JP2018173488A

JP2018173488A - Developing device

Info

Publication number: JP2018173488A
Application number: JP2017070481A
Authority: JP
Inventors: 良平寺田; Ryohei Terada
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2017-03-31
Filing date: 2017-03-31
Publication date: 2018-11-08

Abstract

PROBLEM TO BE SOLVED: To provide a developing device with which it is possible to suppress the scattering of toner in a developer while suppressing an increase in cost, irrespective of whether a development voltage has an AC component, and reduce the contamination of toner in an image forming device, thereby lowering maintenance frequency.SOLUTION: The developing device comprises: a developer carrier provided with a magnet roll; a separation wall, located at a position spaced apart from the developer carrier, for separating a first passage along a first direction and a second passage along a second direction different from the first direction with regard to an air flow generated by rotation of a developer carrier; a first electrode provided on the separation wall at a position opposite the developer carrier and not spaced apart from the separation wall; and a second electrode provided on the first electrode at a position opposite the developer carrier and spaced apart from the first electrode. The first electrode is provided with a first potential that is same as the developer carrier, and the second electrode is provided with a second potential smaller in absolute value than the absolute value of potential of the first electrode.SELECTED DRAWING: Figure 6

Description

本発明は、現像装置に関し、複写機、プリンタ、ＦＡＸ、或いは、これら複数の機能を備えた複合機等の画像形成装置に好適なものである。 The present invention relates to a developing device, and is suitable for an image forming apparatus such as a copying machine, a printer, a FAX, or a multifunction machine having a plurality of these functions.

オフィスやオンデマンドの軽印刷で用いられるレーザープリンタやレーザー複合機などと呼ばれる電子写真方式を用いた画像形成装置において、現像装置として高速出力や高画質出力を行う機種では二成分現像方式を採用しているものがある。二成分現像装置では、現像装置内でトナーと磁性粒子であるキャリアを攪拌搬送することで摩擦帯電させ、現像部では静電潜像に対しトナーのみを付着させる。 In image forming devices using electrophotography called laser printers and laser multifunction devices used in office and on-demand light printing, the two-component development method is used for models that produce high-speed output and high-quality output as developing devices. There is something that is. In the two-component developing device, the toner and the magnetic particle carrier are agitated and conveyed in the developing device to be frictionally charged, and in the developing unit, only the toner is attached to the electrostatic latent image.

画像形成装置では、出力画像の高速化や高画質化を求められるとともに、メンテナンスの簡略化が求められている。このメンテナンス簡略化の中の一つとして、画像形成装置内部のトナー汚染の低減化が挙げられる。画像形成装置内部がトナー汚染すると、出力画像の汚れなどの不良とともに、現像ユニットや感光ドラムユニットの交換時に清掃が必要になる。また、各駆動系に付着した場合、滑りなどが発生し、正確な駆動ができなくなってしまう。 In the image forming apparatus, it is required to increase the speed and quality of the output image and to simplify the maintenance. One of the maintenance simplifications is reduction of toner contamination inside the image forming apparatus. When the inside of the image forming apparatus is contaminated with toner, it is necessary to clean the replacement of the developing unit and the photosensitive drum unit as well as defects such as contamination of the output image. In addition, when it adheres to each drive system, slipping or the like occurs and accurate driving cannot be performed.

画像形成装置内部のトナー汚染の原因の一つとして、二成分現像ではトナーが現像装置内から飛散してしまうトナー飛散という問題がある。通常、現像装置内部では上述したようにトナーとキャリアとが摩擦帯電しているため、トナーとキャリアは静電気力で付着している。しかし、何らかの衝撃でこの付着が解放され、キャリアから遊離したトナーが現像装置内部から空気とともに排出されてしまう場合にトナー飛散となる。 As one of the causes of toner contamination in the image forming apparatus, there is a problem of toner scattering in which toner is scattered from the developing apparatus in the two-component development. Usually, since the toner and the carrier are frictionally charged in the developing device as described above, the toner and the carrier are adhered by electrostatic force. However, when this adhesion is released by some impact and the toner released from the carrier is discharged together with air from the inside of the developing device, toner scattering occurs.

このトナー飛散に対する対策として、トナーは摩擦帯電により電荷を有しているため、現像装置内部からの空気排出経路に電圧を印加することで、排出空気からトナー取り除くことが従来より知られている。 As a countermeasure against the scattering of toner, it is conventionally known that toner has a charge due to frictional charging, and therefore, the toner is removed from the discharged air by applying a voltage to the air discharge path from the inside of the developing device.

特許文献１には、現像スリーブに導電性部材を対向配置させ、導電性部材に電源より現像剤の摩擦帯電極性と同極性の電圧を印加するものが記載されている。そして。これにより導電部材と現像スリーブ間に電位差を発生させ、トナーが現像スリーブ方向に押し付けられて、排出空気からトナーが取り除かれることが記載されている。この結果、トナー飛散が効果的に抑制できる。 Japanese Patent Application Laid-Open No. H10-228561 describes a configuration in which a conductive member is disposed opposite to a developing sleeve, and a voltage having the same polarity as the triboelectric charging polarity of the developer is applied to the conductive member from a power source. And then. This describes that a potential difference is generated between the conductive member and the developing sleeve, the toner is pressed toward the developing sleeve, and the toner is removed from the discharged air. As a result, toner scattering can be effectively suppressed.

特開平８−１７１２８２号公報JP-A-8-171282

しかしながら、特許文献１のような方式は非常に効果的な反面、導電性部への電圧印加のために現像電圧と別に電源が必要となりコストの増加を招く。そして、このコスト上昇を抑える手段として、現像電圧として直流電圧に交流電圧を重畳する形式のものでは、専用の基板を設置して交流成分を整流し直流成分を取り出すことが必要となる。 However, while the method as disclosed in Patent Document 1 is very effective, a power source is required separately from the development voltage for applying a voltage to the conductive portion, resulting in an increase in cost. As a means for suppressing this cost increase, in the type in which an AC voltage is superimposed on a DC voltage as a developing voltage, it is necessary to install a dedicated substrate to rectify the AC component and extract the DC component.

本発明の目的は、現像電圧の交流成分の有無に拘らず、コストの増加を抑えながら現像剤におけるトナー飛散を抑制し、画像形成装置内のトナー汚染を低減することでメンテナンス頻度を下げることができる現像装置を提供することにある。 An object of the present invention is to reduce the frequency of maintenance by suppressing toner scattering in the developer while suppressing an increase in cost regardless of the presence or absence of an AC component of the development voltage, and reducing toner contamination in the image forming apparatus. An object of the present invention is to provide a developing device that can be used.

上記目的を達成するため、本発明に係る現像装置は、内部にマグネットロールとして像担持体との最近接部である現像領域に対応する第１の磁極と、前記第１の磁極と異なる第２の磁極を備え、現像剤を担持して回転可能な現像剤担持体と、前記現像剤担持体から離間した位置にあって、前記現像剤担持体の回転により生成される気流に関して、第１の方向に沿う第１の流路と、前記第１の方向と異なる第２の方向に沿う第２の流路と、を分離する分離壁と、前記分離壁に対し前記現像剤担持体と反対側で前記分離壁から離間しない位置に設けられる第１の電極と、前記第１の電極に対し前記現像剤担持体と反対側であって前記第１の電極から離間した位置に設けられる第２の電極と、を有し、前記第１の電極は、前記現像剤担持体と同じ第１の電位を備え、前記第２の電極は、前記第１の電極の電位の絶対値よりも小さい絶対値の第２の電位を備えることを特徴とする。 In order to achieve the above object, a developing device according to the present invention includes a first magnetic pole corresponding to a developing region which is a closest part to an image carrier as a magnet roll, and a second magnetic pole different from the first magnetic pole. A developer carrying body that can carry and rotate with a developer, and an air flow that is spaced apart from the developer carrying body and is generated by the rotation of the developer carrying body. A separation wall that separates a first flow path along a direction and a second flow path along a second direction different from the first direction, and the side opposite to the developer carrier relative to the separation wall A first electrode provided at a position not separated from the separation wall, and a second electrode provided at a position opposite to the developer carrying member with respect to the first electrode and separated from the first electrode. The first electrode is the same as the developer carrier. Comprises a potential, the second electrode, characterized in that it comprises a second potential of absolute value smaller absolute value than the potential of the first electrode.

本発明によれば、現像電圧の交流成分の有無に拘らず、コストの増加を抑えながら現像剤におけるトナー飛散を抑制し、画像形成装置内のトナー汚染を低減することでメンテナンス頻度を下げることができる現像装置を提供することができる。 According to the present invention, regardless of the presence or absence of an AC component of the development voltage, it is possible to reduce toner maintenance in the image forming apparatus by suppressing toner scattering while suppressing an increase in cost and reducing toner contamination in the image forming apparatus. A developing device capable of being provided can be provided.

