JP2004085701A

JP2004085701A - Transport device, developing device and image forming apparatus using same

Info

Publication number: JP2004085701A
Application number: JP2002243634A
Authority: JP
Inventors: Akihiko Noda; 野田　明彦; Yoshifumi Ozaki; 尾崎　善史; Shota Oba; 大場　正太; Masaaki Yamaura; 山浦　正彰
Original assignee: Fuji Xerox Co Ltd
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2002-08-23
Filing date: 2002-08-23
Publication date: 2004-03-18
Anticipated expiration: 2022-08-23
Also published as: JP4254161B2

Abstract

PROBLEM TO BE SOLVED: To provide a transport device which maintains a fixed mixture-ratio between two or more kinds of particles or developer without using a sensor or a powder supply motor, and prevents particular particles from excessively taken in without being affected by a change in an amount of particles composing the mixed powder, and to provide a developing device and an image forming apparatus using the transport device. SOLUTION: The transport device selectively transports, depending on the specific physical properties of an entire mixed powder 2, the mixed powder 2 composed of two or more kinds of particles which are different in the specific physical properties from each other. The transport device has a transport member 1 which attracts the mixed powder to the surface by the specific physical properties. The transport member 1 is moved in such a manner that, after attracting the mixed powder 2, the surface of the transport member 1 is held in a substantially vertical direction and then in a substantially horizontal direction. The developing device and image forming apparatus which use the developing device are also described. COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、特定の物理的性質が異なる２種以上の粒子からなる混合粉体を、該混合粉体全体としての前記特定の物理的性質に応じて選択的に搬送する搬送装置に関し、特に、複写機、プリンター等電子写真式の現像装置において、現像剤を搬送するのに適した搬送装置、並びに、これを用いた現像装置および画像形成装置である。
【０００２】
【従来の技術】
電子写真方式に用いられる現像方式は、現像剤として着色剤粒子であるトナーのみを用いる１成分現像方式と、現像剤として磁性体粒子からなるキャリアおよび着色剤粒子であるトナーとを混合攪拌したものを用いる２成分現像方式に大きく分けられる。
【０００３】
１成分現像方式には、磁性体粒子を含有する磁性トナーを用いる磁性１成分現像方式と、含有しない非磁性１成分現像方式とが有って、磁性トナーは、含まれる磁性体粒子によって光を透過し得ないため黒トナーとしてのみ主に用いられている。非磁性１成分現像方式は、カラー化に適しているが、トナーの維持性が短いという問題があり、今のところ低速機を中心に用いられている。
【０００４】
２成分現像方式は、磁性体粒子からなるキャリアを媒介してトナーを取り扱うため磁気吸引力を用いることができ、非磁性トナーに関しても取り扱いが容易であると共に、特に維持性に優れていることから、フルカラー機や高速機を中心に広く用いられている。
【０００５】
従来、電子写真方式の２成分現像装置を用いた画像形成装置としては、図１３に示すものが一般的なものとして挙げられる。ここで図１３は、一般的な２成分現像装置を用いた画像形成装置の概略構成図である。図１３において、１０１は矢印Ａ方向に回転駆動する潜像担持体であり、その周囲に順に、潜像担持体１０１表面を均一帯電する帯電器１０２と、潜像担持体１０１表面に像様の光を照射して静電潜像を形成する書き込み装置１０３と、トナーおよびキャリアからなる２成分現像剤を収容し、これを現像剤担持体１１１により潜像担持体１０１表面に供給して静電潜像を現像してトナー画像を得る２成分現像装置１０４と、潜像担持体１０１表面に形成されたトナー画像を被記録材１１０に転写する転写器１０６と、潜像担持体１０１表面に残存するトナーを除去するクリーニング装置１０８と、潜像担持体１０１表面の静電潜像を除去する除電器１０９と、が配されてなる。
【０００６】
図１３に示す画像形成装置における２成分現像装置の模式断面図を図１４に示す。図１４において、現像剤担持体１１１は、内部に固定磁石１１７を有すると共に外側に円筒形で矢印Ｂ方向に回動自在なスリーブ１１８を有している。このスリーブ１１８の表面にキャリアおよびトナーを混合攪拌した現像剤１１９を磁気吸引力により担持して搬送し、規制部材１２０によって量を規制して層を形成して、現像部において潜像担持体１０１と対向させて、現像剤１１９中のトナーを潜像担持体１０１に供給し現像させ、トナー画像を得る。現像が終了してトナーの一部を失った現像剤１１９は、現像剤担持体１１１下部に搬送され、同極（Ｎ）の固定磁石１２１、１２２によって、そのスリーブ１１８回転方向の中間に磁気的吸引力の弱いまたは無い部分を設け、重力の働きによって現像剤１１９を現像剤担持体１１１表面から落下させる。落下した現像剤１１１は、搬送部材１２３によってスクリューオーガー１２４に運ばれ、スクリューオーガー１２４の回転軸方向に運ばれて、図示しない受け渡し部でスクリューオーガー１２５に渡されそこでトナー送り機構１１４から新しいトナーが追加されて、攪拌を受けながら先ほどとは反対方向に送られて逆の受け渡し部でスクリューオーガー１２４に再び受け渡されて軸方向に運ばれると共に徐々に搬送部材１２３によって現像剤担持体１１１付近に搬送されて磁気的吸引力によって現像剤担持体１１１表面に付着し、再び搬送、層形成、現像される工程を繰り返す。
【０００７】
トナーの補給については、現像剤１１９中のトナー濃度変化を検知するセンサー１１５によってトナー濃度を電気信号に換え、この信号がＣＰＵ１１６に送られ、ここで上記電気信号から、基準値と比較してトナー濃度が不足と判断されるとトナー補給用モーター１１３に駆動信号が送られてトナーボックス１１２内のトナーがトナー送り機構１１４によって現像器内に送られる。
【０００８】
２成分現像方式におけるトナーとキャリアとの間の吸着には、トナーとキャリアとを混合攪拌する際の摩擦帯電によって、トナーおよびキャリアの表面がそれぞれ逆極性に帯電する結果、静電的に吸着し合うことを利用している。そのため、上記例のようにトナーを補給した現像剤１１９を搬送しながら混合攪拌することが必要となる。現像部においては、現像剤１１９が潜像担持体１０１に程よく接触しかつ詰まり等を起こさないように現像剤搬送量を一定範囲内に制御する必要がある。そのため、規制部材１２０を設けてスリーブ１１８表面に担持される現像剤１１９の層を形成している。
【０００９】
また、現像部においては潜像担持体１０１と現像剤担持体１１１および現像剤１１９との間に形成される電界によってトナーが現像されるため、一般的に現像剤担持体１１１には、電源装置１０５によって現像バイアス電圧が印加される。その時に現像されるトナー量（現像トナー量）は、画像濃度を決定するため、画質に関わる諸特性の中でも特に重要である。現像トナー量は、上記現像部の電界をトナーの電荷により中和することによって決定されるため、トナーの電荷を一定に保つことが非常に重要である。図１５に示すように、２成分現像方式においては、現像剤中のトナー濃度とトナー電荷量との間に反比例関係が有るので、トナーの消費量に合わせて補給量を調節することによってトナー濃度を制御し、トナー電荷量をほぼ一定にすることが求められる。
【００１０】
トナーの消費量に合わせて補給量を調節するため、現像剤中のトナー濃度や現像トナー量を検知してその検知信号に応じてトナー補給用のモーターを動かしてトナーを補給する方法（例えば、図１３に示される画像形成装置の方法）においては、検知するためのセンサー（図１３においてはセンサー１１５）やトナー補給用のモーター（同トナー補給用モーター１１３）などのコストが比較的大きな割合を占めている。４色のトナーを用いてそれぞれを現像するカラー機では、これらのコストアップ分が４倍になることもあって、コストアップの１つの大きな要因となっている。
【００１１】
そこで、特開昭６１−８０１８１号公報、特開昭６３−２２５２６６号公報、特開平８−１８５０５２号公報、特開２０００−２８４５９５号公報などに開示されているように、トナー濃度を検知するセンサーや、トナー補給用のモーターを別途設けずに自律的にトナーを補給し、一定のトナー濃度を保つ方法が提案されている。
【００１２】
しかしながら、これらはいずれも現像剤の体積がトナー濃度によって変化する現象を用いているため、現像剤中のキャリアが何らかの理由でこぼれたり感光体に付着する等により持ち出されて減少してしまうと、現像剤全体の体積が減少してトナーを過剰に取り込んでしまう。一般に経時によってトナー帯電量は劣化し、下降する傾向があるが、トナー過剰取り込みによってトナーの帯電はより低下し、かぶりやトナークラウドになり易いという欠点があった。
【００１３】
また、これらの方法はキャリアに接触するトナーだけでなくキャリアの隙間に入ったトナーをも搬送してしまうためにトナーの取り込みが過剰になりやすいという特徴を持っている。この結果、トナーの帯電は低く、逆極性トナーも多くなりやすい。磁性トナーでは、マグネットロール上においてはキャリアから離れにくいため低帯電でもかぶりやトナークラウドになり難いが、非磁性トナーでは防止しきれない。
【００１４】
【発明が解決しようとする課題】
したがって、本発明は、２種類以上の粒子からなる混合粉体ないし現像剤について、センサーや粉体補給用のモーターなどを用いずに、これら２種類以上の粒子の混合割合を一定に保持することが可能であるとともに、混合粉体構成粒子の量変動に左右されず（例えば、キャリアの減少に左右されず）、一部の粒子を過剰に取り込むことのない搬送装置、並びに、これを用いた現像装置および画像形成装置を提供することを目的とする。
【００１５】
【課題を解決するための手段】
上記目的は、以下の本発明により達成される。
すなわち、本発明の搬送装置は、特定の物理的性質が異なる２種以上の粒子からなる混合粉体を、該混合粉体全体としての前記特定の物理的性質に応じて選択的に搬送する搬送装置であって、
前記特定の物理的性質により、前記混合粉体を表面に吸着する搬送部材を有し、該搬送部材の表面が、前記混合粉体を吸着した後、略鉛直方向に保持され、さらに略水平方向に保持されるように移動することを特徴とする。
【００１６】
以上の構成の本発明によれば、前記混合粉体を吸着した搬送部材の表面が略鉛直方向に保持されると、前記混合粉体には、前記特定の物理的性質による吸着力と、前記搬送部材表面と平行方向下方に落ちようとする重力とが作用する。この時、前記特定の物理的性質による吸着力が前記重力に勝るとそのまま保持され、そのまま略水平方向に保持されて搬送される。逆に、前記特定の物理的性質による吸着力が前記重力に劣ると前記混合粉体は落下し、搬送されずに残ることとなる。つまり、前記特定の物理的性質による吸着力が一定水準よりも大きいと搬送され、小さいと搬送されないという、選択的な搬送が実現できる。
【００１７】
特定の物理的性質が異なる２種以上の粒子からなる混合粉体の、該混合粉体全体としての前記特定の物理的性質は、結局のところ、前記２種以上の粒子の混合割合により決するため、本発明による搬送は、前記混合粉体中における前記２種以上の粒子の混合割合に応じて、選択的に行われる。
【００１８】
このように本発明によれば、センサーや粉体補給用のモーターなどを用いずに、２種類以上の粒子の混合割合を一定に保持することが可能であるとともに、混合粉体構成粒子の量変動に左右されず、一部の粒子を過剰に取り込むことがない。
【００１９】
本発明の搬送装置においては、前記搬送部材において、その表面が略鉛直方向に保持される位置よりも、前記混合粉体を吸着する位置の方が、前記特定の物理的性質による前記混合粉体の表面吸着力が大きくなるように構成されていることが好ましい。前記混合粉体を吸着する位置（以下、「（ピックアップ位置）」という場合がある。）で表面吸着力が大きければ、有効に前記混合粉体をピックアップすることができ、前記搬送部材の表面が略鉛直方向に保持される位置（以下、「選択位置」という場合がある。）での選択に、前記混合粉体を確実に供することができる。例えば、ピックアップ位置において、前記搬送部材の表面が鉛直方向よりも下方を向いている場合、重力は選択位置と同じないしそれ以上に作用し、選択位置まで搬送される前に前記混合粉体が落下してしまう懸念があるが、ピックアップ位置での、前記特定の物理的性質による前記混合粉体の表面吸着力が大きくなるように構成しておけば、前記混合粉体が確実に選択位置まで搬送され、ここで正確に搬送の可否が選択される。
【００２０】
本発明の搬送装置においては、前記搬送部材の表面が略水平方向に保持される位置、ないしその前記搬送部材の移動方向下流において、前記特定の物理的性質による前記混合粉体の表面吸着力が小さくなるように構成され、その位置で前記搬送部材表面から前記混合粉体が引き離されることが好ましい。前記搬送部材の表面が略水平方向に保持される位置、ないしその前記搬送部材の移動方向下流で、選択的に搬送された前記混合粉体が引き離されることで（前記混合粉体が引き離される位置を「脱離位置」という場合がある。）、これを他の場所に移動して用いることができる。
【００２１】
前記特定の物理的性質としては、例えば、磁気的性質や静電的性質が挙げられる。前者の場合、前記混合粉体中の粒子は相互に磁気的性質が異なり（強磁性と弱磁性、磁性と非磁性等）、これを搬送部材が磁力により吸着する構成となる。一方、後者の場合、前記混合粉体中の粒子は相互に静電的性質が異なり（高帯電と低帯電、帯電と非帯電等）、これを搬送部材が静電気力により吸着する構成となる。
【００２２】
この他、搬送部材表面が粗い場合に、微細な粒子はその表面に吸着され、また粒子形状が不定形であれば粉体流動性が低下し、粒子相互の動きが規制される。これらの力は、摩擦力と解することができ、この摩擦力についても選択位置での重力との拮抗に影響を及ぼす。したがって、この摩擦力による付着の性質も本発明にいう「特定の物理的性質」の概念に含まれる。さらに粘度等粉体の付着力に影響を及ぼすあらゆる因子が本発明にいう「特定の物理的性質」の概念に含まれる。
【００２３】
本発明においては、この「特定の物理的性質」の少なくとも１つが、磁気的性質であることが好ましい。磁気的性質が異なる２種以上の粒子からなる混合粉体については、前記搬送部材の表面における磁場を調整することにより、選択的な搬送の条件を適宜制御することができる。
【００２４】
前記搬送部材としては、軸が略水平に保持された回転体であることが好ましい。前記搬送部材として回転体を用いることで、本発明の搬送装置を簡便かつ低コストで制作することができる。また、前記搬送部材として回転体を用いることで、ピックアップ位置、選択位置および脱離位置を周囲に配置して、装置のコンパクト化を図ることができ、また、回転を連続的に行うことで、本発明の搬送装置による一連の搬送動作を連続的に、停止することなく行うことができる。
【００２５】
特に、前記特定の物理的性質の少なくとも１つが、磁気的性質である場合には、回転体として非磁性の材質の物を用い、その内部に磁石を配置することで最適な搬送部材とすることができる。すなわち、ピックアップ位置や選択位置での磁場を最適なものとし、かつ、脱離位置で磁場を小さくないしゼロにする等、内部の磁石の極、磁力、回転体との距離、個数等を適切に選択することにより、所望の磁場を形成することができる。
【００２６】
本発明の搬送装置において、前記搬送部材として回転体を採用した場合、前記回転体の下方ないしその回転方向周辺のいずれかの領域が、前記混合粉体を吸着する位置（ピックアップ位置）、その回転方向下流直近の鉛直部周辺が、前記表面が略鉛直方向に保持される位置（選択位置）、その回転方向下流であって、前記混合粉体を吸着する位置よりも上流のいずれかの領域が、前記搬送部材表面から前記混合粉体が引き離される位置（脱離位置）、とすることができる。
【００２７】
また、前記回転体として長めの物を用いれば、当該回転体の軸方向のいずれかの領域の周面に上記機能を発揮する構成を担わせ、前記回転体の軸方向の他の領域の周面において、前記回転体の下方ないしその回転方向上流の領域で前記特定の物理的性質による前記混合粉体の表面吸着力が大きくなり、その下流で前記表面吸着力が小さくなるように構成して、上記機能と逆方向の粉体搬送機能を併せ持つようにすることもできる。この場合、逆方向の粉体搬送機能は、条件にかかわらず吸着−脱離が行われるため、選択的な搬送ではないが、２つの場所の間で前記混合粉体を往来させることができる。
【００２８】
本発明の搬送装置は、前記混合粉体が、電子写真用のトナーとキャリアとを含む、すなわち２成分系現像剤の搬送に適している。２成分系現像剤において、キャリアは磁性体の粒子であり、トナーは非磁性の粒子であることから磁気的性質が異なる粒子の混合粉体に相当し、本発明の搬送装置により適切に選択的な搬送を実現することができる。
【００２９】
一方、本発明の現像装置は、少なくとも、トナーおよびキャリアを含む現像剤を担持して潜像担持体の潜像を現像する現像剤担持体と、前記現像剤を収容し、それを前記現像剤担持体に供給する現像剤収容部と、該現像剤収容部に隣接し補給用のトナーおよびキャリアを含む補給剤を収容する補給剤収容部と、該補給剤収容部と前記現像剤収容部との間で前記現像剤および／または前記補給剤を相互に搬送する搬送装置と、を備える現像装置であって、前記搬送装置が上記本発明の搬送装置であり、前記混合粉体が前記現像剤であることを特徴とする。
【００３０】
本発明の現像装置では、前記本発明の搬送装置を含む現像装置とすることによって、現像剤の状態に応じて、現像剤を分離することが可能となる。例えば、前記現像剤収容部中の前記現像剤における、非磁性体であるトナーの混合割合が小さくなり、磁性体を含むキャリアの割合が増えると、現像剤全体としての磁気的性質が変化する（強磁性になる）ので、この性質変化を利用してかかる場合にのみ、前記現像剤収容部から前記補給剤収容部へと選択的に前記現像剤を搬送することができる。したがって、トナー濃度の低下した現像剤をトナー濃度の低下していない現像剤と分離することができる。
【００３１】
前記搬送装置によって搬送された前記現像剤については、前記補給剤と接触混合され補給剤となり、再び前記現像剤収容部に戻るように構成されることが望ましい。このように構成することによって、通常現像剤に必要とされるトナー送り機構やトナー供給用モーター、センサーなどを省略でき、低コスト化することができる。
【００３２】
本発明の現像装置においては、前記現像剤収容部内に前記現像剤を流動させる流動手段を有し、前記搬送装置が配されて前記現像剤を吸着する位置の下部周辺が、前記現像剤の流動経路となっており、該流動経路の少なくとも一部にその上下方向を仕切る仕切り部材が配されてなることが好ましい。かかる仕切り部材を配することによって、ピックアップ位置での前記混合粉体のピックアップ量を均一化することができ、トナー濃度の低下した現像剤をトナー濃度の低下していない現像剤と分離する条件を安定化させることができる。
【００３３】
そして、本発明の画像形成装置は、少なくとも、潜像担持体と、該潜像担持体表面に静電潜像を形成する潜像形成手段と、前記潜像担持体表面に形成された静電潜像を可視像化する現像手段と、を含む画像形成装置であって、
前記現像手段として、上記本発明の現像装置を用いたことを特徴とする。上記本発明のの現像装置を含む画像形成装置とすることによって、低コストでかぶり等がなく安定した画像形成装置とすることができる。
【００３４】
【発明の実施の形態】
以下、本発明を好ましい実施形態を挙げて図に基づき説明する。
＜本発明の作用機構＞
まず、本発明の作用機構について説明する。本説明においては、搬送部材として回転体を、特定の物理的性質として磁気的性質（さらに一部摩擦力）を用いた例により説明する。図１に本発明の作用機構を説明するための模式説明図を示す。図１において、１は、内部に配された固定磁石３，３’の周りを非接触で矢印Ａ方向に回転する搬送部材であり、非磁性体（例えばアルミニウム）で構成され、固定磁石３，３’の磁力の影響で、その表面に磁場が形成されている。２は、磁気的特性の異なる２種以上の粒子からなる混合粉体であり、例えば、磁性体を含むキャリアと非磁性体のトナーとからなる現像剤などが挙げられる。固定磁石３，３’は、固定磁石３がＮ極を固定磁石３’がＳ極を搬送部材１内周面に向けて配置され、固定磁石３が強磁界を固定磁石３’が弱磁界を生成している。
【００３５】
