JP2005010351A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which an electrostatic charging roll is prevented from being contaminated with a residual toner. <P>SOLUTION: The image forming apparatus is equipped with: a brush 16_1 which rotates in the direction of the arrow B while coming into contact with the surface of a photoreceptor drum 11 (drum) rotating in the direction of the arrow A and which thereby recovers the toner remaining on the drum 11; a roll 16_2 which is arranged downstream from the brush 16_1 in the moving direction of the drum 11, which rotates in the direction of the arrow C while coming into contact with the brush 16_1 and the drum 11, and which, receiving the toner recovered by the brush 16_1, discharges the received toner onto the drum 11; and a power source section 16_3 which has a brush power source 16_3a and a roll power source 16_3b each applying a prescribed voltage to the brush 16_1 and the roll 16_2, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本実施形態の各画像形成部には、給電シャフトの外周に導電性弾性体層と表面層を被覆した２層構成の帯電ロールを用いている。
【００３３】
帯電ロールの表面層には、イソシアネート処理を施したエピクロロヒドリンゴムを用いている。このエピクロロヒドリンゴムは高離型性を有しており、トナーその他の異物が極めて付着しにくい。
【００３４】
導電性弾性体層には低硬度の発泡ウレタンを用いている。
【００３５】
給電シャフトの直径は６ｍｍ、弾性体層の肉厚は１．５ｍｍ、表面層の肉厚は０．５ｍｍ、帯電ロールの外径は１０ｍｍ、硬度は２８度（ＡｓｋｅｒＣ硬度）である。
【００３６】
本実施形態の帯電ロールの表面層は高離型性を有しており、通常の帯電ロールに比べてトナーその他の異物が付着しにく。さらに、導電性弾性層として発泡ウレタンを使用することによって低硬度を実現させており、トナーや異物が極めて付着しにくくなっている。
【００３７】
帯電ロールの印加電圧はＶｐ−ｐ＝１．３ＫＶ、ｆ＝６５０Ｈｚ、Ｖｄｃ＝−５２０Ｖである。なお、本実施の形態では、交流電圧に直流電圧を重畳した印加方式を用いたが、直流のみを印加する方式を用いてもよい。
【００３８】
帯電ロールは、上記の構成に限定されるものではなく、例えば、給電シャフトの外周面に棒状または管状の導電性弾性体層を形成し、その上に抵抗層、および表面保護層を被覆した３層構造のものなどを用いてもよい。
【００３９】
帯電ロールの各層には、イオン導電性物質、あるいは電子導電性物質、あるいはその双方が分散されている。イオン導電性物質としては、例えば過塩素酸リチウム、過塩素酸ナトリウム、過塩素酸アンモニウム、第四級アンモニウムクロールイド等の過塩素酸塩やアンモニウム塩などが用いられる。電子導電性物質としては、例えば、カーボンブラック、グラファイトなどの他、アルミニウム、ステンレス鋼（ＳＵＳ）等の各種導電性金属、または合金、酸化錫、酸化インジウム、酸化チタン、酸化錫−酸化アンチモン複合酸化物、酸化錫−酸化インジウム複合酸化物等の各種導電性金属酸化物などの微粉末を用いることができる。
【００４０】
帯電ロールの給電シャフトは、電極部材としての機能の他に、帯電ロールの支持部材としての機能を有しており、例えばアルミニウム、銅合金、ＳＵＳ等の金属または合金、クロム、ニッケル等で鍍金処理を施した鉄、合成樹脂などの導電性の材質で構成される。
【００４１】
導電性弾性体層は、帯電ロールが適切なニップ幅ないしニップ圧でもって感光体ドラム表面に接触して感光体ドラム表面を均一に帯電できるよう、帯電ロールを所定の抵抗値および硬度に収めるために設けられる。この導電性弾性体層は、上述のようなイオン導電性物質および電子導電性物質から選ばれた少なくとも１種の物質（以下、導電剤という）をゴム材料中に分散させることによって形成される。ゴム材料としては、例えばイソプレンゴム、クロロプレンゴム、エピクロルヒドリン系ゴム、ブチルゴム、シリコーンゴム、ウレタンゴム、フッ素ゴム、ＳＢＲ、ＮＢＲ、ＥＰＤＭ、スチレン−ブタジエンゴム−スチレン、これらのブレンドゴム等が挙げられる。導電性弾性体層の体積抵抗率については、抵抗層の体積抵抗率と密接に関連するが、１０^４Ωｃｍ〜１０^９Ωｃｍの範囲内にあることが好ましい。
【００４２】
抵抗層は、帯電ロールを所定の抵抗値に調整するために設けられるものであり、ポリアミド、ポリエチレン、ポリウレタン、アクリル樹脂、エピクロルヒドリン系ゴム等の高分子材料に導電剤を分散させた薄膜から形成される。抵抗層の体積抵抗率は１０^４Ωｃｍ〜１０^９Ωｃｍの範囲内にあることが好ましい。
【００４３】
表面保護層は、感光体ドラム表面にタック（導電剤が沁み出し感光体とくっついてしまう現象）が発生する恐れがある場合や抵抗層の磨耗を防止するために設けられるものであり、ポリアミド、ポリエチレン、ポリウレタン、アクリル樹脂等の高分子材料に導電剤を分散させた薄膜から形成される。表面保護層の体積抵抗率は１０^４Ωｃｍ〜１０^９Ωｃｍの範囲内にあることが好ましい。
【００４４】
表面保護層は、上述のタック発生等の恐れがない場合には敢えて設ける必要はない。
【００４５】
また、帯電ロールの抵抗値を表面保護層で調整することによって抵抗層を不要とすることもできる。さらに、導電性弾性体層から軟化剤やゴム材料等がブリードしてくる恐れのある場合は、導電性弾性体層と抵抗層の間にポリアミド、ポリウレタン等に導電剤を分散させた中間層を設けることが好ましい。
【００４６】
帯電ロールの体積抵抗率は、１０^４Ωｃｍ〜１０^９Ωｃｍの範囲内にあることが好ましい。これは、前述した導電性弾性体層、抵抗調整層、および表面保護層等の各構成材料の体積抵抗率と膜厚とを適宜組み合わせることによって、この範囲内に調整することが可能である。
【００４７】
本実施形態の画像形成装置には、離型性の高い球形トナーが使用される。
【００４８】
次に、この画像形成装置１００の基本的な画像形成動作について説明する。
【００４９】
先ず、イエローの画像形成部１０Ｙによるトナー像形成が開始され、矢印Ａ方向に回転する感光体ドラム１１Ｙ表面に、帯電ロール１２Ｙにより所定の電荷が付与される。次に、露光装置１３Ｙにより感光体ドラム１１Ｙ表面にイエロー画像に相当する露光光が照射されイエローの潜像が形成される。その潜像は現像器１４Ｙによりイエローのトナーで現像されて感光体ドラム１１Ｙ上にイエローのトナー像が形成される。そのトナー像は一次転写ロール１５Ｙにより中間転写ベルト１７に転写される。
【００５０】
中間転写ベルト１７は矢印Ｂ方向に循環移動しており、中間転写ベルト１７上に転写されたイエローのトナー像が次の色の画像形成部１０Ｍの一次転写ロール１５Ｍに到達するタイミングに合わせて、次の色のマゼンタのトナー像が一次転写ロール１５Ｍに到達するように、マゼンタの画像形成部１０Ｍによるトナー像形成が行われる。こうして形成されたマゼンタのトナー像は、一次転写ロール１５Ｍにおいて中間転写ベルト１７上のイエローのトナー像の上に重ねて転写される。
【００５１】
続いて、シアンおよび黒の画像形成部１０Ｃ，１０Ｋによるトナー像形成が上記と同様のタイミングで行われ、一次転写ロール１５Ｃ，１５Ｋにおいて中間転写ベルト１７上のイエローおよびマゼンタのトナー像の上に順次重ねて転写される。
【００５２】
こうして、中間転写ベルト１７上に転写された多色トナー像は、二次転写ロール１９により用紙Ｐ上に二次転写され、多色トナー像は用紙Ｐとともに矢印Ｄ方向に搬送され、定着器２０により用紙Ｐ上に定着されてカラー画像が形成される。
【００５３】
次に、クリーニング部について説明する。
【００５４】
本実施形態のクリーニング部の詳細を説明する前に、本発明者らが行ったクリーニングテストの結果について説明する。
【００５５】
ブラシとしては、外径５ｍｍの回転軸表面に導電性を有するナイロンの毛を放射状に植毛して形成した外径１０ｍｍのブラシを用いた。毛の長さは２．５ｍｍ、毛の太さは約２デニール、毛の密度は４３０Ｋｆ／ｉｎｃｈ^２である。
