JP2004001972A - Double-side printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-side printer capable of reducing a loop volume in a buffer device, and buffering a large amount of papers, resulting in a small and simple structure. <P>SOLUTION: This device comprises a feeding means installed between first and second printers and feeding a continuous form; a buffer device absorbing a difference of feeding speeds between both printers; and a control means for controlling a regular feeding and a reverse feeding of the continuous form with either of the first and second printers, and the regular feeding and the reverse feeding of the continuous form with the buffer device. When either of the first and second printers feeds the continuous form in a reverse direction, the paper in the buffer device is simultaneously fed in a reverse direction. <P>COPYRIGHT: (C)2004,JPO

Description

【００３７】
すなわち、通常、第一、第二プリンタ２、３がともに印刷を終了して停止している場合、第一ループ部４７ではループ下端が「設定値Ｌ１」よりも上側（ループ量はＬ１以下）となり、第二ループ部４８ではループ下端が「設定値Ｌ３」と「設定値Ｌ４」との間になっている。第一、第二プリンタ２、３が同時に用紙搬送を開始した場合、搬送ローラ４０、４１も同時に回転し、連続印刷状態となる。この場合は、第一、第二ループ部４７、４８のループ量がプリンタとバッファ装置５ａの立ち上がり時間差によりループ量が増減した場合であっても、「表１」に示す一旦停止条件とならない分だけあればよい。
【００３８】
図４は、第一プリンタ２が単独で印刷（用紙搬送）を開始した場合のフローチャートを示している。すなわち、先ず第一プリンタ２が単独で用紙搬送を開始した際には、搬送ローラ４０、４１は第一、第二プリンタ２、３の停止とともに、その駆動が停止しているので、第一プリンタ２から搬送された用紙により第一ループ部４７のループ量は増加している。ここで、第一ループ部４７のループ量が「設定値Ｌ１」以上か否かの判定がセンサ４３により行われ（ステップＳ４００）、ループ量がＬ１以上（Ｌ１の位置より、下側）である場合には、搬送ローラ４０の正搬送が開始される（ステップＳ４０１）。
【００３９】
具体的には、プリンタ制御部５０から正回転信号が送出され回転制御手段４９により搬送ローラ４０の正搬送が行われる。これにより、第一ループ部４７のループ量をほぼＬ１付近で安定させることができる。そして、搬送ローラ４０、４１の正回転により搬送された用紙は第二ループ部４８に滞留する。
【００４０】
次いで、第二ループ部４８のループ量が「設定値Ｌ４」に到達しているか否かの判定が行われる（ステップＳ４０２）。さらに第二プリンタ３が印刷を開始したかの判定が行われる（ステップＳ４０３）。つまり、第二ループ部４８のループ量がＬ４に到達する前に、第二プリンタ３が印刷を開始した場合には、第一、第二プリンタ２、３の正搬送（ステップＳ４０４）が行われるとともに、バッファ装置５ａの搬送ローラ４０、４１の正搬送が行われ、一時停止することなく用紙が搬送される（ステップＳ４０５）。
【００４１】
一方、ステップＳ４０３の処理において、第二プリンタ３が起動されない場合、第二ループ部４８のループ量はさらに増大してＬ４以上となるため、搬送ローラ４０を停止させる（ステップＳ４０６）。
【００４２】
以下、第一プリンタ２で印刷を行い、次いで、第一ループ部４７のループ量が増大した際に「設定値Ｌ２」に到達するか否かの判定を行う（ステップＳ４０７）。また、第一ループ部４７のループ量が増大した際に、再度「設定値Ｌ４」に到達するか否かの判定を行う（ステップＳ４０８）。
【００４３】
前記ステップＳ４０７〜ステップＳ４０８の判定により、ループ量がＬ２、Ｌ４に到達したと判断した場合、第一プリンタ２の印刷を中断する。具体的には、第一プリンタ２の逆搬送動作を行った後、一旦印刷を停止する（ステップＳ４０９）。ここで、第一プリンタ２の逆搬送動作時には、同時に搬送ローラ４０の逆搬送動作も行う（ステップＳ４１０）。
【００４４】
また、この第一プリンタ２の一旦停止後に第二プリンタ３が印刷を開始した場合には（ステップＳ４１１）、第二ループ部４８のループ下端が上昇し、第二ループ部４８のループ量が「設定値Ｌ４」に到達するか否かの判定を行う（ステップＳ４１２）。そして、「設定値Ｌ４」より上側となった時に第一プリンタ２の一旦停止が解除され、第一プリンタ２が印刷を再開する（ステップＳ４１３）。
【００４５】
なお、前述したように第一プリンタ２が印刷中断する際、第一プリンタ２の逆搬送動作と共に、搬送ローラ４０が逆搬送を行うため、第一プリンタ２が逆搬送を停止した時点で第二ループ部４８のループ量が「設定値Ｌ４」以下となる場合もある。この場合、第一プリンタ２を一旦停止させた後、直ちに印刷を再開する。
【００４６】
図５は、第二プリンタ３から印刷（用紙搬送）を開始する場合のフローチャートを示している。すなわち、第二プリンタ３から用紙搬送を開始した際には、第二プリンタ３の用紙搬送とともに、搬送ローラ４０、４１の両者とも正方向に回転するため第一ループ部４７のループ量が減少する。このため、第一ループ部４７のループ量が「設定値Ｌ１」以下か否かの判定を行い（ステップＳ５００）、ループ量がＬ１以下である場合には、搬送ローラ４０の回転を停止させている（ステップＳ５０１）。
【００４７】
次いで、第二ループ部４８のループ量が「設定値Ｌ３」以下であるかの判定が行われ（ステップＳ５０２）、さらに第一プリンタ２が印刷を開始したか否かの判定が行われる（ステップＳ５０３）。つまり、第二ループ部４８のループ量がＬ３以下となる前に第一プリンタ２が印刷を開始し、第一ループ部４７のループ量がＬ１以上となる場合には、第一、第二プリンタ２、３の正搬送（ステップＳ５０４）を行うとともに、同時にバッファ装置５ａの搬送ローラ４０、４１の正搬送も行う（ステップＳ５０５）。これにより、第一、第二ループ部４７、４８でのループ量が安定するため好適な連続印刷状態が可能となる。
【００４８】
一方、ステップＳ５０３の処理において第一プリンタ２が起動されない場合、第二ループ部４８のループ量が減少してＬ３以下となると、第二プリンタ３が一旦停止する（ステップＳ５０７）。以下、第二プリンタ３が一旦停止する時に用紙を逆搬送するが、同時に搬送ローラ４０、４１も逆搬送を行い第一ループ部４７のループ量が増大するため、バッファ装置５ａと第二プリンタ３の間に用紙が滞留することはない。
【００４９】
