JP2004117748A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized image forming apparatus which can operate with low power supply voltage and provides an image of good quality, and an image forming method. <P>SOLUTION: In the image forming apparatus equipped with a photoreceptor 1, an electrifying device 51, a developing device 21 and a transfer device 31, an electrifying roller 52 for the electrifying device 51 and the photoreceptor 1 are rotated so that the moving directions of the counter surfaces in the direction in which the surfaces pass each other at the closest position are opposite to each other, then, toner 61 and carrier 62 remaining on the photoreceptor 1 after a transfer process are attracted to the electrifying roller 52, and removed from the photoreceptor 1, and also, the photoreceptor 1 is electrified by the electrifying roller 52. <P>COPYRIGHT: (C)2004,JPO

Description

【００９５】
表１に示すように、帯電ローラ５２によってトナー６１およびキャリア６２を回収することにより、良好な画像を得ることができる。
【００９６】
本実施の形態において、上記帯電ローラ５２と感光体１とは、帯電ローラ５２の回転軸に対する回転方向と、上記感光体１の回転軸に対する回転方向とが同じ方向に回転するように設けられている。すなわち、上記帯電ローラ５２と感光体１とは、互いに異なる駆動系により、上記帯電ローラ５２互いに行き違う方向にと感光体１との最近接位置にて、互いに対面する面の移動方向が互いに逆方向となるように回転（アゲンスト回転）するように設けられている。
【００９７】
これにより、転写後に上記感光体１上に残留している上記逆帯電トナー６１ｂやキャリア６２等の異物は、該異物が上記帯電ローラ５２の放電面と感光体１との最近接位置におけるギャップである帯電ギャップＣを通過する前に、上記帯電ローラ５２に吸着されて除去される。また、上記帯電装置５１は、上記帯電ローラ５２に当接して設けられ、上記帯電ローラ５２に吸着された異物を掻き取り、現像ローラ２３よりも奥に備えられている現像槽２２内に回収する異物回収手段（残留現像剤成分回収手段）として、クリーニングブレードとトナー搬送スクリューとからなマイラーマイラーるクリーニングフィルム５４を有している。該クリーニングフィルム５４の材質としては、例えばポリエチレンテレフタートが用いられる。上記異物回収手段としてクリーニングフィルム５４を設けることにより、上記帯電ローラ５２に吸着された逆帯電トナー６１ｂ等の異物は、現像槽２２に戻され、前記正規帯電トナー６１ａ同様、現像槽２２内にて十分な攪拌帯電が与えられる。この結果、帯電が大きく変化した上記逆帯電トナー６１ｂもまた再利用が可能となる。また、このように上記帯電ローラ５２に、感光体１表面の異物を回収するための異物回収手段としてのクリーニングフィルム５４を設けることにより、上記異物を除去、回収するための手段を上記帯電装置５１とは別に設ける必要がなく、上記画像形成装置の構造の簡素化を図ることができる。
【００９８】
このように、上記帯電ローラ５２は、感光体１に対し、アゲンスト回転しており、転写後に上記感光体１上に残留している上記異物を該帯電ローラ５２に吸着させて上記感光体１表面から除去することで、帯電ローラ５２と感光体１との間の帯電ギャップＣに、例えば転写材Ｐの白地の領域に逆帯電トナー６１ｂが付着し、現像されてかぶりとなる画像かぶり等の画質劣化の原因となる逆帯電トナー６１ｂやキャリア等の異物が食い込まれることなく、感光体１表面から、確実かつ積極的に、該異物を除去、回収することができる。
【００９９】
すなわち、上記帯電ローラ５２と感光体１とが、帯電ローラ５２の回転軸に対する回転方向と、上記感光体１の回転軸に対する回転方向とが異なる方向に回転することで両者の最近接位置にて互いに同方向に回転（ウィッズ回転）する場合、逆帯電トナー６１ｂが帯電領域５を通過することになるのに対し、両者がアゲンスト回転することで、逆帯電トナー６１ｂ等の異物は、帯電領域５よりも感光体１の回転方向上流側近傍で帯電ローラ５２に吸着される。この結果、これら異物の帯電ギャップＣへの侵入を防止し、これら異物、特に、逆帯電トナー６１ｂが帯電領域５を通過することを防止することができる
また、上記帯電ローラ５２に重畳電圧（ＡＣ重畳バイアス）を印加した場合、帯電領域５の終了部付近では感光体１の表面電位は直流バイアスの電圧とほぼ同一に帯電されているので、ウィッズ回転においては逆帯電トナー６１ｂを静電的に回収する能力が大幅に減少するのに対して、アゲンスト回転では、該逆帯電トナー６１ｂは、感光体１への帯電が開始される帯電領域５よりも感光体１の回転方向上流側近傍で回収、搬送されるので、帯電ローラ５２のＡＣ重畳バイアスの直流（ＤＣ）成分が、逆帯電トナー６１ｂの静電回収に有効に寄与する。
【０１００】
特に反転現像においては、逆帯電トナー６１ｂが未露光部に残留する状態で現像領域４に侵入すると、感光体１への静電吸引力が強いので現像ローラ２３に回収されず、現像領域４で正規帯電トナー６１ａを静電的に吸引し、感光体１上のトナー６１の量が増幅された状態で転写工程に移るため、顕著な白地汚れを発生させてしまう。このため、逆帯電トナー６１ｂの回収には、アゲンスト回転が特に有効である。
【０１０１】
よって、本実施の形態にかかる画像形成装置によれば、感光体１上に残留している異物を除去するための専用のクリーニング装置を必要とせず、装置の小型化を図ることができ、電源電圧を低くすることができる。また、この結果、クリーニングによる感光体１の膜減り、摺擦痕の発生を防止することができると共に、感光体１の負荷トルクを低減させることができる。
【０１０２】
さらに、本実施の形態にかかる画像形成装置によれば、上記帯電ローラ５２が上記感光体１に対しアゲンスト回転していることで、上記異物が上記帯電ローラ５２と感光体１との間の帯電ギャップＣを通過する前に、該異物を上記帯電ローラ５２に吸着させることができると共に、上記帯電ローラ５２に吸着された異物を、上記帯電ギャップＣを通過することなく除去、回収することができることから、上記帯電ギャップＣを通過する異物による帯電ムラを防止することができる。
【０１０３】
つまり、上記帯電ギャップＣに上記逆帯電トナー６１ｂ等の異物が存在すると、例えば該逆帯電トナー６１ｂが電荷チャージされ、該逆帯電トナー６１ｂが除去された部分に、チャージアップ（電荷チャージ）帯電されない影が生じることになる。しかしながら、上記の構成によれば、上記異物、特に、逆帯電トナー６１ｂが、帯電領域５よりも感光体１の回転方向上流側近傍で帯電ローラ５２に吸着されるので、上記異物の帯電ギャップＣへの侵入を防止することができ、帯電特性を向上させることができる。
【０１０４】
特に、本実施の形態にかかる画像形成装置によれば、現像装置２１に対し、感光体１の回転方向上流側に設けられた上記帯電ローラ５２によって、画質劣化、特に前記した画像かぶりの原因となる逆帯電トナー６１ｂが回収されるため、現像装置とクリーニング装置とを一体化した現像クリーニング方式にて、良好な画像を維持することができる。また、このように現像装置とクリーニング装置とを一体化することにより、さらに画像形成装置の小型化を図ることができる。また、上記画像形成装置によれば、上記帯電ローラ５２において、キャリア６２によって逆帯電トナー６１ｂが積極的に掻き取られるため、正規帯電トナー６１ａの回収効率を高めることができる。
【０１０５】
また、本実施の形態にかかる上記画像形成装置によれば、上記帯電ギャップＣへの異物の侵入を阻止することができることから、上記帯電ギャップＣを、該帯電ギャップＣに例えばキャリア６２が挟まれることなく通過することができるように広げる必要はなく、上記帯電ギャップＣを狭くすることができる。このように帯電ギャップＣの間隔を小さくすることにより、気中放電における放電開始電圧を示す「パッシェの実験式」（６．２Ｖ／μｍ）より感光体１の下流側から該感光体１の帯電面がリフレッシュされ、チャージアップに効果的でありのチャージアップのからも明らかなように、電源電圧を低くすることができる。上記画像形成装置においては、上記帯電ギャップＣへの異物の侵入を阻止することができることから、上記帯電ギャップＣを狭くしても、キャリア６２等の比較的硬い異物の通過により上記帯電ローラ５２表面あるいは感光体１表面に傷が付くといった問題を生じることがない。
【０１０６】
さらに、上記帯電ローラ５２が上記感光体１に対しアゲンスト回転していることで、上記帯電ローラ５２と感光体１との最近接位置における上記帯電ローラ５２の帯電面と上記感光体１の帯電面との、相対走行距離が拡大される。このため帯電ローラの部分的な抵抗値変動等による帯電変動が均一化され、該感光体１の帯電特性が向上すると共に、帯電領域５、具体的には帯電ギャップＣに、上記感光体１の下流側、すなわち、帯電の終了側（帯電領域５下流側）から、上記帯電ローラの帯電面となるべき面（被帯電面）が進入することにより、帯電ローラ５２自体が帯電してしまう影響を低減することができる。
【０１０７】
なお、上記効果は、抵抗層５２ｂの抵抗値が高い場合、特に顕著となる。上記抵抗層５２ｂの抵抗値、すなわち、上記帯電ローラ５２における抵抗は、異常放電の防止、並びに、重畳における帯電の平滑化に寄与する。このため、上記抵抗が小さすぎると、異常放電や帯電ムラが発生し易くなる。一方、上記抵抗が高すぎると、必要帯電時間が長くなり、正規の帯電電位まで上昇させることが困難となり、帯電不足による電位低下や帯電ムラを招来するおそれがある。よって、上記抵抗層５２ｂにおける抵抗値としては、１０^８Ωｃｍ以下となるように設定されることが好ましい。
【０１０８】
また、上記帯電ローラ５２に印加される重畳電圧が放電開始電圧以下では、重畳電圧とすることの効果を得ることはできない。一方、上記重畳電圧が高すぎると、異常放電による帯電ムラが発生するおそれがある。このため、上記重畳電圧としては、波高値で放電開始電圧以上、感光体１の絶縁耐力−直流（ＤＣ）電圧６００以下の電圧値に設定されることが望ましく、具体的には、４５０（Ｖｏ−ｐ）〜１３００（Ｖｏ−ｐ）の範囲内で設定されることが望ましい。
【０１０９】
一方、上記磁場が小さすぎるとキャリア６２を回収することが困難となる。このため、上記帯電ローラ５２における磁場は、前記した二成分現像に用いられる現像ローラ２３と同様、４００〜８００ガウス（ｇａｕｓｓ）の範囲内で設定されることが望ましい。
【０１１０】
また、上記重畳電圧には、放電開始電圧を支配する上記帯電ローラ５２と感光体１との間の帯電ギャップＣが関与する。
【０１１１】
上記帯電ローラ５２と感光体１との間の帯電ギャップＣは、キャリア６２の粒径（キャリア径）よりも小さく、かつ、トナー６１の粒径（トナー径）よりも大きく設定されていることが好ましい。上記帯電ギャップＣを上記感光体１に付着しているキャリア６２の粒径よりも小さく設定することにより、上記帯電ギャップＣへのキャリア６２の侵入を確実に排除することができる。これにより、キャリア６２が帯電ギャップＣに侵入することによって感光体１や帯電ローラ５２が傷付けられることをより一層確実に防止することができる。
【０１１２】
図２〜図５並びに表２に、上記帯電ギャップＣの間隔を種々変更して上記感光体１の帯電安定性の評価を行った結果を示す。測定条件は以下の通りである。帯電ローラ５２には、Ｉｐｓｉｏ社製の純正帯電ローラ（直径（Φ）：１１ｃｍ、抵抗値：４０ＭΩ、抵抗層５２ｂの体積抵抗率：１０^７Ω・ｃｍ）を使用し、帯電バイアスとして、−６００Ｖの直流成分に、ピーク間電圧が１．８ＫＶｐｐＶ、周波数が９００Ｈｚの交流電圧（重畳電圧）を印加した。また、感光体１の直径（Φ）は３５ｃｍ、膜３の厚みは１７μｍ、プロセス速度は１３０ｍｍ／ｓとした。
【０１１３】
【表２】

【０１１４】
測定の結果、図２〜図４に示すように、上記帯電ギャップＣの間隔が２５μｍ以上、５５μｍ以下、特に、２５μｍ以上、４０μｍ以下の範囲内において、感光体１の安定帯電が確認された。なお、図２〜図５において、縦軸は感光体１の表面電位（−Ｖ）を示し、横軸は時間（ｓｅｃ）を示す。
【０１１５】
上記測定結果より、上記帯電ギャップＣの間隔をキャリア径よりも小さく設定することにより、感光体１の帯電状態を安定化できることが判った。例えば粒径６０μｍのキャリア６２を使用する場合、帯電ギャップＣの間隔を、キャリア６２の粒径である６０μｍよりも小さくなるように設定することにより、帯電ローラ５２におけるキャリア回収効率を高くすることができる。
【０１１６】
また、図６および図７に、帯電ギャップＣの設定値（設定ギャップ）に対する感光体１の帯電電位の変動を示す。上記帯電ギャップＣの間隔は、図６および図７に示すように６０μｍを超えると異常放電を起こしやすくなる。よって、上記帯電ギャップＣの間隔を、６０μｍ以下とすることにより、異常放電の発生を低減し、異常放電による感光体１の帯電ムラを低減することができる。なお、図６および図７において、縦軸は帯電電位変動（｜ΔＶ｜（Ｖ））を示し、横軸は帯電ギャップＣの設定ギャップ（μ）を示す。
【０１１７】
図６および図７に示すように、特に、直流バイアスで帯電を行った場合、加工誤差等により帯電ギャップＣの間隔が設定値より変動（約１０μｍ程度は考慮する必要有り）した場合を考慮し、上記帯電ギャップＣの間隔を５５μｍ以下に設定することにより、感光体１の帯電電位変動を減少させることができる。
【０１１８】
以上のように、上記帯電ギャップＣの間隔は、キャリア径、具体的には、６０μｍよりも小さく設定することにより、感光体１の帯電状態が安定化できるため、良好な画質を得ることができる。
【０１１９】
また、図３、図４および表２に示すように、帯電ギャップＣの間隔が５５μｍを越えると、感光体１の帯電状態が安定し難くなる。現像特性から、感光体１の表面電位が１５０Ｖ低下すると、前記した画像かぶりを生じる。よって、感光体１の表面電位は、その変動値が、１５０Ｖｐｐ以下であることが好ましく、中間調の安定を確保するためには３０Ｖｐｐ以下であることがより好ましい。このため、転写材Ｐとして例えば転写紙を用いた場合、該転写紙の白地に黒が発生する場合がある。このため、帯電ギャップＣの間隔を５５μｍ以下、特に、前記したように４０μｍ以下に設定することで、異常放電の発生をさらに低減し、異常放電による感光体１の帯電ムラを防止することができる。
【０１２０】
このように、帯電ローラ５２におけるキャリア回収効率を高くし、異常放電による感光体１の帯電ムラを防止することにより、転写紙における白地における黒点の発生を防ぐことができる。
【０１２１】
一方、逆帯電トナー６１ｂおよびキャリア６２のクリーニングを行うために、逆帯電トナー６１ｂを帯電ローラ５２により捕獲する場合に、帯電ギャップＣを上記感光体１に付着しているトナー６１の粒径よりも大きな間隔とすることによって、帯電ローラ５２への残留トナー、すなわち、トナー６１の融着を防止することができる。なお、通常のトナー径は約７μｍであることから、上記帯電ギャップＣの間隔は、７μｍ以上に設定されることが好ましい。
【０１２２】
さらに、上記帯電ギャップＣの間隔は、粉体工学上、トナー径の３倍以上、９倍未満であることが好ましい。すなわち、トナー径が約７μｍとすると、帯電ギャップＣの間隔は、２１μｍ以上、６３μｍ以下の範囲内であることが好ましい。
【０１２３】
粉体の噴出現象は、粒径の３倍未満にて顕著に起こる。このため、帯電ギャップＣをトナー径の３倍以上とすることによって、トナー６１の噴出を防止することができる。
【０１２４】
また、いわゆる粉体のブリッジアーチは、粒径の約９倍にて顕著に発生する。このため、帯電ギャップＣをトナー径の９倍未満とすることによって、トナー６１のブリッジアーチによる帯電ローラ５２へのトナー６１の融着を防止することができる。しかも、上記の構成によれば、トナー６１の凝集魂が帯電ギャップＣを通過することを妨げることができるため、トナー６１の凝集魂が感光体１と現像ローラ２３とが近接する現像領域４へ侵入することによって起こる画質劣化を防止することができる。
【０１２５】
また、一般的な紙の厚さは約７０μｍ〜１００μｍの範囲内であるため、この厚さよりも帯電ギャップＣの間隔を狭く設けることにより、帯電ギャップＣへのジャム紙の侵入を防止し、帯電ローラ５２へのジャム紙の巻き込みを防ぐことができる。これにより、上記現像領域４へのジャム紙の侵入を防止できるため、ジャム紙の除去が容易になる。
【０１２６】
上記感光体１に対する帯電ローラ５２の周速比（帯電ローラ周速／感光体周速）は、周速比０（周速比なし）、すなわち固定では、帯電ローラ５２表面に付着した異物を除去することができないため帯電不良を起こすが、本願発明のように上記感光体１に対し、上記帯電ローラ５２がアゲンスト回転することで周速比を有している場合、上記周速比（帯電周速比）は、帯電特性の面からは、特に限定されるものではない。しかながら、回収した異物の飛散や、帯電ローラ５２端部に、ハチマキ上環状にテープ（図示せず）を巻いて感光体１に押し当て、テープ厚みで帯電ギャップ管理をする場合のテープ当接面の磨耗低減等を考慮すると、上記帯電周速比は、０．２〜１．０の範囲内において設定されることが望ましい。本実施の形態では、帯電ギャップを４０μｍ、アゲンスト回転で、上記帯電周速比を例えば０．５に設定している。
【０１２７】
なお、上記感光体１に対し、上記帯電ローラ５２が周速比を有している、つまり、上記帯電ローラ５２と感光体１とが周速比を有しているとは、上記帯電ローラ５２が回転しており、かつ、帯電領域５において、対面する帯電ローラ５２の表面と感光体１の表面とが相対速度を有して回転していることを示す。
【０１２８】
さらに、上記画像形成装置は、図１に示すように、上記帯電装置５１に対して感光体１の回転方向上流側、より詳しくは、上記感光体１表面において上記帯電ローラ５２が近接する領域である帯電領域５の上流側に、異物攪乱手段としての異物攪乱装置４１を備え、上記感光体１上の異物、例えば、転写工程後に、転写材Ｐに転写されずに感光体１上に残留したトナー６１（残留トナー）や、キャリア６２等の残留現像剤成分（残留物）や感光体１表面に付着した紙粉等を攪乱するようになっていることが好ましい。
【０１２９】
本実施の形態にかかる上記異物攪乱装置４１は、上記帯電装置５１に対して感光体１の回転方向上流側、より詳しくは、上記感光体１表面において帯電ローラ５２が近接する領域である帯電領域５の上流側に、上記感光体１と接触して配設された導電性ブラシ４２を備え、該導電性ブラシ４２により、上記感光体１上の異物を攪乱するようになっている。
【０１３０】
上記導電性ブラシ４２には、電圧（ブラシバイアス）印加手段としての電源４３により、正規現像であるか反転現像であるかに応じて、反転現像の場合にはトナー６１の主帯電極性（−）に対して逆極性（＋）、または、転写バイアス（＋）と同極性のバイアス（＋）が印加され、正規現像の場合にはトナー６１の主帯電極性（＋）に対して同極性（＋）、または、転写バイアス（−）と逆極性のバイアス（＋）が印加される。これにより、上記異物攪乱装置４１は、上記導電性ブラシ４２を介して、感光体１上の異物、具体的には、転写後に上記感光体１上に残留しているトナー６１（残留トナー）に、反転現像の場合には、用いたトナー６１の主帯電極性（−）に対して逆極性（＋）、または、転写バイアス（＋）と同極性のバイアス（＋）を印加し、正規現像の場合には、用いたトナー６１の主帯電極性（＋）に対して同極性（＋）、または、転写バイアス（−）と逆極性のバイアス（＋）を印加するようになっている。
【０１３１】
上記したように異物攪拌手段をブラシ構造とすることにより、上記した残留現像剤成分等の異物がブラシの隙間を通り抜け、これにより、異物の滞留を防止して該異物を攪乱することができると共に、感光体１表面に傷が付くことを防止することができる。
【０１３２】
このように帯電領域５の上流側に異物攪乱手段を設け、転写されずに感光体１表面に残った残留現像剤成分等の異物を攪乱（攪拌）し、ほぐすことによって、帯電ローラ５２においての異物の回収効率を高めることができる。
【０１３３】
また、上記したように上記導電性ブラシ４２に、反転現像の場合にはトナー６１の主帯電極性（−）に対して逆極性（＋）、または、転写バイアス（＋）と同極性のバイアス（＋）が印加され、正規現像の場合にはトナー６１の主帯電極性（＋）に対して同極性（＋）、または、転写バイアス（−）と逆極性のバイアス（＋）が印加されることで、感光体１上の異物である残留現像剤成分の電荷を調節することができる。つまり、本実施の形態のように反転現像を行う場合、現像領域４で（−）電荷を帯びているトナー６１は、前記したように転写領域では、転写バイアス（＋２ｋＶ）で若干のプラス（＋）電荷を帯びるようになるが、さらに上記導電性ブラシ４２により、例えば＋５００ｋＶの電圧を印加すれば、トナー６１は積極的に逆帯電、つまり、プラス（＋）帯電するようになり、これにより、より効率よく帯電ローラ５２でトナー６１、つまり、逆帯電トナー６１ｂを除去することができる。すなわち、上記導電性ブラシ４２は、それ自身、異物攪乱手段としての機能を有すると共に、上記残留現像剤成分の電荷を調節する電荷調整手段としての機能を兼ね備えている。
【０１３４】
上記の構成によれば、上記導電性ブラシ４２に上記バイアスを印加することで、残留現像剤成分、例えば残留トナーが現像時に有していた初期の電荷を失わせることができ、トナー像メモリを防止することができると共に、感光体１上に残留している残留電位を平坦化することができるので、感光体１の電位および残留現像剤成分の電圧調整が可能となる。
【０１３５】
なお、上記導電性ブラシ４２に印加されたバイアス電圧（ブラシバイアス）により、残留現像剤成分等の異物が該導電性ブラシ４２に付着することはなく、該導電性ブラシ４２に付着した異物により異物が滞留し、攪乱効果が低下するといった不具合が生じることはない。
【０１３６】
表３に、導電性ブラシ４２として抵抗値が１０^４Ω・ｃｍの導電性ブラシを使用し、ブラシバイアスとして＋５００Ｖまたは−５００Ｖの直流電圧を印加した場合、電圧を印加しない（電気的接続無）場合（フローティング）、接地した場合（０Ｖ）における画質の状態（像メモリ）を示す。
【０１３７】
【表３】

【０１３８】
また、図８に、導電性ブラシ４２として抵抗値が１０^４Ω・ｃｍの導電性ブラシを使用し、ブラシバイアスとして＋５００Ｖまたは−５００Ｖの直流電圧を印加した場合、並びに、接地した場合（０Ｖ）における、▲１▼現像時、▲２▼転写直前（未転写）、▲３▼導電性ブラシ４２通過後、▲４▼帯電ローラ５２による帯電後の、トナー６１の帯電量を測定した結果を示す。
【０１３９】
図８において縦軸はトナー６１の帯電量（Ｃ）を示し、横軸は上記した各ステップを示す。図８中、「◇」は−５００Ｖの直流電圧を印加した場合、「□」は電圧を印加しなかった場合、「△」は＋５００Ｖの直流電圧を印加した場合、「○」は上記導電性ブラシ４２を用いなかった（ブラシ無し）の場合を示す。
【０１４０】
図８に示すように、導電性ブラシ４２に、＋５００Ｖの直流電圧を印加した場合にトナー６１が逆帯電（＋）となることが判る。
【０１４１】
また、上記図８並びに表３に示す結果から、上記導電性ブラシ４２にて残留トナーの電荷調節を行って残留トナーを逆帯電（＋）させることにより、メモリが大幅に改善できることが判る。ここで、メモリが大幅に改善できるとは、正規帯電トナー６１ａが現像時に有していた初期の電荷を失わせることができることを示し、これにより、トナー像メモリを防止することができる。
【０１４２】
ここで、上記の構成の画像形成装置における画像形成プロセスについて、図１を参照しながら以下に説明する。
【０１４３】