【００５６】
ブラシの感光体ドラムへの食い込み量は０．５ｍｍとした。
【００５７】
ブラシが、Ａｇａｉｎｓｔ（アゲインスト）回転、すなわち感光体ドラムと対向する部分が感光体ドラムの移動方向とは反対の方向に移動する向きに回転する場合と、ブラシが、Ｗｉｔｈ（ウイズ）回転、すなわち感光体ドラムと対向する部分が感光体ドラムの移動方向と同じ方向に移動する向きに回転する場合の２つの場合とについてそれぞれテストを行った。なお、ブラシの周速度は感光体ドラムの表面速度の２倍とした。
【００５８】
ロールとしては、外径５ｍｍの回転軸表面に、発泡ウレタン製の弾性層を形成しその上にエピクロロヒドリンゴム製の表面層を形成した外径１０ｍｍのロールを用いた。
【００５９】
ブラシのロールへの食い込み量は０．５ｍｍ、感光体ドラムへのロールの食い込み量は０．４ｍｍとした。
【００６０】
ロールの回転方向は感光体ドラムの回転方向に対してＷｉｔｈ（ウイズ）回転とした。なお、ロールの周速度は感光体ドラムの表面速度と同速度とした。
【００６１】
表１は、上記のブラシおよびロールによるクリーニングテストの結果を示す表である。
【００６２】
【表１】

【００６３】
ここで、トナー回収性能とは、クリーニング装置をすり抜けるトナー量を０．０２ｇ／ｍ^２以下に抑制する転写残留トナー量で表したものである。
【００６４】
表１に示したテスト結果をグラフとして表したものを図２および図３に示す。
【００６５】
図２は、各方式のクリーニング部材のトナー回収性能を示すグラフである。
【００６６】
図２に示すように、ブラシのトナーすり抜け量は、Ａｇａｉｎｓｔ回転の場合は、０．５ｇ／ｍ^２と最も高い値を示している。ブラシをＷｉｔｈ回転とした場合は、トナーすり抜け量は０．３ｇ／ｍ^２であり、Ａｇａｉｎｓｔ回転よりも低い値を示している。また、Ｗｉｔｈ回転のロールのトナーすり抜け量は０．２５ｇ／ｍ^２と最も低い値を示している。なお、本実施形態の画像形成装置のトナー回収性能については後述する。
【００６７】
図３は、各方式のクリーニング部材のトナー吐き出し率を示すグラフである。
【００６８】
図３に示すように、ブラシのトナー吐き出し率は、Ａｇａｉｎｓｔ回転の場合は、７０％と最も低い値を示している。ブラシをＷｉｔｈ回転とした場合は、トナー吐き出し率は９５％であり、Ａｇａｉｎｓｔ回転よりも高い値を示している。また、Ｗｉｔｈ回転のロールのトナー吐き出し率は９９．５％と最も高い値を示している。なお、本実施形態の画像形成装置のトナー吐き出し率については後述する。
【００６９】
従って、クリーニング工程ではＡｇａｉｎｓｔ回転を行い、吐き出し工程ではＷｉｔｈ回転を行うブラシを１個設けることにより、トナー回収性能と吐き出し性能を両立させたクリーニング部を得ることが可能である。しかし、そのためには、ブラシの回転方向を切り換える機構を組み込まなければならず、大幅にコストアップする恐れがあり好ましくない。また、吐き出し率の観点からは、ブラシよりもロールの方が好ましい。
【００７０】
次に、本実施形態のクリーニング部について詳細に説明する。
【００７１】
図１に示したように、本実施形態のクリーニング部１６Ｙ，１６Ｍ，１６Ｃ，１６Ｋは、一次転写ロール１５Ｙ，１５Ｍ，１５Ｃ，１５Ｋよりも感光体ドラム１１Ｙ，１１Ｍ，１１Ｃ，１１Ｋの回転方向下流側に配備されており、転写後の各感光体ドラム上に残留する残留トナーを除去する。
【００７２】
図４は、本実施形態の画像形成装置のクリーニング部の詳細図である。
【００７３】
図４に示すように、このクリーニング部１６は、ブラシ１６＿１と、ロール１６＿２と、電源部１６＿３とを備えており、感光体ドラム１１上のトナーをブラシ１６＿１に回収して回収したトナーをロール１６＿２に受け渡すクリーニング工程と、ロール１６＿２に受け渡されたトナーを感光体ドラム１１上に吐き出す吐き出し工程とを有している。
【００７４】
ブラシ１６＿１は、矢印Ａ方向に回転する感光体ドラム１１表面に接触しながら矢印Ｂ方向に回転し、感光体ドラム１１上に残留したトナーを回収する。
【００７５】
ロール１６＿２は、ブラシ１６＿１よりも感光体ドラム１１の移動方向下流側に配備され、ブラシ１６＿１および感光体ドラム１１と接触しながら矢印Ｃ方向に回転し、ブラシ１６＿１が回収したトナーを受け取り、受け取ったトナーを感光体ドラム１１上に吐き出す。
【００７６】
電源部１６＿３は、ブラシ１６＿１およびロール１６＿２にそれぞれ所定の電圧を印加するブラシ電源１６＿３ａおよびロール電源１６＿３ｂを備えている。
【００７７】
次に、本発明の実施例について説明する。
［実施例１］
この実施例１は、転写後の感光体ドラム上に、プラストナーが多く残留するケースに対応する実施例である。
【００７８】
図５は、実施例１における回収動作（ａ）および受け渡し動作（ｂ）を示す図である。
【００７９】
図５（ａ）に示すように、ブラシ１６＿１にはブラシ電源１６＿３ａからマイナスの電圧が印加されており、ロール１６＿２にはブラシ１６＿１への印加電圧よりも絶対値で大きいマイナスの電圧が印加される。すなわち、ブラシ１６＿１に印加される電圧は−２５０Ｖであり、ロール１６＿２に印加される電圧は−５００Ｖである。
【００８０】
ブラシ１６＿１の回転方向は、矢印Ａ方向に回転する感光体ドラム１１に対してＡｇａｉｎｓｔ回転となるＢ方向であるため、感光体ドラム１１上のプラストナーｔ１は、高い回収効率でブラシ１６＿１に回収される。
【００８１】
実際にトナーすり抜け量を測定した結果、図２に示した通り極めて優れた値が得られた。
【００８２】
次に、図５（ｂ）に示すように、ブラシ１６＿１に回収されたプラストナーｔ１は、ブラシ１６＿１に接触しながら矢印Ｃ方向に回転するロール１６＿２に受け渡される。このとき、ロール１６＿２の回転方向は、矢印Ｂ方向に回転するブラシ１６＿１に対してＷｉｔｈ回転回転となるので、ブラシ１６＿１上のプラストナーｔ１は、Ａｇａｉｎｓｔ回転の場合に比べて、極めて高い効率でロール１６＿２上に受け渡されることになる。一度ロール１６＿２上に受け渡されたプラストナーｔ１は感光体ドラム１１とロール１６＿２の電位差の関係で、ロール１６＿２上に保持されたままとなる。
【００８３】
図６は、実施例１における吐き出し動作を示す図である。
【００８４】
図６に示すように、ブラシ１６＿１およびロール１６＿２にはブラシ電源１６＿３’からプラスの電圧が印加されている。なお、ブラシ１６＿１およびロール１６＿２に印加される電圧はともに＋４００Ｖである。
【００８５】
ロール１６＿２に受け渡されたプラストナーｔ１は、感光体ドラム１１とロール１６＿２の電位差の関係で感光体ドラム１１上に吐き出される。
【００８６】
この吐き出し工程は、ロールから感光体への吐き出しであるため、図３に示した通り、高い吐き出し率が得られた。
【００８７】
なお、この実施例１では、ブラシ１６＿１が、感光体ドラム１１の回転方向とは反対の方向に回転し、かつ、ロール１６＿２が、感光体ドラム１１の回転方向と同じ方向に回転する場合の例について説明したが、本発明は、必ずしも上記の回転方向のみに制限されるものではなく、ブラシ、ロールともに、いずれの回転方向であってもよいが、図２および図３に示したテスト結果からみて、ブラシはＡｇａｉｎｓｔ回転、ロールはＷｉｔｈ回転であることが好ましい。
［実施例２］
この実施例２は、転写後の感光体ドラム１１上に、マイナストナーが多く残留するケースに対応する実施例である。
【００８８】
図７は、実施例２における回収動作（ａ）および受け渡し動作（ｂ）を示す図である。
【００８９】
図７（ａ）に示すように、ブラシ１６＿１にはブラシ電源１６＿３ａからプラスの電圧が印加されており、ロール１６＿２にはブラシ１６＿１への印加電圧よりも絶対値で大きいプラスの電圧が印加される。すなわち、ブラシ１６＿１に印加される電圧は＋２５０Ｖであり、ロール１６＿２に印加される電圧は＋５００Ｖである。
【００９０】
ブラシ１６＿１の回転方向は、実施例１と同様、矢印Ａ方向に回転する感光体ドラム１１に対してＡｇａｉｎｓｔ回転回転となるＢ方向であるため、感光体ドラム１１上のマイナストナーｔ２は、高い回収効率でブラシ１６＿１に回収される。
【００９１】
実際にトナーすり抜け量を測定した結果、図２に示した実施例１とほぼ同様の極めて優れた値が得られた。
【００９２】
次に、図７（ｂ）に示すように、ブラシ１６＿１に回収されたマイナストナーｔ２は、ブラシ１６＿１に接触しながら矢印Ｃ方向に回転するロール１６＿２に受け渡される。このとき、ロール１６＿２の回転方向は、実施例１と同様、矢印Ｂ方向に回転するブラシ１６＿１に対してＷｉｔｈ回転となるので、ブラシ１６＿１上のマイナストナーｔ２は、Ａｇａｉｎｓｔ回転の場合に比べて、極めて高い効率でロール１６＿２上に受け渡されることになる。一度ロール１６＿２上に受け渡されたマイナストナーｔ２は感光体ドラム１１とロール１６＿２の電位差の関係で、ロール１６＿２上に保持されたままとなる。
【００９３】
図８は、実施例２における吐き出し動作を示す図である。
【００９４】
