JP3574975B2 - Image forming device - Google Patents

Description

【００１９】
以上のような値を用いることにより、如何なる色調においても、ドット画像部の線、及びベタ画像部での色調の差は殆どなくなった。
【００２０】
この調整は操作パネル上のつまみ又はホスト１００からの信号により行なわれる。上記の例は３法式のステップとして説明したが図１１に示すように連続的に変化をさせてもよい。
【００２１】
又、以上のような調整法を用いることによりカラー画像を希望の色で行なうことができる。
【００２２】
次に前記画像形成装置のプロセスを使用したプリンター装置の構成を説明する。
【００２３】
図６において１は画像形成装置の下部枠体で、該下部枠体１内には転写体である記録紙Ｐを給紙する半月状の給紙ローラ２を設け、前記記録紙Ｐを複数枚内蔵した給紙カセット３を前記下部枠体１に着脱自在に設けられている。給紙カセット３内にはスプリング５により押上げられる押上板４が設けられており、前記記録紙Ｐを載置し、給紙カセット３の一部に回動自在に設けた分離爪６を記録紙Ｐの先端最上部に係止する。７は記録紙Ｐの両側を案内する案内板で記録紙のサイズにより調整可能に設けられている。以上の構成が給紙カセット３内に設けられている。８は下部枠体１に設けられた記録紙Ｐの搬送ローラで、給紙ローラ２で給紙された記録紙Ｐの先端を案内する案内板９と反転案内板１０の間に設けられている。
【００２４】
１１は記録紙Ｐを反転給紙した後、レジストローラ１２に案内するための案内板で、前記レジストローラ１２に記録紙Ｐを案内する。１３は前記レジストローラ１２の位置で記録紙Ｐを検知するためのセンサーＳ_１をＯＮ，ＯＦＦする揺動部材である。１４はレジストローラ１２を通過した記録紙Ｐを転写ベルト１５方向に給紙案内する案内板で、前記転写ベルト１５は転写用ローラ１６とローラ１７及び駆動ローラ１８に懸架されている。１５ａは前記転写ベルト１５の表面をクリーニングするクリーニング手段である。１９は記録紙Ｐ上に転写された像を定着する定着装置で、定着用加熱ローラ２０と圧着ローラ２１よりなり、前記定着用加熱ローラ２０にはクリーニングローラ２０ａを圧接し、回転に応じてクリーニングする。２２は定着装置１９より記録紙Ｐを排出する排紙ローラで、記録紙Ｐの排紙確認するためセンサーＳ_２をＯＮ，ＯＦＦする揺動部材２３を排紙時に記録紙により作動させる。排紙された記録紙Ｐは記録紙案内部材２４と、上部枠体１ｃに形成された案内通路２５及び案内搬送ローラ２６，２７により上部枠体１ｃ上部の略全面に設けられた排紙トレイ２８に記録紙Ｐが排紙されるよう構成されている。次に上部枠体１ｃの略中央部には画像形成用の像担持体２９（以下感光体ドラム２９と云う）を設け、該感光体ドラム２９の面に沿って上部より４組の現像装置３０，３１，３２，３３を夫々配設し得るようにした現像装置枠体３０ａがある。３４はポリゴンミラーでレーザ光源（図示せず）より発光されたレーザ光をｆθレンズ３５を通し、反射ミラー３６，３７，３８で反射し、前記感光体ドラム２９を露光する。３９は前記ポリゴンミラー３４、反射ミラー３６，３７，３８等の光学系を一体に組込んだ光学系枠体で、上部枠体１ｃの最上部に組込まれている。
【００２５】
４０は感光体ドラム２９の全面を帯電するための帯電極で、上部枠体１ｃの一部に設けられている。４１は感光体ドラム２９より記録紙Ｐに画像を転写後、該感光体ドラム２９面に付着している残留現像剤をクリーニングするクリーニングブレードで、クリーニングされた現像剤を受け外部に排出するための搬送装置４３を設け、前記クリーニングブレードで掻落とされた現像剤を搬送装置４３に効率的に送る現像剤受部材４２をクリーニングブレード４１の下部に設ける。搬送装置４３により外部に搬送された現像剤はコンベア４５により容器４４に搬送し、適宜の量迄容器４４内に蓄積し得るようにし、取外して廃棄できるように構成する。４６は前記現像装置３０，３１，３２，３３に夫々現像剤を供給するための現像剤容器で、図示された現像剤容器は一組のみであるが４組並設して設け、前記現像装置３０，３１，３２，３３に例えばシアン、マゼンタ、イエロー、黒のカラー現像剤を供給し、カラー現像を行なうように構成している。４７は記録紙Ｐを手差しにより供給できる手差台である。尚下部枠体１と上部枠１ｃは支軸１ｂを中心に記録紙Ｐの搬送経路を開放できるように組立てられており、記録紙Ｐが給紙搬送中、不良搬送状態となり、記録紙Ｐが少なくとも定着装置１９まで達しない場合には上部枠体１ｃを支軸１ｂを中心に開放し、記録紙Ｐを取り出すことができる。又下部枠体１に設けた記録紙Ｐを他の給紙装置（図示せず）より供給可能にした案内板１ａが設けられている。
【００２６】
尚、感光体ドラム２９はクリーニングブレード４１を設けた枠体４１ａに支軸２９ａを介して設けられており、支軸２９ａが前記上部枠体１ｃに軸支する構成となっている。
【００２７】
上記の画像形成装置を用いて、前記感光体ドラム２９は図５に示すようにホスト１００よりプリンタコントローラ１０１を介してレーザ光源３５を変調するための画像信号を出力することにより、帯電極４０にて１次帯電した感光体ドラム２９面を像露光する。この像露光は前記のように図１（ｂ）に示す１色目の像露光となる。
【００２８】
次に１色目として現像装置３０でイエローのカラートナーの現像を行ない図１（ｄ）のように帯電極４０で再帯電し、図１（ｅ）に示すように前記レーザ光源により２色目の像露光を行なった後、現像装置３１でマゼンタのカラートナーを重ね合せて現像する。
【００２９】
以後同様に３色目としてシアンのカラートナー、４色目としてブラックトナーを順次重ねて再帯電像露光・現像を行なうことにより４色のカラートナー像が感光体ドラム２９面上に形成される。
【００３０】
感光体と現像剤担持体との間隙（以下ＤＳＤと云う）は０．２ｍｍから０．８ｍｍであって現像剤は磁性体粒子であるキャリヤと非磁性粒子であるトナーとの混合物よりなる２成分現像剤を用いている。
【００３１】
キャリヤの重量平均粒径は、本実施例では１５〜８０ミクロンで好ましくは２０〜５０ミクロンあり、トナーの重量平均粒径は５から２０ミクロンである。現像剤は現像剤担持体上に層厚規制手段によって所望の層厚に規制される。層厚は感光体と現像剤担持体との間隙よりわずかに薄い方が望ましい。現像剤担持体は導体または表面に絶縁層をもうけた導体からなり感光体との間に現像バイアスとして、ＤＣまたは交番（ＡＣ）電界が印加される。
【００３２】
以上のように回転する感光体ドラム２９面上に順次帯電、像露光、現像を行ない、カラートナーを重ね合わせ、露光制御にて正確なカラー画像に形成したトナー像を記録紙Ｐに転写ベルト１５にて転写し定着装置１９にてトナー像を記録紙上に定着する。
【００３３】
つぎに他の色調調整方法について述べる。
【００３４】
