JP4167795B2

JP4167795B2 - Image forming apparatus

Info

Publication number: JP4167795B2
Application number: JP2000132757A
Authority: JP
Inventors: 俊昭本橋
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2000-05-01
Filing date: 2000-05-01
Publication date: 2008-10-22
Anticipated expiration: 2020-05-01
Also published as: JP2001312155A

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、プリンタ等の画像形成装置に係り、詳しくは、トナー像を担持する像担持体と、該像担持体に向けて転写材を搬送する転写材搬送手段と、該像担持体と該転写材との間の転写領域に転写電界を形成し、該像担持体上のトナー像を該転写材上に転写する転写手段とを備える画像形成装置に関するものである。
【０００２】
【従来の技術】
従来この種の画像形成装置としては、転写電界形成手段と像担持体との間を転写材が通過するように、転写材搬送手段によって転写材を搬送し、転写電界形成手段により像担持体と転写材との間の転写領域に転写電界を形成して、像担持体上に形成されたトナー像を転写材に転写するように構成されたものが知られている。この種の画像形成装置においては、転写性をよくするために転写領域において像担持体と転写材とを密着させる必要がある。
【０００３】
例えば、図５に示すように、像担持体として中抵抗材料からなる中間転写ベルト１００を設け、この中間転写ベルト１００と転写電界形成手段としての転写ローラ１０１との間を転写材１０２が通過するように、図示しない転写材搬送手段により転写材１０２を搬送するように構成した装置がある。ここでは、転写材搬送手段により送り出される転写材１０２を入口ガイド部材１０３に沿って進行させながら、転写材１０２を中間転写ベルト１００に突き当たらせるようなかたちで中間転写ベルト１００上に搬送し、中間転写ベルト１００と転写材１０２とを静電的吸着によって密着させている。
【０００４】
【発明が解決しようとする課題】
ところが、従来の画像形成装置において、図５に示すように、入口ガイド部材１０３に沿いつつ進行した転写材１０２は、中間転写ベルト１００に突き当たると転写材搬送部材による搬送力を受けて矢印ａ方向で示すように図中上方にゆるやかに湾曲し、前記入口ガイド部材１０３に押さえつけられる。また、搬送された転写紙の先端は、転写ローラ１０１とその対向ローラ１０４とに挟まれる。そのため、湾曲した転写材１０２の反力が矢印ｂ方向で示すように発生し、この反力が転写領域に入る直前にある転写材１０２に矢印ｃ方向で示すように作用して、中間転写ベルト１００と転写材１０２との間に微小なギャップが生じることがあった。その結果、このギャップに転写電界が働いて異常な放電が起こり、トナーチリが発生する不具合が生じていた。
【０００５】
本発明は以上の問題点に鑑みなされたものであり、その目的とするところは、トナーチリの発生を防止して良好な画質が得られることができる画像形成装置を提供することである。
【０００６】
【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、トナー像を担持する像担持体と、該像担持体に向けて転写材を搬送する転写材搬送手段と、該像担持体と該転写材との間の転写領域に転写電界を形成し、該像担持体上のトナー像を該転写材上に転写する転写手段とを備える画像形成装置において、該像担持体と該転写領域の転写材搬送方向上流側にある該転写材とを密着させる密着手段を設け、上記密着手段は、回転体であり、上記転写材が該像担持体上に搬送されると同時に、上記転写領域の転写材搬送方向上流側にある該転写材に接触して、該像担持体と該転写材とを密着せしめ、上記転写領域の転写材搬送方向上流側にある上記転写材に接触しながら、該転写材の搬送方向と同方向に移動し、上記密着手段の移動速度が上記転写材の搬送速度よりも遅くなるように制御する制御手段を設けたことを特徴とするものである。
【０００７】
この画像形成装置においては、上記密着部材により、像担持体と転写領域の転写材搬送方向上流側にある転写材とを強制的に密着せしめる。これにより、像担持体と転写領域に入る直前にある転写材との間にギャップが発生することを防止できる。例えば転写材搬送部材により搬送された転写材が像担持体に突き当たり湾曲し、その反動が転写領域に入る直前にある転写材に作用して、像担持体と転写領域に入る直前にある転写材との間にギャップを生じさせようとする力が働いても、密着部材が転写材と像担持体とを強制的に密着させているので、該ギャップが発生することがない。したがって、このギャップに転写電界が働いて異常な放電が起こり、トナーチリが発生することもない。
また、この画像形成装置においては、転写材が像担持体上に搬送されると同時に、上記密着手段が移動して、該転写領域の転写材搬送方向上流側にある転写材に接触する。そして、上記密着手段は、回転しながら転写領域に入る直前にある転写材と像担持体とを強制的に密着させるので、転写材の搬送を損なうことなく、像担持体と転写領域に入る直前にある転写材との間にギャップが発生することを防止できる。
また、この画像形成装置においては、上記密着手段が転写材の搬送方向と同方向に移動するため、固定された位置で当接する場合に比べ、移動した分だけ広い範囲に亘って転写材に当接することができる。したがって、Ａ３等の大きなサイズの転写材に対しても、より高い密着性が得られる。なお、密着手段は最初に当接した位置から転写領域直前までの全域に亘って転写材に当接することが好ましい。
