JP2004258185A

JP2004258185A - Image forming apparatus

Info

Publication number: JP2004258185A
Application number: JP2003047399A
Authority: JP
Inventors: Koichiro Takashima; 弘一郎高島; Tetsuya Kobayashi; 哲也小林; Taishin Aso; 泰臣麻生
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2003-02-25
Filing date: 2003-02-25
Publication date: 2004-09-16
Anticipated expiration: 2023-02-25
Also published as: JP4047193B2

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a fogged image arises because a photoreceptive drum is extremely shaved by a use state due to the long rotation time of the photoreceptive drum when time for image forming operation is made long. <P>SOLUTION: Even in the case that image information having a large information quantity is sent from a host computer and the time for the image forming operation is made long during continuous printing, image processing time is calculated from the image information quantity by a CPU, so that the rotation of the photoreceptive drum is stopped in accordance with the image processing time. Also, the rotation of the photoreceptive drum is stopped in accordance with the detected temperature of a temperature thermistor at the end part of a fixing part even in the case that the time for the image forming operation is made long by suppressing temperature rising at the paper non-feeding part of a fixing unit when the continuous printing is performed on paper whose width is small. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電子写真感光体・静電記録誘電体等の像担持体の被帯電体の被帯電面を帯電する帯電装置を備え、像担持体上に形成された静電潜像を現像剤（トナー）で可視化する画像形成装置に関する。
【０００２】
【従来の技術】
図１は従来の画像形成装置の概略断面図である。
【０００３】
まず、画像形成手段による画像形成動作について説明する。
【０００４】
図１において、静電潜像担持体としての感光ドラム１１０は、矢印方向に回転する。まず感光ドラム１１０は、帯電装置１０７によって一様に帯電される。その後、露光手段であるレーザ光学装置１０８からのレーザ光１０９により露光され、その表面に静電潜像が形成される。
【０００５】
この静電潜像を、感光ドラム１１０に所定の侵入量をもって押圧、接触し配設された現像装置１１１によって現像し、トナー像として可視化する。
【０００６】
可視化された感光ドラム１１０上のトナー像は、転写ローラ１１２によって転写材としての記録メディア１０１に転写される。転写されずに感光ドラム１１０上に残存した転写残トナーは、クリーニング部材であるクリーニングブレード１１３により掻き取られ、廃トナー容器に収納される。クリーニングされた感光ドラム１１０は上述作用を繰り返し、画像形成を行う。
【０００７】
一方、トナー像を転写された記録メディア１０１は、定着装置１１４によって永久定着された後、機外に排紙される。
【０００８】
このような画像形製装置には以下のような問題点がある。
【０００９】
感光ドラム１１０が帯電される際、帯電装置１０７から感光ドラム１１０へ放電電流が流れ、この放電電流により、感光ドラム１１０の安定帯電が可能となるが、このとき、放電電流の電気エネルギーは、全て感光ドラム１１０の帯電に使われるのでなく、放電電流の電気エネルギーの一部は感光ドラム表面の高分子材料を電気的に刺激することで、高分子材料の分子結合に欠陥が生じ易くなる。これにより、感光ドラム表面は、トナーを介してのクリーニングブレード１１３との摺察により、削れ易くなっている。つまり、感光ドラムの削れ量は、感光ドラムの回転数（時間）と比例している。
【００１０】
感光ドラム１１０が過剰に削れてしまった場合、帯電装置１０７による感光ドラム１１０への帯電電位が下がることにより、カブリ画像が発生している。
【００１１】
このような問題を解決するには、感光ドラム１１０の感光層の膜厚を十分に厚くしてやればよいが、膜厚のアップに伴う感光ドラム１１０の製造ラインでの効率ダウンや、材料費の増加により、画像形成装置がコストアップするという不具合がある。したがって、従来は画像形成装置を設計する際、感光ドラム１１０の感光層の膜厚はプリント保証枚数においての感光ドラム１１０の回転時間を計算して、感光ドラム削れによるカブリ画像の発生しない膜厚に設定している。
【００１２】
【発明が解決しようとする課題】
しかしながら、近年の画像形成装置は記録材の多様化や情報量の大きい画像の印刷をよりいっそう求められている。こういった状況下では、紙サイズや、ホストコンピュータから送られるジョブ内容によっては、連続プリント動作において画像形成動作間の時間が長くなる場合がある。例えば、幅の小さい小サイズ紙を通紙することで起きる定着器の非通紙部昇温という現象があり、このとき非通紙部昇温を防ぐために画像形成動作間の時間を長くする場合や、別の例においては、ホストコンピュータから送られた画像情報の情報量が大きいときに、画像形成装置内の情報処理がプリントスピードにたいして遅れると、情報処理が律速になるため画像形成動作間の時間が長くなる場合があり、使用状況によっては、公称寿命内においても感光ドラム削れによるカブリ画像を生じることがある。
【００１３】
従って、本発明の目的は、画像形成装置において、連続プリント中に画像形成動作間の時間が長くなるような場合に、感光ドラム削れを減らし、かぶり画像を発生することなしに、低コストな画像形成装置を提供することである。
【００１４】
【課題を解決するための手段】
本発明は下記のような構成を有することを特徴とする画像形成装置である。
（１）像担持体と、像担持体に接触して像担持体表面を清掃するクリーニング部材と、を有する画像形成装置において、複数イメージのプリントジョブ処理中に画像形成動作間の時間に応じて、像担持体の駆動速度を変化させる、ことを特徴とする画像形成装置。
（２）像担持体と、像担持体に接触して像担持体表面を清掃するクリーニング部材と、像担持体に接触して現像する現像ローラと、を有する画像形成装置において、像担持体と現像ローラが離接する機構を有し、複数イメージのプリントジョブ処理中に画像形成動作間の時間に応じて、像担持体と現像ローラを離接させ、かつ、像担持体の駆動速度を変化させる、ことを特徴とする画像形成装置。
（３）複数イメージのプリントジョブ処理中に画像形成動作間の時間に応じて、像担持体の駆動を停止させることを特徴とする（１）、（２）記載の画像形成装置。
（４）画像形成動作間の時間は、像担持体回転の減速・加速時間よりも長いことを特徴とする（１）〜（３）記載の画像形成装置。
（５）像担時体と現像ローラの離接・接触時間が像担持体回転の減速・加速時間よりも長いとき、画像形成動作間の時間は、像担時体と現像ローラの離接・接触時間よりもよりも長いことを特徴とする（２）、（３）記載の画像形成装置。
（６）ＣＰＵを備え、ホストコンピュータから送られた画像情報の情報量をもとにＣＰＵが画像形成動作間の時間を計算することを特徴とする（１）〜（５）記載の画像形成装置。
（７）画像形成部において未定着画像を形成した記録材と、この記録材を通過させて未定着画像を記録材に加熱定着させる定着器と、を備えて、非通紙域温度情報をもとに画像形成動作間の時間を変えることを特徴とする（１）〜（６）記載の画像形成装置。
（８）非通紙域温度情報は定着部の非通紙域を測定できる温度検知手段によって知ることを特徴とする（７）記載の画像形成装置。
（９）記録材の先端位置を検知する記録材先端検知手段を備えて、複数イメージのプリントジョブ中に画像形成動作間の時間を測定する（１）〜（８）記載の画像形成装置
（１０）記録材の後端位置を検知する記録材後端検知手段と、記録材の先端位置を検知する記録材先端検知手段と、を備えて、複数イメージのプリントジョブ中に記録材後端位置と記録材先端位置から画像形成動作間の時間を測定することを特徴とする（１）〜（８）記載の画像形成装置
（１１）記録材が画像形成装置内を移動する道程において、記録材先端検知手段が像転写位置よりも先に位置し、記録材先端が記録材先端検知手段から像転写位置までを通過する時間が、現像ローラ回転の減速・加速時間よりも長いことを特徴とする（９）、（１０）記載の画像形成装置
（１２）像担持体に接触して現像する現像ローラを有し、像担持体と現像ローラが離接する機構を有し、記録材先端が記録材先端検知手段から像転写位置までを通過する時間が、像担時体と現像ローラの離接時間、かつ現像ローラ回転の減速・加速時間よりも長いことを特徴とする（９）、（１０）記載の画像形成装置
【００１５】
【発明の実施の形態】
（実施例１）
（画像形成装置）
図１は本発明の第１の実施例による画像形成装置の一例を示す概略構成図である。本例の画像形成装置は電子写真プリンタである。給紙カセット１０２に格納された紙１０１は、不図示のカセットに配設している紙サイズ検知装置により、紙サイズが認識されている、そして、紙１０１は給紙ピックアップ１０３によって引き出されて給紙経路に導入され、搬送ローラ１０４によってレジストローラ１０６まで搬送される。レジセンサ１０５がシ一ト１０１の先端を検知した時点を基準として以降のプロセスが順次実行される。
【００１６】
レジストローラ１０６が矢印に示す方向に所定のプロセススピード（周速度）で回転駆動され、紙１０１を搬送する。感光体ドラム１１０は有機感光体やアモルファスシリコン感光体で表面をコートされた担持体であり、矢印で示す方向に所定のプロセススピードで回転駆動される。感光体ドラム１１０はその回転過程で帯電ローラなどの帯電装置１０７で所定の極性・電位の一様な帯電処理を受ける。
【００１７】
ついで、その帯電処理面にレーザスキャナ１０８から出力されるレーザ光１０９による、目的の画像情報の走査露光処理を受け該目的画像情報に対応した静電潜像が形成される。レーザスキャナ１０８は不図示の画像読み取り装置などの画像信号発生装置からの目的画像情報の時系列電気デジタル画素信号に対応して、変調（オン／オフ）したレーザ光１０９を出力する。
【００１８】
感光ドラム１１０上に形成された静電潜像は、現像装置１１１の作動でトナー画像として現像される。転写ローラ１１２は感光体ドラム１１０と近接して該感光体ドラムと同じ周速度で矢印に示す方向に回転駆動され、さらにバイアス電位を与られる。この転写ローラ１１２と感光体ドラム１１０の間に紙１０１を挟持通紙すると、転写ローラ１１２と感光体ドラム１１０の間の電位差により、感光体ドラム１１０上のトナー画像が紙１０１表面に転写される。
【００１９】
紙１０１表面へのトナー画像転写後の回転感光体ドラム１１０面は、クリーナ１１３によって転写残りトナーなどの付着残留物の除去を受けて清掃され、つぎの画像形成に供される。クリーナ１１３はウレタンゴムの弾性ブレードで感光ドラム表面にエッジ当接しており、当接圧は５０ｇ／ｃｍである。クリーナ１１３はこの構成に限るものではなく、クリーナ１１３が感光ドラム１１０に接触して、感光ドラム上の付着残留物を剥ぎ取るものであれば良い。表面ヘトナー画像を転写された紙１０１は定着器１１４へ導入され、未定着トナー画像の加熱定着処理を受ける。
【００２０】
（帯電装置）
図２は接触式帯電装置の一例の概略図を示す。本実施例では、導電性弾性ゴムローラによる接触帯電方式を採用したが、帯電方式はこれに限るものではなく、放電電流を用いて非帯電面を帯電する方式であれば良い。図２に示す帯電装置は、帯電ローラ２２および電源２３を備えている。帯電部材としての帯電ローラ２２は、中心の芯金２２ｃと、その外周に形成した導電層２２ｂと、さらにその外周に形成した抵抗層２２ａとからなる。帯電ローラ２２は、被帯電体としてのドラム状の感光ドラム２１に平行に配置されるとともに、芯金２２ｃの左右両端部（軸方向の両端部）を不図示の軸受け部材によって回転自由に支持されている。帯電ローラ２２は、また、押圧手段（不図示）によって感光ドラム２１表面の被帯電面２１ａに対して総圧１６００ｇで当接させ、感光ドラム２１の矢印Ｒ１方向の回転に伴って矢印Ｒ２方向に従動回転する。なお、ギア等を取り付け、モータから駆動を受け、強制駆動することも可能である。また、感光ドラム２１における２１ｂはアルミニウム等の基体層を図示している。
【００２１】
感光ドラム２１には、この電源２３により帯電ローラ２２を介して、感光ドラム２１の帯電開始電圧の２倍以上のピーク間電圧ＶＰＰを有する振動電圧ＶＡＣと直流電圧ＶＤＣとを重畳した電圧（ＶＡＣ＋ＶＤＣ）が印加され、これにより、回転駆動されている感光ドラム２１の表面は均一に帯電される。
【００２２】
帯電ローラ２２について詳述する。本実施例で使用した帯電ローラ２２は、図２に示すように、芯金２２ｃの上にＥＰＤＭ等の１０^４〜１０^５Ω・ｃｍの導電ゴム層２２ｂを設け、その上にヒドリンゴム等からなる１０^７〜１０^９Ω・ｃｍ程度の中抵抗層２２ａ２を設け、その上にトレジン（注：帝国科学（株）の商標）等のナイロン系物質からなる１０^７〜１０^１０Ω・ｃｍのブロッキング層２２ａ１を表層として設けた、硬度がＡｓｋｅｒ−ｃ測定で５０〜７０°程度のものを用いた。
【００２３】
（画像処理時間に応じた画像形成動作間の現像ローラ回転制御）
次に画像情報に応じた画像形成動作間の感光ドラム回転制御の説明をする。本実施例で説明する画像形成動作間の時間とは、複数イメージを連続プリントする場合に、あるイメージの紙後端と次のイメージの紙先端との間の時間である。
ホストコンピュータから送られる画像情報量が大きく、画像形成装置内にあるＣＰＵが画像情報を画像形成装置エンジン部にビットデータとして出力するまでの時間（以下、画像処理時間）がかかってしまい、連続プリント中に画像形成動作間の時間が長くなる場合に、従来は、感光ドラムが回転しつづけていたのにたいして、本実施例では、画像形成動作間の時間だけ感光ドラムの回転を停止する制御を行う。
【００２４】
本実施例の複数イメージを連続プリントしているときの画像形成タイミングを図３（い）、感光ドラムの回転の状態を図（ろ）で説明する。図はイメージ１２ａ、イメージ１２ｂ、イメージ１２ｃの複数イメージを連続プリントしたときの模式図である。ここで、画像形成間の時間１３ａｂは通常の状態で、画像形成動作間の時間１３ｂｃは画像形成動作間の時間が長くなった状態を示す。通常の画像形成動作間の時間１３ａｂは本実施例では０．５５ｓｅｃに設定されている。これに対して感光ドラムが停止、回転するまでの時間（以降、感光ドラム停止・回転時間）を計算すると、イメージ１２ｂの紙後端が転写ニップを通過して感光ドラムを停止する電気信号を発信してから完全に停止するまでの時間が０．６ｓｅｃ、感光ドラムを回転する電気信号を発信してから画像形成時の周速になるまでの時間が０．６ｓｅｃ、感光ドラムが画像形成時の周速で回転して帯電位置から転写ニップに移動する時間が０．７ｓｅｃなので、感光ドラム停止・回転時間は１．９ｓｅｃである。したがって、通常の画像形成動作間の時間１３ａｂのときは、感光ドラムの停止・回転を行わない。現像ローラの停止・回転を行うときは、画像形成１２ｂが終了した時点で、次のイメージの画像処理１１ｃの最中で、かつその時点から画像処理を終えて次の画像形成を始めるまでの時間（残画像処理時間）１４が感光ドラム停止・回転時間よりも長いときである。
【００２５】
また、本発明は感光ドラム削れを防ぐために感光ドラム回転数を極力減らすことが目的であるため、感光ドラム回転停止時間で感光ドラムの回転を停止させなくとも良く、感光ドラムの周速を画像形成時のスピードより遅くするだけで感光ドラム削れを抑制でき、効果がある。これは後に記載する実施例すべてに当てはまる。
【００２６】
実際に、情報量の大きい画像を連続プリントして従来例と本実施例との比較を行った。
【００２７】
【表１】

