JP2004085877A

JP2004085877A - Development device

Info

Publication number: JP2004085877A
Application number: JP2002246662A
Authority: JP
Inventors: Kunio Shigeta; 重田　邦男; Hiroshi Akita; 秋田　宏; Takenobu Kimura; 木村　丈信; Yotaro Sato; 佐藤　洋太郎
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2002-08-27
Filing date: 2002-08-27
Publication date: 2004-03-18

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device applied to an image forming apparatus which prevents troubles such as fog, toner scattering and inhomogeneous density, even when images are formed continuously at a high print rate with small-particle diameter toner and carrier for improving image quality, by using a hollow cylindrical member with a spiral rib on its internal face as a developer transport means for mixing, stirring, and transporting a developer, and by defining the conditions of a structure for fully bringing out its performance. <P>SOLUTION: In the development apparatus, if the width of a developer carrier in the direction of its rotary shaft is W1 (mm), the width of a first developer transport means in the direction of its rotary shaft is W2 (mm), and the width of the hollow cylinder composing the second developer conveying means in the direction of its rotary shaft is W3 (mm), the relationship therebetween is given by W1<W3<W2. Replenishment toner is supplied to the first developer transport means or the external portion of the hollow cylindrical member of the second developer conveying means. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、電子写真方式の複写機、プリンタ、ファックス等の画像形成装置に関するものである。
【０００２】
【従来の技術】
従来より、トナーとキャリアからなる２成分現像剤（以下、現像剤と称す）を用いる現像装置としては、現像剤担持体の回転軸方向に平行に、互いに逆方向に現像剤を搬送する複数の現像剤搬送手段により、現像剤を混合撹拌しつつ循環搬送しているのが一般的である。
【０００３】
近年、画像形成装置のカラー化に伴い、高印字率の画像を形成する機会が増加しつつある。これは、１枚あたりのトナー使用量が増加し、それに伴いトナー補給量も増加するということである。
【０００４】
また、高画質化のために、現像剤を構成するトナーとして体積平均粒径が３〜５μｍ程度の小粒径トナーが用いられるようになってきた。さらに、このトナー小粒径化に伴いキャリアも５〜１０μｍ程度に小粒径化されてきている。
【０００５】
具体的には、従来の２成分現像剤を用いる現像装置としては、現像剤搬送手段としてスクリュウオーガを用い、スクリュウオーガ近傍に起こる局所的剪断と容器内での粉体の循環流（移動流）により現像剤を混合しながら撹拌する方式が、一般に用いられている。この方式では、上記の高印字率化によるトナー補給量の増加に対応するため、現像剤の混合、撹拌を速くし補給されたトナーの帯電立ち上がりを速くするために、スクリュウオーガの形状を工夫したり、回転数を高く設定したりする等の工夫がおこなわれている。
【０００６】
一方、内周に螺旋状のリブを有する中空円筒部材を、現像剤搬送手段として用いるものが特開昭５６−７０５７６号に開示されている。この公報には、内側に螺旋状のリブを固設した円筒を回転させ、現像剤が上方へ持ち上げられ、落下することを繰り返すことで、十分な撹拌混合を受けつつ他端へ搬送することで現像剤の劣化を防止する提案が記載されている。
【０００７】
【発明が解決しようとする課題】
近年増加しつつある、高印字率の画像形成には、上述のようにトナーを多く必要とし、このトナー消費に対応して、補給するトナーも増加することになる。従来の２成分現像剤を用いる現像装置を用いて高印字率の画像を連続して形成した場合、現像装置内を循環搬送される現像剤と大量に補給されたトナーとが十分に混合撹拌されず、トナーは帯電が不十分な状態（未帯電や弱帯電）のまま、現像に供され（現像剤担持体に供給され）、かぶりやトナー飛散（機内汚れ）等の問題を発生させていた。この問題は、画像形成装置が高速になればなるほど、現像装置内の現像剤の循環速度が速くなる（トナーが補給されてから現像に供されるまでの時間が短くなる）ので、特に顕著になる。
【０００８】
加えて、高画質化のための上述の小粒径化されたトナーおよびキャリアを用いる場合には、従来の大粒径のトナーやキャリアの場合よりも混合撹拌性が悪く、上記の問題は、さらに深刻となる。
【０００９】
これらの問題に対し、従来から行われているスクリュウオーガの形状を工夫し、現像剤にかかる剪断力を大きくして混合、撹拌性能を向上させようとする対策は、現像剤にかかる負担を大きくし、現像剤を長期にわたり繰り返し使用する場合には、現像剤の耐久性がなくなるという問題を新たに引き起こしている。
【００１０】
一方、特開昭５６−７０５７６号に記載されている方法は、中空円筒部材と、該中空円筒部材と併せて用いるスクリュウオーガ（現像剤搬送手段）との構造条件が適切でないと、混合撹拌や搬送（現像剤担持体の回転軸方向の移動）が十分おこなわれず、上記と同様のかぶりやトナー飛散、濃度むら等を発生させてしまうことになる。
【００１１】
本発明は、上記の問題点を鑑み、内周に螺旋状リブを有する中空円筒部材を現像剤の混合、撹拌、搬送のための現像剤搬送手段に用い、十分にその性能を発揮させるための構造条件を明確にすることで、高画質化のための小粒径トナーおよび小粒径キャリアを使用して、高印字率の画像形成を連続的におこなった場合でも、かぶり、トナー飛散、濃度むら等の問題の発生しない画像形成装置に適用される、現像装置を提供することを目的とするものである。
【００１２】
【課題を解決するための手段】
上記目的は、トナーとキャリアからなる現像剤を担持して搬送する現像剤担持体と、該現像剤担持体に供給される現像剤及び前記現像剤担持体から回収された現像剤を、混合撹拌しながら、前記現像剤担持体の回転軸と略平行な方向に搬送する第１の現像剤搬送手段と、該第１の現像剤搬送手段によって搬送された現像剤と補給されたトナーとを混合撹拌しながら、前記第１の現像剤搬送手段による現像剤搬送方向と、略平行で且つ逆方向に搬送し、前記第１の現像剤搬送手段へと供給する第２の現像剤搬送手段とを有する現像装置において、前記第１の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒を有する中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、前記現像剤担持体の回転軸方向の幅をＷ１（ｍｍ）、前記第１の現像剤搬送手段であるスクリュウオーガの回転軸方向の幅をＷ２（ｍｍ）、前記第２の現像剤搬送手段を構成する中空円筒の回転軸方向の幅をＷ３（ｍｍ）としたとき、Ｗ１＜Ｗ３＜Ｗ２であり、前記第１の現像剤搬送手段または前記第２の現像剤搬送手段の、前記中空円筒部材の外側部分に補給トナーを供給するようにしたことを特徴とする現像装置（第１の発明）によって達成される。
【００１３】
また、上記目的は、トナーとキャリアからなる現像剤を担持して搬送する現像剤担持体と、該現像剤担持体に供給される現像剤及び前記現像剤担持体から回収された現像剤を、混合撹拌しながら、前記現像剤担持体の回転軸と略平行な方向に搬送する第１の現像剤搬送手段と、該第１の現像剤搬送手段によって搬送された現像剤と補給されたトナーとを混合撹拌しながら、前記第１の現像剤搬送手段による現像剤搬送方向と、略平行で且つ逆方向に搬送し、前記第１の現像剤搬送手段へと供給する第２の現像剤搬送手段とを有する現像装置において、前記第１の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段を両側端で支持させるスクリュウオーガの回転軸を一体で形成することを特徴とする現像装置（第２の発明）によって達成される。
【００１４】
また、上記目的は、トナーとキャリアからなる現像剤を担持して搬送する現像剤担持体と、該現像剤担持体に供給される現像剤及び前記現像剤担持体から回収された現像剤を、混合撹拌しながら、前記現像剤担持体の回転軸と略平行な方向に搬送する第１の現像剤搬送手段と、該第１の現像剤搬送手段によって搬送された現像剤と補給されたトナーとを混合撹拌しながら、前記第１の現像剤搬送手段による現像剤搬送方向と、略平行で且つ逆方向に搬送し、前記第１の現像剤搬送手段へと供給する第２の現像剤搬送手段とを有する現像装置において、前記第１の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段は回転円筒の内周に螺旋状のリブを形成した中空円筒部材からなり、該中空円筒部材の内径は前記スクリュウオーガの外径より大きいことを特徴とする現像装置（第３の発明）によって達成される。
【００１５】
また、上記目的は、トナーとキャリアからなる現像剤を担持して搬送する現像剤担持体と、該現像剤担持体に供給される現像剤を、混合撹拌しながら、前記現像剤担持体の回転軸と略平行な方向に搬送する第１の現像剤搬送手段と、前記現像剤担持体から回収された現像剤を混合撹拌しながら、前記第１の現像剤搬送手段による現像剤搬送方向と、略平行で且つ同方向に搬送する第３の現像剤搬送手段と、前記第１および第３の現像剤搬送手段により搬送された現像剤と補給されたトナーとを、混合撹拌しながら、前記第１および第３の現像剤搬送手段による現像剤の搬送方向と、略平行で且つ逆方向に搬送し、前記第１の現像剤搬送手段へと供給する第２の現像剤搬送手段とを有する現像装置において、前記第１および第３の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒を有する中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、前記現像剤担持体の回転軸方向の幅をＷ１１（ｍｍ）、前記第１の現像剤搬送手段であるスクリュウオーガの回転軸方向の幅をＷ２１（ｍｍ）、前記第２の現像剤搬送手段を構成する中空円筒の回転軸方向の幅をＷ３１（ｍｍ）、前記第３の現像剤搬送手段であるスクリュウオーガの回転軸方向の幅をＷ４（ｍｍ）としたとき、Ｗ４≦Ｗ２１の場合、Ｗ１１＜Ｗ３１＜Ｗ２１であり、Ｗ２１＜Ｗ４の場合、Ｗ１１＜Ｗ３１＜Ｗ４であり、前記第１または第３の現像剤搬送手段の下流側、または第２の現像剤搬送手段の上流側の、前記中空円筒部材の外側部分に補給トナーを供給するようにしたことを特徴とする現像装置（第４の発明）によって達成される。
【００１６】
また、上記目的は、トナーとキャリアからなる現像剤を担持して搬送する現像剤担持体と、該現像剤担持体に供給される現像剤を、混合撹拌しながら、前記現像剤担持体の回転軸と略平行な方向に搬送する第１の現像剤搬送手段と、前記現像剤担持体から回収された現像剤を混合撹拌しながら、前記第１の現像剤搬送手段による現像剤搬送方向と、略平行で且つ同方向に搬送する第３の現像剤搬送手段と、前記第１および第３の現像剤搬送手段により搬送された現像剤と補給されたトナーとを、混合撹拌しながら、前記第１および第３の現像剤搬送手段による現像剤の搬送方向と、略平行で且つ逆方向に搬送し、前記第１の現像剤搬送手段へと供給する第２の現像剤搬送手段とを有する現像装置において、前記第１および第３の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段を両側端で支持させるスクリュウオーガの回転軸を一体で形成することを特徴とする現像装置（第５の発明）によって達成される。
【００１７】
また、上記目的は、トナーとキャリアからなる現像剤を担持して搬送する現像剤担持体と、該現像剤担持体に供給される現像剤を、混合撹拌しながら、前記現像剤担持体の回転軸と略平行な方向に搬送する第１の現像剤搬送手段と、前記現像剤担持体から回収された現像剤を混合撹拌しながら、前記第１の現像剤搬送手段による現像剤搬送方向と、略平行で且つ同方向に搬送する第３の現像剤搬送手段と、前記第１および第３の現像剤搬送手段により搬送された現像剤と補給されたトナーとを、混合撹拌しながら、前記第１および第３の現像剤搬送手段による現像剤の搬送方向と、略平行で且つ逆方向に搬送し、前記第１の現像剤搬送手段へと供給する第２の現像剤搬送手段とを有する現像装置において、前記第１および第３の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、前記第２の現像剤搬送手段は回転円筒の内周に螺旋状のリブを形成した中空円筒部材からなり、該中空円筒部材の内径は前記スクリュウオーガの外径より大きいことを特徴とする現像装置（第６の発明）によって達成される。
