JP3972690B2

JP3972690B2 - Development device

Info

Publication number: JP3972690B2
Application number: JP2002066533A
Authority: JP
Inventors: 英明宮田; 宏偉楊
Original assignee: Fuji Xerox Co Ltd; Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2002-03-12
Filing date: 2002-03-12
Publication date: 2007-09-05
Anticipated expiration: 2022-03-12
Also published as: JP2003263031A

Description

【０００１】
【発明の属する技術分野】
本発明は、電子写真方式等を利用したプリンタ、複写機、複合機等の画像形成装置に使用される、磁性現像剤による現像を行う現像装置に係り、特に、その磁性現像剤を磁力により担持して搬送する円筒状の現像ロールの軸方向両端部と本体との間の間隙部分から現像剤が漏れ出ることをより確実に防止し得る現像装置に関するものである。
【０００２】
【従来の技術】
従来、この種の現像装置では、図２０に例示するように、磁性現像剤を収容する本体１２０に回転する円筒状ロール（例えばスリーブ）１０１とこのロールの中空部に固定設置される磁石部材（例えば磁石ロール）１０２とからなる現像ロール１００が装備されているが、この現像ロール１００の軸方向両端部と本体１２０との間隙部分における現像剤の漏れを防止するために、その現像ロール両端部と対向する本体１２０の部位にロール外周面に沿うような状態で鉄等の磁性部材１３０を設置している（特開平５−４０４０２号公報、特開平７−２０７２０号公報など）。
【０００３】
ここで、磁石部材１０２は、円筒状ロール１０１の外周面に磁性現像剤を磁力により担持するための複数の磁極（例えば４つの磁極Ｎ₁，Ｓ₁，Ｎ₂，Ｓ₂）が適宜配置されている。図中の符号１４０は円筒状ロール１０１の外周面の長手方向に当接して磁性現像剤の層厚を規制する弾性ブレード、１５０は現像剤搬送用の回転部材である。
【０００４】
そして、上記磁性部材１３０を設置することにより、磁石部材１０２の磁極からの磁力により磁石部材１０２と磁性部材１３０との間で磁界が形成されて円筒状ロール１０１の外周面上に磁性部材１３０との間隙を埋めるように磁性現像剤による磁気ブラシ（ＥＢ）が形成され、この磁気ブラシによって当該間隙から現像剤が漏れ出ることが防止されるという仕組み（いわゆる磁気シール構造）になっている。
【０００５】
【発明が解決しようとする課題】
しかし、このような磁気シール構造を採用した現像装置では、図２０に示すように磁極間(図示の例では磁極Ｎ₁と磁極Ｓ₁の間や磁極Ｓ₂と磁極Ｎ₁の間)において当該隣り合う磁極による磁力がおよばず磁界がきわめて弱い部位（Ｑ）が存在し、かかる部位（Ｑ）では磁気ブラシがほとんど形成されないか又は十分に形成されないため現像剤が漏れ出てしまうという問題があった。
【０００６】
特に、このような現像剤の漏れは、現像装置又はこれを含むカートリッジを画像形成装置の本体に装着する際に、必要以上に激しく振ったときや何かにぶつけて衝撃を加えたときなどに顕著に発生する傾向がある。これにより、その装着の作業者をはじめ装置自体や装置設置場所を現像剤で汚してしまうことがある。また、上記現像剤の漏れは、装置の高速化や現像剤の小径化が進むにつれて発生しやすくなるおそれがある。
【０００７】
ちなみに、特開平１０−２６８８４号公報には、このような問題を解決するための現像装置として、磁性部材の現像ロール側となる内面に複数の溝を形成し、その溝に発生する漏れ磁力によって磁気ブラシを形成して現像剤の漏れを防止するようにしたものが提案されている。しかし、かかる漏れ磁力により形成される磁気ブラシでは、強固な磁気ブラシとならないため現像剤の漏れを十分に防止することが困難であった。
【０００８】
本発明は、このような事情に鑑みなされたものであり、その主な目的とするところは、磁石部材の長手方向端部の磁極間となる部位に対向する円筒状ロールの外周面部分と本体部分との間隙からの現像剤の漏れについても確実に防止することができる現像装置を提供することにある。
【０００９】
【課題を解決するための手段】
上記目的を達成し得る本発明（第１発明）の現像装置は、磁性現像剤が収容され、その現像剤により現像を行う現像領域と対向させる開口部を有する容器状の本体と、この本体の前記開口部付近に外周面の一部を露出させた状態で回転可能に設置される現像剤担持搬送用の円筒状ロールと、この円筒状ロールの中空部の軸方向にわたって固定して設置され、そのロール外周面に前記磁性現像剤を磁力により担持させるための複数の磁極を配置してなる磁石部材と、この磁石部材の長手方向の両端部が位置する前記円筒状ロールの外周面部分と対向する前記本体の所定部位に当該外周面部分と所定の間隔をあけて設置される磁性部材とを備えた現像装置であって、前記磁石部材の長手方向の両端部における所定の磁極間となる部位と対向する前記本体の所定部位に補助磁石を設けたことを特徴とするものである。
【００１０】
上記補助磁石は、その磁石と対向する円筒状ロールの外周面部分との間に十分な磁気ブラシを形成するに足る磁力を発揮できるものであればよい。所定の磁極間とは、現像剤漏れを防止すべきところに位置する磁極と磁極の間をいう。上記本体の所定部位とは、現像剤の漏れを防止すべき対象となる部分である。補助磁石は、通常、本体の所定部位に設置される磁性部材と重複する部位に設けられることになるが、その場合は、例えば磁性部材を一部切り欠いた部分に一致させた状態で設けることが望ましい。磁性現像剤は、磁性粒子を有する現像剤であればよく、通常が一成分現像剤であるが、この他にも例えば非磁性トナーと磁性キャリアを含む２成分現像剤であってよい。磁性部材としては、例えば磁性のステンレス、鉄、合金等からなるものが使用される。
【００１１】
この第１発明の現像装置によれば、円筒状ロールの両端部部分と磁性部材との間には磁石部材の磁極の磁力にもとづく磁界が形成されて磁性現像剤による磁気ブラシが形成される一方で、磁石部材の所定の磁極間となる部位に対応する円筒ロール部分と補助磁石との間には補助磁石の磁力にもとづく強力な磁界が確実に形成されて強固な磁気ブラシが形成されるようになる。
【００１２】
また、第１発明における補助磁石については、前記円筒状ロールの外周面の軸方向にわたって先端部側の部位が当接するように固定して設置され、そのロール外周面に担持される磁性現像剤の層厚を規制する当接部材を備えている場合、前記当接部材の円筒状ロールとの当接部に少なくとも達する状態で設けるとともに、その当接部材の長手方向の端部とその長手方向において間隔をあけた状態で設けるとよい。
【００１３】
この場合、上記間隔は、補助磁石の磁力により形成される磁気ブラシが補助部材と当接部材の端部との間隙を埋めるように存在し得るような間隔であればよい。このように補助部材を設けることにより、当接部材の長手方向端部と本体との間隙における現像剤漏れを磁気ブラシにより防止できるようになる。
【００１４】
さらに、第１発明における各補助磁石については、前記当接部材の円筒状ロールとの当接部を通過して当該ロール回転方向の下流側となる部位まで達する状態で設けるとよい。この場合には、当接部材の長手方向端部と本体との間隙で発生し得る現像剤漏れを磁気ブラシによって確実に防止できるようになる。
【００１５】
また、上記目的を達成し得る本発明（第２発明）の現像装置は、磁性現像剤が収容され、その現像剤により現像を行う現像領域と対向させる開口部を有する容器状の本体と、この本体の前記開口部付近に外周面の一部を露出させた状態で回転可能に設置される現像剤担持搬送用の円筒状ロールと、この円筒状ロールの中空部の軸方向にわたって固定して設置され、そのロール外周面に前記磁性現像剤を磁力により担持させるための複数の磁極を配置してなる磁石部材とを備えた現像装置であって、前記磁石部材の長手方向の両端部における所定の磁極間となる部位に少なくとも補助磁石を設けるとともに、その補助磁石と少なくとも対向する前記本体の部位に前記円筒状ロールの外周面に沿って所定の隙間を形成するための隙間形成突起を設けることを特徴とするものである。
【００１６】
上記補助磁石は、その磁石と対向する円筒状ロールの外周面部分とその外周面部分と対向する本体部位との間に十分な磁気ブラシを形成するに足る磁力を発揮できるものであればよい。所定の磁極間とは、現像剤漏れを防止すべきところに位置する磁極と磁極の間をいう。上記隙間形成突起の円筒状ロール外周面との所定の隙間とは、補助磁石の磁力がおよんで磁気ブラシが形成されるに足る間隙である。補助磁石は、例えば磁石部材の一部を切り欠いた部分に磁石を取り付けるように設けるか、あるいは、磁石部材の該当部分を所定の磁極に着磁処理することで設けるようにする。また、補助磁石を磁石部材の磁極部分に設けない場合には、必要に応じてその部分と対向する本体の部位に磁気ブラシを形成するための磁性部材を設けるようにする。
【００１７】
この第２発明の現像装置によれば、磁石部材の磁極間となる部位に対向する円筒ロール部分と本体の隙間形成突起との間に、その補助磁石の磁力にもとづく強力な磁界が確実に形成されて強固な磁気ブラシが形成されるようになる。この補助磁石を磁石部材の磁極間のみに限らず磁極部分を含む現像剤漏れ防止の対象領域全体にわたって設けた場合には、その現像剤漏れ防止の対象領域に当たる円筒状ロールと本体の隙間形成突起との間に補助磁石の磁力による磁気ブラシが形成されるようになる。また、補助磁石をその磁極間だけに設けた場合には、その補助磁石が存在しない領域に対向する本体部位に磁性部材を設置することにより、磁石部材の磁極の磁力による磁気ブラシが形成されるようになる。
【００１８】
