JP2004163754A - Transfer belt unit and image forming apparatus using the unit - Google Patents

Transfer belt unit and image forming apparatus using the unit Download PDF

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JP2004163754A
JP2004163754A JP2002331028A JP2002331028A JP2004163754A JP 2004163754 A JP2004163754 A JP 2004163754A JP 2002331028 A JP2002331028 A JP 2002331028A JP 2002331028 A JP2002331028 A JP 2002331028A JP 2004163754 A JP2004163754 A JP 2004163754A
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transfer belt
guide member
belt unit
transfer
intermediate transfer
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JP4171639B2 (en
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Takashi Seto
隆 瀬戸
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Ricoh Co Ltd
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Ricoh Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer belt unit which prevents image deterioration caused by vibration or sudden movement of an image carrier or a transfer belt unit, and to provide an image forming apparatus using the unit. <P>SOLUTION: A primary transfer device 3 as the transfer belt unit transfers toner images formed on photoreceptors 17Y, M, C, and K as image carriers onto an intermediate transfer belt 12 as an endless belt which is stretched by support rollers 10, 11, and 15 as support members and rotationally driven. In the primary transfer device 3, a guide member 13 having a fixed width is provided near one of widthwise ends of the intermediate transfer belt 12 and over the circumference of the surface of the belt 12. The intermediate transfer belt 12 is rotated while the guide member 13 is restricted in the widthwise position relative to the reference end face A of a black photoreceptor 17K and the reference end face B of a yellow photoreceptor 17Y as guide parts. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、複写機、ファクシミリ、プリンター等の電子写真方式の画像形成装置及び該装置に用いられる転写ベルトユニットに関するものである。詳しくは、像担持体上に形成されたトナー像を、複数の支持部材に張架されて回転駆動される無端ベルト上、または、無端ベルトに担持搬送される転写体上に転写する転写ベルトユニット及び該ユニットを用いた画像形成装置に関するものである。
【０００２】
【従来の技術】
従来、上記画像形成装置では、中間転写ベルトや転写搬送ベルト等の無端ベルトをもちいた転写装置が実用化されている。無端ベルトを駆動する駆動方法としては、無端ベルトを駆動ローラおよび従動ローラに架け渡して張架して、駆動ローラを回転駆動することで無端ベルトを回転駆動する。しかし、このような駆動方法では、各ローラの設置の際の僅かな傾斜や、無端ベルトの回転中の局部的な摩擦等によって、無端ベルトが蛇行して横方向に偏位してしまう。このため、転写位置が左右にずれてしまうという問題がある。
【０００３】
このような問題を解決するため、無端ベルトの両側縁に移動方向に沿って突起状に形成された蛇行防止のガイドを備えた無端ベルトが提案されている（例えば、特許文献１参照）。この無端ベルトでは、両側縁のガイドの端面が各ローラの端面に摺接して、無端ベルトが幅方向に偏位することを規制する。これにより、無端ベルトの蛇行を低減する。
【０００４】
図１２は、上記特許文献１で開示された無端ベルトの両側縁に移動方向に沿って蛇行防止のガイドを固定した装置の概略構成を示す上面図である。図１２において、ローラ１０，１１を両側縁のガイド４０の間に収めるためには、ガイド４０の内側の側面間の距離Ｍを、ローラ幅Ｌ以上にすることが必要である。一方、ガイド４０の内側の側面が各ローラ１０，１１の側面に摺接するよう、ガイド４０の内側の側面とローラ１０，１１の側面との隙間はできるだけ少なくしたい。
【０００５】
上記無端ベルト１２の幅は転写体の幅よりも広くする必要があり、通常３００ｍｍ以上となる。このような無端ベルト１２の両端縁に、ガイド４０を貼り付けまたは溶着等で固定するが、無端ベルトの幅が広く、ガイド４０の内側の側面間の距離Ｂの寸法管理が難しい。そこで、一般的にはローラ幅Ａより１〜２ｍｍ大きく余裕を持った距離Ｂで貼り付けまたは溶着している。この余裕分は無端ベルト１２とローラ１０，１１との隙間となり、隙間の分だけ走行中の無端ベルト１２は走行方向と直角方向に蛇行してしまう虞がある。
【０００６】
このような駆動方法を用いた無端ベルトの転写装置を、複数の像担持体を一列に配置するタンデム型のカラー画像形成装置に用いると、上記余裕分による蛇行が各像担持体間で転写ずれを引き起こして、色ずれを発生させる。特に、近年実用化されているデジタルカラー画像形成装置に用いると、主走査色ずれとなって顕れる。また、デジタルカラー画像形成装置では高密度化が進んでいるが、６００ＤＰＩ以上の書き込み密度では、上記主走査色ずれが著しい画質劣化を引き起こしてしまう。
【０００７】
そこで、本出願人は、無端ベルトの裏面中央近傍にガイド部材を設け、このガイド部材を無端ベルトの支持部材に設けた係合部に係合させるカラー画像形成装置を提案した（特願２００２−７９４５１号）。このカラー画像形成装置は、無端ベルトの蛇行を低減して転写ずれを防止し、主走査色ずれの少ないカラー画像を形成することができる。また、このカラー画像形成装置は、従来無端ベルトの両端縁にガイド部材を二箇所固定するものに較べ、中央近傍にガイド部材を一箇所固定するのみなので、寸法管理が容易であり、ガイド部材の端面と係合部の端面との隙間を小さく抑えている。
【０００８】
【特許文献１】
実開平５−７５２６４号公報（第１頁、第２図）
【０００９】
【発明が解決しようとする課題】
無端ベルトを用いた転写装置はメンテナンスやジャム処理を考慮して、通常画像形成装置本体の手前方向や上下方向に一体で移動できるように、感光体とは別のユニットとして構成されている。このため、転写装置と感光体とはそれぞれ別々に振動する。また、ベルト張架ローラと軸受とのガタや、感光体と軸受とのガタなどによって、無端ベルトと感光体とはそれぞれ別々に軸方向（主走査方向）に移動する場合もある。すると、転写装置で無端ベルトの蛇行を抑えて回転移動したとしても、無端ベルトと感光体との間で互いに主走査方向の位置ずれが生じ、転写画像の直線性が損なわれて画像劣化が生じる。特に、カラー画像ではモノカラー画像に比べて、主走査色ずれとなってより目立つ画像劣化を生じる。このような画像劣化は、以上の構成に限らず、無端ベルトをローラで張架して回転駆動し、感光体上の画像を無端ベルト上、または、無端ベルトに担持搬送される転写体上に転写する構成であれば、生じ得る。
【００１０】
本発明は、上記背景に鑑みなされたものであり、その目的とするところは、像担持体や転写ベルトユニットの振動やガタに伴う画像劣化を防止することができる転写ベルトユニット及び該ユニットを用いた画像形成装置を提供することである。
【００１１】
【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、像担持体上に形成されたトナー像を、複数の支持部材に張架されて回転駆動される無端ベルト上、または、無端ベルトに担持搬送される転写体上に転写する転写ベルトユニットにおいて、上記無端ベルトの幅方向の端部のうち少なくともいずれか一方の近傍に表面全周にわたって一定幅のガイド部材を設け、該無端ベルトは該ガイド部材が上記像担持体に設けられたガイド部で幅方向の位置を規制されながら回転駆動されることを特徴とするものである。
請求項２の発明は、請求項１の転写ベルトユニットにおいて、上記ガイド部材を上記無端ベルトの幅方向の端部のうちいずれか一方の近傍に設け、かつ、上記無端ベルトに対して該ガイド部材が設けられた幅方向の端部と反対側の端部方向に寄せる力を付与するベルト寄せ手段を設けたことを特徴とするものである。
請求項３の発明は、請求項１又は２の転写ベルトユニットにおいて、複数の像担持体を上記無端ベルトの回転移動方向に並べて該無端ベルトに対向させ、該複数の像担持体のうち、該無端ベルトの回転移動方向に対して最上流側と最下流側との少なくとも２つの像担持体に上記ガイド部を設けたことを特徴とするものである。
請求項４の発明は、請求項２の転写ベルトユニットにおいて、上記ガイド部材が設けられた上記無端ベルトの幅方向の端部は、上記像担持体への作像基準位置側の端部であることを特徴とするものである。
請求項５の発明は、請求項２又は４の転写ベルトユニットにおいて、上記ガイド部材を設けた上記無端ベルトの幅方向の端部側から、転写ベルトユニットを上記像担持体に対して脱着可能に構成したことを特徴とするものである。
請求項６の発明は、請求項２、４又は５の転写ベルトユニットにおいて、上記ベルト寄せ手段による上記無端ベルトの幅方向の張力を解除する張力解除手段を設けたことを特徴とするものである。
請求項７の発明は、請求項６の転写ベルトユニットにおいて、上記ガイド部材と上記ガイド部とを離間させる離間手段を設けたことを特徴とするものである。請求項８の発明は、請求項２、４、５、６又は７の転写ベルトユニットにおいて、上記ベルト寄せ手段を、上記無端ベルトの上記ガイド部材を設けた端部と反対側の端部の裏面近傍に全周にわたって設けられた張力受け部材と、上記像担持体に対向する転写部材の同軸上に配設され軸方向に移動可能な該転写部材と略同一径であって、該張力受け部材に接触して張力を付与する張力付与部材と、該張力付与部材に該張力受け部材側への付勢力を付与する付勢部材とを用いて構成したことを特徴とするものである。
請求項９の発明は、請求項８の転写ベルトユニットにおいて、上記張力付与部材を金属材料に比べ摺動性の良い材料を用いて構成したことを特徴とするものである。
請求項１０の発明は、請求項８又は９の転写ベルトユニットにおいて、上記ガイド部材が上記ガイド部に当接した状態で、該ガイド部材が設けられた側の上記転写部材の端面の位置が、該ガイド部材の幅方向外側の端部と同じ位置、または、該端部よりも外側の位置にくるように、該転写部材の長さを設定したことを特徴とするものである。
請求項１１の発明は、請求項８、９又は１０の転写ベルトユニットにおいて、上記ガイド部材が上記ガイド部に当接した状態で、上記張力受け部材が設けられた側の上記像担持体の端面の位置が、該張力受け部材の幅方向外側の端部と同じ位置、または、該端部よりも外側の位置にくるように、該像担持体の長さを設定したことを特徴とするものである。
請求項１２の発明は、請求項８、９、１０又は１１の転写ベルトユニットにおいて、上記転写部材の上記像担持体の作像範囲に対応した部分の表面に弾性部材を設けたことを特徴とするものである。
請求項１３の発明は、請求項２、４、５、６又は７の転写ベルトユニットにおいて、上記ベルト寄せ手段を、上記支持部材の少なくとも１つを上記無端ベルトの回転移動方向と直交する方向に対して斜めに配設することにより、もしくは、上記支持部材の少なくとも１つを直径が変化するテーパローラを用いて構成したことを特徴とするものである。
請求項１４の発明は、請求項１、２、３、４、５、６、７、８、９、１０、１１、１２又は１３の転写ベルトユニットにおいて、上記ガイド部が上記ガイド部材と勘合する溝であることを特徴とするものである。
請求項１５の発明は、請求項１、２、３、４、５、６、７、８、９、１０、１１、１２、１３又は１４の転写ベルトユニットにおいて、上記ガイド部材と上記ガイド部の少なくとも一方に面取りを施したことを特徴とするものである。
請求項１６の発明は、請求項１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４又は１５の転写ベルトユニットにおいて、上記ガイド部材の表面に等ピッチのマーキングと、該マーキングを検出する検出手段と、上記無端ベルトの回転駆動を制御する回転駆動制御手段とを備え、該検出手段により検出された結果に基づき無端ベルトの走行速度を算出し、該算出された走行速度に基づき走行速度が一定になるよう回転駆動制御手段により無端ベルトの回転駆動を制御することを特徴とするものである。
請求項１乃至１６の転写ベルトユニットによれば、無端ベルトの幅方向端部のうち少なくともいずれか一方の端部に設けられたガイド部材が、像担持体に設けられたガイド部で幅方向の位置が規制される。そして、無端ベルトが回転駆動されると、ガイド部材はガイド部に摺動しながら移動し、該無端ベルトは像担持体を基準として幅方向（主走査方向）の位置が規制される。これにより、幅方向では無端ベルトは像担持体に追従し、該無端ベルトと該像担持体との幅方向の相対的位置関係は一定で変化せず、転写ベルトユニットや該像担持体の振動やガタがあっても影響を受け難い。よって、転写画像の直線性を損なうことがなく、画像劣化を防ぐことができる。