まず、感光体１の表面が帯電装置５１によって均一に帯電される。次いで、この均一帯電された感光体１の表面に、露光装置１１のレーザ光源１１ａから、形成する画像情報に基づいて変調されたレーザ光１２が照射され、感光体１表面を主走査方向に１ライン単位で順次露光することにより、感光体１上に静電潜像が形成される。
【０１４４】
次いで、この静電潜像が現像装置２１を通過する際に、現像領域４において、上記感光体１上に、現像ローラ２３からトナー６１が供給されることで、該トナー６１が感光体１上の静電潜像に対して静電的に吸着し、静電潜像がトナー像として可視像化（トナー像化）される。
【０１４５】
感光体１上に形成されたトナー像は、該感光体１と転写装置３１とのニップ部（転写部）を通過する際に、図示しない給紙手段から給紙された転写材Ｐに転写される。その後、転写材Ｐは図示しない定着装置に搬送され、ここでトナー像が転写材Ｐに定着されることにより、永久可視像化される。そして、定着済みの転写材Ｐは、図示しない排出手段により、図示しない排出トレイ等に排出される。
【０１４６】
転写部で転写材Ｐに転写されずに感光体１上に残留した残留現像剤は、導電性ブラシ４２により攪乱（攪拌）されてほぐされる一方、該導電性ブラシ４２により、反転現像の場合にはトナー６１の主帯電極性（−）に対して逆極性（＋）、または、転写バイアス（＋）と同極性のバイアス（＋）が印加され、正規現像の場合にはトナー６１の主帯電極性（＋）に対して同極性（＋）、または、転写バイアス（−）と逆極性のバイアス（＋）が印加されて電荷調節される。
【０１４７】
その後、上記感光体１上に残留している残留現像剤成分、特に、逆帯電トナー６１ｂおよびキャリア６２は、帯電ローラ５２によって、帯電ギャップＣよりも感光体１の回転方向上流側で、磁気的あるいは静電的に吸着されてクリーニングされる。上記帯電ローラ５２に吸着された残留現像剤成分は、クリーニングマイラー磁気的吸着フィルム５４により帯電ローラ５２から除去され、現像槽２２内に戻される。上記残留現像剤成分が除去された感光体１は、上記帯電ローラ５２により、再度、均一帯電され、所定枚数の転写が終了するまで、露光、露光、現像、転写、クリーニングが繰り返される。
【０１４８】
また、上記帯電ローラ５２通過後に上記感光体１上に残留している未除去の残留現像剤成分（正規帯電トナー６１ａ）は、上記現像装置２１を通過する際に、現像領域４よりも感光体１の回転方向上流側で、現像ローラ２３に形成された図示しない磁気ブラシの摺擦によって静電的あるいは機械的に回収されて現像槽２２内に戻される。
【０１４９】
なお、上記実施の形態では、上記感光体１として感光体ドラムを例に挙げて説明したが、本発明はこれに限定されるものではなく、上記感光体ドラムに代えて、無端状の導電性ベルトが、間隔を置いて回転可能に設けた支持ローラ間に張装された、いわゆる感光体ベルトを用いてもよい。また、同様に、上記実施の形態では、転写手段として、転写ローラを備えた転写装置３１を例に挙げて説明したが、上記転写装置としては、無端状の導電性ベルトが、間隔をおいて回転可能に設けた支持ローラ間に張装された、いわゆる転写ベルトを用いてもよい。
【０１５０】
また、上記実施の形態では、帯電装置５１が、異物回収手段としてのクリーニングマイラーマイラーマイラーマイラーフィルム５４を備え、該クリーニングフィルム５４により、帯電ローラ５２に吸着された異物を掻き取り、現像槽２２内に回収する構成としたが、本発明はこれに限定されるものではなく、例えば、上記クリーニングフィルム５４を使用する代わりに、クリーニングブレードで掻き取った異物を回収容器に回収することで、掻き取った異物を現像槽２２内に戻すことなく回収あるいは除去する構成としても構わない。しかしながら、前記したように、上記画像形成装置が、異物回収手段としてのクリーニングフィルム５４、または、未除去残留現像剤成分回収手段としての現像ローラ２３を備えていることで、キャリア６２、帯電が大きく変化した逆帯電トナー６１ｂ、または正規帯電トナー６１ａを、現像ローラ２３よりも奥に備えられている現像槽２２に戻して十分な攪拌帯電を与えて再利用することができる。
【０１５１】
以上のように、本実施の形態にかかる画像形成装置は、表面に潜像が形成される像担持体と、上記像担持体の周囲に上記像担持体表面とは非接触に配置した帯電部材に電圧を印加して上記像担持体を帯電させる帯電装置と、上記像担持体表面に帯電電荷により形成される潜像を、少なくともトナーを含む現像剤により現像してトナー像化する現像手段と、上記像担持体上に形成されたトナー像を転写材に転写する転写手段とを備えた画像形成装置であって、上記帯電装置は、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて上記像担持体上から除去すると共に上記像担持体を帯電させる帯電兼クリーニング装置であり、上記帯電部材と像担持体とは、最近接位置にて互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転するように設けられている構成を有している。そして、特に、本実施の形態にかかる画像形成装置は、トナーおよびキャリアを含む二成分系現像剤を用いた二成分現像方式の画像形成装置であり、上記帯電部材と像担持体との最近接位置における間隔は、残留現像剤成分であるキャリアの粒径よりも小さく、かつ、残留現像剤成分であるトナーの粒径よりも大きく設定されている。
【０１５２】
より具体的には、本実施の形態にかかる画像形成装置は、感光体を帯電させる帯電装置を上記感光体の表面に近接させて配置し、上記帯電装置は、導電性の円筒または円柱形状の部材およびその表面を被う抵抗層を備えた帯電ローラあるいは抵抗層を備えた帯電ベルト、帯電ブラシ等を有し、上記感光体上に形成される潜像を、少なくともトナーおよびキャリアを含む現像剤により現像する画像形成装置において、上記帯電ローラの回転軸に対する回転方向と、上記記感光体の回転軸に対する回転方向とが同じ方向に回転し（アゲンスト回転）、上記帯電装置の放電面と上記感光体との最近接位置における間隔（帯電ギャップ）を、上記感光体に付着しているキャリアよりも小さく、かつ上記感光体に付着しているトナーよりも大きく設定している。
【０１５３】
また、本実施の形態にかかる画像形成方法は、表面に潜像が形成される像担持体と、上記像担持体の周囲に上記像担持体表面とは非接触に配置した帯電部材に電圧を印加して上記像担持体を帯電させる帯電装置と、上記像担持体表面に帯電電荷により形成される潜像を、少なくともトナーを含む現像剤により現像してトナー像化する現像手段と、上記像担持体上に形成されたトナー像を転写材に転写する転写手段とを備えた画像形成装置を用いた画像形成方法であって、上記帯電部材と像担持体とを、最近接位置にて互いに行き違う方向に互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転させ、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて上記像担持体上から除去する一方で、上記像担持体を帯電させる方法である。
【０１５４】
このように、本実施の形態によれば、上記帯電部材と像担持体とが、最近接位置にて対面する面の移動方向が互いに逆方向となるようにそれぞれ回転（アゲンスト回転）することで、転写後に像担持体上に残留している逆帯電トナー等の残留現像剤成分は、上記帯電部材の放電面と像担持体との最近接位置における帯電ギャップを通過する前に、上記帯電部材に吸着されて除去される。このため、上記帯電ギャップへの逆帯電トナー等の残留現像剤成分の侵入を防止することができると共に、該残留現像剤成分を、像担持体表面から、確実かつ積極的に除去、回収することができる。このため、本実施の形態によれば、小型でかつ電源電圧を低くすることができると共に、良好な画質を得ることができる画像形成装置並びに画像形成方法を提供することができる。なお、上記帯電部材は、上記残留現像剤成分を除去、回収するに際し、上記帯電部材によって吸着される残留現像剤成分に付着している転写材屑等の異物（残留物）もまた同時に、上記像担持体上から除去、回収することができる。すなわち、上記上記帯電装置は、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて該残留現像剤成分を含む異物（残留物）を上記像担持体上から除去する。
【０１５５】
さらに、上記間隔（帯電ギャップ）は、トナー径の３倍以上、９倍未満に設定されている構成であってもよい。粉体の噴出現象は、粒径の３倍以下にて顕著に起こるため、上記の構成によれば、トナーの噴出を防止することができる。また、粉体がブリッジ状になり帯電ギャップに詰まった状態は、帯電ギャップが粒径の約９倍の間隔を有する場合に顕著に発生するため、帯電ギャップをトナー径の９倍未満とすることによって、トナーのブリッジによる帯電ローラへのトナーの融着を防止することができると共に、トナーの凝集魂が帯電ギャップを通過することを妨げることができるため、トナーの凝集魂が現像領域へ侵入することによって生じる画質劣化を防止することができる。
【０１５６】
〔実施の形態２〕
本発明の実施の他の形態について図９に基づいて説明すれば、以下の通りである。なお、前記実施の形態１では、トナー６１およびキャリア６２を含む二成分現像剤を用いた二成分現像方式を採用した画像形成装置を例に挙げて説明した。本実施の形態では、二成分現像方式に代えて、キャリア６２を使用しない一成分現像剤を用いた一成分現像方式を採用した画像形成装置を例に挙げて説明するものとする。本実施の形態では、主に、前記実施の形態１との相違点について説明するものとし、説明の便宜上、前記実施の形態１と同様の機能を有する構成要素には同一の番号を付し、その説明を省略する。
【０１５７】
本実施の形態に係る画像形成装置は、図９に示すように、像担持体としての感光体１の周囲に、露光装置１１、現像装置７１、転写装置３１、異物攪乱装置４１、帯電装置８１が、露光位置、すなわち、上記露光装置１１によるレーザ光１２の照射位置から、感光体１の回転方向にこの順に配設されている構成を有している。
【０１５８】
本実施の形態では、現像剤９０として、磁性トナーである前記実施の形態１に記載のトナー６１を含む一成分現像剤を用いている。以下、本実施の形態においても、反転現像の場合を例に挙げて説明するものとするが、本発明はこれに限定されるものではない。
【０１５９】
現像装置７１は、現像槽７２に収容された現像剤９０を感光体１に供給する現像剤供給手段としての現像ローラ７３、並びに、該現像ローラ７３に、現像槽７２に収容された現像剤９０を供給する供給ローラ７４を備え、該現像ローラ７３、供給ローラ７４に、電圧印加手段としての電源７５，７６から所定の現像バイアス並びに供給バイアスが印加されることで、上記露光装置１１による露光により感光体１上に形成された静電潜像を、トナー６１により現像、すなわち可視像（トナー像）化するようになっている。また、上記現像装置７１は、上記現像ローラ７３表面の現像剤層の厚さを規制する層厚規制部材７７を備え、該層厚規制部材７７と感光体１との間隔を調節すると共に、該層厚規制部材７７に電源７８から所定のバイアスが印加されることで、前記実施の形態１にかかる現像装置２１同様、感光体１上に供給される現像剤量を調節するようになっている。
【０１６０】
本実施の形態では、上記現像装置７１として、導電性素管７３ａ並びに導電性素管７３ａの表面を覆うスリーブ７３ｂからなる現像ローラ７３を有する現像装置を用いている。上記現像装置７１は、該現像ローラ７３に現像バイアスが印加されることにより、スリーブ７３ｂの表面に現像剤９０を静電吸着することが可能であり、上記現像剤９０を現像槽７２から感光体１に供給して感光体１表面の静電潜像を現像する一方、上記現像ローラ７３と感光体１とが近接する現像領域４よりも上記感光体１の回転方向上流側において感光体１表面に残留している未除去の残留現像剤成分（回収後残留物）、具体的には、転写されずに感光体１上に残留した現像剤９０のうち、帯電装置８１で回収されなかった正規帯電トナー６１ａ（図１中、「−」にて示す）を、上記スリーブ７３ｂの表面に静電吸着することで、該正規帯電トナー６１ａ、並びに、該正規帯電トナー６１ａに付着した紙等の異物を、上記感光体１表面から除去するようになっている。
【０１６１】
つまり、本実施の形態にかかる上記現像ローラ７３もまた、感光体１の表面電位（例えば−６００Ｖ）よりも正極となる現像バイアス（例えば−４２０Ｖ）を印加することで、上記現像ローラ７３に、上記感光体１上に残留した、マイナス（−）帯電している正規帯電トナー６１ａ等の異物を静電吸着することが可能であり、該現像ローラ７３もまた、前記実施の形態１にかかる現像ローラ２３同様、上記現像領域４における上記感光体１の回転方向上流側近傍において、上記感光体１上に残留した正規帯電トナー６１ａ等の異物を、現像槽７２内に回収（現像クリーニング方式）する未除去残留現像剤成分回収手段（正規帯電トナー回収手段）として機能する。
【０１６２】
これにより、上記現像装置７１は、現像兼クリーニング装置として、上記帯電装置８１通過後に上記感光体１上に残留している未除去の正規帯電トナー６１ａ等の異物を、上記現像ローラ７３による感光体１への現像剤９０の供給位置よりも感光体１の回転方向上流側において、上記現像ローラ７３により回収することで、上記現像とあわせて上記感光体１のクリーニングを行うようになっている。
【０１６３】
上記現像ローラ７３により回収された正規帯電トナー６１ａは、現像ローラ７３よりも奥に備えられている現像槽７２に戻される。これにより、現像槽７２内にて、回収された正規帯電トナー６１ａに、図示しない攪拌ローラにより、十分な攪拌帯電を与えることができ、回収された正規帯電トナー６１ａ互いに行き違う方向にの電荷を所定の電荷量に調整した後に、再度、現像に利用することができる。この結果、トナー像メモリを防止し、回収された正規帯電トナー６１ａを再利用することが可能となる。
【０１６４】
上記現像ローラ７３もまた、前記実施の形態１における現像ローラ２３と同様、上記感光体１に対し、周速比を有していることが好ましい。すなわち、上記現像ローラ７３は回転可能に設けられていることが好ましい。
【０１６５】
これにより、上記正規帯電トナー６１ａの回収効率をさらに高めることができる。なお、上記感光体１に対する現像ローラ７３の周速比（現像周速比）は、現像剤層の厚みを規定するドクターギャップ並びに現像剤９０のトナー濃度（Ｔ／Ｄ）、および要求現像量により適宜設定すればよく、特に限定されるものではないが、実施の形態１における現像ローラ２３と同様に設定されることが好ましい。
【０１６６】
また、上記現像ローラ７３も上記感光体１とは非接触に設けられ、上記感光体１との最近接位置にて上記感光体１と対面（対向）する面の移動方向が、上記感光体１における上記現像ローラ７３と対面（対向）する面の移動方向と逆方向となるように回転（アゲンスト回転）するように設けられていることが好ましい。すなわち、上記現像ローラ７３は、上記感光体１とは異なる駆動系により、該現像ローラ７３の回転軸に対する回転方向と、上記感光体１の回転軸に対する回転方向とが同じ方向に回転するように設けられていることが好ましい。これにより、上記未除去の残留現像剤成分（正規帯電トナー６１ａ）の回収効率をさらに高めることができる。
【０１６７】
また、上記帯電装置８１は、実施の形態１において、帯電ローラ５２に、マグネットローラを用いない以外は、前記実施の形態１における帯電装置５１と同様の構成を有している。すなわち、本実施の形態にかかる帯電装置８１は、円筒状または円柱状の帯電部材として、導電性素管８２ａおよび該導電性素管８２ａの表面を覆う抵抗層８２ｂを備えた構成を有し、該帯電ローラ８２における上記導電性素管８２ａに電源５３から電圧を印加することにより、上記抵抗層８２ｂを介して上記感光体１表面を帯電させるようになっている。
【０１６８】
上記帯電ローラ８２もまた、前記実施の形態１にかかる帯電ローラ５２同様、帯電ギャップ調整手段としてのバネ５５の付勢により、上記感光体１の周囲に、上記感光体１と非接触に近接して設けられていると共に、感光体１とは異なる駆動系により、感光体１との最近接位置にて互いに行き違う方向に、感光体１と、互いに対面する面の移動方向が互いに逆方向となるように回転（アゲンスト回転）するように設けられている。つまり、本実施の形態においても、上記帯電ローラ８２と感光体１とは、帯電ローラ８２の回転軸に対する回転方向と、感光体１の回転軸に対する回転方向とが同じ方向に回転するように設けられている。そして、上記帯電ローラ８２もまた、帯電バイアスとしてマイナス（−）の直流電圧が印加されていることで、プラス（＋）電荷を有する逆帯電トナー６１ｂを静電吸着することができるようになっている。
【０１６９】
これにより、本実施の形態にかかる上記帯電装置８１は、帯電兼クリーニング装置として、転写後に上記感光体１上に残留している残留現像剤成分、具体的には、転写されずに感光体１上に残留した現像剤９０における逆帯電トナー６１ｂ（図１中、「＋」にて示す）を、上記抵抗層８２ｂの表面に吸着することで、該逆帯電トナー６１ｂ、並びに、該逆帯電トナー６１ｂに付着した正規帯電トナーや紙等の異物、例えば、トナー６１、紙等の転写材屑６３の凝集魂を、実施の形態１にかかる帯電装置５１同様、上記帯電ローラ８２の放電面と感光体１との最近接位置におけるギャップである帯電ギャップＤを通過する前に、感光体１表面から除去するようになっている。よって、本実施の形態においても、前記実施の形態１と同様の効果を得ることができる。
【０１７０】
なお、上記帯電装置８１においても、上記帯電ローラ８２に、直流成分、この場合はマイナス（−）の直流成分電流マイラー（直流電圧）に交流電圧が重畳された重畳電圧が印加されていることで、感光体１表面の残留物である逆帯電トナー６１ｂ等の異物を加振することができ、該異物の感光体１からの離脱を促進することができると共に、上記逆帯電トナー６１ｂを効率良く静電吸着することができ、上記逆帯電トナー６１ｂの除去効率を高くすることができる。
【０１７１】
また、上記帯電装置８１においても、上記帯電ローラ８２に当接して、異物回収手段としてのクリーニングフィルム５４が設けられていることで、上記帯電ローラ８２に吸着された逆帯電トナー６１ｂ等の異物は、現像槽７２に戻され、現像槽７２内にて十分な攪拌帯電が与えマイラーられることで、再利用される。また、このように上記帯電ローラ８２に、感光体１表面の異物を回収するための異物回収手段としてのクリーニングフィルムを上記帯電装置８１とは別に設ける必要がなく、上記画像形成装置の構造の簡素化を図ることができる。
【０１７２】
上記帯電ローラ８２と感光体１との間の帯電ギャップＤは、転写時に用いられる転写材、すなわち、感光体１に付着している記録（転写）紙等の転写材Ｐの厚みよりも小さく、かつ、トナー６１の粒径（トナー径）よりも大きく設定されていることが好ましい。
【０１７３】
電子写真方式の画像形成装置で用いられる転写材Ｐは、例えば記録紙で、薄いもので約６０ｇ／ｍ^２、厚みとしては約６０〜８０μｍである。このため、帯電ギャップＤの間隔を上記記転写材Ｐ（記録紙）よりも小さく、すなわち、例えば６０μｍ以下とすることにより、転写電荷により感光体１に静電吸着している転写材Ｐ（記録紙）の剥離に失敗した時に、吸着した転写材Ｐ（記録紙）が現像領域４に侵入し、ジャム（紙ジャム）からの復旧作業をより困難にするとともに復旧作業者の手や衣服をトナー６１で汚すのを防止することができ、転写領域において感光体１に吸着した転写材Ｐ（記録紙）を帯電ローラ８２で確実に剥離し、該転写材Ｐ（記録紙）の現像領域４への侵入を防止することができる。
【０１７４】
また、帯電ギャップＤの間隔は、前記実施の形態１で示したように６０μｍを超えると異常放電を起こしやすくなる。このため、帯電ギャップＤの間隔を６０μｍ以下とすることにより、異常放電の発生を低減し、異常放電による感光体１の帯電ムラを防止することができる。
【０１７５】
また、前記実施の形態１で示したように、加工誤差等により帯電ギャップＤの間隔が設定値より変動した場合を考慮して、上記帯電ギャップＤは、５５μｍ以下に設定することが、帯電電位変動を減少させる上で好ましく、４０μｍ以下に設定することが、安定帯電を行う上でより好ましい。
【０１７６】
また、本実施の形態においても、逆帯電トナー６１ｂのクリーニングを行うために、逆帯電トナー６１ｂを帯電ローラ８２により捕獲する場合に、帯電ギャップＤを上記感光体１に付着しているトナー６１の粒径よりも大きな間隔とすることによって、帯電ローラ８２への残留トナー、すなわち、トナー６１の融着を防止することができる。なお、通常のトナー径は約７μｍであることから、上記帯電ギャップＤの間隔は、前記したように、７μｍ以上に設定されることが好ましい。
【０１７７】
さらに、本実施の形態においても、気中放電における放電閾値より開始電圧を示す「パッシェの実験式」からも明らかなように、このように帯電ギャップＤの間隔を小さくすることで、電源電圧を低くすることができる。
【０１７８】
以上のように、本実施の形態にかかる画像形成装置もまた、表面に潜像が形成される像担持体と、上記像担持体の周囲に上記像担持体表面とは非接触に配置した帯電部材に電圧を印加して上記像担持体を帯電させる帯電装置と、上記像担持体表面に帯電電荷により形成される潜像を、少なくともトナーを含む現像剤により現像してトナー像化する現像手段と、上記像担持体上に形成されたトナー像を転写材に転写する転写手段とを備えた画像形成装置であって、上記帯電装置は、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて上記像担持体上から除去すると共に上記像担持体を帯電させる帯電兼クリーニング装置であり、上記帯電部材と像担持体とは、最近接位置にて互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転するように設けられている構成を有している。
【０１７９】
すなわち、本実施の形態にかかる画像形成方法もまた、前記実施の形態１に示したように、表面に潜像が形成される像担持体と、上記像担持体の周囲に上記像担持体表面とは非接触に配置した帯電部材に電圧を印加して上記像担持体を帯電させる帯電装置と、上記像担持体表面に帯電電荷により形成される潜像を、少なくともトナーを含む現像剤により現像してトナー像化する現像手段と、上記像担持体上に形成されたトナー像を転写材に転写する転写手段とを備えた画像形成装置を用いた画像形成方法であって、上記帯電部材と像担持体とを、最近接位置にて互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転させ、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて上記像担持体上から除去する一方で、上記像担持体を帯電させる方法である。
【０１８０】
そして、特に、本実施の形態にかかる画像形成装置は、上記帯電部材と像担持体との最近接位置における間隔は、上記可視像が転写される転写材の厚みよりも小さく、かつ、残留現像剤成分であるトナーの粒径よりも大きく設定されている。
【０１８１】
なお、本実施の形態においては、一成分系現像剤を用いた一成分現像方式の画像形成装置を例に挙げて説明したが、本実施の形態にかかる画像形成装置はこれに限定されるものではなく、当該画像形成装置は、上記現像剤として、一成分系現像剤のみならず、二成分系現像剤を用いる場合にも適用することができる。
【０１８２】
より具体的には、本実施の形態にかかる画像形成装置は、感光体を帯電させる帯電装置を上記感光体の表面に近接させて配置し、上記帯電装置は、導電性の円筒または円柱形状の部材およびその表面を被う抵抗層を備えた帯電ローラを有し、上記感光体上に形成される潜像を、少なくともトナーおよびキャリアを含む現像剤により現像する画像形成装置において、上記帯電ローラの回転軸に対する回転方向と、上記記感光体の回転軸に対する回転方向とが同じ方向に回転し（アゲンスト回転）、上記帯電装置の放電面と上記感光体との最近接位置における間隔（帯電ギャップ）を、上記感光体に付着している記録紙よりも小さく、かつ上記感光体に付着しているトナーよりも大きく設定している。
【０１８３】
このように、本実施の形態において、上記帯電部材と像担持体とが、最近接位置にて互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転（アゲンスト回転）することで、転写後に像担持体上に残留している逆帯電トナー等の残留現像剤成分は、上記帯電部材の放電面と像担持体との最近接位置における帯電ギャップを通過する前に、上記帯電部材に吸着されて除去される。このため、上記帯電ギャップへの逆帯電トナー等の残留現像剤成分の侵入を防止することができると共に、該残留現像剤成分を、像担持体表面から、確実かつ積極的に除去、回収することができる。このため、本実施の形態によれば、小型でかつ電源電圧を低くすることができると共に、良好な画質を得ることができる画像形成装置並びに画像形成方法を提供することができる。
