JP4069350B2 - Cleaning device - Google Patents

Description

【００２５】
形状係数ＭＬ²／Ａは、トナーの投影面積と、それに外接する円の面積との比で表しており、真球の場合１００となり、形状が崩れるにつれ増加する。形状係数は、トナー粒子複数個に対して計算され、その平均値を代表値とする。本実施の形態では、形状係数１２５以下の略球形なトナーを用いた。
また、離型性を高めるため、該トナーに、平均粒径１０〜１５０ｎｍのシリカ及び酸化チタン（チタニア）等の無機微粒子を外添剤として適宜量外添し、平均粒径３５μｍのフェライトビーズからなるキャリアと混合し現像剤とした。
尚、トナーとしては、本製造法により作成したトナー以外にも、懸濁重合法、溶解懸濁法、乳化重合法、混練粉砕法等により形成された球形トナーあるいは非球形トナーを使用してもよく、また、上述したようなトナーとキャリアとを混在させた二成分系現像剤でも、トナーのみの一成分系現像剤でも構わないことは勿論である。
【００２６】
図３及び図４には、本実施の形態に係るベルトクリーナ６０の拡大断面図を示す。ここで、図３はクリーニング動作時の状態を示す図、図４は非クリーニング動作時の状態を示す図である。
これらの図において、ベルトクリーナ６０は、前記中間転写ベルト２０の像担持面側（図中残留トナーを符号Ｔで示す）に配設される導電性ブラシロール６１と、この導電性ブラシロール６１からみて前記中間転写ベルト２０の移動方向下流側に配設されるクリーニングブレード６２と、これら導電性ブラシロール６１及びクリーニングブレード６２が収容されるクリーナハウジング６３とを有している。尚、符号６３ａは前記中間転写ベルト２０に対向して開口するクリーナハウジング６３の開口部を示している。
【００２７】
ここで、前記導電性ブラシロール６１は、前記中間転写ベルト２０との対向部において当該中間転写ベルト２０の移動方向Ｂとは逆方向に回転するようになっている。また、導電性ブラシロール６１は、中間転写ベルト２０に対して１．５ｍｍくい込むように配置されている。そして、導電性ブラシロール６１は金属製の芯金（φ６ｍｍ）に１０デニールの導電性ナイロン（商品名：ベルトロン）が１平方インチあたり８００００本の密度で植毛され、外径が１８ｍｍになるよう刈り揃えてある。そして、ブラシ繊維部の軸方向の長さは３１２ｍｍとし、回転数は約２３５ｒｐｍ（周速度２２０ｍｍ／ｓ）とした。
【００２８】
また、前記導電性ブラシロール６１には、その対向部において当該導電性ブラシロール６１とは逆方向に回転する回収ロール６４が接触配置されている。ここで、回収ロール６４は、アルミニウムの円筒ロールの表面に、タフラム処理（General Magnaplate社の商標）により絶縁皮膜を形成したものであって、食い込み量２ｍｍで前記導電性ブラシロール６１と回収ニップ部Ｎを形成している。また、回収ロール６４も、前記導電性ブラシロール６１と同回転数の２３５ｒｐｍ（周速度２２０ｍｍ／ｓ）で回転する。
更に、前記回収ロール６４には、その回転方向からみて所謂ドクター方向にスクレーパ６５が圧接配置されている。
【００２９】
尚、符号６６は、導電性ブラシロール６１からみて中間転写ベルト２０の移動方向Ｂ上流側に設けられ除去された残留トナーＴの外部への飛び散りを防止するためのフィルムシール、符号６７は、前記クリーナハウジング６３にクリーニングブレード６２を固定するＬ字状プレート、符号６８は、クリーナハウジング６３内部の下部側に設けられ、クリーナハウジング６３内に回収された残留トナーＴを図示しない廃トナー容器へ排出する排出オーガである。
【００３０】
また、本実施の形態では、前記回収ロール６４に、図示しない電源により＋８００Ｖのバイアス（回収バイアス）が印加され、一方、前記導電性ブラシロール６１には、図示しない電源により＋４００Ｖのバイアス（除去バイアス）が印加されるようになっている。
そして、中間転写ベルト２０を挟んだ導電性ブラシロール６１の裏面側には、Ｖ字状の形状を有し、その平面部が当該中間転写ベルト２０に接触配置される金属プレート７１が配置されている。この金属プレート７１は接地されており、前記導電性ブラシロール６１との間に所定の電界を形成するようになっている。
【００３１】
更に、前記クリーナハウジング６３の側面には、板金８１が取り付けられている。この板金８１は、前記フィルムシール６６からみて中間転写ベルト２０の移動方向Ｂ上流側に設けられた回転軸８２を中心に揺動自在となっており、これにより、クリーナハウジング６３（及び導電性ブラシロール６１、クリーニングブレード６２等も含む）が揺動自在になっている。そして、この板金８１には、図中上方に向かって付勢するばね（図示せず）が取り付けられている。
また、板金８１の自由端側の上方端部には、シャフト８３が取り付けられている。このシャフト８３には、図示しない偏心カムが押圧配置されており、導電性ブラシロール６１やクリーニングブレード６２等を中間転写ベルト２０から離間させる際には、前記シャフト８３を図中下側に押圧するようになっている。
【００３２】
そして、本実施の形態では、前記クリーナハウジング６３の背面側に排気口６９が開設されており、この排気口６９には、当該排気口６９に対向する部位に開口部９０ａを有するダクト９０が設置されている。
このダクト９０は筒状の形状を有しており、その側面には、図示しない吸気ファンに連通する排出口９１が配設されている。尚、この排出口９１内には、図示しないフィルタが設けられており、前記排気口６９を介して吸引された残留トナーＴが、吸気ファンまで到達できないようになっている。
【００３３】
更に、本実施の形態では、図３及び図４に示すように、ベルトクリーナ６０の圧接時と離間時とで、クリーナハウジング６３の排気口６９とダクト９０の開口部９０ａとの対向面積が変化するように、具体的には、圧接時（図３参照）に比べて離間時（図４参照）の対向面積が略半分となるように設定されている。
【００３４】
次に、本実施の形態に係るカラー画像形成装置の作像プロセスについて説明する。
今、図示外のスタートスイッチがオンされると、所定の作像プロセスが実行される。
まず、感光体ドラム１１上に静電潜像の書き込みが行われ、この静電潜像に対応した現像器によって現像される。
これは、例えば感光体ドラム１１上に書き込まれた静電潜像がイエロの画像情報に対応したものであれば、この静電潜像はイエロのトナーを内包する現像器１５で現像され、感光体ドラム１１上にはイエロのトナー像Ｔが形成される。
そして、感光体ドラム１１上に形成されたトナー像Ｔは、感光体ドラム１１と中間転写ベルト２０とが接する一次転写位置で感光体ドラム１１から中間転写ベルト２０の表面に転写される。一方、一次転写後に感光体ドラム１１上に残留したトナーはドラムクリーナ１９によって除去される。
【００３５】
このとき、単色画像を形成する場合には、中間転写ベルト２０に一次転写されたトナー像Ｔを直ちに用紙３０に二次転写するのであるが、複数色のトナー像Ｔを重ね合わせたカラー画像を形成する場合には、感光体ドラム１１上でのトナー像Ｔ形成並びにこのトナー像Ｔの一次転写の工程が色数分だけ繰り返される。
例えば、４色のトナー像Ｔを重ね合わせたフルカラー画像を形成する場合には、感光体ドラム１１上にはその一回転毎にイエロ、マゼンタ、シアン及びブラックのトナー像Ｔが形成され、これらトナー像Ｔは順次中間転写ベルト２０に一次転写される。一方、中間転写ベルト２０は最初に一次転写されたトナー像Ｔを保持したまま感光体ドラム１１と同一周期で回動し、中間転写ベルト２０上にはその一回転毎にマゼンタ、シアン及びブラックのトナー像Ｔが転写される。
【００３６】
このようにして中間転写ベルト２０に一次転写されたトナー像Ｔは、中間転写ベルト２０の回動に伴って二次転写位置へと搬送される。
一方、用紙３０はレジストロール５２にて所定のタイミングで二次転写位置へと供給され、バックアップロール２６に対して二次転写ロール２８が用紙３０をニップする。