【００２８】
表１に示すように情報量の大きい画像（Ａ４サイズ）を公称寿命の１００００枚連続プリント試験を行った結果、かぶりが８０００枚に発生していたが、本実施例は１００００枚を通じてかぶりが発生しなかった。
【００２９】
以上から、情報量の大きい画像を連続プリントして画像形成動作間の時間が長くなるような場合においても、ＣＰＵで画像情報量から画像処理時間を計算し、画像処理時間に応じて感光ドラムの回転を停止することで、本実施例の画像形成装置は感光ドラム削れを防ぎ、かぶり画像の発生を防いだ。
【００３０】
（定着器温度検知による画像形成動作間の感光ドラム回転制御）
次に、定着器温度検知による画像形成動作間の感光ドラム回転制御の説明をする。
【００３１】
図３に加熱定着装置の構成を示す。図３において、芯金３１の外側にシリコンゴムやフッ素ゴム等の耐熱ゴムあるいはシリコンゴムを発泡して形成された弾性層３０からなる加圧ローラがある。この上にＰＦＡ、ＰＴＦＥ、ＦＥＰ等の離型性層３２を形成してもよい。
【００３２】
また、定着部材３３は以下の部材から構成される。３４は熱容量の小さな定着フィルムであり、耐熱性、熱可塑性を有するポリイミド、ポリアミドイミド、ＰＥＥＫ、ＰＥＳ、ＰＰＳ、ＰＦＡ、ＰＴＦＥ、ＦＥＰ等の定着フィルムである。さらにオフセット防止や記録材の分離性を確保するために表層にはＰＦＡ、ＰＴＦＥ、ＦＥＰ等の離型性の良好な耐熱樹脂を混合ないし単独で被覆したものである。また、サーミスタ３５，ヒーター基板３６，発熱体３７で構成される定着フィルム３４の内部に具備される加熱用ヒーターは、記録材上のトナー像３８を溶融、定着させるニップ部Ｎ‘の加熱を行う。３９は加熱用ヒーターを保持し、ニップと反対方向への放熱を防ぐための断熱支持部材であり、液晶ポリマー、フェノール樹脂、ＰＰＳ、ＰＥＥＫ等により形成されており、定着フィルム３４が矢印の方向に余裕を持って回れるような形状と大きさを持っている。また、定着フィルム３４は内部の加熱用ヒーター（構成３５，３６，３７）および断熱支持部材３９に摺擦しながら回転するため、加熱用ヒーター（構成３５，３６，３７）および断熱支持部材３９と定着フィルム３４の間の摩擦抵抗を小さく抑える必要がある。このため加熱用ヒーター（構成３５，３６，３７）および断熱支持部材３９の表面に耐熱性グリースなどの潤滑剤を少量介在させてある。これにより定着フィルム３４はスムーズに回転することが可能である。
【００３３】
上記のように現像器から記録材上に未定着状態で送られてきたトナーは、加熱定着器の加圧ローラと定着フィルムによるニップの間を通過することにより、熱と圧縮力により溶融され、定着される。このときの搬送力は加圧ローラ駆動型定着フィルム定着器の場合は、加圧ローラのみに限られ、定着フィルム自体は、従動する形をとり、記録材と共に移動する。
【００３４】
小サイズ紙が連続で通紙された場合、非通紙部における昇温は蓄積され、非通紙部の昇温はフィルムガイドの部材や加熱用ヒーター、定着フィルムなどを痛めてしまう程度の温度となってしまう恐れがある。また、小サイズ記録材などを連続的に流し、非通紙部昇温を発生させた直後、Ａ４紙などのような大きなサイズの記録材を通紙した場合、直前の小サイズの非通紙部に相当する箇所で、極端に高温となってしまった場合は、ホットオフセットなどの問題が生じてしまう。そこで、非通紙部昇温対策として、温度検知用サーミスタを二つもしくはそれ以上に増やし、温調用温度サーミスタと、非通紙部昇温検知用温度サーミスタとし、非通紙部昇温検知用サーミスタの検知温度に従って、異常高温にならぬよう、スループットを低下させ、非通紙部昇温を克服してある。
【００３５】
しかしながら、端部サーミスタなどの温度検知手段から得られる温度情報をもとに、スループットダウンを行った場合、非通紙部の昇温温度に応じてスループットを低下させ、非通紙部昇温を抑えることが可能になるものの、従来のスループットダウン中は画像形成動作間の時間が長くなり、その間感光ドラムが回転するため、感光ドラム削れが促進される。本実施例では非通紙部昇温を抑制するためスループットダウンを行い、かつ画像形成動作間の時間において感光ドラムの回転を停止する。実際には以下のような制御を行う。
【００３６】
【表２】

