JP4700800B2

JP4700800B2 - Image forming apparatus

Info

Publication number: JP4700800B2
Application number: JP2000368793A
Authority: JP
Inventors: 雅博鈴木; 克彦大庭
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2000-12-04
Filing date: 2000-12-04
Publication date: 2011-06-15
Anticipated expiration: 2020-12-04
Also published as: JP2002169403A

Description

【０００１】
【発明の属する技術分野】
本発明は、電子写真方式等の画像形成装置に関するものである。
【０００２】
【従来の技術】
従来、電子写真方式等を採用する画像形成装置は、潜像を担持する潜像担持体と、該潜像担持体に現像剤を付与することにより上記潜像を現像剤像として可視化する現像装置と、該現像装置による現像剤像を記録材に転写する転写手段と、該転写手段によって上記現像剤像の転写を受けた上記記録材を加熱及び加圧することにより上記現像剤像を上記記録材に定着させる定着装置と、転写手段によって一方の面に現像剤像が転写された記録材の定着処理後に該記録材の他方の面に現像剤像が形成されるよう再度該記録材を上記転写手段に搬送可能な再搬送手段とを備える画像形成装置が知られている。
【０００３】
かかる画像形成装置にあっては、定着装置が、互いに圧接してニップを形成し回転する定着体及び加圧体と、該定着体又は該加圧体を回転駆動する駆動手段とを備え、上記ニップで上記記録材を挟持搬送しながら加熱及び加圧することにより上記未定着像を上記記録材に定着させるようになっている。
【０００４】
かかる画像形成装置の一例たる画像形成装置１００Ａについて、図４に基づき説明する。
【０００５】
画像形成装置１００Ａにあっては、転写手段１０２によって一方の面に現像剤像たるトナー像の転写を受けた記録材たる転写材Ｓが、定着装置１０３によって上記トナー像の定着受けた後、画像形成装置１００Ａ本体とは別個に設けられた両面装置２００Ａに搬送される。
【０００６】
そして、両面装置２００Ａに搬送された転写材Ｓは、他方の面の画像形成のため、搬送路２０２へ搬送され、転写材Ｓの搬送方向の後端が分岐部２０４に到達したときにスイッチバックされ、搬送路２０３へと搬送される。
【０００７】
その後、転写材Ｓは、両面部２０６の再搬送手段たる両面手段（図示せず）で斜行や横方向のずれを修正され、レジストローラ対１０１へと再給紙される。
【０００８】
レジストローラ対１０１に再給紙された転写材Ｓは、他方の面にトナー像の転写及び定着がなされ機外に排紙され、両面に画像を得ることとなる。
【０００９】
【発明が解決しようとする課題】
しかしながら、上述の画像形成装置１００Ａにおいては、両面装置２００Ａ内の搬送ローラ２０５−１〜４や両面部２０６の両面手段を駆動させるための複数の駆動モータ（図示せず）を両面装置２００Ａ内に配置させる必要があり、部品点数の増加や、装置全体の大型化という問題が生じる。
【００１０】
上記問題を解決するため、定着装置の定着体又は加圧体を回転駆動する駆動手段の正方向又は負方向に切り換え可能とし、上記駆動手段の正方向回転時に定着処理を行い負方向回転時にその回転駆動力を搬送ローラ２０５−１〜４や両面部２０６の両面手段の駆動に使用することが考えられる。しかし、上記駆動手段の負方向回転時に上記定着体及び加圧体が定着処理時の回転方向と逆方向に回転された場合、定着体及び加圧体に余計な負荷がかかり装置の耐久性が低下すると共に、定着処理ができずスループットを低下させてしまうこととなる。
【００１１】
そこで、本発明は、定着装置の耐久性及びスループットの低下を抑えつつ、部品点数を増加することなく定着装置から再搬送手段へ記録材を搬送できる画像形成装置の提供を目的とする。
【００１２】
【課題を解決するための手段】
上述の課題を解決するための本発明は、潜像を担持する潜像担持体と、該潜像担持体に現像剤を付与することにより上記潜像を現像剤像として可視化する現像装置と、該現像装置による現像剤像を記録材に転写する転写手段と、該転写手段によって上記現像剤像の転写を受けた上記記録材を加熱及び加圧することにより上記現像剤像を上記記録材に定着させる定着装置と、転写手段によって一方の面に現像剤像が転写された記録材の定着処理後に該記録材の他方の面に現像剤像が形成されるよう再度該記録材を上記転写手段に搬送可能な再搬送手段とを備える画像形成装置であって、定着装置が、円筒状の定着ベルトと、該定着ベルトをガイドするベルトガイド部材と、定着ベルトを介してベルトガイド部材と共にニップを形成する加圧ローラと、該定着ベルト又は該加圧ローラを回転駆動する駆動手段とを備え、上記ニップで上記記録材を挟持搬送しながら加熱及び加圧することにより上記未定着像を上記記録材に定着させる画像形成装置において、一方の面の定着処理後の記録材を再搬送手段に向ける順方向に搬送可能な搬送部材を備え、駆動手段は、定着ベルト及び加圧ローラを回転駆動するとともに上記搬送部材による記録材の搬送方向を順方向又はその逆方向に切換可能に上記搬送部材を駆動するようになっており、搬送手段は、上記駆動手段による逆方向駆動時に記録材を排紙方向に搬送し、上記定着ベルト及び上記加圧ローラは、上記駆動手段による上記搬送部材の搬送方向に係りなく記録材を上記搬送部材に向けて搬送する方向に回転駆動されるよう構成されていることを特徴とする。
【００１４】
【発明の実施の形態】
以下、添付図面に沿って、本発明の実施の形態について説明する。
【００１５】
図１は、本発明の一実施形態にかかるカラー画像形成装置の概略構成を示す断面図である。
【００１６】