また、この画像形成装置においては、上記制御手段により、密着手段の移動速度が転写材の搬送速度よりも遅くなっているので、像担持体上の転写材が搬送方向上流側に若干引っ張られることになる。そのため、転写紙は像担持体上で緊張した状態で密着部材により密着せしめられるので、転写材と像担持体との密着性が高まる。
【０００８】
特に、請求項２の発明は、請求項１の画像形成装置において、上記密着手段は、上記像担持体に対し接離可能であることを特徴とするものである。
【００１０】
また、請求項３の発明は、請求項２の画像形成装置において、上記密着手段は、上記転写材と該密着手段との接触点における該転写材の面に垂直な面に対して転写材搬送方向上流側から該転写材に接近することを特徴とするものである。
【００１１】
この画像形成装置においては、上記密着手段が転写材と密着手段との接触点における転写材の面に垂直な面に対して転写材搬送方向上流側から転写材に接近するため、転写材搬送方向下流側から接近する場合に比べ、転写材への抵抗が少ない状態で該転写材に接触することができる。したがって、密着部材は、転写材の搬送を損ねることなく、像担持体と転写材とをより確実に密着できる。
【００１５】
この画像形成装置においては、上記制御手段により、密着手段の移動速度が転写材の搬送速度よりも遅くなっているので、像担持体上の転写材が搬送方向上流側に若干引っ張られることになる。そのため、転写紙は像担持体上で緊張した状態で密着部材により密着せしめられるので、転写材と像担持体との密着性が高まる。
【００１６】
請求項４の発明は、請求項１、２または３の画像形成装置において、上記制御手段は、上記転写材の種類に応じて、該転写材と上記密着手段との抵抗が小さくなるときには、該転写材と該密着手段との抵抗が大きいときよりも、該転写材の搬送速度と該密着手段の移動速度との速度差を大きく変化させることを特徴とするものである。
【００１７】
この画像形成装置においては、上記制御手段により転写材の種類に応じて密着部材の移動速度と転写材の搬送速度との速度差を変化させることによって、密着部材が転写材の搬送を妨げることがないように、密着部材と転写材との密着性をより高める。例えば、薄い転写材の場合には、コシが弱いために密着部材への巻きつきが大きく密着部材と転写材との抵抗が大きくなり、転写材の搬送が妨げられて画像ズレが生じやすくなるので、速度差を小さくする。厚い転写材の場合には、コシが強いために密着部材への巻きつきが小さく密着部材と転写材との抵抗が小さいため、速度差が大きくてもさほど問題がない。そのため、速度差を大きくして転写材と密着部材との密着性をより高めるようにする。
請求項５の発明は、請求項４の画像形成装置において、上記制御手段は、上記転写材が厚紙の場合は、上記転写材が薄紙の場合よりも、該転写材の搬送速度と上記密着手段の移動速度との速度差を大きくさせることを特徴とするものである。
【００１８】
【発明の実施の形態】
以下、本発明を画像形成装置であるフルカラー複写機（以下、単に「複写機」という。）に適用した一実施形態について説明する。図１は、本実施形態に係る複写機の全体的な構成を示す概略構成図であり、図２は、該複写機の転写部周辺の構成を示す概略構成図である。図１及び図２において、潜像担持体としての感光体ドラム１は、矢印Ａ方向に回転駆動されながら、その表面が帯電手段としての帯電チャージャ２により一様に帯電された後、レーザ光学装置３から発せられるレーザ光がミラー３ａにより所定方向に導かれることにより、画像情報に基づき走査露光されて該表面に静電潜像が形成される。
【００１９】
上記画像情報は、画像読取手段であるスキャナ４により読み取られた原稿情報に応じて適切な画像処理が行われて得られる。この画像情報は所望のフルカラー画像をイエロー、マゼンタ、シアン及びブラックの色情報に分解した単色の画像情報である。感光体ドラム１上に形成された静電潜像は、現像手段としての回転型現像装置５により各々所定の現像剤としてのイエロー、マゼンタ、シアン及びブラックトナーで現像され、これにより、感光体ドラム１上に各色のトナー像が形成される。
【００２０】
感光体ドラム１上に形成された各色のトナー像は、該感光体ドラム１と同期して図中矢印Ｂ方向に回転する像担持体としての中間転写ベルト６上に、イエロー、マゼンタ、シアン及びブラックのトナー像毎に順次重ね合わされて一次転写される。この中間転写ベルト６は、一次転写バイアスローラ７ａ、アースローラ７ｂ、ベルト駆動ローラ７ｃ、紙転写対向ローラ７ｄ、テンションローラ７ｅに張架されている。そして、この中間転写ベルト６上への各色のトナー像の転写は、感光体ドラム１と中間転写ベルト６との接触部において、一次転写バイアスローラ７ａに所定のバイアス電圧が印加されることで行なわれる。
【００２１】
この像担持体としての中間転写ベルト６には、厚さ１５０μｍでＰＶｄＦ（ポリフッ化ビニリデン）等の材質からなり、体積抵抗率が１０^８〜１０^１１Ωｃｍ（ＪＩＳｋ６９１１に記載されている測定方法で１００Ｖ、１０秒値）で、表面抵抗率が１０^８〜１０^１４Ω／（三菱化学製の抵抗測定器ハイレスタＩＰで測定５００Ｖ、１０秒値）のものを使用している。
【００２２】
このようにして中間転写ベルト６上に重ね合わされて一次転写されたイエロー、マゼンタ、シアン及びブラックのカラートナー像は、給紙カセット８又は手差しトレイから転写材搬送部としての給紙レジスト部９に設けられたレジストローラ９ａにより所定のタイミングで給紙される転写材としての転写紙１０に二次転写される。
【００２３】
この二次転写は、上記紙転写対向ローラ７ｄと弾性転写部材からなる転写ローラ１１との間の転写領域としての二次転写部に、転写紙を通過させることにより行われる。転写ローラ１１は、転写紙１０が上記二次転写部に進入するタイミングに合わせて、図示しない転写ローラ上昇クラッチにより揺動され、転写紙１０を介して中間転写ベルト６に当接する。また、この転写ローラ１１は、図示しない位置決め手段によって、上記紙転写対向ローラ７ｄとの平行度が保たれている。
【００２４】