また、第二プリンタ３の一旦停止後に第一プリンタ２が印刷を開始すると、第二ループ部４８のループ下端が下降し、Ｌ３より下側となった時に第二プリンタ３の一旦停止が解除され、第二プリンタ３が印刷を再開し、第一、第二プリンタ２、３とバッファ装置５ａが全て動作状態となり、第一、第二ループ部４７、４８のループ量が安定して連続して用紙を搬送する。
【００５０】
ここで、第一、第二プリンタ２、３が同時に停止する場合、用紙の逆搬送動作も第一、第二プリンタ２、３で同時に同じ量だけ行われる。この時、回転制御手段４９の作動により搬送ローラ４０、４１も同時に逆回転するため、用紙の逆搬送が行われる。これにより、第一ループ部４７のループ量が「設定値Ｌ１」を越えたり、第二ループ部４８のループ量が「設定値Ｌ４」以上となることはない。
【００５１】
つまり、第一、第二ループ部４７、４８はともに印刷中と停止後のループ量に変化はない。これにより、第一ループ部４７と第二ループ部４８のループ量はともに第一、第二プリンタ２、３とバッファ装置５ａの停止までの時間差分に相当するだけループ量に余裕があればよい。
【００５２】
図６は、第一プリンタ２が先に印刷を終了して逆搬送を行う場合の判断処理についてのフローチャートを示している。すなわち、先ず、第一プリンタ２が先に印刷を終了していたか否かの判定を行い（ステップＳ６００）、第一プリンタ２が先に印刷を終了した場合には、第一プリンタ２の逆搬送を行う（ステップＳ６０１）。
【００５３】
この時、搬送ローラ４０の逆回転も同時に行なわれる（ステップＳ６０２）。従って、第一プリンタ２が逆搬送を行っている間、第一ループ部４７でのバッファ量はほとんど変化しない。つまり、このバッファ量は、第一プリンタ２とバッファ装置５ａの起動／停止時間差分だけである。従って、本実施の形態による「設定値Ｌ１」は、従来のバッファ装置５のように逆搬送分以上の余裕を有する設定位置としなくてもよい。
【００５４】
次いで、第二プリンタ３および搬送ローラ４１の正搬送動作（印刷動作）を行うとともに、搬送ローラ４０の逆回転を行う。これら、第二プリンタ３および搬送ローラ４１の正搬送と搬送ローラ４０の逆回転により第二ループ部４８のループ下端は上昇し「設定値Ｌ３」より上側とすることができる。
【００５５】
このため、第二ループ部４８におけるループ量が「設定値Ｌ３」の上側であるか否かの判定を行い（ステップＳ６０３）、ループ下端がＬ３より上側となった際には、第二プリンタ３に対して一旦停止要求を送出する（ステップＳ６０４）。ここで、第二プリンタ３は、印刷中のページの処理が終了すると停止する。
【００５６】
また、第二プリンタ３が一旦停止する際、逆搬送動作を行い（ステップＳ６０５）、同時に、搬送ローラ４１の逆回転を行う（ステップＳ６０６）。この第二プリンタ３の逆搬送および搬送ローラ４１の逆回転により第二ループ部４８へ用紙を送り込むことになる。そして、第二ループ部４８へ逆搬送して送り込まれた分の用紙は第一ループ部４７へ逆搬送される。このため、第一プリンタ２が逆搬送を停止した後、第二プリンタ３と搬送ローラ４０、４１が逆搬送を停止するまでの間は第一ループ部４７でのループ量が増大するものとなる。
【００５７】
図７は、第二プリンタ３が先に印刷を終了して逆搬送を行う場合の判断処理についてのフローチャートを示している。すなわち、第二プリンタ３が先に印刷終了していたか否かの判定を行い（ステップＳ７００）、第二プリンタ３が先に印刷を終了した場合には、この第二プリンタ３による逆搬送を行う（ステップＳ７０１）。この時、搬送ローラ４１の逆回転も同時に行う（ステップＳ７０２）。
【００５８】
次いで、第二ループ部４８おけるループ量が「設定値Ｌ４」の下側であるか否かの判定を行い（ステップＳ７０３）、ループ下端がＬ４より下側となった際には、第一プリンタ２に対して一旦停止要求を送出する（ステップＳ７０４）。また、第一プリンタ２が一旦停止する際、この第一プリンタ２による逆搬送動作を行い（ステップＳ７０５）、同時に、搬送ローラ４０の逆回転を行う（ステップＳ７０６）。つまり、第二ループ部４８のループ下端が「設定値Ｌ４」より下側となることで第一プリンタ２に一旦停止要求が出され、第一プリンタ２が一旦停止して、第一プリンタ２と搬送ローラ４０が逆搬送を行う。
【００５９】
以下、第二プリンタ３と搬送ローラ４１による逆搬送が終了した時点で、次いで、第一プリンタ２と搬送ローラ４０による逆搬送が行われるため、第二ループ部４８のループ下端が上昇してＬ４より上側とすることができる。
【００６０】
図８は、プリンタの用紙搬送方向の判断処理についてのフローチャートを示している。先ず、バッファ装置５ａの駆動が停止しているか否かの判定を行う（ステップＳ８００）。次いで、バッファ装置５ａの駆動停止時に、滞留量検出部１０ａによる滞留量の状態が順次変化しているか否かの判定を行う（ステップＳ８０１）。
【００６１】
具体的には、バッファ装置５ａの内部に設けた第一ループ部４７のループ量を検出するセンサ４３、４４および第二ループ部４８のループ量を検出するセンサ４５、４６によりバッファ装置５ａの駆動停止時のループ量の変化を判定する（ステップＳ８０２）。
【００６２】
そして、この判定により「ループ量が大→小」の場合には、第一プリンタ２が用紙を逆方向に搬送しているものと判断することができる（ステップＳ８０３）。一方、ステップＳ８０２の判定により、「ループ量が小→大」の場合には、第二プリンタ３が用紙を逆方向に搬送しているものと判断することができる（ステップＳ８０４）。
【００６３】
ここで、上述した第一、第二プリンタ２、３における用紙搬送方向の判断処理はバッファ装置５ａで用紙搬送方向を判定する方法であるが、第一、第二プリンタ２、３からバッファ装置５ａに入力されるクロック信号による判断方法もある。すなわち、第一、第二プリンタ２、３が逆方向へ用紙を搬送している場合に所定量逆方向へ搬送するごとに出力されるクロック信号をバッファ装置５ａに入力し、そのクロック信号に基づいてバッファ装置５ａが用紙を逆方向へ搬送する。
【００６４】
または、用紙の移動方向を表す信号（正逆搬送信号）と用紙の搬送方向に関係なく所定量搬送されるごとに出力されるクロック信号をバッファ装置５ａに入力し、このバッファ装置５ａは正逆搬送信号とクロック信号により用紙を正搬送或いは逆搬送する。
【００６５】
この時、搬送ローラ４０は第一、第二プリンタ２、３の各信号のうち第一プリンタ２からの信号を優先して判断を行うものとする。なお、第一プリンタ２が逆搬送、第一プリンタ２が正搬送の場合は逆搬送とする。また、第二プリンタ３のみが動作している場合、搬送ローラ４０の搬送方向は第一プリンタ２に従う。この時、搬送ローラ４１による搬送は常に第二プリンタ３と同じ方向へ搬送を行うものとする。
【００６６】
なお、以上の説明では２台の第一、第二プリンタ２、３と１台のバッファ装置５ａを利用した両面印刷装置について説明したが、プリンタの設置台数は２台に限定されず、３台以上のプリンタとそれぞれのプリンタ間に配置した複数のバッファ装置による両面印刷装置（印刷システム）に本発明を適用することができる。そして、この場合には、従来よりも大きくコスト低減を図ることができるうえ、多色カラー印刷の可能な両面印刷装置（システム）を実現構成することが可能である。
【００６７】
以上に述べたように、本発明の一実施の形態によれば、プリンタの搬送に連動してバッファ装置５ａでも逆搬送を行うので、バッファ装置５ａ内でのループ量を縮小することが可能となることから、このバッファ装置５ａを小型化とすることができる（Ｈ´＜Ｈ）。また、大量に用紙をバッファ可能とすることができるうえ、用紙のセット時にバッファ装置５ａ内を含む装置間に存在する印刷が行われない白紙の量を削減することが可能となり、簡単な制御で連続紙の表裏面に位置ずれなく正確に印刷を行なうことができる。