また、第２発明における隙間形成突起については、非磁性の部材で形成することができる。この場合には、隙間形成突起を、通常非磁性となるように形成される本体と同じ材料（例えば合成樹脂）で形成することが可能になる。特に補助磁石を磁石部材の磁極間のみに限らず磁極部分を含む現像剤漏れ防止の対象領域全体にわたって設けた場合において隙間形成突起を非磁性部材にて形成したときには、磁性部材を一切に使用する必要がなくなる。なお、隙間形成突起と補助磁石との間により強い磁界を形成したい場合には、その隙間形成突起を磁性部材で形成すればよい。
【００１９】
また、第２発明における補助磁石については、前記円筒状ロールの外周面の軸方向にわたって先端部側の部位が当接するように固定して設置され、そのロール外周面に担持される磁性現像剤の層厚を規制する当接部材を備えている場合、前記当接部材の円筒状ロールとの当接部に少なくとも達する状態で設けるとともに、その当接部材の長手方向の端部から前記磁石部材に垂直に下ろした平面と交わる位置に外側から接近した状態で設けるとよい。
【００２０】
この場合、外側から接近した状態とは、磁石部材の長手方向端部側から中央部側に向く方向であって、補助磁石の端部が当該平面と交わる位置と一致する位置か又はきわめて近い位置にある状態をいう。このように補助磁石を設けることにより、補助磁石の磁力が強い部分が当接部材の長手方向端部との間に有効に及ぶこととなり、磁気ブラシが十分に形成されるようになる。
【００２１】
さらに、以上の第２発明における補助磁石については、前記当接部材の円筒状ロールとの当接部を通過して当該ロール回転方向の下流側となる部位まで達する状態で設けるとよい。この場合には、当接部材の長手方向端部と本体との間隙で発生し得る現像剤漏れを磁気ブラシによって確実に防止できるようになる。
【００２２】
【発明の実施の形態】
［実施の形態１］
図１及び図２は本発明の実施の形態１を示すものであり、図１は本発明の現像装置を示す概略断面図、図２はその現像装置を使用する画像形成装置を示す概略図である。
【００２３】
画像形成装置１はレーザープリンタ等であり、図２に示すように、その本体１０内に感光ドラム１１が回転可能に設置されており、その感光ドラム１１の周囲にロール式の帯電装置１２、レーザビーム式の露光装置１３、一成分現像方式の現像装置２、ロール式の転写装置１４、ブレード式のクリーニング装置１５等がこの順に配置されている。また、本体１０内には、感光ドラム１１と転写装置１５の間の転写部位に搬送する記録用紙Ｐを収容して１枚ずつ供給する図示しない給紙装置や、その転写部位でトナー像が転写された記録用紙Ｐを通過させて定着処理を行う、加熱ロール１６ａ及び加圧ロール１６ｂからなる定着装置１６が設置されている。特に、この画像形成装置は、感光ドラム１１、帯電装置１２、現像装置２及びクリーニング装置１５が一体化されて本体１０に対して着脱可能に装着されるプロセスカートリッジとして構成されている。図２中の符号１７は記録用紙Ｐを所定のタイミングで転写部位にむけて送り出すレジストロール、１８は用紙搬送ガイド板、矢付き一点破線は記録用紙の搬送経路を示す。
【００２４】
このような画像形成装置では次のようにして画像の形成が行われる。
【００２５】
まず、矢印方向に回転する感光ドラム１１の外周面が帯電装置１２により一様に帯電された後、その帯電された外周面に露光装置１３により外部機器（原稿読み取り装置、ホストコンピュータなど）から入力される画像情報に基づいて変調されたレーザビーム光（ＬＢ）が照射されて静電潜像が形成される。ついで、その静電潜像が現像装置２から供給される一成分現像剤（磁性一成分トナー）により現像されてトナー像とされる。この感光ドラム１１上のトナー像は、このトナー像形成タイミングに合わせて転写部位に供給される記録用紙Ｐに転写装置１４により静電的に転写される。この転写後の感光ドラム１１の外周面はクリーニング装置１５により残留トナーが除去されて清掃される。また、トナー像が転写された記録用紙Ｐは、定着装置１６の加熱ロール１６ａと加圧ロール１６ｂの圧接部に送り込まれて加熱加圧されることによりそのトナー像が用紙上に定着される。この定着後の記録用紙Ｐは、定着装置１６を抜け出た後に本体１０の外部に排出される。
【００２６】
また、この画像形成装置１に使用される現像装置２は、以下のような構成になっている。
【００２７】
すなわち、現像装置２は、図１や図３等に示すように、磁性一成分トナーＧを収容する容器形態の本体２０を備えており、その本体２０の前記感光ドラム１１の現像すべき領域と対向する部位に形成される開口部２０ａに現像ロール２１が配置されている。本体２０は、ＨＩＰＳ（ハイインパクトポリスチレン）、ＡＢＳ等の合成樹脂を用いて形成されている。また、その本体２０には、一成分トナーＧを回転して攪拌搬送する攪拌搬送部材（アジテータなど）２５ａ、２５ｂや、攪拌搬送部材２５で攪拌搬送される一成分トナーＧを回転して現像ロール２１側に供給する供給部材２６や、現像ロール２１の表面に供給される一成分トナーＧの層厚を規制するように先端部２７ａ側がそのロール表面に当接する弾性ブレード２７が設置されている。弾性ブレード２７は支持プレート２８を介して本体２０に取り付けられている。
【００２８】
現像ロール２１は、アルミニウム等の非磁性材料で形成されて矢印方向に回転する円筒状のスリーブ２２と、このスリーブ２２の中空部に複数の磁極が磁化されて固定設置された磁石ロール２３とで構成されている。磁石ロール２３は、そのロール周面に所定の磁極（４つの磁極Ｎ₁，Ｓ₁，Ｎ₂，Ｓ₂）が交互に配置された構造になっており、図３ｂに示すように、その長手方向の両端部に形成された軸部２３ａが本体１０の側壁部１０ｂに固定されている。一方、スリーブ２２は、その両端部が端部支持体２４で支持されており、その端部支持体２４が軸受け２９ａを介して磁石ロールの軸２３ａに回転自在に取り付けられているとともに軸受け２９ｂを介して本体１０の側壁部に回転自在に取り付けられた構造になっている。また、スリーブ２２は図示しない駆動モータからの回転力がギア等を介して伝達されるようになっている。
【００２９】
この現像装置２による現像は次のようにして行われる。まず、本体２０内の一成分トナーＧが矢印方向に回転する攪拌搬送部材２５，２６により攪拌搬送され、矢印方向に回転する供給部材２７により現像ロール２１であるスリーブ２２の外周面に供給されて磁石ロール２３の磁極の磁力により吸着担持される。次に、スリーブ２２上の一成分トナーＧは、弾性ブレード２７のスリーブ表面との当接部を通過する際にその通過量が規制されるとともに摩擦帯電されることにより薄層状に担持された状態となり、その後、スリーブの回転にともなって感光ドラム１１と対向する現像領域まで搬送される。現像領域ではスリーブ２２上のトナーの一部が感光ドラム１１の静電潜像に付着し、これにより現像が行われる。この現像に供されなかった残りのトナーは本体２０内に戻されて再利用される。
【００３０】
そして、この現像装置２では、現像ロール２１の両端部と本体２０との間の間隙から一成分トナーＧが漏れ出ることを防ぐため、図３や図４に示すように、磁石ロール２３の長手方向の両端部が位置するスリーブ２２の外周面部分と対向する本体２０の現像剤漏れ防止対象部位に、その外周面部分と所定の間隔（０．５〜１．０ｍｍ）をあけて磁性のステンレスからなる半円筒板状の磁性部材３０を設けている。
【００３１】
また、この現像装置１では、磁石ロール２３の長手方向両端部における磁極間となる部位（磁極Ｎ₁と磁極Ｓ₁の間）と少なくとも対向する本体２０の部位に補助磁石４０を設けている。なお、補助磁石４０は、必要であれば図３に例示するように磁極Ｓ₂と磁極Ｎ₁の間にも設けるように構成してもよい。
【００３２】
この実施の形態１では、補助磁石４０として、スリーブ２２の外周面と相応する曲面（磁性部材３０と同じ曲率からなる面）４０ａを有した板形状のものを使用し、これを磁性部材３０の内側部３０ａの一部を切り欠いた部分に嵌め込んで一致させたような状態（磁石の曲面４０ａが磁性部材の内周面と一致して連続する状態）で本体２０に固着している。補助磁石４０は、例えば磁性部材３０の一部を切り欠くことなくその部材３０の下面（裏面）側に設けると、スリーブ２２との間に磁気ブラシが形成されにくくなる。また、補助磁石４０は、その一端部４０ｂが弾性ブレード２８のスリーブ２２との当接部Ｎｐを通過してスリーブ２２の回転方向下流側の位置まで達するように延長した状態で設けている。さらに、補助磁石４０は、図５に示すように弾性ブレード２８の長手方向端部２８ｂとその長手方向において間隔ｄ（０．５〜１．０ｍｍ）をあけた状態で設けている。
【００３３】
また、補助磁石４０としては、図６に示すように片面にＮ極、その他面にＳ極を配置（着磁）したものを使用した。これにより、同図に示すように磁力線Ｅを片面から他面にむけて発生させることができる。その磁力は、スリーブ２２の外周面との間隔を０．５〜１．０ｍｍとする場合、２０ｍＴ以上あればよい。
【００３４】
このような磁性部材３０や補助磁石４０を設けた現像装置２によれば、現像ロール２１のスリーブ２２の両端部と磁性部材３０との間では、磁石ロール２３の磁極（Ｎ₁，Ｓ₁，Ｓ₂）の磁力により磁性一成分トナーＧによる磁気ブラシが形成される。しかも、これに加えて、磁石ロール２３の所定の磁極間（磁極Ｎ₁と磁極Ｓ₁の間）となる部位に対応するスリーブ２２の部分と補助磁石４０との間では、補助磁石４０の磁力により強力な磁界が確実に形成されて強固な磁気ブラシが形成される。特にこの補助磁石４０の磁力によりスリーブ２２との間に形成される磁気ブラシは、補助磁石４０を磁性部材３０の切り欠き部にはめ込むような状態で設けているので、前記磁極の磁力によりスリーブ２２と磁性部材３０の間に形成される磁気ブラシと連続した状態でほぼ均一に形成される。
【００３５】
この結果、スリーブ２２の両端部と本体２０との間隙のうちで磁石ロール２３の磁極に対応する間隙部分での現像剤漏れが防止されることに加え、磁石ロール２３の所定の磁極間に対応する間隙部分での現像剤漏れも確実に防止されるようになる。
【００３６】