【００１８】
【発明の実施の形態】
１．（１）本発明に使用する現像装置の撹拌構造について
本発明では、第２の現像剤搬送手段として内周に固着された螺旋状のリブを有する中空円筒部材を用い、この中空円筒内に２成分現像剤を入れて回転させ、容器内壁と粉体との摩擦力により、粉体を持ち上げ、重力の作用で自由落下させながら混合する方式により、現像に供されてトナー濃度が低下した現像剤と補給トナーとを混合撹拌している。この方式を、本件では容器回転型と称す。
【００１９】
これに対し従来の現像装置に用いられる撹拌スクリュウを回転させ、スクリュウ近傍に起こる局所的な剪断と容器内での粉体の循環流（移動流）により２成分現像剤を混合しながら撹拌する容器固定型の構造がある。
【００２０】
剪断力で混合する容器固定型にくらべ容器回転型は、自由落下で混合するため、混合も良好でありかつ現像剤に対する負担も少ない利点がある。
【００２１】
１．（２）非一循環構成の現像装置における現像剤搬送手段の幅関係の条件式（請求項１）
後に述べる非一循環構成の現像装置において、第１の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒を有する中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、現像剤担持体の回転軸方向の幅をＷ１（ｍｍ）、第１の現像剤搬送手段であるスクリュウオーガの回転軸方向の幅をＷ２（ｍｍ）、第２の現像剤搬送手段を構成する中空円筒の回転軸方向の幅をＷ３（ｍｍ）としたとき、
Ｗ１＜Ｗ３＜Ｗ２
であり、第１の現像剤搬送手段または第２の現像剤搬送手段の、中空円筒部材の外側部分に補給トナーを供給するようにするものである。
【００２２】
上記の条件式を満たすことにより、本発明の課題を解消することができる。また上記条件式を満たさないと、現像装置に補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌されず、かぶりやトナー飛散等の問題が発生する。
【００２３】
１．（３）非一循環構成の現像装置における現像剤搬送手段の構造（請求項２）
後に述べる非一循環構成の現像装置において、第１の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段を両端で支持させるスクリュウオーガの回転軸を一体で形成するものである。
【００２４】
上記の構造を満たすことにより、本発明の課題を解消することができる。また上記構造を満たさないと、回転時の中空円筒部材の振れが大きくなり、中空円筒部材での、補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌されず、かぶりやトナー飛散等の問題が発生する。
【００２５】
１．（４）非一循環構成の現像装置における現像剤搬送手段間の構造関係（請求項３）
後に述べる非一循環構成の現像装置において、第１の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段は回転円筒の内周に螺旋状のリブを形成した中空円筒部材からなり、中空円筒部材の内径をスクリュウオーガの外径より大きく設定するものである。
【００２６】
上記の構造を満たすことにより、本発明の課題を解消することができる。また上記構造を満たさないと、中空円筒部材の撹拌途中で現像剤が滞溜され、かぶりやトナー飛散等の問題が発生する。
【００２７】
１．（５）一循環構成の現像装置における現像剤搬送手段の幅関係の条件式（請求項５）
後に述べる一循環構成の現像装置において、第１および第３の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒を有する中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、現像剤担持体の回転軸方向の幅をＷ１１（ｍｍ）、第１の現像剤搬送手段であるスクリュウオーガの回転軸方向の幅をＷ２１（ｍｍ）、第２の現像剤搬送手段を構成する中空円筒の回転軸方向の幅をＷ３１（ｍｍ）、第３の現像剤搬送手段であるスクリュウオーガの回転軸方向の幅をＷ４（ｍｍ）としたとき、
Ｗ４≦Ｗ２１の場合、
Ｗ１１＜Ｗ３１＜Ｗ２１
であり、
Ｗ２１＜Ｗ４の場合、
Ｗ１１＜Ｗ３１＜Ｗ４
であり、第１または第３の現像剤搬送手段の下流側、または第２の現像剤搬送手段の上流側の、中空円筒部材の外側部分に補給トナーを供給するようにするものである。
【００２８】
上記の条件式を満たすことにより、本発明の課題を解消することができる。また上記条件式を満たさないと、現像装置に補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌されず、かぶりやトナー飛散等の問題が発生する。
【００２９】
１．（６）一循環構成の現像装置における現像剤搬送手段の構造（請求項６）
後に述べる一循環構成の現像装置において、第１および第３の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段は、回転軸方向の中央部分が内周に螺旋状のリブを形成した中空円筒部材からなり、回転軸方向の両側部分が外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段を両端で支持させるスクリュウオーガの回転軸を一体で形成するものである。
【００３０】
上記の構造を満たすことにより、本発明の課題を解消することができる。また上記構造を満たさないと、回転時の中空円筒部材の振れが大きくなり、中空円筒部材での、補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌されず、かぶりやトナー飛散等の問題が発生する。
【００３１】
１．（７）一循環構成の現像装置における現像剤搬送手段間の構造関係（請求項７）
後に述べる一循環構成の現像装置において、第１および第３の現像剤搬送手段は回転軸の外周に螺旋状のリブを有するスクリュウオーガからなり、第２の現像剤搬送手段は回転円筒の内周に螺旋状のリブを形成した中空円筒部材からなり、中空円筒部材の内径をスクリュウオーガの外径より大きく設定するものである。
【００３２】
上記の構造を満たすことにより、本発明の課題を解消することができる。また上記構造を満たさないと、中空円筒部材の撹拌途中でが滞溜され、かぶりやトナー飛散等の問題が発生する。
【００３３】
２．次に本発明を適用する現像装置について、説明する。
図１は、請求項１，２，３に該当する現像剤非一循環構成の現像装置の概略の断面レイアウト３種を示したものである。
【００３４】
なお、現像剤担持体に供給する現像剤を搬送する手段と、現像剤担持体から回収した現像剤を搬送する手段を別々に設け、現像剤担持体から回収した現像剤は、トナー補給部（トナー補給手段）を通過してからでないと、現像剤担持体に供給されないようにした構成を、現像剤一循環構成と称し、そうでない構成（現像剤担持体から回収した現像剤がトナー補給される前に再び現像剤担持体へ供給される構成）を現像剤非一循環構成と称すものである。
【００３５】
図１において、４１は現像剤担持体（現像ローラ）、４５は第１の現像剤搬送手段であるスクリュウオーガであり、４６は第２の現像剤搬送手段である内周に螺旋状リブを有する中空円筒部材であり、４４は現像剤担持体へ現像剤を供給するための現像剤供給手段であるパドル状の撹拌羽根である。図１（Ａ）及び（Ｂ）は、現像剤下剥ぎタイプであり、（Ｃ）は現像剤上剥ぎタイプである。
【００３６】
図２は、図１（Ａ）をより詳しくしたもので、現像剤の搬送と動作の概略を説明する。図２において、４１、４４、４５、４６は、図１と同じである。５０は現像装置枠体、１は感光体ドラムであり、４３は現像剤層厚規制板、５３は隔壁で構成されており、５３の隔壁は切り欠き部を有している。５４はトナー補給手段である。
【００３７】
現像ローラ４１は、静電潜像を担持する感光体ドラム１に対向して配置され、回転可能に支持されており、それぞれ図２の矢印方向に回転する。現像ローラ４１は、その内部にマグネット（不図示）があり、パドル状の撹拌羽根４４により供給される現像剤を吸着し、現像ローラ４１上に付着させ感光体ドラムへトナーを供給する。その後、図示しない現像ローラ内部のマグネットの反発磁界領域でパドル状の撹拌羽根４４へ受け渡す。この受け渡された現像剤は、パドル状の撹拌羽根によりスクリュウオーガ４５へ移動され、スクリュウオーガ４５の回転により、混合撹拌されながら回転軸方向へ搬送され、隔壁５３の一方の端部に設けられた切り欠き部を通して、回転軸方向の中央の中空円筒４６ａ部分の内周に螺旋リブを有する中空円筒部材４６へ搬送される。
【００３８】
切り欠き部近傍には、図示しないトナー濃度検知手段が設けられ、この検知手段により検知されたトナー濃度がトナー補給を必要と判断される場合は、トナー補給手段５４からトナー補給される。中空円筒部材４６は、前述のように円筒と螺旋状リブが一体で回転し円筒内壁と現像剤との摩擦力により現像剤を持ち上げ、自由落下させながら、現像剤と補給されたトナーを混合撹拌する。中空円筒部材４６の現像剤搬送方向は、スクリュウオーガ４５の搬送方向と逆方向であり、混合撹拌された現像剤は隔壁５３のもう一方の切り欠き部からスクリュウオーガ４５へ移動される。スクリュウオーガ４５は、この中空円筒部材４６からの現像剤と前述のパドル状の撹拌羽根４４から受け渡された現像剤を混合撹拌しつつ回転軸方向に搬送しながら、現像に供される現像剤をパドル状撹拌羽根４４へ供給する。これが図２に示す現像剤非一循環タイプの現像装置の動作の概略である。
【００３９】
また、図１および図２にて述べた非一循環構成の現像装置における、第１の現像剤搬送手段であるスクリュウオーガ４５は回転軸方向の両側部分の外周に螺旋状のリブを有するスクリュウオーガからなる。
【００４０】
また現像非一循環タイプの現像装置において、スクリュウオーガ４５の回転方向は、現像ローラ４１に対向または近接する位置の移動方向が、現像ローラ４１の移動方向と逆方向に回転するようになっている。
【００４１】
またスクリュウオーガ４５の外周には回転軸と平行に螺旋状リブを横切るようにパドルを設けた構造でもよい。
【００４２】
さらに、中空円筒部材４６とスクリュウオーガ４５とは、中空円筒部材４６の両端部の支持軸部に螺旋状リブ及びまたはパドル状撹拌羽根を設ける。
【００４３】
また回転軸方向の関係を図３に示すが、図において５５、５６は現像装置の側壁であり、現像ローラ４１の軸方向の幅をＷ１とし、スクリュウオーガ４５の螺旋状リブ部の軸方向の幅をＷ２、中空円筒部材４６の中空円筒部の軸方向の幅をＷ３としたとき、
Ｗ１＜Ｗ３＜Ｗ２
と設定し、且つ、スクリュウオーガ４５の下流側で斜線で示す側壁５５の外側部分、または中空円筒部材４６の上流側で、中空円筒部材４６の中空円筒４６ａの斜線で示す側壁５５の外側部分に補給トナーを供給する。
【００４４】
上記により、現像装置に補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌され、かぶりやトナー飛散による機内汚れが発生しない現像装置の提供が可能となる。
【００４５】
また中空円筒部材４６の内径はスクリュウオーガ４５の外径より大きく設定する。具体的には、図２に示すように、スクリュウオーガ４５の外径をＤ１（ｍｍ）、中空円筒部材４６の中空円筒４６ａの内径をＤ２（ｍｍ）としたとき、
Ｄ１＜Ｄ２≦１．７×Ｄ１
であることが好ましい。
【００４６】
上記により、中空円筒部材の撹拌途中で、補給されたトナーと現像装置内を循環搬送される現像剤との滞溜が発せず、かぶりやトナー飛散等の発生がない。
【００４７】
図４は、請求項５，６，７に該当する現像剤一循環構成の現像装置の概略の断面レイアウト３種を示したものである。図４において、図１と、機能と名称の同じものは同番号としてある。ここで、４９は第３の現像剤搬送手段であるスクリュウオーガで、４７は現像剤回収手段であるマグロールである。図４（Ａ）は、現像剤下剥ぎタイプであり、（Ｂ）、（Ｃ）は現像剤上剥ぎタイプである。
【００４８】
図５は、図４（Ａ）をより詳しくしたもので、現像剤の搬送と動作の概略について、説明する。
【００４９】
現像ローラ４１は、静電潜像を担持する感光体ドラム１に対向して配置され、回転可能に支持されており、図５の矢印方向に回転する。現像ローラ４１は、その内部にマグネットがあり、パドル状の撹拌羽根４４により供給される現像剤を吸着し、現像ローラ４１上に付着させ感光体ドラム１へトナーを供給する。その後、現像ローラ内部のマグネットの反発磁界領域で、現像剤回収手段であるマグロール４７へ受け渡す。この回収された現像剤は、第３の現像剤搬送手段であるスクリュウオーガ４９へ移動され、スクリュウオーガ４９の回転により回転軸方向へ搬送され、スクリュウオーガ４９の回転軸方向の下流側端部において、スクリュウオーガ４５へ移動され、スクリュウオーガ４５により搬送される現像剤と、スクリュウオーガ４９により搬送された現像剤とが混合撹拌されながらスクリュウオーガ４５の回転軸方向へ搬送され、隔壁５３の一方の端部に設けられた切り欠き部を通して、回転軸方向の中央の中空円筒４６ａ部分の内周に螺旋リブを有する中空円筒部材４６へ搬送される。
【００５０】
切り欠き部近傍には、図示しないトナー濃度検知手段が設けられ、この検知手段により検知されたトナー濃度がトナー補給を必要と判断される場合は、トナー補給手段５４からトナー補給される。中空円筒部材４６は、前述のように円筒と螺旋状リブが一体で回転し円筒内壁と現像剤との摩擦力により現像剤を持ち上げ、自由落下させながら、現像剤と補給されたトナーを混合撹拌する。中空円筒部材４６の現像剤搬送方向は、スクリュウオーガ４５の搬送方向と逆方向であり、混合撹拌された現像剤は隔壁５３のもう一方の切り欠き部からスクリュウオーガ４５へ移動される。スクリュウオーガ４５は、この中空円筒部材４６からの現像剤と前述のパドル状の撹拌羽根４４から受け渡された現像剤を混合撹拌しつつ回転軸方向に搬送しながら、現像に供される現像剤をパドル状撹拌羽根４４へ供給する。これが図５に示す現像剤一循環タイプの現像装置の動作の概略である。
