JP2004101889A - Color slurring correcting device for color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accurate color slurring correcting device capable of always performing color slurring correction in appropriate timing without causing the increase of downtime more than necessary and the fluctuation of color slurring exceeding tolerance even when the relation of the fluctuation of the detected temperature by a temperature sensor inside an image forming apparatus to the fluctuation of color slurring differs according to various printing states. <P>SOLUTION: The color slurring correcting device has a 1st temperature detection means for detecting temperature near an image forming means or an endless belt or a transfer means and a 2nd temperature detection means for detecting in-machine temperature other than the temperature detected by the 1st temperature detection means. By deciding the timing to actuate a color slurring correction means based on a temperature difference between the 1st and the 2nd temperature detection means at the time of actuating the color slurring correction means and the fluctuation of the detected temperature by at least either temperature detection means, color slurring correcting operation is always performed in the appropriate timing without causing the increase of downtime more than necessary and the fluctuation of the color slurring exceeding the tolerance even when the relation of the fluctuation of the detected temperature by the temperature sensor inside the apparatus to the fluctuation of the color slurring differs according to the various printing states. <P>COPYRIGHT: (C)2004,JPO

Description

となる。
【００２３】
主走査方向に関して、左右各々の各色の色ずれ量δｅｍｆ、δｅｍｒは、
ｄｍｆＢｋ＝ｖ＊（ｔｍｆ１−ｔｓｆ１）　（式４）
ｄｍｆＹ　＝ｖ＊（ｔｍｆ２−ｔｓｆ２）　（式５）
ｄｍｆＭ　＝ｖ＊（ｔｍｆ３−ｔｓｆ３）　（式６）
ｄｍｆＣ　＝ｖ＊（ｔｍｆ４−ｔｓｆ４）　（式７）
と
ｄｍｒＢｋ＝ｖ＊（ｔｍｒ１−ｔｓｒ１）　（式８）
ｄｍｒＹ　＝ｖ＊（ｔｍｒ２−ｔｓｒ２）　（式９）
ｄｍｒＭ　＝ｖ＊（ｔｍｒ３−ｔｓｒ３）　（式１０）
ｄｍｒＣ　＝ｖ＊（ｔｍｒ４−ｔｓｒ４）　（式１１）
から、
δｅｍｆＹ＝ｄｍｆＹ−ｄｍｆＢｋ　　　　（式１２）
δｅｍｆＭ＝ｄｍｆＭ−ｄｍｆＢｋ　　　　（式１３）
δｅｍｆＣ＝ｄｍｆＣ−ｄｍｆＢｋ　　　　（式１４）
と
δｅｍｒＹ＝ｄｍｒＹ−ｄｍｒＢｋ　　　　（式１５）
δｅｍｒＭ＝ｄｍｒＭ−ｄｍｒＢｋ　　　　（式１６）
δｅｍｒＣ＝ｄｍｒＣ−ｄｍｒＢｋ　　　　（式１７）
となり、式１２〜式１７の計算結果の正負からずれ方向が判断でき、δｅｍｆから書き出し位置のずれを検出し、δｅｍｒ−δｅｍｆから主走査幅のずれを検出し、それぞれ補正する。
【００２４】
搬送ベルト上に色ずれ検出パターンを形成して各種調整を実施する。この色ずれ補正の実行タイミングは、電源ＯＮ時や、消耗品である感光ドラム等の画像形成手段が抜き差しされた時や、装置内部に設置された温度センサの検出温度変動量等に応じて決定された時などである。
【００２５】
この中でも重要なのは、検出温度変動量等に応じて決定された色ずれ補正の実行タイミングである。
【００２６】
その理由は、色ずれの量は、概して温度変動に伴って変動するためである。
【００２７】
例えば、一般的なカラー画像形成装置においては、プリントを行っていると、記録材を搬送するベルトが定着器により温められ、さらに温められたベルトにより、ベルトが懸架されたローラが昇温する。
【００２８】
ローラは、薄いゴム層で表面が覆われており、温度が高くなるほどゴム層の厚さが増加する。そして、ベルトを駆動する駆動ローラの径が大きくなると、ベルトの速度が増加して、色ずれが発生する。
【００２９】
このように、検出温度変動量は、色ずれの変動量（以下色ずれ変動量という）と重要なつながりを持つ。
【００３０】
そこで、検出温度変動量等に応じて色ずれ補正の実行のタイミングを決定しているのである。
【００３１】
【発明が解決しようとする課題】
しかしながら、上記従来例では、以下のような欠点があった。
【００３２】
装置の設置環境の変動による温度の上昇や下降、および、プリント動作による装置内部の温度の上昇に対し、装置内部の温度センサの検出温度変動量と色ずれ変動量の関係は、装置内部に設置された１個の温度センサの検出温度変動量に基づいて色ずれ補正動作の実行のタイミングを決定した場合、必ずしも適切なタイミングで色ずれ補正動作が実行されなかった。
【００３３】
暫くの期間プリント動作を行わない状態からの温度変動による色ずれと、プリント動作を頻繁に行い、装置内部の温度がある程度上昇した状態からの温度変動による色ずれは、色ずれを発生させる要因および色ずれ変動量が異なる。すなわち、装置内部に設置された１個の温度センサの検出温度変動量に基づいて色ずれ補正動作を実行した場合、色ずれ補正動作の実行タイミングが遅れ、色ずれ変動量が許容量を越える場合や、逆に、必要以上に速いタイミングで色ずれ補正動作を実行し、連続プリント時のダウンタイム（プリント動作中断時間）が増加し、パフォーマンスの低下を招いていた。
【００３４】
本発明は上記のような課題を解消するためになされたもので、種々のプリント状態により装置内部の温度センサの検出温度変動量と色ずれ変動量の関係が異なる場合にも、必要以上のダウンタイムの増加や、許容量を越える色ずれ変動量の発生を防ぎ、常に適切なタイミングで色ずれ補正動作を実行する、高精度の色ずれ補正装置を提供することを目的とする。
【００３５】
【課題を解決するための手段】
このため、本発明においては、下記の各項（１）ないし（４）のいずれかに示すカラー画像形成装置の色ずれ補正装置を提供することにより、前記目的を達成しようとするものである。
【００３６】
（１）各々、光学部と潜像形成媒体を有する複数の画像形成手段と、前記複数の画像形成手段を順次通過する無端状ベルト手段と、形成された画像を、前記無端状ベルト手段上又は前記無端状ベルト手段上に保持されつつ搬送される記録材上に転写する複数の転写手段と、前記無端状ベルトを駆動する駆動手段と、前記無端状ベルト手段上に色ずれ検出用パターンを形成し、前記色ずれ検出用パターンの検出結果に基づき、電気的及び機械的に色ずれを補正する色ずれ補正手段と、を有するカラー画像形成装置の色ずれ補正装置において、前記画像形成手段、無端状ベルト手段、転写手段のうちの１つの手段の近傍の温度を検出する第１の温度検出手段と、前記第１の温度検出手段以外に前記カラー画像形成装置内の温度を検出する第２の温度検出手段と、前記第１と第２の温度検出手段の少なくとも一方の検出温度変動量に基づいて、前記色ずれ補正手段の作動タイミングを決定する作動タイミング決定手段と、を備えて成り、前記作動タイミング決定手段により、前記色ずれ補正手段の作動時の前記第１と第２の温度検出手段の検出温度に基づき、前記色ずれ補正手段の作動タイミングを可変制御することを特徴とするカラー画像形成装置の色ずれ補正装置。
【００３７】
（２）前記作動タイミング決定手段は、前記色ずれ補正手段の作動時の前記第１と第２の温度検出手段の検出温度差が小さい場合の方が大きい場合に比べ、前記第１又は第２の検出手段の検出温度変動量が少ないタイミングで色ずれ補正手段を作動させることを特徴とする、前項（１）記載のカラー画像形成装置の色ずれ補正装置。
【００３８】
（３）前記第１の温度検出手段は、前記無端状ベルト手段が懸架されたベルト駆動ローラの近傍の温度を検出することを特徴とする、前項（１）記載のカラー画像形成装置の色ずれ補正装置。
