JP4353678B2 - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

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JP4353678B2
JP4353678B2 JP2002158213A JP2002158213A JP4353678B2 JP 4353678 B2 JP4353678 B2 JP 4353678B2 JP 2002158213 A JP2002158213 A JP 2002158213A JP 2002158213 A JP2002158213 A JP 2002158213A JP 4353678 B2 JP4353678 B2 JP 4353678B2
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fixing
recording
pressure
nip
separating
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JP2003107947A (en
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淳 中藤
清 大嶋
廣和 池上
純 由良
尚志 菊地
貴史 藤田
聡彦 馬場
重夫 黒高
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株式会社リコー
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Priority to JP2001167346 priority
Priority to JP2001-222186 priority
Priority to JP2001222186 priority
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【0001】
【発明の属する技術分野】
本発明は、加熱される定着部材と、該定着部材に圧接する加圧部材とを有し、定着すべきトナー像を担持した記録材を、そのトナー像が前記定着部材に接する向きにして、前記定着部材と加圧部材との圧接により形成されたニップを通過させて、熱と圧力の作用により前記トナー像を記録材に定着させる定着装置を有する画像形成装置に関するものである。
【0002】
【従来の技術】
複写機、プリンタ、ファクシミリ或いはこれらの少なくとも2つの機能を備えた複合機などとして構成される画像形成装置に上記形式の定着装置を採用することは従来より周知である。この形式の定着装置においては、記録材に担持されたトナーが定着部材と加圧部材により形成されたニップを通過するとき、そのニップ内で溶融するので、トナーが粘着剤として作用し、ニップを出た記録材が定着部材の表面から分離せずにその表面に巻きついてしまうおそれがある。特に、フルカラー画像を形成する画像形成装置においては、記録材上に異なった色の複数のトナー像が重ね合わされて形成され、かかる重ね合わせトナー像が定着装置により定着されるので、ニップ内で多量のトナーが溶融することになり、これによってトナーの粘着力が高まり、記録材が定着部材に一層巻きつきやすくなる。
【0003】
そこで、従来より、複数の分離爪より成る分離手段を定着部材の表面に当接させ、ニップを出た記録材を分離爪によって定着部材表面から分離し、記録材が定着部材の表面に巻きつくことを防止できるように構成している。ところが、分離爪は、その先端が定着部材の表面に接触しているので、分離爪によって定着部材の表面に傷がつけられるおそれがある。定着部材の表面に傷がつくと、ニップを通過するトナー像にその傷に対応する跡ができ、定着後のトナー像の画質が劣化する。
【0004】
このような欠点を除去するため、分離爪を定着部材表面から離間させて配置した定着装置が提案されている。ところが、分離爪を定着部材表面に対して非接触状態で配置すると、ニップを出た記録材が、定着部材の表面に付着したまま、定着部材と分離爪の間に入り込み、その記録材が定着部材に巻きついてしまうおそれがある。このように定着部材から離間した分離爪を用いると、記録材の分離機能が低下し、記録材が定着部材に巻きつく可能性が高まるのである。
【0005】
【発明が解決しようとする課題】
本発明の目的は、定着部材への記録材の巻きつきを効果的に防止でき、しかも定着後のトナー像の画質が劣化する不具合を効果的に抑えることのできる冒頭に記載した形式の定着装置を有する画像形成装置を提供することにある。
【0006】
【課題を解決するための手段】
本発明は、上記目的を達成するため、冒頭に記載した形式の画像形成装置において、搬送される記録材の搬送方向先端側の余白部だけが前記ニップを出た時、該先端側の余白部が、前記ニップの記録材搬送方向下流側端と該ニップの記録材搬送方向上流側端を結ぶ直線の延長線よりも加圧部材側を向くように構成すると共に、前記ニップを出た記録材を前記定着部材の表面から分離するためのシート状の分離部材を、前記定着部材の表面に対して非接触状態で配置し、前記ニップの記録材搬送方向下流側端と前記分離部材の先端との間のギャップを、前記記録材の搬送方向先端側の余白部の、該搬送方向における幅よりも小さく設定し、前記分離部材には、その厚み方向に貫通している開口が形成されていることを特徴とする画像形成装置を提案する(請求項1)。
【0007】
また、本発明は、上記目的を達成するため、冒頭に記載した形式の画像形成装置において、前記ニップを出た記録材を前記定着部材の表面から分離するためのシート状の分離部材を、前記定着部材の表面に対して非接触状態で配置し、前記ニップにおける加圧部材の表面のアスカーC硬度を、該ニップにおける定着部材の表面のアスカーC硬度よりも高く設定し、前記ニップの記録材搬送方向下流側端と前記分離部材の先端との間のギャップを、前記記録材の搬送方向先端側の余白部の、該搬送方向における幅よりも小さく設定し、前記分離部材には、その厚み方向に貫通している開口が形成されていることを特徴とする画像形成装置を提案する(請求項2)。
【0008】
さらに、上記請求項1又は2に記載の画像形成装置において、前記定着部材は、ガイド部材に巻き掛けられた無端状の定着ベルトより成り、前記加圧部材は、前記定着ベルトを介して、前記ガイド部材に圧接し、加圧部材の表面のアスカーC硬度が、前記ガイド部材に巻き掛けられた定着ベルト部分の表面のアスカーC硬度よりも高く設定されていると有利である(請求項3)。
【0009】
また、本発明は、上記目的を達成するため、冒頭に記載した形式の画像形成装置において、前記ニップを出た記録材を前記定着部材の表面から分離するためのシート状の分離部材を、前記定着部材の表面に対して非接触状態で配置し、前記ニップにおいて、凸状をなした加圧部材が前記定着部材を凹状に弾性変形させていて、前記ニップの記録材搬送方向下流側端と前記分離部材の先端との間のギャップを、前記記録材の搬送方向先端側の余白部の、該搬送方向における幅よりも小さく設定し、前記分離部材には、その厚み方向に貫通している開口が形成されていることを特徴とする画像形成装置を提案する(請求項4)。
【0010】
さらに、上記請求項4に記載の画像形成装置において、前記ニップを出た記録材を前記加圧部材の表面から分離するための加圧部材側分離手段を設け、該加圧部材側分離手段の先端部を加圧部材の表面に当接させると有利である(請求項5)。
【0011】
また、請求項1乃至5のいずれかに記載の画像形成装置において、前記記録材搬送方向に対して直交する向きの前記分離部材の各端部にギャップ保持部材を設け、該ギャップ保持部材を前記定着部材の記録材非通過領域に当接させて、該分離部材の先端と定着部材の表面との間の間隔を保持するように構成すると有利である(請求項6)。
【0012】
さらに、上記請求項1乃至6のいずれかに記載の画像形成装置において、前記分離部材を、記録材搬送方向に対して直交する向きに引張るテンション付与手段を設けると有利である(請求項7)。
【0013】
さらに、上記請求項1乃至7のいずれかに記載の画像形成装置において、前記トナー像が、少なくとも樹脂、着色剤及びワックスを含有するトナーにより形成されると有利である(請求項8)。
【0014】
【発明の実施の形態】
以下、本発明の実施形態例を図面に従って詳細に説明する。
【0015】
図1は画像形成装置の概略を示す垂直断面図であり、その画像形成装置本体1内には、記録材にトナー像を形成する作像手段2と、その作像手段に記録材を給送する給送手段3と、記録材上に形成されたトナー像を定着する定着装置4とが設けられている。図1には、定着装置4を単なるブロックで示してあるが、その具体的構成例は後述する。ここでは、先ず、作像手段2の概要を明らかにする。
【0016】
ここに例示した作像手段2は、像担持体の一例であるドラム状の感光体5を有し、この感光体5が時計方向に回転するとき、帯電装置6により感光体表面が所定の極性に帯電される。その帯電面に、露光装置の一例であるレーザ書き込みユニット7から出射する光変調されたレーザビームLが照射され、これによって感光体表面に静電潜像が形成される。この静電潜像は現像装置8によってトナー像として可視像化され、そのトナー像は、給送手段3から送り出された記録材上に、転写装置9の作用により転写される。トナー像転写後の感光体表面に付着する転写残トナーはクリーニング装置10により除去される。
【0017】
給送手段3は、例えば転写紙又は樹脂シートなどから成る記録材Pを収容したカセット11を有し、給送ローラ12の回転によって、最上位の記録材Pがカセット11から送り出される。その送り出された記録材はレジストローラ対13の回転によって、感光体5と転写装置9との間の転写部に給送され、ここで、前述のように感光体5上のトナー像が記録材上に転写される。このようにしてトナー像を担持した記録材は、矢印Aで示すように定着装置4に送り込まれてその定着装置4を通り、このとき、後述するように記録材上のトナー像が定着される。定着装置4を通過した記録材は、機外のトレイ14上に排出される。
【0018】
図2は定着装置4の一例を示す拡大断面図であり、ここに示した定着装置4は、定着ローラ15として構成された定着部材と、この定着ローラ15に圧接した加圧ローラ16として構成された加圧部材とを有し、これらのローラ15,16が互いに圧接することによりニップNが形成される。定着ローラ15と加圧ローラ16は、その外周が円形状の横断面形状を有する円柱状に形成されている。図示した例では、これらのローラ15,16は、内部が中空な円筒状に形成され、かかる定着ローラ15は時計方向に回転し、加圧ローラ16は反時計方向に回転する。
【0019】
両ローラ15,16の圧接により形成されたニップNは、加熱手段によってトナー像の定着に適した適正温度に制御される。この例では、定着ローラ15と加圧ローラ16の内部に熱源としてのハロゲンヒータ17,18がそれぞれ設けられ、図示していない温度制御手段によって、ヒータ17,18への通電のON,OFFが制御され、ニップNの温度が適正温度に保たれる。
【0020】
未定着トナー像Tを担持した記録材Pは、矢印Aで示すように定着装置4に送り込まれ、当該記録材Pは、そのトナー像Tが定着ローラ15の表面に接する向きにして、ニップNを通過し、熱と圧力によりトナー像Tが記録材P上に定着される。
【0021】
上述のように、定着装置は、加熱されながら回転する定着部材と、この定着部材に圧接しながら回転する加圧部材とを有し、定着すべきトナー像を担持した記録材を、そのトナー像が定着部材に接する向きにして、定着部材と加圧部材との圧接により形成されたニップを通過させて、熱と圧力の作用により上記トナー像を記録材に定着させるように構成されている。かかる基本構成は、後述する各例の定着装置においても変りはない。前述のように、図2に示した例では、定着部材が回転する定着ローラ15により構成され、加圧部材はその定着ローラ15に圧接しながら回転する加圧ローラ16により構成されているが、後述する如く、定着部材を、ガイド部材に巻き掛けられて回転する無端状の定着ベルトにより構成し、また加圧部材を、ガイド部材に巻き掛けられて回転する無端状の加圧ベルトにより構成することもできる。このように、定着部材と加圧部材は各種の形態に構成することができる。
【0022】
ここで、図2に示した定着装置4において、記録材Pに担持されたトナー像Tが定着ローラ15と加圧ローラ16との間のニップNを通過するとき、トナーはニップN内で溶融する。このときのトナーの粘着力によってニップNから出た記録材Pが定着ローラ15の表面に巻きつくことを防止するために次の構成が採用されている。
【0023】
図3は、定着ローラ15と加圧ローラ16とにより形成されたニップNと、このニップNを通過する記録材Pの拡大説明図である。図2及び図3に示すように、ニップNの出口近傍に、ニップNを出た記録材Pを、定着部材(この例では定着ローラ15)の表面から分離するための定着部材側分離手段19が、当該定着部材の表面に対して非接触状態で配置されている。定着部材側分離手段は適宜な形態に構成できるが、ここに示した定着部材側分離手段19はシート状の分離部材20によって構成されている。
【0024】
一方、記録材Pには、図4に斜線を付し、かつ符号IAを付して示した画像領域にトナー像が形成され、その画像領域IAの外側の縁領域は、トナー像の形成されない余白部Mとなっている。記録材Pは矢印Aで示す方向に搬送されて定着装置4に進入するが、その搬送方向先端側の余白部M1の、当該搬送方向Aにおける幅をWとする。この幅Wは例えば2乃至5mm程度である。図2及び図3は、上記先端側の余白部M1だけが丁度ニップNから出た時の様子を示している。これは、図5乃至図10においても同様である。
【0025】
ここで、図3に示すようにニップNの出口端、すなわちニップNの記録材搬送方向下流側端NEと、分離部材20の定着部材を向いた側の先端との間のギャップをGとすると、そのギャップGは、記録材Pの搬送方向先端側の余白部M1の、該搬送方向Aにおける前述の幅Wよりも小さく設定されている(G<W)。従って、図2及び図3に示したように、記録材Pの先端側の余白部M1の全体だけがニップNから出た時には、定着部材側分離手段19の先端は、その余白部M1と定着ローラ15との間の空間領域に入り込んだ状態で位置する。
【0026】
一方、加圧ローラ16の表面のアスカー(Asker)C硬度は、定着ローラ15の表面のアスカーC硬度よりも高く設定され、好ましくは、加圧ローラ16の表面のアスカーC硬度が定着ローラ15の表面のアスカーC硬度よりも20乃至40Hs大きくなるように構成されている。このようにニップNにおける加圧部材(この例では加圧ローラ16)の表面のアスカーC硬度を、該ニップNにおける定着部材(この例では定着ローラ15)の表面のアスカーC硬度よりも高く設定することにより、図2及び図3に示す如く、加圧ローラ16は、定着ローラ15の側に食い込むように、その定着ローラ15の表面を圧縮変形させる。ニップNにおいて、凸状をなした加圧部材が定着部材を凹状に弾性変形させるのである。
【0027】
従って、図2及び図3に示すように、記録材Pの先端側の余白部M1だけがニップNから出た時には、その余白部M1は、加圧ローラ16の周面に沿った姿勢、すなわち定着ローラ15の周面から大きく離れた向きの姿勢をとる。先端側の余白部M1にはトナー像が形成されていないので、その余白部M1がトナーの粘着力によって定着ローラ15の表面に付着しようとせず、余白部M1は、ニップNにおいて定着ローラ15の側に食い込んだ加圧ローラ16の周面に沿うようにしてニップNから排出されるのである。このとき、余白部M1と定着ローラ15の表面とは大きな距離をあけており、この状態で記録材Pの余白部M1が定着ローラ15の表面に巻きつくようなことはない。ニップNの記録材搬送方向下流側端NEと、このニップNの記録材搬送方向上流側端NSを結ぶ直線をLAとすると、搬送される記録材Pの搬送方向先端側の余白部M1だけがニップNを出た時、その先端側の余白部M1が、上記直線LAの記録材搬送方向側に引いた延長線LAAよりも加圧部材(この例では加圧ローラ16)側を向くように構成されているのである。
【0028】
記録材Pが図2及び図3に示した状態よりもさらに矢印A方向に搬送されると、図4に示した画像領域IAがニップNから排出され始まる。すると、その画像領域IA上のトナーの粘着力により記録材Pが定着ローラ15の表面に付着し、ないしは付着しようとするので、記録材Pは定着ローラ15の側に引張られていく。薄紙のような腰の弱い記録材の場合にはその傾向が顕著となる。
【0029】
