JP2004117962A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus at a low cost in which a residual developer can be efficiently removed from the surface of an image carrier by simple constitution and in which defective cleaning is less liable to occur, with respect to an image forming apparatus using a contact charging system by AC+DC application and a contact developing system. <P>SOLUTION: In the image forming apparatus, the pressing pressure of a developer carrier 8a to an image carrier 1 is regulated to 0.88-1.76 N/cm and AC peak-to-peak voltage applied to a charging member 2 is regulated to <2.0 kVpp. <P>COPYRIGHT: (C)2004,JPO

Description

【００９７】
【表２】

【００９８】
表１に示した低温低湿環境下での比較結果では、帯電部材に印加するＡＣピーク間電圧値が１．４ｋＶｐｐ未満（即ち、放電開始電圧未満）になると、出力画像上に砂地と呼ばれる画像欠陥が発生する。この画像欠陥は特にハーフトーン画像上でザラつきとして視認されるものである。
【００９９】
一方、帯電部材に印加するＡＣピーク間電圧値が２．０ｋＶｐｐを超える場合には、感光ドラム上の現像剤を回収出来ずに出力画像上に縦筋を生じる、クリーニング不良が発生する。
【０１００】
また、感光ドラム１に対する現像ローラ８ａの押付け圧を、１ｃｍ幅当たり１．７６Ｎ（１８０ｇ）を超える様に設定した際にも、前述したクリーニング不良が発生している。
【０１０１】
更に、感光ドラム１に対する現像ローラ８ａの押付け圧を１ｃｍ幅当たり０．８８Ｎ（９０ｇ）未満とした際に、現像中に感光ドラム１と現像ローラ８ａが離間する事によって現像が行われない箇所が生じる、「画像白抜け」と呼ばれる画像欠陥が発生する。
【０１０２】
ところが、上述の傾向は表２に示す通り、高温高湿環境下で少し異なっている。
【０１０３】
高温高湿環境下では低温低湿環境下と比較し、諸条件に対する「画像白抜け」や「砂地」の発生傾向に大きな変化は見られないが、帯電ローラ２に印加するＡＣピーク間電圧がより大きく、また感光ドラム１に対する現像ローラ８ａの押付け圧がより高くなった場合にもクリーニング不良が発生し辛くなっている事が分かる。
【０１０４】
また、一般的な環境下（２４℃／６０％程度）における各々の画像欠陥の発生傾向は、上述した高温高湿環境下及び低温低湿環境下の中間的な傾向を示す事が分かった。
【０１０５】
従って、より幅広い環境下で効果的に画像欠陥の発生を抑止する事を考慮するならば、低温低湿環境において諸問題が発生していない条件（表１中太枠内）で画像形成装置を構成すれば良い。
【０１０６】
よって本画像形成装置では、前記像担持体に対する現像剤担持体の押付け圧を０．８８Ｎ／ｃｍ以上１．７６Ｎ／ｃｍ以下（９０ｇ／ｃｍ以上１８０ｇ／ｃｍ以下）の範疇に入る様１．１７Ｎ／ｃｍ（１２０ｇ／ｃｍ）に設定した。
【０１０７】
また本画像形成装置では、帯電ローラ２に印加する電圧のＡＣピーク間電圧が帯電電位収束電圧以上２．０ｋＶｐｐ未満となる様設定を行う。但し、本実施例の画像形成装置では帯電ＡＣバイアスについて定電流制御方式を採るため、図２に示すグラフに示されたＡＣピーク間電圧とＡＣ電流値の関係から、前記帯電ＡＣ電流の制御ターゲット値を約１０００μＡに決定した。
【０１０８】
以上述べた通り、本実施例の画像形成装置では、簡潔な構成で像担持体表面から効率良く残留現像剤を除去出来る様にし、クリーニング不良や砂地等の画像欠陥が発生し難い画像形成装置を安価に提供する事が出来る様になった。
【０１０９】
〈実施例２〉
図５に示すのは、本発明の第２の実施例であるフルカラー画像形成装置の模式図である。
【０１１０】
このフルカラー画像形成装置は、主に像担持体としての感光ドラム１１と、感光ドラム１１を一様に帯電する帯電手段としての帯電ローラ１２と、画像情報の露光を行うレーザースキャナ１３と、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｂｋ）に対応した４色の現像器１４ｙ、１４ｍ、１４ｃ、１４ｋを支持する回転式現像装置１４を備えている。
【０１１１】
また、本実施例のフルカラー画像形成装置では、感光ドラム１１上に順次形成される可視像を、駆動ローラ１５ａ、従動ローラ１５ｂ及び二次転写対向ローラ１５ｃの３本のローラ間に、ベルト部材を張架してなる中間転写体ベルト１５表面に重ねて転写した後、記録紙Ｐ上に一括転写することによってフルカラー画像が形成される。
【０１１２】
更に、本実施例のフルカラー画像形成装置では上述の画像形成動作に伴い、転写後に感光ドラム１１上に残留する現像剤や異物を除去するため、金属性の支持板金１６ａとウレタンゴム部１６ｂで構成されるクリーニングブレード１６と、前記クリーニングブレード１６の両端を支持し、且つ前記クリーニングブレード１６により感光ドラム１１表面から回収された現像剤の収容部を兼ねた廃現像剤容器１７から成るクリーニング装置１８が具備される。
【０１１３】
尚、上述のクリーニング装置１８は、本発明における第１の実施例の画像形成装置で用いたものを利用してある。
【０１１４】
また、現像剤として形状係数ＳＦ−１の値が１００〜１６０であり、且つＳＦ−２の値が１００〜１４０である球形トナー粒子と、無機微粉体及びハイドロタルサイト類化合物を混合した物を用い、各色の現像剤に含有されるハイドロタルサイト類化合物の総量を、各々現像剤１００重量部に対して０．１重量部としたことを特徴とする。
【０１１５】
図５において、感光ドラム１１は矢印Ｄ方向に回転されており、帯電ローラ１２に印加されるＡＣバイアスとＤＣバイアスを重畳した振動電圧よって、その周面が所定の電位に帯電される。
【０１１６】
本実施例の画像形成装置では、帯電ローラ１２に印加する電圧のＡＣピーク間電圧を、本発明の第１の実施例の画像形成装置で見出した値、即ち帯電電位収束電圧以上２．０ｋＶｐｐ未満の範疇に入る様に設定を行った。この際、特にクリーニング不良が発生し易い低温低湿環境下でのＡＣピーク間電圧値を考慮し、定電流制御を行う際のターゲット電流値を約１０００μＡに決定した（図２に示すグラフを参照）。
【０１１７】
その後、レーザースキャナ１３により各々の色（現像器１４ｙ〜１４ｋ内に充填される各色の現像剤、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｂｋ））に対応した静電潜像が、順次感光ドラム１１表面に形成される。
【０１１８】
まず１色目、例えばイエロー現像剤に対応する静電潜像が感光ドラム１１上に形成されると、回転式現像装置１４に収容されたイエロー現像器１４ｙが感光ドラム１１に対向され、現像ローラ１４ａに担持されたイエロー現像剤によって接触現像が行われる。
【０１１９】
先述した通り、本実施例の画像形成装置では各々の色の現像剤として、形状係数ＳＦ−１の値が１００〜１６０、ＳＦ−２の値が１００〜１４０であり、結着剤と着色剤を含有する球形トナー粒子に、無機微粉体であるシリカを現像剤１００重量部に対して０．１重量部、更に現像剤１００重量部に対して０．１重量部のハイドロタルサイト類化合物を混合したものを用いる。
【０１２０】
尚、回転現像装置１４内の現像器１４ｙ〜１４ｋを、感光ドラム１１に対向しない位置で停止させ、現像器１４ｙ〜１４ｋに対する加圧を解除することで、何れの現像器の現像ローラ１４ａも感光ドラム１１より完全に離間される。また、現像器１４ｙ〜１４ｋの現像ローラ１４ａは現像位置において、加圧動作が行われた後に駆動力が得られる様に構成される。
【０１２１】
更に、現像器１４ｙ〜１４ｋの前記加圧・離間動作は、従来例で説明に用いた図１３の加圧装置によって行なわれる。
【０１２２】
一方、感光ドラム１１に対する現像ローラ１４ａの押付け圧のコントロールは、前記加圧装置におけるカム部のカムプロフィール（図１３中に不図示）を変更し、現像器１４ｙ〜１４ｋの動作ストロークを増減する事により行なう。
【０１２３】
また、本実施例の画像形成装置では感光ドラム１１に対する現像ローラ１４ａの押付け圧を、本発明の第１の実施例の画像形成装置で見出した値、即ち０．８８Ｎ／ｃｍ以上１．７６Ｎ／ｃｍ以下（９０ｇ／ｃｍ以上１８０ｇ／ｃｍ以下）の範疇に入る様に１．１７Ｎ／ｃｍ（１２０ｇ／ｃｍ）に設定した。
【０１２４】
続いて、感光ドラム１１上に形成されたイエローの現像剤像は、一次転写部１９において中間転写ベルト１５上に一次転写される。
【０１２５】
また、感光ドラム１１上の残留トナーは、弾性ブレードを利用したクリーニング装置１７で清掃される。
【０１２６】
その後、２色目のマゼンタ現像剤に対応する静電潜像が感光ドラム１１上に形成され、マゼンタ現像剤が収容されたマゼンタ現像器１４ｍにより、マゼンタの現像剤像が形成される。前述のマゼンタ現像剤像は、一次転写部１９において、既に１色目のイエローの現像剤像が転写されている中間転写ベルト１５上に重ねて転写される。更に、１色目のイエロー画像を形成する際と同じく、一次転写後に感光ドラム１１上に残留した現像剤は、クリーニング装置１８で清掃される。
【０１２７】
これらの動作を、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｂｋ）に対応する４回行い、中間転写ベルト１５上に４層に重ねられた現像剤像は、二次転写部２０において記録紙Ｐに一括転写され、その後定着装置２２によって融解固着される。
【０１２８】
また、前述二次転写部２０における一括転写の後、中間転写ベルト１５上に残留する現像剤は、所定のタイミングで中間転写ベルト１５に当接・離間する様に構成された中間転写ベルト用帯電ローラ２１により、中間転写ベルト１５上の画像形成域とは逆極性のバイアス（感光ドラム１１の帯電極性に対しても逆極性）を印加されて、前記中間転写ベルト１５から感光ドラム１１に吐出される。前述の通り、感光ドラム１１上に吐出された現像剤は、次画像の形成が行なわれるまでにクリーニング装置１８によって除去される。
【０１２９】
帯電の際のＡＣピーク間電圧と、感光ドラム１１に対する現像ローラ１４ａの押付け圧を上述した通りに設定する事で、本発明における第１の実施例の画像形成装置と同様に画像欠陥が発生し難くなる。
【０１３０】
一方、各色の現像剤に対するハイドロタルサイト類化合物の混合量を、現像剤１００重量部に対し０．１重量部（本実施例における設定値）、０．２重量部の２水準準備し、ハイドロタルサイト類化合物を含まない現像剤を用いた本発明の第１の画像形成装置との比較を行うため、低温低湿環境下における耐久評価を行った。
【０１３１】
その結果を、以下の表３及び表４に示す。尚、表中の記号は、それぞれ以下の画像欠陥を示す。
【０１３２】
○・・・画像欠陥無し（ＯＫ）
砂・・・砂地（帯電不良）
抜・・・画像白抜け（現像ローラの押付け圧不足）
Ｃ・・・クリーニング不良
また、以上の記号に対し△が付けられた個所は、各々の画像欠陥が実使用上問題とされない水準であると判断したものである。
【０１３３】
【表３】

【０１３４】
【表４】

【０１３５】
表３に示す通り、本実施例の画像形成装置では、同様のクリーニング装置を用いる本実施例の第１の実施例の画像形成装置に対して、帯電ＡＣピーク間電圧値をより高く、また感光ドラムに対する現像ローラの当接圧をより高くした際までクリーニング不良が発生し辛くなっている事が分かる。
【０１３６】
また表４に示す通り、各色の現像剤に含有されるハイドロタルサイト類化合物の量を０．２重量部とした場合には前述の傾向が更に顕著になり、クリーニング性とハイドロタルサイト類化合物の量に密接な関係が有る事が分かる。
【０１３７】
これは、高いすり抜け性を有していた球形トナーを主とする現像剤の流動性が、ハイドロタルサイト類化合物の量を増加させる事により低下し、弾性ブレードを用いて感光ドラム表面から現像剤を除去し易くなるためと見られる。
