JP4240425B2

JP4240425B2 - Image forming apparatus

Info

Publication number: JP4240425B2
Application number: JP30805898A
Authority: JP
Inventors: 隆夫熊坂; 明細谷
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1998-10-29
Filing date: 1998-10-29
Publication date: 2009-03-18
Anticipated expiration: 2018-10-29
Also published as: JP2000132016A

Description

【０００１】
【発明の属する技術分野】
本発明は、複写機，プリンタなどの電子写真方式の画像形成装置に関するものである。
【０００２】
【従来の技術】
従来の画像形成装置において、用紙上に画像形成を行う前に、用紙上に形成する画像の濃度を所定のレベルにする画像濃度制御を行うものが知られている。
【０００３】
画像濃度制御は、例えば、図１２に示すように、感光体１上にトナー画像５を形成し、形成したトナー画像の濃度を光センサ６で検出し、光センサ６の検出値に基づいて、感光体１の電位，露光量、及び、現像バイアス電源９等のトナー付着量に関するパラメータの値を制御するものである。
【０００４】
又、光センサ６としてはトナー画像５の反射率を検出する光センサが用いられ、反射率から画像濃度を求めていた。
【０００５】
このような、画像濃度制御を行う画像形成装置に関しては、特開平9−244391 号，特開平9−244313 号，特開昭63−131152号等がある。
【０００６】
【発明が解決しようとする課題】
しかし、従来の画像形成装置においては、濃度センサとして光センサを用いているので、機内に浮遊するトナーにより光センサ表面が汚染され、誤検出や誤動作を引き起こす傾向があった。特に、印刷量が多い高速機においては、上記のトナー汚染が増加する傾向にあった。
【０００７】
本発明の第１の目的は、センサの誤検出や誤動作等の異常がなく、センサの寿命を長くでき、且つ簡易な測定系で、高画質な画像を記録可能な画像形成装置を提供する。
【０００８】
また、本発明の第２の目的は、感光体の偏心に伴う濃度ムラがなく、画像濃度をより均一で安定可能な画像形成装置を提供する。
【０００９】
【課題を解決するための手段】
上記目的を達成するために、本発明は、感光体と、照射光を導く照射用ファイバー束及び反射光を導く受光用ファイバー束を有した光ファイバーセンサと、前記光ファイバーセンサにて測定された結果に基づいて制御する画像濃度制御部とを備えた画像形成装置において、
前記感光体に反射率が略一定の反射面である基準反射面を設け、前記光ファイバーセンサは、前記感光体の表面に対向し、前記光ファイバーセンサと対向する検出物との間隙と前記光ファイバーセンサ出力関係がピーク近傍になる領域で、且つ前記基準反射面と前記光ファイバーセンサ出力関係が間隙に略比例する領域となるように配置され、前記画像濃度制御部は、前記感光体に形成されたテストパッチを前記光ファイバーセンサで測定した結果に基づいて、画像濃度を制御することを特徴としている。
【００１０】
このように、異常判断部を設けることにより、センサや感光体、または測定系の異常による画像の劣化が発生する前に、異常を知ることができ、センサの誤検出や誤動作等の異常がなく、センサの寿命を長くでき、且つ簡易な測定系で、高画質な画像を記録可能な画像形成装置を提供することができる。
【００１１】
また、上記センサに光ファイバーセンサを用いることにより、光ファイバーセンサの特性に応じて画像濃度の測定と、距離の測定とを測定し、簡易な測定系で、高精度な測定により高画質な画像を記録可能な画像形成装置を提供することができる。
【００１２】
画像濃度制御部は、感光体の回転方向の各位置に形成された複数のテストパッチを光ファイバーセンサで測定した結果に基づいて画像濃度制御を行うことを特徴としている。
【００１３】
このような構成により、感光体の偏心に伴う濃度ムラがなく、画像濃度をより均一で安定可能な画像形成装置を提供することができる。
【００１４】
【発明の実施の形態】
以下、図面を参照し本発明の実施の形態について説明する。
【００１５】
〔第１の実施の形態〕
図１は本発明の第１の実施の形態に係る画像形成装置の概略構成図である。画像形成装置２３は、感光体巻取り口１６を有し、繰り出しローラ１８と巻取りローラ１９を設けた巻取り型の感光体１の周辺に配置される帯電器２と、露光装置３と、現像機４と、現写器７，クリーナ４１，定着器４２などの印写ユニットと、現像バイアス電源９と、光センサ６と、汚れ除去手段１２と、汚れ除去手段１２を制御する汚れ除去制御部４３とポンプ４４と、画像濃度制御部８などから構成される。
【００１６】
帯電器２は感光体１の表面電位を制御するため、コロナ放電を行う放電ワイヤと制御電極を有するスコロトロン帯電器を用いた。表面電位は、制御電極に印加するグリッド電圧を変化させ制御することができる。
【００１７】
露光装置３は、レーザとその走査光学系などから成る。またＬＥＤアレイとロッドレンズなどの光学系を組み合わせても良い。
【００１８】
現像機４は、現像ロール１０に内蔵される磁石体の磁気力によりトナー６０と磁性キャリアを含む現像剤３９を保持し、その現像剤３９を感光体１上の静電潜像と接触させることによりトナー画像５を形成するものである。又、現像機４と現像ロール１０の他に、現像剤３９の搬送量を規制する規制板と、消費したトナーを補うためのトナーホッパーと、補給ロールと、補給されたトナー６０と現像剤３９を混合し摩擦帯電を良好にするため撹拌部材と、トナーと磁性キャリアとの混合比を検知するための磁気センサなどが配置されている。磁性キャリアとトナー６０は、摩擦帯電により互いに逆極性に帯電しており、磁気ブラシ状の現像剤３９を感光体１に回転させ接触させる際に、現像ロール１０に現像バイアス電源９よりバイアス電圧を印加し、現像ロール１０と感光体１との間に電界を作用させ、感光体１上にトナー画像５を形成していた。
【００１９】
現像剤３９は、粒径が４０乃至１００μｍの樹脂コート・磁性キャリアと粒径６μｍ乃至１１μｍのトナー６０を平均トナー濃度（≡１００×トナー重量／現像剤）が１.５乃至５（Ｗｔ％）、より望ましくは２乃至４（Ｗｔ％）の現像剤を使用した。
【００２０】
トナー混合比の制御は、磁気センサにより磁性体含有量を検知し、トナー混合比が所定値を下回る場合は補給信号を発生させ、トナーを補給することによりトナー混合比を略一定に制御するものである。
【００２１】
光センサはトナー画像の反射率を検知するものであるが、反射率と画像濃度とは１対１の関係にあるので、画像濃度（ベタ画像や網点画像の光学濃度）を測定することができる。
【００２２】
光センサとしては、照射光を導く照射用ファイバー束２８と反射光を導く受光用のファイバー束２９を有する光ファイバーセンサ１１を用いることができる。光ファイバーセンサ１１は、ガラスファイバーを用いることにより温度変化に対しても安定にでき、又、棒状であるので設置スペースを小さくでき、さらに、アンプなどの回路基板を測定部から離して配置できるのでコロナ放電を伴う帯電手段が近傍に配置されていても測定誤差となるノイズが発生しない利点がある。
【００２３】
反射率を検出する光ファイバーセンサ１１の場合、センサ出力は反射面の反射率と反射面との間隙の影響を受ける。
【００２４】
図４に、反射面がほぼ鏡面の場合の光ファイバーセンサ１１と対向する検出物との間隙とセンサ出力との関係を示す。出力特性は山状で、出力が間隙に略比例する領域Ｌ１及び領域Ｌ２と出力がピーク近傍で略平坦な領域Ｚ（間隙値はＧｒ近傍）を有している。従って、次の（１),（２）が可能であることが判る。
【００２５】
（１）反射率が略一定の反射面（以下、基準反射面と称する。）に対し光ファイバーセンサ１１を領域Ｌ１又は領域Ｌ２に配置すれば、出力が間隙に略比例するので、間隙の測定が可能である。
【００２６】
（２）又、間隙が略一定に保持される反射面に対し光ファイバーセンサ１１を領域Ｚに配置すれば、センサ出力は間隙の影響を受けないので、反射面の反射率を測定することが可能である。
【００２７】
本発明はこれら（１）（２）の知見に基づいて、図３に示すように、トナー画像５が形成される感光体１表面に対し光ファイバーセンサ１１を領域Ｚに（すなわち、間隙をＧｒとなるように）配置し、基準反射面として感光体巻取り口１６に（厚さがＧｒ−Ｇ１）凸部１７を設け凸部１７と光ファイバーセンサ１１との間隙がＧ１（間隙が図４の領域Ｌ１）となるように構成し、図１に示すように、光ファイバーセンサ１１により検出した複数の画像濃度データの平均値などを演算する濃度演算部４５と、光ファイバーセンサ１１により検出した複数の間隙データの平均値などを演算する間隙演算部４６と、光センサによる間隙測定値と既知の間隙設定値とが不整合の場合に異常と判断する異常判定部４７と、光センサのトナー汚れを除去する汚れ除去手段１２と、画像濃度制御部８と、プロセス制御部４８を配置したものである。
【００２８】
一例として、光ファイバーセンサ１１として、断面が２つの半円状（図７と同様）のファイバー束２６，２７から成り、直径が２.５mm の場合、Ｇｒ≒４.３ mm，Ｚ≒１mm，１.０≦Ｇ１≦３.０mmであるので、１.３≦Ｇｒ−Ｇ１≦３.３mm、すなわち、間隙Ｇｒを４.３mm に設定し、感光体１の表面から１.３乃至３mm突出した凸部１７を設ければよい。
【００２９】
汚れ除去手段１２としては、例えば、図１，図２に示すように、光ファイバーセンサ１１の表面に気流２０を形成する一対の噴出ノズル２１と吸引ノズル２２を配置したものを使用することができる。汚れ除去手段１２の詳細について、図１のＺ−Ｚ線断面視図である図２を用いて、以下、説明する。
【００３０】
汚れ除去手段１２は光ファイバーセンサ１１の表面に気流２０を流動させるため、図２に示すように、必要に応じて、気流を導くガイド部材５５を介在させ、一対の噴出ノズル２１と吸引ノズル２２を配置して構成したもので、入口側空気流２４を導く入口側ダクト１４，出口側空気流２５を導く出口側ダクト１５と連通している。
【００３１】
又、前記一対の噴出ノズル２１，吸引ノズル２２に加えて、前記光ファイバーセンサ１１に近接し、前記感光体１の回転方向上流側に遮断板１３を配置することが望ましい。
【００３２】
さらに、遮断板１３は、一対の噴出ノズル２１と吸引ノズル２２よりも、感光体１側に突出させることがより望ましい。これは、感光体１の回転に伴う回転気流の影響により、光ファイバーセンサ１１の表面の気流２０を乱さないようにする為である。又、現像機４周辺でトナー６０や現像剤３９の飛散が生じた場合でも回転気流により下方に選ばれたトナー６０や現像剤３９が、直接、光ファイバーセンサ１１表面に付着しないようにする為である。
【００３３】
一般に、光ファイバーセンサ１１の作動距離（光ファイバーセンサ１１と感光体１との間隔）は、０.５乃至１５mmであるが、一対の噴出ノズル２１，吸引ノズル２２を配置するには工動距離が１.５mm 以上必要であり、作動距離が３mm以上であることがさらに望ましい。噴出ノズル２１の幅が狭いと充分な流量が得られないだけでなく、圧力損失が増え入口側空気流２４を導く入口側ダクト１４の内圧が高くなり、堅牢なダクトやより大型の送風機が必要になるからである。
【００３４】
汚れ除去手段１２は、光センサの汚れを検出した際に光センサの表面に気流２０を形成し付着したトナーや紙粉を除去するものである。汚れ除去手段１２においては、常時、気流２０を形成しエアカーテン効果によりトナーが光センサに付着することが抑制し、付着物が多量になった場合には通常より流速の高い気流２０を発生させ汚れ除去を行うことが望ましい。
【００３５】
尚、上記した光ファイバーセンサ１１としては、光ファイバーの部分が数ｍと長いものや、発光素子と受光素子とレンズ等が一体で構成された一体型ホトセンサに数cm乃至数１０cmの長さの光ファイバーを組み込んだものを使用することもできる。
【００３６】
このような構成においては、光ファイバーセンサ１１による凸部の間隙測定値を異常判定部に送り、異常判定部において既知の間隙設定値とが不整合の場合に異常（汚染状態）と判断し、汚れ除去制御部において汚れ除去手段１２を作動させる指令を発するようにし、この指令を受けた汚れ除去手段１２は光ファイバーセンサ１１の表面に気流２０を形成し付着したトナーや紙粉の除去を行うことができるので、光ファイバーセンサ１１のトナー汚染に伴うトナー画像濃度の誤検出を防止できる。又、上記の異常検出工程は、ウォームアップ時，用紙交換時，一定時間毎、のいずれかに行うよう予め設定されており、プロセス制御部４８において制御される。
【００３７】
従って、長期の印刷においても、光センサのトナー汚染による画像濃度制御系の誤動作や誤検出を防止できる効果がある。
【００３８】
又、光ファイバーセンサ１１による凸部の間隔測定値と既知の間隔設定値とが整合する場合には、異常判定部４７において正常（汚染なし）と判断し、トナー画像を形成し画像濃度を検出する工程を行い、画像濃度の検出値を異常判定部４７を経由して画像濃度制御部８に送り、画像濃度制御を行う。
【００３９】
ベタ画像の画像濃度制御は、例えば、図１に示すように、記録媒体である感光体１上にテストパッチとしてベタ・トナー画像５を形成し、形成したトナー画像５の画像濃度を光ファイバーセンサ１１で検出し、画像濃度制御部８において光ファイバーセンサ１１の検出値と基準値との比較に基づいて、現像バイアス電源９の電圧を変化させ、ベタ画像濃度を所定の値に制御するものである。
【００４０】
又、その際、表面電位と現像バイアス電圧との差が所定の範囲を超えるとカブリやキャリア付着が増加したり、細線や網点の再現に影響を及ぼすので、帯電器２のグリッド電圧を変化させ表面電位を修正する。
【００４１】
又、網点画像濃度制御は、感光体１上にテストパッチとして網点・トナー画像５を形成し、網点・トナー画像５の画像濃度を光ファイバーセンサ１１で検出し、画像濃度制御部８において光ファイバーセンサ１１の検出値と基準値との比較に基づいて、露光装置３の露光量又はドット露光時間（パルス幅）を変化させ網点画像濃度を所定の値に制御するものである。
【００４２】
尚、上記した例では、基準反射面として感光体巻取り口６に凸部１７を設けその面を使用したが光センサとの間隙がＧ２（間隙が図４の領域Ｌ２）となる様な凹部（感光体表面からの凹み量が１.３〜３.０mm）を設け基準反射面としても、同様な効果が得られる。
【００４３】
又、上記した例では、光ファイバーセンサ１１を感光体１に対向させて配置したが、用紙４０の搬送経路に光センサとの間隙がＧ２（間隙が図４の領域Ｌ２）となる凹部（用紙面よりも１.３〜３.０mm凹んだ）を設け、光ファイバーセンサ１１を用紙４０に対向させて配置し用紙上のトナー画像の画像濃度と用紙経路の凹部との間隔を測定するようにしても良い。
【００４４】
さらに又、１本の光ファイバーセンサを配置しその設定間隙を画像濃度測定時にはＧｒに、間隙測定時にはＧ１（又はＧ２）に切り換える様にしても良い。この場合、間隙を切り換える機構が必要となるが基準反射面は感光体表面(切肌部)を用いるので凹凸を感光体上に設ける必要がない利点がある。
【００４５】
又、光センサ出力の異常（所定の範囲外となる）の要因としては、光センサ表面のトナー汚れの他に、温度変化や経時劣化に伴う発生素子の光量変化，受光素子の感度変化や感光体のクリーニング不良や傷，摩耗に伴う感光体表面の変化がある。従って、異常信号が発せられた場合、感光体１の清掃を行う工程や感光体１の清掃後に光センサの校正を行う工程を介在させ、しかる後、再度、異常信号が発せられた場合に限って、光ファイバーセンサ１１の汚れ除去手段１２を作動させるようにプロセス制御を行ってもよい。
【００４６】
尚、光センサの校正は、所定の反射面（地肌部又は、校正板）を測定した出力電圧と発光をＯＦＦした場合の出力電圧との差が所定の値となるように発光素子の発光駆動電流を調整すれば良い。
【００４７】
〔第２の実施の形態〕
第２の実施例は、第１の実施例に対し光センサ部の構成が異なっており、図５に示すように、光センサ部を第１，第２の光ファイバーセンサ３０，３３を配置して構成したものである。
【００４８】
第１，第２の光ファイバーセンサ３０，３３は、図７に示すように、照射光を導く照射用ファイバー束２８，３１と反射光を導く反射用ファイバー束２９，３２とが同一半円状に構成され、第１の光ファイバーセンサ３０のファイバー束の直径よりも第２の光ファイバーセンサ３３のファイバー束の直径を大きく構成される。
【００４９】