【００５１】
また、図４および図５にて述べた一循環構成の現像装置における、第１の現像剤搬送手段であるスクリュウオーガ４５および第３の現像剤搬送手段であるスクリュウオーガ４９は回転軸方向の両側部分の外周に螺旋状のリブを有するスクリュウオーガからなる。
【００５２】
また現像剤一循環タイプの現像装置において、スクリュウオーガ４５の回転方向は、現像ローラ４１に対向または近接する位置の移動方向が、現像ローラ４１の移動方向と逆方向に回転するようになっている。
【００５３】
またスクリュウオーガ４５およびスクリュウオーガ４９の外周には回転軸と平行に螺旋状リブを横切るようにパドルを設けた構造でもよい。
【００５４】
また中空円筒部材４６の回転方向は、スクリュウオーガ４５に対向または近接する位置における移動方向が、下方から上方に向かう方向となっている。
【００５５】
さらに、中空円筒部材４６とスクリュウオーガ４５とは、中空円筒部材４６の両端部の支持軸部に螺旋状リブ及びまたはパドル状撹拌羽根を設ける。
【００５６】
また、後に述べるようにスクリュウオーガ４５の両側部分に設けられるスクリュウオーガ４５の軸の外径は中央部分の軸の外径より大きくなるようにし、両端部分の軸との中央部分の軸とを一体とする回転軸が中空円筒部材４６の内周に形成される螺旋状のリブとは接触しない構成とする。
【００５７】
また回転軸方向の関係を図６に示すが、図において５５、５６は現像装置の側壁であり、また図の実線矢印は前述した現像剤の流れを示すものであり、点線矢印は現像剤搬送手段から溢れた現像剤の流れを示すものである。回転軸方向の関係は、現像ローラ４１の軸方向の幅をＷ１１とし、スクリュウオーガ４５の螺旋状リブ部の軸方向の幅をＷ２１、中空円筒部材４６の中空円筒部の軸方向の幅をＷ３１、スクリュウオーガ４９の螺旋状リブ部の軸方向の幅をＷ４１としたとき、スクリュウオーガ４５の螺旋状リブ部の軸方向の幅Ｗ２１がスクリュウオーガ４９の螺旋状リブ部の軸方向の幅Ｗ４より大きい（Ｗ４＜Ｗ２１）の場合（図４（Ｂ）、（Ｃ）に示すスクリュウオーガ４９がスクリュウオーガ４５の上部に設けられる場合）、
Ｗ１１＜Ｗ３１＜Ｗ２１
と設定し、且つ、スクリュウオーガ４５の下流側で斜線で示す側壁５５の外側部分、または中空円筒部材４６の上流側で、中空円筒部材４６の中空円筒４６ａの斜線で示す側壁５５の外側部分に補給トナーを供給する。
【００５８】
またスクリュウオーガ４５の螺旋状リブ部の軸方向の幅Ｗ２１がスクリュウオーガ４９の螺旋状リブ部の軸方向の幅Ｗ４より小さい（Ｗ２１＜Ｗ４）の場合（図４（Ａ）に示すスクリュウオーガ４５がスクリュウオーガ４９の上部に設けられる場合）、
Ｗ１１＜Ｗ３１＜Ｗ４
と設定し、且つ、スクリュウオーガ４９の下流側で斜線で示す側壁５５の外側部分、または中空円筒部材４６の上流側で、中空円筒部材４６の中空円筒４６ａの斜線で示す側壁５５の外側部分に補給トナーを供給する。
【００５９】
上記により、現像装置に補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌され、かぶりやトナー飛散による機内汚れが発生しない現像装置の提供が可能となる。
【００６０】
なお上記において、スクリュウオーガ４５の螺旋状リブ部の軸方向の幅Ｗ２１とスクリュウオーガ４９の螺旋状リブ部の軸方向の幅Ｗ４とを等しく（Ｗ２１＝Ｗ４）設け、
Ｗ１１＜Ｗ３１＜Ｗ２１またはＷ４
と設定するような構成としてもよい。
【００６１】
また中空円筒部材４６の内径は、スクリュウオーガ４５の外径およびスクリュウオーガ４９の外径より大きく設定する。具体的には、図５に示すように、スクリュウオーガ４５の外径をＤ１１（ｍｍ）、中空円筒部材４６の内径をＤ２１（ｍｍ）、スクリュウオーガ４９の外径をＤ３（ｍｍ）としたとき、
Ｄ３≦Ｄ１１　かつ　Ｄ１１＜Ｄ２１≦１．７×Ｄ１１
であることが好ましい。
【００６２】
上記により、中空円筒部材の撹拌途中で、補給されたトナーと現像装置内を循環搬送される現像剤との滞溜が発せず、かぶりやトナー飛散等の発生がない。
【００６３】
３．中空円筒部材の構造、組立方法および現像剤の搬送方法の概要
各現像装置に設けられる螺旋リブを有する中空円筒部材の構造の概要と中空円筒部材の組み立て方法とを図７に示す。
【００６４】
中空円筒部材としては、図７（Ａ）にその代表例を示すように、螺旋リブ４６ｂの両端部の軸４６ｃの中央部に軸４６ｄを取り付けた一体的な回転軸（符号なし）を用いる。一体的な回転軸により中空円筒部材４６が両側端で支持される。端部の軸４６ｃの軸径は螺旋リブ４６ｂの内径と同じで、中央部の軸４６ｄの軸径は端部の軸４６ｃの軸径より細いものを用いる。中央部の軸４６ｄの軸径を細くすることにより、中空円筒部材４６を回転させる際に、現像剤が自由落下する空間を確保している。また両端部の軸４６ｃと中央部の軸４６ｄとを一体の回転軸として形成（通し軸と）しているので、回転時の中空円筒部材４６の振れが大きくなることを防止し、振れを小さくしている。図７（Ｂ）に示す中空円筒部材４６は、中空円筒４６ａと１重構造の螺旋リブ４６ｂと該螺旋リブ４６ｂの両端部の軸４６ｃとにより構成され、中空円筒４６ａに中心部が中空となる螺旋リブ４６ｂを取り付け、１重構造の螺旋リブ４６ｂの両端部に軸４６ｃ（分離軸）を取り付けたものである。図７（Ｂ）に示す中空円筒部材４６は、１本の通し軸にせず両端部分の軸４６ｃが分離して別々の部材からなる構成としているので、中空円筒部材４６の振れが大きくなり、中空円筒部材４６の両側部分のスクリュウオーガと中央部分の中空円筒４６ａとの接合がうまくいかず、隙間に現像剤が入り込んでしまう。また中空円筒４６ａは両端部の軸４６ｃと一体となって回転し、中空円筒４６ａの外周が側壁５５には接触しないはずであるが、振れが大きくなると中空円筒４６ａの外周と側壁５５とが擦れてしまい、中空円筒部材４６が安定して回転しなくなったり、擦れた部分の削れかすが現像剤の中に混入してしまうこともある。これらにより現像剤の撹拌状態が不均一になってかぶりやトナー飛散が発生したり、撹拌部分の振動が現像器の振動になって画像濃度むら（段むら）や文字散り等が発生する。上記の如く、図７（Ｂ）に示す構造の中空円筒部材４６はあまり好ましくない。
【００６５】
具体的な中空円筒部材４６の製造方法の一例としては、以下の如く行われる。
▲１▼　板状部材を、内部の軸４６ｄと両端部の軸４６ｃとを一体として形成した回転軸（符号なし）に螺旋状に巻き、螺旋リブ４６ｂの部分を作る。このとき螺旋リブ４６ｂの軸方向の長さは中空円筒４６ａよりも長目にする。
【００６６】
▲２▼　中空円筒４６ａの中に螺旋リブ４６ｂを挿入し、螺旋リブ４６ｂと中空円筒４６ａの両側部分とを接着（溶接）する。螺旋リブ４６ｂの中央部分も接着（溶接）したい場合は、中空円筒４６ａに穴を空けて接着（溶接）後に穴をふさぐようにする。
【００６７】
▲３▼　螺旋リブ４６ｂの両端部と両端の軸４６ｃとを接着（溶接）する。
また螺旋リブの構造は、上記図７にて説明した１重の螺旋の他に、２重構造（多重構造）の螺旋を有する中空円筒部材であってもよい。
【００６８】
また上記図７（Ａ）の中空円筒部材を用いることにより、回転時の中空円筒部材４６の振れが少なくなり、また、現像剤は中空円筒４６ａの内壁に押し付けられながら持ち上げられ、中空円筒４６ａ内部で自由落下されながら搬送され、現像装置に補給されたトナーと現像装置内を循環搬送される現像剤とが十分に混合撹拌され、かぶりやトナー飛散（による機内汚れ）の発生が起こらず、また高印字率の画像形成を連続して行った場合でも、ページ内やページ間の濃度むらが発生せず、高画質の画像が得られる現像装置の提供が可能となる。
【００６９】
４．画像形成装置の概略および現像剤
図８は、本発明の現像装置を適用した画像形成装置の一実施形態である、カラー画像形成装置の概略断面構成図である。図８において、画像形成装置ＧＳは、画像形成装置本体ＧＨと画像読取装置ＹＳとから構成される。
【００７０】
画像読取装置ＹＳは、自動原稿送り装置２０１と原稿画像走査露光装置２０２からなり画像形成装置本体ＧＨの上部に画像読取装置ＹＳが設置されている。自動原稿送り装置２０１の原稿台上に載置された原稿ｄは、搬送手段により搬送され、原稿画像走査露光装置２０２の光学系により、原稿の片面または両面の画像が走査露光され、ラインイメージセンサ（例えばＣＣＤ）にて読み込まれる。
【００７１】
ラインイメージセンサにより光電変換されたアナログ信号は、画像処理部において、アナログ処理、Α／Ｄ変換、シェーディング補正、画像圧縮処理等を行った後、画像書き込み部（露光手段）３Ｙ、３Ｍ、３Ｃ、３Ｋに信号として送られる。
【００７２】
自動原稿送り装置２０１は、自動両面原稿搬送手段を備え、原稿載置台上から給送される多数枚の原稿ｄの内容を、連続して一挙に読み取り、図示しない記憶手段に蓄積が可能であり（電子ＲＤＨ機能）、複写機能により多数枚の原稿内容を複写する場合、或いはファクシミリ機能により多数枚の原稿ｄを送信する場合に使用される。
【００７３】
画像形成装置本体ＧＨは、タンデム型カラー画像形成装置と称されるもので、複数組の画像形成部１０Ｙ、１０Ｍ、１０Ｃ、１０Ｋとベルト状の中間転写体６と給紙搬送手段２０〜２３、２５、２６及び定着装置２４とからなる。
【００７４】
イエロー（Ｙ）の画像を形成する画像形成部１０Ｙは、潜像担持体としての感光体ドラム１Ｙの周囲に配置された帯電手段２Ｙ、露光手段３Ｙ、現像装置４Ｙ及びクリーニング手段８Ｙが配置されている。マゼンタ（Ｍ）の画像を形成する画像形成部１０Ｍは、像担持体としての感光体ドラム１Ｍの周囲に配置された帯電手段２Ｍ、露光手段３Ｍ、現像装置４Ｍ及びクリーニング手段８Ｍが配置されている。シアン（Ｃ）の画像を形成する画像形成部１０Ｃは、像担持体としての感光体ドラム１Ｃの周囲に配置された帯電手段２Ｃ、露光手段３Ｃ、現像装置４Ｃ及びクリーニング手段８Ｃが配置されている。黒（Ｋ）の画像を形成する画像形成部１０Ｋは、像担持体としての感光体ドラム１Ｋの周囲に配置された帯電手段２Ｋ、露光手段３Ｋ、現像装置４Ｋ及びクリーニング手段８Ｋが配置されている。帯電手段２Ｙと露光手段３Ｙ、帯電手段２Ｍと露光手段３Ｍ、帯電手段２Ｃと露光手段３Ｃ、帯電手段２Ｋと露光手段３Ｋ、はそれぞれ潜像形成手段を構成している。
【００７５】
中間転写体６は、複数のローラにより巻回され、回動可能に支持されている。
画像形成部１０Ｙ、１０Ｍ、１０Ｃ及び１０Ｋで形成された各色の画像は、回動する中間転写体６上に転写手段７Ｙ、７Ｍ、７Ｃ及び７Ｋにより逐次転写され（１次転写）、合成されたカラー画像が形成される。給紙カセット２０内に収容された記録紙Ｐは、給紙手段２１により給紙され、給紙ローラ２２Ａ、２２Ｂ、２２Ｃ、２２Ｄ、レジストローラ２３等を経て転写手段７Ａに搬送された後、中間転写体６上にて合成されたカラー画像が記録紙Ｐ上に転写される（２次転写）。転写された記録紙Ｐ上のカラー画像は定着装置２４により、定着処理され、排紙ローラ２５に挟持されて機外の排紙トレイ２６上に載置される。
【００７６】
４Ｙ、４Ｍ、４Ｃ、４Ｋはイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、及び黒（Ｋ）の、小粒径のトナーとキャリアからなる２成分現像剤を内包する現像装置であり、５Ｙ、５Ｍ、５Ｃ、５Ｋは、現像装置４Ｙ、４Ｍ、４Ｃ、４Ｋにそれぞれ新規のトナーを補給するトナー補給手段である。
【００７７】
なお、ここで用いられる２成分現像剤の、トナーとキャリアについて説明する。トナーとしては、の体積平均粒径をＤｔ（μｍ）としたとき、
３≦Ｄｔ≦５
である重合トナー（体積平均粒径が３〜５μｍの重合トナー）が好ましく用いられる。小粒径の重合トナーを用いることにより、高解像力であり、濃度の安定した、かぶりの発生が極めて少ない画像形成が可能となる。
【００７８】
重合トナーは以下のような製造方法により製造される。
例えば、懸濁重合または乳化重合等の重合反応と、その後に行われる粒子同士の融着工程を経て得られ、原料モノマーまたはプレポリマーを水系で均一に分散した後に重合させることにより粒度分布及び形状の均一なトナーが得られる。
【００７９】
上記の体積平均粒径は、コールカウンターＴΑ−ＩＩ、コールターマルチサイザー、ＳＬΑＤ１１００（島津製作所製レーザー回折式粒径測定装置）等を用いて測定できる。
【００８０】
体積平均粒径が、３μｍを下回ると、かぶりやトナー飛散が起こりやすくなる。一方、５μｍを越えると、高解像力の画像を形成できなくなる場合がある。
【００８１】
体積平均粒径が３〜５μｍのトナーと共に用いるキャリアとしては、キャリアの体積平均粒径をＤｃ（μｍ）としたとき、
５≦Ｄｃ／Ｄｔ≦１０
であるキャリア（体積平均粒径がトナーの体積平均粒径の５〜１０倍のキャリア）を用いることが好ましい。また、磁化量が２．５〜８．８×１０^−５ｗｂ・ｍ／ｋｇの磁性粒子からなるキャリアが好ましい。このような粒径、磁化量のキャリアを用いることにより、かぶりやトナー飛散を起こさず、キャリア付着も生せず、均一な濃度の画像を安定して形成できる。キャリア粒径がトナー粒径の５倍より小さなキャリアや、磁化量が２．５〜８．８×１０^−５ｗｂ・ｍ／ｋｇを下回るキャリアでは、キャリア付着が生じやすくなることがある。またキャリア粒径が、トナー粒径の１０倍を越える大きなキャリアでは、均一な濃度の画像が形成されない場合があり、磁化量が２．５〜８．８×１０^−５ｗｂ・ｍ／ｋｇを上回るキャリアでは、荒れたハーフトーン画像とる場合がある。
【００８２】
【実施例】
前述の現像剤搬送手段の幅関係の条件、現像剤搬送手段の構造、現像剤搬送手段間の構造関係とを本発明の条件内の場合と、条件外の場合とで比較実験を行った。
【００８３】
なお本実験では、すべて図８に示す画像形成装置を使用した。また、（実施例１）〜（実施例５）については、図２の現像装置を使用し、（実施例６）〜（実施例１０）については、図５の現像装置を使用したものである。また、（実施例１）〜（実施例４）、（実施例６）〜（実施例９）については、図７（Ａ）の通し軸の中空円筒部材を用い、（実施例５）、（実施例１０）については、図７（Ｂ）の分離軸の中空円筒部材を用いた。
【００８４】
（実施例１）
設定条件は、以下の通りである。
【００８５】