【００６８】
（付記１）連続紙の両面に印刷を行う両面印刷装置であって、
前記連続紙の第一面に印刷を行う第一プリンタと、
前記連続紙の搬送方向において前記第一プリンタより後方に設けられ、連続紙の第二面に印刷を行う第二プリンタと、
前記第一、第二プリンタに対して第一面、第二面に印刷を行う印刷データを送信する上位装置と、
前記第一、第二プリンタとの間に設けられ、前記第一プリンタから搬送された連続紙を前記第二プリンタに搬送する搬送手段を有するとともに、両プリンタ間での搬送速度差を吸収するバッファ装置と、
前記第一、第二プリンタのいずれかのプリンタによる連続紙の正搬送および逆搬送と、前記バッファ装置による連続紙の正搬送および逆搬送とを制御する制御手段と、
を備えることを特徴とする両面印刷装置。
（付記２）前記制御手段は、前記第一、第二プリンタのいずれかのプリンタにより前記連続紙を逆方向へ搬送する際に、印刷と同時に前記バッファ装置内の連続紙を逆方向へ搬送することを特徴とする付記１に記載の両面印刷装置。
（付記３）前記制御手段は、前記搬送手段の回転方向を制御する回転方向制御手段を有し、当該回転方向制御手段による搬送方向の切り換えにより連続紙の逆搬送を行うことを特徴とした付記１または２に記載の両面印刷装置。
（付記４）前記バッファ装置は、前記連続紙の滞留により形成される第一、第二ループ部を有するとともに、これら第一、第二ループ部での連続紙の滞留量を検出する滞留量検出部を備え、当該滞留量検出部により検出された連続紙のループ量の変化に基いて、前記バッファ装置内の連続紙を逆搬送させることを特徴とする付記１、２または３に記載の両面印刷装置。
（付記５）前記バッファ装置の内部に滞留する連続紙の滞留量が第一の滞留量未満の場合にのみ、前記第一プリンタに連動して前記連続紙の逆搬送を開始し、前記滞留量が第二の滞留量以上の場合にのみ、前記第二プリンタに連動して前記連続紙の逆搬送を開始することを特徴とする付記１〜４のいずれか一つに記載の両面印刷装置。
（付記６）前記第一、第二プリンタのいずれかのプリンタが逆方向に連続紙を搬送していることを検出する搬送方向検出手段をさらに備え、当該搬送方向検出手段による逆搬送信号に基づいて、前記バッファ装置内の連続紙を逆方向に搬送することを特徴とする付記１〜５のいずれか１つに記載の両面印刷装置。
（付記７）搬送方向検出手段により送出される信号はクロック信号であり、当該クロック信号の送出に同期して前記バッファ装置内の連続紙を逆方向に搬送することを特徴とする付記６に記載の両面印刷装置。
【００６９】
【発明の効果】
以上説明したように、本発明によれば、プリンタの搬送に連動して用紙バッファ装置でも逆搬送を行うので、バッファ装置内でのループ量を縮小することが可能となることから、大量に用紙をバッファ可能とすることができるうえ、用紙のセット時にバッファ装置内を含む装置間に存在する印刷が行われない白紙の量を削減することが可能となり、簡単な制御で連続紙の表裏面に位置ずれなく正確に印刷を行なうことができるという効果を奏する。
【００７０】
また、本発明によれば、バッファ装置により紙送り速度の差（紙送り速度）を吸収して両プリンタ間に常に適当量の用紙たるみを持たせることができるので、用紙ジャムや用紙切れを防止するとともに、簡単な制御で連続紙の表裏面に位置ずれなく正確な印刷を行うことができるうえ、バッファ装置内でのループ量を縮小することが可能となることから、設置スペースの削減を実現することができコストの嵩まない簡易構造となるバッファ装置を備えた両面印刷装置を構築できるという効果を奏する。
【図面の簡単な説明】
【図１】この発明の実施の形態に係る両面印刷装置を示す全体構成図である。
【図２】図１に示した両面印刷装置の制御系を示す全体ブロック図である。
【図３】図１に示した両面印刷装置の動作概略を示すタイミングチャートである。
【図４】第一プリンタが単独で印刷を開始する処理手順を示すフローチャートである。
【図５】第二プリンタが単独で印刷を開始する処理手順を示すフローチャートである。
【図６】第一プリンタが先に印刷を終了して逆搬送を行う場合の判断処理についてのフローチャートである。
【図７】第二プリンタが先に印刷を終了して逆搬送を行う場合の判断処理についてのフローチャートである。
【図８】バッファ装置で用紙搬送方向を判定する処理手順を示すフローチャートである。
【図９】従来の両面印刷装置を示す構成図である。
【図１０】図９に示した両面印刷装置の制御系を示す全体ブロック図である。
【図１１】図９に示した両面印刷装置の動作概略を示すタイミングチャートである。
【符号の説明】
１、１ａ　両面印刷装置
２　第一プリンタ
３　第二プリンタ
４　上位装置
５、５ａ　バッファ装置
６、７、８、４０、４１　搬送ローラ
１０、１０ａ　滞留量検出部
１１、１２、１３、４３、４４、４５、４６　センサ
１５、４７　第一ループ部
１６、４８　第二ループ部
２０、２１、５０、５１　プリンタ制御部
２２、２３　印刷機構
２９　ホッパ
３０　感光ドラム
３１　光学ユニット
３２　帯電器
３３　現像部
３４　転写帯電器
３５　定着部
４９　回転制御手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a two-sided printing apparatus that prints on both sides of continuous paper by interlocking two or more printers, and more particularly to a two-sided printing apparatus that uses a buffer device that adjusts the transport speed and paper loop amount between the two printers. Alternatively, the present invention relates to a double-sided printing device that performs multicolor printing.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a duplex printing apparatus using continuous paper as a print medium has been proposed. In such a duplex printing apparatus, the paper is conveyed while a tractor pin or the like is hooked on the holes provided on both sides of the continuous paper, so that a paper jam does not occur during the conveyance of the paper. Since printing is performed on the paper, it is widely used for double-sided printing, two-color printing, and the like because the paper can be effectively used.
