JP4407084B2

JP4407084B2 - Image forming apparatus

Info

Publication number: JP4407084B2
Application number: JP2001227534A
Authority: JP
Inventors: 昌隆八木; 健太郎鹿取; 満小原
Original assignee: Konica Minolta Business Technologies Inc
Current assignee: Konica Minolta Business Technologies Inc
Priority date: 2001-07-27
Filing date: 2001-07-27
Publication date: 2010-02-03
Anticipated expiration: 2021-07-27
Also published as: JP2003043758A

Description

【０００１】
【発明の属する技術分野】
本発明は、現像剤付着量を検出するための光学式センサを有する画像形成装置に関し、より詳しくは、前記光学式センサの発光量の調整方法に関する。
【０００２】
【従来の技術】
従来、画像形成装置における光学式センサは、現像剤であるトナーの付着量を検出するのに２つの受光センサを用いて、高付着トナーを測定する際は一方の受光センサで拡散反射成分（乱反射成分）を検出し、低付着トナーを測定する際は他方の受光センサで鏡面反射成分（正反射成分）を検出するのが一般的である。これは、受光センサを１つにした場合には、拡散反射成分または鏡面反射成分の一方の成分だけでは、低濃度（低付着量）から高濃度（高付着量）まで良好な感度を得ることが難しいことによるものである。
【０００３】
【発明が解決しようとする課題】
しかしながら、拡散反射と鏡面反射の２成分を検出するための光学式センサは機構が複雑で高価であった。そこで、受光センサを１つだけ用いた単純で安価な鏡面反射（正反射）型センサで、低濃度から高濃度まで良好な感度を得るための新しい方法が求められていた。
【０００４】
受光センサを１つだけ用いた正反射型の光学式センサでは、低濃度から高濃度までの良好な感度を得るには、低濃度時には発光部材の発光量を小さく設定し、高濃度時には発光部材の発光量を大きく設定することが望ましい。その理由は、図１３に示すように、小光量時のグラフＡは低付着量範囲（すなわち低濃度範囲）では感度（すなわち傾き）があるのでトナー付着量を正確に検出できるが、狙いとする高付着量（例えば６ｇ／ｍ^２）付近では感度がほとんどなくなるのでトナー付着量の正確な検出ができず、一方、大光量時のグラフＢおよびＣは前記狙いとする高付着量付近で感度を有するのでトナー付着量を正確に検出できるからである。
【０００５】
ところが、光学式センサに用いられる受光センサの出力値には上限値ａが決まっているのが一般的である。そのため、発光部材を大発光量で発光させた場合には、被検出体である像担持体の裸面上で正反射した反射光が受光センサにより多量に検出され、受光センサの出力値が前記上限値ａで飽和してしまう。その結果、像担持体裸面における大光量時のセンサ出力ｂ，ｃを得ることができないために、高濃度検出用の大発光量を正確に設定することができず、高付着トナー量を精度よく検出することが困難であった。
【０００６】
そこで、本発明の目的は、発光部材の小発光量および大発光量を正確に自動調整することができ、低濃度から高濃度まで精度よく検出できる光学式センサを有する画像形成装置を提供することにある。
【０００７】
【課題を解決するための手段】
前記目的を達成するため、本発明の第１の画像形成装置は、現像剤を用いて画像形成を行う画像形成装置であって、
現像剤像が形成される被検出体に対し、被検出体上への現像剤の付着量を検出するために光を照射する発光手段と前記被検出体で反射された光を受光する受光手段とからなる光学式センサを備え、
前記受光手段の出力値が飽和していない範囲で前記被検出体の裸面について得られる第１の発光量および第１の受光出力からなる第１の組み合わせと、前記受光手段の出力値が飽和していない範囲で前記被検出体の裸面について得られる前記第１の発光量とは異なる設定の第２の発光量および第２の受光出力からなる第２の組み合わせとから、発光量と受光出力との関係を近似式として求め、前記近似式から、予め定められた狙いの受光出力に対応する前記発光手段の現像剤が付着した被検出体への発光量を決定する決定手段を有することを特徴とするものである。
【０００８】
本発明の第１の画像形成装置では、前記決定された発光量が、低付着現像剤を検出するための小発光量と、高付着現像剤を検出するための大発光量を含んでもよい。この場合、前記小発光量を階調制御もしくは位置検出制御に用い、前記大発光量を最大付着量制御に用いるのが好ましい。
【０００９】
また、本発明の第１の光量調整方法は、現像剤を用いて画像形成を行う画像形成装置において、発光手段から現像剤像が形成される被検出体に光を照射して前記被検出体で反射された光を受光手段で受光することにより前記被検出体上の現像剤付着量を検出する光学式センサの光量調整方法であって、
前記受光手段の出力値が飽和していない範囲で前記被検出体の裸面について得られた第１の発光量および第１の受光出力からなる第１の組み合わせと、前記受光手段の出力値が飽和していない範囲で前記被検出体の裸面について得られた前記第１の発光量とは異なる設定の第２の発光量および第２の受光出力からなる第２の組み合わせとから、発光量と受光出力との関係を近似式として求め、前記近似式から、前記発光手段の現像剤が付着した被検出体への発光量を予め定められた狙いの受光出力に対応する値に決定して調整するものである。
【００１３】
本発明の第３の画像形成装置は、現像剤を用いて画像形成を行う画像形成装置であって、
現像剤像が形成される被検出体に対し、被検出体上への現像剤の付着量を検出するために光を照射する発光手段と前記被検出体で反射された光を受光する受光手段とからなる光学式センサを備え、
前記被検出体の裸面について、前記受光手段の出力値が飽和していない範囲の所定の受光出力が得られる前記発光手段の第１の発光量と前記受光手段の第１のゲインとの第１の組み合わせと、前記被検出体の裸面について、前記所定の受光出力が得られる前記発光手段の第１の発光量とは異なる第２の発光量と前記受光手段の前記第１のゲインとは異なる第２のゲインとの第２の組み合わせに基づいて、予め定められた狙いの受光出力に対応する前記発光手段の発光量を現像剤が付着した被検出体への発光量として決定する決定手段を有することを特徴とするものである。
