JP2004302152A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speed up the throughput of a small-sized sheet, as for an image forming apparatus having a film heating system fixing means. <P>SOLUTION: The image forming apparatus is provided with the film heating system fixing means, a 1st temperature detecting means 5a for detecting the temperature of a heating body with reference to all the recording materials made to pass, a 2nd temperature detecting means 5b arranged in a position becoming a non-paper passing area when a recording material which has narrow paper width passes, a means for counting the number of passing recording materials, power supply control means 112 to 114 for controlling the power supply to the heating body 1 in accordance with the temperature detected by the 1st temperature detecting means 5a, and wherein a threshold temperature is set with reference to the temperature T detected by the 2nd temperature detecting means 5b, and the apparatus is provided with a control means 112 for prolonging the paper feeding interval when the detected temperature T exceeds the threshold temperature, and the prescribed number α of sheets is prepared, and the apparatus is provided with a control mode of not prolonging the paper feeding interval while the prescribed number α of sheets is in passing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１９】
図１４に、従来例の枚数切替制御のフローチャートを示す。Ｓ１において、小サイズ紙の印刷をスタートする。Ｓ２で印刷予定枚数Ｒを記憶する。Ｓ３で、給紙枚数Ｑをクリアし（Ｑ＝０）、Ｓ４で給紙する。Ｓ５で、上記の通紙枚数をカウントする手段によって、給紙された通紙枚数がカウントされる（Ｑ＝Ｑ＋１）。Ｓ６で、通紙枚数Ｑが印刷予定枚数Ｒに達していない場合は、Ｓ７で、表２の通紙枚数Ｑから給紙間隔の段階Ｋを決定し、設定された給紙間隔にしたがって再び給紙を行う（Ｓ７→Ｓ４）。Ｓ６で、通紙枚数Ｑが印刷予定枚数Ｒに達した場合は、ラスト紙が画像形成装置から排出された後、全ての印刷制御を終了する（Ｓ８）。
【００２０】
このように、通紙枚数によって段階的に給紙間隔を延長することで、小サイズ紙を連続通紙しても、非通紙部昇温を抑制して、加圧ローラなどの熱劣化を防ぎ、かつ、非通紙部昇温による画像不良の発生を抑制することができる。
【００２１】
ただし、このような枚数切替制御では、非通紙部昇温が比較的緩やかな小サイズ紙（より幅広で薄い記録材、例えばＥＸＥ、Ｂ５サイズの薄紙）の連続通紙においてでも、非通紙部昇温の急激な小サイズ紙と同じ枚数で、段階的に給紙間隔を延長してしまう。
【００２２】
▲２▼：非通紙部の温度を検知して給紙間隔を切り替える（温度切替制御）
市場において、ＣＯＭ１０封筒のような紙は、Ｂ５やＥＸＥサイズの薄紙と比較すると、使用される頻度はかなり低い。そこで、小サイズ紙の中でもより汎用される、Ｂ５サイズ・ＥＸＥサイズのスループットを高速化することを目的に、記録材の種類によって非通紙部昇温が異なることに注目し、非通紙部昇温を第二の温度検知手段で検知して、段階的に給紙間隔を切り替える制御、いわゆる温度切替制御が発明され、実用されている。このような制御は、例えば特許文献５に開示されている。
【００２３】
先述した温度検知手段を第一の温度検知手段、今回の温度検知手段を第二の温度検知手段とする。定着装置に２つ以上の温度検知手段を配置する構成は提案され、すでに実施されている。２つの温度検知手段を有する構成の例を説明する。図１５に２つの温度検知手段の配置を示す。第一の温度検知手段５ａは、通紙されうる全てのサイズの記録材において、通紙領域に配置する。第一温度検知素子５ａは、常に良好な定着性が得られるように、通紙領域の温度を監視して検知温度を制御回路に伝え、ヒータへの通電制御にフィードバックさせている。第二温度検知素子５ｂは、小サイズの非通紙領域となる場所に配置する。これは、非通紙部昇温を検知して温度切替制御をおこなうほかに、例えば第一の温度検知手段５ａの誤作動によるヒータ１の異常な高温や、記録材の重送などを検知することで、定着装置の熱劣化、破損の防止を行うことができる。
【００２４】
表２に、従来例の温度切替制御の各設計値を示す。
【００２５】
【表２】