図８に示すように、ブラシ１６＿１およびロール１６＿２にはブラシ電源１６＿３’からマイナスの電圧が印加されている。なお、ブラシ１６＿１およびロール１６＿２に印加される電圧はともに−４００Ｖである。
【００９５】
ロール１６＿２に受け渡されたマイナストナーｔ２は、感光体ドラム１１とロール１６＿２の電位差の関係で感光体ドラム１１上に吐き出される。
【００９６】
この吐き出し工程は、ロールから感光体への吐き出しなので、図２に示した実施例１とほぼ同様の高い吐き出し率が得られた。
【００９７】
なお、この実施例２では、ブラシ１６＿１が、感光体ドラム１１の回転方向とは反対の方向に回転するものであり、かつ、ロール１６＿２が、感光体ドラム１１の回転方向と同じ方向に回転するようにした場合の例について説明したが、本発明は、必ずしも上記の回転方向のみに制限されるものではなく、ブラシ、ロールともに、いずれの回転方向であってもよいが、図２および図３に示したテスト結果からみて、ブラシはＡｇａｉｎｓｔ回転、ロールはＷｉｔｈ回転であることが好ましい。
［実施例３］
この実施例３は、転写後の感光体ドラム１１上に、マイナストナーおよびプラストナーの双方が残留するケースに対応する実施例である。
【００９８】
図９は、実施例３におけるクリーニング工程での回収動作を示す図である。
【００９９】
図９（ａ）に示すように、ブラシ１６＿１にはブラシ電源２６＿３から交番電圧が印加されており、また同じくロール１６＿２にはブラシ電源２６＿３’からの交番電圧が印加される。すなわち、ブラシ１６＿１に印加されるＡＣ電圧はＶｐ−ｐ：６００Ｖ、周波数３ＫＨｚであり、ロール１６＿２にも同じ電圧が印加される。
【０１００】
ブラシ１６＿１の回転方向は、実施例１と同様、矢印Ａ方向に回転する感光体ドラム１１に対してＡｇａｉｎｓｔ回転となるＢ方向であるため、感光体ドラム１１上のプラストナーｔ１およびマイナストナーｔ２の双方が高い回収効率でブラシ１６＿１に回収される。
【０１０１】
図１０は、実施例３における吐き出し動作を示す図である。
【０１０２】
図１０（ａ）に示すように、ブラシ１６＿１に、感光体ドラム１１の電位からみてマイナスの電圧−５００Ｖを印加するとともに、ロール１６＿２に、ブラシ１６＿１への印加電圧よりも絶対値で小さいマイナスの電圧−２５０Ｖを印加する。
【０１０３】
図１０（ａ）に示すように、ブラシ１６＿１に回収されたプラストナーｔ１およびマイナストナーｔ２のうちマイナストナーｔ２は、ブラシ１６＿１に接触しながら矢印Ｃ方向に回転するロール１６＿２に受け渡される。このとき、ロール１６＿２の回転方向は、実施例１と同様、矢印Ｂ方向に回転するブラシ１６＿１に対してＷｉｔｈ回転となるので、ブラシ１６＿１上のマイナストナーｔ２は、Ａｇａｉｎｓｔ回転の場合に比べて、極めて高い効率でロール１６＿２上に受け渡されることになる。一度ロール１６＿２上に受け渡されたマイナストナーｔ２は感光体ドラム１１とロール１６＿２の電位差の関係で、感光体ドラム１１に吐き出される。
【０１０４】
次に、図１０（ｂ）に示すように、ブラシ１６＿１に、感光体ドラム１１の電位からみてプラスの電圧＋５００Ｖを印加するとともに、ロール１６＿２に、ブラシ１６＿１への印加電圧よりも絶対値で小さいプラスの電圧＋２５０Ｖを印加する。
【０１０５】
図１０（ｂ）に示すように、ブラシ１６＿１上のプラストナーｔ１は、ブラシ１６＿１に接触しながら矢印Ｃ方向に回転するロール１６＿２に受け渡される。このとき、ロール１６＿２の回転方向は、実施例１と同様、矢印Ｂ方向に回転するブラシ１６＿１に対してＷｉｔｈ回転となるので、ブラシ１６＿１上のプラストナーｔ１は、Ａｇａｉｎｓｔ回転の場合に比べて、極めて高い効率でロール１６＿２上に受け渡されることになる。一度ロール１６＿２上に受け渡されたプラストナーｔ１は感光体ドラム１１とロール１６＿２の電位差の関係で、感光体ドラム１１に吐き出される。
【０１０６】
実施例３においても、実施例１とほぼ同様の優れたクリーニング性能を得ることができた。
［実施例４］
この実施例４は、前述の実施例３と同様、転写後の感光体ドラム１１上に、マイナストナーおよびプラストナーの双方が残留するケースに対応する実施例の変形である。
【０１０７】
この実施例４のクリーニング工程は、実施例３におけるクリーニング工程と同様であるが、吐き出し動作における電源部の極性が実施例３における電源部の極性とは異なっている。
【０１０８】
すなわち、吐き出し工程では、先ず、ブラシ１６＿１（図１０参照）に、感光体ドラム１１の電位からみてプラスの電圧：＋５００Ｖを印加するとともに、ロール１６＿２に、ブラシ１６＿１への印加電圧よりも絶対値で小さいプラスの電圧：＋２５０Ｖを印加し、次に、ブラシ１６＿１に、感光体ドラム１１の電位からみてマイナスの電圧：−５００Ｖを印加するとともに、ロール１６＿２に、ブラシ１６＿１への印加電圧よりも絶対値で小さいマイナスの電圧：−２５０Ｖを印加する。
【０１０９】
吐き出し工程における電源部の印加電圧以外は、実施例３と同様である。
【０１１０】
実施例４においても、実施例１とほぼ同様の優れたクリーニング性能を得ることができた。
【０１１１】
【発明の効果】
以上、説明したように、本発明の画像形成装置によれば、ブラシにより像担持体上に残留したトナーが効率よく回収され、そのトナーがロールにより像担持体上に効率よく吐き出されるので、帯電ロールの汚染が防止された画質のよい画像形成装置を実現することができる。
【０１１２】
また、この画像形成装置はブレードレスクリーニングシステムとして構成されるので、長寿命の画像形成装置を実現することができる。
【図面の簡単な説明】
【図１】本発明の画像形成装置の一実施形態を示す概略構成図である。
【図２】各方式のクリーニング部材のトナー回収性能を示すグラフである。
【図３】各方式のクリーニング部材のトナー吐き出し率を示すグラフである。
【図４】本実施形態の画像形成装置のクリーニング部の詳細図である。
【図５】実施例１における回収動作（ａ）および受け渡し動作（ｂ）を示す図である。
【図６】実施例１における吐き出し動作を示す図である。
【図７】実施例２における回収動作（ａ）および受け渡し動作（ｂ）を示す図である。
【図８】実施例２における吐き出し動作を示す図である。
【図９】実施例３におけるクリーニング工程での回収動作を示す図である。
【図１０】実施例３における吐き出し動作を示す図である。
【符号の説明】
１１，１１Ｙ，１１Ｍ，１１Ｃ，１１Ｋ 感光体ドラム
１２Ｙ，１２Ｍ，１２Ｃ，１２Ｋ 帯電ロール
１３Ｙ，１３Ｍ，１３Ｃ，１３Ｋ 露光装置
１４Ｙ，１４Ｍ，１４Ｃ，１４Ｋ 現像器
１５Ｙ，１５Ｍ，１５Ｃ，１５Ｋ 一次転写ロール
１６，１６Ｙ，１６Ｍ，１６Ｃ，１６Ｋ クリーニング部
１６＿１ ブラシ
１６＿２ ロール
１６＿３，１６＿３’，２６＿３ａ’ 電源部
１６＿３ａ ブラシ電源
１６＿３ｂ ロール電源
１７ 中間転写ベルト
１８ 中間転写ベルトクリーナ
１９ 二次転写ロール
２０ 定着器
１００ 画像形成装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a printer, or a fax machine, after a toner image formed on an image carrier is transferred to a transfer target, residual toner remaining on the image carrier is removed with a blade or the like. There is known an image forming apparatus including a cleaning device that scrapes and collects.
[0003]
However, this type of image forming apparatus is not preferable from the viewpoint of environmental management because it is necessary to take out and discard the toner collected by the cleaning device. Therefore, in recent years, a so-called bladeless (cleanerless) type image forming apparatus that does not have a blade type cleaning apparatus that generates waste toner has been developed and widely used.
[0004]
In this bladeless image forming apparatus, the residual toner remaining on the image carrier is finally collected by the developing device, but the residual toner adheres to the charging roll disposed upstream of the developing device. As a result, the charging performance of the charging roll is deteriorated, so that there is a problem that an image carrier is poorly charged and causes an image defect.