【０１８４】
また、上記した各実施の形態１および２では、帯電部材に、直流電圧に交流電圧が重畳された電圧（重畳電圧）を印加する構成としたが、本発明は、これに限定されるものではなく、上記帯電部材に直流電圧を印加する構成としてもよい。すなわち、本発明にかかる画像形成方法（画像形成装置）は、上記帯電部材に、直流電圧、もしくは直流電圧に交流電圧が重畳された電圧（重畳電圧）を印加する方法
（構成）であってもよい。
【０１８５】
上記帯電部材に上記電圧を印加した場合、帯電領域の終了部付近では上記像担持体の表面電位は帯電の進行に伴って所定の電圧に上昇するので、上記帯電部材と像担持体とが、最近接位置にて互いに同じ方向に回転するウィッズ回転においては逆帯電トナーを静電的に回収する能力が大幅に減少するのに対して、本発明のようにアゲンスト回転した場合、該逆帯電トナーは、上記像担持体への帯電が開始される帯電領域よりも上記像担持体の回転方向上流側近傍で回収、搬送されるので、上記重畳電圧の直流成分（直流電圧）が逆帯電トナーの静電回収に有効に寄与する。このため、上記の構成によれば、逆帯電トナーを効率良く静電吸着することができる。そして、特に、上記帯電部材に、直流電流電流圧に交流電圧が重畳された電圧が印加されていることで、転写後に上記像担持体表面に残留している残留現像剤成分等の異物（残留物）を加振することができ、上記像担持体からの上記残留現像剤成分等の異物の離脱を促進することができる。このため、上記逆帯電トナーの除去効率を高くすることができる。
【０１８６】
また、この場合、特に、上記帯電部材に、直流電圧に交流電圧が重畳された電圧（重畳電圧）が印加されていると共に、磁場が形成されている構成とすることで、上記帯電部材に上記重畳電圧を印加した場合、前記したように帯電領域の終了部付近では上記像担持体の表面電位は所定の電圧に帯電されているので、上記ウィッズ回転においては逆帯電トナーを静電的に回収する能力が大幅に減少するのに対して、本発明のようにアゲンスト回転した場合、前記したように上記重畳電圧の直流成分（直流電圧）が逆帯電トナーの静電回収に有効に寄与し、逆帯電トナーを効率良く静電吸着することができる。このとき、特に、キャリア等の質量が大きい異物（残留物）は、静電吸着では負担が大きく、回収効率が低下するが、上記の各構成によれば、上記帯電部材に磁場が形成されていることで、キャリアを非機械的に磁気吸引力により回収することができる。このため、キャリア等の質量が大きい異物（残留物）の回収効率を高くすることができる。
【０１８７】
したがって、上記の構成によれば、帯電ギャップへのキャリアおよびトナー等の異物の侵入を抑制することができ、像担持体および帯電部材が傷つけられることを防止できると共に、画像かぶり等の画質劣化の原因となる逆帯電トナーを除去することができる。
【０１８８】
さらに、磁性一成分現像等、磁性トナーを用いる装置においては、静電的な回収が困難な、正規帯電トナー、あるいは帯電量が微少、もしくは未帯電トナーも磁気的に回収することができる。
【０１８９】
また、本発明は上述した各実施形態に限定されるものではなく、請求項に示した範囲で種々の変更が可能である。
【０１９０】
例えば、帯電部材に吸着させた残留現像剤成分を現像剤供給槽（ホッパー）を経由して現像槽内に回収してもよい。
【０１９１】
また、現像剤供給手段に直流に交番電圧を重畳した現像バイアスを印加することにより像担持体上の残留現像剤に対して離脱を促進する静電力を付与し像担持体からの回収を促進してもよい。
【０１９２】
さらに、異なる実施形態にそれぞれ開示された技術的手段を適宜組み合わせて得られる実施形態についても本発明の技術的範囲に含まれる。
【０１９３】
【発明の効果】
本発明に係る画像形成装置は、以上のように、表面に潜像が形成される像担持体と、上記像担持体の周囲に上記像担持体表面とは非接触に配置した帯電部材に電圧を印加して上記像担持体を帯電させる帯電装置と、上記像担持体表面に帯電電荷により形成される潜像を、少なくともトナーを含む現像剤により現像してトナー像化する現像手段と、上記像担持体上に形成されたトナー像を転写材に転写する転写手段とを備えた画像形成装置において、上記帯電装置は、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて上記像担持体上から除去すると共に上記像担持体を帯電させる帯電兼クリーニング装置であり、上記帯電部材と像担持体とは、最近接位置にて互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転するように設けられている構成である。
【０１９４】
また、本発明にかかる画像形成方法は、以上のように、表面に潜像が形成される像担持体と、上記像担持体の周囲に上記像担持体表面とは非接触に配置した帯電部材に電圧を印加して上記像担持体を帯電させる帯電装置と、上記像担持体表面に帯電電荷により形成される潜像を、少なくともトナーを含む現像剤により現像してトナー像化する現像手段と、上記像担持体上に形成されたトナー像を転写材に転写する転写手段とを備えた画像形成装置を用いた画像形成方法において、上記帯電部材と像担持体とを、最近接位置にて互いに行き違う方向に対面する面の移動方向が互いに逆方向となるようにそれぞれ回転させ、転写後に上記像担持体上に残留している残留現像剤成分を上記帯電部材に吸着させて上記像担持体上から除去する一方で、上記像担持体を帯電させる構成である。
【０１９５】
それゆえ、転写後に像担持体上に残留している逆帯電トナー等の残留現像剤成分は、上記帯電部材の放電面と像担持体との最近接位置における帯電ギャップを通過する前に、上記帯電部材に吸着されて除去される。このため、上記帯電ギャップへの逆帯電トナー等の残留現像剤成分の侵入を防止することができると共に、該残留現像剤成分を、像担持体表面から、確実かつ積極的に除去、回収することができる。したがって、従来のような専用のクリーニング装置を必要とせず、装置の小型化を図ることができ、電源電圧を低くすることができる。
【０１９６】
特に、反転現像を用いた場合には、重要課題となる、像担持体表面の白地の領域に付着した逆帯電トナーに起因した画像かぶりを、その原因となる逆帯電トナーを除去することで防止することができ、画質改善に顕著な効果を発揮することができる。
【０１９７】
また、上記の各構成によれば、クリーニングによる像担持体の膜減り、摺擦痕の発生を防止することができると共に、像担持体の負荷トルクを低減させることができる。
【０１９８】
さらに、上記の各構成によれば、上記帯電部材が上記像担持体に対しアゲンスト回転していることで、上記残留現像剤成分の帯電ギャップへの侵入を抑制することができると共に、上記帯電部材と像担持体との最近接位置における上記帯電部材の帯電面と上記像担持体の帯電面との、相対走行距離が拡大されるので、像担持体の帯電特性が向上する。
【０１９９】
よって、上記の各構成によれば、小型でかつ電源電圧を低くすることができると共に、良好な画質を得ることができる画像形成装置を提供することができるという効果を奏する。
【０２００】
本発明にかかる画像形成装置は、以上のように、上記帯電部材と像担持体との最近接位置における間隔（帯電ギャップ）は、上記可視像が転写される転写材の厚みよりも小さく、かつ、残留現像剤成分であるトナーの粒径よりも大きい構成である。
【０２０１】
また、本発明にかかる画像形成方法は、以上のように、上記帯電部材と像担持体との最近接位置における間隔を、上記可視像が転写される転写材の厚みよりも小さく、かつ、残留現像剤成分であるトナーの粒径よりも大きく設定する構成である。
【０２０２】
上記の各構成によれば、上記帯電部材と像担持体との最近接位置における間隔（帯電ギャップ）を上記転写材の厚みよりも小さく設定することにより、転写電荷により像担持体に静電吸着している転写材の剥離に失敗した時に、吸着した転写材が現像領域に侵入し、ジャム（紙ジャム）からの復旧作業をより困難にするとともに復旧作業者の手や衣服をトナーで汚すのを防止することができ、転写領域において上記像担持体に吸着した転写材を上記帯電部材で確実に剥離し、該転写材の現像領域への侵入を防止することができる。また、上記の構成によれば、一般的な転写材の厚みから考えて、上記帯電ギャップを上記転写材の厚みよりも小さく設定することにより、異常放電の発生を低減し、異常放電による上記像担持体の帯電ムラを防止することができる。さらに、上記帯電ギャップを小さく設定することで、「パッシェの実験式」よりからも明らかなように、電源電圧を低くすることができる。
【０２０３】
また、残留現像剤成分、特に、逆帯電トナーを行うために、逆帯電トナーを帯電部材により捕獲する場合に、上記帯電ギャップをトナーの粒径よりも大きくすることによって、上記帯電部材へのトナーの融着（逆帯電トナーの融着）を防止することができるという効果を併せて奏する。
【０２０４】
本発明にかかる画像形成装置は、以上のように、当該画像形成装置は、トナーおよびキャリアを含む二成分系現像剤を用いた二成分現像方式の画像形成装置であり、上記帯電部材と像担持体との最近接位置における間隔（帯電ギャップ）は、残留現像剤成分であるキャリアの粒径よりも小さく、かつ、残留現像剤成分であるトナーの粒径よりも大きい構成である。
【０２０５】
また、本発明にかかる画像形成方法は、以上のように、上記現像剤として、トナーおよびキャリアを含む二成分系現像剤を用いる場合、上記帯電部材と像担持体との最近接位置における間隔を、残留現像剤成分であるキャリアの粒径よりも小さく、かつ、残留現像剤成分であるトナーの粒径よりも大きく設定する構成である。
【０２０６】
上記の各構成によれば、上記帯電部材と像担持体との最近接位置における間隔（帯電ギャップ）が、残留現像剤成分であるキャリアの粒径よりも小さく設定されていることで、該帯電ギャップへのキャリアの侵入を完全に排除することができる。また、上記帯電ギャップをキャリアの粒径よりも小さく設定することにより、像担持体の帯電状態を安定化できるため、良好な画質を得ることができる。しかも、上記の各構成によれば、一般的なキャリアの粒径から考えて、上記帯電ギャップを上記キャリアの粒径よりも小さく設定することにより、異常放電の発生を低減し、異常放電による上記像担持体の帯電ムラを防止することができる。さらに、上記帯電ギャップを小さく設定することで、「パッシェの実験式」よりからも明らかなように、電源電圧を低くすることができる。
【０２０７】
また、残留現像剤成分、特に、逆帯電トナーおよびキャリアのクリーニングを行うために、逆帯電トナーを帯電部材により捕獲する場合に、上記帯電ギャップをトナーの粒径よりも大きくすることによって、上記帯電部材へのトナーの融着（逆帯電トナーの融着）を防止することができるという効果を併せて奏する。
電流電流電流電　本発明にかかる画像形成装置は、以上のように、上記帯電部材には、直流電圧に交流電圧が重畳された電圧が印加されている構成である。
【０２０８】
また、本発明にかかる画像形成方法は、以上のように、上記帯電部材に、直流電圧に交流電圧が重畳された電圧を印加する構成である。
【０２０９】
本発明のようにアゲンスト回転した場合、該逆帯電トナーは、上記像担持体への帯電が開始される帯電領域よりも上記像担持体の回転方向上流側近傍で回収、搬送されるので、上記重畳電圧の直流成分（直流電圧）が逆帯電トナーの静電回収に有効に寄与する。このため、上記の各構成によれば、逆帯電トナーを効率良く静電吸着することができる。また、上記の各構成によれば、上記帯電部材には、直流電流電流電流電流電流電流圧に交流電圧が重畳された電圧が印加されていることで、転写後に上記像担持体表面に残留している残留現像剤成分等の異物（残留物）を加振することができ、上記像担持体からの上記残留現像剤成分等の異物の離脱を促進することができる。このため、上記逆帯電トナーの除去効率を高くすることができるという効果を併せて奏する。
【０２１０】
本発明にかかる画像形成装置は、以上のように、上記帯電部材には磁場が形成されている構成である。
【０２１１】
また、本発明にかかる画像形成方法は、以上のように、上記帯電部材には磁場が形成されている構成である。
【０２１２】
上記の各構成によれば、上記帯電部材に磁場が形成されていることで、質量が大きいキャリア、あるいは磁性トナー等の磁性体を、非機械的に磁気吸引力により回収することができる。このため、キャリア等の回収効率を高くすることができる。
【０２１３】
したがって、上記の各構成によれば、帯電ギャップへのキャリアやトナー等の異物の侵入を抑制することができる。これにより、キャリア等が帯電ギャップへ侵入することによって、像担持体および帯電部材が傷つけられることを防止できる。また、本来、白地の領域に逆帯電トナーが付着し、現像されてかぶりとなる画像かぶり等の画質劣化の原因となる逆帯電トナーを除去することができるという効果を奏する。
【０２１４】
さらに、磁性一成分現像等、磁性トナーを用いる装置においては、静電的な回収が困難な、正規帯電トナー、あるいは帯電量が微少、もしくは未帯電トナーも磁気的に回収することができるという効果を奏する。
【０２１５】
本発明にかかる画像形成装置は、以上のように、上記帯電装置は、上記帯電部材に吸着させた残留現像剤成分を、上記現像手段における現像槽内に回収する残留現像剤成分回収手段を有している構成である。
【０２１６】
上記の構成によれば、上記帯電装置が、上記帯電部材に吸着させた残留現像剤成分を回収する残留現像剤成分回収手段を有していることで、上記帯電部材に吸着させた残留現像剤成分を回収して再利用する特に、上記現像剤として、トナーおよびキャリアを含む二成分系現像剤を用いる場合、上記残留現像剤成分を帯電部材に吸着させる際、並びに、上記帯電部材に吸着させた残留現像剤成分を、残留現像剤成分にて回収する際に、キャリアによって、トナーが積極的に掻き取られる。この結果、上記帯電部材、残留現像剤成分回収手段によって、残留現像剤成分、特に逆帯電トナーの回収効率が向上するため、上記帯電装置通過後に上記像担持体上に残留した未除去の残留現像剤成分（正規帯電トナー）の回収効率を高めることができる。、回収された残留現像剤成分が現像時に有していた初期の電荷を失わせことができるとともに、帯電部材に吸着した残留現像剤成分が再度、帯電領域に進入した際に起きる帯電不良等を未然に防止することができる。
【０２１７】
また、上記の構成によれば、上記帯電部材に吸着させた残留現像剤成分を、上記現像手段における現像槽内に回収し、該現像槽内にて十分な攪拌帯電を回収された残留現像剤成分に与えることにより該残留現像剤成分を所定の電荷量に調整した後、再度、現像に利用することができる。この結果、トナー像メモリ等の画像劣化を防止することができるという効果を併せて奏する。
【０２１８】
本発明にかかる画像形成装置は、以上のように、上記帯電部材よりも上記像担持体の回転方向上流側に、上記像担持体上の異物を攪乱させる異物攪乱手段を有している構成である。
【０２１９】
上記の構成によれば、転写手段により転写されずに上記像担持体表面に残った残留現像剤成分等の異物を攪乱（攪拌）し、ほぐすことによって、上記帯電部材における異物の回収効率を高めると共に、残留現像剤成分に起因する像メモリを機械的に防止することができるという効果を奏する。
【０２２０】
本発明にかかる画像形成装置は、以上のように、上記異物攪乱手段は、上記像担持体上の残留現像剤成分に、反転現像の場合にはトナーの主帯電極性に対して逆極性、または、転写バイアスと同極性のバイアスを印加し、正規現像の場合にはトナーの主帯電極性に対して同極性、または、転写バイアスと逆極性のバイアスを印加して、上記残留現像剤成分の電荷を調節する電荷調節手段を有している構成である。
【０２２１】
また、本発明にかかる画像形成方法は、以上のように、上記残留現像剤成分を上記帯電部材に吸着させて除去する前に、予め、上記像担持体上の残留現像剤成分に、反転現像の場合にはトナーの主帯電極性に対して逆極性、または、転写バイアスと同極性のバイアスを印加し、正規現像の場合にはトナーの主帯電極性に対して同極性、または、転写バイアスと逆極性のバイアスを印加して、上記残留現像剤成分の電荷を調節する構成である。
【０２２２】
上記の各構成によれば、上記異物攪乱手段は、上記電荷調節手段を介して上記像担持体上の残留現像剤成分、具体的には残留トナーに、反転現像の場合にはトナーの主帯電極性（−）に対して逆極性（＋）、または、転写バイアス（＋）と同極性のバイアス（＋）を印加し、正規現像の場合にはトナーの主帯電極性（＋）に対して同極性（＋）、または、転写バイアス（−）と逆極性のバイアス（＋）を印加して、上記残留現像剤成分（残留トナー）の電荷を調節することで、転写後に上記像担持体上に残留したトナーは積極的に逆帯電、すなわち、プラス（＋）に帯電するようになり、これにより、より効率良く、上記帯電部材により、逆帯電トナー等の異物を除去することができる。
【０２２３】
また、上記の各構成によれば、上記電荷調節手段を介して上記像担持体上の残留現像剤成分に上記バイアス電圧を印加することで、残留現像剤成分、例えば残留トナーが現像時に有していた初期の電荷を失わせることができ、トナー像メモリを防止することができると共に、像担持体上に残留している残留電位を平坦化することができるので、上記像担持体の電位および残留現像剤成分の電圧調整が可能となるという効果を併せて奏する。
【０２２４】
本発明にかかる画像形成装置は、以上のように、上記異物攪乱手段は導電性ブラシを備えている構成である。
【０２２５】
上記の構成によれば、上記異物攪乱手段が導電性ブラシを備えていることにより、上記した残留現像剤成分等の異物は上記導電性ブラシの隙間を通り抜けることができる。これにより、異物の滞留を防止して該異物を攪乱することができると共に、上記像担持体表面に傷が付くことを防止することができるという効果を奏する。
【０２２６】
本発明にかかる画像形成装置は、以上のように、上記現像手段は、上記帯電装置通過後に上記像担持体上に残留している未除去の残留現像剤成分を回収する未除去残留現像剤成分回収手段を有する現像兼クリーニング装置である構成である。
【０２２７】
また、本発明にかかる画像形成方法は、以上のように、上記帯電装置通過後に上記像担持体上に残留している未除去の残留現像剤成分を、上記現像手段にて回収する構成である。
【０２２８】
上記の各構成によれば、上記現像兼クリーニング装置よりも、像担持体の回転方向上流側に位置する帯電部材によって、残留現像剤成分、特に、画質劣化、そのなかでも特に画像かぶりの原因となる逆帯電トナーが回収されるため、現像クリーニング方式にて良好な画像を維持することができる。
【０２２９】
また、上記の構成によれば、現像装置とクリーニング装置とを一体化することにより、上記画像形成装置の小型化を図ることができるという効果を併せて奏する。
【０２３０】
本発明にかかる画像形成装置は、以上のように、上記現像剤供給手段と上記像担持体とは周速比を有している構成である。
【０２３１】
上記の構成によれば、上記現像剤供給手段と上記像担持体とが周速比を有していることで、上記帯電装置通過後に上記像担持体上に残留している未除去の残留現像剤成分の回収効率をさらに高めることができるという効果を奏する。
【０２３２】
本発明にかかる画像形成装置は、以上のように、上記現像剤供給手段は、上記像担持体との最近接位置にて互いに行き違う方向に、上記像担持体と、対面する面の移動方向が互いに逆方向となるように回転するように設けられている構成である。
【０２３３】
上記の構成によれば、上記帯電装置通過後に上記像担持体上に残留している未除去の残留現像剤成分を、該残留現像剤成分が現像ギャップを通過する前に回収することができる。このため、上記未除去の残留現像剤成分の回収効率をさらに高めることができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の一実施の形態にかかる画像形成装置の要部の概略構成図である。
【図２】上記画像形成装置において帯電ギャップを２５μｍとしたときの感光体の帯電安定性を示すグラフである。
【図３】上記画像形成装置において帯電ギャップを４０μｍとしたときの感光体の帯電安定性を示すグラフである。
【図４】上記画像形成装置において帯電ギャップを５５μｍとしたときの感光体の帯電安定性を示すグラフである。
【図５】上記画像形成装置において帯電ギャップを１９０μｍとしたときの感光体の帯電安定性を示すグラフである。
【図６】設定ギャップに対する感光体の帯電電位の変動を示すグラフである。
【図７】設定ギャップに対する感光体の帯電電位の変動を示す他のグラフである。
【図８】ブラシバイアスとトナーの帯電量との関係を示すグラフである。
【図９】本発明の他の実施の形態にかかる画像形成装置の要部の概略構成図である。
【符号の説明】
１　　感光体（像担持体）
４　　現像領域
５　　帯電領域
１１　　露光装置
２１　　現像装置（現像手段）
２２　　現像槽
２３　　現像ローラ（残留現像剤成分回収手段）
２３ａ　マグネットロール
２３ｂ　スリーブ
２５　　電源
３１　　転写装置（転写手段）
３２　　転写ローラ
３３　　電源
４１　　異物攪乱装置（異物攪乱手段）
４２　　導電性ブラシ（電荷調節手段）
４３　　電源
５１　　転写装置
５２　　帯電ローラ（帯電部材）
５２ａ　導電性素管
５２ｂ　抵抗層
５３　　電源
５４　　クリーニングマイラーフィルム（残留現像剤成分回収手段）
６０　　現像剤
６１　　トナー
６１ａ　正規帯電トナー
６１ｂ　逆帯電トナー
６２　　キャリア
６３　　転写材屑
７１　　現像装置（現像手段）
７２　　現像槽
７３　　現像ローラ（残留現像剤成分回収手段）
７３ａ　導電性素管
７３ｂ　スリーブ
７５　　電源
８１　　帯電装置
８２　　帯電ローラ（帯電部材）
８２ａ　導電性素管
８２ｂ　抵抗層
９０　　現像剤
Ａ　　ドクターギャップ
Ｂ　　現像ギャップ
Ｃ　　帯電ギャップ
Ｄ　　帯電ギャップ
Ｐ　転写材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic method, such as a printer, a copying machine, and a facsimile, and an image forming method using the same. More specifically, the present invention relates to a charging member arranged close to an image carrier. TECHNICAL FIELD The present invention relates to an image forming apparatus and an image forming method using a proximity charging method for charging an image carrier by using the method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an image forming apparatus such as an electrophotographic copying machine, for example, the surface of a photoconductor (member to be charged) is uniformly charged to a specific polarity by corona discharge means, and then the charge on the photoconductor is exposed by image exposure. Is selectively removed to form an electrostatic latent image, and a corona discharge method is used in which a developer is supplied to the surface of the photoreceptor by a developer supply member to which an appropriate developing bias is applied to develop the electrostatic latent image. Known image forming apparatuses are known.