また、上記目的を達成するために、請求項１７の発明は、像担持体上に潜像を形成する潜像形成手段と、該像担持体上の静電潜像をトナー像化する現像手段と、該像担持体上に形成されたトナー像を、複数の支持部材に張架されて回転駆動される無端ベルト上、または、無端ベルトに担持搬送される転写体上に転写する転写手段とを備えた画像形成装置において、上記転写手段として、請求項１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４、１５又は１６に記載のいずれかの転写ベルトユニットを用いることを特徴とするものである。請求項１８の発明は、請求項１７の画像形成装置において、上記潜像形成手段がデジタル書込み手段を備えたことを特徴とするものである。
請求項１７乃至１８の画像形成装置によれば、転写ベルトユニット及び像担持体の振動やガタの影響を受け難いので、転写画像の直線性を損なうことがなく、画像劣化を防ぐことができる。
【００１２】
【発明の実施の形態】
以下、本発明を画像形成装置であるタンデム型間接転写方式のデジタル複写機（以下、複写機という）に適用した一実施形態について説明する。
まず、本実施形態に係る複写機の全体的な構成について説明する。図１は、本実施形態に係る複写機の概略構成図である。この複写機は、複写装置本体１００、この複写機本体を載せる給紙テーブル２００、複写装置本体上に取り付けるスキャナ３００、さらにその上に取り付ける原稿自動搬送装置（ＡＤＦ）４００から主に構成されている。
【００１３】
複写装置本体１００には、中央に、無端の中間転写ベルト１２を設ける。この中間転写ベルト１２を、支持部材としての支持ローラ１０，１１，１５に掛け回して図中時計回り方向に回転搬送可能とする。中間転写ベルト１２の上方には、その搬送方向に沿って、イエロー，マゼンタ，シアン，ブラックの４つの画像形成手段を横に並べて配置してタンデム画像形成装置を構成する。そのタンデム画像形成装置の上方には、デジタル書き込み装置５を設ける。
【００１４】
中間転写ベルト１２の内部には、中間転写ベルト１２を挟んで感光体１７Ｙ，Ｍ，Ｃ，Ｋに押し当てる１次転写ローラ１８Ｙ，Ｍ，Ｃ，Ｋを配設し、１次転写装置３を構成する。また、中間転写ベルト１２を挟んでタンデム画像形成装置と反対の側には、２次転写装置７を備える。２次転写装置７は、２つのローラ３１、３２間に、無端ベルトである２次転写ベルト３０を掛け渡して構成し、中間転写ベルト１２上の画像をシートに転写する。また、２本の支持ローラ１１，１５の間に、２次転写後に中間転写ベルト１２上に残留する残留トナーを除去するクリーニングブレード２３を備えた中間転写体クリーニング装置２２を設ける。また、２次転写装置７の横には、シート上の転写画像を定着する定着装置８を設ける。この２次転写装置７には、画像転写後のシートをこの定着装置８へと搬送するシート搬送機能も備えてなる。
【００１５】
上記構成の複写機では、スキャナ３００を駆動し、原稿内容を読み取る。また、不図示の駆動モータで支持ローラ１０を回転駆動して支持ローラ１１，１５を従動回転し、中間転写ベルト１２を回転駆動する。同時に、個々の画像形成手段でその感光体１７Ｙ，Ｍ，Ｃ，Ｋを回転して各感光体上にそれぞれ、イエロー，マゼンタ，シアン，ブラックの単色画像を形成する。そして、中間転写ベルト１２を回転駆動して搬送するとともに、それらの単色画像を順次転写して中間転写ベルト１２上に合成カラー画像を形成する。一方、給紙テーブル２００では給紙カセットからシートを繰り出し、複写装置本体１００内の給紙路に搬送する。そして、中間転写ベルト１２上の合成カラー画像にタイミングを合わせて、中間転写ベルト１２と２次転写装置７との間にシートを送り込み、２次転写装置７で転写してシート上にカラー画像を記録する。画像転写後のシートは、２次転写装置７で搬送して定着装置８へと送り込み、定着装置８で熱と圧力とを加えて転写画像を定着して、機外へ排出する。一方、画像転写後の中間転写ベルト１２は、中間転写体クリーニング装置２２で、画像転写後に中間転写ベルト１２上に残留する残留トナーを除去し、タンデム画像形成装置による再度の画像形成に備える。
【００１６】
次に、タンデム画像形成装置の個々の画像形成手段について説明する。画像形成手段は、ドラム状の感光体１７Ｙ，Ｍ，Ｃ，Ｋのまわりに、帯電装置１Ｙ，Ｍ，Ｃ，Ｋ、現像装置２Ｙ，Ｍ，Ｃ，Ｋ、１次転写ローラ１８Ｙ，Ｍ，Ｃ，Ｋ、感光体クリーニング装置４Ｙ，Ｍ，Ｃ，Ｋ、図示しない除電装置などを備えてなる。なお、上記各符号の後のＹ，Ｍ，Ｃ，Ｋは、それぞれイエローの場合がＹを、マゼンタの場合がＭを、シアンの場合がＣを、ブラックの場合がＫを示す。
【００１７】
このような構成の画像形成手段では、感光体１７Ｙ，Ｍ，Ｃ，Ｋの回転とともに、まず帯電装置１Ｙ，Ｍ，Ｃ，Ｋで各感光体の表面を一様に帯電する。次いでスキャナ３００の読取り内容に応じてデジタル書き込み装置５からレーザやＬＥＤ等による書込み光を照射して感光体１７Ｙ，Ｍ，Ｃ，Ｋ上に静電潜像を形成する。そして、現像装置２Ｙ，Ｍ，Ｃ，Ｋによりトナーが付着され静電潜像を可視像化し、その可視像を１次転写ローラ１８Ｙ，Ｍ，Ｃ，Ｋで中間転写ベルト１２上に転写する。画像転写後の感光体１７Ｙ，Ｍ，Ｃ，Ｋの表面は、感光体クリーニング装置４Ｙ，Ｍ，Ｃ，Ｋで残留トナーを除去して清掃し、除電装置で除電して再度の画像形成に備える。
【００１８】
〔実施例１〕
次に、中間転写ベルト１２を用いた１次転写装置３について詳しく説明する。図２は、１次転写装置３の斜視図である。また、図３は、１次転写装置３の側面図である。中間転写ベルト１２は、３本の支持ローラ１０，１１，１５に掛け回して図中時計回り方向に回転搬送可能とする。そして、３本の支持ローラのうち２本の支持ローラ１０，１１間に張り渡した中間転写ベルト１２に対向するよう、イエロー，マゼンタ，シアン，ブラックの４つの感光体１７Ｙ，Ｍ，Ｃ，Ｋを横に並べて配置してある。また、図３において、機枠（不図示）に設置されたテンションスプリング２０で付勢されたテンションローラ２１により、中間転写ベルト１２を外側から緊張させている。２次転写位置よりも中間転写ベルト１２の回転方向下流側には、ベルトクリーニングユニット２２が設けられ、余剰トナーをクリーニングブレード２３等で掻き取っている。また、ベルトクリーニングユニット２２に対向するよう中間転写ベルト１２内部に対向ローラ１４を配置してある。
【００１９】
図２において、上記中間転写ベルト１２の手前側端部のベルト外周面には、凸状に形成された一定幅のガイド部材１３が溶着または両面テープによる貼り付けで接合されている。このガイド部材１３は１０〜２０ｍｍ程度の一定幅のテープ状のものであり、黒感光体１７Ｋの基準端面Ａと、イエロー感光体１７Ｙの基準端面Ｂとに摺接しながら移動可能となっている。よって、中間転写ベルト１２を回転搬送するときに、ベルトに対して図中奥側に引っ張り力を作用させることで、ガイド部材１３の側面が基準端面Ａと基準端面Ｂとに摺接しながら移動し、ベルトの幅方向位置が規制される。これにより４つの感光体１７Ｙ，Ｍ，Ｃ，Ｋとの対向部において中間転写ベルト１２が走行方向と直角方向に蛇行することを防止することができる。この結果、転写ずれを防いで色ずれのない高品質な画像を形成することができる。ここで、中間転写ベルト１２の蛇行を抑えるため、上記基準端面Ａ，Ｂの振れができるだけ少なくなるように、黒感光体１７Ｋ及びイエロー感光体１７Ｙの加工・組立て精度を確保している。また、黒感光体１７Ｋ及びイエロー感光体１７Ｙは、従来主走査方向を規制していた支持ローラ１０，１１，１５よりも径が大きいので、加工精度が同等で端面の振れが同じであれば蛇行周期がより大きくなる。このため主走査方向のバンディングが目立ちにくくなる。なお、図２に示す例では、中間転写ベルト１２の片側の端部表面にガイド部材１３を設けているが、ガイド部材１３を両端部の表面に設けて、黒感光体１７Ｋ及びイエロー感光体１７Ｙで、幅方向の位置を規制してもよい。
【００２０】
なお、図２に示すように、３本の支持ローラ１０，１１，１５はガイド部材１３を規制しないので、中間転写ベルト１２の幅とほぼ同じ幅で構成される。また、１次転写ローラ１８Ｙ，Ｍ，Ｃ，Ｋや対向ローラ１４も中間転写ベルト１２の幅とほぼ同じ幅で構成される。一方、中間転写ベルト１２の外側に設けられるテンションローラ２１や２次転写ローラ３１は、ガイド部材１３との干渉を避けるため、図示の例ではローラ幅をガイド部材１３の内側になるように構成している。或いは、この構成に替えて、ガイド部材１３との干渉が生じない幅と深さとをもった溝を設けてもよい。
【００２１】
さらに、図４に示すように、ガイド部材１３の角部に面取りＨを施すことによって、ガイド部材１３と、基準端面Ａ及び基準端面Ｂとの摺接がスムーズになって回転駆動中の負荷や騒音を低減することができる。また、ガイド部材１３と、黒感光体１７Ｋ及びイエロー感光体１７Ｙとの角こすれによる経時劣化を防止することができる。なお、面取りＨは、ガイド部材１３の角部に限らず、黒感光体１７Ｋ及びイエロー感光体１７Ｙの角部に施してもよく、或いは、両方の角部に設けてもよい。
【００２２】
本実施形態に係る１次転写装置３では、中間転写ベルト１２に対して幅方向（以下、「主走査方向」ともいう。）の引張り力を作用させて張力を付与し、中間転写ベルト１２をガイド部材１３と反対側に寄せるようになっている。図４は、中間転写ベルト１２に対して幅方向の引張り力を作用させる構成を説明するための、黒１次転写ローラ１８Ｋ近傍におけるベルト搬送方向の断面図である。中間転写ベルト１２には、ガイド部材１３が設けられた端部と反対側のベルト端部の内周面全体に、張力受け部材として凸状に形成された一定幅の第二ガイド部材３０が溶着または両面テープによる貼り付けで接合されている。また、第二ガイド部材３０の右端面に当接するような分割コロ３１Ｋが、黒１次転写ローラ１８Ｋと同軸上に設けられている。この分割コロ３１Ｋは、黒１次転写ローラ１８Ｋの軸方向にスライド可能に構成され、圧縮スプリング３２Ｋにより、図中左方向に付勢される。これにより、第二ガイド部材３０に左方向の引張り力が作用し、中間転写ベルト１２に対して主走査方向の張力を付与することができる。このように、中間転写ベルト１２には図中左側方向への力が加わることで、ガイド部材１３の左端面が黒感光体１７Ｋの基準端面Ａに確実に接触するようになり、感光体（右端面）基準で中間転写ベルト１２を回転駆動することができる。
【００２３】
上記分割コロ３１Ｋは、中間転写ベルト１２の幅方向外側に付勢された状態で、中間転写ベルト１２の内周面及びローラ軸３４Ｋに対して摺動しながら移動する。このため、鉄等の金属材料に比べてポリアセタール（ＰＯＭ）等の摺動抵抗の小さい材質のもので構成することが望ましい。また、上記圧縮スプリング３２Ｋは、その内径がローラ軸３４Ｋよりも大きく、かつ外径が分割コロ３１よりも小さく構成する。これにより、圧縮スプリング３２は中間転写ベルト１２の内周面に接触することなく、分割コロ３１をベルト幅方向外側に付勢することができる。なお、圧縮スプリング３２に替えて、発泡ウレタン材やゴム材等の弾性部材を円筒状に加工して、１次転写ローラ１８Ｋと分割コロ３１Ｋとの間に挟み込む構成としても、同様の効果が得られる。
【００２４】
上記分割コロ３１Ｋ及び圧縮スプリング３２Ｋと同じものが、イエロー１次転写ローラ１８Ｙにも設けられているため、ガイド部材１３の左端面がイエロー感光体１７Ｙの基準端面Ｂに確実に接触する。これにより、黒感光体１７Ｋ及びイエロー感光体１７Ｙとの間の２ヶ所の１次転写位置で、中間転写ベルト１２は幅方向に張力がかかって拡げられる。この結果、駆動中の中間転写べルト１２表面の張力ばらつきによる緩みや歪みが抑えられ、中間転写ベルトを適度に張られた良好な状態で駆動でき、特に主走査方向のドット位置の安定を図ることができる。
【００２５】
また、図４に示すように、作像基準位置側（例えば光学系書き込みスタート位置Ｋ側）と同じ側にガイド部材１３を設けている。よって、中間転写ベルト１２の主走査方向の規制位置と作像基準位置とを近くに構成でき、容易に両者間の距離ばらつきを少なくできる。これにより、主走査方向のドット位置ずれを抑え込むことができる。なお、上記光書込みスタート位置Ｋ側とは、一般に装置の組立において基準となる構造体基準側でもある。
また、光学系ハウジング等で黒感光体１７Ｋのスラスト方向（主走査方向）ガタを規制するように構成すれば主走査方向のドット位置を全て感光体基準で行えるようになる。これにより、さらに主走査方向の高精度なドット位置精度を確保することができる。
【００２６】
また、図４に示すように、黒１次転写ローラ１８Ｋの幅方向の中央部分には作像範囲に渡って適度な硬度を持ったウレタン材１８１Ｋが設けられている。よって、黒感光体１７Ｋと対向する１次転写位置では、ウレタン材１８１Ｋが弾性変形し、このウレタン材を設けない場合に比べて転写ニップ幅を大きく構成することができる。これにより、転写性能を向上させることができ、黒感光体１７Ｋ上の黒トナー像をより確実に中間転写ベルト１２に転写することができる。また特に、中間転写ベルト１２に替えて、転写紙を搬送する転写搬送ベルトを用いた場合には、転写ニップ幅を大きくすることで、転写電界における転写紙と感光体とのギャップが安定し、良好な転写性能を得ることができる。
【００２７】
一般的に、ベルト幅方向の左右両端部に凸状のガイド部材を設けたガイド方式では、回転駆動中にガイド部材端部とローラ端部との摺動の悪さから、ガイド部材の乗り上げ現象が希に起こる場合がある。図７は、中間転写ベルト１２表面の両端部近傍にガイド部材１３を設けて、黒感光体１７Ｋで幅方向の位置規制を行なう場合の、ガイド部材１３の乗り上げ現象の説明図である。ベルト１周毎に同じ箇所で周期的に起こることもある。このガイド部材の乗り上げは、主走査方向のドット位置ずれ要因となる。
上記乗り上げを防止するため、本実施形態に係る複写機では、図４に示すようにガイド部材１３が設けられた側の黒１次転写ローラ１８Ｋを少なくともガイド部材１３の長さ以上に設定（図中寸法Ｃに相当）する。また、第２ガイド部材３０が設けられた側の黒感光体１７Ｋを少なくとも第２ガイド部材３０の長さ以上に設定（図中寸法Ｄに相当）する。これらのことにより、１次転写ローラ１８Ｋ及び黒感光体１７Ｋの延長部分の円周面によって裏打ちの効果が生まれ、乗り上げを生じさせる中間転写ベルト１２の変形が妨げられ、ガイド部材１３や第２ガイド部材３０の乗り上げを防ぐことができる。また、中間転写ベルト１２の支持ローラ１０，１１，１５からの脱落を防ぐこともできる。