【０１３８】
但し、前記ハイドロタルサイト類化合物の添加量を極端に増加させた場合、感光ドラム表面への現像剤成分の融着や、低温低湿環境下での現像剤のチャージアップ等の問題が発生し易くなる事も分かっている。
【０１３９】
本実施例の画像形成装置では充分なクリーニング性が余裕を持って得られる様に、帯電の際のＡＣピーク間電圧と、感光ドラム１１に対する現像ローラ１４ａの押付け圧を上述した通りに設定し、ハイドロタルサイト類化合物の添加量を適宜最小限にコントロールする事で、球形トナーを用いた場合に得られる高い現像性と転写性を損なう事無く、出力画像の品位を高める事が出来た。
【０１４０】
〈実施例３〉
図６に示すのは、本発明の第３の実施例である画像形成装置の模式図である。
【０１４１】
本実施例の画像形成装置では、本発明の第１の実施例である画像形成装置（図１）において、画像形成を行う画像形成プロセスの構成要素の内、像担持体である感光ドラム１と、該感光ドラム１表面を帯電する帯電手段の一部である帯電ローラ２と、現像剤Ｔ’を収容する現像剤現像器８と、クリーニングブレード３及び廃現像剤容器４からなるクリーニング装置５を一体化し、画像形成装置本体と着脱可能なプロセスカートリッジ２３として構成したものである。その他の構成は図１の画像形成装置と同様であるから再度の説明を省略する。
【０１４２】
本画像形成装置では、前記像担持体１に対する現像剤担持体８ａの押付け圧を１．１７Ｎ／ｃｍ（１２０ｇ／ｃｍ）とし、且つ帯電ローラ２に印加する電圧のＡＣピーク間電圧が帯電電位収束電圧以上２．０ｋＶｐｐ未満となる様制御が行われる。
【０１４３】
上記構成を採る事で、帯電部材の振動に伴う像担持体表面の変位が抑えられ、前述の通り変位する像担持体表面に追従するために、厳密に管理されていた像担持体１に対する弾性ブレード部材３の当接圧の製造公差を比較的大きく設定する事が出来た。また、像担持体１に対する接触現像手段８ａの押圧により変動する、像担持体１に対する弾性ブレード部材３の当接圧の変化量が抑えられる
従って、簡潔な構成で像担持体表面から効率良く残留現像剤を除去出来る様にし、クリーニング不良や砂地等の画像欠陥が発生し難い画像形成装置を安価に提供する事が出来る様になった。
【０１４４】
更に、プロセスカートリッジ２３を交換するという簡単な操作を行うだけで、現像剤Ｔ’の補給に加え、感光ドラム１や帯電ローラ２等の消耗部材の交換が行える様になるため、諸々のメンテナンス作業に係わる使用者の労力を軽減出来、安定した出力画像を容易に得られる様になった。
【０１４５】
〈実施例４〉
図７に示すのは、本発明の第４の実施例であるフルカラー画像形成装置の模式図である。
【０１４６】
本実施例の画像形成装置では、本発明の第２の実施例である画像形成装置（図５）において、中間転写ベルト１５を従動ローラ１５ｂと、駆動ローラ１５ａ及び二次転写対向ローラ１５ｃを一体化し、それぞれの機能を併せ持つ駆動ローラ１５ｄの２軸で懸架したことを特徴とする。
【０１４７】
また、画像形成を行う画像形成プロセスの構成要素の内、像担持体である感光ドラム１と、該感光ドラム１表面を帯電する帯電手段の一部である帯電ローラ２と、クリーニングブレード１６及び廃現像剤容器１７で構成されたクリーニング装置１８、更には中間転写ベルト１５をも一体化し、フルカラー画像形成装置本体と着脱可能なプロセスカートリッジ２４として構成したものである。
【０１４８】
更に、本実施例の画像形成装置には、固有のＡＣ帯電電流目標値を記憶した記憶媒体２５が備えられ、前記記憶媒体２５中に格納された固有のＡＣ帯電電流目標値を読み出すＡＣ帯電電流目標値読出し手段２６と、前記ＡＣ帯電電流目標値を参照してＡＣ電流値を変化させるＡＣ電流値切換え手段手段３０とを備え、ＡＣピーク間電圧が２．０ｋＶｐｐ未満となる様に帯電電流値のコントロールを行う事を特徴とする。上記において記憶媒体２５はプロセスカートリッジ２４側に具備させてある。
【０１４９】
上述した固有のＡＣ帯電電流目標値とは、プロセスカートリッジ２４が画像形成装置本体に装着され画像形成が行われる際、帯電ローラ１２に印加されるＡＣピーク間電圧が帯電電位収束電圧以上２．０ｋＶｐｐ未満となる様、前記プロセスカートリッジ２４に搭載される帯電ローラ１２に応じて個別に設定した制御ターゲット値である。
前記ＡＣ帯電電流目標値はより正確な値を設定するため、プロセスカートリッジ２４の製造工程において帯電バイアス印加を行い、上述条件を満たすＡＣ帯電電流としてフィードバックされる値を記憶媒体２５内に記憶させる事が好適である。
【０１５０】
その他の構成は図５の画像形成装置と同様であるから再度の説明を省略する。
【０１５１】
図８に、プロセスカートリッジ２４に搭載された記憶媒体２５と、画像形成装置本体に設けられた各手段との接続を説明するブロック図を、また図９に本実施例のフルカラー画像形成装置で行われるＡＣ帯電電流値のコントロール動作を説明するフローチャートを示した。
【０１５２】
本実施例のフルカラー画像形成装置本体にプロセスカートリッジ２４が装着される（Ｓ１）と、コネクタ２７を介し記憶媒体２５とＡＣ帯電電流目標値読出し手段２６とが接続される。この際、プロセスカートリッジ２４の有無検知手段２８によりプロセスカートリッジ２４が装着された事が検出され、制御部２８にその信号が与えられる（Ｓ２）。
【０１５３】
続いて、制御部２８がプロセスカートリッジ２４の装着を認知すると、ＡＣ帯電電流目標値読出し手段２６を用い、記憶媒体２５内のＡＣ帯電電流目標値の読出しを行う。（Ｓ３）
更に制御部２８は、前述の通り読出された記憶媒体２５内のＡＣ帯電電流目標値を参照して、ＡＣ帯電電流値切換え手段３０が選択するＡＣ帯電電流目標値を変更し（Ｓ４）、画像形成動作準備が完了する。（Ｓ５）
上述した動作により画像形成準備を完了した画像形成装置では、画像形成の度にＡＣ帯電電流値切換え手段が選択したＡＣ帯電電流目標値に準じて、帯電バイアスがコントロールされるため、簡潔な構成で感光ドラム１１表面から効率良く残留現像剤を除去可能となり、クリーニング不良や砂地等の画像欠陥が発生し難い画像形成装置、及び前記画像形成装置に使用するプロセスカートリッジ２４を安価に提供する事が出来る様になった。
【０１５４】
更に、プロセスカートリッジを交換するという簡単な操作を行うだけで、現像剤Ｔ’補給に加え、感光ドラム１や中間転写ベルト１５等の消耗部材の交換が行える様になるため、諸々のメンテナンス作業に係わる使用者の労力を軽減出来、安定した出力画像を容易に得られる様になった。
【０１５５】
〈その他〉
１）情報書き込み手段としての露光手段３は、実施例のレーザビームスキャナに限られず、ＬＥＤアレイ、蛍光灯等の光源と液晶シャッターとの組み合わせ等の他のデジタル露光装置であってもよいし、原稿画像を結像投影するアナログ露光装置であってもよい。
【０１５６】
２）像担持体１は、静電記録誘電体であってもよい。この場合は該誘電体面を所定の極性・電位に一様に帯電した後、除電針アレイ・電子銃等の除電手段（情報書き込み手段）で選択的に除電して画像情報の静電潜像を書き込み形成する。
【０１５７】
３）像担持体１はドラム型に限られず、回動ベルト（エンドレスベルト）、回動ベルト状の支持体に取り付け保持させた有端のシート状のもの等であってもよい。
【０１５８】
４）静電潜像のトナー現像方式・手段は任意である。反転現像方式でも正規現像方式でもよい。
【０１５９】
５）帯電手段２や現像装置４に印加するバイアスのＡＣ成分（交流電圧）の波形としては、正弦波、矩形波、三角波等適宜使用可能である。交流バイアスは、例えば直流電源を周期的にＯＮ，ＯＦＦすることによって形成された矩形波の電圧を含む。
【０１６０】
６）像担持体としては、たとえば、基体の表面に形成した電荷発生層と、この電荷発生層の表面に形成した電荷輸送層とを基本構成体とするものを用いることができる。具体的には、ＯＰＣ感光体上にＳｎＯ_２等の導電性粒子を分散させた表層（電荷注入層）をコーティングしたＯＣＬ感光体、α−Ｓｉ（アモルファスシリコン、非晶質シリコン）の表層を有する感光体などを用いることができる。
【０１６１】
７）球形トナーは実質的に球形状のトナーであり、形状的に転がりやすく、摩擦帯電性がよく、現像性、転写効率等がよい。本発明ではトナーの球形度を表す形状係数として、ＳＦ−１及びＳＦ−２を用いた。
【０１６２】
ＳＦ−１はトナーの丸さ度合いを表すものであり、完全な球形で１００となり、値が大きくなるに連れて球形から不定形になる。
【０１６３】
ＳＦ−２はトナーの凹凸度合いを表すものであり、完全な球形で１００となり、この値が大きくなるに連れてトナー表面の凹凸が顕著になる。
【０１６４】
本発明に適するＳＦ−１及びＳＦ−２の値は、
ＳＦ−１値＝１００〜１６０
ＳＦ−２値＝１００〜１４０
であり、より好ましくは、
ＳＦ−１値＝１００〜１４０
ＳＦ−２値＝１００〜１２０
である。
【０１６５】
ＳＦ−１及びＳＦ−２の値は、日立製作所製ＦＥ−ＳＥＭ（Ｓ−８００）を用いて、倍率５００倍に拡大したトナー像を無作為に１００個サンプリングし、その画像情報をインターフェイスを介してニコレ社製画像解析装置（ＬＵＺＥＸ３）に導入して解析を行い、下式より算出した値である（図１４、図１５参照）
ＳＦ−１値＝
｛（ＭＸＬＮＧ）^２／ＡＲＥＡ｝×（Π／４）×１００
ＳＦ−２値＝
｛（ＰＥＲＩ）^２／ＡＲＥＡ｝×（１／４Π）×１００
ＡＲＥＡ：トナー投影面積
ＭＸＬＮＧ：絶対最大長
ＰＥＲＩ：周長
また、トナーへの均一な電荷付与を行い、より高い転写効率を得るために、個数分布における変動係数（Ａ）が３５％以下であることが好ましい。変動係数（Ａ）は下式で表される。
【０１６６】
変動係数（Ａ）＝（Ｓ／Ｄ１）×１００
Ｓ：トナーの個数分布における標準偏差値
Ｄ１：トナー粒子の個数平均粒径（ΜＭ）
また、高画質化を目的として微小ドットを忠実に現像するためには、トナー粒径は重量平均粒径で１０ΜＭ以下が好ましく、より好ましくは重量平均粒径４〜８ΜＭである。個数分布の測定は、コールターカウンターＴＡＩＩ型（コールター社製）を用いた。
【０１６７】
また上述のような球形トナーの製法はさまざま有り、たとえば乳化重合法、懸濁重合法、分散重合法などの重合反応を利用したものがよく利用される。また、重合法以外にも、粉砕トナーを溶剤により溶解させながら球形化する方法もあり、特に球形トナーを得る製法は限定するものではない。
【０１６８】
本実施例では、モノマーやワックスや荷電制御剤や開始剤などを含む原材料を分散剤を含む分散媒（通常は水）中に懸濁化させ、重合反応によってトナーを生成する懸濁重合法を用いた。
【０１６９】
【発明の効果】
以上説明したように本発明によれば、
▲１▼．簡潔な構成で像担持体表面から効率良く残留現像剤を除去出来る様にし、クリーニング不良が発生し難い画像形成装置を安価に提供する事ができる。
【０１７０】
▲２▼．環境条件によらず安定して像担持体の帯電を行える様にし、出力画像の安定性が高い画像形成装置を提供することができる。
【０１７１】
▲３▼．簡潔な構成で像担持体表面から効率良く残留現像剤を除去出来る様にし、クリーニング不良が発生し難い多色画像形成装置を安価に提供する事ができる。
【０１７２】
▲４▼．出力画像の品位を向上し、且つクリーニング不良の発生を防止する事ができる。
【０１７３】
▲５▼．像担持体や帯電部材の交換等、画像形成装置のメンテナンス作業に要する使用者の労力を軽減し、簡潔な操作で長期に亘り安定性の高い出力画像が得られる画像形成装置を提供する事ができる。
【０１７４】
▲６▼．少なくとも接触帯電部材を含む複数の構成要素を一体化し、画像形成装置本体に着脱自在としたプロセスカートリッジで、使用者に複雑な操作を強いる事無く前記プロセスカートリッジに搭載される接触帯電部材に応じた諸設定を行え、クリーニング不良や帯電不良等の画像欠陥の発生を安価に防止出来るプロセスカートリッジを提供する事ができる。
【図面の簡単な説明】
【図１】本発明の第１の実施例である、画像形成装置の模式図である。
【図２】環境条件により変化する、ＡＣピーク間電圧とＡＣ電流値の相関を示すグラフである。
【図３】帯電ＡＣピーク間電圧と、帯電電位収束電圧の関係を示すグラフである。
【図４】本発明の第１の実施例である画像形成装置の、クリーニング装置を説明する模式図である。
【図５】本発明の第２の実施例である、画像形成装置の模式図である。
【図６】本発明の第３の実施例である、画像形成装置の模式図である。
【図７】本発明の第４の実施例であるフルカラー画像形成装置の模式図である。
