JP4138412B2

JP4138412B2 - Image forming apparatus

Info

Publication number: JP4138412B2
Application number: JP2002260051A
Authority: JP
Inventors: 勝田中
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2002-09-05
Filing date: 2002-09-05
Publication date: 2008-08-27
Anticipated expiration: 2022-09-05
Also published as: JP2004101623A

Description

【０００１】
【発明の属する技術分野】
この発明は、ファクシミリ、複写機、プリンタ、複合機などに用いられる２成分現像装置を具えた画像形成装置に関するものである。
【０００２】
【従来の技術】
一般に、複写機やプリンタなどの画像形成装置に具えられた現像装置は、その内部に多量の現像剤を収容しており、装置内で現像剤を攪拌して現像剤担持体に供給する構成が知られている。特に、トナーとキャリアとを混合した現像剤を用いる、いわゆる二成分系の現像装置では、トナー補給部から供給されたトナーが、スクリューやパドルなどの搬送供給部材によってキャリアに混合されながら、現像剤担持体へ搬送されて供給される。その後、画像形成によってトナーが消費された現像剤は、再度トナー補給部を通過するように搬送され、このトナー補給部でトナーが補給されて、再びキャリアとの混合、攪拌、搬送が繰り返される。
【０００３】
この現像剤のトナーとキャリアの比率は、濃度センサによって検知されており、この比率が画像形成によるトナーの消費状態に応じて変化するので、トナー補給部からトナーが補給されて、比率を一定に保つようにしている。すなわち、例えばトナーの透磁率やトナーの帯電量を測定することによって、現像剤中のトナー濃度が判別される。このトナー濃度に基づき、トナー濃度を一定に調整する制御をおこなって、画像濃度の安定化が図られる。すなわち、トナー濃度が低い場合には、不足したトナーを補充する一方、トナー濃度が高い場合には、トナーの補給を抑制または停止している。
【０００４】
しかしながら、現像剤が循環する途中で、現像剤に部分的な滞留が生じることがあるので、この部分的な滞留によって、濃度センサの誤検知が発生しやすいという問題があった。そのため、スクリュー形状の変更や、トナー濃度に関連した制御の変更などによって改善を図っており、各種の提案がおこなわれている。すなわち、スクリューの一部を切り欠いて、濃度センサのセンサ面を現像剤の循環経路を形成する壁面から突出させた構成が知られている（例えば、特許文献１参照。）。この構成によれば、壁面の凹部内に濃度センサのセンサ面が位置していないので、この凹部にトナーなどが停留したことによるセンサの誤検知が回避できるとされている。充分に攪拌した状態の現像剤で実際にトナー濃度を検出し、この検出値と設定値とを比較して補正値を決定し、この補正値によりトナー濃度検知の補正をおこなう構成が知られている（例えば、特許文献２参照。）。この構成によれば、トナー濃度制御の精度を向上できるとされている。現像剤の濃度分布の不均一を修正した後に、濃度の測定をおこなう構成が知られている（例えば、特許文献３参照。）。この構成によれば、正確なトナー濃度の測定が可能になるとされている。スクリューのピッチ間のトナー濃度センサに対応した箇所に他よりも大きな攪拌板を設け、この攪拌板によって、軸長手方向に進む現像剤量よりも軸径方向に寄せ集められる現像剤量の比率を大きくすることにより、トナー濃度センサが設置された近傍の箇所のみ現像剤面を高めた構成が知られている（例えば、特許文献４参照。）。この構成によれば、このように現像剤面を高めて、濃度センサの検知対象である現像剤の層厚を充分に確保しているので、正確なトナー濃度の測定が可能になるとされている。濃度センサ付近のスクリューピッチに比べて、トナー補給部からのトナーが補給される補給口付近のスクリューピッチを大きくすることにより、補給部付近で現像剤が搬送される流速を速くし、濃度センサ付近で遅くした構成が知られている（例えば、特許文献５参照。）。この構成によれば、補給部付近では現像剤面が低くなるので、補給したトナーが現像剤と混合せずに剤面に浮いてしまうことがなくなり、攪拌性の向上が図れるとともに、濃度センサ付近では現像剤面を高められることから、正確なトナー濃度の測定が可能になるとされている。
【０００５】
ところが上記の各構成では、濃度センサによるトナー濃度の測定精度が充分に得られない問題があった。すなわち、各構成の濃度センサは現像剤を搬送させる経路を形成する壁側に固定されて設けられ、この搬送される現像剤の流れの外周側を検知するようにしている。このため、壁側付近のトナーとキャリアとの混合程度の少ない成分が片寄った部分や、トナーが補給されても濃度が補給前と変わらない滞留した部分を濃度センサが検知する機会が頻繁に生じる。したがって、ある巾で変動したトナー濃度の測定値が得られることになる。特に、高濃度にトナー濃度が設定されている場合には、この測定値の変動巾が増大する傾向にある。この結果、測定値の変動に影響されてトナー濃度の制御が不安定となるので、形成した画像の地汚れや画像濃度が過多となったり、不足したりする事態が生じて、画質が低下するおそれがある。
【０００６】
他方、近年の傾向として省スペース化に対応するために、画像形成装置の小型化が望まれている。このため、各種のセンサ類も各ユニット内に配置して、他の機能部品と融合化させることにより、機能部品用のスペースをセンサ用のスペースとして兼用させて、結果的にセンサ用のスペースを削減することが要請されている。
【０００７】
【特許文献１】
特許２８６４１８２号公報
【特許文献２】
特開平７−２７１１７４号公報
【特許文献３】
特開平７−１３４４８８７号公報
【特許文献４】
特開２００１−３４３８２５号公報
【特許文献５】
特開２００１−２０９２４０号公報
【０００８】
【発明が解決しようとする課題】
そこでこの発明は、前記のような従来の問題点を解決し、現像剤のトナー濃度の測定精度を向上でき、装置の小型化を図れる画像形成装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記目的を達成するために、請求項１に記載の発明は、潜像担持体と、この潜像担持体の潜像を現像化する現像装置とを具え、前記現像装置は、トナーとキャリアからなる２成分現像剤を収容してトナー補給部からトナーが補給可能な収容部と、前記潜像担持体に対向して設置され前記現像剤を担持する剤担持体と、前記収容部に設けられた搬送経路内において前記現像剤を搬送して前記剤担持体に供給する搬送供給部材と、前記２成分現像剤のトナー濃度を検知する濃度センサとを有し、この濃度センサの測定したトナー濃度に基づきトナー補給部からトナーを前記収容部に補給してトナーとキャリアとの比率を略一定に保つように構成された画像形成装置において、前記現像装置には、前記搬送供給部材として、第１の搬送供給部材と第２の搬送供給部材とが設けられ、これら第１の搬送供給部材及び第２の搬送供給部材は、それぞれ前記剤担持体の軸と平行な回転軸と、該回転軸に形成された螺旋状の羽根とを有するスクリュー状に形成されており、第１の搬送供給部材は、前記搬送路のトナー補給部側に、第２の搬送供給部材は、前記搬送路の前記剤担持体に近接して配設され、第１の搬送供給部材と第２の搬送供給部材を互いに逆方向に回転させて前記剤担持体の軸方向に沿って前記現像剤を攪拌しながら前記搬送経路内を一方向に回転循環させて、前記剤担持体へ前記現像剤を供給するように構成され、前記濃度センサが、第２の搬送供給部材の回転軸上に設けられていることを特徴とする。
【００１０】
請求項２に記載の発明は、潜像担持体と、この潜像担持体の潜像を現像化する現像装置とを具え、前記現像装置は、トナーとキャリアからなる２成分現像剤を収容してトナー補給部からトナーが補給可能な収容部と、前記潜像担持体に対向して設置され前記現像剤を担持する剤担持体と、前記収容部に設けられた搬送経路内において前記現像剤を搬送して前記剤担持体に供給する搬送供給部材と、前記２成分現像剤のトナー濃度を検知する濃度センサとを有し、この濃度センサの測定したトナー濃度に基づきトナー補給部からトナーを前記収容部に補給してトナーとキャリアとの比率を略一定に保つように構成された画像形成装置において、前記現像装置には、前記搬送供給部材として、第１の搬送供給部材と第２の搬送供給部材とが設けられ、これら第１の搬送供給部材及び第２の搬送供給部材は、それぞれ前記剤担持体の軸と平行な回転軸と、該回転軸に形成された螺旋状の羽根とを有するスクリュー状に形成されており、第１の搬送供給部材は、前記搬送路のトナー補給部側に、第２の搬送供給部材は、前記搬送路の前記剤担持体に近接して配設され、第１の搬送供給部材と第２の搬送供給部材を互いに逆方向に回転させて前記剤担持体の軸方向に沿って前記現像剤を攪拌しながら前記搬送経路内を一方向に回転循環させて、前記剤担持体へ前記現像剤を供給するように構成され、前記濃度センサが、第２の搬送供給部材の螺旋状の羽根上に設けられていることを特徴とする。