混合粉体２が収容された不図示の容器の上に、軸が略水平に保持された状態である程度離間して搬送部材１が配された態様を想定する。その状態で搬送部材１が矢印Ａ方向に回転すると、まず、不図示の容器に近接し、かつ、固定磁石３が内周面に配された位置の周辺（ピックアップ位置（ａ））では、固定磁石３による強磁界に混合粉体２が引き寄せられ、吸着する（ピックアップされる）。ピックアップ位置（ａ）での力の関係を詳しく見ると、当該位置における混合粉体２には、固定磁石３の強磁界による磁気吸引力Ｍａと重力Ｇａとが作用する。ピックアップ位置（ａ）では、磁気吸引力Ｍａの垂直成分Ｍａ’が重力Ｇａよりも十分に大きく、混合粉体２は搬送部材１表面に吸い寄せられた状態のまま搬送される。
【００３６】
搬送部材１の矢印Ａ方向への回転によって、吸着した混合粉体２は、搬送部材１表面が略鉛直方向に保持される位置（選択位置（ｂ））まで搬送される。ここで、選択位置（ｂ）よりも上方に混合粉体２を搬送しようとする力は、混合粉体２に対する搬送部材１表面方向への磁気吸引力Ｍｂ、および、混合粉体２と搬送部材１表面または混合粉体２同士の摩擦係数を掛けあわせて得られる搬送力Ｈｂであり、逆向きの力は重力Ｇｂとなる。搬送力Ｈｂが重力Ｇｂより大きければさらに搬送され、小さければ混合粉体２はここで矢印Ｂ方向に落下する。すなわち、混合粉体２の磁気的性質、さらには粉体流動性や搬送部材１の表面粗さに基づく摩擦係数に応じて、この選択位置（ｂ）において、搬送／非搬送が選択される。
【００３７】
さらに搬送部材１が矢印Ａ方向へ回転すると、その表面に付着し搬送された混合粉体２が受ける重力Ｇｃのうち、一部が搬送部材１に引きつける力（重力分力Ｇｃ’）に加わり、しかも回転と共に大きくなるため、搬送力Ｈｃは強くなり、その分逆向きの力（重力分力Ｇｃ”）は徐々に弱くなる。したがって、選択位置（ｂ）以降、搬送部材１表面が略水平方向に保持される位置（真上）までの間で、混合粉体２が搬送部材１表面から離脱することはない。
【００３８】
そして、搬送部材１が矢印Ａ方向へ回転して表面が略水平方向に保持される位置（真上）まで来ると、磁気吸引力に頼らずに重力のみで混合粉体２が搬送部材１表面に保持され、搬送される。したがって、搬送部材１表面が略水平方向に保持される位置以降は、混合粉体２が脱離して不図示の容器に戻ってしまう心配が無く、この選択的に搬送された混合粉体２を適宜引き離し、これを他の場所に移動して用いることができる。
【００３９】
このようなメカニズムに沿って考えると、選択位置（ｂ）における搬送と非搬送の選択は、磁気吸引力Ｍｂおよび摩擦係数によって生じる搬送力Ｈｂと、重力Ｇｂとのバランスによって決まるので、前記搬送と非搬送の選択を、混合粉体２の特定の物理的性質の状態変化によって生じさせるためには、磁気吸引力、摩擦係数、重力などを調整すればよく、混合粉体２中の２種以上の各粒子の粒径（摩擦係数、重力）、形状（摩擦係数）、流動性（摩擦係数）、比重（重力）、磁気特性（磁気吸引力）、混合割合（磁気吸引力、摩擦係数）、量（重力）、固定磁石３，３’の磁極条件（磁気吸引力）、搬送部材の表面粗さ（摩擦係数）などを、それぞれの条件に応じて調整して、搬送と非搬送の選択を制御してやればよい（括弧内は、その条件により特に影響を与える「特定の物理的性質」）。したがって、これらの条件は、本発明において特に固定されるものではない。ただし、これらの中でも、現像剤中のトナー濃度変化によって搬送／非搬送を作り出すために、「特定の物理的性質」に磁気的性質を用いる場合には、トナーの磁気特性とキャリアの磁気特性とが異なることが必須条件となる。
【００４０】
以上説明した本発明の作用機構においては、搬送部材として回転体を用いた例で説明したが、搬送部材の形状としてはこのような回転体に限定されず、表面が略鉛直および略水平に保持され得る形状であれば問題ない。特に、表面が保持される状態を、略鉛直、略水平その他の角度に連続的に変え得る形状であることが好ましく、具体的には例えば、本例の如き回転体の他、無端ベルト状などが挙げられる。
【００４１】
また、磁石は固定磁石２つの態様で説明したが、磁石は固定磁石に限定されるものではなく、またその数に関しても２個に限定されず、装置の設計条件に応じて必要な個数、形状、磁極等を適宜制御してやればよい。
【００４２】
さらに、「特定の物理的性質」として、主に時期的性質を挙げて説明したが、これに限定されるものではなく、例えば、静電的性質を採用することもできる。静電的性質を採用する場合には、混合粉体中に高帯電と低帯電、帯電と非帯電等静電的性質の異なる２種以上の粒子が含まれ、搬送部材表面を混合粉体と逆極性に帯電させるか、あるいは電気で強制的に荷電させることで、静電気力により吸着する構成となる。
【００４３】
＜本発明の実施形態＞
次に、本発明の好ましい実施形態をいくつか挙げて、本発明をより詳細に説明する。
図２は、本発明の搬送装置の例示的１態様である実施形態を示す、概略断面図である。図２において、混合粉体１２が収容された収容容器１４内には、スクリューオーガー１６ａ，１６ｂが配され、これによって混合粉体１２が収容容器１４内で搬送される。
収容容器１４内の搬送経路の一部の上方には、軸が略水平に保持された非磁性の回転体である搬送ロール２０と、その内部に配置された固定磁石１８とからなる搬送部材１０が配される。固定磁石１８は、所定の磁極パターンＭｐを有するものが用いられ、軸２２を中心にして、基準となる角度から＋方向（図面上右回り方向）または−方向（図面上左回り方向）に回転させることができ、この回転による微調整で、磁極パターンＭｐを変化させて、搬送ロール２０表面の磁場を制御することができる構成になっている。一方、搬送ロール２０は、非磁性の円筒体であり、固定磁石１８とは独立に回動自在であって、矢印Ｃ方向（図面上反時計周り方向）に回転する。
【００４４】
磁極パターンＭｐの異なる２つの固定磁石を、搬送ロール２０内部にある固定磁石１８に適用して、搬送試験を行った。具体的には、ピックアップ磁極Ｍｐの強い磁極パターンＭｐである図３（ａ）の固定磁石と、ピックアップ磁極Ｍｐの弱い磁極パターンＭｐである図３（ｂ）の固定磁石と、の２つである。なお、図中Ｍｈは、搬送極である。
【００４５】
さらに、搬送ロール２０として、その表面粗さＲｚが、１μｍ以下（以下、説明の容易化のため、単に「０μｍ」と表記する。）である極めて平滑な物と、２０μｍである表面の粗い物とを用意した。なお、当該搬送試験には、混合粉体１２として、体積平均粒径３５μｍのフェライトキャリアと体積平均粒径５．８μｍの樹脂トナーとを混合攪拌した現像剤を用いた。
【００４６】
まず、「ピックアップ磁極Ｍｐの強い固定磁石と、表面粗さＲｚ＝２０μｍの搬送ロールとの組み合わせ」、「ピックアップ磁極Ｍｐの弱い固定磁石と、表面粗さＲｚ＝２０μｍの搬送ロールとの組み合わせ」および「ピックアップ磁極Ｍｐの弱い固定磁石と、表面粗さＲｚ＝０μｍの搬送ロールとの組み合わせ」の３水準で試験を行った。この時、各水準においては、トナー濃度（ＴＣ）３質量％の現像剤が確実に層形成するように、固定磁石１８の回転角度を調整した。
この状態でトナー濃度を振って、搬送量（搬送ロール２０の矢印Ｃ方向への回転により、選択位置（ｂ）で重力により落とされずに上方に搬送される量）を測定した。結果を図４（ａ）に示す。
【００４７】
次に、上記３水準に「ピックアップ磁極Ｍｐの強い固定磁石と、表面粗さＲｚ＝０μｍの搬送ロールとの組み合わせ」を加えた４水準で、各水準において、トナー濃度（ＴＣ）１５質量％の現像剤が確実に辛うじて搬送されないように、固定磁石１８の回転角度を調整して、同様に試験を行った。結果を図４（ｂ）に示す。
【００４８】
なお、図４（ａ）および（ｂ）において、横軸はこの混合粉体１２である現像剤中におけるトナー濃度（質量％）、縦軸は搬送ロール２０にピックアップされて矢印Ｃ方向への回転により、ピックアップされた側から反対側（図２における搬送ロール２０の左側）に搬送された混合粉体１２の単位面積当たり質量（搬送量）である。また図中、凡例の括弧内には、各グラフの条件のうち、搬送ロール２０の表面粗さと、基準となるある角度から、軸２２を中心に固定磁石１８を回転させた角度である（＋や−の符号は、既述の説明の通りである）。
【００４９】
図４（ａ）および（ｂ）の各グラフに示される結果から、磁極パターンや角度、搬送ロール２０表面の表面粗さなどの調整によって、混合粉体１２である現像剤中のトナー濃度の違いに応じて、自立的に混合粉体の搬送と非搬送の状態を作れることが確認される。
【００５０】
次に、図２と同様の装置において、スクリューオーガー１６ａ，１６ｂを除去し、収容容器１４内における混合粉体１２がピックアップされる付近に仕切り板２４を設けた、図５に示される搬送装置を用いて搬送試験を行った。また、固定磁石１８の磁極パターンは、図６に示すように、ピックアップ磁極Ｍｐの強いものとした。
【００５１】
仕切り板２４は、基準の高さｘからｙだけ高さを変動させ（マイナス符号は、ｘよりも位置が低いことを示す。）、その上に一定量の混合粉体１２を載せて、上記と同様に、搬送ロール２０により搬送される混合粉体１２の搬送量を測定した。その結果を図７に示す。
【００５２】
図７に示されるグラフからわかるように、ｙ＝−１４ｍｍのときにトナー濃度の違いによって搬送／非搬送を完全に分けることができている。また、他の条件によっても、ある程度搬送／非搬送を分けることができている。以上のことから、混合粉体１２を搬送ロール２０にピックアップできる高さによっても搬送、非搬送を制御できることがわかる。
【００５３】
図８は、ピックアップした混合粉体を別の場所にピックオフすることができる搬送装置の例である。本例の搬送装置は、トナー濃度の低い現像剤３２を収容する収容容器４２と、それに隣接して配置された、トナー濃度の高い現像剤３４を収容する収容容器４４と、の間の上方に配置された搬送部材３０である。搬送部材３０は、矢印Ｄ方向に回転する非磁性の回転体である搬送ロール４０と、その内部に配された固定磁石３８とにより構成される。ピックアップ位置や選択位置における磁極パターンは、既述の図２や図５に示される搬送装置と同様であるが、収容容器４２と収容容器４４との間の位置における磁極パターンは、磁極として双方Ｎ極である同一の極性が隣接する部分が形成されている。このような磁極パターンとすることによって、選択的に搬送された現像剤３２が、当該磁気パターンの領域（脱離位置）で引き離され、収容容器４４へと搬送される。つまり、本例の搬送装置によれば、磁性粒子であるキャリアを含む現像剤のピックアップとピックオフとを制御することができる。
【００５４】
脱離位置におけるピックオフを確実に実現するためには、同極（Ｎ−Ｎ極）中央部の磁束密度絶対値が十分小さくなるようにする必要がある。一般的には、７ｍＴ以下程度にすることが好ましい。
【００５５】
図９は、図８に示される搬送装置にさらに改造を加えたものを用いて、自律的にトナー濃度が一定となるようにした現像装置のトナー濃度制御部分の例であり、図９（ａ）は平面図、図９（ｂ）は図９（ａ）におけるＥ−Ｅ矢視断面図である。本例の搬送装置は、トナー濃度の低い現像剤５２を収容する収容容器６２と、それに隣接して配置された、トナーまたはトナー濃度の高い現像剤５４が循環する搬送路６４と、の間の上方に配置された搬送部材５０である。搬送部材５０は、矢印Ｆ方向に回転する非磁性の回転体である搬送ロール６０と、その内部に配された固定磁石（不図示）とにより構成される。
【００５６】
収容容器６２内では、スクリューオーガー５６，５８により、現像剤５２が矢印Ｊ_１，Ｊ_２，Ｊ_３，Ｊ_４の方向に循環されている。一方、搬送路６４内では、スクリューオーガー６６により、現像剤５４が矢印Ｉ_１，Ｉ_２，Ｉ_３の方向に搬送されている。
【００５７】
搬送部材５０内部に配された固定磁石は、軸方向の中央で異なる磁極パターンに分れるように配され、搬送部材５０を、実質的に搬送方向の異なる搬送部５０Ａと５０Ｂとに機能分離させている。図１０に搬送部５０Ａにおける磁極パターン［パターンＡ］および搬送部５０Ｂにおける磁極パターン［パターンＢ］を示す。この磁気パターンは、図９（ｂ）と同一の方向から見たものである。搬送部５０Ａでは、［パターンＡ］に示されるように、図８と同様の磁極パターンである固定磁石６８Ａが搬送ロール６０内に配され、搬送部５０Ｂでは、［パターンＢ］に示されるように、搬送部５０Ａとは全く異なる磁極パターンの固定磁石６８Ｂが搬送ロール６０内に配されている。
【００５８】
搬送部５０Ａでは、［パターンＡ］に示されるように、ピックアップ位置（ａ）である搬送部５０Ａ下方かつ収容容器６２の上方の位置で、トナー濃度の低い現像剤５２がピックアップされ矢印Ｇ’方向に搬送され、選択位置（ｂ）で搬送／非搬送が選択される。トナー濃度が低い、すなわちキャリア濃度が高いことから磁性の強い現像剤５２は、かなりの量がそのまま搬送され、矢印Ｇ，Ｇ”の方向に搬送されていく。そして、Ｎ−Ｎの同極が隣り合って磁界が消えた脱離位置（ｃ）で、搬送されてきた現像剤５２が引き離され搬送路６４に送られる。
【００５９】
一方、搬送部５０Ｂでは、［パターンＢ］に示されるように、搬送部５０Ｂ下方かつ搬送路６４の上方の位置で、トナーまたはトナー濃度の高い現像剤５４がピックアップされる。そして、Ｎ−Ｎの同極が隣り合って磁界が消えた位置で引き離され、収容容器６２に送られる。すなわち、現像剤５４は矢印Ｈに示される経路を辿って搬送される。ここでは、選択的な搬送は為されない。
【００６０】
このように、搬送部５０Ａと搬送部５０Ｂとで、逆方向の搬送が行われる。すなわち、搬送ロール６０が矢印Ｆ方向に回転すると、トナー濃度の低下した現像剤５２が搬送ロール６０の下方を通過するときに、搬送部５０Ａにおいてピックアップされ、搬送路６４のトナーまたはトナー濃度の高い現像剤５４の流れの中にピックオフされる。この現像剤は、スクリューオーガー６６によってしばらく搬送されることによってトナーが十分に追加されトナー濃度の高い現像剤５４となる。そして、搬送部５０Ｂの下方に差し掛かるとこれにピックアップされ、トナー濃度の低下した現像剤５２の流れの中に戻される。戻された現像剤５４は周囲の現像剤５２よりも過剰にトナー濃度が高くなっているが、スクリューオーガー５６，５８により攪拌・循環されるに従って、周囲に拡散され、適切なトナー濃度に自立的に調整される。
【００６１】
最後に、図９に示される搬送装置を用いた現像装置の実施形態を図１１に示す。なお、図１１において、図９に示される搬送装置と同一の機能を有する部材には、同一の符号を付して、その詳細な説明は省略する。なお、本現像装置においては、収容容器６２が本発明にいう現像剤収容部、搬送路６４が本発明にいう補給剤収容部となる。
【００６２】
搬送部材５０からなる搬送装置により、自立的にトナー濃度が制御された現像剤５２は、スクリューオーガー５８，５６、および攪拌羽根７４により現像ロール（現像剤担持体）７０近傍に送られる。現像ロール７０で磁気的に引き寄せられた現像剤５２が、矢印Ｋ方向に回転する現像ロール７０により搬送されると、規制部材７２により層厚が制御されながら、いわゆる磁気ブラシを形成しつつ、矢印Ｌ方向に回転する感光体（潜像担持体）７６に対向する位置まで送られる。そこで、現像剤５２中のトナーにより感光体７６表面に形成された静電潜像が可視像化され、トナーが消費される。そして、トナーが消費されトナー濃度が低くなった現像剤５２は、攪拌羽根７４、およびスクリューオーガー５６，５８により搬送部材５０からなる搬送装置近傍まで送られ、再びトナー濃度が自立的に調整される。
【００６３】
本発明の画像形成装置は、少なくとも、潜像担持体と、該潜像担持体表面に静電潜像を形成する潜像形成手段と、前記潜像担持体表面に形成された静電潜像を可視像化する現像手段と、を含む画像形成装置であって、現像手段が、例えば図１１に示すような構成のものである。具体的な構成は、図１３に示すものと同様のものが挙げられ、本発明に特徴的な搬送装置以外の構成は、特に限定されるものではない。
【００６４】
図１１に示される現像装置を含む電子写真方式の画像形成装置を用いて走行テストを行った。この時用いた画像形成装置の諸元は、以下の通りである。
（画像形成装置の諸元）
・プロセススピード：　１０８ｍｍ／ｓｅｃ．
・現像ロールの周速：　２１５ｍｍ／ｓｅｃ．
・現像ロール−感光体間のギャップ：　０．４ｍｍ
・現像ロール表面の現像剤搬送量：　３５０ｇ／ｍ^２
・現像ロール径：　１８ｍｍ
・感光体径：　８４ｍｍ
・感光体の帯電電位：　−６５０Ｖ
・感光体の画像部位の電位：　−２００Ｖ
・現像ロールのバイアス電位：　Ｖ_Ｐ−Ｐ＝１．５ｋＶ、Ｖ_ＤＣ＝−５００Ｖ、Ｄｕｔｙ＝５０％、ｆ＝２ｋＨｚ
・トナー：　粉砕トナーで、分級により体積平均粒径６．５μｍに揃えたもの、Ｂｌａｃｋ、外添剤処理品、負帯電
・キャリア：　体積平均粒径５０μｍ、フェライトコアに樹脂コートしたもの
・現像剤量：　３５０ｇ
【００６５】
当該走行テストでは、Ａ４用紙を用い、印字密度５％、２０％、５０％、１００％（面積比）の全面ハーフトーンまたはベタ画像のプリントを各２０枚ずつ印字し、白紙を２０枚流した後、紙面上の位置で左半分、右半分、上半分、下半分の半面ベタ画像を各２０枚ずつ印字し、最後に白紙を２０枚流した。これを１セットとして、合計５セット繰り返し、計１０００枚の走行テストを行った。
【００６６】
上記走行テストにおける、用紙の進行方向左右での画像濃度の推移を、図１２に示す。図１２のグラフからわかるように、本発明の画像形成装置において、濃度再現性は非常に安定しており、かつ、かぶりなども全く見られなかった。
【００６７】
以上説明した実施形態では、特定の物理的性質が異なる２種以上の粒子からなる混合粉体として、主に、磁気的性質が異なるトナーおよびキャリアからなる現像剤を例に挙げて説明したが、本発明の搬送装置はこれに限定されず、静電的特性が異なる粒子等、特定の物理的性質が異なる２種以上の粒子からなる各種混合粉体に対して適用することができる。また、特定の物理的性質が異なる粒子の種類として、主としてトナーおよびキャリアの２種類の例を挙げて説明したが、３種以上の粒子が含まれていても構わない。
【００６８】
【発明の効果】
以上説明したように本発明よれば、２種類以上の粒子からなる混合粉体ないし現像剤について、センサーや粉体補給用のモーターなどを用いずに、これら２種類以上の粒子の混合状態（例えば、トナー濃度などの割合）に応じて選択的に搬送／非搬送が自立的に選択され、たとえばトナー濃度を一定に保持することが可能であるとともに、混合粉体構成粒子の量変動に左右されず、一部の粒子を過剰に取り込むことのない搬送装置、並びに、これを用いた現像装置および画像形成装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の作用機構を説明するための模式説明図である。
【図２】本発明の搬送装置の一例を示す概略断面図である。
【図３】図２の搬送装置に適用した２種の固定磁石の磁極パターンを示す模式図であり、（ａ）はピックアップ磁極の強い磁極パターンの固定磁石のもの、（ｂ）はピックアップ磁極の弱い磁極パターンの固定磁石のものである。
【図４】図２の搬送装置を用いて行った搬送試験の結果を表すグラフである。
【図５】本発明の搬送装置の他の一例を示す概略断面図である。
【図６】図５の搬送装置に適用した固定磁石の磁極パターンを示す模式図である。
【図７】図５の搬送装置を用いて行った搬送試験の結果を表すグラフである。
【図８】本発明の搬送装置のさらに他の一例を示す概略断面図である。
【図９】図８に示される搬送装置にさらに改造を加えた、本発明の搬送装置の一例を示す概略断面図である。
【図１０】図９の搬送装置における、２つの搬送部における磁極パターンを示す模式図である。
【図１１】本発明の現像装置の一例を示す概略断面図である。
【図１２】図１１の現像装置を含む電子写真方式の画像形成装置を用いて行った走行テストの結果（画像濃度の推移）を示すグラフである。
【図１３】一般的な２成分現像装置を用いた画像形成装置の概略構成図である。
【図１４】図１３に示す画像形成装置における２成分現像装置の模式断面図である。
【図１５】２成分現像方式の現像剤におけるトナー濃度とトナー電荷量との関係を示すグラフである。
【符号の説明】
１　搬送部材
２　混合粉体
３、３’、３８　　、６８Ａ、６８Ｂ　固定磁石（磁石）
１０、３０、５０　搬送部材
１２　混合粉体
１４　収容容器
１６ａ，１６ｂ　スクリューオーガー
１８　固定磁石
２０、４０、６０　搬送ロール（回転体）
２４　仕切り板
３２、３４、５２、５４　現像剤（混合粉体）
６２　収容容器（現像剤収容部）
６４　搬送路（補給剤収容部）
７０　現像ロール（現像剤担持体）
７６　感光体（潜像担持体）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transport device that selectively transports a mixed powder composed of two or more types of particles having different specific physical properties according to the specific physical properties of the mixed powder as a whole, A transport device suitable for transporting a developer in an electrophotographic developing device such as a copying machine and a printer, and a developing device and an image forming device using the transport device.
[0002]
[Prior art]
The development method used in the electrophotographic method is a one-component development method using only toner that is colorant particles as a developer, and a method in which a carrier composed of magnetic particles and a toner that is colorant particles are mixed and stirred as a developer. And a two-component development method using
[0003]
