JP2004085629A - Developing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably and uniformly coat a developing sleeve with a developer into a thin layer, especially upstream even in the case of using magnetic one-component developer. <P>SOLUTION: The 1st magnetic pole (N2 pole) of a fixed magnet roller 3h and the 2nd magnetic pole (S1 pole) of a fixed magnet roller 3i arranged to be fixed respectively in the respective developing sleeves 3a and 3b arranged to be opposed proximately are adapted to have a different polarity from each other, and the half value width of the magnetic force pattern of the 1st magnetic pole (N2 pole) of the roller 3h in the normal direction of the sleeve 3a in the vicinity of the proximately opposed positions of the sleeves 3a and 3b is made larger on a photoreceptor drum side than on the inner part side of a developing container, whereby the sleeve 3a is stably and uniformly coated with the developer of the thin layer. <P>COPYRIGHT: (C)2004,JPO

Description

【００６７】
なお、式中のＲ_１、Ｒ_２、Ｒ_３、Ｒ_４は、夫々置換基を有してもよいアルキル基、置換基を有してもよいアリール基、アルアルキル基を表わし、Ｒ_１〜Ｒ_４は夫々同一でも或いは異なっていてもよい。Ｘ⁻は、酸の陰イオンを表わす。
【００６８】
上記の化学式において、Ｘ⁻の酸イオンの具体例としては、有機硫酸イオン、有機スルホン酸イオン、有機リン酸イオン、モリブデン酸イオン、タングステン酸イオン、モリブデン原子或いはタングステン原子を含むヘテロポリ酸等が挙げられる。
【００６９】
また、下記の化学式に示すように、フェノール樹脂に特定の第４級アンモニウム塩化合物を添加した樹脂組成物を使用して被覆層を形成すると、上述したように結着樹脂であるフェノール樹脂を加熱硬化させて被覆層を形成した場合に、該第４級アンモニウム塩化合物がフェノール樹脂の構造中に取り込まれる。このため、ネガ性シリカ粒子或いはネガ性テフロン（登録商標）粒子等のような粒子添加系の場合と異なり、部分的にではなく、被覆層全体として正帯電性現像剤（ポジトナー）に対する正摩擦帯電付与性が向上する。更に、粒子添加系の被膜と異なり、加工性が損なわれたり、被覆層の強度低下を生じることもない。
【００７０】
【化２】

【００７１】
本実施の形態に好適に用いられる第４級アンモニウム塩化合物としては、具体的には下記の各化学式に示すようなものが挙げられるが、勿論、これらに限定されるものではない。
【００７２】
【化３】