ところが、定着ローラ15の近傍に定着部材側分離手段19が設けられているので、図3に鎖線で示すように、記録材Pが定着部材側分離手段19に当り、その分離手段19によって案内され、記録材Pが定着ローラ15の表面に巻きつくことが阻止される。定着部材側分離手段19は定着ローラ15の表面から離間して配置されてはいるが、ギャップGが余白部M1の幅Wよりも小さく設定されているので、トナーの粘着力により定着ローラ15の側に引張られた記録材Pが、定着ローラ15の表面に付着したまま、ギャップGを通って定着ローラ15の表面に巻きついてしまうことが阻止される。ニップNを出た記録材Pは、引き続き、上側に位置する定着部材側分離手段19と、その下方に位置するガイド部材21によって案内されながら搬送される。
【0030】
上述のように、ニップNを出た記録材Pが定着ローラ15の表面に巻きつくことを防止でき、しかも定着部材側分離手段19は定着ローラ15の表面に接触していないので、硬度が低く、従って傷の付きやすい定着ローラ15の表面に、定着部材側分離手段19によって傷がつけられる不具合を阻止できる。
【0031】
図1に示した画像形成装置は、記録材P上に単色、通常は黒色のトナー像を形成するように構成されているが、カラー画像を形成する画像形成装置においては、記録材上に、例えばイエロートナー像、マゼンタトナー像、シアントナー像及び黒色トナー像が重ねて形成され、かかる重ねトナー像を定着装置によって定着するので、従来は記録材が特に定着部材に巻きつきやすかったが、カラー画像を形成する画像形成装置の場合も、上述の構成を採用することによって、定着部材に傷がつくことを阻止しつつ、記録材が定着部材に巻きつくことを防止することができる。
【0032】
ここで、図2に示した定着装置4のより具体的な構成例を説明する。
【0033】
定着ローラ15は、芯金23と、その外周面に積層された弾性層24を有し、その弾性層24の外周面に離型層25が積層され、定着ローラ15の外径は、例えば40mmである。芯金23は、例えば外径が34mm、肉厚が1mmの鉄製中空ローラにより構成され、弾性層24は、例えば厚さ3mmのシリコーンゴムにより形成され、離型層25は例えば10μm乃至30μmの厚さのPFAチューブにより構成される。かかる離型層25を設けることにより、トナーの粘着力によって記録材Pが定着ローラ表面に付着することを抑制できる。
【0034】
加圧ローラ16は、例えば外径38mm、肉厚が1mmの鉄製中空ローラより成る芯金26と、その外周面に積層された弾性層27と、その外周面に積層された離型層28から成り、弾性層27は例えば層厚1mmのシリコーンゴムより成り、離型層28は例えば層厚10μm乃至30μmのPFAチューブにより構成される。
【0035】
定着ローラ15の表面硬度はアスカーC硬度で例えば45Hs、加圧ローラ16の表面硬度は同じくアスカーC硬度で例えば80Hsに設定されている。このように加圧ローラ16の方が硬いので、その加圧ローラ16が定着ローラ15の表面に食い込んだ状態で定着ローラ15を弾性変形させ、ニップNは加圧ローラ16の外形に沿った形態に形成される。
【0036】
図5に示した定着装置4においては、定着部材が無端状の定着ベルト15Aにより構成されている。この定着ベルト15Aは、2つのガイドローラ15B,15Cより成るガイド部材に巻き掛けられている。ガイド部材の数は3以上であってもよい。一方、加圧部材は、図2に示した定着装置と同様に円筒状の加圧ローラ16により構成され、この加圧ローラ16と、ガイドローラ15B,15Cは、その外周が円形となった横断面形状を有する円柱状に形成されている。図5に示した例では、いずれのローラ15B,15C,16も内部が中空な円筒状に形成されている。
【0037】
加圧ローラ16は、定着ベルト15Aを介して一方のガイドローラ15Bに圧接しており、これにより加圧ローラ16の外周面が定着ベルト15Aの外周面に圧接し、その圧接によりニップNが形成される。ガイドローラ15B,15Cと加圧ローラ16はそれぞれ矢印方向に回転し、これによって定着ベルト15Aが矢印B方向に回転駆動される。このように無端状の定着ベルト15Aが回転するとき、ガイドローラ15B,15Cは、その定着ベルト15Aを案内する用をなし、しかも加圧ローラ16に対向した一方のガイドローラ15Bは、加圧ローラ16と協働してニップNを形成し、他方のガイドローラ15Cは、定着ベルト15Aに張力を付与するテンションローラとしての用をなす。後述すように、ガイドローラ以外のガイド部材を用い、そのガイド部材に定着ベルト15Aを巻き掛けてもよく、また加圧ローラ16を定着ベルト15Aを介して複数のガイド部材に圧接させてもよい。定着部材を、複数のガイド部材に巻き掛けられて回転する無端状の定着ベルトにより構成し、加圧部材を、定着ベルトを介して、少なくとも1つのガイド部材に圧接して回転する加圧ローラにより構成するのである。
【0038】
両ガイドローラ15B,15Cの上述した機能に着目し、以下の説明では、必要に応じて、一方のガイドローラ15Bを対向ローラと称し、他方のガイドローラ15Cをテンションローラと称することにする。
【0039】
また、図5に示した定着装置においては、テンションローラ15Cと加圧ローラ16の内部にヒータ17A,18が設けられ、これらのヒータ17A,18によって定着ベルト15Aと加圧ローラ16が加熱され、該ヒータ17A,18への通電がON,OFF制御されて、ニップNの温度がトナー像の定着に適した適正温度に保たれる。
【0040】
この例の場合も、定着すべきトナー像Tを担持した記録材Pが、矢印Aで示すように、そのトナー像Tが定着ベルト15Aの表面に接する向きにしてニップNを通過し、熱と圧力の作用によりトナー像Tが記録材P上に定着される。
【0041】
図5に示した定着装置4においても、加圧ローラ16より成る加圧部材の表面のアスカーC硬度が、ガイド部材(図の例では対向ローラ15B)に巻き掛けられた定着ベルト部分の表面で測定したアスカーC硬度よりも高く設定されている。このように、図5に示した定着装置4も、ニップNにおける加圧ローラ16の表面のアスカーC硬度をニップNにおける定着ベルト15Aの表面のアスカーC硬度よりも高く設定することにより、図2に示した定着装置の場合と同じく、搬送される記録材の搬送方向先端側の余白部M1だけがニップNを出た時、その先端側の余白部M1が、ニップNの記録材搬送方向下流側端NEと該ニップNの記録材搬送方向上流側端NSを結ぶ直線LAの記録材搬送方向側への延長線LAAよりも加圧部材(図の例では加圧ローラ16)の側を向く。しかもニップNを出た記録材Pを定着ベルト15Aより成る定着部材の表面から分離するための定着部材側分離手段19が、その定着部材の表面に対して非接触状態で配置され、ニップNの記録材搬送方向下流側端NEと定着部材側分離手段19の定着部材を向いた側の先端との間のギャップGが、記録材Pの搬送方向先端側の余白部M1の、該搬送方向における幅Wよりも小さく設定されている。
【0042】
上記構成により、図2及び図3に示した定着装置と全く同様に、記録材Pが定着ベルト15Aより成る定着部材に巻きつくことを防止し、定着部材側分離手段19によって定着ベルト15Aの表面に傷がつけられることを阻止でき、定着後のトナー像の画質を高め、定着ベルト15Aの寿命を伸ばすことができる。ニップNを出た記録材Pは、定着部材側分離手段19と、ガイド部材21により案内され搬送され、トレイ14(図1)に排出されることも図2及び図3に示した定着装置と変りはない。
【0043】
図5に示した定着装置4のより具体的な構成例を説明すると、対向ローラ15B及び加圧ローラ16は、図2に示した定着装置の定着ローラ15及び加圧ローラ16とそれぞれ同じく構成できる。定着ベルト15Aは、例えば、厚さ50μmのポリイミド樹脂の基体上に、アスカーC硬度で30Hsのシリコーンゴムを0.2mm厚で積層し、その上に離型層としてPFAを厚さ5μmにコーティングしたものを用いることができる。また、図5に示したニップNは、加圧ローラ16が対向ローラ15Bに対向しない部位で定着ベルト15Aのみに当接する第1のニップ部分と、加圧ローラ16が定着ベルト15Aを介して対向ローラ15Bに当接した第2のニップ部分により形成されている。これにより、定着ベルト15Aの周方向に広い範囲のニップNを形成でき、加圧ローラ16と定着ベルト15Aとの圧接力を比較的小さくし、しかもニップNの適正温度を低くすることができる。
【0044】
また、図2に示した定着装置においては、定着ローラ15が、熱伝導率の悪いゴム性の弾性層24の内部からヒータ17により加熱されるので、定着装置の立上げ時に定着ローラ15がトナー像の定着に適した温度に上昇するまでに長い時間を必要とするが、図5に示した定着装置では、厚さが薄く、熱容量が小なる定着ベルト15Aを定着部材として用い、しかもその定着ベルト15Aを、対向ローラ15Bの内部から加熱するのではなく、厚さの薄いテンションローラ15C内のヒータ17Aによって加熱しているので、定着ベルト15Aがトナー像の定着に適した温度に上昇するまでの時間を短縮することができる。
【0045】
図2及び図5に示した定着装置においては、記録材Pの先端側余白部M1だけがニップNを出た時、その余白部M1が延長線LAAよりも加圧部材側を向くようにするために、定着ローラ15又は定着ベルト15Aにより構成された定着部材の表面硬度と、加圧ローラ16より成る加圧部材の表面硬度を前述のように設定したが、その際、定着部材が定着ベルト15Aより成るときは、前述のように、その定着部材表面の硬度は、対向ローラ15Bに巻き掛けられた定着ベルト部分の表面において測定したときの硬度である。要は、定着部材がいずれの形態であるときも、ニップNの記録材搬送方向下流側端NEにおける加圧部材の表面のアスカーC硬度を、ニップNの記録材搬送方向下流側端NEにおける定着部材の表面のアスカーC硬度よりも高く設定することにより、先端側余白部M1だけがニップNを出た時、その余白部M1が、延長線LAAよりも加圧部材側を向くように構成することができる。
【0046】
図6及び図7に定着装置4の他の例を示す。ここに示した定着装置4の基本構成は、図2に示した定着装置と実質的に変りはない。よって、図2に示した定着装置4の各部分に対応する図6に示した定着装置の各部分には、図2と同じ符号を付してその基本構成とその作用の説明は省略する。
【0047】
図6及び図7に示した定着装置4が図2に示した定着装置と異なるところは、定着ローラ15より成る定着部材の表面のアスカーC硬度と、加圧ローラ16より成る加圧部材の表面のアスカーC硬度が、ほぼ等しく設定されている点である。このように定着ローラ15と加圧ローラ16の表面硬度を設定することにより、定着ローラ15と加圧ローラ16で形成されるニップNにおいて両ローラ15,16はほぼ平坦な形態に圧縮変形して、直線状のニップNが形成される。従って、図7に示すように、搬送される記録材Pの搬送方向先端側の余白部M1だけがニップNを出た時、その先端側の余白部M1が、ニップNの記録材搬送方向下流側端NEと該ニップNの記録材搬送方向上流側端NSを結ぶ直線LBの記録材搬送方向側への延長線LBBの方向をほぼ向くことになる。また、図6及び図7に示した定着装置4にも、ニップNを出た記録材Pを定着ローラ15より成る定着部材の表面から分離するための定着部材側分離手段19が、その定着部材の表面に対して非接触状態で配置され、ニップNの記録材搬送方向下流側端NEと、定着部材側分離手段19の定着部材を向いた側の先端との間のギャップGが、記録材Pの搬送方向先端側の余白部M1の、該搬送方向における幅Wよりも小さく設定されている。
【0048】
図6及び図7に示したように、記録材Pの先端側余白部M1だけがニップNを出た時に、その余白部M1にはトナー像が形成されていないので、その余白部M1がトナーの粘着力によって定着ローラ15の表面に付着しようとせず、余白部M1は、ニップNの延長線LBBに沿ってニップNから排出され、この状態で記録材Pの余白部M1が定着ローラ15の表面に巻きつくようなことはない。記録材Pが図6及び図7に示した状態よりもさらに矢印A方向に搬送されると、図4に示した画像領域IAがニップNから排出され始まり、その画像領域IA上のトナーの粘着力により記録材Pが定着ローラ15の表面に付着し、ないしは付着しようとするので、記録材Pは定着ローラ15の側に引張られていくが、定着ローラ15の近傍に定着部材側分離手段19が設けられているので、記録材Pが定着部材側分離手段19に当り、その分離手段19によって案内され、記録材Pが定着ローラ15の表面に巻きつくことが阻止される。この場合も、定着部材側分離手段19は定着ローラ15
の表面から離間して配置されてはいるが、ギャップGが余白部M1の幅Wよりも小さく設定されているので、トナーの粘着力により定着ローラ15の側に引張られた記録材Pが、定着ローラ15の表面に付着したまま、ギャップGを通って定着ローラ15の表面に巻きついてしまうことが阻止される。定着装置4を通過した記録材Pは図1に示したトレイ14上に排出される。
【0049】
上述のように、図6及び図7に示した定着装置4においても、ニップNを出た記録材Pが定着ローラ15の表面に巻きつくことを防止でき、しかも定着部材側分離手段19は定着ローラ15の表面に接触していないので、硬度が低く、従って傷の付きやすい定着ローラ15の表面に、定着部材側分離手段19によって傷がつけられる不具合を阻止できる。しかも、ニップNが平坦な形状となっているので、図2及び図5に示した例のようにニップNが湾曲している場合よりも、ニップを出た記録材がカールし難くなる利点も得られる。
【0050】
図6に示した定着装置4の定着ローラ15と加圧ローラ16は、例えば、図2に示した定着装置4の定着ローラ16と同様に構成することができる。また、図6に示した定着ローラ15及び加圧ローラ16の表面硬度は、アスカーC硬度で例えば45Hsとすることができる。このように両ローラ15,16の表面が略同一の硬度であるため、ニップNは略平坦な形態に形成される。
【0051】
図8にさらに他の定着装置4の例を示す。ここに示した定着装置4の基本構成は、図5に示した定着装置と実質的に変りはない。図5に示したテンションローラ15Cは、対向ローラ15Bの右方に位置しているのに対し、図8に示したテンションローラ15Cは対向ローラ15Bの上方に位置しているが、この相違は基本的な相違ではない。よって図5に示した定着装置の各部分に対応する図8に示した定着装置の各部分には、図5と同じ符号を付し、その基本構成とその作用の説明は省略する。
【0052】
図8に示した定着装置が図5に示した定着装置と異なるところは、対向ローラ15Bに巻き掛けられた定着ベルト15Aの部分の表面で測定したアスカーC硬度が、加圧部材の一例である加圧ローラ16の表面のアスカーC硬度とほぼ同一に構成されている点である。従って、図8に示した定着装置4においても、図6及び図7に示した定着装置の場合と同じく、搬送される記録材Pの搬送方向先端側の余白部M1だけがニップNを出た時、その先端側の余白部M1が、ニップNの記録材搬送方向下流側端NEと該ニップNの記録材搬送方向上流側端NSを結ぶ直線LBの記録材搬送方向側への延長線LBBの方向をほぼ向く。しかも、ニップNを出た記録材Pを定着ベルト15Aより成る定着部材の表面から分離するための定着部材側分離手段19が、その定着部材の表面に対して非接触状態で配置され、ニップNの記録材搬送方向下流側端NEと定着部材側分離手段19の定着部材を向いた側の先端との間のギャップGが、記録材Pの搬送方向先端側の余白部M1の、該搬送方向における幅Wよりも小さく設定されている。これにより、図6及び図7に示した定着装置と同様に、記録材Pが定着ベルト15Aの表面に巻き付くことを阻止でき、しかも定着ベルト15Aの表面に、定着部材側分離手段19によって傷がつけられる不具合を阻止でき、さらにニップNを出た記録材Pがカールしやすくなる不具合も防止できる。
【0053】
図6乃至図8に示した定着装置においては、記録材Pの先端側余白部M1だけがニップNを出た時、その余白部M1が延長線LBBの方向をほぼ向くようにするために、定着ローラ15又は定着ベルト15Aにより構成された定着部材の表面硬度と、加圧ローラ16より成る加圧部材の表面硬度を前述のようにほぼ等しく設定したが、この場合も、定着部材が定着ベルト15Aより成るときは、その定着部材表面の硬度は、対向ローラ15Bに巻き掛けられた定着ベルト部分の表面において測定したときの硬度である。要は、定着部材がいずれの形態であるときも、ニップNの記録材搬送方向下流側端NEにおける定着部材の表面のアスカーC硬度と、ニップNの記録材搬送方向下流側端NEにおける加圧部材の表面のアスカーC硬度とをほぼ等しく設定することにより、先端側余白部M1だけがニップNを出た時、その余白部M1が、ほぼ延長線LBBの方向を向くように構成することができる。
【0054】
ところで、図1に示した画像形成装置は、記録材Pの一方の面にだけトナー像を形成するように構成されているが、記録材の一方の面に感光体上のトナー像を転写し、そのトナー像を定着装置により定着した後、当該記録材を、その表裏を反転させて再び感光体に送り込み、その記録材の他方の面に感光体上のトナー像を転写し、その転写トナー像を定着装置によって定着する画像形成装置も従来より周知である。記録材の一方の面に形成されたトナー像と、記録材の他方の面に形成されたトナー像とを区別する必要のあるときは、前者を第1トナー像、後者を第2トナー像と称することにする。