【００１１】
請求項３に記載の発明は、請求項１又は２において、前記現像装置が、前記剤担持体の剤量を規制するドクター部材を有していることを特徴とする。
【００１２】
請求項４に記載の発明は、請求項１ないし３のいずれかにおいて、前記濃度センサが、検知したトナー濃度を無線により送信していることを特徴とする。
【００１５】
【発明の実施の形態】
この発明の第１の実施形態を図面により説明する。図１は、この第１の実施形態の画像形成装置を説明し、その全体の概略構成を示す断面図であり、図２は、搬送供給部材の全体構成を示す側面図であり、図３は、現像剤の循環経路の概略を示す斜視図である。
【００１６】
この第１の実施形態の画像形成装置１は、図１に示すように、像担持体としての感光体２と、感光体２を一様に帯電する図示しない帯電ローラと、露光で感光体２上に静電潜像を形成する図示しない書き込み手段と、静電潜像を現像しトナー像として可視像化する現像装置３と、感光体２上のトナー像を用紙に転写する転写手段４と、トナー像を用紙に固定する図示しない定着装置となどを有している。
【００１７】
現像装置３は、感光体２に対向して設置された現像剤担持体としての現像スリーブ６と、トナーとキャリア（磁性体粒子）からなる２成分現像剤Ｄを収容する収容部７と、この収容部７にトナーを補給する図示しないトナー補給部と、収容部７に補給されたトナーをキャリアに攪拌混合し現像剤Ｄとして現像スリーブ６に搬送して供給する第１の搬送供給部材８および第２の搬送供給部材９と、現像スリーブ６上の剤量を規制するドクターブレード部材１０とから主に構成され、第２の搬送供給部材９に現像剤Ｄのトナー濃度を測定する濃度センサ１１が設けられている。
【００１８】
第１の搬送供給部材８と第２の搬送供給部材９とは、それぞれ回転軸８ａ，９ａと、この回転軸８ａ，９ａに形成された螺旋状の羽根８ｂ，９ｂとを有し、収容部７に形成された凹部内に互いの回転軸８ａ，９ａを平行にして回転駆動が可能に収容され、第２の搬送供給部材９が現像スリーブ６の下方に対向されて配置されている。したがって、これらの第１および第２の搬送供給部材８，９によって、現像剤Ｄを現像スリーブ６の軸方向に攪拌しながら搬送して供給するようにしている。
【００１９】
すなわち、第１および第２の搬送供給部材８，９は、図２に示すように、それぞれ所定の軸径が確保された回転軸８ａ，９ａに羽根８ｂ，９ｂが同じ回り方向に螺旋状に形成されている。したがって、これらの羽根８ａ，９ｂにより螺旋状の連続面が形成され、この連続面は、所定の同一のピッチが設定されかつ同一の外周径を確保するようにしている。これらの第１および第２の搬送供給部材８，９の回転軸８ａ，９ａの一端部には、図３に示すように、ギア８ｃ，９ｃが設けられ、これらのギア８ｃ，９ｃは、電動モータなどにより駆動される減速ギア列１２の最終の出力ギア１２ａに噛合されている。したがって、第１および第２の搬送供給部材８，９は、互いに逆方向に回転駆動され、現像剤Ｄをそれぞれ軸方向の反対方向に搬送するようになっている。
【００２０】
すなわち、これらの第１の搬送供給部材８と第２の搬送供給部材９との間は、収容部７が有する図示しない仕切り壁で区画され、これらの第１および第２の搬送供給部材８，９の回転駆動に伴ない、現像剤Ｄをそれぞれの軸方向に搬送するようにしている。この収容部７の軸方向の前後端部に位置した仕切り壁には図示しない切欠き部が形成され、この切欠き部を介して一方から他方に現像剤Ｄの受け渡しができるようにしている。すなわち、現像剤Ｄは、第１の搬送供給部材８の回転軸８ａの手前側から奥側に向けて軸方向に沿って攪拌されながら搬送され、この奥側で図示しない切欠き部を介して第２の搬送供給部材９へと引き渡される。次に、現像剤Ｄは、第２の搬送供給部材９の回転軸９ａの奥側から手前側に向けて軸方向に沿って攪拌されながら搬送され、この搬送経路の途中で現像スリーブに６に所定のトナー濃度の現像剤Ｄが供給され、この手前側で図示しない切欠き部を介して第１の搬送供給部材８へと引き渡され、再び第１の搬送供給部材８により搬送される。このように、現像剤Ｄは、図３中に矢印で示されるように、略四角形状に形成された経路を一定の方向に循環するようにしている。
【００２１】
この第２の搬送供給部材９の回転軸９ａには、図４（ａ）に示すように、濃度センサ１１が設けられている。この濃度センサ１１は、収容部７内の現像剤Ｄのトナー濃度を磁気などを用いて検知するようにしている。この濃度センサ１１のセンサ面１１ａは、回転軸９ａの周面から僅かに突出するように設けられ、センサ面１１ａを凹部内に配置しないようにしている。このため、センサ面１１ａに現像剤Ｄが滞留することが防止される。
【００２２】
この濃度センサ１１の第２の搬送供給部材９上での設置箇所は、上記の現像剤Ｄの循環経路で、図示しないトナー補給部によりトナーが補給される箇所Ａよりも下流側の充分な攪拌が期待できる箇所であればよく、このような箇所からトナーの補給の直前の箇所までの循環経路上の範囲内で自由に選択することができる。特に例えば、トナーの補給箇所の直前の箇所Ｂとなるように、第２の搬送供給部材９に濃度センサ１１を設けた構成としてもよい。したがって、この場合には、トナーが補給される直前の箇所Ｂに濃度センサ１１を設置したので、トナーが補給される直前、つまり現像スリーブ６によりトナーが消費された状態の現像剤Ｄのトナー濃度を測定できることになり、必要なトナー補給量を正確に把握することができる。この濃度センサ１１は、回転型接点１３を介して、画像形成装置１の本体側に電気的に接続されている。
【００２３】
すなわち、図４（ｂ）に示すように、搬送供給部材９の回転軸９ａは中空状に形成され、この中空部分を通過して濃度センサ１１からの電源線１４ａ，接地線１４ｂおよび測定信号線１４ｃが回転軸９ａの一端部に向けて設置されており、その軸端には回転型接点１３が設けられている。この回転型接点１３は、搬送供給部材９側に設けられた端面部材１５と、これに対向して配置された本体側の固定部材１６とから構成され、リング状の接点端子１５ａ，１５ｂ，１５ｃが端面部材１５に設けられ、これらのリング状の接点端子１５ａ，１５ｂ，１５ｃにしゅう接されるピン状の接点端子１６ａ，１６ｂ，１６ｃが固定部材１６に設けられている。すなわち、この端面部材１５は、非導電性材質により円盤状に形成され、回転軸９ａの軸端に同心状に装着され、回転軸９ａの回転に従動して回転される。この端面部材１５は、その中心に所定半径の円形に形成された導電性の接点端子１５ａ，とこの中心と同心状に半径が異なるリング状に形成された導電性の接点端子１５ｂ，１５ｃとが設けられ、各接点端子１５ａ，１５ｂ，１５ｃにはそれぞれ濃度センサ１１からの電源線１４ａ，接地線１４ｂおよび測定信号線１４ｃが接続されている。他方、固定部材１６は、非導電性材質により円盤状に形成され、その中心から外周に向けて端面部材１５の接点端子１５ａ，１５ｂ，１５ｃに対応した間隔でピン状の接点端子１６ａ，１６ｂ，１６ｃが突出して設けられ、それぞれの接点端子１６ａ，１６ｂ，１６ｃは、本体側に設置された図示しないトナー濃度制御に関連したコントローラや電源などからの配線がそれぞれ所定に接続され、接点端子１６ａには電源から５Ｖ電圧の駆動電流が供給されている。したがって、第２の搬送供給部材９の搬送動作に伴なって端面部材１５が回転しても、それぞれ、固定部材１６側のピン状の接点端子１６ａ，１６ｂ，１６ｃが、対応した端面部材１５のリング状の接点端子１５ａ，１５ｂ，１５ｃの周上を移動してしゅう接されるので、電気的な接続が維持される。このため、第２の搬送供給部材９が回転駆動されても、回転型接点１３を介して、画像形成装置１の本体側から濃度センサ１１に駆動電流が供給されるとともに、濃度センサ１１からトナー濃度を示す測定信号を同本体側に取得させることができる。
【００２４】
このように構成された第１の実施形態によれば、図５のグラフに示されるように、トナー濃度の測定精度を向上させることができた。すなわち、トナーの平均粒径が９．５μｍ、キャリアの平均粒径が５０μｍ、トナー濃度の変動巾が１ｗｔ％〜９ｗｔ％（重量％）、第１および第２の搬送供給部材８，９の回転数が１００ｒｐｍ〜５００ｒｐｍに設定した条件下で、従来構成の濃度センサとこの第１の実施形態の濃度センサ１１とによって、トナー濃度の測定をおこない、これらの濃度センサで測定したトナー濃度と、実際のトナー濃度とを対比してグラフ化した。従来の構成では、図５中に破線で示すように、トナー濃度が高くなるのに応じて、濃度センサ１１による測定値のバラツキ巾つまり変動巾が大きくなることが解る。これは、トナー濃度が高いと現像剤Ｄの流動性が低下するので、第１および第２の搬送供給部材８，９の羽根９ｂと収容部７の壁部との間に現像剤Ｄの滞留が発生しやすくなるためである。すなわち、従来の収容部７の壁部側に固定されて設置された濃度センサでは、このような滞留部分を検知する機会が多く、しかもトナー濃度が高いことから、この滞留部分に偏在するトナー濃度の片寄りが増大している。このため、従来の濃度センサが検知するトナー濃度の変動巾が拡大される。