[0003]
As such an image forming method using a corona discharge type image forming apparatus, for example, a dedicated cleaning device is not provided by using a developing and cleaning device, and further, it is not transferred onto the photoreceptor after the transfer process. There has been proposed a regular development process using a magnetic toner, which has a toner disturbance step using a conductive brush for disturbing residual toner (see, for example, Patent Document 1).
[0004]
According to the regular developing process described in Patent Document 1, the size of the image forming apparatus can be reduced by integrating the developing device and the cleaning device.
[0005]
However, an apparatus using a corona discharge unit, such as the image forming apparatus described in Patent Document 1, is susceptible to the use environment such as humidity and dust. Have the problem of harm to
[0006]
Therefore, as a method for solving the above problem, for example, a charging member (conductive member) such as a charging roller to which a voltage obtained by superimposing an AC voltage on a DC voltage is applied to a member to be charged by contacting the member to be charged. A charging method using a contact charging method for performing charging is known.
[0007]
However, when relatively hard foreign matter such as a carrier adheres to the surface of the member to be charged or the surface of the charging member in such a contact charging system, the foreign matter is interposed between the charging member and the member to be charged. In this state, the surface of the member to be charged comes into contact with the surface of the member to be charged. Further, when a foreign substance such as a carrier adheres to the charging member, there arises a problem that uneven charging occurs in an area of the member to be charged corresponding to the foreign substance adhered portion on the charging member.
[0008]
In order to solve the problems of the contact charging method, such as damage due to the attachment of foreign matter to the member to be charged and the charging member and uneven charging, and to achieve ozone-less, which is the greatest advantage of the contact charging method. In recent years, a charging method using a proximity charging method in which a charging member is arranged close to a photoconductor (non-contact) and an image forming apparatus using the charging method have been proposed.
[0009]
For example, in an image forming apparatus provided with a developing device using a two-component developing method, a gap at a closest position between a discharge surface of a charging member and a photoconductor as a member to be charged is larger than a carrier particle diameter of the developer. An image forming apparatus has been proposed (for example, see Patent Document 2).
[0010]
In addition, the charging member is disposed on the surface of the member to be charged using the proximity charging method via an air gap of 120 μm or less, and an alternating voltage obtained by superimposing a DC voltage and a low-frequency AC voltage between these members is applied. A charging method for charging a member to be charged has been proposed (for example, see Patent Document 3).
[0011]
Further, a charging method has been proposed in which a charging member is disposed in contact with the member to be charged via an air gap of 30 μm to 240 μm, and an electrode bias of a DC component is applied to the charging member to charge the member to be charged. (For example, see Patent Document 4).
[0012]
[Patent Document 1]
Japanese Patent Publication No. 6-50416 (publication date June 29, 1994)
[0013]
[Patent Document 2]
JP 2001-188403 A (publication date: July 10, 2001)
[0014]
[Patent Document 3]
JP-A-5-307279 (Published November 19, 1993)
[0015]
[Patent Document 4]
JP-A-7-301973 (Published November 14, 1995)
[0016]
[Problems to be solved by the invention]
In the image forming apparatus described in Patent Document 2, since the gap at the closest position between the discharge surface of the charging member and the photoconductor is larger than the carrier particle diameter of the developer, the gap between the photoconductor and the charging member is reduced. In addition, there is no problem that the carrier and the toner adhering to the carrier are caught. Therefore, the photosensitive member and the charging member are not damaged or stained by the carrier.
[0017]
However, on the other hand, in the image forming apparatus described in Patent Document 2, the gap at the closest position between the discharge surface of the charging member and the photosensitive member is larger than the carrier particle diameter of the developer. Accordingly, there is a problem that the voltage required to charge the photoconductor increases. In addition, the charged state of the member to be charged tends to become unstable as the gap increases, and increasing the gap causes a reduction in image quality.
[0018]
Further, when the gap is reduced to avoid such a problem, particularly when the gap is smaller than the particle diameter of a foreign substance, for example, a carrier of a developer, damage and contamination of the charged member and the charging member are prevented. In order to prevent the problem, it is necessary to clean the member to be charged on the upstream side of the charging member without fail. Trigger.
[0019]
Further, such a cleaning problem is not limited to the case where the two-component developing method is used. That is, when the gap at the closest position between the discharge surface of the charging member and the member to be charged is reduced as disclosed in Patent Document 3 and Patent Document 4, when the toner passes through the gap, There is a case where toner is caught or toner adheres to the charging member, charging unevenness occurs in a region of the member to be charged corresponding to the toner adhering portion on the charging member, and the image quality deteriorates. In order to prevent such uneven charging, it is necessary to reliably clean the member to be charged upstream of the charging member regardless of the developing method.
[0020]
Further, when the proximity charging method is used, the image forming apparatus tends to be larger and the power supply voltage tends to be higher than when the contact charging method is used.
[0021]
Therefore, an image forming apparatus and an image forming method that can solve the above-mentioned conventional problems are keenly desired.
[0022]
The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an image forming apparatus and an image forming method that are compact, can reduce a power supply voltage, and can obtain good image quality. Is to provide.
[0023]
[Means for Solving the Problems]
In order to solve the above-described problems, an image forming apparatus according to the present invention includes an image carrier (for example, a photoconductor such as a photoconductor drum and a photoconductor belt) on which a latent image is formed, A charging device for charging the image carrier by applying a voltage to a charging member (eg, a charging roller, a charging belt, etc.) disposed around the surface of the image carrier in a non-contact manner; Developing means (for example, a developing device as a developing and cleaning device) for developing a latent image formed by the above with a developer containing at least a toner, and transferring the toner image formed on the image carrier In an image forming apparatus provided with transfer means (for example, a transfer device having a transfer roller, a transfer belt, and the like) for transferring to a material (for example, recording paper), the charging device remains on the image carrier after transfer. Remains A charging and cleaning device that removes the developer component from the image carrier by adsorbing to the charging member and charges the image carrier, wherein the charging member and the image carrier are separated from each other at the closest position. It is characterized by being provided so as to rotate so that the movement directions of the surfaces facing each other are opposite to each other.
[0024]
According to another aspect of the present invention, there is provided an image forming method, comprising: an image bearing member having a latent image formed on a surface thereof (for example, a photosensitive member such as a photosensitive drum or a photosensitive belt); A charging device that applies a voltage to a charging member (for example, a charging roller, a charging belt, or the like) disposed around the body in a non-contact manner with the surface of the image carrier to charge the image carrier; Developing means (for example, a developing device as a developing and cleaning device) for developing a latent image formed by the charged charges with a developer containing at least a toner, and a toner image formed on the image carrier An image forming apparatus provided with a transfer unit (for example, a transfer device having a transfer roller, a transfer belt, and the like) for transferring an image onto a transfer material, the charging member and the image bearing member being positioned closest to each other. At each other In the direction opposite to each other, the surfaces facing each other are rotated so that the directions of movement thereof are opposite to each other, and the residual developer component remaining on the image carrier after transfer is adsorbed to the charging member. Then, the image carrier is charged while being removed from the image carrier.
[0025]
According to each of the above-described configurations, the charging member and the image carrier rotate (agenst rotation) so that the movement directions of the surfaces facing each other at the closest position are opposite to each other, so that the image after the transfer is transferred. Residual developer components such as oppositely charged toner remaining on the carrier are adsorbed on the charging member before passing through the charging gap at the closest position between the discharge surface of the charging member and the image carrier. Removed. For this reason, according to each of the above-described configurations, it is possible to prevent the residual developer component such as the oppositely charged toner from entering the charging gap, and to reliably and reliably remove the residual developer component from the surface of the image carrier. It can be positively removed and collected. Further, when the charging member removes and collects the residual developer component, foreign matter (residual material) such as transfer material dust adhering to the residual developer component adsorbed by the charging member is also simultaneously removed by the charging member. It can be removed and collected from the image carrier.
[0026]
For this reason, according to each of the above-described configurations, a dedicated cleaning device as in the related art is not required to remove foreign matters such as a residual developer component remaining on the image carrier, and the size of the device can be reduced. Power supply voltage can be reduced. As a result, it is possible to prevent the image carrier from being reduced in film thickness due to the cleaning and to prevent the occurrence of rubbing marks, and to reduce the load torque of the image carrier.
[0027]
Further, according to each of the above-described configurations, it is possible to suppress the penetration of the residual developer component into the charging gap. Therefore, the residual developer component is charged up by passing through the charging gap. The charged surface is refreshed, and it is possible to suppress the occurrence of uncharged portions which are shadowed by the developer component (effective for charge-up), and improve the charging characteristics of the image carrier.
[0028]
In addition, according to each of the above configurations, since the charging member is rotated against the image carrier, the charging surface of the charging member and the image at the closest position between the charging member and the image carrier are rotated. The relative traveling distance with respect to the charging surface of the carrier is increased. For this reason, it is possible to prevent charging unevenness due to a partial variation of the resistance value of the charging member, to make charging uniform, and to provide a charging area, specifically, the charging gap, with the downstream of the image carrier. Influence that the charging member itself is charged by the charging operation when the surface to be charged (charging surface) of the charging member enters from the charging side (charging end side (downstream side of charging area)). The charged surface of the charged member that has been refreshed after removing the developer component and the like on the charged member that has been collected enters the charging gap, thereby preventing the influence of the collected material. As a result, the charging characteristics of the image carrier are improved.
[0029]
Therefore, according to each of the above-described configurations, it is possible to provide an image forming apparatus that is small in size, can reduce the power supply voltage, and can obtain good image quality.
[0030]
In the image forming apparatus according to the present invention, in order to solve the above-mentioned problem, the distance (charging gap) between the charging member and the image carrier at the closest position is determined by the thickness of the transfer material onto which the visible image is transferred. And a size larger than the particle size of the toner as the residual developer component.
[0031]
Further, in order to solve the above-mentioned problems, the image forming method according to the present invention may be configured such that the distance (charging gap) between the charging member and the image carrier at the closest position is set to a transfer material on which the visible image is transferred. Is set to be smaller than the thickness of the toner and larger than the particle diameter of the toner as the residual developer component.
[0032]
According to each of the above configurations, the distance (charging gap) at the closest position between the charging member and the image carrier is set smaller than the thickness of the transfer material, so that the electrostatic charge is applied to the image carrier by the transfer charge. When the transfer material that has been removed fails, the adsorbed transfer material enters the developing area, making recovery work from jams (paper jam) more difficult and soiling the hands and clothes of the recovery worker with toner. The transfer material adsorbed on the image carrier in the transfer area can be reliably peeled off by the charging member, and the transfer material can be prevented from entering the development area. Further, according to the above configuration, considering the thickness of a general transfer material, by setting the charging gap to be smaller than the thickness of the transfer material, the occurrence of abnormal discharge is reduced, and the image due to abnormal discharge is reduced. It is possible to prevent charging unevenness of the carrier. Further, by setting the charging gap to be small, it is possible to lower the discharge starting voltage as shown by “Pasche's empirical formula”, and thus to lower the power supply voltage.
[0033]
In addition, when the oppositely charged toner is captured by a charging member in order to perform the remaining developer component, particularly, the oppositely charged toner, the charging gap is made larger than the particle diameter of the toner, whereby the toner to the charging member is formed. (Fusion of the oppositely charged toner) can be prevented.
[0034]
In order to solve the above-mentioned problems, the image forming apparatus according to the present invention is an image forming apparatus of a two-component developing method using a two-component developer containing a toner and a carrier, and The distance (charging gap) at the closest position between the member and the image carrier is smaller than the particle size of the carrier as the residual developer component and larger than the particle size of the toner as the residual developer component. And
[0035]
Further, in order to solve the above-mentioned problems, the image forming method according to the present invention, when a two-component developer containing a toner and a carrier is used as the developer, the nearest neighbor between the charging member and the image carrier. The distance between the positions is set to be smaller than the particle size of the carrier as the residual developer component and larger than the particle size of the toner as the residual developer component.
[0036]
According to each of the above configurations, the distance (charging gap) at the closest position between the charging member and the image carrier is set to be smaller than the particle diameter of the carrier as the residual developer component. Intrusion of carriers into the gap can be completely eliminated. Further, by setting the charging gap smaller than the particle diameter of the carrier, the charging state of the image carrier can be stabilized, so that good image quality can be obtained. According to each of the above-described structures, the occurrence of abnormal discharge is reduced by setting the charging gap to be smaller than the particle size of the carrier, in consideration of the particle size of a general carrier, and the image bearing due to the abnormal discharge is reduced. Non-uniform charging of the body can be prevented. Further, by setting the charging gap to be small, it is possible to lower the discharge starting voltage as shown by “Pasche's empirical formula”, and thus to lower the power supply voltage.
[0037]
Further, when the oppositely charged toner is captured by a charging member in order to clean the residual developer component, in particular, the oppositely charged toner and the carrier, the charging gap is made larger than the toner particle size, so that the charging is performed. The fusion of the toner to the member (fusion of the oppositely charged toner) can be prevented.
[0038]
In the image forming apparatus according to the present invention, in order to solve the above-described problem, a voltage (superimposed voltage) in which an alternating voltage is superimposed on a direct current, current, current, current, current, or current pressure is applied to the charging member. It is characterized by having.
[0039]
Further, the image forming method according to the present invention is characterized in that in order to solve the above-mentioned problem, a voltage (superimposed voltage) in which an AC voltage is superimposed on a DC voltage is applied to the charging member.
[0040]
When the superimposed voltage is applied to the charging member, the surface potential of the image carrier near the end of the charging area rises to a predetermined voltage as charging proceeds, so that the charging member and the image carrier However, in the Wids rotation in which the toners rotate in the same direction at the closest position, the ability to electrostatically collect the oppositely charged toner is greatly reduced. The charged toner is collected and conveyed near the upstream side in the rotation direction of the image carrier from the charging area where the charging of the image carrier is started, so that the DC component (DC voltage) of the superimposed voltage is reversely charged. It effectively contributes to electrostatic recovery of toner. Therefore, according to the above configuration, the oppositely charged toner can be efficiently electrostatically attracted. According to the above configuration, the charging member is applied with a voltage obtained by superimposing an AC voltage on a DC current / current pressure, so that the residual developer remaining on the surface of the image carrier after transfer is applied. Foreign matter (residues) such as components can be vibrated, and detachment of the foreign matters such as the residual developer component from the image carrier can be promoted. Therefore, the efficiency of removing the oppositely charged toner can be increased.
[0041]
An image forming apparatus according to the present invention is characterized in that a magnetic field is formed on the charging member in order to solve the above-mentioned problems.
[0042]
The image forming method according to the present invention is characterized in that in order to solve the above-mentioned problems, a magnetic field is formed on the charging member.
[0043]
Particularly, a foreign substance (residue) having a large mass such as a carrier has a large burden in electrostatic adsorption, and the collection efficiency is reduced. On the other hand, according to each of the above-described configurations, since the magnetic field is formed in the charging member, the carrier can be collected non-mechanically by magnetic attraction. For this reason, the collection efficiency of foreign substances (residues) having a large mass such as a carrier can be improved.
[0044]
Therefore, according to each of the above-described configurations, it is possible to prevent foreign substances such as carrier and toner from entering the charging gap. Thereby, it is possible to prevent the image carrier and the charging member from being damaged by, for example, the carrier entering the charging gap. Further, the reversely charged toner which originally adheres to the white background area and is developed and causes image quality deterioration such as image fogging which is fogged can be removed.
[0045]
Further, in an apparatus using a magnetic toner such as magnetic one-component development, it is possible to magnetically collect a normally charged toner or a toner having a small charge amount or an uncharged toner, which is difficult to collect electrostatically.
[0046]
In order to solve the above-described problems, the image forming apparatus according to the present invention is configured such that the charging device collects a residual developer component adsorbed on the charging member into a developing tank in the developing unit. It is characterized by having a collecting means.
[0047]
According to the above configuration, the charging device has the residual developer component recovery unit that recovers the residual developer component adsorbed on the charging member, so that the residual developer adsorbed on the charging member is provided. In particular, when a two-component developer containing a toner and a carrier is used as the developer, when the residual developer component is adsorbed on the charging member, and when the two-component developer is adsorbed on the charging member, When the residual developer component is collected by the residual developer component, the toner is positively scraped off by the carrier. As a result, the recovery efficiency of the residual developer component, particularly the oppositely charged toner, is improved by the charging member and the residual developer component recovery means, so that the remaining undeveloped residual developer remaining on the image carrier after passing through the charging device is improved. The collection efficiency of the agent component (normally charged toner) can be improved.
Can be eliminated, and a charging failure or the like that occurs when the residual developer component adsorbed on the charging member enters the charging area again can be prevented.
[0048]
Further, according to the above configuration, the residual developer component adsorbed on the charging member is recovered in the developing tank of the developing unit, and the residual developer having been sufficiently stirred and charged in the developing tank is recovered. After the residual developer component is adjusted to a predetermined charge amount by giving it to the component, it can be used again for development. As a result, it is possible to prevent image deterioration of the toner image memory and the like.
