JP4553554B2 - Image forming apparatus - Google Patents

Description

【００７０】
表１に示すように、環境条件が、常温常湿（ＮＮ）（温度２５℃，湿度５０％）の場合、転写電圧を２ＫＶ又は３ＫＶに設定すると、「剥ぎ取り易さ」、「搬送性」及び「周辺部の汚れ」について良好な結果が得られた。その他の設定（０ＫＶ及び0 ．5 ＫＶ）では、「剥ぎ取り易さ」、「搬送性」に問題があった。
【００７１】
一方、低温低湿（ＬＬ）（温度５℃，湿度３０％）の場合には、転写電圧対応の吸着力が大となるため、常温常湿（ＮＮ）の場合よりも転写電圧を下げるのが好ましく、0 ．5 ＫＶに設定すれば、「剥ぎ取り易さ」、「搬送性」、「周辺部の汚れ」について良好な結果が得られた。その他の設定（２ＫＶ、３ＫＶ）では、「剥ぎ取り易さ」に問題があり、０ＫＶでは、「剥ぎ取り易さ」及び「搬送性」に問題があった。
【００７２】
以上の結果から、常温常湿の場合には、転写電圧を２ＫＶに、低温低湿の場合には、0 ．5 ＫＶに設定するのが好ましい。表記のＬ及びＬ′については、図４に示すように、Ｌは、最下流の転写ベルト駆動ローラ７１とヒートローラ３１の間の距離、Ｌ′は、転写ベルト駆動ローラ７１からシートの先端までの距離、をそれぞれを示す。
【００７３】
なお、画像形成時の転写バイアスは、画質調整により良好な画像形成ができるように調整されるが、ジャム発生時に環境条件に応じて予め設定された電圧に一致する場合は画像形成時の転写バイアスを継続すればよいが、異なる場合は予め設定された電圧に切換えられる。また、転写担持体が停止している場合は転写バイアスをＯＦＦにしている。
【００７４】
さらに、本実施の形態では、環境条件に応じて、シートに対する転写バイアスの印加範囲をも制御するようにしている。この印加範囲とジャム処理の関係についての実験では、表２に示すように、環境条件を、高温多湿（ＨＨ）、常温常湿（ＮＮ）、低温低湿（ＬＬ）の３つに分けている。
【００７５】
【表２】

【００７６】
高温多湿（ＨＨ）（温度３５℃，湿度８５％）の場合、印加範囲を「シートの全面」に設定すると、「剥ぎ取り易さ」及び「搬送性」について良好な結果が得られたが、「シートの後端側５０ｍｍ」に設定すると「剥ぎ取り易さ」及び「搬送性」について問題があった。
【００７７】
常温常湿（ＮＮ）（温度２５℃，湿度５０％）の場合、印加範囲を「シートの後端側５０ｍｍ」に設定すると「剥ぎ取り易さ」及び「搬送性」について良好な結果が得られたが、「シートの全面」に設定すると「剥ぎ取り易さ」に若干問題があった。
【００７８】
低温低湿（ＬＬ）（温度５℃，湿度３０％）の場合、印加範囲を「シートの後端側５０ｍｍ」に設定すると「剥ぎ取り易さ」及び「搬送性」について良好な結果が得られたが、「シートの全面」に設定すると「剥ぎ取り易さ」に問題があった。
【００７９】
以上の結果から、高温多湿の場合には、転写バイアスの印加範囲を「シートの全面」とし、常温常湿及び低温低湿の場合には、「シートの後端側５０ｍｍ」に設定するのが好ましいが、この範囲に限らず画像形成装置の特性や使用するシート記録材の種類などに応じてより適切な範囲に設定されてよいのは言うまでもない。なお、Ｌ及びＬ′については、図４に示すように、Ｌは、転写ベルト駆動ローラ７１とヒートローラ３１の間の距離、Ｌ′は、転写ベルト駆動ローラ７１からシートの先端までの距離、をそれぞれを示す。
【００８０】
ところで、ジャム処理作業を行う時には、前述したように、定着部１２を画像形成装置本体から引き出すことによって、定着部１２を外部に開放し、その前後両側からジャム処理を行えるが、図１１に示すように、その開放部がジャムの発生した画像形成部に対して側方からのアクセスになるため上流側の感光体ドラム３と転写ベルト７との間にシートが残っている場合には、これを見つけ出すのが困難なことが多い。
【００８１】
特に、サイズの小さなシートは見過ごすことが多い。そこで、ジャム処理時には、このような見つけにくい上流側の位置に停滞しているシートをも確実に見つけ出して容易に取り除くことができるように、上述の実験結果をも勘案して、ジャム処理制御手段により、以下のような転写バイアスの制御を行っている。なお、このジャム処理は、全ての感光体ドラム３を使用する多色モード時のジャム処理の制御について説明している。
【００８２】
すなわち、例えば、図１３のフローチャートに示すように、画像形成動作の開始後、搬送ジャムが発生すると、画像形成に関わるすべての動作（例えば、露光ユニット１による感光体ドラム３への書込み動作、感光体ドラム３の回転動作、帯電器５による帯電動作、現像器２による現像動作、転写ローラ６による転写バイアスの印加動作、シート記録部材の搬送動作、定着部の定着動作等）を緊急停止させる（ｓ１〜ｓ３）と共に、切換手段３８を動作させて、転写ベルト７を感光体ドラム３ａを除く感光体ドラム３ｂ，３ｃ，３ｄから離間させる（ｓ４）。これは、シートを転写ベルト７に吸着させるためにも働く感光体ドラム３ｂ，３ｃ，３ｄからの電荷の供給を断ち、後に行うシートを転写ベルト７から剥ぎ取るときの力をなるべく小さくするためである。
【００８３】
なお、反転現像方式を用いる場合に、上述のステップｓ３にて緊急停止させるすべての動作のうち、感光体ドラム３が回転するときに画像形成に関わらずに必要となる動作として、帯電器５の帯電動作がある。これは、感光体ドラム３が回転した場合に感光体ドラム３が帯電されないと現像材が付着してしまうからである。従って、以下のＳ９（及び図１４のＳ９´）等におけるシート記録材の搬送動作に伴って感光体ドラム３も回転する場合は、回転する感光体ドラムへ３ａに対する帯電器５ａの帯電動作を行うようにしている。
【００８４】
また、ステップｓ４にて、転写ベルト７を感光体ドラム３ａを除く感光体ドラム３ｂ，３ｃ，３ｄから離間させた場合について説明したが、離間させなくとも、転写ローラ６ｂ，６ｃ，６ｄの転写バイアスをＯＦＦするか、適切な値に設定することで、同様な効果を得ることができる。
【００８５】
上述のステップｓ４で、転写ベルト７を感光体ドラム３ａを除く感光体ドラム３ｂ，３ｃ，３ｄから離間させた後、操作部にジャム発生の表示がなされ操作者がジャム処理（復帰作業）を行う（ｓ５）。その復帰作業は、定着部１２を画像形成装置本体から引き出して、その動作により転写搬送ベルトユニット８が再び移動させられ感光体ドラム３ａと転写ベルト７とを、（離接機構により）完全に離間させて行われる。この復帰作業により、例えば、図３に示すように、ヒートローラ３１に巻き付いたシートを取り除くことができる。なお、完全な離間状態は、図５、図６（ｂ）、図７（ｂ）、図８（ｂ）に示されている。
【００８６】
このジャム処理は、例えば定着装置の下流に位置している検出器（例えばシート検出器Ｂ）にシートが到達しない場合で定着部１２でのジャムと判断された場合に行う制御として実施される。このジャム処理が終了した後は、定着部１２を画像形成装置本体に挿入して転写搬送ベルトユニット８を定着部１２を引き出す前の状態に復帰させる。なお、ステップｓ３にて、安全のため、定着部１２のヒータへの通電はＯＦＦされる。
【００８７】
次に、ステップｓ６で先のジャム発生時にシート検出器Ａの状態を監視していたときの情報を基に、他にシート検出器Ａを通過したシートが転写ベルト上に存在するか否かが判断される。また、ステップｓ７では、シート検出器Ａにてレジストローラ１４に挟持されているシートが存在するか否かが判断される。ステップｓ６またはｓ７でシートが存在すると判断された場合には、環境条件に応じて転写バイアスの印加電圧を設定し、シートに転写バイアスを印加する（ｓ８）。
【００８８】
次いで、ステップｓ９で定着部１２を停止させたままシートの搬送動作を開始し、ステップｓ１０で、シートが（取り出しやすい）定着部１２のローラ部材３１，３２に噛み込まれた状態（図４の破線で示すシートの状態）または、ローラ部材３１，３２に噛み込まれる手前の状態（図４の実線で示すシートの状態）でシートの搬送を停止させる。そのシートの搬送動作では、転写ベルト７への環境条件に応じた転写バイアスの印加により、シートを確実に搬送することができる。
【００８９】
このとき、転写ベルト７の感光体ドラム３からの離間状態を維持し、シートを転写ベルト７に吸着させるためにも働く感光体ドラム３ｂ，３ｃ，３ｄからの電荷の供給を断つ。これは、後に行うシートを転写ベルト７から剥ぎ取るときの力をなるべく小さくするためである。
【００９０】
本例では、環境条件に応じた転写バイアスを転写ベルト７に印加しているため、環境条件がきびしくなっても、シート記録材の搬送不良を招くことがなく、シート記録材を所定の搬送量だけ搬送した後（ｓ１０）、ステップｓ１１で操作者が定着部１２を開放し再度ジャム処理（復帰作業）を行う。
【００９１】
このとき、定着部１２の開放動作に連動する離接機構により、転写ベルトユニット８が全ての感光体ドラム３から離間する位置に移動しているため、図５に示すように、残っていたシートの先端が掴みやすくなり、容易にジャム処理を行える。また、ジャム発生後すぐに転写ローラ６への転写バイアスの印加を停止し、転写ベルト７を感光体ドラム３ｂ，３ｃ，３ｄから離間させているので、転写ベルト７に吸着しているシートの吸着力が低下しているためにシートを転写ベルト７から剥ぎ取りやすい状態になっていることも、ジャム処理の容易化に大きく寄与している。
【００９２】
ジャム処理をした後に定着部１２をもとに戻すとステップｓ７に戻り再びシート検出器Ａでシートの滞留が再度検出され、シートの滞留が無ければステップｓ１２に進み切換手段３８を動作させ転写ベルト７を感光体ドラム３全てに接触させる。その後、ステップｓ１３にてプロセス部の予備動作である前回転動作（感光体ドラム３や転写ベルト７のクリーニング等の準備作業）を開始し、ステップｓ１４にて前回転動作が修了すればステップｓ１５にて操作部のレディーランプを点灯させ画像形成可能な状態で待機状態となる。
【００９３】
一方、ステップｓ６で転写ベルト上に滞留するシートが無いと判断され、ステップｓ７にて、シート検出器Ａでシートが検出されない場合は、ジャム処理が完全に終了していると判断し、ステップｓ１２に進み、転写ベルト７を感光体ドラム３の全てに接触させる。その後、ステップｓ１３，１４に進み前記した前回転動作の終了を待って、画像形成準備の完了したことを示すレディーランプを点灯させる（ｓ６〜ｓ１５）。本実施の形態では、レディーランプを点灯させて動作の再開を促しているが、自動的に画像形成動作を再開させてもよい。
【００９４】
このように、定着部１２を画像形成装置本体から引き出して、一旦、ジャム処理を行った後、画像形成装置の上流側に残っている後続のシートがあれば、これを下流側の取り出し易い位置に搬送して、再度、ジャム処理を行うことで、シートを取り残すことなく、確実に復帰作業を完了することができる。その取り出し易い位置は、例えば、シートの少なくとも一部が定着部１２のエリアと転写ベルト７のエリアにまたがる位置であればよい。
【００９５】
なお、搬送ジャムと判断された場合には上流側のシート搬送手段の内レジストローラ１４を含む上流のシート搬送手段の駆動は停止される。ただし、レジストローラ１４に噛み込んで転写ベルト７の領域に入り込んだシートがある場合には、転写ベルト７よりその先端が定着部１２のローラ部材３１，３２に噛み込まれるまで、または、噛み込まれる手前まで搬送される。この時、レジストローラ１４の駆動側のローラには図示しない駆動系との間に設けた図示しない一方向クラッチにより、レジストローラ１４が従動回転するようになっている。また、レジストローラ１４を含む上流側のシートを挟持しているローラを駆動しても良い。
【００９６】
また、上述した２回目のジャム処理の際に、緊急停止時に上流側に滞留している後続のシートをより確実に搬出するために、例えば、図１４の制御フローに示すように、環境条件に応じて転写バイアスの印加電圧を設定し、シートに転写バイアスを印加（ｓ８′）した後、シート搬送動作を開始するときに定着部１２の回転動作も開始させシートの搬送動作を停止させる前に、所定時間、例えば、図６（ａ）に示すように、シートを定着ローラ（ローラ部材）３１，３２に噛み込ませるまでに要する時間だけ、転写ベルト７を転動させた（ｓ９′）後、シートの搬送動作を停止（ｓ１０′）させて、ジャム処理を行うようにしてもよい。
【００９７】
この場合、定着部１２を画像形成装置本体から引き出すと、図６（ｂ）に実線で示すように、定着ローラ３１，３２に噛み込まれたシートを容易に画像形成装置内より引き抜くことができ、転写ベルト７からシートを剥ぎ取る操作を容易に行うことができる。このように、ｓ９′〜１０′のシート搬送過程を設定することで、特に、小サイズのシートをも画像形成の内部に落下させることなく定着部１２のローラ３１，３２に噛み込ませた状態で取り出し易い位置に確実に搬出することができる。
【００９８】
上記の複数回に分けて行うジャム処理は、特に、定着部１２でジャムが発生した場合に有効で、シートが異常発熱して焦げたり煙を発生し、そのまま放置すると大きなトラブルに発展する可能性があるため、画像形成装置を緊急に停止させすぐに定着部を引き出しジャム処理をする場合についての動作として説明したが、定着部１２以外の部分でジャム処理を行ってもよい。
【００９９】
次の例は、ジャムの発生が検出された場合に定着部１２の上流側のシート搬送手段の回転動作を即停止させない場合である。例えば、図１５に示すように、画像形成動作の開始後にジャムが発生した場合（ｓ２１〜ｓ２２）、画像形成動作（露光ユニット１による感光体ドラムへ３の書込み動作、現像器２による現像動作等）と定着部の動作（ヒータによる加熱動作、ローラ類３１，３２の回転動作）を停止させる（ｓ２３）。次いで、環境条件に応じて転写バイアスの印加電圧を設定し、シートに転写バイアスを印加する（ｓ２４）。なお、ステップｓ２３（及びｓ４３）での画像形成動作とは、露光ユニット１による露光動作、現像器２による現像動作を指し、現像器２の現像動作の停止は、現像バイアスの印加制御あるいは現像器２の感光体ドラム３との距離（離接）制御にて行う。
【０１００】
さらに、切換手段３８を動作させ転写搬送ユニット８を回転移動させ、転写ベルト７を感光体ドラム３ｂ，３ｃ，３ｄから離間させる（ｓ２５）。これは、前述した通り、シートの転写ベルト７への吸着力をできるだけ減じて転写ベルト７からシートを剥がしやすくするためであり、かつ、すでに感光体ドラム３ｂ、３ｃ、３ｄに形成されてしまっている画像がシートに転写されるのを防止するためでもある。
【０１０１】
そして、同時に、転写ローラ６ｂ，６ｃ，６ｄへの転写バイアスの印加も停止させる（ｓ２６）。これは、シートの転写ベルト７への吸着力を減じるためである。また、このとき、シートの転写ベルト７への吸着力が減少しにくい場合には前述した転写ローラ６ｂ，６ｃ，６ｄへの高電圧印加をＡＣの高電圧出力に切換え積極的に吸着力を減少させてもよい。
【０１０２】
次いで、転写ベルト７上に吸着され担持されているシートを感光体ドラム３ｂ，３ｃ，３ｄと非接触の状態で搬送し続け、定着部１２のエリアにシートの先端が充分に進入するまでの時間、転写ベルト７によるシートの搬送を継続した後にシートの搬送を停止させる（ｓ２８〜ｓ２９）。これは、転写ベルト７上に２枚のシートが搬送されている状態のときに、転写部１２のローラ部材３１，３２の手前に先頭のシートと後続のシートとを集め、同時に（一度に）ジャム処理をするためである。
【０１０３】
このとき、後続のシートが下流に位置する搬送手段であるレジストローラ１４等に挟持されている場合は、そのローラ部材を駆動させることによりシートがスムーズに搬送されるようにする。
