JP2004061855A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for forming an image of high image quality over a long period by reducing a load applied to a cleaning blade for an imaging element. <P>SOLUTION: The image forming apparatus is provided with a plurality of toner image forming units, a primary transfer mechanism, a secondary transfer mechanism and a fixing device. The toner image forming unit is provided with a lubricant applying means for applying lubricant to the surface of the imaging element, and an imaging element cleaning means. When r<SB>b</SB>stands for the volume mean diameter of black toner and r<SB>c</SB>for<SB></SB>the volume mean diameter of color toner, r<SB>b</SB>> r<SB>c</SB>+1 and r<SB>c</SB>=3 to 7 hold. The quantity of the lubricant applied to the outer circumferential surface of the imaging element employing the black toner is made larger than that applied to the outer circumferential surface of the imaging element employing the color toner. <P>COPYRIGHT: (C)2004,JPO

Description

【００６０】
上記式において、「粒度分布より真球と仮定して算出された比表面積」とは、日本電子社販売のレーザ回折式粒度分布測定装置ヘロス（ＨＥＲＯＳ）により測定されたものであり、５０ｃｃのビーカに測定試料と界面活性剤と分散媒である水とを添加した後、出力１５０Ｗの超音波ホモジナイザーにより６０秒間にわたって混合することによりトナー粒子の分散が行われる。また、「ＢＥＴ比表面積」は、島津製作所製のマイクロメリテックス・フローソープＩＩ２３００型により測定されたものである。
【００６１】
この形状係数を制御する方法は特に限定されるものではない。例えばトナー粒子を熱気粒中に噴霧する方法、またはトナー粒子を気相中において衝撃力による機械的エネルギーを繰り返して付与する方法、あるいはトナーを溶解しない溶媒中に添加し旋回流を付与する方法などによりトナーを調製する方法、または、いわゆる重合トナーを調製する段階で全体の形状を制御する方法がある。
【００６２】
上記方法の中では、重合トナーが製造方法として簡便である点と、粉砕トナーに比較して表面の均一性に優れる点などで好ましい。
【００６３】
上記の画像形成装置においては、次のようにして画像記プロセスが行われる。すなわち、トナー像形成ユニット２０Ｙにおいては、例えば、回転される感光体２１Ｙの表面が、帯電手段２２により所定の極性（例えば負極性）に順次に帯電され、この状態において感光体２１Ｙの表面に露光手段２３Ｙにより選択的に光が照射されることにより、照射箇所（露光領域）の電位が低下して原稿画像に対応した静電潜像が形成される。
【００６４】
一方、現像器２４Ｙを構成する現像スリーブ２４１Ｙの表面に対して、感光体２１Ｙの表面電位と同じ極性（例えば負極性）の現像バイアスが図示しない電源より印加され、現像スリーブ２４１Ｙの表面電位と同じ極性（例えば負極性）に帯電されたトナーを含む現像剤が、その搬送量が規制された状態で現像領域ＰＹに搬送される。そして、現像領域ＰＹにおいて、現像スリーブ２４１Ｙ上のトナーが感光体２１Ｙの露光領域に付着して反転現像が行われて、感光体２１Ｙ上にトナー像が形成される。
【００６５】
このような動作が、各トナー像形成ユニット２０Ｍ、２０Ｃおよび２０Ｋにおいて行われて、各色のトナー像が形成される。
【００６６】
トナー像形成ユニット２０Ｙ、２０Ｍ、２０Ｃおよび２０Ｋの各々において形成された各色のトナー像は、それぞれの一次転写領域Ｔ１Ｙ、Ｔ１Ｍ、Ｔ１Ｃ、Ｔ１Ｋにおいて中間転写ベルト１０上に順次に一次転写されて、中間転写ベルト１０上で各色のトナー像が重ね合わせられることにより一次転写トナー像が形成され、この一次転写トナー像は、中間転写ベルト１０に担持されたまま二次転写領域Ｔ２へと搬送され、二次転写領域Ｔ２において、二次転写ローラ４１と駆動ローラ１２とにより形成される転写電界の作用により、中間転写ベルト１０に担持された一次転写トナー像と同期がとられた状態で搬送路に沿って搬送されてきた画像記録材Ｒ上に二次転写されて二次転写トナー像が形成される。その後、定着装置５０により熱定着されて画像記録材Ｒ上にカラー画像が形成される。
【００６７】
そして、二次転写領域Ｔ２を通過した中間転写ベルト１０上に残留する未転写トナーは、中間転写体クリーニング手段４５における中間転写体クリーニングブレード４６により除去される。
【００６８】
ここで、トナー像形成ユニット２０Ｙにおいては、感光体２１Ｙの回転方向に対して一次転写領域Ｔ１Ｙの下流に設けられた塗布領域Ｓ３において、その外周表面に対して潤滑剤塗布手段３０Ｙにより潤滑剤の塗布が行われる。
【００６９】
すなわち、上述のトナー像の形成工程が行われるのと同時にフリッカーローラ３３が特定の方向（図２においては、反時計回り方向）に回転駆動されることにより、掻取領域Ｓ１において、その外周表面に潤滑剤ストック３４が掻き取られると共に、接触領域Ｓ２において、同様に特定の方向（図２においては、時計回り方向）に回転駆動されたブラシローラ３２に潤滑剤がフリッカーローラ３３から拭き取られるように採取され、更に、塗布領域Ｓ３において、潤滑剤付着した状態のブラシローラ３２が、感光体２１Ｙの外周表面に接触することにより、当該感光体２１Ｙの外周表面に予め設定された量の潤滑剤塗布される。
ここで、フリッカーローラ３３は、その回転方向における接触領域Ｓ２の下流領域において、スクレーパ３５により、その外周表面に残留した潤滑剤が除去され、これによりクリーニングされた状態が達成される。
【００７０】
以上において、ブラシローラ３２は、感光体２１Ｙに潤滑剤を塗布すると同時に、未転写トナーの一部を除去するプレ−クリーニング手段としての作用をも有するものである。すなわち、塗布領域において、感光体２１Ｙとブラシローラ３２とが接触することにより、感光体２１Ｙの外周表面に残留した未転写トナーがブラシローラ３２のブラシ繊維に付着し、この未転写トナーは、当該ブラシ繊維がフリッカーローラ３３と接触することにより除去される。更に、フリッカーローラ３３の表面に付着した未転写トナーは、上述のようにスクレーパ３５により、前記潤滑剤３３と共に、除去されてクリーニングされる。
【００７１】
このようなトナー像形成ユニット２０Ｙにおける潤滑剤の塗布動作は、各トナー像形成ユニット２０Ｍ、２０Ｃおよび２０Ｋの感光体２１Ｍ、２１Ｃ、および２１Ｋの各々に対しても行われる。
【００７２】
ここで、各トナー像形成ユニット２０Ｙ、２０Ｍ、２０Ｃおよび２０Ｋにおいては、一回の画像形成プロセスにおいて感光体２１Ｙ、２１Ｍ、２１Ｃ、２１Ｋに対して塗布される潤滑剤の量が適宜に調整されるものである。
【００７３】
例えばトナー像形成ユニット２０Ｋにおいて一回の画像形成プロセス毎に感光体２１Ｋの外周表面に対して塗布される潤滑剤の量が、トナー像形成ユニット２０Ｙ、２０Ｍおよび２０Ｃにおいて一回の画像形成プロセス毎に、感光体２１Ｙ、２１Ｍ、および２１Ｃの各々の外周表面に対して塗布される潤滑剤の量より多くなるよう、潤滑剤塗布手段３０Ｙ、３０Ｍ、３０Ｃ、３０Ｋの各々が制御される。
【００７４】
ここで、感光体２１Ｙ、２１Ｍ、２１Ｃ、２１Ｋに対する潤滑剤の塗布量の制御は、押圧機構３６におけるカム板３６１を回転させることにより行うことが可能であり、例えばカム板３６１を回転させることにより生じるカム作用を利用して、他方の支持板３６３をバネ３６４を収縮させながら一方の支持板３６２に対して押圧し、これにより潤滑剤ストック３４に対して、フリッカーローラ３３に対する弾発力よりなる押圧力を作用させて、当該フリッカーローラ３３に対する潤滑剤ストック３４の押圧力を可変的に高くすることにより、感光体２１Ｙ、２１Ｍ、２１Ｃ、２１Ｋに塗布される潤滑剤の量を適宜に増やすことができる。
【００７５】
トナー像形成ユニット２０Ｋにおいては、一回の画像形成プロセス毎に感光体２１Ｋの外周表面に対して、感光体２１Ｙ、２１Ｍ、２１Ｃの各々に対して塗布される潤滑剤の量の１５０％以上、好ましくは２００％以上の量の潤滑剤が塗布されるよう潤滑剤塗布手段３０Ｋが制御される。
具体的には、感光体２１Ｋに対して感光体２１Ｙ、２１Ｍ、２１Ｃの各々に対して塗布される潤滑剤の量の１５０〜３００％、特に好ましくは、２００〜２５０％の量の潤滑剤が塗布されるよう潤滑剤塗布手段３０Ｋが制御される。
【００７６】
また、一回の画像形成プロセス毎に感光体２１Ｙ、２１Ｍ、２１Ｃ、２１Ｋの外周表面に対して塗布される潤滑剤の量は、例えば各感光体２１Ｙ、２１Ｍ、２１Ｃ、２１Ｋにおいて行われた画像形成プロセス数の累計に応じて、または現像処理が行われる環境における環境湿度に応じて塗布される潤滑剤の量を調整することができる。
【００７７】
