JP4232403B2

JP4232403B2 - Contact-type charging device and image forming apparatus using the same

Info

Publication number: JP4232403B2
Application number: JP2002205831A
Authority: JP
Inventors: 忠男森; 真樹須藤
Original assignee: Fuji Xerox Co Ltd; Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2002-07-15
Filing date: 2002-07-15
Publication date: 2009-03-04
Anticipated expiration: 2022-07-15
Also published as: JP2004045977A

Description

【０００１】
【発明が属する技術分野】
この発明は、電子写真方式を適用した複写機、プリンタ、ファクシミリあるいはこれらの複合機等、記録用紙、カードなどの記録媒体に画像を記録する画像形成装置に用いられる接触式の帯電装置、及び帯電装置用の導電性芯部材並びに画像形成装置に係り、特に、例えば、感光体ドラム等の被帯電体を帯電する新規な構造の帯電装置用の導電性芯部材、及びこれを用いた接触式の帯電装置、並びに画像形成装置に関するものである。
【０００２】
【従来の技術】
従来、上記電子写真方式を適用した複写機、プリンタ、ファクシミリあるいはこれらの複合機等の画像形成装置に用いられる帯電装置としては、外部から電圧を印加した導電性中空体（チューブ）を被帯電体に対して圧接し、当該導電性中空体（チューブ）を従動させて被帯電体を帯電もしくは除電する接触式の帯電装置が、特開平６−２０８２７８号公報や特開平６−２５８９１６号公報、特開平８−１４６７０９号公報、特開平９−１６０３５０号公報、特開平９−２３０６７１号公報などに開示されているように、既に種々提案されている。
【０００３】
上記特開平６−２０８２７８号公報に係る画像形成装置に用いるに適した帯電装置は、被帯電面に当接するローラ状の帯電部材に交流を含むバイアス電圧を印加して被帯電面を帯電させる帯電装置において、前記帯電部材が中空のチューブ状導電性部材からなるように構成したものである。
【０００４】
また、上記特開平６−２５８９１６号公報に係る接触帯電装置は、帯電部材を被帯電体に当接させてこれの帯電を行なう接触帯電装置において、前記帯電部材がチューブ状の当接部材を支持部材により被帯電体に当接させて構成したものである。
【０００５】
さらに、上記特開平８−１４６７０９号公報に係る接触帯電装置は、可動の被帯電体に接触される中空の導電性可撓性チューブから成り、該チューブに帯電電圧が印加され、接触している被帯電体の帯電が行われる接触帯電装置において、前記中空の導電性可撓性チューブ内には、該チューブとは非接触で延びている導電性の回転軸が設けられ、該チューブの両端は、該回転軸に嵌め込まれている導電性のゴムリングに固定され、前記回転軸から導電性ゴムリングを介して導電性可撓性チューブに帯電電圧が印加されると共に、前記導電性可撓性チューブは、１０⁸乃至１０¹⁰Ωの範囲の体積抵抗を有するものであり、前記導電性ゴムリングは、１０²乃至１０⁸の範囲の体積抵抗を有しているように構成したものである。
【０００６】
又、上記特開平９−１６０３５０号公報に係る接触帯電装置は、被帯電体に対して帯電体を接触させて従動回転し被帯電体を帯電もしくは除電する接触帯電装置において、前記帯電体を導電性チューブで構成し、その両端部に弾性部材を介入させるとともに前記帯電体を押圧手段によって前記被帯電体へ接触させるように構成したものである。
【０００７】
更に、上記特開平９−２３０６７１号公報に係る接触帯電部材は、像担持体に接触配置されるとともに電圧が印加されて前記像担持体を帯電させる接触帯電部材において、前記像担持体に接触配置される支持部材と、該支持部材の外周面を覆う被覆部材と、該支持部材の内側を軸方向に貫通する芯材と、該芯材と前記支持部材との間に介装されて前記支持部材を保持する弾性体と、を備えるように構成したものである。
【０００８】
【発明が解決しようとする課題】
しかし、上記従来技術の場合には、次のような問題点を有している。すなわち、上記特開平９−１６０３５０号公報及び特開平９−２３０６７１号公報に係る帯電装置の場合には、芯の両端部に配設される弾性部材によって導電性チューブを支持し、当該弾性部材が芯に対して軸受けの機構も兼ねている。そのため、帯電装置を被帯電体に押圧する押圧力によっては、芯の軸受け部分に相当する弾性部材の摺動抵抗が、従動から得られる回転力より大きくなってしまう場合があり、従動回転が妨げられ、均一に帯電することができないという問題点を有していた。逆に、帯電装置の被帯電体に対する押圧力を低減していくと、従動に必要な回転が得られず、又被帯電体との均一な接触も得られなくなり、やはり均一に帯電することができないという問題点を有している。
【０００９】
また、上記特開平６−２０８２７８号公報、特開平８−１４６７０９号公報、特開平９−２３０６７１号公報に係る帯電装置の場合には、弾性部材によって両端部が固定された中空のチューブ状導電性部材が、芯の撓みやチューブ状導電性部材自身の回転触れ等によって中央部が接触しにくいという問題点を有していた。また、それを回避するためには、中空のチューブ状導電性部材の内部に弾性体ブラシ等を、当該中空のチューブ状導電性部材の全周に挿入して、形状を制御したり、芯の径を太くすることが考えられるが、この場合には、コストアップにつながるという新たな問題点が生じる。
【００１０】
さらに、上記特開平６−２０８２７８号公報、特開平６−２５８９１６号公報、特開平８−１４６７０９号公報、特開平９−１６０３５０号公報、特開平９−２３０６７１号公報に係る接触帯電装置の場合には、中空のチューブ状導電性部材が回転するときに、芯スラスト方向へ動く力が働く。これを固定するためには、芯に対してチューブ状導電性部材を固定する固定部品の追加が必要となり、部品点数の増加に伴うコストアップという問題点を有していた。
【００１１】
また更に、上記特開平８−１４６７０９号公報、特開平９−１６０３５０号公報、特開平９−２３０６７１号公報に係る接触帯電装置の場合には、芯と弾性部材が回転摺動しているので安定した導通が得られないため、被帯電体に対して均一な帯電を行うことができないという問題点を有していた。
【００１２】
そこで、この発明は、上記従来技術の問題点を解決するためになされたものであり、その目的とするところは、帯電部材を被帯電体に押圧する押圧力によらずに、帯電部材を安定して回転させることができ、均一に帯電することが可能な帯電装置を提供することにある。
【００１３】
また、この発明の他の目的とするところは、弾性体ブラシを全周に挿入したり、芯部材の径を太くすることなく、帯電部材をその軸方向に沿って一様に接触させることが可能な帯電装置を提供することにある。
【００１４】
さらに、この発明の他の目的とするところは、部品点数の増加に伴うコストアップを招くことなく、帯電部材がスラスト方向に移動するのを防止することが可能な帯電装置を提供することにある。
【００１５】
また更に、この発明の他の目的とするところは、芯部材と帯電部材との安定した導通を得ることができ、被帯電体に対して均一な帯電を行うことが可能な帯電装置を提供することにある。
【００１６】
【課題を解決するための手段】
【００２６】
上記目的を達成するため、請求項１に記載された発明は、被帯電体の表面に弾性力を有する円筒状導電部材を接触させて、当該円筒状導電部材を回転させることにより、前記被帯電体の表面を帯電もしくは除電する接触式の帯電装置において、
前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材とを備え、
前記導電性芯部材は、断面矩形状の金属製中空シャフトと、当該中空シャフトの両端部に固定された軸部材と、前記中空シャフトと軸部材との間に中空シャフト側の外径を大きく設定した円筒形状の段差部とから構成し、前記段差部に前記軸受け部材を取り付けるとともに、前記中空シャフト両端の段差部に取り付けられた前記軸受け部材の間隔を、前記円筒状導電部材の軸方向に沿った自由長以上に設定し、前記円筒状導電部材自身が有する弾性力によって、当該円筒状導電部材のスラスト方向への移動を防止したことを特徴とする接触式の帯電装置である。
【００２７】
さらに、請求項２に記載された発明は、被帯電体の表面に弾性力を有する円筒状導電部材を接触させて、当該円筒状導電部材を回転させることにより、前記被帯電体の表面を帯電もしくは除電する接触式の帯電装置において、
前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材と、前記導電性芯部材の軸方向に沿った帯電領域に渡って保持され、前記円筒状導電部材を被帯電体の表面に押圧する導電性弾性部材とを備え、
前記導電性芯部材は、断面矩形状の金属製中空シャフトと、当該中空シャフトの両端部に固定された軸部材と、前記中空シャフトと軸部材との間に中空シャフト側の外径を大きく設定した円筒形状の段差部とから構成し、前記段差部に前記軸受け部材を取り付けるとともに、前記中空シャフト両端の段差部に取り付けられた前記軸受け部材の間隔を、前記円筒状導電部材の軸方向に沿った自由長以上に設定し、前記円筒状導電部材自身が有する弾性力によって、当該円筒状導電部材のスラスト方向への移動を防止したことを特徴とする接触式の帯電装置である。
【００２８】
ここで、上記導電性弾性部材は、例えば、導電性芯部材の軸方向に沿った帯電領域に渡って取り付けられ、当該導電性芯部材から円筒状導電部材が被帯電体と接触する部分にのみ配設される。
【００２９】
又、請求項３に記載された発明は、前記導電性芯部材は、その軸方向の両端部に端部側の外径を小さく設定した段差を有するとともに、前記軸受け部材は、その内周の少なくとも一部に前記導電性芯部材の段差を越えない内径を有し、かつ外周に弾性層を有することを特徴とする請求項１又は２記載の接触式の帯電装置である。
【００３０】
更に、請求項４に記載された発明は、前記導電性芯部材は、その軸方向の両端部が少なくとも円柱状に形成されているとともに、その中間部には、周方向の一部に軸方向に沿った平面を有することを特徴とする請求項１乃至３のいずれかに記載の接触式の帯電装置である。
【００３１】
また更に、請求項５に記載された発明は、前記導電性芯部材は、その軸方向の両端部が少なくとも円柱状に形成されているとともに、当該円柱状に形成された両端部の少なくとも一方に、前記導電性芯部材を所定の角度で回り止め状態に取り付ける断面Ｄ形状の基準平面が形成されていることを特徴とする請求項４記載の接触式の帯電装置である。
【００３４】
また、請求項６に記載された発明は、弾性力を有する円筒状導電部材を像担持体の表面に接触させて、当該円筒状導電部材を回転させることにより、前記像担持体の表面を帯電させる接触式の帯電装置を備えた画像形成装置において、
前記接触式の帯電装置は、前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材とを備え、
前記導電性芯部材は、断面矩形状の金属製中空シャフトと、当該中空シャフトの両端部に固定された軸部材と、前記中空シャフトと軸部材との間に中空シャフト側の外径を大きく設定した円筒形状の段差部とから構成し、前記段差部に前記軸受け部材を取り付けるとともに、前記中空シャフト両端の段差部に取り付けられた前記軸受け部材の間隔を、前記円筒状導電部材の軸方向に沿った自由長以上に設定し、前記円筒状導電部材自身が有する弾性力によって、当該円筒状導電部材のスラスト方向への移動を防止したことを特徴とする画像形成装置である。
【００３５】
【発明の実施の形態】
以下に、この発明の実施の形態について図面を参照して説明する。
【００３６】
実施の形態１
図２はこの発明の実施の形態１に係る接触式の帯電装置を適用した画像形成装置としてのタンデム型のフルカラープリンタを示すものである。
【００３７】
