JP4021334B2

JP4021334B2 - Development device

Info

Publication number: JP4021334B2
Application number: JP2003024750A
Authority: JP
Inventors: 正之藤島; 雄二神山
Original assignee: Kyocera Mita Corp
Current assignee: Kyocera Document Solutions Inc
Priority date: 2003-01-31
Filing date: 2003-01-31
Publication date: 2007-12-12
Anticipated expiration: 2023-01-31
Also published as: JP2004233865A

Description

【０００１】
【発明の属する技術分野】
本発明は、プリンタ、複写機及びファクシミリなどの静電式画像形成機に備えられる、静電潜像をトナー像に現像するための現像装置、特に、磁性キャリアと非磁性トナーとからなる現像剤を使用する、画像形成機の現像装置に関する。
【０００２】
【従来の技術】
上記したような画像形成機に備えられている現像装置の一つの典型例は、磁性キャリアと非磁性トナーとからなる現像剤を収容するハウジングと、ハウジングに回転自在に支持された現像スリーブと、現像スリーブ内に配置された静止永久磁石と、ハウジング内に収容された現像剤を撹拌搬送する撹拌搬送手段とを備えている。ハウジング内には、無端状の現像剤循環搬送路が形成されている。この循環搬送路は、現像スリーブに平行に延在する第１の搬送路と、第１の搬送路と現像スリーブとの間をそれらに沿って延在する第２の搬送路と、第１及び第２の搬送路の両端領域間をそれぞれ連通する連通路とからなる。撹拌搬送手段は、第１の搬送路に配設された第１の回転螺旋羽根部材と、第２の搬送路に配設された第２の回転螺旋羽根部材とからなる。第２の搬送路に配設された第２の回転螺旋羽根部材は、現像スリーブに沿って延在する。循環搬送路内の現像剤は、第２の回転螺旋羽根部材によって現像スリーブの軸方向の一端部から他端部にわたって撹拌搬送されながら現像スリーブに供給されるので、現像スリーブの軸方向両端部から、現像剤を構成する磁性キャリア及び非磁性トナーが外部に漏れる、という問題が存在する。
【０００３】
このような現像剤の漏出を防止するため、現像スリーブの両端部における外周面にウレタンゴムなどからなる弾性シール部材を当接させるシール手段があるが、磨耗により弾性シール部材の一部が剥離してハウジング内に混入する、あるいは、現像スリーブの駆動トルクが増大する、などの問題を有している。そこで、一対の磁気シール体を、現像スリーブ又は帯電スリーブの長手方向両端部の外周面に対しそれぞれ隙間をおいて対向するようハウジングに配設してなる、非接触式シール手段が提案されている（例えば、特許文献１、特許文献２参照）。これらのシール手段において、磁気シール体の各々は、磁性板部材と、磁性板部材に一体に配設された永久磁石とからなる。磁気シール体の各々における磁性板部材は、現像スリーブ又は帯電スリーブの外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する円弧面と、現像スリーブ又は帯電スリーブの軸方向に対して直交する一側面とを備えている。磁気シール体の各々における永久磁石は、対応する磁性板部材の一側面に配設されると共に現像スリーブ又は帯電スリーブの外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する円弧面を備えている。
【０００４】
上記したシール手段によれば、磁気シール体の各々における永久磁石の磁力線は、現像スリーブ又は帯電スリーブの軸方向に隣接した、透磁率の高い磁性板部材に向かって集中的に流れるので、現像スリーブ又は帯電スリーブの軸方向両端部からの磁性キャリアもしくはトナーの漏出が防止される、とされている。
【０００５】
しかしながら、上記シール手段における磁気シール体の各々において、永久磁石の各々の円弧面は、対応する磁性板部材の円弧面に対し、同一面上に位置付けられているので、磁気シール体の各々における永久磁石の磁力線は、現像スリーブ又は帯電スリーブの軸方向に隣接した磁性板部材に向かって集中的に流れるものの、磁気シール体の該軸方向外方まで比較的広く広がるおそれがあり、したがってその拘束力は十分であるとはいえない。その結果、磁気シール体の各々における永久磁石の磁力が、上記磁力線に沿って形成されたキャリアチェーンの端部に作用する剥離力に打ち勝つことができず、現像スリーブ又は帯電スリーブの軸方向両端部からの磁性キャリアもしくはトナーの漏出を防止できないおそれがある。
【０００６】
【特許文献１】
特開平１１−１６７２８４号公報。
【特許文献２】
特開平２００１−３５０３１７号公。
【０００７】
【発明が解決しようとする課題】
本発明の目的は、非接触式シール手段である磁気シール体を使用して、現像スリーブの両端部からの磁性キャリアもしくはトナーの漏出を確実に防止することを可能にする、新規な現像装置を提供することである。
【０００８】
【課題を解決するための手段】
本発明によれば、
磁性キャリアと非磁性トナーとからなる現像剤を収容するハウジングに回転自在に支持された現像スリーブと、現像スリーブの軸方向両端部の外周面に対しそれぞれ隙間をおいて対向するようハウジングに配設された一対の磁気シール体とを備え、磁気シール体の各々は、磁性板部材と、磁性板部材に一体に配設された永久磁石とからなる現像装置において、
磁気シール体の各々における磁性板部材は、現像スリーブの外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する円弧面と、現像スリーブの軸方向に対して直交しかつ該軸方向に相互に対向する内側面とを備え、磁気シール体の各々における永久磁石は、対応する磁性板部材の該内側面に配設されると共に現像スリーブの外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する円弧面を備え、
永久磁石の各々の円弧面が、対応する磁性板部材の円弧面に対し、半径方向外方に一定の距離だけ後退して位置付けられて、永久磁石の各々の円弧面と、永久磁石の各々に対し該軸方向に隣接した磁性板部材の円弧面との間に、永久磁石の各々の円弧面が後退する段差部が形成される、
ことを特徴とする現像装置、が提供される。
磁気シール体の各々における磁性板部材は、磁性板部材の円弧面における周方向の両端からそれぞれ該半径方向外方に延びる周方向端面を備え、磁気シール体の各々における永久磁石は、永久磁石の円弧面における周方向の両端からそれぞれ該半径方向外方に延びる周方向端面を備え、永久磁石の各々の該周方向の一端面又は両端面が、対応する磁性板部材の該周方向の一端面又は両端面に対し、それぞれ実質的に周方向に一定の距離だけ後退して位置付けられて、永久磁石の各々の該周方向の一端面又は両端面と、永久磁石の各々に対し該軸方向に隣接した磁性板部材の該周方向の一端面又は両端面との間に、永久磁石の各々の該周方向の一端面又は両端面が後退する段差部が形成される、ことが好ましい。
磁性板部材の各々の該内側面における円弧面の内側部には、円弧面に沿って一定の幅で延在しかつ該内側面から直角に一定の高さ延び出す位置決め壁が形成され、対応する永久磁石の円弧面は、位置決め壁の、対応する内側面に当接されることにより位置決めされる、ことが好ましい。
【０００９】
【発明の実施の形態】
以下、本発明に従って構成された現像装置の好適な実施の形態を、添付図面を参照して更に詳細に説明する。
【００１０】
図１及び図２には、本発明に従って構成された現像装置の好適実施形態が図示されている。全体を番号２で示す図示の現像装置は、現像剤、実施形態においては磁性キャリアと非磁性トナーとからなる２成分現像剤を収容することができるハウジング４を備えている。適宜の合成樹脂から成形することができるハウジング４は、底壁６と、側壁８及び１０と、天井壁１２と、後端壁１４とを有している。ハウジング４の前端（図１において左端）には、開口部１５が形成されている。底壁６の前後方向（図１において左右方向）のほぼ中間部には、実質的に鉛直上方に延びる隔壁１６が形成されており、隔壁１６の両側には、それぞれ直線状径路である第１の搬送路１８及び第２の搬送路２０が規定されている。隔壁１６の両端は、ハウジング４の両側壁８及び１０の内面からそれぞれ離隔されており、隔壁１６の長手方向両端と側壁８及び１０の内面との間には間隙が存在する。