【００１４】
本発明の第３の画像形成装置では、前記決定された発光量が、低付着現像剤を検出するための小発光量と、高付着現像剤を検出するための大発光量を含んでもよい。この場合、前記小発光量を階調制御もしくは位置検出制御に用い、前記大発光量を最大付着量制御に用いるのが好ましい。
【００１５】
また、本発明の第３の光量調整方法は、現像剤を用いて画像形成を行う画像形成装置において、発光手段から現像剤像が形成される被検出体に光を照射して前記被検出体で反射された光を受光手段で受光することにより前記被検出体上の現像剤付着量を検出する光学式センサの光量調整方法であって、
前記被検出体の裸面について、前記受光手段の出力値が飽和していない範囲の所定の受光出力が得られる前記発光手段の第１の発光量と前記受光手段の第１のゲインとの第１の組み合わせと、前記被検出体の裸面について、前記所定の受光出力が得られる前記発光手段の第１の発光量とは異なる第２の発光量と前記受光手段の前記第１のゲインとは異なる第２のゲインとの第２の組み合わせに基づいて、前記発光手段の現像剤が付着した被検出体への発光量を予め定められた狙いの受光出力に対応する値に決定して調整するものである。
【００１６】
【発明の効果】
本発明の画像形成装置および光量調整方法によれば、発光部材の発光量について、受光手段で検出可能な出力範囲となる小発光量を正確に決定できるだけでなく、受光手段の出力上限値を越えることとなる大発光量も正確に決定できる。したがって、受光手段を１つだけ有する単純で安価な正反射型光学式センサで、低濃度から高濃度まで精度よく検出できる。
【００１７】
【発明の実施の形態】
以下、本発明の実施の形態について添付図面を参照して説明する。
図１は、本発明にかかる正反射型光学式センサ１０の概略構成を示す。このセンサ１０は、例えばＬＥＤなどの発光手段である発光部材１２と、例えば感光体や中間転写体などの被検出体である像担持体１００に対して前記発光部材１２と正反射位置に配置された例えばフォトダイオードなどの受光手段である受光センサ１４とを有している。発光部材１２および受光センサ１４はそれぞれコントローラ（決定手段）１６に電気的に接続されている。
【００１８】
続いて、前記正反射型光学式センサ１０における発光部材１２の発光量を設定するための第１の方法について図２を参照して説明する。
第１の方法では、まず、受光センサ１４の出力可能範囲（すなわちセンサ出力値が飽和していない範囲、以下に同じ）内で、発光部材１２の発光量と像担持体裸面（すなわちトナーが付着していない面、以下に同じ）について得られる受光出力（すなわちセンサ出力、以下に同じ）の関係を２つ以上の点で測定する。これにより、第１の発光量および第１の受光出力からなる第１の組み合わせと、第２の発光量および第２の受光出力からなる第２の組み合わせとを得ることができる。なお、発光部材１２の発光量がゼロのときのセンサ出力値があらかじめ分かっていればこれを第１の組み合わせとし、１点についてだけ測定を行って第２の組み合わせを得るようにしてもよい。
【００１９】
コントローラ１６は、これら２つの組み合わせから発光量と受光出力との関係を近似式として求める。本実施形態では、この近似式は直線関係になるものとする。そして、コントローラ１６は、この近似式を用いて算出することで発光部材１２の所望の発光量を決定する。この所望の発光量には、センサ出力可能範囲内にある狙い出力（小）が得られる低付着量トナー検出用の小発光量と、センサ出力可能範囲外にある狙い出力（大）が得られる高付着量トナー検出用の大発光量とが含まれる。そして、コントローラ１６は、発光部材１２の発光量を前記近似式より求めた小発光量および大発光量に調整する。実際の画像安定化制御においては、小発光量を用いて後述する階調補正制御や位置検出制御を実施し、大発光量を用いて後述する最大付着量制御を実施する。
【００２０】
具体的には、センサ出力可能範囲ａ＝５Ｖ、光量１＝１５ｍＷ、光量２＝３０ｍＷ、そのときのセンサ出力値はそれぞれ出力１＝２Ｖ、出力２＝４Ｖとなっており、この２点を使用して関係近似式を作成する。この場合、関係近似式は「センサ出力（Ｖ）＝０．１３３（Ｖ／ｍＷ）×発光量（ｍＷ）」となる。階調補正制御に使用する発光部材１２の発光量は小さい方が感度がよいため、像担持体１００の裸面について得られる狙い出力（小）＝４．７Ｖとなるように前記近似式から算出した小発光量＝３５ｍＷに発光部材１２の発光量を設定する。一方、最大付着量制御に使用する発光部材１２の発光量は大きい方が感度がよいため、像担持体１００の裸面について得られる狙い出力（大）＝１２Ｖ（センサ出力可能範囲ａ＝５Ｖである受光センサ１４では実際には検出不可能）となるように前記近似式から算出した大発光量＝９０ｍＷに発光部材１２の発光量を設定する。
【００２１】
次に、本実施の形態の参考例として、前記正反射型光学式センサ１０における発光部材１２の発光量を設定するための第２の方法について図３を参照して説明する。
まず、コントローラ１６は、像担持体１００の裸面について、センサ出力可能範囲内にある狙いのセンサ出力となるように発光部材１２の小発光量を調整する。これにより、像担持体１００の裸面についての第１の発光量および第１の受光出力からなる第１の組み合わせが得られる。ついで、像担持体１００上にトナーパッチ（現像剤像）を形成する。コントローラ１６は、そのトナーパッチについて前記調整された小発光量で測定し、そのときのセンサ出力が狙いの出力値になるように現像条件を変えてトナーパッチのトナー付着量を調整する。トナー付着量が所望値に調整されたトナーパッチが形成されたら、コントローラ１６はそのトナーパッチを利用して発光部材１２の大発光量を調整する。この場合、トナーパッチであれば像担持体裸面とは異なり発光量を大きくしてもセンサ出力が飽和することがないので、センサ出力が飽和することはない。ここでは、トナーパッチについて得られるセンサ出力が、像担持体１００の裸面について前記調整された小発光量で得られたセンサ出力と同値になるように大発光量が設定される。これにより、トナーパッチについての第２の発光量および第２の受光出力からなる第２の組み合わせが得られる。このようにして前記第１の組み合わせから発光部材１２の低付着トナー検出用の小発光量が決定され、前記第２の組み合わせから発光部材１２の高付着トナー検出用の大発光量が決定される。実際の画像安定化制御においては、小発光量を用いて後述する階調補正制御や位置検出制御を実施し、大発光量を用いて後述する最大付着量制御を実施する。