第１の光ファイバーセンサ３０は、ピーク値が与える間隙値（Ｇｒ）と等しく設定し、第２の光ファイバーセンサ３３のファイバー束の直径は間隙値（Ｇｒ）において出力と間隙との関係が略直線となるように第２の光ファイバーセンサ３３のファイバー束の直径を第１の光ファイバーセンサ３３のファイバー束の直径よりも大きく構成したものである。
【００５０】
すなわち、本例の場合、第１，第２の光ファイバーセンサ３０，３３のセンサ出力特性は、それぞれ、図６のＡ，Ｂに示すように、第１の光ファイバーセンサ３０の場合は間隙Ｇｒで出力のピークを与えるのに対し、ファイバー束の直径がより大きい第２の光ファイバーセンサ３３のピークは間隙が大きい側にシフトし出力と間隙との関係が略直線となる特性となる。
【００５１】
一例として、第１の光ファイバーセンサ３０の直径を２.５mm 、第２の光ファイバーセンサ３０の直径を４.３mm のものを用いたところ、第１の光ファイバーセンサ３０の出力のピークを与える間隙Ｇｒは４.３mm 、第２の光ファイバーセンサ３３の出力が直線となる領域は０.８から５.１mm となり、間隙を４.３mm に設定した。
【００５２】
尚、第１，第２の光ファイバーセンサ３０，３３のセンサは設定間隔が等しいので汚れ除去手段の配置が容易な構成となっているが、さらに、トナー汚れの防止や除去の観点から、両者を一体化し先端部を窓部材で覆うことが望ましい。
【００５３】
このような構成においては、センサの数が１本増するが、第１の光ファイバーセンサ３０を用い感光体１上のトナー画像の画像濃度を測定でき、第１の光ファイバーと同一の間隙Ｇｒに設定した第２の光ファイバーセンサ３３を用いて間隙測定ができる。すなわち、本例では、間隙を測定するための基準反射面として感光体表面（地肌部）を用いることができるので、第１の実施例と比較して感光体１上に凸部（又は凹部）を設ける必要がない利点がある。
【００５４】
尚、同一の直径の２本の光ファイバーを用い、画像濃度測定用は間隔をＧｒに、間隔測定用は間隔をＧ１又はＧ２に設定しても良い。この場合、基準反射面として感光体表面（地肌部）を用いることができるので、第２の実施例と同様、感光体１上に凸部（又は凹部）を設ける必要がない利点がある。
【００５５】
〔第３の実施の形態〕
本例は、第２の実施例の変形例であり、第２の光ファイバーセンサ３３の先端部の断面形状が、第２の実施例と異なる構成としたものである。
【００５６】
第１の光ファイバーセンサ３０を、図８に示すように、照射光を導く照射用ファイバー束２８と反射光を導く受光用ファイバー束２９とが同一の半円状に構成したのに対し、第２の光ファイバーセンサ３３は、照射光を導く照射用ファイバー束３４は円形に、反射光を導く受光用ファイバー束３５は照射用ファイバー束３４の周囲に同心状に配置し、さらに、第１の光ファイバーセンサ３０は、ピーク値が与える間隙値（Ｇｒ）と等しく設定し、第２の光ファイバーセンサ３３は間隙値（Ｇｒ）において出力と間隙との関係が略直線となるように構成したものである。
【００５７】
すなわち、本例の場合も、第１，第２の光ファイバーセンサ３０，３３のセンサ出力特性は、それぞれ、図６のＡ，Ｂに示すように、第１の光ファイバーセンサ３０の場合は間隙Ｇｒで出力のピークを与えるのに対し、第２の光ファイバーセンサ３３のピークは間隙が大きい側にシフトし出力と間隙との関係が略直線となる特性となる。
【００５８】
このような構成においても、第２の実施例と同様に、センサの数が１本増えるが、第１の光ファイバーセンサ３０を用い感光体１上のトナー画像の画像濃度を測定でき、間隙Ｇｒに設定した第２の光ファイバーセンサ３３を用いて間隙測定ができる。従って、本例においても、間隙を測定するための基準反射面として感光体表面（地肌部）を用いることができるので、第１の実施例と比較して感光体１上に凸部（又は凹部）を設ける必要がない利点がある。
【００５９】
〔第４の実施の形態〕
第４の実施例は、第３の実施例の改良例であり、第１の実施例における光ファイバーセンサ１１の代わりに図９に示す通り、１つの光ファイバーセンサ３７を配置して構成したものである。以下、図１０，図１１，図６を用いて説明する。本例の光ファイバーセンサ３７は、図１０に先端部断面形状を示すように、３分割のファイバー束２８，３５，３６から成り、ファイバー束２８，３６は同一の半円状の断面を有し、ファイバー束３５はファイバー束２８，３６の周囲に同心円状の断面を有している。
【００６０】
又、図１１の（ａ）（ｂ）に示すように、画像濃度測定時と間隙測定時とで、ファイバーセンサ３７内の光路を切り替える光路切り替え部３８を受・発光素子５１，５２の前段に設けたものである。発光素子５２としては、ＧａＡｓ赤外発光ダイオードや半導体レーザ，受光素子５１としてはＳｉホトトランジスタなどを使用することができる。
【００６１】
画像濃度測定時は、ファイバー束２８により照射光５３を導き、ファイバー束３６により反射光５４を導くように光路４９を設定し、さらに、光ファイバーセンサ３７の間隙は、センサ出力がピーク値を与える間隙値（Ｇｒ）と等しく設定されている。従って、画像濃度測定時におけるセンサ出力特性は、図６のＡと等しい特性となる。
【００６２】
又、間隙の測定時においては、光路切り替え部３８により、画像濃度測定時の光路４９と異なる光路５０に切り替えられ、ファイバー束２８とファイバー束３６により照射光５３を導き、ファイバー３５により反射光５４を導くように構成され、さらに、光ファイバーセンサ３７の出力は、間隙値（Ｇｒ）付近で出力と間隙との関係が略直線となるように構成されている。従って、間隙の測定時におけるセンサ出力特性は、図６のＢと等しい特性となる。
【００６３】
尚、光路切り替え部３８はミラーやビームスプリッタやプリズムなどの光学素子を用いたり、光ファイバー束や導波路などにより構成可能である。
【００６４】
このような構成においては、光路切り替え部３８により光路を切り替える機構が付加するが、１本の光ファイバーセンサ３７を用いてトナー画像の画像濃度と間隔の測定ができ、且つ、基準反射面として感光体表面（地肌部）を用いることができるので、感光体１上に凸部（又は凹部）を設ける必要がない利点がある。
尚、上記した第２ないし第４の実施例では、光ファイバーセンサ１１を感光体１に対向させて配置したが、光ファイバーセンサ１１を中間転写体や用紙搬送経路に対向させて配置し、センサとの間隙や中間転写体や用紙上のトナー画像の画像濃度を測定するようにしても良い。
【００６５】
〔第５の実施の形態〕
第２乃至第４の実施例に記載した光ファイバーセンサ（３０及び３３、又は３７）のいずれかを用い、感光体１の各位置の間隙を測定し、感光体１の偏心情報を考慮し画像濃度制御を行うようにしたものである。
【００６６】
すなわち、テストパッチの画像濃度を光センサにより測定し、その測定値に基づいて現像バイアスを制御する際、画像濃度制御部８において感光体１の回転方向の各位置において偏心情報（間隙値）を考慮し現像バイアス電源９を制御するものである。
【００６７】
従って、本例では、感光体１の偏心に伴う濃度ムラを防止でき、画像濃度をより均一で安定にできる効果がある。
【００６８】
【発明の効果】
本発明によれば、センサの誤検出や誤動作等の異常がなく、センサの寿命を長くでき、且つ簡易な測定系で、高画質な画像を記録可能な画像形成装置を提供することができる。
【００６９】
また、感光体の偏心に伴う濃度ムラがなく、画像濃度をより均一で安定可能な画像形成装置を提供することができる。
【図面の簡単な説明】
【図１】本発明からなる画像形成装置の一実施例を示す図である。
【図２】本発明の光センサ汚れ除去部の一実施例を示す図である。
【図３】本発明の光ファイバーセンサ測定部の一実施例を示す図である。
【図４】本発明の光ファイバーセンサの出力特性の一実施例を示す図である。
【図５】本発明の光ファイバーセンサ測定部の他の実施例を示す図である。
【図６】本発明の光ファイバーセンサの出力特性の他の実施例を示す図である。
【図７】本発明の光ファイバーセンサの部分断面の一実施例を示す図である。
【図８】本発明の光ファイバーセンサの部分断面の他の実施例を示す図である。
【図９】本発明の光ファイバーセンサ測定部の他の実施例を示す図である。
【図１０】本発明の光ファイバーセンサの部分断面の他の実施例を示す図である。
【図１１】本発明の光ファイバーセンサ測定部の他の実施例を示す図である。
【図１２】従来の画像形成装置を説明する図である。
【符号の説明】
１…感光体、２…帯電器、３…露光装置、４…現像機、５…トナー画像、６…光センサ、７…転写器、８…画像濃度制御部、９…現像バイアス電源、１０…現像ロール、１１，３７…光ファイバーセンサ、１２…汚れ除去手段、１３…遮断板、１４…入口側ダクト、１５…出口側ダクト、１６…感光体巻取り口、１７…凸部、１８…繰り出しローラ、１９…巻取りローラ、２０…気流、２１…噴出ノズル、２２…吸引ノズル、２３…画像形成装置、２４…入口側空気流、２５…出口側空気流、２６，２７，２８，２９，３１，３２，３４，３５，３６…ファイバー束、３０…第１の光ファイバーセンサ、３２…第２の光ファイバーセンサ、３８…光路切り替え部、３９…現像剤、４０…用紙、４１…クリーナ、４２…定着器、４３…汚れ除去制御部、４４…ポンプ、４５…濃度演算部、４６…間隙演算部、４７…異常判定部、４８…プロセス制御部、４９，５０…光路、５１…受光素子、５２…発光素子、５３…照射光、５４…反射光、５５…ガイド部材、６０…トナー。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.
[0002]
[Prior art]
2. Description of the Related Art Conventional image forming apparatuses are known that perform image density control that sets the density of an image formed on a sheet to a predetermined level before forming the image on the sheet.
[0003]
For example, as shown in FIG. 12, the image density control forms a toner image 5 on the photoreceptor 1, detects the density of the formed toner image with the optical sensor 6, and based on the detection value of the optical sensor 6, It controls the values of the parameters relating to the toner 1 adhesion amount such as the potential of the photoreceptor 1, the exposure amount, and the developing bias power source 9.
[0004]
Further, as the optical sensor 6, an optical sensor for detecting the reflectance of the toner image 5 is used, and the image density is obtained from the reflectance.
[0005]
Examples of such image forming apparatuses that perform image density control include Japanese Patent Laid-Open Nos. 9-244391, 9-244313, and 63-131152.
[0006]
[Problems to be solved by the invention]
However, in the conventional image forming apparatus, since the optical sensor is used as the density sensor, the surface of the optical sensor is contaminated by the toner floating in the apparatus, and there is a tendency that erroneous detection or malfunction is caused. In particular, in a high-speed machine having a large printing amount, the toner contamination tends to increase.
[0007]
SUMMARY OF THE INVENTION A first object of the present invention is to provide an image forming apparatus that is free from abnormalities such as erroneous detection and malfunction of a sensor, can extend the life of the sensor, and can record high-quality images with a simple measurement system.
[0008]
A second object of the present invention is to provide an image forming apparatus that is free from density unevenness due to the eccentricity of the photoconductor and is capable of stabilizing the image density more uniformly.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is based on the results measured by the optical fiber sensor, the optical fiber sensor having the photosensitive fiber bundle having the irradiation fiber bundle for guiding the irradiation light and the receiving fiber bundle for guiding the reflected light. In an image forming apparatus including an image density control unit that performs control based on
The photoconductor is provided with a reference reflecting surface, which is a reflecting surface having a substantially constant reflectivity, and the optical fiber sensor is opposed to the surface of the photoconductor, and a gap between the optical fiber sensor and an object to be detected and an output of the optical fiber sensor. A test patch formed on the photoconductor, wherein the image density control unit is arranged in a region where the relationship is in the vicinity of a peak and the output relationship between the reference reflecting surface and the optical fiber sensor is substantially proportional to the gap. The image density is controlled based on the result measured by the optical fiber sensor.
[0010]
