JP2005010511A - Cleaning device for image carrier, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning device capable of preventing the deterioration of a cleaning performance due to the accumulation of toner and the aggregated body of external additive, preventing the wear and chipping of a blade edge due to the particles of large-sized diameter without loading excessive burdens on the blade. <P>SOLUTION: The cleaning device 300 is arranged along a photoreceptor drum 200 on the downstream side of a transfer device 40 in the rotating direction of the photoreceptor drum 200. The rubber blade 340 is arranged in the opening of the housing 310 of the cleaning device 300, so that the blade 340 may come in tight contact with the photoreceptor drum 200, then, the residual toner is removed by the blade. An air discharge nozzle 322 for discharging the compressed air near a press-contact part of the blade 340 with the photoreceptor drum 200 is arranged on the upstream side of the blade 340, and the air is suitably discharged to near the press contact part. The particles of large-sized diameter accumulated on the press contact part and causing the wear of the blade 340 are blown away by the air discharge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１４】
トナーには、平均粒径１０〜１５０ｎｍの外添剤が添加される。外添剤は、トナーに付着して、トナーの帯電を制御したり、トナー間に適度な隙間を形成したりするためのものである。本実施形態において、外添剤には、シリカ（ＳｉＯ_２）系、又はチタニア（ＴｉＯ_２）系の無機微粒子が用いられている。また、トナーに電荷を付与するためのキャリアは、平均粒径３５μｍのフェライトビーズである。
【００１５】
画像形成装置１００の説明に戻る。感光体ドラム２００の表面に形成された可視画像であるトナー像は、転写装置４０によって転写材４１に転写される。そして、トナー像を保持した転写材４１は、図示せぬ定着装置によって、加熱、加圧などの定着処理がなされた後、装置外に排出される。画像形成装置１００による画像形成は大略このような過程で行われている。
【００１６】
一方、感光体ドラム２００から転写材４１への現像剤の転写効率は、１００％ではない。従って転写装置４０を通過した後の感光体ドラム２００には、その表面にいわゆる残留トナーが付着している。無論、外添剤も同様に感光体ドラム上に残留しているが、ここではそれらを含めて残留トナーと称することとする。この残留トナーをこのまま放置すると、画質劣化の要因となることは既に述べた。画像形成装置１００においては、本実施形態に係るクリーニング装置３００によって、この残留トナーが除去されている。
【００１７】
＜クリーニング装置３００の構成＞
図２は、図１においてクリーニング装置３００を矢印Ａの方向からみた断面図である。以下に、図１及び図２を適宜使用して、本発明の第１実施形態に係るクリーニング装置３００について説明する。
【００１８】
クリーニング装置３００は、転写装置４０よりも感光体ドラム２００の回転方向下流側（以降、単に「下流」とし、「上流」も同様に定義する）に設けられており、感光体ドラム２００に沿って設置されたハウジング３１０、ハウジング３１０内に一部が設置された、エア吐出装置３２０及び除去トナー搬送装置３３０、そしてハウジング３１０に一端が固定されたクリーニングブレード３４０（以降「ブレード３４０」とする）からなる。
【００１９】
ハウジング３１０は、感光体ドラム２００の軸方向に渡って細長く開口した開口部を、感光体ドラム２００と近接させた状態で固定されている。図１に示すように、ハウジング３１０の内部は、この開口部からハウジング３１０内部に向かうに連れ、下方に徐々に広まった空間となっている。また、ハウジング３１０の側面の一部には、ハウジング３１０内の気圧上昇を防止するための排出口３１１が設けられている。排出口３１１は、図示せぬフィルタで覆われている。
【００２０】
図１において、ハウジング３１０の開口部上端には、ハウジング３１０の開口辺と略同一の長さを有するブレード３４０の一端が固定されている。ブレード３４０の自由端は、感光体ドラム２００の表面に圧接されている。かかる構成の下、ブレード３４０は、感光体ドラム２００の表面に付着したままハウジング３１０内に進入した残留トナーを、その圧接部において塞き止め、感光体ドラム２００から除去する。
尚、本実施形態において、ブレード３４０は、ＪＩＳＡ硬度が「７５」、反発弾性が４７％、厚さ２ｍｍ、自由長８ｍｍのウレタンゴムで構成されている。ブレード３４０は、感光体ドラム２００に対し、２５度の当接角度でそのエッジ部分を感光体ドラム２００の表面に１ｍｍ食い込ませ、３．５ｇｆ／ｍｍの押圧力で感光体ドラム２００に押圧されている。ここで、「３．５ｇｆ」とは、３．５ｇの質量を有する物質に作用する押圧力のことである。
【００２１】
ハウジング３１０内には、エア吐出装置３２０、及び除去トナー搬送装置３３０のそれぞれ一部が設けられている。まずエア吐出装置３２０から説明する。エア吐出装置３２０は、感光体ドラム２００上に圧縮されたエアを吐出する装置であり、エア搬送路３２１、エア吐出ノズル３２２、及び圧縮エア供給装置３２３から構成されている。
【００２２】
図３は、圧縮エア供給装置３２３のブロック図である。圧縮エア供給装置３２３は、エアポンプ３２４、エアタンク３２５、エアタンク３２５に設けられた電磁弁３２６、及び電磁弁３２６の開閉を始め圧縮エア供給装置３２３の動作を制御する制御装置３２７から構成される。
【００２３】
このような構成の下、エアタンク３２５には、エアポンプ３２４から適宜エアが送りこまれ蓄積されている。エアタンク３２５内のエアの蓄積量が十分になると、制御装置３２７は所望のタイミングで電磁弁３２６を開弁する。エアタンク３２５にはエア搬送路３２１が電磁弁３２６を介して繋がっており、電磁弁３２６が開くことによって、エアタンク３２５内で圧縮されたエアが、エア搬送路３２１に供給される。エア搬送路３２１は、ハウジング３１０内に設けられたエア吐出ノズル３２２に繋がっている。ハウジング３１０の外壁部分とエア搬送路３２１の外壁部分とは、ハウジング３１０内の気体がハウジング外に漏出しないよう、気密性を保って接合されている。
【００２４】