【００２５】
これに対して、この第１の実施形態の構成によれば、トナー濃度測定値の変動巾を従来の構成に比べて５０％以下に低減させることができた。すなわち、濃度センサ１１を第２の搬送供給部材９の回転軸９ａに設けたことにより、濃度センサ１１の検知箇所が、収容部７の壁部から離れた現像剤が搬送される流れの内側の箇所になり、しかも従来の固定されたポイントではなく、回転軸９ａの外径の円周上を移動されているので、濃度センサ１１の検知範囲が拡大されることになる。このため、トナー濃度が片寄った部分や、攪拌が少ないためにトナーが補給されても濃度が補給前と変わらない部分を検知する機会が減少され、搬送供給部材９により攪拌されて搬送される現像剤Ｄを主体に検知でき、しかもこの流れを横切る箇所を検知範囲としてトナー濃度の測定をおこなえることになる。このように実際に現像スリーブ６に搬送されて現像スリーブ６が利用する現像剤Ｄの全体的なトナー濃度を取得できるので、トナー濃度を適切に検知できることになる。この結果、現像剤Ｄのトナー濃度を調節する制御を安定して適切におこなえるので、画像品質を向上することができる。他方、収容部７内に収容されている搬送供給部材９に濃度センサ１１を設けているので、濃度センサ１１が装置構成の深奥部に配置されることになり、濃度センサ１１の保護を充分に確保することができる。さらに、現像スリーブ６や収容部７、トナー補給部などがユニットとして一体化され、このユニットをトナーの全量消費により交換するようにしている場合には、従来の画像成形装置１の本体側に濃度センサを設けた構成と異なり、濃度センサ１１も同時に新たなものに交換されることになる。このため、経年劣化などによるセンサ性能の低下が防止され、高精度で安定した濃度測定がおこなえる。特に、この構成の場合には、トナー補給部により補給されるキャリアやトナーの成分特性、トナー濃度の設定条件などに応じた最適な濃度センサ１１をユニット毎に選択することが可能となり、これによっても測定精度の向上を図ることができる。
【００２６】
次に、この発明の第２の実施の形態を説明する。この実施の形態の画像形成装置においては、図６に示すように、濃度センサ１７を羽根９ｂに設け、回転駆動される搬送供給部材９側と固定された収容部７側との中間の領域のトナー濃度を測定するようにしている。なお、上記の第１の実施形態と同一の構成の部材には、同一の符号を付して、説明を簡略化することにする。
【００２７】
すなわち、上記の第１および第２の搬送供給部材８，９は、その回転軸８ａ，９ａが比較的に太径に形成され、その周囲に螺旋状の羽根８ｂ，９ｂが一体に形成されて、この羽根８ｂ，９ｂが回転軸８ａ，９ａの補強リブとなるので、軸としての剛性強度を充分に確保するようにしている。しかしながら、比較的にその軸長が長く、しかも粉体の現像剤Ｄを軸方向に搬送するため大きな負荷が掛かるので、その軸にねじれが生じることがある。このため、回転する羽根８ｂ，９ｂの最外周端が軸の半径方向に僅かに変位するので、この外周端が収容部７の壁部に接触することを回避するために、これらの両者の間には、図７（ｂ）に示すように、予め所定の隙間σが確保されている。
【００２８】
したがって、この隙間σが大きくなるほど、搬送供給部材との接触範囲から離れた空間が大きくなり、この隙間σに滞留する現像剤Ｄが多くなる。このため、図７のグラフに示すように、回転軸９ａに設けた濃度センサ１１により測定したトナー濃度と、この隙間σに滞留した現像剤Ｄのトナー濃度との対応関係が、正比例の関係から劣化する傾向にある。すなわち、隙間σが大きくなるほど、搬送供給部材９の回転軸９ａ付近の濃度センサが検知したトナー濃度と、搬送供給部材９の羽根９ｂよりも外側の濃度センサが検知したトナー濃度との格差が大きくなる。このため、回転軸９ａに設けた濃度センサ１１および、収容部７の壁に設けた従来構成の濃度センサのいずれでも、実際の現像剤Ｄのトナー濃度が測定できないことになる。他方、隙間σを減少させるために、搬送供給部材９の軸の剛性強度を高めることは、搬送供給部材９を強度アップするためのコストの増加や、強度アップによる搬送供給部材９の重量化によって装置各部の構造の強化が必要となったり、搬送供給部材９を回転駆動させるエネルギー消費が増大したりして、コストダウンや小型化が要請されている実情にそぐわないことになる。
【００２９】
そこで、この第２の実施の形態では、濃度センサ１７を搬送供給部材９の羽根９ｂに設けることにより、搬送供給部材９の回転軸９ａでその半径方向の回転軸９ａと収容部７の壁部との中間の領域のトナー濃度を検知して、両者の中間の測定値を得るようにしている。すなわち、この濃度センサ１７は、現像剤Ｄを押圧して搬送する側の羽根９ｂの面で、回転軸９ａの半径方向で羽根９ｂの外周半径の略中間の位置に設置されている。この濃度センサ１７から、上記の第１の実施の形態と同様に配線され、同様な回転型接点１３を介して、画像形成装置１の本体側に接続されている。この濃度センサ１７のセンサ面１７ａは、僅かに羽根９ｂの外面から突出して設けられ、このセンサ面１７ａに現像剤Ｄが停留しないようにしている。
【００３０】
このように第２の実施形態によれば、濃度センサ１７を搬送供給部材９の羽根９ｂに設けたことにより、搬送動作状態の羽根９ｂと収容部７の側壁との間に形成される隙間σが例えば１ｍｍ以上とされた構成の場合でも、現像剤Ｄのトナー濃度を小さな変動巾で正確に測定でき、トナー濃度の制御が向上できるので、この結果として得られる画像の画質を安定化および向上させることが可能となる。すなわち、搬送供給部材９から外側の収容部７の壁付近に滞留している現像剤Ｄのトナー濃度と、回転軸９ａ付近の攪拌移動されている現像剤Ｄのトナー濃度との中間のトナー濃度を測定することができる。他方、第１の実施形態の濃度センサ１１の検知範囲が回転軸９ａの外周半径により規定される周上の範囲となっているのに対して、この第２の実施形態の濃度センサ１７の検知範囲は、濃度センサ１７が羽根９ｂの径方向の略中間に設けられているので、第１の実施形態よりも大きな半径により規定される周上の範囲となっている。さらに、例えば従来の濃度センサが収容部７の壁部に設けられ、そのセンサ面の向きが、現像剤の流れ方向に平行な面となっているので、この流れの断面における外周の一部である線状の範囲を濃度センサが検知していることになる。これらに対して、この第２の実施形態の濃度センサ１７が搬送供給部材９の羽根９ｂに設けられ、そのセンサ面が羽根９ｂの表面と同様に現像剤の流れ方向と交差する横断面に斜めに向けられて、この横断面の所定半径の周上を移動しているので、この流れに対して円錐ベルト状の範囲を濃度センサ１７が検知していることになる。このため、濃度センサ１７が担当する検知範囲を大幅に拡大することができ、現像剤の全体のトナー濃度をより正確に把握することが可能となる。さらに、濃度センサ１７が羽根９ｂの現像剤Ｄを押圧して搬送する側の面に設置されているので、そのセンサ面１７ａと現像剤との接触が充分に図れることになり、これによっても測定精度の向上を図ることが可能となる。
【００３１】
次に、この発明の第３の実施の形態を説明する。この実施の形態の画像形成装置は、図８に示すように、濃度センサ１９のワイヤレス化を図って、センサ用の配線を不要としたものである。なお、上記の第１の実施形態と同一の構成の部材には、同一の符号を付して、説明を簡略化することにする。
【００３２】
すなわち、この濃度センサ１９は、上記の第１の実施の形態と同様に第２の搬送供給部材９の回転軸９ａに設置された構成とされ、回転軸９ａの周面から突出するように設けられたセンサ面１９ａを有している。この濃度センサ１９には、バッテリーなどからなる図示しない電源部と無線送信機とが内蔵され、画像形成装置の本体側には、図示しない無線受信機が設置されている。したがって、この濃度センサ１１は、外部から独立したトナー濃度の測定動作を可能にしているとともに、測定したトナー濃度を弱電波により画像形成装置の本体側に送信するようにしている。
【００３３】
このように構成された第３の実施形態によれば、濃度センサ１９が独立電源のワイヤレス化されているので、濃度センサ１９用に配線する必要が無くなることに加えて、上記の第１および第２の実施形態が有していた回転駆動される搬送供給部材９と固定された装置本体側との間を電気的に接続する回転型接点１３も無くすことができる。この結果、濃度センサ１９に関連した構成が簡素化され、コストダウンを図ることができる。濃度センサ１９の単体としての独立性が確保されているので、濃度センサ１９を簡便に取り扱えることになり、濃度センサ１９を保守や修理のために取付け取り外す作業を簡素化することができる。他方、濃度センサ１９と装置本体との連絡に無線を用いているので、この無線の到達範囲内ならば、搬送供給部材９側の濃度センサ１９および装置本体側の無線受信機の配置を自由に選択できるので、レイアウトなどの設計の自由度を向上することができる。
【００３４】