【００１１】
隔壁１６の一端と側壁８との間の間隙は、第１の搬送路１８及び第２の搬送路２０の各々の一端領域を連通する連通路２２を規定し、また、隔壁１６の他端と側壁１０との間の間隙は、第１の搬送路１８及び第２の搬送路２０の各々の他端領域を連通する連通路２４を規定する。従って、相互に平行に延在する第１の搬送路１８及び第２の搬送路２０は、両端領域において連通路２２及び２４を介して相互に連通されており、全体として現像剤の、無端状の循環径路が規定されている。
【００１２】
上述した循環径路を規定する第１の搬送路１８には、第１の搬送路１８に沿って延在する第１の回転螺旋羽根部材２６と、第２の搬送路２０に沿って延在する第２の回転螺旋羽根部材２８とがそれぞれ配設されている。第１の回転螺旋羽根部材２６はハウジング４の両側壁８及び１０間に回転自在に装着され、第１の搬送路１８に沿って直線状に延びている。第２の回転螺旋羽根部材２８はハウジング４の両側壁８及び１０間に回転自在に装着され、第２の搬送路２０に沿って直線状に延びている。ハウジング８の前端部における側壁８及び１０間には現像スリーブ３０が回転自在に配設されている。現像スリーブ３０内には、複数の図示しない磁極を有する静止永久磁石３２が配置されている。
【００１３】
第１の回転螺旋羽根部材２６の中心軸部の一端部及び第２の回転螺旋羽根部材２８の中心軸部の一端部は、それぞれ側壁１０を貫通して突出させられており、これらの突出端には、それぞれ図示しない被駆動歯車が固定されている。また、回転可能に保持された現像スリーブ３０の端部は細径化されて側壁１０を貫通して突出させられており、この突出端には図示しない被駆動歯車が固定されている。側壁１０の外側には図示しない他の被駆動歯車が回転自在に支持されている。現像装置２が図示しない画像形成機における画像形成機本体の所定位置に装着されると、これらの被駆動歯車は、画像形成機に設けられた図示しない伝動歯車に噛み合わされ、電動モータでよい駆動源（不図示）に駆動連結されて回転駆動されるよう構成されている。第１及び第２の回転螺旋羽根部材２６及び２８と現像スリーブ３０は、それぞれ図１で示されている矢印方向に回転駆動させられる。ハウジング４内に収容された現像剤は、第１及び第２の搬送路１８及び２０と、連通路２２及び２４とからなる循環路に沿って、図２に示されている矢印方向に撹拌搬送される。なお、現像装置２が図示しない画像形成機本体の所定位置に装着されると、現像スリーブ３０の外周面は、画像形成機本体に配設された感光体ドラム１の外周面に対し、所定の隙間をおいて対向するよう位置付けられる。
【００１４】
ハウジング４の上記天井壁１２には、現像剤の層厚規制ブレード３４が、天井壁１２から下方に延び出すよう取り付けられている。層厚規制ブレード３４の下端である先端面は、現像スリーブ３０の周表面に対し所定の隙間をおいて位置付けられている。
【００１５】
ハウジング４の両側部には、一対の磁気シール体１００が、現像スリーブ３０の軸方向両端部の外周面に対しそれぞれ隙間をおいて対向するよう配設されている。磁気シール体１００の各々は、各々間の中央を通り、現像スリーブ３０の軸線に直交する仮想面を挟んで相互に対称形状をなし、したがって相互に実質的に同じ構成を有しているので、以下、片方の磁気シール体１００の構成について説明する。
【００１６】
図３〜図６を参照して、磁気シール体１００は、磁性板部材４０と、磁性板部材４０に一体に配設された板状の永久磁石５０とから構成されている。磁気シール体１００の磁性板部材４０は、円弧状部４２と、円弧状部４２の一端部から、円弧状部４２の軸心に対し半径方向外方に延び出す直線状部４４とを備えている。円弧状部４２は、半径方向内側面である円弧面４２ａと、円弧面４２ａと同心の半径方向外側面である円弧面４２ｂと、周方向の一端において円弧状部４２の軸心に対し半径方向外方に直線状に延びる周方向の一端面４２ｃとを備えている。直線状部４４は、円弧状部４２の周方向の他端から円弧状部４２の軸心に対し半径方向外方に直線状に延びる一側面４４ａ（換言すれば、円弧状部４２の周方向の他端において円弧状部４２の軸心に対し半径方向外方に直線状に延びる周方向の他端面４４ａ）と、一側面４４ａに対し平行に延びる他側面４４ｂと、一側面４４ａ及び他側面４４ｂの各々に対し直角に、一側面４４ａ及び他側面４４ｂの各々の先端間を延在する先端面４４ｃとを備えている。直線状部４４の一側面４４ａの基端は円弧状部４２の円弧面４２ａの他端に連続し、また他側面４４ｂの基端は円弧状部４２の円弧面４２ｂの他端に連続している。
【００１７】
磁性板部材４０は、全体として、同じ厚さＴ及び幅Ｗを有し、かつ、片面４０Ａと、他面４０Ｂとを有している（したがって、円弧状部４２及び直線状部４４は、それぞれ相互に同じ厚さＴ及び幅Ｗを有し、かつ、片面４０Ａと、他面４０Ｂとを有している）。この実施形態において、磁性板部材４０の円弧状部４２の半径方向内側面である円弧面４２ａは、ほぼ半円形状をなし、その半径は、現像スリーブ３０の外周面の半径よりも若干大きく規定されている。なお、一対の磁気シール体１００が、ハウジング４の上記天井壁１２に配設された状態で、磁性板部材４０の各々の片面４０Ａは、現像スリーブ３０の軸方向に相互に対向する内側面を構成する。
【００１８】
磁気シール体１００の永久磁石５０は、円弧状部５２と、円弧状部５２の一端部から、円弧状部５２の軸心に対し半径方向外方に延び出す直線状部５４とを備えている。円弧状部５２は、半径方向内側面である円弧面５２ａと、円弧面５２ａと同心の半径方向外側面である円弧面５２ｂと、周方向の一端において円弧状部５２の軸心に対し半径方向外方に直線状に延びる周方向の一端面５２ｃとを備えている。直線状部５４は、円弧状部５２の周方向の他端から円弧状部５２の軸心に対し半径方向外方に直線状に延びる一側面５４ａ（換言すれば、円弧状部５２の周方向の他端において円弧状部５２の軸心に対し半径方向外方に直線状に延びる周方向の他端面５４ａ）と、一側面５４ａに対し平行に延びる他側面５４ｂと、一側面５４ａ及び他側面５４ｂの各々に対し直角に、一側面５４ａ及び他側面５４ｂの各々の先端間を延在する先端面５４ｃとを備えている。直線状部５４の一側面５４ａの基端は円弧状部５２の円弧面５２ａの他端に連続し、また他側面５４ｂの基端は円弧状部５２の円弧面５２ｂの他端に連続している。
【００１９】
永久磁石５０は、全体として、同じ厚さｔ及び幅ｗを有し、かつ、片面５０Ａと、他面５０Ｂとを有している（したがって、円弧状部５２及び直線状部５４は、それぞれ相互に同じ厚さｔ及び幅ｗを有し、かつ、片面５０Ａと、他面５０Ｂとを有している）。永久磁石５０の幅ｗは、磁性板部材４０の幅Ｗよりも狭く形成され、円弧面５２ａの半径は、磁性板部材４０の円弧面４２ａの半径よりも若干大きく規定され、また、円弧面５２ｂの半径は、磁性板部材４０の円弧面４２ｂの半径よりも小さく規定されている。永久磁石５０の直線状部５４の長さは、磁性板部材４０の直線状部４４の長さよりも短く規定されている。
【００２０】
上述したように構成された永久磁石５０は、磁性板部材４０の片面４０Ａに一体に配設される。実施形態において、永久磁石５０の他面５０Ｂが、磁性板部材４０の片面４０Ａに重合させられ、適宜の接着剤により貼着される。この装着状態において、永久磁石５０の円弧状部５２の半径方向内側面である円弧面５２ａは、磁性板部材４０の円弧状部４２の半径方向内側面である円弧面４２ａと同心に位置付けられる。永久磁石５０の円弧面５２ａは、磁性板部材４０の円弧面４２ａに対し、半径方向外方に一定の距離ｄだけ後退して位置付けられる。永久磁石５０の周方向の一端面５２ｃは、磁性板部材４０の周方向の一端面４２ｃに対し、それぞれ実質的に周方向に（図３において右方に）一定の距離ｄだけ後退して位置付けられる。永久磁石５０の直線状部５４における一側面５４ａは、磁性板部材４０の一側面４４ａに対し、実質的に周方向に（図３において右方に）一定の距離ｄだけ後退して位置付けられ、他側面５４ｂは、磁性板部材４０の他側面４４ｂに対し、実質的に逆の周方向に（図３において左方に）適宜の一定の距離だけ後退して位置付けられ、また、先端面５４ｃは、磁性板部材４０の直線状部４４の先端面４４ｃに対し、永久磁石５０の円弧面５２ａの軸心に対する半径方向内方に比較的長い適宜の距離だけ後退して位置付けられ、永久磁石５０の半径方向外側面である円弧面５２ｂは、磁性板部材４０の半径方向外側面である円弧面４２ｂに対し、半径方向内方に適宜の一定の距離だけ後退して位置付けられる。