上記設定条件にて、印字率５０％の画像パターン（Ａ４横）を連続２００枚出力した。
【００８６】
（実施例１の検討結果）
スタートから連続２００枚出力後に至るまで、かぶりや濃度むらの発生がなく高濃度の画像が安定して得られた。また連続印字終了後に現像装置を画像形成装置外に取り出してトナー飛散状況を観察したが、トナー飛散の発生は全く見られなかった。
【００８７】
（実施例２）
（実施例１）の設定条件のうち、以下の条件のみ変更した。
【００８８】

（実施例２の検討結果）
連続印字に従って画像形成装置の奥側の画像濃度が急激に低下し、引き続いて手前側の画像濃度も低下し、２０枚出力時点で奥側の画像が出なくなった。現像装置を画像形成装置外に取り出して確認したところ、中空円筒４６ａの内部の手前側付近から現像装置の手前側の連通部（即ち、スクリュウオーガ４５に搬送された現像剤が中空円筒部材４６に移動する切り欠き部）に至る領域では現像剤がパッキング状態となっていた。一方中空円筒４６ａの出口付近から奥側の連通部（即ち、中空円筒部材４６に搬送された現像剤がスクリュウオーガ４５に移動する切り欠き部）に至る領域には現像剤が殆どなく、現像ローラ４１の奥側部分では磁気ブラシが形成されていなかった。
【００８９】
（実施例３）
（実施例１）の設定条件のうち、以下の条件のみ変更した。
【００９０】

（実施例３の検討結果）
連続印字に従って画像形成装置の手前側の画像濃度が徐々に低下し、手前や奥の濃度差（濃度むら）が非常に大きくなり、１００枚出力時点で画像形成を中断した。現像装置を画像形成装置外に取り出して確認したところ、現像装置の奥側の連通部（即ち、中空円筒部材４６に搬送された現像剤がスクリュウオーガ４５に移動する切り欠き部）周辺に現像剤が片寄って、手前側の連通部（即ち、スクリュウオーガ４５に搬送された現像剤が中空円筒部材４６に移動する切り欠き部）周辺には現像剤が殆どなく、補給されたトナーが現像剤から遊離した状態で溜まっていた。
【００９１】
（実施例４）
（実施例１）の設定条件のうち、以下の条件のみ変更した。
【００９２】

（実施例４の検討結果）
９０枚出力以降かぶりが発生するようになり、連続印字に伴ってかぶりのレベルは徐々に悪化した。また濃度むらも目立つようになった。連続印字終了後に現像装置を画像形成装置外に取り出して確認したところ、トナー飛散が発生しており、現像装置の下顎にはトナーが堆積し始めていた。
【００９３】
（実施例５）
（実施例１）の設定条件のうち、以下の条件のみ変更した。
【００９４】

（実施例５の検討結果）
中空円筒部材４６の振れが大きく、現像装置枠体５０と中空円筒部材４６の外周とが擦れ、異常音が発生した。そのまま無視して画像を出力したが、段むらが激しく、印字テストを中止した。
【００９５】
（実施例６）
設定条件は、以下の通りである。
【００９６】

上記設定条件にて、印字率５０％の画像パターン（Ａ４横）を連続２００枚出力した。
【００９７】
（実施例６の検討結果）
スタートから連続２００枚出力後に至るまで、かぶりや濃度むらの発生がなく高濃度の画像が安定して得られた。また連続印字終了後に現像装置を画像形成装置外に取り出してトナー飛散状況を観察したが、トナー飛散の発生は全く見られなかった。
【００９８】
（実施例７）
（実施例６）の設定条件のうち、以下の条件のみ変更した。
【００９９】

（実施例７の検討結果）
連続印字に従って画像形成装置の奥側の画像濃度が徐々に低下し、１５枚出力時点で奥側の画像が出なくなった。現像装置を画像形成装置外に取り出して確認したところ、中空円筒４６ａの内部に現像剤がパッキング状態となって詰まっていた。一方奥側の連通部（即ち、中空円筒部材４６に搬送された現像剤がスクリュウオーガ４５に移動する切り欠き部）周辺には現像剤が殆どなく、現像ローラ４１の奥側部分では磁気ブラシが形成されていなかった。
【０１００】
（実施例８）
（実施例６）の設定条件のうち、以下の条件のみ変更した。
【０１０１】

（実施例８の検討結果）
連続印字に従って画像形成装置の手前側の画像濃度が徐々に低下し、手前や奥の濃度差（濃度むら）が非常に大きくなった。連続印字終了後に現像装置を画像形成装置外に取り出して確認したところ、現像装置の奥側の連通部（即ち、中空円筒部材４６に搬送された現像剤がスクリュウオーガ４５に移動する切り欠き部）周辺に現像剤が片寄って、手前側の連通部（即ち、スクリュウオーガ４５に搬送された現像剤が中空円筒部材４６に移動する切り欠き部）周辺には現像剤が殆どなく、補給されたトナーが現像剤から遊離した状態で溜まっていた。
【０１０２】
（実施例９）
（実施例６）の設定条件のうち、以下の条件のみ変更した。
【０１０３】

（実施例９の検討結果）
６０枚出力以降かぶりが発生するようになり、連続印字に伴ってかぶりのレベルは徐々に悪化した。また濃度むらも目立つようになった。連続印字終了後に現像装置を画像形成装置外に取り出して確認したところ、トナー飛散が発生しており、現像装置の下顎にはトナーが堆積し始めていた。
【０１０４】
（実施例１０）
（実施例６）の設定条件のうち、以下の条件のみ変更した。
【０１０５】