かかるカラー画像形成装置は、図１に示すように、４個の潜像担持体たる感光体ドラム１（１ａ，１ｂ，１ｃ，１ｄ）を備えており、それぞれの感光体ドラム１の周囲には、その回転方向に従って順に、感光体ドラム１表面を均一に帯電する帯電手段２（２ａ，２ｂ，２ｃ，２ｄ）、画像情報に基づいてレーザービームを照射し感光体ドラム１上の静電潜像を形成する露光手段３（３ａ，３ｂ，３ｃ，３ｄ）、該静電潜像にトナーを付着させてトナー像として顕像化する現像装置４（４ａ，４ｂ，４ｃ，４ｄ）、感光体ドラム１上のトナー像を記録材たる転写材に転写させる転写手段たる転写ローラ５（５ａ，５ｂ，５ｃ，５ｄ）、転写後の感光体ドラム１表面に残った転写後トナーを除去するクリーニング手段６（６ａ，６ｂ，６ｃ，６ｄ）等が配設されて画像形成手段が構成されている。
【００１７】
ここで、感光体ドラム１と帯電手段２、現像装置４、トナーを除去するクリーニング手段６は一体的にカートリッジ化されプロセスカートリッジ７（７ａ，７ｂ，７ｃ，７ｄ）を形成している。
【００１８】
又、給送部８から給送された転写材Ｓは、搬送ベルトで構成した転写搬送手段９によって上記画像形成手段へ搬送され、各色トナー像が順次転写されてカラー画像が記録された後、定着装置１０で画像定着されて一対の回転体である搬送部材たる排紙ローラ１１，１２によって排紙部１３へ排紙される。
【００１９】
又、両面印字の際は、定着装置１０で定着処理を受けた転写材Ｓが排紙ローラ１１，１２によって排紙される前に、排紙ローラ１１，１２を逆回転させることにより、両面搬送路１５に搬送される（矢印Ａ方向）。両面搬送路１５に搬送された転写材Ｓは、装置本体正面にある再搬送手段たる両面手段１６Ａで斜送ローラ１６ａを通過し、Ｕターンローラ１７まで垂直下方向に搬送され、Ｕターンローラ１７及びレジストローラ８ｄによって画像形成部まで再搬送される。
【００２０】
次に、各部の構成及び動作について順次説明する。
【００２１】
先ず、給送部８について説明する。
【００２２】
給送部８は、給紙カセット８ａ、マルチ給紙トレイ８ｂ、マルチ給送部８ｃ及びレジストローラ８ｄから構成されている。
【００２３】
給紙カセット８ａは、複数枚の転写材Ｓを収納し、装置本体内底部に装填される。給紙カセット８ａからの画像形成時には、カセットピックアップローラ８ａ１によって一枚づつ転写材Ｓが分離搬送され、カセット搬送ローラ８ａ２及びレジストローラ８ｄによって上記画像形成手段の画像形成部まで搬送される。
【００２４】
マルチ給紙トレイ８ｂは、通常は装置本体正面に格納されているが、使用時に装置本体からマルチ給紙トレイ８ｂを回動して開き、複数枚の転写材Ｓをセットする。マルチ給紙トレイ８ｂからの画像形成時には、マルチピックアップローラ８ｃ１によって一枚づつ転写材Ｓが分離搬送され、マルチ搬送ローラ８ｃ２及びレジストローラ８ｄによって上記画像形成部まで搬送される。
【００２５】
給紙カセット８ａ、マルチ給送部８ｃにおける用紙の分離や搬送は、給送部にあるの給紙モータ（図示せず）によりギア駆動列を介して行われる。
【００２６】
次に、画像形成部について説明する。
【００２７】
像担持体としての感光体ドラム１は、アルミニウム製シリンダの外周面に有機光導伝体層（ＯＰＣ）を塗布して構成したものである。感光体ドラム１は、その両端部をフランジによって回転自在に支持されており、一方の端部に駆動モータ（図示せず）から駆動力を伝達することにより、反時計周り矢印方向に回転駆動される。
【００２８】
各帯電手段２は、ローラ状に形成された導電性ローラで、このローラを感光体ドラム１表面に当接させるとともに、電源（図示せず）によって帯電バイアス電圧を印加することにより、感光体ドラム１表面を一様に帯電させるものである。
【００２９】
露光手段３は、ポリゴンミラーを有し、このポリゴンミラーにはレーザーダイオード（図示せず）から画像信号に対応する画像光が照射される。
【００３０】
現像装置４は、それぞれブラック、シアン、マゼンタ、イエローの各色のトナーを収納したトナー収納部４ａ１，４ｂ１，４ｃ１，４ｄ１、感光体ドラム１表面に隣接し、駆動部（図示せず）により回転駆動されると共に、現像バイアス電源（図示せず）により現像バイアス電圧を印加することにより現像を行う現像ローラ４ａ２，４ｂ２，４ｃ２，４ｄ２等から構成される。
【００３１】
又、後述する転写搬送ベルト９ａの内側には、４個の感光体ドラム１ａ，１ｂ，１ｃ，１ｄに対向して転写搬送ベルト９ａに当接する転写ローラ５ａ，５ｂ，５ｃ，５ｄがそれぞれ併設されている。これら転写ローラ５は、転写バイアス用電源（図示せず）に接続されており、転写ローラ５から正極性の電荷が転写搬送ベルト９ａを介して転写材に印加され、この電界により、感光体ドラム１に接触中の転写材に、感光体ドラム１上の負極性の各色トナー像が順次転写され、カラー画像が形成される。
【００３２】
次に、転写材Ｓの搬送構成について説明する。
【００３３】
転写材Ｓは、給送部８から転写搬送手段９によって画像形成部に搬送される。
【００３４】
転写搬送手段９を構成する転写材担持体としての転写搬送ベルト９ａは、駆動ローラ９ｂと従動ローラ９ｃ，９ｄ，９ｅの４本のローラで張架支持され、すべての感光体ドラム１ａ，１ｂ，１ｃ，１ｄに対向し配設されている。
【００３５】
そして、転写搬送ベルト９ａは、感光体ドラム１に対向する外周面に転写材Ｓを静電吸着して感光体ドラム１に転写材Ｓを接触させるべく駆動ローラ９ｂによって循環移動する。これにより、転写材Ｓは転写搬送ベルト９ａにより転写位置まで搬送され、感光体ドラム１上のトナー像が転写される。
【００３６】
又、転写搬送ベルト９ａの転写材Ｓの搬送方向の最上流位置には、転写搬送ベルト９ａとともに転写材Ｓを挟持し、且つ転写材Ｓを転写搬送ベルト９ａに吸着させる吸着ローラ９ｆが配設されている。転写材Ｓの搬送に際しては、吸着ローラ９ｆに電圧を印加することで、対向している接地されたローラ９ｃとの間に電界を形成し、転写搬送ベルト９ａ及び転写材Ｓの間に誘電分極を発生させて両者に静電吸着力を生じさせるようになっている。
【００３７】