[0003]
Hereinafter, the configuration of a conventional duplex printing apparatus will be described with reference to FIGS. FIG. 9 is an overall configuration diagram of the duplex printing apparatus 1 (system), and is an example of a configuration including a buffer device 5 between two printers 2 and 3 for absorbing a difference in transport speed between the two printers. FIG. 10 is a block diagram showing a control system of the duplex printing apparatus 1.
[0004]
9 and 10, reference numeral 2 denotes a first printer (page printer) for printing on one surface (first surface) of the continuous paper, and reference numeral 3 denotes a printer provided behind the first printer (page printer) in the continuous paper transport direction. And a second printer 4 for printing on the other side (second side) of the continuous paper, and a higher-level device (host) for transmitting print data (front side, back side) to the first and second printers 2 and 3. The computer 5 is a buffer device provided between the first and second printers 2 and 3. Further, a turn bar (not shown) for turning over the sheet is provided behind the first printer 2 (between the first printer 2 and the buffer device 5).
[0005]
The buffer device 5 has a function of providing an appropriate amount of paper slack between the first and second printers 2 and 3 to absorb a printing speed difference (paper feeding speed difference) and a difference between start / stop timings of the two printers 2 and 3. In the inside thereof, there are provided conveying rollers 6, 7, 8 for conveying the continuous paper, and a staying amount detecting unit 10 for detecting the staying amount of the paper in the buffer device 5. The stay amount detection unit 10 has three sets of sensors 11, 12, and 13 each including a light emitting element and a light receiving element. Reference numerals 15 and 16 denote first and second loop portions indicating a slack (loop) region of the continuous paper.
[0006]
Reference numerals 20 and 21 denote printer control units for performing overall control of the first and second printers 2 and 3, and reference numerals 22 and 23 denote printing mechanisms. In the printing mechanisms 22 and 23, 29 is a hopper for supplying continuous paper, 30 is a photosensitive drum having a photoconductor (photoreceptor) on its surface, and 31 is a laser beam irradiated on the photosensitive drum 30 to form an electrostatic latent image. An exposure optical unit to be formed; 32, a charger for uniformly charging the surface of the photosensitive drum 30; 33, a developing unit for developing the electrostatic latent image into a visible image (toner image); And a fixing unit 35 for fixing the transferred visible image. Reference numeral 40 'denotes a storage unit for storing continuous paper printed on both sides.
[0007]
Although not shown, the printing mechanisms 22 and 23 each include an optical charge eliminator that removes a charge on the photosensitive drum 30 by light irradiation and a cleaning unit that removes and cleans toner remaining on the photosensitive drum 30. Have. Here, the image forming process is well known, and thus the details thereof are omitted.
[0008]
Hereinafter, the operation of the conventional double-sided printing apparatus 1 will be briefly described with reference to a timing chart of FIG. In the timing chart of FIG. 11, the horizontal axis indicates time, and the vertical axis indicates ON / OFF states. That is, in the double-sided printing apparatus 1 configured as described above, the first and second printers 2 and 3 both convey the printed page to the fixing unit 35 at the end of printing to fix the image. Control is performed to convey the boundary between the printed page and the unprinted page to the transfer charger 34 in the reverse direction (the reverse conveyance distance is about 1 to 2 m). Dotted lines (FIG. 10) of the first and second loop portions 15 and 16 indicate loop amounts when the reverse conveyance is completed. This is to prevent a blank page from being formed between a printed page and the first page of the next print.
[0009]
In this case, the reverse transport timings of the first and second printers 2 and 3 are simultaneous. T1, T2, and T3 in the figure adjust the loop length in the first and second loop units 15 and 16 by transporting the paper by the first and second printers 2 and 3 and stopping the activation of the buffer device 5. It is a period that is. The adjustment of the loop length is performed based on the outputs of the sensors 11, 12, and 13.
[0010]
The sensor 11 provided in the first loop unit 15 has a function as a first loop amount detection unit. That is, while the first printer 2 is transporting the paper in the forward direction (the direction of the arrow in the drawing) by the sensor 11, the lower end of the first loop portion 15 is below the "set value L1" (more than the reverse transport). Only in the case of (1), the buffer device 5 is operated so as to convey the continuous paper. This is to prevent the continuous paper from running out even if the first printer 2 performs reverse conveyance.
[0011]
The two sensors 12 and 13 provided in the second loop unit 16 have a function as second and third loop amount detection units. That is, the second loop amount is detected by the sensor 12, the second printer 3 is stopped when the lower end of the second loop unit 16 becomes higher than the “set value L2”, and the second loop amount is detected by the sensor 13. Control is performed to stop the first printer 2 when the lower end of the unit 16 is below the “set value L3”.
[0012]
Here, when the second printer 3 stops, the paper is conveyed backward. At this time, if the lower end of the loop touches the ground, the paper becomes dirty or bent, so that the third loop amount from the “set value L3” Further, a loopable amount is ensured so that the sheet does not come into contact with the floor even if the sheet is accumulated for the reverse conveyance. Further, when the second printer 3 is temporarily stopped by the sensor 13 to absorb the speed difference, one of the first printers 2 is controlled not to stop.
[0013]
[Problems to be solved by the invention]
However, the above-described conventional double-sided printing apparatus has various problems (1) to (5) below. That is, (1) when there is a difference between the activation time of the first printer 2 and the activation time of the buffer device 5, the difference causes the amount of continuous paper staying in the first loop unit 15 to be anticipated. You have to decide how much you can buffer. Therefore, the loop amount of the first loop unit 15 needs to be “more than the reverse transport distance + startup time difference”.
[0014]
(2) If the lower end of the first loop portion 15 comes into contact with the floor, the paper will be soiled, and if it comes into contact, the bent portion will be transported as it is and the paper will run out. In the case of a simple U-shape, the height of the first loop portion 15 needs to be １ ／ or more of the first loop amount.
[0015]
(3) The “set value L2” set by the sensor 12 must be equal to or longer than the distance for feeding the continuous paper after the stop instruction is issued to the second printer 3 until the second printer 3 is actually stopped. Specifically, before the second printer 3 stops, it is necessary to process each of the page transferring the image from the photosensitive drum 30 to the sheet and the page exposing the photosensitive drum 30 on the paper. The distance between the pages needs to be two or more pages.