すなわち、感光体２１Ｋおいて行われる画像形成プロセス数の累計が０〜５００００回である場合には、感光体２１Ｙ、２１Ｍ、２１Ｃに塗布される潤滑剤の量の１５０〜２５０％の量の潤滑剤を、感光体２１Ｋの外周表面に対して塗布することが好ましく、特に当該画像形成プロセス数の累計が５００００回を超える場合には、感光体２１Ｙ、２１Ｍ、２１Ｃに塗布される潤滑剤の量の２００〜３００％の量の潤滑剤を、感光体２１Ｋの外周表面に対して塗布することが好ましい。
【００７８】
また、湿度センサー２６Ｋにおいて測定された環境湿度が１０〜４０％であ　る場合には、感光体２１Ｙ、２１Ｍ、２１Ｃに塗布される潤滑剤の量の２００〜３００％の量の潤滑剤を感光体２１Ｋに対して塗布することが好ましく、特に、環境湿度が４０％を超える場合には、感光体２１Ｙ、２１Ｍ、２１Ｃに塗布される潤滑剤の量の１５０〜２５０％の量の潤滑剤を感光体２１Ｋに対して塗布することが好ましい。
【００７９】
以上において、上述のようにブラックトナーに係る感光体２１Ｋに対して塗布する潤滑剤の量を設定した後において、当該塗布量の基準となったカラートナーに係る感光体２１Ｙ、２１Ｍ、２１Ｃに塗布される潤滑剤の量が少なくなるよう制御することにより、画像形成装置全体における潤滑剤の総使用量を抑制することが可能である。
【００８０】
本発明の画像形成装置によれば、ブラックトナーに係る像形成体の外周表面に対して塗布される潤滑剤の量を、ブラックトナー以外のカラートナーに係る像形成体の外周表面に対して塗布される潤滑剤の量に比較して多くすることにより、カラートナーと比較して、大きい体積平均粒径を有するブラックトナーを用いた場合であっても、トナー像における中抜け現象の発生が抑制されると共に、像形成体の外周表面において高いクリーニング効果を得ることができるため、像形成体および像形成体クリーニング手段を構成するクリーニングブレードに対する負荷が低減される。
【００８１】
その結果、使用頻度の高いブラックトナーに係るトナー像形成ユニットにおいても、像形成体および像形成体クリーニングブレードの磨耗速度を低減させることができることにより、所期のクリーニング効果を長期間にわたって得ることができ、従って、高い画質の画像を長期にわたって安定的に形成することが可能である。
【００８２】
本発明の他の態様によれば、ブラックトナーに係る像形成体の外周表面に対して塗布される潤滑剤の量を、カラートナーに係る像形成体の外周表面に対して塗布される潤滑剤の量に比較して多くすることにより、カラートナーと比較して球形度が小さいブラックトナーを用いた場合であっても、トナー像の転写効率が向上して像形成体の外周表面に残留する未転写トナーが低減すると共に、像形成体の外周表面において高いクリーニング効果を得ることができるため、像形成体および像形成体クリーニング手段を構成するクリーニングブレードに対する負荷が低減される。
【００８３】
その結果、使用頻度の高いブラックトナーに係るトナー像形成ユニットにおいても、像形成体および像形成体クリーニングブレードの磨耗速度が低減させることができることにより、所期のクリーニング効果を長期間にわたって得ることができ、従って、高い画質の画像を長期にわたって安定的に形成することが可能である。
【００８４】
以上において、像形成体の外周表面に対して塗布される潤滑剤の量を、画像形成プロセス数の累計に応じて調整することにより、画像形成プロセスを行うに従って、クリーニングブレードが次第に劣化した場合においても、既述のように高い効率により前記トナー像における中抜け現象の発生を抑制し、または、トナー像の転写効率の向上により像形成体の外周表面に残留する未転写トナーを低減させることができて、前記像形成体の外周表面における高いクリーニング効果を確実に得ることができる。その結果、所期のクリーニング効果を長期間にわたって得ることができ、従って、高い画質の画像を長期にわたって安定的に形成することが可能である。
【００８５】
また、像形成体の外周表面に対して塗布される潤滑剤の量を、環境湿度に応じて調整することにより、環境湿度が変化して転写条件が変動した場合においても、既述のように高い効率により前記トナー像における中抜け現象の発生を抑制し、または、トナー像の転写効率の向上により像形成体の外周表面に残留する未転写トナーを低減させることができ、前記像形成体の外周表面における高いクリーニング効果を確実に得ることができる。その結果、所期のクリーニング効果を長期間にわたって得ることができ、従って、高い画質の画像を長期にわたって安定的に形成することが可能である。
【００８６】
以上において、カラートナーに係る像形成体に対して塗布される潤滑剤の量を少なくすることによって、本発明の効果を良好に達成することができると共に、画像形成装置全体において消費される潤滑剤の総量を抑制することが可能である。
【００８７】
以上、本発明の実施の形態について説明したが、本発明は上記の態様に限定されるものではなく、種々の変更を加えることができる。
例えば、感光体に対して塗布される潤滑剤の量の調整は、潤滑剤の硬度を調整することにより行うこと、フリッカーローラおよびブラシローラが回転駆動される線速度を制御すること、フリッカーローラを構成する潤滑剤掻取層の材質、表面処理状態を制御すること、更にはブラシローラを形成するブラシ繊維の径、長さ、材質および植設密度などを適宜選択することなどによっても可能である。
【００８８】
また、ブラシローラは、導電性を有するブラシ繊維により構成されると共に、直流電源に接続されることにより、当該ブラシ繊維に対して電圧の印加が可能な構成とされていてもよく、この場合には、感光体に対する高い予備クリーニング効果を得ることが可能である。
【００８９】
＜実験例＞
以下、本発明の実験例について説明する。
図１に示す構成に従って、図２に示す潤滑剤塗布手段が設けられてなるデジタルカラー複写機を製造した。
【００９０】
（１）感光体
感光体は、外径６０ｍｍ、厚み１ｍｍのアルミニウムよりなるドラム状の金属基体の外周面に、フタロシアニン顔料を含有せしめたポリカーボネートよりなる厚さ２５μｍの感光層が形成された有機感光体を用い、線速度を２８０ｍｍ／ｓｅｃとなる状態に設定した。
【００９１】
（２）現像器
現像器は、回転駆動される外径２５ｍｍの現像スリーブを備え、この現像スリーブに感光体の表面電位と同極性のバイアス電圧が印加されて反転現像が行われるものを使用した。
【００９２】
（３）中間転写ベルト
中間転写ベルトは、グンゼ株式会社製のポリイミドベルトを使用し、線速度を２８０ｍｍ／ｓｅｃとなる状態に設定した。
【００９３】
（４）中間転写体クリーニング装置
中間転写体クリーニングブレードとしては、ウレタンゴムよりなる厚さが２．００ｍｍのものを用いた。
【００９４】
（５）潤滑剤塗布手段
潤滑剤塗布手段は、径が６．２５ｄ、長さが３．５ｍｍの導電性アクリル樹脂よりなるブラシ繊維が、６００００本／ｉｎｃｈ^２となる植設密度で植毛されて形成された、最大径が２０ｍｍのブラシローラと、外径が１０ｍｍ、厚みが１．０ｍｍのアルミニウムよりなるフリッカーローラと、ＰＥＴよりなる厚さが２ｍｍのスクレーパとにより構成した。
ここで、ブラシローラは、線速度を３００ｍｍ／ｓｅｃとなる状態に設定し、フリッカーローラは、線速度を１５０ｍｍ／ｓｅｃとなる状態に設定した。
【００９５】
（６）感光体クリーニング手段
感光体クリーニングブレードとしては、ＰＥＴよりなる厚さが２ｍｍのものを用い、作動状態において、クリーニングブレードの先端部が感光体の移動方向と反対方向（カウンター方向）に向く状態となるよう設置すると共に、感光体に対する当接角度が１０°、当接荷重が１３ｇ／　ｃｍとなるよう設定した。
【００９６】
（７）バイアス電圧印加手段
二次転写ローラに接続されるバイアス電圧印加手段は、トナーの帯電電位と逆極性（正極性）およびトナーの帯電電位と同極性（負極性）のいずれの極性のバイアス電圧であっても二次転写ローラに印加可能に構成されたものを使用し、原稿画像に対応するトナー像を転写紙に転写するに際して、転写機能が制限されない状態において、＋６００Ｖの転写バイアス電圧が二次転写ローラに印加されるよう設定した。
【００９７】
＜実験例１＞
上記の構成の画像形成装置において、現像剤として、体積平均粒径が５．０μｍであるイエロートナー粒子、マゼンタトナー粒子、シアントナー粒子と共に、体積平均粒径が６．０μｍであるブラックトナー粒子を用い、かつ、画像形成プロセス毎におけるブラックトナーに係る感光体に対する潤滑剤の塗布量を、カラートナーに係る感光体の各々に対する潤滑剤の塗布量の２００％とする条件において画像形成プロセスを１０００００回行い、形成された画像における中抜け現象の発生を目視にて評価した。
その結果、形成された画像のすべてにおいて中抜け現象を確認することはできず、長期にわたって高い画質画像の形成を安定的に行うことができることが確認された。
【００９８】
＜実験例２＞
上記の構成の画像形成装置において、現像剤として、形状係数が０．９６であって、体積平均粒径が５．０μｍであるイエロートナー粒子、マゼンタトナー粒子、シアントナー粒子と共に、形状係数が０．９４であって、体積平均粒径が５．０μｍであるブラックトナー粒子を用い、かつ、画像形成プロセス毎におけるブラックトナーに係る感光体に対する潤滑剤の塗布量を、カラートナーに係る感光体の各々に対する潤滑剤の塗布量の２００％とする条件において画像形成プロセスを１０００００回行い、クリーニングブレードと感光体における劣化の状態を目視にて評価した。
その結果、クリーニングブレードと感光体との両方において、良好な状態が維持されており、画像形成プロセスにおいてこの両者にかかる負荷が低減されたことが確認された。
【００９９】
以上、本発明の画像形成装置について詳細に説明したが、この画像形成装置においては、以下のような制御を行うことも可能である。
すなわち、イエロートナー、マゼンタトナー、シアントナーの各々に係るトナー像形成ユニット２０Ｙ、２０Ｍおよび２０Ｃにおいて、一回の画像形成プロセス毎に感光体２１Ｙ、２１Ｍおよび２１Ｃの各々の外周表面に対して塗布される潤滑剤の量が、ブラックトナーに係るトナー像形成ユニット２０Ｋにおいて一回の画像形成プロセス毎に、感光体２１Ｋの外周表面に対して塗布される潤滑剤の量より多くなるよう、潤滑剤塗布手段３０Ｙ、３０Ｍ、３０Ｃ、３０Ｋの各々を制御することが可能である。