このように転写ローラ１１が中間転写ベルト６に当接することで、上記紙転写対向ローラ７ｄ上の中間転写ベルト６と転写ローラ１１とによって転写ニップが形成される。このときの当接圧は、転写ローラ１１に設けられた図示しない位置決めコロにより一定に維持される。この転写ローラ１１にトナーと逆極性の転写バイアスを印加することで、該転写ニップにおいて中間転写ベルト６上のカラートナー像が転写紙１０上に二次転写される。
【００２５】
二次転写終了後の転写紙１０は、紙除電チャージャ１２によって中間転写ベルト６から分離して、定着装置１３へと進行する。そして、この転写紙１０は、定着装置１３によりトナー像が定着された後、機外に排出される。
【００２６】
この複写機は、中間転写ベルト６上の非画像領域に設けられた位置検出用マーク（図示せず）を、ベルトマークセンサ１４で検出し、該ベルトマークセンサ１４が位置検出用マークを検出するタイミングに合わせて、画像形成処理を開始するように構成されている。なお、この複写機によりモノクロのコピー画像を形成する場合には、ベルトマークセンサ１４による位置検出用マークの検出を行わずに画像形成処理を開始してもよい。
【００２７】
なお、上記中間転写ベルト６上への一次転写後の感光体ドラム１上に若干残留した一次転写残留トナーは、該感光体ドラム１の再使用に備えて感光体用クリーニング装置１５で清掃される。
【００２８】
また、上記転写紙１０上に二次転写されなかった中間転写ベルト６上の二次転写残留トナーは、該中間転写ベルト６に隣接して接離可能に設けられている中間転写ベルト用クリーニング装置１６によって該中間転写ベルト６から除去される。この中間転写ベルト用クリーニング装置１６には、中間転写ベルト６に当接して中間転写ベルト６上の残留トナーを除去するクリーングブレード１６ａと、板状に形成された潤滑剤よりなるコーティングバー１６ｂを研磨して中間転写ベルト６上に塗布する潤滑剤塗布ブラシ１６ｃとが備えられている。転写ローラ１１上に付着した付着物は、該転写ローラ１１に当接しているクリーニングブレード１７によって除去された後、紙転写回収ケース１８に収納される。クリーニング後の転写ローラ１１表面にはコーティングバー１９によって潤滑剤が塗布される。
【００２９】
ところで、上述したように、転写紙１０は、給紙レジスト部９から給紙された後、入口ガイドマイラー２０と下ガイド板２１との間を通過して、中間転写ベルト６上に搬送され、二次転写部に送られる。本実施形態に係る複写機においては、中間転写ベルト６とこの二次転写部へ向けて搬送される転写紙１０とを密着させる密着部材２２を設けたことを特徴とするものである。
【００３０】
図３は、二次転写部の概略構成を示し、密着部材２２の移動方向を説明する概略構成図である。図３に示すように、密着部材２２は、転写紙１０の搬送方向と直交する方向の全域に亘って当接するように当接面が形成されたロール形状により形成され、中間転写ベルト６に対して接離可能な状態で配設され、中間転写ベルト６に接している際には、中間転写ベルト６の回転方向（矢印Ｂ方向）と順方向に連れ回りながら回転する。なお、この密着部材２２の当接面は、転写紙１０に対して密着性と搬送性を両立させるために、ゴム等のグリップ力のある材質で構成している。
【００３１】
そして、この密着部材１１は、転写紙１０が給紙レジスト部９により送り出され、該転写紙１０の先端が中間転写ベルト６上に届くと同時に、矢印Ｃ方向で示すように水平方向に移動して中間転写ベルト６上の転写紙１０に接触し、転写紙１０と中間転写ベルト６とを強制的に密着させる。密着部材２２が転写紙１０に接触する際、転写紙１０と密着手段２２との接触点における転写紙１０の面に垂直な面に対して転写紙搬送方向上流側から接近するように構成すれば、例えば図３中水平方向に移動するように構成すれば、転写紙搬送方向下流側から接近する場合に比べ、密着部材２２が与える転写紙１０への抵抗が少なく、転写紙１０の搬送を損ねることがない。
【００３２】
給紙レジスト部９により搬送された転写紙１０は、入口ガイドマイラー２０に沿いつつ、中間転写ベルト６に突き当たると給紙レジスト部９による搬送力を受けて図３中上方に湾曲する。上方に湾曲した転写紙１０は入口ガイドマイラー２０に押さえつけられる。そのため、この反力が転写ニップ直前にある転写紙１０部分に作用して、従来では中間転写ベルト６と転写紙１０との間に微小なギャップが生じる可能性があった。そして、この微小なギャップに転写電界が働いて異常な放電が起こり、トナーチリが発生する可能性があった。その結果、トナーチリによるプレ転写が発生することがあった。
【００３３】
しかし、上述したように、本実施形態に係る複写機においては、密着部材が転写ニップの転写紙搬送方向上流側にある転写紙１０に当接し、中間転写ベルト６と転写紙１０とが静電的密着力だけではなく密着部材２２により強制的に密着させられているので、中間転写ベルト６と転写紙１０との間にギャップが発生することがない。したがって、トナーチリが発生する心配もない。
【００３４】
さらに、上記密着部材２２は、転写紙１０に接触した後、転写紙１０の搬送方向と同方向に移動するようにしてもよい。図４は、二次転写部の概略構成を示し、転写紙の搬送方向と同方向に移動可能な密着部材を説明する概略構成図である。図４に示すように、密着部材２２は、転写紙１０の先端が中間転写ベルト６に届くと同時に転写紙１０に接触し（図中点線で示す）、回転しながら矢印Ｄ方向に転写ニップ直前まで移動する。これにより、最初に密着部材２２が転写紙１０に接触した位置から転写ニップ直前までの広い範囲に亘って密着部材が転写紙１０に当接することになる。その結果、Ａ３等の大きなサイズの転写紙に対しても、より高い密着性が得られる。
【００３５】