The one-component developing method includes a magnetic one-component developing method using a magnetic toner containing magnetic particles and a non-magnetic one-component developing method using no magnetic toner. The magnetic toner emits light by the contained magnetic particles. Since it cannot be transmitted, it is mainly used only as a black toner. The non-magnetic one-component developing method is suitable for colorization, but has a problem that toner maintenance is short, and is currently used mainly for low-speed machines.
[0004]
In the two-component developing method, magnetic attraction can be used because the toner is handled via a carrier composed of magnetic particles, and the non-magnetic toner is easy to handle and has particularly excellent maintainability. It is widely used mainly in full-color machines and high-speed machines.
[0005]
Conventionally, as an image forming apparatus using an electrophotographic two-component developing apparatus, an image forming apparatus shown in FIG. 13 is generally used. Here, FIG. 13 is a schematic configuration diagram of an image forming apparatus using a general two-component developing device. In FIG. 13, reference numeral 101 denotes a latent image carrier that is driven to rotate in the direction of arrow A. Around the periphery, a charger 102 for uniformly charging the surface of the latent image carrier 101 and an image-like image on the surface of the latent image carrier 101 are arranged. A writing device 103 for irradiating light to form an electrostatic latent image, and a two-component developer composed of toner and carrier are accommodated. A two-component developing device 104 for developing a latent image to obtain a toner image; a transfer device 106 for transferring the toner image formed on the surface of the latent image carrier 101 to a recording material 110; A cleaning device 108 for removing the toner to be removed and a static eliminator 109 for removing the electrostatic latent image on the surface of the latent image carrier 101 are provided.
[0006]
FIG. 14 is a schematic sectional view of the two-component developing device in the image forming apparatus shown in FIG. In FIG. 14, the developer carrier 111 has a fixed magnet 117 inside and a sleeve 118 which is cylindrical and is rotatable in the direction of arrow B on the outside. A developer 119 in which a carrier and a toner are mixed and agitated is carried and conveyed on the surface of the sleeve 118 by a magnetic attraction force, and the amount is regulated by a regulating member 120 to form a layer. The toner contained in the developer 119 is supplied to the latent image carrier 101 and developed to obtain a toner image. The developer 119 which has lost a part of the toner after the development is completed is conveyed to a lower portion of the developer carrier 111 and is fixed by a fixed magnet 121 or 122 having the same polarity (N) to a middle of the sleeve 118 in the rotation direction. A portion having a weak or no suction force is provided, and the developer 119 is dropped from the surface of the developer carrier 111 by the action of gravity. The dropped developer 111 is transported to the screw auger 124 by the transport member 123, transported in the rotation axis direction of the screw auger 124, and delivered to the screw auger 125 at a transfer section (not shown), where new toner is transferred from the toner feed mechanism 114. In addition, while being agitated, it is sent in the opposite direction to the previous one, and is again transferred to the screw auger 124 at the opposite transfer part, is conveyed in the axial direction, and is gradually moved to the vicinity of the developer carrier 111 by the conveying member 123. The steps of being conveyed and adhered to the surface of the developer carrying member 111 by magnetic attraction force, and the steps of conveying, forming a layer, and developing are repeated again.
[0007]
Regarding the toner replenishment, the sensor 115 that detects a change in the toner concentration in the developer 119 converts the toner concentration into an electric signal, and this signal is sent to the CPU 116, where the electric signal is compared with a reference value, When it is determined that the density is insufficient, a drive signal is sent to the toner supply motor 113, and the toner in the toner box 112 is sent into the developing device by the toner feeding mechanism 114.
[0008]
In the adsorption between the toner and the carrier in the two-component developing method, the surfaces of the toner and the carrier are charged to opposite polarities by frictional charging when the toner and the carrier are mixed and stirred, so that the toner and the carrier are electrostatically adsorbed. Use to fit. Therefore, it is necessary to mix and stir while transporting the developer 119 to which the toner has been supplied as in the above example. In the developing section, it is necessary to control the amount of the developer to be transported within a certain range so that the developer 119 contacts the latent image carrier 101 moderately and does not cause clogging. Therefore, the regulating member 120 is provided to form a layer of the developer 119 carried on the surface of the sleeve 118.
[0009]
In the developing section, toner is developed by an electric field formed between the latent image carrier 101 and the developer carrier 111 and the developer 119. By 105, a developing bias voltage is applied. The amount of toner developed at that time (developed toner amount) determines the image density, and is therefore particularly important among various characteristics related to image quality. Since the amount of the developed toner is determined by neutralizing the electric field of the developing section with the electric charge of the toner, it is very important to keep the electric charge of the toner constant. As shown in FIG. 15, in the two-component developing method, there is an inversely proportional relationship between the toner concentration in the developer and the toner charge amount. Therefore, the toner concentration is adjusted by adjusting the replenishment amount in accordance with the toner consumption amount. Is controlled to make the toner charge amount substantially constant.
[0010]
In order to adjust the replenishment amount in accordance with the toner consumption amount, a method of detecting the toner concentration or the amount of the developed toner in the developer and moving the toner replenishing motor in accordance with the detection signal to replenish the toner (for example, In the method of the image forming apparatus shown in FIG. 13, the cost of a sensor for detection (the sensor 115 in FIG. 13) and a motor for supplying toner (the motor 113 for supplying toner) are relatively large. is occupying. In the case of a color machine that develops each of the toners using four color toners, the increase in cost may be quadrupled, which is one of the major factors of the increase in cost.
[0011]
Therefore, as disclosed in JP-A-61-80181, JP-A-63-225266, JP-A-8-185052, JP-A-2000-284595, etc., a sensor for detecting a toner concentration is disclosed. Also, there has been proposed a method of autonomously replenishing toner without separately providing a toner replenishing motor and maintaining a constant toner density.
[0012]
However, since all of them use a phenomenon in which the volume of the developer changes according to the toner concentration, if the carrier in the developer is taken out due to spilling or adhering to the photoreceptor for some reason, the carrier decreases. The volume of the entire developer decreases, and excessive toner is taken in. In general, the toner charge amount tends to deteriorate and decrease with the passage of time, but there has been a disadvantage that the toner charge is further reduced due to excessive intake of toner, and fog or a toner cloud tends to occur.
[0013]
Further, these methods have a feature that not only the toner that comes into contact with the carrier but also the toner that has entered the gap between the carriers is conveyed, so that the intake of the toner tends to be excessive. As a result, the charge of the toner is low, and the amount of the opposite polarity toner tends to increase. In the case of a magnetic toner, it is difficult to separate from a carrier on a magnet roll, so that fogging and toner cloud hardly occur even with a low charge.
[0014]
[Problems to be solved by the invention]
Therefore, the present invention is to maintain a constant mixing ratio of two or more types of particles of a mixed powder or developer composed of two or more types of particles without using a sensor or a motor for powder replenishment. And a transport device that is not influenced by fluctuations in the amount of particles constituting the mixed powder (for example, is not affected by the decrease in the number of carriers) and does not take in some of the particles excessively. It is an object to provide a developing device and an image forming apparatus.
[0015]
[Means for Solving the Problems]
The above object is achieved by the present invention described below.
That is, the transport device of the present invention is a transporter that selectively transports a mixed powder composed of two or more types of particles having different specific physical properties according to the specific physical properties of the mixed powder as a whole. A device,
Due to the specific physical property, the device has a conveying member that adsorbs the mixed powder on a surface, and the surface of the conveying member is held in a substantially vertical direction after adsorbing the mixed powder, and further, in a substantially horizontal direction. It is characterized in that it is moved so as to be held in.
[0016]