【０１０４】
つまり、ジャム発生後すぐに画像形成動作および定着部１２の回転動作を停止させてから、所定時間経過後に、図７（ａ）に示すような状態になったときにシートの搬送動作を完全に停止させる。そして、ステップｓ３０にて、復帰作業が実施される。すなわち、操作者によって、まず、図７（ｂ）に示すように定着部１２を画像形成装置本体から引き出す操作により、連動する離接機構によって、転写搬送ユニット８がさらに移動させられ転写ベルト７が全ての感光体ドラム３から離間される。そして、操作者が前述したように２枚のシートを取り出す復帰作業（ジャム処理）を実施する。ジャム処理が終了した後は、定着部１２を画像形成装置本体に挿入して転写搬送ユニット８を元の状態（感光体ドラム３ａのみが転写ベルト７に接触している状態）に復帰させる。
【０１０５】
次いで、ステップｓ３１にて、シート検出器Ａによりレジストローラ１４にシートが滞留していないかを確認し、シートの滞留が認められたら、ｓ３６〜ｓ３７で前述したと同様に滞留しているシートの先端が定着部１２のエリアに侵入あるいは充分に浸入するまでシートの搬送を行い、ステップｓ３８にて再度、操作者が復帰作業を行う。
【０１０６】
復帰作業後は、再度ステップｓ３１に戻り、シートの滞留状態が確認される。ステップｓ３１でシートの滞留が認められなかった場合は、復帰作業（ジャム処理）が完了したと判断し、ステップｓ３２に進み転写ベルト７を感光体ドラム３全てに接触させる。
【０１０７】
その後、ステップｓ３３にてプロセス部の予備動作である前回転動作（感光体ドラム３や転写ベルト７のクリーニング等の準備作業）を開始し、ステップｓ３４にて前回転動作が修了すれば、ステップｓ３５にて操作部のレディーランプを点灯させ画像形成可能な待機状態となる。
【０１０８】
また、ステップｓ３１からステップｓ３６〜ｓ３８，ｓ３１に戻るフローは念のために行われる動作であり、先に説明したステップｓ８〜ｓ１０，ｓ７に戻る動作と同一の動作であるので説明を省略する。
【０１０９】
次に、図１６に示す例では、さらに効率よく容易かつ確実にジャム処理を行えるようにするために、ジャムが発生した時に、転写ベルト７上に複数枚のシートが存在している場合で、先頭のシートを定着部１２のローラ３１，３２で狭持した状態で定着部１２から下流側に搬送されないように搬送を停止させ、後続のシートを定着部１２のローラ３１，３２の手前に集めてジャム処理を行うようにしている。
【０１１０】
その制御フローについて説明すると、画像形成動作の開始後に、ジャムの発生が検出された場合に（ｓ４１，ｓ４２）、ステップｓ４２にて、まず、画像形成動作（露光ユニット１による感光体ドラムへ３の書込み動作，現像器２による現像動作等）を停止させる。このとき定着部１２の動作はヒータによる加熱動作は停止しても良いが、ローラ３１，３２の回転動作は継続させてシートの搬送を続行させる（ｓ４３）。そして、ステップｓ４４にて、環境条件に応じて転写バイアスの印加電圧を設定し、シートに転写バイアスを印加する。なお、ステップｓ４３にて、シートの搬送動作の継続中には、は画像形成動作が停止されているため、ジャム処理時に画像形成装置内の汚れを少なくすることができる。
【０１１１】
次いで、ステップｓ４５にて、切換手段３８を動作させ転写搬送ユニット８を回転移動させ、転写ベルト７を感光体ドラム３ｂ，３ｃ，３ｄから離間させる。これは、前述した通りシートの転写ベルト７への吸着力をできるだけ減じて転写ベルト７からシートを剥がしやすくするためと、すでに感光体ドラム３ｂ、３ｃ、３ｄに形成されてしまっている画像がシートに転写されることをも防止するためである。同時に、ステップｓ４５にて転写ローラ６ｂ，６ｃ，６ｄへの転写バイアスの印加も停止させる（ｓ４６）。
【０１１２】
また、このとき、積極的に吸着力が減少するように転写ローラ６ｂ，６ｃ，６ｄにＡＣの高電圧を印加してもよい。これは、シートの転写ベルト７への吸着力が高すぎる場合等にその吸着力を減じるためである。
【０１１３】
そして、離間させた感光体ドラム３ｂ，３ｃ，３ｄの回転を停止させ（ｓ４７）、所定量シートを搬送した後（ｓ４８）、転写ベルト７等によるシートの搬送を停止させる（ｓ４９）。
【０１１４】
次いで、ステップｓ５０にて、先に述べたと同様に復帰作業を行う。シートは図８（ａ）に示す状態で停止されており、図８（ｂ）に示すように定着部１２を引き出すことで復帰作業が容易に行える。この時の、それぞれのシートの搬送の停止は、シート検出器Ａを基準にタイマにてコントロールされるが、シートの上流に位置するシート検出器Ｂやシート検出器Ｃにより検出しても良い。
【０１１５】
すなわち、まず、画像形成動作のみを停止（定着ローラは駆動）させた後、シート検出器Ａによる検出タイミングを基準として、またはシート検出器Ｂ、シート検出器Ｃでシートが検出された後、つまり所定時間が経過するのを待って、定着部１２の動作を停止させ、さらに、所定時間経過するのを待って、シートの搬送動作を完全に停止させ、しかる後に、定着部１２を画像形成装置本体から引き出して離接機構を連動させ、転写搬送ユニット８を全ての感光体ドラム３から離間する位置に移動させて、復帰作業（ジャム処理）を行う（ｓ４３〜ｓ５０）。
【０１１６】
上述のステップｓ４２でジャムの発生を検出したときに画像形成動作を停止してから、ステップｓ４８で、シートを所定量搬送してから定着部１２の動作を停止させるのは、図８（ａ）に示すように先頭のシートを定着部１２のローラ部材（３１，３２）に噛み込ませるためである。この時、後続のシート（破線参照）はローラ部材（３１，３２）に噛み込まれる手前の位置にあり、これをさらに搬送することにより定着部１２のローラ部材（３１，３２）に突き当たる所に搬送させることができる。
【０１１７】
このように、先頭のシートをローラ部材（３１，３２）に噛み込ませておき、後続のシートを定着部１２の所まで搬送させることにより、定着部１２を引き出した時に先頭および後続のシートを同時に取り出すことができ、１度でジャム処理を完了させることができる。
【０１１８】
また、ステップｓ５１以降のステップｓ５１〜ｓ５８は、前述した方法のところで説明したステップｓ７〜ｓ１４、ｓ３０〜ｓ３７に記載した内容と同一であり説明を省略する。さらに、ステップｓ５２〜ｓ５５も前述の方法と同一であり説明を省略する。
【０１１９】
さらに、転写バイアスの印加範囲を制御する場合（表２参照）については、例えば、図１７に示すように、画像形成動作の開始後にジャムが発生した場合（ｓ６１〜ｓ６２）、画像形成動作（露光ユニット１による感光体ドラムへ３の書込み動作，現像器２による現像動作等）と定着部の動作（ヒータによる加熱動作，ローラ類３１，３２の回転動作）を停止させる（ｓ６３）。次いで、環境条件に応じて転写バイアスの印加範囲を設定し、その範囲に転写バイアスを印加すればよい（ｓ６４）。それ以降のステップについては、図１５のステップｓ２５以降と同様であり、説明を省略する。
【０１２０】
また、例えば、図１８に示すように、画像形成動作の開始後に、ジャムの発生が検出された場合に（ｓ８１，ｓ８２）、ステップｓ８２にて、まず、画像形成動作（露光ユニット１による感光体ドラムへ３の書込み動作，現像器２による現像動作等）を停止させる。このとき定着部１２の動作はヒータによる加熱動作は停止しても良いが、ローラ３１，３２の回転動作は継続させてシートの搬送を続行させる（ｓ８３）。次いで、ステップｓ８４にて、環境条件に応じて転写バイアスの印加範囲を設定し、その範囲に転写バイアスを印加すればよい（ｓ８４）。それ以降のステップについては、図１６のステップｓ４５以降と同様であり、説明を省略する。
【０１２１】
以上説明したように、本発明では、ジャム処理の際に、シートを取り出し易い位置まで搬出方向に移動させて取り出し易い位置まで移動させると共に、環境条件に応じた転写バイアスの制御または転写バイアスの印加範囲の制御を行うことで、ジャム処理を容易かつ確実に行うことができる。
【０１２２】
なお、本発明は、以上説明した実施の形態に限定されることなく、発明の要旨を逸脱しない限りにおいて、必要に応じて、適宜、設計変更や改良等は自由である。すなわち、本実施の形態では、シートのジャムが発生した場合に、転写ベルト７を感光体ドラム３ｂ，３ｃ，３ｄから離間させシートを搬送しているが、離間させないでシートを搬送させる画像形成装置においても、転写ローラ６への転写バイアスの印加電圧を制御すれば、シートの転写ベルト７への吸着力を制御でき同様な効果を得ることができるのは言うまでもない。しかし、すでに感光体ドラム３ｂ，３ｃ，３ｄに画像が形成されている場合には、シートにその画像が転写されてしまうので、ジャムが発生後に転写ベルト７を感光体ドラム３ｂ，３ｃ，３ｄから離間させてシートを搬送する方が好ましい。
【０１２３】
また、画像形成装置は、図１，図２に示す構成に限定されることなく、像担持体上に形成されたトナー像を転写担持体上に吸着搬送されるシート記録材に転写し定着装置で前記シート記録材上に前記トナー像を定着させると共に、ジャム処理制御手段により、前記シート記録材の搬送異常を判断し、かつ、搬送異常時にはその搬送動作を停止させるようにした画像形成装置であれば、構成や形式の如何を問わない。
【０１２４】
【発明の効果】
以上の説明から明らかなように、本発明は、以下の効果を奏する。
【０１２５】
（１）搬送ジャムなどにより異常停止（緊急停止）をした後に画像形成装置内に残っているシート記録材を取り出す等の復帰作業を行った場合には、シート記録材を取り出しやすい位置に搬送する時にシート記録材に与える転写バイアスを環境条件に応じて制御するので、シート記録材を取り出しやすい位置に確実に搬出することができ、かつ、シート記録材に対する吸着力が転写担持体から引き剥がしやすい程度に調整されるので、常にシート記録材の取り出し作業が容易かつ確実となる。
また、シート記録材を、定着装置のエリアと転写担持体が位置するエリアにまたがった位置に停止させ、かつ、その停止位置が、シート記録材の先端が定着装置のローラ部材に噛み込まれた位置であるので、定着装置を画像形成装置から開放する動作により、定着装置のローラ部材に挟み込まれたシート記録材が一緒に引き出され、転写担持体に静電吸着しているシート記録材を容易に取り出すことができる。
シート記録材の搬送異常が検出された場合に、転写担持体によるシート記録材の搬送が停止する以前に、切換手段により、転写担持体の前記像担持体に対する離間動作を開始し、かつ、転写担持体を、特定の像担持体を除く他の像担持体から離間させるので、像担持体とシート記録材の接触状態を一部解除しシートを定着部のエリアに向かって搬送する場合に、ジャム発生前に像担持体に形成されたトナー像のシート記録材への転写がすくなくなると共に、像担持体と対を成す転写ローラによる転写担持体に対するシート記録材への必要以上の吸着力の追加を断つことができるため、転写担持体からシート記録材を剥がしやすくなり、かつ、ジャム処理時の装置内部へのトナー汚れやシート記録材を掴む手へのトナー汚れ等を減じることができ容易なジャム処理を行える。
さらに、離間されなかった像担持体と対を成す転写ローラによりシート記録材を転写担持体に吸着させる電荷を適正に供給できるため、シート記録材を定着装置のエリアに確実に搬送させることができる。また、転写担持体の搬送方向下流側を離間させれば、シート記録材が停止している定着ローラに当って搬送が阻止された後に、シート記録材を過度に撓ませたりジャムさせることなく、転写担持体上で滑らせることができ未定着トナーにより画像形成装置の内部がトナーで汚れることを減じることができる効果もある。
また、転写バイアスを、湿度が低い時には、湿度が高い時よりも低く設定するので、転写担持体からシート記録材を引き剥がすために必要となる力の変動を抑制することができる。
【０１２６】
（２）搬送ジャムなどにより異常停止（緊急停止）をした後に画像形成装置内に残っているシート記録材を取り出す等の復帰作業を行った場合には、シート記録材を取り出しやすい位置に搬送する時にシート記録材に与える転写バイアスを環境条件に応じて制御するので、シート記録材を取り出しやすい位置に確実に搬出することができ、かつ、シート記録材に対する吸着力が転写担持体から引き剥がしやすい程度に調整されるので、常にシート記録材の取り出し作業が容易かつ確実となる。
また、シート記録材を、定着装置のエリアと転写担持体が位置するエリアにまたがった位置に停止させ、かつ、その停止位置が、シート記録材の先端が定着装置のローラ部材に噛み込まれた位置であるので、定着装置を画像形成装置から開放する動作により、定着装置のローラ部材に挟み込まれたシート記録材が一緒に引き出され、転写担持体に静電吸着しているシート記録材を容易に取り出すことができる。
シート記録材の搬送異常が検出された場合に、転写担持体によるシート記録材の搬送が停止する以前に、切換手段により、転写担持体の前記像担持体に対する離間動作を開始し、かつ、転写担持体を、特定の像担持体を除く他の像担持体から離間させるので、像担持体とシート記録材の接触状態を一部解除しシートを定着部のエリアに向かって搬送する場合に、ジャム発生前に像担持体に形成されたトナー像のシート記録材への転写がすくなくなると共に、像担持体と対を成す転写ローラによる転写担持体に対するシート記録材への必要以上の吸着力の追加を断つことができるため、転写担持体からシート記録材を剥がしやすくなり、かつ、ジャム処理時の装置内部へのトナー汚れやシート記録材を掴む手へのトナー汚れ等を減じることができ容易なジャム処理を行える。
さらに、離間されなかった像担持体と対を成す転写ローラによりシート記録材を転写担持体に吸着させる電荷を適正に供給できるため、シート記録材を定着装置のエリアに確実に搬送させることができる。また、転写担持体の搬送方向下流側を離間させれば、シート記録材が停止している定着ローラに当って搬送が阻止された後に、シート記録材を過度に撓ませたりジャムさせることなく、転写担持体上で滑らせることができ未定着トナーにより画像形成装置の内部がトナーで汚れることを減じることができる効果もある。
また、シート記録材に対する転写バイアスの印加範囲を、湿度が低い時には、湿度が高い時よりも、狭くなるように制御するので、転写担持体からシート記録材を引き剥がすために必要となる力の変動を抑制することができる。
【０１２８】
（３）シート搬送異常が検出された場合に画像形成動作を停止させてシート記録材の搬送動作を継続させ、転写担持体を含む上流側のシート記録材搬送手段に存在するシート記録材を定着装置のエリアと転写担持体が位置するエリアとにまたがる取り出しやすい位置に搬送させ停止させると共に、搬送異常を判断した後の前記転写担持体上のシート記録材へ与える転写バイアスを、環境条件に応じて制御するので、一度の搬送ジャム復帰作業を行うことで画像形成装置を復帰させることができる。
また、シート記録材の搬送動作の継続中に、画像形成動作を停止するので、画像形成装置内の汚れを少なくすることができる。そして、そのジャム処理作業では、シート記録材へ与える転写バイアスが環境条件に応じて制御されているので、シート記録材に対する吸着力が転写担持体から引き剥がしやすい程度に調整されており、常にシート記録材の取り出し作業が容易かつ確実となる。
さらに、シート記録材を、定着装置のエリアと転写担持体が位置するエリアにまたがった位置に停止させ、かつ、その停止位置が、シート記録材の先端が定着装置のローラ部材に噛み込まれた位置であるので、定着装置を画像形成装置から開放する動作により、定着装置のローラ部材に挟み込まれたシート記録材が一緒に引き出され、転写担持体に静電吸着しているシート記録材を容易に取り出すことができる。