例としては反転現像を考える。感光体の表面電位は像露光部すなわち現像領域を−５０Ｖ非露光部すなわち白地部分を７５０Ｖとする。各色の現像バイアスは標準条件として−６００ＶのＤＣ電圧とピーク・ツー・ピーク２．５ｋＶの交番電圧が印加されている。ＤＣまたは交番電圧を高くすると現像は促進される。したがって、例えばイエローを強調したければ、イエローの現像バイアスを高くすれば良い。
【００３５】
以上のカラー現像装置を用いて現像剤は重量平均粒径４５μｍの絶縁性キャリヤでフェライトコアに樹脂コーティングを行ったキャリヤと、重量平均粒径８μｍの系色縁性トナーよりなる２成分現像剤を用いて非接触現像方法により現像を行なうとき、現像バイアス電圧は以下の値に設定して現像する。そしてイエロー、マゼンタ、シアンの各カラートナーを用いた時、現像バイアスの交流電圧をＶａ、周波数をｆＡｃ、直流電圧をＶｄｃとし、第１の調整手段として、表２に示す。
【００３６】
【表２】

【００３７】
そして第２調整手段としてレーザ光による露光のパルス幅のＤｕｔｙを以下イエロー表３で示す。
【００３８】
【表３】

【００３９】
次に表１の第１調整手段に対し他の第１調整手段としてイエロー、マゼンタ、シアンの各カラートナーの現像バイアス電圧値を表４として示す。
【００４０】
【表４】

【００４１】
次に第２調整としてレーザ光により露光のパルス幅Ｄｕｔｙを以下マゼンタを表５で示す。
【００４２】
【表５】

【００４３】
以上のような半導体レーザのパルス幅変調制御により露光量を制御し、カラー画像の色調整を行ない、レーザプリンタにより記録紙Ｐにカラー画像を形成することができるが、更に本発明の他の実施例としてカラー画像調整方法として、図７（ａ）に示すように前記現像装置の現像用スリーブと像担持体間の間隔を調整することにより色調整を行なうこともできる。即ち、現像装置３０で構成された現像装置枠体３０１内には前記像担持体２９と対向した位置に現像用スリーブ３０２を回動可能に設け、Ｎ，Ｓに磁化された磁石３０３を現像用スリーブ３０２内に固定して設ける。３０４，３０５は現像装置枠体３０１内に設けた現像剤３０６を撹拌する撹拌部材で撹拌された現像剤３０６は搬送規制部材３０７にて前記現像用スリーブ３０２にて搬送される現像剤３０６を一定の厚さと量に規制する。そして搬送された現像剤３０６は現像用スリーブ３０２と像担持体２９間では図示の如く一定の間隔ＤＳＤ１で保持されている。該保持構成としては、例えば図２に示す制御手段１０２の上部機枠１ｃの一部に設けたコロ３０８，３０９上に現像装置枠体３０１を載置し上部機枠１ｃに対し移動自在に設け、一方現像装置枠体３０１をスプリング３１０，３１１にて現像スリーブ３０２を像担持体２９より引離す方向に常時弾性的に支持し弾持し、更に駆動手段３１２に連動したカム部材３１３面で図７（ａ）に示す如く現像装置枠体３０１を阻止している。
【００４４】
以上のように構成された現像装置３０を用い画像制御を行なう時、図２に示すプリンタコントローラ１０１より出力されたビデオ信号で文字、線等はドット信号として出力され、又ベタ画像部は、ベタ画像信号として出力され、夫々エッジ部を検出して出力される。
【００４５】
前記したようにベタ画像部の１色目のＤｕｔｙを６０％、２色目のＤｕｔｙを１００％とし、エッジ部の１色目Ｄｕｔｙを８０％、２色目Ｄｕｔｙを１００％にすることにより、ドット画像と、線及びベタ画像の色調の差が殆んどなくなる。そこで、例えばレッド色やグリーン色に対し、イエロー色を強くしたいとき、図６に示すイエローの現像器３０のＤＳＤを０．６ｍｍであったものを０．５ｍｍ迄小さくすることで行なう。このような操作として、前記した駆動手段３１２を駆動してカム部材３１３面でスプリング３０１、３１１の弾力に抗して現像装置枠体３０１を押動し、像担持体２９と現像スリーブ３０２間のＤＳＤ１間を前記のような値とすることができる。この時ベタ画像部のＤｕｔｙは変化させずにエッジ部の１色目Ｄｕｔｙを６０％、２色目Ｄｕｔｙを１００％となるように調整されるようにした。このように調整することにより、ドット画像部、線、ベタ画像部の色調の差が殆んどくなった。
【００４６】
以上のような操作により希望するカラー色を得ることができる。
【００４７】
次に図７（ｂ）の実施例を説明すると、図７（ｂ）は図７（ａ）の他の実施例で、現像装置枠体３０１の一部に雄ねじ杆３１５を前記現像装置枠体３０１の移動方向に突出して設け、雌ねじを設けた歯車３１６を螺合する。該歯車３１６にはピニオン３１７を噛合し、該ピニオン３１７には駆動手段３１８を直結して設ける。尚前記歯車３１６は上部機枠１Ｃの一部に対し回転自在に設けると共に左右動を阻止するように構成する。前記同様に１０１はプリンタコントローラ、１０２はレーザプリンタ本体の制御部である。
【００４８】
本実施例は駆動手段３１８の駆動回転によりピニオン３１７を回動し、歯車３１６を回動する。歯車３１６は上部枠体１ｃ内で回動のみ可能に設けられているため、前記歯３１６の右方又は左の回動により雄ねじ杆３１５が図示上で左右何れかの方向に微動する。従って一体に設けられた現像装置枠体３０１と共に前記現像スリーブ３０２が移動し、前記像担持体２９と該現像スリーブ３０２内のＤＳＤ２の間隔を変化させることができる。本構成は極めて微少なＤＳＤ２の調整が可能であり、且つ画像信号に対し辺速な対応が可能である。以上のようなＤＳＤの調整により図７（ａ）で説明したようなカラー調整が可能である。
【００４９】
次に図８に示す実施例について説明する。本実施例は、前記現像装置３０と同様の実施例を用いて説明すると、現像装置枠体３０１の開口部に回転する現像スリーブ３０２を設け、該現像スリーブ３０２内にＮＳの固定された磁石３０３を設ける、３０４，３０５は現像装置枠体３０１内に設けた撹拌部材で現像剤を撹拌する。３１９は前記現像スリーブ３０２を回動する駆動源で、該駆動源の回転を制御する回転制御手段３２０を介して前記レーザプリンタ制御手段１０２を介してプリンタコントローラ１０１に接続している。
【００５０】
以上のように構成された現像装置３０を用い画像制御を行なう時、図２に示すプリンタコントローラ１０１より出力されたビデオ信号で、文字、線等はドット信号として出力され、又ベタ画像部はベタ画像部分として出力され夫々エッジ部を検出して出力されるが、前記図７（ａ）、（ｂ）の実施例で説明したように、前記したようにベタ画像部の１色目のＤｕｔｙを６０％、２色目のＤｕｔｙを１００％とし、エッジの１色目Ｄｕｔｙを８０％、２色目Ｄｕｔｙを１００％にすることによりドット画像と、線及びベタ画像の色調の差が殆んどなくなる。
【００５１】
以上のようなカラー調整を行なうためにここで本実施例においてはドット部とベタ画像部分の信号を受けて、レーザプリンタ制御手段１０２より駆動源の回転制御手段３２０により駆動源３１９を制御する。従って、前記ドット画像部分がベタ画像部分により現像スリーブ３０２の回転が制御される。
【００５２】
