JP2004117895A - Developing device, method for controlling the same, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To insure that the control voltage after correction obtained by arithmetic processing can be supplied to a toner concentration sensor without depending on the initial regulation of the toner concentration such as in feeding of a developer during changing of a linear velocity and that the stable toner concentration can be controlled by each of the respective linear velocities. <P>SOLUTION: The developing device is provided with a developer carrier 41 disposed rotatably within a developing container 40D in order to attach the developer 18, the toner concentration sensor SD attached in the developing container 40D to detect the permeability of the developer 18, a control means 15 for controlling the concentration by replenishing toners into the developing container 40D in accordance with the output voltage from the sensor SD and the linear velocity of the developer carrier 41, and a memory means 13 for storing the correction information for regulating the control voltage of the sensor SD. The device detects the control voltage of the sensor SD in changing the linear velocity after the start of the device, reads the correction information out of the memory means 13 and drives the sensor SD by the voltage after correcting the control voltage of the sensor SD. <P>COPYRIGHT: (C)2004,JPO

Description

【０１０６】
なお、このときに適用する制御電圧の値Ｖｃは標準線速でのトナー濃度初期調整の際に決定される制御電圧の値Ｖｃでなくても、各線速毎に同じ値であればよい。
【０１０７】
また、ステップＢ６で当該トナー濃度センサＳＤでトナー濃度Ｔｃ一定を示す出力電圧の値ＶＬ、例えば、２．５０Ｖが得られる制御電圧の値Ｖｃを各線速（１／２，１／３毎に検出する。標準線速については先に検出しているのでそれ以外の線速について検出する。補正係数ΔＶＬ／ΔＶｃを求めるためである。この例では、１／２速時のトナー濃度センサＳＤの制御電圧の値Ｖｃ２は６．６４Ｖであり、１／３速時の制御電圧の値Ｖｃ３は６．２５Ｖである。
【０１０８】
そして、ステップＢ７に移行して標準線速に対する各線速（１／２，１／３）での制御電圧の差（ΔＶｃ）を算出して不揮発メモリ２９に格納する。この例では、１／２速時の制御電圧の差ΔＶｃ_２１＝（Ｖｃ２−Ｖｃ１）は０．３７Ｖであり、１／３速時の制御電圧の差ΔＶｃ_３１＝（Ｖｃ３−Ｖｃ１）は０．７６Ｖである。不揮発メモリ２９には表２に示すような内容の値が格納される。
【０１０９】
【表２】

【０１１０】
その後、ステップＢ８で各線速におけるトナー濃度センサＳＤの出力電圧の差ΔＶＬ_２１、ΔＶＬ_３１及び制御電圧の差ΔＶｃ_２１、ΔＶｃ_３１に基づいて線速変更時の補正係数ΔＶＬ／ΔＶｃを求める。この例では、１／２速時の補正係数ΔＶＬ_２１／ΔＶｃ_２１は０．５４１であり、１／３速時の補正係数ΔＶＬ_３１／ΔＶｃ_３１は０．５３９である。これらのトナー濃度センサＳＤの制御電圧の値Ｖｃを調整するための補正係数ΔＶＬ_２１／ΔＶｃ_２１及びΔＶＬ_３１／ΔＶｃ_３１は不揮発メモリ２９に格納される。不揮発メモリ２９には表３に示すような内容の値が格納される。
【０１１１】
【表３】

【０１１２】
その後、ステップＢ９に移行して他の処理が実行される。例えば、帯電可能な感光体１に形成された静電潜像を現像すべく、感光体１に現像剤１８を担持して付着するような処理や、トナー濃度センサＳＤからの出力電圧の値ＶＬ及び現像剤担持体４１の線速に基づいて現像容器４０Ｄ内にトナーを補給し濃度を制御手段１５によって制御する処理が含まれる。そして、ステップＢ１０に移行する。ステップＢ１０では当該画像形成処理を終了するかが判断される。制御手段１５では電源オフ情報等を検出して画像形成処理を終了する。電源オフ情報が検出されない場合はステップＢ９に戻って上述の処理を繰り返すようになされる。
【０１１３】
なお、不揮発メモリ２９に格納された補正係数ΔＶＬ_２１／ΔＶｃ_２１及びΔＶＬ_３１／ΔＶｃ_３１等は、現像剤投入時以外の線速変更時に使用される。また、補正係数ΔＶＬ／ΔＶｃの値は初期調整のみに行なうのではなく、所定間隔毎に求め直してもよい。例えば、現像スリーブの周動距離５ｋｍが経過する毎といったように、ある決まった現像履歴に基づいて補正係数ΔＶＬ／ΔＶｃの値を求め直してもよい。
【０１１４】
［現像剤投入時以外のトナー濃度初期調整時］
図８はカラー画像形成装置１００のトナー濃度制御時の動作例（現像剤投入時以外）を示すフローチャートである。
この例では、当該カラー画像形成装置１００のウォームアップ時には標準線速のみトナー濃度初期調整を実施する。プロセス線速は操作部１４によってマニュアルにより、或いは、制御手段１５によって自動によって変更がなされる。マニュアルの場合には操作部１４に「光沢」「厚紙」或いはプロセス線速等が表示された選択釦が設けられていて、押釦によってプロセス線速は例えば１１０ｍｍ／ｓに切り替え指示がなされる。また自動の場合には使用する用紙Ｐの紙厚検知等によって制御手段１５から切り替え指示がなされる。
【０１１５】
なお、線速変更時には、その線速変更指示が有った時から所定時間経過後（数秒後）のトナー濃度センサＳＤの出力電圧の値ＶＬ２や、ＶＬ３等を読み込み、標準線速時の出力電圧の値ＶＬ１との差をΔＶＬ１−ΔＶＬ２や、ΔＶＬ１−ΔＶＬ３等を算出し、その後、不揮発メモリ２９から読み出した補正係数ΔＶｃ／ΔＶＬや、標準線速時の制御電圧Ｖｃ及び制御電圧の差ΔＶｃから線速変更時の補正値ΔＶｃ２やＶｃ３を求めて、標準線速でのＶｃ値に加算する。これにより、線速変更時の制御電圧の値を決定するようになされる。
【０１１６】
制御手段１５では決定したプロセス線速に対応した回転数変更用のパルスＣＬＫを駆動手段６０に出力し、画像記録が行われる。また制御手段１５は、Ｙ，Ｍ，Ｃ，Ｋ各色毎に決定されたプロセス線速に対応した制御電圧Ｖｃ値を不揮発メモリ２９から呼び出してトナー濃度センサＳＤに印加し、センサ出力を得る。ここで検出されたセンサ出力は閾値（２．５Ｖ）と比較され、この比較結果に基づいてトナー補給制御が行われる。
【０１１７】
これを動作条件にして、図８に示すフローチャートのステップＣ１で電源スイッチＳＷをオンして当該カラー画像形成装置１００を起動する。このとき、電源スイッチＳＷのＯＮによって制御手段１５ではウォーミングアップ時間中に、ＲＯＭから画像調整プログラムを呼び出して画像調整を行う。そして、ステップＣ２に移行して現像剤担持体４１を標準線速（１／１）で回転してトナー濃度初期調整を行う。
【０１１８】
このとき、制御手段１５では標準線速でトナー濃度センサＳＤの出力に応じたトナー濃度制御を実行し、適正なトナー濃度に調整してから標準線速でトナー濃度センサＳＤによるトナー濃度初期調整を実行する。この例では、標準線速で例えば、出力電圧の値ＶＬ１＝２．５２Ｖが得られるトナー濃度センサＳＤの制御電圧の値Ｖｃが決定される。この例では制御電圧の値ＶｃはＶｃ１＝７．０２Ｖである。
【０１１９】
次に、ステップＣ３で制御電圧の値Ｖｃ１＝７．０２Ｖにおいて、各線速毎の当該トナー濃度センサＳＤの出力電圧の値ＶＬ２，ＶＬ３を検出する。この例では、１／２速時のトナー濃度センサＳＤの出力電圧の値ＶＬ２は２．６８Ｖであり、１／３速時の出力電圧の値ＶＬ３は２．７５Ｖである。そして、ステップＣ４に移行して線速変更が有ったかがチェックされる。線速変更は制御手段１５の外部、例えば図５に示した操作部１４等から線速変更要求信号Ｓ１を入力することで画像成形制御がなされる。
【０１２０】
線速変更が有った場合はステップＣ５に移行して制御手段１５では標準線速から線速降下への変更があったかがチェックされる。標準線速から線速降下への変更があった場合はステップＣ６に移行する。ステップＣ６では所定時間が経過したかがチェックされる。ここでは例えば、２秒〜３秒間程度が経過するまで、トナー濃度センサＳＤの出力値に関係なく、トナー補給制御を中止するようになされる。こうすることで、センサ出力時の不安定によるトナー過補給を防ぐことができ、トナー飛散や画像かぶりを防ぐことができる。
【０１２１】
この所定時間が経過すると、ステップＣ７に移行して、現像剤担持体４１の標準線速におけるトナー濃度センサＳＤの出力電圧の値ＶＬと、線速変更時のトナー濃度センサＳＤの出力電圧の値ＶＬとの電圧差ΔＶＬを算出する。例えば、標準線速１／１から１／２速へ変更指示された場合、現像剤担持体４１の標準線速におけるトナー濃度センサＳＤの出力電圧の値ＶＬ１＝２．５２Ｖと、１／２速変更時のトナー濃度センサＳＤの出力電圧の値ＶＬ２＝２．６８との電圧差ΔＶＬ_１２を算出する。この例では電圧差ΔＶＬ_１２は−０．１６Ｖである。
【０１２２】
その後、ステップＣ８に移行して補正係数ΔＶＬ_２１／ΔＶｃ_２１に基づいて１／２線速変更時の制御電圧の差ΔＶｃ_１２を算出する。この例では制御電圧の差ΔＶｃ_１２はΔＶＬ_１２／補正係数で与えられることから、ΔＶｃ_１２＝ΔＶＬ_１２／ΔＶＬ_２１／ΔＶｃ_２１＝−０．３Ｖとなる。この制御電圧の差ΔＶｃ_１２に基づいて当該センサＳＤの制御電圧の値Ｖｃを決定するようになされる。この例では１／２線速変更時の制御電圧の値Ｖｃ２は標準線速時の制御電圧Ｖｃ＋制御電圧の差ΔＶｃ_１２で与えられることから、Ｖｃ２＝Ｖｃ１＋ΔＶｃ_１２＝６．７２Ｖとなる。表４には１／２速変更時の補正後の制御電圧の値Ｖｃ２＝６．７２Ｖや１／３速変更時の補正後の制御電圧の値Ｖｃ３＝６．５９Ｖを示している。
【０１２３】
【表４】

【０１２４】
このように、１／Ｎ線速変更時の制御電圧の値Ｖｃは標準線速時の制御電圧Ｖｃ＋制御電圧の差ΔＶｃにより算出することができ、１／２速，１／３速などの制御電圧の値Ｖｃ２やＶｃ３等を演算処理により求めることができる。ここで演算された制御電圧の値Ｖｃ２等はステップＣ９で当該トナー濃度センサＳＤに設定される。その後、ステップＣ１１に移行する。
【０１２５】
なお、ステップＣ４で線速変更要求が無い場合はステップＣ１０に移行して画像形成処理を実行する。このとき、帯電可能な感光体ドラム１Ｙ、１Ｍ、１Ｃ、１Ｋに形成された静電潜像を現像すべく、感光体ドラム１Ｙ、１Ｍ、１Ｃ、１Ｋに現像剤１８を担持して付着するような処理や、トナー濃度センサＳＤからの出力電圧の値ＶＬ及び現像剤担持体４１の線速に基づいて現像容器４０Ｄ内にトナーを補給し濃度を制御手段１５によって制御する処理が含まれる。その後、ステップＣ１１に移行する。ステップＣ１１では当該画像形成処理を終了するかが判断される。制御手段１５では電源オフ情報等を検出して画像形成処理を終了する。電源オフ情報が検出されない場合はステップＣ４に戻って上述の処理を繰り返すようになされる。
【０１２６】
図９は効果確認テストに係る対策前後のトナー濃度Ｔｃ［％］の検出例を示す特性比較図である。図９に示す縦軸は対策前後のトナー濃度Ｔｃ［％］である。横軸はコピー数［ｋｃ］であり、１０００００枚プリントを示している。
【０１２７】
この効果確認テストでは、トナー濃度制御を実行しながら、１枚目の用紙Ｐから１０００００枚目の用紙Ｐに至るプリントを実行し、そのトナー濃度安定性をテストしたものであって、プロセス線速を標準（１／１）速以外に、例えば、２０Ｋｃ、４０Ｋｃ、６０Ｋｃ等で線速を、（１／２）速、（１／３）速モードに変更した形態で実施した場合の結果を示している。
【０１２８】
図９に示す特性比較図によれば、トナー濃度Ｔｃ＝８質量％を基準にしたとき、黒抜き四角印を実線で結んだ特性は、本発明方式によるものである。黒抜き菱形印を実線で結んだ特性は従来方式によるものである。従来方式のような対策前の特性によれば、スタート時のトナー濃度Ｔｃが８質量％であったものが、線速を変更する度に、１０００００プリント中逸脱して大きなバラツキが認められ、安定したトナー濃度制御がなされていなかった。
【０１２９】
これに対して、本発明方式によれば、定着手段１７のウォームアップ時間を延長させることなく、複数のプロセス線速モードにおいて、トナー濃度Ｔｃのほぼ８質量％前後に制御がなされ、安定したトナー濃度制御を行うことができた。この１０００００枚プリントにおいて、画像かぶりやトナー飛散のない良好なプリント画像が得られた。しかも、目標値のトナー濃度Ｔｃ＝８質量％に対して、Ｙ，Ｍ，Ｃ，Ｋ４色のトナー濃度Ｔｃは何れも±０．１％以内に制御され、Ｙ，Ｍ，Ｃ，Ｋ４色のトナー濃度Ｔｃの平均値は±０．０５％以内に維持されていることが認められた。
【０１３０】
このように、本発明に係る実施例としてカラー画像形成装置１００によれば、Ｙ、Ｍ、Ｃ及びＫ色用の現像装置４Ｙ、４Ｍ、４Ｃ、４Ｋに関して、本発明に係る現像装置４０が応用されるので、帯電可能な感光体ドラム１Ｙ、１Ｍ、１Ｃ、１Ｋに形成された静電潜像を現像する場合に、当該装置起動後の線速変更時に、制御手段１５はトナー濃度センサＳＤの制御電圧の値Ｖｃを検出すると共に、不揮発メモリ２９から補正係数ΔＶＬ／ΔＶｃを読み出して当該トナー濃度センサＳＤの制御電圧の値Ｖｃを補正し、補正後の制御電圧の値Ｖｃで当該トナー濃度センサＳＤを駆動するようになされる。
【０１３１】
従って、朝一のウォームアップ時間を延長させることなく、非常に安定したトナー濃度制御を行なうことができるばかりか、当該装置起動後の線速変更時に、現像剤投入時のようなトナー濃度初期調整を行なうことなく、演算処理によって得た補正後の制御電圧の値Ｖｃをトナー濃度センサＳＤに印加することができる。これにより、当該装置１００のウォームアップ時には標準線速に係るトナー濃度センサＳＤの出力調整のみで済むので、ウォームアップ時間を延長させることなく、各線速毎に安定したトナー濃度制御を行なうことができる。従って、当該カラー画像形成装置１００を応用したカラー用のディジタル複合機等を提供することができる。
【０１３２】
また、線速ダウン時の初期的なセンサ出力不安定から生じるトナー飛散や、画像かぶりも発生せず、安定した画像を得ることができた。上述した感光体についてはドラム状の場合について説明したが、これに限られることはなく、中間転写体を兼用したベルト状の感光体にも本発明を適用することができる。
【０１３３】
【発明の効果】
以上説明したように、本発明に係る現像装置によれば、帯電可能な感光体に形成された静電潜像を現像する場合に、現像剤の透磁率を検出する検出手段からの出力電圧の値及び現像剤担持体の線速に基づいて容器内にトナーを補給し濃度を制御する制御手段を備え、当該装置起動後の線速変更時に、制御手段は検出手段の制御電圧の値を検出すると共に、記憶手段から補正情報を読み出して当該検出手段の制御電圧を補正し、補正後の制御電圧で当該検出手段を駆動するようにしたものである。