【００２６】
本例では、第二の温度検知手段５ｂの検知温度Ｔの最高温度Ｔｍａｘに対してしきい温度ａ＝２２０℃を設け、Ｔｍａｘ＞２２０℃となった場合は、給紙間隔の段階ＫをＫ１→Ｋ２→Ｋ３→Ｋ４と延長する例を示す。
【００２７】
図１６に、従来例の温度切替手段のフローチャートを示す。Ｓ１〜Ｓ３は上記の枚数切替と同じ制御である。Ｓ４で、通紙初期の給紙間隔の段階をＫ１とする。Ｓ５で、第二の温度検知手段の温度検知を開始し、検知温度Ｔの最高温度Ｔｍａｘを記憶・更新し続ける。Ｓ６〜Ｓ８は、枚数切替制御と同様である。Ｓ９で現在の給紙間隔の段階ＫがＫ４でなければ、Ｓ１０に進む。Ｓ１０で、Ｔｍａｘがしきい温度ａ＝２２０℃（表２参照）を超えていないか判断する。Ｔｍａｘ＞２２０℃であれば、Ｓ１１で給紙間隔を延長する（Ｋ＝Ｋ＋１）。Ｔｍａｘ＞２２０℃でなければ、給紙間隔は変更しない（Ｓ１２）。Ｓ９で、Ｋ＝Ｋ４であれば、Ｋ４は最も遅い給紙間隔の段階なので、給紙間隔の延長は行わない。Ｓ１３では、Ｔｍａｘを一旦消去し、再び、逐次検知される検知温度Ｔの最高温度Ｔｍａｘを記憶・更新しつづける。その後、Ｓ１１、Ｓ１２で決定した給紙間隔に従って、再び給紙を行う（Ｓ１３→Ｓ６）。Ｓ８で、通紙枚数Ｑが印刷予定枚数Ｒに達した場合は、ラスト紙が画像形成装置から排出された後、全ての印刷制御を終了する（Ｓ１４）。
【特許文献１】
特開昭６３−３１３１８２号公報
【特許文献２】
特開平２−１５７８７８号公報
【特許文献３】
特開平４−４４０７５号公報
【特許文献４】
特開平４−２０４９８０号公報
【特許文献５】
特開平５−８０６０４号公報
【００２８】
【発明が解決しようとする課題】
スループットの高速化は、ユーザーの強い要望である。上記の温度切替制御において、さらなるスループットの高速化を図るために、先行紙の後端が定着ニップから排出される前に後続紙の給紙間隔の延長を判断するほど、給紙間隔を短くした場合、以下のような課題が発生する。
【００２９】
図５に、初期の給紙間隔Ｋ１を、先行紙の後端が定着ニップから排出される前に後続紙を給紙するほど短く設定して、従来例の温度切替制御を用いて（図１５、表２参照）、記録材を・・・→Ｐ１→Ｐ２→Ｐ３→Ｐ４→Ｐ５→・・・と連続給紙したときの、給紙タイミングと、各記録材において非通紙部の温度が最大となるタイミングを示す。横軸は時間の経過を示している。
【００３０】
給紙間隔の延長を判断するタイミングについて、ここではまず、給紙直前（図中△）まで、給紙間隔の延長を行うことができる、とする。
【００３１】
１枚の記録材において、非通紙部が最も高温となるタイミングは、記録材の後端が定着ニップから排出されたとき（図中▲）である。これは、記録材が定着ニップを通過している間では、通紙部の熱量が記録材に奪われ続けるのに対し、非通紙部は発熱体から熱量を供給され続けられるためである。
【００３２】
従って、図に示すように、記録材Ｐ３を給紙したのちに、記録材Ｐ２での検知温度Ｔがしきい温度ａを超える可能性がある。このとき、記録材Ｐ３の給紙間隔は延長されないため、記録材Ｐ３での検知温度Ｔもしきい温度ａ以上（Ｔ＞ａ）となる。この結果、給紙間隔の延長は、記録材Ｐ４，Ｐ５に対して２回連続しておこなわれ、スループットは必要以上に落ちてしまう。
【００３３】
本例では、給紙間隔の延長の判断を“給紙直前まで、給紙間隔の延長を行うことができる”としたが、汎用されている画像形成装置においては、“先行紙の記録材の搬送を検知したとき”とするものもある。これは例えば、枚数切替制御で記したフォトインタラプタを用いて、正常な給紙・搬送が行われたことを確認してから後続紙の給紙をおこなう制御である。後者の制御では、前者の制御よりも給紙間隔延長の判断が早まる。従って、２回連続して給紙間隔が延長されることに変わりない。
【００３４】
本発明では、上記の課題を克服して小サイズ紙のスループットの高速化を達成することができる画像形成装置を提案するものである。
【００３５】
【課題を解決するための手段】
本発明は、
記録材の搬送方向に直交する方向を長手として配置された加熱体と、該加熱体に接触して移動するフィルムと、該フィルムを介して加熱体と圧接してニップを形成する加圧部材と、を有し、前記ニップの前記フィルムと前記加圧部材との間に未定着トナー像を担持した記録材を挟持搬送させることによって前記フィルムを介した前記加熱体の熱により加熱してトナー像を記録材上に定着させる定着手段と、
通紙されうる全ての記録材において通紙領域となる位置に配置されて加熱体の温度を検知する第一の温度検知手段と、
紙幅の狭い記録材が通紙されるときに非通紙領域となる位置に配置される第二の温度検知手段と、
記録材の通紙枚数をカウントする手段と、
前記第一の温度検知手段が検知する温度によって加熱体を通電制御する通電制御手段と、
前記第二の温度検知手段が検知した温度Ｔに対してしきい温度を設け、前記検知温度Ｔが該しきい温度を超えたときに給紙間隔を延長する制御手段と、
を有する画像形成装置であり、
所定枚数αを設け、該所定枚数αの通紙中は、給紙間隔を延長しないことを特徴とする制御モードを有する画像形成装置、である。
【００３６】
即ち、第二の温度検知手段での非通紙部の検知温度が、しきい温度以上となったときに、給紙間隔を延長する小サイズシーケンス（いわゆる温度切替制御）の、紙間が短いスループット段階での給紙間隔切替を最適化するものである。
【００３７】
【発明の実施の形態】
（１）画像形成装置例
図１は本発明に従う画像形成装置の一例の概略構成模型図である。本例の画像形成装置は転写式電子写真プロセス利用の複写機あるいはレーザプリンタである。
【００３８】
１０１は像担持体としての回転ドラム型の電子写真感光体（以下、感光ドラムと記す）であり、矢印の時計方向に所定の制御周速度で回転駆動される。
【００３９】
１０２は帯電手段としての帯電ローラであり、回転する感光ドラム１０１の外周面を所定の極性・電位に一様に帯電処理する。
【００４０】
１０３は原稿画像のスリット露光機構やレーザスキャナ等の画像露光装置であり、回転する感光ドラム１０１の一様帯電処理面に画像露光Ｌする。これにより感光ドラム面に露光パターンに対応した静電潜像が形成される。
【００４１】
１０４は現像装置であり、感光ドラム面の静電潜像をトナー像として現像する。
【００４２】
１０５は転写手段としての転写ローラであり、感光ドラム１０１に対して所定の押圧力で接触して転写ニップＴを形成している。この転写ニップＴに給紙機構部から記録材Ｐが所定の制御タイミングにて給送されて転写ニップＴを挟持搬送されていく。また転写ローラ１０５には所定の制御タイミングで所定の転写バイアスが印加される。これにより、転写ニップＴを挟持搬送される記録材Ｐの面に感光ドラム１０１面側のトナー像が順次に静電転写される。
【００４３】
転写ニップＴを出た記録材Ｐは感光ドラム１０１面から分離されて定着装置１１１に導入される。定着装置１１１は導入された記録材Ｐ上の未定着トナー像を永久固着画像として加熱定着し、該記録材Ｐを排出搬送する。
【００４４】
１０６は感光ドラムクリーニング器であり、記録材分離後の感光ドラム上の転写残トナーを除去する。転写残トナーが除去されて清浄面化された感光ドラム面は繰り返して作像に供される。
【００４５】
１０７は給紙機構部に装着した給紙カセットであり、記録材Ｐを積載収納してある。該給紙カセット１０７内の記録材Ｐは給紙開始信号に基いて回転駆動される給紙ローラ１０８により１枚分離給紙され、レジストローラ対１１０により感光ドラム上での作像進行と同期が取られて転写ニップＴに所定の制御タイミングにて給紙される。
【００４６】
１０９は通紙枚数カウント手段であり、給紙カセット１０７よりも記録材搬送方向下流側でレジストローラ対１１０よりも記録材搬送方向上流側の記録材搬送経路に配設してある。本例ではこの通紙枚数カウント手段としてフォトインタラプタを用いた。
【００４７】
フォトインタラプタは、発信部と受信部と、棒状の動揺部材によって構成される。発信部と受信部は互いに向き合い、発信部は、制御回路から電圧を印加されて発信部から受信部に向かって光信号を発信する。発信部と受信部の間では、動揺部材の１端が行き来できるようにする。動搖部のもう一端は、記録材の搬送経路に突出し、通過する記録材と接触することで動揺部材全体を動揺する。動揺部の動揺が、発信部から受信部に向けて発信された光信号を遮断したり、遮断しなかったりすることで、記録材の通過を検知する。検知された記録材の通過は、電気信号で制御手段に伝達され、制御手段は、通紙枚数をカウントする。
【００４８】
１１２は制御手段としての制御回路（制御基板）であり、画像形成装置の全ての作像プロセス機器の制御を司り、作像シーケンス制御を司る。
【００４９】
（２）定着装置１１１
図２は定着装置１１１の拡大模型図である。本例の定着装置１１１は、円筒状の定着フィルムを用いた、加圧ローラ駆動タイプの、フィルム加熱方式の加熱装置である。
【００５０】
１は加熱体としてのセラミックヒータであり、図面に垂直方向を長手とする、横長、薄肉の低熱容量の部材である。３は横断面略半円弧状樋型のフィルムガイドである。前記のヒータ１はこのフィルムガイド３の下面中央部に該部材の長手に沿って形成具備させたヒータ嵌め込み溝に嵌め込んで、保持させてある。２は円筒状の定着フィルムであり、上記のようにヒータ１を保持させたフィルムガイド３にルーズに外嵌させてある。４は加圧部材としての弾性加圧ローラである。
【００５１】
弾性加圧ローラ４は、鉄、ステンレス、もしくはアルミニウムの芯金４ａと、弾性、断熱性、耐熱性に優れたシリコンゴム層４ｂによって構成される。芯金４ａの両端部側を軸受けを介して定着装置の側板間に回転自由に軸受け保持させて配設してある。また、芯金４ａの一端部側にはギヤを嵌め、駆動モータＭによって加圧ローラ４を矢印の反時計方向に回転駆動するようにしてある。そしてこの加圧ローラ４の上側に該加圧ローラ４に並行させて上記のヒータ１・フィルムガイド３・円筒状定着フィルム２の組み立て物をヒータ１側を下向きにして配列し、フィルムガイド３を不図示の付勢部材で加圧ローラ４の弾性に抗して加圧ローラ４に押圧状態にさせることで、ヒータ１と加圧ローラ４とを定着フィルム２を挟ませて圧接させることで、加圧ローラ４のシリコンゴム層４ｂの弾性歪により所定幅の圧接ニップ（定着ニップ）Ｎを形成させてある。
【００５２】
定着フィルム２は加圧ローラ４の回転駆動により定着ニップＮにおいて摩擦力で回転トルクを受け、定着ニップＮにおいて内面がヒータ１の面に密着して摺動しながら所定の周速度でフィルムガイド３の外回りを従動回転状態になる。フィルム２とヒータ１との摺動抵抗を低減するために両者間に耐熱性グリス等の潤滑剤を介在させることもできる。
【００５３】
そして、ヒータ１に対する通電が開始され、また加圧ローラ４の回転駆動、およびこれに従動して円筒状定着フィルムが回転し、ヒータ１が所定の温度に立ち上がって温調状態になり、加圧ローラ４と定着フィルム２の回転が安定化した状態において、定着ニップＮの定着フィルム２と加圧ローラ４との間に未定着トナー像ｔを担持している記録材Ｐが導入されて挟持搬送され、記録材Ｐがその未定着トナー像担持面が定着フィルム２の外面に密着して定着フィルム２と一緒の重なり状態で定着ニップを通過していく。
【００５４】
この記録材Ｐの定着ニップ通過過程で記録材Ｐはヒータ１の熱を定着フィルム２を介して受けて加熱され、未定着トナー像ｔが記録材Ｐ面に加熱加圧定着される。記録材Ｐは定着ニップＮの記録材出口部において定着フィルム２の外面から曲率分離して排出搬送される。
【００５５】
定着フィルム２は、熱劣化や摩擦の防止、省電力、クイックスタート性、オフセットなどの画像不良を抑制するために、耐熱性、耐久性、低熱容量、離型性に優れることが望ましい。例えばＰＩ（ポリイミド）などの基材フィルムの上に、ＰＦＡやＰＴＦＥなどの離型性を有する耐熱樹脂を被覆したものがよく使用される。
【００５６】
本例において、定着フィルム２は長さ２２６ｍｍ、内径２４ｍｍ、肉厚５５μｍの円筒状ポリイミドフィルムの外面にＰＴＦＥを１０μｍコートしたものである。
【００５７】
フィルムガイド３は、耐熱性、絶縁性、剛性に優れることが望ましい。例えば、ＰＰＳ（ポリフェニレンサルファイド）、ＰＡＩ（ポリアミドイミド）、ＰＩ（ポリイミド）、ＰＥＥＫ（ポリエーテルエーテルケトン）などの材料を型成形したものがよく使用される。
【００５８】
加圧ローラ４は外径８ｍｍのアルミニウムの芯金４ａに肉厚５ｍｍのシリコンゴム層４ｂを設けたものである。
【００５９】
ヒータ１は、熱応力による破壊の防止、非通紙部昇温の抑制、省電力、クイックスタート性などを図るために、耐熱性、高熱伝導性、低熱容量に優れることが望ましい。一般的に、フィルム加熱方式の定着装置で使用されるヒータは、ヒータ基板の上に、発熱体、導電パターン、ガラス層を有する積層構造となっている。ヒータ基板は耐熱性、低熱容量、熱伝導性、電気絶縁性に優れる材料が好ましく、窒化アルミあるいはアルミナなどのセラミックがよく使用される。発熱体は、例えば銀パラジウム（Ａｇ／Ｐｂ）、Ｔａ_２Ｎなどの電気抵抗材料ペーストを、ヒータ基板にスクリーン印刷・焼成することで形成する。導電パターンとしての電極部、導電部は、例えば銀ペーストなどの良導体材料を基板にスクリーン印刷・焼成することで形成する。電極部、導電部、発熱体は電気回路を構成し、制御手段によってこの電気回路への通電を制御することで、ヒータ１を目的の温度に温調する。ヒータ１は記録材の搬送方向に直交する方向を長手として配置される。
【００６０】
図３は本例で用いたヒータ１の構造模型図である。このヒータ１は、
▲１▼．ヒータ基板１ａとしての、幅７ｍｍ、長さ２３５ｍｍ、厚み１．０ｍｍの窒化アルミ基板、
▲２▼．このヒータ基板の表面側に基板長手に沿って銀パラジウム（Ａｇ／Ｐｄ）などの電気抵抗材料ペーストをスクリーン印刷して１１Ωの抵抗値となるように形成具備させた、並行２本の往復発熱体１ｂ、
▲３▼．この並行２本の往復発熱体１ｂの一端部側を電気的に直列に導通させた導電性パターン１ｃ、
▲４▼．各発熱体１ｂの他端部に電気的に導通させて具備させた給電用電極パターン１ｄ、
▲５▼．ヒータ基板の表面側において発熱体１ｂと導電性パターン１ｃとを覆わせて設けた、薄層のガラスコート層等の絶縁保護摺動層１ｅ、
等からなる。
【００６１】
また、ヒータ基板１ａの裏面側には、それぞれヒータ温度をモニタする第一と第二の２つの温度検知手段５ａ・５ｂを配設してある。
【００６２】
そしてこのヒータ１を、フィルムガイド２の下面中央部に該部材の長手に沿って形成具備させたヒータ嵌め込み溝内にヒータ表面側を外側に露呈させて嵌め込入れて保持させてある。
【００６３】
本例において通紙は中央基準搬送であり、第一の温度検知手段５ａは、通紙されうる全てのサイズの記録材において、通紙領域に配置する。第一温度検知素子５ａは、常に良好な定着性が得られるように、通紙領域の温度を監視して検知温度を制御回路１１２に伝え、ヒータ１への通電制御にフィードバックさせている。第二の温度検知素子５ｂは、小サイズの非通紙領域となる場所に配置する。第一の温度検知手段５ａ、第二の温度検知手段５ｂは、ヒータ長手で発熱体中心から給電用電極パターン１ｄと反対側に、それぞれ１５ｍｍ、９７ｍｍの位置に配置した。本例においては両温度検知手段５ａ・５ｂとも外部当接型サーミスタを用いた。この２つの温度検知手段５ａ・５ｂはそれぞれバネによって１Ｎ程度の圧力でヒータ１に圧接した。
【００６４】
温度検知手段５ａ・５ｂは、例えば、温度によって抵抗値が変化する温度検知素子５１を有するサーミスタを使用することができる。温度検知の方法としては、例えば、温度検知素子と、抵抗値が既知な抵抗を、制御手段にリンクする電気回路に組み込み、この電気回路に微弱な一定電圧を印加し、抵抗値が既知である前記抵抗の分圧を測定することで、温度検知素子の検知温度を知ることができる。
【００６５】
サーミスタには主に、ヒータ一体型と、外部当接型があり、どちらも汎用されている。図４の（ａ）にヒータ一体型サーミスタの概略図を、（ｂ）に外部当接型サーミスタの概略図を示す。
【００６６】
ヒータ一体型サーミスタは、ヒータ１上に、温度検知素子５１と、銀ペーストなどによる電極部５２、導電部５３を搭載したものである。温度検知素子は半田５４などによって導電部５３、ヒータ１に接着する。温度検知素子５１には、外部より電極部５２、導電部５３を介して電圧を印加する。
【００６７】
外部当接型サーミスタは、ヒータとは独立したサーミスタユニットで、温度検知素子５１と、ジュメット線などによる電気回路５５、断熱性、絶縁性、弾性を有するセラミックペーパー５６、耐熱性樹脂の支持体５７、カプトンシートなどの絶縁膜５８、ガスケットなどの接着剤５９で構成される。
【００６８】
本例においては第一と第二の両温度検知手段５ａ・５ｂとも外部当接型サーミスタを用いたが、後述する給紙間隔を切り替える設定値を適正化すれば、ヒータ一体型でも良い。
【００６９】
第一と第二の両温度検知手段５ａ・５ｂのヒータ温度検知情報は制御回路１１２に入力する。制御回路１１２は第一の温度検知手段５ａの検知情報に基いてＡＣ電源１１３とトライアック１１４からなる給電回路を制御して、第一の温度検知手段５ａで検知されるヒータ温度が所定の目標温度（定着温度）に維持されるように発熱体１ｂへの給電電力を制御してヒータ温度を温調する。
【００７０】
制御回路１１２は第二の温度検知手段５ｂの検知情報に基いて、後述（３）項の給紙間隔切替制御をする。
【００７１】
制御回路１１２は通紙枚数カウント手段１０９の記録材通過検知信号に基いて通紙枚数をカウントする。
【００７２】
制御回路１１２は上記の他に画像形成装置の全ての作像プロセス機器の制御を司り、作像シーケンス制御を司る。
【００７３】
（３）給紙間隔切替制御
１）実施例１
表３に、本実施例１における給紙間隔切替制御の各設定値を示す。
【００７４】
【表３】