そこで例えば、前記図７（ａ）（ｂ）の実施例のようにレッド色やグリーン色に対しイエロー色を強くしたい場合には前記現像スリーブ３０２の像担持体と前記現像スリーブ３０２との線速比を３より２に小さくして現像剤の供給を落す回転数にした。このときベタ画像部のＤｕｔｙは変わらずにエッジ部の１色目Ｄｕｔｙが６０％、２色目のＤｕｔｙが１００％となるように調整された、これにより、ドット画像、線、ベタ画像の色調の差が殆んどなくなり、略完全な色調整が可能となった。
【００５３】
次に図９の実施例について説明する。
【００５４】
像担持体２９に現像用スリーブ３０２に現像剤供給側にトナー濃度を検知し、且つ制御するトナー濃度制御手段３２１を設け、該トナー濃度制御手段３２１で検知された信号を入力する入出力手段３２２を介してトナー濃度の濃淡を入力し、調整すると共に前記プリンタコントローラ１０１より画像情報を入力する画像濃度調整手段３２５設ける。そして画像濃度調整手段３２５よりトナーホッパー３２６に設けたトナー補給手段３２３を駆動する駆動手段３２４に接続する。
【００５５】
尚現像装置３０は前記同様の構成を用いているので説明を略す。以上のように構成された実施例において、プリンタコントローラ１０１から出力されたビデオ信号を孤立ドット画像部であるかエッジ部であるかを検出してベタ画像部と区別して判別信号が出力され、前記画像濃度調整手段３２５に入力される。
【００５６】
前記したように、色調調整が標準の場合ベタ画像部の１色目のＤｕｔｙを６０％、２色目のＤｕｔｙを１００％とし、エッジ部の１色目Ｄｕｔｙを８０％、２色目Ｄｕｔｙを１００％にすることにより、ドット画像と線及びベタ画像の色調の差が殆んどなくなる。そこで例えばレッド色やグリーン色に対し、イエロー色を強くしたいとき、図６に示すイエローの現像器３０のカラートナー濃度をキャリヤに対し８％であったものを１０％まで増加させる。この時ベタ画像部のＤｕｔｙは変化させずにエッジ部の１色目をＤｕｔｙ６０％、２色目Ｄｕｔｙを１００％となるようにカラートナーを調整することにより、ドット画像と線及びベタ画像の色調の差が殆んどなくなり、略完全な色調整が可能となった。
【００５７】
即ち、前記のように例えばイエローの濃度を濃くしたい場合、イエローの現像器３０のトナー濃度を高くする、この場合も、前記実施例同様、ドット画像、ベタ画像部、線等の色調が変らないようにエッジ部の１色目、２色目とベタ画像部の１色目、２色目のＤｕｔｙを適当に選択することにより解決される。
【００５８】
以上が、２色のカラートナーの現像によるカラー画像形成法について説明したが、３色以上、あるいは１色のみの画像形成制御を前記総ての実施例により適用できることは勿論である。尚この場合ドット画像部のＤｕｔｙをベタ画像部のＤｕｔｙと変えることにより、画像のつぶれや、切れがなくなり、ベタ画像部の画像濃度調整ができる。
【００５９】
本願発明の露光手段として、レーザ光による露光手段のみを説明したが、例えばＬＥＤアレイ、液晶等の露光手段を用いてもよいことは勿論である。何れの露光手段であっても、パルス幅変調もしくは、強度変調方式によりトナーの付着量を制御することができる。以上の実施例は第１の調整手段として像露光、または現像条件を変えることにより行ったが、他の条件例えば、帯電条件を変えてもよい。
【００６０】
【発明の効果】
本発明は、単色画像を再生する場合、線画、孤立点（ドット）、ベタ部のエッジもベタ部と同様に美しく再生される。特に黒色の線画網点画、ベタ画像混在画の再生画が高画質となる。また、以上のようにＣＰＵあるいは画像メモリより出力する画像によりレーザ光、ＬＥＤアレイ、液晶等による光源を用いて露光しカラートナーの現像を行なう時複数現像装置を用いて１色目の現像と２色目のに現像を行なう作用で、前記現像装置による現像作用を制御して正確なカラー画像となし、ドット画像、線、ベタ画像等のあらゆる形態のカラー画像を正確な色調として再現できる効果がある。
【図面の簡単な説明】
【図１】（ａ）〜（ｆ）は、従来の帯電、露光、制御、現像の２回現像方式を示す画像形成手段のプロセス図。
【図２】（ａ），（ｂ）は、ＣＰＵ入力よりレーザプリンタ迄を示す画像形成装置の配置説明図。
【図３】（ａ）〜（ｃ）は、画像のドット及びベタ画像における露光制御の説明図。
【図４】（ａ）〜（ｄ）は、従来のドット及びベタ画像におけるカラートナーの現像を示す説明図。
【図５】（ａ）〜（ｆ）は、本発明のドット及びベタ画像におけるカラートナーの現像を示す説明図。
【図６】本発明の画像形成手段を用いた画像形成装置の縦断面図。
【図７】（ａ），（ｂ）は、現像装置を移動し、カラートナー現像を行なう現像装置の断面図。
【図８】本発明の現像装置の現像スリーブの回転数を変えてカラートナー現像を行なう手段を示す断面図。
【図９】本発明の現像装置のトナー量を制御することによりカラートナー現像を行なう手段を示す断面図。
【符号の説明】
１ 下部枠体
１ｃ 上部枠体
２ 給紙ローラ
３ 給紙カセット
７，９，１０，１１，１４ 案内板
１２ レジストローラ
１５ 転写ベルト
２０ 定着用加熱ローラ
２０ａ クリーニングローラ
２８ 排紙トレイ
２９，２０１，３０１，３０５，３０９ 感光体ドラム（像担持体）
３０，３１，３２，３３，２０４，２０７，２１０，３０４，３０８，３１２ 現像装置
３０ａ 現像装置枠体
３４ ポリゴンミラー
３５，２０３，２０６，２０９，３０３，３０７，３１１ レーザ光源
３６，３７，３８ 反射ミラー
４０，２０２，２０５，２０８，３０２，３０５，３１０ 帯電極[0001]
[Industrial applications]
The present invention is an apparatus for forming a color image by forming a pattern-like electrostatic latent image on an image carrier using, for example, a laser light source in an image forming apparatus, and repeating the process of developing with a color toner a plurality of times. Using a plurality of color toners, when forming a color image, an image in which an isolated dot or an edge dot in the image is detected, and an exposure condition is changed to obtain a faithful color image or a monocolor image, respectively. It relates to a forming apparatus.