【００２２】
具体的には、まず、像担持体１００の裸面についてのセンサ出力が出力可能範囲の上限値ａ＝５Ｖより低い４．７Ｖになるように発光部材１２の小発光量を調整する。この小発光量は例えば３５ｍＷであり、階調補正制御用の光量として使用される。しかし、３５ｍＷでは光量が小さいために感度がなくなるので、最大付着量制御（トナーの狙い付着量が６ｇ／ｍ^２）には使えない。とは言え、４ｇ／ｍ^２程度までのトナー付着量には感度がある。そこで、現像バイアスを変えることで１００％露光画像のトナー付着量を調整しつつトナーパッチを形成し、そのトナーパッチについて前記３５ｍＷの小発光量でトナー付着量の測定を繰り返し行い、トナー付着量が４ｇ／ｍ^２のトナーパッチを形成する。このトナー付着量４ｇ／ｍ^２のトナーパッチを大発光量調整のための校正用トナーパッチとする。そして、この校正用トナーパッチについて発光部材１２の発光量を変えながら測定し、そのときのセンサ出力が像担持体裸面についての小発光量時のセンサ出力４．７Ｖと同値になったときの発光量（例えば９０ｍＷ）を大発光量とし、これを最大付着量制御の光量として使用する。
【００２３】
次に、前記正反射型光学式センサ１０における発光部材１２の発光量を設定するための第３の方法について図４を参照して説明する。
まず、コントローラ１６は、受光センサ１４のゲインをある値ｇ（第１のゲイン）に設定し、そのゲインにて像担持体１００の裸面について狙いのセンサ出力となるように発光部材１２の光量を調整する。これにより、受光センサ１４が第１のゲインにあるときの第１の発光量および第１の受光出力からなる第１の組み合わせが得られる。ついで、コントローラ１６は、受光センサ１４のゲインを前記値ｇより小さい値（第２のゲイン）に設定し、同様に、そのゲインにて像担持体１００の裸面について狙いのセンサ出力（ゲインｇのときの狙いのセンサ出力と同値）となるように発光部材１２の光量を調整する。このとき、受光センサ１４のゲインを下げているため、大きい光量（ゲインを変えなければセンサ出力が飽和してしまうような光量）でも像担持体１００の裸面にて調整できる。これにより、受光センサ１４が第２のゲインにあるときの第２の発光量および第２の受光出力からなる第２の組み合わせが得られる。そして、前記第１の組み合わせから発光部材１２の低付着トナー検出用の小発光量が決定され、前記第２の組み合わせから発光部材１２の高付着トナー検出用の大発光量が決定される。実際の画像安定化制御では受光センサ１４のゲインを前記値ｇに戻して、前記決定された小発光量で階調補正制御や位置検出制御を実施し、前記決定された大発光量で最大付着量制御を実施する。
【００２４】
具体的には、まず、受光センサ１４のゲインをある値ｇに設定し、像担持体１００の裸面についてのセンサ出力が出力可能範囲の上限値ａ＝５Ｖより低い４．７Ｖになるように発光部材１２の光量を調整する。この光量は例えば３５ｍＷであり、階調補正制御用の小発光量として使用される。ついで、受光センサ１４のゲインの値をｇ／４に設定し、同様に、像担持体１００の裸面についてのセンサ出力が４．７Ｖになるように発光部材１２の光量を調整する。この光量は例えば１４０ｍＷであり、最大付着量制御用の大発光量として使用される。実際の画像安定化制御では、発光部材１２の発光量はそれぞれ設定した小発光量および大発光量（３５ｍＷ，１４０ｍＷ）であるが、受光センサ１４のゲインは同じ値ｇに設定したまま行う。最大付着量制御時には、ゲインをｇとし、発光量を１４０ｍＷとしているので、像担持体１００の裸面でのセンサ出力は、実測不能ではあるが、ほぼ１８．８Ｖ相当（＝４．７Ｖ×４）になっている。
【００２５】
以上に説明した第１及び第３の方法のいずれかで発光部材１２の発光量を設定することで、受光センサ１４で検出可能な出力範囲となる小発光量を正確に決定できるだけでなく、受光センサ１４の出力上限値を越えることとなる大発光量も正確に決定できる。したがって、受光センサ１４を１つだけ有する単純で安価な正反射型光学式センサ１０で、低濃度から高濃度までトナー付着量を精度よく検出できる。
【００２６】
また、上述したような発光部材１２の発光量の調整を、例えば画像安定化制御前に常に行うか、所定回数の画像安定化制御毎に行うか、所定枚数の画像形成毎に行うか、あるいは、不定期に行うことにより、経時的なトナー汚れやセンサ１０と像担持体１００間の距離変化などの影響によるセンサ出力の変動をなくすように発光部材１２の発光量を校正することができ、光学式センサ１０の精度を保持できる。
【００２７】
上述した第１又は第３の方法により調整された光学式センサ１０の発光量のうち小発光量を用いて階調補正制御および位置検出制御を実施し、大発光量を用いて最大付着量制御を実施するが、次にこれらの制御について簡単に説明する。
【００２８】
階調補正制御は、例えばプリンタで中間調画像を印字したとき、入力データ（面積率）と実画像の反射濃度が一致しないときに行われる。ここでは、パソコンからの入力データが５０％の面積率の中間調画像であるのに、紙にプリントしたときにベタ画像（１００％面積率）の半分の濃度になっていない場合に行う階調補正を例にとって説明する。
【００２９】
図５に示すように、ベタ画像の５０％の濃度では受光センサ１４のセンサ出力値がいくらになるのか、予めデータを採取しておく。この場合のセンサ出力は２Ｖであるとする。
【００３０】
そして、図６に示すように、面積率の分かった中間調パターンをプリントし、光学式センサ１０でその濃度（反射率）を測定する。この場合、狙いの濃度になる２Ｖの出力値が、パターン２（面積率５０％）とパターン３（面積率６０％）の各センサ出力値２．３Ｖおよび１．７Ｖの間にある。そこで、図７に示すように、露光データが何％になれば、狙いの２Ｖのセンサ出力になるのかを次式で算出すると、露光データ５５％が紙上反射濃度５０％に対応していることが分かる。
【００３１】
【数１】
Ｘ＝{(2.3V-2V)/(2.3V-1.7V)}×(60％-50％)＋50％
＝55％
【００３２】
このことから、図８に示すように、パソコン（ＰＣ）からの濃度データ５０％に対応して、露光データを５０％に変換するような補正カーブを選択すればよい。この場合、カーブＣを補正カーブとすれば、パソコンからの入力データと紙上反射濃度が直線関係になり、これにより階調補正が実行される。
【００３３】
続いて、位置検出（レジスト）制御について説明する。
