JP3589602B2

JP3589602B2 - Tandem type image forming apparatus

Info

Publication number: JP3589602B2
Application number: JP34652099A
Authority: JP
Inventors: 敏明楠田; 学宮地
Original assignee: Kyocera Mita Corp
Current assignee: Kyocera Document Solutions Inc
Priority date: 1999-12-06
Filing date: 1999-12-06
Publication date: 2004-11-17
Anticipated expiration: 2019-12-06
Also published as: JP2001166554A

Description

【０００１】
【発明の属する技術分野】
本発明は，タンデム型画像形成装置に係り，詳しくは，感光体ドラムと現像装置とを含む複数の画像形成ユニットが用紙搬送経路に沿って一列に配設され，支持部材間に取り付けられた駆動系を介して各感光体ドラムに連結された単一の感光体ドラム用駆動源により各感光体ドラムを駆動するタンデム型画像形成装置に関するものである。
【０００２】
【従来の技術】
タンデム型のカラー画像形成装置は，複数の異なる色毎に感光体ドラムや現像装置などからなる画像形成ユニットを用紙搬送経路に沿って一列に配設したものである。前記用紙搬送経路を用紙が通過する際，ブラック，マゼンダ，イエロー，シアンに対応する画像が順次用紙に転写され，最後の画像形成ユニットを通過したときには，４色が重ね合わされたカラー画像が用紙上に形成される。
前記タンデム型カラー画像形成装置では，このように画像形成が行われるため，高速なカラー画像の出力が可能であるが，各感光体ドラムや用紙を搬送する転写ベルトなどの駆動精度が低いと，各色の画像が用紙上でずれてしまい，適正な出力が得られない恐れがある。
このため，各感光体ドラムそれぞれに対して個別の駆動モータを配設するなどして，高い駆動精度を得ようとする装置が多い。但し，個別に駆動モータを設けると，コストが上昇するし，装置の小型化の面でも好ましくない。
コストを抑えるには，各感光体ドラムを単一の駆動モータにより駆動することが好ましく，その上で高い駆動精度を確保することが必要である。単一の駆動モータによって各感光体ドラムを駆動しながら高い駆動精度を確保することを図った技術が，例えば特開平７−２０９９４７号公報などに開示されている。
前記公報に記載の技術は，単一の駆動モータの回転軸と各感光体ドラムの回転軸との間をギアを用いて連結する。前記単一の駆動モータは，一列に配設された４つの画像形成ユニットの中央に配置される。前記単一の駆動モータの回転軸に取り付けられたギアが，その両側にある２つの感光体ドラムの回転軸に取り付けられた感光体ギアと嵌合することによって，前記単一の駆動モータの駆動力が両感光体ドラムに伝達される。残りの２つの感光体ドラムの感光体ギアは，前記駆動モータの両側にある感光体の感光体ギアとアイドルギアを介して，前記駆動モータに連結される。
このように前記単一の駆動モータを４つの画像形成ユニットの中央に配置すれば，前記単一の駆動モータの回転軸と各感光体ドラムの回転軸とを連結するのに必要なギアの枚数を少なくすることができ，回転誤差を抑えるなど様々な利点を得ることができる。
【０００３】
【発明が解決しようとする課題】
ところで，各画像形成ユニットによって各色の画像を用紙上に形成するには，前記感光体ドラムを駆動する他，当然ながら現像装置を駆動する必要がある。この現像装置も各色毎に設けられているが，コスト低減や装置の小型化のためには，前記感光体ドラムと同じく単一の駆動モータによって駆動するのが好ましい。この場合，前記感光体ドラムと前記現像装置とで２つの駆動モータが必要になり，前記公報に記載の技術のように，各感光体ドラムを駆動するための駆動モータを中央に配置することが難しくなる。
各感光体ドラム及び各現像装置全ての駆動を単一の駆動モータで担うことも不可能ではないが，前記感光体ドラムと前記現像装置とでは回転数も駆動トルクも異なり，さらに駆動する対象が倍に増えることになるため，駆動系が複雑になり過ぎ，却ってコストは増加してしまう。
このため，例えば図８に示すように，各感光体ドラム２（２ａ，２ｂ，２ｃ，２ｄ）を駆動する駆動モータ２００と各現像装置４（４ａ，４ｂ，４ｃ，４ｄ）を駆動する駆動モータ４００とは，一列に配列された各感光体ドラム２又は各現像装置４の中央から用紙搬送経路に沿っていずれか偏った位置に配置せざるを得ない。
各感光体ドラム２又は各現像装置４をそれぞれ駆動する単一の駆動モータ２００，４００を設ける位置を各画像形成ユニット１（１ａ，１ｂ，１ｃ，１ｄ）に対して偏らせると，４つの感光体ドラム２ａ〜２ｄ，又は現像装置４ａ〜４ｄの中に駆動モータ２００，４００から著しく遠い感光体ドラム又は現像装置ができてしまう。この場合，必要なギア枚数は増加し，必然的に駆動系が占める空間が大きくなってしまう。
また，前記駆動系にある各ギアの軸は一対の側板によって支持されるが，多くの枚数のギアを前記側板間に納めるべく前記側板間の距離を広げると，ギアの回転ムラが生じ易くなり，画像に悪影響を与えるという問題も発生するため，前記駆動系が占める空間を制限無しに広げることはできない。
従って，例えば前記感光体ドラムの駆動系を前記側板間に先に配置すると前記側板間の空間に余裕をそれほど設けることはできず，さらに前記現像装置用の駆動系を前記側板間に配置しようとすると，前記側板間に各ギアの軸を配置することが難しくそのため一部のギアの位置が干渉したり，一部のギアが前記側板間に納まらなかったりして，結果的に各感光体ドラム及び各現像装置の駆動系を全て配置することができなかった。
本発明は，このような従来の技術における課題を解決するために，タンデム型画像形成装置を改良し，複数配設された現像装置又は感光体ドラムのうち一部の装置についてはギア群を介して現像装置用駆動源又は感光体ドラム用駆動源に連結せず，前記現像装置用駆動源又は感光体ドラム用駆動源に連結された出力軸と当該現像装置又は感光体ドラムの駆動入力部とに前記ギア群の支持部材間の外側で巻き回された無端状の駆動ベルトを介して連結すると共に，前記ギア群に含まれるアイドルギアを前記出力軸及び前記支持部材間に配置される軸固定型クラッチの固定軸のいずれか一方又は両方に回動自在に設けることにより，前記支持部材間に配置する必要のある軸やギアの数を抑えつつ前記支持部材間の軸やギアの配置を効率的に行い，各感光体ドラムと各現像装置とをそれぞれ単一の駆動源により駆動しながら，必要な駆動精度を保つことができるタンデム型画像形成装置を提供することを目的とするものである。
【０００４】
【課題を解決するための手段】
前記目的を達成するために，請求項１に係る発明は，感光体ドラムと現像装置とを含む複数の画像形成ユニットが用紙搬送経路に沿って一列に配設され，支持部材間に取り付けられた駆動系を介して各感光体ドラムに連結された単一の感光体ドラム用駆動源により各感光体ドラムを駆動するタンデム型画像形成装置において，各現像装置を駆動するための単一の現像装置用駆動源を具備し，前記現像装置及び前記感光体ドラムの長手方向と同方向に出力軸が連結された前記現像装置用駆動源又は前記感光体ドラム用駆動源の少なくともいずれか一方が前記複数の画像形成ユニットの配設方向の一方端側に配設され，前記複数の画像形成ユニットの他方端に配設された黒色に対応する一の現像装置又は一の感光体ドラムの前記駆動系として，前記現像装置用駆動源又は前記感光体ドラム用駆動源に連結された出力軸と当該一の現像装置又は当該一の感光体ドラムの駆動入力部とに前記支持部材間の外側で巻き回された無端状の駆動ベルトが用いられてなると共に，前記黒色に対応する一の現像装置又は一の感光体ドラムを除く残りの前記現像装置及び前記感光体ドラムの前記駆動系として，ギア群が用いられてなり，各現像装置又は各感光体ドラムと前記現像装置用駆動源又は前記感光体ドラム用駆動源とを連結し，且つ，前記ギア群に含まれるアイドルギアを前記出力軸及び前記支持部材間に配置される軸固定型クラッチの固定軸のいずれか一方又は両方に回動自在に設けたことを特徴とするタンデム型画像形成装置として構成されている。