[0005]
Therefore, in order to solve this problem, a rotatable brush is provided on the upstream side of the charging roll, and residual toner is electrostatically collected by this brush during image formation and held in the brush. A bladeless type image forming apparatus is considered in which held toner is discharged to the surface of an image carrier during non-image formation.
[0006]
In this brush type cleaning device, when the rotation direction of the brush is opposite to the rotation direction of the image carrier, the recovery performance is good, but the discharge performance is low, and the non-image forming unit frequently discharges. Even if the process is performed, the toner gradually accumulates in the brush, and eventually, the cleaning limit occurs beyond the limit holding amount of the brush. On the other hand, when the rotation direction of the brush is the same as the rotation direction of the image carrier, although the discharge performance is good, the collection performance is low, and cleaning failure tends to occur from the beginning.
[0007]
Thus, it is difficult to achieve both recovery performance and discharge performance with a brush-type cleaning device.
[0008]
Therefore, in a cleaning apparatus having a cleaning roll for collecting toner and a cleaning roll for discharging toner that rotate in the same direction as the rotation direction of the image carrier while being in contact with the image carrier, the rotation speeds of these two cleaning rollers are set appropriately. Therefore, there has been proposed an image forming apparatus that achieves good toner collection and discharge. (For example, refer to Patent Document 1).
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-333514 (pages 2 and 3, FIG. 2)
[0010]
[Problems to be solved by the invention]
However, since the cleaning device of the method of Patent Document 1 uses a cleaning roll for toner recovery, there is a problem that the toner recovery performance does not reach the toner recovery performance of the brush-type cleaning device described above.
[0011]
The cleaning device is also required to have a function of removing discharge products generated from the charger. The brush type cleaning device can also remove the discharge products, but the roll type cleaning device can meet this requirement. There is also a problem that cannot be done.
[0012]
In view of the above circumstances, an object of the present invention is to provide an image forming apparatus in which contamination of a charging roll by residual toner is prevented.
[0013]
[Means for Solving the Problems]
The image forming apparatus of the present invention that achieves the above object provides:
An image carrier that moves in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, and a transfer unit that transfers a toner image formed by the toner image forming unit to a predetermined transfer target And an image forming apparatus having a cleaning unit that removes toner remaining on the image carrier without being transferred to the transfer target,
The cleaning unit is disposed on the downstream side in the moving direction of the image carrier with respect to the rotatable brush for collecting the toner remaining on the image carrier while contacting the surface of the image carrier, A rotatable roll that receives toner collected by the brush while contacting the brush and the image carrier, and discharges the received toner onto the image carrier, and a power supply unit that applies a predetermined voltage to the brush and the roll A cleaning step of collecting the toner on the image carrier with the brush and delivering the collected toner to the roll; and discharging the toner delivered to the roll onto the image carrier It has a process, It is characterized by the above-mentioned.