【０１３４】
この構成によって、当該装置起動後の線速変更時に、現像剤投入時のようなトナー濃度初期調整を行なうことなく、演算処理によって得た補正後の制御電圧を検出手段に供給することができる。従って、当該装置のウォームアップ時には標準線速に係る検出手段の出力調整のみで済むので、ウォームアップ時間を延長させることなく、各線速毎に安定したトナー濃度制御を行なうことができる。
【０１３５】
本発明に係る現像装置の制御方法によれば、現像装置に取り付けられたトナー濃度検出用のセンサ系の制御電圧の値を調整する場合に、現像剤投入時に、標準線速を含む所定の１／Ｎ線速についてトナー濃度初期調整を行い、センサ系の制御電圧の値及び出力電圧の値と、当該センサ系で現像濃度一定を示す出力電圧が得られる制御電圧と、標準線速時のセンサ系の出力電圧と１／Ｎ線速時におけるセンサ系の出力電圧との差及び、標準線速時のセンサ系の制御電圧と１／Ｎ線速時におけるセンサ系の制御電圧との差を各々求め、これらに基づいて線速変更時の補正係数を求め、当該装置起動後の線速変更時には、この補正係数に基づいて当該センサ系の制御電圧の値を演算し、ここで演算された制御電圧値を当該センサ系に設定するようになされる。
【０１３６】
この構成によって、当該装置起動後の線速変更時に、現像剤投入時のようなトナー濃度初期調整を行なうことなく、演算処理によって得た補正後の制御電圧をセンサ系に供給することができる。従って、当該装置のウォームアップ時には標準線速に係るセンサ出力調整のみで済むので、ウォームアップ時間を延長させることなく、各線速毎に安定したトナー濃度制御を行なうことができる。
【０１３７】
本発明に係る画像形成装置によれば、本発明に係る現像装置が応用されるので、帯電可能な感光体に形成された静電潜像を現像する場合に、当該装置起動後の線速変更時に、制御手段は検出手段の制御電圧を検出すると共に、記憶手段から補正情報を読み出して当該検出手段の制御電圧を補正し、補正後の制御電圧で当該検出手段を駆動するようになされる。
【０１３８】
この構成によって、当該装置起動後の線速変更時に、現像剤投入時のようなトナー濃度初期調整を行なうことなく、演算処理によって得た補正後の制御電圧を検出手段に供給することができる。従って、当該装置のウォームアップ時には標準線速に係る検出手段の出力調整のみで済むので、ウォームアップ時間を延長させることなく、各線速毎に安定したトナー濃度制御を行なうことができる。
【０１３９】
この発明は、複写機能、ファクシミリ機能及びプリンタ機能を備えた白黒用及びカラー用のディジタル複合機や複写機等に適用して極めて好適である。
【図面の簡単な説明】
【図１】本発明の実施形態としての現像装置４０の構成例を示すブロック図である。
【図２】現像装置４０のトナー濃度制御時の動作例を示すフローチャートである。
【図３】本発明に係る実施例としてのカラー画像形成装置１００の構成例を示す断面の概念図である。
【図４】カラー画像形成装置１００に実装される現像装置４Ｙ等の構成例を示す断面図である。
【図５】カラー画像形成装置１００の制御系の構成例を示すブロック図である。
【図６】トナー濃度センサＳＤのセンサ出力対トナー濃度の関係例を示す動作特性図である。
【図７】カラー画像形成装置１００のトナー濃度制御時の動作例（現像剤投入時）を示すフローチャートである。
【図８】カラー画像形成装置１００のトナー濃度制御時の動作例（現像剤投入時以外）を示すフローチャートである。
【図９】効果確認テストに係る対策前後のトナー濃度Ｔｃ［％］の検出例を示す特性比較図である。
【図１０】従来例に係るトナー濃度センサによる検出例を示す特性図である。
【符号の説明】
１　感光体
１Ｙ，１Ｍ，１Ｃ，１Ｋ　感光体ドラム
２Ｙ，２Ｍ，２Ｃ，２Ｋ　帯電手段
３Ｙ，３Ｍ，３Ｃ，３Ｋ　露光手段
４Ｙ，４Ｍ，４Ｃ，４Ｋ　現像手段
６　中間転写ベルト（転写手段）
１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋ　画像形成ユニット（画像形成手段）
１３　記憶手段
１４　操作部
１５　制御手段
１７　定着手段
１８　現像剤
２９　不揮発メモリ（記憶手段）
３３　画像メモリ
４０　現像装置
４０Ｄ　現像容器
４１　現像担持体
６０　駆動手段
１００　カラー画像形成装置（画像形成装置）
ＳＤ　トナー濃度センサ（検出手段）[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, a control method thereof, and an image forming apparatus suitable for being applied to a black-and-white or color digital multifunction peripheral or copying machine having a copying function, a facsimile function and a printing function.
[0002]
[Prior art]
2. Description of the Related Art In recent years, digital color copiers that form a color image based on red (R), green (G), and blue (B) color image data acquired from a colored original image have been used. . In this copying machine, image information of a document is read by a scanner or the like, and color image data relating to the image information of the document is temporarily stored in an image memory. When the color image data is stored in the memory, shading correction, timing control, line-to-line correction, and the like are performed.
[0003]
The color image data relating to the RGB colors after the correction processing is subjected to γ correction, scaling processing, spatial filtering, image compression processing, and the like. Here, a color image based on the image-processed color image data is formed on predetermined paper by an image forming means (printer). At this time, the Y, M, C, and BK photoconductors uniformly charged by each charging unit are exposed and scanned by the exposure unit for each color based on the color image data, and the photoconductor for each color is scanned. An electrostatic latent image is formed thereon.
[0004]
This electrostatic latent image is developed by a developing device prepared for each color. Such charging, exposure and development are performed at least once, and the color toner image formed on the photoconductor is transferred to a transfer material by a transfer unit. The toner image transferred onto the predetermined sheet is fixed by a fixing unit. As a result, the color document image can be copied.
[0005]
This type of developing device is disclosed in an image forming apparatus of Patent Document 1, and this developing device is provided with a developing container. The container contains a non-magnetic toner for developing an electrostatic latent image and a developer comprising a magnetic carrier. The developer container is provided with a developer carrier rotatably in the developer container to carry the developer and adhere to the photoreceptor. A toner density sensor is attached to the developing container, and detects the magnetic permeability of the developer in order to control the toner density. The developing device replenishes the toner in the developing container and controls the density based on the voltage output from the toner density sensor and the linear velocity of the developer carrier.
[0006]
Further, in a color copying machine or the like, an operation is performed so as to change the process linear velocity in order to secure the fixing property and the glossiness. In this case, at least in the configuration in which the driving means of the developing device stirring section is common to the photosensitive member and the developer carrying member, it is necessary to change the linear speed of the developing device itself at the same time as the linear speed of the developer carrying member. Come.
[0007]
FIG. 10 is a characteristic diagram showing an example of detection by a conventional toner density sensor. In FIG. 10, the vertical axis is the output value (V) of the toner density sensor, and the horizontal axis is the sensor drive time (h). The characteristics obtained by connecting the black diamonds with solid lines are the output characteristics of the toner density sensor at the standard linear velocity (1/1). The characteristics obtained by connecting the black squares with solid lines are the output characteristics of the toner density sensor at 1/2 speed. The characteristics obtained by connecting the white triangles with solid lines are the output characteristics of the toner density sensor at 1/3 speed. These characteristics indicate that the output value of the toner density sensor increases when the linear speed is decreased from the standard linear speed.
[0008]
Therefore, in order to perform correct toner supply control, at the time of initial adjustment of toner concentration, the control voltage value is corrected so that the sensor output for each linear speed becomes a correct output voltage value. For example, when the developer is supplied, the toner density sensors of Y, M, C, and BK output sensor outputs for predetermined toner densities of 1/2 and 1/3 speeds including the standard linear speed 1/1. Determines the control voltage value at which the threshold value becomes 2.5V. The control voltage value determined here is stored in a non-volatile memory, and when the toner density is detected, the control voltage value is called from the non-volatile memory and applied to the toner density sensor to obtain a sensor output. By the way, if the control voltage value is not corrected for each linear speed, the toner density increases by an amount corresponding to the increase in the sensor output.
[0009]
[Patent Document 1]
JP-A-11-184236
[0010]
[Problems to be solved by the invention]
However, the color copier equipped with the conventional developing device has the following problems.