シート記録材の搬送異常が検出された場合に、転写担持体によるシート記録材の搬送が停止する以前に、切換手段により、転写担持体の前記像担持体に対する離間動作を開始し、かつ、転写担持体を、特定の像担持体を除く他の像担持体から離間させるので、像担持体とシート記録材の接触状態を一部解除しシートを定着部のエリアに向かって搬送する場合に、ジャム発生前に像担持体に形成されたトナー像のシート記録材への転写がすくなくなると共に、像担持体と対を成す転写ローラによる転写担持体に対するシート記録材への必要以上の吸着力の追加を断つことができるため、転写担持体からシート記録材を剥がしやすくなり、かつ、ジャム処理時の装置内部へのトナー汚れやシート記録材を掴む手へのトナー汚れ等を減じることができ容易なジャム処理を行える。
さらに、離間されなかった像担持体と対を成す転写ローラによりシート記録材を転写担持体に吸着させる電荷を適正に供給できるため、シート記録材を定着装置のエリアに確実に搬送させることができる。また、転写担持体の搬送方向下流側を離間させれば、シート記録材が停止している定着ローラに当って搬送が阻止された後に、シート記録材を過度に撓ませたりジャムさせることなく、転写担持体上で滑らせることができ未定着トナーにより画像形成装置の内部がトナーで汚れることを減じることができる効果もある。
また、転写バイアスを、湿度が低い時には、湿度が高い時よりも低く設定するので、転写担持体からシート記録材を引き剥がすために必要となる力の変動を抑制することができる。
【０１２９】
（４）シート搬送異常が検出された場合に画像形成動作を停止させてシート記録材の搬送動作を継続させ、転写担持体を含む上流側のシート記録材搬送手段に存在するシート記録材を定着装置のエリアと転写担持体が位置するエリアとにまたがる取り出しやすい位置に搬送させ停止させると共に、搬送異常を判断した後の前記転写担持体上のシート記録材へ与える転写バイアスを、環境条件に応じて制御するので、一度の搬送ジャム復帰作業を行うことで画像形成装置を復帰させることができる。
また、シート記録材の搬送動作の継続中に、画像形成動作を停止するので、画像形成装置内の汚れを少なくすることができる。そして、そのジャム処理作業では、シート記録材へ与える転写バイアスが環境条件に応じて制御されているので、シート記録材に対する吸着力が転写担持体から引き剥がしやすい程度に調整されており、常にシート記録材の取り出し作業が容易かつ確実となる。
さらに、シート記録材を、定着装置のエリアと転写担持体が位置するエリアにまたがった位置に停止させ、かつ、その停止位置が、シート記録材の先端が定着装置のローラ部材に噛み込まれた位置であるので、定着装置を画像形成装置から開放する動作により、定着装置のローラ部材に挟み込まれたシート記録材が一緒に引き出され、転写担持体に静電吸着しているシート記録材を容易に取り出すことができる。
シート記録材の搬送異常が検出された場合に、転写担持体によるシート記録材の搬送が停止する以前に、切換手段により、転写担持体の前記像担持体に対する離間動作を開始し、かつ、転写担持体を、特定の像担持体を除く他の像担持体から離間させるので、像担持体とシート記録材の接触状態を一部解除しシートを定着部のエリアに向かって搬送する場合に、ジャム発生前に像担持体に形成されたトナー像のシート記録材への転写がすくなくなると共に、像担持体と対を成す転写ローラによる転写担持体に対するシート記録材への必要以上の吸着力の追加を断つことができるため、転写担持体からシート記録材を剥がしやすくなり、かつ、ジャム処理時の装置内部へのトナー汚れやシート記録材を掴む手へのトナー汚れ等を減じることができ容易なジャム処理を行える。
さらに、離間されなかった像担持体と対を成す転写ローラによりシート記録材を転写担持体に吸着させる電荷を適正に供給できるため、シート記録材を定着装置のエリアに確実に搬送させることができる。また、転写担持体の搬送方向下流側を離間させれば、シート記録材が停止している定着ローラに当って搬送が阻止された後に、シート記録材を過度に撓ませたりジャムさせることなく、転写担持体上で滑らせることができ未定着トナーにより画像形成装置の内部がトナーで汚れることを減じることができる効果もある。
また、シート記録材に対する転写バイアスの印加範囲を、湿度が低い時には、湿度が高い時よりも、狭くなるように制御するので、転写担持体からシート記録材を引き剥がすために必要となる力の変動を抑制することができる。
【０１３０】
（５）シート記録材に対する転写バイアスの印加範囲を、高湿時には、シート記録材の全面とし、低湿時には、シート記録材の搬送方向後端側のみとするので、転写担持体からシートを引き剥がすために必要となる力の変動を抑制することができる。
【０１３５】
（６）シート記録材の搬送異常が検出された場合に、転写担持体を像担持体より離間させ像担持体とシート記録材の接触状態を解除しシートを定着部のエリアに搬送した後にシート記録材の搬送を停止させ、その間に、シート記録材（または転写担持体）と非接触となった像担持体の回転を停止させるので、非接触となった像担持体の不必要な回転を停止させ像担持体の寿命の延長を図ることができる。また、シート記録材または転写担持体と接触している像担持体は転写担持体が停止されるまで回転動作が継続されるので、シート記録材や転写担持体によって擦られないので寿命の短命化が阻止される。
【０１３６】
（７）シート記録材に異常搬送が検出された場合には、転写担持体と像担持体との接触状態を単色モードとするので、転写担持体が多くの像担持体から離間されるため、シート記録材を取り出しやすくなり、ジャム処理作業が容易となる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る画像形成装置の要部構成図である。
【図２】同定着部を引き出した状態の要部構成図である。
【図３】同転写担持体が緊急停止した状態の説明図である。
【図４】同シート記録材が転写担持体上に残っている状態の説明図である。
【図５】同定着部を引き出してジャム処理を行う時の説明図である。
【図６】同他の例の説明図である。
【図７】同転写担持体上にシート記録材が２枚残った場合のジャム処理を行う時の説明図である。
【図８】同他の例の説明図である。
【図９】同多色モードにおける転写担持体の状態を示す説明図である。
【図１０】同単色モードにおける転写担持体の状態を示す説明図である。
【図１１】同定着部を引き出している状態の説明図である。
【図１２】同ジャム処理制御手段の制御系統ブロック図である。
【図１３】同ジャム処理制御の一例を示すフローチャートである。
【図１４】同他の例を示すフローチャートである。
【図１５】同異なる例を示すフローチャートである。
【図１６】同さらに異なる例を示すフローチャートである。
【図１７】同別の例を示すフローチャートである。
【図１８】同さらに別の例を示すフローチャートである。
【符号の説明】
３−像担持体
７−転写担持体
１２−定着装置（定着部）
３１，３２−ローラ部材
１００ａ−ジャム処理制御手段
Ｒ−離接手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, or a fax machine that forms various images on a sheet recording material, and more particularly to a jam processing technique when a sheet recording material is abnormally conveyed.
[0002]
[Prior art]
Conventionally, after a toner image formed on an image carrier is electrostatically adsorbed and transferred to a sheet recording member by a transfer carrier, the toner image is fixed on the sheet recording member by a fixing device. There is an image forming apparatus that performs the above. Among such image forming apparatuses, in particular, in a tandem type image forming apparatus in which a plurality of image forming stations in which the respective process units are arranged around the image carrier are arranged, a single image is formed over the image carriers of all the image forming stations. Since the transfer carrier is formed oppositely, the transfer carrier is formed long.
[0003]
Therefore, if any of the sheet recording members that are continuously conveyed causes a conveyance abnormality such as a jam during conveyance and the image forming apparatus stops urgently, the sheet recording is performed between the image carrier and the transfer carrier. The member is often stopped. In particular, when a conveyance jam occurs in the fixing unit, the operation must be stopped urgently. In such a case, there is a high possibility that the subsequent sheet recording member is stopped between the image carrier and the transfer carrier.
[0004]
When the sheet recording member is stopped between the image carrier and the transfer carrier, the sheet recording member is electrostatically adsorbed to the transfer carrier, and the image carrier and the transfer carrier are in contact with each other. Therefore, it is difficult to grasp and pull out the sheet recording member remaining after stopping. Therefore, for example, when a jam occurs, the transfer carrier is reversed in the direction opposite to the moving direction at the time of copying, and the sheet recording member is returned to a position where it can be easily taken out to carry out the jam handling. An apparatus and a defective peeling paper processing apparatus have been proposed (see, for example, Patent Documents 1 and 2).
[0005]
In addition, when a jam occurs in the sheet recording member, an image forming apparatus is proposed in which only the fixing unit is stopped and the other parts are driven for a certain period of time, and the sheet recording member is conveyed to the front of the fixing unit to facilitate the jam processing. (For example, see Patent Document 3).
[0006]
Furthermore, when the jam occurs, the transfer bias applied to the transfer carrier when the sheet recording member is transported before the fixing unit is cut off, thereby reducing the adsorption force between the sheet recording member and the transfer carrier to some extent. An image forming apparatus that facilitates jam processing has been proposed (see, for example, Patent Document 4).
[0007]
[Patent Document 1]
JP-A-62-264144
[Patent Document 2]
JP-A-7-281534
[Patent Document 3]
JP-A-5-53405 (paragraphs “0013” and “0016”)
[Patent Document 4]
JP 11-119490 A (paragraphs “0055” and “0066”)
[0008]
[Problems to be solved by the invention]
However, it is difficult to visually find the sheet recording material present between the transfer carrier and the image carrier, and usually, there is provided a means for detecting the sheet recording material present on the transfer carrier. In most cases, the image forming apparatus itself and the user cannot determine whether or not the sheet recording material remains adsorbed to the transfer carrier during a jam.