また、本実施形態に係る画像形成装置においては、図４に示すように、密着部材２２が転写紙１０の搬送方向と同方向に移動する際、密着部材２２の移動速度を転写紙１０の搬送速度よりも遅くなるように制御する制御手段２３を設けるとよい。制御手段２３によって密着部材２２の移動速度を転写紙１０の搬送速度より遅くすることで、中間転写ベルト６上の転写紙１０は、密着部材２２によって搬送方向上流側に若干引っ張られることになる。そのため、転写紙１０は中間転写ベルト６上で緊張し、転写紙１０と中間転写ベルトとが密着部材２２によりしっかり密着されるようになる。
【００３６】
また、上記制御手段２３は、転写紙１０の紙種に応じて、密着部材２２の移動速度と転写紙１０の搬送速度との速度差を変化させる。例えば、例えば、薄紙の場合には、コシが弱いために密着部材２２への巻きつきが大きく密着部材２２と転写紙１０との抵抗が大きくなり、転写紙１０の搬送が妨げられて画像ズレを生じやすくなるので、速度差を小さくする。厚紙の場合には、コシが強いために密着部材２２への巻きつきが小さく密着部材２２と転写紙１０との抵抗が小さいため、速度差が大きくてもさほど問題がない。そのため、速度差を大きくして転写紙１０と密着部材２２との密着性をより高める。このように、制御手段によって紙種に応じた速度差をもたせることで、転写紙１０の搬送を妨げることなく、転写紙１０と密着部材２２との密着性をより高めることができる。
【００３７】
また、上述した実施形態では、密着部材２２が転写紙の搬送方向と直交する方向の全域に亘って転写紙１０と当接する当接面が形成されたロール形状である場合について説明したが、密着部材の形状は、これに限定されるものではない。例えば、密着部材として、断面形状が円形や半月状の回転可能なコロ部材を複数設け、転写紙の搬送方向と直交する方向に部分的に転写紙と当接するようにしてもよい。断面形状が半月状のような密着部材等の場合には、当接面が転写材と接するように密着部材の回転を制御する制御手段を設けてもよい。また、密着部材の当接面の材質は、転写紙に対して密着性と搬送性を両立させることができれば、特に限定されるものではない。また、この当接面は、平面であっても、凹凸が形成されていてもよい。
【００３８】
また、上述した実施形態では、像担持体が中間転写ベルトである場合について説明したが、例えばドラム状若しくはベルト状感光体から直接転写材に転写するときにも同様に適用することができる。このときは像担持体が感光体となる。また、上述した実施形態では、二次転写部の静電転写方式として、転写ローラを用いる場合について説明したが、転写チャージャや、転写材の搬送を兼ねて転写ベルトを用いる場合にも適用することができる。
【００３９】
【発明の効果】
請求項１乃至５の発明によれば、密着部材が像担持体と転写領域の転写材搬送方向上流側にある転写材とを強制的に密着せしめているので、像担持体と転写材との間にギャップが発生することがなく、トナーチリない良好な画質が得られるという優れた効果がある。
また、密着手段が移動した分だけ広い範囲に亘って転写材に当接するので、像担持体と転写材との間により高い密着性が得られるという優れた効果がある。
また、密着手段が転写材を搬送方向上流側に引っ張りながら当接するので、像担持体と転写材との間により高い密着性が得られるという優れた効果がある。
【００４０】
特に、請求項２の発明によれば、密着部材が像担持体に対して接離可能な回転体からなるので、転写材の搬送を損ねることなく像担持体と転写材とを強制的に密着せしめることができるという優れた効果がある。
【００４１】
また、請求項３の発明によれば、密着部材が転写材に接触する際、転写材への抵抗が少ないので、転写材の搬送を損ねることなく、像担持体と転写材とをより確実に密着できるという優れた効果がある。
【００４４】
また、請求項４の発明によれば、転写材の種類に応じて、転写材と密着部材との抵抗が小さくなるときには、転写材と密着部材との抵抗が大きいときよりも、密着部材の移動速度と転写材の搬送速度との速度差が大きく変化するので、転写材の搬送を損ねることなく、像担持体と転写材との密着性を高めることができるという効果がある。
また、請求項５の発明によれば、制御手段によって厚紙または薄紙といった紙種に応じた速度差をもたせることで、転写材の搬送を妨げることなく、転写材と密着部材との密着性をより高めることができる。
【００４５】
【図面の簡単な説明】
【図１】本発明の実施形態に係る複写機の全体的な構成を示す概略構成図。
【図２】同複写機の二次転写部位周辺の構成を示す概略構成図。
【図３】同二次転写部の密着部材の移動方向を説明する概略構成図。
【図４】同二次転写部の密着部材の移動方向を説明する概略構成図。
【図５】従来の二次転写部の構成を示す概略構成図。
【符号の説明】
１感光体ドラム
６中間転写ベルト
７ａバイアスローラ
７ｂアースローラ
７ｃベルト駆動ローラ
７ｄ紙転写対向ローラ
７ｅテンションローラ
９給紙レジスト部
１０転写紙
１１転写ローラ
２０入口ガイドマイラー
２１下ガイド板
２２密着部材
２３制御手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, or a printer. More specifically, the present invention relates to an image carrier that carries a toner image, a transfer material conveyance unit that conveys a transfer material toward the image carrier, The present invention relates to an image forming apparatus including a transfer unit that forms a transfer electric field in a transfer region between an image carrier and a transfer material, and transfers a toner image on the image carrier onto the transfer material.