[0011]
(1) In the initial adjustment, good toner replenishment is performed. However, when the operating environment in the apparatus such as temperature and humidity changes, or when the deterioration of the developer proceeds, the sensor output moves, and good toner replenishment is not performed. Become like Therefore, in addition to the time when the developer is supplied, at the time of warm-up in the morning, that is, before the fixing unit reaches a predetermined temperature, the toner density is adjusted according to the output of the toner density sensor, and then the standard line is adjusted. The initial adjustment of the toner density must be performed for each of the linear speeds, such as the speed, 1/2 speed, and 1/3 speed. This results in a longer warm-up time in the morning.
[0012]
{Circle around (2)} According to the developing device in which the photosensitive member, the developer carrying member, etc., and the developing device stirring section are driven by a common driving unit, the process linear velocity is lowered from the viewpoint of fixability and glossiness. When the linear speed change control is executed, the output itself of the toner density sensor also fluctuates according to the process linear speed. As a result, correct toner supply control is not performed, which hinders stable toner density control.
[0013]
{Circle around (3)} The output of the toner density sensor is not stabilized within a predetermined time (about 2 to 3 seconds) after changing from the standard speed to a low linear speed such as 1/2 speed or 1/3 speed. In addition, excessive replenishment of the toner may occur, and problems such as toner scattering and image fogging due to insufficient rise of the toner charge amount may occur.
[0014]
Therefore, the present invention has solved the above-mentioned problem, and does not depend on the initial adjustment of the toner concentration such as when the developer is supplied at the time of changing the linear velocity, and uses the corrected control voltage obtained by the arithmetic processing as a sensor system. And a control method and an image forming apparatus which can control the toner concentration stably for each linear speed.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, a developing device according to the present invention is a developing device for developing an electrostatic latent image formed on a chargeable photoconductor, and a non-magnetic toner for developing the electrostatic latent image. A container containing a developer comprising a magnetic carrier, a developer carrier rotatably provided in the container to carry the developer and adhere to the photoreceptor, and a developer attached to the container. Detecting means for detecting the magnetic permeability, controlling means for supplying toner into the container and controlling the density based on the output voltage from the detecting means and the linear velocity of the developer carrier, and adjusting the control voltage of the detecting means Storage means for storing correction information for detecting the control voltage of the detection means and reading the correction information from the storage means at the time of changing the linear velocity after the start of the apparatus. And the corrected control voltage It is characterized in that for driving the detection means.
[0016]
According to the developing device of the present invention, when developing an electrostatic latent image formed on a chargeable photosensitive member, a non-magnetic toner and a magnetic material for developing the electrostatic latent image are provided in a predetermined container. A developer composed of a carrier is stored. A developer carrier is rotatably mounted in the container, and the developer is carried on and adhered to the photoconductor. The container is provided with detection means, and the magnetic permeability of the developer in the container is detected.
[0017]
In addition, correction information for adjusting the control voltage of the detection means is stored in the storage means in advance. The control means replenishes toner into the container and controls the density based on the output voltage from the detection means and the linear velocity of the developer carrying member. On the premise of this, when changing the linear velocity after starting the apparatus, the control means detects the control voltage of the detection means, reads correction information from the storage means, corrects the control voltage of the detection means, and corrects the control voltage of the detection means. The detection means is driven by the control voltage.
[0018]
Therefore, when the linear velocity is changed after the start of the apparatus, the corrected control voltage obtained by the arithmetic processing can be supplied to the detecting means without performing the initial adjustment of the toner concentration as when the developer is supplied. Thus, at the time of warm-up of the apparatus, only the output adjustment of the detection means relating to the standard linear velocity is required, so that stable toner density control can be performed for each linear velocity without extending the warm-up time.
[0019]
A method for controlling a developing device according to the present invention is a method for adjusting a control voltage of a sensor system for detecting a toner concentration attached to a developing device including a developer carrier. The initial adjustment of the toner density is performed for a predetermined 1 / N linear velocity (N = 2, 3...) Including the standard linear velocity of the above-mentioned standard linear velocity, and the control voltage and output voltage of the sensor system are obtained. The control voltage at which a constant output voltage is obtained is obtained, and the difference between the sensor system output voltage at the standard linear speed and the sensor system output voltage at the 1 / N linear speed and the sensor system output at the standard linear speed are obtained. A difference between the control voltage and the control voltage of the sensor system at the time of 1 / N linear velocity is obtained, and correction information for changing the linear velocity is obtained based on the difference between the output voltage of the sensor system and the difference between the control voltages. When changing the linear speed after startup, based on the correction information It calculates the control voltage of the sensor system, the calculated control voltage where is characterized in that set in the sensor system.
[0020]
According to the control method of the developing device according to the present invention, when adjusting the control voltage of the sensor system for detecting the toner concentration attached to the developing device, when changing the linear speed after the start of the device, the developer supply time is adjusted. The corrected control voltage obtained by the arithmetic processing can be supplied to the sensor system without performing such initial adjustment of the toner concentration.
[0021]
Therefore, at the time of warm-up of the apparatus, only the sensor output adjustment for the standard linear speed is required, so that stable toner density control can be performed for each linear speed without extending the warm-up time.
[0022]
An image forming apparatus according to the present invention is an apparatus for forming an image based on arbitrary image data, a rotatable photoconductor, a charging unit for uniformly charging the photoconductor, and a photoconductor charged by the charging unit. Exposure means for exposing and scanning the body based on image data to form an electrostatic latent image on the photoreceptor, a developing device for developing the electrostatic latent image exposed by the exposure means, and charging, exposing, and developing at least A transfer unit for transferring the toner image formed on the photoreceptor once to a transfer material, and a fixing unit for fixing the toner image transferred to the transfer material; Containing a developer comprising a non-magnetic toner and a magnetic carrier, a developer carrier rotatably provided in the container to carry the developer and adhere to the photoreceptor, and a container To detect the magnetic permeability of the developer Detecting means, controlling means for replenishing toner in the container and controlling the density based on the output voltage from the detecting means and the linear velocity of the developer carrier, and correction information for adjusting the control voltage of the detecting means. When the linear velocity is changed after starting the apparatus, the control means detects the control voltage of the detection means, reads correction information from the storage means and corrects the control voltage of the detection means, The detecting means is driven by the corrected control voltage.
[0023]
According to the image forming apparatus of the present invention, since the developing device of the present invention is applied, when developing an electrostatic latent image formed on a chargeable photoreceptor, changing the linear velocity after starting the apparatus. Sometimes, the control means detects the control voltage of the detection means, reads the correction information from the storage means, corrects the control voltage of the detection means, and drives the detection means with the corrected control voltage.
[0024]
Therefore, when the linear velocity is changed after the start of the apparatus, the corrected control voltage obtained by the arithmetic processing can be supplied to the detecting means without performing the initial adjustment of the toner concentration as when the developer is supplied. Thus, at the time of warm-up of the apparatus, only the output adjustment of the detection means relating to the standard linear velocity is required, so that stable toner density control can be performed for each linear velocity without extending the warm-up time.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a developing device, a control method thereof, and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
(1) Embodiment
FIG. 1 is a block diagram illustrating a configuration example of a developing device 40 as an embodiment of the present invention.
In this embodiment, when developing an electrostatic latent image formed on a chargeable photoconductor, toner is stored in a container based on an output voltage based on detection of magnetic permeability of the developer and a linear velocity of the developer carrier. Control means for replenishing and controlling the concentration, detecting the control voltage of the detecting means when the linear velocity changes after the start of the apparatus, reading the correction information from the storage means and correcting the control voltage of the detecting means, By driving the detection means with the later control voltage, the corrected control voltage obtained by the arithmetic processing can be supplied to the detection means without depending on the initial adjustment of the toner concentration such as when the developer is supplied. In addition, a stable toner density can be controlled for each linear velocity.
[0026]
The developing device 40 shown in FIG. 1 is a device that develops an electrostatic latent image formed on the chargeable photoconductor 1. The photoconductor 1 is assumed to have a drum shape or a belt shape, for example. Image data is written on the photoreceptor 1 by laser light L from exposure means (not shown). Around the photoreceptor 1, a charging unit 2, an image forming body cleaning unit 8, and the like are arranged and used.
[0027]
The developing device 40 is suitable for being applied to a black-and-white and color digital multifunction peripheral or a copying machine having a copying function, a facsimile function and a printer function. The developing device 40 has a developing container 40D of a predetermined shape, and accommodates a developer 18 composed of a non-magnetic toner and a magnetic carrier for developing an electrostatic latent image. In the developing device 40, a two-component mixture of a toner having a particle size of 8.0 μm or less and a carrier having a particle size of 65 μm or less is used as the developer 18.
[0028]
At least a developer carrier 41 is rotatably provided in the developing container 40D, and the developer 18 is carried on and adhered to the photoconductor 1. In the figure, reference symbol DR denotes a development nip portion, which is a portion that transfers the developer 18 from the developer carrier 41 to the photoconductor 1. The developer carrier 41 is rotated at a predetermined 1 / N linear speed (N = 2, 3,...) Including a standard linear speed. At the bottom of the developing container 40D, for example, a toner density sensor SD as an example of a detecting unit is attached so as to detect the magnetic permeability of the developer 18 stirred in the developing container 40D. The toner density is detected based on the magnetic permeability of the developer 18.
[0029]
The control means 15 is connected to the toner density sensor SD, and the toner is stored in the developing container 40D based on the value VL of the output voltage from the sensor SD and the linear speed (rotation speed) of the developer carrier 41. It is made to supply and control the density. A CPU (Central Processing Unit) or the like is used for the control means 15.
[0030]
The control unit 15 is connected to the storage unit 13 and stores correction information for adjusting the value Vc of the control voltage of the toner density sensor SD, for example, a correction coefficient ΔVL / ΔVc. A non-volatile memory such as a flash memory is used for the storage unit 13. A flash memory is a read-only memory in which information can be written and data is not erased even when the power is turned off.
[0031]
The storage unit 13 controls the toner density sensor SD for at least a predetermined 1 / N linear velocity including the standard linear velocity of the developer carrier 41 obtained by performing the initial adjustment of the toner density when the developer is supplied. The voltage value Vc and the output voltage value VL, the control voltage value Vc at which the output voltage value VL indicating the constant development density is obtained by the toner density sensor SD, and the output voltage of the toner density sensor SD at the standard linear speed VL and the first voltage difference ΔVL obtained from the output voltage value VL of the toner density sensor SD at the 1 / N linear speed, and the control voltage value Vc of the toner density sensor SD at the standard linear speed and 1 / N linear speed, the second voltage difference ΔVc obtained from the control voltage value Vc of the toner density sensor SD, the output voltage difference ΔVL of the toner density sensor SD, and the control voltage difference ΔVc. A correction coefficient .DELTA.VL / [Delta] Vc at line speed change is stored.
[0032]
A power switch SW is connected to the control means 15 to start the device 40. When the linear velocity is changed after the start of the apparatus, the control unit 15 detects the value Vc of the control voltage of the toner density sensor SD and reads the correction coefficient ΔVL / ΔVc from the storage unit 13 to read the control voltage of the toner density sensor SD. The value Vc is corrected, and the toner density sensor SD is driven by the corrected control voltage value Vc.
[0033]
In this example, when the linear speed is changed after the start of the apparatus, the control unit 15 determines the output voltage value VL1 of the toner density sensor SD at the standard linear speed of the developer carrier 41 and the output voltage VL1 of the toner density sensor SD when the linear speed is changed. A voltage difference Δ (VL1−VL2) from the output voltage value VL2 is calculated, and a correction coefficient ΔVL / ΔVc read from the storage unit 13 is calculated as a voltage difference Δ (VL1−VL2) to control the voltage at the time of changing the linear velocity. The difference Δ (Vc1−Vc2) is calculated, and the control voltage value Vc of the toner density sensor SD is determined based on the control voltage difference Δ (Vc1−Vc2). Further, a toner replenishing unit 410 is connected to the control unit 15 so as to execute toner replenishment control based on a toner replenishment control signal S21.
[0034]
Next, an operation example of the developing device 40 according to the present invention when controlling the toner concentration of the developing device 40 will be described. FIG. 2 is a flowchart illustrating an operation example of the developing device 40 when controlling the toner concentration.
[0035]
In this embodiment, a predetermined developing container 40D stores a developer 18 composed of a non-magnetic toner and a magnetic carrier for developing an electrostatic latent image. A developer carrier 41 is rotatably provided in the developing container 40D, and a toner density sensor SD (sensor system for detecting toner density) is attached to the bottom of the developing container 40D. The magnetic permeability of the developer 18 is detected. Then, it is assumed that the value Vc of the control voltage of the toner density sensor SD attached to the developing device 40 including the developer carrier 41 is adjusted.