前記請求項１に係る発明では，感光体ドラムと現像装置とを含む複数の画像形成ユニットが用紙搬送経路に沿って一列に配設され，支持部材間に取り付けられた駆動系を介して各感光体ドラムに連結された単一の感光体ドラム用駆動源により各感光体ドラムを駆動するタンデム型画像形成装置において，各現像装置又は各感光体ドラムのうち，黒色に対応する一の装置については前記駆動系にギア群が用いられず，前記現像装置用駆動源又は前記感光体ドラム用駆動源に連結された出力軸と当該現像装置又は感光体ドラムの駆動入力部とに前記支持部材間の外側で巻き回された無端状の駆動ベルトが用いられる。また，前記ギア群に含まれるアイドルギアが，前記出力軸及び前記支持部材間に配置される軸固定型クラッチの固定軸のいずれか一方又は両方に回動自在に設けられる。
例えば前記現像装置用駆動源と前記現像装置用駆動源から最も遠い現像装置とをギアを介して連結した場合，多くのギアが必要となり駆動精度を確保することも難しくなるが，両者を前記駆動ベルトを介して連結することによって，前記支持部材間に配置する必要のある軸やギアの数を減少させることができ，必要な駆動精度も比較的簡単に確保することができる。また，前記ギア群に含まれるアイドルギアには，前記支持部材間への取り付けのために別個の固定軸が設けられていたが，前記出力軸や軸固定型クラッチの固定軸に取り付けることによって，各ギアの軸を少なくして各ギアが干渉するのを防止することができる。
これにより，前記支持部材間に配置する必要のある軸やギアの数を抑えつつ前記支持部材間に前記ギア群を効率的に配置することが可能となり，各感光体ドラムと各現像装置とをそれぞれ単一の駆動源により駆動しながら，必要な駆動精度を保つことが可能となる。
【０００５】
【発明の実施の形態】
以下，添付図面を参照して，本発明の実施の形態につき説明し，本発明の理解に供する。尚，以下の実施の形態は，本発明の具体例であって，本発明の技術的範囲を限定する性格のものではない。
ここに，図１は本発明の実施の形態に係るタンデム型フルカラープリンタの要部となる駆動系の全体構成を示す図，図２は図１に示した全体構成のうちのドラム駆動系を抽出した図，図３は図１に示した全体構成のうちの現像駆動系を抽出した図，図４は図１に示した全体構成のうち特徴的な構成のみを抽出した図，図５は図４に示した特徴的な構成をさらに簡素に示した図，図６は前記タンデム型フルカラープリンタの全体構成を概略的に示す図，図７は前記タンデム型フルカラープリンタの画像形成ユニット周辺の構成を拡大して示した図である。
【０００６】
本実施の形態に係るタンデム型フルカラープリンタは，本発明に係る画像形成装置を具体化したものである。まず図６及び図７を用いて，前記タンデム型フルカラープリンタの全体構成を概略的に説明する。
前記タンデム型フルカラープリンタの本体内には，４つの画像形成ユニット１（１ａ〜１ｄ）が用紙搬送経路に沿って一列に配設されている。各画像形成ユニット１（１ａ〜１ｄ）は，それぞれ異なる４色（ブラック，マゼンダ，イエロー，シアン）の画像形成を担当しており，全て同じ構成を有している。
例えば，画像形成ユニット１（１ａ〜１ｄ）は，感光体ドラム２（２ａ〜２ｄ），転写ローラ３（３ａ〜３ｄ），現像装置４（４ａ〜４ｄ），露光器５（５ａ〜５ｄ），帯電器６（６ａ〜６ｄ），クリーニング装置７（７ａ〜７ｄ）等を具備している（画像形成部１ｂ〜１ｄについてはこれらの各要素の符号の図示を一部省略した）。
また，前記画像形成ユニット１ａ〜１ｄのそれぞれの転写ローラ３ａ〜３ｄ，それらの前後に配置された駆動ローラ２１，従動ローラ２２，及び補助ローラ２３には，無端状の転写ベルト２４が巻き回されており，該転写ベルト２４は前記駆動ローラ２１の駆動により矢印Ｙ１方向に回動される。各画像形成ユニット１ａ〜１ｄにとっては，前記転写ベルト２４の各画像形成ユニット１ａ〜１ｄ側の周面が用紙搬送経路になる。
また，前記転写ベルト２４の上流側にはレジストローラ２５が，下流側には定着ローラ２６が設置されており，また本体下部には２つの用紙カセット２７ａ，２７ｂが，本体上部には用紙の排紙トレー２８がそれぞれ設けられている。
【０００７】
以上の通りの概略構成を有するタンデム型フルカラープリンタの画像形成動作を簡単に説明すると，まず，用紙カセット２７ａ若しくは２７ｂから給紙路２９を矢印Ｙ２のように搬送された用紙は，レジストローラ２５により，画像形成タイミングに合わせて画像形成ユニット１ａに向けて送出される。前記レジストローラ２５から送出された用紙は，その先端を前記転写ベルト２４に沿わせた状態で，画像形成ユニット１ａの感光体ドラム２ａと転写ローラ３ａとの対向部（以下，転写部）に挿入される。前記転写ベルト２４によって搬送されつつ，画像形成ユニット１ａの転写部に挿入された用紙に，現像装置４ａにより感光体ドラム２ａ表面に形成されたトナー像（例えば黒画像）がまず転写される。前記用紙が前記転写ベルト２４によって各画像形成ユニット１ａ〜１ｄの転写部を順次搬送されることにより，前記用紙上に４色のトナー像が順次重ね転写され，前記用紙上にフルカラー画像が形成される。前記各画像形成ユニット１ａ〜１ｄを通過した用紙は，定着ローラ２６において転写画像が定着された後，排紙路３０を矢印Ｙ３のように搬送され，排紙トレー２８上に排出される。
【０００８】
次に，本実施の形態に係るタンデム型フルカラープリンタの要部詳細について説明を行う。
はじめに，図１乃至図５に付した符号の説明をしておく。
図１及び図２において，２００は感光体ドラム駆動用の駆動モータ（感光体ドラム用駆動源の一例）であり，２０１は該駆動モータ２００の回転軸，２０２（２０２ａ〜２０２ｄ）は前記感光体ドラム２ａ〜２ｄそれぞれの回転軸に取り付けられた駆動入力ギア，２０３は前記回転軸２０１と前記駆動入力ギア２０２とを連結するためのギア群である。
また，図１及び図３において，４００は現像装置駆動用の駆動モータ（現像装置用駆動源の一例）であり，４０１は該駆動モータ４００の回転軸，４０２（４０２ａ〜４０２ｄ）は前記現像装置４ａ〜４ｄそれぞれの回転軸に取り付けられた駆動入力ギア，４０３は前記回転軸４０１と前記駆動入力ギア４０２ｂ〜４０２ｄとを連結するためのギア群である。
また，図１乃至図５において，３００は前記ギア群２０３及び前記ギア群４０３に含まれる各ギアの軸を支持するための側板（支持部材の一例）であり，４０４は前記回転軸４０１に前記ギア群４０３のうちのギア４０３１〜４０３６をこの順に介して連結された出力軸，４０５は前記出力軸４０４の前記側板３００間外側に延長された延長部４０４Ｅと前記駆動入力ギア４０２ａの回転軸（駆動入力部の一例）４０２１ａとの間に巻き回された無端状の駆動ベルト，２０４は前記回転軸２０１に前記ギア群２０３のうちのギア２０３１〜２０３４をこの順に介して連結されるアイドルギアであって，前記アイドルギア２０４は前記ギア群２０３のうちのギア２０３５を介して前記駆動入力ギア２０２ｄに連結される。
【０００９】
図２に簡明に示す通り，本実施の形態に係るタンデム型フルカラープリンタは，上述した４つの感光体ドラム２ａ〜２ｄが，側板３００間に取り付けられたギア群（駆動系の一部）２０３を介して各感光体ドラム２ａ〜２ｄの駆動入力ギア２０２ａ〜２０２ｄに連結された駆動モータ２００のみによって駆動される点で従来のものと同様である。
より具体的には，前記４つの感光体ドラム２ａ〜２ｄのうちの前記感光体ドラム２ａの駆動入力ギア２０２ａは，前記駆動モータ２００の回転軸２０１と，ギア２０３６，２０３７，２０３８，２０３９，２０４０，２０４１をこの順に介して連結されている。また，前記感光体ドラム２ｂの駆動入力ギア２０２ｂは，前記駆動モータ２００の回転軸２０１と，ギア２０３１，２０３２，２０４２，２０４３，２０４４，２０４５をこの順に介して連結されている。また，前記感光体ドラム２ｃの駆動入力ギア２０２ｃは，前記駆動モータ２００の回転軸２０１と，ギア２０３１，２０３２，２０３３，２０３４，２０４６，２０４７をこの順に介して連結されている。また，前記感光体ドラム２ｄの駆動入力ギア２０２ｄは，ギア２０３１，２０３２，２０３３，２０３４，アイドルギア２０４，ギア２０３５をこの順に介して連結されている。
【００１０】
一方，本実施の形態に係るタンデム型フルカラープリンタが，従来のものと異なるのは，図４及び図５に簡明に示すように，各現像装置４ａ〜４ｄが駆動モータ４００のみによって駆動され，現像装置４ａ（一部の現像装置の一例）については，前記駆動モータ４００に連結された出力軸４０４と当該現像装置４ａの駆動入力用の回転軸４０２１ａとに前記側板３００間の外側で巻き回された前記駆動ベルト４０５を介し，残りの現像装置４ｂ〜４ｄについては，前記ギア群２０３，４０３のうちの前記ギア群４０３を介して，各現像装置４ａ〜４ｄと前記駆動モータ４００とを連結すると共に，前記ギア群２０３，４０３のうちの前記ギア群２０３に含まれる前記アイドルギア２０４を前記出力軸４０４に回動自在に設けた点である。
