JP2004077587A - Developing device and image forming apparatus - Google Patents

Developing device and image forming apparatus Download PDF

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Publication number
JP2004077587A
JP2004077587A JP2002234604A JP2002234604A JP2004077587A JP 2004077587 A JP2004077587 A JP 2004077587A JP 2002234604 A JP2002234604 A JP 2002234604A JP 2002234604 A JP2002234604 A JP 2002234604A JP 2004077587 A JP2004077587 A JP 2004077587A
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developer
chamber
stirring
transporting
conveying
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Japanese (ja)
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Kunio Shigeta
重田　邦男
Hiroshi Akita
秋田　宏
Seiko Itagaki
板垣　整子
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Konica Minolta Inc
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Konica Minolta Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device and an image forming apparatus capable of yielding a clear image well-balanced in terms of density balance and color balance and excellent in the followability of a printing rate without causing irregularity in image density even in the case of consecutively forming toner images each of whose printing rate is high by repeatedly using developer consisting of toner and carrier so as to form the image. <P>SOLUTION: The developing device is constituted so that a developer supply part is separated from a developer recovery part, the recovered developer is circularly carried to the developer supply part by necessarily passing through a toner replenishing part, and the path of a stirring part is provided to be long by arranging two stirring screws 43A and 44A. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、キャリアとトナーとからなる２成分系現像剤を用いて画像形成を行う現像装置、及び該現像装置を搭載した画像形成装置に関する。
【０００２】
【従来の技術】
トナーとキャリアよりなる２成分系現像剤を用い現像器を介して感光体ドラム等の像担持体上の静電潜像を現像する画像形成装置では、現像領域となる現像スリーブ上に、キャリアで磁気ブラシを形成し、磁気ブラシを介して像担持体上にトナーを供給し静電潜像を現像する。
【０００３】
すなわち、現像装置内ではトナーとキャリアとが均一分散する様に撹拌され、トナーは帯電された後、現像スリーブ上に現像剤の供給が行われて、像担持体上の静電潜像をトナーにより顕像化する。そして、像担持体上の静電潜像の顕像化に使用された現像剤は、現像スリーブより除去、回収され、回収現像剤に画像形成で消費された分のトナーを補給して画像形成に繰返し使用している。
【０００４】
従来の現像装置は、現像スリーブへ現像剤を供給する現像剤供給部と現像に供された現像剤を現像スリーブより回収する現像剤回収部とが共通に設けられているため、回収現像剤が再び現像スリーブに供給され、混入した回収現像剤の影響でトナー画像の画質不良を発生させる。すなわち、回収現像剤は画像形成でトナーが消費された分トナー濃度（現像剤中におけるトナー含有量のこと）が低く、消費分のトナー補給を行わないと適正な濃度やバランスを有するトナー画像が形成できなくなる。トナー濃度の低い回収現像剤が混入した現像剤を現像領域に供給して画像形成を行うとトナー画像上に濃度むらが発生する。
【０００５】
特に、高印字率の画像を連続で画像形成すると、トナー消費量が多い分だけ回収現像剤のトナー含有量がより低下するのでトナー画像上の濃度むらの傾向が顕著になる。特に、カラーの画像形成では、トナー画像上の濃度むらによってカラーバランスが崩れて良好な色再現性や色調が得られなくなり、画像品質を著しく劣化させる。
【０００６】
そこで、特開平６−５１６３４号公報で、現像剤供給部と現像剤回収部とを分離し現像器内で現像剤の循環搬送を行うことが提案され、回収現像剤の現像剤供給部からの混入による現像剤のトナー濃度むらの問題は大幅に解消した。しかしながら、この文献の現像器は、回収現像剤の一部がトナー補給部を通過せずに循環搬送される構造を有していたため、トナー補給を受けていない回収現像剤が存在した状態で現像供給され、高印字率の画像を出力する場合に、印字率追従性と呼ばれる１つの画像内、或いは画像間におけるトナー画像の濃度ばらつきに対する安定性が不十分で、連続で画像形成を行うと濃度ばらつきの顕著なトナー画像となった。
【０００７】
上記の問題を鑑みて、回収現像剤に確実にトナー補給を行い、よく撹拌して現像剤中でトナーが均一に分散して現像剤中におけるトナー濃度がばらつかない現像剤の得られる現像装置の開発が進められた。そして、特開平９−１４６３３５号公報、特開２００１−２９０３６８公報及び特開２００１−２４９５４５公報に、現像剤供給部、現像剤回収部、及び現像剤撹拌部を設け、回収した現像剤はトナー補給部を経て撹拌された後、現像領域に供給される様にした構成の現像装置が提案された。これらの文献に開示された現像装置では、現像剤撹拌部を設けることにより、補給トナーの現像剤中における均一分散が可能となり、現像剤中におけるトナー濃度むらの問題を解消した。
【０００８】
特に、特開２００１−２４９５４５公報と特開２００１−２９０３６８公報には、スクリュオーガを１本追加して回収した現像剤を均一に撹拌した後にトナー補給を行う現像装置も提案された。
【０００９】
【発明が解決しようとする課題】
上記文献に提案された現像装置では、現像剤中でトナー濃度が局所的にばらつくトナー濃度不均一の問題は改善されたが、現像装置内の現像剤循環速度が遅い場合、現像領域への現像剤供給が間に合わなくなり、現像装置内で現像剤が枯渇した領域が発生し、この枯渇領域により現像領域上に局所的に現像剤が供給されていない領域の発生する現像剤供給むらと呼ばれる問題が発生した。
【００１０】
そこで、現像装置内における現像剤の循環、搬送速度を速くすると、現像剤撹拌部における現像剤の滞留時間が短縮されたため、トナーに十分な帯電性を付与することができなくなった。
【００１１】
特に、回収現像剤のトナー消費分を補うために添加された補給トナーは、十分に帯電が立ち上がっていない段階で現像領域に供給され、帯電立ち上がり不良のトナーが画像形成装置内に飛散し、トナー飛散によるトナー汚染を発生させた。また、作製されたトナー画像も画像濃度が不均一で、バランスの乱れたものとなったり、カブリが発生したり、特に、カラーの画像形成では色再現性や色調の乱れた画像となった。また、高速の画像形成装置では、像担持体の周速或いはプロセス速度が速く、現像剤の循環速度がさらに速くなるので、帯電立ち上がり不良による問題がより顕著になった。
【００１２】
また、キャリアとトナーよりなる現像剤では、画像形成を繰返すことによりキャリアの表面が変化して帯電付与性能が低下するという問題を有しており、繰り返し使用しても安定した帯電付与性能の得られる現像装置の開発が急務となっていた。
【００１３】
本発明は、この様な問題に鑑みて見出されたものである。すなわち、本発明は、トナーとキャリアよりなる現像剤を繰返し画像形成に用いても、印字率追従性に優れ高印字率のトナー画像を連続作成しても、画像濃度にむらが生ずることなく、濃度バランスやカラーバランスの整った美しいトナー画像の得られる現像装置を提供することを目的とする。
【００１４】
また、本発明の第２の目的は、高印字率の画像を連続して形成しトナーが大量に供給された場合でも補給されたトナーが現像剤中で均一に分散されてトナー濃度むらがなく、しかも画像形成可能で十分な帯電量が得られ、帯電立ち上がり不良によるトナー飛散の発生しない現像装置を提供することである。
【００１５】
また、本発明の第３の目的は、画像形成を繰り返し行っても常に安定した帯電性能が得られ、トナーの帯電立ち上がり不良に起因する問題の発生しない現像装置を提供することである。
【００１６】
また、本発明の第４の目的は、色調や色再現性に優れた高速のカラー画像形成装置を提供することである。
【００１７】
【課題を解決するための手段】
本発明者は、鋭意検討を重ねた結果、現像剤供給部と現像剤回収部とを分離し、回収現像剤が必ずトナー補給部を経て現像剤供給部に循環搬送される構造を有するとともに、撹拌スクリューを２本配置して撹拌部の経路を長く設けた構造を有する現像装置を見出した。
【００１８】
すなわち、本発明に係る現像装置は、現像剤一循環構造と呼ばれる、現像剤供給部と現像剤回収部とを分離し、回収現像剤が必ずトナー補給部を経て現像剤供給部に循環搬送される構造を採ることにより、回収現像剤を再び現像領域に供給した時にトナー濃度むらの発生しない現像装置の開発を可能にした。
【００１９】
また、本発明では、撹拌スクリューを２本配置して撹拌部の経路を長くすることにより、現像剤一循環構造の現像装置で現像剤循環速度が速い状態にあってもトナーの帯電立ち上がりが十分に行える様になり、帯電立ち上がり不良と現像剤枯渇の２つの問題を同時に解決することを可能にした。
【００２０】
この様に、本発明に係る現像装置では、現像剤を速い速度で循環させても、帯電立ち上がり不良も現像剤供給むらの問題も発生することがなく、また、高印字率のトナー画像を連続作成し大量のトナー供給を繰り返しても、補給トナーは現像剤中に均一に分散されて、しかも十分な帯電性が得られるので、画像濃度にむらがなく画像濃度やカラーバランスの整った印字率追従性に優れた美しい画質を有し帯電立ち上がり不良によるトナー飛散の発生しないトナー画像が得られる様になった。
【００２１】
すなわち、本発明者は、請求項１から請求項３、及び請求項８のいずれか１項に記載された構成の現像装置により、上記効果を有することを見出した。
【００２２】
また、本発明者は、現像剤供給部と現像剤回収部とを分離し、回収現像剤が必ずトナー／キャリア補給部を経て現像剤供給部に循環搬送される構造を有するとともに、撹拌スクリューを２本配置して撹拌部の経路を長く設けた構造を有する現像装置を見出した。
【００２３】
すなわち、本発明に係る第２の現像装置は、回収現像剤にトナーとともにキャリアも供給するもので、新しいキャリアを添加することで画像形成に繰返し使用され、表面が変化して帯電付与性能の低下したキャリアを現像装置の外に排出することが可能なので、現像装置内の現像剤を構成するキャリアは常に安定した帯電付与性能を有するものになる。
【００２４】
その結果、本発明に係る第２の現像装置では、前述の現像装置で得られた効果に加えて、画像形成を繰り返し行ってもキャリアは常に安定した帯電付与性能を有するので、キャリアの表面変化に起因するトナーの帯電立ち上がり不良のない現像装置の開発を可能にした。
【００２５】
すなわち、本発明者は、請求項４から請求項８のいずれか１項に記載された構成の現像装置により、前述の効果を有することを見出した。
【００２６】
また、本発明では、請求項９に記載の構成を選択することにより、現像剤を構成するトナーが、体積平均粒径が３μｍ〜５μｍの小粒径トナーを使用することで、高解像性と優れた細線再現性を発揮し、同時に画像濃度の安定した、トナー飛散によるかぶりの発生のないトナー画像の形成を可能にした。
【００２７】
また、本発明では、請求項１０に記載の構成を選択すること、すなわち、現像剤を構成するキャリアの体積平均粒径が、トナーの体積平均粒径の５倍〜１０倍の範囲内であることにより、かぶりやトナー飛散或いはキャリア付着といった問題が発生することなく、均一な画像濃度のトナー画像を安定して形成することが可能であることを見出した。
【００２８】
さらに、本発明では、前述した様に本発明に係る現像装置が、高印字率の画像を連続出力する場合でもトナーとキャリアとが十分に混合撹拌され、帯電立ち上がりの十分なトナーが確実に得られるという効果を有することから、請求項１１に記載の構成により、色再現性やカラーバランスの優れた高画質のカラー画像を高速で作成することを可能にした。
【００２９】
なお、本発明に係るカラー画像形成装置は、高速で画像形成を行うことを特徴とするものであり、プロセス速度と呼ばれる感光体ドラム上に印字を行う際の感光体ドラムの線速度が２００ｍｍ／ｓｅｃ以上のものを指す。
【００３０】
なお、本発明でいう印字率追従性とは、例えばプレゼンテーション用のＯＨＰ資料や写真画像の様に背景部を一面塗りつぶした高印字率の画像を連続して出力した様な場合に、現像剤のトナー含有量（トナー濃度）の変動に起因してトナー画像上の画像濃度に変動を来す程度を表すものである。すなわち、連続で画像形成を行った時に得られるプリント画像中或いは頁間で、画像濃度に差が発生する様な場合は印字率追従性が悪く、画像濃度に差がなくむらのない美しい仕上りの画像の得られる場合は印字追従性が良いと判断する。
【００３１】
また、本発明でいう印字率とは、転写紙単位面積あたりにおけるトナードット数の様なトナーの密度を言うもので、１頁あたりにおける全画素数に対する露光を実行する画素数を百分率で示した値（（露光を実行した画素数／全画素数）×１００）、或いはパルス幅変調（ＰＷＭ）により調整した画素毎の濃度（トナー付着量）の積算値によって表される値である。なお、画素毎の濃度は、ＰＷＭにより例えば２５６階調を再現する画像形成装置の場合には、ｘ／２５６等という分数または当該分数を百分率に換算した値で表せる。
【００３２】
また、本発明でいうトナー濃度（％）とは、２成分現像剤中のトナー含有量を意味するもので、現像剤に含有されるトナーの濃度を質量百分率で示したものである。
【００３３】
【発明の実施の形態】
以下、本発明の実施の形態を説明するが、以下の記載は本発明に係る請求項の技術的範囲や用語の意義を限定するものではない。なお、文中において現像装置を構成する現像剤担持体のことを現像ローラ、現像スリーブ、或いは現像領域とも言い、現像剤回収搬送手段、現像剤撹拌搬送手段、現像剤供給搬送手段を総称して現像剤搬送手段、或いは搬送手段とも言い、現像剤回収搬送室、現像剤撹拌搬送室、現像剤供給搬送室を総称して現像剤搬送室、或いは搬送室とも言う。
【００３４】
最初に、本発明に係る現像装置を搭載した画像形成装置について説明する。
図１は、本発明の第１実施形態、又は第３実施形態である像担持体の横側方に配置する現像装置（以下現像手段、現像器とも言う。）を搭載したカラー画像形成装置の構成を示す模式図である。
【００３５】
このカラー画像形成装置は、タンデム型カラー画像形成装置と称せられるもので、縦列配置された複数組の画像形成部１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋと、複数のローラにより巻回され回動可能に支持された半導電性エンドレスベルト状の中間転写体７と、給紙搬送手段、及び定着装置８とからなる。
【００３６】
イエロー色の画像を形成する画像形成部１０Ｙは、像担持体（感光体）１Ｙの周囲に配置された帯電手段２Ｙ、露光手段３Ｙ、本発明に係る現像装置４Ｙ、一次転写手段５Ｙ、クリーニング手段６Ｙを有する。マゼンタ色の画像を形成する画像形成部１０Ｍは、像担持体（感光体）１Ｍ、帯電手段２Ｍ、露光手段３Ｍ、本発明に係る現像装置４Ｍ、一次転写手段５Ｍ、クリーニング手段６Ｍを有する。シアン色の画像を形成する画像形成部１０Ｃは、像担持体（感光体）１Ｃ、帯電手段２Ｃ、露光手段３Ｃ、本発明に係る現像装置４Ｃ、一次転写手段５Ｃ、クリーニング手段６Ｃを有する。黒色画像を形成する画像形成部１０Ｋは、像担持体（感光体）１Ｋ、帯電手段２Ｋ、露光手段３Ｋ、本発明に係る現像装置４Ｋ、一次転写手段５Ｋ、クリーニング手段６Ｋを有する。
【００３７】
画像形成部１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋより形成された各色の画像は、一次転写手段５Ｙ，５Ｍ，５Ｃ，５Ｋにより、回動する中間転写体７上に逐次転写されて、合成されたカラー画像が形成される。給紙カセット２０内に収容された転写材（以下、用紙またはシートとも称す）Ｐは、給紙手段２１により給紙され、複数の中間ローラ２２Ａ，２２Ｂ，２２Ｃ，２２Ｄ、レジストローラ２３を経て、二次転写手段５Ａに搬送され、用紙Ｐ上にカラー画像が一括転写される。カラー画像が転写された用紙Ｐは、定着装置８により定着処理され、排紙ローラ２４に挟持されて機外の排紙トレイ２５上に載置される。
【００３８】
両面画像形成時には、定着装置８から排出された第１面に画像形成された用紙Ｐは、分岐手段２６により用紙排紙路から分岐され、下方の反転通紙路２７Ａ，２７Ｂ，２７Ｃを通過して、中間ローラ２２Ｄにおいて合流する。反転搬送された用紙Ｐは、レジストローラ２３を経て、二次転写手段５Ａに搬送され、用紙Ｐの第２面上にカラー画像が一括転写される。カラー画像が転写された用紙Ｐは、定着装置８により定着処理され、排紙ローラ２４に挟持されて機外の排紙トレイ２５上に載置される。
【００３９】
一方、二次転写手段５Ａにより用紙Ｐにカラー画像を転写後、用紙Ｐを曲率分離した中間転写体７は、クリーニング手段６Ａにより残留トナーが除去される。
【００４０】
画像形成処理中、一次転写手段５Ｋは常時、感光体１Ｋに圧接している。他の一次転写手段５Ｙ，５Ｍ，５Ｃはカラー画像形成時にのみ、それぞれ対応する感光体１Ｙ，１Ｍ，１Ｃに圧接する。二次転写手段５Ａは、ここを用紙Ｐが通過して二次転写が行われる時にのみ、中間転写体７に圧接する。
【００４１】
図２は、本発明の第２実施形態、又は第４実施形態である像担持体の下方に配置する現像装置（以下現像手段、現像器とも言う。）を搭載した画像形成装置の構成を示す模式図である。図において、画像形成装置は、自動原稿搬送装置（通称ＡＤＦ）Ａと、自動原稿搬送装置により搬送される原稿の画像を読みとるための原稿画像読取部Ｂと、読み取った原稿の画像を符号化してデータ処理する画像処理手段Ｃと、書き込み部Ｄと、感光ドラムからなる像担持体１と、像担持体１に対して少なくとも、帯電器２、本発明に係る現像装置４、クリーニング部材６を備え、像担持体１上にトナー画像を形成する画像形成ユニットＥと、画像形成用の用紙（以下、シートという）Ｐを収納する給紙ユニット１２２、１２４と、シートの表裏の反転を行う反転路１８０と、を有している。
【００４２】
自動原稿搬送装置Ａは、原稿載置台１３７と、ローラＲ１を含むローラ群および原稿の移動通路を適宜切り替えるための切換手段等（参照記号なし）を含む原稿搬送処理部１３６とを有している。原稿画像読み取り部Ｂは、天板ガラスＧの下にあり、光路長を保って往復移動できる２つのミラーユニット１３０、１３１、固定の結像レンズ１３３、撮像素子１３５等からなる。書き込み部Ｄは、レーザー光源、ポリゴンミラー等からなる。なお、シートＰの搬送方向からみて、転写器５の手前側に示す一対のローラはレジストローラＲ１０であり、分離電極１２０の下流側に示す一対のローラは熱源を有する定着ローラＲ１５である。
【００４３】
まず、シートに画像を形成するプロセスを以下に説明する。