図９に示すように光学式センサ１０が中間転写ベルト２０に対向配置されている中間転写方式のフルカラー画像形成装置における位置検出制御は、次のように行われる。
まず、第１色目のライン状トナーパターン２２を中間転写ベルト（中間転写体）２０上に形成する。トナーパターン２２は、画像域外（例えば、像間、ベルト幅方向の端部など）に形成される。そして、そのトナーパターン２２を光学式センサ１０で検出し、そのタイミングを次の色の画像書き出し（露光）タイミングに利用する。そうすることによって、中間転写ベルト２０上で４色の画像位置を一致させることができ、これによりレジスト制御が実行される。
なお、ここでは光学式センサ１０が中間転写体２０に対向配置された例を示したが、光学式センサ１０は感光体ドラム、感光体ベルト、用紙搬送ベルトなどに対向配置されてもよい。
【００３４】
続いて、最大付着量制御について説明する。
図１０，１１に示すように、像担持体である感光体ドラム（または中間転写ベルト）上に、現像バイアスＶｂを予め決められた値（−２００Ｖ，−２５０Ｖ，−３００Ｖ，−３５０Ｖ）に切り替えながら４つのトナーパターンを形成する。これらのパターン形成時には、露光器による１００％露光を用いる。ついで、これらのトナーパターンについて、光学式センサ１０を用いて大発光量で反射率を検出し、それぞれ検出されたセンサ出力をメモリに格納する。そして、図１２に示すように、メモリに記憶された各センサ出力に基づき、狙いとするセンサ出力となるような現像バイアスＶｂを下記の式により演算する。具体的には、狙いとするセンサ出力が１Ｖである場合、この１Ｖの値は現像バイアス−３００Ｖ（Ｖｂ１）で形成されたパターン３のセンサ出力１．８Ｖ（Ｓ１）と現像バイアス−３５０Ｖ（Ｖｂ２）で形成されたパターン４のセンサ出力０．６Ｖ（Ｓ２）との間にあるため、これら２つのセンサ出力から狙いセンサ出力１Ｖに相当する現像バイアスＶｂを算出する。その算出されたＶｂ＝―３３３．３Ｖに現像バイアスを設定することにより、最大付着力制御が実行される。
【００３５】
【数２】
Vb=Vb1+{-(Vb1-Vb2)×(S1-1)}/(S1-S2)
=-300+{-(-300+350)×(1.8-1)}/(1.8-0.6)
=-333.3(V)
【００３６】
なお、以上の画像安定化制御の説明では反転現像を例に説明したが、本発明は正規現像の画像形成装置についても適用可能である。
【図面の簡単な説明】
【図１】正反射型光学式センサの概略構成図。
【図２】第１の光量調整方法を説明するための図。
【図３】第２の光量調整方法を説明するための図。
【図４】第３の光量調整方法を説明するための図。
【図５】階調補正制御を説明するための図。
【図６】階調補正制御を説明するための図。
【図７】階調補正制御を説明するための図。
【図８】階調補正制御を説明するための図。
【図９】位置検出制御を説明するための図。
【図１０】最大付着量制御を説明するための図。
【図１１】最大付着量制御を説明するための図。
【図１２】最大付着量制御を説明するための図。
【図１３】従来の光学式センサで小発光量と大発光量とを用いた場合のトナー付着量とセンサ出力の関係を示す図。
【符号の説明】
１０…正反射型光学式センサ、１２…発光部材（発光手段）、１４…受光センサ（受光手段）、１６…コントローラ（決定手段）、１００…像担持体（被検出体）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus having an optical sensor for detecting a developer adhesion amount, and more particularly to a method for adjusting a light emission amount of the optical sensor.
[0002]
[Prior art]
Conventionally, an optical sensor in an image forming apparatus uses two light receiving sensors to detect the amount of toner that is a developer. When measuring highly adhered toner, one of the light receiving sensors detects diffuse reflection components (diffuse reflection). In general, when the low adhering toner is measured, the other light receiving sensor detects the specular reflection component (regular reflection component). This is because when only one light receiving sensor is used, only one component of the diffuse reflection component or the specular reflection component can obtain a good sensitivity from a low concentration (low adhesion amount) to a high concentration (high adhesion amount). This is due to difficulties.
[0003]
[Problems to be solved by the invention]
However, the optical sensor for detecting two components of diffuse reflection and specular reflection has a complicated mechanism and is expensive. Therefore, a new method for obtaining a good sensitivity from a low density to a high density with a simple and inexpensive specular reflection (regular reflection) type sensor using only one light receiving sensor has been demanded.