[0009]
For this reason, as described in Patent Documents 1 and 2, if the sheet is not always present on the transfer carrier but the transfer carrier is always reversely rotated when a jam occurs, useless time is consumed. There is a problem that there are cases where it must be done and it becomes uneconomical. Further, when a detector for detecting the sheet recording material present on the transfer carrier is provided, there are problems that the size of the image forming unit is increased and the manufacturing cost and assembly cost are increased.
[0010]
Further, in Patent Document 3, when a sheet recording material jam occurs, only the fixing unit is stopped and the other parts are driven for a certain period of time to convey the sheet recording material to the front of the fixing unit to facilitate jam processing. ing. Further, Patent Document 4 discloses that when a jam occurs, the transfer bias applied to the transfer carrier when the sheet recording material is conveyed to the front of the fixing unit is cut off, so that the sheet recording material and the transfer carrier are separated. The contents that reduce the suction force to some extent and facilitate the jam processing are disclosed.
[0011]
However, the adsorption force between the transfer carrier and the sheet recording material changes due to changes in environmental conditions, particularly humidity, and if the transfer bias is turned off, the adsorption force of the sheet recording material on the transfer carrier decreases and the fixing unit Another problem is that the sheet recording material cannot be conveyed. Further, even if the transfer bias is continuously applied as it is, there may be a case where the adsorption force is reduced and the conveyance becomes impossible at high humidity. On the other hand, when the humidity is low, the transfer carrier and the sheet recording material may be transported while maintaining a high adsorbing force.
[0012]
As described above, since the sheet adsorption force varies greatly depending on the environmental conditions, the transferability of the sheet recording material by the transfer carrier and the difficulty of the work of peeling the sheet from the transfer carrier change, and the adsorption force is low. Has a problem in that workability is still not improved when the suction force is high.
[0013]
The present invention has been made in view of such circumstances, and provides an image forming apparatus capable of easily performing the work of peeling and taking out a sheet from a transfer carrier without causing a conveyance failure of the sheet recording material. Objective.
[0014]
[Means for Solving the Problems]
In the present invention, means for solving the above-described problems are configured as follows.
[0015]
  (1) The toner image formed on the image carrier is transferred to a sheet recording material sucked and conveyed in the sheet conveyance direction on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device. When the conveyance of the sheet recording material is abnormal, the jam processing control means stops the conveyance operation of the sheet recording material in the fixing device and the sheet recording material on the transfer carrier,
  A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
  When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
  Slide means capable of pulling out the fixing device unitized with a side cover of the image forming apparatus main body in a sheet conveying direction by the transfer carrier;
  In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
  The jam processing control means includes:
  When the presence of a sheet recording material in the middle of conveyance is confirmed immediately after or after restarting the conveyance operation of the sheet recording material on the transfer carrier after carrying out a return operation after stopping the conveyance operation in the case of the conveyance abnormality In
  A sheet recording material on the transfer carrier is conveyed, at least a part of which is a position that spans an area of the fixing device and an area where the transfer carrier is located in the sheet conveyance direction, and the transfer carrier The sheet recording material on the transfer carrier is stopped at a position where the leading edge of the upper sheet recording material is engaged with the roller member of the fixing device, and the transfer is performed when the sheet recording material on the transfer carrier is conveyed. Transfer bias applied to the sheet recording material on the carrier,When the humidity near the transfer carrier is low, it should be set lower than when the humidity near the transfer carrier is high.It is characterized by.
[0016]
In this configuration, for example, when a return operation such as taking out the sheet recording material remaining in the image forming apparatus after performing an abnormal stop (emergency stop) due to a conveyance abnormality such as a conveyance jam in the fixing unit is easy to overlook. When the sheet recording material left between the image carrier and the transfer carrier remains without being taken out, or when the sheet recording material is left undesirably difficult to take out, the image forming apparatus is tried to operate again. At that time, it is detected that the sheet recording material still remains in the image forming apparatus.
[0017]
  At this time, the transfer bias applied to the sheet recording material when the sheet recording material is transported to a position where the sheet recording material is easily taken out is controlled according to the environmental conditions, so that the sheet recording material can be reliably taken out to a position where the sheet recording material can be easily taken out The sheet recording material can be taken out and adjusted so that the adsorption force to the sheet recording material can be easily peeled off from the transfer carrier, so that the sheet recording material can be taken out easily and reliably at all times. it can.
  Further, by the operation of pulling out the fixing device from the image forming apparatus, the sheet recording material sandwiched between the roller members of the fixing device is pulled out together, and the sheet recording material electrostatically adsorbed to the transfer carrier can be easily taken out. it can.
  In this configuration, when the sheet recording material is abnormally conveyed, the transfer carrier is separated from the image carrier excluding the specific image carrier, and the contact state between the image carrier and the sheet recording material is partially released to remove the sheet recording material. When transporting toward the area of the fixing unit, transfer to the sheet recording material of the toner image formed on the image carrier before jamming is reduced, and a transfer carrier by a transfer roller that forms a pair with the image carrier Can be applied to the sheet recording material more than necessary, making it easier to peel off the sheet recording material from the transfer carrier and gripping toner contamination and sheet recording material inside the device during jam processing. This makes it possible to reduce toner stains and the like, and to perform easy jam processing.
  Further, since the charge for adsorbing the sheet recording material to the transfer carrier can be appropriately supplied by the transfer roller paired with the image carrier not separated, the sheet recording material can be reliably conveyed to the area of the fixing device. . Further, if the downstream side in the conveyance direction of the transfer carrier is separated, the transfer carrier is prevented from excessively bending or jamming after the sheet recording material hits the fixing roller where the sheet recording material is stopped to prevent conveyance. Since the toner can be slid on the surface, the inside of the image forming apparatus can be reduced from being contaminated with toner due to unfixed toner.
  Also, in this configuration, it is necessary to peel off the sheet recording material from the transfer carrier by lowering the applied voltage when the humidity at which the adsorption force is high is low compared to when the humidity at which the adsorption force is low is high. It is possible to suppress fluctuations in force.
[0018]
  (2) The toner image formed on the image carrier is transferred to a sheet recording material sucked and conveyed in the sheet conveyance direction on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device. When the conveyance of the sheet recording material is abnormal, the jam processing control means stops the conveyance operation of the sheet recording material in the fixing device and the sheet recording material on the transfer carrier,
  A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
  When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
  Slide means capable of pulling out the fixing device unitized with a side cover of the image forming apparatus main body in a sheet conveying direction by the transfer carrier;
  In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
  The jam processing control means includes:
  When the presence of a sheet recording material in the middle of conveyance is confirmed immediately after or after restarting the conveyance operation of the sheet recording material on the transfer carrier after carrying out a return operation after stopping the conveyance operation in the case of the conveyance abnormality In
  A sheet recording material on the transfer carrier is conveyed, at least a part of which is a position that spans an area of the fixing device and an area where the transfer carrier is located in the sheet conveyance direction, and the transfer carrier The sheet recording material on the transfer carrier is stopped at a position where the leading edge of the upper sheet recording material is engaged with the roller member of the fixing device, and the transfer is performed when the sheet recording material on the transfer carrier is conveyed. Sheet recording material on carrierThe application range of the transfer bias is reduced when the humidity near the transfer carrier is low than when the humidity near the transfer carrier is high.It is characterized by controlling.
[0019]
  In this configuration, for example, when a return operation such as taking out the sheet recording material remaining in the image forming apparatus after performing an abnormal stop (emergency stop) due to a conveyance abnormality such as a conveyance jam in the fixing unit is easy to overlook. When the sheet recording material left between the image carrier and the transfer carrier remains without being taken out, or when the sheet recording material is left undesirably difficult to take out, the image forming apparatus is tried to operate again. At that time, it is detected that the sheet recording material still remains in the image forming apparatus.
  At this time, the transfer bias applied to the sheet recording material when the sheet recording material is transported to a position where it can be easily taken out is controlled according to the environmental conditions, so that the sheet recording material can be reliably removed to a position where it can be easily taken out (without causing a conveyance failure). The sheet recording material can be taken out and adjusted so that the adsorption force to the sheet recording material can be easily peeled off from the transfer carrier, so that the sheet recording material can be taken out easily and reliably at all times. it can.
  Further, by the operation of pulling out the fixing device from the image forming apparatus, the sheet recording material sandwiched between the roller members of the fixing device is pulled out together, and the sheet recording material electrostatically adsorbed to the transfer carrier can be easily taken out. it can.
  In this configuration, when the sheet recording material is abnormally conveyed, the transfer carrier is separated from the image carrier excluding the specific image carrier, and the contact state between the image carrier and the sheet recording material is partially released to remove the sheet recording material. When transporting toward the area of the fixing unit, transfer to the sheet recording material of the toner image formed on the image carrier before jamming is reduced, and a transfer carrier by a transfer roller that forms a pair with the image carrier Can be applied to the sheet recording material more than necessary, making it easier to peel off the sheet recording material from the transfer carrier and gripping toner contamination and sheet recording material inside the device during jam processing. This makes it possible to reduce toner stains and the like, and to perform easy jam processing.
  Further, since the charge for adsorbing the sheet recording material to the transfer carrier can be appropriately supplied by the transfer roller paired with the image carrier not separated, the sheet recording material can be reliably conveyed to the area of the fixing device. . Further, if the transfer carrier is separated from the downstream side in the conveyance direction, the transfer carrier is prevented from excessively bending or jamming after the sheet recording material hits the fixing roller where the sheet recording material is stopped to prevent conveyance. Since the toner can be slid on the surface, the inside of the image forming apparatus can be reduced from being contaminated with toner due to unfixed toner.
  In this configuration, by reducing the application range when the humidity is low compared to when the humidity is high, it is possible to suppress fluctuations in the force required to peel off the sheet recording material from the transfer carrier.
[0020]
  (3) The toner image formed on the image carrier is transferred to a sheet recording material sucked and conveyed on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device. The image forming apparatus is configured to stop the image forming operation by the jam processing control means at the time of the conveyance abnormality,
  A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
  When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
  Slide means capable of pulling out the fixing device unitized with a side cover of the image forming apparatus main body in a sheet conveying direction by the transfer carrier;
  In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
  The jam processing control means includes:
  When the conveyance is abnormal, the conveyance operation of the sheet recording material on the transfer carrier is continued, and the sheet recording material existing in the upstream sheet recording material conveyance means including the transfer carrier is transferred to the fixing device in the sheet conveyance direction. And a position that spans the area and the area where the transfer carrier is located, and the leading edge of the sheet recording material on the transfer carrier is transported to a position where it is bitten by the roller member of the fixing device and stopped. Transfer bias applied to the sheet recording material on the transfer carrier,When the humidity near the transfer carrier is low, it should be set lower than when the humidity near the transfer carrier is high.It is characterized by.
[0021]
  In this configuration, the image forming apparatus can be returned by performing a single conveyance jam return operation, and the image forming operation is stopped while the sheet recording material is being conveyed in an abnormal sheet conveyance. The contamination in the image forming apparatus can be reduced, and the function and effect described in the item (1) can be obtained.
[0022]
  (4) The toner image formed on the image carrier is transferred to a sheet recording material sucked and conveyed on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device. The image forming apparatus is configured to stop the image forming operation by the jam processing control means at the time of the conveyance abnormality,
  A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
  When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
  Slide means capable of pulling out the fixing device unitized with the side cover of the image forming apparatus main body in the sheet conveying direction by the transfer carrier;
  In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
  The jam processing control means includes:
  When the conveyance is abnormal, the conveyance operation of the sheet recording material on the transfer carrier is continued, and the sheet recording material existing in the upstream sheet recording material conveyance means including the transfer carrier is transferred to the fixing device in the sheet conveyance direction. And a position that spans the area and the area where the transfer carrier is located, and the leading edge of the sheet recording material on the transfer carrier is transported to a position where it is bitten by the roller member of the fixing device and stopped. Sheet recording material on transfer carrierThe application range of the transfer bias is reduced when the humidity near the transfer carrier is low than when the humidity near the transfer carrier is high.It is characterized by controlling.
[0023]
  In this configuration, the image forming apparatus can be returned by performing a single conveyance jam return operation, and the image forming operation is stopped while the sheet recording material is being conveyed in an abnormal sheet conveyance. The contamination in the image forming apparatus can be reduced, and the function and effect described in the item (2) can be obtained.
[0024]
(5) The jam processing control means is characterized in that the application range is set only on the entire surface of the sheet recording material when the humidity is high, and only on the rear end side in the conveyance direction of the sheet recording material when the humidity is low.
[0025]
In this configuration, by reducing the application range when the humidity is low compared to when the humidity is high, it is possible to suppress fluctuations in the force required to peel off the sheet recording material from the transfer carrier. Since at least the rear end of the sheet recording material can always be given an attracting force, it can be reliably conveyed even if the conveyance amount is large.
[0033]
  (6) The switching means
  When the conveyance abnormality occurs, the transfer carrier starts separating operation before the transfer of the sheet recording material by the transfer carrier stops.
  The rotation of the image carrier separated from the transfer carrier is stopped, and the rotation of the image carrier in contact with the transfer carrier in the image carrier is stopped in accordance with the stop of conveyance of the transfer carrier. It is characterized by being stopped.
[0034]
In this configuration, when the conveyance of the sheet recording material is abnormal, the transfer carrier is separated from the image carrier, the contact state between the image carrier and the sheet recording material is released, and the sheet is conveyed to the fixing unit area. Stop conveyance. During this time, by stopping the rotation of the image carrier that is not in contact with the sheet recording material (or transfer carrier), unnecessary rotation of the image carrier that is not in contact is stopped, and the life of the image carrier is reduced. Can be extended. Further, the image carrier that is in contact with the sheet recording material or the transfer carrier is kept rotating until the sheet recording material (or the transfer carrier) is stopped, so that it is rubbed by the sheet recording material or the transfer carrier. Therefore, shortening of life is prevented.