[0036]
With this as an operating condition, the power switch is turned on at step A1 in the flowchart shown in FIG. Thereafter, the process shifts to step A2 to detect whether or not the developer 18 is supplied. At this time, the control unit 15 controls the toner supply unit 410 based on the output voltage value VL obtained from the toner density sensor SD. For example, a toner replenishment control signal S21 is output to the toner replenishment unit 410 to execute developer supply replenishment. When the developer 18 is not supplied, the process proceeds to Step A7.
[0037]
When the developer 18 is supplied, the process proceeds to step A3, and the toner density initial adjustment is performed for a predetermined 1 / N linear speed (N = 2, 3,...) Including the standard linear speed of the developer carrier 41. To obtain the control voltage value Vc and the output voltage value VL of the toner density sensor SD. In step A4, a control voltage value Vc at which an output voltage value VL indicating a constant development density is obtained by the toner density sensor SD is obtained. This is for obtaining the correction coefficient ΔVL / ΔVc.
[0038]
Then, the process proceeds to step A5, wherein the difference ΔVL between the output voltage value VL of the sensor system at the standard linear speed and the output voltage value VL of the sensor system at the 1 / N linear speed, and the sensor system at the standard linear speed , And the difference ΔVc between the control voltage value Vc of the sensor system at 1 / N linear speed is obtained. Thereafter, in step A6, a correction coefficient ΔVL / ΔVc for changing the linear velocity is obtained based on the difference ΔVL between the output voltages of the sensor system and the difference ΔVc between the control voltages. The correction coefficient ΔVL / ΔVc for adjusting the value Vc of the control voltage of the toner density sensor SD is stored in the storage unit 13.
[0039]
Then, after the normal use including the restart of the developing device 40, the process proceeds to step A7 to check whether the linear speed has been changed. The line speed is changed by inputting a line change request signal S1 from outside the control unit 15, for example, an operation unit (not shown) or the like, so that the development control is performed. If there is a change in the linear velocity, the process proceeds to step A8, and the control voltage value Vc of the sensor system is calculated based on the correction coefficient ΔVL / ΔVc. For example, the voltage difference Δ (VL1−VL2) between the sensor system output voltage VL1 at the standard linear speed of the developer carrier 41 and the sensor system output voltage VL2 when the linear speed is changed is calculated. After that, the control voltage difference Δ (Vc1−Vc2) when the linear velocity is changed is calculated based on the correction information ratio ΔVL / ΔVc. The value Vc of the control voltage of the sensor is determined based on the control voltage difference ΔVc.
[0040]
The control voltage value Vc calculated here is set to the toner density sensor SD in step A9. Thereafter, the process proceeds to step A11. If there is no request for changing the linear speed in step A7, the flow shifts to step A10 to execute another process. Examples of other processing here include, for example, processing for carrying and attaching the developer 18 to the photoconductor 1 in order to develop an electrostatic latent image formed on the chargeable photoconductor 1, The process includes replenishing toner in the developing container 40D based on the output voltage value VL from the sensor SD and the linear velocity of the developer carrier 41 and controlling the density by the control unit 15.
[0041]
Thereafter, the process proceeds to step A11. In step A11, it is determined whether or not to end the development processing. The control means 15 detects the power-off information and the like, and ends the development processing. If no power-off information is detected, the process returns to step A7 to repeat the above processing.
[0042]
As described above, according to the developing device and the control method thereof according to the embodiment of the present invention, when developing the electrostatic latent image formed on the chargeable photoreceptor 1, the linear velocity change after starting the device is performed. At this time, the control means 15 detects the control voltage value Vc of the toner density sensor SD, reads the correction information from the storage means 13 and corrects the control voltage value Vc of the toner density sensor SD. Is driven at the value Vc.
[0043]
Therefore, when the linear velocity is changed after the start of the apparatus, the corrected control voltage value Vc obtained by the arithmetic processing is supplied to the toner density sensor SD without performing the initial adjustment of the toner density as when the developer is supplied. Can be. Accordingly, when the device 40 is mounted on an image forming apparatus or the like, at the time of warm-up, only the output adjustment of the toner density sensor SD relating to the standard linear velocity is required, so that the warm-up time of the image forming apparatus is not extended, Stable toner density control can be performed for each linear speed. Therefore, the developing device 40 can be sufficiently applied to a black-and-white or color digital multifunction peripheral or a copying machine having a copying function, a facsimile function and a printer function.
[0044]
(2) Example
FIG. 3 is a conceptual diagram of a cross section showing a configuration example of a color image forming apparatus 100 as an embodiment according to the present invention.
In this embodiment, the color image forming apparatus 100 incorporating the developing device 40 is configured, and has a plurality of process speeds. Even when the linear speed is changed, a stable toner density control is performed by the toner density sensor SD to increase the warm-up time. The color image forming apparatus 100 can be executed without extension, and can provide a color image forming apparatus 100 free from toner scattering and image fogging.
[0045]
The color image forming apparatus 100 shown in FIG. 3 is an apparatus that forms an image based on arbitrary image data, and has a copy mode for changing a process linear velocity from the viewpoint of fixability and glossiness. In this example, the process linear speed can be switched to a plurality of stages. For example, the process linear speed is switched between (1/2) speed and (1/3) speed with respect to the standard linear speed (1/1). Is possible. When the standard linear velocity is 220 mm / s, it is variable at 110 mm / s at 1/2 linear velocity and at 73 mm / s at 1/3 linear velocity. In the following description, such a variable case will be described, but of course, the present invention is also applied to other multi-stage switching.
[0046]
The color image forming apparatus 100 includes an image forming apparatus main body 101 and an image reading apparatus 102. An image reading device 102 including an automatic document feeder 201 and a document image scanning / acquisition device 202 is installed on an upper portion of the image forming apparatus main body 101, and reads an arbitrary color document to read red (R) and green (G) colors. , An analog color image signal of blue (B) color (hereinafter also simply referred to as an analog signal Sin). For example, a colored document d placed on a document table of the automatic document feeder 201 is transported by a transport unit, and an image on one side or both sides of the document d is scanned by an optical system of the document image scanning / acquisition device 202, and a line is scanned. The data is read into the image sensor CCD.
[0047]
The image forming apparatus main body 101 is provided with a control unit 15 for performing image processing on the color image data Din. For example, the analog signal Sin photoelectrically converted by the above-described line image sensor CCD is subjected to analog signal processing by the control unit 15, and then analog-to-digital (A / D) conversion. The image data after the A / D conversion is subjected to shading correction, timing control, line-to-line correction, and the like by the control unit 15. The data relating to the RGB colors after the correction processing becomes the color image data Din.
[0048]
The color image data Din is controlled by the control unit 15 based on a three-dimensional color conversion table based on the yellow (hereinafter simply referred to as Y), magenta (hereinafter simply referred to as M), cyan (hereinafter simply referred to as C), black (hereinafter simply referred to as K or BK), and the converted color image data DY, DM, DC, and DK are converted to color image data of the image forming units 10Y, 10M, 10C, and 10K, which are examples of image forming means. Means) sent to 3Y, 3M, 3C, 3K. This is for forming a color image based on a predetermined operation mode.
[0049]
Further, the automatic document feeder 201 includes an automatic double-sided document transport unit. The automatic document feeder 201 reads the contents of a large number of documents d fed from a document mounting table at a time, and accumulates the contents of the documents in a storage means (electronic RDH function). This electronic RDH function is conveniently used when copying the contents of a large number of documents by the copying function, or when transmitting a large number of documents d by the facsimile function.
[0050]
The image forming apparatus main body 101 is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless intermediate transfer belt 6 as an example of a transfer unit, and The image forming apparatus includes a sheet feeding / conveying unit including a sheet feeding mechanism (ADU mechanism) and a fixing unit 17 for fixing a toner image.
[0051]
The image forming unit 10Y for forming an image of Y color includes a photosensitive drum 1Y, a charging unit 2Y for Y color, an exposing unit 3Y, a developing device 4Y, and a cleaning unit for the image forming body, which are arranged around the photosensitive drum 1Y. It has means 8Y. The photoconductor drum 1Y uses an OPC photoconductor or the like, and is rotatable in a direction indicated by an arrow at a predetermined process linear velocity.
[0052]
The charging unit 2Y includes a scorotron charger and the like, and is configured to uniformly charge the photosensitive drum 1Y. In the exposing unit 3Y, the photosensitive drum 1Y charged by the charging unit 2Y is exposed and scanned with laser light L based on the Y image data, and an electrostatic latent image based on dot exposure is formed on the photosensitive drum 1Y. You. The developing device 4Y develops the electrostatic latent image exposed by the exposure unit 3Y. The developing device 40 according to the present invention is used as the developing device 4Y.
[0053]
The image forming unit 10M for forming an image of M color has a photosensitive drum 1M, a charging unit 2M for M color, an exposure unit 3M, a developing device 4M, and a cleaning unit 8M for an image forming body. The photoreceptor drum 1M is also rotatable at a predetermined process linear speed. The charging means 2M uniformly charges the photosensitive drum 1M. In the exposure unit 3M, the photosensitive drum 1M charged by the charging unit 2M is exposed and scanned with a laser beam L based on the M image data, and an electrostatic latent image is formed on the photosensitive drum 1M. The developing device 4M develops the electrostatic latent image exposed by the exposure unit 3M. The developing device 40 according to the present invention is also used for the developing device 4M.
[0054]
The image forming unit 10C for forming an image of C color has a photosensitive drum 1C, a charging unit 2C for C color, an exposing unit 3C, a developing device 4C, and a cleaning unit 8C for an image forming body. The photosensitive drum 1C is also rotatable at a predetermined process linear speed. The charging means 2C uniformly charges the photosensitive drum 1C. In the exposure unit 3C, the photosensitive drum 1C charged by the charging unit 2C is exposed and scanned with the laser beam L based on the C image data, and an electrostatic latent image is formed on the photosensitive drum 1C. The developing device 4C develops the electrostatic latent image exposed by the exposure unit 3C. The developing device 40 according to the present invention is also used for the developing device 4C.
[0055]
The image forming unit 10K for forming an image of BK color has a photosensitive drum 1K, a charging unit 2K for BK color, an exposure unit 3K, a developing device 4K, and a cleaning unit 8K for an image forming body. The photosensitive drum 1K is also rotatable at a predetermined process linear speed. The charging means 2K uniformly charges the photosensitive drum 1K. In the exposure unit 3K, the photosensitive drum 1K charged by the charging unit 2K is exposed and scanned with a laser beam L based on BK image data, so that an electrostatic latent image is formed on the photosensitive drum 1K. The developing device 4K develops the electrostatic latent image exposed by the exposure unit 3K. The developing device 40 according to the present invention is also used for the developing device 4K.
[0056]
The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute an image forming unit. The development by the developing devices 4Y, 4M, 4C, and 4K is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity (negative polarity in the present embodiment) as the polarity of the toner to be used is applied. . The intermediate transfer belt 6 is wound around a plurality of rollers and is rotatably supported.
[0057]
Here, an outline of the image forming process will be described below. In the color image forming apparatus 100, charging, exposure, and development are performed at least once, and the toner images formed on the photosensitive drums 1Y, 1M, 1C, 1K, etc. are transferred to the intermediate transfer belt 6 through the intermediate transfer belt 6. Transferred to P. In other words, an image of each color formed by the image forming units 10Y, 10M, 10C and 10K is applied with a primary transfer bias (not shown) having the opposite polarity (positive in this embodiment) to the toner to be used. The next transfer rollers 7Y, 7M, 7C and 7K sequentially transfer (primary transfer) onto the rotating intermediate transfer belt 6 to form a combined color image (color image: color toner image). The color image is transferred from the intermediate transfer belt 6 to the sheet P.
[0058]
Paper feed cassettes 20A, 20B, and 20C are provided below the image forming apparatus main body 101, and the sheets P stored in the respective paper feed cassettes 20A, 20B, and 20C are respectively stored in the paper feed cassettes 20A, 20B, and 20C. Paper is fed by a feed-out roller 21 and a paper feed roller 22A provided, and is conveyed to a secondary transfer roller 7A via conveyance rollers 22B, 22C, 22D, a registration roller 23, and the like. The color images are collectively transferred (secondary transfer).
[0059]
The paper P to which the color image has been transferred is subjected to a fixing process for fixing the toner image by the fixing unit 17, and is sandwiched by the paper ejection rollers 24 and placed on the paper ejection tray 25 outside the machine. The untransferred toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is cleaned by the image forming body cleaning means 8Y, 8M, 8C, and 8K and enters the next image forming cycle.