本実施の形態に係るタンデム型フルカラープリンタでは，各現像装置４ａ〜４ｄは駆動モータ４００のみによって駆動される。前記駆動モータ４００は，前記駆動モータ２００とは別個のものである。両駆動モータ２００，４００と各々の被駆動体との距離をほぼ均等にするために，前記駆動モータ２００，４００は各画像形成ユニット１ａ〜１ｄの中央に配置されず，例えば図１に示すように中央から偏った位置に配置される。このため，４つの現像装置４ａ〜４ｄのうち現像装置４ａは，前記駆動モータ４００からかなり遠くなる。
前記駆動モータ４００からの距離が比較的近くなる３つの現像装置４ｂ〜４ｄについては，前記感光体ドラム１ａ〜１ｄの駆動系と同様に，各現像装置４ｂ〜４ｄの駆動入力ギア４０２ｂ〜４０２ｄと前記駆動モータ４００とがギアを介して連結される。
より具体的には，図３に示す如く，前記現像装置４ｂの駆動入力ギア４０２ｂは，前記駆動モータ４００の回転軸４０１と，ギア４０３７，４０３８，４０３９，４０４０，４０４１，４０４２，４０４３，４０４４，４０４５をこの順に介して連結される。また，前記現像装置４ｃの駆動入力ギア４０２ｃは，前記駆動モータ４００の回転軸４０１と，ギア４０３７，４０３８，４０３９，４０４６，４０４７をこの順に介して連結される。また，前記現像装置４ｄの駆動入力ギア４ｄの駆動入力ギア４０２ｄは，前記駆動モータ４００の回転軸と，ギア４０３７，４０３８，４０３９，４０４６，４０４８，４０４９，４０５０をこの順に介して連結される。
【００１１】
前記３つの現像装置４ｂ〜４ｄは，マゼンダ，イエロー，シアンの３色に対応するものであるが，白黒印刷を行う場合には，これらの現像装置４ｂ〜４ｄを駆動する必要はない。このため，前記ギア４０３７と前記ギア４０３８との間にはクラッチが設けられており，このクラッチをオン・オフすることにより，白黒印刷のときの動作と，カラー印刷のときの動作が切り替えられる。
これら３つの現像装置３ｂ〜３ｄに対し，前記駆動モータ４００からの距離が遠い前記現像装置４ａは，前記駆動モータ４００と前記駆動ベルト４０５を介して連結される。
図１，図３，及び図４に示す通り，前記駆動モータ４００の回転軸４０１には，ギア４０３１，４０３２，４０３３，４０３４，４０３５，４０３６を介して前記出力軸４０４が連結されている。
この出力軸４０４の一方の軸端は，前記側板３００間の外側に配置されており，前記側板３００の外側にある前記出力軸４０４の延長部４０４Ｅには，無端状の駆動ベルト４０５が巻き回されている。
この駆動ベルト４０５は，前記現像装置４ａの駆動入力ギア４０２ａの回転軸４０２１ａにも巻き回されており，前記ギア４０３１〜４０３６，前記出力軸４０４，前記駆動ベルト４０５を介して前記現像装置４ａの駆動入力ギア４０２ａの回転軸４０２１ａに前記駆動モータ４００の駆動力が伝達される。
このように前記側板３００間の外側で前記出力軸４０４と前記回転軸４０２１ａとの間に前記駆動ベルト４０５を巻き回して前記駆動モータ４００により前記現像装置４ａを駆動することによって，前記現像装置４ａと前記駆動モータ４００とをギアによって連結する場合に必要となる多くの軸やギアを前記側板３００間に配置する必要がなくなり，前記側板３００間に前記ギア群２０３，４０３を配置するときの互いの干渉を抑制することができる。上述の通り前記現像装置４ａよりも前記駆動モータ４００に近い前記現像装置４ｂを駆動するのにも，ギアが９枚程必要となることを考慮すると，前記現像装置４ａを前記駆動ベルト４０５を用いて前記駆動モータ４００に連結することにより前記側板３００間に配置しなくてすむ軸やギアの抑制数は著しいものがある。また，前記駆動モータ４００から最も遠い前記現像装置４ａの駆動に多くの枚数のギアを用いないから，前記駆動モータ４００が前記画像形成ユニット１の中央に配置されていなくても，良好な駆動精度を確保することができる。前記駆動ベルト４０５による駆動誤差は，多くの枚数のギアに渡って誤差が累積する場合と較べてかなり少ない。
また，前記現像装置４ａのみを前記駆動ベルト４０５により駆動することにしたのは，前記現像装置４ａが前記駆動モータ４００から最も遠くなることもあるが，前記現像装置４ａがブラックに対応するものであり，白黒印刷時に単独使用を行う場合があるという理由もある。上述の通り，前記現像装置４ａと前記現像装置４ｂ〜４ｄとで連結系統を異ならせていれば，白黒印刷とカラー印刷の切り替えは容易である。
【００１２】
また，本実施の形態に係るタンデム型フルカラープリンタでは，前記側板３００間に前記ギア群２０３，４０３を効率的に配置するために，前記駆動モータ２００と前記感光体ドラム２ｄの駆動入力ギア２０２ｄとを連結するのに用いる前記ギア群のうちのアイドルギア２０４が，前記駆動ベルト４０５を駆動するために回転する前記出力軸４０４に回動自在に設けられる。
前記出力軸４０４に本来取り付けられるのは，図１，図３，図４，及び図５に示す前記ギア４０３６のみである。この前記ギア４０３６は前記出力軸４０４に固定的に取り付けられており，図４に簡明に示す通り，前記駆動モータ４００の回転軸４０１から前記ギア４０３１〜４０３５を介して伝達されてきた駆動力を，前記出力軸４０４に伝達し，前記出力軸４０４を回転させる。
前記アイドルギア２０４は，既述の通り，前記駆動モータ２００からの駆動力をギア２０３１〜２０３４を介して受け，ギア２０３５を介して前記駆動入力ギア２０２ｄに伝達するものである（主に図４参照）。前記アイドルギア２０４は，従来前記側板３００間に別個の固定軸を配置し，その固定軸に対して回動自在に設けていたが，上述の通り前記ギア群２０３，４０３からなる多数のギアを前記側板３００に配置しようとすると，前記アイドルギア２０４を別個の固定軸に設けていては，前記ギア群２０３，４０３に含まれるギアの一部の干渉が避けられい恐れがある。これは，前記駆動ベルト４０５を用いて前記側板３００間に必要な枚数を減らした場合でも起こりうる問題である。
そこで，図４及び図５に簡明に示す通り，前記ギア４０３６が固定的に取り付けられるのと同じ前記出力軸４０４に前記アイドルギア２０４を回動自在に設けた。
これにより，前記出力軸４０４が前記アイドルギア２０４の軸を兼ねるので，前記側板３００間に必要な軸の本数を減少させることができ，前記側板３００間でのギアの干渉を抑制することができる。
さらに，前記アイドルギア２０４と前記出力軸４０４の回転方向が同じになるようにすれば，前記アイドルギア２０４を固定軸に取り付ける場合と較べて，前記アイドルギア２０４とその軸との相対的な周速差が小さくなり，前記アイドルギアの磨耗を減少させることもできる。
このように，本実施の形態に係る複写機では，感光体ドラムと現像装置とを含む複数の画像形成ユニットが用紙搬送経路に沿って一列に配設され，支持部材間に取り付けられた駆動系を介して各感光体ドラムに連結された単一の感光体ドラム用駆動源により各感光体ドラムを駆動するタンデム型画像形成装置において，各現像装置のうち一装置については前記駆動系にギア群が用いられず，各現像装置を駆動する単一の現像装置用駆動源に連結された出力軸と当該現像装置の駆動入力部とに前記支持部材間の外側で巻き回された無端状の駆動ベルトが用いられると共に，前記ギア群に含まれるアイドルギアが，前記出力軸に回動自在に設けられるため，前記支持部材間に配置する必要のある軸やギアの数を抑えつつ前記支持部材間に前記ギア群を効率的に配置することが可能となり，各感光体ドラムと各現像装置とをそれぞれ単一の駆動源により駆動しながら，必要な駆動精度を保つことが可能となる。
【００１３】
【実施例】
前記実施の形態では，前記アイドルギア２０４を前記出力軸４０４に回動自在に取り付けた。前記出力軸４０４には，前記アイドルギア２０４の他，前記ギア４０３６しか取り付けられていなかったが，例えば前記出力軸４０４からさらに他の系統に駆動力を出力する必要があれば，前記出力軸４０４の前記側板３００間にある部分に，前記アイドルギア２０４，前記ギア４０３６の他，前記出力軸４０４から駆動力を出力するためのギアを固定的に取り付けるようにしてもよい。