[0002]
[Prior art]
A color image method in which a desired color image is obtained by superimposing color toners by a conventional electrophotographic method will be described. First, FIG. 1A shows that a surface potential V is applied to an image carrier E2 for forming a color toner image. _S The first charge is applied by the band electrode E1 so that Next, only a portion where an image, that is, a character or a line image is to be formed, is image-exposed with a laser beam or the like as shown in FIG. After the image exposure is completed, only the exposed portions are erased, and the surface potential V _S Is V _L And the charges in other non-image portions are not erased. Next, as shown in FIG. 1 (c), the image carrier E2 is moved in the direction of the arrow by the developing device D to perform the first or first color development. The charge is erased in a well-shaped potential by the image exposure in FIG. 1B, and the first color toner adheres to the erased portion and is developed to form a first color toner image. Next, as shown in FIG. 1D, the second charging is performed on the band electrode E1 including the toner image portion of the first color (recharging). The surface potential is almost equal to the potential V at the time of the first charging. _S Is controlled so that For the sake of explanation, the first color toner image is separated from the image carrier E2, and the surface potential V _S It is shown in the position of the part. Next, as shown in FIG. 1 (e), the second image exposure is performed on the first color toner image, so that the electric charge is erased only in the image exposed portion in a well-shaped potential as in FIG. 1 (b). In the second image exposure, the light passes through the first color toner image and reaches the image carrier. _L To the potential V of the toner image ₁ Potential (V _L + V ₁ )become. Then, on the image carrier E2 shown in FIG. 1B, the developing device D develops the next second color toner by superimposing it on the first color toner. When developing the third color, recharging, image exposure and development may be repeated. The above is the basic process of forming a color image on an image carrier by superimposing color toners.
[0003]
The above-described color toner image formation by superposition of toners is performed by an electrophotographic apparatus in which image information is input from the outside via an interface circuit, and subjected to necessary processing and recorded, that is, a photosensitive member using a so-called image carrier. Performed by printer. Of course, a color copying machine that reads a color original, converts it into an electric signal, and records and copies it in a recording unit may be used. For example, a computer (hereinafter referred to as a CPU) is incorporated in FIG. 2A, and a host 100 equipped with a display and the like, a printer controller 101, and a laser printer unit 102 are used for recording in a recording unit in the CPU. The image information such as characters, lines, and solid images stored in the magnetic storage unit is output to the printer controller 101. After the video signal from the printer controller 101 is subjected to a process for color recording, a recording signal is created, and the semiconductor laser is modulated by this to be recorded by the laser printer 102. For example, a red A character is sequentially output as a dot image, and only the character portion is input to the laser printer 102 with a dot signal, and the laser printer 102 performs the operations shown in FIGS. 1 (a), (b), (c), ( The toner images are formed in the order of d), (e) and (f).
[0004]
As a modulation method of a semiconductor laser, a recording signal is converted into a pulse width within one pixel or a plurality of pixels, and a pulse width modulation method is used as a laser modulation signal. There is an intensity modulation method for forming large and small, and both are used as a modulation method for image exposure of a color toner superposition method. This is convenient when changing the size of the recording dots of the first color and the second color.
[0005]
For example, when creating a red color color with yellow and magenta, it is necessary to delicately adjust the color in the case where yellow is weakened and magenta is weakened, and conversely in the case where yellow is weakened and magenta is strengthened, A desired color image is obtained by adjusting the mixing ratio by superimposing the color toners by changing the exposure conditions. In the above-described color image formation, particularly when charging and exposing the color toner on the first color, exposure for the second color has a disadvantage that the influence of the toner layer of the first color is extremely large and development control of the color toner is difficult.
[0006]
However, the above tone control has the following disadvantages. That is, as shown in FIG. 3, the image signal output from the CPU of FIG. 2 to the printer controller 101 includes a dot signal which is a character, a dotted line, and a solid image signal. It is desirable that the pattern be the same. However, the color tone control cannot always change the color tone in the same manner. For example, when the duty of the lighting time of the exposure apparatus is changed, a so-called pulse width modulation method will be described first with reference to FIG. Assuming that signals are sequentially input from the left side of FIG. 3B, first, a solid image signal is input at intervals of a dot signal, and the input signal is converted into a video signal from the printer controller 101 by the control unit of the laser printer 102. Is output to
[0007]
The video signal is converted into a pulse signal by a pulse width modulation circuit (not shown) in the control unit of the laser printer 102, an ON signal is generated by outputting a dot, and a pulse of a constant width is formed. Next, a video signal of a solid image is input to the laser printer 102 at intervals, and the signal is emitted when a pulse signal having a constant width and a constant interval is turned on. For example, when DUTY is set to 50% to limit the amount of adhesion of the first color and 100% for the second color, the distribution of the light energy density received by the photoconductor as shown in FIG. When the duty of the solid image is 50%, a large difference occurs in the energy density. That is, since the solid image is the sum of the energies of adjacent dots, the average energy is greater than the energy of a single isolated dot, a single dot line, or the edge of a solid image portion (hereinafter referred to as a dot portion). Therefore, the difference in light energy between the case where the duty of the solid portion is 50% and the case where the duty is 100% is small as shown in FIG. 3A, and this state is changed to the surface on which the image carrier of FIG. 1B is exposed. FIG. 3B shows a potential curve. First, VS is 50% at the dot portion and VS at the 100% duty ratio. ₁ And the value of the surface potential is large. That is, when the duty is 50% and the duty is 100%, the surface potential is ΔVS. ₁ Just get bigger.
[0008]
In such a state, the surface potential is ΔVS as shown in the figure even if charge elimination by image exposure is performed for the solid image portion at a duty of 50% and a duty of 100%. ₂ Very few like. After performing the above-described charging and image exposure processing and developing processing, and then performing an image forming process as shown in the order of FIGS. 1 (c), (d), (e), and (f) above. First, the state of charge erasure by image exposure at a duty of 50% is shown in FIG. Since the potential drop of the dot portion is small between the dot portion and the solid image portion, when the development is performed by the developing device D as shown in FIG. 4A, the toner adhesion amount is extremely small, and the potential drop in the solid image portion is small. The toner is sufficiently adhered because it is large. Next, as shown in FIG. 4B, recharging is performed from the toner image of the first color development, and a second 100% duty image exposure is performed for the second color development as shown in FIG. 4C. In the case, during the development of the first color, the dot portion has a small amount of toner attached to the image carrier E2, so that a large amount of light energy is projected at the time of image exposure of the second color, so that the potential drops greatly, and the solid image portion has a large amount of toner attached. Therefore, projection of light energy at the time of image exposure of the second color is small, and therefore, as shown in the figure, the potential drop is smaller than that of the dot portion. When the duty is reduced in this manner, a large difference occurs in the reduction in potential between the dot and the solid image portion. Here, when the second color toner development is performed by the developing device E1, a large amount of toner adheres to the solid image portion because the dot portion is largely erased and the charge is erased. FIG. 4 shows a case where the duty ratio at the time of image exposure of the second color is larger than that of the first color (from 50% to 100). At this time, the toner adhesion amount of the second color is much larger than the toner amount of the first color. That is, the color tone of the dot and the solid image portion changes, and the color adjustment is required. Here, even if a desired color image is obtained because the toner adhesion amounts of the first color and the second color in the solid image portion are substantially uniform, the color tone of the dot portion is different.