エア吐出ノズル３２２は、ハウジング３１０内において、ハウジング３１０の開口部を介して感光体ドラム２００と対向配置されている。エア吐出ノズル３２２は、先端に当該開口部の長辺と略同じ長さのスリット状の吐出口を有し、その吐出口を、感光体ドラム２００とブレード３４０との圧接部分（以下、単に『圧接部』とする）に向けている。エア吐出ノズル３２２は、ブレード３４０と感光体ドラム２００との圧接点から上流側２．５ｍｍの位置において、感光体ドラム２００表面から垂直に２ｍｍ離れた位置に吐出口が配置されるように設置位置が決められている。エア吐出ノズル３２２の吐出口のスリット幅は０．３ｍｍで、エア搬送路３２１との接続部に向かうに連れ、その幅は若干広がっている。エア吐出ノズル３２２からは、最大流速５０ｍ／ｓｅｃの圧縮エアが吐出される。
【００２５】
続いて、除去トナー搬送装置３３０について説明する。
ハウジング３１０と、エア搬送路３２１との接合面下部には、円筒状の除去トナー搬送管３３１の一端部が接合され、ハウジング３１０とその内部において繋がっている。この接合部において、ハウジング３１０の外壁と除去トナー搬送管３３１の外壁とは、前述のエア搬送路３２１と同様に気密的に接合されている。除去トナー搬送管３３１の、他端部付近には、下方に向かってトナー回収タンク３３２が設置されている。
【００２６】
ハウジング３１０内の、エア搬送路３２１下方には搬送オーガ３３３が設置されている。搬送オーガ３３３は、感光体ドラム２００の軸方向に向かって延びる回転軸に、板状部材を螺旋状に設けてなる。搬送オーガ３３３の回転軸は、除去トナー搬送管３３１とハウジング３１０との接合部を通過して、除去トナー搬送管の端部にその一端が固定されており、図示せぬ他端部は、図示せぬ駆動装置に接続され、回転可能となっている。この回転によって、搬送オーガ３３３は、付近に存在する微粒子をゆっくりと図２における左方向へ運ぶことができる。
【００２７】
＜クリーニング装置３００の動作＞
かかる構成を有するクリーニング装置３００の動作について説明する。
感光体ドラム２００の回転に伴って、圧接部には残留トナーが蓄積する。既に述べたように、この残留トナーには、トナーの他に外添剤も含まれるものとする。ブレード３４０によって感光体ドラム２００から除去される、この残留トナーの内、一部の粒子は、重力によって搬送オーガ３３３の設置空間に自然に落下する。搬送オーガ３３３は、前述のように回転しているから、これらの微粒子は、除去トナー搬送管内をゆっくりと図２において左方向に移動し、最終的にトナー回収タンク３３２に向かって落下する。
【００２８】
このように自然に圧接部から乖離するもの以外は、圧接部にある程度の期間堆積することとなる。図４は、圧接部近傍の拡大図である。図示のように、圧接部から、その上流側にかけて、空間は楔形になっており、圧接部に近い程、感光体ドラム２００とブレード３４０との間隙は小さくなっている。従って、この圧接部に堆積する粒子は、自然とその大きさによって存在領域が異なってくる。本実施形態においては、圧接部からその上流側に向かって、小粒径の外添剤、大粒径の外添剤、外添剤の凝集体そしてトナーの順で蓄積されている。
【００２９】
エア吐出装置３２０は、制御装置３２７によって、そのエア吐出のタイミング及び吐出時間が制御されている。本実施形態において、制御装置３２７は、一回の画像形成が終了する毎に、０．５秒間エアを吐出するように制御を行っている。エア吐出ノズル３２２の吐出口は、圧接部に向けて配設されているから、吐出されたエアは、圧接部に直接到達する。この際、図４から明らかなように、吐出されたエアが接触するのは、最も外側に堆積しているトナーとなる。このトナーは、エアによって圧接部から乖離させられ、ハウジング３１０内を飛散する。また、このようにトナーが圧接部から乖離させられるのに伴って生じる隙間を通して、トナーの内側に堆積している外添剤の凝集体にも吐出されたエアの一部が到達する。このエアにより、外添剤の凝集体の一部も、トナーと同様に圧接部より乖離させられ、ハウジング３１０内を飛散する。そして、これら飛散したトナーや外添剤の凝集体は、重力によって自然に搬送オーガ付近まで落下し、除去トナー搬送管３３１内を通過して、トナー回収タンクに回収される。結果として、圧接部からは、残留トナーの内、トナーや外添剤の凝集体など比較的大粒径の粒子が除去される。
【００３０】
本実施形態に係るクリーニング装置は、このようにして、圧接部上流に蓄積した、主にトナーや外添剤の凝集体からなる大粒径粒子を確実に除去することができる。従って、ブレード３４０が、これら大粒径粒子によって破損または磨耗することを防止することができる。尚、このエア吐出によっても、ブレード３４０のエッジ近傍に堆積する小粒径粒子（小粒径の外添剤又は大粒径の外添剤）は、吹き飛ばされずに当該圧接部に残留する場合が多い。しかしながら、これら小粒径の微粒子は、ブレード３４０と感光体ドラム２００との間の摩擦力を低減する効果があるため、必ずしも除去する必要がない。
【００３１】
本実施形態に係るクリーニング装置３００は、上記した様に制御装置３２７によって、エア吐出を間欠で行う制御がなされ、不要に大量のエアを吐出させないように構成されている。従って非常に経済的である。また、本実施形態に係るエア吐出ノズル３２２は、先端部のエア吐出口のスリット幅が、エア搬送路３２１との接合部の幅よりも小さく構成されている。従って、少ないエア供給量で非常に大きいエア流速を得ることができる。このため、上記した間欠式のエア吐出制御とあいまって、圧縮エア供給装置３２３、ひいてはクリーニング装置３００は、非常にコンパクト且つ簡易に構成されている。従って、クリーニング装置３００は高い設置性を有している。また、エア供給量が少ないため、ハウジング３１０内の空気圧上昇を抑えられるので、ハウジング３１０の開口部などから、トナーや外添剤などの除去物質が噴出することも回避できる。
【００３２】
また、本実施形態に係るクリーニング装置３００は、エア吐出によって残留トナーを除去しているが、エアを使用した態様はこれに限定されず、エアで吸引する装置を用いても残留トナーを除去することができる。然るに、エア吸引は、エア吐出程の残留トナー除去効率を有さない場合が多い。それは、吸引されるエアが、吐出されるエア程指向性を有さない為である。更には、エア吸引によるクリーニングを行うためには設置上の制約も多い。本実施形態の態様によれば、これらの問題が生じず、エア吸引によるクリーニングと比較して、非常に簡便な構成によって微粒子を除去することができるので好ましい。
【００３３】
本実施形態に係るクリーニング装置３００において、ハウジング３１０には複数の排出口３１１が設けられており、ここからエアが排出されるようになっている。また排出口３１１にはフィルタが設けられているから、ここから、除去されたトナがハウジング外に飛散することはない。ハウジング３１０内に圧縮エアが吐出されると、ハウジング３１０内の圧力が上昇する懸念があるが、この排出口３１１から適宜エアが排出されるので、本実施形態において、ハウジング３１０内部の圧力上昇は極僅かに留まっている。従って、ハウジング３１０内部の圧力上昇によって、除去されたトナーがハウジング外に噴出するような事態は生じない。
また、エアは圧接部に直接吐出される為、圧接部近傍は、局所的に圧力上昇を起こしやすいが、ハウジング３１０の内部は、開口部から内部下方に向かうに連れ、徐々に広まった空間となっているから、この圧力上昇は、この空間によって直ちに緩和される。このように、本実施形態に係るクリーニング装置３００においては、ハウジング３１０内部の圧力上昇が極めて起こりにくくなっているのである。
【００３４】
尚、本実施形態に係る画像形成装置１００は、転写材４１に直接トナー像が転写されるが、画像形成装置の態様はこれに限定されない。例えば、無端ベルト形状を有する中間転写体に一旦トナー像を転写し、更に中間転写体上のトナー像を転写材に転写する中間転写方式の画像形成装置であっても、本実施形態と同様の効果を得ることができる。
また、クリーニング装置のクリーニング対象も、本実施形態の態様に限定されない。例えば、上記した中間転写体の表面の残留トナー除去に使用されても好適である。更には、像担持体を有する画像形成装置であれば、その像担持体上の残留トナー除去に本発明に係るクリーニング装置を使用することができる。