次に、転写材Ｓの補助搬送構成について説明する。
【００３８】
本実施形態では、転写搬送ベルト９ａで転写材Ｓを搬送する際、補助部材によって転写材Ｓが転写搬送ベルト９ａから剥がれないように構成しているが、この補助部材は転写搬送ベルト９ａ上の転写材を担持する側にあって、後述するように転写搬送ベルト９ａを第２の位置へ移動させる移動手段としても機能するものである。
【００３９】
具体的には、転写搬送ベルト９ａの表面側に従動回転可能な複数個の補助部材としての補助搬送ローラ１４が配設されており、この補助搬送ローラ１４がカム機構（図示せず）によって左右方向に一体的に移動可能に構成されている。
【００４０】
そして、カラー記録を行う場合には補助搬送ローラ１４が左方へ退避して転写搬送ベルト９ａから離間している。一方、モノクロ記録を行う場合には、カム機構が動作して補助搬送ローラ１４を右方へ移動させ、転写搬送ベルト９ａに当接するとともに、該ベルト９ａを押し込む。これにより、転写搬送ベルト９ａはブラック感光体ドラム１ｄとは当接したままではあるが、他の感光体ドラム１ａ，１ｂ，１ｃからは離間するようになっている。
【００４１】
次に、定着装置１０について説明する。
【００４２】
定着装置１０は、転写材Ｓ上に形成された画像に熱及び圧力を加えて転写材Ｓ上に定着させるものである。
【００４３】
定着装置１０は、電磁誘導発熱層を有する円筒状の定着体たる定着ベルト１０ａを有しており、定着ベルト１０ａが、励磁コイルとＴ型の磁性コアとからなる磁場発生手段を内蔵したベルトガイド部材１０ｃにガイドされている。
【００４４】
又、定着装置１０は、弾性の加圧体たる加圧ローラ１０ｂを有しており、加圧ローラ１０ｂが、定着ベルト１０ａを挟みベルトガイド部材１０ｃと所定の圧接力をもって所定幅の定着ニップ部Ｎを形成している。
【００４５】
定着装置１０にあっては、加圧ローラ１０ｂが後述の駆動手段たる定着モータ１０ｄにより回転駆動され、それに伴って円筒状の定着ベルト１０ａが回転し、励磁回路（図示せず）から励磁コイルへの給電により定着ベルト１０ａの電磁誘導発熱がなされる。
【００４６】
定着ニップ部Ｎが所定の温度に立ち上がって温調された状態において、画像形成部から搬送された未定着トナー画像が形成された転写材Ｓが定着ニップ部Ｎの定着ベルト１０ａと加圧ローラ１０ｂとの間に画像面が上向き、即ち定着ベルト１０ａ面に対向して導入され、定着ニップ部Ｎにおいて画像面が定着ベルト１０ａの外面に密着して定着ベルト１０ａと一緒に定着ニップ部Ｎを扶持搬送されていく。
【００４７】
この定着ニップ部Ｎを定着ベルト１０ａと一緒に転写材Ｓが挟持搬送されていく過程において定着ベルト１０ａの電磁誘導発熱で加熱され転写材Ｓ上の未定着トナー画像が転写材Ｓに加熱定着される。
【００４８】
次に、上記構成の画像形成装置によって画像記録を行う場合の動作について説明する。
【００４９】
先ず、カラー画像記録を行う場合には、図１に示すように、補助搬送ローラ１４は左方へ退避させておく。この状態では転写搬送ベルト９ａは４個の感光体ドラム１ａ，１ｂ，１ｃ，１ｄに当接しており（第１の位置）、給送部８から給送された転写材Ｓが転写搬送ベルト９ａに吸着されて搬送される問に画像形成手段で各色のトナー像が順次転写されてカラー画像が形成され、定着装置１０で定着された後に排紙部１３へ排紙される。
【００５０】
一方、黒印字（モノクロ印字）の場合にあっては、ブラック感光体ドラム１ｄのみによるモノクロ画像記録が選択されると、カム機構（図示せず）が駆動して補助搬送ローラ１４を右方へ移動させ、補助搬送ローラ１４が転写搬送ベルト９ａを押し込むことで、ブラック感光体ドラム１ｄを除く他の感光体ドラム１ａ，１ｂ，１ｃから転写搬送ベルト９ａを離間させる。
【００５１】
この状態でブラック感光体ドラム１ｄで形成したブラックトナー像を転写材に転写し、定着装置１０で定着された後に排紙部１３へ排紙する。
【００５２】
次に、両面画像形成時における転写材Ｓの両面搬送動作について説明する。
【００５３】
上述のように表面にトナー像を転写された転写材Ｓが定着装置１０で定着され、排紙部１３へ排紙される途中、排紙センサ１８が転写材Ｓの後端通過を検知する。排紙ローラ１１，１２は排紙センサ１８の転写材Ｓ後端検知のタイミングから転写材Ｓの後端が分岐部Ｐに到達するある所定時間後に回転を停止する。転写材Ｓの後端はそのコシにより両面搬送路１５へと分岐し、排紙ローラ１１、１２を逆回転させることで転写材Ｓは両面部１９へと搬送される。
【００５４】
両面部１９は、後述する両面手段１６Ａである、斜送ローラ１６ａ、横レジストガイド１６ｂ、横レジスト基準部材１６ｃ、及び搬送ガイド（図示せず）から構成される。
【００５５】
両面部１９へ搬送された転写材Ｓは、両面手段１６Ａにより転写材Ｓの斜行（傾き）、横方向の位置ずれを修正された後、Ｕターンローラ１７により搬送され、レジストローラ８ｄへと再給紙される。
【００５６】
レジストローラ８ｄへ再給紙された転写材Ｓは、表面（一方の面）と同様に未画像形成面（他方の面）にトナー像を転写されて画像が記録された後、定着装置１０で画像定着されて排紙ローラ１１，１２によって排紙部１３へ排紙され、表面、裏面の両面印字を完了する。
【００５７】
図１、図２、図３を参照して、本実施の形態における画像形成装置の定着装置を詳述する。
【００５８】
図２は、定着装置１０の駆動を説明するための斜視図である。
【００５９】
図２において、Ａは表面の未定着トナー像の定着及び、転写材の搬送状態を示すものである。このとき、駆動手段たる定着モータ１０ｄ及び加圧ローラ１０ｂ、排紙ローラ１１，１２は図中時計回りに回転し、転写材Ｓは矢印方向に搬送されて行く。上述したように、排紙センサ（図示せず）が転写材Ｓの後端を検知した後、定着モータ１０ｄを逆回転させることで排紙ローラ１２を逆回転させる。転写材Ｓは図２Ｂに示すように矢印方向へと搬送の向きを変えて両面部へと搬送される。排紙ローラ１１，１２は転写材Ｓを図１に示す両面部１９の両面手段１６Ａまで搬送する。又、図２Ｂの状態においても加圧ローラ１０ｂはＡの状態と同一方向に回転している。Ａの状態ではワンウェイギア１０ｅｌ，１０ｅ２のうちギア１０ｅｌで加圧ローラ１０ｂに駆動を伝達し、Ｂの状態ではギア１０ｅ２で伝達するため加圧ローラ１０ｂは１方向のみに回転するものである。