According to the present invention having the above configuration, when the surface of the conveying member that has adsorbed the mixed powder is held in a substantially vertical direction, the mixed powder has an adsorbing force due to the specific physical property, Gravity that acts to fall downward in the direction parallel to the surface of the conveying member acts. At this time, if the attraction force due to the specific physical property exceeds the gravity, it is held as it is, and is held and transported in a substantially horizontal direction. Conversely, if the adsorption force due to the specific physical property is inferior to the gravity, the mixed powder will fall and remain without being transported. In other words, it is possible to realize a selective conveyance in which the sheet is conveyed when the attraction force due to the specific physical property is larger than a certain level, and is not conveyed when the suction force is smaller than the predetermined level.
[0017]
Since the specific physical properties of the mixed powder composed of two or more kinds of particles having different specific physical properties as a whole of the mixed powder are ultimately determined by the mixing ratio of the two or more kinds of particles. The transport according to the present invention is selectively performed according to the mixing ratio of the two or more types of particles in the mixed powder.
[0018]
As described above, according to the present invention, it is possible to maintain a constant mixing ratio of two or more types of particles without using a sensor or a motor for powder replenishment, and to reduce the amount of particles constituting the mixed powder. It does not depend on the fluctuation and does not take in some particles excessively.
[0019]
In the transporting device of the present invention, in the transporting member, the position at which the mixed powder is adsorbed is located at a position at which the mixed powder is adsorbed, rather than at a position at which the surface thereof is held in a substantially vertical direction. Is preferably configured to increase the surface attraction force. If the surface attraction force is large at the position where the mixed powder is adsorbed (hereinafter, sometimes referred to as “(pickup position)”), the mixed powder can be effectively picked up, and the surface of the transport member is The mixed powder can be reliably used for selection at a position held in a substantially vertical direction (hereinafter, may be referred to as “selected position”). For example, at the pick-up position, if the surface of the conveying member faces downward from the vertical direction, the gravity acts on the selected position or more, and the mixed powder drops before being conveyed to the selected position. However, if the configuration is such that the surface adsorbing force of the mixed powder due to the specific physical property at the pickup position is increased, the mixed powder is reliably transported to the selected position. Here, whether or not the transport is possible is accurately selected.
[0020]
In the transport device of the present invention, at a position where the surface of the transport member is held in a substantially horizontal direction, or downstream of the transport member in the moving direction, the surface adsorption force of the mixed powder due to the specific physical property is reduced. It is preferable that the mixed powder is configured to be small and the mixed powder is separated from the surface of the conveying member at that position. A position where the surface of the conveying member is held in a substantially horizontal direction, or at a position downstream of the moving direction of the conveying member, the selectively conveyed mixed powder is separated (a position where the mixed powder is separated). May be referred to as a “detachment position”). This can be moved to another location and used.
[0021]
Said specific physical propertiesWhenFor example, magnetic properties and electrostatic properties are mentioned. In the former case, the particles in the mixed powder have different magnetic properties (ferromagnetic and weak magnetic, magnetic and non-magnetic, etc.), and the transport member attracts the particles by magnetic force. On the other hand, in the latter case, the particles in the mixed powder have different electrostatic properties (highly charged and lowly charged, charged and non-charged, etc.), and the transport member adsorbs the particles by electrostatic force.
[0022]
In addition, when the surface of the conveying member is rough, fine particles are adsorbed on the surface, and if the particle shape is irregular, powder fluidity is reduced, and movement of the particles is restricted. These forces can be interpreted as frictional forces, which also affect the antagonism of gravity at the selected position. Therefore, the property of adhesion by the frictional force is also included in the concept of “specific physical property” in the present invention. Further, all factors such as viscosity which affect the adhesion of the powder are included in the concept of “specific physical properties” in the present invention.
[0023]
In the present invention, it is preferable that at least one of the “specific physical properties” is a magnetic property. With respect to a mixed powder composed of two or more types of particles having different magnetic properties, the conditions for selective transport can be appropriately controlled by adjusting the magnetic field on the surface of the transport member.
[0024]
It is preferable that the transport member is a rotating body whose axis is held substantially horizontally. By using a rotating body as the transfer member, the transfer device of the present invention can be manufactured simply and at low cost. Further, by using a rotating body as the transporting member, a pickup position, a selection position, and a detachment position are arranged around the apparatus, thereby making it possible to downsize the apparatus. A series of transport operations by the transport device of the present invention can be performed continuously without stopping.
[0025]
In particular, when at least one of the specific physical properties is a magnetic property, a non-magnetic material is used as the rotating body, and a magnet is arranged in the inside of the rotating body to provide an optimal transport member. Can be. That is, the magnetic field at the pickup position or the selected position is optimized, and the magnetic field at the desorption position is made small or zero. By selection, a desired magnetic field can be formed.
[0026]
In the transport device of the present invention, when a rotating body is employed as the transporting member, any area below the rotating body or around the rotating direction thereof adsorbs the mixed powder (pickup position), and its rotation A vertical portion immediately downstream in the direction is a position (selection position) where the surface is held in a substantially vertical direction, and any region that is downstream in the rotational direction and upstream of the position where the mixed powder is adsorbed is located. And a position (detachment position) at which the mixed powder is separated from the surface of the transport member.
[0027]
In addition, when a long object is used as the rotating body, the peripheral surface in any region in the axial direction of the rotating body is configured to exhibit the above function, and the circumferential surface in another region in the axial direction of the rotating body is used. On the surface, the surface adsorption force of the mixed powder due to the specific physical property is increased in a region below the rotator or upstream in the rotation direction, and the surface adsorption force is reduced downstream thereof. Alternatively, the above-described function may be combined with a powder conveying function in the opposite direction. In this case, since the adsorption and desorption are performed regardless of the conditions in the powder conveying function in the reverse direction, the mixed powder can be moved between two places although it is not a selective conveyance.
[0028]
The transport device of the present invention is suitable for transporting a two-component developer in which the mixed powder contains a toner and a carrier for electrophotography. In the two-component developer, the carrier is a magnetic particle, and the toner is a non-magnetic particle, and thus corresponds to a mixed powder of particles having different magnetic properties. Transport can be realized.
[0029]
On the other hand, a developing device of the present invention contains a developer carrying a developer containing at least a toner and a carrier to develop a latent image of the latent image carrier, and contains the developer, and A developer accommodating portion to be supplied to the carrier, a replenishing agent accommodating portion adjacent to the developer accommodating portion for accommodating a replenishing agent including a replenishing toner and a carrier, the replenishing agent accommodating portion and the developer accommodating portion; And a transport device for transporting the developer and / or the replenisher to each other between the developer and the developer. The transport device is the transport device of the present invention, and the mixed powder is the developer. It is characterized by being.
[0030]
In the developing device according to the present invention, the developing device including the transport device according to the present invention can separate the developer according to the state of the developer. For example, when the mixing ratio of the non-magnetic toner in the developer in the developer accommodating portion decreases and the ratio of the carrier including the magnetic material increases, the magnetic properties of the entire developer change ( Therefore, the developer can be selectively conveyed from the developer accommodating section to the replenishing agent accommodating section only in such a case using the property change. Therefore, the developer whose toner concentration has decreased can be separated from the developer whose toner concentration has not decreased.