なお、上記の各実施形態では、搬送供給部材８，９をその回転軸８ａ，９ａに螺旋状の羽根９ａ，９ｂによって同一のピッチで同一の外周半径が確保された連続的な面を形成するように構成したが、これに限られることなく、間歇的な面を形成したり、所定の箇所でピッチや外周半径を変更したり、多数枚の互いに独立したスクリュウ羽根を設けたりした構成としてもよい。他方、搬送供給部材８，９が既に有している部材に濃度センサ１１，１７，１９を設けた構成としたが、新たに濃度センサのための専用部材を追加して設け、この専用部材に濃度センサを設置した構成としてもよい。したがって、この構成によれば、濃度センサのセンサ面の向きを、送供給部材９の回転軸９ａの外周面や羽根９ｂの表面の向きと異ならせて、搬送経路上における現像剤の攪拌状態などに応じるように任意に設定できるので、よりトナー濃度の測定精度を向上させることが可能となる。
【００３５】
【発明の効果】
請求項１の発明によれば、潜像担持体と、この潜像担持体の潜像を現像化する現像装置とを具え、前記現像装置は、トナーとキャリアからなる２成分現像剤を収容してトナー補給部からトナーが補給可能な収容部と、前記潜像担持体に対向して設置され前記現像剤を担持する剤担持体と、前記収容部に設けられた搬送経路内において前記現像剤を搬送して前記剤担持体に供給する搬送供給部材と、前記２成分現像剤のトナー濃度を検知する濃度センサとを有し、この濃度センサの測定したトナー濃度に基づきトナー補給部からトナーを前記収容部に補給してトナーとキャリアとの比率を略一定に保つように構成された画像形成装置において、前記現像装置には、前記搬送供給部材として、第１の搬送供給部材と第２の搬送供給部材とが設けられ、これら第１の搬送供給部材及び第２の搬送供給部材は、それぞれ前記剤担持体の軸と平行な回転軸と、該回転軸に形成された螺旋状の羽根とを有するスクリュー状に形成されており、第１の搬送供給部材は、前記搬送路のトナー補給部側に、第２の搬送供給部材は、前記搬送路の前記剤担持体に近接して配設され、第１の搬送供給部材と第２の搬送供給部材を互いに逆方向に回転させて前記剤担持体の軸方向に沿って前記現像剤を攪拌しながら前記搬送経路内を一方向に回転循環させて、前記剤担持体へ前記現像剤を供給するように構成され、前記濃度センサが、第２の搬送供給部材の前記回転軸上に設けられていることにより、濃度センサの検知する箇所が、搬送路内を循環搬送される現像剤の流れの内側となり、しかも搬送供給部材の搬送、回転攪拌動作に伴ない常に現像剤に対して濃度センサの測定箇所が相対的に変位されることになる。このため、濃度センサが現像剤の流れの全体的なトナー濃度を検知することができ、現像剤の滞留部分などの濃度が片寄った部分を検知する機会が減少され、現像剤全体のトナー濃度が反映された変動巾の少ないトナー濃度の測定値を得ることができる。このようにトナー濃度を適切に検知できることになるので、現像剤のトナー濃度の制御を安定して適正におこなえる。この結果、形成した画像の地汚れや画像濃度の過多、低下を防止することができ、画質の安定化と向上とを図ることができる。さらに、従来の搬送供給部材の周囲の部材に設けていた濃度センサ用の設置スペースが削減されるので、装置が小型され、省スペース化を図ることができる。
また、濃度センサを第２の搬送供給部材の回転軸に設けたことにより、この濃度センサが搬送供給部材により攪拌搬送されて流動状態となった現像剤のトナー濃度を検知できることになる。このため、現像剤の滞留部分を検知することが解消され、誤検知を未然に回避することができる。この結果、現像剤のトナー濃度を正確に測定することが可能となり、トナー濃度制御の適正化が図れるので、画像の画質の安定化と向上とが可能となる。
【００３６】
請求項２の発明によれば、潜像担持体と、この潜像担持体の潜像を現像化する現像装置とを具え、前記現像装置は、トナーとキャリアからなる２成分現像剤を収容してトナー補給部からトナーが補給可能な収容部と、前記潜像担持体に対向して設置され前記現像剤を担持する剤担持体と、前記収容部に設けられた搬送経路内において前記現像剤を搬送して前記剤担持体に供給する搬送供給部材と、前記２成分現像剤のトナー濃度を検知する濃度センサとを有し、この濃度センサの測定したトナー濃度に基づきトナー補給部からトナーを前記収容部に補給してトナーとキャリアとの比率を略一定に保つように構成された画像形成装置において、前記現像装置には、前記搬送供給部材として、第１の搬送供給部材と第２の搬送供給部材とが設けられ、これら第１の搬送供給部材及び第２の搬送供給部材は、それぞれ前記剤担持体の軸と平行な回転軸と、該回転軸に形成された螺旋状の羽根とを有するスクリュー状に形成されており、第１の搬送供給部材は、前記搬送路のトナー補給部側に、第２の搬送供給部材は、前記搬送路の前記剤担持体に近接して配設され、第１の搬送供給部材と第２の搬送供給部材を互いに逆方向に回転させて前記剤担持体の軸方向に沿って前記現像剤を攪拌しながら前記搬送経路内を一方向に回転循環させて、前記剤担持体へ前記現像剤を供給するように構成され、前記濃度センサが、第２の搬送供給部材の螺旋状の羽根上に設けられていることにより、濃度センサの検知する箇所が、搬送路内を循環搬送される現像剤の流れの内側となり、しかも搬送供給部材の搬送、回転攪拌動作に伴ない常に現像剤に対して濃度センサの測定箇所が相対的に変位されることになる。このため、濃度センサが現像剤の流れの全体的なトナー濃度を検知することができ、現像剤の滞留部分などの濃度が片寄った部分を検知する機会が減少され、現像剤全体のトナー濃度が反映された変動巾の少ないトナー濃度の測定値を得ることができる。このようにトナー濃度を適切に検知できることになるので、現像剤のトナー濃度の制御を安定して適正におこなえる。この結果、形成した画像の地汚れや画像濃度の過多、低下を防止することができ、画質の安定化と向上とを図ることができる。さらに、従来の搬送供給部材の周囲の部材に設けていた濃度センサ用の設置スペースが削減されるので、装置が小型され、省スペース化を図ることができる。
また、濃度センサを第２の搬送供給部材の螺旋状の羽根上に設けたので、搬送供給部材の外周箇所と搬送供給部材の回転軸の近傍箇所との中間の領域のトナー濃度を検知することができる。このため、搬送供給部材の外周側に滞留している現像剤のトナー濃度と、回転軸付近の攪拌され搬送されている現像剤のトナー濃度との中間のトナー濃度を測定できることになり、これらの両者のトナー濃度が反映された測定値を得ることができる。この結果、現像剤の滞留が多い構成でも、現像剤のトナー濃度を高精度に測定できるので、トナー濃度を調整する制御が安定化されて容易となり、画質の向上を図ることができる。
【００３７】
請求項３の発明によれば、濃度センサによるトナー濃度の検知精度が向上され、しかも現像装置が、剤担持体の剤量を規制するドクター部材を有した構成とされているので、現像剤へのトナーの補給量が適正化され、余分なトナー消費を解消することができる。このため、形成可能な画像数の増加が図れ、画像形成装置の性能を向上させることが可能となる。
【００３８】
請求項４の発明によれば、濃度センサが検知したトナー濃度を無線により送信する構成とされているので、この濃度センサ用の配線が不要となり、構成や組付け作業が簡素化され、コストダウンを図ることができる。
【図面の簡単な説明】
【図１】この発明の第１の実施形態の画像形成装置を説明し、その概略構成を示す縦断面図である。
【図２】この搬送供給部材の全体構成を示す側面図である。
【図３】この第１の実施形態の画像形成装置を説明し、現像剤が循環する状態を示す概略斜視図である。
【図４】この第１の実施形態の濃度センサを説明し、（ａ）は、回転軸に設置した状態を示す斜視図、（ｂ）は、配線状態を示す縦断面図、（ｃ）は、回転型接点の斜視図である。
【図５】この第１の実施形態の濃度センサと従来の濃度センサとによる測定結果を対比したグラフである。
【図６】この発明の第２の実施形態の濃度センサを説明し、（ａ）は、濃度センサを羽根に設置した状態を示す斜視図、（ｂ）は、隙間σを説明する搬送供給部材の正面図である。
【図７】この第２の実施形態を説明し、搬送供給部材の回転軸付近と搬送供給部材の外側である収容部の壁部付近のトナー濃度の測定結果を対比したグラフである。
【図８】この発明の第３の実施形態の濃度センサを示す斜視図である。
【符号の説明】
１画像形成装置２感光体（像担持体）
３現像装置４転写手段
６現像スリーブ（剤担持体）７現像剤の収容部
８第１の搬送供給部材８ａ第１の搬送供給部材の回転軸
８ｂ第１の搬送供給部材の羽根９第２の搬送供給部材
９ａ第２の搬送供給部材の回転軸９ｂ第２の搬送供給部材の羽根
１１，１７，１９濃度センサ
１１ａ，１７ａ，１９ａ濃度センサのセンサ面
Ｄ現像剤[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus including a two-component developing device used for a facsimile, a copying machine, a printer, a multifunction machine, and the like.
