減速装置において、前記弾性部材が前記内側部の外周面と前記外側部の内周面とに形成した切り欠き部に嵌合させて設けられていることを特徴とするものである。
また、請求項３の発明は、駆動源の回転数よりも低い回転数で回転する像担持体を備えた画像形成装置において、上記駆動源の回転数を、上記像担持体が必要とする回転数まで減速し、該駆動源からの回転力を伝達するための減速手段として、請求項１又は２の遊星差動歯車減速装置を用いたことを特徴とするものである。
【００２２】
請求項１乃至２の遊星差動歯車減速装置、及び、請求項３の画像形成装置においては、同軸上に配置される出力歯車と固定歯車のそれぞれに、単一の遊星歯車がそれぞれ２つ噛み合う構成となる。ここで、２つの遊星歯車を遊星回転の中心軸について互いに軸対称となる位置に配置しているので、上述したように、各部品の加工誤差や組立誤差によって、遊星回転の半周期に相当する周波数で、出力歯車の角速度が変動することがある。
ここで、上記先願に係る遊星差動歯車減速装置を用い、その出力軸に加わる負荷トルクを変更したときの角速度変動率を測定した実験について説明する。この実験の結果は、図１９に示すとおりである。この実験結果からすると、出力軸に加わる負荷トルクを大きくすれば、角速度変動率を抑制することは可能であることがわかる。しかし、負荷トルクは、駆動対象によって様々であり、例えば図１６に示した遊星差動歯車減速装置のように出力軸が感光体ドラムに接続されるものである場合には、その負荷トルクはおよそ２〜３ｋｇｆ・ｃｍ程度である。この場合、上記先願に係る遊星差動歯車減速装置では、角速度変動率はおよそ１〜３％であり、角速度変動を十分に抑制しているとはいえない。ここで、上記実験結果について考察したところ、負荷トルクが大きくなると角速度変動率が小さくなるのは、大きな負荷トルクによって歯車の歯が変形し、又は大きな負荷トルクによって歯車が変位したことで、２つの遊星歯車の両方が出力歯車及び固定歯車に対して噛み合った状態になったためだと考えられる。その結果、出力歯車に対して２つの遊星歯車が交互に噛み合う上述した構成のように出力歯車への回転力の伝達ルートが切り替わる時期が存在しない。したがって、この切り替わり時期に生じていた急激なトルク変動が生じることもなく、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制することができたものと考えられる。
そこで、請求項１乃至２の遊星差動歯車減速装置では、出力歯車及び固定歯車のうちの少なくとも一方が、互いに別体の歯車中心に近い内側部と該中心から遠い外側部とからなる二重構造を有し、該内側部の外周面と該外側部の内周面との間には間隔を有し、該間隔に複数の弾性部材が配置され上記弾性部材により上記内側部と上記外側部との周方向の相対的な移動が規定されるので、駆動対象が回転駆動している間の噛み合いによって生じる接触圧によって上記弾性部材の変形で上記外側部が変位可能である。これにより、出力歯車の角速度変動を抑制することができる。すなわち、例えば変位可能な歯車が出力歯車である場合、駆動対象の回転駆動時には出力歯車のピッチ円と一方の遊星歯車のピッチ円とが交差する部分が存在すると、その部分での噛み合いにより、出力歯車は上記一方の遊星歯車から離れる向きの力を受けることになる。この力により、出力歯車が他方の遊星歯車側に変位することになる。よって、出力歯車の中心軸と２つの遊星歯車の遊星回転中心軸との軸ズレが少なくなる。したがって、駆動対象の回転駆動中、２つの遊星歯車の両方が出力歯車及び固定歯車に対して常に噛み合った状態を確保することができるようになる。その結果、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制することができる。
【００２３】
なお、２つの遊星歯車は、固定歯車に噛み合う固定歯車用噛合部分と出力歯車に噛み合う出力歯車用噛合部分の歯数が同一歯数であっても異なる歯数であってもよい。しかし、同一歯数とした場合、固定歯車の歯数が出力歯車の歯数よりも少ないので、単に、これら歯車に単一の遊星歯車をそれぞれ２つ噛み合わせるだけでは、スムーズな回転駆動が実現できない。そのため、特願２００１−２３１４０７号で提案した遊星差動歯車減速装置のように、出力歯車、固定歯車、並びに、遊星歯車の固定歯車用噛合部分及び遊星歯車の出力歯車用噛合部分のうち、少なくとも１つを転位歯車で構成することが必要となる。これにより、同軸上に配置された歯数の異なる固定歯車と出力歯車に対して、単一の遊星歯車を適正に噛み合わせることが可能となり、スムーズな回転駆動が実現することが可能となる。また、固定歯車と出力歯車と噛み合う遊星歯車の各噛合部分の歯数は同数であると、遊星差動歯車減速装置により得られる減速比は、上記数２を変形した下記数６により求められる。尚、下記の数６において、Ｎ₁は、入力軸の回転数を示し、Ｎ₅は、出力軸の回転数を示し、また、Ｚ₃は、固定歯車の歯数を示し、Ｚ₅は、出力歯車の歯数を示す。
【数６】
Ｎ₅＝Ｎ₁×（Ｚ₅−Ｚ₃）／Ｚ₅
この式から解かるように、遊星歯車の各噛合部分の歯数は同数である場合の減速比は、遊星歯車の歯数に関係なく、固定歯車と出力歯車の歯数に基づいて得られることになる。これにより、従来より固定歯車と出力歯車の歯数が少なくても、高い減速比を得ることができる。すなわち、従来と同じ減速比を得る場合でも、固定歯車と出力歯車の歯数が少なくて済む。よって、これら固定歯車と出力歯車の直径を小さくすることができる。例えば、１／２０の減速比を得る場合、固定歯車と出力歯車の歯数差を２枚とするときは、各歯車の歯数はそれぞれ３８枚と４０枚とすればよく、また、固定歯車と出力歯車の歯数差を１枚とするときは、各歯車の歯数はそれぞれ１９枚と２０枚とすればよい。また、これら固定歯車と出力歯車の直径を小さくできることで、高い回転数が入力されて遊星歯車が高速に遊星回転しても、その回転半径は小さいものとなる。この結果、回転バランスがとりやすく、スムーズな回転駆動が実現することが可能となる。更に、上述のように、減速比は遊星歯車の歯数に影響を受けないので、遊星歯車の歯数は任意に設定できる。この結果、遊星歯車の直径も小さくすることが可能となる。これにより、遊星歯車が固定歯車及び出力歯車の外周を遊星回転するために必要なスペースも小さくでき、固定歯車と出力歯車の径方向における装置寸法をコンパクトにすることができる。
【００２４】
【発明の実施の形態】
〔実施形態１〕
以下、本発明を、画像形成装置である電子写真方式のカラー複写機（以下、「複写機」という。）に適用した一実施形態（以下、本実施形態を「実施形態１」という。）について説明する。尚、本実施形態１における複写機は、いわゆるタンデム式の画像形成装置であって、乾式二成分現像剤を用いた乾式二成分現像方式を採用したものである。
【００２５】
図２は、本実施形態１に係る複写機における画像形成部全体の概略構成図である。この複写機は、図示しない画像読取部から画像情報である画像データを受け取って画像形成処理を行う。この複写機には、図に示すように、イエロー（以下、「Ｙ」と省略する。）、マゼンタ（以下、「Ｍ」と省略する。）、シアン（以下、「Ｃ」と省略する。）、ブラック（以下、「Ｂｋ」と省略する。）の各色用の４個の回転体としての潜像担持体である感光体ドラム１Ｙ，１Ｍ，１Ｃ，１Ｂｋが並設されている。これら感光体ドラム１Ｙ，１Ｍ，１Ｃ，１Ｂｋは、駆動ローラを含む回転可能な複数のローラに支持された無端ベルト状の中間転写ベルト５に接触するように、そのベルト移動方向に沿って並んで配置されている。また、感光体ドラム１Ｙ，１Ｍ，１Ｃ，１Ｂｋの周りには、それぞれ、帯電器２Ｙ，２Ｍ，２Ｃ，２Ｂｋ、各色対応の現像装置９Ｙ，９Ｍ，９Ｃ，９Ｂｋ、クリーニング装置４Ｙ，４Ｍ，４Ｃ，４Ｂｋ、除電ランプ３Ｙ，３Ｍ，３Ｃ，３Ｂｋ等の電子写真プロセス用部材がプロセス順に配設されている。
【００２６】
本実施形態１に係る複写機でフルカラー画像を形成する場合、まず、図２に示すように、後述する感光体駆動装置により、感光体ドラム１Ｙを図中矢印の方向に回転駆動しながら帯電器２Ｙで一様帯電した後、図示しない光書込装置からの光ビームＬ_Ｙを照射して感光体ドラム１Ｙ上にＹ静電潜像を形成する。このＹ静電潜像は、現像装置９Ｙにより、現像剤中のＹトナーにより現像される。現像時には、現像ローラと感光体ドラム１Ｙとの間に所定の現像バイアスが印加され、現像ローラ上のＹトナーは、感光体ドラム１Ｙ上のＹ静電潜像部分に静電吸着する。
【００２７】
このように現像されて形成されたＹトナー像は、感光体ドラム１Ｙの回転に伴い、感光体ドラム１Ｙと中間転写ベルト５とが接触する１次転写位置に搬送される。この１次転写位置において、中間転写ベルト５の裏面には、１次転写ローラ６Ｙにより所定のバイアス電圧が印加される。そして、このバイアス印加によって発生した１次転写電界により、感光体ドラム１Ｙ上のＹトナー像を中間転写ベルト５側に引き寄せ、中間転写ベルト５上に１次転写する。以下、同様にして、Ｍトナー像、Ｃトナー像、Ｂｋトナー像も、中間転写ベルト５上のＹトナー像に順次重ね合うように１次転写される。
【００２８】
このように、中間転写ベルト５上に４色重なり合ったトナー像は、中間転写ベルト５の回転に伴い、２次転写ローラ７と対向する２次転写位置に搬送される。また、この２次転写位置には、図示しないレジストローラにより所定のタイミングで転写紙が搬送される。そして、この２次転写位置において、２次転写ローラ７により転写紙の裏面に所定のバイアス電圧が印加され、そのバイアス印加により発生した２次転写電界及び２次転写位置での当接圧により、中間転写ベルト５上のトナー像が転写紙上に一括して２次転写される。その後、トナー像が２次転写された転写紙は、定着ローラ対８により定着処理がなされた後に装置外に排出される。
【００２９】
次に、本発明の特徴部分である、減速手段としての遊星差動歯車減速装置を備える駆動手段としての減速機構付き駆動装置である感光体駆動装置について説明する。尚、各感光体ドラム１Ｙ，１Ｍ，１Ｃ，１Ｂｋは、同一構成の感光体駆動装置により回転駆動されているので、以下、感光体ドラム１Ｙの感光体駆動装置について説明する。
【００３０】
図３は、本実施形態１における感光ドラム１の軸方向一端部外方に設置される感光体駆動装置の部分断面図である。この感光ドラム１の軸方向両端には、その感光体ドラム１の軸方向端部面を塞ぐように、円板状のドラムフランジ１ａが固定されている。このドラムフランジ１ａの円板中心は、感光体駆動装置１０の出力軸１１の端部に固定されており、その出力軸１１からの回転力が伝達されるように構成されている。また、この出力軸１１は、滑らかな回転が可能となるように、本実施形態１に係る複写機の内部筺体を構成する側板１００の軸受１００ａにより回転可能に軸受けされ、支持されている。また、感光体駆動装置１０は、側板１００に対して感光体ドラム１とは反対側に位置し、その側板１００の表面に固定されている。
【００３１】
図１は、感光体駆動装置１０の内部構成を示す断面図である。また、図４は、感光体駆動装置１０の斜視図である。この感光体駆動装置１０の外面は、円筒状のケース１２と、そのケース１２の開口部を塞ぐ円板状の蓋部材１３により構成されている。出力軸１１は、その蓋部材１３の円板中心に挿通され、本感光体駆動装置１０を貫通している。また、ケース１２は、出力軸１１を回転可能に支持する軸受１２ａを有し、また、蓋部材１３は、出力軸１１を回転可能に支持する軸受１３ａを有している。蓋部材１３が有する軸受１３ａは、蓋部材１３に圧入カシメられて固定された固定歯車１４に固定されている。このようにして、感光体駆動装置１０を貫通する出力軸１１の両端が回転可能に支持されている。ここで、出力軸１１を滑らかに回転させるため、各軸受１２ａ，１３ａは、高精度な同軸度を必要とする。このため、各軸受１２ａ，１３ａは、位置決めピン１５等により精度を維持しながら、ネジや円周カシメ等の方法で組立構成されている。尚、高精度な同軸度を出すための手段としては、茶筒（インロー）嵌合などの方法もある。
【００３２】
また、感光体駆動装置１０のケース１２の内部には、出力軸１１に圧入などの方法で強固に固定された出力歯車１６、及び、デスク軸受１７ａを介して出力軸１１に対し回転自在に取り付けられた動力入力部材としての回転ディスク１７等が設けられている。この回転ディスク１７には、その出力軸１１を中心として回転するアウターロータ１８がカシメや圧入、接着材などで強固に固定されている。このアウターロータ１８の内部には、出力軸１１と平行な内周面上に回転力伝達部材としての磁石１９が固定配置されている。また、その内周面と出力軸１１との間のスペースには、ケース１２に固定された２つの駆動源としてのステータコア２０が存在し、これらステータコア２０は、磁石１９との最適な位置関係となるように、出力軸１１に対して対称位置に配置されている。
【００３３】