また，前記ギア群２０３，４０３には，前記アイドルギア２０４の他にもアイドルギアが存在する。これらのアイドルギアを，例えば前記側板３００間に配置された軸固定型クラッチの固定軸に回動自在に取り付けるようにしてもよい。軸固定型クラッチの固定軸と前記アイドルギアの固定軸とを別個に設けなければ，それだけ前記側板３００間の空間を効率的に利用することができる。各アイドルギアを前記出力軸と前記軸固定型クラッチの固定軸とに回動自在に取り付ければ最も前記側板間の空間に余裕を確保することができるが，どちらか一方でもよい。
また，前記実施の形態では，前記駆動モータ４００から最も遠い現像装置４ａを駆動ベルト４０５を用いて駆動したが，他の現像装置，例えば現像装置４ｂを駆動ベルト４０５により駆動するようにしてもよい。また，もう一本ベルトを配置することが可能であれば，両方を駆動ベルトにより駆動するようにしてもよい。
また，前記現像装置４ａを駆動ベルト４０５を用いて駆動する代わりに，各感光体ドラム２ａ〜２ｄのうちの一部の感光体ドラム，例えば感光体ドラム２ａを駆動モータ２００に駆動ベルトを用いて連結するようにし，他の装置（感光体ドラム２ｂ〜２ｄ，現像装置４ａ〜４ｄ）をギア群を用いて駆動モータ２００，４００に連結するようにしてもよい。
また，前記実施の形態では，タンデム型のフルカラープリンタについて本発明を適用したが，これに限られるものではなく，タンデム型の他の画像形成装置，例えば複写機などについても本発明を適用することは可能である。
【００１４】
【発明の効果】
以上説明した通り，前記請求項１に記載の画像形成装置によれば，複数配設された現像装置又は感光体ドラムのうち，黒色に対応する一の装置については駆動系にギア群が用いられず，現像装置用駆動源又は感光体ドラム用駆動源に連結された出力軸と当該現像装置又は感光体ドラムの駆動入力部とに支持部材間の外側で巻き回された無端状の駆動ベルトが駆動系に用いられると共に，前記ギア群に含まれるアイドルギアが前記出力軸及び前記支持部材間に配置される軸固定型クラッチの固定軸のいずれか一方又は両方に回動自在に設けられるため，前記支持部材間に配置する必要のある軸やギアの数を抑えつつ前記支持部材間のギアの配置を効率的に行い，各感光体ドラムと各現像装置とをそれぞれ単一の駆動源により駆動しながら，必要な駆動精度を保つことができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係るタンデム型フルカラープリンタの要部となる駆動系の全体構成を示す図。
【図２】図１に示した全体構成のうちのドラム駆動系を抽出した図。
【図３】図１に示した全体構成のうちの現像駆動系を抽出した図。
【図４】図１に示した全体構成のうち特徴的な構成のみを抽出した図。
【図５】図４に示した特徴的な構成をさらに簡素に示した図。
【図６】前記タンデム型フルカラープリンタの全体構成を概略的に示す図。
【図７】前記タンデム型フルカラープリンタの画像形成ユニット周辺の構成を拡大して示した図。
【図８】従来のタンデム型画像形成装置における課題を説明するための図。
【符号の説明】
１…画像形成ユニット
２…感光体ドラム
４…現像装置
２００，４００…駆動モータ
２０３，４０３…ギア群
２０４…アイドルギア
３００…側板
４０４…出力軸
４０５…駆動ベルト[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem image forming apparatus, and more particularly, to a tandem type image forming apparatus in which a plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a sheet conveying path and are mounted between support members. The present invention relates to a tandem-type image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source connected to each photosensitive drum via a system.
[0002]
[Prior art]
In the tandem type color image forming apparatus, an image forming unit including a photosensitive drum and a developing device for each of a plurality of different colors is arranged in a line along a sheet conveying path. When the paper passes through the paper transport path, images corresponding to black, magenta, yellow, and cyan are sequentially transferred to the paper. When the paper passes through the last image forming unit, a color image in which four colors are superimposed is printed on the paper. Formed.
In the tandem-type color image forming apparatus, since the image is formed in this way, a high-speed color image can be output. There is a possibility that the images of the respective colors are shifted on the paper, and an appropriate output cannot be obtained.
For this reason, there are many devices that attempt to obtain high drive accuracy by disposing a separate drive motor for each photosensitive drum. However, providing a separate drive motor increases costs and is not preferable in terms of miniaturization of the device.
In order to reduce the cost, it is preferable to drive each photosensitive drum by a single drive motor, and it is necessary to ensure high drive accuracy. A technique for ensuring high drive accuracy while driving each photosensitive drum by a single drive motor is disclosed in, for example, JP-A-7-209947.
According to the technique described in the above publication, the rotation shaft of a single drive motor and the rotation shaft of each photosensitive drum are connected using a gear. The single drive motor is arranged at the center of four image forming units arranged in a line. The gear attached to the rotation shaft of the single drive motor engages with the photoreceptor gears attached to the rotation shafts of the two photoreceptor drums on both sides to drive the single drive motor. Force is transmitted to both photosensitive drums. The photoreceptor gears of the remaining two photoreceptor drums are connected to the drive motor via photoreceptor gears on both sides of the drive motor and idler gears.