【0055】
記録材を定着装置のニップに通過させて第2トナー像を定着するとき、記録材の一方の面に既に定着されている第1トナー像もニップを通過し、その第1トナー像が加圧部材に接触する。このとき、加圧部材も加熱されているので、第1トナー像がその熱によって溶融し、ニップを出た記録材が加圧部材の表面に巻きつくおそれがある。
【0056】
そこで、図2及び図5に示した定着装置4においては、ニップNを出た記録材Pを加圧部材(図の例では加圧ローラ16)の表面から分離するための加圧部材側分離手段22が設けられており、しかもその分離手段22の加圧部材を向いた側の先端部が加圧部材の表面に当接している。加圧部材側分離手段22は、例えば、加圧ローラ16の軸方向に配列された複数の分離爪、或いは1枚のシート状の分離部材などから構成される。
【0057】
図2および図5に示すように、ニップNに進入する記録材Pの一方の面に既に定着されている第1トナー像TAが担持され、記録材Pの他方の面に定着装置4により定着すべき第2トナー像Tが担持されている場合には、この記録材PがニップNを通過するとき、第1のトナー像TAも加熱されて溶融するので、ニップNを出た記録材Pが加圧ローラ16の表面に巻き付くことがあるが、この場合には、加圧ローラ16の表面に当接した加圧部材側分離手段22によって、記録材Pが加圧ローラ16の表面から分離される。
【0058】
加圧部材側分離手段22は、その先端部が加圧ローラ16より成る加圧部材の表面に当接しているので、加圧ローラ16の表面に巻きつこうとする記録材を確実にその表面から分離することができる。その際、前述のように加圧ローラ16の表面硬度は定着ローラ15の表面硬度よりも高く、加圧ローラ16の表面は傷がつき難くなっているので、当該表面に当接する加圧部材側分離手段22によって加圧ローラ16の表面に傷が付けられる不具合を防止できる。
【0059】
また、図6乃至図8に示した定着装置においては、前述のように、搬送される記録材Pの先端側余白部M1だけがニップNを出た時、その先端側余白部M1が、延長線LBBの方向をほぼ向くように構成されているが、そのほか、ニップNを出た記録材Pを、加圧ローラ16より成る加圧部材の表面から分離するための加圧部材側分離手段19Aが、その加圧部材の表面に対して非接触状態で配置され、ニップNの記録材搬送方向下流側端NEと、加圧部材側分離手段19Aの加圧部材を向いた側の先端との間のギャップGAが、記録材Pの搬送方向先端側の余白部M1の、該搬送方向における幅Wよりも小さく設定されている。この加圧部材側分離手段19Aも適宜な形態に構成できるが、ここに示した加圧部材側分離手段19Aは、シート状の分離部材20Aによって構成されている。
【0060】
ニップNに進入する記録材Pの一方の面に既に定着されている第1トナー像TAが担持され、その他方の面に定着装置4によって定着すべき第2トナー像Tが担持されている場合、第1トナー像TAがニップNを通過するとき、そのトナーが溶融し、これによって記録材Pが加圧ローラ16の表面に付着したとき、加圧部材側分離手段19Aが、定着部材側分離手段19の場合と全く同様にして、その記録材が加圧ローラ16の表面に巻きつくことを防止する。また、加圧部材側分離手段19Aも、加圧ローラ16の表面から離間しているので、その表面に傷がつけられる不具合を阻止できる。
【0061】
また、図6乃至図8に示した定着装置においては、前述の定着部材側分離手段19と、上述の加圧部材側分離手段19Aが共に設けられているので、記録材Pが定着部材と加圧部材のいずれの表面に巻き付くことも防止でき、かつこれらの部材の表面に分離手段の接触による傷が付けられることを阻止できる。
【0062】
図9に示した定着装置4も記録材が加圧部材の表面に巻きつくことを防止できるように構成されている。図9に示した定着装置の基本構成とその基本的な動作は、図2に示した定着装置と変りはない。異なるところは、加圧ローラ16の表面のアスカーC硬度が、定着ローラ15の表面のアスカーC硬度よりも低く設定され、ニップNにおいて定着ローラ15が加圧ローラ16を弾性的に圧縮変形させている点である。また、図9に示した定着装置では、加圧ローラ16内にはヒータは設けられておらず、定着ローラ15内にヒータ17が設けられ、このヒータ17によって定着ローラ15が加熱され、ニップNがトナー像の定着に適した適正温度に保たれる。定着ローラ15の表面硬度と加圧ローラ16の表面硬度の差は、この場合も、アスカーC硬度で例えば20乃至40Hs程度に設定される。
【0063】
記録材Pの一方の面には、既に定着されている第1トナー像TAが担持され、記録材Pの他方の面には、定着装置4により定着すべき未定着の第2トナー像Tが担持され、かかる記録材Pが矢印方向に回転する定着ローラ15と加圧ローラ16の間のニップNに矢印Aで示すように送り込まれ、ここを通過することによって、第2トナー像Tが記録材Pに定着される。
【0064】
このとき、第1トナー像TAのトナーも加熱されて溶融するが、ニップNを出た記録材Pが、第1トナー像のトナーの溶融により加圧ローラ16の表面に巻きつくことを防止するため、ニップNを出た記録材Pを加圧ローラ16より成る加圧部材の表面から分離するための加圧部材側分離手段19Aが、その加圧部材の表面に対して非接触状態で配置されている。図9も、記録材Pの搬送方向先端側の余白部M1の全体が丁度、ニップNから出た時の状態を示しているが、この図から判るように、ニップNの記録材搬送方向下流側端NEと加圧部材側分離手段19Aの加圧部材を向いた側の先端との間のギャップGAが、記録材Pの搬送方向先端側の余白部M1の、該搬送方向における幅Wよりも小さく設定されている。かかる加圧部材側分離手段19Aも、例えばシート状の分離部材20Aにより構成される。
【0065】
図9に示した定着装置では、定着ローラ15の表面硬度の方が、加圧ローラ16の表面硬度よりも高く設定されているので、搬送される記録材Pの先端側余白部M1だけがニップNから出た時、その余白部M1は定着ローラ15の表面に沿った姿勢をとり、加圧ローラ16の表面から大きく離間する。搬送される記録材Pの搬送方向先端側の余白部M1だけがニップNを出た時、該先端側の余白部M1が、ニップNの記録材搬送方向下流側端NEと該ニップNの記録材搬送方向上流側端NSを結ぶ直線LCの記録材搬送方向側の延長線LCCよりも定着部材側を向くように構成されているのである。
【0066】
記録材Pの画像領域IA(図4参照)がニップNを出ると、他方の面に担持された第2トナー像TのトナーがニップNで溶融するので、記録材Pが定着ローラ15の側に引張られることがあるが、記録材Pの一方の面に形成された第1トナー像TAのトナーもニップNで溶融するので、記録材Pが加圧ローラ16の側に引張られることもある。ギャップGAが余白部M1の幅Wよりも小さく、しかも加圧ローラ16の表面硬度が定着ローラ15の表面硬度よりも低く、余白部M1だけがニップNから出たとき、その余白部M1が加圧ローラ16の表面にトナーの粘着力で付着することはないので、記録材Pが加圧ローラ16の側に引張られたとき、記録材Pが加圧ローラ16の表面に巻きつくことはない。しかも、加圧部材側分離手段19Aは、表面硬度が低く、したがって傷がつきやすい加圧ローラ16の表面から離間して位置しているので、その表面に傷がつけられることもない。
【0067】
また、定着ローラ15の表面には又はシート状の分離部材などから成る定着部材側分離手段22Aの先端部が当接しており、従ってニップNを出た記録材Pが定着ローラ15の表面に付着しても、その記録材Pは即座に定着部材側分離手段22Aによって定着ローラ15の表面から分離され、記録材Pが定着ローラ15の表面に巻きつくことはない。定着部材側分離手段22Aは定着ローラ15の表面に当接しているが、その定着ローラ15の表面硬度が高いので、その表面に傷がつけられることを防止できる。このように、定着部材側分離手段22Aを定着ローラ15の表面に当接させることにより、定着ローラ15への記録材Pの巻き付きを確実に防止することができる。ニップNを出た記録材Pは加圧部材側分離手段19Aと、その上方に配置されたガイド部材21Aによって案内されながら搬送される。
【0068】
上述のように、記録材Pが定着ローラ15と加圧ローラ16に巻きつくことを阻止でき、しかも両ローラ15,16の表面に傷がつくことも防止でき、ニップNを通過した後の記録材Pの各面に形成された第1及び第2トナー像の品質が低下することを防止できる。
【0069】
図9に示した定着装置4のより具体的な構成を、その一例として説明すると、定着ローラ15としては、例えば、外径が40mmで肉厚が0.6mmの鉄製中空ローラの外周面にフッ素樹脂より成る離型層をコーティングしたものを使用できる。また加圧ローラ16としては、例えば、外径40mmのアルミニウム製の芯金上に厚さ5mmの発泡シリコーンゴム層を形成し、その外周面に厚さ30μmのPFAチューブを被せたものを使用することができる。この構成では、定着ローラ15に弾性層が設けられていないので、定着ローラ15の熱容量が小さくなり、電源ONから定着ローラ15が定着可能な温度に達するまでの立ち上がり時間を短くすることができる。
【0070】
また、定着部材の表面側の硬度を加圧部材の表面側の硬度よりも大きくする構成は、定着部材が定着ベルトより成るときも適用でき、図10にその一例を示す。図10に示した定着装置4の基本的な思想は図9に示した定着装置と変らないため、簡単に説明すると、ヒータ17A,17Bにより加熱される定着部材が、複数のガイド部材、この例では対向ローラ15Bとテンションローラ15Cに巻き掛けられて矢印B方向に回転する無端状の定着ベルト15Aにより構成され、定着部材に圧接する加圧部材は、定着ベルト15Aを介して、少なくとも1つのガイド部材、図10の例では対向ローラ15Bに圧接して矢印方向に回転する加圧ローラ16により構成されている。加圧ローラ16の表面のアスカーC硬度は、対向ローラ15Bに巻き掛けられた定着ベルト部分の表面で測定したアスカーC硬度よりも低く設定されている。
【0071】
定着すべき第2トナー像Tを担持した記録材Pは、その第2トナー像Tが、定着ベルト15Aに接する向きにして定着ベルト15Aと加圧ローラ16との圧接により形成されたニップNを通過し、熱と圧力の作用で第2トナー像Tが記録材Pに定着される。
【0072】
その際、上述の構成により、搬送される記録材Pの搬送方向先端側の余白部M1だけがニップNを出た時、その先端側の余白部M1は、ニップNの記録材搬送方向下流側端NEと該ニップNの記録材搬送方向上流側端NSを結ぶ直線LCの記録材搬送方向側の延長線LCCよりも定着ベルト15Aより成る定着部材側を向く。
【0073】
矢印Aで示すようにニップNに進入する記録材Pの一方の面には、既に定着されている第1トナー像TAが形成されている。そして、ニップNを出た記録材Pを加圧ローラ16より成る加圧部材の表面から分離するための加圧部材側分離手段19Aが、その加圧部材の表面に対して非接触状態で配置され、ニップNの記録材搬送方向下流側端NEと加圧部材側分離手段19Aの加圧部材を向いた側の先端との間のギャップGAが、記録材Pの搬送方向先端側の余白部M1の、該搬送方向における幅Wよりも小さく設定されており、この構成によって、図9に示した定着装置の場合と同様に、記録材Pが加圧ローラ16に巻きつくことを防止でき、加圧部材側分離手段19Aによって表面硬度の低い加圧ローラに傷がつけられることも阻止できる。また定着ベルト15Aの表面に当接した定着部材側分離手段22Aによって、記録材Pが定着ベルト15Aに巻きつくことを防止できる。ニップNを出た記録材Pは、加圧部材側分離手段19Aとガイド部材21Aによって案内されて搬送される。
【0074】
図9及び図10に示した定着装置4の場合も、記録材Pの先端側余白部M1だけがニップNを出たとき、その余白部M1が延長線LCCよりも定着部材側を向くように、ニップNの記録材搬送方向下流側端NEにおける定着部材の表面のアスカーC硬度が、該ニップNの記録材搬送方向下流側端NEにおける加圧部材の表面のアスカーC硬度よりも高く設定されている。しかも、前述のように、ニップNを出た記録材Pを定着部材から分離するための定着部材側分離手段22Aが設けられ、その定着部材側分離手段22Aの先端部が定着部材の表面に当接しているので、記録材が定着部材に巻き付くことを効果的に阻止できる。その際、定着部材の表面の硬度が高いので、接触する定着部材側分離手段22Aにより定着部材の表面に傷がつくことを防止できる。
【0075】
ところで、上述した各実施形態例において、定着部材に対して離間して位置する定着部材側分離手段19の先端と、ニップNの記録材搬送方向下流側端NEとの間のギャップGは、記録材Pの搬送方向先端側の余白部M1の幅Wよりも小さく設定されているので、定着部材側分離手段19の先端は定着部材の表面に近接して位置する。定着部材側分離手段19をこのような位置に正しく配置するため、次の構成を採用すると有利である。
【0076】
図11は、図2及び図6に示した定着ローラ15に対して、シート状の分離部材20よりなる定着部材側分離手段19を位置決めするための一構成例を示している。図11に示すように、記録材の搬送方向に対して直交する向きの定着部材20の各端部に、ギャップ保持部材29がそれぞれ固定され、その各ギャップ保持部材29は、ねじ30を介して、支持部材31に支持されている。この支持部材31は、圧縮ばねなどからなる加圧部材32によって定着ローラ15の表面に向けて加圧されている。これにより、両ギャップ保持部材29が定着ローラ15の表面に当接する。その際、図12にも示すように、両ギャップ保持部材29は定着ローラ15の記録材非通過領域PA、すなわち記録材Pが通過しない定着ローラの長手方向各端部領域に当接する。これにより、記録材が通過する領域、すなわち記録材通過領域PBに対向した定着部材側分離手段19の先端と、定着ローラ15の表面との間の間隔と前述のギャップGが正しく保たれる。
【0077】
定着ローラ15の表面の位置は、そのローラの熱膨張や、偏心の影響を受けて一定ではないが、上述のように定着部材側分離手段19を位置決めすることにより、ギャップGを定着部材側分離手段19の長手方向全体に亘って常にほぼ一定に保つことができる。しかもギャップ保持部材29は、定着ローラ15の記録材非通過領域PAに当接するので、ギャップ保持部材29が定着ローラ15の記録材通過領域PBに傷を付けることはなく、ギャップ保持部材29が定着ローラ15の表面に当接することによる影響がトナー像に及ぼされることもない。
【0078】
定着部材が図5及び図8に示した定着ベルト15Aより成るときも、上述したところと全く同様にギャップ保持部材29を定着ベルト15Aの記録材非通過領域に当接させることによって、定着部材側分離手段19と定着ベルト15Aの表面との間の間隔とギャップGを正しく規制することができる。
【0079】
上述のように、記録材搬送方向に対して直交する向きの分離部材の各端部にギャップ保持部材を設け、その両ギャップ保持部材を定着部材の記録材非通過領域に当接させて、分離部材の先端と定着部材の表面との間の間隔を保持することにより、簡単に分離部材の先端を定着部材に近接させて正しく位置決めすることが可能となる。
【0080】
図6、図8、図9及び図10に示した定着装置の加圧部材側分離手段19Aを加圧ローラ16の表面に近接させて配置するためにも、図11及び図12に示した構成を採用できる。この場合には、図11及び図12に示した定着ローラ15の代りに、図6、図8、図9又は図10に示した加圧ローラ16が配置される。このように、記録材搬送方向に対して直交する向きの加圧部材側分離手段各端部にギャップ保持部材を設け、該ギャップ保持部材を加圧部材の記録材非通過領域に当接させて、加圧部材側分離手段の先端と加圧部材の表面との間の間隔を保持することができ、これによって加圧部材側分離手段を加圧部材の表面に近接させて正しく位置決めすることができる。しかも、ギャップ保持部材は、加圧部材の記録材非通過領域に当接するので、加圧部材の記録材通過領域に傷が付けられる不具合を防止できる。
【0081】