図２において、01はタンデム型のフルカラープリンタの本体を示すものであり、このプリンタ本体01の内部には、大別して、フルカラーの画像形成を行うプリントヘッドデバイス（Print Head Device ）02と、このプリントヘッドデバイス02の静電潜像担持体としての４つの感光体ドラム11, 12, 13, 14に画像露光を施す露光装置としてのＲＯＳ（Raster Output Scanner ）03と、上記プリントヘッドデバイス02の各色の現像装置41, 42, 43, 44に対応する色のトナーを供給する４つのトナーカートリッジ04Y,04M,04K,04C と、上記プリントヘッドデバイス02に記録媒体としての記録用紙Ｐを供給する給紙カセット05と、上記プリントヘッドデバイス02からトナー像が転写された記録用紙Ｐに対して、定着処理を施す定着装置06と、この定着装置06によって片面に画像が定着された記録用紙Ｐを、表裏を反転した状態で、再度プリントヘッドデバイス02の転写部へと搬送する両面用搬送経路07と、プリンタ本体01の外部から所望の記録用紙Ｐを給紙する手差し給紙手段08と、プリンタの動作を制御する制御回路や、画像信号に対して画像処理を施す画像処理回路等からなるコントローラ09と、高圧電源回路等からなる電気回路10とが設けられている。なお、図２中、T は画像が形成された記録用紙Ｐを排出する排出トイレを示すものであり、この排出トイレT は、プリンタ本体01の上部に一体的に配置されている。
【００３８】
上記プリンタ本体01の内部に配設される種々の部材のうち、露光装置としてのＲＯＳ03は、イエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色に対応した画像データに基づいて点灯駆動される４つの半導体レーザや、これら４つの半導体レーザから出射される４本のレーザ光を、偏向走査するためのｆ−θレンズやポリゴンミラー、あるいは複数枚の反射ミラーなどから構成されている。
【００３９】
図３はこの発明の実施の形態１に係る画像形成装置としてのタンデム型フルカラープリンタのプリントヘッドデバイスを示すものである。尚、図３中の矢印は、各回転部材の回転方向を示している。
【００４０】
このプリントヘッドデバイス02は、図３に示すように、イエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）用の各感光体ドラム（像担持体）11, 12, 13, 14を有する画像形成部1, 2, 3, 4と、これら感光体ドラム11, 12, 13, 14に接触する本発明の実施の形態１に係る一次帯電用の接触式帯電装置21, 22, 23, 24と、イエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色のレーザ光31, 32, 33, 34を照射するＲＯＳ（露光装置）03（図２参照）と、上記感光体ドラム11, 12, 13, 14上に形成された静電潜像を、イエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色のトナーで現像する現像装置41, 42, 43, 44と、上記４つの感光体ドラム11, 12, 13, 14のうちの２つの感光体ドラム11, 12に接触する第１の一次中間転写ドラム（中間転写体）51及び他の２つの感光体ドラム13, 14に接触する第２の一次中間転写ドラム（中間転写体）52と、上記第１、第２の一次中間転写ドラム51, 52に接触する二次中間転写ドラム（中間転写体）53と、この二次中間転写ドラム53に接触する最終転写ロール（転写部材）60とで、その主要部が構成されている。
【００４１】
感光体ドラム11, 12, 13, 14は、共通の接平面M を有するように一定の間隔をおいて配置されている。また、第１の一次中間転写ドラム51及び第２の一次中間転写ドラム52は、各回転軸が該感光体ドラム11, 12, 13, 14軸に対し平行かつ所定の対称面を境界とした面対称の関係にあるように配置されている。さらに、二次中間転写ドラム53は、該感光体ドラム11, 12, 13, 14と回転軸が平行であるように配置されている。
【００４２】
各色毎の画像情報に応じた信号は、電気回路10（図２参照）に配設された画像処理回路によりラスタライジングされてＲＯＳ03に入力される。このＲＯＳ03では、イエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色のレーザ光31, 32, 33, 34が変調され、対応する色の感光体ドラム11, 12, 13, 14に照射される。
【００４３】
上記各感光体ドラム11, 12, 13, 14の周囲では、周知の電子写真方式による各色毎の画像形成プロセスが行なわれる。まず、上記感光体ドラム11, 12, 13, 14としては、例えば、直径３０ｍｍのＯＰＣ感光体を用いた感光体ドラムが用いられ、これらの感光体ドラム11, 12, 13, 14は、例えば、１０４ｍｍ／ｓｅｃの回転速度で回転駆動される。上記感光体ドラム11, 12, 13, 14の表面は、図３に示すように、後に詳述する接触式の帯電装置21, 22, 23, 24に、約-840ＶのＤＣ電圧を印加することによって、例えば約-300Ｖ程度に帯電される。また、感光体ドラム11, 12, 13, 14の表面を帯電させるために、この実施の形態では、ＤＣのみ印加の帯電方式をとっているが、ＡＣ＋ＤＣ印加の帯電方式を用いても良い。
【００４４】
その後、感光体ドラム11, 12, 13, 14の表面には、露光装置としてのＲＯＳ03によってイエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色に対応したレーザ光31, 32, 33, 34が照射され、各色毎の入力画像情報に応じた静電潜像が形成される。感光体ドラム11, 12, 13, 14は、ＲＯＳ03で静電潜像が書き込まれた際に、その画像露光部の表面電位は-60 Ｖ以下程度にまで除電される。
【００４５】
また、上記感光体ドラム11, 12, 13, 14の表面に形成されたイエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色に対応した静電潜像は、対応する色の現像装置41, 42, 43, 44によって現像され、感光体ドラム11, 12, 13, 14上にイエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色のトナー像として可視化される。
【００４６】
この実施の形態では、現像装置41, 42, 43, 44として、磁気ブラシ接触型の二成分現像方式を採用しているが、この発明の適用範囲はこの現像方式に限定されるものではなく、非接触型の現像方式においてもこの発明を充分に適用することができることは勿論である。
【００４７】
現像装置41, 42, 43, 44には、それぞれ色の異なったイエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）色のトナーと、キャリアからなる現像剤が充填されている。これらの現像装置41, 42, 43, 44には、図２に示すように、対応する色のトナーカートリッジ04Y,04M,04K,04C からトナーが補給されると、この補給されたトナーは、オーガー401 ，402 で充分にキャリアと攪拌されて摩擦帯電される。現像ロール403 の内部には、複数の磁極を所定の角度に配置したマグネットロール（不図示）が固定した状態で配置されている。この現像ロール403 に現像剤を搬送するオーガー402 によって、当該現像ロール403 の表面近傍に搬送された現像剤は、現像剤量規制部材404 によって現像部に搬送される量が規制される。この実施の形態では、上記現像剤の量は、30〜50ｇ／ｍ²であり、また、このとき現像ロール403 上に存在するトナーの帯電量は、概ね-20 〜35μＣ／g 程度である。
【００４８】
上記現像ロール403 上に供給されたトナーは、マグネットロールの磁力によって、キャリアとトナーで構成された磁気ブラシ状となっており、この磁気ブラシが感光体ドラム11, 12, 13, 14と接触している。この現像ロール403 にAC＋DCの現像バイアス電圧を印加して、現像ロール403 上のトナーを感光体ドラム11, 12, 13, 14上に形成された静電潜像に現像することにより、トナー像が形成される。この実施の形態では、例えば、現像バイアス電圧のAC成分が4 ｋＨｚ、1.5 ｋＶppで、ＤＣ成分が-230Ｖ程度に設定されている。
【００４９】
この実施の形態では、上記現像装置41, 42, 43, 44において、トナーとして略球形状のトナーである所謂”球形トナー”であって、その平均粒径が３〜１０μｍ程度のものが使用され、例えば、ブラック色のトナーの平均粒径は８μｍ、カラートナーの平均粒径は７μｍに設定される。
【００５０】
次に、上記各感光体ドラム11, 12, 13, 14上に形成されたイエロー（Ｙ）、マゼンタ（Ｍ）、ブラック（Ｋ）、シアン（Ｃ）の各色のトナー像は、第１の一次中間転写ドラム51及び第２の一次中間転写ドラム52上に、静電的に二次転写される。感光体ドラム11, 12上に形成されたイエロー（Ｙ）およびマゼンタ（Ｍ）色のトナー像は、第１の一次中間転写ドラム51上に、感光体ドラム13, 14上に形成されたブラック（Ｋ）、シアン（Ｃ）色のトナー像は、第２の一次中間転写ドラム52上に、それぞれ転写される。従って、第１の一次中間転写ドラム51上には、感光体ドラム11または12のどちらから転写された単色像と、感光体ドラム11及び12の両方から転写された２色のトナー像が重ね合わされた二重色像が形成されることになる。また、第２の一次中間転写ドラム52上にも、感光体ドラム13,14 から同様な単色像と二重色像が形成される。
【００５１】
上記第１及び第２の一次中間転写ドラム51,52 上に感光体ドラム11,12,13,14 からトナー像を静電的に転写するために必要な表面電位は、+250〜500 Ｖ程度である。この表面電位は、トナーの帯電状態や雰囲気温度、湿度によって最適値に設定されることになる。この雰囲気温度や湿度は、雰囲気温度や湿度によって抵抗値が変化する特性を持った部材の抵抗値を検知することで簡易的に知ることが可能である。上述のように，トナーの帯電量が-20 〜35μＣ／g の範囲内にあり、常温常湿環境下にある場合には、第１及び第２の一次中間転写ドラム51,52 の表面電位は、+380Ｖ程度が望ましい。
【００５２】
この実施の形態で用いる第１、第２の一次中間転写ドラム51, 52は、例えば、外径が60ｍｍに形成され、抵抗値は１０⁸Ω程度に設定される。第１、第２の一次中間転写ドラム51, 52は、単層、あるいは複数層からなる表面が可撓性、もしくは弾性を有する円筒状の回転体であり、一般的にはＦｅやＡｌ等からなる金属製コアとしての金属パイプの上に、導電性シリコーンゴム等で代表される低抵抗弾性ゴム層（Ｒ＝10²〜10³Ω）が、厚さ0.1 〜10mm程度に設けられている。更に、第１、第２の中間転写ドラム51, 52の最表面は、代表的にはフッ素樹脂微粒子を分散させたフッ素ゴムを厚さ3 〜100 μｍの高離型層（Ｒ＝10⁵〜10⁹Ω）として形成し、シランカップリング剤系の接着剤（プライマ）で接着されている。ここで重要なのは、抵抗値と表面の離型性であり、高離型層の抵抗値がＲ＝10⁵〜10⁹Ω程度であり、高離型性を有する材料であれば、特に材料は限定されない。
【００５３】
このように第１、第２の一次中間転写ドラム51, 52上に形成された単色又は二重色のトナー像は、二次中間転写ドラム53上に静電的に３次転写される。従って、二次中間転写ドラム53上には、単色像からイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｋ）色の四重色像までの最終的なトナー像が形成されることになる。
【００５４】
この二次中間転写ドラム53上へ第１及び第２の一次中間転写ドラム51,52 からトナー像を静電的に転写するために必要な表面電位は、+600〜1200Ｖ程度である。この表面電位は、感光体ドラム11, 12, 13, 14から第１の一次中間転写ドラム51及び第２の一次中間転写ドラム52へ転写するときと同様に、トナーの帯電状態や雰囲気温度、湿度によって最適値に設定されることになる。また、転写に必要なのは、第１及び第２の一次中間転写ドラム51,52 と二次中間転写ドラム53との間の電位差であるので、第１及び第２の一次中間転写ドラム51,52 の表面電位に応じた値に設定することが必要である。上述のように、トナーの帯電量が-20 〜35μＣ／g の範囲内にあり、常温常湿環境下であって、第１及び第２の一次中間転写ドラム51,52 の表面電位が+380Ｖ程度の場合には、二次中間転写ドラム53の表面電位は、+880Ｖ程度、つまり第１及び第２の一次中間転写ドラム51,52 と二次中間転写ドラム53との間の電位差は、+500Ｖ程度に設定することが望ましい。
【００５５】