本発明の実施形態に係る現像装置を搭載した画像形成装置を説明する図1 is a diagram illustrating an image forming apparatus equipped with a developing device according to an embodiment of the present invention. 本発明の実施形態に係る現像装置の長手断面を説明する図The figure explaining the longitudinal cross-section of the image development apparatus concerning embodiment of this invention. 第１の実施形態に係る現像装置の短手断面を説明する図The figure explaining the short section of the development device concerning a 1st embodiment. 第１の実施形態に係る現像装置の長手方向における分離壁の端部の効果を説明する図The figure explaining the effect of the edge part of the separation wall in the longitudinal direction of the developing device which concerns on 1st Embodiment. 第１の実施形態における飛散防止電圧を説明する図The figure explaining the scattering prevention voltage in 1st Embodiment 第１の実施形態における機能・作用を説明する図The figure explaining the function and effect | action in 1st Embodiment 第１の実施形態の検証実験結果を示す図The figure which shows the verification experiment result of 1st Embodiment 第２の実施形態に係る現像装置の短手断面を説明する図The figure explaining the short section of the development device concerning a 2nd embodiment. 従来構成の現像装置の短手断面を説明する図The figure explaining the short section of the development device of the conventional composition 従来構成の現像装置の短手断面で現像剤坦持体近傍の気流を説明する図The figure explaining the airflow near a developer carrier in the short section of the development device of the conventional composition 従来構成の飛散防止電圧を説明する図The figure explaining the scattering prevention voltage of a conventional structure 従来構成の飛散防止電圧の印加を説明する図The figure explaining the application of the scattering prevention voltage of a conventional structure

以下に、本発明の実施の形態を添付の図面に基づいて詳細に説明する。 Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

《第１の実施形態》
（画像形成装置の全体構成）
先ず図１を用い、画像形成装置全体の動作を説明する。この画像形成装置は、ＰＣなどの情報端末からの信号に従って画像を形成し出力することを目的とした、二成分接触現像方式の電子写真方式のカラーレーザビームプリンタである。 << First Embodiment >>
(Overall configuration of image forming apparatus)
First, the operation of the entire image forming apparatus will be described with reference to FIG. This image forming apparatus is a two-component contact developing type electrophotographic color laser beam printer intended to form and output an image in accordance with a signal from an information terminal such as a PC.

図１の構成では、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｋ）の４色によるカラー画像形成装置の構成例である。この画像形成装置では、Ｙ、Ｍ、Ｃ、Ｋの各ステーションの像坦持体上にそれぞれの色に対応した画像を造り、中間転写体２４上に４色の画像を重ねた後、一括で記録体である紙面に転写し定着しカラー画像を出力する方式を用いている。 The configuration of FIG. 1 is a configuration example of a color image forming apparatus using four colors of yellow (Y), magenta (M), cyan (C), and black (K). In this image forming apparatus, an image corresponding to each color is created on the image carrier of each of the Y, M, C, and K stations, and after the four color images are overlaid on the intermediate transfer member 24, the images are collectively collected. A system is used in which a color image is output after being transferred and fixed on a paper surface as a recording medium.

図１に示すＹ、Ｍ、Ｃ、Ｋの各ステーションは、それぞれほぼ同様の構成である。以下の説明において、例えば現像装置１とあれば、Ｙ、Ｍ、Ｃ、Ｋ各ステーションにおける現像装置１Ｙ、現像装置１Ｍ、現像装置１Ｃ、現像装置１Ｋを共通して指すものとする。 The stations Y, M, C, and K shown in FIG. 1 have substantially the same configuration. In the following description, for example, with the developing device 1, the developing device 1Y, the developing device 1M, the developing device 1C, and the developing device 1K in each of the Y, M, C, and K stations are commonly referred to.

ここで、各ステーションでの画像形成動作を説明する。図中の１０が、本画像形成装置における像担持体の感光ドラムである。この感光ドラム１０は、まず帯電部２１によって一様に表面を負電荷に帯電される。次に、感光ドラム１０に対しＰＣなどからの画像情報に応じた位置に光源２２からレーザー光またはＬＥＤ光で露光されることにより、感光ドラム１０は内部の電荷生成層において正電荷を生成する。生成された正電荷が、電荷輸送層を通じ感光ドラム表面に輸送されて前記負電荷を打ち消し、感光ドラム１０は表面に画像情報に応じた静電潜像を形成する。 Here, an image forming operation at each station will be described. In the figure, reference numeral 10 denotes a photosensitive drum of an image carrier in the image forming apparatus. First, the surface of the photosensitive drum 10 is uniformly charged to a negative charge by the charging unit 21. Next, the photosensitive drum 10 is exposed to laser light or LED light from the light source 22 at a position corresponding to image information from a PC or the like, so that the photosensitive drum 10 generates a positive charge in the internal charge generation layer. The generated positive charge is transported to the surface of the photosensitive drum through the charge transport layer to cancel the negative charge, and the photosensitive drum 10 forms an electrostatic latent image corresponding to the image information on the surface.

感光ドラム１０は、現像部で静電潜像に着色樹脂であるトナーを付着され、トナー像を形成する。この現像過程及びこれを実行する現像装置１については、後に詳述する。表面にトナー像を形成された感光ドラム１０は、一次転写装置２３によって、圧力と静電気力を用い中間転写体２４にトナー像を転写する。転写後、感光ドラム１０は、クリーニング装置２６によって中間転写体２４に転写されずに残ったトナーが除去される。その後、感光ドラム１０は除電装置５１の光源によって一様に露光され、全域に渡り正電荷を生成し、感光ドラム１０表面は除電され、静電潜像が消去される。 The photosensitive drum 10 forms a toner image by attaching toner, which is a colored resin, to the electrostatic latent image at the developing unit. The developing process and the developing device 1 that executes the developing process will be described in detail later. The photosensitive drum 10 having the toner image formed on the surface transfers the toner image to the intermediate transfer member 24 by the primary transfer device 23 using pressure and electrostatic force. After the transfer, the toner remaining on the photosensitive drum 10 without being transferred to the intermediate transfer member 24 by the cleaning device 26 is removed. Thereafter, the photosensitive drum 10 is uniformly exposed by the light source of the static eliminator 51 to generate a positive charge over the entire area, the surface of the photosensitive drum 10 is neutralized, and the electrostatic latent image is erased.

Ｙ、Ｍ、Ｃ、Ｋの各ステーションで転写された画像は、順次中間転写体２４上に重ねられることになる。中間転写体２４に写されたトナー像は、二次転写装置２７において圧力と静電気力を用い、４色同時に紙面に転写される。紙面に転写されたトナー像は、定着部２５において熱と圧力が加えられる。これにより、溶融圧縮されることで紙面に定着がされて、最終的な画像形成がされる。 The images transferred at the Y, M, C, and K stations are sequentially superimposed on the intermediate transfer member 24. The toner image transferred to the intermediate transfer member 24 is simultaneously transferred to the paper surface by four colors using the pressure and electrostatic force in the secondary transfer device 27. The toner image transferred to the paper surface is subjected to heat and pressure at the fixing unit 25. Accordingly, the image is fixed on the paper surface by being melted and compressed, and a final image is formed.

（現像装置）
従来構成の現像装置１の構成について、図２に示す長手断面は本実施形態と同様であるが、短手断面を図９に示す。二成分現像では、現像剤として着色樹脂であるトナーと磁性粒子であるキャリアが一定の比率で混合されている二成分現像剤を用いる。現像過程でこの現像剤を現像装置１と感光ドラム１０が近接し対向する現像部に輸送し、感光ドラム１０表面の静電潜像にトナーのみを付着させ、トナー像を形成することで顕像化する。 (Developer)
Regarding the configuration of the developing device 1 of the conventional configuration, the longitudinal cross section shown in FIG. 2 is the same as that of this embodiment, but the short cross section is shown in FIG. In the two-component development, a two-component developer in which a toner that is a colored resin and a carrier that is a magnetic particle are mixed at a certain ratio is used as a developer. In the developing process, the developer is transported to a developing unit where the developing device 1 and the photosensitive drum 10 are close to each other and face each other, and only the toner is attached to the electrostatic latent image on the surface of the photosensitive drum 10 to form a toner image. Turn into.

この現像剤は、現像装置１の現像容器１１内に収容されている。現像容器１１内は、略中央部に延在する隔壁１７によって、現像室とその隣室の攪拌室に区画されている。そして、それぞれ回転可能な状態で現像室に第１の搬送スクリュー１５、攪拌室には第１の搬送スクリュー１５と対向するように第２の搬送スクリュー１６が設置されている。第１及び第２の搬送スクリュー１５、１６はともに回転軸にらせん形状の羽根が巻付いた形状をしている。この回転軸とらせん羽根の形状は、その場所に求めるスクリューの性能によって適宜変更される。 This developer is accommodated in the developing container 11 of the developing device 1. The inside of the developing container 11 is divided into a developing chamber and a stirring chamber adjacent to the developing chamber by a partition wall 17 extending substantially in the center. The first conveying screw 15 is installed in the developing chamber in a rotatable state, and the second conveying screw 16 is installed in the stirring chamber so as to face the first conveying screw 15. Both the first and second conveying screws 15 and 16 have a shape in which spiral blades are wound around the rotation shaft. The shape of the rotating shaft and the spiral blade is appropriately changed depending on the performance of the screw required for the location.