[0016]
(4) The “setting value L3” set by the sensor 13 is set so that the first printer 2 does not stop when the second printer 3 stops temporarily to absorb the speed difference. It is necessary to add the distance that the sheet is conveyed during the stopped time and the “set value L2” of the second loop amount.
[0017]
(5) To prevent the continuous paper from being stained or bent by the second loop unit 16 even when the second printer 3 stops when the continuous paper stays at the position of the “set value L3”. The paper must be able to stay up to the value obtained by adding the reverse transport distance of the continuous paper to the "set value L3".
[0018]
Accordingly, the loopable amount in the second loop unit 16 is “overrun until the second printer 3 stops + paper transport while the second printer 3 is temporarily stopped + paper reverse transport distance” (second loop in FIG. 9). (Corresponding to the dotted line portion of the portion 16). More specifically, the loopable amount is required to be about 3 to 4 m, depending on the apparatus configuration. When the buffer apparatus has a U-shaped buffer structure, the height is 1.5 to 2 m. It will be about the height.
[0019]
(5) A buffer device having a structure in which the continuous paper stays in a W-shape in the second loop portion 16 is also conceivable. However, in this case, the structure becomes complicated and the cost increases due to an increase in the number of parts. There's a problem. In addition, when paper is set in the apparatus, the paper becomes blank and cannot be used for printing, thus causing waste.
[0020]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and it is possible to reduce a loop amount of continuous paper in a buffer device and to buffer a large amount of paper. To provide a double-sided printing apparatus having a simple structure that does not increase cost.
[0021]
[Means for Solving the Problems]
In order to solve the problems described above and to achieve the object, the present invention is a double-sided printing apparatus that performs printing on both sides of continuous paper, the first printer that performs printing on the first side of the continuous paper, and the continuous paper. A second printer that is provided behind the first printer in the transport direction and prints on the second surface of the continuous paper, and performs printing on the first and second surfaces for the first and second printers. An upper device that transmits print data, and a transport unit that is provided between the first and second printers and that transports continuous paper transported from the first printer to the second printer; A buffer device that absorbs a difference in transport speed between the first and second printers, and controls forward and reverse transport of continuous paper by one of the first and second printers, and forward and reverse transport of continuous paper by the buffer device. Control means to It is characterized in further comprising a.
[0022]
According to the present invention, a control unit for controlling forward and reverse transport of continuous paper by one of the first and second printers and forward and reverse transport of continuous paper by the buffer device is provided. When one of the first and second printers conveys the continuous paper in the reverse direction, the paper is conveyed in the reverse direction at the same time as the printer, so that the loop amount of the continuous paper in the buffer device can be reduced. In addition, a large number of sheets can be buffered, thereby realizing a double-sided printing apparatus having a simple structure.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of a duplex printing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.
[0024]
FIG. 1 is an overall configuration diagram of a two-sided printing apparatus 1a, which is an example of a configuration including a buffer device 5a between two printers for absorbing a difference in transport speed between the two printers. The arrow in FIG. 1 indicates the normal paper transport direction (forward direction). FIG. 2 is a block diagram of a control system in the duplex printing apparatus 1a, and FIG. 3 is a timing chart showing a control operation. In the timing chart, the horizontal axis indicates time, and the vertical axis indicates ON / OFF states. The same components as those in the conventional example are denoted by the same reference numerals, and the description thereof will be omitted.
[0025]
In FIG. 1, reference numeral 2 denotes a first printer (page printer) for printing on one surface (first surface) of the continuous paper, and 3 denotes a rear side of the first printer (page printer) in the continuous paper transport direction. The second printer 4 for printing on the other surface (second surface) of the continuous paper, and the upper device (host computer) 4 for transmitting print data to be printed on the front and back surfaces of each of the first and second printers is provided. I have.
[0026]
Reference numeral 5a denotes a buffer device provided between the first and second printers 2 and 3 for absorbing a difference in paper feeding (printing) speed between the two printers 2 and 3, and absorbing a shift in start / stop timing. A reversing mechanism such as a turn bar for reversing the front and back of the sheet is provided behind the first printer 2. Specifically, the sheet is folded 90 degrees in the conveying direction, and the sheet is turned over.
[0027]
Inside the buffer device 5a, there are provided two sets of transport rollers 40 and 41 for transporting continuous paper, and a retention amount detection unit 10a for detecting the retention amount of the paper in the buffer device 5a. Reference numeral 42 denotes a round bar-like bar through which continuous paper conveyed from the first printer 2 is passed.
[0028]
The staying amount detection unit 10a has four sets of sensors (light emitting element LEE, light receiving element LRE) 43, 44, 45, and 46. 46 detects the loop amount of the second loop unit 48. The loop amount detected by these sensors 43, 44, 45, 46 is transmitted to the staying amount detecting unit 10a.
[0029]
Further, the staying amount detector 10a inputs the outputs of the sensors 43, 44, 45, 46 to the printer controllers 50, 51, respectively. The printer control units 50 and 51 monitor the staying amount of the paper based on the outputs from the sensors 43, 44, 45 and 46, and control the stop and restart of printing based on the staying amount of the paper. The printer control unit 50 and the printer control unit 51 are configured to be able to communicate with each other, and communicate a printer status signal to the other party, so that the first and second printers 2 and 3 can start printing simultaneously or stop printing at the same time. It has become.
[0030]
Further, the printer control units 50 and 51 perform on / off control of various motors in the printing mechanisms 22 and 23, on / off control of various chargers, control of input of print images, and the like, and are provided in the printing mechanisms 22 and 23. Signals from the various sensors are received, and the printing mechanisms 22 and 23 are controlled based on the sensor signals. The printer control units 50 and 51 also perform ON / OFF control of a rotation control unit 49 described later.
[0031]
The printer controllers 50 and 51 output control signals (motor on / off signal, charging on / off signal, etc.) to the printing mechanism, and control printing of the first and second printers 2 and 3 as well as printing. An I / O port for receiving various sensor signals and other signals from the mechanism, an I / O port for receiving signals from the sensors 43 to 46 from the stay amount detection unit 10a, and a communication interface for performing data communication with the other printer control unit ( (Not shown). In FIG. 3, Ta and Tb indicate periods in which the printer is transporting paper, but the buffer device 5a is stopped and the loop length is adjusted based on the outputs of the sensors 43 to 46. .
[0032]
Here, when printing is completed and both the first and second printers 2 and 3 are stopped, the paper is conveyed in reverse so that the loop amount of the first loop unit 47 is reduced by the reverse conveyance of the first printer 2. And the loop amount of the second loop unit 48 is increased by the reverse transport of the second printer 3. For this reason, the distance in which the maximum loop amount of the first and second loop portions 47 and 48 is reversely conveyed by causing the buffer device 5a to reversely convey the paper in conjunction with the operation of the first and second printers 2 and 3. The number of loops can be reduced by reducing the amount of loops.