【００２１】
磁性板部材４０の片面４０Ａにおける、直線状部４４の他側面４４ｂの内側部及び円弧面４２ｂの内側部には、他側面４４ｂ及び円弧面４２ｂに沿って一定の幅で延在する位置決め壁４０Ｃが形成されている。位置決め壁４０Ｃは、片面４０Ａから直角に一定の高さ延び出すよう形成されている。永久磁石５０の直線状部５４の他側面５４ｂ及び円弧面５２ｂは、位置決め壁４０Ｃの、対応する内側面に当接されることにより位置決めされる。なお、位置決め壁４０Ｃを形成しない他の実施形態もある。
【００２２】
磁気シール体１００の磁性板部材４０の片面４０Ａに貼着された永久磁石５０の磁極面は、実施形態においては、片面５０Ａの全面と他面５０Ｂの全面との間に形成され、片面５０ＡがＮ極、他面５０ＢがＳ極となるよう形成（着磁）されているが、片面５０ＡがＳ極、他面５０ＢがＮ極であってもよい。また、永久磁石５０の磁極面を、円弧面５２ａ及び一側面５４ａと、円弧面５２ｂ及び他側面５４ｂとの間に形成する他の実施形態（円弧面５２ａ及び一側面５４ａをＮ極（又はＳ極）とした場合、円弧面５２ｂ及び他側面５４ｂがＳ極（又はＮ極）とされる）、更にはまた、永久磁石５０の磁極面を、円弧面５２ａ及び一側面５４ａからなる細長い面の短辺に沿って、交互に異極となるよう形成する更に他の実施形態もある。
【００２３】
図１〜図３を参照して、以上のように構成された磁気シール体１００の各々は、現像スリーブ３０の軸方向両端部の外周面に対しそれぞれ隙間をおいて対向するようハウジング４の両側部に配設される。磁気シール体１００の各々の、ハウジング４に対する装着は、例えば、天井壁１２から垂下する一対の支持フランジに、磁性板部材４０における円弧状部４２の円弧面４２ｂと直線状部４４の他側面４４ｂとを接着することによりにより行うことができる。
【００２４】
磁気シール体１００の各々がハウジング４の両側部に配設された状態において、磁気シール体１００の各々における磁性板部材４０の円弧面４２ａは、現像スリーブ３０の外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在し、磁性板部材４０の片面４０Ａは、現像スリーブ３０の軸方向に対して直交しかつ該軸方向に相互に対向する内側面を構成する。磁気シール体１００の各々における永久磁石５０は、対応する磁性板部材４０の片面４０Ａ（該内側面）に配設される。永久磁石５０の各々の円弧面５２ａは、現像スリーブ３０の外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する。先に述べたように、永久磁石５０の各々の円弧面５２ａは、対応する磁性板部材４０の円弧面４２ａに対し、半径方向外方に一定の距離ｄだけ後退して位置付けられる。永久磁石５０の周方向の一端面５２ｃ及び他端面５４ａは、磁性板部材４０の周方向の一端面４２ｃ及び他端面４４ａに対し、それぞれ実質的に周方向に（図３において右方に）一定の距離ｄだけ後退して位置付けられる。
【００２５】
上記現像装置２において、図示しない上記駆動源が付勢されると、現像スリーブ３０が図１において反時計方向に回転させられる。現像スリーブ３０はその周表面上に現像剤を保持し、この現像剤を感光体ドラム１に対向する現像域を通して搬送する。層厚規制ブレード３４は、現像スリーブ３０の周表面に保持されて現像域に搬送される現像剤の層厚さを規制する。現像域においては現像剤に含まれるトナーが、感光体ドラム１の周表面に形成された現像すべき静電潜像に適用され、静電潜像がトナー像に現像される。
【００２６】
第１及び第２の回転螺旋羽根部材２６及び２８と現像スリーブ３０は、それぞれ図１で示されている矢印方向に回転駆動させられる。ハウジング４内に収容された現像剤は、第１及び第２の回転螺旋羽根部材２６及び２８により、第１及び第２の搬送路１８及び２０と、連通路２２及び２４とからなる循環路に沿って、図２に示されている矢印方向に撹拌搬送される。
【００２７】
第２の搬送路２０内の現像剤は、第２の回転螺旋羽根部材２８によって現像スリーブ３０の軸方向の一端部から他端部にわたって（図２において左端部から右端部にわたって）撹拌搬送されながら供給されるので、現像スリーブ３９の軸方向両端部から現像剤を構成する磁性キャリア及び非磁性トナーが外部に漏れるおそれがあるが、本発明による上記現像装置２によれば、このような問題を解消することができる。
【００２８】
すなわち、本発明による上記現像装置２においては、磁気シール体１００の各々における磁性板部材４０は、現像スリーブ３０の外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する円弧面４２ａと、現像スリーブ３０の軸方向に対して直交しかつ該軸方向に相互に対向する内側面４０Ａとを備えている。磁気シール体１００の各々における永久磁石５０は、対応する磁性板部材４０の該内側面４０Ａに配設されると共に現像スリーブ３０の外周面に対し実質的に一定の隙間をおいて該外周面に沿って延在する円弧面５２ａを備えている。そして、永久磁石５０の各々の円弧面５２ａは、対応する磁性板部材４０の円弧面４２ａに対し、半径方向外方に一定の距離ｄだけ後退して位置付けられる。永久磁石５０の各々の該周方向の一端面５２ｃ及び他端面５４ａは、対応する磁性板部材４０の該周方向の一端面４２ｃ及び他端面４４ａに対し、それぞれ実質的に周方向に一定の距離ｄだけ後退して位置付けられる。
【００２９】
つまり、磁気シール体１００の各々において、磁性板部材４０の、現像スリーブ３０に対向する面である円弧面４２ａと、永久磁石５０の、現像スリーブ３０に対向する面である円弧面５２ａとの間、及び、磁性板部材４０における円弧面４２ａの周方向両端面４２ｃ及び４４ａと、永久磁石５０における円弧面５２ａの周方向両端面５２ｃ及び５４ａとの間には、それぞれ、現像スリーブ３０の軸方向内側に存在する永久磁石５０側が後退するような段差が形成されているので、磁気シール体１００の各々における永久磁石５０の磁力線は、現像スリーブ３０の軸方向に隣接した磁性板部材４０の段差部に向かって特に集中的に流れる。その結果、現像スリーブ３０の軸方向両端部から外方に漏出しようとする磁性キャリアは、先ず永久磁石５０により効果的に捕捉される。そして、永久磁石５０及び磁性板部材４０の両者の協働により、上記段差部において、特に集中的にキャリアチェーンが形成されるので、該キャリアチェーンの端部まで磁力による拘束力が十分に作用し、現像スリーブ３０ブの軸方向両端部からの磁性キャリアもしくはトナーの漏出を効果的に防止する。また、上記段差部において、特に集中的にキャリアチェーンが形成されることに起因して、該キャリアチェーンが効果的にシール機能を発揮するので、トナーの漏出を効果的に防止する。
【００３０】
先に述べたように、磁気シール体１００の各々における永久磁石５０の磁力線が、現像スリーブ３０の軸方向に隣接した磁性板部材４０の段差部に向かって特に集中的に流れることに起因して、永久磁石５０の磁力線が、磁気シール体１００の該軸方向外方まで比較的広く広がることはなく、したがって、この面においても、現像スリーブ３０の軸方向両端部からの磁性キャリアもしくはトナーの漏出を効果的に防止することが可能になる。
【００３１】
永久磁石５０の各々の円弧面５２ａが、対応する磁性板部材４０の円弧面４２ａに対し、半径方向外方に後退させられる該一定の距離ｄ、及び永久磁石５０の各々の該周方向の一端面５２ｃ及び他端面５２ｄが、対応する磁性板部材４０の該周方向の一端面４２ｃ及び他端面４２ｄに対し、それぞれ実質的に周方向に後退させられる該一定の距離ｄは、０．４ｍｍ〜１．０ｍｍに規定される、ことが好ましい。本発明者による実験の結果、該一定の距離ｄを、０．４ｍｍ〜１．０ｍｍに規定した場合には、現像スリーブ３０の両端部から外部へのトナーの漏出は認められなかった。これに対し、上記距離ｄを、０ｍｍ〜０．４ｍｍ未満とした場合、及び上記距離ｄを、１．０ｍｍを越えた距離に設定した場合には、いずれも現像スリーブ３０の両端部から外部へのトナーの漏出が認められた。
【００３２】