[0049]
The image forming apparatus according to the present invention has a foreign matter disturbing means for disturbing foreign matter on the image carrier, on the upstream side in the rotation direction of the image carrier from the charging member, in order to solve the above problem. It is characterized by having.
[0050]
According to the above configuration, the foreign matter such as the residual developer component remaining on the surface of the image carrier without being transferred by the transfer unit is disturbed (stirred) and loosened, thereby improving the efficiency of collecting the foreign matter in the charging member. In addition, the image memory caused by the residual developer component can be mechanically prevented.
[0051]
In the image forming apparatus according to the present invention, in order to solve the above-described problem, the foreign matter disturbing unit may be configured to detect a residual developer component on the image carrier and a main charging polarity of the toner in the case of reversal development. By applying a reverse polarity or a bias having the same polarity as the transfer bias, and in the case of regular development, applying a bias having the same polarity as the main charging polarity of the toner or a reverse polarity to the transfer bias, the residual It is characterized by having charge control means for controlling the charge of the agent component.
[0052]
Further, in order to solve the above-mentioned problem, the image forming method according to the present invention may be configured such that the residual developer component is adsorbed to the charging member and removed beforehand. In the case of reversal development, a polarity opposite to the main charging polarity of the toner, or a bias having the same polarity as the transfer bias is applied, and in the case of regular development, the same polarity as the main charging polarity of the toner, or The bias of the polarity opposite to the transfer bias is applied to adjust the charge of the residual developer component.
[0053]
According to each of the above configurations, the foreign matter disturbing means supplies the residual developer component on the image carrier, specifically, the residual toner via the charge adjusting means, to the main charge of the toner in the case of reversal development. Apply a reverse polarity (+) to the polarity (-) or a bias (+) having the same polarity as the transfer bias (+). In the case of normal development, the same bias is applied to the main charging polarity (+) of the toner. By applying a polarity (+) or a bias (+) having a polarity opposite to that of the transfer bias (-) to adjust the charge of the residual developer component (residual toner), the image is transferred onto the image carrier after transfer. The remaining toner is positively charged reversely, that is, positively (+), whereby foreign matters such as reversely charged toner can be more efficiently removed by the charging member.
[0054]
Further, according to each of the above configurations, the bias voltage is applied to the residual developer component on the image carrier through the charge adjusting unit, so that the residual developer component, for example, the residual toner has during development. The initial charge can be lost, the toner image memory can be prevented, and the residual potential remaining on the image carrier can be flattened. The voltage of the residual developer component can be adjusted.
[0055]
According to each of the above configurations, foreign matter such as a residual developer component does not adhere to the charge adjusting means due to the bias voltage applied to the charge adjusting means, and the foreign matter adheres to the charge adjusting means. Problems such as stagnation and reduced disturbance effects do not occur.
[0056]
The image forming apparatus according to the present invention is characterized in that, in order to solve the above-mentioned problems, the foreign matter disrupting means includes a conductive brush.
[0057]
According to the arrangement, since the foreign matter disturbing means includes the conductive brush, the foreign matter such as the residual developer component can pass through the gap of the conductive brush. This can prevent the foreign matter from staying and disturb the foreign matter, and can prevent the surface of the image carrier from being damaged.
[0058]
In order to solve the above-mentioned problems, the image forming apparatus according to the present invention is configured such that the developing unit recovers an unremoved residual developer component remaining on the image carrier after passing through the charging device. The present invention is characterized in that it is a developing and cleaning device having a residual developer component collecting means.
[0059]
Further, in order to solve the above-mentioned problem, the image forming method according to the present invention recovers an unremoved residual developer component remaining on the image carrier after passing through the charging device by the developing unit. It is characterized by doing.
[0060]
According to each of the above configurations, the charging, that is, the collection of the residual developer component (residue) such as the oppositely charged toner is performed by the charging member of the developing / cleaning device / cleaning device. An unremoved residual developer component remaining on the image carrier after passing through the charging and cleaning device can be collected by the developing and cleaning device. According to each of the above-described configurations, the residual developer component, in particular, image quality deterioration, and particularly the cause of image fogging, is caused by the charging member located upstream of the developing and cleaning device in the rotation direction of the image carrier. Is recovered, and a good image can be maintained by the developing cleaning method.
[0061]
Further, according to each of the above configurations, the size of the image forming apparatus can be reduced by integrating the developing device and the cleaning device.
[0062]
In this case, in particular, the unremoved residual developer component remaining on the image carrier after passing through the charging device is recovered in a developing tank of the developing unit, so that the developer is collected in the developing tank. Sufficient stirring charge can be given to the recovered residual developer component, and the recovered residual developer component can lose the initial charge that was possessed at the time of development. After that, it can be used again for development. As a result, the toner image memory can be prevented, and the collected developer components can be efficiently reused.
[0063]
An image forming apparatus according to the present invention is characterized in that in order to solve the above-mentioned problems, the developer supply unit and the image carrier have a peripheral speed ratio.
According to the above configuration, the developer supply means and the image carrier have a peripheral speed ratio, and thus remain on the image carrier after passing through the charging device. The recovery efficiency of the unremoved residual developer component can be further increased. Here, that the developer supply means and the image carrier have a peripheral speed ratio means that the developer supply means (specifically, the developing roller) is rotating and in the development area, This indicates that the surface of the developer supply means (developing roller) and the surface of the image carrier facing each other are rotating at a relative speed.
[0064]
In the image forming apparatus according to the present invention, in order to solve the above-described problem, the developer supply unit may be configured such that a movement direction of a surface facing the image carrier at a position closest to the image carrier. It is characterized in that it is provided so as to rotate in directions opposite to each other.
[0065]
According to the above configuration, the unremoved residual developer component remaining on the image carrier after passing through the charging device can be collected before the residual developer component passes through the developing gap. Therefore, the recovery efficiency of the unremoved residual developer component can be further increased.
[0066]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
One embodiment of the present invention will be described below with reference to FIGS.
[0067]
As shown in FIG. 1, an image forming apparatus according to the present embodiment includes an exposure device 11, a developing device 21, a transfer device 31, a foreign matter disturbing device 41, and a charging device 51 around a photoreceptor 1 as an image carrier. Are arranged in this order from the exposure position, that is, the irradiation position of the laser beam 12 by the exposure device 11 in the rotation direction of the photoconductor 1.
[0068]
The photoconductor 1 is a photoconductor drum that is driven to rotate in the direction of an arrow (clockwise), and a charge generation layer (CGL) such as a photoconductive material or an organic photoconductive material, It has a configuration in which a film 3 made of a transport layer (CTL) or the like is formed, and on its surface, forms an electrostatic latent image (latent image) due to charged charges and a toner image formed by developing the electrostatic latent image. You can do it.
[0069]
An exposure device 11 serving as a latent image forming device (exposure device) has a laser light source 11a, and is disposed downstream of the photoconductor 1 in the rotation direction of the photoconductor 1 with respect to the charging device 51 and separated from the photoconductor 1. I have. The exposure device 11 includes digital data (such as image information input from a scanner unit (document reading device) not shown) or a host computer (not shown) connected to the outside, or image information such as FAX information transmitted by communication or the like. The charged light on the photoconductor 1 is selected by irradiating the laser beam 12 modulated based on the image signal) onto the surface of the photoconductor 1 uniformly charged by the charging device 51 and exposing (scanning) the same. And an electrostatic latent image (latent image) is formed on the photoreceptor 1.
[0070]
The developing device 21 includes a developing roller 23 as a developer supply unit that supplies the developer 60 accommodated in the developing tank 22 to the photoconductor 1, and a power supply as a voltage (developing bias) applying unit. By applying a predetermined developing bias from 25, the electrostatic latent image formed on the photoreceptor 1 by the exposure by the exposure device 11 is developed by the toner 61, that is, a visible image (toner image) is formed. It has become.
[0071]
The developing device 21 includes a layer thickness regulating member 24 that regulates the thickness of the developer layer on the surface of the developing roller 23, and adjusts the distance (doctor gap A) between the layer thickness regulating member 24 and the photoconductor 1. At the same time, when a predetermined bias is applied to the layer thickness regulating member 24 from a power source (not shown), the amount of the developer supplied onto the photoconductor 1 is adjusted.
[0072]
In the present embodiment, in addition to the toner 61 which is a magnetic toner, a carrier 62 (toner carrier, indicated by “C” in FIG. 1) made of an inorganic magnetic material such as magnetite or ferrite is used as the developer 60. Containing two-component developer. Specific examples of the carrier 62 include, but are not particularly limited to, an inorganic magnetic material such as iron powder, magnetite, ferrite, and triiron tetroxide.
[0073]
For example, as shown in FIG. 1, when the photoconductor 1 is charged to minus (-), the toner 61 is charged positive (+) in the case of regular development (positive development), and minus (-) in the case of reversal development. −) It is charged. Hereinafter, in the present embodiment, the case of reversal development will be described as an example, but the present invention is not limited to this.
[0074]
In this embodiment, the developing roller 23 is applied with a developing bias (for example, −400 V) that is more positive than the surface potential of the photoconductor 1 (for example, −600 V). It is possible to electrostatically adsorb foreign matter such as the negatively (−) charged regular charged toner 61 a remaining on the photoreceptor 1.
[0075]
In this embodiment, a developing device having a developing roller 23 including a magnet roll 23a and a sleeve 23b covering the magnet roll 23a is used as the developing device 21. Thus, the developing device 21 can magnetically attract the developer 60 to the surface of the sleeve 23b by the magnetic force generated from the magnet roll 23a. To develop the electrostatic latent image on the surface of the photoreceptor 1, while developing the electrostatic latent image on the surface of the photoreceptor 1 more upstream than the developing region 4 where the developing roller 23 and the photoreceptor 1 are close to each other in the rotation direction of the photoreceptor 1. The remaining unremoved residual developer components (residue after collection), specifically, the regular charge of the developer 60 remaining on the photoreceptor 1 without being transferred and not collected by the charging device 51 By rubbing the toner 61a (indicated by "-" in FIG. 1) with a magnetic brush (not shown) formed on the surface of the sleeve 23b, the normally charged toner 61a and the normally charged toner 61a are rubbed. Toner 6 Foreign substances such as paper attached to a, from the surface of photoreceptor 1, so as to electrostatically or mechanically removed.
[0076]
That is, the developing roller 23 collects the foreign matter such as the normally charged toner 61 a remaining on the photoconductor 1 in the developing tank 22 near the upstream side in the rotation direction of the photoconductor 1 in the developing area 4 (developing). It functions as an unremoved residual developer component collecting means (cleaning method) (normally charged toner collecting means).
[0077]
As a result, the developing device 21 acts as a developing and cleaning device to remove foreign matter such as the unremoved regular charged toner 61 a remaining on the photoreceptor 1 after passing through the charging device 51 in the developing area 4. In the vicinity of the upstream side in the rotational direction of the body 1, for example, in the upstream side in the rotational direction of the photosensitive body 1 from the supply position of the developer 60 to the photosensitive body 1 by the developing roller 23, the photosensitive material is collected together with the development. The cleaning of the body 1 is performed. As described above, the image forming apparatus according to the present embodiment including the developing device 21 which is the developing and cleaning device is not limited to the two-component developing method, and the above-described image forming apparatus can be used even when the one-component developing method is used. The normally charged toner 61a as a residue on the photoconductor 1 can be collected in the developing tank 22.
[0078]
The normally charged toner 61a attracted to the developing roller 23 is returned to the developing tank 22 provided in the back of the developing roller 23 with the rotation of the developing roller 23. As a result, in the developing tank 22, a sufficient stirring charge can be given to the collected normally charged toner 61 a by a stirring roller (not shown) provided in the developing tank 22. After adjusting the electric charge of 600, which causes the initial electric charge at the time of development to be lost, to a predetermined electric charge amount, it can be used again for development. As a result, the toner image memory can be prevented, and the collected normal charged toner 61a can be reused.
[0079]
It is desirable that the magnetic field in the developing roller 23 be set within a range of 400 to 800 Gauss (Gs).
[0080]
Further, it is preferable that the developing roller 23 and the photoconductor 1 have a peripheral speed ratio. That is, the developing roller 23 is preferably rotatably provided. Thereby, the collection efficiency of the regular charged toner 61a can be further increased.
[0081]
The phrase “the developing roller 23 and the photoconductor 1 have a peripheral speed ratio” means that the developing roller 23 is rotating, and that the surface of the developing roller 1 shows that the surface is rotating with a relative speed.
[0082]
The peripheral speed ratio of the developing roller 23 to the photosensitive member 1 (developing peripheral speed ratio) is appropriately determined according to the doctor gap A that defines the thickness of the developer layer, the toner concentration (T / D) of the developer 60, and the required development amount. The setting is not particularly limited, but is preferably set in the range of 1 to 4 times. If the developing peripheral speed ratio is too small, the developing amount tends to be insufficient. If the developing peripheral speed ratio is too large, the deterioration of the developer 60 is accelerated, which may cause problems such as shortening the life and causing fusion of the toner 61 to the developing roller 23. There is.
[0083]
Further, the developing roller 23 is provided in non-contact with the photoconductor 1, and moves in a direction in which the developing roller 23 faces the photoconductor 1 in a direction in which the developing roller 23 crosses each other at a position closest to the photoconductor 1. It is preferable that the photosensitive member 1 be rotated (against rotation) so that the direction is opposite to the moving direction of the surface of the photosensitive member 1 facing (opposing) the developing roller 23. That is, the developing roller 23 is driven by a drive system different from that of the photoconductor 1 so that the rotation direction of the developing roller 23 with respect to the rotation axis and the rotation direction of the photoconductor 1 with respect to the rotation axis are rotated in the same direction. Preferably, it is provided. As a result, foreign matter such as the unremoved normally charged toner 61 a remaining on the photoconductor 1 after passing through the charging device 51 is removed by the gap at the closest position between the developing roller 23 and the photoconductor 1. Before passing through a certain developing gap B, more specifically, as described above, the toner can be collected in the vicinity of the developing area 4 near the upstream side in the rotation direction of the photoconductor 1. For this reason, the collection efficiency of the unremoved residual developer component (normally charged toner 61a) can be further increased.
[0084]
In the present embodiment, for example, when a toner having a particle diameter of 8 μm using styrene acrylic resin as a binder resin is used as the toner 61 and an iron powder carrier having a particle diameter of 60 μm is used as the carrier 62, Are set such that the charging potential is -600 V, the developing bias is -400 V, the doctor gap A is 1.5 mm, the developing gap B is 2 mm, and the development peripheral speed ratio is 2.251.25 with the rotation of the agonist.
[0085]
Further, the transfer device 31 includes a transfer roller 32 as a transfer unit that rotates following the rotation of the photoconductor 1, and the rotation direction of the transfer roller 32 with respect to the rotation axis is the rotation axis of the photoconductor 1. The transfer material P is conveyed to a nip portion (transfer area) between the photoreceptor 1 and the transfer roller 32 by rotating in the direction opposite to the rotation direction with respect to. A predetermined transfer bias is applied to the transfer roller 32 from a power supply 33 as a voltage (transfer bias) application unit, and the transfer roller 32 contacts (presses) the photoconductor 1 via the transfer material P, The toner image formed on the photoconductor 1 is transferred to the transfer material P.
[0086]
In the present embodiment, for example, the transfer roller 32 is rotationally driven so that the transfer bias is +2 kv and the process speed is 130 mm / s. As a result, the toner 61 having a negative (-) charge in the developing region 4 has a slight positive (+) charge at the transfer bias (+2 kV) in the transfer region.
[0087]
The charging device 51 is configured such that a charging roller (charging member) 52 is provided around the photosensitive member 1 in a non-contacting manner with the photosensitive member 1 by urging a spring 55 as a charging gap adjusting means. Is provided.
[0088]
The charging roller 52 is, for example, a magnet roller including a conductive element tube 52a and a resistance layer 52b that covers the surface of the conductive element pipe 52a. A voltage (charging) is applied to the conductive element tube 52a of the charging roller 52. By applying a voltage from a power supply 53 as a bias) applying unit, the surface of the photoconductor 1 is charged via the resistance layer 52b.
[0089]
The charging device 51 according to the present embodiment is configured to control the residual developer component remaining on the photoconductor 1 after the transfer, specifically, the reverse of the developer 60 remaining on the photoconductor 1 without being transferred. By adsorbing the charged toner 61b (indicated by “+” in FIG. 1) and the carrier 62 (indicated by “c” in FIG. 1) on the surface of the resistance layer 52b, these oppositely charged toner 61b and The carrier 62 and foreign matter such as the normally-charged toner and paper adhered to the oppositely-charged toner 61 b and the carrier 62, for example, the agglomeration soul of the transfer material dust 63 such as the toner 61, the carrier 62 and the paper are transferred to the surface of the photoconductor 1 It is a charging and cleaning device for removing from the cleaning.
[0090]
A voltage (superimposed voltage) in which an AC voltage is superimposed on a DC current voltage is applied to the charging roller 52, and a magnetic field is formed. In the present embodiment, an AC voltage having a peak-to-peak voltage of 1.8 KVpp and a frequency of 900 Hz is superimposed on a DC component of -600 V and applied.
[0091]
In the present embodiment, by applying a negative (-) DC voltage as a charging bias to the charging roller 52, the oppositely charged toner 61b having a positive (+) charge can be electrostatically attracted. It has become. In particular, by applying the superimposed voltage, in this case, the superimposed voltage in which the AC voltage is superimposed on the negative (-) DC component current difficult (DC voltage) to the charging roller 52, The foreign matter, which is a residue on the surface of the photoreceptor 1, can be vibrated, the detachment of the foreign matter from the photoreceptor 1 can be promoted, and the reversely charged toner 61b can be efficiently electrostatically attracted. As a result, the efficiency of removing the oppositely charged toner 61b can be increased.
[0092]
In addition, since the carrier 62 has a large mass, a load on the charging roller 52 is large in electrostatic attraction, and it is inefficient to collect the carrier 62 by electrostatic force. Therefore, the collection efficiency of the carrier 62 is low in the electrostatic adsorption. However, since a magnetic field is formed on the charging roller 52, the recovery efficiency of the carrier 62 can be increased by non-mechanically recovering the carrier 62 by magnetic attraction.
[0093]
Table 1 shows the effect of collecting the toner 61 and the carrier 62 by the charging roller 52.
[0094]
[Table 1]

[0095]
As shown in Table 1, by collecting the toner 61 and the carrier 62 by the charging roller 52, a good image can be obtained.
[0096]
In the present embodiment, the charging roller 52 and the photoconductor 1 are provided such that the rotation direction of the charging roller 52 with respect to the rotation axis and the rotation direction of the photoconductor 1 with respect to the rotation axis rotate in the same direction. I have. In other words, the charging roller 52 and the photosensitive member 1 are driven by different driving systems so that the moving directions of the surfaces facing each other are opposite to each other in the direction in which the charging roller 52 crosses each other and at the closest position to the photosensitive member 1. It is provided so as to rotate in the direction (Agenst rotation).
[0097]
As a result, foreign matter such as the oppositely charged toner 61b and the carrier 62 remaining on the photoreceptor 1 after the transfer is transferred to the gap between the discharge surface of the charging roller 52 and the photoreceptor 1 at the closest position. Before passing through a certain charging gap C, it is adsorbed and removed by the charging roller 52. The charging device 51 is provided in contact with the charging roller 52, scrapes off foreign matter adsorbed on the charging roller 52, and collects the foreign matter in the developing tank 22 provided behind the developing roller 23. As a foreign matter collecting means (remaining developer component collecting means), there is a cleaning film 54 such as a mylar having a cleaning blade and a toner conveying screw. As a material of the cleaning film 54, for example, polyethylene terephthalate is used. By providing the cleaning film 54 as the foreign matter collecting means, the foreign matter such as the oppositely charged toner 61b adsorbed on the charging roller 52 is returned to the developing tank 22, and like the regular charged toner 61a, the foreign matter is removed in the developing tank 22. Sufficient stirring charge is provided. As a result, the oppositely charged toner 61b whose charge has changed significantly can also be reused. Also, by providing the charging roller 52 with the cleaning film 54 as a foreign matter collecting means for collecting foreign matter on the surface of the photoreceptor 1, the means for removing and collecting the foreign matter can be provided by the charging device 51. It is not necessary to provide the image forming apparatus separately, and the structure of the image forming apparatus can be simplified.
[0098]
As described above, the charging roller 52 is rotating with respect to the photoreceptor 1, and the foreign matter remaining on the photoreceptor 1 after transfer is attracted to the charging roller 52 to transfer the foreign matter to the surface of the photoreceptor 1. , The oppositely charged toner 61b adheres to the charging gap C between the charging roller 52 and the photoreceptor 1, for example, in a white background region of the transfer material P, and is developed, and the image quality such as image fogging becomes fog. It is possible to reliably and positively remove and collect the foreign matter from the surface of the photoreceptor 1 without the foreign matter such as the oppositely charged toner 61b and the carrier, which may cause deterioration, penetrating.
[0099]
That is, the charging roller 52 and the photoconductor 1 rotate in a direction different from the rotation direction of the charging roller 52 with respect to the rotation axis of the charging roller 52 and the rotation direction of the photoconductor 1 with respect to the rotation axis. When rotating in the same direction as each other (with rotation), the oppositely charged toner 61b passes through the charged area 5, while foreign matter such as the oppositely charged toner 61b is rotated by the opposite rotation. The photosensitive member 1 is attracted to the charging roller 52 in the vicinity of the upstream side in the rotation direction. As a result, it is possible to prevent these foreign substances from entering the charging gap C, and prevent these foreign substances, particularly, the oppositely charged toner 61b from passing through the charged area 5.
When a superimposed voltage (AC superimposed bias) is applied to the charging roller 52, the surface potential of the photoreceptor 1 is charged almost the same as the DC bias voltage near the end of the charging area 5, so that the Wids rotation is performed. , The ability to electrostatically recover the oppositely charged toner 61b is greatly reduced, whereas in the opposite rotation, the oppositely charged toner 61b is larger than the charged area 5 where charging of the photoconductor 1 is started. Since the photoreceptor 1 is collected and conveyed near the upstream side in the rotation direction, the direct current (DC) component of the AC superimposed bias of the charging roller 52 effectively contributes to the electrostatic collection of the oppositely charged toner 61b.