【図８】本発明の第４の実施例であるフルカラー画像形成装置で行われる、ＡＣ帯電電流値変更に係わる各手段の関係を説明するブロック図である。
【図９】本発明の第４の実施例であるフルカラー画像形成装置で行われる、ＡＣ帯電電流目標値の変更手順を説明するフローチャートである。
【図１０】従来の画像形成装置を説明する模式図である。
【図１１】従来の画像形成装置における、現像ローラの接離機構の一例を説明する模式図
である。
【図１２】回転式現像装置備えた、従来の多色画像形成装置を説明する模式図である。
【図１３】回転式現像装置の拡大図である。
【図１４】トナー形状係数ＳＦ−１の説明図
【図１５】トナー形状係数ＳＦ−２の説明図
【図１６】現像ローラの押し圧測定方法の説明図
【符号の説明】
感光ドラム、２．帯電ローラ、３．クリーニングブレード、４．廃現像剤容器、５．クリーニング装置、６．弾性ブレード（現像ブレード）、１７．クリーニングブレード、１８．クリーニング装置、２３．プロセスカートリッジ、２４．プロセスカートリッジ、２５．記憶媒体、２６．ＡＣ帯電電流目標値読出し手段、２７．コネクタ、２８．制御部、２９．プロセスカートリッジの有無検知手段、３０．ＡＣ帯電電流値切換え手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile that forms an image by an electrophotographic method, an electrostatic recording method, or the like, and a process cartridge used in the image forming apparatus.
In particular, the present invention relates to an image forming apparatus which visualizes an electrostatic latent image formed on an image carrier by contact development and cleans the image carrier using an elastic blade, and a process cartridge used in the image forming apparatus. .
[0002]
Further, in the visualizing step of the electrostatic latent image formed on the image carrier by the developing device, the electrostatic latent image on the image carrier and the developer carrier provided in the developing device are supported. The present invention relates to an image forming apparatus that is performed while making contact with a developer layer, and a process cartridge used for the image forming apparatus.
[0003]
[Prior art]
FIG. 10 shows an image carrier, a contact developing device as a means for visualizing an electrostatic latent image formed on the image carrier, and a device for cleaning the image carrier using an elastic blade. This is an example of a monocolor image forming apparatus that forms an image by transferring a developer image formed on an image carrier by the contact developing device onto a recording material.
[0004]
Reference numeral 101 denotes a photosensitive drum as an image carrier formed in a cylindrical shape. The photosensitive drum 101 is a so-called organic photosensitive member in which a charge generation layer is formed on a core metal made of aluminum or the like, and a charge transport layer is formed thereon.
[0005]
An AC bias and a DC bias are applied to a metal core 102a of the charging roller 102 as a contact charging member from a power source (not shown) provided in the image forming apparatus main body via a sliding electrode (not shown) brought into contact with the metal core. Is applied. As a result, while the photosensitive drum 101 rotates in the direction of the arrow A, the peripheral surface thereof is uniformly contact-charged to obtain a predetermined potential.
[0006]
It is known that the amount of ozone generated at the time of charging is smaller in the contact charging device as described above than in a charging device using a corona discharge method. In addition, the contact charging device includes an AC + DC application method in which an AC bias and a DC bias are superimposed and applied, and a DC application method in which only a DC bias is applied.
[0007]
However, in the case of the charging device of the DC application type, there is a disadvantage that when the resistance value of the charging member changes due to environmental changes such as temperature and humidity, the charging potential of the non-charging member easily changes accordingly.
[0008]
Generally, when the temperature rises, the resistance value of the charging member decreases. However, when such a DC application method is used, the temperature and humidity of the environment where the charging device is placed are always detected, and based on the detection result. Generally, a voltage or a current applied to the charging member is controlled by using a conventional method (for example, see Patent Documents 1 to 3).
[0009]
Next, a scanning exposure is performed on the charged surface of the photosensitive drum 101 by laser light emitted from a laser scanner 104 mounted on the image forming apparatus side to form an electrostatic latent image of target image information.
[0010]
On the other hand, the developing device 105 contacts the photosensitive drum 101 and performs development while rotating in the direction of arrow B. By rotating in the direction of arrow C, the non-magnetic toner T ′ as a developer is developed. A supply roller 105b as developer supply means for supplying to the roller 105a; a developing blade 105c as developer control means for controlling the amount of application and charge of the toner T 'on the development roller 105a; It is composed of a stirring member 105d and the like that supplies the mixture 105b and performs stirring.
[0011]
The electrostatic latent image reaches a portion facing the developing device 105 by the rotation of the photosensitive drum 101 that is performed subsequently.
[0012]
The developing device 105 performs the following operation in conjunction with the above operation. The toner T ′ stirred by the stirring member 105d is supplied onto the developing roller 105a by sliding friction between the developing roller 105a rotating in the direction of arrow B and the supply roller 105b rotating in the direction of arrow C. The toner T ′ on the developing roller 105a is provided with a desired charge amount by the developing blade 105c, the toner amount (toner layer thickness) is regulated, and the toner T ′ layer is carried on the developing roller 105a.