【００３９】
（４）前記第１と第２の温度検出手段の相対的な検出温度誤差補正値を保持する検出温度誤差補正値保持手段を有することを特徴とする、前項（１）記載のカラー画像形成装置の色ずれ補正装置。
【００４０】
上記構成において、種々のプリント状態により装置内部の温度センサの検出温度変動量と色ずれ変動量の関係が異なる場合にも、必要以上のダウンタイムの増加や、許容量を越える色ずれ変動量の発生を防ぎ、常に適切なタイミングで色ずれ補正動作を実行する。
【００４１】
【発明の実施の形態】
以下、本発明の実施の形態を複数の実施例に基づいて詳細に説明する。
【００４２】
なお、本実施例のカラー画像形成装置は、４色すなわち、イエローＹ、マゼンタＭ、シアンＣ、ブラックＢｋの画像形成手段を備えたカラー画像形成装置である。
【００４３】
（第１の実施例）
まず、図１〜図６を用いて、第１の実施例を説明する。
【００４４】
図１は、本発明の実施例に係る画像形成装置の全体を説明する図である。
【００４５】
１ａ、１ｂ、１ｃ、１ｄは、静電潜像を形成する潜像形成媒体である感光ドラム（ａ、ｂ、ｃ、ｄは各々Ｙ、Ｍ、Ｃ、Ｂｋ用を示す）、２ａ、２ｂ、２ｃ、２ｄは、画像信号に応じて露光を行い、感光ドラム１ａ〜１ｄ上に静電潜像を形成する光学部であるレーザスキャナ（ａ、ｂ、ｃ、ｄは各々Ｙ、Ｍ、Ｃ、Ｂｋ用を示す）で、感光ドラム１ａ〜１ｄと、レーザスキャナ２ａ〜２ｄとによって画像形成手段１０２ａ、１０２ｂ、１０２ｃ、１０２ｄを構成する。
【００４６】
３は、感光ドラム１ａ〜１ｄに形成されたトナー像を順次転写し搬送する無端状ベルト手段である中間転写ベルト、４は、モータとギア等からなる駆動手段１９ａと接続され、中間転写ベルト３を駆動するベルト駆動ローラ、５は、中間転写ベルト３の移動に従って回転し、且つ中間転写ベルト３に一定の張力を付与するベルト従動ローラ、６は、中間転写ベルト３によって搬送されたトナー像を用紙に転写する２次転写ローラ、７は用紙カセット、８は、用紙上に転写されたトナー像を熱で溶かし定着する定着器、９は、用紙の両面にプリントを行う為に用紙の表裏を逆転する両面ユニット、１０は、用紙を両面ユニット９に送る場合に搬送経路を切換えるフラッパ、１１は、中間転写ベルト３上に形成された色ずれ検知用パターンを検出する、中間転写ベルト３の両サイドに設けられた１対の光センサ、１２ａは、駆動ローラ４の近傍の温度を検出する第１の温度検出手段であるベルト駆動ローラ温度センサ、１３ａは、プリンタ装置内温度を検出する第２の温度検出手段である環境センサである。
【００４７】
１０３ａ、１０３ｂ、１０３ｃ、１０３ｄは、それぞれ形成された画像を中間転写ベルト３上に転写する転写手段である。
【００４８】
図２は、本発明の実施例に係る制御部の全体を説明する図である。
【００４９】
１４は、作像タイミング決定手段であって装置全体の制御管理をも行うＣＰＵ，１５は、プリンタとＰＣとの通信を司るホストＩ／Ｆ部、１６は、プリントデータ、各種パラメータ、各種情報等を保持するメモリ、１７は、ＰＣからプリンタに送られたプリントデータをプリンタエンジンの方式に適したデータに変換する画像制御部、１８は、プリンタ各部の状態を検出するセンサ制御部、１９は、プリンタエンジンのアクチュエータ類、レーザ、高圧電源等の駆動制御を司る駆動制御部、１９ａは、駆動制御部１９により、感光ドラム１ａ〜１ｄやベルト駆動ローラ４を駆動させる、モータやギア等からなる駆動手段である。
【００５０】
次に、画像形成装置の作用を説明する。
【００５１】
プリントデータが、ＰＣからホストＩ／Ｆ部１５を通ってプリンタに送られてくると、画像制御部１７にてプリントデータをプリンタエンジンの方式に適したデータに変換する。
【００５２】
そして、変換されたデータがメモリ１６に保持され、いわゆるプリント可能状態となると、駆動制御部１９により、モータやギア等からなる駆動手段１９ａが駆動され、この駆動手段１９ａと接続された、感光ドラム１ａ〜１ｄやベルト駆動ローラ４も駆動を開始する。
【００５３】
次に、各色の画像信号が各色のレーザスキャナ２ａ〜２ｄに送られ、感光ドラム１ａ〜１ｄ上に静電潜像が形成され、図示しない現像器でトナーが現像され、転写手段１０３ａ〜１０３ｄにより中間転写ベルト３上に転写される。
【００５４】
本実施例では、図１に示すように、Ｙ、Ｍ、Ｃ、Ｂｋの順に順次画像形成される。それと同時に、中間転写ベルト３上の画像位置とタイミングを合わせて、記録材である用紙が用紙カセット７から２次転写ローラ６に供給され、トナー像が用紙上に転写され、定着器８で熱によってトナー像が用紙上に定着され、外部へ排出される。
【００５５】
この間、センサ制御部１８により装置内部の様子が監視され、ＣＰＵ１４により全体が制御されている。
【００５６】
次に、図３〜図５を用いて、本発明の実施例の検出温度変動量と色ずれの関係を説明する。
【００５７】
図３〜図５の（ａ）は、時間経過に対する色ずれ変動量の推移を、（ｂ）は（ａ）と同じ時間経過に対する、温度変動の推移を示す。
【００５８】
２６ａ、２６ｂ、２６ｃは、後述する色ずれ要因に起因する色ずれ変動量を、２７ａ、２７ｂ、２７ｃは、後述する、２６ａ、２６ｂ、２６ｃとは異なる色ずれ要因に起因する色ずれ変動量を、２８ａ、２８ｂ、２８ｃは、各々、２６ａと２７ａ、２６ｂと２７ｂ、２６ｃと２７ｃの色ずれ要因を合わせたトータルの色ずれ変動量を示す。
【００５９】
２９ａ、２９ｂ、２９ｃは、ベルト駆動ローラ温度センサ１２ａの検出温度変動量を、３０ａ、３０ｂ、３０ｃは、環境センサ１３ａの検出温度変動量を示す。
【００６０】
領域ａ、領域ｂ、領域ｃは、後述する、温度変動量と色ずれ変動量の関係が異なる、複数の領域を示す。Δｃｐｒは、色ずれの許容量、Δｔ１、Δｔ１’、Δｔ２、Δｔ２’は、色ずれ変動量がΔｃｐｒ時のベルト駆動ローラ温度センサ１２ａの温度変動量を示す。
【００６１】
図３（ａ）、（ｂ）において、プリント動作により機内温度が上昇した場合の色ずれ変動量と温度変動量の関係を説明する。
【００６２】
画像形成装置は、プリント動作を行うと、定着器８及び図示しないモータ、回路等の動作により装置内温度が上昇する（機内昇温）。ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの検出温度変動量２９ａと３０ａは、プリント動作中の時間経過に対し、ほぼ一定の割合で上昇する。但し、定着器８により温められた中間転写ベルト３が懸架された、ベルト駆動ローラ４の近傍の温度を検出するベルト駆動ローラ温度センサ１２ａの変動量の方が、熱源より遠い環境センサ１３ａより温度変動量が大きい。
【００６３】
この機内昇温によって、色ずれが発生する。色ずれの要因は種々存在する。以下に代表的な２つの要因、色ずれ２６ａと色ずれ２７ａの色ずれを説明する。
【００６４】
最初に色ずれ２６ａについて説明する。
【００６５】
中間転写ベルト３が定着器８により温められ、中間転写ベルト３が懸架された、ベルト駆動ローラ４が昇温する。ベルト駆動ローラ４は、薄いゴム層で表面が覆われており、昇温によりゴム層の厚さが増加する。ベルト駆動ローラ４の径が大きくなると、中間転写ベルト３の速度が増加して、色ずれが発生する。例えば、Ｙの感光ドラム１ａとＢｋの感光ドラム１ｄ間の距離が３００ｍｍの場合、０．０２％の速度変動で、３００ｍｍ＊２／１００００＝６０μｍの色ずれが発生する。この様な色ずれは、ベルト駆動ローラ温度センサ１２ａの検出温度変動量２９ａの推移に比例して、プリント動作中の時間経過に対しほぼ一定の割合で上昇する。
【００６６】
次に色ずれ２７ａについて説明する。
【００６７】
画像形成手段１０２ａ〜１０２ｄが、定着器８により温められた中間転写ベルト３の転写手段１０３ａ〜１０３ｄの通過、及び、図示しないモータ、回路等の動作で昇温する。この時、各々Ｙ、Ｍ、Ｃ、Ｂｋに対応した画像形成手段１０２ａ〜１０２ｄは一様には昇温しない為、色間の温度差によって、レーザスキャナ２ａ〜２ｄの、図示しないレンズ等の光学部品の変形による露光位置のずれ量や、感光ドラム１ａ〜１ｄの位置のずれ量が色間で異なり、それにより色ずれが発生する。プリント待機状態で、色間の温度差が無い状態から、プリント動作により機内温度が上昇した場合は、昇温初期において色間の温度差が変動する為、色ずれ量が変動し、一定時間経過後には温度差が一定となり、色ずれ量が安定する。この様な色ずれ量は、前述の色ずれ２６ａの色ずれと異なり、ベルト駆動ローラ温度センサ１２ａや環境センサ１３ａの検出温度変動量２９ａや３０ａの推移に対し、昇温初期は比例し、一定時間経過後には色ずれが安定してしまう為、比例しなくなる。
【００６８】
よって、トータルの色ずれ変動量と温度変動量の関係は、トータルの色ずれ変動量２８ａの様に、領域ａ、領域ｂ、領域ｃで異なる挙動を示す。色ずれ許容量Δｃｐｒの変動量に対する、ベルト駆動ローラ温度センサ１２ａの検出温度変動量が、領域ａではΔｔ１であり小さく、領域ｂではΔｔ２であり大きい。領域ｃは、機内昇温による温度変動が飽和し、温度変動、色ずれ変動が共に発生していない領域である。
【００６９】
図４（ａ）、（ｂ）において、プリント動作により機内温度が上昇した後、プリント待機状態になり機内温度が下降した場合の色ずれ変動量と温度変動量の関係を説明する。
【００７０】
図４は、図３の領域ｃにてプリント動作が停止し、プリント待機状態となった場合である。図３と異なる点のみ説明する。
【００７１】
ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの検出温度変動量２９ｂと３０ｂは、図３の場合とは逆に、プリント待機中の時間経過に対しほぼ一定の割合で下降する。図３の場合と同様に、ベルト駆動ローラ温度センサ１２ａの方が、環境センサ１３ａより温度変動量が大きい。