When the single drive motor is disposed at the center of the four image forming units, the number of gears required to connect the rotation shaft of the single drive motor and the rotation shaft of each photosensitive drum is formed. Can be reduced, and various advantages such as suppression of a rotation error can be obtained.
[0003]
[Problems to be solved by the invention]
In order to form each color image on paper by each image forming unit, it is necessary to drive the developing device in addition to driving the photosensitive drum. Although this developing device is also provided for each color, it is preferable that the developing device be driven by a single drive motor like the photosensitive drum in order to reduce costs and downsize the device. In this case, two drive motors are required for the photosensitive drum and the developing device, and a drive motor for driving each photosensitive drum is disposed at the center as in the technique described in the above-mentioned publication. It becomes difficult.
Although it is not impossible to drive all the photosensitive drums and all the developing devices by a single drive motor, the number of rotations and the driving torque of the photosensitive drum and the developing device are different, and the object to be further driven is different. Since the number of times increases, the drive system becomes too complicated, and the cost increases.
Therefore, for example, as shown in FIG. 8, a drive motor 200 for driving each photosensitive drum 2 (2a, 2b, 2c, 2d) and a drive motor for driving each developing device 4 (4a, 4b, 4c, 4d) 400 means that the photosensitive drums 2 or the developing devices 4 arranged in a line must be arranged at a position deviated from the center of the photosensitive drums 2 or the developing devices 4 along the sheet transport path.
If the positions of the single drive motors 200 and 400 for driving the respective photosensitive drums 2 or the respective developing devices 4 are biased with respect to the respective image forming units 1 (1a, 1b, 1c and 1d), four photosensitive drums can be obtained. In the body drums 2a to 2d or the developing devices 4a to 4d, photosensitive drums or developing devices far from the drive motors 200 and 400 are formed. In this case, the required number of gears increases, and the space occupied by the drive system naturally increases.
The shaft of each gear in the drive system is supported by a pair of side plates. However, if the distance between the side plates is increased to accommodate a large number of gears between the side plates, uneven rotation of the gears is likely to occur. However, there is a problem that the image is adversely affected, so that the space occupied by the drive system cannot be expanded without limitation.
Therefore, for example, if the drive system of the photosensitive drum is disposed first between the side plates, it is not possible to provide much space in the space between the side plates, and further, it is attempted to arrange the drive system for the developing device between the side plates. Then, it is difficult to arrange the shafts of the respective gears between the side plates, so that the positions of some of the gears interfere with each other, and some of the gears do not fit between the side plates, and as a result, each of the photosensitive drums In addition, all the driving systems of the respective developing devices cannot be arranged.