[0004]
In a specular reflection type optical sensor using only one light receiving sensor, in order to obtain good sensitivity from a low density to a high density, the light emission amount of the light emitting member is set small at a low density, and the light emitting member at a high density. It is desirable to set a large amount of light emission. The reason for this is that, as shown in FIG. 13, the graph A at a small light amount has a sensitivity (that is, an inclination) in the low adhesion amount range (that is, the low concentration range), so that the toner adhesion amount can be accurately detected. In the vicinity of a high adhesion amount (for example, 6 g / m ² ), the sensitivity is almost lost, so that the toner adhesion amount cannot be accurately detected. On the other hand, the graphs B and C when the light quantity is large show the sensitivity near the target high adhesion amount. This is because the toner adhesion amount can be accurately detected.
[0005]
However, the upper limit value a is generally determined for the output value of the light receiving sensor used in the optical sensor. For this reason, when the light emitting member emits light with a large light emission amount, a large amount of reflected light regularly reflected on the bare surface of the image carrier that is the detection object is detected by the light receiving sensor, and the output value of the light receiving sensor is Saturates at the upper limit a. As a result, since the sensor outputs b and c at the large light amount on the bare surface of the image carrier cannot be obtained, the large light emission amount for high density detection cannot be set accurately, and the high adhesion toner amount is accurately determined. It was difficult to detect well.
[0006]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus having an optical sensor capable of automatically and accurately adjusting a small light emission amount and a large light emission amount of a light emitting member and accurately detecting from a low density to a high density. It is in.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a first image forming apparatus of the present invention is an image forming apparatus that performs image formation using a developer,
Against the detection object which the developer image is formed, light receiving means for receiving the light reflected by the object to be detected and the light emitting means for irradiating light to detect the deposition amount of the developer onto the object to be detected An optical sensor consisting of
The first combination of the first light emission amount and the first light receiving output obtained with respect to the bare surface of the detected object in a range where the output value of the light receiving means is not saturated, and the output value of the light receiving means are saturated. The light emission amount and the light reception from the second combination of the second light emission amount and the second light reception output, which are different from the first light emission amount obtained for the bare surface of the object to be detected in a range that is not performed A determining unit that obtains a relationship with the output as an approximate expression and determines a light emission amount to the detection target to which the developer of the light emitting unit corresponding to a predetermined target light receiving output is attached from the approximate expression. It is characterized by.
[0008]
In the first image forming apparatus of the present invention, the determined light emission amount may include a small light emission amount for detecting the low adhesion developer and a large light emission amount for detecting the high adhesion developer. In this case, it is preferable that the small light emission amount is used for gradation control or position detection control, and the large light emission amount is used for maximum adhesion amount control.
[0009]
The first light quantity adjustment method of the present invention is the image forming apparatus for forming an image using a developer, wherein the object to be detected is irradiated with light from the light emitting means to form the object to be detected. A light amount adjusting method of an optical sensor that detects the amount of developer adhering on the detected body by receiving light reflected by the light receiving means,
The first combination of the first light emission amount and the first light reception output obtained for the bare surface of the detection object in a range where the output value of the light reception means is not saturated, and the output value of the light reception means A light emission amount from a second combination of a second light emission amount and a second light reception output set differently from the first light emission amount obtained for the bare surface of the object to be detected in a range not saturated. And the received light output as an approximate expression, and from the approximate expression, the amount of light emitted to the detected object to which the developer of the light emitting means is attached is determined to be a value corresponding to a predetermined target received light output. To be adjusted.
[0013]
A third image forming apparatus of the present invention is an image forming apparatus that forms an image using a developer,
Against the detection object which the developer image is formed, light receiving means for receiving the light reflected by the object to be detected and the light emitting means for irradiating light to detect the deposition amount of the developer onto the object to be detected An optical sensor consisting of
A first light emission amount of the light emitting means and a first gain of the light receiving means for obtaining a predetermined light receiving output in a range where the output value of the light receiving means is not saturated with respect to the bare surface of the detected object. 1 combination, a second light emission amount different from the first light emission amount of the light emitting means for obtaining the predetermined light reception output, and the first gain of the light receiving means for the bare surface of the detection object based on the second combination of the second gain that is different from, determines the amount of light emission of the light emitting means corresponding to the light receiving output of the aimed predetermined as a light-emitting amount to the detected body which the developer is adhered It has the determination means to do.
[0014]
In the third image forming apparatus of the present invention, the determined light emission amount may include a small light emission amount for detecting the low adhesion developer and a large light emission amount for detecting the high adhesion developer. In this case, it is preferable that the small light emission amount is used for gradation control or position detection control, and the large light emission amount is used for maximum adhesion amount control.
[0015]
The third light amount adjusting method according to the present invention is an image forming apparatus for forming an image using a developer, wherein the object to be detected is irradiated with light from a light emitting means to form the object to be detected. A light amount adjusting method of an optical sensor that detects the amount of developer adhering on the detected body by receiving light reflected by the light receiving means,
A first light emission amount of the light emitting means and a first gain of the light receiving means for obtaining a predetermined light receiving output in a range where the output value of the light receiving means is not saturated with respect to the bare surface of the detected object. 1 combination, a second light emission amount different from the first light emission amount of the light emitting means for obtaining the predetermined light reception output, and the first gain of the light receiving means for the bare surface of the detection object is based on the second combination of the second gain that different, determine the value corresponding to the received light output of a predetermined aim the light emission amount of the object to be detected that the developer is adhered to the light emitting means To make adjustments.
[0016]
【The invention's effect】
According to the image forming apparatus and the light amount adjustment method of the present invention, not only the light emission amount of the light emitting member can be accurately determined, but also the output upper limit value of the light receiving device is exceeded. The large amount of light emission can be determined accurately. Therefore, a simple and inexpensive specular reflection type optical sensor having only one light receiving means can accurately detect from low density to high density.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a schematic configuration of a regular reflection optical sensor 10 according to the present invention. The sensor 10 is disposed at a regular reflection position with respect to the light emitting member 12 that is a light emitting means such as an LED and the image carrier 100 that is a detected body such as a photosensitive member or an intermediate transfer member. In addition, the light receiving sensor 14 is a light receiving means such as a photodiode. The light emitting member 12 and the light receiving sensor 14 are each electrically connected to a controller (determining means) 16.