【０１００】
斯かる態様で画像形成プロセスを行うことにより、ブラックトナーと比較して小さい体積平均粒径を有するイエロートナー、マゼンタトナー、シアントナーを用いた場合であっても、トナー像の転写効率が向上して像形成体の外周表面に残留する未転写トナーが低減すると共に、像形成体の外周表面における高いクリーニング性を得ることができるため、像形成体および像形成体クリーニング手段を構成するクリーニングブレードに対する負荷が低減される。
【０１０１】
また、ブラックトナーと比較して、球形度が高いイエロートナー、マゼンタトナー、シアントナーを用いた場合であっても、トナー像における中抜け現象の発生が抑制されると共に、像形成体の外周表面における高いクリーニング性を得ることができるため、像形成体および像形成体クリーニング手段を構成するクリーニングブレードに対する負荷が低減される。
【０１０２】
この結果、イエロートナー、マゼンタトナー、シアントナーの各々に係るトナー像形成ユニットにおいても、像形成体および像形成体クリーニングブレードの磨耗速度を低減させることができることにより、所期のクリーニング効果を長期間にわたって得ることができ、結局、高い画質のカラー画像を長期にわたって安定的に形成することが可能である。
【０１０３】
【発明の効果】
本発明の画像形成装置によれば、特定の範囲の体積平均粒径を有する、ブラックトナー以外のカラートナーとの関係において設定される固有の体積平均粒径を有するブラックトナー、または、特定の範囲の形状係数を有するカラートナーとの関係において設定される固有の形状係数を有するブラックトナーを用いると共に、当該ブラックトナーに係るトナー像形成ユニットにおける像形成体に対する潤滑剤の塗布量を、カラートナーに係るトナー像形成ユニットにおける像形成体の各々に対する潤滑剤の塗布量より多くすることによって、ブラックトナーを用いた画像形成プロセスの過程においてトナー像の転写効率が向上するために像形成体の外周表面に残留する未定着トナーの割合が小さくなり、また、中抜け現象の発生が抑制されるため、当該像形成体および像形成体に係るクリーニングブレードに対する負荷が小さいものとなる。
【図面の簡単な説明】
【図１】本発明の画像形成装置の一例における構成の概略を示す説明図である。
【図２】トナー像形成ユニットの構成を示す説明用断面図である。
【符号の説明】
１０　中間転写ベルト
１２　駆動ローラ
１３　テンションローラ
１４　対接ローラ
２０Ｙ、２０Ｍ、２０Ｃ、２０Ｋ　トナー像形成ユニット
２１Ｙ、２１Ｍ、２１Ｃ、２１Ｋ　感光体
２２Ｙ、２２Ｍ、２２Ｃ、２２Ｋ　帯電手段
２３Ｙ、２３Ｍ、２３Ｃ、２３Ｋ　露光手段
２４Ｙ、２４Ｍ、２４Ｃ、２４Ｋ　現像器
２４１Ｙ　現像スリーブ
２５Ｙ、２５Ｍ、２５Ｃ、２５Ｋ　一次転写ローラ
２６Ｙ、２６Ｍ、２６Ｃ、２６Ｋ　湿度センサー
３０Ｙ、３０Ｍ、３０Ｃ、３０Ｋ　潤滑剤塗布手段
３１Ｙ、３１Ｍ、３１Ｃ、３１Ｋ　感光体クリーニングブレード
３２　ブラシローラ
３３　フリッカーローラ
３４　潤滑剤ストック
３５　スクレーパ
３６　押圧機構
３６１　カム板
３６１Ａ　回転中心支点
３６２　支持板
３６３　支持板
３６４　バネ
４０　二次転写機構
４１　二次転写ローラ
４２　バイアス電圧印加手段
４５　中間転写体クリーニング手段
４６　中間転写体クリーニングブレード
５０　定着装置
５１　加熱ローラ
５１１　加熱源
５２　加圧ローラ
ＰＹ、ＰＭ、ＰＣ、ＰＫ　現像領域
Ｒ　画像記録材
Ｓ１　掻取領域
Ｓ２　接触領域
Ｓ３　塗布領域
Ｔ１Ｙ、Ｔ１Ｍ、Ｔ１Ｃ、Ｔ１Ｋ　一次転写領域
Ｔ２　二次転写領域[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus.
[0002]
[Prior art]
At present, for example, in some types of color image forming apparatuses that form a color image by an electrophotographic method, a plurality of toner image forming units including an image forming body on which a toner image is formed are sequentially arranged, The toner images of each color formed by these toner image forming units are sequentially primary-transferred to a common endless intermediate transfer belt and stacked on the intermediate transfer body to form a primary transfer toner image. The secondary transfer toner image is formed by collectively secondary transferring the primary transfer toner image thus formed onto an image recording material such as transfer paper, and fixing the secondary transfer toner image to the image recording material by an appropriate method. Has been adopted.
[0003]
In the toner image forming unit of such an image forming apparatus, in the rotation direction of the image forming body, the toner image formed on the outer peripheral surface is formed in a downstream area of the primary transfer area where the toner image is transferred to the intermediate transfer body. A lubricant applying means for applying a lubricant to the outer peripheral surface of the body and an image forming body cleaning means for removing untransferred toner remaining on the image forming body after passing through the primary transfer area are provided. ing.
[0004]
As the lubricant applying means, for example, a means for applying a solid lubricant to the outer peripheral surface of the image forming body by using an appropriate method such as a brush roller is used.
As the image forming body cleaning means, for example, a flat cleaning blade made of an elastic body is brought into contact with the outer peripheral surface of the image forming body and the surface is rubbed, so that the untransferred portion remaining on the image forming body is A blade cleaning method for mechanically removing toner is used.
[0005]
In recent years, there has been a strong demand for higher image quality in such image forming apparatuses. For example, it has been demanded that a high quality image equivalent to that formed by printing can be formed. In response to the request, for example, a toner having a small particle diameter or a toner having a high sphericity has been used.
[0006]
On the other hand, a toner having a small particle diameter or a high sphericity is liable to cause so-called “slip-through” or the like and is inferior in cleaning property. In order to achieve a desired cleaning effect in an image forming body, an image is required. In the formed body cleaning means, it is necessary to increase the contact pressure of the cleaning blade against the image forming body to enhance the cleaning effect.