【００７３】
【化４】

【００７４】
【化５】

【００７５】
【化６】

【００７６】
【化７】

【００７７】
【化８】

【００７８】
【化９】

【００７９】
【化１０】

【００８０】
本実施の形態において使用する結着樹脂を構成するフェノール樹脂として、その製造工程において触媒として含窒素化合物を用いて製造されたものを用いると、特に、加熱硬化時に第４級アンモニウム塩化合物がフェノール樹脂の構造中に取り込まれ易く、トナーのチャージアップ防止に好ましいことが分かった。
【００８１】
従って、本実施の形態においては、このような作用を有する、その製造工程において触媒として含窒素化合物を用いて製造されたフェノール樹脂を、現像スリーブ３ａ，３ｂ上の被覆層を構成する材料の１つとして用いれば、トナーのチャージアップを防止することが可能となる。
【００８２】
本実施の形態で好適に使用し得る、フェノール樹脂の製造工程において触媒として用いられる含窒素化合物としては、例えば、酸性触媒としては、硫酸アンモニウム、燐酸アンモニウム、スルファミド酸アンモニウム、炭酸アンモニウム、酢酸アンモニウム、マレイン酸アンモニウムといったアンモニウム塩又はアミン塩類が挙げられ、塩基性触媒としては、アンモニア、或は、ジメチルアミン、ジエチルアミン、ジイソプロピルアミン、ジイソブチルアミン、ジアミルアミン、トリメチルアミン、トリエチルアミン、トリｎ−ブチルアミン、トリアミルアミン、ジメチルベンジルアミン、ジエチルベンジルアミン、ジメチルアニリン、ジエチルアニリン、Ｎ，Ｎ−ジｎ−ブチルアニリン、Ｎ，Ｎ−ジアミルアニリン、Ｎ，Ｎ−ジｔ−アミルアニリン、Ｎ−メチルエタノールアミン、Ｎ−エチルエタノールアミン、ジエタノールアミン、トリエタノールアミン、ジメチルエタノールアミン、ジエチルエタノールアミン、エチルジエタノールアミン、ｎ−ブチルジエタノールアミン、ジｎ−ブチルエタノールアミン、トリイソプロパノールアミン、エチレンジアミン、へキサメチレンテトラミン等のアミノ化合物、ピリジン、α−ピコリン、β−ピコリン、γ−ピコリン、２，４−ルチジン、２，６−ルチジン等のピリジン及びその誘導体、キノリン化合物、イミダゾール、２−メチルイミダゾール、２，４−ジメチルイミダゾール、２−エチル−４−メチルイミダゾール、２−フェニルイミダゾール、２−フェニル−４−メチルイミダゾール、２−へプタデシルイミダゾール等のイミダゾール及びその誘導体等の含窒素複素環式化合物等が挙げられる。
【００８３】
また、上記被覆層の抵抗値を、上記の値に調整するためには、下記に挙げる導電性物質を被覆層中に含有させることが好ましい。この際に使用される導電性物質としては、例えば、アルミニウム、銅、ニッケル、銀等の金属粉体、酸化アンチモン、酸化インジウム、酸化スズ等の金属酸化物、カーボンファイバー、カーボンブラック、グラファイト等の炭素物等が挙げられる。
【００８４】
本実施の形態においては、これらのうちカーボンブラック、とりわけ導電性のアモルファスカーボンは特に電気伝導性に優れ、高分子材料に充填して導電性を付与したり、その添加量をコントロールするだけで、ある程度任意の導電度を得ることができるため、好適に用いられる。
【００８５】
そして、最終的なコート膜は、フェノール樹脂２５０重量部に対して平均粒径７．５μｍのグラファイト９０重量部、カーボン１０重量部、４級アンモニウム７０部を混合して形成されている。ちなみに、グラファイトとカーボンの比は膜全体の抵抗の安定化のため、グラファイトをカーボンの３倍以上にすることが好ましい。そして、上記のコート膜を吹き付け法により現像スリーブ３ａ，３ｂ表面に塗付後、１５０℃で３０分間乾燥させる。
【００８６】
上記した本実施の形態におけるコート膜を現像スリーブ３ａ，３ｂ表面にそれぞれ形成することで、通常は下流側の現像スリーブ３ｂ表面のトリボ（帯電量）が大きいのに対して、本実施の形態では、現像スリーブ３ａ表面で９μＣ／ｇ、現像スリーブ３ｂで９．２μＣ／ｇと略同等な値に制御することができた。これにより、高温高湿や常温低湿など環境の変化に対しても各現像スリーブ３ａ，３ｂ表面のトリボ（帯電量）が最適化されることによって、安定した現像特性を得ることができた。
【００８７】
また、現像スリーブ３ａ，３ｂ内には、図１６に示すように固定マグネットローラ３ｈ、３ｉがそれぞれ固定配置されている。現像スリーブ３ａ内の固定マグネットローラ３ｈは、図４に示すような磁場パターンを有する各磁極（Ｎ１、Ｎ２、Ｎ３、Ｓ１、Ｓ２）が配置されている。一方、現像スリーブ３ｂ内の固定マグネットローラ３ｉは、図５に示すような磁場パターンを有する各磁極（Ｎ１、Ｎ２、Ｓ１、Ｓ２）が配置されている。
【００８８】
現像スリーブ３ａ，３ｂは、感光ドラム１の回転速度（プロセススピード）に対して１２５％の速度で回転し、現像位置での現像スリーブ３ａ，３ｂと感光ドラム１間の隙間（ギャップ）はそれぞれ２５０μｍである。固定マグネットローラ３ｈの磁力によって現像スリーブ３ａ上に担持されるトナーは層厚規制ブレード３ｄでコート厚が規制され、固定マグネットローラ３ｉの磁力によって現像スリーブ３ｂ上に担持されるトナーは現像スリーブ３ａでコート厚が規制される。なお、現像スリーブ３ａと現像スリーブ３ｂの回転中心を結ぶ直線上における現像スリーブ３ａと現像スリーブ３ｂ間の隙間（ギャップ）は４００μｍである。
【００８９】
現像スリーブ３ａ，３ｂには、現像バイアス電源（不図示）から−５５０Ｖの直流バイアスと交流バイアス（本実施の形態では、図６に示すようなピーク間電圧（Ｖｐｐ）１５００Ｖ、周波数２．７ｋＨｚの矩形波）を重畳した現像バイアスが印加されることにより、トナー（磁性一成分トナー）を感光ドラム１側に飛翔させて静電潜像を非接触現像する。この時の現像コントラストは飛翔方向に３５０Ｖであり、かぶりとりコントラストは１５０Ｖである。
【００９０】
また、本実施の形態においても、実施の形態１と同様に図１４（ａ）に示したように、現像スリーブ３ａと現像スリーブ３ｂの対向位置における現像スリーブ３ａ側の磁極Ａの法線方向の磁極パターンの半値幅が、感光ドラム側を現像器内部側よりも大きくなるように構成されており、本実施の形態では、現像スリーブ３ａ側の磁極Ａの法線方向における磁極パターンの半値幅は、感光ドラム側を現像器内部側の２倍とした。
【００９１】
具体的には、現像スリーブ３ａ側の磁極Ａの法線方向における磁極パターンの半値幅は６０°であり、感光ドラム側を４０°、現像器内部側を２０°とした。
【００９２】
そして、本実施の形態においても、図１３、図１５に示した実施の形態１と同様の検討を行った結果、実施の形態１と同様の結果を得ることができた。
【００９３】
このように本実施の形態では、現像装置３の現像スリーブ３ａ，３ｂに上記したコート膜をそれぞれ形成することにより、上流側の現像スリーブ３ａ上でのトナーのつれ回りを低減してトナー劣化を低減し、かつ、現像スリーブ３ａ，３ｂ表面に担持されるトナーのトリボを良好に制御することができる。
【００９４】
また、本実施の形態においても、実施の形態１と同様に、上流側の現像スリーブ３ａ上及び下流側の現像スリーブ３ｂ上にも安定して均一に現像剤（磁性一成分トナー）を薄層にコートすることができるので、現像スリーブ３ｂ上のトナーコートの状態が良く、濃度ムラのない良好な出力画像を得ることができる。
【００９５】
〈実施の形態３〉
図１７は、本実施の形態に係る現像装置を備えた画像形成装置を示す概略構成図である。なお、実施の形態１、２に示した現像装置を備えた画像形成装置と同一機能を有する部材には同一符号を付し、重複する説明は省略する。
【００９６】
本実施の形態における画像形成装置では、一次帯電器２により例えば−７００Ｖに帯電された矢印方向（時計方向）に所定の周速（本実施の形態では５００ｍｍ／ｓｅｃ）で回転している直径１０８ｍｍの感光ドラム１上に露光装置（不図示）により６００ｄｐｉで画像露光Ｌが与えられ、入力される画像情報に応じた静電潜像が形成される。
【００９７】
そして、この静電潜像に、現像部位にて感光ドラム１の帯電極性と同極性の現像バイアス（ＤＣ成分にＡＣ成分を重畳したバイアス）が印加された現像装置３の２つの現像スリーブ３ａ，３ｂにより、感光ドラム１の帯電極性と同極性に帯電された現像剤（本実施の形態では磁性一成分ネガトナー）ｔを付着させて、ジャンピング現像法により反転現像してトナー像として可視像化する。本実施の形態における現像バイアスは、周波数２４００Ｈｚ、ピーク間電圧１５００Ｖｐｐ、Ｄｕｔｙ５０％の交流電圧に＋２００Ｖの直流電圧を重畳したバイアス電圧を現像スリーブ３ａ，３ｂに印加した。
【００９８】
そして、トナー像が形成された感光ドラム１表面を転写前帯電器（ポスト帯電器）４で転写前帯電する。そして、感光ドラム１表面のトナー像が感光ドラム１と転写帯電器５間の転写部に到達すると、このタイミングに合わせて給紙カセット（不図示）内の用紙などの転写材Ｐが転写部に搬送されて、トナーと逆極性の転写電圧が印加された転写帯電器５によりトナー像が転写材Ｐに転写される。そして、トナー像が転写された転写材Ｐは分離帯電器６で感光ドラム１から分離されて定着装置８に搬送され、定着装置８の定着ローラ８ａと加圧ローラ８ｂ間の定着ニップ部にてトナー像を転写材Ｐに加熱、加圧して熱定着した後に、外部に排出する。
【００９９】
また、トナー像転写後の感光ドラム１表面に残留している転写残トナーは、クリーニング装置７によって除去され回収される。そして、クリーニング装置７に回収された廃トナー（リユーストナー）を、搬送パイプ１２を通してトナー補給容器１３に戻す。搬送パイプ１２にはスクリュー状の搬送部材（不図示）が内部に設けられており、この搬送部材（不図示）を回転することで廃トナー（リユーストナー）を搬送する。また、新しいトナーはトナー補給容器９に収納されている。
【０１００】
そして、実施の形態１で述べたように、トナー補給容器９とトナー補給容器１３にそれぞれ設けられているマグローラ９ａ、１３ａによる磁力でそれぞれのトナーが引きつけられ、マグローラ９ａ、１３ａが回転することにより現像容器３ｃ内にトナーが補給される。そして、現像容器３ｃ内で混ぜられたトナーは再び現像スリーブ３ａ，３ｂに送られ、感光ドラム１上の静電潜像をジャンピング現像法により反転現像してトナー像として可視像化する。なお、本実施の形態では、廃トナー（リユーストナー）と新しいトナーを現像容器３ｃ内で混ぜる構成であったが、トナー補給容器９とトナー補給容器１３の下部に混合するスペースを設けて混ぜても構わない。
【０１０１】
トナー補給容器９のマグローラ９ａの通常の回転速度は２回転／分で一定であり、トナー補給容器１３のマグローラ１３ａの回転速度を変化させる。マグローラ９ａとマグローラ１３ａは、現像容器３ｃ内のトナー量検知センサ（不図示）による検知信号に基づいて回転制御される。
【０１０２】
また、本実施の形態においても、実施の形態１と同様に図１４（ａ）に示したように、現像装置３の現像スリーブ３ａと現像スリーブ３ｂの対向位置における現像スリーブ３ａ側の磁極Ａの法線方向における磁極パターンの半値幅が、感光ドラム側を現像器内部側よりも大きくなるように構成されており、本実施の形態では、現像スリーブ３ａ側の磁極Ａの法線方向における磁極パターンの半値幅は、感光ドラム側を現像器内部側の２倍とした。具体的には、現像スリーブ３ａ側の磁極Ａの法線方向における磁極パターンの半値幅は６０°であり、感光ドラム側を４０°、現像容器３ｃ内部側を２０°とした。
【０１０３】
また、本実施の形態においても、実施の形態２と同様に現像スリーブ３ａ，３ｂ表面に上記したコート膜が形成されている。
【０１０４】
このように、回収した廃トナー（リユーストナー）を新しいトナーと共に現像容器３ｃに補給する本実施の形態の画像形成装置では、廃トナー（リユーストナー）は新しいトナーに比較してトリボが極端に小さいために反転成分トナー量が多く、現像スリーブ３ａ，３ｂ上のトナーの帯電安定性やトナーコート性が更に悪くなるが、本実施の形態では、実施の形態２で述べた構成の現像装置３を有しているので、上流側の現像スリーブ３ａ上でのトナーのつれ回りを低減してトナー劣化を低減し、かつ現像スリーブ３ａ，３ｂ表面に担持されるトナーのトリボを良好に制御することができる。
【０１０５】
また、本実施の形態においても、実施の形態１と同様に、上流側の現像スリーブ３ａ上及び下流側の現像スリーブ３ｂ上にも安定して均一に現像剤（磁性一成分トナー）を薄層にコートすることができるので、現像スリーブ３ｂ上のトナーコートの状態が良く、濃度ムラのない良好な出力画像を得ることができる。
【０１０６】
【発明の効果】
以上説明したように本発明によれば、第１の磁界発生部材の第１磁極と第２の磁界発生部材の第２磁極を異極性とし、第１の磁界発生部材の第１磁極の、第１及び第２の現像剤担持体の近接対向位置近傍における第１の現像剤担持体の法線方向の磁力パターンの半値幅を、現像容器内部側よりも像担持体側を大きくしたことにより、上流側の第１現像剤担持体上に安定して均一に現像剤を薄層にコートすることができるので、良好な現像動作を行うことができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１に係る現像装置を備えた画像形成装置を示す概略構成図。
【図２】本発明の実施の形態１に係る現像装置を示す概略断面図。
【図３】本発明の実施の形態１に係る現像装置の現像スリーブ内に設けた固定マグネットローラの磁極を示す図。
【図４】本発明の実施の形態１における上流側の現像スリーブ内に設けた固定マグネットローラの磁場パターンを示す図。
【図５】本発明の実施の形態１における下流側の現像スリーブ内に設けた固定マグネットローラの磁場パターンを示す図。
【図６】現像スリーブに印加する交流バイアスの波形を示す図。
【図７】各現像スリーブの端部近傍に設けた磁気シールを示す図。
【図８】各現像スリーブの端部近傍に設けた磁気シールを示す図。
【図９】本発明の実施の形態１における各現像スリーブの近接対向部での磁極Ａと磁極Ｂを示す図。
【図１０】本発明の実施の形態１における各現像スリーブの近接対向部での磁極Ａと磁極Ｂの極性を変えた場合における、下流側に位置する現像スリーブ上のトナーコート状態の検討結果を示す図。
【図１１】本発明の実施の形態１における上流側に位置する現像スリーブ上のトナーコート状態を説明するための図。
【図１２】本発明の実施の形態１における上流側に位置する現像スリーブ上のトナーコート状態を説明するための図。
【図１３】本発明の実施の形態１における各現像スリーブの近接対向部での磁極Ａと磁極Ｂの磁力を変化させた場合における、上流側に位置する現像スリーブ上のトナーコート状態の検討結果を示す図。
【図１４】（ａ）は、本発明の実施の形態１における、上流側に位置する現像スリーブの磁極Ａの法線方向の磁力パターンを示す図、（ｂ）は、従来例における、上流側に位置する現像スリーブの磁極Ａの法線方向の磁力パターンを示す図。
【図１５】本発明の実施の形態の上流側に位置する現像スリーブ３ａの磁極Ａの磁力が７０〜９０ｍＴの場合の磁極Ａの法線方向の磁力パターンの半値における、感光ドラム側の領域Ｘと現像器側の領域Ｙの幅を角度で示し、この角度を変化させたときの下流側に位置する現像スリーブ上のトナーコート状態の検討結果を示す図。
【図１６】本発明の実施の形態２に係る現像装置の現像スリーブ内に設けた固定マグネットローラの磁極を示す図。
【図１７】本発明の実施の形態３に係る現像装置を備えた画像形成装置を示す概略構成図。
【図１８】従来例における現像装置を備えた画像形成装置を示す概略構成図。
【図１９】従来例における現像装置の現像スリーブを示す図。
【図２０】従来例における現像装置の近接対向配置した２つの現像スリーブを示す図。
【図２１】従来例における現像装置の近接対向配置した２つの現像スリーブ上での二成分現像剤の流れを示す図。
【図２２】従来例における現像装置の近接対向配置した２つの現像スリーブ上での一成分現像剤の流れを示す図。
【符号の説明】
１　　　　感光ドラム（像担持体）
２　　　　一次帯電器
３　　　　現像装置
４　　　　転写前帯電器
５　　　　転写帯電器
６　　　　分離帯電器
７　　　　クリーニング装置
８　　　　定着装置
３ａ、３ｂ　　　　現像スリーブ（第１及び第２の現像剤担持体）
３ｃ　　　現像容器
３ｈ、３ｉ　　　　固定マグネットローラ（磁界発生部材）
９、１３　　　　　トナー補給容器
９ａ、１３ａ　　　マグローラ
１１ａ、１１ｂ　　磁気シール部材
１２　　　搬送パイプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device that develops an electrostatic latent image formed on an image carrier such as a photoreceptor to form a developer image, and a copying machine that includes the developing device and forms an image by an electrophotographic method or the like. And an image forming apparatus such as a printer and a facsimile.
[0002]
[Prior art]
FIG. 18 is a schematic configuration diagram showing a main part of a conventional electrophotographic image forming apparatus. This image forming apparatus includes a photosensitive drum 100 as an image carrier. The photosensitive drum 100 has a photoconductive layer such as OPC or a-Si on its surface, and is driven to rotate in the direction of an arrow (clockwise). .
[0003]
Then, after the surface of the photosensitive drum 100 is uniformly charged to, for example, −700 V by the primary charger 101, an image exposure L according to an image signal is performed to reduce the surface potential of the exposed portion on the photosensitive drum 100 to, for example, −. The voltage is attenuated to 200 V, and an electrostatic latent image is formed on the photosensitive drum 100 according to the image signal of the image. Then, the developing sleeve 102a of the developing device 102 to which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 100 is applied to the electrostatic latent image by a developing unit, the charging polarity (negative polarity) of the photosensitive drum 100 is applied. ), A developer (toner) t charged to the same polarity as that of the above is adhered and reversely developed, thereby visualizing the toner image.
[0004]
Then, the surface of the photosensitive drum 100 on which the toner image is formed is charged by the pre-transfer charger (post-charger) 103 before transfer. By weakening the electrostatic attraction generated at the time of transfer by the pre-transfer charging, the transfer material (paper) P can be easily separated from the surface of the photosensitive drum 100 stably after the next transfer step.
[0005]
Then, when the toner image on the surface of the photosensitive drum 100 reaches the transfer portion between the photosensitive drum 100 and the transfer charger 104, a transfer material P such as paper in a paper feed cassette (not shown) is transferred to the transfer portion at this timing. The toner image is transferred onto the transfer material P by the transfer charger 104 to which the transfer voltage having the polarity opposite to that of the toner is applied. Then, the transfer material P on which the toner image has been transferred is separated from the photosensitive drum 1 by the separation charger 105 and conveyed to the fixing device 107, and is transferred to a fixing nip portion between the fixing roller 107 a and the pressure roller 107 b of the fixing device 107. After the toner image is heated and pressed to the transfer material P and thermally fixed, the toner image is discharged to the outside.