[0009]
There is another color tone control, for example, a method of controlling the amount of developed toner by changing development conditions for each color. However, this method also results in a different amount of adhesion depending on the image pattern, resulting in a change in color tone. In a developing method in which an AC voltage is applied to the developing device, the amount of developing toner can be controlled by changing the intensity of the AC voltage. However, it has been found that when the AC voltage is increased, the amount of the developing toner is larger in the dots and lines than in the solid image, and thus there is a disadvantage that the color tone changes between the solid and the dots or lines. In addition to the drawbacks described above, when adjusting the image density of a monochrome image, even if the solid image portion has a desired density, characters may be crushed, blurred, or a thin line may be cut off. is there. When a color image is reproduced, even when a solid portion is reproduced in a desired color even when color adjustment is performed, the end portion of the solid image portion, dots and lines may not be reproduced in a desired color.
[0010]
Furthermore, when color adjustment is performed during reproduction of a color image, the resolution is changed, characters and the like become unclear, and the image quality is degraded.
[0011]
[Problems to be solved by the invention]
The present invention is a device specifically conceived to remedy the above disadvantages. That is, when the density of a monochrome image is adjusted, a solid image portion, a dot portion, characters, and fine lines are all clearly reproduced. Also, in reproducing a color image, when a desired color is reproduced by performing color adjustment, a solid image portion, a dot portion, characters, and lines are all reproduced in the same color.
[0012]
[Means for Solving the Problems]
A first adjusting unit that adjusts the amount of toner image attached in an image forming apparatus that forms a latent image on an image carrier using an exposure unit based on an image forming signal and forms a toner image with a developing unit using toner; A determining unit that determines an isolated dot or an edge dot; and a second adjusting unit that adjusts a toner image adhesion amount in accordance with a result of the determination by the determining unit. Based on the result of the discrimination by the discriminating means, the amount of toner adhering to an isolated dot or an edge dot and other portions The exposure amount for the isolated dots or edge dots of the first color is made larger than the exposure amount for portions other than the isolated dots or edge dots of the first color, and the exposure amount for the isolated dots or edge dots of the first color is If the exposure amount for the second color isolated dot or edge dot is different and the exposure amount for the first color non-isolated dot or non-dot portion is different from the exposure amount for the second color non-isolated dot or non-dot portion of the edge. Adjust by letting The problem has been solved by using a control means to make it possible.
[0013]
【Example】
In FIG. 6, the entire surface of the image carrier 29 is charged by the band electrode 40 of the scorotron method. Next, as shown in FIGS. 2A and 2B, characters, lines, dotted lines, etc. are output as dot signals from the printer controller 101 as video signals, and solid portions are output as solid image signals, and mixed image signals are output. Is output as the first color. Means for selecting the dot signal or the solid image signal is used. The control means in the laser printer 102 receives the video signal emitted by the printer controller 101. As shown in FIG. 2B, the control means in the laser printer 102 has a recording having an edge detection circuit section 104, a color recording correction circuit section 105, an image density adjustment section, a color tone adjustment section, and a gamma correction section 106. An image signal processing unit 103 is built in, and a mechanical controller control unit 107 and a laser driving unit 108 are further provided. With the above-described configuration, when, for example, the character A shown in FIG. 2A is output as a dot image by a video signal, the edge detection circuit unit 104 detects an edge portion. This edge portion detection uses a matrix of 3 × 3 pixels and determines whether the pixel of interest is an isolated dot, an edge portion, or a non-edge portion on a pixel-by-pixel basis by checking the density change between adjacent pixels in the main scanning and sub scanning directions. . Further, the color recording correction circuit unit 105 corrects the color recording image and the gamma correction unit 106 corrects the gamma, performs input / output control with the mechanical controller control unit 107, and further controls the mechanical controller control unit 107 and the laser drive. Input / output control is also performed with the unit 108. A signal for discriminating the isolated dot or the edge portion or the non-edge portion for each pixel is sent to the laser driving portion 108, and the laser driving portion 108 controls a laser light source to thereby produce an isolated or edge dot or solid image signal. In the case of a dot as an electric signal to the laser printer 102, the pulse width L is determined by the modulation signal of the laser beam. ₁ Is exposed at a value of Duty 40% to 100%, and in the case of a solid image, the modulation pulse width L of the laser light is ₂ Is exposed at a constant interval to a value of Duty 20% to 100%.
[0014]
It is preferable that an isolated or edge dot portion has a duty of 50% to 100% with respect to 100% of full pixels, and a solid image has a duty of 30% to 100% with respect to 100% of full pixels.
[0015]
As shown in FIG. 5 (a), when an isolated or edge dot image portion is image-exposed with a laser modulation pulse width of 80% duty and a solid image portion with a 60% duty laser modulation pulse width, the potential on the image carrier is isolated or the dot image portion of the edge portion is also exposed. The solid image portion is also at substantially the same level. When development is performed by the developing device 30 in this state, as shown in FIG. 5C, the toner of the first color is isolated, or the dot image portion and the solid image portion of the edge portion are developed with substantially the same toner adhesion amount. Next, the entire surface is recharged by the band electrode 40 on the image carrier, a charge is applied, and an image is formed on the isolated or edge dot image portion and the solid image using both laser modulation pulse widths of 100% duty. Is going. As described above, at the time of the first color image exposure, the duty of the laser modulation pulse width is selected to be larger in the isolated dot portion or the dot image portion in the edge portion than in the solid image portion. By setting the duty to 100% in both cases, the amount of toner adhered during the development of the toner image is substantially the same in the isolated or edge dot image portion and the solid image portion of the first color, so that the potential drop of the second color is substantially the same. As shown in FIG. 5 (b), even when the development is finally performed using the developing device 31 for the second color, the toner adhesion amounts of the two are almost the same and the toner adhesion amount of the first color is the same.
[0016]
The first adjusting means, that is, when the image exposure is performed by pulse width modulation as the color tone adjustment, and the second adjusting means, that is, the adjusting means for controlling the isolated dots or edges so as to be different from other portions ( An example in which image exposure is performed by pulse width modulation as dot adjustment means) will be described.
[0017]
For example, if the first color is to be weaker than the standard color tone with yellow in the case of red, the duty of the first color of the solid image is 20%, the duty of the second color is 100%, the first color of the edge image is 50%, and the second color is 50%. Is adjusted to be 100%. Conversely, when it is desired to enhance the first color, the duty is set to 100% for both the first color and the second color of the solid image, and the adjustment is performed so that both the first color and the second color of the edge image become 100%. This is described below as Table 1.
[0018]
[Table 1]

[0019]
By using the above values, the difference in the color tone between the line in the dot image portion and the color tone in the solid image portion was almost eliminated in any color tone.
[0020]
This adjustment is performed by a knob on the operation panel or a signal from the host 100. Although the above example has been described as steps of three formulas, the steps may be changed continuously as shown in FIG.