（実施例１０の検討結果）
中空円筒部材４６の振れが大きく、現像装置枠体５０と中空円筒部材４６の外周とが擦れ、異常音が発生した。そのまま無視して画像を出力したが、段むらが激しく、印字テストを中止した。
【０１０６】
【発明の効果】
本発明によれば、現像装置に設けられる中空円筒部材と、該中空円筒部材と併せて用いるスクリュウオーガ（現像剤搬送手段）との適正な構造条件を規定することにより、現像装置に補給されたトナーと現像装置内を循環搬送される現像剤との混合、撹拌が十分に行われ、かぶりやトナー飛散による機内汚れが発生しない現像装置の提供が可能となり、また高印字率の画像形成を連続して行った場合でも、ページ内やページ間の濃度むらが発生せず、高画質な画像が得られる現像装置の提供が可能となる。
【図面の簡単な説明】
【図１】本発明に係わる現像剤非一循環構成の現像装置の概略基本構成である。
【図２】図１の現像装置における代表例を示し、現像剤の流れを説明するための概略断面図である。
【図３】図２の現像装置における現像剤担持体の幅と、第１および第２の現像剤搬送手段の幅との関係、およびトナー補給手段の位置を示す図である。
【図４】本発明に係わる現像剤一循環構成の現像装置の概略基本構成である。
【図５】図４の現像装置における代表例を示し、現像剤の流れを説明するための概略断面図である。
【図６】図４の現像装置における現像剤担持体の幅と、第１、第２および第３の現像剤搬送手段の幅との関係、およびトナー補給手段の位置を示す図である。
【図７】各現像装置に設けられる螺旋リブを有する中空円筒部材の構造の概要と中空円筒部材の組み立て方法とを示す図である。
【図８】本発明の現像装置を用いた画像形成装置の一実施形態を示す、カラー画像形成装置の概要断面構成図である。
【符号の説明】
１　感光体ドラム
４１　現像ローラ
４３　現像剤層厚規制板
４４　パドル状の撹拌羽根
４５　スクリュウオーガ（第１の現像剤搬送手段）
４６　中空円筒部材（第２の現像剤搬送手段）
４６ａ　中空円筒
４６ｂ　螺旋リブ
４６ｃ，４６ｄ　軸
４７　マグロール（現像剤回収手段）
４９　スクリュウオーガ（第３の現像剤搬送手段）
５０　現像装置枠体
５４　トナー補給手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a developing device using a two-component developer composed of a toner and a carrier (hereinafter, referred to as a developer), a plurality of developing devices that convey the developer in opposite directions to each other in parallel to the rotation axis direction of the developer carrier are used. In general, the developer is circulated and transported while being mixed and stirred by the developer transporting means.
[0003]
In recent years, with the colorization of image forming apparatuses, opportunities for forming images with a high printing rate have been increasing. This means that the amount of toner used per sheet increases, and the amount of toner replenishment increases accordingly.
[0004]
Further, in order to improve the image quality, toner having a volume average particle diameter of about 3 to 5 μm has been used as a toner constituting the developer. Further, with the reduction in the particle size of the toner, the size of the carrier has also been reduced to about 5 to 10 μm.
[0005]
Specifically, as a developing device using a conventional two-component developer, a screw auger is used as a developer conveying means, and local shearing occurring near the screw auger and circulating flow (moving flow) of powder in a container are performed. In general, a method of stirring while mixing a developer is generally used. In this method, the shape of the screw auger was devised in order to respond to the increase in the amount of toner replenishment due to the above-mentioned high printing rate, in order to speed up the mixing and stirring of the developer and to increase the charge rise of the replenished toner. And the number of revolutions is set high.
[0006]
On the other hand, Japanese Patent Application Laid-Open No. Sho 56-70576 discloses a technique in which a hollow cylindrical member having a spiral rib on the inner periphery is used as a developer conveying means. According to this publication, a cylinder having a spiral rib fixed inside is rotated, and the developer is repeatedly lifted up and dropped, thereby being conveyed to the other end while being sufficiently stirred and mixed. A proposal for preventing the deterioration of the developer is described.
[0007]
[Problems to be solved by the invention]
As described above, a large amount of toner is required for forming an image with a high printing rate, which is increasing in recent years, and the amount of toner to be replenished increases in accordance with the consumption of the toner. When a high printing rate image is continuously formed using a conventional developing device using a two-component developer, the developer circulated through the developing device and the toner replenished in a large amount are sufficiently mixed and stirred. However, the toner is subjected to development (supplied to the developer carrying member) while being in an insufficiently charged state (uncharged or weakly charged), causing problems such as fogging and toner scattering (dirt in the machine). . This problem is particularly conspicuous because the higher the speed of the image forming apparatus, the faster the circulation speed of the developer in the developing apparatus (the shorter the time from the replenishment of the toner to the development). Become.
[0008]
In addition, when the above-described toner and carrier having a small particle size for high image quality are used, the mixing and stirring properties are worse than in the case of the conventional toner and carrier having a large particle size, and the above-described problem is caused. It becomes even more serious.
[0009]
To solve these problems, measures to improve the mixing and agitation performance by increasing the shearing force applied to the developer by devising the shape of the screw auger that has been conventionally performed increase the burden on the developer. However, when the developer is repeatedly used for a long period of time, there is a new problem that the durability of the developer is lost.
[0010]
On the other hand, in the method described in JP-A-56-70576, if the structural conditions of a hollow cylindrical member and a screw auger (developer conveying means) used in combination with the hollow cylindrical member are not appropriate, mixing and stirring, Conveyance (movement of the developer carrying member in the direction of the rotation axis) is not sufficiently performed, and the same fog, toner scattering, density unevenness, and the like are generated as described above.
[0011]
In view of the above problems, the present invention uses a hollow cylindrical member having a helical rib on an inner periphery thereof as a developer transporting unit for mixing, stirring, and transporting a developer, and to sufficiently exhibit its performance. By clarifying the structural conditions, fog, toner scattering, and density can be maintained even when images with a high printing rate are continuously formed using a small particle size toner and a small particle size carrier for high image quality. It is an object of the present invention to provide a developing device that is applied to an image forming apparatus that does not cause a problem such as unevenness.
[0012]
[Means for Solving the Problems]
The object is to mix and stir a developer carrier that carries and transports a developer including a toner and a carrier, a developer supplied to the developer carrier, and a developer recovered from the developer carrier. A first developer conveying unit that conveys the developer in a direction substantially parallel to the rotation axis of the developer carrier, and the developer conveyed by the first developer conveying unit and the supplied toner are mixed. While stirring, a second developer transport unit that transports the developer in a direction substantially parallel to and opposite to the developer transport direction of the first developer transport unit and supplies the developer to the first developer transport unit. In the developing device having the first developer conveying means, a screw auger having a helical rib on the outer periphery of a rotating shaft is provided, and the second developer conveying means has a central portion in the rotating shaft direction on an inner periphery. Has a hollow cylinder with helical ribs The first developer transfer member is formed of a hollow cylindrical member, and a screw auger having a helical rib on the outer periphery on both sides in the rotation axis direction, wherein the width of the developer carrier in the rotation axis direction is W1 (mm), When the width of the screw auger as the means in the rotation axis direction is W2 (mm) and the width of the hollow cylinder constituting the second developer conveying means in the rotation axis direction is W3 (mm), W1 <W3 <W2 Wherein the first developer conveying means or the second developer conveying means supplies replenishing toner to an outer portion of the hollow cylindrical member. ).
[0013]
Further, the above-described object is to provide a developer carrier that carries and transports a developer including a toner and a carrier, a developer supplied to the developer carrier, and a developer recovered from the developer carrier. A first developer conveying unit that conveys the developer in a direction substantially parallel to the rotation axis of the developer carrier while mixing and stirring; and a developer conveyed by the first developer conveying unit and a replenished toner. While mixing and stirring, the second developer transporting unit transports the developer in a direction substantially parallel and opposite to the developer transporting direction by the first developer transporting unit, and supplies the developer to the first developer transporting unit. Wherein the first developer conveying means comprises a screw auger having a helical rib on the outer periphery of a rotating shaft, and the second developer conveying means has a central portion in the rotating shaft direction. Hollow cylinder with spiral ribs around its circumference A screw auger having a spiral rib on the outer periphery on both sides in the direction of the rotation axis, and integrally forming a rotation shaft of the screw auger for supporting the second developer conveying means at both ends. This is achieved by a developing apparatus (second invention).
[0014]
Further, the above-described object is to provide a developer carrier that carries and transports a developer including a toner and a carrier, a developer supplied to the developer carrier, and a developer recovered from the developer carrier. A first developer conveying unit that conveys the developer in a direction substantially parallel to the rotation axis of the developer carrier while mixing and stirring; and a developer conveyed by the first developer conveying unit and a replenished toner. While mixing and stirring, the second developer transporting unit transports the developer in a direction substantially parallel and opposite to the developer transporting direction by the first developer transporting unit, and supplies the developer to the first developer transporting unit. Wherein the first developer transport means comprises a screw auger having a helical rib on the outer periphery of a rotating shaft, and the second developer transport means comprises a helical screw on the inner circumference of a rotary cylinder. It consists of a hollow cylindrical member with ribs, Inner diameter of the hollow cylindrical member is achieved by the developing device (third invention), wherein the greater than the outer diameter of the screw auger.
[0015]
The above object is also achieved by mixing and stirring a developer carrying member that carries and transports a developer including a toner and a carrier, and the developer supplied to the developer carrying member. A first developer transport unit that transports the developer in a direction substantially parallel to the axis, and a developer transport direction of the first developer transport unit while mixing and stirring the developer collected from the developer carrier. A third developer conveying unit that is substantially parallel and conveyed in the same direction, and the developer conveyed by the first and third developer conveying units and the replenished toner are mixed and stirred with the third developer conveying unit. A developing device having a second developer conveying unit that conveys the developer in a direction substantially parallel to and opposite to the conveying direction of the developer by the first and third developer conveying units and supplies the developer to the first developer conveying unit; In the apparatus, the first and third developer transporters Is composed of a screw auger having a helical rib on the outer periphery of the rotating shaft, and the second developer conveying means is a hollow cylinder having a hollow cylinder having a helical rib formed on the inner periphery in the center portion in the direction of the rotating shaft. A screw auger having helical ribs on the outer periphery on both sides in the rotation axis direction, wherein the width of the developer carrier in the rotation axis direction is W11 (mm), and the width of the developer carrier is W11 (mm). The width of the certain screw auger in the rotation axis direction is W21 (mm), the width of the hollow cylinder constituting the second developer conveyance means in the rotation axis direction is W31 (mm), and the third developer conveyance means. When the width of the screw auger in the rotation axis direction is W4 (mm), W11 <W31 <W21 if W4 ≦ W21, and W11 <W31 <W4 if W21 <W4, and Three A developing device configured to supply replenishment toner to an outer portion of the hollow cylindrical member on a downstream side of the image agent conveying unit or on an upstream side of the second developer conveying unit (a fourth invention) Achieved by
[0016]
The above object is also achieved by mixing and stirring a developer carrying member that carries and transports a developer including a toner and a carrier, and the developer supplied to the developer carrying member. A first developer transport unit that transports the developer in a direction substantially parallel to the axis, and a developer transport direction of the first developer transport unit while mixing and stirring the developer collected from the developer carrier. A third developer conveying unit that is substantially parallel and conveyed in the same direction, and the developer conveyed by the first and third developer conveying units and the replenished toner are mixed and stirred with the third developer conveying unit. A developing device having a second developer conveying unit that conveys the developer in a direction substantially parallel to and opposite to the conveying direction of the developer by the first and third developer conveying units and supplies the developer to the first developer conveying unit; In the apparatus, the first and third developer transporters Is composed of a screw auger having a helical rib on the outer periphery of the rotating shaft, and the second developer conveying means is formed of a hollow cylindrical member having a helical rib formed on the inner periphery at a central portion in the rotating shaft direction. The developing device is characterized in that a screw auger having spiral ribs on the outer periphery on both sides in the direction of the rotation axis is formed, and a rotation shaft of the screw auger for supporting the second developer conveying means at both ends is integrally formed. This is achieved by a device (a fifth invention).
[0017]
The above object is also achieved by mixing and stirring a developer carrying member that carries and transports a developer including a toner and a carrier, and the developer supplied to the developer carrying member. A first developer transport unit that transports the developer in a direction substantially parallel to the axis, and a developer transport direction of the first developer transport unit while mixing and stirring the developer collected from the developer carrier. A third developer conveying unit that is substantially parallel and conveyed in the same direction, and the developer conveyed by the first and third developer conveying units and the replenished toner are mixed and stirred with the third developer conveying unit. A developing device having a second developer conveying unit that conveys the developer in a direction substantially parallel to and opposite to the conveying direction of the developer by the first and third developer conveying units and supplies the developer to the first developer conveying unit; In the apparatus, the first and third developer transporters Is composed of a screw auger having a helical rib on the outer periphery of the rotating shaft, and the second developer conveying means is a hollow cylindrical member having a helical rib formed on the inner periphery of the rotating cylinder. This is achieved by a developing device (sixth invention) in which the inner diameter is larger than the outer diameter of the screw auger.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
1. (1) About the stirring structure of the developing device used in the present invention
In the present invention, a hollow cylindrical member having a helical rib fixed to the inner periphery is used as the second developer conveying means, and the two-component developer is put in the hollow cylinder and rotated, so that the inner wall of the container and the powder are mixed. With the frictional force between the developer and the powder, the powder is mixed while being dropped by the action of gravity, and the developer and the replenishment toner, which have been subjected to the development and have a reduced toner concentration, are mixed and stirred. This method is referred to as a container rotating type in the present case.
[0019]
In contrast, a container in which a stirring screw used in a conventional developing device is rotated to mix and mix a two-component developer by local shearing occurring near the screw and circulating flow (moving flow) of powder in the container. There is a fixed type structure.
[0020]
Compared to the fixed container type that mixes by shearing force, the container rotating type mixes by free fall, so that there is an advantage that mixing is good and the burden on the developer is small.
[0021]
1. (2) Conditional expression for the width relation of the developer conveying means in the developing device having a non-circular configuration (claim 1)
In a non-circular developing device described later, the first developer conveying means comprises a screw auger having a helical rib on the outer periphery of the rotating shaft, and the second developer conveying means comprises a central portion in the direction of the rotating shaft. Consists of a hollow cylindrical member having a hollow cylinder with a spiral rib formed on the inner periphery, and a screw auger having a spiral rib on the outer periphery on both sides in the rotation axis direction. The width is W1 (mm), the width in the rotation axis direction of the screw auger as the first developer conveying means is W2 (mm), and the width of the hollow cylinder constituting the second developer conveying means in the rotation axis direction is W3. (Mm)
W1 <W3 <W2
That is, the replenishment toner is supplied to an outer portion of the hollow cylindrical member of the first developer transport unit or the second developer transport unit.
[0022]
By satisfying the above conditional expression, the problem of the present invention can be solved. If the above conditional expression is not satisfied, the toner supplied to the developing device and the developer circulated and transported in the developing device are not sufficiently mixed and stirred, and problems such as fogging and toner scattering occur.
[0023]
1. (3) The structure of the developer conveying means in the developing device having a non-circular configuration.
In a non-circular developing device described later, the first developer conveying means comprises a screw auger having a helical rib on the outer periphery of the rotating shaft, and the second developer conveying means comprises a central portion in the direction of the rotating shaft. A screw auger having a hollow cylindrical member having a spiral rib formed on the inner periphery thereof, and a screw auger having a spiral rib formed on the outer periphery on both sides in the rotation axis direction, and supporting the second developer conveying means at both ends. The rotary shaft of the auger is formed integrally.
[0024]
By satisfying the above structure, the problem of the present invention can be solved. If the above structure is not satisfied, the swing of the hollow cylindrical member during rotation increases, and the replenished toner and the developer circulated and transported in the developing device in the hollow cylindrical member are not sufficiently mixed and stirred, Problems such as fogging and toner scattering occur.
[0025]
1. (4) Structural relationship between developer conveying means in a non-circular developing device (Claim 3)
In a non-circular developing device described later, the first developer conveying means comprises a screw auger having a helical rib on the outer periphery of a rotating shaft, and the second developer conveying means comprises a helical screw on the inner periphery of the rotating cylinder. The inner diameter of the hollow cylindrical member is set to be larger than the outer diameter of the screw auger.
[0026]
By satisfying the above structure, the problem of the present invention can be solved. If the above structure is not satisfied, the developer accumulates during the stirring of the hollow cylindrical member, causing problems such as fogging and toner scattering.
[0027]
1. (5) Conditional expression of the width relation of the developer conveying means in the developing device having a single circulation configuration (Claim 5)
In the developing device having a one-circle configuration described later, the first and third developer conveying means include a screw auger having a helical rib on the outer periphery of a rotating shaft, and the second developer conveying means includes a screw auger in a rotating shaft direction. The central portion is formed of a hollow cylindrical member having a hollow cylinder having a spiral rib formed on the inner periphery, and both side portions in the rotation axis direction are formed of a screw auger having a spiral rib formed on the outer periphery. Is W11 (mm), the width of the screw auger as the first developer conveying means in the rotation axis direction is W21 (mm), and the width of the hollow cylinder constituting the second developer conveyance means in the rotation axis direction is W11 (mm). Is W31 (mm), and the width of the screw auger, which is the third developer conveying means, in the rotation axis direction is W4 (mm).
When W4 ≦ W21,
W11 <W31 <W21
And
If W21 <W4,
W11 <W31 <W4
That is, the replenishment toner is supplied to the outer portion of the hollow cylindrical member on the downstream side of the first or third developer conveying means or on the upstream side of the second developer conveying means.
[0028]
By satisfying the above conditional expression, the problem of the present invention can be solved. If the above conditional expression is not satisfied, the toner supplied to the developing device and the developer circulated and transported in the developing device are not sufficiently mixed and stirred, and problems such as fogging and toner scattering occur.
[0029]
1. (6) The structure of the developer conveying means in the developing device having a single circulation configuration.
In the developing device having a one-circle configuration described later, the first and third developer conveying means include a screw auger having a helical rib on the outer periphery of a rotating shaft, and the second developer conveying means includes a screw auger in a rotating shaft direction. A central portion is formed of a hollow cylindrical member having a spiral rib formed on the inner periphery, and both side portions in the rotation axis direction are formed of a screw auger having a spiral rib formed on the outer periphery, and both ends support the second developer conveying means. The rotary shaft of the screw auger to be formed is integrally formed.
[0030]
By satisfying the above structure, the problem of the present invention can be solved. If the above structure is not satisfied, the swing of the hollow cylindrical member during rotation increases, and the replenished toner and the developer circulated and transported in the developing device in the hollow cylindrical member are not sufficiently mixed and stirred, Problems such as fogging and toner scattering occur.
[0031]
1. (7) Structural relationship between developer conveying means in the developing device having a single circulation configuration.
In a developing device having a one-circle configuration, which will be described later, the first and third developer conveying means include a screw auger having a helical rib on the outer periphery of a rotating shaft, and the second developer conveying means includes an inner circumferential surface of a rotating cylinder. The inner diameter of the hollow cylindrical member is set to be larger than the outer diameter of the screw auger.
[0032]
By satisfying the above structure, the problem of the present invention can be solved. If the above structure is not satisfied, the hollow cylindrical member will accumulate in the course of stirring, causing problems such as fogging and toner scattering.
[0033]
2. Next, a developing device to which the present invention is applied will be described.
FIG. 1 shows three kinds of schematic sectional layouts of a developing device having a non-circulating developer configuration according to the first, second, and third aspects.
[0034]
Means for transporting the developer supplied to the developer carrier and means for transporting the developer recovered from the developer carrier are separately provided, and the developer recovered from the developer carrier is supplied to the toner supply unit ( A configuration in which the developer is not supplied to the developer carrying member until after passing through the toner supplying means is referred to as a developer one-circulation configuration. Before the developer is supplied to the developer carrier again) is referred to as a developer non-circulating configuration.
[0035]
In FIG. 1, reference numeral 41 denotes a developer carrying member (developing roller); 45, a screw auger as a first developer conveying means; and 46, a spiral rib on an inner periphery as a second developer conveying means. A hollow cylindrical member 44 is a paddle-shaped stirring blade serving as a developer supply unit for supplying the developer to the developer carrier. FIGS. 1A and 1B show a developer-peeling type, and FIG. 1C shows a developer-peeling type.
[0036]
FIG. 2 is a more detailed version of FIG. 1A, and outlines the transport and operation of the developer. In FIG. 2,