【００３５】
尚、本実施形態において、制御装置３２７は、画質への悪影響を避けるため、画像形成終了時にエアを吐出するように電磁弁３２６の開閉を制御しているが、エア吐出のタイミングはこれに限定されない。画像形成中であっても、画像と画像の間のいわゆるインターイメージ部でエア吐出を行っても良い。更には、画像形成に影響のない範囲で、画像形成中にエア吐出を行っても良い。
【００３６】
また、本実施形態において、エアの吐出時間は０．５秒となっているが、実施の態様はこれに限定されない。これより長くても本実施形態にかかる効果が阻害されることはない。更には、エアの吐出を間欠ではなく常時吐出としても良い。また、エア流速も、本態様に限定されることなく、圧接部上流側の大粒径粒子を除去できる範囲で自由に決定される。このエア流速は、圧縮エア供給装置の構成、及び、エア搬送路又はエア吐出ノズルの構造次第で自在に設定することができる。従って、例えば、エア吐出時間を更に短くしたい場合には、エア流速を高めて残留トナー除去性を高める、といったことも容易に実現可能である。
【００３７】
本実施形態は、ブレード３４０の自由端が下方を向く画像形成装置を使用しているが、ブレードの設置形態はこれに限定されない。ブレードの自由端を上方に向けて感光体ドラムに圧接する画像形成装置においては、圧接部における残留トナーの蓄積がより顕著であるが、このような画像形成装置に対しても、本発明に係るクリーニング装置を使用することができる。
【００３８】
本実施形態において、エア吐出ノズル３２２は、その吐出口から圧接部に直接エアが吹き付けられる位置に設置されているが、エア吐出ノズル、及びエア吐出口の位置は、これに限定されない。エア吐出口から吐出されたエアが、圧接部上流側に位置する大粒径粒子に到達し、これを除去できれば良い。例えば、本実施形態よりも更に上流側にエア吐出口が設けられていても、上述したようにエア流速を制御すれば、容易に圧接部上流にエアを到達させることができる。
尚、本実施形態では、残留トナーを除去するために圧縮エアを吐出しているが、吐出する気体はこれに限定されない。例えば、アルゴンガス等、化学的に不活性なガスを使用しても良い。
【００３９】
＜第２実施形態＞
さて、上述の第１実施形態において、エア吐出口の向きは、感光体ドラム２００の回転軸に対して、ほぼ垂直である。このような向きでエアを吐出すると、圧接部におけるエアの対流領域が小さく、局所的に圧力上昇が起こって十分に残留トナー除去効果が得られなくなる可能性がある。ここでは、そのような問題を解決し得るクリーニング装置について説明する。
【００４０】
図５は、本発明の第２実施形態に係るクリーニング装置４００と、その設置環境を説明する断面図である。尚、図１と重複する箇所には同一の符号を付してその説明を省略する。本実施形態に係るエア吐出装置３２０は、エア吐出ノズル３２２の代わりに、複数のエア吐出ノズル４０１を有する点が第１実施形態と異なっている。
【００４１】
エア吐出ノズル４０１は、円錐の頂点付近を切り取ったような、吐出口に向かうに従って先端がすぼまった形状を有するノズルである。ノズルの吐出口径は２．５ｍｍで、感光体ドラム２００の軸方向に沿って２０ｍｍのピッチで複数配設されている。エア吐出ノズル４０１の吐出口の位置は、第１実施形態と同様である。また、エア吐出ノズル４０１から吐出されるエアの最大流速は１００ｍ／ｓｅｃである。エア吐出ノズル４０１は、エア吐出口が、感光体ドラム２００の回転軸に対して直交しないように、且つ吐出されたエアが、図５におけるハウジング３１０左端部に設けられた排出口３１１に向かうように、適度に傾いた状態で配設されている。
【００４２】
かかる構成の下、エア吐出ノズル４０１から圧縮エアが吐出されると、エアは感光体ドラム２００の表面に沿って回転軸方向に流れる。吐出されたエアは、まず圧接部上流の各吐出口と対向した部分に直接噴射され、その部分に堆積した残留トナーを感光体ドラム２００の回転軸方向に吹き飛ばした後、同方向に沿って流れ、この吹き飛ばされたトナーに隣接する残留トナーを、同じく感光体ドラム２００の回転軸方向に吹き飛ばす。
【００４３】
このように、本実施形態の態様によれば、エア吐出ノズルを感光体ドラム２００の軸方向に、感光体ドラム２００の全幅に渡って設ける必要が生じない。従って、エア吐出装置３２０で使用されるエアの量を軽減することができ、更なるコストダウンを図ることができる。また、吐出されたエアは、感光体ドラムの軸方向にそって流れ、ハウジング３１０に設けられた排出口３１１に向かう。従って、吐出されたエアが、密閉空間に入り込むことによって不要な圧力が発生することがなく、残留トナー除去効果が一層高められる。
【００４４】
【発明の効果】
以上説明したように、本発明に係るクリーニング装置は、圧接部近傍の上流側に堆積した、トナーや外添剤の凝集体等の大粒径粒子を、安価な構成によって当該圧接部から確実に除去することができる。従って、従来これら大粒径の粒子によって生じていたクリーニングブレードの欠損や磨耗を防止することができる。
また、本発明に係る画像形成装置は、本発明に係るクリーニング装置によって感光体ドラムから残留トナーが除去される。従って、クリーニング不良や、クリーニングブレード磨耗・欠損による画質劣化が生じにくく、またクリーニングブレードの寿命が延びることによって、装置のランニングコストを低下させることができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係るクリーニング装置３００と、その設置環境を示す断面図。
【図２】図１においてＡ方向から見たクリーニング装置３００の断面図。
【図３】同クリーニング装置３００における圧縮エア供給装置３２３のブロック図。
【図４】同実施形態に係るブレード３４０と感光体ドラム２００との圧接部付近の拡大図。
【図５】本発明の第２実施形態に係るクリーニング装置４００の断面図。
【符号の説明】
１０・・・バイアス帯電ロール、２０・・・露光ビーム、３０・・・現像装置、３１・・・現像ロール、４０・・・転写装置、４１・・・転写材、１００・・・画像形成装置、２００・・・感光体ドラム、３００・・・クリーニング装置、３１０・・・ハウジング、３１１・・・排出口、３２０・・・エア吐出装置、３２１・・エア搬送路、３２２・・・エア吐出ノズル、３２３・・・圧縮エア供給装置、３２４・・・エアポンプ、３２５・・・エアタンク、３２６・・・電磁弁、３２７・・・制御装置、３３０・・・除去トナー搬送装置、３３１・・・除去トナー搬送管、３３２・・・トナー回収タンク、３３３・・・搬送オーガ、３４０・・・クリーニングブレード、４００・・・クリーニング装置、４０１・・・エア吐出ノズル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning device mainly used for removing residual toner on an image carrier and an image forming apparatus using the same.
[0002]
[Prior art]
A device using a rubber blade is widely used as a residual toner cleaning device on an image carrier in an image forming apparatus such as an electrophotographic copying machine. In this cleaning device, a rubber blade pressed against the surface of the image carrier blocks the residual toner at the edge portion and removes the residual toner by scraping it off. The rubber blade has various advantages such as high adhesion to the surface of the image carrier, less damage to the surface, and easy setting of the contact pressure with the image carrier.