ところで、定着部材又は加圧部材から離間した定着部材側分離手段19と加圧部材側分離手段19Aとして、シート状の分離部材20,20Aの他に、1枚の板材より成る分離爪などによって構成された分離手段や、定着部材又は加圧部材の表面に沿って配置された複数の分離爪より成る分離手段などを適宜用いることができるが、定着部材側分離手段19と、加圧部材側分離手段19Aは定着部材または加圧部材に対して非接触で配置されるものであるため、その各分離手段19,19Aとして、図示した例のようなシート状又は板材などから成る1つの分離部材を用いることができる。分離手段が定着部材又は加圧部材の表面に当接していると、複数の分離爪より成る分離手段を用い、ばねによって、その各分離爪と定着部材又は加圧部材に対する当接圧を調整して、その当接圧が全て均一となるように構成する必要があるが、本例の定着部材側分離手段19と加圧部材側分離手段19Aは、定着部材又は加圧部材に接触していないので、その当接圧を調整する必要はなく、1つの分離部材により構成された定着部材側分離手段19と加圧部材側分離手段19Aを採用できるのである。各分離手段19,19Aをこのように構成することにより、部品点数の低減と、そのコストの低減を達成できる。また、定着部材側分離手段19と加圧部材側分離手段19Aが定着部材や加圧部材に当接する当接圧を調整するばねを設けなくともよいため、各分離手段19,19Aを記録材用のガイド部材や定着装置の筐体(図示せず)などと一体に形成することもできる。
【0082】
また、図11に示したように、定着部材側分離手段19を構成する1つの分離部材20に、通気のための1又は複数の開口36を形成すると、ニップNで加熱された記録材Pから出る水蒸気をその開口36を通して、例えば上方に逃がすことができ、これによって水蒸気が記録材Pに結露して、その品質を低下させる不具合を防止できる。開口36は、シート状の分離部材20の厚み方向に貫通している。同様に、加圧部材側分離手段19Aを構成する1つの分離部材20Aにも、通気のための1又は複数の開口を形成すると、その開口を通して、記録材から出る水蒸気を逃がすことができる。
【0083】
図示した例のように、定着部材側分離手段19と加圧部材側分離手段19Aをシート状の分離部材20,20Aにより構成した場合、特にその厚さが薄いと、これらの分離部材自体の熱膨張による波打ちや、その分離部材20,20Aに記録材が接触することによる変形によって、分離部材20,20Aと定着部材又は加圧部材との間の間隔が分離部材の長手方向において不均一となるおそれがある。そこで、定着部材側分離手段19及び加圧部材側分離手段19Aを、シート状の分離部材20,20Aにより構成した場合、その分離部材20,20Aを、記録材搬送方向に対して直交する向きに引張るテンション付与手段を設けることが望ましい。これにより、上記不具合の発生を防止できる。
【0084】
図11に示した分離部材20は、その長手方向各端部がギャップ保持部材29にそれぞれ固定され、その両ギャップ保持部材29がねじ30を介して支持部材31に支持されているが、そのねじ30を回すことにより、分離部材20を矢印方向に引張り、これに張力を付与し、該分離部材20を平坦に保つことができ、分離部材20と定着ローラ15との間の間隔を一定に保つことができる。このように、ねじ30は分離部材を引張るテンション付与手段の一例を構成している。加圧部材側分離手段19Aの分離部材20Aを引張るテンション付与手段も同様に構成することができる。
【0085】
シート状の分離部材20,20Aとしては、耐熱性の樹脂や金属より成る薄板を使用でき、例えば厚さ0.1mmのポリイミドシートの表面にフッ素樹脂をコーティングしたものを用いることができる。また、この分離部材20,20Aとして、厚さが0.2mm以上の金属シート又は金属製の板材を用いた場合、その剛性が高まるため、上述のテンション付与手段を設けなくとも、分離部材と定着部材又は加圧部材との間の間隔を一定に保つことが可能となる。
【0086】
ところで、以上説明した各定着装置において、定着部材又は加圧部材への記録材の巻きつきをより確実に防止するため、これらにシリコーンオイルなどの離型剤を塗布することができる。ところが、この構成を採用すると、記録材にオイルが付着して記録材が汚れたり、オイル塗布のためのメンテナンスが煩雑となり、しかもオイル塗布のための塗布部材が必要となって定着装置のコストが上昇する欠点を免れない。
【0087】
そこで、トナーとしてワックス含有のトナーを用い、トナー像が、少なくとも樹脂、着色剤及びワックスを含有するトナーにより形成されるように構成すると、離型剤の塗布を省いた所謂オイルレス化が可能となり、上述した不具合を除去することができる。
【0088】
以上説明した各構成は、上述した形式以外の定着装置にも広く適用できる。例えば、図5、図8及び図10に示した定着装置4においては、定着ベルト15Aを巻き掛けるガイド部材として、ガイドローラ、すなわち対向ローラ15Bとテンションローラ15Cを用いたが、図13に示した定着装置4においては、2つのガイドローラ33,34と、ヒータ35として構成されたガイド部材が用いられ、これらのガイド部材に定着ベルト15Aが巻き掛けられている。ヒータ35は、図に示していないが一対の電極と、その電極間に配置され、かつ定着ベルト15Aの内面に接触した抵抗体とを有し、その抵抗体に電流を供給することによって抵抗体を発熱させ、これによって定着ベルト15Aを加熱するように構成されている。かかる定着装置にも、図5、図8及び図10に関連して先に説明した構成を採用することができる。
【0089】
さらに、先にも説明したように、加圧部材を複数のガイド部材に巻き掛けられて回転駆動される加圧ベルトにより構成することもできる。この場合も、ガイド部材に巻き掛けられた加圧ベルト部分が定着部材に当接してニップが形成されるように構成した場合には、加圧ベルトの表面のアスカーC硬度は、ガイド部材に巻き掛けられた加圧ベルト部分の表面で測定した硬度である。なお、本明細書に記載したアスカーC硬度の値はアスカーC硬度計を用いてローラ又はベルトの表面硬度を直接測定した数値である。
【0090】
【発明の効果】
本発明によれば、記録材が定着部材に巻きつくことを防止できると共に、分離部材により定着部材の表面に傷がつけられる欠点を防止できる。
【0091】
請求項5乃至8に係る各発明によれば、記録材が加圧部材に巻きつくことを防止できる。
【図面の簡単な説明】
【図1】 画像形成装置の一例を示す概略断面図である。
【図2】 定着装置の一例を示す断面図である。
【図3】 図2に示した定着装置の拡大説明図である。
【図4】 記録材の余白部を説明する図である。
【図5】 定着装置の他の例を示す断面図である。
【図6】 定着装置のさらに他の例を示す断面図である。
【図7】 図6に示した定着装置の拡大説明図である。
【図8】 定着装置のさらに別の例を示す断面図である。
【図9】 定着装置のさらに他の例を示す断面図である。
【図10】 定着装置のさらに別の例を示す断面図である。
【図11】 分離部材支持装置の一例を示す平面図である。
【図12】 図11に示したギャップ保持部材が定着ローラの表面に当接した様子を示す斜視図である。
【図13】 定着装置のさらに他の例を示す説明図である。
【符号の説明】
4 定着装置
20 分離部材
22 加圧部材側分離手段
29 ギャップ保持部材
36 開口
G ギャップ
LA 直線
LAA 延長線
M1 余白部
N ニップ
NE 記録材搬送方向下流側端
NS 記録材搬送方向上流側端
P 記録材
PA 記録材非通過領域
T トナー像
W 幅
[0001]
BACKGROUND OF THE INVENTION
The present invention includes a fixing member to be heated and a pressure member that is in pressure contact with the fixing member, and a recording material carrying a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. The present invention relates to an image forming apparatus having a fixing device that passes through a nip formed by pressure contact between the fixing member and a pressure member and fixes the toner image onto a recording material by the action of heat and pressure.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, it is well known to employ a fixing device of the above type in an image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions. In this type of fixing device, when the toner carried on the recording material passes through the nip formed by the fixing member and the pressure member, the toner melts in the nip. There is a possibility that the recording material that has come out is wound around the surface of the fixing member without being separated. In particular, in an image forming apparatus that forms a full-color image, a plurality of toner images of different colors are formed on a recording material by superimposition, and the superimposed toner images are fixed by a fixing device. This melts the toner, which increases the adhesive strength of the toner and makes it easier to wind the recording material around the fixing member.
[0003]
Therefore, conventionally, a separating means comprising a plurality of separating claws is brought into contact with the surface of the fixing member, and the recording material exiting the nip is separated from the fixing member surface by the separating claws, and the recording material is wound around the surface of the fixing member. This is configured to prevent this. However, since the tip of the separation claw is in contact with the surface of the fixing member, the surface of the fixing member may be damaged by the separation claw. When the surface of the fixing member is damaged, a mark corresponding to the damage is formed on the toner image passing through the nip, and the image quality of the toner image after fixing is deteriorated.
[0004]
In order to eliminate such drawbacks, a fixing device has been proposed in which the separation claw is arranged apart from the surface of the fixing member. However, if the separation claw is arranged in a non-contact state with respect to the surface of the fixing member, the recording material exiting the nip enters between the fixing member and the separation claw while adhering to the surface of the fixing member, and the recording material is fixed. There is a risk of wrapping around the member. If the separation claw separated from the fixing member is used in this way, the recording material separating function is lowered, and the possibility that the recording material is wound around the fixing member is increased.
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to effectively fix a recording material around a fixing member and to effectively suppress a problem that the image quality of a toner image after fixing is deteriorated. Is to provide an image forming apparatus.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, when only the margin portion on the leading end side in the conveyance direction of the recording material to be conveyed exits the nip, the margin portion on the leading end side Is configured to face the pressure member side with respect to a linear extension line connecting the downstream end of the nip in the recording material conveyance direction and the upstream end of the nip in the recording material conveyance direction, and the recording material exiting the nip A sheet-like separation member for separating the sheet from the surface of the fixing member in a non-contact state with respect to the surface of the fixing member, and a downstream end of the nip in the recording material conveyance direction and a tip of the separation member Is set to be smaller than the width in the conveyance direction of the blank portion on the leading end side in the conveyance direction of the recording material, and the separation member has an opening penetrating in the thickness direction. An image forming apparatus characterized by To draft (claim 1).