原稿載置台１３７上に載置される原稿（図示せず）の１枚が原稿搬送処理部１３６中で搬送され、ローラＲ１の下を通過して、固定位置にあるミラーユニット１３０、１３１およびレンズ１３３を経て撮像素子１３５上に結像され、読みとられる。読みとられた原稿の画像情報は画像処理手段Ｃにより処理され、符号化された画像情報のデータは画像メモリーに格納される。図示しない駆動源により回転する像担持体１上に、画像メモリに格納された画像情報のデータに従って、書き込み部Ｄはレーザー光源を駆動しレーザー光を回転する像担持体１に照射して露光を行う。露光に先立ち、矢印方向（反時計方向）に回転する像担持体１は、帯電器２のコロナ放電作用により所定の表面電位を付与されているが、レーザー光の露光により、露光部位の電位が露光量に応じて減じ、結果として、画像情報のデータに応じた静電潜像が像担持体１上に形成される。静電潜像は、本発明に係る現像装置４から供給された現像剤のトナーにより可視化されてトナー画像となる。
【００４４】
一方、給紙ユニット１２２には、図示しないコイルバネ等の付勢手段により、常時、自由端が上方向に付勢される可動板が配置され、最上位のシートＰが送り出しローラ１５０に接触するようになっている。送り出しローラ１５０に接触したシートＰは、給紙ユニット１２２から送り出され、一対の回転可能なローラである駆動ローラ１５１と従動ローラ１５２に送り出される。駆動ローラ１５１は、回転してシートＰを１枚づつ分離して、ループ作成ローラ１５７に向けて搬送する。ループ作成ローラ１５７は、シートの搬送する方向からみて、レジストローラＲ１０の上流側に設けられ、回転してシートＰの搬送を行い回転を開始する前のレジストローラＲ１０にシートの先端を当ててシートＰのループ形成を行う。ループ形成により搬送によるシートＰの斜行が補正される。その後、レジストローラＲ１０は、像担持体１に形成されたトナー画像と同期して回転を開始し、シートＰを搬送する。像担持体１と同期して搬送されたシートＰに像担持体１のトナー画像が重なり、転写器５の付勢によりシートＰにトナー画像が転写される。シートＰは分離電極１２０の付勢により像担持体１から分離した後、定着ローラＲ１５の加圧、加熱作用によりトナー画像を形成するトナー粉末はシートＰ上に溶融定着される。トナーが定着されたシートＰは、排紙ローラ１７９を介して、排紙トレイＴ上に排紙される。
【００４５】
次に、本発明に係る現像装置について説明する。
図３と図４は、本発明の第１実施形態として像担持体の横側方に配置する現像装置４の模式図で、図３（ａ）〜（ｄ）は図４中の破線矢印で表すａａ、ｂｂ、ｃｃ及びｄｄより見た要部断面図である。また、図４は、図３（ａ）に示す様に現像装置４をＹ方向よりみた平面図で、左側は下部、右側は上部を示す。また、図３（ａ）〜（ｄ）中の太い矢印は、現像装置内における現像剤の搬送方向を示し、現像剤搬送手段であるスクリュー中央に黒丸（●）を付したものは現像剤を図の奥側より手前側に向けて搬送することを表し、スクリュー中央に×印を付したものは現像剤を図の手前側より奥側に向けて搬送することを表す。図４で太い矢印は現像剤搬送量の多いことを、細い矢印は搬送量の少ないことを表す。
【００４６】
本発明に係る現像装置４は、以下の構成よりなる。すなわち、現像装置本体４０、現像剤担持体である現像ローラ（現像スリーブとも言う。）４１、現像剤回収搬送手段である回収搬送スクリュー４２Ａ、第１の現像剤撹拌搬送手段である第１撹拌搬送スクリュー４３Ａ、第２の現像剤撹拌搬送手段である第２撹拌搬送スクリュー４４Ａ、現像剤供給搬送手段である供給搬送スクリュー４５Ａ、現像剤規制部材（穂切り部材）４６を有している。
【００４７】
現像装置本体４０には、現像ローラに隣接して回収搬送スクリュー４２Ａを内蔵する現像剤回収搬送室（以下回収搬送室とも言う。）４２が、第１撹拌搬送スクリュー４３Ａを内蔵する第１の現像剤撹拌搬送室である第１現像剤撹拌搬送室（以下第１撹拌搬送室とも言う。）４３が回収搬送室４２に隣接して設けられている。さらに、第２撹拌搬送スクリュー４４Ａを内蔵する第２の現像剤撹拌搬送室である第２現像剤撹拌搬送室（以下第２撹拌搬送室とも言う。）４４が第１撹拌搬送室４３の上方に設けられ、供給搬送スクリュー４５Ａを内蔵する現像剤供給搬送室（以下供給搬送室とも言う。）４５が第２撹拌搬送室４４と現像ローラ４１に隣接して設けられている。
【００４８】
また、現像装置本体４０内には、現像剤回収搬送室４２と第１現像剤撹拌搬送室４３の間に設けられ、回収搬送スクリュー４２Ａにより搬送された現像剤を第１撹拌搬送室に移送する第１の連通部である第１連通部４２Ｂと、第１現像剤撹拌搬送室４３と第２現像剤撹拌搬送室４４の間に設けられ、第１撹拌搬送スクリュー４３Ａにより搬送された現像剤を第２撹拌搬送室４４に移送する第２の連通部である第２連通部４３Ｂを有している。
【００４９】
また、第２現像剤撹拌搬送室４４と現像剤供給搬送室４５の間には、第２撹拌搬送スクリュー４４Ａにより搬送された現像剤を供給搬送室４５に移送する第３の連通部である第３連通部４４Ｂと、供給搬送室４５より現像ローラ４１に供給されることなく供給搬送室４５内を最下流まで搬送された現像剤を第２撹拌搬送室４４に移送する第４の連通部である第４連通部４５Ｂの２つの連通部が設けられている。
【００５０】
そして、供給搬送室４５には前述の第４連通部４５Ｂよりも上方に位置する様に、供給搬送室４５内の現像剤を回収搬送室４２に移送する第５の連通部である第５連通部４５Ｂ′が設けられ、第１連通部４２Ｂの近傍には現像ローラより回収された現像剤にトナー補給を行うトナー補給部４７が設けられている。
【００５１】
本発明に係る現像装置４では、図３及び図４で矢印で示す様に、以下の様な現像剤の循環搬送が行われている。
【００５２】
先ず、現像ローラ４１は、例えば図１に示す像担持体１に対向して配置され、現像領域と呼ばれる現像ローラ表面にトナーとキャリアからなる現像剤を担持し、前述の像担持体１にトナー供給を行っている。現像ローラ４１は筒状の導体で、回転可能な現像スリーブと、現像スリーブに内蔵される図示しない複数の磁極より構成され、現像ローラ４１に隣接する現像剤供給搬送スクリュー４５Ａより供給されるトナーとキャリアよりなる２成分現像剤を用いて、像担持体１上の静電潜像を現像する。現像ローラ４１上への現像剤供給は、前述した複数の磁極のうち現像剤受け入れ用磁極と呼ばれる磁極からの磁界の作用で現像剤を現像ローラ上に吸引して行われる。また、現像ローラ４１上に供給される現像剤の量は、現像ローラ４１表面と一定間隔のギャップを開けて配置されている現像剤規制部材（穂切り部材）４６により規制される。
【００５３】
現像に使用された現像剤は、現像ローラ４１の中心より下部領域で前述した現像ローラ内に配置されている複数の磁極のうち、釈放磁極と呼ばれる磁極からの反発磁界の作用で現像ローラ４１より除去される。なお、本発明に係る現像装置では、画像形成に使用された現像剤を一旦現像ローラ４１表面より完全に除去した後に供給スクリュー４５Ａより現像ローラ４１表面に新しい現像剤供給を行う構成としている。
【００５４】
現像ローラ４１表面より除去された現像剤は、現像剤回収搬送手段である回収搬送ローラ４２Ａにより回収されながら回収搬送室４２内を搬送される。なお、回収搬送室４２内では現像に使用された現像剤の他に、後述する第５連通部４５Ｂ′より搬送されてきた現像剤も搬送されている。図３では、現像剤の搬送方法の一例として回収搬送室４２内の現像剤は、図４に示す様に図の奥側より手前側に向かって搬送されている。
【００５５】
次に、回収搬送室４２内を搬送された現像剤は、図４に示す様に回収搬送室４２の最下流領域に設けられた第１連通部４２Ｂを経由して第１撹拌搬送室４３に移送される。なお、本発明に係る現像装置では、第１連通部４２Ｂの近傍にトナー補給部４７を設け、トナー含有量（トナー濃度）の減少した回収現像剤へのトナー補給の実施を可能にしている。
【００５６】
第１撹拌搬送室４３では、第１撹拌搬送スクリュー４３Ａにより補給トナーＨＴの添加された現像剤が撹拌、搬送される。図３及び図４に示す様に、第１撹拌搬送室４３では、前段階の回収搬送室４２における現像剤の搬送方向と逆方向に現像剤は搬送される。なお、図３及び図４では搬送方向の一例として、第１撹拌搬送室内における現像剤の搬送方向は、図の手前側より奥側に向かって搬送することが図示されている。
【００５７】
第１撹拌搬送スクリュー４３Ａにより撹拌、搬送された現像剤は、図３（ａ）と図４に示す様に、第１撹拌搬送室４３の最下流領域で第２連通部４３Ｂを経由して第１撹拌搬送室４３の上方に隣接する第２撹拌搬送室４４に移送される。第２撹拌搬送室４４では、第２撹拌搬送スクリュー４４Ａにより第１撹拌搬送室４３同様に現像剤の撹拌、搬送が行われるが、第２撹拌搬送室４４内では、図３及び図４に示す様に前段階の第１撹拌搬送室４３における現像剤の搬送方向と逆方向に現像剤が搬送される。なお、図３及び図４では第２撹拌搬送室における現像剤の搬送方向は、図の奥側より手前側に向かって搬送されることが示されている。
【００５８】
第１撹拌搬送スクリュー４３Ａ及び第２撹拌搬送スクリュー４４Ａは、現像剤を構成するトナーとキャリアとが均一分散する様に、そしてトナーに十分な帯電性を付与する様に撹拌、搬送を行っている。
【００５９】
前述した様に、本発明に係る現像装置４では、第１撹拌搬送室４３内及び第２撹拌搬送室４４内で補給トナーの撹拌を行うので、従来技術における現像装置よりもはるかに長時間撹拌を行っている。その結果、現像ローラに供給される時には画像形成に十分な摩擦帯電が行われ、帯電立ち上がり不良の問題を解消している。
【００６０】
第２撹拌搬送室４４で撹拌、搬送された現像剤は、図３（ｃ）と図４に示す様に、第２撹拌搬送室４４の最下流に設けられた第３連通部４４Ｂを経由して、第２撹拌搬送室の横に隣接する供給搬送室４５に移送される。供給搬送室４５では、現像剤は供給搬送スクリュー４５Ａにより供給搬送室４５内を搬送しながら、供給搬送室４５に隣接する現像ローラ４１上に供給される。供給搬送室４５内で現像剤は第２撹拌搬送室における搬送方向と逆方向に搬送される。
【００６１】
本発明では、供給搬送室４５の端部近傍まで搬送され、現像ローラ４１に供給されることのなかった現像剤を、図３（ａ）と図４に示す様に、第４連通部４５Ｂを経由して再度第２撹拌搬送室内に移送し、第２撹拌スクリュー４４Ａにより再度撹拌、搬送して供給搬送室４５に移送している。
【００６２】
この様に、本発明に係る現像装置では、供給搬送室４５の最下流領域に第２撹拌搬送室に現像剤を移送する第４連通部を設け、供給搬送室４５で現像ローラ４１に供給されなかった現像剤を第２撹拌搬送室に戻し、短時間で再度現像ローラ４１への供給の機会を増大させている。
【００６３】
また、本発明に係る現像装置４は、供給搬送室４５内において現像剤の量が一定量をオーバーした時にのみ第５連通部４５Ｂ′を経由して供給搬送室４５内の現像剤が回収搬送室４２に移送する様にした。その結果、所定のトナー濃度に調整され、しかもトナーの帯電が十分に行われた現像剤が、供給搬送室４５から回収搬送室４２に無駄に回収されることなく、その量を激減させることを可能にするとともに、現像ローラより回収され、現像に供されてトナー濃度の不足した現像剤はトナー補給を行った後に十分に撹拌し、トナーの帯電を十分に行うことを可能にした。
【００６４】
この様に、本発明に係る第１の実施形態である現像装置４では現像剤の循環搬送が行われ、現像ローラ４１上では画像形成に使用された現像剤が一旦完全に除去された後、新たに現像剤供給が行われ、像担持体１上に形成された静電潜像を現像する。
【００６５】
次に、本発明に係る現像装置の第２実施形態として、像担持体の下方に配置する現像装置４を図５，６に基づいて説明する。
【００６６】
図５と図６は、例えば図２に示す画像形成装置に使用される本発明の第２実施形態として像担持体の下方に配置される現像装置４の模式図で、図５（ａ）〜（ｄ）は図６中の破線矢印で表すａａ、ｂｂ、ｃｃ及びｄｄより見た要部断面図で、図６は現像装置４を図５（ａ）のＸ方向よりみた時の側面図で、上側は要部断面図の左側を、下側は要部断面図の右側を示している。図５（ａ）〜（ｄ）中の矢印は図３と同様、現像装置内における現像剤の搬送方向を示し、図６の太い矢印は搬送量の多いことを、細い矢印は搬送量の少ないことを表している。
【００６７】
図５及び図６に示される現像装置４は、以下の手段より構成される。すなわち、現像装置本体４０、現像剤担持体である現像ローラ（現像スリーブとも言う。）４１、現像剤回収搬送手段である回収搬送スクリュー４２Ａ、第１の現像剤撹拌搬送手段である第１撹拌搬送スクリュー４３Ａ、第２の現像剤撹拌搬送手段である第２撹拌搬送スクリュー４４Ａ、現像剤供給搬送手段である供給搬送スクリュー４５Ａ、現像剤規制部材（穂切り部材）４６を有している。
【００６８】
現像装置本体４０には、回収搬送スクリュー４２Ａを内蔵する現像剤回収搬送室（以下回収搬送室とも言う。）４２が現像ローラ４１の下方に隣接して設けられ、第１撹拌搬送スクリュー４３Ａを内蔵する第１の現像剤撹拌搬送室である第１現像剤撹拌搬送室（以下第１撹拌搬送室とも言う。）４３が回収搬送室４２の下方に隣接して設けられ、第２撹拌搬送スクリュー４４Ａを内蔵する第２の現像剤撹拌搬送室である第２現像剤撹拌搬送室（以下第２撹拌搬送室とも言う。）４４が第１撹拌搬送室４３の側方に隣接して設けられ、供給搬送スクリュー４５Ａを内蔵する現像剤供給搬送室（以下供給搬送室とも言う。）４５が第２撹拌搬送室４４の上方と現像ローラ４１の下方に隣接する様に設けられている。
【００６９】
また、現像装置本体４０内には、現像剤回収搬送室４２と第１現像剤撹拌搬送室４３の間に設けられ、回収搬送スクリュー４２Ａにより搬送された現像剤を第１撹拌搬送室に移送する第１の連通部である第１連通部４２Ｂ、第１現像剤撹拌搬送室４３と第２現像剤撹拌搬送室４４の間に設けられ、第１撹拌搬送スクリュー４３Ａにより搬送された現像剤を第２撹拌搬送室４４に移送する第２の連通部である第２連通部４３Ｂを有し、第２現像剤撹拌搬送室４４と現像剤供給搬送室４５の間には、第２撹拌搬送スクリュー４４Ａにより搬送された現像剤を供給搬送室４５に移送する第３の連通部である第３連通部４４Ｂと、供給搬送室４５より現像ローラ４１に供給されることなく供給搬送室４５内を最下流まで搬送された現像剤を第２撹拌搬送室４４に移送する第４の連通部である第４連通部４５Ｂを有している。そして、供給搬送室４５には前述の第４連通部４５Ｂよりも上方に位置する様に、供給搬送室４５内の現像剤を回収搬送室４２に移送する第５の連通部である第５連通部４５Ｂ′が設置されている。さらに第１連通部４２Ｂの近傍には現像ローラより回収された現像剤にトナー補給を行うトナー補給部４７が設けられている。
【００７０】
図５及び図６に示される現像装置４では、図３及び図４で説明した本発明の第１実施形態の現像装置と同様の搬送形態で、図５及び図６中の矢印で示す搬送経路で現像剤が循環搬送され、供給搬送スクリュー４５Ａより現像ローラ４１に現像剤供給が行われている。なお、図５及び図６に示す本発明の第２実施形態の現像装置４における現像剤の搬送形態は、前述の本発明の第１実施形態の現像装置と同様であるので、ここでは詳細な説明を省略する。
【００７１】
また、図５及び図６に示す本発明の第２実施形態の現像装置も、第１実施形態の現像装置と同様に、供給搬送室４５の最下流領域に第２撹拌搬送室に現像剤を移送する第４連通部を設け、供給搬送室４５で現像ローラ４１に供給されなかった現像剤を第２撹拌搬送室に戻すことで、十分に帯電させたトナーを含有する現像剤を現像ローラ４１に供給する機会を増やしている。
【００７２】
また、供給搬送室４５内において現像剤の量が一定量をオーバーした時にのみ第５連通部４５Ｂ′を経由して供給搬送室４５内の現像剤が回収搬送室４２に移送する様にした。その結果、所定のトナー濃度に調整され、しかもトナーの帯電が十分に行われた現像剤が、供給搬送室４５から回収搬送室４２に無駄に回収されることなく、その量を激減させるとともに、現像ローラより回収された現像剤はトナー補給を行った後で十分に撹拌してトナー帯電を確実に実施することを可能にした。
【００７３】
なお、上記第１及び第２の実施形態の現像装置では、供給搬送室４５内において所定量をオーバーした現像剤のみが回収搬送室４２に移送されるが、回収搬送室４２に移送される現像剤は、第５の連通部を供給搬送室４５と第２撹拌搬送室４４の間にある２つの連通部、すなわち、第３の連通部４４Ｂと第４の連通部４５Ｂよりも上方に設けるとともに、供給搬送室４５内の図３及び図４のａａで示される搬送下流側の底面に、例えば特開２００１−１６６５９３公報に記載される障壁や仕切板等を第４連通部を介して第２撹拌搬送室への現像剤搬送を邪魔しない様に設け、これらの障壁や仕切板を乗り越えた現像剤のみが回収搬送室４２に搬送される構成となっている。
【００７４】
次に、本発明の第３及び第４の実施形態の現像装置について説明する。
本発明の第３及び第４の実施形態の現像装置は、トナー補給手段及びキャリア補給手段と、供給搬送室内で所定量オーバーした分の現像剤を現像装置外に排出する排出手段を有するものである。本発明の第３及び第４の実施形態の現像装置では、トナー補給手段及びキャリア補給手段より現像装置内に新たな現像剤の供給を行うとともに、現像剤供給によるオーバーフロー分の現像剤を現像装置外に排出して、繰り返しの画像形成に使用されて劣化したキャリアに代えて新しいキャリアを補充することで現像剤の劣化に伴う帯電性能の低下を解消している。
【００７５】
本発明の第３の実施形態の現像装置の例を図７に、第４の実施形態の現像装置の例を図８に示す。図７に示される本発明の第３の実施形態の現像装置は前述の図３及び図４に示した現像装置と同様、像担持体の横側方に設置されるタイプで、図８に示される本発明の第４の実施形態の現像装置は前述の図５及び図６に示した現像装置と同様、像担持体の下方に設置するタイプである。図７と図８の現像装置では、図示されたキャリア補給部４８により補給キャリアＨＣのキャリア補給に伴い、供給搬送室４５内に収容され所定量をオーバーした分の現像剤を現像装置外に排出する現像剤排出部４９を第２撹拌搬送室４４或いは供給搬送室４５の外壁に設置している。
【００７６】
図７及び図８の現像装置４は、現像装置本体４０、現像剤担持体である現像ローラ（現像スリーブとも言う。）４１、現像剤回収搬送手段である回収搬送スクリュー４２Ａ、第１の現像剤撹拌搬送手段である第１撹拌搬送スクリュー４３Ａ、第２の現像剤撹拌搬送手段である第２撹拌搬送スクリュー４４Ａ、現像剤供給搬送手段である供給搬送スクリュー４５Ａ、現像剤規制部材（穂切り部材）４６を有している。
【００７７】
現像装置本体４０には、第１実施形態及び第２実施形態の現像装置と同様に、現像ローラに隣接して回収搬送スクリュー４２Ａを内蔵する現像剤回収搬送室（以下回収搬送室とも言う。）４２が、第１撹拌搬送スクリュー４３Ａを内蔵する第１の現像剤撹拌搬送室である第１現像剤撹拌搬送室（以下第１撹拌搬送室とも言う。）４３が設けられ、第２撹拌搬送スクリュー４４Ａを内蔵する第２の現像剤撹拌搬送室である第２現像剤撹拌搬送室（以下第２撹拌搬送室とも言う。）４４が設けられ、供給搬送スクリュー４５Ａを内蔵する現像剤供給搬送室（以下供給搬送室とも言う。）４５が設けられている。
【００７８】
また、現像装置本体４０内には、第１実施形態及び第２実施形態の現像装置と同様に、現像剤回収搬送室４２と第１現像剤撹拌搬送室４３の間に設けられ、回収搬送スクリュー４２Ａにより搬送された現像剤を第１撹拌搬送室４３に移送する第１の連通部である第１連通部４２Ｂ、第１現像剤撹拌搬送室４３と第２現像剤撹拌搬送室４４の間に設けられ、第１撹拌搬送スクリュー４３Ａにより搬送された現像剤を第２撹拌搬送室４４に移送する第２の連通部である第２連通部４３Ｂを有し、第２現像剤撹拌搬送室４４と現像剤供給搬送室４５の間には、第２撹拌搬送スクリュー４４Ａにより搬送された現像剤を供給搬送室４５に移送する第３の連通部である第３連通部４４Ｂと、供給搬送室４５より現像ローラ４１に供給されることなく供給搬送室４５内を最下流まで搬送された現像剤を第２撹拌搬送室４４に移送する第４の連通部である第４連通部４５Ｂを有している。
【００７９】
さらに、図７及び図８に示される現像装置の現像装置本体４０の供給搬送室４５の最下流領域には、第１連通部４２Ｂの近傍に現像ローラ４１より回収された現像剤にトナー補給及びキャリア補給を行うトナー補給部４７とキャリア補給部４８とが設けられている。また、供給搬送室４５には、前述の第４連通部４５Ｂよりも上方に位置する様に、供給搬送室４５内の現像剤を現像装置外に排出させる現像剤排出部４９が設けられている。
【００８０】
この様に、本発明の第３実施形態及び第４実施形態に係る現像装置４は、図７と図８の各（ａ）〜（ｃ）に示す様に、トナー補給部４７に加えてキャリア補給部４８と現像剤排出部４９を有し、第５連通部を有していない点を除くと、本発明の第１実施形態及び第２実施形態に係る現像装置と共通の手段及び搬送室より構成されている。なお、図７と図８の（ａ）は（ｃ）の矢印ｐｐより見た要部断面を示し、（ｂ）は（ｃ）の矢印ｑｑより見た要部断面を示す。