[0100]
In particular, in the reversal development, if the reversely charged toner 61b enters the developing area 4 while remaining in the unexposed area, the electrostatic attraction to the photoreceptor 1 is strong, so that the toner is not collected by the developing roller 23. The normally charged toner 61a is electrostatically attracted, and the process proceeds to the transfer process in a state where the amount of the toner 61 on the photoconductor 1 is amplified, so that a noticeable white background stain is generated. For this reason, the opposite rotation is particularly effective for collecting the oppositely charged toner 61b.
[0101]
Therefore, according to the image forming apparatus of the present embodiment, a dedicated cleaning device for removing foreign matter remaining on the photoconductor 1 is not required, and the device can be downsized. The voltage can be reduced. In addition, as a result, it is possible to prevent the photoreceptor 1 from being reduced in film thickness due to cleaning and to prevent the occurrence of rubbing marks, and to reduce the load torque of the photoreceptor 1.
[0102]
Further, according to the image forming apparatus of the present embodiment, the foreign matter is charged between the charging roller 52 and the photoconductor 1 by the rotation of the charging roller 52 against the photoconductor 1. Before passing through the gap C, the foreign matter can be adsorbed to the charging roller 52, and the foreign matter adsorbed by the charging roller 52 can be removed and collected without passing through the charging gap C. Accordingly, it is possible to prevent uneven charging due to foreign matter passing through the charging gap C.
[0103]
That is, when foreign matter such as the oppositely charged toner 61b is present in the charging gap C, for example, the oppositely charged toner 61b is charged, and the portion from which the oppositely charged toner 61b is removed is not charged up (charged). Shadows will occur. However, according to the above configuration, the foreign matter, in particular, the oppositely charged toner 61b is attracted to the charging roller 52 near the upstream side of the charging area 5 in the rotation direction of the photoconductor 1, so that the charging gap C of the foreign matter is reduced. Intrusion into the toner can be prevented, and the charging characteristics can be improved.
[0104]
In particular, according to the image forming apparatus according to the present embodiment, the charging roller 52 provided on the upstream side in the rotation direction of the photoconductor 1 with respect to the developing device 21 causes image quality deterioration, particularly, the above-described cause of image fogging. Since the oppositely charged toner 61b is collected, a good image can be maintained by the developing cleaning method in which the developing device and the cleaning device are integrated. Further, by integrating the developing device and the cleaning device in this way, the size of the image forming apparatus can be further reduced. Further, according to the image forming apparatus, since the oppositely charged toner 61b is positively scraped off by the carrier 62 in the charging roller 52, the collection efficiency of the normally charged toner 61a can be increased.
[0105]
Further, according to the image forming apparatus according to the present embodiment, since the intrusion of foreign matter into the charging gap C can be prevented, the charging gap C is sandwiched between the charging gap C and the carrier 62, for example. There is no need to widen the charging gap so that the charging gap can pass without causing the charging gap C to narrow. By reducing the interval of the charging gap C in this manner, the charging of the photosensitive member 1 from the downstream side of the photosensitive member 1 from the “Pasche's empirical formula” (6.2 V / μm) indicating the discharge starting voltage in the air discharge. The surface is refreshed, which is effective for charge-up. As is apparent from the charge-up, the power supply voltage can be lowered. In the image forming apparatus, since the intrusion of foreign matter into the charging gap C can be prevented, even if the charging gap C is narrowed, relatively hard foreign matter such as the carrier 62 passes through the surface of the charging roller 52. Alternatively, there is no problem that the surface of the photoconductor 1 is damaged.
[0106]
Further, since the charging roller 52 is rotated against the photosensitive member 1, the charged surface of the charging roller 52 and the charged surface of the photosensitive member 1 at the closest position between the charging roller 52 and the photosensitive member 1 are formed. , The relative mileage is increased. Therefore, the charging fluctuation due to the partial resistance value fluctuation of the charging roller and the like is made uniform, the charging characteristics of the photoconductor 1 are improved, and the charging area 5, specifically, the charging gap C is placed in the charging gap C. The effect that the charging roller 52 itself is charged when a surface (charged surface) to be a charging surface of the charging roller enters from a downstream side, that is, a charging end side (downstream of the charging area 5). Can be reduced.
[0107]
Note that the above effect is particularly remarkable when the resistance value of the resistance layer 52b is high. The resistance value of the resistance layer 52b, that is, the resistance of the charging roller 52, contributes to prevention of abnormal discharge and smoothing of charging in superposition. For this reason, if the resistance is too small, abnormal discharge and uneven charging tend to occur. On the other hand, if the resistance is too high, the required charging time will be long, and it will be difficult to raise the charging potential to the normal charging potential, which may lead to a reduction in potential due to insufficient charging and uneven charging. Therefore, the resistance value of the resistance layer 52b is 10 ⁸ It is preferable to set the resistance to Ωcm or less.
[0108]
If the superimposed voltage applied to the charging roller 52 is equal to or lower than the discharge starting voltage, the effect of setting the superimposed voltage cannot be obtained. On the other hand, if the superimposed voltage is too high, charging unevenness due to abnormal discharge may occur. For this reason, the superimposed voltage is equal to or higher than the discharge starting voltage at the peak value, and the dielectric strength of the photoconductor 1. -Direct current (DC) voltage It is desirable to set the voltage value to 600 or less, specifically, it is desirable to set the voltage value in the range of 450 (Vo-p) to 1300 (Vo-p).
[0109]
On the other hand, if the magnetic field is too small, it will be difficult to recover the carrier 62. For this reason, it is desirable that the magnetic field of the charging roller 52 be set in the range of 400 to 800 gauss, similarly to the developing roller 23 used for the two-component development.
[0110]
The superimposed voltage involves a charging gap C between the charging roller 52 and the photoconductor 1 that governs a discharge starting voltage.
[0111]
The charging gap C between the charging roller 52 and the photoconductor 1 may be set to be smaller than the particle diameter (carrier diameter) of the carrier 62 and larger than the particle diameter (toner diameter) of the toner 61. preferable. By setting the charging gap C to be smaller than the particle size of the carrier 62 attached to the photoconductor 1, it is possible to reliably prevent the carrier 62 from entering the charging gap C. Accordingly, it is possible to more reliably prevent the photoconductor 1 and the charging roller 52 from being damaged by the carrier 62 entering the charging gap C.
[0112]
2 to 5 and Table 2 show the results of evaluating the charging stability of the photoreceptor 1 by variously changing the interval of the charging gap C. The measurement conditions are as follows. The charging roller 52 is a genuine charging roller manufactured by Ipsio (diameter (Φ): 11 cm, resistance value: 40 MΩ, volume resistivity of the resistance layer 52 b: 10). ⁷ Ω · cm) and an AC voltage (superimposed voltage) having a peak-to-peak voltage of 1.8 KVppV and a frequency of 900 Hz was applied to a DC component of −600 V as a charging bias. The diameter (Φ) of the photoconductor 1 was 35 cm, the thickness of the film 3 was 17 μm, and the process speed was 130 mm / s.
[0113]
[Table 2]

[0114]
As a result of the measurement, as shown in FIGS. 2 to 4, stable charging of the photoconductor 1 was confirmed when the interval of the charging gap C was in the range of 25 μm or more and 55 μm or less, particularly, in the range of 25 μm or more and 40 μm or less. 2 to 5, the vertical axis represents the surface potential (-V) of the photoconductor 1, and the horizontal axis represents time (sec).
[0115]
From the above measurement results, it was found that the charging state of the photoconductor 1 can be stabilized by setting the interval of the charging gap C smaller than the carrier diameter. For example, when the carrier 62 having a particle diameter of 60 μm is used, the carrier collection efficiency in the charging roller 52 can be increased by setting the interval of the charging gap C to be smaller than the particle diameter of the carrier 62 of 60 μm. it can.
[0116]
6 and 7 show the variation of the charging potential of the photoconductor 1 with respect to the set value (set gap) of the charging gap C. When the interval of the charging gap C exceeds 60 μm as shown in FIGS. 6 and 7, abnormal discharge is likely to occur. Therefore, by setting the interval of the charging gap C to 60 μm or less, occurrence of abnormal discharge can be reduced, and uneven charging of the photoconductor 1 due to abnormal discharge can be reduced. In FIGS. 6 and 7, the vertical axis indicates the charging potential fluctuation (| ΔV | (V)), and the horizontal axis indicates the set gap (μ) of the charging gap C.
[0117]
As shown in FIGS. 6 and 7, in particular, when charging is performed with a DC bias, the case where the interval of the charging gap C fluctuates from the set value due to processing errors or the like (it is necessary to consider about 10 μm) is considered. By setting the interval of the charging gap C to 55 μm or less, the fluctuation of the charging potential of the photoconductor 1 can be reduced.
[0118]
As described above, by setting the interval of the charging gap C to be smaller than the carrier diameter, specifically, 60 μm, the charging state of the photoconductor 1 can be stabilized, so that good image quality can be obtained. .
[0119]
Further, as shown in FIGS. 3 and 4 and Table 2, when the interval of the charging gap C exceeds 55 μm, the charging state of the photoconductor 1 becomes difficult to stabilize. From the development characteristics, when the surface potential of the photoconductor 1 drops by 150 V, the above-described image fog occurs. Therefore, the fluctuation value of the surface potential of the photoreceptor 1 is preferably 150 Vpp or less, and more preferably 30 Vpp or less in order to ensure the stability of halftone. Therefore, when, for example, transfer paper is used as the transfer material P, black may occur on a white background of the transfer paper. For this reason, by setting the interval of the charging gap C to 55 μm or less, particularly to 40 μm or less as described above, occurrence of abnormal discharge can be further reduced, and uneven charging of the photoconductor 1 due to abnormal discharge can be prevented. .
[0120]
As described above, by increasing the carrier collection efficiency of the charging roller 52 and preventing the charging unevenness of the photoconductor 1 due to the abnormal discharge, it is possible to prevent the occurrence of black spots on a white background on the transfer paper.
[0121]
On the other hand, when the oppositely charged toner 61b is captured by the charging roller 52 in order to clean the oppositely charged toner 61b and the carrier 62, the charging gap C is set larger than the particle diameter of the toner 61 adhering to the photosensitive member 1. By setting the large interval, it is possible to prevent the residual toner, that is, the toner 61, from being fused to the charging roller 52. Incidentally, since the normal toner diameter is about 7 μm, the interval of the charging gap C is preferably set to 7 μm or more.
[0122]
Further, the interval of the charging gap C is preferably 3 times or more and less than 9 times the toner diameter in terms of powder engineering. That is, assuming that the toner diameter is about 7 μm, the interval between the charging gaps C is preferably in the range of 21 μm or more and 63 μm or less.
[0123]
The powder ejection phenomenon occurs remarkably at less than three times the particle size. Therefore, by making the charging gap C three times or more the toner diameter, it is possible to prevent the ejection of the toner 61.
[0124]
Also, the so-called powder bridge arch is remarkably generated at about 9 times the particle size. Therefore, by setting the charging gap C to be less than nine times the toner diameter, the fusion of the toner 61 to the charging roller 52 due to the bridge arch of the toner 61 can be prevented. In addition, according to the above configuration, the aggregation of the toner 61 can be prevented from passing through the charging gap C. Therefore, the aggregation of the toner 61 is transferred to the developing area 4 where the photoconductor 1 and the developing roller 23 are close to each other. It is possible to prevent image quality degradation caused by intrusion.
[0125]
Further, since the thickness of the general paper is in the range of about 70 μm to 100 μm, by providing the gap of the charging gap C narrower than this thickness, the intrusion of jammed paper into the charging gap C is prevented, The jam paper can be prevented from being entangled in the roller 52. Thus, the jammed paper can be prevented from entering the developing area 4, and the jammed paper can be easily removed.
[0126]
The peripheral speed ratio of the charging roller 52 to the photosensitive member 1 (the peripheral speed of the charging roller / the peripheral speed of the photosensitive member) is 0 (there is no peripheral speed ratio). However, when the charging roller 52 has a peripheral speed ratio with respect to the photoreceptor 1 by the opposite rotation as in the invention of the present application, the peripheral speed ratio (charging peripheral Speed ratio) is not particularly limited in terms of charging characteristics. However, the collected foreign matter is scattered, and a tape (not shown) is wound around the end of the charging roller 52 in an annular shape and pressed against the photoreceptor 1, and the tape abuts when the charging gap is controlled by the tape thickness. In consideration of reduction of surface wear and the like, the charging peripheral speed ratio is desirably set in the range of 0.2 to 1.0. In the present embodiment, the charging gap is set to 40 μm, and the rotation speed ratio is set to, for example, 0.5 with the rotation of the axis.
[0127]
It should be noted that the charging roller 52 has a peripheral speed ratio with respect to the photosensitive member 1, that is, the charging roller 52 and the photosensitive member 1 have a peripheral speed ratio. Indicate that the surface of the charging roller 52 and the surface of the photoconductor 1 facing each other are rotating at a relative speed in the charging area 5.
[0128]
Further, as shown in FIG. 1, the image forming apparatus is arranged on the upstream side in the rotation direction of the photoconductor 1 with respect to the charging device 51, more specifically, in a region where the charging roller 52 is close to the surface of the photoconductor 1. On the upstream side of a certain charged area 5, a foreign matter disturbing device 41 as foreign matter disturbing means is provided, and foreign matter on the photoreceptor 1, for example, remains on the photoreceptor 1 without being transferred to the transfer material P after the transfer step. It is preferable to disturb the toner 61 (residual toner), residual developer components (residue) such as the carrier 62, paper powder attached to the surface of the photoconductor 1, and the like.
[0129]
The foreign substance disturbing device 41 according to the present embodiment includes a charging area, which is an upstream side in the rotation direction of the photoconductor 1 with respect to the charging device 51, more specifically, an area where the charging roller 52 is close to the surface of the photoconductor 1. 5, a conductive brush 42 is provided in contact with the photoconductor 1, and foreign matter on the photoconductor 1 is disturbed by the conductive brush 42.
[0130]
In the case of reversal development, the main brush polarity (-) of the toner 61 is applied to the conductive brush 42 by a power supply 43 as a voltage (brush bias) applying means, depending on whether the development is the regular development or the reversal development. , Or a bias (+) having the same polarity as the transfer bias (+) is applied. In the case of normal development, the same polarity (+) as the main charging polarity (+) of the toner 61 is applied. ) Or a bias (+) having a polarity opposite to that of the transfer bias (−). Accordingly, the foreign matter disturbing device 41 causes the foreign matter on the photoconductor 1, specifically, the toner 61 (residual toner) remaining on the photoconductor 1 after the transfer, via the conductive brush 42. In the case of reversal development, a reverse polarity (+) or a bias (+) having the same polarity as the transfer bias (+) with respect to the main charging polarity (-) of the used toner 61 is applied to perform normal development. In this case, a bias (+) having the same polarity (+) as the main charging polarity (+) of the used toner 61 or a polarity opposite to the transfer bias (-) is applied.
[0131]
By using a brush structure for the foreign matter stirring means as described above, the foreign matter such as the residual developer component described above passes through the gap between the brushes, thereby preventing the foreign matter from staying and disturbing the foreign matter. In addition, it is possible to prevent the surface of the photoconductor 1 from being damaged.
[0132]
As described above, the foreign matter disturbing means is provided on the upstream side of the charging area 5, and the foreign matter such as the residual developer component remaining on the surface of the photoreceptor 1 without being transferred is disturbed (stirred) and loosened. The efficiency of collecting foreign substances can be improved.
[0133]
Further, as described above, in the case of reversal development, the conductive brush 42 has a polarity (+) opposite to the main charging polarity (-) of the toner 61 or a bias (+) having the same polarity as the transfer bias (+). +), And in the case of regular development, a bias (+) having the same polarity (+) as the main charging polarity (+) of the toner 61 or a polarity opposite to the transfer bias (−) is applied. Thus, the charge of the residual developer component, which is a foreign substance on the photoconductor 1, can be adjusted. That is, when the reversal development is performed as in the present embodiment, the toner 61 having the (−) charge in the development region 4 is slightly positive (+2 kV) in the transfer region as described above due to the transfer bias (+2 kV). The toner 61 is positively charged, that is, positively charged (+) by applying a voltage of, for example, +500 kV by the conductive brush 42. The toner 61, that is, the oppositely charged toner 61b can be more efficiently removed by the charging roller 52. That is, the conductive brush 42 itself has a function as a foreign matter disturbing means, and also has a function as a charge adjusting means for adjusting the charge of the residual developer component.
[0134]
According to the above configuration, by applying the bias to the conductive brush 42, the residual developer component, for example, the initial charge that the residual toner has at the time of development can be lost. In addition, the residual potential remaining on the photoconductor 1 can be flattened, so that the potential of the photoconductor 1 and the voltage of the residual developer component can be adjusted.
[0135]
In addition, due to the bias voltage (brush bias) applied to the conductive brush 42, foreign matter such as a residual developer component does not adhere to the conductive brush 42. Does not occur and the disturbance effect is reduced.
[0136]
Table 3 shows that the conductive brush 42 has a resistance of 10 ⁴ When a conductive brush of Ω · cm is used and a DC voltage of +500 V or −500 V is applied as a brush bias, no voltage is applied (no electrical connection) (floating), and when grounded (0 V), the image quality is improved. Shows the state (image memory).
[0137]
[Table 3]

[0138]
FIG. 8 shows the conductive brush 42 having a resistance value of 10 ⁴ When using a conductive brush of Ω · cm and applying a DC voltage of +500 V or −500 V as a brush bias and grounding (0 V), (1) during development, (2) immediately before transfer (untransferred) 3) shows the results of measuring the amount of charge of the toner 61 after (3) passing through the conductive brush 42 and (4) after being charged by the charging roller 52.
[0139]
In FIG. 8, the ordinate indicates the charge amount (C) of the toner 61, and the abscissa indicates each step described above. In FIG. 8, “◇” indicates a case where a DC voltage of −500 V is applied, “□” indicates a case where no voltage is applied, “場合” indicates a case where a DC voltage of +500 V is applied, and “○” indicates the above-described conductivity. The case where the brush 42 is not used (no brush) is shown.
[0140]
As shown in FIG. 8, it can be seen that when a DC voltage of +500 V is applied to the conductive brush 42, the toner 61 is reversely charged (+).
[0141]
Also, from the results shown in FIG. 8 and Table 3, it can be seen that the memory can be significantly improved by adjusting the charge of the residual toner by the conductive brush 42 and reversely charging the residual toner (+). Here, that the memory can be greatly improved means that the initial charge of the normally charged toner 61a at the time of development can be lost, whereby the toner image memory can be prevented.
[0142]
Here, an image forming process in the image forming apparatus having the above configuration will be described below with reference to FIG.
[0143]
First, the surface of the photoconductor 1 is uniformly charged by the charging device 51. Next, the uniformly charged surface of the photoconductor 1 is irradiated with a laser beam 12 modulated based on image information to be formed from a laser light source 11a of the exposure device 11, and the surface of the photoconductor 1 is moved in the main scanning direction by one. By sequentially exposing in line units, an electrostatic latent image is formed on the photoconductor 1.
[0144]
Next, when the electrostatic latent image passes through the developing device 21, the toner 61 is supplied from the developing roller 23 onto the photosensitive member 1 in the developing area 4, so that the toner 61 Is electrostatically attracted to the electrostatic latent image, and the electrostatic latent image is visualized (toned) as a toner image.
[0145]
The toner image formed on the photoreceptor 1 is transferred to a transfer material P fed from a paper supply unit (not shown) when passing through a nip portion (transfer portion) between the photoreceptor 1 and the transfer device 31. You. Thereafter, the transfer material P is conveyed to a fixing device (not shown), where the toner image is fixed on the transfer material P, so that a permanent visible image is formed. Then, the fixed transfer material P is discharged to a discharge tray (not shown) by a discharge unit (not shown).
[0146]
Residual developer remaining on the photoreceptor 1 without being transferred to the transfer material P at the transfer unit is disturbed (stirred) by the conductive brush 42 and is loosened. Is applied with a reverse polarity (+) to the main charging polarity (-) of the toner 61 or a bias (+) having the same polarity as the transfer bias (+). In the case of normal development, the main charging polarity of the toner 61 is applied. The charge is adjusted by applying a bias (+) of the same polarity (+) or a polarity (+) opposite to the transfer bias (−) to (+).
[0147]
Thereafter, the residual developer component remaining on the photoconductor 1, in particular, the oppositely charged toner 61 b and the carrier 62 are magnetically charged by the charging roller 52 upstream of the charging gap C in the rotation direction of the photoconductor 1. Alternatively, it is electrostatically attracted and cleaned. The residual developer component adsorbed on the charging roller 52 is removed from the charging roller 52 by the cleaning Mylar magnetic attraction film 54 and returned to the developing tank 22. The photoreceptor 1 from which the residual developer component has been removed is uniformly charged again by the charging roller 52, and exposure, exposure, development, transfer, and cleaning are repeated until transfer of a predetermined number of sheets is completed.
[0148]
Further, the unremoved residual developer component (normally charged toner 61 a) remaining on the photoreceptor 1 after passing through the charging roller 52, when passing through the developing device 21, causes the photoreceptor 1 to move away from the developing area 4. On the upstream side in the rotation direction of the developing roller 23, the toner is collected electrostatically or mechanically by the sliding of a magnetic brush (not shown) formed on the developing roller 23 and returned into the developing tank 22.
[0149]
In the above embodiment, a photoconductor drum is described as an example of the photoconductor 1, but the present invention is not limited to this. Instead of the photoconductor drum, an endless conductive material is used. The belt may be a so-called photoreceptor belt stretched between support rollers rotatably provided at intervals. Similarly, in the above-described embodiment, the transfer device 31 including the transfer roller has been described as an example of the transfer unit. However, as the transfer device, an endless conductive belt is provided at intervals. A so-called transfer belt stretched between rotatably provided support rollers may be used.