この実施の形態で用いる二次中間転写ドラム53は、例えば、外径が第１及び第２の一次中間転写ドラム51,52 と同じ60ｍｍに形成され、抵抗値は１０¹¹Ω程度に設定される。また、上記二次中間転写ドラム53も第１、第２の一次中間転写ドラム51, 52と同様、単層、あるいは複数層からなる表面が可撓性、もしくは弾性を有する円筒状の回転体であり、一般的にはＦｅやＡｌ等からなる金属製コアとしての金属パイプの上に、導電性シリコーンゴム等で代表される低抵抗弾性ゴム層（Ｒ＝10²〜10³Ω）が、厚さ0.1 〜10mm程度に設けられている。更に、二次中間転写ドラム53の最表面は、代表的にはフッ素樹脂微粒子を分散させたフッ素ゴムを厚さ3 〜100 μｍの高離型層として形成し、シランカップリング剤系の接着剤（プライマ）で接着されている。ここで、二次中間転写ドラム53の抵抗値は、第１及び第２の一次中間転写ドラム51,52 よりも高く設定する必要がある。そうしないと、二次中間転写ドラム53が第１及び第２の一次中間転写ドラム51,52 を帯電してしまい、第１及び第２の一次中間転写ドラム51,52 の表面電位の制御が難しくなる。このような条件を満たす材料であれば、特に材料は限定されない。
【００５６】
次に、上記二次中間転写ドラム53上に形成された単色像から四重色像までの最終的なトナー像は、最終転写ロール60によって、用紙搬送路を通る用紙Ｐに３次転写される。この用紙Ｐは、不図示の紙送り工程を経て用紙搬送ロール90を通過し、二次中間転写ドラム53と最終転写ロール60のニップ部に送り込まれる。この最終転写工程の後、用紙上に形成された最終的なトナー像は、定着装置70によって定着され、一連の画像形成プロセスが完了する。
【００５７】
ところで、この実施の形態に係る接触式の帯電装置は、被帯電体の表面に円筒状導電部材を接触させて、当該円筒状導電部材を従動回転させることにより、前記被帯電体の表面を帯電もしくは除電する接触式の帯電装置において、前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材と、前記導電性芯部材の軸方向に沿った帯電領域に渡って保持され、前記円筒状導電部材を被帯電体の表面に押圧する導電性弾性部材とを備えるように構成されている。
【００５８】
また、この実施の形態では、前記導電性芯部材は、その軸方向の両端部に端部側の外径を小さく設定した段差を有するとともに、前記軸受け部材は、その内周の少なくとも一部に前記導電性芯部材の段差を越えない内径を有し、かつ外周に弾性層を有するように構成されている。
【００５９】
さらに、この実施の形態では、前記導電性芯部材は、その軸方向の両端部が少なくとも円柱状に形成されているとともに、その中間部には、周方向の一部に軸方向に沿った平面を有するように構成されている。
【００６０】
また更に、この実施の形態では、前記導電性芯部材は、その軸方向の両端部が少なくとも円柱状に形成されているとともに、当該円柱状に形成された両端部の少なくとも一方に、前記導電性芯部材を所定の角度で回り止め状態に取り付ける断面Ｄ形状の基準平面が形成されるように構成されている。
【００６１】
図１及び図４はこの発明の実施の形態１に係る接触式の帯電装置を示す構成図である。
【００６２】
すなわち、この実施の形態に係る接触式の帯電装置21, 22, 23, 24は、すべて同様に構成されており、これらの接触式の帯電装置21, 22, 23, 24は、図１及び図５に示すように、大別して、導電性芯部材210 と、軸受け部材220 と、円筒状導電部材230 と、導電性弾性部材240 とを備えるように構成されている。
【００６３】
上記導電性芯部材210 は、図５に示すように、ステンレスや鉄、アルミニウム等の金属からなり、長尺な断面矩形状（図示例では、断面正方形状）の金属製中空シャフト211 と、前記金属製中空シャフト211 の両端部に嵌合固定され、軸方向の外側に向けて円柱状に突出した軸部材212,213 とを有するように構成されている。上記金属製中空シャフト211 は、例えば、５ｍｍの幅に設定されている。上記導電性芯部材210 の軸部材212,213 には、中空シャフト211 側の端部に、当該中空シャフト211 側の端部の外径を大きく、軸方向の外側の外径を小さく設定した段差部214,215 が設けられているとともに、一方の軸部材213 の先端部には、断面矩形状の中空シャフト211 の一端面211 ａと一致した平面からなる断面Ｄ形状の基準面216 が設けられている。上記上記導電性芯部材210 の段差部214,215 によって後述するように決定される軸受け部221 の間隔は、円筒状導電部材230 の自由長と等しいか、あるいは円筒状導電部材230 の自由長より若干長く設定され、軸受け部221 に円筒状導電部材230 を嵌合固定した状態で、当該円筒状導電部材230 に若干張力が作用するように構成するのが望ましい。このように構成することにより、軸受け部221 に円筒状導電部材230 を嵌合固定した状態で、円筒状導電部材230 に若干張力が作用し、円筒状導電部材230 がスラスト方向に移動する所謂蛇行の発生を防止することが可能となる。
【００６４】
なお、上記導電性芯部材210 としては、断面矩形状の金属製中空シャフトをを用いるのが望ましいが、図１（ｃ）に示すように、円柱形状や円筒形状に形成したものを用いても良い。
【００６５】
また、上記軸受け部材220 は、図６に示すように、導電性芯部材210 の段差部214,215 に嵌合された状態で取り付けられるように構成されている。この軸受け部材220 は、図１及び図５に示すように、導電性芯部材210 の段差部214,215 に嵌合される合成樹脂製の軸受け部221 と、当該軸受け部221 の外周に圧入及び両面テープによる接着等によって固着されたポロン等の合成樹脂やゴム製のスポンジ状部材からなる弾性層222 とから構成されている。さらに、上記軸受け部材220 の軸受け部221 には、導電性芯部材210 の段差部214,215 に嵌合される段差223 が、その内周に形成されている。
【００６６】
さらに、上記円筒状導電部材230 は、図１及び図５に示すように、例えば、１０⁵〜１０⁸Ωの体積抵抗を有するゴム或いは合成樹脂製の中空チューブであり、例えば、直径（外径）が１０ｍｍ、肉厚が１ｍｍに形成されている。ここでは、この円筒状導電部材230 として、ＥＰＤＭ（エチレン・プロピレン・ジエン３元共重合体）或いはエピクロルヒドリンゴムに、カーボンブラック或いは金属錯体粉を添加して、１０⁵〜１０⁸Ωの体積抵抗に調整したゴムチューブを使用しており、かつその表面にはフッ素化合物でシランカップリング処理が施されている。
【００６７】
更にまた、上記導電性弾性部材240 は、１０⁶Ω以下の体積抵抗を有する金属、合成樹脂、ゴム或いは繊維束からなるように構成されている。この実施の形態では、導電性弾性部材240 として、厚さ０．１ｍｍの導電性ＰＥＴからなる薄いシート状の部材を用いており、当該導電性弾性部材240 は、図５に示すように、幅の狭い長尺な長方形のシート状に形成されている。この導電性弾性部材240 は、導電性芯部材210 の回転方向上流側に位置する一側面211aに、両面テープ241 による接着等の手段で固着されており、当該導電性芯部材210 の一側面から下方に向けて所定の長さだけ突出するように配設されている。上記導電性弾性部材240 の長さは、円筒状導電部材230 を感光体ドラム11, 12, 13, 14の表面に押圧する際の押圧力を決定するものであり、適宜設定されるが、当該円筒状導電部材230 の内径よりも若干長く設定するのが望ましい。
【００６８】
以上の構成において、この実施の形態に係る接触式の帯電装置においては、次のようにして、帯電部材を被帯電体に押圧する押圧力によらずに、帯電部材を安定して従動回転させることができ、均一に帯電することが可能となっている。
【００６９】
また、この実施の形態に係る接触式の帯電装置においては、次のようにして、弾性体ブラシを用いたり、芯の径を太くすることなく、帯電部材をその軸方向に沿って一様に接触させることが可能となっている。
【００７０】
さらに、この実施の形態に係る接触式の帯電装置においては、次のようにして、部品点数の増加に伴うコストアップを招くことなく、帯電部材がスラスト方向に移動するのを防止することが可能となっている。
【００７１】
また更に、この実施の形態に係る接触式の帯電装置においては、次のようにして、芯と帯電部材との安定した導通を得ることができ、被帯電体に対して均一な帯電を行うことが可能となっている。
【００７２】
すなわち、この実施の形態に係る接触式の帯電装置21, 22, 23, 24においては、図１、図６乃至図８に示すように、中空チューブからなる円筒状導電部材230 の長手方向の両端部に、軸受け部材220 が嵌合された状態で固定され、当該軸受け部材220 は、導電性芯部材210 の軸部材212,213 に設けられた段差部214,215 に嵌合された状態で回転自在に取り付けられている。したがって、上記中空チューブからなる円筒状導電部材230 は、その長手方向の両端部に配設された軸受け部材220 を介して、固定配置された導電性芯部材210 に回転自在に取り付けられている。
【００７３】
また、上記接触式の帯電装置21, 22, 23, 24においては、図１及び図７に示すように、中空チューブからなる円筒状導電部材230 の内部に、導電性芯部材210 に保持された導電性弾性部材240 が配設されており、当該円筒状導電部材230 は、被帯電体としての感光体ドラム11, 12, 13, 14の表面に、導電性弾性部材240 によって所定の当接状態で押圧されるようになっている。
【００７４】
そのため、上記接触式の帯電装置21, 22, 23, 24においては、円筒状導電部材230 が感光体ドラム11, 12, 13, 14の表面に押圧される押圧力を、円筒状導電部材230 を感光体ドラム11, 12, 13, 14の表面に押圧する押圧力によらずに、導電性弾性部材240 の当接状態で制御することができ、円筒状導電部材230 の感光体ドラム11, 12, 13, 14表面に対する押圧力を、常に適切な状態に維持することができる。しかも、上記接触式の帯電装置21, 22, 23, 24においては、円筒状導電部材230 の従動回転を、当該円筒状導電部材230 の両端部に嵌合固定された軸受け部材を、感光体ドラム11, 12, 13, 14の表面に押圧することによって行っているため、円筒状導電部材230 を被帯電体に押圧する押圧力によらずに、円筒状導電部材230 を安定して従動回転させることができ、均一に帯電することが可能となっている。
【００７５】
また、上記接触式の帯電装置21, 22, 23, 24においては、円筒状導電部材230 の内部に配設された導電性芯部材210 に、導電性弾性部材240 を保持して、当該導電性弾性部材240 によって円筒状導電部材230 を感光体ドラム11, 12, 13, 14の表面に押圧しているため、弾性体ブラシを用いたり、芯の径を太くすることなく、円筒状導電部材230 をその軸方向に沿って一様に接触させることが可能となっている。
【００７６】
さらに、上記接触式の帯電装置21, 22, 23, 24においては、円筒状導電部材230 の両端部に軸受け部材220 を嵌合固定し、当該軸受け部材220 を導電性芯部材210 に設けられた段差部214,215 に嵌合して位置決めしているため、当該段差部214,215 によって位置決めされる軸受け部材220 の間隔を、円筒状導電部材230 の長さに等しいか、若干長く設定することにより、円筒状導電部材230 自身が有する弾性力等によって、当該円筒状導電部材230 がスラスト方向に移動するのを防止することができる。したがって、部品点数の増加に伴うコストアップを招くことなく、円筒状導電部材230 がスラスト方向に移動するのを防止することが可能となっている。
【００７７】
また更に、上記接触式の帯電装置21, 22, 23, 24においては、円筒状導電部材230 に対して、導電性芯部材210 に所定の電圧を印加することにより、当該導電性芯部材210 に帯電領域にわたって保持された導電性弾性部材240 を介して、円筒状導電部材230 の帯電領域に確実に通電することができ、導電性芯部材210 と円筒状導電部材230 との安定した導通を得ることができ、感光体ドラム11, 12, 13, 14に対して均一な帯電を行うことが可能となっている。
【００７８】
このように、上記実施の形態に係る接触式の帯電装置21, 22, 23, 24の場合には、図１、図７及び図８に示すように、外部から電圧を印加した中空体としての円筒状導電部材230 を、被帯電体としての感光体ドラム11, 12, 13, 14に対し従動させ、被帯電体を帯電もしくは除電する接触式の帯電装置において、中空体の両端部にトラクションコントロール可能な回転駆動機構を持った軸受け部材220 が被帯電体に対し接触するため、中空体で不安定となりやすい接触部の摩擦抵抗などにかかわらず安定した従動回転を得られる。又、導電性芯部材210 に固定した円筒状導電部材230 により円筒状導電部材230 が安定して感光体ドラム11, 12, 13, 14に接触できるので、感光体ドラム11, 12, 13, 14を安定かつ均一に帯電できる。