ここで、黒１次転写ローラ１８Ｋ及び黒感光体１７Ｋの両方の長さを設定する構成について説明したが、これに限られるものではなく、どちらか一方のみの長さを設定してもよい。例えば、乗り上げが生じやすい側のみ所定の長さに設定してもよい。なお、イエロー１次転写ローラ１７Ｙ及びイエロー感光体１７も同様の長さ設定になっているものとする。
【００２８】
上記中間転写ベルト１２は、メンテナンスや部品交換及びジャム処理のために、１次転写装置３ごと各感光体１７Ｙ，Ｍ，Ｃ，Ｋから離間させて、複写機の手前側に引き出すことができる構成となっている。
このため、ガイド部材１３を１次転写装置３の引き出し方向側の中間転写ベルト１２端部に設けている。これにより、１次転写装置３を引き出す際にガイド部材１３が各感光体１７Ｙ，Ｍ，Ｃ，Ｋの端部と干渉するのを避けることができ、１次転写装置３をスムーズに引き出すことができる。
【００２９】
また、１次転写装置３を複写機本体１００から引き出すときには、まず１次転写装置３を一旦下側に移動させて中間転写ベルト１２を各感光体１７Ｙ，Ｍ，Ｃ，Ｋから離間させる。このとき、中間転写ベルト１２に幅方向の引張り力が作用したまま黒感光体１７Ｋから離間させると、ガイド部材１３が黒感光体の端面から外れるときに左側面が黒感光体の右端部に擦られてしまう。この擦れは、ガイド部材１３がイエロー感光体１７Ｙの端面と当接している部分でも起こる。ガイド部材１３はウレタン等を一定幅に加工して中間転写ベルト表面に貼付もしくは溶着されているので、上記擦れによって剥がれや劣化が起こり、ベルトの良好な蛇行規制を行えなくなるおそれがある。
【００３０】
そこで、本実施形態に係る複写機では、中間転写ベルト１２の幅方向の張力を解除する張力解除機構を設けている。図５は、黒１次転写ローラ１８Ｋによる張力を解除する構成及び動作の説明図である。また図６は、張力を付与するときの動作説明図である。なお、同様の張力解除機構がイエロー１次転写ローラ１８Ｙ近傍にも設けられているものとする。この張力解除機構はアクチュエータ６０Ｋと、固定ピン６１Ｋと、レバー６２Ｋとからなる。アクチュエータ６０Ｋの先端部６０１Ｋは分割コロ３３Ｋの溝部と勘合し、長孔６０２Ｋは転写装置側の固定ピン６１Ｋと係合している。また、アクチュエータ６０Ｋの右端はレバー６２Ｋの作用点６２１Ｋと回転自在に係合され、さらにレバー６２Ｋは転写装置の固定点６３Ｋに揺動可能に支持される。
【００３１】
図５に示すように、レバー６２Ｋを時計回り方向に回転して解除位置まで倒すと、アクチュエータ６０Ｋが右方向に移動する。これと同時に分割コロ３３Ｋの溝部と勘合している先端部６０１Ｋが圧縮スプリング３２Ｋの付勢力に抗して分割コロ３３Ｋを右方向に移動させる。分割コロ３３Ｋには第２ガイド部材３０よりも若干大きめの溝が形成されており、この溝の左側面が第２ガイド部材３０の左側面を押すことになり、中間転写ベルト１２が右側に移動される。このベルト移動によりガイド部材１３と黒感光体１７Ｋの右端面（基準端面Ａ）との間に隙間Ｅが生じる。この状態で、１次転写装置３を各感光体１７Ｙ，Ｍ，Ｃ，Ｋから離間させることで、ガイド部材１３と各感光体端部とが干渉することなく、中間転写ベルト１２をスムーズに各感光体から離間することができる。
また、図６に示すように、中間転写ベルト１２を黒感光体１７Ｋに当接させてから、レバー６２Ｋを反時計回り方向に回転して張力をかけることにより、ガイド部材１３と黒感光体端部が干渉してガイド部材が変形してしまうことを防止することができる。
【００３２】
なお、上記解除機構は、メンテナンスや部品交換及びジャム処理をする場合に用いるものであるが、例えばソレノイド等のレバー駆動装置（不図示）を設けて、作像動作中以外は主走査方向のテンションを解除する構成とすることもできる。作像動作中以外は中間転写ベルト１２やガイド部材１３に主走査方向のテンションをかけておく必要はないので、この場合にはレバー駆動装置を制御して中間転写ベルト１２やガイド部材にかかる主走査方向のテンションを解除する。これにより、中間転写ベルト１２やガイド部材１３の耐久性を向上させて長寿命化が図れる。
【００３３】
さらに、図２に示すように、ガイド部材１３の中間転写ベルト１２に接合される以外の一面全長に渡って、等ピッチの濃度差のあるマーキング２４を施す。また、マーキング２４を光学的に読み取る検出センサ２５を設ける。中間転写ベルト１２の回転駆動時、検出センサ２５によりマーキング２４を検出し、検出結果から中間転写ベルト１２の速度変動を算出する。そして、速度変動の算出結果に基づき、支持ローラ１０の回転数を変えるよう不図示の駆動モータを制御することで、中間転写ベルト１２の速度が常に一定になるようにフィードバック制御を行う。このように、中間転写ベルト１２の搬送速度を安定させることで、中間転写ベルト１２の走行方向（副走査方向）に関しても、各色画像形成手段間での色ずれを少なくすることができる。
図８に、フィードバック制御のブロック図を示す。このブロック図を用いてより詳しく説明する。検出センサ２５に入力されたパルス信号は、制御部２６のＣＰＵ２６１を介して発振器２６２による一定時間毎にカウンタ２６３で数えられ、ＲＯＭ２７に取り込まれて規定パルス数（所望スピードに対するパルス数）と比較検討される。比較検討した結果の増減分をステッピングモータコントローラ２８にフィードバックする。つまり、規定速度に達していない場合はステッピングモータ２９の回転周波数を多く、逆の場合は少なくするよう周波数変換することで中間転写ベルト１２を等速に駆動させる。
【００３４】
〔実施例２〕
上記実施例１では、黒感光体１７Ｋ及びイエロー感光体１７Ｙの基準端面Ａ，Ｂにガイド部材１３を接触させる構成について説明したが、感光体の端部近傍に溝を設け、これにガイド部材を勘合させても良い。中間転写ベルトの幅方向剛性が充分に高く、一方の端部のみでベルト全体の幅方向位置を充分に規制できる場合には、ベルト幅方向にテンションを付与する上記分割コロ３１や圧縮スプリング３２等を設けなくてもよい構成とできる。
図９は本実施例に係る黒感光体１７Ｋの近傍の説明図である。図示のように、黒感光体１７Ｋの右端にフランジ１７１Ｋが圧入されることで溝１７２Ｋが形成される。１次転写装置３の着脱をスムーズに行うため、ガイド部材１３の両肩部にはＣ０．５〜Ｃ１．５ｍｍ程度の大きめの面取りＪが施されている。
【００３５】
ガイド部材１３はテープ状の加工で、幅方向の寸法規制が容易に行える。また、溝１７２Ｋの幅はガイド部材１３に勘合するよう１０〜２０ｍｍ程度の一定幅で形成されるが、一定幅のスペーサ（不図示）を挟み込みながら圧入することで容易に高精度の溝形成が行える。これらのことにより、ガイド部材１３と黒感光体１７Ｋの溝１７２Ｋとの隙間は、２０〜５０μｍ程度に抑えることができる。
【００３６】
〔実施例３〕
上記実施例１及び２では、図４に示すように、分割コロ３１Ｋと圧縮スプリング３２Ｋとを設けて、中間転写ベルト１２に左側の力を与えて張力を付与してガイド部材１３と反対側に寄せるように構成した。しかし、本発明はこれに限るものでなく、ベルト支持ローラの形状又は取付形態によって中間転写ベルト１２がガイド部材１３を設けた側と反対方向に斜行させて寄せるように構成しても良い。図１０は、本実施例に係る１次転写装置３を上から見た平面図である。中間転写ベルト１２を張架して従動回転する支持ローラ１１を、ベルトの回転移動方向と直交する方向から微少角度傾斜して配置している。このため支持ローラ１０の回転駆動力によって中間転写ベルト１２を図中矢印方向に駆動させると、中間転写ベルト１２は左側方向に斜行するようになる。これにより、ガイド部材１３の左端面が黒感光体１７Ｋ及びイエロー感光体１７Ｙの基準端面Ａ，Ｂ（不図示）に確実に接触するようになり、感光体（右端面）基準で中間転写ベルト１２を回転駆動することができる。
また、図１１に示すようなテーパローラ６５を用いてもよい。このテーパローラ６５が回転すると中間転写ベルト１２に対して径が大きい方へ移動させる力が作用し、中間転写ベルト１２を左側方向に斜行するよう走行駆動でき、上記方式と同様の効果を得ることができる。
このように、上記実施例１で説明した構成に比べて、中間転写ベルト１２へ幅方向の張力を付与する分割コロ３１等の部材を設けなくて済み、構成を簡略化することができる。
【００３７】
以上本実施形態では、各色感光体上のトナー像を中間転写ベルト１２上に１次転写した後、転写紙１９へ２次転写する間接転写方式の中間転写ベルトの蛇行防止等について説明したが、本発明はこれに限られるものではない。用紙を搬送ベルト上に吸着させて、各色感光体から順次、直接トナー像を転写する直接転写方式の搬送ベルトにガイド部材を設けたり、ガイド部材にマーキングを施したりすることにより、中間転写ベルトと同様に蛇行防止等の効果が得られる。
【００３８】
以上述べたように、本実施形態によれば、像担持体としての感光体上に形成されたトナー像を、複数の支持部材としての支持ローラに張架されて回転駆動される無端ベルトとしての中間転写ベルト上に転写する転写ベルトユニットとしての１次転写装置において、上記中間転写ベルトの幅方向の端部のうち少なくともいずれか一方の近傍に表面全周にわたって一定幅のガイド部材を設け、中間転写ベルトはガイド部材がガイド部としての感光体端部に幅方向の位置を規制されながら回転駆動される。これにより、転写画像の直線性を損なうことなく、画像劣化を防ぐことができる。なお、上記実施形態では、本発明を、トナー像を中間転写ベルト上に１次転写した後、転写紙上２次転写する間接転写装置を用いて説明した。本発明はこれに限るものでなく、転写ベルトで転写紙を搬送し、各色感光体から順次転写紙上にトナー像を転写して重ね合わせる直接転写装置においても適用可能であり、同様の効果が得られる。
また、ガイド部材を中間転写ベルトの幅方向の端部のうちいずれか一方に設け、かつ、中間転写ベルトに対してガイド部材が設けられた幅方向の端部と反対側の端部方向にベルトを寄せる力を付与するベルト寄せ手段を設けた。よって、中間転写ベルトが幅方向に拡げられることで駆動中のべルト表面の張力ばらつきによる緩みや歪みを抑えることができる。これにより、中間転写ベルトを適度に張られた良好な状態で駆動でき、特に主走査方向のドット位置精度を高めることができる。また、中間転写ベルトに幅方向の張力を付与することで、同時に黒感光体と軸受との軸方向のガタを抑え込むことができ、黒感光体の光学系に対する位置ずれを防ぎ、主走査方向のドット位置精度をさらに高めることができる。
また、複数の感光体を中間転写ベルトの回転移動方向に並べて中間転写ベルトに対向させ、これら複数の感光体のうち、中間転写ベルトの回転移動方向に対して最上流側のイエロー感光体と最下流側の黒感光体との少なくとも２つの感光体の端部で中間転写ベルトの幅方向を規制する。例えば距離の近いシアン感光体とマゼンタ感光体との２ヶ所で中間転写ベルトの幅方向位置を規制する場合に比べ、より距離の離れた感光体間で規制する方が、ベルトの蛇行をより確実に抑えることができる。よって、カラー画像を形成する場合に、中間転写ベルトの蛇行を低減して転写ずれを防ぎ、主走査色ずれの少ない画像を形成することが可能となる。
また、ガイド部材が設けられた中間転写ベルトの幅方向の端部は、感光体への作像基準位置側である光書込み開始側の端部である。このように、光書込み開始側と同じ側で中間転写ベルトの幅方向（主走査方向）位置を規制する。よって、中間転写ベルトの主走査方向の規制位置と作像基準位置とを近くに構成でき、作像基準位置と反対側でベルト位置を規制する場合に比べ、両者間の距離ばらつきを少なくできる。この結果、主走査方向のドット位置ずれをより抑えることができる。
また、ガイド部材を中間転写ベルトの幅方向の端部のうちいずれか一方の片側に設け、ガイド部材を設けた片側の端部側から、転写ベルトユニットを感光体に対して脱着可能に構成した。これにより、メンテナンスや部品交換及びジャム処理のために転写ベルトユニットを感光体から脱着する場合に、ガイド部材と反対の端部側から転写ベルトユニットを脱着する場合に比べ、ガイド部材と感光体との干渉を防ぐことができる。よって、転写ベルトユニットをスムーズに脱着することができるとともに、ガイド部材の損傷を防ぐことができる。
また、上記ベルト寄せ手段による中間転写ベルトの張力の付与を解除する張力解除手段としてのアクチュエータ等を設けた。これにより、作像動作中以外や転写ベルトユニットの脱着時には、中間転写ベルトやガイド部材にかかる幅方向のテンションを解除することが可能となる。よって、中間転写ベルトやガイド部材の耐久性が向上して長寿命化を図ることが可能となる。
また、ガイド部材と感光体端部とを離間させる離間手段として分割コロ等を設けた。ガイド部材と感光体端部とが当接した状態で転写ベルトユニットを複写機本体から引き出すと、ガイド部材が感光体端部と干渉して変形し、ガイド部材の寿命短縮や損傷を生じる場合がある。この転写ベルトユニットでは、ガイド部材と感光体端部との当接を解除して両者を離間させてから転写ベルトユニットを引き出すことができるので、ガイド部材の変形による寿命短縮や損傷を防ぐことができる。
また、上記ベルト寄せ手段を、中間転写ベルトのガイド部材を設けた端部と反対側の端部の裏面近傍に全周にわたって設けられた張力受け部材としての第２ガイド部材と、感光体に対向する転写部材としての１次転写ローラの同軸上に配設され軸方向に移動可能な該転写部材と略同一径であって、第２ガイド部材に接触して張力を付与する張力付与部材としての分割コロと、分割コロに第２ガイド部材側への付勢力を付与する付勢部材としての圧縮スプリングとを用いて構成した。よって、中間転写ベルトのガイド部材は感光体端部と当接して幅方向の位置が規制されているので、圧縮スプリングで分割コロを中間転写ベルトの第２ガイド部材に付勢することで、中間転写ベルトに幅方向の張力を付与することができる。また、１次転写ローラが中間転写ベルトに幅（主走査）方向の張力を付与することになり、ベルトに回転移動（副走査）方向の駆動力を伝える駆動ローラ等には幅方向のストレスがかからないので、ベルト走行ムラを抑えることもできる。また、上記分割コロを金属材料に比べて摺動性の良い材質を用いて構成した。よって、分割コロを例えばポリアセタールで構成することにより、ローラ軸や中間転写ベルトの裏面と良好に摺動しながら移動し、駆動負荷を増大させることなく、スムーズに中間転写ベルトに主走査方向の張力を付与することができる。
また、ガイド部材が感光体端部に当接した状態で、ガイド部材が設けられた側の１次転写ローラの端面の位置が、ガイド部材の幅方向外側の端部と同じ位置、または、この端部よりも外側の位置にくるように、１次転写ローラの長さを設定した。これにより、ガイド部材が設けられている部分の中間転写ベルトの内側まで１次転写ローラが当接して、ガイド部材が設けられている中間転写ベルトの端部が内側へ折れ曲がるのを防ぐことができる。よって、ガイド部材の感光体への乗り上げや中間転写ベルトの支持ローラからの脱落を防止して安定した駆動を得ることができる。