また、補助磁石４０を弾性ブレード２７のスリーブ２２との当接部Ｎｐに至る位置まで設け、しかも弾性ブレードの長手方向端部２７ｂとの間に間隔ｄをあけて設けているため、補助磁石４０の磁力により形成される磁気ブラシＥＢが弾性ブレードの長手方向端部２７ｂに接触するような状態で存在するようになる。この結果、弾性ブレード端部２７ｂにおける隙間からの現像剤の漏れも防止できる。さらに、この実施の形態１では、その補助磁石４０の一端部４０ｂを弾性ブレード２７のスリーブ２２との当接部Ｎｐを通過した状態で延長して設けていることにより、弾性ブレード端部２７ｂにおける隙間からの現像剤漏れをより確実に防止できる。
【００３７】
特にこの弾性ブレード端部２７ｂにおける現像剤漏れは磁気ブラシによって実現されるため、従来のようにウレタンスポンジ等からなるシール部材を弾性ブレード端部２７ｂからスリーブ２２にかけて接触するような状態で取り付けていた場合に比べ、弾性ブレード２７に余分な負荷をかけることがなくなり、また、そのシール部材の存在により弾性ブレード２７に接触することで発生していた現像剤のブロッキングや固着等の不具合が解消されるようになった。
【００３８】
なお、実施の形態１では、補助磁石４０を磁石ロール２２の所定の磁極間（磁極Ｎ₁と磁極Ｓ₁の間）となる部位に対応する本体２０の部分のみに設けるようにしてもよいが、好ましくはその一端部４０ｂが弾性ブレード２７のスリーブ２２との当接部Ｎｐに達する部位まで設けるとよい。
【００３９】
また、実施の形態１において補助磁石４０の弾性ブレード端部２７ｂと対向する面に磁気ブラシを多く形成したい場合は、補助磁石４０として、図７ａに例示するように弾性ブレード端部２７ｂと対向する片面に磁極Ｎ，Ｓを交互に繰り返して配置するパターンを採用すればよい。これにより、その片面に磁極Ｎ，Ｓ間で磁力線Ｅが発生するため磁気ブラシを形成することができる。このような繰り返しパターンからなる磁極Ｎ，Ｓの配置は、例えばラバーマグネットや、多極にパターン着磁した部材等を用いて形成することができる。また、補助磁石４０の弾性ブレード端部２７ｂと実際に対向する必要な面にだけ磁気ブラシを主に形成する一方で、その他の部位ではスリーブ２２との間に磁気ブラシを形成するという機能配分という観点からは、図７ｂに例示するように、補助磁石４０の片面に一部（弾性ブレード端部２７ｂと対向する部分のみ）に磁極Ｎ，Ｓを交互に繰り返すように配置し、その残り部分は１つの磁極（例えばＳ極）を配置するように構成してもよい。
【００４０】
［実施の形態２］
図８は、実施の形態２に係る現像装置２の要部を示すものである。この現像装置２は、補助磁石（４０）の設置位置を変更するとともに磁性部材（３０）を設置しないで代替手段を採用した以外は実施の形態２に係る現像装置２と同じ構成からなるものである。したがって、実施の形態１に係る現像装置２と共通する部位には同じ符号を付し、その説明については省略する。
【００４１】
この現像装置２では、磁石ロール２３の長手方向両端部における所定の磁極間（磁極Ｎ₁と磁極Ｓ₁の間：図１１参照）となる部位に少なくとも補助磁石４５を設けるとともに、その補助磁石４５と少なくとも対向する本体２０の部位にスリーブ２２の外周面に沿って所定の隙間ｓを形成するための隙間形成突起５０を設けている。
【００４２】
補助磁石４５は、図９や図１０に示すように、磁石ロール２３の長手方向両端部における所定の磁極間となる部位に補助磁石４５を装着するための切り欠き部２３ｄを形成し、その切り欠き部２３ｄに嵌めこんだ状態で固着している。ちなみに、補助磁石４５を設ける磁石ロール２３の端部は現像に影響を与えない部位とすべきであることは言うまでもない。補助磁石４５としては、図１０ｂに示すように、片面にＮ極、その他面にＳ極を配置（着磁）してなる全体が湾曲した板状のものを使用した。その磁力については、隙間形成突起５０とスリーブ２２の外周面との間隔ｓを０．５〜１．０ｍｍとする場合、２０ｍＴ以上としている。
【００４３】
また、補助磁石４５は、図８ａに示すように、その一端部４５ｂが弾性ブレード２７のスリーブ２２との当接部Ｎｐを通過してスリーブ２２の回転方向下流側の位置まで達するように延長した状態で設けている。さらに、補助磁石４５は、図８ｂに示すように、その磁石内側の面が、弾性ブレード２７の長手方向端部２７ｂから磁石ロール２３に垂直に下ろした平面（Ｈ）と交わる位置に当該ロール２３の外側から接近してほぼ一致するような状態で設けている。
【００４４】
この補助磁石４５を設けた磁石ロール２３の両端部における垂直磁力線の分布について、かかる補助磁石４５を設けない磁石ロール２３Ａの場合（図１２）と比較してみると、図１１ａに示すように、その補助磁石４５が存在する磁極間（磁極Ｎ₁と磁極Ｓ₁の間、磁極Ｓ₁と磁極Ｎ₂の間）となるロール中心部における半径方向の磁力線が増幅されて補強された状態になる。ちなみに、磁極Ｓ₁に対向するスリーブ２２の外周面が弾性ブレード２７の当接部Ｎｐにほぼ相当する。
【００４５】
一方、隙間形成突起５０は、図８や図９等に示すように、本体２０と同じ材質（合成樹脂）により一体的に成形してなる連続した突条形態のものであり、そのスリーブ２２の周面との間隔ｓが１ｍｍ程度になるよう形成している。特に隙間形成突起５０の磁極Ｎ₁と対向する端部の突起部分５０ａは、磁石ロール２３の軸方向に沿って連続した状態で形成されている（図８ａ）。
【００４６】
このような補助磁石４５と隙間形成突起５０を設けた現像装置２によれば、その補助磁石４５と隙間形成突起５０の間では、補助磁石４５の磁力により強力な磁界が確実に形成されて強固な磁気ブラシが連続して均一に形成される。この結果、スリーブ２２の両端部と本体２０との間隙のうちで磁石ロール２３の磁極に対応する間隙部分での現像剤漏れが防止されることに加え、磁石ロール２３の所定の磁極間に対応する間隙部分での現像剤漏れも確実に防止されるようになる。また、補助磁石４５を弾性ブレード２７のスリーブ２２との当接部Ｎｐに至る位置まで設けているため、補助磁石４５の磁力により形成される磁気ブラシＥＢが弾性ブレードの長手方向端部２７ｂに接触するような状態で存在するようになる。この結果、弾性ブレード端部２７ｂにおける隙間からの現像剤の漏れも防止できる。
【００４７】
また、この実施の形態２では特に、補助磁石４５を弾性ブレード２７の端部２７ｂと接近した状態で設けているため、図１３に示すように、補助磁石４５からの磁力線Ｅが弾性ブレード端部２７ｂを通過するような状態で隙間形成突起５０に達するようになって磁気ブラシも良好に形成されるようになり、この結果、弾性ブレード端部２７ｂ付近における本体２０との間隙からの現像剤漏れについても確実に防止されるようになる。さらに、隙間形成突起５０の磁極Ｎ₁と対向する端部の突起部分５０ａを磁石ロール２３の軸方向に沿って連続した状態で形成しているため、図１４に示すように当該突起部分５０ａと磁石ロール２３の間隙においても磁極Ｎ₁の磁力による磁気ブラシが良好に形成されるようになり、この結果、かかる間隙からの現像剤漏れについても確実に防止されるようになる。
【００４８】
また、この現像装置２では、補助磁石４５が磁石ロール２３と同じ材料で形成することが可能であるため、磁石ロール２３と一体化されたままでリサイクルが可能である。しかも、隙間形成突起５０についても本体２０と同じ材料で形成しているため、本体２０と一体化された状態のままでリサイクルが可能となる。
【００４９】
なお、実施の形態２において、補助磁石４５と本体２０との間により強力な磁界を発生させてより強固な磁気ブラシを形成したい場合は、図１５に例示するように、隙間形成突起５０に代えてスリーブ２２と所定の間隔ｓをあけた状態で磁性部材３５を本体２０に設置するとよい。
【００５０】
また、実施の形態２では、補助磁石４５を磁石ロール２２の所定の磁極間（磁極Ｎ₁と磁極Ｓ₁の間）となる部位に対応する本体２０の部分のみに設けるようにしてもよい。この場合には、その補助磁石がなく磁石ロール２２の上記磁極に対向する本体２０の部位に磁性部材を設置して磁気ブラシを形成するように構成する。ただし、補助磁石４５は、好ましくは図１６に例示するように、その一端部４０ｂが弾性ブレード２７のスリーブ２２との当接部Ｎｐに達する部位まで設けるとよい。このときの磁石ロール端部における磁力線の分布状態は、図１７に示すようになる。この場合においても、補助磁石４５を設けた上記磁極間のロール中心部における磁力線は、かかる補助磁石を設けない場合（図１２）にくらべて補強される（図１７ｂ）。
【００５１】
さらに、実施の形態２では、補助磁石４５として図１８に例示するように磁石ロールの内周側にＮ極を、その外周側にＳ極を位置させるように配置（着磁）して全体が湾曲した形態のものを使用しても構わない。このように配置した構成にすると、磁気ブラシの形成位置やそのブラシ（穂立ち）の強さを調整しやすくなる等のメリットがある。また、補助磁石４５は、磁石ロール２３の両端部に対して所定の磁極を直接着磁することにより設けるようにしてもよい。
【００５２】
【発明の効果】
以上説明したように、本発明の現像装置によれば、補助磁石等を設けているため、磁石部材の長手方向端部の磁極間となる部位に対向する円筒状ロールの外周面部分と本体部分との間隙からの現像剤の漏れについても確実に防止することができる。
【図面の簡単な説明】
【図１】実施の形態１（２）に係る現像装置を示す概略断面図。
【図２】図１の現像装置を使用した画像形成装置を示す概略構成図。
【図３】（ａ）は現像装置の要部（現像ロールとその周辺部）を示す概略断面図、（ｂ）は（ａ）のＢ−Ｂ線に沿う断面図。
【図４】補助磁石の設置状態を示す要部斜視図。
【図５】図４のＢ−Ｂ線に沿う一部断面図。
【図６】補助磁石の構成を示す斜視図。
【図７】補助磁石の他の構成例を示す斜視図。
【図８】（ａ）は実施の形態２に係る現像装置の要部（現像ロールとその周辺部）を示す概略断面図、（ｂ）は（ａ）のＢ−Ｂ線に沿う断面図。
【図９】補助磁石と隙間形成突起の形成状態を示す要部斜視図。
【図１０】（ａ）は補助磁石と磁石ロールの構成を示す一部分解斜視図、（ｂ）は補助磁石の構成を示す斜視図。
【図１１】（ａ）は磁石ロールの磁極配置状態と補助磁石の設置状態とを示す説明図、（ｂ）はその補助磁石を設けた磁石ロールの磁力線分布を示す説明図。