【００８１】
そして、図７及び図８に示す現像装置も図３〜図６で説明した現像装置と同様に、第２撹拌搬送室４４と供給搬送室４５の間に第２撹拌搬送室４４より搬送されてきた現像剤を供給搬送室４５に移送する第３連通部４４Ｂに加えて、供給搬送室４５を搬送中に現像ローラ４１に供給されなかった現像剤を第２撹拌搬送室４４に戻すための第４連通部４５Ｂを設けることにより、現像ローラ４１に短時間の内に再度の現像剤供給を行う機会を増やしている。
【００８２】
また、図７及び図８の現像装置は、図中のｑｑで示す領域にトナー補給部４７とともにキャリア補給部４８とを設け、画像形成によりトナーの含有量（トナー濃度）の減少した現像剤にトナー補給を行うとともにキャリア補給を行う。
【００８３】
さらに、図７及び図８の現像装置は、現像剤排出部４９を供給搬送室４５の外壁に設け、現像剤の補充に伴って供給搬送室４５内の現像剤量が所定量をオーバーした時に、オーバー分の現像剤を現像装置外に排出し、現像装置内の現像剤量を常に一定に保っている。
【００８４】
この様に、本発明に係る第３及び第４の実施形態の現像装置では、キャリア補給部４８と現像剤排出部４９とを設けることにより、新しいキャリアを定期的に現像装置内に供給し、代わりに繰り返しの画像形成に使用され、現像装置内で受けた負荷によって、劣化、破損したキャリアを現像装置外に排出しているため、キャリア劣化に伴うトナーの帯電性付与機能の低下の問題を解消し、常時安定したキャリアによるトナーへの摩擦帯電が行われている。
【００８５】
なお、図７及び図８ではトナー補給部４７とキャリア補給部４８とは各々独立した形態で設けているが、本発明に係る現像装置ではトナーとキャリアとが混合状態で供給される場合の様に、１つの供給口を介して現像剤供給を行うものであってもよい。
【００８６】
図７及び図８の現像装置では、いずれも現像剤排出部４９より排出される現像剤が供給搬送室４５内で所定量オーバーしたものが排出されるが、現像剤排出部４９を第２撹拌搬送室４４と供給搬送室４５の間に設けられる２つの連通部、すなわち第３連通部４４Ｂ及び第４連通部４５Ｂの設置個所よりも上方に位置する様に図７のｐｐで示される供給搬送室４５内の搬送下流側に、例えば特開２００１−１６６５９３公報に記載される様な障壁や仕切板等を第２撹拌搬送室への現像剤搬送を邪魔しない様に設け、これらの障壁や仕切板を乗り越えた現像剤のみが現像剤排出部４９より排出する様に構成されている。
【００８７】
本発明に係る現像装置における供給搬送手段は、現像剤担持体である現像ローラ表面に均一かつ等量に現像剤供給可能な性能を有するものであれば特に限定されるものではないが、現像ローラ表面に均一かつ等量に現像剤供給可能な性能を有する好ましい部材としては回転部材が挙げられる。回転部材の具体例としては、例えばスクリューオーガが挙げられる。
【００８８】
本発明で供給搬送手段として好ましく使用される回転部材は、現像ローラとの対向部において現像ローラの回転方向に対し順方向に回転するものであっても、或いは逆方向に回転するものあってもよい。本発明に係る供給搬送手段として使用される回転部材である供給搬送スクリュー４５Ａの回転方向の例として、図３では現像ローラ４１の回転方向と逆方向に回転するものが示され、図５には現像ローラ４１の回転方向に対し順方向に回転するものが示されている。
【００８９】
また、本発明に係る現像装置に使用される供給搬送手段として、スクリューオーガを使用する場合、以下の式（１）を満足する様に各条件を設定することが好ましい。
【００９０】
式（１）：５ＶＬＷ≦｛π（Ｄ１ ２−Ｄ２ ２）ＰＲ｝ρ≦２０ＶＬＷ
式中、Ｖ：現像剤担持体の周速（ｍｍ／ｓｅｃ）
Ｌ：現像剤担持体上の現像剤層の回転軸方向の長さ（ｍｍ）
Ｗ：現像剤担持体上の単位面積当たりの現像剤質量（ｍｇ／ｃｍ２）
ρ：現像剤の嵩密度（ｇ／ｃｍ３）
Ｄ１：現像剤供給搬送手段（スクリューオーガ）の外径（ｍｍ）
Ｄ２：現像剤供給搬送手段（スクリューオーガ）の軸径（ｍｍ）
Ｐ：現像剤供給搬送手段（スクリューオーガ）のピッチ（ｍｍ）
Ｒ：現像剤供給搬送手段（スクリューオーガ）の回転数（ｒｐｍ）
また、本発明に係る現像装置における他の搬送手段、すなわち、回収搬送手段、第１撹拌搬送手段及び第２撹拌搬送手段についても、通常使用されるものであれば特に限定されないが、スクリューオーガを使用する上記搬送手段として使用する場合には、上記式を満足する様に各条件を設定することが好ましい。
【００９１】
次に、本発明で好ましく用いられる現像剤を構成するトナーとキャリアについて説明する。最初に、本発明に好ましく用いられるトナーについて説明する。
【００９２】
本発明で用いられるトナーの粒径は、体積平均粒径で３〜５μｍの重合トナーが好ましく用いられる。この粒径は、トナー粒子の製造方法において、凝集剤（塩析剤）の濃度や有機溶媒の添加量、融着時間、重合体の組成によって制御することができる。
【００９３】
体積平均粒径が３〜５μｍの小粒径トナーを用いることにより、高解像力を有し、画像濃度の安定した、かぶりの発生の少ない、しかも細線再現性の優れたトナー画像の得られる画像形成が可能となる。
【００９４】
なお、トナーの体積平均粒径の測定は、コールターカウンターＴＡ−ＩＩ、コールターマルチサイザー（いずれもコールター社製）、ＳＬＡＤ１１００（島津製作所社製レーザ回折式粒径測定装置）等を用いて測定することができる。本発明においては、コールターマルチサイザーを用い、粒度分布を出力するインターフェース（日科機社製）、パーソナルコンピュータを接続し測定、算出したものである。本発明に係る現像装置に使用される現像剤を構成するトナーとしては、特開２０００−２１４６２９公報に記載された小粒径で分布の揃った、粒子上に角のない丸みを有するトナーが好ましく用いられる。
【００９５】
上記のトナーは、例えば、特開平５−２６５２５２号公報、特開平６−３２９９４７号公報、特開平９−１５９０４号公報に記載される様なトナー粒子を構成する樹脂粒子を、水分含有率が５０質量％以上の水系媒体中で凝集させて製造する方法により得られるものが好ましく使用される。
【００９６】
体積平均粒径が、３μｍを下回ると、かぶりやトナー飛散が発生し易くなり、また、５μｍを超えると高解像力の画像形成ができなくなる場合がある。
【００９７】
また、本発明に使用される二成分現像剤を構成するキャリアとしては、体積平均粒径がトナーの体積平均粒径の５〜１０倍で、磁化量が２．５〜８．８×１０−５Ｗｂ・ｍ／ｋｇの磁性粒子よりなるキャリアが好ましい。この様な体積平均粒径と磁化量を有するキャリアを用いることにより、かぶりやトナー飛散或いはトナーのキャリア付着といった問題を発生させずに、均一な画像濃度のトナー画像を安定して形成することが可能である。
【００９８】
また、本発明で使用されるキャリアの磁性粒子として、鉄、フェライト、マグネタイト等の金属、それらの金属とアルミニウム、鉛等の金属との合金等の従来から公知の材料を用いることが出来る。特にフェライト粒子が好ましい。
【００９９】
なお、本発明で使用されるキャリアの体積平均粒径がトナーの体積平均粒径の５倍に満たない場合や、磁化量が２．５×１０−５Ｗｂ・ｍ／ｋｇに満たない場合、キャリア付着が発生し易くなる傾向を有している。また、キャリアの体積平均粒径がトナーの体積平均粒径の１０倍を超える場合や、磁化量が８．８×１０−５Ｗｂ・ｍ／ｋｇを上回るキャリアを使用すると、荒れたハーフトーン画像となることがあるので好ましくない。
【０１００】
なお、キャリアの体積平均粒径の測定は、代表的には湿式分散機を備えたレーザ回折式粒度分布測定装置「ヘロス（ＨＥＬＯＳ）」（シンパティック（ＳＹＭＰＡＴＥＣ）社製）により測定することができる。
【０１０１】
キャリアは、磁性粒子が更に樹脂により被覆されているもの、あるいは樹脂中に磁性粒子を分散させたいわゆる樹脂分散型キャリアが好ましい。コーティング用の樹脂組成としては、特に限定は無いが、例えば、オレフィン系樹脂、スチレン系樹脂、スチレン−アクリル系樹脂、シリコーン系樹脂、エステル系樹脂或いはフッ素含有重合体系樹脂等が用いられる。また、樹脂分散型キャリアを構成するための樹脂としては、特に限定されず公知のものを使用することができ、例えば、スチレン−アクリル系樹脂、ポリエステル樹脂、フッ素系樹脂、フェノール樹脂等を使用することができる。
【０１０２】
本発明に係る現像装置に好ましく用いられる現像剤としては、以上述べた様なキャリア粒子とトナーとを混合した現像剤が好ましく用いられるが、キャリアとして、一般のコーティングキャリア（密度５〜８ｇ／ｃｍ３）を使用した場合、現像剤中のトナー濃度は２〜３０質量％、好ましくは５〜２０質量％である。
【０１０３】
トナー濃度が、２質量％より小さいと、現像に必要なトナー数が確保できなくなり、被覆率が低下するため帯電過剰、現像性低下を招く。
【０１０４】
３０質量％より大きいと、被覆率が大となり、帯電不良、トナー飛散が起こり易くなる。
【０１０５】
【実施例】
以下、実施例を挙げて本発明を詳細に説明するが、本発明の態様はこれに限定されるものではない。
【０１０６】
（実施例１）
図１の画像形成装置におけるマゼンタ及びシアンの現像装置に、図３／図４に記載の現像装置を搭載して、以下の設定条件で画像形成の実験を行った。
【０１０７】
プロセス速度（感光体ドラム周速）：２２０ｍｍ／ｓｅｃ
印字速度：５０枚／分（Ａ４横送り）
〔現像装置の条件〕
▲１▼現像ローラ
外径　　　：３０ｍｍ
周速（Ｖ）：３３０〜４４０ｍｍ／ｓｅｃ
現像ローラ上の現像剤層の回転軸方向の長さ（Ｌ）：３１０ｍｍ
現像ローラ上の単位面積当たりの現像剤質量（Ｗ）：３０ｍｇ／ｃｍ２
▲２▼供給搬送スクリュー
外径（Ｄ１）：２４ｍｍ
軸径（Ｄ２）：６ｍｍ
ピッチ（Ｐ）：３０ｍｍ
回転軸方向の長さ：３２０ｍｍ
回転数（Ｒ）：４００ｒｐｍ
▲３▼回収搬送スクリュー及び第１撹拌搬送スクリュー
回転軸方向の長さを４２０ｍｍとした以外は、上記供給搬送スクリューと同一条件に設定した。
▲４▼第２撹拌搬送スクリュー
外径、軸径、ピッチ、回転軸方向の長さ、及び回転数を上記供給搬送スクリューと同一条件に設定した。
〔現像剤〕
以下に示す条件でマゼンタ用の現像剤及びシアン用の現像剤を調製した。
▲１▼トナー平均粒径：４．５μｍ
▲２▼キャリア平均粒径：２５μｍ
▲３▼画像形成開始時におけるトナー濃度：８質量％
▲４▼現像剤の嵩密度（ρ）：２．２ｇ／ｃｍ３
▲５▼現像装置内における現像剤充填量：１３００ｇ
以上の条件下で、マゼンタ及びシアンの印字率がともに５０％のカラー画像パターン（Ａ４横）を連続２００枚出力し、該カラー画像パターンの画質を評価した。
【０１０８】
実験の結果、スタートから連続２００枚出力後に至るまでの間、かぶりや濃度むらの発生が全く見られず、高濃度の画像が安定して得られた。
【０１０９】
また、マゼンタ、シアンのソリッド部パッチ、ならびにブルーのソリッド部パッチのページ内及びページ間の色差（ΔＥ）は、連続２００枚を通じていずれも５以下であった。
【０１１０】
さらに、連続印字終了後に現像装置を画像形成装置より取り外し、トナー飛散状況を目視にて観察したが、トナー飛散の発生は全く見られなかった。
【０１１１】
（実施例２）
次に、図２に示す画像形成装置における現像装置として、図５／図６に記載の現像装置を搭載し、以下の設定条件で画像形成の実験を行った。
【０１１２】
プロセス速度（感光体ドラム周速）：３２０ｍｍ／ｓｅｃ
印字速度：６５枚／分（Ａ４横送り）
〔現像装置の条件〕
▲１▼現像ローラ
外径　　　：３０ｍｍ
周速（Ｖ）：４８０〜６４０ｍｍ／ｓｅｃ
現像ローラ上の現像剤層の回転軸方向の長さ（Ｌ）：３１０ｍｍ
現像ローラ上の単位面積当たりの現像剤質量（Ｗ）：３０ｍｇ／ｃｍ２
▲２▼供給搬送スクリュー
外径（Ｄ１）：２４ｍｍ
軸径（Ｄ２）：６ｍｍ
ピッチ（Ｐ）：３０ｍｍ
回転軸方向の長さ：３２０ｍｍ
回転数（Ｒ）：４００ｒｐｍ
▲３▼回収搬送スクリュー
外径、軸径、ピッチ、回転軸方向の長さ、及び回転数を上記供給搬送スクリューと同一条件に設定した。
▲４▼第１撹拌搬送スクリュー及び第２撹拌搬送スクリュー
回転軸方向の長さを４２０ｍｍに設定した他は、上記供給搬送スクリューと同一条件に設定した。
〔現像剤〕
以下に示す条件で現像剤の調製を行った。
▲１▼トナー平均粒径：４．５μｍ
▲２▼キャリア平均粒径：２５μｍ
▲３▼画像形成開始時におけるトナー濃度：８質量％
▲４▼現像剤の嵩密度（ρ）：２．２ｇ／ｃｍ３
▲５▼現像装置内における現像剤充填量：１３００ｇ
以上の条件下で、印字率が８０％のシアン単色画像パターン（Ａ４横）を連続２００枚出力し、該画像パターンの画質を評価した。
【０１１３】
実験の結果、スタートから連続２００枚出力後に至るまでの間、かぶりや濃度むらの発生が全く見られず、高濃度の画像が安定して得られた。
【０１１４】
また、マゼンタ、シアンのソリッド部パッチ、ならびにブルーのソリッド部パッチのページ内及びページ間の色差（ΔＥ）は、連続２００枚を通じていずれも５以下であった。
【０１１５】
さらに、連続印字終了後に現像装置を画像形成装置より取り外し、トナー飛散状況を目視にて観察したが、トナー飛散の発生は全く見られなかった。
【０１１６】
【発明の効果】
この様に、本発明では、請求項１〜請求項１１のいずれか１項に記載の構成により、前述の課題が解決可能であることを見出した。
【０１１７】
先ず、請求項１〜３のいずれか１項に記載の発明は、現像剤供給部と現像剤回収部とを分離し、回収現像剤が必ずトナー補給部を経て現像剤供給部に循環搬送される構造を有するとともに、撹拌スクリューを２本配置して撹拌部の経路を長く設けた構造を有する現像装置に関するものである。
【０１１８】
請求項１〜３のいずれか１項に記載の現像装置では、現像剤を速く循環させても、帯電立ち上がり不良も現像剤枯渇の問題も発生せず、また、高印字率のトナー画像を連続作成して大量のトナー供給を繰り返しても、補給トナーが現像剤中に均一に分散されて、しかも十分な帯電性が得られるので、画像濃度やカラーバランスにむらのない印字率追従性に優れた美しい画質を有するトナー画像の得られる現像装置の提供を可能にした。
【０１１９】
次に、請求項４〜８のいずれか１項に記載の発明は、現像剤供給部と現像剤回収部とを分離し、回収現像剤が必ずトナー／キャリア補給部を経て現像剤供給部に循環搬送される構造を有するとともに、撹拌スクリューを２本配置して撹拌部の経路を長く設けた構造を有する現像装置に関するものである。
【０１２０】
請求項４〜８のいずれか１項に記載の発明によれば、前述の請求項１〜３のいずれか１項に係る現像装置で得られた効果に加えて、画像形成を繰り返し行ってもキャリアが常に安定した帯電付与性能を有することが可能なので、キャリアの表面変化に起因するトナーの帯電立ち上がり不良のない現像装置の提供を可能にした。
【０１２１】
また、請求項９に記載の発明では、現像剤を構成するトナーが、体積平均粒径が３μｍ〜５μｍの小粒径トナーを使用することで、高解像性と優れた細線再現性を発揮し、同時に画像濃度の安定した、トナー飛散によるかぶりの発生のないトナー画像の形成可能な現像装置の提供を可能にした。
【０１２２】
また、請求項１０に記載の発明では、現像剤を構成するキャリアの体積平均粒径をトナーの体積平均粒径の５倍〜１０倍の範囲のものとすることで、かぶりやトナー飛散或いはキャリア付着といった問題が発生することなく、均一な画像濃度を有するトナー画像の安定形成可能な現像装置の提供を可能にした。
【０１２３】
さらに、請求項１１に記載の発明では、前述した本発明に係る現像装置を用いることで高印字率の画像を連続出力する場合でもトナーとキャリアとが十分に混合撹拌され、帯電立ち上がりの十分なトナーが確実に得られる結果、色再現性やカラーバランスの優れた高画質カラー画像を高速で形成可能な画像形成装置の提供を可能にした。
【図面の簡単な説明】
【図１】像担持体の横側方に現像装置を設けたカラー画像形成装置の断面構成を示す模式図である。
【図２】像担持体の下方に現像装置を設けた画像形成装置の断面構成を示す模式図である。
【図３】像担持体の横側方に配置される現像装置の要部断面の模式図である。
【図４】像担持体の横側方に配置される現像装置の上方よりみた模式図である。
【図５】像担持体の下方に配置される現像装置の要部断面の模式図である。
【図６】像担持体の下方に配置される現像装置の側面よりみた模式図である。
【図７】像担持体の横側方に設置され、現像剤排出口とキャリア補給部とを有する現像装置の模式図である。
【図８】像担持体の下方に設置され、現像剤排出口とキャリア補給部とを有する現像装置の模式図である。
【符号の説明】
１　像担持体（感光体）
４　現像装置
１０　画像形成部
４０　現像装置本体
４１　現像ローラ
４２　回収搬送室
４３　第１撹拌搬送室
４４　第２撹拌搬送室
４５　供給搬送室
４６　現像剤規制部材（穂切り部材）
４７　トナー補給部
４８　キャリア補給部
４９　現像剤排出部
４２Ａ　回収搬送スクリュー
４２Ｂ　第１連通部
４３Ａ　第１撹拌搬送スクリュー
４３Ｂ　第２連通部
４４Ａ　第２撹拌搬送スクリュー
４４Ｂ　第３連通部
４５Ａ　供給搬送スクリュー
４５Ｂ　第４連通部
４５Ｂ′　第５連通部
ＨＣ　補給キャリア
ＨＴ　補給トナー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device for forming an image using a two-component developer including a carrier and a toner, and an image forming apparatus equipped with the developing device.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus that develops an electrostatic latent image on an image carrier such as a photosensitive drum through a developing device using a two-component developer including a toner and a carrier, a carrier is placed on a developing sleeve serving as a development area. A magnetic brush is formed, toner is supplied onto the image carrier via the magnetic brush, and the electrostatic latent image is developed.
[0003]
That is, in the developing device, the toner and the carrier are agitated so as to be uniformly dispersed, and after the toner is charged, the developer is supplied onto the developing sleeve, and the electrostatic latent image on the image carrier is transferred to the toner. To visualize. The developer used to visualize the electrostatic latent image on the image carrier is removed and collected from the developing sleeve, and the collected developer is replenished with the toner consumed in the image formation to form the image. Is used repeatedly.
[0004]
