JP2004212815A - Electrified-member cleaning method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method which prevents deterioration of developer, degradation in development reliability, etc., and removes developer from the electrified members of an image forming apparatus using an optical induction electrification system in order to effectively remove sticking developer, and to provide the image forming apparatus using the cleaning method. <P>SOLUTION: The cleaning method involves: the step of applying a DC voltage and an AC voltage overlapping each other to a development roller 13 so that the maximum voltage and the minimum voltage have the same polarity and the reverse of the polarity of developer electrified by the optical induction electrification system; and the step of irradiating electron emission part 15 with irradiation light from an ultraviolet ray irradiation means 16. Thus, developer sticking to the electrified members such as a photoreceptor 2 and an electron emission part 15 is effectively removed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０１１３】
表１における検討条件は、一方の平行平板に飽和帯電量の現像剤を０．５ｍｇ均一散布し、この平行平板に模擬電圧（−８００Ｖ）を印加した。また、もう一方の対抗平板との空隙距離を０．５ｍｍに設定し、対抗平板には上記表１に示す周波数の矩形波のＡＣ電圧を、印加電圧の最大電圧が＋１５００Ｖ、最小電圧が＋２５０Ｖとなるように２秒印加した。
【０１１４】
この結果より、低周波数では、同一電界を印加しても、トナーを一方の平行平板から対抗平板まで、離脱・飛翔させるにいたる電界は発生しないが、おおよそ３０ＨＺを超える周波数のＡＣ電圧を印加すると、トナーを一方の平行平板から対抗平板まで、離脱・飛翔させることができる、すなわち、付着トナーを除去するためのクリーニング方法が可能であることがわかった。
【０１１５】
また、周波数が１５０ＨＺを超えると、残存トナーは平行平板から剥離するが、矩形波のＰｅａｋとＰｅａｋとの間（ＰＥＡＫ ＴＯ ＰＥＡＫ）で、平行平板の空隙間を飛翔し続け、後述の矩形波の印加電圧をＯＦＦにするタイミングで平行平板に戻る場合と、対抗平板に吸着されてクリーニングされる場合とが生じる。また、上記平行平板の空隙間で反復飛翔を行っている際に、トナーは完全球体でないため、飛翔方向が変化し、両平行平板の空隙間から外れて、両平行平板の空隙間の外へと離脱するトナーが発生する。これは、画像形成装置１１０においては、現像装置１０周辺の部材におけるトナー汚れの原因となる。
【０１１６】
さらに、印加する電圧の最大電圧および最小電圧は、矩形波のＡＣ電圧を印加中に印加極性が変化しないことと、印加電圧が高すぎた場合に発生する気中放電を未然に解決できる程度に最大電圧および最小電圧を設定した。
【０１１７】
また、通常、クリーニング動作の条件である、電圧印加サイクルは、クリーニングするべき部材（本実施の形態では感光体２、電子放出部（光電面）１５、制御電極等の帯電した部材）が固定式である場合と、回転式である場合とでは異なる。すなわち、本実施の形態における感光体２上の残留トナーをクリーニングする場合は、感光体２が回転を始めてから連続した印加が必要となるが、ここでは、説明を省略している光誘起帯電のための電子放出部１５やダイレクトトーニング方式の制御電極等の移動しない部材をクリーニングする場合は、上記電圧の印加サイクルを数サイクル〜１０数サイクルとするべきである。
【０１１８】
これにより、大量の除去すべきトナーを一度に上記帯電した部材から離脱・飛翔させた場合にトナー同士が衝突することによって、トナーの帯電極性、帯電量の変化が生じる事態を防止することができる。また、トナー同士の衝突によって、トナーの飛翔方向が変化して、画像形成装置１１０における装置内飛散等が発生するという不具合を解消することができる。したがって、クリーニングサイクルを分割印加する方がクリーニング効率の向上が図れる。
【０１１９】
▲５▼矩形波のＡＣ電圧の印加をＯＦＦにするタイミング
上記クリーニング対象部材が固定式の矩形波を印加することによって、残存トナーを除去するクリーニング方法においては、印加した電圧をＯＦＦするタイミングが重要である。すなわち、矩形波のＰｅａｋとＰｅａｋとの間で、トナーが対象部材に付着する場合と、現像ローラ１３に付着する場合がある。したがって、矩形波のＡＣ電圧の印加をＯＦＦするタイミングは、現像ローラ１３にトナーが付着した後とする必要がある。
【０１２０】
上述したように、本発明の要旨に従い、感光体２上に残存する残留トナーのクリーニング方法を▲１▼〜▲５▼を基に説明したが、本発明のクリーニング方法、すなわち、電圧印加方法を用いることによって、帯電した部材に付着した残留トナーの除去を容易に行うことができる。さらに画像形成装置１１０への機内飛散を解消できるとともに、画像形成装置１１０におけるクリーニング機構の構造の簡素化が可能となる。
【０１２１】
また、本実施の形態における電子放出部１５に付着するトナーのクリーニングサイクルについて、以下に図７〜図１２を用いて詳細に説明する。
【０１２２】
まず、従来、付着したトナーのクリーニングのために行っていたＤＣ電圧の印加サイクルを図７（ａ）に示す。従来のクリーニング方法では、電子放出部１５にトナーが付着し汚れた時点（図中のＺのポイント）でクリーニングを行う方法が多く用いられる。すなわち、電子放出部１５に対してのクリーニングを行うまでの時間を少しでも長くし、電子の放出によるトナーの帯電効率を良くすることを目的として、クリーニングサイクルの決定がなされていた。
【０１２３】
ここで、図８に、この図７（ａ）に示す場合における電子放出部１５の光電面層１５２へのトナーの付着状況を図示する。なお、図７（ａ）および図８中のＡ１、Ｂ１、Ａ２、Ｂ２、Ａ３ポイントはそれぞれ対応している。
【０１２４】
図８に示すように、初期状態（Ａ１ポイント）の電子放出部１５の光電面層１５２は当然汚れがなく、印字要求が開始されることによる現像ローラ１３の回転、並びに現像ローラ１３の周辺に配置されるトナー規制ブレード１４との摩擦によって飽和帯電に至らないトナーが現像ローラ１３から離脱・浮遊し、光電面層１５２に付着する（Ｂ１ポイント）。このＢ１ポイントでのトナー付着状態を簡単に説明すると、上述の説明のように、光照射によって多量の電子を放出する電子放出部１５の電子放出面（光被照射面）１５４には初期からのトナー付着はないが、電子放出部１５における光が照射されない現像ローラ１３側の面１５３には初期状態でトナーが付着する。そして、この電子放出部１５の現像ローラ１３側の面１５３へのトナー付着量が多くなると、電子放出部１５における電子放出面１５４に浮遊トナーが付着する。なお、電子放出部１５における光が照射されない現像ローラ１３側の面１５３は、光電子の発生が少ない部分であり、電子放出部１５の電子放出面（光被照射面）１５４は、光電子の発生が多い部分である。
【０１２５】
このように、電子放出部１５における現像ローラ１３側の面１５３から電子放出面１５４側へと徐々に付着トナー量が増加する場合、上述の従来のクリーニング方法のように、電子放出部１５が汚れた時点でクリーニングを実行する（クリーニング電圧を現像ローラに印加する）と（図７（ａ）のＢ１参照）、電子放出部１５に付着するトナーは、電子放出部１５における現像ローラ１３側の面１５３のトナーのみが現像スリーブに飛翔し、電子放出面１５４側のトナーは残留してしまう（Ａ２ポイント）。このような状態を継続してクリーニングを行うと（Ｂ１〜Ａ３ポイント）、電子放出面１５４側に残留するトナーが電子放出部１５において光電子の発生が多い部分を遮蔽してしまい、光照射を行っても電子の放出が得られない状態、すなわち現像ローラ１３上のトナーに電子を振掛ける（供給する）ことができない状態が発生する（Ａ３ポイント）。
【０１２６】
したがって、本発明においては、図７（ｂ）に示すように、電子放出部１５が完全に汚れる状態（Ｂ１ポイント）以前に（Ｃ１ポイント）クリーニングを行うことが好ましい。ここで、図９に、この図７（ｂ）に示す場合における電子放出部１５へのトナーの付着状況を図示する。
【０１２７】
すなわち、図９に示すように、電子放出部１５の現像ローラ１３側の面１５３のみにトナーが付着する状態（Ｃ１ポイント）で、第１回目のクリーニング動作を実行することによって、第２回目以降のクリーニングサイクルを実行しても、電子放出部１５の電子放出面１５４がトナーで覆われることがなく、継続的に電子放出部１５から光電子の放出が可能となる。
【０１２８】
より具体的には、通常のクリーニングサイクルでは、例えばＡ１ポイントからＢ１ポイントまでの時間経過は、現像ローラ１３の周速度が１００ｍｍ／ｓｅｃ．で、トナー層厚が２０〜３０μｍ、現像ローラ１３と電子放出部１５の面１５３とのギャップが１５０μｍの時は、約７〜１０ｍｉｎ．となる。
【０１２９】
これに対し、本発明のクリーニング方法では、第１回目のクリーニング動作実行開始時間をＡ１ポイントが経過後の約３〜５ｍｉｎ．とする（Ｃ１ポイント）。さらに、このように第１回目のクリーニング動作を実行すると、電子放出部１５における現像ローラ１３側の面１５３に残留する付着トナーは、後述の図１０に示すように、クリーニング動作による現像ローラ１３における電界と光照射による電子放出部１５からの電子放出とによって、現像ローラ１３から電子放出部１５に付着した状態に比べ、帯電量が変化する。この帯電量が変化したトナーは、次工程で飛散してくるトナーを弾き飛ばす効果が発生するため、電子放出部１５へのトナー付着を阻害し、現像ローラ１３に再付着させる効果を有する。
【０１３０】
したがって、図７（ｂ）に示すように、現像ローラ１３の回転開始から第１回目のクリーニング動作を実行するまでの時間（例えばＡ１ポイントからＣ１ポイントまでの時間経過をα１とする）に比較し、第２回目以降のクリーニング動作を実行する時間の間隔（例えばＤ１ポイントからＣ２ポイントまでの時間経過をα２とする）が長くなる（約１０〜１５ｍｉｎ．）とともに、電子放出部１５の電子放出面１５４側へのトナー付着がなくなり、電子放出が長期間にわたり安定した状態を維持することが可能となる。
【０１３１】
すなわち、本発明のクリーニング方法では、電子放出部１５が完全に汚れた状態になる以前に、すなわち、電子放出部１５の電子放出面１５４に現像剤が付着する以前に、第１回目のクリーニング動作が実行されることが好ましい。この第１回目のクリーニング動作の開始タイミングは、電子放出部１５の電子放出面１５４に現像剤が付着する以前であればよく、特に限定されるものではない。
【０１３２】
なお、本実施の形態における検討では、電子放出部１５へのトナー付着が従来と比較して少量であったため、クリーニング動作の際に現像ローラ１３に対して印加する電圧の印加時間を短縮した検討を行ったが、他にも、従来と同一の時間でクリーニング動作を行い、印加電圧を低減する方法も可能である。すなわち、クリーニング動作を実行において、電圧の印加時間と印加電圧の大きさとの積が、小さくなるように設定して行うことができる。
【０１３３】
次に、上記説明におけるクリーニング動作の際に、現像ローラ１３に対して電圧を印加することによって、現像ローラ１３上のトナーや電子放出部１５上に付着したトナー等の帯電量変化について以下に説明する。本検討に際しては、各サンプルのトナーを採取した後に、「トナー帯電量分布」の測定機として一般的に使用される、「イースパート測定機」を用いて。各サンプルのトナーの帯電量分布を測定した。その結果を図１０に示す。
【０１３４】
まず、本実施の形態におけるトナーは、現像ローラ１３（現像スリーブ）上で正規に電子放出部（光電面）１５からの電子がトナー上に降りかかった場合には、図１０（ａ）に示すような帯電量分布を有する。なお、この帯電量分布は、従来行われている摩擦帯電方式によって帯電されるトナーの帯電量分布と略近似した帯電量分布である。
【０１３５】
この図１０（ａ）のトナーに対し、現像ローラ１３（現像スリーブ）の周速度、並びにトナー規制ブレード１４の摩擦力によって現像ローラ１３から離脱する飛散トナーの帯電量分布を図１０（ｂ）に示す。この図１０（ｂ）は、通常、現像ローラ１３にはトナーの帯電極性とは逆の電圧が印加され（現像バイアス）、帯電したトナーを現像ローラ１３に吸着させるシステムとなっているにも関わらず、飛散するトナーの帯電量分布を示している。すなわち、図１０（ａ）に示すトナーの帯電特性に比べて、図１０（ｂ）のトナー帯電特性は、逆の極性の帯電を有するトナー分が多く、さらに図１０（ａ）に示すトナーに較べ帯電量の小さいトナーがあることがわかる。
【０１３６】
このようなトナーが、現像ローラ１３と電子放出部１５との空隙に飛散するわけであるが、飛散中のトナーは、帯電工程で上述の電子放出部１５への光照射により発生した光電子の供給（振掛け）によって、その一部は現像ローラ１３に戻るが、戻りきれないトナーや逆極性（図１０（ａ）の場合のトナーと較べて）の帯電を有するトナーが電子放出部１５の現像ローラ１３側の面１５３に付着することになる。
【０１３７】
このような電子放出部（光電面）１５に付着したトナーの帯電特性を示すのが図１０（ｃ）である。電子放出部１５に付着したトナーは、図１０（ａ）に示すトナーに較べ、逆極性の帯電を有するトナーの比率が高くなっているが、その理由は上述の通りである。また、正規帯電極性のトナーの帯電量が上昇している理由は、電子放出部１５には帯電工程で電子放出を促進する電位が印加されているため、その電界により未帯電トナーが電荷注入され帯電量が上昇したことによるものである。なお、この図１０（ｃ）は、図７（ｂ）および図９のＢ１、Ｃ１ポイントに示す付着トナーの電位を示すものである。
【０１３８】
このようにして、付着したトナーをクリーニングすると、その大部分は現像ローラ１３に戻るが、一部は電子放出部１５に付着したままとなる。
【０１３９】
すなわち、本実施の形態におけるクリーニングサイクルでは、上述のように、現像ローラ１３にＤＣ成分の電圧に加えてＡＣ成分の電圧を印加して、重畳した交番電界を印加するため、電子放出部１５に付着したトナーに強力な電荷が注入され、正規帯電になったトナーが、交番電界の印加中に電子放出部１５から離脱・飛翔し現像ローラ１３に付着する。このときの現像ローラ１３上に付着するトナーの帯電量分布を図１０（ｄ）に示す。図１０（ｄ）の帯電量分布は、図１０（ａ）に示すトナーとよく近似しており、上記浮遊したトナーが交番電界によって正規に帯電したことを示している。
【０１４０】
一方、電子放出部１５に付着し続けるトナーは、図１０（ｃ）に示すトナーの大部分が図１０（ｄ）に示すトナーとなってなくなることから、図１０（ｅ）に示すような帯電量分布を示すこととなる。このトナーは、大部分が図１０（ａ）のトナーと較べて、逆極性の帯電を有するトナーである。これは、ある見方をすれば、クリーニングサイクルでの交番電界、並びに電子放出部１５からの電子の供給（振掛け）によって、帯電極性が変質したトナーのみが電子放出部１５における現像ローラ１３側の面１５３に残留したといえる。
【０１４１】
本発明においては、この変質したトナーが重要なファクターとなる。すなわち、第１回目のクリーニング動作（図７（ｂ）および図９のＣ１ポイント）で変質したトナーが、電子放出部１５における現像ローラ１３側の面１５３に残存することによって、上記の浮遊トナーが電子放出部１５に付着することを阻害しているため（図１０（ｂ）と（ｅ）とを対比すると、図１０（ｂ）と図１０（ｅ）には共に逆極性トナー（図１０（ａ）に示すトナーと比較した場合に逆極性）が多いため、静電的な効果によって、浮遊するトナーを電子放出部１５に吸着させることなく浮遊させ続け、電子放出部１５から放出される電子によって帯電量が安定し、現像ローラ１３に戻る現象が発生している。）、第２回目以降クリーニング動作実行の間隔が延びることとなる。
【０１４２】
このようなクリーニングサイクルの際の電圧印加ならびに光照射のタイミングを図示したものが図１１である。図１１（ａ）は従来技術、すなわち、図７（ａ）のクリーニング方法における、現像ローラ１３（現像スリーブ）に対して電圧印加を行うタイミングを示している。一方図１１（ｂ）は、本発明のクリーニング方法における、現像ローラ１３（現像スリーブ）に対して電圧印加をするタイミングと、光照射を行うための露光手段に対して印加を行うタイミングを示している。
【０１４３】