【００７９】
また、上記実施の形態に係る接触式の帯電装置21, 22, 23, 24の場合には、円筒状導電部材230 が軸受け部材220 を介して、感光体ドラム11, 12, 13, 14に従動回転するのみであるので、ギアレスで回転速度の安定した良好な従動回転が得られる。
【００８０】
さらに、本発明に比較して、硬度のある中実ロールでは押し付け圧力により安定した従動回転が得られるが、その押し付け圧力により表面付着トナーを押し潰し、被帯電体表面にフィルミングを生じさせたり、微小なスリップにより表面を削ってしまい被帯電体の磨耗や表面キズによる寿命低下を招いてしまう。
【００８１】
また更に、本発明に比較して、トラクションに頼らないギアによる回転駆動はギアピッチの帯電ムラを引き起こしやすいことが周知である。
【００８２】
これに対して、上記実施の形態に係る接触式の帯電装置21, 22, 23, 24の場合には、残留トナーなどの来ない画像領域外の軸方向端部の領域を自在な圧力で当接させることが可能であるため、安定した回転駆動力を得ることができる。
【００８３】
又、上記実施の形態に係る接触式の帯電装置21, 22, 23, 24の場合には、回転駆動用構成とニップ部形成機能が分離しているため、ニップ用の押し付け荷重は、弾性層を有する軸受け部材220 で独立に最適化が可能であり、不安定な形状の中空体からなる円筒状導電部材230 であっても、肝心な帯電ニップ部においては常に一定した当接形状及びその両端の微小ギャップ形状を形成することが可能である。
【００８４】
更に、中空の部材を回転駆動させる場合、左右の圧力差により通常スラスト（軸）方向に力が生じる、所謂蛇行（ウオーク）が発生するが、本発明では、圧力自体が軽いので蛇行力も弱く、さらには芯部材に加工された軸両端部の軸受けの中央側への移動規制となり、円筒状導電部材230 の張力と合わせて円筒状導電部材230 のスラスト方向への移動阻止機能を果たすため、蛇行を防止できる。
【００８５】
さらに又、上述したが、均一帯電性能を得るために帯電ニップ形状は非常に重要であり、このため、帯電部材には非常に高い外形の寸法制度が求められる。これはそのままコスト高を引き起こし、研磨工程の追加等で生産性をも低下させてしまう。これに対し、本発明は、円筒状導電部材230 と組み合わせて、軸受け部材220 や導電性弾性部材240 を用いることにより、円筒状導電部材230 そのものに、高い外径や寸法精度を必要としていない。また、構造自体も簡素であるため量産性も高い。
【００８６】
なお、前記導電性弾性部材としては、例えば、図９に示すように、導電性芯部材210 の接着されたスポンジ状の導電性弾性部材を用いても良い。
【００８７】
【発明の効果】
以上説明したように、この発明によれば、帯電部材を被帯電体に押圧する押圧力によらずに、帯電部材を安定して回転させることができ、均一に帯電することが可能な帯電装置を提供することができる。
【００８８】
また、この発明によれば、弾性体ブラシを全周に挿入したり、芯部材の径を太くすることなく、帯電部材をその軸方向に沿って一様に接触させることが可能な帯電装置を提供することができる。
【００８９】
さらに、この発明によれば、部品点数の増加に伴うコストアップを招くことなく、帯電部材がスラスト方向に移動するのを防止することが可能な帯電装置を提供することができる。
【００９０】
また更に、この発明によれば、芯部材と帯電部材との安定した導通を得ることができ、被帯電体に対して均一な帯電を行うことが可能な帯電装置を提供することができる。
【図面の簡単な説明】
【図１】図１はこの発明の実施の形態１に係る接触式の帯電装置を示す構成図である。
【図２】図２はこの発明の実施の形態１に係る接触式の帯電装置を適用した画像形成装置としてのタンデム型のカラープリンタを示す構成図である。
【図３】図３はこの発明の実施の形態１に係る接触式の帯電装置を適用した画像形成装置としてのタンデム型のカラープリンタの画像形成部を示す構成図である。
【図４】図４はこの発明の実施の形態１に係る接触式の帯電装置を示す外観斜視図である。
【図５】図５はこの発明の実施の形態１に係る接触式の帯電装置を示す分解斜視図である。
【図６】図６はこの発明の実施の形態１に係る接触式の帯電装置の部材を示す斜視図である。
【図７】図７はこの発明の実施の形態１に係る接触式の帯電装置の使用状態を示す断面図である。
【図８】図８はこの発明の実施の形態１に係る接触式の帯電装置の使用状態を示す断面図である。
【図９】図９はこの発明の実施の形態１に係る接触式の帯電装置の変形例を示す断面図である。
【図１０】図１０（ａ）〜（ｃ）はこの発明に係る帯電装置用の導電性芯部材をそれぞれ示す構成図である。
【符号の説明】
21, 22, 23, 24：接触式の帯電装置、210 ：導電性芯部材、220 ：軸受け部材、230 ：円筒状導電部材、240 ：導電性弾性部材。[0001]
[Technical field to which the invention belongs]
The present invention relates to a contact-type charging device used in an image forming apparatus for recording an image on a recording medium such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, such as recording paper or a card, and a charging device. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive core member for an apparatus and an image forming apparatus, and in particular, for example, a conductive core member for a charging device having a novel structure for charging a charged object such as a photosensitive drum, and a contact type using the same. The present invention relates to a charging device and an image forming apparatus.
[0002]
[Prior art]
Conventionally, as a charging device used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using the electrophotographic method, a conductive hollow body (tube) to which a voltage is applied from the outside is used. A contact-type charging device that presses against and charges or neutralizes a charged body by driving the conductive hollow body (tube) is disclosed in JP-A-6-208278 and JP-A-6-258916. Various proposals have already been made as disclosed in Kaihei 8-146709, JP-A-9-160350, JP-A-9-230671, and the like.
[0003]
A charging device suitable for use in the image forming apparatus according to Japanese Patent Application Laid-Open No. 6-208278 is a charging device that charges a charged surface by applying a bias voltage including alternating current to a roller-shaped charging member that contacts the charged surface. In the apparatus, the charging member is constituted by a hollow tubular conductive member.
[0004]
Further, the contact charging device according to the above-mentioned Japanese Patent Application Laid-Open No. 6-258916 is a contact charging device in which a charging member is brought into contact with an object to be charged to charge it, and the charging member supports a tubular contact member. The member is configured to be in contact with a member to be charged by a member.
[0005]
Further, the contact charging device according to the above-mentioned Japanese Patent Application Laid-Open No. 8-146709 is composed of a hollow conductive flexible tube that is in contact with a movable object to be charged, and a charging voltage is applied to the tube for contact. In a contact charging device in which a charged object is charged, a conductive rotating shaft extending in a non-contact manner with the tube is provided in the hollow conductive flexible tube, and both ends of the tube are connected to each other. The conductive flexible ring is fixed to a conductive rubber ring fitted on the rotating shaft, and a charging voltage is applied from the rotating shaft to the conductive flexible tube through the conductive rubber ring. The tube is 10⁸10^TenThe conductive rubber ring has a volume resistance in the range of Ω,²10⁸It is configured to have a volume resistance in the range of.
[0006]
Further, the contact charging device according to the above-mentioned Japanese Patent Application Laid-Open No. 9-160350 is a contact charging device in which a charged body is brought into contact with a charged body and driven to rotate to charge or remove the charged body. And an elastic member is interposed at both ends of the tube, and the charged body is brought into contact with the charged body by pressing means.