[0150]
Further, in the above-described embodiment, the charging device 51 includes the cleaning Mylar Mylar Mylar film 54 serving as a foreign material collecting unit, and the cleaning film 54 scrapes off the foreign material adsorbed on the charging roller 52. However, the present invention is not limited to this. For example, instead of using the above-described cleaning film 54, foreign matter scraped by a cleaning blade is collected in a collection container, so that the scraping is performed. It is also possible to adopt a configuration in which foreign matter collected or removed without returning to the inside of the developing tank 22. However, as described above, since the image forming apparatus is provided with the cleaning film 54 as the foreign matter collecting unit or the developing roller 23 as the unremoved residual developer component collecting unit, the carrier 62 and the charge are large. The changed oppositely-charged toner 61b or the normally-charged toner 61a can be returned to the developing tank 22 provided at a position deeper than the developing roller 23 so as to be sufficiently stirred and charged to be reused.
[0151]
As described above, the image forming apparatus according to the present embodiment includes an image carrier on which a latent image is formed on the surface, and a charging member disposed around the image carrier without contact with the surface of the image carrier. A charging device that applies a voltage to the image carrier to charge the image carrier, and a developing unit that develops a latent image formed by the charged charges on the surface of the image carrier with a developer containing at least a toner to form a toner image. A transfer unit for transferring a toner image formed on the image carrier to a transfer material, wherein the charging device comprises: a residual developing unit remaining on the image carrier after the transfer. A charging / cleaning device for adsorbing an agent component onto the charging member to remove the agent component from the image carrier and to charge the image carrier, wherein the charging member and the image carrier move toward each other at a closest position. Move faces facing in different directions Has a configuration in which direction is provided so as to respectively rotate so that the opposite directions to each other. In particular, the image forming apparatus according to the present embodiment is a two-component developing type image forming apparatus using a two-component developer containing a toner and a carrier. The interval at the position is set smaller than the particle size of the carrier as the residual developer component and larger than the particle size of the toner as the residual developer component.
[0152]
More specifically, in the image forming apparatus according to the present embodiment, a charging device for charging a photoconductor is disposed close to the surface of the photoconductor, and the charging device has a conductive cylindrical or columnar shape. A developer including a charging roller including a member and a resistance layer covering the surface thereof, or a charging belt including a resistance layer, a charging brush, and the like, wherein a latent image formed on the photosensitive member includes at least a toner and a carrier In the image forming apparatus, the rotation direction of the charging roller with respect to the rotation axis and the rotation direction of the photosensitive member with respect to the rotation axis rotate in the same direction (Agenst rotation), and the discharge surface of the charging device and the photosensitive surface rotate. An interval (charging gap) at a position closest to the body is set smaller than the carrier attached to the photoconductor and larger than the toner attached to the photoconductor. There.
[0153]
Further, in the image forming method according to the present embodiment, a voltage is applied to an image carrier on which a latent image is formed on a surface, and a charging member arranged around the image carrier in a non-contact manner with the surface of the image carrier. A charging device that applies the electric charge to the image carrier, a developing unit that develops a latent image formed by the charged charges on the surface of the image carrier with a developer containing at least toner to form a toner image, An image forming method using an image forming apparatus provided with a transfer unit for transferring a toner image formed on a carrier to a transfer material, wherein the charging member and the image carrier are mutually moved at a closest position. Rotate the surfaces facing each other in the opposite directions so that the directions of movement are opposite to each other, and adsorb the residual developer component remaining on the image carrier after transfer to the charging member. To remove from the image carrier That while a method of charging the image bearing member.
[0154]
As described above, according to the present embodiment, the charging member and the image carrier are rotated (against rotation) so that the moving directions of the surfaces facing each other at the closest position are opposite to each other. The residual developer component such as the oppositely charged toner remaining on the image carrier after transfer passes through the charging member before passing through the charging gap at the closest position between the discharge surface of the charging member and the image carrier. It is adsorbed to and removed. Therefore, it is possible to prevent the residual developer component such as the oppositely charged toner from entering the charging gap, and to reliably and positively remove and collect the residual developer component from the surface of the image carrier. Can be. For this reason, according to the present embodiment, it is possible to provide an image forming apparatus and an image forming method which can be reduced in size, reduce the power supply voltage, and obtain good image quality. When the charging member removes and recovers the residual developer component, foreign matter (residue) such as transfer material dust adhering to the residual developer component adsorbed by the charging member is also removed from the charging member at the same time. It can be removed and collected from the image carrier. That is, the charging device adsorbs the residual developer component remaining on the image carrier after the transfer to the charging member, and removes foreign matter (residue) containing the residual developer component on the image carrier. Remove from
[0155]
Further, the interval (charging gap) may be set to be three times or more and less than nine times the toner diameter. Since the powder ejection phenomenon occurs remarkably when the particle diameter is three times or less, the above configuration can prevent toner ejection. In addition, since the state in which the powder becomes a bridge and becomes clogged in the charging gap occurs remarkably when the charging gap has an interval of about 9 times the particle diameter, the charging gap should be smaller than 9 times the toner diameter. As a result, the fusion of the toner to the charging roller due to the bridge of the toner can be prevented, and the aggregation of the toner can be prevented from passing through the charging gap, so that the aggregation of the toner enters the developing area. Therefore, it is possible to prevent the image quality from deteriorating.
[0156]
[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIG. In the first embodiment, an image forming apparatus employing a two-component developing method using a two-component developer including a toner 61 and a carrier 62 has been described as an example. In the present embodiment, an image forming apparatus employing a one-component developing method using a one-component developer that does not use the carrier 62 instead of the two-component developing method will be described as an example. In the present embodiment, differences from the first embodiment will be mainly described, and for convenience of description, components having the same functions as those in the first embodiment will be denoted by the same reference numerals, The description is omitted.
[0157]
As shown in FIG. 9, the image forming apparatus according to the present embodiment includes an exposing device 11, a developing device 71, a transfer device 31, a foreign substance disturbing device 41, and a charging device 81 around a photoreceptor 1 as an image carrier. Are arranged in this order from the exposure position, that is, the irradiation position of the laser beam 12 by the exposure device 11 in the rotation direction of the photoconductor 1.
[0158]
In the present embodiment, a one-component developer including the toner 61 described in the first embodiment, which is a magnetic toner, is used as the developer 90. Hereinafter, also in the present embodiment, the case of reversal development will be described as an example, but the present invention is not limited to this.
[0159]
The developing device 71 includes a developing roller 73 serving as a developer supply unit that supplies the developer 90 stored in the developing tank 72 to the photoconductor 1, and the developing roller 73 includes a developer 90 stored in the developing tank 72. A predetermined developing bias and a supply bias are applied to the developing roller 73 and the supply roller 74 from power supplies 75 and 76 as voltage applying means, so that exposure by the exposure device 11 The electrostatic latent image formed on the photoconductor 1 is developed by the toner 61, that is, a visible image (toner image) is formed. Further, the developing device 71 includes a layer thickness regulating member 77 that regulates the thickness of the developer layer on the surface of the developing roller 73, and adjusts the distance between the layer thickness regulating member 77 and the photoconductor 1, and By applying a predetermined bias from a power supply 78 to the layer thickness regulating member 77, the amount of developer supplied onto the photoreceptor 1 is adjusted similarly to the developing device 21 according to the first embodiment. .
[0160]
In the present embodiment, as the developing device 71, a developing device having a conductive roller 73 composed of a conductive element tube 73a and a sleeve 73b that covers the surface of the conductive element tube 73a is used. The developing device 71 is capable of electrostatically attracting the developer 90 to the surface of the sleeve 73 b by applying a developing bias to the developing roller 73. 1 to develop the electrostatic latent image on the surface of the photoconductor 1, while the surface of the photoconductor 1 is located on the upstream side in the rotation direction of the photoconductor 1 from the developing area 4 where the developing roller 73 and the photoconductor 1 are close to each other. Of the unremoved residual developer component (residue after recovery) remaining on the photosensitive member 1 without being transferred, specifically, the regular developer that has not been recovered by the charging device 81 The charged toner 61a (indicated by “-” in FIG. 1) is electrostatically adsorbed to the surface of the sleeve 73b, so that the regular charged toner 61a and foreign matters such as paper adhered to the regular charged toner 61a. From the surface of the photoreceptor 1 It is adapted to remove.
[0161]
That is, the developing roller 73 according to the present exemplary embodiment also applies a developing bias (eg, −420 V) that is more positive than the surface potential of the photoconductor 1 (eg, −600 V), so that the developing roller 73 It is possible to electrostatically attract foreign matters such as the negatively (−) charged normally charged toner 61a remaining on the photoreceptor 1, and the developing roller 73 is also used for the development according to the first embodiment. As with the roller 23, foreign matter such as the normally charged toner 61a remaining on the photoconductor 1 is collected in the developing tank 72 near the upstream side of the photoconductor 1 in the rotation direction in the developing area 4 (developing cleaning method). It functions as an unremoved residual developer component collecting means (normally charged toner collecting means).
[0162]
As a result, the developing device 71 serves as a developing and cleaning device to remove foreign matter such as the unremoved regular charged toner 61 a remaining on the photoconductor 1 after passing through the charging device 81 by the developing roller 73. At a position upstream of the supply position of the developer 90 to the photosensitive member 1 in the rotation direction of the photosensitive member 1, the photosensitive member 1 is cleaned together with the development by being collected by the developing roller 73.
[0163]
The normally charged toner 61a collected by the developing roller 73 is returned to the developing tank 72 provided at a position deeper than the developing roller 73. As a result, in the developing tank 72, a sufficient stirring charge can be given to the collected normal charged toner 61a by a stirring roller (not shown), and the collected normal charged toner 61a is charged in a direction in which the collected normal charged toner 61a crosses each other. After being adjusted to a predetermined charge amount, it can be used again for development. As a result, the toner image memory can be prevented, and the collected normal charged toner 61a can be reused.
[0164]
It is preferable that the developing roller 73 also has a peripheral speed ratio with respect to the photosensitive member 1 similarly to the developing roller 23 in the first embodiment. That is, the developing roller 73 is preferably rotatably provided.
[0165]
Thereby, the collection efficiency of the regular charged toner 61a can be further increased. The peripheral speed ratio of the developing roller 73 to the photosensitive member 1 (developing peripheral speed ratio) depends on the doctor gap that defines the thickness of the developer layer, the toner concentration (T / D) of the developer 90, and the required development amount. It may be set as appropriate, and is not particularly limited, but is preferably set in the same manner as the developing roller 23 in the first embodiment.
[0166]
The developing roller 73 is also provided in non-contact with the photoconductor 1, and the direction of movement of the surface facing the photoconductor 1 at the closest position to the photoconductor 1 is the same as that of the photoconductor 1. It is preferable to be provided so as to rotate (against rotation) in a direction opposite to the moving direction of the surface facing (opposing) the developing roller 73 in the above. That is, the developing roller 73 is rotated by a drive system different from that of the photoconductor 1 so that the rotation direction of the developing roller 73 with respect to the rotation axis and the rotation direction of the photoconductor 1 with respect to the rotation axis are rotated in the same direction. Preferably, it is provided. Thereby, the collection efficiency of the unremoved residual developer component (normally charged toner 61a) can be further increased.
[0167]
The charging device 81 has the same configuration as the charging device 51 in the first embodiment, except that the charging roller 52 in the first embodiment does not include a magnet roller. That is, the charging device 81 according to the present embodiment has a configuration including, as a cylindrical or columnar charging member, the conductive element tube 82a and the resistance layer 82b that covers the surface of the conductive element tube 82a. By applying a voltage from the power supply 53 to the conductive element tube 82a of the charging roller 82, the surface of the photoconductor 1 is charged via the resistance layer 82b.
[0168]
Similarly to the charging roller 52 according to the first embodiment, the charging roller 82 is brought into close proximity to the photoconductor 1 in a non-contact manner by the urging of a spring 55 as a charging gap adjusting unit. The photosensitive member 1 and a surface facing each other are moved in opposite directions at a position closest to the photosensitive member 1 by a driving system different from the photosensitive member 1. It is provided so as to rotate (Agenst rotation). That is, also in the present embodiment, the charging roller 82 and the photoconductor 1 are provided such that the rotation direction of the charging roller 82 with respect to the rotation axis and the rotation direction of the photoconductor 1 with respect to the rotation axis rotate in the same direction. Have been. The charging roller 82 is also capable of electrostatically adsorbing the oppositely charged toner 61b having a positive (+) charge by applying a negative (-) DC voltage as a charging bias. I have.
[0169]
As a result, the charging device 81 according to the present embodiment functions as a charging and cleaning device, and a residual developer component remaining on the photoconductor 1 after transfer, specifically, the photoconductor 1 without being transferred. The oppositely charged toner 61b (indicated by “+” in FIG. 1) of the developer 90 remaining on the upper surface of the developer 90 is adsorbed on the surface of the resistance layer 82b, thereby forming the oppositely charged toner 61b and the oppositely charged toner. As in the case of the charging device 51 according to the first embodiment, foreign matter such as normally charged toner and paper, such as toner 61 and paper, which adhere to the discharge surface of the charging roller 82, are attached to the discharge surface of the charging roller 82. Before passing through a charging gap D which is a gap at a position closest to the body 1, the photosensitive body 1 is removed from the surface of the photosensitive body 1. Therefore, also in the present embodiment, the same effect as in the first embodiment can be obtained.
[0170]
In addition, also in the charging device 81, a superimposed voltage in which an AC voltage is superimposed on a DC component, in this case, a negative (-) DC component current mylar (DC voltage) is applied to the charging roller 82. In addition, foreign matter such as the oppositely charged toner 61b, which is a residue on the surface of the photoreceptor 1, can be vibrated, and the detachment of the foreign matter from the photoreceptor 1 can be promoted. It can be electrostatically attracted and the efficiency of removing the oppositely charged toner 61b can be increased.
[0171]
Also, in the charging device 81, since the cleaning film 54 is provided as a foreign matter collecting means in contact with the charging roller 82, foreign matter such as the oppositely charged toner 61b adsorbed on the charging roller 82 can be removed. The toner is returned to the developing tank 72, and sufficiently stirred and charged in the developing tank 72 to be reused by being subjected to Mylar. In addition, there is no need to provide a cleaning film as a foreign matter collecting means for collecting foreign matter on the surface of the photoconductor 1 on the charging roller 82 in this way, separately from the charging device 81, and the structure of the image forming apparatus is simplified. Can be achieved.
[0172]
The charging gap D between the charging roller 82 and the photoconductor 1 is smaller than the thickness of a transfer material used at the time of transfer, that is, a transfer material P such as a recording (transfer) sheet adhered to the photoconductor 1. Further, it is preferable that the diameter is set to be larger than the particle diameter (toner diameter) of the toner 61.
[0173]
The transfer material P used in the electrophotographic image forming apparatus is, for example, a recording paper, which is thin and about 60 g / m2. ² The thickness is about 60 to 80 μm. For this reason, by setting the interval of the charging gap D to be smaller than the recording material P (recording paper), that is, for example, 60 μm or less, the transfer material P (recording) electrostatically attracted to the photoreceptor 1 by the transfer charge is formed. When the peeling of the paper (paper) fails, the adsorbed transfer material P (recording paper) invades the developing area 4 to make the recovery work from the jam (paper jam) more difficult and to remove the hands and clothes of the recovery worker with toner. The transfer material P (recording paper) adsorbed on the photoreceptor 1 in the transfer area is reliably peeled off by the charging roller 82, and the transfer material P (recording paper) is transferred to the developing area 4 of the transfer material P. Intrusion can be prevented.
[0174]
If the interval between the charging gaps D exceeds 60 μm as described in the first embodiment, abnormal discharge is likely to occur. Therefore, by setting the interval of the charging gap D to 60 μm or less, occurrence of abnormal discharge can be reduced and uneven charging of the photoconductor 1 due to abnormal discharge can be prevented.
[0175]
Further, as described in the first embodiment, the charging gap D is set to 55 μm or less in consideration of a case where the interval of the charging gap D fluctuates from a set value due to a processing error or the like. It is preferable to reduce the fluctuation, and it is more preferable to set the thickness to 40 μm or less in order to perform stable charging.
[0176]
Also, in the present embodiment, when the oppositely charged toner 61b is captured by the charging roller 82 in order to perform cleaning of the oppositely charged toner 61b, the charging gap D of the toner 61 adhering to the photoconductor 1 is set. By setting the interval to be larger than the particle size, it is possible to prevent the residual toner, that is, the toner 61, from being fused to the charging roller 82. Since the normal toner diameter is about 7 μm, it is preferable that the interval of the charging gap D is set to 7 μm or more as described above.
[0177]
Further, also in the present embodiment, as is clear from the “Pasche's empirical formula” indicating the start voltage from the discharge threshold value in the air discharge, the power supply voltage is reduced by reducing the interval of the charging gap D in this manner. Can be lower.
[0178]
As described above, the image forming apparatus according to the present embodiment also includes an image carrier on which a latent image is formed on the surface, and a charging device arranged around the image carrier without contact with the surface of the image carrier. A charging device that applies a voltage to the member to charge the image carrier, and a developing unit that develops a latent image formed by the charged charge on the surface of the image carrier with a developer containing at least a toner to form a toner image And a transfer unit for transferring the toner image formed on the image carrier to a transfer material, wherein the charging device is configured to remove the residual image remaining on the image carrier after the transfer. A charging and cleaning device that removes the developer component from the image carrier by adsorbing to the charging member and charges the image carrier, wherein the charging member and the image carrier are separated from each other at the closest position. On the side facing in the wrong direction Has a structure in which dynamic direction are provided so as to respectively rotate so that the opposite directions to each other.
[0179]
That is, the image forming method according to the present embodiment also includes, as described in the first embodiment, an image carrier on which a latent image is formed on the surface, and the image carrier surface around the image carrier. A charging device that applies a voltage to a charging member arranged in a non-contact manner to charge the image carrier, and develops a latent image formed by the charged charge on the surface of the image carrier with a developer containing at least toner. An image forming method using an image forming apparatus, comprising: a developing unit that forms a toner image by performing the transfer, and a transfer unit that transfers the toner image formed on the image carrier to a transfer material. The image developer is rotated so that the moving directions of the surfaces facing each other at the closest position are opposite to each other, and the remaining developer components remaining on the image carrier after transfer are rotated. To the charging member While it removed from the image bearing member, a method for charging the image bearing member.
[0180]
In particular, in the image forming apparatus according to the present embodiment, the distance between the charging member and the image carrier at the closest position is smaller than the thickness of the transfer material to which the visible image is transferred, and The diameter is set to be larger than the particle diameter of the toner as the developer component.
[0181]
In the present embodiment, the description has been given by exemplifying the image forming apparatus of the one-component developing method using the one-component developer, but the image forming apparatus according to the present embodiment is not limited to this. Instead, the image forming apparatus can be applied to a case where not only a one-component developer but also a two-component developer is used as the developer.
[0182]
More specifically, in the image forming apparatus according to the present embodiment, a charging device for charging a photoconductor is disposed close to the surface of the photoconductor, and the charging device has a conductive cylindrical or columnar shape. An image forming apparatus comprising: a charging roller having a member and a resistance layer covering the surface thereof; and developing the latent image formed on the photoconductor with a developer containing at least a toner and a carrier. The rotation direction with respect to the rotation axis and the rotation direction with respect to the rotation axis of the photoconductor rotate in the same direction (Agenst rotation), and the distance between the discharge surface of the charging device and the photoconductor at the closest position (charging gap). Is set to be smaller than the recording paper adhered to the photoconductor and larger than the toner adhered to the photoconductor.
[0183]
As described above, in the present embodiment, the charging member and the image carrier are respectively rotated (Agenst rotation) such that the movement directions of the surfaces facing each other at the closest position are opposite to each other. By doing so, the residual developer component such as the oppositely charged toner remaining on the image carrier after the transfer, before passing through the charging gap at the closest position between the discharge surface of the charging member and the image carrier, It is absorbed and removed by the charging member. Therefore, it is possible to prevent the residual developer component such as the oppositely charged toner from entering the charging gap, and to reliably and positively remove and collect the residual developer component from the surface of the image carrier. Can be. For this reason, according to the present embodiment, it is possible to provide an image forming apparatus and an image forming method which can be reduced in size, reduce the power supply voltage, and obtain good image quality.
[0184]
Further, in each of Embodiments 1 and 2 described above, a configuration in which a DC voltage is superimposed on an AC voltage (superimposed voltage) is applied to the charging member, but the present invention is not limited to this. Instead, a configuration in which a DC voltage is applied to the charging member may be adopted. That is, the image forming method (image forming apparatus) according to the present invention is a method of applying a DC voltage or a voltage in which an AC voltage is superimposed on a DC voltage (superimposed voltage) to the charging member.
(Configuration).
[0185]
When the voltage is applied to the charging member, the surface potential of the image carrier rises to a predetermined voltage with the progress of charging in the vicinity of the end of the charging area, so that the charging member and the image carrier are In the Wids rotation, which rotates in the same direction at the closest position, the ability to electrostatically recover the oppositely charged toner is greatly reduced, whereas when the opposite rotation is performed as in the present invention, the oppositely charged toner is removed. Is collected and conveyed near the upstream side in the rotation direction of the image carrier from the charging area where charging of the image carrier is started, so that the DC component (DC voltage) of the superimposed voltage is Effectively contributes to electrostatic recovery. Therefore, according to the above configuration, the oppositely charged toner can be efficiently electrostatically attracted. In particular, since a voltage in which an AC voltage is superimposed on a DC current and a current pressure is applied to the charging member, foreign matter such as a residual developer component remaining on the surface of the image carrier after transfer (remaining residual material). ) Can be vibrated, and detachment of the foreign matter such as the residual developer component from the image carrier can be promoted. Therefore, the efficiency of removing the oppositely charged toner can be increased.
[0186]
Further, in this case, in particular, a voltage (superimposed voltage) obtained by superimposing an AC voltage on a DC voltage is applied to the charging member and a magnetic field is formed on the charging member. When the superimposed voltage is applied, the surface potential of the image carrier is charged to a predetermined voltage near the end of the charged area as described above, so that the oppositely charged toner is electrostatically collected in the whisper rotation. In contrast to the present invention, in the case where the axis rotation is performed as in the present invention, the DC component of the superimposed voltage (DC voltage) effectively contributes to the electrostatic recovery of the oppositely charged toner, as described above. The oppositely charged toner can be efficiently electrostatically attracted. At this time, in particular, a foreign substance (residue) having a large mass such as a carrier causes a large load in the electrostatic adsorption and lowers the collection efficiency. However, according to each of the above configurations, a magnetic field is formed on the charging member. By doing so, the carrier can be recovered non-mechanically by magnetic attraction. For this reason, the collection efficiency of foreign substances (residues) having a large mass such as a carrier can be improved.