図１１（ａ）（ｂ）に示すように、従来のクリーニング方法と本発明のクリーニング方法とは、第２回目以降のクリーニング実行の間隔が異なる。すなわち、図１１（ａ）のＴ２よりも図１１（ｂ）のＴ４の方が、時間がより長くなる。これは、電子放出部１５が完全に汚れた状態で第１回目のクリーニング動作が実行される従来のクリーニング方法と異なり、本発明にかかるクリーニング方法では、完全に電子放出部１５が汚れる前に第１回目のクリーニング動作が実行されるために、効率的に電子放出部１５に付着したトナーを除去することができ、電子放出部１５に残留するトナーの量を低減させることができるため、および上述したように、浮遊トナーが電子放出部１５に付着することを防止できるため、電子放出部１５の汚れるまでの時間が長くなり、その結果第２回目以降のクリーニング動作の実行間隔が長くなる。
【０１４４】
また、本発明のクリーニング方法によれば、クリーニング時間（現像ローラ１３への電圧の印加時間）の短縮が可能である。すなわち、図１１（ａ）のＴ１よりも図１１（ｂ）のＴ３の方がより時間が短くなる。これは、上記と同様の理由によって、本発明にかかるクリーニング方法では、従来のクリーニング方法に較べて、電子放出部１５の汚れるまでの時間が長くなり、その結果クリーニング動作の実行時間が短縮できる。また、クリーニング時間を短縮するのではなく、クリーニング時間を一定にして、現像ローラ１３への印加電圧の大きさを小さくしてもよい。すなわち、本発明のクリーニング方法では、現像ローラ１３への電圧印加時間と印加電圧の大きさとの積が、従来のクリーニング方法よりも小さくなるといえる。
【０１４５】
また、本発明のクリーニング方法では、クリーニング動作の際に現像ローラ（現像スリーブ）１３に対して電圧を印加するとともに、電子放出部１５への光照射を行っている。これは、従来のクリーニング方法にはないものである。これは、電子放出部１５から離脱・飛翔するトナーに、さらに電子を供給する（振掛ける）ことにより、現像ローラ１３へのトナーの飛翔を促進し、クリーニング効率の向上を図るためのものである。
【０１４６】
さらに、このようなクリーニングサイクルを、実際の画像形成装置１１０の印字サイクルに導入した場合のフローの一例を図１２に示す。図１２を用いて、印字サイクル中の電子放出部１５のクリーニングを説明する。
【０１４７】
最初に、画像形成装置１１０に印字要求がなされる（Ｓｔｅｐ１、以下Ｓｔｅｐを単にＳと称する）。印字要求を受けると画像形成装置１１０は、待機状態から印字可能状態となるため、感光体２、光学ユニット（原稿読取り用、画像情報書込み用）の初期化動作、並びに定着装置の待機状態からの昇温工程等の印字前処理工程に移行する（Ｓ２）。この印字前処理工程で現像装置１０のトナーの帯電極性を正規の飽和帯電とするため現像ローラ（現像スリーブ）１３の回転、並びに電子発生部材である露光手段（光源）の光照射、および各部材への電圧印加がなされる。
【０１４８】
次いで、印字前処理工程が終了すると、印字前処理を開始してからの現像ローラ（現像スリーブ）１３の回転時間を、図示しない制御部が積算している（Ｓ３）。その積算時間が、電子放出部１５に対する上記第１回目のクリーニング動作実行開始までの時間α１（図７（ｂ）参照）に到達していない場合には、画像形成装置１１０は印字工程にすすみ印字動作を実行する（Ｓ４）。この印字動作実行中も図示しない制御部は、現像ローラ（現像スリーブ）１３の回転時間を積算し（Ｓ５）、回転時間がＴｘに到達していない場合は、次印字の有無（Ｓ６）によって待機状態、若しくはＳ４へ戻る。
【０１４９】
また、Ｓ３において、回転時間がα１（図７（ｂ）参照）に到達していると、画像形成装置１１０は、Ｓ４の印字動作に移行する前に、電子放出部１５等帯電した部材の第１回目のクリーニング動作を実行する（Ｓ７）。クリーニング動作時間が上述の所定時間Ｔ３（図１１（ｂ）参照）であると（Ｓ８）、画像形成装置１１０は、Ｓ４に移行して印字動作を実行する。一方Ｓ８において、クリーニング動作時間が所定時間Ｔ３でない場合、再びＳ７に戻って、クリーニング動作を実行する。
【０１５０】
また、Ｓ５において、すなわち、印字動作中に上記制御部の現像ローラ（現像スリーブ）１３の回転積算時間が所定時間Ｔｘに到達すると、その時に印字されている用紙の印字が終了後、すぐにクリーニング動作を実行する（Ｓ９）。ここで、積算時間Ｔｘは、上記Ｓ３で時間α１（図７（ｂ）参照）を経過していないときは、積算時間Ｔｘがα１となったときに、第１回目のクリーニング動作が実行される。一方、Ｓ３で第１回目のクリーニング動作が終了している場合、Ｓ５における積算時間Ｔｘが、第２回目以降のクリーニングに適した積算時間、すなわち図７（ｂ）におけるＤ１ポイントからＣ２ポイントまでの時間経過α２となった際に第２回目以降のクリーニング動作が実行されることになる。なお、この場合は、例えば、クリーニング動作が１回終了するごとに積算時間Ｔｘをリセットすることが好ましい。また、この他にも、第２回目以降のクリーニング動作実行までの積算時間Ｔｘをα１＋α２×Ｎ（Ｎは整数）としてもよい。
【０１５１】
Ｓ１０において、クリーニング動作時間が所定時間Ｔ３である場合、Ｓ６に移行し、次の印字要求があるか否かを判断する（Ｓ６）。次の印字要求がない場合は、待機モードに移行して終了する。次の印字要求がある場合は、Ｓ４に移行し、再び処理を行う。一方、Ｓ１０において、クリーニング動作時間が所定時間Ｔ３でない場合、再びＳ９に戻って、クリーニング動作を実行することになる。なお、印字動作の後に、従来公知の印字後処理を行ってもよい。
【０１５２】
上記のように、本発明のクリーニング方法によって電子放出部１５のクリーニングを実施することにより、電子放出部１５の汚れ状態を常に一定に保つことができ、さらに電子発生の主要部分である電子放出部１５における光照射される電子放出面１５４に浮遊トナーの付着が防止でき、安定した電子発生が可能であり、結果として、安定した現像ローラ１３上のトナーの帯電化が可能となる。また、クリーニング動作時間の短縮できること、および印加電圧の大きさを小さくすることが可能であるため、電子放出部１５が受ける電界疲労が少なくなり、電子放出部１５の長寿命化が可能となり、画像形成装置１１０における現像装置１０のロングライフに効果を奏する。
【０１５３】
また、本発明に係る帯電した部材のクリーニング方法及び画像形成装置によれば、付着した現像剤を除去するというクリーニングの対象となる、電荷を帯びた部材が、画像形成装置１１０の感光体２であったり、光誘起帯電方式の電子放出部（光電面）１５であったりしても、感光体２にキズや破損が生じることによる感度低下（印字品位の低下）や、光電面１５２の破損によるリーク、および電子放出量の低下等の問題を発生させることなく、確実に効率的なクリーニングを行うことが可能である。また、上記帯電した部材に付着する現像剤の粒子径が一定でなくとも、安定したクリーニング、すなわち、確実に付着した現像剤を除去することが可能である。
【０１５４】
また、浮遊している現像剤を効率良く回収できるため、画像形成装置１１０全体として見た場合の装置の汚れ、すなわちトナーに起因する機内飛散が減少し、各部材を構成する駆動源等々の消耗が少なく、装置の長寿命化を図ることができる。
【０１５５】
すなわち、ＤＣ電圧にＡＣを重畳し、その印加電圧極性を常に残留現像剤とは逆極性に保持することによって、クリーニング性能の向上を図るとともに、電子放出部１５のクリーニング動作の条件（クリーニングサイクル、および電圧印加時間、印加電圧の大きさ等の印加条件等）を変化させ、常に電子放出部１５からの電子放出を安定化させ、現像ローラ（現像スリーブ）１３上に搬送されるトナーに電子を振掛け、安定したトナーの帯電特性を得ることができる。
【０１５６】
さらに詳細には、現像スリーブにクリーニング電圧として印加するＡＣ電圧の条件を上述のようにするとともに、クリーニングタイミングを電子放出部１５の被照射面に付着トナーが生じないタイミング（付着トナーは光電面の現像スリーブ側のみに発生する状態）でクリーニングすることによって、現像ローラ１３に飛翔する付着トナーと光電面に残留する付着トナーとに分離し、残留する付着トナーがクリーニング条件で印加される電圧によって帯電特性が変質することを利用し、現像ローラ１３から発生する浮遊トナーが電子放出部１５に付着する量を低減することができる。
【０１５７】
また、本発明は、現像剤（トナー）の劣化防止、すなわちトナーの破壊やブレードヘの融着防止を可能とし、現像の信頼性を向上させることができる現像装置、特に、定着エネルギーを削減するために軟化点を低減したトナーや、着色力を高めるために顔料部数を増加させたトナーにも適合できる光誘起帯電方式を採用する現像装置における電子発生部材である電子放出部１５に付着する浮遊現像剤を効率よく現像スリーブに回収する手法を提供するものである。
【０１５８】
すなわち、付着する現像剤を所定空間を介してクリーニングするために印加する電圧の絶対値を付着している現像剤の逆極性で保持しながら、ＤＣ成分の電圧にＡＣ成分を重畳しつつ、その印加波形を矩形波とし、ＡＣの周波数を付着現像剤の飽和帯電量と空間距離を基に算出し、さらに印加サイクルを印加時間に対し分割した電圧印加を行い、そのクリーニングサイクルを印字工程の途中に行う事によって対象物の汚れを低減し電子発生の継続した電子の発生が可能とする事を、効率良い付着現像剤のクリーニング手法を提案するものである。
【０１５９】
本発明は上述した各実施形態に限定されるものではなく、請求項に示した範囲で種々の変更が可能であり、異なる実施形態にそれぞれ開示された技術的手段を適宜組み合わせて得られる実施形態についても本発明の技術的範囲に含まれる。
【０１６０】
【発明の効果】
本発明の帯電した部材のクリーニング方法は、以上のように、光照射手段の照射光により、電子を発生する光電面を有し、上記光電面から発生する電子によって現像スリーブ上の現像剤を帯電させ現像工程に寄与する帯電電位とする光誘起帯電方式により現像剤を帯電させる画像形成装置で行われる帯電した部材のクリーニング方法において、電圧の最大電圧および最小電圧が、同一極性であり、かつ上記光誘起帯電方式により帯電した現像剤の帯電極性と逆極性となるように、上記現像スリーブに対して、ＤＣ電圧とＡＣ電圧とを重畳させて印加するとともに、上記光照射手段の照射光を上記光電面に対して照射する構成である。
【０１６１】
それゆえ、光電面等に対して現像剤が付着しにくくなるとともに、光電面や感光体等の帯電した部材に付着した現像剤を効率的に除去することができるという効果を奏する。これにより、常に光電面から安定して電子放出を行うことが可能となり、現像スリーブ上に担持搬送される現像剤に電子を安定供給でき、現像剤の帯電特性を得ることができる。
【０１６２】
また、本発明の帯電した部材のクリーニング方法は、摩擦帯電方式による現像剤の帯電化およびメカクリーニング方法を利用していないため、現像剤の破壊を生じることがないだけでなく、感光体、光電面等の破損により、印字品質の低下および現像剤の帯電特性の低下を防止することができるという効果を奏する。
【０１６３】
さらに、現像スリーブに対してＤＣ成分とＡＣ成分とを重畳して（重ねて）電圧印加しており、現像スリーブの電界が常に一定とはならないため、小粒子径の現像剤に対するクリーニング性能が低下することも回避できるという効果を奏する。
【０１６４】
また、本発明の帯電した部材のクリーニング方法は、光誘起帯電方式を採用する現像装置を有する画像形成装置において行われるものであるため、定着エネルギーを削減するために軟化点を低減した現像剤、または着色力を高めるために顔料部数を増加させた現像剤が、電子発生部材である光電面に付着した場合でも、上記現像剤を効率よく現像スリーブに回収することができるという効果を奏する。
【０１６５】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記現像スリーブの回転開始から第１回目のクリーニング動作を開始するまでの時間（α１）と第２回目以降のクリーニング動作間隔の時間（α２）とが異なる構成である。
【０１６６】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記α１は、α２よりも短い構成である。
【０１６７】
それゆえ、光電面や感光体等の帯電した部材に、大量の現像剤が付着する前にクリーニングを行うこととなる。したがって、完全に汚れる前にクリーニングすることができるため、短い時間で効率的に光電面や感光体等の帯電した部材から現像剤を除去するクリーニングを行うことができるという効果を奏する。すなわち、完全に汚れた状態でのクリーニングする場合と異なり、第２回目以降のクリーニング実行の間隔が長くなる。
【０１６８】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記第１回目のクリーニング動作の条件と第２回目以降のクリーニング動作の条件とは異なる構成である。
【０１６９】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記クリーニング動作の条件は、上記現像スリーブに印加する印加電圧の大きさ、または上記現像スリーブへの電圧印加時間の長さである構成である。
【０１７０】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記第１回目のクリーニング動作では、第２回目以降のクリーニング動作よりも、上記現像スリーブに印加する印加電圧が大きいこと、または上記現像スリーブへの電圧印加時間が長い構成である。
【０１７１】
それゆえ、第１回目のクリーニング動作は、第２回目以降のクリーニング動作に比べて、より多くの現像剤を帯電した部材から取り除くことができるという効果を奏する。これにより、第２回目以降のクリーニング動作の際には、帯電した部材には、それほど多くの現像剤が付着していないこととなる。このため、第２回目以降のクリーニング動作の条件を緩和することができる。すなわち、第２回目以降のクリーニング動作の際の時間を短時間化、またはクリーニング動作の際の印加電圧を小さくできる。このため、光電面、感光体等の帯電した部材が受ける電界疲労が少なくなり、光電面、感光体等の帯電した部材の長寿命化が可能となり、現像装置や画像形成装置自体の長寿命化が図れるという効果を奏する。
【０１７２】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記現像スリーブの回転開始後における第１回目のクリーニング動作は、上記光照射手段からの光照射を受けて電子を放出する光電面の電子放出面に対して、トナーが付着する前に実行される構成である。
【０１７３】
それゆえ、光電面の電子放出面（被光照射面）にトナーが多量に付着することによって光電面からの電子放出ができなくなることを防止でき、継続的に安定して光電面からの電子放出を行うことができるという効果を奏する。したがって、現像スリーブ上の現像剤に対して安定した電子供給が可能となり、安定した印字性能を得ることができる。すなわち、この手法を用いることによって、光電面の汚れ状態は常に一定で、さらに電子発生の主要部分である光電面の光照射される部分への浮遊トナーの付着が防止でき、安定した電子発生による現像スリーブ上のトナーの帯電が可能となる。
【０１７４】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記第１回目および第２回目以降のクリーニング動作の条件は、上記光電面の現像スリーブと対向する面に付着するトナーの一部を残して除去するという動作条件である構成である。
【０１７５】
それゆえ、現像スリーブから発生する浮遊現像剤が光電面に付着することを抑制でき、クリーニング性能を向上させることができるという効果を奏する。
【０１７６】
さらに、浮遊現像剤を効率良く回収できるため、画像形成装置全体として見た時の現像剤に起因する装置の汚れ、すなわち現像剤の装置内飛散が減少し、各部材を構成する駆動源等の消耗も少なくなり、装置の長寿命化を図ることができるという効果を奏する。
【０１７７】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記クリーニング動作は、上記現像スリーブの回転開始時からの積算時間によって実行される構成である。
【０１７８】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記クリーニング動作は、画像形成装置の印字前処理中または印字後処理中にあっては、印字前処理または印字後処理を一旦停止して実行される構成である。
【０１７９】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記クリーニング動作は、画像形成装置の印字動作中にあっては、印字動作中の印字用紙への印字動作終了後であって、次の印字用紙への印字動作を行う前に実行される構成である。
【０１８０】
それゆえ、本発明の帯電した部材のクリーニング方法を画像形成装置の印字サイクルに、容易に導入することができ、画像形成装置における現像装置のクリーニングを効率的に行うことができるという効果を奏する。また、浮遊現像剤を効率良く回収できるため、画像形成装置全体として見た場合の現像剤に起因する装置の汚れ、すなわち現像剤の装置内飛散が減少し、各部材を構成する駆動源等の消耗も少なくなり、装置の長寿命化を図ることができるという効果を奏する。
【０１８１】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記現像スリーブに印加するＰＥＡＫ ＴＯ ＰＥＡＫの電圧振幅は、１５００Ｖ／ｍｍ以下であり、最大電圧は２０００Ｖ以下である構成である。
【０１８２】
それゆえ、帯電した部材に付着した現像剤を効率よく除去することができ、クリーニング性能を向上させることができるという効果を奏する。
【０１８３】
また、本発明の帯電した部材のクリーニング方法は、以上のように、上記現像スリーブに対して重畳印加するＡＣ成分の電圧の周波数は、３０ＨＺ〜１５０ＨＺの範囲であり、その波形は矩形波である構成である。