すると、二次転写位置では、二次転写装置４０である二次転写ロール２８とバックアップロール２６との間に形成される転写電界の作用で、中間転写ベルト２０に担持されたトナー像Ｔが二次転写位置において用紙３０に静電転写される。その後、二次転写された用紙３０は、搬送ベルト５３を経て定着器５４へと搬送されて用紙３０上のトナー像Ｔが定着され、一方、二次転写位置を通過した中間転写ベルト２０の像担持面側は、ベルトクリーナ６０によってクリーニングされる。
【００３７】
ここで、ベルトクリーナ６０による中間転写ベルト２０のクリーニングプロセスは、次の通りである。
図３及び図４において、二次転写が終了すると、図示しない偏心カムによって板金８１が揺動せしめられ、クリーナハウジング６３は回転軸８２を中心に揺動し、フィルムシール６６、導電性ブラシロール６１，クリーニングブレード６２の順に中間転写ベルト２０に圧接していく。
【００３８】
そして、中間転写ベルト２０上の残留トナーＴ（負極性に帯電）が導電性ブラシロール６１との対向部に到達すると、この残留トナーＴは当該導電性ブラシロール６１と金属プレート７１との間の電位差（＋４００Ｖ）によって導電性ブラシロール６１上に転移する。そして、導電性ブラシロール６１に転移した残留トナーＴが回収ロール６４との対向部に到達すると、今度は、当該回収ロール６４と導電性ブラシロール６１との間の電位差（＋８００Ｖ−（＋４００Ｖ）＝＋４００Ｖ）によって回収ロール６４上に転移する。そして、回収ロール６４上に転移した残留トナーＴは、スクレーパ６５により掻き取られクリーナハウジング６３内に落下する。
一方、導電性ブラシロール６１上に転移しなかった残留トナーＴは、クリーニングブレード６２により掻き取られ、クリーナハウジング６３内に落下する。
そして、クリーナハウジング６３内の残留トナーＴは、排出オーガ６８により外部へと排出される。
【００３９】
その後、クリーニングが終了すると、図示しない偏心カムによって再び板金８１が揺動せしめられ、クリーナハウジング６３は回転軸８２を中心に今度は逆側に揺動し、クリーニングブレード６２、導電性ブラシロール６１、フィルムシール６６の順に中間転写ベルト２０から離間していく。
【００４０】
本実施の形態では、この一連のクリーニングプロセスの間、図示しない吸引ファンによってダクト９０より吸気が行われる。
まず始めに、クリーニング動作実行時（図３参照）においては、クリーナハウジング６３の排気口６９及びダクト９０の開口部９０ａが全面で対向しているため、吸引ファンの吸引力がそのままクリーナハウジング６３内に伝わることとなるが、クリーナハウジング６３の開口部６３ａと中間転写ベルト２０とが密着している（フィルムシール６６及びクリーニングブレード６２が中間転写ベルト２０に接しており、隙間がほとんどない）ため、この時点での吸引量はきわめて少ない。
【００４１】
次に、クリーニング動作終了時すなわち離間動作開始時においては、上記と同様にクリーナハウジング６３の排気口６９及びダクト９０の開口部９０ａが全面で対向しているため、吸引ファンの吸引力がそのままクリーナハウジング６３内に伝わることとなる一方、クリーナハウジング６３の離間動作に伴ってクリーナハウジング６３の開口部６３ａと中間転写ベルト２０との間（具体的には中間転写ベルト２０とクリーニングブレード６２との間）には隙間が生じるため、クリーニング動作時とは異なり吸引量は大きくなる。
このとき、導電性ブラシロール６１及びクリーニングブレード６２は、中間転写ベルト２０からの離間に伴って弾性変形し、これらに付着していた残留トナーＴが飛び散ろうとするが、吸引によってクリーナハウジング６３内に引き込まれるため、飛び散った残留トナーＴの中間転写ベルト２０への再付着は防止される。そして、クリーナハウジング６３内に引き込まれた残留トナーＴは、ダクト９０側に引き込まれるか、あるいは、落下して排出オーガ６８によって排出される。尚、ダクト９０側に引き込まれた残留トナーＴは、その後排出口９１から図示しない吸引ファンに向かって移動していくが、吸引ファンの手前に設けられたフィルタ（図示せず）によって捕獲される。
このように、吸引を行わせることにより、離間動作時に導電性ブラシロール６１及びクリーニングブレード６２に付着した残留トナーＴが飛び散るという事態を回避させるようにしたので、飛び散ったトナーが中間転写ベルト２０に再付着することで発生する次画像の画質欠陥や、飛び散ったトナーがカラー画像形成装置内を舞うことによって生じる機内のトナー汚れ等を防止することができる。
【００４２】
更に、離間動作終了時においては、図４に示すように、クリーナハウジング６３の排気口６９及びダクト９０の開口部９０ａがこれまでとは異なり半面で対向しているため、吸引ファン（図示せず）による吸引力は略半分となってクリーナハウジング６３内に伝わることとなる。
これにより、ダクト９０側に引き込まれる残留トナーＴは少なくなるため、前記フィルタ（図示せず）に捕獲されるトナー量も少なくなり、その分フィルタの寿命を延ばすことが可能となる。
【００４３】
また、本実施の形態では、図５に示すように、導電性ブラシロール６１及び回収ロール６４の回収ニップ部Ｎから飛び散るトナーの飛散方向Ｃが、クリーナハウジング６３の開口部６３ａに向かわないように設定されているので、この回収ニップ部Ｎから飛散した残留トナーＴが中間転写ベルト２０に再付着するという事態も生じにくい。更に、このトナーの飛散方向Ｃが前記クリーナハウジング６３の排気口６９側に向くようにしているので、飛び散ったトナーは吸引によってダクト９０側に引き込まれ易くなり、その分、中間転写ベルト２０側への飛び散りを更に抑制することが可能である。
【００４４】
更にまた、本実施の形態では、図５に示すように、前記回収ニップ部Ｎのクリーナハウジング６３側に空間Ｄを設けると共に、当該空間Ｄから排出オーガ６８に向かう部位におけるクリーナハウジング６３の内壁を傾斜させることで、排出オーガ６８側に移動し易くなるようにしたので、導電性ブラシロール６１から離脱したトナーが当該導電性ブラシロール６１に再付着するという事態に回避することができる。
【００４５】
本発明者は、吸引とトナー飛散との関係を調査するため、以下の実験を行った。
図６は、この実験で用いたクリーニング装置を示す。
同図において、符号１２０は中間転写ベルトであり、駆動ロール１２１を含む複数の張架ロール（図示せず）に張架されて矢印方向に回動するようになっている。
また、ベルトクリーナ１６０は、前記中間転写ベルト１２０の像担持面側に配設される導電性ブラシロール１６１と、中間転写ベルト１２０の移動方向下流側に配設されるクリーニングブレード１６２と、これら導電性ブラシロール１６１及びクリーニングブレード１６２が収容されるクリーナハウジング１６３とを有するクリーニングユニット１６４を備えている。ここで、導電性ブラシロール１６１は、中間転写ベルト１２０との対向部において逆方向に回転するようになっており、中間転写ベルト１２０上の残留トナーを静電的に引きつけるためのクリーニングバイアス電源１６５（＋４００Ｖ）が接続されている。また、導電性ブラシロール１６１からみて中間転写ベルト１２０の移動方向上流側には、除去された残留トナーの外部への飛び散りを防止するためのフィルムシール１６６が取り付けられている。
【００４６】
一方、前記導電性ブラシロール１６１に対向する前記中間転写ベルト１２０の像担持面裏面側には、当該中間転写ベルト１２０の回動に伴って従動回転する対向ロール１６７が接触配置されており、この対向ロール１６７を接地することで、導電性ブラシロール１６１と中間転写ベルト１２０との間にトナーを除去するためのクリーニング電界が形成されるようになっている。
尚、前記導電性ブラシロール１６１には、その対向部において逆方向に回転する回収ロール１６８が接触配置されており、当該導電性ブラシロール１６１に付着した残留トナーを静電的に引きつけるための回収バイアス電源１６９（＋８００Ｖ）が接続されている。更に、前記回収ロール１６８にはスクレーパ１７０が圧接配置されており、当該回収ロール１６８に付着した残留トナーを掻き落としてクリーナハウジング１６３内に収容するようになっている。