第１及び第２の搬送スクリュー１５、１６は、回転軸に対し現像装置１外部に位置する駆動源から駆動されることによって回転し、現像剤を撹拌しながら予め決めた一定方向に搬送する。第１及び第２の搬送スクリュー１５、１６は、外部駆動源からの駆動によってそれぞれ逆方向に現像剤を搬送するよう配置されている。 The first and second conveying screws 15 and 16 are rotated by being driven from a driving source located outside the developing device 1 with respect to the rotation shaft, and convey the developer in a predetermined direction while stirring the developer. The first and second conveying screws 15 and 16 are arranged to convey the developer in the opposite directions by driving from an external driving source.

現像容器１は、隔壁１７の端部付近に位置し現像室の第１の搬送スクリュー１５の搬送方向上流かつ攪拌室の第２の搬送スクリュー１６の搬送方向下流に位置する第１の連通口１３１を備える。また、現像室の第１の搬送スクリュー１５の搬送方向下流かつ攪拌室の第１の搬送スクリュー１６の搬送方向上流に位置する第２の連通口１３２とを備える。 The developing container 1 is located near the end of the partition wall 17 and is located at the first communication port 131 located upstream in the transport direction of the first transport screw 15 in the developing chamber and downstream in the transport direction of the second transport screw 16 in the stirring chamber. Is provided. In addition, a second communication port 132 is provided that is located downstream in the transport direction of the first transport screw 15 in the developing chamber and upstream in the transport direction of the first transport screw 16 in the stirring chamber.

第１及び第２の搬送スクリュー１５、１６で搬送された現像剤は、この第１及び第２の連通口１３１、１３２を通じて、対向するスクリューに受け渡される。現像剤は、これらの第１の連通口１３１と第２の連通口１３２を通じて、現像室と攪拌室との間で一定方向に回転するように循環する。 The developer conveyed by the first and second conveying screws 15 and 16 is delivered to the opposing screw through the first and second communication ports 131 and 132. The developer circulates through the first communication port 131 and the second communication port 132 so as to rotate in a fixed direction between the developing chamber and the stirring chamber.

現像容器１１の感光ドラム１０に対向した位置には、開口部が設けられている。現像剤担持体である現像スリーブ１８は、この開口部を介して現像剤を現像容器１１内の現像室から現像領域へ輸送する工程を担っている。 An opening is provided at a position of the developing container 11 facing the photosensitive drum 10. The developing sleeve 18 that is a developer carrying member is responsible for a step of transporting the developer from the developing chamber in the developing container 11 to the developing region through the opening.

（現像スリーブ）
現像スリーブ１８は円筒構造の非磁性金属であり、回転可能な状態で現像容器１１の開口部に面するように配設されている。現像スリーブ１８表面には現像剤の搬送性を大きくする加工（ブラスト加工やローレット加工など）が施されており、現像スリーブ１８は坦持する現像剤を摩擦力によって搬送する。現像スリーブ１８内部には５つの磁極を有する非回転のマグネットローラー（マグネットロール）１８’が配されている。現像スリーブ１８における現像剤の担持や剥離は、このマグネットローラー１８’の磁極を利用している。 (Development sleeve)
The developing sleeve 18 is a cylindrical nonmagnetic metal, and is disposed so as to face the opening of the developing container 11 in a rotatable state. The surface of the developing sleeve 18 is subjected to processing (such as blasting or knurling) that increases the developer transportability, and the developing sleeve 18 transports the developer carried by frictional force. A non-rotating magnet roller (magnet roll) 18 ′ having five magnetic poles is arranged inside the developing sleeve 18. The developer sleeve 18 supports and peels off the developer using the magnetic poles of the magnet roller 18 '.

ここで、現像スリーブ１８に担持・搬送される現像剤の動きに従って、マグネットローラー１８’の磁極とその機能を説明する。先ず、現像室で攪拌搬送されている現像剤は、くみ上げ極Ｓ３の磁力によって現像スリーブ１８に坦持される。現像スリーブ１８によって坦持された現像剤は、現像スリーブ１８の回転によってくみ上げ極Ｓ３下流に位置するカット極Ｎ２付近に搬送される。 Here, the magnetic pole of the magnet roller 18 ′ and its function will be described in accordance with the movement of the developer carried and conveyed by the developing sleeve 18. First, the developer stirred and conveyed in the developing chamber is carried on the developing sleeve 18 by the magnetic force of the pumping pole S3. The developer carried by the developing sleeve 18 is conveyed by the rotation of the developing sleeve 18 to the vicinity of the cut pole N2 positioned downstream of the pumping pole S3.

マグネットローラー１８’の磁極近傍の現像剤は、マグネットローラー１８’の磁極の作る磁力線に従って、キャリアがチェーン状に整列する磁気穂と呼ばれる状態になる。磁気穂にはそれぞれ斥力が働いており、この斥力によって一定間隔以上の距離が保たれる。この磁力線に従った磁気穂の状態で、現像剤は、現像スリーブ１８とカット極Ｎ２に略対向する現像ブレード１２間の間隙を通過することで、磁気穂の高さが制限される。そして、
現像スリーブ１８に担持された現像剤の層厚を規制する現像剤規制部材としての現像ブレード１２を用いることで、現像スリーブ１８上で薄層化し現像剤搬送量が規制される。 The developer in the vicinity of the magnetic pole of the magnet roller 18 ′ is in a state called a magnetic spike in which the carriers are aligned in a chain according to the magnetic field lines formed by the magnetic pole of the magnet roller 18 ′. Each magnetic ear has a repulsive force, and this repulsive force maintains a distance of a certain distance or more. In the state of magnetic spikes according to the lines of magnetic force, the developer passes through the gap between the developing blade 12 and the developing sleeve 18 and the cut pole N2, so that the height of the magnetic spikes is limited. And
By using the developing blade 12 as a developer regulating member that regulates the layer thickness of the developer carried on the developing sleeve 18, the developer is thinned on the developing sleeve 18 and the developer transport amount is regulated.

カット極Ｎ２で流量を規制された現像剤は、現像容器１１の開口を通過し現像容器１１外部に露出される。そして、現像剤は、現像スリーブ１８の回転によって、感光ドラム１０の現像部（感光ドラム１０との最近接部）に略対向している現像極（第１の磁極）Ｓ１の位置へ輸送される。この現像部において、感光ドラム１０の静電潜像に対し静電気力でトナーのみを飛翔させ現像する。このとき、静電気力を用いるために、現像スリーブ１８には負の直流電圧、もしくは負の直流電圧に交流電圧を重畳させたものを印加する。 The developer whose flow rate is regulated by the cut pole N2 passes through the opening of the developing container 11 and is exposed to the outside of the developing container 11. The developer is transported to the position of the developing pole (first magnetic pole) S1 that is substantially opposed to the developing portion (the closest portion to the photosensitive drum 10) of the photosensitive drum 10 by the rotation of the developing sleeve 18. . In the developing unit, only the toner is ejected and developed with respect to the electrostatic latent image on the photosensitive drum 10 by electrostatic force. At this time, in order to use electrostatic force, a negative DC voltage or a negative DC voltage superimposed with an AC voltage is applied to the developing sleeve 18.

すなわち、上述した露光によって、感光ドラム１のトナーを載せるべき領域の電位がこの直流電圧よりも正の電位差にすることで、負帯電のトナーを感光ドラム１０に飛翔させる。また、トナーを載せるべきでない領域の電位を直流電圧よりも負の電位差にすることで、トナーを飛翔させないままにすることができる。 That is, the negatively charged toner is caused to fly to the photosensitive drum 10 by making the potential of the region on the photosensitive drum 1 where the toner is to be placed a positive potential difference with respect to the DC voltage by the above-described exposure. Further, by setting the potential of the region where the toner should not be placed to a potential difference that is more negative than the DC voltage, it is possible to keep the toner from flying.

以上により、感光ドラム１０の静電潜像に対し選択的にトナーを飛翔させ現像することができる。なお、このとき、キャリアは静電気力とともに現像極Ｓ１の磁気力によって現像スリーブ１８側に引き寄せられているため、感光ドラム１０に飛翔することはなく現像スリーブ１８表面上にとどまっている。 As described above, the toner can be selectively ejected and developed on the electrostatic latent image on the photosensitive drum 10. At this time, since the carrier is attracted to the developing sleeve 18 side by the magnetic force of the developing pole S1 together with the electrostatic force, it does not fly to the photosensitive drum 10 but stays on the surface of the developing sleeve 18.