[0014]
According to the image forming apparatus of the present invention, the toner remaining on the image carrier is efficiently collected by the brush, and the toner is efficiently discharged onto the image carrier by the roll, so that the charging roll is prevented from being contaminated. An image forming apparatus with good image quality can be realized.
[0015]
Here, the brush rotates in a direction in which a portion facing the image carrier moves in a direction opposite to the moving direction of the image carrier, and
The roll may rotate in a direction in which a portion facing the image carrier moves in the same direction as the moving direction of the image carrier.
[0016]
When the image forming apparatus of the present invention is configured in this way, the toner collection performance by the brush and the toner discharge rate by the roll can be further improved.
[0017]
In the cleaning step, the power supply unit applies a negative voltage to the brush as viewed from the potential of the image carrier, and applies a negative voltage to the roll that is larger in absolute value than the voltage applied to the brush. In the discharging step, a positive voltage may be applied to the brush and the roll as viewed from the potential of the image carrier.
[0018]
When the image forming apparatus of the present invention is configured in this way, plus toner can be efficiently collected and discharged.
[0019]
In the cleaning step, the power supply unit applies a positive voltage to the brush as viewed from the potential of the image carrier, and applies a positive voltage to the roll that is larger in absolute value than the voltage applied to the brush. In the discharging step, a negative voltage may be applied to the brush and the roll as viewed from the potential of the image carrier.
[0020]
When the image forming apparatus of the present invention is configured in this manner, minus toner can be efficiently collected and discharged.
[0021]
The power supply unit applies a voltage including at least an alternating voltage to the brush in the cleaning step, and first applies a negative voltage to the brush in terms of the potential of the image carrier in the discharge step. In addition, a negative voltage smaller in absolute value than the voltage applied to the brush is applied to the roll, and then a positive voltage is applied to the brush as viewed from the potential of the image carrier. In addition, a positive voltage smaller in absolute value than the voltage applied to the brush may be applied.
[0022]
When the image forming apparatus of the present invention is configured in this way, both positive toner and negative toner can be efficiently collected and discharged.
[0023]
In the cleaning step, the power supply unit applies a voltage including at least an alternating voltage to the brush. In the discharge step, first, a positive voltage is applied to the brush as viewed from the potential of the image carrier. A positive voltage smaller in absolute value than the voltage applied to the brush is applied to the roll, and then a negative voltage is applied to the brush as viewed from the potential of the image carrier. In addition, a negative voltage smaller in absolute value than the voltage applied to the brush may be applied.
[0024]
When the image forming apparatus of the present invention is configured in this way, both positive toner and negative toner can be efficiently collected and discharged.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0026]
FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.
[0027]
As shown in FIG. 1, the image forming apparatus 100 includes photosensitive drums 11Y, 11M, 11C, and 11K, charging rolls 12Y, 12M, 12C, and 12K, exposure apparatuses 13Y, 13M, 13C, and 13K, and developing units 14Y and 14M. , 14C, 14K, primary transfer rolls 15Y, 15M, 15C, 15K, cleaning units 16Y, 16M, 16C, 16K, an intermediate transfer belt 17, an intermediate transfer belt cleaner 18, a secondary transfer roll 19, and a fixing device 20. Yes.
[0028]
Note that the symbols Y, M, C, and K added to the end of each component described above indicate components for forming yellow, magenta, cyan, and black images, respectively.
[0029]
Note that the photosensitive drums 11Y, 11M, 11C, and 11K in the present embodiment correspond to the image carrier referred to in the present invention, and the charging rolls 12Y, 12M, 12C, and 12K serve as the charging unit referred to in the present invention. The exposure devices 13Y, 13M, 13C, and 13K correspond to the latent image forming portion referred to in the present invention, and the developing devices 14Y, 14M, 14C, and 14K correspond to the developing portion referred to in the present invention. The primary transfer rolls 15Y, 15M, 15C, and 15K correspond to the transfer portion referred to in the present invention, and the intermediate transfer belt 17 corresponds to the predetermined transfer target referred to in the present invention. It is.
[0030]
The image forming units 10Y, 10M, 10C, and 10K for the respective colors are constituted by the photosensitive drums for each color, the charging roll, the exposure device, the developing device, the primary transfer roll, and the cleaning unit.
[0031]
The specifications of the main part of the image forming apparatus will be described below.
[0032]

Each image forming unit of the present embodiment uses a charging roll having a two-layer structure in which a conductive elastic body layer and a surface layer are coated on the outer periphery of the power supply shaft.
[0033]
Epichlorohydrin rubber subjected to isocyanate treatment is used for the surface layer of the charging roll. This epichlorohydrin rubber has a high releasability and is extremely difficult for toner and other foreign matters to adhere to it.
[0034]
Low-hardness urethane foam is used for the conductive elastic layer.
[0035]
The diameter of the feeding shaft is 6 mm, the thickness of the elastic layer is 1.5 mm, the thickness of the surface layer is 0.5 mm, the outer diameter of the charging roll is 10 mm, and the hardness is 28 degrees (Asker C hardness).
[0036]
The surface layer of the charging roll of this embodiment has a high releasability, and toner and other foreign matters are less likely to adhere as compared with a normal charging roll. Furthermore, low hardness is achieved by using urethane foam as the conductive elastic layer, and toner and foreign matter are extremely difficult to adhere.
[0037]
The applied voltage of the charging roll is Vp-p = 1.3 KV, f = 650 Hz, and Vdc = −520V. In this embodiment, an application method in which a DC voltage is superimposed on an AC voltage is used, but a method in which only DC is applied may be used.
[0038]
The charging roll is not limited to the above configuration. For example, the charging roll is formed by forming a rod-like or tubular conductive elastic layer on the outer peripheral surface of the power supply shaft, and covering the resistance layer and the surface protective layer thereon 3 A layer structure or the like may be used.
[0039]
In each layer of the charging roll, an ionic conductive material, an electronic conductive material, or both are dispersed. As the ion conductive substance, for example, perchlorate or ammonium salt such as lithium perchlorate, sodium perchlorate, ammonium perchlorate, quaternary ammonium chlorid, etc. are used. Examples of the electronic conductive material include carbon black and graphite, various conductive metals such as aluminum and stainless steel (SUS), or alloys, tin oxide, indium oxide, titanium oxide, and tin oxide-antimony oxide composite oxide. And fine powders of various conductive metal oxides such as tin oxide-indium oxide composite oxide can be used.
[0040]
The power supply shaft of the charging roll has a function as a support member for the charging roll in addition to the function as an electrode member. For example, a metal or alloy such as aluminum, copper alloy, SUS, or the like is plated with chromium, nickel It is made of a conductive material such as iron or synthetic resin.
[0041]
The conductive elastic layer is used to keep the charging roll at a predetermined resistance and hardness so that the charging roll can be uniformly charged by contacting the surface of the photosensitive drum with an appropriate nip width or nip pressure. Is provided. The conductive elastic layer is formed by dispersing at least one substance selected from the above-described ion conductive substance and electronic conductive substance (hereinafter referred to as a conductive agent) in a rubber material. Examples of the rubber material include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, silicone rubber, urethane rubber, fluororubber, SBR, NBR, EPDM, styrene-butadiene rubber-styrene, and blended rubber thereof. The volume resistivity of the conductive elastic layer is closely related to the volume resistivity of the resistance layer. ⁴ Ωcm to 10 ⁹ It is preferably within the range of Ωcm.