[0018]
Next, a first method for setting the light emission amount of the light emitting member 12 in the regular reflection optical sensor 10 will be described with reference to FIG.
In the first method, first, within the possible output range of the light receiving sensor 14 (that is, the range in which the sensor output value is not saturated, the same applies hereinafter), the light emission amount of the light emitting member 12 and the image carrier bare surface (that is, the toner is The relationship of the received light output (that is, the sensor output, the same below) obtained for the non-attached surface, the same below) is measured at two or more points. Thereby, the 1st combination which consists of the 1st emitted light quantity and the 1st received light output , and the 2nd combination which consists of the 2nd emitted light quantity and the 2nd received light output can be obtained. In addition, if the sensor output value when the light emission amount of the light emitting member 12 is zero is known in advance, this may be used as the first combination to measure only one point to obtain the second combination.
[0019]
The controller 16 obtains the relationship between the light emission amount and the light reception output as an approximate expression from these two combinations. In this embodiment, this approximate expression is assumed to have a linear relationship. And the controller 16 determines the desired light emission amount of the light emitting member 12 by calculating using this approximate expression. For this desired light emission amount, a low light emission amount for detecting a low adhesion amount toner capable of obtaining a target output (small) within the sensor output possible range and a target output (large) outside the sensor output possible range are obtained. And a large light emission amount for detecting a high adhesion amount toner. Then, the controller 16 adjusts the light emission amount of the light emitting member 12 to the small light emission amount and the large light emission amount obtained from the approximate expression. In actual image stabilization control, gradation correction control and position detection control described later are performed using a small amount of light emission, and maximum adhesion amount control described below is performed using a large amount of light emission.
[0020]
Specifically, the sensor output range a = 5V, the light quantity 1 = 15 mW, the amount of light 2 = 30 m W, has become its respective sensor output values Output 1 = 2V when, the output 2 = 4V, the two points Create a relational approximation using. In this case, the relational approximate expression is “sensor output (V) = 0.133 (V / mW) × light emission amount (mW)”. Since the smaller the light emission amount of the light emitting member 12 used for gradation correction control, the higher the sensitivity, the target output (small) obtained for the bare surface of the image carrier 100 is calculated from the above approximate expression so that 4.7V is obtained. The light emission amount of the light emitting member 12 is set to the small light emission amount = 35 mW. On the other hand, the larger the light emission amount of the light emitting member 12 used for the maximum adhesion amount control, the better the sensitivity. Therefore, the target output (large) obtained for the bare surface of the image carrier 100 = 12V (sensor output possible range a = 5V). The light emission amount of the light emitting member 12 is set to 90 mW, which is a large light emission amount calculated from the approximate expression so that the light reception sensor 14 cannot actually detect the light reception sensor 14.
[0021]
Next, as a reference example of the present embodiment, a second method for setting the light emission amount of the light emitting member 12 in the regular reflection type optical sensor 10 will be described with reference to FIG.
First, the controller 16 adjusts the small light emission amount of the light emitting member 12 so that the target sensor output is within the sensor output possible range for the bare surface of the image carrier 100. As a result, a first combination of the first light emission amount and the first light reception output for the bare surface of the image carrier 100 is obtained. Next, a toner patch (developer image) is formed on the image carrier 100. The controller 16 measures the toner patch with the adjusted small light emission amount, and adjusts the toner adhesion amount of the toner patch by changing the development condition so that the sensor output at that time becomes a target output value. When the toner patch in which the toner adhesion amount is adjusted to a desired value is formed, the controller 16 adjusts the large light emission amount of the light emitting member 12 using the toner patch. In this case, unlike the bare surface of the image carrier, the sensor output does not saturate even if the light emission amount is increased, so that the sensor output does not saturate. Here, the large light emission amount is set so that the sensor output obtained for the toner patch is the same value as the sensor output obtained for the bare light surface of the image carrier 100 with the adjusted small light emission amount. As a result, a second combination of the second light emission amount and the second light receiving output for the toner patch is obtained. In this manner, the small light emission amount for detecting the low adhesion toner of the light emitting member 12 is determined from the first combination, and the large light emission amount for detecting the high adhesion toner of the light emitting member 12 is determined from the second combination. . In actual image stabilization control, gradation correction control and position detection control described later are performed using a small amount of light emission, and maximum adhesion amount control described below is performed using a large amount of light emission.
[0022]
Specifically, first, the small light emission amount of the light emitting member 12 is adjusted so that the sensor output on the bare surface of the image carrier 100 is 4.7 V, which is lower than the upper limit value a = 5 V of the output possible range. The small light emission amount is, for example, 35 mW, and is used as a light amount for gradation correction control. However, at 35 mW, since the amount of light is small, the sensitivity is lost, so it cannot be used for maximum adhesion amount control (target adhesion amount of toner is 6 g / m ² ). However, the toner adhesion amount up to about 4 g / m ² is sensitive. Therefore, by changing the developing bias, a toner patch is formed while adjusting the toner adhesion amount of the 100% exposure image, and the toner adhesion amount is repeatedly measured with the small emission amount of 35 mW for the toner patch. A toner patch of 4 g / m ² is formed. This toner patch with a toner adhesion amount of 4 g / m ² is used as a calibration toner patch for adjusting a large light emission amount. The calibration toner patch was measured while changing the light emission amount of the light emitting member 12, and the sensor output at that time was the same as the sensor output 4.7V when the light emission amount on the bare surface of the image carrier is small. A light emission amount (for example, 90 mW) is set as a large light emission amount, and this is used as a light amount for maximum adhesion amount control.
[0023]
Next, a third method for setting the light emission amount of the light emitting member 12 in the regular reflection type optical sensor 10 will be described with reference to FIG.