[0035]
  (7) A multicolor mode in which an image is formed using all the image carriers and a single color mode in which an image is formed using a specific image carrier among the image carriers are selectable. ,
  The jam processing control means sets the contact state of the image carrier and the transfer carrier to the state of the monochromatic mode when a sheet recording material conveyance abnormality is detected in the multicolor mode.
[0036]
In this configuration, when the sheet recording material is abnormally conveyed, the contact state between the transfer carrier and the image carrier is set to the monochromatic mode, so that the transfer carrier is separated from many image carriers. It becomes easy to take out the jam, and the jam handling work becomes easy.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0038]
<Image forming apparatus>
FIG. 1 shows the configuration of an image forming apparatus. This image forming apparatus is multicolored or single-colored for a predetermined sheet recording material (recording paper, hereinafter referred to as a sheet) according to image data transmitted from the outside. The exposure unit 1, the developing device 2, the photosensitive drum (image carrier) 3, the charger 5, the cleaner unit 4, the transfer transport belt unit 8, the fixing unit 12, the paper transport path S, A paper feed tray 10 and a paper discharge tray 15 are provided.
[0039]
Image data handled in this image forming apparatus corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, the exposure unit 1 (1a, 1b, 1c, 1d), the developing device 2 (2a, 2b, 2c, 2d), the photosensitive drum 3 (3a, 3b, 3c, 3d), and the charger 5 (5a, 5b, 5c, 5d) and the cleaner unit 4 (4a, 4b, 4c, 4d) each form four image stations Pa (black), Pb (cyan), Pc (in order to form four types of latent images corresponding to the respective colors. Magenta) and Pd (yellow) are set.
[0040]
The photosensitive drum 3 is disposed almost at the center of the image forming apparatus, and the charger 5 is a charging unit for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to roller-type and brush-type chargers, charger-type chargers are used as shown in the figure.
[0041]
The exposure unit 1 uses, for example, an LED writing head in which light emitting elements are arranged in an array, or a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror described in the drawings. The photosensitive drum 3 charged by the charger 5 is exposed by the exposure unit 1 according to the image data, whereby an electrostatic latent image corresponding to the image data is formed on the surface.
[0042]
The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with (K, C, M, Y) toner. The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum after development and image transfer.
[0043]
The transfer conveyance unit 8 disposed below the photosensitive drum 3 includes a transfer belt 7, a transfer belt driving roller 71, a transfer belt tension roller 73, a plurality of transfer belt driven rollers 72 and 73, and a transfer roller 6 (6a and 6b). , 6c, 6d) and a transfer belt cleaning unit 9. The transfer belt drive roller 71, the transfer belt driven rollers 72 and 74, and the transfer belt tension roller 73 stretch the transfer belt 7 and rotate the transfer belt 7 in the direction of arrow B.
[0044]
The transfer roller 6 is rotatably supported by a housing (not shown) inside the transfer conveyance unit 8, and is transferred together with the transfer belt drive roller 71, the transfer belt driven rollers 72 and 74, and the transfer belt tension roller 73. The belt 7 is stretched. The transfer roller 6 transfers the toner image on the photosensitive drum 3 to a sheet that is attracted and conveyed on the transfer belt 7.
[0045]
The transfer belt 7 is formed endlessly using a film having a thickness of about 100 to 150 μm, and is provided so as to be detachable from each photosensitive drum 3. In the multi-color mode in which the transfer belt 7 forms an image by contacting all of the photosensitive drums 3 (see FIG. 9), the toner images of the respective colors formed on the photosensitive drums 3 are sequentially superimposed on the sheet. It has a function of forming a color toner image (multicolor toner image) by transferring.
[0046]
In the single color mode in which the transfer belt 7 is brought into contact with only the photosensitive drum 3a and separated from the other photosensitive drums 3b, 3c, 3d to form an image (see FIG. 10) (see FIG. 10), a black toner image ( It has a function of forming a monochrome image by transferring a single color toner image) to a sheet.
[0047]
The switching operation of the transfer belt 7 between the two modes is performed by the switching means 38 as shown in FIGS. That is, the switching unit 38 causes the cam 43 rotated by a driving source such as a stepping motor (not shown) to slide in contact with the support piece 50 of the transfer conveyance unit 8, so that the transfer roller 6 a provided in the housing of the transfer conveyance unit 8. The transfer conveyance unit 8 is configured to rotate up and down around a fulcrum shaft provided at a position where the axis of the shaft is extended.
[0048]
The transfer of the toner image from the photosensitive drum 3 to the sheet (recording paper) is performed by the transfer roller 6 (6a, 6b, 6c, 6d) in contact with the back side of the transfer belt 7. Each transfer roller 6 has a high voltage (high voltage opposite to the toner charging polarity (-)) (high voltage opposite to the toner charging polarity (-)) or a sheet conveyance jam for transferring a toner image. An AC high voltage for neutralizing the transfer belt 7 is applied according to the situation at the time of occurrence.
[0049]
The transfer roller 6 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). By this conductive elastic material, a high voltage can be uniformly applied to the sheet.
[0050]
Further, the toner adhering to the transfer belt 7 from the photosensitive drum 3 causes the back surface of the sheet to become dirty, and is removed and collected by the transfer belt cleaning unit 9.
[0051]
The paper feed tray 10 is a tray for storing sheets (recording paper) used for printing, and is provided below the image forming unit of the image forming apparatus. A paper discharge tray 15 provided in the upper part of the image forming apparatus is a tray for placing printed sheets face down. A paper discharge tray 33 provided on the side of the image forming apparatus is a tray for placing printed sheets face up.
[0052]
In addition, the image forming apparatus is provided with an S-shaped paper conveyance path S for sending the sheets in the paper feed tray 10 to the paper discharge tray 15 via the transfer conveyance unit 8 and the fixing unit 12. . Further, in the vicinity of the sheet conveyance path S from the sheet feed tray 10 to the sheet discharge tray 15 and the sheet discharge tray 33, a pickup roller 16, a registration roller 14, a fixing unit 12, a conveyance direction switching gate 34, a conveyance roller 25, and the like. It is arranged.
[0053]
The conveyance rollers 25 are small rollers for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 25 are provided along the sheet conveyance path S. The pickup roller 16 is a pull-in roller that is provided at the end of the paper feed tray 10 and supplies sheets from the paper feed tray 10 to the paper transport path S one by one.
[0054]
The conveyance direction switching gate 34 is rotatably provided on the side cover 35, and separates the sheet from the middle of the sheet conveyance path S by switching from the position state indicated by the solid line to the position state indicated by the broken line, and is placed on the sheet discharge tray 33. Discharge.
[0055]
On the other hand, in the position state indicated by the solid line, the sheet passes through the conveyance unit S ′ (part of the sheet conveyance path S) formed between the fixing unit 12, the side cover 35, and the conveyance switching guide 34 and is discharged at the upper part. It is discharged to the paper tray 15.
[0056]
Further, the registration roller 14 disposed on the most upstream side of the transfer belt 7 temporarily holds the sheet being conveyed through the sheet conveyance path S. The sheet has a function of transporting the sheet with good timing in accordance with the rotation of the photosensitive drum 3 so that the toner image on the photosensitive drum 3 can be satisfactorily transferred onto the sheet.
[0057]
That is, based on the detection signal output from the sheet detector A, the registration roller 14 is set to convey the sheet so that the leading edge of the toner image on each photosensitive drum 3 is aligned with the leading edge of the printing range on the sheet. To do. The sheet detector A monitors the sheet conveyance timing. Sheet jam detection or the like is performed based on the signal from the sheet detector A.
[0058]
The fixing unit 12 includes a heat roller 31, a pressure roller 32, and the like, and the heat roller 31 and the pressure roller 32 rotate with a sheet interposed therebetween. Further, the heat roller 31 is controlled to turn on and off a heater lamp (not shown) based on an output value of a temperature detector (not shown) so as to reach a predetermined fixing temperature. The single color toner image or the multicolor toner image transferred to the sheet is melted, mixed, and pressed to be thermally fixed to the sheet.
[0059]
The sheet on which the toner image has been fixed by the fixing unit 12 is selectively discharged onto the discharge tray 33 or 15 by the transport rollers 25. At this time, the sheet detector B, the sheet detector C, a sheet detector (not shown) and the like monitor the conveyance state of the sheet after fixing.
[0060]
Here, a color image forming apparatus is described, but a color image forming apparatus having a single image forming station (monochrome image forming apparatus) may be used. In the present embodiment, the image forming apparatus main body is placed on a paper feed desk device having a three-stage paper feed tray. A paper feeding device may be selected.
[0061]
《Configuration for jam processing》
In the image forming apparatus configured as described above, in the present embodiment, in order to efficiently and easily and reliably perform jam processing when a paper jam (conveyance jam) occurs during conveyance of a sheet, A control unit having a jam processing control unit for controlling the transfer bias according to environmental conditions is provided, and the following configuration is adopted.
[0062]
First, as shown in FIG. 2, the fixing unit 12 unitized with the side cover 35 provided with the paper discharge tray 33 by the slide members 36 provided laterally on the front and rear sides of the image forming apparatus main body is transferred to the transfer conveyance belt unit 8. Can be pulled out toward the downstream side in the conveying direction (sheet conveying direction) (see FIG. 11). At the time of jam processing, the transfer belt 7 can be separated from all the photosensitive drums 3 in conjunction with the operation of pulling out the fixing unit 12 together with the side cover 35 from the main body of the image forming apparatus. It is configured to be able to return to the original state in conjunction with the storage operation.
[0063]
That is, in the present embodiment, a separation / contact mechanism (for separating / contacting) the transfer belt 7 supported by the transfer belt unit (transfer carrier device) 8 with respect to all the photosensitive drums 3 (3a to 3d). The connecting / disconnecting mechanism R) is linked to the slide operation (see FIG. 11) of the slide member 36 integral with the fixing unit 12 and transfers a cam mechanism (not shown) provided on the slide member 36 by transfer. By engaging the unit 8 and the switching means 38, the transfer belt 7 can be separated from all the photosensitive drums 3 and returned to the original state in conjunction with the storing operation of the fixing unit 12. It is configured to be able to.
[0064]
The above-described slide member 36 preferably uses, for example, a high-accuracy slide bearing such as an aclide to support the relatively heavy fixing unit 12 with high accuracy so that it can move smoothly. Other slide means may be used as long as high-precision positioning is possible when 12 is returned to a predetermined position of the image forming apparatus main body.
[0065]
In the present embodiment, the transfer conveyance unit 8 including the transfer belt 7 is provided in the housing portion of the transfer conveyance unit 8 located at an extension of the shaft of the upstream transfer roller 6a as described above. A fulcrum shaft (not shown) is used as a center of rotation, and the downstream side is rotatably supported with respect to the image forming apparatus main body. 9 is switched to the multicolor mode state shown in FIG. 9 and the single color mode state shown in FIG. 10 where the downstream portion is lowered and only the photosensitive drum 3 a is in contact with the transfer belt 7. In addition to the above-described sheet detector A, sheet detector B, and sheet detector C, a plurality of similar sheet detectors are provided in the conveyance path S as detection means for detecting the position of the sheet being conveyed. ing.
[0066]
The control by the jam processing control unit based on the detection timing of the sheet detector A disposed upstream of the fixing unit 12 has been described with reference to the flowcharts of FIGS. The sheet detector B and the sheet detector C arranged on the downstream side detect the discharge state of the sheet to the paper discharge tray 33 and the paper discharge tray 15, and in addition to the sheet detector A, the sheet detector B and the sheet The same control can be performed using the detector C.
[0067]
As shown in FIG. 12 showing a control system block diagram of the image forming apparatus, the jam processing control means is provided as a jam processing control unit 100a in a control unit composed of a CPU, a ROM, and a RAM. A, B, and C are connected. Further, on the output side, a driving source for driving the transfer belt 7, a transport mechanism unit including a clutch of a registration roller 14 as a sheet transport unit on the upstream side of the transfer belt 7, and a transfer belt unit 8 are provided. A separation / contact mechanism (including separation / contact means R and switching means 38) for separating / contacting the photosensitive drum 3 (3a to 3d) is connected, and power is supplied to the transfer roller 6. High-voltage power supplies 60a to 60d (transfer section) are also connected. In the present invention, the sheet conveying means on the upstream side of the transfer belt 7 is not limited to the registration roller 14, and is provided in the conveying path S on the upstream side of the transfer belt 7 as described later. A sheet conveying roller may be included in the sheet conveying means.
[0068]
The transfer bias control (voltage control) according to the environmental conditions described above is performed based on experimental results on the relationship between the transfer bias and the jam processing. The experiment was performed by dividing the environmental conditions into two cases of normal temperature and normal humidity (NN) and low temperature and low humidity (LL), and experimental results as shown in Table 1 were obtained. The environment detector E is installed near the image forming process unit and detects the humidity and temperature, for example, avoiding the vicinity of the fixing unit 12 where the temperature and humidity in the image forming apparatus tend to change relatively rapidly. (See FIG. 1).
[0069]
[Table 1]

[0070]
As shown in Table 1, when the environmental conditions are normal temperature and normal humidity (NN) (temperature 25 ° C., humidity 50%), when the transfer voltage is set to 2 KV or 3 KV, “easy to peel” and “transportability” And good results were obtained for “dirt on the periphery”. With other settings (0 KV and 0.5 KV), there was a problem in “easy to peel” and “transportability”.
[0071]
On the other hand, in the case of low-temperature and low-humidity (LL) (temperature 5 ° C., humidity 30%), the adsorbing power corresponding to the transfer voltage becomes large. Therefore, it is preferable to lower the transfer voltage than in the case of room temperature and normal humidity (NN). , 0. When it was set to 5 KV, good results were obtained with respect to “easy stripping”, “transportability”, and “dirt on the periphery”. At other settings (2 KV, 3 KV), there was a problem in “ease of peeling”, and at 0 KV, there were problems in “ease of peeling” and “transportability”.
[0072]
From the above results, the transfer voltage is 2 KV in the case of normal temperature and humidity, and 0. It is preferably set to 5 KV. As shown in FIG. 4, L is the distance between the most downstream transfer belt drive roller 71 and the heat roller 31, and L 'is from the transfer belt drive roller 71 to the leading edge of the sheet. Each distance.