[0002]
[Prior art]
Conventionally, in this type of image forming apparatus, a transfer material is conveyed by a transfer material conveying means so that the transfer material passes between the transfer electric field forming means and the image carrier, and the transfer electric field forming means There is known a configuration in which a transfer electric field is formed in a transfer region between a transfer material and a toner image formed on an image carrier is transferred to the transfer material. In this type of image forming apparatus, it is necessary to bring the image carrier and the transfer material into close contact with each other in the transfer region in order to improve transferability.
[0003]
For example, as shown in FIG. 5, an intermediate transfer belt 100 made of a medium resistance material is provided as an image carrier, and a transfer material 102 passes between the intermediate transfer belt 100 and a transfer roller 101 as transfer electric field forming means. As described above, there is an apparatus configured to transport the transfer material 102 by a transfer material transport unit (not shown). Here, while the transfer material 102 sent out by the transfer material conveying means is advanced along the entrance guide member 103, the transfer material 102 is conveyed onto the intermediate transfer belt 100 in such a manner as to abut against the intermediate transfer belt 100. The intermediate transfer belt 100 and the transfer material 102 are brought into close contact by electrostatic adsorption.
[0004]
[Problems to be solved by the invention]
However, in the conventional image forming apparatus, as shown in FIG. 5, when the transfer material 102 that has advanced along the entrance guide member 103 hits the intermediate transfer belt 100, the transfer material 102 receives the conveyance force by the transfer material conveyance member and is in the direction of arrow a. As shown by, the curve is gently curved upward in the figure and is pressed against the inlet guide member 103. Further, the leading edge of the transferred transfer paper is sandwiched between the transfer roller 101 and the counter roller 104. Therefore, a reaction force of the curved transfer material 102 is generated as indicated by the arrow b direction, and this reaction force acts on the transfer material 102 immediately before entering the transfer region as indicated by the arrow c direction, so that the intermediate transfer belt In some cases, a minute gap is generated between the transfer material 100 and the transfer material 102. As a result, a transfer electric field acts on the gap and abnormal discharge occurs, resulting in a problem that toner dust is generated.
[0005]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing generation of toner dust and obtaining good image quality.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 includes an image carrier that carries a toner image, a transfer material conveyance unit that conveys a transfer material toward the image carrier, the image carrier, and the transfer material. In an image forming apparatus comprising a transfer means for forming a transfer electric field in a transfer area between a transfer material and transferring a toner image on the transfer medium onto the transfer material. A close contact means for contacting the transfer material upstream in the material transport direction is provided , and the close contact means is a rotating body, and at the same time the transfer material is transported onto the image carrier, the transfer of the transfer area is performed. The image carrier and the transfer material are brought into close contact with the transfer material on the upstream side in the material conveyance direction, and the transfer material is in contact with the transfer material on the upstream side in the transfer material conveyance direction of the transfer region. Moving in the same direction as the conveying direction of the material, and the moving speed of the contact means is In which it characterized in that a control means for controlling so as to be slower than the speed.
[0007]
In the image forming apparatus, the image bearing member and the transfer material on the upstream side of the transfer region in the transfer material conveyance direction are forcibly brought into close contact by the contact member. Thereby, it is possible to prevent a gap from being generated between the image carrier and the transfer material immediately before entering the transfer region. For example, the transfer material conveyed by the transfer material conveying member abuts against the image carrier and curves, and the reaction acts on the transfer material just before entering the transfer region, so that the transfer material just before entering the image carrier and the transfer region Even if a force for generating a gap acts between the transfer member and the image carrier, the gap does not occur. Therefore, an abnormal electric discharge occurs due to the transfer electric field acting on the gap, and toner dust does not occur.
Further, in this image forming apparatus, at the same time as the transfer material is conveyed onto the image carrier, the contact means moves and contacts the transfer material on the upstream side of the transfer region in the transfer material conveyance direction. The contact means forcibly brings the transfer material and the image carrier immediately before entering the transfer area while rotating, so that the transfer of the transfer material is not impaired and immediately before entering the transfer area. It is possible to prevent a gap from occurring between the transfer material and the transfer material.
Further, in this image forming apparatus, the contact means moves in the same direction as the transfer material conveyance direction. You can touch. Accordingly, higher adhesion can be obtained even for a transfer material having a large size such as A3. It is preferable that the contact means abuts on the transfer material over the entire area from the position where it first abuts to immediately before the transfer area.
Further, in this image forming apparatus, since the moving speed of the contact means is slower than the transfer speed of the transfer material by the control means, the transfer material on the image carrier is slightly pulled upstream in the transport direction. become. For this reason, the transfer paper is brought into close contact with the contact member in a tensioned state on the image carrier, so that the adhesion between the transfer material and the image carrier is enhanced.
[0008]
In particular, the invention of claim 2, the image forming apparatus according to claim 1, said contact means is characterized in that a separable available-to the image carrier.
[0010]
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the contact unit conveys the transfer material to a surface perpendicular to the surface of the transfer material at a contact point between the transfer material and the contact unit. The transfer material is approached from the upstream side in the direction.
[0011]
In this image forming apparatus, since the contact means approaches the transfer material from the upstream side in the transfer material transport direction with respect to a surface perpendicular to the surface of the transfer material at the contact point between the transfer material and the contact means, the transfer material transport direction Compared to when approaching from the downstream side, the transfer material can be contacted with less resistance to the transfer material. Therefore, the contact member can more securely contact the image carrier and the transfer material without impairing the transfer of the transfer material.
[0015]
In this image forming apparatus, since the moving speed of the contact means is slower than the transfer speed of the transfer material by the control means, the transfer material on the image carrier is slightly pulled upstream in the transport direction. . For this reason, the transfer paper is brought into close contact with the contact member in a tensioned state on the image carrier, so that the adhesion between the transfer material and the image carrier is enhanced.
[0016]
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, when the resistance between the transfer material and the contact means becomes small according to the type of the transfer material, the control means than when resistance is large between the transfer material and said seal fixing device is also characterized in significantly changing the speed difference between the moving speed of the conveyance speed and said contact means of the transfer material.