また、前記クリーニングユニット１６４は、軸１６３ａを中心に揺動自在に配設されており、中間転写ベルト１２０に対して当接及び離間可能となっている。そして、感光体ドラム（図示せず）から中間転写ベルト１２０に各色のトナー像を一次転写する動作が行われているときには、中間転写ベルト１２０表面から導電性ブラシロール１６１、クリーニングブレード１６２及びフィルムシール１６６を離間させ、一方、中間転写ベルト１２０から転写紙へのトナー像の一括転写が終了した後には、中間転写ベルト１２０に導電性ブラシロール１６１、クリーニングブレード１６２及びフィルムシール１６６を接触させ、残留トナーをクリーニングするような制御が行われるようになっている。
【００４７】
また、このクリーニング装置においては、前記クリーニングブレード１６２の下側に吸気用のチューブ群１７１が取り付けられている。
このチューブ群１７１は、図７に示すように、クリーニングブレード１６２の一端部側に開口を有する第一チューブ１７１ａと、略中央部に開口を有する第二チューブ１７１ｂと、逆側の一端部側に開口を有する第三チューブ１７１ｃとを備えている。そして、これら各チューブ１７１ａ〜１７１ｃは、チューブ１７１ｃの開口が形成される側の端部で一つチューブ１７１ｄにまとめられ、図示しない吸気ファンに接続されるようになっている。
【００４８】
また、この実験においては、吸気量を測定するため、前記各チューブ１７１ａ〜１７１ｃの手前側（中間転写ベルト１２０側、図６参照）に対応する位置に流速センサ１７２（具体的には１７２ａ〜１７２ｃ）を配設した。但し、流速センサ１７２ａについては、レイアウトの都合から、前記第一チューブ１７１ａの開口から３０ｍｍずれた位置に配設した。
【００４９】
上述したクリーニング装置を用い、まず初めに、トナー飛散を防止するために必要なエア流速及びクリーナハウジング１６３内の気圧（圧接時における大気圧との静圧差）について検討を行った。
この実験においては、中間転写ベルト１２０上に画像を連続形成し、形成される画像にトナー飛散によるトナー点のどの程度発生するか調査した。このとき、画像中に０．３ｍｍ以上のトナー点が発生したものをα、０．３ｍｍ以下のトナー点が２ｍｍ以内の間隔で発生したものをβ、０．３ｍｍ以下のトナー点が２ｍｍを超える間隔で発生したものをγに分類し、１００枚当たりの発生枚数で評価した。
【００５０】
結果を図８に示す。
吸引を行わない場合にはαが５．３枚／１００枚となったのに対し、吸引を行った場合にはαの値が小さくなり、大気圧との静圧差が０．０８（ｍｍＨ₂Ｏ）以上であれば、αが目標値の２．０枚／１００枚以下となることが判明した。
【００５１】
次に、上記結果を踏まえ、エアの吸引タイミングについて、調査を行った。
評価は、上記と同様の実験によって行った。また、吸引タイミングについては、常時吸引を行うもの、圧接時のみ吸引を行うもの、離間時のみ吸引を行うものの三者とした。
【００５２】
結果を図９に示す。
常時吸引を行った場合は、吸引を行わない場合よりα、β、γの値が著しく小さくなり、また、クリーニングブレード１６２に堆積するトナーも少なくなることが確認された。但し、その一方でチューブ群１７１内に吸い込まれるトナー量（吸引トナー重量）が多くなってしまうことも分かった。この吸引トナー重量が多すぎると、チューブ群１７１やフィルタ（図示せず）の目詰まりを誘発するおそれがある。
また、圧接時のみ吸引を行った場合は、確かに吸引を行わない場合よりもα、β、γの値が小さくなるが、目標値（α≦２．０）には達せず、また、クリーニングブレード１６２に堆積するトナーが多くなってしまうことが判明した。
一方、離間時のみ吸引を行った場合は、吸引を行わない場合よりα、β、γの値が小さくなり、また、クリーニングブレード１６２に堆積するトナーも少なくなることが確認された。更に、吸引トナー重量も少なくなることも確認された。以上の結果より、実用上は、離間時のみ吸引動作を行わせることが好ましいことがわかった。
【００５３】
更に、本発明者は、上記結果を踏まえ、クリーニング動作終了時における導電性ブラシロール１６１（以下必要に応じてＥＳＢ（Electric Static Brushの略）という）の回転停止タイミング（バイアス印加停止タイミング）と中間転写ベルト１２０からの離間タイミングとの関係について調査を行った。
【００５４】
結果を図１０に示す。
これによれば、離間動作開始と同時にＥＳＢ１６１の回転及びバイアス印加を停止させる場合と比較して、離間動作開始の０．１秒前にＥＳＢ１６１の回転及びバイアス印加を停止させた方が、トナー飛散枚数α〜γを低減できることが確認された。
【００５５】
【発明の効果】
以上説明したように、本発明によれば、像担持体からのクリーニング部材の接離動作時にクリーニング部材より飛散するトナーを吸引するようにしたので、簡易な構成で像担持体から除去した残留トナーの当該像担持体への再付着及びこれに伴う画質欠陥の発生を有効に防止することができる。
特に、本発明では、吸引手段は、クリーニング部材の接離動作に応じてクリーナハウジングの吸引口の面積が圧接時に比べて離間時の方が狭くなるように変化するため、クリーニング部材の離間動作開始直後に吸引手段による吸引力を大きくし、離間動作終了時には前記吸引力を小さくすることができる。このため、クリーナハウジング内の残留トナーを吸引し過ぎることなく、クリーニング部材の離間動作開始直後にクリーニング部材から飛散しようとするトナーを効率的に吸引することができる。
更に、本発明では、接離手段が、回転軸を中心にクリーナユニットを回転させることで像担持体に対してクリーナユニットを進退させ、クリーニング部材と像担持体とを接離させる一方、吸引手段が、クリーニング部材の接離位置に対して回転軸と反対側に設けられ、接離手段によるクリーニング部材の接離動作に応じてクリーナハウジングの吸引口に対しクリーナユニットの離間動作に伴ってクリーナハウジングの開口部と像担持体との間に生じた隙間のうち間隙が大きい隙間から遠い側を塞ぐことでクリーナハウジングの吸引口の面積が圧接時に比べて離間時の方が狭くなるように変化するため、上述したように、吸引口の面積を小さくすることでクリーニング部材の離間動作終了時には吸引力を小さくし、かつ、クリーナハウジングの開口部と像担持体との間に生じた隙間のうち間隙が大きい隙間に対して吸引口による吸引作用を働かせることができる。
【００５６】
また、本発明において、導電性ブラシと回収体との当接部から飛び散ったトナーが、クリーナハウジングの開口部に向かわないようにすれば、簡易な構成で像担持体から除去した残留トナーの当該像担持体への再付着及びこれに伴う画質欠陥の発生を有効に防止することができる。
【図面の簡単な説明】
【図１】 本発明に係るクリーニング装置の概要図である。
【図２】 本発明に係るクリーニング装置が適用されたカラー画像形成装置の実施の一形態の概要構成図である。
【図３】 クリーニング装置のクリーニング時の状態を示す説明図である。
【図４】 クリーニング装置の非クリーニング時の状態を示す説明図である。
【図５】 クリーニング装置の回収ニップ部近傍に関する説明図である。
【図６】 実験で用いたクリーニング装置の概略構成図である。
【図７】 実験で用いたクリーニング装置のクリーニングブレード近傍の拡大図である。
【図８】 第一の実験結果を示す図表である。
【図９】 第二の実験結果を示す図表である。
【図１０】 第三の実験結果を示す図表である。
【符号の説明】
１…像担持体，２…クリーナハウジング，２ａ…開口部，２ｂ…吸引口，３…クリーニング部材，３ａ…導電性ブラシ，４…クリーナユニット，５…接離手段，６…吸引手段，７…吸引量可変手段，８…回収体，Ｔ…残留トナー，Ｎ…当接部 [0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning device for cleaning an image carrier used in an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to an improvement of a cleaning device of a type provided so as to be able to come in contact with and separate from an image carrier. .