In the conventional developing device, a developer supply unit for supplying the developer to the developing sleeve and a developer collecting unit for collecting the developer used for the development from the developing sleeve are provided in common. The toner is supplied to the developing sleeve again, and the image quality of the toner image is poor due to the influence of the collected developer. In other words, the collected developer has a low toner concentration (toner content in the developer) by the amount of toner consumed in image formation, and a toner image having an appropriate concentration and balance can be obtained without replenishing the consumed toner. It cannot be formed. When an image is formed by supplying a developer mixed with a recovered developer having a low toner concentration to the development area, density unevenness occurs on the toner image.
[0005]
In particular, when an image having a high printing rate is continuously formed, the toner content of the collected developer is further reduced by the amount of toner consumption, so that the density unevenness on the toner image becomes remarkable. In particular, in color image formation, the color balance is lost due to uneven density on the toner image, so that good color reproducibility and color tone cannot be obtained, and the image quality is significantly deteriorated.
[0006]
Therefore, Japanese Patent Application Laid-Open No. 6-51634 proposes that a developer supply section and a developer recovery section be separated to carry out circulation and transport of the developer in a developing device. The problem of uneven toner concentration in the developer due to contamination has been largely eliminated. However, since the developing device of this document has a structure in which a part of the collected developer is circulated and conveyed without passing through the toner replenishing section, the developing device is developed in a state where the collected developer that is not supplied with the toner is present. When an image with a high printing rate is supplied and output, the stability with respect to the density variation of the toner image within one image or between the images, which is called the printing rate following property, is insufficient. A toner image having remarkable variation was obtained.
[0007]
In view of the above problems, a developing device that reliably supplies toner to a recovered developer, stirs well, uniformly distributes the toner in the developer, and obtains a developer in which the toner concentration in the developer does not vary. Was developed. In JP-A-9-146335, JP-A-2001-290368 and JP-A-2001-249545, a developer supply section, a developer collection section, and a developer stirring section are provided, and the collected developer is supplied with toner. There has been proposed a developing device having a configuration in which the developer is supplied to a developing area after being stirred through a section. In the developing devices disclosed in these documents, by providing the developer agitating section, the replenishment toner can be uniformly dispersed in the developer, and the problem of uneven toner concentration in the developer has been solved.
[0008]
In particular, JP-A-2001-249545 and JP-A-2001-290368 have also proposed a developing device in which one screw auger is added, the collected developer is stirred uniformly, and then toner is supplied.
[0009]
[Problems to be solved by the invention]
In the developing device proposed in the above document, the problem of uneven toner concentration in which the toner concentration locally varies in the developer has been improved.However, when the developer circulation speed in the developing device is low, the developing The supply of the developer is not in time, and a region where the developer is depleted occurs in the developing device, and this depleted region causes a region where the developer is not locally supplied on the developing region, which is a problem called developer supply unevenness. Occurred.
[0010]
Therefore, when the circulation and transport speeds of the developer in the developing device are increased, the residence time of the developer in the developer stirring section is shortened, so that it is no longer possible to impart sufficient chargeability to the toner.
[0011]
In particular, the replenishment toner added to supplement the toner consumption of the recovered developer is supplied to the developing area at a stage where charging has not sufficiently risen, and the toner with poor charging rise scatters in the image forming apparatus, and This caused toner contamination due to scattering. Further, the produced toner image also had an uneven image density and an imbalanced balance, fogging occurred, and particularly in a color image formation, an image having disturbed color reproducibility and color tone. In a high-speed image forming apparatus, the peripheral speed or the process speed of the image carrier is high, and the circulation speed of the developer is further increased.
[0012]
Further, in a developer comprising a carrier and a toner, there is a problem that the surface of the carrier is changed by repeating image formation, and the charging performance is deteriorated. The development of a developing device has been urgently needed.
[0013]
The present invention has been made in view of such a problem. That is, the present invention, even if a developer consisting of a toner and a carrier is repeatedly used for image formation, even if a toner image having a high printing rate excellent in printing rate followability is continuously produced, without causing unevenness in image density. An object of the present invention is to provide a developing device capable of obtaining a beautiful toner image with a well-balanced density and color balance.
[0014]
Further, a second object of the present invention is to provide a method for continuously forming an image having a high printing rate and even when a large amount of toner is supplied, the replenished toner is uniformly dispersed in the developer so that the toner concentration is not uneven. Further, an object of the present invention is to provide a developing device capable of forming an image, obtaining a sufficient amount of charge, and preventing toner scattering due to charging failure.
[0015]
Further, a third object of the present invention is to provide a developing device which can always obtain a stable charging performance even when image formation is repeatedly performed and does not cause a problem due to poor charging start of the toner.
[0016]
A fourth object of the present invention is to provide a high-speed color image forming apparatus having excellent color tone and color reproducibility.
[0017]
[Means for Solving the Problems]
The inventor of the present invention has conducted a intensive study and, as a result, has a structure in which the developer supply unit and the developer collection unit are separated, and the collected developer is always circulated to the developer supply unit via the toner supply unit. A developing device having a structure in which two stirring screws are arranged to provide a long path for the stirring section has been found.
[0018]
That is, the developing device according to the present invention separates the developer supply section and the developer recovery section, which is called a developer one circulation structure, and the recovered developer is always circulated to the developer supply section via the toner supply section. By adopting such a structure, it is possible to develop a developing device that does not cause uneven toner concentration when the collected developer is supplied to the developing area again.
[0019]
Further, in the present invention, by setting two stirring screws to lengthen the path of the stirring section, the toner can be sufficiently charged up even when the developer circulation speed is high in the developing device having the developer-circulating structure. This makes it possible to simultaneously solve the two problems of poor charging start-up and developer depletion.
[0020]
As described above, in the developing device according to the present invention, even if the developer is circulated at a high speed, there is no problem of poor charging start and uneven developer supply, and a toner image having a high printing rate can be continuously formed. Even after repeated preparation and supply of a large amount of toner, the replenishment toner is evenly dispersed in the developer and sufficient chargeability is obtained, so that the printing rate is uniform without uneven image density and color balance. It has become possible to obtain a toner image having a beautiful image quality with excellent followability and free from toner scattering due to poor charging rise.
[0021]
That is, the inventor of the present invention has found that the above effects can be obtained by the developing device having the configuration described in any one of claims 1 to 3 and 8.
[0022]
In addition, the present inventor has a structure in which a developer supply section and a developer recovery section are separated, and the recovered developer is always circulated and conveyed to the developer supply section via a toner / carrier supply section. A developing device having a structure in which two channels are arranged to provide a long path for the stirring unit has been found.