[0003]
On the other hand, removed toner, external additives, and the like are accumulated in the vicinity of the pressure contact portion (hereinafter simply referred to as “pressure contact portion”) between the edge of the rubber blade and the surface of the image carrier. If the rubber blade is used for a long time, the load due to these accumulations increases, the edge is lifted, and the cleaning performance may be deteriorated.
As the cleaning performance decreases, the external additive having a small particle diameter passes through the pressure contact portion. If the external additive or toner that has passed in this way is fixed or embedded in the image carrier, it is not preferable because it causes deterioration of image quality. Further, the toner and the external additive may be aggregated because they stay while receiving pressure from the edge portion for a long time. Such an agglomerate promotes partial edge breakage and wear, and as a result, causes a so-called cleaning failure in which toner or the like is not removed.
[0004]
In order to avoid such a situation, a technique for preventing deterioration of the blade edge by reciprocating a rubber blade in the axial direction of the image carrier is known. According to this technique, the reciprocating motion gives a minute deformation to the blade edge, and the toner and the external additive are less likely to accumulate in the pressure contact portion. However, if excessive vibration is applied to the image carrier, the image quality may be deteriorated. Therefore, in this technique, image quality deterioration is prevented by controlling the stroke or speed of the reciprocating motion of the blade. Such a conventional technique is disclosed in Patent Document 1, for example.
[0005]
[Patent Document 1]
JP-A-64-40875
[0006]
[Problems to be solved by the invention]
By the way, in recent years, the demand for higher image quality in image forming apparatuses is severe, and the toner tends to become smaller in diameter and spherical. In order to remove the small-diameter and spherical toner with the rubber blade, it is necessary to increase the pressing force with the image carrier or to improve the adhesion to the image carrier. However, if the blade is reciprocated under such a condition that the frictional force with the image carrier is increased, the deterioration of the blade is promoted, which is not preferable.
The present invention has been made in view of the above-described circumstances, and reduces the cleaning performance due to accumulation of toner, external additives, etc. without applying an excessive burden on the blade, and the blade edge due to an aggregate of these fine particles. An object of the present invention is to provide an image carrier cleaning device capable of preventing wear and loss of the image and an image forming apparatus using the same.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the image carrier cleaning device according to the present invention has a blade shape in particular to block and remove deposits such as residual toner attached to the surface of the image carrier that is driven to rotate. The apparatus is characterized by comprising deposit removing means and gas discharge means for discharging gas to the deposit accumulated in the vicinity of the blocked position.