【００７５】
本例では、給紙間隔の段階Ｋを４段階設け、第二の温度検知手段５ｂの検知温度Ｔの最高温度Ｔｍａｘに対してしきい温度ａ＝２１０℃を設け、Ｔｍａｘ＞ａ＝２１０℃となった場合は、給紙間隔の段階ＫをＫ１→Ｋ２→Ｋ３→Ｋ４と延長するように設定した。
【００７６】
本実施例の特徴は、所定枚数αを設定し、しきい温度ａを超えたあとのα枚では、Ｔｍａｘ＞２１０℃であっても、給紙間隔の延長を行わない、とすることにある。
【００７７】
これを満たすために、本実施例では、同じ給紙間隔で連続通紙された枚数θをカウントし、該θの枚数に対して前記所定枚数αを設け、通紙初期での給紙間隔の段階Ｋ１での所定枚数α＝０枚とした。
【００７８】
所定枚数αの設定について、従来の温度切替手段を用いて、急激な非通紙部昇温を発生するＣＯＭ１０封筒を用いて、図５のように連続通紙をおこない、前記検知温度Ｔが初めてしきい温度ａを超えた次の記録材からカウントして、Ｔ＞ａとなる記録材の枚数を設定した。
【００７９】
初めてａを超えた紙をＰ２とすると、Ｐ３は必ずＴ＞ａとなり、Ｐ４では給紙間隔が延長されたためにＰ３枚目より温度が低くなり始め、Ｐ５では必ずａ以下の温度となった。
【００８０】
従って、しきい温度ａを超えても給紙間隔を切り替えない枚数α＝２枚（Ｐ３，Ｐ４に相当）と設定できる。また、しきい温度ａは、非通紙部が最も高温となったＰ３枚目においても、加圧ローラ温度が熱劣化温度に到達せず、非通紙部昇温による画像不良が発生しないように設定した。
【００８１】
図６に、本実施例１の給紙間隔切替制御のフローチャートを示す。Ｓ１で小サイズ紙の印刷動作がスタートされる。Ｓ２で、印刷予定枚数Ｒを記憶する。Ｓ３で、通紙枚数Ｑと、同じ給紙間隔での通紙枚数θをクリアする（Ｑ＝０、θ＝０）。Ｓ４で、通紙初期の給紙間隔の段階ＫをＫ１とし、Ｓ５で第二の温度検知手段５ｂによる温度検知を開始する。ここでは、逐次検知される検知温度Ｔの最大値をＴｍａｘとして記憶・更新し続ける。
【００８２】
Ｓ７で、前記のフォトインタラプタによって、通紙枚数Ｑ、同じ通紙枚数での通紙枚数θをカウントする（Ｑ＝Ｑ＋１、θ＝θ＋１）。Ｓ８で通紙枚数Ｑが印刷予定枚数Ｒに達していない場合は、Ｓ９に移行する。Ｓ９で、現在の給紙間隔の段階ＫがＫ４でない場合、Ｓ１０で、θ≦αであるか判断する。
【００８３】
ここで表３から、α＝２枚である。θ≦αである場合、給紙間隔の段階は変更しない。θ≦αでい場合は、Ｓ１１でＴｍａｘがしきい温度ａ＝２２０℃を超えていないか判断する（表３参照）。Ｔｍａｘ＞２２０℃であれば、Ｓ１２で給紙間隔を延長し（Ｋ＝Ｋ＋１）、同じ給紙間隔での通紙枚数θをクリア（θ＝０）する。Ｔｍａｘ＞ａでなければ、給紙間隔は変更しない（Ｓ１３）。
【００８４】
Ｓ９で、Ｋ＝Ｋ４であれば、Ｋ４は最終的な給紙間隔の段階なので、給紙間隔の延長は行わない。Ｓ１２、Ｓ１３で給紙間隔を決定したら、Ｓ１４で、Ｔｍａｘを一旦クリアし、再び、逐次検知される検知温度Ｔの最大値Ｔｍａｘを記憶・更新する。Ｓ１２、Ｓ１３で決定した給紙間隔に従って再び給紙を行う（Ｓ１４→Ｓ６）。Ｓ８で、通紙枚数Ｑが印刷予定枚数Ｒに達した場合は、ラスト紙が画像形成装置から排出された後、全ての印刷制御を終了する（Ｓ１５）。
【００８５】
連続通紙初期のスループットを高速化したときの実施例の効果１を、図７に示す。上図に、連続通紙したときのスループットの変化を、下図に、そのときの加圧ローラの、記録材１枚ごとの非通紙部の最高温度を示す。実線は本実施例の給紙間隔切替制御を用いたときの様子で、破線は従来の温度切替制御を用いたときの様子である。従来の温度切替制御では、２回連続して給紙間隔を延長した。実施例１の給紙間隔切替制御では、給紙間隔の延長を連続して行うことはなく、加圧ローラ温度も、熱劣化温度以下の安定した温度で推移している。すなわち、実施例１の制御によって、加圧ローラの熱劣化を抑制しながら、スループットの高速化が図ることができた。また、非通紙部昇温による画像不良が発生もなかった。すなわち課題を解決した。
【００８６】
なお、本実施例では、給紙間隔の段階Ｋ＝Ｋ２，Ｋ３に対し、所定枚数αとして同一の値α＝２枚を設定したが、各給紙間隔の段階に対して、異なる値を設定しても良い。
２）実施例２
実施例１では、給紙間隔を延長したあとの所定枚数αは、しきい温度ａに関わらず、給紙間隔を切り替えない制御であった。しかし、万が一、ＣＯＭ１０封筒よりも非通紙昇温が急激である未知の記録材が通紙された場合や、記録材が重送された場合などを考慮すると、上記αに相当した枚数に対しても、給紙間隔を延長できる制御とした方が好ましい。そこで、本実施例では、実施例１のαと上記しきい温度ａとは異なるしきい温度ｂ（ｂ＞ａ）を設け、該所定枚数αの通紙中は、前記検知温度Ｔがしきい温度ｂを超えたときは、給紙間隔を延長することを特徴とした。
【００８７】
表４に、実施例２の給紙間隔切替制御の各設定値を示す。
【００８８】
【表４】

【００８９】
所定枚数α、しきい温度ａは、実施例１と同様に設定した。しきい温度ｂは、図５において、ＣＯＭ１０を連続通紙してもＰ２枚目の検知温度Ｔがｂ＞Ｔとなる温度で、加圧ローラが熱劣化温度に達するときの検知温度よりも低い温度で、かつ非通紙部昇温による画像不良が発生しない温度に設定する。
【００９０】
図８に、実施例２の給紙間隔切替制御のフローチャートを示す。図８のＳ１４以外は実施例１と同様である。Ｓ１０で、θ≦αでないときは、Ｓ１４で、第二検知手段の検知温度の最大値Ｔｍａｘをしきい温度ｂ（ｂ＞ａ）と比較する。Ｔｍａｘ＞ｂのときは、Ｓ１２で、給紙間隔を延長する。Ｔｍａｘ＞ｂでないときは、Ｓ１３に進み、給紙間隔の延長は行わない。
【００９１】
このような制御とすることで、実施例１と同様の効果を得るとともに、非常に非通紙部昇温が急激な未知の紙種が通紙された場合や、記録材が重送された場合などでは、２段階連続で給紙間隔を延長して、加圧ローラの熱劣化や、非通紙部昇温による画像不良などを抑制することができる。
【００９２】
本実施例では、給紙間隔の段階Ｋ＝Ｋ２，Ｋ３に対し、所定枚数αとして同一の値α＝２枚を設定したが、各給紙間隔の段階に対して、異なる値を設定しても良い。
３）実施例３
実施例１〜２において、給紙間隔は段階的に延長する制御としたが、非通紙部の温度が十分に緩和された場合は、再び給紙間隔を短くする制御も提案されている（例えば、特開２００２−１６９４１３号公報に開示）。
【００９３】
このような制御でも、スループットを高速化するために給紙間隔を短くすると、課題の項に述べたことと同様に、給紙間隔を２回連続で切り替えてしまう可能性がある。この場合は、給紙間隔を２回連続で短縮してしまう。
【００９４】
そこで本実施例では、給紙間隔を短縮した直後のβ枚では、検知温度Ｔがしきい温度ｃを下回っても、給紙間隔の短縮を行わない、該通紙枚数βを設定することに特徴がある。
【００９５】
表５に、実施例３の給紙間隔切替制御の各設定値を示す。
【００９６】
【表５】

【００９７】
これを満たすために、本実施例では、同じ給紙間隔で連続通紙された枚数θをカウントし、該θの枚数に対して前記所定枚数βを設け、通紙初期での給紙間隔の段階Ｋ１での所定枚数β＝０枚とした。
【００９８】
図９に実施例３の給紙間隔切替制御フローチャートを示す。Ｓ１〜９は実施例１と同様である。Ｓ１０において、同じ給紙間隔で通紙された枚数θが所定枚数よりも大きいとき、Ｓ１１で検知温度の最最高温度Ｔｍａｘとしきい温度ｃを比較する。Ｔｍａｘ＜ｃのときは、Ｓ１２で給紙間隔を短縮する。Ｔｍａｘ＜ｃでないときは、給紙間隔の短縮は行わない（Ｓ１３）。Ｓ１０で、θ≦βでないときは、給紙間隔の短縮は行わない（Ｓ１３）。
【００９９】
以下の制御は、実施例１と同様である。
【０１００】
本実施例では、給紙間隔の段階Ｋ＝Ｋ２，Ｋ３に対し、所定枚数βとして同一の値β＝２枚を設定したが、各給紙間隔の段階に対して、異なる値設定しても良い。
【０１０１】
４）実施例４
実施例３では、給紙間隔を短縮したあとの所定枚数βは、しきい温度ｃに関わらず、給紙間隔を切り替えないとしたが、所定枚数βの通紙中に、しきい温度ｃとは異なるしきい温度ｄ（ｄ＜ｃ）を設定し、しきい温度ｄをも下回った場合は２回連続で給紙間隔を短縮する制御としても良い。
【０１０２】
表６に、実施例４の給紙間隔切替制御の各設定値を示す。所定枚数β、しきい温度ｃは、実施例１と同様に設定した。
【０１０３】
【表６】

【０１０４】
しきい温度ｄは、ｄ＜ｃであり、２回連続で給紙間隔を短くしても、加圧ローラの温度が熱劣化温度に達しないように、あるいは、非通紙部昇温による画像不良が発生しないように設定する。
【０１０５】
図１０に、実施例４の給紙間隔切替制御のフローチャートを示す。図１０のＳ１４以外は実施例３と同様である。Ｓ１０で、θ≦βでないときは、Ｓ１４で、第二検知手段の検知温度の最大値Ｔｍａｘをしきい温度ｄ（ｄ＜ｃ）と比較する。Ｔｍａｘ＜ｄのときは、Ｓ１２で、給紙間隔を延長する。Ｔｍａｘ＜ｄでないときは、Ｓ１３に進み、給紙間隔の延長は行わない。
【０１０６】
本実施例では、給紙間隔の段階Ｋ＝Ｋ２，Ｋ３に対し、所定枚数βとして同一の値β＝２枚を設定したが、各給紙間隔の段階に対して、異なる値を設定しても良い。
【０１０７】
５）実施例５
実施例１，２は、給紙間隔を延長する制御に対して、実施例３，４は給紙間隔を短縮する制御に対して、課題を克服する制御を提案したが、実施例１，２の制御が、実施例３，４のいずれかの制御を有しても良い。
【０１０８】
このような制御での効果を、図１１に示す。ここでは、ＣＯＭ１０封筒を連続通紙して給紙間隔を延長したあとに、比較的非通紙昇温の緩やかなＥＸＥサイズの記録材を連続通紙した（図中↑の地点）。上図に、連続通紙したときのスループットの変化を、下図に、そのときの加圧ローラの、記録材１枚ごとの非通紙部最高温度を示す。実線は本実施例の給紙間隔切替制御を用いたときの様子で、破線は従来の温度切替制御を用いたときの様子である。途中からＥＸＥサイズの記録材を通紙することで、加圧ローラ非通紙部の温度が低下し始める。加圧ローラ温度が十分低下したあとで、給紙間隔を短くする制御が働く。従来例では、２回連続で給紙間隔が短縮され、急激な昇温が発生し、加圧ローラの熱劣化温度を超えてしまうことがあった。
【０１０９】
一方、本実施例では、連続して給紙間隔を切り替えることがなく、加圧ローラ非通紙部の温度も安定した状態で、連続通紙を行うことができた。このように、本実施例によって、加圧ローラの非通紙部の温度が熱劣化温度に達することなく、スループットの高速化を図ることができた。
【０１１０】
６）実施例６
第二の温度検知手段５ｂの検知温度Ｔが非常な高温を検知したとき、ヒータ１の発熱を停止する制御が実用されている。これは、記録材の重層搬送によって非通紙部の温度が高温化したとき、あるいは、第一の温度検知手段５ａの検知温度と制御手段の異常によって、ヒータの温度制御に異常をきたしたときなど、ヒータ温度が非常な高温に達したときに、定着装置の熱劣化や、ヒータの破損、あるいは火災の発生を防止するための制御である。このような異常時は、しきい温度や通紙枚数に関わらず、ヒータの発熱を停止したほうが安全である。そこで本実施例は、実施例１〜５に記載の画像形成装置において、異常温度を検知するためのしきい温度ｅ（ｅ＞ａ，ｂ，ｃ，ｄ）を検知したときは、所定枚数α、βに関わらず、ヒータの発熱を停止することを特徴とする。
【０１１１】
表７に、実施例６の給紙間隔切替制御の各設定値を示す。
【０１１２】
【表７】