[0007]
However, when the contact pressure in the cleaning blade is increased, the cleaning effect is improved, but the image forming body and the cleaning member are inevitably caused by a large frictional force inevitably generated between the cleaning blade and the image forming body. The load on the blade becomes excessive, and the progress of deterioration or wear in both cases increases. As a result, blade turning and chattering are apt to occur, and the cleaning effect is reduced. As a result, it is difficult to form a high quality image stably for a long period of time.
[0008]
In the toner image forming unit for the black toner, the frequency of use is higher than that for the toner image forming unit for the color toner. There is a problem that it is particularly noticeable.
[0009]
[Problems to be solved by the invention]
In view of the above problems, by increasing the particle size of the black toner or decreasing the sphericity of the black toner, the cleaning property of the black toner itself is improved, and the cleaning of the image forming body and the image forming body is performed. It is also contemplated to reduce the load on the cleaning blade in the means.
[0010]
However, when toner particles having a large particle diameter are used, a hollowing-out phenomenon is likely to occur in the course of the image forming process, and when toner particles having a low sphericity are used, the primary transfer area is reduced. The transfer efficiency of the toner image decreases, the amount of untransferred toner remaining on the outer peripheral surface of the image forming body increases, and the load on the cleaning blade becomes large. There is a problem that cannot be formed.
[0011]
The present invention has been made based on the above circumstances, and an object thereof is to provide a toner image forming unit in which a load on an image forming body and a cleaning blade related to the image forming body is small, and an image of high image quality is obtained. An object of the present invention is to provide an image forming apparatus that can stably form the image over a long period.
[0012]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes an image forming body that is driven to rotate, and forms a toner image by developing an electrostatic latent image formed on the image forming body using black toner and color toner. A plurality of toner image forming units, a primary transfer mechanism that stacks and transfers the toner images to an intermediate transfer body in a primary transfer area to form a primary transfer toner image, and the primary transfer toner image on an image recording material. A secondary transfer mechanism that collectively transfers and forms a secondary transfer toner image, and a fixing device that fixes the secondary transfer toner image to an image recording material,
A toner application unit configured to apply a lubricant to a surface of the image forming body in a downstream area of the primary transfer area in a rotation direction of the image forming body; An image forming apparatus having an image forming body cleaning unit that removes untransferred toner remaining on the formed body by a cleaning blade made of an elastic body, which is provided to be in contact with the surface of the image forming body,
The volume average particle diameter [μm] of the black toner constituting the toner image in each toner image forming unit is represented by r _b The volume average particle size [μm] of the color toner _c When
r _b > R _c +1 [μm], and
r _c = 3-7 [μm]
In the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is one time in the toner image forming unit for the color toner. The amount of the lubricant applied to the outer peripheral surface of the image forming body is set to be larger for each process.
[0013]
In the above, the amount of the lubricant applied to the outer peripheral surface of the image forming body in one image forming process in the toner image forming unit for the black toner is one time in the toner image forming unit for the color toner. It is preferable that the amount is set to 150% or more of the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process.
[0014]
Further, in the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is controlled according to the total number of the image forming processes. Is preferred.
Further, it is preferable that the amount of the lubricant applied to the outer peripheral surface of the image forming body in one image forming process in the toner image forming unit for the black toner is controlled according to the environmental humidity.
[0015]
An image forming apparatus according to the present invention includes an image forming body that is driven to rotate, and forms a toner image by developing an electrostatic latent image formed on the image forming body using black toner and color toner. A plurality of toner image forming units, a primary transfer mechanism that stacks and transfers the toner images to an intermediate transfer body in a primary transfer area to form a primary transfer toner image, and the primary transfer toner image on an image recording material. A secondary transfer mechanism that collectively transfers and forms a secondary transfer toner image, and a fixing device that fixes the secondary transfer toner image to an image recording material,
A toner application unit configured to apply a lubricant to a surface of the image forming body in a downstream area of the primary transfer area in a rotation direction of the image forming body; An image forming apparatus having an image forming body cleaning unit that removes untransferred toner remaining on the formed body by a cleaning blade made of an elastic body, which is provided to be in contact with the surface of the image forming body,
The shape factor of the black toner constituting the toner image in each toner image forming unit is k _b , The shape factor of the color toner is k _c When
k _b > K _c −0.01, and
k _c = 0.94 to 0.98,
In the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is one time in the toner image forming unit for the color toner. The amount of the lubricant applied to the outer peripheral surface of the image forming body is set to be larger for each process.
[0016]
Here, in the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body in one image forming process is one time in the toner image forming unit for the color toner. It is preferable that the amount is set to 150% or more of the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process.
[0017]
Further, in the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is controlled according to the total number of the image forming processes. Is preferred.
It is preferable that the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process in the toner image forming unit for the black toner is controlled according to the environmental humidity.
Further, the volume average particle diameter of the black toner and the color toner is preferably 3 to 7 μm.
[0018]
[Action]
According to the image forming apparatus of the present invention, it is set in relation to a color toner other than the black toner (hereinafter, also simply referred to as “color toner”) having a specific range of volume average particle diameter. A black toner having a specific volume average particle diameter, or a black toner having a specific shape coefficient set in relation to a color toner having a shape coefficient in a specific range, and a toner image related to the black toner. The process of the image forming process using the black toner by making the amount of the lubricant applied to the image forming unit in the forming unit larger than the amount of the lubricant applied to each of the image forming units in the toner image forming unit for the color toner Unfixed toner remaining on the outer peripheral surface of the image forming body in order to improve the transfer efficiency of the toner image at Ratio of decreases, and since the occurrence of poor transfer phenomenon is suppressed, it becomes load on the cleaning blade according to the image forming body and the image forming member is small.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view schematically showing the configuration of an example of the image forming apparatus of the present invention, and FIG. 2 is a cross-sectional view for explaining the configuration of a toner image forming unit.
This image forming apparatus sequentially transfers each color toner image formed by each of the four toner image forming units to an intermediate transfer member, thereby superimposing the respective color toner images on the intermediate transfer member, and forming the color toner images thereon. The secondary transfer toner image is transferred onto the image recording material such as transfer paper at a time, thereby forming a secondary transfer toner image on the image recording material. A visible image is formed by fixing to a recording material.
[0020]
More specifically, the color image forming apparatus includes an endless intermediate transfer belt 10 which is an intermediate transfer member. In the toner image forming unit arrangement area of the intermediate transfer belt 10, the intermediate transfer belt 10 is provided. The four toner image forming units 20Y, 20M, 20C, and 20K, which will be described later, are provided in this order along the moving direction.
[0021]
The intermediate transfer belt 10 is provided with toner image forming units 20Y, 20M, 20C, and 20K by primary transfer rollers 25Y, 25M, 25C, and 25K provided corresponding to the toner image forming units 20Y, 20M, 20C, and 20K, respectively. Are stretched around a support roller group including, for example, a drive roller 12 and a tension roller 13 so as to be circulated and moved while being in contact with each of the photoconductors 21Y, 21M, 21C, and 21K, which are image forming bodies. It is arranged in.
[0022]
At a position downstream of the toner image forming unit arrangement area in the moving direction of the intermediate transfer belt 10, a secondary transfer roller 41 as a secondary transfer unit is pressed by the drive roller 12 via the intermediate transfer belt 10 to perform secondary transfer. The secondary transfer roller 41 is provided with a bias voltage applying means 42 for applying an appropriate transfer bias voltage, thereby forming a primary transfer toner on the image recording material R. A secondary transfer mechanism 40 for transferring an image is configured.
[0023]
At a position downstream of the secondary transfer area T2 in the movement direction of the intermediate transfer belt 10, the leading edge abuts on the surface of the intermediate transfer belt 10 so as to face the contact roller 14 via the intermediate transfer belt 10. An intermediate transfer member cleaning means 45 provided with a blade cleaning mechanism having a plate-like intermediate transfer member cleaning blade 46 made of an elastic material such as urethane rubber and arranged to extend in the width direction of the intermediate transfer belt 10. ing.
[0024]
In FIG. 1, a fixing device 50 fixes the secondary transfer toner image formed on the image recording material R by the secondary transfer mechanism 40. The fixing device 50 includes a heating roller 51 having a heating source 511 therein, A pressure roller 52 is provided so as to be in pressure contact with the heating roller 51 to form a fixing nip portion.
[0025]
Here, the intermediate transfer belt 10 is made of, for example, a resin material such as polycarbonate (PC), polyimide (PI), polyamide imide (PAI), polyvinylidene fluoride (PVDF), and tetrafluoroethylene-ethylene copolymer (ETFE). , Conductive material such as carbon dispersed in rubber material such as ethylene-propylene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), polyurethane rubber, or ionic conductive material Can be used.
[0026]
The volume resistivity of the intermediate transfer belt 10 is, for example, 10 ¹² -10 ^Fifteen It is preferably Ω · cm.
The thickness of the intermediate transfer belt 10 is preferably, for example, 50 to 200 μm for a resin material and 300 to 700 μm for a rubber material.