【００６０】
又、図３に示すように、定着温度制御は定着モータ１０ｄが正転から逆転へと切り替わるタイミングよりも前に停止される。そして、定着モータの１０ｄの逆転が開始され目標の回転数に到達した後定着温度制御が開始される。このように制御することで、次の転写材が定着ニップ部Ｎに突入する前には定着ベルト１０ａを最適な定着温度にすることが可能となる。
【００６１】
上述のように、加圧ローラ１０ｂの回転方向が１方向のみなので、定着ベルト１０ａも１方向のみにしか回転せず、定着ベルト１０ａへの負荷を低減することが可能となり、定着ベルト１０ａの破損防止、耐久性の向上が可能となる。更に、定着モータ１０ｄが逆回転している間も定着温度制御を行うことで、定着ベルト１０ａは常に最適な定着温度を維持ことができる。これにより、定着ベルト１０ａの温度が定着可能な温度になるまで待つ必要がなくなるので、スループットをおとすことなく転写材を搬送することが可能となる。又、排紙ローラ１１，１２から両面手段１６Ａまでに搬送ローラ等を必要としないので、部品点数の増加を防止ができる。
【００６２】
【発明の効果】
以上説明したように、本出願にかかる第一の発明によれば、駆動手段が、定着体及び加圧体を回転駆動するとともに上記搬送部材による記録材の搬送方向を順方向又はその逆方向に切換可能に上記搬送部材を駆動するようになっており、搬送手段が、上記駆動手段による逆方向駆動時に記録材を排紙方向に搬送し、上記定着体及び上記加圧体が、上記駆動手段による上記搬送部材の搬送方向に係りなく記録材を上記搬送部材に向けて搬送する方向に回転駆動されるようになっているので、定着装置の耐久性及びスループットの低下を抑えつつ、部品点数を増加することなく定着装置から再搬送手段へ記録材を搬送できる。
【００６３】
又、本出願にかかる第二の発明によれば、駆動手段が、駆動手段が、定着体及び加圧体を回転駆動するとともに上記搬送部材による記録材の搬送方向を順方向又はその逆方向に切換可能に上記搬送部材を駆動するようになっており、搬送手段が、上記駆動手段による逆方向駆動時に記録材を排紙方向に搬送し、上記定着体及び上記加圧体が、上記駆動手段による上記搬送部材の搬送方向に係りなく記録材を上記搬送部材に向けて搬送する方向に回転駆動されるようになっていると共に、駆動手段による搬送部材の逆方向駆動時にも制御手段による加熱手段の加熱駆動の制御がなされるようになっているので、定着装置の耐久性及びスループットの低下を抑えつつ、部品点数を増加することなく定着装置から再搬送手段へ記録材を搬送できる。
【図面の簡単な説明】
【図１】本発明の実施の形態にかかる画像形成装置の概略構成を示す縦断面図である。
【図２】図１の画像形成装置に備えられた定着装置の駆動を説明するための図である。
【図３】本発明の実施の形態における定着装置の駆動手段の回転駆動方向と定着体の温度との関係を示す図である。
【図４】従来の画像形成装置の概略構成を示す縦断面図である。
【符号の説明】
１ａ，１ｂ，１ｃ，１ｄ感光体ドラム（潜像担持体）
４現像装置
５ａ，５ｂ，５ｃ，５ｄ転写ローラ（転写手段）
１０定着装置
１０ａ定着ベルト（定着体）
１０ｂ加圧ローラ（加圧体）
１０ｄ定着モータ（駆動手段）
１１，１２排紙ローラ（搬送部材）
１６Ａ両面手段（再搬送手段）
Ｎ定着ニップ部（ニップ）
Ｓ転写材（記録材）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus employing an electrophotographic system or the like includes a latent image carrier that carries a latent image, and a developing device that visualizes the latent image as a developer image by applying a developer to the latent image carrier. And a transfer means for transferring the developer image by the developing device to the recording material; and the recording material that has received the transfer of the developer image by the transfer means is heated and pressed to apply the developer image to the recording material. A fixing device for fixing the recording material to the recording medium, and the recording material is transferred again so that a developer image is formed on the other surface of the recording material after fixing processing of the recording material on which the developer image is transferred on one surface by the transfer means. An image forming apparatus including a re-conveying unit that can be conveyed to the unit is known.