According to such a cleaning apparatus, the aggregate of toner and external additive accumulated near the pressure contact portion between the deposit removing means and the image carrier surface is blown off by the gas discharge means, so that an excessive burden is applied to the blade edge. Therefore, there is little risk of blade wear or breakage. Accordingly, the life of the blade is extended, and as a result, the durability and reliability of the image forming apparatus on which the cleaning device is mounted can be improved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0009]
<First Embodiment>
<Outline of Image Forming Apparatus 100>
FIG. 1 is a sectional view of a cleaning device 300 according to the first embodiment of the present invention and its installation environment. The cleaning device 300 is a device that is used in the image forming apparatus 100 and removes residual toner attached on the photosensitive drum 200 that is an image carrier. First, the image forming apparatus 100 will be described.
[0010]
The photosensitive drum 200 is rotationally driven at 220 mm / sec in the direction of the arrow a by a driving device (not shown). This rotational speed is a linear speed that an arbitrary point has in the tangential direction on the surface of the photosensitive drum 200.
The bias charging roll 10 is a charging device for charging the photosensitive drum 200, and a voltage in which an AC voltage is superimposed on a DC voltage is applied. The bias charging roll 10 and the photosensitive drum 200 face each other with a minute gap therebetween, and the surface of the photosensitive drum 200 is uniformly charged by a discharge generated in the gap. In this embodiment, the charging potential is −700V.
The exposure beam 20 is an exposure beam emitted from an exposure apparatus (not shown). The photosensitive drum 200 has photoconductivity, and the portion irradiated with the exposure beam 20 becomes conductive, and the charged charge escapes, and the charged charge remains only in the portion that is not exposed. The exposure apparatus irradiates the surface of the photosensitive drum 200 with the exposure beam 20 according to an exposure pattern based on an image pattern to be formed in advance. The exposed portion has a reduced surface potential. In the present embodiment, the surface potential of the exposed portion is −300V. When this exposure is completed, an electrostatic latent image is formed on the surface of the photosensitive drum 200 due to charged charges.
[0011]
The developing device 30 is a device that visualizes the electrostatic latent image formed on the photosensitive drum 200. The developing roll 31 of the developing device 30 includes a rotatable developing sleeve (not shown) made of a nonmagnetic material such as aluminum or SUS, and a magnet roll (not shown) fixedly disposed in the developing sleeve. While the gap between the developing sleeve and the peripheral surface of the photosensitive drum 200 is kept constant, the photosensitive drum 200 is rotationally driven at 1.75 times the rotational speed of the photosensitive drum 200, that is, 385 mm / sec. The rotational speed here is also a linear speed that an arbitrary point in the surface of the developing roll 31 has in the tangential direction, like the photosensitive drum 200.
[0012]
Inside the developing device 30, a two-component developer composed of toner (including an external additive) and a carrier is stirred, and the toner is frictionally charged by the stirring. The two-component developer adheres onto the developing sleeve by the magnetic force of the magnet roll, and is carried to a developing position close to the photosensitive drum 200 as the developing sleeve rotates. Here, a developing bias is applied to the developing roll 31, and the developer adheres to the photosensitive drum 200, so that the electrostatic latent image becomes a toner image that is a visible image. In the present embodiment, a developing bias is used in which a rectangular wave AC voltage having a peak-to-peak voltage of 1.0 kV, a frequency of 4.0 kHz, and a duty ratio of 0.6 is superimposed on a DC voltage of −580V.
[0013]
Here, the developer will be described.
The toner used in this embodiment is prepared by an emulsion polymerization method and has a volume average particle size of 5.8 μm. That is, it is an embodiment of a small-diameter toner having a particle diameter of 3 to 7 μm, which is difficult to remove with a conventional blade. A toner shape factor is a numerical value representing the shape of the toner. The toner shape factor is obtained by calculating the area ratio between the projected area of the toner and the circle circumscribing the toner for a plurality of toner particles and taking a representative value thereof. The calculation formula is represented by the following formula (1). The toner shape factor is “100” when the toner is a true sphere, and increases as the shape collapses. In the present embodiment, the toner shape factor is “130”, which is close to a true sphere. That is, the toner used in this embodiment is a small-diameter and spherical toner.
[Expression 1]

[0014]
An external additive having an average particle diameter of 10 to 150 nm is added to the toner. The external additive adheres to the toner and controls charging of the toner or forms an appropriate gap between the toners. In this embodiment, the external additive includes silica (SiO 2 ₂ ) Or titania (TiO) ₂ ) -Based inorganic fine particles are used. The carrier for imparting electric charge to the toner is ferrite beads having an average particle diameter of 35 μm.
[0015]
Returning to the description of the image forming apparatus 100. A toner image that is a visible image formed on the surface of the photosensitive drum 200 is transferred to the transfer material 41 by the transfer device 40. Then, the transfer material 41 holding the toner image is subjected to fixing processing such as heating and pressing by a fixing device (not shown), and is then discharged out of the device. Image formation by the image forming apparatus 100 is generally performed in such a process.
[0016]
On the other hand, the transfer efficiency of the developer from the photosensitive drum 200 to the transfer material 41 is not 100%. Therefore, so-called residual toner adheres to the surface of the photosensitive drum 200 after passing through the transfer device 40. Of course, external additives remain on the photosensitive drum in the same manner, but here they are referred to as residual toner. As described above, if the residual toner is left as it is, it causes deterioration of image quality. In the image forming apparatus 100, the residual toner is removed by the cleaning device 300 according to the present embodiment.
[0017]
<Configuration of Cleaning Device 300>
FIG. 2 is a cross-sectional view of the cleaning device 300 in FIG. Hereinafter, the cleaning apparatus 300 according to the first embodiment of the present invention will be described using FIGS. 1 and 2 as appropriate.
[0018]
The cleaning device 300 is provided downstream of the transfer device 40 in the rotation direction of the photosensitive drum 200 (hereinafter, simply referred to as “downstream”, and “upstream” is also defined in the same manner), and along the photosensitive drum 200. From the installed housing 310, the air ejection device 320 and the removal toner transport device 330 partially installed in the housing 310, and the cleaning blade 340 (hereinafter referred to as “blade 340”) having one end fixed to the housing 310. Become.