[0027]
The secondary transfer roller 41 is configured by, for example, forming a semiconductive coating layer made of an elastic material on the outer peripheral surface of a conductive metal core made of stainless steel.
The elastic body constituting the coating layer is not particularly limited. For example, an elastic body in which a conductive filler such as carbon is dispersed in a rubber material such as polyurethane, EPDM, or silicone, or an ionic And the like containing the conductive material described above.
[0028]
As described above, the toner image forming unit 20Y disposed at the most upstream position with respect to the moving direction of the intermediate transfer belt 10 includes a drum-shaped photoconductor 21Y that is driven to rotate as shown in FIG. In the outer peripheral surface area of the body 21Y, a charging unit 22Y, a humidity sensor 26Y for measuring environmental humidity, an exposure unit 23Y serving as an image writing unit, and a developer containing a yellow toner in the developing area PY with respect to the rotation direction of the photoconductor 21Y. And developing devices 24Y for performing the development are arranged in the order of operation.
[0029]
A primary transfer roller that transfers a toner image formed on the photoconductor 21Y to the intermediate transfer belt 10 by applying an appropriate transfer electric field to a position downstream of the developing area PY with respect to the rotation direction of the photoconductor 21Y. 25Y are provided, thereby constituting a primary transfer mechanism including a primary transfer area T1Y.
[0030]
Further, in an area downstream of the primary transfer area T1Y in the rotation direction of the photoconductor 21Y, a lubricant application unit 30Y that applies a lubricant to the outer peripheral surface of the photoconductor 21Y in the application area S3, and a photoconductor cleaning unit Is provided.
[0031]
The photoreceptor 21Y is formed of a drum-shaped metal substrate made of, for example, aluminum and having a photosensitive layer formed on the outer peripheral surface thereof, and extends in the width direction of the intermediate transfer belt 10 (in FIG. 2, a direction perpendicular to the paper surface). It is arranged as follows.
[0032]
The photosensitive layer is made of, for example, selenium, arsenic selenium, amorphous selenium (a-Se), cadmium sulfide (CdS), zinc oxide (ZnO). ₂ ), An inorganic photosensitive layer made of amorphous silicon (a-Si) or the like, an organic photosensitive layer made of an organic photoconductive compound, or the like.
[0033]
A preferred embodiment of the photoreceptor 21Y is an organic photoreceptor (OPC) in which a photosensitive layer made of a resin containing an organic photoconductor is formed, in which a charge transport layer and a charge generation layer are laminated. A function-separated type is particularly preferred.
[0034]
The charging unit 22Y is composed of, for example, a scorotron charger, and is disposed to face the photoconductor 21Y so as to extend in the rotation axis direction of the photoconductor 21Y.
[0035]
The exposure unit 23Y is configured by a digital optical system that converts the digitized image data into an optical signal and exposes the photoreceptor 21Y, for example, a laser irradiation device, and includes a light source (not shown) including, for example, a laser diode. Is scanned by an optical system including various optical lenses and optical mirrors, and is selectively irradiated onto the surface of the photoconductor 21Y.
[0036]
The developing device 24Y includes a developing sleeve 241Y which is a developer carrying member arranged to face the photoconductor 21Y via the developing area PY. The developing sleeve 241Y has, for example, a plurality of magnetic poles. A developing magnet composed of a plurality of columnar magnet bodies is fixedly provided.
[0037]
As shown in FIG. 2, the lubricant applying means 30 </ b> Y contacts the lubricant stock 34 formed of a solid lubricant having a generally elongated rectangular parallelepiped shape, and the surface of the lubricant stock 34 in the scraping area S <b> 1. A cylindrical flicker roller 33 extending in a direction along the axis of rotation (perpendicular to the paper surface in FIG. 2); In the outer peripheral surface area, a brush roller 32 that is driven to rotate while contacting the flicker roller 33 in a contact area S2 opposite to the lubricant stock 34, and supports the lubricant stock 34 so as to press against the flicker roller 33. It comprises a pressing mechanism 36.
[0038]
At a position downstream of the contact area S2 with respect to the rotation direction of the flicker roller 33, for example, PET formed so as to extend in the width direction of the flicker roller 33 with its leading edge abutting on the outer peripheral surface of the flicker roller 33. A plate scraper 35 made of a plate or the like is provided.
[0039]
The pressing mechanism 36 comes into contact with the other support plate 363, which is disposed via a spring 364 on one support plate 362 that supports the lubricant stock 34 in a mounted state, and the back surface of the other support plate 363. The pressing force applied to the lubricant stock 34 can be adjusted by a cam mechanism including an elliptical cam plate 361 provided to rotate around the rotation center fulcrum 361A. Here, the cam plate 361 is connected to a drive source (not shown).
[0040]
In such a lubricant applying unit 30Y, the consumption of the lubricant stock 34 is 0.02 to 1.0 mg / number of image forming processes, particularly preferably 0.05 to 0.3 mg / number of image forming processes. Any material having a function of applying a lubricant to the outer peripheral surface of the photoconductor 21Y under the conditions may be used.
[0041]
The magnitude of the pressing force applied by the pressing mechanism 36 to press the lubricant stock 34 against the flicker roller 33 may be appropriately determined according to various conditions such as the material constituting the flicker roller 32 and the rotation speed. Although good, it is preferably, for example, 5 to 30 g / cm, and particularly preferably 10 to 20 g / cm.
[0042]
According to the pressing mechanism 36 described above, the pressing force for pressing the lubricant stock 34 against the flicker roller 33 can be adjusted to an appropriate magnitude. The lubricant stock 34 can reliably contact the roller 33.
[0043]
Examples of the material of the brush fibers forming the brush roller 32 include conductive acrylic resin, acrylic resin, rayon, nylon, polycarbonate, polyester, methacrylic acid resin, polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene, polyvinyl acetate, and styrene. -Butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, phenol formaldehyde resin, and the like. Can be used alone or in combination of two or more.
[0044]
The brush fibers constituting the brush have a diameter of, for example, 2.0 to 15.0 denier (d), particularly 3.0 to 7.0 denier (d), and furthermore, 6.25 denier (d). It is preferable that the planting density is (the number of brush fibers per unit area), for example, 50 to 200,000 fibers / inch. ² , Especially 50,000 to 200,000 / inch ² , And 60000 pieces / inch ² The length is preferably 1.0 to 6.0 mm, particularly 3.0 to 5.0 mm, and more preferably 3.5 mm.
[0045]
Here, the brush roller 32 has a state where the bite amount with respect to the flicker roller 33 is, for example, 0.5 to 1.0 mm, and / or a state where the bite amount with respect to the photoconductor 21Y is, for example, 0.5 to 1.0 mm. It is preferable that Here, “the amount of bite into the flicker roller 33” or “the amount of bite into the photoconductor 21Y” refers to the case where the flicker roller 33 or the photoconductor 21Y does not exist, the tip of the brush fiber is normal to the outer periphery of each brush fiber. It is the maximum value of the amount (length) that protrudes inward in the direction.
[0046]
The rotation speed of the brush roller 32 is determined in relation to the linear speed of the photoconductor 21Y and / or the flicker roller 33. For example, when the linear speed of the photoconductor 21Y is 60 to 240 mm / sec. In addition, the linear velocity is preferably 30 to 360 mm / sec, and particularly preferably 90 to 300 mm / sec.
[0047]
As the flicker roller 33, a roller formed by forming a lubricant scraping layer on the outer peripheral surface of a drum-shaped metal base made of, for example, aluminum is used.
Further, the rotation speed of the flicker roller 33 is preferably a linear speed of 20 to 240 mm / sec, and particularly preferably 30 to 160 mm / sec.
[0048]
As the lubricant forming the lubricant stock 34, for example, a fatty acid metal salt such as zinc stearate or the like can be preferably used, and if necessary, an appropriate additive is added to thereby adjust the hardness of the lubricant. Agent stock 34 can be used.
[0049]
The photoconductor cleaning blade (hereinafter, also simply referred to as “cleaning blade”) 31 </ b> Y is arranged to extend in the width direction of the photoconductor 21 </ b> Y with its leading edge abutting on the outer peripheral surface of the photoconductor 21 </ b> Y. It is a plate-like thing made of an elastic body such as.
[0050]
The contact load of the cleaning blade 31Y on the photoreceptor 21Y is preferably 0.1 to 30 g / cm, more preferably 1 to 25 g / cm. If the contact load is too small, the intended cleaning effect cannot be obtained, and image stains are likely to occur. On the other hand, when the contact load is excessive, the abrasion of the photoreceptor 21Y and the cleaning blade 31Y increases, and fog, image blur, and the like are likely to occur.
The contact load can be measured by pressing the leading edge of the cleaning blade 31Y against the balance, or by arranging a sensor such as a load cell at the contact position between the photoconductor 21Y and the leading edge of the cleaning blade 31Y, And the like.