First, the controller 16 sets the gain of the light receiving sensor 14 to a certain value g (first gain), and the light quantity of the light emitting member 12 is set so that the target sensor output is obtained with respect to the bare surface of the image carrier 100 with the gain. Adjust. Thereby, the first combination of the first light emission amount and the first light reception output when the light receiving sensor 14 is at the first gain is obtained. Next, the controller 16 sets the gain of the light receiving sensor 14 to a value smaller than the value g (second gain), and similarly, a target sensor output (gain g for the bare surface of the image carrier 100 with the gain. The light quantity of the light emitting member 12 is adjusted so that the sensor output becomes the same value as the target sensor output at the time of (1). At this time, since the gain of the light receiving sensor 14 is lowered, even a large light amount (a light amount that saturates the sensor output unless the gain is changed) can be adjusted on the bare surface of the image carrier 100. Thereby, the second combination of the second light emission amount and the second light reception output when the light receiving sensor 14 is at the second gain is obtained. Then, the small light emission amount for detecting the low adhesion toner of the light emitting member 12 is determined from the first combination, and the large light emission amount for detecting the high adhesion toner of the light emitting member 12 is determined from the second combination. In actual image stabilization control, the gain of the light receiving sensor 14 is returned to the value g, gradation correction control and position detection control are performed with the determined small light emission amount, and maximum adhesion is performed with the determined large light emission amount. Perform quantity control.
[0024]
Specifically, first, the gain of the light receiving sensor 14 is set to a certain value g so that the sensor output for the bare surface of the image carrier 100 is 4.7 V which is lower than the upper limit value a = 5 V of the output possible range. The light quantity of the light emitting member 12 is adjusted. This light amount is, for example, 35 mW, and is used as a small light emission amount for gradation correction control. Next, the gain value of the light receiving sensor 14 is set to g / 4, and similarly, the light amount of the light emitting member 12 is adjusted so that the sensor output for the bare surface of the image carrier 100 becomes 4.7V. This light amount is, for example, 140 mW, and is used as a large light emission amount for controlling the maximum adhesion amount. In actual image stabilization control, the light emission amount of the light emitting member 12 is the set small light emission amount and large light emission amount (35 mW, 140 mW), respectively, but the gain of the light receiving sensor 14 is set to the same value g. At the time of maximum adhesion amount control, the gain is set to g and the light emission amount is set to 140 mW. Therefore, the sensor output on the bare surface of the image carrier 100 is approximately 18.8 V (= 4.7 V × 4) although it cannot be measured. )It has become.
[0025]
By setting the light emission amount of the light emitting member 12 by any one of the first and third methods described above, not only can the small light emission amount within the output range detectable by the light receiving sensor 14 be accurately determined, The large amount of light emission that will exceed the output upper limit value of the sensor 14 can also be accurately determined. Therefore, the simple and inexpensive regular reflection optical sensor 10 having only one light receiving sensor 14 can accurately detect the toner adhesion amount from low density to high density.
[0026]
Further, the adjustment of the light emission amount of the light emitting member 12 as described above is always performed before the image stabilization control, is performed every predetermined number of times of image stabilization control, is performed every time a predetermined number of images are formed, or By performing irregularly, it is possible to calibrate the light emission amount of the light emitting member 12 so as to eliminate fluctuations in the sensor output due to the influence of the toner contamination with time and the change in the distance between the sensor 10 and the image carrier 100. The accuracy of the optical sensor 10 can be maintained.
[0027]
The gradation correction control and the position detection control are performed using the small light emission amount among the light emission amounts of the optical sensor 10 adjusted by the first or third method described above, and the maximum adhesion amount control is performed using the large light emission amount. Next, these controls will be briefly described.
[0028]
The gradation correction control is performed, for example, when a halftone image is printed by a printer and the input data (area ratio) and the reflection density of the actual image do not match. In this case, the gradation to be performed when the input data from the personal computer is a halftone image having an area ratio of 50% but is not half the density of a solid image (100% area ratio) when printed on paper. The correction will be described as an example.
[0029]
As shown in FIG. 5, data is collected in advance to determine how much the sensor output value of the light receiving sensor 14 is at 50% density of the solid image. The sensor output in this case is assumed to be 2V.
[0030]
Then, as shown in FIG. 6, a halftone pattern whose area ratio is known is printed, and its density (reflectance) is measured by the optical sensor 10. In this case, the output value of 2V at the target density is between the sensor output values 2.3V and 1.7V of pattern 2 (area ratio 50%) and pattern 3 (area ratio 60%). Therefore, as shown in FIG. 7, when the exposure data reaches what percentage, the target 2V sensor output is calculated by the following formula, the exposure data 55% corresponds to the reflection density on paper of 50%. I understand.
[0031]
[Expression 1]
X = {(2.3V-2V) / (2.3V-1.7V)} × (60% -50%) + 50%
= 55%
[0032]
Accordingly, as shown in FIG. 8, a correction curve that converts exposure data to 50% corresponding to density data 50% from a personal computer (PC) may be selected. In this case, if the curve C is a correction curve, the input data from the personal computer and the reflection density on the paper have a linear relationship, and tone correction is thereby performed.
[0033]
Next, position detection (registration) control will be described.
As shown in FIG. 9, the position detection control in the intermediate transfer type full-color image forming apparatus in which the optical sensor 10 is disposed opposite to the intermediate transfer belt 20 is performed as follows.
First, a linear toner pattern 22 of the first color is formed on the intermediate transfer belt (intermediate transfer member) 20. The toner pattern 22 is formed outside the image area (for example, between images, the end in the belt width direction, etc.). Then, the toner pattern 22 is detected by the optical sensor 10, and the timing is used as the next color image writing (exposure) timing. By doing so, it is possible to match the image positions of the four colors on the intermediate transfer belt 20, thereby performing registration control.
Although the example in which the optical sensor 10 is disposed opposite to the intermediate transfer member 20 is shown here, the optical sensor 10 may be disposed opposite to a photosensitive drum, a photosensitive belt, a paper transport belt, and the like.
[0034]
Next, the maximum adhesion amount control will be described.