[0017]
In this image forming apparatus, the contact member prevents the transfer material from being conveyed by changing the speed difference between the transfer speed of the contact member and the transfer material according to the type of the transfer material. As a result, the adhesion between the adhesion member and the transfer material is further enhanced. For example, in the case of a thin transfer material, since the stiffness is weak, the wrapping around the close contact member is large and the resistance between the close contact member and the transfer material is increased, and the transfer of the transfer material is hindered and image misalignment is likely to occur. Reduce the speed difference. In the case of a thick transfer material, since the stiffness is strong, the winding around the contact member is small, and the resistance between the contact member and the transfer material is small, so there is no problem even if the speed difference is large. Therefore, the speed difference is increased to further improve the adhesion between the transfer material and the adhesion member.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the transfer material is a thick paper, the control unit is configured to transfer the transfer material and the contact unit when the transfer material is a thin paper. This is characterized in that the difference in speed from the moving speed of is increased.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a full-color copying machine (hereinafter simply referred to as “copying machine”) that is an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram showing an overall configuration of a copying machine according to the present embodiment, and FIG. 2 is a schematic configuration diagram showing a configuration around a transfer unit of the copying machine. 1 and 2, the surface of a photosensitive drum 1 as a latent image carrier is uniformly charged by a charging charger 2 as a charging means while being rotated in the direction of arrow A, and then a laser optical device. The laser light emitted from 3 is guided in a predetermined direction by the mirror 3a, and is subjected to scanning exposure based on image information to form an electrostatic latent image on the surface.
[0019]
The image information is obtained by performing appropriate image processing according to the document information read by the scanner 4 serving as image reading means. This image information is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. The electrostatic latent image formed on the photosensitive drum 1 is developed with yellow, magenta, cyan, and black toners as predetermined developers by a rotary developing device 5 as a developing unit. A toner image of each color is formed on 1.
[0020]
The toner images of the respective colors formed on the photosensitive drum 1 are yellow, magenta, cyan, and cyan on an intermediate transfer belt 6 as an image carrier that rotates in the direction of arrow B in the figure in synchronization with the photosensitive drum 1. Each black toner image is sequentially superimposed and primarily transferred. The intermediate transfer belt 6 is stretched around a primary transfer bias roller 7a, an earth roller 7b, a belt driving roller 7c, a paper transfer counter roller 7d, and a tension roller 7e. The toner images of the respective colors are transferred onto the intermediate transfer belt 6 by applying a predetermined bias voltage to the primary transfer bias roller 7a at the contact portion between the photosensitive drum 1 and the intermediate transfer belt 6. It is.
[0021]
The intermediate transfer belt 6 as an image carrier is made of a material such as PVdF (polyvinylidene fluoride) with a thickness of 150 μm, and has a volume resistivity of 10 ⁸ to 10 ¹¹ Ωcm (100 V by the measurement method described in JISk6911). 10 sec value) and a surface resistivity of 10 ⁸ to 10 ¹⁴ Ω / (measured with a resistance measuring instrument Hiresta IP manufactured by Mitsubishi Chemical, 500 V, 10 sec value) is used.
[0022]
The yellow, magenta, cyan, and black color toner images superimposed and primarily transferred onto the intermediate transfer belt 6 in this way are fed from the paper feed cassette 8 or the manual feed tray to the paper feed resist unit 9 as a transfer material transport unit. Secondary transfer is performed on a transfer sheet 10 as a transfer material fed at a predetermined timing by the provided registration roller 9a.
[0023]
This secondary transfer is performed by passing the transfer paper through a secondary transfer portion as a transfer area between the paper transfer counter roller 7d and the transfer roller 11 made of an elastic transfer member. The transfer roller 11 is swung by a transfer roller raising clutch (not shown) at the timing when the transfer paper 10 enters the secondary transfer portion, and contacts the intermediate transfer belt 6 via the transfer paper 10. The transfer roller 11 is maintained in parallel with the paper transfer facing roller 7d by positioning means (not shown).
[0024]
As the transfer roller 11 contacts the intermediate transfer belt 6 in this way, a transfer nip is formed by the intermediate transfer belt 6 and the transfer roller 11 on the paper transfer counter roller 7d. The contact pressure at this time is kept constant by a positioning roller (not shown) provided on the transfer roller 11. By applying a transfer bias having a polarity opposite to that of the toner to the transfer roller 11, the color toner image on the intermediate transfer belt 6 is secondarily transferred onto the transfer paper 10 at the transfer nip.
[0025]
The transfer paper 10 after the completion of the secondary transfer is separated from the intermediate transfer belt 6 by the paper discharger 12 and proceeds to the fixing device 13. The transfer paper 10 is discharged to the outside after the toner image is fixed by the fixing device 13.
[0026]
In this copying machine, a position detection mark (not shown) provided in a non-image area on the intermediate transfer belt 6 is detected by a belt mark sensor 14, and the belt mark sensor 14 detects a position detection mark. The image forming process is started in accordance with the timing. When a monochrome copy image is formed by this copying machine, the image forming process may be started without detecting the position detection mark by the belt mark sensor 14.
[0027]
The primary transfer residual toner slightly remaining on the photosensitive drum 1 after the primary transfer onto the intermediate transfer belt 6 is cleaned by the photosensitive member cleaning device 15 in preparation for reuse of the photosensitive drum 1. .