[0042]
The resistance layer is provided to adjust the charging roll to a predetermined resistance value, and is formed from a thin film in which a conductive agent is dispersed in a polymer material such as polyamide, polyethylene, polyurethane, acrylic resin, epichlorohydrin rubber. The The volume resistivity of the resistive layer is 10 ⁴ Ωcm to 10 ⁹ It is preferably within the range of Ωcm.
[0043]
The surface protective layer is provided in order to prevent tack on the surface of the photosensitive drum (a phenomenon in which the conductive agent oozes out and adheres to the photosensitive member) or to prevent abrasion of the resistance layer. It is formed from a thin film in which a conductive agent is dispersed in a polymer material such as polyethylene, polyurethane, and acrylic resin. The volume resistivity of the surface protective layer is 10 ⁴ Ωcm to 10 ⁹ It is preferably within the range of Ωcm.
[0044]
The surface protective layer does not need to be provided when there is no fear of the above-described tack generation.
[0045]
Further, the resistance layer can be eliminated by adjusting the resistance value of the charging roll with the surface protective layer. Furthermore, if there is a possibility that softeners or rubber materials may bleed from the conductive elastic layer, an intermediate layer in which a conductive agent is dispersed in polyamide, polyurethane or the like is interposed between the conductive elastic layer and the resistance layer. It is preferable to provide it.
[0046]
The volume resistivity of the charging roll is 10 ⁴ Ωcm to 10 ⁹ It is preferably within the range of Ωcm. This can be adjusted within this range by appropriately combining the volume resistivity and the film thickness of each constituent material such as the conductive elastic layer, the resistance adjusting layer, and the surface protective layer.
[0047]
In the image forming apparatus of this embodiment, spherical toner having high releasability is used.
[0048]
Next, a basic image forming operation of the image forming apparatus 100 will be described.
[0049]
First, toner image formation by the yellow image forming unit 10Y is started, and a predetermined charge is applied to the surface of the photosensitive drum 11Y rotating in the direction of arrow A by the charging roll 12Y. Next, the exposure device 13Y irradiates the surface of the photosensitive drum 11Y with exposure light corresponding to a yellow image to form a yellow latent image. The latent image is developed with yellow toner by the developing device 14Y, and a yellow toner image is formed on the photosensitive drum 11Y. The toner image is transferred to the intermediate transfer belt 17 by the primary transfer roll 15Y.
[0050]
The intermediate transfer belt 17 circulates in the direction of the arrow B, and is synchronized with the timing at which the yellow toner image transferred onto the intermediate transfer belt 17 reaches the primary transfer roll 15M of the next color image forming unit 10M. The toner image is formed by the magenta image forming unit 10M so that the magenta toner image of the next color reaches the primary transfer roll 15M. The magenta toner image formed in this way is transferred onto the yellow toner image on the intermediate transfer belt 17 while being superimposed on the primary transfer roll 15M.
[0051]
Subsequently, toner image formation by the cyan and black image forming units 10C and 10K is performed at the same timing as described above, and sequentially on the yellow and magenta toner images on the intermediate transfer belt 17 in the primary transfer rolls 15C and 15K. It is transcribed again.
[0052]
Thus, the multicolor toner image transferred onto the intermediate transfer belt 17 is secondarily transferred onto the paper P by the secondary transfer roll 19, and the multicolor toner image is conveyed along with the paper P in the direction of the arrow D, and the fixing device 20. As a result, the image is fixed on the paper P and a color image is formed.
[0053]
Next, the cleaning unit will be described.
[0054]
Before describing the details of the cleaning unit of the present embodiment, the results of a cleaning test conducted by the present inventors will be described.
[0055]
As the brush, a brush having an outer diameter of 10 mm formed by radially implanting conductive nylon hair on the surface of the rotating shaft having an outer diameter of 5 mm was used. Hair length is 2.5mm, hair thickness is about 2 denier, hair density is 430Kf / inch ² It is.
[0056]
The amount of brush biting into the photosensitive drum was 0.5 mm.
[0057]
When the brush rotates in the Against rotation, that is, in the direction in which the portion facing the photosensitive drum moves in the direction opposite to the moving direction of the photosensitive drum, the brush rotates in the With rotation, that is, A test was performed for each of the two cases where the portion facing the photosensitive drum rotates in the direction of movement in the same direction as the movement direction of the photosensitive drum. The peripheral speed of the brush was twice the surface speed of the photosensitive drum.
[0058]
As the roll, a roll having an outer diameter of 10 mm in which an elastic layer made of urethane foam was formed on the surface of the rotating shaft having an outer diameter of 5 mm and a surface layer made of epichlorohydrin rubber was formed thereon.
[0059]
The amount of biting into the roll of the brush was 0.5 mm, and the amount of biting of the roll into the photosensitive drum was 0.4 mm.
[0060]
The rotation direction of the roll was With rotation with respect to the rotation direction of the photosensitive drum. The peripheral speed of the roll was the same as the surface speed of the photosensitive drum.
[0061]
Table 1 is a table showing the results of the cleaning test using the brush and roll.
[0062]
[Table 1]

[0063]
Here, the toner recovery performance refers to the amount of toner passing through the cleaning device of 0.02 g / m. ² This is expressed in terms of the amount of residual transfer toner to be suppressed below.
[0064]
FIG. 2 and FIG. 3 show the test results shown in Table 1 as graphs.
[0065]
FIG. 2 is a graph showing the toner recovery performance of each type of cleaning member.
[0066]
As shown in FIG. 2, the amount of toner passing through the brush is 0.5 g / m in the case of Gainst rotation. ² And shows the highest value. When the brush is rotated with With, the toner slip-through amount is 0.3 g / m. ² Which is lower than the Gainst rotation. Also, the amount of toner passing through the roll of With rotation is 0.25 g / m. ² And shows the lowest value. The toner collection performance of the image forming apparatus according to this embodiment will be described later.
[0067]
FIG. 3 is a graph showing the toner discharge rate of each type of cleaning member.
[0068]
As shown in FIG. 3, the toner discharge rate of the brush shows the lowest value of 70% in the case of Gainst rotation. When the brush is rotated with Whit, the toner discharge rate is 95%, which is higher than the Gainst rotation. In addition, the toner discharge rate of the Whit roll is 99.5%, which is the highest value. The toner discharge rate of the image forming apparatus according to the present embodiment will be described later.
[0069]
Therefore, it is possible to obtain a cleaning unit that achieves both toner recovery performance and discharge performance by performing against rotation in the cleaning process and providing one brush for performing the Whit rotation in the discharge process. However, for that purpose, a mechanism for switching the rotation direction of the brush has to be incorporated, which may cause a significant increase in cost, which is not preferable. Moreover, from the viewpoint of the discharge rate, a roll is preferable to a brush.
[0070]
Next, the cleaning unit of this embodiment will be described in detail.
[0071]
As shown in FIG. 1, the cleaning units 16Y, 16M, 16C, and 16K of the present embodiment are downstream of the primary transfer rolls 15Y, 15M, 15C, and 15K in the rotational direction of the photosensitive drums 11Y, 11M, 11C, and 11K. The residual toner remaining on each photosensitive drum after transfer is removed.
[0072]
FIG. 4 is a detailed view of the cleaning unit of the image forming apparatus of the present embodiment.