現像後の現像剤は、搬送極Ｎ１の磁力によって、現像スリーブ１８に坦持したまま搬送される。この搬送極Ｎ１前後で、現像剤は、再び現像容器１１の開口を通過し現像容器１１内に取り込まれる。この現像スリーブ１８上の現像剤が、現像容器１１に取り込まれる開口部分を、取り込み部と呼ぶ。搬送極Ｎ１によって搬送されながら現像容器に取り込まれた現像剤は、はぎ取り極（第２の磁極）Ｓ２に輸送される。はぎ取り極Ｓ２はくみ上げ極Ｓ３と同極であり、極間には反発力を生じている。 The developed developer is transported while being carried on the developing sleeve 18 by the magnetic force of the transport pole N1. The developer passes through the opening of the developing container 11 again and is taken into the developing container 11 before and after the transport pole N1. The opening portion where the developer on the developing sleeve 18 is taken into the developing container 11 is referred to as a taking-in portion. The developer taken into the developing container while being transported by the transport pole N1 is transported to the stripping pole (second magnetic pole) S2. The stripping pole S2 is the same pole as the lifting pole S3, and a repulsive force is generated between the poles.

この極間の反発力により、はぎ取り極Ｓ２の下流で、現像剤は現像スリーブ１８の回転方向に対し逆方向に磁気力を受ける。現像スリーブ１８の回転方向に対し逆方向に働く磁気力の影響で現像剤の回転は止められ、はぎ取り極Ｓ２からその下流付近に現像剤は滞留部を生じる。ここで、この現像剤滞留部をはぎ取り滞留部と呼ぶ。はぎ取り滞留部の最大滞留量は、はぎ取り極Ｓ２の磁力その他で決定する。しかし、はぎ取り滞留部には現像スリーブ１８上流より現像剤が供給され続けるので、どこかのタイミングで現像剤は最大滞留量を超えることになる。 Due to the repulsive force between the poles, the developer receives a magnetic force in the direction opposite to the rotation direction of the developing sleeve 18 downstream of the stripping pole S2. The rotation of the developer is stopped by the influence of the magnetic force acting in the opposite direction to the rotation direction of the developing sleeve 18, and the developer stays in the vicinity of the downstream side from the stripping pole S <b> 2. Here, this developer retaining portion is referred to as a peel-off retaining portion. The maximum retention amount of the stripping staying portion is determined by the magnetic force of the stripping pole S2 and others. However, since the developer continues to be supplied from the upstream side of the developing sleeve 18 to the stripping and staying portion, the developer exceeds the maximum staying amount at some timing.

最大滞留量を超えて供給される現像剤は、現像スリーブ１８に坦持できなくなり落下する。そして、落下した現像剤を現像室に回収することで、再び現像室で攪拌搬送されることになる。このプロセスを繰り返すことにより、現像装置１は感光ドラム１０にトナーを供給し、静電潜像をトナー像化している。 The developer supplied exceeding the maximum residence amount cannot be carried on the developing sleeve 18 and falls. Then, by collecting the dropped developer in the developing chamber, the developer is stirred and conveyed again in the developing chamber. By repeating this process, the developing device 1 supplies toner to the photosensitive drum 10 to convert the electrostatic latent image into a toner image.

上述したように、現像後の現像剤は画像形成装置の出力画像に応じた量のトナーを消費し、トナー濃度が下がっている。このトナー濃度が下がった現像剤が現像室に戻され、再び現像容器１１内に循環する。そのため、現像容器１１内を循環する現像剤のトナー濃度を一定に保つには、出力画像に応じたトナー消費分と同量のトナーを循環する現像剤として補給する必要がある。そこで、現像容器１１には消費されたトナーを補給するための補給口１４にトナーカートリッジが取り付けられ、該トナーカートリッジ内のトナーが補給口１４を介して現像剤循環路に補給される。 As described above, the developer after development consumes an amount of toner corresponding to the output image of the image forming apparatus, and the toner density is lowered. The developer having the lowered toner concentration is returned to the developing chamber and circulates again in the developing container 11. Therefore, in order to keep the toner concentration of the developer circulating in the developing container 11 constant, it is necessary to replenish the same amount of toner as the developer that circulates the amount of toner consumed according to the output image. Therefore, a toner cartridge is attached to the replenishing port 14 for replenishing consumed toner in the developing container 11, and the toner in the toner cartridge is replenished to the developer circulation path via the replenishing port 14.

（現像スリーブ近傍の気流）
次に、現像スリーブ１８近傍の気流の発生について説明する。基本的に上記現像剤を坦持した現像スリーブ１８の回転は、回転方向に空気を巻き込み気流を生成する。さらに、上述したように、現像極Ｓ１や搬送極Ｎ１といった磁極上では現像剤は、各磁極の磁力線に沿ったチェーン状の構造である磁気穂を形成する。磁極直前に磁気穂が前方に立ち上がり、磁極上を通過すると磁気穂は前傾し倒れる。このとき、磁気穂の回転は現像スリーブ１８の方向と同一方向であり、先端速度は現像スリーブ１８の回転速度より早い。さらに、磁気穂の状態では間隙が大きく且最大高さが高い。 (Airflow near the developing sleeve)
Next, the generation of an air flow near the developing sleeve 18 will be described. Basically, the rotation of the developing sleeve 18 carrying the developer entrains air in the rotational direction and generates an air flow. Further, as described above, on the magnetic poles such as the development pole S1 and the transport pole N1, the developer forms a magnetic spike having a chain structure along the magnetic field lines of each magnetic pole. The magnetic spike rises forward immediately before the magnetic pole, and when it passes over the magnetic pole, the magnetic spike tilts forward and falls. At this time, the rotation of the magnetic spike is in the same direction as the direction of the developing sleeve 18, and the tip speed is faster than the rotating speed of the developing sleeve 18. Furthermore, in the state of magnetic spikes, the gap is large and the maximum height is high.

よって、この極上の磁気穂となる領域は、磁気穂以外の領域と比較し、気流を生成する駆動力が大きいと考えられる。したがって、現像スリーブ１８上の気流駆動力は現像極Ｓ１や搬送極Ｎ１上で大きく、現像極Ｓ１−搬送極Ｎ１間や搬送極Ｎ１−はぎ取り極Ｓ２間で小さいと予測される。 Therefore, it is considered that the region that becomes the highest magnetic ear has a larger driving force for generating airflow than the region other than the magnetic ear. Therefore, it is predicted that the airflow driving force on the developing sleeve 18 is large on the developing electrode S1 and the conveying electrode N1, and is small between the developing electrode S1 and the conveying electrode N1 and between the conveying electrode N1 and the peeling electrode S2.

本実施形態において、現像スリーブ１８の回転により、搬送極Ｎ１前後の取り込み部から現像容器１１内部に空気が取り込まれる。搬送極Ｎ１を通過した気流は、現像スリーブ１８に担持された現像剤とともにはぎ取り極Ｓ２部へ流れる。しかし、はぎ取り極Ｓ２で現像剤ははぎ取り滞留部を形成している。上述したとおり、このはぎ取り滞留部では現像スリーブ１８上の現像剤流速が抑えられて滞留し、定常的に最大滞留量を坦持した状態となる。 In the present embodiment, the rotation of the developing sleeve 18 causes air to be taken into the developing container 11 from the taking portions before and after the transport pole N1. The airflow that has passed through the transport pole N1 flows to the stripping pole S2 portion together with the developer carried on the developing sleeve 18. However, the developer forms a stripping and staying portion at the stripping pole S2. As described above, in this stripping staying portion, the developer flow rate on the developing sleeve 18 is restrained and stays, and the maximum staying amount is steadily carried.

現像スリーブ１８近傍の気流にとって、このはぎ取り滞留部は障害となる。障害であるはぎ取り滞留部Ｈにぶつかった気流は、はぎとり滞留部に沿って流れ、現像スリーブ１８近傍から離れる。ここで、はぎとり滞留部に沿って流れ、現像スリーブ１８近傍から離れた後の気流を予測する。空気は流体であるため、連続の方程式が適用できる。現像容器１１内の内圧をｐ、空気の流速をｖ、密度をρとすると、現像室内で空気の湧き出しがないため、以下のように記述できる。 For the airflow in the vicinity of the developing sleeve 18, this peel-off staying part becomes an obstacle. The airflow that has hit the peel-off retention portion H, which is an obstacle, flows along the peel-off retention portion and leaves the vicinity of the developing sleeve 18. Here, the airflow after flowing along the stripping staying portion and leaving the vicinity of the developing sleeve 18 is predicted. Since air is a fluid, a continuous equation can be applied. Assuming that the internal pressure in the developing container 11 is p, the flow velocity of air is v, and the density is ρ, there is no air outflow in the developing chamber.

上述した搬送極Ｎ１前後の取り込み部からの空気流入を考えると、次第に内圧ｐは上昇する。内圧ｐの上昇は時間とともに緩和され、定常状態になる。定常状態を考えると、現像室内の各領域において密度ρは一定となっている。そのため、上記式は以下のように記述できる。 Considering the inflow of air from the intake portions before and after the transport pole N1, the internal pressure p gradually increases. The increase in the internal pressure p is relaxed with time and becomes a steady state. Considering the steady state, the density ρ is constant in each region in the developing chamber. Therefore, the above equation can be described as follows.