[0003]
In such an image forming apparatus, the fixing device includes a fixing body and a pressure body that rotate in contact with each other to form a nip, and a driving unit that rotationally drives the fixing body or the pressure body. The unfixed image is fixed on the recording material by heating and pressurizing the recording material while nipping and conveying the recording material at the nip.
[0004]
An image forming apparatus 100A as an example of such an image forming apparatus will be described with reference to FIG.
[0005]
In the image forming apparatus 100A, the transfer material S, which is a recording material that has received the transfer of the toner image as the developer image on one surface by the transfer unit 102, is fixed by the fixing device 103, and then the image is transferred to the image forming apparatus 100A. It is conveyed to a double-sided apparatus 200A provided separately from the main body of the forming apparatus 100A.
[0006]
The transfer material S conveyed to the double-sided device 200A is conveyed to the conveyance path 202 for image formation on the other surface, and is switched back when the rear end of the transfer material S in the conveyance direction reaches the branching portion 204. And transported to the transport path 203.
[0007]
Thereafter, the transfer material S is corrected for skew and lateral deviation by a double-side means (not shown) as a re-transport means for the double-sided portion 206, and is fed again to the registration roller pair 101.
[0008]
When the transfer material S is re-fed to the registration roller pair 101, the toner image is transferred and fixed on the other side of the transfer material S, and is discharged to the outside of the apparatus to obtain images on both sides.
[0009]
[Problems to be solved by the invention]
However, in the image forming apparatus 100A described above, a plurality of drive motors (not shown) for driving the conveying rollers 205-1 to 205-4 and the double-side means of the double-sided portion 206 in the double-sided apparatus 200A are provided in the double-sided apparatus 200A. It is necessary to arrange them, which causes problems such as an increase in the number of parts and an increase in the size of the entire apparatus.
[0010]
In order to solve the above problem, the fixing means or the pressure body of the fixing device can be switched to the positive direction or the negative direction of the driving means for rotationally driving, and the fixing process is performed when the driving means rotates in the positive direction, and the driving means when rotating in the negative direction. It is conceivable to use the rotational driving force for driving the conveying rollers 205-1 to 205-4 and the double-side means of the double-sided portion 206. However, if the fixing member and the pressure member are rotated in the opposite direction to the rotation direction during the fixing process when the driving unit is rotated in the negative direction, an extra load is applied to the fixing member and the pressure member, and the durability of the apparatus is increased. At the same time, the fixing process cannot be performed and the throughput is reduced.
[0011]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of conveying a recording material from a fixing device to a re-conveying unit without increasing the number of parts while suppressing a decrease in durability and throughput of the fixing device.
[0012]
[Means for Solving the Problems]
The present invention for solving the above-described problems includes a latent image carrier that carries a latent image, a developing device that visualizes the latent image as a developer image by applying a developer to the latent image carrier, Transfer means for transferring the developer image to the recording material by the developing device, and fixing the developer image to the recording material by heating and pressurizing the recording material that has received the transfer of the developer image by the transfer means. And the fixing device to transfer the recording material to the transfer device again so that a developer image is formed on the other surface of the recording material after fixing processing of the recording material on which the developer image has been transferred to one surface by the transferring device. An image forming apparatus including a re-conveying unit capable of conveying, wherein the fixing device forms a nip together with a cylindrical fixing belt, a belt guide member for guiding the fixing belt, and the belt guide member via the fixing belt. Pressurized low When, and drive means for rotationally driving the fixing belt or the pressure roller, an image forming for fixing the unfixed image on the recording material by heating and pressing while holding and conveying the recording material in the nip The apparatus includes a conveyance member capable of conveying the recording material after fixing on one surface in a forward direction toward the re-conveyance means, and the driving means rotationally drives the fixing belt and the pressure roller and records by the conveyance member. The conveyance member is driven so that the conveyance direction of the material can be switched between the forward direction and the reverse direction, and the conveyance unit conveys the recording material in the paper discharge direction when driven in the reverse direction by the driving unit. fixing belt and the pressure roller, has a recording material irrespective to the conveying direction of the conveying member by the drive means is configured to be rotated in a direction to convey toward the conveying member It is characterized in.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 is a cross-sectional view showing a schematic configuration of a color image forming apparatus according to an embodiment of the present invention.
[0016]
As shown in FIG. 1, the color image forming apparatus includes four photosensitive drums 1 (1a, 1b, 1c, 1d) as latent image carriers, and around each photosensitive drum 1. The charging means 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum 1 in order according to the rotation direction, and the electrostatic latent image on the photosensitive drum 1 by irradiating a laser beam based on the image information An exposure means 3 (3a, 3b, 3c, 3d) for forming a toner, a developing device 4 (4a, 4b, 4c, 4d) for developing a toner image by attaching toner to the electrostatic latent image, and a photosensitive drum 1 is a transfer roller 5 (5a, 5b, 5c, 5d) as transfer means for transferring the toner image on the transfer material as a recording material, and a cleaning means 6 for removing the post-transfer toner remaining on the surface of the photosensitive drum 1 after transfer. (6a, 6b, 6c, 6d Etc. there is provided by the image forming means is constituted.