永久磁石５０の各々における磁極面の磁力は、０．０３ｍＴ（ミリテスラ）〜０．０５ｍＴ（ミリテスラ）である、ことが好ましい。本発明者による実験の結果、上記磁力を０．０３ｍＴ〜０．０５ｍＴに設定した場合には、キャリアチェーンが効果的にシール機能を果たし、現像スリーブ３０の両端部から外部へのキャリア及びトナーの漏出は認められなかった。これに対し、磁力を０．０３ｍＴ未満とした場合には、磁力が弱すぎてキャリアチェーンの端部が剥離し、シール機能を果たすことができなかった。また、磁力を０．０５ｍＴを越えた値に設定した場合には、キャリアを取り込みすぎて、キャリアチェーンが現像スリーブ３８と接触することにより、キャリアが溢れ出して、ハウジング４の端部から溢れ出す現象が発生した。
【００３３】
上記実施形態における実施例は次のとおりである。
Ｔ＝１．０ｍｍ、Ｗ＝４．０ｍｍ、ｔ＝１．０ｍｍ、ｗ＝３．５ｍｍである。また、現像スリーブ３０の外周面と磁性板部材４０の円弧面４２ａとの隙間は、０．５ｍｍである。
【００３４】
本発明による上記実施形態において、永久磁石５０は、磁性板部材４０に対しほぼ相似形をなしており、磁性板部材４０の片面４０Ａにおける長手方向のほぼ全域にわたって貼着されているが、特に磁性キャリアもしくはトナーが漏出し易い領域に貼着する、他の実施形態もある。例えば、図７に示されているように、永久磁石５０（１）を、磁性板部材４０の円弧状部４２の一端部領域及び直線状部４４の基端部領域に跨って貼着する他の第１の実施形態、永久磁石５０（２）を、磁性板部材４０の円弧状部４２の他端部領域に貼着する他の第２の実施形態、及び、永久磁石５０（３）を、磁性板部材４０の円弧状部４２の中間部領域に貼着する他の第３の実施形態、これらを適宜に組み合わせた更に他の実施形態、などを挙げることができる。これらの他の実施形態における基本的構成は、先の実施形態におけるのと実質的に同じである。
【００３５】
本発明による現像装置の上記実施形態においては、現像スリーブ３０内に配設された静止永久磁石３２の磁気作用及びトナーへの帯電作用などにより、現像スリーブ３０の外周面には磁性キャリア及び非磁性トナーが保持されて現像域まで搬送され、トナーのみが感光体ドラム１の表面に形成された潜像に供給されるよう構成されている。しかしながら、本発明は上記実施形態に限定されるものではなく、例えば、いわゆるハイブリッド型現像装置にも適用可能である。ハイブリッド型現像装置は、磁性キャリアと非磁性トナーとからなる現像剤を磁気保持しながら帯電させる磁気ローラと、磁気ローラの磁気ブラシと搬送バイアスを利用して磁気ローラからトナーを移送して表面にトナーのみの薄層を形成する現像スリーブと、現像スリーブと感光体ドラムの現像領域に現像バイアスを印加して感光体ドラムの表面の潜像にトナーを供給して現像を行うよう構成されている。本発明はこのような現像装置においても上記した作用効果により、現像スリーブの両端部から外部へのキャリアもしくはトナーの漏出を効果的に防止することができる。
【００３６】
【発明の効果】
本発明による現像装置によれば、非接触式シール手段である磁気シール体を使用して、現像スリーブの両端部からの磁性キャリアもしくはトナーの漏出を確実に防止することを可能にする。
【図面の簡単な説明】
【図１】本発明に従って構成された現像装置の好適実施形態を示す断面概略図。
【図２】図１に示す現像装置の平面概略図であって、天井壁を省略して示す平面概略図。
【図３】図１及び図２に示す現像装置に備えられている磁気シール体の一方の実施形態を、図２においてＡ矢視方向に見た正面図。
【図４】図３に示されている磁気シール体の斜視図。
【図５】図３のＢ−Ｂ矢視断面拡大図。
【図６】図３のＣ−Ｃ矢視断面拡大図。
【図７】磁気シール体の他の実施形態を示す正面図。
【符号の説明】
２現像装置
４ハウジング
３０現像スリーブ
４０磁性板部材
４０Ａ片面（内側面）
４２円弧状部
４２ａ円弧面
４２ｃ一端面
４２ｄ他端面
４４直線状部
５０永久磁石
５２円弧状部
５２ａ円弧面
５２ｃ一端面
５２ｄ他端面
５４直線状部
１００磁気シール体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device for developing an electrostatic latent image into a toner image provided in an electrostatic image forming machine such as a printer, a copying machine, and a facsimile, and in particular, a developer comprising a magnetic carrier and a non-magnetic toner. The present invention relates to a developing device for an image forming machine.
[0002]
[Prior art]
One typical example of the developing device provided in the image forming machine as described above includes a housing that stores a developer composed of a magnetic carrier and a non-magnetic toner, a developing sleeve that is rotatably supported by the housing, A stationary permanent magnet disposed in the developing sleeve and an agitating / conveying means for agitating and conveying the developer accommodated in the housing are provided. An endless developer circulation conveyance path is formed in the housing. The circulation conveyance path includes a first conveyance path extending parallel to the developing sleeve, a second conveyance path extending between the first conveyance path and the developing sleeve, It consists of the communicating path which connects between the both ends area | regions of a 2nd conveyance path, respectively. The stirring and conveying means includes a first rotating spiral blade member disposed in the first conveying path and a second rotating spiral blade member disposed in the second conveying path. The second rotating spiral blade member disposed in the second transport path extends along the developing sleeve. The developer in the circulation conveyance path is supplied to the developing sleeve while being agitated and conveyed from one end portion to the other end portion in the axial direction of the developing sleeve by the second rotating spiral blade member. There is a problem that the magnetic carrier and the non-magnetic toner constituting the developer leak to the outside.