As described above, by providing the abnormality determination unit, it is possible to know the abnormality before the deterioration of the image due to the abnormality of the sensor, the photoconductor, or the measurement system, and there is no abnormality such as erroneous detection or malfunction of the sensor. It is possible to provide an image forming apparatus capable of extending the life of the sensor and recording a high-quality image with a simple measurement system.
[0011]
In addition, by using an optical fiber sensor as the above sensor, image density measurement and distance measurement are measured according to the characteristics of the optical fiber sensor, and high-quality images are recorded with high-accuracy measurement with a simple measurement system. A possible image forming apparatus can be provided.
[0012]
The image density control unit is characterized in that image density control is performed based on a result of measuring a plurality of test patches formed at respective positions in the rotation direction of the photosensitive member with an optical fiber sensor.
[0013]
With such a configuration, it is possible to provide an image forming apparatus in which there is no density unevenness due to the eccentricity of the photoconductor and the image density can be made more uniform and stable.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
[First Embodiment]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. The image forming apparatus 23 has a photoreceptor take-up port 16, a charger 2 disposed around a take-up type photoreceptor 1 provided with a feed roller 18 and a take-up roller 19, an exposure device 3, and a developing device. A stain removal control unit for controlling the machine 4, a printing unit such as the current copying machine 7, the cleaner 41, and the fixing device 42, a developing bias power source 9, an optical sensor 6, a stain removal unit 12, and a stain removal unit 12. 43, a pump 44, an image density controller 8 and the like.
[0016]
As the charger 2, a scorotron charger having a discharge wire for performing corona discharge and a control electrode was used to control the surface potential of the photoreceptor 1. The surface potential can be controlled by changing the grid voltage applied to the control electrode.
[0017]
The exposure apparatus 3 includes a laser and its scanning optical system. Further, an optical system such as an LED array and a rod lens may be combined.
[0018]
The developing machine 4 holds the developer 39 including the toner 60 and the magnetic carrier by the magnetic force of the magnet body built in the developing roll 10, and brings the developer 39 into contact with the electrostatic latent image on the photoreceptor 1. Thus, the toner image 5 is formed. In addition to the developing device 4 and the developing roll 10, a regulating plate for regulating the transport amount of the developer 39, a toner hopper for supplementing the consumed toner, a replenishing roll, the replenished toner 60 and the developer 39. A stirring member and a magnetic sensor for detecting the mixing ratio of the toner and the magnetic carrier are arranged to improve the frictional electrification. The magnetic carrier and the toner 60 are charged with opposite polarities by frictional charging, and a bias voltage is applied to the developing roll 10 from the developing bias power source 9 when the magnetic brush-like developer 39 is rotated and brought into contact with the photosensitive member 1. The toner image 5 was formed on the photoconductor 1 by applying an electric field between the developing roll 10 and the photoconductor 1.
[0019]
The developer 39 is composed of a resin-coated magnetic carrier having a particle diameter of 40 to 100 μm and a toner 60 having a particle diameter of 6 to 11 μm with an average toner concentration (≡100 × toner weight / developer) of 1.5 to 5 (Wt%). More desirably, 2 to 4 (Wt%) developer was used.
[0020]
Toner mixing ratio is controlled by detecting the magnetic substance content by a magnetic sensor, generating a replenishment signal when the toner mixing ratio falls below a predetermined value, and controlling the toner mixing ratio to be substantially constant by replenishing the toner. It is.
[0021]
The optical sensor detects the reflectance of the toner image. Since the reflectance and the image density are in a one-to-one relationship, the image density (the optical density of a solid image or a halftone image) can be measured. it can.
[0022]
As the optical sensor, the optical fiber sensor 11 having the irradiation fiber bundle 28 for guiding the irradiation light and the light receiving fiber bundle 29 for guiding the reflected light can be used. The optical fiber sensor 11 can be stabilized against temperature changes by using glass fiber, and can be installed in a small space because it is rod-shaped. Furthermore, since a circuit board such as an amplifier can be arranged away from the measuring unit, the corona There is an advantage that noise that causes a measurement error does not occur even if a charging means that accompanies discharge is disposed in the vicinity.
[0023]
In the case of the optical fiber sensor 11 that detects the reflectance, the sensor output is affected by the reflectance between the reflecting surfaces and the gap between the reflecting surfaces.
[0024]
FIG. 4 shows the relationship between the sensor output and the gap between the optical fiber sensor 11 and the object to be detected when the reflecting surface is substantially a mirror surface. The output characteristics are mountain-shaped, and have regions L1 and L2 where the output is substantially proportional to the gap, and a region Z where the output is substantially flat near the peak (gap value is near Gr). Therefore, it can be seen that the following (1) and (2) are possible.
[0025]
(1) If the optical fiber sensor 11 is disposed in the region L1 or the region L2 with respect to a reflection surface having a substantially constant reflectivity (hereinafter referred to as a reference reflection surface), the output is substantially proportional to the gap, so that the measurement of the gap is possible. Is possible.
[0026]
(2) Further, if the optical fiber sensor 11 is arranged in the region Z with respect to the reflecting surface where the gap is held substantially constant, the sensor output is not affected by the gap, so that the reflectance of the reflecting surface can be measured. It is.
[0027]
In the present invention, based on the knowledge of (1) and (2), as shown in FIG. 3, the optical fiber sensor 11 is placed in the region Z with respect to the surface of the photoreceptor 1 on which the toner image 5 is formed (that is, the gap is Gr. And a convex portion 17 (thickness Gr-G1) is provided as a reference reflecting surface at the photosensitive member winding port 16, and the gap between the convex portion 17 and the optical fiber sensor 11 is G1 (the gap is the region L1 in FIG. 4). 1, and as shown in FIG. 1, a density calculator 45 that calculates an average value of a plurality of image density data detected by the optical fiber sensor 11, and a plurality of gap data detected by the optical fiber sensor 11. A gap calculation unit 46 that calculates an average value, an abnormality determination unit 47 that determines that there is an abnormality when the gap measurement value by the optical sensor and the known gap setting value do not match, and toner contamination of the optical sensor is removed. And soil removal unit 12, an image density control unit 8, is obtained by placing the process control unit 48.