【００３７】
表２のように非通紙部昇温を端部サーミスタによって監視して、非通紙部温度の段階に対応した画像形成動作間の時間を設定した。
このとき、感光ドラム停止・回転時間は１．９ｓｅｃなので、段階２の画像形成動作間の時間２．０５ｓｅｃ以上で画像形成動作間の時間中に感光ドラムの回転を停止する。また、本実施例では非通紙部昇温を端部サーミスタによって実測するが、定型サイズ紙を一定枚数通紙すると非通紙部昇温を経験から予測できるのであれば、端部サーミスタを使用せずとも、紙サイズと通紙枚数によってスループットダウンを行い、その画像形成動作間の時間に応じて感光ドラムの回転を制御しても良い。
実際に封筒（洋形４号）を通紙し、連続プリント試験して従来例と本実施例との比較をした。
【００３８】
【表３】

【００３９】
表３に示すように封筒（洋形４号）を公称寿命（洋形４号換算）の２５０００枚連続プリント試験を行った結果、従来例ではかぶり画像が１２０００枚に発生していたが、本実施例は２５０００枚を通じてかぶり画像が発生しなかった。
【００４０】
以上から、幅の小さい紙を連続プリントして、定着器の非通紙部昇温を抑制し、画像形成動作間の時間が長くなるような場合においても、端部温度サーミスタの検知温度に応じて、現像ローラの回転を停止して、本実施例の画像形成装置は感光ドラム削れを防ぎ、かぶり画像の発生を防いだ。
【００４１】
本実施例の画像形成装置において、ホストコンピュータから情報量の大きい画像情報が送られ、連続プリント中に画像形成動作間の時間が長くなる場合も、ＣＰＵで画像情報量から画像処理時間を計算し、画像処理時間に応じて感光ドラムの回転を停止することにより、また、幅の小さい紙を連続プリントして、定着器の非通紙部昇温を抑制し、画像形成動作間の時間が長くなるような場合においても、端部温度サーミスタの検知温度に応じて、感光ドラムの回転を停止することによって、感光ドラムの削れをなくし、かぶり画像の発生を防ぎ、画像形成装置の低コスト化が実現化する。
【００４２】
（実施例２）
本実施例は実施例１と画像形成動作間の時間を検知する手段が異なる画像形成装置である。したがって、本実施例では、実施例１と異なる点、画像形成動作間の時間における制御についてのみ説明する。
【００４３】
（紙先端検知装置、紙後端検知装置による画像形成動作間の現像ローラ回転制御）
本実施例は紙間隔が画像形成間隔と同じであることを利用し、紙間隔の測定をすることで画像形成間隔の測定を行っている。画像形成装置内の構成は実施例１と比べ図１のレジセンサ１０５が異なる。レジセンサ１０５は紙の先端位置と後端位置がわかるものである。また、レジセンサから転写ニップまでの間を紙先端が通過する時間（以下、レジセンサ・転写ニップ間時間）は、感光ドラム停止・回転時間より長くなっており、感光ドラム停止・回転時間は１．９ｓｅｃ、レジセンサ・転写ニップ間時間が２．０ｓｅｃである。これは、レジセンサ・転写ニップ間時間が、感光ドラム停止・回転時間より長くなることで、画像形成動作間隔中に確実に感光ドラムの停止・回転を行えるためである。必ずしも、レジセンサ・転写ニップ間時間を、感光ドラム停止・回転時間より長くする必要はない。
【００４４】
図５（い）のように紙５２ａと紙５２ｂの間隔Ｃが１．９ｓｅｃ以下のとき、感光ドラム停止・回転動作は行わない。図５（ろ）のようにレジセンサ１０５と紙後端の間隔Ｄが１．９ｓｅｃより大きいとき、紙後端が転写ニップを通過後、感光ドラムの回転を停止する。つぎに、図５（は）のように紙間隔Ｅを測定したら、感光ドラム停止・回転時間が間隔Ｅになるようにする。そして、間隔Ｅを過ぎると同時に感光ドラムは所定のスピード９０ｍｍ／ｓｅｃで回転し、画像形成を始める。
【００４５】
本実施例では、紙後端を実測していたが、あらかじめ紙サイズのわかっている定型紙でプリントする場合は、紙先端が検知できると、紙後端もわかるので紙後端検知装置は必ずしも必要ではないが、この場合不定形サイズ紙は対応できない。また、紙５２ａの画像形成が終了した時点で紙５２ｂ先端を検知していないとき、感光ドラムの回転を停止して、紙５２ｂの紙先端を検知してから画像形成動作間の時間を決定しても良く、紙後端検知装置は必ずしも必要ではないが、この場合、紙先端検知装置の位置が転写ニップから離れると感光ドラムを停止する機会が減ってしまう。
【００４６】
以上のように制御することで、連続プリント中に画像形成動作間の時間が長くなる場合に、レジセンサを用いて紙間隔を測定し、紙間隔、すなわち画像形成動作間の時間中に感光ドラムの回転を停止することで、感光ドラムの削れをなくし、かぶり画像の発生を防ぎ、画像形成装置の低コスト化が実現化する。
【００４７】
（実施例３）
本実施例は、実施例１と比べ、図４のように画像形成装置内の装置の構成は現像離接装置１２４を新たに加え、現像方式は接触現像方式を採用している。その他のプロセス設定は変えていない。したがって、現像離接装置１２４と、それに伴う画像形成動作間の制御について本実施例では説明する。
【００４８】
（現像離接）
実施例１、２の場合、画像形成動作間の時間で感光ドラムが停止している間も、感光ドラムに接触して現像ローラは回転しているため、感光ドラムは現像ニップ部分で極端に削られ、画像上、ドラムピッチバンディングが発生する。本実施例はドラムピッチバンディングを防ぐために感光ドラムの回転を停止すると同時に現像ローラと感光ドラムを離接する。このときの離接するシーケンスを図７で説明する。まず、ステップＳ１１にて画像形成動作間の時間Ａを測定する。測定方法は実施例１、２のいずれの方法でも良い。ステップ１２にて時間Ａが現像ローラの離接時間Ｂより短いのであれば、離接動作は行わずステップ１６にて次の画像形成を開始する。時間Ａが現像ローラの離接時間Ｂより長いのであれば、次のステップ１３に進み、時間Ａが感光ドラムの停止・回転時間Ｃより短いのであれば、ステップ１４にて時間Ａの間、現像ローラを感光ドラムから離間し、ステップ１６に進む。時間Ａが感光ドラムの停止・回転時間Ｃより長いのであれば、ステップ１５にて、時間Ａの間、現像ローラを感光ドラムから離間して感光ドラムを停止し、ステップ１６に進む。ステップ１６にて、感光ドラムを回転して、現像ローラを接触させて画像形成動作を開始したら、ステップ１１に戻り次の画像形成動作間間の時間を測定する。以上、複数イメージの連続プリント中の各画像形成動作間の時間に対して上記シーケンスを繰り返す。
【００４９】
本実施例では現像ローラと感光ドラムの離間に要する時間は０．３ｓｅｃ、現像ローラと感光ドラムの接触に要する時間は０．３ｓｅｃなので、現像ローラと感光ドラムの離接時間Ｂは０．６ｓｅｃとなる。感光ドラム停止・回転時間Ｃは１．９ｓｅｃと、離接時間Ｂが感光ドラム停止・回転時間Ｃより短いので、まずステップ１１にて離接時間Ｂと画像形成動作間の時間Ａの比較を行った。したがって、離接時間Ｂが現像ローラ停止・回転時間Ｃよりも長い場合は、ステップ１１にて、感光ドラム停止・回転時間Ｃと時間Ａの比較を行い、ステップ１２にて、離接時間Ｂと時間Ａの比較を行っても良い。また、このとき実施例２の形態のように紙間隔を測定することで画像形成動作間隔の測定をする場合は、紙先端がレジセンサ・転写ニップ間を通過する時間は、離接時間より長くして、画像形成動作間の時間中に確実に感光ドラムと現像ローラが接触するようにする。
【００５０】
実際に封筒（洋形４号）を通紙し、連続プリント試験して従来例と本実施例との比較をした。
【００５１】
【表４】