[0021]
In addition, a color image can be formed with a desired color by using the above-described adjustment method.
[0022]
Next, a configuration of a printer device using the process of the image forming apparatus will be described.
[0023]
In FIG. 6, reference numeral 1 denotes a lower frame of the image forming apparatus, in which a half-moon-shaped paper feed roller 2 for feeding a recording sheet P as a transfer body is provided. A built-in paper feed cassette 3 is detachably provided on the lower frame 1. A push-up plate 4 that is pushed up by a spring 5 is provided in the paper feed cassette 3. The recording paper P is placed on the push-up plate 4, and a separation claw 6 rotatably provided on a part of the paper feed cassette 3 is recorded. The paper P is locked at the top of the leading end. Reference numeral 7 denotes a guide plate for guiding both sides of the recording paper P, which is provided so as to be adjustable depending on the size of the recording paper. The above configuration is provided in the paper feed cassette 3. Reference numeral 8 denotes a transport roller for the recording paper P provided on the lower frame 1 and is provided between a guide plate 9 for guiding the leading end of the recording paper P fed by the paper feed roller 2 and a reverse guide plate 10. .
[0024]
A guide plate 11 guides the recording paper P to the registration roller 12 after the recording paper P is reversely fed, and guides the recording paper P to the registration roller 12. Reference numeral 13 denotes a sensor S for detecting the recording paper P at the position of the registration roller 12. ₁ Is a swing member that turns ON and OFF. A guide plate 14 guides the recording paper P that has passed through the registration rollers 12 toward the transfer belt 15. The transfer belt 15 is suspended by a transfer roller 16, a roller 17, and a drive roller 18. Reference numeral 15a denotes cleaning means for cleaning the surface of the transfer belt 15. Reference numeral 19 denotes a fixing device for fixing an image transferred onto the recording paper P, which comprises a heating roller 20 for fixing and a pressure roller 21. A cleaning roller 20 a is pressed against the heating roller 20 for fixing, and cleaning is performed according to rotation. I do. Reference numeral 22 denotes a discharge roller for discharging the recording paper P from the fixing device 19, and a sensor S for confirming the discharge of the recording paper P. ₂ Is turned on and off by the recording paper when the paper is discharged. The discharged recording paper P is provided on a recording paper guide member 24, a discharge passage 28 formed in the upper frame 1 c, and a discharge tray 28 provided on substantially the entire upper surface of the upper frame 1 c by guide conveyance rollers 26 and 27. Is configured to discharge the recording paper P. Next, an image carrier 29 (hereinafter, referred to as a photosensitive drum 29) for image formation is provided substantially at the center of the upper frame 1c, and four sets of developing devices 30 are arranged along the surface of the photosensitive drum 29 from above. , 31, 32, and 33, respectively, are provided. Reference numeral 34 denotes a polygon mirror, which reflects a laser beam emitted from a laser light source (not shown) through an fθ lens 35 and reflects it on reflection mirrors 36, 37, and 38 to expose the photosensitive drum 29. Reference numeral 39 denotes an optical system frame in which optical systems such as the polygon mirror 34 and the reflection mirrors 36, 37, and 38 are integrally incorporated. The optical system frame 39 is incorporated in the uppermost portion of the upper frame 1c.
[0025]
Reference numeral 40 denotes a band electrode for charging the entire surface of the photosensitive drum 29, which is provided on a part of the upper frame 1c. Reference numeral 41 denotes a cleaning blade for transferring the image from the photosensitive drum 29 to the recording paper P and then cleaning the residual developer adhered to the surface of the photosensitive drum 29. The cleaning blade 41 receives and discharges the cleaned developer to the outside. A transport device 43 is provided, and a developer receiving member 42 that efficiently sends the developer scraped by the cleaning blade to the transport device 43 is provided below the cleaning blade 41. The developer conveyed to the outside by the conveying device 43 is conveyed to the container 44 by the conveyor 45, and can be accumulated in the container 44 to an appropriate amount, and can be removed and discarded. Reference numeral 46 denotes a developer container for supplying a developer to each of the developing devices 30, 31, 32, and 33. Although only one set of the illustrated developer containers is provided, four sets are provided side by side. For example, cyan, magenta, yellow, and black color developers are supplied to 30, 31, 32, and 33 to perform color development. Reference numeral 47 denotes a hand stand that can manually supply the recording paper P. Note that the lower frame 1 and the upper frame 1c are assembled so that the transport path of the recording paper P can be opened around the support shaft 1b. At least when the fixing device 19 is not reached, the upper frame 1c is opened around the support shaft 1b, and the recording paper P can be taken out. Further, a guide plate 1a is provided to enable the recording paper P provided on the lower frame 1 to be supplied from another paper feeding device (not shown).
[0026]
The photosensitive drum 29 is provided on a frame 41a provided with the cleaning blade 41 via a support shaft 29a, and the support shaft 29a is supported by the upper frame 1c.
[0027]
By using the above-described image forming apparatus, the photosensitive drum 29 outputs an image signal for modulating the laser light source 35 from the host 100 via the printer controller 101 as shown in FIG. The surface of the photosensitive drum 29 which has been primary charged is image-exposed. This image exposure is the first color image exposure shown in FIG.
[0028]
Next, as a first color, the yellow color toner is developed by the developing device 30 and recharged by the band electrode 40 as shown in FIG. 1D, and the second color image is formed by the laser light source as shown in FIG. After the exposure, the developing device 31 superimposes and develops the magenta color toner.
[0029]
Thereafter, similarly, a cyan color toner as the third color and a black toner as the fourth color are sequentially superimposed and recharged image exposure and development are performed, thereby forming a four color toner image on the surface of the photosensitive drum 29.
[0030]
The gap (hereinafter referred to as DSD) between the photoreceptor and the developer carrier is 0.2 mm to 0.8 mm, and the developer is a two-component mixture of a carrier as magnetic particles and a toner as non-magnetic particles. A developer is used.
[0031]
The weight average particle diameter of the carrier is 15 to 80 microns in this embodiment, preferably 20 to 50 microns, and the weight average particle diameter of the toner is 5 to 20 microns. The developer is regulated to a desired layer thickness on the developer carrier by a layer thickness regulating means. It is desirable that the layer thickness is slightly smaller than the gap between the photoconductor and the developer carrier. The developer carrier is made of a conductor or a conductor having an insulating layer on the surface, and a DC or alternating (AC) electric field is applied as a developing bias between the developer carrier and the photosensitive member.
[0032]
The charging, image exposure, and development are sequentially performed on the surface of the rotating photosensitive drum 29 as described above, color toner is superimposed, and the toner image formed into an accurate color image by exposure control is transferred onto the recording paper P by the transfer belt 15. Then, the toner image is fixed on the recording paper by the fixing device 19.
[0033]
Next, another color tone adjustment method will be described.
[0034]
As an example, consider reversal development. The surface potential of the photoreceptor is set to -50 V in the image exposed portion, that is, the developing region, and 750 V in the non-exposed portion, that is, the white background portion. As the developing bias for each color, a DC voltage of -600 V and an alternating voltage of 2.5 kV peak-to-peak are applied as standard conditions. Higher DC or alternating voltages promote development. Therefore, for example, if yellow is to be emphasized, the yellow developing bias may be increased.