[0028]
As an example, when the optical fiber sensor 11 is composed of fiber bundles 26 and 27 having two semicircular cross sections (similar to FIG. 7) and the diameter is 2.5 mm, Gr≈4.3 mm, Z≈1 mm, 1 Since 0.0.ltoreq.G1.ltoreq.3.0 mm, 1.3.ltoreq.Gr-G1.ltoreq.3.3 mm, that is, the gap Gr is set to 4.3 mm, and the protrusion protrudes from the surface of the photoreceptor 1 by 1.3 to 3 mm. What is necessary is just to provide the part 17. FIG.
[0029]
As the dirt removing means 12, for example, as shown in FIGS. 1 and 2, a device in which a pair of ejection nozzles 21 and suction nozzles 22 that form an airflow 20 are arranged on the surface of the optical fiber sensor 11 can be used. Details of the dirt removing means 12 will be described below with reference to FIG. 2 which is a sectional view taken along the line ZZ of FIG.
[0030]
Since the dirt removing means 12 causes the airflow 20 to flow on the surface of the optical fiber sensor 11, as shown in FIG. 2, a guide member 55 that guides the airflow is interposed as necessary, and a pair of the ejection nozzle 21 and the suction nozzle 22 are provided. It is configured by being arranged, and communicates with the inlet side duct 14 that guides the inlet side air flow 24 and the outlet side duct 15 that guides the outlet side air flow 25.
[0031]
In addition to the pair of ejection nozzles 21 and suction nozzles 22, it is desirable that a blocking plate 13 be disposed in the vicinity of the optical fiber sensor 11 and upstream in the rotation direction of the photoreceptor 1.
[0032]
Furthermore, it is more desirable that the blocking plate 13 protrudes toward the photoreceptor 1 than the pair of ejection nozzles 21 and suction nozzles 22. This is to prevent the airflow 20 on the surface of the optical fiber sensor 11 from being disturbed by the influence of the rotating airflow accompanying the rotation of the photoconductor 1. Further, even when the toner 60 and the developer 39 are scattered around the developing machine 4, the toner 60 and the developer 39 selected below by the rotating air current are not directly attached to the surface of the optical fiber sensor 11. is there.
[0033]
In general, the working distance of the optical fiber sensor 11 (interval between the optical fiber sensor 11 and the photosensitive member 1) is 0.5 to 15 mm. However, in order to arrange the pair of ejection nozzles 21 and suction nozzles 22, the working distance is 1 More than 0.5 mm is required, and the working distance is more preferably 3 mm or more. When the width of the ejection nozzle 21 is narrow, not only a sufficient flow rate cannot be obtained, but also the pressure loss increases and the internal pressure of the inlet side duct 14 leading the inlet side air flow 24 increases, and a robust duct and a larger blower are required. Because it becomes.
[0034]
The dirt removing means 12 is for removing toner and paper dust adhering to the surface of the optical sensor by forming an air flow 20 when the dirt of the optical sensor is detected. The dirt removing means 12 always forms an air flow 20 and suppresses toner from adhering to the optical sensor due to the air curtain effect. When the amount of adhering material increases, an air flow 20 having a higher flow velocity than usual is generated. It is desirable to remove dirt.
[0035]
As the optical fiber sensor 11 described above, an optical fiber having a length of several centimeters to several tens of centimeters is used for a long optical fiber portion of several meters, or an integrated photosensor in which a light emitting element, a light receiving element, a lens, and the like are integrally formed. The built-in one can also be used.
[0036]
In such a configuration, the measurement value of the gap of the convex portion by the optical fiber sensor 11 is sent to the abnormality determination unit, and when the abnormality determination unit does not match the known gap setting value, it is determined as abnormal (contamination state), and dirt The removal control unit issues a command to operate the dirt removing unit 12, and the dirt removing unit 12 that has received this command forms an air flow 20 on the surface of the optical fiber sensor 11 to remove the adhered toner and paper dust. Therefore, it is possible to prevent erroneous detection of toner image density due to toner contamination of the optical fiber sensor 11. Further, the abnormality detection step is set in advance so as to be performed at any one of the time of warm-up, paper replacement, and fixed time, and is controlled by the process control unit 48.
[0037]
Therefore, even in long-term printing, there is an effect that it is possible to prevent malfunction and detection of the image density control system due to toner contamination of the optical sensor.
[0038]
If the measured distance between the convex portions by the optical fiber sensor 11 matches the known set distance, the abnormality determination unit 47 determines that the state is normal (no contamination), forms a toner image, and detects the image density. The process is performed, and the detected value of the image density is sent to the image density control unit 8 via the abnormality determination unit 47 to perform image density control.
[0039]
For example, as shown in FIG. 1, the solid image 5 is formed as a test patch on the photosensitive member 1 serving as a recording medium, and the image density of the formed toner image 5 is determined by the optical fiber sensor 11. The image density control unit 8 changes the voltage of the developing bias power source 9 based on the comparison between the detection value of the optical fiber sensor 11 and the reference value, and controls the solid image density to a predetermined value.
[0040]
At that time, if the difference between the surface potential and the developing bias voltage exceeds a predetermined range, fogging and carrier adhesion increase, and the reproduction of fine lines and halftone dots is affected, so the grid voltage of the charger 2 is changed. And correct the surface potential.
[0041]
In the halftone image density control, a halftone dot / toner image 5 is formed as a test patch on the photosensitive member 1, and the image density of the halftone dot / toner image 5 is detected by the optical fiber sensor 11. Based on the comparison between the detection value of the optical fiber sensor 11 and the reference value, the exposure amount or dot exposure time (pulse width) of the exposure device 3 is changed to control the halftone image density to a predetermined value.
[0042]
In the above example, the convex portion 17 is provided on the photosensitive body winding port 6 as the reference reflecting surface, and the surface is used. However, the concave portion (gap is the region L2 in FIG. 4) with the optical sensor is used. The same effect can be obtained by providing a dent amount from the surface of the photosensitive member of 1.3 to 3.0 mm) as a reference reflecting surface.
[0043]