[0060]
At the time of double-sided image formation, the sheet P on which an image is formed on one surface (front side) and discharged from the fixing unit 17 is branched from a sheet discharge path by a branching unit 26, and each of the sheets P constitutes a sheet feeding and conveying unit. After passing through the circulating paper path 27A, the sheet is turned upside down by a reversing conveyance path 27B, which is a re-feeding mechanism (ADU mechanism), passes through a re-feeding conveyance section 27C, and joins at a sheet feeding roller 22D. The sheet P that has been reversed and conveyed here is again conveyed to the secondary transfer roller 7A via the registration roller 23, and a color image (color toner image) is collectively transferred onto the other surface (back surface) of the sheet P. The paper P on which the color image has been transferred is subjected to a fixing process by the fixing unit 17, is sandwiched by the paper discharge rollers 24, and is placed on a paper discharge tray 25 outside the apparatus.
[0061]
On the other hand, after the color image is transferred to the sheet P by the secondary transfer roller 7A, the intermediate transfer belt 6 from which the sheet P is separated by the curvature is removed by a cleaning unit 8A for the intermediate transfer belt. At the time of forming these images, the paper P is 52.3-63.9 kg / m ² (1000 sheets) of thin paper or 64.0-81.4 kg / m ² (1000 sheets) of plain paper or 83.0 to 130.0 kg / m ² (1000 sheets) or 150.0kg / m ² It is preferable to use a set of super thick paper of about (1000 sheets), a linear velocity of about 80 to 350 mm / sec, and environmental conditions of a temperature of about 5 to 35 ° C. and a humidity of about 15 to 85%. The thickness (paper thickness) of the paper P is about 0.05 to 0.15 mm.
[0062]
FIG. 4 is a cross-sectional view illustrating a configuration example of the developing device 4Y and the like mounted on the color image forming apparatus 100. The developing device 4Y has a structure in which at least the developer carrier 41 and the stirring unit in the developing container 40D are driven by a common driving unit (motor) 60 (not shown). Note that the other developing devices 4M, 4C, and 4K have the same configuration as the developing device 4Y, and a description thereof will be omitted.
[0063]
The developing device 4Y or the like shown in FIG. 4 has a developing container 40D of a predetermined shape, and stores a developer 18 composed of a non-magnetic toner for developing an electrostatic latent image and a magnetic carrier. . The developing device 4Y includes, in addition to the developing container 40D, a developer carrier 41 composed of a developing roller, a magnet roll 42 for generating a magnetic field, a regulating device 43 composed of a cutting board, a water wheel type supply device 44, and a supply / supply composed of a screw. It comprises a transport device 45, a stirring / transport device 46 composed of a screw, a transport roller 47, a stripping plate 48, a collecting device 49 composed of a screw, and the like.
[0064]
These are driven by the same driving means 60 (not shown) as the photosensitive drum 1Y and the like. Therefore, when the number of rotations of the developer carrier 41 is changed in the developing device 4Y or the like, a mechanism for changing the number of rotations of the supply device 44, the supply / transport device 45, and the stirring / transport device 46 is provided. , Having a plurality of process linear velocities.
[0065]
The developing container 40 </ b> D supports a lower frame body 40 </ b> A that supports the developer carrier 41, a transport roller 47, a supply device 44, a supply / transport device 45, and a stirring / transport device 46, and a stripping plate 48 and a recovery device 49. It comprises a middle frame 40B and an upper lid 40C for closing the upper opening of the middle frame 40B. Part of the middle frame 40B closes the upper opening of the stirring / transporting unit 402. The supply unit 401 and the stirring / transporting unit 402 are formed on both sides of the first partition 404 that stands upright from the bottom of the lower frame body 40A.
[0066]
Further, a second partition 405 is formed at the bottom of the middle frame 40B that rotatably supports the collection device 49, and separates the supply unit 401 from the collection unit 403. The downstream side of the developer transport of the collection unit 403 and the downstream side of the developer transport of the supply unit 401 communicate with each other through a first opening 406 formed near the end of the second partition 405. The lower frame body 40A forms a supply unit 401 that accommodates the supply device 44 and the supply / transport device 45, and a stirring / transport unit 402 that accommodates the stirring / transport device 46.
[0067]
The developer carrier 41 is disposed to face the photosensitive drum 1Y and the like, is rotatably supported by the developing container 40D, and rotates in the direction indicated by the arrow to move the developer 18 to the developing nip DR. The developer 18 is carried in the development nip DR, and a layer of the developer 18 necessary for development is formed on the photosensitive drum 1Y and the like. This is for visualizing the electrostatic latent image.
[0068]
The supply device 44, the supply / transport device 45, and the stirring / transport device 46 are provided in the lower frame body 40A with the first partition 404 interposed therebetween. In the agitating / transporting device 46, the replenished new toner and the developer circulated from the supplying / transporting device 45 are mixed, agitated, and transported to the upstream portion of the supplying / transporting device 45. A supply / transport device 45 is disposed in the lower frame body 40A in parallel with the stirring / transport device 46 via the first partition 404, and the developer conveyed from the stirring / transport device 46 is rotated in the direction of its rotation axis. While being conveyed to the supply device 44.
[0069]
Further, a supply device 44 is provided in parallel with and adjacent to the supply / transport device 45. The supply device 44 is a rotatable water wheel type transport unit that supplies the developer to the developer carrier 41, and transfers the developer transported from the supply / transport device 45 to the developer receiving magnetic pole S 3 of the developer carrier 41. It is made to supply uniformly to the vicinity. Note that the supply device 44 may be a screw having a transport function in the rotation axis direction.
[0070]
In the vicinity of the developer stripping magnetic pole S2 of the developer carrier 41, a transport roller 47 is disposed. The transport roller 47 includes a rotatable rotating member (sleeve) 47A, and a columnar magnet body 47B housed inside the rotating member 47A and fixed to the developing container 40D. Further, a collecting device 49 is rotatably arranged in the collecting section 403 partitioned by the second partition 405, and collects and collects the developer which is peeled off and dropped by the transport roller 47 and the peeling plate 48. The developer is transported downstream of the supply / transport device 45 in the transport direction and outside the image forming area of the developer carrier 41.
[0071]
If the developer does not return to the developer carrier 41, the collected developer is supplied to the downstream of the supply / transport device 45 in the transport direction and into the development area of the developer carrier 41. Is also good. Alternatively, the developer recovered by the recovery device 49 may be circulated upstream of the stirring / transporting unit 402. Each of the supply / conveyance device 45, the stirring / conveyance device 46, and the recovery device 49 is formed of a spiral screw, and conveys the developer in the rotation axis direction while stirring the developer, and transfers the developer in a direction substantially perpendicular to the rotation axis. Made to emit.
[0072]
An opening formed in the vicinity of one end of the first partition wall 404 is between the downstream side of the developer transport of the supply unit 401 and the upstream side of the developer transport of the stirring / transporting unit 402 in the lower frame body 40A. (Not shown). Therefore, the developer peeled off by the transport roller 47 and the peeling plate 48 is recovered in the recovery unit 403, and the recovered developer is transported by the recovery device 49 to the downstream side of the developer transport. Reflux to 401.
[0073]
The developer in the supply unit 401 is supplied from the supply / transport device 45 into an agitating / transport unit 402 through an opening (not shown) formed at one end of the first partition 404 as indicated by an arrow W1. Transported to The developer conveyed into the stirring / conveying unit 402 is mixed and stirred by the stirring / conveying device 46 with the toner discharged from the toner container 40T and replenished from the toner replenishing opening 409 with the developer. Then, the air is discharged from an opening (not shown) formed in the other end of the first partition 404 and returned to the supply unit 401 as shown by an arrow W2.
[0074]
In the supply unit 401, the developer is conveyed in the axial direction by the supply / conveyance device 45, discharged, and supplied to the supply device 44. The supply device 44 radiates the developer while conveying it in the axial direction, and supplies the developer to the developer carrier 41. In FIG. 4, B (DC) is a DC bias power supply for applying a DC bias to the developer carrier 41, and D (AC) is an AC bias power supply for applying an AC bias to the developer carrier 41. The development control is performed by the means 14, and the AC bias is superimposed on the DC bias and applied to perform the development.
[0075]
In the developing device 4Y or the like, the developer 18 is developed using a two-component developer composed of a toner having a particle diameter of 8.0 μm or less and a carrier having a particle diameter of 65 μm or less. As the toner, for example, a polymerized toner having a mass average particle diameter of 3 to 8 μm is preferable. By using the polymerized toner, it is possible to form an image having a high resolution, a stable density, and extremely low occurrence of image fog. The polymerized toner is manufactured by the following manufacturing method.
[0076]
The formation of the binder resin for the toner and the shape of the toner are obtained by polymerization of the raw material monomer or prepolymer of the binder resin and subsequent chemical treatment. More specifically, it is obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a step of fusing particles together, and in a polymerized toner, the raw material monomer or prepolymer is uniformly dispersed in an aqueous system. Since the toner is manufactured by polymerization after dispersion, a toner having a uniform particle size distribution and shape of the toner can be obtained.
[0077]
In this embodiment, a toner having a mass average particle diameter of 3 to 8 μm is used. The mass average particle diameter is an average particle diameter on a mass basis, and is a value measured by a “Coulter counter TA-II” or a “Coulter multisizer” (both manufactured by Coulter Co., Ltd.) equipped with a wet disperser. When the mass average particle diameter is less than 3 μm, image fogging and toner scattering are likely to occur. The upper limit of 8 μm is the upper limit of the particle size that enables formation of the high image quality targeted in the present invention. As the carrier, a carrier composed of magnetic particles having a mass average particle diameter of 30 to 65 μm and a magnetization amount of 20 to 70 emu / g is preferable. Carriers having a particle size smaller than 30 μm tend to cause carrier adhesion. Further, in the case of a carrier having a particle size larger than 65 μm, a case where an image having a uniform density may not be formed may occur.
[0078]
In this example, a toner density sensor SD is attached to the bottom of the lower frame 40A (supply unit 401) of the developing container 40D shown in FIG. The magnetic permeability of the agitated developer 18 is detected. The toner density is detected based on the magnetic permeability of the developer 18. The toner density sensor SD generally has a coil wound inside (L detection sensor).
[0079]
FIG. 5 is a block diagram illustrating a configuration example of a control system of the color image forming apparatus 100. The color image forming apparatus 100 shown in FIG. The control means 15 may be provided for each of Y, M, C, and K colors, or one control device may be provided for Y, M, C, and K colors. In this example, only the control system for the Y color will be described. A similar configuration is adopted for the other control systems for M, C, and K colors. The control means 15 is connected to a toner concentration sensor SD for Y color, detects the magnetic permeability of the developer 18 stirred in the development container 40D for Y color, and controls the output voltage VL. Is output. The control unit 15 replenishes the toner in the developing container 40D based on the output voltage VL from the sensor SD and the linear speed (rotation speed) of the developer carrier 41, and controls the density. A CPU (Central Processing Unit) or the like is used for the control means 15.
[0080]
The control unit 15 is connected to a nonvolatile memory 29 as an example of a storage unit, and stores a correction coefficient ΔVL / ΔVc for adjusting the value Vc of the control voltage of the toner density sensor SD. For example, in the nonvolatile memory 29, when the developer is supplied, the standard linear speed of the developer carrier 41 obtained by performing the initial adjustment of the toner concentration, and the linear speeds of 1/2 and 1/3 speed are obtained. The control voltage values Vc1, Vc2, and Vc3 at which the control voltage value Vc1 and the output voltage values VL1, VL2, and VL3 of the toner density sensor SD and the output voltage value VL that indicates the constant development density at the toner density sensor SD are obtained. Is recorded.
[0081]
In this embodiment, the control voltage value Vc is set so that the output voltage value VL from the toner density sensor SD becomes a predetermined output voltage value (VL = 2.5 V) at the standard toner density (Tc = 8% by mass). Is adjusted, and the adjusted control voltage value Vc is stored in the nonvolatile memory 29.
[0082]
In addition to these voltage values, the output voltage value VL of the toner density sensor SD at standard linear speed and the output voltage value VL of the toner density sensor SD at 1/2 and 1/3 speeds are obtained. 2, the control voltage value Vc of the toner density sensor SD at the standard linear velocity, and the second control voltage value Vc of the toner density sensor SD at the 1/2 and 1/3 speeds. And a correction coefficient ΔVL / ΔVc at the time of changing the linear velocity obtained based on the difference ΔVL1 between the output voltage of the toner density sensor SD and the difference ΔVc between the control voltages.