[0023]
That is, the second developing device according to the present invention supplies the carrier together with the toner to the collected developer, and is repeatedly used for image formation by adding a new carrier, and the surface is changed to deteriorate the charging performance. The discharged carrier can be discharged out of the developing device, so that the carrier constituting the developer in the developing device always has a stable charging performance.
[0024]
As a result, in the second developing device according to the present invention, in addition to the effects obtained by the above-described developing device, the carrier always has a stable charge imparting performance even when image formation is repeated, so that the surface change of the carrier can be improved. This makes it possible to develop a developing device free from toner charging failure caused by the above.
[0025]
That is, the present inventor has found that the developing device having the configuration described in any one of claims 4 to 8 has the above-described effects.
[0026]
Further, in the present invention, by selecting the configuration described in claim 9, the toner constituting the developer uses a small particle diameter toner having a volume average particle diameter of 3 μm to 5 μm, thereby achieving high resolution. And excellent fine line reproducibility, and at the same time, it was possible to form a toner image with stable image density and no fogging caused by toner scattering.
[0027]
In the present invention, the constitution described in claim 10 is selected, that is, the volume average particle diameter of the carrier constituting the developer is in the range of 5 to 10 times the volume average particle diameter of the toner. As a result, it has been found that a toner image having a uniform image density can be stably formed without causing problems such as fogging, toner scattering or carrier adhesion.
[0028]
Further, in the present invention, as described above, even when the developing device according to the present invention continuously outputs an image with a high printing rate, the toner and the carrier are sufficiently mixed and stirred, and a toner having a sufficient charge rising can be reliably obtained. Therefore, the configuration according to claim 11 makes it possible to create a high-quality color image with excellent color reproducibility and color balance at high speed.
[0029]
The color image forming apparatus according to the present invention is characterized by forming an image at a high speed, and the linear speed of the photosensitive drum at the time of printing on the photosensitive drum called a process speed is 200 mm /. It refers to those that are longer than sec.
[0030]
Incidentally, the printing rate follow-up property in the present invention is, for example, when continuously outputting a high printing rate image in which the background portion is filled on one side, such as an OHP material for presentation or a photographic image, when the developer is used. This indicates the degree to which the image density on the toner image fluctuates due to the fluctuation of the toner content (toner density). That is, in the case where a difference occurs in the image density in a printed image or between pages obtained when image formation is performed continuously, the printing rate following performance is poor, and there is no difference in the image density and a beautiful finish with no unevenness. If an image can be obtained, it is determined that the print followability is good.
[0031]
Further, the printing ratio in the present invention refers to the density of toner such as the number of toner dots per unit area of the transfer paper, and the percentage of the number of pixels on which exposure is performed for all the pixels per page is shown as a percentage. This is a value ((number of pixels subjected to exposure / number of all pixels) × 100) or a value represented by an integrated value of density (toner adhesion amount) for each pixel adjusted by pulse width modulation (PWM). In the case of an image forming apparatus that reproduces, for example, 256 gradations by PWM, the density of each pixel can be represented by a fraction such as x / 256 or a value obtained by converting the fraction into a percentage.
[0032]
Further, the toner concentration (%) in the present invention means the content of the toner in the two-component developer, and indicates the concentration of the toner contained in the developer in percentage by mass.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described, but the following description does not limit the technical scope of the claims and the meaning of the terms according to the present invention. In the description, the developer carrying member constituting the developing device is also referred to as a developing roller, a developing sleeve, or a developing area, and collectively refers to a developer collecting / conveying unit, a developer stirring / conveying unit, and a developer supplying / conveying unit. Also referred to as a developer transport unit or a transport unit, the developer collection transport chamber, the developer stirring transport chamber, and the developer supply transport chamber are also collectively referred to as a developer transport chamber or a transport chamber.
[0034]
First, an image forming apparatus equipped with the developing device according to the present invention will be described.
FIG. 1 shows a color image forming apparatus according to a first embodiment or a third embodiment of the present invention, which is provided with a developing device (hereinafter, also referred to as a developing unit and a developing device) arranged laterally of an image carrier. It is a schematic diagram which shows a structure.
[0035]
This color image forming apparatus is referred to as a tandem type color image forming apparatus, and is rotatably supported by a plurality of sets of image forming units 10Y, 10M, 10C, and 10K arranged in tandem and wound by a plurality of rollers. And an intermediate transfer member 7 in the form of a semiconductive endless belt, a sheet feeding and conveying means, and a fixing device 8.
[0036]
The image forming unit 10Y for forming a yellow image includes a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, a primary transfer unit 5Y, and a cleaning unit according to the present invention, which are arranged around an image carrier (photoconductor) 1Y. 6Y. The image forming unit 10M that forms a magenta image has an image carrier (photoconductor) 1M, a charging unit 2M, an exposure unit 3M, a developing device 4M according to the present invention, a primary transfer unit 5M, and a cleaning unit 6M. The image forming unit 10C for forming a cyan image has an image carrier (photoconductor) 1C, a charging unit 2C, an exposure unit 3C, a developing device 4C according to the present invention, a primary transfer unit 5C, and a cleaning unit 6C. The image forming unit 10K for forming a black image has an image carrier (photoconductor) 1K, a charging unit 2K, an exposure unit 3K, a developing device 4K according to the present invention, a primary transfer unit 5K, and a cleaning unit 6K.
[0037]
The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating intermediate transfer body 7 by the primary transfer units 5Y, 5M, 5C, and 5K, and are combined into a color image. Is formed. The transfer material (hereinafter, also referred to as a sheet or a sheet) P stored in the sheet cassette 20 is fed by a sheet feeding unit 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D, a registration roller 23, and The sheet is conveyed to the secondary transfer means 5A, and the color image is collectively transferred onto the sheet P. The paper P to which the color image has been transferred is subjected to a fixing process by the fixing device 8, and is held by a paper discharge roller 24 and placed on a paper discharge tray 25 outside the apparatus.
[0038]
At the time of double-sided image formation, the sheet P on which the image has been formed on the first surface discharged from the fixing device 8 is branched from the sheet discharge path by the branching unit 26 and passes through the lower reverse sheet passing paths 27A, 27B, 27C. Then, they merge at the intermediate roller 22D. The sheet P that has been reversely conveyed is conveyed to the secondary transfer unit 5A via the registration roller 23, and the color image is collectively transferred onto the second surface of the sheet P. The paper P to which the color image has been transferred is subjected to a fixing process by the fixing device 8, and is held by a paper discharge roller 24 and placed on a paper discharge tray 25 outside the apparatus.
[0039]
On the other hand, after the color image is transferred onto the paper P by the secondary transfer means 5A, the residual toner is removed by the cleaning means 6A from the intermediate transfer body 7 obtained by separating the paper P by curvature.
[0040]
During the image forming process, the primary transfer unit 5K is always in pressure contact with the photoconductor 1K. The other primary transfer units 5Y, 5M, and 5C are in pressure contact with the corresponding photoconductors 1Y, 1M, and 1C only during color image formation. The secondary transfer unit 5A comes into pressure contact with the intermediate transfer member 7 only when the sheet P passes through the secondary transfer unit and secondary transfer is performed.
[0041]
FIG. 2 shows a configuration of an image forming apparatus equipped with a developing device (hereinafter, also referred to as a developing unit or a developing device) disposed below an image carrier according to a second embodiment or a fourth embodiment of the present invention. It is a schematic diagram. In the figure, an image forming apparatus includes an automatic document feeder (ADF) A, a document image reading unit B for reading an image of a document conveyed by the automatic document feeder, and an image of the read document. An image processing unit C for performing data processing, a writing unit D, an image carrier 1 formed of a photosensitive drum, and at least a charger 2, a developing device 4 according to the present invention, and a cleaning member 6 for the image carrier 1 are provided. An image forming unit E for forming a toner image on the image carrier 1, sheet feeding units 122 and 124 for storing image forming sheets (hereinafter, referred to as sheets) P, and a reversing path for reversing the front and back of the sheets. 180.
[0042]
The automatic document feeder A has a document placing table 137, and a document feed processing unit 136 including a roller group including a roller R1 and switching means for appropriately switching a document moving path (no reference symbol). . The original image reading unit B is located under the top glass G and includes two mirror units 130 and 131 that can reciprocate while maintaining the optical path length, a fixed imaging lens 133, an image sensor 135, and the like. The writing unit D includes a laser light source, a polygon mirror, and the like. Note that, when viewed from the transport direction of the sheet P, a pair of rollers shown on the front side of the transfer device 5 is a registration roller R10, and a pair of rollers shown on the downstream side of the separation electrode 120 is a fixing roller R15 having a heat source.
[0043]
First, a process for forming an image on a sheet will be described below.
One of the originals (not shown) placed on the original placing table 137 is transported in the original transport processing unit 136, passes under the roller R1, and has the mirror units 130 and 131 and the lens at the fixed position. The image is formed on the image sensor 135 via 133 and read. The read image information of the document is processed by the image processing means C, and the encoded image information data is stored in the image memory. The writing unit D drives a laser light source to irradiate the rotating image carrier 1 with a laser beam to perform exposure on the image carrier 1 which is rotated by a driving source (not shown) in accordance with image information data stored in an image memory. Do. Prior to the exposure, the image carrier 1 rotating in the direction of the arrow (counterclockwise) is given a predetermined surface potential by the corona discharge action of the charger 2, but the exposure of the laser beam causes the potential of the exposed portion to be reduced. As a result, the electrostatic latent image corresponding to the data of the image information is formed on the image carrier 1. The electrostatic latent image is visualized by the toner of the developer supplied from the developing device 4 according to the present invention, and becomes a toner image.
[0044]
On the other hand, a movable plate whose free end is constantly urged upward by an urging means such as a coil spring (not shown) is arranged in the paper feeding unit 122 so that the uppermost sheet P comes into contact with the feed roller 150. It has become. The sheet P that has come into contact with the feed roller 150 is sent out from the paper feed unit 122, and is sent to a pair of rotatable rollers, a drive roller 151 and a driven roller 152. The driving roller 151 rotates to separate the sheets P one by one and conveys the sheets P toward the loop forming roller 157. The loop forming roller 157 is provided on the upstream side of the registration roller R10 when viewed from the sheet conveyance direction. The loop creation roller 157 rotates to convey the sheet P, and abuts on the registration roller R10 before rotating to start sheet rotation. The loop of P is formed. By forming a loop, skew of the sheet P due to conveyance is corrected. Thereafter, the registration roller R10 starts rotating in synchronization with the toner image formed on the image carrier 1, and conveys the sheet P. The toner image of the image carrier 1 overlaps the sheet P conveyed in synchronization with the image carrier 1, and the toner image is transferred to the sheet P by the urging of the transfer device 5. After the sheet P is separated from the image carrier 1 by the bias of the separation electrode 120, the toner powder for forming the toner image is melted and fixed on the sheet P by the pressing and heating of the fixing roller R15. The sheet P on which the toner has been fixed is discharged onto a discharge tray T via a discharge roller 179.
[0045]
Next, the developing device according to the present invention will be described.
FIGS. 3 and 4 are schematic views of the developing device 4 arranged on the lateral side of the image carrier as the first embodiment of the present invention, and FIGS. 3 (a) to 3 (d) are indicated by broken arrows in FIG. It is principal part sectional drawing seen from aa, bb, cc, and dd showing. FIG. 4 is a plan view of the developing device 4 as viewed from the Y direction as shown in FIG. 3A, where the left side shows the lower part and the right side shows the upper part. Thick arrows in FIGS. 3A to 3D indicate the direction in which the developer is transported in the developing device, and a black circle (●) in the center of the screw, which is a developer transport unit, indicates the developer. It indicates that the developer is conveyed toward the front side from the back side of the figure, and a cross mark in the center of the screw indicates that the developer is conveyed toward the back side from the front side of the figure. In FIG. 4, a thick arrow indicates that the amount of transported developer is large, and a thin arrow indicates that the amount of transported developer is small.
[0046]
The developing device 4 according to the present invention has the following configuration. That is, the developing device main body 40, a developing roller (also referred to as a developing sleeve) 41 as a developer carrying member, a collecting and conveying screw 42A as a developer collecting and conveying means, and a first stirring and conveying as a first developer stirring and conveying means. It has a screw 43A, a second stirring / conveying screw 44A as a second developer stirring / conveying means, a supply / conveying screw 45A as a developer supplying / conveying means, and a developer regulating member (spike member) 46.
[0047]
In the main body 40 of the developing device, a developer collection and transfer chamber (hereinafter also referred to as a collection and transfer chamber) 42 having a built-in collection and transfer screw 42A adjacent to the developing roller is provided with a first development and a first stirring and transfer screw 43A. A first developer stirring / transfer chamber (hereinafter, also referred to as a first stirring / transfer chamber) 43 which is a developer stirring / transfer chamber is provided adjacent to the recovery / transfer chamber 42. Further, a second developer stirring and transporting chamber (hereinafter, also referred to as a second stirring and transporting chamber) 44 which is a second developer stirring and transporting chamber containing the second stirring and transporting screw 44 </ b> A is provided above the first stirring and transporting chamber 43. A developer supply / transfer chamber (hereinafter, also referred to as “supply / transfer chamber”) 45 having a built-in supply / conveyance screw 45 </ b> A is provided adjacent to the second stirring / transfer chamber 44 and the developing roller 41.
[0048]
In the developing device main body 40, a developer is provided between the developer collection and transfer chamber 42 and the first developer stirring and transfer chamber 43, and transfers the developer transferred by the collection and transfer screw 42A to the first stirring and transfer chamber. A first communication section 42B, which is a first communication section, is provided between the first developer stirring and conveying chamber 43 and the second developer stirring and conveying chamber 44, and the developer conveyed by the first stirring and conveying screw 43A is supplied to the first communication section 42B. It has a second communication portion 43 </ b> B which is a second communication portion for transferring to the second stirring and transporting chamber 44.
[0049]
Further, between the second developer stirring / transporting chamber 44 and the developer supply / transporting chamber 45, a third communication portion which is a third communication portion for transferring the developer transported by the second stirring / transporting screw 44 </ b> A to the supply / transporting chamber 45. A third communication portion 44 </ b> B and a fourth communication portion that transfers the developer conveyed to the most downstream in the supply conveyance chamber 45 without being supplied to the developing roller 41 from the supply conveyance chamber 45 to the second stirring conveyance chamber 44. Two communication portions of a certain fourth communication portion 45B are provided.
[0050]
The fifth communication portion which is a fifth communication portion for transferring the developer in the supply / transport chamber 45 to the collection / transport chamber 42 so as to be located above the fourth communication portion 45B in the supply / transport chamber 45. A portion 45B 'is provided, and a toner replenishing portion 47 for replenishing toner to the developer collected from the developing roller is provided near the first communication portion 42B.
[0051]
In the developing device 4 according to the present invention, as shown by arrows in FIGS. 3 and 4, the following circulating conveyance of the developer is performed.
[0052]
First, the developing roller 41 is arranged, for example, opposite to the image carrier 1 shown in FIG. 1, and carries a developer composed of toner and carrier on the surface of the developing roller called a developing area. Supplying. The developing roller 41 is a cylindrical conductor and includes a rotatable developing sleeve and a plurality of magnetic poles (not shown) built in the developing sleeve, and a toner supplied from a developer supply / conveyance screw 45A adjacent to the developing roller 41. The electrostatic latent image on the image carrier 1 is developed using a two-component developer composed of a carrier. The developer is supplied onto the developing roller 41 by attracting the developer onto the developing roller by the action of a magnetic field from a magnetic pole called a developer receiving magnetic pole among the plurality of magnetic poles described above. Further, the amount of the developer supplied onto the developing roller 41 is regulated by a developer regulating member (spike member) 46 which is arranged with a predetermined gap from the surface of the developing roller 41.
[0053]
The developer used for development is separated from the developing roller 41 by an action of a repulsive magnetic field from a magnetic pole called a release magnetic pole among a plurality of magnetic poles arranged in the developing roller in a region below the center of the developing roller 41. Removed. The developing device according to the present invention is configured such that the developer used for image formation is once completely removed from the surface of the developing roller 41, and then a new developer is supplied to the surface of the developing roller 41 from the supply screw 45A.
[0054]
The developer removed from the surface of the developing roller 41 is conveyed in the collection and conveyance chamber 42 while being collected by the collection and conveyance roller 42A as a developer collection and conveyance unit. Note that, in the collection and transfer chamber 42, in addition to the developer used for the development, the developer transferred from a fifth communication portion 45B 'described later is also transferred. In FIG. 3, as an example of the method of transporting the developer, the developer in the recovery transport chamber 42 is transported from the back side to the front side in the figure as shown in FIG. 4.
[0055]
Next, the developer conveyed in the collection / transfer chamber 42 is transferred to the first stirring / transfer chamber 43 via a first communication section 42B provided in the most downstream area of the collection / transfer chamber 42 as shown in FIG. Be transported. In the developing device according to the present invention, a toner replenishing portion 47 is provided near the first communication portion 42B, so that toner can be supplied to the recovered developer having a reduced toner content (toner concentration).
[0056]
In the first stirring and conveying chamber 43, the developer to which the replenishment toner HT is added is stirred and transferred by the first stirring and conveying screw 43A. As shown in FIGS. 3 and 4, in the first stirring and transporting chamber 43, the developer is transported in a direction opposite to the transporting direction of the developer in the previous collection and transporting chamber 42. FIGS. 3 and 4 show, as an example of the transport direction, that the developer is transported from the near side to the far side in the first stirring and transporting chamber.