[0033]
That is, the present embodiment is characterized in that when any one of the first and second printers 2 and 3 conveys paper in the reverse direction, the paper is also conveyed in the buffer device 5a in the reverse direction. . For this reason, the transport rollers 40 and 41 provided inside the buffer device 5a are transport rollers that can rotate forward and backward, so that the continuous paper can be transported not only in the forward direction but also in the reverse direction.
[0034]
Specifically, as shown in FIG. 2, a rotation control means 49 such as an electromagnetic clutch is provided on the driving side of the transport rollers 40 and 41, and the rotation control means 49 (electromagnetic clutch) is turned on / off. The rotation direction of the transport rollers 40 and 41 is controlled. The rotation control unit 49 performs forward rotation or reverse rotation of the transport rollers 40 and 41 according to an instruction from the printer control unit 50. The forward / reverse rotation control of the transport rollers 40 and 41 may employ a method of simply controlling the rotation direction for driving the drive system of the buffer device 5a without using an electromagnetic clutch.
[0035]
In the present embodiment, the operating conditions of the transport rollers 40 and 41 and the first and second printers 2 and 3 are performed based on the conditions shown in Table 1 below.
[0036]
[Table 1]

[0037]
That is, normally, when both the first and second printers 2 and 3 finish printing and are stopped, the lower end of the loop is higher than the “set value L1” in the first loop unit 47 (the amount of loop is L1 or less). In the second loop section 48, the lower end of the loop is between “set value L3” and “set value L4”. When the first and second printers 2 and 3 start conveying paper at the same time, the conveying rollers 40 and 41 also rotate at the same time, resulting in a continuous printing state. In this case, even if the loop amount of the first and second loop units 47 and 48 is increased or decreased due to the rise time difference between the printer and the buffer device 5a, the temporary stop condition shown in Table 1 is not satisfied. I just need.
[0038]
FIG. 4 shows a flowchart when the first printer 2 starts printing (paper conveyance) independently. That is, first, when the first printer 2 starts sheet conveyance independently, the conveyance rollers 40 and 41 are stopped and the driving of the first and second printers 2 and 3 is stopped. The loop amount of the first loop portion 47 is increased by the sheet transported from the second position. Here, it is determined by the sensor 43 whether or not the loop amount of the first loop unit 47 is equal to or greater than the “set value L1” (step S400), and the loop amount is equal to or greater than L1 (below the position of L1). In this case, the normal conveyance of the conveyance roller 40 is started (Step S401).
[0039]
Specifically, a forward rotation signal is sent from the printer control unit 50, and the forward control of the transport roller 40 is performed by the rotation control unit 49. This makes it possible to stabilize the loop amount of the first loop portion 47 substantially near L1. The paper transported by the forward rotation of the transport rollers 40 and 41 stays in the second loop 48.
[0040]
Next, it is determined whether the loop amount of the second loop unit 48 has reached the “set value L4” (step S402). Further, it is determined whether the second printer 3 has started printing (step S403). That is, if the second printer 3 starts printing before the loop amount of the second loop unit 48 reaches L4, the first and second printers 2 and 3 perform normal transport (step S404). At the same time, the normal conveyance of the conveyance rollers 40 and 41 of the buffer device 5a is performed, and the sheet is conveyed without a temporary stop (Step S405).
[0041]
On the other hand, if the second printer 3 is not activated in the process of step S403, the loop amount of the second loop unit 48 further increases to L4 or more, so that the transport roller 40 is stopped (step S406).
[0042]
Hereinafter, printing is performed by the first printer 2, and then it is determined whether or not the set value L2 is reached when the loop amount of the first loop unit 47 increases (step S407). Further, when the loop amount of the first loop unit 47 increases, it is determined whether or not the set value L4 is reached again (step S408).
[0043]
If it is determined in steps S407 to S408 that the loop amount has reached L2 or L4, the printing of the first printer 2 is interrupted. Specifically, after performing the reverse transport operation of the first printer 2, the printing is temporarily stopped (step S409). Here, at the time of the reverse transport operation of the first printer 2, the reverse transport operation of the transport roller 40 is also performed at the same time (step S410).
[0044]
Further, when the second printer 3 starts printing after the first printer 2 temporarily stops (step S411), the lower end of the loop of the second loop unit 48 rises, and the loop amount of the second loop unit 48 becomes “ It is determined whether or not the value reaches the “set value L4” (step S412). Then, when the value becomes higher than the “set value L4”, the temporary stop of the first printer 2 is released, and the first printer 2 resumes printing (step S413).
[0045]
As described above, when the first printer 2 interrupts the printing, the transport roller 40 performs the reverse transport together with the reverse transport operation of the first printer 2, so that the second printer is stopped when the first printer 2 stops the reverse transport. The loop amount of the loop unit 48 may be equal to or less than the “set value L4”. In this case, printing is restarted immediately after the first printer 2 is temporarily stopped.
[0046]
FIG. 5 shows a flowchart when printing (paper conveyance) is started from the second printer 3. That is, when the paper transport from the second printer 3 is started, both the transport rollers 40 and 41 rotate in the forward direction together with the paper transport of the second printer 3, so that the loop amount of the first loop portion 47 decreases. . Therefore, it is determined whether or not the loop amount of the first loop unit 47 is equal to or less than the “set value L1” (step S500). If the loop amount is equal to or less than L1, the rotation of the transport roller 40 is stopped. (Step S501).
[0047]
Next, it is determined whether the loop amount of the second loop unit 48 is equal to or less than the “set value L3” (step S502), and further, it is determined whether the first printer 2 has started printing (step S502). S503). That is, when the first printer 2 starts printing before the loop amount of the second loop unit 48 becomes L3 or less, and when the loop amount of the first loop unit 47 becomes L1 or more, the first and second printers In addition to performing a few forward transports (step S504), the forward transports of the transport rollers 40 and 41 of the buffer device 5a are simultaneously performed (step S505). Thereby, the loop amount in the first and second loop portions 47 and 48 is stabilized, so that a suitable continuous printing state is possible.
[0048]
On the other hand, when the first printer 2 is not activated in the process of step S503, when the loop amount of the second loop unit 48 decreases to L3 or less, the second printer 3 temporarily stops (step S507). Hereinafter, when the second printer 3 temporarily stops, the sheet is reversely conveyed. At the same time, the conveying rollers 40 and 41 also reversely convey and increase the loop amount of the first loop unit 47. The paper does not stay in between.
[0049]
Further, when the first printer 2 starts printing after the second printer 3 is temporarily stopped, the lower end of the loop of the second loop unit 48 is lowered, and when the lower end is below L3, the pause of the second printer 3 is released. , The second printer 3 resumes printing, the first and second printers 2 and 3 and the buffer device 5a are all in operation, and the loop amounts of the first and second loop units 47 and 48 are stable and continuous. Conveys paper.