また、ガイド部材が感光体端部に当接した状態で、第２ガイド部材が設けられた側の感光体の端面の位置が、第２ガイド部材の幅方向外側の端部と同じ位置、または、この端部よりも外側の位置にくるように、感光体の長さを設定した。これにより、第２ガイド部材が設けられている部分の中間転写ベルトの外側まで感光体が当接して、第２ガイド部材が設けられている中間転写ベルトの端部が外側へ折れ曲がるのを防ぐことができる。よって、第２ガイド部材の１次転写ローラへの乗り上げや中間転写ベルトの支持ローラからの脱落を防止して安定した駆動を得ることができる。
また、１次転写ローラの感光体の作像範囲に対応した部分の表面に弾性部材としてのウレタン材を設けた。よって、感光体と対向する１次転写位置では、ウレタン材が弾性変形し、ウレタン材を設けない場合に比べて転写ニップ幅を大きく構成することができる。これにより、転写性能を向上させることができ、感光体上のトナー像をより確実に中間転写ベルトに転写することができる。また特に、中間転写ベルトに替えて、転写紙を搬送する転写搬送ベルトを用いた場合には、転写ニップ幅を大きくすることで、転写紙と感光体とのギャップが安定し、良好な転写性能を得ることができる。
また、上記ベルト寄せ手段を、支持ローラの少なくとも１つを中間転写ベルトの回転移動方向と直交する方向に対して斜めに配設することにより、もしくは、支持ローラの少なくとも１つを直径が変化するテーパローラを用いて構成した。支持ローラを中間転写ベルトの回転移動方向と直交する方向に対して斜めに配設すると、中間転写ベルトを回転移動させたときに、ベルトを斜行させる力が作用する。よって、ガイド部材と反対側の端部方向に中間転写ベルトを斜行させることで、中間転写ベルトをガイド部材と反対側に寄せると同時に幅方向に張力を付与できる。また、テーパローラが回転すると中間転写ベルトに対して径が大きい方へ移動させる力が作用し、中間転写ベルトをガイド部材と反対側の端部方向に斜行させることで、中間転写ベルトをガイド部材と反対側に寄せると同時に幅方向に張力を付与できる。このように、圧縮スプリング等の弾性部材等を設けることなく、簡単な構成で中間転写ベルトをガイド部材と反対側に寄せると同時に、幅方向の張力を付与することができる。
また、上記ガイド部が上記ガイド部材と勘合する溝である。よって、ガイド部材が溝に勘合して中間転写ベルトの蛇行を防止できるので、両側にガイド部材を設ける方式に比べ、片側１箇所だけで済み、ベルトのコストダウンを図ることができる。また、ガイド部材の幅及び溝の幅の加工は、容易かつ安価に十分な加工精度を確保できるので、勘合時に中間転写ベルトの安定した回転移動が得られる隙間を維持することができる。
また、ガイド部材と感光体端部もしくは溝との少なくとも一方に面取りを施す。これにより、ガイド部材と感光体端部もしくは溝との摺接をスムーズにし、回転駆動中の負荷や騒音を低減する。また、ガイド部材や感光体端部もしくは溝の角こすれによる経時劣化を防止して、長期に渡って安定して中間転写ベルトの蛇行を低減する。
また、ガイド部材の表面に等ピッチのマーキングと、マーキング検出する検出手段と、中間転写ベルトの回転駆動を制御する制御手段とを備える。そして、検出手段により検出された結果に基づき中間転写ベルトの走行速度を算出し、算出された走行速度に基づき走行速度が一定になるよう中間転写無端ベルトの回転駆動を制御する。中間転写ベルトの走行速度を安定させることで、中間転写ベルトの走行方向（副走査方向）に関しても、各色画像形成手段間での色ずれを少なくすることができる。
また、感光体上に潜像を形成する潜像形成手段ととしての光書込み装置と、感光体上の静電潜像をトナー像化する現像手段としての現像装置と、感光体上に形成されたトナー像を、複数の支持ローラに張架されて回転駆動される中間転写ベルト上、または、転写搬送ベルトに担持搬送される転写紙上に転写する転写手段としての１次転写装置とを備えた画像形成装置としての複写機において、上記１次転写装置として、上記転写ベルトユニットを用いる。
また、感光体上に潜像を形成する手段としてデジタル書込み装置を用いた、デジタルカラー複写機とする。デジタルカラー複写機では、中間転写ベルトの蛇行による各感光体の転写ずれが主走査色ずれとなって顕れ、著しい画質劣化を引き起こす。そこで、本発明をデジタルカラー複写機に適応することで、走査色ずれを防止し、良質な画像を得るという優れた効果がある。
【００３９】
【発明の効果】
請求項１乃至１８の発明においては、像担持体や転写ベルトユニットの振動やガタに伴う画像劣化を防止することができるという優れた効果がある。
【図面の簡単な説明】
【図１】本実施形態に係る複写機の概略構成図。
【図２】１次転写装置の斜視図。
【図３】１次転写装置の側面図。
【図４】黒１次転写ローラ近傍のベルト寄せ手段の説明図。
【図５】黒１次転写ローラ近傍の張力解除機構の説明図。
【図６】黒１次転写ローラ近傍の張力解除機構の説明図。
【図７】ガイド部材の乗り上げ現象の説明図。
【図８】中間転写ベルト走行速度制御のブロック図。
【図９】黒感光体にガイド部材と勘合する溝を設けた構成図。
【図１０】支持ローラのうち１本を傾斜して配置した状態を示す１次転写装置の平面図。
【図１１】支持ローラのうち１本をテーパローラとした構成を示す１次転写装置の平面図。
【図１２】従来の中間転写ベルトの駆動方法の説明図。
【符号の説明】
１ 帯電装置
２ 現像装置
３ １次転写装置
４ 感光体クリーニング装置
５ デジタル書き込み装置
７ ２次転写装置
８ 定着装置
９ ２次転写ベルト
１０，１１，１５ 支持ローラ
１３ ガイド部材
１４ クリーニング対向ローラ
１７Ｙ，Ｍ，Ｃ，Ｋ 感光体
１８Ｙ，Ｍ，Ｃ，Ｋ １次転写ローラ
１９ 転写紙
２０ テンションローラ
２１ スプリング
２２ 中間転写体クリーニング装置
２３ クリーニングブレード
２４ マーキング
２５ 検出手段
３０ 第２ガイド部材
３１Ｋ，３３Ｋ 分割コロ
３２Ｋ 圧縮スプリング
６０Ｋ アクチュエータ
６１Ｋ 固定ピン
６２Ｋ レバー
１００ 複写装置本体
１７１Ｋ フランジ
１７２Ｋ 溝
２００ 給紙テーブル
３００ スキャナ
４００ 原稿自動搬送装置（ＡＤＦ）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile, a printer, and the like, and a transfer belt unit used in the apparatus. More specifically, a transfer belt unit that transfers a toner image formed on an image carrier onto an endless belt that is stretched over a plurality of support members and driven to rotate, or onto a transfer body that is carried and conveyed by the endless belt. And an image forming apparatus using the unit.
[0002]
[Prior art]
Conventionally, in the image forming apparatus, a transfer device using an endless belt such as an intermediate transfer belt or a transfer conveyance belt has been put to practical use. As a driving method for driving the endless belt, the endless belt is stretched over a driving roller and a driven roller, and the driving roller is driven to rotate, whereby the endless belt is driven to rotate. However, in such a driving method, the endless belt is meandering and laterally displaced due to a slight inclination at the time of installation of each roller, local friction during rotation of the endless belt, and the like. For this reason, there is a problem that the transfer position is shifted left and right.
[0003]
In order to solve such a problem, there has been proposed an endless belt having guides formed on both sides of the endless belt in a protruding shape along the moving direction to prevent meandering (for example, see Patent Document 1). In this endless belt, the end surfaces of the guides on both side edges are in sliding contact with the end surfaces of the respective rollers, thereby restricting the endless belt from being displaced in the width direction. Thereby, meandering of the endless belt is reduced.
[0004]
FIG. 12 is a top view showing a schematic configuration of a device in which a guide for preventing meandering is fixed to both side edges of the endless belt disclosed in Patent Document 1 along a moving direction. In FIG. 12, in order to fit the rollers 10 and 11 between the guides 40 on both side edges, the distance M between the inner side surfaces of the guides 40 needs to be equal to or greater than the roller width L. On the other hand, the gap between the inner side surface of the guide 40 and the side surfaces of the rollers 10 and 11 is desired to be as small as possible so that the inner side surface of the guide 40 is in sliding contact with the side surfaces of the rollers 10 and 11.
[0005]
The width of the endless belt 12 needs to be wider than the width of the transfer body, and is usually 300 mm or more. The guides 40 are fixed to both end edges of the endless belt 12 by bonding or welding, but the width of the endless belt is wide, and it is difficult to control the distance B between the inner side surfaces of the guides 40. Therefore, in general, they are pasted or welded at a distance B having a margin larger than the roller width A by 1 to 2 mm. This margin is a gap between the endless belt 12 and the rollers 10 and 11, and the endless belt 12 running during the running may be meandered in a direction perpendicular to the running direction.
[0006]
When an endless belt transfer device using such a driving method is used in a tandem-type color image forming apparatus in which a plurality of image carriers are arranged in a line, the meander due to the above-described margin causes transfer misalignment between the image carriers. To cause color shift. In particular, when used in a digital color image forming apparatus that has been put into practical use in recent years, main scanning color shift appears. In the digital color image forming apparatus, the density has been increased. However, at a writing density of 600 DPI or more, the main scanning color shift causes a significant deterioration in image quality.