回転デスク１７には、固定歯車１４及び出力歯車１６を太陽歯車とする遊星歯車２１の遊星歯車軸２２が圧入などの方法で固定されている。この遊星歯車軸２２には、平歯車で構成された遊星歯車２１が回転自在に取り付けられている。遊星歯車軸２２は、出力軸１１に平行に設置され、出力軸１１に対して対称位置となるように、回転デスク１７上に２つ設置されている。また、この遊星歯車軸２２は、出力軸１１との軸間距離が、遊星歯車２１と、固定歯車１４及び出力歯車１６とがそれぞれ互いに噛み合うのに最適な距離となるように配置されている。また、回転中に遊星歯車２１が遊星歯車軸２２から飛び出さず、かつ、遊星歯車２１と固定歯車１４及び出力歯車１６とがそれぞれ噛み合うときの位置関係を保持するために、遊星歯車２１は、軸止輪２３等によって遊星歯車軸２２上に保持されている。
【００３４】
アウターロータ１８が回転すると、回転デスク１７が出力軸１１を中心に回転する。これにより、固定歯車１４の周りを遊星歯車２１が自転しながら遊星回転（公転）する。遊星歯車２１は、出力歯車１６とも噛み合っているので、出力歯車１６は、固定歯車１４との歯数の差分だけ回転することになる。ここで、固定歯車１４及び出力歯車１６と遊星歯車２１とが噛み合うときの各歯車１４，１６の実際の噛み合いピッチ円が同じになるように、固定歯車１４又は出力歯車１６の少なくとも一方の歯車は、転位歯車として構成されている。これにより、遊星歯車２１は、歯数の異なる固定歯車１４及び出力歯車１６にそれぞれ適正に噛み合うことができるようになっている。
【００３５】
図５は、感光体駆動装置１０を、出力軸１１の軸方向から見た正面図である。図示のように、固定歯車１４と出力歯車１６は、ともに出力軸１１と同軸に配置されいる。２つの遊星歯車２１は、遊星回転の中心軸について軸対称を維持しながら遊星回転（公転）する。ここで、固定歯車１４と出力歯車１６の歯数差が偶数のとき、遊星歯車２１は、図６に示すように、固定歯車１４に噛み合う固定歯車用噛合部分と出力歯車１６に噛み合う出力歯車用噛合部分とが同一構造を有する。一方、固定歯車１４と出力歯車１６の歯数差が奇数のとき、遊星歯車２１は、図７に示すように、固定歯車１４に噛み合う固定歯車用噛合部分２１ａと出力歯車１６に噛み合う出力歯車用噛合部分２１ｂの一方が他方に対して半ピッチずれた構造を有する。このように半ピッチをズラす方法としては、例えば、遊星歯車２１が金属で歯切りされたものである場合、圧入やカシメにより一体の歯車として構成できる。また、遊星歯車２１が成形部品である場合には、２分割金型を用いることで容易に製作することができる。このように半ピッチずらすことにより、固定歯車用噛合部分２１ａと出力歯車用噛合部分２１ｂの位相差分を補正することができる。
【００３６】
また、２個の遊星歯車の一方を、シザーズ歯車として構成してもよい。図８（ａ）乃至（ｃ）に、遊星歯車２１をシザーズ歯車として構成した場合の一例を示す。図８（ａ）は、シザーズ歯車として構成される遊星歯車１２１の軸方向断面図であり、図８（ｂ）は、この遊星歯車１２１の固定歯車１４に噛み合う部分１２１ａを、出力歯車１６に噛み合う部分１２１ｂ側から見た側面図であり、図８（ｃ）は、これら２つの遊星歯車部分１２１ａ，１２１ｂを互いに逆回転方向に付勢するための弾性体としての板バネ１２１ｃを示す外観図である。
【００３７】
この遊星歯車１２１は、固定歯車１４に噛み合う遊星歯車部分１２１ａに設けられる切欠部１２４に、出力歯車１６に噛み合う遊星歯車部分１２１ｂに設けられるピンが挿入された状態で組み立てられる。このとき、出力歯車１６に噛み合う遊星歯車部分１２１ｂにも、同様の切欠部１２４が設けられており、固定歯車１４に噛み合う遊星歯車部分１２１ａに設けられるピン１２５が同様に挿入される。また、このとき、各遊星歯車部分１２１ａ，１２１ｂのピン１２５は、図８（ｃ）に示すように、板バネ１２１ｃに設けられる２つの挿入穴にそれぞれ挿入される。これにより、シザーズ歯車で構成される遊星歯車１２１の各遊星歯車部分１２１ａ，１２１ｂは、板バネ１２１ｃにより、互いに逆回転方向に付勢されるが、その付勢力は、出力軸１１の必要伝達トルクの１／２に相当するトルクが出力歯車１６に伝達されるように設定される。また、各遊星歯車部分１２１ａ，１２１ｂが互いに回転できる最大可動範囲は、各ピン１２５と切欠部１２４により０．５ピッチに設定されている。
【００３８】
図９は、上記アウターロータモータの代わりに、インナーロータ型ＤＣモータを適用した感光体駆動装置１０の部分断面図である。出力軸１１上には、このインナーロータ型ＤＣモータのモータ軸１１８ａが回転自在に取り付けられており、このモータ軸１１８ａには、インナーロータ１１８が固定されている。また、このインナーロータの外周部には、磁石１１９が取り付けられている。このインナーロータ１１８のモータケース１１２ａ，１１２ｂには、ステータコア１２０が固定されている。モータ軸１１８ａの遊星歯車２１側の端部には、回転ディスク１７が圧入などにより固定されている。また、回転ディスク１７には、遊星歯車軸２２が圧入などで固定されており、この遊星歯車軸２２には、上記と同様に、遊星歯車２１が回転自在に取り付けられている。尚、ここでは、ＤＣモータを使用しているが、ステッピングモータやＡＣモータ等であっても同様に適用することができる。
【００３９】
ここで、本実施形態１においては、出力歯車１６をプラスチック材、具体的にはＰＯＭ（ポリアセタール樹脂）で形成しているので、その出力歯車１６の歯部分は弾性部材である。そのため、出力歯車１６と遊星歯車２１との噛合い部分に発生する負荷トルクによる歯変位が、速度変動の要因となる偏心量を吸収することになる。この偏心を吸収する程度の歯変位を実現する歯対剛性となるように、本実施形態１における出力歯車１６の縦弾性係数を設定すれば、後述する同様の効果を得ることが可能である。この歯対剛性とは、歯と歯が噛合っているときの負荷による弾性変形に対する硬さを示すもので、歯車の歯対によるばね剛性であって、かみあい剛性とも呼ばれている。なお、固定歯車１４及び遊星歯車２１は、比較的剛性の高い金属（鉄、黄銅等）製または高密度のＰＯＭ製の歯車で構成されており、出力歯車１６と遊星歯車２１との間の歯対剛性は、固定歯車１４と遊星歯車２１との間の歯対剛性よりも１桁以上小さいものとなっている。
【００４０】
感光体ドラム１Ｙが回転駆動すると、出力歯車１６に負荷がかかり、その負荷によって生じる力が出力歯車１６の歯部分を弾性変形させる。これにより、後述する実施例で説明するように、感光体ドラム１Ｙの回転駆動中、２つの遊星歯車２１の両方が出力歯車１６及び固定歯車１４に対して常に噛み合った状態を確保することができ、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制できるという効果を得ることができる。なお、この効果は、２つの遊星歯車２１又は固定歯車１４の歯部分を、ＰＯＭ等からなる弾性部材で構成しても同様に得ることができる。一例を挙げると、固定歯車１４が出力軸１１の軸受を兼ねている場合には、固定歯車１４をＰＯＭで形成し、遊星歯車２１を金属で形成し、出力歯車１６をＰＯＭで形成するようにしてもよい。
なお、どの歯部分をＰＯＭ等からなる弾性部材で構成するかは、駆動対象を回転駆動したときにその歯部分に加わる力の大きさや、加工誤差及び組立誤差の程度などによって適宜決めることになる。例えば、駆動対象を回転駆動したときにその歯部分に加わる力の大きさが小さい場合、固定歯車１４、出力歯車１６及び遊星歯車２１のすべてを弾性部材で構成してもよい。
【００４１】
また、２つの遊星歯車２１の両方が出力歯車１６及び固定歯車１４に対して常に噛み合った状態になるために必要となる変形量は、遊星回転（公転）の中心軸と各遊星歯車２１の回転（自転）軸との距離のズレ、同軸上に配置されるべき遊星回転の中心軸と出力歯車１６の軸又は固定歯車１４の軸との間の軸ズレ、固定歯車１４の偏心などに関わる加工精度や組立精度によって変わってくる。上述のように弾性変形させる歯部分にどの程度の縦弾性係数をもたせるかは、この必要とする変形量に応じて決まる。なお、この必要とする変形量は、歯部分に対して力が加わる位置や、その歯部分をもつ出力歯車１６のモジュール及び歯幅等によっても変わるので、これらも考慮した上で用いる弾性部材を選定するのが望ましい。
【００４２】
〔実施形態２〕
次に、本発明を、上記実施形態１と同様に複写機に適用した他の実施形態（以下、本実施形態を「実施形態２」という。）について説明する。
本実施形態２に係る複写機の基本構成及び動作は上記実施形態１と同様である。しかし、上記実施形態１では、遊星歯車２１の個数に応じた周波数で発生する角速度変動を抑制する方法として、出力歯車２１の歯部分を弾性変形させる方法を採用しているのに対し、本実施形態２では、出力歯車を変位させる方法を採用する。以下、この点についてのみ説明する。
【００４３】
図１０は、本実施形態２における出力軸１１１を示す軸方向断面図である。本実施形態２では、出力軸１１１上に軸径が細くなった変位手段としての軸変形手段である軸細部分１１１ａを備えている。そして、出力歯車１１６は、この軸細部分１１１ａに固定されている。この軸細部分１１１ａの軸径は、最低限伝達すべきトルクに耐えられる軸強度を確保できるものに設定されている。なお、本実施形態２では、すべての歯車は、比較的剛性の高い金属（鉄、黄銅等）製の歯車で構成されている。
【００４４】
本実施形態２では、各歯車にはインボリュート歯車が用いられているので、感光体ドラム１Ｙが回転駆動すると、出力歯車１１６と遊星歯車２１とが噛み合って、これらの歯車１１６，２１には２０度の圧力角方向に力が加わる。この力は、出力歯車１１６を介して、この出力歯車１１６が固定された出力軸１１１の軸細部分１１１ａに伝わる。この力により、その軸細部分１１１ａは変形することになる。この変形により、出力歯車１１６は、出力歯車１１６の中心軸と２つの遊星歯車２１の遊星回転中心軸との軸ズレが少なくなる方向に変位する。その結果、感光体ドラム１Ｙの回転駆動中、２つの遊星歯車２１の両方が出力歯車１１６及び固定歯車１４に対して常に噛み合った状態を確保することができ、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制できるという効果を得ることができる。なお、この効果は、遊星回転の中心軸と固定歯車１４の軸との間で軸ズレが発生している場合や、固定歯車１４が偏心している場合等においては、固定歯車１４が固定された軸を弾性部材で構成しても同様に得ることができる。
【００４５】
２つの遊星歯車２１の両方が出力歯車１１６及び固定歯車１４に対して常に噛み合った状態になるために必要となる変形量は、遊星回転（公転）の中心軸と各遊星歯車２１の回転（自転）軸との距離のズレ、同軸上に配置されるべき遊星回転の中心軸と出力歯車１１６の軸又は固定歯車１４の軸との間の軸ズレ、固定歯車１４の偏心などに関わる加工精度や組立精度によって変わってくる。上述のように変形させる出力軸１１１の軸細部分１１１ａの軸径をどの程度にするか、その軸細部分１１１ａの縦弾性係数をどの程度にするかは、この必要とする変形量に応じて決まる。なお、そのような軸径、縦弾性係数等をもったものであれば、その軸細部分１１１ａは鉄でもプラスチックでもよい。なお、出力軸１１１に加わる力は、出力歯車１１６の歯部分に対して力が加わる位置や、出力歯車１１６のモジュール及び歯幅等によっても変わるので、これらも考慮した上で軸細部分の軸径や縦弾性係数を設定するのが望ましい。
【００４６】
なお、本実施形態２では、出力軸１１１に軸細部分１１１ａを形成して出力軸１１１を変形させる構成について説明したが、出力軸１１１が所定方向に撓みやすいように切り欠きを形成したり、出力軸１１１を弾性部材で構成したりしても同様の効果を得ることができる。
【００４７】
〔変形例〕
次に、上記実施形態２における変形例について説明する。本変形例は、上記実施形態２と同様に出力歯車を変位させる方法を採用するが、出力歯車を変位させる構成が上記実施形態２とは相違する。以下、この相違点についてのみ説明する。
【００４８】
図１１（ａ）は、本変形例における出力歯車２１６を出力軸１１の軸上で部分的に切断したときの断面図である。図１１（ｂ）は、出力歯車２１６を出力軸１１の軸方向から見た側面図である。
本変形例における出力歯車２１６は、出力軸１１に固定された内側部２１６ｂと、外周面に歯を備える外側部２１６ａとから構成されている。外側部２１６ａは、内側部２１６ｂの径方向外側に配置されており、外側部２１６ａと内側部２１６ｂとの間には、スペースＳが形成されている。また、外側部２１６ａの内周面及び内側部２１６ｂの外周面には、それぞれ、弾性部材２１７を嵌め込むための切り欠きが３箇所に設けられている。この切り欠きに弾性部材２１７が圧入される。この弾性部材２１７によって、遊星歯車２１と噛み合う外側部２１６ａに回転力が伝達されると、内側部２１６ｂは外側部２１６ａと一体的に回転することができる。なお、弾性部材２１７は、ゴムやプラスチックなどでもよく、またスプリングピンなどでもよい。
【００４９】