[0013]
When the toner T ′ layer carried on the developing roller 105a reaches a portion facing the photosensitive drum 101, a DC developing bias is applied from a power supply (not shown) to the developing roller 105a, and the developing roller 105a The toner T ′ is developed by transferring the toner T ′ to the formed electrostatic latent image. On the other hand, the toner T ′ that does not contribute to the development and remains on the surface of the developing roller 105a is collected in the developing device 105 via the supply roller 105b.
[0014]
In a contact developing device that uses the rigid photosensitive drum 101 to perform development by bringing the developing roller 105a into contact with the photosensitive drum 101, the developing roller 105a is generally made of an elastic material.
[0015]
As the above-mentioned material having elasticity, solid rubber or the like is used. In addition to forming the developing roller 105a with a single layer using an elastic material, for example, a solid rubber that is coated with a resin in consideration of the charging property to the toner is generally used.
[0016]
Further, the toner T ′ on the photosensitive drum 101 reaches a portion facing the transfer charger 106 by the subsequent rotation of the photosensitive drum 101, and is transferred onto the transfer paper P by the transfer charger 106. The toner T ′ on the transfer paper P is thermally melted by the fixing device 107 and discharged as a fixed image to the outside of the image forming apparatus.
[0017]
On the other hand, the toner T ′ remaining on the photosensitive drum 101 at the time of transfer reaches the charging roller 102 due to the rotation of the photosensitive drum 101 that is subsequently performed, and before the charging is performed again, the urethane rubber 108 a Are scraped off by a cleaning blade 108 configured to be attached thereto, and accumulated in the waste toner container 109.
[0018]
In the image forming apparatus described above, the waste toner container 109 is configured to also serve as a support for the photosensitive drum 101 and the cleaning blade 108, and the support plate 108 b of the cleaning blade 108 is fixed to the waste toner container 109. Many products have improved productivity and recyclability.
[0019]
Further, as described above, in the image forming apparatus in which the developing roller 105a having a particularly elastic property is disposed in contact with the photosensitive drum 101, in order to prevent the developing roller 105a from being deformed in the contact portion, the photosensitive drum 101 and the photosensitive drum 101 are prevented from being deformed. Many devices have a contact / separation mechanism between the developing devices 105.
[0020]
An example of the mechanism is shown in FIG. The developing device 105 is arranged so as to press the developing roller 105a against the surface of the photosensitive drum 101 by a pressure spring 105e. Except during development, the cam 105f operates in the direction of the arrow Z to move the developing device 105 to a position indicated by a broken line about the fulcrum 105g, thereby separating the photosensitive drum 101 and the developing roller 105a.
[0021]
Further, as shown in FIG. 12, a plurality of developing units (developing means) 113y, 113m, 113c, and 113k that respectively store toners of different colors are provided. A color image forming apparatus that obtains a multicolor image by sequentially contact-developing an electrostatic latent image on a drum 110 is well known.
[0022]
The multicolor image forming apparatus provided with a plurality of contact developing type developing units shown in FIG. 12 mainly includes a photosensitive drum 110 as an image carrier, and a charger 111 as a charging unit for uniformly charging the photosensitive drum 110. , A laser scanner 112 that provides image information, a rotary developing device 113 that supports a plurality of developing units 113y, 113m, 113c, and 113k corresponding to each color, and an intermediate transfer member 114.
[0023]
FIG. 13 is an enlarged view of the rotary developing device 113. The rotary developing device 113 is a system in which one of the four developing devices 113y to 113k is fixed at a developing position by rotating the support 115. The rotary developing device 113 has developing openings of the developing units 113y to 113k on the same circumference centered on the support rotating shaft 115a.
[0024]
The developing units 113y to 113k have developing rollers 116y, 116m, 116c, and 116k, respectively, which are developer carrying members, for transporting the toner to a contact portion with the photosensitive drum 110. Further, around the developing rollers 116y to 116k, supply rollers 117y, 117m, 117c, and 117k for supplying a non-magnetic one-component toner onto the developing rollers 116y to 116k while rotating, and toner on the developing rollers 116y to 116k. Regulator blades 118y, 118m, 118c, and 118k that provide a desired amount of charge and regulate the amount of toner are provided, and a developing bias voltage power supply 119 (FIG. 12) that applies a developing bias voltage to developing rollers 116y to 116k is provided. .
[0025]
The rotary developing device 115 presses the developing devices 113y to 113k with the pressurizing device 120 only at the time of development, thereby bringing the developing rollers 116y to 116k in the developing devices 113y to 113k into contact with the photosensitive drum 101, and While the developing device 115 is rotating or during non-development, the pressing operation of the pressing device 120 is released to separate the photosensitive drum 110 from the developing rollers 116y to 116k in the developing devices 113y to 113k. ing.
[0026]
In FIG. 12, the photosensitive drum 110 is rotated in the direction of arrow E, is uniformly charged by the charger 111, and then an electrostatic latent image is formed on the photosensitive drum 110 by the laser scanner 112.
[0027]
The latent images described above are latent images corresponding to the color developers in the developing units 113y to 113k, yellow (Y), magenta (M), cyan (C), and black (Bk).
[0028]
More specifically, first, an electrostatic latent image corresponding to the first color, for example, a yellow developer is formed on the photosensitive drum 110, visualized by the developing device 103 y containing the yellow developer, and then transferred to the intermediate transfer member 114. . Subsequently, after the residual toner on the photosensitive drum 110 is cleaned by the cleaning device 121, a second color, for example, an electrostatic latent image corresponding to the magenta developer is formed on the photosensitive drum 110, and the developing device in which the magenta developer is stored is formed. After being visualized by the container 103m, the image is superimposed and transferred onto the intermediate transfer member 114 on which the first color yellow-visible image has already been transferred.
[0029]
After the above operation is performed a plurality of times, the developers stacked in a plurality of layers on the intermediate transfer body 114 are collectively transferred to the transfer material P, and are fused and fixed by the fixing device 122.
[0030]
In the above-described multicolor image forming apparatus, the developing units 113y to 113k in the rotary developing unit 115 are stopped at a position not facing the photosensitive drum 110 during non-image formation, and the pressure on the developing units 113y to 113k is also reduced. By releasing, the photosensitive drum 110 and the developing rollers 116y to 116k are completely separated. The developing rollers 104a to 104d are configured so as to obtain a driving force after a pressing operation is performed at a position where the developing rollers 104a to 104d are in contact with the photosensitive drum 101.
[0031]
In order to facilitate maintenance such as replenishment of the developer and replacement of the photosensitive drum, a plurality of components of the image process (the photosensitive drum 101, the charging roller 102, the developing device 105, etc. in FIG. 10) are integrated. As a result, a process cartridge which is detachable from the image forming apparatus main body has been put to practical use.
[Patent Document 1]
JP-A-9-79383
[Patent Document 2]
JP-A-5-66662
[Patent Document 3]
Japanese Patent Publication No. 3-52058
[0032]
[Problems to be solved by the invention]
As described in the background art, as the contact charging means of the image bearing member, an AC + DC applying method which can obtain a stable charging property relatively easily is adopted.
[0033]
In an image forming apparatus that performs development by bringing a developing roller, which is a developer carrier, into contact with a photosensitive drum, which is an image carrier, the photosensitive drum does not separate during development. In many cases, the developing roller is brought into contact with a high pressing pressure.
[0034]
Further, in an image forming apparatus having a rotary developing device, the rotary developing device is often composed of a large number of components in a complicated manner, and the contact pressure of the developer carrier with respect to the image carrier is set higher. To increase stability.
[0035]
For this reason, in the cleaning apparatus in which the waste toner container 109 also serves as a support for the photosensitive drum 101 and the cleaning blade 108, the cleaning blade support sheet metal 108b and the waste toner container portion serving as the support are used for the development. When the cleaning blade 108 is bent by the pressing pressure of the roller 105a, it is difficult to bring the cleaning blade 108 into contact with the photosensitive drum 101 with a constant pressure.
[0036]
In particular, when the supporting plate 108b of the cleaning blade 108 is fixed to the waste toner container 109, high precision and strength are required for mounting the cleaning blade 108 in order to minimize fluctuations in the pressing pressure of the cleaning blade 108 against the photosensitive drum. Will be done.
[0037]
The present invention has been made in view of such a problem, and an object thereof is to provide an image forming apparatus as described above.
▲ 1 ▼. An object of the present invention is to provide an inexpensive image forming apparatus in which a residual developer can be efficiently removed from the surface of an image carrier with a simple configuration, and in which poor cleaning hardly occurs.
[0038]
▲ 2 ▼. An object of the present invention is to provide an image forming apparatus capable of stably charging an image carrier irrespective of environmental conditions and having high stability of an output image.
[0039]
(3). It is an object of the present invention to provide a multicolor image forming apparatus in which a residual developer can be efficiently removed from the surface of an image carrier with a simple configuration, and in which a cleaning failure hardly occurs.
[0040]
▲ 4 ▼. The purpose is to improve the quality of the output image and prevent the occurrence of cleaning failure.
[0041]
▲ 5 ▼. By providing an image forming apparatus which can reduce the labor of the user required for maintenance work of the image forming apparatus such as replacement of an image carrier and a charging member, and which can obtain a stable output image over a long period with a simple operation. is there.
[0042]
▲ 6 ▼. A process cartridge that integrates at least a plurality of components including a contact charging member and is detachable from an image forming apparatus main body. The process cartridge can be mounted on the process cartridge without forcing a user to perform a complicated operation. An object of the present invention is to provide a process cartridge capable of performing various settings and inexpensively preventing the occurrence of image defects such as cleaning failure and charging failure.
[0043]
[Means for Solving the Problems]
The present invention is an image forming apparatus and a process cartridge having the following configurations.
[0044]
(1) The surface of the image carrier is charged by applying a voltage in which a DC component and an AC component are superimposed on the image carrier while the charging member is in contact with the image carrier. Contact charging means for performing, a latent image forming means for forming an electrostatic latent image on a charged surface of the image carrier, and a developer carrying a developer with the electrostatic latent image formed on the surface of the image carrier. A contact developing unit for performing development by bringing the carrier into contact with the image carrier; and a developer remaining on the surface of the image carrier after transferring a developer image on the surface of the image carrier onto a recording material by a transfer unit. A cleaning means for removing by an elastic blade abutted on the image carrier, the image forming apparatus,
The pressing pressure of the developer carrier against the image carrier is 0.88 N / cm or more and 1.76 N / cm or less (90 g / cm or more and 180 g / cm or less), and the voltage between the AC peaks of the voltage applied to the charging member is An image forming apparatus characterized in that the voltage is less than 2.0 kVpp.