[0006]
The transfer residual toner remaining on the surface of the photosensitive drum 100 after the transfer of the toner image is removed and collected by the cleaning device 106.
[0007]
The developing device 102 in this conventional example is a developing device that performs jumping development using a magnetic one-component toner as a developer. Since the developing device 102 is simple and does not require replacement of a carrier or the like, high durability and a long life can be obtained.
[0008]
That is, in the developing device 102, as shown in FIG. 19, a layer thickness regulating blade 102b is arranged close to the surface of a rotating developing sleeve 102a arranged with a predetermined gap with respect to the photosensitive drum 100. When the magnetic roller 102a passes through the layer thickness regulating blade 102b, the magnetic mono-component toner carried on the developing sleeve 102a is frictionally charged by the magnetic force of the magnet roller 102c fixed and formed inside to form a thin layer. I do. Then, a developing bias is applied to the developing sleeve 102a, and the toner is caused to fly toward the photosensitive drum 100 by a potential difference between the electrostatic latent image on the photosensitive drum 100 and the developing sleeve 102a, thereby inverting and developing the electrostatic latent image.
[0009]
In recent years, in an image forming apparatus such as a copying machine or a printer, a developing sleeve of a developing device is rotated at a high speed with an increase in the speed of an image forming operation. For this reason, the time required for the toner carried on the developing sleeve to fly on the photosensitive drum for development is shortened, and development defects are likely to occur. For this reason, as shown in FIG. 20, a developing device in which a plurality of (two in FIG. 20) developing sleeves 102d and 102e are arranged in the rotation direction of the photosensitive drum 1 in the vicinity of the photosensitive drum 100 has been proposed. . Inside the developing sleeves 102d and 102e, magnet rollers 102f and 102g each having a plurality of magnetic poles are fixedly arranged.
[0010]
In the developing device having two developing sleeves 102d and 102e shown in FIG. 20, the developing sleeve 102d located on the upstream side with respect to the rotation direction of the photosensitive drum 100 has a coating thickness of the developer (toner) by a layer thickness regulating blade 102b. The developing sleeve 102e located on the downstream side of the developing sleeve 102d with respect to the rotation direction of the photosensitive drum 100 has a coating thickness of the developer (toner) by the upstream developing sleeve 102d which is disposed close to the developing sleeve 102e. Be regulated.
[0011]
[Problems to be solved by the invention]
By the way, in the developing device having the two developing sleeves 102d and 102e as described above, the flow of the developer (toner) when a two-component developer containing a non-magnetic toner and a magnetic carrier (two-component toner) is used is as follows. As shown in FIG. 21, the developer is transferred from the developing sleeve 102d to the developing sleeve 102e in a region on the photosensitive drum 100 side where the upstream developing sleeve 102d and the downstream developing sleeve 102e are close to each other. . That is, the developer is transported along the circumference of the developing sleeves 102d and 102e facing the photosensitive drum 100. This is because the two-component developer mainly charges the toner with the carrier, and therefore only needs to be conveyed.
[0012]
On the other hand, when the above-mentioned magnetic one-component toner (one-component developer) is used, it is necessary to coat the developing sleeve in a thin layer to sufficiently charge the toner. For this reason, the flow of the conventional developer (toner) when the magnetic one-component toner is used as the developer is, as shown in FIG. 22, the circumferential direction of the upstream developing sleeve 102d and the downstream developing sleeve 102e. A developer (toner) is transported along the upper side.
[0013]
Due to the conveyance of the developer (toner), in the gap between the developing sleeve 102d and the developing sleeve 102e, the conveying direction of the developer (toner) on the developing sleeve 102d and the conveyance of the developer (toner) on the developing sleeve 102e. When the directions are opposite to each other, the transport of the developer (toner) in the region on the photosensitive drum 100 side where the developing sleeve 102d and the developing sleeve 102e are close to each other causes disturbance.
[0014]
For this reason, when the magnetic one-component toner (one-component developer) is used, it is difficult to coat the developer (toner) in a thin layer stably and uniformly, particularly on the upstream developing sleeve 102d. Could not be developed.
[0015]
Therefore, the present invention provides a developing device that can stably and uniformly coat a thin layer of a developer (toner) on a developing sleeve particularly on the upstream side even when a magnetic one-component toner (one-component developer) is used. And an image forming apparatus.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is directed to a rotatable first and second developer carrier that is sequentially arranged along a moving direction of an image carrier, carries a magnetic one-component developer, and transports the developer to a developing unit. And a first and second magnetic field generating member having a plurality of magnetic poles fixedly disposed in the first and second developer carriers, respectively, and supplying the first and second developer carriers, respectively. A developer container containing a magnetic one-component developer, wherein the first and second developer carriers rotate in the same direction as each other, and are located upstream with respect to the moving direction of the image carrier. A first developer carrier that reduces a developer amount on the second developer carrier located downstream of the first developer carrier with respect to a moving direction of the image carrier to a predetermined amount; In a developing device which is disposed close to the second developer carrier to such an extent that it is regulated, The first magnetic pole of the first magnetic field generating member and the second magnetic pole of the second magnetic field generating member, which are respectively disposed near the opposed positions of the first and second developer carriers, have different polarities. And a half of the magnetic force pattern in the normal direction of the first developer carrier near the position where the first magnetic pole of the first magnetic field generating member is close to and opposed to the first and second developer carriers. The value width is larger on the image carrier side than on the inner side of the developing container.
[0017]
Further, the half width of the magnetic force pattern is twice or more larger on the image carrier side than on the inner side of the developing container.
[0018]
In addition, the first magnetic pole and the second magnetic pole have a magnetic force that satisfies a relationship of (first magnetic pole ≧ second magnetic pole ≧ 50 mT).
[0019]
Further, the arrangement of the first magnetic pole and the second magnetic pole from the rotation center of the first and second developer carriers with respect to a line connecting the rotation centers of the first and second developer carriers, respectively. An angle formed by a line extending to the position is not less than −5 ° and not more than 20 ° when the image carrier side is minus (−).
[0020]
Further, a bias in which a DC component is superimposed on an AC component is applied to the first and second developer carriers.
[0021]
Further, an image forming apparatus according to the present invention includes an image carrier on which an electrostatic latent image is formed, and a developing device according to any one of claims 1 to 5.
[0022]
Further, the image forming apparatus according to the present invention may further include a transfer unit configured to transfer a developer image visualized by developing the electrostatic latent image with the developing device to a transfer material, and the image carrier after the transfer by the transfer unit. Cleaning means for removing and recovering the residual developer remaining on the body, wherein the residual developer recovered by the cleaning means is returned to the developing container and reused.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
[0024]
<Embodiment 1>
FIG. 1 is a schematic configuration diagram showing an image forming apparatus provided with a developing device according to an embodiment of the present invention.
[0025]
The image forming apparatus includes a primary charger 2, a developing device 3, a pre-transfer charger (post-charger) around a photosensitive drum (positively charged a-Si photosensitive member in the present embodiment) 1 as an image carrier. 4, a transfer charger 5, a separation charger 6, and a cleaning device 7. Further, a fixing device 8 is disposed downstream of the transfer section formed between the photosensitive drum 1 and the transfer charger 5 in the transfer material transport direction.
[0026]
At the time of image formation, the photosensitive drum 1 having a diameter of 108 mm rotating at a predetermined peripheral speed (470 mm / sec in the present embodiment) in a direction indicated by an arrow (clockwise) charged to, for example, +450 V by the primary charger 2. Is subjected to image exposure L at 600 dpi by an exposure device (not shown), and an electrostatic latent image corresponding to input image information is formed.