本変形例では、感光体ドラム１Ｙが回転駆動すると、出力歯車２１６と遊星歯車２１とが噛み合って、これらの歯車２１６，２１には２０度の圧力角方向に力が加わる。この力は、出力歯車２１６の外側部２１６ａに伝わる。この力が外側部２１６ａに伝わると、弾性部材２１７が変形し、スペースＳが設けられているため、内側部２１６ｂに対して外側部２１６ａが変位することになる。この変位により、出力歯車２１６の中心軸と２つの遊星歯車２１の遊星回転中心軸との軸ズレが少なくなる。その結果、感光体ドラム１Ｙの回転駆動中、２つの遊星歯車２１の両方が出力歯車２１６及び固定歯車１４に対して常に噛み合った状態を確保することができ、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制できるという効果を得ることができる。
【００５０】
なお、出力歯車２１６のスペースＳの大きさをどの程度にするか、弾性部材２１７の縦弾性係数をどの程度にするかは、上述した実施形態２の場合と同様に、必要とする変形量に応じて決まる。
【００５１】
なお、出力歯車を変位させる方法としては、本変形例のほか、例えば、図１２に示す構成を採用してもよい。図示の出力歯車３１６では、出力軸１１に固定する部分が貫通孔を有する弾性部材３１７で構成されており、その貫通孔に出力軸１１を挿入され、固定される。この場合、出力歯車３１６と遊星歯車２１との噛み合い時に出力歯車３１６に伝わる力によって、弾性部材３１７が変形し、出力歯車３１６が変位することになる。
また、出力軸１１を軸受けする軸受部が変位する構成としても、同様に出力歯車を変位させることができる。
【００５２】
〔実施例〕
次に、上記実施形態１における感光体駆動装置１０の実施例について説明する。
図１３は、感光体駆動装置１０の２つの遊星歯車２１と出力歯車１６との噛み合い部分で発生するトルクを測定したときの測定結果を示すグラフである。図１８に示したグラフの場合、２つの遊星歯車のうちのいずれか一方しか出力歯車１６と噛み合っていなかったため、出力歯車への回転力の伝達ルートが一方の遊星歯車から他方の遊星歯車に切り替わるとき、出力歯車には急激なトルク変動が生じた。これに対し、本実施例に係る感光体駆動装置１０では、歯部分が弾性変形したために、図１３に示すとおり、２つの遊星歯車２１の両方が常に出力歯車と噛み合っている状態が確保されている。その結果、出力歯車１６に伝達されるトルクは、図１４に示すようになる。なお、図１４は、図１３に示した各遊星歯車２１の負荷トルクを足し合わせたものである。このように、出力歯車１６に対する２つの遊星歯車２１からの回転力の伝達は、スムーズに行われることとなる。なお、このときの角速度変動率は、０．３％であった。
【００５３】
〔実験例〕
次に、所望の角速度変動率を得るのに必要となる出力歯車１６の材質条件を得るための実験例について説明する。
本実験例では、上記実施形態１における感光体駆動装置１０であって、出力軸１１が２０μｍだけ偏心しているものに、遊星歯車２１との間の歯対剛性が互いに異なる出力歯車１６を取り付け、各出力歯車ごとに出力歯車の角速度変動率を求める実験を行った。歯対剛性は、解析面では、歯部をＦＥＭ（有限要素法）モデル化し、負荷荷重に対する変形量を求め、それをもとに剛性を算出したり、歯部を梁でモデル化したＬｅｗｉｓの式を使ったりして得られるものである。また、実験面では、歯部を取り出し（歯部以外を削り取り）、負荷に対するたわみを計測することで求めることができる。本実験例では、所定のマスターギア（たわみ量が微小なステンレス製などの金属ギア）の歯部と噛合わせて出力歯車１６の歯部の変位量を計測して、その歯対剛性を得た。本実験例では、５．７６×１０⁵Ｎ／ｍ、１．１５×１０⁶Ｎ／ｍ、２．８８×１０⁶Ｎ／ｍ、５．７６×１０⁶Ｎ／ｍの４つの歯対剛性を有する出力歯車１６を用いた。
【００５４】
図１５は、本実験例の実験結果を示すグラフである。
このグラフからわかるように、金属製の遊星歯車２１とＰＯＭ製の出力歯車１６との間の歯対剛性が低いものほど、負荷トルクに対する角速度変動率が小さくなる。ここで、一般的な加工精度の場合、出力軸１１の偏心は１０〜３０μｍ程度が発生してしまうが、角速度変動率は０．３％以下にするのが望ましい。このような条件からすると、本実験例の結果によると、遊星歯車２１に対して、５．７６×１０⁵Ｎ／ｍ以上１．１５×１０⁶Ｎ／ｍ以下程度の歯対剛性を有する出力歯車１６を用いれば、角速度変動率を０．３％以下に抑えることが可能である。
【００５５】
また、上記実施例でも説明したように、角速度変動率を低く抑えるためには、２つの遊星歯車２１の両方が常に出力歯車１６と噛み合っている状態が確保されていることが重要となる。そのためには、出力歯車１６がこれに噛み合う２つの遊星歯車２１から接触圧を受けたときに、出力歯車の歯部分が、２つの遊星歯車２１の両方が常に出力歯車１６と噛み合っている状態が確保される程度、変形しなければならない。
ここで、互いに噛み合う２つの歯車に負荷トルクＴｆが加わったときに、その噛み合い部分に加わる力Ｆは、基礎円半径をｒｂとし、噛み合い率をｎとすると、Ｆ＝Ｔｆ／（ｒｂ×ｎ）から求められる。また、歯対剛性をＫとした場合、歯の変位量δは、Ｆ／Ｋで求めることができる。すなわち、歯の変位量δは、下記の数７に示す演算式から求めることができる。
【数７】
δ ＝ Ｔｆ／（ｒｂ×ｎ×Ｋ）
【００５６】
例えば、負荷トルクが３ｋｇｆｃｍ、モジュールｍが０．５、樹脂材質の歯対剛性が５．７６Ｎ／ｍ、基礎円半径ｒｂが５．６ｍｍ、噛み合い率が３．２８である場合、歯の変位量は２８μｍとなる。よって、このような条件の場合、２８μｍ程度、出力歯車１６の歯が変位するので、これ以内の偏心であれば、歯変位の影響の方が大きく、２つの遊星歯車２１の両方が常に出力歯車１６と噛み合っている状態が確保される。
【００５７】
以上、上記実施形態１の複写機は、駆動対象である感光体ドラム１Ｙの駆動装置として、駆動源であるステータコア２０の回転数を感光体ドラム１Ｙが必要とする回転数まで減速し、ステータコア２０からの回転力を伝達するための遊星差動歯車減速装置を備えている。この遊星差動歯車減速装置は、感光体ドラム１Ｙに連結される出力軸１１に固定された出力歯車１６を備えている。また、その出力歯車１６よりも少ない歯数を有し、その出力歯車１６と同軸上に配置され、かつ、回転不能に固定された固定歯車１４を備えている。また、ステータコア２０からの回転力により出力歯車１６及び固定歯車１４の外周を回転駆動される遊星歯車軸２２に回転自在に支持され、出力歯車１６及び固定歯車１４の双方に噛み合いながら遊星回転する２つの遊星歯車２１を備えている。２つの遊星歯車２１は、遊星回転の中心軸について互いに軸対称となる位置に配置されている。そして、出力歯車１６の歯部分は、感光体ドラム１Ｙが回転駆動している間の噛み合いによって生じる接触圧によって変形可能な弾性部材で構成されている。これにより、上記のとおり、感光体ドラム１Ｙの回転駆動中、２つの遊星歯車２１の両方が出力歯車１６及び固定歯車１４に対して常に噛み合った状態を確保することができ、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制できるという効果を得ることができる。
また、上記実施形態１において、出力歯車１６の歯部分の縦弾性係数は、その歯部分に接触圧が加わったときに変形する変形量が出力歯車１６の偏心量とその出力歯車１６の角速度変動の許容範囲とに基づいて求められる必要な変形量となるような縦弾性係数を有している。これにより、遊星歯車の個数に応じた周波数で発生していた角速度変動を許容範囲内に収めることができる。
また、上記実施形態２の複写機は、上記実施形態１の複写機と同様の遊星差動歯車減速装置を備えているが、この遊星差動歯車減速装置においては、出力歯車１１６，２１６，３１６を、感光体ドラム１Ｙが回転駆動している間の噛み合いによって生じる接触圧によって変位させるための変位手段を備えている。これにより、上記のとおり、感光体ドラム１Ｙの回転駆動中、２つの遊星歯車２１の両方が出力歯車１１６，２１６，３１６及び固定歯車１４に対して常に噛み合った状態を確保することができ、遊星歯車の個数に応じた周波数で発生していた角速度変動を抑制できるという効果を得ることができる。
特に、上記実施形態２では、上記変位手段として、この変位手段により変位する出力歯車１１６が固定された出力軸１１１を上記接触圧によって変形させるための軸変形手段として、出力軸１１１上に軸細部分１１１ａを備えている。これにより、簡単な構成で上記接触圧によって出力歯車１６を変位させることができる。
また、上記変形例で説明したように、上記変位手段として、この変位手段により変位する出力歯車が固定された出力軸を上記接触圧によって変位させるための軸変位手段として、出力軸１１を軸受けする軸受部を変位させる機構を用いても、同様に出力歯車を変位させることができる。
【００５８】
なお、上記実施形態１及び上記実施形態２の構成を互いに組み合わせてもよい。
また、上記実施形態１及び上記実施形態２では、本発明を、感光体ドラム１を駆動対象の回転体とする感光体駆動装置１０に適用した場合について説明したが、モータの回転数を、必要な回転数に減速させる必要がある回転体の減速装置として広く利用することができる。例えば、本実施形態１に係る複写機であれば、例えば、中間転写ベルト５を回転駆動させるための駆動ローラ、定着ローラ対８、現像装置９の現像ローラ、１次転写ローラ６、２次転写ローラ７、レジストローラ等の回転体と駆動源との間の減速装置として利用することができる。また、本発明の減速装置は、複写機に限らず、他の技術分野における減速装置にも適用することができる。
【００５９】
【発明の効果】
請求項１乃至３の発明によれば、高コストとなる高精度な加工や組み付けなどを行うことなく、遊星歯車の個数に応じた周波数で発生する角速度変動を抑制することが可能となるという優れた効果がある。
【図面の簡単な説明】
【図１】実施形態１に係る複写機における感光体駆動装置の内部構成を示す断面図。
【図２】同複写機における画像形成部全体の概略構成図。
【図３】同複写機における感光ドラムの軸方向一端部外方に設置される感光体駆動装置の部分断面図。
【図４】同感光体駆動装置の斜視図。
【図５】同感光体駆動装置を出力軸の軸方向から見た正面図。
【図６】同感光体駆動装置における固定歯車と出力歯車の歯数差が偶数のときの遊星歯車の構造を示す外観図。
【図７】同感光体駆動装置における固定歯車と出力歯車の歯数差が奇数のときの遊星歯車の構造を示す外観図。
【図８】（ａ）は、シザーズ歯車として構成される遊星歯車の軸方向断面図。
（ｂ）は、同遊星歯車の固定歯車に噛み合う部分を、出力歯車に噛み合う部分側から見た側面図。
（ｃ）は、同遊星歯車の各遊星歯車部分を互いに逆回転方向に付勢するための板バネを示す外観図。
【図９】同感光体駆動装置のアウターロータモータの代わりに、インナーロータ型ＤＣモータを適用した感光体駆動装置の部分断面図。
【図１０】実施形態２に係る複写機における感光体駆動装置の出力軸を示す軸方向断面図。
【図１１】（ａ）は、変形例における出力歯車を出力軸の軸上で部分的に切断したときの断面図。
（ｂ）は、同出力歯車を出力軸の軸方向から見た側面図。
【図１２】（ａ）は、出力歯車を変位させる他の構成に係る出力歯車を出力軸の軸上で部分的に切断したときの断面図。
（ｂ）は、同出力歯車を出力軸の軸方向から見た側面図。
【図１３】実施例における感光体駆動装置の２つの遊星歯車と出力歯車との噛み合い部分で発生するトルクを測定したときの測定結果を示すグラフ。
【図１４】同感光体駆動装置の出力歯車に伝達されるトルクを示すグラフ。
【図１５】実験例の実験結果を示すグラフ。
【図１６】本発明者らが実験機として使用した遊星差動歯車減速装置を、出力軸上で部分的に切断したときの断面図。
【図１７】同遊星歯車減速装置における各歯車のピッチ円を示す説明図。
【図１８】同遊星歯車減速装置における２つの遊星歯車と出力歯車との噛み合い部分で発生するトルクを測定したときの測定結果を示すグラフ。
【図１９】同遊星差動歯車減速装置を用い、その出力軸に加わる負荷トルクを変更したときの角速度変動率を測定した実験結果を示すグラフ。
【符号の説明】
１ 感光体ドラム
５ 中間転写ベルト
６ １次転写ローラ
７ ２次転写ローラ
８ 定着ローラ対
９ 現像装置
１０ 感光体駆動装置
１１，１１１，２１１，４１１ 出力軸
１４，４１１ 固定歯車
１６，１１６，２１６，３１６，４１６ 出力歯車
１７ 回転ディスク
１８，４１８ アウターロータ
１９ 磁石
２０ ステータコア
２１，１２１，４２１ 遊星歯車
１１８ インナーロータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a planetary differential gear reduction device and a planetary differential gear reduction device for transmitting a rotational force from the drive source while reducing the rotation number of the drive source to a rotation number required by the drive target. The present invention relates to an image forming apparatus using the above.