この式から空気の流量ρｖは保存されることが分かり、閉空間を仮定した場合の流量ρｖの収支は０となることが分かる。すなわち、流量ρｖの収支は０であることから、図９のように現像装置の短手断面が略閉空間であり且開口が取り込み部のみの場合、平衡状態では取り込み部から流入する気流と同一流量の気流が取り込み部から外部に対し発生することになる。 From this equation, it can be seen that the air flow rate ρv is conserved, and that the balance of the flow rate ρv is 0 when a closed space is assumed. That is, since the balance of the flow rate ρv is 0, when the short cross section of the developing device is a substantially closed space as shown in FIG. 9 and the opening is only the intake portion, it is the same as the airflow flowing from the intake portion in the equilibrium state. A flow of airflow is generated from the intake portion to the outside.

気流の駆動要素は、現像スリーブ１８及びそれに搬送される現像剤である。このことから、図１０に示すように、取り込み部の現像スリーブ１８と近い側に現像容器１１に流入する気流（気流１）、取り込み部の現像スリーブ１８と遠い側に現像容器１１から排出する気流（気流２）を生じることになる。 The driving element for the airflow is the developing sleeve 18 and the developer conveyed to the developing sleeve 18. Therefore, as shown in FIG. 10, an airflow (airflow 1) flows into the developing container 11 on the side closer to the developing sleeve 18 of the taking-in portion, and an airflow discharged from the developing container 11 on the side far from the developing sleeve 18 in the taking-in portion. (Airflow 2) is generated.

（トナー飛散）
ここで、本実施形態において解決しようとするトナー飛散について説明する。トナーは、上述したように摩擦帯電によるキャリアに、静電付着力、及び表面の非静電付着力によって付着している。しかし、強い衝撃やせん断力を受ける場合、これらの付着力を超えてトナーがキャリアから遊離する。トナー遊離の箇所は大きく２つに分類され、一つは現像容器１１の開口の外、もう一つは現像容器１１の内部である。 (Toner scattering)
Here, toner scattering to be solved in the present embodiment will be described. As described above, the toner adheres to the carrier by frictional charging by electrostatic adhesion force and surface non-electrostatic adhesion force. However, when subjected to a strong impact or shearing force, the toner is released from the carrier beyond these adhesion forces. The location where the toner is released is roughly classified into two, one being outside the opening of the developing container 11 and the other being inside the developing container 11.

前者としては、現像スリーブ１８のカット極Ｎ１、現像ブレード１２で現像スリーブ１８上の流量を規制する部位、現像スリーブ１８上の現像剤挙動のうち磁極上で磁気穂が倒れる部位が挙げられ、そのままトナー飛散となる。この対策としては、これら部位をマイラなどのシール部材を用い、飛散トナーを留めておく手法で対策がとられている。 Examples of the former include a cut pole N1 of the developing sleeve 18, a portion where the flow rate on the developing sleeve 18 is regulated by the developing blade 12, and a portion of the developer behavior on the developing sleeve 18 where the magnetic spike falls on the magnetic pole. Toner scatters. As a measure against this, a measure is taken by using a sealing member such as Mylar to keep the scattered toner at these portions.

後者としては、現像容器１１内で第１及び第２の搬送スクリュー１５、１６によって攪拌搬送される部位、現像スリーブ１８のはぎ取り極Ｓ２によってはぎ取り滞留部を形成する部位などが挙げられる。そして、現像容器１１内部から現像装置１１外部へ排出される上述した気流２によって輸送されてトナー飛散となる。 Examples of the latter include a part that is stirred and conveyed by the first and second conveying screws 15 and 16 in the developing container 11 and a part that forms a tear-off retaining portion by the tear-off pole S2 of the developing sleeve 18. Then, the toner is scattered by being transported by the above-described airflow 2 discharged from the inside of the developing container 11 to the outside of the developing device 11.

現像容器１１から排出された飛散トナーは、画像形成装置内を汚染し様々な良くない影響を及ぼす。中でも、現像工程の前後工程である露光工程や転写工程で影響が出易い。特に、転写部ではトナー飛散は中間転写体２４の汚れを生じさせる。また、トナーの汚れが蓄積した場合、中間転写体２４や一次転写装置２３の端部などにトナー塊を形成することもある。さらに、中間転写体２４体の裏に付着した場合、駆動ローラーが汚れ駆動不良を生じる。 The scattered toner discharged from the developing container 11 contaminates the inside of the image forming apparatus and has various bad effects. In particular, the exposure process and the transfer process, which are the processes before and after the development process, are easily affected. In particular, the toner scattering in the transfer portion causes the intermediate transfer member 24 to become dirty. Further, when toner stains accumulate, a toner lump may be formed at the end of the intermediate transfer member 24 or the primary transfer device 23. Further, when the toner adheres to the back of the intermediate transfer member 24, the drive roller causes a stain drive failure.

これらにより、成果物である印刷画像のスジやかぶりなどの品質不良につながる。また、トナー飛散によって現像装置１自身も汚染される。そのため、現像装置１の交換時に汚れの問題を引き起こし、清掃や調整などの作業が必要となる。 These lead to quality defects such as streaks and fogging of the printed image that is the product. Further, the developing device 1 itself is also contaminated by toner scattering. For this reason, a problem of contamination is caused when the developing device 1 is replaced, and operations such as cleaning and adjustment are required.

（飛散防止電極）
ここで、搬送極Ｎ１前後の上述した取り込み部からの空気の排出に伴い発生する現像装置１内部からのトナー飛散による問題を解決するために、従来、飛散防止電極１９を用いた構成が用いられている。飛散防止電極１９は、図１１に示すように、現像スリーブ１８に対しトナー帯電と同極に飛散防止電圧Ｖｆを印加し、飛散トナーを現像スリーブ１８側に押しつけ、電界フィルターの効果を得るものである。 (Spattering prevention electrode)
Here, in order to solve the problem caused by the scattering of the toner from the inside of the developing device 1 that occurs due to the discharge of the air from the above-described intake portion before and after the transport electrode N1, a configuration using the scattering prevention electrode 19 is conventionally used. ing. As shown in FIG. 11, the scattering prevention electrode 19 applies a scattering prevention voltage Vf to the developing sleeve 18 in the same polarity as the toner charging, and presses the scattering toner toward the developing sleeve 18 to obtain the effect of an electric field filter. is there.

飛散防止電極１９の周りの構成について、図１２に示す。飛散防止電極１９は導電性の電極であり、上述した取り込み部において搬送極に対向し長手方向に延在するように現像容器１１に設置する。このような従来例においては、現像電圧が印加された現像スリーブ１８よりも電圧の絶対値において大きくなるように、現像装置１外部の飛散防止電極用の電源部からこの飛散防止電極１９に対しトナーの帯電と同極に電圧を印加する。 The configuration around the scattering prevention electrode 19 is shown in FIG. The anti-scattering electrode 19 is a conductive electrode, and is installed in the developing container 11 so as to be opposed to the conveyance electrode and extend in the longitudinal direction in the above-described capturing portion. In such a conventional example, the toner for the scattering prevention electrode 19 is supplied from the power supply unit for the scattering prevention electrode outside the developing device 1 so that the absolute value of the voltage is larger than that of the developing sleeve 18 to which the development voltage is applied. A voltage is applied to the same polarity as the charging.

その結果、トナーから見て、飛散防止電極１９から現像スリーブ１２の方向に電位差が生じる。この電位差の作用により、現像容器１１内部から気流２によって排出されつつあるトナーは、取り込み部で現像スリーブ１８側に押し付けられ気流１に合流することにより、現像容器１１内部に戻される。なお、取り込み部は上述したように現像剤が通過するため、キャリアが通電しリークの可能性がある。そのため、飛散防止電極１９の表面に絶縁処理が従来されている。 As a result, a potential difference is generated in the direction from the scattering prevention electrode 19 to the developing sleeve 12 when viewed from the toner. By the action of this potential difference, the toner being discharged from the inside of the developing container 11 by the air flow 2 is pressed toward the developing sleeve 18 at the take-in portion and merged with the air current 1 to be returned to the inside of the developing container 11. Since the developer passes through the capturing portion as described above, the carrier may be energized and may leak. For this reason, the surface of the anti-scattering electrode 19 has been conventionally insulated.

このような従来の飛散防止電極１９を用いる場合の課題として、上述したように現像とは別に電源が必要となり、画像形成装置のコスト上昇や大型化につながる。そして、現像に交流電圧を重畳して用いる方式では、交流電圧を整流して負の直流電圧を形成する場合があり、この場合についても整流基盤が必要となりコストが上昇する。 As a problem when using such a conventional anti-scattering electrode 19, as described above, a power source is required separately from the development, leading to an increase in cost and size of the image forming apparatus. In the method of using an AC voltage superimposed on development, the AC voltage may be rectified to form a negative DC voltage. In this case as well, a rectification base is required and the cost increases.