[0017]
Here, the photosensitive drum 1, the charging unit 2, the developing device 4, and the cleaning unit 6 for removing the toner are integrated into a cartridge to form a process cartridge 7 (7 a, 7 b, 7 c, 7 d).
[0018]
The transfer material S fed from the feeding unit 8 is conveyed to the image forming unit by a transfer conveying unit 9 constituted by a conveying belt, and after each color toner image is sequentially transferred and a color image is recorded, The image is fixed by the fixing device 10, and is discharged to the paper discharge unit 13 by the paper discharge rollers 11 and 12 as a pair of rotating members.
[0019]
In double-sided printing, the transfer material S that has been subjected to the fixing process by the fixing device 10 is reversely rotated before the transfer material S is discharged by the discharge rollers 11 and 12, thereby carrying the double-sided conveyance. It is conveyed to the path 15 (arrow A direction). The transfer material S conveyed to the double-sided conveyance path 15 passes through the oblique feeding roller 16a by the double-sided means 16A as the re-conveying means on the front surface of the apparatus main body, and is conveyed vertically downward to the U-turn roller 17. Then, the image is re-conveyed to the image forming unit by the registration roller 8d.
[0020]
Next, the configuration and operation of each unit will be sequentially described.
[0021]
First, the feeding unit 8 will be described.
[0022]
The feeding unit 8 includes a paper feed cassette 8a, a multi-feed tray 8b, a multi-feed unit 8c, and a registration roller 8d.
[0023]
The paper feed cassette 8a stores a plurality of transfer materials S and is loaded on the inner bottom of the apparatus main body. At the time of image formation from the paper feed cassette 8a, the transfer material S is separated and conveyed one by one by the cassette pickup roller 8a1, and conveyed to the image forming unit of the image forming means by the cassette conveyance roller 8a2 and the registration roller 8d.
[0024]
The multi-feed tray 8b is normally stored in front of the apparatus main body, but when used, the multi-feed tray 8b is rotated and opened from the apparatus main body, and a plurality of transfer materials S are set. When forming an image from the multi-feed tray 8b, the transfer material S is separated and conveyed one by one by the multi-pickup roller 8c1, and is conveyed to the image forming unit by the multi-conveying roller 8c2 and the registration roller 8d.
[0025]
Separation and conveyance of paper in the paper feed cassette 8a and the multi-feed unit 8c are performed via a gear drive train by a paper feed motor (not shown) in the feed unit.
[0026]
Next, the image forming unit will be described.
[0027]
The photosensitive drum 1 as an image carrier is configured by applying an organic optical conductor layer (OPC) to the outer peripheral surface of an aluminum cylinder. Both ends of the photosensitive drum 1 are rotatably supported by flanges, and are driven to rotate in the counterclockwise arrow direction by transmitting driving force to one end from a driving motor (not shown). The
[0028]
Each charging means 2 is a conductive roller formed in the shape of a roller. The roller is brought into contact with the surface of the photosensitive drum 1, and a charging bias voltage is applied by a power source (not shown), whereby the photosensitive drum. One surface is charged uniformly.
[0029]
The exposure means 3 has a polygon mirror, and this polygon mirror is irradiated with image light corresponding to an image signal from a laser diode (not shown).
[0030]
The developing device 4 is adjacent to the toner storage portions 4a1, 4b1, 4c1, 4d1 and the surface of the photosensitive drum 1 storing toners of black, cyan, magenta, and yellow, respectively, and is driven to rotate by a drive unit (not shown). In addition, the developing roller 4a2, 4b2, 4c2, 4d2, and the like are configured to perform development by applying a developing bias voltage from a developing bias power source (not shown).
[0031]
In addition, transfer rollers 5a, 5b, 5c, and 5d that are in contact with the transfer and transport belt 9a so as to face the four photosensitive drums 1a, 1b, 1c, and 1d are provided inside the transfer transport belt 9a, which will be described later. ing. These transfer rollers 5 are connected to a transfer bias power source (not shown), and positive charges are applied from the transfer roller 5 to the transfer material via the transfer conveyance belt 9a. 1 are sequentially transferred to the transfer material in contact with the photosensitive drum 1 to form a color image.
[0032]
Next, the conveyance configuration of the transfer material S will be described.
[0033]
The transfer material S is conveyed from the feeding unit 8 to the image forming unit by the transfer conveying unit 9.
[0034]
A transfer conveyance belt 9a as a transfer material carrier constituting the transfer conveyance means 9 is stretched and supported by four rollers of a driving roller 9b and driven rollers 9c, 9d, and 9e, and all the photosensitive drums 1a, 1b, 1c and 1d are arranged facing each other.
[0035]
The transfer conveyance belt 9 a is circulated and moved by a driving roller 9 b so that the transfer material S is electrostatically adsorbed on the outer peripheral surface facing the photosensitive drum 1 and the transfer material S is brought into contact with the photosensitive drum 1. As a result, the transfer material S is transported to the transfer position by the transfer transport belt 9a, and the toner image on the photosensitive drum 1 is transferred.
[0036]
Further, an adsorption roller 9f that holds the transfer material S together with the transfer conveyance belt 9a and adsorbs the transfer material S to the transfer conveyance belt 9a is disposed at the most upstream position of the transfer conveyance belt 9a in the conveyance direction of the transfer material S. Has been. When the transfer material S is conveyed, an electric field is formed between the oppositely grounded roller 9c by applying a voltage to the suction roller 9f, and dielectric polarization is generated between the transfer conveyance belt 9a and the transfer material S. To generate an electrostatic adsorption force between the two.
[0037]
Next, the auxiliary conveyance configuration of the transfer material S will be described.
[0038]
In the present embodiment, when the transfer material S is conveyed by the transfer conveyance belt 9a, the transfer material S is configured not to be peeled off from the transfer conveyance belt 9a by the auxiliary member. On the side carrying the transfer material, it also functions as a moving means for moving the transfer conveyance belt 9a to the second position as will be described later.