【０１８４】
それゆえ、帯電した部材に付着した現像剤を効率よく除去することができ、クリーニング性能を向上させることができるという効果を奏する。
【図面の簡単な説明】
【図１】本実施の一形態に係る画像形成装置におけるプロセス部（現像装置を含む）の構造を模式的に示す図である。
【図２】（ａ）はトナー規制ブレード１４の構造を模式的に示す正面図であり、（ｂ）は、（ａ）をＣ−Ｃ’で切断した断面図である。
【図３】本実施の一形態に係る画像形成装置１１０の全体的な構造を示す図である。
【図４】（ａ）〜（ｃ）は、種々のＤＣ成分の電圧に対して、同程度のＡＣ成分の電圧を重畳して印加した場合の印加電圧の極性を示す図である。
【図５】（ａ）〜（ｃ）は、それぞれ図４（ａ）〜（ｃ）のように電圧を印加した場合に残留トナー（現像剤）がどのように挙動するかを模式的に示した図である。
【図６】（ａ）〜（ｃ）は、本実施の形態において、ＤＣ成分の電圧に対して、それぞれサイン波、三角波、矩形波のＡＣ成分の電圧を重ねて印加した場合の印加電圧の極性を示す図である。
【図７】（ａ）は、付着したトナーのクリーニングのために行っていた従来のＤＣ電圧の印加サイクルを示す図であり、（ｂ）は付着したトナーのクリーニングのために行う本実施の一形態の電圧印加サイクルを示す図である。
【図８】図７（ａ）に示すクリーニング動作における光電面へのトナーの付着状況を示す図である。
【図９】図７（ｂ）に示すクリーニング動作における光電面へのトナーの付着状況を示す図である。
【図１０】本実施の形態における各サンプルのトナーの帯電量分布を測定した結果を示す図である。
【図１１】（ａ）は、従来のクリーニング方法における現像ローラに対して電圧印加を行うタイミングを示す図であり、（ｂ）は、本発明のクリーニング方法における現像ローラに対して電圧印加を行うタイミングと、光照射を行うための露光手段への印加を行うタイミングとを示す図である。
【図１２】本実施の一形態に係るクリーニング方法を画像形成装置の印字サイクルに導入した場合のフローの一例を示す図である。
【図１３】従来の画像形成装置における現像装置近傍の構造を模式的に示す図である。
【符号の説明】
２ 感光体
１０ 現像装置
１３ 現像ローラ（現像スリーブ）
１４ トナー規制ブレード
１５ 電子放出部（光電面）
１６ 紫外線照射器（光照射手段）
１１０ 画像形成装置
１５３ 光電面における現像ローラ側の面
１５４ 光電面の電子放出面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for cleaning a developer attached to a member charged by static electricity or the like in an image forming apparatus, and an image forming apparatus using the cleaning method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electrophotographic apparatus (image forming apparatus) such as a copying machine, a printer, and a facsimile has a developing device. In such a developing device, a toner (developer) is supplied by a developing unit to a photoconductor that carries and conveys the electrostatic latent image, and the electrostatic latent image on the surface of the photoconductor is developed (visualized) by the toner. This is transferred to a recording sheet to perform an image forming process.
[0003]
Hereinafter, a conventional image forming technique will be described more specifically with reference to FIG. 13 which schematically shows a configuration near a developing device in a conventional image forming apparatus.
[0004]
As shown in FIG. 13, in the developing device 210, the toner is sequentially supplied to the surface of the developing roller 213 from the circumferential direction by the supply roller 212, and is carried and conveyed toward the photoconductor 202 by the rotation of the developing roller 213.
[0005]
At this time, the toner layer formed on the developing roller 213 is formed on the developing roller 213 by a blade 214 provided on the downstream side of the supply roller 212 in the rotation direction of the developing roller 213 (the direction of arrow B in the drawing). The thickness is controlled. At the same time, the toner is charged by friction with the blade 214 (friction charging method).
[0006]
The charged toner is conveyed to a portion facing the photosensitive member 202 located downstream of the blade 214 in the rotation direction of the developing roller 213 while being carried on the developing roller 213, and is charged on the surface of the photosensitive member 202. The electrostatic latent image is supplied electrostatically to the latent image, and is developed (visualized) as a toner image. The visualized toner image is transferred onto a recording sheet by a transfer unit 204, and then heated and pressed by a fixing unit 205, and is fixed on the recording sheet P.
[0007]
Here, as a technique for charging the toner by a method other than the above-described frictional charging method, a method of charging a toner with a photochromic compound or the like that reacts to light having a special wavelength, and directly irradiating the toner with light inside the developing device. (For example, see Patent Documents 1, 2, and 3).
[0008]
Further, a developer (toner) composed of two layers, a layer containing a photochromic material and a layer containing a thermoplastic resin, and a binder resin and a colorant containing two or more materials sensitive to different energies (For example, see Patent Documents 4 and 5).
[0009]
On the other hand, as a method of removing a developer (toner) attached to a member charged by static electricity in the developing device, generally, (1) a mechanical cleaning method, (2) a magnetic cleaning method, and (3) an electric field cleaning method Is used.
[0010]
Here, in the mechanical cleaning method, in order to remove the adhered developer, a cleaning unit 203 made of an elastic member such as rubber is pressed against a charged member (for example, the photoconductor 202) to remove the mechanically attached developer. Is the way. Further, the magnetic field cleaning method is a method in which a developer attached to a charged member is suction-cleaned using a magnetic force. Further, the electric field cleaning method is a method in which a developer attached to a charged member is adsorbed and cleaned using an electric field. In the magnetic cleaning method and the electric field cleaning method, the polarity (+ pole,-pole) of the magnetic force is determined based on the polarity of the developer attached to the charged member (for example, see Patent Documents 6 and 7). ).
[0011]
[Patent Document 1]
JP-A-7-295327 (publication date: November 10, 1995)
[0012]
[Patent Document 2]
JP-A-7-281473 (Published October 27, 1995)
[0013]
[Patent Document 3]
Japanese Patent Application Laid-Open No. 9-6132 (published January 10, 1997)
[0014]
[Patent Document 4]
JP-A-4-220657 (publication date: August 11, 1992)
[0015]
[Patent Document 5]
JP-A-7-234536 (publication date September 5, 1995)
[0016]
[Patent Document 6]
JP-A-8-320640 (publication date: December 3, 1996)
[0017]
[Patent Document 7]
JP 2000-29364 A (publication date: January 28, 2000)
[0018]
[Problems to be solved by the invention]
However, in the above-described method of charging the toner by the frictional charging method, since the toner is charged by friction with the blade 214, the blade 214 is charged with the developing roller 213 in order to give a desired charge amount to the toner. It is necessary to press against with a relatively large pressing force (F). As described above, in the configuration in which the blade 214 applies a large pressing force to the toner, there is a problem that the toner is destroyed by the pressing force.
[0019]
In the energy balance of the friction charging method, the driving energy (Ek) of the developing roller 213 is converted into a toner layer thickness control energy (Es) and a toner charging energy (Et) by the action of the blade 214. The part is consumed as heat loss energy (El). The toner is softened by the heat loss energy (El) generated at this time. This causes a problem that the destruction of the toner is further promoted, or a problem that the softened toner is fused to the surface of the blade 214 to deteriorate the frictional charging characteristics of the toner.
[0020]
Further, the techniques described in Patent Documents 1 to 7 described above charge the toner by irradiating the toner containing a special photochromic compound with light. Nothing was suggested.
[0021]
In recent years, in particular, in recent years, as an energy-saving technology, fixing energy has been reduced by lowering the softening point of toner, or coloring power has been increased by increasing the number of pigments in the toner (the destruction resistance of the toner has been reduced). Improvement of toner is progressing.
[0022]
However, the conventional frictional charging method described above has a problem that it cannot be applied to such a toner because the pressing force and the thermal load on the toner are large.
[0023]
Further, as for the method of removing the developer (toner) attached to the member charged by the static electricity in the developing device, any of the above methods (1) to (3) has advantages and disadvantages.