[0057]
As shown in FIGS. 3A and 4, the developer stirred and conveyed by the first stirring and conveying screw 43A passes through the second communication portion 43B in the most downstream region of the first stirring and conveying chamber 43. It is transferred to the second stirring / transporting chamber 44 adjacent above the first stirring / transporting chamber 43. In the second stirring and conveying chamber 44, the developer is stirred and transferred by the second stirring and conveying screw 44A in the same manner as in the first stirring and conveying chamber 43. However, in the second stirring and conveying chamber 44, as shown in FIGS. As described above, the developer is transported in the direction opposite to the developer transport direction in the first stirring transport chamber 43 in the previous stage. FIGS. 3 and 4 show that the developer is transported in the second stirring and transporting chamber from the back side to the near side in the drawing.
[0058]
The first stirring / conveying screw 43A and the second stirring / conveying screw 44A stir and convey such that the toner and the carrier constituting the developer are uniformly dispersed and that the toner is sufficiently charged. .
[0059]
As described above, in the developing device 4 according to the present invention, the replenishment toner is stirred in the first stirring and conveying chamber 43 and in the second stirring and conveying chamber 44, so that the stirring is performed for a much longer time than the developing device in the related art. It is carried out. As a result, when the toner is supplied to the developing roller, frictional charging sufficient for image formation is performed, and the problem of poor charging rise is solved.
[0060]
The developer stirred and conveyed in the second stirring and conveying chamber 44 passes through a third communication portion 44B provided at the most downstream of the second stirring and conveying chamber 44, as shown in FIGS. Then, it is transferred to the supply transfer chamber 45 adjacent to the second stirring transfer chamber. In the supply and transport chamber 45, the developer is supplied onto the developing roller 41 adjacent to the supply and transport chamber 45 while being transported in the supply and transport chamber 45 by the supply and transport screw 45A. The developer is transported in the supply transport chamber 45 in a direction opposite to the transport direction in the second stirring transport chamber.
[0061]
In the present invention, as shown in FIGS. 3A and 4, the developer that has been transported to the vicinity of the end of the supply transport chamber 45 and has not been supplied to the developing roller 41 is transferred to the fourth communication portion 45 </ b> B. Via the second stirring screw 44 </ b> A, and is transferred again to the supply / transfer chamber 45 via the second stirring screw 44 </ b> A.
[0062]
As described above, in the developing device according to the present invention, the fourth communication portion that transfers the developer to the second stirring and transporting chamber is provided in the most downstream area of the supply and transport chamber 45, and the fourth communication portion is supplied to the developing roller 41 in the supply and transport chamber 45. The missing developer is returned to the second stirring and conveying chamber, and the chance of supplying the developer to the developing roller 41 again in a short time is increased.
[0063]
Further, the developing device 4 according to the present invention collects and transports the developer in the supply / transport chamber 45 via the fifth communication portion 45B 'only when the amount of the developer in the supply / transport chamber 45 exceeds a certain amount. It was transferred to the chamber 42. As a result, the amount of the developer adjusted to the predetermined toner concentration and sufficiently charged with the toner can be drastically reduced without being wastefully collected from the supply transfer chamber 45 to the collection transfer chamber 42. In addition to this, the developer recovered from the developing roller and supplied for development and having insufficient toner concentration is sufficiently stirred after replenishing the toner, thereby enabling sufficient charging of the toner.
[0064]
As described above, in the developing device 4 according to the first embodiment of the present invention, the developer is circulated and conveyed, and the developer used for image formation is once completely removed on the developing roller 41. The developer is newly supplied, and the electrostatic latent image formed on the image carrier 1 is developed.
[0065]
Next, as a second embodiment of the developing device according to the present invention, a developing device 4 arranged below the image carrier will be described with reference to FIGS.
[0066]
FIGS. 5 and 6 are schematic views of a developing device 4 disposed below an image carrier as a second embodiment of the present invention used in the image forming apparatus shown in FIG. 2, for example. 6D is a cross-sectional view of a main part viewed from aa, bb, cc, and dd indicated by broken arrows in FIG. 6, and FIG. 6 is a side view when the developing device 4 is viewed from the X direction in FIG. The upper side shows the left side of the main part sectional view, and the lower side shows the right side of the main part sectional view. Arrows in FIGS. 5A to 5D indicate the direction of transport of the developer in the developing device, as in FIG. 3; thick arrows in FIG. 6 indicate that the transport amount is large, and thin arrows indicate a small transport amount. It represents that.
[0067]
The developing device 4 shown in FIGS. 5 and 6 includes the following units. That is, the developing device main body 40, a developing roller (also referred to as a developing sleeve) 41 as a developer carrying member, a collecting and conveying screw 42A as a developer collecting and conveying means, and a first stirring and conveying as a first developer stirring and conveying means. It has a screw 43A, a second stirring / conveying screw 44A as a second developer stirring / conveying means, a supply / conveying screw 45A as a developer supplying / conveying means, and a developer regulating member (spike member) 46.
[0068]
In the developing device main body 40, a developer collection and transfer chamber (hereinafter also referred to as a collection and transfer chamber) 42 having a collection and transfer screw 42A built therein is provided below and adjacent to the developing roller 41, and includes a first stirring and transfer screw 43A. A first developer stirring / transfer chamber (hereinafter, also referred to as a first stirring / transfer chamber) 43 which is a first developer stirring / transfer chamber to be provided is provided below and below the recovery / transfer chamber 42, and a second stirring / transfer screw 44A is provided. A second developer stirring / transporting chamber (hereinafter also referred to as a second stirring / transferring chamber) 44 which is a second developer stirring / transporting chamber containing therein is provided adjacent to the first stirring / transporting chamber 43 and supplied. A developer supply transfer chamber (hereinafter, also referred to as a supply transfer chamber) 45 containing a transfer screw 45 </ b> A is provided adjacent to the upper part of the second stirring transfer chamber 44 and the lower part of the developing roller 41.
[0069]
In the developing device main body 40, a developer is provided between the developer collection and transfer chamber 42 and the first developer stirring and transfer chamber 43, and transfers the developer transferred by the collection and transfer screw 42A to the first stirring and transfer chamber. A first communication portion 42B, which is a first communication portion, is provided between the first developer stirring and transporting chamber 43 and the second developer stirring and transporting chamber 44, and transfers the developer transported by the first stirring and transporting screw 43A to the first. A second communication portion 43B, which is a second communication portion for transferring to the second stirring / conveying chamber 44; a second stirring / conveying screw 44A is provided between the second developer stirring / conveying chamber 44 and the developer supply / conveying chamber 45; And a third communication portion 44B, which is a third communication portion for transferring the developer conveyed to the supply conveyance chamber 45, to the supply conveyance chamber 45 without being supplied to the developing roller 41 from the supply conveyance chamber 45 at the most downstream position. The developer transported to And a fourth communicating portion 45B is a fourth communicating portion for transferring the chamber 44. The fifth communication portion which is a fifth communication portion for transferring the developer in the supply / transport chamber 45 to the collection / transport chamber 42 so as to be located above the fourth communication portion 45B in the supply / transport chamber 45. A portion 45B 'is provided. Further, a toner replenishing portion 47 for replenishing the developer collected by the developing roller with toner is provided near the first communication portion 42B.
[0070]
The developing device 4 shown in FIGS. 5 and 6 has the same transport mode as the developing device of the first embodiment of the present invention described with reference to FIGS. 3 and 4, and has a transport path indicated by an arrow in FIGS. The developer is circulated and transported, and the developer is supplied to the developing roller 41 from the supply transport screw 45A. Note that the manner of transporting the developer in the developing device 4 of the second embodiment of the present invention shown in FIGS. 5 and 6 is the same as that of the above-described developing device of the first embodiment of the present invention. Description is omitted.
[0071]
The developing device according to the second embodiment of the present invention shown in FIGS. 5 and 6 also has the developer in the second stirring and transporting chamber in the most downstream region of the supply and transporting chamber 45, similarly to the developing device of the first embodiment. By providing a fourth communication part for transferring the developer, the developer not supplied to the developing roller 41 in the supply transport chamber 45 is returned to the second stirring transport chamber, so that the developer containing the sufficiently charged toner can be transferred to the developing roller 41. The opportunity to supply to is increasing.
[0072]
Further, the developer in the supply / transport chamber 45 is transferred to the collection / transport chamber 42 via the fifth communication portion 45B 'only when the amount of the developer in the supply / transport chamber 45 exceeds a certain amount. As a result, the amount of the developer adjusted to the predetermined toner concentration and sufficiently charged with the toner is not wastefully collected from the supply transfer chamber 45 to the collection transfer chamber 42, and the amount thereof is drastically reduced. The developer collected from the developing roller is sufficiently stirred after the toner is supplied, so that the toner can be charged reliably.
[0073]
In the developing devices of the first and second embodiments, only the developer exceeding a predetermined amount in the supply / transport chamber 45 is transferred to the collection / transfer chamber 42. The agent provides the fifth communication section above the two communication sections between the supply transfer chamber 45 and the second stirring transfer chamber 44, that is, the third communication section 44B and the fourth communication section 45B. A barrier or a partition plate described in, for example, JP-A-2001-166593 is provided on the bottom surface on the downstream side of the transfer indicated by aa in FIGS. 3 and 4 in the supply transfer chamber 45 through the fourth communication portion. The developer conveyance to the stirring conveyance chamber is provided so as not to disturb, and only the developer which has passed over these barriers and the partition plate is conveyed to the collection conveyance chamber.
[0074]
Next, the developing devices according to the third and fourth embodiments of the present invention will be described.
The developing devices according to the third and fourth embodiments of the present invention include a toner replenishing unit and a carrier replenishing unit, and a discharging unit that discharges a developer exceeding a predetermined amount in the supply / transport chamber to the outside of the developing device. is there. In the developing devices according to the third and fourth embodiments of the present invention, a new developer is supplied into the developing device from the toner replenishing unit and the carrier replenishing unit, and the developer corresponding to the overflow caused by the developer supply is supplied to the developing device. By discharging the toner to the outside and replenishing it with a new carrier instead of the carrier used for repeated image formation and deteriorating, the deterioration of the charging performance due to the deterioration of the developer is eliminated.
[0075]
FIG. 7 shows an example of a developing device according to the third embodiment of the present invention, and FIG. 8 shows an example of a developing device according to the fourth embodiment. The developing device according to the third embodiment of the present invention shown in FIG. 7 is of the type installed on the lateral side of the image carrier, similar to the developing device shown in FIGS. The developing device according to the fourth embodiment of the present invention is of a type installed below the image carrier, similarly to the developing device shown in FIGS. 5 and 6 described above. In the developing device of FIGS. 7 and 8, the excess amount of the developer stored in the supply / transport chamber 45 and discharged by a predetermined amount is discharged out of the developing device in accordance with the supply of the supply carrier HC by the illustrated carrier supply unit 48. The developer discharge section 49 is installed on the outer wall of the second stirring / transfer chamber 44 or the supply / transfer chamber 45.
[0076]
The developing device 4 in FIGS. 7 and 8 includes a developing device main body 40, a developing roller (also referred to as a developing sleeve) 41 as a developer carrier, a collecting and conveying screw 42A as a developer collecting and conveying unit, and a first developer. A first stirring / conveying screw 43A as a stirring / conveying means, a second stirring / conveying screw 44A as a second developer stirring / conveying means, a supply / conveying screw 45A as a developer supplying / conveying means, and a developer regulating member (an ear cutting member) 46.
[0077]
In the developing device main body 40, similarly to the developing devices of the first and second embodiments, a developer collecting and transporting chamber (hereinafter also referred to as a collecting and transporting chamber) having a built-in collecting and transporting screw 42A adjacent to the developing roller. Reference numeral 42 denotes a first developer stirring / transporting chamber (hereinafter, also referred to as a first stirring / transporting chamber) 43 which is a first developer stirring / transporting chamber containing a first stirring / transporting screw 43A, and a second stirring / transporting screw is provided. A second developer stirring / transfer chamber (hereinafter, also referred to as a second stirring / transfer chamber) 44 which is a second developer stirring / transfer chamber containing 44A is provided, and a developer supply / transfer chamber (# 2) containing a supply / transport screw 45A is provided. Hereinafter, it is also referred to as a supply transfer chamber.) 45 is provided.
[0078]
Further, similarly to the developing devices of the first and second embodiments, the developing device main body 40 is provided between the developer collecting and transporting chamber 42 and the first developer stirring and transporting chamber 43 and includes a collecting and transporting screw. A first communication portion 42B which is a first communication portion for transferring the developer conveyed by 42A to the first stirring / conveying chamber 43, between the first developer stirring / conveying chamber 43 and the second developer stirring / conveying chamber 44. A second communication portion 43B which is a second communication portion for transferring the developer conveyed by the first stirring and conveying screw 43A to the second stirring and conveying chamber 44; A third communication portion 44B, which is a third communication portion for transferring the developer conveyed by the second stirring / conveying screw 44A to the supply / transport chamber 45, is provided between the developer supply / transport chamber 45 and the supply / transport chamber 45. Supplied without being supplied to the developing roller 41 The Okushitsu 45 has a fourth communicating portion 45B is a fourth communicating portion for transferring the developer conveyed to the most downstream in the second agitation transport chamber 44.
[0079]
Further, in the most downstream region of the supply / transport chamber 45 of the developing device main body 40 of the developing device shown in FIGS. 7 and 8, toner is supplied to the developer collected from the developing roller 41 near the first communication portion 42B. A toner supply unit 47 and a carrier supply unit 48 for supplying a carrier are provided. Further, the supply / transport chamber 45 is provided with a developer discharge section 49 for discharging the developer in the supply / transport chamber 45 to the outside of the developing device so as to be located above the fourth communication section 45B. .
[0080]
As described above, the developing device 4 according to the third embodiment and the fourth embodiment of the present invention includes the carrier in addition to the toner replenishing section 47 as shown in FIGS. Except for having a replenishing section 48 and a developer discharging section 49 and not having a fifth communicating section, means and transport chambers common to the developing apparatuses according to the first and second embodiments of the present invention are provided. It is composed of 7 (a) and 8 (a) show a cross section of a main part viewed from an arrow pp in FIG. 7 (c), and FIG. 7 (b) shows a cross section of a main part viewed from an arrow qq in (c).
[0081]
The developing device shown in FIGS. 7 and 8 is also transported from the second stirring and transporting chamber 44 between the second stirring and transporting chamber 44 and the supply and transporting chamber 45, similarly to the developing devices described with reference to FIGS. In addition to the third communication portion 44 </ b> B for transferring the developer that has been supplied to the supply / transport chamber 45, the third communication portion 44 </ b> B for returning the developer not supplied to the developing roller 41 to the second stirring / transport chamber 44 during the transport in the supply / transport chamber 45. Providing the four communicating portions 45B increases the chance of supplying the developer to the developing roller 41 again in a short time.
[0082]
7 and 8 are provided with a toner replenishing unit 47 and a carrier replenishing unit 48 in a region indicated by qq in the figure, and are used for a developer having a reduced toner content (toner density) due to image formation. The toner supply and the carrier supply are performed.
[0083]
Further, the developing device shown in FIGS. 7 and 8 has a developer discharge section 49 provided on the outer wall of the supply / transport chamber 45, and when the amount of the developer in the supply / transport chamber 45 exceeds a predetermined amount with the replenishment of the developer. The excess developer is discharged outside the developing device, and the amount of the developer in the developing device is always kept constant.
[0084]
As described above, in the developing devices of the third and fourth embodiments according to the present invention, by providing the carrier replenishing unit 48 and the developer discharging unit 49, a new carrier is periodically supplied to the developing device. Instead, it is used for repetitive image formation, and due to the load received inside the developing device, the deteriorated and damaged carrier is discharged out of the developing device. Thus, frictional charging of the toner by the stable carrier is always performed.
[0085]
In FIGS. 7 and 8, the toner replenishing section 47 and the carrier replenishing section 48 are provided independently of each other. However, in the developing device according to the present invention, the toner and the carrier are supplied in a mixed state. Alternatively, the developer may be supplied through one supply port.
[0086]
7 and 8, the developer discharged from the developer discharge unit 49 exceeds a predetermined amount in the supply / transport chamber 45 and is discharged. The supply transfer indicated by pp in FIG. 7 so as to be located above the installation positions of the two communication portions provided between the transfer chamber 44 and the supply transfer chamber 45, that is, the third communication portion 44B and the fourth communication portion 45B. On the downstream side of the transfer in the chamber 45, for example, a barrier or a partition plate as described in JP-A-2001-166593 is provided so as not to hinder the developer transfer to the second stirring and transfer chamber. Only the developer that has passed over the plate is discharged from the developer discharge section 49.
[0087]
The supply / conveyance means in the developing device according to the present invention is not particularly limited as long as it has a capability of supplying a uniform and equal amount of the developer to the surface of the developing roller as the developer carrying member. As a preferable member having a performance capable of supplying the developer uniformly and in an equal amount on the surface, a rotating member is exemplified. A specific example of the rotating member is, for example, a screw auger.