[0031]
It is preferable that the developer conveyed by the conveyance device is configured to be mixed with the replenishing agent in contact with the replenishing agent, and to return to the developer accommodating portion again. With this configuration, it is possible to omit a toner feed mechanism, a toner supply motor, a sensor, and the like, which are usually required for the developer, and to reduce the cost.
[0032]
In the developing device according to the aspect of the invention, the developing device may further include a flow unit configured to flow the developer in the developer storage unit. It is preferable that a partition member is provided on at least a part of the flow path to partition the flow path in the vertical direction. By arranging such a partition member, the pickup amount of the mixed powder at the pickup position can be made uniform, and the conditions for separating the developer with the reduced toner concentration from the developer with the toner concentration not reduced are set. Can be stabilized.
[0033]
The image forming apparatus according to the present invention includes at least a latent image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the latent image carrier, and an electrostatic image formed on the surface of the latent image carrier. Developing means for visualizing the latent image, and an image forming apparatus,
The present invention is characterized in that the developing device of the present invention is used as the developing means. By using the image forming apparatus including the developing device of the present invention, a stable image forming apparatus without fogging at low cost can be provided.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the drawings with reference to preferred embodiments.
<Action mechanism of the present invention>
First, the operation mechanism of the present invention will be described. In this description, an example will be described in which a rotating body is used as a conveying member, and magnetic properties (partially frictional force) are used as specific physical properties. FIG. 1 is a schematic explanatory view for explaining the operation mechanism of the present invention. In FIG. 1, reference numeral 1 denotes a conveying member which rotates in the direction of arrow A in a non-contact manner around fixed magnets 3 and 3 'arranged inside, and is made of a non-magnetic material (for example, aluminum). Under the influence of the magnetic force of 3 ', a magnetic field is formed on the surface. Reference numeral 2 denotes a mixed powder composed of two or more kinds of particles having different magnetic properties, such as a developer composed of a carrier containing a magnetic material and a non-magnetic toner. The fixed magnets 3, 3 ′ are arranged such that the fixed magnet 3 faces the N pole and the fixed magnet 3 ′ faces the S pole toward the inner peripheral surface of the conveying member 1. The fixed magnet 3 applies a strong magnetic field and the fixed magnet 3 ′ applies a weak magnetic field. Has been generated.
[0035]
It is assumed that the conveying member 1 is arranged on a container (not shown) in which the mixed powder 2 is accommodated, with the shaft being held substantially horizontally, with a certain distance therebetween. When the transport member 1 rotates in the direction of the arrow A in this state, first, in the vicinity of the position where the fixed magnet 3 is arranged on the inner peripheral surface (the pickup position (a)), the fixed magnet 3 is fixed. The mixed powder 2 is attracted to and attracted (picked up) by the strong magnetic field generated by the magnet 3. Looking at the relationship of the forces at the pickup position (a) in detail, the magnetic attraction Ma due to the strong magnetic field of the fixed magnet 3 and the gravity Ga act on the mixed powder 2 at the position. At the pickup position (a), the vertical component Ma 'of the magnetic attractive force Ma is sufficiently larger than the gravity Ga, and the mixed powder 2 is conveyed while being attracted to the surface of the conveying member 1.
[0036]
By the rotation of the conveying member 1 in the direction of arrow A, the adsorbed mixed powder 2 is conveyed to a position where the surface of the conveying member 1 is held substantially vertically (selected position (b)). Here, the force for conveying the mixed powder 2 above the selected position (b) includes a magnetic attraction Mb toward the surface of the conveying member 1 with respect to the mixed powder 2 and the mixed powder 2 and the conveying member. The conveying force Hb is obtained by multiplying the friction coefficient between one surface or the mixed powder 2 and the force in the opposite direction is the gravity Gb. If the conveying force Hb is larger than the gravity Gb, the conveyed material is further conveyed. If the conveyed force Hb is smaller, the mixed powder 2 falls in the direction of arrow B here. That is, transport / non-transport is selected at the selected position (b) in accordance with the magnetic properties of the mixed powder 2 and the friction coefficient based on the powder fluidity and the surface roughness of the transport member 1.
[0037]
When the conveying member 1 further rotates in the direction of the arrow A, a part of the gravitational force Gc received by the mixed powder 2 adhered to the surface thereof and conveyed is applied to a force (gravity component Gc ′) attracting to the conveying member 1, In addition, since the transport force Hc increases with rotation, the transport force Hc increases, and the reverse force (gravity component Gc ″) gradually decreases accordingly. Therefore, after the selected position (b), the surface of the transport member 1 is substantially horizontal. The mixed powder 2 does not separate from the surface of the conveying member 1 until the position (directly above) where the mixed powder 2 is held.
[0038]
When the conveying member 1 rotates in the direction of arrow A and reaches a position (directly above) where the surface is held in a substantially horizontal direction, the mixed powder 2 is transferred to the surface of the conveying member 1 by gravity alone without relying on magnetic attraction. And transported. Therefore, after the position where the surface of the conveying member 1 is held in a substantially horizontal direction, there is no fear that the mixed powder 2 is detached and returned to a container (not shown). It can be appropriately separated and moved to another place for use.
[0039]
Considering such a mechanism, the selection of the conveyance and the non-conveyance at the selected position (b) is determined by the balance between the conveyance force Hb generated by the magnetic attraction force Mb and the coefficient of friction and the gravity Gb. In order to select the non-conveyance by changing the state of a specific physical property of the mixed powder 2, the magnetic attraction force, the coefficient of friction, the gravity, and the like may be adjusted. Particle size (friction coefficient, gravity), shape (friction coefficient), fluidity (friction coefficient), specific gravity (gravity), magnetic characteristics (magnetic attraction force), mixing ratio (magnetic attraction force, friction coefficient), Adjust the amount (gravity), the magnetic pole conditions of the fixed magnets 3 and 3 '(magnetic attraction force), the surface roughness of the conveying member (friction coefficient), etc., according to the respective conditions, and select transport or non-transport. You can control it. More particularly affect "certain physical properties"). Therefore, these conditions are not particularly fixed in the present invention. However, among these, when magnetic properties are used for “specific physical properties” in order to create transport / non-transport by changing the toner concentration in the developer, the magnetic properties of the toner and the magnetic properties of the carrier are not considered. Must be different.
[0040]
In the action mechanism of the present invention described above, an example is described in which a rotating body is used as the transporting member. However, the shape of the transporting member is not limited to such a rotating body, and the surface is held substantially vertically and substantially horizontally. There is no problem as long as the shape can be used. In particular, it is preferable that the shape in which the surface is held can be continuously changed to a substantially vertical, substantially horizontal or other angle, and specifically, for example, in addition to the rotating body as in this example, an endless belt shape or the like Is mentioned.
[0041]
Further, although the magnet has been described in the form of two fixed magnets, the number of magnets is not limited to fixed magnets, and the number thereof is not limited to two. , Magnetic poles and the like may be appropriately controlled.
[0042]
Furthermore, the "specific physical property" has mainly been described with reference to the temporal property. However, the present invention is not limited to this. For example, an electrostatic property may be employed. When the electrostatic property is adopted, two or more kinds of particles having different electrostatic properties such as high charge and low charge, charged and uncharged are included in the mixed powder, and the surface of the conveying member is mixed with the mixed powder. By being charged to the opposite polarity or being forcibly charged with electricity, the structure is made to be attracted by electrostatic force.
[0043]
<Embodiment of the present invention>
Next, the present invention will be described in more detail with reference to some preferred embodiments of the present invention.