【０１１３】
これは、実施例２の制御に、ヒータの加熱を停止するしきい温度ｅ（ｅ＞ａ，ｂ）を設定したものである。
【０１１４】
図１２に、実施例６の給紙間隔切替制御のフローチャートを示す。図１２のＳ９以外は実施例２と同様である。Ｓ９で、検知温度の最大値ＴｍａｘがＴｍａｘ＞ｃとなる場合は、所定枚数αにかかわらず、Ｓ１０でヒータをｏｆｆし、全ての制御を停止する（Ｓ１７）。
【０１１５】
本実施例は、実施例２に対してしきい温度ｅを設けているが、実施例１〜５のいずれの制御に対しても、しきい温度ｅを設定し、Ｔｍａｘ＞ｃであるときは、枚数α，βに関わらずヒータをＯＦＦするという制御を組み込めば、同様の目的を達成することができる。
【０１１６】
７）以上実施例１〜６で説明したように、実施例１、３のように、所定枚数α、もしくはβを設け、給紙間隔を変更したあとの該所定枚数α、もしくはβの通紙中は、給紙間隔を切り替えない制御とすることで、先行紙の後端が定着ニップから排出される以前に後続紙の給紙間隔の切り替え判断をおこなうほど、給紙間隔の短い制御においてでも、給紙間隔を連続して延長されることがない制御とすることができる。
【０１１７】
あるいは実施例２のように、該所定枚数αにおいては、通常のしきい温度ａとは異なるしきい温度ｂ（ｂ＞ａ）を有することで、非常に非通紙部昇温の厳しい記録材が通紙された場合や、記録材が重送された場合など、非通紙部昇温が非常に大きなときは、２回連続して給紙間隔を延長することができる。
【０１１８】
あるいは実施例３〜５のように、該所定枚数βにおいては、通常のしきい温度ｃとは異なるしきい温度ｄ（ｄ＜ｃ）を有することで、非通紙部昇温が小さい場合、あるいは連続通紙の途中から非通紙部昇温の緩やかな記録材の通紙を行った場合などでは、給紙間隔を連続して短縮することのない制御とすることができる。
【０１１９】
その結果、加圧ローラなどの定着装置の熱劣化や、非通紙昇温による画像不良の発生を防止しつつ、スループットの高速化を達成することができる。
【０１２０】
また、実施例６のように、所定枚数α，β、しきい温度ｅを設定することで、ヒータの異常高温を検知し、所定枚数α，βに関わらず、ヒータの通電をｏｆｆすることで、定着装置の熱劣化や、ヒータの破損、あるいは火災の発生を防止することができる。
【０１２１】
（４）その他
１）加熱体としてのセラミックヒータ１の構成は実施例に示したものに限られるものではないことは勿論である。また加熱体はセラミックヒータに限られない。
【０１２２】
２）定着フィルム２は実施例の円筒状のものに限られず、複数の支持部材間に懸回張設したエンドレスベルト状のものにして回転させる、ロール巻きにした長尺の有端ウエブ状のものにしてこれを繰り出しながら走行移動させる装置構成にすることができる。
【０１２３】
３）フィルム加熱方式の定着装置は実施例の加圧回転体駆動式に限られず、フィルムを駆動して加圧回転体は従動回転させる装置構成にすることができる。
【０１２４】
以上、本発明の様々な例と実施例が示され説明されたが、当業者であれば、本発明の趣旨と範囲は本明細書内の特定の説明と図に限定されるのではなく、本願特許請求の範囲に全て述べられた様々の修正と変更に及ぶことが理解されるであろう。
【０１２５】
４）本発明においては、定着手段には、未定着画像を記録材に仮定着せしめｓる仮定着装置、定着画像を担持した記録材を再加熱してつや等の画像表面性を改質する像加熱装置も含むものとする。これ等の装置にも本発明の装置構成・制御を有効に適用することができる。
【０１２６】
本発明の実施態様の例を以下に列挙する。
【０１２７】
〔実施態様１〕 記録材の搬送方向に直交する方向を長手として配置された加熱体と、該加熱体に接触して移動するフィルムと、該フィルムを介して加熱体と圧接してニップを形成する加圧部材と、を有し、前記ニップの前記フィルムと前記加圧部材との間に未定着トナー像を担持した記録材を導入して挟持搬送させることによって前記フィルムを介した前記加熱体の熱により加熱してトナー像を記録材上に定着させる定着手段と、
通紙されうる全ての記録材において通紙領域となる位置に配置されて加熱体の温度を検知する第一の温度検知手段と、
紙幅の狭い記録材が通紙されるときに非通紙領域となる位置に配置される第二の温度検知手段と、
記録材の通紙枚数をカウントする手段と、
前記第一の温度検知手段が検知する温度によって加熱体を通電制御する通電制御手段と、
前記第二の温度検知手段が検知した温度Ｔに対してしきい温度を設け、前記検知温度Ｔが該しきい温度を超えたときに給紙間隔を延長する制御手段と、
を有する画像形成装置であり、
所定枚数αを設け、該所定枚数αの通紙中は、給紙間隔を延長しないことを特徴とする制御モードを有する画像形成装置。
【０１２８】
〔実施態様２〕 前記検知温度Ｔに対するしきい温度をａとする、実施態様１に記載の画像形成装置において、前記所定枚数αは、検知温度Ｔがしきい温度ａを超えた次の記録材から数えられる通紙枚数であることを特徴とする制御モードを有する画像形成装置。
【０１２９】
〔実施態様３〕 記録材の搬送方向に直交する方向を長手として配置された加熱体と、該加熱体に接触して移動するフィルムと、該フィルムを介して加熱体と圧接してニップを形成する加圧部材と、を有し、前記ニップの前記フィルムと前記加圧部材との間に未定着トナー像を担持した記録材を導入して挟持搬送させることによって前記フィルムを介した前記加熱体の熱により加熱してトナー像を記録材上に定着させる定着手段と、
記録材の通紙枚数をカウントする手段と、
前記第一の温度検知手段が検知する温度によって加熱体を通電制御する通電制御手段と、
前記第二の温度検知手段が検知した温度Ｔに対してしきい温度を設け、前記検知温度が該しきい温度を超えたときに給紙間隔を延長する制御手段と、
を有する画像形成装置であり、
前記しきい温度を、常に１つ有し、通常のしきい温度はａとし、かつ、所定枚数αを設け、該所定枚数αの通紙中は、上記ａとは異なる温度ｂ（ｂ＞ａ）をしきい温度とすることを特徴とする制御モードを有する画像形成装置。
【０１３０】
〔実施態様４〕 実施態様３に記載の画像形成装置において、前記所定枚数αは、前記検知温度Ｔが前記しきい温度（ａもしくはｂ）を超えた次の記録材から数えられる通紙枚数であることを特徴とする制御モードを有する画像形成装置。
【０１３１】
〔実施態様５〕 記録材の搬送方向に直交する方向を長手として配置された加熱体と、該加熱体に接触して移動するフィルムと、該フィルムを介して加熱体と圧接してニップを形成する加圧部材と、を有し、前記ニップの前記フィルムと前記加圧部材との間に未定着トナー像を担持した記録材を導入して挟持搬送させることによって前記フィルムを介した前記加熱体の熱により加熱してトナー像を記録材上に定着させる定着手段と、
記録材の通紙枚数をカウントする手段と、
前記第一の温度検知手段が検知する温度によって加熱体を通電制御する通電制御手段と、
前記第二の温度検知手段が検知した温度Ｔに対してしきい温度を設け、前記検知温度Ｔが該しきい温度を下回ったときに、給紙間隔を短縮する制御手段と、
を有する画像形成装置であり、
所定枚数βを設け、該所定枚数βの通紙中は、給紙間隔を短縮しないことを特徴とする制御モード有する画像形成装置。
【０１３２】
〔実施態様６〕 前記検知温度Ｔに対するしきい温度をｃとする、実施態様５に記載の画像形成装置において、前記所定枚数βは、前記検知温度Ｔがしきい温度ｃを下回った次の記録材から数えられる通紙枚数であることを特徴とする制御モードを有する画像形成装置。
【０１３３】
〔実施態様７〕 記録材の搬送方向に直交する方向を長手として配置された加熱体と、該加熱体に接触して移動するフィルムと、該フィルムを介して加熱体と圧接してニップを形成する加圧部材と、を有し、前記ニップの前記フィルムと前記加圧部材との間に未定着トナー像を担持した記録材を導入して挟持搬送させることによって前記フィルムを介した前記加熱体の熱により加熱してトナー像を記録材上に定着させる定着手段と、
記録材の通紙枚数をカウントする手段と、
前記第一の温度検知手段が検知する温度によって加熱体を通電制御する通電制御手段と、
前記第二の温度検知手段が検知した温度Ｔに対してしきい温度を設け、前期検知温度Ｔが該しきい温度を下回ったときに給紙間隔を短縮する制御手段と、
を有する画像形成装置であり、
前記しきい温度を、常時１つ有し、通常のしきい温度はｃとし、かつ、所定枚数βを設け、該所定枚数βの通紙中は、上記ｃとは異なる温度ｄ（ｄ＜ｃ）をしきい温度とすることを特徴とする制御モードを有する画像形成装置。
【０１３４】
〔実施態様８〕 実施態様７に記載の画像形成装置において、前記所定枚数βは、前記検知温度Ｔがしきい温度（ｃもしくはｄ）を下回った次の記録材から数えられる通紙枚数であることを特徴とする制御モードを有する画像形成装置。
【０１３５】
〔実施態様９〕 実施態様２と４に記載のいずれかの制御モードと、実施態様６と８に記載のいずれかの制御モードを同時に有する画像形成装置。
【０１３６】
〔実施態様１０〕 実施態様１〜９の何れかに記載の画像形成装置において、定着手段のフィルムは回転体であることを特徴とする画像形成装置。
【０１３７】
【発明の効果】
以上説明したように本発明によれば、第二の温度検知手段での非通紙部の検知温度が、しきい温度以上となったときに、給紙間隔を延長する小サイズシーケンス（いわゆる温度切替制御）の、紙間が短いスループット段階での給紙間隔切替を最適化することで、従来の課題を克服して小サイズ紙のスループットの高速化を達成することができる画像形成装置を提案することができる。
【図面の簡単な説明】
【図１】実施例１の画像形成装置の概略図
【図２】フィルム加熱方式の定着装置の概略図
【図３】加熱体としてのセラミックヒータの構成模型図
【図４】ヒータ一体型サーミスタと外部当接型サーミスタの概略図
【図５】給紙タイミングと、定着ニップにおける紙通過タイミングと、非通紙部が最も高温となるタイミングのタイミングチャート
【図６】実施例１の給紙間隔切替制御のフローチャート
【図７】実施例の効果１の説明図
【図８】実施例２の給紙間隔切替制御のフローチャート
【図９】実施例３の給紙間隔切替制御のフローチャート
【図１０】実施例４の給紙間隔切替制御のフローチャート
【図１１】実施例の効果２の説明図
【図１２】実施例６の給紙間隔切替制御のフローチャート
【図１３】発熱長手における非通紙部の昇温の様子を示した図
【図１４】従来例の枚数切替制御のフローチャート
【図１５】２つの温度検知手段の配置図
【図１６】従来例の温度切替制御のフローチャート
【符号の説明】
１・・加熱体、２・・定着フィルム、３・・フィルムガイド、４・・加圧ローラ、５（ａ，ｂ）・・温度検知手段、５１・・温度検知素子、５２・・サーミスタの電極部、５３・・サーミスタの導通部、５４・・半田、５５・・ジュメット線、５６・・セラミックペーパー、５７・・支持体、５８・・絶縁膜、５９・・接着剤、Ｎ・・定着ニップ、Ｐ・・記録材、Ｐ１，Ｐ２，Ｐ３・・・、連続通紙される記録材、Ｒ・・印刷予定枚数、θ・・同じ給紙間隔で通紙された枚数、Ｋ・・現在の給紙間隔、Ｋ１，Ｋ２，Ｋ３，Ｋ４・・設定された給紙間隔の段階、Ｔ・・第二の温度検知手段の検知温度、Ｔｍａｘ・・逐次更新されるＴの最高温度、ａ，ｂ・・給紙間隔を延長するしきい温度（ｂ＞ａ）、ｃ，ｄ・・給紙間隔を短くするしきい温度（ｄ＞ｃ）、ｅ・・ヒータをｏｆｆするしきい温度、α・・給紙間隔を延長したあとの所定枚数、β・・給紙間隔を短縮したあとの所定枚数[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying apparatus and an electrostatic information recording apparatus having a film heating type fixing unit. More specifically, the present invention relates to fixing control of the image forming apparatus.
[0002]
[Prior art]
(1) Film heating type fixing device
2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying apparatus and an electrostatic information recording apparatus, as a fixing unit for fixing an unfixed toner image formed and supported on a recording material by a transfer method or a direct method by heating or pressing, In many cases, a film heating type fixing device (heating device, image heating device) is used.
[0003]
Patent Documents 1 to 4 disclose a film heating type fixing device. This fixing device forms a nip by pressing a heating body disposed in contact with the heating body, a film moving in contact with the heating body, and a heating body arranged in such a manner that the direction perpendicular to the conveying direction of the recording material is a longitudinal direction. Pressurizing member, the recording medium carrying an unfixed toner image being introduced between the film and the pressurizing member of the nip, and nipped and conveyed. The toner image is fixed on the recording material by heating by the heat of the recording medium.
[0004]
The film heating type fixing device can reduce the heat capacity of the heating body itself or the film which is a member disposed between the heating body and the recording material, as compared with other well-known fixing devices such as a heat roller system. It is excellent in power saving and quick start performance (reduction of wait time).
[0005]
As the heating element, for example, a so-called ceramic heater that is a heating element having a low heat capacity can be used. As the film, for example, a thin heat-resistant resin film or a metal film having a thickness of several tens to several hundreds of μm can be used. it can.
[0006]
FIG. 13 shows a model diagram of an example of the ceramic heater 1 as a heating element. The heater 1 has a basic structure including a heater substrate 1a and a heating element 1b formed on the surface of the heater substrate and generating heat by energization.
[0007]
The heater substrate 1a is a heat-resistant, low-heat-capacity, good-heat-conductivity, electrically-insulating, horizontally-long, thin-walled member having a length in a direction perpendicular to the transport direction.
[0008]
The heating element 1b is formed on the surface of the heater substrate along its length, and is made of silver palladium or Ta. ₂ It is an electric resistor that generates heat when energized such as N. The heater of this example includes two parallel reciprocating heating elements 1b having one end electrically connected in series with a conductive pattern 1c, and the other end of each heating element 1b is electrically connected to a power supply. Electricity is supplied from a power supply circuit (not shown) between the electrode patterns 1d for use to generate heat in the heating element 1b. The temperature of the heater 1 rises sharply due to the heat generated by the heating element 1b.
[0009]
Reference numeral 5 denotes a temperature detecting means such as a thermistor for detecting the temperature of the heater 1. The temperature detecting means 5 is disposed in contact with the surface of the heater substrate 1a opposite to the surface provided with the heating element 1b, and detects the heater temperature and transmits it to a control circuit (not shown). The control circuit controls the power supply from the power supply circuit to the heating element 1b to control the temperature of the heater so that the heater temperature detected by the temperature detecting means 5 is maintained at a predetermined target temperature (fixing temperature).
[0010]
In this example, the paper is passed by the center reference conveyance, and the temperature detecting means 5 is arranged at a location which is a paper passing area at the longitudinal position of the heater in all sizes of the recording material that can be passed. The temperature detecting means 5 monitors the temperature of the paper passing area, transmits the detected temperature to a control circuit, and feeds it back to the control of energization to the heater for the purpose of always obtaining good fixing performance.
[0011]
(2) Non-sheet-passing section temperature rise and conventional solution to non-sheet-passing section temperature rise
By the way, in the above-described fixing device, there is a problem of so-called “non-sheet passing portion temperature rise”. This is a phenomenon in which, when a so-called small-size recording material such as B5, an envelope, or a postcard is continuously passed, the temperature rises in a heating element area of the heater and a non-sheet passing area.
FIG. 13 shows how the temperature of the non-sheet passing portion rises in the longitudinal direction of the heating element. The temperature of the paper passing portion is controlled to be constant by the amount of heat supplied from the heater, while the amount of heat is deprived by the recording material. On the other hand, in the non-sheet passing area, the heat amount is not deprived, and the heat amount is supplied from the heater. The non-sheet-passing portion temperature rises more rapidly as the paper width is narrower or the paper thickness is thicker. When the temperature of the non-sheet passing portion becomes high, the components of the fixing device, for example, the pressure roller, are thermally degraded. Further, when a recording material of a plain paper size is passed while the temperature of the non-sheet passing portion is increasing, an edge hot offset or the like occurs due to an excessively high temperature in the non-sheet passing portion region.
[0012]
As a method for solving such a problem, when continuously feeding small-size paper in which the temperature of the non-sheet-passing portion is high, the feeding interval is extended longer than when continuous feeding of recording material of a plain paper size. There is a method for alleviating the temperature rise in the non-sheet passing portion. Further, in order to increase the throughput at the initial stage of paper passing, a method of extending the paper feed interval stepwise during continuous paper passing is widely used.
[0013]
The following two methods (1) and (2) are in practical use for control for extending the paper feed interval during continuous paper feeding.
[0014]
{Circle around (1)}: Control to extend the paper feed interval depending on the number of sheets passed (number switching control)
This is control (so-called sheet number switching control) in which the sheet feeding interval is extended stepwise according to the number of sheets of recording material passed.
[0015]
The number of sheets for which the paper feeding interval is extended is such that the paper feeding interval is extended by the number of papers that does not cause thermal deterioration in the fixing device even when a recording material having a very high temperature in a non-paper passing portion such as a COM10 envelope is used. Are set in advance and incorporated in the control in advance.
[0016]
A photo-interrupter can be used as a means for counting the number of passed recording materials. The detected passage of the recording material is transmitted to the control unit by an electric signal, and the control unit counts the number of passed sheets.
[0017]
Table 1 shows each set value of the conventional sheet number switching control. In the present embodiment, four stages K of the paper feed interval are provided, and the stage K of the paper feed interval is set to be switched from K1 to K2 to K3 to K4 according to the number Q of sheets passed.
[0018]
[Table 1]