[0007]
Further, the contact charging member according to Japanese Patent Laid-Open No. 9-230671 is arranged in contact with the image carrier in the contact charging member that is placed in contact with the image carrier and charges the image carrier by applying a voltage. A supporting member, a covering member that covers an outer peripheral surface of the supporting member, a core member that passes through the inside of the supporting member in the axial direction, and the support member that is interposed between the core member and the supporting member. And an elastic body that holds the member.
[0008]
[Problems to be solved by the invention]
However, the above prior art has the following problems. That is, in the case of the charging device according to the above-mentioned JP-A-9-160350 and JP-A-9-230671, the conductive tube is supported by elastic members disposed at both ends of the core, and the elastic member It also serves as a bearing mechanism for the core. Therefore, depending on the pressing force that presses the charging device against the member to be charged, the sliding resistance of the elastic member corresponding to the bearing portion of the core may be larger than the rotational force obtained from the driven, and the driven rotation is hindered. Therefore, there is a problem that it cannot be uniformly charged. Conversely, if the pressing force of the charging device against the object to be charged is reduced, the rotation required for the follower cannot be obtained, and uniform contact with the object to be charged cannot be obtained, so that the charging can be performed uniformly. It has the problem that it cannot be done.
[0009]
In addition, in the case of the charging device according to the above-mentioned JP-A-6-208278, JP-A-8-146709, and JP-A-9-230671, a hollow tubular conductive material having both ends fixed by elastic members. The member has a problem that it is difficult for the central portion to come into contact with the core due to the deflection of the core or the rotational contact of the tubular conductive member itself. In order to avoid this, an elastic brush or the like is inserted into the hollow tubular conductive member around the entire circumference of the hollow tubular conductive member to control the shape or Although it is conceivable to increase the diameter, in this case, there arises a new problem that leads to an increase in cost.
[0010]
Further, in the case of the contact charging device according to the above-mentioned JP-A-6-208278, JP-A-6-258916, JP-A-8-146709, JP-A-9-160350, JP-A-9-230671. When the hollow tubular conductive member rotates, a force that moves in the core thrust direction acts. In order to fix this, it is necessary to add a fixing component for fixing the tube-shaped conductive member to the core, and there is a problem that the cost increases with an increase in the number of components.
[0011]
Furthermore, in the case of the contact charging device according to the above-mentioned JP-A-8-146709, JP-A-9-160350, and JP-A-9-230671, the core and the elastic member are slidably rotated and thus stable. Therefore, there is a problem that uniform charging cannot be performed on the member to be charged.
[0012]
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to stabilize the charging member regardless of the pressing force that presses the charging member against the member to be charged. It is an object of the present invention to provide a charging device that can be rotated and charged uniformly.
[0013]
Another object of the present invention is to uniformly contact the charging member along the axial direction without inserting an elastic brush around the entire circumference or increasing the diameter of the core member. It is to provide a charging device that can be used.
[0014]
Furthermore, another object of the present invention is to provide a charging device capable of preventing the charging member from moving in the thrust direction without causing an increase in cost due to an increase in the number of parts. .
[0015]
Still another object of the present invention is to provide a charging device that can obtain stable conduction between the core member and the charging member and can uniformly charge the object to be charged. There is.
[0016]
[Means for Solving the Problems]
[0026]
In order to achieve the above object, the invention described in claim 1 is provided on the surface of an object to be charged.Has elasticityIn a contact-type charging device for charging or discharging the surface of the object to be charged by contacting the cylindrical conductive member and rotating the cylindrical conductive member,
A conductive core member disposed along the axial direction inside the cylindrical conductive member, and a bearing member rotatably disposed at both ends of the conductive core member and provided with an elastic layer on the outer periphery thereof And a cylindrical conductive member fitted on the outer periphery of the conductive core member and having both longitudinal ends thereof fitted and fixed to the outer periphery of the bearing member.Prepared,
The conductive core member has a hollow metal shaft having a rectangular cross section, a shaft member fixed to both ends of the hollow shaft, and a large outer diameter on the hollow shaft side between the hollow shaft and the shaft member. A cylindrical stepped portion, and the bearing member is attached to the stepped portion, and the interval between the bearing members attached to the stepped portions at both ends of the hollow shaft is set along the axial direction of the cylindrical conductive member. The cylindrical conductive member itself is prevented from moving in the thrust direction by the elastic force of the cylindrical conductive member itself.This is a contact-type charging device.
[0027]
Furthermore, the invention described in claim 2 is provided on the surface of the charged body.Has elasticityIn a contact-type charging device for charging or discharging the surface of the object to be charged by contacting the cylindrical conductive member and rotating the cylindrical conductive member,
A conductive core member disposed along the axial direction inside the cylindrical conductive member, and a bearing member rotatably disposed at both ends of the conductive core member and provided with an elastic layer on the outer periphery thereof A cylindrical conductive member that is fitted to the outer periphery of the conductive core member and whose both ends in the longitudinal direction are fitted and fixed to the outer periphery of the bearing member, and charging along the axial direction of the conductive core member A conductive elastic member that is held over a region and presses the cylindrical conductive member against the surface of the member to be charged.Prepared,
The conductive core member has a hollow metal shaft having a rectangular cross section, a shaft member fixed to both ends of the hollow shaft, and a large outer diameter on the hollow shaft side between the hollow shaft and the shaft member. A cylindrical stepped portion, and the bearing member is attached to the stepped portion, and the interval between the bearing members attached to the stepped portions at both ends of the hollow shaft is set along the axial direction of the cylindrical conductive member. The cylindrical conductive member itself is prevented from moving in the thrust direction by the elastic force of the cylindrical conductive member itself.This is a contact-type charging device.
[0028]
Here, the conductive elastic member is attached over, for example, a charging region along the axial direction of the conductive core member, and only from the conductive core member to the portion where the cylindrical conductive member contacts the member to be charged. Arranged.
[0029]
or,Claim 3The conductive core member has a step in which the outer diameter on the end side is set to be small at both ends in the axial direction, and the bearing member is provided on at least a part of its inner periphery. It has an inner diameter that does not exceed the step of the conductive core member, and has an elastic layer on the outer periphery.Claim 1 or 2It is a contact-type charging device described.
[0030]
Furthermore,Claim 4In the invention described in the above, the conductive core member is formed such that both end portions in the axial direction are at least cylindrical, and a plane along the axial direction is formed in a part of the circumferential direction in the intermediate portion. It is characterized by havingClaims 1 to 3Any one of the contact-type charging devices.
[0031]
Furthermore,Claim 5In the invention described in the above, the conductive core member has both ends in the axial direction formed at least in a columnar shape, and at least one of the both ends formed in the columnar shape is provided with the conductive core member. A reference plane having a D-shaped cross section that is attached in a non-rotating state at a predetermined angle is formed.Claim 4It is a contact-type charging device described.
[0034]
Also,Claim 6The invention described inHas elasticityIn an image forming apparatus including a contact-type charging device that charges the surface of the image carrier by bringing the cylindrical conductive member into contact with the surface of the image carrier and rotating the cylindrical conductive member.
The contact-type charging device includes a conductive core member disposed along the axial direction inside the cylindrical conductive member, and rotatably disposed at both ends of the conductive core member, and an outer periphery thereof. A bearing member provided with an elastic layer, and a cylindrical conductive member fitted on the outer periphery of the conductive core member and having both longitudinal ends fitted and fixed to the outer periphery of the bearing member.Prepared,
The conductive core member has a hollow metal shaft having a rectangular cross section, a shaft member fixed to both ends of the hollow shaft, and a large outer diameter on the hollow shaft side between the hollow shaft and the shaft member. A cylindrical stepped portion, and the bearing member is attached to the stepped portion, and the interval between the bearing members attached to the stepped portions at both ends of the hollow shaft is set along the axial direction of the cylindrical conductive member. The cylindrical conductive member itself is prevented from moving in the thrust direction by the elastic force of the cylindrical conductive member itself.An image forming apparatus characterized by the above.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0036]
Embodiment 1
FIG. 2 shows a tandem type full-color printer as an image forming apparatus to which the contact type charging device according to Embodiment 1 of the present invention is applied.
[0037]
In FIG. 2, reference numeral 01 denotes a main body of a tandem type full-color printer. The printer main body 01 is roughly divided into a print head device (Print Head Device) 02 for forming a full-color image and this print. ROS (Raster Output Scanner) 03 as an exposure device that performs image exposure on the four photosensitive drums 11, 12, 13, and 14 as the electrostatic latent image carrier of the head device 02, and each color of the print head device 02 Four toner cartridges 04Y, 04M, 04K, 04C that supply toner of colors corresponding to the developing devices 41, 42, 43, and 44, and a paper feed cassette that supplies recording paper P as a recording medium to the print head device 02 05, a fixing device 06 for performing a fixing process on the recording paper P on which the toner image is transferred from the print head device 02, and an image is fixed on one side by the fixing device 06 A double-sided conveyance path 07 for conveying the recording sheet P to the transfer unit of the print head device 02 again with the front and back sides reversed, and a manual sheet feeding unit for feeding a desired recording sheet P from the outside of the printer main body 01 08, a control circuit that controls the operation of the printer, a controller 09 that includes an image processing circuit that performs image processing on an image signal, and an electric circuit 10 that includes a high-voltage power supply circuit and the like. In FIG. 2, T denotes a discharge toilet for discharging the recording paper P on which an image is formed. The discharge toilet T is integrally disposed on the upper portion of the printer main body 01.
[0038]
Of the various members arranged in the printer main body 01, ROS03 as an exposure device is image data corresponding to each color of yellow (Y), magenta (M), black (K), and cyan (C). From four semiconductor lasers that are driven to light based on the above, four laser beams emitted from these four semiconductor lasers, f-θ lenses for deflecting scanning, polygon mirrors, or a plurality of reflection mirrors It is configured.
[0039]
FIG. 3 shows a print head device of a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. In addition, the arrow in FIG. 3 has shown the rotation direction of each rotation member.
[0040]
As shown in FIG. 3, the print head device 02 includes yellow (Y), magenta (M), black (K), and cyan (C) photosensitive drums (image carriers) 11, 12, 13, and the like. 14 and image forming units 1, 2, 3, 4 and contact charging devices 21, 22, 22, for primary charging according to Embodiment 1 of the present invention, which are in contact with these photosensitive drums 11, 12, 13, 14. 23, 24 and ROS (exposure device) 03 for irradiating laser beams 31, 32, 33, 34 of yellow (Y), magenta (M), black (K), and cyan (C) colors (see FIG. 2) Then, the electrostatic latent images formed on the photosensitive drums 11, 12, 13, and 14 are developed with yellow (Y), magenta (M), black (K), and cyan (C) toners. Development device 41, 42, 43, 44 and a first primary intermediate transfer drum (medium that contacts two of the four photosensitive drums 11, 12, 13, and 14 among the four photosensitive drums 11 and 12) Intermediate transfer member) 51 and the second primary intermediate transfer drum (intermediate transfer member) 52 that contacts the other two photosensitive drums 13 and 14, and the first and second primary intermediate transfer drums 51 and 52. The secondary intermediate transfer drum (intermediate transfer member) 53 and the final transfer roll (transfer member) 60 in contact with the secondary intermediate transfer drum 53 constitute the main part.