[0045]
By using the above means, the displacement of the surface of the image carrier due to the vibration of the charging member is suppressed, and the elastic blade for the image carrier which is strictly controlled in order to follow the surface of the image carrier displaced as described above. The manufacturing tolerance of the contact pressure of the members can be set relatively large.
[0046]
Further, the amount of change in the contact pressure of the elastic blade member with respect to the image carrier, which fluctuates due to the pressing of the contact developing means against the image carrier, can be suppressed, and the support for supporting the elastic blade can be configured relatively simply. Therefore, the cleaning of the non-magnetic one-component developer including the spherical toner can be stably performed, and the image forming apparatus having the above-described cleaning unit can be provided at low cost.
[0047]
(2) A means for controlling the AC voltage applied to the charging member with a constant current is provided, and the constant current control means controls the AC peak-to-peak voltage to change within a range from the charging potential convergence voltage to less than 2.0 kVpp. The image forming apparatus according to (1), wherein
[0048]
By using the above means, it is possible to stably obtain a high-quality output image without causing an image defect called sand and defective cleaning under a wide range of environmental conditions.
[0049]
(3) After a desired developing unit of the developing means having a plurality of developing units is sequentially moved to a developing position opposed to the image carrier and the electrostatic latent image formed on the image carrier is contact-developed, The image forming apparatus according to (1) or (2), wherein multiple transfer is performed on an intermediate transfer member or a recording material.
[0050]
By using the above-mentioned means, a high-quality multicolor image can be stably obtained without causing an image defect called sand and defective cleaning under a wide range of environmental conditions.
[0051]
(4) A developer containing toner particles containing at least a binder resin and a colorant, an inorganic fine powder and a hydrotalcite compound, and having a shape factor SF-1 value of 100 measured by an image analyzer of the toner. The image forming apparatus according to any one of (1) to (3), wherein contact development is performed using a developer having a value of SF-2 and a value of SF-2 of 100 to 140.
[0052]
By using the above means, by adjusting the amount of the hydrotalcite compound contained in the developer, it is possible to easily control the fluidity of the developer having a high slip-through property, the elastic blade It is easy to remove the developer from the surface of the image carrier by using. Further, by using the spherical toner having the above-mentioned shape coefficient, high developability and transferability can be obtained, and the quality of an output image can be improved.
[0053]
(5) Image formation in which a plurality of components related to image formation are integrated with a storage medium storing a unique AC charging current target value, and image formation is performed using a process cartridge that is detachably attached to the image forming apparatus main body. The apparatus comprises: means for reading at least a unique AC charging current target value stored in the storage medium; and AC current value changing means for changing the AC current value with reference to the AC charging current target value. The image forming apparatus according to any one of (1) to (4), wherein control is performed such that a peak-to-peak voltage is less than 2.0 kVpp.
[0054]
By using the above-described means, it is possible to easily replace consumable members such as an image carrier and a charging member with only a simple operation of replacing a process cartridge, thereby reducing user's labor involved in various maintenance operations. And a stable output image can be obtained over a long period of time. In addition, even if the characteristics of the charging member change due to the above-described replacement operation, the AC peak-to-peak voltage is controlled to be less than 2.0 kVpp in accordance with the specific AC charging current target value stored in the storage medium. In addition, the occurrence of defective cleaning can be prevented.
[0055]
(6) The image forming apparatus according to any one of (1) to (5), wherein the latent image forming unit is an exposing unit.
[0056]
(7) The image forming apparatus according to any one of (1) to (6), wherein the developer is a non-magnetic one-component developer including a spherical toner.
[0057]
(8) A process cartridge which integrates at least a plurality of components including at least a contact charging unit and a storage medium and is detachable from an image forming apparatus main body. A unique AC charging current target value predetermined in accordance with a mounted charging member is stored in the storage medium so that a voltage is twice the discharge start voltage to less than 2.0 kVpp. Process cartridge.
[0058]
By using the above means, the information of the storage medium mounted on the process cartridge can be used for determining the AC charging current value to be applied to the charging member incorporated in the process cartridge. An image can be formed by applying an optimal charging current to the charging member without providing the charging member.
[0059]
Therefore, in various image forming apparatus main bodies in which an image is formed by mounting the process cartridge, occurrence of image defects such as charging failure and cleaning failure can be prevented.
[0060]
BEST MODE FOR CARRYING OUT THE INVENTION
<Example 1>
FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention.
[0061]
In the image forming apparatus of this embodiment, a charging roller 2 serving as a contact charging unit is brought into contact with a photosensitive drum 1 serving as an image carrier, and a voltage in which an AC component is superimposed on a DC component is applied to the charging roller 2. The surface of the photosensitive drum 1 is charged.
[0062]
Further, the electrostatic latent image formed on the surface of the image carrier in the process of forming an image by the image forming apparatus is developed by a contact developing unit using a non-magnetic one-component developer containing a spherical toner.
[0063]
In order to remove the developer remaining on the surface of the photosensitive drum 1, a cleaning blade 3 composed of a metal supporting plate 3a and a urethane rubber portion 3b, both ends of the cleaning blade 3 are supported and the cleaning blade 3 is supported. A cleaning device 5 including a waste developer container 4 also serving as a storage section for the developer collected from the surface of the photosensitive drum 1 by the blade 3 is provided.
[0064]
Further, in this image forming apparatus, the pressing pressure of the developer carrier against the image carrier is set to 0.88 N / cm or more and 1.76 N / cm or less (90 g / cm or more and 180 g / cm or less) and applied to the charging member. The AC peak-to-peak voltage of the applied voltage is less than 2.0 kVpp.
[0065]
Hereinafter, details of the image forming operation performed by the image forming apparatus of FIG. 1 will be described.
[0066]
In FIG. 1, a photosensitive drum 1 is a so-called organic photoconductor in which a charge generation layer 1b is formed on a core metal 1a made of aluminum or the like, and a charge transport layer 1c is formed thereon.
An oscillation voltage in which an AC bias and a DC bias are superimposed on a core metal 2a of the charging roller 2 from a power supply unit 6 provided in the image forming apparatus main body via a sliding electrode (not shown) brought into contact with the core metal 2a. Is applied. Thus, the photosensitive drum 1 is uniformly contact-charged on its peripheral surface while rotating in the direction of arrow A in FIG. 1 to obtain a predetermined potential (following a DC bias value applied in a superimposed manner).
[0067]
In the oscillating voltage applied from the power supply section 6, the constant current control is performed by the constant current control means so that the current value of the AC bias is always constant. That is, when the load of the power supply unit 6 changes due to changes in various conditions such as the resistance of the charging roller 2, the AC peak-to-peak voltage is maintained while the AC current value is kept constant at the bias applied to the charging roller 2. Only changes.
[0068]
Thus, when the present image forming apparatus is installed in a typical environment, the correlation between the current value of the AC bias applied to the charging roller 2 and the voltage between AC peaks is shown in a graph in FIG.
[0069]
From the graph of FIG. 2, the AC peak-to-peak voltage increases in a low-temperature and low-humidity environment where the resistance value of each member tends to increase, and conversely, the AC voltage increases in a high-temperature and high-humidity environment where the resistance value of each member tends to decrease. It can be seen that the peak-to-peak voltage decreases.
[0070]
Further, the graph of FIG. 3 shows the result of examining the transition of the charging potential on the surface of the photosensitive drum 1 by changing the AC peak-to-peak voltage in the image forming apparatus of this embodiment.
[0071]
From the graph of FIG. 3, as the AC peak-to-peak voltage is increased, the potential on the surface of the photosensitive drum 1 is made constant from a certain peak-to-peak voltage value in accordance with the applied DC bias value. It can be seen that the value is about 1.4 kVpp.
[0072]
That is, when the peak-to-peak voltage value exceeds about 1.4 kVpp, stable discharge is repeatedly performed by the charging roller 2, and the surface potential of the photosensitive drum 1 is charged to a predetermined value (similar to the value of the DC bias superimposed at the same time). Is done. In addition, a peak-to-peak voltage value of 1.4 kVpp at which the surface potential of the photosensitive drum 1 is stabilized by repeatedly performing stable discharge from the charging roller 2 is defined as a charging potential convergence voltage in the present embodiment.
[0073]
Further, in consideration of the cleaning property of the developer T ′ from the photosensitive drum 1, it is necessary to carefully set the bias applied to the charging roller 2, and the details will be described later.
[0074]
Next, the charged surface of the photosensitive drum 1 is scanned and exposed by a laser beam emitted from a laser scanner 7 mounted on the image forming apparatus, thereby forming an electrostatic latent image of target image information.
[0075]
On the other hand, the developing device 8 is in contact with the photosensitive drum 1 and performs development while rotating in the direction of arrow B in FIG. 1, and rotates in the direction of arrow C in FIG. A supply roller 8b as a developer supply means for supplying the developer T 'to the developing roller 8a; and a developing blade 8c as a developer regulating means for regulating the amount of application and charge of the developer T' on the development roller 8a. And a stirring member 8d for supplying the developer T 'to the supply roller 8b and stirring the developer.
[0076]
The developer T 'stirred by the stirring member 8d is rubbed between the developing roller 108a rotating in the direction of arrow B in FIG. 1 and the supply roller 8b rotating in the direction of arrow C in FIG. Supplied.
[0077]
The developer T ′ on the developing roller 8a is provided with a desired amount of charge by the developing blade 8c, the amount of the developer (developer layer thickness) is regulated, and the developer T ′ layer is carried on the developing roller 8a. Is done.
[0078]
In the image forming apparatus according to the present embodiment, the developing roller 8a is separated from the photosensitive drum 1 by the contact / separation mechanism shown in FIG.
[0079]
When the electrostatic latent image reaches a portion facing the developing device 8 due to the subsequent rotation of the photosensitive drum 1, a DC developing bias is applied to the developing roller 8a from a power supply (not shown).
[0080]
Subsequently, the developing roller 8a is brought into contact with the photosensitive drum 1 by the above-mentioned contact / separation mechanism, and development is performed by transferring the developer T 'from the developing roller 8a to the electrostatic latent image.
[0081]
Note that the developer T ′ that does not contribute to the development and remains on the surface of the developing roller 8a is collected into the developing device 8 via the supply roller 8b.
[0082]
Here, the pressing pressure of the developing roller 8a against the photosensitive drum 1, the "image omission" caused by the separation of the developing roller 8a from the photosensitive drum 1 during development, and the cleaning property of the developer T 'from the photosensitive drum 1 And a strong correlation was found between them, the details of which will be described later.