[0073]
As shown in FIG. 4, the cleaning unit 16 includes a brush 16_1, a roll 16_2, and a power supply unit 16_3. The toner on the photosensitive drum 11 is collected by the brush 16_1 and the collected toner is collected by the roll 16_2. And a discharging step of discharging the toner transferred to the roll 16_2 onto the photosensitive drum 11.
[0074]
The brush 16_1 rotates in the direction of arrow B while contacting the surface of the photosensitive drum 11 rotating in the direction of arrow A, and collects the toner remaining on the photosensitive drum 11.
[0075]
The roll 16_2 is disposed downstream of the brush 16_1 in the moving direction of the photosensitive drum 11, and rotates in the direction of arrow C while contacting the brush 16_1 and the photosensitive drum 11, and receives and receives the toner collected by the brush 16_1. The toner is discharged onto the photosensitive drum 11.
[0076]
The power supply unit 16_3 includes a brush power supply 16_3a and a roll power supply 16_3b that apply predetermined voltages to the brush 16_1 and the roll 16_2, respectively.
[0077]
Next, examples of the present invention will be described.
[Example 1]
The first embodiment corresponds to a case where a large amount of plus toner remains on the photosensitive drum after transfer.
[0078]
FIG. 5 is a diagram illustrating a collection operation (a) and a delivery operation (b) in the first embodiment.
[0079]
As shown in FIG. 5A, a negative voltage is applied to the brush 16_1 from the brush power source 16_3a, and a negative voltage larger in absolute value than the applied voltage to the brush 16_1 is applied to the roll 16_2. . That is, the voltage applied to the brush 16_1 is -250V, and the voltage applied to the roll 16_2 is -500V.
[0080]
Since the rotation direction of the brush 16_1 is the B direction which is Against rotation with respect to the photosensitive drum 11 rotating in the arrow A direction, the plus toner t1 on the photosensitive drum 11 is collected by the brush 16_1 with high collection efficiency. The
[0081]
As a result of actually measuring the toner slip-through amount, an extremely excellent value was obtained as shown in FIG.
[0082]
Next, as shown in FIG. 5B, the plus toner t1 collected by the brush 16_1 is delivered to a roll 16_2 that rotates in the direction of arrow C while being in contact with the brush 16_1. At this time, since the rotation direction of the roll 16_2 is the Whit rotation with respect to the brush 16_1 rotating in the direction of the arrow B, the plus toner t1 on the brush 16_1 rolls with extremely high efficiency compared to the case of the Gainst rotation. 16_2 will be handed over. The positive toner t1 once transferred onto the roll 16_2 remains held on the roll 16_2 because of the potential difference between the photosensitive drum 11 and the roll 16_2.
[0083]
FIG. 6 is a diagram illustrating a discharge operation according to the first embodiment.
[0084]
As shown in FIG. 6, a positive voltage is applied to the brush 16_1 and the roll 16_2 from the brush power source 16_3 ′. Note that the voltages applied to the brush 16_1 and the roll 16_2 are both + 400V.
[0085]
The positive toner t1 transferred to the roll 16_2 is discharged onto the photosensitive drum 11 due to the potential difference between the photosensitive drum 11 and the roll 16_2.
[0086]
Since this discharging step is discharging from the roll to the photosensitive member, a high discharging rate was obtained as shown in FIG.
[0087]
In the first embodiment, the brush 16_1 rotates in a direction opposite to the rotation direction of the photosensitive drum 11, and the roll 16_2 rotates in the same direction as the rotation direction of the photosensitive drum 11. However, the present invention is not necessarily limited only to the rotation direction described above, and both the brush and the roll may be in any rotation direction, but from the test results shown in FIGS. Accordingly, it is preferable that the brush is Against rotation and the roll is With rotation.
[Example 2]
The second embodiment corresponds to a case where a lot of minus toner remains on the photosensitive drum 11 after the transfer.
[0088]
FIG. 7 is a diagram illustrating a collection operation (a) and a delivery operation (b) in the second embodiment.
[0089]
As shown in FIG. 7A, a positive voltage is applied to the brush 16_1 from the brush power supply 16_3a, and a positive voltage larger in absolute value than the applied voltage to the brush 16_1 is applied to the roll 16_2. . That is, the voltage applied to the brush 16_1 is + 250V, and the voltage applied to the roll 16_2 is + 500V.
[0090]
As in the first embodiment, the rotation direction of the brush 16_1 is the B direction that is Against rotation rotation with respect to the photosensitive drum 11 that rotates in the direction of arrow A. Therefore, the minus toner t2 on the photosensitive drum 11 is highly recovered. It is recovered by the brush 16_1 with efficiency.
[0091]
As a result of actually measuring the toner slip-through amount, an extremely excellent value almost the same as in Example 1 shown in FIG. 2 was obtained.
[0092]
Next, as shown in FIG. 7B, the negative toner t2 collected by the brush 16_1 is delivered to a roll 16_2 that rotates in the direction of arrow C while being in contact with the brush 16_1. At this time, the rotation direction of the roll 16_2 is a Whit rotation with respect to the brush 16_1 rotating in the direction of the arrow B, as in the first embodiment. Therefore, the minus toner t2 on the brush 16_1 is compared with the case of the Against rotation. It is transferred onto the roll 16_2 with extremely high efficiency. The negative toner t2 once transferred onto the roll 16_2 remains held on the roll 16_2 because of the potential difference between the photosensitive drum 11 and the roll 16_2.
[0093]
FIG. 8 is a diagram illustrating a discharge operation according to the second embodiment.
[0094]
As shown in FIG. 8, a negative voltage is applied to the brush 16_1 and the roll 16_2 from the brush power source 16_3 ′. The voltage applied to the brush 16_1 and the roll 16_2 is both −400V.
[0095]
The negative toner t2 transferred to the roll 16_2 is discharged onto the photosensitive drum 11 due to the potential difference between the photosensitive drum 11 and the roll 16_2.
[0096]
Since this discharging step is discharging from the roll to the photosensitive member, a high discharging rate almost the same as that of Example 1 shown in FIG. 2 was obtained.
[0097]
In the second embodiment, the brush 16_1 rotates in the direction opposite to the rotation direction of the photosensitive drum 11, and the roll 16_2 rotates in the same direction as the rotation direction of the photosensitive drum 11. Although the example in the case of doing so was demonstrated, this invention is not necessarily restricted only to said rotation direction, Both a brush and a roll may be any rotation direction, but FIG.2 and FIG.3. In view of the test results shown in Fig. 1, it is preferable that the brush is in the Against rotation and the roll is in the With rotation.
[Example 3]
The third embodiment corresponds to a case where both negative toner and positive toner remain on the photosensitive drum 11 after transfer.
[0098]
FIG. 9 is a diagram illustrating a collecting operation in the cleaning process according to the third embodiment.
[0099]
As shown in FIG. 9A, an alternating voltage is applied from the brush power supply 26_3 to the brush 16_1, and an alternating voltage from the brush power supply 26_3 ′ is applied to the roll 16_2. That is, the AC voltage applied to the brush 16_1 is Vp-p: 600V, and the frequency is 3 KHz, and the same voltage is also applied to the roll 16_2.
[0100]
As in the first embodiment, the rotation direction of the brush 16_1 is the B direction that is Against rotation with respect to the photosensitive drum 11 that rotates in the direction of arrow A. Therefore, the positive toner t1 and the negative toner t2 on the photosensitive drum 11 are rotated. Both are collected by the brush 16_1 with high collection efficiency.
[0101]
FIG. 10 is a diagram illustrating a discharge operation according to the third embodiment.