[0002]
[Prior art]
Generally, a developing device provided in an image forming apparatus such as a copying machine or a printer contains a large amount of developer therein, and the developer is stirred in the apparatus and supplied to the developer carrier. Are known. In particular, in a so-called two-component developing device using a developer in which a toner and a carrier are mixed, the developer supplied from the toner replenishing unit is mixed with the carrier by a conveyance supply member such as a screw or paddle. It is conveyed to the carrier and supplied. Thereafter, the developer whose toner has been consumed by the image formation is conveyed so as to pass through the toner replenishing portion again, and the toner is replenished by this toner replenishing portion, and mixing, stirring, and transportation with the carrier are repeated again.
[0003]
The ratio of the toner and carrier of the developer is detected by a density sensor, and this ratio changes according to the consumption state of the toner due to image formation. Therefore, the toner is replenished from the toner replenishing unit, and the ratio is kept constant. I try to keep it. That is, for example, the toner concentration in the developer is determined by measuring the magnetic permeability of the toner and the charge amount of the toner. Based on this toner density, control is performed to adjust the toner density to be constant, thereby stabilizing the image density. That is, when the toner density is low, the shortage of toner is replenished, while when the toner density is high, the replenishment of toner is suppressed or stopped.
[0004]
However, a partial stagnation may occur in the developer in the middle of the circulation of the developer, and there has been a problem that erroneous detection of the density sensor is likely to occur due to this partial stagnation. For this reason, improvements have been made by changing the screw shape and control related to toner concentration, and various proposals have been made. That is, a configuration is known in which a part of the screw is cut out and the sensor surface of the density sensor is protruded from the wall surface forming the developer circulation path (see, for example, Patent Document 1). According to this configuration, since the sensor surface of the density sensor is not located in the concave portion of the wall surface, it is possible to avoid erroneous detection of the sensor due to toner or the like remaining in the concave portion. A configuration is known in which the toner density is actually detected with a sufficiently agitated developer, a correction value is determined by comparing the detected value with a set value, and toner density detection correction is performed based on the correction value. (For example, refer to Patent Document 2). According to this configuration, the accuracy of toner density control can be improved. A configuration is known in which density measurement is performed after correcting the uneven density distribution of the developer (see, for example, Patent Document 3). According to this configuration, it is supposed that accurate toner concentration measurement is possible. A stirrer plate larger than the others is provided at a location corresponding to the toner density sensor between the pitches of the screw, and this stirrer plate allows the ratio of the developer amount gathered in the axial direction to be collected in the axial direction rather than the amount of developer proceeding in the axial direction. A configuration is known in which the developer surface is increased only in the vicinity where the toner density sensor is installed by increasing the size (for example, see Patent Document 4). According to this configuration, the developer surface is increased in this way, and the layer thickness of the developer that is the detection target of the density sensor is sufficiently secured, so that accurate toner density measurement can be performed. . Compared with the screw pitch near the density sensor, the screw pitch near the replenishing port where the toner from the toner replenishing part is replenished is increased to increase the flow rate of the developer around the replenishing part, and near the density sensor. (See, for example, Patent Document 5). According to this configuration, since the developer surface is low in the vicinity of the replenishing portion, the replenished toner is not mixed with the developer and does not float on the surface of the agent, improving the agitation and improving the vicinity of the density sensor. However, since the developer surface can be raised, it is said that accurate toner concentration measurement is possible.
[0005]
However, each of the above-described configurations has a problem that the toner density measurement accuracy cannot be sufficiently obtained by the density sensor. That is, the density sensor of each configuration is provided fixed to the wall side that forms a path for transporting the developer, and detects the outer peripheral side of the flow of the transported developer. For this reason, there are frequent opportunities for the density sensor to detect a portion near the wall where a component with little mixing of toner and carrier is offset or a portion where the concentration remains unchanged even after the toner is replenished. . Therefore, a measured value of the toner density that fluctuates by a certain width can be obtained. In particular, when the toner density is set to a high density, the fluctuation range of the measured value tends to increase. As a result, the toner density control becomes unstable due to fluctuations in the measured value, resulting in a situation in which the formed image has excessive or insufficient image density and image quality deteriorates. There is a fear.
[0006]
On the other hand, downsizing of the image forming apparatus is desired in order to cope with space saving as a recent trend. For this reason, by arranging various sensors in each unit and fusing them with other functional parts, the space for functional parts is also used as the space for sensors, and as a result, the space for sensors is reduced. Reduction is required.
[0007]
[Patent Document 1]
Japanese Patent No. 2864182
[Patent Document 2]
JP 7-271174 A
[Patent Document 3]
Japanese Patent Laid-Open No. 7-1344887
[Patent Document 4]
JP 2001-343825 A
[Patent Document 5]
JP 2001-209240 A
[0008]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide an image forming apparatus that solves the conventional problems as described above, can improve the measurement accuracy of the toner density of the developer, and can reduce the size of the apparatus.
[0009]
[Means for Solving the Problems]
In order to achieve the object, the invention described in claim 1 comprises a latent image carrier and a developing device for developing the latent image of the latent image carrier, and the developing device. Is , A two-component developer consisting of toner and carrier An accommodating portion that can be accommodated and replenished with toner from the toner replenishing portion, and is placed opposite to the latent image carrier to carry the developer. An agent carrier; In the conveyance path provided in the storage unit, Transport the developer In the agent carrier A transport supply member to supply The two components A density sensor that detects the toner density of the developer And Possess The toner is replenished from the toner replenishing unit to the storage unit based on the toner density measured by the density sensor, so that the ratio of the toner and the carrier is kept substantially constant In the image forming apparatus, In the developing device, The conveyance supply member As the first transport supply member and the second transport supply member, the first transport supply member and the second transport supply member are respectively parallel to the axis of the agent carrier. It has a rotating shaft and a spiral blade formed on the rotating shaft. The first transport supply member is disposed on the toner replenishing portion side of the transport path, and the second transport supply member is disposed in the vicinity of the agent carrier on the transport path. The first transport supply member and the second transport supply member are rotated in opposite directions to rotate and circulate in the transport path in one direction while stirring the developer along the axial direction of the agent carrier. Configured to supply the developer to the agent carrier, The concentration sensor is Second Rotation axis of conveyance supply member Up It is provided in.
[0010]
The invention described in claim 2 A latent image carrier and a developing device for developing the latent image of the latent image carrier are provided. The developing device contains a two-component developer composed of toner and carrier and can be replenished with toner from a toner replenishing portion. A container, a developer carrier that is installed opposite to the latent image carrier, and carries the developer, and conveys the developer in a conveyance path provided in the container, to the agent carrier. A conveyance supply member for supplying the toner, and a density sensor for detecting the toner concentration of the two-component developer; and supplying toner from the toner replenishing unit to the housing unit based on the toner concentration measured by the density sensor; In the image forming apparatus configured to keep the ratio to the carrier substantially constant, the developing device is provided with a first transport supply member and a second transport supply member as the transport supply member. First transport supply The material and the second conveyance supply member are each formed in a screw shape having a rotation axis parallel to the axis of the agent carrier and a spiral blade formed on the rotation axis. The supply member is disposed on the toner replenishing portion side of the conveyance path, and the second conveyance supply member is disposed in proximity to the agent carrier on the conveyance path, and the first conveyance supply member and the second conveyance supply are arranged. The members are rotated in opposite directions to rotate and circulate in the transport path in one direction while stirring the developer along the axial direction of the agent carrier to supply the developer to the agent carrier. The concentration sensor is provided on the spiral blade of the second transport supply member. It is characterized by that.
[0011]
Claim 3 The invention described in claim 1 Or 2 The developing device has a doctor member that regulates the amount of the agent carrier.
[0012]
Claim 4 The invention described in claim 1 to claim 1 3 In any of the above, the density sensor transmits the detected toner density wirelessly.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating the overall configuration of the image forming apparatus according to the first embodiment, FIG. 2 is a side view illustrating the overall configuration of the conveyance supply member, and FIG. FIG. 3 is a perspective view schematically showing a developer circulation path.
[0016]
As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment includes a photosensitive member 2 as an image carrier, a charging roller (not shown) that uniformly charges the photosensitive member 2, and the photosensitive member 2 by exposure. A writing means (not shown) for forming an electrostatic latent image thereon, a developing device 3 for developing the electrostatic latent image to visualize it as a toner image, and a transfer means 4 for transferring the toner image on the photoreceptor 2 to a sheet. And a fixing device (not shown) for fixing the toner image to the paper.