[0039]
Specifically, a plurality of auxiliary conveyance rollers 14 as auxiliary members that can be driven and rotated on the front side of the transfer conveyance belt 9a are arranged, and these auxiliary conveyance rollers 14 are left and right by a cam mechanism (not shown). It is configured to be movable integrally in the direction.
[0040]
When performing color recording, the auxiliary conveyance roller 14 is retracted to the left and is separated from the transfer conveyance belt 9a. On the other hand, when performing monochrome recording, the cam mechanism operates to move the auxiliary conveyance roller 14 to the right, abut against the transfer conveyance belt 9a, and push the belt 9a. As a result, the transfer conveyance belt 9a remains in contact with the black photosensitive drum 1d, but is separated from the other photosensitive drums 1a, 1b, and 1c.
[0041]
Next, the fixing device 10 will be described.
[0042]
The fixing device 10 applies heat and pressure to the image formed on the transfer material S and fixes the image on the transfer material S.
[0043]
The fixing device 10 includes a fixing belt 10a which is a cylindrical fixing body having an electromagnetic induction heat generating layer, and the fixing belt 10a includes a belt guide having a built-in magnetic field generating unit including an exciting coil and a T-shaped magnetic core. Guided by the member 10c.
[0044]
Further, the fixing device 10 has a pressure roller 10b as an elastic pressure member, and the pressure roller 10b sandwiches the fixing belt 10a and a fixing nip portion having a predetermined width with a predetermined pressure contact force with the belt guide member 10c. N is formed.
[0045]
In the fixing device 10, the pressure roller 10b is rotationally driven by a fixing motor 10d, which will be described later, and the cylindrical fixing belt 10a rotates accordingly, from an excitation circuit (not shown) to an excitation coil. The electromagnetic induction heat generation of the fixing belt 10a is performed by the power supply.
[0046]
In a state where the fixing nip N rises to a predetermined temperature and is temperature-controlled, the transfer material S on which the unfixed toner image conveyed from the image forming unit is formed is the fixing belt 10a and the pressure roller 10b of the fixing nip N. The image surface faces upward, i.e., is opposed to the surface of the fixing belt 10a, and the fixing nip portion N holds the fixing nip portion N together with the fixing belt 10a with the image surface closely contacting the outer surface of the fixing belt 10a. It will be transported.
[0047]
In the process in which the transfer material S is nipped and conveyed through the fixing nip N together with the fixing belt 10a, the unfixed toner image on the transfer material S is heated and fixed to the transfer material S by heating by the electromagnetic induction heat of the fixing belt 10a. The
[0048]
Next, an operation when image recording is performed by the image forming apparatus having the above configuration will be described.
[0049]
First, when performing color image recording, as shown in FIG. 1, the auxiliary conveyance roller 14 is retracted to the left. In this state, the transfer conveyance belt 9a is in contact with the four photosensitive drums 1a, 1b, 1c, and 1d (first position), and the transfer material S fed from the feeding unit 8 is transferred to the transfer conveyance belt 9a. The toner images of the respective colors are sequentially transferred by the image forming means to be attracted and conveyed by the image forming unit, and a color image is formed. After being fixed by the fixing device 10, the toner image is discharged to the paper discharge unit 13.
[0050]
On the other hand, in the case of black printing (monochrome printing), when monochrome image recording using only the black photosensitive drum 1d is selected , a cam mechanism (not shown) is driven to move the auxiliary transport roller 14 to the right. The transfer conveyance belt 9a is moved away from the photosensitive drums 1a, 1b, and 1c other than the black photosensitive drum 1d by the auxiliary conveyance roller 14 pushing the transfer conveyance belt 9a.
[0051]
In this state, the black toner image formed on the black photosensitive drum 1 d is transferred to a transfer material, fixed by the fixing device 10, and then discharged to the paper discharge unit 13.
[0052]
Next, the double-sided conveyance operation of the transfer material S during double-sided image formation will be described.
[0053]
As described above, the transfer material S having the toner image transferred onto the surface is fixed by the fixing device 10 and is discharged to the paper discharge unit 13, and the paper discharge sensor 18 detects the passage of the rear end of the transfer material S. The paper discharge rollers 11 and 12 stop rotating after a predetermined time when the rear end of the transfer material S reaches the branch portion P from the timing of detection of the rear end of the transfer material S by the paper discharge sensor 18. The trailing edge of the transfer material S branches to the double-sided conveyance path 15 due to the stiffness, and the transfer material S is conveyed to the double-sided portion 19 by rotating the paper discharge rollers 11 and 12 in reverse.
[0054]
The double-sided portion 19 includes a double-sided means 16A, which will be described later, and includes an oblique feeding roller 16a, a lateral registration guide 16b, a lateral registration reference member 16c, and a conveyance guide (not shown).
[0055]
The transfer material S conveyed to the double-sided portion 19 is corrected by the double-side means 16A for skew (inclination) and lateral displacement of the transfer material S, and then conveyed by the U-turn roller 17 to the registration roller 8d. Re-feed.
[0056]
The transfer material S re-fed to the registration roller 8d has a toner image transferred onto the non-image forming surface (the other surface) and the image is recorded in the same manner as the front surface (the one surface). After the image is fixed, the paper is discharged to the paper discharge unit 13 by the paper discharge rollers 11 and 12, and the double-sided printing on the front surface and the back surface is completed.
[0057]
The fixing device of the image forming apparatus according to the present embodiment will be described in detail with reference to FIGS.
[0058]
FIG. 2 is a perspective view for explaining driving of the fixing device 10.