【００５２】
以上から、本実施例の画像形成装置において、ホストコンピュータから情報量の大きい画像情報が送られ、連続プリント中に画像形成動作間の時間が長くなる場合も、ＣＰＵで画像情報量から画像処理時間を計算し、画像処理時間に応じて現像ローラと感光ドラムを離接して感光ドラムの回転を停止することにより、また、幅の小さい紙を連続プリントして、定着器の非通紙部昇温を抑制し、画像形成動作間の時間が長くなるような場合においても、定着部端部温度サーミスタの検知温度に応じて、現像ローラと感光ドラムを離接して感光ドラムの回転を停止することにより、また、紙間隔から画像形成動作間の時間を測定し、画像形成動作間の時間が長いときに現像ローラと感光ドラムを離接し、感光ドラムの回転を停止することによって、感光ドラムの削れをなくし、かぶり画像の発生を防ぎ、感光ドラムピッチバンディングのない、低コストな画像形成装置が実現化する。
【００５３】
【発明の効果】
以上説明したように、本発明によれば、ホストコンピュータから情報量の大きい画像情報が送られ、連続プリント中に画像形成動作間の時間が長くなる場合も、ＣＰＵが画像情報量から画像処理時間を計算することによって、画像処理時間に応じて感光ドラムの回転を停止するため、また、幅の小さい紙を連続プリントして、定着器の非通紙部昇温を抑制し、画像形成動作間の時間が長くなるような場合においても、定着部端部温度サーミスタの検知温度に応じて、感光ドラムの回転を停止するため、感光ドラムの削れをなくし、かぶり画像の発生を防ぎ、低コストな画像形成装置を提供する効果がある。
【００５４】
また、連続プリント中に画像形成動作間の時間が長くなる場合に、レジセンサを用いて紙間隔を測定し、紙間隔、すなわち画像形成動作間の時間中に現像ローラと感光ドラムを離接し、感光ドラムの回転を停止することで、感光ドラムの削れをなくし、かぶり画像の発生を防ぎ、低コストな画像形成装置を提供する効果がある。
【００５５】
また、画像形成動作間の時間を測定し、画像形成動作間の時間中、現像ローラを停止させ、かつ現像ローラと感光ドラムを離接するので、感光ドラムの削れをなくし、かぶり画像の発生を防ぎ、感光ドラムピッチバンディングのない、画像形成装置を低コストに提供する効果がある。
【図面の簡単な説明】
【図１】実施例１に用いた画像形成装置の概略構成図
【図２】実施例１に用いた画像形成装置の帯電装置の概略構成図
【図３】実施例１に用いた画像形成装置の画像処理時間と画像形成動作間隔の関係を示した模式図
【図４】実施例１に用いた画像形成装置の加熱定着器の概略構成図
【図５】実施例２の紙間隔測定方法の模式図
【図６】実施例３に用いた画像形成装置の概略構成図
【図７】実施例３に用いた画像形成装置のシーケンスを示した模式図
【符号の説明】
１０１紙
１０２給紙カセット
１０３給紙ピックアップ
１０４搬送ローラ
１０５レジセンサ
１０６レジストローラ
１０７帯電装置
１０８レーザスキャナ
１０９レーザ光
１１０感光ドラム
１１１現像装置
１１２転写ローラ
１１３クリーナ
１１４定着器
１１５定着加熱部
１１６加圧ローラ
１１７後レジセンサ
１１８排紙ローラ
１１９排紙ローラ
１２０温度センサ
１２１切替フラップ
１２３再給紙搬送ローラ
１２４現像離接装置
１１画像処理時間
１２画像形成時間
１３画像形成動作間隔
１４残画像処理時間
２１感光ドラム
２２帯電ローラ
２３電源装置
３０弾性層
３１芯金
３２離型性層
３３定着部材
３４定着フィルム
３５サーミスタ
３６基盤
３７発熱抵抗体
３８トナー像
３９断熱支持部材
５１転写ニップ
５２紙、記録材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention includes a charging device for charging a charged surface of a charged member of an image bearing member such as an electrophotographic photosensitive member or an electrostatic recording dielectric, and a developing device that forms an electrostatic latent image formed on the image bearing member with a developer. The present invention relates to an image forming apparatus visualizing with (toner).
[0002]
[Prior art]
FIG. 1 is a schematic sectional view of a conventional image forming apparatus.
[0003]
First, an image forming operation by the image forming unit will be described.
[0004]
In FIG. 1, a photosensitive drum 110 as an electrostatic latent image carrier rotates in the direction of the arrow. First, the photosensitive drum 110 is uniformly charged by the charging device 107. Thereafter, exposure is performed by a laser beam 109 from a laser optical device 108 as an exposure unit, and an electrostatic latent image is formed on the surface.
[0005]
The electrostatic latent image is developed by a developing device 111 disposed in contact with and pressed against the photosensitive drum 110 with a predetermined penetration amount, and is visualized as a toner image.
[0006]
The visualized toner image on the photosensitive drum 110 is transferred to a recording medium 101 as a transfer material by a transfer roller 112. The transfer residual toner remaining on the photosensitive drum 110 without being transferred is scraped off by a cleaning blade 113 as a cleaning member, and is stored in a waste toner container. The cleaned photosensitive drum 110 repeats the above operation to form an image.
[0007]
On the other hand, the recording medium 101 to which the toner image has been transferred is permanently fixed by the fixing device 114 and then discharged outside the apparatus.
[0008]
Such an image forming apparatus has the following problems.
[0009]
When the photosensitive drum 110 is charged, a discharging current flows from the charging device 107 to the photosensitive drum 110, and the discharging current enables stable charging of the photosensitive drum 110. At this time, the electric energy of the discharging current is all Some of the electric energy of the discharge current, instead of being used for charging the photosensitive drum 110, electrically stimulates the polymer material on the surface of the photosensitive drum, so that a defect is likely to occur in the molecular bond of the polymer material. Accordingly, the surface of the photosensitive drum is easily scraped by sliding with the cleaning blade 113 via the toner. That is, the shaving amount of the photosensitive drum is proportional to the rotation speed (time) of the photosensitive drum.
[0010]
When the photosensitive drum 110 is excessively scraped, a fog image is generated due to a reduction in the charging potential of the photosensitive drum 110 by the charging device 107.
[0011]
In order to solve such a problem, the thickness of the photosensitive layer of the photosensitive drum 110 may be sufficiently increased. However, the efficiency of the photosensitive drum 110 in the production line is reduced due to the increase in the thickness, and the material cost is increased. Therefore, there is a problem that the cost of the image forming apparatus increases. Therefore, conventionally, when designing an image forming apparatus, the film thickness of the photosensitive layer of the photosensitive drum 110 is calculated by calculating the rotation time of the photosensitive drum 110 at the guaranteed number of prints, so that a fog image due to scraping of the photosensitive drum does not occur. You have set.
[0012]
[Problems to be solved by the invention]
However, image forming apparatuses in recent years are increasingly required to diversify recording materials and print images with a large amount of information. Under these circumstances, the time between image forming operations in a continuous printing operation may be long, depending on the paper size and the content of the job sent from the host computer. For example, there is a phenomenon in which the temperature of the non-paper passing portion of the fixing device rises due to the passage of small-sized paper having a small width. In this case, when the time between image forming operations is increased to prevent the non-paper passing portion from being heated. In another example, when the information amount of the image information sent from the host computer is large and the information processing in the image forming apparatus is slower than the print speed, the information processing becomes rate-determining, so The time may be long, and a fog image due to scraping of the photosensitive drum may occur even within the nominal life depending on the use condition.
[0013]
Accordingly, an object of the present invention is to provide a low-cost image forming apparatus that can reduce abrasion of a photosensitive drum and generate no fog image when the time between image forming operations becomes long during continuous printing in an image forming apparatus. It is to provide a forming device.
[0014]
[Means for Solving the Problems]
The present invention is an image forming apparatus having the following configuration.
(1) In an image forming apparatus including an image carrier and a cleaning member that contacts the image carrier and cleans the surface of the image carrier, a time interval between image forming operations during print job processing of a plurality of images. An image forming apparatus that changes a driving speed of an image carrier.
(2) In an image forming apparatus including an image carrier, a cleaning member that contacts the image carrier to clean the surface of the image carrier, and a developing roller that contacts and develops the image carrier, the image carrier includes: The developing roller has a mechanism for separating and contacting the image bearing member, and separates the image bearing member from the developing roller and changes the driving speed of the image bearing member according to the time between image forming operations during print job processing of a plurality of images. An image forming apparatus characterized in that:
(3) The image forming apparatus according to (1) or (2), wherein the driving of the image carrier is stopped according to the time between image forming operations during the print job processing of a plurality of images.
(4) The image forming apparatus according to (1) to (3), wherein a time between image forming operations is longer than a deceleration / acceleration time of rotation of the image carrier.
(5) When the separation / contact / contact time between the image bearing member and the developing roller is longer than the deceleration / acceleration time of the rotation of the image bearing member, the time between image forming operations is determined by the distance between the image bearing member and the developing roller. The image forming apparatus according to (2) or (3), wherein the image forming apparatus is longer than the contact time.
(6) The image forming apparatus according to any one of (1) to (5), further including a CPU, wherein the CPU calculates a time between image forming operations based on an amount of image information sent from the host computer. .
(7) A recording material on which an unfixed image is formed in the image forming section, and a fixing device which passes the recording material and heat-fixes the unfixed image to the recording material are provided. The image forming apparatus according to any one of (1) to (6), wherein the time between image forming operations is changed.