【図１２】（ａ）は補助磁石を設けない磁石ロールの磁極配置を示す説明図、（ｂ）は補助磁石を設けない磁石ロールの磁力線分布を示す説明図。
【図１３】補助磁石と弾性ブレード端部における磁極線の発生状態を示す要部説明図。
【図１４】現像ロール（磁石ロール）の周囲に形成される磁気ブラシの状態を示す説明図。
【図１５】隙間形成突起に代えて磁性部材を設置した変形例の要部を示す概略構成図。
【図１６】補助磁石の設置状態を変更した変形例の要部を示す概略構成図。
【図１７】（ａ）は図１６の磁石ロールの磁極配置状態と補助磁石の設置状態とを示す説明図、（ｂ）はその補助磁石を設けた磁石ロールの磁力線分布を示す説明図。
【図１８】補助磁石の他の構成例を示す斜視図。
【図１９】補助磁石を設けた磁石ロールの他の構成例を示す斜視図。
【図２０】従来の磁気シール構造を採用した現像装置の要部を示す概略断面図。
【符号の説明】
２…現像装置、２０…本体、１０ａ…開口部、２２…スリーブ（円筒状ロール）、２３…磁石ロール（磁石部材）、２７…弾性ブレード（当接部材）、３０…磁性部材、４０，４５…補助磁石、５０…隙間形成突起、Ｇ…磁性一成分トナー（磁性現像剤）、Ｓ，Ｎ，…磁極、Ｎｐ…当接部、ｓ…間隙。[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing with a magnetic developer used in an image forming apparatus such as a printer, a copying machine, or a multi-function machine using an electrophotographic method, and more particularly, the magnetic developer is supported by a magnetic force. The present invention relates to a developing device that can more reliably prevent the developer from leaking out from a gap portion between both ends in the axial direction of a cylindrical developing roll conveyed and the main body.
[0002]
[Prior art]
Conventionally, in this type of developing device, as illustrated in FIG. 20, a cylindrical roll (for example, a sleeve) 101 that rotates on a main body 120 that contains a magnetic developer and a magnet member (fixed and installed in a hollow portion of the roll) For example, in order to prevent the developer from leaking in the gap between the axial end portions of the developing roll 100 and the main body 120, both end portions of the developing roll 100 are provided. A magnetic member 130 such as iron is installed at a portion of the main body 120 opposite to the outer peripheral surface of the roll (JP-A-5-40402, JP-A-7-20720, etc.).
[0003]
Here, the magnet member 102 has a plurality of magnetic poles (for example, four magnetic poles N) for supporting the magnetic developer on the outer peripheral surface of the cylindrical roll 101 by a magnetic force. ₁ , S ₁ , N ₂ , S ₂ ) Are appropriately arranged. Reference numeral 140 in the figure denotes an elastic blade that abuts in the longitudinal direction of the outer peripheral surface of the cylindrical roll 101 to regulate the layer thickness of the magnetic developer, and 150 denotes a rotating member for transporting the developer.
[0004]
By installing the magnetic member 130, a magnetic field is formed between the magnetic member 102 and the magnetic member 130 by the magnetic force from the magnetic pole of the magnetic member 102, and the magnetic member 130 is placed on the outer peripheral surface of the cylindrical roll 101. A magnetic brush (EB) made of a magnetic developer is formed so as to fill the gap, and the magnetic brush prevents the developer from leaking out of the gap (so-called magnetic seal structure).
[0005]
[Problems to be solved by the invention]
However, in a developing device employing such a magnetic seal structure, as shown in FIG. ₁ And magnetic pole S ₁ Between and magnetic pole S ₂ And magnetic pole N ₁ Between the two magnetic poles, there is a portion (Q) where the magnetic force by the adjacent magnetic pole does not reach and the magnetic field is very weak, and the magnetic brush is hardly formed or not sufficiently formed at the portion (Q), so that the developer leaks out. There was a problem that.
[0006]
In particular, such developer leakage occurs when a developing device or a cartridge including the developer is attached to the main body of the image forming apparatus, when it is shaken more intensely than necessary or when an impact is applied to something. There is a tendency to occur remarkably. As a result, the apparatus itself and the installation location of the apparatus, including the wearing operator, may be soiled with the developer. Further, the developer leakage may easily occur as the speed of the apparatus increases and the developer diameter decreases.
[0007]
Incidentally, in Japanese Patent Laid-Open No. 10-26884, as a developing device for solving such a problem, a plurality of grooves are formed on the inner surface on the developing roll side of a magnetic member, and leakage magnetic force generated in the grooves is used. There has been proposed a magnetic brush that prevents developer leakage. However, since the magnetic brush formed by such a leakage magnetic force does not become a strong magnetic brush, it has been difficult to sufficiently prevent developer leakage.