reference numerals

41, 44, 45, and 46 are the same as those in FIG. Reference numeral 50 denotes a developing device frame, 1 denotes a photosensitive drum, 43 denotes a developer layer thickness regulating plate, 53 denotes a partition, and the partition 53 has a notch. 54 is a toner replenishing means.
[0037]
The developing roller 41 is arranged to face the photosensitive drum 1 carrying an electrostatic latent image, is rotatably supported, and rotates in the direction of the arrow in FIG. The developing roller 41 has a magnet (not shown) inside, and absorbs the developer supplied by a paddle-like stirring blade 44, attaches the developer on the developing roller 41, and supplies the toner to the photosensitive drum. After that, it is transferred to the paddle-like stirring blade 44 in a repulsive magnetic field region of a magnet (not shown) inside the developing roller. The transferred developer is moved to the screw auger 45 by paddle-shaped stirring blades, and is conveyed in the rotation axis direction while being mixed and stirred by the rotation of the screw auger 45, and provided at one end of the partition wall 53. Through the cut-out portion, it is conveyed to a hollow cylindrical member 46 having a helical rib on the inner periphery of the hollow cylinder 46a at the center in the rotation axis direction.
[0038]
In the vicinity of the notch, a toner concentration detecting unit (not shown) is provided. When the toner concentration detected by the detecting unit determines that toner supply is necessary, toner is supplied from the toner supply unit 54. As described above, the hollow cylindrical member 46 rotates the cylinder and the helical rib integrally, lifts the developer by the frictional force between the inner wall of the cylinder and the developer, and mixes and stirs the developer and the supplied toner while freely falling. I do. The developer conveying direction of the hollow cylindrical member 46 is opposite to the conveying direction of the screw auger 45, and the mixed and stirred developer is moved to the screw auger 45 from the other cutout of the partition wall 53. The screw auger 45 mixes the developer from the hollow cylindrical member 46 and the developer delivered from the paddle-shaped stirring blades 44 and conveys the developer in the rotation axis direction while mixing and stirring the developer. Is supplied to the paddle-shaped stirring blade 44. This is an outline of the operation of the developer non-circulating type developing device shown in FIG.
[0039]
The screw auger 45 as the first developer conveying means in the developing device having a non-circular configuration described with reference to FIGS. 1 and 2 has a screw auger having spiral ribs on the outer periphery of both sides in the rotation axis direction. Consists of
[0040]
In the developing device of the non-circular developing type, the screw auger 45 rotates in a direction opposite to the moving direction of the developing roller 41 such that the moving direction of the position facing or close to the developing roller 41 rotates in the opposite direction. .
[0041]
Further, a paddle may be provided on the outer periphery of the screw auger 45 so as to cross the spiral rib parallel to the rotation axis.
[0042]
Further, the hollow cylindrical member 46 and the screw auger 45 are provided with spiral ribs and / or paddle-shaped stirring blades at support shafts at both ends of the hollow cylindrical member 46.
[0043]
FIG. 3 shows the relationship in the rotation axis direction. In FIG. 3,

reference numerals

55 and 56 denote side walls of the developing device, wherein the width of the developing roller 41 in the axial direction is W1, and the spiral rib portion of the screw auger 45 is in the axial direction. When the width is W2 and the axial width of the hollow cylindrical portion of the hollow cylindrical member 46 is W3,
W1 <W3 <W2
And at the outer portion of the side wall 55 indicated by oblique lines on the downstream side of the screw auger 45, or on the outer side portion of the side wall 55 indicated by oblique lines of the hollow cylinder 46a of the hollow cylindrical member 46 on the upstream side of the hollow cylindrical member 46. Supply replenishment toner.
[0044]
As described above, it is possible to provide a developing device in which the toner supplied to the developing device and the developer circulated and conveyed in the developing device are sufficiently mixed and agitated, and the inside of the device due to fogging and toner scattering does not occur.
[0045]
The inner diameter of the hollow cylindrical member 46 is set to be larger than the outer diameter of the screw auger 45. Specifically, as shown in FIG. 2, when the outer diameter of the screw auger 45 is D1 (mm) and the inner diameter of the hollow cylinder 46a of the hollow cylindrical member 46 is D2 (mm),
D1 <D2 ≦ 1.7 × D1
It is preferable that
[0046]
As a result, during the stirring of the hollow cylindrical member, the replenished toner and the developer circulated and conveyed in the developing device do not accumulate, and no fogging or toner scattering occurs.
[0047]
FIG. 4 shows three types of schematic sectional layouts of a developing device having a one-circle developer configuration according to the fifth, sixth, and seventh aspects. In FIG. 4, those having the same functions and names as those in FIG. Here, reference numeral 49 denotes a screw auger as third developer conveying means, and 47 denotes a mag roll as developer collecting means. FIG. 4A shows a developer stripping type, and FIGS. 4B and 4C show a developer stripping type.
[0048]
FIG. 5 is a more detailed version of FIG. 4A, and the outline of the transport and operation of the developer will be described.
[0049]
The developing roller 41 is arranged to face the photosensitive drum 1 carrying an electrostatic latent image, is rotatably supported, and rotates in the direction of the arrow in FIG. The developing roller 41 has a magnet inside, and adsorbs the developer supplied by the paddle-like stirring blade 44, attaches the developer on the developing roller 41, and supplies the toner to the photosensitive drum 1. Thereafter, the developer is transferred to a mag roll 47 as a developer collecting means in a repulsive magnetic field region of a magnet inside the developing roller. The collected developer is moved to the screw auger 49 as the third developer transfer means, is transferred in the rotation axis direction by the rotation of the screw auger 49, and at the downstream end of the screw auger 49 in the rotation axis direction. The developer transported to the screw auger 45 and transported by the screw auger 45 and the developer transported by the screw auger 49 are mixed and agitated and transported in the rotation axis direction of the screw auger 45 to form one of the partition walls 53. Through the notch provided at the end, the sheet is conveyed to the hollow cylindrical member 46 having a spiral rib on the inner periphery of the hollow cylinder 46a at the center in the rotation axis direction.
[0050]
In the vicinity of the notch, a toner concentration detecting unit (not shown) is provided. When the toner concentration detected by the detecting unit determines that toner supply is necessary, toner is supplied from the toner supply unit 54. As described above, the hollow cylindrical member 46 rotates the cylinder and the helical rib integrally, lifts the developer by the frictional force between the inner wall of the cylinder and the developer, and mixes and stirs the developer and the supplied toner while freely falling. I do. The developer conveying direction of the hollow cylindrical member 46 is opposite to the conveying direction of the screw auger 45, and the mixed and stirred developer is moved to the screw auger 45 from the other cutout of the partition wall 53. The screw auger 45 mixes the developer from the hollow cylindrical member 46 and the developer delivered from the paddle-shaped stirring blades 44 and conveys the developer in the rotation axis direction while mixing and stirring the developer. Is supplied to the paddle-shaped stirring blade 44. This is an outline of the operation of the developing device of the developer one circulation type shown in FIG.
[0051]
4 and 5, the screw auger 45 as the first developer conveying means and the screw auger 49 as the third developer conveying means in the one-circulation developing device described in FIGS. It consists of a screw auger with helical ribs on the periphery of the part.
[0052]
In the developer-circulation type developing device, the rotation direction of the screw auger 45 is such that the movement direction of the position facing or close to the development roller 41 rotates in the opposite direction to the movement direction of the development roller 41. .
[0053]
Further, a paddle may be provided on the outer periphery of the screw auger 45 and the screw auger 49 so as to cross the spiral rib parallel to the rotation axis.
[0054]
The direction of rotation of the hollow cylindrical member 46 is such that the direction of movement at a position facing or close to the screw auger 45 is upward from below.
[0055]
Further, the hollow cylindrical member 46 and the screw auger 45 are provided with spiral ribs and / or paddle-shaped stirring blades at support shafts at both ends of the hollow cylindrical member 46.
[0056]
In addition, as described later, the outer diameter of the shaft of the screw auger 45 provided on both sides of the screw auger 45 is set to be larger than the outer diameter of the shaft of the central portion, and the shafts of both ends and the central portion are integrated. Is not in contact with the spiral rib formed on the inner periphery of the hollow cylindrical member 46.
[0057]
FIG. 6 shows the relationship in the direction of the rotation axis. In the figure, 55 and 56 are side walls of the developing device, solid arrows in the figure indicate the flow of the developer described above, and dotted arrows indicate the developer conveyance. This shows the flow of the developer overflowing from the means. Regarding the relationship in the rotation axis direction, the axial width of the developing roller 41 is W11, the axial width of the spiral rib portion of the screw auger 45 is W21, and the axial width of the hollow cylindrical portion of the hollow cylindrical member 46 is W31. When the axial width of the spiral rib portion of the screw auger 49 is W41, the axial width W21 of the spiral rib portion of the screw auger 45 is greater than the axial width W4 of the spiral rib portion of the screw auger 49. When it is large (W4 <W21) (when the screw auger 49 shown in FIGS. 4B and 4C is provided above the screw auger 45),
W11 <W31 <W21
And at the outer portion of the side wall 55 indicated by oblique lines on the downstream side of the screw auger 45, or on the outer side portion of the side wall 55 indicated by oblique lines of the hollow cylinder 46a of the hollow cylindrical member 46 on the upstream side of the hollow cylindrical member 46. Supply replenishment toner.
[0058]
Further, when the axial width W21 of the spiral rib portion of the screw auger 45 is smaller than the axial width W4 of the spiral rib portion of the screw auger 49 (W21 <W4) (the screw auger 45 shown in FIG. 4A). Is provided above the screw auger 49),
W11 <W31 <W4
And the outer portion of the side wall 55 indicated by oblique lines downstream of the screw auger 49 or the outer portion of the side wall 55 indicated by oblique lines of the hollow cylinder 46a of the hollow cylindrical member 46 upstream of the hollow cylindrical member 46. Supply replenishment toner.
[0059]
As described above, it is possible to provide a developing device in which the toner supplied to the developing device and the developer circulated and conveyed in the developing device are sufficiently mixed and agitated, and the inside of the device due to fogging and toner scattering does not occur.
[0060]
In the above, the axial width W21 of the spiral rib portion of the screw auger 45 and the axial width W4 of the spiral rib portion of the screw auger 49 are equal (W21 = W4).
W11 <W31 <W21 or W4
May be set.
[0061]
The inner diameter of the hollow cylindrical member 46 is set to be larger than the outer diameter of the screw auger 45 and the outer diameter of the screw auger 49. Specifically, as shown in FIG. 5, when the outer diameter of the screw auger 45 is D11 (mm), the inner diameter of the hollow cylindrical member 46 is D21 (mm), and the outer diameter of the screw auger 49 is D3 (mm). ,
D3 ≦ D11 and D11 <D21 ≦ 1.7 × D11
It is preferable that
[0062]
As a result, during the stirring of the hollow cylindrical member, the replenished toner and the developer circulated and conveyed in the developing device do not accumulate, and no fogging or toner scattering occurs.
[0063]
3. Outline of structure of hollow cylindrical member, method of assembling, and method of transporting developer
FIG. 7 shows an outline of a structure of a hollow cylindrical member having a spiral rib provided in each developing device and a method of assembling the hollow cylindrical member.
[0064]
As a hollow cylindrical member, as shown in a typical example in FIG. 7A, an integral rotating shaft (no reference numeral) having a shaft 46d attached to the center of a shaft 46c at both ends of a spiral rib 46b is used. The hollow cylindrical member 46 is supported at both ends by an integral rotating shaft. The shaft diameter of the shaft 46c at the end is the same as the inside diameter of the spiral rib 46b, and the shaft diameter of the shaft 46d at the center is smaller than the shaft diameter of the shaft 46c at the end. By narrowing the diameter of the shaft 46d at the center, a space where the developer freely falls when the hollow cylindrical member 46 is rotated is secured. Further, since the shaft 46c at both ends and the shaft 46d at the center are formed as an integral rotation shaft (through shaft), the vibration of the hollow cylindrical member 46 during rotation is prevented from increasing and the vibration is reduced. are doing. The hollow cylindrical member 46 shown in FIG. 7B includes a hollow cylinder 46a, a spiral rib 46b having a single structure, and shafts 46c at both ends of the spiral rib 46b, and the hollow cylinder 46a has a hollow central portion. The spiral rib 46b is attached, and shafts 46c (separation axes) are attached to both ends of the single-structure spiral rib 46b. The hollow cylindrical member 46 shown in FIG. 7B has a configuration in which the shafts 46c at both end portions are separated from each other instead of one through shaft, so that the swing of the hollow cylindrical member 46 becomes large and the hollow cylindrical member 46 becomes hollow. The screw augers on both sides of the cylindrical member 46 and the hollow cylinder 46a in the central portion do not join well, and the developer enters the gap. Also, the hollow cylinder 46a rotates integrally with the shafts 46c at both ends, and the outer periphery of the hollow cylinder 46a should not contact the side wall 55. However, if the runout increases, the outer periphery of the hollow cylinder 46a rubs against the side wall 55. As a result, the hollow cylindrical member 46 may not stably rotate, or shavings of the rubbed portion may be mixed into the developer. As a result, the stirring state of the developer becomes non-uniform, and fogging and toner scattering occur, and the vibration of the stirring part becomes the vibration of the developing device, causing image density unevenness (step unevenness) and character scattering. As described above, the hollow cylindrical member 46 having the structure shown in FIG.
[0065]
An example of a specific method for manufacturing the hollow cylindrical member 46 is performed as follows.
{Circle around (1)} The plate-shaped member is spirally wound around a rotating shaft (no symbol) formed integrally with the inner shaft 46d and the shafts 46c at both ends to form a spiral rib 46b. At this time, the axial length of the spiral rib 46b is longer than that of the hollow cylinder 46a.
[0066]
(2) The spiral rib 46b is inserted into the hollow cylinder 46a, and the spiral rib 46b and both sides of the hollow cylinder 46a are bonded (welded). When the center part of the spiral rib 46b is also to be bonded (welded), a hole is formed in the hollow cylinder 46a, and the hole is closed after bonding (welding).
[0067]
{Circle around (3)} Both ends of the spiral rib 46b and the shafts 46c at both ends are bonded (welded).
Further, the structure of the spiral rib may be a hollow cylindrical member having a double structure (multiple structure) spiral in addition to the single spiral described in FIG.
[0068]
By using the hollow cylindrical member shown in FIG. 7A, the swing of the hollow cylindrical member 46 at the time of rotation is reduced, and the developer is lifted while being pressed against the inner wall of the hollow cylinder 46a. The toner replenished to the developing device and the developer circulated and transported in the developing device are sufficiently mixed and stirred, so that fog and toner scattering (in-machine contamination) do not occur. Even when image formation with a high printing rate is performed continuously, it is possible to provide a developing device that does not generate density unevenness within a page or between pages and can obtain a high-quality image.
[0069]
4. Outline of image forming apparatus and developer
FIG. 8 is a schematic cross-sectional configuration diagram of a color image forming apparatus, which is an embodiment of the image forming apparatus to which the developing device of the present invention is applied. In FIG. 8, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading device YS.
[0070]
The image reading device YS includes an automatic document feeder 201 and a document image scanning exposure device 202, and the image reading device YS is installed above the image forming device main body GH. A document d placed on a document table of the automatic document feeder 201 is conveyed by conveyance means, and an image of one or both sides of the document is scanned and exposed by an optical system of a document image scanning and exposing device 202, and a line image sensor is provided. (For example, a CCD).
[0071]
The analog signal photoelectrically converted by the line image sensor is subjected to analog processing, Α / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then to an image writing unit (exposure unit) 3Y, 3M, 3C, It is sent as a signal to 3K.
[0072]
The automatic document feeder 201 includes an automatic double-sided document feeder, and is capable of continuously reading the contents of a large number of documents d fed from a document mounting table at once, and storing the contents in storage means (not shown). (Electronic RDH function), used when copying the contents of a large number of documents by the copying function, or when transmitting a large number of documents d by the facsimile function.
[0073]
The image forming apparatus main body GH is referred to as a tandem type color image forming apparatus, and includes a plurality of sets of