In the above-described example, the optical fiber sensor 11 is disposed so as to face the photoconductor 1, but a concave portion (paper surface) in which the gap between the optical sensor and the optical sensor is G2 (gap is the region L2 in FIG. 4) in the conveyance path of the paper 40. And the optical fiber sensor 11 is disposed so as to face the paper 40, and the distance between the image density of the toner image on the paper and the concave portion of the paper path is measured. good.
[0044]
Furthermore, a single optical fiber sensor may be arranged, and the set gap may be switched to Gr when measuring the image density and to G1 (or G2) when measuring the gap. In this case, a mechanism for switching the gap is required. However, since the reference reflecting surface uses the surface of the photoconductor (cut surface portion), there is an advantage that it is not necessary to provide unevenness on the photoconductor.
[0045]
In addition to the toner contamination on the surface of the optical sensor, the cause of abnormalities in the optical sensor output (outside the predetermined range), the change in the light amount of the generated element due to temperature change and deterioration over time, the change in sensitivity of the light receiving element and the sensitivity There are changes in the surface of the photoreceptor due to poor cleaning, scratches, and wear of the body. Therefore, when an abnormal signal is issued, a process of cleaning the photoconductor 1 or a process of calibrating the photosensor after cleaning of the photoconductor 1 is interposed, and then only when an abnormal signal is issued again. Then, the process control may be performed so that the dirt removing means 12 of the optical fiber sensor 11 is operated.
[0046]
The calibration of the light sensor is performed by driving the light emitting element so that the difference between the output voltage measured on a predetermined reflecting surface (background portion or calibration plate) and the output voltage when the light emission is turned off becomes a predetermined value. What is necessary is just to adjust an electric current.
[0047]
[Second Embodiment]
The second embodiment is different from the first embodiment in the configuration of the optical sensor unit. As shown in FIG. 5, the first and second optical fiber sensors 30, 33 are arranged as the optical sensor unit. It is composed.
[0048]
As shown in FIG. 7, in the first and second optical fiber sensors 30 and 33, the irradiation fiber bundles 28 and 31 for guiding the irradiation light and the reflection fiber bundles 29 and 32 for guiding the reflection light are formed in the same semicircular shape. The diameter of the fiber bundle of the second optical fiber sensor 33 is configured to be larger than the diameter of the fiber bundle of the first optical fiber sensor 30.
[0049]
The first optical fiber sensor 30 is set equal to the gap value (Gr) given by the peak value, and the diameter of the fiber bundle of the second optical fiber sensor 33 is such that the relationship between the output and the gap is substantially linear at the gap value (Gr). Thus, the diameter of the fiber bundle of the second optical fiber sensor 33 is configured to be larger than the diameter of the fiber bundle of the first optical fiber sensor 33.
[0050]
That is, in the case of this example, the sensor output characteristics of the first and second optical fiber sensors 30 and 33 are output at the gap Gr in the case of the first optical fiber sensor 30 as shown in FIGS. On the other hand, the peak of the second optical fiber sensor 33 having a larger fiber bundle diameter is shifted to the larger gap, and the relationship between the output and the gap becomes a substantially straight line.
[0051]
As an example, when the diameter of the first optical fiber sensor 30 is 2.5 mm and the diameter of the second optical fiber sensor 30 is 4.3 mm, the gap Gr that gives the peak of the output of the first optical fiber sensor 30 is The region where the output of the second optical fiber sensor 33 is 4.3 mm is a straight line from 0.8 to 5.1 mm, and the gap is set to 4.3 mm.
[0052]
Since the first and second optical fiber sensors 30 and 33 have the same set interval, the arrangement of the dirt removing means is easy. However, from the viewpoint of preventing and removing the toner dirt, both of them are used. It is desirable to integrate and cover the tip with a window member.
[0053]
In such a configuration, the number of sensors increases by one, but the image density of the toner image on the photosensitive member 1 can be measured using the first optical fiber sensor 30 and set to the same gap Gr as that of the first optical fiber. The gap can be measured by using the second optical fiber sensor 33. That is, in this example, the photosensitive member surface (background portion) can be used as a reference reflecting surface for measuring the gap, so that a convex portion (or a concave portion) is formed on the photosensitive member 1 as compared with the first embodiment. There is an advantage that it is not necessary to provide.
[0054]
Two optical fibers having the same diameter may be used, and the interval may be set to Gr for image density measurement, and the interval may be set to G1 or G2 for interval measurement. In this case, since the surface of the photosensitive member (background portion) can be used as the reference reflecting surface, there is an advantage that it is not necessary to provide a convex portion (or a concave portion) on the photosensitive member 1 as in the second embodiment.
[0055]
[Third Embodiment]
This example is a modification of the second example, and the sectional shape of the tip of the second optical fiber sensor 33 is different from that of the second example.
[0056]
In the first optical fiber sensor 30, as shown in FIG. 8, the irradiation fiber bundle 28 for guiding the irradiated light and the light receiving fiber bundle 29 for guiding the reflected light are configured in the same semicircular shape. In the optical fiber sensor 33, the irradiation fiber bundle 34 for guiding the irradiation light is arranged in a circular shape, and the light receiving fiber bundle 35 for guiding the reflected light is arranged concentrically around the irradiation fiber bundle 34. Further, the first optical fiber sensor 30 is set equal to the gap value (Gr) given by the peak value, and the second optical fiber sensor 33 is configured such that the relationship between the output and the gap is substantially a straight line at the gap value (Gr).
[0057]
That is, also in the case of this example, the sensor output characteristics of the first and second optical fiber sensors 30 and 33 are the gap Gr in the case of the first optical fiber sensor 30 as shown in FIGS. Whereas the peak of the output is given, the peak of the second optical fiber sensor 33 is shifted to the side where the gap is larger, and the relationship between the output and the gap becomes a substantially straight line.
[0058]
Even in such a configuration, the number of sensors is increased by one as in the second embodiment, but the image density of the toner image on the photosensitive member 1 can be measured using the first optical fiber sensor 30, and the gap Gr can be measured. The gap can be measured using the set second optical fiber sensor 33. Accordingly, also in this example, since the surface of the photosensitive member (background portion) can be used as a reference reflecting surface for measuring the gap, a convex portion (or a concave portion) is formed on the photosensitive member 1 as compared with the first embodiment. ).