[0003]
In order to prevent such leakage of the developer, there is a sealing means in which an elastic seal member made of urethane rubber or the like is brought into contact with the outer peripheral surface at both end portions of the developing sleeve. However, a part of the elastic seal member is peeled off due to wear. In the housing, or the driving torque of the developing sleeve increases. In view of this, a non-contact type sealing means has been proposed in which a pair of magnetic seal members are disposed in a housing so as to face each other with a gap from the outer peripheral surfaces of both ends in the longitudinal direction of the developing sleeve or charging sleeve. (For example, refer to Patent Document 1 and Patent Document 2). In these sealing means, each of the magnetic seal bodies is composed of a magnetic plate member and a permanent magnet disposed integrally with the magnetic plate member. The magnetic plate member in each of the magnetic seal bodies includes an arc surface extending along the outer peripheral surface with a substantially constant gap with respect to the outer peripheral surface of the developing sleeve or the charging sleeve, and an axis of the developing sleeve or the charging sleeve. And one side surface orthogonal to the direction. The permanent magnet in each of the magnetic seal bodies is disposed on one side surface of the corresponding magnetic plate member and extends along the outer peripheral surface with a substantially constant gap with respect to the outer peripheral surface of the developing sleeve or the charging sleeve. It has an existing arc surface.
[0004]
According to the sealing means described above, the magnetic lines of force of the permanent magnet in each of the magnetic seal bodies intensively flow toward the magnetic plate member having a high magnetic permeability adjacent to the axial direction of the developing sleeve or the charging sleeve. Alternatively, leakage of the magnetic carrier or toner from both ends in the axial direction of the charging sleeve is prevented.
[0005]
However, in each of the magnetic seal bodies in the sealing means, each arc surface of the permanent magnet is positioned on the same plane with respect to the arc surface of the corresponding magnetic plate member. Although the magnetic field lines of the magnet flow intensively toward the magnetic plate member adjacent to the developing sleeve or the charging sleeve in the axial direction, there is a possibility that the magnetic force spreads relatively widely to the outside of the magnetic seal body in the axial direction. Is not enough. As a result, the magnetic force of the permanent magnet in each of the magnetic seal bodies cannot overcome the peeling force acting on the end of the carrier chain formed along the magnetic field lines, and both end portions in the axial direction of the developing sleeve or the charging sleeve There is a possibility that leakage of the magnetic carrier or toner from the toner cannot be prevented.
[0006]
[Patent Document 1]
JP-A-11-167284.
[Patent Document 2]
Japanese Laid-Open Patent Publication No. 2001-350317.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a novel developing device that can reliably prevent leakage of a magnetic carrier or toner from both ends of a developing sleeve using a magnetic seal body that is a non-contact type sealing means. Is to provide.
[0008]
[Means for Solving the Problems]
According to the present invention,
A developing sleeve rotatably supported by a housing containing a developer composed of a magnetic carrier and a non-magnetic toner is disposed in the housing so as to face the outer peripheral surfaces of both end portions in the axial direction of the developing sleeve with a gap therebetween. A pair of magnetic seal bodies, each of the magnetic seal bodies in a developing device comprising a magnetic plate member and a permanent magnet integrally disposed on the magnetic plate member,
The magnetic plate member in each of the magnetic seal bodies is orthogonal to the arc surface extending along the outer circumferential surface with a substantially constant gap from the outer circumferential surface of the developing sleeve and the axial direction of the developing sleeve. And permanent magnets in each of the magnetic seal bodies are disposed on the inner surface of the corresponding magnetic plate member and substantially with respect to the outer peripheral surface of the developing sleeve. An arc surface extending along the outer circumferential surface with a certain gap,
Each arc surface of the permanent magnetBut, Set back by a certain distance radially outward with respect to the arc surface of the corresponding magnetic plate memberThus, a step portion in which each arc surface of the permanent magnet recedes is formed between each arc surface of the permanent magnet and the arc surface of the magnetic plate member adjacent to the permanent magnet in the axial direction. ,
A developing device is provided.
The magnetic plate member in each of the magnetic seal bodies has a circumferential end surface extending outward in the radial direction from both ends in the circumferential direction of the arc surface of the magnetic plate member, and the permanent magnet in each of the magnetic seal bodies is a permanent magnet One end face or both end faces in the circumferential direction of each of the permanent magnets, each having a circumferential end face extending radially outward from both ends in the circumferential direction on the arc surfaceBut, Each of the corresponding magnetic plate members is positioned so as to recede by a certain distance in the circumferential direction with respect to one end surface or both end surfaces in the circumferential direction.Between the one end surface or both end surfaces in the circumferential direction of each of the permanent magnets and the one end surface or both end surfaces in the circumferential direction of the magnetic plate member adjacent to each of the permanent magnets in the axial direction. It is preferable that a step portion in which one end surface or both end surfaces in the circumferential direction of each of these are retreated is formed.
On the inner side of the arc surface on each inner surface of each magnetic plate member, a positioning wall extending along the arc surface with a certain width and extending at a certain height perpendicularly from the inner surface is formed. The circular arc surface of the permanent magnet is preferably positioned by abutting against the corresponding inner surface of the positioning wall.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a developing device configured according to the present invention will be described in more detail with reference to the accompanying drawings.
[0010]
1 and 2 illustrate a preferred embodiment of a developing device constructed in accordance with the present invention. The illustrated developing apparatus generally indicated by reference numeral 2 includes a housing 4 that can store a developer, in the embodiment, a two-component developer composed of a magnetic carrier and a non-magnetic toner. The housing 4 that can be molded from an appropriate synthetic resin has a bottom wall 6, side walls 8 and 10, a ceiling wall 12, and a rear end wall 14. An opening 15 is formed at the front end (left end in FIG. 1) of the housing 4. A partition wall 16 extending substantially vertically upward is formed at a substantially middle portion of the bottom wall 6 in the front-rear direction (left-right direction in FIG. 1), and a first straight path is formed on both sides of the partition wall 16. The transport path 18 and the second transport path 20 are defined. Both ends of the partition wall 16 are separated from the inner surfaces of both side walls 8 and 10 of the housing 4, and a gap exists between both longitudinal ends of the partition wall 16 and the inner surfaces of the side walls 8 and 10.
[0011]
The gap between one end of the partition wall 16 and the side wall 8 defines a communication path 22 that communicates with one end region of each of the first transport path 18 and the second transport path 20. The gap between the side wall 10 defines a communication path 24 that communicates the other end region of each of the first transport path 18 and the second transport path 20. Therefore, the first conveyance path 18 and the second conveyance path 20 extending in parallel with each other are communicated with each other via the communication paths 22 and 24 in both end regions, and the developer is endless in shape as a whole. The circulation path is defined.
[0012]
The first conveyance path 18 that defines the circulation path described above extends along the first rotation spiral blade member 26 that extends along the first conveyance path 18 and the second conveyance path 20. A second rotating spiral blade member 28 is provided. The first rotating spiral blade member 26 is rotatably mounted between the side walls 8 and 10 of the housing 4 and extends linearly along the first conveying path 18. The second rotating spiral blade member 28 is rotatably mounted between the side walls 8 and 10 of the housing 4 and extends linearly along the second conveyance path 20. A developing sleeve 30 is rotatably disposed between the side walls 8 and 10 at the front end portion of the housing 8. In the developing sleeve 30, a plurality of stationary permanent magnets 32 having magnetic poles (not shown) are arranged.