[0017]
The developing device 3 includes a developing sleeve 6 serving as a developer carrying member disposed opposite to the photosensitive member 2, a storage unit 7 that stores a two-component developer D composed of toner and carrier (magnetic particles), A toner replenishing unit (not shown) that replenishes toner in the housing unit 7, a first transport supply member 8 that stirs and mixes the toner replenished in the housing unit 7 with the carrier, transports the toner to the developing sleeve 6 as a developer D, and A density sensor 11 that mainly includes a second conveyance supply member 9 and a doctor blade member 10 that regulates the amount of agent on the developing sleeve 6, and measures the toner concentration of the developer D on the second conveyance supply member 9. Is provided.
[0018]
The first transport supply member 8 and the second transport supply member 9 have rotating shafts 8a and 9a and spiral blades 8b and 9b formed on the rotating shafts 8a and 9a, respectively, 7 is accommodated in the recess formed in the recess 7 so that the rotation shafts 8a and 9a are parallel to each other and can be rotationally driven, and the second conveyance supply member 9 is disposed below the developing sleeve 6 so as to face the lower side. Therefore, the developer D is conveyed and supplied by the first and second conveying and supplying members 8 and 9 while being stirred in the axial direction of the developing sleeve 6.
[0019]
That is, as shown in FIG. 2, the first and second transport supply members 8 and 9 are spirally formed in the same direction of rotation with the blades 8b and 9b on the rotary shafts 8a and 9a each having a predetermined shaft diameter. Is formed. Accordingly, a spiral continuous surface is formed by the blades 8a and 9b, and the continuous surface is set to have the same predetermined pitch and ensure the same outer diameter. As shown in FIG. 3, gears 8c and 9c are provided at one end portions of the rotary shafts 8a and 9a of the first and second transport supply members 8 and 9, and these gears 8c and 9c are electrically driven. It meshes with the final output gear 12a of the reduction gear train 12 driven by a motor or the like. Accordingly, the first and second transport supply members 8 and 9 are rotationally driven in opposite directions to transport the developer D in the opposite direction of the axial direction.
[0020]
That is, a space between the first transport supply member 8 and the second transport supply member 9 is partitioned by a partition wall (not shown) included in the housing portion 7, and the first and second transport supply members 8, With the rotational drive of 9, the developer D is transported in the respective axial directions. A notch (not shown) is formed in the partition wall located at the front and rear end portions in the axial direction of the housing portion 7 so that the developer D can be transferred from one to the other through the notch. That is, the developer D is transported while being stirred along the axial direction from the front side of the rotation shaft 8a of the first transport supply member 8 toward the back side, and on the back side through a notch not shown. Delivered to the second transport and supply member 9. Next, the developer D is transported while being stirred along the axial direction from the back side to the near side of the rotation shaft 9a of the second transport supply member 9, and is transferred to the developing sleeve 6 in the middle of this transport path. A developer D having a predetermined toner concentration is supplied, is delivered to the first transport supply member 8 through a notch portion (not shown) on the near side, and is transported by the first transport supply member 8 again. As described above, the developer D circulates in a certain direction along a path formed in a substantially square shape as indicated by an arrow in FIG.
[0021]
As shown in FIG. 4A, a concentration sensor 11 is provided on the rotation shaft 9 a of the second transport supply member 9. The density sensor 11 detects the toner density of the developer D in the container 7 using magnetism or the like. The sensor surface 11a of the concentration sensor 11 is provided so as to slightly protrude from the peripheral surface of the rotating shaft 9a, and the sensor surface 11a is not disposed in the recess. This prevents the developer D from staying on the sensor surface 11a.
[0022]
The location where the density sensor 11 is installed on the second conveyance supply member 9 is the above-described developer D circulation path, and sufficient agitation is provided downstream of the location A where toner is supplied by a toner supply unit (not shown). Can be selected within the range on the circulation path from such a location to the location immediately before the toner replenishment. In particular, for example, the density sensor 11 may be provided in the second transport and supply member 9 so as to be the location B immediately before the toner supply location. Therefore, in this case, since the density sensor 11 is installed at the location B immediately before the toner is replenished, the toner density of the developer D immediately before the toner is replenished, that is, in a state where the toner is consumed by the developing sleeve 6. Therefore, it is possible to accurately grasp the necessary toner replenishment amount. The density sensor 11 is electrically connected to the main body side of the image forming apparatus 1 through a rotary contact 13.
[0023]
That is, as shown in FIG. 4B, the rotation shaft 9a of the conveyance supply member 9 is formed in a hollow shape, and passes through the hollow portion to supply the power line 14a, the ground line 14b, and the measurement signal line from the concentration sensor 11. 14c is installed toward one end of the rotary shaft 9a, and a rotary contact 13 is provided at the end of the shaft. The rotary contact 13 includes an end face member 15 provided on the conveyance supply member 9 side, and a main body side fixing member 16 disposed to face the end surface member 15, and ring-shaped contact terminals 15a, 15b, 15c. Are provided on the end face member 15, and pin-shaped contact terminals 16 a, 16 b, 16 c that are in contact with the ring-shaped contact terminals 15 a, 15 b, 15 c are provided on the fixing member 16. That is, the end face member 15 is formed in a disk shape from a non-conductive material, is concentrically mounted on the shaft end of the rotating shaft 9a, and is rotated by the rotation of the rotating shaft 9a. The end face member 15 has a conductive contact terminal 15a formed in a circular shape with a predetermined radius at the center thereof, and conductive contact terminals 15b and 15c formed in a ring shape having a different radius concentrically with the center. A power line 14a, a ground line 14b, and a measurement signal line 14c from the concentration sensor 11 are connected to the contact terminals 15a, 15b, and 15c, respectively. On the other hand, the fixing member 16 is formed in a disk shape from a non-conductive material, and pin-shaped contact terminals 16a, 16b, 16b are spaced at intervals corresponding to the contact terminals 15a, 15b, 15c of the end member 15 from the center toward the outer periphery. The contact terminals 16a, 16b, and 16c are respectively provided with predetermined wirings connected to a controller and a power source (not shown) related to toner density control (not shown) installed on the main body side, and are connected to the contact terminals 16a. Is supplied with a drive current of 5V voltage from the power source. Therefore, even if the end face member 15 is rotated in accordance with the transport operation of the second transport supply member 9, the pin-shaped contact terminals 16 a, 16 b, 16 c on the fixing member 16 side respectively correspond to the corresponding end face member 15. Since the ring-shaped contact terminals 15a, 15b, and 15c are moved around the periphery of the contact terminals 15a, 15b, and 15c, electrical connection is maintained. For this reason, even if the second conveyance supply member 9 is rotationally driven, a driving current is supplied from the main body side of the image forming apparatus 1 to the density sensor 11 via the rotary contact 13 and the toner from the density sensor 11 is supplied. A measurement signal indicating the concentration can be acquired on the main body side.
[0024]
According to the first embodiment configured as described above, as shown in the graph of FIG. 5, the measurement accuracy of the toner density can be improved. That is, the average particle diameter of the toner is 9.5 μm, the average particle diameter of the carrier is 50 μm, the fluctuation range of the toner density is 1 wt% to 9 wt% (wt%), and the first and second transport supply members 8 and 9 are rotated. Under the condition that the number is set to 100 rpm to 500 rpm, the toner density is measured by the density sensor of the conventional configuration and the density sensor 11 of the first embodiment, and the toner density measured by these density sensors is actually measured. The toner density was graphed in comparison with the toner density. In the conventional configuration, as shown by a broken line in FIG. 5, it can be understood that the variation width of the measurement value by the density sensor 11, that is, the fluctuation width increases as the toner density increases. This is because when the toner concentration is high, the fluidity of the developer D decreases, so that the developer D stays between the blades 9b of the first and second transport and supply members 8 and 9 and the wall portion of the accommodating portion 7. It is because it becomes easy to generate | occur | produce. That is, in the conventional density sensor that is fixedly installed on the wall side of the housing portion 7, there are many opportunities to detect such a stay portion, and the toner concentration is high. The deviation of is increasing. For this reason, the fluctuation range of the toner density detected by the conventional density sensor is expanded.
[0025]
On the other hand, according to the configuration of the first embodiment, the fluctuation range of the toner density measurement value can be reduced to 50% or less compared to the conventional configuration. That is, by providing the density sensor 11 on the rotation shaft 9 a of the second transport supply member 9, the detection location of the density sensor 11 is located on the inner side of the flow in which the developer away from the wall portion of the storage unit 7 is transported. In addition, the detection range of the density sensor 11 is expanded because it is moved on the circumference of the outer diameter of the rotating shaft 9a instead of the conventional fixed point. For this reason, the opportunity to detect the part where the toner density is offset or the part where the toner density is not changed even if the toner is replenished due to less agitation is reduced. It is possible to detect the agent D as a main component, and to measure the toner density using a detection range as a position crossing this flow. As described above, since the entire toner concentration of the developer D actually transported to the developing sleeve 6 and used by the developing sleeve 6 can be acquired, the toner concentration can be detected appropriately. As a result, since the control for adjusting the toner density of the developer D can be performed stably and appropriately, the image quality can be improved. On the other hand, since the density sensor 11 is provided in the conveyance supply member 9 accommodated in the accommodating part 7, the density sensor 11 is disposed in the deep part of the apparatus configuration, and the density sensor 11 is sufficiently protected. Can be secured. Further, when the developing sleeve 6, the accommodating portion 7, the toner replenishing portion and the like are integrated as a unit and this unit is replaced by the consumption of the total amount of toner, the density is placed on the main body side of the conventional image forming apparatus 1. Unlike the configuration in which the sensor is provided, the density sensor 11 is also replaced with a new one at the same time. For this reason, the sensor performance is prevented from deteriorating due to deterioration over time and the like, and highly accurate and stable concentration measurement can be performed. In particular, in the case of this configuration, it is possible to select an optimum density sensor 11 for each unit according to the carrier replenished by the toner replenishing unit, the toner component characteristics, the toner density setting conditions, and the like. Also, the measurement accuracy can be improved.