[0059]
[Fourth Embodiment]
The fourth embodiment is an improved example of the third embodiment, and is configured by arranging one optical fiber sensor 37 as shown in FIG. 9 instead of the optical fiber sensor 11 in the first embodiment. . Hereinafter, description will be made with reference to FIGS. 10, 11, and 6. As shown in FIG. 10, the optical fiber sensor 37 of this example includes three-part fiber bundles 28, 35, and 36, and the fiber bundles 28 and 36 have the same semicircular cross section. The fiber bundle 35 has a concentric cross section around the fiber bundles 28 and 36.
[0060]
Further, as shown in FIGS. 11A and 11B, an optical path switching unit 38 that switches the optical path in the fiber sensor 37 between the image density measurement and the gap measurement is provided in front of the light receiving / emitting elements 51 and 52. It is provided. As the light emitting element 52, a GaAs infrared light emitting diode or a semiconductor laser can be used, and as the light receiving element 51, a Si phototransistor or the like can be used.
[0061]
At the time of image density measurement, the optical path 49 is set so that the irradiation light 53 is guided by the fiber bundle 28 and the reflected light 54 is guided by the fiber bundle 36. Further, the gap of the optical fiber sensor 37 is a gap where the sensor output gives a peak value. It is set equal to the value (Gr). Therefore, the sensor output characteristic at the time of image density measurement is the same as that of A in FIG.
[0062]
At the time of measuring the gap, the optical path switching unit 38 switches the optical path 50 to be different from the optical path 49 at the time of image density measurement. The irradiation light 53 is guided by the fiber bundle 28 and the fiber bundle 36, and the reflected light 54 is reflected by the fiber 35. Further, the output of the optical fiber sensor 37 is configured such that the relationship between the output and the gap is substantially a straight line near the gap value (Gr). Accordingly, the sensor output characteristic at the time of measuring the gap is the same characteristic as B in FIG.
[0063]
The optical path switching unit 38 can be configured by using an optical element such as a mirror, a beam splitter, or a prism, or by an optical fiber bundle or a waveguide.
[0064]
In such a configuration, a mechanism for switching the optical path by the optical path switching unit 38 is added, but the image density and interval of the toner image can be measured using one optical fiber sensor 37, and the photoconductor as a reference reflecting surface Since the surface (background part) can be used, there is an advantage that it is not necessary to provide a convex part (or a concave part) on the photoreceptor 1.
In the second to fourth embodiments described above, the optical fiber sensor 11 is disposed so as to face the photoconductor 1, but the optical fiber sensor 11 is disposed so as to face the intermediate transfer member and the sheet conveyance path. You may make it measure the image density of the toner image on a gap | interval, an intermediate transfer body, or a paper.
[0065]
[Fifth Embodiment]
Using any one of the optical fiber sensors (30 and 33, or 37) described in the second to fourth embodiments, the gap at each position of the photoconductor 1 is measured, and the image density is taken into consideration by taking the eccentricity information of the photoconductor 1 into consideration. Control is performed.
[0066]
That is, when the image density of the test patch is measured by the optical sensor and the developing bias is controlled based on the measured value, the image density control unit 8 provides the eccentricity information (gap value) at each position in the rotation direction of the photoreceptor 1. The developing bias power source 9 is controlled in consideration.
[0067]
Therefore, in this example, density unevenness due to the eccentricity of the photoreceptor 1 can be prevented, and the image density can be more uniform and stable.
[0068]
【The invention's effect】
According to the present invention, it is possible to provide an image forming apparatus in which there is no abnormality such as erroneous detection or malfunction of the sensor, the life of the sensor can be extended, and a high-quality image can be recorded with a simple measurement system.
[0069]
In addition, it is possible to provide an image forming apparatus in which there is no density unevenness due to the eccentricity of the photosensitive member and the image density can be more uniform and stable.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a diagram showing an embodiment of the optical sensor dirt removing unit of the present invention.
FIG. 3 is a diagram illustrating an example of an optical fiber sensor measurement unit according to the present invention.
FIG. 4 is a diagram showing an example of output characteristics of the optical fiber sensor of the present invention.
FIG. 5 is a diagram showing another embodiment of the optical fiber sensor measurement unit of the present invention.
FIG. 6 is a diagram showing another example of output characteristics of the optical fiber sensor of the present invention.
FIG. 7 is a diagram showing an example of a partial cross section of the optical fiber sensor of the present invention.
FIG. 8 is a view showing another embodiment of the partial cross section of the optical fiber sensor of the present invention.
FIG. 9 is a diagram showing another embodiment of the optical fiber sensor measurement unit of the present invention.
FIG. 10 is a view showing another embodiment of the partial cross section of the optical fiber sensor of the present invention.
FIG. 11 is a diagram showing another embodiment of the optical fiber sensor measurement unit of the present invention.
FIG. 12 is a diagram illustrating a conventional image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Charger, 3 ... Exposure apparatus, 4 ... Developing machine, 5 ... Toner image, 6 ... Optical sensor, 7 ... Transfer device, 8 ... Image density control part, 9 ... Development bias power supply, 10 ... Developing roller 11, 37 ... Optical fiber sensor, 12 ... Dirt removing means, 13 ... Blocking plate, 14 ... Inlet duct, 15 ... Outlet duct, 16 ... Photoreceptor winding port, 17 ... Convex part, 18 ... Feeding roller, DESCRIPTION OF SYMBOLS 19 ... Winding roller, 20 ... Air flow, 21 ... Jet nozzle, 22 ... Suction nozzle, 23 ... Image forming apparatus, 24 ... Inlet side air flow, 25 ... Outlet side air flow, 26, 27, 28, 29, 31, 32, 34, 35, 36 ... Fiber bundle, 30 ... First optical fiber sensor, 32 ... Second optical fiber sensor, 38 ... Optical path switching unit, 39 ... Developer, 40 ... Paper, 41 ... Cleaner, 42 ... Fixer 43 ... Dirt removal Control unit 44 ... pump 45 ... concentration calculation unit 46 ... gap calculation unit 47 ... abnormality determination unit 48 ... process control unit 49, 50 ... light path 51 ... light receiving element 52 ... light emitting element 53 ... irradiation Light, 54 ... reflected light, 55 ... guide member, 60 ... toner.