[0187]
Therefore, according to the above configuration, it is possible to prevent foreign substances such as carrier and toner from entering the charging gap, to prevent the image carrier and the charging member from being damaged, and to prevent deterioration of image quality such as image fogging. It is possible to remove the oppositely charged toner that causes the toner.
[0188]
Further, in an apparatus using a magnetic toner such as magnetic one-component development, it is possible to magnetically collect a normally charged toner or a toner having a small charge amount or an uncharged toner, which is difficult to collect electrostatically.
[0189]
Further, the present invention is not limited to the above embodiments, and various modifications can be made within the scope shown in the claims.
[0190]
For example, the residual developer component adsorbed on the charging member may be collected in the developing tank via a developer supply tank (hopper).
[0191]
In addition, by applying a developing bias in which an alternating voltage is superimposed on a direct current to the developer supply means, an electrostatic force that promotes separation of the residual developer on the image carrier is applied to promote recovery from the image carrier. You may.
[0192]
Further, embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.
[0193]
【The invention's effect】
As described above, the image forming apparatus according to the present invention is configured such that a voltage is applied to the image carrier on which the latent image is formed on the surface and the charging member disposed around the image carrier in a non-contact manner with the surface of the image carrier. A developing device for developing a latent image formed by the charged charges on the surface of the image carrier with a developer containing at least a toner to form a toner image; An image forming apparatus including a transfer unit configured to transfer a toner image formed on the image carrier to a transfer material, wherein the charging device removes the residual developer component remaining on the image carrier after the transfer. A charging and cleaning device that removes the image carrier from the image carrier by attracting the same to the charging member and charges the image carrier. The charging member and the image carrier face each other in a direction in which they pass each other at a closest position. Direction of the moving surface In a configuration that is provided so as to respectively rotate so that the opposite direction.
[0194]
Further, as described above, the image forming method according to the present invention includes an image carrier on which a latent image is formed on a surface, and a charging member arranged around the image carrier without contact with the surface of the image carrier. A charging device that applies a voltage to the image carrier to charge the image carrier, and a developing unit that develops a latent image formed by the charged charges on the surface of the image carrier with a developer containing at least a toner to form a toner image. An image forming method using an image forming apparatus including a transfer unit that transfers a toner image formed on the image carrier to a transfer material, wherein the charging member and the image carrier are disposed at the closest position. The image bearing members are rotated so that the directions of movement of the surfaces facing each other in opposite directions are opposite to each other, and the residual developer component remaining on the image carrier after transfer is adsorbed to the charging member and the image carrier is transferred. While removing from the body, A structure for charging a Kizo carrier.
[0195]
Therefore, the residual developer component such as the oppositely charged toner remaining on the image carrier after transfer passes through the charging gap at the closest position between the discharge surface of the charging member and the image carrier. It is absorbed and removed by the charging member. Therefore, it is possible to prevent the residual developer component such as the oppositely charged toner from entering the charging gap, and to reliably and positively remove and collect the residual developer component from the surface of the image carrier. Can be. Therefore, it is possible to reduce the size of the apparatus and reduce the power supply voltage without requiring a dedicated cleaning apparatus as in the related art.
[0196]
In particular, when reversal development is used, image fogging caused by the oppositely charged toner adhered to the white background area on the surface of the image carrier, which is an important issue, is prevented by removing the oppositely charged toner that causes the image fogging. And a remarkable effect for improving the image quality can be exerted.
[0197]
Further, according to each of the above configurations, it is possible to prevent the film of the image carrier from being reduced due to the cleaning, to prevent the occurrence of the rubbing trace, and to reduce the load torque of the image carrier.
[0198]
Further, according to each of the above configurations, since the charging member is rotated against the image carrier, the residual developer component can be prevented from entering the charging gap, and the charging member can be suppressed. Since the relative traveling distance between the charging surface of the charging member and the charging surface of the image carrier at the position closest to the image carrier and the image carrier is increased, the charging characteristics of the image carrier are improved.
[0199]
Therefore, according to each of the above configurations, it is possible to provide an image forming apparatus that is small in size, can reduce the power supply voltage, and can obtain good image quality.
[0200]
As described above, in the image forming apparatus according to the present invention, the distance (charging gap) between the charging member and the image carrier at the closest position is smaller than the thickness of the transfer material on which the visible image is transferred. Further, the configuration is larger than the particle size of the toner as the residual developer component.
[0201]
In the image forming method according to the present invention, as described above, the distance between the charging member and the image carrier at the closest position is smaller than the thickness of the transfer material on which the visible image is transferred, and In this configuration, the particle diameter is set to be larger than the particle diameter of the toner that is the residual developer component.
[0202]
According to each of the above configurations, the distance (charging gap) at the closest position between the charging member and the image carrier is set smaller than the thickness of the transfer material, so that the electrostatic charge is applied to the image carrier by the transfer charge. When the transfer material that has been removed fails, the adsorbed transfer material enters the developing area, making recovery work from jams (paper jam) more difficult and soiling the hands and clothes of the recovery worker with toner. The transfer material adsorbed on the image carrier in the transfer area can be reliably peeled off by the charging member, and the transfer material can be prevented from entering the development area. Further, according to the above configuration, considering the thickness of a general transfer material, by setting the charging gap to be smaller than the thickness of the transfer material, the occurrence of abnormal discharge is reduced, and the image due to abnormal discharge is reduced. It is possible to prevent charging unevenness of the carrier. Further, by setting the charging gap to be small, the power supply voltage can be lowered as is clear from the “Pasche's empirical formula”.
[0203]
In addition, when the oppositely charged toner is captured by a charging member in order to perform the remaining developer component, particularly, the oppositely charged toner, the charging gap is made larger than the particle diameter of the toner, whereby the toner to the charging member is formed. (Fusing of the oppositely charged toner) can be prevented.
[0204]
As described above, the image forming apparatus according to the present invention is an image forming apparatus of a two-component developing system using a two-component developer including a toner and a carrier, and includes the charging member and the image bearing member. The distance (charging gap) at the position closest to the body is smaller than the particle size of the carrier as the residual developer component and larger than the particle size of the toner as the residual developer component.
[0205]
In the image forming method according to the present invention, as described above, when a two-component developer containing a toner and a carrier is used as the developer, the distance between the charging member and the image carrier at the closest position is set. In this configuration, the particle diameter is set smaller than the particle diameter of the carrier as the residual developer component and larger than the particle diameter of the toner as the residual developer component.
[0206]
According to each of the above configurations, the distance (charging gap) at the closest position between the charging member and the image carrier is set to be smaller than the particle diameter of the carrier as the residual developer component. Intrusion of carriers into the gap can be completely eliminated. Further, by setting the charging gap smaller than the particle diameter of the carrier, the charging state of the image carrier can be stabilized, so that good image quality can be obtained. Moreover, according to each of the above-described configurations, the occurrence of abnormal discharge is reduced by setting the charging gap to be smaller than the particle size of the carrier, considering the particle size of a general carrier. It is possible to prevent charging unevenness of the image carrier. Further, by setting the charging gap to be small, the power supply voltage can be lowered as is clear from the “Pasche's empirical formula”.
[0207]
Further, when the oppositely charged toner is captured by a charging member in order to clean the residual developer component, in particular, the oppositely charged toner and the carrier, the charging gap is made larger than the toner particle size, so that the charging is performed. The effect of preventing the fusion of the toner to the member (the fusion of the oppositely charged toner) can be achieved.
As described above, the image forming apparatus according to the present invention has a configuration in which a voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging member.
[0208]
Further, the image forming method according to the present invention has a configuration in which a voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging member as described above.
[0209]
When the opposite rotation is performed as in the present invention, the oppositely charged toner is collected and conveyed near the rotation direction upstream side of the image carrier from the charged area where charging to the image carrier is started. The DC component (DC voltage) of the superimposed voltage effectively contributes to the electrostatic recovery of the oppositely charged toner. For this reason, according to each of the above configurations, the oppositely charged toner can be efficiently electrostatically attracted. According to each of the above configurations, the charging member is applied with a voltage in which an AC voltage is superimposed on a DC current, a current, a current, or a current pressure, so that the charging member remains on the surface of the image carrier after transfer. It is possible to vibrate foreign substances (residues) such as residual developer components, and to promote the detachment of the foreign substances such as residual developer components from the image carrier. For this reason, the effect that the efficiency of removing the oppositely charged toner can be increased is also exhibited.
[0210]
As described above, the image forming apparatus according to the present invention has a configuration in which a magnetic field is formed on the charging member.
[0211]
Further, the image forming method according to the present invention has a configuration in which a magnetic field is formed on the charging member as described above.
[0212]
According to each of the above-described configurations, since a magnetic field is formed in the charging member, a carrier having a large mass or a magnetic material such as a magnetic toner can be non-mechanically recovered by magnetic attraction. For this reason, the collection efficiency of the carrier and the like can be increased.
[0213]
Therefore, according to each of the above-described configurations, it is possible to prevent foreign substances such as carriers and toner from entering the charging gap. Accordingly, it is possible to prevent the image carrier and the charging member from being damaged due to the entry of the carrier and the like into the charging gap. Another effect is that the oppositely charged toner that originally adheres to the white background area and is developed and causes image quality deterioration such as image fogging that is fogged can be removed.
[0214]
Further, in an apparatus using a magnetic toner such as magnetic one-component development, an effect that electrostatic collection is difficult, a normally charged toner, or a minutely charged or uncharged toner can also be collected magnetically. To play.
[0215]
As described above, in the image forming apparatus according to the present invention, the charging device has a residual developer component collecting unit that collects the residual developer component adsorbed on the charging member into the developing tank in the developing unit. This is the configuration.
[0216]
According to the above configuration, the charging device has the residual developer component recovery unit that recovers the residual developer component adsorbed on the charging member, so that the residual developer adsorbed on the charging member is provided. In particular, when a two-component developer containing a toner and a carrier is used as the developer, when the residual developer component is adsorbed on the charging member, and when the two-component developer is adsorbed on the charging member, When the residual developer component is collected by the residual developer component, the toner is positively scraped off by the carrier. As a result, the recovery efficiency of the residual developer component, particularly the oppositely charged toner, is improved by the charging member and the residual developer component recovery means, so that the remaining undeveloped residual developer remaining on the image carrier after passing through the charging device is improved. The collection efficiency of the agent component (normally charged toner) can be improved. In addition to being able to lose the initial charge that the collected residual developer component had at the time of development, poor charging and the like that occur when the residual developer component adsorbed on the charging member reenters the charging area. It can be prevented before it happens.
[0217]
Further, according to the above configuration, the residual developer component adsorbed on the charging member is recovered in the developing tank of the developing unit, and the residual developer having been sufficiently stirred and charged in the developing tank is recovered. After the residual developer component is adjusted to a predetermined charge amount by giving it to the component, it can be used again for development. As a result, an effect that image deterioration of a toner image memory or the like can be prevented can be achieved.
[0218]
As described above, the image forming apparatus according to the present invention has a configuration in which the foreign matter disturbing unit that disturbs the foreign matter on the image carrier is provided upstream of the charging member in the rotation direction of the image carrier. is there.
[0219]
According to the above configuration, the foreign matter such as the residual developer component remaining on the surface of the image carrier without being transferred by the transfer unit is disturbed (stirred) and loosened, thereby improving the efficiency of collecting the foreign matter in the charging member. At the same time, there is an effect that the image memory caused by the residual developer component can be mechanically prevented.
[0220]
As described above, in the image forming apparatus according to the present invention, as described above, the foreign matter disturbing unit is configured such that the residual developer component on the image carrier has a polarity opposite to the main charging polarity of the toner in the case of reversal development, or A bias having the same polarity as the transfer bias is applied, and in the case of normal development, a bias having the same polarity as the main charging polarity of the toner or a bias having a polarity opposite to the transfer bias is applied to charge the residual developer component. This is a configuration having a charge adjusting means for adjusting.
[0221]
Further, as described above, the image forming method according to the present invention, before adsorbing the residual developer component to the charging member and removing the same, removes the residual developer component on the image carrier in advance by reversal development. In the case of, a polarity opposite to the main charging polarity of the toner, or a bias having the same polarity as the transfer bias is applied, and in the case of normal development, the same polarity as the main charging polarity of the toner, or with the transfer bias. In this configuration, a bias of the opposite polarity is applied to adjust the charge of the residual developer component.
[0222]
According to each of the above configurations, the foreign matter disturbing means supplies the residual developer component on the image carrier, specifically, the residual toner via the charge adjusting means, to the main charge of the toner in the case of reversal development. Apply a reverse polarity (+) to the polarity (-) or a bias (+) having the same polarity as the transfer bias (+). In the case of normal development, the same bias is applied to the main charging polarity (+) of the toner. By applying a polarity (+) or a bias (+) having a polarity opposite to that of the transfer bias (-) to adjust the charge of the residual developer component (residual toner), the image is transferred onto the image carrier after transfer. The remaining toner is positively charged reversely, that is, positively (+), whereby foreign matters such as reversely charged toner can be more efficiently removed by the charging member.
[0223]
Further, according to each of the above configurations, the bias voltage is applied to the residual developer component on the image carrier through the charge adjusting unit, so that the residual developer component, for example, the residual toner has during development. The initial charge can be lost, the toner image memory can be prevented, and the residual potential remaining on the image carrier can be flattened. This also has the effect that the voltage of the residual developer component can be adjusted.
[0224]
As described above, the image forming apparatus according to the present invention has a configuration in which the foreign substance disrupting unit includes a conductive brush.
[0225]
According to the arrangement, since the foreign matter disturbing means includes the conductive brush, the foreign matter such as the residual developer component can pass through the gap of the conductive brush. This has the effect of preventing stagnation of foreign matter and disturbing the foreign matter, and preventing the surface of the image carrier from being damaged.
[0226]
As described above, the image forming apparatus according to the present invention is configured such that the developing unit recovers an unremoved residual developer component remaining on the image carrier after passing through the charging device. The configuration is a development / cleaning device having a collection unit.
[0227]
Further, the image forming method according to the present invention is configured such that the unremoved residual developer component remaining on the image carrier after passing through the charging device is recovered by the developing unit as described above. .
[0228]
According to each of the above-described configurations, the residual developer component, particularly, the image quality deterioration, and especially the cause of image fogging, due to the charging member located on the upstream side in the rotation direction of the image carrier with respect to the developing and cleaning device. Since the oppositely charged toner is recovered, a good image can be maintained by the developing cleaning method.
[0229]
Further, according to the above configuration, by integrating the developing device and the cleaning device, there is also an effect that the size of the image forming apparatus can be reduced.
[0230]
As described above, the image forming apparatus according to the present invention has a configuration in which the developer supply unit and the image carrier have a peripheral speed ratio.
[0231]
According to the above configuration, since the developer supply unit and the image carrier have a peripheral speed ratio, unremoved residual development remaining on the image carrier after passing through the charging device. There is an effect that the recovery efficiency of the agent component can be further increased.
[0232]
As described above, in the image forming apparatus according to the present invention, as described above, the developer supply unit moves in the direction in which the developer and the image bearing member face each other at a position closest to the image bearing member. Are provided so as to rotate in opposite directions.
[0233]
According to the above configuration, the unremoved residual developer component remaining on the image carrier after passing through the charging device can be collected before the residual developer component passes through the developing gap. For this reason, there is an effect that the recovery efficiency of the unremoved residual developer component can be further increased.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing charging stability of a photoconductor when a charging gap is set to 25 μm in the image forming apparatus.
FIG. 3 is a graph showing charging stability of a photoconductor when a charging gap is set to 40 μm in the image forming apparatus.
FIG. 4 is a graph showing charging stability of a photoconductor when a charging gap is set to 55 μm in the image forming apparatus.
FIG. 5 is a graph showing the charging stability of the photoconductor when the charging gap is 190 μm in the image forming apparatus.
FIG. 6 is a graph showing a variation of a charging potential of a photoconductor with respect to a set gap.
FIG. 7 is another graph showing a variation of a charging potential of a photoconductor with respect to a set gap.
FIG. 8 is a graph showing a relationship between a brush bias and a charge amount of toner.
FIG. 9 is a schematic configuration diagram of a main part of an image forming apparatus according to another embodiment of the present invention.
[Explanation of symbols]
1 Photoconductor (image carrier)
4 Development area
5 Charged area
11 Exposure equipment
21 Developing device (developing means)
22 Developing tank
23 Developing roller (remaining developer component collecting means)
23a Magnet roll
23b sleeve
25 Power supply
31 Transfer device (transfer means)
32 transfer roller
33 power supply
41 Foreign substance disturbing device (foreign substance disturbing means)
42 conductive brush (charge adjusting means)
43 Power
51 Transfer device
52 Charging roller (charging member)
52a conductive tube
52b resistance layer
53 power supply
54 Cleaning Mylar Film (Residual developer component recovery means)
60 developer
61 Toner
61a Regularly charged toner
61b reverse charge toner
62 career
63 Transfer material waste
71 Developing device (developing means)
72 Developing tank
73 developing roller (remaining developer component collecting means)
73a conductive tube
73b sleeve
75 Power
81 Charging device
82 charging roller (charging member)
82a conductive tube
82b resistance layer
90 Developer
A Doctor gap
B Development gap
C charging gap
D Charging gap
P transfer material

Claims (19)

An image carrier on which a latent image is formed on the surface, and a charging device for charging the image carrier by applying a voltage to a charging member disposed in non-contact with the image carrier surface around the image carrier. Developing means for developing a latent image formed by the charged charges on the surface of the image carrier with a developer containing at least toner to form a toner image; and transferring the toner image formed on the image carrier to a transfer material. An image forming apparatus having a transfer unit for transferring,
The charging device is a charging and cleaning device that adsorbs the residual developer component remaining on the image carrier after transfer to the charging member to remove the developer component from the image carrier and charges the image carrier. The charging member and the image bearing member are an image forming apparatus of a one-component developing system using a four-component developer in a direction in which the charging member and the image carrier cross each other at the closest position.
An image forming apparatus characterized by being provided so as to rotate so that the movement directions of two facing surfaces are opposite to each other. The distance between the charging member and the image carrier at the closest position is smaller than the thickness of the transfer material on which the visible image is transferred, and larger than the particle size of the toner as the residual developer component. The image forming apparatus according to claim 1. The image forming apparatus is a two-component developing type image forming apparatus using a two-component developer including a toner and a carrier,
The distance between the charging member and the image carrier at the closest position is smaller than the particle size of the carrier as the residual developer component and larger than the particle size of the toner as the residual developer component. The image forming apparatus according to claim 1. The image forming apparatus according to claim 1, wherein a voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging member. The image forming apparatus according to claim 1, wherein a magnetic field is formed on the charging member. 2. The image according to claim 1, wherein said charging device has a residual developer component collecting means for collecting the residual developer component adsorbed on said charging member into a developing tank in said developing means. Forming equipment. 2. The image forming apparatus according to claim 1, further comprising: a foreign matter disturbing unit that disturbs foreign matter on the image carrier at a position upstream of the charging member in a rotation direction of the image carrier. In the case of reversal development, the foreign matter disturbing means applies a reverse polarity to the main charging polarity of the toner, or a bias having the same polarity as the transfer bias, to the residual developer component on the image carrier, and performs normal development. In the case of (1), a charge adjusting means for adjusting the charge of the residual developer component by applying a bias having the same polarity as the main charging polarity of the toner or a polarity opposite to the transfer bias is provided. The image forming apparatus according to claim 7, wherein 8. The image forming apparatus according to claim 7, wherein said foreign matter disturbing means includes a conductive brush. The developing means is a developing and cleaning device having an unremoved residual developer component recovery means for recovering an unremoved residual developer component remaining on the image carrier after passing through the charging device. The image forming apparatus according to claim 1. 11. The image forming apparatus according to claim 10, wherein the developer supply unit and the image carrier have a peripheral speed ratio. The developer supply means is provided so as to rotate in a direction in which the developer and the surface facing each other cross each other at a position closest to the image carrier so that the moving directions of the surfaces facing each other are opposite to each other. The image forming apparatus according to claim 10, wherein: An image carrier on which a latent image is formed, and a charging device that charges the image carrier by applying a voltage to a charging member disposed in a non-contact manner with the image carrier surface around the image carrier. Developing means for developing a latent image formed by the charged charges on the surface of the image carrier with a developer containing at least toner to form a toner image; and transferring the toner image formed on the image carrier to a transfer material. In an image forming method using an image forming apparatus having a transfer unit for transferring,
When using the one-component developer as the developer, the charging member and the image carrier are moved in mutually opposite directions at the closest position. Rotating, removing the residual developer component remaining on the image carrier after the transfer from the image carrier by adsorbing to the charging member, and charging the image carrier. Image forming method. The distance between the charging member and the image carrier at the closest position is set smaller than the thickness of the transfer material on which the visible image is transferred, and larger than the particle size of the toner as the residual developer component. 14. The image forming method according to claim 13, wherein: When a two-component developer containing a toner and a carrier is used as the developer, the distance between the charging member and the image carrier at the closest position is smaller than the particle size of the carrier as a residual developer component, and 14. The image forming method according to claim 13, wherein the particle size is set to be larger than the particle size of the toner as the residual developer component. The image forming method according to claim 13, wherein a voltage obtained by superimposing an AC voltage on a DC voltage is applied to the charging member. 14. The image forming method according to claim 13, wherein a magnetic field is formed by applying a voltage in which an alternating current is superimposed on a direct current in a state where the charging member is in contact with the charging member. Before adsorbing and removing the residual developer component by the charging member, in advance, the residual developer component on the image carrier, in the case of reversal development, the polarity opposite to the main charging polarity of the toner, or A bias having the same polarity as the transfer bias is applied, and in the case of normal development, a bias having the same polarity as the main charging polarity of the toner or a bias having a polarity opposite to the transfer bias is applied to charge the residual developer component. 14. The image forming method according to claim 13, wherein is adjusted. 14. The image forming method according to claim 13, wherein an unremoved residual developer component remaining on the image carrier after passing through the charging device is collected by the developing unit.

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