[0059]
In FIG. 2, A indicates the fixing of the unfixed toner image on the surface and the transfer state of the transfer material. At this time, the fixing motor 10d, the pressure roller 10b, and the paper discharge rollers 11 and 12 as driving means rotate clockwise in the drawing, and the transfer material S is conveyed in the direction of the arrow. As described above, after the paper discharge sensor (not shown) detects the rear end of the transfer material S, the paper discharge roller 12 is reversely rotated by reversely rotating the fixing motor 10d. As shown in FIG. 2B, the transfer material S is transported to both sides while changing the transport direction in the direction of the arrow. The paper discharge rollers 11 and 12 convey the transfer material S to the double-sided means 16A of the double-sided portion 19 shown in FIG. Also in the state of FIG. 2B, the pressure roller 10b rotates in the same direction as the state of A. In the state A, the driving force is transmitted to the pressure roller 10b by the gear 10el out of the one-way gears 10el and 10e2, and in the state B, the transmission is transmitted by the gear 10e2, so the pressure roller 10b rotates only in one direction.
[0060]
As shown in FIG. 3, the fixing temperature control is stopped before the timing at which the fixing motor 10d is switched from forward rotation to reverse rotation. Then, after 10d reverse rotation of the fixing motor is started and the target rotational speed is reached, the fixing temperature control is started. By controlling in this way, the fixing belt 10a can be brought to the optimum fixing temperature before the next transfer material enters the fixing nip portion N.
[0061]
As described above, since the rotation direction of the pressure roller 10b is only one direction, the fixing belt 10a also rotates only in one direction, so that it is possible to reduce the load on the fixing belt 10a and damage the fixing belt 10a. Prevention and improvement of durability are possible. Further, by performing the fixing temperature control while the fixing motor 10d is rotating in the reverse direction, the fixing belt 10a can always maintain the optimum fixing temperature. As a result, there is no need to wait until the temperature of the fixing belt 10a reaches a temperature at which fixing can be performed, so that the transfer material can be conveyed without reducing the throughput. Further, since no conveying roller or the like is required from the paper discharge rollers 11 and 12 to the double-side means 16A, an increase in the number of parts can be prevented.
[0062]
【The invention's effect】
As described above, according to the first invention of the present application, the driving unit rotates the fixing body and the pressure body, and the conveyance direction of the recording material by the conveyance member is the forward direction or the opposite direction. The conveying member is driven to be switchable, and the conveying means conveys the recording material in the paper discharge direction when driven in the reverse direction by the driving means, and the fixing body and the pressure body are the driving means. The recording material is rotated in the direction in which the recording material is conveyed toward the conveying member regardless of the conveying direction of the conveying member, so that the number of parts can be reduced while suppressing the deterioration of the durability and throughput of the fixing device. The recording material can be conveyed from the fixing device to the re-conveying unit without increasing.
[0063]
Further, according to the second invention of the present application, the driving means, the driving means rotationally drives the fixing body and the pressure body, and the recording material is conveyed in the forward direction or the opposite direction by the conveying member. The conveying member is driven to be switchable, and the conveying means conveys the recording material in the paper discharge direction when driven in the reverse direction by the driving means, and the fixing body and the pressure body are the driving means. The recording medium is rotated in the direction in which the recording material is conveyed toward the conveying member regardless of the conveying direction of the conveying member, and the heating means by the control means is also driven when the conveying member is driven in the reverse direction by the driving means. Therefore, the recording material can be conveyed from the fixing device to the re-conveying means without increasing the number of parts, while suppressing a decrease in durability and throughput of the fixing device.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.
2 is a diagram for explaining driving of a fixing device provided in the image forming apparatus of FIG. 1; FIG.
FIG. 3 is a diagram illustrating a relationship between a rotational driving direction of a driving unit of a fixing device and a temperature of a fixing body in an embodiment of the present invention.
FIG. 4 is a longitudinal sectional view showing a schematic configuration of a conventional image forming apparatus.
[Explanation of symbols]
1a, 1b, 1c, 1d Photosensitive drum (latent image carrier)
4 Developing devices 5a, 5b, 5c, 5d Transfer roller (transfer means)
10 Fixing Device 10a Fixing Belt (Fixing Body)
10b Pressure roller (Pressure body)
10d Fixing motor (drive means)
11, 12 Paper discharge roller (conveying member)
16A Double-sided means (re-carrying means)
N Fixing nip (nip)
S Transfer material (recording material)

Claims

A latent image carrier for carrying a latent image, a developing device for visualizing the latent image as a developer image by applying a developer to the latent image carrier, and transferring the developer image by the developing device to a recording material Transfer means, a fixing device for fixing the developer image to the recording material by heating and pressurizing the recording material that has received the developer image transferred by the transfer means, and a transfer means on one surface. An image forming apparatus comprising: a re-conveying unit capable of conveying the recording material to the transfer unit again so that the developer image is formed on the other surface of the recording material after fixing the recording material to which the developer image has been transferred. a is, the fixing device includes a cylindrical fixing belt, and the belt guide member for guiding the fixing belt, a pressure roller which forms a nip with belt guide member via the fixing belt, the fixing belt or the pressure the pressure roller An image forming apparatus for fixing the unfixed image to the recording material by heating and pressurizing the recording material while nipping and conveying the recording material at the nip. A conveying member capable of conveying the recording material in the forward direction toward the re-conveying means is provided, and the driving means rotates and drives the fixing belt and the pressure roller and forwards the recording material by the conveying member in the forward direction or the reverse direction. The conveyance member is driven so as to be switchable to the conveyance member, and the conveyance unit conveys the recording material in the paper discharge direction when driven in the reverse direction by the drive unit, and the fixing belt and the pressure roller are driven by the drive unit. An image forming apparatus configured to be rotationally driven in a direction in which a recording material is transported toward the transport member regardless of a transport direction of the transport member by the means.

The fixing device has a heating means for heating the fixing belt, a temperature detecting means for detecting a temperature of the fixing belt, the temperature sensed by the temperature sensing means for controlling the heating drive of the heating means so that a predetermined temperature The image forming apparatus according to claim 1, further comprising: a control unit configured to control the heating drive of the heating unit even when the conveying member is driven in the reverse direction by the driving unit. .