[0083]
The pressing pressure of the developing roller 8a is measured by using a measuring device as shown in FIG. 16, and is defined as follows.
[0084]
In FIG. 16, reference numeral 31 denotes a dummy drum having the same outer diameter as the photosensitive drum 1 and having a cylindrical shape with a width of 1 cm in the rotation axis direction of the photosensitive drum 1. The above-mentioned dummy drum 31 is attached to a support member 32 so as to be freely rotatable about a rotation shaft 31a. The support member 32 is connected to a load sensor 33, and the output value of the load sensor 33 can be read by a voltmeter 35 by being amplified by an amplifier 34.
[0085]
In order to actually measure the pressing pressure of the developing roller 8a, the dummy drum 31 is attached to the image forming apparatus main body instead of the photosensitive drum 1, and while the developing roller 8a is pressed against the surface of the photosensitive drum 1, The members are driven to rotate as in the case of image formation, and the value of the voltmeter 35 is read. At this time, the pressing force of the developing roller 8a is calculated by associating the load per unit voltage determined in advance with the read value of the voltmeter 35.
[0086]
The pressing pressure of the developing roller 8a is controlled by increasing or decreasing the repulsive force of a pressure spring (not shown in FIG. 1).
[0087]
On the other hand, the image of the developer T ′ on the photosensitive drum 1 reaches a portion facing the transfer roller 9 by the subsequent rotation of the photosensitive drum 1, and is transferred onto the transfer paper P by the transfer roller 9. The developer T ′ on the transfer paper P is thermally melted by the fixing device 10 and is discharged outside the image forming apparatus as a fixed image.
[0088]
On the other hand, the developer T ′ remaining on the photosensitive drum 1 at the time of the transfer reaches the charging roller 2 by the rotation of the photosensitive drum 1 that is subsequently performed, and before the charging is performed again, the urethane rubber T The toner is scraped off by the cleaning blade 3 having the mounting member 3b and accumulated in the waste developer container 4.
[0089]
As shown in FIG. 4, in the image forming apparatus of the present embodiment, the waste developer container 4 is configured to also serve as a support for the photosensitive drum 1 and the cleaning blade 3, and the cleaning blade 3 has a support plate 3a. The waste developer container 4 is fixed to the waste developer container 4 by being screwed directly to the waste developer container 4.
[0090]
By attaching the photosensitive drum 1 to the waste developer container 4, the cleaning blade 3 comes into contact with the photosensitive drum 1 at a linear pressure of about 0.588 to 0.88 N / cm (about 60 to 90 g / cm). Is done.
[0091]
As described above, in consideration of the cleaning property of the developer T ′ from the photosensitive drum 1, it is necessary to carefully set the bias applied to the charging roller 2.
[0092]
Further, the pressing pressure of the developing roller 8a against the photosensitive drum 1, the "image omission" caused by the separation of the developing roller 8a from the photosensitive drum 1 during development, and the cleaning property of the developer T 'from the photosensitive drum 1 are improved. There is a strong correlation between the two.
[0093]
Therefore, in the image forming apparatus of this embodiment, the bias applied to the charging roller 2 and the pressing pressure of the developing roller 8a against the photosensitive drum 1 (denoted by D in Table 1) are determined. (10 ° C./10%) and under a high-temperature, high-humidity environment (30 ° C./85%), the respective conditions were varied to extract a problem.
[0094]
The results are shown in Tables 1 and 2 below. The symbols in the table indicate the following image defects, respectively.
[0095]
○ ・ ・ ・ No image defect (OK)
Sand: sandy ground (poor charging)
Deletion: Image blank (insufficient pressing pressure of developing roller)
C: Cleaning failure
In addition, the places where △ is attached to the above-mentioned symbols indicate that each image defect is judged to be at a level that does not cause a problem in practical use.
[0096]
[Table 1]

[0097]
[Table 2]

[0098]
According to the comparison results under the low-temperature and low-humidity environment shown in Table 1, when the AC peak-to-peak voltage applied to the charging member is less than 1.4 kVpp (that is, less than the discharge starting voltage), an image defect called sand is displayed on the output image. Occurs. This image defect is particularly visually recognized as a grain on a halftone image.
[0099]
On the other hand, if the AC peak-to-peak voltage value applied to the charging member exceeds 2.0 kVpp, the developer on the photosensitive drum cannot be collected and vertical streaks appear on the output image, resulting in poor cleaning.
[0100]
Further, when the pressing pressure of the developing roller 8a against the photosensitive drum 1 is set to exceed 1.76 N (180 g) per 1 cm width, the above-described cleaning failure occurs.
[0101]
Further, when the pressing pressure of the developing roller 8a against the photosensitive drum 1 is set to less than 0.88 N (90 g) per 1 cm width, a portion where the developing is not performed due to the separation between the photosensitive drum 1 and the developing roller 8a during the development. As a result, an image defect called “image white spot” occurs.
[0102]
However, the above tendency is slightly different under a high temperature and high humidity environment as shown in Table 2.
[0103]
In the high-temperature and high-humidity environment, there is no significant change in the tendency of the occurrence of “image white spots” or “sandy grounds” with respect to various conditions as compared with the low-temperature and low-humidity environment. It can be seen that even when the pressure is large and the pressing pressure of the developing roller 8a against the photosensitive drum 1 becomes higher, it is difficult to cause a cleaning failure.
[0104]
It was also found that the tendency of image defects to occur under a general environment (about 24 ° C./60%) is intermediate between the above-described high-temperature, high-humidity environment and low-temperature, low-humidity environment.
[0105]
Therefore, if it is considered that the occurrence of image defects is effectively suppressed in a wider environment, the image forming apparatus is configured under conditions in which various problems do not occur in a low-temperature and low-humidity environment (in a thick frame in Table 1). Just do it.
[0106]
Therefore, in this image forming apparatus, the pressing pressure of the developer carrier against the image carrier is set to 1.17 N to fall within the range of 0.88 N / cm to 1.76 N / cm (90 g / cm to 180 g / cm). / Cm (120 g / cm).
[0107]
In the present image forming apparatus, the setting is made such that the voltage between the AC peaks of the voltage applied to the charging roller 2 is equal to or higher than the charging potential converging voltage and lower than 2.0 kVpp. However, since the image forming apparatus of this embodiment employs the constant current control method for the charging AC bias, the control target of the charging AC current is determined from the relationship between the AC peak voltage and the AC current value shown in the graph shown in FIG. The value was determined to be about 1000 μA.
[0108]
As described above, in the image forming apparatus of the present embodiment, the image forming apparatus is configured such that the residual developer can be efficiently removed from the surface of the image carrier with a simple configuration and image defects such as poor cleaning and sand are less likely to occur. It can be offered at a low price.
[0109]
<Example 2>
FIG. 5 is a schematic view of a full-color image forming apparatus according to a second embodiment of the present invention.
[0110]
This full-color image forming apparatus mainly includes a photosensitive drum 11 as an image carrier, a charging roller 12 as a charging unit for uniformly charging the photosensitive drum 11, a laser scanner 13 for exposing image information, and a yellow ( There is provided a rotary developing device 14 that supports developing devices 14y, 14m, 14c, and 14k of four colors corresponding to Y), magenta (M), cyan (C), and black (Bk).
[0111]
Further, in the full-color image forming apparatus of the present embodiment, a visible image sequentially formed on the photosensitive drum 11 is transferred between three rollers of a driving roller 15a, a driven roller 15b, and a secondary transfer facing roller 15c by a belt member. Is superimposed on the surface of the intermediate transfer belt 15 on which the image is stretched, and then transferred collectively onto the recording paper P to form a full-color image.
[0112]
Further, in the full-color image forming apparatus of the present embodiment, a metal supporting plate 16a and a urethane rubber portion 16b are used to remove the developer and foreign matters remaining on the photosensitive drum 11 after the transfer in accordance with the above-described image forming operation. The cleaning device 18 includes a cleaning blade 16 to be cleaned and a waste developer container 17 that supports both ends of the cleaning blade 16 and also serves as a storage unit for the developer collected from the surface of the photosensitive drum 11 by the cleaning blade 16. Provided.
[0113]
Note that the cleaning device 18 described above uses the one used in the image forming apparatus of the first embodiment of the present invention.
[0114]
Further, as a developer, a mixture of spherical toner particles having a shape factor SF-1 value of 100 to 160 and a SF-2 value of 100 to 140, an inorganic fine powder and a hydrotalcite compound is used. The total amount of the hydrotalcite compounds contained in the developers of the respective colors was 0.1 parts by weight with respect to 100 parts by weight of the developers.
[0115]
In FIG. 5, the photosensitive drum 11 is rotated in the direction of arrow D, and its peripheral surface is charged to a predetermined potential by a vibration voltage obtained by superimposing an AC bias and a DC bias applied to the charging roller 12.
[0116]
In the image forming apparatus of this embodiment, the AC peak-to-peak voltage of the voltage applied to the charging roller 12 is set to the value found in the image forming apparatus of the first embodiment of the present invention, that is, the charging potential convergence voltage or more and less than 2.0 kVpp. Was set to fall into the category. At this time, the target current value at the time of performing the constant current control was determined to be about 1000 μA in consideration of the AC peak-to-peak voltage value particularly in a low-temperature and low-humidity environment where cleaning failure easily occurs (see the graph shown in FIG. 2). .
[0117]
After that, the electrostatic force corresponding to each color (the developer of each color filled in the developing units 14y to 14k, yellow (Y), magenta (M), cyan (C), and black (Bk)) is scanned by the laser scanner 13. Latent images are sequentially formed on the surface of the photosensitive drum 11.
[0118]
First, when an electrostatic latent image corresponding to the first color, for example, a yellow developer, is formed on the photosensitive drum 11, the yellow developing device 14y accommodated in the rotary developing device 14 faces the photosensitive drum 11, and the developing roller 14a The contact development is performed by the yellow developer carried on the substrate.
[0119]
As described above, in the image forming apparatus of the present embodiment, as the developer of each color, the value of the shape factor SF-1 is 100 to 160, the value of SF-2 is 100 to 140, and the binder and the colorant are used. And 0.1 parts by weight of a hydrotalcite compound per 100 parts by weight of the developer, and 0.1 part by weight of the hydrotalcite compound based on 100 parts by weight of the developer. Use a mixture.