[0026]
Next explained is the second embodiment of the invention. In the image forming apparatus of this embodiment, as shown in FIG. 6, a density sensor 17 is provided on the blade 9b, and an intermediate region between the rotationally driven conveyance supply member 9 side and the fixed accommodating portion 7 side is provided. The toner density is measured. Note that members having the same configurations as those of the first embodiment are denoted by the same reference numerals, and the description will be simplified.
[0027]
That is, the first and second transport and supply members 8 and 9 have the rotation shafts 8a and 9a formed with a relatively large diameter, and spiral blades 8b and 9b formed integrally therewith. Since the blades 8b and 9b serve as reinforcing ribs for the rotary shafts 8a and 9a, the rigidity as the shaft is sufficiently ensured. However, since the axial length is relatively long and a large load is applied to transport the powder developer D in the axial direction, the shaft may be twisted. For this reason, since the outermost peripheral ends of the rotating blades 8b and 9b are slightly displaced in the radial direction of the shaft, in order to avoid the outer peripheral end from contacting the wall portion of the accommodating portion 7, the distance between both As shown in FIG. 7B, a predetermined gap σ is secured in advance.
[0028]
Therefore, the larger the gap σ, the larger the space away from the contact area with the transport supply member, and the more developer D stays in the gap σ. For this reason, as shown in the graph of FIG. 7, the correspondence between the toner density measured by the density sensor 11 provided on the rotating shaft 9a and the toner density of the developer D staying in the gap σ is a directly proportional relationship. It tends to deteriorate. That is, as the gap σ increases, the difference between the toner density detected by the density sensor near the rotation shaft 9a of the transport supply member 9 and the toner density detected by the density sensor outside the blade 9b of the transport supply member 9 increases. Become. For this reason, neither the density sensor 11 provided on the rotating shaft 9a nor the conventional density sensor provided on the wall of the container 7 can measure the actual toner density of the developer D. On the other hand, in order to reduce the gap σ, increasing the rigidity strength of the shaft of the transport supply member 9 is due to an increase in cost for increasing the strength of the transport supply member 9 and weight of the transport supply member 9 due to the increase in strength. The structure of each part of the apparatus needs to be strengthened, and the energy consumption for rotationally driving the transport supply member 9 is increased, which is not suitable for the situation where cost reduction and downsizing are required.
[0029]
Therefore, in the second embodiment, by providing the density sensor 17 on the blade 9b of the conveyance supply member 9, the rotation axis 9a of the conveyance supply member 9 and the wall portion of the accommodating portion 7 in the radial direction thereof. The toner density in the middle region is detected to obtain a measurement value intermediate between the two. That is, the density sensor 17 is installed on the surface of the blade 9b on the side that presses and conveys the developer D, at a position approximately in the middle of the outer peripheral radius of the blade 9b in the radial direction of the rotating shaft 9a. The density sensor 17 is wired in the same manner as in the first embodiment, and is connected to the main body side of the image forming apparatus 1 through the same rotary contact 13. A sensor surface 17a of the density sensor 17 is provided so as to slightly protrude from the outer surface of the blade 9b so that the developer D does not stay on the sensor surface 17a.
[0030]
As described above, according to the second embodiment, by providing the density sensor 17 on the blade 9b of the transport supply member 9, the gap σ formed between the blade 9b in the transport operation state and the side wall of the storage unit 7 is formed. For example, even in the case of a configuration of 1 mm or more, the toner density of the developer D can be accurately measured with a small fluctuation range, and the toner density control can be improved, so that the image quality of the resulting image is stabilized and improved. It becomes possible to make it. That is, the toner density intermediate between the toner density of the developer D staying in the vicinity of the wall of the outer accommodating portion 7 from the conveyance supply member 9 and the toner density of the developer D being stirred and moved near the rotating shaft 9a. Can be measured. On the other hand, the detection range of the concentration sensor 11 of the first embodiment is a range on the circumference defined by the outer peripheral radius of the rotary shaft 9a, whereas the detection of the concentration sensor 17 of the second embodiment. Since the density sensor 17 is provided substantially in the radial direction of the blade 9b, the range is a circumferential range defined by a larger radius than in the first embodiment. Further, for example, a conventional density sensor is provided on the wall portion of the container 7, and the direction of the sensor surface is a plane parallel to the flow direction of the developer. That is, the density sensor detects a certain linear range. On the other hand, the density sensor 17 of the second embodiment is provided on the blade 9b of the conveyance supply member 9, and the sensor surface is oblique to the transverse section intersecting with the flow direction of the developer similarly to the surface of the blade 9b. Therefore, the density sensor 17 detects a conical belt-shaped range with respect to this flow. For this reason, the detection range handled by the density sensor 17 can be greatly expanded, and the total toner density of the developer can be grasped more accurately. Further, since the density sensor 17 is installed on the surface of the blade 9b on the side where the developer D is pressed and conveyed, the sensor surface 17a and the developer can be sufficiently brought into contact with each other. The accuracy can be improved.
[0031]
Next explained is the third embodiment of the invention. In the image forming apparatus according to this embodiment, as shown in FIG. 8, the density sensor 19 is made wireless so that no sensor wiring is required. Note that members having the same configurations as those of the first embodiment are denoted by the same reference numerals, and the description will be simplified.
[0032]
That is, the concentration sensor 19 is configured to be installed on the rotating shaft 9a of the second transport and supply member 9 as in the first embodiment, and is provided so as to protrude from the peripheral surface of the rotating shaft 9a. Sensor surface 19a. The density sensor 19 includes a power supply unit (not shown) made of a battery and a wireless transmitter, and a wireless receiver (not shown) is installed on the main body side of the image forming apparatus. Therefore, the density sensor 11 enables the toner density measurement operation independent from the outside, and transmits the measured toner density to the main body side of the image forming apparatus by weak radio waves.
[0033]
According to the third embodiment configured as described above, since the density sensor 19 is wirelessly operated as an independent power source, it is not necessary to perform wiring for the density sensor 19, and in addition, the first and the first described above are used. It is also possible to eliminate the rotary contact 13 that electrically connects between the conveyance supply member 9 that is rotationally driven and the fixed apparatus main body side that the second embodiment has. As a result, the configuration related to the density sensor 19 is simplified, and the cost can be reduced. Since the independence of the density sensor 19 as a single unit is ensured, the density sensor 19 can be handled easily, and the work of attaching and removing the density sensor 19 for maintenance and repair can be simplified. On the other hand, since the wireless communication is used for communication between the density sensor 19 and the apparatus main body, the arrangement of the concentration sensor 19 on the conveyance supply member 9 side and the wireless receiver on the apparatus main body side can be freely set within this wireless reachable range. Since it can be selected, the degree of freedom of design such as layout can be improved.
[0034]
In each of the above-described embodiments, the transport supply members 8 and 9 are formed on the rotary shafts 8a and 9a with continuous surfaces having the same outer peripheral radius secured at the same pitch by the spiral blades 9a and 9b. However, the present invention is not limited to this, and it is also possible to form an intermittent surface, change the pitch or outer radius at a predetermined location, or provide a large number of independent screw blades. Good. On the other hand, the density sensors 11, 17, and 19 are provided on the members already provided in the transport supply members 8 and 9, but a dedicated member for the density sensor is newly provided. It is good also as a structure which installed the density | concentration sensor. Therefore, according to this configuration, the direction of the sensor surface of the density sensor is made different from the direction of the outer peripheral surface of the rotation shaft 9a of the feeding / supplying member 9 and the surface of the blade 9b, and the developer agitation state on the conveyance path, etc. Therefore, the toner density measurement accuracy can be further improved.