[0083]
A power switch SW is connected to the control means 15 so as to activate the device 40. When the linear velocity is changed after the start of the apparatus, the control unit 15 detects the control voltage value Vc of the toner density sensor SD, reads the correction coefficient ΔVL / ΔVc from the nonvolatile memory 29, and reads the control voltage of the toner density sensor SD. The value Vc is corrected, and the toner density sensor SD is driven by the corrected control voltage value Vc.
[0084]
When the linear speed is changed during the printing operation, the control unit 15 controls the output voltage value VL of the toner density sensor SD at the standard linear speed of the developer carrier 41 and the output voltage of the toner density sensor SD when the linear speed is changed. The voltage difference ΔVL from the value VL is calculated. For example, when an instruction to change the standard linear speed from 1/1 to 1/2 speed is issued, the output voltage value VL1 of the toner density sensor SD at the standard linear speed of the developer carrier 41 and the toner Voltage difference ΔVL from output voltage value VL2 of density sensor SD ₁₂ Is calculated.
[0085]
Further, the control means 15 corrects the correction coefficient ΔVL ₂₁ / ΔVc ₂₁ Control voltage difference ΔVc at the time of 1/2 linear velocity change based on ₁₂ Is calculated. In this example, the control voltage difference ΔVc ₁₂ Is ΔVL ₁₂ / Vc given by the correction coefficient, ΔVc ₁₂ = ΔVL ₁₂ / ΔVL ₂₁ / ΔVc ₂₁ It becomes. This control voltage difference ΔVc ₁₂ Is determined based on the control voltage value Vc of the sensor SD. Then, the control voltage value Vc2 at the time when the 1/2 linear velocity is changed is the control voltage Vc at the standard linear velocity + the difference ΔVc of the control voltage. ₁₂ Vc2 = Vc1 + ΔVc ₁₂ It becomes.
[0086]
The control unit 15 includes a power switch SW, a toner density sensor SD, and a non-volatile memory 29, a fixing temperature sensor STH, an exposure unit 3Y, an operation unit 14, a paper supply unit 30, an image memory 33, an image processing unit 35, The ROM 53, the drive unit 60, the display unit 87, the image reading device 101, and the toner supply unit 410 are connected.
[0087]
The fixing temperature sensor STH is provided in the fixing roller portion of the fixing unit 17 shown in FIG. 3 and detects the temperature of the fixing unit 17 and outputs a temperature detection signal S3 to the control unit 15. The image data DY for Y color is output to the exposure unit 3Y, and the photosensitive drum 1Y charged by the charging unit 2Y is exposed and scanned with the laser beam L based on the image data DY for Y color. An electrostatic latent image based on dot exposure is formed on 1Y.
[0088]
The operation unit 14 manually changes the process linear velocity. The operation unit 14 forms a touch panel together with the display unit 87, and is provided with a selection button on which “gloss”, “thick paper”, or a process linear speed is displayed, and an instruction to switch the process linear speed to, for example, 110 mm / s is provided by a push button. Done. According to this instruction, a linear speed change request signal S1 is output to the control means 15. On the display section 87, a setting screen for image forming conditions and the like is displayed based on the display signal S4.
[0089]
The paper feeding means 30 feeds the paper P from the paper feeding cassettes 20A, 20B, 20C and the like based on the cassette control signal S5 from the control means 15. In the image processing unit 35, under the control of the control unit 15, the image acquisition data after A / D conversion obtained by the line image sensor CCD of the image reading device 102 performs shading correction, timing control, line-to-line correction, and the like. Done. The data relating to the RGB colors after the correction processing becomes the color image data Din and is recorded in the image memory 33.
[0090]
The ROM 53 stores a system program for controlling the image forming apparatus. For example, the system program includes an image adjustment program, and a toner density detection condition setting program is prepared in a lower hierarchy of the image adjustment program. The driving unit 60 drives the developer carrier 41 and the stirring unit in the developing container 40D based on the clock signal CLK for changing the rotation speed and the control signal CNT output from the control unit 15.
[0091]
The driving means 60 drives the photosensitive drum 1Y and the like in the same manner. Therefore, when the rotation speed of the developer carrier 41 is changed by the developing device 4Y or the like, the driving unit 60 also changes the rotation speeds of the supply device 44, the supply / transport device 45, and the stirring / transport device 46. Of the process linear velocity. The above-described toner supply unit 410 is controlled to supply toner from the toner container 40T to the developing container 40D based on the toner supply control signal S21 output from the control unit 15. The toner density in the developing container 40D is detected by the toner density sensor SD.
[0092]
FIG. 6 is an operation characteristic diagram showing an example of the relationship between the sensor output of the toner density sensor SD and the toner density Tc.
The vertical axis shown in FIG. 6 is the sensor output VL [V] of the toner density sensor SD. The horizontal axis represents the toner concentration Tc [%] of the developer 18. As the toner density sensor SD, a sensor which outputs a sensor linearly with respect to the toner density Tc as shown in the graph is used. The control voltage value Vc is an adjustment value for adjusting the sensor operation characteristics. The initial adjustment of the toner density refers to the initial adjustment of the toner density sensor SD when the developer 18 is charged into the developing device, and the value Vc of the control voltage is adjusted so that the operating characteristics desired by the sensor SD are obtained. To do.
[0093]
In the toner density initial adjustment, when the toner density control is performed using the toner density sensor SD that detects the magnetic permeability of the developer 18, the initial adjustment is performed when the developer 18 is charged into the developing device. This is an act of adjusting the control voltage Vc of the L detection sensor so that the output value of the L detection sensor becomes a predetermined output value in the developer 18 of the initial adjustment.
[0094]
{Circle around (1)} shows the operating characteristics when the control voltage Vc is 7.0 V. {Circle around (2)} is the operating characteristic at the control voltage Vc = 6.5V. (3) is an operation characteristic when the control voltage Vc is 6.0 V. For example, when it is desired to select the operation characteristic (1), the control voltage value Vc is set to 7.0 V, and when it is desired to change this to the operation characteristic (3), the control voltage value Vc is set to 6.0 V. It is made to do.
[0095]
Further, in order to obtain a toner density of 8% with the sensor output V = 2.5V, the operation characteristic (3) of the control voltage Vc = 6.0V is set. In order to select the operation characteristic (2) of the control voltage Vc = 6.5 V and obtain the sensor output V = 2.5 V and the toner density of 8%, the control voltage Vc is changed from (2) to (▲) at the time of the initial adjustment of the toner density. The transition is made to the position 3). Similarly, in order to select the operation characteristic (1) of the control voltage Vc = 7.0 V and obtain the sensor output V = 2.5 V and the toner density of 8%, the control voltage Vc is set to (1) at the time of the initial adjustment of the toner density. The transition is made from ▼ to ③.
[0096]
Next, an operation example at the time of toner density control in the color image forming apparatus 100 according to the present invention will be described.
In this embodiment, a predetermined developing container 40D stores a developer 18 composed of a non-magnetic toner and a magnetic carrier for developing an electrostatic latent image. A developer carrier 41 is rotatably provided in the developing container 40D, and a toner density sensor SD (sensor system for detecting toner density) is attached to the bottom of the developing container 40D. The magnetic permeability of the developer 18 is detected. Then, it is assumed that the value Vc of the control voltage of the toner density sensor SD attached to the developing device 4Y for Y color including the developer carrier 41 is adjusted. The same applies to the developing devices 4M, 4C, 4K, etc. for the other colors, but the description is omitted because it is the same as the developing device 4Y for the Y color.
[0097]
The development conditions are as follows. The linear speed is 180 mm / sec, and the peripheral speed ratio between the photosensitive drum and the developing magnet roller is 1.8 → the variable range is 0.5 to 3.0. The amount of developer transported on the developing magnet roller is 20 mg / cm ² It is. The developing bias DC is from -500 V to -200 to -700 V in the variable range. The developing AC bias is 1.0 kV in ACp-p, the AC frequency is 3 kHz, and the AC waveform is a rectangular wave. The developing roller diameter is 25 cmφ, and the peeling roller diameter is 18 cmφ. The developer 18 is an emulsion polymerization toner in which a carrier having a particle size of 35 μm and a toner having a particle size of 6.5 μm are mixed. The developer amount is 850 g (Tc = 8%).
[0098]
In the following, the description will be made separately for the toner concentration initial adjustment other than when the developer is supplied and when the developer is supplied.
[Initial adjustment of toner concentration when developer is supplied]
FIG. 7 is a flowchart showing an operation example (at the time of supplying a developer) of the color image forming apparatus 100 when controlling the toner density. In the initial adjustment of the toner density, the voltage detection process is performed at the standard linear speed (1/1), and the value Vc of the control voltage of the toner density sensor SD at the standard linear speed is determined. With respect to the toner density sensors SD of the Y, M, C, and K colors, sensor outputs are given for predetermined toner densities (Tc = 8% by mass) at process linear speeds of 220 mm / s, 110 mm / s, and 73 mm / s. This is for adjusting and determining the value of the control voltage Vc that becomes the threshold value of 2.5 V. The control voltage Vc value determined here is stored in the nonvolatile memory 29.
[0099]
Then, the output voltage value VL obtained from the toner density sensor SD is detected for each linear speed with the control voltage value Vc. Then, a difference ΔVL between the output voltage VL at each linear speed and the output voltage value VL at the standard linear speed is calculated. At the same time, a difference ΔVc between the control voltage Vc at each linear velocity and the control voltage Vc at the standard linear velocity is obtained, and a ratio of the difference, that is, a correction coefficient ΔVL / ΔVc is calculated and stored in the nonvolatile memory 29.
[0100]
With this as an operating condition, the power switch SW is turned on to start the color image forming apparatus 100 in step B1 of the flowchart shown in FIG. When the power switch SW is turned on, the control unit 15 detects the temperature of the fixing temperature sensor STH provided at the fixing roller portion of the fixing unit 17. If the detected sensor temperature is equal to or lower than the predetermined temperature, warm-up is performed until the temperature detected by the fixing temperature sensor STH rises to a predetermined temperature at which fixing is possible, and the process proceeds to an image adjustment step.
[0101]
In this image adjustment step, the surface potential is measured by a potential sensor (not shown) for measuring the surface potential of the photosensitive drum 1Y and the like, and the applied voltage is adjusted by the charging means 2Y and the like based on the measured surface potential. I do. Also, solid and non-solid patches are formed on the photoreceptor by the exposure means 3Y, and the reflection density of the patch portion is measured by a reflection density sensor (not shown). And the like.
[0102]
In this embodiment, a toner density detection condition setting program is prepared in the image adjustment program. In accordance with this program, the control means 15 first sets a clock for changing the number of revolutions to the drive means 60 so that the process linear velocity becomes the standard linear velocity (220 mm / s). The toner concentration in the developer is measured, and toner replenishment control is performed so that the sensor output becomes a threshold value (VL = 2.5 V).
[0103]
Accordingly, the process proceeds to step B2, where the developer 18 is charged into the developing container 40D. At this time, the control unit 15 outputs a toner supply control signal S2 to the toner supply unit 410 to execute developer supply. This is for controlling the toner replenishing unit 410 based on the value VL of the output voltage obtained from the toner density sensor SD. Thereafter, the process proceeds to step B3, where the developer carrier 41 is rotated at the standard linear speed (1/1) to perform the initial adjustment of the toner concentration. At this time, the voltage detection process is performed at the standard linear speed, and the control voltage value Vc of the toner density sensor SD that can obtain, for example, the output voltage value VL1 = 2.50 V at the standard linear speed is determined. In this example, the control voltage value Vc is Vc1 = 7.01V.
[0104]
Next, in step B4, at the control voltage Vc1 = 7.01V, the output voltage values VL2 and VL3 of the toner density sensor SD for each linear speed are detected. In this example, the output voltage value VL2 of the toner density sensor SD at 1/2 speed is 2.70V, and the output voltage value VL3 at 1/3 speed is 2.91V. Then, the process shifts to step B5 to calculate the difference (ΔVL) between the output voltage at each linear speed (２ ，, ３) with respect to the standard linear speed and stores it in the nonvolatile memory 29. In this example, the output voltage difference ΔVL at the half speed ₂₁ = (VL2−VL1) is 0.2V, and the difference ΔVL of the output voltage at the 1/3 speed ₃₁ = (VL3-VL1) is 0.41V. The nonvolatile memory 29 stores values having the contents shown in Table 1.