[0002]
[Prior art]
In the field of image forming apparatuses, as a mechanism for transmitting a rotational force from a driving source such as a motor through a speed reducing means, a mechanism using a toothed wheel train, a mechanism using a worm gear, a mechanism using a belt speed reducing mechanism, etc. are generally used. Is used. The rotating body in the image forming apparatus includes an image carrier such as a photosensitive member and an intermediate transfer member, a recording material conveying member that conveys a recording material, a fixing roller, and the like. Rotate with. On the other hand, the rotational speed of the drive source that transmits the rotational force to the rotating body is generally several thousand rpm, and in order to obtain the rotational speed necessary for the rotating body, it has a reduction ratio of about 1/10 to 1/30. Deceleration means is required. The rotational accuracy of the rotating body in the image forming apparatus has a great influence on the image quality. However, with conventional reduction means, high-speed constant rotational force from the drive source for reasons such as part processing accuracy and assembly accuracy. It was difficult to transmit to the rotating body.
[0003]
In order to realize high-accuracy constant-speed rotational force transmission in a range where there is no practical problem in the image forming apparatus, for example, transmission angular velocity fluctuations (hereinafter referred to as “angular velocity fluctuations” as appropriate) are generated by reducing the number of deceleration stages. A method of reducing the number of points is mentioned. According to this method, effects such as cost reduction by reducing the number of parts, suppression of reduction in transmission efficiency, and noise reduction due to gear meshing can be expected. Furthermore, the effect of space saving and downsizing of the apparatus can be expected. An example of a reduction gear having a large reduction ratio and a small number of reduction stages is a planetary differential gear reduction device described in Non-Patent Document 1.
[0004]
The planetary differential gear reduction device described in Non-Patent Document 1 adopts a four-bar planetary gear having two external meshing gears, and two planetary gears (at the end of an arm fixed to the input shaft) Number of teeth: Z₂, Z_Four) Are arranged coaxially. Each planetary gear is a fixed gear (number of teeth: Z_Three) And output gear fixed on the output shaft (number of teeth: Z_Five) With each other. However, in this planetary differential gear reduction device, the two planetary gears have different numbers of teeth Z from each other.₂, Z_FourTherefore, in order to configure the input shaft and the output shaft coaxially in the same module, the relationship of the number of teeth between the gears needs to satisfy the relational expression shown in the following equation (1). Further, the reduction ratio obtained by the planetary differential gear reduction device is obtained from the following equation (2). In the following formula 2, N₁Indicates the rotational speed of the input shaft, N_FiveIndicates the rotational speed of the output shaft.
[Expression 1]
Z₂+ Z_Three= Z_Four+ Z_Five
[Expression 2]
N_Five= N₁× (Z₂× Z_Five-Z_Three× Z_Four) / (Z₂× Z_Five)
[0005]
In order to obtain a reduction ratio of about 1/10 by the planetary differential gear reduction device, the number of teeth of each gear is, for example, Z₂And Z_Five20 sheets both, Z_ThreeAnd Z_FourWill be 19 in both cases. In order to obtain a reduction ratio of about 1/20, for example, Z₂And Z_Five40 sheets, Z_ThreeAnd Z_FourBoth will be 39. In order to obtain a reduction ratio of about 1/30, for example, Z₂And Z_FiveAre both 60, Z_ThreeAnd Z_FourBoth will be 59. Thus, in the planetary differential gear reduction device, in order to obtain a high reduction ratio of 1/20 to 1/30 as the reduction ratio, the number of teeth of each gear is increased correspondingly, resulting in a large gear configuration. turn into. As a result, the diameter of the planetary rotation (revolution) of the planetary gear provided at the end of the arm on the input shaft becomes large, which is not suitable for high-speed rotation, and the apparatus becomes large.
[0006]
[Non-Patent Document 1]
Ivan Ivanovich Altvorevsky, “Handbook of Examples of Modern Mechanical Technology”, published by Hyundai Engineering, Vol. 679
[0007]
[Problems to be solved by the invention]
In view of this, the present applicant has proposed a planetary differential gear reduction device in Japanese Patent Application No. 2001-231407, which requires only a small number of teeth of the fixed gear and the output gear even when a large reduction ratio is obtained. This device has an output gear fixed to an output shaft connected to a drive target, and has a smaller number of teeth than the output gear, is arranged coaxially with the output gear, and is fixed so as not to rotate. And a fixed gear. Further, this device is a planetary gear that is supported by a planetary gear shaft that is driven to rotate around the outer periphery of an output gear and a fixed gear by a rotational force from a drive source, and rotates planetarily while meshing with both the output gear and the fixed gear. It has. In this planetary gear, the fixed gear meshing portion meshing with the fixed gear and the output gear meshing portion meshing with the output gear have the same number of teeth, and the output gear, the fixed gear, the planetary gear meshing portion, and the planetary gear output. At least one of the gear meshing portions is constituted by a shift gear. In this device, since the number of teeth of the fixed gear and the output gear are different from each other, smooth rotation drive cannot be realized just by meshing these gears with a single planetary gear as it is. Rotation drive is possible. The reduction ratio obtained by this device is obtained based on the number of teeth of the fixed gear and the output gear regardless of the number of teeth of the planetary gear. The number of teeth of the fixed gear and the output gear can be small. Therefore, it is possible to reduce the size of the apparatus.
[0008]
However, the planetary differential gear reduction device according to the above-mentioned prior application reduces the number of reduction stages to suppress the influence of the overall angular speed fluctuation, but the influence of the angular speed fluctuation at each location that causes the angular speed fluctuation is reduced. It is not suppressed. Here, it is difficult to suppress the angular velocity fluctuation itself for reasons such as machining accuracy and assembly accuracy of the parts as described above, but a method for preventing the influence of the angular velocity fluctuation generated at each location from causing a practical problem. Is conceivable. For example, in the case of a planetary differential gear reduction device used in an image forming apparatus, a pitch nonuniformity band (occurrence of angular velocity fluctuations) is prevented so that the influence of angular velocity fluctuations is not visible on the image while being visible to the human eye. There is a method for increasing the frequency corresponding to the period. If this method is applied to, for example, driving force transmission to an image carrier or recording material conveying member of an image forming apparatus, image quality deterioration such as image density unevenness due to periodic image expansion and contraction caused by angular velocity fluctuations is practically used. It is possible to make it a problem-free range, that is, a range that is difficult to confirm with human eyes. Note that the pitch unevenness band is a frequency band of angular velocity fluctuations that occur in the meshing cycle of gears (1 pitch period). With conventional gear pair reduction mechanisms, the pitch unevenness band can generally be recognized by human vision. It is recognized as density unevenness on the image because it is located in a frequency band of 1 kHz or less, which is said to be, but in this planetary differential gear reduction device, the pitch unevenness band is set to a frequency band of 1 kHz or more with the same reduction ratio. be able to.
[0009]
Hereinafter, in the planetary differential gear speed reduction device according to the above-mentioned prior application, the cause of image density unevenness due to angular velocity fluctuations will be described.
FIG. 16 is a cross-sectional view of the planetary differential gear reduction device used by the present inventors as an experimental machine, partially cut on the output shaft.
In an experiment conducted by the present inventors, the output shaft 411 of this planetary differential gear reduction device is connected to the shaft of a photosensitive drum (not shown). In this planetary differential gear reduction device, the fixed gear 414 has 37 teeth and the output gear 416 has 35 teeth. Further, this planetary differential gear reduction device is provided with two planetary gears 421 having 31 teeth. Each planetary gear 421 meshes with both the fixed gear 414 and the output gear 416, and is disposed at a position facing each other across the fixed gear 414 and the output gear 416. The modules of these gears are 0.3, and all of them are composed of helical teeth. The planetary gear reduction device has a reduction ratio of 17.5. The rated load torque of the output shaft 411 was 5 kgf · cm, and the experiment was conducted by rotating the outer rotor 418 at 1670 rpm. At this time, the rotational speed of the planetary gear 421 is 1995 rpm, and the rotational speed of the output gear 416 is 95.5 rpm.
The angular velocity fluctuation is usually caused by machining errors (eccentricity, accumulated tooth pitch error, single tooth error, etc.) and assembly errors (axial deviation, etc.) of each part. Therefore, if each part is processed with high accuracy or assembled with high accuracy, it is possible to sufficiently suppress fluctuations in angular velocity, but this is not practical because the cost of the components increases. Therefore, in the planetary differential gear speed reduction device of this experiment, parts machined with the third or fourth grade machining accuracy defined in JIS standard B1702 are used.
[0010]
Under such conditions, the angular velocity fluctuation due to the processing error and the assembly error is about 28 Hz corresponding to the rotational speed of the outer rotor 418, about 33 Hz corresponding to the rotational speed (rotation) of the planetary gear 421, and the rotational speed of the output gear 416. Is generated at about 1.6 Hz corresponding to the above, and about 1060 Hz (meshing frequency) depending on the tooth profile accuracy of each gear. In addition, the angular velocity variation occurs even at about 56 Hz corresponding to the planetary rotation frequency multiplied by the number of planetary gears 421. With respect to this angular velocity fluctuation, since the two planetary gears 421 are opposed to each other in this experimental machine, the frequency at which this angular velocity fluctuation occurs is a frequency (about 28 Hz) corresponding to the rotational speed of the outer rotor 418. The frequency is about 56 Hz which is doubled (a half cycle). Here, since the frequency of the angular velocity fluctuation generated by the tooth profile accuracy is larger than 1 kHz, this angular velocity fluctuation can hardly be confirmed by human eyes as image density unevenness. Therefore, there is no problem in practical use. On the other hand, the frequency corresponding to the number of rotations of the outer rotor 418, the planetary gear 421, and the output gear 416 and the frequency corresponding to the number of the planetary gears 421 are relatively low frequencies of 1 kHz or less. The image density unevenness may be confirmed by human eyes, which may cause a problem in practical use.