image forming units

10Y, 10M, 10C, and 10K, a belt-shaped intermediate transfer body 6, and sheet feeding and conveying units 20 to 23, 25, 26 and a fixing device 24.
[0074]
The image forming unit 10Y for forming a yellow (Y) image includes a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 8Y arranged around a photosensitive drum 1Y as a latent image carrier. I have. The image forming unit 10M for forming a magenta (M) image includes a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 8M arranged around a photosensitive drum 1M as an image carrier. . The image forming unit 10C for forming a cyan (C) image includes a charging unit 2C, an exposing unit 3C, a developing unit 4C, and a cleaning unit 8C arranged around a photosensitive drum 1C as an image carrier. . The image forming unit 10K that forms a black (K) image includes a charging unit 2K, an exposing unit 3K, a developing unit 4K, and a cleaning unit 8K arranged around a photosensitive drum 1K as an image carrier. . The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K each constitute a latent image forming unit.
[0075]
The intermediate transfer member 6 is wound around a plurality of rollers and is rotatably supported.
The images of the respective colors formed by the

image forming units

10Y, 10M, 10C and 10K are sequentially transferred (primary transfer) onto the rotating intermediate transfer body 6 by the

transfer units

7Y, 7M, 7C and 7K (primary transfer) and synthesized. A color image is formed. The recording paper P accommodated in the paper feed cassette 20 is fed by the paper feed means 21 and is conveyed to the transfer means 7A via the

paper feed rollers

22A, 22B, 22C, 22D, the registration rollers 23, etc. The color image synthesized on the transfer body 6 is transferred onto the recording paper P (secondary transfer). The transferred color image on the recording paper P is subjected to a fixing process by a fixing device 24, and is sandwiched by paper discharge rollers 25 and placed on a paper discharge tray 26 outside the apparatus.
[0076]

Reference numerals

4Y, 4M, 4C, and 4K denote developing devices that include a two-component developer composed of a toner and a carrier having a small particle diameter of yellow (Y), magenta (M), cyan (C), and black (K). , 5Y, 5M, 5C, and 5K are toner replenishing units that replenish new toner to the developing

devices

4Y, 4M, 4C, and 4K, respectively.
[0077]
The toner and carrier of the two-component developer used here will be described. When the volume average particle diameter of the toner is Dt (μm),
3 ≦ Dt ≦ 5
(Polymerized toner having a volume average particle diameter of 3 to 5 μm) is preferably used. By using a polymerized toner having a small particle size, it is possible to form an image having a high resolution, a stable density, and extremely low occurrence of fog.
[0078]
The polymerized toner is manufactured by the following manufacturing method.
For example, it is obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and a subsequent step of fusing particles to each other.The particle size distribution and shape are obtained by uniformly dispersing the raw material monomer or prepolymer in an aqueous system and then polymerizing. Is obtained.
[0079]
The above-mentioned volume average particle diameter can be measured using a Coal Counter T-II, Coulter Multisizer, SL # D1100 (Shimadzu Corporation laser diffraction particle size analyzer) and the like.
[0080]
When the volume average particle size is less than 3 μm, fogging and toner scattering tend to occur. On the other hand, if it exceeds 5 μm, it may not be possible to form an image with high resolution.
[0081]
As a carrier used together with a toner having a volume average particle diameter of 3 to 5 μm, when the volume average particle diameter of the carrier is Dc (μm),
5 ≦ Dc / Dt ≦ 10
(A carrier having a volume average particle diameter of 5 to 10 times the volume average particle diameter of the toner) is preferably used. Further, the magnetization amount is 2.5 to 8.8 × 10 ^-5 Carriers comprising magnetic particles of wb · m / kg are preferred. By using a carrier having such a particle size and a magnetization amount, an image having a uniform density can be stably formed without causing fogging or toner scattering, causing no carrier adhesion. A carrier having a carrier particle size smaller than 5 times the toner particle size or a magnetization amount of 2.5 to 8.8 × 10 ^-5 If the carrier is less than wb · m / kg, carrier adhesion may easily occur. Further, with a large carrier having a carrier particle size exceeding 10 times the toner particle size, an image having a uniform density may not be formed, and the magnetization amount may be 2.5 to 8.8 × 10 4 ^-5 With a carrier exceeding wb · m / kg, a rough halftone image may be obtained.
[0082]
【Example】
Comparative experiments were conducted on the above-mentioned conditions of the width relationship of the developer conveying means, the structure of the developer conveying means, and the structural relation between the developer conveying means under the conditions of the present invention and under the conditions outside the conditions.
[0083]
In this experiment, the image forming apparatus shown in FIG. 8 was used. Further, for (Example 1) to (Example 5), the developing device of FIG. 2 is used, and for (Example 6) to (Example 10), the developing device of FIG. 5 is used. . For (Example 1) to (Example 4) and (Example 6) to (Example 9), the hollow cylindrical member having the through shaft of FIG. In Example 10), a hollow cylindrical member having a separation shaft shown in FIG. 7B was used.
[0084]
(Example 1)
The setting conditions are as follows.
[0085]

Under the above set conditions, 200 image patterns (A4 landscape) with a printing rate of 50% were continuously output.
[0086]
(Examination result of Example 1)
From the start to after continuous output of 200 sheets, a high-density image was obtained stably without fogging or density unevenness. After the continuous printing, the developing device was taken out of the image forming apparatus and the toner scattering state was observed, but no toner scattering was observed.
[0087]
(Example 2)
Of the setting conditions of the first embodiment, only the following conditions were changed.
[0088]

(Examination result of Example 2)
The image density on the back side of the image forming apparatus sharply decreased in accordance with the continuous printing, and subsequently the image density on the near side also decreased, and no image on the back side appeared at the time of outputting 20 sheets. When the developing device was taken out of the image forming apparatus and confirmed, it was confirmed that the developer conveyed to the screw auger 45 from the near side inside the hollow cylinder 46a to the front side of the developing device (ie, the hollow cylindrical member 46). The developer was in a packing state in a region reaching the notch (moving notch). On the other hand, there is almost no developer in the region from the vicinity of the exit of the hollow cylinder 46a to the communication part on the back side (that is, the notch where the developer conveyed to the hollow cylinder member 46 moves to the screw auger 45). No magnetic brush was formed on the back side of 41.
[0089]
(Example 3)
Of the setting conditions of the first embodiment, only the following conditions were changed.
[0090]

(Examination result of Example 3)
The image density on the front side of the image forming apparatus gradually decreased in accordance with the continuous printing, and the density difference (density unevenness) on the front side and the back side became very large, and the image formation was interrupted at the time of outputting 100 sheets. When the developing device was taken out of the image forming apparatus and checked, it was confirmed that the developer was located around the communicating portion on the back side of the developing device (that is, the notch portion where the developer conveyed to the hollow cylindrical member 46 moved to the screw auger 45). Is deviated, and there is almost no developer around the communication portion on the front side (that is, the notch portion where the developer conveyed to the screw auger 45 moves to the hollow cylindrical member 46), and the replenished toner is removed from the developer. It had accumulated in a free state.
[0091]
(Example 4)
Of the setting conditions of the first embodiment, only the following conditions were changed.
[0092]

(Examination result of Example 4)
Fog began to occur after 90 sheets were output, and the fog level gradually deteriorated with continuous printing. In addition, density unevenness became noticeable. After the continuous printing was completed, the developing device was taken out of the image forming apparatus and checked. As a result, toner scattering had occurred, and toner had started to accumulate on the lower jaw of the developing device.
[0093]
(Example 5)
Of the setting conditions of the first embodiment, only the following conditions were changed.
[0094]

(Examination result of Example 5)
The vibration of the hollow cylindrical member 46 was large, and the developing device frame 50 and the outer periphery of the hollow cylindrical member 46 rubbed, and an abnormal sound was generated. The image was output, ignoring it as it was, but the printing unevenness was severe and the printing test was stopped.
[0095]
(Example 6)
The setting conditions are as follows.
[0096]

Under the above set conditions, 200 image patterns (A4 landscape) with a printing rate of 50% were continuously output.
[0097]
(Examination result of Example 6)
From the start to after continuous output of 200 sheets, a high-density image was obtained stably without fogging or density unevenness. After the continuous printing, the developing device was taken out of the image forming apparatus and the toner scattering state was observed, but no toner scattering was observed.
[0098]
(Example 7)
Of the setting conditions of (Example 6), only the following conditions were changed.
[0099]