[0105]
[Table 1]

[0106]
The control voltage value Vc applied at this time is not limited to the control voltage value Vc determined at the time of the initial adjustment of the toner density at the standard linear speed, but may be the same value for each linear speed.
[0107]
In step B6, a value VL of an output voltage indicating that the toner density Tc is constant, for example, a control voltage Vc at which 2.50 V is obtained by the toner density sensor SD is detected at each linear speed (1/2, 1/3). Since the standard linear velocity has been detected first, the other linear velocity is detected to obtain the correction coefficient ΔVL / ΔVc.In this example, the control of the toner density sensor SD at the 1/2 speed is performed. The voltage value Vc2 is 6.64V, and the control voltage value Vc3 at 1/3 speed is 6.25V.
[0108]
Then, the process proceeds to step B7 to calculate the difference (ΔVc) between the standard linear speed and the control voltage at each linear speed (１ ／, ３), and stores the difference in the nonvolatile memory 29. In this example, the control voltage difference ΔVc at 1/2 speed ₂₁ = (Vc2−Vc1) is 0.37 V, and the control voltage difference ΔVc at 1/3 speed ₃₁ = (Vc3-Vc1) is 0.76V. The nonvolatile memory 29 stores values having contents as shown in Table 2.
[0109]
[Table 2]

[0110]
Thereafter, in step B8, the difference ΔVL between the output voltages of the toner density sensor SD at each linear velocity ₂₁ , ΔVL ₃₁ And control voltage difference ΔVc ₂₁ , ΔVc ₃₁ The correction coefficient ΔVL / ΔVc for changing the linear velocity is obtained based on In this example, the correction coefficient ΔVL at 1/2 speed ₂₁ / ΔVc ₂₁ Is 0.541, the correction coefficient ΔVL at the 1/3 speed ₃₁ / ΔVc ₃₁ Is 0.539. A correction coefficient ΔVL for adjusting the value Vc of the control voltage of the toner density sensor SD. ₂₁ / ΔVc ₂₁ And ΔVL ₃₁ / ΔVc ₃₁ Are stored in the nonvolatile memory 29. The nonvolatile memory 29 stores values having contents as shown in Table 3.
[0111]
[Table 3]

[0112]
After that, the process shifts to step B9 to execute another process. For example, in order to develop the electrostatic latent image formed on the chargeable photoconductor 1, a process of carrying and attaching the developer 18 to the photoconductor 1 or a value VL of the output voltage from the toner density sensor SD may be used. Further, a process of replenishing the toner in the developing container 40D based on the linear velocity of the developer carrier 41 and controlling the density by the control unit 15 is included. Then, control goes to a step B10. In step B10, it is determined whether to end the image forming process. The control unit 15 detects the power-off information and the like, and ends the image forming processing. If the power-off information is not detected, the process returns to step B9 to repeat the above-described processing.
[0113]
The correction coefficient ΔVL stored in the nonvolatile memory 29 ₂₁ / ΔVc ₂₁ And ΔVL ₃₁ / ΔVc ₃₁ Are used when the linear velocity is changed other than when the developer is supplied. Further, the value of the correction coefficient ΔVL / ΔVc may be obtained not only at the initial adjustment but also at predetermined intervals. For example, the value of the correction coefficient ΔVL / ΔVc may be calculated again based on a fixed development history, for example, every time when the circumferential movement distance of the developing sleeve is 5 km.
[0114]
[At the time of initial adjustment of toner concentration other than when the developer is supplied]
FIG. 8 is a flowchart illustrating an example of operation of the color image forming apparatus 100 at the time of toner density control (other than when the developer is supplied).
In this example, at the time of warm-up of the color image forming apparatus 100, the toner density initial adjustment is performed only at the standard linear speed. The process linear velocity is changed manually by the operation unit 14 or automatically by the control unit 15. In the case of a manual operation, the operation unit 14 is provided with a selection button on which "gloss", "thick paper", or a process linear speed is displayed. In the case of automatic operation, a switching instruction is issued from the control means 15 by detecting the thickness of the paper P to be used.
[0115]
When the linear velocity is changed, the output voltage values VL2, VL3, etc. of the toner density sensor SD after a predetermined time (several seconds) have passed from the time when the linear velocity change instruction is issued, are read, and the output at the standard linear velocity The difference from the voltage value VL1 is calculated as ΔVL1-ΔVL2, ΔVL1-ΔVL3, etc., and thereafter, the correction coefficient ΔVc / ΔVL read from the non-volatile memory 29, the difference between the control voltage Vc at the standard linear velocity and the control voltage ΔVc. Then, the correction values ΔVc2 and Vc3 at the time of changing the linear velocity are obtained and added to the Vc value at the standard linear velocity. As a result, the value of the control voltage at the time of changing the linear velocity is determined.
[0116]
The control means 15 outputs a pulse CLK for changing the rotation speed corresponding to the determined process linear velocity to the drive means 60, and the image is recorded. Further, the control unit 15 reads out the control voltage Vc value corresponding to the process linear velocity determined for each of the colors Y, M, C, and K from the nonvolatile memory 29, applies the control voltage Vc value to the toner density sensor SD, and obtains a sensor output. The detected sensor output is compared with a threshold value (2.5 V), and toner supply control is performed based on the comparison result.
[0117]
With this as an operating condition, the power switch SW is turned on in step C1 of the flowchart shown in FIG. At this time, when the power switch SW is turned on, the control unit 15 calls the image adjustment program from the ROM during the warm-up time to perform the image adjustment. Then, the process proceeds to step C2, in which the developer carrier 41 is rotated at the standard linear speed (1/1) to perform the initial adjustment of the toner concentration.
[0118]
At this time, the control means 15 executes toner density control according to the output of the toner density sensor SD at the standard linear speed, adjusts the toner density to an appropriate value, and then performs initial toner density adjustment by the toner density sensor SD at the standard linear speed. Execute. In this example, the control voltage value Vc of the toner density sensor SD that can obtain, for example, the output voltage value VL1 = 2.52 V at the standard linear speed is determined. In this example, the control voltage value Vc is Vc1 = 7.02V.
[0119]
Next, in step C3, when the control voltage value Vc1 is 7.02V, the output voltage values VL2 and VL3 of the toner density sensor SD for each linear speed are detected. In this example, the output voltage value VL2 of the toner density sensor SD at 1/2 speed is 2.68V, and the output voltage value VL3 at 1/3 speed is 2.75V. Then, the process shifts to step C4 to check whether the linear velocity has been changed. The linear velocity change is performed by inputting a linear velocity change request signal S1 from outside the control unit 15, for example, the operation unit 14 shown in FIG.
[0120]
If there is a change in the linear speed, the process proceeds to step C5, and the control unit 15 checks whether there has been a change from the standard linear speed to the linear speed drop. When there is a change from the standard linear velocity to the linear velocity descent, the flow shifts to step C6. In step C6, it is checked whether a predetermined time has elapsed. Here, for example, until about 2 to 3 seconds elapse, the toner supply control is stopped regardless of the output value of the toner density sensor SD. By doing so, it is possible to prevent excessive toner replenishment due to instability at the time of sensor output, and it is possible to prevent toner scattering and image fogging.
[0121]
After the elapse of the predetermined time, the process proceeds to step C7, in which the output voltage value VL of the toner density sensor SD at the standard linear speed of the developer carrier 41 and the output voltage value of the toner density sensor SD when the linear speed is changed A voltage difference ΔVL from VL is calculated. For example, when an instruction to change the standard linear speed from 1/1 to 1/2 speed is given, the output voltage value VL1 of the toner density sensor SD at the standard linear speed of the developer carrier 41 is VL1 = 2.52V, and Voltage difference ΔVL from output voltage value VL2 = 2.68 of toner density sensor SD at the time of change ₁₂ Is calculated. In this example, the voltage difference ΔVL ₁₂ Is -0.16V.
[0122]
Thereafter, the process proceeds to step C8, where the correction coefficient ΔVL ₂₁ / ΔVc ₂₁ Control voltage difference ΔVc at the time of 1/2 linear velocity change based on ₁₂ Is calculated. In this example, the control voltage difference ΔVc ₁₂ Is ΔVL ₁₂ / Vc given by the correction coefficient, ΔVc ₁₂ = ΔVL ₁₂ / ΔVL ₂₁ / ΔVc ₂₁ = −0.3V. This control voltage difference ΔVc ₁₂ Is determined based on the control voltage value Vc of the sensor SD. In this example, the control voltage value Vc2 when the 1/2 linear velocity is changed is the control voltage Vc at the standard linear velocity + the control voltage difference ΔVc. ₁₂ Vc2 = Vc1 + ΔVc ₁₂ = 6.72V. Table 4 shows the corrected control voltage value Vc2 = 6.72V when changing the 1/2 speed and the corrected control voltage value Vc3 = 6.59V when changing the 1/3 speed.
[0123]
[Table 4]

[0124]
As described above, the control voltage value Vc at the time of changing the 1 / N linear speed can be calculated by the control voltage Vc at the time of the standard linear speed + the difference ΔVc of the control voltage. The voltage values Vc2, Vc3, and the like can be obtained by arithmetic processing. The calculated control voltage value Vc2 and the like are set in the toner density sensor SD in step C9. Thereafter, the process proceeds to step C11.
[0125]
If there is no request for changing the linear speed in step C4, the process proceeds to step C10 to execute the image forming process. At this time, in order to develop the electrostatic latent images formed on the chargeable photosensitive drums 1Y, 1M, 1C, and 1K, the developer 18 is carried and adhered to the photosensitive drums 1Y, 1M, 1C, and 1K. And a process in which the toner is supplied into the developing container 40D based on the output voltage value VL from the toner density sensor SD and the linear velocity of the developer carrier 41, and the density is controlled by the control unit 15. Thereafter, the process proceeds to step C11. In step C11, it is determined whether to end the image forming process. The control unit 15 detects the power-off information and the like, and ends the image forming processing. If no power-off information is detected, the process returns to step C4 to repeat the above processing.
[0126]
FIG. 9 is a characteristic comparison diagram showing an example of detecting the toner concentration Tc [%] before and after the countermeasures in the effect confirmation test. The vertical axis shown in FIG. 9 is the toner concentration Tc [%] before and after the countermeasure. The horizontal axis is the number of copies [kc], and indicates 100,000 prints.
[0127]
In this effect confirmation test, printing from the first sheet P to the 100000th sheet P is performed while toner density control is being performed, and the toner density stability is tested. Shows the results when the linear speed is changed to (1/2) speed or (1/3) speed mode at, for example, 20 Kc, 40 Kc, 60 Kc, etc. in addition to the standard (1/1) speed. ing.
[0128]
According to the characteristic comparison diagram shown in FIG. 9, when the toner concentration Tc is 8% by mass as a reference, the characteristics obtained by connecting the black squares with solid lines are based on the method of the present invention. The characteristics obtained by connecting the black diamonds with solid lines are based on the conventional method. According to the characteristics before the countermeasure such as the conventional method, the toner density Tc at the start was 8% by mass, but every time the linear speed was changed, a large deviation was recognized during 100,000 prints, and stable. The toner density control has not been performed.
[0129]
On the other hand, according to the method of the present invention, without increasing the warm-up time of the fixing unit 17, in a plurality of process linear speed modes, control is performed at approximately 8% by mass of the toner concentration Tc, and stable toner Concentration control could be performed. In this 100,000-sheet print, a good print image without image fogging or toner scattering was obtained. In addition, the toner concentration Tc of each of the four colors Y, M, C, and K is controlled within ± 0.1% with respect to the target toner concentration Tc of 8% by mass. It was recognized that the average value of the toner concentration Tc was maintained within ± 0.05%.
[0130]
As described above, according to the color image forming apparatus 100 as an embodiment according to the present invention, the developing device 40 according to the present invention is applied to the developing devices 4Y, 4M, 4C, and 4K for Y, M, C, and K colors. Therefore, when developing the electrostatic latent images formed on the chargeable photosensitive drums 1Y, 1M, 1C, and 1K, when the linear velocity is changed after the apparatus is started, the control unit 15 controls the toner density sensor SD. The control voltage value Vc is detected, the correction coefficient ΔVL / ΔVc is read from the non-volatile memory 29, and the control voltage value Vc of the toner density sensor SD is corrected. It is made to drive SD.