[0051]
The contact angle of the cleaning blade 31Y with respect to the photoreceptor 21Y is preferably 0 to 40 °, more preferably 0 to 25 °. If the contact angle is too small, the cleaning ability is reduced, and image stains are likely to occur. On the other hand, if the contact angle is excessive, the so-called “blade turn-up” in which the leading edge of the cleaning blade 31Y reverses following the photoreceptor 21Y easily occurs. Here, the “contact angle with respect to the photoconductor 21Y” refers to a tangent plane of the photoconductor 21Y at a contact position between the leading edge of the cleaning blade 31Y and the photoconductor 21Y, and an inner surface of a base end portion of the cleaning blade 31Y ( In FIG. 2, it refers to an angle between the photosensitive member 21Y and a surface facing the surface of the photosensitive member 21Y.
[0052]
Each of the other toner image forming units 20M, 20C, and 20K has the same configuration as the first toner image forming unit 20Y for the yellow toner, and includes charging units 22M, 22C, 22K, and humidity sensors 26M, 26C, 26K, exposure units 23M, 23C, 23K, developing units 24M, 24C, 24K for developing with a developer containing magenta toner, cyan toner and black toner, and primary transfer rollers 25M, 25C, 25K, respectively. The lubricant applying means 30M, 30C, and 30K and the photoconductor cleaning means including the cleaning blades 31M, 31C, and 31K are arranged in the order of operation with respect to the rotation direction of the photoconductors 21M, 21C, and 21K.
[0053]
As the toner constituting the developer used in the present invention, a color toner may have a volume average particle diameter r. _c 3 to 7 μm, particularly preferably 3.5 to 6.5 μm, and more preferably 4 to 6 μm. Thereby, the occurrence of the hollow phenomenon is suppressed, and an image having high image quality can be formed.
[0054]
Further, as a black toner, a volume average particle diameter r _b Is r _b > R _c +1 [μm]. As a result, the black toner itself has higher cleaning properties than the color toner, and as a result, the desired cleaning effect can be reliably obtained in the photoconductor 21Y.
[0055]
As a toner constituting a developer used in the present invention, a color toner has a shape coefficient k _c Of toner particles having a particle size of 0.94 to 0.98 can be preferably used. Thereby, excellent transfer efficiency is exhibited, and an image having high image quality can be formed.
[0056]
Further, as the black toner, the shape coefficient k _b Is k _b > K _c -0.01 is satisfied. As a result, the black toner itself has a higher cleaning property than the color toner, and as a result, the desired cleaning effect can be reliably obtained in the photoconductor 21.
[0057]
Here, as the black toner and the color toner having the shape coefficient in the above range as the developer, those having a volume average particle diameter of 3 to 7 μm are used, and particularly preferably, the respective volume average particles are used. One having a diameter of 4.5 to 6.5 μm is used.
[0058]
In the above, the shape factor of the toner of the present invention is represented by the following equation, and indicates the degree of roundness of the toner particles.
[0059]
(Equation 1)

[0060]
In the above formula, the “specific surface area calculated assuming a true sphere from the particle size distribution” is a value measured by a laser diffraction type particle size distribution measuring device HEROS sold by JEOL Ltd., and is a 50 cc beaker. After adding a measurement sample, a surfactant, and water as a dispersion medium, the mixture is mixed with an ultrasonic homogenizer having an output of 150 W for 60 seconds to disperse the toner particles. The “BET specific surface area” is measured by using Micromeritex Flow Soap II2300 manufactured by Shimadzu Corporation.
[0061]
The method for controlling the shape factor is not particularly limited. For example, a method in which toner particles are sprayed into hot air particles, a method in which toner particles are repeatedly applied with mechanical energy in a gas phase by an impact force, or a method in which a toner particle is added to a solvent in which a toner is not dissolved and a swirling flow is applied. And a method of controlling the overall shape at the stage of preparing a so-called polymerized toner.
[0062]
Among the above methods, a polymerized toner is preferable in that it is simple as a production method, and is superior in surface uniformity as compared with a pulverized toner.
[0063]
In the above image forming apparatus, the image recording process is performed as follows. That is, in the toner image forming unit 20Y, for example, the surface of the rotating photoconductor 21Y is sequentially charged to a predetermined polarity (for example, negative polarity) by the charging unit 22, and in this state, the surface of the photoconductor 21Y is exposed. By selectively irradiating the light with the means 23Y, the potential of the irradiated area (exposed area) is reduced, and an electrostatic latent image corresponding to the original image is formed.
[0064]
On the other hand, a developing bias having the same polarity (for example, negative polarity) as the surface potential of the photoconductor 21Y is applied to the surface of the developing sleeve 241Y constituting the developing device 24Y from a power source (not shown), and the same as the surface potential of the developing sleeve 241Y. The developer containing the toner charged to the polarity (for example, negative polarity) is transported to the development area PY with the transport amount regulated. Then, in the development area PY, the toner on the development sleeve 241Y adheres to the exposure area of the photoconductor 21Y, and the reversal development is performed, so that a toner image is formed on the photoconductor 21Y.
[0065]
Such an operation is performed in each of the toner image forming units 20M, 20C, and 20K to form a toner image of each color.
[0066]
The toner image of each color formed in each of the toner image forming units 20Y, 20M, 20C, and 20K is sequentially primary-transferred onto the intermediate transfer belt 10 sequentially in each of the primary transfer areas T1Y, T1M, T1C, and T1K. A primary transfer toner image is formed by superimposing the toner images of each color on the transfer belt 10, and the primary transfer toner image is conveyed to the secondary transfer area T <b> 2 while being carried on the intermediate transfer belt 10, and In the next transfer area T2, the transfer electric field formed by the secondary transfer roller 41 and the drive roller 12 causes the transfer path along the conveyance path to be synchronized with the primary transfer toner image carried on the intermediate transfer belt 10. The secondary transfer toner image is formed on the image recording material R conveyed by the second transfer. Thereafter, the image is thermally fixed by the fixing device 50 to form a color image on the image recording material R.
[0067]
Then, untransferred toner remaining on the intermediate transfer belt 10 that has passed through the secondary transfer area T2 is removed by the intermediate transfer member cleaning blade 46 in the intermediate transfer member cleaning unit 45.
[0068]
Here, in the toner image forming unit 20Y, in the application area S3 provided downstream of the primary transfer area T1Y with respect to the rotation direction of the photoreceptor 21Y, the lubricant is applied to the outer peripheral surface by the lubricant applying means 30Y. Application is performed.
[0069]
That is, the flicker roller 33 is rotationally driven in a specific direction (counterclockwise in FIG. 2) at the same time that the above-described toner image forming step is performed, so that the outer peripheral surface of the scraping area S1 is formed. In the contact area S2, the lubricant is wiped off from the flicker roller 33 by the brush roller 32, which is also driven to rotate in a specific direction (clockwise in FIG. 2). The brush roller 32 with the lubricant adhered thereto in the application area S3 comes into contact with the outer peripheral surface of the photoconductor 21Y, so that a predetermined amount of lubrication is applied to the outer peripheral surface of the photoconductor 21Y. The agent is applied.
Here, the lubricant remaining on the outer peripheral surface of the flicker roller 33 is removed by the scraper 35 in the downstream area of the contact area S2 in the rotation direction, and the cleaned state is achieved.
[0070]
In the above, the brush roller 32 has a function as a pre-cleaning means for applying a lubricant to the photoreceptor 21Y and at the same time removing a part of the untransferred toner. That is, in the application area, when the photoconductor 21Y and the brush roller 32 come into contact with each other, the untransferred toner remaining on the outer peripheral surface of the photoconductor 21Y adheres to the brush fibers of the brush roller 32, and this untransferred toner is The brush fibers are removed by contact with the flicker roller 33. Further, the untransferred toner attached to the surface of the flicker roller 33 is removed and cleaned by the scraper 35 together with the lubricant 33 as described above.
[0071]
The operation of applying the lubricant in the toner image forming unit 20Y is also performed on each of the photoconductors 21M, 21C, and 21K of each of the toner image forming units 20M, 20C, and 20K.
[0072]
Here, in each of the toner image forming units 20Y, 20M, 20C and 20K, the amount of the lubricant applied to the photoconductors 21Y, 21M, 21C and 21K in one image forming process is appropriately adjusted. Things.
[0073]
For example, in the toner image forming unit 20K, the amount of the lubricant applied to the outer peripheral surface of the photoreceptor 21K for each image forming process is changed by the toner image forming units 20Y, 20M, and 20C for each image forming process. Then, each of the lubricant applying units 30Y, 30M, 30C, and 30K is controlled so that the amount of the lubricant applied to the outer peripheral surface of each of the photoconductors 21Y, 21M, and 21C is larger than that.