Claims

A photoconductor, an optical fiber sensor having an irradiation fiber bundle for guiding irradiation light and a light receiving fiber bundle for guiding reflected light, and an image density control unit for controlling based on the result measured by the optical fiber sensor In the image forming apparatus,
The photoconductor is provided with a reference reflecting surface, which is a reflecting surface having a substantially constant reflectivity, and the optical fiber sensor is opposed to the surface of the photoconductor, and a gap between the optical fiber sensor and an object to be detected and an output of the optical fiber sensor. A test patch formed on the photoconductor, wherein the image density control unit is arranged in a region where the relationship is in the vicinity of a peak and the output relationship between the reference reflecting surface and the optical fiber sensor is substantially proportional to the gap. An image forming apparatus, wherein the image density is controlled based on the result of measurement by the optical fiber sensor.

2. The image forming apparatus according to claim 1, wherein the reference reflecting surface is a concave portion or a convex portion with respect to the surface of the photoconductor.

An optical fiber sensor having a photosensitive member, a paper conveyance path, an irradiation fiber bundle for guiding irradiation light, and a light receiving fiber bundle for guiding reflected light, and image density control controlled based on a result measured by the optical fiber sensor An image forming apparatus comprising:
A reference reflection surface which is a reflection surface having a substantially constant reflectivity with respect to the sheet conveyance path is provided in the sheet conveyance path, and the optical fiber sensor faces the sheet conveyance path and faces the optical fiber sensor. The image density control unit is arranged so that the gap between the detected object and the optical fiber sensor output relationship is in the vicinity of the peak, and the reference reflection surface and the optical fiber sensor output relationship are substantially proportional to the gap. An image forming apparatus that controls image density based on a result of measuring a test patch formed on the photosensitive member by the optical fiber sensor.

A photoconductor, an optical fiber sensor having an irradiation fiber bundle for guiding irradiation light and a light receiving fiber bundle for guiding reflected light, and an image density control unit for controlling based on the result measured by the optical fiber sensor In the image forming apparatus,
The optical fiber sensor is disposed at a position facing the surface of the photoconductor, and the image forming apparatus includes a region where the gap between the detection object facing the optical fiber sensor and the output relationship of the optical fiber sensor is near a peak, A mechanism is provided for switching the optical fiber sensor output relationship between the detection object facing the optical fiber sensor and a region in which the optical fiber sensor output is substantially proportional to the gap, and the image density control unit measures the test patch formed on the photoconductor with the optical fiber sensor. An image forming apparatus that controls the image density based on the result.

Control is performed based on the results measured by the two optical fiber sensors, the first and second optical fiber sensors having the photosensitive member, the irradiation fiber bundle for guiding the irradiation light, and the light receiving fiber bundle for guiding the reflected light. In an image forming apparatus including an image density control unit,
The diameter of the second optical fiber sensor is larger than the diameter of the first optical fiber sensor, the two optical fiber sensors are opposed to the surface of the photoconductor, and the detection object is opposed to the first optical fiber sensor. The image density control unit is arranged in a region where the relationship between the gap of the optical fiber sensor and the output of the optical fiber sensor is in the vicinity of the peak, and the image density control unit determines the image density based on the result of measuring the test patch formed on the photoconductor An image forming apparatus that controls the image forming apparatus.