[0028]
Further, the secondary transfer residual toner on the intermediate transfer belt 6 that has not been secondarily transferred onto the transfer paper 10 is provided adjacent to the intermediate transfer belt 6 so as to be able to contact and separate. 16 from the intermediate transfer belt 6. In this intermediate transfer belt cleaning device 16, a cleaning blade 16a that contacts the intermediate transfer belt 6 to remove residual toner on the intermediate transfer belt 6 and a coating bar 16b made of a lubricant formed in a plate shape are polished. Then, a lubricant application brush 16c applied on the intermediate transfer belt 6 is provided. Deposits adhering to the transfer roller 11 are removed by the cleaning blade 17 in contact with the transfer roller 11 and then stored in the paper transfer recovery case 18. A lubricant is applied to the surface of the transfer roller 11 after cleaning by a coating bar 19.
[0029]
By the way, as described above, after the transfer paper 10 is fed from the paper feed resist unit 9, it passes between the entrance guide mylar 20 and the lower guide plate 21 and is conveyed onto the intermediate transfer belt 6. Sent to the secondary transfer section. The copying machine according to the present embodiment is characterized in that a close contact member 22 is provided for closely contacting the intermediate transfer belt 6 and the transfer paper 10 conveyed toward the secondary transfer portion.
[0030]
FIG. 3 is a schematic configuration diagram illustrating a schematic configuration of the secondary transfer unit and illustrating a moving direction of the contact member 22. As shown in FIG. 3, the contact member 22 is formed in a roll shape in which a contact surface is formed so as to contact over the entire region in a direction orthogonal to the transfer direction of the transfer paper 10, and the intermediate contact belt 6 is in contact with the intermediate transfer belt 6. When the intermediate transfer belt 6 is in contact with the intermediate transfer belt 6 and is in contact with the intermediate transfer belt 6, the intermediate transfer belt 6 rotates while rotating in the forward direction (in the direction of arrow B). The contact surface of the contact member 22 is made of a material having a gripping force such as rubber in order to achieve both adhesion and transportability to the transfer paper 10.
[0031]
The contact member 11 moves in the horizontal direction as indicated by the arrow C at the same time as the transfer paper 10 is fed out by the paper feed resist unit 9 and the leading edge of the transfer paper 10 reaches the intermediate transfer belt 6. The transfer paper 10 on the intermediate transfer belt 6 is brought into contact, and the transfer paper 10 and the intermediate transfer belt 6 are forcibly brought into close contact with each other. When the contact member 22 is in contact with the transfer paper 10, the contact member 22 may be configured to approach the surface perpendicular to the surface of the transfer paper 10 at the contact point between the transfer paper 10 and the contact means 22 from the upstream side in the transfer paper transport direction. For example, if it is configured to move in the horizontal direction in FIG. 3, the resistance to the transfer paper 10 provided by the contact member 22 is less than that when approaching from the downstream side in the transfer paper transport direction, and transport of the transfer paper 10 is impaired. There is nothing.
[0032]
When the transfer paper 10 conveyed by the paper feed resist unit 9 abuts the intermediate transfer belt 6 along the entrance guide mylar 20, the transfer paper 10 receives the conveyance force by the paper feed resist unit 9 and curves upward in FIG. The transfer paper 10 curved upward is pressed against the entrance guide mylar 20. Therefore, this reaction force acts on the transfer paper 10 portion immediately before the transfer nip, and there has been a possibility that a minute gap is generated between the intermediate transfer belt 6 and the transfer paper 10 conventionally. Then, a transfer electric field acts on the minute gap and abnormal discharge occurs, which may cause toner dust. As a result, pre-transfer due to toner dust may occur.
[0033]
However, as described above, in the copying machine according to the present embodiment, the contact member abuts on the transfer paper 10 on the upstream side of the transfer nip in the transfer paper conveyance direction, and the intermediate transfer belt 6 and the transfer paper 10 are electrostatically connected. Since the adhesive member 22 is forcibly brought into close contact not only with the close contact force, there is no gap between the intermediate transfer belt 6 and the transfer paper 10. Therefore, there is no concern about toner dust.
[0034]
Furthermore, the contact member 22 may move in the same direction as the transfer direction of the transfer paper 10 after contacting the transfer paper 10. FIG. 4 is a schematic configuration diagram illustrating a schematic configuration of the secondary transfer unit and illustrating a contact member that can move in the same direction as the transfer paper conveyance direction. As shown in FIG. 4, the contact member 22 contacts the transfer paper 10 at the same time as the leading edge of the transfer paper 10 reaches the intermediate transfer belt 6 (indicated by a dotted line in the figure), and rotates in the direction of arrow D immediately before the transfer nip. Move up. As a result, the contact member contacts the transfer paper 10 over a wide range from the position where the contact member 22 first contacts the transfer paper 10 to immediately before the transfer nip. As a result, higher adhesion can be obtained even for large size transfer paper such as A3.
[0035]
Further, in the image forming apparatus according to the present embodiment, as shown in FIG. 4, when the contact member 22 moves in the same direction as the transfer direction of the transfer paper 10, the moving speed of the contact member 22 is controlled to transfer the transfer paper 10. Control means 23 for controlling to be slower than the speed may be provided. By making the moving speed of the contact member 22 slower than the transport speed of the transfer paper 10 by the control means 23, the transfer paper 10 on the intermediate transfer belt 6 is slightly pulled upstream in the transport direction by the contact member 22. For this reason, the transfer paper 10 is tensioned on the intermediate transfer belt 6, and the transfer paper 10 and the intermediate transfer belt are brought into close contact with each other by the contact member 22.
[0036]
Further, the control means 23 changes the speed difference between the moving speed of the contact member 22 and the transport speed of the transfer paper 10 according to the type of the transfer paper 10. For example, in the case of thin paper, since the stiffness is weak, the winding around the contact member 22 is large, the resistance between the contact member 22 and the transfer paper 10 is increased, and the transfer of the transfer paper 10 is hindered to cause image misalignment. Since this is likely to occur, the speed difference is reduced. In the case of thick paper, since the stiffness is strong, the winding around the contact member 22 is small, and the resistance between the contact member 22 and the transfer paper 10 is small, so there is no problem even if the speed difference is large. Therefore, the speed difference is increased to further improve the adhesion between the transfer paper 10 and the adhesion member 22. In this way, by providing the control means with a speed difference corresponding to the paper type, the adhesion between the transfer paper 10 and the contact member 22 can be further enhanced without hindering the transfer of the transfer paper 10.