[0008]
The present invention has been made in view of such circumstances, and the main object thereof is an outer peripheral surface portion and a main body of a cylindrical roll that are opposed to a portion between the magnetic poles at the longitudinal ends of the magnet member. An object of the present invention is to provide a developing device that can reliably prevent leakage of developer from a gap with a portion.
[0009]
[Means for Solving the Problems]
The developing device of the present invention (first invention) capable of achieving the above object includes a container-shaped main body containing an opening that faces a developing region in which a magnetic developer is accommodated and development is performed with the developer. A cylindrical roll for developer carrying that is rotatably installed with a part of the outer peripheral surface exposed in the vicinity of the opening, and fixed and installed over the axial direction of the hollow portion of the cylindrical roll, A magnet member in which a plurality of magnetic poles for supporting the magnetic developer by a magnetic force is arranged on the outer peripheral surface of the roll, and the outer peripheral surface portion of the cylindrical roll where both ends in the longitudinal direction of the magnet member are located A developing device comprising a magnetic member installed at a predetermined distance from the outer peripheral surface portion at a predetermined portion of the main body, wherein the portion is located between predetermined magnetic poles at both ends in the longitudinal direction of the magnet member Before facing It is characterized in that an auxiliary magnet to a predetermined site of the body.
[0010]
The auxiliary magnet is not particularly limited as long as it can exhibit a magnetic force sufficient to form a sufficient magnetic brush between the magnet and the outer peripheral surface portion of the cylindrical roll facing the magnet. The predetermined gap between the magnetic poles means a gap between the magnetic poles located where the developer leakage should be prevented. The predetermined portion of the main body is a portion that is a target for preventing leakage of the developer. The auxiliary magnet is usually provided in a part overlapping with the magnetic member installed in a predetermined part of the main body. In this case, for example, the auxiliary member is provided in a state where the magnetic member is partially cut away. Is desirable. The magnetic developer only needs to be a developer having magnetic particles, and is usually a one-component developer, but may also be a two-component developer including, for example, a non-magnetic toner and a magnetic carrier. As the magnetic member, for example, one made of magnetic stainless steel, iron, alloy or the like is used.
[0011]
According to the developing device of the first aspect of the present invention, a magnetic field based on the magnetic force of the magnetic pole of the magnet member is formed between the both end portions of the cylindrical roll and the magnetic member, thereby forming a magnetic brush by the magnetic developer. Thus, a strong magnetic brush based on the magnetic force of the auxiliary magnet is reliably formed between the cylindrical roll portion corresponding to the portion between the predetermined magnetic poles of the magnet member and the auxiliary magnet, so that a strong magnetic brush is formed. become.
[0012]
The auxiliary magnet according to the first aspect of the present invention is a magnetic developer which is fixedly installed so that a portion on the tip end side is in contact with the axial direction of the outer peripheral surface of the cylindrical roll and is carried on the outer peripheral surface of the roll. When the contact member for regulating the layer thickness is provided, the contact member is provided in a state where it reaches at least the contact portion with the cylindrical roll of the contact member, and the longitudinal end portion of the contact member and the longitudinal direction thereof It is good to provide in the state which left the space | interval.
[0013]
In this case, the interval may be an interval such that the magnetic brush formed by the magnetic force of the auxiliary magnet can exist so as to fill the gap between the auxiliary member and the end of the contact member. By providing the auxiliary member in this way, it becomes possible to prevent the developer leakage in the gap between the longitudinal end portion of the contact member and the main body by the magnetic brush.
[0014]
Further, each auxiliary magnet in the first invention may be provided in a state of passing through a contact portion with the cylindrical roll of the contact member and reaching a downstream portion in the roll rotation direction. In this case, developer leakage that may occur in the gap between the longitudinal end of the contact member and the main body can be reliably prevented by the magnetic brush.
[0015]
Further, the developing device of the present invention (second invention) capable of achieving the above object includes a container-shaped main body having an opening facing a developing region in which a magnetic developer is accommodated and developing with the developer. A cylindrical roll for carrying and carrying a developer, which is rotatably installed with a part of the outer peripheral surface exposed in the vicinity of the opening of the main body, and fixed in the axial direction of the hollow portion of the cylindrical roll. And a magnet member in which a plurality of magnetic poles for carrying the magnetic developer by a magnetic force are arranged on the outer peripheral surface of the roll, and a predetermined amount at both end portions in the longitudinal direction of the magnet member. At least an auxiliary magnet is provided at a portion between the magnetic poles, and a gap forming protrusion for forming a predetermined gap along the outer peripheral surface of the cylindrical roll is provided at a portion of the main body at least facing the auxiliary magnet. And it is characterized in Rukoto.
[0016]
The auxiliary magnet is not particularly limited as long as it can exhibit a magnetic force sufficient to form a sufficient magnetic brush between the outer peripheral surface portion of the cylindrical roll facing the magnet and the main body portion facing the outer peripheral surface portion. The predetermined gap between the magnetic poles means a gap between the magnetic poles located where the developer leakage should be prevented. The predetermined gap between the gap-forming protrusion and the outer peripheral surface of the cylindrical roll is a gap sufficient to form a magnetic brush by the magnetic force of the auxiliary magnet. For example, the auxiliary magnet is provided so that the magnet is attached to a part of the magnet member that is notched, or is provided by magnetizing the corresponding part of the magnet member to a predetermined magnetic pole. Further, when the auxiliary magnet is not provided in the magnetic pole portion of the magnet member, a magnetic member for forming a magnetic brush is provided in a portion of the main body facing the portion as necessary.
[0017]
According to the developing device of the second aspect of the present invention, the magnetic force of the auxiliary magnet is based on the space between the cylindrical roll portion facing the portion between the magnetic poles of the magnet member and the gap forming protrusion of the main body. Powerful A strong magnetic brush is formed with a reliable magnetic field. When this auxiliary magnet is provided not only between the magnetic poles of the magnet member but also over the entire target area for preventing developer leakage including the magnetic pole part, the cylindrical roll corresponding to the target area for preventing developer leakage and the gap forming protrusion between the main body A magnetic brush is formed by the magnetic force of the auxiliary magnet. In addition, when the auxiliary magnet is provided only between the magnetic poles, a magnetic brush is formed by the magnetic force of the magnetic pole of the magnet member by installing the magnetic member in the main body portion facing the region where the auxiliary magnet does not exist. It becomes like this.
[0018]
In addition, the gap forming protrusion in the second invention can be formed of a nonmagnetic member. In this case, the gap forming protrusion can be formed of the same material (for example, synthetic resin) as that of the main body that is normally formed to be non-magnetic. In particular, when the auxiliary magnet is provided not only between the magnetic poles of the magnet member but also over the entire target area for preventing developer leakage including the magnetic pole portion, the magnetic member is used at all when the gap forming protrusion is formed of the nonmagnetic member. There is no need. If a stronger magnetic field is to be formed between the gap forming protrusion and the auxiliary magnet, the gap forming protrusion may be formed of a magnetic member.
[0019]
The auxiliary magnet according to the second aspect of the present invention is a magnetic developer that is fixedly installed so that a portion on the tip end side is in contact with the axial direction of the outer peripheral surface of the cylindrical roll and is carried on the outer peripheral surface of the roll. When the contact member for regulating the layer thickness is provided, the contact member is provided in a state where it reaches at least the contact portion with the cylindrical roll of the contact member, and the magnet member is provided from the longitudinal end of the contact member. It is good to provide in the state which approached from the outer side to the position which cross | intersects the plane drawn down vertically.
[0020]
In this case, the state of approaching from the outside is the direction from the longitudinal end of the magnet member toward the center, and the position where the end of the auxiliary magnet coincides with the position where it intersects the plane or is very close The state that is in. By providing the auxiliary magnet in this way, the portion where the magnetic force of the auxiliary magnet is strong extends effectively between the end portions in the longitudinal direction of the contact member, and the magnetic brush is sufficiently formed.
[0021]
Further, the auxiliary magnet according to the second aspect of the present invention may be provided in a state of passing through the contact portion of the contact member with the cylindrical roll and reaching the downstream side in the roll rotation direction. In this case, developer leakage that may occur in the gap between the longitudinal end of the contact member and the main body can be reliably prevented by the magnetic brush.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
1 and 2 show Embodiment 1 of the present invention. FIG. 1 is a schematic sectional view showing a developing device of the present invention, and FIG. 2 is a schematic diagram showing an image forming apparatus using the developing device. is there.