[0011]
The main factor that causes the angular velocity fluctuation in the low frequency band is the eccentricity of the output gear 416, the fixed gear 414, and the planetary gear 421 caused by machining errors. The angular velocity fluctuation due to the eccentricity of each gear appears at a frequency corresponding to the rotation period of the gear if the shape of the gear is a perfect circle. Further, if the shape of the gear is a rice ball shape, an elliptical shape, or the like, it may appear even at the second and third harmonic frequencies. In addition, as a result of trial calculation in consideration of the machining error of each gear, the frequency other than about 56 Hz corresponding to the number of planetary gears 421 is reasonable as a result caused by the machining error. If a control mechanism such as feedback is added, image density unevenness caused by this can be kept within an allowable range. However, the angular velocity fluctuation generated at a frequency of about 56 Hz corresponding to the number of planetary gears 421 is different from the angular velocity fluctuation caused by the eccentricity of each gear, and is larger than the allowable range. The reason is considered as follows.
[0012]
Angular velocity fluctuations occur at a frequency of about 56 Hz corresponding to the number of planetary gears 421 because the distance between the center axis of planetary rotation (revolution) and the rotation (spinning) axis of each planetary gear 421 is coaxial. The main factors are the axial shift between the center axis of the planetary rotation to be performed and the center axis of the output gear 416 or the center axis of the fixed gear 414 and the eccentricity of the fixed gear 414. In the following description, an explanation will be given by taking as an example the axial misalignment between the central axis of the planetary rotation to be arranged coaxially and the central axis of the output gear 416, but the same applies to other factors. In the following description, it is assumed that each gear has no eccentricity.
[0013]
FIG. 17 is an explanatory diagram showing the pitch circle of each gear in the planetary gear reduction device. In the figure, O₀Indicates the central axis of the fixed gear 414, P₀Indicates a pitch circle of the fixed gear 414. The two planetary gears 421 are connected to the central axis O of the fixed gear 414.₀With the center axis of planetary rotation as the outer rotor 418 rotates, the planet rotates in the clockwise direction in the figure (the direction of arrow A in the figure), and the axis orbits of these planetary gears 421 are indicated by dotted lines in the figure. ing. Here, the central axis O of the fixed gear 414₀That is, the center axis of the output gear 416 to be arranged coaxially with the center axis of the planetary rotation is O in the figure.₁It is assumed that the position is shifted. The shaft misalignment amount e at this time is caused by a backlash of the bearing portion that supports the shaft of the output gear 416, an assembly error, or the like.
[0014]
Here, when the planetary gear 421 rotates (revolves), the planetary gear 421 rotates (spins) by meshing with the fixed gear 414, and the output gear 416 that meshes with the planetary gear 421 rotates (spinning). To do. That is, the route when the driving force from the outer rotor 418 is normally transmitted is the fixed gear 414, the planetary gear 421, and the output gear 416 in this order. However, as shown in the figure, if an axial shift occurs between the output gear 416 and the fixed gear 414, the center axis O of the output gear 416₁And the planetary rotation center of the planetary gear 421 are shifted from each other. Therefore, while the planetary gear 421 performs one planetary rotation, the pitch circle P of the output gear 416 is₁And the pitch circle P of the planetary gear 421₂The positional relationship with the fluctuates. Specifically, the pitch circle P of the output gear 416₁And pitch circle P of one planetary gear₂When one is approaching (when one planetary gear is located in the right half of the figure), the pitch circle P of the other planetary gear is₂And the pitch circle P of the output gear₁Will leave. Therefore, only the one planetary gear meshes with the output gear 416, and the other planetary gear does not mesh. As a result, torque is transmitted to the output gear 416 only from one of the two planetary gears 421. In order to confirm this point, the present inventors measured the torque generated at the meshing portion between the two planetary gears 421 and the output gear 416.
[0015]
FIG. 18 is a graph showing measurement results when the torque generated at the meshing portion between the two planetary gears 421 and the output gear 416 is measured.
While the two planetary gears 421 perform one planet rotation (about 28 Hz), during the period indicated by the symbol A in the figure, torque is applied only between one planetary gear and the output gear 416, and the other planetary gear. No torque is applied between the output gear 416 and the output gear 416. Conversely, during the period indicated by the symbol B in the figure, torque is applied only between the other planetary gear and the output gear 416, and no torque is applied between the one planetary gear and the output gear 416. Therefore, from this measurement result, as described above, it has been found that the rotational force is transmitted to only one of the two planetary gears 421 to the output gear 416.
[0016]
As a result of the above measurement, when the transmission route of the rotational force to the output gear 416 is switched from one planetary gear to the other planetary gear, a sudden torque fluctuation occurs in the output gear 416 as shown in the graph of FIG. I understand that. Such torque fluctuation occurs twice during one planetary rotation when there are two planetary gears 421. Therefore, in the present experiment in which the outer rotor 418 is rotated at 1670 rpm as described above, the torque fluctuation occurs at a frequency of about 56 Hz. Will occur. As a result of such torque fluctuations, angular speed fluctuations occur at a frequency of about 56 Hz corresponding to the number of planetary gears 421.
[0017]
In addition, the angular velocity fluctuation generated at about 56 Hz corresponding to the number of planetary gears 421 is increased by the reduction ratio of the planetary differential gear reduction device according to the present experiment and then transmitted to the drive target. . More specifically, the angular velocity of the outer rotor 418, that is, the angular velocity of the planetary rotation is 10 rad / s, and the central axis O of the fixed gear 414 is₀That is, the center axis O of the output gear 416 with respect to the center axis of the planetary rotation.₁Assuming that the axial displacement amount e is 40 μm, the angular velocity fluctuation rate at this time reaches 28.7% from the arithmetic expressions shown in the following equations 3, 4, and 5. Therefore, the angular velocity fluctuation caused by the axial deviation between the output gear 416 and the fixed gear 414 is much larger than the angular velocity fluctuation caused by the eccentricity of the gear described above.
The arithmetic expression shown in Expression 3 is obtained by obtaining the rotation (spinning) angular velocity of the planetary gear 421 between the fixed gear 414 and the planetary gear 421. The arithmetic expression shown in Expression 4 is the output gear 416 and the planetary gear 421. Is the rotational angular velocity of the output gear 416. Further, Equation 5 is obtained by calculating the angular velocity fluctuation rate from the results of the arithmetic expressions of Equation 3 and Equation 4. Further, in Equations 3 and 4, ω₁, Ω₂, Ω_ThreeIndicates the angular velocity of planetary rotation (revolution), the rotational (rotational) angular velocity of the planetary gear 421, and the rotational angular velocity of the output gear 416, respectively.₁, Z₂, Z_ThreeIndicates the number of teeth of the fixed gear 414, the number of teeth of the planetary gear 421, and the number of teeth of the output gear 416, respectively.₂, R_ThreeIndicates the diameter of the planetary gear 421 and the diameter of the output gear 416, respectively.
[0018]
[Equation 3]

[Expression 4]

[Equation 5]

[0019]
In the above description, the configuration in which the number of teeth of the fixed gear meshing portion meshing with the fixed gear 414 and the output gear meshing portion meshing with the output gear 416 in the planetary gear 421 is the same, but the number of teeth is not the same. Also in the differential gear reduction device, the angular velocity fluctuation as described above occurs.
[0020]
The present invention has been made in view of the above problems, and the object of the present invention is to change the angular velocity generated at a frequency corresponding to the number of planetary gears without performing high-precision processing or assembly that is expensive. It is an object of the present invention to provide a planetary differential gear reduction device and an image forming apparatus capable of suppressing the above-described problem.
[0021]
[Means for Solving the Problems]
  In order to achieve the above object, the invention of claim 1 reduces the rotational speed of the drive source to the rotational speed required by the drive target, and reduces the planetary differential gear for transmitting the rotational force from the drive source. In the apparatus, the output gear fixed to the output shaft coupled to the drive target, the number of teeth less than that of the output gear, the coaxial arrangement with the output gear, and the non-rotatable fixed A planetary gear is rotatably supported by a fixed gear and a planetary gear shaft that is driven to rotate around the output gear and the outer periphery of the fixed gear by the rotational force from the drive source, and planetary rotation while meshing with both the output gear and the fixed gear. The two planetary gears are arranged at positions symmetrical with respect to the central axis of the planetary rotation, and at least one of the output gear and the fixed gear is separated from each other. At the center of the body gear The inner part and the outer part far from the center have a double structure, and there is a gap between the outer peripheral surface of the inner part and the inner peripheral surface of the outer part, and there are a plurality of elasticities in the gap. Members are arranged, and the elastic member defines relative movement in the circumferential direction between the inner part and the outer part.The elastic member is deformed by the amount of deformation of the elastic member and the angular velocity of the output gear when contact pressure generated by meshing during rotation of the image carrier is applied. A material having a longitudinal elastic modulus so that the amount of deformation obtained based on the allowable range of fluctuation was used.It is characterized by this.
  According to a second aspect of the present invention, in the planetary differential gear reduction device according to the first aspect, the elastic member is fitted into a notch formed on the outer peripheral surface of the inner portion and the inner peripheral surface of the outer portion. It is characterized by being provided.
MaClaim3In the image forming apparatus including the image carrier that rotates at a lower rotational speed than the rotational speed of the drive source, the rotational speed of the drive source is reduced to the rotational speed required by the image carrier. The speed reduction means for transmitting the rotational force from the drive source is claimed in claim 1.Or 2The planetary differential gear speed reducer is used.
[0022]
  Claims 1 to2Planetary differential gear speed reducer and claim3In the image forming apparatus, two single planetary gears mesh with each of the output gear and the fixed gear arranged on the same axis. Here, since the two planetary gears are arranged at positions symmetrical with respect to the central axis of the planetary rotation, as described above, this corresponds to a half cycle of the planetary rotation due to processing errors and assembly errors of each part. The angular speed of the output gear may vary with frequency.
  Here, the experiment which measured the angular velocity fluctuation rate when changing the load torque added to the output shaft using the planetary gear reduction device according to the above-mentioned prior application will be described. The result of this experiment is as shown in FIG. From this experimental result, it is understood that the angular velocity fluctuation rate can be suppressed by increasing the load torque applied to the output shaft. However, the load torque varies depending on the object to be driven. For example, when the output shaft is connected to the photosensitive drum as in the planetary differential gear reduction device shown in FIG. It is about 2 to 3 kgf · cm. In this case, in the planetary differential gear speed reduction device according to the previous application, the angular velocity fluctuation rate is approximately 1 to 3%, and it cannot be said that the angular velocity fluctuation is sufficiently suppressed. Here, when the above experimental results are considered, the rate of change in angular velocity decreases as the load torque increases, because the gear teeth are deformed by a large load torque or the gear is displaced by a large load torque. This is probably because both planetary gears are in mesh with the output gear and the fixed gear. As a result, there is no time when the transmission route of the rotational force to the output gear is switched as in the above-described configuration in which the two planetary gears are alternately meshed with the output gear. Therefore, it is considered that the fluctuation of the angular velocity generated at the frequency corresponding to the number of planetary gears could be suppressed without causing the rapid torque fluctuation that occurred at this switching time.
  Accordingly, claims 1 to2In the planetary differential gear speed reduction device, at least one of the output gear and the fixed gear has a double structure including an inner portion near the gear center and a outer portion far from the center, which are separate from each other. There is a gap between the outer peripheral surface of the part and the inner peripheral surface of the outer part, and a plurality of elastic members are arranged in the gap, and the elastic member causes the relative relation in the circumferential direction between the inner part and the outer part. Therefore, the outer portion can be displaced by the deformation of the elastic member by the contact pressure generated by the meshing while the drive target is rotationally driven. Thereby, the angular velocity fluctuation | variation of an output gear can be suppressed. That is, for example, when the displaceable gear is an output gear, when there is a portion where the pitch circle of the output gear intersects with the pitch circle of one planetary gear at the time of rotational drive of the driven object, the output is caused by meshing at that portion. The gear receives a force in a direction away from the one planetary gear. This force causes the output gear to be displaced toward the other planetary gear. Therefore, the axial shift between the central axis of the output gear and the planetary rotation central axis of the two planetary gears is reduced. Therefore, it is possible to ensure that the two planetary gears are always meshed with the output gear and the fixed gear during the rotational drive of the drive target. As a result, it is possible to suppress fluctuations in angular velocity that have occurred at a frequency corresponding to the number of planetary gears.