[0131]
Therefore, not only can the toner concentration control be performed very stably without extending the warm-up time in the morning, but also at the time of changing the linear speed after starting the apparatus, the initial adjustment of the toner concentration such as when the developer is supplied is performed. Without performing this, the corrected control voltage value Vc obtained by the arithmetic processing can be applied to the toner density sensor SD. As a result, at the time of warm-up of the apparatus 100, only the output adjustment of the toner density sensor SD relating to the standard linear speed is required, so that stable toner density control can be performed for each linear speed without extending the warm-up time. . Therefore, it is possible to provide a digital multifunction peripheral for color to which the color image forming apparatus 100 is applied.
[0132]
In addition, a stable image could be obtained without toner scattering or image fogging caused by initial instability of the sensor output at the time of linear velocity reduction. Although the above-described photoconductor has been described in the case of a drum, the present invention is not limited thereto, and the present invention can be applied to a belt-shaped photoconductor that also serves as an intermediate transfer member.
[0133]
【The invention's effect】
As described above, according to the developing device of the present invention, when developing the electrostatic latent image formed on the chargeable photoconductor, the output voltage of the detecting unit that detects the magnetic permeability of the developer is developed. Control means for replenishing toner in the container and controlling the density based on the value and the linear velocity of the developer carrying member, and when the linear velocity changes after the apparatus is started, the control means detects the value of the control voltage of the detecting means In addition, the correction information is read from the storage means, the control voltage of the detection means is corrected, and the detection means is driven by the corrected control voltage.
[0134]
With this configuration, when the linear velocity is changed after the start of the apparatus, the corrected control voltage obtained by the arithmetic processing can be supplied to the detecting unit without performing the initial adjustment of the toner concentration as when the developer is supplied. Therefore, at the time of warm-up of the apparatus, only the output adjustment of the detection means relating to the standard linear velocity is required, so that stable toner density control can be performed for each linear velocity without extending the warm-up time.
[0135]
According to the control method of the developing device according to the present invention, when adjusting the value of the control voltage of the sensor system for detecting the toner concentration attached to the developing device, when the developer is supplied, the predetermined one including the standard linear velocity is used. / N linear velocity is initially adjusted for toner concentration, the control voltage value and output voltage value of the sensor system, the control voltage at which an output voltage indicating constant development density is obtained by the sensor system, and the sensor at the standard linear velocity The difference between the system output voltage and the sensor system output voltage at 1 / N linear velocity, and the difference between the sensor system control voltage at standard linear velocity and the sensor system control voltage at 1 / N linear velocity, respectively. Then, a correction coefficient at the time of changing the linear velocity is obtained based on these, and at the time of changing the linear velocity after the start of the apparatus, the control voltage value of the sensor system is calculated based on the correction coefficient. Set the voltage value to the sensor system It is.
[0136]
With this configuration, when the linear speed is changed after the apparatus is started, the corrected control voltage obtained by the arithmetic processing can be supplied to the sensor system without performing the initial adjustment of the toner concentration as when the developer is supplied. Therefore, at the time of warm-up of the apparatus, only the sensor output adjustment for the standard linear speed is required, so that stable toner density control can be performed for each linear speed without extending the warm-up time.
[0137]
According to the image forming apparatus of the present invention, since the developing device of the present invention is applied, when developing an electrostatic latent image formed on a chargeable photoreceptor, the linear velocity is changed after the start of the apparatus. Sometimes, the control means detects the control voltage of the detection means, reads the correction information from the storage means, corrects the control voltage of the detection means, and drives the detection means with the corrected control voltage.
[0138]
With this configuration, when the linear velocity is changed after the start of the apparatus, the corrected control voltage obtained by the arithmetic processing can be supplied to the detecting unit without performing the initial adjustment of the toner concentration as when the developer is supplied. Therefore, at the time of warm-up of the apparatus, only the output adjustment of the detection means relating to the standard linear velocity is required, so that stable toner density control can be performed for each linear velocity without extending the warm-up time.
[0139]
INDUSTRIAL APPLICABILITY The present invention is very suitable when applied to a black-and-white or color digital multifunction peripheral or a copier having a copying function, a facsimile function and a printer function.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a developing device 40 as an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation example of the developing device 40 when controlling the toner density.
FIG. 3 is a conceptual diagram of a cross section showing a configuration example of a color image forming apparatus 100 as an embodiment according to the present invention.
FIG. 4 is a cross-sectional view illustrating a configuration example of a developing device 4Y and the like mounted on the color image forming apparatus 100.
FIG. 5 is a block diagram illustrating a configuration example of a control system of the color image forming apparatus 100.
FIG. 6 is an operation characteristic diagram showing an example of the relationship between the sensor output of the toner density sensor SD and the toner density.
FIG. 7 is a flowchart illustrating an operation example (at the time of supplying a developer) of the color image forming apparatus 100 when controlling the toner density.
FIG. 8 is a flowchart illustrating an operation example (other than when a developer is supplied) of the color image forming apparatus 100 when controlling the toner density.
FIG. 9 is a characteristic comparison diagram showing an example of detecting the toner density Tc [%] before and after the countermeasure in the effect confirmation test.
FIG. 10 is a characteristic diagram illustrating an example of detection by a toner density sensor according to a conventional example.
[Explanation of symbols]
1 Photoconductor
1Y, 1M, 1C, 1K photoreceptor drum
2Y, 2M, 2C, 2K Charging means
3Y, 3M, 3C, 3K exposure means
4Y, 4M, 4C, 4K developing means
6 Intermediate transfer belt (transfer means)
10Y, 10M, 10C, 10K Image forming unit (image forming means)
13 Storage means
14 Operation unit
15 control means
17 Fixing means
18 Developer
29 Nonvolatile memory (storage means)
33 Image memory
40 Developing device
40D developing container
41 Development carrier
60 Driving means
100 color image forming apparatus (image forming apparatus)
SD Toner density sensor (detection means)

Claims (14)

A developing device for developing an electrostatic latent image formed on a chargeable photoconductor,
A container containing a developer comprising a non-magnetic toner and a magnetic carrier for developing the electrostatic latent image,
A developer carrier rotatably provided in the container to carry the developer and adhere to the photoconductor,
Detecting means attached to the container for detecting the magnetic permeability of the developer,
Control means for replenishing toner in the container and controlling the density based on the output voltage from the detection means and the linear velocity of the developer carrying member;
Storage means for storing correction information for adjusting the control voltage of the detection means,
When changing the linear speed after starting the device,
The control means,
While detecting the control voltage of the detection means, read the correction information from the storage means to correct the control voltage of the detection means,
A developing device, wherein the detection unit is driven by the corrected control voltage. In the storage means, at least,
The control of the detection means for a predetermined 1 / N linear velocity (N = 2, 3,...) Including a standard linear velocity of the developer carrier obtained by performing the initial adjustment of the toner concentration when the developer is supplied. Voltage and output voltage;
A control voltage at which an output voltage indicating a constant development density is obtained by the detection means;
A first voltage difference obtained from the output voltage of the detection means at the standard linear velocity and the output voltage of the detection means at the 1 / N linear velocity;
A second voltage difference obtained from the control voltage of the detection means at the standard linear velocity and the control voltage of the detection means at the 1 / N linear velocity;
2. The developing device according to claim 1, wherein a correction coefficient at the time of changing the linear velocity obtained based on the first voltage difference and the second voltage difference of the detection unit is stored. The control means includes:
When changing the linear speed after starting the device,
A voltage difference between the output voltage of the detecting means at the standard linear velocity of the developer carrier and the output voltage of the detecting means at the time of changing the linear velocity is calculated, and the correction information read from the storage means is calculated as the voltage difference. To calculate the control voltage difference when changing the linear velocity,
2. The developing device according to claim 1, wherein a control voltage of said detection means is determined based on said control voltage difference. The control means,
When the device warms up,
Executing a toner density control according to the output of the detection means at a standard linear velocity;
2. The developing device according to claim 1, wherein after the toner density is adjusted to an appropriate value, the initial adjustment of the toner density by the detection unit is performed at a standard linear speed. The control means,
2. The developing device according to claim 1, wherein when changing from the standard linear velocity to the linear velocity descent, the toner replenishment control is not performed within a predetermined time regardless of an output value of the detection unit. In the developer,
2. The developing device according to claim 1, wherein a two-component mixture comprising a toner having a particle size of 8.0 [mu] m or less and a carrier having a particle size of 65 [mu] m or less is used. A method for adjusting a control voltage of a sensor system for detecting a toner concentration attached to a developing device including a developer carrier,
When the developer is supplied, the toner concentration is initially adjusted for a predetermined 1 / N linear velocity (N = 2, 3,...) Including the standard linear velocity of the developer carrier, and the control voltage and the output voltage of the sensor system are adjusted. And a control voltage at which an output voltage indicating a constant development density is obtained by the sensor system,
The difference between the output voltage of the sensor system at the standard linear velocity and the output voltage of the sensor system at the 1 / N linear velocity, and the control voltage of the sensor at the standard linear velocity and the sensor system at the 1 / N linear velocity Find the difference from the control voltage,
Find correction information at the time of linear velocity change based on the difference between the output voltage of the sensor system and the difference between the control voltages,
When changing the linear speed after starting the developing device,
Calculating a control voltage of the sensor system based on the correction information;
A control method for a developing device, wherein the calculated control voltage is set in the sensor system. When changing the linear speed after starting the developing device,
Calculate the voltage difference between the output voltage of the sensor system at the standard linear speed of the developer carrier and the output voltage of the sensor system at the time of changing the linear speed, calculate the correction information for the voltage difference, and calculate the correction information at the time of changing the linear speed. Calculate the control voltage difference,
8. The method according to claim 7, wherein the control voltage of the sensor is determined based on the control voltage difference. An apparatus for forming an image based on arbitrary image data,
A rotatable photoconductor,
Charging means for uniformly charging the photoconductor,
An exposure unit configured to form an electrostatic latent image on the photoconductor by performing exposure scanning on the photoconductor charged by the charging unit based on the image data;
A developing device for developing the electrostatic latent image exposed by the exposure unit,
Transfer means for performing the charging, exposure, and development at least once to transfer a toner image formed on the photoconductor to a transfer material;
Fixing means for fixing the toner image transferred on the transfer material,
The developing device includes:
A container containing a developer comprising a non-magnetic toner and a magnetic carrier for developing the electrostatic latent image,
A developer carrier rotatably provided in the container to carry the developer and adhere to the photoconductor,
Detecting means attached to the container for detecting the magnetic permeability of the developer,
Control means for replenishing toner in the container and controlling the density based on the output voltage from the detection means and the linear velocity of the developer carrying member;
Storage means for storing correction information for adjusting the control voltage of the detection means,
When changing the linear speed after starting the device,
The control means includes:
While detecting the control voltage of the detection means, read the correction information from the storage means to correct the control voltage of the detection means,
An image forming apparatus, wherein the detection unit is driven by the corrected control voltage. In the storage means, at least,
The control of the detection means for a predetermined 1 / N linear velocity (N = 2, 3,...) Including a standard linear velocity of the developer carrier obtained by performing the initial adjustment of the toner concentration when the developer is supplied. Voltage and output voltage;
A control voltage at which an output voltage indicating a constant development density is obtained by the detection means;
A first voltage difference obtained from the output voltage of the detection means at the standard linear velocity and the output voltage of the detection means at the 1 / N linear velocity;
A second voltage difference obtained from the control voltage of the detection means at the standard linear velocity and the control voltage of the detection means at the 1 / N linear velocity;
The image forming apparatus according to claim 9, wherein a linear velocity change correction coefficient obtained based on the first voltage difference and the second voltage difference of the detection unit is stored. The control means,
When changing the linear speed after starting the device,
A voltage difference between an output voltage of the detection unit at a standard linear speed of the developer carrier and an output voltage of the detection unit when the linear speed is changed is calculated, and correction information read from the storage unit is calculated as the voltage difference. To calculate the control voltage difference when changing the linear velocity,
The image forming apparatus according to claim 9, wherein a control voltage of the detection unit is determined based on the control voltage difference. The control means includes:
When the device warms up,
Executing a toner density control according to the output of the detection means at a standard linear velocity,
10. The image forming apparatus according to claim 9, wherein the toner density initial adjustment is performed by the detection unit at a standard linear speed. The control means,
10. The image forming apparatus according to claim 9, wherein when changing from the standard linear velocity to the linear velocity drop, the toner supply control is not performed within a predetermined time regardless of an output value of the detection unit. In the developer,
10. The image forming apparatus according to claim 9, wherein a two-component mixture comprising a toner having a particle diameter of 8.0 μm or less and a carrier having a particle diameter of 65 μm or less is used.

Images