[0041]
The photosensitive drums 11, 12, 13, and 14 are arranged at a constant interval so as to have a common tangential plane M.sub.2. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 are surfaces whose rotational axes are parallel to the photosensitive drums 11, 12, 13, and 14 and have predetermined symmetry planes as boundaries. They are arranged in a symmetrical relationship. Further, the secondary intermediate transfer drum 53 is arranged so that the rotation axis thereof is parallel to the photosensitive drums 11, 12, 13, and 14.
[0042]
A signal corresponding to the image information for each color is rasterized by an image processing circuit disposed in the electric circuit 10 (see FIG. 2) and input to the ROS03. In this ROS03, the laser beams 31, 32, 33, and 34 of yellow (Y), magenta (M), black (K), and cyan (C) are modulated, and the corresponding photosensitive drums 11, 12, and 12 are modulated. 13 and 14 are irradiated.
[0043]
Around each of the photosensitive drums 11, 12, 13, and 14, an image forming process for each color is performed by a known electrophotographic method. First, as the photoconductor drums 11, 12, 13, and 14, for example, photoconductor drums using an OPC photoconductor with a diameter of 30 mm are used. These photoconductor drums 11, 12, 13, and 14 are, for example, It is rotationally driven at a rotational speed of 104 mm / sec. As shown in FIG. 3, a DC voltage of about −840 V is applied to the surface of the photosensitive drums 11, 12, 13, and 14 to contact-type charging devices 21, 22, 23, and 24 that will be described in detail later. For example, it is charged to about -300V. Further, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, in this embodiment, a charging method in which only DC is applied is used, but a charging method in which AC + DC is applied may be used.
[0044]
Thereafter, laser light 31 corresponding to each color of yellow (Y), magenta (M), black (K), and cyan (C) is formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 by ROS03 as an exposure device. , 32, 33, and 34 are irradiated, and an electrostatic latent image corresponding to input image information for each color is formed. When the electrostatic latent image is written by ROS03, the photosensitive drums 11, 12, 13, and 14 are discharged to a surface potential of the image exposure portion of about −60 V or less.
[0045]
In addition, electrostatic latent images corresponding to yellow (Y), magenta (M), black (K), and cyan (C) colors formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 Are developed by the developing devices 41, 42, 43, and 44, and yellow (Y), magenta (M), black (K), and cyan (C) colors are formed on the photosensitive drums 11, 12, 13, and 14, respectively. Visualized as a toner image.
[0046]
In this embodiment, as the developing devices 41, 42, 43, 44, a magnetic brush contact type two-component developing method is adopted, but the scope of application of the present invention is not limited to this developing method, Needless to say, the present invention can be sufficiently applied to a non-contact type developing system.
[0047]
The developing devices 41, 42, 43, and 44 are filled with yellow (Y), magenta (M), black (K), and cyan (C) toners of different colors and a developer composed of a carrier. Yes. As shown in FIG. 2, when toner is supplied from the corresponding toner cartridges 04Y, 04M, 04K, and 04C, the supplied toner is supplied to the developing devices 41, 42, 43, and 44. 401 and 402 are sufficiently agitated with the carrier and triboelectrically charged. Inside the developing roll 403, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is fixed. The amount of developer conveyed to the vicinity of the surface of the developing roll 403 is regulated by the developer amount regulating member 404 by the auger 402 that conveys the developer to the developing roll 403. In this embodiment, the amount of the developer is 30 to 50 g / m.²At this time, the charge amount of the toner existing on the developing roll 403 is about -20 to 35 μC / g.
[0048]
The toner supplied onto the developing roll 403 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 11, 12, 13, and 14. ing. A developing bias voltage of AC + DC is applied to the developing roll 403 to develop the toner on the developing roll 403 into an electrostatic latent image formed on the photosensitive drums 11, 12, 13, and 14. It is formed. In this embodiment, for example, the AC component of the developing bias voltage is set to 4 kHz, 1.5 kVpp, and the DC component is set to about -230V.
[0049]
In this embodiment, in the developing devices 41, 42, 43, and 44, so-called “spherical toner” that is a substantially spherical toner is used, and an average particle diameter of about 3 to 10 μm is used. For example, the average particle diameter of the black toner is set to 8 μm, and the average particle diameter of the color toner is set to 7 μm.
[0050]
Next, the yellow (Y), magenta (M), black (K), and cyan (C) toner images formed on the photosensitive drums 11, 12, 13, and 14 are first primary images. The secondary transfer is electrostatically performed on the intermediate transfer drum 51 and the second primary intermediate transfer drum 52. The yellow (Y) and magenta (M) color toner images formed on the photosensitive drums 11 and 12 are formed on the first primary intermediate transfer drum 51 on the black ( The toner images of K) and cyan (C) are transferred onto the second primary intermediate transfer drum 52, respectively. Therefore, on the first primary intermediate transfer drum 51, the single color image transferred from either the photosensitive drum 11 or 12 and the two color toner images transferred from both the photosensitive drums 11 and 12 are superimposed. A double color image is formed. In addition, similar single-color images and double-color images are also formed on the second primary intermediate transfer drum 52 from the photosensitive drums 13 and 14.
[0051]
The surface potential necessary for electrostatically transferring the toner image from the photosensitive drums 11, 12, 13, 14 onto the first and second primary intermediate transfer drums 51, 52 is about +250 to 500V. It is. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. The ambient temperature and humidity can be easily known by detecting the resistance value of a member having a characteristic that the resistance value varies depending on the ambient temperature and humidity. As described above, when the charge amount of the toner is in the range of −20 to 35 μC / g and is in a normal temperature and humidity environment, the surface potential of the first and second primary intermediate transfer drums 51 and 52 is + 380V is desirable.
[0052]
For example, the first and second primary intermediate transfer drums 51 and 52 used in this embodiment are formed to have an outer diameter of 60 mm and a resistance value of 10 mm.⁸It is set to about Ω. The first and second primary intermediate transfer drums 51 and 52 are cylindrical rotating bodies having a single layer or a plurality of layers whose surfaces are flexible or elastic, and are generally made of Fe, Al, or the like. A low resistance elastic rubber layer represented by conductive silicone rubber (R = 10) on a metal pipe as a metal core²~Ten^ThreeΩ) is provided in a thickness of about 0.1 to 10 mm. Furthermore, the outermost surfaces of the first and second intermediate transfer drums 51 and 52 are typically high release layers (R = 10) of fluororubber in which fluororesin fine particles are dispersed and having a thickness of 3 to 100 μm.^Five~Ten⁹Ω) and bonded with a silane coupling agent-based adhesive (primer). What is important here is the resistance value and the releasability of the surface, and the resistance value of the high release layer is R = 10.^Five~Ten⁹The material is not particularly limited as long as it is about Ω and has a high releasability.
[0053]
The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 in this way are electrostatically and tertiary-transferred onto the secondary intermediate transfer drum 53. Therefore, a final toner image from a single color image to a quadruple color image of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the secondary intermediate transfer drum 53. Will be.
[0054]
The surface potential necessary for electrostatically transferring the toner image from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200V. This surface potential is the same as when the toner is transferred from the photosensitive drums 11, 12, 13, 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Will be set to the optimum value. Further, since what is necessary for the transfer is a potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 52 have different potentials. It is necessary to set the value according to the surface potential. As described above, the charge amount of the toner is in the range of −20 to 35 μC / g, and the surface potential of the first and second primary intermediate transfer drums 51 and 52 is +380 V in a normal temperature and humidity environment. The surface potential of the secondary intermediate transfer drum 53 is about +880 V, that is, the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is + It is desirable to set it to about 500V.
[0055]
For example, the secondary intermediate transfer drum 53 used in this embodiment has an outer diameter of 60 mm, which is the same as the first and second primary intermediate transfer drums 51 and 52, and has a resistance value of 10 mm.¹¹It is set to about Ω. Similarly to the first and second primary intermediate transfer drums 51 and 52, the secondary intermediate transfer drum 53 is a cylindrical rotating body having a single layer or a plurality of layers whose surface is flexible or elastic. In general, a low resistance elastic rubber layer (R = 10) represented by conductive silicone rubber or the like on a metal pipe as a metal core made of Fe, Al or the like.²~Ten^ThreeΩ) is provided in a thickness of about 0.1 to 10 mm. Further, the outermost surface of the secondary intermediate transfer drum 53 is typically formed by forming a fluororubber in which fluororesin fine particles are dispersed as a high release layer having a thickness of 3 to 100 μm, and a silane coupling agent-based adhesive. (Primer). Here, the resistance value of the secondary intermediate transfer drum 53 needs to be set higher than that of the first and second primary intermediate transfer drums 51 and 52. Otherwise, the secondary intermediate transfer drum 53 will charge the first and second primary intermediate transfer drums 51, 52, making it difficult to control the surface potential of the first and second primary intermediate transfer drums 51, 52. Become. The material is not particularly limited as long as the material satisfies such conditions.
[0056]
Next, the final toner image from the single color image to the quadruple color image formed on the secondary intermediate transfer drum 53 is tertiary transferred onto the paper P passing through the paper conveyance path by the final transfer roll 60. . The paper P passes through a paper transporting roll 90 through a paper feeding process (not shown), and is fed into the nip portion between the secondary intermediate transfer drum 53 and the final transfer roll 60. After this final transfer step, the final toner image formed on the paper is fixed by the fixing device 70, and a series of image forming processes is completed.
[0057]
By the way, the contact-type charging device according to this embodiment charges the surface of the charged body by bringing the cylindrical conductive member into contact with the surface of the charged body and rotating the cylindrical conductive member in a driven manner. Alternatively, in the contact-type charging device for removing static electricity, the conductive core member is disposed along the axial direction inside the cylindrical conductive member, and is rotatably disposed at both ends of the conductive core member. A bearing member having an elastic layer on its outer periphery, a cylindrical conductive member fitted on the outer periphery of the conductive core member, and having both longitudinal ends thereof fitted and fixed to the outer periphery of the bearing member, and the conductive member And a conductive elastic member that is held over a charging region along the axial direction of the core member and presses the cylindrical conductive member against the surface of the member to be charged.
[0058]
Further, in this embodiment, the conductive core member has a step in which the outer diameter on the end side is set to be small at both end portions in the axial direction, and the bearing member is provided on at least a part of the inner periphery thereof. It has an inner diameter that does not exceed the step of the conductive core member, and has an elastic layer on the outer periphery.
[0059]
Furthermore, in this embodiment, the conductive core member has both end portions in the axial direction formed at least in a columnar shape, and a flat portion along the axial direction at a part in the circumferential direction at the intermediate portion. It is comprised so that it may have.
[0060]
Still further, in this embodiment, the conductive core member has both ends in the axial direction formed at least in a columnar shape, and at least one of the both ends formed in the columnar shape has the conductive material. A reference plane having a D-shaped cross section for attaching the core member in a non-rotating state at a predetermined angle is formed.
[0061]
1 and 4 are configuration diagrams showing a contact-type charging device according to Embodiment 1 of the present invention.