As shown in FIGS. 10 and 11, the developing bias Vb is switched to predetermined values (−200 V, −250 V, −300 V, −350 V) on the photosensitive drum (or intermediate transfer belt) as an image carrier. However, four toner patterns are formed. When these patterns are formed, 100% exposure using an exposure device is used. Next, the reflectance of these toner patterns is detected with a large light emission amount using the optical sensor 10, and the detected sensor outputs are stored in the memory. Then, as shown in FIG. 12, based on each sensor output stored in the memory, a developing bias Vb that becomes a target sensor output is calculated by the following equation. Specifically, when the target sensor output is 1V, the value of 1V is the sensor output 1.8V (S1) of the pattern 3 formed with the developing bias of −300 V (Vb1) and the developing bias of −350 V (Vb2). ), The development bias Vb corresponding to the target sensor output 1V is calculated from these two sensor outputs. By setting the developing bias to the calculated Vb = −333.3 V, the maximum adhesion force control is executed.
[0035]
[Expression 2]
Vb = Vb1 + {-(Vb1-Vb2) × (S1-1)} / (S1-S2)
= -300 + {-(-300 + 350) × (1.8-1)} / (1.8-0.6)
= -333.3 (V)
[0036]
In the above description of image stabilization control, reversal development has been described as an example. However, the present invention can also be applied to a regular development image forming apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a regular reflection optical sensor.
FIG. 2 is a diagram for explaining a first light amount adjustment method.
FIG. 3 is a diagram for explaining a second light amount adjustment method;
FIG. 4 is a diagram for explaining a third light amount adjustment method;
FIG. 5 is a diagram for explaining gradation correction control.
FIG. 6 is a diagram for explaining gradation correction control.
FIG. 7 is a diagram for explaining gradation correction control.
FIG. 8 is a diagram for explaining gradation correction control.
FIG. 9 is a diagram for explaining position detection control;
FIG. 10 is a diagram for explaining maximum adhesion amount control.
FIG. 11 is a diagram for explaining maximum adhesion amount control.
FIG. 12 is a diagram for explaining maximum adhesion amount control.
FIG. 13 is a diagram illustrating a relationship between toner adhesion amount and sensor output when a small light emission amount and a large light emission amount are used in a conventional optical sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Regular reflection type optical sensor, 12 ... Light emitting member (light emitting means), 14 ... Light receiving sensor (light receiving means), 16 ... Controller (deciding means), 100 ... Image carrier (detected body).

Claims

An image forming apparatus that forms an image using a developer,
Against the detection object which the developer image is formed, light receiving means for receiving the light reflected by the object to be detected and the light emitting means for irradiating light to detect the deposition amount of the developer onto the object to be detected An optical sensor consisting of
The first combination of the first light emission amount and the first light receiving output obtained with respect to the bare surface of the detected object in a range where the output value of the light receiving means is not saturated, and the output value of the light receiving means are saturated. The light emission amount and the light reception from the second combination of the second light emission amount and the second light reception output, which are different from the first light emission amount obtained for the bare surface of the object to be detected in a range that is not performed A determining unit that obtains a relationship with the output as an approximate expression and determines a light emission amount to the detection target to which the developer of the light emitting unit corresponding to a predetermined target light receiving output is attached from the approximate expression. An image forming apparatus.

The image forming apparatus according to claim 1, wherein the determined light emission amount includes a small light emission amount for detecting a low adhesion developer and a large light emission amount for detecting a high adhesion developer. .

In an image forming apparatus that forms an image using a developer, by irradiating light to a detected body on which a developer image is formed from a light emitting means and receiving light reflected by the detected body by a light receiving means A method for adjusting the amount of light of an optical sensor for detecting a developer adhesion amount on the detection object,
The first combination of the first light emission amount and the first light reception output obtained for the bare surface of the detection object in a range where the output value of the light reception means is not saturated, and the output value of the light reception means A light emission amount from a second combination of a second light emission amount and a second light reception output set differently from the first light emission amount obtained for the bare surface of the object to be detected in a range not saturated. And the received light output as an approximate expression, and from the approximate expression, the amount of light emitted to the detected object to which the developer of the light emitting means is attached is determined to be a value corresponding to a predetermined target received light output. A method for adjusting a light amount of an optical sensor in an image forming apparatus.

An image forming apparatus that forms an image using a developer,
Against the detection object which the developer image is formed, light receiving means for receiving the light reflected by the object to be detected and the light emitting means for irradiating light to detect the deposition amount of the developer onto the object to be detected An optical sensor consisting of
A first light emission amount of the light emitting means and a first gain of the light receiving means for obtaining a predetermined light receiving output in a range where the output value of the light receiving means is not saturated with respect to the bare surface of the detected object. 1 combination, a second light emission amount different from the first light emission amount of the light emitting means for obtaining the predetermined light reception output, and the first gain of the light receiving means for the bare surface of the detection object based on the second combination of the second gain that is different from, determines the amount of light emission of the light emitting means corresponding to the light receiving output of the aimed predetermined as a light-emitting amount to the detected body which the developer is adhered An image forming apparatus comprising: a determination unit that performs determination.

The image forming apparatus according to claim 4, wherein the determined light emission amount includes a small light emission amount for detecting a low adhesion developer and a large light emission amount for detecting a high adhesion developer. .

In an image forming apparatus that forms an image using a developer, by irradiating light to a detected body on which a developer image is formed from a light emitting means and receiving light reflected by the detected body by a light receiving means A method for adjusting the amount of light of an optical sensor for detecting a developer adhesion amount on the detection object,
A first light emission amount of the light emitting means and a first gain of the light receiving means for obtaining a predetermined light receiving output in a range where the output value of the light receiving means is not saturated with respect to the bare surface of the detected object. 1 combination, a second light emission amount different from the first light emission amount of the light emitting means for obtaining the predetermined light reception output, and the first gain of the light receiving means for the bare surface of the detection object is based on the second combination of the second gain that different, determine the value corresponding to the received light output of a predetermined aim the light emission amount of the object to be detected that the developer is adhered to the light emitting means Adjusting the light amount of the optical sensor in the image forming apparatus.