[0002]
[Prior art]
As a conventional intermediate transfer type image forming apparatus, for example, a developing device for each color component of yellow (Y), magenta (M), cyan (C), and black (Bk) is provided around the photosensitive drum, and the photosensitive drum is used. For example, a belt-like intermediate transfer member (intermediate transfer belt) is disposed opposite to the photosensitive drum, and the toner images of the respective color components formed on the photosensitive drum for each rotation of the photosensitive drum are sequentially applied to the intermediate transfer belt. It is known that after the primary transfer, the composite primary transfer image superimposed on the intermediate transfer belt is batch-transferred (secondarily transferred) to a sheet to form a desired color image on the sheet.
[0003]
In this type of image forming apparatus, if the residual toner remaining on the intermediate transfer belt after the secondary transfer is left as it is, the next image formed on the intermediate transfer belt will be stained. A cleaning device (belt cleaner) for removing residual toner on the intermediate transfer belt after the transfer is provided.
[0004]
Such a belt cleaner includes, for example, a cleaner housing having an opening at a portion facing the intermediate transfer belt, and a cleaning member disposed at a location facing the opening of the cleaner housing. Is known. Here, as the cleaning member, for example, a blade cleaner that presses against the intermediate transfer belt to scrape the residual toner, a brush roll cleaner that contacts the intermediate transfer belt and electrostatically adsorbs the residual toner, or the like is used.
In the image forming apparatus described above, when the primary transfer of each color component toner image from the photosensitive drum to the intermediate transfer belt is performed, the cleaning member is separated from the surface of the intermediate transfer belt, and the sheet is transferred from the intermediate transfer belt A contact / separation mechanism that presses the cleaning member against the intermediate transfer belt after the secondary transfer of the toner image to the toner image is provided.
[0005]
[Problems to be solved by the invention]
However, in the cleaning device described above, when the cleaning member pressed against the intermediate transfer belt is separated, the residual toner adhering to the cleaning member is scattered and reattached on the intermediate transfer belt, and this is included in the next image. There has been a technical problem that a dot-like image quality defect (hereinafter, referred to as a toner spot as required) due to scattered toner occurs.
[0006]
In order to prevent the occurrence of such toner spots, for example, a technique is provided in which an openable / closable shutter is provided at the opening of the cleaner housing, and the opening is closed at the time of separation in conjunction with the operation of the contact / separation mechanism. (See Japanese Patent No. 2867567). However, there is a concern that the apparatus may be increased in size, and there is a possibility that toner scattering may be induced by the airflow generated by the opening / closing operation of the shutter. is there.
[0007]
In addition, a seal member is disposed at the end of the opening of the lower cleaner housing as viewed from the cleaning member, and a swing mechanism is attached to each of the cleaning member, for example, a brush roll cleaner and a blade cleaner, and the seal member. In some cases, the toner is scattered from the cleaning member by being pressed against the intermediate transfer belt in the order of the seal member → brush roll cleaner → blade cleaner, while being separated from the intermediate transfer belt in the order of the blade cleaner → brush roll cleaner → seal member at the time of separation. Has also been proposed (see Japanese Patent Application Laid-Open No. 10-69146) for preventing the toner from jumping out of the cleaner housing.
However, in this type, there is a technical problem that the apparatus becomes complicated and the size is unavoidable because the cleaning member and the seal member each need to be provided with a contact / separation mechanism.
[0008]
On the other hand, in a mode in which a brush roll cleaner that electrostatically adsorbs residual toner is used as the cleaning member, a removal bias having a polarity opposite to the charged polarity of the residual toner is applied to the brush roll cleaner so as to remove the residual toner from the image carrier. While removing the residual toner, the brush roll cleaner is disposed in contact with the brush roll cleaner so that a collection roll having the same polarity as the removal bias and applied with a collection bias larger than the removal bias is rotatably contacted. A toner that removes residual toner is known.
[0009]
However, in this type, residual toner is likely to scatter due to flicking at the pressure contact portions of the brush roll cleaner and the recovery roll, and if the scattered toner reattaches to the intermediate transfer belt, the toner There was also a technical problem that caused the generation of dots.
[0010]
The present invention has been made in order to solve the above technical problem, and has a simple configuration, the residual toner removed from the image carrier is reattached to the image carrier, and the image quality defect is caused accordingly. It is an object of the present invention to provide a cleaning device that can effectively prevent the above-described problems.
[0011]
[Means for Solving the Problems]
  That is, as shown in FIG. 1, the present invention is provided in a cleaner housing 2 in which an opening 2 a is opened at a portion facing the image carrier 1, and a location facing the opening 2 a of the cleaner housing 2. A cleaner unit 4 having a cleaning member 3 from which residual toner T on the image carrier 1 is removed;By rotating the cleaner unit 4 around the rotation axisThe cleaner unit 4 isFor the image carrier 1Advance and retreat,Contact / separation means 5 for contacting / separating the cleaning member 3 and the image carrier 1;Provided on the opposite side of the rotating shaft with respect to the contact / separation position of the cleaning member 3;According to the contact / separation operation of the cleaning member 3 by the contact / separation means 5 while sucking the air in the cleaner housing 2.SaidOf the cleaner housing 2The gap between the opening 2a of the cleaner housing 2 and the image carrier 1 accompanying the separation operation of the cleaner unit 4 with respect to the suction port 2b is blocked by closing the side far from the gap having a large gap. Of the cleaner housing 2Suction port2bThe suction means 6 has an area that changes so that the area at the time of separation becomes narrower than that at the time of pressure contact.
[0012]
In such technical means, the cleaning member 3 may be appropriately selected from a blade member, a roll member, a brush member, or the like as long as the residual toner T on the image carrier 1 can be removed.
[0013]
The suction means 6 may be appropriately selected as long as it can suck the air in the cleaner housing 2.
From the viewpoint of making the suction amount by the suction means 6 appropriate, the suction amount variable means 7 for varying the suction amount by the suction means 6 according to the contact / separation operation of the contact / separation means 5 is provided. Is preferred.
Further, the execution timing of the suction operation by the suction means 6 may be always executed. However, in order to prevent the scattered toner from reattaching to the image carrier 1, at least during the separation operation, that is, the image carrier. It is preferable that the suction operation is executed when the body 1 and the cleaning member 3 are shifted from the pressure contact state in which the body 1 and the cleaning member 3 are in pressure contact to the separated state.