[0023]
The two planetary gears may have the same number of teeth or different number of teeth in the meshing portion for the fixed gear meshing with the stationary gear and the meshing portion for the output gear meshing with the output gear. However, if the number of teeth is the same, the number of teeth of the fixed gear is less than the number of teeth of the output gear. Therefore, simply rotating two single planetary gears on these gears realizes smooth rotation drive. Can not. Therefore, as in the planetary differential gear reduction device proposed in Japanese Patent Application No. 2001-231407, at least of the output gear, the fixed gear, and the fixed gear meshing portion of the planetary gear and the planetary gear output gear meshing portion, It is necessary to configure one with a shift gear. As a result, a single planetary gear can be properly meshed with a fixed gear and an output gear arranged on the same axis and having different numbers of teeth, and smooth rotation drive can be realized. Further, if the number of teeth of each meshing portion of the planetary gear meshing with the fixed gear and the output gear is the same, the reduction ratio obtained by the planetary differential gear reduction device can be obtained by the following formula 6 obtained by modifying the above formula 2. In the following equation 6, N₁Indicates the rotational speed of the input shaft, N_FiveIndicates the rotational speed of the output shaft, and Z_ThreeIndicates the number of teeth of the fixed gear, and Z_FiveIndicates the number of teeth of the output gear.
[Formula 6]
N_Five= N₁× (Z_Five-Z_Three) / Z_Five
As can be seen from this equation, when the number of teeth of each meshing portion of the planetary gear is the same, the reduction ratio can be obtained based on the number of teeth of the fixed gear and the output gear regardless of the number of teeth of the planetary gear. become. Thereby, even if there are few teeth of a fixed gear and an output gear conventionally, a high reduction ratio can be obtained. That is, even when the same reduction ratio as that in the prior art is obtained, the number of teeth of the fixed gear and the output gear can be reduced. Therefore, the diameters of the fixed gear and the output gear can be reduced. For example, to obtain a reduction ratio of 1/20, if the difference in the number of teeth between the fixed gear and the output gear is two, the number of teeth on each gear may be 38 and 40, respectively. When the difference in the number of teeth of the output gear is one, the number of teeth of each gear may be 19 and 20, respectively. Further, since the diameters of the fixed gear and the output gear can be reduced, even if a high rotational speed is input and the planetary gear rotates at high speed, the rotation radius becomes small. As a result, it is easy to balance the rotation and smooth rotation driving can be realized. Further, as described above, since the reduction ratio is not affected by the number of teeth of the planetary gear, the number of teeth of the planetary gear can be arbitrarily set. As a result, the diameter of the planetary gear can be reduced. Thereby, the space required for the planetary gear to planetarily rotate around the outer periphery of the fixed gear and the output gear can be reduced, and the device dimensions in the radial direction of the fixed gear and the output gear can be made compact.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
Hereinafter, an embodiment (hereinafter, this embodiment is referred to as “embodiment 1”) in which the present invention is applied to an electrophotographic color copying machine (hereinafter referred to as “copying machine”) that is an image forming apparatus. explain. The copying machine according to the first embodiment is a so-called tandem image forming apparatus that employs a dry two-component developing system using a dry two-component developer.
[0025]
FIG. 2 is a schematic configuration diagram of the entire image forming unit in the copying machine according to the first embodiment. This copying machine receives image data as image information from an image reading unit (not shown) and performs image forming processing. In this copying machine, as shown in the drawing, yellow (hereinafter abbreviated as “Y”), magenta (hereinafter abbreviated as “M”), cyan (hereinafter abbreviated as “C”). , Black (hereinafter abbreviated as “Bk”), photosensitive drums 1Y, 1M, 1C, and 1Bk, which are latent image carriers as four rotating bodies for each color, are arranged side by side. These photosensitive drums 1Y, 1M, 1C, and 1Bk are arranged along the belt moving direction so as to contact the endless belt-shaped intermediate transfer belt 5 supported by a plurality of rotatable rollers including a driving roller. Has been placed. Further, around the photosensitive drums 1Y, 1M, 1C, and 1Bk, chargers 2Y, 2M, 2C, and 2Bk, developing devices 9Y, 9M, 9C, and 9Bk corresponding to the respective colors, and cleaning devices 4Y, 4M, 4C, and 4B, respectively. Electrophotographic process members such as 4Bk and static elimination lamps 3Y, 3M, 3C, and 3Bk are arranged in the order of processes.
[0026]
When a full-color image is formed by the copying machine according to the first embodiment, first, as shown in FIG. 2, a charger is used while rotating the photosensitive drum 1Y in the direction of the arrow in the drawing by a photosensitive member driving device described later. After being uniformly charged with 2Y, a light beam L from an optical writing device (not shown)_YTo form a Y electrostatic latent image on the photosensitive drum 1Y. This Y electrostatic latent image is developed with Y toner in the developer by the developing device 9Y. During development, a predetermined developing bias is applied between the developing roller and the photosensitive drum 1Y, and the Y toner on the developing roller is electrostatically attracted to the Y electrostatic latent image portion on the photosensitive drum 1Y.
[0027]
The Y toner image developed and formed in this way is conveyed to a primary transfer position where the photosensitive drum 1Y and the intermediate transfer belt 5 come into contact with the rotation of the photosensitive drum 1Y. At the primary transfer position, a predetermined bias voltage is applied to the back surface of the intermediate transfer belt 5 by the primary transfer roller 6Y. The Y toner image on the photosensitive drum 1Y is drawn toward the intermediate transfer belt 5 by the primary transfer electric field generated by this bias application, and is primarily transferred onto the intermediate transfer belt 5. Thereafter, similarly, the M toner image, the C toner image, and the Bk toner image are also primarily transferred so as to sequentially overlap the Y toner image on the intermediate transfer belt 5.
[0028]
As described above, the toner images having the four colors superimposed on the intermediate transfer belt 5 are conveyed to the secondary transfer position facing the secondary transfer roller 7 as the intermediate transfer belt 5 rotates. Further, the transfer paper is conveyed to the secondary transfer position at a predetermined timing by a registration roller (not shown). At this secondary transfer position, a predetermined bias voltage is applied to the back surface of the transfer paper by the secondary transfer roller 7, and due to the secondary transfer electric field generated by the bias application and the contact pressure at the secondary transfer position, The toner image on the intermediate transfer belt 5 is secondarily transferred onto the transfer paper at once. Thereafter, the transfer paper on which the toner image is secondarily transferred is subjected to fixing processing by the fixing roller pair 8 and then discharged outside the apparatus.
[0029]
Next, a photosensitive member driving device which is a driving device with a speed reduction mechanism as a driving means including a planetary differential gear speed reduction device as a speed reduction means, which is a feature of the present invention, will be described. Since each of the photosensitive drums 1Y, 1M, 1C, and 1Bk is rotationally driven by the photosensitive member driving device having the same configuration, the photosensitive member driving device for the photosensitive drum 1Y will be described below.
[0030]
FIG. 3 is a partial cross-sectional view of the photosensitive member driving device installed outside one end in the axial direction of the photosensitive drum 1 according to the first exemplary embodiment. Disk-shaped drum flanges 1 a are fixed to both ends of the photosensitive drum 1 in the axial direction so as to close the end surfaces of the photosensitive drum 1 in the axial direction. The center of the disk of the drum flange 1a is fixed to the end of the output shaft 11 of the photoconductor driving device 10, and is configured to transmit the rotational force from the output shaft 11. The output shaft 11 is rotatably supported and supported by a bearing 100a of the side plate 100 constituting the internal casing of the copying machine according to the first embodiment so that the output shaft 11 can be smoothly rotated. The photoconductor driving device 10 is positioned on the side opposite to the photoconductor drum 1 with respect to the side plate 100 and is fixed to the surface of the side plate 100.
[0031]
FIG. 1 is a cross-sectional view showing the internal configuration of the photosensitive member driving device 10. FIG. 4 is a perspective view of the photoconductor driving device 10. The outer surface of the photosensitive member driving device 10 includes a cylindrical case 12 and a disk-like lid member 13 that closes an opening of the case 12. The output shaft 11 is inserted through the center of the disc of the lid member 13 and penetrates the photoconductor driving device 10. The case 12 has a bearing 12a that rotatably supports the output shaft 11, and the lid member 13 has a bearing 13a that rotatably supports the output shaft 11. The bearing 13 a included in the lid member 13 is fixed to a fixed gear 14 that is press-fitted and fixed to the lid member 13. In this way, both ends of the output shaft 11 penetrating the photoconductor driving device 10 are rotatably supported. Here, in order to rotate the output shaft 11 smoothly, each bearing 12a, 13a requires a highly accurate coaxiality. For this reason, the bearings 12a and 13a are assembled and configured by a method such as a screw or circumferential caulking while maintaining accuracy by the positioning pins 15 and the like. As a means for obtaining a highly accurate coaxiality, there is a method such as a tea tube (inlay) fitting.
[0032]
Further, the output gear 16 that is firmly fixed to the output shaft 11 by a method such as press-fitting or the like and a desk bearing 17a are rotatably attached to the output shaft 11 inside the case 12 of the photosensitive member driving device 10. A rotating disk 17 is provided as a power input member. An outer rotor 18 that rotates about the output shaft 11 is firmly fixed to the rotating disk 17 by caulking, press-fitting, an adhesive, or the like. Inside the outer rotor 18, a magnet 19 as a rotational force transmitting member is fixedly disposed on an inner peripheral surface parallel to the output shaft 11. Further, in the space between the inner peripheral surface and the output shaft 11, there are two stator cores 20 as drive sources fixed to the case 12, and these stator cores 20 have an optimal positional relationship with the magnet 19. In this way, they are arranged symmetrically with respect to the output shaft 11.
[0033]
A planetary gear shaft 22 of a planetary gear 21 having a fixed gear 14 and an output gear 16 as sun gears is fixed to the rotary desk 17 by a method such as press fitting. A planetary gear 21 composed of a spur gear is rotatably attached to the planetary gear shaft 22. Two planetary gear shafts 22 are installed on the rotary desk 17 so as to be parallel to the output shaft 11 and to be symmetrical with respect to the output shaft 11. Further, the planetary gear shaft 22 is arranged such that the inter-axis distance with the output shaft 11 is an optimum distance for the planetary gear 21, the fixed gear 14, and the output gear 16 to mesh with each other. In order to maintain the positional relationship when the planetary gear 21 does not jump out of the planetary gear shaft 22 during rotation and the planetary gear 21, the fixed gear 14, and the output gear 16 mesh with each other, It is held on the planetary gear shaft 22 by a shaft retaining ring 23 or the like.
[0034]
When the outer rotor 18 rotates, the rotary desk 17 rotates about the output shaft 11. As a result, the planetary gear 21 rotates around the fixed gear 14 while rotating around the planet (revolution). Since the planetary gear 21 is also meshed with the output gear 16, the output gear 16 rotates by a difference in the number of teeth from the fixed gear 14. Here, at least one gear of the fixed gear 14 or the output gear 16 is set so that the actual meshing pitch circles of the gears 14 and 16 when the fixed gear 14 and the output gear 16 mesh with the planetary gear 21 are the same. It is configured as a shift gear. As a result, the planetary gear 21 can properly mesh with the fixed gear 14 and the output gear 16 having different numbers of teeth.
[0035]
FIG. 5 is a front view of the photoconductor driving device 10 as viewed from the axial direction of the output shaft 11. As illustrated, the fixed gear 14 and the output gear 16 are both arranged coaxially with the output shaft 11. The two planet gears 21 rotate (revolve) in a planetary manner while maintaining axial symmetry with respect to the central axis of planet rotation. Here, when the difference in the number of teeth between the fixed gear 14 and the output gear 16 is an even number, the planetary gear 21 is for the output gear meshed with the fixed gear meshing portion meshed with the fixed gear 14 and the output gear 16 as shown in FIG. The meshing part has the same structure. On the other hand, when the difference in the number of teeth between the fixed gear 14 and the output gear 16 is an odd number, the planetary gear 21 is for the output gear meshed with the output gear 16 and the meshed portion 21a for the fixed gear meshed with the fixed gear 14, as shown in FIG. One of the meshing portions 21b has a structure shifted by a half pitch with respect to the other. As a method of shifting the half pitch in this way, for example, when the planetary gear 21 is gear-cut with a metal, it can be configured as an integral gear by press-fitting or caulking. Further, when the planetary gear 21 is a molded part, it can be easily manufactured by using a two-part mold. The phase difference between the fixed gear meshing portion 21a and the output gear meshing portion 21b can be corrected by shifting by a half pitch in this way.