【００７２】
ベルト駆動ローラ４が要因の色ずれ２６ｂは、図３の場合とは逆に、ベルト駆動ローラ温度センサ１２ａの検出温度変動量２９ｂの推移に比例して、プリント待機中の時間経過に対しほぼ一定の割合で下降する。
【００７３】
レーザスキャナ２ａ〜２ｄの露光位置や、感光ドラム１ａ〜１ｄの位置が要因の色ずれ２７ｂは、図３の場合とは異なり、プリント動作状態において色間の温度差が一定であった状態から、プリント待機状態になり機内温度が下降した場合、色間の温度差がプリント待機中の時間経過に対しほぼ一定の割合で減少するので、ベルト駆動ローラ４が要因の色ずれ２６ｂと同様に、ベルト駆動ローラ温度センサ１２ａの検出温度変動量２９ｂの推移に比例して、プリント待機中の時間経過に対し、ほぼ一定の割合で下降する。
【００７４】
よって、トータルの色ずれ変動量２８ｂの色ずれ許容量Δｃｐｒと、ベルト駆動ローラ温度センサ１２ａの検出温度変動量Δｔ２’の関係は、検出温度変動量が大きい、図３の領域ｂに近くなる。
【００７５】
図５（ａ）、（ｂ）において、プリント待機中にプリンタ設置環境温度が上昇した場合の色ずれ変動量と温度変動量の関係を説明する。
【００７６】
図５は、時間経過に対しほぼ一定の割合で温度が上昇した場合である。図３と異なる点のみ説明する。
【００７７】
図３と異なり、機内昇温がないので、ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの検出温度変動量２９ｃと３０ｃの変動量は、ほぼ同じとなる。
【００７８】
ベルト駆動ローラ４が要因の色ずれ２６ｃは、図３の場合と同様に、ベルト駆動ローラ温度センサ１２ａの検出温度変動量２９ｃの推移に比例して、時間経過に対し、ほぼ一定の割合で上昇する。しかし、図３の場合と異なり、温度上昇が機内で一様であるので、色ずれ許容量Δｃｐｒの変動量に対する、ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの検出温度変動量２９ｃと３０ｃが小さい。すなわち、図３の様なプリント動作による機内昇温の場合に比べ、ベルト駆動ローラ４の温度変動量に対する色ずれ変動量の割合が大きい。
【００７９】
レーザスキャナ２ａ〜２ｄの露光位置や、感光ドラム１ａ〜１ｄの位置が要因の色ずれ２７ｃは、図３の場合と異なり、色間の温度差が無いので発生しない。
【００８０】
よって、トータルの色ずれ変動量２８ｃは、ベルト駆動ローラ４が要因の色ずれ変動量２６ｃとほぼ同じになる。また、この時の色ずれ許容量Δｃｐｒと、ベルト駆動ローラ温度センサ１２ａの検出温度変動量Δｔ１’の関係は、検出温度変動量が小さい、図３の領域ａに近くなる。
【００８１】
逆に、時間経過に対し、ほぼ一定の割合で温度が下降した場合は、温度及び色ずれ共、方向が図５と逆になる以外は、図５と同じであるので、説明は省略する。
【００８２】
上記図３〜図５の場合は、色ずれ補正動作を行わない場合の色ずれの推移であり、この様な色ずれが発生しない様、色ずれ変動量がΔｃｐｒに達する前に、色ずれ補正動作を行う必要がある。
【００８３】
図６は、本発明の第１の実施例に係る色ずれ補正タイミングの決定を説明するフローチャートである。
【００８４】
ｔ１は、ベルト駆動ローラ温度センサ１２ａの検出温度、ｔ２は、環境センサ１３ａの検出温度、ｔ１（０）は、色ずれ補正実行時のベルト駆動ローラ温度センサ１２ａの検出温度で、ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａのプリンタ機内での設置位置の関係から、常にｔ１≧ｔ２となる。ＲＥＦ１は、色ずれ補正実行時のベルト駆動ローラ温度センサ１２ａと環境センサ１３ａとの温度差の大小を判別する閾値、ＲＥＦ２は、色ずれ補正実行後のベルト駆動ローラ温度センサ１２ａの検出温度変動量に基づき、色ずれ補正動作タイミングを決定する可変閾値で、色ずれ補正実行時のベルト駆動ローラ温度センサ１２ａと環境センサ１３ａとの温度差の大小の判別結果に基づき、後述のΔｔ１またはΔｔ２が設定される。Δｔ１は、色ずれ補正実行時のベルト駆動ローラ温度センサ１２ａと環境センサ１３ａとの温度差が小と判別された場合ＲＥＦ２に設定する、色ずれ補正後のベルト駆動ローラ温度センサ１２ａの検出温度変動量、Δｔ２は、色ずれ補正実行時のベルト駆動ローラ温度センサ１２ａと環境センサ１３ａとの温度差が大と判別された場合ＲＥＦ２に設定する、色ずれ補正後のベルト駆動ローラ温度センサ１２ａの検出温度変動量で、Δｔ１＜Δｔ２の関係がある。
【００８５】
図６において、本発明の第１の実施例に係る色ずれ補正タイミングの決定を説明する。
【００８６】
色ずれ補正動作タイミングは、ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの検出温度に基づいて決定する。温度の検出及び閾値の判定は、ＣＰＵ１４がセンサ制御部１８を介して実行する。
【００８７】
色ずれ補正動作の実行時、ベルト駆動ローラ温度センサ１２ａの検出温度ｔ１（０）をメモリ１６に保持する。また、ベルト駆動ローラ温度センサ１２ａの検出温度ｔ１と環境センサ１３ａの検出温度ｔ２の差を、ＲＥＦ１と比較する。ＲＥＦ１は、例えば１℃に設定されている。ｔ１とｔ２の温度差が１℃以内の場合は、ＲＥＦ２にΔｔ１を設定する。Δｔ１は例えば、３℃に設定されている。ｔ１とｔ２の温度差が１℃を越える場合は、ＲＥＦ２にΔｔ２を設定する。Δｔ２は例えば、５℃に設定されている。
【００８８】
その後、ベルト駆動ローラ温度センサ１２ａの検出温度ｔ１を逐次検出し、閾値ＲＥＦ２と色ずれ補正動作実行後のベルト駆動ローラ温度センサ１２ａの温度変動量ｔ１−ｔ１（０）を比較判別する。ｔ１−ｔ１（０）が、閾値ＲＥＦ２を越えた時点で、色ずれ変動量が規定値Δｃｐｒに達すると判断して、色ずれ補正動作を実行する。
【００８９】
以後、同様の動作を繰返す。
【００９０】
このように、検出温度変動量ｔ１−ｔ１（０）だけでなく、機内の異なる箇所に設置された２個の温度センサの色ずれ補正実行時の検出温度差ｔ１−ｔ２を用いて、色ずれ補正タイミングを決定することで、適切なタイミングで色ずれ補正動作を実行することができる。
【００９１】
すなわち、図３〜図５において、色ずれ許容量Δｃｐｒの変動量に対する、ベルト駆動ローラ温度センサ１２ａの検出温度変動量が小さいΔｔ１である領域ａと、Δｔ１より大きいΔｔ２である領域ｂは、色ずれ補正実行時のベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの温度差で判別できる。
【００９２】
ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの温度差が小さい場合は、プリント待機状態が長く続き、プリンタ内部の温度分布が一様で、その後の温度変動で、色ずれ量が大きく変動すると判断でき、一方、ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの温度差が大きい場合は、プリント動作による機内昇温でプリンタ内の温度分布が一様ではなく、その後の温度変動による色ずれ変動用が小さいと判断できる。
【００９３】
なお、色ずれ補正動作後の温度変動量の検出は、変動量が大きいベルト駆動ローラ温度センサ１２ａを用いる。
【００９４】
色ずれ補正タイミングが決定された後の具体的な色ずれ補正動作の内容は、従来の技術の説明と同様であるので説明を省略する。
【００９５】
（第２の実施例）
次に図７を用いて、第２の実施例を説明する。
【００９６】
第２の実施例は、第１の実施例の構成に基づいて色ずれ補正を行った際に生じる、検出温度と電圧値との間のバラツキを補正することを特徴とする。
【００９７】
従って、第１の実施例の図１と同一の構成については同一の符号を付し、その説明の詳細は省略する。
【００９８】
図７は、ベルト駆動ローラ温度センサ１２ａ、または環境センサ１３ａの検出温度と出力電圧の関係を示す図である。３１ａは、バラツキの最高値（Ｍａｘ．）を出力するセンサの場合の温度と出力電圧の関係を、３１ｂは、バラツキの標準値（Ｔｙｐ．）を出力するセンサの場合の温度と出力電圧の関係を、３１ｃは、バラツキの最低値（Ｍｉｎ．）を出力するセンサの場合の温度と出力電圧の関係を示す。
【００９９】
これらの温度センサは、検出温度を電圧値として出力している。しかし、部品精度にはバラツキがある。
【０１００】
同じ温度ｔ０に対し、出力電圧には、標準値に対し、Δｖ１やΔｖ２の差が発生する。
【０１０１】
この様な状態で、色ずれ補正実行時に、ベルト駆動ローラ温度センサ１２ａの検出温度ｔ１と環境センサ１３ａの検出温度ｔ２との温度差を、温度差の大小を判別する閾値ＲＥＦ１と比較すると、各センサのバラツキにより、正しい判別が行えない場合が発生する。例えば、ＲＥＦ１が１℃で、プリンタ待機状態が続き、ｔ１とｔ２が等しい場合に、ベルト駆動ローラ温度センサ１２ａの温度と出力電圧の関係がＭａｘ．の３１ａで、環境センサ１３ａの温度と出力電圧の関係がＭｉｎ．の３１ｃであった場合、ｔ１とｔ２の差が１℃を越えると判断してしまう。本来は、色ずれ補正動作タイミングを決定する可変閾値ＲＥＦ２には、例えば、３℃のΔｔ１を設定するべきところを、例えば、５℃のΔｔ２を設定してしまい、次回の色ずれ補正動作の実行タイミングが遅れ、色ずれが許容量のΔｃｐｒを越えてしまう。
【０１０２】
そこで、本実施例では、ベルト駆動ローラ温度センサ１２ａと環境センサ１３ａのバラツキに基づいた補正値を、予めプリンタの組立て時等にメモリ１６に設定し、保持しておく。図７においては、補正値に基づき、検出電圧がｖ０の場合、Ｔｙｐ．特性のセンサでは、温度はｔ４と判断し、Ｍａｘ．特性のセンサでは、温度はｔ５と判断し、Ｍｉｎ．特性のセンサでは、温度はｔ３と判断する。