[0007]
Therefore, the present applicant has proposed a color image forming apparatus in which a guide member is provided near the center of the back surface of the endless belt, and the guide member is engaged with an engagement portion provided on a support member of the endless belt (Japanese Patent Application No. 2002-208). No. 79451). This color image forming apparatus can prevent transfer deviation by reducing meandering of the endless belt, and can form a color image with less main scanning color deviation. Further, in this color image forming apparatus, since the guide member is fixed only at one place near the center as compared with the conventional one in which the guide member is fixed at both ends of the endless belt, dimensional management is easy, and The gap between the end face and the end face of the engaging portion is kept small.
[0008]
[Patent Document 1]
Japanese Utility Model Laid-Open No. 5-75264 (Page 1, FIG. 2)
[0009]
[Problems to be solved by the invention]
The transfer device using the endless belt is configured as a unit separate from the photoconductor so that it can be moved integrally in the front direction or the vertical direction of the main body of the image forming apparatus in consideration of maintenance and jam processing. Therefore, the transfer device and the photoconductor vibrate separately. In addition, the endless belt and the photoconductor may move separately in the axial direction (main scanning direction) due to backlash between the belt stretching roller and the bearing, or between the photoconductor and the bearing. Then, even if the endless belt is rotationally moved while suppressing the meandering of the endless belt by the transfer device, the endless belt and the photosensitive member are mutually displaced in the main scanning direction, and the linearity of the transferred image is impaired and image deterioration occurs. . In particular, in the case of a color image, a main scanning color shift occurs and a more conspicuous image deterioration occurs than in a monocolor image. Such image deterioration is not limited to the above-described configuration, and the endless belt is stretched by rollers and driven to rotate, and the image on the photoconductor is transferred onto the endless belt or onto the transfer body carried and transported by the endless belt. This can occur with a transfer configuration.
[0010]
The present invention has been made in view of the above background, and an object of the present invention is to use a transfer belt unit and a transfer belt unit that can prevent image deterioration due to vibration and play of an image carrier and a transfer belt unit. To provide an image forming apparatus.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a toner image formed on an image carrier is supported on an endless belt that is stretched around a plurality of support members and driven to rotate, or is carried on an endless belt. In the transfer belt unit for transferring onto the conveyed transfer body, a guide member having a constant width is provided over the entire circumference of the surface near at least one of the widthwise ends of the endless belt. The member is driven to rotate while its position in the width direction is regulated by a guide portion provided on the image carrier.
According to a second aspect of the present invention, in the transfer belt unit according to the first aspect, the guide member is provided near one of the widthwise ends of the endless belt, and the guide member is provided with respect to the endless belt. And a belt shifting means for applying a force toward the end in the direction opposite to the end in the width direction provided with the belt.
According to a third aspect of the present invention, in the transfer belt unit according to the first or second aspect, a plurality of image carriers are arranged in the rotational movement direction of the endless belt and opposed to the endless belt. The guide section is provided on at least two image carriers on the most upstream side and the most downstream side with respect to the rotational movement direction of the endless belt.
According to a fourth aspect of the present invention, in the transfer belt unit according to the second aspect, an end in the width direction of the endless belt provided with the guide member is an end on an image forming reference position side on the image carrier. It is characterized by the following.
According to a fifth aspect of the present invention, in the transfer belt unit according to the second or fourth aspect, the transfer belt unit can be detachably attached to the image carrier from the widthwise end of the endless belt provided with the guide member. It is characterized by comprising.
According to a sixth aspect of the present invention, in the transfer belt unit of the second, fourth or fifth aspect, a tension releasing means for releasing the tension in the width direction of the endless belt by the belt shifting means is provided. .
According to a seventh aspect of the present invention, in the transfer belt unit of the sixth aspect, a separating means for separating the guide member from the guide portion is provided. According to an eighth aspect of the present invention, in the transfer belt unit according to the second, fourth, fifth, sixth, or seventh aspect, the belt shifting means is provided on the back surface of the end of the endless belt opposite to the end provided with the guide member. A tension receiving member provided in the vicinity of the entire circumference and a transfer member which is disposed coaxially with the transfer member facing the image carrier and has substantially the same diameter as the transfer member movable in the axial direction; And a biasing member that applies a biasing force to the tension receiving member toward the tension receiving member.
According to a ninth aspect of the present invention, in the transfer belt unit of the eighth aspect, the tension applying member is made of a material having better slidability than a metal material.
According to a tenth aspect of the present invention, in the transfer belt unit according to the eighth or ninth aspect, in a state where the guide member is in contact with the guide portion, the position of the end surface of the transfer member on the side where the guide member is provided, The length of the transfer member is set so as to be at the same position as the outer end in the width direction of the guide member or at a position outside the end.
According to an eleventh aspect of the present invention, in the transfer belt unit according to the eighth, ninth or tenth aspect, the end surface of the image carrier on the side where the tension receiving member is provided in a state where the guide member is in contact with the guide portion. The length of the image carrier is set such that the position of the image carrier is the same as the outer end of the tension receiving member in the width direction or the outer position of the end. It is.
According to a twelfth aspect of the present invention, in the transfer belt unit of the eighth, ninth, tenth or eleventh aspect, an elastic member is provided on a surface of a portion of the transfer member corresponding to an image forming range of the image carrier. Is what you do.
According to a thirteenth aspect of the present invention, in the transfer belt unit according to the second, fourth, fifth, sixth, or seventh aspect, the belt shifter is configured to move at least one of the support members in a direction orthogonal to a rotational movement direction of the endless belt. It is characterized by being arranged obliquely with respect to the above, or at least one of the above-mentioned supporting members is constituted by using a taper roller whose diameter changes.
According to a fourteenth aspect of the present invention, in the transfer belt unit according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, thirteenth, or thirteenth, the guide portion engages with the guide member. It is a groove.
The invention according to claim 15 is the transfer belt unit according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the guide member and the guide portion At least one is chamfered.
The invention according to claim 16 is the transfer belt unit according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein Equi-pitch marking, detecting means for detecting the marking, and rotational drive control means for controlling the rotational drive of the endless belt, and calculates the traveling speed of the endless belt based on the result detected by the detecting means. The rotational drive of the endless belt is controlled by the rotational drive control means so that the traveling speed becomes constant based on the calculated traveling speed.
According to the transfer belt unit of the present invention, the guide member provided on at least one of the width direction ends of the endless belt is formed by the guide portion provided on the image carrier in the width direction. Position is regulated. When the endless belt is driven to rotate, the guide member moves while sliding on the guide portion, and the position of the endless belt in the width direction (main scanning direction) with respect to the image carrier is regulated. As a result, the endless belt follows the image carrier in the width direction, the relative positional relationship between the endless belt and the image carrier in the width direction is constant and does not change, and the vibration of the transfer belt unit and the image carrier is not changed. Even if there is backlash, it is hard to be affected. Therefore, image deterioration can be prevented without impairing the linearity of the transferred image.
According to another aspect of the present invention, there is provided a latent image forming means for forming a latent image on an image carrier, and a developing means for forming an electrostatic latent image on the image carrier into a toner image. Transfer means for transferring the toner image formed on the image carrier onto an endless belt which is stretched around a plurality of support members and driven to rotate, or onto a transfer body carried and conveyed by the endless belt; and 17. The image forming apparatus according to claim 1, wherein the transfer unit is any one of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16. Such a transfer belt unit is used. An eighteenth aspect of the present invention is the image forming apparatus according to the seventeenth aspect, wherein the latent image forming means includes a digital writing means.
According to the image forming apparatus of the present invention, since the transfer belt unit and the image carrier are hardly affected by the vibration and the backlash, the linearity of the transferred image is not impaired and the image deterioration can be prevented.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a tandem-type indirect transfer type digital copying machine (hereinafter, referred to as a copying machine) which is an image forming apparatus will be described.
First, the overall configuration of the copying machine according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. The copying machine mainly includes a copying apparatus main body 100, a paper feed table 200 on which the copying machine main body is mounted, a scanner 300 mounted on the copying apparatus main body, and an automatic document feeder (ADF) 400 mounted thereon. .
[0013]
An endless intermediate transfer belt 12 is provided at the center of the copying apparatus main body 100. The intermediate transfer belt 12 is wrapped around support rollers 10, 11, and 15 as support members so that the intermediate transfer belt 12 can be rotated and conveyed in a clockwise direction in FIG. Above the intermediate transfer belt 12, four image forming units of yellow, magenta, cyan, and black are arranged side by side along the transport direction to constitute a tandem image forming apparatus. A digital writing device 5 is provided above the tandem image forming apparatus.
[0014]
Inside the intermediate transfer belt 12, primary transfer rollers 18Y, M, C, and K that press against the photoconductors 17Y, 17M, 17C, and 17K with the intermediate transfer belt 12 interposed therebetween are provided. Constitute. Further, a secondary transfer device 7 is provided on the opposite side of the intermediate transfer belt 12 from the tandem image forming apparatus. The secondary transfer device 7 is configured by extending a secondary transfer belt 30 as an endless belt between two rollers 31 and 32, and transfers an image on the intermediate transfer belt 12 to a sheet. Further, between the two support rollers 11 and 15, an intermediate transfer body cleaning device 22 including a cleaning blade 23 for removing residual toner remaining on the intermediate transfer belt 12 after the secondary transfer is provided. A fixing device 8 for fixing a transferred image on a sheet is provided beside the secondary transfer device 7. The secondary transfer device 7 also has a sheet conveying function for conveying the sheet after image transfer to the fixing device 8.
[0015]
In the copying machine having the above configuration, the scanner 300 is driven to read the contents of the document. In addition, the support roller 10 is driven to rotate by a drive motor (not shown), the support rollers 11 and 15 are driven to rotate, and the intermediate transfer belt 12 is driven to rotate. At the same time, the photoconductors 17Y, 17M, 17C, and 17K are rotated by individual image forming means to form a single color image of yellow, magenta, cyan, and black on each photoconductor. Then, the intermediate transfer belt 12 is rotated and conveyed, and the monochrome images are sequentially transferred to form a composite color image on the intermediate transfer belt 12. On the other hand, the sheet is fed from the sheet cassette in the sheet feeding table 200 and is conveyed to a sheet feeding path in the copying apparatus main body 100. Then, a sheet is fed between the intermediate transfer belt 12 and the secondary transfer device 7 in synchronization with the timing of the composite color image on the intermediate transfer belt 12 and transferred by the secondary transfer device 7 to form a color image on the sheet. Record. The sheet after image transfer is conveyed by the secondary transfer device 7 and sent to the fixing device 8, where the transferred image is fixed by applying heat and pressure by the fixing device 8, and is discharged out of the apparatus. On the other hand, the intermediate transfer belt 12 after the image transfer is removed by the intermediate transfer body cleaning device 22 to remove the residual toner remaining on the intermediate transfer belt 12 after the image transfer, so that the tandem image forming apparatus is ready for the next image formation.
[0016]
Next, individual image forming units of the tandem image forming apparatus will be described. The image forming means includes charging devices 1Y, M, C, and K, developing devices 2Y, M, C, and K, and primary transfer rollers 18Y, M, and C around drum-shaped photoconductors 17Y, 17M, 17C, and 17K. , K, photoreceptor cleaning devices 4Y, M, C, K, a static eliminator (not shown), and the like. In addition, Y, M, C, and K after each of the above codes indicate Y for yellow, M for magenta, C for cyan, and K for black.
[0017]
In the image forming means having such a configuration, first, the surfaces of the respective photoconductors are uniformly charged by the charging devices 1Y, M, C, and K as the photoconductors 17Y, 17M, 17C, and 17K rotate. Next, in accordance with the contents read by the scanner 300, writing light is emitted from the digital writing device 5 using a laser, an LED, or the like to form an electrostatic latent image on the photoconductors 17Y, 17M, 17C, and 17K. Then, toner is adhered by the developing devices 2Y, M, C, and K to visualize the electrostatic latent image, and the visible image is transferred onto the intermediate transfer belt 12 by the primary transfer rollers 18Y, M, C, and K. I do. The surfaces of the photoconductors 17Y, 17M, 17C, and 17K after the image transfer are cleaned by removing the residual toner by the photoconductor cleaning devices 4Y, 4M, 4C, and 4K, and the charge is removed by the charge removing device to prepare for the image formation again. .
[0018]
[Example 1]
Next, the primary transfer device 3 using the intermediate transfer belt 12 will be described in detail. FIG. 2 is a perspective view of the primary transfer device 3. FIG. 3 is a side view of the primary transfer device 3. The intermediate transfer belt 12 is wound around three support rollers 10, 11, and 15 so as to be rotatable and conveyable in a clockwise direction in the figure. The four photoconductors 17Y, M, C, and K of yellow, magenta, cyan, and black are opposed to the intermediate transfer belt 12 stretched between the two support rollers 10, 11 among the three support rollers. Are arranged side by side. In FIG. 3, the intermediate transfer belt 12 is tensioned from the outside by a tension roller 21 urged by a tension spring 20 installed on a machine frame (not shown). A belt cleaning unit 22 is provided downstream of the secondary transfer position in the rotation direction of the intermediate transfer belt 12, and scrapes excess toner with a cleaning blade 23 or the like. Further, a facing roller 14 is arranged inside the intermediate transfer belt 12 so as to face the belt cleaning unit 22.