[0019]
The housing 310 is fixed in a state where an opening that is elongated in the axial direction of the photosensitive drum 200 is close to the photosensitive drum 200. As shown in FIG. 1, the inside of the housing 310 is a space that gradually spreads downward as it goes from the opening to the inside of the housing 310. Further, a discharge port 311 for preventing an increase in atmospheric pressure in the housing 310 is provided in a part of the side surface of the housing 310. The discharge port 311 is covered with a filter (not shown).
[0020]
In FIG. 1, one end of a blade 340 having substantially the same length as the opening side of the housing 310 is fixed to the upper end of the opening of the housing 310. The free end of the blade 340 is in pressure contact with the surface of the photosensitive drum 200. Under such a configuration, the blade 340 blocks the residual toner that has entered the housing 310 while adhering to the surface of the photosensitive drum 200 at the press contact portion, and removes the residual toner from the photosensitive drum 200.
In this embodiment, the blade 340 is made of urethane rubber having a JISA hardness of “75”, a rebound resilience of 47%, a thickness of 2 mm, and a free length of 8 mm. The blade 340 bites the edge portion of the photosensitive drum 200 1 mm into the surface of the photosensitive drum 200 at a contact angle of 25 degrees, and is pressed against the photosensitive drum 200 with a pressing force of 3.5 gf / mm. Yes. Here, “3.5 gf” is a pressing force acting on a substance having a mass of 3.5 g.
[0021]
In the housing 310, a part of each of the air discharge device 320 and the removal toner transport device 330 is provided. First, the air discharge device 320 will be described. The air discharge device 320 is a device that discharges compressed air onto the photosensitive drum 200, and includes an air conveyance path 321, an air discharge nozzle 322, and a compressed air supply device 323.
[0022]
FIG. 3 is a block diagram of the compressed air supply device 323. The compressed air supply device 323 includes an air pump 324, an air tank 325, an electromagnetic valve 326 provided in the air tank 325, and a control device 327 that controls the operation of the compressed air supply device 323 including opening and closing of the electromagnetic valve 326.
[0023]
Under such a configuration, air is appropriately fed from the air pump 324 and accumulated in the air tank 325. When the accumulated amount of air in the air tank 325 becomes sufficient, the control device 327 opens the electromagnetic valve 326 at a desired timing. An air conveyance path 321 is connected to the air tank 325 via an electromagnetic valve 326, and the air compressed in the air tank 325 is supplied to the air conveyance path 321 by opening the electromagnetic valve 326. The air conveyance path 321 is connected to an air discharge nozzle 322 provided in the housing 310. The outer wall portion of the housing 310 and the outer wall portion of the air conveyance path 321 are joined while maintaining airtightness so that the gas in the housing 310 does not leak out of the housing.
[0024]
The air discharge nozzle 322 is disposed in the housing 310 so as to face the photosensitive drum 200 through the opening of the housing 310. The air discharge nozzle 322 has a slit-like discharge port having a length substantially the same as the long side of the opening at the tip, and the discharge port is a press-contact portion between the photosensitive drum 200 and the blade 340 (hereinafter, simply “ "Pressing part"). The air discharge nozzle 322 is installed at a position 2.5 mm upstream from the pressure contact between the blade 340 and the photoconductive drum 200 so that the discharge port is arranged at a position 2 mm perpendicularly away from the surface of the photoconductive drum 200. Is decided. The slit width of the discharge port of the air discharge nozzle 322 is 0.3 mm, and the width is slightly increased toward the connection portion with the air conveyance path 321. Compressed air having a maximum flow velocity of 50 m / sec is discharged from the air discharge nozzle 322.
[0025]
Next, the removal toner conveyance device 330 will be described.
One end of a cylindrical removal toner transport pipe 331 is joined to the lower part of the joint surface between the housing 310 and the air transport path 321, and is connected to the housing 310 inside thereof. In this joint portion, the outer wall of the housing 310 and the outer wall of the removal toner transport pipe 331 are airtightly joined in the same manner as the air transport path 321 described above. In the vicinity of the other end of the removed toner transport pipe 331, a toner recovery tank 332 is installed downward.
[0026]
A transport auger 333 is installed in the housing 310 below the air transport path 321. The transport auger 333 is provided with a plate-like member spirally provided on a rotating shaft extending in the axial direction of the photosensitive drum 200. The rotation axis of the conveyance auger 333 passes through the joint portion between the removal toner conveyance tube 331 and the housing 310, and one end thereof is fixed to the end portion of the removal toner conveyance tube. It is connected to a drive device (not shown) and is rotatable. By this rotation, the transfer auger 333 can slowly carry the particles present in the vicinity to the left in FIG.
[0027]
<Operation of Cleaning Device 300>
The operation of the cleaning apparatus 300 having such a configuration will be described.
As the photosensitive drum 200 rotates, residual toner accumulates in the pressure contact portion. As described above, the residual toner includes an external additive in addition to the toner. Some of the residual toner removed from the photosensitive drum 200 by the blade 340 naturally falls into the installation space of the transport auger 333 by gravity. Since the transport auger 333 rotates as described above, these fine particles slowly move leftward in FIG. 2 in the removed toner transport pipe, and finally fall toward the toner collection tank 332.
[0028]
Except those that naturally deviate from the pressure contact portion, the material is deposited on the pressure contact portion for a certain period of time. FIG. 4 is an enlarged view of the vicinity of the pressure contact portion. As shown in the figure, the space is wedge-shaped from the pressure contact portion to the upstream side, and the closer to the pressure contact portion, the smaller the gap between the photosensitive drum 200 and the blade 340. Therefore, the particles deposited on the pressure contact portion have different areas depending on the size of the particles. In the present embodiment, from the press contact portion toward the upstream side, the external additive having a small particle size, the external additive having a large particle size, the aggregate of the external additive, and the toner are accumulated in this order.