【０１０３】
（第３の実施例）
次に、図８を用いて、第３の実施例を説明する。
【０１０４】
第３の実施例に特徴的な点のみ説明し、その他の構成については第１の実施例と同一であり、同一の構成については同一の符号を付し、その説明の詳細は省略する。
【０１０５】
図８は、本発明の第３の実施例に係る画像形成装置の全体を説明する図である。
第１及び第２の実施例のベルト駆動ローラ温度センサ１２ａと環境センサ１３ａの替わりに、各々、画像形成手段１０２ａ〜１０２ｄの周囲温度を検出する画像形成手段温度センサ１２ｂと、用紙カセット７近傍の温度を検出する環境センサ１３ｂ（１３ａとは異なる）を用いる。
【０１０６】
画像形成手段１０２ａ〜１０２ｄの周囲は、プリント動作中に、定着器８により温められた中間転写ベルト３の転写手段１０３ａ〜１０３ｄの通過、及び、図示しないモータ、回路等の動作で昇温する。
【０１０７】
よって、画像形成手段温度センサ１２ｂは、第１及び第２の実施例のベルト駆動ローラ温度センサ１２ａと同様の機能を有する。
【０１０８】
一方、用紙カセット７の近傍は、プリント動作による機内昇温の影響を受け難い位置にある。
【０１０９】
よって、環境センサ１３ｂは、第１及び第２の実施例の環境センサ１３ａと同様の機能を有する。
【０１１０】
画像形成手段温度センサ１２ｂと環境センサ１３ｂを用いて、第１の実施例または第２の実施例と同様の動作を実行する。
【０１１１】
なお、機内の温度センサは、これらの位置に限定されるものではない。
【０１１２】
２個の温度センサの検出温度差、及び検出温度差変動量に基づく色ずれ補正実行タイミングは、前記実施例に述べられた比較判断手段に限定されるものではない。例えば、検出温度差、及び検出温度変動量を複数のレベルに分けて、テーブル値を保持しても良い。
【０１１３】
（第４の実施例）
第３の実施例についても、第１の実施例に対する第２の実施例と同様に、第３の実施例の構成に基づいて色ずれ補正を行った際に生じる、検出温度と電圧値との間のバラツキを補正する機構を設けることができる（図示せず）。
【０１１４】
【発明の効果】
以上説明したように、本発明によれば、２個の温度センサを、装置内昇温の異なる箇所に設置し、色ずれ補正動作実行時の２個の温度センサの温度差と、色ずれ補正動作実行後の、少なくとも一方の温度センサの検出温度変動量とに基づいて、次回の色ずれ補正動作実行タイミングを決定することにより、種々のプリント状態により装置内部の温度センサの検出温度変動量と色ずれ変動量の関係が異なる場合にも、必要以上のダウンタイムの増加や、許容量を越える色ずれ変動量の発生が無く、常に適切なタイミングで色ずれ補正動作を実行する、高精度の色ずれ補正装置を提供できる。
【０１１５】
さらに、本発明によれば、色ずれ補正実行時の、２個の温度センサの温度差が小さい場合の方が大きい場合に比べ、少なくとも一方の温度センサの検出温度変動量が少ないタイミングで色ずれ補正を実行するので、暫くの期間プリント動作を行わない状態からの温度変動による色ずれの場合に、許容量を越える色ずれ変動量の発生が無く、またプリント動作を頻繁に行い、装置内部の温度がある程度上昇した状態からの温度変動による色ずれの場合に、必要以上のダウンタイムの増加が無く、常に適切なタイミングで色ずれ補正動作を実行する、高精度の色ずれ補正装置を提供できる。
【０１１６】
さらに、本発明によれば、プリント動作による昇温が大きい箇所の近傍に一方の温度センサを設置するので、一方の温度センサの検出温度変動量に基づき、より適切に色ずれ補正動作実行タイミングを検出でき、常に適切なタイミングで色ずれ補正動作を実行する、高精度の色ずれ補正装置を提供できる。
【０１１７】
なおさらに、本発明によれば、２個の温度センサの検出誤差補正値を保持するので、色ずれ補正実行時の、２個の温度センサの温度差をより正確に検出し、より適切に色ずれ補正動作実行タイミングを設定でき、常に適切なタイミングで色ずれ補正動作を実行する、高精度の色ずれ補正装置を提供できる。
【図面の簡単な説明】
【図１】本発明の第１の実施例に係る画像形成装置の全体を示す説明図
【図２】本発明の第１の実施例に係る制御部の全体を説明するブロック図
【図３】（ａ）（ｂ）　本発明の第１の実施例に係るプリント動作により機内温度が上昇した場合の検出温度変動量と色ずれ変動量の関係を説明する対の図
【図４】（ａ）（ｂ）　本発明の第１の実施例に係るプリント動作により機内温度が上昇した後、プリント待機状態になり機内温度が下降した場合の検出温度変動量と色ずれ変動量の関係を説明する対の図
【図５】（ａ）（ｂ）　本発明の第１の実施例に係るプリント待機中にプリンタ設置環境温度が上昇した場合の検出温度変動量と色ずれ変動量の関係を説明する対の図
【図６】本発明の第１の実施例に係る色ずれ補正タイミングの決定方法を説明するフローチャート
【図７】本発明の第２の実施例に係る温度センサの検出温度と出力電圧の関係を説明する図
【図８】本発明の第３の実施例に係る画像形成装置の全体を示す説明図
【図９】（ａ）（ｂ）（ｃ）（ｄ）　各種色ずれを説明する図
【図１０】色ずれ検出用パターンを説明する図
【符号の説明】
１ａ、１ｂ、１ｃ、１ｄ　感光ドラム
２ａ、２ｂ、２ｃ、２ｄ　レーザスキャナ
３　中間転写ベルト
４　ベルト駆動ローラ
６　２次転写ローラ
７　用紙カセット
８　定着器
９　両面ユニット
１１　色ずれ検出センサ
１２ａ　ベルト駆動ローラ温度センサ
１２ｂ　画像形成手段温度センサ
１３ａ、１３ｂ　環境センサ
２０　本来の画像位置
２１ａ、２１ｂ、２１ｃ、２１ｄ　色ずれが発生している場合の画像位置
１０２ａ、１０２ｂ、１０２ｃ、１０２ｄ　画像形成手段
１０３ａ、１０３ｂ、１０３ｃ、１０３ｄ　転写手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color misregistration correction apparatus for a color image forming apparatus such as a color printer and a color copying machine, and more particularly to a color misregistration correction apparatus for an electrophotographic color image forming apparatus having a plurality of image forming units.
[0002]
[Prior art]
In an electrophotographic color image forming apparatus, various methods have been proposed which have a plurality of image forming means for speeding up and sequentially transfer images of different colors onto a recording material held on a transport belt. I have.
[0003]
However, problems with the apparatus having a plurality of image forming units include uneven movement of the plurality of photosensitive drums and the conveyor belt and the outer peripheral surface of the photosensitive drum and the transfer belt at the transfer position of each image forming unit due to factors such as mechanical accuracy. It is known that the relationship of the amount of movement of each color and the like occurs separately for each color, does not match when images are superimposed, and causes color misregistration.
[0004]
In particular, in an apparatus including a laser scanner and a plurality of image forming units having a photosensitive drum, there is an error in the distance between the laser scanner and the photosensitive drum in each image forming unit, and if this error is different between the image forming units. In this case, a difference occurs in the scanning width of the laser beam on the photosensitive drum, and a color shift occurs.
[0005]
FIG. 9 shows an example of color misregistration.