[0050]
Here, when the first and second printers 2 and 3 are simultaneously stopped, the reverse conveyance operation of the sheet is also performed by the first and second printers 2 and 3 simultaneously by the same amount. At this time, the conveyance rollers 40 and 41 are simultaneously rotated in reverse by the operation of the rotation control means 49, so that the paper is reversely conveyed. Accordingly, the loop amount of the first loop unit 47 does not exceed the “set value L1”, and the loop amount of the second loop unit 48 does not exceed the “set value L4”.
[0051]
That is, the first and second loop units 47 and 48 do not change the loop amount during printing and after the printing is stopped. As a result, the loop amount of the first loop unit 47 and the loop amount of the second loop unit 48 need only have a margin in the loop amount corresponding to the time difference until the stop of the first and second printers 2 and 3 and the buffer device 5a. .
[0052]
FIG. 6 is a flowchart illustrating a determination process when the first printer 2 finishes printing first and performs reverse conveyance. That is, first, it is determined whether or not the first printer 2 has finished printing first (step S600). If the first printer 2 has finished printing first, the reverse transport of the first printer 2 is performed. Is performed (step S601).
[0053]
At this time, the reverse rotation of the transport roller 40 is also performed simultaneously (step S602). Therefore, while the first printer 2 is performing reverse conveyance, the buffer amount in the first loop unit 47 hardly changes. That is, this buffer amount is only the difference between the start / stop time of the first printer 2 and the buffer device 5a. Therefore, the “set value L1” according to the present embodiment does not have to be a set position having a margin equal to or more than the reverse transport unlike the conventional buffer device 5.
[0054]
Next, the forward transport operation (printing operation) of the second printer 3 and the transport roller 41 is performed, and the transport roller 40 is rotated in the reverse direction. Due to the normal transport of the second printer 3 and the transport roller 41 and the reverse rotation of the transport roller 40, the lower end of the loop of the second loop portion 48 can be raised to be above the "set value L3".
[0055]
Therefore, it is determined whether or not the loop amount in the second loop unit 48 is above the “set value L3” (step S603). When the loop lower end is above L3, the second printer 3 (Step S604). Here, the second printer 3 stops when the processing of the page being printed ends.
[0056]
When the second printer 3 temporarily stops, the reverse transport operation is performed (step S605), and at the same time, the reverse rotation of the transport roller 41 is performed (step S606). The sheet is fed into the second loop section 48 by the reverse transport of the second printer 3 and the reverse rotation of the transport roller 41. Then, the amount of paper conveyed by being reversely conveyed to the second loop portion 48 is conveyed to the first loop portion 47 in the reverse direction. For this reason, after the first printer 2 stops the reverse transport, the loop amount in the first loop unit 47 increases until the second printer 3 and the transport rollers 40 and 41 stop the reverse transport. .
[0057]
FIG. 7 is a flowchart illustrating a determination process when the second printer 3 finishes printing first and performs reverse conveyance. That is, it is determined whether or not the second printer 3 has finished printing first (step S700). If the second printer 3 has finished printing first, reverse conveyance by the second printer 3 is performed. (Step S701). At this time, the reverse rotation of the transport roller 41 is performed simultaneously (step S702).
[0058]
Next, it is determined whether or not the loop amount in the second loop unit 48 is below the “set value L4” (step S703). Then, a stop request is sent once to Step 2 (Step S704). When the first printer 2 temporarily stops, the reverse transport operation by the first printer 2 is performed (step S705), and at the same time, the reverse rotation of the transport roller 40 is performed (step S706). That is, when the lower end of the loop of the second loop unit 48 is below the “set value L4”, a stop request is issued to the first printer 2 temporarily, and the first printer 2 temporarily stops and The transport roller 40 performs reverse transport.
[0059]
Thereafter, when the reverse transport by the second printer 3 and the transport rollers 41 is completed, then the reverse transport by the first printer 2 and the transport rollers 40 is performed. It can be higher.
[0060]
FIG. 8 is a flowchart illustrating a process of determining the sheet conveyance direction of the printer. First, it is determined whether the driving of the buffer device 5a is stopped (step S800). Next, when the driving of the buffer device 5a is stopped, it is determined whether or not the state of the staying amount by the staying amount detecting unit 10a is sequentially changing (step S801).
[0061]
Specifically, the driving of the buffer device 5a is performed by the sensors 43 and 44 for detecting the loop amount of the first loop portion 47 and the sensors 45 and 46 for detecting the loop amount of the second loop portion 48 provided inside the buffer device 5a. A change in the loop amount at the time of stop is determined (step S802).
[0062]
If the determination indicates that the loop amount is large → small, it can be determined that the first printer 2 is transporting the sheet in the reverse direction (step S803). On the other hand, if the determination in step S802 indicates that the loop amount is small to large, it can be determined that the second printer 3 is transporting the paper in the reverse direction (step S804).
[0063]
Here, the above-described processing of determining the paper transport direction in the first and second printers 2 and 3 is a method of determining the paper transport direction in the buffer device 5a. There is also a determination method based on a clock signal input to the CPU. That is, when the first and second printers 2 and 3 are transporting paper in the reverse direction, a clock signal output every time the paper is transported in the reverse direction by a predetermined amount is input to the buffer device 5a, and based on the clock signal. The buffer device 5a conveys the sheet in the reverse direction.
[0064]
Alternatively, a signal (forward / reverse transport signal) representing the moving direction of the paper and a clock signal output every time the paper is transported by a predetermined amount regardless of the transport direction of the paper are input to the buffer device 5a. The sheet is transported forward or backward by the transport signal and the clock signal.
[0065]
At this time, it is assumed that the transport roller 40 gives priority to the signal from the first printer 2 among the signals from the first and second printers 2 and 3 to make the determination. In addition, when the first printer 2 performs reverse conveyance and the first printer 2 performs normal conveyance, reverse conveyance is performed. When only the second printer 3 is operating, the transport direction of the transport roller 40 follows the first printer 2. At this time, the conveyance by the conveyance roller 41 is always performed in the same direction as the second printer 3.
[0066]
In the above description, a two-sided printing apparatus using two first and second printers 2 and 3 and one buffer device 5a has been described. However, the number of printers is not limited to two and three printers may be used. The present invention can be applied to a double-sided printing device (printing system) using the above printers and a plurality of buffer devices disposed between the respective printers. In this case, the cost can be greatly reduced as compared with the related art, and a double-sided printing apparatus (system) capable of multicolor printing can be realized and configured.
[0067]
As described above, according to the embodiment of the present invention, the reverse transport is performed in the buffer device 5a in conjunction with the transport of the printer, so that the loop amount in the buffer device 5a can be reduced. Therefore, the size of the buffer device 5a can be reduced (H ′ <H). In addition, it is possible to buffer a large amount of paper, and it is possible to reduce the amount of blank paper that is present between the devices including the buffer device 5a and is not printed when the paper is set. Printing can be performed accurately on the front and back surfaces of the continuous paper without any displacement.