(8) The image forming apparatus according to (7), wherein the non-sheet passing area temperature information is obtained by temperature detecting means capable of measuring the non-sheet passing area of the fixing unit.
(9) The image forming apparatus according to any one of (1) to (8), further including a recording material front end detecting unit that detects a front end position of the recording material, and measuring a time between image forming operations during a print job of a plurality of images.
(10) A recording material trailing edge detecting means for detecting the trailing edge position of the recording material, and a recording material leading edge detecting means for detecting the leading edge position of the recording material, and the recording material trailing edge during a print job of a plurality of images. The image forming apparatus according to (1) to (8), wherein a time between image forming operations is measured from the position and the leading end position of the recording material.
(11) The time when the recording material leading edge detecting means is located before the image transfer position and the leading edge of the recording material passes from the recording material leading edge detecting means to the image transfer position in the process of moving the recording material in the image forming apparatus. Wherein the image forming apparatus is longer than the deceleration / acceleration time of the rotation of the developing roller.
(12) A developing roller for developing by contacting the image carrier, a mechanism for separating the image carrier and the developing roller from each other, and a time required for the leading edge of the recording material to pass from the leading edge detecting means of the recording material to the image transfer position. The image forming apparatus according to (9) or (10), wherein the time is longer than the separation / contact time between the image bearing member and the developing roller and the deceleration / acceleration time of rotation of the developing roller.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
(Image forming device)
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to a first embodiment of the present invention. The image forming apparatus of this example is an electrophotographic printer. The paper size of the paper 101 stored in the paper feed cassette 102 is recognized by a paper size detection device provided in a cassette (not shown), and the paper 101 is pulled out by the paper feed pickup 103 and fed. The sheet is introduced into the paper path, and is conveyed to the registration roller 106 by the conveying roller 104. Subsequent processes are sequentially executed based on the time when the registration sensor 105 detects the leading end of the sheet 101.
[0016]
The registration roller 106 is driven to rotate at a predetermined process speed (peripheral speed) in the direction indicated by the arrow, and conveys the paper 101. The photoconductor drum 110 is a carrier whose surface is coated with an organic photoconductor or an amorphous silicon photoconductor, and is driven to rotate at a predetermined process speed in a direction indicated by an arrow. The photosensitive drum 110 undergoes a uniform charging process of a predetermined polarity and potential by a charging device 107 such as a charging roller during the rotation process.
[0017]
Next, a scanning exposure process of target image information is performed on the charged surface by the laser beam 109 output from the laser scanner 108 to form an electrostatic latent image corresponding to the target image information. The laser scanner 108 outputs a modulated (on / off) laser beam 109 in response to a time-series electric digital pixel signal of target image information from an image signal generator such as an image reader (not shown).
[0018]
The electrostatic latent image formed on the photosensitive drum 110 is developed as a toner image by the operation of the developing device 111. The transfer roller 112 is driven to rotate in the direction indicated by the arrow at the same peripheral speed as the photosensitive drum 110 in the vicinity of the photosensitive drum 110, and is further supplied with a bias potential. When the paper 101 is nipped and passed between the transfer roller 112 and the photosensitive drum 110, the toner image on the photosensitive drum 110 is transferred to the surface of the paper 101 due to the potential difference between the transfer roller 112 and the photosensitive drum 110. .
[0019]
After the transfer of the toner image to the surface of the paper 101, the surface of the rotating photoconductor drum 110 is cleaned by the cleaner 113 after removing the adhered residue such as untransferred toner, and is used for the next image formation. The cleaner 113 is in edge contact with the surface of the photosensitive drum with an elastic blade of urethane rubber, and the contact pressure is 50 g / cm. The cleaner 113 is not limited to this configuration, and may be any as long as the cleaner 113 comes into contact with the photosensitive drum 110 and strips off the residue remaining on the photosensitive drum. The paper 101 on which the toner image has been transferred to the front surface is introduced into the fixing device 114, and undergoes heat fixing processing of the unfixed toner image.
[0020]
(Charging device)
FIG. 2 shows a schematic view of an example of the contact type charging device. In this embodiment, the contact charging method using the conductive elastic rubber roller is employed, but the charging method is not limited to this, and any method may be used as long as the non-charged surface is charged using a discharge current. The charging device shown in FIG. 2 includes a charging roller 22 and a power supply 23. The charging roller 22 as a charging member includes a central metal core 22c, a conductive layer 22b formed on the outer periphery thereof, and a resistance layer 22a formed on the outer periphery thereof. The charging roller 22 is disposed in parallel with the drum-shaped photosensitive drum 21 as a member to be charged, and is rotatably supported at both left and right ends (both axial ends) of a cored bar 22c by bearing members (not shown). ing. The charging roller 22 is brought into contact with the charged surface 21a on the surface of the photosensitive drum 21 at a total pressure of 1600 g by a pressing means (not shown), and rotates in the direction of arrow R2 with the rotation of the photosensitive drum 21 in the direction of arrow R1. It is driven and rotated. It is also possible to attach a gear or the like, receive driving from a motor, and forcibly drive. Reference numeral 21b in the photosensitive drum 21 indicates a substrate layer such as aluminum.
[0021]
A voltage (VAC + VDC) obtained by superimposing a DC voltage VDC and a vibration voltage VAC having a peak-to-peak voltage VPP equal to or more than twice the charging start voltage of the photosensitive drum 21 on the photosensitive drum 21 via the charging roller 22 by the power supply 23. Is applied, whereby the surface of the rotating photosensitive drum 21 is uniformly charged.
[0022]
The charging roller 22 will be described in detail. As shown in FIG. 2, the charging roller 22 used in the present embodiment has a 10 bar of EPDM or the like on a cored bar 22c. ⁴ -10 ⁵ A conductive rubber layer 22b of Ω · cm is provided, and a conductive rubber layer ⁷ -10 ⁹ A medium resistance layer 22a2 of about Ω · cm is provided, and a nylon-based material such as resin (Note: trademark of Teikoku Science Co., Ltd.) ⁷ -10 ¹⁰ The one having a blocking layer 22a1 of Ω · cm as a surface layer and a hardness of about 50 to 70 ° as measured by Asker-c was used.
[0023]
(Control of rotation of developing roller during image forming operation according to image processing time)
Next, the control of the rotation of the photosensitive drum during the image forming operation according to the image information will be described. The time between image forming operations described in this embodiment is the time between the trailing edge of a certain image and the leading edge of the next image when a plurality of images are continuously printed.
The amount of image information sent from the host computer is large, and it takes a long time (hereinafter, image processing time) for the CPU in the image forming apparatus to output the image information as bit data to the engine unit of the image forming apparatus. In the present embodiment, when the time between image forming operations becomes longer while the photosensitive drum continues to rotate, control is performed to stop the rotation of the photosensitive drum only during the time between image forming operations. .
[0024]
The image forming timing when a plurality of images are continuously printed according to the present embodiment will be described with reference to FIG. 3A, and the rotation state of the photosensitive drum will be described with reference to FIG. The figure is a schematic diagram when a plurality of