In order to solve the problems in the prior art, the present invention has improved a tandem type image forming apparatus, and some of a plurality of developing devices or photosensitive drums are connected via a gear group. And an output shaft connected to the drive source for the developing device or the photosensitive drum, and a drive input portion for the developing device or the photosensitive drum. And an endless drive belt wound around the outer side between the support members of the gear group, and an idle gear included in the gear group is fixed to a shaft disposed between the output shaft and the support member. By rotatably providing one or both of the fixed shafts of the mold clutch, the number of shafts and gears that need to be arranged between the support members can be reduced, and the arrangement of the shafts and gears between the support members can be efficiently performed. Done While the photosensitive drum and the developing devices driven by each single driving source, it is an object to provide a tandem type image forming apparatus which can maintain the driving accuracy required.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a sheet transport path and attached between support members. A single developing device for driving each developing device in a tandem image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source connected to each photosensitive drum via a drive system Drive source for At least one of the developing device drive source or the photosensitive drum drive source, the output shaft of which is connected in the same direction as the longitudinal direction of the developing device and the photosensitive drum, is provided with the plurality of image forming units. One corresponding to the black color provided at the other end of the plurality of image forming units and provided at the other end of the plurality of image forming units. Developing device or One Photoconductor drum of The drive system As , The driving source for the developing device or the photosensitive drum Drive source Output shaft connected to One Developing device or One An endless drive belt wound around the drive input portion of the photosensitive drum and between the support members Is used , Excluding one developing device or one photosensitive drum corresponding to the black color Remaining the developing device and the photosensitive drum of The drive system As , Gear group Is used Connecting each developing device or each photosensitive drum to the driving source for the developing device or the driving source for the photosensitive drum And A tandem image wherein an idle gear included in the gear group is rotatably provided on one or both of a fixed shaft of a fixed shaft clutch disposed between the output shaft and the support member. It is configured as a forming device.
According to the first aspect of the present invention, a plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a paper transport path, and each photosensitive drum is connected via a drive system mounted between support members. In a tandem-type image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source connected to the photosensitive drum, each developing device or each photosensitive drum is , One corresponding to black No gear group is used in the drive system, and the output shaft connected to the developing device drive source or the photosensitive drum drive source and the drive input unit of the developing device or the photosensitive drum are not used. An endless drive belt wound around the outside between the support members is used. An idle gear included in the gear group is rotatably provided on one or both of a fixed shaft of a fixed shaft clutch disposed between the output shaft and the support member.
For example, when the driving source for the developing device and the developing device farthest from the driving source for the developing device are connected via gears, many gears are required, and it is difficult to ensure the driving accuracy. By connecting via a belt, the number of shafts and gears that need to be arranged between the support members can be reduced, and the required driving accuracy can be relatively easily secured. The idle gear included in the gear group is provided with a separate fixed shaft for attachment between the support members. However, by attaching the fixed shaft to the output shaft or the fixed shaft of the fixed shaft clutch, The number of shafts of each gear can be reduced to prevent each gear from interfering.
This makes it possible to efficiently arrange the gear group between the support members while suppressing the number of shafts and gears that need to be arranged between the support members. The required driving accuracy can be maintained while each is driven by a single driving source.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention.
FIG. 1 is a diagram showing the overall configuration of a drive system that is a main part of a tandem-type full-color printer according to an embodiment of the present invention, and FIG. 2 is an illustration of a drum drive system extracted from the overall configuration shown in FIG. 3, FIG. 3 is a diagram in which the developing drive system is extracted from the entire configuration shown in FIG. 1, FIG. 4 is a diagram in which only a characteristic configuration is extracted from the entire configuration shown in FIG. 1, and FIG. 4 is a diagram more simply showing the characteristic configuration shown in FIG. 4, FIG. 6 is a diagram schematically showing the entire configuration of the tandem type full color printer, and FIG. 7 is a configuration around the image forming unit of the tandem type full color printer. It is the figure which expanded and shown.
[0006]
A tandem-type full-color printer according to the present embodiment embodies the image forming apparatus according to the present invention. First, the overall configuration of the tandem-type full-color printer will be schematically described with reference to FIGS.
In the main body of the tandem-type full-color printer, four image forming units 1 (1a to 1d) are arranged in a line along a sheet transport path. Each of the image forming units 1 (1a to 1d) is in charge of forming images of four different colors (black, magenta, yellow, and cyan), and all have the same configuration.
For example, the image forming unit 1 (1a to 1d) includes a photosensitive drum 2 (2a to 2d), a transfer roller 3 (3a to 3d), a developing device 4 (4a to 4d), an exposure device 5 (5a to 5d), A charger 6 (6a to 6d), a cleaning device 7 (7a to 7d), and the like are provided (for the image forming units 1b to 1d, reference numerals of these elements are partially omitted).
An endless transfer belt 24 is wound around the transfer rollers 3a to 3d of the image forming units 1a to 1d, the driving roller 21, the driven roller 22, and the auxiliary roller 23 disposed before and after the transfer rollers 3a to 3d. The transfer belt 24 is rotated in the direction of arrow Y1 by the drive of the drive roller 21. For each of the image forming units 1a to 1d, the peripheral surface of the transfer belt 24 on the side of each of the image forming units 1a to 1d becomes a sheet transport path.
A registration roller 25 is provided on the upstream side of the transfer belt 24, and a fixing roller 26 is provided on the downstream side. Two paper cassettes 27a and 27b are provided at a lower portion of the main body, and paper is discharged at an upper portion of the main body. Paper trays 28 are provided, respectively.
[0007]
The image forming operation of the tandem-type full-color printer having the above-described schematic configuration will be briefly described. First, the paper conveyed from the paper cassette 27a or 27b through the paper feed path 29 as indicated by the arrow Y2 by the registration rollers 25. Are sent to the image forming unit 1a in synchronization with the image forming timing. The sheet sent from the registration roller 25 is inserted into an opposing portion (hereinafter, a transfer portion) of the image forming unit 1a between the photosensitive drum 2a and the transfer roller 3a with its leading end along the transfer belt 24. Is done. While being conveyed by the transfer belt 24, the toner image (for example, a black image) formed on the surface of the photosensitive drum 2a is first transferred by the developing device 4a to the sheet inserted into the transfer portion of the image forming unit 1a. The paper is sequentially conveyed by the transfer belt 24 through the transfer sections of the image forming units 1a to 1d, so that four color toner images are sequentially superimposed and transferred on the paper, and a full-color image is formed on the paper. You. The sheet that has passed through each of the image forming units 1a to 1d is conveyed along the sheet discharge path 30 as indicated by an arrow Y3 and discharged onto the sheet discharge tray 28 after the transfer image is fixed by the fixing roller 26.
[0008]
Next, the details of the main part of the tandem type full color printer according to the present embodiment will be described.
First, reference numerals given to FIGS. 1 to 5 will be described.
1 and 2, reference numeral 200 denotes a drive motor for driving the photosensitive drum (an example of a drive source for the photosensitive drum); 201, a rotating shaft of the drive motor 200; and 202 (202a to 202d), the photosensitive drum. A drive input gear 203 attached to the rotation shaft of each of the drums 2a to 2d is a gear group for connecting the rotation shaft 201 and the drive input gear 202.