[0019]
FIG. 14 shows a flowchart of the conventional sheet number switching control. In S1, printing of small-size paper is started. At S2, the planned number of prints R is stored. At S3, the number of sheets Q to be fed is cleared (Q = 0), and the sheets are fed at S4. In S5, the number of fed sheets is counted by the means for counting the number of fed sheets (Q = Q + 1). In S6, if the number Q of sheets passed has not reached the number R of sheets to be printed, in S7, the stage K of the sheet feeding interval is determined from the number Q of sheets passed in Table 2, and the sheet feeding is performed again according to the set sheet feeding interval. Paper is performed (S7 → S4). In S6, when the number of sheets Q reaches the number R of sheets to be printed, after the last sheet is discharged from the image forming apparatus, all the printing controls are ended (S8).
[0020]
In this way, by gradually increasing the paper feed interval according to the number of sheets passed, even if small size paper is continuously passed, the temperature rise in the non-sheet passing portion is suppressed, and thermal deterioration of the pressure roller and the like is suppressed. Thus, it is possible to prevent the occurrence of an image defect due to an increase in the temperature of the non-sheet passing portion.
[0021]
However, in such a sheet number switching control, even when the non-sheet passing portion continuously heats a small-sized sheet (a wider and thinner recording material, for example, a thin sheet of EXE or B5 size) in which the temperature rise is relatively gentle, the non-sheet passing section does not increase the temperature. With the same number of small-size paper sheets whose temperature rises rapidly, the paper supply interval is extended stepwise.
[0022]
{Circle around (2)}: Detecting the temperature of the non-sheet passing portion and switching the sheet feeding interval (temperature switching control)
On the market, paper such as COM10 envelopes are used much less frequently than B5 or EXE sized thin paper. Therefore, in order to speed up the throughput of B5 size / EXE size, which is more commonly used among small size papers, it is noted that the temperature rise of the non-paper passing portion differs depending on the type of recording material. A control in which the temperature rise is detected by a second temperature detecting means and the paper feed interval is switched stepwise, that is, a so-called temperature switching control has been invented and put into practical use. Such control is disclosed in Patent Document 5, for example.
[0023]
The above-mentioned temperature detecting means is defined as a first temperature detecting means, and the current temperature detecting means is defined as a second temperature detecting means. A configuration in which two or more temperature detecting means are arranged in a fixing device has been proposed and has already been implemented. An example of a configuration having two temperature detecting units will be described. FIG. 15 shows an arrangement of two temperature detecting means. The first temperature detecting means 5a is arranged in a paper passing area in all sizes of recording materials that can be passed. The first temperature detecting element 5a monitors the temperature in the paper passing area, transmits the detected temperature to a control circuit, and feeds it back to the control of energization to the heater so that good fixing performance is always obtained. The second temperature detecting element 5b is arranged at a location that is a small size non-sheet passing area. This means that, besides detecting the temperature rise of the non-sheet passing portion and performing the temperature switching control, for example, detecting abnormally high temperature of the heater 1 due to malfunction of the first temperature detecting means 5a, double feeding of the recording material, and the like. This can prevent the fixing device from being thermally degraded and damaged.
[0024]
Table 2 shows design values of the conventional temperature switching control.
[0025]
[Table 2]