[0006]
Reference numeral 20 denotes an original image position, and reference numerals 21a, 21b, 21c, and 21d denote image positions when a color shift occurs.
[0007]
Note that (b) and (c) show the case where there is a color shift in the main scanning direction, but for the sake of explanation, two lines are drawn apart in the transport direction.
[0008]
(A) shows the inclination shift of the main scanning line, which occurs when there is an inclination between the optical unit and the photosensitive drum.
[0009]
On the other hand, the contents of the color misregistration correction operation include, for example, correction in the direction of the arrow by adjusting the positions of the optical unit, the photosensitive drum, and the lens.
[0010]
7B shows a color shift due to a variation in the width of the main scanning line, which is caused by a difference in the distance between the optical unit and the photosensitive drum. This is likely to occur when the optical unit is a laser scanner.
[0011]
In contrast, the content of the color misregistration correction operation includes, for example, adjusting the positions of the optical unit, the photosensitive drum, and the lens, or finely adjusting the image frequency (if the scanning width is long, increase the frequency) to perform scanning. For example, by changing the length of the line, it is corrected in the direction of the arrow.
[0012]
(C) shows a writing start position error in the main scanning direction.
[0013]
On the other hand, the content of the color misregistration correction operation includes, for example, adjusting the write start timing from the beam detection position in the direction of the arrow if the optical unit is a laser scanner.
[0014]
(D) shows the writing start position error in the paper transport direction.
[0015]
On the other hand, the contents of the color misregistration correction operation include, for example, correction in the direction of the arrow by adjusting the writing start timing of each color from the detection of the leading edge of the sheet.
[0016]
To correct these color shifts, specifically, a pattern for color shift detection is formed on the conveyor belt for each color, and detected by a pair of optical sensors provided on both sides of the downstream portion of the conveyor belt. Various adjustments as described above are performed according to the detected shift amount.
[0017]
An example of a color misregistration detection pattern will be described with reference to FIG.
[0018]
FIG. 10 is a diagram illustrating a color misregistration detection pattern.
[0019]
22a, 22b, 22c, 22d, 23a, 23b, 23c, and 23d are patterns for detecting the amount of color shift in the paper transport direction, and 24a, 24b, 24c, 24d, 25a, 25b, 25c, and 25d are the paper transport patterns. This pattern is for detecting the amount of color misregistration in the main scanning direction orthogonal to the direction, and in this example, a to d of 22, 23, 24, and 25 are black (hereinafter, Bk) and yellow ( Y), magenta (hereinafter M), and cyan (hereinafter C).
[0020]
tsf1 to 4, tmf1 to 4, tsr1 to 4, and tmr1 to 4 indicate the detection timing of each pattern, and the arrows indicate the moving direction of the transport belt.
[0021]
The transport speed of the transport belt is vmm / s, Bk is the reference color, and the theoretical distance between each color of the paper transport direction pattern and the Bk pattern is dsYmm, dsMmm, dsCmm, the paper transport direction pattern of each color, and the main scanning direction pattern. The actual measured distance between the terminals is dmfBkmm, dmfYmm, dmfMmm, dmfCmm, dmrBkmm, dmrYmm, dmrMmm, and dmrCmm, respectively.
[0022]
With Bk as a reference color, the color shift amount δes of each color in the transport direction is

It becomes.
[0023]
With respect to the main scanning direction, the color shift amounts δemf and δemr of the left and right colors are
dmfBk = v * (tmf1-tsf1) (Equation 4)
dmfY = v * (tmf2-tsf2) (Equation 5)
dmfM = v * (tmf3-tsf3) (Equation 6)
dmfC = v * (tmf4-tsf4) (Equation 7)
When
dmrBk = v * (tmr1-tsr1) (Equation 8)
dmrY = v * (tmr2-tsr2) (Equation 9)
dmrM = v * (tmr3-tsr3) (Equation 10)
dmrC = v * (tmr4-tsr4) (Equation 11)
From
δemfY = dmfY−dmfBk (Equation 12)
δemfM = dmfM−dmfBk (Equation 13)
δemfC = dmfC−dmfBk (Equation 14)
When
δemrY = dmrY−dmrBk (formula 15)
δemrM = dmrM−dmrBk (formula 16)
δemrC = dmrC−dmrBk (formula 17)
The shift direction can be determined from the sign of the calculation results of Equations 12 to 17, the shift of the writing start position is detected from δemf, and the shift of the main scanning width is detected from δemr−δemf, and each is corrected.
[0024]
Various adjustments are performed by forming a color misregistration detection pattern on the conveyor belt. The execution timing of the color misregistration correction is determined when the power is turned on, when a consumable image forming unit such as a photosensitive drum is inserted or removed, or based on a detected temperature fluctuation amount of a temperature sensor installed inside the apparatus. Such as when it was done.
[0025]
What is important among these is the execution timing of the color misregistration correction determined according to the detected temperature fluctuation amount and the like.
[0026]
The reason for this is that the amount of color shift generally fluctuates with temperature fluctuation.
[0027]
For example, in a general color image forming apparatus, during printing, a belt that conveys a recording material is heated by a fixing device, and the heated belt heats a roller on which the belt is suspended.
[0028]
The surface of the roller is covered with a thin rubber layer, and as the temperature increases, the thickness of the rubber layer increases. When the diameter of the driving roller for driving the belt increases, the speed of the belt increases and color shift occurs.
[0029]
As described above, the detected temperature fluctuation amount has an important connection with the color deviation fluctuation amount (hereinafter, referred to as color deviation fluctuation amount).
[0030]
Therefore, the execution timing of the color misregistration correction is determined according to the detected temperature fluctuation amount or the like.
[0031]
[Problems to be solved by the invention]
However, the conventional example has the following disadvantages.
[0032]
The relationship between the temperature fluctuation detected by the temperature sensor inside the device and the color shift fluctuation is set inside the device in response to temperature rise and fall due to fluctuations in the installation environment of the device and temperature rise inside the device due to printing operation. When the execution timing of the color misregistration correction operation is determined based on the detected temperature fluctuation amount of one temperature sensor, the color misregistration correction operation is not necessarily executed at an appropriate timing.
[0033]
The color shift due to temperature fluctuation from the state where the printing operation is not performed for a while and the color shift due to the temperature fluctuation from the state where the printing operation is frequently performed and the temperature inside the apparatus is increased to some extent are factors causing the color shift and The color shift fluctuation amounts are different. That is, when the color misregistration correction operation is performed based on the detected temperature fluctuation amount of one temperature sensor installed inside the apparatus, the execution timing of the color misregistration correction operation is delayed, and the color deviation fluctuation amount exceeds the allowable amount. Conversely, the color misregistration correction operation is performed at a timing that is unnecessarily fast, and the downtime during continuous printing (print operation interruption time) increases, leading to a decrease in performance.
[0034]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and even when the relationship between the detected temperature fluctuation amount of the temperature sensor inside the apparatus and the color misregistration fluctuation amount differs depending on various printing states, unnecessary downsizing occurs. It is an object of the present invention to provide a high-accuracy color misregistration correction device that prevents an increase in time and a color misregistration fluctuation amount exceeding an allowable amount and always performs a color misregistration correction operation at an appropriate timing.
[0035]
[Means for Solving the Problems]
Therefore, in the present invention, the object is achieved by providing a color misregistration correction apparatus for a color image forming apparatus described in any of the following items (1) to (4).
[0036]
(1) A plurality of image forming units each having an optical unit and a latent image forming medium, an endless belt unit sequentially passing through the plurality of image forming units, and a formed image is transferred onto the endless belt unit or A plurality of transfer means for transferring onto a recording material conveyed while being held on the endless belt means; a driving means for driving the endless belt; and a color misregistration detection pattern formed on the endless belt means. A color misregistration correction unit that electrically and mechanically corrects the color misregistration based on the detection result of the color misregistration detection pattern. First temperature detecting means for detecting a temperature near one of the belt means and the transferring means, and a second temperature detecting means for detecting the temperature in the color image forming apparatus other than the first temperature detecting means. Warm Detecting means for determining an operating timing of the color misregistration correcting means based on a detected temperature fluctuation amount of at least one of the first and second temperature detecting means. Color image forming, wherein the timing determining means variably controls the operation timing of the color misregistration correction means based on the detected temperatures of the first and second temperature detection means at the time of operation of the color misregistration correction means. Color shift correction device for the device.
[0037]
(2) The operation timing determination means is configured to determine whether the difference between the first and second temperature detection means during the operation of the color misregistration correction means is small, as compared with the case where the difference between the first and second temperature detection means is large. The color misregistration correction device for a color image forming apparatus according to (1), wherein the color misregistration correction device is operated at a timing when the detected temperature fluctuation amount of the detection device is small.
[0038]
(3) The color misregistration of the color image forming apparatus according to (1), wherein the first temperature detecting means detects a temperature near a belt driving roller on which the endless belt means is suspended. Correction device.
[0039]
(4) The color image forming apparatus as described in (1) above, further comprising a detected temperature error correction value holding unit that holds a relative detected temperature error correction value of the first and second temperature detecting units. Color shift correction device.
[0040]
In the above configuration, even when the relationship between the detected temperature fluctuation amount of the temperature sensor inside the apparatus and the color deviation fluctuation amount differs depending on various printing conditions, the downtime is increased more than necessary or the color deviation fluctuation amount exceeding the allowable amount is increased. The occurrence of color shift is prevented, and the color misregistration correction operation is always performed at appropriate timing.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail based on a plurality of examples.