[0024]
First, the mechanical cleaning method (1) allows simple design of the mechanism without burdening the control unit with ease of design. However, the cleaning unit 203 composed of the elastic member and a charged member (for example, There is a problem that it is difficult to set a contact pressure with the photoconductor 202, a photo-induced charging photocathode (not shown), a direct toning type control electrode (not shown), and the like.
[0025]
Further, since pressure is applied to the surface of the photoconductor 202 and the photocathode, there is a problem that the surface is scraped. For example, in the photoconductor 202, the cleaning of the surface protection layer on the surface of the photoconductor 202 by the cleaning unit 203 (referred to as film verging phenomenon) occurs at a rate of several μm to several tens μm / 10,000 sheets printed. Therefore, not only is it necessary to develop the photoconductor 202 in consideration of the film verging phenomenon from the design stage of the photoconductor 202, but also there is a problem of a sustained change (so-called deterioration) of the print quality set in the initial state. Come.
[0026]
In the magnetic field cleaning method or the electric field (electric field by DC voltage) cleaning method of the above methods (2) and (3), if the developer has a constant charge amount and the particle diameter of the developer is constant, , The applied magnetic or electric field can be determined. However, the particle size of the developer that normally adheres varies, and the amount of electrostatic adhesion between the charged member and the developer is different.Therefore, a constant magnetic field or electric field deteriorates the cleaning performance for the developer having a small particle size. Therefore, there is a problem that stable cleaning performance cannot be obtained. That is, in the cleaning method using a magnetic field or an electric field, there is a problem that a magnetic force or an electric field of a developer to be attached becomes a problem, and a certain cleaning performance cannot be obtained.
[0027]
In the electric field cleaning method, a method of applying an AC voltage may be considered to solve the above problem. However, the voltage of the AC component includes both components of (+) polarity and (−) polarity, and the cleaning performance is poor. This is lower than the DC voltage electric field cleaning method.
[0028]
The present invention has been made in view of the above problems, and its purpose is to prevent the deterioration of the developer and decrease the reliability of development, and to efficiently remove the adhered developer, It is an object of the present invention to provide a cleaning method for removing a developer from a charged member in an image forming apparatus employing a photo-induced charging system, and an image forming apparatus using the cleaning method.
[0029]
[Means for Solving the Problems]
The method for cleaning a charged member of the present invention has a photocathode that generates electrons by irradiation light of a light irradiation unit, and solves the above-mentioned problem. In a method for cleaning a charged member performed in an image forming apparatus in which a developer is charged by a photo-induced charging method in which a developer is charged to a charging potential that contributes to a developing process, a maximum voltage and a minimum voltage of a voltage have the same polarity. And applying a DC voltage and an AC voltage in a superimposed manner to the developing sleeve so as to have a polarity opposite to the charging polarity of the developer charged by the light-induced charging method, It is characterized in that irradiation light is applied to the photocathode.
[0030]
According to the above configuration, the developing sleeve always has a charge having a polarity opposite to that of the developer charged by the photo-induced charging method. For this reason, the developer attached to the charged member (for example, the photoconductor, the photocathode of photo-induced charging, the control electrode of the direct toning method, etc.) flies toward the developing sleeve. That is, the developer attached to the charged member such as the photocathode can be blown toward the developing sleeve. At this time, by further irradiating the photocathode with light, electrons can be supplied to the developer that separates from a charged member such as the photocathode or the photoconductor and flies toward the developing sleeve. This makes it possible to efficiently promote separation and flight of the developer from the charged member to the developing sleeve. Therefore, the developer once detached and flies hardly adheres again to the photocathode or the like, and the developer adhering to a charged member such as the photocathode or the photoconductor can be efficiently removed. As a result, electrons can be stably emitted from the photocathode at all times, electrons can be stably supplied to the developer carried and transported on the developing sleeve, and charging characteristics of the developer can be obtained.
[0031]
In addition, the method for cleaning a charged member of the present invention does not use a method of charging a developer by a frictional charging method and a mechanical cleaning method. It is possible to prevent the print quality from deteriorating and the charging characteristics of the developer from deteriorating due to surface damage.
[0032]
Further, the voltage of the DC component and the voltage of the AC component are superimposed (superimposed) on the developing sleeve, and the electric field of the developing sleeve is not always constant. A decrease in cleaning performance can also be avoided.
[0033]
Further, since the method for cleaning a charged member of the present invention is performed in an image forming apparatus having a developing device employing a photo-induced charging method, a developer having a reduced softening point in order to reduce fixing energy, Alternatively, even when the developer in which the number of pigments is increased to increase the coloring power adheres to the photocathode, which is an electron generating member, the developer can be efficiently collected in the developing sleeve.
[0034]
The magnitude of the voltage applied to the developing sleeve, the time for applying the voltage, the timing for executing the cleaning operation, and the like can be appropriately set, and are not particularly limited.
[0035]
Further, in order to solve the above-mentioned problems, the method for cleaning a charged member of the present invention requires a time (α1) from the start of the rotation of the developing sleeve to the start of the first cleaning operation, and the time after the second cleaning. It is characterized in that the time (α2) of the cleaning operation interval is different.
[0036]
Further, in order to solve the above-mentioned problems, the method for cleaning a charged member of the present invention is characterized in that α1 is shorter than α2.
[0037]
According to the above configuration, cleaning is performed before a large amount of developer adheres to a charged member such as a photocathode or a photoconductor. Therefore, since cleaning can be performed before the surface is completely stained, cleaning for efficiently removing the developer from a charged member such as a photocathode or a photoconductor can be performed in a short time. That is, unlike the case where cleaning is performed in a completely dirty state, the interval between the second and subsequent cleanings is increased.
[0038]
The “cleaning operation” refers to the execution (execution) of the method for cleaning a charged member according to the present invention.
[0039]
Further, in order to solve the above problem, the method for cleaning a charged member according to the present invention is characterized in that the conditions for the first cleaning operation are different from the conditions for the second and subsequent cleaning operations.
[0040]
Further, in the method for cleaning a charged member according to the present invention, in order to solve the above-described problem, the condition of the cleaning operation is determined by setting a magnitude of an applied voltage applied to the developing sleeve or a time of applying a voltage to the developing sleeve. It is characterized by the length.
[0041]
According to the method for cleaning a charged member of the present invention, in order to solve the above-described problem, in the first cleaning operation, the applied voltage applied to the developing sleeve is higher than in the second and subsequent cleaning operations. It is characterized in that it is large or the voltage application time to the developing sleeve is long.
[0042]
According to the above configuration, in the first cleaning operation, more developer can be removed from the charged member than in the second and subsequent cleaning operations. As a result, during the second and subsequent cleaning operations, not so much developer adheres to the charged member. Therefore, the conditions for the second and subsequent cleaning operations can be relaxed. That is, the time for the second and subsequent cleaning operations can be shortened, or the voltage applied during the cleaning operation can be reduced. For this reason, the electric field fatigue applied to the charged members such as the photocathode and the photoconductor is reduced, and the life of the charged members such as the photocathode and the photoconductor can be extended, and the life of the developing device and the image forming apparatus itself can be prolonged. Can be achieved.
[0043]
When the applied voltage is changed during the first and second and subsequent cleaning operations, it is preferable that the application time is constant. In addition, when the application time is changed during the first and second and subsequent cleaning operations, it is preferable that the applied voltage is constant. Further, it is preferable that the product of the magnitude of the applied voltage and the length of the application time in the first cleaning operation is larger than that in the second and subsequent cleaning operations.
[0044]
In order to solve the above-mentioned problems, the first cleaning operation after the rotation of the developing sleeve is started by receiving the light irradiation from the light irradiation unit. This is performed before the toner adheres to the electron emission surface of the photoelectric surface that emits light.
[0045]
According to the above configuration, it is possible to prevent a large amount of toner from adhering to the electron emission surface (light-irradiated surface) of the photocathode, thereby preventing the electron emission from the photocathode from becoming impossible, and to stably maintain the photocathode. Can emit electrons. Accordingly, stable supply of electrons to the developer on the developing sleeve becomes possible, and stable printing performance can be obtained. That is, by using this method, the contamination state of the photocathode is always constant, and furthermore, it is possible to prevent the floating toner from adhering to the light-irradiated portion of the photocathode, which is a main part of electron generation, and to achieve stable electron generation. The toner on the developing sleeve can be charged.
[0046]
In the cleaning method for a charged member of the present invention, in order to solve the above-mentioned problems, the first and second and subsequent cleaning operations are performed under the following conditions: The operation condition is that the toner is removed while leaving a part of the toner.
[0047]
According to the above configuration, a state occurs in which the developer slightly remains (adheres) on the surface of the photoelectric surface facing the developing sleeve (the surface of the photoelectric surface facing the developing sleeve). Since the residual developer has the same polarity as the developer floating near the developing device, the floating developer can be kept floating without being attracted to the photocathode by an electrostatic effect. Then, the charge amount of the developer floating due to the electrons emitted from the photocathode is stabilized, and the developer returns to the developing sleeve. Therefore, the floating developer generated from the developing sleeve can be prevented from adhering to the photocathode, and the cleaning performance can be improved.
[0048]
Furthermore, since the floating developer can be efficiently collected, the contamination of the device due to the developer when viewed as the entire image forming apparatus, that is, the scattering of the developer in the device is reduced, and the driving source and the like constituting each member are reduced. Wear is reduced, and the life of the device can be extended.
[0049]
In order to solve the above-mentioned problems, the method for cleaning a charged member according to the present invention is characterized in that the cleaning operation is performed based on an integrated time from the start of rotation of the developing sleeve.
[0050]
In order to solve the above-described problems, the cleaning operation of the charged member according to the present invention is performed such that the cleaning operation is performed during pre-print processing or post-print processing of the image forming apparatus. Post-processing is temporarily stopped and executed.
[0051]
Further, in order to solve the above-mentioned problem, the cleaning operation of the charged member according to the present invention is performed such that, during the printing operation of the image forming apparatus, the printing operation on the printing paper during the printing operation is completed. It is performed later and before the printing operation on the next printing paper is performed.
[0052]
According to the above configuration, the method for cleaning a charged member of the present invention can be easily introduced into a printing cycle of an image forming apparatus, and the cleaning of the developing device in the image forming apparatus can be efficiently performed. In addition, since the floating developer can be efficiently collected, the contamination of the device due to the developer when viewed as the entire image forming apparatus, that is, the scattering of the developer in the device is reduced, and the driving source and the like constituting each member are reduced. Wear is reduced, and the life of the device can be extended.
[0053]
Note that “pre-printing process” and “post-printing process” are processes performed in the image forming apparatus before and after the printing operation, respectively. This refers to a process of forming an image (printing), and the details of these processes may be conventionally known processes, and are not particularly limited. Further, “accumulation from the rotation start time of the developing sleeve” means accumulation from the start of rotation of the developing sleeve during the operation of the image forming apparatus.
[0054]
In order to solve the above-mentioned problems, in the method for cleaning a charged member of the present invention, the voltage amplitude of PEAK TO PEAK applied to the developing sleeve is 1500 V / mm or less, and the maximum voltage is 2000 V or less. It is characterized by:
[0055]
According to the above configuration, the developer attached to the charged member can be efficiently removed, and the cleaning performance can be improved. It should be noted that “PEAK TOPEAK” means between one peak of a waveform and a continuous peak.
[0056]
Further, in the method for cleaning a charged member of the present invention, in order to solve the above-mentioned problem, the frequency of the voltage of the AC component superimposedly applied to the developing sleeve is in a range of 30 Hz to 150 Hz, and its waveform is It is a rectangular wave.
[0057]
According to the above configuration, the developer attached to the charged member can be efficiently removed, and the cleaning performance can be improved. It is more preferable that the frequency of the voltage of the AC component superimposedly applied to the developing sleeve is in the range of 50 to 100 Hz.
[0058]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of a method for cleaning a charged member and an image forming apparatus according to the present invention will be described below with reference to FIGS.
[0059]
First, an outline of the overall structure of the image forming apparatus of the present invention will be described with reference to FIG.
[0060]
(1) Outline of overall structure of image forming apparatus according to the present invention
FIG. 3 is a diagram illustrating an overall structure of the image forming apparatus 110 according to the embodiment. As shown in FIG. 3, the image forming apparatus 110 has a document table 670 made of transparent glass or the like on the upper surface. An optical system for reading a document is provided below the document table 670. This optical system includes an exposure light source 671 for irradiating light to a document placed on a document table 670, and a plurality of reflecting mirrors 672 for guiding light to an imaging lens and a photoelectric conversion element (hereinafter referred to as a CCD) 673. Be composed.
[0061]
An automatic document feeder 680 that automatically conveys a document and performs a document reading operation is provided above the document table 670. When the originals are set on the paper feed tray 681, the automatic document feeder 680 feeds the originals one by one and feeds them into the paper feed path 682. The fed document is temporarily stopped with its leading end pressed against the PS roller 683. This synchronizes with the printing unit and prevents the document from being sent to the reading unit in a skewed state. When the clutch (not shown) is turned on, the PS roller 683 is connected to the drive unit of the transport motor (not shown), and the transportation of the temporarily stopped document is resumed.
[0062]
The above-described exposure light source 671 is moved to a position immediately below the document reading unit 688, and the document is irradiated with light in synchronization with the start of document transport. The light is guided to the CCD 673 through each part of the optical system described above.
[0063]
Original image data read by the CCD 673 is subjected to image processing, and a laser scanning unit (hereinafter, referred to as LSU) irradiates a laser beam onto the surface of an image carrier (hereinafter, referred to as a photoconductor) 2 to form an electrostatic latent image. Is formed.
[0064]
The photoconductor 2 is formed in a drum shape and is driven to rotate. Around the photosensitive member 2, a developing device 10 for developing an electrostatic latent image on the surface of the photosensitive member 2 exposed by a laser from a laser irradiation point toward a rotating direction of the photosensitive member 2 into a visible image with toner is disposed. You. A transfer charger 613 for transferring the toner image on the photoconductor 2 to paper; a cleaning device for removing residual toner on the surface of the photoconductor 2; a charging unit for charging the surface of the photoconductor 2 to a predetermined potential; LSUs for irradiating the laser toward are arranged in order. Since the photosensitive member 2 and the periphery of the developing device 10 are characteristic portions of the present invention, the details will be described later.