[0026]
In this example, a threshold temperature a = 220 ° C. is provided for the maximum temperature Tmax of the detected temperature T of the second temperature detecting means 5b, and when Tmax> 220 ° C., the stage K of the sheet feeding interval is set to K1. An example is shown in which K2 → K3 → K4 is extended.
[0027]
FIG. 16 shows a flowchart of the conventional temperature switching means. S1 to S3 are the same control as the above-described number switching. In step S4, the stage of the paper feed interval at the beginning of paper passing is set to K1. In S5, the temperature detection by the second temperature detecting means is started, and the maximum temperature Tmax of the detected temperature T is stored and updated. Steps S6 to S8 are the same as the sheet number switching control. If the current paper feed interval stage K is not K4 in S9, the process proceeds to S10. In S10, it is determined whether Tmax does not exceed the threshold temperature a = 220 ° C. (see Table 2). If Tmax> 220 ° C., the paper feed interval is extended in S11 (K = K + 1). If Tmax> 220 ° C., the paper feed interval is not changed (S12). In S9, if K = K4, K4 is the stage of the latest paper feeding interval, so that the paper feeding interval is not extended. In S13, Tmax is temporarily erased, and the maximum temperature Tmax of the sequentially detected temperature T is stored and updated again. Thereafter, paper is fed again according to the paper feed interval determined in S11 and S12 (S13 → S6). In S8, if the number Q of sheets passed reaches the number R of sheets to be printed, after the last sheet is discharged from the image forming apparatus, all the printing controls are ended (S14).
[Patent Document 1]
JP-A-63-313182
[Patent Document 2]
JP-A-2-15778
[Patent Document 3]
JP-A-4-44075
[Patent Document 4]
JP-A-4-204980
[Patent Document 5]
JP-A-5-80604
[0028]
[Problems to be solved by the invention]
Higher throughput is a strong demand of users. In the above-described temperature switching control, in order to further increase the throughput, the feeding interval is shortened so as to determine the extension of the feeding interval of the succeeding paper before the trailing edge of the preceding paper is discharged from the fixing nip. In such a case, the following problems occur.
[0029]
In FIG. 5, the initial paper feed interval K1 is set short enough to feed the succeeding paper before the trailing edge of the preceding paper is discharged from the fixing nip, and the conventional temperature switching control is used (FIG. 15). , P2, P3, P4, P5,..., When the recording material is continuously fed, and the temperature of the non-sheet passing portion of each recording material is This shows the maximum timing. The horizontal axis shows the passage of time.
[0030]
Regarding the timing for determining the extension of the paper feed interval, here, it is assumed that the paper feed interval can be extended until immediately before the paper feed (△ in the figure).
[0031]
The timing at which the temperature of the non-sheet passing portion becomes the highest in one recording material is when the rear end of the recording material is discharged from the fixing nip (in the figure). This is because while the recording material is passing through the fixing nip, the heat amount of the paper passing portion continues to be robbed by the recording material, whereas the non-paper passing portion is continuously supplied with the heat amount from the heating element.
[0032]
Therefore, as shown in the figure, after the recording material P3 is fed, there is a possibility that the detected temperature T of the recording material P2 exceeds the threshold temperature a. At this time, since the feeding interval of the recording material P3 is not extended, the detected temperature T of the recording material P3 also becomes equal to or higher than the threshold temperature a (T> a). As a result, the paper feed interval is extended twice consecutively for the recording materials P4 and P5, and the throughput is reduced more than necessary.
[0033]
In this example, the determination of the extension of the paper feed interval is “the paper feed interval can be extended until immediately before the paper feed”. In some cases, "when the conveyance is detected". This is, for example, a control in which, using the photo interrupter described in the sheet number switching control, it is confirmed that normal paper feeding and conveyance have been performed, and then the subsequent paper is fed. In the latter control, the determination of the paper feed interval extension is earlier than in the former control. Therefore, the feeding interval is continuously extended twice.
[0034]
The present invention proposes an image forming apparatus capable of overcoming the above problems and achieving high-speed small-size paper throughput.
[0035]
[Means for Solving the Problems]
The present invention
A heating member arranged with the direction perpendicular to the conveying direction of the recording material as a longitudinal direction, a film that moves in contact with the heating member, and a pressure member that forms a nip by pressing the heating member through the film. A recording material carrying an unfixed toner image is nipped and conveyed between the film and the pressure member of the nip, so that the recording material is heated by the heat of the heating element via the film to form a toner image. Fixing means for fixing the image on the recording material;
A first temperature detection unit that is disposed at a position that becomes a paper passing area in all recording materials that can be passed and detects the temperature of the heating body,
A second temperature detecting means arranged at a position that becomes a non-sheet passing area when a recording material having a small sheet width is passed,
Means for counting the number of sheets of recording material passed;
Energization control means for controlling the energization of the heating element by the temperature detected by the first temperature detection means,
Control means for setting a threshold temperature for the temperature T detected by the second temperature detection means, and extending a paper feed interval when the detected temperature T exceeds the threshold temperature;
An image forming apparatus having
An image forming apparatus having a control mode in which a predetermined number of sheets α is provided, and a sheet feeding interval is not extended while the predetermined number of sheets α is passed.
[0036]
That is, when the detected temperature of the non-sheet passing portion detected by the second temperature detecting means becomes equal to or higher than the threshold temperature, the short interval of the small-size sequence for extending the paper feed interval (so-called temperature switching control) is short. This is to optimize the paper feed interval switching at the throughput stage.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
(1) Example of image forming apparatus
FIG. 1 is a schematic configuration model diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus of this embodiment is a copying machine or a laser printer using a transfer type electrophotographic process.
[0038]
Reference numeral 101 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which is driven to rotate at a predetermined control peripheral speed in a clockwise direction indicated by an arrow.
[0039]
Reference numeral 102 denotes a charging roller as charging means, which uniformly charges the outer peripheral surface of the rotating photosensitive drum 101 to a predetermined polarity and potential.
[0040]
Reference numeral 103 denotes an image exposure device such as a document image slit exposure mechanism or a laser scanner, which performs image exposure L on the uniformly charged surface of the rotating photosensitive drum 101. As a result, an electrostatic latent image corresponding to the exposure pattern is formed on the surface of the photosensitive drum.
[0041]
A developing device 104 develops the electrostatic latent image on the photosensitive drum surface as a toner image.
[0042]
Reference numeral 105 denotes a transfer roller as a transfer unit, which contacts the photosensitive drum 101 with a predetermined pressing force to form a transfer nip T. The recording material P is fed to the transfer nip T from the paper feed mechanism at a predetermined control timing, and is nipped and conveyed by the transfer nip T. A predetermined transfer bias is applied to the transfer roller 105 at a predetermined control timing. As a result, the toner image on the photosensitive drum 101 side is sequentially electrostatically transferred onto the surface of the recording material P which is nipped and conveyed by the transfer nip T.
[0043]
The recording material P that has left the transfer nip T is separated from the surface of the photosensitive drum 101 and introduced into the fixing device 111. The fixing device 111 heats and fixes the introduced unfixed toner image on the recording material P as a permanent fixed image, and discharges and conveys the recording material P.
[0044]
Reference numeral 106 denotes a photosensitive drum cleaning device that removes transfer residual toner on the photosensitive drum after the recording material is separated. The surface of the photosensitive drum whose surface has been cleaned by removing the transfer residual toner is repeatedly subjected to image formation.
[0045]
Reference numeral 107 denotes a paper feed cassette mounted on the paper feed mechanism unit, in which recording materials P are stacked and stored. The recording material P in the paper feed cassette 107 is separated and fed one by one by a paper feed roller 108 which is driven to rotate based on a paper feed start signal, and a registration roller pair 110 synchronizes with the image formation on the photosensitive drum. The sheet is then fed to the transfer nip T at a predetermined control timing.
[0046]
Reference numeral 109 denotes a sheet passing number counting means, which is disposed on the recording material transport path downstream of the sheet cassette 107 in the recording material transport direction and upstream of the registration roller pair 110 in the recording material transport direction. In this embodiment, a photo interrupter is used as the sheet passing number counting means.
[0047]
The photo interrupter includes a transmitting unit, a receiving unit, and a rod-shaped swinging member. The transmitting unit and the receiving unit face each other, and the transmitting unit receives a voltage from the control circuit and transmits an optical signal from the transmitting unit to the receiving unit. One end of the rocking member can move back and forth between the transmitting unit and the receiving unit. The other end of the oscillating portion protrudes into the recording material conveyance path, and oscillates the entire oscillating member by coming into contact with the passing recording material. The movement of the rocking unit blocks or does not block the optical signal transmitted from the transmitting unit to the receiving unit, thereby detecting the passage of the recording material. The detected passage of the recording material is transmitted to the control unit by an electric signal, and the control unit counts the number of passed sheets.
[0048]
Reference numeral 112 denotes a control circuit (control board) as control means, which controls all image forming process devices of the image forming apparatus and controls image forming sequence control.
[0049]
(2) Fixing device 111
FIG. 2 is an enlarged model diagram of the fixing device 111. The fixing device 111 of this example is a film heating type heating device of a pressure roller drive type using a cylindrical fixing film.
[0050]
Reference numeral 1 denotes a ceramic heater as a heating element, which is a horizontally long, thin, low-heat-capacity member having a longitudinal direction perpendicular to the drawing. Reference numeral 3 denotes a gutter-shaped film guide having a substantially semicircular cross section. The heater 1 is fitted and held in a heater fitting groove formed at the center of the lower surface of the film guide 3 along the length of the member. Reference numeral 2 denotes a cylindrical fixing film, which is loosely fitted to the film guide 3 holding the heater 1 as described above. Reference numeral 4 denotes an elastic pressure roller as a pressure member.
[0051]
The elastic pressure roller 4 includes a core metal 4a made of iron, stainless steel, or aluminum, and a silicon rubber layer 4b having excellent elasticity, heat insulation, and heat resistance. Both ends of the cored bar 4a are rotatably supported by bearings between side plates of the fixing device via bearings. A gear is fitted on one end of the cored bar 4a, and the pressure roller 4 is driven to rotate in a counterclockwise direction by an arrow by a drive motor M. Then, an assembly of the heater 1, the film guide 3, and the cylindrical fixing film 2 is arranged above the pressure roller 4 in parallel with the pressure roller 4 with the heater 1 side facing downward. By pressing the pressure roller 4 against the elasticity of the pressure roller 4 with an urging member (not shown), the heater 1 and the pressure roller 4 are pressed against each other with the fixing film 2 interposed therebetween. A pressure contact nip (fixing nip) N having a predetermined width is formed by elastic strain of the silicon rubber layer 4b of the pressure roller 4.
[0052]
The fixing film 2 receives a rotational torque by a frictional force in the fixing nip N by the rotation of the pressure roller 4, and the inner surface of the fixing nip N slides in close contact with the surface of the heater 1 at a predetermined peripheral speed while sliding. Becomes the driven rotation state. A lubricant such as heat-resistant grease may be interposed between the film 2 and the heater 1 in order to reduce the sliding resistance.
[0053]
Then, the power supply to the heater 1 is started, the rotation of the pressure roller 4 is driven, and the cylindrical fixing film is rotated in accordance with the rotation, and the heater 1 rises to a predetermined temperature to be in a temperature-controlled state. In a state where the rotation of the roller 4 and the fixing film 2 is stabilized, the recording material P carrying the unfixed toner image t is introduced between the fixing film 2 of the fixing nip N and the pressure roller 4 and nipped and conveyed. Then, the recording material P passes through the fixing nip in a state where the unfixed toner image carrying surface is in close contact with the outer surface of the fixing film 2 and overlaps with the fixing film 2.
[0054]
During the passage of the recording material P through the fixing nip, the recording material P is heated by receiving the heat of the heater 1 via the fixing film 2, and the unfixed toner image t is heated and pressed on the surface of the recording material P. The recording material P is discharged and conveyed at the recording material outlet of the fixing nip N with a curvature separated from the outer surface of the fixing film 2.
[0055]
The fixing film 2 is desirably excellent in heat resistance, durability, low heat capacity, and releasability in order to prevent image deterioration such as thermal deterioration and friction, power saving, quick start property, and offset. For example, a substrate film such as PI (polyimide) coated with a heat-resistant resin having releasability such as PFA or PTFE is often used.
[0056]
In this example, the fixing film 2 is a cylindrical polyimide film having a length of 226 mm, an inner diameter of 24 mm, and a thickness of 55 μm, and the outer surface thereof is coated with 10 μm of PTFE.
[0057]
It is desirable that the film guide 3 has excellent heat resistance, insulation properties, and rigidity. For example, a material obtained by molding a material such as PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), and PEEK (polyether ether ketone) is often used.
[0058]
The pressure roller 4 has a 5 mm-thick silicon rubber layer 4b provided on an aluminum core 4a having an outer diameter of 8mm.
[0059]
The heater 1 is desirably excellent in heat resistance, high thermal conductivity, and low heat capacity in order to prevent breakage due to thermal stress, suppress the temperature rise in the non-sheet passing portion, save power, and perform quick start. Generally, a heater used in a film heating type fixing device has a laminated structure having a heating element, a conductive pattern, and a glass layer on a heater substrate. The heater substrate is preferably made of a material having excellent heat resistance, low heat capacity, thermal conductivity, and electrical insulation. A ceramic such as aluminum nitride or alumina is often used. The heating element is, for example, silver palladium (Ag / Pb), Ta ₂ An electric resistance material paste such as N is formed on the heater substrate by screen printing and baking. The electrode portion and the conductive portion as the conductive pattern are formed by screen printing and firing a good conductive material such as a silver paste on the substrate. The electrode section, the conductive section, and the heating element constitute an electric circuit, and the heater 1 is controlled to a target temperature by controlling the energization of the electric circuit by the control means. The heater 1 is disposed with a direction perpendicular to the recording material conveyance direction as a longitudinal direction.
[0060]
FIG. 3 is a structural model diagram of the heater 1 used in this example. This heater 1
▲ 1 ▼. An aluminum nitride substrate having a width of 7 mm, a length of 235 mm, and a thickness of 1.0 mm as a heater substrate 1a;
▲ 2 ▼. An electric resistance material paste such as silver palladium (Ag / Pd) is screen-printed on the surface side of the heater substrate along the substrate length to form a resistance value of 11Ω. 1b,
(3). A conductive pattern 1c in which one end side of the two parallel reciprocating heating elements 1b is electrically connected in series;
▲ 4 ▼. A power supply electrode pattern 1d electrically connected to the other end of each heating element 1b;
▲ 5 ▼. An insulating protective sliding layer 1e such as a thin glass coat layer provided on the front side of the heater substrate so as to cover the heating element 1b and the conductive pattern 1c;
Etc.
[0061]
Further, on the back side of the heater substrate 1a, first and second two temperature detecting means 5a and 5b for monitoring the heater temperature are provided.
[0062]
The heater 1 is fitted into the heater fitting groove formed in the center of the lower surface of the film guide 2 along the longitudinal direction of the member, with the heater surface exposed to the outside, and held.
[0063]
In the present example, the paper passing is the center reference conveyance, and the first temperature detecting unit 5a is arranged in the paper passing area in the recording materials of all the sizes that can be passed. The first temperature detecting element 5a monitors the temperature of the sheet passing area, transmits the detected temperature to the control circuit 112, and feeds it back to the control of energization of the heater 1 so that good fixing performance is always obtained. The second temperature detecting element 5b is arranged at a location that is a small size non-sheet passing area. The first temperature detecting means 5a and the second temperature detecting means 5b are arranged at positions of 15 mm and 97 mm, respectively, on the opposite side of the power supply electrode pattern 1d from the center of the heater in the longitudinal direction of the heater. In this embodiment, an external contact type thermistor is used for both the temperature detecting means 5a and 5b. The two temperature detecting means 5a and 5b were pressed against the heater 1 by springs at a pressure of about 1N.
[0064]
As the temperature detecting means 5a and 5b, for example, a thermistor having a temperature detecting element 51 whose resistance value changes with temperature can be used. As a method of temperature detection, for example, a temperature detection element and a resistor having a known resistance value are incorporated in an electric circuit linked to the control means, and a weak constant voltage is applied to this electric circuit, and the resistance value is known. By measuring the partial pressure of the resistor, the detected temperature of the temperature detecting element can be known.
[0065]
Thermistors mainly include a heater integrated type and an external contact type, both of which are widely used. FIG. 4A is a schematic diagram of a heater-integrated thermistor, and FIG. 4B is a schematic diagram of an external contact type thermistor.
[0066]
The heater-integrated thermistor has a heater 1 on which a temperature detecting element 51, an electrode section 52 made of silver paste or the like, and a conductive section 53 are mounted. The temperature detecting element is bonded to the conductive portion 53 and the heater 1 by solder 54 or the like. A voltage is externally applied to the temperature detecting element 51 via the electrode section 52 and the conductive section 53.
[0067]
The external contact type thermistor is a thermistor unit independent of the heater, and includes a temperature detecting element 51, an electric circuit 55 such as a dumet wire, a ceramic paper 56 having heat insulating, insulating and elastic properties, and a support 57 made of a heat-resistant resin. , An insulating film 58 such as a Kapton sheet, and an adhesive 59 such as a gasket.
[0068]
In the present embodiment, the first and second temperature detecting means 5a and 5b both use an external contact thermistor. However, if the set value for switching the paper feed interval described later is optimized, a heater integrated type may be used.
[0069]
Heater temperature detection information of the first and second temperature detection means 5a and 5b is input to the control circuit 112. The control circuit 112 controls the power supply circuit composed of the AC power supply 113 and the triac 114 based on the detection information of the first temperature detecting means 5a, and the heater temperature detected by the first temperature detecting means 5a is set to a predetermined target temperature. The power supply power to the heating element 1b is controlled so as to be maintained at (fixing temperature), and the temperature of the heater is adjusted.
[0070]
The control circuit 112 performs the feed interval switching control described in (3) below based on the detection information of the second temperature detection means 5b.
[0071]
The control circuit 112 counts the number of passed sheets based on the recording material passage detection signal of the passed sheet number counting means 109.
[0072]
In addition to the above, the control circuit 112 controls all the image forming process devices of the image forming apparatus and controls the image forming sequence.
[0073]
(3) Feeding interval switching control
1) Example 1
Table 3 shows each set value of the paper feed interval switching control in the first embodiment.
[0074]
[Table 3]