(Study result of Example 7)
The image density on the back side of the image forming apparatus gradually decreased according to the continuous printing, and the image on the back side did not appear at the time of output of 15 sheets. When the developing device was taken out of the image forming apparatus and checked, it was found that the developer was packed in the hollow cylinder 46a in a packing state. On the other hand, there is almost no developer around the communication part on the back side (that is, the notch part where the developer conveyed to the hollow cylindrical member 46 moves to the screw auger 45), and the magnetic brush is provided on the back side part of the developing roller 41. Had not been formed.
[0100]
(Example 8)
Of the setting conditions of (Example 6), only the following conditions were changed.
[0101]

(Examination result of Example 8)
The image density on the front side of the image forming apparatus gradually decreased according to the continuous printing, and the difference in density between the front and the back (density unevenness) became extremely large. After the continuous printing was completed, the developing device was taken out of the image forming apparatus and checked. As a result, a communication portion on the back side of the developing device (that is, a notch portion in which the developer conveyed to the hollow cylindrical member 46 moved to the screw auger 45). The developer is biased to the periphery, and there is almost no developer around the communicating portion on the front side (that is, the notch portion where the developer conveyed to the screw auger 45 moves to the hollow cylindrical member 46), and the replenished toner Accumulated in a state of being separated from the developer.
[0102]
(Example 9)
Of the setting conditions of (Example 6), only the following conditions were changed.
[0103]

(Examination result of Example 9)
Fog began to occur after the output of 60 sheets, and the level of fog gradually deteriorated with continuous printing. In addition, density unevenness became noticeable. After the continuous printing was completed, the developing device was taken out of the image forming apparatus and checked. As a result, toner scattering had occurred, and toner had started to accumulate on the lower jaw of the developing device.
[0104]
(Example 10)
Of the setting conditions of (Example 6), only the following conditions were changed.
[0105]

(Examination result of Example 10)
The vibration of the hollow cylindrical member 46 was large, and the developing device frame 50 and the outer periphery of the hollow cylindrical member 46 rubbed, and an abnormal sound was generated. The image was output, ignoring it as it was, but the printing unevenness was severe and the printing test was stopped.
[0106]
【The invention's effect】
According to the present invention, the hollow cylindrical member provided in the developing device and the screw auger (developer conveying means) used in conjunction with the hollow cylindrical member are provided with appropriate structural conditions, whereby the hollow cylindrical member is supplied to the developing device. Sufficient mixing and agitation of the toner and the developer circulated and transported in the developing device makes it possible to provide a developing device free from fogging and in-machine contamination due to toner scattering, and also enables continuous image formation with a high printing rate. Even in the case of performing the above, it is possible to provide a developing device capable of obtaining a high-quality image without generating density unevenness within a page or between pages.
[Brief description of the drawings]
FIG. 1 is a schematic basic configuration of a developing device of a non-circulating developer configuration according to the present invention.
FIG. 2 is a schematic cross-sectional view illustrating a representative example of the developing device of FIG. 1 and illustrating a flow of a developer.
FIG. 3 is a diagram illustrating a relationship between a width of a developer carrier and widths of first and second developer conveying units and a position of a toner replenishing unit in the developing device of FIG. 2;
FIG. 4 is a schematic basic configuration of a developing device of a developer circulation type according to the present invention.
FIG. 5 is a schematic cross-sectional view illustrating a representative example of the developing device in FIG. 4 and illustrating a flow of a developer.
6 is a diagram illustrating a relationship between a width of a developer carrier and widths of first, second, and third developer conveying units in the developing device of FIG. 4, and a position of a toner replenishing unit;
FIG. 7 is a diagram showing an outline of a structure of a hollow cylindrical member having a spiral rib provided in each developing device and a method of assembling the hollow cylindrical member.
FIG. 8 is a schematic cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus using the developing device of the present invention.
[Explanation of symbols]
1 Photoconductor drum
41 Developing roller
43 Developer layer thickness regulation plate
44 paddle-shaped stirring blade
45 screw auger (first developer conveying means)
46 hollow cylindrical member (second developer conveying means)
46a hollow cylinder
46b spiral rib
46c, 46d axis
47 Magroll (developer collecting means)
49 screw auger (third developer conveying means)
50 Developing device frame
54 Toner replenishing means

Claims

A developer carrying member that carries and conveys a developer including a toner and a carrier,
A first developing device that transports the developer supplied to the developer carrier and the developer recovered from the developer carrier in a direction substantially parallel to the rotation axis of the developer carrier while mixing and stirring. Agent delivery means,
While mixing and agitating the developer conveyed by the first developer conveying means and the replenished toner, the developer is conveyed in a direction substantially parallel to and opposite to the developer conveying direction by the first developer conveying means. And a second developer conveying means for supplying to the first developer conveying means,
The first developer conveying means includes a screw auger having a helical rib on the outer periphery of a rotating shaft,
The second developer conveying means includes a hollow cylindrical member having a hollow cylinder having a spiral rib formed on an inner periphery at a central portion in a rotation axis direction, and spiral ribs formed on both sides in a rotation axis direction on an outer periphery. Consisting of a screw auger with
The width in the rotation axis direction of the developer carrier is W1 (mm), the width in the rotation axis direction of the screw auger as the first developer conveyance means is W2 (mm), and the second developer conveyance means is W1 (mm). When the width of the constituting hollow cylinder in the rotation axis direction is W3 (mm),
W1 <W3 <W2
And
The developing device according to claim 1, wherein a supply toner is supplied to an outer portion of said hollow cylindrical member of said first developer transport means or said second developer transport means.

A developer carrying member that carries and conveys a developer including a toner and a carrier,
A first developing device that transports the developer supplied to the developer carrier and the developer recovered from the developer carrier in a direction substantially parallel to the rotation axis of the developer carrier while mixing and stirring. Agent delivery means,
While mixing and agitating the developer conveyed by the first developer conveying means and the replenished toner, the developer is conveyed in a direction substantially parallel to and opposite to the developer conveying direction by the first developer conveying means. And a second developer conveying means for supplying to the first developer conveying means,
The first developer conveying means includes a screw auger having a helical rib on the outer periphery of a rotating shaft,
The second developer conveying means is a screw auger having a hollow cylindrical member having a spiral rib formed on the inner periphery at a central portion in the rotation axis direction, and having spiral ribs on both outer periphery in the rotation axis direction. Consisting of
A developing device, wherein a rotary shaft of a screw auger for supporting the second developer conveying means at both ends is integrally formed.

A developer carrying member that carries and conveys a developer including a toner and a carrier,
A first developing device that transports the developer supplied to the developer carrier and the developer recovered from the developer carrier in a direction substantially parallel to the rotation axis of the developer carrier while mixing and stirring. Agent delivery means,
While mixing and agitating the developer conveyed by the first developer conveying means and the replenished toner, the developer is conveyed in a direction substantially parallel to and opposite to the developer conveying direction by the first developer conveying means. And a second developer conveying means for supplying to the first developer conveying means,
The first developer conveying means includes a screw auger having a helical rib on the outer periphery of a rotating shaft,
The second developer conveying means is formed of a hollow cylindrical member having a spiral rib formed on the inner periphery of the rotating cylinder,
The developing device according to claim 1, wherein an inner diameter of said hollow cylindrical member is larger than an outer diameter of said screw auger.

When the outer diameter of the screw auger as the first developer conveying means is D1 (mm) and the inner diameter of the hollow cylindrical member as the second developer conveying means is D2 (mm),
D1 <D2 ≦ 1.7 × D1
The developing device according to claim 3, wherein

A developer carrying member that carries and conveys a developer including a toner and a carrier,
A first developer transport unit that transports the developer supplied to the developer carrier in a direction substantially parallel to a rotation axis of the developer carrier while mixing and stirring;
While mixing and stirring the developer collected from the developer carrying member, a third developer transport unit that transports the developer substantially in parallel with and in the same direction as the developer transport direction of the first developer transport unit;
While mixing and agitating the developer transported by the first and third developer transporting units and the supplied toner, the developer transporting direction by the first and third developer transporting units is substantially the same as that of the first and third developer transporting units. A second developer transport unit that transports the developer in parallel and in the opposite direction, and supplies the developer to the first developer transport unit.
The first and third developer conveying means include a screw auger having a helical rib on the outer periphery of a rotating shaft,
The second developer conveying means includes a hollow cylindrical member having a hollow cylinder having a spiral rib formed on an inner periphery at a central portion in a rotation axis direction, and spiral ribs formed on both sides in a rotation axis direction on an outer periphery. Consisting of a screw auger with
The width of the developer carrier in the rotation axis direction is W11 (mm), the width of the screw auger as the first developer conveyance unit in the rotation axis direction is W21 (mm), and the width of the second developer conveyance unit is W21 (mm). When the width of the constituting hollow cylinder in the rotation axis direction is W31 (mm), and the width of the screw auger as the third developer conveying means in the rotation axis direction is W4 (mm),
When W4 ≦ W21,
W11 <W31 <W21
And
If W21 <W4,
W11 <W31 <W4
And
Developing means for supplying replenishment toner to an outer portion of the hollow cylindrical member on the downstream side of the first or third developer conveying means or on the upstream side of the second developer conveying means; apparatus.

A developer carrying member that carries and conveys a developer including a toner and a carrier,
A first developer transport unit that transports the developer supplied to the developer carrier in a direction substantially parallel to a rotation axis of the developer carrier while mixing and stirring;
While mixing and stirring the developer collected from the developer carrying member, a third developer transport unit that transports the developer substantially in parallel with and in the same direction as the developer transport direction of the first developer transport unit;
While mixing and agitating the developer transported by the first and third developer transporting units and the supplied toner, the developer transporting direction by the first and third developer transporting units is substantially the same as that of the first and third developer transporting units. A second developer transport unit that transports the developer in parallel and in the opposite direction, and supplies the developer to the first developer transport unit.
The first and third developer conveying means include a screw auger having a helical rib on the outer periphery of a rotating shaft,
The second developer conveying means is a screw auger having a hollow cylindrical member having a spiral rib formed on the inner periphery at a central portion in the rotation axis direction, and having spiral ribs on both outer periphery in the rotation axis direction. Consisting of
A developing device, wherein a rotary shaft of a screw auger for supporting the second developer conveying means at both ends is integrally formed.

A developer carrying member that carries and conveys a developer including a toner and a carrier,
A first developer transport unit that transports the developer supplied to the developer carrier in a direction substantially parallel to a rotation axis of the developer carrier while mixing and stirring;
While mixing and stirring the developer collected from the developer carrying member, a third developer transport unit that transports the developer substantially in parallel with and in the same direction as the developer transport direction of the first developer transport unit;
While mixing and agitating the developer transported by the first and third developer transporting units and the supplied toner, the developer transporting direction by the first and third developer transporting units is substantially the same as that of the first and third developer transporting units. A second developer transport unit that transports the developer in parallel and in the opposite direction, and supplies the developer to the first developer transport unit.
The first and third developer conveying means include a screw auger having a helical rib on the outer periphery of a rotating shaft,
The second developer conveying means is formed of a hollow cylindrical member having a spiral rib formed on the inner periphery of the rotating cylinder,
The developing device according to claim 1, wherein an inner diameter of said hollow cylindrical member is larger than an outer diameter of said screw auger.

The outer diameter of the screw auger as the first developer transport means is D11 (mm), the inner diameter of the hollow cylindrical member as the second developer transport means is D21 (mm), and the third developer transport means is When the outside diameter of the screw auger is D3 (mm),
D3 ≦ D11 and D11 <D21 ≦ 1.7 × D11
The developing device according to claim 7, wherein

The rotating shafts of the screw augers provided on both sides of the second developer conveying means are configured such that the outer diameter of both sides is larger than the outer diameter of the central portion, and the central portion of the rotating shaft and the inside of the hollow cylindrical member The developing device according to claim 2, wherein the developing device does not come into contact with a spiral rib formed around the periphery.

The rotation direction of the second developer transport unit is such that, when viewed from the rotation axis direction of the first developer transport unit and the second developer transport unit, the rotation direction of the second developer transport unit is lower on the side sandwiched by the rotary shaft. The developing device according to any one of claims 1 to 9, wherein the developing device rotates in a direction from above to above.

The rotation direction of the first developer conveying means is clockwise when the developer carrier is clockwise when viewed from the rotation axis direction, and when the developer carrier is counterclockwise. The developing device according to claim 1, wherein the developing device is counterclockwise.

12. The device according to claim 1, wherein the first developer conveying means has a paddle provided on an outer periphery of a rotating shaft so as to cross the spiral rib in parallel with the rotating shaft. 2. The developing device according to claim 1.

A paddle-shaped stirring blade that supplies the developer conveyed by the first developer conveying unit between the first developer conveying unit and the developer carrier is supplied to the developer carrier. The developing device according to claim 1, further comprising a developer supply unit.

Developer recovery for recovering the developer carried on the developer carrier between the third developer carrier and the developer carrier to the third developer carrier. The developing device according to claim 1, further comprising a unit.

When the volume average particle diameter of the toner is Dt (μm), 3 ≦ Dt ≦ 5
The developing device according to claim 1, wherein the toner is:

When the volume average particle diameter of the carrier is Dc (μm), 5 ≦ Dc / Dt ≦ 10
The developing device according to claim 1, wherein a carrier having the following formula is used.