Control is performed based on the results measured by the two optical fiber sensors, the first and second optical fiber sensors having the photosensitive member, the irradiation fiber bundle for guiding the irradiation light, and the light receiving fiber bundle for guiding the reflected light. In an image forming apparatus including an image density control unit,
The diameters of the first and second optical fiber sensors are the same, and the first optical fiber sensor faces the surface of the photosensitive member, and the gap between the optical fiber sensor and the detection object facing the optical fiber sensor and the optical fiber sensor output relationship. The second optical fiber sensor is disposed in a region where the optical fiber sensor output relationship with the detection object facing the optical fiber sensor is substantially proportional to the gap, and the image density control unit An image forming apparatus, wherein an image density is controlled based on a result of measuring a test patch formed on a photoconductor with the two optical fiber sensors.

A photoconductor, an optical fiber sensor having irradiation fiber bundles for guiding irradiation light, and first and second light receiving fiber bundles for guiding reflected light, and an image density controlled based on a result measured by the optical fiber sensor In an image forming apparatus comprising a control unit,
An optical path for switching to the image forming apparatus between when the light irradiated from the irradiation fiber bundle and reflected by the reflecting surface is guided to the first light receiving fiber bundle and when guided to the second light receiving fiber bundle. The optical fiber sensor faces the surface of the photoconductor, and when the light irradiated from the irradiation fiber bundle and reflected by the reflecting surface is guided to the first light receiving fiber bundle, The optical fiber sensor is disposed in a region where the gap between the detection object facing the optical fiber sensor and the output relationship of the optical fiber sensor is near the peak, and the image density control unit is a result of measuring the test patch formed on the photoconductor with the optical fiber sensor. An image forming apparatus that controls image density based on the above.

8. The image forming apparatus according to claim 5, wherein the image density control unit measures a plurality of test patches formed at respective positions in a rotation direction of the photoconductor using the optical fiber sensor. An image forming apparatus that performs image density control based on the above.

Control based on the results measured by the two optical fiber sensors, the first and second optical fiber sensors having the intermediate transfer member, the irradiation fiber bundle for guiding the irradiation light, and the light receiving fiber bundle for guiding the reflected light. In an image forming apparatus provided with an image density control unit
The diameter of the second optical fiber sensor is larger than the diameter of the first optical fiber sensor, the two optical fiber sensors are opposed to the intermediate transfer member, and the detection object is opposed to the first optical fiber sensor. The image density control unit is arranged in an area where the gap and the optical fiber sensor output relationship are in the vicinity of the peak, and the image density control unit determines the image density based on the result of measuring the test patch formed on the intermediate transfer body with the two optical fiber sensors. An image forming apparatus that controls the image forming apparatus.

Control based on the results measured by the two optical fiber sensors, the first and second optical fiber sensors having the intermediate transfer member, the irradiation fiber bundle for guiding the irradiation light, and the light receiving fiber bundle for guiding the reflected light. In an image forming apparatus provided with an image density control unit
The diameters of the first and second optical fiber sensors are the same. The first optical fiber sensor faces the intermediate transfer member, and a relationship between a gap between the optical fiber sensor and a detection object facing the optical fiber sensor and the optical fiber sensor output relationship are In the region close to the peak, the second optical fiber sensor is disposed in a region where the optical fiber sensor output relationship with the detection object facing the optical fiber sensor is substantially proportional to the gap, and the image density control unit An image forming apparatus, wherein image density is controlled based on a result of measuring a test patch formed on a transfer body with the two optical fiber sensors.

An intermediate transfer member, an optical fiber sensor having irradiation fiber bundles for guiding irradiation light and first and second light receiving fiber bundles for guiding reflected light, and an image to be controlled based on a result measured by the optical fiber sensor In an image forming apparatus including a density control unit,
An optical path for switching to the image forming apparatus between when the light irradiated from the irradiation fiber bundle and reflected by the reflecting surface is guided to the first light receiving fiber bundle and when guided to the second light receiving fiber bundle. The optical fiber sensor includes a switching unit, and the optical fiber sensor faces the intermediate transfer body, and when the light irradiated from the irradiation fiber bundle and reflected by the reflecting surface is guided to the first light receiving fiber bundle, the optical fiber sensor As a result of measuring the test patch formed on the intermediate transfer body with the optical fiber sensor, the image density control unit is disposed in a region where the gap between the sensor and the detected object and the output relationship of the optical fiber sensor is near the peak. An image forming apparatus that controls image density based on the above.

Control based on the results measured by the two optical fiber sensors, the first and second optical fiber sensors having a paper conveyance path, an irradiation fiber bundle for guiding the irradiation light, and a light receiving fiber bundle for guiding the reflected light In an image forming apparatus provided with an image density control unit
The diameter of the second optical fiber sensor is larger than the diameter of the first optical fiber sensor, the two optical fiber sensors are opposed to the paper transport path, and are detected objects facing the first optical fiber sensor. It is arranged in a region where the gap and the optical fiber sensor output relationship are in the vicinity of the peak, and the image density control unit controls the image density based on the result of measuring the toner image on the paper by the two optical fiber sensors. An image forming apparatus.

Control based on the results measured by the two optical fiber sensors, the first and second optical fiber sensors having a paper conveyance path, an irradiation fiber bundle for guiding the irradiation light, and a light receiving fiber bundle for guiding the reflected light In an image forming apparatus provided with an image density control unit
The diameters of the first and second optical fiber sensors are the same, and the first optical fiber sensor is opposed to the paper transport path, and the relationship between the gap between the optical fiber sensor and the detected object and the optical fiber sensor output relationship is the same. In the region near the peak, the second optical fiber sensor is disposed in a region where the output relationship of the optical fiber sensor with the detection object facing the optical fiber sensor is substantially proportional to the gap, and the image density control unit An image forming apparatus, wherein the image density is controlled based on a result of measuring the toner image of the toner image by the two optical fiber sensors.

An optical fiber sensor having a paper conveyance path, an irradiation fiber bundle for guiding the irradiation light, and first and second light receiving fiber bundles for guiding the reflected light, and an image controlled based on a result measured by the optical fiber sensor In an image forming apparatus including a density control unit,
An optical path for switching to the image forming apparatus between when the light irradiated from the irradiation fiber bundle and reflected by the reflecting surface is guided to the first light receiving fiber bundle and when guided to the second light receiving fiber bundle. The optical fiber sensor includes a switching unit, and the optical fiber sensor faces the paper transport path, and when the light irradiated from the irradiation fiber bundle and reflected by the reflecting surface is guided to the first light receiving fiber bundle, the optical fiber sensor The image density control unit is arranged based on the result of measuring the toner image on the paper by the optical fiber sensor. An image forming apparatus that controls density.

15. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that an abnormality is detected when a gap measurement value by the optical fiber sensor and a known gap setting value are inconsistent. If the distance measurement value of the reference reflecting surface by the optical sensor matches a known distance setting value, the abnormality determination unit determines that it is normal, forms a test patch, and sets the image density. An image forming apparatus that performs image density control by sending the detected value of the image density to the image density control unit via the abnormality determination unit after performing the detecting step.

The image forming apparatus according to claim 15, further comprising a cleaning unit that cleans the sensor when the abnormality determination unit determines that an abnormality has occurred.

17. The image forming apparatus according to claim 16, wherein the image density control unit is provided in the image forming apparatus based on a detection value obtained by detecting an image density of a test patch formed on the photoconductor with the optical fiber sensor. An image forming apparatus, wherein a voltage of a certain developing bias power source is changed to control an image density to a predetermined value.

17. The image forming apparatus according to claim 16, wherein the image density control unit is provided in the image forming apparatus based on a detection value obtained by detecting an image density of a test patch formed on the photoconductor with the optical fiber sensor. An image forming apparatus that controls a grid voltage of a certain charger and controls an image density to a predetermined value.

17. The image forming apparatus according to claim 16, wherein the image density control unit is arranged in the image forming apparatus based on a detection value obtained by detecting the image density of a test patch formed on the photoconductor with the optical fiber sensor. An image forming apparatus, wherein an image density is controlled to a predetermined value by changing an exposure amount or a dot exposure time of an exposure apparatus.