[0027]
The two developing sleeves 3a, 3a of the developing device 3, in which a developing bias having the same polarity as the charging polarity of the photosensitive drum 1 (a bias in which an AC component is superposed on a DC component) is applied to the electrostatic latent image at a developing site. 3b, a developer (a magnetic one-component toner in this embodiment) charged to the same polarity as the charged polarity of the photosensitive drum 1 is adhered, and the toner image is visualized as a toner image by reversal development by a jumping development method. (The details of the developing device 3 in the present embodiment will be described later).
[0028]
Then, the surface of the photosensitive drum 1 on which the toner image is formed is charged by the pre-transfer charger (post-charger) 4 before transfer. When the toner image on the surface of the photosensitive drum 1 reaches the transfer portion between the photosensitive drum 1 and the transfer charger 5, a transfer material P such as a sheet in a sheet cassette (not shown) is transferred to the transfer portion at this timing. The toner image is transferred onto the transfer material P by the transfer charger 5 to which the toner is conveyed and a transfer voltage having a polarity opposite to that of the toner is applied. Then, the transfer material P on which the toner image has been transferred is separated from the photosensitive drum 1 by the separation charger 6 and conveyed to the fixing device 8, where the toner image is transferred to a fixing nip portion between the fixing roller 8 a and the pressure roller 8 b of the fixing device 8. After the toner image is heated and pressed to the transfer material P and thermally fixed, the toner image is discharged to the outside.
[0029]
The transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is removed and collected by the cleaning device 7.
[0030]
Next, the developing device 3 in the present embodiment will be described in detail.
[0031]
As shown in FIGS. 1 and 2, the developing device 3 according to the present embodiment carries a developer carrier rotatable in the direction of an arrow (counterclockwise) so as to face the photosensitive drum 1 at the opening of the developing container 3c. Developing sleeves 3a and 3b as a body are arranged along the rotation direction of the photosensitive drum 1, respectively. The developing sleeve 3a is located on the upstream side of the developing unit facing the photosensitive drum 1 with respect to the rotating direction of the photosensitive drum 1, and the developing sleeve 3b is located on the downstream side of the developing sleeve 3a with respect to the rotating direction of the photosensitive drum 1. positioned.
[0032]
The developing sleeve 3a located on the upstream side with respect to the rotation direction of the photosensitive drum 1 has a coating thickness of the toner t regulated by the layer thickness regulating blade 3d, and is located on the downstream side with respect to the rotating direction of the photosensitive drum 1. 3b, the coat thickness of the toner t is regulated by the upstream developing sleeve 3a disposed close to the developing sleeve 3a.
[0033]
In the developing container 3c, two toner stirring members 3e and 3f for stirring and transporting the toner t in the developing container 3c to the developing sleeve 3a side, and a toner amount detecting sensor 3g for detecting the toner amount in the developing container 3c. have. The toner (magnetic one-component toner) t used in the present embodiment is a positive toner, has a weight average particle size of 8.0 μm, and is made of a styrene acrylic resin, and contains 90 parts by weight of a magnetic material. Also, 0.8% (% by weight) of SiO 2 was used as an external additive. ₂ Is painted.
[0034]
A toner supply container 9 containing toner (magnetic one-component toner) t to be supplied into the developing container 3c is provided above the developing container 3c. The amount of the toner t in the developing container 3c during development is reduced. When the toner amount detecting sensor 3g detects that the toner amount has decreased below the predetermined amount, the mag roller 9a provided at the replenishing port of the toner replenishing container 9 is rotated by a control signal from the control device 10, and the toner in the toner replenishing container 9 is rotated. t is supplied into the developing container 3c.
[0035]
More specifically, the toner t in the toner supply container 9 is attracted to the surface of the mag roller 9a by the magnetic force of the mag roller 9a, and the mag roller 9a is rotated, so that a predetermined gap (gap) between the mag roller 9a and the opposed toner regulating plate 9b is provided. Thus, the amount of the toner t carried on the surface of the mag roller 9a is regulated. Then, a predetermined amount of toner carried on the surface of the mag roller 9a is scraped off by the toner scraping plate 9c abutted on the mag roller 9a, and dropped into the developing container 3c, whereby the toner t is supplied into the developing container 3c. You.
[0036]
The developing sleeves 3a and 3b were subjected to blast treatment with FG # 600 on SUS305 having a diameter of 20 mm, which is a non-magnetic member, to have a surface roughness Rz of 3 μm. For the measurement of the surface roughness Rz, a contact type surface roughness meter (Surfcoder SE-3300, Kosaka Laboratory) was used. The measurement conditions are a cutoff value of 0.8 mm, a measurement length of 2.5 mm, a feed speed of 0.1 mm / sec, and a magnification of 5,000.
[0037]
In the developing sleeves 3a and 3b, fixed magnet rollers 3h and 3i are fixedly arranged as shown in FIG. Each magnetic pole (N1, N2, N3, S1, S2) having a magnetic field pattern as shown in FIG. 4 is arranged on the fixed magnet roller 3h in the developing sleeve 3a. On the other hand, the fixed magnet roller 3i in the developing sleeve 3b is provided with magnetic poles (N1, N2, S1, S2) having a magnetic field pattern as shown in FIG.
[0038]
The developing sleeves 3a and 3b rotate at a speed of 150% of the rotation speed (process speed) of the photosensitive drum 1, and the gap between the developing sleeves 3a and 3b and the photosensitive drum 1 at the developing position is 250 μm. It is. The coat thickness of the toner carried on the developing sleeve 3a by the magnetic force of the fixed magnet roller 3h is regulated by the layer thickness regulating blade 3d, and the toner carried on the developing sleeve 3b by the magnetic force of the fixed magnet roller 3i is produced by the developing sleeve 3a. The coat thickness is regulated. Note that a gap (gap) between the developing sleeve 3a and the developing sleeve 3b on a straight line connecting the rotation centers of the developing sleeve 3a and the developing sleeve 3b is 400 μm.
[0039]
A DC bias of +300 V and an AC bias (in this embodiment, 1200 V peak-to-peak voltage (Vpp) and a rectangular shape having a frequency of 2.5 kHz as shown in FIG. 6) are applied to the developing sleeves 3a and 3b from a developing bias power supply (not shown). By applying a developing bias superimposed on the toner (magnetic wave), the toner (magnetic one-component toner) is caused to fly toward the photosensitive drum 1 to perform non-contact development of the electrostatic latent image. The development contrast at this time is 200 V in the flight direction, and the fog removal contrast is 150 V.
[0040]
As described above, in the present embodiment, the AC bias is applied to the developing sleeves 3a and 3b so as to be superimposed on the DC bias, so that excess toner not contributing to the development by the developing sleeve 3a is carried on the developing sleeve 3b. Then, the toner can be returned to the inside of the developing container 3c, so that the toner consumption can be reduced. For example, when a 6% original image is output as an image, the toner consumption is 50 to 60 mg / sheet in a conventional developing device using a magnetic one-component toner, but in the case of the developing device 3 of the present embodiment. The toner consumption was about 40 mg / sheet.
[0041]
As shown in FIGS. 7 and 8, magnetic seal members 11a and 11b are arranged on the peripheral surfaces near both ends in the longitudinal direction of the developing sleeves 3a and 3b, respectively. The magnetic seal members 11a and 11b are mainly made of moldalloy (KN plating, magnetic permeability 10 to 6) mainly made of iron, and the gap between the surface of each of the developing sleeves 3a and 3b and each of the magnetic seal members 11a and 11b is 400 μm. ± 100 μm.
[0042]
It is preferable that the mounting positions of the magnetic seal members 11a and 11b coincide with the end positions of the fixed magnet rollers 3h and 3i. This is because when the fixed magnet rollers 3h and 3i come out of the outside of the magnetic seal members 11a and 11b, a magnetic force is also present outside in the longitudinal direction, so that the toner is carried out by the magnetic force and toner leakage occurs. Is to cause.
[0043]
On the other hand, if the ends of the fixed magnet rollers 3h and 3i are too far inside the outer ends of the magnetic seal members 11a and 11b, the gap between the magnetic seal members 11a and 11b and the fixed magnet rollers 3h and 3i should be increased. A magnetic brush is formed so that the magnetic seal members 11a and 11b are provided on each of the developing sleeves 3a and 3b at the width of the magnetic seal members 11a and 11b, despite the absence of magnetic force at the outer ends thereof. This is because the outer toner leaks from the ends of the developing sleeves 3a and 3b, and the thickness of the toner layer also increases, causing dropping.
[0044]
Next, the developing sleeves 3a and 3b of the developing device 3 according to the present embodiment will be described in more detail.
[0045]