[0065]
The paper is stored in the paper cassette 630. At the leading end of the paper cassette 630, a half-moon roller 631 for feeding the paper into the paper feed path 633 is arranged downstream (for convenience, the paper flow <cassette side> is upstream, and the paper discharge side). (Not shown) A pre-registration detection switch (not shown) for detecting the passage of the paper, a PS roller 632 for aligning the toner image on the photoconductor 2 with the paper based on the signal of the pre-registration detection switch, a paper A fixing roller 5 for fixing the upper toner image to the sheet by a heating roller and a pressure roller, a fixing sheet detection switch (not shown) for detecting that the sheet has passed through the fixing roller 5, and a sheet A paper discharge detection switch (not shown) for detecting the passage and a paper discharge roller 636 for discharging the paper are arranged.
[0066]
The sheet passes through the above-described members from the sheet cassette 630 and is discharged to the sheet discharge tray 660, thereby completing a series of image forming steps.
[0067]
(2) Around the developing device according to the present invention
The structure of the developing device according to the present invention and the step of charging the developer will be described below with reference to FIGS.
[0068]
FIG. 1 schematically shows the structure of a developing device 10 according to the embodiment. As shown in FIG. 1, a developing device 10 includes a container-like developing tank 11 for storing a developer (toner), a supply roller (developer supply means) 12, a developing roller (developer carrier, a developing sleeve) 13, A toner regulating blade 14 (layer thickness controlling blade), an electron emitting section (photoelectric surface) 15, and an ultraviolet irradiator (light irradiating means) 16 are provided.
[0069]
As shown in FIG. 1, the developing device 10 is arranged so as to face the photoconductor 2 (latent image carrier), and is formed by irradiating the surface of the photoconductor 2 with a light beam (indicated by L in the figure). The electrostatic latent image is developed using a developer (for example, a one-component nonmagnetic toner (developer)). The photoconductor 2 is provided so as to be rotatable in a direction indicated by an arrow A in the figure.
[0070]
The supply roller 12 is disposed in the developing tank 11 and is rotatably connected to the developing roller 13 such that the outer peripheral surfaces of the supplying roller 12 face each other. To supply. The developing roller 13 is rotatably disposed at a position facing the photoconductor 2 in the developing tank 11, and carries the developer supplied by the supply roller 12 toward the photoconductor 2. . Further, the supply roller 12 and the developing roller 13 are rotatably provided in a direction indicated by an arrow B in the figure. That is, the rotation direction of the supply roller 12 and the development roller 13 is opposite to the rotation direction of the photoconductor 2.
[0071]
Further, the toner regulating blade 14 is disposed downstream of the supply roller 12 and upstream of the photoconductor 2 in contact with the developing roller 13 with respect to the rotation direction of the developing roller 13, and is formed on the surface of the developing roller 13. It regulates (controls) the thickness of the developer layer. Further, an electron emission section 15 is provided on a part of the toner regulating blade 14. An ultraviolet irradiator (light irradiating unit) 16 for irradiating the electron emitting unit 15 with ultraviolet light is provided so as to sandwich the electron emitting unit 15 between the ultraviolet irradiator (light irradiating unit) 16 and the developing roller 13. I have. The electron emission section 15 is provided with an electron emission surface 154 that receives photo-electrons in response to ultraviolet rays from the ultraviolet irradiator 16 and a surface on the side of the development roller 13 that is provided to face (oppose) the development roller 13. 153. The electron emitting section 15 and the ultraviolet irradiator (light irradiating means) 16 are provided in the developing device 10 with a toner charging means (developer charging means) for charging the developer supplied to the photoreceptor 2 to a predetermined charge amount. ). Details of the toner charging means will be described later.
[0072]
Further, a peripheral portion of the developing device 10, that is, a process portion in an image forming apparatus (electrophotographic apparatus) will be briefly described.
[0073]
As shown in FIG. 1, the process section 20 mainly includes a photoconductor 2, a charging roller 3, an exposure unit (not shown), a developing device 10, a transfer discharge roller 4, a cleaning unit (not shown), Means (not shown) and a fixing roller 5. In FIG. 1, P indicates a recording sheet, and L indicates a light beam emitted from the exposure unit and writing an electrostatic latent image on the surface of the photoconductor 2.
[0074]
The photoreceptor 2 is rotating in a predetermined direction (the direction of the arrow A shown in FIG. 1), and the outer peripheral surface is first uniformly charged by the charging roller 3. The uniformly charged surface of the photoconductor 2 is irradiated with a light beam L controlled according to image data by the above-mentioned exposure means, and an electrostatic latent image is formed.
[0075]
Then, the electrostatic latent image formed on the surface of the photoconductor 2 is moved to a position facing the developing device 10 by the rotation of the photoconductor 2, and is supplied with the developer by the developing device 10 to be visualized ( A toner image is formed on the photoconductor 2). At this time, the developing roller 13 of the developing device 10 is rotating in a predetermined direction (the direction of the arrow B shown in FIG. 1) in order to carry and transport the developer to be supplied to the photoconductor 2.
[0076]
In the present embodiment, the photoconductor 2 is made of, for example, an organic optical semiconductor, is charged to −700 V (the amount of charge by the charging roller 3), and rotates in the direction A at a peripheral speed of 50 mm / s. , But is not particularly limited.
[0077]
The developing roller 13 is made of, for example, a cylindrical conductive rubber elastic material, and rotates in the B direction at a peripheral speed equal to that of the photoconductor 2 when a developing bias of −400 V is applied. The supply roller 12 is made of, for example, a cylindrical foamed rubber elastic material, and rotates in the B direction at the same peripheral speed as the photoconductor 2.
[0078]
The transfer discharge roller 4 transfers the toner image formed on the photoconductor 2 by the developing device 10 to the paper P. Further, on the downstream side of the transfer discharge roller 4 in the rotation direction of the photoconductor 2, a cleaning unit and a charge removing unit are further disposed. The cleaning unit is for removing the residual developer on the surface of the photoconductor 2 after the transfer, and the power supply unit is for removing the charge on the surface of the photoconductor 2.
[0079]
The paper P on which the toner image has been transferred is conveyed toward the fixing roller 5, and the paper P is heated and pressed when passing between the pair of upper and lower fixing rollers 5, Is fixed on the sheet P.
[0080]
Next, the developing process in the developing device 10 will be described in detail.
[0081]
In the developing device 10, as described above, the developer is sequentially supplied to the surface of the developing roller 13 by the supply roller 12, and thereafter, the developing roller 13 rotates while holding the developer. Thus, the developer conveyed by the developing roller 13 is guided between the developing roller 13 and the contact area Ws of the toner regulating blade 14, and the layer thickness of the developer on the developing roller 13 is regulated (controlled). The contact area Ws is provided near the tip of the toner regulating blade 14.
[0082]
The developer whose layer thickness is regulated on the developing roller 13 by the toner regulating blade 14 is charged by the electron emitting section 15 and the ultraviolet irradiator 16 which constitute the toner charging means, and is charged up to the charge amount necessary for development. Be charged. That is, by irradiating the ultraviolet rays from the ultraviolet irradiator 16 to the electron emitting portion 15 formed (provided) on the toner regulating blade 14, a photoelectric effect is generated, and photoelectrons are induced from the electron emitting portion 15. . The photoelectrons are emitted toward the developer on the developing roller 13, and the developer is charged to a desired charge amount (photo-induced charging). It is preferable that the light emission of the ultraviolet irradiator 16 be synchronized with the rotation of the developing roller 13 because unnecessary light emission leading to an increase in power consumption can be suppressed. Further, although not shown, it is preferable that the space between the electron emitting portion 15 and the ultraviolet irradiator 16 is sealed so that the developer does not enter and hinder the light irradiation.
[0083]
Further, in the toner charging unit having the above configuration, the electron emission portion 15 is formed at a position different from the contact area Ws on the toner regulating blade 14, and the electron emission portion 15 is different from the developer on the developing roller 13. It is provided so as not to contact. In other words, the electron emission unit 15 is configured to prevent the developing roller 13 and the developer on the developing roller 13 from coming into contact with the toner regulating blade 14, and to irradiate the developing roller 13 with the ultraviolet light from the ultraviolet irradiator 16. It can be said that the agent should be provided so as to supply photoelectrons to the agent. For this reason, charging can be performed in a state where no load is applied to the developer on the developing roller 13 (a state where a thermal load and / or a mechanical pressure is not applied). That is, in the developing device 10, the toner regulating blade 14 only needs to be pressed against the developing roller 13 with at least a force necessary for regulating the layer thickness of the developer. Pressing force and thermal load can be significantly reduced.
[0084]
Further, since the formation region of the electron emission portion 15 is completely out of contact with the developing roller 13, the surface roughness of the electron emission portion 15 does not affect the formation of the developer layer. Is not subject to design restrictions.
[0085]
The developer charged to a predetermined charge amount by the toner charging unit is further fed to the opposing portion between the photosensitive member 2 and the developing roller 13 by the rotation of the developing roller 13, and the static electricity on the surface of the photosensitive member 2 is The electrostatic latent image is electrostatically supplied to the electrostatic latent image, and the electrostatic latent image is developed (visualized) as a toner image.
[0086]
Next, a specific configuration of the toner regulating blade 14 will be described with reference to FIGS. FIG. 2A is a front view schematically showing the structure of the toner regulating blade 14, and FIG. 2B is a cross-sectional view of FIG. 2A taken along the line CC '.
[0087]
As the toner regulating blade 14, for example, a SUS metal (that is, a conductive substrate) is used as a base material, and in a region where the electron emission portion 15 is formed, as shown in FIGS. As described above, the plurality of openings 151 are provided by etching or the like. Further, in a region where the electron emitting portion 15 is formed, a thin film of aluminum is laminated as the photoelectric surface layer 152 by, for example, evaporation.
[0088]
In FIG. 2A, the opening 151 has a configuration in which a large number of small circular holes are formed. However, in the present invention, the shape of the opening 151 is not particularly limited, and may be an elliptical shape. , A quadrangle, a triangle, or the like, or a slit-shaped opening.
[0089]
The material for forming the photocathode layer 152 is not limited to aluminum as described above. Any material may be used as long as a photoelectric effect is generated when irradiated with light. , Ta or other metals, alloys such as Mg-Ag, semiconductors, conductive polymers, and the like. Further, the photoelectric surface layer 152 is not necessarily formed on both surfaces of the toner regulating blade 14 as shown in FIG. 2B, and is formed at least on the surface facing the ultraviolet irradiator 16. Just fine.
[0090]
Further, the light applied to the electron-emitting portion 15 is not limited to the ultraviolet light as described above, but may be any light having a wavelength that can cause a photoelectric effect on the material forming the photoelectric surface layer 152. , Visible light or X-rays.
[0091]
In the toner regulating blade 14 having the above-described configuration, when the photoelectric surface layer 152 of the electron emission section 15 is irradiated with ultraviolet rays, photoelectrons are induced and emitted by the photoelectric surface layer 152 by the photoelectric effect. The photoelectrons are mainly generated on the surface of the electron emission portion 15 irradiated with the ultraviolet light (surface to be irradiated), that is, on the surface facing the ultraviolet irradiator 16. The light is radiated toward the developer from the side facing the developing roller 13 through the opening 151 of the electron emission section 15 and contributes to the charging of the toner.
[0092]
Further, in the electron emitting section 15, if the electron emitting section 15 is in an electrically floating state, it can be easily understood that the photoelectric surface layer 152 of the electron emitting section 15 cannot continuously emit photoelectrons. For this reason, it is preferable that the electron emission unit 15 be configured to be able to externally supply the electrons emitted from the photocathode layer 152. For example, in the present embodiment, the electron emission section 15 has a configuration in which an aluminum thin film is deposited as the photoelectric surface layer 152 on the base material of the toner control blade 14 made of SUS or the like. The above configuration can be easily realized by grounding.
[0093]
As described above, the developing device 10 according to the present invention can significantly reduce the pressing force of the toner regulating blade 14 as compared with a conventional developing device using a frictional charging system. As a result, the mechanical pressure and thermal load on the developer by the toner regulating blade 14 are significantly reduced, and problems such as destruction of the developer and fusion of the developer to the toner regulating blade 14 can be avoided.
[0094]
(3) Cleaning method according to the present invention
A method of cleaning the toner adhered to the photoreceptor 2 and the electron emission unit 15 during the developing process by the developing device 10 will be described in detail below.
[0095]
In the method for cleaning a charged member according to the present embodiment, the maximum voltage and the minimum voltage of the voltage applied to the developing roller 13 are the same polarity, and the charged developer is charged by a photo-induced charging method. By applying a voltage for superimposing a DC component and an AC component to the developing roller 13 so as to have a polarity opposite to the polarity, and irradiating the photoelectric surface 152 with ultraviolet rays from the ultraviolet irradiator 16. In addition, the developer attached to the charged members such as the electron emission unit 15 and the photoconductor 2 is blown toward the developing roller 13 to clean the charged members such as the electron emission unit 15 and the photoconductor 2.
[0096]
Therefore, first, the voltage (potential) applied to the developing roller 13 will be described below.
[0097]
(1) Types of applied voltage
It is necessary to apply a voltage having a polarity opposite to the charged polarity of the charged residual developer (for example, the developer attached to the photoconductor 2 and the electron emission unit 15). At this time, if a DC voltage is simply applied, at the start of the application of the voltage, a potential gap with 0 V is generated, and the developer separates from the electron emission section 15 and flies. However, when a DC voltage is continuously applied, the surface potential of the photoconductor 2 (about -800 V in the present embodiment) and the saturation charge amount of the developer (about 20 to 30 μC / g), a cleaning potential for peeling off the residual developer adsorbed on the photoconductor 2 is required. For example, in the case of this embodiment, a voltage application of at least +800 V is required. When such a strong voltage having a polarity opposite to the charging polarity of the photoconductor 2 is applied to the developing roller 13, a defect of the (+) polarity memory of the photoconductor 2 (the occurrence of background fog (shaving) at the printing stage) is caused. In addition, there is a problem that the print quality is deteriorated or the photosensitive layer of the photosensitive member 2 is destroyed.