[0120]
The developing devices 14y to 14k in the rotary developing device 14 are stopped at positions not facing the photosensitive drum 11, and the pressure applied to the developing devices 14y to 14k is released, so that the developing rollers 14a of all the developing devices are also exposed to light. It is completely separated from the drum 11. Further, the developing rollers 14a of the developing devices 14y to 14k are configured such that a driving force is obtained after a pressing operation is performed at a developing position.
[0121]
Further, the pressurizing and separating operations of the developing units 14y to 14k are performed by the pressurizing device shown in FIG.
[0122]
On the other hand, the control of the pressing pressure of the developing roller 14a against the photosensitive drum 11 is performed by changing the cam profile (not shown in FIG. 13) of the cam portion of the pressing device to increase or decrease the operation stroke of the developing devices 14y to 14k. Performed by
[0123]
Further, in the image forming apparatus of the present embodiment, the pressing pressure of the developing roller 14a against the photosensitive drum 11 is the value found in the image forming apparatus of the first embodiment of the present invention, that is, 0.88 N / cm or more and 1.76 N /. cm (not less than 90 g / cm and not more than 180 g / cm) was set at 1.17 N / cm (120 g / cm).
[0124]
Subsequently, the yellow developer image formed on the photosensitive drum 11 is primarily transferred onto the intermediate transfer belt 15 in the primary transfer section 19.
[0125]
The residual toner on the photosensitive drum 11 is cleaned by a cleaning device 17 using an elastic blade.
[0126]
Thereafter, an electrostatic latent image corresponding to the second color magenta developer is formed on the photosensitive drum 11, and a magenta developer image is formed by the magenta developing device 14m containing the magenta developer. The above-mentioned magenta developer image is transferred in the primary transfer section 19 onto the intermediate transfer belt 15 on which the first color yellow developer image has already been transferred. Further, the developer remaining on the photosensitive drum 11 after the primary transfer is cleaned by the cleaning device 18 as in the case of forming the first color yellow image.
[0127]
These operations are performed four times corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk). The developer images superimposed in four layers on the intermediate transfer belt 15 are The transfer unit 20 collectively transfers the recording paper P onto the recording paper P, and thereafter, is fused and fixed by the fixing device 22.
[0128]
Further, after the batch transfer in the secondary transfer section 20, the developer remaining on the intermediate transfer belt 15 contacts and separates from the intermediate transfer belt 15 at a predetermined timing. The roller 21 applies a bias having a polarity opposite to that of the image forming area on the intermediate transfer belt 15 (the polarity is also opposite to the charging polarity of the photosensitive drum 11), and is discharged from the intermediate transfer belt 15 to the photosensitive drum 11. You. As described above, the developer discharged onto the photosensitive drum 11 is removed by the cleaning device 18 until the next image is formed.
[0129]
By setting the AC peak-to-peak voltage during charging and the pressing pressure of the developing roller 14a against the photosensitive drum 11 as described above, an image defect occurs as in the image forming apparatus of the first embodiment of the present invention. It becomes difficult.
[0130]
On the other hand, two levels of the mixing amount of the hydrotalcite compound with respect to the developer of each color were prepared: 0.1 part by weight (set value in this embodiment) and 0.2 part by weight with respect to 100 parts by weight of the developer. In order to compare with the first image forming apparatus of the present invention using a developer containing no talcite compound, the durability was evaluated in a low-temperature and low-humidity environment.
[0131]
The results are shown in Tables 3 and 4 below. The symbols in the table indicate the following image defects, respectively.
[0132]
○ ・ ・ ・ No image defect (OK)
Sand: sandy ground (poor charging)
Deletion: Image whiteout (insufficient pressing pressure of developing roller)
C: Cleaning failure
In addition, the places where △ is attached to the above-mentioned symbols indicate that each image defect is judged to be at a level that does not cause a problem in practical use.
[0133]
[Table 3]

[0134]
[Table 4]

[0135]
As shown in Table 3, the image forming apparatus of the present embodiment has a higher charging AC peak-to-peak voltage value and a higher sensitivity than the image forming apparatus of the first embodiment of the present embodiment using the same cleaning device. It can be seen that poor cleaning is hard to occur even when the contact pressure of the developing roller with respect to the drum is increased.
[0136]
Further, as shown in Table 4, when the amount of the hydrotalcite compound contained in the developer of each color was 0.2 parts by weight, the above tendency became more remarkable, and the cleaning property and the hydrotalcite compound were increased. It can be seen that there is a close relationship with the quantity of
[0137]
This is because the fluidity of the developer mainly composed of spherical toner, which had a high slip-through property, was reduced by increasing the amount of the hydrotalcite compound, and the developer was removed from the surface of the photosensitive drum using an elastic blade. Is likely to be easily removed.
[0138]
However, when the addition amount of the hydrotalcite compound is extremely increased, problems such as fusion of the developer component to the photosensitive drum surface and charge-up of the developer in a low-temperature and low-humidity environment are likely to occur. I know it will.
[0139]
In the image forming apparatus of the present embodiment, the AC peak-to-peak voltage and the pressing pressure of the developing roller 14a against the photosensitive drum 11 are set as described above so that sufficient cleaning performance can be obtained with a margin. By appropriately controlling the addition amount of the hydrotalcite compound, the quality of the output image could be improved without impairing the high developability and transferability obtained when using a spherical toner.
[0140]
<Example 3>
FIG. 6 is a schematic diagram of an image forming apparatus according to a third embodiment of the present invention.
[0141]
In the image forming apparatus according to the present embodiment, in the image forming apparatus (FIG. 1) according to the first embodiment of the present invention, of the components of the image forming process for forming an image, the photosensitive drum 1 as an image carrier and A charging device 2 for charging the surface of the photosensitive drum 1; a developing device 8 containing a developer T '; a cleaning device 3 including a cleaning blade 3 and a waste developer container 4; It is integrated and configured as a process cartridge 23 that is detachable from the image forming apparatus main body. Other configurations are the same as those of the image forming apparatus of FIG.
[0142]
In this image forming apparatus, the pressing pressure of the developer carrier 8a against the image carrier 1 is 1.17 N / cm (120 g / cm), and the voltage between the AC peaks of the voltage applied to the charging roller 2 converges on the charging potential. Control is performed so that the voltage becomes equal to or higher than the voltage and lower than 2.0 kVpp.
[0143]
By adopting the above configuration, the displacement of the surface of the image carrier due to the vibration of the charging member is suppressed, and the elasticity with respect to the image carrier 1 strictly controlled in order to follow the surface of the image carrier displaced as described above. The manufacturing tolerance of the contact pressure of the blade member 3 can be set relatively large. Further, the amount of change in the contact pressure of the elastic blade member 3 with respect to the image carrier 1, which fluctuates due to the pressing of the contact developing means 8a against the image carrier 1, can be suppressed.
Therefore, the residual developer can be efficiently removed from the surface of the image carrier with a simple configuration, and an image forming apparatus in which image defects such as poor cleaning and sandy ground are hardly generated can be provided at low cost.
[0144]
Further, by simply performing the simple operation of replacing the process cartridge 23, it becomes possible to replace the consumable members such as the photosensitive drum 1 and the charging roller 2 in addition to the replenishment of the developer T '. Thus, the user's labor concerning the above can be reduced, and a stable output image can be easily obtained.
[0145]
<Example 4>
FIG. 7 is a schematic diagram of a full-color image forming apparatus according to a fourth embodiment of the present invention.
[0146]
In the image forming apparatus according to the present embodiment, in the image forming apparatus according to the second embodiment of the present invention (FIG. 5), the intermediate transfer belt 15 is integrally formed with the driven roller 15b, the driving roller 15a, and the secondary transfer facing roller 15c. And is suspended by two axes of a drive roller 15d having both functions.
[0147]
Among the components of an image forming process for forming an image, a photosensitive drum 1 as an image carrier, a charging roller 2 as a part of a charging unit for charging the surface of the photosensitive drum 1, a cleaning blade 16, The cleaning device 18 including the developer container 17 and the intermediate transfer belt 15 are also integrated, and are configured as a process cartridge 24 that is detachable from the main body of the full-color image forming apparatus.
[0148]
Further, the image forming apparatus of the present embodiment is provided with a storage medium 25 storing a unique AC charging current target value, and reading the unique AC charging current target value stored in the storage medium 25. A target value reading means 26 and AC current value switching means means 30 for changing the AC current value with reference to the AC charging current target value, wherein the charging current value is set so that the AC peak-to-peak voltage becomes less than 2.0 kVpp. It is characterized by performing control of. In the above, the storage medium 25 is provided on the process cartridge 24 side.
[0149]
The above-mentioned specific AC charging current target value is defined as a voltage between the AC peak applied to the charging roller 12 and the charging potential convergence voltage of 2.0 kVpp or more when the process cartridge 24 is mounted on the image forming apparatus main body and an image is formed. This is a control target value that is individually set according to the charging roller 12 mounted on the process cartridge 24 so as to be less than the above.
In order to set the AC charging current target value more accurately, a charging bias is applied in the manufacturing process of the process cartridge 24, and a value fed back as the AC charging current satisfying the above conditions is stored in the storage medium 25. Is preferred.
[0150]
Other configurations are the same as those of the image forming apparatus of FIG.
[0151]
FIG. 8 is a block diagram illustrating the connection between the storage medium 25 mounted on the process cartridge 24 and each unit provided in the image forming apparatus main body. FIG. 9 is a block diagram illustrating the operation of the full-color image forming apparatus of the present embodiment. The flowchart for explaining the control operation of the AC charging current value is shown.
[0152]
When the process cartridge 24 is mounted on the main body of the full-color image forming apparatus of this embodiment (S1), the storage medium 25 and the AC charging current target value reading means 26 are connected via the connector 27. At this time, the presence / absence of the process cartridge 24 is detected by the presence / absence detecting means 28 of the process cartridge 24, and the signal is given to the control unit 28 (S2).
[0153]
Subsequently, when the control unit 28 recognizes the mounting of the process cartridge 24, the AC charging current target value reading unit 26 reads the AC charging current target value in the storage medium 25. (S3)
Further, the control unit 28 changes the AC charging current target value selected by the AC charging current value switching means 30 with reference to the AC charging current target value in the storage medium 25 read out as described above (S4), and Preparation for forming operation is completed. (S5)
In the image forming apparatus whose image forming preparation is completed by the above-described operation, the charging bias is controlled in accordance with the AC charging current target value selected by the AC charging current value switching means every time an image is formed. The residual developer can be efficiently removed from the surface of the photosensitive drum 11, and an image forming apparatus in which image defects such as poor cleaning and sandy ground are unlikely to occur, and a process cartridge 24 used in the image forming apparatus can be provided at low cost. It became like.