（トナー飛散の抑制）
本実施形態では、現像電圧の交流成分の有無にかかわらずコストの上昇を抑えながら、図６（ｂ）に示すように第１の電極１９１および第２の電極１９２との間で電界フィルターの機能を備える。現像スリーブ１８の回転軸線方向（長手方向）から見たときの、本実施形態の構成を図３に示す。 (Suppression of toner scattering)
In the present embodiment, the function of the electric field filter is provided between the first electrode 191 and the second electrode 192 as shown in FIG. 6B while suppressing an increase in cost regardless of the presence or absence of the AC component of the development voltage. Is provided. FIG. 3 shows the configuration of the present embodiment when viewed from the rotation axis direction (longitudinal direction) of the developing sleeve 18.

本実施形態では、現像スリーブ１８のはぎ取り極Ｓ２に対応する現像スリーブ１８上のはぎ取り剤だまり（はぎ取り滞留部）と、はぎ取り滞留部に対向する現像容器１１との間に、現像容器１１の長手方向に延在した分離壁１１１を設ける。分離壁１１１は、現像スリーブ１８から離間した位置にあって、現像スリーブ１８の回転により生成される気流に関して、第１の方向に沿う第１の流路と、第１の方向と異なる第２の方向に沿う第２の流路と、を分離する。 In the present embodiment, the longitudinal direction of the developing container 11 is between the peeling agent pool (peeling staying portion) on the developing sleeve 18 corresponding to the peeling pole S2 of the developing sleeve 18 and the developing container 11 facing the stripping staying portion. A separating wall 111 is provided. The separation wall 111 is located at a position separated from the developing sleeve 18, and the air flow generated by the rotation of the developing sleeve 18 is different from the first flow path along the first direction and the second direction different from the first direction. A second flow path along the direction is separated.

現像スリーブ１８の回転により生成される気流に関し、本実施形態では、はぎ取り滞留部に衝突し現像スリーブ１８から離間した気流をこの分離壁１１１と現像容器１１との間を通して取り込み部へ戻す。この分離壁１１１と現像容器１１の間とに気流を通すことを考慮すると、現像スリーブ１８上の現像剤薄層を除いた現像スリーブ１８と分離壁１１１との間隙よりも、分離壁１１１と現像容器１１との間隙を大きくすることが望ましい。分離壁１１１により気流が現像スリーブ１８と逆方向に回転する経路（上述した第２の流路）を、ここでは気流循環経路と呼ぶ。 With respect to the air flow generated by the rotation of the developing sleeve 18, in this embodiment, the air flow that collides with the stripping and staying portion and is separated from the developing sleeve 18 is returned to the intake portion through the space between the separation wall 111 and the developing container 11. Considering that an air flow is passed between the separation wall 111 and the developing container 11, the separation wall 111 and the developing wall are larger than the gap between the developing sleeve 18 and the separation wall 111 excluding the developer thin layer on the developing sleeve 18. It is desirable to increase the gap with the container 11. A path (the second flow path described above) in which the airflow rotates in the opposite direction to the developing sleeve 18 by the separation wall 111 is referred to as an airflow circulation path here.

ここで、図４を用いて、現像容器１１の長手方向における端部近傍の気流を考える。現像スリーブ１８の長手方向において、気流循環経路の端部が現像スリーブ１８の現像剤坦持領域の端部よりも内側（中央部側）となることが望ましい。現像スリーブ１８最端部で取り込まれてはぎ取り剤だまりで離脱した気流は、現像容器１１に衝突し圧力の抜け道である気流循環経路に向かう。そのため、気流としては長手方向で中央方向に向かう。 Here, the airflow in the vicinity of the end in the longitudinal direction of the developing container 11 will be considered with reference to FIG. In the longitudinal direction of the developing sleeve 18, it is desirable that the end portion of the air flow circulation path is on the inner side (center side) than the end portion of the developer carrying region of the developing sleeve 18. The airflow taken in at the extreme end of the developing sleeve 18 and separated from the degassing agent pool collides with the developing container 11 and travels toward the airflow circulation path where the pressure is released. Therefore, the airflow goes in the longitudinal direction toward the center.

ここで、気流循環経路の端部が現像スリーブ１８の現像剤坦持領域よりも端部側（外側）である場合、現像スリーブ１８最端部で取り込まれてはぎ取り剤だまりで離脱した気流は、やはり圧力の抜け道である気流循環経路に向かう。しかし、現像スリーブ１８現像剤坦持領域外側は気流の搬送力がなく気圧が低いため、気流は端部（外側）方向に向かう。そして、この気流につられ端部方向の現像容器１１内を汚染するトナーの発生が懸念される。 Here, when the end of the air flow circulation path is on the end side (outside) of the developer carrying region of the developing sleeve 18, the air flow taken in at the outermost end of the developing sleeve 18 and separated from the pool of the stripping agent is It goes to the air flow circulation path that is also a passage of pressure. However, the outside of the developer carrying region of the developing sleeve 18 has no airflow conveying force and the air pressure is low, so the airflow is directed toward the end (outside). Then, there is a concern about the generation of toner that is contaminated in the developing container 11 in the end direction by the air flow.

以上、気流循環経路は現像スリーブ１８の現像剤坦持領域より中央部側（内側）にあること、つまり長手方向において分離壁１１１の端部は現像スリーブ１８の現像剤坦持領域の端部より内側にあることが望ましい。 As described above, the air flow circulation path is on the center side (inside) from the developer carrying region of the developing sleeve 18, that is, the end of the separation wall 111 in the longitudinal direction is from the end of the developer carrying region of the developing sleeve 18. It is desirable to be inside.

本実施形態では、この分離壁１１１上にトナーの飛散防止電極（第１の電極）１９１を設置する。この第１の電極１９１には、現像電圧（図５）を分岐して印加している。さらに、分離壁１１１と対向する部位の現像容器１１に第２の電極）１９２を配置する。そして、この第２の電極１９２に第１の電極１９１の電位の絶対値よりも小さい絶対値の第２の電位となるよう、現像電圧よりも小さい値の電圧を印加する。この場合、最も現像電圧との差を確保できるのは電極を接地して０Ｖにする（第２の電極を接地電極とする）場合である。 In this embodiment, a toner scattering prevention electrode (first electrode) 191 is installed on the separation wall 111. A developing voltage (FIG. 5) is branched and applied to the first electrode 191. Further, a second electrode 192 is disposed in the developing container 11 at a portion facing the separation wall 111. Then, a voltage having a value smaller than the developing voltage is applied to the second electrode 192 so that the second potential has an absolute value smaller than the absolute value of the potential of the first electrode 191. In this case, the difference from the development voltage can be secured most when the electrode is grounded to 0 V (the second electrode is the ground electrode).

本実施形態において、第２の電極）１９２には捕集したトナーが堆積するが、この堆積したトナーは分離壁１１１及び第１の電極１９１に落下する。このとき、分離壁１１１及び第１の電極１９１が水平の場合は、分離壁１１１及び第１の電極１９１上にトナーが堆積し続ける。そのため、分離壁１１１及び第１の電極１９１は、水平面よりも４５度以上傾いて配置されることが望ましい。 In the present embodiment, the collected toner is deposited on the second electrode 192, and this deposited toner falls on the separation wall 111 and the first electrode 191. At this time, when the separation wall 111 and the first electrode 191 are horizontal, toner continues to accumulate on the separation wall 111 and the first electrode 191. Therefore, it is desirable that the separation wall 111 and the first electrode 191 be disposed at an angle of 45 degrees or more with respect to the horizontal plane.

以下、図６（ｂ）において、気流循環路中でトナーを第２の電極１９２にて補足するための条件を考える。現像スリーブ１８の回転軸線方向から見て、第１の電極１９１と第２の電極１９２の距離（間隔）をｄ、第１の電極１９１及び第２の電極１９２の幅をＤ、トナーの電荷をｑ、気流に乗って排出されるトナーのｘ方向の速度ｖ、トナーの重量をｍとする。また、第１の電極１９１と第２の電極１９２との電位差（本実施形態では現像電圧）をＶとする。 Hereinafter, in FIG. 6B, a condition for supplementing the toner with the second electrode 192 in the airflow circulation path will be considered. When viewed from the rotation axis direction of the developing sleeve 18, the distance (interval) between the first electrode 191 and the second electrode 192 is d, the widths of the first electrode 191 and the second electrode 192 are D, and the charge of the toner is q, the velocity v in the x direction of the toner discharged in the air current, and the toner weight m. Further, the potential difference (the development voltage in this embodiment) between the first electrode 191 and the second electrode 192 is V.

図６（ｂ）で、第１の電極１９１の上流付近の電荷ｑが、電場Ｅの中で第２の電極１９２のＤｘの位置に時間ｔ（＝Ｄｘ／ｖ）で到達するとする。電荷ｑが受ける力をＦ、ｘ方向に直交するｙ方向の加速度をαとすると、Ｆ＝ｑＥ＝ｍαであり、Ｅ＝Ｖ／ｄであることから、α＝ｑＶ／ｍｄとなる。また、ｙ方向における速度（＝αｔ）の時間積分がｄとなることから、以下の式が成立する。 In FIG. 6B, it is assumed that the charge q near the upstream side of the first electrode 191 reaches the position of Dx of the second electrode 192 in the electric field E at time t (= Dx / v). When the force received by the charge q is F and the acceleration in the y direction orthogonal to the x direction is α, F = qE = mα and E = V / d, and therefore α = qV / md. Further, since the time integration of the velocity (= αt) in the y direction becomes d, the following equation is established.