As shown in FIG. 9, the present inventor has determined the polarity (the magnetic pole A on the side of the developing sleeve 3a and the magnetic pole A on the side of the developing sleeve 3b, The state of the toner coat on the developing sleeve 3b located on the downstream side when the magnetic pole B) was changed was examined. FIG. 10 shows the result of this study. The magnetic force at each of the magnetic poles A and B was 70 mT.
[0046]
As is apparent from the examination results, when the magnetic poles A and B have the same polarity, the state of the toner coat is poor (×), and when the magnetic poles A and B have different polarities, the state of the toner coat is good (○). Met.
[0047]
Further, according to the study of the present inventor, as shown in FIG. 11, when the magnetic poles at the close opposing portions of the developing sleeve 3a and the developing sleeve 3b have different polarities (N2 pole and S1 pole in the figure), the developing sleeve 3a If there is a magnetic region of 0 to 10 mT on the side of the developing sleeve 3a at the close opposing portion of the developing sleeve 3a and the developing sleeve 3b, the toner t stays on the developing sleeve 3a because the toner conveying force is almost eliminated. Thus, it was found that a coating defect occurred. In particular, this phenomenon becomes more conspicuous as the speed of rotation of the developing sleeve 3a rotating at a high speed does not catch up with the toner conveyance.
[0048]
Therefore, as shown in FIG. 12, the present inventor has proposed a case in which the magnetic poles at the close opposing portions of the developing sleeve 3a and the developing sleeve 3b have different polarities (the magnetic pole A on the developing sleeve 3a side and the magnetic pole B on the developing sleeve 3b side). The state of the toner coat on the developing sleeve 3a when the magnetic force between the magnetic poles A and B was changed was examined. FIG. 13 shows the result of this study.
[0049]
As is clear from the examination results, the magnetic force of the magnetic pole B on the developing sleeve 3b side is always larger than the magnetic force of the magnetic pole A on the developing sleeve 3a side, and the magnetic force of the magnetic pole B is at least 50 mT or more. When A ≧ magnetic pole B ≧ 50 mT, the state of the toner coat was good (○), and under other magnetic force conditions, the state of the toner coat was poor (×).
[0050]
According to the study of the present inventor, the toner coat on the developing sleeve 3b located on the downstream side is controlled by the developing sleeve 3a on the upstream side so that the magnetic pole A on the developing sleeve 3a side is fixed to the developing sleeve 3a. It was found that if the line is too far from the photosensitive drum 1 side (outside) than the line connecting the rotation center of the developing sleeve 3a and the developing sleeve 3b, toner coating failure on the developing sleeve 3b occurs and toner charging cannot be stabilized.
[0051]
Therefore, as shown in FIG. 14A, the inventor sets the half width of the magnetic force pattern in the normal direction of the magnetic pole A on the side of the developing sleeve 3a to the photosensitive drum side (the magnetic force of the magnetic force pattern of FIG. 14A). The region X located on the left side of the dashed line connecting the maximum value and the position where the magnetic force is 0 is a broken line connecting the maximum value of the magnetic force of the magnetic force pattern of FIG. It was configured to be larger than the region Y) located on the right side. FIG. 14B shows a magnetic force pattern in the normal direction of the magnetic pole A on the conventional developing sleeve 3a side, and shows the photosensitive drum side (region X on the left side in FIG. The area Y) on the right side of 14 (a) is substantially the same.
[0052]
Further, the inventor of the present invention has shown a graph of the half-width of the magnetic force pattern in the normal direction of the magnetic pole A when the magnetic force of the magnetic pole A on the side of the developing sleeve 3a of this embodiment shown in FIG. The width of the area X on the left side of the photosensitive drum and the area Y on the right side of the developing device in FIG. 14A are indicated by angles, and the state of the toner coat on the developing sleeve 3b when this angle is changed was examined. FIG. 15 shows the results of this study, where ○ and ◎ indicate that the state of the toner coat is good, and X indicates that the state of the toner coat is poor.
[0053]
As is apparent from the examination result, when the angle of the region X on the photosensitive drum side is larger than the region Y on the developing device side, that is, the half width of the magnetic pole pattern in the normal direction of the magnetic pole A is smaller than that of the photosensitive drum side. The larger the side, the better the state of the toner coat on the developing sleeve 3b.
[0054]
Further, the present inventor has developed the developing sleeve 3a of the magnetic poles of different polarities (N2 pole (magnetic pole A) and S1 pole (magnetic pole B) in the figure) at the close opposing portion of the developing sleeve 3a and the developing sleeve 3b shown in FIG. , 3b and the state of the toner coat on the developing sleeve 3b when the angle (θ) with respect to the line connecting the respective rotating centers of the developing sleeves 3a, 3b were changed. The angles (θ) of the developing sleeves 3a and 3b are the same. Further, the angle on the photosensitive drum 1 side with respect to the line connecting the rotation centers of the developing sleeves 3a and 3b is set to minus (-).
[0055]
According to this study, when the angle (θ) was −5 ° to 20 °, the state of the toner coat on the developing sleeve 3b was good, and a good output image without density unevenness could be obtained.
[0056]
As described above, by using the developing device 3 of the present embodiment, both the upstream developing sleeve 3a and the downstream developing sleeve 3b can stably and uniformly coat the developer (magnetic one-component toner) in a thin layer. Therefore, good image formation can be performed.
[0057]
In the above-described embodiment, the configuration in which the reversal development is performed by using the positively charged photosensitive drum and the positive toner is described. However, the same effect can be obtained by the configuration in which the reversal development is performed by using the negatively charged photosensitive drum and the negative toner. Obtainable.
[0058]
<Embodiment 2>
Also in the present embodiment, description will be made using an image forming apparatus provided with the developing device according to the first embodiment shown in FIGS.
[0059]
Generally, in the developing sleeves 3a and 3b made of aluminum, SUS, or the like, it is difficult to control the tribo of the developer (toner). However, in view of this, in this embodiment, the tribo of the toner on the developing sleeves 3a and 3b is reduced. In order to control, it was decided to apply an optimum coat formula.
[0060]
The image forming apparatus of the present embodiment uses an OPC photosensitive member having a diameter of 108 mm as the photosensitive drum 1, and has a process speed of 470 mm / sec. The developer (magnetic one-component toner) used was a negatively chargeable toner having a weight average particle diameter of 7.5 μm, and the resin was made of a polyester resin and contained 90 parts by weight of a magnetic material. In addition, as an external additive, 1.0% (% by weight) of SiO ₂ Is covered. Note that, except for the coating film processing on the surfaces of the developing sleeves 3a and 3b of the developing device 3, it is substantially the same as the first embodiment, and the description thereof will be omitted in the present embodiment. In the present embodiment, a coating film described below is formed on the surfaces of the developing sleeves 3a and 3b made of aluminum A2017 having a diameter of 20 mm, which is a non-magnetic member.
[0061]
Next, the formulation of the coating film on the surfaces of the developing sleeves 3a and 3b in the present embodiment will be described.
[0062]
As a coating film on the surfaces of the developing sleeves 3a and 3b, a film obtained by mixing a phenol resin, crystalline graphite, and carbon at a certain weight ratio, and curing the film at a thickness of 10 μm in an environment of 150 ° C. was used. The thickness of this coat film is about 20 μm for forming a stable and uniform film. Further, when the weight of the phenol resin was B and the weight of other materials (crystalline graphite + carbon) was P, the P / B ratio was 1 / 2.5.
[0063]
When the amount of toner coating on the surface of the developing sleeve 3b on the downstream side is regulated by the developing sleeve 3a on the upstream side as in the developing device 3 in the present embodiment, the charging characteristics are slightly higher than the negative polarity toner. Therefore, in the present embodiment, in order to control this, a phenol resin having 70 parts by weight of a quaternary ammonium salt is used only in the developing sleeve 3b.
[0064]
When the quaternary ammonium salt compound is added, the quaternary ammonium salt compound is uniformly dispersed in the phenol resin, and is further incorporated into the structure of the phenol resin when heat-cured to form a film. The resin composition itself changes to a substance having negative chargeability. Therefore, if the developing sleeves 3a and 3b having the coating layers formed using such materials are used, the developer (toner) can be charged slightly lower.
[0065]
Examples of the quaternary ammonium salt compound having the above-mentioned functions suitably used in the present embodiment include a compound represented by the following chemical formula.
[0066]
Embedded image