[0014]
  In addition, the present inventionpreferableAs shown in FIG.Cleaner unit 4A cleaner housing 2 in which an opening 2 a is opened at a portion facing the image carrier 1, and a residual toner on the image carrier 1 that is rotatably disposed at a position facing the opening 2 a of the cleaner housing 2. A conductive brush 3a to which a removal bias having a polarity opposite to the charging polarity of T is applied, and a collection that is rotatably contacted to the conductive brush 3a, has the same polarity as the removal bias, and is larger than the removal bias And a collection body 8 to which a bias is applied.AndThe scattering direction of the toner scattered from the contact portion N between the conductive brush 3a and the collection body 8 and the opening 2a are arranged so as not to face each other.Is.
  Thus, by setting the toner scattering direction to be different from the opening 2 a, that is, the image carrier 1, it is possible to prevent the scattered toner from reattaching to the image carrier 1.
[0015]
  In such a technical means, in the aspect in which the suction means 6 for sucking the air inside the cleaner housing 2 is provided, it is scattered from the contact portion N.tonerFrom the viewpoint of reliably removing the toner, it is preferable to arrange a suction port 2b connected to the suction means 6 in the cleaner housing 2 on the toner scattering direction side.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 2 shows a schematic configuration of an embodiment of a color image forming apparatus (a color electrophotographic copying machine in the present embodiment) to which a cleaning device according to the present invention is applied.
In the figure, reference numeral 11 denotes a photosensitive drum (latent image carrier), and a charging device 12 and an exposure apparatus (not shown) (exposing beam shown in FIG. An electrostatic latent image corresponding to the image information is formed by a known electrophotographic process such as (shown).
Around the photosensitive drum 11, a developing unit 14 including developing units 15 to 18 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk) is disposed. The electrostatic latent image formed on the photosensitive drum 11 is developed by any of the developing devices to form a toner image T.
In this embodiment, the photosensitive drum 11 is configured to be negatively charged, and development is performed by a reversal development method. Therefore, all the toners used are of a negatively charged type.
[0017]
Reference numeral 20 denotes an intermediate transfer belt disposed so as to be in contact with the surface of the photosensitive drum 11, and is stretched around a plurality of (six in the present embodiment) rolls 21 to 26 and is indicated by an arrow B It is designed to rotate in the direction.
Here, in this embodiment, reference numerals 21 and 25 are driven rolls, 22 is a metal idler roll (Idler roll) used for positioning of the intermediate transfer belt 20 and formation of a flat primary transfer surface, and 23 is an intermediate. A tension roll for controlling the tension of the transfer belt 20 to be constant, 24 is a drive roll for the intermediate transfer belt 20, and 26 is a counter roll (backup roll) for secondary transfer.
[0018]
Further, in the present embodiment, as the intermediate transfer belt 20, an appropriate amount of carbon black is contained as an antistatic agent in a resin such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate, acrylic, vinyl chloride, or various rubbers. The volume resistivity is 10⁶-10¹⁴The one with Ωcm and thickness of 0.1 mm is used.
[0019]
Further, a primary transfer device (primary transfer roll in the present embodiment) 27 is disposed on the back side of the intermediate transfer belt 20 at a portion (primary transfer position) facing the photosensitive drum 11 of the intermediate transfer belt 20. The toner image T on the photosensitive drum 11 is transferred to the intermediate transfer belt 20 by applying a primary transfer bias to the primary transfer roll 27 with a polarity opposite to the charging polarity of the toner (positive polarity in this embodiment). Electrostatic attraction.
Reference numeral 19 denotes a drum cleaner for removing the toner remaining on the photosensitive drum 11 after the primary transfer.
[0020]
Further, a secondary transfer device 40 is disposed at the secondary transfer position of the intermediate transfer belt 20 facing the conveyance path of the sheet 30 as a recording medium. In this embodiment, the toner transfer of the intermediate transfer belt 20 is carried out. A secondary transfer roll 28 is disposed in pressure contact with the surface side, and a counter roll (backup roll) 26 that is disposed on the back side of the intermediate transfer belt 20 and forms a counter electrode of the secondary transfer roll 28.
In this embodiment, the secondary transfer roll 28 is grounded, and a secondary transfer bias having the same polarity as the toner charging polarity is stably applied to the backup roll 26 via the power supply roll 29. Has been.
[0021]
Further, a belt cleaner 60 for removing toner remaining on the intermediate transfer belt 20 after the secondary transfer is provided on the downstream side of the secondary transfer device 40.
The secondary transfer roll 28 and the belt cleaner 60 are disposed so as to be able to come into contact with and separate from the intermediate transfer belt 20, and when a color image of a plurality of colors is formed, the toner image before the final color is formed. These are separated from the intermediate transfer belt 20 until T passes through the secondary transfer roll 28 and the belt cleaner 60. Details of the belt cleaner 60 and the contact / separation mechanism of the belt cleaner 60 will be described later.
[0022]
In the present embodiment, the paper transport system feeds the paper 30 from the paper tray 50 by the feed roll 51, temporarily stops the positioning by the registration roll (registration roll) 52, and then performs secondary transfer at a predetermined timing. Further, the sheet 30 is fed to the position, and the sheet 30 after the secondary transfer is guided to the conveyance belt 53 through a sheet conveyance guide (not shown), and the conveyance belt 53 leads to the fixing device 54. It is designed to be transported.
[0023]
In the present embodiment, as each color component toner, styrene acrylic resin fine particles and yellow, magenta, cyan, and black pigment fine particles are aggregated and combined to prepare a volume average particle diameter of about 3 to 7 μm. The toner produced by the emulsion aggregation and coalescence method (EA method) was used. The particle size distribution index (GSD) was 1.23. The average particle diameter is a value of a volume average particle diameter measured with a Coulter counter (manufactured by Coulter). Then, the heating time and the heating temperature during the polymerization were adjusted, and four types (four colors) of toners having substantially the same average particle size and particle size distribution were prepared.
The shape of the toner is the shape factor ML²This is a value calculated by the following equation 1 by performing image analysis on an enlarged photograph of the toner obtained with an optical microscope (Microphoto FXA; manufactured by Nikon Corporation) using an image analyzer Luzex3 (manufactured by NIRECO). .
[0024]
[Expression 1]

[0025]
Shape factor ML²/ A is represented by the ratio of the projected area of the toner to the area of the circle circumscribing the toner, and is 100 for a true sphere, which increases as the shape collapses. The shape factor is calculated for a plurality of toner particles, and the average value is used as a representative value. In the present embodiment, a substantially spherical toner having a shape factor of 125 or less is used.
In addition, in order to improve the releasability, an appropriate amount of inorganic fine particles such as silica and titanium oxide (titania) having an average particle diameter of 10 to 150 nm is externally added to the toner as an external additive, and ferrite toner having an average particle diameter of 35 μm is used. A developer was mixed with the carrier.
In addition to the toner prepared by this production method, a spherical toner or a non-spherical toner formed by a suspension polymerization method, a dissolution suspension method, an emulsion polymerization method, a kneading pulverization method, or the like may be used as the toner. Of course, a two-component developer in which the toner and the carrier are mixed as described above or a one-component developer containing only the toner may be used.
[0026]
3 and 4 are enlarged sectional views of the belt cleaner 60 according to the present embodiment. Here, FIG. 3 is a diagram showing a state during a cleaning operation, and FIG. 4 is a diagram showing a state during a non-cleaning operation.