1 and 3, reference numeral 400 denotes a driving motor for driving the developing device (an example of a driving source for the developing device), 401 denotes a rotating shaft of the driving motor 400, and 402 (402a to 402d) denote the developing device. A drive input gear 403 attached to each of the rotation shafts 4a to 4d is a gear group for connecting the rotation shaft 401 and the drive input gears 402b to 402d.
1 to 5, reference numeral 300 denotes a side plate (an example of a support member) for supporting the shafts of the respective gears included in the gear group 203 and the gear group 403. An output shaft 405 connected to the gears 4031 to 4036 of the gear group 403 via the gears 403 to 4036 in this order includes an extension 404 </ b> E extended to the outside of the output shaft 404 between the side plates 300 and a rotation shaft of the drive input gear 402 a ( An example of a drive input unit) An endless drive belt 204 wound around 4021a is an idle gear connected to the rotating shaft 201 through gears 2031 to 2034 of the gear group 203 in this order. The idle gear 204 is connected to the drive input gear 202d through a gear 2035 of the gear group 203.
[0009]
As shown in FIG. 2, the tandem type full-color printer according to the present embodiment includes a gear group (part of the drive system) 203 in which the four photosensitive drums 2 a to 2 d are mounted between the side plates 300. It is the same as the conventional one in that it is driven only by the drive motor 200 connected to the drive input gears 202a to 202d of the respective photosensitive drums 2a to 2d via the photoconductor drums 2a to 2d.
More specifically, the four photosensitive drums 2 a ~ 2 the photosensitive drum of d 2 The drive input gear 202a is connected to the rotating shaft 201 of the drive motor 200 via gears 2036, 2037, 2038, 2039, 2040, and 2041 in this order. Also, the photosensitive drum 2 The drive input gear 202b of b is connected to the rotating shaft 201 of the drive motor 200 and gears 2031, 2032, 2042, 2043, 2044 and 2045 in this order. Also, the photosensitive drum 2c The drive input gear 202c is connected to the rotating shaft 201 of the drive motor 200 and gears 2031, 2032, 2033, 2034, 2046, 2047 in this order. Also, the photosensitive drum 2 d of the drive input gear 202d are gears 2031, 2032, 2033 2034 The idle gear 204 and the gear 2035 are connected in this order.
[0010]
On the other hand, the tandem type full-color printer according to the present embodiment is different from the conventional one in that the developing devices 4a to 4d are driven only by the drive motor 400 and the The device 4a (an example of a part of the developing device) is wound around the output shaft 404 connected to the drive motor 400 and the rotating shaft 4021a for driving input of the developing device 4a outside the side plate 300. The drive belt 405 With respect to the remaining developing devices 4b to 4d, the developing devices 4a to 4d are connected to the drive motor 400 via the gear group 403 of the gear groups 203 and 403, and the gear group is connected. The point that the idle gear 204 included in the gear group 203 among the gears 203 and 403 is rotatably provided on the output shaft 404.
In the tandem type full-color printer according to the present embodiment, each of the developing devices 4a to 4d is driven only by the drive motor 400. The drive motor 400 is separate from the drive motor 200. In order to make the distance between both drive motors 200, 400 and each driven body substantially equal, the drive motors 200, 400 are not arranged at the center of each of the image forming units 1a to 1d, for example, as shown in FIG. Is located at a position deviated from the center. Therefore, the developing device 4a of the four developing devices 4a to 4d is considerably far from the drive motor 400.
As for the three developing devices 4b to 4d whose distances from the drive motor 400 are relatively short, similarly to the drive system of the photosensitive drums 1a to 1d, the drive input gears 402b to 402d of the respective developing devices 4b to 4d are used. The driving motor 400 is connected via a gear.
More specifically, as shown in FIG. 3, the drive input gear 402b of the developing device 4b includes a rotating shaft 401 of the drive motor 400 and gears 4037, 4038, 4039, 4040, 4041, 4042, 4043, 4044. 4045 are connected in this order. The drive input gear 402c of the developing device 4c is connected to the rotating shaft 401 of the drive motor 400 via gears 4037, 4038, 4039, 4046, and 4047 in this order. The drive input gear 402d of the drive input gear 4d of the developing device 4d is connected to the rotating shaft of the drive motor 400 via gears 4037, 4038, 4039, 4046, 4048, 4049, and 4050 in this order.
[0011]
The three developing devices 4b to 4d correspond to three colors of magenta, yellow, and cyan. However, when performing monochrome printing, it is not necessary to drive these developing devices 4b to 4d. For this reason, a clutch is provided between the gear 4037 and the gear 4038. By turning on and off the clutch, the operation for monochrome printing and the operation for color printing are switched.
With respect to these three developing devices 3b to 3d, the developing device 4a far from the drive motor 400 is connected to the drive motor 400 via the drive belt 405.
As shown in FIGS. 1, 3, and 4, the output shaft 404 is connected to the rotating shaft 401 of the drive motor 400 via gears 4031, 4032, 4033, 4034, 4035, and 4036.
One shaft end of the output shaft 404 is disposed outside the side plate 300, and an endless drive belt 405 is wound around an extension 404E of the output shaft 404 outside the side plate 300. Have been.
The drive belt 405 is also wound around a rotation shaft 4021a of a drive input gear 402a of the developing device 4a, and is connected to the output shaft 404 of the developing device 4a via the gears 4031 to 4036 and the drive belt 405. Drive input gear 4 The drive force of the drive motor 400 is transmitted to the rotary shaft 4021a of the drive motor 02a.
As described above, the driving belt 405 is wound around the output shaft 404 and the rotation shaft 4021a outside the side plate 300, and the developing device 4a is driven by the driving motor 400. There is no need to arrange many shafts and gears between the side plates 300 necessary for connecting the drive motor 400 and the drive motor 400 with gears. Interference can be suppressed. Considering that about nine gears are required to drive the developing device 4b closer to the drive motor 400 than the developing device 4a as described above, the developing device 4a is driven by the drive belt 405. The number of shafts and gears that need not be disposed between the side plates 300 by being connected to the drive motor 400 is remarkable. Further, since a large number of gears are not used to drive the developing device 4a farthest from the drive motor 400, even if the drive motor 400 is not disposed at the center of the image forming unit 1, good driving accuracy can be obtained. Can be secured. The drive error caused by the drive belt 405 is considerably smaller than the case where errors are accumulated over a large number of gears.
The reason that only the developing device 4a is driven by the drive belt 405 is that the developing device 4a is farthest from the drive motor 400, but the developing device 4a corresponds to black. There is also a reason that there is a case where a single use is performed at the time of monochrome printing. As described above, if the connecting system is different between the developing device 4a and the developing devices 4b to 4d, switching between monochrome printing and color printing is easy.
[0012]
In the tandem-type full-color printer according to the present embodiment, the drive motor 200 and the photosensitive drum 200 are arranged to efficiently dispose the gear groups 203 and 403 between the side plates 300. 2d Drive input gear 2 The idle gear 204 of the group of gears used to connect the drive belt 02d to the output shaft 404 is rotatably provided on the output shaft 404 which rotates to drive the drive belt 405.