[0102]
As shown in FIG. 10A, a negative voltage −500 V as viewed from the potential of the photosensitive drum 11 is applied to the brush 16_1, and a negative value smaller than the applied voltage to the brush 16_1 is applied to the roll 16_2. Apply a voltage of -250V.
[0103]
As shown in FIG. 10A, of the positive toner t1 and the negative toner t2 collected by the brush 16_1, the negative toner t2 is delivered to the roll 16_2 that rotates in the direction of arrow C while being in contact with the brush 16_1. At this time, the rotation direction of the roll 16_2 is a Whit rotation with respect to the brush 16_1 rotating in the direction of the arrow B, as in the first embodiment. Therefore, the minus toner t2 on the brush 16_1 is compared with the case of the Against rotation. It is transferred onto the roll 16_2 with extremely high efficiency. The minus toner t2 once transferred onto the roll 16_2 is discharged to the photosensitive drum 11 due to the potential difference between the photosensitive drum 11 and the roll 16_2.
[0104]
Next, as shown in FIG. 10B, a positive voltage +500 V is applied to the brush 16_1 as viewed from the potential of the photosensitive drum 11, and the absolute value is smaller than the applied voltage to the brush 16_1 to the roll 16_2. A positive voltage + 250V is applied.
[0105]
As shown in FIG. 10B, the positive toner t1 on the brush 16_1 is transferred to a roll 16_2 that rotates in the direction of arrow C while being in contact with the brush 16_1. At this time, the rotation direction of the roll 16_2 is the Whit rotation with respect to the brush 16_1 rotating in the direction of the arrow B as in the first embodiment, and therefore, the plus toner t1 on the brush 16_1 is compared with the case of the Gainst rotation. It is transferred onto the roll 16_2 with extremely high efficiency. The positive toner t1 once transferred onto the roll 16_2 is discharged to the photosensitive drum 11 due to the potential difference between the photosensitive drum 11 and the roll 16_2.
[0106]
In Example 3 as well, excellent cleaning performance similar to that in Example 1 could be obtained.
[Example 4]
The fourth embodiment is a modification of the embodiment corresponding to the case where both the negative toner and the positive toner remain on the photosensitive drum 11 after the transfer, as in the third embodiment.
[0107]
The cleaning process of the fourth embodiment is the same as the cleaning process of the third embodiment, but the polarity of the power supply unit in the discharge operation is different from the polarity of the power supply unit in the third embodiment.
[0108]
That is, in the discharging step, first, a positive voltage: +500 V as viewed from the potential of the photosensitive drum 11 is applied to the brush 16_1 (see FIG. 10), and an absolute value is applied to the roll 16_2 with respect to the brush 16_1. A small positive voltage: +250 V is applied, and then a negative voltage: −500 V as viewed from the potential of the photosensitive drum 11 is applied to the brush 16_1, and an absolute value is applied to the roll 16_2 than the voltage applied to the brush 16_1. A small negative voltage: -250V is applied.
[0109]
The third embodiment is the same as the third embodiment except for the voltage applied to the power supply unit in the discharge process.
[0110]
In Example 4, excellent cleaning performance similar to that in Example 1 could be obtained.
[0111]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, the toner remaining on the image carrier is efficiently collected by the brush, and the toner is efficiently discharged onto the image carrier by the roll. An image forming apparatus with good image quality in which contamination of the roll is prevented can be realized.
[0112]
Further, since this image forming apparatus is configured as a blade rescreening system, a long-life image forming apparatus can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention.
FIG. 2 is a graph showing the toner recovery performance of each type of cleaning member.
FIG. 3 is a graph showing the toner discharge rate of each type of cleaning member.
FIG. 4 is a detailed view of a cleaning unit of the image forming apparatus according to the present exemplary embodiment.
FIG. 5 is a diagram illustrating a collection operation (a) and a delivery operation (b) in the first embodiment.
FIG. 6 is a diagram showing a discharge operation in the first embodiment.
FIG. 7 is a diagram illustrating a collection operation (a) and a delivery operation (b) in the second embodiment.
FIG. 8 is a diagram illustrating a discharge operation according to the second embodiment.
FIG. 9 is a view showing a collecting operation in a cleaning process in the third embodiment.
FIG. 10 is a diagram illustrating a discharge operation according to the third embodiment.
[Explanation of symbols]
11, 11Y, 11M, 11C, 11K Photosensitive drum
12Y, 12M, 12C, 12K Charging roll
13Y, 13M, 13C, 13K exposure equipment
14Y, 14M, 14C, 14K Developer
15Y, 15M, 15C, 15K Primary transfer roll
16, 16Y, 16M, 16C, 16K Cleaning section
16_1 Brush
16_2 roll
16_3, 16_3 ', 26_3a' power supply unit
16_3a Brush power supply
16_3b Roll power supply
17 Intermediate transfer belt
18 Intermediate transfer belt cleaner
19 Secondary transfer roll
20 Fixing device
100 Image forming apparatus

Claims (6)

An image carrier that moves in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, and a transfer unit that transfers a toner image formed by the toner image forming unit to a predetermined transfer target And an image forming apparatus having a cleaning unit that removes toner remaining on the image carrier without being transferred to the transfer body,
The cleaning unit is
A rotatable brush that collects toner remaining on the image carrier while being in contact with the surface of the image carrier, and the brush and the image carrier disposed downstream of the brush in the moving direction of the image carrier. A rotatable roll that receives toner collected by the brush while in contact with the body, and discharges the received toner onto the image carrier, and a power supply unit that applies a predetermined voltage to the brush and the roll; and A cleaning step of collecting the toner on the image carrier with the brush and transferring the collected toner to the roll; and a discharging step of discharging the toner transferred to the roll onto the image carrier. An image forming apparatus comprising: The brush rotates in a direction in which a portion facing the image carrier moves in a direction opposite to the moving direction of the image carrier, and the roll has a portion facing the image carrier. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus rotates in a direction in which the image carrier moves in the same direction. In the cleaning step, the power supply unit applies a negative voltage to the brush as viewed from the potential of the image carrier, and applies a negative voltage, which is larger in absolute value than the voltage applied to the brush, to the roll. 3. The image forming apparatus according to claim 1, wherein in the discharging step, a positive voltage is applied to the brush and the roll as viewed from the potential of the image carrier. 4. In the cleaning step, the power supply unit applies a positive voltage to the brush as viewed from the potential of the image carrier, and applies a positive voltage that is larger in absolute value than the voltage applied to the brush to the roll. 3. The image forming apparatus according to claim 1, wherein in the discharging step, a negative voltage is applied to the brush and the roll as viewed from the potential of the image carrier. In the cleaning step, the power supply unit applies a voltage including at least an alternating voltage to the brush, and in the discharge step, first, a negative voltage is applied to the brush as viewed from the potential of the image carrier, A negative voltage smaller in absolute value than the voltage applied to the brush is applied to the roll, and then a positive voltage is applied to the brush as viewed from the potential of the image carrier. 3. The image forming apparatus according to claim 1, wherein a positive voltage smaller in absolute value than a voltage applied to the brush is applied. In the cleaning step, the power supply unit applies a voltage including at least an alternating voltage to the brush, and in the discharge step, first, a positive voltage is applied to the brush as viewed from the potential of the image carrier, A positive voltage smaller in absolute value than the voltage applied to the brush is applied to the roll, and then a negative voltage is applied to the brush as viewed from the potential of the image carrier. 3. The image forming apparatus according to claim 1, wherein a negative voltage smaller in absolute value than a voltage applied to the brush is applied.

Images