[0035]
Using the above color developing device, the developer is a two-component developer consisting of a carrier obtained by resin-coating a ferrite core with an insulating carrier having a weight average particle size of 45 μm and a toner having a system color margin having a weight average particle size of 8 μm. When performing development using a non-contact development method, the developing bias voltage is set to the following value and development is performed. When the yellow, magenta, and cyan color toners are used, the AC voltage of the developing bias is Va, the frequency is fAc, and the DC voltage is Vdc. Table 2 shows the first adjusting means.
[0036]
[Table 2]

[0037]
The duty of the pulse width of the exposure by the laser beam as the second adjusting means is shown in Yellow Table 3 below.
[0038]
[Table 3]

[0039]
Next, Table 4 shows the developing bias voltage values of the yellow, magenta, and cyan color toners as other first adjusting means with respect to the first adjusting means in Table 1.
[0040]
[Table 4]

[0041]
Next, as a second adjustment, Table 5 shows a pulse width Duty of exposure by a laser beam, and magenta below.
[0042]
[Table 5]

[0043]
Although the exposure amount is controlled by the pulse width modulation control of the semiconductor laser as described above, the color adjustment of the color image is performed, and the color image can be formed on the recording paper P by the laser printer. As an example, as a color image adjustment method, as shown in FIG. 7A, color adjustment can be performed by adjusting the distance between the developing sleeve of the developing device and the image carrier. That is, a developing sleeve 302 is rotatably provided in a developing device frame 301 composed of the developing device 30 at a position facing the image carrier 29, and a magnet 303 magnetized into N and S is used for developing. It is fixedly provided in the sleeve 302. Reference numerals 304 and 305 denote the developer 306 stirred by the stirring member provided in the developing device frame 301 to stir the developer 306 conveyed by the developing sleeve 302 by the conveyance regulating member 307. Regulate on the thickness and quantity. The transported developer 306 is held at a fixed interval DSD1 between the developing sleeve 302 and the image carrier 29 as shown in the figure. As the holding structure, for example, the developing device frame 301 is mounted on rollers 308 and 309 provided on a part of the upper machine frame 1c of the control means 102 shown in FIG. 2 and is provided movably with respect to the upper machine frame 1c. On the other hand, the developing device frame 301 is always elastically supported and held elastically in the direction in which the developing sleeve 302 is separated from the image carrier 29 by springs 310 and 311, and the cam member 313 is interlocked with the driving means 312. As shown in FIG. 7A, the developing device frame 301 is blocked.
[0044]
When performing image control using the developing device 30 configured as described above, characters, lines, and the like are output as dot signals in a video signal output from the printer controller 101 shown in FIG. It is output as an image signal, and each edge portion is detected and output.
[0045]
As described above, the duty of the first color of the solid image portion is set to 60%, the duty of the second color is set to 100%, and the duty of the first color of the edge portion is set to 80%, and the duty of the second color is set to 100%. There is almost no difference in the color tone between the line and the solid image. Therefore, for example, when it is desired to make yellow more intense than red or green, the DSD of the yellow developing unit 30 shown in FIG. 6 is reduced from 0.6 mm to 0.5 mm. As such an operation, the above-described driving means 312 is driven to push the developing device frame 301 against the elasticity of the springs 301 and 311 on the cam member 313 surface, so that the image carrier 29 and the developing sleeve 302 are moved. The value between DSD1 can be set as described above. At this time, the duty of the solid image portion was not changed, and the duty of the first color at the edge portion was adjusted to 60%, and the duty of the second color was adjusted to 100%. By performing such adjustment, the difference in the color tone between the dot image portion, the line, and the solid image portion became almost zero.
[0046]
The desired color can be obtained by the above operation.
[0047]
Next, the embodiment of FIG. 7B will be described. FIG. 7B is another embodiment of FIG. 7A, in which a male screw rod 315 is provided at a part of the developing device frame 301 by the developing device frame. A gear 316 provided to protrude in the direction of movement of 301 and provided with a female screw is screwed. A pinion 317 is meshed with the gear 316, and a drive means 318 is directly connected to the pinion 317. The gear 316 is provided so as to be rotatable with respect to a part of the upper machine casing 1C, and is configured to prevent a left-right movement. As described above, 101 is a printer controller, and 102 is a control unit of the laser printer main body.
[0048]
In this embodiment, the pinion 317 is rotated by the driving rotation of the driving means 318, and the gear 316 is rotated. Since the gear 316 is provided so as to be rotatable only in the upper frame 1c, the male screw rod 315 is slightly moved in the left or right direction in the drawing by the right or left rotation of the tooth 316. Accordingly, the developing sleeve 302 moves together with the developing device frame 301 provided integrally, and the distance between the image carrier 29 and the DSD 2 in the developing sleeve 302 can be changed. This configuration can adjust the DSD 2 very finely and can respond to the image signal at the edge speed. The color adjustment as described with reference to FIG. 7A can be performed by adjusting the DSD as described above.
[0049]
Next, an embodiment shown in FIG. 8 will be described. This embodiment will be described using an embodiment similar to the developing device 30. A rotating developing sleeve 302 is provided at an opening of a developing device frame 301, and a magnet 303 having NS fixed therein is provided in the developing sleeve 302. 304 and 305 are agitating members provided in the developing device frame 301 to agitate the developer. Reference numeral 319 denotes a drive source for rotating the developing sleeve 302, which is connected to the printer controller 101 via the laser printer control unit 102 via a rotation control unit 320 for controlling the rotation of the drive source.
[0050]
When performing image control using the developing device 30 configured as described above, characters, lines, and the like are output as dot signals in a video signal output from the printer controller 101 shown in FIG. The image is output as an image portion, and each edge portion is detected and output. As described in the embodiment of FIGS. 7A and 7B, the duty of the first color of the solid image portion is set to 60 as described above. %, The duty of the second color is set to 100%, and the duty of the first color of the edge is set to 80%, and the duty of the second color is set to 100%, so that there is almost no difference in the color tone between the dot image, the line, and the solid image.
[0051]
In this embodiment, the driving source 319 is controlled by the laser printer control unit 102 by the rotation control unit 320 of the driving source in response to the signals of the dot portion and the solid image portion in order to perform the above color adjustment. Accordingly, the rotation of the developing sleeve 302 is controlled by the solid image portion of the dot image portion.
[0052]
Therefore, for example, when it is desired to make yellow more intense than red or green as in the embodiment of FIGS. 7A and 7B, the linear velocity between the image carrier of the developing sleeve 302 and the developing sleeve 302 is increased. The ratio was reduced from 2 to 3 so that the number of rotations at which the supply of the developer was reduced was set. At this time, the duty of the solid image portion was not changed, and the duty of the first color at the edge portion was adjusted to be 60%, and the duty of the second color was adjusted to be 100%. Thereby, the color tone difference between the dot image, the line, and the solid image was adjusted. Almost disappeared, and almost perfect color adjustment became possible.
[0053]
Next, the embodiment of FIG. 9 will be described.