In these drawings, a belt cleaner 60 includes a conductive brush roll 61 disposed on the image carrying surface side of the intermediate transfer belt 20 (residual toner is indicated by a symbol T in the figure), and the conductive brush roll 61. Accordingly, it has a cleaning blade 62 disposed on the downstream side in the moving direction of the intermediate transfer belt 20, and a cleaner housing 63 in which the conductive brush roll 61 and the cleaning blade 62 are accommodated. Reference numeral 63 a denotes an opening of the cleaner housing 63 that opens to face the intermediate transfer belt 20.
[0027]
Here, the conductive brush roll 61 rotates in a direction opposite to the moving direction B of the intermediate transfer belt 20 at a portion facing the intermediate transfer belt 20. In addition, the conductive brush roll 61 is disposed so as to penetrate the intermediate transfer belt 20 by 1.5 mm. The conductive brush roll 61 is cut so that 10 denier conductive nylon (trade name: Beltron) is flocked at a density of 80000 per square inch on a metal core (φ6 mm), and the outer diameter is 18 mm. Aligned. The axial length of the brush fiber portion was 312 mm, and the rotation speed was about 235 rpm (circumferential speed 220 mm / s).
[0028]
Further, a collection roll 64 that rotates in the opposite direction to the conductive brush roll 61 is disposed in contact with the conductive brush roll 61. Here, the collection roll 64 is formed by forming an insulating film on the surface of an aluminum cylindrical roll by a taffram treatment (trademark of General Magnaplate), and the conductive brush roll 61 and the collection nip portion with a bite amount of 2 mm. N is formed. The collection roll 64 also rotates at 235 rpm (circumferential speed 220 mm / s), which is the same rotational speed as the conductive brush roll 61.
Furthermore, a scraper 65 is disposed in pressure contact with the recovery roll 64 in a so-called doctor direction as viewed from the rotational direction.
[0029]
Reference numeral 66 denotes a film seal provided on the upstream side in the moving direction B of the intermediate transfer belt 20 as viewed from the conductive brush roll 61 to prevent the residual toner T removed from being scattered outside. Reference numeral 67 denotes the above-described film seal. An L-shaped plate, 68, for fixing the cleaning blade 62 to the cleaner housing 63, is provided on the lower side inside the cleaner housing 63, and discharges the residual toner T collected in the cleaner housing 63 to a waste toner container (not shown). It is a discharge auger.
[0030]
In the present embodiment, a bias (recovery bias) of +800 V is applied to the recovery roll 64 from a power source (not shown), while a bias (removal bias) of +400 V is applied to the conductive brush roll 61 from a power source (not shown). ) Is applied.
A metal plate 71 having a V-shape and having a flat surface in contact with the intermediate transfer belt 20 is disposed on the back side of the conductive brush roll 61 across the intermediate transfer belt 20. Yes. The metal plate 71 is grounded so as to form a predetermined electric field with the conductive brush roll 61.
[0031]
Further, a sheet metal 81 is attached to the side surface of the cleaner housing 63. The sheet metal 81 is swingable about a rotation shaft 82 provided on the upstream side in the moving direction B of the intermediate transfer belt 20 as viewed from the film seal 66, whereby the cleaner housing 63 (and the conductive brush). The roll 61, the cleaning blade 62, etc. are also swingable. A spring (not shown) that biases upward in the drawing is attached to the sheet metal 81.
A shaft 83 is attached to the upper end of the sheet metal 81 on the free end side. An eccentric cam (not shown) is pressed on the shaft 83. When the conductive brush roll 61, the cleaning blade 62, and the like are separated from the intermediate transfer belt 20, the shaft 83 is pressed downward in the drawing. It is like that.
[0032]
In the present embodiment, an exhaust port 69 is opened on the back side of the cleaner housing 63, and a duct 90 having an opening 90 a at a portion facing the exhaust port 69 is installed in the exhaust port 69. Has been.
The duct 90 has a cylindrical shape, and a discharge port 91 communicating with an intake fan (not shown) is disposed on the side surface. A filter (not shown) is provided in the discharge port 91 so that the residual toner T sucked through the exhaust port 69 cannot reach the intake fan.
[0033]
Furthermore, in the present embodiment, as shown in FIGS. 3 and 4, the facing area between the exhaust port 69 of the cleaner housing 63 and the opening 90 a of the duct 90 changes between when the belt cleaner 60 is pressed and separated. Specifically, the opposing area at the time of separation (see FIG. 4) is set to be approximately half as compared to that at the time of pressure contact (see FIG. 3).
[0034]
Next, an image forming process of the color image forming apparatus according to the present embodiment will be described.
Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed.
First, an electrostatic latent image is written on the photosensitive drum 11 and developed by a developing device corresponding to the electrostatic latent image.
For example, if the electrostatic latent image written on the photosensitive drum 11 corresponds to yellow image information, the electrostatic latent image is developed by the developing device 15 containing yellow toner, and is exposed to light. A yellow toner image T is formed on the body drum 11.
The toner image T formed on the photosensitive drum 11 is transferred from the photosensitive drum 11 to the surface of the intermediate transfer belt 20 at a primary transfer position where the photosensitive drum 11 and the intermediate transfer belt 20 are in contact with each other. On the other hand, the toner remaining on the photosensitive drum 11 after the primary transfer is removed by the drum cleaner 19.
[0035]
At this time, when forming a single-color image, the toner image T primarily transferred to the intermediate transfer belt 20 is immediately secondary-transferred to the paper 30. However, a color image obtained by superimposing a plurality of color toner images T is used. In the case of forming, the toner image T formation on the photosensitive drum 11 and the primary transfer process of the toner image T are repeated for the number of colors.
For example, when a full color image is formed by superposing four color toner images T, yellow, magenta, cyan, and black toner images T are formed on the photosensitive drum 11 for each rotation. The image T is sequentially primary transferred onto the intermediate transfer belt 20. On the other hand, the intermediate transfer belt 20 is rotated at the same cycle as that of the photosensitive drum 11 while holding the toner image T that has been primarily transferred first, and magenta, cyan, and black are transferred on the intermediate transfer belt 20 for each rotation. The toner image T is transferred.
[0036]
The toner image T primarily transferred to the intermediate transfer belt 20 in this way is conveyed to the secondary transfer position as the intermediate transfer belt 20 rotates.
On the other hand, the sheet 30 is supplied to the secondary transfer position by the registration roll 52 at a predetermined timing, and the secondary transfer roll 28 nips the sheet 30 with respect to the backup roll 26.
Then, at the secondary transfer position, the toner image T carried on the intermediate transfer belt 20 is secondly transferred by the action of a transfer electric field formed between the secondary transfer roll 28 and the backup roll 26 which are the secondary transfer device 40. It is electrostatically transferred to the paper 30 at the next transfer position. Thereafter, the sheet 30 that has been secondarily transferred is conveyed to the fixing device 54 via the conveyance belt 53 and the toner image T on the sheet 30 is fixed, while the image of the intermediate transfer belt 20 that has passed the secondary transfer position. The carrying surface side is cleaned by the belt cleaner 60.
[0037]
Here, the cleaning process of the intermediate transfer belt 20 by the belt cleaner 60 is as follows.
3 and 4, when the secondary transfer is completed, the sheet metal 81 is swung by an unillustrated eccentric cam, and the cleaner housing 63 is swung around the rotation shaft 82, and the film seal 66 and the conductive brush roll 61 are swung. The cleaning blade 62 is pressed against the intermediate transfer belt 20 in this order.
[0038]
When the residual toner T (negatively charged) on the intermediate transfer belt 20 reaches a portion facing the conductive brush roll 61, the residual toner T is placed between the conductive brush roll 61 and the metal plate 71. It is transferred onto the conductive brush roll 61 by the potential difference (+400 V). When the residual toner T transferred to the conductive brush roll 61 reaches the portion facing the recovery roll 64, this time, the potential difference between the recovery roll 64 and the conductive brush roll 61 (+ 800V − (+ 400V) = + 400V) to transfer onto the collection roll 64. Then, the residual toner T transferred onto the collecting roll 64 is scraped off by the scraper 65 and falls into the cleaner housing 63.