[0067]
Note that R in the formula ₁ , R ₂ , R ₃ , R ₄ Represents an alkyl group which may have a substituent, an aryl group which may have a substituent, and an aralkyl group; ₁ ~ R ₄ May be the same or different. X ⁻ Represents an anion of an acid.
[0068]
In the above formula, X ⁻ Specific examples of the acid ion include organic sulfate ion, organic sulfonate ion, organic phosphate ion, molybdate ion, tungstate ion, molybdenum atom or heteropolyacid containing a tungsten atom.
[0069]
Further, as shown in the following chemical formula, when a coating layer is formed using a resin composition obtained by adding a specific quaternary ammonium salt compound to a phenol resin, the phenol resin as a binder resin is heated as described above. When cured to form a coating layer, the quaternary ammonium salt compound is incorporated into the structure of the phenolic resin. Therefore, unlike the case of a particle-added system such as a negative silica particle or a negative Teflon (registered trademark) particle, the positive triboelectric charge to the positively chargeable developer (positive toner) is not formed partially but as the entire coating layer. The impartability is improved. Further, unlike the particle-based coating film, there is no loss of workability and no reduction in the strength of the coating layer.
[0070]
Embedded image

[0071]
Specific examples of the quaternary ammonium salt compound suitably used in the present embodiment include those represented by the following chemical formulas, but are not limited thereto.
[0072]
Embedded image