[0036]
One of the two planetary gears may be configured as a scissor gear. FIGS. 8A to 8C show an example in which the planetary gear 21 is configured as a scissor gear. FIG. 8A is an axial cross-sectional view of the planetary gear 121 configured as a scissor gear, and FIG. 8B meshes a portion 121 a that meshes with the fixed gear 14 of the planetary gear 121 with the output gear 16. FIG. 8C is an external view showing a leaf spring 121c as an elastic body for urging these two planetary gear portions 121a and 121b in the reverse rotation direction with respect to each other. is there.
[0037]
The planetary gear 121 is assembled in a state in which a pin provided in the planetary gear portion 121b meshing with the output gear 16 is inserted into a notch 124 provided in the planetary gear portion 121a meshing with the fixed gear 14. At this time, a similar notch 124 is also provided in the planetary gear portion 121b meshed with the output gear 16, and the pin 125 provided in the planetary gear portion 121a meshed with the fixed gear 14 is similarly inserted. At this time, as shown in FIG. 8C, the pins 125 of the planetary gear portions 121a and 121b are respectively inserted into two insertion holes provided in the leaf spring 121c. As a result, the planetary gear portions 121a and 121b of the planetary gear 121 constituted by scissor gears are urged in the reverse rotation direction by the leaf spring 121c, and the urging force is a necessary transmission torque of the output shaft 11. Is set so that a torque corresponding to ½ of the torque is transmitted to the output gear 16. The maximum movable range in which the planetary gear portions 121a and 121b can rotate with each other is set to 0.5 pitch by the pins 125 and the notches 124.
[0038]
FIG. 9 is a partial cross-sectional view of the photoreceptor driving device 10 to which an inner rotor type DC motor is applied instead of the outer rotor motor. A motor shaft 118a of the inner rotor type DC motor is rotatably mounted on the output shaft 11, and the inner rotor 118 is fixed to the motor shaft 118a. A magnet 119 is attached to the outer periphery of the inner rotor. A stator core 120 is fixed to the motor cases 112 a and 112 b of the inner rotor 118. A rotating disk 17 is fixed to the end of the motor shaft 118a on the planetary gear 21 side by press fitting or the like. Further, the planetary gear shaft 22 is fixed to the rotating disk 17 by press fitting or the like, and the planetary gear 21 is rotatably attached to the planetary gear shaft 22 in the same manner as described above. Although a DC motor is used here, a stepping motor, an AC motor, or the like can be similarly applied.
[0039]
Here, in the first embodiment, since the output gear 16 is formed of a plastic material, specifically, POM (polyacetal resin), the tooth portion of the output gear 16 is an elastic member. Therefore, the tooth displacement due to the load torque generated at the meshing portion between the output gear 16 and the planetary gear 21 absorbs the eccentric amount that causes the speed fluctuation. If the longitudinal elastic modulus of the output gear 16 in the first embodiment is set so as to achieve tooth-to-rigidity that achieves tooth displacement that absorbs this eccentricity, the same effect as described later can be obtained. This tooth pair rigidity indicates the hardness against elastic deformation caused by a load when the teeth are engaged with each other, and is the spring rigidity due to the tooth pair of the gear, and is also called the meshing rigidity. The fixed gear 14 and the planetary gear 21 are made of a relatively high-stiffness metal (iron, brass, etc.) or high-density POM gear, and the teeth between the output gear 16 and the planetary gear 21. The rigidity against the teeth is one digit or more smaller than the rigidity between the teeth between the fixed gear 14 and the planetary gear 21.
[0040]
When the photosensitive drum 1Y is rotationally driven, a load is applied to the output gear 16, and the force generated by the load elastically deforms the tooth portion of the output gear 16. As a result, as will be described in an embodiment described later, it is possible to ensure that the two planetary gears 21 are always meshed with the output gear 16 and the fixed gear 14 during the rotational driving of the photosensitive drum 1Y. Thus, it is possible to obtain an effect that the fluctuation of the angular velocity that has occurred at a frequency corresponding to the number of planetary gears can be suppressed. This effect can be obtained in the same manner even if the tooth portions of the two planetary gears 21 or the fixed gear 14 are made of an elastic member made of POM or the like. For example, when the fixed gear 14 also serves as a bearing for the output shaft 11, the fixed gear 14 is formed of POM, the planetary gear 21 is formed of metal, and the output gear 16 is formed of POM. May be.
It should be noted that which tooth portion is constituted by an elastic member made of POM or the like is appropriately determined depending on the magnitude of force applied to the tooth portion when the drive target is rotationally driven, the degree of processing error and assembly error, and the like. . For example, when the magnitude of the force applied to the tooth portion when the drive target is rotationally driven is small, all of the fixed gear 14, the output gear 16, and the planetary gear 21 may be constituted by elastic members.
[0041]
The amount of deformation necessary for both the two planetary gears 21 to always mesh with the output gear 16 and the fixed gear 14 is the center axis of planetary rotation (revolution) and the rotation of each planetary gear 21. (Rotation) Processing related to displacement of the shaft, displacement of the center axis of the planetary rotation to be arranged coaxially with the shaft of the output gear 16 or the shaft of the fixed gear 14, the eccentricity of the fixed gear 14, etc. It depends on the accuracy and assembly accuracy. As described above, how much the longitudinal elastic coefficient is given to the tooth portion to be elastically deformed depends on the required amount of deformation. The required amount of deformation varies depending on the position where the force is applied to the tooth part, the module of the output gear 16 having the tooth part, the tooth width, and the like. It is desirable to select.
[0042]
[Embodiment 2]
Next, another embodiment in which the present invention is applied to a copying machine as in the first embodiment (hereinafter, this embodiment is referred to as “second embodiment”) will be described.
The basic configuration and operation of the copying machine according to the second embodiment are the same as those of the first embodiment. However, in the first embodiment, the method of elastically deforming the tooth portion of the output gear 21 is employed as a method of suppressing the angular velocity fluctuation generated at the frequency corresponding to the number of the planetary gears 21, whereas the present embodiment is implemented. In the second embodiment, a method of displacing the output gear is adopted. Only this point will be described below.
[0043]
FIG. 10 is an axial sectional view showing the output shaft 111 in the second embodiment. In the second embodiment, a thin shaft portion 111a is provided on the output shaft 111. The thin shaft portion 111a is a shaft deformation means serving as a displacement means having a thin shaft diameter. The output gear 116 is fixed to the thin shaft portion 111a. The shaft diameter of the thin shaft portion 111a is set to ensure a shaft strength that can withstand a torque that should be transmitted at a minimum. In the second embodiment, all gears are made of gears made of metal (iron, brass, etc.) having relatively high rigidity.
[0044]
In the second embodiment, an involute gear is used for each gear. Therefore, when the photosensitive drum 1Y is rotationally driven, the output gear 116 and the planetary gear 21 are engaged with each other, and the gears 116 and 21 are 20 degrees apart. A force is applied in the pressure angle direction. This force is transmitted through the output gear 116 to the shaft narrow portion 111a of the output shaft 111 to which the output gear 116 is fixed. Due to this force, the thin shaft portion 111a is deformed. Due to this deformation, the output gear 116 is displaced in a direction in which the axial deviation between the center axis of the output gear 116 and the planetary rotation center axis of the two planetary gears 21 is reduced. As a result, it is possible to ensure that both the two planetary gears 21 are always meshed with the output gear 116 and the fixed gear 14 during the rotational driving of the photosensitive drum 1Y, with a frequency corresponding to the number of planetary gears. The effect that the fluctuation | variation of the angular velocity which generate | occur | produced can be suppressed can be acquired. Note that this effect is obtained when the fixed gear 14 is fixed when an axial deviation occurs between the center axis of the planetary rotation and the fixed gear 14 or when the fixed gear 14 is eccentric. Even if the shaft is made of an elastic member, it can be obtained similarly.
[0045]
The amount of deformation required for both of the two planetary gears 21 to always mesh with the output gear 116 and the fixed gear 14 is the center axis of planetary rotation (revolution) and the rotation (rotation) of each planetary gear 21. ) Displacement of the distance from the shaft, misalignment between the center axis of the planetary rotation to be arranged on the same axis and the shaft of the output gear 116 or the shaft of the fixed gear 14, the machining accuracy related to the eccentricity of the fixed gear 14, etc. It depends on the assembly accuracy. The degree of the shaft diameter of the thin shaft portion 111a of the output shaft 111 to be deformed as described above and the length of the longitudinal elastic modulus of the shaft thin portion 111a depend on the required amount of deformation. Determined. In addition, as long as it has such a shaft diameter, a longitudinal elastic modulus, etc., the shaft thin part 111a may be made of iron or plastic. Note that the force applied to the output shaft 111 varies depending on the position where the force is applied to the tooth portion of the output gear 116, the module and the tooth width of the output gear 116, and the like. It is desirable to set the diameter and the longitudinal elastic modulus.
[0046]
In the second embodiment, the configuration in which the thin shaft portion 111a is formed on the output shaft 111 to deform the output shaft 111 has been described, but a cutout is formed so that the output shaft 111 is easily bent in a predetermined direction, The same effect can be obtained even if the output shaft 111 is made of an elastic member.
[0047]
[Modification]
Next, a modification of the second embodiment will be described. This modification employs a method of displacing the output gear as in the second embodiment, but the configuration for displacing the output gear is different from that of the second embodiment. Only this difference will be described below.
[0048]
FIG. 11A is a cross-sectional view when the output gear 216 in the present modification is partially cut on the axis of the output shaft 11. FIG. 11B is a side view of the output gear 216 as viewed from the axial direction of the output shaft 11.
The output gear 216 in this modification is configured by an inner portion 216b fixed to the output shaft 11 and an outer portion 216a having teeth on the outer peripheral surface. The outer portion 216a is disposed on the radially outer side of the inner portion 216b, and a space S is formed between the outer portion 216a and the inner portion 216b. Further, the inner peripheral surface of the outer portion 216a and the outer peripheral surface of the inner portion 216b are provided with three notches for fitting the elastic member 217, respectively. The elastic member 217 is press-fitted into the notch. When the elastic member 217 transmits a rotational force to the outer part 216a meshing with the planetary gear 21, the inner part 216b can rotate integrally with the outer part 216a. The elastic member 217 may be rubber, plastic, or a spring pin.
[0049]
In this modification, when the photosensitive drum 1Y is rotationally driven, the output gear 216 and the planetary gear 21 are engaged with each other, and a force is applied to the gears 216 and 21 in a pressure angle direction of 20 degrees. This force is transmitted to the outer portion 216 a of the output gear 216. When this force is transmitted to the outer portion 216a, the elastic member 217 is deformed and the space S is provided, so that the outer portion 216a is displaced with respect to the inner portion 216b. Due to this displacement, an axial deviation between the center axis of the output gear 216 and the planetary rotation center axis of the two planetary gears 21 is reduced. As a result, it is possible to ensure that both the two planetary gears 21 are always meshed with the output gear 216 and the fixed gear 14 during the rotation of the photosensitive drum 1Y, with a frequency corresponding to the number of planetary gears. The effect that the fluctuation | variation of the angular velocity which generate | occur | produced can be suppressed can be acquired.
[0050]
It should be noted that how much the space S of the output gear 216 is to be made and how much the longitudinal elastic coefficient of the elastic member 217 is to be made are the same as in the case of the above-described second embodiment. It depends on your needs.
[0051]
As a method for displacing the output gear, for example, the configuration shown in FIG. In the illustrated output gear 316, the portion fixed to the output shaft 11 is constituted by an elastic member 317 having a through hole, and the output shaft 11 is inserted into the through hole and fixed. In this case, the elastic member 317 is deformed by the force transmitted to the output gear 316 when the output gear 316 and the planetary gear 21 are engaged, and the output gear 316 is displaced.
Further, the output gear can be similarly displaced even when the bearing portion for bearing the output shaft 11 is displaced.
[0052]
〔Example〕
Next, examples of the photoconductor driving device 10 according to the first embodiment will be described.
FIG. 13 is a graph showing the measurement results when the torque generated at the meshing portion of the two planetary gears 21 and the output gear 16 of the photosensitive member driving device 10 is measured. In the graph shown in FIG. 18, since only one of the two planetary gears is engaged with the output gear 16, the transmission route of the rotational force to the output gear is switched from one planetary gear to the other planetary gear. At that time, a sudden torque fluctuation occurred in the output gear. On the other hand, in the photosensitive member driving device 10 according to the present embodiment, since the tooth portion is elastically deformed, as shown in FIG. 13, a state where both the two planetary gears 21 are always meshed with the output gear is ensured. Yes. As a result, the torque transmitted to the output gear 16 is as shown in FIG. FIG. 14 shows the sum of the load torques of the planetary gears 21 shown in FIG. Thus, the transmission of the rotational force from the two planetary gears 21 to the output gear 16 is performed smoothly. The angular velocity fluctuation rate at this time was 0.3%.