FIG. 2 is a schematic cross-sectional view showing an embodiment, which is one exemplary embodiment of the transport apparatus of the present invention. In FIG. 2, screw augers 16 a and 16 b are arranged in a storage container 14 in which the mixed powder 12 is stored, whereby the mixed powder 12 is transported in the storage container 14.
Above a part of the transport path in the storage container 14, a transport member 10 including a transport roll 20, which is a non-magnetic rotating body whose axis is held substantially horizontally, and a fixed magnet 18 disposed therein. Is arranged. The fixed magnet 18 having a predetermined magnetic pole pattern Mp is used. The fixed magnet 18 is rotated around a shaft 22 in a positive direction (clockwise direction in the drawing) or a negative direction (clockwise direction in the drawing) from a reference angle. With the fine adjustment by the rotation, the magnetic pole pattern Mp is changed to control the magnetic field on the surface of the transport roll 20. On the other hand, the transport roll 20 is a non-magnetic cylindrical body, is rotatable independently of the fixed magnet 18, and rotates in the direction of arrow C (counterclockwise in the drawing).
[0044]
A transfer test was performed by applying two fixed magnets having different magnetic pole patterns Mp to the fixed magnet 18 inside the transfer roll 20. More specifically, the fixed magnet shown in FIG. 3A, which is a strong magnetic pole pattern Mp of the pickup magnetic pole Mp, and the fixed magnet shown in FIG. 3B, which is a weak magnetic pole pattern Mp of the pickup magnetic pole Mp. . In the drawing, Mh is a transport pole.
[0045]
Further, as the transport roll 20, an extremely smooth material having a surface roughness Rz of 1 μm or less (hereinafter simply referred to as “0 μm” for simplicity of description) and a rough material having a surface roughness of 20 μm. And prepared. In the transport test, a developer prepared by mixing and stirring a ferrite carrier having a volume average particle diameter of 35 μm and a resin toner having a volume average particle diameter of 5.8 μm was used as the mixed powder 12.
[0046]
First, “combination of a fixed magnet having a strong pickup magnetic pole Mp and a transport roll having a surface roughness Rz of 20 μm”, “combination of a fixed magnet having a weak pickup magnetic pole Mp and a transport roll having a surface roughness of Rz = 20 μm” and The test was conducted at three levels of “combination of a fixed magnet having a weak pickup magnetic pole Mp and a transport roll having a surface roughness Rz of 0 μm”. At this time, at each level, the rotation angle of the fixed magnet 18 was adjusted so that the developer having a toner concentration (TC) of 3% by mass formed a layer surely.
In this state, the toner density was varied, and the amount of conveyance (the amount of conveyance of the conveyance roll 20 in the direction indicated by the arrow C without being dropped by gravity at the selected position (b)) was measured. The results are shown in FIG.
[0047]
Next, in addition to the above three levels, “combination of a fixed magnet having a strong pickup magnetic pole Mp and a transport roll having a surface roughness Rz of 0 μm” was added to the four levels. In each level, the toner concentration (TC) was 15% by mass. The same test was performed by adjusting the rotation angle of the fixed magnet 18 to ensure that the developer was barely conveyed. The results are shown in FIG.
[0048]
4A and 4B, the horizontal axis represents the toner concentration (% by mass) in the developer as the mixed powder 12, and the vertical axis represents the rotation in the direction of arrow C picked up by the transport roll 20. Is the mass per unit area (conveyed amount) of the mixed powder 12 conveyed from the picked-up side to the opposite side (the left side of the convey roll 20 in FIG. 2). In the figure, the angle in parentheses in the legend is an angle obtained by rotating the fixed magnet 18 about the axis 22 from the surface roughness of the transport roll 20 and a certain angle serving as a reference among the conditions of each graph (+ And the sign of-is as described above).
[0049]
From the results shown in the graphs of FIGS. 4A and 4B, the difference in the toner concentration in the developer as the mixed powder 12 is adjusted by adjusting the magnetic pole pattern and angle, the surface roughness of the surface of the transport roll 20, and the like. It is confirmed that the state of transporting and non-transporting of the mixed powder can be made autonomously according to the conditions.
[0050]
Next, in the same apparatus as that of FIG. 2, the screw auger 16a, 16b is removed, and a partition plate 24 is provided near the mixed powder 12 in the storage container 14 where the mixed powder 12 is picked up. A transfer test was performed using the above. Further, the magnetic pole pattern of the fixed magnet 18 has a strong pickup magnetic pole Mp as shown in FIG.
[0051]
The partition plate 24 fluctuates in height from the reference height x by y (a minus sign indicates that the position is lower than x), and a fixed amount of the mixed powder 12 is placed thereon, and Similarly to the above, the transport amount of the mixed powder 12 transported by the transport roll 20 was measured. FIG. 7 shows the result.
[0052]
As can be seen from the graph shown in FIG. 7, when y = −14 mm, conveyance / non-conveyance can be completely separated depending on the difference in toner density. Also, depending on other conditions, it is possible to separate transport / non-transport to some extent. From the above, it can be seen that conveyance and non-conveyance can also be controlled by the height at which the mixed powder 12 can be picked up by the conveyance roll 20.
[0053]
FIG. 8 shows an example of a transfer device capable of picking off the mixed powder that has been picked up to another place. The transport device of the present example is provided between a storage container 42 that stores the developer 32 having a low toner concentration and a storage container 44 that is disposed adjacent thereto and stores the developer 34 having a high toner concentration. The transport member 30 is disposed. The transport member 30 includes a transport roll 40, which is a non-magnetic rotating body that rotates in the direction of arrow D, and a fixed magnet 38 disposed therein. The magnetic pole patterns at the pickup position and the selected position are the same as those of the transfer device shown in FIGS. 2 and 5 described above, but the magnetic pole pattern at the position between the storage container 42 and the storage container 44 Adjacent portions having the same polarity as the poles are formed. With such a magnetic pole pattern, the developer 32 that has been selectively transported is separated in the area of the magnetic pattern (separation position) and transported to the storage container 44. That is, according to the transport device of the present embodiment, it is possible to control the pick-up and pick-off of the developer containing the carrier that is the magnetic particle.
[0054]
In order to reliably realize the pick-off at the detached position, it is necessary to make the absolute value of the magnetic flux density at the center of the same pole (N-N pole) sufficiently small. Generally, it is preferred to be about 7 mT or less.
[0055]
FIG. 9 shows an example of a toner density control portion of a developing device in which the toner density is autonomously kept constant by using a further modified version of the transport device shown in FIG. 9) is a plan view, and FIG. 9B is a cross-sectional view taken along the line EE in FIG. 9A. The transport device of the present example includes a storage container 62 that stores the developer 52 having a low toner concentration and a transport path 64 that is disposed adjacent to the container 62 and circulates the toner or the developer 54 having a high toner concentration. This is the transport member 50 arranged above. The transporting member 50 includes a transporting roll 60, which is a non-magnetic rotating body that rotates in the direction of arrow F, and a fixed magnet (not shown) disposed therein.
[0056]
In the storage container 62, the developer 52 is moved by the arrow J by screw augers 56 and 58.₁, J₂, J₃, J₄It is circulating in the direction. On the other hand, in the transport path 64, the developer 54 is moved by an arrow I by a screw auger 66.₁, I₂, I₃Transported in the direction of
[0057]
The fixed magnets arranged inside the transfer member 50 are arranged so as to be separated into different magnetic pole patterns at the center in the axial direction, and separate the function of the transfer member 50 into transfer portions 50A and 50B having substantially different transfer directions. ing. FIG. 10 shows a magnetic pole pattern [pattern A] in the transport unit 50A and a magnetic pole pattern [pattern B] in the transport unit 50B. This magnetic pattern is viewed from the same direction as in FIG. 9B. In the transport unit 50A, as shown in [Pattern A], a fixed magnet 68A having a magnetic pole pattern similar to that shown in FIG. 8 is disposed in the transport roll 60, and in the transport unit 50B, as shown in [Pattern B]. The fixed magnet 68 B having a magnetic pole pattern completely different from that of the transport unit 50 A is disposed in the transport roll 60.
[0058]
In the transport unit 50A, as shown in [Pattern A], the developer 52 having a low toner concentration is picked up at a position below the transport unit 50A, which is the pickup position (a), and above the storage container 62, and is taken in the direction of arrow G '. Is transported, and transport / non-transport is selected at the selected position (b). Since the toner concentration is low, that is, the carrier concentration is high, a considerable amount of the developer 52 having strong magnetism is transported as it is, and is transported in the directions of arrows G and G ″. At the detached position (c) where the magnetic field has disappeared adjacently, the transported developer 52 is separated and sent to the transport path 64.