[0088]
The rotating member preferably used as the supply / conveying means in the present invention may be one that rotates in a forward direction with respect to the rotation direction of the developing roller at a portion facing the developing roller, or one that rotates in the reverse direction. Good. As an example of the rotation direction of the supply / conveyance screw 45A which is a rotating member used as the supply / conveyance means according to the present invention, FIG. 3 shows a rotation in the direction opposite to the rotation direction of the developing roller 41, and FIG. The rotation in the forward direction with respect to the rotation direction of the developing roller 41 is shown.
[0089]
Further, when a screw auger is used as the supply / conveyance means used in the developing device according to the present invention, it is preferable to set each condition so as to satisfy the following expression (1).
[0090]
Formula (1): 5VLW ≦ ｛π (D1 2-D2 2) PR｝ ρ ≦ 20VLW
In the formula, V: peripheral speed of the developer carrier (mm / sec)
L: Length (mm) of the developer layer on the developer carrier in the rotation axis direction
W: mass of developer per unit area on developer carrier (mg / cm2)
ρ: bulk density of developer (g / cm3)
D1: Outer diameter (mm) of developer supply / conveyance means (screw auger)
D2: Shaft diameter (mm) of developer supply / conveyance means (screw auger)
P: Pitch (mm) of developer supply / conveyance means (screw auger)
R: Number of rotations (rpm) of developer supply / conveyance means (screw auger)
Further, other conveying means in the developing device according to the present invention, that is, the collecting and conveying means, the first stirring and conveying means, and the second stirring and conveying means are not particularly limited as long as they are commonly used. When used as the transporting means to be used, it is preferable to set each condition so as to satisfy the above formula.
[0091]
Next, the toner and the carrier constituting the developer preferably used in the present invention will be described. First, the toner preferably used in the present invention will be described.
[0092]
As for the particle diameter of the toner used in the present invention, a polymerized toner having a volume average particle diameter of 3 to 5 μm is preferably used. This particle size can be controlled by the concentration of the coagulant (salting agent), the amount of the organic solvent added, the fusing time, and the composition of the polymer in the method for producing the toner particles.
[0093]
By using a small particle size toner having a volume average particle size of 3 to 5 μm, image formation having high resolution, stable image density, less occurrence of fog, and excellent fine line reproducibility can be obtained. Becomes possible.
[0094]
The volume average particle size of the toner is measured using a Coulter Counter TA-II, a Coulter Multisizer (all manufactured by Coulter), a SLAD1100 (a laser diffraction type particle size measuring device manufactured by Shimadzu Corporation), or the like. Can be. In the present invention, measurement and calculation are performed using a Coulter Multisizer, an interface for outputting a particle size distribution (manufactured by Nikkaki Co., Ltd.), and a personal computer connected. As the toner constituting the developer used in the developing device according to the present invention, a toner having a small particle size and a uniform distribution described in JP-A-2000-214629 and having roundness with no corners on the particles is preferable. Used.
[0095]
The toner described above is, for example, a resin having toner particles having a water content of 50 as described in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. Those obtained by a method of producing by coagulation in an aqueous medium of not less than mass% are preferably used.
[0096]
If the volume average particle diameter is less than 3 μm, fogging and toner scattering tend to occur, and if it exceeds 5 μm, it may not be possible to form a high-resolution image.
[0097]
The carrier constituting the two-component developer used in the present invention has a volume average particle diameter of 5 to 10 times the volume average particle diameter of the toner and a magnetization amount of 2.5 to 8.8 × 10 4.-5A carrier comprising magnetic particles of Wb · m / kg is preferred. By using a carrier having such a volume average particle diameter and a magnetization amount, it is possible to stably form a toner image having a uniform image density without causing a problem such as fogging, toner scattering or toner carrier adhesion. It is possible.
[0098]
Further, as the magnetic particles of the carrier used in the present invention, conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Particularly, ferrite particles are preferable.
[0099]
When the volume average particle diameter of the carrier used in the present invention is less than 5 times the volume average particle diameter of the toner, or when the amount of magnetization is 2.5 × 10-5If it is less than Wb · m / kg, carrier adhesion tends to occur. When the volume average particle size of the carrier exceeds 10 times the volume average particle size of the toner, or when the magnetization amount is 8.8 × 10-5It is not preferable to use a carrier exceeding Wb · m / kg because a rough halftone image may be obtained.
[0100]
The volume average particle size of the carrier can be typically measured by a laser diffraction type particle size distribution analyzer “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser. .
[0101]
The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin-dispersed carrier in which magnetic particles are dispersed in a resin. Although there is no particular limitation on the resin composition for coating, for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for constituting the resin dispersion type carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to.
[0102]
As the developer preferably used in the developing device according to the present invention, a developer obtained by mixing the above-described carrier particles and a toner is preferably used.3), The toner concentration in the developer is 2 to 30% by mass, preferably 5 to 20% by mass.
[0103]
If the toner concentration is less than 2% by mass, the number of toners required for development cannot be secured, and the coverage decreases, resulting in excessive charging and a decrease in developability.
[0104]
If it is more than 30% by mass, the coverage becomes large, and poor charging and toner scattering easily occur.
[0105]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto.
[0106]
(Example 1)
The magenta and cyan developing devices in the image forming device of FIG. 1 were equipped with the developing devices shown in FIGS. 3 and 4, and an image forming experiment was performed under the following setting conditions.
[0107]
Process speed (photosensitive drum peripheral speed): 220 mm / sec
Printing speed: 50 sheets / min (A4 landscape feed)
[Conditions of developing device]
(1) Developing roller
Outer diameter: 30 mm
Peripheral speed (V): 330 to 440 mm / sec
Length (L) of the developer layer on the developing roller in the rotation axis direction: 310 mm
Developer mass per unit area on developing roller (W): 30 mg / cm2
(2) Supply conveyance screw
Outer diameter (D1): 24 mm
Shaft diameter (D2): 6mm
Pitch (P): 30mm
Length in rotation axis direction: 320mm
Rotation speed (R): 400 rpm
(3) Recovery / conveyance screw and first stirring / conveyance screw
Except that the length in the direction of the rotation axis was 420 mm, the conditions were set to the same as those of the above-mentioned supply / conveyance screw.
(4) Second stirring and conveying screw
The outer diameter, the shaft diameter, the pitch, the length in the direction of the rotation axis, and the number of rotations were set to the same conditions as those of the above-mentioned supply and conveyance screw.
(Developer)
Under the following conditions, a magenta developer and a cyan developer were prepared.
{Circle around (1)} Average toner particle size: 4.5 μm
{Circle around (2)} Average carrier particle size: 25 μm
{Circle around (3)} Toner concentration at the start of image formation: 8% by mass
{Circle around (4)} Bulk density (ρ) of the developer: 2.2 g / cm3
{Circle around (5)} Amount of developer charged in the developing device: 1300 g
Under the above conditions, 200 continuous color image patterns (A4 landscape) having a printing ratio of 50% for both magenta and cyan were output, and the image quality of the color image patterns was evaluated.
[0108]
As a result of the experiment, no fogging or density unevenness was observed at all from the start until after continuous output of 200 sheets, and a high density image was stably obtained.
[0109]
Further, the color difference (ΔE) within and between the pages of the magenta and cyan solid portion patches and the blue solid portion patch was 5 or less throughout the continuous 200 sheets.
[0110]
Further, after the continuous printing was completed, the developing device was removed from the image forming apparatus, and the toner scattering state was visually observed, but no toner scattering was observed.
[0111]
(Example 2)
Next, as a developing device in the image forming apparatus shown in FIG. 2, the developing device shown in FIGS. 5 and 6 was mounted, and an image forming experiment was performed under the following setting conditions.
[0112]
Process speed (photosensitive drum peripheral speed): 320 mm / sec
Printing speed: 65 sheets / min (A4 landscape feed)
[Conditions of developing device]
(1) Developing roller
Outer diameter: 30 mm
Peripheral speed (V): 480-640 mm / sec
Length (L) of the developer layer on the developing roller in the rotation axis direction: 310 mm
Developer mass per unit area on developing roller (W): 30 mg / cm2
(2) Supply conveyance screw
Outer diameter (D1): 24 mm
Shaft diameter (D2): 6mm
Pitch (P): 30mm
Length in rotation axis direction: 320mm
Rotation speed (R): 400 rpm
(3) Collection and conveyance screw
The outer diameter, the shaft diameter, the pitch, the length in the direction of the rotation axis, and the number of rotations were set to the same conditions as those of the above-mentioned supply and conveyance screw.
(4) First stirring and conveying screw and second stirring and conveying screw
Except that the length in the rotation axis direction was set to 420 mm, the conditions were set to be the same as those of the above-mentioned supply / conveyance screw.
(Developer)
A developer was prepared under the following conditions.
{Circle around (1)} Average toner particle size: 4.5 μm
{Circle around (2)} Average carrier particle size: 25 μm
{Circle around (3)} Toner concentration at the start of image formation: 8% by mass
{Circle around (4)} Bulk density (ρ) of the developer: 2.2 g / cm3
{Circle around (5)} Amount of developer charged in the developing device: 1300 g
Under the conditions described above, 200 continuous cyan single-color image patterns (A4 landscape) with a printing rate of 80% were output, and the image quality of the image patterns was evaluated.
[0113]
As a result of the experiment, no fogging or density unevenness was observed at all from the start until after continuous output of 200 sheets, and a high density image was stably obtained.
[0114]
Further, the color difference (ΔE) within and between the pages of the magenta and cyan solid portion patches and the blue solid portion patch was 5 or less throughout the continuous 200 sheets.
[0115]
Further, after the continuous printing was completed, the developing device was removed from the image forming apparatus, and the toner scattering state was visually observed, but no toner scattering was observed.
[0116]
【The invention's effect】
As described above, according to the present invention, it has been found that the above-described problem can be solved by the configuration according to any one of claims 1 to 11.
[0117]
First, in the invention according to any one of claims 1 to 3, the developer supply section and the developer recovery section are separated, and the recovered developer is always circulated and transported to the developer supply section via the toner supply section. The present invention relates to a developing device having a structure in which two stirring screws are arranged and a long path of a stirring unit is provided.
[0118]
In the developing device according to any one of claims 1 to 3, even if the developer is rapidly circulated, there is no problem of insufficient charging rise or the depletion of the developer, and a toner image having a high printing rate is continuously formed. Even if a large amount of toner is repeatedly prepared and supplied, the replenishment toner is evenly dispersed in the developer and sufficient chargeability is obtained, so it has excellent print ratio tracking performance without unevenness in image density and color balance. It is possible to provide a developing device capable of obtaining a toner image having beautiful image quality.
[0119]
Next, in the invention according to any one of claims 4 to 8, the developer supply section and the developer recovery section are separated, and the recovered developer is always supplied to the developer supply section via the toner / carrier supply section. The present invention relates to a developing device having a structure of being circulated and conveyed and having a structure in which two stirring screws are arranged to provide a long path for a stirring unit.
[0120]
According to the invention described in any one of claims 4 to 8, in addition to the effects obtained by the developing device according to any one of claims 1 to 3, the image formation can be performed repeatedly. Since the carrier can always have a stable charge providing performance, it is possible to provide a developing device free from toner charging failure due to a change in the surface of the carrier.
[0121]
According to the ninth aspect of the present invention, the toner constituting the developer exhibits high resolution and excellent fine line reproducibility by using a small particle diameter toner having a volume average particle diameter of 3 μm to 5 μm. At the same time, it has become possible to provide a developing device capable of forming a toner image with stable image density and no fogging due to toner scattering.
[0122]
Further, in the invention according to claim 10, the volume average particle diameter of the carrier constituting the developer is in the range of 5 to 10 times the volume average particle diameter of the toner, so that fog, toner scattering or carrier This makes it possible to provide a developing device capable of stably forming a toner image having a uniform image density without causing a problem such as adhesion.
[0123]
Further, in the invention according to the eleventh aspect, by using the developing device according to the present invention described above, the toner and the carrier are sufficiently mixed and agitated even when an image with a high printing rate is continuously output, so that the charging start-up is sufficient. As a result of reliably obtaining toner, it has become possible to provide an image forming apparatus capable of forming a high-quality color image with excellent color reproducibility and color balance at high speed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a cross-sectional configuration of a color image forming apparatus in which a developing device is provided on a lateral side of an image carrier.
FIG. 2 is a schematic diagram illustrating a cross-sectional configuration of an image forming apparatus provided with a developing device below an image carrier.
FIG. 3 is a schematic cross-sectional view of a main part of a developing device arranged on a lateral side of an image carrier.
FIG. 4 is a schematic view of a developing device disposed on a lateral side of an image carrier as viewed from above.
FIG. 5 is a schematic cross-sectional view of a main part of a developing device disposed below the image carrier.
FIG. 6 is a schematic diagram illustrating a side view of a developing device disposed below an image carrier.
FIG. 7 is a schematic diagram of a developing device provided on a lateral side of an image carrier and having a developer outlet and a carrier replenishing unit;
FIG. 8 is a schematic diagram of a developing device provided below the image carrier and having a developer outlet and a carrier replenishing unit.