[0074]
Here, the amount of the lubricant applied to the photoconductors 21Y, 21M, 21C, and 21K can be controlled by rotating the cam plate 361 of the pressing mechanism 36. For example, by rotating the cam plate 361, Utilizing the generated cam action, the other support plate 363 is pressed against the one support plate 362 while contracting the spring 364, whereby the lubricating stock 34 has a resilient force against the flicker roller 33. By applying a pressing force to variably increase the pressing force of the lubricant stock 34 against the flicker roller 33, the amount of the lubricant applied to the photoconductors 21Y, 21M, 21C, 21K is appropriately increased. Can be.
[0075]
In the toner image forming unit 20K, at least 150% of the amount of the lubricant applied to each of the photoconductors 21Y, 21M, and 21C on the outer peripheral surface of the photoconductor 21K in each image forming process; Preferably, the lubricant applying means 30K is controlled so that a lubricant of 200% or more is applied.
Specifically, the amount of the lubricant applied to each of the photoconductors 21Y, 21M, and 21C with respect to the photoconductor 21K is 150 to 300%, particularly preferably 200 to 250%. The lubricant applying means 30K is controlled so as to be applied.
[0076]
The amount of the lubricant applied to the outer peripheral surfaces of the photoconductors 21Y, 21M, 21C, and 21K for each image forming process is, for example, the amount of the lubricant applied to each of the photoconductors 21Y, 21M, 21C, and 21K. The amount of the lubricant to be applied can be adjusted according to the total number of forming processes or according to the environmental humidity in the environment where the development processing is performed.
[0077]
That is, when the total number of image forming processes performed on the photoconductor 21K is 0 to 50,000 times, the lubrication of 150 to 250% of the amount of the lubricant applied to the photoconductors 21Y, 21M, and 21C is performed. It is preferable that the agent is applied to the outer peripheral surface of the photoconductor 21K. In particular, when the total number of the image forming processes exceeds 50,000, the amount of the lubricant applied to the photoconductors 21Y, 21M, and 21C It is preferable to apply 200 to 300% of the lubricant to the outer peripheral surface of the photoconductor 21K.
[0078]
When the environmental humidity measured by the humidity sensor 26K is 10 to 40%, the lubricant of 200 to 300% of the amount of the lubricant applied to the photoconductors 21Y, 21M, and 21C is exposed to light. It is preferable to apply the lubricant to the body 21K. In particular, when the environmental humidity exceeds 40%, a lubricant having an amount of 150 to 250% of the amount of the lubricant applied to the photoconductors 21Y, 21M, and 21C is used. It is preferable to apply to the photoreceptor 21K.
[0079]
As described above, after setting the amount of the lubricant to be applied to the photoconductor 21K for the black toner as described above, the lubricant is applied to the photoconductors 21Y, 21M, and 21C for the color toner, which is the reference of the application amount. By controlling the amount of the lubricant to be reduced, it is possible to suppress the total amount of the lubricant used in the entire image forming apparatus.
[0080]
According to the image forming apparatus of the present invention, the amount of the lubricant applied to the outer peripheral surface of the image forming body related to the black toner is applied to the outer peripheral surface of the image forming body related to the color toner other than the black toner. By increasing the amount of the lubricant compared to the amount of the lubricant, even when a black toner having a large volume average particle size is used as compared with the color toner, the occurrence of a hollow phenomenon in the toner image is suppressed. In addition, since a high cleaning effect can be obtained on the outer peripheral surface of the image forming body, the load on the image forming body and the cleaning blade constituting the image forming body cleaning unit is reduced.
[0081]
As a result, even in a toner image forming unit for a frequently used black toner, the desired cleaning effect can be obtained for a long period of time because the wear speed of the image forming body and the image forming body cleaning blade can be reduced. Therefore, a high-quality image can be stably formed for a long period of time.
[0082]
According to another aspect of the present invention, the amount of the lubricant applied to the outer peripheral surface of the image forming body related to the black toner is changed by the amount of the lubricant applied to the outer peripheral surface of the image forming body related to the color toner. When the black toner having a smaller sphericity than the color toner is used, the transfer efficiency of the toner image is improved and the toner remains on the outer peripheral surface of the image forming body. Since the untransferred toner is reduced and a high cleaning effect can be obtained on the outer peripheral surface of the image forming body, the load on the image forming body and the cleaning blade constituting the image forming body cleaning unit is reduced.
[0083]
As a result, even in the toner image forming unit relating to the frequently used black toner, the desired cleaning effect can be obtained for a long period of time because the wear speed of the image forming body and the image forming body cleaning blade can be reduced. Therefore, a high-quality image can be stably formed for a long period of time.
[0084]
In the above, the amount of the lubricant applied to the outer peripheral surface of the image forming body is adjusted according to the total number of image forming processes, so that as the image forming process is performed, the cleaning blade gradually deteriorates. Also, as described above, it is possible to suppress the occurrence of the hollow phenomenon in the toner image with high efficiency, or to reduce the untransferred toner remaining on the outer peripheral surface of the image forming body by improving the transfer efficiency of the toner image. As a result, a high cleaning effect on the outer peripheral surface of the image forming body can be reliably obtained. As a result, the desired cleaning effect can be obtained for a long period of time, and therefore, a high-quality image can be stably formed for a long period of time.
[0085]
Also, by adjusting the amount of the lubricant applied to the outer peripheral surface of the image forming body according to the environmental humidity, even when the environmental humidity changes and the transfer condition fluctuates, as described above, It is possible to suppress the occurrence of the hollow phenomenon in the toner image by high efficiency, or to reduce the untransferred toner remaining on the outer peripheral surface of the image forming body by improving the transfer efficiency of the toner image. A high cleaning effect on the outer peripheral surface can be reliably obtained. As a result, the desired cleaning effect can be obtained over a long period of time, and therefore, a high-quality image can be stably formed over a long period of time.
[0086]
In the above, the effect of the present invention can be satisfactorily achieved by reducing the amount of the lubricant applied to the image forming body relating to the color toner, and the lubricant consumed in the entire image forming apparatus Can be suppressed.
[0087]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.
For example, adjustment of the amount of the lubricant applied to the photoconductor is performed by adjusting the hardness of the lubricant, controlling the linear speed at which the flicker roller and the brush roller are rotationally driven, and controlling the flicker roller. It is also possible to control the material and the surface treatment state of the constituent lubricant scraping layer, and furthermore, to appropriately select the diameter, length, material and planting density of the brush fiber forming the brush roller. .
[0088]
In addition, the brush roller may be configured by a brush fiber having conductivity, and may be configured to be able to apply a voltage to the brush fiber by being connected to a DC power supply. Can obtain a high preliminary cleaning effect on the photoconductor.
[0089]
<Example of experiment>
Hereinafter, experimental examples of the present invention will be described.
According to the configuration shown in FIG. 1, a digital color copying machine provided with the lubricant applying means shown in FIG. 2 was manufactured.
[0090]
(1) Photoconductor
The photosensitive member is an organic photosensitive member in which a photosensitive layer having a thickness of 25 μm made of polycarbonate containing a phthalocyanine pigment is formed on the outer peripheral surface of a drum-shaped metal substrate made of aluminum having an outer diameter of 60 mm and a thickness of 1 mm. The speed was set to be 280 mm / sec.
[0091]
(2) Developing device
The developing device was provided with a developing sleeve having an outer diameter of 25 mm which was driven to rotate, and to which a bias voltage having the same polarity as the surface potential of the photoreceptor was applied to perform a reversal development.
[0092]
(3) Intermediate transfer belt
As the intermediate transfer belt, a polyimide belt manufactured by Gunze Co., Ltd. was used, and the linear velocity was set to be 280 mm / sec.
[0093]
(4) Intermediate transfer member cleaning device
As the intermediate transfer member cleaning blade, a blade made of urethane rubber and having a thickness of 2.00 mm was used.
[0094]
(5) Lubricant application means
The lubricating agent applying means is 60,000 brush fibers / inch, made of conductive acrylic resin having a diameter of 6.25d and a length of 3.5mm. ² A brush roller having a maximum diameter of 20 mm, a flicker roller made of aluminum having an outer diameter of 10 mm and a thickness of 1.0 mm, and a scraper having a thickness of 2 mm made of PET and having a maximum diameter of 20 mm. It was constituted by.
Here, the brush roller was set to have a linear velocity of 300 mm / sec, and the flicker roller was set to have a linear velocity of 150 mm / sec.
[0095]
(6) Photoconductor cleaning means
As the photoconductor cleaning blade, a photoconductor cleaning blade having a thickness of 2 mm is used. The photoconductor cleaning blade is installed so that the tip of the cleaning blade faces the opposite direction (counter direction) to the moving direction of the photoconductor in the operating state. The contact angle to the photoreceptor was set to 10 °, and the contact load was set to 13 g / cm.