[0059]
On the other hand, in the transport section 50B, as shown in [Pattern B], the toner or the developer 54 having a high toner concentration is picked up at a position below the transport section 50B and above the transport path 64. Then, at the position where the N-N same poles are adjacent to each other and the magnetic field disappears, they are separated and sent to the container 62. That is, the developer 54 is transported along the path indicated by the arrow H. Here, selective conveyance is not performed.
[0060]
In this way, the conveyance in the opposite direction is performed by the conveyance unit 50A and the conveyance unit 50B. That is, when the transport roll 60 rotates in the direction indicated by the arrow F, the developer 52 having a reduced toner density passes through the lower portion of the transport roll 60 and is picked up by the transport unit 50A, and the toner or the toner having a high toner density in the transport path 64. It is picked off in the flow of the developer 54. This developer is conveyed by the screw auger 66 for a while, so that the toner is sufficiently added to become the developer 54 having a high toner concentration. Then, when approaching below the transporting section 50B, it is picked up by this, and returned into the flow of the developer 52 having the reduced toner concentration. The returned developer 54 has an excessively higher toner concentration than the surrounding developer 52, but is diffused around as it is agitated and circulated by the screw augers 56 and 58, and becomes autonomously at an appropriate toner concentration. It is adjusted to.
[0061]
Finally, FIG. 11 shows an embodiment of a developing device using the transport device shown in FIG. In FIG. 11, members having the same functions as those of the transfer device shown in FIG. 9 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present developing device, the storage container 62 corresponds to the developer storage section according to the invention, and the transport path 64 corresponds to the supply agent storage section according to the invention.
[0062]
The developer 52, the toner concentration of which has been independently controlled by the transfer device including the transfer member 50, is sent to the vicinity of the developing roll (developer carrier) 70 by the screw augers 58 and 56 and the stirring blade 74. When the developer 52 magnetically attracted by the developing roll 70 is conveyed by the developing roll 70 rotating in the direction of arrow K, while the layer thickness is controlled by the regulating member 72, a so-called magnetic brush is formed while forming a so-called magnetic brush. The sheet is fed to a position facing a photoconductor (latent image carrier) 76 rotating in the L direction. Then, the electrostatic latent image formed on the surface of the photoconductor 76 is visualized by the toner in the developer 52, and the toner is consumed. Then, the developer 52 whose toner concentration has been reduced due to consumption of the toner is sent to the vicinity of the transfer device including the transfer member 50 by the stirring blade 74 and the screw augers 56 and 58, and the toner concentration is again adjusted independently. .
[0063]
An image forming apparatus according to the present invention includes at least a latent image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the latent image carrier, and an electrostatic latent image formed on the surface of the latent image carrier. And a developing unit for visualizing the image. The developing unit has a configuration as shown in FIG. 11, for example. The specific configuration is the same as that shown in FIG. 13, and the configuration other than the transport device characteristic of the present invention is not particularly limited.
[0064]
A running test was performed using an electrophotographic image forming apparatus including the developing device shown in FIG. The specifications of the image forming apparatus used at this time are as follows.
(Specifications of image forming apparatus)
・ Process speed: @ 108 mm / sec.
・ Circumferential speed of developing roll: # 215 mm / sec.
-Gap between the developing roll and the photoconductor: 0.4 mm
・ Amount of developer transported on the surface of the developing roll: 350 g / m²
・ Developing roll diameter: $ 18mm
・ Photoreceptor diameter: $ 84mm
・ Charge potential of photoconductor: -650V
・ Potential of image portion of photoconductor: -200V
・ Bias potential of developing roll: ΔV_PP= 1.5 kV, V_DC= -500V, Duty = 50%, f = 2kHz
・ Toner: ① Pulverized toner, which has been classified to have a volume average particle size of 6.5 μm by classification, Black, treated with external additives, negatively charged
・ Carrier: △ Volume average particle size 50μm, Ferrite core coated with resin
・ Amount of developer: $ 350g
[0065]
In the running test, A4 paper was used to print 20 sheets each of halftone or solid images with a printing density of 5%, 20%, 50%, and 100% (area ratio), and 20 blank sheets were run. Thereafter, the left half, the right half, the upper half, and the lower half of the half-surface solid image were printed at a position on the paper, 20 sheets each, and finally 20 blank sheets were flown. With this set as one set, a total of five sets were repeated, and a running test was performed for a total of 1000 sheets.
[0066]
FIG. 12 shows the transition of the image density in the traveling direction of the sheet in the running test. As can be seen from the graph of FIG. 12, in the image forming apparatus of the present invention, the density reproducibility was very stable, and no fogging was observed at all.
[0067]
In the embodiment described above, as the mixed powder composed of two or more kinds of particles having specific physical properties different from each other, a description has been mainly given by taking as an example a developer composed of toner and carrier having different magnetic properties. The transfer device of the present invention is not limited to this, and can be applied to various mixed powders composed of two or more types of particles having different specific physical properties, such as particles having different electrostatic characteristics. In addition, two types of particles having specific physical properties different from each other, that is, a toner and a carrier have been mainly described, but three or more types of particles may be included.
[0068]
【The invention's effect】
As described above, according to the present invention, for a mixed powder or developer composed of two or more types of particles, the mixed state of these two or more types of particles (for example, without using a sensor or a motor for supplying powder). , The ratio of toner concentration, etc.), the conveyance / non-conveyance is selected autonomously, for example, it is possible to keep the toner concentration constant and to be influenced by the fluctuation of the amount of the particles constituting the mixed powder. In addition, it is possible to provide a transport device that does not take in some of the particles excessively, and a developing device and an image forming device using the transport device.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view for explaining an operation mechanism of the present invention.
FIG. 2 is a schematic cross-sectional view illustrating an example of the transfer device of the present invention.
3A and 3B are schematic diagrams showing magnetic pole patterns of two types of fixed magnets applied to the transport device of FIG. 2, wherein FIG. 3A shows a fixed magnet having a strong magnetic pole pattern of a pickup magnetic pole, and FIG. It is a fixed magnet with a weak magnetic pole pattern.
FIG. 4 is a graph showing a result of a transfer test performed using the transfer device of FIG. 2;
FIG. 5 is a schematic sectional view showing another example of the transfer device of the present invention.
FIG. 6 is a schematic diagram showing a magnetic pole pattern of a fixed magnet applied to the transfer device of FIG.
FIG. 7 is a graph showing the results of a transport test performed using the transport device of FIG.
FIG. 8 is a schematic sectional view showing still another example of the transfer device of the present invention.
FIG. 9 is a schematic cross-sectional view showing an example of the transfer device of the present invention in which the transfer device shown in FIG. 8 is further modified.
FIG. 10 is a schematic diagram illustrating magnetic pole patterns in two transfer units in the transfer device of FIG. 9;
FIG. 11 is a schematic sectional view showing an example of the developing device of the present invention.
12 is a graph showing the results (transition of image density) of a running test performed using an electrophotographic image forming apparatus including the developing device of FIG.
FIG. 13 is a schematic configuration diagram of an image forming apparatus using a general two-component developing device.
14 is a schematic sectional view of a two-component developing device in the image forming apparatus shown in FIG.
FIG. 15 is a graph showing a relationship between toner density and toner charge amount in a two-component developing system developer.
[Explanation of symbols]
1 Transport member
2 mixed powder
3, 3 ', 38, 68A, 68B fixed magnet (magnet)
10, 30, 50 ° conveying member
12 mixed powder
14 container
16a, 16b screw auger
18 fixed magnet
20, 40, 60 ° transport roll (rotary body)
24mm divider
32, 34, 52, 54 Developer (mixed powder)
62 container (developer container)
64 conveyance path (supplement storage section)
70 ° developing roll (developer carrier)
76mm photoconductor (latent image carrier)