images

12a, 12b, and 12c are continuously printed. Here, the time 13ab between image forming operations is a normal state, and the time 13bc between image forming operations indicates a state where the time between image forming operations is long. The time 13ab between normal image forming operations is set to 0.55 sec in this embodiment. On the other hand, when the time until the photosensitive drum stops and rotates (hereinafter, photosensitive drum stop / rotation time) is calculated, an electric signal for stopping the photosensitive drum by transmitting the rear end of the image 12b through the transfer nip is transmitted. The time from when the photosensitive drum is rotated to the peripheral speed at the time of image formation is 0.6 sec. Since the time for rotating at the peripheral speed and moving from the charging position to the transfer nip is 0.7 sec, the stop / rotation time of the photosensitive drum is 1.9 sec. Therefore, when the time 13ab is between normal image forming operations, the photosensitive drum is not stopped or rotated. When the developing roller is stopped / rotated, at the time when the image formation 12b is completed, during the image processing 11c of the next image, and from the time until the image processing is completed and the next image formation is started. (Remaining image processing time) 14 is longer than the photosensitive drum stop / rotation time.
[0025]
Further, since the present invention aims to reduce the number of rotations of the photosensitive drum as much as possible in order to prevent the photosensitive drum from being scraped, it is not necessary to stop the rotation of the photosensitive drum during the photosensitive drum rotation stop time. It is possible to suppress the scraping of the photosensitive drum simply by making the speed slower than the speed at the time, which is effective. This applies to all the examples described below.
[0026]
Actually, an image having a large amount of information was continuously printed, and a comparison was made between the conventional example and this embodiment.
[0027]
[Table 1]

[0028]
As shown in Table 1, an image (A4 size) having a large amount of information was subjected to a continuous print test of 10,000 sheets of nominal life, and as a result, fog occurred on 8000 sheets. In this embodiment, fog occurred on 10,000 sheets. Did not.
[0029]
As described above, even in the case where the time between image forming operations is long by continuously printing an image having a large amount of information, the CPU calculates the image processing time from the amount of image information and sets the photosensitive drum in accordance with the image processing time. By stopping the rotation, the image forming apparatus of the present embodiment prevented the photosensitive drum from being scraped, and prevented the generation of a fog image.
[0030]
(Rotation control of the photosensitive drum during the image forming operation by detecting the temperature of the fixing unit)
Next, the rotation control of the photosensitive drum during the image forming operation based on the detection of the fixing device temperature will be described.
[0031]
FIG. 3 shows the configuration of the heat fixing device. In FIG. 3, a pressure roller formed of an elastic layer 30 formed by foaming heat-resistant rubber such as silicon rubber or fluorine rubber or silicon rubber is provided outside the metal core 31. A releasable layer 32 of PFA, PTFE, FEP or the like may be formed thereon.
[0032]
The fixing member 33 includes the following members. Numeral 34 denotes a fixing film having a small heat capacity, which is a fixing film having heat resistance and thermoplasticity, such as polyimide, polyamideimide, PEEK, PES, PPS, PFA, PTFE, and FEP. Further, in order to prevent offset and ensure the separation of the recording material, the surface layer is coated with a heat-resistant resin having good releasability such as PFA, PTFE, or FEP, or coated alone. Further, a heating heater provided inside the fixing film 34 including the thermistor 35, the heater substrate 36, and the heating element 37 heats the nip portion N ′ for melting and fixing the toner image 38 on the recording material. . Reference numeral 39 denotes a heat insulating support member for holding a heater for heating and preventing heat radiation in a direction opposite to the nip. The heat insulating support member 39 is formed of a liquid crystal polymer, a phenol resin, PPS, PEEK, or the like. It has a shape and size that allow it to rotate easily. Further, since the fixing film 34 rotates while rubbing against the internal heating heaters (

configurations

35, 36, and 37) and the heat insulating support member 39, the heating film (

configurations

35, 36, and 37) and the heat insulating support member 39 are connected to each other. It is necessary to reduce the frictional resistance between the fixing films 34. For this reason, a small amount of lubricant such as heat-resistant grease is interposed on the surfaces of the heating heaters (