[0075]
In this example, four stages K of paper feed intervals are provided, and a threshold temperature a = 210 ° C. is provided with respect to the maximum temperature Tmax of the detected temperature T of the second temperature detecting means 5b, and Tmax> a = 210 ° C. If it does, the paper feed interval stage K is set to extend from K1 to K2 to K3 to K4.
[0076]
The feature of the present embodiment is that a predetermined number of sheets α is set, and the sheet feeding interval is not extended for α sheets after the threshold temperature a is exceeded even if Tmax> 210 ° C. .
[0077]
In order to satisfy this, in the present embodiment, the number of sheets θ continuously passed at the same sheet feeding interval is counted, and the predetermined number α is provided with respect to the number of sheets θ, and the sheet feeding interval at the initial sheet feeding time is set. In step K1, the predetermined number α = 0.
[0078]
With respect to the setting of the predetermined number α, continuous paper passing is performed as shown in FIG. 5 by using a conventional temperature switching unit, using a COM10 envelope that generates a rapid temperature rise in a non-paper passing section, and Counting from the next recording material exceeding the threshold temperature a, the number of recording materials satisfying T> a was set.
[0079]
Assuming that the paper exceeding a for the first time is P2, P3 always becomes T> a, and in P4, the paper feed interval is extended, so that the temperature starts to become lower than the P3 sheet, and in P5, the temperature always becomes lower than a.
[0080]
Accordingly, it is possible to set the number of sheets α = 2 (corresponding to P3 and P4) in which the sheet feeding interval is not switched even when the temperature exceeds the threshold temperature a. The threshold temperature a is set so that the temperature of the pressure roller does not reach the thermal deterioration temperature even in the P3 sheet where the non-sheet passing portion has the highest temperature, and image failure due to the temperature rise of the non-sheet passing portion does not occur. Set to.
[0081]
FIG. 6 shows a flowchart of the paper feed interval switching control according to the first embodiment. At S1, the printing operation of the small size paper is started. In S2, the planned number of prints R is stored. In S3, the number of sheets θ at the same sheet feeding interval as the number of sheets Q is cleared (Q = 0, θ = 0). In step S4, the stage K of the paper feeding interval at the initial stage of paper passing is set to K1, and in S5, the temperature detection by the second temperature detecting means 5b is started. Here, the maximum value of the sequentially detected temperature T is continuously stored and updated as Tmax.
[0082]
In S7, the number of sheets Q and the number of sheets θ at the same number of sheets are counted by the photo interrupter (Q = Q + 1, θ = θ + 1). If the number Q of sheets passed has not reached the number R of sheets to be printed in S8, the process proceeds to S9. If the current paper feed interval stage K is not K4 in S9, it is determined in S10 whether θ ≦ α.
[0083]
Here, from Table 3, α = 2. If θ ≦ α, the stage of the paper feed interval is not changed. If θ ≦ α, it is determined in step S11 whether Tmax does not exceed the threshold temperature a = 220 ° C. (see Table 3). If Tmax> 220 ° C., the paper feed interval is extended in step S12 (K = K + 1), and the number of sheets passed at the same paper feed interval θ is cleared (θ = 0). If Tmax> a, the paper feed interval is not changed (S13).
[0084]
If K = K4 in S9, K4 is the final paper feed interval stage, so the paper feed interval is not extended. After the paper feed interval is determined in S12 and S13, Tmax is cleared once in S14, and the maximum value Tmax of the sequentially detected temperature T is stored and updated again. Paper feeding is performed again according to the paper feeding interval determined in S12 and S13 (S14 → S6). In S8, if the number Q of sheets passed reaches the number R of sheets to be printed, after the last sheet is discharged from the image forming apparatus, all the printing controls are ended (S15).
[0085]
FIG. 7 shows Effect 1 of the embodiment when the throughput at the initial stage of continuous paper feeding is increased. The upper diagram shows the change in throughput when continuous paper is passed, and the lower diagram shows the maximum temperature of the non-sheet passing portion of the pressure roller for each recording material at that time. The solid line shows the state when the paper feed interval switching control of this embodiment is used, and the broken line shows the state when the conventional temperature switching control is used. In the conventional temperature switching control, the paper feed interval is extended twice consecutively. In the feed interval switching control according to the first embodiment, the feed interval is not continuously extended, and the temperature of the pressure roller also changes at a stable temperature equal to or lower than the thermal deterioration temperature. That is, according to the control of the first embodiment, the throughput can be increased while suppressing the thermal deterioration of the pressure roller. Further, there was no occurrence of an image defect due to an increase in the temperature of the non-sheet passing portion. That is, the problem was solved.
[0086]
In the present embodiment, the same value α = 2 sheets is set as the predetermined number α for the sheet feeding intervals K = K2 and K3, but different values are set for the respective sheet feeding intervals. You may.
2) Example 2
In the first embodiment, the control is such that the predetermined number of sheets α after the extension of the sheet feeding interval is not switched regardless of the threshold temperature a. However, in the unlikely event that an unknown recording material whose temperature rises more rapidly than the COM10 envelope is passed or that the recording material is multi-fed, the number of sheets corresponding to the above α is considered. However, it is preferable that the control is such that the paper feed interval can be extended. Therefore, in the present embodiment, a threshold temperature b (b> a) different from α of the first embodiment and the above threshold temperature a is provided, and the detected temperature T becomes the threshold during the passage of the predetermined number α of sheets. When the temperature exceeds b, the paper feed interval is extended.
[0087]
Table 4 shows each set value of the paper feed interval switching control according to the second embodiment.
[0088]
[Table 4]

[0089]
The predetermined number α and the threshold temperature a were set in the same manner as in Example 1. In FIG. 5, the threshold temperature b is a temperature at which the detection temperature T of the P2 sheet becomes b> T even when the COM 10 is continuously passed, and is lower than the detection temperature when the pressure roller reaches the thermal deterioration temperature. The temperature is set to a temperature that does not cause an image defect due to a rise in the temperature of the non-sheet passing portion.
[0090]
FIG. 8 shows a flowchart of the paper feed interval switching control according to the second embodiment. Except for S14 in FIG. 8, the configuration is the same as that of the first embodiment. If θ ≦ α is not satisfied in S10, the maximum value Tmax of the detected temperature of the second detecting means is compared with a threshold temperature b (b> a) in S14. If Tmax> b, the paper feed interval is extended in S12. If Tmax> b is not satisfied, the process proceeds to S13, and the sheet feeding interval is not extended.
[0091]
With this control, the same effect as in the first embodiment can be obtained, and when an unknown paper type whose temperature rises extremely rapidly in a non-paper-passing portion is passed, or when a recording material is fed multiple times. In some cases, for example, the paper feed interval can be extended two steps in a row to suppress thermal deterioration of the pressure roller and image defects due to a rise in the temperature of the non-paper passing portion.
[0092]
In the present embodiment, the same value α = 2 sheets is set as the predetermined number α for the sheet feeding intervals K = K2 and K3, but different values are set for the respective sheet feeding intervals. Is also good.
3) Example 3
In the first and second embodiments, the paper feed interval is controlled to be extended stepwise. However, if the temperature of the non-sheet passing portion is sufficiently relaxed, a control for shortening the paper feed interval again has been proposed ( For example, it is disclosed in JP-A-2002-169413.
[0093]
Even in such a control, if the paper feed interval is shortened in order to increase the throughput, there is a possibility that the paper feed interval is switched twice consecutively, as described in the section of the subject. In this case, the paper feed interval is shortened twice consecutively.
[0094]
Therefore, in the present embodiment, for the β sheets immediately after the shortening of the sheet feeding interval, the sheet feeding interval is not shortened even if the detected temperature T falls below the threshold temperature c. There are features.
[0095]
Table 5 shows each set value of the paper feed interval switching control of the third embodiment.
[0096]
[Table 5]

[0097]
In order to satisfy this, in the present embodiment, the number of sheets θ continuously passed at the same sheet feeding interval is counted, and the predetermined number β is provided for the number of sheets θ, and the sheet feeding interval in the initial sheet feeding period is set. In step K1, the predetermined number β = 0.
[0098]
FIG. 9 shows a flow chart of the paper feed interval switching control according to the third embodiment. S1 to S9 are the same as in the first embodiment. In S10, when the number θ of sheets passed at the same sheet feeding interval is larger than the predetermined number, in S11, the maximum detected temperature Tmax and the threshold temperature c are compared. If Tmax <c, the paper feed interval is reduced in S12. If Tmax <c, the paper feed interval is not shortened (S13). If θ ≦ β is not satisfied in S10, the paper feed interval is not shortened (S13).
[0099]
The following control is the same as in the first embodiment.
[0100]
In the present embodiment, the same value β = 2 sheets is set as the predetermined number β for the sheet feeding intervals K = K2 and K3, but different values may be set for the respective sheet feeding intervals. good.
[0101]
4) Example 4
In the third embodiment, the predetermined number of sheets β after the shortening of the sheet feeding interval is not switched regardless of the threshold temperature c. May be set such that a different threshold temperature d (d <c) is set, and if the temperature falls below the threshold temperature d, the paper feed interval is reduced twice consecutively.
[0102]
Table 6 shows each set value of the paper feed interval switching control according to the fourth embodiment. The predetermined number β and the threshold temperature c were set in the same manner as in Example 1.
[0103]
[Table 6]

[0104]
The threshold temperature d is d <c, so that the temperature of the pressure roller does not reach the heat deterioration temperature even if the paper feed interval is shortened twice consecutively, or the image is formed by raising the temperature of the non-paper passing portion. Make settings so that no defects occur.
[0105]
FIG. 10 shows a flowchart of the paper feed interval switching control according to the fourth embodiment. Except for S14 in FIG. 10, the configuration is the same as that of the third embodiment. If it is not determined in S10 that θ ≦ β, in S14, the maximum value Tmax of the detected temperature of the second detecting means is compared with a threshold temperature d (d <c). If Tmax <d, the paper feed interval is extended in S12. If Tmax <d, the process proceeds to S13, and the sheet feeding interval is not extended.
[0106]
In the present embodiment, the same value β = 2 sheets is set as the predetermined number β for the sheet feeding intervals K = K2 and K3, but different values are set for the respective sheet feeding intervals. Is also good.
[0107]
5) Example 5
The first and second embodiments propose a control for overcoming the problem with respect to the control for extending the paper feed interval, and the third and fourth embodiments propose a control for overcoming the problem with respect to the control for shortening the paper feed interval. May have any of the controls of the third and fourth embodiments.
[0108]
The effect of such control is shown in FIG. Here, after the COM10 envelope was continuously passed and the paper feeding interval was extended, the EXE-size recording material having a relatively non-paper rising temperature was continuously passed (point ↑ in the figure). The upper diagram shows the change in throughput when continuous paper is passed, and the lower diagram shows the maximum temperature of the non-sheet passing portion of the pressure roller for each recording material at that time. The solid line shows the state when the paper feed interval switching control of this embodiment is used, and the broken line shows the state when the conventional temperature switching control is used. By passing the EXE-size recording material in the middle, the temperature of the pressure roller non-sheet passing portion starts to decrease. After the temperature of the pressure roller has been sufficiently reduced, control for shortening the paper feed interval is performed. In the conventional example, the paper feed interval is shortened twice consecutively, and a rapid temperature rise occurs, sometimes exceeding the thermal deterioration temperature of the pressure roller.
[0109]
On the other hand, in the present embodiment, continuous paper feeding could be performed without changing the paper feeding interval continuously and with the temperature of the pressure roller non-paper passing portion being stable. As described above, according to the present embodiment, the throughput can be increased without the temperature of the non-sheet passing portion of the pressure roller reaching the thermal deterioration temperature.
[0110]
6) Example 6
When the detected temperature T of the second temperature detecting means 5b detects a very high temperature, a control for stopping the heat generation of the heater 1 is practically used. This occurs when the temperature of the non-sheet passing portion rises due to the multi-layer conveyance of the recording material, or when an abnormality occurs in the temperature control of the heater due to an abnormality in the control temperature and the temperature detected by the first temperature detecting means 5a. For example, when the heater temperature reaches a very high temperature, the control is performed to prevent thermal deterioration of the fixing device, breakage of the heater, or occurrence of fire. In such an abnormal situation, it is safer to stop the heat generation of the heater regardless of the threshold temperature and the number of passed sheets. Therefore, in the present embodiment, when a threshold temperature e (e> a, b, c, d) for detecting an abnormal temperature is detected in the image forming apparatus described in the first to fifth embodiments, a predetermined number of sheets α , Β, the heating of the heater is stopped.
[0111]
Table 7 shows each set value of the feed interval switching control of the sixth embodiment.
[0112]
[Table 7]