[0053]
[Experimental example]
Next, an experimental example for obtaining the material condition of the output gear 16 necessary for obtaining a desired angular velocity fluctuation rate will be described.
In the present experimental example, the output gear 16 having different tooth-to-rigidity with the planetary gear 21 is attached to the photoreceptor driving device 10 according to the first embodiment in which the output shaft 11 is eccentric by 20 μm. An experiment was conducted to determine the angular velocity fluctuation rate of the output gear for each output gear. In terms of analysis of tooth-to-rigidity, Lewis's FEM (finite element method) model is used to calculate the amount of deformation with respect to the load, and the rigidity is calculated based on that. It can be obtained by using an expression. Moreover, in an experimental surface, it can obtain | require by taking out a tooth | gear part (scraping except a tooth | gear part), and measuring the deflection | deviation with respect to a load. In this experimental example, the amount of displacement of the tooth portion of the output gear 16 was measured by meshing with the tooth portion of a predetermined master gear (a metal gear made of stainless steel having a small amount of deflection), and the tooth pair rigidity was obtained. . In this experimental example, 5.76 × 10^FiveN / m, 1.15 × 10⁶N / m, 2.88 × 10⁶N / m, 5.76 × 10⁶An output gear 16 having four tooth-pair stiffnesses of N / m was used.
[0054]
FIG. 15 is a graph showing the experimental results of this experimental example.
As can be seen from this graph, the lower the tooth pair rigidity between the metallic planetary gear 21 and the POM output gear 16, the smaller the angular velocity fluctuation rate with respect to the load torque. Here, in the case of general machining accuracy, the eccentricity of the output shaft 11 occurs about 10 to 30 μm, but it is desirable that the angular velocity fluctuation rate is 0.3% or less. Under such conditions, according to the result of this experimental example, the planetary gear 21 is 5.76 × 10 5^FiveN / m or more 1.15 × 10⁶If the output gear 16 having a tooth-to-rigidity of about N / m or less is used, the angular velocity fluctuation rate can be suppressed to 0.3% or less.
[0055]
As described in the above embodiment, in order to keep the angular velocity fluctuation rate low, it is important to ensure that both the two planetary gears 21 are always meshed with the output gear 16. For this purpose, when the output gear 16 receives contact pressure from the two planetary gears 21 meshing with the output gear 16, the teeth of the output gear are in a state where both the two planetary gears 21 are always meshed with the output gear 16. It must be deformed to the extent that it is secured.
Here, when load torque Tf is applied to two gears meshing with each other, the force F applied to the meshing portion is F = Tf / (rb × n), where the base circle radius is rb and the meshing rate is n. It is requested from. Further, when the tooth pair rigidity is K, the tooth displacement δ can be obtained by F / K. That is, the tooth displacement amount δ can be obtained from the arithmetic expression shown in Equation 7 below.
[Expression 7]
δ = Tf / (rb × n × K)
[0056]
For example, when the load torque is 3 kgfcm, the module m is 0.5, the tooth-to-rigidity of the resin material is 5.76 N / m, the basic circle radius rb is 5.6 mm, and the meshing rate is 3.28, the tooth displacement amount Is 28 μm. Therefore, in such a condition, the teeth of the output gear 16 are displaced by about 28 μm. If the eccentricity is within this range, the influence of the tooth displacement is greater, and both the two planetary gears 21 are always output gears. 16 is ensured.
[0057]
As described above, in the copying machine of the first embodiment, as the driving device for the photosensitive drum 1Y to be driven, the rotational speed of the stator core 20 that is the driving source is reduced to the rotational speed required by the photosensitive drum 1Y. A planetary differential gear reduction device for transmitting the rotational force from the This planetary differential gear reduction device includes an output gear 16 fixed to an output shaft 11 connected to the photosensitive drum 1Y. Further, a fixed gear 14 having a smaller number of teeth than that of the output gear 16, disposed coaxially with the output gear 16 and fixed so as not to rotate is provided. Further, the outer periphery of the output gear 16 and the fixed gear 14 is rotatably supported by a planetary gear shaft 22 that is rotationally driven by the rotational force from the stator core 20, and rotates planetarily while meshing with both the output gear 16 and the fixed gear 14. Two planetary gears 21 are provided. The two planetary gears 21 are disposed at positions that are axisymmetric with respect to the central axis of planetary rotation. The tooth portion of the output gear 16 is composed of an elastic member that can be deformed by contact pressure generated by meshing while the photosensitive drum 1Y is rotationally driven. Thereby, as described above, during the rotational drive of the photosensitive drum 1Y, it is possible to ensure that both of the two planetary gears 21 are always meshed with the output gear 16 and the fixed gear 14, and the number of planetary gears is increased. It is possible to obtain an effect that the fluctuation of the angular velocity generated at the corresponding frequency can be suppressed.
In the first embodiment, the longitudinal elastic modulus of the tooth portion of the output gear 16 is such that the deformation amount when the contact pressure is applied to the tooth portion is the eccentric amount of the output gear 16 and the angular velocity fluctuation of the output gear 16. The longitudinal elastic modulus is such that the required amount of deformation is obtained based on the allowable range. Thereby, the angular velocity fluctuation | variation which generate | occur | produced with the frequency according to the number of planetary gears can be settled in a tolerance | permissible_range.
The copying machine of the second embodiment includes a planetary differential gear reduction device similar to the copying machine of the first embodiment. In this planetary differential gear reduction device, the output gears 116, 216, and 316 are provided. Is provided with a displacing means for displacing the photoconductive drum by contact pressure generated by meshing while the photosensitive drum 1Y is rotationally driven. As a result, as described above, it is possible to ensure that the two planetary gears 21 are always meshed with the output gears 116, 216, 316 and the fixed gear 14 during rotation of the photosensitive drum 1Y. It is possible to obtain an effect that the fluctuation of the angular velocity generated at the frequency corresponding to the number of gears can be suppressed.
In particular, in the second embodiment, as the displacement means, the output shaft 111 on which the output gear 116 displaced by the displacement means is fixed is deformed on the output shaft 111 as the shaft deformation means for deforming by the contact pressure. A portion 111a is provided. Thereby, the output gear 16 can be displaced by the contact pressure with a simple configuration.
Further, as described in the modification, the output shaft 11 is supported as the displacement means as the shaft displacement means for displacing the output shaft to which the output gear displaced by the displacement means is fixed by the contact pressure. Even when a mechanism for displacing the bearing portion is used, the output gear can be similarly displaced.
[0058]
In addition, you may combine the structure of the said Embodiment 1 and the said Embodiment 2 mutually.
In the first embodiment and the second embodiment, the case where the present invention is applied to the photoconductor driving device 10 that uses the photoconductor drum 1 as a rotating body to be driven has been described. It can be widely used as a speed reducing device for a rotating body that needs to be decelerated to an appropriate rotational speed. For example, in the case of the copying machine according to the first embodiment, for example, a driving roller for rotating the intermediate transfer belt 5, a fixing roller pair 8, a developing roller of the developing device 9, a primary transfer roller 6, and a secondary transfer. It can be used as a speed reduction device between a rotating body such as the roller 7 and the registration roller and a drive source. The speed reduction device of the present invention can be applied not only to a copying machine but also to speed reduction devices in other technical fields.
[0059]
【The invention's effect】
  Claims 1 to3According to this invention, there is an excellent effect that it is possible to suppress fluctuations in angular velocity that occur at a frequency corresponding to the number of planetary gears without performing high-precision processing and assembly that are expensive.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an internal configuration of a photoreceptor driving device in a copying machine according to a first embodiment.
FIG. 2 is a schematic configuration diagram of an entire image forming unit in the copier.
FIG. 3 is a partial cross-sectional view of a photosensitive member driving device installed outside one axial end of a photosensitive drum in the copier.
FIG. 4 is a perspective view of the photoreceptor driving device.
FIG. 5 is a front view of the photoreceptor driving device as viewed from the axial direction of the output shaft.
FIG. 6 is an external view showing the structure of a planetary gear when the difference in the number of teeth between the fixed gear and the output gear is an even number in the photoreceptor driving device.
FIG. 7 is an external view showing the structure of the planetary gear when the difference in the number of teeth between the fixed gear and the output gear is an odd number in the photoreceptor driving device.
FIG. 8A is an axial sectional view of a planetary gear configured as a scissor gear.
(B) is the side view which looked at the part mesh | engaged with the fixed gear of the planetary gear from the part side mesh | engaged with an output gear.
(C) is an external view showing a leaf spring for urging the planetary gear portions of the planetary gear in the reverse rotation direction.
FIG. 9 is a partial cross-sectional view of a photoconductor driving device to which an inner rotor type DC motor is applied instead of the outer rotor motor of the photoconductor driving device.
FIG. 10 is an axial sectional view showing an output shaft of a photoreceptor driving device in a copying machine according to a second embodiment.
FIG. 11A is a cross-sectional view when the output gear in the modification is partially cut on the axis of the output shaft.
(B) is the side view which looked at the same output gear from the axial direction of the output shaft.
FIG. 12A is a cross-sectional view of an output gear according to another configuration for displacing the output gear, partially cut on the axis of the output shaft.
(B) is the side view which looked at the same output gear from the axial direction of the output shaft.
FIG. 13 is a graph showing a measurement result when a torque generated at a meshing portion between two planetary gears and an output gear of the photoconductor driving device in the example is measured.
FIG. 14 is a graph showing torque transmitted to an output gear of the photoreceptor driving device.
FIG. 15 is a graph showing experimental results of experimental examples.
FIG. 16 is a cross-sectional view of the planetary differential gear reduction device used by the inventors as an experimental machine, partially cut on the output shaft.
FIG. 17 is an explanatory diagram showing pitch circles of the respective gears in the planetary gear reduction device.
FIG. 18 is a graph showing a measurement result when a torque generated at a meshing portion between two planetary gears and an output gear in the planetary gear reduction device is measured.
FIG. 19 is a graph showing an experimental result of measuring an angular velocity fluctuation rate when the load torque applied to the output shaft is changed using the planetary differential gear speed reducer.
[Explanation of symbols]
1 Photosensitive drum
5 Intermediate transfer belt
6 Primary transfer roller
7 Secondary transfer roller
8 Fixing roller pair
9 Development device
10 Photoconductor drive device
11, 111, 211, 411 Output shaft
14,411 fixed gear
16, 116, 216, 316, 416 Output gear
17 Rotating disc
18,418 Outer rotor
19 Magnet
20 Stator core
21, 121, 421 planetary gear
118 Inner rotor

Claims (3)

In a planetary differential gear reduction device for decelerating the rotational speed of the drive source to the rotational speed required by the image carrier and transmitting the rotational force from the drive source,
An output gear fixed to an output shaft coupled to the image carrier;
A fixed gear having a smaller number of teeth than the output gear, arranged coaxially with the output gear, and fixed non-rotatably;
Two planets rotating planetarily while meshing with both the output gear and the fixed gear, rotatably supported on the planetary gear shaft that is driven to rotate around the output gear and the fixed gear by the rotational force from the drive source. With gears,
The two planetary gears are arranged at positions that are axisymmetric with respect to the central axis of planet rotation,
At least one of the output gear and the fixed gear has a double structure consisting of an inner part close to the center of the separate gear and an outer part far from the center,
There is a gap between the outer peripheral surface of the inner portion and the inner peripheral surface of the outer portion,
A plurality of elastic members are arranged in the interval,
The elastic member defines the relative movement in the circumferential direction between the inner part and the outer part ,
When the elastic member is subjected to contact pressure generated by meshing while the image carrier is being rotationally driven, the amount of deformation of the elastic member is changed by the amount of eccentricity of the outer portion and the angular velocity fluctuation of the output gear. A planetary differential gear reduction device having a longitudinal elastic modulus that is a deformation amount determined based on an allowable range of the planetary differential gear. The planetary differential gear reduction device according to claim 1,
The planetary differential gear reduction device according to claim 1, wherein the elastic member is provided by being fitted into a notch formed on the outer peripheral surface of the inner portion and the inner peripheral surface of the outer portion . An image forming apparatus comprising an image bearing member rotates at a lower rotational speed than the rotational speed of the driving Dogen,
The planetary differential gear reduction device according to claim 1 or 2 , wherein the planetary differential gear reduction device according to claim 1 or 2 is used as a reduction means for reducing the rotation speed of the drive source to a rotation speed required by the image carrier and transmitting a rotational force from the drive source. An image forming apparatus using the apparatus.

Images