[0073]
Embedded image

[0074]
Embedded image

[0075]
Embedded image

[0076]
Embedded image

[0077]
Embedded image

[0078]
Embedded image

[0079]
Embedded image

[0080]
As the phenolic resin constituting the binder resin used in the present embodiment, when a phenolic resin produced using a nitrogen-containing compound as a catalyst in the production process is used, particularly, the quaternary ammonium salt compound becomes It was found that it was easily taken into the structure of the resin and was preferable for preventing charge-up of the toner.
[0081]
Therefore, in the present embodiment, a phenol resin having such an action and manufactured using a nitrogen-containing compound as a catalyst in the manufacturing process is used as a material constituting the coating layer on the developing sleeves 3a and 3b. If one of them is used, it is possible to prevent toner charge-up.
[0082]
Examples of the nitrogen-containing compound which can be suitably used in the present embodiment and which is used as a catalyst in the process of producing a phenolic resin include, for example, ammonium sulfate, ammonium phosphate, ammonium sulfamate, ammonium carbonate, ammonium acetate, and maleic acid. Examples of the basic catalyst include ammonia or dimethylamine, diethylamine, diisopropylamine, diisobutylamine, diamylamine, trimethylamine, triethylamine, tri-n-butylamine, triamylamine, and dimethyl. Benzylamine, diethylbenzylamine, dimethylaniline, diethylaniline, N, N-di-n-butylaniline, N, N-diamyaniline, N, N-di-t-amyl Niline, N-methylethanolamine, N-ethylethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine, ethylenediamine Amino compounds such as xamethylenetetramine, pyridine, α-picoline, β-picoline, γ-picoline, 2,4-lutidine, pyridine such as 2,6-lutidine and derivatives thereof, quinoline compounds, imidazole, 2-methylimidazole; Imids such as 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole and the like Tetrazole and nitrogen-containing heterocyclic compounds such derivatives thereof.
[0083]
In addition, in order to adjust the resistance value of the coating layer to the above value, it is preferable to include the following conductive substance in the coating layer. As the conductive substance used at this time, for example, metal powders such as aluminum, copper, nickel, silver, antimony oxide, indium oxide, metal oxides such as tin oxide, carbon fiber, carbon black, graphite, etc. And carbonaceous materials.
[0084]
In the present embodiment, among these, carbon black, especially conductive amorphous carbon is particularly excellent in electrical conductivity, and is filled with a polymer material to impart conductivity, or only by controlling the addition amount, Since an arbitrary degree of conductivity can be obtained to some extent, it is preferably used.
[0085]
The final coat film is formed by mixing 90 parts by weight of graphite having an average particle size of 7.5 μm, 10 parts by weight of carbon, and 70 parts by weight of quaternary ammonium with 250 parts by weight of a phenol resin. Incidentally, it is preferable that the ratio of graphite to carbon be at least three times that of carbon in order to stabilize the resistance of the entire film. Then, the above coating film is applied to the surfaces of the developing sleeves 3a and 3b by a spraying method, and then dried at 150 ° C. for 30 minutes.
[0086]
By forming the coat film on the surfaces of the developing sleeves 3a and 3b in the above-described embodiment, the triboelectric charge (charge amount) on the surface of the developing sleeve 3b on the downstream side is generally large, whereas in the present embodiment, Thus, the value could be controlled to be substantially equal to 9 μC / g on the surface of the developing sleeve 3a and 9.2 μC / g on the developing sleeve 3b. As a result, stable development characteristics could be obtained by optimizing the tribo (charging amount) on the surface of each of the developing sleeves 3a and 3b even with environmental changes such as high temperature and high humidity and low temperature and normal temperature.
[0087]
Further, fixed magnet rollers 3h, 3i are fixedly arranged in the developing sleeves 3a, 3b, respectively, as shown in FIG. Each magnetic pole (N1, N2, N3, S1, S2) having a magnetic field pattern as shown in FIG. 4 is arranged on the fixed magnet roller 3h in the developing sleeve 3a. On the other hand, the fixed magnet roller 3i in the developing sleeve 3b is provided with magnetic poles (N1, N2, S1, S2) having a magnetic field pattern as shown in FIG.
[0088]
The developing sleeves 3a and 3b rotate at a speed of 125% of the rotation speed (process speed) of the photosensitive drum 1, and the gap between the developing sleeves 3a and 3b and the photosensitive drum 1 at the developing position is 250 μm. It is. The coat thickness of the toner carried on the developing sleeve 3a by the magnetic force of the fixed magnet roller 3h is regulated by the layer thickness regulating blade 3d, and the toner carried on the developing sleeve 3b by the magnetic force of the fixed magnet roller 3i is produced by the developing sleeve 3a. The coat thickness is regulated. Note that a gap (gap) between the developing sleeve 3a and the developing sleeve 3b on a straight line connecting the rotation centers of the developing sleeve 3a and the developing sleeve 3b is 400 μm.
[0089]
The developing sleeves 3a and 3b are provided with a DC bias of -550 V and an AC bias (in this embodiment, 1500 V peak-to-peak voltage (Vpp) and a frequency of 2.7 kHz as shown in FIG. 6) from a developing bias power supply (not shown). When a developing bias on which a rectangular wave is superimposed is applied, the toner (magnetic one-component toner) flies toward the photosensitive drum 1 to perform non-contact development of the electrostatic latent image. The development contrast at this time is 350 V in the flight direction, and the fog removal contrast is 150 V.
[0090]
Also, in the present embodiment, as in the first embodiment, as shown in FIG. 14A, the normal direction of the magnetic pole A on the side of the developing sleeve 3a at the position where the developing sleeve 3a and the developing sleeve 3b face each other. The half width of the magnetic pole pattern is configured to be greater on the photosensitive drum side than on the inner side of the developing device. In the present embodiment, the half width of the magnetic pole pattern in the normal direction of the magnetic pole A on the developing sleeve 3a is The photosensitive drum side was twice as large as the inside of the developing device.
[0091]
Specifically, the half width of the magnetic pole pattern in the normal direction of the magnetic pole A on the developing sleeve 3a side was 60 °, the photosensitive drum side was 40 °, and the inside of the developing device was 20 °.
[0092]
Then, also in the present embodiment, as a result of conducting a study similar to the first embodiment shown in FIGS. 13 and 15, a result similar to the first embodiment was obtained.
[0093]
As described above, in the present embodiment, by forming the above-described coat films on the developing sleeves 3a and 3b of the developing device 3, respectively, the rotation of the toner on the upstream developing sleeve 3a is reduced, and the deterioration of the toner is reduced. It is possible to reduce the amount of toner and satisfactorily control the tribo of the toner carried on the surfaces of the developing sleeves 3a and 3b.
[0094]
Also, in the present embodiment, similarly to the first embodiment, a thin layer of the developer (magnetic one-component toner) is stably and uniformly applied on the upstream developing sleeve 3a and the downstream developing sleeve 3b. Therefore, the state of the toner coat on the developing sleeve 3b is good, and a good output image without density unevenness can be obtained.
[0095]
<Embodiment 3>
FIG. 17 is a schematic configuration diagram illustrating an image forming apparatus including the developing device according to the present embodiment. Members having the same functions as those of the image forming apparatus including the developing device described in Embodiments 1 and 2 are denoted by the same reference numerals, and redundant description will be omitted.
[0096]
In the image forming apparatus according to the present embodiment, the diameter 108 mm rotating at a predetermined peripheral speed (500 mm / sec in the present embodiment) in the direction of an arrow (clockwise) charged by, for example, −700 V by the primary charger 2. An image exposure L is applied to the photosensitive drum 1 at 600 dpi by an exposure device (not shown), and an electrostatic latent image corresponding to input image information is formed.
[0097]
The two developing sleeves 3a, 3a of the developing device 3, in which a developing bias having the same polarity as the charging polarity of the photosensitive drum 1 (a bias in which an AC component is superposed on a DC component) is applied to the electrostatic latent image at a developing site. 3b, a developer (a magnetic one-component negative toner in this embodiment) charged to the same polarity as the charged polarity of the photosensitive drum 1 is adhered, and reversely developed by a jumping developing method to visualize a toner image. I do. As the developing bias in the present embodiment, a bias voltage obtained by superimposing a DC voltage of +200 V on an AC voltage of a frequency of 2400 Hz, a peak-to-peak voltage of 1500 Vpp, and a duty of 50% was applied to the developing sleeves 3a and 3b.
[0098]
Then, the surface of the photosensitive drum 1 on which the toner image is formed is charged by the pre-transfer charger (post-charger) 4 before transfer. When the toner image on the surface of the photosensitive drum 1 reaches the transfer portion between the photosensitive drum 1 and the transfer charger 5, a transfer material P such as a sheet in a sheet cassette (not shown) is transferred to the transfer portion at this timing. The toner image is transferred onto the transfer material P by the transfer charger 5 to which the toner is conveyed and a transfer voltage having a polarity opposite to that of the toner is applied. Then, the transfer material P on which the toner image has been transferred is separated from the photosensitive drum 1 by the separation charger 6 and conveyed to the fixing device 8, where the toner image is transferred to a fixing nip portion between the fixing roller 8 a and the pressure roller 8 b of the fixing device 8. After the toner image is heated and pressed to the transfer material P and thermally fixed, the toner image is discharged to the outside.
[0099]
The transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is removed and collected by the cleaning device 7. Then, the waste toner (reused toner) collected by the cleaning device 7 is returned to the toner supply container 13 through the transport pipe 12. A screw-shaped conveying member (not shown) is provided inside the conveying pipe 12, and the waste toner (reused toner) is conveyed by rotating the conveying member (not shown). New toner is stored in the toner supply container 9.
[0100]
Then, as described in the first embodiment, the toner is attracted by the magnetic force of the mag rollers 9a, 13a provided in the toner supply container 9 and the toner supply container 13, respectively, and the mag rollers 9a, 13a rotate. The toner is supplied into the developing container 3c. Then, the toner mixed in the developing container 3c is sent to the developing sleeves 3a and 3b again, and the electrostatic latent image on the photosensitive drum 1 is reversely developed by a jumping developing method to be visualized as a toner image. In this embodiment, the waste toner (reuse toner) and the new toner are mixed in the developing container 3c. However, a mixing space is provided below the toner supply container 9 and the toner supply container 13 for mixing. No problem.
[0101]
The normal rotation speed of the mag roller 9a of the toner supply container 9 is constant at 2 rotations / minute, and the rotation speed of the mag roller 13a of the toner supply container 13 is changed. The rotation of the mag roller 9a and the mag roller 13a is controlled based on a detection signal from a toner amount detection sensor (not shown) in the developing container 3c.
[0102]
Also in this embodiment, as in the first embodiment, as shown in FIG. 14A, the magnetic pole A on the side of the developing sleeve 3a at the position where the developing sleeve 3a and the developing sleeve 3b of the developing device 3 face each other. The half width of the magnetic pole pattern in the normal direction is configured to be larger on the photosensitive drum side than on the inner side of the developing device. In the present embodiment, the magnetic pole pattern in the normal direction of the magnetic pole A on the developing sleeve 3a side is used. The width at half maximum of the photosensitive drum was twice that of the inside of the developing device. Specifically, the half width of the magnetic pole pattern in the normal direction of the magnetic pole A on the side of the developing sleeve 3a was 60 °, the photosensitive drum side was 40 °, and the inside of the developing container 3c was 20 °.
[0103]
Also, in the present embodiment, the above-described coat film is formed on the surfaces of the developing sleeves 3a and 3b as in the second embodiment.
[0104]
As described above, in the image forming apparatus of the present embodiment in which the collected waste toner (reuse toner) is supplied together with the new toner to the developing container 3c, the tribo of the waste toner (reuse toner) is extremely smaller than that of the new toner. Therefore, the amount of the reversal component toner is large, and the charging stability and the toner coatability of the toner on the developing sleeves 3a and 3b are further deteriorated. However, in the present embodiment, the developing device 3 having the configuration described in the second embodiment is used. Accordingly, it is possible to reduce the toner circling on the upstream developing sleeve 3a to reduce the toner deterioration, and to well control the tribo of the toner carried on the surfaces of the developing sleeves 3a and 3b. it can.
[0105]
Also, in the present embodiment, similarly to the first embodiment, a thin layer of the developer (magnetic one-component toner) is stably and uniformly applied on the upstream developing sleeve 3a and the downstream developing sleeve 3b. Therefore, the state of the toner coat on the developing sleeve 3b is good, and a good output image without density unevenness can be obtained.
[0106]
【The invention's effect】
As described above, according to the present invention, the first magnetic pole of the first magnetic field generating member and the second magnetic pole of the second magnetic field generating member have different polarities, and the first magnetic pole of the first magnetic field generating member has the first magnetic pole. The half width of the magnetic force pattern in the normal direction of the first developer carrier near the opposed position of the first and second developer carriers is made larger on the image carrier side than on the inner side of the developing container, so that the upstream Since a thin layer of the developer can be stably and uniformly coated on the first developer carrier on the side, a favorable developing operation can be performed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus including a developing device according to a first embodiment of the present invention.
FIG. 2 is a schematic sectional view showing a developing device according to the first embodiment of the present invention.
FIG. 3 is a diagram showing magnetic poles of a fixed magnet roller provided in a developing sleeve of the developing device according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a magnetic field pattern of a fixed magnet roller provided in an upstream developing sleeve according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a magnetic field pattern of a fixed magnet roller provided in a downstream developing sleeve according to the first embodiment of the present invention.
FIG. 6 is a diagram illustrating a waveform of an AC bias applied to a developing sleeve.
FIG. 7 is a diagram showing a magnetic seal provided near an end of each developing sleeve.
FIG. 8 is a diagram showing a magnetic seal provided near an end of each developing sleeve.
FIG. 9 is a diagram showing a magnetic pole A and a magnetic pole B at a portion of each developing sleeve in proximity to each other in the first embodiment of the present invention.
FIG. 10 shows a result of study on the state of the toner coat on the downstream developing sleeve when the polarity of the magnetic pole A and the magnetic pole B at the close opposing portion of each developing sleeve are changed in the first embodiment of the present invention. FIG.
FIG. 11 is a diagram for explaining a state of toner coating on a developing sleeve positioned on the upstream side according to the first embodiment of the present invention.
FIG. 12 is a diagram for explaining a state of toner coating on a developing sleeve positioned on the upstream side in the first embodiment of the present invention.
FIG. 13 is a result of studying the state of toner coating on the upstream developing sleeve when the magnetic force of the magnetic pole A and the magnetic pole B at the close-to-opposed portion of each developing sleeve is changed according to the first embodiment of the present invention. FIG.
FIG. 14A is a diagram illustrating a magnetic force pattern in a direction normal to a magnetic pole A of a developing sleeve positioned on an upstream side according to the first embodiment of the present invention, and FIG. 14B is a diagram illustrating an upstream side in a conventional example. FIG. 6 is a diagram showing a magnetic force pattern in the normal direction of the magnetic pole A of the developing sleeve located at the position A.
FIG. 15 shows a region X on the photosensitive drum side in a half value of the magnetic force pattern in the normal direction of the magnetic pole A when the magnetic force of the magnetic pole A of the developing sleeve 3a located on the upstream side of the embodiment of the present invention is 70 to 90 mT. FIG. 9 is a diagram showing the width of a region Y on the side of the developing device and the angle by an angle, and the result of studying the state of toner coating on the developing sleeve located on the downstream side when the angle is changed.
FIG. 16 is a diagram showing magnetic poles of a fixed magnet roller provided in a developing sleeve of the developing device according to the second embodiment of the present invention.
FIG. 17 is a schematic configuration diagram illustrating an image forming apparatus including a developing device according to a third embodiment of the present invention.
FIG. 18 is a schematic configuration diagram illustrating an image forming apparatus including a developing device according to a conventional example.
FIG. 19 is a view showing a developing sleeve of a developing device in a conventional example.
FIG. 20 is a diagram showing two developing sleeves arranged close to and opposed to a developing device in a conventional example.
FIG. 21 is a diagram showing a flow of a two-component developer on two developing sleeves arranged in close proximity to a developing device in a conventional example.
FIG. 22 is a diagram showing a flow of a one-component developer on two developing sleeves arranged in close proximity to a developing device in a conventional example.
[Explanation of symbols]
1. Photosensitive drum (image carrier)
2 Primary charger
3 Developing device
4 Pre-transfer charger
5 Transfer charger
6 Separation charger
7 Cleaning device
8 Fixing device
3a, 3b developing sleeve (first and second developer carrying members)
3c development container
3h, 3i Fixed magnet roller (magnetic field generating member)
9, 13 Toner supply container
9a, 13a Mag roller
11a, 11b Magnetic seal member
12 transport pipe