[0013]
One end of the central shaft portion of the first rotating spiral blade member 26 and one end portion of the central shaft portion of the second rotating spiral blade member 28 are projected through the side wall 10, respectively. A driven gear (not shown) is fixed to each. The end portion of the developing sleeve 30 that is rotatably held is reduced in diameter and protrudes through the side wall 10, and a driven gear (not shown) is fixed to the protruding end. Other driven gears (not shown) are rotatably supported outside the side wall 10. When the developing device 2 is mounted at a predetermined position of the main body of the image forming machine in an image forming machine (not shown), these driven gears are meshed with transmission gears (not shown) provided in the image forming machine and may be driven by an electric motor. It is configured to be rotationally driven by being connected to a source (not shown). The first and second rotating spiral blade members 26 and 28 and the developing sleeve 30 are driven to rotate in the directions of the arrows shown in FIG. The developer accommodated in the housing 4 is stirred and conveyed in the direction of the arrow shown in FIG. 2 along the circulation path including the first and second conveyance paths 18 and 20 and the communication paths 22 and 24. Is done. When the developing device 2 is mounted at a predetermined position of the image forming machine main body (not shown), the outer peripheral surface of the developing sleeve 30 is predetermined with respect to the outer peripheral surface of the photosensitive drum 1 disposed in the image forming machine main body. Positioned to face each other with a gap.
[0014]
A developer layer thickness regulating blade 34 is attached to the ceiling wall 12 of the housing 4 so as to extend downward from the ceiling wall 12. The leading end surface, which is the lower end of the layer thickness regulating blade 34, is positioned with a predetermined gap with respect to the peripheral surface of the developing sleeve 30.
[0015]
On both sides of the housing 4, a pair of magnetic seal bodies 100 are disposed so as to face the outer peripheral surfaces of both ends in the axial direction of the developing sleeve 30 with a gap therebetween. Since each of the magnetic seal bodies 100 has a symmetric shape with respect to each other across a virtual plane orthogonal to the axis of the developing sleeve 30 passing through the center between the magnetic seal bodies 100, the magnetic seal bodies 100 have substantially the same configuration. Hereinafter, the configuration of one magnetic seal body 100 will be described.
[0016]
With reference to FIGS. 3 to 6, the magnetic seal body 100 includes a magnetic plate member 40 and a plate-like permanent magnet 50 disposed integrally with the magnetic plate member 40. The magnetic plate member 40 of the magnetic seal body 100 includes an arc-shaped portion 42 and a linear portion 44 that extends radially outward from one end of the arc-shaped portion 42 with respect to the axis of the arc-shaped portion 42. Yes. The arc-shaped portion 42 includes a circular arc surface 42a that is a radially inner side surface, a circular arc surface 42b that is a radially outer surface concentric with the circular arc surface 42a, and a radial direction with respect to the axial center of the arc-shaped portion 42 at one circumferential end. And a circumferential one end face 42c extending linearly outward. The linear portion 44 has a side surface 44a that extends linearly outward from the other end in the circumferential direction of the arc-shaped portion 42 with respect to the axial center of the arc-shaped portion 42.(In other words, at the other end in the circumferential direction of the arc-shaped portion 42, the other end surface 44a in the circumferential direction extends linearly outward in the radial direction with respect to the axis of the arc-shaped portion 42).A side surface 44b extending parallel to the side surface 44a, and a tip surface 44c extending between the tips of the side surface 44a and the other side surface 44b at right angles to the side surface 44a and the other side surface 44b. I have. The base end of one side surface 44a of the linear portion 44 is continuous with the other end of the arc surface 42a of the arc-shaped portion 42, and the base end of the other side surface 44b is continuous with the other end of the arc surface 42b of the arc-shaped portion 42. Yes.
[0017]
The magnetic plate member 40 as a whole has the same thickness T and width W, and has one side 40A and the other side 40B (therefore, the arcuate part 42 and the linear part 44 are respectively They have the same thickness T and width W, and one side 40A and the other side 40B). In this embodiment, the arc surface 42 a that is the radially inner side surface of the arc-shaped portion 42 of the magnetic plate member 40 has a substantially semicircular shape, and the radius is defined to be slightly larger than the radius of the outer peripheral surface of the developing sleeve 30. Has been. In addition, in a state where the pair of magnetic seal bodies 100 are disposed on the ceiling wall 12 of the housing 4, each one surface 40 </ b> A of the magnetic plate member 40 has an inner surface facing each other in the axial direction of the developing sleeve 30. Constitute.
[0018]
The permanent magnet 50 of the magnetic seal body 100 includes an arc-shaped portion 52 and a linear portion 54 that extends radially outward from one end of the arc-shaped portion 52 with respect to the axis of the arc-shaped portion 52. . The arc-shaped portion 52 includes a circular arc surface 52a which is a radially inner side surface, a circular arc surface 52b which is a radially outer surface concentric with the circular arc surface 52a, and a radial direction with respect to the axial center of the arc-shaped portion 52 at one end in the circumferential direction. And an end face 52c in the circumferential direction extending linearly outward. The linear portion 54 has a side surface 54a that linearly extends radially outward from the other end in the circumferential direction of the arc-shaped portion 52 with respect to the axial center of the arc-shaped portion 52.(In other words, at the other end in the circumferential direction of the arc-shaped portion 52, the other end surface 54a in the circumferential direction extends linearly outward in the radial direction with respect to the axis of the arc-shaped portion 52).A side surface 54b extending parallel to the side surface 54a, and a tip surface 54c extending between the tips of the side surface 54a and the other side surface 54b at right angles to the side surface 54a and the other side surface 54b. I have. The base end of one side surface 54 a of the linear portion 54 is continuous with the other end of the arc surface 52 a of the arc-shaped portion 52, and the base end of the other side surface 54 b is continuous with the other end of the arc surface 52 b of the arc-shaped portion 52. Yes.
[0019]
The permanent magnet 50 as a whole has the same thickness t and width w, and has one side 50A and the other side 50B (therefore, the arc-shaped part 52 and the linear part 54 are mutually connected. Have the same thickness t and width w, and one side 50A and the other side 50B). The width w of the permanent magnet 50 is formed narrower than the width W of the magnetic plate member 40, the radius of the arc surface 52a is defined to be slightly larger than the radius of the arc surface 42a of the magnetic plate member 40, and the arc surface 52b. Is defined to be smaller than the radius of the arc surface 42 b of the magnetic plate member 40. The length of the linear portion 54 of the permanent magnet 50 is defined to be shorter than the length of the linear portion 44 of the magnetic plate member 40.
[0020]
The permanent magnet 50 configured as described above is integrally disposed on one side 40 </ b> A of the magnetic plate member 40. In the embodiment, the other surface 50B of the permanent magnet 50 is polymerized on the one surface 40A of the magnetic plate member 40, and is adhered by an appropriate adhesive. In this mounted state, the arc surface 52a that is the radially inner surface of the arc-shaped portion 52 of the permanent magnet 50 is positioned concentrically with the arc surface 42a that is the radially inner surface of the arc-shaped portion 42 of the magnetic plate member 40. The arc surface 52a of the permanent magnet 50 is positioned so as to recede by a certain distance d outward in the radial direction with respect to the arc surface 42a of the magnetic plate member 40. The one end surface 52c in the circumferential direction of the permanent magnet 50 is positioned with respect to the one end surface 42c in the circumferential direction of the magnetic plate member 40 by retracting substantially a certain distance d in the circumferential direction (to the right in FIG. 3). It is done. One side surface 54a of the linear portion 54 of the permanent magnet 50 is positioned so as to recede from the one side surface 44a of the magnetic plate member 40 substantially in the circumferential direction (to the right in FIG. 3) by a certain distance d. The other side surface 54b is positioned so as to recede from the other side surface 44b of the magnetic plate member 40 in a substantially opposite circumferential direction (to the left in FIG. 3) by an appropriate constant distance, and the front end surface 54c is The magnetic plate member 40 is positioned so as to recede by a relatively long appropriate distance inward in the radial direction with respect to the axial center of the arc surface 52a of the permanent magnet 50 with respect to the tip surface 44c of the linear portion 44 of the permanent magnet member 50. The arc surface 52b, which is the radially outer surface, is positioned so as to recede by an appropriate constant distance radially inward with respect to the arc surface 42b, which is the radially outer surface of the magnetic plate member 40.