[0023]
The image forming apparatus 1 is a laser printer or the like, and as shown in FIG. 2, a photosensitive drum 11 is rotatably installed in a main body 10, and a roll-type charging device 12 and a laser are provided around the photosensitive drum 11. A beam type exposure device 13, a single component development type development device 2, a roll type transfer device 14, a blade type cleaning device 15 and the like are arranged in this order. Further, in the main body 10, a recording paper P to be conveyed to a transfer portion between the photosensitive drum 11 and the transfer device 15 is accommodated and fed one by one, and a toner image is transferred at the transfer portion. A fixing device 16 composed of a heating roll 16a and a pressure roll 16b is installed to perform the fixing process by passing the recording paper P that has been passed. In particular, the image forming apparatus is configured as a process cartridge in which the photosensitive drum 11, the charging device 12, the developing device 2, and the cleaning device 15 are integrated and detachably attached to the main body 10. Reference numeral 17 in FIG. 2 denotes a registration roll that feeds the recording paper P toward the transfer portion at a predetermined timing, 18 denotes a paper transport guide plate, and a dashed line with arrows indicates a transport path of the recording paper.
[0024]
In such an image forming apparatus, an image is formed as follows.
[0025]
First, after the outer peripheral surface of the photosensitive drum 11 rotating in the direction of the arrow is uniformly charged by the charging device 12, the charged outer peripheral surface is input from an external device (such as a document reading device or a host computer) by the exposure device 13. The laser beam light (LB) modulated based on the image information is irradiated to form an electrostatic latent image. Next, the electrostatic latent image is developed with a one-component developer (magnetic one-component toner) supplied from the developing device 2 to form a toner image. The toner image on the photosensitive drum 11 is electrostatically transferred by the transfer device 14 to the recording paper P supplied to the transfer portion in accordance with the toner image formation timing. After the transfer, the outer peripheral surface of the photosensitive drum 11 is cleaned by removing residual toner by the cleaning device 15. Further, the recording paper P onto which the toner image has been transferred is sent to the press contact portion of the heating roll 16a and the pressure roll 16b of the fixing device 16 and is heated and pressed to fix the toner image on the paper. The recording sheet P after the fixing is discharged from the main body 10 after exiting the fixing device 16.
[0026]
The developing device 2 used in the image forming apparatus 1 has the following configuration.
[0027]
That is, as shown in FIGS. 1 and 3, the developing device 2 includes a main body 20 in the form of a container that stores the magnetic one-component toner G, and an area to be developed on the photosensitive drum 11 of the main body 20. A developing roll 21 is disposed in an opening 20a formed in the facing portion. The main body 20 is formed using a synthetic resin such as HIPS (high impact polystyrene) or ABS. Further, the main body 20 is rotated by agitating and conveying members (agitators and the like) 25a and 25b that rotate and convey the one-component toner G, and the one-component toner G that is agitated and conveyed by the agitating and conveying member 25. A supply member 26 supplied to the surface 21 and an elastic blade 27 whose tip 27a abuts against the roll surface are installed so as to regulate the layer thickness of the one-component toner G supplied to the surface of the developing roll 21. The elastic blade 27 is attached to the main body 20 via a support plate 28.
[0028]
The developing roll 21 includes a cylindrical sleeve 22 formed of a non-magnetic material such as aluminum and rotating in the direction of the arrow, and a magnet roll 23 in which a plurality of magnetic poles are magnetized and fixedly installed in the hollow portion of the sleeve 22. It is configured. The magnet roll 23 has predetermined magnetic poles (four magnetic poles N) on its peripheral surface. ₁ , S ₁ , N ₂ , S ₂ ) Are alternately arranged, and as shown in FIG. 3 b, shaft portions 23 a formed at both ends in the longitudinal direction are fixed to the side wall portion 10 b of the main body 10. On the other hand, both ends of the sleeve 22 are supported by end support members 24. The end support members 24 are rotatably attached to the shaft 23a of the magnet roll via the bearings 29a and the bearings 29b. It is the structure attached rotatably to the side wall part of the main body 10 via. The sleeve 22 is adapted to transmit a rotational force from a drive motor (not shown) through a gear or the like.
[0029]
Development by the developing device 2 is performed as follows. First, the one-component toner G in the main body 20 is agitated and conveyed by the agitating / conveying members 25 and 26 rotating in the arrow direction, and supplied to the outer peripheral surface of the sleeve 22 as the developing roll 21 by the supply member 27 rotating in the arrow direction. It is attracted and supported by the magnetic force of the magnetic poles of the magnet roll 23. Next, when the one-component toner G on the sleeve 22 passes through the contact portion of the elastic blade 27 with the sleeve surface, the amount of the toner is regulated and frictionally charged so that it is carried in a thin layer. Then, as the sleeve rotates, it is conveyed to the developing area facing the photosensitive drum 11. In the developing area, a part of the toner on the sleeve 22 adheres to the electrostatic latent image on the photosensitive drum 11, thereby developing. The remaining toner that has not been subjected to the development is returned to the main body 20 and reused.
[0030]
In the developing device 2, in order to prevent the one-component toner G from leaking from the gap between the both ends of the developing roll 21 and the main body 20, as shown in FIG. 3 and FIG. Magnetic stainless steel at a predetermined interval (0.5 to 1.0 mm) from the outer peripheral surface portion of the main body 20 at a portion to be prevented from leakage of the developer that faces the outer peripheral surface portion of the sleeve 22 where both ends of the direction are located. A semi-cylindrical plate-like magnetic member 30 is provided.
[0031]
Further, in the developing device 1, the part (magnetic pole N) between the magnetic poles at both ends in the longitudinal direction of the magnet roll 23. ₁ And magnetic pole S ₁ Auxiliary magnets 40 are provided at least on the part of the main body 20 that is opposed to each other. If necessary, the auxiliary magnet 40 is provided with a magnetic pole S as illustrated in FIG. ₂ And magnetic pole N ₁ You may comprise so that it may provide between.
[0032]
In the first embodiment, the auxiliary magnet 40 is a plate having a curved surface (a surface having the same curvature as the magnetic member 30) 40a corresponding to the outer peripheral surface of the sleeve 22, and this is used as the magnetic member 30. The inner part 30a is fixed to the main body 20 in a state in which a part of the inner part 30a is fitted and matched with the notched part (a state in which the curved surface 40a of the magnet is continuous with the inner peripheral surface of the magnetic member). For example, when the auxiliary magnet 40 is provided on the lower surface (back surface) side of the magnetic member 30 without cutting out a part of the magnetic member 30, it is difficult to form a magnetic brush between the auxiliary magnet 40 and the sleeve 22. In addition, the auxiliary magnet 40 is provided in a state in which one end portion 40b extends so as to pass through a contact portion Np of the elastic blade 28 with the sleeve 22 and reach the downstream side of the sleeve 22 in the rotation direction. Further, as shown in FIG. 5, the auxiliary magnet 40 is provided in a state where a distance d (0.5 to 1.0 mm) is provided between the longitudinal end portion 28 b of the elastic blade 28 and the longitudinal direction thereof.
[0033]
Further, as the auxiliary magnet 40, as shown in FIG. 6, a magnet having an N pole on one side and an S pole on the other side (magnetized) was used. As a result, as shown in FIG. The It can be generated from one side to the other side. The magnetic force may be 20 mT or more when the distance from the outer peripheral surface of the sleeve 22 is 0.5 to 1.0 mm.
[0034]
According to the developing device 2 provided with such a magnetic member 30 and the auxiliary magnet 40, the magnetic pole (N) of the magnet roll 23 is between the both ends of the sleeve 22 of the developing roll 21 and the magnetic member 30. ₁ , S ₁ , S ₂ ), A magnetic brush made of magnetic one-component toner G is formed. In addition, in addition to this, between the predetermined magnetic poles of the magnet roll 23 (magnetic pole N ₁ And magnetic pole S ₁ Between the portion of the sleeve 22 corresponding to the portion between the auxiliary magnet 40 and the auxiliary magnet 40, a strong magnetic field is reliably formed by the magnetic force of the auxiliary magnet 40, and a strong magnetic brush is formed. In particular, the magnetic brush formed between the auxiliary magnet 40 and the sleeve 22 by means of the magnetic force is provided in such a state that the auxiliary magnet 40 is fitted into the cutout portion of the magnetic member 30. And a magnetic brush formed between the magnetic member 30 and the magnetic member 30 in a continuous state.
[0035]
As a result, the developer leakage is prevented in the gap corresponding to the magnetic pole of the magnet roll 23 in the gap between the both ends of the sleeve 22 and the main body 20, and in addition, the gap between the predetermined magnetic poles of the magnet roll 23 is supported. Thus, leakage of the developer at the gap portion is prevented with certainty.
[0036]
In addition, since the auxiliary magnet 40 is provided up to a position reaching the contact portion Np with the sleeve 22 of the elastic blade 27 and is provided at a distance d from the longitudinal end portion 27b of the elastic blade, the auxiliary magnet 40 is provided. The magnetic brush EB formed by the magnetic force of the elastic blade comes into contact with the longitudinal end portion 27b of the elastic blade. As a result, the leakage of the developer from the gap at the elastic blade end portion 27b can also be prevented. Further, in the first embodiment, the one end portion 40b of the auxiliary magnet 40 is extended in a state of passing through the contact portion Np with the sleeve 22 of the elastic blade 27, so that the elastic blade end portion 27b Developer leakage from the gap can be prevented more reliably.