[0019]
In FIG. 2, a guide member 13 having a constant width formed in a convex shape is joined to the outer peripheral surface of the intermediate transfer belt 12 at a front end portion thereof by welding or pasting with a double-sided tape. The guide member 13 is a tape having a constant width of about 10 to 20 mm, and is movable while slidingly contacting the reference end surface A of the black photosensitive member 17K and the reference end surface B of the yellow photosensitive member 17Y. Therefore, when the intermediate transfer belt 12 is rotated and conveyed, the side surface of the guide member 13 moves while slidingly contacting the reference end surface A and the reference end surface B by applying a pulling force to the inner side in the drawing of the belt. , The position of the belt in the width direction is regulated. Thereby, it is possible to prevent the intermediate transfer belt 12 from meandering in a direction perpendicular to the running direction at the portions facing the four photoconductors 17Y, 17M, 17C and 17K. As a result, it is possible to form a high quality image without color shift by preventing transfer shift. Here, in order to suppress the meandering of the intermediate transfer belt 12, processing and assembly accuracy of the black photoreceptor 17K and the yellow photoreceptor 17Y is ensured so that the deflection of the reference end surfaces A and B is minimized. Further, since the diameters of the black photoreceptor 17K and the yellow photoreceptor 17Y are larger than those of the support rollers 10, 11, and 15 which have conventionally restricted the main scanning direction, if the processing accuracy is the same and the end face has the same run-out, meandering is performed. The period becomes larger. Therefore, banding in the main scanning direction becomes less noticeable. In the example shown in FIG. 2, the guide member 13 is provided on one end surface of the intermediate transfer belt 12, but the guide member 13 is provided on both end surfaces to provide the black photosensitive member 17K and the yellow photosensitive member 17Y. Thus, the position in the width direction may be regulated.
[0020]
As shown in FIG. 2, the three support rollers 10, 11, and 15 do not regulate the guide member 13, and are configured to have a width substantially equal to the width of the intermediate transfer belt 12. The primary transfer rollers 18Y, 18M, 18C, 18K and the opposing roller 14 also have a width substantially equal to the width of the intermediate transfer belt 12. On the other hand, the tension roller 21 and the secondary transfer roller 31 provided outside the intermediate transfer belt 12 are configured such that the roller width is inside the guide member 13 in the illustrated example in order to avoid interference with the guide member 13. ing. Alternatively, instead of this configuration, a groove having a width and a depth that does not cause interference with the guide member 13 may be provided.
[0021]
Further, as shown in FIG. 4, by chamfering H at the corners of the guide member 13, the sliding contact between the guide member 13 and the reference end surface A and the reference end surface B becomes smooth, so that the load during rotation driving can be reduced. Noise can be reduced. Further, it is possible to prevent the deterioration over time due to the rubbing of the guide member 13 with the black photoreceptor 17K and the yellow photoreceptor 17Y. The chamfer H is not limited to the corners of the guide member 13, but may be applied to the corners of the black photoreceptor 17K and the yellow photoreceptor 17Y, or may be provided at both corners.
[0022]
In the primary transfer device 3 according to the present embodiment, a tension is applied to the intermediate transfer belt 12 by applying a tensile force in a width direction (hereinafter, also referred to as a “main scanning direction”) to the intermediate transfer belt 12. The guide member 13 is moved toward the opposite side. FIG. 4 is a cross-sectional view of the vicinity of the black primary transfer roller 18K in the belt conveyance direction for explaining a configuration in which a tensile force in the width direction is applied to the intermediate transfer belt 12. The intermediate transfer belt 12 is provided with a second guide member 30 having a constant width formed in a convex shape as a tension receiving member and welded to the entire inner peripheral surface of the belt end opposite to the end where the guide member 13 is provided. Or they are joined by sticking with double-sided tape. Further, a split roller 31K that is in contact with the right end surface of the second guide member 30 is provided coaxially with the black primary transfer roller 18K. The split roller 31K is configured to be slidable in the axial direction of the black primary transfer roller 18K, and is urged leftward in the figure by a compression spring 32K. As a result, a leftward pulling force acts on the second guide member 30, and a tension in the main scanning direction can be applied to the intermediate transfer belt 12. As described above, when a force in the left direction in the drawing is applied to the intermediate transfer belt 12, the left end surface of the guide member 13 comes into contact with the reference end surface A of the black photosensitive member 17K without fail, and the photosensitive member (right end) The intermediate transfer belt 12 can be driven to rotate on a (surface) basis.
[0023]
The split roller 31K moves while sliding against the inner peripheral surface of the intermediate transfer belt 12 and the roller shaft 34K while being urged outward in the width direction of the intermediate transfer belt 12. For this reason, it is desirable to use a material such as polyacetal (POM) having a smaller sliding resistance than a metal material such as iron. The compression spring 32K has a larger inner diameter than the roller shaft 34K and a smaller outer diameter than the divided rollers 31. Thus, the compression spring 32 can urge the divided rollers 31 outward in the belt width direction without contacting the inner peripheral surface of the intermediate transfer belt 12. Note that the same effect can be obtained by a configuration in which an elastic member such as a urethane foam material or a rubber material is processed into a cylindrical shape in place of the compression spring 32 and is sandwiched between the primary transfer roller 18K and the split roller 31K. Can be
[0024]
Since the same components as the split roller 31K and the compression spring 32K are also provided on the yellow primary transfer roller 18Y, the left end surface of the guide member 13 reliably contacts the reference end surface B of the yellow photoconductor 17Y. As a result, at the two primary transfer positions between the black photoreceptor 17K and the yellow photoreceptor 17Y, the intermediate transfer belt 12 is expanded by applying tension in the width direction. As a result, loosening and distortion due to variations in the tension of the surface of the intermediate transfer belt 12 during driving can be suppressed, and the intermediate transfer belt can be driven in a favorable state in which it is appropriately stretched, and in particular, the dot position in the main scanning direction is stabilized. be able to.
[0025]
Further, as shown in FIG. 4, a guide member 13 is provided on the same side as the image forming reference position side (for example, the optical system writing start position K side). Therefore, the regulation position in the main scanning direction of the intermediate transfer belt 12 and the image forming reference position can be configured close to each other, and the distance variation between the two can be easily reduced. As a result, it is possible to suppress the displacement of the dot position in the main scanning direction. Note that the optical writing start position K is also a structure reference side which is generally a reference in assembling the apparatus.
If the optical system housing or the like is configured to regulate the play of the black photoconductor 17K in the thrust direction (main scanning direction), all dot positions in the main scanning direction can be performed on the basis of the photoconductor. As a result, it is possible to further ensure high dot position accuracy in the main scanning direction.
[0026]
As shown in FIG. 4, a urethane material 181K having an appropriate hardness over the image forming range is provided at the central portion in the width direction of the black primary transfer roller 18K. Therefore, at the primary transfer position opposed to the black photoreceptor 17K, the urethane material 181K is elastically deformed, so that the transfer nip width can be configured to be larger than when no urethane material is provided. Thereby, the transfer performance can be improved, and the black toner image on the black photoconductor 17K can be more reliably transferred to the intermediate transfer belt 12. In particular, when a transfer conveyance belt that conveys transfer paper is used instead of the intermediate transfer belt 12, by increasing the transfer nip width, the gap between the transfer paper and the photoconductor in the transfer electric field is stabilized, Good transfer performance can be obtained.
[0027]
In general, in the guide system in which convex guide members are provided at both left and right ends in the belt width direction, the sliding phenomenon of the guide member due to poor sliding between the guide member end and the roller end during the rotation driving causes a phenomenon in which the guide member runs up. Occasionally occurs. FIG. 7 is an explanatory diagram of a phenomenon in which the guide member 13 rides up when the guide members 13 are provided near both ends of the surface of the intermediate transfer belt 12 and the position in the width direction is controlled by the black photoconductor 17K. It may occur periodically at the same place every one belt revolution. The running of the guide member causes a dot displacement in the main scanning direction.
In the copying machine according to the present embodiment, the black primary transfer roller 18K on the side where the guide member 13 is provided is set to be at least the length of the guide member 13 as shown in FIG. (Corresponds to the medium dimension C). Further, the black photoconductor 17K on the side where the second guide member 30 is provided is set to be at least the length of the second guide member 30 (corresponding to the dimension D in the figure). As a result, the backing effect is produced by the circumferential surface of the extension portion of the primary transfer roller 18K and the black photoreceptor 17K, and the deformation of the intermediate transfer belt 12 that causes riding is prevented, and the guide member 13 and the second guide Riding of the member 30 can be prevented. Further, it is possible to prevent the intermediate transfer belt 12 from falling off from the support rollers 10, 11, and 15.
Here, the configuration in which both the lengths of the black primary transfer roller 18K and the black photoconductor 17K are set has been described. However, the present invention is not limited to this, and only one of the lengths may be set. For example, the length may be set to a predetermined length only on the side on which riding easily occurs. The length of the yellow primary transfer roller 17Y and the length of the yellow photoreceptor 17 are also assumed to be the same.
[0028]
The intermediate transfer belt 12 can be separated from the photoconductors 17Y, 17M, 17C, and 17K together with the primary transfer device 3 and pulled out to the near side of the copying machine for maintenance, component replacement, and jam clearance. It has become.
For this reason, the guide member 13 is provided at the end of the intermediate transfer belt 12 on the side of the primary transfer device 3 in the pull-out direction. Thus, when the primary transfer device 3 is pulled out, the guide member 13 can be prevented from interfering with the ends of the photoconductors 17Y, 17M, 17C, 17K, and the primary transfer device 3 can be pulled out smoothly. it can.
[0029]
When pulling out the primary transfer device 3 from the copying machine main body 100, first, the primary transfer device 3 is temporarily moved downward to separate the intermediate transfer belt 12 from the photoconductors 17Y, 17M, 17C, and 17K. At this time, if the guide member 13 is separated from the end surface of the black photosensitive member when the guide member 13 is separated from the end surface of the black photosensitive member when the intermediate transfer belt 12 is separated from the black photosensitive member 17 while the tensile force in the width direction is applied, the left side surface rubs against the right end portion of the black photosensitive member. Will be done. This rubbing also occurs at a portion where the guide member 13 is in contact with the end surface of the yellow photoreceptor 17Y. Since the guide member 13 is formed by processing urethane or the like into a fixed width and affixing or welding to the surface of the intermediate transfer belt, the rubbing may cause peeling or deterioration, and it may not be possible to control the meandering of the belt satisfactorily.
[0030]
Therefore, in the copying machine according to the present embodiment, a tension release mechanism that releases the tension in the width direction of the intermediate transfer belt 12 is provided. FIG. 5 is an explanatory diagram of the configuration and operation for releasing the tension by the black primary transfer roller 18K. FIG. 6 is an explanatory diagram of the operation when the tension is applied. Note that a similar tension release mechanism is also provided near the yellow primary transfer roller 18Y. This tension release mechanism includes an actuator 60K, a fixing pin 61K, and a lever 62K. The tip 601K of the actuator 60K fits into the groove of the split roller 33K, and the long hole 602K engages with the fixing pin 61K on the transfer device side. The right end of the actuator 60K is rotatably engaged with an action point 621K of the lever 62K, and the lever 62K is swingably supported at a fixed point 63K of the transfer device.
[0031]
As shown in FIG. 5, when the lever 62K is rotated clockwise and tilted to the release position, the actuator 60K moves rightward. At the same time, the tip 601K engaging with the groove of the split roller 33K moves the split roller 33K rightward against the urging force of the compression spring 32K. A groove slightly larger than the second guide member 30 is formed in the split roller 33K, and the left side surface of this groove presses the left side surface of the second guide member 30, and the intermediate transfer belt 12 moves to the right side. Is done. Due to this belt movement, a gap E is generated between the guide member 13 and the right end surface (reference end surface A) of the black photoconductor 17K. In this state, by separating the primary transfer device 3 from each of the photoconductors 17Y, 17M, 17C and 17K, the intermediate transfer belt 12 can be smoothly moved without interference between the guide member 13 and each photoconductor end. It can be separated from the photoreceptor.
Also, as shown in FIG. 6, after the intermediate transfer belt 12 is brought into contact with the black photoconductor 17K, the lever 62K is rotated counterclockwise to apply tension, so that the guide member 13 and the black photoconductor end are rotated. It is possible to prevent the guide member from being deformed due to interference of the portions.
[0032]
The release mechanism is used when performing maintenance, component replacement, and jam clearance. For example, a lever drive device (not shown) such as a solenoid is provided, and tension in the main scanning direction is not provided except during the image forming operation. May be cancelled. It is not necessary to apply tension in the main scanning direction to the intermediate transfer belt 12 and the guide member 13 except during the image forming operation. In this case, the lever driving device is controlled to control the main transfer belt 12 and the guide member 13 Release the tension in the scanning direction. As a result, the durability of the intermediate transfer belt 12 and the guide member 13 can be improved, and the life can be extended.
[0033]
Further, as shown in FIG. 2, markings 24 having a uniform pitch and a density difference are applied over the entire length of one surface of the guide member 13 other than being joined to the intermediate transfer belt 12. Further, a detection sensor 25 for optically reading the marking 24 is provided. When the intermediate transfer belt 12 is rotationally driven, the marking 24 is detected by the detection sensor 25, and the speed fluctuation of the intermediate transfer belt 12 is calculated from the detection result. Then, by controlling a drive motor (not shown) so as to change the rotation speed of the support roller 10 based on the calculation result of the speed fluctuation, feedback control is performed so that the speed of the intermediate transfer belt 12 is always constant. As described above, by stabilizing the conveyance speed of the intermediate transfer belt 12, it is possible to reduce color misregistration between the color image forming units also in the running direction (sub-scanning direction) of the intermediate transfer belt 12.
FIG. 8 shows a block diagram of the feedback control. This will be described in more detail with reference to this block diagram. The pulse signal input to the detection sensor 25 is counted by the counter 263 at regular intervals by the oscillator 262 via the CPU 261 of the control unit 26, taken into the ROM 27, and compared with the specified pulse number (the pulse number for the desired speed). Is done. The increase or decrease of the result of the comparison is fed back to the stepping motor controller 28. In other words, the intermediate transfer belt 12 is driven at a constant speed by performing frequency conversion so that the rotation frequency of the stepping motor 29 is increased when the speed has not reached the specified speed, and decreased when the speed is not reached.