On the other hand, the residual toner T that has not transferred onto the conductive brush roll 61 is scraped off by the cleaning blade 62 and falls into the cleaner housing 63.
The residual toner T in the cleaner housing 63 is discharged to the outside by the discharge auger 68.
[0039]
Thereafter, when the cleaning is completed, the sheet metal 81 is again swung by an eccentric cam (not shown), and the cleaner housing 63 is swung to the opposite side around the rotation shaft 82, and the cleaning blade 62, the conductive brush roll 61, The films are separated from the intermediate transfer belt 20 in the order of the film seal 66.
[0040]
In the present embodiment, air is sucked from the duct 90 by a suction fan (not shown) during this series of cleaning processes.
First, when the cleaning operation is performed (see FIG. 3), the exhaust port 69 of the cleaner housing 63 and the opening 90a of the duct 90 are opposed to each other, so that the suction force of the suction fan remains as it is in the cleaner housing 63. However, since the opening 63a of the cleaner housing 63 and the intermediate transfer belt 20 are in close contact (the film seal 66 and the cleaning blade 62 are in contact with the intermediate transfer belt 20, there is almost no gap). The amount of suction at this point is very small.
[0041]
Next, at the end of the cleaning operation, that is, at the start of the separation operation, the exhaust port 69 of the cleaner housing 63 and the opening 90a of the duct 90 face each other in the same manner as described above. While being transmitted into the housing 63, the separation between the cleaner housing 63 and the opening 63 a of the cleaner housing 63 and the intermediate transfer belt 20 (specifically, between the intermediate transfer belt 20 and the cleaning blade 62). ), A gap is generated, so that the amount of suction is increased unlike the cleaning operation.
At this time, the conductive brush roll 61 and the cleaning blade 62 are elastically deformed as they are separated from the intermediate transfer belt 20, and the residual toner T adhering to them tends to scatter. Therefore, the scattered residual toner T is prevented from reattaching to the intermediate transfer belt 20. The residual toner T drawn into the cleaner housing 63 is drawn into the duct 90 side, or falls and is discharged by the discharge auger 68. The residual toner T drawn to the duct 90 side then moves from the discharge port 91 toward a suction fan (not shown), but is captured by a filter (not shown) provided in front of the suction fan. .
In this way, by causing suction, the situation where the residual toner T adhering to the conductive brush roll 61 and the cleaning blade 62 is scattered during the separation operation is avoided, so that the scattered toner is applied to the intermediate transfer belt 20. It is possible to prevent image quality defects in the next image caused by reattachment, toner contamination in the apparatus caused by scattered toner flying in the color image forming apparatus, and the like.
[0042]
Further, at the end of the separation operation, as shown in FIG. 4, the exhaust port 69 of the cleaner housing 63 and the opening 90a of the duct 90 are opposed to each other on the other side, so that a suction fan (not shown) ) Is transmitted to the cleaner housing 63 by substantially halving.
As a result, the residual toner T drawn into the duct 90 is reduced, so that the amount of toner captured by the filter (not shown) is also reduced, and the life of the filter can be extended accordingly.
[0043]
Further, in the present embodiment, as shown in FIG. 5, the scattering direction C of the toner scattered from the collection nip N of the conductive brush roll 61 and the collection roll 64 is not directed toward the opening 63 a of the cleaner housing 63. Therefore, it is difficult for the residual toner T scattered from the collection nip portion N to adhere to the intermediate transfer belt 20 again. Further, since the scattering direction C of the toner is directed to the exhaust port 69 side of the cleaner housing 63, the scattered toner is easily drawn into the duct 90 side by suction, and accordingly, to the intermediate transfer belt 20 side. Can be further suppressed.
[0044]
Furthermore, in the present embodiment, as shown in FIG. 5, a space D is provided on the cleaner housing 63 side of the recovery nip portion N, and the inner wall of the cleaner housing 63 at a portion from the space D toward the discharge auger 68 is provided. By inclining, it becomes easy to move to the discharge auger 68 side, so that it is possible to avoid the situation where the toner detached from the conductive brush roll 61 is reattached to the conductive brush roll 61.
[0045]
The inventor conducted the following experiment in order to investigate the relationship between suction and toner scattering.
FIG. 6 shows the cleaning device used in this experiment.
In the figure, reference numeral 120 denotes an intermediate transfer belt, which is stretched around a plurality of stretch rolls (not shown) including a drive roll 121 and is rotated in the direction of the arrow.
The belt cleaner 160 includes a conductive brush roll 161 disposed on the image carrying surface side of the intermediate transfer belt 120, a cleaning blade 162 disposed on the downstream side in the moving direction of the intermediate transfer belt 120, The cleaning unit 164 includes a cleaning brush 163 and a cleaner housing 163 in which the cleaning blade 162 is accommodated. Here, the conductive brush roll 161 rotates in the opposite direction at the portion facing the intermediate transfer belt 120, and a cleaning bias power source 165 for electrostatically attracting residual toner on the intermediate transfer belt 120. (+ 400V) is connected. In addition, a film seal 166 is attached on the upstream side in the moving direction of the intermediate transfer belt 120 as viewed from the conductive brush roll 161 to prevent the removed residual toner from scattering outside.
[0046]
  On the other hand, on the back side of the image carrying surface of the intermediate transfer belt 120 facing the conductive brush roll 161, a counter roll 167 that rotates following the rotation of the intermediate transfer belt 120 is disposed in contact therewith. By grounding the opposing roll 167, a cleaning electric field for removing toner is formed between the conductive brush roll 161 and the intermediate transfer belt 120.
  The conductive brush roll 161 has a collection roll 168 that rotates in the opposite direction in contact with the conductive brush roll 161, and collects the residual toner adhering to the conductive brush roll 161 electrostatically. A bias power source 169 (+800 V) is connected. Further, the collection roll168A scraper 170 is disposed in pressure contact with the recovery roll.168The residual toner adhering to the toner is scraped off and accommodated in the cleaner housing 163.
  The cleaning unit 164 is swingably disposed around the shaft 163a, and can be brought into contact with and separated from the intermediate transfer belt 120. When a primary transfer of toner images of each color from the photosensitive drum (not shown) to the intermediate transfer belt 120 is performed, the conductive brush roll 161, the cleaning blade 162, and the film seal are transferred from the surface of the intermediate transfer belt 120. On the other hand, after the batch transfer of the toner image from the intermediate transfer belt 120 to the transfer paper is completed, the conductive brush roll 161, the cleaning blade 162, and the film seal 166 are brought into contact with the intermediate transfer belt 120 to remain. Control such as cleaning the toner is performed.
[0047]
Further, in this cleaning device, an intake tube group 171 is attached below the cleaning blade 162.
As shown in FIG. 7, the tube group 171 includes a first tube 171a having an opening at one end portion of the cleaning blade 162, a second tube 171b having an opening at a substantially central portion, and one end portion on the opposite side. And a third tube 171c having an opening. Each of the tubes 171a to 171c is integrated into one tube 171d at the end where the opening of the tube 171c is formed, and is connected to an intake fan (not shown).
[0048]
In this experiment, in order to measure the intake air amount, a flow velocity sensor 172 (specifically, 172a to 172c) is positioned at a position corresponding to the front side of each of the tubes 171a to 171c (the intermediate transfer belt 120 side, see FIG. 6). ) Was disposed. However, the flow rate sensor 172a was disposed at a position shifted by 30 mm from the opening of the first tube 171a for convenience of layout.