[0154]
Further, by simply performing the simple operation of replacing the process cartridge, it becomes possible to replace the consumable members such as the photosensitive drum 1 and the intermediate transfer belt 15 in addition to the replenishment of the developer T ′, so that various maintenance operations can be performed. The labor of the user involved can be reduced, and a stable output image can be easily obtained.
[0155]
<Others>
1) The exposure unit 3 as the information writing unit is not limited to the laser beam scanner of the embodiment, and may be another digital exposure device such as a combination of a light source such as an LED array or a fluorescent lamp and a liquid crystal shutter, An analog exposure device that forms and projects a document image may be used.
[0156]
2) The image carrier 1 may be an electrostatic recording dielectric. In this case, after the dielectric surface is uniformly charged to a predetermined polarity and potential, the charge is selectively removed by a charge removing means (information writing means) such as a charge removing needle array or an electron gun to form an electrostatic latent image of image information. Write and form.
[0157]
3) The image carrier 1 is not limited to the drum type, and may be a rotating belt (endless belt), an end-shaped sheet attached to and held by a rotating belt-shaped support, or the like.
[0158]
4) The toner developing method and means of the electrostatic latent image are arbitrary. A reversal development system or a regular development system may be used.
[0159]
5) As the waveform of the AC component (AC voltage) of the bias applied to the charging unit 2 and the developing device 4, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. The AC bias includes, for example, a rectangular wave voltage formed by periodically turning on and off a DC power supply.
[0160]
6) As the image carrier, for example, one having a charge generating layer formed on the surface of a base and a charge transport layer formed on the surface of the charge generating layer as a basic structure can be used. Specifically, SnO is placed on the OPC photoreceptor. ₂ OCL photoreceptors coated with a surface layer (charge injection layer) in which conductive particles such as are dispersed, a photoreceptor having a surface layer of α-Si (amorphous silicon, amorphous silicon), and the like can be used.
[0161]
7) Spherical toner is a substantially spherical toner, is easy to roll in shape, has good triboelectricity, and has good developability and transfer efficiency. In the present invention, SF-1 and SF-2 are used as shape factors representing the sphericity of the toner.
[0162]
SF-1 represents the degree of roundness of the toner, and is 100 in a perfect spherical shape, and changes from a spherical shape to an indefinite shape as the value increases.
[0163]
SF-2 indicates the degree of unevenness of the toner, and is 100 in a perfect spherical shape. As this value increases, the unevenness of the toner surface becomes more remarkable.
[0164]
SF-1 and SF-2 values suitable for the present invention are:
SF-1 value = 100-160
SF-2 value = 100-140
And more preferably,
SF-1 value = 100-140
SF-2 value = 100-120
It is.
[0165]
The values of SF-1 and SF-2 were randomly sampled using a FE-SEM (S-800) manufactured by Hitachi, Ltd. and 100 toner images magnified 500 times, and the image information was transferred via an interface. It is a value calculated by the following equation after analysis by introducing it into an image analysis device (LUZEX3) manufactured by Nicolet (see FIGS. 14 and 15).
SF-1 value =
｛(MXLNG) ² / AREA ×× (Π / 4) × 100
SF-2 value =
｛(PERI) ² / AREA ×× (Π) × 100
AREA: Projected area of toner
MXLNG: Absolute maximum length
PERI: circumference
Further, in order to uniformly charge the toner and obtain higher transfer efficiency, the coefficient of variation (A) in the number distribution is preferably 35% or less. The variation coefficient (A) is represented by the following equation.
[0166]
Coefficient of variation (A) = (S / D1) × 100
S: Standard deviation value in toner number distribution
D1: Number average particle size of toner particles (ΔM)
Further, in order to faithfully develop fine dots for the purpose of improving the image quality, the toner particle diameter is preferably 10 M or less in weight average particle diameter, and more preferably 4 to 8 M in weight average particle diameter. For the measurement of the number distribution, a Coulter counter TAII type (manufactured by Coulter Inc.) was used.
[0167]
There are various methods for producing the spherical toner as described above, and for example, a method utilizing a polymerization reaction such as an emulsion polymerization method, a suspension polymerization method, or a dispersion polymerization method is often used. In addition to the polymerization method, there is a method in which the pulverized toner is formed into a sphere while being dissolved in a solvent, and the production method for obtaining the spherical toner is not particularly limited.
[0168]
In this embodiment, a suspension polymerization method in which a raw material containing a monomer, a wax, a charge control agent, an initiator, and the like is suspended in a dispersion medium (usually water) containing a dispersant and a toner is generated by a polymerization reaction. Using.
[0169]
【The invention's effect】
According to the present invention as described above,
▲ 1 ▼. With a simple configuration, it is possible to efficiently remove the residual developer from the surface of the image carrier, and it is possible to provide an inexpensive image forming apparatus in which poor cleaning hardly occurs.
[0170]
▲ 2 ▼. It is possible to stably charge the image carrier irrespective of environmental conditions, and to provide an image forming apparatus having high stability of an output image.
[0171]
(3). With a simple configuration, the residual developer can be efficiently removed from the surface of the image carrier, and a multicolor image forming apparatus in which poor cleaning hardly occurs can be provided at low cost.
[0172]
▲ 4 ▼. The quality of the output image can be improved, and the occurrence of cleaning failure can be prevented.
[0173]
▲ 5 ▼. It is possible to provide an image forming apparatus which can reduce a user's labor required for maintenance work of the image forming apparatus such as replacement of an image carrier and a charging member, and can obtain a highly stable output image for a long time with a simple operation. it can.
[0174]
▲ 6 ▼. A process cartridge that integrates at least a plurality of components including a contact charging member and is detachable from an image forming apparatus main body. The process cartridge can be mounted on the process cartridge without forcing a user to perform complicated operations. It is possible to provide a process cartridge capable of performing various settings and inexpensively preventing the occurrence of image defects such as cleaning failure and charging failure.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a graph showing a correlation between an AC peak-to-peak voltage and an AC current value, which changes depending on environmental conditions.
FIG. 3 is a graph showing a relationship between a charging AC peak-to-peak voltage and a charging potential convergence voltage.
FIG. 4 is a schematic diagram illustrating a cleaning device of the image forming apparatus according to the first embodiment of the present invention.
FIG. 5 is a schematic view of an image forming apparatus according to a second embodiment of the present invention.
FIG. 6 is a schematic view of an image forming apparatus according to a third embodiment of the present invention.
FIG. 7 is a schematic diagram of a full-color image forming apparatus according to a fourth embodiment of the present invention.
FIG. 8 is a block diagram illustrating a relationship among various units related to an AC charging current value change performed in a full-color image forming apparatus according to a fourth embodiment of the present invention.
FIG. 9 is a flowchart illustrating a procedure for changing an AC charging current target value performed in a full-color image forming apparatus according to a fourth embodiment of the present invention.
FIG. 10 is a schematic diagram illustrating a conventional image forming apparatus.
FIG. 11 is a schematic diagram illustrating an example of a mechanism for contacting and separating a developing roller in a conventional image forming apparatus.
It is.
FIG. 12 is a schematic diagram illustrating a conventional multicolor image forming apparatus provided with a rotary developing device.
FIG. 13 is an enlarged view of the rotary developing device.
FIG. 14 is an explanatory diagram of a toner shape factor SF-1.
FIG. 15 is an explanatory diagram of a toner shape factor SF-2.
FIG. 16 is an explanatory diagram of a method of measuring a pressing pressure of a developing roller.
[Explanation of symbols]
1. photosensitive drum; Charging roller, 3. 3. cleaning blade; 4. Waste developer container; Cleaning device, 6. 16. elastic blade (developing blade); Cleaning blade, 18. Cleaning device, 23. Process cartridge, 24. Process cartridge, 25. Storage medium, 26. AC charging current target value reading means, 27. Connector, 28. Control unit, 29. 30. means for detecting the presence or absence of a process cartridge; AC charging current value switching means

Claims (8)

Contact charging for charging the surface of the image carrier by applying a voltage in which a DC component and an AC component are superimposed on the charging member while the charging member is in contact with the image carrier; Means, a latent image forming means for forming an electrostatic latent image on the charged surface of the image carrier, and an electrostatic latent image formed on the surface of the image carrier, a developer carrier carrying a developer, A contact developing unit for developing by contacting the image carrier, and a developer remaining on the image carrier surface after transferring a developer image on the image carrier surface onto a recording material by a transfer unit; Cleaning means for removing by an elastic blade abutted on the image carrier,
The pressure of the developer carrier against the image carrier is 0.88 N / cm or more and 1.76 N / cm or less, and the voltage between the AC peaks applied to the charging member is less than 2.0 kVpp. Image forming apparatus. A constant current control means for controlling an AC voltage applied to the charging member, wherein the constant current control means performs control such that an AC peak-to-peak voltage changes in a range from a charging potential convergence voltage to less than 2.0 kVpp. The image forming apparatus according to claim 1. A desired developing unit of a developing unit having a plurality of developing units is sequentially moved to a developing position opposed to the image carrier, and the electrostatic latent image formed on the image carrier is contact-developed. The image forming apparatus according to claim 1, wherein the image forming apparatus performs multiple transfer on a recording material. A toner having at least a binder resin and a colorant, and a developer having an inorganic fine powder and a hydrotalcite compound, and the toner has a shape factor SF-1 value of 100 to 160 measured by an image analyzer. The image forming apparatus according to claim 1, wherein contact development is performed using a developer having a value of SF-2 of 100 to 140. 5. An image forming apparatus in which a plurality of components related to image formation and a storage medium storing a unique AC charging current target value are integrated, and an image is formed using a process cartridge detachably attached to an image forming apparatus main body. At least a means for reading a unique AC charging current target value stored in the storage medium; and an AC current value changing means for changing an AC current value with reference to the AC charging current target value. The image forming apparatus according to any one of claims 1 to 4, wherein the control is performed such that is less than 2.0 kVpp. The image forming apparatus according to claim 1, wherein the latent image forming unit is an exposing unit. The image forming apparatus according to claim 1, wherein the developer is a non-magnetic one-component developer including a spherical toner. A process cartridge that integrates at least a plurality of components including a contact charging unit and a storage medium and is detachable from an image forming apparatus main body. When the process cartridge is mounted on the image forming apparatus, an AC peak-to-peak voltage is discharged. A process cartridge characterized in that a specific AC charging current target value predetermined in accordance with a mounted charging member is stored in the storage medium so as to be twice the starting voltage to less than 2.0 kVpp. .

Images