[0042]
The color image forming apparatus according to the present embodiment is a color image forming apparatus including image forming means for four colors, that is, yellow Y, magenta M, cyan C, and black Bk.
[0043]
(First embodiment)
First, a first embodiment will be described with reference to FIGS.
[0044]
FIG. 1 is a diagram illustrating the entire image forming apparatus according to an embodiment of the present invention.
[0045]
Reference numerals 1a, 1b, 1c, and 1d denote photosensitive drums (a, b, c, and d indicate Y, M, C, and Bk, respectively) as latent image forming media for forming electrostatic latent images. 2c and 2d are laser scanners (a, b, c, and d are Y, M, C, and D, respectively) that are optical units that perform exposure according to an image signal and form an electrostatic latent image on the photosensitive drums 1a to 1d. Bk), the photosensitive drums 1a to 1d and the laser scanners 2a to 2d constitute image forming means 102a, 102b, 102c and 102d.
[0046]
Reference numeral 3 denotes an intermediate transfer belt which is an endless belt means for sequentially transferring and conveying the toner images formed on the photosensitive drums 1a to 1d. Reference numeral 4 denotes a drive means connected to a driving means 19a including a motor and gears. , A belt driven roller that rotates in accordance with the movement of the intermediate transfer belt 3 and applies a constant tension to the intermediate transfer belt 3, and a belt driven roller 6 that applies the toner image conveyed by the intermediate transfer belt 3 A secondary transfer roller for transferring to paper, 7 is a paper cassette, 8 is a fixing device for melting and fixing the toner image transferred on the paper by heat, and 9 is a front and back of the paper for printing on both sides of the paper. A double-sided unit 10 that reverses, a flapper that switches the transport path when the paper is sent to the double-sided unit 9, and 11 detects a color misregistration detection pattern formed on the intermediate transfer belt 3. A pair of optical sensors 12a provided on both sides of the intermediate transfer belt 3 are a belt driving roller temperature sensor as first temperature detecting means for detecting a temperature near the driving roller 4, and a printer 13a is a printer. This is an environment sensor which is a second temperature detecting means for detecting the temperature inside the device.
[0047]
103a, 103b, 103c and 103d are transfer units for transferring the formed images onto the intermediate transfer belt 3.
[0048]
FIG. 2 is a diagram illustrating the entire control unit according to the embodiment of the present invention.
[0049]
Reference numeral 14 denotes a CPU, which is an image forming timing determining unit that also controls and manages the entire apparatus, 15 a host I / F unit that controls communication between the printer and the PC, and 16 a print data, various parameters, various information, and the like. Is an image control unit that converts print data sent from the PC to the printer into data suitable for the printer engine system, 18 is a sensor control unit that detects the status of each unit of the printer, and 19 is A drive control unit 19a that controls driving of actuators, a laser, a high-voltage power supply, and the like of the printer engine. A drive control unit 19 drives the photosensitive drums 1a to 1d and the belt drive roller 4, and includes a motor and gears. Means.
[0050]
Next, the operation of the image forming apparatus will be described.
[0051]
When the print data is sent from the PC to the printer through the host I / F unit 15, the image control unit 17 converts the print data into data suitable for the printer engine.
[0052]
Then, when the converted data is held in the memory 16 and becomes a so-called printable state, the drive control unit 19 drives the drive unit 19a including a motor and gears, and the photosensitive drum connected to the drive unit 19a. The belts 1a to 1d and the belt driving roller 4 also start driving.
[0053]
Next, the image signal of each color is sent to the laser scanners 2a to 2d of each color, an electrostatic latent image is formed on the photosensitive drums 1a to 1d, the toner is developed by a developing unit (not shown), and transferred by transfer units 103a to 103d. The image is transferred onto the intermediate transfer belt 3.
[0054]
In this embodiment, as shown in FIG. 1, images are sequentially formed in the order of Y, M, C, and Bk. At the same time, a sheet as a recording material is supplied from the sheet cassette 7 to the secondary transfer roller 6 in synchronization with the image position on the intermediate transfer belt 3, and the toner image is transferred onto the sheet. As a result, the toner image is fixed on the sheet and discharged to the outside.
[0055]
During this time, the inside of the apparatus is monitored by the sensor control unit 18, and the whole is controlled by the CPU 14.
[0056]
Next, the relationship between the detected temperature fluctuation amount and the color misregistration in the embodiment of the present invention will be described with reference to FIGS.
[0057]
FIGS. 3A to 5A show the transition of the color shift variation with the passage of time, and FIGS. 3B and 5B show the transition of the temperature variation with the passage of the same time as in FIG.
[0058]
26a, 26b and 26c denote color shift fluctuations caused by color shift factors described later, and 27a, 27b and 27c denote color shift fluctuations caused by color shift factors different from 26a, 26b and 26c described later. , 28a, 28b, and 28c indicate the total amount of color shift variation including the color shift factors 26a and 27a, 26b and 27b, and 26c and 27c, respectively.
[0059]
29a, 29b, and 29c indicate the detected temperature fluctuation amounts of the belt drive roller temperature sensor 12a, and 30a, 30b, and 30c indicate the detected temperature fluctuation amounts of the environment sensor 13a.
[0060]
The area a, the area b, and the area c indicate a plurality of areas in which the relationship between the temperature fluctuation amount and the color misregistration fluctuation amount is different, which will be described later. Δcpr indicates the allowable amount of color misregistration, and Δt1, Δt1 ′, Δt2, and Δt2 ′ indicate the amount of temperature fluctuation of the belt drive roller temperature sensor 12a when the amount of color misregistration is Δcpr.
[0061]
3A and 3B, a description will be given of the relationship between the amount of color shift variation and the amount of temperature variation when the internal temperature of the apparatus increases due to a printing operation.
[0062]
When the image forming apparatus performs a printing operation, the temperature inside the apparatus rises due to the operation of the fixing device 8, a motor, a circuit, and the like (not shown) (temperature rise inside the apparatus). The detected temperature fluctuation amounts 29a and 30a of the belt drive roller temperature sensor 12a and the environment sensor 13a increase at a substantially constant rate with respect to the passage of time during the printing operation. However, the fluctuation amount of the belt driving roller temperature sensor 12a that detects the temperature near the belt driving roller 4 on which the intermediate transfer belt 3 warmed by the fixing device 8 is suspended is higher than that of the environment sensor 13a farther than the heat source. The amount of fluctuation is large.
[0063]
Due to the temperature rise in the machine, color misregistration occurs. There are various causes of color misregistration. Hereinafter, two representative factors, that is, the color shift of the color shift 26a and the color shift 27a will be described.
[0064]
First, the color shift 26a will be described.
[0065]
The intermediate transfer belt 3 is heated by the fixing device 8, and the temperature of the belt drive roller 4 on which the intermediate transfer belt 3 is suspended rises. The surface of the belt driving roller 4 is covered with a thin rubber layer, and the thickness of the rubber layer increases as the temperature rises. When the diameter of the belt driving roller 4 increases, the speed of the intermediate transfer belt 3 increases, and color misregistration occurs. For example, when the distance between the Y photosensitive drum 1a and the Bk photosensitive drum 1d is 300 mm, a color shift of 300 mm * 2/10000 = 60 μm occurs with a speed variation of 0.02%. Such color misregistration increases at a substantially constant rate with respect to the lapse of time during the printing operation in proportion to the transition of the detected temperature fluctuation amount 29a of the belt drive roller temperature sensor 12a.
[0066]
Next, the color shift 27a will be described.
[0067]
The temperature of the image forming units 102 a to 102 d is increased by the passage of the intermediate transfer belt 3 heated by the fixing unit 8 through the transfer units 103 a to 103 d and the operation of a motor, a circuit, and the like (not shown). At this time, since the temperature of the image forming units 102a to 102d corresponding to Y, M, C, and Bk, respectively, does not rise uniformly, the temperature difference between the colors causes the laser scanners 2a to 2d to use optical components such as lenses (not shown). The shift amount of the exposure position due to the deformation of the parts and the shift amount of the positions of the photosensitive drums 1a to 1d differ between the colors, thereby causing a color shift. If there is no temperature difference between colors in the print standby state and the temperature inside the machine rises due to the printing operation, the temperature difference between the colors fluctuates at the beginning of the temperature rise, so the amount of color misregistration fluctuates and a certain period of time has passed. Later, the temperature difference becomes constant, and the color shift amount becomes stable. Such an amount of color misregistration is different from the above-described color misregistration of the color misregistration 26a, and is proportional to the transition of the detected temperature fluctuation amounts 29a and 30a of the belt drive roller temperature sensor 12a and the environment sensor 13a in the initial stage of temperature rise, and is constant. After a lapse of time, the color misregistration becomes stable, and is not proportional.
[0068]
Therefore, the relationship between the total color shift variation and the temperature change shows different behaviors in the region a, the region b, and the region c, like the total color shift variation 28a. The detected temperature fluctuation amount of the belt drive roller temperature sensor 12a with respect to the fluctuation amount of the color misregistration allowable amount Δcpr is Δt1 which is small in the region a and Δt2 which is large in the region b. The region c is a region where the temperature fluctuation due to the temperature rise inside the device is saturated, and neither the temperature fluctuation nor the color shift fluctuation occurs.