[0021]
On one side 40A of the magnetic plate member 40, on the inner side of the other side surface 44b of the linear portion 44 and the inner side of the arc surface 42b, a positioning wall 40C extending with a certain width along the other side surface 44b and the arc surface 42b. Is formed. The positioning wall 40C is formed so as to extend from the one surface 40A at a right angle at a certain height. The other side surface 54b and the circular arc surface 52b of the linear portion 54 of the permanent magnet 50 are positioned by contacting the corresponding inner side surface of the positioning wall 40C. There are other embodiments in which the positioning wall 40C is not formed.
[0022]
In the embodiment, the magnetic pole surface of the permanent magnet 50 adhered to one side 40A of the magnetic plate member 40 of the magnetic seal body 100 is formed between the entire surface of the single surface 50A and the entire surface of the other surface 50B. Although the N pole and the other surface 50B are formed (magnetized) so as to be the S pole, the single side 50A may be the S pole and the other surface 50B may be the N pole. In another embodiment in which the magnetic pole surface of the permanent magnet 50 is formed between the arc surface 52a and the one side surface 54a and the arc surface 52b and the other side surface 54b (the arc surface 52a and the one side surface 54a are made of N poles (or S The arc surface 52b and the other side surface 54b are S poles (or N poles), and the magnetic pole surface of the permanent magnet 50 is an elongated surface composed of the arc surface 52a and one side surface 54a. There is still another embodiment in which the electrodes are alternately formed with different polarities along the short side.
[0023]
Referring to FIGS. 1 to 3, each of the magnetic seal bodies 100 configured as described above is disposed on both sides of the housing 4 so as to face the outer peripheral surfaces of both end portions in the axial direction of the developing sleeve 30 with a gap therebetween. Arranged in the section. Each of the magnetic seal bodies 100 is attached to the housing 4 by, for example, attaching a pair of support flanges hanging from the ceiling wall 12 to the arc surface 42b of the arc-shaped portion 42 of the magnetic plate member 40 and the other side surface 44b of the linear portion 44. Can be performed by adhering.
[0024]
In a state where each of the magnetic seal bodies 100 is disposed on both sides of the housing 4, the arc surface 42 a of the magnetic plate member 40 in each of the magnetic seal bodies 100 is substantially constant with respect to the outer peripheral surface of the developing sleeve 30. The one surface 40A of the magnetic plate member 40 extends along the outer peripheral surface with a gap, and constitutes an inner surface that is orthogonal to the axial direction of the developing sleeve 30 and that is opposed to the axial direction. The permanent magnet 50 in each of the magnetic seal bodies 100 is disposed on one side 40 </ b> A (the inner side surface) of the corresponding magnetic plate member 40. Each arcuate surface 52 a of the permanent magnet 50 extends along the outer peripheral surface with a substantially constant gap with respect to the outer peripheral surface of the developing sleeve 30. As described above, each arc surface 52a of the permanent magnet 50 is positioned so as to recede from the arc surface 42a of the corresponding magnetic plate member 40 by a predetermined distance d radially outward. One end surface 52c and the other end surface in the circumferential direction of the permanent magnet 5054aAre one end surface 42c and the other end surface of the magnetic plate member 40 in the circumferential direction.44aOn the other hand, they are positioned substantially backward in the circumferential direction (to the right in FIG. 3) by a certain distance d.
[0025]
In the developing device 2, when the drive source (not shown) is energized, the developing sleeve 30 is rotated counterclockwise in FIG. The developing sleeve 30 holds a developer on its peripheral surface and conveys the developer through a developing area facing the photosensitive drum 1. The layer thickness regulating blade 34 regulates the layer thickness of the developer held on the peripheral surface of the developing sleeve 30 and conveyed to the developing area. In the development area, the toner contained in the developer is applied to the electrostatic latent image to be developed formed on the peripheral surface of the photosensitive drum 1, and the electrostatic latent image is developed into a toner image.
[0026]
The first and second rotating spiral blade members 26 and 28 and the developing sleeve 30 are driven to rotate in the directions of the arrows shown in FIG. The developer accommodated in the housing 4 is made into a circulation path composed of the first and second transport paths 18 and 20 and the communication paths 22 and 24 by the first and second rotating spiral blade members 26 and 28. Agitated and conveyed along the direction of the arrow shown in FIG.
[0027]
The developer in the second conveyance path 20 is stirred and conveyed by the second rotating spiral blade member 28 from one end to the other end in the axial direction of the developing sleeve 30 (from the left end to the right end in FIG. 2). Since the toner is supplied, the magnetic carrier and the non-magnetic toner constituting the developer may leak to the outside from both axial ends of the developing sleeve 39. However, according to the developing device 2 of the present invention, such a problem is caused. Can be resolved.
[0028]
That is, in the developing device 2 according to the present invention, the magnetic plate member 40 in each of the magnetic seal bodies 100 extends along the outer peripheral surface with a substantially constant gap with respect to the outer peripheral surface of the developing sleeve 30. And an inner side surface 40A which is orthogonal to the axial direction of the developing sleeve 30 and faces each other in the axial direction. The permanent magnet 50 in each of the magnetic seal bodies 100 is disposed on the inner surface 40A of the corresponding magnetic plate member 40 and is substantially spaced from the outer peripheral surface of the developing sleeve 30 on the outer peripheral surface. An arc surface 52a extending along the axis is provided. Each arcuate surface 52a of the permanent magnet 50 is positioned so as to recede from the arcuate surface 42a of the corresponding magnetic plate member 40 by a certain distance d radially outward. One end surface 52c and the other end surface in the circumferential direction of each of the permanent magnets 5054aAre one end surface 42c and the other end surface of the corresponding magnetic plate member 40 in the circumferential direction.44aOn the other hand, each of them is set back substantially by a certain distance d in the circumferential direction.
[0029]
That is, in each of the magnetic seal bodies 100, the gap between the arc surface 42 a that is the surface facing the developing sleeve 30 of the magnetic plate member 40 and the arc surface 52 a that is the surface facing the developing sleeve 30 of the permanent magnet 50. And both end faces 42c in the circumferential direction of the arc surface 42a of the magnetic plate member 40, and44aAnd both circumferential end surfaces 52c of the arc surface 52a of the permanent magnet 50, and54aAre formed so that the side of the permanent magnet 50 existing on the inner side in the axial direction of the developing sleeve 30 recedes, so that the magnetic lines of force of the permanent magnet 50 in each of the magnetic seal bodies 100 are different from each other. It flows particularly intensively toward the stepped portion of the magnetic plate member 40 adjacent to the 30 axial direction. As a result, the magnetic carrier that tends to leak outward from both axial ends of the developing sleeve 30 is first effectively captured by the permanent magnet 50. In addition, since the carrier chain is formed in a concentrated manner in the stepped portion by the cooperation of both the permanent magnet 50 and the magnetic plate member 40, the restraining force due to the magnetic force is sufficiently applied to the end of the carrier chain. The leakage of the magnetic carrier or the toner from the axial end portions of the developing sleeve 30 is effectively prevented. In addition, the carrier chain effectively exhibits a sealing function in the stepped portion, particularly due to the concentrated formation of the carrier chain, thereby effectively preventing toner leakage.