[0037]
In particular, since the developer leakage at the elastic blade end portion 27b is realized by a magnetic brush, a sealing member made of urethane sponge or the like is attached so as to be in contact from the elastic blade end portion 27b to the sleeve 22 as in the prior art. Compared to the case, an excessive load is not applied to the elastic blade 27, and problems such as blocking or fixing of the developer caused by contacting the elastic blade 27 due to the presence of the seal member are eliminated. It became so.
[0038]
In the first embodiment, the auxiliary magnet 40 is disposed between predetermined magnetic poles of the magnet roll 22 (magnetic pole N ₁ And magnetic pole S ₁ It may be provided only in the part of the main body 20 corresponding to the part between the elastic blade 27 and the part where the one end 40b reaches the contact part Np with the sleeve 22 of the elastic blade 27.
[0039]
In the first embodiment, when it is desired to form a large number of magnetic brushes on the surface of the auxiliary magnet 40 that faces the elastic blade end 27b, the auxiliary magnet 40 faces the elastic blade end 27b as illustrated in FIG. 7a. A pattern in which the magnetic poles N and S are alternately and repeatedly arranged on one side may be employed. Thereby, since the magnetic force line E generate | occur | produces between the magnetic poles N and S on the single side | surface, a magnetic brush can be formed. The arrangement of the magnetic poles N and S having such a repetitive pattern can be formed by using, for example, a rubber magnet or a member magnetized with multiple patterns. In addition, the magnetic brush is mainly formed only on the necessary surface that actually faces the elastic blade end portion 27b of the auxiliary magnet 40, while the magnetic brush is formed between the sleeve 22 and the other portions. From the viewpoint, as illustrated in FIG. 7b, the magnetic poles N and S are alternately arranged on one side (only the portion facing the elastic blade end portion 27b) on one side of the auxiliary magnet 40, and the remaining portion is You may comprise so that one magnetic pole (for example, S pole) may be arrange | positioned.
[0040]
[Embodiment 2]
FIG. 8 shows a main part of the developing device 2 according to the second embodiment. The developing device 2 has the same configuration as the developing device 2 according to the second embodiment except that the installation position of the auxiliary magnet (40) is changed and an alternative means is adopted without installing the magnetic member (30). is there. Therefore, the same reference numerals are given to portions common to the developing device 2 according to Embodiment 1, and the description thereof is omitted.
[0041]
In the developing device 2, predetermined magnetic poles (magnetic pole N) at both longitudinal ends of the magnet roll 23 are used. ₁ And magnetic pole S ₁ A gap for forming a predetermined gap s along the outer peripheral surface of the sleeve 22 at a portion of the main body 20 at least facing the auxiliary magnet 45 while providing at least a portion of the auxiliary magnet 45 at a portion between the two portions (see FIG. 11). A forming protrusion 50 is provided.
[0042]
As shown in FIGS. 9 and 10, the auxiliary magnet 45 is formed with a notch 23d for attaching the auxiliary magnet 45 to a portion between the predetermined magnetic poles at both ends in the longitudinal direction of the magnet roll 23. It is fixed in a state of being fitted into the notch 23d. Incidentally, it goes without saying that the end of the magnet roll 23 provided with the auxiliary magnet 45 should be a part that does not affect the development. As the auxiliary magnet 45, as shown in FIG. 10 b, a plate-like one that is entirely curved by arranging (magnetizing) an N pole on one side and an S pole on the other side was used. The magnetic force is set to 20 mT or more when the interval s between the gap forming protrusion 50 and the outer peripheral surface of the sleeve 22 is 0.5 to 1.0 mm.
[0043]
Further, as shown in FIG. 8 a, the auxiliary magnet 45 extends so that one end portion 45 b passes through the contact portion Np with the sleeve 22 of the elastic blade 27 and reaches the position downstream of the sleeve 22 in the rotation direction. It is provided in the state. Further, as shown in FIG. 8 b, the auxiliary magnet 45 has a surface on the inner side of the roll 23 at a position where it intersects a plane (H) perpendicular to the magnet roll 23 from the longitudinal end portion 27 b of the elastic blade 27. It is provided in a state where it approaches from the outside and almost matches.
[0044]
Compared with the case of the magnet roll 23A not provided with the auxiliary magnet 45 (FIG. 12), the distribution of the vertical magnetic field lines at both ends of the magnet roll 23 provided with the auxiliary magnet 45 is as shown in FIG. Between the magnetic poles where the auxiliary magnet 45 exists (magnetic pole N ₁ And magnetic pole S ₁ Magnetic pole S during ₁ And magnetic pole N ₂ The magnetic field lines in the radial direction at the center of the roll, which are between (between) and the middle, are amplified and reinforced. By the way, magnetic pole S ₁ The outer peripheral surface of the sleeve 22 that faces is substantially equivalent to the contact portion Np of the elastic blade 27.
[0045]
On the other hand, as shown in FIGS. 8 and 9, etc., the gap forming protrusion 50 has a continuous protrusion shape formed integrally with the same material (synthetic resin) as the main body 20, and the sleeve 22 The gap s with the peripheral surface is formed to be about 1 mm. In particular, the magnetic pole N of the gap forming protrusion 50 ₁ The protrusion part 50a of the edge part which opposes is formed in the state which followed along the axial direction of the magnet roll 23 (FIG. 8a).
[0046]
According to the developing device 2 provided with the auxiliary magnet 45 and the gap forming protrusion 50, a strong magnetic field is reliably formed by the magnetic force of the auxiliary magnet 45 between the auxiliary magnet 45 and the gap forming protrusion 50 and is strong. A continuous magnetic brush is uniformly formed. As a result, the developer leakage is prevented in the gap corresponding to the magnetic pole of the magnet roll 23 in the gap between the both ends of the sleeve 22 and the main body 20, and in addition, the gap between the predetermined magnetic poles of the magnet roll 23 is supported. Thus, leakage of the developer at the gap portion is prevented with certainty. Further, since the auxiliary magnet 45 is provided up to a position reaching the contact portion Np of the elastic blade 27 with the sleeve 22, the magnetic brush EB formed by the magnetic force of the auxiliary magnet 45 contacts the longitudinal end portion 27b of the elastic blade. It comes to exist in such a state. As a result, the leakage of the developer from the gap at the elastic blade end portion 27b can also be prevented.
[0047]
In the second embodiment, in particular, since the auxiliary magnet 45 is provided in a state of being close to the end portion 27b of the elastic blade 27, the magnetic force line E from the auxiliary magnet 45 is applied to the end portion of the elastic blade as shown in FIG. As a result, the magnetic brush is well formed by reaching the gap forming protrusion 50 in a state of passing through 27b. As a result, the developer leaks from the gap with the main body 20 in the vicinity of the elastic blade end portion 27b. Will be surely prevented. Further, the magnetic pole N of the gap forming protrusion 50 ₁ 14 is formed in a state of being continuous along the axial direction of the magnet roll 23, so that the magnetic pole N is also formed in the gap between the protruding portion 50a and the magnet roll 23 as shown in FIG. ₁ As a result, the developer leakage from the gap is surely prevented.
[0048]
In the developing device 2, since the auxiliary magnet 45 can be formed of the same material as the magnet roll 23, it can be recycled while being integrated with the magnet roll 23. Moreover, since the gap forming protrusion 50 is also formed of the same material as that of the main body 20, it can be recycled while being integrated with the main body 20.
[0049]
In the second embodiment, when it is desired to generate a stronger magnetic field between the auxiliary magnet 45 and the main body 20 to form a stronger magnetic brush, the gap forming protrusion 50 is used instead as illustrated in FIG. The magnetic member 35 may be installed on the main body 20 with a predetermined distance s from the sleeve 22.
[0050]
In the second embodiment, the auxiliary magnet 45 is disposed between predetermined magnetic poles of the magnet roll 22 (magnetic pole N ₁ And magnetic pole S ₁ It may be provided only in the portion of the main body 20 corresponding to the portion between the two. In this case, there is no auxiliary magnet, and a magnetic brush is formed by installing a magnetic member at a portion of the main body 20 facing the magnetic pole of the magnet roll 22. However, the auxiliary magnet 45 is preferably provided up to a portion where the one end 40b reaches the contact portion Np with the sleeve 22 of the elastic blade 27, as illustrated in FIG. The distribution state of the lines of magnetic force at the end of the magnet roll at this time is as shown in FIG. Even in this case, the lines of magnetic force at the center of the roll between the magnetic poles provided with the auxiliary magnet 45 are reinforced (FIG. 17b) as compared to the case where the auxiliary magnet is not provided (FIG. 12).
[0051]
Furthermore, in the second embodiment, the auxiliary magnet 45 is arranged (magnetized) so that the N pole is positioned on the inner peripheral side of the magnet roll and the S pole is positioned on the outer peripheral side as illustrated in FIG. A curved shape may be used. Such a configuration is advantageous in that it is easy to adjust the formation position of the magnetic brush and the strength of the brush. Further, the auxiliary magnet 45 may be provided by directly magnetizing a predetermined magnetic pole to both ends of the magnet roll 23.