[0069]
4A and 4B, a description will be given of the relationship between the amount of color shift variation and the amount of temperature variation when the internal temperature rises due to a printing operation and then the printer enters a print standby state and the internal temperature falls.
[0070]
FIG. 4 shows a case where the printing operation is stopped in the area c in FIG. Only differences from FIG. 3 will be described.
[0071]
Contrary to the case of FIG. 3, the detected temperature fluctuation amounts 29b and 30b of the belt drive roller temperature sensor 12a and the environment sensor 13a decrease at a substantially constant rate with respect to the passage of time during the printing standby. As in the case of FIG. 3, the belt drive roller temperature sensor 12a has a larger temperature variation than the environment sensor 13a.
[0072]
The color shift 26b caused by the belt driving roller 4 is almost constant with the lapse of time during the print standby, in proportion to the transition of the detected temperature fluctuation amount 29b of the belt driving roller temperature sensor 12a, contrary to the case of FIG. Falls at the rate of
[0073]
The color shift 27b due to the exposure positions of the laser scanners 2a to 2d and the positions of the photosensitive drums 1a to 1d is different from the case of FIG. 3 because the temperature difference between the colors is constant in the printing operation state. When the temperature in the machine is lowered in the print standby state, the temperature difference between the colors decreases at a substantially constant rate with respect to the elapse of the time during the print standby, so that the belt drive roller 4 causes the belt to shift in the same manner as the color shift 26b. In proportion to the transition of the detected temperature fluctuation amount 29b of the drive roller temperature sensor 12a, the temperature decreases at a substantially constant rate with respect to the lapse of time during the printing standby.
[0074]
Therefore, the relationship between the color shift allowable amount Δcpr of the total color shift fluctuation amount 28b and the detected temperature fluctuation amount Δt2 ′ of the belt drive roller temperature sensor 12a is close to the region b in FIG. 3 where the detected temperature fluctuation amount is large.
[0075]
5A and 5B, a description will be given of the relationship between the amount of color shift variation and the amount of temperature variation when the printer installation environment temperature rises during printing standby.
[0076]
FIG. 5 shows a case where the temperature rises at a substantially constant rate over time. Only differences from FIG. 3 will be described.
[0077]
Unlike FIG. 3, since there is no temperature rise inside the apparatus, the fluctuation amounts of the detected temperature fluctuation amounts 29c and 30c of the belt drive roller temperature sensor 12a and the environment sensor 13a are substantially the same.
[0078]
As in the case of FIG. 3, the color shift 26c caused by the belt driving roller 4 increases in proportion to the transition of the detected temperature fluctuation amount 29c of the belt driving roller temperature sensor 12a at a substantially constant rate over time. I do. However, unlike the case of FIG. 3, since the temperature rise is uniform in the machine, the detected temperature fluctuation amounts 29c and 30c of the belt drive roller temperature sensor 12a and the environment sensor 13a with respect to the fluctuation amount of the color shift allowable amount Δcpr are small. . That is, the ratio of the amount of color misregistration variation to the amount of temperature variation of the belt driving roller 4 is larger than in the case where the temperature inside the apparatus is increased by the printing operation as shown in FIG.
[0079]
The color shift 27c caused by the exposure positions of the laser scanners 2a to 2d and the positions of the photosensitive drums 1a to 1d is different from the case of FIG.
[0080]
Therefore, the total color shift variation 28c is substantially the same as the color shift variation 26c caused by the belt driving roller 4. Further, the relationship between the color misregistration allowable amount Δcpr and the detected temperature fluctuation amount Δt1 ′ of the belt drive roller temperature sensor 12a at this time is close to the area a in FIG. 3 where the detected temperature fluctuation amount is small.
[0081]
Conversely, when the temperature decreases at a substantially constant rate over time, the temperature and color shift are the same as in FIG. 5 except that the direction is opposite to that in FIG. 5, and the description is omitted.
[0082]
3 to 5 show the transition of the color misregistration when the color misregistration correction operation is not performed. In order to prevent such color misregistration from occurring, the color misregistration correction is performed before the color misregistration variation reaches Δcpr. Action is required.
[0083]
FIG. 6 is a flowchart illustrating the determination of the color misregistration correction timing according to the first embodiment of the present invention.
[0084]
t1 is the temperature detected by the belt driving roller temperature sensor 12a, t2 is the temperature detected by the environment sensor 13a, and t1 (0) is the temperature detected by the belt driving roller temperature sensor 12a when color misregistration correction is performed. From the relationship between the installation positions of the sensor 12a and the environment sensor 13a in the printer, t1 ≧ t2 always holds. REF1 is a threshold value for determining the magnitude of the temperature difference between the belt drive roller temperature sensor 12a and the environment sensor 13a when performing color misregistration correction, and REF2 is the detected temperature variation of the belt drive roller temperature sensor 12a after color misregistration correction is performed. And a variable threshold value for determining the color misregistration correction operation timing, and Δt1 or Δt2, which will be described later, is set based on the determination result of the temperature difference between the belt drive roller temperature sensor 12a and the environment sensor 13a during the color misregistration correction. Is done. Δt1 is set to REF2 when it is determined that the temperature difference between the belt drive roller temperature sensor 12a and the environment sensor 13a at the time of color shift correction is small, and the detected temperature fluctuation of the belt drive roller temperature sensor 12a after color shift correction. The amount Δt2 is set to REF2 when the temperature difference between the belt driving roller temperature sensor 12a and the environment sensor 13a at the time of executing the color misregistration correction is set to REF2, and the detection of the belt driving roller temperature sensor 12a after the color misregistration correction is performed. There is a relationship of Δt1 <Δt2 in the amount of temperature fluctuation.
[0085]
6, the determination of the color misregistration correction timing according to the first embodiment of the present invention will be described.
[0086]
The color misregistration correction operation timing is determined based on the temperatures detected by the belt drive roller temperature sensor 12a and the environment sensor 13a. The detection of the temperature and the determination of the threshold are executed by the CPU 14 via the sensor control unit 18.
[0087]
When the color misregistration correction operation is performed, the detected temperature t1 (0) of the belt drive roller temperature sensor 12a is stored in the memory 16. Further, the difference between the detected temperature t1 of the belt drive roller temperature sensor 12a and the detected temperature t2 of the environment sensor 13a is compared with REF1. REF1 is set to 1 ° C., for example. If the temperature difference between t1 and t2 is within 1 ° C., Δt1 is set to REF2. Δt1 is set to, for example, 3 ° C. When the temperature difference between t1 and t2 exceeds 1 ° C., Δt2 is set in REF2. Δt2 is set to 5 ° C., for example.
[0088]
Thereafter, the detection temperature t1 of the belt drive roller temperature sensor 12a is sequentially detected, and the threshold value REF2 is compared with the temperature fluctuation amount t1-t1 (0) of the belt drive roller temperature sensor 12a after the execution of the color misregistration correction operation. When t1−t1 (0) exceeds the threshold value REF2, it is determined that the color shift variation amount reaches the specified value Δcpr, and the color shift correction operation is performed.
[0089]
Thereafter, the same operation is repeated.
[0090]
As described above, not only the detected temperature fluctuation amount t1−t1 (0) but also the color misregistration using the detected temperature difference t1−t2 at the time of performing color misregistration correction of the two temperature sensors installed at different locations in the machine. By determining the correction timing, the color misregistration correction operation can be executed at an appropriate timing.
[0091]
That is, in FIGS. 3 to 5, the region a in which the detected temperature fluctuation amount of the belt drive roller temperature sensor 12a is small Δt1 and the region b in which Δt2 is larger than Δt1 with respect to the fluctuation amount of the color deviation allowable amount Δcpr are color. The determination can be made based on the temperature difference between the belt drive roller temperature sensor 12a and the environment sensor 13a at the time of executing the shift correction.
[0092]
When the temperature difference between the belt drive roller temperature sensor 12a and the environment sensor 13a is small, it can be determined that the print standby state continues for a long time, the temperature distribution inside the printer is uniform, and the color shift amount fluctuates greatly due to subsequent temperature fluctuations. On the other hand, when the temperature difference between the belt drive roller temperature sensor 12a and the environment sensor 13a is large, the temperature distribution in the printer is not uniform due to the temperature rise inside the printer due to the printing operation, and the color shift fluctuation due to the subsequent temperature fluctuation is small. Can be determined.
[0093]
The temperature fluctuation after the color misregistration correction operation is detected using the belt drive roller temperature sensor 12a having a large fluctuation.
[0094]
The specific content of the color shift correction operation after the color shift correction timing is determined is the same as that of the description of the related art, and thus the description is omitted.
[0095]
(Second embodiment)
Next, a second embodiment will be described with reference to FIG.
[0096]
The second embodiment is characterized in that the variation between the detected temperature and the voltage value, which occurs when the color misregistration is corrected based on the configuration of the first embodiment, is corrected.
[0097]
Therefore, the same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.
[0098]
FIG. 7 is a diagram showing the relationship between the detected temperature of the belt drive roller temperature sensor 12a or the environment sensor 13a and the output voltage. 31a shows the relationship between the temperature and the output voltage in the case of the sensor that outputs the maximum value of the variation (Max.), And 31b shows the relationship between the temperature and the output voltage in the case of the sensor that outputs the standard value of the variation (Typ.). And 31c shows the relationship between the temperature and the output voltage in the case of a sensor that outputs the minimum value (Min.) Of the variation.