[0073]
The transfer bias at the time of image formation is adjusted so that a good image can be formed by adjusting the image quality, but if it matches the voltage preset according to the environmental conditions at the time of jam occurrence, the transfer bias at the time of image formation However, if they are different, the voltage is switched to a preset voltage. When the transfer carrier is stopped, the transfer bias is turned off.
[0074]
Furthermore, in this embodiment, the application range of the transfer bias to the sheet is also controlled according to the environmental conditions. In the experiment on the relationship between the application range and the jam treatment, as shown in Table 2, the environmental conditions are divided into three categories: high temperature and high humidity (HH), normal temperature and normal humidity (NN), and low temperature and low humidity (LL).
[0075]
[Table 2]

[0076]
In the case of high temperature and high humidity (HH) (temperature 35 ° C., humidity 85%), when the application range was set to “entire surface of sheet”, good results were obtained for “easiness of peeling” and “conveyability”. When set to “50 mm on the rear end side of the sheet”, there was a problem with “easiness of peeling” and “conveyability”.
[0077]
In the case of room temperature and normal humidity (NN) (temperature 25 ° C, humidity 50%), if the application range is set to "50 mm on the rear end side of the sheet", good results are obtained for "easy to peel" and "conveyability". However, there was a slight problem with “easiness of peeling” when set to “entire sheet”.
[0078]
In the case of low temperature and low humidity (LL) (temperature 5 ° C., humidity 30%), good results were obtained for “easiness of peeling” and “conveyability” when the application range was set to “sheet rear end side 50 mm”. However, when it was set to “entire sheet surface”, there was a problem in “easy to peel off”.
[0079]
From the above results, it is preferable to set the transfer bias application range to “entire surface of sheet” in the case of high temperature and high humidity, and to “sheet rear end side 50 mm” in normal temperature and normal humidity and low temperature and low humidity. However, it goes without saying that the range may be set to a more appropriate range according to the characteristics of the image forming apparatus and the type of sheet recording material to be used. For L and L ′, as shown in FIG. 4, L is the distance between the transfer belt drive roller 71 and the heat roller 31, L ′ is the distance from the transfer belt drive roller 71 to the leading edge of the sheet, Each is shown.
[0080]
By the way, when performing the jam processing operation, as described above, the fixing unit 12 is pulled out from the main body of the image forming apparatus to open the fixing unit 12 to the outside, and the jam processing can be performed from both the front and rear sides. If the sheet remains between the upstream side photosensitive drum 3 and the transfer belt 7 because the open portion becomes an access from the side to the image forming portion where the jam has occurred, Is often difficult to find.
[0081]
In particular, small sheets are often overlooked. Therefore, at the time of jam processing, the jam processing control means is also considered in consideration of the above experimental results so that the sheet stagnating at the upstream position which is difficult to find can be surely found and easily removed. Thus, the following transfer bias is controlled. Note that this jam processing describes the control of the jam processing in the multi-color mode using all the photosensitive drums 3.
[0082]
That is, for example, as shown in the flowchart of FIG. 13, when a jam occurs after the start of the image forming operation, all operations related to image formation (for example, writing operation to the photosensitive drum 3 by the exposure unit 1, photosensitive operation) The rotating operation of the body drum 3, the charging operation by the charger 5, the developing operation by the developing device 2, the application operation of the transfer bias by the transfer roller 6, the conveying operation of the sheet recording member, the fixing operation of the fixing unit, etc. are stopped urgently ( Simultaneously with s1 to s3), the switching means 38 is operated to separate the transfer belt 7 from the photosensitive drums 3b, 3c, 3d except for the photosensitive drum 3a (s4). This is to cut off the supply of electric charges from the photosensitive drums 3b, 3c, and 3d that also act to adsorb the sheet to the transfer belt 7 and to reduce the force when peeling off the sheet to be performed later from the transfer belt 7 as much as possible. is there.
[0083]
Note that, when the reversal development method is used, out of all the operations for emergency stop in the above-described step s3, the operations of the charger 5 are necessary operations regardless of image formation when the photosensitive drum 3 rotates. There is a charging operation. This is because when the photosensitive drum 3 rotates, the developer adheres unless the photosensitive drum 3 is charged. Therefore, when the photosensitive drum 3 is also rotated along with the sheet recording material conveyance operation in S9 (and S9 ′ in FIG. 14) and the like, the charging operation of the charger 5a is performed on the rotating photosensitive drum 3a. I am doing so.
[0084]
Further, although the case where the transfer belt 7 is separated from the photosensitive drums 3b, 3c, 3d excluding the photosensitive drum 3a in step s4 has been described, the transfer bias of the transfer rollers 6b, 6c, 6d is not required. The same effect can be obtained by turning off or setting to an appropriate value.
[0085]
In step s4 described above, after the transfer belt 7 is separated from the photosensitive drums 3b, 3c and 3d excluding the photosensitive drum 3a, a jam occurrence is displayed on the operation unit, and the operator performs jam processing (returning operation). (S5). In the returning operation, the fixing unit 12 is pulled out from the main body of the image forming apparatus, and the transfer / conveying belt unit 8 is moved again by the operation, so that the photosensitive drum 3a and the transfer belt 7 are completely separated (by the contact / separation mechanism). To be done. By this returning operation, for example, as shown in FIG. 3, the sheet wound around the heat roller 31 can be removed. The completely separated state is shown in FIG. 5, FIG. 6 (b), FIG. 7 (b), and FIG. 8 (b).
[0086]
This jam processing is performed as a control that is performed, for example, when a sheet does not reach a detector (for example, sheet detector B) located downstream of the fixing device and it is determined that a jam has occurred in the fixing unit 12. After the jam processing is completed, the fixing unit 12 is inserted into the image forming apparatus main body, and the transfer conveyance belt unit 8 is returned to the state before the fixing unit 12 is pulled out. In step s3, the power supply to the heater of the fixing unit 12 is turned off for safety.
[0087]
Next, based on the information obtained when the state of the sheet detector A was monitored at the time of the previous jam occurrence in step s6, it is determined whether there is another sheet on the transfer belt that has passed the sheet detector A. To be judged. In step s7, it is determined whether or not there is a sheet sandwiched between the registration rollers 14 by the sheet detector A. If it is determined in step s6 or s7 that the sheet exists, the transfer bias application voltage is set according to the environmental conditions, and the transfer bias is applied to the sheet (s8).
[0088]
Next, in step s9, the sheet conveying operation is started while the fixing unit 12 is stopped. In step s10, the sheet is caught in the roller members 31 and 32 of the fixing unit 12 (easy to take out) (see FIG. 4). The conveyance of the sheet is stopped in the state of the sheet indicated by a broken line) or the state before the bite into the roller members 31 and 32 (the state of the sheet indicated by the solid line in FIG. 4). In the sheet conveyance operation, the sheet can be reliably conveyed by applying a transfer bias according to the environmental conditions to the transfer belt 7.
[0089]
At this time, the state where the transfer belt 7 is separated from the photosensitive drum 3 is maintained, and the supply of electric charges from the photosensitive drums 3b, 3c, and 3d, which also serves to attract the sheet to the transfer belt 7, is cut off. This is to reduce the force when peeling off the sheet to be performed later from the transfer belt 7 as much as possible.
[0090]
In this example, since the transfer bias according to the environmental conditions is applied to the transfer belt 7, even if the environmental conditions become severe, the conveyance of the sheet recording material is not caused, and the sheet recording material is conveyed by a predetermined conveyance amount. Then, in step s11, the operator opens the fixing unit 12 and performs jam processing (return operation) again.
[0091]
At this time, since the transfer belt unit 8 is moved to a position away from all the photosensitive drums 3 by the separation / contact mechanism interlocked with the opening operation of the fixing unit 12, as shown in FIG. This makes it easy to grip the tip of the paper and can easily jam. Immediately after the occurrence of the jam, the application of the transfer bias to the transfer roller 6 is stopped, and the transfer belt 7 is separated from the photosensitive drums 3b, 3c, 3d, so that the sheet adsorbed on the transfer belt 7 is adsorbed. The fact that the sheet is easily peeled off from the transfer belt 7 because the force is reduced greatly contributes to the ease of the jam processing.
[0092]
When the fixing unit 12 is returned to its original state after the jam processing, the process returns to step s7, and the sheet detector A detects the sheet retention again. If there is no sheet retention, the process proceeds to step s12 to operate the switching means 38 to operate the transfer belt. 7 is brought into contact with all the photosensitive drums 3. Thereafter, a pre-rotation operation (preparation work such as cleaning of the photosensitive drum 3 and the transfer belt 7), which is a preliminary operation of the process unit, is started in step s13. If the pre-rotation operation is completed in step s14, the process proceeds to step s15. Then, the ready lamp of the operation unit is turned on to enter a standby state in a state where an image can be formed.
[0093]
On the other hand, if it is determined in step s6 that there is no sheet staying on the transfer belt, and if no sheet is detected by the sheet detector A in step s7, it is determined that the jam processing has been completed, and step s12. Then, the transfer belt 7 is brought into contact with all of the photosensitive drum 3. Thereafter, the process proceeds to steps s13 and 14 and waits for the end of the above-mentioned pre-rotation operation to turn on the ready lamp indicating that the image formation preparation is completed (s6 to s15). In this embodiment, the ready lamp is turned on to prompt the restart of the operation. However, the image forming operation may be automatically restarted.
[0094]
As described above, if there is a subsequent sheet remaining on the upstream side of the image forming apparatus after the fixing unit 12 is pulled out from the main body of the image forming apparatus and once jammed, this position can be easily removed on the downstream side. , The jamming process is performed again, so that the return operation can be completed with certainty without leaving the sheet. The position where the sheet can be easily taken out may be, for example, a position where at least a part of the sheet extends over the area of the fixing unit 12 and the area of the transfer belt 7.
[0095]
If it is determined that the jam has occurred, the driving of the upstream sheet conveying unit including the inner registration roller 14 of the upstream sheet conveying unit is stopped. However, if there is a sheet that is caught by the registration roller 14 and enters the area of the transfer belt 7, until the leading end of the transfer belt 7 is caught by the roller members 31 and 32 of the fixing unit 12, or the sheet is caught. It is transported to the front. At this time, the registration roller 14 is driven to rotate by a one-way clutch (not shown) provided between the driving roller of the registration roller 14 and a driving system (not shown). Further, a roller holding the upstream sheet including the registration roller 14 may be driven.
[0096]
Further, in order to carry out the subsequent sheet staying upstream at the time of emergency stop more reliably during the second jam processing described above, for example, as shown in the control flow of FIG. Accordingly, after applying the transfer bias to the sheet and applying the transfer bias to the sheet (s8 ′), before starting the rotation of the fixing unit 12 and stopping the sheet conveyance operation when starting the sheet conveyance operation. After the transfer belt 7 is rolled (s9 ') for a predetermined time, for example, as long as it takes for the sheet to be caught by the fixing rollers (roller members) 31 and 32, as shown in FIG. 6 (a). Alternatively, the sheet conveyance operation may be stopped (s10 ′) to perform jam processing.
[0097]
In this case, when the fixing unit 12 is pulled out from the main body of the image forming apparatus, as shown by a solid line in FIG. 6B, the sheet caught by the fixing rollers 31 and 32 can be easily pulled out from the image forming apparatus. The operation of peeling off the sheet from the transfer belt 7 can be easily performed. In this way, by setting the sheet conveyance process of s9 ′ to 10 ′, in particular, a state where a small-sized sheet is caught in the rollers 31 and 32 of the fixing unit 12 without dropping into the image forming interior. Can be reliably carried out to a position where it can be easily taken out.
[0098]
The above-described jam processing performed in a plurality of times is particularly effective when a jam occurs in the fixing unit 12, and the sheet abnormally generates heat and generates scorching or smoke. Therefore, the operation has been described as the case where the image forming apparatus is urgently stopped and the fixing unit is immediately pulled out to perform jam processing. However, jam processing may be performed in a portion other than the fixing unit 12.
[0099]
The next example is a case where the rotation operation of the sheet conveying means on the upstream side of the fixing unit 12 is not immediately stopped when the occurrence of a jam is detected. For example, as shown in FIG. 15, when a jam occurs after the start of the image forming operation (s21 to s22), the image forming operation (the writing operation to the photosensitive drum 3 by the exposure unit 1, the developing operation by the developing device 2, etc.) ) And the operation of the fixing unit (heating operation by the heater, rotation operation of the rollers 31 and 32) are stopped (s23). Next, the transfer bias application voltage is set according to the environmental conditions, and the transfer bias is applied to the sheet (s24). Note that the image forming operation in step s23 (and s43) refers to the exposure operation by the exposure unit 1 and the development operation by the developing device 2, and the stop of the developing operation of the developing device 2 is the application control of the developing bias or the developing device. This is performed by controlling the distance (separation) of the second photosensitive drum 3.
[0100]
Further, the switching means 38 is operated to rotate and move the transfer / conveying unit 8 to separate the transfer belt 7 from the photosensitive drums 3b, 3c, 3d (s25). As described above, this is to reduce the adsorption force of the sheet to the transfer belt 7 as much as possible so that the sheet can be easily peeled off from the transfer belt 7, and has already been formed on the photosensitive drums 3b, 3c, and 3d. This is also for preventing the transferred image from being transferred to the sheet.
[0101]
At the same time, the application of the transfer bias to the transfer rollers 6b, 6c, 6d is also stopped (s26). This is to reduce the adsorption force of the sheet to the transfer belt 7. At this time, if it is difficult to reduce the adsorption force of the sheet to the transfer belt 7, the application of the high voltage to the transfer rollers 6b, 6c and 6d described above is switched to the AC high voltage output to actively reduce the adsorption force. You may let them.
[0102]
Subsequently, the sheet adsorbed and carried on the transfer belt 7 is continuously conveyed in a non-contact state with the photosensitive drums 3b, 3c, and 3d, and the time until the leading edge of the sheet sufficiently enters the area of the fixing unit 12 is reached. Then, after the conveyance of the sheet by the transfer belt 7 is continued, the conveyance of the sheet is stopped (s28 to s29). This is because when the two sheets are conveyed on the transfer belt 7, the leading sheet and the succeeding sheet are collected before the roller members 31 and 32 of the transfer unit 12 and simultaneously (at a time). This is for jam processing.