[0096]
(7) bias voltage applying means
The bias voltage applying means connected to the secondary transfer roller applies the secondary voltage regardless of the polarity of the polarity (positive polarity) opposite to the toner charging potential and the same polarity (negative polarity) as the toner charging potential. When a transfer roller is used to transfer a toner image corresponding to an original image onto transfer paper using a transfer roller, a transfer bias voltage of +600 V is applied to the secondary transfer roller in a state where the transfer function is not limited. Was set to
[0097]
<Experimental example 1>
In the image forming apparatus having the above configuration, as a developer, black toner particles having a volume average particle diameter of 6.0 μm together with yellow toner particles, magenta toner particles, and cyan toner particles having a volume average particle diameter of 5.0 μm are used. The image forming process was performed 100000 times under the condition that the amount of the lubricant applied to the photoconductor related to the black toner in each of the image forming processes was set to 200% of the amount of the lubricant applied to each of the photoconductors related to the color toner. The occurrence of the hollow phenomenon in the formed image was visually evaluated.
As a result, the hollow phenomenon could not be confirmed in all of the formed images, and it was confirmed that high-quality images could be stably formed over a long period of time.
[0098]
<Experimental example 2>
In the image forming apparatus having the above configuration, the developer has a shape factor of 0.96 together with yellow, magenta, and cyan toner particles having a shape coefficient of 0.96 and a volume average particle diameter of 5.0 μm. 0.94, and using a black toner particle having a volume average particle diameter of 5.0 μm, and applying the lubricant to the photoconductor related to the black toner in each image forming process by using The image forming process was carried out 100,000 times under the condition that the amount of the lubricant applied to each was 200%, and the state of deterioration of the cleaning blade and the photoconductor was visually evaluated.
As a result, it was confirmed that both the cleaning blade and the photoreceptor maintained a good state, and that the load applied to the both during the image forming process was reduced.
[0099]
As described above, the image forming apparatus of the present invention has been described in detail. In this image forming apparatus, the following control can be performed.
That is, in the toner image forming units 20Y, 20M, and 20C for each of the yellow toner, the magenta toner, and the cyan toner, the toner image is applied to the outer peripheral surface of each of the photoconductors 21Y, 21M, and 21C for each image forming process. So that the amount of the lubricant applied to the outer peripheral surface of the photoconductor 21K is larger than the amount of the lubricant applied to the outer peripheral surface of the photoconductor 21K in each image forming process in the toner image forming unit 20K for the black toner. It is possible to control each of the means 30Y, 30M, 30C, 30K.
[0100]
By performing the image forming process in such an aspect, even when a yellow toner, a magenta toner, or a cyan toner having a smaller volume average particle diameter than the black toner is used, the transfer efficiency of the toner image is improved. As a result, the untransferred toner remaining on the outer peripheral surface of the image forming body is reduced, and high cleaning performance on the outer peripheral surface of the image forming body can be obtained. The load is reduced.
[0101]
Even when a yellow toner, a magenta toner, and a cyan toner having a higher sphericity than the black toner are used, the occurrence of the void phenomenon in the toner image is suppressed, and the outer peripheral surface of the image forming body is suppressed. The cleaning performance of the image forming member and the cleaning blade constituting the image forming member cleaning means can be reduced.
[0102]
As a result, in the toner image forming units for each of the yellow toner, the magenta toner, and the cyan toner, the abrasion speed of the image forming body and the image forming body cleaning blade can be reduced. Thus, a high-quality color image can be stably formed over a long period of time.
[0103]
【The invention's effect】
According to the image forming apparatus of the present invention, a black toner having a specific range of volume average particle diameter, a specific volume average particle diameter set in relation to a color toner other than the black toner, or a specific range A black toner having a unique shape factor set in relation to a color toner having a shape factor of is used, and the amount of lubricant applied to the image forming body in the toner image forming unit for the black toner is applied to the color toner. By increasing the amount of the lubricant applied to each of the image forming bodies in the toner image forming unit, the transfer efficiency of the toner image is improved in the course of the image forming process using the black toner. The ratio of the unfixed toner remaining on the toner becomes small, and the occurrence of the hollow phenomenon is suppressed. , It becomes load on the cleaning blade according to the image forming body and the image forming member is small.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of an example of an image forming apparatus of the present invention.
FIG. 2 is an explanatory cross-sectional view illustrating a configuration of a toner image forming unit.
[Explanation of symbols]
10 Intermediate transfer belt
12 Drive roller
13 tension roller
14 Contact roller
20Y, 20M, 20C, 20K Toner image forming unit
21Y, 21M, 21C, 21K photoreceptor
22Y, 22M, 22C, 22K Charging means
23Y, 23M, 23C, 23K Exposure means
24Y, 24M, 24C, 24K developing unit
241Y developing sleeve
25Y, 25M, 25C, 25K primary transfer roller
26Y, 26M, 26C, 26K Humidity sensor
30Y, 30M, 30C, 30K Lubricant application means
31Y, 31M, 31C, 31K Photoconductor cleaning blade
32 brush roller
33 Flicker roller
34 Lubricant stock
35 scraper
36 Pressing mechanism
361 cam plate
361A Rotation center fulcrum
362 support plate
363 support plate
364 spring
40 Secondary transfer mechanism
41 Secondary transfer roller
42 bias voltage applying means
45 Intermediate Transfer Member Cleaning Means
46 Intermediate transfer member cleaning blade
50 Fixing device
51 Heating roller
511 heating source
52 pressure roller
PY, PM, PC, PK Development area
R image recording material
S1 scraping area
S2 Contact area
S3 coating area
T1Y, T1M, T1C, T1K primary transcription regions
T2 Secondary transfer area

Claims (9)

A plurality of toner image forming units each including a rotationally driven image forming body, forming a toner image by developing an electrostatic latent image formed on the image forming body using black toner and color toner, A primary transfer mechanism for stacking and transferring the toner image on the intermediate transfer body in the primary transfer area to form a primary transfer toner image, and a secondary transfer mechanism for transferring the primary transfer toner image collectively onto an image recording material and A secondary transfer mechanism for forming a transfer toner image, and a fixing device for fixing the secondary transfer toner image to an image recording material,
A toner application unit configured to apply a lubricant to a surface of the image forming body in a downstream area of the primary transfer area in a rotation direction of the image forming body; An image forming apparatus having an image forming body cleaning unit that removes untransferred toner remaining on the formed body by a cleaning blade made of an elastic body, which is provided to be in contact with the surface of the image forming body,
Constituting the toner image at each toner image forming unit, a black toner having a volume average particle diameter [μm] and r _b, the volume average particle diameter of the color toner [μm] when the r _c,
a _{r b>} r c +1 [μm], and,
a r _c = 3~7 [μm],
In the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is one time in the toner image forming unit for the color toner. An image forming apparatus, wherein the amount of the lubricant applied to the outer peripheral surface of the image forming body is increased for each process. The amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process in the toner image forming unit for the black toner is determined by one image forming process in the toner image forming unit for the color toner. 2. The image forming apparatus according to claim 1, wherein the amount is set to 150% or more of a lubricant applied to an outer peripheral surface of the image forming body every time. In the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is controlled according to the total number of the image forming processes. The image forming apparatus according to claim 1 or 2, wherein The amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process in the toner image forming unit for the black toner is controlled according to the environmental humidity. The image forming apparatus according to claim 1. A plurality of toner image forming units each including a rotationally driven image forming body, forming a toner image by developing an electrostatic latent image formed on the image forming body using black toner and color toner, A primary transfer mechanism for forming a primary transfer toner image by stacking and transferring the toner image on an intermediate transfer body in a primary transfer area; and a secondary transfer by collectively transferring the primary transfer toner image onto an image recording material. A secondary transfer mechanism for forming a toner image, and a fixing device for fixing the secondary transfer toner image to an image recording material,
A toner application unit configured to apply a lubricant to a surface of the image forming body in a downstream area of the primary transfer area in a rotation direction of the image forming body; An image forming apparatus having an image forming body cleaning unit that removes untransferred toner remaining on the formed body by a cleaning blade made of an elastic body, which is provided to be in contact with the surface of the image forming body,
When the shape factor of the black toner constituting the toner image in each toner image forming unit is k _b and the shape factor of the color toner is k _c ,
k _b> is a _k c -0.01, and,
k _c = 0.94 to 0.98,
In the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is one time in the toner image forming unit for the color toner. An image forming apparatus, wherein the amount of the lubricant applied to the outer peripheral surface of the image forming body is increased for each process. The amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process in the toner image forming unit for the black toner is determined by one image forming process in the toner image forming unit for the color toner. 6. The image forming apparatus according to claim 5, wherein the amount of the lubricant applied to the outer peripheral surface of the image forming body is set to 150% or more every time. In the toner image forming unit for the black toner, the amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process is controlled according to the total number of the image forming processes. The image forming apparatus according to claim 5 or 6, wherein The amount of the lubricant applied to the outer peripheral surface of the image forming body for each image forming process in the toner image forming unit for the black toner is controlled according to the environmental humidity. The image forming apparatus according to claim 5. 9. The image forming apparatus according to claim 5, wherein the volume average particle diameters of the black toner and the color toner are each 3 to 7 [mu] m.

Images