[0034]
[Example 2]
In the first embodiment, the configuration in which the guide member 13 is brought into contact with the reference end surfaces A and B of the black photoreceptor 17K and the yellow photoreceptor 17Y has been described. However, a groove is provided near the end of the photoreceptor, and the guide member is provided therein. You may make it fit. In the case where the widthwise rigidity of the intermediate transfer belt is sufficiently high, and the widthwise position of the entire belt can be sufficiently restricted only at one end, the split roller 31 or the compression spring 32 for applying tension in the belt width direction is used. Can be omitted.
FIG. 9 is an explanatory diagram of the vicinity of the black photoconductor 17K according to the present embodiment. As illustrated, a groove 172K is formed by press-fitting a flange 171K into the right end of the black photoconductor 17K. In order to smoothly attach and detach the primary transfer device 3, both the shoulders of the guide member 13 are provided with a large chamfer J of about C0.5 to C1.5 mm.
[0035]
The guide member 13 is formed in a tape shape, so that the dimension in the width direction can be easily regulated. Further, the width of the groove 172K is formed to have a constant width of about 10 to 20 mm so as to fit into the guide member 13, but it is easy to form the groove with high precision by press-fitting while sandwiching a spacer (not shown) having a constant width. I can do it. As a result, the gap between the guide member 13 and the groove 172K of the black photoconductor 17K can be suppressed to about 20 to 50 μm.
[0036]
[Example 3]
In the first and second embodiments, as shown in FIG. 4, the split roller 31 </ b> K and the compression spring 32 </ b> K are provided, and a left-side force is applied to the intermediate transfer belt 12 to apply tension to the opposite side of the guide member 13. It was configured to approach. However, the present invention is not limited to this, and the intermediate transfer belt 12 may be configured to be skewed in the direction opposite to the side on which the guide member 13 is provided, depending on the shape or mounting form of the belt support roller. FIG. 10 is a plan view of the primary transfer device 3 according to the present embodiment as viewed from above. The support roller 11, which is driven and rotated by stretching the intermediate transfer belt 12, is arranged at a slight angle from a direction perpendicular to the rotational movement direction of the belt. For this reason, when the intermediate transfer belt 12 is driven in the direction of the arrow in the drawing by the rotational driving force of the support roller 10, the intermediate transfer belt 12 is skewed leftward. This ensures that the left end surface of the guide member 13 contacts the reference end surfaces A and B (not shown) of the black photoreceptor 17K and the yellow photoreceptor 17Y, and the intermediate transfer belt 12 is based on the photoreceptor (right end surface). Can be driven to rotate.
Further, a tapered roller 65 as shown in FIG. 11 may be used. When the taper roller 65 rotates, a force to move the intermediate transfer belt 12 to a larger diameter acts on the intermediate transfer belt 12, so that the intermediate transfer belt 12 can be driven to run obliquely to the left side, and the same effect as the above-described method can be obtained. Can be.
As described above, compared with the configuration described in the first embodiment, it is not necessary to provide a member such as the split roller 31 that applies the tension in the width direction to the intermediate transfer belt 12, and the configuration can be simplified.
[0037]
In the present embodiment, the meandering of the intermediate transfer belt of the indirect transfer type in which the toner images on the respective color photosensitive members are primarily transferred onto the intermediate transfer belt 12 and then secondarily transferred onto the transfer paper 19 has been described. The present invention is not limited to this. By adhering the paper onto the transport belt and providing a guide member on the direct transfer type transport belt that directly transfers the toner image sequentially from the photoconductors of each color, or by marking the guide member, the intermediate transfer belt and Similarly, effects such as meandering prevention can be obtained.
[0038]
As described above, according to the present embodiment, the toner image formed on the photoreceptor as the image carrier is formed as an endless belt that is rotated and driven by being stretched around the support rollers as the plurality of support members. In a primary transfer device as a transfer belt unit for transferring an image onto an intermediate transfer belt, a guide member having a constant width is provided around the entire surface of the intermediate transfer belt near at least one of the widthwise ends of the intermediate transfer belt. The transfer belt is driven to rotate while the guide member is restricted in the widthwise position by the end of the photoconductor as a guide. As a result, image deterioration can be prevented without impairing the linearity of the transferred image. In the above-described embodiment, the present invention has been described using the indirect transfer device in which the toner image is primarily transferred onto the intermediate transfer belt and then secondarily transferred onto the transfer paper. The present invention is not limited to this. The present invention is also applicable to a direct transfer device in which a transfer paper is conveyed by a transfer belt, and a toner image is sequentially transferred from each color photoconductor onto a transfer paper and superposed, and the same effect is obtained. Can be
In addition, the guide member is provided at one of the widthwise ends of the intermediate transfer belt, and the belt is provided in a direction opposite to the widthwise end where the guide member is provided with respect to the intermediate transfer belt. Belt shifting means for applying a force to shift the belt. Therefore, loosening and distortion due to tension variations on the belt surface during driving can be suppressed by expanding the intermediate transfer belt in the width direction. As a result, the intermediate transfer belt can be driven in a favorable state in which it is appropriately stretched, and the dot position accuracy in the main scanning direction can be particularly improved. In addition, by applying a tension in the width direction to the intermediate transfer belt, it is possible to suppress the backlash in the axial direction between the black photoconductor and the bearing at the same time. The dot position accuracy can be further improved.
Also, a plurality of photoconductors are arranged in the rotational movement direction of the intermediate transfer belt and opposed to the intermediate transfer belt. The width direction of the intermediate transfer belt is regulated by the ends of at least two photosensitive members with the black photosensitive member on the downstream side. For example, regulating the width of the intermediate transfer belt in the width direction of the intermediate transfer belt at two locations, that is, the cyan photoconductor and the magenta photoconductor, which are close to each other, makes the belt meandering more reliably when regulated between photoconductors that are farther apart. Can be suppressed. Therefore, when forming a color image, it is possible to reduce the meandering of the intermediate transfer belt, prevent transfer deviation, and form an image with less main scanning color deviation.
The end in the width direction of the intermediate transfer belt provided with the guide member is the end on the optical writing start side which is the image forming reference position side on the photoconductor. In this way, the width direction (main scanning direction) position of the intermediate transfer belt is regulated on the same side as the optical writing start side. Therefore, the regulation position of the intermediate transfer belt in the main scanning direction and the image forming reference position can be configured close to each other, and the distance variation between the two can be reduced as compared with the case where the belt position is regulated on the side opposite to the image forming reference position. As a result, it is possible to further suppress the dot displacement in the main scanning direction.
In addition, the guide member is provided on one of the widthwise ends of the intermediate transfer belt, and the transfer belt unit can be attached to and detached from the photoreceptor from one end where the guide member is provided. . As a result, when the transfer belt unit is detached from the photoconductor for maintenance, component replacement, and jam clearance, the guide member and the photoreceptor are compared with the case where the transfer belt unit is detached from the end opposite to the guide member. Interference can be prevented. Therefore, the transfer belt unit can be smoothly attached and detached, and the guide member can be prevented from being damaged.
Further, an actuator or the like is provided as tension releasing means for releasing the application of the tension of the intermediate transfer belt by the belt shifting means. Thus, it is possible to release the tension in the width direction applied to the intermediate transfer belt and the guide member except during the image forming operation or when the transfer belt unit is attached or detached. Therefore, the durability of the intermediate transfer belt and the guide member is improved, and the life can be extended.
Further, a split roller or the like is provided as a separating means for separating the guide member from the end of the photosensitive member. If the transfer belt unit is pulled out of the copying machine in a state where the guide member and the end of the photoconductor are in contact with each other, the guide member may interfere with the end of the photoconductor and be deformed, thereby shortening the life of the guide member or causing damage. is there. In this transfer belt unit, the transfer belt unit can be pulled out after releasing the contact between the guide member and the end of the photoconductor and separating them, so that shortening of the life and damage due to deformation of the guide member can be prevented. it can.
Further, the belt shifting means includes a second guide member as a tension receiving member provided around the back surface of an end opposite to the end where the guide member of the intermediate transfer belt is provided, as a tension receiving member, facing the photoconductor. A transfer member which is disposed coaxially with a primary transfer roller serving as a transfer member, and which has substantially the same diameter as the transfer member which can move in the axial direction, and which is in contact with the second guide member to apply tension. The split roller and a compression spring as an urging member for applying an urging force to the second guide member side are configured. Therefore, since the guide member of the intermediate transfer belt is in contact with the end of the photoreceptor and the position in the width direction is regulated, the split roller is urged against the second guide member of the intermediate transfer belt by the compression spring to urge the intermediate roller. The tension in the width direction can be applied to the transfer belt. In addition, the primary transfer roller applies a tension in the width (main scanning) direction to the intermediate transfer belt, and a stress in the width direction is applied to a driving roller for transmitting a driving force in the rotational movement (sub-scanning) direction to the belt. Since it is not applied, belt running unevenness can also be suppressed. Further, the above-mentioned divided rollers are made of a material having a better sliding property than a metal material. Therefore, by forming the divided rollers from, for example, polyacetal, the roller moves while sliding well on the roller shaft and the back surface of the intermediate transfer belt, and the tension in the main scanning direction is smoothly applied to the intermediate transfer belt without increasing the driving load. Can be given.
Further, in a state in which the guide member is in contact with the end of the photoconductor, the position of the end surface of the primary transfer roller on the side where the guide member is provided is the same as the widthwise outer end of the guide member, or The length of the primary transfer roller was set so as to be located outside the end. Accordingly, the primary transfer roller abuts on the inside of the intermediate transfer belt at the portion where the guide member is provided, and it is possible to prevent the end of the intermediate transfer belt provided with the guide member from being bent inward. . Therefore, stable driving can be obtained by preventing the guide member from riding on the photoconductor and dropping off the support roller of the intermediate transfer belt.
Further, in a state where the guide member is in contact with the end of the photoconductor, the position of the end surface of the photoconductor on the side where the second guide member is provided is the same as the widthwise outer end of the second guide member, or The length of the photoreceptor was set so as to be located outside this end. This prevents the photosensitive member from coming into contact with the portion of the intermediate transfer belt provided with the second guide member to the outside of the intermediate transfer belt, thereby preventing the end of the intermediate transfer belt provided with the second guide member from being bent outward. Can be. Therefore, it is possible to prevent the second guide member from riding on the primary transfer roller and to prevent the intermediate transfer belt from dropping off from the support roller, thereby obtaining stable driving.
A urethane material as an elastic member was provided on the surface of the primary transfer roller corresponding to the image forming range of the photoconductor. Therefore, at the primary transfer position facing the photoreceptor, the urethane material is elastically deformed, and the transfer nip width can be configured to be larger than when no urethane material is provided. As a result, transfer performance can be improved, and the toner image on the photoconductor can be more reliably transferred to the intermediate transfer belt. In particular, when a transfer conveyance belt that conveys transfer paper is used in place of the intermediate transfer belt, the gap between the transfer paper and the photoconductor is stabilized by increasing the transfer nip width, and good transfer performance is obtained. Can be obtained.
Also, the belt shifting means may be configured such that at least one of the support rollers is disposed obliquely to a direction perpendicular to the rotational movement direction of the intermediate transfer belt, or at least one of the support rollers changes in diameter. It was configured using a tapered roller. When the support roller is disposed obliquely to a direction orthogonal to the rotational movement direction of the intermediate transfer belt, a force that obliquely moves the belt acts when the intermediate transfer belt is rotationally moved. Therefore, by skewing the intermediate transfer belt in the end direction opposite to the guide member, tension can be applied in the width direction at the same time as the intermediate transfer belt is moved toward the opposite side to the guide member. Further, when the taper roller rotates, a force for moving the intermediate transfer belt to a larger diameter acts on the intermediate transfer belt, and the intermediate transfer belt is skewed toward an end portion on the opposite side to the guide member, so that the intermediate transfer belt is moved to the guide member. And tension can be applied in the width direction at the same time. As described above, the tension in the width direction can be applied at the same time as the intermediate transfer belt is moved toward the opposite side to the guide member with a simple configuration without providing an elastic member such as a compression spring.
The guide portion is a groove that fits with the guide member. Therefore, since the guide member fits into the groove to prevent meandering of the intermediate transfer belt, only one location is required on one side as compared with a method in which the guide member is provided on both sides, and the cost of the belt can be reduced. Further, since the processing of the width of the guide member and the width of the groove can ensure sufficient processing accuracy easily and inexpensively, it is possible to maintain a gap where stable rotation of the intermediate transfer belt can be obtained at the time of fitting.
In addition, at least one of the guide member and the end portion or the groove of the photoconductor is chamfered. Thereby, the sliding contact between the guide member and the end portion or the groove of the photoconductor is made smooth, and the load and noise during the rotation driving are reduced. Further, the deterioration of the guide member, the end portion of the photoreceptor, or the groove due to corner rubbing with time is prevented, and the meandering of the intermediate transfer belt is stably reduced over a long period of time.
In addition, the image forming apparatus includes markings at equal pitches on the surface of the guide member, detecting means for detecting the marking, and control means for controlling the rotational drive of the intermediate transfer belt. Then, the running speed of the intermediate transfer belt is calculated based on the result detected by the detecting unit, and the rotation drive of the intermediate transfer endless belt is controlled based on the calculated running speed so that the running speed becomes constant. By stabilizing the traveling speed of the intermediate transfer belt, it is possible to reduce color misregistration between the color image forming units also in the traveling direction (sub-scanning direction) of the intermediate transfer belt.