[0007]
In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, a sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is provided. The fixing member is disposed in a non-contact state with respect to the surface of the fixing member, and the Asker C hardness of the surface of the pressure member in the nip is set higher than the Asker C hardness of the surface of the fixing member in the nip. The gap between the downstream end in the transport direction and the leading end of the separation member is set to be smaller than the width in the transport direction of the blank portion on the leading end side of the recording material in the transport direction. An image forming apparatus is proposed in which an opening penetrating in a direction is formed (claim 2).
[0008]
The image forming apparatus according to claim 1 or 2, wherein the fixing member is an endless fixing belt wound around a guide member, and the pressure member is interposed between the fixing belt and the fixing member. It is advantageous that the Asker C hardness of the surface of the pressure member pressed against the guide member is set higher than the Asker C hardness of the surface of the fixing belt wound around the guide member. .
[0009]
In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, a sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is provided. A pressure member that is arranged in a non-contact state with respect to the surface of the fixing member and has a convex shape in the nip elastically deforms the fixing member into a concave shape, and has a downstream end in the recording material conveyance direction of the nip. The gap between the leading end of the separating member is set to be smaller than the width in the conveying direction of the blank portion on the leading end side in the conveying direction of the recording material, and the separating member penetrates in the thickness direction. An image forming apparatus having an opening is proposed.
[0010]
5. The image forming apparatus according to claim 4, further comprising: a pressure member side separating unit for separating the recording material that has exited the nip from the surface of the pressure member. It is advantageous if the tip is brought into contact with the surface of the pressure member (claim 5).
[0011]
6. The image forming apparatus according to claim 1, wherein a gap holding member is provided at each end of the separating member in a direction orthogonal to the recording material conveyance direction, and the gap holding member is It is advantageous that the space between the front end of the separating member and the surface of the fixing member is maintained in contact with the recording material non-passing area of the fixing member.
[0012]
Furthermore, in the image forming apparatus according to any one of claims 1 to 6, it is advantageous to provide a tension applying means for pulling the separating member in a direction orthogonal to the recording material conveyance direction (claim 7). .
[0013]
Furthermore, in the image forming apparatus according to any one of claims 1 to 7, it is advantageous that the toner image is formed by a toner containing at least a resin, a colorant, and a wax (claim 8).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0015]
FIG. 1 is a vertical sectional view showing an outline of an image forming apparatus. In the image forming apparatus main body 1, an image forming means 2 for forming a toner image on a recording material and a recording material are fed to the image forming means. And a fixing device 4 for fixing the toner image formed on the recording material. In FIG. 1, the fixing device 4 is shown as a simple block, and a specific configuration example will be described later. Here, first, the outline of the image forming means 2 will be clarified.
[0016]
The image forming means 2 exemplified here has a drum-shaped photoconductor 5 which is an example of an image carrier, and when the photoconductor 5 rotates in the clockwise direction, the surface of the photoconductor has a predetermined polarity by the charging device 6. Is charged. The charged surface is irradiated with a light-modulated laser beam L emitted from a laser writing unit 7 which is an example of an exposure apparatus, whereby an electrostatic latent image is formed on the surface of the photoreceptor. The electrostatic latent image is visualized as a toner image by the developing device 8, and the toner image is transferred onto the recording material fed from the feeding unit 3 by the action of the transfer device 9. The residual transfer toner adhering to the surface of the photoconductor after the toner image is transferred is removed by the cleaning device 10.
[0017]
The feeding unit 3 includes a cassette 11 that stores a recording material P made of, for example, transfer paper or a resin sheet, and the uppermost recording material P is fed out of the cassette 11 by the rotation of the feeding roller 12. The fed recording material is fed to the transfer portion between the photoconductor 5 and the transfer device 9 by the rotation of the registration roller pair 13, and the toner image on the photoconductor 5 is transferred to the recording material as described above. Transcribed above. The recording material carrying the toner image in this way is sent to the fixing device 4 as shown by an arrow A and passes through the fixing device 4, and at this time, the toner image on the recording material is fixed as will be described later. . The recording material that has passed through the fixing device 4 is discharged onto a tray 14 outside the apparatus.
[0018]
FIG. 2 is an enlarged cross-sectional view showing an example of the fixing device 4. The fixing device 4 shown here is configured as a fixing member configured as a fixing roller 15 and a pressure roller 16 pressed against the fixing roller 15. The nip N is formed when the rollers 15 and 16 are pressed against each other. The fixing roller 15 and the pressure roller 16 are formed in a columnar shape having a circular outer cross section. In the illustrated example, these rollers 15 and 16 are formed in a hollow cylindrical shape, the fixing roller 15 rotates in the clockwise direction, and the pressure roller 16 rotates in the counterclockwise direction.
[0019]
The nip N formed by the pressure contact between the rollers 15 and 16 is controlled to an appropriate temperature suitable for fixing the toner image by the heating means. In this example, halogen heaters 17 and 18 as heat sources are provided inside the fixing roller 15 and the pressure roller 16, respectively, and ON / OFF of energization to the heaters 17 and 18 is controlled by a temperature control means (not shown). Thus, the temperature of the nip N is maintained at an appropriate temperature.
[0020]
The recording material P carrying the unfixed toner image T is fed into the fixing device 4 as indicated by an arrow A, and the recording material P is placed in the nip N so that the toner image T is in contact with the surface of the fixing roller 15. The toner image T is fixed on the recording material P by heat and pressure.
[0021]
As described above, the fixing device includes a fixing member that rotates while being heated, and a pressure member that rotates while being pressed against the fixing member. The toner image is fixed to the recording material by the action of heat and pressure through a nip formed by pressure contact between the fixing member and the pressure member in a direction in contact with the fixing member. Such a basic configuration does not change in the fixing devices of the examples described later. As described above, in the example shown in FIG. 2, the fixing member is constituted by the fixing roller 15 that rotates, and the pressure member is constituted by the pressure roller 16 that rotates while being pressed against the fixing roller 15. As will be described later, the fixing member is composed of an endless fixing belt that is wound around a guide member and rotates, and the pressure member is composed of an endless pressure belt that is wound around the guide member and rotates. You can also. Thus, the fixing member and the pressure member can be configured in various forms.
[0022]
Here, in the fixing device 4 shown in FIG. 2, when the toner image T carried on the recording material P passes through the nip N between the fixing roller 15 and the pressure roller 16, the toner melts in the nip N. To do. In order to prevent the recording material P coming out of the nip N from being wound around the surface of the fixing roller 15 by the adhesive force of the toner at this time, the following configuration is adopted.
[0023]
FIG. 3 is an enlarged explanatory view of the nip N formed by the fixing roller 15 and the pressure roller 16 and the recording material P passing through the nip N. As shown in FIGS. 2 and 3, in the vicinity of the exit of the nip N, the fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member (the fixing roller 15 in this example). Is disposed in a non-contact state with respect to the surface of the fixing member. The fixing member side separation means can be configured in an appropriate form, but the fixing member side separation means 19 shown here is constituted by a sheet-like separation member 20.
[0024]
On the other hand, on the recording material P, a toner image is formed in the image area indicated by hatching in FIG. 4 and indicated by reference numeral IA, and no toner image is formed in the outer edge area of the image area IA. It is a margin part M. The recording material P is transported in the direction indicated by the arrow A and enters the fixing device 4, and the width of the blank portion M <b> 1 on the leading end side in the transport direction in the transport direction A is W. This width W is, for example, about 2 to 5 mm. 2 and 3 show a state where only the margin M1 on the tip end side has just come out of the nip N. FIG. The same applies to FIGS. 5 to 10.
[0025]
Here, as shown in FIG. 3, if the gap between the outlet end of the nip N, that is, the downstream end NE of the nip N in the recording material conveyance direction, and the leading end of the separating member 20 facing the fixing member is G. The gap G is set to be smaller than the aforementioned width W in the conveyance direction A of the margin M1 on the leading end side in the conveyance direction of the recording material P (G <W). Accordingly, as shown in FIGS. 2 and 3, when only the entire margin M1 on the leading end side of the recording material P comes out of the nip N, the leading end of the fixing member side separating means 19 is fixed to the margin M1. It is located in a state of entering a space area between the rollers 15.
[0026]
On the other hand, the Asker C hardness of the surface of the pressure roller 16 is set to be higher than the Asker C hardness of the surface of the fixing roller 15. Preferably, the Asker C hardness of the surface of the pressure roller 16 is It is configured to be 20 to 40 Hs larger than the Asker C hardness of the surface. Thus, the Asker C hardness of the surface of the pressure member (in this example, the pressure roller 16) in the nip N is set higher than the Asker C hardness of the surface of the fixing member (in this example, the fixing roller 15) in the nip N. As a result, as shown in FIGS. 2 and 3, the pressure roller 16 compresses and deforms the surface of the fixing roller 15 so as to bite into the fixing roller 15 side. In the nip N, the pressing member having a convex shape elastically deforms the fixing member into a concave shape.
[0027]
Therefore, as shown in FIGS. 2 and 3, when only the margin M1 on the leading end side of the recording material P comes out of the nip N, the margin M1 is in a posture along the peripheral surface of the pressure roller 16, that is, The posture of the fixing roller 15 is greatly separated from the peripheral surface. Since no toner image is formed on the leading edge margin M1, the margin M1 does not attempt to adhere to the surface of the fixing roller 15 due to the adhesive force of the toner. The ink is discharged from the nip N so as to be along the peripheral surface of the pressure roller 16 biting into the side. At this time, the margin M1 and the surface of the fixing roller 15 are separated from each other by a large distance, and the margin M1 of the recording material P does not wrap around the surface of the fixing roller 15 in this state. If a straight line connecting the downstream end NE of the nip N in the recording material conveyance direction and the upstream end NS of the nip N in the recording material conveyance direction is LA, only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed is present. When leaving the nip N, the margin M1 on the leading end side is directed toward the pressing member (in this example, the pressing roller 16) with respect to the extension line LAA drawn on the recording material conveyance direction side of the straight line LA. It is composed.
[0028]
When the recording material P is further conveyed in the direction of arrow A than in the state shown in FIGS. 2 and 3, the image area IA shown in FIG. Then, the recording material P adheres to or tends to adhere to the surface of the fixing roller 15 due to the adhesive force of the toner on the image area IA, so that the recording material P is pulled toward the fixing roller 15. This tendency is remarkable in the case of a recording material that is weak, such as thin paper.
[0029]
However, since the fixing member side separating means 19 is provided in the vicinity of the fixing roller 15, the recording material P hits the fixing member side separating means 19 and is guided by the separating means 19 as indicated by a chain line in FIG. The recording material P is prevented from being wound around the surface of the fixing roller 15. Although the fixing member side separating means 19 is disposed away from the surface of the fixing roller 15, the gap G is set to be smaller than the width W of the margin portion M1, so that the fixing roller 15 is separated by the adhesive force of the toner. The recording material P pulled to the side is prevented from being wound around the surface of the fixing roller 15 through the gap G while adhering to the surface of the fixing roller 15. The recording material P that has exited the nip N is conveyed while being guided by the fixing member side separating means 19 positioned on the upper side and the guide member 21 positioned on the lower side.
[0030]
As described above, the recording material P that has exited the nip N can be prevented from being wound around the surface of the fixing roller 15, and the fixing member side separation means 19 is not in contact with the surface of the fixing roller 15. Therefore, it is possible to prevent a problem that the surface of the fixing roller 15 that is easily damaged is damaged by the fixing member side separating means 19.
[0031]
The image forming apparatus shown in FIG. 1 is configured to form a monochromatic, usually black, toner image on the recording material P. However, in an image forming apparatus that forms a color image, For example, since a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed in an overlapping manner and the overlapping toner image is fixed by a fixing device, the recording material has been particularly easy to wrap around a fixing member. Also in the case of an image forming apparatus that forms an image, by employing the above-described configuration, it is possible to prevent the recording material from being wound around the fixing member while preventing the fixing member from being damaged.
[0032]
Here, a more specific configuration example of the fixing device 4 shown in FIG. 2 will be described.
[0033]
The fixing roller 15 includes a cored bar 23 and an elastic layer 24 laminated on the outer peripheral surface thereof. A release layer 25 is laminated on the outer peripheral surface of the elastic layer 24. The outer diameter of the fixing roller 15 is, for example, 40 mm. It is. The core metal 23 is constituted by an iron hollow roller having an outer diameter of 34 mm and a wall thickness of 1 mm, for example, the elastic layer 24 is formed by silicone rubber having a thickness of 3 mm, for example, and the release layer 25 has a thickness of 10 μm to 30 μm, for example. The PFA tube. By providing the release layer 25, it is possible to suppress the recording material P from adhering to the surface of the fixing roller due to the adhesive force of the toner.
[0034]
The pressure roller 16 includes, for example, a cored bar 26 made of an iron hollow roller having an outer diameter of 38 mm and a wall thickness of 1 mm, an elastic layer 27 stacked on the outer peripheral surface, and a release layer 28 stacked on the outer peripheral surface. The elastic layer 27 is made of, for example, silicone rubber having a layer thickness of 1 mm, and the release layer 28 is formed of, for example, a PFA tube having a layer thickness of 10 μm to 30 μm.
[0035]
The surface hardness of the fixing roller 15 is set to, for example, 45 Hs in terms of Asker C hardness, and the surface hardness of the pressure roller 16 is also set to, for example, 80 Hs in terms of Asker C hardness. Since the pressure roller 16 is harder in this way, the fixing roller 15 is elastically deformed in a state where the pressure roller 16 bites into the surface of the fixing roller 15, and the nip N is formed along the outer shape of the pressure roller 16. Formed.
[0036]
In the fixing device 4 shown in FIG. 5, the fixing member is composed of an endless fixing belt 15A. The fixing belt 15A is wound around a guide member composed of two guide rollers 15B and 15C. The number of guide members may be 3 or more. On the other hand, the pressure member is constituted by a cylindrical pressure roller 16 as in the fixing device shown in FIG. 2, and the pressure roller 16 and the guide rollers 15B and 15C are crossed with a circular outer periphery. It is formed in a cylindrical shape having a surface shape. In the example shown in FIG. 5, all the rollers 15B, 15C, and 16 are formed in a hollow cylindrical shape.
[0037]
The pressure roller 16 is in pressure contact with one guide roller 15B via the fixing belt 15A, whereby the outer peripheral surface of the pressure roller 16 is in pressure contact with the outer peripheral surface of the fixing belt 15A, and a nip N is formed by the pressure contact. Is done. The guide rollers 15B and 15C and the pressure roller 16 rotate in the direction of the arrow, respectively, whereby the fixing belt 15A is rotationally driven in the direction of the arrow B. When the endless fixing belt 15A rotates in this way, the guide rollers 15B and 15C serve to guide the fixing belt 15A, and the one guide roller 15B facing the pressure roller 16 is a pressure roller. The other guide roller 15C serves as a tension roller that applies tension to the fixing belt 15A. As will be described later, a guide member other than the guide roller may be used, the fixing belt 15A may be wound around the guide member, and the pressure roller 16 may be pressed against a plurality of guide members via the fixing belt 15A. . The fixing member is constituted by an endless fixing belt that is wound around a plurality of guide members and rotates, and the pressure member is pressed by at least one guide member via the fixing belt and rotated by a pressure roller that rotates. Make up.