[0099]
These temperature sensors output the detected temperature as a voltage value. However, there is variation in component accuracy.
[0100]
At the same temperature t0, the output voltage has a difference of Δv1 or Δv2 from the standard value.
[0101]
In such a state, when the color misregistration correction is performed, the temperature difference between the detected temperature t1 of the belt drive roller temperature sensor 12a and the detected temperature t2 of the environment sensor 13a is compared with a threshold value REF1 for determining the magnitude of the temperature difference. There is a case where correct discrimination cannot be performed due to variations in sensors. For example, when REF1 is 1 ° C., the printer standby state continues, and t1 and t2 are equal, the relationship between the temperature of the belt drive roller temperature sensor 12a and the output voltage is Max. 31a, the relationship between the temperature of the environment sensor 13a and the output voltage is Min. If it is 31c, it is determined that the difference between t1 and t2 exceeds 1 ° C. Originally, the variable threshold value REF2 for determining the color misregistration correction operation timing should be set to, for example, Δt1 of 3 ° C., but set to, for example, Δt2 of 5 ° C. The timing is delayed, and the color misregistration exceeds the allowable amount Δcpr.
[0102]
Therefore, in the present embodiment, a correction value based on the variation between the belt driving roller temperature sensor 12a and the environment sensor 13a is set in the memory 16 in advance at the time of assembling the printer, and is held. In FIG. 7, when the detected voltage is v0 based on the correction value, Typ. With the sensor having the characteristic, the temperature is determined to be t4, and Max. With the sensor having the characteristic, the temperature is determined to be t5, and Min. With the characteristic sensor, the temperature is determined to be t3.
[0103]
(Third embodiment)
Next, a third embodiment will be described with reference to FIG.
[0104]
Only the features that are characteristic of the third embodiment will be described, and other configurations are the same as those of the first embodiment. The same components are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0105]
FIG. 8 is a diagram illustrating the entire image forming apparatus according to the third embodiment of the present invention.
Instead of the belt drive roller temperature sensor 12a and the environment sensor 13a of the first and second embodiments, respectively, an image forming unit temperature sensor 12b for detecting the ambient temperature of the image forming units 102a to 102d, An environment sensor 13b (different from 13a) for detecting a temperature is used.
[0106]
During the printing operation, the temperature around the image forming units 102a to 102d is increased by the passage of the intermediate transfer belt 3 heated by the fixing unit 8 through the transfer units 103a to 103d and the operation of motors, circuits, and the like (not shown).
[0107]
Therefore, the image forming unit temperature sensor 12b has the same function as the belt driving roller temperature sensor 12a of the first and second embodiments.
[0108]
On the other hand, the vicinity of the paper cassette 7 is at a position that is hardly affected by the temperature rise in the apparatus due to the printing operation.
[0109]
Therefore, the environment sensor 13b has the same function as the environment sensor 13a of the first and second embodiments.
[0110]
The same operation as in the first embodiment or the second embodiment is executed by using the image forming unit temperature sensor 12b and the environment sensor 13b.
[0111]
The temperature sensor in the machine is not limited to these positions.
[0112]
The color misregistration correction execution timing based on the detected temperature difference between the two temperature sensors and the detected temperature difference fluctuation amount is not limited to the comparison and determination unit described in the above embodiment. For example, the table value may be held by dividing the detected temperature difference and the detected temperature fluctuation amount into a plurality of levels.
[0113]
(Fourth embodiment)
Also in the third embodiment, similarly to the second embodiment with respect to the first embodiment, the difference between the detected temperature and the voltage value generated when the color misregistration is corrected based on the configuration of the third embodiment. A mechanism for correcting the variation between them can be provided (not shown).
[0114]
【The invention's effect】
As described above, according to the present invention, two temperature sensors are installed at different places in the apparatus where the temperature rises, and the temperature difference between the two temperature sensors during the execution of the color misregistration correction operation and the color misregistration correction After the operation is performed, the next color misregistration correction operation execution timing is determined based on the detected temperature fluctuation amount of at least one of the temperature sensors, and the detected temperature fluctuation amount of the temperature sensor inside the apparatus is determined according to various printing conditions. Even when the relationship between the color shift fluctuations is different, there is no unnecessary increase in downtime or the occurrence of color shift fluctuations exceeding the permissible amount, and the color shift correction operation is always executed at the appropriate timing. A color shift correction device can be provided.
[0115]
Further, according to the present invention, the color misregistration is performed at a timing when the detected temperature variation of at least one of the temperature sensors is smaller than when the temperature difference between the two temperature sensors is small when the color misregistration correction is executed. Since the correction is performed, in the case of a color shift due to a temperature change from a state where the printing operation is not performed for a while, there is no occurrence of a color shift fluctuation exceeding an allowable amount, and the printing operation is performed frequently, and In the case of a color shift due to temperature fluctuation from a state where the temperature has risen to some extent, a high-accuracy color shift correction device can be provided which does not unnecessarily increase downtime and always performs a color shift correction operation at an appropriate timing. .
[0116]
Further, according to the present invention, one of the temperature sensors is installed in the vicinity of a portion where the temperature rise due to the printing operation is large, so that the color misregistration correction operation execution timing can be more appropriately determined based on the detected temperature fluctuation amount of the one temperature sensor. It is possible to provide a high-precision color misregistration correction device that can detect and always perform a color misregistration correction operation at appropriate timing.
[0117]
Still further, according to the present invention, since the detection error correction values of the two temperature sensors are held, the temperature difference between the two temperature sensors at the time of performing the color misregistration correction is more accurately detected, and the color difference is more appropriately detected. It is possible to provide a high-accuracy color misregistration correction device that can set the misregistration correction operation execution timing and always performs the color misregistration correction operation at an appropriate timing.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an entire image forming apparatus according to a first embodiment of the present invention;
FIG. 2 is a block diagram illustrating an entire control unit according to the first embodiment of the present invention.
FIGS. 3A and 3B are diagrams illustrating a relationship between a detected temperature fluctuation amount and a color misregistration fluctuation amount when an in-machine temperature is increased by a printing operation according to the first embodiment of the present invention;
FIGS. 4A and 4B: After the internal temperature rises by the printing operation according to the first embodiment of the present invention, the printer enters a print standby state, and the detected temperature fluctuation amount and the color shift fluctuation when the internal temperature falls. Pair diagram illustrating quantity relationships
5A and 5B are diagrams illustrating a relationship between a detected temperature fluctuation amount and a color misregistration fluctuation amount when the printer installation environment temperature rises during a print standby state according to the first embodiment of the present invention.
FIG. 6 is a flowchart illustrating a method for determining a color misregistration correction timing according to the first embodiment of the present invention.
FIG. 7 is a view for explaining a relationship between a detected temperature and an output voltage of a temperature sensor according to a second embodiment of the present invention.
FIG. 8 is an explanatory view showing the entire image forming apparatus according to a third embodiment of the present invention.
9A, 9B, 9C, and 9D are diagrams for explaining various color shifts.
FIG. 10 is a diagram illustrating a color misregistration detection pattern.
[Explanation of symbols]
1a, 1b, 1c, 1d photosensitive drum
2a, 2b, 2c, 2d Laser scanner
3 Intermediate transfer belt
4 Belt drive roller
6 Secondary transfer roller
7 Paper cassette
8 Fixing device
9 Double-sided unit
11 Color shift detection sensor
12a Belt drive roller temperature sensor
12b Image forming means temperature sensor
13a, 13b Environmental sensor
20 Original image position
21a, 21b, 21c, 21d Image position when color misregistration occurs
102a, 102b, 102c, 102d Image forming means
103a, 103b, 103c, 103d transfer means

Claims (4)

A plurality of image forming units each having an optical unit and a latent image forming medium, an endless belt unit sequentially passing through the plurality of image forming units, and a formed image on the endless belt unit or the endless belt unit. A plurality of transfer means for transferring onto a recording material conveyed while being held on a belt means, a driving means for driving the endless belt, and forming a color misregistration detection pattern on the endless belt means, A color misregistration correction device that electrically and mechanically corrects color misregistration based on a detection result of the color misregistration detection pattern;
A first temperature detecting means for detecting a temperature in the vicinity of one of the image forming means, the endless belt means, and the transferring means; and a temperature in the color image forming apparatus other than the first temperature detecting means. Temperature detection means for detecting color shift, and operation timing determination means for determining an operation timing of the color misregistration correction means based on at least one of the detected temperature fluctuation amounts of the first and second temperature detection means. The operation timing of the color misregistration correction means is variably controlled based on the detected temperatures of the first and second temperature detection means at the time of operation of the color misregistration correction means. A color misregistration correction device for a color image forming apparatus. The operation timing determination unit is configured to determine whether the difference between the first and second temperature detection units during the operation of the color misregistration correction unit is small, as compared with the case where the difference is large. 2. The color misregistration correction device for a color image forming apparatus according to claim 1, wherein the color misregistration correction means is operated at a timing when the detected temperature fluctuation amount is small. 2. The color misregistration correction device for a color image forming apparatus according to claim 1, wherein said first temperature detecting means detects a temperature near a belt driving roller on which said endless belt means is suspended. 2. The color image forming apparatus according to claim 1, further comprising a detected temperature error correction value holding unit that holds a relative detected temperature error correction value between the first and second temperature detecting units. apparatus.

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