configurations

35, 36, and 37) and the heat insulating support member 39. Thus, the fixing film 34 can rotate smoothly.
[0033]
As described above, the toner sent from the developing device to the recording material in an unfixed state is melted by heat and compression force by passing between the pressure roller of the heat fixing device and the nip of the fixing film. Be established. In the case of a pressure roller driven fixing film fixing device, the conveying force at this time is limited to only the pressure roller, and the fixing film itself takes a driven shape and moves together with the recording material.
[0034]
When small-size paper is passed continuously, the temperature rise in the non-paper passing area is accumulated, and the temperature rise in the non-paper passing area is a temperature that damages the film guide members, heating heater, fixing film, etc. There is a risk of becoming. Immediately after a small-size recording material is caused to flow and a non-sheet-passing portion temperature rise is generated, when a large-size recording material such as A4 paper is passed, the immediately preceding small-size non-sheet If the temperature corresponding to the portion becomes extremely high, a problem such as hot offset occurs. Therefore, as a measure against the temperature rise in the non-sheet passing portion, the number of thermistors for temperature detection is increased to two or more, and a temperature thermistor for temperature control and a temperature thermistor for the temperature rise in the non-sheet passing portion are provided. According to the temperature detected by the thermistor, the throughput is reduced so that the temperature does not become abnormally high, and the temperature rise in the non-sheet passing portion is overcome.
[0035]
However, when the throughput is reduced based on the temperature information obtained from the temperature detecting means such as an end thermistor, the throughput is reduced in accordance with the temperature rise of the non-sheet passing portion, and the temperature rise of the non-sheet passing portion is reduced. Although it can be suppressed, the time between the image forming operations becomes longer during the conventional throughput reduction, and the photosensitive drum rotates during that time, so that the scraping of the photosensitive drum is promoted. In this embodiment, the throughput is reduced in order to suppress the temperature rise in the non-sheet passing portion, and the rotation of the photosensitive drum is stopped during the time between image forming operations. Actually, the following control is performed.
[0036]
[Table 2]

[0037]
As shown in Table 2, the temperature rise of the non-sheet passing portion was monitored by the end thermistor, and the time between image forming operations corresponding to the temperature of the non-sheet passing portion was set.
At this time, since the stop / rotation time of the photosensitive drum is 1.9 sec, the rotation of the photosensitive drum is stopped during the time between the image forming operations at 2.05 sec or more between the image forming operations in Step 2. In this embodiment, the temperature rise of the non-sheet passing portion is actually measured by an end thermistor. However, if the temperature rise of the non-sheet passing portion can be predicted from experience when a fixed number of fixed-size sheets are passed, an end thermistor is used. Alternatively, the throughput may be reduced depending on the paper size and the number of sheets passed, and the rotation of the photosensitive drum may be controlled according to the time between the image forming operations.
Actually, an envelope (Yogata No. 4) was passed through and a continuous print test was performed to compare the conventional example with the present example.
[0038]
[Table 3]

[0039]
As shown in Table 3, as a result of performing a continuous print test of 25,000 sheets of the envelope (Yokan No. 4) with the nominal life (Yokan No. 4 conversion), a fog image was generated on 12,000 sheets in the conventional example. In the example, no fogged image was generated over 25,000 sheets.
[0040]
As described above, even when the width of the non-sheet-passing portion of the fixing device is increased by continuously printing the narrow width paper and the time between image forming operations becomes longer, the temperature detected by the edge temperature thermistor can be adjusted. Then, the rotation of the developing roller is stopped, and the image forming apparatus of the present embodiment prevents the photosensitive drum from being scraped and prevents the occurrence of a fog image.
[0041]
In the image forming apparatus of the present embodiment, even when a large amount of image information is sent from the host computer and the time between image forming operations becomes longer during continuous printing, the CPU calculates the image processing time from the amount of image information. By stopping the rotation of the photosensitive drum in accordance with the image processing time, and by continuously printing narrow width paper, the temperature rise in the non-paper passing portion of the fixing unit is suppressed, and the time between image forming operations is increased. Even in such a case, the rotation of the photosensitive drum is stopped in accordance with the temperature detected by the end temperature thermistor, thereby eliminating shaving of the photosensitive drum, preventing the occurrence of a fog image, and reducing the cost of the image forming apparatus. Realize.
[0042]
(Example 2)
The present embodiment is an image forming apparatus which differs from the first embodiment in the means for detecting the time between image forming operations. Therefore, in the present embodiment, only the differences from the first embodiment and the control in the time between image forming operations will be described.
[0043]
(Rotation control of developing roller during image forming operation by paper leading edge detector and paper trailing edge detector)
In the present embodiment, the image forming interval is measured by measuring the paper interval, utilizing the fact that the paper interval is the same as the image forming interval. The configuration in the image forming apparatus is different from that of the first embodiment in the registration sensor 105 of FIG. The registration sensor 105 can detect the leading edge position and the trailing edge position of the paper. Also, the time during which the leading edge of the paper passes from the registration sensor to the transfer nip (hereinafter, the time between the registration sensor and the transfer nip) is longer than the photosensitive drum stop / rotation time, and the photosensitive drum stop / rotation time is 1.9 seconds. And the time between the registration sensor and the transfer nip is 2.0 sec. This is because the time between the registration sensor and the transfer nip is longer than the time for stopping and rotating the photosensitive drum, so that the photosensitive drum can be reliably stopped and rotated during the image forming operation interval. It is not always necessary to make the time between the registration sensor and the transfer nip longer than the photosensitive drum stop / rotation time.
[0044]
When the interval C between the paper 52a and the paper 52b is 1.9 sec or less as shown in FIG. 5A, the photosensitive drum stop / rotate operation is not performed. When the distance D between the registration sensor 105 and the rear end of the paper is larger than 1.9 sec as shown in FIG. 5B, the rotation of the photosensitive drum is stopped after the rear end of the paper passes through the transfer nip. Next, after the paper interval E is measured as shown in FIG. 5A, the photosensitive drum stop / rotation time is set to the interval E. The photosensitive drum rotates at a predetermined speed of 90 mm / sec at the same time when the interval E has passed, and starts image formation.
[0045]
In this embodiment, the trailing edge of the paper was actually measured.However, when printing on standard paper of which the paper size is known in advance, if the leading edge of the paper can be detected, the trailing edge of the paper can be detected. Although not required, irregular-size paper cannot be used in this case. When the leading end of the paper 52b is not detected when the image formation on the paper 52a is completed, the rotation of the photosensitive drum is stopped, and the time between the image leading end of the paper 52b and the image forming operation is determined. Although the paper trailing edge detecting device may not necessarily be required, in this case, if the position of the paper leading edge detecting device is separated from the transfer nip, the chance of stopping the photosensitive drum is reduced.
[0046]
By controlling as described above, when the time between image forming operations becomes longer during continuous printing, the paper interval is measured using the registration sensor, and the paper interval, that is, the photosensitive drum during the time between image forming operations is measured. By stopping the rotation, scraping of the photosensitive drum is prevented, occurrence of a fog image is prevented, and cost reduction of the image forming apparatus is realized.
[0047]
(Example 3)
In the present embodiment, as compared with the first embodiment, as shown in FIG. 4, a device in the image forming apparatus is newly provided with a developing / separating / contacting device 124, and a developing system adopts a contact developing system. The other process settings were not changed. Therefore, in this embodiment, the control between the developing / separating / contacting device 124 and the associated image forming operation will be described.
[0048]
(Development and separation)
In the first and second embodiments, even when the photosensitive drum is stopped during the time between image forming operations, the developing roller is in contact with the photosensitive drum and the developing roller is rotating. As a result, drum pitch banding occurs on the image. In this embodiment, in order to prevent drum pitch banding, the rotation of the photosensitive drum is stopped, and at the same time, the developing roller and the photosensitive drum are separated from each other. FIG. 7 shows the sequence of the contact and separation at this time. First, in step S11, a time A between image forming operations is measured. The measuring method may be any of the methods of the first and second embodiments. If the time A is shorter than the separation / contact time B of the developing roller in step 12, the separation / contact operation is not performed and the next image formation is started in step 16. If the time A is longer than the separation / contact time B of the developing roller, the process proceeds to the next step 13. If the time A is shorter than the stop / rotation time C of the photosensitive drum, the process proceeds to step 14 during the time A. The roller is separated from the photosensitive drum, and the process proceeds to Step 16. If the time A is longer than the stop / rotation time C of the photosensitive drum, the developing roller is separated from the photosensitive drum during the time A in step 15 to stop the photosensitive drum, and the process proceeds to step 16. In step 16, the image forming operation is started by rotating the photosensitive drum and bringing the developing roller into contact, and then returning to step 11, the time between the next image forming operations is measured. The above sequence is repeated for the time between each image forming operation during continuous printing of a plurality of images.
[0049]
In this embodiment, the time required for separating the developing roller and the photosensitive drum is 0.3 sec, and the time required for contact between the developing roller and the photosensitive drum is 0.3 sec. Therefore, the separating time B between the developing roller and the photosensitive drum is 0.6 sec. Become. Since the photosensitive drum stop / rotation time C is 1.9 seconds and the separation / contact time B is shorter than the photosensitive drum stop / rotation time C, first, at step 11, the separation / contact time B and the time A between the image forming operations are compared. Was. Therefore, if the separation / contact time B is longer than the developing roller stop / rotation time C, the photosensitive drum stop / rotation time C is compared with the time A in step 11, and in step 12, the separation / contact time B is compared with the photosensitive drum stop / rotation time C. Time A may be compared. Also, at this time, when measuring the image forming operation interval by measuring the paper interval as in the embodiment of the second embodiment, the time for the leading edge of the paper to pass between the registration sensor and the transfer nip should be longer than the separation / contact time. Thus, the photosensitive drum and the developing roller are surely brought into contact with each other during the time between image forming operations.
[0050]
Actually, an envelope (Yogata No. 4) was passed through and a continuous print test was performed to compare the conventional example with the present example.
[0051]
[Table 4]