[0029]
The air discharge device 320 has its air discharge timing and discharge time controlled by the control device 327. In the present embodiment, the control device 327 performs control so that air is discharged for 0.5 seconds every time one image formation is completed. Since the discharge port of the air discharge nozzle 322 is disposed toward the pressure contact portion, the discharged air reaches the pressure contact portion directly. At this time, as is apparent from FIG. 4, the discharged air contacts the toner deposited on the outermost side. The toner is separated from the pressure contact portion by air and scattered in the housing 310. In addition, a part of the discharged air reaches the aggregate of the external additive accumulated on the inside of the toner through the gap generated when the toner is separated from the press contact portion. Due to this air, a part of the aggregate of the external additive is also separated from the press contact portion in the same manner as the toner, and is scattered in the housing 310. The scattered toner and the aggregate of the external additive naturally fall to the vicinity of the conveyance auger by gravity, pass through the removed toner conveyance pipe 331, and are collected in the toner collection tank. As a result, particles having a relatively large particle size such as aggregates of toner and external additives are removed from the residual toner from the press contact portion.
[0030]
In this way, the cleaning device according to the present embodiment can reliably remove the large particle size particles mainly composed of aggregates of toner and external additives accumulated upstream of the pressure contact portion. Therefore, it is possible to prevent the blade 340 from being damaged or worn by these large particle diameter particles. Even with this air discharge, the small particle size particles (small particle size external additive or large particle size external additive) that accumulate near the edge of the blade 340 may remain in the pressure contact portion without being blown off. Many. However, these fine particles having a small particle diameter have an effect of reducing the frictional force between the blade 340 and the photosensitive drum 200, and thus are not necessarily removed.
[0031]
As described above, the cleaning device 300 according to the present embodiment is controlled to intermittently discharge air by the control device 327, and is configured not to discharge a large amount of air unnecessarily. Therefore it is very economical. Further, the air discharge nozzle 322 according to the present embodiment is configured such that the slit width of the air discharge port at the tip is smaller than the width of the joint with the air conveyance path 321. Therefore, a very large air flow rate can be obtained with a small air supply amount. For this reason, combined with the intermittent air discharge control described above, the compressed air supply device 323, and hence the cleaning device 300, is very compact and simple. Therefore, the cleaning device 300 has a high installation property. Further, since the air supply amount is small, an increase in air pressure in the housing 310 can be suppressed, so that it is possible to avoid ejection of a removing substance such as toner or an external additive from the opening of the housing 310 or the like.
[0032]
In addition, the cleaning device 300 according to the present embodiment removes residual toner by air discharge. However, the mode using air is not limited to this, and the residual toner is also removed by using an air suction device. be able to. However, air suction often does not have the residual toner removal efficiency as much as air discharge. This is because the sucked air has less directivity than the discharged air. Furthermore, there are many restrictions on installation in order to perform cleaning by air suction. According to the aspect of the present embodiment, these problems do not occur, and it is preferable because fine particles can be removed with a very simple configuration as compared with cleaning by air suction.
[0033]
In the cleaning device 300 according to the present embodiment, the housing 310 is provided with a plurality of discharge ports 311 from which air is discharged. Further, since the exhaust port 311 is provided with a filter, the removed toner does not scatter from the housing. When compressed air is discharged into the housing 310, there is a concern that the pressure in the housing 310 increases. However, since air is appropriately discharged from the discharge port 311, in this embodiment, the pressure increase in the housing 310 is It stays very little. Therefore, a situation in which the removed toner is ejected out of the housing due to an increase in pressure inside the housing 310 does not occur.
In addition, since air is directly discharged to the pressure contact portion, the pressure in the vicinity of the pressure contact portion tends to increase locally, but the inside of the housing 310 is a space gradually widened from the opening toward the inside downward. Thus, this pressure increase is immediately relieved by this space. As described above, in the cleaning device 300 according to the present embodiment, the pressure increase inside the housing 310 is extremely difficult to occur.
[0034]
In the image forming apparatus 100 according to the present embodiment, the toner image is directly transferred to the transfer material 41, but the aspect of the image forming apparatus is not limited to this. For example, an intermediate transfer type image forming apparatus that once transfers a toner image to an intermediate transfer member having an endless belt shape, and further transfers the toner image on the intermediate transfer member to a transfer material is the same as that of the present embodiment. An effect can be obtained.
Further, the cleaning target of the cleaning device is not limited to the aspect of this embodiment. For example, it may be suitably used for removing residual toner on the surface of the intermediate transfer member. Furthermore, in the case of an image forming apparatus having an image carrier, the cleaning device according to the present invention can be used for removing residual toner on the image carrier.
[0035]
In this embodiment, the control device 327 controls the opening and closing of the electromagnetic valve 326 so that air is discharged at the end of image formation in order to avoid adverse effects on image quality, but the timing of air discharge is limited to this. Not. Even during image formation, air discharge may be performed in a so-called inter-image portion between images. Furthermore, air discharge may be performed during image formation within a range that does not affect image formation.
[0036]
Moreover, in this embodiment, although the discharge time of air is 0.5 second, the aspect of implementation is not limited to this. Even longer than this, the effect according to the present embodiment is not inhibited. Further, the air discharge may be always discharged instead of intermittent. Also, the air flow rate is not limited to this mode, and can be freely determined within a range in which large particle diameter particles upstream of the pressure contact portion can be removed. This air flow rate can be freely set depending on the configuration of the compressed air supply device and the structure of the air conveyance path or the air discharge nozzle. Therefore, for example, when it is desired to further shorten the air discharge time, it is possible to easily realize the residual toner removal property by increasing the air flow rate.
[0037]
Although the present embodiment uses an image forming apparatus in which the free end of the blade 340 faces downward, the installation form of the blade is not limited to this. In an image forming apparatus that presses against the photosensitive drum with the free end of the blade facing upward, accumulation of residual toner in the press contact portion is more conspicuous, but the present invention also relates to such an image forming apparatus. A cleaning device can be used.