[0038]
Focusing on the above-described functions of both guide rollers 15B and 15C, in the following description, one guide roller 15B will be referred to as a counter roller and the other guide roller 15C will be referred to as a tension roller as necessary.
[0039]
In the fixing device shown in FIG. 5, heaters 17A and 18 are provided inside the tension roller 15C and the pressure roller 16, and the fixing belt 15A and the pressure roller 16 are heated by the heaters 17A and 18, The energization of the heaters 17A and 18 is controlled ON and OFF, and the temperature of the nip N is maintained at an appropriate temperature suitable for fixing the toner image.
[0040]
Also in this example, as shown by the arrow A, the recording material P carrying the toner image T to be fixed passes through the nip N in the direction in which the toner image T contacts the surface of the fixing belt 15A, and heat and The toner image T is fixed on the recording material P by the action of pressure.
[0041]
Also in the fixing device 4 shown in FIG. 5, the Asker C hardness of the surface of the pressure member formed of the pressure roller 16 is the surface of the fixing belt portion wound around the guide member (opposing roller 15B in the illustrated example). It is set higher than the measured Asker C hardness. Thus, the fixing device 4 shown in FIG. 5 also sets the Asker C hardness of the surface of the pressure roller 16 at the nip N higher than the Asker C hardness of the surface of the fixing belt 15A at the nip N. As in the case of the fixing device shown in FIG. 5, when only the margin M1 on the leading end side in the conveyance direction of the recording material to be conveyed exits the nip N, the margin M1 on the leading end side is downstream of the nip N in the recording material conveyance direction. The straight line LA connecting the side end NE and the upstream end NS of the nip N in the recording material conveyance direction faces the side of the pressure member (the pressure roller 16 in the illustrated example) toward the recording material conveyance direction side. . Moreover, a fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member made of the fixing belt 15A is disposed in a non-contact state with respect to the surface of the fixing member. A gap G between the recording material conveyance direction downstream end NE and the leading end of the fixing member side separating unit 19 facing the fixing member is a margin portion M1 on the leading end side of the recording material P in the conveyance direction in the conveyance direction. It is set smaller than the width W.
[0042]
With the above-described configuration, the recording material P is prevented from being wound around the fixing member made of the fixing belt 15A, just like the fixing device shown in FIGS. Can be prevented from being damaged, the image quality of the toner image after fixing can be improved, and the life of the fixing belt 15A can be extended. The recording material P that has exited the nip N is guided and conveyed by the fixing member-side separating means 19 and the guide member 21, and is discharged to the tray 14 (FIG. 1) as well as the fixing device shown in FIGS. There is no change.
[0043]
A more specific configuration example of the fixing device 4 shown in FIG. 5 will be described. The opposing roller 15B and the pressure roller 16 can be configured in the same manner as the fixing roller 15 and the pressure roller 16 of the fixing device shown in FIG. . For example, the fixing belt 15A is formed by laminating a silicone rubber having an Asker C hardness of 30Hs with a thickness of 0.2mm on a polyimide resin substrate having a thickness of 50μm, and coating PFA with a thickness of 5μm as a release layer thereon. Things can be used. Further, the nip N shown in FIG. 5 is opposed to the first nip portion where only the fixing belt 15A comes into contact with the pressure roller 16 at a portion where the pressure roller 16 does not face the opposite roller 15B, and the pressure roller 16 faces through the fixing belt 15A. The second nip portion is in contact with the roller 15B. Thereby, a wide nip N can be formed in the circumferential direction of the fixing belt 15A, the pressure contact force between the pressure roller 16 and the fixing belt 15A can be made relatively small, and the proper temperature of the nip N can be lowered.
[0044]
In the fixing device shown in FIG. 2, since the fixing roller 15 is heated by the heater 17 from the inside of the rubber-like elastic layer 24 having poor thermal conductivity, the fixing roller 15 is in contact with the toner when the fixing device is started up. Although a long time is required until the temperature rises to a temperature suitable for image fixing, the fixing device shown in FIG. 5 uses the fixing belt 15A having a small thickness and a small heat capacity as a fixing member. The belt 15A is not heated from the inside of the counter roller 15B, but is heated by the heater 17A in the thin tension roller 15C, so that the fixing belt 15A rises to a temperature suitable for fixing the toner image. Can be shortened.
[0045]
In the fixing device shown in FIGS. 2 and 5, when only the front end side margin M1 of the recording material P exits the nip N, the margin M1 is directed to the pressure member side with respect to the extension line LAA. Therefore, the surface hardness of the fixing member constituted by the fixing roller 15 or the fixing belt 15A and the surface hardness of the pressure member made of the pressure roller 16 are set as described above. In the case of 15A, as described above, the hardness of the surface of the fixing member is the hardness measured on the surface of the fixing belt portion wound around the opposing roller 15B. In short, regardless of the form of the fixing member, the Asker C hardness of the surface of the pressure member at the downstream end NE in the recording material conveyance direction of the nip N is fixed at the downstream end NE of the nip N in the recording material conveyance direction. By setting higher than the Asker C hardness of the surface of the member, when only the front end side margin portion M1 exits the nip N, the margin portion M1 is configured to face the pressing member side with respect to the extension line LAA. be able to.
[0046]
6 and 7 show other examples of the fixing device 4. The basic configuration of the fixing device 4 shown here is substantially the same as that of the fixing device shown in FIG. 6 corresponding to the parts of the fixing device 4 shown in FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and the description of the basic configuration and operation thereof is omitted.
[0047]
The fixing device 4 shown in FIGS. 6 and 7 differs from the fixing device shown in FIG. 2 in that the Asker C hardness of the surface of the fixing member made of the fixing roller 15 and the surface of the pressure member made of the pressure roller 16. The Asker C hardness is set to be approximately equal. By setting the surface hardness of the fixing roller 15 and the pressure roller 16 in this way, both the rollers 15 and 16 are compressed and deformed into a substantially flat shape at the nip N formed by the fixing roller 15 and the pressure roller 16. A linear nip N is formed. Accordingly, as shown in FIG. 7, when only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed exits the nip N, the margin M1 on the leading end is downstream of the nip N in the recording material conveyance direction. The straight line LB connecting the side end NE and the upstream end NS of the nip N in the recording material conveyance direction is almost directed to the direction of the extended line LBB toward the recording material conveyance direction. The fixing device 4 shown in FIGS. 6 and 7 also includes a fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member made of the fixing roller 15. A gap G between the downstream end NE of the nip N in the recording material conveyance direction and the front end of the fixing member side separating means 19 facing the fixing member is arranged in a non-contact state with respect to the surface of the recording material. The margin M1 on the front end side in the transport direction of P is set smaller than the width W in the transport direction.
[0048]
As shown in FIGS. 6 and 7, when only the leading edge side margin portion M1 of the recording material P exits the nip N, no toner image is formed in the margin portion M1, so that the margin portion M1 is the toner. The margin M1 is discharged from the nip N along the extension line LBB of the nip N without adhering to the surface of the fixing roller 15 due to the adhesive force, and in this state, the margin M1 of the recording material P is removed from the fixing roller 15. There is no wrapping around the surface. When the recording material P is further conveyed in the direction of the arrow A than the state shown in FIGS. 6 and 7, the image area IA shown in FIG. 4 starts to be discharged from the nip N, and the sticking of the toner on the image area IA Since the recording material P adheres to or tends to adhere to the surface of the fixing roller 15 due to the force, the recording material P is pulled toward the fixing roller 15, but in the vicinity of the fixing roller 15, the fixing member side separating means 19. Therefore, the recording material P hits the fixing member side separating means 19 and is guided by the separating means 19, and the recording material P is prevented from being wound around the surface of the fixing roller 15. Also in this case, the fixing member side separating means 19 is the fixing roller 15.
However, since the gap G is set to be smaller than the width W of the margin M1, the recording material P pulled toward the fixing roller 15 by the adhesive force of the toner is Wrapping around the surface of the fixing roller 15 through the gap G while being attached to the surface of the fixing roller 15 is prevented. The recording material P that has passed through the fixing device 4 is discharged onto the tray 14 shown in FIG.
[0049]
As described above, in the fixing device 4 shown in FIGS. 6 and 7 as well, the recording material P that has exited the nip N can be prevented from being wound around the surface of the fixing roller 15, and the fixing member side separation means 19 can be fixed. Since it is not in contact with the surface of the roller 15, it is possible to prevent the fixing member 15 from being damaged by the fixing member side separating means 19 on the surface of the fixing roller 15 which has a low hardness and is easily damaged. In addition, since the nip N has a flat shape, the recording material that has exited the nip is less likely to curl than when the nip N is curved as in the example shown in FIGS. can get.
[0050]
The fixing roller 15 and the pressure roller 16 of the fixing device 4 illustrated in FIG. 6 can be configured similarly to the fixing roller 16 of the fixing device 4 illustrated in FIG. 2, for example. Further, the surface hardness of the fixing roller 15 and the pressure roller 16 shown in FIG. As described above, since the surfaces of the rollers 15 and 16 have substantially the same hardness, the nip N is formed in a substantially flat shape.
[0051]
FIG. 8 shows still another example of the fixing device 4. The basic configuration of the fixing device 4 shown here is substantially the same as that of the fixing device shown in FIG. While the tension roller 15C shown in FIG. 5 is located on the right side of the opposing roller 15B, the tension roller 15C shown in FIG. 8 is located above the opposing roller 15B. It ’s not a difference. Therefore, each part of the fixing device shown in FIG. 8 corresponding to each part of the fixing device shown in FIG. 5 is denoted by the same reference numeral as that in FIG.
[0052]
The fixing device shown in FIG. 8 is different from the fixing device shown in FIG. 5 in that the Asker C hardness measured on the surface of the portion of the fixing belt 15A wound around the opposing roller 15B is an example of the pressure member. This is the point that the surface of the pressure roller 16 is almost the same as the Asker C hardness. Therefore, also in the fixing device 4 shown in FIG. 8, only the margin M1 on the leading end side in the transport direction of the recording material P to be transported exits the nip N as in the case of the fixing device shown in FIGS. At that time, the margin M1 on the leading end side is an extension line LBB of the straight line LB connecting the downstream end NE of the nip N in the recording material conveyance direction and the upstream end NS of the nip N to the recording material conveyance direction. The direction is almost facing. In addition, a fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member made of the fixing belt 15A is disposed in a non-contact state with respect to the surface of the fixing member. The gap G between the recording material conveyance direction downstream end NE and the leading end of the fixing member side separating unit 19 facing the fixing member is a conveyance direction of the margin M1 on the leading side of the recording material P in the conveyance direction. Is set to be smaller than the width W. Accordingly, like the fixing device shown in FIGS. 6 and 7, the recording material P can be prevented from being wound around the surface of the fixing belt 15A, and the surface of the fixing belt 15A is scratched by the fixing member side separating means 19. Can be prevented, and further, the problem that the recording material P that has exited the nip N tends to curl can be prevented.
[0053]
In the fixing device shown in FIG. 6 to FIG. 8, when only the leading edge side margin M1 of the recording material P exits the nip N, the margin M1 is directed substantially in the direction of the extension line LBB. The surface hardness of the fixing member constituted by the fixing roller 15 or the fixing belt 15A and the surface hardness of the pressure member composed of the pressure roller 16 are set to be substantially equal as described above. In this case, the fixing member is also the fixing belt. In the case of 15A, the hardness of the surface of the fixing member is a hardness measured on the surface of the fixing belt portion wound around the opposing roller 15B. In short, regardless of the form of the fixing member, the Asker C hardness of the surface of the fixing member at the downstream end NE in the recording material conveyance direction of the nip N and the pressurization at the downstream end NE of the nip N in the recording material conveyance direction. By setting the Asker C hardness of the surface of the member to be substantially equal, when only the front end side margin portion M1 exits the nip N, the margin portion M1 may be configured to substantially face the direction of the extension line LBB. it can.
[0054]
Incidentally, the image forming apparatus shown in FIG. 1 is configured to form a toner image only on one surface of the recording material P, but the toner image on the photosensitive member is transferred to one surface of the recording material. Then, after fixing the toner image by the fixing device, the recording material is reversed and fed back to the photosensitive member, and the toner image on the photosensitive member is transferred to the other surface of the recording material. An image forming apparatus for fixing an image by a fixing device is also well known. When it is necessary to distinguish between the toner image formed on one surface of the recording material and the toner image formed on the other surface of the recording material, the former is the first toner image and the latter is the second toner image. I will call it.
[0055]
When fixing the second toner image by passing the recording material through the nip of the fixing device, the first toner image already fixed on one surface of the recording material also passes through the nip, and the first toner image is pressurized. Contact the member. At this time, since the pressure member is also heated, the first toner image is melted by the heat, and there is a possibility that the recording material exiting the nip is wound around the surface of the pressure member.
[0056]
Therefore, in the fixing device 4 shown in FIGS. 2 and 5, the pressure member side separation for separating the recording material P that has exited the nip N from the surface of the pressure member (the pressure roller 16 in the illustrated example). Means 22 is provided, and the tip of the separating means 22 facing the pressure member is in contact with the surface of the pressure member. The pressure member side separating means 22 is constituted by, for example, a plurality of separation claws arranged in the axial direction of the pressure roller 16, or one sheet-like separation member.
[0057]
As shown in FIGS. 2 and 5, the first toner image TA already fixed on one surface of the recording material P entering the nip N is carried and fixed on the other surface of the recording material P by the fixing device 4. When the second toner image T to be carried is carried, when the recording material P passes through the nip N, the first toner image TA is also heated and melted. May wrap around the surface of the pressure roller 16. In this case, the recording material P is separated from the surface of the pressure roller 16 by the pressure member-side separating means 22 in contact with the surface of the pressure roller 16. To be separated.
[0058]
Since the pressure member side separating means 22 is in contact with the surface of the pressure member made up of the pressure roller 16 at its tip, the recording material to be wound around the surface of the pressure roller 16 is surely placed on the surface. Can be separated from At that time, as described above, the surface hardness of the pressure roller 16 is higher than the surface hardness of the fixing roller 15, and the surface of the pressure roller 16 is not easily scratched. The problem that the surface of the pressure roller 16 is damaged by the separating means 22 can be prevented.
[0059]
In the fixing device shown in FIGS. 6 to 8, as described above, when only the front end side margin M1 of the recording material P being conveyed exits the nip N, the front end side margin M1 is extended. In addition, the pressure member side separation means 19A for separating the recording material P that has exited the nip N from the surface of the pressure member made of the pressure roller 16 is configured so as to be substantially directed in the direction of the line LBB. Is arranged in a non-contact state with respect to the surface of the pressure member, and is formed between the downstream end NE of the nip N in the recording material conveyance direction and the tip of the pressure member side separating means 19A facing the pressure member. The gap GA is set smaller than the width W in the transport direction of the margin M1 on the leading end side of the recording material P in the transport direction. The pressure member side separation means 19A can also be configured in an appropriate form, but the pressure member side separation means 19A shown here is constituted by a sheet-like separation member 20A.