[0030]
As described above, the lines of magnetic force of the permanent magnets 50 in each of the magnetic seal bodies 100 flow particularly intensively toward the step portions of the magnetic plate member 40 adjacent in the axial direction of the developing sleeve 30. The magnetic lines of force of the permanent magnet 50 do not spread comparatively widely to the outside of the magnetic seal body 100 in the axial direction. Therefore, the magnetic carrier or toner leaks from both ends of the developing sleeve 30 in the axial direction also on this surface. Can be effectively prevented.
[0031]
The arcuate surface 52a of each permanent magnet 50 is retracted radially outward from the arcuate surface 42a of the corresponding magnetic plate member 40, and the circumferential direction of each of the permanent magnets 50 is fixed. The constant distance d by which the end face 52c and the other end face 52d are substantially retreated in the circumferential direction with respect to the one end face 42c and the other end face 42d in the circumferential direction of the corresponding magnetic plate member 40 is from 0.4 mm to 0.4 mm. It is preferable to be defined as 1.0 mm. As a result of an experiment by the present inventor, when the constant distance d is set to 0.4 mm to 1.0 mm, no leakage of toner from both ends of the developing sleeve 30 to the outside is recognized. On the other hand, when the distance d is set to 0 mm to less than 0.4 mm, and when the distance d is set to a distance exceeding 1.0 mm, both of the development sleeves 30 are connected to the outside. Leakage of toner was observed.
[0032]
The magnetic force of the magnetic pole surface in each of the permanent magnets 50 is preferably 0.03 mT (millitesla) to 0.05 mT (millitesla). As a result of experiments by the present inventor, when the magnetic force is set to 0.03 mT to 0.05 mT, the carrier chain effectively performs a sealing function, and the carrier and toner from both ends of the developing sleeve 30 to the outside. No leakage was observed. On the other hand, when the magnetic force was less than 0.03 mT, the end of the carrier chain was peeled off because the magnetic force was too weak to perform the sealing function. When the magnetic force is set to a value exceeding 0.05 mT, the carrier is excessively taken in and the carrier chain comes into contact with the developing sleeve 38, so that the carrier overflows and overflows from the end of the housing 4. A phenomenon occurred.
[0033]
Examples of the above embodiment are as follows.
T = 1.0 mm, W = 4.0 mm, t = 1.0 mm, w = 3.5 mm. The gap between the outer peripheral surface of the developing sleeve 30 and the arc surface 42a of the magnetic plate member 40 is 0.5 mm.
[0034]
In the above-described embodiment according to the present invention, the permanent magnet 50 has a substantially similar shape to the magnetic plate member 40 and is adhered over almost the entire region in the longitudinal direction on one side 40A of the magnetic plate member 40. There are other embodiments where the carrier or toner is stuck in an area where leakage is likely. For example, as shown in FIG. 7, the permanent magnet 50 (1) is pasted across one end region of the arc-shaped portion 42 and the base end region of the linear portion 44 of the magnetic plate member 40. The second embodiment, in which the permanent magnet 50 (2) is attached to the other end region of the arc-shaped portion 42 of the magnetic plate member 40, and the permanent magnet 50 (3) Other third embodiments that are attached to the intermediate region of the arc-shaped portion 42 of the magnetic plate member 40, still other embodiments that appropriately combine these, and the like can be mentioned. The basic configuration in these other embodiments is substantially the same as in the previous embodiment.
[0035]
In the above-described embodiment of the developing device according to the present invention, the magnetic carrier and the non-magnetic material are formed on the outer peripheral surface of the developing sleeve 30 by the magnetic action of the stationary permanent magnet 32 disposed in the developing sleeve 30 and the charging action of the toner. The toner is held and transported to the development area, and only the toner is supplied to the latent image formed on the surface of the photosensitive drum 1. However, the present invention is not limited to the above embodiment, and can be applied to, for example, a so-called hybrid developing device. The hybrid developing device uses a magnetic roller for charging a developer composed of a magnetic carrier and a non-magnetic toner while magnetically holding it, and uses a magnetic brush of the magnetic roller and a conveying bias to transfer toner from the magnetic roller to the surface. A developing sleeve that forms a thin layer of only toner, and a developing bias is applied to the developing areas of the developing sleeve and the photosensitive drum to supply the toner to the latent image on the surface of the photosensitive drum for development. . The present invention can effectively prevent leakage of the carrier or toner from both ends of the developing sleeve to the outside also by such a developing device in such a developing device.
[0036]
【The invention's effect】
According to the developing device of the present invention, it is possible to reliably prevent leakage of the magnetic carrier or the toner from both ends of the developing sleeve using the magnetic seal body which is a non-contact type sealing means.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a developing device constructed according to the present invention.
FIG. 2 is a schematic plan view of the developing device shown in FIG. 1, with the ceiling wall omitted.
3 is a front view of one embodiment of the magnetic seal body provided in the developing device shown in FIGS. 1 and 2, as viewed in the direction of arrow A in FIG.
4 is a perspective view of the magnetic seal body shown in FIG. 3. FIG.
5 is a cross-sectional enlarged view taken along the line BB in FIG. 3;
6 is an enlarged cross-sectional view taken along the line CC in FIG. 3;
FIG. 7 is a front view showing another embodiment of a magnetic seal body.
[Explanation of symbols]
2 Development device
4 Housing
30 Development sleeve
40 Magnetic plate members
40A single side (inner side)
42 Arc-shaped part
42a Arc surface
42c one end
42d The other end surface
44 Straight section
50 Permanent magnet
52 Arc-shaped part
52a Circular arc surface
52c one end
52d The other end surface
54 Straight section
100 Magnetic seal body

Claims

A developing sleeve rotatably supported by a housing containing a developer composed of a magnetic carrier and a non-magnetic toner is disposed in the housing so as to face the outer peripheral surfaces of both end portions in the axial direction of the developing sleeve with a gap therebetween. A pair of magnetic seal bodies, each of the magnetic seal bodies in a developing device comprising a magnetic plate member and a permanent magnet integrally disposed on the magnetic plate member;
The magnetic plate member in each of the magnetic seal bodies is orthogonal to the arc surface extending along the outer peripheral surface with a substantially constant gap from the outer peripheral surface of the developing sleeve and the axial direction of the developing sleeve. And permanent magnets in each of the magnetic seal bodies are disposed on the inner surface of the corresponding magnetic plate member and substantially with respect to the outer peripheral surface of the developing sleeve. An arc surface extending along the outer peripheral surface with a certain gap,
Each arc surface of the permanent magnet is positioned with a certain distance outwardly in the radial direction with respect to the arc surface of the corresponding magnetic plate member, and each arc surface of the permanent magnet and each of the permanent magnets are positioned. On the other hand, a step portion in which each arc surface of the permanent magnet recedes is formed between the arc surfaces of the magnetic plate members adjacent in the axial direction.
A developing device.

The magnetic plate member in each of the magnetic seal bodies has a circumferential end surface extending outward in the radial direction from both ends in the circumferential direction of the arc surface of the magnetic plate member, and the permanent magnet in each of the magnetic seal bodies is a permanent magnet A circumferential end surface extending radially outward from both ends of the arc surface in the circumferential direction,
One end face or both end faces of the peripheral direction of each permanent magnet, against one end face or both end faces of the peripheral direction of the corresponding magnetic plate members, are respectively positioned back by substantially constant circumferential distance Between the one end surface or both end surfaces in the circumferential direction of each of the permanent magnets and the one end surface or both end surfaces in the circumferential direction of the magnetic plate member adjacent to each of the permanent magnets in the axial direction. The developing device according to claim 1, wherein a step portion in which one end surface or both end surfaces in the circumferential direction of each of the first and second end surfaces recede is formed .

On the inner side of the arc surface on each inner surface of each magnetic plate member, a positioning wall extending along the arc surface with a certain width and extending at a certain height perpendicularly from the inner surface is formed. The developing device according to claim 1, wherein the arc surface of the permanent magnet is positioned by being brought into contact with a corresponding inner surface of the positioning wall.