[0103]
At this time, when the succeeding sheet is sandwiched between registration rollers 14 or the like which are conveying means located downstream, the sheet is smoothly conveyed by driving the roller member.
[0104]
That is, the sheet forming operation is completely performed when the image forming operation and the rotation operation of the fixing unit 12 are stopped immediately after the jam occurs and the state shown in FIG. Stop. In step s30, a return operation is performed. That is, as shown in FIG. 7B, the operator first pulls out the fixing unit 12 from the main body of the image forming apparatus to move the transfer conveyance unit 8 further by the interlocking contact / separation mechanism. It is separated from all the photosensitive drums 3. Then, as described above, the returning operation (jam processing) for taking out two sheets is performed. After the jam processing is completed, the fixing unit 12 is inserted into the main body of the image forming apparatus, and the transfer conveyance unit 8 is returned to the original state (a state where only the photosensitive drum 3a is in contact with the transfer belt 7).
[0105]
Next, in step s31, the sheet detector A checks whether or not the sheet stays on the registration roller 14, and if the sheet stays, the sheet staying is the same as described above in steps s36 to s37. The sheet is conveyed until the leading end enters the area of the fixing unit 12 or sufficiently enters, and the operator performs the returning operation again in step s38.
[0106]
After the return operation, the process returns to step s31 again, and the staying state of the sheet is confirmed. If no sheet retention is recognized in step s31, it is determined that the return operation (jam processing) has been completed, and the process proceeds to step s32 where the transfer belt 7 is brought into contact with all the photosensitive drums 3.
[0107]
Thereafter, in step s33, a pre-rotation operation (preparation work such as cleaning of the photosensitive drum 3 and the transfer belt 7), which is a preliminary operation of the process unit, is started. If the pre-rotation operation is completed in step s34, step s35 is completed. Then, the ready lamp of the operation unit is turned on to enter a standby state in which image formation is possible.
[0108]
The flow from step s31 to steps s36 to s38, s31 is an operation performed just in case, and is the same as the operation to return to steps s8 to s10, s7 described above, so the description thereof is omitted.
[0109]
Next, in the example shown in FIG. 16, when a jam occurs, a plurality of sheets are present on the transfer belt 7 in order to perform the jam processing more efficiently and reliably. The leading sheet is held by the rollers 31 and 32 of the fixing unit 12, the conveyance is stopped so as not to be conveyed downstream from the fixing unit 12, and the subsequent sheets are collected before the rollers 31 and 32 of the fixing unit 12. Jam processing is performed.
[0110]
The control flow will be described. When occurrence of a jam is detected after the start of the image forming operation (s41, s42), first, in step s42, the image forming operation (to the photosensitive drum 3 by the exposure unit 1) is performed. The writing operation, the developing operation by the developing device 2, etc.) are stopped. At this time, the operation of the fixing unit 12 may stop the heating operation by the heater, but the rotation operation of the rollers 31 and 32 is continued to continue the sheet conveyance (s43). In step s44, the transfer bias application voltage is set according to the environmental conditions, and the transfer bias is applied to the sheet. In step s43, since the image forming operation is stopped while the sheet conveying operation is continued, the contamination in the image forming apparatus can be reduced during the jam processing.
[0111]
Next, in step s45, the switching unit 38 is operated to rotate the transfer conveyance unit 8, and the transfer belt 7 is separated from the photosensitive drums 3b, 3c, 3d. This is because, as described above, to reduce the adsorption force of the sheet to the transfer belt 7 as much as possible so that the sheet can be easily peeled off from the transfer belt 7, the image already formed on the photosensitive drums 3b, 3c, and 3d This is also to prevent the image from being transferred. At the same time, application of the transfer bias to the transfer rollers 6b, 6c, 6d is also stopped in step s45 (s46).
[0112]
At this time, an AC high voltage may be applied to the transfer rollers 6b, 6c, and 6d so as to positively reduce the attractive force. This is to reduce the suction force when the suction force of the sheet to the transfer belt 7 is too high.
[0113]
Then, the rotation of the separated photosensitive drums 3b, 3c, and 3d is stopped (s47), the sheet is conveyed by a predetermined amount (s48), and the conveyance of the sheet by the transfer belt 7 or the like is stopped (s49).
[0114]
Next, in step s50, the return operation is performed in the same manner as described above. The sheet is stopped in the state shown in FIG. 8A, and the returning operation can be easily performed by pulling out the fixing unit 12 as shown in FIG. 8B. Stopping of the conveyance of each sheet at this time is controlled by a timer based on the sheet detector A, but may be detected by the sheet detector B or the sheet detector C located upstream of the sheet.
[0115]
That is, first, only the image forming operation is stopped (the fixing roller is driven), and after the sheet is detected by the sheet detector B and the sheet detector C, based on the detection timing by the sheet detector A, that is, The operation of the fixing unit 12 is stopped after a predetermined time elapses, and further, the sheet conveying operation is completely stopped after a predetermined time elapses. Thereafter, the fixing unit 12 is connected to the image forming apparatus. Pulling out from the main body and interlocking the separation / contact mechanism, the transfer conveyance unit 8 is moved to a position away from all the photosensitive drums 3 to perform a return operation (jam processing) (s43 to s50).
[0116]
FIG. 8A shows that the image forming operation is stopped when the occurrence of a jam is detected in step s42 described above, and then the operation of the fixing unit 12 is stopped after the sheet is conveyed by a predetermined amount in step s48. This is because the leading sheet is caught in the roller members (31, 32) of the fixing unit 12 as shown in FIG. At this time, the succeeding sheet (refer to the broken line) is in a position before being bitten by the roller members (31, 32), and is further conveyed so as to abut against the roller members (31, 32) of the fixing unit 12. Can be transported.
[0117]
In this way, the leading sheet is held in the roller members (31, 32), and the succeeding sheet is conveyed to the fixing unit 12, so that the leading and succeeding sheets are removed when the fixing unit 12 is pulled out. It can be taken out at the same time, and the jam processing can be completed at one time.
[0118]
Further, steps s51 to s58 after step s51 are the same as the contents described in steps s7 to s14 and s30 to s37 described in the above-described method, and the description thereof is omitted. Further, steps s52 to s55 are also the same as those described above, and the description thereof is omitted.
[0119]
Further, when the transfer bias application range is controlled (see Table 2), for example, as shown in FIG. 17, when a jam occurs after the start of the image forming operation (s61 to s62), the image forming operation (exposure) is performed. The writing operation of 3 on the photosensitive drum by the unit 1 and the developing operation by the developing device 2 and the operation of the fixing unit (heating operation by the heater, rotating operation of the rollers 31 and 32) are stopped (s63). Next, a transfer bias application range may be set according to the environmental conditions, and the transfer bias may be applied to the range (s64). The subsequent steps are the same as those after step s25 in FIG.
[0120]
Further, for example, as shown in FIG. 18, when the occurrence of a jam is detected after the start of the image forming operation (s81, s82), first, in step s82, the image forming operation (the photosensitive member by the exposure unit 1) is first performed. The writing operation to the drum 3 and the developing operation by the developing device 2 are stopped. At this time, the operation of the fixing unit 12 may stop the heating operation by the heater, but the rotation operation of the rollers 31 and 32 is continued to continue the sheet conveyance (s83). Next, in step s84, a transfer bias application range may be set according to the environmental conditions, and the transfer bias may be applied to the range (s84). The subsequent steps are the same as those after step s45 in FIG.
[0121]
As described above, according to the present invention, during the jam processing, the sheet is moved to the position where the sheet is easily taken out and moved to the position where the sheet is easily taken out, and the transfer bias is controlled according to the environmental conditions or the transfer bias is applied. By controlling the range, it is possible to easily and reliably perform jam processing.
[0122]
The present invention is not limited to the embodiment described above, and design changes and improvements can be freely made as necessary without departing from the spirit of the invention. That is, in the present embodiment, when a sheet jam occurs, the transfer belt 7 is separated from the photosensitive drums 3b, 3c, and 3d to convey the sheet, but the sheet is conveyed without being separated. However, it goes without saying that by controlling the application voltage of the transfer bias to the transfer roller 6, it is possible to control the adsorption force of the sheet to the transfer belt 7 and obtain the same effect. However, if an image is already formed on the photosensitive drums 3b, 3c, and 3d, the image is transferred to the sheet. Therefore, after the jam occurs, the transfer belt 7 is moved from the photosensitive drums 3b, 3c, and 3d. It is preferable to convey the sheet while being separated.
[0123]
The image forming apparatus is not limited to the configuration shown in FIGS. 1 and 2, and a fixing device that transfers a toner image formed on the image carrier onto a sheet recording material sucked and conveyed onto the transfer carrier. In the image forming apparatus, the toner image is fixed on the sheet recording material, the conveyance error of the sheet recording material is judged by the jam processing control means, and the conveyance operation is stopped when the conveyance abnormality occurs. Any configuration or form is acceptable.
[0124]
【The invention's effect】
As is clear from the above description, the present invention has the following effects.
[0125]
  (1) When a return operation such as taking out the sheet recording material remaining in the image forming apparatus after performing an abnormal stop (emergency stop) due to a conveyance jam or the like, the sheet recording material is conveyed to a position where it can be easily taken out. Since the transfer bias sometimes applied to the sheet recording material is controlled according to the environmental conditions, the sheet recording material can be surely carried out to a position where it can be easily taken out, and the adsorption force to the sheet recording material is easily peeled off from the transfer carrier. Since it is adjusted to the extent, it is always easy and reliable to take out the sheet recording material.
  In addition, the sheet recording material is stopped at a position across the area of the fixing device and the area where the transfer carrier is located, and the stop position is such that the leading edge of the sheet recording material is bitten by the roller member of the fixing device. Because of the position, the sheet recording material sandwiched between the roller members of the fixing device is pulled out together by the operation of releasing the fixing device from the image forming apparatus, and the sheet recording material electrostatically adsorbed to the transfer carrier can be easily obtained. Can be taken out.
  When the conveyance error of the sheet recording material is detected, before the transfer of the sheet recording material by the transfer carrier stops, the switching unit starts the separation operation of the transfer carrier from the image carrier, and the transfer Since the carrier is separated from other image carriers other than the specific image carrier, when the contact state between the image carrier and the sheet recording material is partially released and the sheet is conveyed toward the fixing unit area, The toner image formed on the image carrier prior to the occurrence of a jam is not easily transferred to the sheet recording material, and the transfer roller paired with the image carrier has an excessive adsorption force to the sheet recording material on the transfer carrier. Since the sheet recording material can be easily peeled off from the transfer carrier, it is possible to reduce the toner contamination inside the apparatus during jam processing and the toner contamination on the hand holding the sheet recording material. It performs an easy jam processing.
  Further, since the charge for adsorbing the sheet recording material to the transfer carrier can be appropriately supplied by the transfer roller paired with the image carrier not separated, the sheet recording material can be reliably conveyed to the area of the fixing device. . In addition, if the downstream side in the transport direction of the transfer carrier is separated, the sheet recording material is prevented from being excessively bent or jammed after the sheet recording material has been stopped by striking the fixing roller, There is also an effect that the inside of the image forming apparatus can be prevented from being stained with toner due to unfixed toner that can be slid on the transfer carrier.
  Further, since the transfer bias is set lower when the humidity is low than when the humidity is high, fluctuations in force required to peel the sheet recording material from the transfer carrier can be suppressed.
[0126]
  (2)When a return operation such as removing the sheet recording material remaining in the image forming apparatus after an abnormal stop (emergency stop) due to a conveyance jam or the like is performed, sheet recording is performed when the sheet recording material is conveyed to a position where it can be easily removed. Since the transfer bias applied to the material is controlled according to the environmental conditions, the sheet recording material can be reliably carried out to a position where it can be easily taken out, and the adsorbing force to the sheet recording material is adjusted so that it can be easily peeled off from the transfer carrier. Therefore, the sheet recording material can always be easily and reliably taken out.
In addition, the sheet recording material is stopped at a position across the area of the fixing device and the area where the transfer carrier is located, and the stop position is such that the leading edge of the sheet recording material is bitten by the roller member of the fixing device. Because of the position, the sheet recording material sandwiched between the roller members of the fixing device is pulled out together by the operation of releasing the fixing device from the image forming apparatus, and the sheet recording material electrostatically adsorbed to the transfer carrier can be easily obtained. Can be taken out.
When the conveyance error of the sheet recording material is detected, before the transfer of the sheet recording material by the transfer carrier stops, the switching unit starts the separation operation of the transfer carrier from the image carrier, and the transfer Since the carrier is separated from other image carriers other than the specific image carrier, when the contact state between the image carrier and the sheet recording material is partially released and the sheet is conveyed toward the fixing unit area, The toner image formed on the image carrier prior to the occurrence of a jam is not easily transferred to the sheet recording material, and the transfer roller paired with the image carrier has an excessive adsorption force to the sheet recording material on the transfer carrier. Since the sheet recording material can be easily peeled off from the transfer carrier, it is possible to reduce the toner contamination inside the apparatus during jam processing and the toner contamination on the hand holding the sheet recording material. It performs an easy jam processing.
Further, since the charge for adsorbing the sheet recording material to the transfer carrier can be appropriately supplied by the transfer roller paired with the image carrier not separated, the sheet recording material can be reliably conveyed to the area of the fixing device. . In addition, if the downstream side in the transport direction of the transfer carrier is separated, the sheet recording material is prevented from being excessively bent or jammed after the sheet recording material has been stopped by striking the fixing roller, There is also an effect that the inside of the image forming apparatus can be prevented from being stained with toner due to unfixed toner that can be slid on the transfer carrier.
  In addition, since the application range of the transfer bias to the sheet recording material is controlled to be narrower when the humidity is low than when the humidity is high, the force required to peel the sheet recording material from the transfer carrier is reduced. Variations can be suppressed.