ここで、トナーを第２の電極１９２にて補足するためには、ＤｘがＤより小さいことが必要である。よって、以下の式が私立することとなる。 Here, in order to supplement the toner with the second electrode 192, Dx needs to be smaller than D. Therefore, the following formula will be private.

これより、必要なｄは、以下のようになる。 Thus, the required d is as follows.

ここで、具体例として、トナーの電荷量（ｑ／ｍ）を２０μＣ／ｇ、現像電圧Ｖを２００Ｖ、ｖを前記流量の関係より最大で現像スリーブ１８の速度と同等な速度と推測されるため５００ｍｍ／ｓ、Ｄを５ｍｍとした。この場合、ｄは４．４ｍｍ以下であればよい。この距離ｄは、十分に実現可能なものであるといえる。 Here, as a specific example, the toner charge amount (q / m) is 20 μC / g, the developing voltage V is 200 V, and v is estimated to be a speed equivalent to the speed of the developing sleeve 18 at the maximum from the relationship of the flow rate. 500 mm / s, D was 5 mm. In this case, d may be 4.4 mm or less. This distance d can be said to be sufficiently realizable.

この構成について、検証実験を行った。画像形成装置はキヤノン製の画像形成装置ｉｍａｇｅＲＵＮＮＥＲＡＤＶＡＮＣＥＣ５２５５を改造し用いた。ｉｍａｇｅＲＵＮＮＥＲＡＤＶＡＮＣＥＣ５２５５自体は、上市済みの製品のため、基本的な構成については割愛し、本実施形態への改造個所を中心に説明する。 A verification experiment was conducted on this configuration. As the image forming apparatus, an image forming apparatus image RUNNER ADVANCE C5255 made by Canon was modified and used. Since image RUNNER ADVANCE C5255 itself is a product already on the market, the basic configuration will be omitted, and description will be made with a focus on the modifications to this embodiment.

先ず、分離壁１１１の材質は現像容器１１と同様のＡＢＳ剤を用い、奥行き（幅）を８ｍｍ、厚さを２ｍｍで形成した。そして、形成した分離板１１１を、現像スリーブ１８の回転軸線方向から見て、分離壁１１１と現像スリーブ１８の離間距離（距離）を２ｍｍ、分離壁１１１と現像容器１１の離間距離（距離）を３ｍｍとなるように配置した。さらに、分離壁１１１の両端（現像スリーブ１８の長手方向）は、対向する現像スリーブ１８の現像剤坦持領域の長手方向の端部より１ｍｍ内側(中央部に近い側の位置）になるように設置した。 First, the material of the separation wall 111 was the same ABS agent as that of the developing container 11, and the depth (width) was 8 mm and the thickness was 2 mm. When the formed separation plate 111 is viewed from the rotation axis direction of the developing sleeve 18, the separation distance (distance) between the separation wall 111 and the developing sleeve 18 is 2 mm, and the separation distance (distance) between the separation wall 111 and the developing container 11 is set. It arrange | positioned so that it might become 3 mm. Further, both ends of the separation wall 111 (longitudinal direction of the developing sleeve 18) are 1 mm inside (positions closer to the central portion) than the end in the longitudinal direction of the developer carrying region of the opposing developing sleeve 18. installed.

第１の電極１９１は、分離壁１１１に対し現像スリーブ１８と反対側に、分離壁１１１から離間しないように配置した。そして、第１の電極１９１はアルミ製で、幅は分離壁１１１と同一長さで８ｍｍ、厚さは０．３ｍｍであり、表面には絶縁テープを張り付けてある。この第１の電極１９１に対し、現像容器１１の長手方向の端部（外側）で現像スリーブ１８に対する回路と分岐して、現像電位と同一の電位となるよう現像電圧を印加している。 The first electrode 191 is arranged on the opposite side of the developing sleeve 18 with respect to the separation wall 111 so as not to be separated from the separation wall 111. The first electrode 191 is made of aluminum, the width is 8 mm and the thickness is the same as the separation wall 111, and the thickness is 0.3 mm. An insulating tape is attached to the surface. A developing voltage is applied to the first electrode 191 at a longitudinal end portion (outside) of the developing container 11 so as to branch from the circuit for the developing sleeve 18 so as to have the same potential as the developing potential.

また、第２の電極１９２は第１の電極１９１と同じものを使用し、現像容器１１の内側に貼り付けている。そして、この第２の電極１９２を接地して０Ｖ（ＧＮＤ電位）としている。 The second electrode 192 is the same as the first electrode 191 and is attached to the inside of the developing container 11. The second electrode 192 is grounded to 0 V (GND potential).

温度が２３°Ｃで湿度が５０％の環境の試験室において、１００００枚出力後、以下の項目について官能的に比較を行ったところ、図７の結果が得られた。画像汚れ（出力画像汚れ）、現像器汚れ（現像装置１を取り出し汚れ）、転写部汚れについては、従来例構成と本実施形態（実施例１）では、ほぼ同等であった。つまり、本実施形態は、外部電源のコストをかけずして、従来構成と同等にトナー飛散に対して有効であると考えられる。 In a test room where the temperature was 23 ° C. and the humidity was 50%, after outputting 10,000 sheets, the following items were compared sensuously, and the result of FIG. 7 was obtained. The image contamination (output image contamination), the developing device contamination (deterioration by removing the developing device 1), and the transfer portion contamination were substantially the same in the configuration of the conventional example and the present embodiment (Example 1). In other words, the present embodiment is considered to be as effective against toner scattering as the conventional configuration without the cost of an external power supply.

《第２の実施形態》
本発明の第２の実施形態では、基本的に第１の実施形態における現像装置１の構成を変化させずに、分離板１１１の位置を変えている。第１の実施形態では、上述したように第２の電極１９２で捕捉した飛散トナーが分離壁１１１及び第１の電極１９１に落下するが、水平より４５度の角度をつけ現像室に戻す構成を採った。この状態で大量のトナーが画像形成中に現像室に投下された場合には、現像室の反オス現像剤において部分的にトナー濃度が高い領域が発生する。 << Second Embodiment >>
In the second embodiment of the present invention, the position of the separation plate 111 is basically changed without changing the configuration of the developing device 1 in the first embodiment. In the first embodiment, as described above, the scattered toner captured by the second electrode 192 falls on the separation wall 111 and the first electrode 191, but returns to the developing chamber at an angle of 45 degrees from the horizontal. I took it. In this state, when a large amount of toner is dropped into the developing chamber during image formation, a region having a high toner concentration is partially generated in the anti-male developer in the developing chamber.

そして、上述したようにトナーとキャリアは摩擦帯電しているため、部分的にトナー濃度が高い領域が生じると、キャリアに対するトナーの個数が減少し、トナーあたりの帯電量が減少する。帯電量が少ないトナーが現像スリーブ１８に担持され現像された場合、部分的に感光体上のトナー載り量が増加し現像シミとなる。実際、第１の実施形態の検証検討では、実質的に問題とならないレベルではあるが現像シミが確認できた。 As described above, since the toner and the carrier are frictionally charged, if a region having a high toner density occurs, the number of toners with respect to the carrier decreases, and the charge amount per toner decreases. When toner with a small charge amount is carried on the developing sleeve 18 and developed, the amount of toner applied on the photosensitive member partially increases and develops a stain. Actually, in the verification examination of the first embodiment, although it is a level that does not substantially cause a problem, development spots can be confirmed.

本実施形態では、第１の実施形態の更なる改善として、図８に示すように分離板１１１の位置を隔壁１７上方にした。すなわち、分離板１１１は、隔壁から離間した位置で現像室と撹拌室を跨いで設けられる。これにより、現像容器１１が大型化するものの、第２の電極１９２に堆積したトナーは分離壁１１１及び第１の電極１９１を伝い、攪拌室に落下する。攪拌室は補給剤の攪拌能力が高く、かつ現像スリーブ１８から遠いため、上述した出力画像への影響は無い。 In the present embodiment, as a further improvement of the first embodiment, the position of the separation plate 111 is set above the partition wall 17 as shown in FIG. That is, the separation plate 111 is provided across the developing chamber and the stirring chamber at a position separated from the partition wall. As a result, although the developing container 11 is enlarged, the toner deposited on the second electrode 192 travels along the separation wall 111 and the first electrode 191 and falls into the stirring chamber. Since the stirring chamber has a high ability to stir the replenisher and is far from the developing sleeve 18, there is no influence on the output image described above.