[0060]
When the first toner image TA already fixed is carried on one surface of the recording material P entering the nip N, and the second toner image T to be fixed by the fixing device 4 is carried on the other surface. When the first toner image TA passes through the nip N, the toner melts, and when the recording material P adheres to the surface of the pressure roller 16, the pressure member side separation means 19A separates the fixing member side separation. The recording material is prevented from being wound around the surface of the pressure roller 16 in the same manner as the means 19. Further, since the pressure member side separating means 19A is also separated from the surface of the pressure roller 16, it is possible to prevent a problem that the surface is damaged.
[0061]
Further, in the fixing apparatus shown in FIGS. 6 to 8, since the fixing member side separating means 19 and the pressing member side separating means 19A are provided together, the recording material P is added to the fixing member. It is possible to prevent the pressure member from being wound around any surface, and to prevent the surface of these members from being damaged by the contact of the separating means.
[0062]
The fixing device 4 shown in FIG. 9 is also configured to prevent the recording material from being wound around the surface of the pressure member. The basic configuration and the basic operation of the fixing device shown in FIG. 9 are the same as those of the fixing device shown in FIG. The difference is that the Asker C hardness of the surface of the pressure roller 16 is set lower than the Asker C hardness of the surface of the fixing roller 15, and the fixing roller 15 elastically compresses and deforms the pressure roller 16 at the nip N. It is a point. Further, in the fixing device shown in FIG. 9, no heater is provided in the pressure roller 16, a heater 17 is provided in the fixing roller 15, and the fixing roller 15 is heated by the heater 17, and the nip N Is maintained at an appropriate temperature suitable for fixing the toner image. In this case, the difference between the surface hardness of the fixing roller 15 and the pressure roller 16 is set to, for example, about 20 to 40 Hs in terms of Asker C hardness.
[0063]
A first toner image TA that has already been fixed is carried on one surface of the recording material P, and an unfixed second toner image T to be fixed by the fixing device 4 is held on the other surface of the recording material P. The recording material P, which is carried, is sent to the nip N between the fixing roller 15 and the pressure roller 16 that rotate in the direction of the arrow, as indicated by the arrow A, and passes therethrough, whereby the second toner image T is recorded. It is fixed on the material P.
[0064]
At this time, the toner of the first toner image TA is also heated and melted, but the recording material P that has exited the nip N is prevented from being wound around the surface of the pressure roller 16 due to melting of the toner of the first toner image. Therefore, the pressure member side separating means 19A for separating the recording material P that has exited the nip N from the surface of the pressure member made of the pressure roller 16 is disposed in a non-contact state with respect to the surface of the pressure member. Has been. FIG. 9 also shows a state where the entire margin M1 on the leading end side in the conveyance direction of the recording material P has just exited from the nip N. As can be seen from this drawing, the recording material P downstream in the recording material conveyance direction. The gap GA between the side end NE and the leading end of the pressure member side separating means 19A facing the pressure member is determined by the width W of the margin M1 on the leading end side in the transport direction of the recording material P in the transport direction. Is set too small. The pressure member side separating means 19A is also constituted by, for example, a sheet-like separating member 20A.
[0065]
In the fixing device shown in FIG. 9, since the surface hardness of the fixing roller 15 is set higher than the surface hardness of the pressure roller 16, only the margin M1 on the front end side of the recording material P to be conveyed is nipped. When coming out of N, the margin M1 takes a posture along the surface of the fixing roller 15 and is largely separated from the surface of the pressure roller 16. When only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed exits the nip N, the margin M1 on the leading end side is recorded on the downstream end NE of the nip N in the recording material conveyance direction and the recording on the nip N. The straight line LC connecting the upstream end NS in the material conveyance direction is configured to face the fixing member side with respect to the extended line LCC on the recording material conveyance direction side.
[0066]
When the image area IA (see FIG. 4) of the recording material P exits the nip N, the toner of the second toner image T carried on the other surface is melted at the nip N. Although the toner of the first toner image TA formed on one surface of the recording material P is also melted at the nip N, the recording material P may be pulled toward the pressure roller 16 side. . When the gap GA is smaller than the width W of the blank portion M1, the surface hardness of the pressure roller 16 is lower than the surface hardness of the fixing roller 15, and only the blank portion M1 comes out of the nip N, the blank portion M1 is added. Since the toner does not adhere to the surface of the pressure roller 16 due to the adhesive force of the toner, the recording material P does not wrap around the surface of the pressure roller 16 when the recording material P is pulled toward the pressure roller 16. . In addition, since the pressure member side separating means 19A has a low surface hardness and is therefore located away from the surface of the pressure roller 16 which is easily damaged, the surface is not damaged.
[0067]
Further, the front end portion of the fixing member side separation means 22A made of a sheet-like separation member or the like is in contact with the surface of the fixing roller 15, and therefore the recording material P that has exited the nip N adheres to the surface of the fixing roller 15. Even so, the recording material P is immediately separated from the surface of the fixing roller 15 by the fixing member side separating means 22 </ b> A, and the recording material P does not wrap around the surface of the fixing roller 15. The fixing member side separating means 22A is in contact with the surface of the fixing roller 15, but since the surface hardness of the fixing roller 15 is high, the surface can be prevented from being damaged. In this way, by causing the fixing member side separation means 22A to contact the surface of the fixing roller 15, the recording material P can be reliably prevented from being wound around the fixing roller 15. The recording material P that has exited the nip N is conveyed while being guided by the pressure member side separating means 19A and a guide member 21A disposed above the pressure member side separating means 19A.
[0068]
As described above, it is possible to prevent the recording material P from being wound around the fixing roller 15 and the pressure roller 16 and to prevent the surfaces of the rollers 15 and 16 from being scratched. It is possible to prevent the quality of the first and second toner images formed on each surface of the material P from being deteriorated.
[0069]
A more specific configuration of the fixing device 4 shown in FIG. 9 will be described as an example. As the fixing roller 15, for example, fluorine is formed on the outer peripheral surface of an iron hollow roller having an outer diameter of 40 mm and a wall thickness of 0.6 mm. What coated the release layer which consists of resin can be used. As the pressure roller 16, for example, a foamed silicone rubber layer having a thickness of 5 mm is formed on an aluminum core having an outer diameter of 40 mm and a PFA tube having a thickness of 30 μm is covered on the outer peripheral surface thereof. be able to. In this configuration, since the fixing roller 15 is not provided with an elastic layer, the heat capacity of the fixing roller 15 is reduced, and the rise time from when the power is turned on until the fixing roller 15 reaches a temperature at which the fixing roller 15 can be fixed can be shortened.
[0070]
Further, the configuration in which the hardness on the surface side of the fixing member is larger than the hardness on the surface side of the pressure member can be applied even when the fixing member is formed of a fixing belt, and an example is shown in FIG. Since the basic idea of the fixing device 4 shown in FIG. 10 is the same as that of the fixing device shown in FIG. 9, the fixing member heated by the heaters 17A and 17B is a plurality of guide members. In this case, the endless fixing belt 15A is wound around the opposing roller 15B and the tension roller 15C and rotates in the direction of the arrow B, and the pressure member pressed against the fixing member is at least one guide via the fixing belt 15A. In the example shown in FIG. 10, the pressure roller 16 rotates in the direction of the arrow while being pressed against the opposing roller 15B. The Asker C hardness of the surface of the pressure roller 16 is set lower than the Asker C hardness measured on the surface of the fixing belt portion wound around the opposing roller 15B.
[0071]
The recording material P carrying the second toner image T to be fixed has a nip N formed by the pressure contact between the fixing belt 15A and the pressure roller 16 in the direction in which the second toner image T is in contact with the fixing belt 15A. The second toner image T is fixed to the recording material P by the action of heat and pressure.
[0072]
At that time, when only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed exits the nip N, the margin M1 on the leading end is downstream of the nip N in the recording material conveyance direction. The straight line LC connecting the end NE and the upstream end NS of the nip N in the recording material conveyance direction is directed toward the fixing member made of the fixing belt 15A rather than the extended line LCC on the recording material conveyance direction side.
[0073]
As indicated by an arrow A, a first toner image TA that has already been fixed is formed on one surface of the recording material P that enters the nip N. A pressure member side separating means 19A for separating the recording material P that has exited the nip N from the surface of the pressure member made of the pressure roller 16 is disposed in a non-contact state with respect to the surface of the pressure member. A gap GA between the downstream end NE of the nip N in the recording material conveyance direction and the tip of the pressure member side separating means 19A facing the pressure member is a blank portion on the front side of the recording material P in the conveyance direction. The width M1 is set to be smaller than the width W in the transport direction. With this configuration, the recording material P can be prevented from being wound around the pressure roller 16 as in the case of the fixing device shown in FIG. It is also possible to prevent the pressure roller having a low surface hardness from being damaged by the pressure member side separating means 19A. Further, it is possible to prevent the recording material P from being wrapped around the fixing belt 15A by the fixing member side separating means 22A in contact with the surface of the fixing belt 15A. The recording material P exiting the nip N is guided and conveyed by the pressure member side separating means 19A and the guide member 21A.
[0074]
Also in the fixing device 4 shown in FIGS. 9 and 10, when only the front end side margin M1 of the recording material P exits the nip N, the margin M1 faces the fixing member side from the extension line LCC. The Asker C hardness of the surface of the fixing member at the downstream end NE of the nip N in the recording material conveyance direction is set to be higher than the Asker C hardness of the surface of the pressure member at the downstream end NE of the nip N in the recording material conveyance direction. ing. In addition, as described above, the fixing member side separating means 22A for separating the recording material P that has exited the nip N from the fixing member is provided, and the leading end of the fixing member side separating means 22A contacts the surface of the fixing member. Therefore, the recording material can be effectively prevented from being wound around the fixing member. At that time, since the hardness of the surface of the fixing member is high, it is possible to prevent the surface of the fixing member from being damaged by the fixing member side separating means 22A that comes into contact.
[0075]
By the way, in each of the above-described embodiments, the gap G between the tip of the fixing member side separating means 19 that is located away from the fixing member and the downstream end NE of the nip N in the recording material conveyance direction is a recording gap. Since the width is set smaller than the width W of the margin part M1 on the leading end side in the conveyance direction of the material P, the leading end of the fixing member side separating means 19 is positioned close to the surface of the fixing member. In order to correctly arrange the fixing member side separating means 19 at such a position, it is advantageous to employ the following configuration.
[0076]
FIG. 11 shows an example of a configuration for positioning the fixing member side separating means 19 made of the sheet-like separating member 20 with respect to the fixing roller 15 shown in FIGS. 2 and 6. As shown in FIG. 11, a gap holding member 29 is fixed to each end of the fixing member 20 in a direction orthogonal to the recording material conveyance direction, and each gap holding member 29 is connected via a screw 30. It is supported by the support member 31. The support member 31 is pressurized toward the surface of the fixing roller 15 by a pressure member 32 made of a compression spring or the like. As a result, both gap holding members 29 come into contact with the surface of the fixing roller 15. At that time, as shown in FIG. 12, both gap holding members 29 abut against the recording material non-passing area PA of the fixing roller 15, that is, the respective end areas in the longitudinal direction of the fixing roller through which the recording material P does not pass. As a result, the gap between the region through which the recording material passes, that is, the tip of the fixing member side separating means 19 facing the recording material passage region PB, and the surface of the fixing roller 15 and the gap G described above are correctly maintained.
[0077]
The position of the surface of the fixing roller 15 is not constant due to thermal expansion or eccentricity of the roller, but the gap G is separated from the fixing member side by positioning the fixing member side separating means 19 as described above. It can always be kept substantially constant over the entire longitudinal direction of the means 19. In addition, since the gap holding member 29 contacts the recording material non-passing area PA of the fixing roller 15, the gap holding member 29 does not damage the recording material passing area PB of the fixing roller 15, and the gap holding member 29 is fixed. The toner image is not affected by the contact with the surface of the roller 15.
[0078]
Even when the fixing member is formed of the fixing belt 15A shown in FIGS. 5 and 8, the gap holding member 29 is brought into contact with the recording material non-passing area of the fixing belt 15A in the same manner as described above, thereby fixing the fixing member side. The gap between the separation means 19 and the surface of the fixing belt 15A and the gap G can be regulated correctly.
[0079]
As described above, a gap holding member is provided at each end of the separating member in a direction orthogonal to the recording material conveyance direction, and both the gap holding members are brought into contact with the recording material non-passing area of the fixing member for separation. By maintaining the distance between the front end of the member and the surface of the fixing member, the front end of the separating member can be easily positioned close to the fixing member and correctly positioned.
[0080]
In order to arrange the pressure member side separating means 19A of the fixing device shown in FIGS. 6, 8, 9 and 10 close to the surface of the pressure roller 16, the structure shown in FIGS. Can be adopted. In this case, in place of the fixing roller 15 shown in FIGS. 11 and 12, the pressure roller 16 shown in FIG. 6, 8, 9 or 10 is arranged. In this way, a gap holding member is provided at each end of the pressure member separating means in a direction orthogonal to the recording material conveyance direction, and the gap holding member is brought into contact with the recording material non-passing area of the pressure member. The distance between the tip of the pressure member side separation means and the surface of the pressure member can be maintained, and thereby the pressure member side separation means can be positioned close to the surface of the pressure member and correctly positioned. it can. In addition, since the gap holding member is in contact with the recording material non-passing area of the pressing member, it is possible to prevent a problem that the recording material passing area of the pressing member is damaged.
[0081]
By the way, the fixing member side separation means 19 and the pressure member side separation means 19A separated from the fixing member or the pressure member are constituted by separation claws made of a single plate material in addition to the sheet-like separation members 20 and 20A. The separating means composed of a plurality of separating claws arranged along the surface of the fixing member or the pressure member can be used as appropriate. Since the means 19A is arranged in a non-contact manner with respect to the fixing member or the pressure member, each of the separating means 19 and 19A is a single separating member made of a sheet or plate as shown in the illustrated example. Can be used. When the separation means is in contact with the surface of the fixing member or the pressure member, the separation means composed of a plurality of separation claws is used, and the contact pressure against each of the separation claws and the fixing member or the pressure member is adjusted by a spring. In this example, the fixing member side separation means 19 and the pressure member side separation means 19A are not in contact with the fixing member or the pressure member. Therefore, it is not necessary to adjust the contact pressure, and the fixing member side separating means 19 and the pressure member side separating means 19A constituted by one separating member can be adopted. By configuring the separating means 19 and 19A in this way, it is possible to reduce the number of parts and the cost thereof. Further, since it is not necessary to provide a spring for adjusting the contact pressure with which the fixing member side separating means 19 and the pressure member side separating means 19A abut on the fixing member or the pressure member, each of the separating means 19 and 19A is used for a recording material. It can also be formed integrally with the guide member or the casing (not shown) of the fixing device.