[0062]
That is, the contact-type charging devices 21, 22, 23, and 24 according to this embodiment are all configured in the same manner, and these contact-type charging devices 21, 22, 23, and 24 are illustrated in FIGS. As shown in FIG. 5, it is roughly configured to include a conductive core member 210, a bearing member 220, a cylindrical conductive member 230, and a conductive elastic member 240.
[0063]
As shown in FIG. 5, the conductive core member 210 is made of a metal such as stainless steel, iron, or aluminum, and has a long metal rectangular shaft 211 having a rectangular cross section (in the illustrated example, a square cross section), It is configured to have shaft members 212 and 213 that are fitted and fixed to both ends of the metal hollow shaft 211 and project in a columnar shape toward the outside in the axial direction. The metal hollow shaft 211 is set to have a width of 5 mm, for example. The shaft members 212 and 213 of the conductive core member 210 are stepped portions 214 and 215 in which the outer diameter of the end on the hollow shaft 211 side is set larger and the outer diameter in the axial direction is set smaller on the end on the hollow shaft 211 side. And a reference surface 216 having a D-shaped cross section, which is a flat surface that coincides with one end surface 211a of the hollow shaft 211 having a rectangular cross section, is provided at the tip of one shaft member 213. The interval between the bearing portions 221 determined as described later by the step portions 214 and 215 of the conductive core member 210 is equal to the free length of the cylindrical conductive member 230 or slightly longer than the free length of the cylindrical conductive member 230. It is desirable that the cylindrical conductive member 230 is configured to be slightly tensioned with the cylindrical conductive member 230 fitted and fixed to the bearing portion 221. With this configuration, in a state where the cylindrical conductive member 230 is fitted and fixed to the bearing portion 221, a slight tension is applied to the cylindrical conductive member 230, and the cylindrical conductive member 230 moves in the thrust direction. Can be prevented.
[0064]
As the conductive core member 210, it is desirable to use a metal hollow shaft having a rectangular cross section. However, as shown in FIG. good.
[0065]
Further, as shown in FIG. 6, the bearing member 220 is configured to be attached in a state of being fitted to the step portions 214 and 215 of the conductive core member 210. As shown in FIGS. 1 and 5, the bearing member 220 includes a synthetic resin bearing portion 221 fitted to the step portions 214 and 215 of the conductive core member 210, and press-fitting and double-sided tape on the outer periphery of the bearing portion 221. And an elastic layer 222 made of a sponge-like member made of a synthetic resin such as poron, which is fixed by adhesion or the like. Further, a step 223 fitted to the step portions 214 and 215 of the conductive core member 210 is formed on the inner circumference of the bearing portion 221 of the bearing member 220.
[0066]
Further, as shown in FIGS. 1 and 5, the cylindrical conductive member 230 is, for example, 10^Five-10⁸It is a hollow tube made of rubber or synthetic resin having a volume resistance of Ω, and has a diameter (outer diameter) of 10 mm and a thickness of 1 mm, for example. Here, as the cylindrical conductive member 230, carbon black or metal complex powder is added to EPDM (ethylene / propylene / diene terpolymer) or epichlorohydrin rubber, and 10^Five-10⁸A rubber tube adjusted to a volume resistance of Ω is used, and its surface is subjected to a silane coupling treatment with a fluorine compound.
[0067]
Furthermore, the conductive elastic member 240 has 10⁶It is composed of a metal, a synthetic resin, a rubber or a fiber bundle having a volume resistance of Ω or less. In this embodiment, a thin sheet-like member made of conductive PET having a thickness of 0.1 mm is used as the conductive elastic member 240, and the conductive elastic member 240 has a width as shown in FIG. It is formed in a narrow and long rectangular sheet shape. The conductive elastic member 240 is fixed to one side surface 211a located upstream in the rotation direction of the conductive core member 210 by means such as adhesion using a double-sided tape 241. From one side surface of the conductive core member 210, It is arranged so as to protrude downward by a predetermined length. The length of the conductive elastic member 240 determines the pressing force when the cylindrical conductive member 230 is pressed against the surface of the photosensitive drums 11, 12, 13, and 14, and is appropriately set. It is desirable to set the length slightly longer than the inner diameter of the cylindrical conductive member 230.
[0068]
In the configuration described above, in the contact-type charging device according to this embodiment, the charging member is stably driven to rotate without depending on the pressing force that presses the charging member against the member to be charged as follows. Can be uniformly charged.
[0069]
Further, in the contact-type charging device according to this embodiment, the charging member is made uniform along the axial direction without using an elastic brush or increasing the diameter of the core as follows. It is possible to contact.
[0070]
Furthermore, in the contact-type charging device according to this embodiment, it is possible to prevent the charging member from moving in the thrust direction without causing an increase in cost due to an increase in the number of parts as follows. It has become.
[0071]
Furthermore, in the contact-type charging device according to this embodiment, stable continuity between the core and the charging member can be obtained as follows, and uniform charging is performed on the object to be charged. Is possible.
[0072]
That is, in the contact-type charging devices 21, 22, 23, and 24 according to this embodiment, as shown in FIGS. 1 and 6 to 8, both ends in the longitudinal direction of a cylindrical conductive member 230 made of a hollow tube are used. The bearing member 220 is fixed in a state where the bearing member 220 is fitted, and the bearing member 220 is rotatably attached in a state where the bearing member 220 is fitted to the step portions 214 and 215 provided on the shaft members 212 and 213 of the conductive core member 210. ing. Accordingly, the cylindrical conductive member 230 made of the hollow tube is rotatably attached to the conductive core member 210 fixedly disposed via the bearing members 220 disposed at both ends in the longitudinal direction.
[0073]
Further, in the contact-type charging devices 21, 22, 23, 24, as shown in FIGS. 1 and 7, the conductive core member 210 is held inside a cylindrical conductive member 230 made of a hollow tube. A conductive elastic member 240 is provided, and the cylindrical conductive member 230 is in a predetermined contact state with the conductive elastic member 240 on the surface of the photosensitive drum 11, 12, 13, 14 as a member to be charged. It comes to be pressed by.
[0074]
Therefore, in the contact-type charging devices 21, 22, 23, 24, the cylindrical conductive member 230 is subjected to a pressing force that the cylindrical conductive member 230 is pressed against the surface of the photosensitive drum 11, 12, 13, 14. Regardless of the pressing force applied to the surfaces of the photosensitive drums 11, 12, 13, and 14, the conductive elastic member 240 can be controlled in contact with the photosensitive drums 11, 12, 13, and 14, and the photosensitive drums 11, 12 of the cylindrical conductive member 230 can be controlled. , 13, 14 The pressing force against the surface can always be maintained in an appropriate state. Moreover, in the contact-type charging devices 21, 22, 23, and 24, the driven member of the cylindrical conductive member 230 is rotated, and a bearing member fitted and fixed to both ends of the cylindrical conductive member 230 is used as a photosensitive drum. Since this is performed by pressing the surfaces of 11, 12, 13, and 14, the cylindrical conductive member 230 is stably driven to rotate without depending on the pressing force pressing the cylindrical conductive member 230 against the charged body. Can be uniformly charged.
[0075]
In the contact-type charging devices 21, 22, 23, and 24, the conductive elastic member 240 is held on the conductive core member 210 disposed inside the cylindrical conductive member 230, and the conductive conductive member Since the cylindrical conductive member 230 is pressed against the surface of the photosensitive drums 11, 12, 13, and 14 by the elastic member 240, the cylindrical conductive member 230 is not used without using an elastic brush or increasing the diameter of the core. Can be made to contact uniformly along the axial direction.
[0076]
Further, in the contact-type charging devices 21, 22, 23, and 24, the bearing member 220 is fitted and fixed to both ends of the cylindrical conductive member 230, and the bearing member 220 is provided on the conductive core member 210. Since the positioning is performed by fitting to the stepped portions 214 and 215, the interval between the bearing members 220 positioned by the stepped portions 214 and 215 is set equal to or slightly longer than the length of the cylindrical conductive member 230. The cylindrical conductive member 230 can be prevented from moving in the thrust direction by the elastic force or the like of the conductive member 230 itself. Therefore, it is possible to prevent the cylindrical conductive member 230 from moving in the thrust direction without causing an increase in cost due to an increase in the number of parts.
[0077]
Furthermore, in the contact-type charging devices 21, 22, 23, 24, a predetermined voltage is applied to the conductive core member 210 with respect to the cylindrical conductive member 230, whereby the conductive core member 210 The charged region of the cylindrical conductive member 230 can be reliably energized via the conductive elastic member 240 held over the charged region, and stable conduction between the conductive core member 210 and the cylindrical conductive member 230 is obtained. Therefore, the photosensitive drums 11, 12, 13, and 14 can be uniformly charged.
[0078]
Thus, in the case of the contact-type charging devices 21, 22, 23, and 24 according to the above embodiment, as shown in FIGS. 1, 7, and 8, the hollow body to which a voltage is applied from the outside is used. In a contact-type charging device in which a cylindrical conductive member 230 is driven with respect to the photosensitive drums 11, 12, 13 and 14 as charged bodies to charge or discharge the charged objects, traction control is performed at both ends of the hollow body. Since the bearing member 220 having a possible rotational drive mechanism is in contact with the member to be charged, a stable driven rotation can be obtained regardless of the frictional resistance of the contact portion that tends to be unstable in the hollow body. Further, since the cylindrical conductive member 230 can be stably brought into contact with the photosensitive drums 11, 12, 13, 14 by the cylindrical conductive member 230 fixed to the conductive core member 210, the photosensitive drums 11, 12, 13, 14 Can be charged stably and uniformly.
[0079]
In the case of the contact-type charging devices 21, 22, 23, and 24 according to the above-described embodiment, the cylindrical conductive member 230 is driven by the photosensitive drums 11, 12, 13, and 14 via the bearing member 220. Since it only rotates, it is possible to obtain a good driven rotation that is gearless and has a stable rotation speed.
[0080]
Further, in comparison with the present invention, a solid roll having hardness can obtain a stable driven rotation by the pressing pressure, but the pressing pressure crushes the toner adhering to the surface and causes filming on the surface of the charged body. Then, the surface is scraped by a minute slip, and the life of the member to be charged is reduced due to wear or surface scratches.
[0081]
Furthermore, it is well known that rotational driving by a gear that does not rely on traction is likely to cause uneven charging of the gear pitch as compared with the present invention.
[0082]
On the other hand, in the case of the contact-type charging devices 21, 22, 23, and 24 according to the above-described embodiment, the axial end region outside the image region where residual toner or the like does not come is applied with a free pressure. Since they can be brought into contact with each other, a stable rotational driving force can be obtained.
[0083]
In the case of the contact-type charging devices 21, 22, 23, and 24 according to the above-described embodiments, the rotational driving structure and the nip forming function are separated, so that the pressing load for the nip is an elastic layer. Even in the case of the cylindrical conductive member 230 made of a hollow body having an unstable shape, the contact member 220 having It is possible to form a minute gap shape.