[0052]
【The invention's effect】
As described above, according to the developing device of the present invention, since the auxiliary magnet or the like is provided, the outer peripheral surface portion and the main body portion of the cylindrical roll facing the portion between the magnetic poles at the longitudinal end portion of the magnet member. It is also possible to reliably prevent the developer leakage from the gap.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a developing device according to a first embodiment (2).
FIG. 2 is a schematic configuration diagram illustrating an image forming apparatus using the developing device of FIG.
3A is a schematic cross-sectional view showing a main part (developing roll and its peripheral part) of the developing device, and FIG. 3B is a cross-sectional view taken along line BB in FIG.
FIG. 4 is a perspective view of a main part showing an installed state of an auxiliary magnet.
5 is a partial cross-sectional view taken along line BB in FIG.
FIG. 6 is a perspective view showing a configuration of an auxiliary magnet.
FIG. 7 is a perspective view showing another configuration example of the auxiliary magnet.
8A is a schematic cross-sectional view showing a main part (developing roll and its peripheral part) of the developing device according to the second embodiment, and FIG. 8B is a cross-sectional view taken along line BB in FIG.
FIG. 9 is a perspective view of a main part showing a state in which auxiliary magnets and gap forming protrusions are formed.
10A is a partially exploded perspective view showing the configuration of an auxiliary magnet and a magnet roll, and FIG. 10B is a perspective view showing the configuration of an auxiliary magnet.
11A is an explanatory diagram showing a magnetic pole arrangement state of a magnet roll and an installation state of an auxiliary magnet, and FIG. 11B is an explanatory diagram showing a magnetic force line distribution of a magnet roll provided with the auxiliary magnet.
FIG. 12A is an explanatory diagram showing the magnetic pole arrangement of a magnet roll without an auxiliary magnet, and FIG. 12B is an explanatory diagram showing a magnetic force line distribution of a magnet roll without an auxiliary magnet.
FIG. 13 is a main part explanatory view showing a state in which magnetic pole lines are generated at the auxiliary magnet and the elastic blade end.
FIG. 14 is an explanatory diagram showing a state of a magnetic brush formed around a developing roll (magnet roll).
FIG. 15 is a schematic configuration diagram showing a main part of a modified example in which a magnetic member is installed instead of a gap forming protrusion.
FIG. 16 is a schematic configuration diagram showing a main part of a modified example in which the installation state of the auxiliary magnet is changed.
17A is an explanatory view showing a magnetic pole arrangement state and an auxiliary magnet installation state of the magnet roll of FIG. 16, and FIG. 17B is an explanatory view showing a magnetic force line distribution of the magnet roll provided with the auxiliary magnet.
FIG. 18 is a perspective view showing another configuration example of the auxiliary magnet.
FIG. 19 is a perspective view showing another configuration example of a magnet roll provided with an auxiliary magnet.
FIG. 20 is a schematic cross-sectional view showing a main part of a developing device employing a conventional magnetic seal structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Developing device, 20 ... Main body, 10a ... Opening, 22 ... Sleeve (cylindrical roll), 23 ... Magnet roll (magnet member), 27 ... Elastic blade (contact member), 30 ... Magnetic member, 40, 45 ... auxiliary magnets, 50 ... gap forming protrusions, G ... magnetic one-component toner (magnetic developer), S, N, ... magnetic poles, Np ... abutting portions, s ... gaps.

Claims

A container-shaped main body containing a magnetic developer and having an opening facing a development region where development is performed by the developer;
A cylindrical roll for transporting developer carrying, which is rotatably installed with a part of the outer peripheral surface exposed in the vicinity of the opening of the main body;
A magnet member that is fixedly installed over the axial direction of the hollow portion of the cylindrical roll, and has a plurality of magnetic poles for carrying the magnetic developer by a magnetic force on the outer peripheral surface of the roll ,
It is fixedly installed so that the portion on the tip end side is in contact with the axial direction of the outer peripheral surface of the cylindrical roll, and includes a member that regulates the layer thickness of the magnetic developer carried on the outer peripheral surface of the roll ,
Passing through the contact portion with the cylindrical roll of the member that regulates the layer thickness to a predetermined portion of the main body at least facing a portion between the predetermined magnetic poles at both ends in the longitudinal direction of the magnet member A plate-like auxiliary magnet is provided in a state where it reaches the downstream side in the roll rotation direction ,
In addition, the auxiliary magnet is formed by alternately arranging N poles and S poles on one side facing the end in the longitudinal direction of the member that regulates the layer thickness, while on the remaining part of the one side. developing apparatus is characterized by comprising placing a pole and different magnetic poles of the remaining portion of the one surface to another surface with placing either the N pole or S pole.

A container-shaped main body containing a magnetic developer and having an opening facing a development region where development is performed by the developer;
A cylindrical roll for transporting developer carrying, which is rotatably installed with a part of the outer peripheral surface exposed in the vicinity of the opening of the main body;
A magnet member that is fixedly installed over the axial direction of the hollow portion of the cylindrical roll, and has a plurality of magnetic poles for carrying the magnetic developer by a magnetic force on the outer peripheral surface of the roll,
It is fixedly installed over the axial direction of the outer peripheral surface of the cylindrical roll, and includes a blade that regulates the layer thickness of the magnetic developer carried on the outer peripheral surface of the roll,
Passing through a part facing the cylindrical roll at the tip of the blade to a predetermined part of the main body at least facing a part between the predetermined magnetic poles at both ends in the longitudinal direction of the magnet member, A plate-shaped auxiliary magnet is provided in a state of reaching the downstream part,
The auxiliary magnet is formed by alternately arranging N poles and S poles on one side facing the longitudinal end of the blade, while N poles or S poles on the remaining part of the one side. And a magnetic pole different from the magnetic pole of the remaining portion of the one surface on the other surface .

A semi-cylindrical plate-like magnet installed at a predetermined distance from the outer peripheral surface portion at a predetermined portion of the main body facing the outer peripheral surface portion of the cylindrical roll where both ends in the longitudinal direction of the magnet member are located. Comprising a member,
A part of the auxiliary magnet is formed in a portion of the magnetic member where a part of the inner side which is the central portion in the longitudinal direction of the magnet member is cut out, and one end of the auxiliary magnet is located on the inner periphery of the magnetic member. the developing device according to claim 1 or 2 is provided in a state of being continuous in the circumferential direction of the inner peripheral surface coincident with the surface.

A container-shaped main body containing a magnetic developer and having an opening facing a development region where development is performed by the developer;
A cylindrical roll for transporting developer carrying, which is rotatably installed with a part of the outer peripheral surface exposed in the vicinity of the opening of the main body;
A magnet member that is fixedly installed over the axial direction of the hollow portion of the cylindrical roll, and has a plurality of magnetic poles for carrying the magnetic developer by a magnetic force on the outer peripheral surface of the roll,
It is fixedly installed so that the portion on the tip end side is in contact with the axial direction of the outer peripheral surface of the cylindrical roll, and includes a member that regulates the layer thickness of the magnetic developer carried on the outer peripheral surface of the roll,
The auxiliary magnet is provided at least at a portion between the predetermined magnetic poles at both ends in the longitudinal direction of the magnet member, and a predetermined gap is provided along the outer peripheral surface of the cylindrical roll at a portion of the main body at least facing the auxiliary magnet. Provided with a gap forming protrusion for forming
In addition, the auxiliary magnet is opposed to the abutting portion of the member that regulates the layer thickness as viewed in the circumferential direction of the cylindrical roll with the one end portion on the downstream side in the rotation direction of the cylindrical roll. The magnet member is provided in a state where it reaches at least a position including at least a portion of the magnet member, and the longitudinal direction of the magnet member intersects with a plane perpendicular to the magnet member from the longitudinal end of the member that regulates the layer thickness. A developing device provided in a state of being approached from an end portion in the direction .

A container-shaped main body containing a magnetic developer and having an opening facing a development region where development is performed by the developer;
A cylindrical roll for transporting developer carrying, which is rotatably installed with a part of the outer peripheral surface exposed in the vicinity of the opening of the main body;
A magnet member that is fixedly installed over the axial direction of the hollow portion of the cylindrical roll, and has a plurality of magnetic poles for carrying the magnetic developer by a magnetic force on the outer peripheral surface of the roll,
It is fixedly installed over the axial direction of the outer peripheral surface of the cylindrical roll, and includes a blade that regulates the layer thickness of the magnetic developer carried on the outer peripheral surface of the roll,
And the auxiliary magnet has at least one end portion reaching a position including at least a portion of the magnet member facing the portion facing the cylindrical roll at the tip of the blade when viewed in the circumferential direction of the cylindrical roll. And a developing device , wherein the developing device is provided at a position intersecting with a plane perpendicular to the magnet member from an end portion in the longitudinal direction of the blade in a state of approaching from the end portion in the longitudinal direction of the magnet member. .

The developing device according to claim 4, wherein the gap forming protrusion is provided in a state of reaching at least an end portion in a longitudinal direction of a member or blade that regulates the layer thickness .

The gap forming protrusion is formed in a state where one end thereof is opposed to one magnetic pole of the magnet member and is continuous along the axial direction of the outer peripheral surface of the cylindrical roll. The developing device according to 1.