[0128]
  (3)When a sheet conveyance abnormality is detected, the image forming operation is stopped and the sheet recording material conveying operation is continued, and the sheet recording material existing in the upstream sheet recording material conveying means including the transfer carrier is fixed to the fixing device area. And a transfer bias that is applied to the sheet recording material on the transfer carrier after determining the conveyance abnormality is controlled according to environmental conditions. Therefore, it is possible to return the image forming apparatus by performing a single conveyance jam return operation.
  Further, since the image forming operation is stopped while the sheet recording material conveying operation is continued, the contamination in the image forming apparatus can be reduced. In the jam processing operation, since the transfer bias applied to the sheet recording material is controlled according to the environmental conditions, the adsorption force to the sheet recording material is adjusted to such an extent that it can be easily peeled off from the transfer carrier. The recording material can be taken out easily and reliably.
  Further, the sheet recording material is stopped at a position across the area of the fixing device and the area where the transfer carrier is located, and the stop position is such that the leading edge of the sheet recording material is bitten by the roller member of the fixing device. Because of the position, the sheet recording material sandwiched between the roller members of the fixing device is pulled out together by the operation of releasing the fixing device from the image forming apparatus, and the sheet recording material electrostatically adsorbed to the transfer carrier can be easily obtained. Can be taken out.
  When the conveyance error of the sheet recording material is detected, before the transfer of the sheet recording material by the transfer carrier stops, the switching unit starts the separation operation of the transfer carrier from the image carrier, and the transfer Since the carrier is separated from other image carriers other than the specific image carrier, when the contact state between the image carrier and the sheet recording material is partially released and the sheet is conveyed toward the fixing unit area, The toner image formed on the image carrier prior to the occurrence of a jam is not easily transferred to the sheet recording material, and the transfer roller paired with the image carrier has an excessive adsorption force to the sheet recording material on the transfer carrier. Since the sheet recording material can be easily peeled off from the transfer carrier, it is possible to reduce the toner contamination inside the apparatus during jam processing and the toner contamination on the hand holding the sheet recording material. It performs an easy jam processing.
  Further, since the charge for adsorbing the sheet recording material to the transfer carrier can be appropriately supplied by the transfer roller paired with the image carrier not separated, the sheet recording material can be reliably conveyed to the area of the fixing device. . In addition, if the downstream side in the transport direction of the transfer carrier is separated, the sheet recording material is prevented from being excessively bent or jammed after the sheet recording material has been stopped by striking the fixing roller, There is also an effect that the inside of the image forming apparatus can be prevented from being stained with toner due to unfixed toner that can be slid on the transfer carrier.
  Also,Since the transfer bias is set lower when the humidity is lower than when the humidity is high, fluctuations in force required to peel off the sheet recording material from the transfer carrier can be suppressed.
[0129]
  (4)When a sheet conveyance abnormality is detected, the image forming operation is stopped and the sheet recording material conveying operation is continued, and the sheet recording material existing in the upstream sheet recording material conveying means including the transfer carrier is fixed to the fixing device area. And a transfer bias that is applied to the sheet recording material on the transfer carrier after determining the conveyance abnormality is controlled according to environmental conditions. Therefore, it is possible to return the image forming apparatus by performing a single conveyance jam return operation.
  Further, since the image forming operation is stopped while the sheet recording material conveying operation is continued, the contamination in the image forming apparatus can be reduced. In the jam processing operation, since the transfer bias applied to the sheet recording material is controlled according to the environmental conditions, the adsorption force to the sheet recording material is adjusted to such an extent that it can be easily peeled off from the transfer carrier. The recording material can be taken out easily and reliably.
  Further, the sheet recording material is stopped at a position across the area of the fixing device and the area where the transfer carrier is located, and the stop position is such that the leading edge of the sheet recording material is bitten by the roller member of the fixing device. Because of the position, the sheet recording material sandwiched between the roller members of the fixing device is pulled out together by the operation of releasing the fixing device from the image forming apparatus, and the sheet recording material electrostatically adsorbed to the transfer carrier can be easily obtained. Can be taken out.
  When the conveyance error of the sheet recording material is detected, before the transfer of the sheet recording material by the transfer carrier stops, the switching unit starts the separation operation of the transfer carrier from the image carrier, and the transfer Since the carrier is separated from other image carriers other than the specific image carrier, when the contact state between the image carrier and the sheet recording material is partially released and the sheet is conveyed toward the fixing unit area, The toner image formed on the image carrier prior to the occurrence of a jam is not easily transferred to the sheet recording material, and the transfer roller paired with the image carrier has an excessive adsorption force to the sheet recording material on the transfer carrier. Since the sheet recording material can be easily peeled off from the transfer carrier, it is possible to reduce the toner contamination inside the apparatus during jam processing and the toner contamination on the hand holding the sheet recording material. It performs an easy jam processing.
  Further, since the charge for adsorbing the sheet recording material to the transfer carrier can be appropriately supplied by the transfer roller paired with the image carrier not separated, the sheet recording material can be reliably conveyed to the area of the fixing device. . In addition, if the downstream side in the transport direction of the transfer carrier is separated, the sheet recording material is prevented from being excessively bent or jammed after the sheet recording material has been stopped by striking the fixing roller, There is also an effect that the inside of the image forming apparatus can be prevented from being stained with toner due to unfixed toner that can be slid on the transfer carrier.
  Also,Since the application range of the transfer bias to the sheet recording material is controlled to be narrower when the humidity is low than when the humidity is high, fluctuations in the force required to peel the sheet recording material from the transfer carrier are reduced. Can be suppressed.
[0130]
(5) The application range of the transfer bias to the sheet recording material is the entire surface of the sheet recording material at high humidity, and only at the rear end side in the conveyance direction of the sheet recording material at low humidity, so the sheet is peeled off from the transfer carrier. Therefore, it is possible to suppress the fluctuation of the force necessary for this.
[0135]
  (6) When an abnormal conveyance of the sheet recording material is detected, the transfer carrier is separated from the image carrier, the contact state between the image carrier and the sheet recording material is released, and the sheet is conveyed to the fixing unit area. In the meantime, the rotation of the image carrier that is not in contact with the sheet recording material (or transfer carrier) is stopped, so that unnecessary rotation of the image carrier that is not in contact is stopped. The life of the image carrier can be extended. In addition, the image carrier that is in contact with the sheet recording material or the transfer carrier is continuously rotated until the transfer carrier is stopped, so that it is not rubbed by the sheet recording material or the transfer carrier, thus shortening the life. Is blocked.
[0136]
  (7) When abnormal conveyance is detected in the sheet recording material, the contact state between the transfer carrier and the image carrier is set to the monochromatic mode, so that the transfer carrier is separated from many image carriers. It becomes easy to take out the material, and the jam handling work becomes easy.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a main part configuration diagram in a state where an identification wearing part is pulled out;
FIG. 3 is an explanatory diagram of a state where the transfer carrier is in an emergency stop.
FIG. 4 is an explanatory diagram showing a state in which the sheet recording material remains on the transfer carrier.
FIG. 5 is an explanatory diagram when the identification landing part is pulled out to perform jam processing.
FIG. 6 is an explanatory diagram of another example.
FIG. 7 is an explanatory diagram when jamming is performed when two sheet recording materials remain on the transfer carrier.
FIG. 8 is an explanatory diagram of another example.
FIG. 9 is an explanatory diagram showing a state of the transfer carrier in the multicolor mode.
FIG. 10 is an explanatory diagram showing a state of the transfer carrier in the single color mode.
FIG. 11 is an explanatory diagram of a state in which the identification wearing part is pulled out.
FIG. 12 is a control system block diagram of the jam processing control means.
FIG. 13 is a flowchart showing an example of the jam processing control.
FIG. 14 is a flowchart showing another example.
FIG. 15 is a flowchart showing the same different example.
FIG. 16 is a flowchart showing still another example.
FIG. 17 is a flowchart showing another example.
FIG. 18 is a flowchart showing still another example.
[Explanation of symbols]
3-Image carrier
7-Transfer carrier
12-Fixing device (fixing unit)
31, 32-roller member
100a-Jam processing control means
R-separation means

Claims (7)

The toner image formed on the image carrier is transferred to a sheet recording material sucked and conveyed in the sheet conveying direction on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device, and the sheet recording An image forming apparatus configured to stop the conveyance operation of the sheet recording material in the fixing device and the sheet recording material on the transfer carrier by the jam processing control means when the material conveyance is abnormal.
A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
Slide means capable of pulling out the fixing device unitized with the side cover of the image forming apparatus main body in the sheet conveying direction by the transfer carrier;
In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
The jam processing control means includes:
When the presence of a sheet recording material in the middle of conveyance is confirmed immediately after or after restarting the conveyance operation of the sheet recording material on the transfer carrier after carrying out a return operation after stopping the conveyance operation in the case of the conveyance abnormality In
A sheet recording material on the transfer carrier is conveyed, at least a part of which is a position that spans an area of the fixing device and an area where the transfer carrier is located in the sheet conveyance direction, and the transfer carrier The sheet recording material on the transfer carrier is stopped at a position where the leading edge of the upper sheet recording material is engaged with the roller member of the fixing device, and the transfer is performed when the sheet recording material on the transfer carrier is conveyed. An image forming apparatus, wherein a transfer bias applied to a sheet recording material on a carrier is set lower when the humidity near the transfer carrier is low than when the humidity near the transfer carrier is high . The toner image formed on the image carrier is transferred to a sheet recording material sucked and conveyed in the sheet conveying direction on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device, and the sheet recording An image forming apparatus configured to stop the conveyance operation of the sheet recording material in the fixing device and the sheet recording material on the transfer carrier by the jam processing control means when the material conveyance is abnormal.
A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
Slide means capable of pulling out the fixing device unitized with the side cover of the image forming apparatus main body in the sheet conveying direction by the transfer carrier;
In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
The jam processing control means includes:
When the presence of a sheet recording material in the middle of conveyance is confirmed immediately after or after restarting the conveyance operation of the sheet recording material on the transfer carrier after carrying out a return operation after stopping the conveyance operation in the case of the conveyance abnormality In
A sheet recording material on the transfer carrier is conveyed, at least a part of which is a position that spans an area of the fixing device and an area where the transfer carrier is located in the sheet conveyance direction, and the transfer carrier The sheet recording material on the transfer carrier is stopped at a position where the leading edge of the upper sheet recording material is engaged with the roller member of the fixing device, and the transfer is performed when the sheet recording material on the transfer carrier is conveyed The application range of the transfer bias to the sheet recording material on the carrier is controlled to be narrower when the humidity near the transfer carrier is low than when the humidity near the transfer carrier is high. Image forming apparatus. The toner image formed on the image carrier is transferred to a sheet recording material adsorbed and conveyed on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device, and the conveyance error of the sheet recording material In some cases, the image forming apparatus is configured to stop the image forming operation by the jam processing control unit,
A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
Slide means capable of pulling out the fixing device unitized with the side cover of the image forming apparatus main body in the sheet conveying direction by the transfer carrier;
In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
The jam processing control means includes:
When the conveyance abnormality occurs, the sheet recording material conveying operation on the transfer carrier is continued, and the sheet recording material present in the upstream sheet recording material conveying means including the transfer carrier is moved in the sheet conveying direction by the fixing device. And a position that spans the area and the area where the transfer carrier is located, and the front end of the sheet recording material on the transfer carrier is transported to a position where it is bitten by the roller member of the fixing device and stopped. An image forming apparatus, wherein a transfer bias applied to a sheet recording material on a transfer carrier is set lower when the humidity near the transfer carrier is low than when the humidity near the transfer carrier is high . The toner image formed on the image carrier is transferred to a sheet recording material adsorbed and conveyed on the transfer carrier, and the toner image is fixed on the sheet recording material by a fixing device, and the conveyance error of the sheet recording material In some cases, the image forming apparatus is configured to stop the image forming operation by the jam processing control unit,
A plurality of the image carriers are arranged in the conveyance direction of the sheet recording material along the transfer carrier,
When the conveyance abnormality occurs, the transfer carrier is separated from other image carriers except for a specific image carrier in the image carrier before the transfer of the sheet recording material by the transfer carrier is stopped. Switching means;
Slide means capable of pulling out the fixing device unitized with the side cover of the image forming apparatus main body in the sheet conveying direction by the transfer carrier;
In response to pulling out the fixing device in the sheet conveying direction by the slide means, the transfer carrier is separated from the specific image carrier, while the fixing device is inserted into the image forming apparatus main body. Separation / contact means for bringing the transfer carrier into contact with the specific image carrier;
With
The jam processing control means includes:
When the conveyance abnormality occurs, the sheet recording material conveying operation on the transfer carrier is continued, and the sheet recording material present in the upstream sheet recording material conveying means including the transfer carrier is moved in the sheet conveying direction by the fixing device. And a position that spans the area and the area where the transfer carrier is located, and the front end of the sheet recording material on the transfer carrier is transported to a position where it is bitten by the roller member of the fixing device and stopped. The application range of the transfer bias to the sheet recording material on the transfer carrier is controlled to be narrower when the humidity near the transfer carrier is low than when the humidity near the transfer carrier is high. Image forming apparatus. The jam processing control means, the application range, when high humidity is the entire surface of the sheet recording material, at the time of low humidity, the claims and sets only in the transport direction rear end side of the sheet recording medium 2 or 5. The image forming apparatus according to 4. The switching means is
When the conveyance abnormality occurs, the transfer carrier starts separating operation before the transfer of the sheet recording material by the transfer carrier stops.
The rotation of the image carrier separated from the transfer carrier is stopped, and the rotation of the image carrier in contact with the transfer carrier in the image carrier is stopped in accordance with the stop of conveyance of the transfer carrier. the image forming apparatus according to any one of claims 1, wherein the stopping 5. A multi-color mode in which an image is formed using all the image carriers, and a monochromatic mode in which an image is formed using a specific image carrier among the image carriers are configured to be selectable.
The jam processing control means sets a contact state between the image carrier and the transfer carrier to a state in a single color mode when a conveyance error of the sheet recording material is detected in the multicolor mode. Item 7. The image forming apparatus according to any one of Items 1 to 6.

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