[0037]
In the above-described embodiment, the case where the contact member 22 has a roll shape in which the contact surface that contacts the transfer paper 10 is formed over the entire region in the direction orthogonal to the transfer direction of the transfer paper has been described. The shape of the member is not limited to this. For example, as the contact member, a plurality of rotatable roller members having a circular or half-moon cross-sectional shape may be provided so as to partially contact the transfer paper in a direction perpendicular to the transfer paper transport direction. In the case of a close contact member or the like having a half-moon cross-sectional shape, control means for controlling the rotation of the close contact member may be provided so that the contact surface is in contact with the transfer material. Further, the material of the contact surface of the contact member is not particularly limited as long as it can achieve both adhesion and transportability with respect to the transfer paper. In addition, the abutting surface may be a flat surface or uneven.
[0038]
In the above-described embodiment, the case where the image carrier is an intermediate transfer belt has been described. However, the present invention can be similarly applied to, for example, a transfer from a drum-like or belt-like photosensitive member directly onto a transfer material. At this time, the image carrier becomes the photosensitive member. In the above-described embodiment, the case where the transfer roller is used as the electrostatic transfer method of the secondary transfer unit has been described. However, the present invention can also be applied to the case where the transfer belt is used to transfer the transfer charger and the transfer material. Can do.
[0039]
【The invention's effect】
According to the first to fifth aspects of the present invention, the contact member forcibly contacts the image carrier and the transfer material on the upstream side of the transfer region in the transfer material conveyance direction. There is no gap between them, and there is an excellent effect that a good image quality without toner dust can be obtained.
Further, since the contact means abuts on the transfer material over a wide range by the amount of movement, there is an excellent effect that higher adhesion can be obtained between the image carrier and the transfer material.
Further, since the contact means abuts while pulling the transfer material upstream in the transport direction, there is an excellent effect that higher adhesion can be obtained between the image carrier and the transfer material.
[0040]
In particular, according to the second aspect of the present invention, the contact member is composed of a rotating body that can be brought into contact with and separated from the image carrier, so that the image carrier and the transfer material are forcibly adhered without impairing the transfer of the transfer material. There is an excellent effect that it can be damped.
[0041]
According to the invention of claim 3, since the resistance to the transfer material is small when the contact member comes into contact with the transfer material, the image carrier and the transfer material are more reliably connected without impairing the transfer of the transfer material. There is an excellent effect of being able to adhere.
[0044]
According to the fourth aspect of the present invention, when the resistance between the transfer material and the close contact member is small depending on the type of the transfer material, the close contact member is moved more than when the resistance between the transfer material and the close contact member is large. Since the speed difference between the speed and the transfer speed of the transfer material changes greatly, there is an effect that the adhesion between the image carrier and the transfer material can be improved without impairing the transfer of the transfer material.
Further, according to the invention of claim 5, by providing the control means with a speed difference corresponding to the paper type such as thick paper or thin paper, the adhesion between the transfer material and the contact member can be further improved without disturbing the transfer of the transfer material. Can be increased.
[0045]
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an overall configuration of a copying machine according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing a configuration around a secondary transfer portion of the copier.
FIG. 3 is a schematic configuration diagram illustrating a moving direction of a contact member of the secondary transfer unit.
FIG. 4 is a schematic configuration diagram illustrating a moving direction of a contact member of the secondary transfer unit.
FIG. 5 is a schematic configuration diagram illustrating a configuration of a conventional secondary transfer unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photosensitive drum 6 Intermediate transfer belt 7a Bias roller 7b Ground roller 7c Belt drive roller 7d Paper transfer opposing roller 7e Tension roller 9 Paper feed resist unit 10 Transfer paper 11 Transfer roller 20 Entrance guide mylar 21 Lower guide plate 22 Adhering member 23 Control means

Claims

An image carrier that carries a toner image; transfer material conveyance means that conveys a transfer material toward the image carrier; and a transfer electric field formed in a transfer region between the image carrier and the transfer material, In an image forming apparatus comprising transfer means for transferring a toner image on an image carrier onto the transfer material,
Providing an adhesion means for bringing the image carrier and the transfer material upstream of the transfer region in the transfer material conveyance direction;
The contact means is a rotating body, and at the same time the transfer material is conveyed onto the image carrier, the image carrier is brought into contact with the transfer material on the upstream side of the transfer region in the transfer material conveyance direction. And the transfer material
While in contact with the transfer material upstream of the transfer region in the transfer material conveyance direction, the transfer region moves in the same direction as the transfer material conveyance direction,
An image forming apparatus comprising: a control unit configured to control the moving speed of the contact unit to be slower than the transfer speed of the transfer material.

The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the contact means is capable of contacting and separating from the image carrier.

The image forming apparatus according to claim 2.
The image forming apparatus, wherein the contact means approaches the transfer material from the upstream side in the transfer material conveyance direction with respect to a surface perpendicular to the surface of the transfer material at a contact point between the transfer material and the contact means. .

The image forming apparatus according to claim 1, 2 or 3.
According to the type of the transfer material, the control means transports the transfer material when the resistance between the transfer material and the contact means is smaller than when the resistance between the transfer material and the contact means is large. image forming apparatus characterized by greatly changing the speed difference between the speed and the moving speed of said contact means.

The image forming apparatus according to claim 4.
The control means increases the speed difference between the transfer speed of the transfer material and the moving speed of the contact means when the transfer material is thick paper than when the transfer material is thin paper. Forming equipment.