[0098]
Therefore, it is necessary to reduce the voltage applied to the developing roller 13 and obtain efficient cleaning performance. This is a characteristic part of the present invention. Such portions will be described below.
[0099]
(2) AC superposition method
In the present embodiment, in order to solve the above-described problem and execute an efficient cleaning method, a method of superimposing (overlapping) an AC voltage on the application of a DC voltage is used. This makes it possible to efficiently remove the developer adhering to the electron-emitting portion 15 even at a low potential. Hereinafter, a description will be given of a result of examining how much the developer attached to the photoconductor 2 can be removed when a DC component voltage and an AC component voltage are applied to the developing roller 13 in a superimposed manner.
[0100]
FIGS. 4A to 4C are diagrams illustrating the polarity of the applied voltage when the voltage of the same AC component is superimposed on the voltage of various DC components. FIGS. 5A to 5C schematically show how the residual toner (adhered developer) behaves when a voltage is applied as shown in FIGS. 4A to 4C, respectively. FIG. In this case, the toner is charged to the polarity of (-).
[0101]
FIG. 4A is a diagram illustrating a state in which only the voltage of the AC component is simply applied. In this case, when the voltage is applied, the (+) polarity and the (-) polarity are generated at the same level. At this time, as shown in FIG. 5A, the residual toner (developer) on the photoconductor 2 merely flies back and forth between the photoconductor 2 and the developing roller 13, and the cleaning of the photoconductor 2 is not performed. I can't. Therefore, the residual toner is conveyed to the charged portion in the next step, which results in poor charging and poor printing.
[0102]
Next, FIG. 4B shows a state in which a voltage of an AC component is further applied to a voltage of a certain DC component, and when the voltage is applied, the polarity is (+) polarity and the (−) polarity is It has occurred. However, as compared with FIG. 4A, the (−) polarity portion of the applied voltage is reduced. At this time, the residual toner (developer) on the photoconductor 2 flies back and forth between the photoconductor 2 and the developing roller 13 as shown in FIG. The toner having a large particle diameter (generally, the toner having a small charge per unit surface area) is attracted to the developing roller 13 while flying, but the toner having a small particle diameter (generally, the charge amount per unit surface area is large). The toner) is attracted to the surface potential of the photoconductor 2, causing uneven cleaning of the photoconductor 2.
[0103]
Further, FIG. 4C shows a state in which a voltage of an AC component is further applied to a voltage of a DC component having a (+) polarity larger than that of FIG. 4B. In this case, only the (+) polarity is generated and the (-) polarity portion is not generated when the voltage is applied. At this time, as shown in FIG. 5C, the toner on the photoconductor 2 reciprocates between the photoconductor 2 and the developing roller 13 irrespective of the particle size of the toner. While flying, it is attracted to the developing roller 13. Note that the toner having a small particle diameter takes a longer time to reach the developing roller 13 than the toner having a large particle diameter, which can be sufficiently explained from the above description.
[0104]
As described above, in the cleaning method according to the present invention, the DC component and the AC component are changed so that the maximum voltage and the minimum voltage of the applied voltage are the same polarity and have the opposite polarities to the charging polarity of the developer. By superimposing and applying a voltage, it is possible to efficiently remove the adhered developer from charged members such as the photoconductor 2 and the electron emission unit 15. In the cleaning method of the charged member according to the present invention, when the DC component voltage applied to the developing roller 13 is applied together with the AC component voltage, the maximum voltage and the minimum voltage of the applied voltage are different. And the polarity is the same, and the polarity is opposite to the charging polarity of the developer charged by the photo-induced charging method, and there is no particular limitation.
[0105]
(3) AC waveform
Next, the waveform of the voltage of the AC component superimposed on the developing roller 13 will be described.
[0106]
In the present embodiment, in order to investigate what waveform of the AC component voltage is preferably applied when a voltage of the AC component is superimposed on a predetermined DC component voltage and applied. As shown in FIGS. 6A to 6C, a sine wave, a triangular wave, and a rectangular wave were examined. The results are described below.
[0107]
As shown in FIG. 6A, since the sine wave has a gradual change in potential instantaneously and instantaneously, the change in potential is small in order to remove and fly the residual toner adhering to the photoconductor 2 from the photoconductor 2. It was found to be inappropriate (cleaning failure occurred). Further, the triangular wave shown in FIG. 6B is slightly better than the sine wave, but it has been found that the same reason as the sine wave causes partial cleaning failure. On the other hand, as for the rectangular wave shown in FIG. 6 (c), it has been found that several steps of better cleaning are performed as compared with the above-mentioned both waveforms. It is considered that the reason for this is that in the case of a rectangular wave, a potential change occurs abruptly at the transition point of the potential, and the residual toner adsorbed on the photoreceptor 2 is separated and flies to the developing roller 13 side.
[0108]
Therefore, in the present embodiment, the subsequent examination of the cleaning method was examined using a rectangular wave.
[0109]
(4) Frequency and application cycle of applied voltage of square wave
Hereinafter, the applied voltage and the frequency of the AC component of the rectangular wave will be described.
[0110]
In the conventional jumping development method or the like, a development method in which the frequency of the superimposed AC is set to several hundred Hz to several thousand Hz is adopted. The reason for this is that in the jumping development method, the toner on the developing sleeve is brought into a toner cloud state in a development area (development nip) of the photoconductor, and the toner that has become the toner cloud is applied to the surface potential (image information) of the photoconductor. Accordingly, the toner is attached to the photoreceptor and converted into a developing sleeve. In order to obtain a constant developing density, a high frequency AC voltage is superimposed to activate the movement of the toner.
[0111]
However, in the method for cleaning a charged member of the present invention, when the voltage of the AC component is applied while being superimposed on the voltage of the predetermined DC component, the residual toner on the photoreceptor 2 is uniquely directed to the developing roller 13. It is only necessary to separate and fly, and it is not necessary to apply a high-frequency AC component voltage as in the jumping development. That is, a frequency at which the toner to be cleaned is adsorbed is required for the application time, and at that frequency, it is indispensable that the residual toner separates and flies toward the developing roller 13. In order to clarify the difference in the cleaning performance depending on the frequency, the following Table 1 shows the result of examining at what frequency the toner separates and flies using a parallel plate.
[0112]
[Table 1]

[0113]
The examination conditions in Table 1 were such that 0.5 mg of a developer having a saturated charge amount was uniformly sprayed on one parallel plate, and a simulated voltage (-800 V) was applied to this parallel plate. Further, the gap distance with the other opposing flat plate is set to 0.5 mm, and the AC voltage of the rectangular wave having the frequency shown in Table 1 is applied to the opposing flat plate, the maximum applied voltage is +1500 V, and the minimum voltage is +250 V. For 2 seconds.
[0114]
From this result, at a low frequency, even if the same electric field is applied, an electric field that causes the toner to separate and fly from one parallel flat plate to the opposing flat plate is not generated, but when an AC voltage having a frequency exceeding approximately 30 Hz is applied, It has been found that the toner can be separated and fly from one parallel flat plate to the opposing flat plate, that is, a cleaning method for removing the adhered toner is possible.
[0115]
When the frequency exceeds 150 Hz, the remaining toner peels off from the parallel flat plate, but continues to fly in the gap between the parallel flat plates between the peaks of the square wave (PEAK TO PEAK), and the rectangular wave described later There are cases where the plate returns to the parallel plate at the timing when the applied voltage is turned off, and cases where the plate is attracted to the opposing plate and cleaned. In addition, during repeated flight in the gap between the parallel plates, since the toner is not a perfect sphere, the flying direction changes, and the toner deviates from the gap between the parallel plates and moves out of the gap between the parallel plates. Is generated. This causes toner contamination on members around the developing device 10 in the image forming apparatus 110.
[0116]
Further, the maximum voltage and the minimum voltage of the applied voltage are such that the applied polarity does not change during the application of the rectangular wave AC voltage and that air discharge that occurs when the applied voltage is too high can be solved beforehand. Maximum and minimum voltages were set.
[0117]
The voltage application cycle, which is usually the condition of the cleaning operation, is such that the member to be cleaned (in this embodiment, a charged member such as the photoconductor 2, the electron emission portion (photoelectric surface) 15, and the control electrode) is fixed. Is different from the case of the rotary type. That is, when cleaning the residual toner on the photoconductor 2 in the present embodiment, continuous application is required after the photoconductor 2 starts rotating. In order to clean a non-moving member such as the electron emitting portion 15 or the control electrode of the direct toning method, the voltage application cycle should be several to ten to several cycles.
[0118]
Thereby, when a large amount of toner to be removed is detached and flies from the above-mentioned charged member at once, it is possible to prevent a situation in which the toners collide with each other and change the charge polarity and the charge amount of the toner. . Further, it is possible to solve the problem that the flying direction of the toner is changed due to the collision between the toners and the inside of the image forming apparatus 110 is scattered. Therefore, the cleaning efficiency can be improved by applying the cleaning cycle dividedly.
[0119]
(5) Timing for turning off the application of the rectangular wave AC voltage
In the cleaning method for removing the residual toner by applying a fixed rectangular wave to the member to be cleaned, the timing at which the applied voltage is turned off is important. That is, between the peaks of the rectangular wave, the toner may adhere to the target member or may adhere to the developing roller 13. Therefore, it is necessary to turn off the application of the rectangular wave AC voltage after the toner adheres to the developing roller 13.
[0120]
As described above, according to the gist of the present invention, the method of cleaning the residual toner remaining on the photoreceptor 2 has been described based on (1) to (5), but the cleaning method of the present invention, that is, the voltage applying method is described below. By using this, it is possible to easily remove the residual toner attached to the charged member. Further, it is possible to eliminate scattering inside the image forming apparatus 110 and simplify the structure of the cleaning mechanism in the image forming apparatus 110.
[0121]
Further, a cleaning cycle of the toner adhering to the electron emission section 15 in the present embodiment will be described in detail below with reference to FIGS.
[0122]
First, FIG. 7A shows a DC voltage application cycle conventionally performed for cleaning the adhered toner. In the conventional cleaning method, a method of performing cleaning at the time when toner adheres to the electron emission portion 15 and becomes dirty (point Z in the drawing) is often used. In other words, a cleaning cycle has been determined for the purpose of increasing the time required for cleaning the electron emission unit 15 as much as possible and improving the charging efficiency of the toner due to the emission of electrons.
[0123]
Here, FIG. 8 illustrates a state of toner adhesion to the photoelectric surface layer 152 of the electron emission section 15 in the case shown in FIG. 7A. Note that points A1, B1, A2, B2, and A3 in FIGS. 7A and 8 correspond to each other.
[0124]
As shown in FIG. 8, the photocathode layer 152 of the electron emission portion 15 in the initial state (A1 point) is naturally free of contamination, and the rotation of the developing roller 13 due to the start of the print request and the vicinity of the developing roller 13 The toner that does not reach saturated charging due to friction with the disposed toner regulating blade 14 separates and floats from the developing roller 13 and adheres to the photocathode layer 152 (point B1). The toner adhesion state at the point B1 will be briefly described. As described above, the electron emission surface (light-irradiated surface) 154 of the electron emission unit 15 that emits a large amount of electrons by light irradiation, is provided from the beginning. Although no toner adheres, the toner adheres to the surface 153 of the electron emission section 15 on the developing roller 13 side where light is not irradiated in an initial state. When the amount of toner attached to the surface 153 of the electron emission unit 15 on the side of the developing roller 13 increases, floating toner adheres to the electron emission surface 154 of the electron emission unit 15. The surface 153 of the electron emitting section 15 on the side of the developing roller 13 to which light is not irradiated is a portion where the generation of photoelectrons is small, and the electron emitting surface (light irradiated surface) 154 of the electron emitting section 15 is where the generation of photoelectrons occurs. There are many parts.
[0125]
As described above, when the amount of the adhered toner gradually increases from the surface 153 on the developing roller 13 side to the electron emission surface 154 side of the electron emission unit 15, the electron emission unit 15 becomes dirty as in the above-described conventional cleaning method. At this point, when cleaning is performed (a cleaning voltage is applied to the developing roller) (see B1 in FIG. 7A), the toner adhering to the electron emitting unit 15 is removed from the surface of the electron emitting unit 15 on the developing roller 13 side. Only the toner 153 flies to the developing sleeve, and the toner on the electron emission surface 154 side remains (point A2). If cleaning is performed in such a state (points B1 to A3), the toner remaining on the electron emission surface 154 will block a portion of the electron emission unit 15 where photoelectrons are generated, and light irradiation is performed. However, there occurs a state in which electrons cannot be emitted, that is, a state in which electrons cannot be sprinkled (supplied) on the toner on the developing roller 13 (point A3).
[0126]
Therefore, in the present invention, as shown in FIG. 7B, it is preferable to perform the cleaning (C1 point) before the electron emission portion 15 is completely contaminated (B1 point). Here, FIG. 9 illustrates a state of toner adhesion to the electron emission section 15 in the case shown in FIG. 7B.
[0127]
That is, as shown in FIG. 9, the first cleaning operation is performed in a state where the toner adheres only to the surface 153 of the electron emission unit 15 on the developing roller 13 side (point C1), so that the second and subsequent cleaning operations are performed. Even if the cleaning cycle is performed, the electron emission surface 154 of the electron emission unit 15 is not covered with the toner, and the electron emission unit 15 can continuously emit photoelectrons.
[0128]
More specifically, in the normal cleaning cycle, for example, the time lapse from the point A1 to the point B1 is determined when the peripheral speed of the developing roller 13 is 100 mm / sec. When the thickness of the toner layer is 20 to 30 μm, and the gap between the developing roller 13 and the surface 153 of the electron emission section 15 is 150 μm, about 7 to 10 min. It becomes.