[Explanation of symbols]
1 Image carrier (photoconductor)
4 developing device
10 Image forming unit
40mm developing unit
41 developing roller
42 collection transfer room
43 First stirring transfer chamber
44 ° second stirring transfer chamber
45 ° supply transfer chamber
46 mm developer regulating member (spike member)
47 toner supply section
48 Carrier Supply Department
49 developer discharge section
42A Recovery conveyance screw
42B First communication part
43A First stirring and conveying screw
43B 2nd communication section
44A 2nd stirring and conveying screw
44B 3rd communication section
45A feeding screw
45B 4th communication section
45B '@ 5th communication section
HC supply carrier
HT refill toner

Claims (11)

トナーとキャリアとを含有する現像剤を担持搬送する現像剤担持体と、
前記現像剤担持体より回収された現像剤を前記現像剤担持体の回転軸方向に沿って搬送する現像剤回収搬送手段を有し、前記現像剤担持体に隣接して設けられる現像剤回収搬送室と、
前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送手段の搬送方向と逆方向に搬送しながら撹拌する第１の現像剤撹拌搬送手段を有し、前記現像剤回収搬送室に隣接して設けられる第１の現像剤撹拌搬送室と、
前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら撹拌する第２の現像剤撹拌搬送手段を有し、前記第１の現像剤撹拌搬送室の上方に隣接して設けられる第２の現像剤撹拌搬送室と、
前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら前記現像剤担持体に供給する現像剤供給搬送手段を有し、前記第２の現像剤撹拌搬送室及び前記現像剤担持体に隣接して設けられる現像剤供給搬送室と、
前記現像剤回収搬送室と前記第１の現像剤撹拌搬送室との間に設けられ、前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送室から前記第１の現像剤撹拌搬送室に移送する第１の連通部と、
前記第１の現像剤撹拌搬送室と前記第２の現像剤撹拌搬送室との間に設けられ、前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送室から前記第２の現像剤撹拌搬送室に移送する第２の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送室から前記現像剤供給搬送室に移送する第３の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から前記第２の現像剤撹拌搬送手段に移送する第４の連通部と、
前記第４の連通部の上方近傍に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から前記現像剤回収搬送室に移送する第５の連通部と、
前記第１の連通部の近傍に設けられ、前記現像剤担持体から回収され前記現像剤回収搬送手段により搬送された現像剤にトナー供給を行うトナー供給口と、
を有することを特徴とする現像装置。A developer carrier that carries and transports a developer containing a toner and a carrier,
A developer collection / transport unit configured to convey the developer collected from the developer carrier along the rotation axis direction of the developer carrier; and a developer collection / transport provided adjacent to the developer carrier. Room and
A first developer stirring / conveying unit for stirring the developer conveyed by the developer collecting / conveying unit while conveying the developer in a direction opposite to the conveying direction of the developer collecting / conveying unit; A first developer stirring and conveying chamber provided adjacently;
A second developer stirring and conveying unit that stirs the developer conveyed by the first developer stirring and conveying unit while conveying the developer in a direction opposite to a conveying direction of the first developer stirring and conveying unit; A second developer stirring and conveying chamber provided adjacent to and above the first developer stirring and conveying chamber;
A developer supply / conveyance unit for supplying the developer conveyed by the second developer agitation / conveyance unit to the developer carrier while conveying the developer in a direction opposite to the conveyance direction of the second developer agitation / conveyance unit; A developer supply / transport chamber provided adjacent to the second developer stirring / transport chamber and the developer carrier;
The developer provided between the developer collection and transfer chamber and the first developer stirring and transfer chamber, and transported by the developer collection and transfer means from the developer collection and transfer chamber to the first developer agitation. A first communication portion for transferring to the transfer chamber;
The first developer stirring / transporting unit is provided between the first developer stirring / transporting chamber and the second developer stirring / transporting chamber, and transfers the developer transported by the first developer stirring / transporting unit to the first developer stirring / transporting unit. A second communication section for transferring the developer from the chamber to the second developer stirring and transporting chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, the developer transported by the second developer stirring / transporting means is transferred from the second developer stirring / transporting chamber to the second developer stirring / transporting chamber. A third communication portion that transfers the developer to the developer supply transfer chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, and transported by the developer supply / transporting means from the developer supply / transporting chamber to the second developer stirring / transporting chamber. A fourth communication portion for transferring to the transfer means,
A fifth communication unit provided near and above the fourth communication unit and configured to transfer the developer conveyed by the developer supply and conveyance unit from the developer supply and conveyance room to the developer collection and conveyance room;
A toner supply port provided in the vicinity of the first communication portion, for supplying toner to the developer collected from the developer carrier and conveyed by the developer collection and conveyance unit;
A developing device comprising: トナーとキャリアとを含有する現像剤を担持搬送する現像剤担持体と、
前記現像剤担持体より回収された現像剤を前記現像剤担持体の回転軸方向に沿って搬送する現像剤回収搬送手段を有し、前記現像剤担持体に隣接して設けられる現像剤回収搬送室と、
前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送手段の搬送方向と逆方向に搬送しながら撹拌する第１の現像剤撹拌搬送手段を有し、前記現像剤回収搬送室の下方に隣接して設けられる第１の現像剤撹拌搬送室と、
前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら撹拌する第２の現像剤撹拌搬送手段を有し、前記第１の現像剤撹拌搬送室に隣接して設けられる第２の現像剤撹拌搬送室と、
前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら前記現像剤担持体に供給する現像剤供給搬送手段を有し、前記第２の現像剤撹拌搬送室及び前記現像剤担持体に隣接し前記第２の現像剤撹拌搬送室の上方に設けられる現像剤供給搬送室と、
前記現像剤回収搬送室と前記第１の現像剤撹拌搬送室との間に設けられ、前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送室から前記第１の現像剤撹拌搬送室に移送する第１の連通部と、
前記第１の現像剤撹拌搬送室と前記第２の現像剤撹拌搬送室との間に設けられ、前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送室から前記第２の現像剤撹拌搬送室に移送する第２の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送室から前記現像剤供給搬送室に移送する第３の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から前記第２の現像剤撹拌搬送手段に移送する第４の連通部と、
前記第４の連通部の上方近傍に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から前記現像剤回収搬送室に移送する第５の連通部と、
前記第１の連通部の近傍に設けられ、前記現像剤担持体から回収され前記現像剤回収搬送手段により搬送された現像剤にトナー供給を行うトナー供給口と、
を有することを特徴とする現像装置。A developer carrier that carries and transports a developer containing a toner and a carrier,
A developer collection / transport unit configured to convey the developer collected from the developer carrier along the rotation axis direction of the developer carrier; and a developer collection / transport provided adjacent to the developer carrier. Room and
A first developer stirring and conveying unit that stirs the developer conveyed by the developer collecting and conveying unit while conveying the developer in a direction opposite to the conveying direction of the developer collecting and conveying unit; A first developer stirring and conveying chamber provided adjacently below,
A second developer stirring and conveying unit that stirs the developer conveyed by the first developer stirring and conveying unit while conveying the developer in a direction opposite to a conveying direction of the first developer stirring and conveying unit; A second developer stirring and conveying chamber provided adjacent to the first developer stirring and conveying chamber;
A developer supply / conveyance unit for supplying the developer conveyed by the second developer agitation / conveyance unit to the developer carrier while conveying the developer in a direction opposite to the conveyance direction of the second developer agitation / conveyance unit; A developer supply / transport chamber provided adjacent to the second developer agitating / transporting chamber and the developer carrier and above the second developer agitating / transporting chamber;
The developer provided between the developer collection and transfer chamber and the first developer stirring and transfer chamber, and transported by the developer collection and transfer means from the developer collection and transfer chamber to the first developer agitation. A first communication portion for transferring to the transfer chamber;
The first developer stirring / transporting unit is provided between the first developer stirring / transporting chamber and the second developer stirring / transporting chamber, and transfers the developer transported by the first developer stirring / transporting unit to the first developer stirring / transporting unit. A second communication section for transferring the developer from the chamber to the second developer stirring and transporting chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, the developer transported by the second developer stirring / transporting means is transferred from the second developer stirring / transporting chamber to the second developer stirring / transporting chamber. A third communication portion that transfers the developer to the developer supply transfer chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, and transported by the developer supply / transporting means from the developer supply / transporting chamber to the second developer stirring / transporting chamber. A fourth communication portion for transferring to the transfer means,
A fifth communication unit provided near and above the fourth communication unit and configured to transfer the developer conveyed by the developer supply and conveyance unit from the developer supply and conveyance room to the developer collection and conveyance room;
A toner supply port provided in the vicinity of the first communication portion, for supplying toner to the developer collected from the developer carrier and conveyed by the developer collection and conveyance unit;
A developing device comprising: 前記現像剤供給搬送手段は、前記現像剤担持体との対向部において前記現像剤担持体の回転方向に対し順方向に回転する回転部材であり、
前記第５の連通部は、前記現像剤供給搬送手段の回転軸よりも上方に位置する様に設けられるものであることを特徴とする請求項１又は２に記載の現像装置。The developer supply and conveyance unit is a rotating member that rotates in a forward direction with respect to a rotation direction of the developer carrier at a portion facing the developer carrier,
The developing device according to claim 1, wherein the fifth communication portion is provided so as to be located above a rotation axis of the developer supply / conveyance unit. トナーとキャリアとを含有する現像剤を担持搬送する現像剤担持体と、
前記現像剤担持体より回収された現像剤を前記現像剤担持体の回転軸方向に沿って搬送する現像剤回収搬送手段を有し、前記現像剤担持体に隣接して設けられる現像剤回収搬送室と、
前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送手段の搬送方向と逆方向に搬送しながら撹拌する第１の現像剤撹拌搬送手段を有し、前記現像剤回収搬送室に隣接して設けられる第１の現像剤撹拌搬送室と、
前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら撹拌する第２の現像剤撹拌搬送手段を有し、前記第１の現像剤撹拌搬送室の上方に隣接して設けられる第２の現像剤撹拌搬送室と、
前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら前記現像剤担持体に供給する現像剤供給搬送手段を有し、前記第２の現像剤撹拌搬送室及び前記現像剤担持体に隣接して設けられる現像剤供給搬送室と、
前記現像剤回収搬送室と前記第１の現像剤撹拌搬送室との間に設けられ、前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送室から前記第１の現像剤撹拌搬送室に移送する第１の連通部と、
前記第１の現像剤撹拌搬送室と前記第２の現像剤撹拌搬送室との間に設けられ、前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送室から前記第２の現像剤撹拌搬送室に移送する第２の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送室から前記現像剤供給搬送室に移送する第３の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から前記第２の現像剤撹拌搬送手段に移送する第４の連通部と、
前記現像剤供給搬送室又は前記第２の現像剤撹拌搬送室の外壁に前記第３及び前記第４の連通部よりも上方に位置する様に設けられ、前記現像剤供給搬送手段又は前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記現像剤供給搬送室又は前記第２の現像剤撹拌搬送室から排出する現像剤排出口と、
前記第１の連通部の近傍に設けられ、前記現像剤担持体から回収され前記現像剤回収搬送手段により搬送された現像剤にトナー及びキャリアを供給するトナー／キャリア供給口と、
を有することを特徴とする現像装置。A developer carrier that carries and transports a developer containing a toner and a carrier,
A developer collection / transport unit configured to convey the developer collected from the developer carrier along the rotation axis direction of the developer carrier; and a developer collection / transport provided adjacent to the developer carrier. Room and
A first developer stirring / conveying unit for stirring the developer conveyed by the developer collecting / conveying unit while conveying the developer in a direction opposite to the conveying direction of the developer collecting / conveying unit; A first developer stirring and conveying chamber provided adjacently;
A second developer stirring and conveying unit that stirs the developer conveyed by the first developer stirring and conveying unit while conveying the developer in a direction opposite to a conveying direction of the first developer stirring and conveying unit; A second developer stirring and conveying chamber provided adjacent to and above the first developer stirring and conveying chamber;
A developer supply / conveyance unit for supplying the developer conveyed by the second developer agitation / conveyance unit to the developer carrier while conveying the developer in a direction opposite to the conveyance direction of the second developer agitation / conveyance unit; A developer supply / transport chamber provided adjacent to the second developer stirring / transport chamber and the developer carrier;
The developer provided between the developer collection and transfer chamber and the first developer stirring and transfer chamber, and transported by the developer collection and transfer means from the developer collection and transfer chamber to the first developer agitation. A first communication portion for transferring to the transfer chamber;
The first developer stirring / transporting unit is provided between the first developer stirring / transporting chamber and the second developer stirring / transporting chamber, and transfers the developer transported by the first developer stirring / transporting unit to the first developer stirring / transporting unit. A second communication section for transferring the developer from the chamber to the second developer stirring and transporting chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, the developer transported by the second developer stirring / transporting means is transferred from the second developer stirring / transporting chamber to the second developer stirring / transporting chamber. A third communication portion that transfers the developer to the developer supply transfer chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, and transported by the developer supply / transporting means from the developer supply / transporting chamber to the second developer stirring / transporting chamber. A fourth communication portion for transferring to the transfer means,
The developer supply / transport unit or the second developer supply / transport unit is provided on an outer wall of the developer supply / transport chamber or the second developer stirring / transport chamber so as to be located above the third and fourth communication portions. A developer outlet for discharging the developer conveyed by the developer stirring and conveying means from the developer supply and conveyance chamber or the second developer stirring and conveyance chamber;
A toner / carrier supply port that is provided near the first communication portion and that supplies toner and carrier to the developer collected from the developer carrier and conveyed by the developer collection and conveyance unit;
A developing device comprising: 前記現像剤供給搬送手段は、前記現像剤担持体との対向部において前記現像剤担持体の回転方向に対し順方向に回転する回転部材であり、
前記第２の現像剤撹拌搬送手段は、前記現像剤供給搬送手段との対向部において前記現像剤供給搬送手段の回転方向に対し逆方向に回転する回転部材であり、
前記現像剤排出口は、前記現像剤供給搬送手段の回転軸及び前記第２の現像剤撹拌搬送手段の回転軸よりも上方に位置する様に設けられるものであることを特徴とする請求項４に記載の現像装置。The developer supply and conveyance unit is a rotating member that rotates in a forward direction with respect to a rotation direction of the developer carrier at a portion facing the developer carrier,
The second developer stirring and conveying unit is a rotating member that rotates in a direction opposite to a rotation direction of the developer supplying and conveying unit at a portion facing the developer supplying and conveying unit,
5. The developer discharge port according to claim 4, wherein the developer outlet is provided above a rotation axis of the developer supply and conveyance means and a rotation axis of the second developer stirring and conveyance means. 3. The developing device according to claim 1. トナーとキャリアとを含有する現像剤を担持搬送する現像剤担持体と、
前記現像剤担持体より回収された現像剤を前記現像剤担持体の回転軸方向に沿って搬送する現像剤回収搬送手段を有し、前記現像剤担持体に隣接して設けられる現像剤回収搬送室と、
前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送手段の搬送方向と逆方向に搬送しながら撹拌する第１の現像剤撹拌搬送手段を有し、前記現像剤回収搬送室の下方に隣接して設けられる第１の現像剤撹拌搬送室と、
前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら撹拌する第２の現像剤撹拌搬送手段を有し、前記第１の現像剤撹拌搬送室に隣接して設けられる第２の現像剤撹拌搬送室と、
前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送手段の搬送方向と逆方向に搬送しながら前記現像剤担持体に供給する現像剤供給搬送手段を有し、前記第２の現像剤撹拌搬送室及び前記現像剤担持体に隣接し前記第２の現像剤撹拌搬送室の上方に設けられる現像剤供給搬送室と、
前記現像剤回収搬送室と前記第１の現像剤撹拌搬送室との間に設けられ、前記現像剤回収搬送手段により搬送された現像剤を前記現像剤回収搬送室から前記第１の現像剤撹拌搬送室に移送する第１の連通部と、
前記第１の現像剤撹拌搬送室と前記第２の現像剤撹拌搬送室との間に設けられ、前記第１の現像剤撹拌搬送手段により搬送された現像剤を前記第１の現像剤撹拌搬送室から前記第２の現像剤撹拌搬送室に移送する第２の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記第２の現像剤撹拌搬送手段により搬送された現像剤を前記第２の現像剤撹拌搬送室から前記現像剤供給搬送室に移送する第３の連通部と、
前記第２の現像剤撹拌搬送室と前記現像剤供給搬送室との間に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から前記第２の現像剤撹拌搬送手段に移送する第４の連通部と、
前記現像剤供給搬送室の外壁に前記第３及び前記第４の連通部よりも上方に位置する様に設けられ、前記現像剤供給搬送手段により搬送された現像剤を前記現像剤供給搬送室から排出する現像剤排出口と、
前記第１の連通部の近傍に設けられ、前記現像剤担持体から回収され前記現像剤回収搬送手段により搬送された現像剤にトナー及びキャリアを供給するトナー／キャリア供給口と、
を有することを特徴とする現像装置。A developer carrier that carries and transports a developer containing a toner and a carrier,
A developer collection / transport unit configured to convey the developer collected from the developer carrier along the rotation axis direction of the developer carrier; and a developer collection / transport provided adjacent to the developer carrier. Room and
A first developer stirring and conveying unit that stirs the developer conveyed by the developer collecting and conveying unit while conveying the developer in a direction opposite to the conveying direction of the developer collecting and conveying unit; A first developer stirring and conveying chamber provided adjacently below,
A second developer stirring and conveying unit that stirs the developer conveyed by the first developer stirring and conveying unit while conveying the developer in a direction opposite to a conveying direction of the first developer stirring and conveying unit; A second developer stirring and conveying chamber provided adjacent to the first developer stirring and conveying chamber;
A developer supply / conveyance unit for supplying the developer conveyed by the second developer agitation / conveyance unit to the developer carrier while conveying the developer in a direction opposite to the conveyance direction of the second developer agitation / conveyance unit; A developer supply / transport chamber provided adjacent to the second developer agitating / transporting chamber and the developer carrier and above the second developer agitating / transporting chamber;
The developer provided between the developer collection and transfer chamber and the first developer stirring and transfer chamber, and transported by the developer collection and transfer means from the developer collection and transfer chamber to the first developer agitation. A first communication portion for transferring to the transfer chamber;
The first developer stirring / transporting unit is provided between the first developer stirring / transporting chamber and the second developer stirring / transporting chamber, and transfers the developer transported by the first developer stirring / transporting unit to the first developer stirring / transporting unit. A second communication section for transferring the developer from the chamber to the second developer stirring and transporting chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, the developer transported by the second developer stirring / transporting means is transferred from the second developer stirring / transporting chamber to the second developer stirring / transporting chamber. A third communication portion that transfers the developer to the developer supply transfer chamber;
The developer provided between the second developer stirring / transporting chamber and the developer supply / transporting chamber, and transported by the developer supply / transporting means from the developer supply / transporting chamber to the second developer stirring / transporting chamber. A fourth communication portion for transferring to the transfer means,
The developer supply / transport chamber is provided on the outer wall of the developer supply / transport chamber so as to be located above the third and fourth communication portions, and transfers the developer transported by the developer supply / transport unit from the developer supply / transport chamber. A developer outlet for discharging,
A toner / carrier supply port that is provided near the first communication portion and that supplies toner and carrier to the developer collected from the developer carrier and conveyed by the developer collection and conveyance unit;
A developing device comprising: 前記現像剤供給搬送手段は、前記現像剤担持体との対向部において前記現像剤担持体の回転方向に対し順方向に回転する回転部材であり、
前記現像剤排出口は、前記現像剤供給搬送手段の回転軸よりも上方に位置する様に設けられるものであることを特徴とする請求項６に記載の現像装置。The developer supply and conveyance unit is a rotating member that rotates in a forward direction with respect to a rotation direction of the developer carrier at a portion facing the developer carrier,
7. The developing device according to claim 6, wherein the developer outlet is provided so as to be located higher than a rotation axis of the developer supply / conveying means. 前記現像剤回収搬送手段は、前記現像剤担持体との対向部において前記現像剤担持体の回転方向に対し逆方向に回転する回転部材であることを特徴とする請求項１〜７のいずれか１項に記載の現像装置。8. The developer collection / transportation unit according to claim 1, wherein the developer collection and conveyance unit is a rotating member that rotates in a direction opposite to a rotation direction of the developer carrier at a portion facing the developer carrier. 2. The developing device according to claim 1. 前記現像装置に使用される現像剤を構成するトナーの体積平均粒径が、３μｍ以上５μｍ以下であることを特徴とする請求項１〜８のいずれか１項に記載の現像装置。The developing device according to any one of claims 1 to 8, wherein a volume average particle diameter of a toner constituting a developer used in the developing device is 3 µm or more and 5 µm or less. 前記現像装置に使用される現像剤を構成するキャリアの体積平均粒径が、前記トナーの体積平均粒径の５倍以上１０倍以下であることを特徴とする請求項９に記載の現像装置。The developing device according to claim 9, wherein a volume average particle diameter of a carrier constituting a developer used in the developing device is 5 times or more and 10 times or less of a volume average particle diameter of the toner. 前記請求項１〜１０のいずれか１項に記載の現像装置を搭載し、該現像装置を用いて線速度が２００ｍｍ／ｓｅｃ以上である像担持体上に形成された静電潜像を現像して可視画像を形成し、該可視画像を記録媒体上に転写、定着することを特徴とするカラー画像形成装置。A developing device according to any one of claims 1 to 10, wherein the developing device is used to develop an electrostatic latent image formed on an image carrier having a linear velocity of 200 mm / sec or more. A color image forming apparatus, wherein a visible image is formed on the recording medium, and the visible image is transferred and fixed on a recording medium.
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