Claims

A transport device that selectively transports a mixed powder composed of two or more particles having different specific physical properties according to the specific physical properties of the mixed powder as a whole,
Due to the specific physical property, the device has a conveying member that adsorbs the mixed powder on a surface thereof, and the surface of the conveying member is held in a substantially vertical direction after adsorbing the mixed powder, and further, in a substantially horizontal direction. A transfer device that moves so as to be held by the transfer device.

In the transport member, the position at which the mixed powder is adsorbed is larger at a position at which the mixed powder is adsorbed than at a position at which the surface thereof is held in a substantially vertical direction due to the specific physical property. The transport device according to claim 1, wherein the transport device is configured as follows.

The position where the surface of the conveying member is held in a substantially horizontal direction, or at the downstream of the moving direction of the conveying member, is configured such that the surface adsorption force of the mixed powder due to the specific physical property is reduced, The transport device according to claim 1, wherein the mixed powder is separated from a surface of the transport member at a position.

The transport device according to claim 1, wherein at least one of the specific physical properties is a magnetic property.

The transport device according to any one of claims 1 to 4, wherein the transport member is a rotating body whose axis is held substantially horizontally.

The transport device according to claim 4, wherein the transport member comprises a non-magnetic rotating body whose axis is held substantially horizontally, and a magnet disposed therein.

Any area below the rotator or around the rotation direction is a position where the mixed powder is adsorbed, and the vicinity of a vertical portion immediately downstream of the rotation direction is a position where the surface is held in a substantially vertical direction. Wherein any one of the regions downstream of the rotation direction and upstream of the position at which the mixed powder is adsorbed is a position where the mixed powder is separated from the surface of the conveying member. Item 7. The transfer device according to item 5 or 6.

The peripheral surface of any one of the regions in the axial direction of the rotating body is a range in which the function of the transport device according to claim 7 is exhibited, and the rotation surface of the rotating body in another region in the axial direction of the rotating body is The transfer device according to claim 7, wherein a surface adsorption force of the mixed powder due to the specific physical property is increased in a region below the body or upstream in a rotation direction thereof, and the surface adsorption force is decreased downstream of the mixed powder. 8. The conveying device according to claim 7, wherein the conveying device has a function of conveying the powder in the opposite direction to the function.

The transport device according to any one of claims 1 to 8, wherein the mixed powder includes a toner and a carrier for electrophotography.

A developer carrying member for carrying at least a developer containing a toner and a carrier to develop a latent image on the latent image carrying member; and a developer accommodating portion for containing the developer and supplying the developer to the developer carrying member. A replenishment container that is adjacent to the developer container and stores a replenisher containing toner and carrier for replenishment; and the developer and / or the developer between the replenisher container and the developer container. A transport device for transporting the replenishing agent to each other, wherein the transport device is the transport device according to claim 9.

The transport device may be configured to transport the developer from the developer storage unit to the replenishment storage unit only when the mixing ratio of the toner in the developer in the developer storage unit is reduced. The developing device according to claim 10, wherein:

The developing device according to claim 11, wherein the developer conveyed by the conveying device is configured to contact and mix with the replenishing agent to become a replenishing agent and return to the developer accommodating portion again.

The developer accommodating portion has a flow means for flowing the developer, and a lower part of a position where the transport device is disposed and adsorbs the developer is a flow path of the developer, and The developing device according to any one of claims 10 to 12, wherein a partition member that partitions a vertical direction of the path is disposed on at least a part of the path.
15. An image forming apparatus, wherein the developing device according to claim 10 is used as the developing unit.