Only the gear 4036 shown in FIGS. 1, 3, 4, and 5 is originally attached to the output shaft 404. The gear 4036 is fixedly attached to the output shaft 404, and as shown in FIG. 400 rotation axes The driving force transmitted from 401 through the gears 4031 to 4035 is transmitted to the output shaft 404, and the output shaft 404 is rotated.
As described above, the idle gear 204 receives the driving force from the driving motor 200 via the gears 2031 to 2034 and transmits the driving force to the driving input gear 202d via the gear 2035 (mainly, FIG. 4). reference). Conventionally, the idle gear 204 has a separate fixed shaft disposed between the side plates 300 and is provided rotatably with respect to the fixed shaft. However, as described above, a large number of gears including the gear groups 203 and 403 are used. If the idle gear 204 is provided on a separate fixed shaft when it is arranged on the side plate 300, interference of a part of the gears included in the gear groups 203 and 403 may be unavoidable. This is a problem that may occur even when the required number of sheets between the side plates 300 is reduced using the driving belt 405.
Therefore, as briefly shown in FIGS. 4 and 5, the idle gear 204 is rotatably provided on the output shaft 404 on which the gear 4036 is fixedly attached.
As a result, the output shaft 404 also serves as the shaft of the idle gear 204, so that the number of shafts required between the side plates 300 can be reduced, and interference of the gears between the side plates 300 can be suppressed. .
Furthermore, if the rotation direction of the idle gear 204 and the output shaft 404 are made to be the same, the relative circumference of the idle gear 204 and its shaft is smaller than when the idle gear 204 is mounted on a fixed shaft. The speed difference is reduced, and the wear of the idle gear can be reduced.
As described above, in the copying machine according to the present embodiment, the plurality of image forming units including the photosensitive drums and the developing devices are arranged in a line along the paper transport path, and the drive system mounted between the support members is provided. In a tandem type image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source connected to each photosensitive drum via a photoconductive drum, one of the developing devices includes a gear group in the drive system. Is not used, and an endless drive wound outside the support member around an output shaft connected to a single developing device drive source for driving each developing device and a drive input portion of the developing device. Since a belt is used and an idle gear included in the gear group is rotatably provided on the output shaft, the number of shafts and gears that need to be arranged between the support members is reduced while the number of shafts and gears between the support members is reduced. The said gear The becomes possible to efficiently arranged, while the photosensitive drum and the developing units and was driven by a respective single drive source, it is possible to keep the driving accuracy required.
[0013]
【Example】
In the embodiment, the idle gear 204 is rotatably attached to the output shaft 404. Only the gear 4036 was attached to the output shaft 404 in addition to the idle gear 204. For example, if it is necessary to output a driving force from the output shaft 404 to another system, the output shaft 404 In addition to the idle gear 204 and the gear 4036, a gear for outputting a driving force from the output shaft 404 may be fixedly attached to a portion between the side plates 300.
The gear groups 203 and 403 include an idle gear in addition to the idle gear 204. These idle gears may be rotatably attached to a fixed shaft of a fixed shaft clutch disposed between the side plates 300, for example. If the fixed shaft of the fixed shaft clutch and the fixed shaft of the idle gear are not separately provided, the space between the side plates 300 can be used more efficiently. If each idle gear is rotatably mounted on the output shaft and the fixed shaft of the fixed shaft clutch, the space between the side plates can be secured most, but either one may be used.
In the embodiment, the developing device 4a farthest from the drive motor 400 is driven by using the drive belt 405. However, another developing device, for example, the developing device 4b may be driven by the drive belt 405. . If another belt can be arranged, both may be driven by a drive belt.
Further, instead of driving the developing device 4a using the drive belt 405, a part of the photosensitive drums 2a to 2d, for example, the photosensitive drum 2a is driven by using a drive belt for the drive motor 200. Alternatively, other devices (photosensitive drums 2b to 2d, developing devices 4a to 4d) may be connected to the drive motors 200 and 400 using a group of gears.
In the above embodiment, the present invention is applied to a tandem-type full-color printer. However, the present invention is not limited to this, and the present invention may be applied to other tandem-type image forming apparatuses such as a copying machine. Is possible.
[0014]
【The invention's effect】
As described above, according to the image forming apparatus of the first aspect, the image forming apparatus includes a plurality of developing devices or photosensitive drums. , One corresponding to black In this device, no gear group is used in the drive system, and a support member is provided between the output shaft connected to the drive source for the developing device or the drive source for the photosensitive drum and the drive input portion of the developing device or the photosensitive drum. An endless drive belt wound around the outside is used for a drive system, and an idle gear included in the gear group is one of a fixed shaft of a fixed shaft clutch disposed between the output shaft and the support member. Since one or both are rotatably provided, the arrangement of gears between the support members is efficiently performed while suppressing the number of shafts and gears that need to be arranged between the support members. The required driving accuracy can be maintained while each of the developing device and the developing device is driven by a single driving source.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of a drive system that is a main part of a tandem-type full-color printer according to an embodiment of the present invention.
FIG. 2 is a diagram showing a drum drive system extracted from the overall configuration shown in FIG. 1;
FIG. 3 is a diagram in which a development drive system in the entire configuration shown in FIG. 1 is extracted.
FIG. 4 is a diagram in which only a characteristic configuration is extracted from the entire configuration shown in FIG. 1;
FIG. 5 is a diagram more simply showing the characteristic configuration shown in FIG. 4;
FIG. 6 is a diagram schematically showing an entire configuration of the tandem type full-color printer.
FIG. 7 is an enlarged view showing a configuration around an image forming unit of the tandem type full color printer.
FIG. 8 is a diagram illustrating a problem in a conventional tandem image forming apparatus.
[Explanation of symbols]
1. Image forming unit
2. Photoconductor drum
4. Developing device
200, 400 ... drive motor
203, 403: gear group
204 ... idle gear
300 ... side plate
404 ... Output shaft
405: drive belt

Claims

A plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a sheet transport path, and a single image forming unit connected to each photosensitive drum via a drive system mounted between support members. In a tandem image forming apparatus in which each photosensitive drum is driven by a photosensitive drum drive source,
A single developing device drive source for driving each developing device;
At least one of the developing device drive source or the photosensitive drum drive source, the output shaft of which is connected in the same direction as the longitudinal direction of the developing device and the photosensitive drum, is provided with the plurality of image forming units. At one end in the direction
As the drive system of one of the developing device or the one photosensitive drum corresponding to the black disposed at the other end of said plurality of image forming units, coupled to the developing device drive source or the photosensitive drum drive source with been formed by the endless drive belt which is wound around the outside between the support member used in the driving force input portion of the output shaft and the photosensitive drum of the developing device or the one of the one,
As the remaining of the developing device and the drive system of the photosensitive drum but one of the developing device or the one photosensitive drum corresponding to the black, will be gear group is used,
Connecting each developing device or each photosensitive drum with the driving source for the developing device or the driving source for the photosensitive drum , and
A tandem image forming apparatus wherein an idle gear included in the gear group is rotatably provided on one or both of a fixed shaft of a fixed shaft clutch disposed between the output shaft and the support member. apparatus.