[0082]
Further, as shown in FIG. 11, when one or a plurality of openings 36 for ventilation are formed in one separating member 20 constituting the fixing member side separating means 19, the recording material P heated from the nip N is used. The water vapor that exits can be released, for example, upward through the opening 36, thereby preventing the water vapor from condensing on the recording material P and deteriorating its quality. The opening 36 penetrates in the thickness direction of the sheet-like separation member 20. Similarly, when one or more openings for ventilation are formed in one separation member 20A constituting the pressure member side separation means 19A, water vapor emitted from the recording material can be released through the openings.
[0083]
In the case where the fixing member side separating means 19 and the pressure member side separating means 19A are constituted by sheet-like separating members 20 and 20A as in the illustrated example, particularly when the thickness is thin, the heat of these separating members themselves. The spacing between the separation member 20, 20A and the fixing member or the pressure member becomes non-uniform in the longitudinal direction of the separation member due to undulation due to expansion or deformation due to the recording material coming into contact with the separation member 20, 20A. There is a fear. Therefore, when the fixing member side separating means 19 and the pressure member side separating means 19A are constituted by sheet-like separating members 20, 20A, the separating members 20, 20A are oriented in a direction orthogonal to the recording material conveyance direction. It is desirable to provide tension applying means for pulling. Thereby, generation | occurrence | production of the said malfunction can be prevented.
[0084]
The separation member 20 shown in FIG. 11 is fixed to the gap holding member 29 at each end in the longitudinal direction, and both the gap holding members 29 are supported by the support member 31 via the screws 30. By rotating 30, the separating member 20 is pulled in the direction of the arrow, and tension is applied to the separating member 20 to keep the separating member 20 flat, and the distance between the separating member 20 and the fixing roller 15 is kept constant. be able to. Thus, the screw 30 constitutes an example of tension applying means for pulling the separating member. The tension applying means for pulling the separating member 20A of the pressure member-side separating means 19A can be similarly configured.
[0085]
As the sheet-like separation members 20 and 20A, a thin plate made of heat-resistant resin or metal can be used. For example, a polyimide sheet having a thickness of 0.1 mm coated with a fluororesin can be used. Further, when a metal sheet or metal plate having a thickness of 0.2 mm or more is used as the separation member 20 or 20A, the rigidity is increased. Therefore, the separation member and the fixing member can be fixed without providing the tension applying means. It becomes possible to keep the space | interval between a member or a pressurization member constant.
[0086]
By the way, in each of the fixing devices described above, a release agent such as silicone oil can be applied to the fixing member or the pressure member in order to more reliably prevent the recording material from being wrapped around. However, when this configuration is adopted, the oil adheres to the recording material and the recording material becomes dirty, the maintenance for applying the oil becomes complicated, and the application member for applying the oil is required, and the cost of the fixing device is increased. We cannot escape the rising drawbacks.
[0087]
Therefore, if a wax-containing toner is used as the toner and the toner image is formed by a toner containing at least a resin, a colorant and a wax, so-called oil-less operation without applying a release agent becomes possible. , The above-mentioned problems can be eliminated.
[0088]
Each configuration described above can be widely applied to fixing devices other than the types described above. For example, in the fixing device 4 shown in FIGS. 5, 8, and 10, guide rollers, that is, the opposing roller 15B and the tension roller 15C are used as guide members for winding the fixing belt 15A. In the fixing device 4, two guide rollers 33 and 34 and a guide member configured as a heater 35 are used, and a fixing belt 15 </ b> A is wound around these guide members. Although not shown in the drawing, the heater 35 has a pair of electrodes and a resistor disposed between the electrodes and in contact with the inner surface of the fixing belt 15A. By supplying a current to the resistor, the resistor 35 is provided. Is heated so that the fixing belt 15A is heated. The configuration described above with reference to FIGS. 5, 8, and 10 can also be adopted for such a fixing device.
[0089]
Furthermore, as described above, the pressure member can be constituted by a pressure belt that is wound around a plurality of guide members and rotated. Also in this case, when the pressure belt portion wound around the guide member is in contact with the fixing member so as to form a nip, the Asker C hardness of the surface of the pressure belt is determined by winding around the guide member. It is the hardness measured on the surface of the applied pressure belt portion. In addition, the value of Asker C hardness described in this specification is a numerical value obtained by directly measuring the surface hardness of a roller or a belt using an Asker C hardness meter.
[0090]
【The invention's effect】
According to the present invention, it is possible to prevent the recording material from being wound around the fixing member and to prevent a defect that the surface of the fixing member is damaged by the separation member.
[0091]
According to the inventions according to claims 5 to 8, the recording material can be prevented from being wound around the pressure member.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus.
FIG. 2 is a cross-sectional view illustrating an example of a fixing device.
FIG. 3 is an enlarged explanatory view of the fixing device shown in FIG. 2;
FIG. 4 is a diagram illustrating a margin portion of a recording material.
FIG. 5 is a cross-sectional view illustrating another example of the fixing device.
FIG. 6 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 7 is an enlarged explanatory view of the fixing device shown in FIG.
FIG. 8 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 9 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 10 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 11 is a plan view showing an example of a separation member support device.
12 is a perspective view illustrating a state in which the gap holding member illustrated in FIG. 11 is in contact with the surface of the fixing roller.
FIG. 13 is an explanatory diagram illustrating still another example of the fixing device.
[Explanation of symbols]
4 Fixing device
20 Separation member
22 Pressure member side separating means
29 Gap holding member
36 opening
G gap
LA straight line
LAA extension line
M1 margin
N nip
NE Downstream end in the recording material conveyance direction
NS Upstream end in the recording material conveyance direction
P Recording material
PA recording material non-passing area
T Toner image
W width

Claims (8)

  1. 加熱される定着部材と、該定着部材に圧接する加圧部材とを有し、定着すべきトナー像を担持した記録材を、そのトナー像が前記定着部材に接する向きにして、前記定着部材と加圧部材との圧接により形成されたニップを通過させて、熱と圧力の作用により前記トナー像を記録材に定着させる定着装置を有する画像形成装置において、
    搬送される記録材の搬送方向先端側の余白部だけが前記ニップを出た時、該先端側の余白部が、前記ニップの記録材搬送方向下流側端と該ニップの記録材搬送方向上流側端を結ぶ直線の延長線よりも加圧部材側を向くように構成すると共に、前記ニップを出た記録材を前記定着部材の表面から分離するためのシート状の分離部材を、前記定着部材の表面に対して非接触状態で配置し、前記ニップの記録材搬送方向下流側端と前記分離部材の先端との間のギャップを、前記記録材の搬送方向先端側の余白部の、該搬送方向における幅よりも小さく設定し、前記分離部材には、その厚み方向に貫通している開口が形成されていることを特徴とする画像形成装置。
    A fixing member that is heated and a pressure member that is in pressure contact with the fixing member, and a recording material that carries a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. In an image forming apparatus having a fixing device that passes a nip formed by pressure contact with a pressure member and fixes the toner image on a recording material by the action of heat and pressure.
    When only the margin portion on the leading end side in the conveyance direction of the recording material to be conveyed exits the nip, the margin portion on the leading end side becomes the downstream end in the recording material conveyance direction of the nip and the upstream side in the recording material conveyance direction of the nip. A sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is configured to face the pressure member side with respect to a linear extension line connecting the ends. It is arranged in a non-contact state with respect to the surface, and the gap between the downstream end in the recording material conveyance direction of the nip and the leading end of the separation member is set in the conveyance direction of the blank portion on the leading end side in the recording material conveyance direction. An image forming apparatus, wherein an opening penetrating in the thickness direction is formed in the separation member.
  2. 加熱される定着部材と、該定着部材に圧接する加圧部材とを有し、定着すべきトナー像を担持した記録材を、そのトナー像が前記定着部材に接する向きにして、前記定着部材と加圧部材との圧接により形成されたニップを通過させて、熱と圧力の作用により前記トナー像を記録材に定着させる定着装置を有する画像形成装置において、
    前記ニップを出た記録材を前記定着部材の表面から分離するためのシート状の分離部材を、前記定着部材の表面に対して非接触状態で配置し、前記ニップにおける加圧部材の表面のアスカーC硬度を、該ニップにおける定着部材の表面のアスカーC硬度よりも高く設定し、前記ニップの記録材搬送方向下流側端と前記分離部材の先端との間のギャップを、前記記録材の搬送方向先端側の余白部の、該搬送方向における幅よりも小さく設定し、前記分離部材には、その厚み方向に貫通している開口が形成されていることを特徴とする画像形成装置。
    A fixing member that is heated and a pressure member that is in pressure contact with the fixing member, and a recording material that carries a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. In an image forming apparatus having a fixing device that passes a nip formed by pressure contact with a pressure member and fixes the toner image on a recording material by the action of heat and pressure.
    A sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is disposed in a non-contact state with respect to the surface of the fixing member, and an Asker on the surface of the pressure member in the nip. The C hardness is set to be higher than the Asker C hardness of the surface of the fixing member in the nip, and a gap between the downstream end in the recording material conveyance direction of the nip and the leading end of the separation member is set in the conveyance direction of the recording material. An image forming apparatus, wherein an opening penetrating in a thickness direction is formed in the separation member, the margin being set to be smaller than a width in a conveyance direction of a margin part on a front end side.
  3. 前記定着部材は、ガイド部材に巻き掛けられた無端状の定着ベルトより成り、前記加圧部材は、前記定着ベルトを介して、前記ガイド部材に圧接し、加圧部材の表面のアスカーC硬度が、前記ガイド部材に巻き掛けられた定着ベルト部分の表面のアスカーC硬度よりも高く設定されている請求項1又は2に記載の画像形成装置。The fixing member is composed of an endless fixing belt wound around a guide member, and the pressure member is in pressure contact with the guide member via the fixing belt, and has an Asker C hardness on the surface of the pressure member. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be higher than an Asker C hardness of a surface of the fixing belt portion wound around the guide member.
  4. 加熱される定着部材と、該定着部材に圧接する加圧部材とを有し、定着すべきトナー像を担持した記録材を、そのトナー像が前記定着部材に接する向きにして、前記定着部材と加圧部材との圧接により形成されたニップを通過させて、熱と圧力の作用により前記トナー像を記録材に定着させる定着装置を有する画像形成装置において、
    前記ニップを出た記録材を前記定着部材の表面から分離するためのシート状の分離部材を、前記定着部材の表面に対して非接触状態で配置し、前記ニップにおいて、凸状をなした加圧部材が前記定着部材を凹状に弾性変形させていて、前記ニップの記録材搬送方向下流側端と前記分離部材の先端との間のギャップを、前記記録材の搬送方向先端側の余白部の、該搬送方向における幅よりも小さく設定し、前記分離部材には、その厚み方向に貫通している開口が形成されていることを特徴とする画像形成装置。
    A fixing member that is heated and a pressure member that is in pressure contact with the fixing member, and a recording material that carries a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. In an image forming apparatus having a fixing device that passes a nip formed by pressure contact with a pressure member and fixes the toner image on a recording material by the action of heat and pressure.
    A sheet-like separation member for separating the recording material that has exited the nip from the surface of the fixing member is disposed in a non-contact state with respect to the surface of the fixing member, and a convex shape is added to the nip. The pressure member elastically deforms the fixing member into a concave shape, and a gap between the downstream end of the nip in the recording material conveyance direction and the leading end of the separation member is formed in a blank portion on the leading end side of the recording material in the conveyance direction. The image forming apparatus is characterized in that the width is set smaller than the width in the conveying direction, and the separation member has an opening penetrating in the thickness direction.
  5. 前記ニップを出た記録材を前記加圧部材の表面から分離するための加圧部材側分離手段を設け、該加圧部材側分離手段の先端部を加圧部材の表面に当接させた請求項1乃至4のいずれかに記載の画像形成装置。A pressure member separating means for separating the recording material that has exited the nip from the surface of the pressure member is provided, and the tip of the pressure member separating means is brought into contact with the surface of the pressure member. Item 5. The image forming apparatus according to any one of Items 1 to 4.
  6. 前記記録材搬送方向に対して直交する向きの前記分離部材の各端部にギャップ保持部材を設け、該ギャップ保持部材を前記定着部材の記録材非通過領域に当接させて、該分離部材の先端と定着部材の表面との間の間隔を保持する請求項1乃至5のいずれかに記載の画像形成装置。A gap holding member is provided at each end of the separating member in a direction orthogonal to the recording material conveyance direction, and the gap holding member is brought into contact with the recording material non-passing area of the fixing member, so that the separation member The image forming apparatus according to claim 1, wherein an interval between the front end and the surface of the fixing member is maintained.
  7. 前記分離部材を、記録材搬送方向に対して直交する向きに引張るテンション付与手段を設けた請求項1乃至6のいずれかに記載の画像形成装置。The image forming apparatus according to claim 1, further comprising a tension applying unit that pulls the separation member in a direction orthogonal to the recording material conveyance direction.
  8. 前記トナー像が、少なくとも樹脂、着色剤及びワックスを含有するトナーにより形成される請求項1乃至7のいずれかに記載の画像形成装置。The image forming apparatus according to claim 1, wherein the toner image is formed of a toner containing at least a resin, a colorant, and a wax.
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JP3980527B2 (en) 2003-07-18 2007-09-26 株式会社沖データ Fixing device and image forming apparatus
JP4508692B2 (en) * 2004-03-24 2010-07-21 キヤノン株式会社 Pressure member, image heating apparatus, and image forming apparatus
JP4264410B2 (en) 2004-11-30 2009-05-20 株式会社リコー Fixing apparatus and image forming apparatus
JP4092329B2 (en) * 2004-12-17 2008-05-28 株式会社リコー Fixing device, separation plate, manufacturing method thereof, and image forming apparatus
JP2006243030A (en) * 2005-02-28 2006-09-14 Ricoh Co Ltd Fixing device and image forming apparatus
JP4839170B2 (en) 2006-09-28 2011-12-21 株式会社リコー Fixing apparatus and image forming apparatus
JP2008122431A (en) 2006-11-08 2008-05-29 Ricoh Co Ltd Fixing belt, fixing device having the fixing belt, and image forming apparatus
JP2011164260A (en) * 2010-02-08 2011-08-25 Konica Minolta Business Technologies Inc Fixing device and image forming apparatus
JP2012159547A (en) * 2011-01-30 2012-08-23 Ricoh Co Ltd Fixing device, and image forming apparatus
JP5568505B2 (en) * 2011-04-15 2014-08-06 京セラドキュメントソリューションズ株式会社 Fixing device and image forming apparatus to which the fixing device is applied
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