[0038]
In the present embodiment, the air discharge nozzle 322 is installed at a position where air is directly blown from the discharge port to the pressure contact portion, but the positions of the air discharge nozzle and the air discharge port are not limited thereto. It is only necessary that the air discharged from the air discharge port reaches the large particle diameter particles located on the upstream side of the pressure contact portion and can be removed. For example, even if the air discharge port is provided further upstream than the present embodiment, the air can easily reach the upstream of the pressure contact portion by controlling the air flow rate as described above.
In this embodiment, compressed air is discharged to remove residual toner, but the gas to be discharged is not limited to this. For example, a chemically inert gas such as argon gas may be used.
[0039]
Second Embodiment
In the first embodiment described above, the direction of the air discharge port is substantially perpendicular to the rotation axis of the photosensitive drum 200. If air is discharged in such a direction, the air convection area at the pressure contact portion is small, and the pressure rises locally, and there is a possibility that the residual toner removing effect cannot be obtained sufficiently. Here, a cleaning device capable of solving such a problem will be described.
[0040]
FIG. 5 is a cross-sectional view for explaining the cleaning device 400 according to the second embodiment of the present invention and its installation environment. In addition, the same code | symbol is attached | subjected to the location which overlaps with FIG. 1, and the description is abbreviate | omitted. The air discharge device 320 according to the present embodiment is different from the first embodiment in that it has a plurality of air discharge nozzles 401 instead of the air discharge nozzles 322.
[0041]
The air discharge nozzle 401 is a nozzle having a shape in which the tip is tapered toward the discharge port, such as the vicinity of the apex of a cone. The nozzles have a discharge port diameter of 2.5 mm, and a plurality of nozzles are arranged at a pitch of 20 mm along the axial direction of the photosensitive drum 200. The position of the discharge port of the air discharge nozzle 401 is the same as in the first embodiment. Further, the maximum flow velocity of air discharged from the air discharge nozzle 401 is 100 m / sec. The air discharge nozzle 401 is configured such that the air discharge port is not orthogonal to the rotation axis of the photosensitive drum 200 and the discharged air is directed to the discharge port 311 provided at the left end of the housing 310 in FIG. Further, they are disposed in a moderately inclined state.
[0042]
Under this configuration, when compressed air is discharged from the air discharge nozzle 401, the air flows along the surface of the photosensitive drum 200 in the direction of the rotation axis. The discharged air is first jetted directly to the portion facing each discharge port upstream of the press contact portion, and the residual toner accumulated in that portion is blown off in the direction of the rotation axis of the photosensitive drum 200 and then flows along the same direction. The residual toner adjacent to the blown toner is also blown off in the direction of the rotation axis of the photosensitive drum 200.
[0043]
Thus, according to the aspect of the present embodiment, it is not necessary to provide the air discharge nozzle in the axial direction of the photosensitive drum 200 over the entire width of the photosensitive drum 200. Therefore, the amount of air used in the air discharge device 320 can be reduced, and further cost reduction can be achieved. Further, the discharged air flows along the axial direction of the photosensitive drum and travels toward a discharge port 311 provided in the housing 310. Accordingly, unnecessary pressure is not generated by the discharged air entering the sealed space, and the residual toner removing effect is further enhanced.
[0044]
【The invention's effect】
As described above, the cleaning device according to the present invention ensures that the large particle size particles, such as toner and agglomerates of external additives, deposited on the upstream side in the vicinity of the press contact portion are reliably separated from the press contact portion by an inexpensive configuration. Can be removed. Therefore, it is possible to prevent the cleaning blade from being damaged or worn by the particles having a large particle diameter.
In the image forming apparatus according to the present invention, residual toner is removed from the photosensitive drum by the cleaning device according to the present invention. Therefore, it is difficult to cause image quality deterioration due to poor cleaning or wear or loss of the cleaning blade, and the lifetime of the cleaning blade is extended, so that the running cost of the apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a cleaning apparatus 300 according to a first embodiment of the present invention and its installation environment.
2 is a cross-sectional view of the cleaning device 300 as viewed from the direction A in FIG.
3 is a block diagram of a compressed air supply device 323 in the cleaning device 300. FIG.
FIG. 4 is an enlarged view of the vicinity of a pressure contact portion between a blade 340 and a photosensitive drum 200 according to the embodiment.
FIG. 5 is a sectional view of a cleaning device 400 according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Bias charging roll, 20 ... Exposure beam, 30 ... Developing device, 31 ... Developing roll, 40 ... Transfer device, 41 ... Transfer material, 100 ... Image forming device , 200 ... photosensitive drum, 300 ... cleaning device, 310 ... housing, 311 ... discharge port, 320 ... air discharge device, 321 ... air conveying path, 322 ... air discharge Nozzle, 323 ... Compressed air supply device, 324 ... Air pump, 325 ... Air tank, 326 ... Solenoid valve, 327 ... Control device, 330 ... Removal toner conveying device, 331 ... Removal toner transport pipe, 332... Toner collection tank, 333... Transport auger, 340... Cleaning blade, 400.

Claims (7)

An adhering matter removing means for blocking and removing adhering matters such as residual toner adhering to the surface of the image carrier to be rotated;
A cleaning device for an image carrier, comprising: a gas discharge unit that discharges gas to the deposit accumulated in the vicinity of the blocked position. 2. The image carrier cleaning device according to claim 1, wherein the attached matter removing means has a blade shape, and an end thereof is pressed against the surface of the image carrier. 3. The image carrier cleaning apparatus according to claim 1, wherein the gas discharge unit has a discharge port whose cross-sectional area decreases toward the tip, and discharges the gas from the discharge port. apparatus. 4. The image carrier cleaning apparatus according to claim 1, wherein the gas discharge means includes a plurality of discharge ports and discharges gas in a direction that forms an acute angle with a rotation axis of the image carrier. . 5. The image carrier cleaning device according to claim 1, wherein the gas discharge means discharges gas intermittently. An image carrier for carrying an electrostatic latent image;
An image forming apparatus having a developing device that visualizes the electrostatic latent image with a developer,
An image forming apparatus comprising the image bearing member cleaning device according to claim 1. The image forming apparatus according to claim 6, wherein the image carrier cleaning device removes the developer adhering to the image carrier.

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