[0113]
In this control, a threshold temperature e (e> a, b) at which heating of the heater is stopped is set in the control of the second embodiment.
[0114]
FIG. 12 shows a flowchart of the paper feed interval switching control according to the sixth embodiment. Except for S9 in FIG. 12, the configuration is the same as that of the second embodiment. If the maximum value Tmax of the detected temperature is Tmax> c in S9, the heater is turned off in S10 regardless of the predetermined number α, and all controls are stopped (S17).
[0115]
In the present embodiment, a threshold temperature e is provided for the second embodiment. However, for any control of the first to fifth embodiments, the threshold temperature e is set, and when Tmax> c, The same object can be achieved by incorporating a control for turning off the heater regardless of the number of sheets α and β.
[0116]
7) As described in the first to sixth embodiments, as in the first and third embodiments, the predetermined number of sheets α or β is provided, and the predetermined number of sheets α or β after the feeding interval is changed. During the control, the paper feed interval is not switched, so that it is determined that the feed interval of the succeeding paper is switched before the trailing edge of the preceding paper is ejected from the fixing nip. In addition, the control can be performed so that the paper feeding interval is not continuously extended.
[0117]
Alternatively, as in the second embodiment, when the predetermined number of sheets α has a threshold temperature b (b> a) different from the normal threshold temperature a, the recording material in which the temperature rise in the non-sheet passing portion is extremely severe When the temperature rise of the non-sheet passing portion is extremely large, such as when the sheet is passed or when the recording material is double fed, the sheet feeding interval can be extended twice consecutively.
[0118]
Alternatively, as in the third to fifth embodiments, the predetermined number β has a threshold temperature d (d <c) different from the normal threshold temperature c, so that the temperature rise in the non-sheet passing portion is small. Alternatively, in the case where the recording material is slowly passed through the non-sheet-passing portion in the middle of continuous sheet passing, control can be performed without continuously shortening the sheet feeding interval.
[0119]
As a result, it is possible to achieve high-speed throughput while preventing thermal deterioration of a fixing device such as a pressure roller and occurrence of image defects due to non-sheet passing temperature rise.
[0120]
Further, as in the sixth embodiment, by setting the predetermined number of sheets α and β and the threshold temperature e, an abnormally high temperature of the heater is detected, and the power supply to the heater is turned off regardless of the predetermined number of sheets α and β. Further, it is possible to prevent thermal deterioration of the fixing device, breakage of the heater, and occurrence of fire.
[0121]
(4) Other
1) Needless to say, the configuration of the ceramic heater 1 as a heating element is not limited to that shown in the embodiment. Further, the heating element is not limited to the ceramic heater.
[0122]
2) The fixing film 2 is not limited to the cylindrical film of the embodiment, but is formed into an endless belt having a plurality of supporting members. The apparatus can be configured to travel while moving it out.
[0123]
3) The fixing device of the film heating type is not limited to the pressing rotary member driving type of the embodiment, but may be a device configuration in which the film is driven and the pressing rotary member is driven to rotate.
[0124]
Although various examples and embodiments of the present invention have been shown and described, those skilled in the art will appreciate that the spirit and scope of the present invention is not limited to the specific description and figures herein. It will be appreciated that various modifications and changes are set forth which are all set forth in the following claims.
[0125]
4) In the present invention, the fixing means includes a hypothetical fixing device for presumably applying an unfixed image to the recording material, and an image for improving the image surface properties such as gloss by reheating the recording material carrying the fixed image. It shall include a heating device. The device configuration and control of the present invention can be effectively applied to these devices.
[0126]
Examples of embodiments of the present invention are listed below.
[0127]
[Embodiment 1] A nip is formed by pressing a heating element disposed in a direction perpendicular to the conveying direction of a recording material, a film moving in contact with the heating element, and a heating element via the film. Pressurizing member, the recording medium carrying an unfixed toner image being introduced between the film and the pressurizing member of the nip, and nipped and conveyed. Fixing means for fixing the toner image on the recording material by heating with heat of
A first temperature detection unit that is disposed at a position that becomes a paper passing area in all recording materials that can be passed and detects the temperature of the heating body,
A second temperature detecting means arranged at a position that becomes a non-sheet passing area when a recording material having a small sheet width is passed,
Means for counting the number of sheets of recording material passed;
Energization control means for controlling the energization of the heating element by the temperature detected by the first temperature detection means,
Control means for setting a threshold temperature for the temperature T detected by the second temperature detection means, and extending a paper feed interval when the detected temperature T exceeds the threshold temperature;
An image forming apparatus having
An image forming apparatus having a control mode, wherein a predetermined number of sheets α are provided, and a sheet feeding interval is not extended during the passage of the predetermined number of sheets α.
[0128]
[Embodiment 2] In the image forming apparatus according to Embodiment 1, the threshold temperature with respect to the detected temperature T is a, and the predetermined number α is the next recording material whose detected temperature T has exceeded the threshold temperature a. An image forming apparatus having a control mode, wherein the number of sheets is counted from the number of sheets.
[0129]
[Embodiment 3] A heating body arranged with a direction perpendicular to the conveying direction of a recording material as a length, a film moving in contact with the heating body, and a nip formed by pressing the heating body through the film. Pressurizing member, the recording medium carrying an unfixed toner image being introduced between the film and the pressurizing member of the nip, and nipped and conveyed. Fixing means for fixing the toner image on the recording material by heating with heat of
Means for counting the number of sheets of recording material passed;
Energization control means for controlling the energization of the heating element by the temperature detected by the first temperature detection means,
Control means for providing a threshold temperature for the temperature T detected by the second temperature detection means, and extending a paper feed interval when the detected temperature exceeds the threshold temperature;
An image forming apparatus having
The threshold temperature is always one, the normal threshold temperature is a, and a predetermined number α is provided. During the passing of the predetermined number α, a temperature b (b> a) different from the above a An image forming apparatus having a control mode, wherein
[0130]
[Embodiment 4] In the image forming apparatus according to Embodiment 3, the predetermined number α is the number of sheets passed from the next recording material whose detected temperature T exceeds the threshold temperature (a or b). An image forming apparatus having a control mode.
[0131]
[Embodiment 5] A heating element disposed with a direction perpendicular to the recording material conveyance direction as a longitudinal direction, a film moving in contact with the heating element, and a nip formed by pressing the heating element through the film Pressurizing member, the recording medium carrying an unfixed toner image being introduced between the film and the pressurizing member of the nip, and nipped and conveyed. Fixing means for fixing the toner image on the recording material by heating with heat of
Means for counting the number of sheets of recording material passed;
Energization control means for controlling the energization of the heating element by the temperature detected by the first temperature detection means,
Control means for setting a threshold temperature for the temperature T detected by the second temperature detection means, and for shortening a paper feed interval when the detected temperature T falls below the threshold temperature;
An image forming apparatus having
An image forming apparatus having a control mode, wherein a predetermined number of sheets β is provided, and a sheet feeding interval is not shortened while the predetermined number of sheets β is passed.
[0132]
[Sixth Embodiment] In the image forming apparatus according to the fifth embodiment, wherein the threshold temperature with respect to the detected temperature T is c, the predetermined number β is the next recording when the detected temperature T is lower than the threshold temperature c. An image forming apparatus having a control mode, characterized in that the number of sheets passed is counted from a material.
[0133]
[Embodiment 7] A heating element arranged with the direction perpendicular to the conveying direction of the recording material as a length, a film moving in contact with the heating element, and a nip formed by pressing the heating element through the film Pressurizing member, the recording medium carrying an unfixed toner image being introduced between the film and the pressurizing member of the nip, and nipped and conveyed. Fixing means for fixing the toner image on the recording material by heating with heat of
Means for counting the number of sheets of recording material passed;
Energization control means for controlling the energization of the heating element by the temperature detected by the first temperature detection means,
Control means for setting a threshold temperature for the temperature T detected by the second temperature detection means, and for shortening the sheet feeding interval when the detected temperature T falls below the threshold temperature;
An image forming apparatus having
The threshold temperature is always one, the normal threshold temperature is c, and a predetermined number β is provided. During the passing of the predetermined number β, a temperature d (d <c) different from the above c is used. An image forming apparatus having a control mode, wherein
[0134]
[Eighth Embodiment] In the image forming apparatus according to the seventh embodiment, the predetermined number β is the number of passed sheets counted from the next recording material whose detected temperature T is lower than a threshold temperature (c or d). An image forming apparatus having a control mode.
[0135]
[Embodiment 9] An image forming apparatus having any one of the control modes described in Embodiments 2 and 4 and any one of the control modes described in Embodiments 6 and 8.
[0136]
[Embodiment 10] The image forming apparatus according to any one of Embodiments 1 to 9, wherein the film of the fixing unit is a rotating body.
[0137]
【The invention's effect】
As described above, according to the present invention, when the detected temperature of the non-sheet passing portion by the second temperature detecting means becomes equal to or higher than the threshold temperature, the small-size sequence (the so-called temperature Switching control), an image forming apparatus that can overcome the conventional problems and achieve high-speed throughput of small-size paper by optimizing the paper feed interval switching at the throughput stage where the paper interval is short. can do.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment.
FIG. 2 is a schematic diagram of a film heating type fixing device.
FIG. 3 is a structural model diagram of a ceramic heater as a heating element.
FIG. 4 is a schematic diagram of a heater integrated thermistor and an external contact thermistor.
FIG. 5 is a timing chart of a sheet feeding timing, a sheet passing timing in a fixing nip, and a timing at which a non-sheet passing portion has the highest temperature.
FIG. 6 is a flowchart of paper feed interval switching control according to the first embodiment.
FIG. 7 is an explanatory diagram of effect 1 of the embodiment.
FIG. 8 is a flowchart of paper feed interval switching control according to a second embodiment.
FIG. 9 is a flowchart of sheet feed interval switching control according to a third embodiment.
FIG. 10 is a flowchart of sheet feed interval switching control according to a fourth embodiment.
FIG. 11 is an explanatory diagram of effect 2 of the embodiment.
FIG. 12 is a flowchart of paper feed interval switching control according to a sixth embodiment.
FIG. 13 is a diagram showing a state in which the temperature of a non-sheet passing portion is increased in a heating longitudinal direction.
FIG. 14 is a flowchart of a conventional example of the number switching control.
FIG. 15 is a layout diagram of two temperature detecting means.
FIG. 16 is a flowchart of a conventional temperature switching control.
[Explanation of symbols]
1. Heating body, 2. Fixing film, 3. Film guide, 4. Pressure roller, 5 (a, b) .. Temperature detecting means, 51 .. Temperature detecting element, 52 .. Electrode of thermistor Part, 53 .. conducting part of thermistor, 54 .. solder, 55 .. dumet wire, 56 .. ceramic paper, 57 .. support, 58 .. insulating film, 59 .. adhesive, N .. fixing nip .., P... Recording material, P1, P2, P3,..., Continuous recording material, R... Paper feed interval, K1, K2, K3, K4... The set paper feed interval stage, T... The detected temperature of the second temperature detecting means, Tmax... ..Threshold temperature for extending paper feeding interval (b> a), c, d..Threshold temperature for shortening paper feeding interval d> c), a predetermined number of e · · heaters off to threshold temperature, a predetermined number of after extended alpha · · feeding interval, after shortening the beta · · feeding interval

Claims (1)

A heating element disposed with the direction orthogonal to the recording material conveyance direction as a longitudinal direction, a film that moves in contact with the heating element, and a pressure member that forms a nip by pressing the heating element through the film. A recording material carrying an unfixed toner image is introduced between the film and the pressure member of the nip, and is nipped and conveyed, so that the toner image is heated by the heat of the heating element via the film. Fixing means for fixing the image on the recording material;
A first temperature detection unit that is disposed at a position that becomes a paper passing area in all recording materials that can be passed and detects the temperature of the heating body,
A second temperature detecting means arranged at a position that becomes a non-sheet passing area when a recording material having a small sheet width is passed,
Means for counting the number of sheets of recording material passed;
Energization control means for controlling the energization of the heating element by the temperature detected by the first temperature detection means,
Control means for setting a threshold temperature for the temperature T detected by the second temperature detection means, and extending a paper feed interval when the detected temperature T exceeds the threshold temperature;
An image forming apparatus having
An image forming apparatus having a control mode, wherein a predetermined number of sheets α are provided, and a sheet feeding interval is not extended during the passage of the predetermined number of sheets α.

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