[0068]
(Supplementary Note 1) A double-sided printing apparatus that performs printing on both sides of continuous paper,
A first printer that prints on the first side of the continuous paper,
A second printer that is provided behind the first printer in the transport direction of the continuous paper and performs printing on the second surface of the continuous paper,
The first device, a higher-level device that transmits print data for printing on the first surface and the second surface to the second printer,
A buffer that is provided between the first and second printers and has a transport unit that transports continuous paper transported from the first printer to the second printer, and absorbs a transport speed difference between the two printers Equipment and
Control means for controlling the forward and reverse transport of continuous paper by any of the first and second printers, and the forward and reverse transport of continuous paper by the buffer device,
A double-sided printing apparatus comprising:
(Supplementary Note 2) When the continuous paper is transported in the reverse direction by one of the first and second printers, the control means transports the continuous paper in the buffer device in the reverse direction simultaneously with printing. 2. The double-sided printing apparatus according to claim 1, wherein:
(Supplementary note 3) The control means has a rotation direction control means for controlling a rotation direction of the conveyance means, and performs reverse conveyance of the continuous paper by switching the conveyance direction by the rotation direction control means. 3. The double-sided printing device according to 1 or 2.
(Supplementary Note 4) The buffer device has first and second loop portions formed by staying of the continuous paper, and also detects a staying amount of the continuous paper in the first and second loop portions. 4. The two-sided printing paper according to claim 1, wherein the continuous paper in the buffer device is reversely conveyed based on a change in the loop amount of the continuous paper detected by the staying amount detection unit. Printing device.
(Supplementary Note 5) Only when the staying amount of the continuous paper staying inside the buffer device is less than the first staying amount, the reverse conveyance of the continuous paper is started in conjunction with the first printer, and the staying amount is reduced. The double-sided printing apparatus according to any one of Supplementary notes 1 to 4, wherein the reverse conveyance of the continuous paper is started only in a case where is greater than or equal to a second retention amount.
(Supplementary Note 6) The image forming apparatus further includes a conveyance direction detection unit that detects that one of the first and second printers is conveying the continuous paper in the reverse direction, and based on a reverse conveyance signal from the conveyance direction detection unit. The double-sided printing apparatus according to any one of supplementary notes 1 to 5, wherein the continuous paper in the buffer device is transported in a reverse direction.
(Supplementary note 7) The signal transmitted by the conveyance direction detecting means is a clock signal, and the continuous paper in the buffer device is conveyed in the reverse direction in synchronization with the transmission of the clock signal. Double-sided printing device.
[0069]
【The invention's effect】
As described above, according to the present invention, the reverse transport is also performed in the paper buffer device in conjunction with the transport of the printer, so that the loop amount in the buffer device can be reduced, so that a large amount of paper is Can be buffered, and the amount of blank paper that is not printed between devices including the buffer device when setting paper can be reduced. There is an effect that printing can be performed accurately without displacement.
[0070]
Further, according to the present invention, a difference in paper feed speed (paper feed speed) can be absorbed by the buffer device to always provide an appropriate amount of paper slack between the two printers, thereby preventing paper jam and paper breakage. In addition to simple control, accurate printing can be performed on the front and back sides of continuous paper without misalignment, and the amount of loop in the buffer device can be reduced, thus reducing installation space. This makes it possible to construct a double-sided printing apparatus provided with a buffer device having a simple structure which can be performed at a low cost.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram illustrating a duplex printing apparatus according to an embodiment of the present invention.
FIG. 2 is an overall block diagram showing a control system of the duplex printing apparatus shown in FIG.
FIG. 3 is a timing chart schematically showing the operation of the duplex printing apparatus shown in FIG.
FIG. 4 is a flowchart illustrating a processing procedure in which the first printer starts printing alone.
FIG. 5 is a flowchart illustrating a processing procedure in which the second printer starts printing alone.
FIG. 6 is a flowchart illustrating a determination process when the first printer finishes printing first and performs reverse conveyance.
FIG. 7 is a flowchart of a determination process when the second printer finishes printing first and performs reverse conveyance.
FIG. 8 is a flowchart illustrating a processing procedure for determining a sheet conveyance direction in a buffer device.
FIG. 9 is a configuration diagram illustrating a conventional duplex printing apparatus.
10 is an overall block diagram illustrating a control system of the duplex printing apparatus illustrated in FIG.
FIG. 11 is a timing chart schematically showing the operation of the duplex printing apparatus shown in FIG. 9;
[Explanation of symbols]
1, 1a Double-sided printing device
2 First printer
3 Second printer
4 Host device
5,5a buffer device
6, 7, 8, 40, 41 Transport rollers
10, 10a Retention amount detection unit
11, 12, 13, 43, 44, 45, 46 sensors
15, 47 First loop
16, 48 Second loop part
20, 21, 50, 51 Printer control unit
22, 23 printing mechanism
29 Hopper
30 Photosensitive drum
31 Optical unit
32 charger
33 Developing section
34 Transfer Charger
35 Fixing unit
49 Rotation control means

Claims (5)

A two-sided printing apparatus for printing on both sides of continuous paper,
A first printer that prints on the first side of the continuous paper,
A second printer that is provided behind the first printer in the transport direction of the continuous paper and performs printing on the second surface of the continuous paper,
The first device, a higher-level device that transmits print data for printing on the first surface and the second surface to the second printer,
A buffer that is provided between the first and second printers and has a transport unit that transports continuous paper transported from the first printer to the second printer, and absorbs a transport speed difference between the two printers Equipment and
Control means for controlling the forward and reverse transport of continuous paper by any of the first and second printers, and the forward and reverse transport of continuous paper by the buffer device,
A double-sided printing apparatus comprising: The control means is characterized in that, when the continuous paper is transported in the reverse direction by any one of the first and second printers, the continuous paper in the buffer device is transported in the reverse direction simultaneously with printing. The double-sided printing apparatus according to claim 1. The buffer device has first and second loop portions formed by the stay of the continuous paper, and includes a stay amount detection unit that detects the stay amount of the continuous paper in the first and second loop portions, 3. The double-sided printing apparatus according to claim 1, wherein the continuous paper in the buffer device is reversely conveyed based on a change in the loop amount of the continuous paper detected by the staying amount detection unit. Only when the staying amount of the continuous paper staying inside the buffer device is less than the first staying amount, the reverse transport of the continuous paper is started in conjunction with the first printer, and the staying amount becomes the second staying amount. The double-sided printing apparatus according to claim 1, wherein the reverse conveyance of the continuous paper is started only in a case where the amount of the continuous paper is equal to or more than the staying amount. The printer further comprises a conveyance direction detecting means for detecting that one of the first and second printers is conveying the continuous paper in the reverse direction, and the buffer is provided based on a reverse conveyance signal from the conveyance direction detection means. The two-sided printing apparatus according to claim 1, wherein the continuous paper in the apparatus is transported in a reverse direction.

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