Claims (7)

Rotatable first and second developer carriers that are sequentially arranged along the moving direction of the image carrier, carry a magnetic one-component developer, and transport the developer to a developing unit; and the first and second developing devices. First and second magnetic field generating members each having a plurality of magnetic poles fixedly disposed in a developer carrier, and a developing container containing a magnetic one-component developer to be supplied to the first and second developer carriers, respectively. Wherein the first and second developer carriers rotate in the same direction as each other, and the first developer carrier located on the upstream side in the moving direction of the image carrier carries the image. The second developer carrying member is positioned so that the amount of developer on the second developer carrying member located downstream of the first developer carrying member with respect to the moving direction of the carrier is regulated to a predetermined amount. In the developing device arranged close to the body,
The first magnetic pole of the first magnetic field generating member and the second magnetic pole of the second magnetic field generating member, which are respectively disposed near the opposed positions of the first and second developer carriers, have opposite polarities. Yes,
A half-value width of a magnetic force pattern in a normal direction of the first developer carrier near a position where the first magnetic pole of the first magnetic field generating member is close to and opposed to the first and second developer carriers is The image carrier side is larger than the inside of the developing container,
A developing device, comprising: The half width of the magnetic force pattern is twice or more larger on the image carrier side than on the inner side of the developing container,
The developing device according to claim 1, wherein: The first magnetic pole and the second magnetic pole have a magnetic force that satisfies first magnetic pole ≧ second magnetic pole ≧ 50 mT,
The developing device according to claim 1, wherein: With respect to a line connecting the rotation centers of the first and second developer carriers, the positions of the first magnetic pole and the second magnetic pole are respectively set from the rotation centers of the first and second developer carriers. The angle formed by the extending line is not less than -5 ° and not more than 20 ° when the image carrier side is minus (-).
The developing device according to claim 1, wherein: Applying a bias in which a DC component is superimposed on an AC component to the first and second developer carriers;
The developing device according to claim 1, wherein: An image carrier on which an electrostatic latent image is formed, and the developing device according to any one of claims 1 to 5.
An image forming apparatus comprising: A transfer unit that transfers a developer image visualized by developing the electrostatic latent image with the developing device to a transfer material; and removing a residual developer remaining on the image carrier after the transfer by the transfer unit. Cleaning means for recovering and recovering the residual developer collected by the cleaning means and returned to the developing device for reuse.
The image forming apparatus according to claim 6, wherein:

Images