[0035]
【The invention's effect】
According to the invention of claim 1, A latent image carrier and a developing device for developing the latent image of the latent image carrier are provided. The developing device contains a two-component developer composed of toner and carrier and can be replenished with toner from a toner replenishing portion. A container, a developer carrier that is installed opposite to the latent image carrier, and carries the developer, and conveys the developer in a conveyance path provided in the container, to the agent carrier. A conveyance supply member for supplying the toner, and a density sensor for detecting the toner concentration of the two-component developer; and supplying toner from the toner replenishing unit to the housing unit based on the toner concentration measured by the density sensor; In the image forming apparatus configured to keep the ratio to the carrier substantially constant, the developing device is provided with a first transport supply member and a second transport supply member as the transport supply member. First transport supply The material and the second conveyance supply member are each formed in a screw shape having a rotation axis parallel to the axis of the agent carrier and a spiral blade formed on the rotation axis. The supply member is disposed on the toner replenishing portion side of the conveyance path, and the second conveyance supply member is disposed in proximity to the agent carrier on the conveyance path, and the first conveyance supply member and the second conveyance supply are arranged. The members are rotated in opposite directions to rotate and circulate in the transport path in one direction while stirring the developer along the axial direction of the agent carrier to supply the developer to the agent carrier. The concentration sensor is provided on the rotating shaft of the second conveyance supply member. Therefore, the location detected by the density sensor Circulate in the transport path It is inside the flow of developer to be conveyed, and the conveyance supply member is conveyed , Rotary stirring Always with developer during operation The measurement location of the concentration sensor is It will be displaced relatively. For this reason, A density sensor can detect the overall toner density in the developer flow, Opportunities to detect a portion where the concentration is shifted, such as a staying portion of the developer, are reduced, and a measurement value of the toner concentration with a small fluctuation range reflecting the toner concentration of the entire developer can be obtained. As described above, since the toner density can be detected appropriately, the toner density of the developer can be controlled stably and appropriately. As a result, it is possible to prevent scumming of the formed image and excessive or lowering of the image density, and it is possible to stabilize and improve the image quality. Furthermore, since the installation space for the density sensor provided in the members around the conventional conveyance supply member is reduced, the apparatus can be miniaturized and space can be saved.
Also, Concentration sensor Second By providing it on the rotation shaft of the transport supply member, the toner concentration of the developer that has been transported by stirring and transported by the transport supply member can be detected. For this reason, detection of the staying part of the developer is eliminated, and erroneous detection can be avoided in advance. As a result, the toner density of the developer can be accurately measured and toner density control can be optimized, so that the image quality of the image can be stabilized and improved.
[0036]
Claim 2 According to the invention of A latent image carrier and a developing device for developing the latent image of the latent image carrier are provided. The developing device contains a two-component developer composed of toner and carrier and can be replenished with toner from a toner replenishing portion. A container, a developer carrier that is installed opposite to the latent image carrier, and carries the developer, and conveys the developer in a conveyance path provided in the container, to the agent carrier. A conveyance supply member for supplying the toner, and a density sensor for detecting the toner concentration of the two-component developer; and supplying toner from the toner replenishing unit to the housing unit based on the toner concentration measured by the density sensor; In the image forming apparatus configured to keep the ratio to the carrier substantially constant, the developing device is provided with a first transport supply member and a second transport supply member as the transport supply member. First transport supply The material and the second conveyance supply member are each formed in a screw shape having a rotation axis parallel to the axis of the agent carrier and a spiral blade formed on the rotation axis. The supply member is disposed on the toner replenishing portion side of the conveyance path, and the second conveyance supply member is disposed in proximity to the agent carrier on the conveyance path, and the first conveyance supply member and the second conveyance supply are arranged. The members are rotated in opposite directions to rotate and circulate in the transport path in one direction while stirring the developer along the axial direction of the agent carrier to supply the developer to the agent carrier. The concentration sensor is provided on the spiral blade of the second transport supply member. Therefore, the location detected by the density sensor Circulate in the transport path It is inside the flow of developer to be conveyed, and the conveyance supply member is conveyed , Rotary stirring Always with developer during operation The measurement location of the concentration sensor is It will be displaced relatively. For this reason, A density sensor can detect the overall toner density in the developer flow, Opportunities to detect a portion where the concentration is shifted, such as a staying portion of the developer, are reduced, and a measurement value of the toner concentration with a small fluctuation range reflecting the toner concentration of the entire developer can be obtained. As described above, since the toner density can be detected appropriately, the toner density of the developer can be controlled stably and appropriately. As a result, it is possible to prevent scumming of the formed image and excessive or lowering of the image density, and it is possible to stabilize and improve the image quality. Furthermore, since the installation space for the density sensor provided in the members around the conventional conveyance supply member is reduced, the apparatus can be miniaturized and space can be saved.
Also, Concentration sensor Second Conveying supply member Spiral Feather Up Therefore, it is possible to detect the toner density in an intermediate region between the outer peripheral portion of the transport supply member and the vicinity of the rotation shaft of the transport supply member. Therefore, it is possible to measure an intermediate toner concentration between the toner concentration of the developer staying on the outer peripheral side of the transport supply member and the toner concentration of the developer stirred and transported near the rotation shaft. A measurement value reflecting both toner densities can be obtained. As a result, even in a configuration in which the developer stays much, the toner concentration of the developer can be measured with high accuracy, so that the control for adjusting the toner concentration is stabilized and facilitated, and the image quality can be improved.
[0037]
Claim 3 According to the invention, the detection accuracy of the toner density by the density sensor is improved, and the developing device has the doctor member that regulates the amount of the agent carrier, so that the toner to the developer The replenishment amount is optimized, and excess toner consumption can be eliminated. Therefore, the number of images that can be formed can be increased, and the performance of the image forming apparatus can be improved.
[0038]
Claim 4 According to the invention, since the toner density detected by the density sensor is transmitted wirelessly, the wiring for the density sensor is not required, the configuration and assembly work are simplified, and the cost is reduced. Can do.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a side view showing the overall configuration of the transport and supply member.
FIG. 3 is a schematic perspective view illustrating the image forming apparatus according to the first embodiment and illustrating a state in which a developer circulates.
4A and 4B illustrate the concentration sensor according to the first embodiment, in which FIG. 4A is a perspective view showing a state where the sensor is installed on a rotating shaft, FIG. 4B is a longitudinal sectional view showing a wiring state, and FIG. It is a perspective view of a rotation type contact.
FIG. 5 is a graph comparing the measurement results obtained by the density sensor of the first embodiment and the conventional density sensor.
6A and 6B illustrate a concentration sensor according to a second embodiment of the present invention, in which FIG. 6A is a perspective view showing a state in which the concentration sensor is installed on a blade, and FIG. 6B is a conveyance supply member illustrating a gap σ. FIG.
FIG. 7 is a graph for explaining the second embodiment and comparing the measurement results of the toner density in the vicinity of the rotation axis of the conveyance supply member and in the vicinity of the wall portion of the accommodating portion on the outside of the conveyance supply member;
FIG. 8 is a perspective view showing a concentration sensor according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive body (image carrier)
3 Developing device 4 Transfer means
6 Developer sleeve (agent carrier) 7 Developer container
8 1st conveyance supply member 8a Rotating shaft of 1st conveyance supply member
8b Blades of the first conveyance supply member 9 Second conveyance supply member
9a Rotation shaft of the second conveyance supply member 9b Blade of the second conveyance supply member
11, 17, 19 Density sensor
11a, 17a, 19a Sensor surface of concentration sensor
D Developer

Claims

A latent image carrier and a developing device for developing the latent image of the latent image carrier are provided. The developing device contains a two-component developer composed of toner and carrier and can be replenished with toner from a toner replenishing portion. A container, a developer carrier that is installed opposite to the latent image carrier , and carries the developer, and conveys the developer in a conveyance path provided in the container, to the agent carrier. and conveying supply member for supplying said and a concentration sensor for detecting the toner density of the two-component developer, the toner of the toner from the toner supply unit based on the measured toner concentrations of the density sensor and supplied to the receiving portion In the image forming apparatus configured to keep the ratio with the carrier substantially constant ,
The developing device is provided with a first transport supply member and a second transport supply member as the transport supply member, and the first transport supply member and the second transport supply member are respectively provided with the agent carrying member. and a rotational axis parallel to the axis of the body, is formed in a screw shape to have a and the rotary shaft formed spiral blade, the first conveying supply member, the toner supply section side of the conveying path The second transport supply member is disposed in proximity to the agent carrier of the transport path, and rotates the first transport supply member and the second transport supply member in opposite directions to each other. The developer is supplied to the agent carrier by rotating and circulating in the transport path in one direction while stirring the developer along the axial direction of image type, characterized in that provided on the rotary shaft of the conveying feed member Apparatus.

A latent image carrier and a developing device for developing the latent image of the latent image carrier are provided. The developing device contains a two-component developer composed of toner and carrier and can be replenished with toner from a toner replenishing portion. A container, a developer carrier that is installed opposite to the latent image carrier , and carries the developer, and conveys the developer in a conveyance path provided in the container, to the agent carrier. A conveyance supply member for supplying the toner, and a density sensor for detecting the toner concentration of the two-component developer; and supplying toner from the toner replenishing unit to the housing unit based on the toner concentration measured by the density sensor; In the image forming apparatus configured to keep the ratio with the carrier substantially constant ,
The developing device is provided with a first transport supply member and a second transport supply member as the transport supply member, and the first transport supply member and the second transport supply member are respectively provided with the agent carrying member. and a rotational axis parallel to the axis of the body, is formed in a screw shape to have a and the rotary shaft formed spiral blade, the first conveying supply member, the toner supply section side of the conveying path The second transport supply member is disposed in proximity to the agent carrier of the transport path, and rotates the first transport supply member and the second transport supply member in opposite directions to each other. The developer is supplied to the agent carrier by rotating and circulating in the transport path in one direction while stirring the developer along the axial direction of characterized in that provided on the blade spiral conveyance supplying member Image forming apparatus.

The image forming apparatus according to claim 1, wherein the developing device includes a doctor member that regulates the amount of the agent carrier.

The density sensor, the image forming apparatus according to any one of claims 1 sending the toner concentration detected by the wireless 3.