Further, an optical writing device as a latent image forming means for forming a latent image on the photoreceptor, a developing device as a developing means for converting the electrostatic latent image on the photoreceptor into a toner image, and a developing device formed on the photoreceptor And a primary transfer device as a transfer unit for transferring the toner image onto an intermediate transfer belt that is stretched around a plurality of support rollers and driven to rotate, or onto transfer paper that is carried and conveyed by a transfer / conveyance belt. In a copying machine as an image forming apparatus, the transfer belt unit is used as the primary transfer device.
Further, a digital color copying machine using a digital writing device as a means for forming a latent image on a photoreceptor is provided. In a digital color copying machine, a transfer deviation of each photoconductor due to meandering of the intermediate transfer belt appears as a main scanning color deviation, which causes a significant deterioration in image quality. Therefore, by applying the present invention to a digital color copying machine, there is an excellent effect that scanning color shift is prevented and a high quality image is obtained.
[0039]
【The invention's effect】
The invention according to claims 1 to 18 has an excellent effect that image deterioration due to vibration and play of the image carrier and the transfer belt unit can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment.
FIG. 2 is a perspective view of a primary transfer device.
FIG. 3 is a side view of the primary transfer device.
FIG. 4 is an explanatory diagram of a belt shifting unit near a black primary transfer roller.
FIG. 5 is an explanatory diagram of a tension release mechanism near a black primary transfer roller.
FIG. 6 is an explanatory diagram of a tension release mechanism near a black primary transfer roller.
FIG. 7 is an explanatory diagram of a phenomenon in which a guide member runs over.
FIG. 8 is a block diagram of an intermediate transfer belt traveling speed control.
FIG. 9 is a configuration diagram in which a groove for fitting with a guide member is provided on a black photosensitive member.
FIG. 10 is a plan view of the primary transfer device, showing a state in which one of the support rollers is inclined.
FIG. 11 is a plan view of a primary transfer device showing a configuration in which one of the support rollers is a tapered roller.
FIG. 12 is an explanatory diagram of a conventional driving method of an intermediate transfer belt.
[Explanation of symbols]
1 Charging device
2 Developing device
3 Primary transfer device
4 Photoconductor cleaning device
5 Digital writer
7 Secondary transfer device
8 Fixing device
9 Secondary transfer belt
10,11,15 Support roller
13 Guide member
14 Cleaning opposed roller
17Y, M, C, K photoreceptor
18Y, M, C, K primary transfer roller
19 Transfer paper
20 tension roller
21 Spring
22 Intermediate transfer body cleaning device
23 Cleaning blade
24 Marking
25 Detecting means
30 Second guide member
31K, 33K split roller
32K compression spring
60K actuator
61K fixed pin
62K lever
100 Copier body
171K flange
172K groove
200 paper feed table
300 Scanner
400 Automatic Document Feeder (ADF)

Claims (18)

像担持体上に形成されたトナー像を、複数の支持部材に張架されて回転駆動される無端ベルト上、または、無端ベルトに担持搬送される転写体上に転写する転写ベルトユニットにおいて、
上記無端ベルトの幅方向の端部のうち少なくともいずれか一方の近傍に表面全周にわたって一定幅のガイド部材を設け、該無端ベルトは該ガイド部材が上記像担持体に設けられたガイド部で幅方向の位置を規制されながら回転駆動されることを特徴とする転写ベルトユニット。In a transfer belt unit that transfers the toner image formed on the image carrier onto an endless belt that is stretched over a plurality of support members and driven to rotate, or onto a transfer body that is carried and conveyed by the endless belt,
A guide member having a constant width is provided around at least one of the end portions in the width direction of the endless belt over the entire circumference of the surface, and the endless belt has a width at a guide portion provided on the image carrier. A transfer belt unit which is driven to rotate while its position in the direction is regulated. 請求項１の転写ベルトユニットにおいて、
上記ガイド部材を上記無端ベルトの幅方向の端部のうちいずれか一方の近傍に設け、かつ、上記無端ベルトに対して該ガイド部材が設けられた幅方向の端部と反対側の端部方向に寄せる力を付与するベルト寄せ手段を設けたことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 1,
The guide member is provided in the vicinity of any one of the widthwise ends of the endless belt, and an end direction opposite to the widthwise end provided with the guide member with respect to the endless belt. A transfer belt unit for providing a belt shifting means for applying a force toward the transfer belt. 請求項１又は２の転写ベルトユニットにおいて、
複数の像担持体を上記無端ベルトの回転移動方向に並べて該無端ベルトに対向させ、該複数の像担持体のうち、該無端ベルトの回転移動方向に対して最上流側と最下流側との少なくとも２つの像担持体に上記ガイド部を設けたことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 1 or 2,
A plurality of image carriers are arranged in the rotational movement direction of the endless belt and opposed to the endless belt, and among the plurality of image carriers, the most upstream side and the most downstream side with respect to the rotational movement direction of the endless belt. A transfer belt unit comprising the guide unit provided on at least two image carriers. 請求項２の転写ベルトユニットにおいて、
上記ガイド部材が設けられた上記無端ベルトの幅方向の端部は、上記像担持体への作像基準位置側の端部であることを特徴とする転写ベルトユニット。The transfer belt unit according to claim 2,
A transfer belt unit, wherein an end in the width direction of the endless belt provided with the guide member is an end on an image forming reference position side on the image carrier. 請求項２又は４の転写ベルトユニットにおいて、
上記ガイド部材を設けた上記無端ベルトの幅方向の端部側から、転写ベルトユニットを上記像担持体に対して脱着可能に構成したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 2 or 4,
A transfer belt unit, wherein the transfer belt unit is configured to be attachable to and detachable from the image carrier from an end in the width direction of the endless belt provided with the guide member. 請求項２、４又は５の転写ベルトユニットにおいて、
上記ベルト寄せ手段による上記無端ベルトの幅方向の張力を解除する張力解除手段を設けたことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 2, 4 or 5,
A transfer belt unit comprising a tension releasing means for releasing a tension in a width direction of the endless belt by the belt shifting means. 請求項６の転写ベルトユニットにおいて、
上記ガイド部材と上記ガイド部とを離間させる離間手段を設けたことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 6,
A transfer belt unit provided with a separating means for separating the guide member from the guide portion. 請求項２、４、５、６又は７の転写ベルトユニットにおいて、
上記ベルト寄せ手段を、上記無端ベルトの上記ガイド部材を設けた端部と反対側の端部の裏面近傍に全周にわたって設けられた張力受け部材と、
上記像担持体に対向する転写部材の同軸上に配設され軸方向に移動可能な該転写部材と略同一径であって、該張力受け部材に接触して張力を付与する張力付与部材と、
該張力付与部材に該張力受け部材側への付勢力を付与する付勢部材とを用いて構成したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 2, 4, 5, 6, or 7,
The belt shifting means, a tension receiving member provided over the entire circumference near the back surface of the end of the endless belt opposite to the end provided with the guide member,
A tension-applying member that is disposed on the same axis as the transfer member facing the image carrier, has substantially the same diameter as the transfer member that is movable in the axial direction, and applies tension by contacting the tension-receiving member;
A transfer belt unit comprising: a biasing member that applies a biasing force toward the tension receiving member to the tension applying member. 請求項８の転写ベルトユニットにおいて、
上記張力付与部材を金属材料に比べ摺動性の良い材料を用いて構成したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 8,
A transfer belt unit, wherein the tension applying member is made of a material having better slidability than a metal material. 請求項８又は９の転写ベルトユニットにおいて、
上記ガイド部材が上記ガイド部に当接した状態で、該ガイド部材が設けられた側の上記転写部材の端面の位置が、該ガイド部材の幅方向外側の端部と同じ位置、または、該端部よりも外側の位置にくるように、該転写部材の長さを設定したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 8, wherein
In a state where the guide member is in contact with the guide portion, the position of the end surface of the transfer member on the side where the guide member is provided is the same as the widthwise outer end of the guide member, or A length of the transfer member is set so as to be located outside of the transfer belt unit. 請求項８、９又は１０の転写ベルトユニットにおいて、
上記ガイド部材が上記ガイド部に当接した状態で、上記張力受け部材が設けられた側の上記像担持体の端面の位置が、該張力受け部材の幅方向外側の端部と同じ位置、または、該端部よりも外側の位置にくるように、該像担持体の長さを設定したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 8, 9 or 10,
In the state where the guide member is in contact with the guide portion, the position of the end surface of the image carrier on the side where the tension receiving member is provided is the same as the widthwise outer end portion of the tension receiving member, or A length of the image carrier is set so as to be located outside the end portion. 請求項８、９、１０又は１１の転写ベルトユニットにおいて、
上記転写部材の上記像担持体の作像範囲に対応した部分の表面に弾性部材を設けたことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 8, 9, 10, or 11,
A transfer belt unit, wherein an elastic member is provided on a surface of a portion of the transfer member corresponding to an image forming range of the image carrier. 請求項２、４、５、６又は７の転写ベルトユニットにおいて、
上記ベルト寄せ手段を、上記支持部材の少なくとも１つを上記無端ベルトの回転移動方向と直交する方向に対して斜めに配設することにより、もしくは、上記支持部材の少なくとも１つを直径が変化するテーパローラを用いて構成したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 2, 4, 5, 6, or 7,
By arranging at least one of the support members at an angle to a direction orthogonal to the rotational movement direction of the endless belt, or by changing the diameter of at least one of the support members, A transfer belt unit comprising a taper roller. 請求項１、２、３、４、５、６、７、８、９、１０、１１、１２又は１３の転写ベルトユニットにおいて、
上記ガイド部が上記ガイド部材と勘合する溝であることを特徴とする転写ベルトユニット。The transfer belt unit according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13,
The transfer belt unit, wherein the guide portion is a groove that fits with the guide member. 請求項１、２、３、４、５、６、７、８、９、１０、１１、１２、１３又は１４の転写ベルトユニットにおいて、
上記ガイド部材と上記ガイド部の少なくとも一方に面取りを施したことを特徴とする転写ベルトユニット。The transfer belt unit according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14,
A transfer belt unit, wherein at least one of the guide member and the guide portion is chamfered. 請求項１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４又は１５の転写ベルトユニットにおいて、
上記ガイド部材の表面に等ピッチのマーキングと、該マーキングを検出する検出手段と、上記無端ベルトの回転駆動を制御する回転駆動制御手段とを備え、該検出手段により検出された結果に基づき無端ベルトの走行速度を算出し、該算出された走行速度に基づき走行速度が一定になるよう回転駆動制御手段により無端ベルトの回転駆動を制御することを特徴とする転写ベルトユニット。The transfer belt unit according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15,
Equi-pitch markings on the surface of the guide member, detection means for detecting the markings, and rotation drive control means for controlling the rotation drive of the endless belt, the endless belt based on the result detected by the detection means A transfer speed of the endless belt is controlled by a rotation drive control means so that the running speed becomes constant based on the calculated running speed. 像担持体上に潜像を形成する潜像形成手段と、
該像担持体上の静電潜像をトナー像化する現像手段と、
該像担持体上に形成されたトナー像を、複数の支持部材に張架されて回転駆動される無端ベルト上、または、無端ベルトに担持搬送される転写体上に転写する転写手段とを備えた画像形成装置において、
上記転写手段として、請求項１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４、１５又は１６に記載のいずれかの転写ベルトユニットを用いることを特徴とする画像形成装置。Latent image forming means for forming a latent image on the image carrier,
Developing means for converting the electrostatic latent image on the image carrier into a toner image,
Transfer means for transferring the toner image formed on the image carrier onto an endless belt that is stretched over a plurality of support members and driven to rotate, or onto a transfer body carried and transported by the endless belt. Image forming apparatus,
As the transfer unit, any one of the transfer belt units according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 is used. An image forming apparatus comprising: 請求項１７の画像形成装置において、
上記潜像形成手段がデジタル書込み手段を備えたことを特徴とする画像形成装置。The image forming apparatus according to claim 17,
An image forming apparatus, wherein the latent image forming means includes a digital writing means.
JP2002331028A 2002-11-14 2002-11-14 Transfer belt unit and image forming apparatus using the unit Expired - Fee Related JP4171639B2 (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007293178A (en) * 2006-04-27 2007-11-08 Fuji Xerox Co Ltd Image forming apparatus and transfer unit
JP2007298813A (en) * 2006-05-01 2007-11-15 Fuji Xerox Co Ltd Image forming apparatus and transfer unit
JP2008275928A (en) * 2007-04-27 2008-11-13 Fuji Xerox Co Ltd Image forming apparatus
JP2009103898A (en) * 2007-10-23 2009-05-14 Murata Mach Ltd Image forming apparatus
JP2010175689A (en) * 2009-01-28 2010-08-12 Sharp Corp Endless belt unit and image forming apparatus equipped with the same
KR101123690B1 (en) * 2005-04-29 2012-03-15 삼성전자주식회사 Transfer unit for image forming apparatus

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101123690B1 (en) * 2005-04-29 2012-03-15 삼성전자주식회사 Transfer unit for image forming apparatus
JP2007293178A (en) * 2006-04-27 2007-11-08 Fuji Xerox Co Ltd Image forming apparatus and transfer unit
JP2007298813A (en) * 2006-05-01 2007-11-15 Fuji Xerox Co Ltd Image forming apparatus and transfer unit
JP2008275928A (en) * 2007-04-27 2008-11-13 Fuji Xerox Co Ltd Image forming apparatus
JP2009103898A (en) * 2007-10-23 2009-05-14 Murata Mach Ltd Image forming apparatus
JP2010175689A (en) * 2009-01-28 2010-08-12 Sharp Corp Endless belt unit and image forming apparatus equipped with the same

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