[0052]
As described above, in the image forming apparatus of this embodiment, even when the host computer sends image information having a large amount of information and the time between image forming operations becomes longer during continuous printing, the CPU determines the image processing time from the amount of image information. The developing roller and the photosensitive drum are separated according to the image processing time, and the rotation of the photosensitive drum is stopped, and continuous printing of a small width paper is performed. Even when the time between image forming operations is long, the developing roller and the photosensitive drum are separated from each other and the rotation of the photosensitive drum is stopped in accordance with the temperature detected by the fixing portion end temperature thermistor. Also, by measuring the time between image forming operations from the paper interval, separating the developing roller and the photosensitive drum when the time between image forming operations is long, and stopping the rotation of the photosensitive drum Eliminating the abrasion of the photosensitive drum, it prevents the occurrence of fog image, no photosensitive drum pitch banding, low-cost image forming apparatus is realized.
[0053]
【The invention's effect】
As described above, according to the present invention, even when image information having a large amount of information is sent from the host computer and the time between image forming operations becomes longer during continuous printing, the CPU can reduce the image processing time from the amount of image information. In order to stop the rotation of the photosensitive drum in accordance with the image processing time by calculating the Even when the time is long, the rotation of the photosensitive drum is stopped in accordance with the temperature detected by the fixing unit end-portion temperature thermistor, thereby eliminating shaving of the photosensitive drum, preventing the occurrence of a fog image, and reducing cost. There is an effect of providing an image forming apparatus.
[0054]
Further, when the time between image forming operations becomes longer during continuous printing, the paper interval is measured using a registration sensor, and the developing roller and the photosensitive drum are separated from each other during the paper interval, that is, during the time between image forming operations, and the photosensitive drum is contacted. By stopping the rotation of the drum, there is an effect of eliminating abrasion of the photosensitive drum, preventing generation of a fog image, and providing a low-cost image forming apparatus.
[0055]
In addition, the time between image forming operations is measured, and during the time between image forming operations, the developing roller is stopped, and the developing roller and the photosensitive drum are separated from each other. In addition, there is an effect that the image forming apparatus without the photosensitive drum pitch banding can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus used in a first embodiment.
FIG. 2 is a schematic configuration diagram of a charging device of the image forming apparatus used in the first embodiment.
FIG. 3 is a schematic diagram illustrating a relationship between an image processing time and an image forming operation interval of the image forming apparatus used in the first embodiment.
FIG. 4 is a schematic configuration diagram of a heat fixing device of the image forming apparatus used in the first embodiment.
FIG. 5 is a schematic diagram of a paper interval measuring method according to a second embodiment.
FIG. 6 is a schematic configuration diagram of an image forming apparatus used in a third embodiment.
FIG. 7 is a schematic diagram illustrating a sequence of the image forming apparatus used in the third embodiment.
[Explanation of symbols]
101 paper
102 Paper cassette
103 Paper Pickup
104 transport roller
105 Registration sensor
106 registration roller
107 Charging device
108 Laser Scanner
109 laser beam
110 Photosensitive drum
111 developing device
112 transfer roller
113 Cleaner
114 Fixer
115 Fixing heating section
116 pressure roller
117 Rear registration sensor
118 discharge roller
119 Paper ejection roller
120 temperature sensor
121 Switching flap
123 Re-feed roller
124 Development and Separation Device
11 Image processing time
12 Image formation time
13 Image forming operation interval
14 Remaining image processing time
21 Photosensitive drum
22 Charging roller
23 Power supply
30 elastic layer
31 core
32 Release layer
33 fixing member
34 Fixing film
35 Thermistor
36 Foundation
37 Heating resistor
38 Toner image
39 Insulation support member
51 Transfer nip
52 paper, recording material

Claims

In an image forming apparatus including an image carrier, a charging device, and a cleaning member that contacts the image carrier and cleans the surface of the image carrier, the image forming apparatus has a function according to a time between image forming operations during a print job processing of a plurality of images. And changing the driving speed of the image carrier.

An image forming apparatus comprising: an image carrier; a charging device; a cleaning member that contacts the image carrier to clean the surface of the image carrier; and a developing roller that contacts and develops the image carrier. And a developing roller that separates and contacts the image carrier and the developing roller or changes the driving speed of the image carrier according to the time between image forming operations during print job processing of a plurality of images. And an image forming apparatus.

3. The image forming apparatus according to claim 1, wherein the driving of the image carrier is stopped according to a time between image forming operations during a print job processing of a plurality of images.

The time between image forming operations is the time for changing the driving speed of the image carrier from the speed at the time of image formation to a constant speed, the time to change from the constant speed to the speed at the time of image formation, and the speed at the time of image formation. The time required for the driven image carrier to move from the charging position to the position where the image is transferred to the recording material (hereinafter referred to as the image transfer position) is longer than the combined time (hereinafter referred to as the image carrier rotation deceleration / acceleration time). The image forming apparatus according to claim 1, wherein:

The time between image forming operations is a time obtained by adding a time required for separating the image bearing member and the developing roller and a time required for contacting the image bearing member and the developing roller (hereinafter referred to as a separation / contact time), 4. The image forming apparatus according to claim 2, wherein the time is longer than the deceleration / acceleration time of rotation of the image carrier.

6. The image forming apparatus according to claim 1, further comprising a CPU, wherein the CPU calculates a time between image forming operations based on image information sent from the host computer during a print job processing of a plurality of images. .

An image forming unit that includes a recording material on which an unfixed image is formed, and a fixing device that passes the recording material and heats and fixes the unfixed image on the recording material. 7. The image forming apparatus according to claim 1, wherein a time between forming operations is changed.

8. The image forming apparatus according to claim 7, wherein the non-sheet passing area temperature information is detected by a temperature detecting unit that can measure the non-sheet passing area of the fixing unit.

9. The image forming apparatus according to claim 1, further comprising a recording material front end detecting unit for detecting a front end position of the recording material, and measuring a time between image forming operations during a print job of a plurality of images.

A recording material trailing edge detecting means for detecting a trailing edge position of the recording material, and a recording material leading edge detecting means for detecting a leading edge position of the recording material, and recording the recording material trailing edge position during a print job of a plurality of images. 9. The image forming apparatus according to claim 1, wherein a time between image forming operations is measured from a front end position of the material.

During the travel of the recording material in the image forming apparatus, the recording material leading edge detecting means is located before the image transfer position, and the time required for the recording material leading edge to pass from the recording material leading edge detecting means to the image transfer position depends on the developing time. 11. The image forming apparatus according to claim 9, wherein the time is longer than the deceleration / acceleration time of the rotation of the roller.

It has a developing roller for developing by contacting the image carrier, and has a mechanism for separating and contacting the image carrier and the developing roller, and the time required for the leading edge of the recording material to pass from the leading edge detecting means of the recording material to the image transfer position is reduced. 11. The image forming apparatus according to claim 9, wherein a time required for the separation and contact between the carrier and the developing roller and a time required for deceleration and acceleration of rotation of the developing roller are longer.