[0129]
In contrast, in the cleaning method of the present invention, the first cleaning operation execution start time is set to about 3 to 5 min. (C1 point). Further, when the first cleaning operation is performed as described above, the adhered toner remaining on the surface 153 on the side of the developing roller 13 in the electron emission unit 15 is removed from the developing roller 13 by the cleaning operation as shown in FIG. Due to the electric field and the electron emission from the electron emission unit 15 due to light irradiation, the charge amount changes as compared with the state where the electron emission unit 15 adheres from the developing roller 13. The toner whose charge amount has changed has an effect of repelling the toner scattered in the next process, and thus has an effect of inhibiting the toner from adhering to the electron emission portion 15 and causing the toner to be re-adhered to the developing roller 13.
[0130]
Therefore, as shown in FIG. 7B, the time from the start of rotation of the developing roller 13 to the execution of the first cleaning operation (for example, the time elapsed from the point A1 to the point C1 is α1) is compared with the time. The time interval (for example, the time lapse from the D1 point to the C2 point is α2) for performing the second and subsequent cleaning operations is increased (about 10 to 15 min.), And the electron emission surface of the electron emission unit 15 is increased. No toner adheres to the 154 side, and it becomes possible to maintain a stable state of electron emission for a long period of time.
[0131]
That is, according to the cleaning method of the present invention, the first cleaning operation is performed before the electron emission portion 15 is completely contaminated, that is, before the developer adheres to the electron emission surface 154 of the electron emission portion 15. Is preferably performed. The start timing of the first cleaning operation is not particularly limited as long as it is before the developer adheres to the electron emission surface 154 of the electron emission unit 15.
[0132]
In the study in the present embodiment, since the amount of toner attached to the electron emission portion 15 was smaller than that in the related art, the study was conducted by shortening the application time of the voltage applied to the developing roller 13 during the cleaning operation. However, another method is also possible in which the cleaning operation is performed in the same time as the conventional method to reduce the applied voltage. That is, the cleaning operation can be performed by setting the product of the voltage application time and the magnitude of the applied voltage to be small.
[0133]
Next, a change in the amount of charge of the toner on the developing roller 13 and the toner attached to the electron emission unit 15 by applying a voltage to the developing roller 13 during the cleaning operation described above will be described below. I do. In this study, after collecting the toner of each sample, an "Easpart measuring device", which is generally used as a measuring device for "toner charge amount distribution", was used. The charge distribution of the toner of each sample was measured. The result is shown in FIG.
[0134]
First, the toner according to the present embodiment is shown in FIG. 10A when electrons from the electron emission portion (photoelectric surface) 15 fall onto the toner on the developing roller 13 (developing sleeve). It has such a charge amount distribution. Note that this charge amount distribution is a charge amount distribution substantially similar to the charge amount distribution of the toner charged by the conventional friction charging method.
[0135]
FIG. 10B shows the peripheral speed of the developing roller 13 (developing sleeve) and the charge amount distribution of the scattered toner that separates from the developing roller 13 due to the frictional force of the toner regulating blade 14 with respect to the toner of FIG. Show. FIG. 10B shows a system in which a voltage opposite to the charging polarity of the toner is normally applied to the developing roller 13 (developing bias), and the charged toner is attracted to the developing roller 13. 3 shows the distribution of the charge amount of the scattered toner. That is, as compared with the charging characteristic of the toner shown in FIG. 10A, the toner charging characteristic of FIG. It can be seen that there is a toner having a small charge amount as compared with the toner.
[0136]
Such toner is scattered in the gap between the developing roller 13 and the electron emission unit 15. The toner being scattered supplies the photoelectrons generated by the light irradiation to the electron emission unit 15 in the charging step. By (sprinkling), a part of the toner is returned to the developing roller 13, but the toner that cannot be returned or the toner having the opposite polarity (compared to the toner in FIG. It will adhere to the surface 153 on the roller 13 side.
[0137]
FIG. 10C shows the charging characteristics of the toner attached to the electron-emitting portion (photoelectric surface) 15. The ratio of the toner having the opposite polarity is higher in the toner attached to the electron emission portion 15 than in the toner illustrated in FIG. 10A, for the reason described above. Also, the reason that the charge amount of the toner having the normal charge polarity is increasing is that a potential for promoting electron emission is applied to the electron emission portion 15 in the charging step, and thus the uncharged toner is charged by the electric field. This is because the charge amount has increased. FIG. 10C shows the potential of the adhered toner indicated by points B1 and C1 in FIGS. 7B and 9.
[0138]
When the adhered toner is cleaned in this way, most of the toner returns to the developing roller 13, but a part of the toner remains attached to the electron emission unit 15.
[0139]
That is, in the cleaning cycle according to the present embodiment, as described above, the AC component voltage is applied to the developing roller 13 in addition to the DC component voltage, and the superposed alternating electric field is applied. A strong charge is injected into the adhered toner, and the normally charged toner separates and flies from the electron emission unit 15 during the application of the alternating electric field, and adheres to the developing roller 13. FIG. 10D shows the distribution of the amount of charge of the toner adhering to the developing roller 13 at this time. The distribution of the charge amount in FIG. 10D is very similar to the toner shown in FIG. 10A, and indicates that the floating toner is normally charged by the alternating electric field.
[0140]
On the other hand, most of the toner shown in FIG. 10C does not turn into the toner shown in FIG. It will show the quantity distribution. Most of this toner is a toner having a charge of the opposite polarity as compared with the toner of FIG. This means that, from a certain point of view, only the toner whose charge polarity has changed due to the alternating electric field in the cleaning cycle and the supply (sprinkling) of the electrons from the electron emission unit 15 is located on the developing roller 13 side of the electron emission unit 15. It can be said that it remains on the surface 153.
[0141]
In the present invention, the deteriorated toner is an important factor. That is, the toner that has been altered in the first cleaning operation (point C1 in FIG. 7B and FIG. 9) remains on the surface 153 of the electron emission unit 15 on the side of the developing roller 13, so that the floating toner is removed. 10 (b) and FIG. 10 (e), the opposite polarity toners (FIG. 10 (b) and FIG. a), the toner having the opposite polarity is larger than that of the toner shown in FIG. This causes a phenomenon in which the charge amount is stabilized and returns to the developing roller 13.), and the interval between the execution of the second and subsequent cleaning operations is extended.
[0142]
FIG. 11 illustrates the timing of voltage application and light irradiation during such a cleaning cycle. FIG. 11A shows the timing of applying a voltage to the developing roller 13 (developing sleeve) in the conventional technique, that is, in the cleaning method of FIG. 7A. On the other hand, FIG. 11B shows the timing of applying a voltage to the developing roller 13 (developing sleeve) and the timing of applying a voltage to the exposure means for irradiating light in the cleaning method of the present invention. I have.
[0143]
As shown in FIGS. 11A and 11B, the conventional cleaning method is different from the cleaning method of the present invention in the intervals of the second and subsequent cleaning executions. That is, the time is longer in T4 of FIG. 11B than in T2 of FIG. 11A. This is different from the conventional cleaning method in which the first cleaning operation is performed in a state in which the electron emission unit 15 is completely contaminated, and in the cleaning method according to the present invention, the first cleaning operation is performed before the electron emission unit 15 is completely contaminated. Since the first cleaning operation is performed, the toner attached to the electron emission unit 15 can be efficiently removed, and the amount of toner remaining in the electron emission unit 15 can be reduced. As described above, since it is possible to prevent the floating toner from adhering to the electron emission unit 15, the time until the electron emission unit 15 becomes dirty becomes longer, and as a result, the execution interval of the second and subsequent cleaning operations becomes longer.
[0144]
Further, according to the cleaning method of the present invention, it is possible to shorten the cleaning time (time for applying a voltage to the developing roller 13). That is, the time is shorter in T3 of FIG. 11B than in T1 of FIG. 11A. For the same reason as described above, in the cleaning method according to the present invention, the time until the electron emission unit 15 becomes dirty becomes longer than that in the conventional cleaning method, and as a result, the execution time of the cleaning operation can be shortened. Instead of shortening the cleaning time, the magnitude of the voltage applied to the developing roller 13 may be reduced while keeping the cleaning time constant. That is, in the cleaning method of the present invention, it can be said that the product of the voltage application time to the developing roller 13 and the magnitude of the applied voltage is smaller than that of the conventional cleaning method.
[0145]
Further, in the cleaning method of the present invention, a voltage is applied to the developing roller (developing sleeve) 13 at the time of the cleaning operation, and the electron emission section 15 is irradiated with light. This is not in the conventional cleaning method. This is to further supply (sprinkle) electrons to the toner that separates and flies from the electron emission unit 15 so as to promote the flight of the toner to the developing roller 13 and improve the cleaning efficiency. .
[0146]
FIG. 12 shows an example of a flow when such a cleaning cycle is introduced into an actual printing cycle of the image forming apparatus 110. With reference to FIG. 12, cleaning of the electron emission unit 15 during the printing cycle will be described.
[0147]
First, a print request is made to the image forming apparatus 110 (Step 1, hereinafter Step is simply referred to as S). When the print request is received, the image forming apparatus 110 changes from the standby state to the printable state, so that the photoconductor 2 and the optical unit (for reading the original and for writing the image information) are initialized, and the fixing device is switched from the standby state to the standby state. The process proceeds to a pre-printing process such as a temperature raising process (S2). In this pre-printing process, the developing roller (developing sleeve) 13 is rotated to expose the charged polarity of the toner of the developing device 10 to the normal saturation charge, and light is emitted from an exposure unit (light source) which is an electron generating member. Is applied.
[0148]
Next, when the pre-printing process is completed, the control unit (not shown) adds up the rotation time of the developing roller (developing sleeve) 13 from the start of the pre-printing process (S3). If the accumulated time has not reached the time α1 (see FIG. 7B) until the start of the first cleaning operation for the electron emission unit 15, the image forming apparatus 110 proceeds to the printing process and performs printing. The operation is performed (S4). During the printing operation, the control unit (not shown) integrates the rotation time of the developing roller (developing sleeve) 13 (S5). If the rotation time has not reached Tx, the control unit waits for the next printing (S6). Return to the state or S4.
[0149]
Further, in S3, if the rotation time has reached α1 (see FIG. 7B), the image forming apparatus 110 determines whether the charged member such as the electron emission unit 15 The first cleaning operation is performed (S7). If the cleaning operation time is the above-described predetermined time T3 (see FIG. 11B) (S8), the image forming apparatus 110 proceeds to S4 and executes a printing operation. On the other hand, if the cleaning operation time is not the predetermined time T3 in S8, the flow returns to S7 again to execute the cleaning operation.
[0150]
Further, in S5, that is, when the accumulated rotation time of the developing roller (developing sleeve) 13 of the control unit reaches the predetermined time Tx during the printing operation, the cleaning is immediately performed after the printing of the paper being printed at that time is completed. The operation is performed (S9). Here, if the accumulated time Tx does not exceed the time α1 (see FIG. 7B) in S3, the first cleaning operation is executed when the accumulated time Tx becomes α1. . On the other hand, when the first cleaning operation has been completed in S3, the integrated time Tx in S5 is equal to the integrated time suitable for the second and subsequent cleanings, that is, from the D1 point to the C2 point in FIG. 7B. When the time elapses α2, the second and subsequent cleaning operations are performed. In this case, for example, it is preferable to reset the integrated time Tx every time the cleaning operation is completed once. In addition, the integrated time Tx until the second or subsequent cleaning operation is performed may be set to α1 + α2 × N (N is an integer).
[0151]
If the cleaning operation time is the predetermined time T3 in S10, the process proceeds to S6, and it is determined whether or not there is a next print request (S6). If there is no next print request, the process shifts to the standby mode and ends. If there is a next print request, the process proceeds to S4 and the process is performed again. On the other hand, if the cleaning operation time is not the predetermined time T3 in S10, the process returns to S9 again to execute the cleaning operation. Note that, after the printing operation, a conventionally known post-printing process may be performed.
[0152]
As described above, by performing the cleaning of the electron-emitting portion 15 by the cleaning method of the present invention, the contamination state of the electron-emitting portion 15 can always be kept constant, and furthermore, the electron-emitting portion, which is a main part of electron generation, can be maintained. The floating toner can be prevented from adhering to the electron emission surface 154 irradiated with the light at 15, and stable electrons can be generated. As a result, the toner on the developing roller 13 can be stably charged. Further, since the cleaning operation time can be shortened and the magnitude of the applied voltage can be reduced, the electric field fatigue applied to the electron-emitting portion 15 is reduced, and the life of the electron-emitting portion 15 can be prolonged. This has an effect on the long life of the developing device 10 in the forming device 110.
[0153]
Further, according to the charged member cleaning method and the image forming apparatus according to the present invention, the charged member, which is to be cleaned by removing the adhered developer, is used as the photosensitive member 2 of the image forming apparatus 110. Even if the electron emitting portion (photoelectric surface) 15 of the photo-induced charging method is used, the photoreceptor 2 may be damaged or damaged due to scratches or damage (deterioration of printing quality), or the photoconductive surface 152 may be damaged. Efficient cleaning can be reliably performed without causing problems such as leakage and a decrease in the amount of emitted electrons. Further, even if the particle size of the developer adhering to the charged member is not constant, stable cleaning, that is, the developer adhering to the charged member can be surely removed.
[0154]
In addition, since the floating developer can be efficiently collected, contamination of the apparatus when viewed as the entire image forming apparatus 110, that is, scattering inside the apparatus due to toner is reduced, and consumption of a driving source constituting each member is reduced. And the life of the device can be extended.
[0155]
That is, by superimposing AC on the DC voltage and always maintaining the applied voltage polarity opposite to that of the residual developer, the cleaning performance is improved, and the conditions for the cleaning operation of the electron emission unit 15 (cleaning cycle, And application conditions such as the voltage application time and the magnitude of the applied voltage, etc.) to stabilize the electron emission from the electron emission unit 15 at all times, and to transfer the electrons to the toner carried on the developing roller (developing sleeve) 13. By sprinkling, stable toner charging characteristics can be obtained.