[0084]
Furthermore, when the hollow member is driven to rotate, a so-called meandering (walk) is generated that usually generates a force in the thrust (axial) direction due to the pressure difference between the left and right, but in the present invention, since the pressure itself is light, the meandering force is weak, Furthermore, the movement of the both ends of the shaft processed into the core member is restricted to the center side of the bearing, and in addition to the tension of the cylindrical conductive member 230, the cylindrical conductive member 230 is prevented from moving in the thrust direction. Can be prevented.
[0085]
Furthermore, as described above, the shape of the charging nip is very important in order to obtain uniform charging performance. For this reason, the charging member is required to have a very high dimensional system. This increases the cost as it is, and decreases productivity by adding a polishing process. In contrast, the present invention uses the bearing member 220 and the conductive elastic member 240 in combination with the cylindrical conductive member 230, so that the cylindrical conductive member 230 itself does not require high outer diameter and dimensional accuracy. Moreover, since the structure itself is simple, mass productivity is high.
[0086]
As the conductive elastic member, for example, as shown in FIG. 9, a sponge-like conductive elastic member to which a conductive core member 210 is bonded may be used.
[0087]
【The invention's effect】
As described above, according to the present invention, the charging device can stably rotate the charging member and can uniformly charge the charging member regardless of the pressing force pressing the charging member against the member to be charged. Can be provided.
[0088]
Further, according to the present invention, there is provided a charging device capable of uniformly contacting the charging member along the axial direction without inserting an elastic brush around the entire circumference or increasing the diameter of the core member. Can be provided.
[0089]
Furthermore, according to the present invention, it is possible to provide a charging device capable of preventing the charging member from moving in the thrust direction without causing an increase in cost due to an increase in the number of parts.
[0090]
Furthermore, according to the present invention, it is possible to provide a charging device that can obtain stable conduction between the core member and the charging member and can uniformly charge the object to be charged.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a contact-type charging device according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a tandem type color printer as an image forming apparatus to which a contact type charging device according to Embodiment 1 of the present invention is applied.
FIG. 3 is a block diagram showing an image forming unit of a tandem type color printer as an image forming apparatus to which the contact type charging device according to the first embodiment of the present invention is applied.
FIG. 4 is an external perspective view showing a contact-type charging device according to Embodiment 1 of the present invention.
FIG. 5 is an exploded perspective view showing a contact-type charging device according to Embodiment 1 of the present invention.
FIG. 6 is a perspective view showing members of a contact-type charging device according to Embodiment 1 of the present invention.
FIG. 7 is a sectional view showing a usage state of the contact-type charging device according to the first embodiment of the present invention.
FIG. 8 is a cross-sectional view showing a usage state of the contact-type charging device according to Embodiment 1 of the present invention.
FIG. 9 is a sectional view showing a modification of the contact-type charging device according to Embodiment 1 of the present invention.
FIGS. 10A to 10C are configuration diagrams showing conductive core members for a charging device according to the present invention, respectively.
[Explanation of symbols]
21, 22, 23, 24: contact-type charging device, 210: conductive core member, 220: bearing member, 230: cylindrical conductive member, 240: conductive elastic member.

Claims

被帯電体の表面に弾性力を有する円筒状導電部材を接触させて、当該円筒状導電部材を回転させることにより、前記被帯電体の表面を帯電もしくは除電する接触式の帯電装置において、
前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材とを備え、
前記導電性芯部材は、断面矩形状の金属製中空シャフトと、当該中空シャフトの両端部に固定された軸部材と、前記中空シャフトと軸部材との間に中空シャフト側の外径を大きく設定した円筒形状の段差部とから構成し、前記段差部に前記軸受け部材を取り付けるとともに、前記中空シャフト両端の段差部に取り付けられた前記軸受け部材の間隔を、前記円筒状導電部材の軸方向に沿った自由長以上に設定し、前記円筒状導電部材自身が有する弾性力によって、当該円筒状導電部材のスラスト方向への移動を防止したことを特徴とする接触式の帯電装置。In a contact-type charging device that charges or discharges the surface of the charged body by contacting a cylindrical conductive member having elasticity on the surface of the charged body and rotating the cylindrical conductive member,
A conductive core member disposed along the axial direction inside the cylindrical conductive member, and a bearing member rotatably disposed at both ends of the conductive core member and provided with an elastic layer on the outer periphery thereof And a cylindrical conductive member that is fitted to the outer periphery of the conductive core member, and whose both ends in the longitudinal direction are fitted and fixed to the outer periphery of the bearing member ,
The conductive core member has a hollow metal shaft having a rectangular cross section, a shaft member fixed to both ends of the hollow shaft, and a large outer diameter on the hollow shaft side between the hollow shaft and the shaft member. A cylindrical stepped portion, and the bearing member is attached to the stepped portion, and the interval between the bearing members attached to the stepped portions at both ends of the hollow shaft is set along the axial direction of the cylindrical conductive member. A contact-type charging device characterized in that the cylindrical conductive member itself is prevented from moving in the thrust direction by the elastic force of the cylindrical conductive member itself, which is set to a free length or longer .

被帯電体の表面に弾性力を有する円筒状導電部材を接触させて、当該円筒状導電部材を回転させることにより、前記被帯電体の表面を帯電もしくは除電する接触式の帯電装置において、
前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材と、前記導電性芯部材の軸方向に沿った帯電領域に渡って保持され、前記円筒状導電部材を被帯電体の表面に押圧する導電性弾性部材とを備え、
前記導電性芯部材は、断面矩形状の金属製中空シャフトと、当該中空シャフトの両端部に固定された軸部材と、前記中空シャフトと軸部材との間に中空シャフト側の外径を大きく設定した円筒形状の段差部とから構成し、前記段差部に前記軸受け部材を取り付けるとともに、前記中空シャフト両端の段差部に取り付けられた前記軸受け部材の間隔を、前記円筒状導電部材の軸方向に沿った自由長以上に設定し、前記円筒状導電部材自身が有する弾性力によって、当該円筒状導電部材のスラスト方向への移動を防止したことを特徴とする接触式の帯電装置。In a contact-type charging device that charges or discharges the surface of the charged body by contacting a cylindrical conductive member having elasticity on the surface of the charged body and rotating the cylindrical conductive member,
A conductive core member disposed along the axial direction inside the cylindrical conductive member, and a bearing member rotatably disposed at both ends of the conductive core member and provided with an elastic layer on the outer periphery thereof A cylindrical conductive member that is fitted to the outer periphery of the conductive core member and whose both ends in the longitudinal direction are fitted and fixed to the outer periphery of the bearing member, and charging along the axial direction of the conductive core member held over the region, and a conductive elastic member which presses the cylindrical conductive member on the surface of the member to be charged,
The conductive core member has a hollow metal shaft having a rectangular cross section, a shaft member fixed to both ends of the hollow shaft, and a large outer diameter on the hollow shaft side between the hollow shaft and the shaft member. A cylindrical stepped portion, and the bearing member is attached to the stepped portion, and the interval between the bearing members attached to the stepped portions at both ends of the hollow shaft is set along the axial direction of the cylindrical conductive member. A contact-type charging device characterized in that the cylindrical conductive member itself is prevented from moving in the thrust direction by the elastic force of the cylindrical conductive member itself, which is set to a free length or longer .

前記導電性芯部材は、その軸方向の両端部に端部側の外径を小さく設定した段差を有するとともに、前記軸受け部材は、その内周の少なくとも一部に前記導電性芯部材の段差を越えない内径を有し、かつ外周に弾性層を有することを特徴とする請求項１又は２記載の接触式の帯電装置。The conductive core member has a step with a small outer diameter on both ends in the axial direction, and the bearing member has a step of the conductive core member on at least a part of its inner periphery. 3. The contact-type charging device according to claim 1, wherein the contact-type charging device has an inner diameter not exceeding and an elastic layer on the outer periphery.

前記導電性芯部材は、その軸方向の両端部が少なくとも円柱状に形成されているとともに、その中間部には、周方向の一部に軸方向に沿った平面を有することを特徴とする請求項１乃至３のいずれかに記載の接触式の帯電装置。2. The conductive core member according to claim 1, wherein both end portions in the axial direction of the conductive core member are formed at least in a columnar shape, and a flat portion along the axial direction is provided in a part of the circumferential direction in the intermediate portion. Item 4. The contact-type charging device according to any one of Items 1 to 3.

前記導電性芯部材は、その軸方向の両端部が少なくとも円柱状に形成されているとともに、当該円柱状に形成された両端部の少なくとも一方に、前記導電性芯部材を所定の角度で回り止め状態に取り付ける断面Ｄ形状の基準平面が形成されていることを特徴とする請求項４記載の接触式の帯電装置。The conductive core member has both ends in the axial direction formed at least in a cylindrical shape, and at least one of the both ends formed in the columnar shape prevents the conductive core member from rotating at a predetermined angle. 5. The contact charging device according to claim 4, wherein a reference plane having a D-shaped cross section to be attached to the state is formed.

弾性力を有する円筒状導電部材を像担持体の表面に接触させて、当該円筒状導電部材を回転させることにより、前記像担持体の表面を帯電させる接触式の帯電装置を備えた画像形成装置において、
前記接触式の帯電装置は、前記円筒状導電部材の内部に軸方向に沿って配設される導電性芯部材と、前記導電性芯部材の両端部に回転自在に配設され、かつその外周に弾性層を備えた軸受け部材と、前記導電性芯部材の外周に嵌装され、かつその長手方向の両端部が軸受け部材の外周に嵌合固定された円筒状導電部材とを備え、
前記導電性芯部材は、断面矩形状の金属製中空シャフトと、当該中空シャフトの両端部に固定された軸部材と、前記中空シャフトと軸部材との間に中空シャフト側の外径を大きく設定した円筒形状の段差部とから構成し、前記段差部に前記軸受け部材を取り付けるとともに、前記中空シャフト両端の段差部に取り付けられた前記軸受け部材の間隔を、前記円筒状導電部材の軸方向に沿った自由長以上に設定し、前記円筒状導電部材自身が有する弾性力によって、当該円筒状導電部材のスラスト方向への移動を防止したことを特徴とする画像形成装置。An image forming apparatus provided with a contact-type charging device that charges the surface of the image carrier by bringing the cylindrical conductive member having elasticity into contact with the surface of the image carrier and rotating the cylindrical conductive member In
The contact-type charging device includes a conductive core member disposed along the axial direction inside the cylindrical conductive member, and rotatably disposed at both ends of the conductive core member, and an outer periphery thereof. A bearing member provided with an elastic layer, and a cylindrical conductive member fitted to the outer periphery of the conductive core member and having both longitudinal ends thereof fitted and fixed to the outer periphery of the bearing member ,
The conductive core member has a hollow metal shaft having a rectangular cross section, a shaft member fixed to both ends of the hollow shaft, and a large outer diameter on the hollow shaft side between the hollow shaft and the shaft member. A cylindrical stepped portion, and the bearing member is attached to the stepped portion, and the interval between the bearing members attached to the stepped portions at both ends of the hollow shaft is set along the axial direction of the cylindrical conductive member. An image forming apparatus , wherein the cylindrical conductive member itself is prevented from moving in the thrust direction by an elastic force of the cylindrical conductive member itself .