[0054]
The image carrier 29 is provided with a toner density control means 321 for detecting and controlling the toner density on the developer supply side of the developing sleeve 302 and the input / output means 322 for inputting a signal detected by the toner density control means 321. Image density adjusting means 325 for inputting and adjusting the density of the toner density through the printer controller 101 and inputting image information from the printer controller 101. The image density adjusting means 325 is connected to a driving means 324 for driving a toner replenishing means 323 provided in the toner hopper 326.
[0055]
The description of the developing device 30 is omitted because it has the same configuration as described above. In the embodiment configured as described above, the video signal output from the printer controller 101 is detected as an isolated dot image portion or an edge portion to discriminate it from a solid image portion, and a determination signal is output. It is input to the image density adjusting means 325.
[0056]
As described above, when the color tone adjustment is standard, the duty of the first color of the solid image portion is set to 60%, the duty of the second color is set to 100%, the duty of the first color of the edge portion is set to 80%, and the duty of the second color is set to 100%. As a result, there is almost no difference in color tone between the dot image and the line or solid image. Therefore, for example, when it is desired to increase the yellow color with respect to the red color and the green color, the color toner density of the yellow developing unit 30 shown in FIG. 6 is increased from 8% to 10% with respect to the carrier. At this time, the duty of the solid image portion is not changed, and the color toner is adjusted so that the first color of the edge portion has a Duty of 60% and the second color has a Duty of 100%. Almost disappeared, and almost perfect color adjustment became possible.
[0057]
That is, as described above, for example, when it is desired to increase the density of yellow, the toner density of the yellow developing unit 30 is increased. In this case, similarly to the above-described embodiment, the color tone of the dot image, the solid image portion, and the line does not change. As described above, the problem can be solved by appropriately selecting the first and second colors of the edge portion and the first and second colors of the solid image portion.
[0058]
In the above, the color image forming method by developing two color toners has been described. However, it goes without saying that the image forming control of three or more colors or only one color can be applied to all the embodiments. In this case, by changing the duty of the dot image portion to the duty of the solid image portion, the image is not broken or cut, and the image density of the solid image portion can be adjusted.
[0059]
Although only the exposure means using a laser beam has been described as the exposure means of the present invention, it goes without saying that an exposure means such as an LED array or a liquid crystal may be used. Either exposure means can control the amount of toner adhered by pulse width modulation or intensity modulation. Although the above embodiment is performed by changing the image exposure or development conditions as the first adjusting means, other conditions, for example, the charging conditions may be changed.
[0060]
【The invention's effect】
According to the present invention, when a monochromatic image is reproduced, a line image, an isolated point (dot), and an edge of a solid portion are reproduced beautifully similarly to the solid portion. Particularly, a reproduced image of a black line drawing halftone image and a solid image mixed image has high image quality. Further, as described above, when a color toner is developed by exposing the image output from the CPU or the image memory using a light source such as a laser beam, an LED array, or a liquid crystal, the first color development and the second color development are performed using a plurality of developing devices. In addition, the effect of developing is effective in controlling the developing operation of the developing device to form an accurate color image, and reproducing a color image of any form such as a dot image, a line, and a solid image as an accurate color tone.
[Brief description of the drawings]
FIGS. 1A to 1F are process diagrams of an image forming unit showing a conventional two-time development system of charging, exposure, control, and development.
FIGS. 2A and 2B are explanatory diagrams of an arrangement of an image forming apparatus showing from a CPU input to a laser printer.
FIGS. 3A to 3C are explanatory diagrams of exposure control in image dots and solid images.
FIGS. 4A to 4D are explanatory views showing the development of a color toner in a conventional dot and solid image.
FIGS. 5A to 5F are explanatory diagrams showing the development of a color toner in a dot and solid image of the present invention.
FIG. 6 is a longitudinal sectional view of an image forming apparatus using the image forming unit of the present invention.
FIGS. 7A and 7B are cross-sectional views of a developing device that moves the developing device and performs color toner development.
FIG. 8 is a cross-sectional view showing a means for performing color toner development while changing the rotation speed of a developing sleeve of the developing device of the present invention.
FIG. 9 is a cross-sectional view illustrating a unit that performs color toner development by controlling the amount of toner in the developing device of the present invention.
[Explanation of symbols]
1 lower frame
1c Upper frame
2 Paper feed roller
3 paper cassette
7, 9, 10, 11, 14 Guide plate
12 Registration roller
15 Transfer belt
20 Heating roller for fixing
20a Cleaning roller
28 Output tray
29, 201, 301, 305, 309 Photoconductor drum (image carrier)
30, 31, 32, 33, 204, 207, 210, 304, 308, 312 Developing device
30a Developing device frame
34 polygon mirror
35, 203, 206, 209, 303, 307, 311 Laser light source
36,37,38 Reflecting mirror
40, 202, 205, 208, 302, 305, 310 band electrodes

Claims (9)

In an image forming apparatus that forms a latent image on an image carrier using an exposure unit based on an image forming signal and forms a toner image with a developing unit using toner,
The image forming apparatus is an apparatus that forms a color toner image by sequentially superimposing first and second toner images, and includes a first adjusting unit, a second adjusting unit, and a determining unit.
The first adjusting means adjusts the amount of toner attached to the first and second toner images to adjust the color tone of the image,
The determining means determines an isolated dot or an edge dot in an image,
The second adjusting unit calculates the amount of toner attached to the isolated dot or the edge dot and the other portion based on the result of the determination by the determining unit, and calculates the amount of exposure to the isolated dot or the edge dot of the first color. The exposure amount for the portion other than the isolated dot or the edge dot of the first color is made different from the exposure amount for the isolated dot or the edge dot of the first color and the exposure amount for the isolated dot or the edge dot of the second color. In addition, the image forming apparatus is characterized in that the exposure amount for a portion other than the isolated dot or the edge dot of the first color and the exposure amount for the portion other than the dot portion of the second color are different from each other . 2. The image forming apparatus according to claim 1, wherein a color toner image is adjusted using a developing unit as a first adjusting unit for adjusting the amount of the toner image attached. 2. The image forming apparatus according to claim 1, wherein the discrimination of the isolated dot or the edge dot by the discriminating unit is performed by using a matrix of N × M dots. 2. The image forming apparatus according to claim 1, wherein the first adjusting unit that adjusts the amount of the toner image adhered adjusts a gap between the image carrier and a developing sleeve of a developing device. 2. The image forming apparatus according to claim 1, wherein a rotation of a developing sleeve provided on the image carrier and the developing device is changed as a first adjusting unit for adjusting the amount of the toner image attached. 2. The image forming apparatus according to claim 1, wherein a bias voltage applied to a developing sleeve provided in the developing device is changed as first adjusting means for adjusting the amount of the toner image attached. 2. The image forming apparatus according to claim 1, wherein the first adjusting unit that adjusts the amount of the toner image attached changes a toner concentration in a developer in the developing device. 2. The image forming apparatus according to claim 1, wherein the first adjusting unit that adjusts the amount of the toner image attached is a charging control unit. 2. The image forming apparatus according to claim 1, wherein the first adjusting unit that adjusts the amount of the toner image attached is an exposing unit, and the exposing unit is controlled by intensity modulation or pulse width modulation.

Images