[0156]
More specifically, the conditions of the AC voltage applied to the developing sleeve as the cleaning voltage are set as described above, and the cleaning timing is set at a timing at which no adhered toner is generated on the irradiated surface of the electron emission unit 15 (adhered toner is the photoconductive surface. By cleaning in a state that occurs only on the developing sleeve side), the adhered toner flying on the developing roller 13 and the adhered toner remaining on the photoelectric surface are separated, and the remaining adhered toner is charged by a voltage applied under the cleaning conditions. By utilizing the property change, the amount of the floating toner generated from the developing roller 13 adhering to the electron emitting portion 15 can be reduced.
[0157]
Further, the present invention provides a developing device capable of preventing the deterioration of the developer (toner), that is, preventing the destruction of the toner and the fusion to the blade, and improving the reliability of development, in particular, reducing the fixing energy. Floating development which adheres to the electron emitting portion 15 which is an electron generating member in a developing device adopting a photo-induced charging system which can be adapted to a toner having a reduced softening point or a toner having an increased number of pigments for enhancing coloring power. An object of the present invention is to provide a method for efficiently collecting a developer in a developing sleeve.
[0158]
That is, while maintaining the absolute value of the voltage applied to clean the attached developer through the predetermined space with the opposite polarity of the attached developer, the AC component is superimposed on the DC component voltage, The applied waveform is a rectangular wave, the frequency of AC is calculated based on the saturated charge amount of the adhered developer and the spatial distance, and a voltage is applied by dividing the application cycle with respect to the application time. The present invention proposes an efficient cleaning method for the adhered developer, by reducing the contamination of the target object and making it possible to generate electrons with continuous generation of electrons.
[0159]
The present invention is not limited to the embodiments described above, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.
[0160]
【The invention's effect】
As described above, the method for cleaning a charged member of the present invention has a photocathode that generates electrons by irradiation light of a light irradiation unit, and charges a developer on a developing sleeve by electrons generated from the photocathode. The method for cleaning a charged member performed in an image forming apparatus in which a developer is charged by a photo-induced charging method that sets a charging potential that contributes to a developing process, wherein the maximum voltage and the minimum voltage are the same polarity, and A DC voltage and an AC voltage are superimposed and applied to the developing sleeve so as to have a polarity opposite to the charging polarity of the developer charged by the photo-induced charging method, and the irradiation light of the light irradiation unit is applied to the developing sleeve. This is a configuration for irradiating the photoelectric surface.
[0161]
Therefore, it is possible to effectively prevent the developer from adhering to the photocathode or the like and to efficiently remove the developer adhering to the charged member such as the photocathode or the photoconductor. As a result, electrons can be stably emitted from the photocathode at all times, electrons can be stably supplied to the developer carried and transported on the developing sleeve, and charging characteristics of the developer can be obtained.
[0162]
In addition, the method for cleaning a charged member of the present invention does not use a method of charging a developer by a frictional charging method and a mechanical cleaning method. There is an effect that it is possible to prevent a decrease in print quality and a decrease in charging characteristics of the developer due to damage to the surface or the like.
[0163]
Further, since a DC component and an AC component are applied to the developing sleeve in a superimposed (overlapping) manner, the electric field of the developing sleeve is not always constant, so that the cleaning performance for a developer having a small particle diameter is reduced. This has the effect that it is also possible to avoid doing so.
[0164]
Further, since the method for cleaning a charged member of the present invention is performed in an image forming apparatus having a developing device employing a photo-induced charging method, a developer having a reduced softening point in order to reduce fixing energy, Alternatively, even when a developer in which the number of pigments is increased to increase the coloring power adheres to the photocathode, which is an electron generating member, the developer can be efficiently collected in the developing sleeve.
[0165]
As described above, according to the method for cleaning a charged member of the present invention, the time (α1) between the start of the rotation of the developing sleeve and the start of the first cleaning operation and the interval between the second and subsequent cleaning operations are set. The configuration is different from the time (α2).
[0166]
Further, in the method for cleaning a charged member of the present invention, as described above, α1 is shorter than α2.
[0167]
Therefore, cleaning is performed before a large amount of developer adheres to a charged member such as a photocathode or a photoconductor. Therefore, since cleaning can be performed before the surface is completely stained, there is an effect that cleaning for removing the developer from a charged member such as a photocathode or a photoconductor can be efficiently performed in a short time. That is, unlike the case where cleaning is performed in a completely dirty state, the interval between the second and subsequent cleanings is increased.
[0168]
As described above, the method for cleaning a charged member of the present invention has a configuration in which the conditions for the first cleaning operation are different from those for the second and subsequent cleaning operations.
[0169]
Further, in the method for cleaning a charged member of the present invention, as described above, the condition of the cleaning operation is determined by the magnitude of the voltage applied to the developing sleeve or the length of time of voltage application to the developing sleeve. There is a certain configuration.
[0170]
As described above, in the method for cleaning a charged member of the present invention, the applied voltage applied to the developing sleeve is larger in the first cleaning operation than in the second and subsequent cleaning operations, or The voltage application time to the developing sleeve is long.
[0171]
Therefore, the first cleaning operation has an effect that more developer can be removed from the charged member than the second and subsequent cleaning operations. As a result, during the second and subsequent cleaning operations, not so much developer adheres to the charged member. Therefore, the conditions for the second and subsequent cleaning operations can be relaxed. That is, the time for the second and subsequent cleaning operations can be shortened, or the voltage applied during the cleaning operation can be reduced. For this reason, the electric field fatigue applied to charged members such as the photocathode and the photoconductor is reduced, and the life of the charged members such as the photocathode and the photoconductor can be extended, and the life of the developing device and the image forming apparatus itself can be prolonged. This has the effect of achieving the following.
[0172]
As described above, in the cleaning method of the charged member of the present invention, the first cleaning operation after the start of rotation of the developing sleeve is performed by a photoelectric device which receives light irradiation from the light irradiation unit and emits electrons. This is a configuration that is executed before toner adheres to the electron emission surface of the surface.
[0173]
Therefore, it is possible to prevent a large amount of toner from adhering to the electron emission surface (light-irradiated surface) of the photocathode, thereby preventing electron emission from the photocathode from becoming impossible, and to stably and continuously emit electrons from the photocathode. Is achieved. Accordingly, stable supply of electrons to the developer on the developing sleeve becomes possible, and stable printing performance can be obtained. That is, by using this method, the contamination state of the photocathode is always constant, and furthermore, it is possible to prevent the floating toner from adhering to the light-irradiated portion of the photocathode, which is a main part of electron generation, and to achieve stable electron generation. The toner on the developing sleeve can be charged.
[0174]
Further, as described above, in the method for cleaning a charged member of the present invention, the conditions of the first and second and subsequent cleaning operations are such that the toner adhering to the surface of the photoelectric surface facing the developing sleeve is one of This is a configuration that is an operating condition of removing the part while leaving it.
[0175]
Therefore, it is possible to suppress the floating developer generated from the developing sleeve from adhering to the photocathode, thereby improving the cleaning performance.
[0176]
Furthermore, since the floating developer can be efficiently collected, the contamination of the device due to the developer when viewed as the entire image forming apparatus, that is, the scattering of the developer in the device is reduced, and the driving source and the like constituting each member are reduced. This has the effect of reducing wear and prolonging the life of the device.
[0177]
Further, as described above, the method for cleaning a charged member of the present invention is configured such that the cleaning operation is performed based on an integrated time from the start of rotation of the developing sleeve.
[0178]
Further, as described above, in the method for cleaning a charged member of the present invention, the cleaning operation is performed during the pre-printing process or the post-printing process of the image forming apparatus. This is a configuration that is stopped and executed.
[0179]
Further, in the method for cleaning a charged member of the present invention, as described above, the cleaning operation is performed after the printing operation on the printing paper during the printing operation is completed during the printing operation of the image forming apparatus. , Which are executed before the printing operation on the next printing paper is performed.
[0180]
Therefore, the method for cleaning a charged member of the present invention can be easily introduced into a print cycle of an image forming apparatus, and an effect of efficiently cleaning the developing device in the image forming apparatus can be obtained. In addition, since the floating developer can be efficiently collected, the contamination of the device due to the developer when viewed as the entire image forming apparatus, that is, the scattering of the developer in the device is reduced, and the driving source and the like constituting each member are reduced. This has the effect of reducing wear and prolonging the life of the device.
[0181]
As described above, the method for cleaning a charged member of the present invention has a configuration in which the voltage amplitude of PEAK TO PEAK applied to the developing sleeve is 1500 V / mm or less, and the maximum voltage is 2000 V or less.
[0182]
Therefore, there is an effect that the developer attached to the charged member can be efficiently removed, and the cleaning performance can be improved.
[0183]
Further, in the method for cleaning a charged member of the present invention, as described above, the frequency of the voltage of the AC component superimposedly applied to the developing sleeve is in the range of 30 Hz to 150 Hz, and its waveform is a rectangular wave. Configuration.
[0184]
Therefore, there is an effect that the developer attached to the charged member can be efficiently removed, and the cleaning performance can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a structure of a process unit (including a developing device) in an image forming apparatus according to an embodiment.
FIG. 2A is a front view schematically illustrating the structure of a toner regulating blade 14, and FIG. 2B is a cross-sectional view of FIG.
FIG. 3 is a diagram illustrating an overall structure of an image forming apparatus 110 according to the embodiment.
FIGS. 4A to 4C are diagrams illustrating the polarity of an applied voltage when a voltage of the same level of an AC component is superimposed on various DC component voltages.
FIGS. 5A to 5C schematically show how the residual toner (developer) behaves when a voltage is applied as shown in FIGS. 4A to 4C, respectively. FIG.
FIGS. 6A to 6C are diagrams illustrating applied voltages when a sine wave, a triangular wave, and a rectangular wave AC component voltages are respectively applied to a DC component voltage in the present embodiment; It is a figure which shows a polarity.
FIG. 7A is a diagram illustrating a conventional DC voltage application cycle performed for cleaning attached toner, and FIG. 7B is a diagram illustrating one embodiment of the present embodiment performed for cleaning attached toner. FIG. 4 is a diagram showing a voltage application cycle of the embodiment.
FIG. 8 is a diagram showing a state of toner adherence to a photocathode in the cleaning operation shown in FIG. 7A.
FIG. 9 is a diagram showing a state of toner adhesion to a photocathode in the cleaning operation shown in FIG. 7B.
FIG. 10 is a diagram showing a result of measuring a charge amount distribution of toner of each sample in the present embodiment.
FIG. 11A is a diagram illustrating a timing of applying a voltage to a developing roller in a conventional cleaning method, and FIG. 11B is a diagram illustrating applying a voltage to a developing roller in a cleaning method of the present invention. FIG. 3 is a diagram illustrating timings and timings of applying light to an exposure unit for performing light irradiation.
FIG. 12 is a diagram illustrating an example of a flow when the cleaning method according to the embodiment is introduced into a print cycle of an image forming apparatus.
FIG. 13 is a diagram schematically showing a structure near a developing device in a conventional image forming apparatus.
[Explanation of symbols]
2 Photoconductor
10 Developing device
13 Developing roller (developing sleeve)
14 Toner control blade
15 Electron emission part (photoelectric surface)
16 UV irradiator (light irradiation means)
110 Image Forming Apparatus
153 Surface of Photoelectric Surface on Developing Roller Side
154 Electron emission surface of photocathode

Claims (13)

It has a photocathode which generates electrons by the irradiation light of the light irradiation means, and develops by a photo-induced charging method in which the developer generated on the photocathode charges the developer on the developing sleeve to a charging potential which contributes to the developing process. In the method of cleaning a charged member performed in the image forming apparatus that charges the agent,
The DC voltage and the AC voltage are applied to the developing sleeve so that the maximum voltage and the minimum voltage have the same polarity and have the opposite polarities to the charging polarity of the developer charged by the photo-induced charging method. A method for cleaning a charged member, wherein the method is applied in a superimposed manner, and irradiation light from the light irradiation means is irradiated on the photocathode. 2. The time according to claim 1, wherein a time (α1) from the start of rotation of the developing sleeve to the start of the first cleaning operation is different from a time (α2) between the second and subsequent cleaning operations. 3. A method for cleaning charged members. The method for cleaning a charged member according to claim 2, wherein α1 is shorter than α2. 2. The method for cleaning a charged member according to claim 1, wherein conditions of the first cleaning operation and conditions of the second and subsequent cleaning operations are different. 5. The method for cleaning a charged member according to claim 4, wherein the condition of the cleaning operation is a magnitude of an applied voltage applied to the developing sleeve or a length of time for applying a voltage to the developing sleeve. . 3. The method according to claim 1, wherein in the first cleaning operation, a voltage applied to the developing sleeve is larger or a voltage applying time to the developing sleeve is longer than in the second and subsequent cleaning operations. 6. The method for cleaning a charged member according to 4 or 5. The first cleaning operation after the start of rotation of the developing sleeve is performed before toner adheres to the electron emission surface of the photoelectric surface that emits electrons by receiving light irradiation from the light irradiation unit. 2. The method for cleaning a charged member according to claim 1, wherein: The condition of the first and second and subsequent cleaning operations is an operation condition of removing a part of the toner adhering to a surface of the photoelectric surface facing the developing sleeve while leaving a part thereof. 8. The method for cleaning a charged member according to 7. The method according to any one of claims 1 to 8, wherein the cleaning operation is performed based on an accumulated time from the start of rotation of the developing sleeve. 10. The charging method according to claim 9, wherein the cleaning operation is performed by temporarily stopping the pre-printing process or the post-printing process during the pre-printing process or the post-printing process of the image forming apparatus. Cleaning method for the used members. During the printing operation of the image forming apparatus, the cleaning operation is performed after the printing operation on the printing paper during the printing operation is completed and before the printing operation on the next printing paper is performed. The method according to claim 9, wherein the charged member is cleaned. 12. The charged member according to claim 1, wherein a voltage amplitude of PEAK TO PEAK applied to the developing sleeve is 1500 V / mm or less, and a maximum voltage is 2000 V or less. Cleaning method. The frequency of the voltage of the AC component superimposedly applied to the developing sleeve is in a range of 30 Hz to 150 Hz, and its waveform is a rectangular wave. Cleaning method for charged members.

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