[0049]
Using the above-described cleaning device, first, the air flow rate necessary to prevent toner scattering and the pressure inside the cleaner housing 163 (the difference in static pressure from the atmospheric pressure during pressure contact) were examined.
In this experiment, images were continuously formed on the intermediate transfer belt 120, and the amount of toner spots generated by toner scattering in the formed image was investigated. In this case, α indicates that a toner point of 0.3 mm or more is generated in the image, β indicates that a toner point of 0.3 mm or less is generated within an interval of 2 mm, and a toner point of 0.3 mm or less exceeds 2 mm. Those generated at intervals were classified as γ and evaluated by the number of generated sheets per 100 sheets.
[0050]
The results are shown in FIG.
When suction was not performed, α was 5.3 sheets / 100 sheets, whereas when suction was performed, the value of α was small, and the static pressure difference from the atmospheric pressure was 0.08 (mmH₂If O) or more, it was found that α is the target value of 2.0 sheets / 100 sheets or less.
[0051]
Next, based on the above results, the air suction timing was investigated.
Evaluation was performed by the same experiment as described above. As for the suction timing, there are three types: one that performs suction at all times, one that performs suction only during pressure contact, and one that performs suction only during separation.
[0052]
The results are shown in FIG.
It was confirmed that the values of α, β, and γ were significantly smaller when the suction was always performed and the toner deposited on the cleaning blade 162 was smaller than when the suction was not performed. However, on the other hand, it has also been found that the amount of toner sucked into the tube group 171 (suction toner weight) increases. If the weight of the suction toner is too large, the tube group 171 and the filter (not shown) may be clogged.
When suction is performed only during pressure contact, the values of α, β, and γ are certainly smaller than when suction is not performed, but the target values (α ≦ 2.0) are not reached, and cleaning is performed. It was found that the toner deposited on the blade 162 increased.
On the other hand, it was confirmed that when suction was performed only at the time of separation, the values of α, β, and γ were smaller than when suction was not performed, and toner deposited on the cleaning blade 162 was also reduced. Further, it was confirmed that the weight of the suction toner is reduced. From the above results, it was found that it is preferable that the suction operation is performed only at the time of separation in practice.
[0053]
Further, based on the above result, the present inventor has a rotation stop timing (bias application stop timing) of the conductive brush roll 161 (hereinafter referred to as an abbreviation of “Electric Static Brush” if necessary) and an intermediate state at the end of the cleaning operation. The relationship with the separation timing from the transfer belt 120 was investigated.
[0054]
The results are shown in FIG.
According to this, compared to the case where the rotation and bias application of the ESB 161 are stopped simultaneously with the start of the separation operation, the toner scattering is more effective when the rotation and bias application of the ESB 161 are stopped 0.1 seconds before the start of the separation operation. It was confirmed that the number of sheets α to γ can be reduced.
[0055]
【The invention's effect】
  As described above, according to the present invention, since the toner scattered from the cleaning member is sucked when the cleaning member contacts and separates from the image carrier, the residual toner removed from the image carrier with a simple configuration. Can be effectively prevented from being reattached to the image carrier and the accompanying image quality defects.
  In particular, according to the present invention, the suction means is a suction port of the cleaner housing according to the contact / separation operation of the cleaning member.ofSince the area changes so as to be narrower at the time of separation than at the time of press contact, the suction force by the suction means can be increased immediately after the start of the separation operation of the cleaning member, and the suction force can be reduced at the end of the separation operation. For this reason, it is possible to efficiently suck the toner to be scattered from the cleaning member immediately after the cleaning member starts the separating operation without sucking the residual toner in the cleaner housing too much.
  Further, in the present invention, the contacting / separating means rotates the cleaner unit about the rotation axis to advance and retract the cleaner unit with respect to the image carrier, thereby contacting and separating the cleaning member and the image carrier, while suction means. Is provided on the opposite side of the rotating shaft with respect to the contact / separation position of the cleaning member, and the cleaner housing is moved away from the suction port of the cleaner housing according to the contact / separation operation of the cleaning member by the contact / separation means. The area of the suction port of the cleaner housing changes so that it is narrower at the time of separation compared to that at the time of pressure contact by closing the side far from the gap where the gap is large among the gaps formed between the opening and the image carrier. Therefore, as described above, by reducing the area of the suction port, the suction force is reduced at the end of the separating operation of the cleaning member, and the cleaner housing Can work suction action by the suction mouth relative to the clearance gap is larger among the resulting gap between the mouth portion and the image bearing member.
[0056]
  In addition, the present inventionInPrevents toner scattered from the contact area between the conductive brush and the collection body from going to the cleaner housing opening.if,It is possible to effectively prevent the residual toner removed from the image carrier with a simple structure from reattaching to the image carrier and the accompanying image quality defects.
[Brief description of the drawings]
FIG. 1 is a schematic view of a cleaning device according to the present invention.
FIG. 2 is a schematic configuration diagram of an embodiment of a color image forming apparatus to which a cleaning device according to the invention is applied.
FIG. 3 is an explanatory diagram showing a state during cleaning of the cleaning device.
FIG. 4 is an explanatory view showing a state when the cleaning device is not cleaned.
FIG. 5 is an explanatory diagram relating to the vicinity of a recovery nip portion of the cleaning device.
FIG. 6 is a schematic configuration diagram of a cleaning device used in the experiment.
FIG. 7 is an enlarged view of the vicinity of the cleaning blade of the cleaning device used in the experiment.
FIG. 8 is a chart showing a first experimental result.
FIG. 9 is a chart showing the results of a second experiment.
FIG. 10 is a chart showing the results of a third experiment.
[Explanation of symbols]
  DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Cleaner housing, 2a ... Opening part,2b ... suction port,DESCRIPTION OF SYMBOLS 3 ... Cleaning member, 3a ... Conductive brush, 4 ... Cleaner unit, 5 ... Contact / separation means, 6 ... Suction means, 7 ... Suction amount variable means, 8 ... Collecting body, T ... Residual toner, N: Abutting part

Claims (4)

A cleaner housing having an opening at a portion facing the image carrier, and a cleaning member disposed at a location facing the opening of the cleaner housing and removing residual toner on the image carrier. A cleaner unit,
The cleaner unit by rotating the cleaner unit about an axis of rotation is forward and backward relative to said image bearing member, and a moving means for contacting and separating with said image bearing member and said cleaning member,
Wherein said rotation axis with respect to contact and separation position of the cleaning member provided on the opposite side, the suction port of the cleaner housing according to and away operation of the cleaning member by the moving means while sucking the air in the cleaner housing On the other hand, the area of the suction port of the cleaner housing by closing the side far from the large gap among the gaps formed between the opening of the cleaner housing and the image carrier in association with the separation operation of the cleaner unit. And a suction means that changes so that the distance at the time of separation becomes narrower than that at the time of pressure contact. The cleaning device according to claim 1,
A cleaning apparatus, comprising: a suction amount varying means for varying a suction amount by the suction means in accordance with a contact / separation operation of the contact / separation means. The cleaning device according to claim 1,
The cleaner unit is provided with a cleaner housing having an opening at a portion facing the image carrier, and is rotatably disposed at a position facing the opening of the cleaner housing and charging residual toner on the image carrier. A conductive brush to which a removal bias having a polarity opposite to the polarity is applied, and a recovery bias that is rotatably contacted with the conductive brush and has the same polarity as the removal bias and greater than the removal bias. A recovery body,
A cleaning device, wherein a scattering direction of toner scattered from a contact portion between the conductive brush and the collection body and the opening portion are arranged so as not to face each other. The cleaning device according to claim 3.
A cleaning apparatus comprising: suction means for sucking air in the cleaner housing; and a suction port connected to the suction means in the cleaner housing on the toner scattering direction side.

Images