本実施形態でも、第１の実施形態と同様に、ｉｍａｇｅＲＵＮＮＥＲＡＤＶＡＮＣＥＣ５２５５を改造し検証検討を行った。本実施形態の具体的な構成として、隔壁１７情報を１０ｍｍ切り欠き、間隙を開けて分離板１１１を配置した。分離板１１１の寸法は、第１の実施形態と同等ではあるが、２ｍｍ攪拌室にせり出すように配置した。 Also in this embodiment, the image RUNNER ADVANCE C5255 was remodeled and verified as in the first embodiment. As a specific configuration of the present embodiment, the partition plate 17 information is cut out by 10 mm, and a separation plate 111 is arranged with a gap. Although the dimension of the separation plate 111 is the same as that of the first embodiment, the separation plate 111 is disposed so as to protrude into the 2 mm stirring chamber.

検証実験としては、第１の実施形態と同様に、温度が２３°Ｃで湿度が５０％の環境の試験室において、１００００枚出力後、以下の項目について官能的に比較を行った。第１の実施形態の項目に加え、現像シミの項目を追加した。この結果を図７に併記する。この結果、画像汚れ、現像器汚れ、転写部汚れの項目については、従来例構成や第１の実施形態（実施例１）とほぼ同等であった。さらに、現像シミの項目について、第１の実施形態に対する改善がみられた。以上、本実施形態は、現像部上流のトナー飛散に対しても有効で、且つ画像不良にも強いと考えられる。 As a verification experiment, in the same manner as in the first embodiment, the following items were sensuously compared after outputting 10000 sheets in a test room having a temperature of 23 ° C. and a humidity of 50%. In addition to the item of the first embodiment, an item of development stain was added. The results are also shown in FIG. As a result, the items of image contamination, developing device contamination, and transfer portion contamination were almost the same as those of the conventional configuration and the first embodiment (Example 1). Further, with respect to the item of development stain, an improvement over the first embodiment was observed. As described above, this embodiment is effective against toner scattering upstream of the developing unit and is considered to be strong against image defects.

（変形例）
以上、本発明の好ましい実施形態について説明したが、本発明はこれらの実施形態に限定されず、その要旨の範囲内で種々の変形及び変更が可能である。 (Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

（変形例１）
上述した実施形態では、第２の電極１９２を接地電極として説明をしたが、本発明はこれに限られない。第２の電極１９２に第１の電極１９１の電位の絶対値よりも小さい絶対値の第２の電位となるよう、現像電圧よりも小さい値の電圧を印加するようにしても良い。例えば、第１の電極１９１に現像電圧Ｖとしてマイナス２００Ｖ（絶対値が２００Ｖ）、第２の電極１９２にプラス１０Ｖもしくはマイナス１０Ｖ（絶対値が２００Ｖより小さい１０Ｖ）を印加するようにしても良い。 (Modification 1)
In the above-described embodiment, the second electrode 192 is described as the ground electrode, but the present invention is not limited to this. A voltage having a value smaller than the developing voltage may be applied to the second electrode 192 so that the second potential has an absolute value smaller than the absolute value of the potential of the first electrode 191. For example, minus 200 V (absolute value is 200 V) may be applied to the first electrode 191 as the developing voltage V, and plus 10 V or minus 10 V (absolute value is less than 200 V) may be applied to the second electrode 192.

（変形例２）
上述した現像装置は、画像形成装置の中で使用されるものとしたが、画像形成装置本体の内部に常時固設されるものに限られない。現像装置をカートリッジとして、画像形成装置本体に着脱可能に設けるものであっても良い。 (Modification 2)
The developing device described above is used in the image forming apparatus, but is not limited to the one that is always fixed inside the image forming apparatus main body. The developing device may be detachably provided on the image forming apparatus main body as a cartridge.

１８・・現像スリーブ、１１１・・分離壁、１９１・・第１の電極、１９２・・第２の電極（設置電極）、Ｓ１・・現像極（第１の磁極）、Ｓ２・・はぎ取り極 ··· Development sleeve, 111 ··· Separation wall, 191 ··· First electrode, 192 ··· Second electrode (installation electrode), S1 ··· Development pole (first magnetic pole), S2 ··· Stripping electrode

Claims

内部にマグネットロールとして像担持体との最近接部である現像領域に対応する第１の磁極と、前記第１の磁極と異なる第２の磁極を備え、現像剤を担持して回転可能な現像剤担持体と、
前記現像剤担持体から離間した位置にあって、前記現像剤担持体の回転により生成される気流に関して、第１の方向に沿う第１の流路と、前記第１の方向と異なる第２の方向に沿う第２の流路と、を分離する分離壁と、
前記分離壁に対し前記現像剤担持体と反対側で前記分離壁から離間しない位置に設けられる第１の電極と、
前記第１の電極に対し前記現像剤担持体と反対側であって前記第１の電極から離間した位置に設けられる第２の電極と、
を有し、
前記第１の電極は、前記現像剤担持体と同じ第１の電位を備え、
前記第２の電極は、前記第１の電極の電位の絶対値よりも小さい絶対値の第２の電位を備えることを特徴とする現像装置。 A development that includes a first magnetic pole corresponding to a developing region that is the closest part to the image carrier as a magnet roll, and a second magnetic pole that is different from the first magnetic pole, and is capable of rotating while carrying a developer. An agent carrier;
The first flow path along the first direction and the second flow direction different from the first direction with respect to the air flow generated by the rotation of the developer carrier at a position separated from the developer carrier. A separation wall separating the second flow path along the direction;
A first electrode provided at a position not separated from the separation wall on the side opposite to the developer carrying member with respect to the separation wall;
A second electrode provided at a position opposite to the developer carrier and spaced from the first electrode with respect to the first electrode;
Have
The first electrode has the same first potential as the developer carrier,
The developing device, wherein the second electrode has a second potential having an absolute value smaller than an absolute value of the potential of the first electrode.

前記第１の電極は、前記分離壁に設けられることを特徴とする請求項１に記載の現像装置。 The developing device according to claim 1, wherein the first electrode is provided on the separation wall.

前記第２の電極は、前記現像剤を収容した現像容器に設けられることを特徴とする請求項１または２に記載の現像装置。 The developing device according to claim 1, wherein the second electrode is provided in a developing container that contains the developer.

前記現像剤担持体の回転軸線方向から見て、前記分離壁と前記現像容器との距離は、前記分離壁と前記現像剤担持体の距離から前記現像剤担持体に担持されている現像剤の厚みを覗いた距離より大きいことを特徴とする請求項３に記載の現像装置。 When viewed from the rotation axis direction of the developer carrier, the distance between the separation wall and the developer container is the distance between the separation wall and the developer carrier and the distance of the developer carried on the developer carrier. The developing device according to claim 3, wherein the developing device is larger than a distance viewed through the thickness.

前記第２の電位は、ＧＮＤ電位であることを特徴とする請求項１乃至４のいずれか１項に記載の現像装置。 The developing device according to claim 1, wherein the second potential is a GND potential.

前記第１の電極および前記第２の電極は、前記現像剤担持体の回転軸線方向に延在して設けられることを特徴とする請求項１乃至５のいずれか１項に記載の現像装置。 6. The developing device according to claim 1, wherein the first electrode and the second electrode are provided so as to extend in a rotation axis direction of the developer carrier.

前記現像剤担持体の回転軸線方向から見て、前記分離壁と前記第２の電極は水平面に対し４５度以上傾いて設けられる請求項６に記載の現像装置。 The developing device according to claim 6, wherein the separation wall and the second electrode are provided with an inclination of 45 degrees or more with respect to a horizontal plane when viewed from the rotation axis direction of the developer carrier.

前記現像剤を収容した現像容器を有し、前記現像容器は前記現像剤担持体が設けられる現像室と前記現像室の隣室である攪拌室の間に隔壁を有し、前記現像剤担持体の回転軸線方向から見て前記分離壁は前記現像室に設けられることを特徴とする請求項１乃至７のいずれか１項に記載の現像装置。 A developer container containing the developer, the developer container having a partition wall between a developing chamber in which the developer carrier is provided and a stirring chamber adjacent to the developer chamber; 8. The developing device according to claim 1, wherein the separation wall is provided in the developing chamber when viewed from the direction of the rotation axis. 9.

前記現像剤を収容した現像容器を有し、前記現像容器は前記現像剤担持体が設けられる現像室と前記現像室の隣室である攪拌室の間に隔壁を有し、前記現像剤担持体の回転軸線方向から見て前記分離壁は、前記隔壁から離間した位置で前記現像室と前記攪拌室を跨いで設けられることを特徴とする請求項１乃至８のいずれか１項に記載の現像装置。 A developer container containing the developer, the developer container having a partition wall between a developing chamber in which the developer carrier is provided and a stirring chamber adjacent to the developer chamber; 9. The developing device according to claim 1, wherein the separation wall is provided across the developing chamber and the agitation chamber at a position spaced apart from the partition wall when viewed from the direction of the rotation axis. .

前記現像剤担持体に担持された前記現像剤の層厚を規制する現像剤規制部材を備えることを特徴とする請求項１乃至９のいずれか１項に記載の現像装置。 The developing device according to claim 1, further comprising a developer regulating member that regulates a layer thickness of the developer carried on the developer carrying member.